A kind of clear varnish for traffic vehicle parts and preparation method thereof

Abstract

This invention provides a clear topcoat for transportation vehicle components, comprising the following components: silicone-modified fluorocarbon resin, HDI-blocked isocyanate, IPDI-blocked isocyanate, hexamethoxymethylmelamine-formaldehyde resin, light stabilizer, adhesion promoter, silicone-modified polyacrylate solution, and organic solvent. The HDI-blocked isocyanate crosslinking product exhibits excellent weather resistance, moderate hardness, and flexibility; the IPDI-blocked isocyanate crosslinking product possesses excellent resistance to acid rain and weathering, but the coating is slightly brittle and hard; the hexamethoxymethylmelamine-formaldehyde resin crosslinking product has good toughness and excellent adhesion to the base coat, but slightly poor acid rain resistance; the combined crosslinking product of these three components exhibits good weather resistance, acid resistance, stain resistance, and interlayer compatibility. This invention also provides a method for preparing and applying this clear topcoat for transportation vehicle components.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more specifically to a clear varnish for transportation vehicle components and its preparation method. Background Technology

[0002] The varnish coatings commonly used on existing transportation vehicle parts have relatively weak stain resistance, making it easy for dust to fall onto the surface. Furthermore, the cleaning process is not easy to remove stains, especially for rail transit, which operates at high speeds for long periods of time. In addition to accumulating stains, it is also exposed to sun, wind, and rain. Moreover, as a whole, trains are much more difficult to clean than cars.

[0003] To improve the anti-fouling and decorative properties of traffic components, a protective coating is applied to the surface. The coating structure mainly falls into two categories: First, pretreatment – ​​primer – curing – base coat (or topcoat) – clear coat – curing (130-150℃); Second, pretreatment – ​​primer – curing – base coat (or topcoat) – curing (130-150℃) – transparent powder coating – curing (170-190℃). The clear coat used is primarily acrylic amino transparent varnish, polyester amino transparent varnish, or polysiloxane transparent varnish.

[0004] Patent CN111334189B discloses an anti-fouling self-cleaning coating post-treatment agent and its preparation method. This anti-fouling self-cleaning coating post-treatment agent is used after the coating system has been applied and cured. It features fast drying, high hardness, excellent anti-fouling and self-cleaning properties, and superior aging resistance. The post-treatment agent utilizes silicon-based materials in its formulation, namely siloxanes, silane coupling agents, and polysiloxane oligomers, to undergo a hydrolysis reaction with water molecules in the air to crosslink and form a film. It also combines this with the reaction of polysilazane with the hydroxyl groups of water molecules in the air and the hydroxyl groups generated after the hydrolysis of the silicon-based materials to form a crosslinked film. This allows the anti-fouling self-cleaning coating post-treatment agent system to form a high-hardness, hydrophobic organic-inorganic coating upon curing. When applied to product surfaces in this field, this solution initially provides good anti-graffiti functionality. However, after a period of outdoor exposure or accelerated aging tests under xenon lamps, the anti-graffiti function of the paint film shows a significant decrease. Summary of the Invention

[0005] Based on this, in order to overcome the shortcomings of existing coatings, the present invention provides a stain-resistant and easy-to-clean topcoat varnish and its preparation method, which is applied to the surface of existing varnish or transparent powder coatings to significantly improve the overall stain resistance and easy-to-clean performance of the coating.

[0006] First aspect:

[0007] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0008]

[0009]

[0010] Wherein, isocyanate A is an HDI-blocked isocyanate, isocyanate B is an IPDI-blocked isocyanate, the amino resin is hexamethoxymethyl melamine-formaldehyde resin, and the organic solvent A includes at least one of alcohol solvents, aromatic solvents, ester solvents, and alcohol ether solvents.

[0011] Organosilicon-modified fluorocarbon resins can introduce silicon-containing groups into the main chain and side chains of organofluorocarbon polymers through copolymerization with silicon- and fluorine-containing monomers, forming block network copolymers. These copolymers exhibit good hydrophobicity, with a large contact angle when in contact with rainwater and dust, making them less prone to contamination and easier to clean. Particularly in terms of weather resistance and anti-fouling properties, organosilicon-modified fluorocarbon resins formed through chemical polymerization exhibit superior performance compared to physically blended resins.

[0012] Isocyanate A, isocyanate B, and amino resin can all undergo crosslinking reactions with silicone-modified fluorocarbon resins. Isocyanate A, an HDI-blocked isocyanate, produces a crosslinking product with silicone-modified fluorocarbon resin exhibiting excellent weather resistance, moderate hardness, and flexibility. Isocyanate B, an IPDI-blocked isocyanate, produces a crosslinking product with silicone-modified fluorocarbon resin exhibiting excellent resistance to acid rain and weathering, but the coating is slightly brittle and hard. Amino resin produces a crosslinking product with silicone-modified fluorocarbon resin with good toughness and excellent adhesion to the base coat, but its acid rain resistance is slightly poor. The combination of these three substances compensates for the shortcomings of their respective crosslinking products, resulting in a comprehensive crosslinking product that not only maintains weather resistance, acid resistance, stain resistance, and interlayer compatibility, but also further enhances the long-lasting properties of silicone-modified fluorocarbon resins and delays their decomposition. Particularly for clear coat curing windows in transportation components, the clear coat described in this invention, through the selection of isocyanates and amino resins, maximizes the performance of the main resin.

[0013] Hexamethoxymethyl melamine-formaldehyde resin exhibits excellent coating performance within the curing window of 165-185℃, with a good balance between hardness and toughness after curing. However, most existing polymeric high-imino, high-methyl etherified melamine resins, partially methyl etherified melamine resins, and butyl etherified melamine-formaldehyde resins show increased brittleness in their reaction products within the 165-185℃ curing window, resulting in insufficient interlayer adhesion with the base coat. Furthermore, the weather resistance of urea-formaldehyde and phenyl melamine-formaldehyde resins fails to meet requirements.

[0014] The silicone-modified polyacrylate solution increases the contact angle of the coating after the varnish has cured, further improving its anti-fouling ability. Furthermore, it promotes the cross-linking reaction between the silicone-modified fluorocarbon resin and isocyanate within the system, enhancing inter-coating adhesion. The combined use of the silicone-modified polyacrylate solution and the silicone-modified fluorocarbon resin comprehensively improves both the anti-fouling properties of the cured varnish coating and the inter-coating adhesion.

[0015] The clear varnish for transportation vehicle components described in this invention, through the combined action of its components, greatly improves the anti-graffiti properties of the coating and the retention of anti-graffiti properties after accelerated weathering. It also makes it easier to clean stains after contamination, and has advantages over conventional amino resin crosslinking products.

[0016] As a preferred embodiment, by mass percentage, the organosilicon-modified fluorocarbon resin contains more than 15% fluorocarbon bonds and more than 4% organosilicon in the side chains; the isocyanate A has a solid content of more than 70%, an NCO group content of 9.0-12.6%, and a desealing temperature of 130-150℃; the isocyanate B has a solid content of more than 60%, an NCO group content of 8.0-13.0%, and a desealing temperature of 120-140℃; and the amino resin has a solid content of more than 90%.

[0017] In silicone-modified fluorocarbon resins, increasing the fluorocarbon bond content in the main chain can improve the weather resistance of the varnish after curing and prevent the decomposition of isocyanates. Increasing the silicone content in the side chains can increase the crosslinking density with isocyanates and amino resins. Controlling the NCO group content in isocyanate A can not only control the reaction rate of the system and prevent the varnish from reacting too quickly or unevenly during curing, thus reducing weather resistance, but also control the surface tension of the system within a suitable range, preventing excessive shrinkage during curing and resulting in discontinuous coating. Controlling the NCO group content in isocyanate B can not only control the viscosity of the system and improve the chemical resistance of the product, but also has good polarity, which can improve the anti-fouling properties of the varnish after curing.

[0018] As a preferred embodiment, the organosilicon-modified fluorocarbon resin comprises, by weight percentage: 20-30% organofluorine monomer, 4-8% silane coupling agent, 4-5% needle silicate, 22-28% olefin ester, 24-30% unsaturated olefinic acid, 8-15% organic solvent B, and 0.5-1% initiator;

[0019] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 2-3 atm, heating to 80-90℃, reacting for 4-6 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0020] As a preferred embodiment, the organofluorine monomer is tetrafluoroethylene, the alkane coupling agent is an organosilicon coupling agent containing methoxy and acyloxy groups, the needle silicate is wollastonite, the olefin ester includes at least one of ethylene carbonate and propylene carbonate, the unsaturated olefinic acid includes at least one of linolenic acid and acrylic acid; the organic solvent B includes at least one of cyclohexanone and n-butyl acetate; and the initiator is azobisisobutyronitrile.

[0021] As a preferred embodiment, the organosilicon-modified polyacrylate solution is an organosilicon-modified polyacrylate solution with hydroxyl functional groups. This solution can undergo a cross-linking reaction with the hydroxyl groups in the organosilicon-modified fluorocarbon resin, ensuring tight bonding between the components within the coating. This prevents the migration of components within the coating after the varnish has cured, further improving the coating's long-term durability. In this embodiment, BYK-3700 is selected. This solution not only enhances the varnish's high water and oil repellency, reducing contact with dust and dirt, but also improves the wetting, leveling, and surface smoothness of the base coat, and enhances the varnish's water resistance, anti-blocking properties, and weather resistance.

[0022] As a preferred embodiment, the alcohol solvent includes at least one selected from isopropanol, n-butanol, and isobutanol; the ester solvent includes at least one selected from butyl acetate and propylene glycol methyl ether acetate; the aromatic solvent includes at least one selected from xylene, No. 100 solvent oil, and No. 150 solvent oil; and the alcohol ether solvent includes at least one selected from ethylene glycol butyl ether, propylene glycol methyl ether, and diethylene glycol butyl ether. These organic solvents exhibit good compatibility with the resin system of this invention, have moderate and easily controllable viscosity, and can effectively control the volatilization gradient during varnish curing. Furthermore, in addition to being used as solvents, the organic solvents can also improve the adhesion between coatings and effectively reduce coating peeling.

[0023] As a preferred embodiment, the clear varnish for vehicle components further includes 0.5-2 parts of a light stabilizer, wherein the light stabilizer includes at least one of benzotriazole UV absorbers and triazine UV absorbers. UV absorbers possess excellent thermal stability and weather resistance, effectively delaying the decomposition of crosslinking products after the varnish cures, and effectively improving the long-term effectiveness of anti-fouling properties.

[0024] As a preferred embodiment, the clear varnish for vehicle components further includes 0.5-2 parts of an adhesion promoter, wherein the adhesion promoter is a polyester-based phosphate ester with a solid content greater than 60 wt% and an acid value of 30-80 mg KOH / g. This additive has a mild catalytic effect, and compared to sulfonate additives, the reaction process is easier to control. It can moderately catalyze the reaction between organosilicon-modified fluorocarbon resin and amino resin, thereby improving the adhesion of the clear varnish.

[0025] The second aspect:

[0026] A method for preparing a clear varnish for vehicle components as described in the first aspect comprises the following steps:

[0027] S1: Mix the organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin, and organic solvent A, and disperse them at a speed of 500-1500 rpm for 10-20 min to obtain a dispersion.

[0028] S2: Add the organosilicon-modified polyacrylate solution to the dispersion and mix for 20-30 minutes at a speed of 600-1500 rpm to obtain a mixture;

[0029] S3: Filter the mixture using a 5-15μm filter bag to obtain a clear varnish.

[0030] The clear varnish of this invention uses silicone-modified fluorocarbon resin, HDI blocked isocyanate, IPDI blocked isocyanate, and amino resin as raw materials. After the silicone-modified fluorocarbon resin is uniformly mixed with HDI blocked isocyanate, IPDI blocked isocyanate, and amino resin, a silicone-modified polyacrylate solution is added to further improve the coating's anti-fouling ability and also better utilize the long-lasting advantage of silicone-modified fluorocarbon resin. Finally, the coating is filtered and packaged to obtain a clear varnish for transportation vehicle parts. The preparation process is simple.

[0031] Third aspect:

[0032] The application of a clear varnish for a vehicle component as described in the first aspect includes the following steps:

[0033] Dilute the vehicle component with a clear topcoat to a spray viscosity of 15-20 s / Ford Cup 4 (25°C), and spray it onto the existing clear varnish or transparent powder coating surface to a thickness of 15-35 μm. Cur at 165-185°C for 20-30 minutes. If the viscosity is too high or too low, the appearance after spraying will be poor; if the spray thickness is too low or too high, the anti-graffiti function of the coating or its anti-graffiti function after accelerated weathering will decrease. Detailed Implementation

[0034] To further understand the present invention, the present invention will be described in detail below with reference to the embodiments. However, it should be noted that the embodiments do not constitute a limitation on the scope of protection of the present invention.

[0035] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0036]

[0037] The organosilicon-modified fluorocarbon resin comprises, by mass percentage, the following components: 20-30% organofluorine monomer, 4-8% silane coupling agent, 4-5% needle silicate, 22-28% olefin ester, 24-30% unsaturated olefinic acid, 8-15% organic solvent B, and 0.5-1% initiator; wherein the organofluorine monomer is tetrafluoroethylene; the silane coupling agent is KH560; the needle silicate is wollastonite; the olefin ester includes at least one of ethylene carbonate and propylene carbonate; the unsaturated olefinic acid includes at least one of linolenic acid and acrylic acid; the organic solvent B includes at least one of cyclohexanone and n-butyl acetate; the initiator is azobisisobutyronitrile; the isocyanate A is an HDI-blocked isocyanate, wherein the solid content is greater than 70%, the NCO group content is 9.0-12.6%, and the deblocking temperature is 130-150℃; the isocyanate B is an IPDI-blocked isocyanate, wherein the solid content is greater than 70%, the NCO group content is 9.0-12.6%, and the deblocking temperature is 130-150℃; and the isocyanate B is an IPDI-blocked isocyanate, wherein the solid content is greater than 70%, the NCO group content is 9.0-12.6%, and the deblocking temperature is 130-150℃. The composition is greater than 60%, the NCO group content is 8.0-13.0%, and the unsealing temperature is 120-140℃; the amino resin is hexamethoxymethyl melamine formaldehyde resin, wherein the solid content is greater than 90%; the organosilicon-modified polyacrylate solution is an organosilicon-modified polyacrylate solution with hydroxyl functional groups; the light stabilizer is EV81 from Taiwan Yung-Kuang Chemical Industry Co., Ltd.; the adhesion promoter is Lubrizol 2063; the organic solvent A includes at least one of alcohol solvents, aromatic solvents, ester solvents, and alcohol ether solvents, the alcohol solvent includes at least one of isopropanol, n-butanol, and isobutanol, the aromatic solvent includes at least one of xylene, No. 100 solvent oil, and No. 150 solvent oil, the ester solvent includes at least one of butyl acetate and propylene glycol methyl ether acetate, and the alcohol ether solvent includes at least one of ethylene glycol butyl ether, propylene glycol methyl ether, and diethylene glycol butyl ether.

[0038] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 2-3 atm, heating to 80-90℃, reacting for 4-6 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0039] A method for preparing a clear varnish for vehicle components includes the following steps:

[0040] S1: Mix the organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin, and organic solvent A, and disperse them at a speed of 500-1500 rpm for 10-20 min to obtain a dispersion.

[0041] S2: Add the organosilicon-modified polyacrylate solution, light stabilizer, and adhesion promoter to the dispersion and mix for 20-30 minutes at a speed of 600-1500 rpm to obtain a mixture;

[0042] S3: Filter the mixture using a 5-15μm filter bag to obtain a clear varnish.

[0043] The application of a clear varnish for a vehicle component includes the following steps:

[0044] Dilute the vehicle component with a clear varnish to a spraying viscosity of 15-20 s / Ford Cup 4 (25°C), spray it onto the existing varnish or transparent powder coating surface, with a spray thickness of 15-35 μm, and cure at 165-185°C for 20-30 min.

[0045] Example 1

[0046] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0047]

[0048] The organosilicon-modified fluorocarbon resin comprises, by weight percentage: 20% organofluorine monomer, 8% silane coupling agent, 5% needle silicate, 28% olefin ester, 30% unsaturated olefinic acid, 8% organic solvent B, and 1% initiator; wherein the organofluorine monomer is tetrafluoroethylene, the silane coupling agent is KH560, the needle silicate is wollastonite, the olefin ester is ethylene carbonate, the unsaturated olefinic acid is acrylic acid, the organic solvent B is cyclohexanone, and the initiator is azobisisobutyronitrile. The isocyanate A is Covestro's BL3272; the isocyanate B is Evonik Degussa's B1358A; the amino resin is hexamethoxymethyl melamine-formaldehyde resin with a solid content greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; the light stabilizer is EV81 from Taiwan Yung-Kuang Chemical Co., Ltd.; the adhesion promoter is Lubrizol 2063; and the organic solvent A is ethylene glycol butyl ether.

[0049] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 2 atm, heating to 80°C, reacting for 6 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0050] Example 2

[0051] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0052]

[0053] The organosilicon-modified fluorocarbon resin comprises, by weight percentage: 30% organofluorine monomer, 6% silane coupling agent, 5% needle silicate, 22% olefin ester, 26% unsaturated olefinic acid, 10% organic solvent B, and 1% initiator; wherein the organofluorine monomer is tetrafluoroethylene, the silane coupling agent is KH560, the needle silicate includes wollastonite, the olefin ester is propylene carbonate, the unsaturated olefinic acid is linolenic acid and acrylic acid in a volume ratio of 1:1, the organic solvent B is n-butyl acetate, the initiator is azobisisobutyronitrile, the isocyanate A is Covestro BL3272, and the isocyanate B is Evonik. Degussa's B1358A; the amino resin is hexamethoxymethyl melamine formaldehyde resin with a solid content greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; the light stabilizer is EV81 from Taiwan Yung-Kuang Chemical Co., Ltd.; the adhesion promoter is Lubrizol 2063; and the organic solvent A is propylene glycol methyl ether.

[0054] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 2.5 atm, heating to 85°C, reacting for 5 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0055] Example 3

[0056] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0057]

[0058]

[0059] The organosilicon-modified fluorocarbon resin comprises, by weight percentage: 20.5% organofluorine monomer, 6% silane coupling agent, 4% needle silicate, 28% olefin ester, 24% unsaturated olefinic acid, 15% organic solvent B, and 0.5% initiator; wherein the organofluorine monomer is tetrafluoroethylene, the silane coupling agent is KH560, the needle silicate is wollastonite, the olefin ester is ethylene carbonate, the unsaturated olefinic acid is acrylic acid, the organic solvent B is cyclohexanone and n-butyl acetate in a volume ratio of 1:1, the initiator is azobisisobutyronitrile, the isocyanate A is Covestro BL3272, and the isocyanate B is Evonik. Degussa's B1358A; the amino resin is hexamethoxymethyl melamine formaldehyde resin with a solid content greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; the light stabilizer is EV81 from Taiwan Yung-Kuang Chemical Co., Ltd.; the adhesion promoter is Lubrizol 2063; and the organic solvent A is propylene glycol methyl ether acetate.

[0060] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 3 atm, heating to the reaction temperature of 90°C, reacting for 4 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0061] Example 4

[0062] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0063]

[0064] The organosilicon-modified fluorocarbon resin comprises, by weight percentage: 29.5% organofluorine monomer, 6% silane coupling agent, 4% needle silicate, 22% olefin ester, 30% unsaturated olefinic acid, 8% organic solvent B, and 0.5% initiator; wherein the organofluorine monomer is tetrafluoroethylene, the silane coupling agent is KH560, the needle silicate is wollastonite, the olefin ester is ethylene carbonate, the unsaturated olefinic acid is acrylic acid, the organic solvent B is cyclohexanone and n-butyl acetate in a volume ratio of 1:1, the initiator is azobisisobutyronitrile, the isocyanate A is Covestro BL3272, and the isocyanate B is Evonik. Degussa's B1358A; the amino resin is hexamethoxymethyl melamine formaldehyde resin, wherein the solid content is greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; the organic solvent A is a mixed solution of isopropanol, butyl acetate, and propylene glycol methyl ether acetate in a volume ratio of 1:1:1.

[0065] The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the organofluorine monomer, pressurizing to 2.2 atm, heating to 90°C, reacting for 5 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

[0066] Example 5

[0067] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0068]

[0069] Specifically, by mass percentage, the organosilicon-modified fluorocarbon resin contains more than 15% fluorocarbon bonds and more than 4% organosilicon in the side chains; isocyanate A is Covestro's BL3272; isocyanate B is Evonik Degussa's B1358A; the amino resin is hexamethoxymethyl melamine-formaldehyde resin with a solid content greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; and the organic solvent A is a mixed solution of isobutanol, propylene glycol methyl ether, and propylene glycol methyl ether acetate in a volume ratio of 1:1:1.

[0070] Example 6

[0071] A clear varnish for vehicle components comprises the following components in the indicated mass ratios:

[0072]

[0073] Specifically, by mass percentage, the organosilicon-modified fluorocarbon resin contains more than 15% fluorocarbon bonds and more than 4% organosilicon in the side chains; isocyanate A is Covestro's BL3272; isocyanate B is Evonik Degussa's B1358A; the amino resin is hexamethoxymethyl melamine-formaldehyde resin with a solid content greater than 90%; the organosilicon-modified polyacrylate solution is BYK-3700; and the organic solvent A is ethylene glycol butyl ether.

[0074] Example 7

[0075] The preparation method of the clear varnish for transportation vehicle components described in Examples 1-3 includes the following steps:

[0076] S1: The organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin and organic solvent A are added to the working tank in sequence and dispersed at 1000 rpm for 15 min to obtain a dispersion.

[0077] S2: Adjust the rotation speed of the working cylinder to 500 rpm, then add the organosilicon-modified polyacrylate solution, light stabilizer, and adhesion promoter. After the addition is complete, mix for 25 minutes at a rotation speed of 1000 rpm to obtain a mixture.

[0078] S3: Filter the mixture using a 10μm filter bag to obtain a clear varnish.

[0079] Example 8

[0080] The preparation method of the clear varnish for transportation vehicle components described in Examples 4-5 includes the following steps:

[0081] S1: The organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin and organic solvent A are added to the working tank in sequence and dispersed at a speed of 500 rpm for 20 min to obtain a dispersion.

[0082] S2: Adjust the working cylinder speed to 600 rpm, then add the organosilicon-modified polyacrylate solution. After the addition is complete, mix for 20 minutes at a speed of 1500 rpm to obtain a mixture.

[0083] S3: Filter the mixture using a 15μm filter bag to obtain a clear varnish.

[0084] Example 9

[0085] The method for preparing the clear varnish for vehicle components described in Example 6 includes the following steps:

[0086] S1: The organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin, and organic solvent A are added to the working tank in sequence and dispersed at a speed of 1500 rpm for 10 min to obtain a dispersion.

[0087] S2: Adjust the working cylinder speed to 400 rpm, then add the organosilicon-modified polyacrylate solution. After the addition is complete, mix at 600 rpm for 30 minutes to obtain a mixture.

[0088] S3: Filter the mixture using a 5μm filter bag to obtain a clear varnish.

[0089] Example 10

[0090] The application of the clear varnish for vehicle components described in Examples 1-6 includes the following steps:

[0091] Dilute the vehicle component with a clear varnish to a spraying viscosity of 15-20 s / Ford Cup 4 (25°C), spray it onto the existing varnish or transparent powder coating surface, with a spray thickness of 15-35 μm, and cure at 165-185°C for 20-30 min.

[0092] Comparative Example 1: Sifang Weikai JS200 series solvent-based acrylic amino varnish.

[0093] Comparative Example 2: PPG transparent powder.

[0094] Comparative Example 3: The product reported in patent CN111334189B.

[0095] Table 1: Performance Testing Items, Methods, and Indicators for Clear Coating Products

[0096]

[0097] Table 2: Performance Test Results of Clear Coatings in Examples 1-4

[0098]

[0099]

[0100] Table 3: Performance Test Results of Clear Coatings for Comparative Examples 1-3

[0101]

[0102] Table 1 lists the performance testing items, methods, and indicators for the clear varnish product; Table 2 shows the performance test results of the clear varnish in Examples 1-4; and Table 3 shows the performance test results of the clear varnish in Comparative Examples 1-3. The results in Tables 2-3 indicate that, after curing, the clear varnish for the vehicle components described in this invention exhibits superior or similar performance to the comparative examples in terms of hardness, adhesion, gloss, 1000h neutral salt spray resistance, and 40℃, 480h water resistance tests. After accelerated aging, its anti-graffiti properties are significantly better than the comparative examples. In the anti-graffiti test, the results are also superior to Comparative Examples 1 and 2, and comparable to Comparative Example 3.

[0103] This invention is not limited to the above-described embodiments. If any modifications or variations to this invention do not depart from the spirit and scope of this invention, and if such modifications and variations fall within the scope of the claims and equivalent technologies of this invention, then this invention also intends to include such modifications and variations.

Claims

1. A clear varnish for vehicle components, characterized in that, The components include the following mass ratios: Wherein, isocyanate A is an HDI-blocked isocyanate, isocyanate B is an IPDI-blocked isocyanate, the amino resin is hexamethoxymethyl melamine-formaldehyde resin, the organosilicon-modified polyacrylate solution is an organosilicon-modified polyacrylate solution with hydroxyl functional groups, the organic solvent A includes at least one of alcohol solvents, aromatic solvents, ester solvents, and alcohol ether solvents, and the adhesion promoter is a phosphate ester with polyester as the main chain, a solid content greater than 60 wt%, and an acid value of 30-80 mg KOH / g; The organosilicon-modified fluorocarbon resin contains more than 15% fluorocarbon bonds and more than 4% organosilicon in its side chains, by mass percentage. The organosilicon-modified fluorocarbon resin comprises, by weight percentage: 20-30% tetrafluoroethylene, 4-8% silane coupling agent, 4-5% needle silicate, 22-28% olefin ester, 24-30% unsaturated olefinic acid, 8-15% organic solvent B, and 0.5-1% initiator. By mass percentage, the organosilicon-modified fluorocarbon resin contains more than 15% fluorocarbon bonds and more than 4% organosilicon in the side chains; the isocyanate A has a solid content of more than 70%, an NCO group content of 9.0-12.6%, and a desealing temperature of 130-150℃; the isocyanate B has a solid content of more than 60%, an NCO group content of 8.0-13.0%, and a desealing temperature of 120-140℃; and the amino resin has a solid content of more than 90%. The method for synthesizing the organosilicon-modified fluorocarbon resin includes the following steps: thoroughly mixing the olefin ester, unsaturated olefinic acid, and organic solvent B, adding the initiator, sealing and evacuating, introducing the tetrafluoroethylene, pressurizing to 2-3 atm, heating to 80-90℃, reacting for 4-6 hours, adding the silane coupling agent and the needle-shaped silicate, and continuing the reaction for 1 hour to obtain the organosilicon-modified fluorocarbon resin.

2. The clear varnish for vehicle components according to claim 1, characterized in that, The silane coupling agent is an organosilicon coupling agent containing methoxy and acyloxy groups; the needle silicate is wollastonite; the olefinic ester includes at least one of ethylene carbonate and propylene carbonate; the unsaturated olefinic acid includes at least one of linolenic acid and acrylic acid; the organic solvent B includes at least one of cyclohexanone and n-butyl acetate; and the initiator is azobisisobutyronitrile.

3. The clear varnish for vehicle components according to claim 1, characterized in that, The alcohol solvent includes at least one of isopropanol, n-butanol, and isobutanol; the aromatic solvent includes at least one of xylene, No. 100 solvent oil, and No. 150 solvent oil; the ester solvent includes at least one of butyl acetate and propylene glycol methyl ether acetate; and the alcohol ether solvent includes at least one of ethylene glycol butyl ether, propylene glycol methyl ether, and diethylene glycol butyl ether.

4. The clear varnish for vehicle components according to claim 1, characterized in that, It also includes 0.5-2 parts of light stabilizer, which includes at least one of benzotriazole UV absorbers and triazine UV absorbers.

5. A method for preparing a clear varnish for transportation vehicle components as described in any one of claims 1-4, characterized in that, The steps include: S1: Mix the organosilicon-modified fluorocarbon resin, isocyanate A, isocyanate B, amino resin, and organic solvent A, and disperse them at a speed of 500-1500 rpm for 10-20 min to obtain a dispersion. S2: Add the organosilicon-modified polyacrylate solution to the dispersion and mix for 20-30 minutes at a speed of 600-1500 rpm to obtain a mixture; S3: Filter the mixture using a 5-15μm filter bag to obtain a clear varnish.

6. The application of a clear varnish for vehicle components as described in claim 1, characterized in that, Dilute the vehicle component with a clear varnish to a spraying viscosity of 15-20 s / Ford Cup 4 (25°C), spray it onto the surface of an existing clear varnish or transparent powder coating, with a spraying thickness of 15-35 μm, and cure it at 165-185°C for 20-30 min.

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