Water-based automobile transparent PC highlight varnish and preparation method of coating

Abstract

The invention belongs to the technical field of automobile exterior trimming part coatings, and relates to a preparation method of a water-based automobile transparent PC highlight varnish and a coating thereof.The preparation method of the varnish comprises the steps that firstly, polycarbonate diol and propylene glycol monomethyl ether acetate are subjected to a primary heating reaction; then carrying out a secondary heating reaction with n-butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol monomethyl ether and tert-butyl peroxybenzoate; adding alkali to neutralize, and mixing with water to prepare a water-based polycarbonate modified acrylic acid dispersion; then mixing with a water-based defoaming agent, a water-based flatting agent, a water-based coalescing agent, a thickening agent and an amine neutralizer to obtain a component A; mixing a water-based curing agent with a solvent to obtain a component B; and mixing the component A and the component B to obtain the water-based automobile transparent PC highlight varnish. Compared with the prior art, the invention has the advantages of high luminosity, hardness, aging resistance, excellent PC adhesive force, simple preparation process, low cost, small pollution and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of automotive exterior part coatings, and relates to a waterborne automotive transparent PC high-gloss clear varnish and a preparation method of a coating layer. Background Art

[0002] At present, with the popularization of new energy vehicles and various electronic products, the competition among related automobile manufacturers has become increasingly fierce. In the current era of new energy vehicle consumption with a wide variety of products and high independent selectivity, the styling design of the automobile appearance and the exterior lighting styling products can often attract a large number of young and middle-aged consumers. Continuously improving the quality of the product itself, especially the quality related to the customer experience, is the most effective business strategy to attract and retain customers.

[0003] Compared with automotive exterior lighting styling products (including daytime running lights, illuminated front grilles, rear wing light strips, etc.), what consumers come into contact with the most are automotive interior atmosphere lights and various physical button indicators, and each component is small. The difference between exterior lighting styling products and interiors is that the exteriors are all large parts, and these parts are all large PC transparent parts. The coatings applied directly affect the customer's judgment and perception of the durability and reliability of the automobile appearance. Due to the environmental requirements during consumer use, such parts of the product are required to be coated with three layers of coatings with excellent PC adhesion. Among them, the styling differentiation of the lighting pattern can be easily completed by laser engraving technology for the base color coating layer, and even customer personalized styling can be completed through separate customization, which is deeply loved by consumers. After laser engraving the base color coating film, a high-gloss protective clear varnish film needs to be coated on the outside to protect the appearance of the exterior part and avoid scratches and contamination during driving. However, ordinary high-gloss clear varnishes have poor adhesion on the directly PC transparent parts after laser engraving, resulting in paint peeling, which seriously affects the overall quality of the product and has a great impact on the aesthetic appearance of automotive exterior parts.

[0004] The currently commercially available products are oily PU high-gloss clear varnish films, which do not meet the physical property requirements of excellent product adhesion, and seriously affect the overall quality of the manufacturer and the customer experience. There have also been some waterborne high-gloss clear varnish products on the market, and the instability of the PC adhesion also reduces the competitiveness of the products. Summary of the Invention

[0005] The purpose of the present invention is to provide a waterborne automotive transparent PC high-gloss clear varnish with excellent adhesion on PC substrate parts, simple preparation process, low production cost, and small environmental pollution, as well as a preparation method of a coating layer.

[0006] The varnish prepared by selecting raw materials according to the general idea of the existing technology cannot pass various adhesion tests on PC substrates, especially the simulated high-pressure water gun car wash test. Some researchers wrongly attributed the reason to the acrylic coating formula, only considering the performance of acrylic raw materials, and improving adhesion by adding acrylic raw materials with low hydroxyl value. Although it is helpful to some extent, it cannot completely solve the adhesion problem of the coating film not peeling off during the simulated high-pressure water gun car wash test, and at the same time reduces the high gloss and aging resistance of the varnish.

[0007] The present invention uses a polycarbonate-modified acrylic resin with the same molecular structure as the PC substrate. After being added as a modified raw material to the coating film, due to the principle of similar solubility, it will greatly improve the adhesion to PC without affecting the high gloss and aging resistance of the varnish. After the obtained waterborne automotive transparent PC high-gloss varnish is completely cured, the polycarbonate-modified part in the coating film is used to greatly improve the adhesion of the coating film to the PC substrate, far exceeding the adhesion of ordinary acrylic polyurethane coating films to the PC substrate, and having excellent PC adhesion characteristics.

[0008] The object of the present invention can be achieved by the following technical solutions:

[0009] The first aspect of the present invention provides a preparation method of a waterborne automotive transparent PC high-gloss varnish, comprising the following steps:

[0010] S1: Perform a first heating reaction on polycarbonate diol and propylene glycol monomethyl ether acetate; then perform a second heating reaction with n-butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol methyl ether, and tert-butyl peroxybenzoate; after adding alkali for neutralization, mix with water to prepare a waterborne polycarbonate-modified acrylic dispersion; then mix with a waterborne defoaming agent, a waterborne leveling agent, a waterborne film-forming aid, a thickener, and an amine neutralizing agent to obtain component A;

[0011] Mix the waterborne curing agent with a solvent to obtain component B;

[0012] S2: Mix component A and component B to obtain a waterborne automotive transparent PC high-gloss varnish.

[0013] In some specific embodiments, in step S1, in the first heating reaction, the mass ratio of polycarbonate diol to propylene glycol monomethyl ether acetate is (14 - 18):(12 - 16); the reaction temperature is 130 - 140 °C, and the reaction time is preferably 10 - 12 h.

[0014] In some specific embodiments, after the first heating reaction, the product polycarbonate polyol oligomer is obtained by distillation purification, and its molecular weight is 1100 - 1300 g / mol.

[0015] In some specific embodiments, in step S1, in the secondary heating reaction, the mass ratio of butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol methyl ether, tert-butyl peroxybenzoate to polycarbonate diol is (5 - 7):(4 - 6):(3 - 5):(3.9 - 5):(5 - 6):(3 - 4):(14 - 18); the reaction temperature is 110 - 120 °C, and the reaction time is preferably 6 - 7 h.

[0016] In some specific embodiments, in step S1, in the alkali addition and neutralization, the added alkali is dimethylethanolamine, and the mass ratio of dimethylethanolamine, water and polycarbonate diol is (2 - 4):(35 - 50):(14 - 18).

[0017] In some specific embodiments, in the alkali addition and neutralization, the stirring speed is 500 - 600 rpm, the temperature is 80 - 90 °C, and the end point pH is 7.8 - 8.2.

[0018] In some specific embodiments, when mixing with water, the rotation speed in the stirring and shearing state is 1000 - 1200 rpm.

[0019] In some specific embodiments, the method for preparing the aqueous polycarbonate-modified acrylic dispersion includes the following steps:

[0020] 1) Add polycarbonate diol with 1,4-butanediol and 1,6-hexanediol as raw materials and propylene glycol monomethyl ether acetate into a reaction kettle for heating reaction, and distill to obtain oligomers;

[0021] 2) After cooling, add butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol methyl ether and tert-butyl peroxybenzoate into the reaction kettle, and continue heating reaction;

[0022] 3) Add dimethylethanolamine to the mixed system in step 1) under stirring conditions, and then add the mixed system to deionized water in a stirring and shearing state to finally obtain a modified aqueous dispersion.

[0023] In some specific embodiments, in step S1, the aqueous polycarbonate-modified acrylic dispersion is first dispersed with an aqueous defoaming agent at 600 - 800 rpm for 8 - 12 min; then a leveling agent, a film-forming agent and water are added and stirred and mixed at 800 - 1000 rpm for 15 - 20 min, and after standing, it is mixed with a thickening agent and an amine neutralizing agent at 600 - 700 rpm for 10 - 15 min.

[0024] In some specific embodiments, a method for preparing an aqueous automotive transparent PC high-gloss clear coat as described above, the method includes the following steps:

[0025] (1) Preparation of Component A: By mass parts, under the condition of low-speed stirring, sequentially add aqueous polycarbonate-modified acrylic dispersion, aqueous defoamer, aqueous leveling agent, film-forming aid, and deionized water into the reactor, then stir for a period of time under the condition of high-speed stirring, and then add the thickener and amine neutralizer under the condition of medium-speed stirring and stir for a period of time to obtain Component A;

[0026] (2) Preparation of Component B: By mass parts, add the aqueous curing agent and solvent into the reactor under the condition of low-speed stirring, and then stir for a period of time under the condition of high-speed stirring to obtain Component B;

[0027] (3) Mix Component A and Component B in a mass ratio of 3:1, spray them on the surface of the plastic material and then heat to obtain a waterborne transparent PC high-gloss clear paint film.

[0028] Furthermore, in step (1), the stirring speed in the low-speed stirring state is 300 - 400 rpm; the stirring speed in the high-speed stirring is 800 - 1000 rpm, and the time is 15 - 20 min; the stirring speed in the medium-speed stirring is 600 - 700 rpm, and the time is 10 - 15 min.

[0029] Furthermore, in step (2), the stirring speed in the low-speed stirring state is 300 - 400 rpm; the stirring speed in the high-speed stirring is 800 - 1000 rpm, and the time is 10 - 15 min;

[0030] Furthermore, in step (3), the heating temperature is 75 - 85 °C, and the time is 4 h.

[0031] In some specific embodiments, in step S1, the mass ratio of the aqueous polycarbonate-modified acrylic dispersion to the aqueous defoamer, aqueous leveling agent, aqueous film-forming aid, thickener, amine neutralizer, and water is (75 - 85):(0.3 - 0.5):(0.5 - 1):(1 - 5):(0.5 - 1.5):(0.1 - 0.3):(10 - 15);

[0032] The mass ratio of the aqueous curing agent to the solvent is (73 - 77):(23 - 37).

[0033] In some specific embodiments, in step S1, the aqueous defoamer includes a modified silicone defoamer, preferably BYK-015 defoamer.

[0034] In some specific embodiments, the aqueous leveling agent includes a silicone leveling agent, preferably BYK-346 leveling agent.

[0035] In some specific embodiments, the aqueous film-forming aid is dipropylene glycol methyl ether, preferably DOWANOLD PM.

[0036] In some specific embodiments, the thickener includes a non-ionic polyurethane thickener, preferably the RHEOLATE FX 1010 type thickener.

[0037] In some specific embodiments, the amine neutralizer is the DeuAdd MA-95 type amine neutralizer.

[0038] In some specific embodiments, the aqueous curing agent is a hydrophilic aliphatic polyisocyanate based on hexamethylene diisocyanate (HDI), with an -NCO content of 20 - 25 wt%, a viscosity of 1500 - 3500 mPa·s, and preferably the BAYHYDUR 304 type curing agent is used.

[0039] In some specific embodiments, the solvent is propylene glycol methyl ether acetate.

[0040] In the aqueous automotive transparent PC high-gloss clearcoat of the present invention, various additives added, such as modified silicone leveling agents, modified silicone defoamers, non-ionic polyurethane thickeners, etc., have excellent compatibility and excellent surface effect on the dispersion section of component A. For example, defoaming ability, substrate wetting, and anti-settling stability are both stable and excellent. In the aqueous automotive transparent PC high-gloss clearcoat of the present invention, the selected solvent mainly consists of deionized water, and a proper amount of DPM is added to better improve the film-forming property of the paint and enhance the film appearance after the film dehydrates.

[0041] In some specific embodiments, in step S2, the mass ratio of component A to component B is (2 - 4):1.

[0042] In the aqueous automotive transparent PC high-gloss clearcoat of the present invention, a polycarbonate-modified acrylic dispersion is used, in combination with an aqueous curing agent. Preferably, they are mixed before use at a ratio of dispersion:curing agent of about 2:1 (solid content ratio), so that the coating film has high gloss, good adhesion on the PC substrate, and excellent hydrolysis resistance and aging resistance.

[0043] The second aspect of the present invention provides a method for preparing an aqueous automotive transparent PC high-gloss clearcoat coating, including: spraying the aqueous automotive transparent PC high-gloss clearcoat according to any one of claims 1 to 8 on a polycarbonate substrate, and heating and curing to obtain.

[0044] In some specific embodiments, before spraying, water is added for dilution to improve spraying fluidity.

[0045] In some specific embodiments, during the heating and curing, the curing temperature is 70 - 80 °C, and the time is preferably 2 - 4 h.

[0046] In the waterborne automotive transparent PC high-gloss clear coat of the present invention, a polyurethane film is obtained through the crosslinking and curing reaction of a polycarbonate-modified acrylic dispersion with excellent comprehensive properties and a waterborne curing agent. The polyurethane film has good film physical properties on the PC substrate, and is excellent in terms of adhesion to PC plastics and resistance to high-pressure water gun rinsing. In particular, the polycarbonate-modified acrylic dispersion used is the key to two-component curing and maintaining the adhesion performance of the film. While obtaining a high-performance film, the adhesion of the film can still be maintained. The key requirements for the film are the ability to produce in large quantities quickly and maintain excellent adhesion to the PC substrate on the workpiece. However, the polyurethane film obtained by reacting ordinary acrylic acid with a curing agent cannot meet the requirements for adhesion to the PC substrate of the film.

[0047] The adhesion data of the paint film to the PC substrate in multiple adhesion test items also supports this conclusion:

[0048] Table 1

[0049] Test Items Oil-based varnish Water-based varnish Water-based PC high-gloss varnish Initial adhesion 5B 5B 5B Water resistance at 40°C for 10 days 0B 2B 5B Water resistance at 100°C for 2 hours 0B 0B 5B Simulated high-pressure water gun car wash at 85°C Paint stripping over 3 mm Paint stripping over 2 mm Paint stripping less than 0.5 mm

[0050] The best crosshatch adhesion is 5B (100%), and the worst is 0B (0%).

[0051] Compared with the prior art, the present invention has the following characteristics:

[0052] 1) Good adhesion performance, which can protect the large PC substrates of automotive exterior trims, extend the product safety life, and enhance the appearance experience;

[0053] 2) It will not cause abnormal conditions such as paint peeling and aging during long-term use, and improves the positive evaluation of the product's tolerance performance;

[0054] 3) It meets the requirements of being able to produce in large quantities quickly and having high physical properties of the film on the workpiece;

[0055] 4) The preparation method of this waterborne automotive transparent PC high-gloss clear coat is environmentally friendly and easy to operate and mass-produce. Specific embodiments

[0056] The present invention will be described in detail below in conjunction with specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0057] In the following embodiments, unless otherwise specified for raw material reagents or treatment techniques, it means that they are all conventional commercially available products or conventional treatment techniques in the art.

[0058] Example 1:

[0059] A waterborne automotive transparent PC high-gloss clearcoat, and its preparation method comprises the following steps:

[0060] S1: Weighing of raw material components:

[0061] Table 2

[0062]

[0063] S2: Preparation of Component A:

[0064] S2-1: Add 16 parts of polycarbonate diol (WANTHANCOL WHP-CD, Wanhua Chemical Group Co., Ltd.) and 14 parts of propylene glycol monomethyl ether acetate into the kettle, raise the temperature to 136 °C, and continuously react for 11 h;

[0065] Cool down to 114 °C, and then slowly add a mixture containing 5 parts of n-butyl methacrylate, 4.8 parts of 2-hydroxyethyl acrylate, 4.4 parts of mercaptoethanol, 4 parts of cyclohexyl methacrylate, 5.8 parts of methoxypropyl propionate, and 3.3 parts of tert-butyl peroxybenzoate over 2 h. After the addition, continue to react at the same temperature for 6 h;

[0066] Then cool down to 87 °C, neutralize with 3 parts of dimethylethanolamine under sufficient stirring at 600 rpm, and vigorously stir and add 39.7 parts of deionized water under high shear at 1200 rpm to obtain a waterborne polycarbonate-modified acrylic dispersion;

[0067] S2-2: Add the waterborne polycarbonate-modified acrylic dispersion and defoamer into the container at a mixer speed of 400 rpm, and disperse at 800 rpm for 10 min; then sequentially add the leveling agent, film-forming agent, and deionized water into the container at 500 rpm. After that, stir at a speed of 1000 rpm for 18 min, let it stand for 2 h, then add the thickener and amine neutralizer to adjust the viscosity, and then stir at a speed of 700 rpm for 15 min to obtain Component A;

[0068] S3: Preparation of Component B

[0069] Sequentially add the waterborne curing agent and solvent into the container at a mixer speed of 400 rpm, and then stir at a speed of 800 rpm for 15 min to obtain Component B;

[0070] S4: Curing

[0071] Mix the prepared Component A and Component B according to the mass ratio A:B = 3:1, dilute with a small amount of deionized water to a spraying viscosity of 15 - 18 seconds (Ford cup 4), then evenly coat on the polycarbonate plastic material with a spray gun, let it stand for 15 min, and then bake in an 80 °C oven for 4 h to obtain a waterborne automotive transparent PC high-gloss clearcoat film.

[0072] The performance test results of this waterborne automotive transparent PC high-gloss clearcoat are shown in Table 3 below:

[0073] Table 3

[0074]

[0075]

[0076] The results of the cross-cut adhesion comparison test are shown in Table 4:

[0077] Table 4

[0078]

[0079] *The best cross-cut adhesion is 5B (100%), and the worst is 0B (0%).

[0080] Example 2:

[0081] A waterborne automotive transparent PC high-gloss clearcoat, its preparation method includes the following steps: S1: Weighing of raw material components:

[0082] Table 5

[0083]

[0084] S2: Preparation of Component A:

[0085] Add 15 parts of polycarbonate diol (WANTHANCOL WHP-CD, Wanhua Chemical Group Co., Ltd.) and 13 parts of propylene glycol monomethyl ether acetate into the kettle, raise the temperature to 135°C, and continuously react for 11 h;

[0086] Cool down to 115°C, and then slowly add a mixture containing 5.3 parts of n-butyl methacrylate, 4.9 parts of 2-hydroxyethyl acrylate, 4.6 parts of mercaptoethanol, 3.9 parts of cyclohexyl methacrylate, 5.5 parts of methyl propylene glycol monomethyl ether, and 3.4 parts of tert-butyl peroxybenzoate over 2 h. After the addition, continue to react at the same temperature for 6 h;

[0087] Then cool down to 88°C, neutralize with 2.8 parts of dimethylethanolamine under sufficient stirring at 600 rpm, and vigorously stir and add 41.6 parts of deionized water under high shear at 1200 rpm to obtain a waterborne polycarbonate-modified acrylic dispersion;

[0088] S2-2: Add the aqueous polycarbonate-modified acrylic dispersion and defoamer into a container at a blender speed of 400 rpm, disperse for 12 min at 800 rpm; then successively add the leveling agent, film-forming agent and deionized water into the container at 500 rpm, and then stir at a speed of 1000 rpm for 18 min. After standing for 2 h, add the thickener and amine neutralizer to adjust the viscosity, and then stir at a speed of 700 rpm for 15 min to obtain Component A;

[0089] S3: Preparation of Component B

[0090] Add the aqueous curing agent and solvent into a container successively at a blender speed of 400 rpm, and then stir at a speed of 1000 rpm for 12 min to obtain Component B;

[0091] S4: Curing

[0092] Mix the prepared Component A and Component B according to the mass ratio A:B = 3:1, dilute with a small amount of deionized water to the spraying viscosity of 15 - 18 seconds (Ford Cup 4), and then evenly coat on the polycarbonate plastic material with a spray gun. After standing for 15 min, place it in an 80°C oven and bake for 4 h to obtain a waterborne automotive transparent PC high-gloss clear coat film.

[0093] The performance test results of the waterborne automotive transparent PC high-gloss clear coat are shown in Table 6 below:

[0094] Table 6

[0095]

[0096]

[0097] The results of the cross-cut adhesion comparison test are shown in Table 7:

[0098] Table 7

[0099]

[0100] The cross-cut adhesion of 5B (100%) is the best, and 0B (0%) is the worst.

[0101] In addition to high lightness, hardness, aging resistance and other physical properties, the present invention also has the excellent property of PC adhesion that ordinary PU clear coats do not have. Moreover, the preparation process is simple, the production cost is low, the environmental pollution is small. When mass-producing, the aqueous polycarbonate-modified acrylic dispersion of Component A can be made into an intermediate to simplify the production process.

[0102] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and practice the invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention as disclosed should fall within the protection scope of the present invention.

Claims

1. A method for preparing a water-based automobile transparent PC high-gloss varnish, characterized in that: The method comprises the following steps: S1: heating polycarbonate diol and propylene glycol monomethyl ether acetate for a first reaction; then heating with n-butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol methyl ether, and tert-butyl perbenzoate for a second reaction; after neutralization with alkali, mixing with water to prepare a water-based polycarbonate modified acrylic dispersion; then mixing with a water-based defoamer, a water-based leveling agent, a water-based film-forming aid, a thickener, and an amine neutralizer to obtain component A; Mixing the water-based curing agent with the solvent to obtain component B; S2: Component A is mixed with component B to obtain a water-based automotive transparent PC high-gloss varnish.

2. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S1, in the primary heating reaction, the mass ratio of polycarbonate diol to propylene glycol monomethyl ether acetate is (14-18):(12-16); and the reaction temperature is 130-140°C.

3. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S1, in the secondary heating reaction, the mass ratio of n-butyl methacrylate, 2-hydroxyethyl acrylate, mercaptoethanol, cyclohexyl methacrylate, methyl propylene glycol methyl ether, tert-butyl perbenzoate and polycarbonate diol is (5-7):(4-6):(3-5):(3.9-5):(5-6):(3-4):(14-18); the reaction temperature is 110-120°C.

4. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S1, in the alkali neutralization, the alkali added is dimethylethanolamine, and the mass ratio of dimethylethanolamine, water and polycarbonate diol is (2-4):(35-50):(14-18).

5. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S1, the waterborne polycarbonate modified acrylic dispersion is first dispersed with a waterborne defoamer at 600-800 rpm for 8-12 min; then a leveling agent, a film-forming agent and water are added and stirred and mixed at 800-1000 rpm for 15-20 min, and then the mixture is allowed to stand and then mixed with a thickener and an amine neutralizer at 600-700 rpm for 10-15 min.

6. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 5, characterized in that: In step S1, the mass ratio of the water-based polycarbonate modified acrylic dispersion to the water-based defoamer, water-based leveling agent, water-based film-forming aid, thickener, amine neutralizer, and water is (75-85):(0.3-0.5):(0.5-1):(1-5):(0.5-1.5):(0.1-0.3):(10-15); The mass ratio of the water-based curing agent to the solvent is (73-77):(23-37).

7. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S1, the aqueous defoamer is BYK-015 defoamer; the aqueous leveling agent is BYK-346 leveling agent; the aqueous film-forming aid is dipropylene glycol methyl ether; the thickener is RHEOLATE FX 1010 thickener; the amine neutralizer is DeuAdd MA-95 amine neutralizer; the aqueous curing agent is BAYHYDUR 304 curing agent; and the solvent is propylene glycol methyl ether acetate.

8. The method for preparing the water-based automobile transparent PC high-gloss varnish according to claim 1, characterized in that: In step S2, the mass ratio of component A to component B is (2-4):

1.

9. A method for preparing a water-based automobile transparent PC high-gloss varnish coating, characterized in that: The method comprises: spraying the water-based automobile transparent PC high-gloss varnish as claimed in any one of claims 1 to 8 on a polycarbonate substrate, heating and curing to obtain.

10. The method for preparing a water-based automobile transparent PC high-gloss varnish coating according to claim 9, characterized in that: In the heating curing, the curing temperature is 70-80°C.

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