High-gloss water-based two-component finish paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to a high-gloss water-based two-component finish paint. The high-gloss water-based two-component finish paint comprises a component A and a component B, wherein the component A is prepared from the following raw materials in parts by weight: 70-90 parts of a polyurethane modified water-based acrylate dispersion, 5-10 parts of a water-based high-hydroxyl acrylic acid dispersion, 0.1-1 part of a flatting agent, 0.1-1 part of a wetting agent, 0.1-1 part of a defoaming agent, 1-10 parts of water-based color paste and 5-15 parts of water; and the component B is 5-15 parts by weight of a water-based isocyanate curing agent. The water-based two-component finishing paint provided by the invention can be used for thick coating, miliaria and dark bubbles are not easy to occur, a paint film is good in leveling property, good in fullness and high in glossiness, and the water-based two-component finishing paint is particularly suitable for coating of a metal substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of paint technology, in particular to a high-gloss water-based two-component finish and a preparation method thereof. BACKGROUND

[0002] The finish is not only the outermost protective clothing of the substrate, but also the most direct embodiment of the coating effect of the substrate, and it requires the finish to have the characteristics of high gloss, good fullness, strong adhesion and good mechanical properties. The water-based two-component finish is an environmentally friendly high-performance coating, which uses water as a diluent, has low VOC content and little harm to human health and the environment. The common water-based two-component finish includes a water-based hydroxyl acrylate resin and a water-based isocyanate curing agent. When used, the water-based isocyanate curing agent is generally diluted or directly added to the water-based hydroxyl acrylate resin dispersion or emulsion. However, bubbles, sudden viscosity rise or poor dispersion of the curing agent, and even demulsification may occur, and the activation period is relatively short, generally 1-2 hours. In addition, the water-based two-component finish has a slow drying speed and poor fullness. Thick wet film thickness exceeding 45 μm is prone to sagging, and if the drying speed is increased, blisters or dark bubbles are prone to occur during baking. Therefore, it is extremely urgent to modify the water-based acrylate resin, improve the compatibility of the water-based isocyanate curing agent, and prepare a water-based two-component finish that can be thickly coated without blisters and dark bubbles, has good leveling of the paint film, good fullness, and high gloss. SUMMARY

[0003] The present application aims at the deficiencies of the prior art, and provides a high-gloss water-based two-component finish, which has the advantages of being thickly coated without blisters and dark bubbles, having good leveling of the paint film, good fullness, and high gloss.

[0004] The application objectives of the present application are achieved by the following technical solutions:

[0005] A high-gloss water-based two-component finish, comprising two components A and B.

[0006] The component A is composed of the following components in parts by weight:

[0007] Polyurethane-modified water-based acrylate dispersion 70-90 parts

[0008] Water-based high-hydroxyl acrylate dispersion 5-10 parts

[0009] Leveling agent 0.1-1 part

[0010] Wetting agent 0.1-1 part

[0011] Defoaming agent 0.1-1 part

[0012] Water-based color paste 1-10 parts

[0013] 5-15 parts water

[0014] Component B is an aqueous isocyanate curing agent, with a weight of 5-15 parts;

[0015] The polyurethane-modified aqueous acrylate dispersion has the following composition, by weight parts:

[0016] 40-60 parts of hydrophobic hydroxyl polyurethane (OH-PU), 15-30 parts of hard acrylic monomer, 15-25 parts of soft acrylic monomer, 5-10 parts of cyclic acrylic monomer, 10-20 parts of hydroxyl acrylic monomer, 4-8 parts of hydrophilic acrylic monomer, 30-50 parts of cosolvent, 1-2 parts of initiator, 5-15 parts of solvent, 5-10 parts of neutralizer, and 100-150 parts of water.

[0017] Preferably, the aqueous high-hydroxy acrylic acid dispersion has a hydroxyl content of 3.5%-4.0% (based on 100% solids) and a solid content of 45%-55%. More preferably, the aqueous high-hydroxy acrylic acid dispersion is specifically DB3638, a novel double-bond material. DB3638 has a solid content of 48±2% and a hydroxyl content of 3.8% (based on 100% solids), and features high gloss, high fullness, high toughness, and a thick, bubble-free film.

[0018] Preferably, the hydroxyl value of the polyurethane-modified waterborne acrylate dispersion is 50-100 mg KOH / g.

[0019] Preferably, the hard acrylic monomer is one or two of methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate; the soft acrylic monomer is one or two of butyl acrylate and isooctyl acrylate; the cyclic acrylic monomer is one or two of isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, or cyclohexyl methacrylate; the hydroxy acrylic monomer is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, or hydroxybutyl acrylate; and the hydrophilic acrylic monomer is one or two of acrylic acid or methacrylic acid.

[0020] Preferably, the hydrophobic hydroxyl polyurethane (OH-PU) is composed of the following components by weight: 60-70 parts polyester diol, 40-60 parts polyester resin, 20-30 parts large side-chain modified diol, 5-10 parts small molecule diol, 30-50 parts diisocyanate, 15-25 parts HDI trimer, 3-6 parts hydroxyl acrylic monomer, and 2-5 parts solvent.

[0021] Preferably, the molar ratio of hydroxyl groups to isocyanate groups in each component of the hydrophobic hydroxyl polyurethane (OH-PU) is 1.3-1.5.

[0022] Preferably, the small molecule diol is one of ethylene glycol, 2-methyl-1,3-propanediol, or 1,4-butanediol; the diisocyanate is one of toluene diisocyanate or isophorone diisocyanate; and the solvent is one of acetone, N-methylpyrrolidone, or N-ethylpyrrolidone.

[0023] More specifically, the polyester diol is a polyester diol with a molecular weight of 1000; for example, L3025 from Shanghai Shuyu Chemical Co., Ltd.; the polyester resin is specifically TPR-7812N or TPR-7817H from Guangdong Jiayuan New Materials Co., Ltd.; the large side-chain modified diol is specifically XC-488 from Beijing Baiyuan Chemical Co., Ltd.; the small molecule diol is one of ethylene glycol, 2-methyl-1,3-propanediol, and 1,4-butanediol; the diisocyanate is one of toluene diisocyanate or isophorone diisocyanate; the HDI trimer is specifically Covestro Desmodur N3300; the solvent is one of acetone, N-methylpyrrolidone, and N-ethylpyrrolidone, preferably N-ethylpyrrolidone; the hydroxyacrylate monomer is one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxybutyl acrylate.

[0024] This invention also provides a method for preparing a high-gloss water-based two-component topcoat, comprising the following steps:

[0025] (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU)

[0026] S1. Add HDI trimer, catalyst, and polymerization inhibitor to a reactor. Under conditions of 30-50℃ and N2 purging, slowly add hydroxyacrylic acid monomer and solvent dropwise to the reactor, wherein the molar ratio of NCO to OH is 3:1. Then raise the temperature to 65-70℃ and continue the reaction at this temperature. During the reaction, measure the NCO content. When the NCO content reaches the predetermined value, stop the reaction to obtain prepolymer X with a solid content of 85%-90%.

[0027] S2. Polyester diol, polyester resin, large side-chain modified diol, small molecule diol, catalyst, and polymerization inhibitor are added to a reaction vessel and stirred evenly. The temperature is raised to 50°C. Under the condition of passing N2, diisocyanate and prepolymer X are slowly added dropwise to the reaction vessel. Solvent is added while stirring, and the temperature is raised to 90°C. The reaction continues until the NCO content is 0, and a hydrophobic hydroxyl polyurethane OH-PU with a solid content of about 75% to 85% is obtained.

[0028] (2) Preparation of polyurethane-modified waterborne acrylate dispersion

[0029] Add a co-solvent to a reactor containing hydrophobic hydroxyl polyurethane (OH-PU), stir until homogeneous, heat to 80-90°C, slowly add a mixture of other acrylate monomers and initiators dropwise over 2-3 hours, continue heating for 30 minutes, add the remaining mixture of initiator and co-solvent, continue heating for 1-2 hours, cool to 70°C, add a mixture of neutralizer and solvent for neutralization and viscosity adjustment, and finally hydrate to obtain a polyurethane-modified waterborne acrylate dispersion.

[0030] In this invention, the polyester diol exhibits high flexibility, low viscosity, and good compatibility; the large side-chain modified diol reduces the viscosity of the reaction system and provides strong adhesion to various substrates; the polyester resin enhances the adhesion of hydrophobic hydroxyl-type polyurethane (OH-PU); the unsaturated double bonds in prepolymer X can react with acrylate monomers, improving the compatibility between hydrophobic hydroxyl-type polyurethane (OH-PU) and acrylate resin; the presence of HDI trimer structural units and urethane bonds makes the dispersion of the waterborne isocyanate curing agent more convenient and efficient. Due to the excellent compatibility between the aqueous dispersion and the waterborne curing agent, defoaming of the paint film is easier, and the paint film surface is smoother, more even, and exhibits excellent gloss and fullness.

[0031] In addition, hydroxyl-type polyurethane (OH-PU) is hydrophobic, and the acrylate polymer molecular chains of the grafted reaction have a high acid value. After neutralization and hydration, a core-shell structure is formed with polyurethane (OH-PU) as the core and acrylate polymer as the shell. The dispersion viscosity is low, the waterborne isocyanate curing agent is easy to disperse, and the activation period is also long, exceeding 2 hours.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention is based on the compounding of polyurethane modified waterborne acrylate dispersion and waterborne high hydroxyl acrylic dispersion, which can enhance the fullness and gloss of the coating and make it less prone to prickly heat and dark bubbles. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. However, the embodiments do not limit the present invention in any way. Any technical solution obtained by equivalent substitution or equivalent transformation should be included within the protection scope of the claims of the present invention. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are commercially available raw materials and reagents.

[0035] Example 1

[0036] (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU)

[0037] Add 60g Desmodur N3300, 0.09g p-hydroxyanisole, and 0.06g dibutyltin dilaurate to a reaction vessel. Under N2 conditions at 30-50℃, slowly add a mixture of 13.5g hydroxyethyl methacrylate and 8g N-ethylpyrrolidone dropwise to the reaction vessel over approximately 30 minutes. Then gradually raise the temperature to 60-70℃ and continue the reaction for 3-4 hours, monitoring the NCO content during this period. Stop the reaction when the NCO content reaches the theoretical value to obtain prepolymer X.

[0038] 60g of polyester diol 3025, 50g of polyester resin TPR-7817H, 30g of large side-chain modified diol XC-488, 10g of 2-methyl-1,3-propanediol, 0.08g of dibutyltin dilaurate, and 0.04g of p-hydroxyanisole were added to a reaction vessel and stirred until homogeneous. The mixture was heated to 50°C, and under N2 purging, 40g of isophorone diisocyanate and 22g of prepolymer X were slowly added dropwise to the reaction vessel. After stirring for 30 minutes, 38g of N-ethylpyrrolidone was added dropwise, and the temperature was raised to 90°C. The reaction was continued until the NCO content was 0, yielding hydrophobic hydroxyl polyurethane OH-PU with a solid content of approximately 80%.

[0039] (2) Preparation of polyurethane-modified waterborne acrylate dispersion

[0040] Add 20g of propylene glycol methyl ether and 10g of isopropanol to a reactor containing 50g of hydrophobic hydroxyl-type polyurethane (OH-PU). After stirring evenly, heat to 85±2℃ and slowly add a mixture of 17.5g of methyl methacrylate, 18g of butyl acrylate, 7g of isoborneol methacrylate, 13g of hydroxyethyl methacrylate, 4.5g of acrylic acid, and 1g of benzoyl peroxide. The addition is completed over 2-3 hours. Continue heating for 30 minutes, then add a mixture of 0.5g of benzoyl peroxide and 10g of propylene glycol methyl ether. Continue heating for 1-2 hours, then cool to 70℃. Add a mixture of 6.5g of triethylamine and 10g of N-ethylpyrrolidone for neutralization and viscosity adjustment. Finally, add 150g of deionized water to obtain a slightly transparent, bluish polyurethane-modified waterborne acrylate dispersion with a solid content of approximately 31.5% and a hydroxyl value of approximately 70mg KOH / g.

[0041] The formulation of the high-gloss two-component topcoat is shown in Table 1. The preparation method of the high-gloss two-component topcoat is as follows:

[0042] S1. Add 83g of polyurethane-modified waterborne acrylate dispersion, 5g of waterborne high-hydroxy acrylic dispersion, 0.3g of leveling agent, 0.3g of wetting agent, 0.2g of defoamer, and 6.2g of deionized water to the reactor, stir and disperse evenly, add 5g of waterborne color paste, and filter to obtain component A;

[0043] S2. Add 8.3g of water-based isocyanate curing agent (component B) according to the ratio, disperse evenly at a speed of 300-400r / min, filter, defoam, and obtain a high-gloss two-component topcoat.

[0044] Example 2

[0045] (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU)

[0046] The preparation of hydrophobic hydroxyl polyurethane (OH-PU) is the same as in Example 1.

[0047] (2) Preparation of polyurethane-modified waterborne acrylate dispersion

[0048] Add 16g of propylene glycol methyl ether and 15g of isopropanol to a reactor containing 45g of hydrophobic hydroxyl-type polyurethane (OH-PU). After stirring evenly, heat to 85±2℃ and slowly add a mixture of 26g methyl methacrylate, 10g butyl acrylate, 5g isooctyl acrylate, 8g isobornyl methacrylate, 10g hydroxyethyl methacrylate, 5g acrylic acid, and 0.8g benzoyl peroxide. The addition is completed over 2-3 hours. Continue heating for 30 minutes, then add a mixture of 0.3g benzoyl peroxide and 10g propylene glycol methyl ether. Continue heating for 1-2 hours, then cool to 70℃. Add a mixture of 7g triethylamine and 12g N-ethylpyrrolidone for neutralization and viscosity adjustment. Finally, add 140g deionized water to obtain a slightly transparent, bluish polyurethane-modified waterborne acrylate dispersion with a solid content of approximately 32% and a hydroxyl value of approximately 57mg KOH / g.

[0049] The formulation of the high-gloss two-component topcoat is shown in Table 1, and the preparation method of the high-gloss water-based two-component topcoat is as described in Example 1.

[0050] Example 3

[0051] (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU)

[0052] Add 60g Desmodur N3300, 0.1g p-hydroxyanisole, and 0.06g dibutyltin dilaurate to a reaction vessel. Under N2 conditions at 30-50℃, slowly add a mixture of 15g hydroxybutyl acrylate and 8g N-ethylpyrrolidone dropwise to the reaction vessel over approximately 30 minutes. Then gradually raise the temperature to 60-70℃ and continue the reaction for 3-4 hours, monitoring the NCO content during this period. Stop the reaction when the NCO content reaches the theoretical value to obtain prepolymer X.

[0053] 70g of polyester diol 3025, 50g of polyester resin TPR-7812N, 25g of large side-chain modified diol XC-488, 8g of 2-methyl-1,3-propanediol, 0.1g of dibutyltin dilaurate, and 0.05g of p-hydroxyanisole were added to a reaction vessel and stirred until homogeneous. The mixture was heated to 50°C, and under N2 purging, 32g of isophorone diisocyanate and 22g of prepolymer X were slowly added dropwise to the reaction vessel. After stirring for 30 minutes, 30.5g of N-ethylpyrrolidone was added dropwise, and the temperature was raised to 90°C. The reaction was continued until the NCO content was 0, yielding hydrophobic hydroxyl polyurethane OH-PU with a solid content of approximately 80%.

[0054] (2) Preparation of polyurethane-modified waterborne acrylate dispersion

[0055] Add 20g of propylene glycol methyl ether and 10g of isopropanol to a reactor containing 47.5g of hydrophobic hydroxyl-type polyurethane (OH-PU). After stirring evenly, heat to 85±2℃ and slowly add a mixture of 21.5g of methyl methacrylate, 15g of butyl acrylate, 7g of isoborneol methacrylate, 14g of hydroxybutyl acrylate, 4.5g of acrylic acid, and 0.8g of benzoyl peroxide. The addition is completed over 2-3 hours. Continue heating for 30 minutes, then add a mixture of 0.4g of benzoyl peroxide and 10g of propylene glycol methyl ether. Continue heating for 1-2 hours, then cool to 70℃. Add a mixture of 6.5g of triethylamine and 9.5g of N-ethylpyrrolidone for neutralization and viscosity adjustment. Finally, add 140g of deionized water to obtain a slightly transparent, bluish polyurethane-modified waterborne acrylate dispersion with a solid content of approximately 32.5% and a hydroxyl value of approximately 68mg KOH / g.

[0056] The formulation of the high-gloss two-component topcoat is shown in Table 1, and the preparation method of the high-gloss water-based two-component topcoat is as described in Example 1.

[0057] Example 4

[0058] (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU)

[0059] The preparation of hydrophobic hydroxyl polyurethane (OH-PU) is the same as in Example 3.

[0060] (2) Preparation of polyurethane-modified waterborne acrylate dispersion

[0061] Add 20g of propylene glycol methyl ether and 12g of isopropanol to a reactor containing 40g of hydrophobic hydroxyl-type polyurethane (OH-PU). After stirring evenly, heat to 85±2℃ and slowly add a mixture of 22.5g of methyl methacrylate, 16g of isooctyl acrylate, 9g of isoborneol methacrylate, 16g of hydroxybutyl acrylate, 4.5g of acrylic acid, and 1g of benzoyl peroxide. The addition is completed over 2-3 hours. Continue heating for 30 minutes, then add a mixture of 0.4g of benzoyl peroxide and 10g of propylene glycol methyl ether. Continue heating for 1-2 hours, then cool to 70℃. Add a mixture of 6.5g of triethylamine and 8.5g of N-ethylpyrrolidone for neutralization and viscosity adjustment. Finally, add 135g of deionized water to obtain a slightly transparent, bluish polyurethane-modified waterborne acrylate dispersion with a solid content of approximately 33% and a hydroxyl value of approximately 74mg KOH / g.

[0062] The formulation of the high-gloss two-component topcoat is shown in Table 1, and the preparation method of the high-gloss water-based two-component topcoat is as described in Example 1.

[0063] Comparative Example 1

[0064] Comparative Example 1 is similar to Example 1, except that a general aqueous hydroxy acrylic dispersion is used instead of a polyurethane-modified aqueous acrylic dispersion.

[0065] Preparation of the above-mentioned aqueous hydroxyacrylic acid dispersion

[0066] Add 25g of propylene glycol methyl ether and 15g of isopropanol to the reactor, stir and heat to 85±2℃, then slowly add a mixture of 32.5g of methyl methacrylate, 38g of butyl acrylate, 7g of isoborneol methacrylate, 16g of hydroxyethyl methacrylate, 6.5g of acrylic acid, and 0.8g of benzoyl peroxide. The addition should be completed over 2-3 hours, and the mixture should be kept at this temperature for another 30 minutes. Then, add a mixture of 0.3g of benzoyl peroxide and 10g of propylene glycol methyl ether, and continue to keep the mixture at this temperature for 1-2 hours. Cool to 70℃, then add a mixture of 9g of triethylamine and 6.5g of N-ethylpyrrolidone for neutralization and viscosity adjustment. Finally, add 150g of deionized water to obtain a slightly transparent, bluish-tinged aqueous hydroxyl acrylic dispersion with a solid content of approximately 31.5% and a hydroxyl value of approximately 69mg KOH / g.

[0067] The formulations of the two-component topcoat are shown in Table 1, and the preparation method of the water-based two-component topcoat is as described in Example 1.

[0068] Comparative Example 2

[0069] The difference between Comparative Example 2 and Example 1 is that no aqueous high-hydroxyacrylic acid dispersion was added; the rest of the preparation process was the same as in Example 1.

[0070] The formulations of the two-component topcoat are shown in Table 1. The preparation method of the water-based two-component topcoat is as described in Example 1.

[0071] Table 1. Formulation of high-gloss water-based two-component topcoat

[0072] Note: The experimental substrate was tinplate, and the baking temperature was 70℃ for 30 minutes; *In Comparative Example 1, the prepared waterborne hydroxyl acrylic dispersion was used instead of the polyurethane-modified waterborne acrylic dispersion.

[0073] Performance testing:

[0074] The performance test results of the high-gloss water-based two-component topcoat are shown in Table 2.

[0075] Table 2 Performance Tests

[0076] As shown in Table 2, the high-gloss water-based two-component topcoat of the present invention has good compatibility between component A and component B, and can be directly added to the water-based isocyanate curing agent. It is convenient and efficient to disperse, and the defoaming of the paint film is also easier. Therefore, the paint film has a smooth and flat appearance, and has the characteristics of being able to be thickly coated without easily developing prickly heat or dark bubbles, having good leveling properties, and high gloss.

[0077] Comparative Example 1 uses a conventional water-based acrylate dispersion, which has general compatibility with water-based isocyanate curing agents. When water-based isocyanate curing agents are added directly, the viscosity of the paint increases, the number of bubbles increases, defoaming is relatively difficult, and puffiness and dark bubbles are easy to appear after drying, resulting in poor gloss. Comparative Example 2 does not add DB3638 as a modified dispersion, and its gloss and hardness are not as good as those of the examples.

[0078] The above embodiments of the present invention are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A high-gloss water-based two-component topcoat, characterized in that, It includes two components, A and B; The composition of component A, by weight, is as follows: 70-90 parts of polyurethane-modified waterborne acrylate dispersion 5-10 parts of water-based high-hydroxyacrylic acid dispersion Leveling agent 0.1-1 part Wetting agent 0.1-1 part Defoamer 0.1-1 part 1-10 parts of water-based pigment 5-15 parts water Component B is an aqueous isocyanate curing agent, with a weight of 5-15 parts; The polyurethane-modified aqueous acrylate dispersion has the following composition, by weight parts: 40-60 parts of hydrophobic hydroxyl polyurethane (OH-PU), 15-30 parts of hard acrylic monomer, 15-25 parts of soft acrylic monomer, 5-10 parts of cyclic acrylic monomer, 10-20 parts of hydroxyl acrylic monomer, 4-8 parts of hydrophilic acrylic monomer, 30-50 parts of cosolvent, 1-2 parts of initiator, 5-15 parts of solvent, 5-10 parts of neutralizer, and 100-150 parts of water; The aqueous high-hydroxy acrylic acid dispersion has a hydroxyl content of 3.5%-4.0% and a solid content of 45%-55%.

2. The high-gloss water-based two-component topcoat according to claim 1, characterized in that, The hydroxyl value of the polyurethane-modified waterborne acrylate dispersion is 50-100 mg KOH / g.

3. The high-gloss water-based two-component topcoat according to claim 1, characterized in that, The aqueous high-hydroxy acrylic acid dispersion is DB3638, a novel double-bond material.

4. The high-gloss water-based two-component topcoat according to claim 1, characterized in that, The hard acrylic monomer is one or two of methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate; the soft acrylic monomer is one or two of butyl acrylate and isooctyl acrylate; the cyclic acrylic monomer is one or two of isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, or cyclohexyl methacrylate; the hydroxy acrylic monomer is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, or hydroxybutyl acrylate; and the hydrophilic acrylic monomer is one or two of acrylic acid or methacrylic acid.

5. A high-gloss water-based two-component topcoat according to claim 1, characterized in that, The hydrophobic hydroxyl polyurethane (OH-PU) is composed of the following components by weight: 60-70 parts polyester diol, 40-60 parts polyester resin, 20-30 parts large side-chain modified diol, 5-10 parts small molecule diol, 30-50 parts diisocyanate, 15-25 parts HDI trimer, 3-6 parts hydroxyl acrylic monomer, and 2-5 parts solvent.

6. The high-gloss water-based two-component topcoat according to claim 5, characterized in that, The molar ratio of hydroxyl groups to isocyanate groups in each component of the hydrophobic hydroxyl polyurethane (OH-PU) is 1.3-1.

5.

7. A high-gloss water-based two-component topcoat according to claim 5, characterized in that, The small molecule diol is one of ethylene glycol, 2-methyl-1,3-propanediol, or 1,4-butanediol; the diisocyanate is one of toluene diisocyanate or isophorone diisocyanate; and the solvent is one of acetone, N-methylpyrrolidone, or N-ethylpyrrolidone.

8. A method for preparing a high-gloss water-based two-component topcoat according to claim 5, characterized in that, Includes the following steps: (1) Preparation of hydrophobic hydroxyl-type polyurethane (OH-PU) S1. Add HDI trimer, catalyst, and polymerization inhibitor to a reactor. Under conditions of 30-50℃ and N2 purging, slowly add hydroxyacrylic acid monomer and solvent dropwise to the reactor, wherein the molar ratio of NCO to OH is 3:

1. Then raise the temperature to 65-70℃ and continue the reaction at this temperature. During the reaction, measure the NCO content. When the NCO content reaches the predetermined value, stop the reaction to obtain prepolymer X with a solid content of 85%-90%. S2. Polyester diol, polyester resin, large side-chain modified diol, small molecule diol, catalyst, and polymerization inhibitor are added to a reaction vessel and stirred evenly. The temperature is raised to 50°C. Under the condition of passing N2, diisocyanate and prepolymer X are slowly added dropwise to the reaction vessel. Solvent is added while stirring, and the temperature is raised to 90°C. The reaction continues until the NCO content is 0, and a hydrophobic hydroxyl polyurethane OH-PU with a solid content of about 75%~85% is obtained. (2) Preparation of polyurethane-modified waterborne acrylate dispersion Add a co-solvent to a reactor containing hydrophobic hydroxyl polyurethane (OH-PU), stir until homogeneous, heat to 80-90°C, slowly add a mixture of other acrylate monomers and initiators dropwise over 2-3 hours, continue heating for 30 minutes, add the remaining mixture of initiator and co-solvent, continue heating for 1-2 hours, cool to 70°C, add a mixture of neutralizer and solvent for neutralization and viscosity adjustment, and finally hydrate to obtain a polyurethane-modified waterborne acrylate dispersion.

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