Water-dispersible polyaspartic acid ester resin and water-based automobile finishing varnish and preparation method and application thereof

Abstract

The present invention relates to a water-dispersible polyaspartic acid ester resin and a water-based automobile topcoat varnish and a preparation method and application thereof; the present invention also relates to a two-component water-based polyurea automobile topcoat varnish, characterized in that its resin component (component A) is composed of at least one new water-dispersible polyaspartic acid ester resin aqueous dispersion; the present invention further relates to a preparation method of a two-component water-based polyurea automobile topcoat varnish, characterized in that its resin component (component A) is composed of at least one new water-dispersible polyaspartic acid ester resin aqueous dispersion; the present invention further relates to an application of a two-component water-based polyurea automobile topcoat varnish in automobile painting, which includes painting in automobile original equipment manufacturers (OEMs) and also includes application in automobile sheet metal repair.

Description

Technical Field

[0001] The invention relates to automobile finishing varnish, and specifically to water-dispersible polyaspartic acid ester resin and water-based automobile finishing varnish, and preparation method and application thereof. Background Art

[0002] Currently, in the global automotive coating structure system, except for the topcoat varnish which still uses solvent-based paint, all other coatings have been water-based, that is, water-based paint. Water-based automotive varnish is still a global problem. For decades, major international automotive coatings brands have been working hard to solve the problem, but there has been no breakthrough.

[0003] Compared with solvent-based coatings, water-based coatings have two inherent deficiencies: one is the discontinuous phase film-forming mechanism, and the other is that the molecular chain contains hydrophilic groups. These two deficiencies result in serious defects in the physical and chemical properties and optical properties of water-based coatings.

[0004] Unlike water-based varnishes used in other fields, water-based clearcoat for automobiles must meet the following two requirements: excellent anti-corrosion performance and bright and transparent appearance. Currently, the technical routes of water-based varnishes at home and abroad are almost all based on the water-based transformation of traditional coating resins. The water-based varnishes obtained may be able to meet the application of general industrial fields, but they can never meet the requirements of automobile clearcoat.

[0005] CN110564242 reports a method for preparing a high-performance water-based automotive varnish. The method uses ordinary water-based acrylic resin as a resin component and a blocked water-based isocyanate as a curing agent. However, the patent only reports that the salt spray resistance of the varnish is between 195 and 330 hours, and does not provide data on aging resistance or glossiness. Therefore, it cannot meet the actual requirements of automotive coatings.

[0006] CN109535898 reports a method for preparing a water-based automobile varnish using acrylic emulsion and acrylic resin. However, the patent only lists some indicators related to appearance and touch performance such as glossiness and impact resistance, while the aging resistance, corrosion resistance and water resistance, which are very important for automobile topcoat varnish, are not mentioned.

[0007] CN111320926 reports an environmentally friendly two-component water-based clear varnish for automobiles. The patent also uses a hydroxyl-containing acrylic resin aqueous dispersion, but the patent does not provide information on the performance of the paint film, such as aging resistance, salt spray resistance and water resistance, except that it claims that the glossiness of the paint film is greater than 90%.

[0008] The inventor announced a water-dispersible polyaspartic acid resin and a method for preparing a water-based polyurea coating in CN109761834. The patent first introduces (meth) acrylic acid monomers into the polyaspartic acid structure, and then neutralizes with alkali to obtain a water dispersion of polyaspartic acid. The two-component water-based polyurea coating prepared using this water dispersion maintains the main characteristics of solvent-based polyurea coatings, including rapid curing at room temperature, high gloss, high transparency, and excellent water resistance, corrosion resistance, and aging resistance. Although the comprehensive performance of this water-based polyurea coating is better than that of traditional resin water-based coatings, since its hydrophilicity mainly comes from carboxylic anions, the water resistance and other tolerance properties of this water-based polyurea coating under low-temperature baking conditions are poor, and it cannot meet the low-temperature baking coating requirements including automotive OEM and automotive repair. Summary of the invention

[0009] Purpose of the Invention

[0010] The present invention is an improvement and enhancement of CN109761834, aiming to further improve the optical properties and resistance performance of waterborne polyurea coatings and reduce the coating baking temperature, that is, to provide a new type of water-dispersible polyaspartic acid ester resin, and use it in the preparation of waterborne polyurea automotive topcoat varnish, so that it can meet the requirements of automotive varnish for optical properties, water resistance and other resistance performance even under low-temperature baking conditions.

[0011] Technical Solution

[0012] The present invention relates to a water-dispersible polyaspartic acid ester resin, which is characterized in that the novel water-dispersible polyaspartic acid ester resin has the following structure (Formula 1):

[0013]

[0014] Wherein R1 and R2 can be alkyl groups with the same or different carbon atoms (such as C1-C4 alkyl groups); Y can be an alkylene group (such as: Where n = 0, 1, 2, ...), cycloalkylene (such as: ) or substituent cycloalkyl (such as ); n is a natural number between 5 and 20.

[0015] More specifically:

[0016] The water-dispersible polyaspartic acid ester resin is any one of the following structural formulas:

[0017]

[0018] Where n is a natural number between 5 and 20.

[0019] More specifically:

[0020] The present invention relates to a novel method for preparing a water-dispersible polyaspartic acid ester resin, which is obtained by Michael addition reaction of unsaturated dicarboxylic acid ester, methoxy polyethylene glycol acrylamide (MPEG-ACA) and primary amino compound. The reaction method can be expressed as follows (Formula 2):

[0021]

[0022] Wherein R1 and R2 can be alkyl groups with the same or different carbon atoms (such as C1-C4 alkyl groups); Y can be an alkylene group (such as: Where n = 0, 1, 2, ...), cycloalkylene (such as: ) or substituent cycloalkyl (such as ); n is a natural number between 5 and 20.

[0023] The unsaturated dibasic acid carboxylic acid ester can be a dialkyl maleate including but not limited to diethyl maleate, dipropyl maleate, dibutyl maleate and methylpropyl maleate and mixtures thereof;

[0024] The unsaturated dicarboxylic acid ester may also be a dialkyl fumarate, including but not limited to diethyl fumarate, dipropyl fumarate, dibutyl fumarate and methylpropyl fumarate, and mixtures thereof.

[0025] The methoxy polyethylene glycol acrylamide (MPEG-ACA) includes but is not limited to methoxy polyethylene glycol acrylamide with a degree of polymerization n of polyethylene glycol of 5-20, and the corresponding molecular weight includes but is not limited to 350, 500, 550, 750 and 1000.

[0026] The primary amino compound includes but is not limited to ethylenediamine, 1,2-propylenediamine, 2,5-dimethyl-2,5-hexanediamine, 1,11-undecyldiamine, 1,12-dodecyldiamine, 2,4'-diamino-dicyclohexylmethane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4-toluenediamine or 2,6-toluenediamine, 2,4'-diaminodiphenylmethane or 4,4'-diaminodiphenylmethane and mixtures thereof. The primary amino compound that reacts with unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) also includes but is not limited to 1,4-butanediamine, 1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane and mixtures thereof, etc. The primary amino compound that reacts with unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) also includes but is not limited to terminal amino compounds of polyoxypropylene, polyoxyethylene or copolymers of oxyethylene and oxypropylene, such as Jeffamine D230, D2000, T403, T5000, ED600, ED900, etc. from HUNTSMAN.

[0027] More specifically:

[0028] The dialkyl maleate is preferably diethyl maleate and dipropyl maleate, and most preferably diethyl maleate.

[0029] The dialkyl fumarate is preferably diethyl fumarate and dipropyl fumarate, and most preferably diethyl fumarate.

[0030] The preferred molecular weight of the methoxy polyethylene glycol acrylamide (MPEG-ACA) is 500 and 750, and the most preferred molecular weight is 500.

[0031] The primary amino compound may be a monoamine or a polyamine, preferably a diamine, including 1,6-hexanediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, and most preferably 1,6-hexanediamine and 4,4'-diamino-dicyclohexylmethane.

[0032] The suitable molar ratio between the unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) is 0.95:0.05-0.70:0.30, the preferred molar ratio is 0.90:0.10-0.80:0.20, and the most preferred molar ratio is 0.90:0.10-0.85:0.15.

[0033] The suitable molar ratio of the sum of the moles of the unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) to the primary amino compound is 2:1.10-2:1.00, the preferred molar ratio is 2:1.08-2:1.05, and the most preferred molar ratio is 2:1.03-2:1.00.

[0034] The Michael addition reaction of the unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) with the primary amino compound needs to be carried out in the presence of a catalyst, or may be carried out without a catalyst. The catalyst used may be sodium methoxide, sodium hydroxide, dibutyltin dilaurate, dibutyltin oxide, and 2,4,6-3 (dimethylaminomethyl) phenol, etc. 2,4,6-3 (dimethylaminomethyl) phenol is preferred. The amount of the catalyst used is 0.05%-1% of the total weight of the reactants, and the preferred amount is 0.1%-0.5%.

[0035] More specifically:

[0036] The invention relates to a novel method for preparing water-dispersible polyaspartic acid ester, characterized in that methoxy polyethylene glycol acrylamide (MPEG-CAC) is added in two steps, namely, a measured primary amino compound is first added to a reaction kettle, and then a mixture of a dicarboxylic acid ester and half of the calculated amount of methoxy polyethylene glycol acrylamide is added dropwise, and after the addition is completed, the mixture is reacted for 3 hours, and then the remaining half of the calculated amount of oxy polyethylene glycol acrylamide is added dropwise. After the addition is completed, the reaction is continued until the reaction is completed.

[0037] The present invention relates to a method for preparing a novel water-dispersible polyaspartic acid ester, wherein the temperature of the Michael addition reaction between unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) and primary amino compound is 45°C-80°C, the preferred reaction temperature is 55°C-70°C, and the most preferred reaction temperature is 60°C-65°C.

[0038] The present invention relates to a method for preparing a novel water-dispersible polyaspartic acid ester, wherein the Michael addition reaction time between unsaturated dicarboxylic acid ester and methoxy polyethylene glycol acrylamide (MPEG-ACA) and primary amino compound is 6-24 hours, the preferred reaction time is 8-18 hours, and the most preferred reaction time is 10-16 hours.

[0039] Wherein, R1 and R2 are alkyl groups having the same or different carbon atoms; Y is an alkylene group, a cycloalkylene group or a substituted cycloalkylene group; and n is a natural number of 5-20.

[0040] The present invention further relates to a method for preparing a two-component waterborne polyurea automobile topcoat varnish, which is characterized in that

[0041] The resin component (component A) includes:

[0042] ① At least one aqueous dispersion obtained from the aforementioned novel water-dispersible polyaspartic acid ester resin.

[0043] ② Other suitable resin dispersions containing active hydroxyl groups, where the so-called active hydroxyl groups refer to hydroxyl groups that can react with isocyanate groups.

[0044] ③ Suitable film-forming aid.

[0045] ④ Suitable water-based paint additives.

[0046] ⑤ Suitable pH adjuster.

[0047] ⑥Deionized water.

[0048] The curing agent component (component B) includes:

[0049] ① Water dispersible isocyanate curing agent;

[0050] ② Suitable diluent.

[0051] More specifically:

[0052] The aqueous dispersion ① obtained from the novel water-dispersible polyaspartic acid ester resin refers to the aqueous dispersion obtained by emulsifying the following novel water-dispersible polyaspartic acid ester resins:

[0053]

[0054]

[0055] Where n is a natural number between 5 and 20.

[0056] When the water-dispersible resin (Formula 3, Formula 4, Formula 5) is dispersed and emulsified at high speed, the corresponding polyaspartic acid ester dispersion is obtained. The dispersion method and process can adopt the method and process well known in the art, and the solid content of the water dispersion can be controlled to 40%-60%, preferably 50%.

[0057] The at least one aqueous dispersion obtained from the aforementioned novel water-dispersible polyaspartic acid ester resin is one of the dispersions of formula 3, formula 4, and formula 5, or a combination thereof. When a combination is required, the combination can be in any proportion.

[0058] The aforementioned ② other suitable resin dispersions containing active hydroxyl groups refer to novel water-dispersible polyaspartic acid ester resin dispersions which can be used as the sole resin dispersion in component A or can be used in combination with other resin dispersions containing active hydroxyl groups, where active hydroxyl groups refer to hydroxyl groups that can react with isocyanate groups.

[0059] The other suitable resin dispersions containing active hydroxyl groups include, but are not limited to, hydroxypropylene resin dispersions, hydroxyl-containing polyurethane emulsions, etc. Suitable hydroxypropylene resin dispersions include, but are not limited to, Bayhydrol A 2470 from Covestro, Burnock WD-570 from DIC Synthetic Resins (Zhongshan) Co., Ltd., Acure 2720 from Amino Specialty Chemicals (Shanghai) Co., Ltd., etc.

[0060] The other suitable resin dispersion containing active hydroxyl groups can be one resin dispersion or a combination of multiple resin dispersions. When they need to be combined, they can be combined in any proportion.

[0061] The total amount of the other suitable resin dispersions containing active hydroxyl groups is 0-50% of the total weight of component A, preferably 0-30%.

[0062] The suitable film-forming aids include, but are not limited to, ethylene glycol butyl ether (BCS), propylene glycol diacetate (PGDA), propylene glycol monomethyl ether (PM), propylene glycol butyl ether (PnB), propylene glycol methyl ether acetate (PMA), dipropylene glycol methyl ether (DPM), dipropylene glycol propyl ether (DPnP), tripropylene glycol butyl ether (TPnB), etc. As film-forming aids, they can be used alone or mixed in any proportion.

[0063] The amount of the film-forming aid is 1-10% by weight of component A, the appropriate amount is 2-8%, and the preferred amount is 4-6%.

[0064] The suitable water-based coating additives include but are not limited to water-based leveling agents (such as Digo Flow425), water-based defoaming agents (such as Centron SF561, Digo Foamex825), water-based wetting agents (such as Digo Twin4100, BYK345), water-based thickeners (Hemmings 108, 299), water-based anti-scratch agents (such as BY-5330, Dow Corning 51), water-based catalysts, water-based antioxidants, water-based UV stabilizers, etc.

[0065] The usage amount of the suitable water-based coating additive is in accordance with the recommended range of each supplier, generally 0.3-3% of the total weight of component A.

[0066] The suitable pH adjusting agent includes but is not limited to triethylamine (TEA), dimethylethanolamine (DMEA), 2-aminomethyl-1-propanol (AMP-95), etc.

[0067] The amount of the appropriate pH adjuster used is determined according to the pH value of component A, and the appropriate pH value range is 7-9, and the preferred range is 8-9.

[0068] The deionized water (6) is pure water treated by a water purification device, and its resistivity is not less than 10 megohms.

[0069] The amount of ionized water to be used needs to be determined by first calculating the existing water content according to the existing solid content of each aqueous dispersion, and then calculating according to the set theoretical solid content of component A.

[0070] The present invention also relates to a curing agent component (component B) of a two-component waterborne polyurea automobile topcoat varnish, comprising:

[0071] ① Water dispersible isocyanate curing agent;

[0072] ② Suitable diluent.

[0073] The water-dispersible isocyanate curing agent ① is a hydrophilically modified aliphatic isocyanate, including but not limited to water-dispersible hexamethylene diisocyanate (HDI) trimer (such as Bayhydur XP2655, Aqolin 269), water-dispersible fluoroquinone diisocyanate (IPDI) trimer (such as Bayhydur 401-70), and other suitable water-dispersible isocyanate curing agents.

[0074] The water-dispersible isocyanate curing agent can be used alone or in combination. When used in combination, the proportion of the IPDI system water-dispersible curing agent in the total amount of the curing agent does not exceed 40%.

[0075] The suitable diluents include, but are not limited to, propylene glycol diacetate (PGDA), propylene glycol butyl ether (PnB), propylene glycol methyl ether acetate (PMA), dipropylene glycol propyl ether (DPnP), tripropylene glycol butyl ether (TPnB), etc. As diluents, they can be used alone or mixed in any proportion.

[0076] The usage amount of the suitable diluent can be 0-50% of the weight of component B, the suitable usage amount is 20-40%, and the preferred usage amount is 20-30%.

[0077] The amount of the water-dispersible isocyanate curing agent is calculated based on the average active hydrogen equivalent in component A. The ratio of the average equivalent of cyanate [NCO] in the curing agent component to the average active hydrogen equivalent [H] of the resin component can be 2.0-1.0:1, the appropriate ratio is 1.6:1.0, and the preferred ratio is 1.2:1.

[0078] More specifically:

[0079] The present invention further relates to a method for preparing a two-component waterborne polyurea automobile topcoat varnish, characterized in that the resin component (component A) comprises:

[0080] ① At least one aqueous dispersion obtained from the aforementioned novel water-dispersible polyaspartic acid ester resin.

[0081] ② Other suitable resin dispersions containing active hydroxyl groups, where the so-called active hydroxyl groups refer to hydroxyl groups that can react with isocyanate groups.

[0082] ③ Suitable film-forming aid.

[0083] ④ Suitable water-based paint additives.

[0084] ⑤ Suitable pH adjuster.

[0085] ⑥Deionized water.

[0086] The preparation of component A of the two-component waterborne polyurea automotive topcoat varnish is carried out according to the following steps:

[0087] ① First add the new polyaspartic acid ester resin dispersion into the container, turn on the high-speed disperser, and adjust the speed to 200-300rpm;

[0088] ② Keep stirring and add other suitable resin dispersions containing active hydroxyl groups;

[0089] ③Keep stirring and add film-forming agent

[0090] ④ Keep stirring and add defoamer, leveling agent and wetting agent in sequence;

[0091] ⑤Keep stirring, add pH regulator, and adjust pH value

[0092] ⑥ Keep stirring and add deionized water;

[0093] ⑦ Increase the stirring speed to 1500-2000rpm and maintain high-speed dispersion for 30 minutes; during the dispersion process, the material temperature can be controlled not higher than 40°C by jacket cooling. After high-speed dispersion, component A of the two-component water-based polyurea automotive topcoat varnish is obtained.

[0094] The present invention further relates to a method for preparing a two-component waterborne polyurea automobile topcoat varnish, characterized in that the curing agent component (component B) comprises:

[0095] ① Water dispersible isocyanate curing agent;

[0096] ② Suitable diluent.

[0097] The preparation of component B of the two-component waterborne polyurea automotive topcoat varnish is carried out according to the following steps:

[0098] ① Add measured amount of water-dispersible isocyanate curing agent into the container;

[0099] ② Add measured diluent, then start stirring, maintain the speed at 150-200rpm, until stirring evenly to obtain component B of the two-component water-based polyurea automotive topcoat varnish.

[0100] The mixing of the two-component waterborne polyurea automotive finishing varnish A and B is carried out according to the following steps:

[0101] ①Mix the measured components A and B and stir them thoroughly.

[0102] ② Add 5%-10% of the total amount of components A and B in deionized water and adjust the viscosity to obtain a two-component water-based automotive topcoat varnish.

[0103] The invention patent further relates to the application of a two-component water-based polyurea automotive topcoat varnish in automotive painting, including its application in the automotive original equipment manufacturer (OEM) painting line and in automotive sheet metal spray repair.

[0104] When the two-component waterborne polyurea automobile finishing varnish involved in the present invention is used for OEM painting, the dehydration rate of the color paint film of the previous process of the workpiece (car body) is required to be ≥90%, the workpiece temperature is required to be 20-30°C, the ambient temperature is 25±2°C, the ambient humidity is 65±5%, the ventilation speed is 0.25-0.40m / s, and the baking temperature is 80-110°C. The rest can be implemented with reference to the process requirements and process parameters of the existing solvent-based automobile (OEM) finishing varnish coating. The basic process parameters are provided in one embodiment of the present invention.

[0105] When the two-component water-based polyurea automobile finishing varnish involved in the patent of the present invention is used for automobile sheet metal repair coating, the dehydration rate of the color paint film of the sheet metal (car body) in the previous process is ≥80%, and the workpiece temperature is required to be 20-30°C. The ambient temperature is 25±5°C, the ambient humidity is 60±10%, and the baking temperature is ≥60°C. The rest can be implemented with reference to the process requirements and process parameters of the existing solvent-based automobile repair finishing varnish coating. Basic process parameters are provided in another embodiment of the patent of the present invention.

[0106] Innovations of the present invention:

[0107] ① The present invention utilizes methoxy polyethylene glycol acrylamide to synthesize a brand-new water-dispersible polyaspartic acid ester resin to obtain an aqueous dispersion.

[0108] First, as a water-based automobile finishing varnish, it must simultaneously meet excellent anti-corrosion performance and bright and transparent appearance performance, but the prior art shows that it is difficult to simultaneously meet the two properties. For example, when taking into account the appearance performance, its water resistance and other tolerances are affected, and it is particularly unable to meet the low-temperature baking coating requirements including automobile OEM and automobile repair. Second, as one of the important components of water-based automobile finishing varnish (water dispersion), water-dispersible polyaspartic acid ester resin not only determines water resistance, but also affects other properties. How to obtain a suitable water dispersion to balance water resistance and other properties has become a technical problem in this field. Third, as for the preparation of water-dispersible polyaspartic acid ester resin, its synthesis method is simple, but the choice of reactant is the key factor. The patent of the present invention adopts non-ionic methoxy polyethylene glycol acrylamide (MPEG-ACA) as a hydrophilic monomer, which is added to the polyaspartic acid ester structure to obtain a water-dispersible polyaspartic acid ester resin. Among them, methoxy polyethylene glycol acrylamide is prepared by condensation reaction of polyethylene glycol and acrylamide, has high water solubility, can form a uniform dispersion system in aqueous solution, and is also used as a free radical initiator and ultraviolet induced polymerization agent, but it is rarely used in the preparation of resins. Fourth, the resin synthesized by methoxy polyethylene glycol acrylamide (MPEG-ACA) is a complex system for forming water-based automotive topcoat varnish, and it is impossible to reasonably predict whether the relevant technical requirements of water-based automotive topcoat varnish can be met.

[0109] The invention uses methoxy polyethylene glycol acrylamide to synthesize a brand-new water-dispersible polyaspartic acid ester resin to obtain an aqueous dispersion, which overcomes the defects of the (meth) acrylate hydrophilic monomer in the patent announcement CN109761834 that the anion is easy to migrate and the water absorption rate is high, thereby affecting the water resistance of the water-based polyurea coating. At the same time, as one of the important components for forming a water-based automobile topcoat varnish, it not only has good water resistance, but also meets various performance indicators.

[0110] ② In the synthesis process of the new water-dispersible polyaspartic acid ester resin, MPEG-ACA is added in a two-step method to ensure that the hydrophilic monomer can be evenly distributed in the structure of the polyaspartic acid ester resin, improve the hydrophilicity, and reduce the amount of hydrophilic monomer used.

[0111] Beneficial Effects

[0112] The present invention relates to a two-component waterborne polyurea automotive clearcoat, characterized in that the clearcoat is composed of at least one novel polyaspartic acid ester dispersion, and the polyaspartic acid ester dispersion is prepared based on non-ionic methoxy polyethylene glycol acrylamide (MPEG-ACA) as a hydrophilic monomer. Compared with anionic waterborne polyurea coating (CN109761834), the two-component waterborne polyurea automotive clearcoat of the present invention has the following advantages:

[0113] ① It overcomes the defect of poor water resistance of anionic water-based polyurea coatings: non-ionic hydrophilic groups are more stable in the coating film and less likely to migrate, ensuring the excellent water resistance of water-based polyurea automotive topcoat varnish.

[0114] ② Improved the gloss and transparency of the paint film: The non-ionic hydrophilic group has good compatibility and strong emulsification ability. Therefore, it can improve the compatibility between the components in the coating, thereby increasing the gloss and transparency of the water-based polyurea automotive topcoat varnish.

[0115] ③ Increased cross-linking density and reduced baking temperature: The presence of active hydrogen in the amide group of the hydrophilic monomer increases the cross-linking density of the reaction with the curing agent, which not only further improves the water resistance of the water-based polyurea automotive topcoat varnish, but also can significantly reduce the baking temperature and baking time during the coating process.

[0116] ④ Improved aging resistance and corrosion resistance: The presence of amide groups in the hydrophilic monomer improves the stability of the polymer structure, thereby improving the aging resistance and corrosion resistance of the water-based polyurea automotive topcoat varnish.

[0117] In summary, the two-component waterborne polyurea varnish prepared according to the present invention has further improved appearance performance, water resistance, aging resistance and corrosion resistance, and its coating baking temperature can be further reduced. Therefore, the two-component waterborne polyurea varnish prepared according to the present invention can meet the performance requirements and process requirements of automobile topcoat varnish. BRIEF DESCRIPTION OF THE DRAWINGS

[0118] Figure 1 IR of Diethyl Maleate(DM)

[0119] Figure 2 Infrared image of methoxy polyethylene glycol acrylamide (MPEG-ACA-500) with a molecular weight of 500

[0120] Figure 3 Infrared image of methoxy polyethylene glycol acrylamide (MPEG-ACA-750) with a molecular weight of 750

[0121] Figure 4 Resin R1 infrared image

[0122] Figure 5 Resin R2 infrared image

[0123] Figure 6 Resin R3 infrared image

[0124] Figure 7 Resin R4 infrared image

[0125] Figure 8 Glossiness of F1 coating film in Example 8 (20°)

[0126] Fig. 9 Glossiness of F2 coating film in Example 8 (20°)

[0127] Fig.10 Glossiness of F3 coating film in Example 8 (20°)

[0128] Fig.11 Glossiness of F4 coating film in Example 8 (20°)

[0129] Fig.12 Glossiness (20°) of the F5 coating film in Example 14. DETAILED DESCRIPTION

[0130] 1 The names and structures of the main raw materials used in the synthesis of each resin are shown in Table 1

[0131] Table 1 Names and structures of main raw materials used in the synthesis of each resin

[0132]

[0133] 2 The information of resin dispersion and curing agent used in the preparation of each coating component is shown in Table 2

[0134] Table 2 List of resin dispersions and curing agents used in the preparation of each coating component

[0135]

[0136]

[0137] Example 1 Synthesis of Resin R1

[0138] In a 1000ml four-necked flask equipped with an electric stirrer, a thermometer, a dropping funnel, a nitrogen conduit and a reflux condenser, add 210.36g (1mol) PACM, start stirring, replace the air in the reaction bottle with nitrogen twice and keep nitrogen flowing. Heat to about 45°C, then slowly drop 146.35g (0.85mol) DM and 37.5g (0.075mol) MPEG-ACA with a molecular weight of 500 into the reaction bottle, keep the temperature not exceeding 60°C, and control the addition to be completed within 20-40 minutes. React at 60-65°C for 3 hours, then drop 37.5g (0.075mol) MPEG-ACA with a molecular weight of 500, keep the temperature at 60-65°C, and control the addition to be completed within 10-30 minutes. Then continue to keep warm for 13 hours. Cool to 40°C and discharge to obtain product R1. The product is a light yellow transparent liquid with a chromaticity (Pt-Co) of 25#. The conversion rate measured by the "iodination method" is 86.4%, and the conversion rate measured again after 48 hours is 97.5%. The theoretically calculated amino equivalent is 216.

[0139] Figure 1 , Figure 2 These are the infrared spectra of DM and MPEG-ACA with a molecular weight of 500. The absorption peaks at 1644.98 and 1606.41 are the double bond absorption peaks of DM and MPEG-ACA with a molecular weight of 500, respectively. Figure 4 This is the infrared image of product R1. Figure 4 It can be seen that the absorption peaks at 1644.98 and 1606.417 have disappeared, indicating that DM and MPEG-ACA have participated in the reaction to form product R1.

[0140] The structural formula of R1 (Formula 6):

[0141]

[0142] Example 2 Synthesis of Resin R2

[0143] In a 1000ml four-necked flask equipped with an electric stirrer, a thermometer, a dropping funnel, a nitrogen conduit and a reflux condenser, add 238.41g (1mol) DMDC, start stirring, replace the air in the reaction bottle with nitrogen twice and keep nitrogen flowing. Heat to about 45°C, then slowly drop 146.35g (0.85mol) DM and 37.5g (0.075mol) MPEG-ACA with a molecular weight of 500 into the reaction bottle, keep the temperature not exceeding 60°C, and control the addition to be completed within 20-40 minutes. React at 60-65°C for 3 hours, then drop 37.5g (0.075mol) MPEG-ACA with a molecular weight of 500, keep the temperature at 60-65°C, and control the addition to be completed within 10-30 minutes. Then continue to keep warm for 13 hours. Cool to 40°C and discharge to obtain product R2. The product is a light yellow transparent liquid with a chromaticity (Pt-Co) of 25#. The conversion rate measured by the "iodination method" is 86% at this time, and the conversion rate measured again after 48 hours is 97%. The theoretically calculated amino equivalent is 230.

[0144] Figure 1 , Figure 2 These are the infrared spectra of DM and MPEG-ACA with a molecular weight of 500. The absorption peaks at 1644.98 and 1606.41 are the double bond absorption peaks of DM and MPEG-ACA with a molecular weight of 500, respectively. Figure 5 This is the infrared image of product R2. Figure 5 It can be seen that the absorption peaks at 1644.98 and 1606.41 have disappeared, indicating that DM and MPEG-ACA have participated in the reaction to form product R2.

[0145] The structural formula of R2 (Formula 7):

[0146]

[0147] Example 3 Synthesis of Resin R3

[0148] In a 1000ml four-necked flask equipped with an electric stirrer, a thermometer, a dropping funnel, a nitrogen conduit and a reflux condenser, add 210.36g (1mol) PACM, start stirring, replace the air in the reaction bottle with nitrogen twice and keep nitrogen flowing. Heat to about 45°C, then slowly drop 154.96g (0.90mol) DM and 37.5g (0.05mol) MPEG-ACA with a molecular weight of 750 into the reaction bottle, keep the temperature not exceeding 60°C, and control the addition to be completed within 20-40 minutes. React at 60-65°C for 3 hours, then drop 37.5g (0.05mol) MPEG-ACA with a molecular weight of 750, keep the temperature at 60-65°C, and control the addition to be completed within 10-30 minutes. Then continue to keep warm for 13 hours. Cool to 40°C and discharge to obtain product R3. The product is a light yellow transparent liquid with a chromaticity (Pt-Co) of 25#. The conversion rate measured by the "iodination method" is 85.8% at this time, and the conversion rate measured again after 48 hours is 96.2%. The theoretically calculated amino equivalent is 216.

[0149] Figure 1 , Figure 3 These are the infrared spectra of DM and MPEG-ACA with a molecular weight of 750. The absorption peaks at 16444.98 and 1608.22 are the double bond absorption peaks of DM and MPEG-ACA with a molecular weight of 500, respectively. Figure 6 This is the infrared image of product R3. Figure 6 It can be seen that the absorption peaks at 1644.98 and 1608.22 have disappeared, indicating that DM and MPEG-ACA have participated in the reaction to form product R3.

[0150] The structural formula of R3 (Formula 8):

[0151]

[0152] Example 4 Synthesis of Resin R4

[0153] In a 1000ml four-necked flask equipped with an electric stirrer, a thermometer, a dropping funnel, a nitrogen conduit and a reflux condenser, add 238.41g (1mol) DMDC, start stirring, replace the air in the reaction bottle with nitrogen twice and keep nitrogen flowing. Heat to about 45°C, then slowly drop 154.96g (0.9mol) DM and 37.5g (0.05mol) MPEG-ACA with a molecular weight of 750 into the reaction bottle, keep the temperature not exceeding 60°C, and control the addition to be completed within 20-40 minutes. React at 60-65°C for 3 hours, then drop 37.5g (0.05mol) MPEG-ACA with a molecular weight of 750, keep the temperature at 60-65°C, and control the addition to be completed within 10-30 minutes. Then continue to keep warm for 13 hours. Cool to 40°C and discharge to obtain product R4. The product is a light yellow transparent liquid with a chromaticity (Pt-Co) of 25#. The conversion rate measured by the "iodination method" is 85.7% at this time, and the conversion rate measured again after 48 hours is 96.0%. The theoretically calculated amino equivalent is 230.

[0154] Figure 1 , Figure 3 The infrared spectra of DM and MPEG-ACA with a molecular weight of 750 are shown in Figure 1. The absorption peaks of the double bonds of DM and MPEG-ACA with a molecular weight of 750 are at 1644.98 and 1608.22 respectively. Figure 7 This is the infrared image of product R4. Figure 7 It can be seen that 1644.98 and 1608.22

[0155] The absorption peak at has disappeared, indicating that diethyl maleate and MPEG-ACA have participated in the reaction to form product R4.

[0156] The structural formula of R4 (Formula 9):

[0157]

[0158] Example 5 Preparation of polyaspartic acid ester resin dispersions D1, D2, D3, and D4

[0159] Take 150g of the water-dispersible polyaspartic acid ester resin (R1) prepared in Example 1, slowly add 36g of 25% propylene glycol diacetate (PGDA) aqueous solution under stirring (400rpm), and keep a constant speed (300-500rpm) for 25 minutes. Then slowly add 114g of deionized water, increase the speed to 3000rpm, and keep it for 15 minutes; then adjust the pH value to 8.0-9.0 with 10% 2-amino-2-methyl-1-propanol (AMP-95) aqueous solution, and obtain D1.

[0160] 150 g of each of the water-dispersible polyaspartic acid ester resins R2, R3, and R4 prepared in Examples 2-4 were taken respectively, and the corresponding resin dispersions D2, D3, and D4 were prepared respectively according to the same steps as above.

[0161] The corresponding composition data of D1-D4 are shown in Table 3. The index data related to each dispersion are also listed in Table 3 (weight unit is g).

[0162] Table 3 Composition and index data of each dispersion

[0163]

[0164] Note: The nanoparticle size analyzer model used is Winner800 (Jinan Micro-Nano Particle Instrument Co., Ltd.)

[0165] The high-speed centrifuge model used is LG10-2.4A (Beijing Leiboer)

[0166] Example 6 Preparation of Waterborne Polyurea Automobile Clearcoat Resin Components (Component A) A1, A2, A3, A4

[0167] ① First add 50 parts of resin dispersion D1 into the container, turn on the high-speed disperser, and adjust the speed to 200-300rpm.

[0168] ② While stirring, add 25 parts of WD-570.

[0169] ② While keeping stirring, add 4 parts of PGDA.

[0170] ④ Keep stirring and add 0.3 parts of defoamer SF561, 0.5 parts of leveling agent Tego425, and 0.5 parts of wetting agent Tego4100 in sequence.

[0171] ⑤ While stirring, add about 0.2 parts of 10% AMP-95 aqueous solution to adjust the pH value to 8.0-9.0.

[0172] ⑥ While keeping stirring, add 19.5 parts of deionized water.

[0173] ⑦ Increase the stirring speed to 1500-2000rpm and maintain high-speed dispersion for 30 minutes. During the dispersion process, the material temperature can be controlled to be no higher than 40℃ by jacket cooling.

[0174] After high-speed dispersion, the resin component (component A) of the two-component water-based clear varnish is obtained, namely A1.

[0175] Take resin dispersions D2, D3, and D4 and prepare A2, A3, and A4 respectively according to the above steps.

[0176] Comparative Example 1 Preparation of Waterborne Polyurea Varnish Resin Component C1

[0177] Take resin dispersion E1 and prepare C1 according to the method of Example 6; wherein E1 is prepared according to Example 1 in CN109761834A.

[0178] The formula information of each resin component (component A) of Example 6 and Comparative Example 1 is shown in Table 4.

[0179] Table 4 Formula information of each resin component (component A)

[0180] A1 A2 A3 A4 C1 D1 50 D2 50 D3 50 D4 50 E1 50 WD-570 25 25 25 25 25 Film-forming aid PGDA 4 6 4.5 4 3.5 Defoaming agent SF561 0.3 0.3 0.3 0.3 0.3 Leveling agent Tego425 0.5 0.4 0.4 0.4 0.4 Wetting agent Tego4100 0.5 0.6 0.6 0.6 0.6 Neutralizer 10% AMP-95 0.2 4.2 5.3 6 4 Deionized water 19.5 13.5 13.9 13.7 16.2 total 100 100 100 100 100 Average active hydrogen equivalent 708 745.1 708 745.1 814.4 Average solid content% 36 36 36 36 36

[0181] Example 7 Preparation of waterborne polyurea automotive finish varnish curing agent component (component B)

[0182] ① First add 70 parts of Bayhydur XP2655 into the container

[0183] ② Add 30 parts of propylene glycol diacetate (PGDA), then start stirring, keep the speed at 150-200 rpm, and stir until it is evenly stirred to obtain curing agent component B. Its average NCO content is 14.7%, and the average solid content is 70%.

[0184] Example 8 Preparation of water-based polyurea automobile finishing varnish and spraying and coating film testing on test panels in an auto repair spray booth

[0185] Baseboard preparation:

[0186] Several 170×70×0.8mm cathode electrophoretic steel plates and several 170×70×0.28mm tinplate plates were provided by Biaugeda. Firstly, water-based gray-white epoxy intermediate coating (dry film 35-45μm) was sprayed, and then dried at 70℃×30min. Then, Akzo Xinjin series silver-white water-based automobile repair paint (dry film 15-25μm) was sprayed, and then dried at 70℃×30min for standby use.

[0187] Paint Matching

[0188] According to the mixing ratio of resin component (component A) and curing agent component (component B) given in Table 5, weigh the resin components A1-A4 and C1 and the curing agent component B respectively, stir and mix them evenly, and then add 5-10% deionized water to adjust the viscosity according to the spraying requirements. After standing for 10-15 minutes, spray them on the designated test substrates respectively to obtain varnish coating films of 5 formulations F1-F5.

[0189] Conditions of spraying process requirements for auto repair spray booths:

[0190] ① Requirements for spray booth: temperature 25±5℃, humidity 60±10%, air volume 18000m 3 / h. The downward air flow speed is 0.3-0.6m / s.

[0191] ① Drying room requirements: temperature is 70℃, air flow rate is about 0.05m / s, and fresh air supplement volume is 10-15%.

[0192] ②Spraying method: air spraying, recommended spray gun is SATAjet X5500, nozzle diameter is 1.3-1.5mm, spraying air pressure is 3.0-3.5bar.

[0193] ③ After the varnish is sprayed, the test board is left to stand and level in the paint spray room for 10-15 minutes. After the milky white wet film turns transparent, it is sent to a 70℃ drying room for baking for 30 minutes.

[0194] After baking, each test board was placed at room temperature for 7 days to mature and then tested for various properties. The main performance test results are listed in Table 6.

[0195] Table 5 Mixing ratio of each varnish and curing agent (weight ratio)

[0196] F1 F2 F3 F4 F5 A1 100 A2 100 A3 100 A4 100 C1 100 B 44.4 42.2 44.4 42.2 38.6 [NCO] / [H] 1.2 1.2 1.2 1.2 1.2

[0197] Note: Due to the different contents of various active groups, the content of B is different, the purpose is to achieve the same [NCO] / [H].

[0198] Table 6 Test results of main properties of each varnish coating

[0199]

[0200] Operation time: the time during which the coating can be sprayed continuously and effectively form a film after components A and B are evenly mixed.

[0201] Conventional operation is usually above 140℃, which has high requirements for conditions and is suitable for factory production, but not suitable for later maintenance. This implementation adopts 70℃ drying room for 30 minutes, which is a low-temperature operation. There is no need to purchase a high-demand drying room. The low temperature advantage can ensure that the circuit is not damaged, which can meet general maintenance needs.

[0202] According to the test results of Table 6, it can be clearly seen that the F1, F2, F3 and F4 varnish films can meet the requirements of a domestic automobile brand for the car body paint film, while the gloss, leveling (orange peel), water resistance, aging resistance and salt spray resistance of the F5 varnish film as Comparative Example 1 cannot meet the requirements of automobile paint. It should be noted that F5 is a varnish prepared by the method described in CN109761834A to obtain a composite of E1 and B components, and F1-F5 are prepared using the same [NCO] / [H] equivalent ratio to obtain the varnish. Although the varnish corresponding to the embodiment recorded in CN109761834A in its specification has good performance, its adopted standard is the general varnish standard, such as gloss (60°), etc.; while the present invention adopts the requirements of the car body paint film, the two requirements are different and the present invention has higher requirements. Under higher standards, F5 cannot meet the requirements of automobile paint in terms of gloss, leveling (orange peel), water resistance, aging resistance and salt spray resistance.

[0203] Example 9 Waterborne polyurea automotive topcoat varnish OEM coating line body spraying and coating film testing

[0204] According to the test results in Example 8, the F1 varnish formulation was selected for spraying and testing.

[0205] Construction vehicle preparation

[0206] Five complete vehicle bodies are selected and numbered as vehicle #1, vehicle #2, vehicle #3, vehicle #4, and vehicle #5.

[0207] Paint Matching

[0208] Mix components A and B in proportion according to formula F1, and stir with an electric stirrer for 3 minutes to ensure full mixing. Add appropriate amount of deionized water to adjust the spraying viscosity.

[0209] Spraying

[0210] Under the given construction vehicle conditions, the two-component waterborne polyurea automotive varnish was sprayed on the entire vehicle using an air spray gun. The spraying process parameters are shown in Table 6.

[0211] Table 6 List of parameters for each process of body spraying

[0212]

[0213] *All coatings in the construction vehicle state are water-based paint

[0214] The test results of the coating performance of the vehicle body after spraying are shown in Table 7.

[0215] Table 7 List of car body coating test results*

[0216]

[0217] *The data of each test item are the average values ​​of different test points on the vehicle body. The location of each test point for each test item is determined according to the corporate standard of a certain automobile brand.

[0218] According to Table 6, the baking effect of waterborne polyurea automotive varnish under different baking conditions can be examined. The results show that even without flash drying and initial heating, the wet film of waterborne varnish for cars 2# and 3# directly enters the 110℃ drying tunnel for baking for 30 minutes, and their coating hardness and other appearance qualities also reach excellent indicators (as shown in Table 7). Compared with traditional solvent-based polyurethane automotive varnish, which usually needs to be baked at ≥140℃ for 30 minutes, the waterborne polyurea automotive varnish proposed in the present invention not only greatly reduces the baking temperature, but also shortens the baking time and improves the production efficiency.

Claims

1. A water-dispersible polyaspartic acid ester resin, characterized in that It has the following structural formula: In the formula, R1 and R2 are C1-C4 alkyl groups with the same or different carbon atoms; Y is an alkylene group, a cycloalkylene group or a substituted cycloalkylene group; and n is a natural number of 5-20.

2. The water-dispersible polyaspartic acid ester resin according to claim 1, characterized in that It is any one of the following compounds: Where m is a natural number of 0, 1, 2, or 5, and n is a natural number of 5 to 20.

3. The method for preparing a water-dispersible polyaspartic acid ester resin according to claim 1, characterized in that: It is obtained by Michael addition reaction of unsaturated dicarboxylic acid ester, methoxy polyethylene glycol acrylamide and primary amino compound; Wherein R1 and R2 are C1-C4 alkyl groups with the same or different carbon atoms; Y is an alkylene group, a cycloalkylene group or a substituted cycloalkylene group; n is a natural number of 5-20; The unsaturated dibasic acid carboxylic acid ester is a dialkyl maleate or a dialkyl fumarate; the dialkyl maleate includes diethyl maleate, dipropyl maleate, dibutyl maleate and methyl propyl maleate and mixtures thereof; the dialkyl fumarate includes diethyl fumarate, dipropyl fumarate, dibutyl fumarate and methyl propyl fumarate and mixtures thereof; The methoxy polyethylene glycol acrylamide includes methoxy polyethylene glycol acrylamide with a polymerization degree n of polyethylene glycol of 5-20, and the corresponding molecular weights include 350, 500, 550, 750 and 1000; Primary amino compounds include ethylenediamine, 1,2-propylenediamine, 2,5-dimethyl-2,5-hexanediamine, 1,11-undecyldiamine, 1,12-dodecyldiamine, 2,4 , -Diamino-dicyclohexylmethane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 1,4-butanediamine, 1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 4,4 ， -Diamino-dicyclohexylmethane, 3,3 ， -Dimethyl-4,4 ， - diamino-dicyclohexylmethane and mixtures thereof; The molar ratio of unsaturated dicarboxylic acid ester to methoxy polyethylene glycol acrylamide is 0.95:0.05-0.70:0.30; The molar ratio of the sum of the moles of the unsaturated dicarboxylic acid ester and the methoxy polyethylene glycol acrylamide to the primary amino compound is 2:1.10-2:1.

00.

4. The method according to claim 3, characterized in that The methoxy polyethylene glycol acrylamide is added in a two-step method, that is, the primary amino compound is first added into the reaction kettle, and then a mixture of dicarboxylic acid ester and half amount of methoxy polyethylene glycol acrylamide is added dropwise, and the reaction is carried out for 3 hours after the dropwise addition is completed, and then the remaining half amount of oxy polyethylene glycol acrylamide is added dropwise, and the reaction is continued until the reaction is completed after the dropwise addition is completed; the reaction temperature is 45° C.-80° C.; and the reaction time is 6-24 hours.

5. The method according to claim 3, characterized in that: The dialkyl maleate is diethyl maleate or dipropyl maleate; the dialkyl fumarate is diethyl fumarate or dipropyl fumarate; the molecular weight of the methoxypolyethylene glycol acrylamide is 500 or 750; the primary amino compound is 1,6-hexanediamine or 4,4 ， -Diamino-dicyclohexylmethane.

6. A two-component waterborne polyurea automotive finishing varnish, characterized in that It includes component A and component B; Component A includes: ① An aqueous dispersion obtained from the water-dispersible polyaspartic acid ester resin according to claim 1 or 2; ②Other resin dispersions containing active hydroxyl groups, wherein active hydroxyl groups refer to hydroxyl groups that can react with isocyanate groups; ③ Film-forming aid; ④ Water-based coating additives; ⑤ pH regulator; ⑥Deionized water; Component B includes: ① Water dispersible isocyanate curing agent; ② Suitable diluent.

7. The two-component waterborne polyurea automotive finishing varnish according to claim 6, characterized in that: Component A is: ① The aqueous dispersion is one of the compounds corresponding to the following structural formula or any combination thereof. Where m is a natural number of 0, 1, 2, or 5, and n is a natural number of 5 to 20; ② Other resin dispersions containing active hydroxyl groups include hydroxypropylene resin dispersions, hydroxyl-containing polyurethane emulsions, or any combination of two or more thereof; the total amount of the other resin dispersions containing active hydroxyl groups is 0-50% of the total weight of component A; ③ The film-forming aid includes one or any combination of two or more of ethylene glycol butyl ether, propylene glycol diacetate, propylene glycol monomethyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, dipropylene glycol propyl ether and tripropylene glycol butyl ether; the amount of the film-forming aid is 1-10% by weight of component A; ④ Water-based coating additives include water-based leveling agents, water-based defoaming agents, water-based wetting agents, water-based thickeners, water-based anti-scratch agents, water-based catalysts, water-based antioxidants or water-based UV stabilizers; The amount of the water-based coating additive used is 0.3-3% of the total weight of component A; ⑤ The pH adjuster includes triethylamine, dimethylethanolamine or 2-aminomethyl-1-propanol; the amount of the pH adjuster used is based on the pH of component A 7-9; ⑥ Deionized water, which is pure water treated by a water purification device, and its resistivity is not less than 10 megohms; Component B is: ① Water-dispersible isocyanate curing agents include water-dispersible hexamethylene diisocyanate trimer and water-dispersible fluoroketone diisocyanate trimer; ② Suitable diluents include propylene glycol diacetate, propylene glycol butyl ether, propylene glycol methyl ether acetate, dipropylene glycol propyl ether, tripropylene glycol butyl ether, or any combination of two or more thereof; the amount of the diluent used is 20-40% of the weight of component B; The amount of water-dispersible isocyanate curing agent in component B is calculated based on the average active hydrogen equivalent in component A; The ratio of the average equivalent weight [NCO] of the cyanate group in the water-dispersible isocyanate curing agent component to the average active hydrogen equivalent weight [H] of the resin component is 2.0-1:

1.

8. The two-component waterborne polyurea automotive finishing varnish according to claim 7, characterized in that: Component A is: ① The aqueous dispersion is one of the compounds corresponding to the following structural formula or any combination thereof to form an aqueous dispersion: ②Other resin dispersions containing active hydroxyl groups are Bayhydrol A 2470, Burnock WD-570 or Acure 2720, one or a combination of two or more in any proportion; The ratio of the average equivalent weight of cyanate groups [NCO] in the water-dispersible isocyanate curing agent component to the average active hydrogen equivalent weight [H] in the resin component is 1.2:

1.

9. A method for preparing a two-component waterborne polyurea automobile topcoat varnish according to any one of claims 6 to 8, characterized in that: Mix components A and B as follows: ①Mix the measured components A and B and stir them thoroughly; ② Add 5%-10% of the total amount of components A and B in deionized water and adjust the viscosity to obtain a two-component water-based automotive topcoat varnish.

10. Use of the two-component waterborne polyurea automobile topcoat varnish according to any one of claims 6 to 8 in automobile painting, including use in a painting line of an automobile main engine factory and use in automobile sheet metal spray repair.

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