High-performance water-based floating coat and preparation method thereof

Abstract

The invention belongs to the technical field of coatings, and particularly discloses a high-performance water-based floating coat which comprises a floating coat and a curing agent, and the water-based floating coat comprises the following components in parts by weight: 35-45 parts of water-based hydroxyl polyurethane resin, 0.1-0.5 part of a flatting agent, 0.1-0.5 part of a defoaming agent, 1-4 parts of a dispersing agent, 30-45 parts of pigment filler and 5-15 parts of deionized water; the curing agent is prepared from the following components in parts by weight: 55 to 75 parts of isocyanate and 25 to 45 parts of solvent. The floating coat composition with good construction performance and paint film performance, provided by the invention, has extremely low VOC (Volatile Organic Compounds).

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a high-performance waterborne intermediate coat and a preparation method thereof. Background Art

[0002] For the painting of automobile repair, the currently used 2K intermediate coat is mainly a solvent-based coating. At present, the standard of GB24409 for this type of product is VOC ≤ 630 g / L, which is much higher than the VOC level of waterborne 2K intermediate coat reaching ≤ 150 g / L, or even ≤ 100 g / L. Therefore, from the perspective of reducing VOC emissions, the waterborne conversion of 2K intermediate coat is a very good choice.

[0003] Due to the characteristics of waterborne coatings themselves, waterborne intermediate coats have the following difficulties:

[0004] 1. The latent heat of vaporization of water in waterborne intermediate coats is large, and it is greatly affected by air humidity. It is easy to have problems such as slow drying and sagging, and when the air humidity is high, it has a greater impact on its drying speed, and has a negative impact on the primer (substrate), corresponding waterborne or oil-based topcoat, and the intermediate coat itself, such as interlayer adhesion, sandability, filling property, etc.

[0005] 2. The surface tension of water in waterborne repair intermediate coats is high, which requires high construction processes and substrates. It is more likely to have problems such as cratering, and problems such as insufficient filling and sealing; for systems with high performance requirements, generally oil-based primers or oil-based topcoats are used. If the waterborne intermediate coat has a low tolerance to the primer or topcoat of this system due to improper construction, it is inevitable that the fullness, gloss, and leveling of the entire system are often difficult to meet high requirements.

[0006] 3. For systems with high performance requirements, generally oil-based primers or oil-based topcoats are used. If the waterborne intermediate coat has a low tolerance to the primer or topcoat of this system due to improper construction, it is inevitable that the fullness, gloss, and leveling of the entire system are often difficult to meet high requirements.

[0007] For 2K waterborne intermediate coats, due to the requirements for low-temperature curing agents and weather resistance, the system can only choose waterborne 2K polyurethane. From a chemical structure perspective, the 2K waterborne polyurethane system mainly has the following reactions:

[0008] First, as Figure 2 shown, the reaction of isocyanate and active hydroxyl groups in the resin to form polyurethane is the main reaction.

[0009] Second, as Figure 3 shown, the reaction of isocyanate and carboxyl groups produces amide and CO 2 , which is an unwanted side reaction.

[0010] Third, as Figure 4 shown, the reaction of isocyanate and water produces urea and CO2 , is an unwanted side reaction.

[0011] The first reaction is the main reaction, which is the desired reaction direction. The second and third reactions, especially the third reaction, are side reactions that can cause defects or performance deficiencies and should be avoided as much as possible.

[0012] Ordinary isocyanate curing agents are relatively hydrophobic. When mixed with the main paint, the curing agent cannot be well dispersed in the water phase, resulting in uneven crosslinking density distribution of the paint film, and defects such as cratering, poor local interlayer adhesion, and poor sanding performance are likely to occur. However, isocyanates modified with polyethers or sulfonates will increase hydrophilicity and improve the dispersion state of the isocyanate in water after mixing with the main paint, and it is easy to obtain a uniformly crosslinked paint film. However, due to the introduction of the hydrophilic structure of the curing agent, it is easy to cause a decrease in the water resistance and chemical resistance of the paint film. At the same time, when the paint film is relatively thick, pinhole defects are likely to occur, thus affecting the surface effect of the corresponding topcoat.

[0013] In view of this, it is necessary to invent a high-performance waterborne two-component repair intermediate coat with good drying speed, sanding performance, filling performance, and constructability. Moreover, the overall paint film system has excellent water resistance and chemical resistance. Summary of the Invention

[0014] The purpose of the present invention is to provide a high-performance waterborne intermediate coat and its preparation method to solve the problems raised in the above background technology.

[0015] To achieve the above purpose, the present invention provides the following technical solution: A high-performance waterborne intermediate coat includes a topcoat and a curing agent.

[0016] The topcoat includes the following components in parts by weight:

[0017] 30 - 50 parts of waterborne hydroxyl acrylic resin, 0.3 - 1.1 parts of leveling agent, 0.3 - 1 part of defoaming agent, 1 - 4 parts of dispersant, 20 - 40 parts of filler, 10 - 20 parts of pigment, 5 - 15 parts of deionized water.

[0018] The curing agent includes the following components in parts by weight:

[0019] 55 - 75 parts of isocyanate, 25 - 45 parts of organic solvent, 0.01 - 1 part of water scavenger.

[0020] The intermediate coat further includes the following component in parts by weight:

[0021] 0.3 - 0.8 parts of thickener.

[0022] The curing agent further includes the following component in parts by weight:

[0023] Water removing agent: 0.01 - 1 part.

[0024] Preferably in the present invention, the solid content of the aqueous hydroxyl acrylic resin is 40% - 50%, the hydroxyl content is 3% - 6%, and the acid value is 15 - 30 mgKOH / g; preferably, the hydroxyl content is 3.5% - 5%, and the acid value is 20 - 25 mgKOH / g.

[0025] Preferably in the present invention, the aqueous hydroxyl acrylic resin is selected from at least one of Macrynal VSM 2521W aqueous acrylic resin (purchased from Axalta Coating Systems (Shanghai) Co., Ltd., solid content 42%, hydroxyl value 4.2%), Macrynal SM 6810 aqueous acrylic resin (purchased from Axalta Coating Systems (Shanghai) Co., Ltd., solid content 42%, hydroxyl value 4.1%), Neocryl XK-540 aqueous acrylic resin (purchased from DSM Group, solid content 40%, hydroxyl value 4.2%), Neocryl XK-555 aqueous acrylic resin (purchased from DSM Group, solid content 40%, hydroxyl value 5.0%), Bayhydrol A2470 aqueous acrylic resin (purchased from Covestro (Shanghai) Management Co., Ltd., solid content 45%, hydroxyl value 3.9%), Bayhydrol A2646 aqueous acrylic resin (purchased from Covestro (Shanghai) Management Co., Ltd., solid content 50%, hydroxyl value 3.8%), Bayhydrol A2601 aqueous acrylic resin (purchased from Covestro (Shanghai) Management Co., Ltd., solid content 45%, hydroxyl value 3.9%), Antkote2042 aqueous acrylic resin (purchased from Wanhua Chemical Group Co., Ltd., solid content 46%, hydroxyl value 3.3%), Setaqua 6513 aqueous acrylic resin (purchased from Axalta Coating Systems (Shanghai) Co., Ltd., solid content 42%, hydroxyl value 4.2%), and Setaqua 6514 aqueous acrylic resin (purchased from Axalta Coating Systems (Shanghai) Co., Ltd., solid content 40%, hydroxyl value 3.5%).

[0026] Preferably in the present invention, the leveling agent is selected from at least one of BYK 346 silicone wetting agent (purchased from BYK Chemie), BYK 348 silicone wetting agent (purchased from BYK Chemie), BYK 331 silicone leveling agent (purchased from BYK Chemie), BYK 333 silicone leveling agent (purchased from BYK Chemie), Hydropalat WE3220 wetting agent (purchased from BASF (China) Co., Ltd.), Hydropalat wetting agent (purchased from BASF (China) Co., Ltd.), Surfynol 440 wetting agent (purchased from Air Products and Chemicals, Inc.), EnviroGem AD01 wetting agent (purchased from Air Products and Chemicals, Inc.), Tego Wet 280 wetting agent (purchased from Evonik Industries AG), and Tego Wet 500 wetting agent (purchased from Evonik Industries AG).

[0027] Preferably in the present invention, the defoaming agent is selected from at least one of BYK 011 defoaming agent (purchased from BYK Chemie), BYK 024 defoaming agent (purchased from BYK Chemie), BYK 093 defoaming agent (purchased from BYK Chemie), Foamstar ED2522 (purchased from BASF (China) Co., Ltd.), Foamstar ST 2438 (purchased from BASF (China) Co., Ltd.), Airex 904W (purchased from Evonik Industries AG), and Surfynol 104 defoaming agent (purchased from Air Products and Chemicals, Inc.).

[0028] Preferably in the present invention, the dispersant is selected from dispersant (purchased from BYK Chemie), dispersant (purchased from BYK Chemie), dispersant (purchased from BYK Chemie), Dispex ULTRA PA 4550 dispersant (purchased from BASF (China) Co., Ltd.), Dispex ULTRA PX 4575 dispersant (purchased from BASF (China) Co., Ltd.), Additol VXW 6208 / 60 dispersant (purchased from Axalta Coating Systems (Shanghai) Co., Ltd.), TEGO Dispers 750W dispersant (purchased from Evonik Industries AG), TEGO Dispers 757W dispersant (purchased from Evonik Industries AG), ZetaSperse 1200 dispersant (purchased from Air Products and Chemicals, Inc.), and ZetaSperse 3600 dispersant (purchased from Air Products and Chemicals, Inc.).

[0029] Preferably in the present invention, the pigment is selected from at least one of commonly used automotive pigments such as TIPAQUE CR-97 (purchased from Ishihara Sangyo Co., Ltd.), TIPURE R706 (purchased from DuPont China Group Co., Ltd.), titanium dioxide R-996 (purchased from Longmang Group), MITSUBISHICARBON BLACK MA-100 (purchased from Mitsubishi Chemical Holdings Corporation), RAVEN 5000 carbon black (purchased from Columbian Chemicals Company), BAYFERROX OXIDE YELLOW 3920 (purchased from LANXESS Chemical (Shanghai) Co., Ltd.), HELIOGEN BLUE6870 (purchased from BASF (China) Co., Ltd.).

[0030] Preferably in the present invention, the thickener is selected from at least one of ACRYSOL RM-5000 (purchased from The Dow Chemical Company), ACRYSOL RM-8W (purchased from The Dow Chemical Company), BENTONE DE (purchased from Elementis Specialties Inc.), RHEOLATE299 (purchased from Elementis Specialties Inc.), AEROSIL R972 (purchased from Evonik Industries AG), BYK 420 (purchased from BYK-Chemie GmbH), Additol VXW 6388 (purchased from Axalta Coating Systems (Shanghai) Co., Ltd.).

[0031] Preferably in the present invention, the isocyanate is a weather-resistant isocyanate; preferably at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; more preferably Desmodur N3600 isocyanate (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 100%, NCO content is 23.0%), Desmodur N3900 isocyanate (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 100%, NCO content is 23.0%), Bayhydur 304 (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 100%, NCO content is 18.2%), Bayhydur 401-70 (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 70%, NCO content is 9.4%), Bayhydur XP2655 (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 100%, NCO content is 20.8%), Bayhydur XP2547 (purchased from Covestro (Shanghai) Management Co., Ltd., solid content is 100%, NCO content is 22.5%), Duranate TPA100 isocyanate (purchased from Asahi Kasei Corporation, solid content is 100%, NCO content is 23.0%), Tolonate HDT LV isocyanate (purchased from Perstorp (Shanghai) Chemical Products Trading Co., Ltd., solid content is 100%, NCO content is 23.0%), Tolonate HDT LV2 isocyanate (purchased from Perstorp (Shanghai) Chemical Products Trading Co., Ltd., solid content is 100%, NCO content is 23.0%), Tolonate HDT-100 isocyanate (purchased from Perstorp (Shanghai) Chemical Products Trading Co., Ltd., solid content is 100%, NCO content is 23.0%), Coranate HXLV isocyanate (purchased from Nippon Polyurethane Industry Co., Ltd., solid content is 100%, NCO content is 23.0%), Esaqua X D 401 (purchased from Conry (Shanghai) Trading Co., Ltd., solid content is 85%, NCO content is 15.8%), Aquolin 161 (purchased from Wanhua Chemical Group Co., Ltd., solid content is 100%, NCO content is 18.5%), Aquolin 268 (purchased from Wanhua Chemical Group Co., Ltd., solid content is 100%, NCO content is 20.5%).

[0032] Preferably in the present invention, the water scavenger is selected from at least one of ADDITIVE TI monofunctional isocyanate (purchased from OMG Chemical) and ADDITIVE OF water scavenger (purchased from OMG Chemical).

[0033] The solvent is selected from at least one of propylene glycol methyl ether acetate, butyl 3-methoxypropionate, ethylene glycol butyl ether acetate, ethylene glycol diacetate, propylene glycol diacetate, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0034] In summary, another aspect of the present invention provides a method for preparing a high-performance waterborne intermediate coating, comprising the following steps:

[0035] Add waterborne hydroxyl acrylic resin, dispersant, leveling agent, defoaming agent, and pigment to water, grind to a qualified fineness, add the remaining leveling agent, the remaining defoaming agent, and the remaining part of water under stirring, add a thickener as needed, and adjust the viscosity to be qualified with water; stir evenly and filter to obtain a waterborne intermediate coating.

[0036] Under nitrogen protection, control the moisture content of the solvent to reach the standard, add a water remover as needed, add isocyanate and stir evenly to obtain a curing agent, and obtain the high-performance waterborne intermediate coating.

[0037] Another aspect of the present invention provides a use of the high-performance waterborne two-component intermediate coating composition for automotive paints.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The high-performance waterborne intermediate coating composition obtained by the present invention has fast curing at low temperature, is easy to sand, and has good film properties such as filling property, hardness, water resistance, chemical resistance, and adhesion of the composite coating, as well as good anti-sagging property and limit construction of prickly heat. And it can make the oily or waterborne topcoat have a better surface effect in the composite coating.

[0039] The intermediate coating composition provided by the present invention has good construction performance and film properties, and at the same time has extremely low VOC. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic flow chart of the present invention;

[0041] Figure 2 is a schematic diagram of the reaction of isocyanate and active hydroxyl groups in the resin to form polyurethane;

[0042] Figure 3 is the reaction of isocyanate and carboxyl group to produce amide and CO 2 schematic diagram;

[0043] Figure 4 is the reaction of isocyanate and water in the present invention to form urea and CO 2 schematic diagram. DETAILED DESCRIPTION OF THE INVENTION

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] In the case of clarifying and explaining the purpose of the present invention through the following embodiments, the components of the composition are explained with weight parts as the general standard. Without special instructions, for the sake of simplicity, the "parts" mentioned in the embodiments of the present invention have the same meaning as weight parts.

[0046] Example 1

[0047] As Figure 1 shown, in a container with a stirrer, add 2 parts of deionized water, and add 2.5 parts of dispersant, 11 parts of Neocryl XK-540 acrylic resin, 0.2 parts of BYK 024 defoamer, 0.2 parts of BYK 346 silicone wetting agent, 30 parts of TIPURE R706, 0.5 parts of iron oxide black, 9 parts of talcum powder, 10 parts of calcium carbonate and grind to a fineness of ≤5 μm; add 30 parts of Neocryl XK-540 acrylic resin, 0.1 part of BYK 331 silicone leveling agent, 0.7 part of BYK 093 defoamer, 0.5 part of RHEOLATE 299 thickener, and 3 parts of deionized water under stirring. Stir evenly and filter through a 10-micron filter to obtain the intermediate coat.

[0048] Under nitrogen protection, control the water content of 45 parts of propylene glycol methyl ether acetate solvent to reach the standard, and add 55 parts of Bayhydur XP2655 isocyanate and stir evenly to obtain the curing agent; obtain the high-performance waterborne two-component intermediate coat composition.

[0049] During use, mix the topcoat and the curing agent at a volume ratio of 5:1, stir evenly, and then adjust to the construction viscosity with deionized water or the specified waterborne diluent.

[0050] This topcoat composition is used as automotive paint, having good appearance, construction performance and film performance, and cooperating with the primer and topcoat to provide a perfect appearance film for the car.

[0051] Example 2

[0052] As Figure 1As shown in the figure, in a container equipped with a stirrer, 9 parts of deionized water are added. Under stirring, 2 parts of EFKA 4550 dispersant, 0.2 part of Foamstar ST 2438 defoamer, 0.2 part of Tego Wet 500 wetting agent, 0.2 part of Borchi Gen WNS, 0.5 part of iron oxide black, 12 parts of Longmang R-996 rutile titanium dioxide, 18 parts of calcium carbonate, 9 parts of talcum powder, and 15 parts of Antkote 2042 waterborne acrylic resin are added. It is ground by sanding until the fineness is ≤5 μm; under stirring, 39 parts of Macrynal SM 6810 acrylic resin, 0.4 part of Surfynol 440 wetting agent, 0.4 part of Tego Wet 280 wetting agent, 0.5 part of Surfynol 104 defoamer, and 9 parts of deionized water are added. Stir evenly, filter through a 10-micron filter screen to obtain a waterborne intermediate coat.

[0053] Under nitrogen protection, 0.5 part of ADDITIVE TI monofunctional isocyanate is added to 40 parts of propylene glycol methyl ether acetate solvent, and the moisture content of the solution is controlled to be ≤0.05%. 59.5 parts of 5500 isocyanate are added and stirred evenly to obtain a curing agent, and the high-performance waterborne two-component topcoat composition is obtained.

[0054] When in use, the topcoat and the curing agent are mixed at a volume ratio of 5:1, stirred evenly, and then adjusted to the construction viscosity with deionized water or a specified waterborne diluent.

[0055] This intermediate coat composition is used as an automotive intermediate coat, has construction performance and film performance, and cooperates with the primer and topcoat to provide a perfect appearance film for the car.

[0056] The results of the comparative evaluation of the coating compositions of Example 2 and Comparative Example 1 are shown in Table 1. Comparative Example 1 is the 620-1 oil-based intermediate coat of the company's conventional solvent-based product. Due to the lack of waterborne intermediate coats on the market, the specific grades and manufacturers of competing products cannot be given. The contents of the comparative evaluation include: VOC, sanding property, DOI of the composite coating, impact resistance, flexibility, adhesion, water resistance of the composite coating, and adhesion of the composite coating. Comparative Example 1 and the supporting curing agent LACS2K curing agent (standard) are mixed at a weight ratio of 5:1, stirred evenly, and then the viscosity is adjusted to 18-20 seconds (coat-4 cup, 25 °C) with LACS L102 diluent (please give the specific dosage, specific name); for other properties, it is necessary to spray to the sample board according to the film thickness requirement with a SATA spray gun, and perform performance tests after drying.

[0057] The evaluation methods are as follows:

[0058] VOC: Test VOC according to 10.3 of GB / T 23986-2009.

[0059] DOI: Evaluated using BYK - Gardner AW - 4840.

[0060] Hardness: Tested for pencil hardness according to GB / T 6739 - 2006.

[0061] Impact resistance: Evaluated according to GB / T 1732 - 93.

[0062] Flexibility: Evaluated according to GB / T 1731 - 93.

[0063] Adhesion: Conducted a cross - cut adhesion test for 100 grids according to the standard of GB / T 9286 - 88 using the cross - cut method.

[0064] Water resistance: According to the standard of GB / T 5209 - 85, Examples 6, Comparative Examples 1 and 2 were soaked at 40 °C for 240 hours. After recovery for 1 hour, the appearance of the paint film was observed, and the grade was divided according to the size and density of the bubbles on the paint film surface.

[0065] Adhesion of composite coating: Conducted a cross - cut adhesion test for 100 grids according to the standard of GB / T 9286 - 88 using the cross - cut method.

[0066] Table 1

[0067]

[0068] The explanations of each performance in Table 1 are as follows:

[0069] 1. VOC: The amount of volatile organic solvents in the paint during construction, the lower the better;

[0070] 2. DOI: The fullness and distinctness of image of the paint film, required to be ≥80, the higher the better;

[0071] 3. Hardness: Required to be ≥H, using Mitsubishi pencils, the higher the better, from low to high in sequence: 6B<5B<4B<3B<2B<B<HB<F<H<2H<3H<4H<5H<6H<7H<8H<9H;

[0072] 4. Impact resistance: Required to be ≥50 kg*cm, the ability of the paint film to withstand the impact of heavy objects, the larger the value the better;

[0073] 5. Flexibility: Required to be ≤2 mm, the ability of the paint film to resist bending, the smaller the value the better;

[0074] 6. Adhesion: The bonding force between the topcoat and the substrate or with the lower - layer coating, from high to low in sequence: Gt5<Gt4<Gt3<Gt2<Gt1<Gt0;

[0075] 7. Abrasiveness: Under the same pressure, the same sandpaper, the same number of sanding times and sanding amplitude, the greater the mass loss, the better the abrasiveness.

[0076] 7. Water resistance: The tolerance of the paint film to water, with no change in the paint film being better.

[0077] 8. Adhesion of composite coating: The bonding force between the coating and the substrate and between coatings, in descending order is Gt5 < Gt4 < Gt3 < Gt2 < Gt1 < Gt0.

[0078] Considering all the properties comprehensively, in Example 2 of the present invention, when the VOC is lower than that of Comparative Example 1, the comprehensive properties including VOC, DOI of composite coating, hardness, abrasiveness, impact resistance, flexibility, adhesion, water resistance, adhesion of composite coating are basically close to the level of current solvent-based products. The present invention well solves the problem that existing products cannot simultaneously take into account low VOC and high performance, which is a major breakthrough for waterborne intermediate coatings for transportation vehicles and equipment.

[0079] The present invention provides a use of the high-performance waterborne two-component intermediate coating composition for automotive paints.

[0080] This topcoat composition is used as an intermediate coat for automotive paints. Sprayed with a conventional air spray gun, it has good abrasiveness, filling property, application performance and film properties. Cooperating with the primer and topcoat, it provides a perfect appearance film for the automobile.

[0081] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high performance water-based mid-coat, characterized by: Includes topcoat and curing agent; The topcoat comprises the following components in parts by weight: 30-50 parts of water-based hydroxy acrylic resin, 0.3-1.1 parts of leveling agent, 0.3-1 parts of defoaming agent, 1-4 parts of dispersant, 20-40 parts of filler, 10-20 parts of pigment, 5-15 parts of deionized water; The curing agent comprises the following components in parts by weight: 55-75 parts of isocyanate, 25-45 parts of organic solvent, 0.01-1 parts of water remover; The mid-coat also includes the following components in parts by weight: Thickener 0.3-0.8 parts; The curing agent also includes the following components in parts by weight: Dewatering agent 0.01-1 part.

2. A high performance waterborne mid-coat according to claim 1, characterized in that: The water-based hydroxy acrylic resin has a solid content of 40%-50%, a hydroxy content of 3%-6%, and an acid value of 15-30 mgKOH / g; preferably, the hydroxy content is 3.5%-5%, and the acid value is 20-25 mgKOH / g.

3. A method for preparing a high-performance water-based mid-coat as described in claims 1-2, characterized in that: The following steps are involved: Add water-based hydroxy acrylic resin, dispersant, leveling agent, defoamer, and pigment to water, sand grind to qualified fineness, add the remaining leveling agent, remaining defoamer, and remaining water under stirring, add thickener as needed, and adjust the viscosity to qualified with water; stir evenly and filter to obtain a water-based mid-coat; Under nitrogen protection, the water content of the solvent is controlled to reach a standard, a dehydrating agent is added as needed, isocyanate is added and stirred evenly to obtain a curing agent, thereby obtaining the high-performance water-based two-component mid-coat composition.

4. Use of the high-performance water-based mid-coat as described in claims 1-2 or the mid-coat obtained by the preparation method as described in claim 3 as an automotive paint.

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