A water-based two-component polyurethane coating and its preparation method and application

Abstract

The present invention belongs to the technical field of coating preparation, and specifically relates to a water-based two-component polyurethane coating and a preparation method and application thereof. The water-based two-component polyurethane coating is composed of component A and component B; the component A is composed of deionized water, water-based polyurethane dispersion, titanium dioxide, polyacrylate, anti-rust pigment, film-forming aid, 2-amino-2-methyl-1-propanol, wetting agent, dispersant, defoamer, leveling agent, and anti-settling agent; the component B is composed of hydrophilic polyisocyanate curing agent and propylene glycol methyl ether acetate. The water-based two-component polyurethane coating provided by the present invention has a fast drying speed, good leveling, adhesion and storage stability, and the obtained coating film has no defects such as orange peel and shrinkage cavities, making the coating film smoother and flatter. At the same time, the coating performs well in mechanical properties, chemical resistance and construction convenience, and can provide long-term and reliable protection for metals and other substrates.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation, and specifically relates to a water-based two-component polyurethane coating and a preparation method and application thereof. Background Art

[0002] Polyurethane coatings are widely used in the fields of automobiles, construction, industrial equipment and furniture manufacturing due to their excellent mechanical properties, weather resistance and chemical resistance. This type of coating is usually composed of a polyisocyanate component and a polyol component, which are mixed in a certain proportion before use. The polyurethane chain is formed by the reaction of the isocyanate group (-NCO) and the hydroxyl group (-OH), and then cured into a film. However, since the coating performance of single-component polyurethane coatings is not ideal, and in actual applications, in order to meet the needs of high strength, post-treatments such as baking are often used to improve the cross-linking degree of the film. Since these post-treatments greatly limit its scope of application, the development and research of two-component polyurethane coatings has become very active.

[0003] However, traditional two-component polyurethane coatings have some obvious disadvantages, mainly because their formula contains a large amount of organic solvents, such as xylene, butyl acetate, etc. These organic solvents not only increase the cost of the coating, but also bring environmental pollution and safety hazards. With the continuous improvement of environmental protection awareness, the development of environmentally friendly coatings with low VOC (volatile organic compounds) emissions has become an inevitable trend in the development of the industry.

[0004] Development of waterborne two-component polyurethane coatings Waterborne two-component polyurethane coatings have gradually become an effective alternative to traditional solvent-based coatings with their advantages such as low VOC emissions, good environmental performance and convenient construction. The solvent in waterborne two-component polyurethane coatings is replaced by water, which greatly reduces VOC emissions. However, waterborne two-component polyurethane coatings still face some challenges in practical applications. For example, the drying time of waterborne coatings is usually longer, which affects the construction efficiency and the early performance of the coating; and waterborne coatings are often not as good as solvent-based coatings in terms of water resistance and chemical resistance, especially in extreme environments, and the coating is prone to blistering and shedding. The coating is easily eroded, affecting its protective performance; waterborne coatings are prone to stratification and precipitation during storage, affecting their performance; waterborne coatings may not have the same adhesion on some substrates as solvent-based coatings, especially on smooth surfaces such as metals and plastics.

[0005] Therefore, it is necessary to provide a water-based two-component polyurethane coating that can significantly improve the drying speed, water resistance, chemical resistance and adhesion of the coating. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a water-based two-component polyurethane coating and a preparation method and application thereof.

[0007] The technical solution of the present invention is:

[0008] A water-based two-component polyurethane coating, composed of component A and component B in a weight ratio of 6 to 8:1; the component A includes the following raw materials in parts by weight:

[0009] 8-15 parts of deionized water, 40-50 parts of waterborne polyurethane dispersion, 20-25 parts of titanium dioxide, 8-12 parts of polyacrylate, 8-10 parts of anti-rust pigment, 3-5 parts of film-forming aid, 1-3 parts of 2-amino-2-methyl-1-propanol, 1-2 parts of wetting agent, 0.8-1.6 parts of dispersant, 0.4-0.8 parts of defoaming agent, 0.2-0.6 parts of leveling agent, 0.2-0.5 parts of anti-settling agent;

[0010] The B component includes the following raw materials in parts by weight:

[0011] 30-40 parts of hydrophilic polyisocyanate curing agent and 6-10 parts of propylene glycol methyl ether acetate.

[0012] Furthermore, the A component is composed of the following raw materials in parts by weight:

[0013] 12 parts of deionized water, 45 parts of waterborne polyurethane dispersion, 22 parts of titanium dioxide, 10 parts of polyacrylate, 9 parts of anti-rust pigment, 4 parts of film-forming aid, 2 parts of 2-amino-2-methyl-1-propanol, 1.5 parts of wetting agent, 1.2 parts of dispersant, 0.6 parts of defoaming agent, 0.4 parts of leveling agent, 0.3 parts of anti-settling agent;

[0014] The B component is composed of the following raw materials in parts by weight:

[0015] 35 parts of hydrophilic polyisocyanate curing agent and 8 parts of propylene glycol methyl ether acetate.

[0016] Furthermore, the aqueous polyurethane dispersion is Bayhydrol U XP 2750 produced by Covestro.

[0017] Furthermore, the film-forming aid is composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 1-3:2-5:3, preferably 2:4:3.

[0018] Furthermore, the wetting agent is Tuyile superwet-320.

[0019] Furthermore, the dispersant is composed of BYK 190 and TEGO 270 in a weight ratio of 1 to 3:1.

[0020] Furthermore, the defoaming agent is a polysiloxane-polyether copolymer, preferably TEGO Foamex 825.

[0021] Furthermore, the anti-rust pigment is aluminum tripolyphosphate; and the anti-settling agent is fumed silica.

[0022] Furthermore, the leveling agent is BYKETOL-AQ.

[0023] Furthermore, the hydrophilic polyisocyanate curing agent is Covestro XP2655.

[0024] The present invention also provides a method for preparing the above-mentioned water-based two-component polyurethane coating, comprising the following steps:

[0025] (1) At a speed of 600 to 900 r / min, deionized water, dispersant, wetting agent, defoamer, anti-settling agent, and leveling agent are added respectively, and then the speed is increased to 2000 to 2400 r / min, titanium dioxide and anti-rust pigment are added, and stirring is continued for 30 to 50 minutes, and then grinding is performed with a sand grinder to a particle size of 10 to 25 μm to obtain a color paste;

[0026] (2) taking out the color paste obtained in step (1), adding an aqueous polyurethane dispersion, polyacrylate, a film-forming aid, and 2-amino-2-methyl-1-propanol at a rotation speed of 1000 to 1200 r / min, and continuing to stir for 15 to 20 minutes to obtain component A;

[0027] (3) mixing the polyisocyanate curing agent and propylene glycol methyl ether acetate uniformly to obtain component B;

[0028] (4) Adding the component B obtained in step (3) to the component A obtained in step (2), stirring at a speed of 200 to 400 r / min for 10 to 15 minutes, thereby obtaining a water-based two-component polyurethane coating.

[0029] The water-based two-component polyurethane coating provided by the present invention is used in a proportion of component A and component B to form a high-performance, environmentally friendly coating system. The water-based polyurethane dispersion, polyacrylate, film-forming substance, pigment and various additives provided by component A ensure the basic performance and excellent appearance of the coating; while component B is used in combination with component A through the cross-linking reaction of a hydrophilic polyisocyanate curing agent, which significantly improves the drying speed, water resistance, chemical resistance, adhesion and storage stability of the coating, and can form a tough, wear-resistant and corrosion-resistant protective film on the metal surface, which is suitable for protective coating in various industrial and construction fields.

[0030] Among them, in component A, through the synergistic effect of waterborne polyurethane dispersion and polyacrylate, combined with the cross-linking reaction of hydrophilic polyisocyanate curing agent, the coating can form a protective film with high hardness and good flexibility on the metal surface. This balance allows the coating to remain intact under mechanical impact and friction, and not crack or peel off when the substrate is slightly deformed, providing excellent physical protection.

[0031] The added film-forming aid composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 1 to 3:2 to 5:3 can significantly improve the film-forming performance and overall quality of the coating. Through the different solubility and volatility of each component in the film-forming aid, the three components can more effectively reduce the minimum film-forming temperature through synergistic action, effectively expand the construction temperature range of the coating of the present invention, and improve the possibility of construction under low temperature environment. At the same time, tributyl citrate and CAB, as slower volatile film-forming aids, can maintain the softness of the coating for a long time, while BASF Lusolvan FBH, as a fast volatile film-forming aid, can quickly reduce the MFT in the early stage, ensure the rapid formation of the coating, effectively shorten the drying time, and speed up the construction progress; at the same time, after the film-forming aid is added to the A component of the present invention, the fluidity of the coating can be improved, which is helpful to improve the storage stability of the coating and prevent the occurrence of agglomeration, sedimentation and gelation during transportation and storage.

[0032] Furthermore, in component A, the selection of dispersant also has a very important influence on the quality of the water-based two-component polyurethane coating prepared by the present invention. The degree of dispersion of the pigment in the coating will directly lead to different appearances of the paint film. The dispersant added in the present invention, which is composed of BYK 190 and TEGO 270 in a weight ratio of 1 to 3:1, can make the pigment particles evenly suspended in the water phase system, and use the stirring system to depolymerize the pigment from the collective state into the initial particle state, and evenly suspend it in the system, forming a suitable stable adsorption layer on the surface of the pigment, generating sufficient potential energy to prevent the particles from reaggregating, so that the system has the best stability.

[0033] Compared with the prior art, the water-based two-component polyurethane coating provided by the present invention has the following advantages:

[0034] (1) The water-based two-component polyurethane coating provided by the present invention forms a high-performance, environmentally friendly coating system through the scientific ratio of the substances in component A and component B. The coating has excellent mechanical properties, chemical resistance, water resistance and construction convenience, and can provide long-term and reliable protection for metals and other substrates.

[0035] (2) The water-based two-component polyurethane coating provided by the present invention has a fast drying speed, which improves the construction efficiency. At the same time, it can reduce the surface tension of the coating and improve its fluidity and leveling properties, which helps to eliminate defects such as orange peel and shrinkage holes on the surface of the coating film, making the coating film smoother and flatter. At the same time, good leveling properties can also give the coating a better appearance quality

[0036] (3) The water-based two-component polyurethane coating provided by the present invention has excellent weather resistance and chemical resistance, which significantly increases its service life, reduces the need for frequent maintenance and recoating, and reduces long-term maintenance costs. Its excellent adhesion and compatibility enable it to form a firm protective layer on the surface of different materials, further improving its economic efficiency. DETAILED DESCRIPTION

[0037] The present invention is further illustrated below through the description of specific implementation methods, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0038] In the following examples and comparative examples, reagents not otherwise specified are conventional reagents and can be purchased from conventional reagent production and sales companies. The methods used, unless otherwise specified, are all prior art. Information such as some raw material manufacturers is shown in Table 1:

[0039] Table 1

[0040]

[0041] Example 1

[0042] A water-based two-component polyurethane coating, consisting of component A and component B, wherein component A consists of the following raw materials in parts by weight:

[0043] 8 parts of deionized water, 40 parts of Covestro Bayhydrol U XP 2750 waterborne polyurethane dispersion, 20 parts of titanium dioxide, 8 parts of polyacrylate, 8 parts of aluminum tripolyphosphate, 3 parts of film-forming aid, 1 part of 2-amino-2-methyl-1-propanol, 1 part of Tuyile superwet-320 wetting agent, 0.8 parts of dispersant, 0.4 parts of TEGO Foamex 825 defoamer, 0.2 parts of BYKETOL-AQ leveling agent, and 0.2 parts of fumed silica;

[0044] The B component is composed of the following raw materials in parts by weight:

[0045] 30 parts of Covestro XP2655 hydrophilic polyisocyanate curing agent and 6 parts of propylene glycol methyl ether acetate.

[0046] The film-forming aid is composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 1:5:3.

[0047] The dispersant is composed of BYK 190 and TEGO 270 in a weight ratio of 1:1.

[0048] The preparation method of the water-based two-component polyurethane coating comprises the following steps:

[0049] (1) At a speed of 600 r / min, deionized water, dispersant, wetting agent, TEGO Foamex 825 defoamer, fumed silica, and leveling agent were added respectively, and then the speed was increased to 2000 r / min, titanium dioxide and aluminum tripolyphosphate were added, and stirring was continued for 50 minutes, and then grinding was performed with a sand grinder to a particle size of 10 to 25 μm to obtain a color paste;

[0050] (2) taking out the color paste obtained in step (1), adding Covestro Bayhydrol UXP 2750 waterborne polyurethane dispersion, polyacrylate, film-forming aid, and 2-amino-2-methyl-1-propanol at a speed of 1000 r / min, and continuing to stir for 20 minutes to obtain component A;

[0051] (3) Covestro XP2655 hydrophilic polyisocyanate curing agent and propylene glycol methyl ether acetate are stirred and mixed to obtain component B;

[0052] (4) Adding component B obtained in step (3) to component A obtained in step (2), wherein component A and component B are composed in a weight ratio of 6:1, and stirring at a speed of 200 r / min for 15 minutes to obtain a water-based two-component polyurethane coating.

[0053] Example 2

[0054] A water-based two-component polyurethane coating, consisting of component A and component B, wherein component A consists of the following raw materials in parts by weight:

[0055] The A component is composed of the following raw materials in parts by weight:

[0056] 12 parts of deionized water, 45 parts of waterborne polyurethane dispersion, 22 parts of titanium dioxide, 10 parts of polyacrylate, 9 parts of anti-rust pigment, 4 parts of film-forming aid, 2 parts of 2-amino-2-methyl-1-propanol, 1.5 parts of wetting agent, 1.2 parts of dispersant, 0.6 parts of defoaming agent, 0.4 parts of leveling agent, 0.3 parts of anti-settling agent;

[0057] The B component is composed of the following raw materials in parts by weight:

[0058] 35 parts of hydrophilic polyisocyanate curing agent and 8 parts of propylene glycol methyl ether acetate.

[0059] The film-forming aid is composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 2:4:3.

[0060] The dispersant is composed of BYK 190 and TEGO 270 in a weight ratio of 2:1.

[0061] The preparation method of the water-based two-component polyurethane coating comprises the following steps:

[0062] (1) At a speed of 800 r / min, deionized water, dispersant, wetting agent, TEGO Foamex 825 defoamer, fumed silica, and leveling agent were added respectively, and then the speed was increased to 2200 r / min, titanium dioxide and aluminum tripolyphosphate were added, and stirring was continued for 40 minutes, and then grinding was performed with a sand grinder to a particle size of 10 to 25 μm to obtain a color paste;

[0063] (2) taking out the color paste obtained in step (1), adding Covestro Bayhydrol UXP 2750 waterborne polyurethane dispersion, polyacrylate, film-forming aid, and 2-amino-2-methyl-1-propanol at a rotation speed of 1100 r / min, and continuing to stir for 18 minutes to obtain component A;

[0064] (3) Covestro XP2655 hydrophilic polyisocyanate curing agent and propylene glycol methyl ether acetate are stirred and mixed to obtain component B;

[0065] (4) Adding component B obtained in step (3) to component A obtained in step (2), wherein component A and component B are composed in a weight ratio of 7:1, and stirring at a speed of 300 r / min for 12 minutes to obtain a water-based two-component polyurethane coating.

[0066] Example 3

[0067] A water-based two-component polyurethane coating, consisting of component A and component B, wherein component A consists of the following raw materials in parts by weight:

[0068] 15 parts of deionized water, 50 parts of Bayhydrol U XP 2750 waterborne polyurethane dispersion from Covestro, 25 parts of titanium dioxide, 12 parts of polyacrylate, 10 parts of aluminum tripolyphosphate, 5 parts of film-forming aid, 3 parts of 2-amino-2-methyl-1-propanol, 2 parts of superwet-320 wetting agent from Tuile, 1.6 parts of dispersant, 0.8 parts of TEGO Foamex 825 defoamer, 0.6 parts of BYKETOL-AQ leveling agent, and 0.5 parts of fumed silica;

[0069] The B component is composed of the following raw materials in parts by weight:

[0070] 40 parts of Covestro XP2655 hydrophilic polyisocyanate curing agent and 10 parts of propylene glycol methyl ether acetate.

[0071] The film-forming aid is composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 3:2:3.

[0072] The dispersant is composed of BYK 190 and TEGO 270 in a weight ratio of 3:1.

[0073] The preparation method of the water-based two-component polyurethane coating comprises the following steps:

[0074] (1) At a speed of 900 r / min, deionized water, dispersant, wetting agent, TEGO Foamex 825 defoamer, fumed silica, and leveling agent were added respectively, and then the speed was increased to 2400 r / min, titanium dioxide and aluminum tripolyphosphate were added, and stirring was continued for 30 minutes, and then grinding was performed with a sand grinder to a particle size of 10 to 25 μm to obtain a color paste;

[0075] (2) taking out the color paste obtained in step (1), adding Covestro Bayhydrol UXP 2750 waterborne polyurethane dispersion, polyacrylate, film-forming aid, and 2-amino-2-methyl-1-propanol at a speed of 1200 r / min, and continuing to stir for 15 minutes to obtain component A;

[0076] (3) Covestro XP2655 hydrophilic polyisocyanate curing agent and propylene glycol methyl ether acetate are stirred and mixed to obtain component B;

[0077] (4) Adding component B obtained in step (3) to component A obtained in step (2), wherein component A and component B are composed in a weight ratio of 8:1, and stirring at a speed of 400 r / min for 10 min to obtain a water-based two-component polyurethane coating.

[0078] Comparative Example 1

[0079] Compared with Example 2, the difference is that in the film-forming aid, tributyl citrate is replaced by cellulose acetate butyrate, that is, the film-forming aid consists of cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 6:3, and the other components and preparation method are the same as those in Example 2.

[0080] Comparative Example 2

[0081] Compared with Example 2, the difference is that the cellulose acetate butyrate in the film-forming aid is replaced by cellulose acetate, that is, the film-forming aid is composed of tributyl citrate, cellulose acetate and BASF Lusolvan FBH in a weight ratio of 2:4:3, and the other components and preparation method are the same as those in Example 2.

[0082] Comparative Example 3

[0083] Compared with Example 2, the difference is that TEGO 270 in the dispersant is replaced by TEGO-757W, that is, the dispersant is composed of BYK 190 and TEGO-757W in a weight ratio of 2:1, and other components and preparation methods are the same as those in Example 2.

[0084] Comparative Example 4

[0085] Compared with Example 2, the difference is that in the preparation step (1) of the water-based two-component polyurethane coating, the speed is not controlled in stages, and the speed is 1500 r / min. The specific steps of step (1) are as follows:

[0086] (1) At a rotation speed of 1500 r / min, deionized water, dispersant, wetting agent, TEGO Foamex 825 defoaming agent, fumed silica, leveling agent, titanium dioxide and aluminum tripolyphosphate were added respectively, stirred for 30 minutes, and then ground with a sand grinder to a particle size of 10 to 25 μm to obtain a color paste.

[0087] The other components and preparation methods are the same as those in Example 2.

[0088] Test Example 1: Performance Test

[0089] 1. Test materials: water-based two-component polyurethane coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0090] 2. Test method: The coating films of the water-based two-component polyurethane coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention were tested with reference to the method in Table 2. The test results are shown in Tables 3 and 4.

[0091] Table 2

[0092] Test items Refer to national standard Surface drying time / h GB / T 1728 Impact resistance / (kg·cm) GB / T 1732 Flexibility / mm GB / T 1731 Adhesion / Grade GB / T 1720 Neutral salt spray resistance (1000h) GB / T 1771 Water resistance (40℃, 240h) GB / T 1733

[0093] Table 3

[0094]

[0095] Table 4

[0096]

[0097]

[0098] As shown in Table 3 and Table 4, the water-based two-component polyurethane coatings prepared in Examples 1 to 3 of the present invention have fast drying speed, surface drying time within 30 minutes, and good mechanical properties, impact resistance of about 50kg·cm, flexibility of 1mm, and adhesion of 0 level. At the same time, the coating film also has excellent neutral salt spray resistance and water resistance. After 1000 hours of neutral salt spray resistance, there is no blistering and no corrosion phenomenon. After 240 hours of water resistance, there is no blistering, wrinkling, no shedding, and no discoloration. While Comparative Examples 1 to 3 change the types and ratios of film-forming aids and dispersants in water-based two-component polyurethane coatings, and when the process parameters in the preparation method of water-based two-component polyurethane coatings are changed in Comparative Example 4, the performance of each inspection item has decreased to varying degrees.

[0099] Test Example 2: Coating Storage Stability Test

[0100] According to the method in GB / T 6753.3-1986 "Test Method for Storage Stability of Coatings", the coating was stored at 50±2℃ for 30 days, and the crusting, sedimentation, particles and viscosity changes were continuously tested. The evaluation levels of each index are shown in Table 5, and the test results are shown in Table 6.

[0101] Table 5

[0102]

[0103]

[0104] Table 6

[0105] Group Skinning, corrosion and rancid smell Degree of sedimentation Particles Viscosity changes Example 1 8 10 10 10 Example 2 10 10 10 10 Example 3 10 10 8 10 Comparative Example 1 6 6 4 6 Comparative Example 2 8 6 6 8 Comparative Example 3 6 4 6 6 Comparative Example 4 8 6 6 10

[0106] It can be seen from Table 6 that the water-based two-component polyurethane coatings prepared in Examples 1 to 3 of the present invention did not produce crusting, corruption, sedimentation, etc. after being stored at 50±2°C for 30 days, and the viscosity change was no more than 5%, showing excellent storage stability.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A water-based two-component polyurethane coating, characterized in that: The composition is composed of component A and component B in a weight ratio of 6 to 8:1; the component A includes the following raw materials in parts by weight: 8-15 parts of deionized water, 40-50 parts of waterborne polyurethane dispersion, 20-25 parts of titanium dioxide, 8-12 parts of polyacrylate, 8-10 parts of anti-rust pigment, 3-5 parts of film-forming aid, 1-3 parts of 2-amino-2-methyl-1-propanol, 1-2 parts of wetting agent, 0.8-1.6 parts of dispersant, 0.4-0.8 parts of defoamer, 0.2-0.6 parts of leveling agent, 0.2-0.5 parts of anti-settling agent; The B component includes the following raw materials in parts by weight: 30-40 parts of hydrophilic polyisocyanate curing agent, 6-10 parts of propylene glycol methyl ether acetate; The film-forming aid is composed of tributyl citrate, cellulose acetate butyrate and BASF Lusolvan FBH in a weight ratio of 1-3:2-5:3; The dispersant is composed of BYK 190 and TEGO 270 in a weight ratio of 1 to 3:

1.

2. The water-based two-component polyurethane coating according to claim 1, characterized in that: The A component is composed of the following raw materials in parts by weight: 12 parts of deionized water, 45 parts of waterborne polyurethane dispersion, 22 parts of titanium dioxide, 10 parts of polyacrylate, 9 parts of anti-rust pigment, 4 parts of film-forming aid, 2 parts of ‌2-amino-2-methyl-1-propanol, 1.5 parts of wetting agent, 1.2 parts of dispersant, 0.6 parts of defoaming agent, 0.4 parts of leveling agent, 0.3 parts of anti-settling agent; The B component is composed of the following raw materials in parts by weight: 35 parts of hydrophilic polyisocyanate curing agent and 8 parts of propylene glycol methyl ether acetate.

3. The water-based two-component polyurethane coating according to claim 1 or 2, characterized in that: The aqueous polyurethane dispersion is Bayhydrol U XP 2750 produced by Covestro.

4. The water-based two-component polyurethane coating according to claim 1 or 2, characterized in that: The wetting agent is Tuyile superwet-320.

5. The water-based two-component polyurethane coating according to claim 1 or 2, characterized in that: The defoaming agent is polysiloxane-polyether copolymer; the anti-rust pigment is aluminum tripolyphosphate; and the anti-settling agent is fumed silica.

6. The water-based two-component polyurethane coating according to claim 1 or 2, characterized in that: The leveling agent is BYKETOL-AQ.

7. The water-based two-component polyurethane coating according to claim 1 or 2, characterized in that: The hydrophilic polyisocyanate curing agent is Covestro XP2655.

8. A method for preparing a waterborne two-component polyurethane coating according to any one of claims 1 to 7, characterized in that: The steps include: (1) At a speed of 600-900 r / min, add deionized water, dispersant, wetting agent, defoamer, anti-settling agent, and leveling agent respectively, then increase the speed to 2000-2400 r / min, add titanium dioxide and anti-rust pigment, continue stirring for 30-50 min, and then grind with a sand grinder to a particle size of 10-25 μm to obtain a color paste; (2) The color paste obtained in step (2) is taken out, and an aqueous polyurethane dispersion, polyacrylate, film-forming aid, and 2-amino-2-methyl-1-propanol are added thereto at a rotation speed of 1000-1200 r / min and stirring is continued for 15-20 min to obtain component A; (3) Stir and mix the polyisocyanate curing agent and propylene glycol methyl ether acetate to obtain component B; Add component B obtained in step (3) to component A obtained in step (2), and stir at a speed of 200 to 400 r / min for 10 to 15 minutes to obtain a water-based two-component polyurethane coating.

Images