Two-component polyurethane finish paint and preparation method thereof

Abstract

The invention relates to the technical field of water-based paint, and particularly discloses double-component polyurethane finish paint and a preparation method thereof. The double-component polyurethane finish paint provided by the invention comprises a material A and a material B, the material A is prepared from the following components in parts by weight: 570 to 630 parts of hydroxy acrylic resin, 160 to 180 parts of pigment and filler, 50 to 60 parts of ethylene glycol hexyl ether, 60 to 70 parts of ethylene glycol butyl ether acetate, 8 to 15 parts of a de-foaming agent, 18 to 23 parts of a dispersing agent, 10 to 15 parts of a flatting agent, 2 to 4 parts of a wetting agent, 2 to 4 parts of a thickening agent and 60 to 70 parts of water; the hydroxyl acrylic resin is selected from water-based hydroxyl acrylic resin PA-4827 and / or water-based hydroxyl acrylic resin XK110; and the material B is a BAYHYDUR ultra304 curing agent. The double-component polyurethane finish paint provided by the invention has remarkable advantages in the aspects of adhesive force, hardness, weather resistance, gloss fullness and the like.

Description

Technical Field

[0001] The present application relates to the technical field of water-based coatings, and in particular to a two-component polyurethane topcoat and a preparation method thereof. Background Art

[0002] In the field of construction machinery, the performance of topcoat is crucial. It not only provides excellent protection for the machinery but also possesses outstanding decorative effects and convenient construction performance, directly impacting the appearance and service life of the machinery. With the continuous development of the construction machinery industry, people's requirements for the quality and appearance of construction machinery are becoming increasingly higher. As a key component of the appearance of construction machinery, the performance of topcoat is also attracting increasing attention. High-quality topcoat can enhance the overall quality of construction machinery, protect the machinery from external corrosion, and extend its service life, thus positively promoting the development of the construction machinery industry.

[0003] Traditional solvent-based topcoats are a common choice for construction machinery. These topcoats are made by dissolving resins, pigments, and other ingredients in organic solvents, resulting in a fluid coating that is very easy to apply. However, these traditional solvent-based topcoats contain large amounts of volatile organic compounds (VOCs), which evaporate into the air during construction and use, posing serious risks to the environment and human health. In recent years, with growing awareness of environmental protection, water-based topcoats have begun to gain prominence. Water-based topcoats use water as a solvent, reducing the use of organic solvents to a certain extent. However, existing water-based construction machinery topcoats still have shortcomings in terms of adhesion, hardness, weather resistance, and gloss richness. For example, some water-based topcoats are prone to fading, chalking, and loss of gloss after being used outdoors for a period of time, affecting the appearance and service life of construction machinery. This makes it difficult to meet the needs of long-term use of construction machinery in complex and harsh environments. Summary of the Invention

[0004] In order to address the shortcomings of existing water-based engineering machinery topcoats in terms of adhesion, hardness, weather resistance and gloss fullness, while meeting environmental protection requirements, the present application provides a two-component polyurethane topcoat and a preparation method thereof.

[0005] In the first aspect, the present application provides a two-component polyurethane topcoat, which adopts the following technical solution: A two-component polyurethane topcoat, comprising material A and material B; Calculated by weight of material A, the material A comprises the following components in parts by weight: 570-630 parts of hydroxy acrylic resin, 160-180 parts of pigments and fillers, 50-60 parts of ethylene glycol hexyl ether, 60-70 parts of ethylene glycol butyl ether acetate, 8-15 parts of defoaming agent, 18-23 parts of dispersant, 10-15 parts of leveling agent, 2-4 parts of wetting agent, 2-4 parts of thickener and 60-70 parts of water; The hydroxylated acrylic resin is selected from waterborne hydroxylated acrylic resin PA-4827 and / or waterborne hydroxylated acrylic resin XK110; The material B is BAYHYDUR ultra304 curing agent.

[0006] The present application provides a two-component polyurethane topcoat, which has significant advantages in many aspects such as adhesion, hardness, weather resistance and gloss fullness. In terms of adhesion, in material A, by selecting specific water-based hydroxyl acrylic resin PA-4827 and / or water-based hydroxyl acrylic resin XK110 as the main film-forming substance, when they react with the BAYHYDUR ultra304 curing agent in material B, a stable cross-linked network is formed. This cross-linked network allows the paint film to be closely combined with the surface of engineering machinery, significantly improving adhesion, which means that the paint film can effectively resist mechanical shock and vibration, even if the engineering machinery is subjected to various external forces during operation, the paint film will not fall off easily, ensuring its long-term protection of engineering machinery. From the weather resistance point of view, water-based hydroxy acrylic resin itself has excellent weather resistance, it can resist the influence of ultraviolet rays, rain and extreme temperatures, is exposed to outdoor environments for a long time, can also maintain good performance, no matter whether it is scorching sun exposure, rain scouring or severe cold and heat, will not cause the paint film to fade, powdering and other problems, greatly prolong the service life of coating, ensure the durability and integrity of engineering machinery appearance. In terms of high fullness, after the components in A material are reasonably matched, the resulting topcoat can form a thick, uniform and textured paint film on the substrate surface. In terms of wear resistance, the cross-linked network structure can enhance the hardness of the paint film, so that the wear resistance of the paint film is greatly improved, for the position of frequent friction of engineering machinery, the paint film can effectively resist friction, reduce wear and tear, thereby extending the service life of engineering machinery. In addition, the application uses water as solvent, replaces traditional organic solvents, greatly reduces the emission of volatile organic compounds (VOC), meets increasingly stringent environmental protection requirements, and reduces the harm to environment and human health. In summary, the two-component polyurethane topcoat provided in this application has excellent adhesion, hardness, weather resistance and glossiness on the substrate surface, and can meet the needs of long-term use of engineering machinery in complex and harsh environments.

[0007] Optionally, the hydroxylated acrylic resin is a mixture of water-based hydroxylated acrylic resin PA-4827 and water-based hydroxylated acrylic resin XK110.

[0008] Optionally, the weight ratio of the water-based hydroxylated acrylic resin PA-4827 to the water-based hydroxylated acrylic resin XK110 is (0.5-2.5):1.

[0009] Optionally, the weight ratio of the water-based hydroxylated acrylic resin PA-4827 to the water-based hydroxylated acrylic resin XK110 is (1-2):1.

[0010] In some embodiments, the weight ratio of the water-based hydroxylated acrylic resin PA-4827 to the water-based hydroxylated acrylic resin XK110 can be (0.5-1):1, (0.5-1.5):1, (0.5-1.7):1, (0.5-2):1, (1-1.5):1, (1-1.7):1, (1-2):1, (1-2.5):1, 1, (1.5-1.7):1, (1.5-2):1, (1.5-2.5):1, (1.7-2):1, (1.7-2.5):1, or (2-2.5):1.

[0011] In a specific embodiment, the weight ratio of the waterborne hydroxylated acrylic resin PA-4827 to the waterborne hydroxylated acrylic resin XK110 can also be 0.5:1, 1:1, 1.5:1, 1.7:1, 2:1 or 2.5:1.

[0012] Optionally, in the two-component polyurethane topcoat, the weight ratio of material A to material B is 100:(20-40).

[0013] In some embodiments, the weight ratio of material A to material B is 100:(20-25), 100:(20-30), 100:(20-35), 100:(25-30), 100:(25-35), 100:(25-40), 100:(30-35), 100:(30-40) or 100:(35-40).

[0014] In a specific embodiment, the weight ratio of material A to material B is 100:20, 100:25, 100:30, 100:35 or 100:40.

[0015] Optionally, the defoaming agent is defoaming agent 104E and defoaming agent BYK110; the leveling agent is leveling agent BYK346 and leveling agent BYK381.

[0016] In a second aspect, the present application provides a method for preparing a two-component polyurethane topcoat, comprising the following steps: First, add water into the stirring tank, add part of the defoamer, dispersant and pigments and fillers under stirring, and stir for 15-20 minutes; then grind the mixture until the fineness is 20±5μm to obtain a premixed slurry; Under stirring, add hydroxy acrylic resin to the premixed slurry and stir for 15-20 minutes; then add the remaining defoamer, leveling agent, wetting agent, ethylene glycol hexyl ether and ethylene glycol butyl ether acetate and stir for 15-20 minutes; finally add the thickener and stir for 20-30 minutes to obtain material A; Mix material A and material B according to the proportion to obtain a two-component polyurethane topcoat.

[0017] Optionally, the stirring speed is 300-500 rpm.

[0018] Optionally, in the grinding step, a horizontal disc sand mill is used for grinding, the shaft speed is 700-800 r / min, the slurry flow rate for the first grinding pass is 7-9 L / min, and the slurry flow rate for the second and third grinding passes is 6-7 L / min.

[0019] Thirdly, the present application provides a construction method for a two-component polyurethane topcoat, comprising the following steps: cleaning and pre-treating the surface of the substrate; then evenly applying the two-component polyurethane topcoat on the surface of the substrate by spraying or brushing, flash drying for 1-1.5 hours, and then naturally curing at 20-30°C for 6-8 hours or baking at 80-100°C for 1.5-2 hours to complete the construction.

[0020] In summary, this application has the following beneficial effects: 1. This application uses a hydroxyl acrylic resin selected from water-based hydroxyl acrylic resin PA-4827 and / or water-based hydroxyl acrylic resin XK110 as the film-forming substance in material A, and BAYHYDUR ultra304 curing agent as material B. The obtained two-component polyurethane topcoat, after being applied to the surface of construction machinery, can obtain excellent adhesion, hardness, weather resistance and gloss fullness, meeting the needs of long-term use of construction machinery in complex and harsh environments.

[0021] 2. This application further adopts a hydroxyl acrylic resin, which is a mixture of water-based hydroxyl acrylic resin PA-4827 and water-based hydroxyl acrylic resin XK110, as the film-forming substance in material A, and controls the weight ratio of the two within the range of (1-2):1. The obtained two-component polyurethane topcoat has better adhesion to the surface of engineering machinery and better weather resistance of the paint film.

[0022] 3. This application further controls the weight ratio of material A to material B within the range of 100:(25-35), and the obtained two-component polyurethane topcoat has better adhesion on the surface of engineering machinery and better weather resistance of the paint film. DETAILED DESCRIPTION

[0023] The present application provides a two-component polyurethane topcoat, comprising material A and material B. Material A comprises the following components in parts by weight: 570-630 parts of a hydroxylated acrylic resin, 160-180 parts of pigments and fillers, 50-60 parts of ethylene glycol hexyl ether, 60-70 parts of ethylene glycol butyl ether acetate, 8-15 parts of a defoamer, 18-23 parts of a dispersant, 10-15 parts of a leveling agent, 2-4 parts of a wetting agent, 2-4 parts of a thickener, and 60-70 parts of water. The hydroxylated acrylic resin is selected from water-based hydroxylated acrylic resin PA-4827 and / or water-based hydroxylated acrylic resin XK110. The defoamer is defoamer 104E and defoamer BYK110. The leveling agents are leveling agent BYK346 and leveling agent BYK381. Material B is BAYHYDUR ultra304 curing agent.

[0024] The present application also provides a method for preparing the above-mentioned two-component polyurethane topcoat, comprising the following steps: (1) First, water was added to a stirred tank, and defoamer 104E, dispersant 775w, dispersant 6208, barium sulfate, titanium dioxide 996, 254 red, and pigment red 122 were added under stirring, and stirred for 15-20 minutes; then, the mixture was ground using a horizontal disc sand mill, with a shaft speed of 700-800 r / min, a slurry flow rate of 7-9 L / min for the first grinding pass, and a slurry flow rate of 6-7 L / min for the second and third grinding passes, and ground to a fineness of 20±5 μm to obtain a premixed slurry; (2) Add water-based hydroxylated acrylic resin PA-4827 and / or water-based hydroxylated acrylic resin XK11 to the premixed slurry under stirring and stir for 15-20 minutes; then add defoamer BYK110, leveling agent BYK346, leveling agent BYK346, wetting agent 4100, ethylene glycol hexyl ether and ethylene glycol butyl ether acetate and stir for 15-20 minutes; finally add thickener 299 and stir for 20-30 minutes to obtain material A; (3) Mix material A and material B in proportion to obtain a two-component polyurethane topcoat.

[0025] The present application also provides a construction method for the above-mentioned two-component polyurethane topcoat, comprising the following steps: cleaning and pre-treating the surface of the substrate coated with epoxy primer for construction machinery; then evenly applying the two-component polyurethane topcoat on the surface of the substrate by spraying or brushing, flash drying for 1-1.5 hours, and then naturally curing at 20-30°C for 6-8 hours or baking at 80-100°C for 1.5-2 hours to complete the construction.

[0026] In this application, defoamer 104E was purchased from BASF; dispersant 775w and wetting agent 4100 were both purchased from Digo; dispersant 6208 was purchased from Fuda Micropowder; barium sulfate was 800 mesh and was purchased from Changxing Hongyue; titanium dioxide 996 was purchased from Sichuan Lomon Group; 254 Red and Pigment Red 122 were both purchased from Clariant; water-based hydroxyl acrylic resin PA-4827 and water-based hydroxyl acrylic resin XK110 were both purchased from Guanzhi; defoamer BYK110, leveling agent BYK346, and leveling agent BYK346 were all purchased from BYK; thickener 299 was purchased from Hemmings; curing agent BAYHYDUR ultra304 was purchased from Covestro; the raw materials, reagents, solvents, etc. used in this application can all be obtained commercially.

[0027] The present application is further described in detail below with reference to embodiments and performance testing.

[0028] Examples 1-8 Examples 1-8 each provide a two-component polyurethane topcoat.

[0029] The difference between the above embodiments is that the type and ratio of the hydroxylated acrylic resin in material A are specifically shown in Table 1 below.

[0030] The preparation method of the two-component polyurethane topcoat of Examples 1-8 comprises the following steps: (1) First, 65 g of water was added to a stirred tank, and 5 g of defoamer 104E, 15 g of dispersant 775w, 5 g of dispersant 6208, 80 g of barium sulfate, 3 g of titanium dioxide 996, 65 g of 254 red, and 20 g of pigment red 122 were added under stirring, and stirred for 15 min; then, the mixture was ground using a horizontal disc sand mill with a shaft speed of 800 r / min, a slurry flow rate of 8 L / min for the first grinding pass, and a slurry flow rate of 6.5 L / min for the second and third grinding passes, and ground to a fineness of 20 ± 5 μm to obtain a premixed slurry; (2) Add 600 g of water-based hydroxy acrylic resin to the premixed slurry under stirring and stir for 15 min; then add 5 g of defoamer BYK110, 5 g of leveling agent BYK346, 8 g of leveling agent BYK346, 3 g of wetting agent 4100, 53 g of ethylene glycol hexyl ether and 64 g of ethylene glycol butyl ether acetate and stir for 20 min; finally add 3 g of thickener 299 and stir for 30 min to obtain material A; (3) Material A and material B (BAYHYDUR ultra304 curing agent) were mixed evenly in a ratio of 100:30 to obtain a two-component polyurethane topcoat.

[0031] Table 1 Type and ratio of hydroxy acrylic resin in material A of Examples 1-8 Examples 9-12 Examples 9-12 each provide a two-component polyurethane topcoat.

[0032] The difference between the above embodiment and embodiment 6 is that the weight ratio of material A to material B is shown in Table 2 below.

[0033] Table 2 Weight ratio of material A to material B in Example 6, Examples 9-12 Example Weight ratio of material A to material B 6 100：30 9 100：20 10 100：25 11 100：35 12 100：40 Comparative Example 1 Comparative Example 1 provides a two-component polyurethane topcoat.

[0034] The difference between Comparative Example 1 and Example 1 is that the water-based hydroxylated acrylic resin PA-4827 is replaced by water-based hydroxylated acrylic dispersion AQUAPAC-8533 (Fuqisen).

[0035] Comparative Example 2 Comparative Example 2 provides a two-component polyurethane topcoat.

[0036] The difference between Comparative Example 2 and Example 1 is that the water-based hydroxyl acrylic resin PA-4827 is replaced by the water-based acrylic resin BURNOCK WD-570 (DIC).

[0037] Comparative Example 3 Comparative Example 3 provides a two-component polyurethane topcoat.

[0038] Comparative Example 3 is different from Example 1 in that the water-based hydroxylated acrylic resin PA-4827 is replaced by a water-based hydroxylated acrylic resin PA-4827 and AQUAPAC-8533 water-based hydroxylated acrylic dispersion in a weight ratio of 1.7:1.

[0039] Comparative Example 4 Comparative Example 4 provides a two-component polyurethane topcoat.

[0040] Comparative Example 4 is different from Example 1 in that the water-based hydroxylated acrylic resin PA-4827 is replaced by water-based hydroxylated acrylic resin PA-4827 and water-based acrylic resin BURNOCK WD-570 in a weight ratio of 1.7:1.

[0041] Comparative Example 5 Comparative Example 5 provides a two-component polyurethane topcoat.

[0042] The difference between Comparative Example 5 and Example 1 is that material B is curing agent AQUAPU-298 (Fuqisen).

[0043] Application Examples 1-12 Application Examples 1-12 respectively provide a construction method for a two-component polyurethane topcoat.

[0044] The difference between Application Examples 1-12 is that the two-component polyurethane topcoat used in each application example is derived from Examples 1-12, respectively.

[0045] The construction method of the above-mentioned two-component polyurethane topcoat is as follows: the surface of the substrate coated with epoxy primer of the construction machinery is cleaned and pretreated; then each two-component polyurethane topcoat is evenly applied to the surface of the substrate by spraying, flash-dried for 1 hour, and then naturally cured at 25°C for 6 hours, and the construction is completed.

[0046] Application Example 13 Application Example 13 provides a construction method for a two-component polyurethane topcoat.

[0047] The difference between Application Example 13 and Application Example 6 is that natural curing at 25°C for 6 hours is replaced by baking at 85°C for 2 hours.

[0048] Comparative Application Examples 1-5 Comparative Application Examples 1-5 respectively provide a construction method for a two-component polyurethane topcoat.

[0049] The difference between Comparative Application Examples 1-5 and Application Example 6 is that the two-component polyurethane topcoat used in each comparative application example is derived from Comparative Examples 1-5, respectively.

[0050] Performance testing The glossiness, hardness, adhesion and weather resistance (water resistance, alkali resistance, salt spray resistance and aging resistance) of the surface of the construction machinery after the construction of Example 1-13 and Comparative Example 1-5 were tested, and the results are shown in Table 3 below.

[0051] Glossiness is tested using a gloss meter (spectrophotometer); hardness is tested according to GB / T 6739-2006. Adhesion is tested according to GB / T 9286-1998 (Grade 0: Completely smooth cut edges with no peeling; Grade 1: Slight coating loss at the intersection of the cut, but the peeling area is ≤5%; Grade 2: Coating loss at the cut edge or intersection >5% but ≤15%; Grade 3: Extensive coating loss along the cut edge or partial peeling, with a peeling area >15% but ≤35%; Grade 4: Large-scale coating loss, with a peeling area >35% but ≤65%; Grade 5: Almost complete coating loss, with a peeling area >65%). Water resistance is tested according to GB / T 1733 (Determination of water resistance of paint films) Method A - Water immersion test. Alkali resistance is tested according to GB / T 9274 (Paints and varnishes - Determination of resistance to liquid media: Immersion method, 23±2°C). The salt spray resistance test method is based on GB / T 1771, Determination of Neutral Salt Spray Resistance of Paints and Varnishes: salt spray chamber temperature 35±2°C, salt water concentration 50±10g / l, pH 6.5-7.2. The aging resistance test method is based on GB / T 1865, Artificial Weathering and Artificial Radiation Exposure of Paints and Varnishes to Filtered Xenon Arc Radiation.

[0052] Table 3 Performance test results of the construction machinery surface after construction of the corresponding examples 1-13 and comparative examples 1-5 According to the test results in Table 3, the glossiness of the engineering machinery surface obtained in Application Examples 1-13 is 90-98; the hardness is 2H; the adhesion grade of the paint film is 0-1; after a 240-hour water resistance test, the gloss loss rate is ≤15%, the color difference is ≤2, and the paint film does not blister, crack, or fall off; after a 168-hour alkali resistance test, the gloss loss rate is ≤15%, the color difference is ≤2, and the paint film does not blister, crack, or fall off; after a 1000-hour salt spray resistance test after pickling and phosphating, the single side does not blister, crack, or fall off, and there is slight discoloration; after a 2000-hour aging resistance test, the color difference is <2, and the gloss loss rate is <20%. Therefore, it is explained that this application uses water-based hydroxyl acrylic resin PA-4827 and / or water-based hydroxyl acrylic resin XK110 as the topcoat as the film-forming substance in material A, and BAYHYDUR ultra304 curing agent as material B. The obtained two-component polyurethane topcoat can obtain excellent adhesion, hardness, weather resistance and gloss fullness after being applied to the surface of construction machinery, meeting the needs of long-term use of construction machinery in complex and harsh environments.

[0053] In Comparative Example 1, Fuqisen's water-based hydroxylated acrylic dispersion AQUAPAC-8533 was used as the film-forming substance in Material A. After being applied to the surface of construction machinery, the resulting two-component polyurethane topcoat had a gloss of only 83-85; the paint film had an adhesion grade of 2; and after a 240-h water resistance test, its gloss loss rate was >25%, and its color difference was >3, indicating slightly poor gloss, adhesion, and water resistance.

[0054] Comparative Example 2 uses DIC's water-based acrylic resin BURNOCK WD-570 as the film-forming substance in Material A. After being applied to the surface of construction machinery, the resulting two-component polyurethane topcoat has a surface hardness of only H; the adhesion grade of the paint film is Class 2; and after a 240-h water resistance test, its gloss loss rate is >30%, and its color difference is >2, indicating slightly poor hardness, adhesion, and water resistance.

[0055] Comparative Example 3 uses a water-based hydroxylated acrylic resin PA-4827 and an AQUAPAC-8533 water-based hydroxylated acrylic dispersion in a weight ratio of 1.7:1 as the film-forming substance in Material A. After application to the surface of construction machinery, the resulting two-component polyurethane topcoat has a gloss of only 87-90; the adhesion grade of the paint film is Class 1; and after a 240-h water resistance test, the gloss loss is >20%, the color difference is >2, and the gloss and water resistance are slightly poor.

[0056] Comparative Example 4: A two-component polyurethane topcoat prepared by using water-based hydroxyl acrylic resin PA-4827 and water-based acrylic resin BURNOCK WD-570 in a weight ratio of 1.7:1 as film-forming substances in material A was applied to the surface of construction machinery. The adhesion grade of the paint film was 1. After a 240-h water resistance test, the gloss loss rate of the machinery surface was greater than 25%, and the color difference was greater than 2, indicating that the water resistance was slightly poor.

[0057] Comparative Example 5 uses Fuqisen's curing agent AQUAPU-298 as material B. After the obtained two-component polyurethane topcoat is applied to the surface of construction machinery, the hardness of the mechanical surface is only H; the adhesion grade of the paint film is level 1; after a 240-h water resistance test, its gloss loss rate is greater than 25%, and the color difference is greater than 2. Its hardness, adhesion and water resistance are slightly poor.

[0058] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A two-component polyurethane topcoat, characterized in that: Including A material and B material; Calculated by weight of material A, the material A comprises the following components in parts by weight: 570-630 parts of hydroxy acrylic resin, 160-180 parts of pigments and fillers, 50-60 parts of ethylene glycol hexyl ether, 60-70 parts of ethylene glycol butyl ether acetate, 8-15 parts of defoaming agent, 18-23 parts of dispersant, 10-15 parts of leveling agent, 2-4 parts of wetting agent, 2-4 parts of thickener and 60-70 parts of water; The hydroxylated acrylic resin is selected from waterborne hydroxylated acrylic resin PA-4827 and / or waterborne hydroxylated acrylic resin XK110; The material B is BAYHYDUR ultra304 curing agent.

2. The two-component polyurethane topcoat according to claim 1, characterized in that The hydroxy acrylic resin is a mixture of water-based hydroxy acrylic resin PA-4827 and water-based hydroxy acrylic resin XK110.

3. The two-component polyurethane topcoat according to claim 2, characterized in that The weight ratio of the water-based hydroxylated acrylic resin PA-4827 to the water-based hydroxylated acrylic resin XK110 is (1-2):

1.

4. The two-component polyurethane topcoat according to claim 1, characterized in that In the two-component polyurethane topcoat, the weight ratio of material A to material B is 100:(20-40).

5. The two-component polyurethane topcoat according to claim 1, characterized in that The defoaming agents are defoaming agent 104E and defoaming agent BYK110; the leveling agents are leveling agent BYK346 and leveling agent BYK381.

6. The method for preparing a two-component polyurethane topcoat according to any one of claims 1 to 5, characterized in that: The following steps are involved: First, add water into the stirring tank, add part of the defoamer, dispersant and pigments and fillers under stirring, and stir for 15-20 minutes; then grind the mixture until the fineness is 20±5μm to obtain a premixed slurry; Under stirring, add hydroxy acrylic resin to the premixed slurry and stir for 15-20 minutes; Then add the remaining defoamer, leveling agent, wetting agent, ethylene glycol hexyl ether and ethylene glycol butyl ether acetate, and stir for 15-20 minutes; finally add the thickener and stir for 20-30 minutes to obtain material A; Mix material A and material B according to the proportion to obtain a two-component polyurethane topcoat.

7. The method for preparing a two-component polyurethane topcoat according to claim 6, wherein: The stirring speed is 300-500 rpm.

8. The method for preparing a two-component polyurethane topcoat according to claim 6, wherein: In the grinding step, a horizontal disc sand mill is used for grinding, the shaft speed is 700-800 r / min, the slurry flow rate of the first grinding pass is 7-9 L / min, and the slurry flow rate of the second and third grinding passes is 6-7 L / min.

9. A construction method for a two-component polyurethane topcoat, characterized in that: The following steps are involved: The substrate surface is cleaned and pretreated; then the two-component polyurethane topcoat according to any one of claims 1 to 5 is evenly applied on the substrate surface by spraying or brushing, flash-drying for 1-1.5 hours, and then naturally curing at 20-30°C for 6-8 hours or baking at 80-100°C for 1.5-2 hours to complete the construction.

Images