A coating for color coated steel sheet and a method for preparing the same

Abstract

The application belongs to the technical field of paint and specifically relates to a kind of paint for color coated sheet and a preparation method thereof.The paint for color coated sheet comprises polyester resin 42-48 parts, amino resin 8-12 parts, functional monomer 1.5-4.5 parts, pigment 18-22 parts, nano-aluminum oxide 2-3 parts, catalyst 0.5-0.8 parts, leveling agent 0.4-0.6 parts, defoaming agent 0.2-0.3 parts, dispersing agent 0.6-1.0 parts, solvent 10-15 parts, and dimethyl dicarboxylate 5-8 parts.The functional monomer uses pentaerythritol as a rigid template, is constructed into a spiro ring double carbonate, has a symmetric core containing a urethane bond and a thiol group at the end of the arm, has a multi-arm hydroxyl intermediate containing a sulfide flexible segment, and introduces phenylsiloxane and perfluorobutyl, which helps to improve the hardness, impact resistance, adhesion, corrosion resistance, and wear resistance of the coating.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a coating for color-coated steel sheets and its preparation method. Background Technology

[0002] Coatings for color-coated steel sheets are specialized functional coating materials used to coat the surface of steel sheets. They are a core supporting raw material in the production of color-coated steel sheets, mainly composed of resin matrix, pigments, solvents, and additives. Based on application scenarios and functions, common types include polyester coatings, silicone-modified polyester coatings, fluorocarbon coatings, and epoxy primers, suitable for various applications such as building roofs, curtain walls, appliance casings, and steel structure cladding. These coatings combine decorative and protective properties, forming a continuous and dense protective film on the steel sheet surface. This not only gives the color-coated steel sheets rich colors, patterns, and textured appearance but also isolates them from external moisture, oxygen, acid and alkali media, and ultraviolet radiation, improving the lifespan and appearance preservation of the sheets. Furthermore, they are suitable for continuous roller coating industrial production processes, offering fast curing speed and good coating uniformity, making them a key supporting material for the transformation and upgrading of the steel building materials industry.

[0003] Currently, coatings for color-coated steel sheets (such as polyester coatings) still have significant shortcomings in core performance. For example, in terms of abrasion resistance, conventional coatings have low film hardness or insufficient toughness, resulting in poor scratch and abrasion resistance. During transportation, installation, and wind and sand erosion, the paint surface is prone to scratches, wear, and powdering. Regarding adhesion, conventional coatings have weak interfacial bonding with the substrate, easily leading to adhesion degradation and cracking and peeling after long-term use. In terms of corrosion resistance, conventional coatings have limited resistance to salt spray, acids and alkalis, and damp heat. In coastal high-salt-spray, industrial acid and alkali pollution, and humid environments, they are prone to blistering, discoloration, and rust penetration, with short-lasting protection. This makes it difficult to meet the long-term use requirements under highly corrosive conditions, hindering the widespread application of color-coated steel sheets in high-end, demanding environments. Summary of the Invention

[0004] The primary objective of this invention is to provide a coating for color-coated steel sheets.

[0005] The second objective of this invention is to provide a method for preparing a coating for color-coated steel sheets.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a coating for color-coated steel sheets, comprising the following raw materials in parts by weight: 42-48 parts polyester resin, 8-12 parts amino resin, 1.5-4.5 parts functional monomer, 18-22 parts pigment, 2-3 parts nano-alumina, 0.5-0.8 parts catalyst, 0.4-0.6 parts leveling agent, 0.2-0.3 parts defoamer, 0.6-1.0 parts dispersant, 10-15 parts solvent, and 5-8 parts dimethyl diacid. The preparation method of the functional monomer is as follows: react pentaerythritol and dimethyl carbonate to obtain intermediate 1; react intermediate 1 with cysteine ​​to obtain intermediate 2; react intermediate 2 with hydroxyethyl acrylate to obtain intermediate 3; react intermediate 3 with phenyltrimethoxysilane to obtain intermediate 4; react intermediate 4 with perfluorobutyl isocyanate to obtain the functional monomer.

[0007] Preferably, the method for preparing the functional monomer includes the following steps: (1) Add pentaerythritol and dibutyltin oxide to DMF, heat to 80-90℃ and add dimethyl carbonate, then heat to 110-120℃ and react for 6-8 hours to obtain intermediate 1; (2) Dissolve intermediate 1 in anhydrous ethanol, cool to 10-15℃ and add cysteine, then heat to 45-55℃ and react for 4-6 hours to obtain intermediate 2; (3) Add intermediate 2 and triethylamine to tetrahydrofuran, cool to 0-5℃ and add hydroxyethyl acrylate, then heat to 30-40℃ and react for 3-5h to obtain intermediate 3; (4) Dissolve intermediate 3 in xylene, add p-toluenesulfonic acid, heat to 70-80℃ and add phenyltrimethoxysilane, then react at 80-90℃ for 4-6h to obtain intermediate 4; (5) Add intermediate 4 and dibutyltin dilaurate to butyl acetate, heat to 50-60℃ and add perfluorobutyl isocyanate, then react at 50-60℃ for 4-5 hours to obtain the functional monomer.

[0008] The functional monomer of this invention first uses pentaerythritol as a rigid template to construct a spirocyclic dicarbonate via carbonate esterification. Then, through quantitative double ring-opening of cysteine, a symmetrical core containing highly polar urethane bonds and terminal thiol groups is constructed in situ. Next, thiol-Michael addition is performed using hydroxyethyl acrylate to embed a highly polarizable thioether flexible segment into the molecular chain, forming a multi-arm hydroxyl intermediate skeleton. Finally, by differentially introducing phenylsiloxane anchoring groups and perfluorobutyl self-lubricating segments at the arm ends, a well-ordered hybrid molecule integrating a highly rigid polar center, a stress-buffered thioether chain, and low surface energy functional ends is constructed.

[0009] Preferably, in step (1), the ratio of pentaerythritol, dibutyltin oxide, DMF and dimethyl carbonate is 1 mol: 0.01-0.02 mol: 600-800 mL: 2.2-2.5 mol.

[0010] Preferably, in step (2), the ratio of intermediate 1, anhydrous ethanol, and cysteine ​​is 1 mol: 500-600 mL: 2.0-2.1 mol.

[0011] Preferably, in step (3), the ratio of intermediate 2, triethylamine, tetrahydrofuran, and hydroxyethyl acrylate is 1 mol: 0.05-0.1 mol: 800-1000 mL: 2.0-2.2 mol.

[0012] Preferably, in step (4), the ratio of intermediate 3, xylene, p-toluenesulfonic acid, and phenyltrimethoxysilane is 1 mol: 500-700 mL: 0.005-0.01 mol: 2.0-2.1 mol.

[0013] Preferably, in step (5), the ratio of intermediate 4, dibutyltin dilaurate, butyl acetate, and perfluorobutyl isocyanate is 1 mol: 0.001-0.002 mol: 400-500 mL: 2.0-2.1 mol.

[0014] Preferably, the amino resin is hexamethoxymethyl melamine resin; and the catalyst is blocked p-toluenesulfonic acid.

[0015] Preferably, the pigment is rutile titanium dioxide; the leveling agent is EFKA 3777; the defoamer is TEGO 900; the dispersant is BYK-163; and the solvent is S-150 aromatic solvent.

[0016] The present invention provides a method for preparing the coating for color-coated steel sheets, comprising the following steps: mixing the raw material components according to the specified ratio to obtain the coating for color-coated steel sheets.

[0017] Compared with the prior art, the main advantages of the present invention are as follows: This invention provides a coating for color-coated steel sheets, in which a functional monomer plays a synergistic role among multiple components. This monomer uses pentaerythritol as a rigid core, constructing a high-cohesive energy center through diurethane bonds, and combining with sulfide flexible segments to form a rigid-flexible molecular framework. This allows the coating to maintain a high crosslinking density while balancing hardness and flexibility, providing a certain stress buffering capacity and improving the crack resistance of the color-coated steel sheet. Simultaneously, the phenyldimethoxysilyl groups at both ends of the molecule can undergo condensation reactions with the hydroxyl groups on the substrate surface during film formation to form covalent bonds; the urethane bonds in the molecule can generate strong hydrogen bonds with the metal surface. Both synergistically enhance the coating's adhesion to the metal substrate and interfacial sealing, thereby further improving the coating's corrosion resistance. Furthermore, the low surface energy of the perfluorobutyl segments causes them to tend to migrate and accumulate on the coating surface during film formation, endowing the coating with certain self-lubricating and scratch-resistant capabilities, helping to reduce surface damage during friction. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0019] Example 1 This embodiment provides a coating for color-coated steel sheets, comprising the following raw materials in parts by weight: 46 parts of polyester resin (ETERKYD5055-R-70), 10 parts of amino resin (hexamethoxymethyl melamine resin, CYMEL 303LF), 3 parts of functional monomer, 20 parts of pigment (rutile titanium dioxide), 3 parts of nano-alumina, 0.6 parts of catalyst (blocked p-toluenesulfonic acid, CYCAT4045), 0.5 parts of leveling agent (EFKA 3777), 0.3 parts of defoamer (TEGO 900), 0.8 parts of dispersant (BYK-163), 14 parts of solvent (S-150 aromatic solvent), and 6 parts of dimethyl dicarboxylate. The preparation method of the functional monomer in this embodiment includes the following steps:

[0020] (1) Pentaerythritol and dibutyltin oxide were added to N,N-dimethylformamide (DMF), heated to 85°C, and then dimethyl carbonate was added. The mixture was then heated to 115°C and reacted for 7 hours. The molar ratio of pentaerythritol, dibutyltin oxide, DMF, and dimethyl carbonate was 1 mol: 0.015 mol: 700 mL: 2.3 mol. After the reaction was complete, the solvent was removed under reduced pressure. The resulting solid was recrystallized and dried under vacuum to obtain intermediate 1, with a yield of 88.4%. Intermediate 1... 1 HNMR: (C7H8O6, 400MHz, DMSO-d6) δ: 4.02 (s, 8H). MS (ESI) m / z=188.03[M].

[0021] (2) Intermediate 1 was dissolved in anhydrous ethanol, cooled to 10°C under nitrogen protection, and then cysteamine was added. The mixture was then heated to 50°C and reacted for 5 hours. The molar ratio of intermediate 1, anhydrous ethanol, and cysteamine was 1 mol: 550 mL: 2.1 mol. After the reaction was complete, the reaction solution was concentrated under reduced pressure, recrystallized, filtered, and dried under vacuum to obtain intermediate 2, with a yield of 94.1%. The intermediate 2... 1 HNMR: (C 11 H 22N2O6S2, 400MHz, DMSO-d6) δ: 1.4 (s, 2H), 2.82 (t, 4H), 3.26 (t, 4H), 3.39 (s, 4H), 3.94 (s, 4H), 4.24 (s, 2H), 6.76 (s, 2H). MS (ESI) m / z=342.09[M].

[0022] (3) Intermediate 2 and triethylamine were added to tetrahydrofuran, cooled to 0°C under nitrogen protection, and hydroxyethyl acrylate was added dropwise, maintaining the temperature below 10°C during the addition. The molar ratio of intermediate 2, triethylamine, tetrahydrofuran, and hydroxyethyl acrylate was 1 mol: 0.08 mol: 900 mL: 2.1 mol. After the addition was complete, the temperature was raised to 35°C and the reaction was carried out for 4 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the product was washed and dried under vacuum to obtain intermediate 3, with a yield of 91.3%. Intermediate 3... 1 HNMR: (C 21 H 38 N2O 12 S2, 400MHz, DMSO-d6) δ: 2.58 (t, 4H), 2.70 (t, 4H), 2.83 (t, 4H), 3.33 (t, 4H), 3.3 9 (s, 4H), 3.54 (t, 4H), 3.94 (s, 4H), 4.22-4.24 (m, 6H), 4.89 (s, 2H), 6.76 (s, 2H). MS (ESI) m / z=574.19[M].

[0023] (4) Intermediate 3 was dissolved in xylene, p-toluenesulfonic acid was added, and the mixture was heated to 75°C under nitrogen protection. Then, phenyltrimethoxysilane was added, and the mixture was reacted under vacuum (pressure -0.08 MPa) at 85°C for 5 hours. The ratio of intermediate 3, xylene, p-toluenesulfonic acid, and phenyltrimethoxysilane was 1 mol: 600 mL: 0.008 mol: 2.1 mol. After the reaction was complete, the reaction solution was cooled to room temperature, and insoluble matter was removed by filtration. The filtrate was concentrated under reduced pressure to obtain intermediate 4, with a yield of 85.8%. Intermediate 4... 1 HNMR: (C 37 H 58 N2O 16S2Si2, 400MHz, DMSO-d6) δ: 2.58 (t, 4H), 2.70 (t, 4H), 2.83 (t, 4H), 3.33 (t, 4H), 3.39 (s, 4H), 3. 55 (s, 12H), 3.94 (s, 4H), 4.07 (t, 4H), 4.24-4.27 (m, 6H), 6.76 (s, 2H), 7.18 (m, 4H), 7.27 (m, 6H). MS (ESI) m / z= 907.28[M+H] + .

[0024] (5) Intermediate 4 and dibutyltin dilaurate were added to butyl acetate, heated to 55°C, and then perfluorobutyl isocyanate was added. The reaction was maintained at 55°C for 5 hours. The molar ratio of intermediate 4, dibutyltin dilaurate, butyl acetate, and perfluorobutyl isocyanate was 1 mol: 0.002 mol: 450 mL: 2.1 mol. After the reaction was completed, the solvent was removed from the reaction solution under reduced pressure, and the solution was washed and dried under vacuum to obtain the functional monomer with a yield of 94.7%. 1 HNMR: (C 47 H 58 F 18 N4O 18 S2Si2, 400MHz, DMSO-d6) δ: 2.58 (t, 4H), 2.70 (t, 4H), 2.83 (t, 4H), 3.33 (t, 4H), 3.55 (s, 12H) , 3.94 (s, 8H), 4.07 (t, 4H), 4.27 (t, 4H), 6.76 (s, 2H), 7.18 (m, 4H), 7.27 (m, 6H), 8.18 (s, 2H). MS(ESI) m / z=1429.25[M+H] + .

[0025] This embodiment provides a method for preparing a coating for color-coated steel sheets, including the following steps: mixing the raw material components according to the specified ratio to obtain the coating for color-coated steel sheets.

[0026] Example 2 This embodiment provides a coating for color-coated steel sheets, comprising the following raw materials in parts by weight: 48 parts of polyester resin (ETERKYD5055-R-70), 12 parts of amino resin (hexamethoxymethyl melamine resin, CYMEL 303LF), 4.5 parts of functional monomer, 22 parts of pigment (rutile titanium dioxide), 3 parts of nano-alumina, 0.8 parts of catalyst (blocked p-toluenesulfonic acid, CYCAT4045), 0.6 parts of leveling agent (EFKA 3777), 0.3 parts of defoamer (TEGO 900), 1.0 part of dispersant (BYK-163), 15 parts of solvent (S-150 aromatic solvent), and 8 parts of dimethyl dicarboxylate.

[0027] The preparation method of the functional monomer in this embodiment includes the following steps: (1) Pentaerythritol and dibutyltin oxide were added to N,N-dimethylformamide (DMF), heated to 90°C, and then dimethyl carbonate was added. The mixture was then heated to 120°C and reacted for 6 hours. The molar ratio of pentaerythritol, dibutyltin oxide, DMF, and dimethyl carbonate was 1 mol: 0.02 mol: 800 mL: 2.5 mol. After the reaction was complete, the solvent was removed under reduced pressure. The resulting solid was recrystallized and dried under vacuum to obtain intermediate 1, with a yield of 87.3%. Intermediate 1... 1 HNMR is the same as in Example 1.

[0028] (2) Intermediate 1 was dissolved in anhydrous ethanol, cooled to 15°C under nitrogen protection, and then cysteamine was added. The mixture was then heated to 55°C and reacted for 4 hours. The molar ratio of intermediate 1, anhydrous ethanol, and cysteamine was 1 mol: 600 mL: 2.1 mol. After the reaction was complete, the reaction solution was concentrated under reduced pressure, recrystallized, filtered, and dried under vacuum to obtain intermediate 2, with a yield of 92.4%. The intermediate 2... 1 HNMR is the same as in Example 1.

[0029] (3) Intermediate 2 and triethylamine were added to tetrahydrofuran, cooled to 5°C under nitrogen protection, and hydroxyethyl acrylate was added dropwise, maintaining the temperature below 10°C during the addition. The molar ratio of intermediate 2, triethylamine, tetrahydrofuran, and hydroxyethyl acrylate was 1 mol: 0.1 mol: 1000 mL: 2.2 mol. After the addition was complete, the temperature was raised to 40°C and the reaction was carried out for 3 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the product was washed and dried under vacuum to obtain intermediate 3, with a yield of 89.2%. Intermediate 3... 1 HNMR is the same as in Example 1.

[0030] (4) Intermediate 3 was dissolved in xylene, p-toluenesulfonic acid was added, and the mixture was heated to 80°C under nitrogen protection. Then, phenyltrimethoxysilane was added, and the mixture was reacted at 90°C for 4 hours under vacuum (pressure -0.08 MPa). The ratio of intermediate 3, xylene, p-toluenesulfonic acid, and phenyltrimethoxysilane was 1 mol: 700 mL: 0.01 mol: 2.1 mol. After the reaction was complete, the reaction solution was cooled to room temperature, filtered to remove insoluble matter, and the filtrate was concentrated under reduced pressure to obtain intermediate 4, with a yield of 84.7%. Intermediate 4... 1 HNMR is the same as in Example 1.

[0031] (5) Intermediate 4 and dibutyltin dilaurate were added to butyl acetate, heated to 60°C, and then perfluorobutyl isocyanate was added. The reaction was maintained at 60°C for 4 hours. The ratio of intermediate 4, dibutyltin dilaurate, butyl acetate, and perfluorobutyl isocyanate was 1 mol: 0.002 mol: 500 mL: 2.1 mol. After the reaction was completed, the solvent was removed from the reaction solution under reduced pressure, and the solution was washed and dried under vacuum to obtain the functional monomer with a yield of 92.1%. 1 HNMR is the same as in Example 1.

[0032] The preparation method of the coating for color-coated steel sheets in this embodiment is the same as that in Embodiment 1.

[0033] Example 3 This embodiment provides a coating for color-coated steel sheets, comprising the following raw materials in parts by weight: 42 parts of polyester resin (ETERKYD5055-R-70), 8 parts of amino resin (hexamethoxymethyl melamine resin, CYMEL 303LF), 1.5 parts of functional monomer, 18 parts of pigment (rutile titanium dioxide), 2 parts of nano-alumina, 0.5 parts of catalyst (blocked p-toluenesulfonic acid, CYCAT4045), 0.4 parts of leveling agent (EFKA 3777), 0.2 parts of defoamer (TEGO 900), 0.6 parts of dispersant (BYK-163), 10 parts of solvent (S-150 aromatic solvent), and 5 parts of dimethyl dicarboxylate.

[0034] The preparation method of the functional monomer in this embodiment includes the following steps: (1) Pentaerythritol and dibutyltin oxide were added to N,N-dimethylformamide (DMF), heated to 80°C, and then dimethyl carbonate was added. The mixture was then heated to 110°C and reacted for 8 hours. The molar ratio of pentaerythritol, dibutyltin oxide, DMF, and dimethyl carbonate was 1 mol: 0.01 mol: 600 mL: 2.2 mol. After the reaction was complete, the solvent was removed under reduced pressure. The resulting solid was recrystallized and dried under vacuum to obtain intermediate 1, with a yield of 85.4%. Intermediate 1... 1 HNMR is the same as in Example 1.

[0035] (2) Intermediate 1 was dissolved in anhydrous ethanol, cooled to 10°C under nitrogen protection, and then cysteamine was added. The mixture was then heated to 45°C and reacted for 6 hours. The ratio of intermediate 1, anhydrous ethanol, and cysteamine was 1 mol: 500 mL: 2.0 mol. After the reaction was complete, the reaction solution was concentrated under reduced pressure, recrystallized, filtered, and dried under vacuum to obtain intermediate 2, with a yield of 90.3%. Intermediate 2... 1 HNMR is the same as in Example 1.

[0036] (3) Intermediate 2 and triethylamine were added to tetrahydrofuran, cooled to 0°C under nitrogen protection, and hydroxyethyl acrylate was added dropwise, maintaining the temperature below 10°C during the addition. The molar ratio of intermediate 2, triethylamine, tetrahydrofuran, and hydroxyethyl acrylate was 1 mol: 0.05 mol: 800 mL: 2.0 mol. After the addition was complete, the temperature was raised to 30°C and the reaction was carried out for 5 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the product was washed and dried under vacuum to obtain intermediate 3 with a yield of 87.6%. Intermediate 3... 1 HNMR is the same as in Example 1.

[0037] (4) Intermediate 3 was dissolved in xylene, p-toluenesulfonic acid was added, and the mixture was heated to 70°C under nitrogen protection. Then, phenyltrimethoxysilane was added, and the mixture was reacted under vacuum (pressure -0.08 MPa) at 80°C for 6 hours. The ratio of intermediate 3, xylene, p-toluenesulfonic acid, and phenyltrimethoxysilane was 1 mol: 500 mL: 0.005 mol: 2.0 mol. After the reaction was complete, the reaction solution was cooled to room temperature, filtered to remove insoluble matter, and the filtrate was concentrated under reduced pressure to obtain intermediate 4, with a yield of 83.5%. Intermediate 4... 1 HNMR is the same as in Example 1.

[0038] (5) Intermediate 4 and dibutyltin dilaurate were added to butyl acetate, heated to 50°C, and then perfluorobutyl isocyanate was added. The reaction was maintained at 50°C for 5 hours. The molar ratio of intermediate 4, dibutyltin dilaurate, butyl acetate, and perfluorobutyl isocyanate was 1 mol: 0.001 mol: 400 mL: 2.0 mol. After the reaction was completed, the solvent was removed from the reaction solution under reduced pressure, and the solution was washed and dried under vacuum to obtain the functional monomer with a yield of 90.8%. 1 HNMR is the same as in Example 1.

[0039] The preparation method of the coating for color-coated steel sheets in this embodiment is the same as that in Embodiment 1.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the functional unit is replaced with intermediate 4, while the rest is the same as Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the functional monomer is replaced with intermediate 3, while the rest is the same as Example 1.

[0042] Test case The coatings obtained in Examples 1-3 and Comparative Examples 1-2 were applied to a substrate (steel plate). After curing (dry film thickness of 40 μm), the relevant properties were determined according to the relevant performance test standards. Specifically, hardness was determined according to GB / T6739-2022 "Determination of Hardness of Paint Film by Pencil Method for Paints and Varnishes"; impact resistance was determined according to GB / T1732-2020 "Test Method for Impact Resistance of Paint Films"; adhesion was determined according to GB / T9286-2021 "Cross-cut Test of Paint Films for Paints and Varnishes"; blistering, rusting, and peeling of the sample surface were observed according to GB / T1771-2007 "Determination of Resistance to Neutral Salt Spray for Paints and Varnishes"; and the mass loss (mg) of the sample before and after the test was calculated using a CS-10 grinding wheel with a load of 1000g and a rotation of 1500 revolutions, according to ASTM D4060. The results are shown in Table 1.

[0043] Table 1

[0044] As shown in Table 1, the coatings obtained in Examples 1-3 of this invention exhibit better hardness, impact resistance, adhesion, salt spray resistance, and abrasion resistance compared to Comparative Examples 1-2. The reason for this is that the functional monomer of this invention uses pentaerythritol as a rigid core, constructing a high cohesive energy center through diurethane bonds, and combining with sulfide flexible segments to form a rigid-flexible molecular framework, improving the coating's hardness and impact resistance. Simultaneously, the phenyldimethoxysilyl groups at both ends of the molecule synergistically enhance the coating's adhesion to metal substrates and its corrosion resistance. Furthermore, the low surface energy of the perfluorobutyl segments causes them to tend to migrate and accumulate on the coating surface during film formation, endowing the coating with certain self-lubricating and scratch-resistant capabilities, helping to reduce surface damage during friction.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A coating for color-coated steel sheets, characterized in that, The raw materials include the following parts by weight: 42-48 parts polyester resin, 8-12 parts amino resin, 1.5-4.5 parts functional monomer, 18-22 parts pigment, 2-3 parts nano aluminum oxide, 0.5-0.8 parts catalyst, 0.4-0.6 parts leveling agent, 0.2-0.3 parts defoamer, 0.6-1.0 parts dispersant, 10-15 parts solvent, and 5-8 parts dimethyl dicarboxylate. The preparation method of the functional monomer is as follows: react pentaerythritol and dimethyl carbonate to obtain intermediate 1; react intermediate 1 with cysteine ​​to obtain intermediate 2; react intermediate 2 with hydroxyethyl acrylate to obtain intermediate 3; react intermediate 3 with phenyltrimethoxysilane to obtain intermediate 4; react intermediate 4 with perfluorobutyl isocyanate to obtain the functional monomer.

2. The coating for color-coated steel sheets according to claim 1, characterized in that, The preparation method of the functional monomer includes the following steps: (1) Add pentaerythritol and dibutyltin oxide to DMF, heat to 80-90℃ and add dimethyl carbonate, then heat to 110-120℃ and react for 6-8 hours to obtain intermediate 1; (2) Dissolve intermediate 1 in anhydrous ethanol, cool to 10-15℃ and add cysteine, then heat to 45-55℃ and react for 4-6 hours to obtain intermediate 2; (3) Add intermediate 2 and triethylamine to tetrahydrofuran, cool to 0-5℃ and add hydroxyethyl acrylate, then heat to 30-40℃ and react for 3-5h to obtain intermediate 3; (4) Dissolve intermediate 3 in xylene, add p-toluenesulfonic acid, heat to 70-80℃ and add phenyltrimethoxysilane, then react at 80-90℃ for 4-6h to obtain intermediate 4; (5) Add intermediate 4 and dibutyltin dilaurate to butyl acetate, heat to 50-60℃ and add perfluorobutyl isocyanate, then react at 50-60℃ for 4-5h to obtain the functional monomer.

3. The coating for color-coated steel sheets according to claim 2, characterized in that, In step (1), the ratio of pentaerythritol, dibutyltin oxide, DMF and dimethyl carbonate is 1 mol: 0.01-0.02 mol: 600-800 mL: 2.2-2.5 mol.

4. The coating for color-coated steel sheets according to claim 2, characterized in that, In step (2), the ratio of intermediate 1, anhydrous ethanol, and cysteine ​​is 1 mol: 500-600 mL: 2.0-2.1 mol.

5. The coating for color-coated steel sheets according to claim 2, characterized in that, In step (3), the ratio of intermediate 2, triethylamine, tetrahydrofuran, and hydroxyethyl acrylate is 1 mol: 0.05-0.1 mol: 800-1000 mL: 2.0-2.2 mol.

6. The coating for color-coated steel sheets according to claim 2, characterized in that, In step (4), the ratio of intermediate 3, xylene, p-toluenesulfonic acid and phenyltrimethoxysilane is 1 mol: 500-700 mL: 0.005-0.01 mol: 2.0-2.1 mol.

7. The coating for color-coated steel sheets according to claim 2, characterized in that, In step (5), the ratio of intermediate 4, dibutyltin dilaurate, butyl acetate, and perfluorobutyl isocyanate is 1 mol: 0.001-0.002 mol: 400-500 mL: 2.0-2.1 mol.

8. The coating for color-coated steel sheets according to claim 1, characterized in that, The amino resin is hexamethoxymethyl melamine resin; the catalyst is blocked p-toluenesulfonic acid.

9. The coating for color-coated steel sheets according to claim 1, characterized in that, The pigment is rutile titanium dioxide; the leveling agent is EFKA 3777; the defoamer is TEGO 900; the dispersant is BYK-163; and the solvent is S-150 aromatic solvent.

10. The method for preparing the coating for color-coated steel sheets according to any one of claims 1-9, characterized in that, The process includes the following steps: mixing the raw material components according to the specified ratio to obtain the coating for color-coated steel sheets.

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