A stretchable anti-color change coating

Abstract

This invention discloses a stretchable anti-color change coating. The stretchable anti-color change coating provided by this invention comprises the following raw materials in weight percentages: 60-70% modified polyurethane emulsion, 12-20% modified titanium dioxide, 2-3% defoamer, 2.5-5% high-quality color powder, 0.5-1% organosilicon leveling agent, 5-10% crosslinking agent, and 5-15% deionized water. The coating provided by this invention, firstly, uses waterborne polyurethane with good stretchability as the base material, and the addition of a modified chain extender during synthesis improves the polyurethane's anti-color change properties; secondly, the polyurethane is modified using acrylate to further improve the stretchability of the matrix, and the use of fluorinated monomers and organosilicon monomers in the acrylic acid synthesis improves the water resistance and hydrophobicity of the matrix; finally, the titanium dioxide is modified to further suppress color change of the matrix due to ultraviolet light irradiation and also provides a certain degree of corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically to a stretchable, color-changing resistant coating. Background Technology

[0002] Currently, within the tinplate printing industry, market demands for printed cans are constantly increasing, with a growing need for more complex and irregularly shaped cans. In existing tin can printing processes, conventional coating printing cannot meet the requirements of complex can structures, exhibiting significant drawbacks such as ink blackening, cracking, peeling, discoloration, and susceptibility to rust. Therefore, traditional printing coatings cannot satisfy the diversity of surface finishes and multi-layered color representation. Furthermore, traditional printing coatings have poor tensile strength and are prone to color changes under ultraviolet light and air, resulting in poor colorfastness. In addition, the water resistance and corrosion resistance of traditional coatings are increasingly failing to meet consumer needs.

[0003] Therefore, it is necessary to develop a coating with excellent ductility, colorfastness, water resistance, and corrosion resistance to meet production requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an extensible, color-resistant coating.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An extensible anti-color change coating comprises the following raw materials in weight percentages: 60-70% modified polyurethane emulsion, 12-20% modified titanium dioxide, 2-3% defoamer, 2.5-5% high-quality color powder, 0.5-1% silicone leveling agent, 5-10% crosslinking agent, and 5-15% deionized water.

[0007] The defoamer is BYK-020; the silicone leveling agent is BYK-381; and the crosslinking agent is carbodiimide.

[0008] The modified titanium dioxide is prepared by the following steps:

[0009] Step A1: Add n-pentylamine and 3-(diethylphosphine)propionic acid to a flask containing toluene and stir until homogeneous. Under nitrogen atmosphere, heat to 70-90℃ and react for 2-3 hours. After the reaction is complete, distill for 1-2 hours. After the reaction is complete, filter and dry to obtain the surfactant.

[0010] Furthermore, the ratio of n-pentylamine, 3-(diethylphosphine)propionic acid, and toluene is 0.1-0.2 mol: 0.13-0.23 mol: 20 mL;

[0011] Step A2: Disperse nano-titanium dioxide in deionized water and stir until homogeneous. Add surfactant and heat to 80°C. Stir and react for 3-5 hours. After the reaction is complete, filter and dry to obtain modified titanium dioxide.

[0012] Furthermore, the ratio of nano-titanium dioxide, deionized water, and surfactant is 2-4g: 20mL: 0.02-0.04g.

[0013] The modified polyurethane emulsion is prepared by the following steps:

[0014] Step B1: Disperse 2-aminopropane-1,3-diol and sodium hydroxide in deionized water, denoted as mixture A. Disperse ethylenediamine and sodium hydroxide in deionized water, denoted as mixture B. Add mixture A to a reactor containing cyanuric chloride and acetone, stir and mix evenly, and react at 0°C for 2-4 hours. After the reaction is complete, add half of mixture B dropwise and react at 50°C for 4-5 hours. After the reaction is complete, raise the temperature to 80-90°C, add the remaining mixture B dropwise, and continue reflux for 5-7 hours. After the reaction is complete, cool to room temperature, filter, wash, and dry at 60°C for 12 hours to obtain intermediate 1.

[0015] Furthermore, the ratio of the amounts of mixture A, mixture B, cyanuric chloride, and acetone is 10 mL: 20 mL: 0.01-0.03 mol: 40 mL. The ratio of the amounts of 2-aminopropane-1,3-diol, sodium hydroxide, and deionized water in mixture A is 0.01-0.03 mol: 0.8-1.2 g: 10 mL. The ratio of the amounts of ethylenediamine, sodium hydroxide, and deionized water in mixture B is 0.02-0.06 mol: 1.6-2.4 g: 20 mL.

[0016] Step B2: Disperse intermediate 1 and potassium carbonate in deionized water and stir until homogeneous. Cool to 0°C and slowly add 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride solution. After the addition is complete, continue stirring for 12 hours. After the reaction is complete, let it stand at 5°C for 24 hours. Then, distill the upper organic phase under reduced pressure, wash, centrifuge, and dry to obtain the modified chain extender.

[0017] Furthermore, the ratio of intermediate 1, potassium carbonate, deionized water, and 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution is 0.005-0.015 mol : 0.03-0.09 mol : 12-36 mL : 72-216 mL. The 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution is prepared by mixing β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and benzene in a ratio of 0.03-0.09 mol : 72-216 mL.

[0018] Step B3: Add poly(1,4-butanediol adipate) diol (M) n =2000) and isophorone diisocyanate were added to the reactor and stirred until homogeneous. The temperature was raised to 70-90℃ and reacted for 2-3 hours. After the reaction was completed, the temperature was cooled to 50℃. 3-hydroxy-2-(hydroxymethyl)propionic acid, 1,1,1-tris(hydroxymethyl)ethane, chain extender and acetone were added. The temperature was raised to 80℃ and reacted for 40-60 minutes. After the reaction was completed, the temperature was cooled to 50℃. Dibutyltin dilaurate was added and the temperature was raised to 70℃ and reacted for 3-4 hours. After the reaction was completed, the temperature was cooled to 50℃. Hydroxyethyl acrylate was added and the temperature was raised to 70℃ and reacted for 2 hours. After the reaction was completed, the temperature was cooled to 40℃. Ethyl methacrylate, butyl acrylate, ethyl 2-(perfluorobutyl)acrylate, propyl 3-trimethoxysilane acrylate and triethylamine were added and stirred until homogeneous to obtain the prepolymer.

[0019] Furthermore, the following dosage ratios are used: poly(1,4-butanediol adipate), isophorone diisocyanate, 3-hydroxy-2-(hydroxymethyl)propionic acid, 1,1,1-tris(hydroxymethyl)ethane, modified chain extender, acetone, dibutyltin dilaurate, hydroxyethyl acrylate, ethyl methacrylate, butyl acrylate, ethyl 2-(perfluorobutyl)acrylate, propyl 3-trimethoxysilane acrylate, and triethylamine: 30-50g: 12-23g: 1.5-3g: 0.2-0.45g: 1.3-2.1g: 5-15mL: 0.1-0.2g: 1.2g: 0.5-1.5g: 1-3g: 2.2-6.2g: 3-5g: 5-10g.

[0020] Step B4: Add LRS-10, deionized water, ethylenediamine and ammonium persulfate to the above polyurethane prepolymer and stir until homogeneous. Stir at 600-800 rpm for 20-30 min. After the reaction is complete, heat to 65-85℃ and react for 5-7 h. After the reaction is complete, cool to 40℃, filter through a sieve, and collect the emulsion to obtain the modified polyurethane emulsion.

[0021] Furthermore, LRS-10 accounts for 3% of the total mass fraction of all acrylate monomers, ammonium persulfate accounts for 0.5% of the total mass fraction of all acrylate monomers, and the amounts of deionized water and ethylenediamine are 20 mL and 3 g, respectively.

[0022] The beneficial effects of this invention are:

[0023] The coating provided by this invention firstly uses waterborne polyurethane with good extensibility as the base material, and adds a modified chain extender during synthesis to improve the polyurethane's resistance to color change; secondly, it uses acrylate to modify the polyurethane, further improving the extensibility of the matrix, and in the acrylic acid synthesis, it uses fluorinated monomers and organosilicon monomers to improve the water resistance and hydrophobicity of the matrix; finally, it modifies titanium dioxide to further suppress the color change of the matrix caused by ultraviolet light irradiation, and also has a certain degree of corrosion resistance.

[0024] In the modified polyurethane emulsion, cyanuric chloride is used as an intermediate. Nucleophilic substitution occurs between the chlorine atoms and amino groups in cyanuric chloride, thereby introducing terminal hydroxyl groups and a semi-hindered phenolic structure. The terminal hydroxyl groups can participate in the subsequent synthesis of polyurethane. The introduction of the semi-hindered phenolic structure into the polyurethane improves the polyurethane's resistance to discoloration. This is because the steric hindrance of the ortho-substituents of the hydroxyl groups in the semi-hindered phenolic structure is small, which can inhibit its reaction with oxygen in the air to form chromophores. In addition, the presence of the semi-hindered phenolic structure and the triazine structure also improves the antioxidant properties and heat resistance of the matrix, further making the matrix less prone to discoloration at high temperatures. Secondly, using waterborne polyurethane with good extensibility as the substrate, the polyurethane is modified with acrylate. Due to the excellent flexibility and elasticity of acrylate, the elasticity and extensibility of the polyurethane are further improved, giving the matrix better tensile properties. The presence of fluorinated monomers and organosilicon monomers in the acrylate improves the water resistance and hydrophobicity of the matrix. This is because the CF bonds in the monomers gradually migrate to the surface of the matrix during film formation, reducing the surface energy of the matrix and improving its hydrophobicity. In addition, the siloxanes in the organosilicon monomers hydrolyze into silanol bonds, which can form a cross-linked network structure in the matrix, thereby improving the water resistance of the matrix.

[0025] In the modified titanium dioxide, firstly, a surfactant containing amide and phosphate structures is synthesized; secondly, hydrogen bonds are formed between the amide structure and the hydroxyl groups on the surface of titanium dioxide, thereby coating the surface of titanium dioxide with surfactant, which improves the dispersibility of titanium dioxide in the matrix, inhibits the color change of the matrix caused by ultraviolet light, and further improves the anti-color change performance of the matrix; in addition, the phosphate structure contained in the surfactant improves the corrosion resistance of the matrix. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] An extensible, colorfast coating comprises the following raw materials in weight percentages:

[0029] The composition consists of 60% modified polyurethane emulsion, 18% modified titanium dioxide, 3% defoamer BYK-020, 4% high-quality color powder, 1% silicone leveling agent BYK-381, 8% carbodiimide, and the remainder is deionized water.

[0030] The modified titanium dioxide is prepared by the following steps:

[0031] Step A1: Add 0.1 mol n-pentylamine and 0.13 mol 3-(diethylphosphine)propionic acid to a flask containing 20 mL toluene and stir until homogeneous. Heat to 70 °C for 2 h under nitrogen atmosphere. After the reaction is complete, distill for 1 h. After the reaction is complete, filter and dry to obtain the surfactant.

[0032] Step A2: Disperse 2g of nano titanium dioxide in 20mL of deionized water and stir until homogeneous. Add 0.02g of surfactant and heat to 80℃. Stir and react for 3h. After the reaction is complete, filter and dry to obtain modified titanium dioxide.

[0033] The modified polyurethane emulsion is prepared by the following steps:

[0034] Step B1: Disperse 0.01 mol 2-aminopropane-1,3-diol and 0.8 g sodium hydroxide in 10 mL deionized water, denoted as mixture A. Disperse 0.02 mol ethylenediamine and 1.6 g sodium hydroxide in 20 mL deionized water, denoted as mixture B. Add mixture A to a reactor containing 0.01 mol cyanuric chloride and 40 mL acetone, stir and mix evenly, and react at 0 °C for 2 h. After the reaction is complete, add 10 mL of mixture B dropwise, and react at 50 °C for 4 h. After the reaction is complete, raise the temperature to 80 °C, add the remaining 10 mL of mixture B dropwise, and continue reflux for 5 h. After the reaction is complete, cool to room temperature, filter, wash, and dry at 60 °C for 12 h to obtain intermediate 1.

[0035] Step B2: Disperse 0.005 mol of intermediate 1 and 0.03 mol of potassium carbonate in 12 mL of deionized water and stir until homogeneous. Cool to 0°C and slowly add 72 mL of 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution. After the addition is complete, continue stirring for 12 h. After the reaction is complete, let it stand at 5°C for 24 h. Distill the upper organic phase under reduced pressure, wash, centrifuge, and dry to obtain the modified chain extender. The 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution is prepared by stirring and mixing β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and benzene in a ratio of 0.03 mol: 72 mL.

[0036] Step B3: Add 30g of poly(1,4-butanediol adipate) diol (M) n =2000) and 12g of isophorone diisocyanate were added to the reactor and stirred until homogeneous. The mixture was heated to 70℃ and reacted for 2 hours. After the reaction was completed, the mixture was cooled to 50℃, and 1.5g of 3-hydroxy-2-(hydroxymethyl)propionic acid, 0.2g of 1,1,1-tris(hydroxymethyl)ethane, 1.3g of modified chain extender, and 5mL of acetone were added. The temperature was raised to 80℃ and reacted for 40 minutes. After the reaction was completed, the mixture was cooled to 50℃, and 0.1g of dibutyltin dilaurate was added. The temperature was raised to 70℃ and reacted for 3 hours. After the reaction was completed, the mixture was cooled to 50℃, and 1.2g of hydroxyethyl acrylate was added. The temperature was raised to 70℃ and reacted for 2 hours. After the reaction was completed, the mixture was cooled to 40℃, and 0.5g of ethyl methacrylate, 1g of butyl acrylate, 2.2g of ethyl 2-(perfluorobutyl)acrylate, and 3g of 3-Trimethoxysilane propylene acrylate and 5g triethylamine are stirred and mixed evenly to obtain the prepolymer;

[0037] Step B4: Add LRS-10, 20 mL of deionized water, 3 g of ethylenediamine, and ammonium persulfate to the above polyurethane prepolymer and stir until homogeneous. Stir at 600 rpm for 20 min. After the reaction is complete, heat to 65 °C and react for 5 h. After the reaction is complete, cool to 40 °C, filter through a sieve, and collect the emulsion to obtain the modified polyurethane emulsion. LRS-10 accounts for 3% of the total mass fraction of all acrylate monomers, and ammonium persulfate accounts for 0.5% of the total mass fraction of all acrylate monomers.

[0038] Example 2

[0039] An extensible, colorfast coating comprises the following raw materials in weight percentages:

[0040] Modified polyurethane emulsion 65%, modified titanium dioxide 13%, defoamer BYK-020 2.5%, high-quality color powder 3%, silicone leveling agent BYK-381 0.8%, carbodiimide 7%, balance deionized water;

[0041] The modified titanium dioxide is prepared by the following steps:

[0042] Step A1: Add 0.15 mol n-pentylamine and 0.18 mol 3-(diethylphosphine)propionic acid to a flask containing 20 mL toluene and stir until homogeneous. Heat to 80 °C for 2.5 h under nitrogen atmosphere. After the reaction is complete, distill for 1.5 h. After the reaction is complete, filter and dry to obtain the surfactant.

[0043] Step A2: Disperse 2.5g of nano titanium dioxide in 20mL of deionized water and stir until homogeneous. Add 0.03g of surfactant and heat to 80℃. Stir and react for 4h. After the reaction is complete, filter and dry to obtain modified titanium dioxide.

[0044] The modified polyurethane emulsion is prepared by the following steps:

[0045] Step B1: Disperse 0.02 mol 2-aminopropane-1,3-diol and 1.0 g sodium hydroxide in 10 mL deionized water, denoted as mixture A. Disperse 0.04 mol ethylenediamine and 2.0 g sodium hydroxide in 20 mL deionized water, denoted as mixture B. Add mixture A to a reactor containing 0.02 mol cyanuric chloride and 40 mL acetone, stir and mix evenly, and react at 0 °C for 3 h. After the reaction is complete, add 10 mL of mixture B dropwise and react at 50 °C for 4.5 h. After the reaction is complete, raise the temperature to 85 °C, add the remaining 10 mL of mixture B dropwise, and continue reflux for 6 h. After the reaction is complete, cool to room temperature, filter, wash, and dry at 60 °C for 12 h to obtain intermediate 1.

[0046] Step B2: Disperse 0.01 mol of intermediate 1 and 0.06 mol of potassium carbonate in 24 mL of deionized water and stir until homogeneous. Cool to 0°C and slowly add 144 mL of 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution. After the addition is complete, continue stirring for 12 h. After the reaction is complete, let stand at 5°C for 24 h, then distill the upper organic phase under reduced pressure, wash, centrifuge, and dry to obtain the modified chain extender. The 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution is prepared by stirring and mixing β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and benzene in a volume ratio of 0.06 mol: 144 mL.

[0047] Step B3: Add 40g of poly(1,4-butanediol adipate) diol (M) n=2000) and 16g of isophorone diisocyanate were added to the reactor and stirred until homogeneous. The mixture was heated to 80℃ and reacted for 2.5h. After the reaction was completed, the temperature was cooled to 50℃, and 2.5g of 3-hydroxy-2-(hydroxymethyl)propionic acid, 0.3g of 1,1,1-tris(hydroxymethyl)ethane, 1.8g of modified chain extender, and 10mL of acetone were added. The temperature was raised to 80℃ and reacted for 50min. After the reaction was completed, the temperature was cooled to 50℃, and 0.15g of dibutyltin dilaurate was added. The temperature was raised to 70℃ and reacted for 3.5h. After the reaction was completed, the temperature was cooled to 50℃, and 1.2g of hydroxyethyl acrylate was added. The temperature was raised to 70℃ and reacted for 2h. After the reaction was completed, the temperature was cooled to 40℃, and 1g of ethyl methacrylate, 2g of butyl acrylate, 4.2g of ethyl 2-(perfluorobutyl)acrylate, and 4g of 3-Trimethoxysilane propylene acrylate and 8g triethylamine are stirred and mixed evenly to obtain the prepolymer;

[0048] Step B4: Add LRS-10, 20 mL of deionized water, 3 g of ethylenediamine, and ammonium persulfate to the above polyurethane prepolymer and stir until homogeneous. Stir at 700 rpm for 25 min. After the reaction is complete, heat to 75 °C and react for 6 h. After the reaction is complete, cool to 40 °C, filter through a sieve, and collect the emulsion to obtain the modified polyurethane emulsion. LRS-10 accounts for 3% of the total mass fraction of all acrylate monomers, and ammonium persulfate accounts for 0.5% of the total mass fraction of all acrylate monomers.

[0049] Example 3

[0050] An extensible, colorfast coating comprises the following raw materials in weight percentages:

[0051] The composition consists of 70% modified polyurethane emulsion, 15% modified titanium dioxide, 2% defoamer BYK-020, 2.5% high-quality color powder, 0.5% silicone leveling agent BYK-381, 5% carbodiimide, and the remainder is deionized water.

[0052] The modified titanium dioxide is prepared by the following steps:

[0053] Step A1: Add 0.2 mol n-pentylamine and 0.23 mol 3-(diethylphosphine)propionic acid to a flask containing 20 mL toluene and stir until homogeneous. Heat to 90 °C for 3 h under nitrogen atmosphere. After the reaction is complete, distill for 2 h. After the reaction is complete, filter and dry to obtain the surfactant.

[0054] Step A2: Disperse 4g of nano titanium dioxide in 20mL of deionized water and stir until homogeneous. Add 0.04g of surfactant and heat to 80℃. Stir and react for 5h. After the reaction is complete, filter and dry to obtain modified titanium dioxide.

[0055] The modified polyurethane emulsion is prepared by the following steps:

[0056] Step B1: Disperse 0.03 mol 2-aminopropane-1,3-diol and 1.2 g sodium hydroxide in 10 mL deionized water, denoted as mixture A. Disperse 0.06 mol ethylenediamine and 2.4 g sodium hydroxide in 20 mL deionized water, denoted as mixture B. Add mixture A to a reactor containing 0.03 mol cyanuric chloride and 40 mL acetone, stir and mix thoroughly, and react at 0 °C for 4 h. After the reaction is complete, add 10 mL of mixture B dropwise and react at 50 °C for 5 h. After the reaction is complete, raise the temperature to 90 °C, add the remaining 10 mL of mixture B dropwise, and continue reflux for 7 h. After the reaction is complete, cool to room temperature, filter, wash, and dry at 60 °C for 12 h to obtain intermediate 1.

[0057] Step B2: Disperse 0.015 mol of intermediate 1 and 0.09 mol of potassium carbonate in 36 mL of deionized water and stir until homogeneous. Cool to 0°C and slowly add 216 mL of 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution. After the addition is complete, continue stirring for 12 h. After the reaction is complete, let it stand at 5°C for 24 h. Distill the upper organic phase under reduced pressure, wash, centrifuge, and dry to obtain the modified chain extender. The 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl chloride benzene solution is prepared by stirring and mixing β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and benzene in a ratio of 0.09 mol: 216 mL.

[0058] Step B3: Add 50g of poly(1,4-butanediol adipate) diol (M) n =2000) and 23g of isophorone diisocyanate were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃ and reacted for 3 hours. After the reaction was completed, the temperature was cooled to 50℃, and 3g of 3-hydroxy-2-(hydroxymethyl)propionic acid, 0.45g of 1,1,1-tris(hydroxymethyl)ethane, 2.1g of modified chain extender, and 15mL of acetone were added. The temperature was raised to 80℃ and reacted for 60 minutes. After the reaction was completed, the temperature was cooled to 50℃, and 0.2g of dibutyltin dilaurate was added. The temperature was raised to 70℃ and reacted for 4 hours. After the reaction was completed, the temperature was cooled to 50℃, and 1.2g of hydroxyethyl acrylate was added. The temperature was raised to 70℃ and reacted for 2 hours. After the reaction was completed, the temperature was cooled to 40℃, and 1.5g of ethyl methacrylate, 3g of butyl acrylate, 6.2g of ethyl 2-(perfluorobutyl)acrylate, and 5g of 3-Trimethoxysilane propylene acrylate and 10g triethylamine are stirred and mixed evenly to obtain the prepolymer;

[0059] Step B4: Add LRS-10, 20 mL of deionized water, 3 g of ethylenediamine, and ammonium persulfate to the above polyurethane prepolymer and stir until homogeneous. Stir at 800 rpm for 30 min. After the reaction is complete, heat to 85 °C and react for 7 h. After the reaction is complete, cool to 40 °C, filter through a sieve, and collect the emulsion to obtain the modified polyurethane emulsion. LRS-10 accounts for 3% of the total mass fraction of all acrylate monomers, and ammonium persulfate accounts for 0.5% of the total mass fraction of all acrylate monomers.

[0060] Comparative Example 1

[0061] Compared with Example 3, the modified polyurethane emulsion in this comparative example uses propylene glycol instead of the chain extender, but all other aspects are the same.

[0062] Comparative Example 2

[0063] Compared with Example 3, the modified polyurethane emulsion in this comparative example was not modified with acrylate, but all other aspects were the same.

[0064] Comparative Example 3

[0065] Compared with Example 3, this comparative example uses nano-titanium dioxide instead of modified titanium dioxide, but all other aspects are the same.

[0066] The coatings prepared in Examples 1-3 and Comparative Examples 1-3 were directly applied to 5cm × 5cm tinplate for performance testing: Mechanical property testing: conducted according to GB / T 528-2009 standard; Color change resistance testing: the samples were placed in an 80℃, O2, UV irradiation chamber for 72 hours, and the color of the paint film on the sample surface was observed to change; Contact angle testing: the contact angle of the sample surface was measured using a contact angle measuring instrument; Corrosion resistance testing: the samples were immersed in a 55wt% sodium hydroxide solution for 24 hours, and the presence or absence of blistering on the coating surface was observed. The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As can be seen from Table 1, the coating prepared by the present invention has excellent extensibility, colorfastness, hydrophobicity, water resistance and corrosion resistance.

[0070] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A stretchable, colorfast coating, characterized in that, The raw materials include the following percentages by weight: 60-70% modified polyurethane emulsion, 12-20% modified titanium dioxide, 2-3% defoamer, 2.5-5% high-quality color powder, 0.5-1% silicone leveling agent, 5-10% crosslinking agent, and 5-15% deionized water; The modified titanium dioxide is prepared by the following steps: Step A1: Add n-pentylamine and 3-(diethylphosphine)propionic acid to a flask containing toluene and stir until homogeneous. Under nitrogen atmosphere, heat to 70-90℃ and react for 2-3 hours. After the reaction is complete, distill for 1-2 hours. After the reaction is complete, filter and dry to obtain the surfactant. Step A2: Disperse nano-titanium dioxide in deionized water and stir until homogeneous. Add surfactant and heat to 80°C. Stir and react for 3-5 hours. After the reaction is complete, filter and dry to obtain modified titanium dioxide. The modified polyurethane emulsion is prepared by the following steps: Step B1: Disperse 2-aminopropane-1,3-diol and sodium hydroxide in deionized water, denoted as mixture A. Disperse ethylenediamine and sodium hydroxide in deionized water, denoted as mixture B. Add mixture A to a reactor containing cyanuric chloride and acetone, stir and mix thoroughly, and react at 0°C for 2-4 hours. After the reaction is complete, add half of mixture B dropwise, and react at 50°C for 4-5 hours. After the reaction is complete, raise the temperature to 80-90°C, add the remaining mixture B dropwise, and continue reflux for 5-7 hours. After the reaction is complete, cool to room temperature. The mixture was cooled, filtered, washed, and dried at 60℃ for 12 hours to obtain intermediate 1. The ratio of the amounts of mixture A, mixture B, cyanuric chloride, and acetone was 10 mL: 20 mL: 0.01-0.03 mol: 40 mL. The ratio of the amounts of 2-aminopropane-1,3-diol, sodium hydroxide, and deionized water in mixture A was 0.01-0.03 mol: 0.8-1.2 g: 10 mL. The ratio of the amounts of ethylenediamine, sodium hydroxide, and deionized water in mixture B was 0.02-0.06 mol: 1.6-2.4 g: 20 mL. Step B2: Disperse intermediate 1 and potassium carbonate in deionized water and stir until homogeneous. Cool to 0°C and slowly add β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride solution. After the addition is complete, continue stirring for 12 hours. After the reaction is complete, let it stand at 5°C for 24 hours. Distill the upper organic phase under reduced pressure, wash, centrifuge, and dry to obtain the modified chain extender: intermediate 1, potassium carbonate, deionized water, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride solution. The volume ratio of tert-butyl-4-hydroxyphenyl)propionyl chloride benzene solution is 0.005-0.015 mol : 0.03-0.09 mol : 12-36 mL : 72-216 mL. β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride benzene solution is prepared by mixing β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and benzene in a volume ratio of 0.03-0.09 mol : 72-216 mL. Step B3: Add poly(1,4-butanediol adipate) and isophorone diisocyanate to the reactor and stir until homogeneous. Heat to 70-90℃ and react for 2-3 hours. After the reaction is complete, cool to 50℃, add 3-hydroxy-2-(hydroxymethyl)propionic acid, 1,1,1-tris(hydroxymethyl)ethane, chain extender and acetone, raise the temperature to 80℃ and react for 40-60 minutes. After the reaction is complete, cool to 50℃, add dibutyltin dilaurate, raise the temperature to 70℃ and react for 3-4 hours. After the reaction is complete, cool to 50℃, add hydroxyethyl acrylate, raise the temperature to 70℃ and react for 2 hours. After the reaction is complete, cool to 40℃, add ethyl methacrylate, butyl acrylate, ethyl 2-(perfluorobutyl)acrylate, propyl 3-trimethoxysilane acrylate and triethylamine and stir until homogeneous to obtain the prepolymer. Step B4: Add LRS-10, deionized water, ethylenediamine and ammonium persulfate to the above polyurethane prepolymer and stir until homogeneous. Stir at 600-800 rpm for 20-30 minutes. After the reaction is complete, heat to 65-85℃ and react for 5-7 hours. After the reaction is complete, cool to 40℃, filter through a sieve, and collect the emulsion to obtain the modified polyurethane emulsion.

2. The stretchable anti-color change coating according to claim 1, characterized in that, In step A1, the ratio of n-pentylamine, 3-(diethylphosphine)propionic acid, and toluene is 0.1-0.2 mol: 0.13-0.23 mol: 20 mL.

3. The stretchable anti-color change coating according to claim 1, characterized in that, In step A2, the ratio of nano-titanium dioxide, deionized water, and surfactant is 2-4g: 20mL: 0.02-0.04g.

4. The stretchable anti-color change coating according to claim 1, characterized in that, In step B3, the following proportions of substances are used: poly(1,4-butanediol adipate), isophorone diisocyanate, 3-hydroxy-2-(hydroxymethyl)propionic acid, 1,1,1-tris(hydroxymethyl)ethane, chain extender, acetone, dibutyltin dilaurate, hydroxyethyl acrylate, ethyl methacrylate, butyl acrylate, ethyl 2-(perfluorobutyl)acrylate, propyl 3-trimethoxysilane acrylate, and triethylamine: 30-50g: 12-23g: 1.5-3g: 0.2-0.45g: 1.3-2.1g: 5-15mL: 0.1-0.2g: 1.2g: 0.5-1.5g: 1-3g: 2.2-6.2g: 3-5g: 5-10g.

5. The stretchable anti-color change coating according to claim 1, characterized in that, In step B4, LRS-10 accounts for 3% of the total mass fraction of all acrylate monomers, ammonium persulfate accounts for 0.5% of the total mass fraction of all acrylate monomers, and the amounts of deionized water and ethylenediamine are 20 mL and 3 g, respectively.

6. The stretchable anti-color change coating according to claim 1, characterized in that, The defoamer is BYK-020; the silicone leveling agent is BYK-381; and the crosslinking agent is carbodiimide.

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