A color stainless steel pigment and a method for preparing the same

Abstract

This invention discloses a colored stainless steel pigment and its preparation method. The preparation method includes: reacting stainless steel powder with a silicon source precursor and an aminosilane coupling agent in a sol-gel reaction to obtain stainless steel powder coated with a silica layer; reacting the silica-coated stainless steel powder with dialdehyde and polyethylenepolyamine in a Schiff base condensation reaction to obtain stainless steel powder coated with an amino silica layer; and reacting the amino silica-coated stainless steel powder with an organic pigment containing carboxylic acid groups in an amide condensation reaction to obtain stainless steel powder grafted with organic dyes, which is the colored stainless steel pigment. This invention permanently fixes organic pigments onto the surface of surface-modified stainless steel pigments through chemical bonding, thereby obtaining a colored stainless steel effect pigment with both excellent weather resistance and chemical stability, as well as vibrant colors across the entire color gamut.

Description

Technical Field

[0001] This invention belongs to the field of metal pigment technology, and particularly relates to a colored stainless steel pigment and its preparation method. Background Technology

[0002] Metallic pigments, such as aluminum pigments, are widely used in coatings, inks, and plastics due to their unique luster and decorative effects. Traditional colored aluminum pigments primarily produce color by coating their surface with a layer of metal oxide (such as TiO2 or Fe2O3) interference film. However, aluminum is chemically reactive and easily corrodes in acidic, alkaline, or saline environments, leading to pigment blackening, coating blistering, and failure, severely limiting its application in high-end fields such as heavy-duty corrosion protection and long-lasting outdoor decoration.

[0003] Stainless steel powder is considered an ideal substrate to replace aluminum powder due to its excellent corrosion resistance and mechanical strength. Currently, coloring of stainless steel powder mainly focuses on combining pigments with the powder through physical mixing or simple physical adsorption. However, this method suffers from problems such as poor colorfastness, easy flaking, and poor weather resistance. Some technologies have attempted to directly generate interference-color oxide films on the stainless steel surface, but these result in limited color options, difficulty in process control, and a lack of ability to obtain vibrant colors across the entire color spectrum.

[0004] Therefore, developing a colored pigment that can inherit the excellent stability of stainless steel core and achieve strong, bright and diverse colors, as well as an efficient preparation method, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a colored stainless steel pigment and its preparation method. By permanently fixing organic pigments to the surface of surface-modified stainless steel pigments through chemical bonding, a colored stainless steel effect pigment with both excellent weather resistance and chemical stability and vibrant colors across the entire color spectrum is obtained.

[0006] The present invention provides a method for preparing colored stainless steel pigment, comprising the following steps:

[0007] S1. Stainless steel powder is reacted with silicon source precursor and aminosilane coupling agent in a sol-gel reaction to obtain stainless steel powder coated with silica layer.

[0008] S2. The silica-coated stainless steel powder is subjected to Schiff base condensation reaction with dialdehyde and polyethylene polyamine to obtain aminated silica-coated stainless steel powder.

[0009] S3. The stainless steel powder coated with an aminated silica layer is subjected to an amide condensation reaction with an organic pigment containing a carboxylic acid group to obtain stainless steel powder grafted with organic dye, which is the colored stainless steel pigment.

[0010] In this invention, a silicon source and an aminosilane coupling agent are used as precursors to coat a layer of SiO2 onto the surface of stainless steel powder. Then, the amino groups on the surface of the stainless steel powder coated with the SiO2 layer are modified by Schiff base condensation with dialdehyde and polyethylene polyamine, thereby introducing active amino groups onto the surface of the stainless steel powder coated with the SiO2 layer. Subsequently, an organic pigment with a carboxylic acid group is subjected to an amide condensation reaction with the active amino group, thereby chemically grafting the organic pigment onto the surface of the stainless steel powder. Finally, a colored stainless steel effect pigment with excellent weather resistance and chemical stability as well as bright colors across the entire color spectrum is obtained.

[0011] Preferably, in step S1, the silicon source precursor is at least one of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, butyl orthosilicate, or pentyl orthosilicate; and the aminosilane coupling agent is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, or 3-aminopropylmethyltriethoxysilane.

[0012] The amount of the silicon source precursor is 20-40 wt% of the stainless steel powder, and the amount of the aminosilane coupling agent is 5-20 wt% of the stainless steel powder.

[0013] Preferably, the sol-gel reaction is carried out under an alkaline catalyst, wherein the alkaline catalyst is ammonia or ethylenediamine;

[0014] The sol-gel reaction is carried out at a temperature of 40-70℃ for 5-7 hours.

[0015] Preferably, in step S2, the dialdehyde is at least one of glutaraldehyde, glyoxal, or adipaldehyde; and the polyethylene polyamine is at least one of triethylenetetramine, diethylenetriamine, tetraethylenepentamine, or polyethyleneimine.

[0016] The amount of the dialdehyde is 5-20 wt% of the stainless steel powder, and the amount of the polyethylene polyamine is 1-10 wt% of the stainless steel powder.

[0017] The Schiff base condensation reaction is carried out at a temperature of 50-70℃ for 4-6 hours.

[0018] Preferably, in step S3, the organic pigment is at least one of Direct Brown 95, Cy5 carboxylic acid, 5-carboxyfluorescein, or carboxytetramethylrhodamine.

[0019] The amount of the organic pigment used is 0.5-5 wt% of the stainless steel powder.

[0020] Preferably, the amide condensation reaction is carried out under a condensation reagent, which is 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide or dicyclohexylcarbodiimide and 4-dimethylaminopyridine.

[0021] The condensation reaction is carried out at a temperature of 10-30℃ for 6-8 hours.

[0022] Preferably, the process further includes step S4, whereby the stainless steel powder grafted with organic dye undergoes a Schiff base condensation reaction with p-vinylbenzaldehyde, followed by the addition of a hydrophilic polymer monomer for a polycondensation reaction, to obtain a polymer layer coated with the stainless steel powder grafted with organic dye.

[0023] In this invention, some of the active amino groups on the surface of the grafted organic dye stainless steel powder undergo a condensation reaction with p-vinylbenzaldehyde to obtain composite particles with vinylbenzene end groups. These particles can then polymerize in situ with hydrophilic polymer monomers on the surface of the stainless steel powder under initiator conditions to form a hydrophilic polymer coating layer. This results in polymer-coated stainless steel pigments, which can effectively protect organic pigments and further enhance their color fastness.

[0024] Preferably, the hydrophilic polymer monomer is at least one of poly(ethylene glycol) methacrylate, methoxy polyethylene glycol acrylate, or polyethylene glycol diacrylate.

[0025] The amount of the hydrophilic polymer monomer is 1-20 wt% of the stainless steel powder.

[0026] The present invention also proposes a colored stainless steel pigment prepared by the above preparation method.

[0027] Preferably, the colored stainless steel pigment comprises: stainless steel powder, silica coated on the surface of the stainless steel powder, and organic pigments chemically grafted onto the surface of the silica.

[0028] The beneficial effects of this invention are:

[0029] (1) Excellent performance: Due to the inherent advantages of stainless steel powder, colored stainless steel effect pigments have excellent weather resistance and physical strength, making them suitable for extreme environments.

[0030] (2) Color fastness: Organic pigments form chemical bonds with the silica layer on the metal surface, avoiding pigment loss and bleeding problems caused by physical adsorption, and the color is long-lasting and stable.

[0031] (3) Rich colors: Breaking through the limitation of the single color of traditional interference color stainless steel pigments, it can use the existing full spectrum of organic pigments to achieve the design of any color, providing a rich color selection for high-performance coatings.

[0032] (4) Controllable process: The sol-gel method and surface chemical grafting method are both mature chemical unit operations with mild reaction conditions. The thickness and color depth of the coating layer can be precisely controlled by process parameters, making it easy to achieve large-scale production. Attached Figure Description

[0033] Figure 1 SEM images of the flake stainless steel powder described in Example 1: (a) is an SEM image at 1000x magnification, and (b) is an SEM image at 3000x magnification.

[0034] Figure 2 The SEM images of the silica layer-coated flake stainless steel powder described in Example 1 are as follows: (a) is the SEM image at 1000x magnification, and (b) is the SEM image at 3000x magnification.

[0035] Figure 3 The following are SEM images of the colored stainless steel pigment described in Example 1: (a) is an SEM image at 2000x magnification, and (b) is an SEM image at 3000x magnification. Detailed Implementation

[0036] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0037] Example 1

[0038] This embodiment presents a colored stainless steel pigment, which is prepared by the following method:

[0039] (1) Add the flake stainless steel powder (D50 particle size ≤ 20 μm, 304 austenitic stainless steel) to 1 wt% dilute nitric acid and ultrasonically clean for 10 min. After filtration, wash with deionized water until neutral, add it to a mixed solvent of ethanol-isopropanol-deionized water (volume ratio 1:1:8), and then add silane coupling agent KH560. The amount of silane coupling agent KH560 added is 1 wt% of the flake stainless steel powder. Heat to 100℃, evaporate the solvent in a rotary evaporator, and then dry at 150℃ to obtain pretreated flake stainless steel powder.

[0040] (2) The pretreated sheet stainless steel powder was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added and the system was stirred to adjust the pH value to 10. After heating to 55°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 30 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 15 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 5 hours, the mixture was kept warm and stirred for another 6 hours. The mixture was then filtered, washed with ethanol, and dried to obtain silica-coated stainless steel powder.

[0041] (3) The above-mentioned silica-coated stainless steel powder was added to a methanol-acetic acid mixed solvent (volume ratio of 100:1) and ultrasonically dispersed evenly. Glutaraldehyde was added, and the amount of glutaraldehyde added was 15 wt% of the sheet stainless steel powder. After heating to 60°C, the mixture was stirred for 2 h. Triethylenetetramine was then added, and the amount of triethylenetetramine added was 6 wt% of the sheet stainless steel powder. The mixture was stirred for another 3 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain aminated silica-coated stainless steel powder.

[0042] (4) The above-mentioned aminated silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing Direct Brown 95 was added, with the amount of Direct Brown 95 being 3 wt% of the flake stainless steel powder. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added, with the amount of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide being 0.3 wt% of the flake stainless steel powder and the amount of N-hydroxysuccinimide being 0.3 wt% of the flake stainless steel powder. The mixture was stirred and reacted at room temperature for 5 h. After filtration, the mixture was washed with ethanol and dried to obtain the colored stainless steel pigment.

[0043] Figure 1 The image shows the SEM image of the uncoated flake stainless steel powder from step (1) above. Figure 2 This is a SEM image of the sheet-like stainless steel powder coated with a silica layer but not colored in step (2) above. Figure 3 The image shows the SEM image of the colored stainless steel pigment after coloring in step (4) above. The comparison shows that the original stainless steel powder surface is a flat and smooth sheet-like layer, while the colored stainless steel powder surface has some particles. This is due to the successful grafting of brown 95 onto the stainless steel powder surface.

[0044] Example 2

[0045] This embodiment presents a colored stainless steel pigment, which is prepared by the following method:

[0046] (1) The pretreated sheet stainless steel powder described in Example 1 was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added, and the system was stirred to adjust the pH value to 9. After heating to 70°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 20 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 5 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 3 hours, the mixture was kept warm and stirred for another 5 hours. The mixture was then filtered, washed with ethanol, and dried to obtain stainless steel powder coated with silica layer.

[0047] (2) The above-mentioned silica-coated stainless steel powder was added to a methanol-acetic acid mixed solvent (volume ratio of 100:1) and ultrasonically dispersed evenly. Then glutaraldehyde was added, the amount of glutaraldehyde added was 8 wt% of the flake stainless steel powder. After heating to 50°C, the mixture was stirred for 1 h. Then tetraethylenepentamine was added, the amount of tetraethylenepentamine added was 3 wt% of the flake stainless steel powder. The mixture was stirred for another 3 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain aminated silica-coated stainless steel powder.

[0048] (3) The above-mentioned aminated silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing Cy5 carboxylic acid was added. The amount of Cy5 carboxylic acid added was 2 wt% of the flake stainless steel powder. Then, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added. The amount of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide added was 0.2 wt% of the flake stainless steel powder, and the amount of N-hydroxysuccinimide added was 0.2 wt% of the flake stainless steel powder. The mixture was stirred and reacted at room temperature for 5 h. After filtration, the mixture was washed with ethanol and dried to obtain the colored stainless steel pigment.

[0049] Example 3

[0050] This embodiment presents a colored stainless steel pigment, which is prepared by the following method:

[0051] (1) The pretreated sheet stainless steel powder described in Example 1 was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added, and the system was stirred to adjust the pH value to 11. After heating to 40°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 40 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 20 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 6 hours, the mixture was kept warm and stirred for another 7 hours. The mixture was then filtered, washed with ethanol, and dried to obtain silica-coated stainless steel powder.

[0052] (2) The above-mentioned silica-coated stainless steel powder was added to a methanol-acetic acid mixed solvent (volume ratio of 100:1) and ultrasonically dispersed evenly. Then glutaraldehyde was added, the amount of glutaraldehyde added was 20 wt% of the sheet stainless steel powder. After heating to 60°C, the mixture was stirred for 3 h. Then polyethyleneimine was added, the amount of polyethyleneimine added was 10 wt% of the sheet stainless steel powder. The mixture was stirred for another 3 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain aminated silica-coated stainless steel powder.

[0053] (3) The above-mentioned aminated silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing carboxytetramethylrhodamine was added, with the amount of carboxytetramethylrhodamine added being 5 wt% of the flake stainless steel powder. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added, with the amount of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide added being 0.5 wt% of the flake stainless steel powder and the amount of N-hydroxysuccinimide added being 0.5 wt% of the flake stainless steel powder. The mixture was stirred and reacted at room temperature for 5 h. After filtration, the mixture was washed with ethanol and dried to obtain the colored stainless steel pigment.

[0054] Example 4

[0055] This embodiment presents a colored stainless steel pigment, which is prepared by the following method:

[0056] (1) Add the flake stainless steel powder (D50 particle size ≤ 20 μm, 304 austenitic stainless steel) to 1 wt% dilute nitric acid and ultrasonically clean for 10 min. After filtration, wash with deionized water until neutral, add it to a mixed solvent of ethanol-isopropanol-deionized water (volume ratio 1:1:8), and then add silane coupling agent KH560. The amount of silane coupling agent KH560 added is 1 wt% of the flake stainless steel powder. Heat to 100℃, evaporate the solvent in a rotary evaporator, and then dry at 150℃ to obtain pretreated flake stainless steel powder.

[0057] (2) The pretreated sheet stainless steel powder was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added and the system was stirred to adjust the pH value to 10. After heating to 55°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 30 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 15 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 5 hours, the mixture was kept warm and stirred for another 6 hours. The mixture was then filtered, washed with ethanol, and dried to obtain silica-coated stainless steel powder.

[0058] (3) The above-mentioned silica-coated stainless steel powder was added to a methanol-acetic acid mixed solvent (volume ratio of 100:1) and ultrasonically dispersed evenly. Glutaraldehyde was added, and the amount of glutaraldehyde added was 15 wt% of the flake stainless steel powder. After heating to 60°C, the mixture was stirred for 2 h. Triethylenetetramine was then added, and the amount of triethylenetetramine added was 6 wt% of the flake stainless steel powder. The mixture was stirred for another 3 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain aminated silica-coated stainless steel powder.

[0059] (4) The above-mentioned aminated silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing Direct Brown 95 was added. The amount of Direct Brown 95 added was 3 wt% of the flake stainless steel powder. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added. The amount of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide added was 0.3 wt% of the flake stainless steel powder, and the amount of N-hydroxysuccinimide added was 0.3 wt% of the flake stainless steel powder. The mixture was stirred at room temperature for 5 h, filtered, washed with ethanol, and dried to obtain stainless steel powder grafted with organic dye.

[0060] (5) The above-mentioned grafted organic dye stainless steel powder is added to ethanol and dispersed evenly. Then, p-vinylbenzaldehyde is added, with the amount of p-vinylbenzaldehyde being 1 wt% of the flake stainless steel powder. After heating to 60°C, the mixture is stirred for 1 h. Then, polyethylene glycol methacrylate and benzoyl peroxide are added, with the amount of polyethylene glycol methacrylate being 5 wt% of the flake stainless steel powder and the amount of benzoyl peroxide being 0.05 wt% of the flake stainless steel powder. After stirring and maintaining the temperature for 4 h, the mixture is filtered, washed with ethanol, and dried to obtain the colored stainless steel pigment.

[0061] Comparative Example 1

[0062] This comparative example presents a colored stainless steel pigment, which is prepared by the following method:

[0063] (1) Add the flake stainless steel powder (D50 particle size ≤ 20 μm, 304 austenitic stainless steel) to 1 wt% dilute nitric acid and ultrasonically clean for 10 min. After filtration, wash with deionized water until neutral, add it to a mixed solvent of ethanol-isopropanol-deionized water (volume ratio 1:1:8), and then add silane coupling agent KH560. The amount of silane coupling agent KH560 added is 1 wt% of the flake stainless steel powder. Heat to 100℃, evaporate the solvent in a rotary evaporator, and then dry at 150℃ to obtain pretreated flake stainless steel powder.

[0064] (2) The pretreated sheet stainless steel powder was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added and the system was stirred to adjust the pH value to 10. After heating to 55°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 30 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 15 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 5 hours, the mixture was kept warm and stirred for another 6 hours. The mixture was then filtered, washed with ethanol, and dried to obtain silica-coated stainless steel powder.

[0065] (3) The silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing Direct Brown 95 was added. The amount of Direct Brown 95 added was 3 wt% of the flake stainless steel powder. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added. The amount of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide added was 0.3 wt% of the flake stainless steel powder, and the amount of N-hydroxysuccinimide added was 0.3 wt% of the flake stainless steel powder. The mixture was stirred and reacted at room temperature for 5 h. After filtration, the mixture was washed with ethanol and dried to obtain the colored stainless steel pigment.

[0066] Comparative Example 2

[0067] This comparative example presents a colored stainless steel pigment, which is prepared by the following method:

[0068] (1) Add the flake stainless steel powder (D50 particle size ≤ 20 μm, 304 austenitic stainless steel) to 1 wt% dilute nitric acid and ultrasonically clean for 10 min. After filtration, wash with deionized water until neutral, add it to a mixed solvent of ethanol-isopropanol-deionized water (volume ratio 1:1:8), and then add silane coupling agent KH560. The amount of silane coupling agent KH560 added is 1 wt% of the flake stainless steel powder. Heat to 100℃, evaporate the solvent in a rotary evaporator, and then dry at 150℃ to obtain pretreated flake stainless steel powder.

[0069] (2) The pretreated sheet stainless steel powder was added to an ethanol-water (volume ratio of 8:2) mixed solvent and ultrasonically dispersed evenly. Ammonia water was added and the system was stirred to adjust the pH value to 10. After heating to 55°C, an ethanol solution containing tetraethyl orthosilicate and silane coupling agent KH550 was added dropwise. The amount of tetraethyl orthosilicate added was 30 wt% of the sheet stainless steel powder, and the amount of silane coupling agent KH550 added was 15 wt% of the sheet stainless steel powder. After the dropwise addition was completed in 5 hours, the mixture was kept warm and stirred for another 6 hours. The mixture was then filtered, washed with ethanol, and dried to obtain silica-coated stainless steel powder.

[0070] (3) The above-mentioned silica-coated stainless steel powder was added to a methanol-acetic acid mixed solvent (volume ratio of 100:1) and ultrasonically dispersed evenly. Glutaraldehyde was added, and the amount of glutaraldehyde added was 15 wt% of the sheet stainless steel powder. After heating to 60°C, the mixture was stirred for 2 h. Triethylenetetramine was then added, and the amount of triethylenetetramine added was 6 wt% of the sheet stainless steel powder. The mixture was stirred for another 3 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain aminated silica-coated stainless steel powder.

[0071] (4) The above-mentioned aminated silica-coated stainless steel powder was added to N,N-dimethylformamide (DMF) and ultrasonically dispersed evenly. Then, a DMF solution containing Direct Brown 95 was added. The amount of Direct Brown 95 added was 3 wt% of the flake stainless steel powder. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide were added. The amount of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide added was 0.3 wt% of the flake stainless steel powder, and the amount of N-hydroxysuccinimide added was 0.3 wt% of the flake stainless steel powder. The mixture was stirred at room temperature for 5 h, filtered, washed with ethanol, and dried to obtain stainless steel powder grafted with organic dye.

[0072] (5) The above-mentioned grafted organic dye stainless steel powder is added to ethanol and dispersed evenly. After heating to 60°C, polyethylene glycol methacrylate and benzoyl peroxide are added. The amount of polyethylene glycol methacrylate added is 5 wt% of the flake stainless steel powder, and the amount of benzoyl peroxide added is 0.05 wt% of the flake stainless steel powder. After stirring and reacting for 4 hours, the mixture is filtered, washed with ethanol, and dried to obtain the colored stainless steel pigment.

[0073] Colorimetric analysis was performed on the colored stainless steel pigments described in Examples 1, 2, 4, and Comparative Example 1. Specifically, 1.5 wt% of the colored stainless steel pigment was added to water-based acrylic resin, and a 50 μm thick film was formed on scraper paper using a wet film preparation device. The L, a, b, and C values ​​of the water-based acrylic resin coatings of each group of colored stainless steel pigments were then characterized using a colorimeter. Each group was tested three times, and the average value was taken. Indicates brightness. This indicates the range from magenta to green (where positive values ​​represent the red direction and negative values ​​represent the green direction). The range from yellow to blue is represented (positive values ​​indicate the yellow direction and negative values ​​indicate the blue direction), and the results are shown in Table 1 below.

[0074] Table 1 shows the hue results of the colored stainless steel pigments described in the examples or comparative examples.

[0075]

[0076] As shown in Table 1 above, Examples 1 and 4 exhibit a yellowish-red hue, while Example 2 exhibits a bluish-green hue, indicating that the organic pigments in these examples are bonded to the surface of the stainless steel powder. The color saturation value of Example 4 is greater than that of Example 1, indicating that the polymer layer coating can fix the organic pigments and further enhance the color performance. Although the comparative example also exhibits a yellowish-red hue, its color saturation value is far lower than that of Example 1, indicating that although the simple aminosilane coupling agent can also make the surface of the silica-coated stainless steel powder have amino groups, it cannot form an effective bonding reaction with the organic pigments, and the resulting stainless steel powder cannot obtain an effective color effect.

[0077] The colored stainless steel pigments described in the examples and comparative examples were mixed evenly with ethylene glycol butyl ether (BCS) and water-based acrylic resin at a mass ratio of 7.5:7.5:85, and then sprayed onto a stainless steel plate (15cm in size). The resulting coating thickness was 50 μm on a 7 cm surface. Comparative experiments were then conducted under dry heat (temperature 105℃, time 240 h), damp heat (temperature 80℃, humidity 60%, time 240 h), and UV aging (temperature 25℃, vertical irradiation distance 20 cm, 50W UV lamp, time 480 h). The results are shown in Table 2 below.

[0078] Table 2 shows the aging resistance results of the colored stainless steel pigments described in the examples or comparative examples.

[0079]

[0080] Color difference is calculated using the following formula: ΔE=(ΔL) 2 +Δa 2 +Δb 2 ) 1 / 2 The magnitude of the ΔE value reflects the degree of color change; a larger ΔE value indicates a greater color change, and vice versa.

[0081] As shown in Table 2 above, the color change of the colored stainless steel pigments described in Examples 1-4 after ultraviolet aging is smaller than that in Comparative Example 1, indicating that the colored stainless steel pigments of the present invention have both the effect of bright colors across the entire color spectrum and excellent weather resistance and chemical stability.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a color stainless steel pigment, characterized by, Includes the following steps: S1. Stainless steel powder is reacted with silicon source precursor and aminosilane coupling agent in a sol-gel reaction to obtain stainless steel powder coated with silica layer. S2. The silica-coated stainless steel powder is subjected to Schiff base condensation reaction with dialdehyde and polyethylene polyamine to obtain aminated silica-coated stainless steel powder. S3. The stainless steel powder coated with an aminated silica layer is subjected to an amide condensation reaction with an organic pigment containing a carboxylic acid group to obtain stainless steel powder grafted with organic dye, which is the colored stainless steel pigment. S4. After performing a Schiff base condensation reaction between the stainless steel powder grafted with organic dye and p-vinylbenzaldehyde, a hydrophilic polymer monomer is added to perform a condensation reaction to obtain a polymer layer coated with the grafted organic dye stainless steel powder.

2. The method for preparing colored stainless steel pigment according to claim 1, characterized in that, In step S1, the silicon source precursor is at least one of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, butyl orthosilicate, or pentyl orthosilicate; the aminosilane coupling agent is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, or 3-aminopropylmethyltriethoxysilane. The amount of the silicon source precursor is 20-40 wt% of the stainless steel powder, and the amount of the aminosilane coupling agent is 5-20 wt% of the stainless steel powder.

3. The method for preparing colored stainless steel pigment according to claim 2, characterized in that, The sol-gel reaction is carried out under an alkaline catalyst, which is ammonia or ethylenediamine. The sol-gel reaction is carried out at a temperature of 40-70℃ for 5-7 hours.

4. The process for the preparation of the colored stainless steel pigments according to any one of claims 1 to 3, characterized in that, In step S2, the dialdehyde is at least one of glutaraldehyde, glyoxal, or adipaldehyde; the polyethylene polyamine is at least one of triethylenetetramine, diethylenetriamine, tetraethylenepentamine, or polyethyleneimine. The amount of the dialdehyde is 5-20 wt% of the stainless steel powder, and the amount of the polyethylene polyamine is 1-10 wt% of the stainless steel powder. The Schiff base condensation reaction is carried out at a temperature of 50-80℃ for 4-6 hours.

5. The method for preparing colored stainless steel pigment according to any one of claims 1-3, characterized in that, In step S3, the organic pigment is at least one of Direct Brown 95, Cy5 carboxylic acid, 5-carboxyfluorescein, or carboxytetramethylrhodamine. The amount of the organic pigment used is 0.5-5 wt% of the stainless steel powder.

6. The method for preparing colored stainless steel pigment according to claim 5, characterized in that, The amide condensation reaction is carried out under a condensation reagent, which is 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide or dicyclohexylcarbodiimide and 4-dimethylaminopyridine. The condensation reaction is carried out at a temperature of 10-30℃ for 6-8 hours.

7. The method for preparing colored stainless steel pigment according to claim 1, characterized in that, The hydrophilic polymer monomer is at least one of poly(ethylene glycol) methacrylate, methoxy polyethylene glycol acrylate, or polyethylene glycol diacrylate. The amount of the hydrophilic polymer monomer is 1-20 wt% of the stainless steel powder.

8. A colored stainless steel pigment prepared by the preparation method according to any one of claims 1-7.

9. The colored stainless steel pigment according to claim 8, characterized in that, The colored stainless steel pigment includes: stainless steel powder, silica coating the surface of the stainless steel powder, and organic pigments chemically grafted onto the surface of the silica.

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