Environmentally friendly pigments and methods for their preparation

Abstract

The application discloses an environment-friendly pigment and a preparation method thereof, and relates to the technical field of coatings.The environment-friendly pigment is composed of europium-gadolinium co-doped samarium oxysulfide powder, tetrabutyl titanate, gamma-methacryloyloxypropyl trimethoxysilane, cerium acetylacetone and polytetrafluoroethylene powder; the polytetrafluoroethylene and the coated and modified europium-gadolinium co-doped samarium oxysulfide powder are subjected to heat treatment, a carbon fluoride layer with excellent hydrophobicity and chemical inertia is formed on the surface of the europium-gadolinium co-doped samarium oxysulfide powder, the adsorption and retention of water vapor, oxygen, acid rain and the like on the surface of the pigment are blocked, the reaction chain required by photoaging is cut off, the ultraviolet protection and corrosion prevention barrier effect are enhanced, the Ti-O-Si hybrid shell layer is tightly combined, a double high-temperature protection system is formed, the risk that the pigment is oxidized under high temperature is reduced, and the weather resistance and corrosion resistance of the pigment are improved, and the adverse effects of illumination, high temperature and corrosion environment on the color rendering property of the pigment are effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically referring to an environmentally friendly pigment and its preparation method. Background Technology

[0002] Pigments are coloring substances composed of tiny particles that are insoluble in the application medium. Their main functions include: obtaining rich colors by combining and mixing different colored pigments; providing hiding power to the surface of an object through coating; and improving the lightfastness, heat resistance, and chemical stability of the coated object to ensure its long-term use. Pigments are mainly divided into inorganic pigments and organic pigments. Among them, inorganic pigments have a longer history of application and have a wider application prospect due to their environmental advantages. Therefore, inorganic pigments are widely used in many fields such as paints, coatings, plastics, decorations, cosmetics, and painting.

[0003] The existing technology currently suffers from the following main problems:

[0004] Single inorganic pigments generally have poor corrosion resistance. At the same time, under the influence of light and high temperature, the color performance of pigments is adversely affected, and they are prone to fading, discoloration and other phenomena. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention proposes an environmentally friendly pigment, which is made of the following components in parts by weight: 10-20 parts of europium-gadolinium co-doped samarium oxysulfide powder, 3-6 parts of tetrabutyl titanate, 2-4 parts of γ-methacryloyloxypropyltrimethoxysilane, 0.1-0.3 parts of cerium acetylacetonate, and 0.8-1.6 parts of polytetrafluoroethylene powder.

[0006] The europium-gadolinium co-doped samarium oxysulfide powder is made from the following components in parts by weight: 36-40 parts samarium nitrate hexahydrate, 4-8 parts europium nitrate hexahydrate, and 4-6 parts gadolinium nitrate hexahydrate.

[0007] The preparation method of the europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps:

[0008] (1) Add 3.6-4.0g of samarium hexahydrate to 50mL of deionized water, then add europium hexahydrate and gadolinium hexahydrate in sequence, stir for 5-10min, then add 4.1-4.3g of disodium ethylenediaminetetraacetate, stir for 30-40min, and adjust the pH to 8.0-10.0 by adding concentrated ammonia dropwise while stirring. Then slowly add dilute nitric acid to adjust the pH back to 7.0, stir for 1-2h, and finally transfer to an evaporating dish and dry in an 80℃ oven for 24-48h. Place the resulting dry gel in a muffle furnace. First, the temperature is increased to 300℃ at a rate of 2℃ / min and held for 1-2 hours. Then, the temperature is increased to 600℃ at a rate of 5℃ / min and held for 1-2 hours. After natural cooling, the mixture is removed and ground. Disodium ethylenediaminetetraacetate (EDTA) acts as a strong chelating agent to form soluble complexes with samarium, europium, and gadolinium ions. Through a sol-gel process, the atomic-level uniform mixing of samarium, europium, and gadolinium in three-dimensional space is ensured, thereby obtaining a highly active, high specific surface area, and homogeneous oxide precursor, which lays the foundation for the subsequent sulfidation reaction and yields the precursor powder.

[0009] (2) The precursor powder described in step (1) is evenly spread in an alumina ceramic boat with a powder layer thickness of 2.0-2.8 mm. The alumina ceramic boat is then placed in a tube furnace, a vacuum is drawn, and Ar is introduced at a flow rate of 140 mL / min. The temperature is first raised to 400-450 °C at a rate of 5 °C / min, and then held for 30-40 min. The gas is then switched to an Ar / CS2 mixture, with the total flow rate controlled at 140 mL / min. 40 mL / min is used as a carrier gas, flowing through a CS2 bubble bottle placed in a 0 °C ice-water bath to carry CS2 vapor. This vapor is then mixed with the remaining 100 mL / min bypass Ar to form the reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then raised to 880 °C at a rate of 2 °C / min for sulfidation treatment. The reaction is held for 2- After 3 hours, the temperature is lowered to 200℃ at a rate of 2-3℃ / min. The CS2 gas path is closed, and the furnace tube is purged with pure Ar for 10-20 minutes. Then, the furnace is allowed to cool naturally to room temperature. The product is then removed. CS2 decomposes at high temperature to produce active sulfur species. These sulfur atoms gradually replace some of the oxygen atoms in the oxide precursor to form thermodynamically more stable rare earth oxygen sulfides. At the same time, the overall morphology and uniform doping distribution of the precursor are preserved. The uniform doping of europium and gadolinium in samarium oxygen sulfide forms a more uniform, dense, and chemically inert oxygen sulfide solid solution, which provides a physical barrier protection, prevents the corrosive medium from penetrating into the interior and damaging the europium ions at the luminescent center, and better resists the adverse effects of light, heat and chemical erosion on the coloring performance. It also enhances weather resistance and corrosion resistance, resulting in europium and gadolinium co-doped samarium oxygen sulfide powder.

[0010] Preferably, in step (1), the amounts of europium hexahydrate and gadolinium hexahydrate added are 0.4-0.8g and 0.4-0.6g, respectively. The presence of europium ions in europium hexahydrate makes the color pure and saturated. The gadolinium ions in gadolinium hexahydrate are incorporated as a structural stabilizer. Their ionic radius and chemical properties can optimize lattice defects and improve the stability of the overall structure at high temperatures. At the same time, they can also make the solid solution lattice more compact and improve the overall chemical inertness to media such as acids and alkalis.

[0011] This invention also provides a method for preparing an environmentally friendly pigment, specifically including the following steps:

[0012] S1. Disperse 1.0-2.0g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 30-40min. Then add 0.2-0.3g of polyvinylpyrrolidone and sonicate for 5-10min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 20-30min to form a core dispersion for later use. Disperse 0.3-0.6mL of tetrabutyl titanate in 10mL of anhydrous ethanol, then add cerium acetylacetone and stir for 10-20min. Then add 0... Add 0.05 mL of acetylacetone and stir for 20-30 min to form coating solution I. Disperse 0.2-0.4 mL of γ-methacryloxypropyltrimethoxysilane in 10 mL of anhydrous ethanol and stir for 5-10 min to form coating solution II. Under stirring speed of 600-800 rpm and temperature of 25-30°C, simultaneously add coating solutions I and II dropwise to the nucleus dispersion at a rate of 1 drop / 5 seconds using a dropping funnel, completing the addition within 2 hours. Continue the reaction for 0.5-1 hour, centrifuge, and collect the precipitate according to... The solid material was washed 3-5 times with acetone, anhydrous ethanol, and deionized water. After washing, it was vacuum-dried at 60℃ for 12 hours, then ground. Using europium-gadolinium co-doped samarium oxysulfide powder as the core, a cerium ion-doped titanium dioxide inorganic network was directly grown on the core surface through Ti-O chemical bonds, forming the inner shell. The hydrolysis end of γ-methacryloyloxypropyltrimethoxysilane formed Ti-O-Si bonds with the inner shell, acting as chemical anchoring points and molecular bridges to firmly bond the inorganic and organic layers, further forming the outer shell and ensuring that the coating layer does not detach. Furthermore, the stable Ti-O-Si hybrid network not only has high heat resistance, but also can efficiently absorb and scatter ultraviolet light, blocking ultraviolet light from directly attacking the core material and fundamentally preventing the risk of photodegradation. At the same time, the dense hybrid coating layer can also physically block the penetration and diffusion of water molecules, oxygen, acid radical ions, etc. into the pigment core, cutting off the corrosion reaction channel, which not only enhances corrosion resistance, but also helps to maintain color. Therefore, it still has good color performance under high temperature, light, and corrosive environments, resulting in coated modified europium gadolinium co-doped samarium sulfide powder.

[0013] S2. The modified europium-gadolinium co-doped samarium oxide powder described in step S1 is dry-mixed with polytetrafluoroethylene (PTFE) powder for 30-40 minutes at a mixing speed of 300-400 rpm. The mixture is then transferred to a dedicated atmosphere furnace with a stirrer and heat-treated at 330-340°C for 1-2 hours under N2 protection at a stirring speed of 300-400 rpm. After cooling and grinding, the PTFE forms a fluorocarbon layer with excellent chemical inertness and thermal stability on the surface of the modified europium-gadolinium co-doped samarium oxide powder after heat treatment. Water vapor, oxygen, acid rain, and other substances are difficult to wet and adhere to the pigment surface, fundamentally cutting off the reaction chain required for photoaging and providing an additional ultraviolet protection barrier. The fluorocarbon layer is also tightly combined with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. During subsequent high-temperature processing, it can effectively isolate oxygen and reduce the risk of pigment oxidation at high temperatures. By isolating oxidation, corrosion, and other factors that cause color fading, it effectively improves the weather resistance and corrosion resistance of the pigment, significantly enhances the long-lasting stability of the pigment's coloring ability, and yields environmentally friendly pigments.

[0014] Preferably, in step S1, the amount of cerium acetylacetone added is 0.01-0.03 g. Cerium ions can be doped into the titanium dioxide lattice, refining the titanium dioxide grains and improving high-temperature resistance through a more stable grain structure with fewer defects. 4+ / Ce 3+ The redox couple can capture photogenerated electrons and holes, reduce the self-photocorrosion of the titanium dioxide coating, and enhance the light resistance of the core material.

[0015] Preferably, in step S2, the amount of polytetrafluoroethylene powder added is 0.08-0.16g. Since water is an essential medium for most photodegradation and chemical corrosion reactions, and the superhydrophobic layer formed by polytetrafluoroethylene can effectively block the adsorption and retention of liquid water and moisture on the pigment surface, it significantly slows down the aging reaction rate and delays the discoloration and fading of the pigment. At the same time, the extremely low surface energy of polytetrafluoroethylene physically prevents the spread, penetration and interfacial reaction of corrosive media on the pigment surface, enhances the corrosion resistance of the pigment, and protects the stability of the pigment color by isolating water, corrosive media and other aging and corrosive factors.

[0016] The beneficial effects achieved by this invention are as follows:

[0017] This invention involves heat-treating polytetrafluoroethylene (PTFE) with coated and modified europium-gadolinium co-doped samarium sulfide (SMS) powder. This process forms a fluorocarbon layer with excellent hydrophobicity and chemical inertness on the surface of the SMS powder. This layer not only prevents the adsorption and retention of water vapor, oxygen, and acid rain on the pigment surface, thus interrupting the reaction chain required for photoaging and further enhancing the UV protection and corrosion barrier effects, but also tightly bonds with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. This reduces the risk of pigment oxidation at high temperatures, thereby improving the pigment's weather resistance and corrosion resistance, effectively reducing the adverse effects of light, high temperature, and corrosive environments on pigment color performance, and significantly improving the long-lasting stability of pigment color. The coated and modified europium-gadolinium... In co-doped samarium oxysulfide powder, europium and gadolinium are uniformly doped into samarium oxysulfide, forming a uniform, dense, and chemically inert samarium oxysulfide solid solution. This provides a physical barrier, preventing the penetration of light, oxygen, and corrosive media into the interior and their destruction of the europium ions at the luminescent center. This better resists the adverse effects of light, heat, and chemical corrosion on color performance. The samarium oxysulfide matrix provides a stable, wide-bandgap crystal environment with certain light resistance, heat resistance, and corrosion resistance. The introduction of europium ions results in bright, saturated colors, but under high temperatures and strong ultraviolet irradiation, it is prone to reduction, leading to fading or discoloration. Gadolinium ions can absorb ultraviolet light energy, and through gadolinium ion co-doping and Ar / CS2 gas... High-temperature sulfidation in atmospheric atmosphere stabilizes europium ions in the trivalent state, overcoming the risk of reduction and thus achieving good light and heat resistance. Simultaneously, gadolinium ions promote the formation of dense, uniform crystals, enhancing corrosion resistance by optimizing the crystal microstructure. In the modified europium-gadolinium co-doped samarium oxysulfide powder, the europium-gadolinium co-doped samarium oxysulfide powder serves as the core, with a cerium ion-doped titanium dioxide inorganic network directly grown on the core surface via Ti-O chemical bonds, forming the inner shell. The hydrolysis end of γ-methacryloyloxypropyltrimethoxysilane forms Ti-O-Si bonds with the inner shell, firmly chemically bonding the inorganic and organic layers to form the outer shell. The Ti-O-Si hybrid network within the shell... Not only does it exhibit high heat resistance, but it also efficiently absorbs and scatters ultraviolet light, blocking its attack and degradation on the core material. Simultaneously, the dense hybrid coating physically prevents water molecules, oxygen, and acid radicals from penetrating and diffusing into the pigment core, cutting off the pathways for corrosion reactions. Thus, it retains excellent color performance even under high temperature, light, and corrosive environments. This invention uses europium-gadolinium co-doped samarium sulfide powder, tetrabutyl titanate, γ-methacryloyloxypropyltrimethoxysilane, cerium acetylacetonate, and polytetrafluoroethylene powder to create an environmentally friendly pigment. This improves the pigment's weather resistance and corrosion resistance, effectively reducing the adverse effects of light, high temperature, and corrosive environments on the pigment's color performance, and contributing to the long-lasting stability of the pigment's color. Attached Figure Description

[0018] Figure 1These are color difference results under light and high temperature conditions for Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0019] Figure 2 The images show the color difference results under corrosion conditions in Examples 1-4 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0022] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0023] Example 1

[0024] This embodiment proposes an environmentally friendly pigment, which is made from the following components in parts by weight: 20 parts europium-gadolinium co-doped samarium oxysulfide powder, 6 parts tetrabutyl titanate, 4 parts γ-methacryloyloxypropyltrimethoxysilane, 0.3 parts cerium acetylacetonate, and 1.6 parts polytetrafluoroethylene powder.

[0025] Europium-gadolinium co-doped samarium oxysulfide powder is made from the following components in parts by weight: 40 parts samarium nitrate hexahydrate, 8 parts europium nitrate hexahydrate, and 6 parts gadolinium nitrate hexahydrate.

[0026] The preparation method of europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps:

[0027] (1) Add 4.0g of samarium nitrate hexahydrate to 50mL of deionized water, then add europium nitrate hexahydrate and gadolinium nitrate hexahydrate in sequence. The amounts of europium nitrate hexahydrate and gadolinium nitrate hexahydrate added are 0.8g and 0.6g, respectively. The presence of europium ions in europium nitrate hexahydrate makes the color pure and saturated. The gadolinium ions in gadolinium nitrate hexahydrate are incorporated as a structural stabilizer. Their ionic radius and chemical properties can optimize lattice defects and improve the stability of the overall structure at high temperatures. At the same time, it can also make the solid solution lattice more compact and improve the overall chemical inertness to media such as acids and alkalis. Stir for 10min, then add 4.3g of disodium ethylenediaminetetraacetate and stir for 40min. Under stirring conditions, add concentrated ammonia dropwise to adjust the pH to 10. 0.0, then slowly add dilute nitric acid to adjust the pH to 7.0, stir for 2 hours, and finally transfer to an evaporating dish and dry in an 80℃ oven for 48 hours. The resulting dry gel is placed in a muffle furnace, first heated to 300℃ at a rate of 2℃ / min and held for 2 hours, then heated to 600℃ at a rate of 5℃ / min and held for 2 hours. After natural cooling, it is taken out and ground. Disodium ethylenediaminetetraacetate (EDTA) acts as a strong chelating agent to form soluble complexes with samarium, europium, and gadolinium ions. Through the sol-gel process, the three elements samarium, europium, and gadolinium are ensured to achieve atomic-level uniform mixing in three-dimensional space, thereby obtaining a highly active, high specific surface area, and homogeneous oxide precursor, laying the foundation for the subsequent sulfidation reaction and obtaining precursor powder.

[0028] (2) The precursor powder described in step (1) is evenly spread in an alumina ceramic boat with a powder layer thickness of 2.8 mm. The alumina ceramic boat is then placed in a tube furnace, a vacuum is drawn, and Ar is introduced at a flow rate of 140 mL / min. The temperature is first raised to 450 °C at a rate of 5 °C / min, and then held for 40 min. The gas is then switched to an Ar / CS2 mixture, with the total flow rate controlled at 140 mL / min. 40 mL / min is used as a carrier gas, flowing through a CS2 bubble bottle placed in a 0 °C ice-water bath to carry CS2 vapor. This vapor is then mixed with the remaining 100 mL / min bypass Ar to form the reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then raised to 880 °C at a rate of 2 °C / min for sulfidation treatment, and the reaction is held for 3 h. The temperature was lowered to 200℃ at a rate of 2℃ / min, the CS2 gas path was closed, and the furnace tube was purged with pure Ar for 20 minutes. Then, it was allowed to cool naturally to room temperature. The product was then removed. CS2 decomposed at high temperature, producing active sulfur species. These sulfur atoms gradually replaced some of the oxygen atoms in the oxide precursor, forming a more thermodynamically stable rare earth oxygen sulfide. At the same time, the overall morphology and uniform doping distribution of the precursor were preserved. The uniform doping of europium and gadolinium in samarium oxygen sulfide formed a more uniform, dense, and chemically inert oxygen sulfide solid solution, which provided a physical barrier protection, preventing the corrosive medium from penetrating into the interior and damaging the europium ions at the luminescent center. This better resisted the adverse effects of light, heat, and chemical erosion on the coloring performance, and enhanced weather resistance and corrosion resistance, resulting in europium-gadolinium co-doped samarium oxygen sulfide powder.

[0029] This embodiment provides a method for preparing an environmentally friendly pigment, specifically including the following steps:

[0030] S1. Disperse 2.0g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 40min. Then add 0.3g of polyvinylpyrrolidone and sonicate for 10min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 30min to form a core dispersion for later use. Disperse 0.6mL of tetrabutyl titanate in 10mL of anhydrous ethanol, and then add cerium acetylacetone (0.03g). Cerium ions can be doped into the titanium dioxide lattice, refining the titanium dioxide grains. This results in a more stable grain structure with fewer defects, thus improving high-temperature resistance. 4+ / Ce 3+The redox couple can capture photogenerated electrons and holes, reducing the self-photocorrosion of the titanium dioxide coating layer and enhancing the light resistance of the core material. After stirring for 20 min, 0.05 mL of acetylacetone was added and stirred for 30 min to form coating solution I. 0.4 mL of γ-methacryloyloxypropyltrimethoxysilane was dispersed in 10 mL of anhydrous ethanol and stirred for 10 min to form coating solution II. Under stirring speed of 800 rpm and conditions of 30 °C, coating solutions I and II were simultaneously added dropwise to the core dispersion at a rate of 1 drop / 5 seconds through a dropping funnel, and the addition was completed within 2 h. The reaction continued for 1 h, and the mixture was centrifuged. The precipitate was washed 5 times successively with acetone, anhydrous ethanol, and deionized water. The washed solid material was vacuum dried at 60 °C for 12 h, ground, and then a titanium dioxide inorganic network with europium-gadolinium co-doped samarium sulfide powder as the core and cerium ion doped as the core was formed. Ti-O chemical bonds are directly grown on the core surface to form the inner shell. The hydrolysis end of γ-methacryloxypropyltrimethoxysilane forms Ti-O-Si bonds with the inner shell, serving as a chemical anchor and molecular bridge to firmly bond the inorganic and organic layers, further forming the outer shell. This ensures that the coating layer will not fall off. The stable Ti-O-Si hybrid network not only has high heat resistance but also can efficiently absorb and scatter ultraviolet light, blocking ultraviolet light from directly attacking the core material and fundamentally preventing the risk of photodegradation. At the same time, the dense hybrid coating layer can also physically block the penetration and diffusion of water molecules, oxygen, and acid radical ions into the pigment core, cutting off the corrosion reaction channel. This not only enhances corrosion resistance but also helps maintain color. Therefore, it still has good color performance under high temperature, light, and corrosive environments, resulting in coated modified europium gadolinium co-doped samarium sulfide powder.

[0031] S2. The modified europium-gadolinium co-doped samarium oxide powder described in step S1 is dry-mixed with polytetrafluoroethylene (PTFE) powder for 40 minutes at a mixing speed of 400 rpm. The amount of PTFE powder added is 0.16 g. Since moisture is an essential medium for most photodegradation and chemical corrosion reactions, and the superhydrophobic layer formed by PTFE can effectively block the adsorption and retention of liquid water and moisture on the pigment surface, it significantly slows down the aging reaction rate and delays pigment discoloration and fading. At the same time, the extremely low surface energy of PTFE physically prevents the spread, penetration, and interfacial reaction of corrosive media on the pigment surface, enhancing the pigment's corrosion resistance. By isolating water, corrosive media, and other aging and corrosive factors, the stability of the pigment color is protected. The mixture is then transferred to a special atmosphere furnace with stirring. The mixture was heat-treated at 340℃ for 2 hours under N2 protection at a stirring speed of 400 rpm, followed by cooling and grinding. After heat treatment, polytetrafluoroethylene (PTFE) coated on the surface of modified europium-gadolinium co-doped samarium sulfide powder formed a fluorocarbon layer with excellent chemical inertness and thermal stability. This makes it difficult for water vapor, oxygen, acid rain, etc., to wet and adhere to the pigment surface, fundamentally cutting off the reaction chain required for photoaging and providing an additional UV protection barrier. The fluorocarbon layer is also tightly bonded with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. During subsequent high-temperature treatment, it can effectively isolate oxygen and reduce the risk of pigment oxidation at high temperatures. By isolating oxidation, corrosion, and other factors that cause color fading, the pigment's weather resistance and corrosion resistance are effectively improved, and the long-lasting stability of the pigment's coloring ability is significantly enhanced, resulting in an environmentally friendly pigment.

[0032] Example 2

[0033] This embodiment proposes an environmentally friendly pigment, which is made from the following components in parts by weight: 10 parts europium-gadolinium co-doped samarium oxysulfide powder, 3 parts tetrabutyl titanate, 2 parts γ-methacryloyloxypropyltrimethoxysilane, 0.1 parts cerium acetylacetonate, and 0.8 parts polytetrafluoroethylene powder.

[0034] Europium-gadolinium co-doped samarium oxysulfide powder is made from the following components in parts by weight: 36 parts samarium nitrate hexahydrate, 4 parts europium nitrate hexahydrate, and 4 parts gadolinium nitrate hexahydrate.

[0035] The preparation method of europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps:

[0036] (1) Add 3.6g of samarium nitrate hexahydrate to 50mL of deionized water, then add europium nitrate hexahydrate and gadolinium nitrate hexahydrate in sequence. The amount of europium nitrate hexahydrate and gadolinium nitrate hexahydrate added is 0.4g and 0.4g respectively. The presence of europium ions in europium nitrate hexahydrate makes the color pure and saturated. The gadolinium ions in gadolinium nitrate hexahydrate are incorporated as a structural stabilizer. Their ionic radius and chemical properties can optimize lattice defects and improve the stability of the overall structure at high temperature. At the same time, it can also make the solid solution lattice more compact and improve the overall chemical inertness to media such as acids and alkalis. Stir for 5min, then add 4.1g of disodium ethylenediaminetetraacetate and stir for 30min. Under stirring conditions, add concentrated ammonia dropwise to adjust the pH to 8. 0, then slowly add dilute nitric acid to adjust the pH to 7.0, stir for 1 hour, and finally transfer to an evaporating dish and dry in an 80℃ oven for 24 hours. The resulting dry gel is placed in a muffle furnace, first heated to 300℃ at a rate of 2℃ / min and held for 1 hour, then heated to 600℃ at a rate of 5℃ / min and held for 1 hour. After natural cooling, it is taken out and ground. Disodium ethylenediaminetetraacetate (EDTA) acts as a strong chelating agent to form soluble complexes with samarium, europium, and gadolinium ions. Through the sol-gel process, the three elements samarium, europium, and gadolinium are ensured to achieve atomic-level uniform mixing in three-dimensional space, thereby obtaining a highly active, high specific surface area, and homogeneous oxide precursor, which lays the foundation for the subsequent sulfidation reaction and yields the precursor powder.

[0037] (2) The precursor powder described in step (1) is evenly spread in an alumina ceramic boat with a powder layer thickness of 2.0 mm. The alumina ceramic boat is then placed in a tube furnace, a vacuum is drawn, and Ar is introduced at a flow rate of 140 mL / min. The temperature is first raised to 400 °C at a rate of 5 °C / min, and then held for 30 min. The gas is then switched to an Ar / CS2 mixture, with the total flow rate controlled at 140 mL / min. 40 mL / min is used as a carrier gas, flowing through a CS2 bubble bottle placed in a 0 °C ice-water bath to carry CS2 vapor. This vapor is then mixed with the remaining 100 mL / min bypass Ar to form the reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then raised to 880 °C at a rate of 2 °C / min for sulfidation treatment. The reaction is held for 2 h. The temperature was lowered to 200℃ at a rate of 3℃ / min, the CS2 gas path was closed, and the furnace tube was purged with pure Ar for 10 min. Then, it was allowed to cool naturally to room temperature. The product was then removed. CS2 decomposed at high temperature, producing active sulfur species. These sulfur atoms gradually replaced some of the oxygen atoms in the oxide precursor, forming a more thermodynamically stable rare earth oxygen sulfide. At the same time, the overall morphology and uniform doping distribution of the precursor were preserved. The uniform doping of europium and gadolinium in samarium oxygen sulfide formed a more uniform, dense, and chemically inert oxygen sulfide solid solution, which provided a physical barrier protection, preventing the corrosive medium from penetrating into the interior and damaging the europium ions at the luminescent center. This better resisted the adverse effects of light, heat, and chemical erosion on the coloring performance, and enhanced weather resistance and corrosion resistance, resulting in europium-gadolinium co-doped samarium oxygen sulfide powder.

[0038] This embodiment provides a method for preparing an environmentally friendly pigment, specifically including the following steps:

[0039] S1. Disperse 1.0g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 30min. Then add 0.2g of polyvinylpyrrolidone and sonicate for 5min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 20min to form a core dispersion for later use. Disperse 0.3mL of tetrabutyl titanate in 10mL of anhydrous ethanol, and then add cerium acetylacetone (0.01g). Cerium ions can be doped into the titanium dioxide lattice, refining the titanium dioxide grains. This improves high-temperature resistance through a more stable grain structure with fewer defects. 4+ / Ce 3+The redox couple can capture photogenerated electrons and holes, reducing the self-photocorrosion of the titanium dioxide coating layer and enhancing the light resistance of the core material. After stirring for 10 min, 0.05 mL of acetylacetone was added and stirred for 20 min to form coating solution I. 0.2 mL of γ-methacryloxypropyltrimethoxysilane was dispersed in 10 mL of anhydrous ethanol and stirred for 5 min to form coating solution II. Under the conditions of stirring at 600 rpm and 25 °C, coating solutions I and II were simultaneously added dropwise to the core dispersion at a rate of 1 drop / 5 seconds through a dropping funnel and the addition was completed within 2 h. The reaction was continued for 0.5 h, centrifuged, and the precipitate was washed three times in sequence with acetone, anhydrous ethanol, and deionized water. The washed solid material was vacuum dried at 60 °C for 12 h, ground, and formed an inorganic network of titanium dioxide with europium-gadolinium co-doped samarium oxide powder as the core and cerium ion doped. The inner shell is formed by direct growth of Ti-O chemical bonds on the core surface. The hydrolysis end of γ-methacryloxypropyltrimethoxysilane forms Ti-O-Si bonds with the inner shell, which serve as chemical anchors and molecular bridges to firmly bond the inorganic and organic layers, further forming the outer shell. This ensures that the coating layer will not fall off. The stable Ti-O-Si hybrid network not only has high heat resistance, but also can efficiently absorb and scatter ultraviolet light, blocking the direct attack of ultraviolet light on the core material and fundamentally preventing the risk of photodegradation. At the same time, the dense hybrid coating layer can also physically block the penetration and diffusion of water molecules, oxygen, and acid radical ions into the pigment core, cutting off the corrosion reaction channel. This not only enhances corrosion resistance, but also helps maintain color. Therefore, it still has good color performance under high temperature, light, and corrosive environments, resulting in coated modified europium gadolinium co-doped samarium sulfide powder.

[0040] S2. The modified europium-gadolinium co-doped samarium oxide powder described in step S1 is dry-mixed with polytetrafluoroethylene (PTFE) powder for 30 minutes at a mixing speed of 300 rpm. The amount of PTFE powder added is 0.08 g. Since moisture is an essential medium for most photodegradation and chemical corrosion reactions, and the superhydrophobic layer formed by PTFE can effectively block the adsorption and retention of liquid water and moisture on the pigment surface, it significantly slows down the aging reaction rate and delays pigment discoloration and fading. At the same time, the extremely low surface energy of PTFE physically prevents the spread, penetration, and interfacial reaction of corrosive media on the pigment surface, enhancing the pigment's corrosion resistance. By isolating water, corrosive media, and other aging and corrosive factors, the stability of the pigment color is protected. The mixture is then transferred to a special atmosphere furnace with stirring. The mixture was heat-treated at 330℃ for 1 hour under N2 protection at a stirring speed of 300 rpm, followed by cooling and grinding. After heat treatment, polytetrafluoroethylene (PTFE) coated on the surface of modified europium-gadolinium co-doped samarium sulfide powder formed a fluorocarbon layer with excellent chemical inertness and thermal stability. This makes it difficult for water vapor, oxygen, acid rain, etc., to wet and adhere to the pigment surface, fundamentally cutting off the reaction chain required for photoaging and providing an additional UV protection barrier. The fluorocarbon layer is also tightly bonded with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. During subsequent high-temperature treatment, it can effectively isolate oxygen and reduce the risk of pigment oxidation at high temperatures. By isolating oxidation, corrosion, and other factors that cause color fading, the pigment's weather resistance and corrosion resistance are effectively improved, and the long-lasting stability of the pigment's coloring ability is significantly enhanced, resulting in an environmentally friendly pigment.

[0041] Example 3

[0042] This embodiment proposes an environmentally friendly pigment, which is made from the following components in parts by weight: 15 parts europium-gadolinium co-doped samarium oxysulfide powder, 4.5 parts tetrabutyl titanate, 3 parts γ-methacryloyloxypropyltrimethoxysilane, 0.2 parts cerium acetylacetonate, and 1.2 parts polytetrafluoroethylene powder.

[0043] Europium-gadolinium co-doped samarium oxysulfide powder is made from the following components in parts by weight: 38 parts samarium nitrate hexahydrate, 6 parts europium nitrate hexahydrate, and 5 parts gadolinium nitrate hexahydrate.

[0044] The preparation method of europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps:

[0045] (1) Add 3.8g of samarium nitrate hexahydrate to 50mL of deionized water, then add europium nitrate hexahydrate and gadolinium nitrate hexahydrate in sequence. The amounts of europium nitrate hexahydrate and gadolinium nitrate hexahydrate added are 0.6g and 0.5g, respectively. The presence of europium ions in europium nitrate hexahydrate makes the color pure and saturated. The gadolinium ions in gadolinium nitrate hexahydrate are incorporated as a structural stabilizer. Their ionic radius and chemical properties can optimize lattice defects and improve the stability of the overall structure at high temperatures. At the same time, it can also make the solid solution lattice more compact and improve the overall chemical inertness to media such as acids and alkalis. Stir for 7.5min, then add 4.2g of disodium ethylenediaminetetraacetate and stir for 35min. Under stirring conditions, add concentrated ammonia dropwise to adjust the pH to 9.0. Then, dilute nitric acid was slowly added to adjust the pH to 7.0, and the mixture was stirred for 1.5 hours. Finally, the mixture was transferred to an evaporating dish and dried in an 80°C oven for 36 hours. The resulting dry gel was placed in a muffle furnace and heated to 300°C at a rate of 2°C / min and held for 1.5 hours. Then, the temperature was increased to 600°C at a rate of 5°C / min and held for 1.5 hours. After natural cooling, the gel was removed and ground. Disodium ethylenediaminetetraacetate (EDTA) was used as a strong chelating agent to form soluble complexes with samarium, europium, and gadolinium ions. Through the sol-gel process, the three elements samarium, europium, and gadolinium were ensured to achieve atomic-level uniform mixing in three-dimensional space, thereby obtaining a highly active, high specific surface area, and homogeneous oxide precursor, which laid the foundation for the subsequent sulfidation reaction and yielded the precursor powder.

[0046] (2) The precursor powder described in step (1) is evenly spread in an alumina ceramic boat with a powder layer thickness of 2.4 mm. The alumina ceramic boat is then placed in a tube furnace, a vacuum is drawn, and Ar is introduced at a flow rate of 140 mL / min. The temperature is first raised to 425 °C at a rate of 5 °C / min, and then held for 35 min. The gas is then switched to an Ar / CS2 mixture, with the total flow rate controlled at 140 mL / min. 40 mL / min is used as a carrier gas, flowing through a CS2 bubble bottle placed in a 0 °C ice-water bath to carry CS2 vapor. This vapor is then mixed with the remaining 100 mL / min bypass Ar to form the reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then raised to 880 °C at a rate of 2 °C / min for sulfidation treatment, and the reaction is held for 2.5 h. The temperature was lowered to 200℃ at a rate of 2.5℃ / min, the CS2 gas path was closed, and the furnace tube was purged with pure Ar for 15 min. Then, it was allowed to cool naturally to room temperature. The product was then removed. CS2 decomposed at high temperature, producing active sulfur species. These sulfur atoms gradually replaced some of the oxygen atoms in the oxide precursor, forming a more thermodynamically stable rare earth oxygen sulfide. At the same time, the overall morphology and uniform doping distribution of the precursor were preserved. The uniform doping of europium and gadolinium in samarium oxygen sulfide formed a more uniform, dense, and chemically inert oxygen sulfide solid solution, which provided a physical barrier protection, preventing the corrosive medium from penetrating into the interior and damaging the europium ions at the luminescent center. This better resisted the adverse effects of light, heat, and chemical erosion on the coloring performance, and enhanced weather resistance and corrosion resistance, resulting in europium-gadolinium co-doped samarium oxygen sulfide powder.

[0047] This embodiment provides a method for preparing an environmentally friendly pigment, specifically including the following steps:

[0048] S1. Disperse 1.5g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 35min. Then add 0.25g of polyvinylpyrrolidone and sonicate for 7.5min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 25min to form a core dispersion for later use. Disperse 0.45mL of tetrabutyl titanate in 10mL of anhydrous ethanol, and then add cerium acetylacetone (0.02g). Cerium ions can be doped into the titanium dioxide lattice, refining the titanium dioxide grains. This improves high-temperature resistance through a more stable grain structure with fewer defects. 4+ / Ce 3+The redox couple can capture photogenerated electrons and holes, reducing the self-photocorrosion of the titanium dioxide coating layer and enhancing the light resistance of the core material. After stirring for 15 min, 0.05 mL of acetylacetone was added and stirred for 25 min to form coating solution I. 0.3 mL of γ-methacryloxypropyltrimethoxysilane was dispersed in 10 mL of anhydrous ethanol and stirred for 7.5 min to form coating solution II. Under the conditions of stirring speed of 700 rpm and 27.5 °C, coating solutions I and II were simultaneously added dropwise to the core dispersion at a rate of 1 drop / 5 seconds through a dropping funnel and the addition was completed within 2 h. The reaction continued for 0.75 h. After centrifugation, the precipitate was washed four times in sequence with acetone, anhydrous ethanol, and deionized water. The washed solid material was vacuum dried at 60 °C for 12 h, ground, and then the titanium dioxide inorganic material with europium-gadolinium co-doped samarium oxysulfide powder as the core and cerium ion doped was formed. The network grows directly on the core surface through Ti-O chemical bonds, forming the inner shell. The hydrolysis end of γ-methacryloxypropyltrimethoxysilane forms Ti-O-Si bonds with the inner shell, serving as a chemical anchor and molecular bridge to firmly bond the inorganic and organic layers, further forming the outer shell. This ensures that the coating layer will not fall off. The stable Ti-O-Si hybrid network not only has high heat resistance but also efficiently absorbs and scatters ultraviolet light, blocking ultraviolet light from directly attacking the core material and fundamentally preventing the risk of photodegradation. At the same time, the dense hybrid coating layer can also physically block the penetration and diffusion of water molecules, oxygen, and acid radical ions into the pigment core, cutting off the corrosion reaction channel. This not only enhances corrosion resistance but also helps maintain color. Therefore, it still has good color performance under high temperature, light, and corrosive environments, resulting in coated modified europium gadolinium co-doped samarium sulfide powder.

[0049] S2. The modified europium-gadolinium co-doped samarium oxide powder described in step S1 is dry-mixed with polytetrafluoroethylene (PTFE) powder for 35 minutes at a mixing speed of 350 rpm. The amount of PTFE powder added is 0.12 g. Since moisture is an essential medium for most photodegradation and chemical corrosion reactions, and the superhydrophobic layer formed by PTFE can effectively block the adsorption and retention of liquid water and moisture on the pigment surface, it significantly slows down the aging reaction rate and delays pigment discoloration and fading. Simultaneously, the extremely low surface energy of PTFE physically prevents the spread, penetration, and interfacial reaction of corrosive media on the pigment surface, enhancing the pigment's corrosion resistance. By isolating water, corrosive media, and other aging and corrosive factors, it protects the stability of the pigment color. The mixture is then transferred to a dedicated atmosphere furnace with stirring. After heat treatment at 335℃ for 1.5 hours under N2 protection at 350 rpm, followed by cooling and grinding, polytetrafluoroethylene (PTFE) forms a fluorocarbon layer with excellent chemical inertness and thermal stability on the surface of the modified europium-gadolinium co-doped samarium sulfide powder. This makes it difficult for water vapor, oxygen, acid rain, etc., to wet and adhere to the pigment surface, fundamentally cutting off the reaction chain required for photoaging and providing an additional UV protection barrier. The fluorocarbon layer is also tightly bonded with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. During subsequent high-temperature treatment, it can effectively isolate oxygen and reduce the risk of pigment oxidation at high temperatures. By isolating oxidation, corrosion, and other factors that cause color fading, it effectively improves the pigment's weather resistance and corrosion resistance, significantly enhances the long-term stability of the pigment's coloring ability, and yields an environmentally friendly pigment.

[0050] Example 4

[0051] This embodiment proposes an environmentally friendly pigment, which is made from the following components in parts by weight: 20 parts europium-gadolinium co-doped samarium oxysulfide powder, 6 parts tetrabutyl titanate, 2 parts γ-methacryloyloxypropyltrimethoxysilane, 0.1 parts cerium acetylacetonate, and 0.8 parts polytetrafluoroethylene powder.

[0052] Europium-gadolinium co-doped samarium oxysulfide powder is made from the following components in parts by weight: 40 parts samarium nitrate hexahydrate, 8 parts europium nitrate hexahydrate, and 4 parts gadolinium nitrate hexahydrate.

[0053] The preparation method of europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps:

[0054] (1) Add 4.0g of samarium nitrate hexahydrate to 50mL of deionized water, then add europium nitrate hexahydrate and gadolinium nitrate hexahydrate in sequence. The amounts of europium nitrate hexahydrate and gadolinium nitrate hexahydrate added are 0.8g and 0.4g, respectively. The presence of europium ions in europium nitrate hexahydrate makes the color pure and saturated. The gadolinium ions in gadolinium nitrate hexahydrate are incorporated as a structural stabilizer. Their ionic radius and chemical properties can optimize lattice defects and improve the stability of the overall structure at high temperatures. At the same time, it can also make the solid solution lattice more compact and improve the overall chemical inertness to media such as acids and alkalis. Stir for 10min, then add 4.3g of disodium ethylenediaminetetraacetate and stir for 40min. Under stirring conditions, add concentrated ammonia dropwise to adjust the pH to 10. 0.0, then slowly add dilute nitric acid to adjust the pH to 7.0, stir for 2 hours, and finally transfer to an evaporating dish and dry in an 80℃ oven for 48 hours. The resulting dry gel is placed in a muffle furnace, first heated to 300℃ at a rate of 2℃ / min and held for 2 hours, then heated to 600℃ at a rate of 5℃ / min and held for 2 hours. After natural cooling, it is taken out and ground. Disodium ethylenediaminetetraacetate (EDTA) acts as a strong chelating agent to form soluble complexes with samarium, europium, and gadolinium ions. Through the sol-gel process, the three elements samarium, europium, and gadolinium are ensured to achieve atomic-level uniform mixing in three-dimensional space, thereby obtaining a highly active, high specific surface area, and homogeneous oxide precursor, laying the foundation for the subsequent sulfidation reaction and obtaining precursor powder.

[0055] (2) The precursor powder described in step (1) is evenly spread in an alumina ceramic boat with a powder layer thickness of 2.8 mm. The alumina ceramic boat is then placed in a tube furnace, a vacuum is drawn, and Ar is introduced at a flow rate of 140 mL / min. The temperature is first raised to 450 °C at a rate of 5 °C / min, and then held for 40 min. The gas is then switched to an Ar / CS2 mixture, with the total flow rate controlled at 140 mL / min. 40 mL / min is used as a carrier gas, flowing through a CS2 bubble bottle placed in a 0 °C ice-water bath to carry CS2 vapor. This vapor is then mixed with the remaining 100 mL / min bypass Ar to form the reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then raised to 880 °C at a rate of 2 °C / min for sulfidation treatment, and the reaction is held for 3 h. The temperature was lowered to 200℃ at a rate of 3℃ / min, the CS2 gas path was closed, and the furnace tube was purged with pure Ar for 20 minutes. Then, it was allowed to cool naturally to room temperature. The product was then removed. CS2 decomposed at high temperature, producing active sulfur species. These sulfur atoms gradually replaced some of the oxygen atoms in the oxide precursor, forming a more thermodynamically stable rare earth oxygen sulfide. At the same time, the overall morphology and uniform doping distribution of the precursor were preserved. The uniform doping of europium and gadolinium in samarium oxygen sulfide formed a more uniform, dense, and chemically inert oxygen sulfide solid solution, which provided a physical barrier protection, preventing the corrosive medium from penetrating into the interior and damaging the europium ions at the luminescent center. This better resisted the adverse effects of light, heat, and chemical erosion on the coloring performance, and enhanced weather resistance and corrosion resistance, resulting in europium-gadolinium co-doped samarium oxygen sulfide powder.

[0056] This embodiment provides a method for preparing an environmentally friendly pigment, specifically including the following steps:

[0057] S1. Disperse 2.0g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 40min. Then add 0.3g of polyvinylpyrrolidone and sonicate for 10min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 30min to form a core dispersion for later use. Disperse 0.6mL of tetrabutyl titanate in 10mL of anhydrous ethanol, and then add cerium acetylacetone (0.01g). Cerium ions can be doped into the titanium dioxide lattice, refining the titanium dioxide grains. This results in a more stable grain structure with fewer defects, thus improving high-temperature resistance. 4+ / Ce 3+The redox couple can capture photogenerated electrons and holes, reducing the self-photocorrosion of the titanium dioxide coating layer and enhancing the light resistance of the core material. After stirring for 20 min, 0.05 mL of acetylacetone was added and stirred for 30 min to form coating solution I. 0.2 mL of γ-methacryloxypropyltrimethoxysilane was dispersed in 10 mL of anhydrous ethanol and stirred for 10 min to form coating solution II. Under the conditions of stirring speed of 800 rpm and 30 °C, coating solutions I and II were simultaneously added dropwise to the core dispersion at a rate of 1 drop / 5 seconds through a dropping funnel and the addition was completed within 2 h. The reaction was continued for 1 h, centrifuged, and the precipitate was washed 5 times in sequence with acetone, anhydrous ethanol, and deionized water. The washed solid material was vacuum dried at 60 °C for 12 h, ground, and formed a titanium dioxide inorganic network with europium-gadolinium co-doped samarium oxide powder as the core and cerium ion doped powder as the core. Ti-O chemical bonds are directly grown on the core surface to form the inner shell. The hydrolysis end of γ-methacryloxypropyltrimethoxysilane forms Ti-O-Si bonds with the inner shell, serving as a chemical anchor and molecular bridge to firmly bond the inorganic and organic layers, further forming the outer shell. This ensures that the coating layer will not fall off. The stable Ti-O-Si hybrid network not only has high heat resistance but also can efficiently absorb and scatter ultraviolet light, blocking ultraviolet light from directly attacking the core material and fundamentally preventing the risk of photodegradation. At the same time, the dense hybrid coating layer can also physically block the penetration and diffusion of water molecules, oxygen, and acid radical ions into the pigment core, cutting off the corrosion reaction channel. This not only enhances corrosion resistance but also helps maintain color. Therefore, it still has good color performance under high temperature, light, and corrosive environments, resulting in coated modified europium gadolinium co-doped samarium sulfide powder.

[0058] S2. The modified europium-gadolinium co-doped samarium oxide powder described in step S1 is dry-mixed with polytetrafluoroethylene (PTFE) powder for 40 minutes at a mixing speed of 400 rpm. The amount of PTFE powder added is 0.08 g. Since moisture is an essential medium for most photodegradation and chemical corrosion reactions, and the superhydrophobic layer formed by PTFE can effectively block the adsorption and retention of liquid water and moisture on the pigment surface, it significantly slows down the aging reaction rate and delays pigment discoloration and fading. Simultaneously, the extremely low surface energy of PTFE physically prevents the spread, penetration, and interfacial reaction of corrosive media on the pigment surface, enhancing the pigment's corrosion resistance. By isolating water, corrosive media, and other aging and corrosive factors, it protects the stability of the pigment color. The mixture is then transferred to a dedicated atmosphere furnace with stirring. The mixture was heat-treated at 340℃ for 2 hours under N2 protection at a stirring speed of 400 rpm, followed by cooling and grinding. After heat treatment, polytetrafluoroethylene (PTFE) coated on the surface of modified europium-gadolinium co-doped samarium sulfide powder formed a fluorocarbon layer with excellent chemical inertness and thermal stability. This makes it difficult for water vapor, oxygen, acid rain, etc., to wet and adhere to the pigment surface, fundamentally cutting off the reaction chain required for photoaging and providing an additional UV protection barrier. The fluorocarbon layer is also tightly bonded with the Ti-O-Si hybrid shell, forming a dual high-temperature protection system. During subsequent high-temperature treatment, it can effectively isolate oxygen and reduce the risk of pigment oxidation at high temperatures. By isolating oxidation, corrosion, and other factors that cause color fading, the pigment's weather resistance and corrosion resistance are effectively improved, and the long-lasting stability of the pigment's coloring ability is significantly enhanced, resulting in an environmentally friendly pigment.

[0059] Comparative Example 1

[0060] This comparative example provides an environmentally friendly pigment, which differs from Example 1 in that the europium-gadolinium co-doped samarium sulfide powder does not contain gadolinium nitrate hexahydrate; step (1) of the preparation method of europium-gadolinium co-doped samarium sulfide powder does not add gadolinium nitrate hexahydrate; the preparation method of the environmentally friendly pigment is the same as that of Example 1.

[0061] Comparative Example 2

[0062] This comparative example provides an environmentally friendly pigment, which differs from Example 1 in that the environmentally friendly pigment does not contain γ-methacryloxypropyltrimethoxysilane; the preparation method of europium-gadolinium co-doped samarium sulfide powder is the same as that in Example 1; and γ-methacryloxypropyltrimethoxysilane is not added in step S1 of the preparation method of the environmentally friendly pigment.

[0063] Comparative Example 3

[0064] This comparative example provides an environmentally friendly pigment, which differs from Example 1 in that the environmentally friendly pigment does not contain polytetrafluoroethylene powder; the preparation method of europium-gadolinium co-doped samarium sulfide powder is the same as that of Example 1; the preparation method of the environmentally friendly pigment does not include step S2.

[0065] Experimental Example 1

[0066] Weather resistance test

[0067] Test samples: Environmentally friendly pigments prepared in Examples 1-4 and Comparative Examples 1-3.

[0068] Test method: Weigh 2g of the test sample and mix it with the resin matrix at a ratio of 1:10. Spray the mixture evenly onto a white PVC board with a wet film thickness of 80±10μm to make a standard color board. Place the board in a UV aging chamber and age it for 100h under UVA-340 ultraviolet light. Heat the board to 100℃, remove it and cool it. Then test the color difference value ΔE of the product on a spectrophotometer. ΔE<1.5 indicates a change that is difficult for the human eye to perceive, ΔE between 1.5 and 3.0 indicates a slight change, and ΔE>3.0 indicates a significant change.

[0069] Figure 1 The figures show the color difference results of Examples 1-4 and Comparative Examples 1-3 under illumination and high temperature conditions. As shown, the color difference of Examples 1-4 under illumination and high temperature conditions is 0.3-1.0, indicating that illumination and high temperature have little effect on color development and good weather resistance. The color difference of Comparative Examples 1-3 under illumination and high temperature conditions is 2.5-6.8, indicating that illumination and high temperature have a significant effect on color development and average or poor weather resistance. The europium-gadolinium co-doped samarium oxysulfide powder in Comparative Example 1 does not contain gadolinium hexahydrate, making it impossible to stabilize europium ions in the trivalent state through gadolinium ion doping. This is detrimental to overcoming the risk of europium ion reduction and also hinders the enhancement of the crystal structure's robustness and stability at high temperatures. The environmentally friendly pigments in Comparative Example 2 do not contain γ-methacryloxypropyltrimethoxysilane, thus failing to form an organic-inorganic interwoven Ti-O-Si hybrid network. This prevents the coating layer from enhancing its bonding strength and toughness at high temperatures and also hinders the blocking of ultraviolet rays, oxygen, and water vapor penetration, resulting in a significant impact of light and high temperatures on color development and poor weather resistance. Furthermore, the environmentally friendly pigments in Comparative Example 3 do not contain polytetrafluoroethylene powder, thus failing to form a hydrophobic and thermally stable fluorocarbon layer. This prevents the fundamental interruption of the reaction chain required for photoaging, leading to a significant impact of light and high temperatures on color development and only moderate weather resistance.

[0070] Experiment Example 2

[0071] Corrosion resistance test

[0072] Test samples: Environmentally friendly pigments prepared in Examples 1-4 and Comparative Examples 1-3.

[0073] Test method: Weigh 2g of the test sample and mix it with the resin matrix at a ratio of 1:10. Spray the mixture evenly onto a white PVC board with a wet film thickness of 80±10μm to prepare a standard color board. Then place the standard color board in a salt spray chamber at an angle of 28-30° to the vertical direction. The temperature is 35±2℃, and the salt spray solution deposition rate is 1.5±0.5mL / h. Use a 5% NaCl solution (pH 6.5-7.2) to conduct a salt spray resistance test for 500h. After the test, remove the standard color board and gently rinse the surface with distilled water. Allow it to air dry at room temperature. Then, measure the color difference value ΔE of the product on a spectrophotometer. ΔE<1.5 indicates a change that is difficult for the human eye to perceive, ΔE between 1.5 and 3.0 indicates a slight change, and ΔE>3.0 indicates a significant change.

[0074] Figure 2 The figures show the color difference results under corrosion conditions for Examples 1-4 and Comparative Examples 1-3. As shown, the color difference under corrosion conditions for Examples 1-4 is 0.3-1.1, indicating that corrosion has a relatively small impact on color and good corrosion resistance. The color difference under corrosion conditions for Comparative Examples 1-3 is 2.8-7.3, indicating that corrosion has a significant impact on color and poor corrosion resistance. The europium-gadolinium co-doped samarium oxysulfide powder in Comparative Example 1 does not contain gadolinium hexahydrate nitrate, and therefore cannot promote the formation of dense, uniform crystals through gadolinium ion doping, thus reducing its corrosion resistance. This results in a greater impact of corrosion on color and poor corrosion resistance. Poor corrosion resistance; the environmentally friendly pigment in Comparative Example 2 does not contain γ-methacryloxypropyltrimethoxysilane, which cannot form a strong and dense Ti-O-Si hybrid network, and cannot effectively block the penetration and diffusion of corrosive media into the pigment core, resulting in a significant impact of corrosion on color and poor corrosion resistance; the environmentally friendly pigment in Comparative Example 3 does not contain polytetrafluoroethylene powder, which cannot form a chemically inert fluorocarbon layer on the surface of europium-gadolinium co-doped samarium oxysulfide powder, which is not conducive to the formation of a continuous protective film, and is not conducive to effectively isolating the wetting and penetration of corrosive media, resulting in a significant impact of corrosion on color and poor corrosion resistance.

[0075] The above experimental results show that the color difference of Examples 1-4 of the present invention is significantly better than that of the comparative examples 1-3 under light, high temperature and corrosion conditions. Among them, Example 1, which uses coated modified europium-gadolinium co-doped samarium sulfide powder and polytetrafluoroethylene powder, has better weather resistance and corrosion resistance. The polytetrafluoroethylene and coated modified europium-gadolinium co-doped samarium sulfide powder are heat-treated to form a fluorocarbon layer with excellent hydrophobicity and chemical inertness on the surface of the europium-gadolinium co-doped samarium sulfide powder. This not only blocks the adsorption and retention of water vapor, oxygen, acid rain and other substances on the pigment surface, but also cuts off the reaction chain required for photoaging, further enhancing the ultraviolet protection and anti-corrosion barrier effect. It also tightly combines with the Ti-O-Si hybrid shell to form a dual high temperature protection system, reducing the risk of pigment oxidation at high temperature, thereby improving the weather resistance and corrosion resistance of the pigment, and effectively reducing the adverse effects of light, high temperature and corrosive environment on the color performance of the pigment.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0077] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An environmentally friendly pigment, characterized in that: The environmentally friendly pigment is made from the following components in parts by weight: 10-20 parts europium-gadolinium co-doped samarium sulfide powder, 3-6 parts tetrabutyl titanate, 2-4 parts γ-methacryloyloxypropyltrimethoxysilane, 0.1-0.3 parts cerium acetylacetone, and 0.8-1.6 parts polytetrafluoroethylene powder; the europium-gadolinium co-doped samarium sulfide powder is made from the following components in parts by weight: 36-40 parts samarium nitrate hexahydrate, 4-8 parts europium nitrate hexahydrate, and 4-6 parts gadolinium nitrate hexahydrate.

2. A method for preparing an environmentally friendly pigment according to claim 1, characterized in that: Specifically, the following steps are included: S1. Disperse 1.0-2.0g of europium-gadolinium co-doped samarium oxysulfide powder in 100mL of anhydrous ethanol and sonicate for 30-40min. Then add 0.2-0.3g of polyvinylpyrrolidone and sonicate for 5-10min to form a raw material dispersion. Add acetic acid to the raw material dispersion to adjust the pH to 5.0, and then magnetically stir for 20-30min to form a core dispersion for later use. Disperse 0.3-0.6mL of tetrabutyl titanate in 10mL of anhydrous ethanol, then add cerium acetylacetone and stir for 10-20min. Then add 0.05mL of acetylacetone and stir for 20-30min to form coating solution I for later use. 0.2-0.4 mL of γ-methacryloxypropyltrimethoxysilane was dispersed in 10 mL of anhydrous ethanol and stirred for 5-10 min to form coating solution II. Under the conditions of stirring speed of 600-800 rpm and temperature of 25-30℃, coating solution I and coating solution II were simultaneously added dropwise to the core dispersion at a rate of 1 drop / 5 seconds through a dropping funnel and the addition was completed within 2 h. The reaction was continued for 0.5-1 h, centrifuged, and the precipitate was washed 3-5 times in sequence with acetone, anhydrous ethanol, and deionized water. The washed solid material was vacuum dried at 60℃ for 12 h and ground to obtain coated modified europium gadolinium co-doped samarium oxysulfide powder. S2. The coated and modified europium-gadolinium co-doped samarium oxide powder described in step S1 is mixed with polytetrafluoroethylene powder in a dry powder mixture for 30-40 minutes at a mixing speed of 300-400 rpm. The mixture is then transferred to a special atmosphere furnace with a stirrer and subjected to low-temperature heat treatment at 330-340℃ for 1-2 hours under N2 protection at a stirring speed of 300-400 rpm. After cooling and grinding, an environmentally friendly pigment is obtained.

3. The method for preparing environmentally friendly pigments according to claim 2, characterized in that: In step S1, the amount of cerium acetylacetone added is 0.01-0.03g.

4. The method for preparing the environmentally friendly pigment according to claim 3, characterized in that: In step S2, the amount of polytetrafluoroethylene powder added is 0.08-0.16g.

5. The method for preparing the environmentally friendly pigment according to claim 4, characterized in that: The preparation method of the europium-gadolinium co-doped samarium oxysulfide powder specifically includes the following steps: (1) Add 3.6-4.0g of samarium hexahydrate to 50mL of deionized water, then add europium hexahydrate and gadolinium hexahydrate in sequence, stir for 5-10min, then add 4.1-4.3g of disodium ethylenediaminetetraacetate, stir for 30-40min, add concentrated ammonia dropwise to adjust the pH to 8.0-10.0 under stirring, then slowly add dilute nitric acid to adjust the pH to 7.0, stir for 1-2h, and finally transfer to an evaporating dish and dry in an 80℃ oven for 24-48h. Place the resulting dry gel in a muffle furnace, first heat it to 300℃ at a rate of 2℃ / min, keep it at 1-2h, then heat it to 600℃ at a rate of 5℃ / min, keep it at 1-2h, cool it naturally, take it out and grind it to obtain the precursor powder; (2) Spread the precursor powder described in step (1) evenly in an alumina ceramic boat with a powder layer thickness of 2.0-2.8 mm. Then place the alumina ceramic boat in a tube furnace, evacuate, and introduce Ar at a flow rate of 140 mL / min. First, raise the temperature to 400-450°C at a rate of 5°C / min, and then hold it for 30-40 min. Then, switch the gas to an Ar / CS2 mixture and control the total flow rate to 140 mL / min, of which 40 mL / min is used as a carrier gas and flows through a CS2 mixture placed in a 0°C ice-water bath. Two bubbling flasks are used to carry CS2 vapor, which is then mixed with the remaining 100 mL / min bypass Ar to form a reaction atmosphere. The furnace exhaust port needs to be connected to an alkaline solution and activated carbon tail gas absorption device. The temperature is then increased to 880°C at a rate of 2°C / min for sulfidation treatment. The reaction is held at this temperature for 2-3 hours, and then cooled to 200°C at a rate of 2-3°C / min. The CS2 gas path is then closed, and the furnace tube is purged with pure Ar for 10-20 minutes. The furnace is then allowed to cool naturally to room temperature. The product is then removed to obtain europium-gadolinium co-doped samarium sulfide powder.

6. The method for preparing environmentally friendly pigments according to claim 5, characterized in that: In step (1), the amounts of europium hexahydrate and gadolinium hexahydrate added are 0.4-0.8g and 0.4-0.6g, respectively.

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