Composite coated particle, preparation and application in daily chemical field

Abstract

The invention discloses composite coated particles, preparation and application in the field of daily chemicals, and belongs to the field of functional materials and daily chemical products. Composite melanin is formed through codeposition between polyethyleneimine and the melanin source monomer and coats the surfaces of inorganic particles, so that formation of self-polymerization particles of the melanin source monomer is effectively inhibited, and waste is reduced; the introduction of polyethyleneimine increases reaction active sites of a later modifier, improves the reaction efficiency, effectively reduces the surface hydrophilic performance of original particles, improves the dispersibility and stability of the composite coated particles in a daily chemical oil phase system, and provides a new functional raw material for water-in-oil daily chemical products.

Description

Technical Field

[0001] This invention relates to the fields of functional materials and daily chemical products, and more specifically, to a composite coated particle, its preparation, and its application in the daily chemical field. Background Technology

[0002] In the daily chemical industry, the research and development of sunscreen products has always been a key focus. With increasingly severe environmental problems, the atmospheric ozone layer is thinning and even forming ozone holes, leading to a continuous increase in the intensity of ultraviolet A (UVA, wavelength -320-400nm) and ultraviolet B (UVB, wavelength 280-320nm) radiation, and a corresponding increase in oxygen free radicals. UVA and UVB in sunlight cause numerous damages to human skin. UVA has strong penetrating power, penetrating the epidermis and dermis, gradually damaging elastic fibers, causing muscles to lose elasticity, leading to sagging skin, wrinkles, freckles, and age spots. Excessive exposure can also easily cause skin cancer. UVB, on the other hand, denatures nucleic acids or proteins in skin surface cells, causing redness and erythema (sunburn), promoting melanin formation, and triggering acute dermatitis, i.e., sunburn.

[0003] Regarding organic small-molecule sunscreens, the U.S. Food and Drug Administration (FDA) first published a study in May 2019 comparing the systemic exposure of four common organic active ingredients in different commercially available sunscreens under maximum usage conditions. The results were published in The Journal of the American Medical Association. Although the types and amounts of sunscreen ingredients in commercially available sunscreens are within regulations, the study results indicated that after one day of use, volunteers' blood levels of four chemicals—avobenzone, oxybenzone, octocrylene, and escargot—exceeded the FDA's recommended level of 0.5 nanograms per milliliter. Furthermore, with repeated use of sunscreens, the concentration of these chemicals in the blood continued to increase. This demonstrates that organic small-molecule UV absorbers still pose significant safety risks when used on humans.

[0004] Currently, inorganic nanoparticles such as titanium dioxide are widely used in cosmetic sunscreens due to their excellent UV shielding capabilities. Titanium dioxide is an n-type semiconductor. When exposed to UV radiation with wavelengths less than 400nm, electrons in its valence band absorb the UV light and are excited to the conduction band, simultaneously generating electron-hole pairs. Some of these electron-hole pairs migrate to the surface, causing hydroxyl groups and adsorbed water on the titanium dioxide surface to generate hydroxyl radicals, which have strong oxidizing power and can physically shield against UV radiation. However, nano-titanium dioxide has several problems. On the one hand, in applications, its Ti-O bonds are highly polar, resulting in strong molecular polarity. Its surface easily adsorbs water molecules, forming surface hydroxyl groups, which are highly hydrophilic and prone to aggregation in water. It is difficult to disperse in organic systems, especially in emulsion products with high oil content, where direct addition of untreated titanium dioxide may lead to oil-water separation, affecting product texture and stability. On the other hand, its crystalline structure has strong ionic arrangement and binding forces, resulting in a rough texture and lowering users' expectations for a smooth skin feel in cosmetics. Furthermore, adding large amounts of titanium dioxide can make sunscreen cosmetics appear white and heavy, making them difficult to spread and resulting in a poor consumer experience. my country's "Cosmetic Safety Technical Specifications" (IECIC 2015) stipulates that the maximum addition amount of titanium dioxide is 25%, which to some extent limits its ability to improve sun protection. In addition, recent research shows that when inorganic nanoparticles such as titanium dioxide are applied to the skin surface, some nanoparticles can penetrate the epidermis into the deeper layers of the skin, and even enter the bloodstream, accumulating in areas such as the cardiopulmonary center or the extremities, posing various potential health risks.

[0005] To address these issues, researchers have attempted to modify inorganic particles such as titanium dioxide using surface coating technology. Studies such as patent CN113350207A, which utilize melanin for coating, have gradually gained attention. Melanin, a natural biomolecule, can be coated onto the surface of inorganic particles like titanium dioxide to enhance sun protection while reducing the amount of inorganic particles added, thus alleviating the problems of whitening and heaviness in products.

[0006] However, existing melanin-coated particles, formed by encapsulating inorganic components such as titanium dioxide, suffer from significant waste because melanin monomers tend to self-aggregate during the encapsulation process rather than being coated onto the inorganic particles. Furthermore, melanin molecules are rich in polar groups such as hydroxyl groups, exhibiting strong hydrophilicity. This characteristic makes them difficult to disperse stably in the current mainstream sunscreen formulation—the water-in-oil system. In the water-in-oil system, with oil as the continuous phase, hydrophilic encapsulated particles are prone to aggregation and sedimentation due to differences in interfacial tension, leading to decreased formulation stability and phenomena such as layering and clumping, greatly limiting their application in water-in-oil sunscreen products.

[0007] Currently, although some technologies attempt to modify coated particles with lipophilicity using surfactants or polymers, these methods often suffer from poor modification effects, poor compatibility with sunscreen systems, and increased safety risks due to the introduction of additional chemicals. For example, the physical adsorption of surfactants is easily affected by the system environment and can detach, causing particles to re-aggregate; modification with long-chain polymers may increase the stickiness of the product, ruining the refreshing user experience of sunscreen products.

[0008] Therefore, developing modified lipophilic melanin-encapsulated inorganic particles that combine high-efficiency sun protection performance, good lipophilic dispersibility, and excellent user experience is key to solving the current technological bottlenecks in sun protection products and is of great significance for promoting the upgrading of UV protection products in the daily chemical industry. Summary of the Invention

[0009] To address the problems in existing technologies, this invention provides a composite coated particle, its preparation, and its application in the daily chemical industry. This invention utilizes the co-deposition of polyethyleneimine and melanin-derived monomers to form a composite melanin coating on the surface of inorganic particles. This effectively inhibits the formation of self-polymerized melanin-derived monomer particles, reducing waste. The introduction of polyethyleneimine increases the reactive sites of subsequent modifiers, improving reaction efficiency. Simultaneously, it effectively reduces the hydrophilicity of the original particle surface, enhancing the dispersibility and stability of the composite coated particles in the oil phase of daily chemical products, providing a new functional raw material for water-in-oil daily chemical products.

[0010] One objective of this invention is to provide a composite coated particle, which is composed of inorganic particles, composite melanin, and lipophilic modifier, wherein the mass ratio of inorganic particles, composite melanin, and lipophilic modifier by weight is 100:(0.5-10):(3-15); the composite coated particle exhibits excellent dispersion in water-in-oil daily chemical systems.

[0011] Furthermore, the inorganic particles are one or more of titanium dioxide, zinc oxide, carbon nitride, calcium carbonate, magnesium carbonate, aluminum hydroxide, silicon dioxide, boron nitride, talc, and mica powder, wherein the particle size range of the inorganic particles is 50-500 nm, preferably 80-100 nm.

[0012] Furthermore, the composite melanin is formed by co-deposition of melanin source monomer and polyethyleneimine, wherein the mass ratio of melanin source monomer to polyethyleneimine is 1:(0.05-0.5).

[0013] Furthermore, the lipophilic modifier is one or a combination of two or more of the following: triethoxyoctylsilane, stearyltriethoxysilane, hexyltrimethoxysilane, trimethoxyoctylsilane, perfluorooctyltriethoxysilane, and perfluorooctylethyltriethoxysilane.

[0014] Furthermore, the melanin source monomer is one or a combination of two or more of the following: tyrosine, 3-hydroxy-L-tyrosine, acetyltyrosine, oleoyltyrosine, dopaquinone, dopachrome, 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, dopamine hydrochloride, and cysteine ​​dopa.

[0015] Furthermore, the polyethyleneimine is a branched polyethyleneimine with a molecular weight ≤ 70000 g / mol; the preferred molecular weight of polyethyleneimine is 300, 600, 1200, 1800, or 70000 g / mol; the further preferred molecular weight of polyethyleneimine is 600, 1200, or 1800 g / mol.

[0016] A second objective of this invention is to provide a method for preparing composite coated particles. This method includes the following steps:

[0017] (1) Disperse inorganic particles in deionized water and stir at high speed to form a stable dispersion;

[0018] (2) Add melanin source monomer and polyethyleneimine to the above dispersion, adjust the pH to weakly alkaline, react under an oxygen atmosphere, keep stirring at high speed, filter under pressure and dry under vacuum or forced air at a temperature below 60°C to obtain coated particles.

[0019] (3) Dissolve the lipophilic modifier in an alcohol-water solution, adjust the pH to weakly acidic using an organic acid, and continue stirring at room temperature until completely dissolved;

[0020] (4) Under high-speed stirring, the solution from step (3) is added to the coated particles obtained in step (2) in portions over half an hour. After stirring evenly at high speed, the mixture is kept for a period of time. The solvent is removed by vacuum or forced-air drying at a temperature below 60°C to obtain composite coated particles.

[0021] Further, in step (1), the concentration of inorganic particles in the dispersion is 50-150 g / L, and the high-speed stirring speed is 400-800 rpm; in step (2), the pH is adjusted to 8-10, the high-speed stirring reaction temperature is 40-60℃, and the reaction time is 2-4 hours.

[0022] Further, in step (3), the alcohol-water solution is a mixture of ethanol or isopropanol and water, wherein the mass ratio of alcohol to deionized water is (80-98):(2-20); the pH is adjusted to 4.5-5.5 by organic acid; stirring is continued at room temperature for 0.5-1.5 hours; the concentration of the lipophilic modifier solution is 50-300 g / L; and the organic acid is one of acetic acid, lactic acid, and citric acid.

[0023] Furthermore, in step (4), the high-speed stirring speed is 1000-3000 rpm; after stirring evenly, it is kept at 40-60℃ for 1-3 hours.

[0024] A third objective of this invention is to provide an application of composite-coated particles. These composite-coated particles can be applied to various oil-in-water daily chemical systems, particularly suitable for oil-in-water sunscreens, such as sunscreen lotions, sunscreen creams, sunscreen sprays, sunscreen gels, sunscreen powders, sunscreen gels, sunscreen creams, sunscreen lotions, sunscreen creams, sunscreen gels, etc., or hair products such as leave-in shampoo sprays, shampoos, and conditioners, or beauty products such as setting powders, contour powders, concealers, foundations, and cushion compacts.

[0025] The beneficial effects of this invention are:

[0026] (1) The raw materials of the present invention comply with the "List of Used Cosmetic Raw Materials (IECIC 2015)", and the raw materials are low in cost, safe and non-toxic, and the production process is simple;

[0027] (2) The composite melanin coating effect formed by co-deposition of melanin source monomer and polyethyleneimine is excellent. The introduction of polyethyleneimine disrupts the non-covalent interaction in the aggregates formed by melanin source monomer, effectively inhibits the formation of self-polymerized particles, and ensures the uniformity of its coating on the surface of inorganic particles; at the same time, it provides more primary amino groups for subsequent effective modification reaction sites.

[0028] (3) Polyethyleneimine is alkaline in the system, which is conducive to promoting the oxidation of melanin source monomers to generate melanin; and polyethyleneimine itself has a certain viscosity, which can be added to the system as a suspension stabilizer and dispersant, which is conducive to the stable and uniform dispersion of inorganic particles in the solution and reduces the aggregation between particles.

[0029] (4) The lipophilic modifier can react with the hydroxyl and primary amino groups on the surface of the particles coated with composite melanin, effectively reducing the hydrophilicity of the original particle surface and improving the dispersibility and stability of the composite coated particles in the daily chemical oil phase system, providing new functional raw materials for water-in-oil daily chemical products.

[0030] (5) The use of organic acids avoids the negative impact of the introduction of inorganic ions into the subsequent daily chemical system and reduces the membrane removal process of ions in production.

[0031] (6) The composite coated particles of the present invention can play multiple roles in cosmetics, such as scavenging free radicals, absorbing and scattering ultraviolet rays, stabilizing dispersion, and preventing inorganic nanoparticles from penetrating the skin; at the same time, they can improve the shortcomings of the original inorganic components, such as heavy color and difficulty in dispersion, and reduce stickiness. Attached Figure Description

[0032] Figure 1Digital photographs of Example 3 and Comparative Examples 1-8;

[0033] Figure 2 Digital photographs of Examples 3 and 4 and Comparative Examples 1 and 4 after ultrasonication in aqueous and oil phases (GTCC) and then placed for 0 h and 48 h for dispersion.

[0034] Figure 3 The UV absorption spectra of Examples 3, 4, and Comparative Examples 1, 2, 4, and 8 in the GTCC dispersion phase (0.02 mg / mL);

[0035] Figure 4 The images are scanning electron microscope (SEM) images of the dispersions of the same concentration as those in Example 3 and Comparative Example 1. Detailed Implementation

[0036] Unless otherwise specified, all reagents used in the embodiments of this invention can be purchased commercially.

[0037] It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. In addition to the raw materials used in the embodiments of this invention, any raw material components that contain the same functional groups or include the same structural units involved in this invention, and which are replaced by equivalent substitutions, should be included within the scope of protection of this invention. The invention will be further described below with reference to specific embodiments.

[0038] The present invention provides accompanying drawings of detection results for some embodiments. Other embodiments and comparative examples use the same detection method. Those skilled in the art can directly and without doubt determine the content of the embodiments of the present invention using the detection method provided by the present invention.

[0039] Example 1

[0040] 100g of titanium dioxide (~80nm) was dispersed in 2L of deionized water and stirred at 400rpm to form a stable dispersion (50g / L). 0.5g of a composite melanin (0.476g of dopamine hydrochloride and 0.024g of polyethyleneimine with a molecular weight of 300g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.05) was added to the dispersion. The pH was adjusted to 8, and the reaction was carried out under an oxygen atmosphere at 40°C with high-speed stirring for 2 hours. The mixture was then filtered and dried under forced-air drying at 50°C to obtain the desired product. Coated particles 1 ;

[0041] Dissolve 3g of triethoxyoctylsilane in 60ml of ethanol-water (ethanol:water = 80:20, mass ratio) solution (50g / L), adjust the pH to 4.5 with acetic acid, and continue stirring at room temperature for 0.5 hours. Then, under high-speed stirring at 1000rpm, add the above solution in portions over half an hour. Coated Particle 1 After stirring evenly, maintain at 40°C for 1 hour; then vacuum dry at 50°C to remove the solvent, obtaining... Composite coated particles 1 .

[0042] Example 2

[0043] 100g of titanium dioxide (~80nm) was dispersed in 0.67L of deionized water and stirred at 800rpm to form a stable dispersion (150g / L). 10g of a composite melanin (6.667g of dopamine hydrochloride and 3.333g of polyethyleneimine with a molecular weight of 300g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.5) was added to the dispersion. The pH was adjusted to 10, and the reaction was carried out under an oxygen atmosphere at 60°C with high-speed stirring for 4 hours. The mixture was then filtered under pressure and dried at 50°C by forced air drying to obtain the desired product. Cover Particle 2 ;

[0044] Dissolve 15g of triethoxyoctylsilane in 50ml of ethanol-water (ethanol:water = 98:2, mass ratio) solution (300g / L), adjust the pH to 5.5 with acetic acid, and continue stirring at room temperature for 1.5 hours. Then, while stirring at 3000rpm, add the solution in portions over half an hour. Coated Particle 2 After stirring evenly, maintain at 60°C for 3 hours; then vacuum dry at 50°C to remove the solvent, obtaining... Composite coated particles 2 .

[0045] Example 3

[0046] 100g of titanium dioxide (~80nm) was dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 1g of a composite melanin (0.8g dopamine hydrochloride and 0.2g polyethyleneimine with a molecular weight of 600g / mol, melanin source monomer to polyethyleneimine mass ratio of 1:0.25) was added to the dispersion. The pH was adjusted to 8.5, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 3 hours. The mixture was then filtered and dried at 50°C under forced-air drying to obtain the desired product. Coated Particle 3 ;

[0047] Dissolve 5g of triethoxyoctylsilane in 25ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200g / L), adjust the pH to 5.0 with acetic acid, and continue stirring at room temperature for 1 hour; under high-speed stirring at 2000rpm, add the above solution in portions over half an hour. Coated Particle 3 After stirring evenly, the mixture is kept at 50°C for 1.5 hours; then vacuum dried at 50°C to remove the solvent, yielding... Composite coated particles 3 .

[0048] Example 4

[0049] 100g of titanium dioxide (~80nm) was dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 1g of a composite melanin (0.8g dopamine hydrochloride and 0.2g polyethyleneimine with a molecular weight of 1800g / mol, melanin source monomer to polyethyleneimine mass ratio of 1:0.25) was added to the dispersion, and the pH was adjusted to 8.5. The reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 3 hours. The mixture was then filtered and dried under forced-air drying at 50°C to obtain... Cover Particle 4 ;

[0050] Dissolve 5g of triethoxyoctylsilane in 25ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200g / L), adjust the pH to 5.0 with acetic acid, and continue stirring at room temperature for 1 hour; under high-speed stirring at 2000rpm, add the above solution in portions over half an hour. Coated Particle 4 After stirring evenly, the mixture is kept at 50°C for 1.5 hours; then vacuum dried at 50°C to remove the solvent, yielding... Composite coated particles 4 .

[0051] Example 5

[0052] 80g of titanium dioxide (~80nm) and 20g of zinc oxide (~50nm) were dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 1g of a complex melanin (0.4g dopamine hydrochloride, 0.4g 5,6-dihydroxyindole, and 0.2g polyethyleneimine with a molecular weight of 600g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.25) was added to the dispersion. The pH was adjusted to 8.5, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 3 hours. The mixture was then filtered and dried under forced-air drying at 50°C to obtain the desired product. Coated Particles 5 ;

[0053] Dissolve 4g of triethoxyoctylsilane and 1g of stearyltriethoxysilane in 25ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200g / L), adjust the pH to 5.0 with acetic acid, and continue stirring at room temperature for 1 hour; under high-speed stirring at 2000rpm, add the above solution in portions over half an hour. Coated Particles 5 After stirring evenly, the mixture is kept at 50°C for 1.5 hours; then vacuum dried at 50°C to remove the solvent, yielding... Composite coated particles 5 .

[0054] Example 6

[0055] 50g of silica (~100nm) and 50g of aluminum hydroxide (~500nm) were dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 5g of a complex melanin (2.54g of 3-hydroxy-L-tyrosine, 2g of 5,6-dihydroxyindole, and 0.46g of polyethyleneimine with a molecular weight of 1200g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.1) was added to the dispersion. The pH was adjusted to 9, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 2.5 hours. The mixture was then filtered and dried at 45°C under forced-air drying to obtain the desired product. Encapsulated Particle 6 ;

[0056] Dissolve 7g of triethoxyoctylsilane and 3g of trimethoxyoctylsilane in 40ml of isopropanol-water (isopropanol:water = 95:5, mass ratio) solution (250g / L), adjust the pH to 5.0 with lactic acid, and continue stirring at room temperature for 1.5 hours. Then, under high-speed stirring at 2500rpm, add the above solution in portions over half an hour. Encapsulated Particle 6 After stirring evenly, the mixture was kept at 50°C for 2.5 hours; then vacuum dried at 45°C to remove the solvent, yielding... Composite coated particles 6 .

[0057] Example 7

[0058] 50g of silica (~100nm) and 50g of aluminum hydroxide (~500nm) were dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 5g of a complex melanin (2.54g of 3-hydroxy-L-tyrosine, 2g of 5,6-dihydroxyindole, and 0.46g of polyethyleneimine with a molecular weight of 70000g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.1) was added to the dispersion. The pH was adjusted to 9, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 2.5 hours. The mixture was then filtered and dried at 45°C by forced-air drying to obtain the desired product. Coated Particle 7 ;

[0059] Dissolve 7g of triethoxyoctylsilane and 3g of trimethoxyoctylsilane in 40ml of isopropanol-water (isopropanol:water = 95:5, mass ratio) solution (250g / L), adjust the pH to 5.0 with lactic acid, and continue stirring at room temperature for 1.5 hours. Then, under high-speed stirring at 2500rpm, add the above solution in portions over half an hour. Coated Particle 7 After stirring evenly, the mixture was kept at 50°C for 2.5 hours; then vacuum dried at 45°C to remove the solvent, yielding... Composite coated particles 7 .

[0060] The proportions were all compared with those in Example 3.

[0061] Comparative Example 1 [Titanium Dioxide]

[0062] Commercially available titanium dioxide (~80nm), denoted as Particle 1 .

[0063] Comparative Example 2 [Titanium Dioxide + Melanin]

[0064] 100 g of titanium dioxide (~80 nm) was dispersed in 1 L of deionized water and stirred at 600 rpm to form a stable dispersion (100 g / L). 0.8 g of dopamine hydrochloride was added to the dispersion to adjust the pH to 8.5. The reaction was carried out under an oxygen atmosphere at 50 °C with high-speed stirring for 3 hours. The mixture was then filtered and dried at 50 °C under forced-air drying to obtain the desired product. Particle 2 .

[0065] Comparative Example 3 [Titanium Dioxide + Polyethylene Imide]

[0066] 100 g of titanium dioxide (~80 nm) was dispersed in 1 L of deionized water and stirred at 600 rpm to form a stable dispersion (100 g / L). 0.2 g of polyethyleneimine with a molecular weight of 600 g / mol was added to the dispersion, and the pH was adjusted to 8.5. The reaction was carried out under an oxygen atmosphere at 50 °C with high-speed stirring for 3 hours. The mixture was then filtered under pressure and dried at 50 °C by forced air drying to obtain the desired product. particle 3 .

[0067] Comparative Example 4 [Titanium Dioxide + Melanin + Polyethylene Imine]

[0068] 100g of titanium dioxide (~80nm) was dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 1g of a composite melanin (0.8g dopamine hydrochloride and 0.2g polyethyleneimine with a molecular weight of 600g / mol, melanin source monomer to polyethyleneimine mass ratio of 1:0.25) was added to the dispersion. The pH was adjusted to 8.5, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 3 hours. The mixture was then filtered and dried at 50°C under forced-air drying to obtain the desired product. Particle 4 .

[0069] Comparative Example 5 [Titanium Dioxide + Lipophilic Modifier]

[0070] 100 g of titanium dioxide (~80 nm) was dispersed in 1 L of deionized water and stirred at 600 rpm to form a stable dispersion (100 g / L). 5 g of triethoxyoctylsilane was dissolved in 25 ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200 g / L), and the pH was adjusted to 5.0 with acetic acid. The mixture was then stirred at room temperature for 1 hour. Under high-speed stirring at 2000 rpm, the above solution was added to the particles in portions over half an hour, stirred until homogeneous, and then kept at 50 °C for 1.5 hours. The solvent was removed by vacuum drying at 50 °C to obtain the desired product. Particle 5 .

[0071] Comparative Example 6 [Titanium Dioxide + Melanin + Lipophilic Modifier]

[0072] 100g of titanium dioxide (~80nm) was dispersed in 1L of deionized water and stirred at high speed at 600rpm to form a stable dispersion (100g / L); 0.8g of dopamine hydrochloride was added to the above dispersion to adjust the pH to 8.5. The reaction was carried out under an oxygen atmosphere and stirred at high speed at 50°C for 3 hours. The mixture was then filtered and dried at 50°C by forced air to obtain particles.

[0073] 5 g of triethoxyoctylsilane was dissolved in 25 ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200 g / L), and the pH was adjusted to 5.0 with acetic acid. The mixture was stirred at room temperature for 1 hour. Under high-speed stirring at 2000 rpm, the solution was added to the particles in portions over half an hour, and after thorough mixing, the mixture was kept at 50°C for 1.5 hours. The solvent was removed by vacuum drying at 50°C to obtain the desired product. Particle 6 .

[0074] Comparative Example 7 [Titanium dioxide + polyethyleneimine + lipophilic modifier]

[0075] 100g of titanium dioxide (~80nm) was dispersed in 1L of deionized water and stirred at 600rpm to form a stable dispersion (100g / L). 0.2g of polyethyleneimine with a molecular weight of 600g / mol was added to the dispersion, the pH was adjusted to 8.5, and the reaction was carried out under an oxygen atmosphere at 50°C with high-speed stirring for 3 hours. The mixture was then filtered and dried at 50°C by forced air drying to obtain particles.

[0076] 5 g of triethoxyoctylsilane was dissolved in 25 ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200 g / L), and the pH was adjusted to 5.0 with acetic acid. The mixture was stirred at room temperature for 1 hour. Under high-speed stirring at 2000 rpm, the solution was added to the particles in portions over half an hour, and after thorough mixing, the mixture was kept at 50°C for 1.5 hours. The solvent was removed by vacuum drying at 50°C to obtain the desired product. Particle 7 .

[0077] Comparative Example 8 [Melanin + Polyethyleneimine + Lipophilic Modifier]

[0078] 1 g of composite melanin (0.8 g of dopamine hydrochloride and 0.2 g of polyethyleneimine with a molecular weight of 600 g / mol, with a melanin source monomer to polyethyleneimine mass ratio of 1:0.25) was added to 1 L of deionized water. The pH was adjusted to 8.5, and the reaction was carried out under an oxygen atmosphere at 50 °C with high-speed stirring for 3 hours. The mixture was then filtered under pressure and dried under forced air at 50 °C to obtain particles.

[0079] 5 g of triethoxyoctylsilane was dissolved in 25 ml of isopropanol-water (isopropanol:water = 90:10, mass ratio) solution (200 g / L), and the pH was adjusted to 5.0 with acetic acid. The mixture was stirred at room temperature for 1 hour. Under high-speed stirring at 2000 rpm, the solution was added to the particles in portions over half an hour, and after thorough mixing, the mixture was kept at 50°C for 1.5 hours. The solvent was removed by vacuum drying at 50°C to obtain the desired product. Particle 8 .

[0080] The particle size and polydispersity index of the above examples and comparative examples were determined using a potentiometer. Comparative examples 1-4 were dispersed in water, while other samples were dispersed using GTCC. The results are listed in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] Based on the data in the table above and Figure 1 , 2Analysis shows that the addition of melanin source monomers can effectively form melanin during the reaction process, synergistically absorbing ultraviolet light with inorganic particles; the addition of polyethyleneimine is beneficial to the dispersion of particles in the system, effectively inhibiting the formation of self-polymerized particles and obtaining particles with a more concentrated particle size distribution; the composite melanin coating effect formed by the co-deposition of melanin source monomers and polyethyleneimine is excellent. The introduction of polyethyleneimine disrupts the non-covalent interactions in the aggregates formed by melanin source monomers, ensuring the uniformity of its coating on the surface of inorganic particles, while providing more primary amines for subsequent effective modification reaction sites; the addition of lipophilic modifiers effectively increases the dispersion stability of particles in the oil phase. Comparing Example 3 with Comparative Examples 1-4, it can be seen that particles without lipophilic modifier treatment are difficult to disperse uniformly in GTCC. Comparing Example 3 with Comparative Examples 5 and 7, it can be seen that particles treated only with lipophilic modifiers, or particles composed only of titanium dioxide and polyethyleneimine, have significantly weakened UV absorption because no melanin-derived monomers were added to form melanin. Compared to Comparative Example 6, the addition of polyethyleneimine (PEI) in Example 3 effectively inhibited the formation of self-polymerizing particles, ensuring uniform coating on the surface of inorganic particles, and providing more primary amino groups for subsequent effective modification reaction sites. This resulted in better dispersion of the particles obtained in the GTCC oil phase, effectively improving UV absorption at the same concentration. Comparing Example 3 with Comparative Example 8, it can be seen that inorganic particles without added titanium dioxide only absorb in their characteristic UV absorption areas, without good absorption across the entire UVB and UVA wavelength range.

[0085] pass Figure 4 Scanning electron microscopy analysis shows that, under the same concentration conditions, unlike the dense stacking of particles in Comparative Example 1, the particles in Example 3 of this application have excellent dispersibility in the dispersion.

[0086] The coated particles of this invention exhibit significant hydrophobicity, always floating on the surface of water without settling in the aqueous phase. They also demonstrate excellent dispersibility in the oil phase (GTCC), remaining stable even after 48 hours. Furthermore, the particles are fine and do not adhere to the walls of the container. In contrast, the particles in the comparative example initially show some dispersibility in water, but settle after 48 hours. They are even unable to disperse in the GTCC oil phase, resulting in particle aggregation and severe wall adhesion. This makes them unsuitable for water-in-oil emulsion systems used in sunscreens and other daily chemical products that require a certain degree of water resistance.

[0087] The particles processed by this invention have a particle size greater than 100nm, meeting the "non-nano" requirements of the daily chemical industry, and are safer for the human body.

[0088] Examples 8-9 and Comparative Examples 9-12

[0089] The formulations of Examples 8-9 and Comparative Examples 9-12 are shown in Table 2.

[0090] Using the formulations in Table 2 and the commonly used preparation methods in the aforementioned fields, the water-in-oil system UV-protective daily chemical products of Examples 8-9 and Comparative Examples 9-12 were obtained, based on 100 parts by weight of total cosmetic product volume. Comparative Examples 9-12 used particles prepared in Comparative Examples 5-8; Examples 8-9 used composite coated particles prepared in Examples 3-4. The particles in Comparative Examples 1-4 are hydrophilic and cannot be used in water-in-oil systems.

[0091] The preparation steps of a water-in-oil system for UV-protective daily chemical products are as follows:

[0092] The oil phase and aqueous phase components are dissolved or dispersed at 80℃ to prepare an oil- and hydrophilic mixture, which is then homogenized using a homogenizer. After cooling, an oil-in-water system UV-protective daily chemical product is formed.

[0093] Evaluation Project

[0094] 1. SPF test

[0095] Each sample was uniformly coated with 2 mg / cm² onto a quartz glass plate. 2 Allow to air dry for 15 minutes. Then, irradiate with ultraviolet light at a distance of 10 mm above the glass plate. Use an ultraviolet transmittance analyzer (Labsphere Inc., USA) to randomly measure five points on the quartz glass plate in the range of 280-400 nm to obtain the SPF value. The average of the five measurements is recorded as the SPF.

[0096] 2. Emulsification stability

[0097] The appearance of the test sample after being stored at 25°C for one month was visually inspected and evaluated according to the following criteria.

[0098] ◎: The sample is uniform and stable;

[0099] ○: Emulsion separation was observed in the sample;

[0100] △: Oil floats were observed in the sample;

[0101] ×: The sample is completely separated.

[0102] 3. User experience

[0103] Ten volunteers were selected, and each sample was applied to their face. The stickiness during absorption and the ease of spreading were investigated and evaluated according to the following criteria.

[0104] ◎: 9-10 people answered that it is not sticky and easy to push away;

[0105] ○: 6-8 people answered that it is not sticky and easy to push away;

[0106] △: 3-5 people answered that it is not sticky and easy to push away;

[0107] ×: 0-2 people answered that it is not sticky and easy to push away.

[0108] The test results are shown in Table 2.

[0109] Table 2

[0110]

[0111]

[0112] In practical applications, comparing Examples 8-9 with Comparative Examples 9-12, and considering the aforementioned explanation of the composite coated particles of the present invention, it can be found that the composite coated particles provided by the present invention have a higher SPF value when added to sunscreens. Compared with Examples 8-9 and Comparative Examples 9 and 11, the present invention improves upon the shortcomings of pure titanium dioxide UV protection products, such as excessive whiteness and poor user experience. Compared with Examples 8-9 and Comparative Example 10, the sample without added polyethyleneimine has fewer active sites that react with the lipophilic modifier, resulting in a darker product color. In contrast, the composite coated particles of the present invention are more uniform, resulting in a sunscreen product with superior UV absorption and a higher SPF value. Comparative Example 12, which does not contain inorganic particles such as titanium dioxide, has a poorer SPF value, stability, user experience, and color.

[0113] Those skilled in the art should understand that the above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite coated particle, characterized in that, The composite coated particles are composed of inorganic particles, composite melanin, and lipophilic modifier, wherein the mass ratio of inorganic particles, composite melanin, and lipophilic modifier by weight is 100:(0.5-10):(3-15); the composite coated particles exhibit excellent dispersion in water-in-oil daily chemical systems.

2. The composite coated particles as described in claim 1, characterized in that, The inorganic particles are one or more of titanium dioxide, zinc oxide, carbon nitride, calcium carbonate, magnesium carbonate, aluminum hydroxide, silicon dioxide, boron nitride, talc, and mica powder, wherein the particle size range of the inorganic particles is 50-500 nm.

3. The composite coated particles as described in claim 1, characterized in that, The composite melanin is formed by co-deposition of melanin source monomer and polyethyleneimine, wherein the mass ratio of melanin source monomer to polyethyleneimine is 1:(0.05-0.5); the polyethyleneimine is a branched polyethyleneimine with a molecular weight ≤70000g / mol.

4. The composite coated particles as described in claim 1, characterized in that, The lipophilic modifier is one or a combination of two or more of the following: triethoxyoctylsilane, stearyltriethoxysilane, hexyltrimethoxysilane, trimethoxyoctylsilane, perfluorooctyltriethoxysilane, and perfluorooctylethyltriethoxysilane.

5. The composite coated particles as described in claim 3, characterized in that, The melanin source monomer is one or more of the following: tyrosine, 3-hydroxy-L-tyrosine, acetyltyrosine, oleoyltyrosine, dopaquinone, dopachrome, 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, dopamine hydrochloride, and cysteine ​​dopa, with a molecular weight of polyethyleneimine of 300, 600, 1200, 1800, or 70000 g / mol.

6. A method for preparing composite coated particles according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Disperse inorganic particles in deionized water and stir at high speed to form a stable dispersion; (2) Add melanin source monomer and polyethyleneimine to the above dispersion, adjust the pH to weakly alkaline, react under an oxygen atmosphere, keep stirring at high speed, filter under pressure and dry under vacuum or forced air at a temperature below 60°C to obtain coated particles. (3) Dissolve the lipophilic modifier in an alcohol-water solution, adjust the pH to weakly acidic using an organic acid, and continue stirring at room temperature until completely dissolved; (4) Under high-speed stirring, the solution from step (3) is added to the coated particles obtained in step (2) in portions over half an hour. After stirring evenly at high speed, the mixture is kept for a period of time. The solvent is removed by vacuum or forced-air drying at a temperature below 60°C to obtain composite coated particles.

7. The method for preparing composite coated particles as described in claim 6, characterized in that, In step (1), the concentration of inorganic particles in the dispersion is 50-150 g / L, and the high-speed stirring speed is 400-800 rpm; in step (2), the pH is adjusted to 8-10, the high-speed stirring reaction temperature is 40-60℃, and the reaction time is 2-4 hours.

8. The method for preparing composite coated particles as described in claim 6, characterized in that, In step (3), the alcohol-water solution is a mixture of ethanol or isopropanol and water, wherein the mass ratio of alcohol to deionized water is (80-98):(2-20); the pH is adjusted to 4.5-5.5 with organic acid; stirring is continued at room temperature for 0.5-1.5 hours; the concentration of the lipophilic modifier solution is 50-300 g / L. The organic acid is one of acetic acid, lactic acid, and citric acid.

9. The method for preparing composite coated particles as described in claim 6, characterized in that, In step (4), the high-speed stirring speed is 1000-3000 rpm; after stirring evenly, it is kept at 40-60℃ for 1-3 hours.

10. The application of a composite coated particle according to any one of claims 1-5 or a composite coated particle obtained by the preparation method according to any one of claims 6-9, characterized in that, The composite coated particles can be applied to various oil-in-water daily chemical systems, and are especially suitable for oil-in-water sunscreens.

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