A sunscreen agent, its preparation method and use

Abstract

This application discloses a sunscreen agent, its preparation method, and its application. The preparation method of the sunscreen agent includes the following steps: mixing a dispersion 1 containing triangular cerium dioxide and a dispersion 2 containing hexagonal cerium dioxide; adjusting the pH of the mixture to 1-5; adding hexamethylenediamine for a first ultrasonic dispersion; then adding polyethylene glycol for a second ultrasonic dispersion to obtain the sunscreen agent; wherein the mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 100:4~120; the average particle size of triangular cerium dioxide is 50~500 nm, the average particle size of hexagonal cerium dioxide is 50~1000 nm, the average particle size ratio of hexagonal cerium dioxide to triangular cerium dioxide is 1:2~10:3, and the particle size distribution of both is ≤2.5. The sunscreen agent prepared by this method can form a dense and uniform protective layer with lower addition amounts, exhibiting excellent UV shielding effect, while also improving the skin feel of the coating and preventing whitening.

Description

Technical Field

[0001] This application relates to the field of cosmetic technology, specifically to a sunscreen agent, its preparation method, and its application. Background Technology

[0002] Currently, UV-protective materials (sunscreens) in cosmetics mainly fall into three categories: physical sunscreens, chemical sunscreens, and biological sunscreen ingredients. Physical sunscreens, such as titanium dioxide (TiO2), protect the skin by forming "micromirrors" or "shields" on the skin's surface, reflecting and scattering ultraviolet rays. Their advantages include immediate effect upon application, stability, and low likelihood of causing allergies, making them suitable for sensitive skin, children, and delicate skin around the eyes. However, traditional formulas are thick and can easily leave a "white cast" after application, affecting the feel and appearance.

[0003] Chemical sunscreens reduce skin damage by absorbing ultraviolet rays and converting them into heat. Common ingredients include ethylhexyl methoxycinnamate, octocrylene, avobenzone, and ethylhexyl salicylate. Their advantages include a lightweight, transparent texture that is easy to apply; however, some ingredients may irritate the skin, so those with sensitive skin should use them with caution. They should be applied 15-30 minutes before going outdoors, as their sun protection decreases after chemical bonds break, requiring repeated reapplication. To achieve broad-spectrum sun protection (protecting against both UVA and UVB), commercially available products typically require a combination of multiple chemical sunscreens, increasing formulation complexity and the risk of skin irritation.

[0004] Biological sunscreen ingredients such as vitamins C / E, polyphenols (e.g., green tea extract), carotenoids, and sodium hyaluronate are typically used as auxiliary ingredients to provide "indirect sun protection" by scavenging free radicals generated by ultraviolet rays and repairing damaged cells. However, these ingredients offer short-lasting protection and their effectiveness is inconsistent, making them unsuitable as the primary sun protection barrier on their own.

[0005] In summary, existing sunscreens struggle to achieve a good balance between UV protection effectiveness, skin feel, stability, and low irritation. Summary of the Invention

[0006] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a method for preparing a sunscreen agent.

[0007] This application also provides a sunscreen agent.

[0008] This application also provides the application of the above-mentioned sunscreen agents.

[0009] Specifically, the first aspect of this application relates to a method for preparing a sunscreen agent, comprising the following steps: Dispersion 1 containing triangular cerium dioxide and dispersion 2 containing hexagonal cerium dioxide are provided; Dispersion 1 and dispersion 2 are mixed to obtain a mixture, wherein the mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 100:4~120; Adjust the pH of the mixture to 1-5, add hexamethylenediamine for the first ultrasonic dispersion, then add polyethylene glycol for the second ultrasonic dispersion to obtain the sunscreen agent; The triangular cerium dioxide has an average particle size of 50-500 nm, the hexagonal cerium dioxide has an average particle size of 50-1000 nm, and the average particle size ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 1:2-10:3, with a particle size dispersion of ≤2.5.

[0010] The method for preparing the sunscreen agent according to the first aspect of this application has at least the following beneficial effects: This sunscreen agent is prepared by separately preparing dispersion 1 (containing triangular cerium dioxide) and dispersion 2 (containing hexagonal cerium dioxide), and then mixing the two to form a mixed solution. This achieves preliminary dispersion and morphology separation control of the particles, laying the foundation for subsequent layering and the formation of a uniform protective layer. Adjusting the pH to 1-5 in the mixed solution and performing ultrasonic dispersion can enhance the surface charge state of the particles, improve particle dispersibility, reduce particle agglomeration, and promote the formation of a dense layered structure of triangular and hexagonal cerium dioxide particles.

[0011] Triangular cerium dioxide particles have a moderate size, ensuring UV absorption capacity while maintaining good dispersibility; hexagonal cerium dioxide particles have a larger size, and when combined with triangular particles, they increase the stacking density, achieving a more efficient UV blocking effect. By optimizing the mass ratio of the two types of particles, dispersion stability can be maintained while ensuring UV absorption capacity. Experiments show that an excessively high proportion of triangular particles leads to decreased particle dispersibility, while an excessively low proportion leads to decreased UV absorption capacity. Therefore, by optimizing the ratio, significant UV blocking effects can be achieved at lower addition amounts, while avoiding coating whitening and improving skin feel.

[0012] During the initial ultrasonic dispersion process following the addition of hexamethylenediamine, the amino groups at both ends of the hexamethylenediamine molecule interact with the surface of cerium dioxide particles, thereby forming bridging interactions between cerium dioxide particles of different morphologies. This allows the particles to coalesce into a stable three-dimensional network structure, promoting particle fusion and maintaining the long-term stability of the dispersion. Compared to short-chain diamines such as butanediamine, hexamethylenediamine has a longer chain and better extensibility, making it easier to form a uniform particle network and reducing particle aggregation.

[0013] In the step of adding polyethylene glycol and performing a second ultrasonic dispersion, polyethylene glycol acts as a dispersion stabilizer to prevent particle sedimentation and delamination, and maintain the uniformity and density of the coating.

[0014] Through the synergistic effect of the above steps, the sunscreen agent of this application can form a dense and uniform protective layer with a lower addition amount, providing excellent UV shielding effect, while improving the skin feel of the coating and avoiding whitening.

[0015] According to some embodiments of this application, the average particle size ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 1:2 to 2:1, for example, 1:2, 1:1, 1.5:1, or 2:1.

[0016] Preferably, the average particle size ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 1:2 to 1:1, for example, 0.6:1 to 0.8:1.

[0017] According to some embodiments of this application, the average particle size of the hexagonal cerium dioxide is 100~300nm, for example 100nm, 150nm, 200nm, 250nm, 300nm; the average particle size of the triangular cerium dioxide is 100~300nm, for example 100nm, 150nm, 200nm, 250nm, 300nm.

[0018] According to some embodiments of this application, the particle size distribution of the hexagonal cerium dioxide and the triangular cerium dioxide is 1.1~2.3, for example 1.1, 1.5, 1.7, 2.0, 2.3.

[0019] According to some embodiments of this application, the mass ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 100:20~100, for example 100:20, 100:30, 100:40, 100:50, 100:60, 100:70, 100:80, 100:90, 100:100.

[0020] According to some embodiments of this application, the total mass percentage of triangular cerium dioxide and hexagonal cerium dioxide in the sunscreen agent is 1 to 30 wt%, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%.

[0021] Preferably, the total mass percentage of the triangular cerium dioxide and hexagonal cerium dioxide is 5-30 wt%, more preferably 10-30 wt%, and even more preferably 20-30 wt%.

[0022] According to some embodiments of this application, the solid content of dispersion 1 and dispersion 2 is independently 1 to 30 wt%, for example 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%.

[0023] Preferably, the solid content of dispersion 1 and dispersion 2 is 5-30 wt%, more preferably 10-30 wt%, and even more preferably 20-30 wt%. The dispersion solvent may be water or an alcohol (such as ethanol).

[0024] According to some embodiments of this application, the dispersion 1 is prepared by adding triangular cerium dioxide to water and performing a third ultrasonic dispersion to obtain the dispersion 1.

[0025] Preferably, the frequency of the third ultrasonic dispersion is 50~1000Hz, for example 50Hz, 100Hz, 200Hz, 300Hz, 400Hz; and the dispersion time is 20~100min, for example 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min.

[0026] More preferably, the frequency of the third ultrasonic dispersion is 100~500Hz, and the dispersion time is 20~60min, more preferably 30~60min.

[0027] According to some embodiments of this application, the dispersion 2 is prepared by adding hexagonal cerium dioxide to water and performing a fourth ultrasonic dispersion to obtain the dispersion 1.

[0028] Preferably, the fourth ultrasonic dispersion is 50~1000Hz, for example 50Hz, 100Hz, 200Hz, 300Hz, 400Hz; the dispersion time is 20~100min, for example 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min.

[0029] More preferably, the frequency of the fourth ultrasonic dispersion is 100~500Hz, and the dispersion time is 40~80min.

[0030] According to some embodiments of this application, the temperature of the first ultrasonic dispersion is 40~60℃, for example 40℃, 45℃, 50℃, 55℃, 60℃; the frequency is 50~1000Hz, for example 50Hz, 100Hz, 200Hz, 300Hz, 400Hz; and the dispersion time is 20~180min, for example 20min, 40min, 60min, 80min, 100min, 120min, 140min, 160min, 180min.

[0031] Preferably, the frequency of the first ultrasonic dispersion is 100~500Hz, and the dispersion time is 40~160min, more preferably 60~120min.

[0032] According to some embodiments of this application, the temperature of the second ultrasonic dispersion is 40~60℃, for example 40℃, 45℃, 50℃, 55℃, 60℃; the frequency is 50~1000Hz, for example 50Hz, 100Hz, 200Hz, 300Hz, 400Hz; and the dispersion time is 5~30min, for example 5min, 10min, 15min, 20min, 25min, 30min.

[0033] Preferably, the frequency of the second ultrasonic dispersion is 100~500Hz, and the dispersion time is 5~20min.

[0034] According to some embodiments of this application, the sunscreen agent contains hexamethylenediamine at a mass percentage of 0.1% to 0.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0035] Preferably, the mass percentage of the hexamethylenediamine is 0.1% to 0.3%.

[0036] According to some embodiments of this application, the pH of the mixture is 2 to 4, for example 2, 2.5, 3, 3.5, or 4.

[0037] According to some embodiments of this application, the weight-average molecular weight of the polyethylene glycol is 2,000 to 40,000, preferably 5,000 to 40,000, more preferably 10,000 to 40,000, and even more preferably 10,000 to 30,000.

[0038] According to some embodiments of this application, the sunscreen agent contains polyethylene glycol at a mass percentage of 0.01% to 0.1%, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0039] Preferably, the polyacrylic acid has a mass percentage content of 0.05% to 0.1%.

[0040] The second aspect of this application relates to a sunscreen agent prepared using the aforementioned preparation method.

[0041] The sunscreen agent in this application can form a dense and continuous protective film at a low dosage, effectively blocking ultraviolet rays. The particles in the system are uniformly distributed, have good dispersibility, are stable during long-term storage, and are not prone to sedimentation or stratification. It feels comfortable on the skin during use, does not cause whitening, and has minimal skin irritation, making it suitable for daily protection.

[0042] The third aspect of this application relates to the use of the sunscreen agent in the preparation of cosmetics.

[0043] The use of the aforementioned sunscreen agent in the preparation of cosmetics can significantly improve [the product's effectiveness].

[0044] This sunscreen agent can be used to prepare face creams, lotions, sunscreen creams, sunscreen lotions, sunscreen gels, sunscreen sprays, sunscreen sticks, and makeup products. It can be used alone or in combination with other skincare ingredients, and the appropriate concentration can be selected according to sun protection needs. This sunscreen agent can form a uniform and dense protective layer at a low dosage, effectively blocking UVA and UVB, and improving broad-spectrum protection. Its particles are evenly distributed and well-dispersed, resulting in a smooth and natural feel on the skin after application, without whitening or heaviness. Simultaneously, the system has high stability, is not prone to sedimentation or stratification during long-term storage, facilitates formulation and manufacturing, and its low-irritation characteristics make it suitable for all skin types.

[0045] In this article, the average particle size refers to the particle size characteristic value measured by a laser particle size analyzer, which is the particle size corresponding to 50% of the cumulative volume distribution in the particle volume distribution, i.e., the volume reference median particle size Dv50.

[0046] "Approximately" indicates that the allowable error range is ±5%. For example, approximately 100 means 100 ± 5% × 100.

[0047] The numerical ranges involved all include endpoint values ​​and cover any value within that range or any smaller range, such as the range obtained by any combination of the specifically listed numerical values.

[0048] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0049] Figure 1 The coating appearance of the control group titanium dioxide and the sunscreen agent of Example 1 is shown. Detailed Implementation

[0050] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0051] In the following examples and comparative examples, triangular cerium dioxide and hexagonal cerium dioxide were prepared using the method disclosed in patent CN120841557A, as detailed below:

[0052] Unless otherwise specified, all raw materials or equipment mentioned are commercially available and can be purchased directly from the market.

[0053] Example 1 Cerium dioxide is as follows: The average particle size of hexagonal cerium dioxide is 200 nm, with a particle size distribution of 1.67; the average particle size of triangular cerium dioxide is 280 nm, with a particle size distribution of 1.67. The mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 100:37.

[0054] A method for preparing sunscreen includes the following steps: (1) Preparation of cerium dioxide dispersion: Triangular cerium dioxide was dispersed in deionized water, the powder mass concentration was controlled at 30% w / w, and ultrasonic (300 Hz) was used for dispersion for 40 min to obtain dispersion 1; hexagonal cerium dioxide was dispersed in deionized water, the powder mass concentration was controlled at 30% w / w, and ultrasonic (300 Hz) was used for dispersion for 60 min to obtain dispersion 2.

[0055] (2) Mix dispersion 1 and dispersion 2 at a mass ratio of 37:100, add nitric acid to adjust the pH of the mixture to 3.5, add the accelerator hexamethylenediamine, so that the ratio of the accelerator to the total mass of the system is 1:500, and sonicate (200Hz) at 50℃ for 90 min.

[0056] (3) Add PEG-20000 to make the PEG-20000 mass concentration reach 0.1%, and continue ultrasonic dispersion for 10 min under the same conditions as in step (2) to obtain the sunscreen agent.

[0057] Example 2 Cerium dioxide is as follows: The average particle size of hexagonal cerium dioxide is 120 nm, with a particle size distribution of 2.07; the average particle size of triangular cerium dioxide is 190 nm, with a particle size distribution of 2.15. The mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 1:1.

[0058] A method for preparing sunscreen includes the following steps: (1) Preparation of cerium dioxide dispersion: Triangular cerium dioxide was dispersed in deionized water, the powder mass concentration was controlled at 30% w / w, and ultrasonic (300 Hz) was used for dispersion for 40 min to obtain dispersion 1; hexagonal cerium dioxide was dispersed in deionized water, the powder mass concentration was controlled at 30% w / w, and ultrasonic (400 Hz) was used for dispersion for 60 min to obtain dispersion 2.

[0059] (2) Mix dispersion 1 and dispersion 2 at a mass ratio of 100:100, add nitric acid to adjust the pH of the mixture to 3.5, add the accelerator hexamethylenediamine, so that the ratio of the accelerator to the total mass of the system is 1:500, and sonicate (200Hz) at 50℃ for 90 min.

[0060] (3) Add PEG-20000 to make the PEG-20000 mass concentration reach 0.1%, and continue ultrasonic dispersion for 10 min under the same conditions as in step (2) to obtain the sunscreen agent.

[0061] Comparative Example 1 Compared with Example 1, the difference is that the hexagonal cerium dioxide is changed to an average particle size of 230 nm and a particle size distribution of 7.67; the triangular cerium dioxide is changed to an average particle size of 220 nm and a particle size distribution of 5.77, while the other conditions remain unchanged.

[0062] Comparative Example 2 Compared with Example 1, the difference is that the triangular cerium dioxide is changed to: average particle size of 220 nm, particle size distribution of 5.77, and other conditions remain unchanged.

[0063] Comparative Example 3 Compared with Example 2, the difference is that the hexagonal cerium dioxide is changed to an average particle size of 230 nm and a particle size distribution of 7.67, while the other conditions remain unchanged.

[0064] Comparative Example 4 Compared with Example 1, the difference is that the mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 37:100, while the other conditions remain the same.

[0065] Comparative Example 5 Compared with Example 1, the difference is that only hexagonal cerium dioxide is added, while the other conditions remain the same.

[0066] Comparative Example 6 Compared with Example 1, the difference is that only triangular cerium dioxide is added, while the other conditions remain the same.

[0067] Comparative Example 7 Compared with Example 1, the difference is that in step (1), the frequency of ultrasonic oscillation is changed to 2000Hz and the time is shortened to 10min, while the other conditions remain unchanged.

[0068] Comparative Example 8 Compared with Example 1, the difference is that hexamethylenediamine in step (2) is replaced with ethylenediamine, while other conditions remain unchanged.

[0069] UVA and UVB average transmittance test Weigh 2g of the powder to be tested and prepare a paste with deionized water and petroleum jelly. The paste contains 10% petroleum jelly and 5% powder. Coat the paste evenly onto a 2mm thick transparent PMMA plate with a coating amount of 0.2g / cm². Then cover with another identical PMMA plate, ensuring the sample is evenly distributed between the two plates. Measure using a UV-Vis spectrophotometer. Use the two uncoated PMMA plates as blank controls for baseline correction. The UVB test band is 280–320nm, and the UVA test band is 320–400nm. Record the transmittance at each wavelength, taking values ​​every 5nm, and calculate the average transmittance in the UVA and UVB bands.

[0070] The test results are shown in Table 1.

[0071] Table 1

[0072] In Table 1, the control group was formed by replacing the spherical cerium dioxide powder in the paste with nano-titanium dioxide in the UVA and UVB average transmittance tests, and increasing the titanium dioxide content to 10 wt%, with an average particle size D50 of 200 nm. Figure 1 The control group titanium dioxide () was shown. Figure 1 A) and the sunscreen agent of Example 1 ( Figure 1 B) Coating appearance. The total powder content in both coating solutions was 10 wt%, petrolatum was 10 wt%, and the remainder was deionized water. The results showed that the titanium dioxide coating in the control group exhibited a noticeable whitening effect, while the sunscreen coating in Example 1 presented a thin and transparent appearance.

[0073] As shown in Table 1, the average transmittance of UVA in the examples is 0.2%~0.3%, and the average transmittance of UVB is about 0.02%, both of which are at a low level, showing excellent ultraviolet shielding effect.

[0074] A comparison of Comparative Example 1 and Example 1 shows that when the average particle sizes of hexagonal and triangular cerium dioxide are similar, a significant increase in particle size distribution leads to an increase in both average UVA and UVB transmittance, resulting in a significant decrease in sun protection performance. This may be because uneven particle size distribution leads to unstable particle packing structures, resulting in insufficient shielding or agglomeration in localized areas, thereby reducing the absorption and scattering capacity of ultraviolet rays.

[0075] Comparison of Example 2 and Example 1 shows that when only the triangular cerium dioxide was replaced with particles with a larger particle size distribution, the average UVA transmittance increased to 0.405% and the average UVB transmittance increased to 0.04%. This indicates that when the triangular cerium dioxide particle size distribution is too wide, it is difficult for the triangular particles to form a uniform and dense composite shielding structure with the hexagonal particles, resulting in an increase in ultraviolet transmittance.

[0076] Comparison of Example 3 and Example 2 shows that, by simply replacing the hexagonal cerium dioxide with particles with a larger particle size distribution, the average UVA transmittance increased from 0.297% to 0.574%, and the average UVB transmittance increased from 0.021% to 0.035%. This indicates that when the particle size distribution of hexagonal cerium dioxide is too large, the uniformity of the arrangement and filling of hexagonal particles decreases, which is also not conducive to the formation of a continuous and effective ultraviolet blocking structure.

[0077] Comparison Example 4 with Example 1 shows that when the mass ratio of hexagonal cerium dioxide to triangular cerium dioxide was adjusted from 100:37 to 37:100, the average UVA transmittance increased to 0.614%, and the average UVB transmittance increased to 0.044%, indicating a significant decrease in sun protection performance. This demonstrates that the ratio of the two morphologies of cerium dioxide has a significant impact on sun protection effectiveness. When the content of triangular cerium dioxide is too high, the synergistic filling and layering effect between particles decreases, leading to an increase in ultraviolet transmittance.

[0078] Comparison Examples 5 and 6 with Example 1 show that when only hexagonal cerium dioxide or only triangular cerium dioxide is used, the average UVA transmittance is 0.309% and 0.333%, respectively, and the average UVB transmittance is 0.031% and 0.032%, respectively, both higher than that of Example 1. This indicates that the reasonable combination of the two particle morphologies can further reduce UVA and UVB transmittance through complementary filling and synergistic shielding effects between particles.

[0079] Comparison of Example 7 and Example 1 shows that when the ultrasonic oscillation frequency in step (1) is increased to 2000 Hz and the time is shortened to 10 min, the average UVA transmittance increases to 0.572% and the average UVB transmittance increases to 0.059%, resulting in a significant decrease in sun protection performance. This may be because the ultrasonic dispersion conditions are unsuitable, leading to insufficient dispersion and agglomeration of cerium dioxide particles, making it difficult to form a uniform and dense protective structure.

[0080] Comparing Comparative Example 8 with Example 1, it was found that replacing hexamethylenediamine with ethylenediamine increased the average UVA transmittance to 0.301% and the average UVB transmittance to 0.031%, resulting in a decrease in sun protection performance. This indicates that the molecular chain length of the accelerator affects the connection and dispersion state of cerium dioxide particles. Compared with ethylenediamine, hexamethylenediamine has a longer molecular chain and better chain segment flexibility, which is more conducive to forming stable connections between cerium dioxide particles, improving particle dispersion uniformity and system stability, thereby enhancing the UV shielding effect.

[0081] In summary, optimizing the morphology combination, average particle size, particle size distribution, mass ratio of the two morphologies, type of accelerator, and ultrasonic dispersion conditions of cerium dioxide particles can effectively reduce UVA / UVB transmittance and achieve superior sun protection performance. This allows for a reduction in the amount added while maintaining sun protection effectiveness, improving skin feel, avoiding whitening or heaviness, and maintaining good dispersion stability, facilitating practical application and use.

Claims

1. A method for preparing a sunscreen agent, characterized in that, Includes the following steps: Dispersion 1 containing triangular cerium dioxide and dispersion 2 containing hexagonal cerium dioxide are provided; Dispersion 1 and dispersion 2 are mixed to obtain a mixture, wherein the mass ratio of hexagonal cerium dioxide to triangular cerium dioxide is 100:4~120; Adjust the pH of the mixture to 1-5, add hexamethylenediamine for the first ultrasonic dispersion, then add polyethylene glycol for the second ultrasonic dispersion to obtain the sunscreen agent; The triangular cerium dioxide has an average particle size of 50-500 nm, the hexagonal cerium dioxide has an average particle size of 50-1000 nm, and the average particle size ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 1:2-10:3, with a particle size dispersion of ≤2.

5.

2. The preparation method according to claim 1, characterized in that, The average particle size ratio of the hexagonal cerium dioxide to the triangular cerium dioxide is 1:2 to 2:1; And / or, the particle size distribution of the hexagonal cerium dioxide and the triangular cerium dioxide is 1.1~2.

3. And / or, the average particle size of the hexagonal cerium dioxide is 100~300nm; the average particle size of the triangular cerium dioxide is 100~300nm.

3. The preparation method according to claim 1, characterized in that, In the sunscreen agent, the total mass percentage of triangular cerium dioxide and hexagonal cerium dioxide is 1~30wt%.

4. The preparation method according to claim 1, characterized in that, The dispersion 1 is prepared by the following method: triangular cerium dioxide is added to water and subjected to a third ultrasonic dispersion to obtain the dispersion 1; the frequency of the third ultrasonic dispersion is 50~1000Hz and the dispersion time is 20~100min; And / or, the dispersion 2 is prepared by the following method: adding hexagonal cerium dioxide to water and performing a fourth ultrasonic dispersion to obtain the dispersion 1; the frequency of the fourth ultrasonic dispersion is 50~1000Hz and the dispersion time is 20~100min.

5. The preparation method according to claim 1, characterized in that, The solid content of dispersion 1 and dispersion 2 is 1~30wt% independently.

6. The preparation method according to claim 1, characterized in that, The temperature of the first ultrasonic dispersion is 25~85℃, the frequency is 50~1000Hz, and the dispersion time is 20~180min; And / or, the temperature of the second ultrasonic dispersion is 25~85℃, the frequency is 50~1000Hz, and the dispersion time is 5~30min.

7. The preparation method according to claim 1, characterized in that, The sunscreen agent contains hexamethylenediamine at a mass percentage of 0.1% to 0.5%.

8. The preparation method according to claim 1, characterized in that, The weight-average molecular weight of the polyethylene glycol is 2000~40000; And / or, in the sunscreen agent, the mass percentage of polyethylene glycol is 0.01% to 0.1%.

9. A sunscreen agent, characterized in that, The sunscreen agent is prepared by the preparation method described in any one of claims 1 to 8.

10. The use of the sunscreen agent as described in claim 9 in the preparation of cosmetics.

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