Composite particles with ultraviolet synergistic absorption performance, and preparation method and application thereof

Abstract

The application belongs to the technical field of fine chemicals, and discloses a kind of composite particles with ultraviolet synergistic absorption performance and its preparation method and application.The composite particles are bisethylhexyloxyphenol methoxyphenyl triazine / polyvinyl alcohol (BEMT / PVA) with core-shell structure, which is composed of nanospheres and film shell.The core of nanospheres is BEMT microspheres with particle size of 0.4-6 μm, and the shell is PVA film with thickness of 0.1-2.45 μm.The particle size of composite particles is 0.6-9 μm.The BEMT microspheres are spray dried with PVA aqueous solution to obtain composite particles with core-shell structure.The ultraviolet absorption performance of BEMT in the composite particles is 107.3% of raw material BEMT with only 47.64% of the original amount, while the light aging performance and hydrophilicity of BEMT are enhanced, and the dispersion performance and light stability in water are also enhanced, which is applied in the field of sunscreen and skincare products.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemicals, more particularly, it relates to a composite particle bisethylhexyloxyphenol methoxyphenyl triazine / polyvinyl alcohol (BEMT / PVA) with ultraviolet synergistic absorption performance and a preparation method and application thereof. BACKGROUND

[0002] A small amount of ultraviolet radiation can promote metabolism and vitamin D formation in the body, but excessive exposure of the skin to ultraviolet light can cause skin aging, tanning, sunburn, and even skin cancer. Studies have shown that UVA with a wavelength of 320-400 nm can penetrate the skin into the dermis, causing cells to produce melanin, causing the skin to tan and discolor, and also causing skin aging and wrinkle formation. UVB with a wavelength of 290-320 nm can directly damage the stratum corneum and epidermal tissue, causing skin redness, burns, sunburn, and is also a major cause of skin cancer. Therefore, it is very important to take effective sun protection measures when exposed to sunlight for a long time.

[0003] Sunscreen is a cosmetic product used to protect the skin from ultraviolet radiation, which can effectively absorb, reflect and scatter ultraviolet radiation to avoid skin damage and disease caused by ultraviolet radiation. It is generally divided into physical sunscreen and chemical sunscreen. Common physical sunscreens such as titanium dioxide and zinc oxide can efficiently reflect or scatter ultraviolet radiation, but they can cause white or blue-gray residues on the skin surface due to their tendency to accumulate on the skin surface, and their activity can decrease under long-term strong ultraviolet radiation, losing their protective effect. Therefore, physical sunscreens have certain limitations. Chemical sunscreens have strong sunscreen ability, but they can undergo photodegradation after absorbing ultraviolet radiation, and also penetrate into skin cells and produce highly active free radicals, damaging biomacromolecules and cells, further causing skin aging and skin cancer. At the same time, since most chemical sunscreens are oil-soluble substances, they can penetrate into the skin along with oil substances, causing adverse reactions such as skin photoallergy, phototoxicity and skin irritation. In view of the above problems, many scholars at home and abroad have developed a series of technologies such as modification, grafting and coating of chemical sunscreens, aiming to improve the stability of chemical sunscreens and isolate chemical sunscreens from the skin to reduce the toxicity of chemical sunscreens to the skin.

[0004] BEMT (bis-ethylhexyloxyphenol methoxyphenyl triazine, trade name: Tinosorb-S) is an oil-soluble chemical sunscreen widely used in daily chemicals, which has good UV protection effect due to its unique molecular structure. However, due to its molecular structure, BEMT can only be dissolved in polar oils, which limits the use of BEMT. The microcapsule technology is a technology for embedding, storing and forming a solid particle by using a film-forming material to encapsulate solids, liquids or gases, which can improve the stability, dispersibility, control the release rate, and change the odor of the substance. In recent years, it has been widely used in the cosmetics industry. Existing researches have proved that encapsulating chemical sunscreens in microcapsules can not only improve the safety, stability and protection ability of chemical sunscreens, but also effectively isolate the skin from the contact with chemical sunscreens, reduce the adverse reactions of chemical sunscreens on the skin, and reduce the irritation of chemical sunscreens on the skin. Therefore, the coating technology of chemical sunscreens has wide application prospect, strong operability, and is more likely to obtain new sunscreen with high stability and safety. SUMMARY

[0005] In order to solve the above problems existing in the prior art and overcome the defects and shortcomings, the purpose of the present application is to provide a kind of composite particles with synergistic ultraviolet absorption performance. The composite particle is a core-shell structure, which has better ultraviolet absorption capacity than pure BEMT, and improves its hydrophilicity and light stability. It can be well dispersed in aqueous solution and also improve its anti-aging performance.

[0006] Another purpose of the present application is to provide a preparation method of the above-mentioned composite particles. The method is to prepare the composite particles by spray drying of BEMT microspheres treated by solvent evaporation and PVA.

[0007] Another purpose of the present application is to provide the application of the above-mentioned composite particles.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A kind of composite particles with synergistic ultraviolet absorption performance, the composite particle is bis-ethylhexyloxyphenol methoxyphenyl triazine / polyvinyl alcohol, abbreviated as BEMT / PVA, which has a core-shell structure, composed of nanospheres and a thin film shell. The core of the nanosphere is a BEMT microsphere with a particle size of 0.4-6 μm, and the shell is a PVA film with a thickness of 0.1-2.45 μm. The particle size of the composite particle is 0.6-9 μm.

[0010] The preparation method of the composite particle with synergistic ultraviolet absorption performance comprises the following steps:

[0011] S1. Dissolving BEMT powder in dichloromethane to obtain a BEMT / dichloromethane solution, adding a PVA solution to obtain a BEMT / dichloromethane / PVA solution, and then high-speed homogenizing the mixed solution to obtain a BEMT / dichloromethane / PVA emulsion;

[0012] S2. Removing dichloromethane solvent from the BEMT / dichloromethane / PVA emulsion at room temperature under a negative pressure of -0.6 to -0.8 MPa by rotary evaporation to obtain a BEMT microsphere / PVA suspension;

[0013] S3. Spraying and drying the BEMT / PVA microsphere suspension to obtain a composite particle having ultraviolet synergistic absorption performance.

[0014] Preferably, the PVA solution in step S1 has a PVA molecular weight of 70,000 to 8,000 and an alcoholysis degree of 92 to 99%.

[0015] Preferably, the high-speed homogenization in step S1 is performed for 3 to 8 min at a speed of 8 to 16 krpm.

[0016] Preferably, the BEMT powder in step S1 has a mass fraction of 20 to 40% in dichloromethane; the mass ratio of the PVA solution to BEMT / dichloromethane is 1:(2 to 7); and the mass concentration of the PVA solution is 1 to 10%.

[0017] Preferably, the BEMT / PVA microsphere suspension in step S2 has a mass ratio of BEMT to PVA of 1:(0.8 to 1.3).

[0018] Preferably, the spraying and drying in step S3 are performed at an inlet temperature of 110 to 160℃, an atomization pressure of 0.5 to 2 MPa, and a feeding speed of 5 to 12 mL / min.

[0019] The composite particle having ultraviolet synergistic absorption performance is used in the preparation of a sunscreen product.

[0020] The composite particle of the present application has a core-shell structure, PVA with high alcoholysis degree is used as the wall material of the composite particle, and BEMT is used as the core material. Since the PVA aqueous solution is a high-viscosity, transparent and uniform solution, the BEMT is dissolved in dichloromethane by the shearing force of a high-speed homogenizer, so as to micronize the BEMT, and the BEMT / dichloromethane solution can be quickly dispersed in the PVA solution to form an oil-in-water emulsion. Therefore, the PVA aqueous solution can be used as the emulsifying medium of BEMT / dichloromethane and as the emulsifying agent of dichloromethane. The micronized BEMT is coated by a spray drying method through PVA to obtain the composite particle with the synergistic ultraviolet absorption performance. The composite particle can avoid the direct contact between BEMT and the skin, reduce the absorption of the skin to the BEMT dissolved in oil, and has a certain safety. The PVA used in the present application has excellent hydrophilicity, and the attachment of the PVA on the surface of BEMT can improve the hydrophilicity of BEMT. The obtained composite particle has excellent dispersibility in water. Since the PVA film has the optical transparency, it will not block the ultraviolet absorption of the BEMT core material. At the same time, the micronization of the composite particle can also increase the reflection and scattering of light, so as to enhance the ultraviolet absorption performance of the composite particle, achieve the physical-chemical synergistic sunscreen effect, and improve the sunscreen performance and the anti-photoaging ability.

[0021] The BEMT molecular structure has three benzene rings and a triazine ring, and the hydroxyl and methoxyl groups on the benzene ring act as electron donors, and the N atom on the ethyl triazine ring forms an intramolecular hydrogen bond with the phenolic hydroxyl group. When ultraviolet light is irradiated to the BEMT, it absorbs the ultraviolet light and converts into an excited state, and at the same time, the hydrogen bond of the BEMT is broken, and the absorbed ultraviolet light energy is dissipated in the form of heat, light (singlet fluorescence or triplet phosphorescence) or both, and then the hydrogen bond of the BEMT is reformed, so that the BEMT has good ultraviolet absorption performance. However, the molecular structure of BEMT itself determines that BEMT is a hydrophobic substance, which must be used by dissolving in oil. Polyvinyl alcohol (PVA) is a polymer with good thermal stability, chemical stability, biocompatibility, water solubility, non-toxicity, easy degradation and good hydrophilicity. PVA also has good light transmittance, which avoids the decrease of absorbance caused by the fact that ultraviolet light cannot irradiate to the chemical sunscreen, and is very suitable as an encapsulating material for BEMT. Spray drying is a process in which liquid or slurry material is atomized into fine particles, and then the particles are sprayed into a hot gas stream for rapid dehydration and drying in a short time, and finally powder particles are formed. Therefore, a transparent polymer film can be formed on the surface of BEMT by spray drying method, and the BEMT is encapsulated to obtain composite particles with ultraviolet synergistic absorption performance. The preparation process is simple, low in cost and green, effectively improves the problems of poor dispersibility in water and penetration into the skin of the oil-soluble chemical sunscreen such as BEMT, and the unique core-shell structure of the composite particles can also act as a physical sunscreen to reflect and scatter ultraviolet light, achieving physical-chemical synergistic sunscreen and improving the sunscreen performance and anti-aging performance.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1. The composite particles prepared by the present application have ultraviolet synergistic absorption performance in the wavelength range of 400-320 nm. By adjusting the loading rate of BEMT in the composite particles and the morphology change of the composite particles, the chemical absorption and physical refraction are synergized, which has a physical-chemical synergistic sunscreen effect, can further enhance the ultraviolet protection effect, and enhances the ultraviolet absorption performance of BEMT compared with BEMT. Compared with the same mass of BEMT, only 40-50% of BEMT is needed, and the ultraviolet absorption performance is improved by 0.3-7.3%.

[0024] 2. The composite particles of the present application have good hydrophilicity and water dispersibility, and can form a homogeneous aqueous dispersion at a high concentration (100 mg / mL). Since the wall material is a hydrophilic polymer, it has good compatibility and excellent dispersibility in the aqueous cream system.

[0025] 3. The composite particles prepared by this invention use only 47.64% of the original amount of BEMT, and the ultraviolet absorption performance is 107.3% of that of the raw material BEMT. At the same time, it enhances the photoaging performance and hydrophilicity of BEMT, and enhances its dispersion performance and photostability in water. It has great application prospects in the field of sunscreen skin care products.

[0026] 4. This invention employs a spray drying method to first nanosphereize BEMT, then encapsulates the BEMT with PVA as the wall material to obtain composite particles. Because the PVA solution possesses certain stability, no additional emulsifiers or crosslinking agents are required. The preparation process is simple, environmentally friendly, and low-cost.

[0027] 5. The composite particles of the present invention can achieve SPF50+ by adding only 6% to the basic cream formula of ISO:24443-2012. At the same time, there is a good linear relationship between the amount of composite particles added (0-6%) and the SPF / PFA value of the cream. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of the BEMT / PVA composite particles of the present invention.

[0029] Figure 2 This is a schematic diagram illustrating the principle of synergistic ultraviolet absorption of BEMT / PVA composite particles in this invention.

[0030] Figure 3 Scanning electron microscope image of BEMT powder transformed into BEMT microspheres;

[0031] Figure 4 A comparison diagram of the particle size distribution of BEMT microspheres and BEMT / PVA composite particles from Example 1;

[0032] Figure 5 The UV absorption spectra of BEMT powder and BEMT / PVA composite particles from Examples 1-5 are shown.

[0033] Figure 6 This is a scanning electron microscope image of the BEMT / PVA composite particles of the present invention;

[0034] Figure 7 Thermogravimetric curves of BEMT and BEMT / PVA composite particles from Examples 1-5 are shown.

[0035] Figure 8 For based on Figure 7 The encapsulation efficiency and loading rate of BEMT in BEMT / PVA composite particles were calculated from the thermogravimetric curves.

[0036] Figure 9Figure for water contact angle of BEMT / PVA composite particles of Example 1-5;

[0037] Figure 10 Figure for SPF / PFA values of base cream formula with 1% to 6% content of BEMT / PVA composite particles of Example 1;

[0038] Figure 11 Figure for comparison of SPF / PFA values of base cream, 5% BEMT cream, 5% Example 1, 10% Example 1, 50 SPF + commercially available sunscreen cream;

[0039] Figure 12 Figure for UV aging of BEMT / PVA composite particles of Example 1 at 30 min, 60 min, 120 min, 180 min. DETAILED DESCRIPTION

[0040] The present application will be further described in conjunction with specific examples, but should not be construed as a limitation of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art. Unless specifically indicated, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0041] The BEMT powder used in the examples of the present application is bis-ethylhexyloxyphenol methoxyphenyl triazine provided by Guangdong Gaoliang Technology Co., Ltd., CAS: 187393-00-6, and the molecular formula is shown in formula (1):

[0042]

[0043] The PVA has a molecular weight of 70000-8000 and an alcoholysis degree of 92%-99%, is a water-soluble polymer that can be dissolved only in hot water above 60°C, and has a CAS: 9002-89-5, and the molecular formula is shown in formula (2):

[0044]

[0045] Example 1

[0046] 1. 4 g of bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) powder was dissolved in 12 mL of dichloromethane to obtain a clear yellow BEMT / dichloromethane solution, then 40 g of 10% polyvinyl alcohol (PVA) solution and 20 mL of deionized water were added for dilution to obtain a BEMT / dichloromethane / PVA solution, and the solution was homogenized in a high-speed homogenizer at a speed of 13 krpm for 5 min to obtain a BEMT / dichloromethane / PVA emulsion.

[0047] 2. The BEMT / methylene chloride / PVA emulsion was removed of the methylene chloride solvent by rotary evaporation at room temperature under 0.06 MPa vacuum to obtain a BEMT / PVA microsphere suspension.

[0048] 3. The BEMT / PVA microsphere suspension was slowly input into a spray dryer by a peristaltic pump, the inlet temperature was set to 130 °C, the atomization pressure was 1.5 MPa, and the feeding speed was 8 mL / min. The light yellow powder obtained after drying was the BEMT / PVA composite particles with synergistic ultraviolet absorption performance.

[0049] Example 2

[0050] 1. 2 g of BEMT powder was dissolved in 12 mL of methylene chloride to obtain a clear yellow BEMT / methylene chloride solution, then 40 g of 10% PVA solution and 20 mL of deionized water were added for dilution to obtain a BEMT / methylene chloride / PVA solution. The solution was homogenized in a high-speed homogenizer at a speed of 13 krpm for 5 min to obtain a BEMT / methylene chloride / PVA emulsion.

[0051] 2. The BEMT / methylene chloride / PVA emulsion was removed of the methylene chloride solvent by rotary evaporation at room temperature under 0.06 MPa vacuum to obtain a BEMT / PVA microsphere suspension.

[0052] 3. The BEMT / PVA microsphere suspension was slowly input into a spray dryer by a peristaltic pump, the inlet temperature was set to 135 °C, the atomization pressure was 1.5 MPa, and the feeding speed was 8 mL / min. The light yellow powder obtained after drying was the BEMT / PVA composite particles with synergistic ultraviolet absorption performance.

[0053] Example 3

[0054] 1. 5 g of BEMT powder was dissolved in 20 mL of methylene chloride to obtain a clear yellow BEMT / methylene chloride solution, then 40 g of 10% PVA solution and 60 mL of deionized water were added for dilution to obtain a BEMT / methylene chloride / PVA solution. The solution was homogenized in a high-speed homogenizer at a speed of 13 krpm for 5 min to obtain a BEMT / methylene chloride / PVA emulsion.

[0055] 2. The BEMT / methylene chloride / PVA emulsion was removed of the methylene chloride solvent by rotary evaporation at room temperature under 0.06 MPa vacuum to obtain a BEMT / PVA microsphere suspension.

[0056] 3. The BEMT / PVA microspheres suspension was slowly input into the spray dryer by peristaltic pump, the inlet temperature was set to 135℃, the atomization pressure was 2.0 MPa, and the feeding speed was 8 mL / min. The light yellow powder obtained after drying was the BEMT / PVA composite particles with synergistic ultraviolet absorption performance.

[0057] Example 4

[0058] 1. 4 g of BEMT powder was dissolved in 12 mL of dichloromethane to obtain a clear yellow BEMT / dichloromethane solution, then 8 g of 10% PVA solution and 52 mL of deionized water were added for dilution to obtain a BEMT / dichloromethane / PVA solution. The solution was homogenized in a high-speed homogenizer at a speed of 13 krpm for 5 min to obtain a BEMT / dichloromethane / PVA emulsion.

[0059] 2. The BEMT / dichloromethane / PVA emulsion was removed by rotary evaporation under the condition of room temperature-0.06 MPa vacuum to obtain a BEMT / PVA microspheres suspension.

[0060] 3. The BEMT / PVA microspheres suspension was slowly input into the spray dryer by peristaltic pump, the inlet temperature was set to 135℃, the atomization pressure was 2.0 MPa, and the feeding speed was 8 mL / min. The light yellow powder obtained after drying was the BEMT / PVA composite particles with synergistic ultraviolet absorption performance.

[0061] Example 5

[0062] 1. 4.5 g of BEMT powder was dissolved in 13 mL of dichloromethane to obtain a clear yellow BEMT / dichloromethane solution, then 9 g of 10% PVA solution and 85 mL of deionized water were added for dilution to obtain a BEMT / dichloromethane / PVA solution. The solution was homogenized in a high-speed homogenizer at a speed of 13 krpm for 5 min to obtain a BEMT / dichloromethane / PVA emulsion.

[0063] 2. The BEMT / dichloromethane / PVA emulsion was removed by rotary evaporation under the condition of room temperature-0.06 MPa vacuum to obtain a BEMT / PVA microspheres suspension.

[0064] 3. The BEMT / PVA microspheres suspension was slowly input into the spray dryer by peristaltic pump, the inlet temperature was set to 135℃, the atomization pressure was 2.0 MPa, and the feeding speed was 8 mL / min. The light yellow powder obtained after drying was the BEMT / PVA composite particles with synergistic ultraviolet absorption performance.

[0065] The preparation procedure of BEMT / PVA composite particles prepared in Examples 1-5 is shown in Figure 1 The prepared BEMT / PVA composite particles were subjected to various tests as shown in Figure 2

[0066] 1. Particle size test: Malvern Mastersizer 3000 laser diffraction particle size analyzer was used to determine the particle size and particle size distribution of BEMT microspheres and BEMT / PVA composite particles. The dispersed sample was loaded into the sample cell provided with the instrument, the measurement temperature was 25°C, the dispersion system was water, and the lower limit of the light shielding degree was 10% and the upper limit was 15%. Among them, the refractive index of BEMT microspheres and BEMT / PVA composite particles was set to 1.56.

[0067] 2. Powder UV absorption test: Take an appropriate amount of BEMT / PVA composite particle powder and scatter it in the center of the sample dish. After tightening the sample dish, directly test its solid UV absorption spectrum and the UV absorption spectrum after aging with SHIMADZU, UV-3600Plus ultraviolet visible near-infrared spectrophotometer.

[0068] 3. Scanning electron microscope: Take an appropriate amount of BEMT / PVA composite particle powder and ultrasonically disperse it in ethanol. After uniform dispersion, use a pipette gun to take 20ul of solution on a silicon wafer. After drying the silicon wafer, it was observed by Hitachi SU8220 scanning electron microscope after gold spraying treatment.

[0069] 4. Thermogravimetric analysis: NETZSCH / STA449F5 type thermogravimetric analyzer was used to determine the thermogravimetric curve, the temperature range was from 50°C to 700°C, the heating rate was 10°C / min, the atmosphere was N2, and the flow rate was 10ml / min. The thermal decomposition of the ultraviolet absorption composite particles was analyzed to calculate the encapsulation rate and loading rate of BEMT in PVA. The encapsulation rate formula: encapsulation rate = M3 / M2*100%; loading rate = M3 / M1*100%; wherein, M1 is the total mass of the ultraviolet absorption composite particles; M2 is the total mass of BEMT; M3 is the mass of BEMT in the composite particles;

[0070] 5. Water contact angle test: BEMT raw material powder and composite particles of Examples 1-5 were pressed into tablets by a tablet press, and then the water contact angle was tested by Dataphysics, OCA100 water contact angle tester.

[0071] ​6. SPF / PFA test: SPF / PFA values of sunscreen creams were tested according to ISO: 24443-2012 standard. The base cream formula (water phase and oil phase) in Table 1 was added with C phase (BEMT / PVA composite particles or BEMT) to make sunscreen cream, which was applied on a high-transmittance PMMA sheet with a size of 2 cm x 5 cm x 0.2 mm. The concentration of the cream on the sheet was 2 mg / cm 2 . The absorbance of the sample in the range of 290-400 nm was tested by SHIMADZU, UV-3600Plus UV-Vis-NIR spectrophotometer. The SPF / PFA values were calculated. -1

[0072] The calculation formula is as follows:

[0073]

[0074] Wherein, E(λ), P(λ) and I(λ) are fixed values, the definition, parameters and information of which can be obtained in ISO: 24443-2012; SPF is a specific numerical value representing the ability of the product to defend against medium wave ultraviolet light, which is a protective index for evaluating the ability of sunscreen cosmetics to protect the skin from sunburn erythema / burn. PFA is the MPPD value of the skin with sunscreen cream / MPPD value of the skin without sunscreen cream. The higher the PFA value, the longer the protection time. MPPD (Minimal Persistent Pigmentation Dose) is the minimum dose of ultraviolet light (J / m 2 ) or the shortest irradiation time required to cause visible melanosis or pigmentation.

[0075] Table 1 is the cream formula used for testing of the present application

[0076]

[0077] Figure 2 The schematic diagram of the principle of ultraviolet synergistic absorption of the composite particles of the present application. Figure 2 ​It can be known that the composite particle of the application is a spherical aggregate completely wrapping the core, and the structure can make the ultraviolet light continuously refract and scatter in the sphere, thereby improving the ultraviolet light absorption. Since PVA is a crystalline transparent polymer, when a certain amount of PVA is used, PVA can form a transparent film with uniform thickness on the surface. And the ultraviolet light refracts and scatters multiple times in the interior of the composite particle or between the composite particles, thereby continuously weakening the ultraviolet light intensity to improve the ultraviolet light absorption performance. Therefore, by adjusting the loading rate of BEMT in the composite particle and the morphology change of the composite particle, the chemical absorption and physical refraction are synergized, which has a physical-chemical synergistic sunscreen effect, can further enhance the ultraviolet protection effect, and enhances the ultraviolet light absorption performance of BEMT compared with BEMT. In addition, the nanoscale microspherization of the composite particle can also increase the reflection and scattering of light, so that the composite particle enhances the ultraviolet light absorption performance, achieves the physical-chemical synergistic sunscreen effect, and improves the sunscreen performance and light aging resistance. Figure 3 It is a scanning electron microscope graph of BEMT microspheres converted from BEMT powder. It can be observed from the scanning electron microscope that the BEMT powder is irregular in shape, and the BEMT can be prepared into a spherical shape by the method of dissolving in dichloromethane solvent, emulsifying and then evaporating the solvent, and then the microspherical composite particles can be obtained by spraying and drying the PVA aqueous solution. Figure 3 It is a particle size distribution comparison graph of BEMT microspheres and example 1. Figure 4 It can be known that the average particle size of the composite particles of example 1 is 4.76 um, and the average particle size of the BEMT microspheres is 2.31 um, which is due to the fact that the polyvinyl alcohol forms a film on the surface of the BEMT microspheres under the preparation conditions of example 1, resulting in an increase in particle size. Therefore, the average thickness of the shell of the composite particles prepared in example 1 is 2.45 um.

[0078] Figure 5 It is an ultraviolet absorption spectrum graph of BEMT powder and BEMT / PVA composite particles of examples 1-5. Figure 5 As shown in the figure, the absorption bands of BEMT powder and examples 1-5 almost cover the absorption regions of UVA and UVB, and the prepared BEMT / PVA composite particles have a certain ultraviolet light absorption performance. The test results show that the BEMT / PVA composite particles obtained in example 1 have higher ultraviolet light absorption performance. By integrating the spectral area in the range of 290-400 nm, the absorption performance of example 1 is improved by 7.3% compared with BEMT powder, Figure 6 It is a scanning electron microscope graph of ultraviolet light absorbing BEMT / PVA composite particles. Among them, (a) is example 5, (b) is example 1, (c) is example 4, and (d) is example 2. Figure 6It can be found that the BEMT / PVA composite particles prepared in Example 5 are broken and the core is exposed, indicating that the BEMT / PVA composite particles have a core-shell structure, and this broken structure participates in ultraviolet absorption in the form of a PVA-BEMT blend. Therefore, the BEMT / PVA composite particles prepared in Example 5 have the worst ultraviolet absorption performance; while the composite particles of Example 1 are a complete spherical aggregate of the core, and this structure can make the ultraviolet light continuously refract and scatter within the sphere, improving the ultraviolet absorption. When a certain amount of crystalline transparent polymer PVA is used, the PVA will form a uniform thickness transparent film on the surface. And the ultraviolet light refracts and scatters multiple times inside the BEMT / PVA composite particles or between the BEMT / PVA composite particles, thereby continuously weakening the intensity of the ultraviolet light to improve the ultraviolet absorption performance, and at the same time, the size of BEMT is further compressed and uniformized by solvent evaporation, which brings certain benefits to the improvement of ultraviolet absorption performance. Overall, through the synergistic effect of chemical absorption and physical absorption, as the amount of PVA gradually increases, it is observed that the composite particles prepared in Example 4 form a cubic multiple enclosure, which causes the ultraviolet light to be refracted or scattered prematurely before reaching the BEMT core, resulting in a decrease in ultraviolet absorption. It can be observed that the composite particles prepared in Example 2 have irregular shapes due to a large amount of PVA film, and at the same time, the PVA film plays a role in "shielding" the ultraviolet light, preventing the core from transmitting to the core, thereby further reducing the absorption of ultraviolet light, which is the same as the dependence of the ultraviolet absorption performance on the size and transmittance of the particles.

[0079] Figure 8 The thermogravimetric curve of BEMT and the ultraviolet absorbing BEMT / PVA composite particles of Examples 1-5, Figure 8 The thermogravimetric curve of BEMT and the ultraviolet absorbing BEMT / PVA composite particles of Examples 1-5, Figure 7The encapsulation efficiency and loading efficiency of BEMT in the composite particles calculated from the thermogravimetric curve, and the encapsulation efficiency and loading efficiency of BEMT change with the amount of PVA under the determined spray drying process. Generally speaking, the higher the content of BEMT, the better the ultraviolet absorption performance. However, the final result of the ultraviolet absorption performance is affected by many factors, including the above-mentioned morphological influence and content influence. The composite particles in Example 3 and Example 5 cannot be completely wrapped by PVA, and part of the BEMT will adhere to the wall of the drying chamber of the spray dryer due to the viscosity of BEMT, so the encapsulation efficiency is only 76.56% and 73.44%, while the encapsulation efficiency of the composite particles in Example 1 and Example 4 reaches 95.29% and 98.2%, and the encapsulation efficiency of Example 2 is 80.9%. This may be due to the high content of PVA in the system, and due to the randomness of spray drying, PVA is sprayed alone, resulting in part of the PVA blank powder in the final product, thereby reducing the loading rate, and the BEMT microspheres also adhere to the wall of the spray drying chamber again and cannot be collected. In summary, from the encapsulation efficiency and loading efficiency and the particle morphology, it can be seen that the composite particles of Example 1 are used for subsequent research.

[0080] Figure 9 The water contact angle diagram of the BEMT / PVA composite particles of Examples 1-5 can be found that the BEMT / PVA composite particles of the application have excellent hydrophilicity. Since the molecular structure of BEMT contains aromatic hydrocarbons and two hydrophobic segments, BEMT is a hydrophobic material, and its water contact angle is 96.8°. The BEMT / PVA composite particles of Example 3, Example 5, Example 1, Example 4, and Example 2 are hydrophilic materials, and their water contact angles are 72.2°, 69.1°, 65.2°, 58.2°, and 56.7°, respectively. This shows that the hydrophilicity of the BEMT / PVA composite particles gradually increases with the increase of the amount of PVA.

[0081] Figure 10 The SPF / PFA value diagram of the basic cream formula with 1-6% content of the composite particles of Example 1 shows that when only 1% of the BEMT / PVA composite particles are added, the SPF / PFA increases from 2.58 / 2.06 to 10.78 / 6.4, and the SPF / PFA increases linearly with the increase of the content of the composite particles. 2 The linear trend is good, and the SPF / PFA values are 57.07 / 25.37 at a dosage of 6%, which is the effect of a commercially available 50SPF+ sunscreen. BEMT or BEMT / PVA composite particles are added to the basic formula in Table 1. Figure 11SPF / PFA value comparison chart of base cream, 5% BEMT cream, 5% Example 1, 10% Example 1, 50 SPF + commercially available sunscreen. The 50 SPF + commercially available sunscreen is the Man Shui Leidun Shuangbi moisturizing sunscreen cream. From Figure 11 It can be known from the above that the SPF / PFA value of the base cream is 2.6 / 2.1, the SPF / PFA of the composite particles of 5% BEMT and 5% Example 1 are 39.9 / 19.3 and 41.6 / 14.8 respectively, and the values are similar, but it is worth noting that the loading rate of BEMT in the BEMT / PVA composite particles of Example 1 is 47.64%, that is, only half of the BEMT is used, and the sunscreen index of the original BEMT usage is reached. When 10% of the BEMT / PVA composite particles of Example 1 are added to the base cream formula, the SPF / PFA is 81.9 / 39.2 (5% BEMT loading), which exceeds the commercially available sunscreen with SPF 50 (SPF / PFA is 58.6 / 26.8). Figure 12 The above is the ultraviolet aging chart of the BEMT / PVA composite particles of Example 1 at 30 min, 60 min, 120 min, and 180 min. After 240 min of irradiation, the ultraviolet absorption performance of BEMT decreased to 91.8%. However, the BEMT / PVA composite particles of Example 1 still have 95.8% ultraviolet protection, which shows that the use of PVA to wrap BEMT enhances the anti-ultraviolet aging performance of BEMT.

[0082] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A composite particle having ultraviolet light synergistic absorption properties, characterized by, The composite particle is BEMT / PVA, which has a core-shell structure and is composed of a nanosphere and a film shell, the core of the nanosphere is a BEMT microsphere with a particle size of 0.4-6 µm, the shell is a PVA film with a thickness of 0.1-2.45 µm, and the particle size of the composite particle is 0.6-9 µm. The composite particle is prepared by dissolving BEMT powder in dichloromethane to obtain a BEMT / dichloromethane solution, adding a PVA solution to obtain a BEMT / dichloromethane / PVA solution, high-speed homogenizing the mixed solution to obtain a BEMT / dichloromethane / PVA emulsion, removing the dichloromethane solvent by rotary evaporation under the condition of room temperature and a negative pressure of-0.6 to-0.8 MPa to obtain a BEMT microsphere / PVA suspension, and then spray drying; the mass fraction of the BEMT powder in the dichloromethane is 20-40%; the mass ratio of the PVA solution to the BEMT / dichloromethane is 1: (2-7); the mass concentration of the PVA solution is 1-10%; and the mass ratio of BEMT to PVA in the BEMT / PVA microsphere suspension is 1: (0.8-1.3).

2. The method for producing a composite particle having ultraviolet synergistic absorption properties according to claim 1, characterized by, The method comprises the following steps: S1. dissolving BEMT powder in dichloromethane to obtain a BEMT / dichloromethane solution, adding a PVA solution to obtain a BEMT / dichloromethane / PVA solution, and then high-speed homogenizing the mixed solution to obtain a BEMT / dichloromethane / PVA emulsion; S2. removing the dichloromethane solvent by rotary evaporation under the condition of room temperature and a negative pressure of-0.6 to-0.8 MPa to obtain a BEMT microsphere / PVA suspension; S3. spray drying the BEMT / PVA microsphere suspension to obtain a composite particle with ultraviolet synergistic absorption performance.

3. The method for producing a composite particle having ultraviolet synergistic absorption properties according to claim 2, characterized by, In step S1, the PVA in the PVA solution has a molecular weight of 70,000-80,000 and an alcoholysis degree of 92-99%.

4. The method for producing the composite particle having ultraviolet synergistic absorption performance according to claim 2, characterized by, In step S1, the high-speed homogenization is performed for 3-8 min at a speed of 8-16 krpm.

5. The method for producing the composite particle having ultraviolet synergistic absorption performance according to claim 2, characterized by, In step S3, the spray drying is performed at an inlet temperature of 110-160 °C, an atomization pressure of 0.5-2 MPa, and a feeding speed of 5-12 mL / min.

6. Use of the composite particle with ultraviolet synergistic absorption performance in claim 1 in the preparation of a sunscreen product.

Images