Oil-in-water pure physical sunscreen lotion and preparation method thereof

Abstract

The invention discloses an oil-in-water pure physical sunscreen lotion and a preparation method thereof. The composition specifically comprises a humectant; a film forming agent; modifying the sun-screening agent slurry; a preservative; a grease; a thickening agent; an emulsifier; filling powder; and the balance of water. The preparation method comprises the following steps: uniformly pre-mixing the modified sun-screening agent slurry, the filling powder and the film-forming agent, and homogenizing at a high speed to obtain a mixture 1; uniformly mixing and dispersing a humectant, distilled water, a preservative and a thickening agent to obtain a mixture 2; heating and uniformly stirring the grease and the emulsifier to obtain a mixture 3; under a heating condition, slowly adding the mixture 2 into the mixture 3, and stirring to obtain a mixture 4; slowly adding the mixture 1 into the mixture 4, and performing high-shear homogenization to obtain the oil-in-water pure physical sunscreen lotion. The oil-in-water pure physical sunscreen lotion prepared by the invention is fresh and cool in skin feeling, free of irritation, free of whitening, good in durability and relatively strong in sunscreen effect, and belongs to the field of cosmetics.

Description

Technical Field

[0001] This invention relates to the field of daily cosmetics technology, and in particular to a water-in-oil pure physical sunscreen and its preparation method. Background Technology

[0002] Prolonged exposure to ultraviolet (UV) radiation can easily lead to sunburn, inflammation, and even cancer. Therefore, it is essential to take sun protection measures. Common sun protection methods include using sun-protective clothing for physical protection, or applying sunscreen products to block or absorb UV rays.

[0003] In recent years, many sunscreen cosmetics have appeared on the market. These products primarily protect the skin by using physical sunscreens that block, reflect, or scatter ultraviolet (UV) rays, or chemical sunscreens that absorb UV rays. Existing sunscreen products have two main systems: "oil-in-water" and "water-in-oil." "Oil-in-water" sunscreens offer good water resistance but tend to feel thicker, oilier, and suffocating on the skin. "Water-in-oil" sunscreens, on the other hand, feel lightweight and comfortable, spread easily, and are easier to wash off. Most sunscreen cosmetics on the market combine chemical and physical sunscreens to enhance their sun protection effect. Chemical sunscreens have a strong absorption effect on ultraviolet rays and a wider range of protection. They can convert absorbed ultraviolet radiation into infrared radiation or heat energy. Therefore, most sunscreen cosmetics contain chemical sunscreens. However, the addition of chemical sunscreens can have certain impacts on human health and the environment, and they are prone to degradation and inactivation. Physical sunscreens, because they are not absorbed by the skin, have a better safety value for human health and are safer for the environment than chemical sunscreens. Therefore, the development of sunscreen products containing physical sunscreens has gradually become a focus.

[0004] Patent CN117959212A discloses a physical sunscreen composed of the following ingredients by weight percentage: 16%–26% physical sunscreen agent, 14.6%–38% moisturizer, 13.9%–50% emulsifier, 4%–12% skin moisturizer, 1%–10% thickener, 0.1%–2% filler, 0.1%–2% antioxidant, and the remainder being water. This patented invention combines zinc oxide and titanium dioxide in the physical sunscreen with the antioxidant p-hydroxyacetophenone, resulting in a synergistic effect in sun protection and producing unexpected technical results. While this oil-in-water sunscreen claims to be refreshing, non-greasy, and without dryness or irritation, it lacks a film-forming agent to firmly adhere the sunscreen ingredients to the skin. When the skin sweats, the sunscreen ingredients will be washed away, leading to poor sun protection duration.

[0005] Patent CN116440017A discloses a water-in-oil pure physical sunscreen lotion for infants. Through the combination of emulsifiers and thickeners, the viscosity of the resulting sunscreen lotion is less than 6000 mPa·s. The sunscreen agent used is non-nano titanium dioxide, combined with a sunscreen synergist to avoid the whitening effect caused by high titanium dioxide content, while still ensuring a certain level of sun protection. It also avoids the potential irritation risks to infants' skin from small-molecule chemical sunscreens. In addition to good stability, it also has good spreadability, easy application, and a gentle and safe feel. It can be washed off with water, avoiding the irritation problems caused by cleansing products to infants' skin. However, this patent, for a water-in-oil pure physical sunscreen lotion for infants, uses non-nano titanium dioxide for its sun protection value due to safety concerns. This results in a lower SPF and weaker protection. Furthermore, the use of a water-based film-forming agent can cause the sunscreen agent to detach during sweating in summer, weakening the sun protection effect.

[0006] In existing technologies, physical sunscreens such as titanium dioxide and zinc oxide are prone to photocatalytic reactions under ultraviolet radiation, producing reactive oxygen species (ROS), such as hydroxyl radicals. The presence of ROS can easily lead to the oxidation of organic ingredients in the formula, shortening the shelf life of sunscreen products.

[0007] This invention relates to a water-in-oil pure physical sunscreen lotion and its preparation method. The pure physical sunscreen lotion uses pure physical sunscreen agents that are not easily absorbed by the skin, and has a better safety value for the human body than chemical sunscreen agents. It uses sunscreen synergistic ingredients in combination with physical sunscreen agents, and the modified physical sunscreen agents are fully ground and evenly spread on the skin to improve the sun protection factor and ensure safety without whitening. In terms of process, this invention uses a phase inversion process to put the sunscreen ingredients and sunscreen synergistic ingredients into the inner phase, so that the sunscreen agents will not be washed off by sweating and wiping away sweat, which would lead to insufficient sun protection durability. Summary of the Invention

[0008] To address the above technical problems, this invention provides a water-in-oil pure physical sunscreen emulsion and its preparation method.

[0009] The first objective of this invention is to provide a water-in-oil pure physical sunscreen lotion, comprising the following components, listed in weight fractions: Moisturizer 5-10%, film-forming agent 0-5%, modified sunscreen slurry 20-40%, preservative 0.5-2%, oil 10-45%, thickener 0-5%, emulsifier 0.5-5%, filler powder 1-5%, balance is distilled water.

[0010] In some embodiments of the present invention, the humectant includes one or more of glycerin, butylene glycol, propylene glycol, oat beta-glucan, and sugar isomers.

[0011] In some embodiments of the present invention, the film-forming agent is one or more of trimethylsiloxysilicate, acrylic (ester) / polydimethylsiloxane copolymer (molecular weight of 80,000-150,000), acrylic (ester) / polytrimethylsiloxane / methacrylate copolymer (molecular weight of 120,000-200,000), and VP / hexadecene copolymer.

[0012] In some embodiments of the present invention, the active material of the modified sunscreen slurry has a core-shell structure, with a physical sunscreen agent as the core, and a catechin layer and a triethoxyoctylsilane coating layer sequentially coated on the surface of the core; the physical sunscreen agent includes titanium dioxide and / or zinc oxide; the particle size of the modified sunscreen agent is 10-80 nm. Further, it includes titanium dioxide double-coated with catechin and triethoxyoctylsilane, zinc oxide double-coated with catechin and triethoxyoctylsilane, and a mixture of zinc oxide and titanium dioxide double-coated with catechin and triethoxyoctylsilane. The present invention, by coating the surface of the physical sunscreen agent with antioxidant catechin, can effectively remove reactive oxygen species, thereby reducing the oxidation degree of the sunscreen product and improving its lifespan. Combined with the triethoxyoctylsilane coating layer, the physical sunscreen agent can not only resist oxidation but also have better dispersibility and improved sun protection effect.

[0013] In some embodiments of the present invention, the specific preparation method of the modified sunscreen slurry is as follows: (1) Calcining physical sunscreen nanoparticles (particle size 10~80nm) at 350~450℃ for 1~2h (to remove impurities) to obtain pretreated physical sunscreen nanoparticles; (2) Provide an ethanol aqueous solution with a volume concentration of 10-20% and a PBS buffer solution with a pH of 8.0, and use the ethanol aqueous solution to prepare a catechin solution with a concentration of 1mM-5mM, and adjust the pH to 8.0-8.5; (3) Disperse the physical sunscreen nanoparticles obtained in step (1) in an ethanol aqueous solution to obtain a dispersion with a concentration of 0.1~0.8 mg / mL; (4) Add the dispersion obtained in step (3) to the catechin solution, shake the reaction in an inert atmosphere in the dark, centrifuge to separate the solid phase, wash and dry to obtain the catechin-modified encapsulated physical sunscreen, i.e., the catechin coating layer.

[0014] (5) The catechin-modified physical sunscreen obtained in step (4) is surface-treated with triethoxyoctylsilane. First, triethoxyoctylsilane is prepared into a 5-50% ethanol solution and activated at 25-85℃ for 1-5 hours. The triethoxyoctylsilane solution is then evenly sprayed onto the surface of the catechin-modified physical sunscreen. The catechin-modified physical sunscreen is obtained by combining with siloxane bonds and hydroxyl groups under vacuum drying. The modified physical sunscreen is obtained by forming a triethoxyoctylsilane coating layer on the surface of the catechin coating layer.

[0015] (6): The modified sunscreen agent is ground into a slurry using a high-pressure nano-dispersion device. The modified sunscreen agent content is 30-70%, the solvent is 20-60%, the dispersant is 1-15%, the cooling water is kept at a constant temperature of 30-60℃, the speed is 2000-8000rpm / min, and the time is 2-8h. After grinding, the modified sunscreen agent slurry is obtained by filtering through a 200-mesh sieve.

[0016] In some embodiments of the present invention, in step (1), the physical sunscreen nanoparticles are titanium dioxide and / or zinc oxide.

[0017] In step (4), the mass ratio of catechin and physical sunscreen nanoparticles is (1~2):5. Inert atmospheres contain inert gases including nitrogen and / or argon.

[0018] The temperature range for the light-shielded vibration reaction is 25~35℃. The cleaning solution includes ethanol and deionized water, and the cleaning is performed at least three times; vacuum drying is carried out at 65~70℃ for 1~2 hours.

[0019] In step (5), the mass ratio of the catechin-modified encapsulated physical sunscreen to triethoxyoctylsilane is (1~3):4; The reaction conditions for the treatment are as follows: Triethoxyoctylsilane is first prepared into a 5-50% ethanol solution and activated at 25-85℃ for 1-5 hours. The activated triethoxyoctylsilane solution is then evenly sprayed onto the surface of the catechin-modified physical sunscreen. The sunscreen is obtained by vacuum drying through the binding of silicon-oxygen bonds and hydroxyl groups.

[0020] In step (6), the modified sunscreen agent content is 30-70%, solvent is 20-60%, dispersant is 1-15%, cooling water is kept at a constant temperature of 30-60℃, speed is 2000-8000rpm / min, time is 2-8h, and after grinding, it is filtered through a 200-mesh sieve to obtain the modified sunscreen agent slurry.

[0021] In some embodiments of the present invention, the preservative is one or a mixture of two or more of the following: phenoxyethanol, ethylhexylglycerin, octyl glycol, pentylene glycol, and decanediol.

[0022] In some embodiments of the present invention, the grease is one or a mixture of two or more of the following: polydimethylsiloxane, isohexadecane, isododecane, butyloctyl salicylate, C12-15 benzoyl alcohol, caprylic / decanoic acid triglyceride, hydrogenated polyisobutylene, hydrogenated polydecene, dioctyl carbonate, tocopheryl acetate, and polyisobutylene.

[0023] In some embodiments of the present invention, the thickener is one or more of xanthan gum, gum arabic, polyacrylate crosspolymer-6, polyacrylate-13, cetearyl alcohol, and tamarindusindinica.

[0024] In some embodiments of the present invention, the emulsifier is one or more of PEG-100 stearate, polyglycerol-3 polyricinoleate, PEG-30 dihydroxystearate, polysorbate-20, polysorbate-80, bis-PEG / PPG-16 / 16 polydimethylsiloxane, potassium cetyl phosphate, and cetearyl alcohol polyether-20.

[0025] In some embodiments of the present invention, the filler powder is one or more of silica, polymethylsilsesquioxane, boron nitride, mica, and synthetic fluorophlogopite.

[0026] A second objective of this invention is to provide a method for preparing the aforementioned water-in-oil pure physical sunscreen, comprising the following steps: The modified sunscreen slurry, filler powder, and film-forming agent are premixed evenly and homogenized at 5000-12000 rpm for 1-10 min to obtain mixture 1; the humectant, distilled water, preservative, and thickener are mixed and dispersed evenly to obtain mixture 2; the oil and emulsifier are heated and stirred evenly at 50-90℃ to obtain mixture 3. At 50-90℃, mixture 2 is slowly added to mixture 3 and stirred at 100-800 rpm for 30 minutes to obtain mixture 4; at 50-90℃, mixture 1 is slowly added to mixture 4 and homogenized at 5000-12000 rpm for 1-10 minutes to obtain water-in-oil pure physical sunscreen.

[0027] The technical solution of the present invention has the following advantages compared with the prior art: This invention utilizes the phenolic hydroxyl groups in catechins to bind with the metal oxide surface of physical sunscreens through coordination bonds. Under weakly alkaline conditions (pH 7.5-8.5), the metal oxide surface carries a negative charge, while catechins (EGCG) are partially deprotonated at pH > 8. Adsorption is enhanced through hydrogen bonding and hydrophobic interactions, ultimately forming a catechin coating layer.

[0028] This invention employs a phase inversion process that enables the conversion of internal and external phases. By adding oils and sunscreens separately and encapsulating them in the internal phase, the sunscreens in the product are prevented from binding together through physical or chemical forces to form large agglomerates that would affect the sun protection effect. Furthermore, this process improves the product's feel on the skin and avoids a greasy sensation during use due to excessive oils and the effects of sunscreens, thereby enhancing the user experience of the sunscreen.

[0029] The water-in-oil pure physical sunscreen lotion involved in this invention uses physical sunscreen agents titanium dioxide and zinc oxide, which are ground into a slurry using a grinder to reduce the particle size. Combined with spherical filler powder, the sunscreen agent is more evenly spread on the skin surface. It also reflects ultraviolet light back through diffuse reflection and extends the light path to improve the sunscreen agent's absorption efficiency of ultraviolet rays, resulting in a synergistic effect. The use of an oil-based film-forming agent can form a protective film on the skin surface to improve the waterproof performance of the physical sunscreen lotion, ensuring that it will not smudge due to sweat and improving the longevity effect. On the other hand, the film-forming agent can be pre-mixed with the sunscreen agent to improve the adhesion of the sunscreen powder and filler powder. Moreover, the weather resistance of the film-forming agent effectively resists ultraviolet rays, also achieving a synergistic effect with the sunscreen agent.

[0030] This invention uses pure physical sunscreens and employs spherical filler powder, film-forming agents, and high-shear homogenization processes to synergistically enhance sun protection. The pure physical sunscreens use small particle sizes and are ground into a slurry using a grinder to break down the secondary particle sizes, resulting in a high SPF, a refreshing feel, good durability, and no white cast. Detailed Implementation

[0031] Firstly, the core principle of a water-in-oil physical sunscreen is to ensure high sun protection while preventing whitening after application. Those skilled in the art should understand that using pure physical sunscreens to create a water-in-oil physical sunscreen with high sun protection requires adding a high concentration of physical sunscreens, which can lead to a whitening or unnatural whitening effect on the skin. To address this issue, the present invention employs the following approach: Physical sunscreens are the core of this invention's formula. Physical sunscreens are insoluble and not easily absorbed by the skin, making them safer and less likely to harm the skin compared to chemical sunscreens. The physical sunscreens utilize zinc oxide and titanium dioxide with a particle size of 10-80 nm. Their sun protection principle is to reflect / scatter ultraviolet rays, and the nano-sized sunscreens can also absorb ultraviolet rays and convert them into heat energy, thus preventing ultraviolet rays from directly reaching the skin. Zinc oxide and titanium dioxide can cause a whitening effect when applied to the skin. To reduce this whitening effect, smaller particle sizes of titanium dioxide and zinc oxide are selected. Therefore, this invention uses titanium dioxide and zinc oxide with a particle size of 10-80 nm, achieving highly effective sun protection without leaving a white cast.

[0032] Secondly, the selected physical sunscreen agent is ground into a slurry using a grinder. The particle size of the powder can be divided into primary particle size, secondary particle size, and tertiary particle size. The primary particle size refers to the size of the particles when they are initially formed, which is usually determined by the synthesis or preparation process. The secondary particle size refers to the size of the aggregates or clusters formed by the particles under specific conditions (such as dispersion, agglomeration, or processing). Due to the interaction between particles, the secondary particle size is usually larger than the primary particle size, reflecting the state of the particles in actual application. The tertiary particle size refers to the size of the larger aggregates or composite structures formed by the particles during further processing or application. Therefore, the particle size of titanium dioxide and zinc oxide as sunscreen agents is nanoscale. The nanoscale particle size mentioned is the primary particle size. After the powder is modified and added to the formula, there may be secondary and tertiary particle sizes, which will reduce the sun protection effect. Therefore, in this invention, titanium dioxide and zinc oxide are first ground into a slurry in oil using a grinder to grind the sunscreen powder with secondary particle size into the primary particle size, so as to maximize the sun protection effect of the sunscreen powder.

[0033] Finally, ingredients that enhance sun protection when combined with sunscreen agents are selected, including film-forming agents and filler powders. Film-forming agents are one or more mixtures of trimethylsiloxysilicate, acrylate / polydimethylsiloxane copolymer, acrylate / polytrimethylsiloxane methacrylate copolymer, and VP / hexadecene copolymer. Film-forming agents in cosmetics are mainly used to form a protective film, providing moisturizing, sun protection, sweat and water resistance, and shaping effects. Film-forming agents possess properties such as water resistance, weather resistance, adhesion, and flexibility. Water resistance forms a waterproof film on the skin surface to protect it; weather resistance resists environmental factors such as ultraviolet radiation and temperature changes; film-forming agents enhance UV resistance and can synergistically enhance the sun protection factor (SPF) with physical sunscreens; adhesion ensures firm adhesion to the substrate surface, encapsulating the physical sunscreen and then adhering it to the skin for long-lasting sun protection; flexibility maintains elasticity to prevent cracking. Water-based film-forming agents primarily use water as the dispersion medium. They can also form transparent films, providing a certain degree of protection. Oil-based film-forming agents are high-molecular polymers that can form a continuous, dense film on the material surface. This film has low surface tension, hydrophobic groups, good adhesion, and chemical resistance, giving it waterproof properties. Oil-based film-forming agents have better waterproof performance than water-based film-forming agents. In summer, when people sweat, water-based film-forming agents are more likely to cause sunscreen ingredients to fall off, making their sun protection time less long-lasting. Therefore, this invention uses oil-based film-forming agents.

[0034] The filler powder is a mixture of one or more of silica, polymethylsilsesquioxane, boron nitride, mica, and synthetic fluorophlogopite. Further selection of silica and polymethylsilsesquioxane as filler powders is preferred. This filler powder is spherical and, after mixing with the sunscreen agent, adheres to the skin, allowing for more even distribution of the sunscreen powder on the skin surface. The selected silica has a spherical porous structure; when ultraviolet light shines on the silica surface, it scatters, with some ultraviolet light being directly reflected back, while some ultraviolet light passes through the porous silica, extending the light path and further increasing the absorption of ultraviolet light by the sunscreen agent, thereby enhancing the sunscreen's effectiveness.

[0035] In the preparation process, high-shear homogenization utilizes the high tangential velocity and high-frequency mechanical effects generated by the high-speed rotation of the rotor in a high-shear homogenizer. This strong kinetic energy subjectes the material to intense mechanical and hydraulic shearing, centrifugal extrusion, liquid layer friction, impact tearing, and turbulence within the narrow gap between the stator and rotor, forming a suspension (solid / liquid). This allows the immiscible solid, liquid, and gas phases to be instantly and uniformly dispersed and emulsified under the combined action of appropriate processing techniques and additives. Through repeated circulation in a high-frequency inline high-shear homogenizer, a stable product is ultimately obtained. High-shear homogenization reduces the particle size range to the nanoscale. Nanoscale particles can scatter and absorb ultraviolet (UV) radiation, especially UVA and UVB bands, thus enhancing sun protection. The scattering effect is optimal when the particle size is comparable to the UV wavelength. Nanoscale particles can effectively scatter UV radiation, reducing its damage to the skin. Therefore, high-shear homogenization is chosen in the preparation process to enhance sun protection. Using high-shear homogenization ensures uniform particle size distribution within the internal phase and improves the fineness and skin feel of the material.

[0036] Step (4) involves adding the aqueous phase to the oil phase to initially encapsulate the aqueous phase interface. By increasing the rotation speed and operating at high temperatures, the emulsion is transformed from an oil-in-water emulsion to an oil-in-water emulsion under high shear homogenization through the action of the water-in-oil emulsion and the influence of intermolecular forces. Under the action of the aqueous phase thickener, the oil is encapsulated in the inner phase. Sunscreen is then added later. The particle size of the sunscreen in the inner phase is reduced and the particle size distribution of the sunscreen is made uniform through high shear homogenization. This avoids collisions between the oil and the sunscreen, thus avoiding affecting the skin feel of the oil and the uniformity of the sunscreen's adhesion to the skin. This improves the skin feel of the physical sunscreen without affecting the sun protection effect.

[0037] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0038] Most of the raw materials used in the examples are commercially available common raw materials; the relevant explanations are as follows: Sunscreen gel: NanoT4560 Manufacturer: Jiangxi Liankai Technology Co., Ltd. The ingredients are: titanium dioxide & triethoxyoctylsilane & C12-15 alcohol benzoate & aluminum hydroxide & PEG-30 dimerized hydroxystearate, where "&" means "and".

[0039] Sunscreen gel: NanoT6060 Manufacturer: Jiangxi Liankai Technology Co., Ltd., Ingredients: Zinc oxide & C12-15 benzoate & triethoxyoctylsilane & polyglycerol-3 polyricinoleate.

[0040] Emulsifier: SEPIPLUS400 Manufacturer: SEPIPLUS, France; Composition: Polyacrylate-13 & Polyisobutylene & Polysorbate 20.

[0041] Examples 1-15 focus on physical sunscreens containing catechin and triethoxyoctylsilane-coated nano-titanium dioxide and nano-zinc oxide. An orthogonal experiment was used to screen for the optimal ratio of these components. Examples 16-17 used this ratio to sample and screen for the optimal ratio under these conditions. Comparative Example 1 is a water-in-oil physical sunscreen emulsion made from unground sunscreen powder using high-shear homogenization. Comparative Example 2 is a water-in-oil pure physical sunscreen emulsion made using ordinary processes. Comparative Example 3 uses the same raw materials and components as Example 17, except that triethoxyoctylsilane is used to treat the titanium dioxide and zinc oxide.

[0042] Examples 1-15 use a combination of catechin and triethoxyoctylsilane to double-encapsulate nano-titanium dioxide and zinc oxide paste, trimethylsiloxysilicate as a film-forming agent, and silica as a filler. Through orthogonal experiments, the superior proportions of raw material components are selected based on a comprehensive evaluation of factors such as refreshing feel, oiliness, whitening, smoothness, irritation, and sun protection effect.

[0043] Examples 16-17: Based on the raw material component combinations screened in Examples 1-15, the sampling was further refined to obtain the best-performing raw material component ratios.

[0044] Examples 1-9: This embodiment provides a method for preparing a water-in-oil pure physical sunscreen emulsion, as detailed below: 1. The formula is shown in Table 1, by mass parts; 2. Preparation steps: (1) Mix all raw materials of phase B according to the formula weight, heat and stir at 85°C to disperse evenly, and then homogenize under high shear for 5 min.

[0045] (2) Mix all raw materials of phase C according to the formula weight, and heat and stir at 85°C to disperse evenly.

[0046] (3) Mix all raw materials of phase A according to the formula weight and heat and stir evenly at 85°C.

[0047] (4) At 85°C, the mixture of phase C is slowly added to the mixture of phase A, stirred at 500 rpm for 30 min, and homogenized at 10000 rpm for 5 min to obtain the mixture of phases AC. At 85°C, the mixture of phase B is slowly added to the mixture of phases AC, and homogenized at 10000 rpm for 5 min; the temperature of the stirring paddle is naturally cooled to below 45°C to obtain the water-in-oil pure physical sunscreen emulsion.

[0048] The specific preparation methods for the two modified sunscreen agents (modified zinc oxide nanoparticles and modified titanium dioxide nanoparticles, respectively) are as follows: (1) Physical sunscreen agents (zinc oxide nanoparticles and titanium dioxide nanoparticles) with a particle size of 10~80nm were calcined at 350℃ for 2h to remove impurities and obtain pretreated physical sunscreen nanoparticles. (2) Prepare a 15% ethanol aqueous solution and a PBS buffer solution with a pH of 8.0. Prepare a 1mM catechin solution using the ethanol aqueous solution and adjust the pH to 8.0. (3) Disperse the physical sunscreen nanoparticles obtained in step (1) in an ethanol aqueous solution to obtain a dispersion with a concentration of 0.5 mg / mL; (4) Under a nitrogen atmosphere, the dispersion obtained in step (3) is added to the catechin solution (the mass ratio of catechin to physical sunscreen nanoparticles is 1:4), and the reaction is carried out at 25°C in the dark with shaking for 3 hours. The solid phase is separated by centrifugation and washed three times with ethanol and deionized water. The sunscreen with a catechin coating layer is obtained by vacuum drying at 65°C for 2 hours. (5) The catechin-modified physical sunscreen obtained in step (4) is surface-treated with triethoxyoctylsilane. First, triethoxyoctylsilane is prepared into a 20wt% ethanol solution and activated at 45°C for 3 hours. The activated triethoxyoctylsilane solution is then evenly sprayed onto the surface of the catechin-modified physical sunscreen. The catechin-modified physical sunscreen is then combined with hydroxyl groups through silicon-oxygen bonds and vacuum dried at 65°C for 10 hours to obtain a double-modified physical sunscreen, i.e., a triethoxyoctylsilane coating layer is formed on the surface of the catechin coating layer, and finally the modified sunscreen is obtained.

[0049] (6): The modified sunscreen agent was ground into a slurry using a high-pressure nano-dispersing device. The modified sunscreen agent content was 70wt%, the solvent was 20wt%, and the dispersant was 10wt% (here, the dispersant used for modified titanium dioxide was PEG-30 dihydroxystearate, and the dispersant used for modified zinc oxide was polyglycerol-3 polyricinoleate). The cooling water was kept at a constant temperature of 50℃, the speed was 6000rpm / min, and the time was 8h. After grinding, the slurry was filtered through a 200-mesh sieve to obtain the modified sunscreen agent slurry, namely the modified titanium dioxide nanoparticle slurry and the modified zinc oxide nanoparticle slurry.

[0050] Table 1 .

[0051] Examples 10-17, Example 18, and Comparative Examples 1 and 3: This embodiment provides a method for preparing a water-in-oil pure physical sunscreen emulsion, as detailed below: 1. The formula is shown in Table 2, by mass parts; 2. Preparation steps: (1) Mix all raw materials of phase B according to the formula weight, heat and stir at 85°C to disperse evenly, and then homogenize under high shear for 5 min.

[0052] (2) Mix all raw materials of phase C according to the formula weight, and heat and stir at 85°C to disperse evenly.

[0053] (3) Mix all raw materials of phase A according to the formula weight and heat and stir evenly at 85°C.

[0054] (4) At 85°C, the mixture of phase C is slowly added to the mixture of phase A, stirred at 500 rpm for 30 min, and homogenized at 10000 rpm for 5 min to obtain the mixture of phases AC. At 85°C, the mixture of phase B is slowly added to the mixture of phases AC, and homogenized at 10000 rpm for 5 min; stirring is then performed to lower the temperature to below 45°C to obtain the water-in-oil pure physical sunscreen emulsion.

[0055] Comparative Example 3 This comparative example uses similar raw materials and preparation methods as shown in Example 17, except that the zinc oxide and titanium dioxide are treated with triethoxyoctylsilane.

[0056] Table 2 . Comparative Example 2: Comparative Example 2 uses similar raw materials as Example 17, except that a conventional preparation method is used.

[0057] This comparative example provides a method for preparing a water-in-oil pure physical sunscreen emulsion, as detailed below: 1. The formula is shown in Table 3, by mass parts.

[0058] Table 3 .

[0059] 2. The preparation process is as follows: First, mix all the raw materials of phase A and stir them in an 85°C water bath. Then, homogenize them at 12,000 rpm for 5 minutes to obtain the mixture.

[0060] Xanthan gum in phase B was pre-dispersed evenly with glycerol and butylene glycol. Finally, the other raw materials were stirred and dispersed evenly at 85°C to obtain a mixture.

[0061] Slowly add the mixture of phase B to the mixture of phase A and emulsify for 1-10 minutes.

[0062] Slowly stir and cool down until the temperature drops below 45℃. The experiment ends, and a water-in-oil pure physical sunscreen lotion is obtained.

[0063] 1: Product skin feel test The physical sunscreens obtained in Examples 1-17 and the physical sunscreens obtained in Comparative Examples 1, 2, and 3 were used as samples for blind testing and scoring.

[0064] The testing items included refreshing feel, oiliness, white cast, smoothness, and irritation. Each item was scored from 1 to 10, with 1 representing the worst effect and 10 representing the best effect. Ten professionals were selected to test the skin feel of the samples, scoring each item, and the average score was taken. (Higher scores for oiliness, white cast, and irritation indicate that the product is not oily, does not leave a white cast, and is non-irritating.) The test results are shown in Table 4.

[0065] Table 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 refreshing feeling 9.5 9.4 9.4 9.2 8.8 9.4 9.3 9.2 8.9 9.1 greasy feeling 9.8 9.6 9.5 9.4 9.0 9.6 9.4 9.5 9.0 9.3 Pale 9.9 9.9 9.8 9.7 9.3 9.8 9.5 9.1 8.8 8.5 Stimulation 9.4 9.4 9.3 9.0 8.8 9.1 9.1 8.8 9.4 8.9 Delicacy 9.8 9.7 9.8 9.5 8.9 9.7 9.8 9.5 9.0 9.5 .

[0066] Table 5 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Comparative Example 1 Comparative Example 2 Comparative Example 3 refreshing feeling 9.3 8.7 9.0 8.8 8.7 9.5 9.4 9.1 9.0 9.1 greasy feeling 9.5 8.9 9.2 9.0 8.8 9.8 9.5 9.2 7.6 9.1 Pale 8.3 8.0 7.2 7.5 6..9 9.5 9.4 7.8 8.2 9.2 Stimulation 9.2 9.2 9.2 9.3 9.4 9.2 9.3 7.5 8.9 9.1 Delicacy 9.3 9.0 9.4 8.9 8.7 9.8 9.8 6.3 8.4 9.4 .

[0067] The data above shows that when the content of nano-titanium dioxide coated with catechin and triethoxyoctylsilane exceeds 17%, it begins to turn white. When the amount of film-forming agent added exceeds 3%, the skin will feel irritated. At present, we need to determine the amount of physical sunscreen and film-forming agent added. Moreover, the material made by high shear homogenization is more delicate, which can improve the skin feel and make the material more delicate.

[0068] 2: Product sun protection capability test The physical sunscreens obtained in Examples 1-17 and Comparative Examples 1 and 2 were used as samples and tested according to the human body method of the "Cosmetic Safety Technical Specifications". The SPF and PA values ​​of the sunscreens were tested using a sun protection factor tester (UV-2000S). The higher the SPF value, the better the sun protection effect of the product, and the same applies to the PA value.

[0069] Table 6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 SPF value 27.2 28.3 29.2 35.2 37.3 46.7 51.2 58.2 50.3 52.4 49.3 PA value ++ ++++ ++++ ++++ ++++ ++ ++++ ++++ ++++ ++ ++++ .

[0070] Table 7 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Comparative Example 1 Comparative Example 2 Comparative Example 3 SPF value 50.4 53.1 55.4 57.3 52.4 55.3 25.2 15.3 52.7 PA value ++++ ++ ++++ ++ ++++ ++++ ++ + +++ .

[0071] As shown in Tables 6 and 7 above, catechins and triethoxyoctylsilane encapsulating titanium dioxide and zinc oxide can enhance the sun protection effect and improve its durability. Silica and trimethylsiloxysilicate have a synergistic effect on sun protection. However, when silica is added in a certain amount, the contact area of ​​the silica spherical structure on the skin is small, making it easy to fall off and take away some of the sunscreen. Therefore, a film-forming agent is needed to work in conjunction with it. The two work synergistically to improve the sun protection effect of pure physical sunscreens. The high-shear homogenized formula encapsulates the sunscreen ingredients in the oil phase, and when the sunscreen is used, the sunscreen ingredients are slowly released, which also improves the durability of the sun protection effect.

[0072] 3: Antioxidant test: The physical sunscreens obtained in Example 17 and Comparative Example 3 were subjected to total free radical testing using a paramagnetic resonance (EPR) spectrometer. The higher the value, the more free radicals were present.

[0073] Table 8 Example 17 Comparative Example 3 Total free radicals (spins / g) <![CDATA[3.589×10 9 ]]> <![CDATA[4.501×10 11 ]]> .

[0074] The table above shows that catechins and triethoxyoctylsilane encapsulating titanium dioxide and zinc oxide can reduce the free radical content of free radical powders and mitigate the damage to the skin caused by free radicals in powders.

[0075] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An oil-in-water pure physical sunscreen emulsion, characterized in that, The composition comprises the following components by weight fraction: moisturizer 5-10%, film forming agent 0-5%, modified sunscreen slurry 20-40%, preservative 0.5-2%, oil 10-45%, thickening agent 0-5%, emulsifier 0.5-5%, filling powder 1-5%, and the balance is distilled water.

2. The oil-in-water pure physical sunscreen emulsion according to claim 1, characterized in that, The moisturizer comprises one or more of glycerin, butylene glycol, propylene glycol, oat glucan, and sugar isomer.

3. The oil-in-water physical sunscreen emulsion according to claim 1, wherein The film forming agent is a mixture of one or more of trimethylsiloxy silicate, acrylate / dimethicone copolymer, acrylate / polymethylsiloxane / methacrylate copolymer, and VP / hexadecene copolymer.

4. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The active substance of the modified sunscreen slurry has a core-shell structure, with a physical sunscreen as the core, and a catechin layer and a triethoxyoctylsilane coating layer successively coated on the surface of the core; the physical sunscreen comprises titanium dioxide and / or zinc oxide; the particle size of the modified sunscreen is 10-80 nm.

5. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The preservative is one or more of phenoxyethanol, ethylhexylglycerin, caprylyl glycol, pentylene glycol, and decylene glycol.

6. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The oil is one or more of dimethicone, isohexadecane, isododecane, butyloctyl salicylate, C12-15 alcohol benzoate, caprylic / capric triglyceride, hydrogenated polyisobutene, hydrogenated polydecene, dicaprylyl carbonate, tocopheryl acetate, and polyisobutene.

7. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The thickening agent is one or more of xanthan gum, gum acacia, polyacrylate crosspolymer-6, polyacrylate-13, cetearyl alcohol, and mesquite gum.

8. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The emulsifier is one or more of PEG-100 stearate, polyglyceryl-3 polyricinoleate, PEG-30 dipolyhydroxystearate, polysorbate-20, polysorbate-80, bis-PEG / PPG-16 / 16 dimethicone, potassium cetyl phosphate, and ceteareth-20.

9. The oil-in-water physical sunscreen emulsion of claim 1, wherein, The filling powder is one or more of silica, polymethylsilsesquioxane, boron nitride, mica, and synthetic fluorphlogopite.

10. A process for the preparation of an oil-in-water physical sunscreen emulsion as claimed in any one of claims 1 to 9, characterised in that, The method comprises the following steps: The modified sunscreen slurry, filling powder, and film forming agent are pre-mixed uniformly, homogenized at 5000 rpm-12000 rpm for 1-10 min to obtain mixture 1; the moisturizer, distilled water, preservative, and thickening agent are mixed and dispersed uniformly to obtain mixture 2; the oil and emulsifier are heated and stirred uniformly at 50-90°C to obtain mixture 3; Under the condition of 50-90°C, mixture 2 is added to mixture 3, stirred at a speed of 100-800 rpm for 30 min to obtain mixture 4; under the condition of 50-90°C, mixture 1 is slowly added to mixture 4, and high-shear homogenization is performed for 1-10 min to obtain an oil-in-water physical sunscreen emulsion.