Two-phase powder slurry composition, application thereof, oil-in-water sunscreen system and preparation method of oil-in-water sunscreen system

Abstract

The invention relates to a double-phase powder slurry composition and application thereof, an oil-in-water sunscreen system and a preparation method thereof, and the double-phase powder slurry composition comprises the following components in parts by weight: 4-6.5 parts of hydrophilic nano titanium dioxide powder slurry; and 1.5-4 parts by weight of a lipophilic micron titanium dioxide powder slurry, wherein nanoscale titanium dioxide in the hydrophilic nanometer titanium dioxide powder is subjected to hydrophilic surface treatment of hydrated silica and lecithin, and the average primary particle size is 10-100 nm; micron-sized titanium dioxide in the lipophilic micron-sized titanium dioxide powder slurry is subjected to hydrophobization surface treatment of triethoxyoctyl silane, and the average primary particle size is 1-10 [mu] m; the solid mass ratio of the nanoscale titanium dioxide to the micron-sized titanium dioxide is (1: 0.5)-(1: 1). Through the synergistic effect of the hydrophilic nano-scale titanium dioxide and the oleophylic micron-scale titanium dioxide in the two-phase powder slurry composition, the oil-in-water sunscreen emulsion which has a high SPF value, high water resistance, natural optical brightening, refreshing skin feeling and long-term stability is obtained.

Description

Technical Field

[0001] This disclosure relates to the field of cosmetic formulation technology, specifically to a biphasic powder-slurry combination and its application, and an oil-in-water sunscreen system and its preparation method. Background Technology

[0002] As consumers' skincare concepts become more sophisticated, the market's requirements for sunscreen products have evolved from basic UV protection to a pursuit of "multi-functional" composite protection. An ideal sunscreen product, especially a "sunscreen primer" that also functions as a makeup base, must meet the following four stringent requirements: (1) high SPF and broad-spectrum UV protection (high SPF / PA value); (2) excellent and long-lasting water and sweat resistance to cope with daily sweating or water exposure; (3) immediate, natural, and non-whitening skin brightening and correction effects to achieve a "no-makeup" makeup look; and (4) a light, refreshing, breathable, and non-sticky feel to ensure a comfortable experience all day long.

[0003] The mainstream sunscreen formulations on the market are divided into water-in-oil (W / O) and oil-in-water (O / W) types. While the W / O system has an inherent advantage in water resistance, its inherent drawbacks—such as a greasy and heavy feel, poor breathability, tendency to cause breakouts, and difficulty in makeup removal—run counter to the current market demand for a "light and breathable" feel, greatly limiting its application. Therefore, the O / W system, with its lighter and more refreshing texture, has become the preferred choice for consumers. However, current O / W systems cannot achieve the aforementioned high-performance indicators, specifically exhibiting the following three inherent contradictions: First, there's the contradiction between a refreshing feel and long-lasting water resistance. O / W systems use water as the continuous external phase; when exposed to water (sweat), water-soluble components are easily lost, and the sunscreen film is easily damaged. To improve water resistance, the amount of film-forming agent usually needs to be significantly increased, but this inevitably leads to a heavier film feel and a sticky texture, contradicting the refreshing intention of the O / W system.

[0004] Second, there is a conflict between the high-efficacy ingredient load and system stability. To achieve a high SPF value, formulations often require a high concentration of organic (chemical) sunscreen agents and inorganic (physical) sunscreen powders. These highly polar oil-phase components and high content of solid powders (especially easily agglomerated inorganic powders) are extremely difficult to coexist stably in an O / W system, which can easily lead to the collapse of the emulsion system, stratification, oil separation, or particle sedimentation, severely limiting the upper limit of product functionality and shelf life.

[0005] Third, there's the conflict between immediate corrective power and a natural makeup look. To brighten skin tone and conceal imperfections, powders like titanium dioxide are often added to the formula. However, simply adding nano-sized powders can easily result in a "pale" or "grayish" appearance, while micron-sized powders can create a "mask-like" look and a heavy makeup effect, making it difficult to achieve a natural, three-dimensional optical corrective effect. Furthermore, unstable powder dispersion can easily cause pilling during application.

[0006] Existing technologies typically adjust the sun protection and modification effects by modifying the proportions of materials in the sunscreen system. For example, CN110772439A discloses a sunscreen composition and its preparation method, wherein the sunscreen composition includes hydrophilic-coated titanium dioxide, lipophilic-coated titanium dioxide, hydrophilic-coated zinc oxide, and lipophilic-coated zinc oxide, with a mass ratio of 8-16:8-16:8-16:8-16. This method improves the sun protection effect and reduces skin irritation by modifying the reasonable ratio of titanium dioxide and zinc oxide. However, the water resistance and skin feel of this sunscreen composition have not been fully verified, and the system stability is easily affected by environmental factors (such as temperature and pH value), which may lead to component separation or decreased effectiveness during long-term storage or use. Summary of the Invention

[0007] Therefore, the purpose of this disclosure is to improve the UV protection capability, water resistance, stability, and skin feel of water-in-oil sunscreen systems in order to meet the current complex needs of consumers for sunscreen products.

[0008] To achieve the above objectives, this disclosure provides a two-phase slurry composition, comprising: Hydrophilic nano-titanium dioxide slurry, 4~6.5 parts by weight; and Oil-loving micron-sized titanium dioxide slurry, 1.5~4 parts by weight; The nano-sized titanium dioxide in the hydrophilic nano-titanium dioxide powder undergoes hydrophilic surface treatment with hydrated silica and lecithin, and the average primary particle size is 10~100 nm. The micron-sized titanium dioxide in the oleophilic micron-sized titanium dioxide slurry undergoes hydrophobic surface treatment with triethoxyoctylsilane, resulting in an average primary particle size of 1~10 μm. The solid mass ratio of the nano-sized titanium dioxide to the micron-sized titanium dioxide is 1:0.5 to 1:1.

[0009] Preferably, the hydrophilic nano-titanium dioxide slurry comprises, by mass percentage: 40-45% of the aforementioned nano-sized titanium dioxide, 30-40% of butanediol, 15-25% of hydrated silica, 1-1.5% of lecithin and 1.5-2.5% of polysorbate-80.

[0010] More preferably, the oleophilic micron-sized titanium dioxide slurry comprises, by mass percentage: 60-70% of the micron-sized titanium dioxide, 1-1.5% of triethoxyoctylsilane and 30-35% of dibutyl adipate.

[0011] To achieve the above objectives, this disclosure also provides an application of the biphase powder combination described in any of the preceding claims in an oil-in-water sunscreen system.

[0012] Preferably, the water-in-oil sunscreen system includes a water-in-oil emulsifier, a thickener, an aqueous phase, and an oil phase; In the biphase slurry combination, the hydrophilic nano-titanium dioxide slurry is dispersed in the aqueous phase, and the oleophilic micron-sized titanium dioxide slurry is dispersed in the oil phase.

[0013] More preferably, the aqueous phase includes a humectant and an antioxidant, and the oil phase includes a film-forming agent and a filler powder.

[0014] Preferably, the moisturizer comprises one or more of glycerin, butylene glycol, or pentanediol; The antioxidant includes p-hydroxyacetophenone; The film-forming agent includes hydrogenated polycyclopentadiene; The filler powder includes one or more of silica, talc, or mica.

[0015] More preferably, the thickener includes ammonium acryloyldimethyl taurate / VP copolymer, xanthan gum, and silachlorite hydrate; The oil-in-water emulsifier includes one or more of sucrose polystearate, cetyl palmitate, polysorbate-60, or potassium cetyl phosphate.

[0016] To achieve the above objectives, this disclosure also provides a water-in-oil sunscreen system comprising any of the foregoing dual-phase powder-based combinations, comprising, by weight, 100 parts: 5-20 parts of chemical sunscreen; 1-6 parts of oil-in-water emulsifier; Film-forming agent 0.5~2 parts; 5-20 parts of moisturizer; 4-6.5 parts of hydrophilic nano-titanium dioxide powder slurry; 1.5 to 4 parts of oleophilic micron-sized titanium dioxide powder slurry; Colorant 0.01~0.02 parts; Thickener 0.2~0.6 parts; 5-10 parts of moisturizer; 1-2 parts of filler powder; Antioxidant 0.3~0.5 parts; Water balance; The solid mass ratio of nano-sized titanium dioxide to micron-sized titanium dioxide is 1:0.5 to 1:1.

[0017] To achieve the above objectives, this disclosure also provides a method for preparing the aforementioned water-in-oil sunscreen system, comprising the following steps: S1. Mix the oil-in-water emulsifier, emollient, chemical sunscreen and film-forming agent to obtain phase A, heat to 75~80℃ and stir until completely dissolved; S2. Uniformly mix the oleophilic micron-sized titanium dioxide powder slurry and colorant to obtain phase B, add phase A, and homogenize and stir at 75~80℃ until phase A is completely dispersed to obtain the oil phase; S3. Mix water, humectant, thickener, antioxidant and oil-in-water emulsifier to obtain phase C, stir and heat to 75~80℃ until the thickener is completely swollen to form an aqueous phase; S4. The oil phase is slowly added to the aqueous phase, and homogenized and emulsified at 75~80°C to form a uniform emulsion system; S5. Cool the emulsified system to below 50°C, add hydrophilic nano-titanium dioxide powder slurry, and stir until the system is homogeneous and stable to obtain the water-in-oil sunscreen system.

[0018] The technical solution claimed in this disclosure achieves the following beneficial effects: The design of the dual-phase powder paste combination, through the directional distribution and uniform dispersion of nano and micro titanium dioxide in the water-oil dual phase, achieves improved water resistance and effective maintenance of film integrity in the water-in-oil sunscreen without significantly increasing the amount of film-forming agent and maintaining a refreshing skin feel. It can still maintain high-efficiency protection even after sweating or contact with water. Through precise anchoring and optimal ratio control of biphasic powders in their respective phases, and the synergistic effect of "external phase brightening" and "internal phase filling" of the biphasic powder combination, even if the sunscreen formula contains high concentrations of organic sunscreen agents and biphasic powders, it can still maintain excellent long-term storage stability, avoiding the defects of high-load O / W formulas being prone to stratification and instability. By synergistically optimizing the photoprotection path through multi-scale titanium dioxide particles, the continuity and density of the sunscreen film are enhanced, improving UV protection efficacy while achieving optical correction balance. This results in a significant improvement in skin tone brightness (L value) while naturally correcting red / yellow tones (a, b* values), achieving a "natural brightening without looking fake white" makeup effect. It gives the skin a natural radiance and effectively avoids the whitening and heavyness problems that are common with traditional high SPF products. By employing phase-separation pretreatment and gradient emulsification processes, the directional distribution and stability of different titanium dioxide powders in their corresponding phases are ensured, avoiding performance degradation and skin feel defects caused by powder agglomeration, while simultaneously achieving efficient fusion of the multiphase interface. The process design of introducing hydrophilically modified titanium dioxide slurry after cooling ensures its full dispersion in the aqueous phase while preventing damage to the surface modification layer at high temperatures, thus maintaining the original functional properties of the particles. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 The particle size distribution of the sunscreens in Application Examples 1-3 and Comparative Examples 1-5 is shown. Figure 1 In the examples, a to c correspond to the particle size distribution of the sunscreens in Examples 1 to 3, respectively. Figure 1 The values ​​d to h in the figure correspond to the particle size distribution of sunscreens in ratios 1 to 5, respectively.

[0021] Figure 2 The results of LUM stability analysis of the sunscreens used in Examples 1-3 are shown. Figure 2 In the diagrams, a to c correspond to the LUM spectra of the sunscreens in Examples 1 to 3, respectively.

[0022] Figure 3 The results of LUM stability analysis for the sunscreens in Comparative Examples 1-5 are shown. Figure 3 In the diagrams, a to e correspond to the LUM spectra of sunscreens in proportions 1 to 5, respectively.

[0023] Figure 4 The results of the reflection wavelength analysis are shown for the sunscreens used in Examples 1-3 and Comparative Examples 1-5. Among them, Figure 4 In the blank group, 'a' represents the reflected wavelength, and 'b' to 'd' correspond to the reflected wavelengths of the sunscreens in Examples 1 to 3, respectively. Figure 4 In the equations e to i, the reflected wavelengths of the sunscreens in ratios 1 to 5 are respectively represented.

[0024] Figure 5 The images show the coating and spreading results of the sunscreens used in Examples 1-3 and Comparative Examples 1-5 on a black and white cardstock background. Figure 5 In the examples, a to c correspond to the application and spreading results of the sunscreen lotion in Examples 1 to 3, respectively. Figure 5 The values ​​d to h correspond to the application and spreading results of sunscreen lotions in ratios 1 to 5, respectively. Detailed Implementation

[0025] To make the objectives, technical solutions, and beneficial effects of the embodiments in this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0026] Unless otherwise specified, all raw materials and supplies used in this section were purchased through general commercial channels. Water was prepared using a Millipore pure water system; Cetyl phosphate potassium was purchased from DSM Nutrition China. Butanediol was purchased from Shandong Haike New Energy Materials Technology Co., Ltd. The ammonium acryloyldimethyl taurate / VP copolymer was purchased from Clariant Chemicals (China) Co., Ltd. Xanthan gum was purchased from Danisco (China) Co., Ltd. Ethylhexyl methoxycinnamate was purchased from Anhui Shengnuobei Chemical Technology Co., Ltd. Dibutyl adipate, hexyl diethylaminohydroxybenzoyl benzoate, sucrose polystearate and cetyl palmitate (mixed together), and bis-ethylhexyloxyphenol methoxyphenyl triazine were purchased from BASF. Titanium dioxide and hydrated silicon were purchased from Imperial Chemical Industries. Lecithin was purchased from Shanghai Zhirou Chemical Co., Ltd. Polydimethylsiloxane was purchased from Shin-Etsu Chemical Industry Co., Ltd. p-Hydroxyacetophenone was purchased from Symrise (Shanghai) Co., Ltd. 1,2-Pentanediol was purchased from Lanxess Chemicals (China) Co., Ltd. Ethylhexyltriazine was purchased from Hubei Meifeng Chemical Co., Ltd. Poly(C10-30) alkyl acrylate was purchased from Evonik (China) Co., Ltd. Dioctyl carbonate, silachlorite, and propylene glycol carbonate (the three were mixed together) were purchased from Haiming Sideqian (Shanghai) Co., Ltd. Hydrogenated polycyclopentadiene and isododecane (mixed together) were purchased from KONEO Trading (Shanghai) Co., Ltd. Polysorbate-80 and polysorbate-60 were purchased from Croda Chemical (China) Co., Ltd. Silica was purchased from Sanhao Cosmetic Materials (Suzhou) Co., Ltd. Titanium dioxide, triethoxyoctylsilane, and iron oxides (a mixture of iron oxide red and iron oxide yellow) were purchased from Advanced Beauty Technology Co., Ltd. Humosalide was purchased from Yidu Huayang Chemical Co., Ltd.

[0027] <Example 1> This embodiment provides a two-phase powder paste combination for use in water-in-oil sunscreens. This combination is not a physical mixture of two powders, but rather an internally ordered system composed of two functional units with clearly defined functional positioning and precise spatial distribution, arranged in a specific synergistic ratio. The two-phase powder paste combination includes a hydrophilic nano-titanium dioxide powder paste and an oleophilic micron-sized titanium dioxide powder paste.

[0028] The hydrophilic nano-titanium dioxide powder paste is composed of nano-sized titanium dioxide, butylene glycol, hydrated silica, lecithin, and polysorbate-80. By weight, it contains 42.5% nano-sized titanium dioxide, 35% butylene glycol, 19% hydrated silica, 1.4% lecithin, and 2.1% polysorbate-80. The function of this hydrophilic nano-titanium dioxide powder paste is to form a uniform, dense, and highly transparent base optical film on the skin surface after sunscreen application, as the moisture rapidly evaporates, providing an immediate and natural brightening effect, and serving as a base for subsequent structured composite films.

[0029] The oleophilic micron-sized titanium dioxide slurry is composed of micron-sized titanium dioxide, triethoxyoctylsilane, and dibutyl adipate. By weight, the micron-sized titanium dioxide content is 65.3%, the triethoxyoctylsilane content is 1.3%, and the dibutyl adipate content is 33.4%. The functional role of this oleophilic micron-sized titanium dioxide slurry is that during film formation, these hydrophobic micron-sized titanium dioxide particles are released from the oil phase and physically fill the microscopic voids in the base film formed by nano-titanium dioxide, thereby enhancing the scattering and blocking of UVA / UVB. More importantly, its strong hydrophobic properties construct a hydrophobic network framework "inside" the composite film, greatly improving the overall hydrophobicity and integrity of the film layer.

[0030] The average primary particle size of titanium dioxide in the hydrophilic nano-titanium dioxide slurry (used as an external phase film formation and optical brightening agent in sunscreens) is controlled to be 10–100 nm, and it undergoes a composite hydrophilication surface treatment with hydrated silica and lecithin. The hydrophilication surface treatment can be performed as follows: 1. Add untreated nano-titanium dioxide powder to deionized water, shear at high speed, and add water-soluble silicate to the slurry while stirring; 2. Controlling the pH value of the system and neutralizing the alkalinity triggers the hydrolysis of silicates. The monosilicic acid (Si(OH)4) generated by hydrolysis is extremely unstable and will rapidly condense and deposit on the surface and in the gaps of titanium dioxide particles to form an amorphous hydrated silica (SiO2·nH2O) layer. 2. Remove byproduct salts (such as sodium sulfate) generated during the reaction by centrifugation or filtration and repeated washing with water to obtain a filter cake; 3. Redisperse the filter cake from the first stage in deionized water and adjust it to a suitable solids content and pH value; 4. Add polysorbate-80 (Tween 80) and lecithin to the system in step 3, and mix and grind them thoroughly using a high-shear homogenizer or grinder to ensure that the surfactant is uniformly and firmly adsorbed on the surface of each particle and to break up any soft agglomerates that may exist. 5. Adjust the pH, viscosity, and fineness of the final slurry as needed to obtain the final water-based slurry.

[0031] Untreated nano-titanium dioxide (especially that used for sun protection) is prone to agglomeration and cannot be stably dispersed in water. Hydrated silica, a porous amorphous silica with a high specific surface area, can coat the surface of titanium dioxide particles like a layer of "sand" through physical adsorption, forming a rough intermediate layer rich in silanol (-SiOH) groups. These -SiOH groups are strongly hydrophilic and can form hydrogen bonds with water molecules. The hydrophilic surface treatment is equivalent to building an intermediate framework with a large number of hydrophilic "handles" outside the titanium dioxide core. At this time, polysorbate-80, which has hydrophilic polyoxyethylene ether long chains and lipophilic fatty acid chains, has its lipophilic fatty acid chains anchored to the silica-modified titanium dioxide surface, while the hydrophilic polyoxyethylene ether long chains strongly extend into the aqueous phase, forming steric hindrance and preventing particles from agglomerating. Lecithin is a natural amphiphilic phospholipid, possessing both hydrophobic fatty acid chains and hydrophilic phosphocholine groups. It can synergistically interact with polysorbate-80 and adsorb onto the powder surface, with the hydrophilic head facing outwards, further enhancing its hydrophilicity. The titanium dioxide particles as a whole exhibit extremely strong hydrophilicity and dispersion stability, easily integrating into oil-in-water systems. This hydrophilic surface treatment ensures that titanium dioxide can be stably and uniformly dispersed in the aqueous phase (continuous phase) over a long period.

[0032] The oleophilic micro-sized titanium dioxide slurry (used as an internal phase filler and water-resistant enhancer in sunscreens) has an average primary particle size of 1-10 μm and undergoes a hydrophobic surface treatment with triethoxyoctylsilane. The hydrophobic surface treatment can be performed as follows: 1. First, place the untreated micron-sized titanium dioxide powder in an oven and dry it for later use; 2. Dissolve triethoxyoctylsilane in a mixed solvent of ethanol and water, adjust the pH to 4.0-5.5 with acetic acid or dilute hydrochloric acid, and stir to hydrolyze; 3. Add the dried micron-sized titanium dioxide powder to a high-speed mixer, and spray the above hydrolysate in a mist while stirring to ensure uniform spraying and carry out the chemical reaction; 4. After the reaction is complete, centrifuge the product and wash it 1-2 times with a small amount of ethanol to remove unreacted silane. Then dry and sieve the product to obtain the corresponding micron-sized hydrophobic titanium dioxide powder. 5. Add dibutyl adipate (as the main dispersion medium and steric hindrance stabilizer) to the dispersion vessel, and add micron-sized hydrophobic titanium dioxide powder while stirring; 6. Disperse at high speed until a uniform paste is formed, then put the pre-dispersed slurry into a ball mill and grind it in a circulating manner until the fineness meets the standard.

[0033] The ethoxy group of triethoxyoctylsilane undergoes hydrolysis and condenses with the hydroxyl groups on the surface of titanium dioxide to form a strong Ti-O-Si covalent bond. When titanium dioxide with octyl chains grafted onto its surface is dispersed in dibutyl adipate, the long-chain molecules of dibutyl adipate exhibit good compatibility and entanglement with the octyl chains on the particle surface, forming an adsorption layer around the particles. This constitutes a combination of "chemical bonding anchoring + solvation long-chain steric hindrance." The first layer, permanently anchored by silane covalent bonds, solves the "desorption" problem; the second layer, formed by dibutyl adipate as a dense steric hindrance layer, solves the "powder agglomeration" problem. As a nonpolar or weakly polar ester solvent, dibutyl adipate exhibits good affinity with hydrophobic surfaces, reducing interfacial energy, effectively isolating and preventing powder particles from re-agglomerating, and synergistically improving spreadability and skin feel. This achieves uniform and stable dispersion of micron-sized titanium dioxide powder in the oil phase, while also filling fine lines and providing soft-focus effects. This hydrophobic surface treatment ensures that micron-sized titanium dioxide can be firmly locked inside the oil phase (dispersed phase) droplets.

[0034] In this embodiment, the mass ratio of the solid content of titanium dioxide in the hydrophilic nano-titanium dioxide slurry to the oleophilic micron-sized titanium dioxide slurry ranges from 1:0.5 to 1:1. The synergistic mechanism between the hydrophilic nano-titanium dioxide slurry and the oleophilic micron-sized titanium dioxide slurry lies in the balance of structured film formation: at this ratio, the aqueous phase nanoparticles are sufficient to form a continuous and complete substrate film, while the number of oil phase micron-sized particles is just enough to fully fill the gaps in the film without excessive aggregation that would damage the uniformity of the film. Together, they construct a gradient, structured composite sunscreen film of "nano-substrate-micron reinforcement". This ratio results in a synergistic leap in the product's water resistance and optical performance, and is also the critical point for long-term physical stability. This combination, through directional distribution and gradient film formation in the two phases, ensures a high SPF value while improving the product's high water resistance and natural brightening effect, and avoids problems such as delamination and precipitation caused by high temperatures or long-term storage. This allows sunscreens prepared based on this combination to maintain excellent sensory experience and functional consistency under different environmental conditions.

[0035] <Example 2> This embodiment provides a high-protection, brightening, water-in-oil physical-chemical sunscreen system comprising the dual-phase powder-based formula of Embodiment 1, specifically a sunscreen emulsion. By weight, the water-in-oil sunscreen emulsion comprises the following components: 5-20 parts of chemical sunscreen; 1-6 parts of oil-in-water emulsifier; Film-forming agent 0.5~2 parts; 5-20 parts of moisturizer; 4-6.5 parts of hydrophilic nano-titanium dioxide powder slurry; 1.5 to 4 parts of oleophilic micron-sized titanium dioxide powder slurry; Colorant 0.01~0.02 parts; Thickener 0.2~0.6 parts; 5-10 parts of moisturizer; 1-2 parts of filler powder; Antioxidant 0.3~0.5 parts; Water balance; The mass ratio of titanium dioxide solid content in the hydrophilic nano titanium dioxide slurry to that in the oleophilic micron titanium dioxide slurry is 1:0.5~1.

[0036] Among them, chemical sunscreens are four or more of the following: ethylhexyl methoxycinnamate, bis-ethylhexyloxyphenol methoxyphenyl triazine, diethylaminohydroxybenzoylhexyl benzoate, ethylhexyl triazine ketone, and homosalate.

[0037] The emulsifier is one or more of sucrose polystearate, cetyl palmitate, polysorbate-60, or potassium cetyl phosphate.

[0038] The emollient is one or more of the following: polydimethylsiloxane, dibutyl adipate, poly(C10-30) alkanol acrylate, dioctyl carbonate, propylene glycol carbonate, and isododecane.

[0039] The film-forming agent is hydrogenated polycyclopentadiene.

[0040] The moisturizer is one or more of glycerin, butylene glycol, or pentanediol.

[0041] The antioxidant is p-hydroxyacetophenone.

[0042] The thickeners are ammonium acryloyl dimethyl taurate / VP copolymer, xanthan gum, and silachlorite. The mass ratio of ammonium acryloyl dimethyl taurate / VP copolymer to xanthan gum is 3:1.

[0043] The filler powder is one or more of silica, talc or mica, with a particle size of 5~15μm, which helps to improve the spreadability and skin feel of the formula.

[0044] The colorant is an iron oxide, including one or more of iron oxide red, iron oxide yellow, or iron oxide black.

[0045] As a further preferred technical solution, the water-in-oil sunscreen emulsion in this embodiment may specifically be composed of, for example, the following components in parts by weight: Phase A: 2 parts of sucrose polystearate and cetyl palmitate 9 parts of ethylhexyl methoxycinnamate 1.5 parts of bis-ethylhexyloxyphenol methoxyphenyl triazine 2.5 parts of diethylaminohydroxybenzoyl benzoate 1 part of ethylhexyl triazine 2.5 parts of homosalate 1 part of polyC10-30 alkyl acrylate 1 part of silachlorite hydrate, dioctyl carbonate and propylene glycol carbonate 1 part hydrogenated polycyclopentadiene and isododecane 3 parts of polydimethylsiloxane 5 parts of dibutyl adipic acid 1.5 parts silica; Phase B: 2.25 parts of oleophilic micronized titanium dioxide powder slurry 0.012 parts of iron oxide; Phase C: 5 parts of butylene glycol 3 parts pentylene glycol 0.1 parts xanthan gum 0.3 parts of ammonium acryloyldimethyl taurate / VP copolymer 0.25 parts of p-hydroxyacetophenone 0.5 parts of potassium cetyl phosphate Polysorbate-60 0.5 parts Add deionized water to a total of 100 parts; Phase D: Five parts of hydrophilic nano-titanium dioxide powder slurry.

[0046] In the "two-phase powder distribution" design of the water-in-oil sunscreen system of this embodiment, the nano-titanium dioxide in the aqueous phase evaporates rapidly with the water, forming a uniform and transparent basic sunscreen film on the skin surface, providing instant brightening. The micron-sized hydrophobic titanium dioxide in the oil phase is then released, physically filling any microscopic gaps in the nanofilm. Due to its stronger light scattering ability, it significantly enhances UV protection, synergistically improving SPF and water resistance. Simultaneously, the nanoparticles provide transparent brightening, while the micron-sized particles produce a soft-focus effect; the combination of these two elements achieves a natural, three-dimensional, and non-whitening skin tone correction.

[0047] In a more preferred embodiment, the water-in-oil physicochemical sunscreen emulsion in this example is prepared according to the following steps: S1. Mix the A phase raw materials and heat to 75~80℃ while stirring until completely dissolved; S2. After premixing the B phase raw material evenly, add the A phase and stir homogenously at 75~80℃ for 20 minutes to fully disperse the oleophilic micron titanium dioxide powder slurry. S3. Mix the C phase raw materials, stir and heat to 75~80℃, and wait until the xanthan gum and ammonium acryloyl dimethyl taurate / VP copolymer are completely swollen to form a homogeneous aqueous solution; S4. Slowly add the oil phase obtained in S2 to the aqueous phase obtained in S3, start homogenization emulsification at 75~80℃, set the speed to 3000rpm, and continue emulsification for 3~5 minutes to form a homogeneous emulsion system; S5. Cool the emulsion system obtained in S4 to below 50°C (preferably 40~50°C), add D-phase hydrophilic nano titanium dioxide powder slurry pre-dissolved in a small amount of deionized water, and homogenize at low speed until the system is completely homogeneous and stable, avoiding the introduction of too many air bubbles. S6. Bottle and discharge the material to obtain the final stable water-in-oil physicochemical sunscreen.

[0048] The sunscreen emulsion in this embodiment not only comprises hydrophilic nano-titanium dioxide powder and oleophilic micron-sized titanium dioxide powder, but its preparation process also closely serves the construction of this synergistic two-phase powder combination: the addition of the hydrophilic nano-titanium dioxide powder is staged after the emulsification system is completed and cooled to 40-50°C. This "low-temperature post-addition" process is crucial, on the one hand to avoid the high-temperature emulsification process from damaging its hydrophilic surface modification layer, ensuring long-term dispersion stability in the aqueous phase, and on the other hand to prevent it from being encapsulated by the oil phase or undergoing interfacial migration at high temperatures, thereby ensuring that it is positioned in the aqueous phase (external phase) and realizing its design function of "external phase film formation and optical brightening".

[0049] The following examples further verify the technical effects of the dual-phase powder combination in Example 1 and the water-in-oil physical-chemical sunscreen in Example 2.

[0050] <Application Example 1> In this application example, an oil-in-water physical and chemical sunscreen emulsion was prepared according to the method in Example 2. The specific formula by weight is shown in Table 1.

[0051] Table 1. Components of sunscreens in Application Examples 1-3 and Comparative Examples 1-5

[0052] <Application Example 2> The formulation is shown in Table 1. The only difference between this application example and Application Example 1 is the amount of oleophilic micronized titanium dioxide slurry used. Specifically, in this application example, the mass proportion of oleophilic micronized titanium dioxide slurry in the system is increased from 2.25% to 3.25%.

[0053] <Application Example 3> The formulation is shown in Table 1. The only difference between this application example and Application Example 1 is the amount of oleophilic micronized titanium dioxide slurry used. Specifically, in this application example, the mass proportion of oleophilic micronized titanium dioxide slurry in the system is reduced from 2.25% to 1.65%.

[0054] <Comparative Example 1> The formulations are shown in Table 1. As a baseline control, the two-phase slurry combination in Application Example 1 was excluded, and only colorants (iron oxides) were included to evaluate the basic performance without powder synergy.

[0055] <Comparative Example 2> The formulation is shown in Table 1. It contains only lipophilic micronized titanium dioxide powder paste, which is used to verify whether the product's water resistance, brightening effect, and skin feel are intact when hydrophilic nano-titanium dioxide powder paste is missing.

[0056] <Comparative Example 3> The formulation is shown in Table 1. It contains only hydrophilic nano-titanium dioxide powder paste, which is used to verify whether the water resistance and modification effect of the product are sufficient when oleophilic micron-sized titanium dioxide powder paste is lacking.

[0057] <Comparative Example 4> The formulation is shown in Table 1. An imbalance in the ratio of the two-phase powder paste was achieved (the amount of hydrophilic nano-titanium dioxide powder paste was halved, below the lower limit of the ratio) to investigate the changes in system stability, water resistance, and brightening effect when the hydrophilic nano-titanium dioxide powder paste was insufficient, and to verify the lower limit critical point of the ratio.

[0058] <Comparative Example 5> The formulation is shown in Table 1. The ratio of the two-phase powder paste was made unbalanced (the amount of lipophilic micronized titanium dioxide powder paste was doubled, exceeding the upper limit of the ratio) to investigate the changes in system stability, water resistance, skin feel, and makeup effect (whether it looks fake white) when the lipophilic micronized titanium dioxide powder paste was in excess, and to verify the upper limit critical point of the ratio.

[0059] <Test Example 1> Table 1 shows the particle size of each sunscreen formulation as observed using a LEICA DM2700M microscope. Figure 1 As shown, under the same magnification, it is obvious that the particle size of Comparative Example 4 and Comparative Example 5 is significantly larger.

[0060] Using the LUMiSizer (a laboratory instrument for analyzing and predicting the stability of dispersions such as emulsions and suspensions), centrifugation accelerates the sedimentation or flotation of particles in a sample, shortening an unstable process that might take months or even years in reality to a few hours within the instrument. During centrifugation, a parallel light source (near-infrared or blue light) penetrates the rotating sample tube, and a high-precision sensor continuously monitors changes in transmittance along the entire sample length. The resulting spectrum accurately displays particle migration speed, separation interface formation, etc., thereby quantifying stability. LUMiSizer test results are shown below. Figure 2 and Figure 3 As shown.

[0061] from Figure 2 and Figure 3 The graphs show that both Comparative Examples 4 and 5 exhibited oil release under high-temperature accelerated centrifugation. This indicates that in the presence of both phases of powder, increasing the amount of lipophilic micron-sized titanium dioxide slurry and decreasing the amount of hydrophilic nano-sized titanium dioxide slurry leads to instability in the formulation system. Increasing the amount of lipophilic micron-sized titanium dioxide slurry exacerbates this problem. In contrast, Application Examples 1-3 and Comparative Examples 1-3 showed uniform particle size distribution and good system stability, without significant stratification or oil release. These results suggest that only when the solid content ratio of hydrophilic nano-sized titanium dioxide to lipophilic micron-sized titanium dioxide is within the range of 1:0.5 to 1:1 (Application Examples 1-3) can the sunscreen emulsion system maintain high homogeneity and stability under accelerated centrifugation. An imbalance in the ratio, especially an excess of lipophilic powder (Comparative Example 5), leads to excessive structuring of the oil phase, resulting in severe oil release and particle agglomeration (significantly increased particle size). This microstructural instability directly foreshadows defects in macroscopic film-forming properties and provides the root cause of the subsequently observed water resistance collapse. This demonstrates the crucial role of scale range in maintaining the integrity of the entire synergistic system architecture.

[0062] <Test Example 2> This test example uses the standard in vitro testing method of Colipa 2011 to evaluate the sun protection effect of the sunscreen lotion formulations by measuring the ultraviolet absorbance or transmittance of the sunscreen lotion formulations in Application Examples 1-3 and Comparative Examples 1-5. This test example uses a UV2000s sun protection factor analyzer (manufactured by Labsphere).

[0063] The sample was evenly applied to a polymethyl methacrylate (PMMA) plate. After being protected from light for 30 minutes, the pre-bath SPF value of each group of samples was tested using an ultraviolet light transmission analyzer. Then, each group of PMMA plates was placed at the bottom of a container, ensuring that the plate surface was parallel to the water flow direction. After immersion for 40 minutes, the plates were removed and dried in the dark for 1 hour. The post-bath SPF value was then tested. The waterproof performance retention rate was calculated according to the formula: %WRtn = SPFtn / SPFt0 × 100, where: SPFt0 represents the initial SPF value before immersion, and SPFtn represents the SPF value after immersion (n represents the immersion time). The waterproof performance of each group of products was evaluated in this way, and the results are shown in Table 2.

[0064] Table 2. Results of SPF and water resistance tests for sunscreens in Application Examples 1-3 and Comparative Examples 1-5. Sample / Indicator SPF before bathing Post-bath SPF Water resistance retention rate / % Waterproof products Application Example 1 243 221 90.95 yes Application Example 2 240 217 90.42 yes Application Example 3 235 212 90.21 yes Comparative Example 1 118 38 32.20 no Comparative Example 2 128 68 53.13 yes Comparative Example 3 123 70 56.91 yes Comparative Example 4 173 78 45.09 no Comparative Example 5 234 114 48.72 no According to industry standards, the average % WR of waterproof products is ≥ 50%, while the average % WR of non-waterproof products is < 50%. As can be seen from the results of comparative examples 2 and 3, adding any phase of powder alone will increase the post-bath value.

[0065] The water resistance data in Table 2 convincingly demonstrate the synergistic effect of the two-phase powder slurry combination. In Application Examples 1-3, the SPF retention rate after bathing was unexpectedly stable at over 90% at their respective proportions, forming a significant high-performance platform. In contrast, Comparative Examples 2 and 3, containing only single-phase powder, had a retention rate of only ~55%, indicating that a single functional unit cannot construct an efficient water-resistant film. More importantly, Comparative Examples 4 and 5 show that using powders exceeding the specified proportions leads to decreased formulation stability, uneven film formation, and indirectly reduced water resistance; even with a relatively high SPF value before bathing, the water resistance immediately experiences a "cliff-like drop" (retention rate <50%). This result is completely consistent with the structural instability observed in Test Example 1. Therefore, the synergistic effect of the hydrophilic nano-titanium dioxide powder slurry and the oleophilic micro-titanium dioxide powder slurry not only affects system stability but also directly influences film uniformity and waterproof performance.

[0066] The results of this test strongly demonstrate that the mass ratio of titanium dioxide solid content in hydrophilic nano-titanium dioxide slurry to oleophilic micron-sized titanium dioxide slurry (1:0.5~1:1) is a "critical performance ratio." Within this ratio, the two-phase slurry produces a water-resistant enhancement effect (1+1>2) through a "gradient-structured synergistic film formation" mechanism; however, once deviated from this ratio, the synergistic effect disappears, and the performance regresses or even falls below the normal level. This highly ratio-sensitive, non-linear performance change cannot be predicted by those skilled in the art through conventional optimization.

[0067] <Test Example 3> This test case examines the synergistic effect of the optical properties of sunscreen formulations corresponding to Examples 1-3 and Comparative Examples 1-5. Ideally, brightening should simultaneously increase the L value (brightness) and optimize the a and b* values ​​(reducing unnatural red / yellow tones). This experiment uses a high-precision portable spectrophotometer CM-26dG to test the change in skin brightness (ITA value) before and after sunscreen application. This instrument employs a d / 8 integrating sphere optical structure, enabling precise measurement of the color of object surfaces. The results are shown in Table 3, where the blank group represents the original color of skin without any sample applied.

[0068] As shown in Table 3, adding only iron oxide darkens the skin (Comparative Example 1), while adding only lipophilic micronized titanium dioxide powder (Comparative Example 2) provides better coverage than adding only hydrophilic nano-titanium dioxide powder (Comparative Example 3). Reducing the content of hydrophilic nano-titanium dioxide (Comparative Example 4) decreases skin translucency, while increasing the content of lipophilic micronized titanium dioxide (Comparative Example 5) increases whiteness and improves coverage, but also increases the appearance of a fake white complexion. Examples 1-3 represent the optimal ratio while ensuring long-term product stability and balancing skin brightening with a natural makeup look; their ITA values ​​are significantly improved, indicating excellent color-correcting effects. While Comparative Example 5 has high whiteness, it exhibits a noticeable fake white appearance. Examples 1-3 show better coordination in L*, a*, and b* values, appearing closer to a healthy skin tone, making them suitable for daily use by Asian skin types and possessing good market application prospects. Further data on reflectance wavelengths (such as...) show... Figure 4 As shown in the examples 1-3, the application exhibits more uniform scattering characteristics in the visible light range, effectively reducing color cast and improving skin tone uniformity. Combined with optical modification principles, it achieves a natural brightening effect similar to "no-makeup makeup".

[0069] The results in this test case can be attributed to the specific combination and ratio of biphase titanium dioxide particle sizes in the biphase powder composition. The hydrophilic nano-titanium dioxide powder provides a transparent base for brightening, while the oleophilic micron-sized titanium dioxide powder produces a soft-focus effect. At the optimal ratio, the two achieve an ideal balance in visible light scattering, thus simultaneously resolving the long-standing industry contradiction between "brightening" and "naturalness." Comparative Example 3, containing only nano-titanium dioxide powder, lacks sufficient brightening and has poor coverage; Comparative Example 2, containing only micron-sized titanium dioxide powder, results in a heavy makeup look. This further confirms the indispensability of the biphase design and its specific ratio.

[0070] Table 3. Color change indicators of each group of water-in-oil physical-chemical sunscreen lotions applied to the skin

[0071] <Test Example 4> Ten skin feel reviewers with an average age of 25 were selected to evaluate the refreshing feel of sunscreens in test cases 1-3 and comparative examples 1-5, respectively. The evaluation method assigned specific scores from 1 to 10 for sensory skin feel indicators (higher scores indicate better user experience), and the average score was used as the user experience evaluation result, as shown in Table 4.

[0072] In this test example, the coating applicator was first sprayed with 95% alcohol and wiped clean. The same weight of foundation sample was then dropped onto one end of the coating test card. The sample was spread evenly on the paper. The four-sided coating applicator (BYK Chemical (Tongling) Co., Ltd.) of the automatic coating machine was placed on the front end of the sample on the card (near the starting end of the automatic coating machine), with the 120 μm thick side of the applicator facing down. The speed of the automatic coating machine was set to 100 mm / s to perform the coating operation on the sample.

[0073] Table 4. The lightness of sunscreens in Application Examples 1-3 and Comparative Examples 1-5

[0074] As shown in Table 4, the spreading properties of Application Examples 1-3 are quite similar to those of Comparative Examples 2, 4, and 5. However, comparing Application Example 1 with Comparative Example 5 reveals that increasing the oleophilic micronized titanium dioxide slurry reduces the lightness, because excessive internal phase powder makes the material thicker and stickier. Comparing Application Example 1 with Comparative Example 4 shows that decreasing the hydrophilic nano-titanium dioxide slurry also reduces the lightness. The hydrophilic nano-titanium dioxide slurry improves the spreadability of the oil-in-water product and helps form a uniform, breathable film, avoiding the heavy, closed feeling of oil-in-water products. Application Examples 1-3 exhibit superior fluidity and extensibility during spreading, resulting in a light and breathable feel after film formation, significantly better than the comparative examples.

[0075] The results demonstrate that the specific ratio of the two-phase powder foundation combination not only ensures functionality but also guarantees a comfortable feel on the skin. Furthermore, the addition of the hydrophilic nano-titanium dioxide powder foundation at low temperatures ensures its complete hydration layer, thus forming a breathable film on the skin; an appropriate amount of lipophilic micronized titanium dioxide powder is locked within the oil phase, avoiding the heavy feeling that would result from direct skin contact. Therefore, the synergistic effect of the hydrophilic nano-titanium dioxide powder foundation and the lipophilic micronized titanium dioxide powder foundation in a specific ratio not only ensures sun protection performance but also effectively balances lightness and coverage, meeting consumers' core demand for a "natural makeup feel" and breaking the stereotype that "high protection must be heavy."

[0076] Secondly, by using a black and white cardstock background, the true color of the product after application can be more accurately determined, as well as whether it may produce an unnatural grayish-white tone on the skin (especially noticeable in the black area). By comparing the degree to which the samples cover the black and white grids, its ability to cover blemishes (black area) or its potential to present a natural and clear makeup effect (white area) can be visually judged. A comprehensive observation of the performance in both black and white areas reveals (results are as follows) Figure 5 As shown in the figures, Application Examples 1-3 exhibit excellent natural transitions in both black and white areas, with no obvious boundary, indicating that they can achieve harmonious integration against different skin tone backgrounds. While the coating and spreading results of Comparative Examples 2 and 4 on black and white cardstock backgrounds are not significantly different from Application Examples 1-3, as mentioned earlier, due to the absence of hydrophilic nano-titanium dioxide powder or a reduced amount of hydrophilic nano-titanium dioxide powder, their stability, sun protection, and water resistance are poor. Comparative Example 5, although showing significant brightening in bright areas, has excessive coverage in dark areas, easily forming color blocks and affecting overall adherence. The results in this test further demonstrate that Application Examples 1-3 benefit from the synergistic regulation of hydrophilic nano-titanium dioxide powder and oleophilic micronized titanium dioxide powder, which reduces interfacial tension, promotes uniform dispersion of the emulsion system, and thus improves the film's extensibility and transparency.

[0077] This disclosure proposes the theory of "directional distribution and synergistic film formation of biphase powder" and, for the first time, reveals and verifies the key ratio of hydrophilic nano-titanium dioxide to lipophilic micro-titanium dioxide solid content of 1:0.5 to 1:1. This innovatively solves the industry problem that water-in-oil sunscreen systems cannot simultaneously achieve high water resistance, natural brightening, high load stability, and a refreshing skin feel. Test data fully demonstrates that this ratio is the decisive factor in producing unexpected technical effects such as >90% ultra-high water resistance and a natural optical makeup effect. Deviating from this ratio results in a synergistic collapse of all performance characteristics. The innovative application of this biphase powder provides new ideas and technical support for the formulation design of water-in-oil physical and chemical sunscreens.

[0078] The embodiments and application examples described above are merely illustrative descriptions of this disclosure and are not intended to limit the scope of this disclosure. Any modifications and improvements made by those skilled in the art to the technical solutions of this disclosure without departing from the spirit of this disclosure should fall within the protection scope defined by this disclosure.

Claims

1. A two-phase slurry composition, characterized in that, include: Hydrophilic nano-titanium dioxide slurry, 4~6.5 parts by weight; and Oil-loving micron-sized titanium dioxide slurry, 1.5~4 parts by weight; The nano-sized titanium dioxide in the hydrophilic nano-titanium dioxide slurry undergoes hydrophilic surface treatment with hydrated silica and lecithin, and the average primary particle size is 10~100 nm. The micron-sized titanium dioxide in the oleophilic micron-sized titanium dioxide slurry undergoes hydrophobic surface treatment with triethoxyoctylsilane, resulting in an average primary particle size of 1~10 μm. The solid mass ratio of the nano-sized titanium dioxide to the micron-sized titanium dioxide is 1:0.5 to 1:

1.

2. The two-phase slurry combination according to claim 1, characterized in that, The hydrophilic nano-titanium dioxide slurry comprises, by weight percentage: 40-45% of the aforementioned nano-sized titanium dioxide, 30-40% of butanediol, 15-25% of hydrated silica, 1-1.5% of lecithin and 1.5-2.5% of polysorbate-80.

3. The two-phase slurry combination according to claim 1, characterized in that, The oleophilic micron-sized titanium dioxide slurry comprises, by mass percentage: 60-70% of the micron-sized titanium dioxide, 1-1.5% of triethoxyoctylsilane and 30-35% of dibutyl adipate.

4. The application of a biphasic powder composition according to any one of claims 1 to 3 in an oil-in-water sunscreen system.

5. The application according to claim 4, characterized in that, The water-in-oil sunscreen system includes a water-in-oil emulsifier, a thickener, an aqueous phase, and an oil phase; In the biphase slurry combination, the hydrophilic nano-titanium dioxide slurry is dispersed in the aqueous phase, and the oleophilic micron-sized titanium dioxide slurry is dispersed in the oil phase.

6. The application according to claim 5, characterized in that, The aqueous phase includes humectants and antioxidants, and the oil phase includes film-forming agents and filler powders.

7. The application according to claim 6, characterized in that, The moisturizer includes one or more of glycerin, butylene glycol or pentanediol; The antioxidant includes p-hydroxyacetophenone; The film-forming agent includes hydrogenated polycyclopentadiene; The filler powder includes one or more of silica, talc, or mica.

8. The application according to claim 5, characterized in that, The thickeners include ammonium acryloyldimethyl taurate / VP copolymer, xanthan gum, and silachlorite hydropyrite. The oil-in-water emulsifier includes one or more of sucrose polystearate, cetyl palmitate, polysorbate-60, or potassium cetyl phosphate.

9. A water-in-oil sunscreen system comprising the biphasic powder-based formula according to any one of claims 1 to 3, characterized in that, Based on 100 parts by weight, it includes: 5-20 parts of chemical sunscreen; 1-6 parts of oil-in-water emulsifier; Film-forming agent 0.5~2 parts; 5-20 parts of moisturizer; 4-6.5 parts of hydrophilic nano-titanium dioxide powder slurry; 1.5 to 4 parts of oleophilic micron-sized titanium dioxide powder slurry; Colorant 0.01~0.02 parts; Thickener 0.2~0.6 parts; 5-10 parts of moisturizer; 1-2 parts of filler powder; Antioxidant 0.3~0.5 parts; Water balance; The solid mass ratio of nano-sized titanium dioxide to micron-sized titanium dioxide is 1:0.5 to 1:

1.

10. A method for preparing the water-in-oil sunscreen system according to claim 9, characterized in that, Includes the following steps: S1. Mix the oil-in-water emulsifier, emollient, chemical sunscreen and film-forming agent to obtain phase A, heat to 75~80℃ and stir until completely dissolved; S2. Uniformly mix the oleophilic micron-sized titanium dioxide powder slurry and colorant to obtain phase B, add phase A, and homogenize and stir at 75~80℃ until phase A is completely dispersed to obtain the oil phase; S3. Mix water, humectant, thickener, antioxidant and oil-in-water emulsifier to obtain phase C, stir and heat to 75~80℃ until the thickener is completely swollen to form an aqueous phase; S4. The oil phase is slowly added to the aqueous phase, and homogenized and emulsified at 75~80°C to form a uniform emulsion system; S5. Cool the emulsified system to below 50°C, add hydrophilic nano-titanium dioxide powder slurry, and stir until the system is homogeneous and stable to obtain the water-in-oil sunscreen system.

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