White oil nano-emulsion, preparation process and application of white oil nano-emulsion in personal care products

Abstract

The invention relates to the technical field of care products, in particular to a white oil nano-emulsion, a preparation process and application of the white oil nano-emulsion in personal care products. The emulsion comprises the following raw materials: white oil with the viscosity of 5-30cSt, a compound emulsifier, a co-emulsifier, a water phase regulator and the balance of deionized water. According to the invention, through molecular design of single white oil and a specific compound emulsifier, and in combination with a process path of sectional temperature control and stepped energy input, a synergistic effect is achieved from two aspects of molecular interface behavior and macroscopic preparation process; the problems of sticky skin feeling, easy layering and the like caused by large particle size and unstable interface of the traditional white oil emulsion are fundamentally solved, and the white oil nano-emulsion which is high in stability, excellent in refreshing skin feeling, good in mildness and suitable for large-scale production is successfully prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of care products, in particular to a white oil nanoemulsion, a preparation process and application in personal care products. BACKGROUND

[0002] In the field of personal care products, the performance of raw materials directly determines the use experience, stability and safety of the product. Among them, oil-based ingredients, as one of the core raw materials, bear the key functions of moisturizing, nourishing, repairing and film-forming, and are an indispensable part of product systems such as skin care, hair care and makeup products.

[0003] White oil (mineral oil) as a kind of deeply refined mineral oil, has the remarkable advantages of stable chemical properties, no odor, low irritation, strong compatibility, etc., and also has excellent lubricity, sealing and anti-static properties, so it is widely used in many kinds of personal care products such as cream, emulsion, hair conditioner and makeup remover, which can effectively reduce skin water loss, improve dry and rough skin state, and improve the smoothness and comfort of the product.

[0004] However, the application of traditional white oil in personal care products still faces the following technical bottlenecks: On the one hand, white oil is a typical hydrophobic substance, and its compatibility with water phase system is poor. Directly added to water-based formula, it is easy to have stability problems such as stratification, oil floating and precipitation, and often needs to rely on a large amount of emulsifier for dispersion. Excessive emulsifier not only may cause skin irritation or allergy risk, but also affects the overall mildness of the product; On the other hand, the particle size of white oil emulsion prepared based on traditional emulsification process is usually micron level, resulting in low transparency of product appearance, thick and sticky skin feel, obvious oil film feeling after application, and difficulty in meeting the current market demand for "light, thin and easy to absorb" care quality. In addition, such large particle size emulsion is easy to be affected by temperature changes and mechanical shearing during storage, transportation or use, and demulsification, stratification and other phenomena occur, which seriously affect the shelf life and actual use effect of the product.

[0005] In summary, the current application of white oil in personal care products is still limited by its poor compatibility with water phase and the insufficient skin feel and stability caused by large particle size of traditional emulsion, while the existing nanoemulsion preparation technology also faces the problems of complex process, high cost and imperfect application system, which restricts its further application in high-quality care products with high efficiency, mildness and superior experience. SUMMARY

[0006] The purpose of this invention is to overcome the problems of poor compatibility, insufficient emulsion stability, and heavy skin feel of traditional white oil in water-based personal care product systems, as well as the complex preparation process, high cost, and imperfect application system of existing nanoemulsions. The invention provides a white oil nanoemulsion solution that combines excellent stability, refreshing skin feel, and gentleness, and is suitable for large-scale production.

[0007] The purpose of this invention is to provide a white oil nanoemulsion, its preparation process, and its application in personal care products. By using a simplified single oil phase and a specific composite emulsification system with low addition amount, a white oil nanoemulsion with excellent stability, refreshing skin feel, and gentleness can be prepared.

[0008] To achieve the above objectives, one objective of this invention is to provide a white oil nanoemulsion comprising the following raw materials in the following mass percentages: The composition consists of 10-20% white oil with a viscosity of 5-30 cSt, 3-5% composite emulsifier, 1-2% co-emulsifier, 0.15-0.40% aqueous phase conditioner, and the balance being deionized water. The composite emulsifier comprises polyglycerol fatty acid esters with an HLB value of 12-14 and cocamidopropyl betaine, and the weight ratio of polyglycerol fatty acid esters to cocamidopropyl betaine is 1-3:1.

[0009] As a further improvement to this technical solution, the co-emulsifier is glycerol or propylene glycol.

[0010] As a further improvement to this technical solution, the aqueous phase regulator is xanthan gum or hydroxyethyl cellulose.

[0011] The white oil with a viscosity of 5-30 cSt serves as a single oil-phase base component, providing the system with the necessary spreadability, lubricity, and sealing properties. Its defined viscosity range ensures a balance between a refreshing feel and moisturizing performance in the final emulsion. The composite emulsifier is composed of polyglycerol fatty acid ester with an HLB value of 12-14 and cocamidopropyl betaine. The polyglycerol fatty acid ester penetrates into the oil phase with its long-chain hydrophobic structure and forms steric hindrance, while cocamidopropyl betaine anchors to the outside of the interface with its zwitterionic properties to provide electrostatic repulsion and a hydration layer. The two work together to construct a high-strength composite interface film with both spatial and electrostatic stability. The co-emulsifier, acting as an interface modifier and moisturizing factor, assists emulsification by reducing interfacial tension and increases the consistency of the aqueous phase to inhibit droplet aggregation, while simultaneously imparting basic moisturizing properties to the final product. The aqueous phase modifier, acting as a continuous phase structure enhancer, hydrates in deionized water to form a three-dimensional weak gel network. The deionized water, serving as both the dispersion medium and the continuous phase matrix, constitutes the matrix of the emulsion system, and its purity ensures the fundamental chemical stability of the system. The second object of the present application is to provide a preparation process for preparing the white oil nanoemulsion described above, comprising the following steps: Step S1: weighing raw materials according to mass ratio; Then, in a stirring container, part of the deionized water and the water phase regulator and the co-emulsifier are mixed to prepare a colloidal solution; Step S2: in another container, add white oil, then add the composite emulsifier into the white oil to form an oil phase mixture; Stir and heat the oil phase mixture to make the composite emulsifier completely dissolved in the white oil to form a uniform oil phase-emulsifier premix system; Step S3: add the oil phase-emulsifier premix system into the colloidal solution in the heat preservation container through a homogenizing stirrer, then keep shearing for 5-10 min to complete the dispersion and preliminary emulsification of the oil phase in the water phase to form a coarse emulsion; Transfer the above coarse emulsion to a high-pressure homogenizer for homogenization circulation; Step S4: transfer the emulsion to a cooling kettle for stirring, and open the cooling water to cool the emulsion to room temperature, and add the remaining deionized water to make up for the evaporation loss during the cooling process; Finally, filter with 200-400 mesh filter cloth to obtain the white oil nanoemulsion.

[0012] As a further improvement of the present technical solution, in step S1, add 70-80% of the formula amount of deionized water in the stirring container, and stir at 300-500 rpm; Then slowly and evenly sprinkle the water phase regulator into the liquid surface, continue to stir until the water phase regulator is completely hydrated and uniformly dispersed; Then add the co-emulsifier, stir and mix uniformly, and heat the formed water phase to 70-75°C to obtain a colloidal solution.

[0013] As a further improvement of the present technical solution, in step S2, the heating temperature is 70-75°C.

[0014] As a further improvement of the present technical solution, in step S3, the homogenizing stirrer is used to add the oil phase-emulsifier premix system into the colloidal solution in the heat preservation container at 3000-5000 rpm.

[0015] As a further improvement of the present technical solution, in step S3, the homogenization circulation is carried out 1-3 times at a temperature of 50-70°C.

[0016] As a further improvement of the present technical solution, in step S4, the stirring speed in the cooling kettle is 200-400 rpm.

[0017] The third object of the present application is to apply the prepared white oil nanoemulsion to personal care products.

[0018] Compared with the prior art, the present application has the following advantages: In the white oil nanoemulsion, the preparation process and the application in personal care products, the high HLB value polyglyceryl fatty acid ester and cocamidopropyl betaine form a high-efficiency low-addition composite emulsifying system, wherein the polyglyceryl ester is preferentially anchored in the inside of the oil-water interface to form a spatial barrier due to its strong affinity with the long polyglyceryl chain of the white oil molecules, and the betaine molecules are stably distributed on the outside of the interface due to their zwitterionic characteristics, and form a strong hydration layer with the water phase through electrostatic repulsion, and the two work together to build a high-strength composite interface film with both steric hindrance and electrostatic stability. In the phase inversion emulsification process, the slow addition rate of the oil phase to the water phase is strictly controlled, and high-speed shearing is used to guide the system to spontaneously form a water-in-oil primary emulsion and quickly change into an oil-in-water coarse emulsion, and the subsequent high-pressure homogenization is carried out at 50-70℃, through strong cavitation effect and shearing force, the oil droplets in the coarse emulsion are broken to nanoscale, and the composite emulsifier is rearranged on the surface of the new oil droplets to build a thermodynamically stable interface structure, and the water phase regulator network structure is restructured and fully stretched, and finally the structure of the entire nano-dispersion system is solidified, fundamentally solving the problems of traditional white oil emulsion, such as sticky skin feel, easy layering, etc. caused by large particle size and unstable interface, and preparing a white oil nanoemulsion with high stability, excellent refreshing skin feel, good mildness and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The figure is a schematic diagram of the preparation process of the present application. Figure 2 The figure is a schematic diagram of the performance test results of the body lotion. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] The application of traditional white oil in personal care products still faces a series of technical application bottlenecks, such as the application of white oil in personal care products is still limited by the poor compatibility of white oil with water phase, the skin feel and stability problems caused by the large particle size of traditional emulsion. In order to break through the above limitations, nanoemulsion technology has gradually become the research focus of improving the application performance of oil-based raw materials in personal care products. Nanoemulsion is a colloidal dispersion system with particle size of dispersed phase between 10-100 nm, which has the characteristics of high thermodynamic stability, transparent or semi-transparent appearance, good uniformity, etc., which can significantly improve the compatibility of hydrophobic oil and water phase, reduce the amount of emulsifier, and give the product better skin feel and absorption performance.

[0022] However, the preparation of white oil nanoemulsion still has many challenges at present: the existing process depends on complex equipment and high energy consumption process such as high pressure homogenization, ultrasonic emulsification, which is tedious to operate and difficult to scale up; some methods need to use a specific emulsifier compound system, which not only increases the cost of raw materials, but also may cause the emulsion stability to decrease or the skin feel to deteriorate due to improper ratio; at the same time, the application of existing white oil nanoemulsion in products is not strong, and there is no systematic solution that has high stability, good mildness and functional adaptability, so the promotion in high-end personal care products is still limited.

[0023] Therefore, one of the purposes of the present application is to provide a white oil nanoemulsion, which comprises the following mass ratio of raw materials: White oil with viscosity of 5-30 cSt 10-20%, composite emulsifier 3-5%, co-emulsifier 1-2%, water phase regulator 0.15-0.40%, and the balance is deionized water.

[0024] The composite emulsifier comprises polyglyceryl fatty acid ester (polyglyceryl-4 isostearate is preferred in the present application) with HLB value of 12-14 and cocamidopropyl betaine, and the weight ratio of polyglyceryl fatty acid ester to cocamidopropyl betaine is 1-3:1; the co-emulsifier is glycerol or propylene glycol; and the water phase regulator is xanthan gum or hydroxyethyl cellulose.

[0025] The second purpose of the present application is also to provide a preparation process for preparing the above-mentioned white oil nanoemulsion, which comprises the following steps: Step S1: weigh the raw materials according to the mass ratio; Then add about 70-80% of the formula amount of deionized water in the stirring container, and stir at 300-500 rpm. Then slowly and evenly sprinkle the water phase regulator (xanthan gum or hydroxyethyl cellulose) on the liquid surface to avoid clumping. Continue stirring until the water phase regulator is completely hydrated and uniformly dispersed.

[0026] Then add a co-emulsifier (glycerol or propylene glycol) and stir until homogeneous. Heat the resulting aqueous phase to 70-75°C to obtain a colloidal solution, and maintain this temperature for later use.

[0027] Step S2: In another container, add white oil, and then add the composite emulsifier to the white oil to form an oil phase mixture.

[0028] Stir and heat the oil phase mixture to 70-75°C to completely dissolve the composite emulsifier in the white oil, forming a homogeneous oil phase-emulsifier premix system.

[0029] Step S3: Using a homogenizer at 3000-5000 rpm, slowly and uniformly add the above oil phase-emulsifier premix system to the insulated colloidal solution.

[0030] Maintain high-speed shearing for 5-10 minutes to complete the dispersion and initial emulsification of the oil phase in the aqueous phase, forming a crude emulsion. During this process, specific high-HLB value polyglycerol esters and betaine synergistically encapsulate oil droplets even at low addition levels.

[0031] The crude emulsion was transferred to a high-pressure homogenizer and homogenized 1-3 times at a temperature of 50-70°C, with the homogenization pressure set to 80-150 MPa.

[0032] This step is crucial for forming nanoscale emulsions and directly affects the refreshing feel and physical stability of the final product.

[0033] Step S4: Transfer the homogenized emulsion to a cooling vessel equipped with slow stirring (200-400 rpm), turn on the cooling water, and slowly cool the emulsion to room temperature (25-30°C). During the cooling process, the remaining deionized water can be added to make up for evaporation losses.

[0034] When cooled to below 40°C, the final pH value can be adjusted to a mild range of 5.5-7.0 using a small amount of acid or alkali adjuster (such as citric acid or dilute sodium hydroxide solution) according to the product's pH requirements.

[0035] Finally, filter with a 200-400 mesh filter cloth to obtain a clear or semi-transparent, low-viscosity white oil nanoemulsion.

[0036] The following specific embodiments will further illustrate the white oil nanoemulsion, its preparation process, and its application in personal care products provided by the present invention.

[0037] Example 1 Step S1: Weigh out 20% of white oil with a viscosity of 5 cSt, 3% of composite emulsifier, 2% of co-emulsifier, and 0.15% of aqueous phase conditioner according to the mass ratio, with the remainder being deionized water. The composite emulsifier includes polyglycerol fatty acid esters with an HLB value of 12-14, such as polyglycerol-4 isostearate and cocamidopropyl betaine, and the weight ratio of polyglycerol-4 isostearate to cocamidopropyl betaine is 3:1. Next, add approximately 70% of the formula amount of deionized water to the mixing container and stir at 500 rpm. Then, slowly and evenly sprinkle the aqueous phase conditioner (xanthan gum) onto the liquid surface, avoiding clumping. Continue stirring until the aqueous phase conditioner is completely hydrated and evenly dispersed.

[0038] Then add the co-emulsifier (glycerol) and stir until well mixed. Heat the formed aqueous phase to 70°C to obtain a colloidal solution and keep it at this temperature for later use.

[0039] Step S2: In another container, add white oil, and then add the composite emulsifier to the white oil to form an oil phase mixture.

[0040] Stir and heat the oil phase mixture to 75°C to completely dissolve the composite emulsifier in the white oil, forming a homogeneous oil phase-emulsifier premix system.

[0041] Step S3: Using a homogenizer at 3000 rpm, slowly and uniformly add the above oil phase-emulsifier premixed system to the insulated colloidal solution.

[0042] Maintain high-speed shearing for 10 minutes to complete the dispersion and initial emulsification of the oil phase in the aqueous phase, forming a crude emulsion.

[0043] The crude emulsion was transferred to a high-pressure homogenizer and homogenized three times at 50°C with a homogenization pressure of 80 MPa.

[0044] Step S4: Transfer the homogenized emulsion to a cooling vessel equipped with slow stirring (400 rpm), turn on the cooling water, and slowly cool the emulsion to room temperature. Add the remaining deionized water during the cooling process to compensate for evaporation losses.

[0045] Finally, the mixture was filtered through a 200-mesh filter cloth to obtain a white oil nanoemulsion.

[0046] Example 2 Step S1: Weigh out 15% of white oil with a viscosity of 20 cSt, 4% of composite emulsifier, 2% of co-emulsifier, and 0.30% of aqueous phase conditioner according to the mass ratio, with the remainder being deionized water. The composite emulsifier includes polyglycerol fatty acid esters with an HLB value of 12-14, such as polyglycerol-4 isostearate and cocamidopropyl betaine, and the weight ratio of polyglycerol-4 isostearate to cocamidopropyl betaine is 2:1. Next, add approximately 75% of the formulation amount of deionized water to the mixing container and stir at 400 rpm. Then, slowly and evenly sprinkle the aqueous phase conditioner (hydroxyethyl cellulose) onto the liquid surface, avoiding clumping. Continue stirring until the aqueous phase conditioner is completely hydrated and evenly dispersed.

[0047] Then add the co-emulsifier (glycerol) and stir until well mixed. Heat the formed aqueous phase to 70°C to obtain a colloidal solution and keep it at this temperature for later use.

[0048] Step S2: In another container, add white oil, and then add the composite emulsifier to the white oil to form an oil phase mixture.

[0049] Stir and heat the oil phase mixture to 70°C to completely dissolve the composite emulsifier in the white oil, forming a homogeneous oil phase-emulsifier premix system.

[0050] Step S3: Using a homogenizer at 4000 rpm, slowly and uniformly add the above oil phase-emulsifier premixed system to the insulated colloidal solution.

[0051] Maintain high-speed shearing for 8 minutes to complete the dispersion and initial emulsification of the oil phase in the aqueous phase, forming a crude emulsion.

[0052] The crude emulsion was transferred to a high-pressure homogenizer and homogenized twice at a temperature of 60°C. The homogenization pressure was set to 120 MPa.

[0053] Step S4: Transfer the homogenized emulsion to a cooling vessel equipped with slow stirring (300 rpm), turn on the cooling water, and slowly cool the emulsion to room temperature. Add the remaining deionized water during the cooling process to compensate for evaporation losses.

[0054] Finally, the mixture was filtered through a 300-mesh filter cloth to obtain a white oil nanoemulsion.

[0055] Example 3 Step S1: Weigh out 10% of white oil with a viscosity of 30 cSt, 5% of composite emulsifier, 1% of co-emulsifier, and 0.40% of aqueous phase conditioner according to the mass ratio, with the remainder being deionized water. The composite emulsifier includes polyglycerol fatty acid esters with an HLB value of 12-14, such as polyglycerol-4 isostearate and cocamidopropyl betaine, and the weight ratio of polyglycerol-4 isostearate to cocamidopropyl betaine is 1:1. Next, add approximately 80% of the formulation amount of deionized water to the mixing container and stir at 300 rpm. Then, slowly and evenly sprinkle the aqueous phase conditioner (hydroxyethyl cellulose) onto the liquid surface, avoiding clumping. Continue stirring until the aqueous phase conditioner is completely hydrated and evenly dispersed.

[0056] Then add the co-emulsifier (propylene glycol) and stir until homogeneous. Heat the resulting aqueous phase to 75°C to obtain a colloidal solution, and maintain this temperature for later use.

[0057] Step S2: In another container, add white oil, and then add the composite emulsifier to the white oil to form an oil phase mixture.

[0058] Stir and heat the oil phase mixture to 70°C to completely dissolve the composite emulsifier in the white oil, forming a homogeneous oil phase-emulsifier premix system.

[0059] Step S3: Using a homogenizer at 5000 rpm, slowly and uniformly add the above oil phase-emulsifier premix system to the insulated colloidal solution.

[0060] Maintain high-speed shearing for 5 minutes to complete the dispersion and initial emulsification of the oil phase in the aqueous phase, forming a crude emulsion.

[0061] The crude emulsion was transferred to a high-pressure homogenizer and homogenized once at 70°C with a homogenization pressure of 150 MPa.

[0062] Step S4: Transfer the homogenized emulsion to a cooling vessel equipped with slow stirring (200 rpm), turn on the cooling water, and slowly cool the emulsion to room temperature. Add the remaining deionized water during the cooling process to compensate for evaporation losses.

[0063] Finally, the mixture was filtered through a 400-mesh filter cloth to obtain a white oil nanoemulsion.

[0064] White oil nanoemulsions were prepared according to Examples 1-3, and then subjected to sensory evaluation of refreshing skin feel and accelerated testing of mildness and stability.

[0065] 1. Sensory evaluation of refreshing skin feel Based on common sensory analysis methods and cosmetic industry practices, this test uses linear scaling to quantitatively evaluate the refreshing feel (with stickiness as the core indicator) of white oil nanoemulsion.

[0066] I. Sample Preparation Sensory evaluation samples: Take at least 3 independent samples from the same batch of emulsion, 20 mL for each sample, and dispense them into standard sample bottles (e.g., 20 mL transparent glass bottles). Equilibrate the samples in a constant temperature and humidity environment (temperature (25±1)℃, relative humidity (50±5)%) for 24 h.

[0067] II. Testing Environment and Evaluation Team The evaluation was conducted in a dedicated sensory evaluation room with a temperature of (22±2)℃ and a relative humidity of (50±10)%, under uniform lighting and free from interfering odors. Evaluators, numbering no fewer than 10, were selected and trained, familiar with stickiness evaluation, and able to provide accurate quantitative descriptions.

[0068] III. Test Steps a) Evaluation indicators and scale: The main evaluation criteria are the stickiness on the skin immediately after application (0 min), 1 min, and 5 min. A continuous straight line of 15 cm in length is used as the scale, with the left end anchored as "no stickiness" (0 points) and the right end anchored as "extreme stickiness" (15 points).

[0069] b) Sample Presentation: Samples are randomly numbered and presented to evaluators in a single-blind manner. The evaluation order uses a Latin square design to eliminate ordering errors.

[0070] c) Evaluation procedure: The evaluator takes about 0.05 mL of sample and applies it evenly to clean skin on the inside of the forearm (area about 4 cm²). After massaging for 10 seconds in a specified number of circles, the evaluator marks the intensity of the perceived stickiness on the scale line at the specified time point.

[0071] d) Data Recording and Analysis: Measure the distance from each marker point to the left end (accurate to 0.1 cm) as the score for that time point. Calculate the average score for each sample at each time point, using the score 5 minutes after application as the core evaluation indicator for a refreshing feel. Use statistical methods such as analysis of variance (ANOVA) to determine the significance of differences in scores between different samples (p≤0.05). Record the results in Table 1 (Note: The lower the score, the more refreshing the feel. A score ≤3.0 is considered "Excellent," >3.0 and ≤6.0 is considered "Good," and >6.0 indicates insufficient refreshing feel.) 2. Accelerated testing of mildness and stability. This test references general methods for in vitro toxicology and formulation stability studies to evaluate the mildness and physical stability of white oil nanoemulsions.

[0072] I. Sample Preparation Mildness test samples: Dilute the white oil nanoemulsion with cell culture medium (such as DMEM containing 10% fetal bovine serum) to prepare sample extracts with concentrations of 100%, 50%, 25%, and 12.5%, and filter them through a 0.22μm filter membrane for sterilization before use.

[0073] Stability test samples: Take at least 3 samples, each 10 mL, from the same batch of emulsion, dispense them into transparent glass bottles, and seal them.

[0074] II. Test Environment Conditions Mildness test: Cell culture was carried out in a constant temperature incubator at 37°C and 5% CO2, and the operation was completed in a clean bench.

[0075] Stability tests: High-temperature stability was conducted in a constant temperature chamber at (40±2)℃; low-temperature stability was conducted in a refrigerator at (-10±2)℃; centrifugal stability was conducted using a centrifuge at room temperature.

[0076] III. Test Steps A. Mildness test (in vitro cytotoxicity test): a) Cell culture and treatment: Human immortalized keratinocytes (HaCaT) were used at a density of 1 × 10⁶ cells per well. 4 Cells were seeded into 96-well plates and cultured for 24 hours until adherence. The old culture medium was discarded, and different concentrations of sample extract were added. Five replicates were set for each concentration, and negative control (cell culture medium) and positive control (0.1% SDS solution) were also set up.

[0077] b) Incubation and detection: After culturing for another 24 hours, add 10 μL of MTT solution (5 mg / mL) to each well and incubate for 4 hours. Carefully aspirate the supernatant, add 100 μL of DMSO to each well, shake to dissolve the formazan crystals, and measure the absorbance at 570 nm (OD570) using a microplate reader.

[0078] c) Calculate cell viability: Cell viability (%) = (OD sample group - OD blank) / (OD negative control group - OD blank) × 100%.

[0079] B. Stability Acceleration Test: a) High-temperature stability: The sample was placed in a constant temperature chamber at (40±2)℃ and stored for 28 days. The appearance was observed on days 0, 7, 14, and 28, and the average particle size (e.g., D50) and polydispersity index (PDI) were measured using a laser particle size analyzer. Particle size change rate (%) = [(D50 after storage - initial D50) / initial D50] × 100%.

[0080] b) Low temperature stability: The sample was placed in a refrigerator at (-10±2)℃ for 7 days, and then restored at 25℃ for 24 hours. The condition was then observed.

[0081] c) Centrifugation stability: Take a sample and centrifuge at 4000 rpm for 30 min, observing the stratification. The sedimentation index can be further calculated: the percentage of sediment or stratification height at the bottom of the centrifuge tube to the total height. Record the results in Table 1 (Note: Mildness: A cell viability ≥80% indicates no significant cytotoxicity; record the cell viability at 100% concentration).

[0082] Stability: After 28 days of high-temperature storage, if the particle size change rate is ≤15%, the PDI does not increase significantly (e.g., the increase is <0.1) and the appearance is uniform, it can be judged as stable; after low-temperature recovery, there should be no crystallization, precipitation or demulsification; after centrifugation, there should be no visible stratification or sedimentation index ≤5%.

[0083] Table 1. Performance comparison of white oil nanoemulsions prepared in Examples 1-3

[0084] According to Table 1, the white oil nanoemulsions prepared in Examples 1-3 all had a stickiness score of ≤3.0, which is excellent, and the cell survival rate at 100% concentration was ≥80%, which means there is no obvious cytotoxicity. After 28 days of storage at 40℃, the particle size change rate was ≤15%, indicating stability. Furthermore, the increase in PDI change was <0.1 after 28 days of storage at 40℃, indicating stable distribution and good high-temperature stability. After 7 days of storage at -10℃, the particles were homogeneous and fluid, with no phase separation, crystallization, or demulsification, indicating good low-temperature stability. After centrifugation at 4000 rpm for 30 minutes, the particles were free of stratification or had a sedimentation index ≤5%, indicating good centrifugal stability.

[0085] In this invention, a high-efficiency, low-addition-amount composite emulsification system is constructed using polyglycerol fatty acid esters with high HLB values ​​(12-14) and cocamidopropyl betaine. The polyglycerol esters, with their long polyglycerol chains and strong affinity for white oil molecules, preferentially anchor themselves on the inner side of the oil-water interface, forming a spatial barrier. Meanwhile, the betaine molecules, with their zwitterionic properties, are stably distributed on the outer side of the interface, forming a strong hydration layer with the aqueous phase through electrostatic repulsion. Together, they construct a high-strength composite interfacial film that combines steric hindrance and electrostatic stability. Simultaneously, the aqueous phase regulator rapidly hydrates in deionized water, forming a weak gel three-dimensional network that penetrates the continuous phase. This not only imparts thixotropy to the system to prevent oil droplet aggregation but also significantly inhibits the Ostwald ripening and aggregation tendency of nanodroplets through spatial confinement and synergistic effects with the interfacial film. The co-emulsifier acts as a bridge between the interface and the bulk phase, further promoting the uniform and stable breakup of nanodroplets during high-pressure homogenization by adjusting interfacial tension and increasing the viscosity of the aqueous phase.

[0086] During the preparation stage, simultaneous and precise heating of the aqueous and oil phases ensures complete dissolution of the composite emulsifier in the white oil, peak interfacial activity, and reduces the viscosity of the aqueous phase, creating optimal thermodynamic and rheological conditions for subsequent efficient emulsification. In the phase-inversion emulsification process, strict control of the slow addition rate of the oil phase to the aqueous phase, coupled with high-speed shearing, guides the system to spontaneously form a water-in-oil primary emulsion and rapidly transform into a water-in-oil crude emulsion. This process fully utilizes the efficient spreading and rapid adsorption capabilities of the composite emulsifier system. Subsequent high-pressure homogenization at 50-70℃, through strong cavitation and shearing forces, breaks the oil droplets in the crude emulsion to the nanoscale, promoting a tight rearrangement of the composite emulsifier on the surface of the newly formed oil droplets. This constructs a thermodynamically stable interfacial structure, allowing the aqueous phase modifier network structure to be orderly reconstructed and fully expanded, ultimately solidifying the entire nano-dispersion system.

[0087] In summary, this invention, through the simplified molecular design of the oil phase and specific composite emulsifiers, combined with a process path of segmented temperature control and stepwise energy input, works synergistically from both the molecular interface behavior and macroscopic preparation process levels. This fundamentally solves the problems of traditional white oil emulsions, such as stickiness and easy stratification caused by large particle size and unstable interface, and successfully prepares white oil nanoemulsions with high stability, excellent refreshing feel, good mildness, and suitability for large-scale production.

[0088] Experimental Example 1 To verify that the specific combination of high HLB value polyglycerol ester and cocamidopropyl betaine (hereinafter referred to as the "specific composite emulsion system"), the single and simplified oil phase, and the high-pressure homogenization process are key to achieving the core performance in the white oil nanoemulsion system of this invention, this experimental example is based on the formulation and process of Example 2, changing only a single variable, and designing the following three sets of comparative experiments: Comparative Group D1: The cocamidopropyl betaine in the composite emulsifier was replaced with an equal mass of a single nonionic emulsifier (such as PEG-20 methyl glucosesquistearate) with a similar HLB value (approximately 13-14). The remaining raw materials and preparation process were exactly the same as in Example 2.

[0089] Objective: To verify the advantages of the synergistic stabilizing system of zwitterionic emulsifier and polyglycerol ester in this invention compared with the traditional single nonionic emulsifier system.

[0090] Comparative Group D2: The oil phase was changed from a single 20cSt white oil to a mixed oil phase consisting of 10% 20cSt white oil and 10% high viscosity (e.g., 100cSt) white oil, without changing the composition and amount of the composite emulsifier. The other raw materials and preparation process were exactly the same as in Example 2.

[0091] Objective: To verify the necessity of limiting the white oil to a single viscosity range (5-30 cSt) as a single oil phase in this invention for obtaining a refreshing skin feel and high stability.

[0092] Comparative group D3: The high-pressure homogenization step (step S3) was completely omitted, and emulsification was carried out only by increasing the high-speed shearing time to 20 min. The other raw materials and process parameters were exactly the same as in Example 2.

[0093] Objective: To verify the key role of the stepped energy input process of "high-speed shear pre-emulsification + high-pressure homogenization and refining" in this invention in obtaining nanoscale particle size and corresponding properties.

[0094] The products of the above-mentioned comparative groups D1, D2, and D3 were subjected to performance tests according to the same "refreshing skin feel sensory evaluation test" and "mildness and stability accelerated test" methods as in Examples 1-3 above, and the results were compared with those of Example 2 (representing the present invention). The results are shown in Table 2.

[0095] Table 2 Performance comparison between Example 2 and control groups D1-D3

[0096] Based on the comparative data in Table 2, the following conclusions can be drawn: The Importance of Specific Composite Emulsion Systems (Example 2 and Comparative Group D1) Results: The control group D1, which used a single nonionic emulsifier, had a significantly higher stickiness score (5.2 points), and its high temperature, low temperature and centrifugal stability were all significantly reduced. The initial particle size increased and the distribution became wider (PDI increased).

[0097] Mechanism: Single nonionic emulsifiers (such as PEGs) mainly rely on steric hindrance for stability, resulting in interfacial films with insufficient mechanical strength and lack of electrostatic repulsion. Under high temperature or centrifugal stress, droplets are more prone to collision and aggregation. In this invention, the introduction of cocamidopropyl betaine provides strong electrostatic repulsion and a hydration layer at the interface, synergistically with the steric hindrance of polyglycerol ester to construct a high-strength composite interfacial film with dual "steric-electrostatic" stability. This is not only more thermodynamically stable, but its rapid spreading and adsorption characteristics also facilitate the formation of smaller, more uniform initial droplets, thus directly resulting in a more refreshing skin feel.

[0098] The necessity of a single oil phase and viscosity limitation (Example 2 and Comparative Group D2) Results: The control group D2 used a mixed oil phase (containing high-viscosity white oil), which resulted in a worse skin feel score (4.8 points), an increased initial particle size, and decreased long-term stability (especially high-temperature stability).

[0099] Mechanism: Oil phases of different viscosities have different polarities and molecular configurations, resulting in varying diffusion and interfacial adsorption rates during emulsification. Mixed oil phases lead to uneven distribution of the emulsifier at the interface, making it difficult to form a uniform and dense interfacial film. Simultaneously, the high-viscosity oil phase itself has poor molecular mobility, making it more difficult to break down into small droplets during homogenization. Furthermore, larger droplets are more prone to Ostwald ripening (migration of smaller droplet molecules to larger droplets), leading to particle size increase and decreased stability during storage. This invention limits the use of white oil within a single viscosity range (5-30 cSt), ensuring the uniformity of the oil phase molecules. This allows the composite emulsifier to construct the most optimized and densest interfacial structure, which is the foundation for achieving long-term stability and a refreshing skin feel.

[0100] The key role of high-pressure homogenization process (Example 2 and Comparative Group D3) Results: In control group D3, the high-pressure homogenization step was omitted, resulting in a sharp deterioration in all performance aspects. It had an extremely sticky feel (6.5 points), an initial particle size in the micrometer range (450 nm), and failed all stability tests.

[0101] Mechanism: High-speed shearing can only prepare crude emulsions. The extreme shear force, cavitation effect, and collision action generated by high-pressure homogenization are the only effective means to break crude emulsion droplets down to the nanoscale. The nanoscale particle size significantly reduces the visible light and tactile sensation of oil droplets on the skin, which is the physical basis for achieving a refreshing and transparent skin feel. At the same time, the small particle size means a larger interfacial area and a lower driving force for oil droplet aggregation, which is a prerequisite for obtaining a thermodynamically stable system. Omitting this step will completely prevent the acquisition of the properties of nanoemulsions, reverting to the traditional unstable and thick crude emulsion state.

[0102] Experimental Example 2 To illustrate the application effect of the white oil nanoemulsion of the present invention in personal care products, this embodiment uses it as the core oil component to formulate a skin care body lotion, and focuses on evaluating its refreshing skin feel performance, comparing it with common commercially available products.

[0103] I. Sample Preparation Example Sample: Using the white oil nanoemulsion prepared in Example 2 above as raw material, body lotion was formulated according to the following basic formula: White oil nanoemulsion: 15.0%; Glycerin (moisturizer): 5.0%; Carbomer 934 (thickener): 0.2%; Triethanolamine (pH adjuster): appropriate amount (adjust pH to 6.0); Preservative: appropriate amount; Fragrance: appropriate amount; Deionized water: to 100% Comparative sample: Comparative Example C1 (Conventional Emulsion): The same basic formulation as the example sample was used, but the white oil nanoemulsion was replaced with an equal amount of conventional white oil emulsion that was not nano-sized (using the same emulsifier, but only emulsified by high-speed shear, with an average particle size D50 > 500 nm).

[0104] Comparative Example C2 (competitive products on the market): Select a mainstream commercial body lotion product that claims to have refreshing and moisturizing functions.

[0105] II. Performance Testing Content and Methods 1. Sensory evaluation of refreshing skin feel Evaluation Method: Referring to the aforementioned sensory evaluation method, a 15cm linear scale was used. Fifteen trained evaluators quantified the stickiness of the three samples (0 points: no stickiness; 15 points: extremely sticky). Evaluation time points were immediately after application (0 min), 10 min, 30 min, and 60 min.

[0106] Evaluation area: Inner side of the arm.

[0107] The results are as follows Figure 2 As shown, the sample containing the white oil nanoemulsion of this invention had significantly lower stickiness scores than the two comparative examples at all four evaluation time points. This directly verifies that the stable interface constructed by nano-sized oil droplets (small particle size) and the specific composite emulsion system can greatly reduce the stickiness of the product on the skin and provide a continuously refreshing user experience. Comparative example C1 (traditional emulsion) received the highest score due to its large particle size and thick texture.

[0108] In summary, applying the white oil nano-emulsion described in this invention at a concentration of 15% to body lotion significantly enhances the overall performance of the final product: while ensuring excellent long-lasting moisturizing effects, it achieves a revolutionary refreshing feel, successfully resolving the technical contradiction of traditional white oil-containing skincare products being "heavy and sticky" while "effectively moisturizing." This fully demonstrates its broad application prospects in high-end personal care products.

[0109] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process for a white oil nanoemulsion, characterized in that, Includes the following steps: Step S1: Weigh out 10-20% of white oil with a viscosity of 5-30 cSt, 3-5% of composite emulsifier, 1-2% of co-emulsifier, and 0.15-0.40% of aqueous phase conditioner according to the mass ratio, with the remainder being deionized water. The composite emulsifier includes polyglycerol fatty acid ester with an HLB value of 12-14 and cocamidopropyl betaine, and the weight ratio of polyglycerol fatty acid ester to cocamidopropyl betaine is 1-3:

1. Then, a colloidal solution is prepared by mixing a portion of deionized water, an aqueous phase conditioner, and a co-emulsifier in a stirring container. Step S2: In another container, add white oil, and then add the composite emulsifier to the white oil to form an oil phase mixture; Stir and heat the oil phase mixture to completely dissolve the composite emulsifier in the white oil, forming a homogeneous oil phase-emulsifier premix system; Step S3: Add the oil phase-emulsifier premixed system to the insulated colloidal solution using a homogenizer, and then maintain shear for 5-10 minutes to complete the dispersion and preliminary emulsification of the oil phase in the aqueous phase, forming a crude emulsion; The crude emulsion was transferred to a high-pressure homogenizer for homogenization and circulation. Step S4: Transfer the emulsion to a cooling tank and stir it. Turn on the cooling water and cool the emulsion to room temperature. During the cooling process, add the remaining deionized water to make up for the evaporation loss. Finally, the mixture was filtered through a 200-400 mesh filter cloth to obtain a white oil nanoemulsion.

2. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S1, the co-emulsifier is glycerol or propylene glycol.

3. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S1, the aqueous phase regulator is xanthan gum or hydroxyethyl cellulose.

4. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S1, 70-80% of the formula amount of deionized water is added to the stirring container and stirred at 300-500 rpm. Then slowly and evenly sprinkle the aqueous phase conditioner into the liquid surface, and continue stirring until the aqueous phase conditioner is completely hydrated and evenly dispersed; Then, add the emulsifier, stir and mix evenly, and heat the formed aqueous phase to 70-75℃ to obtain a colloidal solution.

5. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S2, the heating temperature is 70-75℃.

6. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S3, the oil phase-emulsifier premix system is added to the insulated colloidal solution at a homogenizing mixer at 3000-5000 rpm.

7. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S3, the homogenization cycle is performed 1-3 times at a temperature of 50-70℃.

8. The preparation process of the white oil nanoemulsion according to claim 1, characterized in that: In step S4, the mixture in the cooling vessel is stirred at a speed of 200-400 rpm.

9. A white oil nanoemulsion prepared by the preparation process according to any one of claims 1-8, characterized in that, Including the following raw materials: The components include white oil with a viscosity of 5-30 cSt, a complex emulsifier, a co-emulsifier, an aqueous phase conditioner, and deionized water, wherein: The white oil with a viscosity of 5-30 cSt serves as a single oil-phase base component, providing the system with the necessary spreadability, lubricity, and sealing properties. Its defined viscosity range ensures a balance between a refreshing feel and moisturizing performance in the final emulsion. The composite emulsifier is composed of polyglycerol fatty acid ester with an HLB value of 12-14 and cocamidopropyl betaine. The polyglycerol fatty acid ester penetrates into the oil phase with its long-chain hydrophobic structure and forms steric hindrance, while cocamidopropyl betaine anchors to the outside of the interface with its zwitterionic properties to provide electrostatic repulsion and a hydration layer. The two work together to construct a high-strength composite interface film with both spatial and electrostatic stability. The co-emulsifier, acting as an interface regulator and moisturizing factor, assists in emulsification by reducing interfacial tension and increases the consistency of the aqueous phase to inhibit droplet aggregation, while simultaneously imparting basic moisturizing properties to the final product. The aqueous phase regulator, acting as a continuous phase structure enhancer, hydrates in deionized water to form a three-dimensional weak gel network. The deionized water, as a dispersion medium and the main continuous phase, constitutes the matrix of the emulsion system, and its purity ensures the foundation of the system's chemical stability.

10. The application of the white oil nanoemulsion according to claim 9 in personal care products.

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