Self-emulsifying skin care emulsion with rhamnolipids, preparation method therefor, and use thereof

Abstract

Disclosed in the present application are a self-emulsifying skin care emulsion with rhamnolipids, a preparation method therefor, and use thereof. Specifically, disclosed is use of rhamnolipids in maintaining skin pH, keeping skin moisturized, or promoting skin absorption, and further disclosed is a self-emulsifying skin care emulsion with rhamnolipids. The raw materials comprise an aqueous phase and an oil phase, wherein the aqueous phase may contain an acid or a base, and the mass ratio of rhamnolipids in the skin care emulsion is greater than or equal to 0.2%; the pH value of the skin care emulsion is between 5.0 and 6.0. The skin care emulsion of the present application not only possesses high moisturization, stability, and permeability, but also has the advantage of long-term maintenance of skin pH.

Description

A skin care emulsion with rhamnolipid self-emulsification, its preparation method and application Technical Field

[0001] This application relates to the field of skin care lotion preparation technology, specifically to a rhamnolipid self-emulsifying skin care lotion, its preparation method, and its application. Background Technology

[0002] Rhamnolipids, as a biosurfactant synthesized by microorganisms, have advantages such as being green and safe, environmentally friendly, mild, and highly active. Rhamnolipids are one of the longest-researched and most technologically mature biosurfactants.

[0003] As a crucial means for microorganisms to obtain nutrients from the natural environment, rhamnolipids possess a chemical structure remarkably similar to cell membrane phospholipids, enabling them to be constructed into micelles that can easily cross cell membranes for substance delivery. Furthermore, the chemical structure of rhamnolipids contains both hydrophilic sugar rings and lipophilic carbon chains, and when prepared into a uniform dispersion system, it can easily spread on the skin surface to form a liquid film, thus exhibiting its amphiphilic activity. In conclusion, it is easy to see that rhamnolipids also have value as emulsifiers and penetration enhancers in skincare products.

[0004] However, in the personal care products industry, rhamnolipin is usually promoted as a surfactant for body cleaning, and there are already end products such as shampoos and facial mousses containing rhamnolipin on the market.

[0005] However, using rhamnolipids only as a cleaning surfactant, skin care emulsifier, or penetration enhancer does not fully realize their performance advantages.

[0006] Summary of the Invention

[0007] The technical problem to be solved by this application is to provide a rhamnolipin self-emulsifying skin care emulsion, its preparation method and application, which further expands the performance advantages of rhamnolipin.

[0008] Application of rhamnolipin in maintaining skin pH balance.

[0009] The rhamnolipin also includes applications in skin moisturizing and / or penetration enhancement, wherein the rhamnolipin is mainly of the Rha-Rha-C10-C10 type, and the Rha-Rha-C10-C10 type accounts for 40% or more of the mass of the rhamnolipin.

[0010] First, this application provides the application of rhamnolipin in maintaining skin pH, that is, when the rhamnolipin is applied in a skin lotion, it has the effect of maintaining skin pH.

[0011] Secondly, this application provides the application of rhamnolipin in skin moisturizing, that is, when the rhamnolipin is applied to skin lotion, it has the effect of skin moisturizing. When the rhamnolipin is mainly of the Rha-Rha-C10-C10 type and the mass percentage of the Rha-Rha-C10-C10 type in the rhamnolipin is 40% or more, the skin moisturizing function of the skin lotion can be further improved.

[0012] Furthermore, this application provides the application of rhamnolipin in promoting penetration, that is, when the rhamnolipin is applied to skin lotion, it has the effect of promoting penetration. When the rhamnolipin is mainly of the Rha-Rha-C10-C10 type and the mass ratio of Rha-Rha-C10-C10 type in the rhamnolipin is 40% or more, the penetration-promoting function of the skin lotion can be further improved.

[0013] This application also provides a rhamnolipin self-emulsifying skin lotion, the raw materials of which include an aqueous phase and an oil phase, wherein the aqueous phase may contain an acid or an alkali, the mass percentage of rhamnolipin in the skin lotion is ≥0.2%, and the pH value of the skin lotion is 5.0-6.0.

[0014] Rhamnolipids include four common configurations: Rha-C10, Rha-C10-C10, Rha-Rha-C10, and Rha-Rha-C10-C10. Additionally, special structures such as Rha-Rha-C8-C10, Rha-C8-C10, Rha-Rha-C10-C12, Rha-C10-C12, Rha-Rha-C10-C12:1, and Rha-C10-C12:1 are permitted. The rhamnolipids described in this application are preferably those with Rha-Rha-C10-C10 as the main component, and the Rha-Rha-C10-C10 type rhamnolipid accounts for more than 40% of the total rhamnolipids by mass. Optionally, the Rha-Rha-C10-C10 type rhamnolipid accounts for 50%-99% of the total rhamnolipids by mass.

[0015] In this application, the oil phase and rhamnolipids account for 2%-80% of the mass of the skin care lotion; optionally, the oil phase and rhamnolipids account for 5%-40% of the mass of the skin care lotion. The aqueous phase accounts for 20%-98% of the mass of the skin care lotion; optionally, the aqueous phase accounts for 60%-95% of the mass of the skin care lotion. The oil phase may simultaneously contain one, more, or all of various types of oils and fats; optionally, it may contain at least one of esters, hydrocarbon oils and fats, natural oils and fats, alkanols, fatty acids, and silicone oils.

[0016] The esters include triglycerides and at least one of monoesters, diesters, polyesters, etc., other than triglycerides. The triglycerides in this application may optionally include at least one of the following chemical substances obtained by esterification of fatty acids and glycerol: caprylic / capric triglyceride (GTCC), C10-C18 fatty acid triglycerides, trihedrin, tris(2-methyl-2-methyl-2-ethylhexyl) ester, etc. The monoesters, diesters, polyesters, etc., other than triglycerides may optionally include isononyl isononanoate, isopropyl myristate, ethylhexyl palmitate, dibutyl adipate, ester waxes, diisostearyl malate, triisostearyl citrate, pentaerythritol tetrastearate, etc., containing one or more ester groups.

[0017] The hydrocarbon oils mainly include hydrocarbon skin care oils containing only carbon and hydrogen elements, and optionally include at least one of squalane, squalene, white oil, hydrocarbon wax, hydrogenated polyisobutylene, isododecane, isohexadecane, etc.

[0018] The natural oils include oils extracted from various animal and plant products and minerals, and are generally mixtures of organic oils with various chemical structures. Optionally, they include at least one of meadowfoam seed oil, jojoba oil, sweet almond oil, camellia oil, coconut oil, macadamia nut oil, avocado oil, shea butter, cocoa seed butter, mango seed butter, grape seed oil, marula oil, Rosa damascena flower oil, sunflower seed oil, wild soybean oil, beeswax, ceresin wax, carnauba wax, and candelilla wax.

[0019] The alkanols mainly include higher fatty alcohols of C12 and above, and optionally include at least one of cetearyl alcohol, behenyl alcohol, lauryl alcohol, myristyl alcohol, arachidyl alcohol, beeswax alcohol, etc.

[0020] The fatty acids mainly include higher fatty acids with C12 and above, and optionally include at least one of stearic acid, palmitic acid, myristic acid, etc.

[0021] The silicone oil mainly includes polydimethylsiloxane and its various modified forms after grafting, block, and crosslinking, and optionally includes at least one of cyclopentasiloxane, 6-viscosity silicone oil, 100-viscosity silicone oil, 350-viscosity silicone oil, phenyl silicone oil, octyl silicone oil, and silicone elastomers.

[0022] In one embodiment, the aqueous phase includes water, a preservative, and an acid or alkali. Optionally, the aqueous phase may also include at least one of a humectant, a thickener, an emulsifier, etc.

[0023] In this application, "water" refers to a large volume of liquid used as a solvent and dispersion medium, which may be deionized water, purified mineral water, purified seawater, plant tissue sap (such as loofah water, bamboo sap, birch sap, etc.), fermentation filtrate, etc., whose main component is water.

[0024] The preservatives described in this application mainly comprise compounds that can inhibit microbial activity and effectively delay the spoilage and deterioration of emulsion systems; for example, the preservatives include at least one of organic acids, parabens, formaldehyde releasers, and alcohols, and optionally include at least one of phenoxyethanol, sodium benzoate, potassium sorbate, hexanediol, p-hydroxyacetophenone, caprylyl glycol, capryloyl hydroxamic acid, pentanediol, methylparaben, ethylparaben, ethylhexylglycerin, etc.

[0025] The alkali described in this application is an inorganic or organic compound that, when dissolved in water, makes the solution pH alkaline. The alkali is capable of neutralizing the carboxyl group in the unneutralized rhamnolipid structure. The alkali may optionally include at least one of potassium hydroxide, sodium hydroxide, triethanolamine, aminomethylpropanol, arginine, and ammonia. The acid described in this application is an inorganic or organic compound that, when dissolved in water, makes the solution pH acidic. The acid is capable of acidifying the carboxylate ion in the rhamnolipid structure to generate a carboxyl group. The acid may optionally include at least one of citric acid, lactic acid, fruit acid, and salicylic acid.

[0026] The moisturizers in this application mainly include cosmetic ingredients that can have an affinity for water and increase and maintain skin moisture over a relatively wide range of humidity changes and a relatively long period of time; for example, the moisturizers may optionally include at least one of polyols, polysaccharides, polyethylene glycols, and natural factors, specifically at least one of glycerin, propylene glycol, butylene glycol, pentylene glycol, isopentylene glycol, hexanediol, sorbitol, xylitol, hyaluronic acid, sodium hyaluronate, fructooligosaccharides, trehalose, polyethylene glycol, sodium lactate, amino acids, betaine, pyrrolidone carboxylic acid and its salts, urea, etc.

[0027] The thickeners described in this application mainly include high molecular weight polymers that, when dispersed in water, can undergo hydrogen bonding, volume expansion, and molecular chain entanglement with water, ultimately leading to a significant increase in water viscosity and changes in rheological properties. For example, the thickeners include at least one of polyacrylic acid, polysaccharides, polyurethanes, natural gums, and polyoxyethylene, and optionally include at least one of carbomer, ammonium acryloyldimethyl taurate / VP copolymer, hydroxyethyl acrylate / sodium acryloyldimethyl taurate copolymer, acrylate / C10-30 alkanol acrylate cross-linked copolymer, polyacryloyldimethyl taurate, xanthan gum, sodium alginate, guar gum, sodium polyacrylate, sodium polyacrylate grafted starch, gellan gum, cellulose, and polyacrylate cross-linked polymer-6.

[0028] This application also provides methods for preparing the above-mentioned skin care lotion, including direct self-emulsification and post-dispersion self-emulsification; the direct emulsification method is applicable to rhamnolipids of all forms and pH conditions, while the post-dispersion self-emulsification method is mainly suitable for pure acid rhamnolipids.

[0029] The direct self-emulsification method includes: aqueous phase acquisition, preparing an aqueous phase composition containing acid or alkali; oil phase acquisition, preparing an oil phase composition; and skin care emulsion acquisition, adding the aqueous phase composition containing acid or alkali to the oil phase composition to obtain a skin care emulsion. The rhamnolipid can be added to any step of aqueous phase acquisition, oil phase acquisition, or skin care emulsion acquisition. The rhamnolipid includes neutralized rhamnolipid and unneutralized rhamnolipid. Since neutralized rhamnolipid has better hydrophilicity and unneutralized rhamnolipid has better lipophilicity, optionally, unneutralized rhamnolipid is added to the oil phase acquisition step, and neutralized rhamnolipid is added to the aqueous phase acquisition step.

[0030] As a specific implementation method, the process is as follows: The oil phase composition containing rhamnolipids is heated to 70℃-95℃, optionally 80℃-85℃. After the oil phase composition melts and mixes into a homogeneous liquid or turbid gel, an aqueous phase composition containing acid or alkali at the same temperature is added dropwise to the hot oil phase composition while stirring at 100rpm-700rpm or homogenizing at 3000rpm-10000rpm, optionally while stirring at 300rpm-500rpm or homogenizing at 5000rpm-8000rpm. It can be observed that as the aqueous phase composition is added to the system, the system gradually changes from a liquid or turbid gel. The gel transforms into a whitish emulsion. Depending on the composition of the oil and water phases, a significant phase inversion may occur. Initially, the system is a water-in-oil emulsion when the aqueous phase is added. As the water content reaches a certain level, the phases invert: the water migrates to become the external continuous phase, and the oil phase becomes the internal dispersed phase, ultimately forming a water-in-oil emulsion. After the emulsion forms, it is stirred at approximately 60℃-70℃ for 10-30 minutes, or optionally at approximately 60℃-65℃ for 20-30 minutes, at a stirring speed of 100rpm-700rpm, optionally 200rpm-300rpm. The mixture is then gradually cooled to room temperature, and stirring is stopped to obtain the rhamnolipin self-emulsifying skin care emulsion. It is important to note that when preparing the rhamnolipin self-emulsifying skin care emulsion using the direct (neutralization) emulsification method, the temperatures of the water and oil phases should be consistent, or the aqueous phase temperature should be slightly higher than the oil phase temperature. Otherwise, the oil phase may solidify upon cooling, leading to difficulties in neutralization and unsatisfactory emulsification.

[0031] In the above preparation process, rhamnolipids and other oil phase compositions are preheated and mixed at a temperature of 70℃-95℃, optionally 80℃-85℃. After heating and mixing evenly, the acid or alkali is directly added to the aqueous phase composition. Under stirring conditions of 100rpm-500rpm or homogenization conditions of 3000rpm-10000rpm, when the water and oil phases are at the same temperature, or when the water phase temperature is slightly higher than the oil phase temperature, the aqueous phase is gradually added to the oil phase. Depending on the formulation composition, a clear and observable phase inversion process may occur. After the phase inversion is completed, the mixture is kept at around 60℃-70℃ and stirred for 10min-30min at a stirring speed of 100rpm-700rpm.

[0032] The dispersion-after-emulsification method includes: aqueous phase acquisition, preparing an acid- and alkali-free aqueous phase composition; oil phase acquisition, preparing an oil phase composition; and skin care emulsion acquisition, wherein the acid- and alkali-free aqueous phase composition and the oil phase composition are mixed evenly to obtain an oil-water mixture, and an acid or alkali is added to the oil-water mixture to obtain a skin care emulsion. The rhamnolipid can be added to any step of aqueous phase acquisition, oil phase acquisition, or skin care emulsion acquisition. The rhamnolipid includes neutralized rhamnolipid and unneutralized rhamnolipid. Since neutralized rhamnolipid has better hydrophilicity and unneutralized rhamnolipid has better lipophilicity, optionally, unneutralized rhamnolipid is added to the oil phase acquisition step, and neutralized rhamnolipid is added to the aqueous phase acquisition step.

[0033] As a specific implementation method, the process is as follows: The oil phase composition containing rhamnolipids and the acid-base-free aqueous phase composition are heated to 70℃-95℃, optionally 80℃-85℃, respectively. After the oil phase composition is heated and melted and mixed into a uniform liquid, the water and oil phases are mixed while ensuring that the water and oil phases are at the same temperature or the water phase temperature is slightly higher than the oil phase temperature. The stirring speed during mixing is 100rpm-700rpm, optionally 300rpm-500rpm, or the homogenization speed is 3000rpm-10000rpm, optionally 5000rpm-8000rpm. Under the condition of running a stirring paddle or homogenizer, the water and oil phases are directly stirred into a dispersion in which the oil phase is dispersed in the aqueous phase in the form of extremely small droplets. While maintaining constant stirring or homogenization conditions, add an appropriate amount of calculated acid or alkali. Maintain the temperature at approximately 60℃-70℃ and stir for 10-30 minutes, or optionally at 60℃-65℃ and stir for 20-30 minutes at a stirring speed of 100rpm-700rpm, or optionally 200rpm-300rpm. After stirring, gradually cool to room temperature and stop stirring to obtain the rhamnolipin self-emulsifying skincare emulsion. It should be noted that if the oil phase is difficult to disperse uniformly under stirring or homogenization conditions due to compositional differences between the oil and water phases, a small amount of commonly used cosmetic emulsifiers, such as monoglycerides, PEGs, polyglycerols, glycosides, polysorbates, and sorbitans, can be added to the formulation, accounting for 0.05%-0.5% of the entire formulation system, optionally 0.2%-0.3%. This amount cannot stably emulsify all oil phase components; it only serves as an auxiliary dispersant.

[0034] In the above preparation process, rhamnolipids and other oil phase compositions are preheated and melted, and then mixed evenly; acidic and alkaline substances are not directly mixed with the aqueous phase composition, but are added to the system after oil-water dispersion; the two phases are mixed when the water and oil phases are at the same temperature, or the water phase temperature is slightly higher than the oil phase temperature, under stirring conditions of 100-500 rpm or homogenization conditions of 3000-10000 rpm; the temperature is kept at around 60℃-70℃ and stirred for 10-30 minutes at a stirring speed of 100-700 rpm; there is no phase inversion process; if the oil phase is difficult to disperse, 0.05%-0.5% emulsifier is added to assist dispersion.

[0035] In both preparation methods described above, the addition of acid or alkali should optionally maintain the pH range of the emulsion system between 5.0 and 6.0. Within this pH range, some of the carboxyl groups in rhamnolipids are neutralized into ions, while others retain their carboxyl structure. Neutralized rhamnolipids exhibit high surface activity, while unneutralized rhamnolipids are lipophilic. The ionized rhamnolipids emulsify the unneutralized rhamnolipids along with other oily components into an emulsion; hence, this type of emulsion is called a rhamnolipid self-emulsifying emulsion.

[0036] The technical solution of this application has the following advantages:

[0037] 1. When the rhamnolipin provided in this application is applied to skin lotion, it can not only achieve the emulsification effect already disclosed by rhamnolipin itself, but also achieve the effect of maintaining the skin's pH balance for a long time, which has the advantage of effectively expanding the performance of rhamnolipin; and it can also effectively maintain good skin moisturizing and penetration promotion effects.

[0038] 2. The rhamnolipin self-emulsifying skin lotion provided in this application uses rhamnolipin as an emulsifier and controls the mass percentage of rhamnolipin in the skin lotion to be ≥0.2%. Under this formula, the skin lotion has the effects of high moisturizing, high stable emulsification, high penetration promotion, and long-lasting maintenance of skin pH.

[0039] The mechanism by which this application achieves the aforementioned effects of high moisturizing, stable emulsification, high penetration, and long-lasting maintenance of skin pH may be as follows:

[0040] Stable emulsion: Before being neutralized by alkali, the carboxyl group attached to the end of the carbon chain in the chemical structure of rhamnolipid exists stably as a nonionic group. However, it can undergo anionic-nonionic structural transformation under different pH conditions. That is, when unneutralized rhamnolipid encounters alkaline substances, the carboxyl group will be neutralized and ionized to generate rhamnolipid salts. At this time, rhamnolipid exhibits high surface activity and has strong cleaning ability and emulsion stabilization ability. This characteristic of rhamnolipid can be used to adjust the surface activity of rhamnolipid and the stability of colloidal system.

[0041] High penetration enhancement: As one of the important means for microorganisms to obtain nutrients from the natural environment, rhamnolipin has a chemical structure that is very similar to cell membrane phospholipids. It can be constructed into micelles that can easily pass through the cell membrane for substance delivery. Taking advantage of this characteristic of rhamnolipin, it can be used as a penetration enhancer in skin care products to improve the penetration effect, thereby increasing the transdermal absorption rate of the functional ingredients it carries, thus achieving a more efficient skin care effect.

[0042] High moisturizing effect: Rhamnolipids have both hydrophilic sugar rings and lipophilic carbon chains in their chemical structure. After being made into a uniform dispersion system, they can be easily spread on the skin surface to form a liquid film and exert their amphiphilic activity. Utilizing this special structure, rhamnolipids can not only reduce the evaporation of water from the skin surface, but also have an affinity for water molecules, effectively increasing the moisture content of the skin surface and achieving a high moisturizing effect.

[0043] Long-lasting maintenance of skin pH: The carboxyl groups in the chemical structure of rhamnolipin are partially neutralized into ions under the action of an appropriate amount of alkali, giving it emulsifying and stabilizing capabilities. Furthermore, because rhamnolipin has a pH buffering effect, when the pH of the emulsion system is adjusted between 5.0 and 6.0, the pH value of the applied skin area is maintained within a stable range that matches the pH conditions of healthy skin, ensuring the skin's pH level during application. Simultaneously, verification shows that the use of rhamnolipin can effectively maintain the skin's pH level within a suitable range for a relatively long period, with significant effects. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Figure 1 is a chemical structure diagram of the Rha-Rha-C10-C10 type rhamnolipid in Example 1 of this application, including the structure before and after neutralization (the alkaline substance used for neutralization is potassium hydroxide as an example), a is the structure before neutralization, and b is the structure after neutralization;

[0046] Figure 2 is a physical image of the skin lotion prepared in Example 1 of this application. Detailed Implementation

[0047] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0048] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0049] The raw materials used in the following examples and comparative examples are from the following sources:

[0050] Rhamnol, 1,3-Butanediol, and Carbomer are from Wanhua Chemical; Isoamyl glycol is from Kuraray; AVC is from Clariant; Glycerin and Cetearyl Alcohol are from Procter & Gamble; Niacinamide is from DSM-Firmware; Shea Butter, Phenoxyethanol, and Caprylic / Capric Triglycerides are from BASF; Trihedrin is from Eulian; p-Hydroxyacetophenone and 1,2-Hexanediol are from Symrise; Sodium Benzoate is from Merck; PHL is from Indispensable; Squalane, Isopropyl Myristate, and Glyceryl Stearate / PEG-100 Glyceryl Stearate (A165) are from Croda; Ceramide 3 and Polyglycerol-3-Methyl Glucose Distearate (TEGO Care 450) are from Evonik; Cholesterol is from Coin; 100% Viscose Silicone Oil is from Dow Corning; Tween-80, Methanol, Arginine, and Isopropanol are from Aladdin.

[0051] In the table below, all raw materials without specified mass are listed in kg, and rhamnose lipids are calculated based on the amount added in pure form.

[0052] Example 1

[0053] The ingredients of the skin lotion are shown in Table 1.

[0054] Table 1

[0055] Note: In the table, 2R2C is the abbreviation of Rha-Rha-C10-C10. The structure of Rha-Rha-C10-C10 is shown in Figure 1. 30% 2R2C means that the mass percentage of rhamnolipin with the 2R2C structure in the total rhamnolipin is 30%, and the same applies below.

[0056] The preparation process of the above-mentioned skin care lotion is as follows:

[0057] 1. Prepare aqueous and oil phase compositions according to their solubility characteristics;

[0058] 2. Heat the aqueous phase and oil phase composition separately to approximately 85°C in the same water bath;

[0059] 3. Keep the heating conditions unchanged, turn on the agitator, and stir the oil phase at 500 rpm;

[0060] 4. Under the same insulation conditions, the aqueous phase is added dropwise to the oil phase while it is being stirred, at a dropping rate of approximately 60 d / s;

[0061] 5. After all the aqueous phase has been added, maintain the temperature at around 60℃ and stir for 30 minutes;

[0062] 6. After cooling to room temperature, the material can be discharged to obtain the skin care lotion shown in Figure 2.

[0063] Example 2

[0064] The ingredients of the skin lotion are shown in Table 2.

[0065] Table 2

[0066] The preparation process of the above-mentioned skin care lotion is as follows:

[0067] 1. Prepare the aqueous and oil phase compositions according to their solubility characteristics, but do not add the alkali to the aqueous phase for the time being;

[0068] 2. In the same water bath, heat the aqueous and oil phase compositions (which do not contain alkali) to approximately 85°C respectively;

[0069] 3. Keeping the heating conditions constant, mix the water and oil phases and homogenize them at 4000 rpm;

[0070] 4. Add the alkali to the homogenizing system and mix thoroughly;

[0071] 5. After cooling, maintain the temperature at around 60℃ and stir for 30 minutes at a stirring speed of 300 rpm;

[0072] 6. Once cooled to room temperature, the material can be discharged.

[0073] Example 3

[0074] The ingredients of the skin lotion are shown in Table 3.

[0075] Table 3

[0076] The preparation process of the above-mentioned skin care lotion is as follows:

[0077] 1. Prepare aqueous and oil phase compositions according to their solubility characteristics;

[0078] 2. Heat the aqueous phase and oil phase composition separately to approximately 85°C in the same water bath;

[0079] 3. Keep the heating conditions unchanged, turn on the agitator, and stir the oil phase at 500 rpm;

[0080] 4. Under the same insulation conditions, the aqueous phase is added dropwise to the oil phase while it is being stirred, at a dropping rate of approximately 60 d / s;

[0081] 5. After all the aqueous phase has been added, maintain the temperature at around 60℃ and stir for 30 minutes;

[0082] 6. Once cooled to room temperature, the material can be discharged.

[0083] The preparation methods and formulation components in Examples 1-3 above can be changed to a certain extent. The formulation in Example 1 can also be used to prepare the emulsion using the process provided in Example 2 of this application. There is no strict correspondence between the formulation and the preparation process, and they can be used interchangeably. Under the preparation process parameters disclosed in this application, the purpose of this application can be achieved.

[0084] The stability of the skin care lotions in Examples 1-3 was tested. The appearance of the skin care lotion in Examples 1-1 is shown in Figure 2. The skin care lotions in these examples maintained emulsification stability without oil production or emulsion breakage after being stored at 50°C for three months, centrifuged at 5000 rpm for 30 minutes, and subjected to eight freeze-thaw cycles. The pH range of the skin care lotions in these examples is between 5.0 and 6.0, and the viscosity range is 500 cps to 80000 cps. Depending on the desired efficacy, the skin care lotions in this application may selectively incorporate appropriate active ingredients, such as bisabolol, ectoine, VC-IP, niacinamide, and 377, into the aqueous or oil phase composition. When using, apply an appropriate amount evenly to the skin.

[0085] The skin care lotion in this application has the moisturizing effect of slowing down the loss of human epidermal moisture and increasing the water content of human epidermal tissue. It also has the effect of regulating the acid-base environment of human epidermal tissue and maintaining the stability of the acid-base environment of human epidermal tissue for a considerable period of time. It has a chemical structure similar to phospholipids in biological cell membranes, which can promote the transdermal absorption and efficacy of other functional ingredients encapsulated by its micelles.

[0086] To verify the above efficacy, the following experimental example is provided.

[0087] Experiment 1 - pH Adjustment Effect

[0088] The skin pH regulation efficacy of the sample lotion was determined using a pH test probe from the German CK non-invasive skin efficacy testing instrument. Subjects with poor skin conditions were selected, and their epidermal pH values ​​were measured beforehand. Healthy epidermal pH should be around 5. For subjects with damaged skin barriers or dry skin, the epidermal pH may be greater than 6, or even greater than 7. Similarly, a pH that is too low, such as 4, may lead to oily skin and breakouts, which is also an unhealthy skin condition. Subjects with excessively high or low pH values ​​were selected. For each subject, a corresponding number of 3cm × 3cm areas were marked out in the test area. All test samples prepared in the examples were applied in duplicate to each sample's test area. The areas without sample application served as a blank control group. It is recommended that the sampling areas be the cheeks, forehead, outer lower legs, and inner forearms, with the selection based on each subject's physical condition. Upon arrival, the test area was first gently rinsed with running water, then gently patted dry with a soft cotton washcloth. This patting motion was repeated twice, avoiding vigorous rubbing to prevent damage to the stratum corneum. After rinsing, the subject sat quietly for at least 30 minutes to allow the body's physiological activities to slow down and stabilize. The corresponding test areas were marked with a marker. Following the established method, the transdermal water loss and water content probes of a non-invasive skin function testing instrument were used to measure the values. Three measurements were taken: baseline, 5 minutes after product application, and 120 minutes after application. The average value of each sample was calculated. Subjects were required to discontinue the use of all leg cleansing and moisturizing products, including soap, lotion, sunscreen, and insect repellent, during a 3-day pre-test conditioning period. Three days before the test and 24 hours after the measurement, subjects were allowed to gently shave their hair, but scratching was prohibited. Exercise, hot drinks, or caffeinated beverages were avoided for 2 hours before each test, as these could affect the accuracy and reliability of the measurement results. Any activity that caused sweating was strictly prohibited. The temperature and relative humidity of the testing site were controlled at 20℃±2℃ and 50%±10%, respectively.

[0089] The test results of the above embodiments are shown in Table 4 below:

[0090] Table 4. Verification data on the effect of skin pH regulation

[0091] As shown in Table 4, subjects whose skin pH deviated from the normal range experienced varying degrees of improvement in their skin pH after using this product. This is not only related to the fact that the rhamnolipin self-emulsifying emulsion itself has a pH of 5.0-6.0, but more importantly, the presence of carboxyl groups and other functional groups in the rhamnolipin structure allows it to be considered an organic acid, thus exhibiting a pH buffering effect. This is a crucial point, enabling the rhamnolipin self-emulsifying skincare emulsion to maintain the skin pH within a reasonable range for a considerable period, preventing significant fluctuations due to changes in internal and external factors. This property is not found in commonly used nonionic emulsifiers and emollients, including A165 and Tween-80. Therefore, compared to traditional nonionic emulsifiers and emollients, emulsions prepared using rhamnolipin, while meeting general stability and efficacy requirements, also possess additional skin pH regulation and stabilization effects. Rhamnolipin offers rich skincare benefits and broad application prospects.

[0092] Experiment Example 2 - Moisturizing Effect

[0093] The moisturizing efficacy of the emulsion samples in the examples was determined using the transdermal water loss and moisture content testing probe of the German CK non-invasive skin efficacy testing instrument. Qualified subjects were selected. For each subject, a corresponding number of 3cm × 3cm areas were marked out in the test area. All test samples prepared in the examples were applied in duplicate to each sample's respective test area. Areas without sample application served as a blank control group. It is recommended that sampling areas include both cheeks, forehead, outer lower legs, and inner forearms; the selected areas depend on each subject's physical condition. Upon arrival, the test area was first gently rinsed with running water, then gently patted dry with a soft cotton washcloth. This patting motion was repeated twice. Vigorous rubbing was avoided to prevent damage to the stratum corneum. After rinsing, the subject sat quietly for at least 30 minutes to allow the body's physiological functions to slow down and stabilize. The corresponding test areas were marked with a marker. Following the established method, the transdermal water loss and water content probes of a non-invasive skin function testing instrument were used to measure the values. Three measurements were taken: baseline, 5 minutes after product application, and 120 minutes after application. The average value of each sample was calculated. Subjects were required to discontinue the use of all leg cleansing and moisturizing products, including soap, lotion, sunscreen, and insect repellent, during a 3-day pre-test conditioning period. Three days before the test and 24 hours after the measurement, subjects were allowed to gently shave their hair, but scratching was prohibited. Exercise, hot drinks, or caffeinated beverages were avoided for 2 hours before each test, as these could affect the accuracy and reliability of the measurement results. Any activity that caused sweating was strictly prohibited. The temperature and relative humidity of the testing site were controlled at 20℃±2℃ and 50%±10%, respectively.

[0094] The test results of the above embodiments are shown in Tables 5 and 6 below:

[0095] Table 5. Data on transdermal water loss verification

[0096] Table 6. Verification data on epidermal moisture content

[0097] As shown in Tables 5 and 6, the rhamnolipin self-emulsifying skin lotion of this application significantly reduces transepidermal water loss and increases epidermal moisture content compared to skin lotions prepared using A165 and Tween-80 as emulsifiers. This is because the rhamnolipin structure not only possesses a lipophilic carbon chain structure, making it easy to form a film and a complete protective layer after application to the epidermis, but also has hydrophilic sugar rings and carboxyl ends that absorb and associate water, maintaining sufficient moisture in the skin for a longer period. While the carbon chains and hydrophilic chains in the A165 and Tween-80 structures also have dual lipophilic and hydrophilic functions, their moisturizing and water-locking effects are not as ideal as those of rhamnolipin. Furthermore, rhamnolipin can act not only as a self-emulsifying emulsifier in formulations but also as a moisturizer, allowing for a larger dosage compared to A165, thus resulting in a more pronounced moisturizing effect. The transepidermal water loss data in the table clearly shows that when the amount of 2R2C rhamnolipin in the formulation increases, as in Examples 1-1 to 1-4, the transepidermal water loss of the skin after using the corresponding emulsion is correspondingly smaller, and the epidermal water content is also increased. This indicates that the moisturizing effect of rhamnolipin is positively correlated with its 2R2C rhamnolipin content. Therefore, rhamnolipin with a 2R2C configuration content higher than 40% has a significantly better moisturizing and water-locking effect than rhamnolipin self-emulsifying emulsions with a 2R2C configuration content lower than 40%, due to its higher proportion of hydrophilic sugar rings.

[0098] Furthermore, it's worth mentioning that most participants reported a significantly lighter and more refreshing feel to the skin compared to A165 and Tween-80 emulsions. This is because rhamnolipin, when aggregated, forms a soft paste, and after neutralization, it becomes a highly water-soluble, low-viscosity fluid. Compared to A165 and Tween-80, rhamnolipin has a lighter and more viscous texture, providing a thinner and more comfortable feel without causing the skin to feel stuffy, suffocated, or excessively oily, leading to breakouts. The highly water-soluble rhamnolipin also helps to remove excess oil as the body gradually produces sweat and sebum, controlling the amount of oil on the skin's surface within a reasonable range and preventing excessive oil accumulation, thus providing a long-lasting refreshing feeling.

[0099] Experimental Example 3 - Permeation Enhancement Effect

[0100] Take a complete piece of pigskin, remove the surface hair and subcutaneous fat without damaging the stratum corneum. Thaw the treated skin with PBS buffer for 20 minutes, then cut it into the desired size (approximately 2.5cm × 2.5cm squares). The side of the pigskin with the stratum corneum faces the donor cavity of the Franz diffusion cell. Fill the recipient cavity of the Franz diffusion cell with PBS buffer (containing 5% Tween 80). Add 1g of a skin care lotion prepared with A165 as an emulsifier (Comparative Example 3) and 1g of a ceramide 3 skin care lotion prepared by rhamnolipid self-emulsification (Example 3) to the donor cavity of different groups to test the permeability to the pigskin, with 3 parallel samples in each group. Maintain the recipient cavity in a water bath at 37°C for 12 hours, with a stirring speed of 300 rpm during diffusion. After 12 hours, remove the pigskin from the diffusion cell. Remove the remaining sample by washing and gently wiping the surface of the pigskin with degreased cotton. After removing the keratin layer of the pigskin, the pigskin was cut into small pieces and soaked in an equal volume of methanol for ultrasonic extraction for 20 min. The content of ceramide 3 in the extract was determined using high-performance liquid chromatography (HPLC). Chromatographic conditions: SHIMADZU Shim-pack VP-C18ODS (150 mm × 4.6 mm, 5 μm) column, C18ODS guard column, mobile phase V(methanol):V(isopropanol) = 55:45, flow rate 1.0 mL·min -1 The column temperature was 30℃, the UV detector was used at a wavelength of 205nm, and the detection cell temperature was 40℃. The detection results are shown in Table 7 below.

[0101] Table 7. Data on Infiltration Activation Verification

[0102] As shown in Table 7, the rhamnolipin self-emulsifying skin lotion prepared using this application promotes the penetration of ceramide 3 into the skin better than skin lotions prepared using A165 and Tween-80. Furthermore, rhamnolipin with a 2R2C configuration content ≥40% exhibits significantly better penetration-enhancing effects than rhamnolipin self-emulsifying emulsions with a 2R2C configuration content below 40%. This is because the chemical structure of rhamnolipin is very similar to the phospholipid structure of biological cell membranes, effectively delivering substances encapsulated within rhamnolipin micelles into cells and promoting the transdermal absorption of these encapsulated substances. Microorganisms in nature also utilize this characteristic, secreting rhamnolipin as one of their important means of absorbing organic nutrients from the external environment. Utilizing rhamnolipin as a penetration enhancer for functional substances is an approach that aligns with natural selection and has unique and positive application significance.

[0103] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. Application of rhamnolipin in maintaining skin pH.

2. The application according to claim 1, characterized in that, It also includes applications in skin moisturizing and / or penetration enhancement, wherein the rhamnolipin is a rhamnolipin mainly of the Rha-Rha-C10-C10 type, and the Rha-Rha-C10-C10 type accounts for 40% or more of the mass of the rhamnolipin.

3. A skin lotion with rhamnolipid self-emulsification, characterized in that, The raw materials include an aqueous phase and an oil phase, wherein the aqueous phase contains an acid or alkali, and the mass percentage of rhamnolipid in the skin care lotion is ≥0.2%; the pH value of the skin care lotion is 5.0-6.

0.

4. The skin lotion according to claim 3, characterized in that, The oil phase also includes at least one of esters, hydrocarbon oils, natural oils, alkanols, fatty acids, and silicone oils; And / or, the aqueous phase includes water, a preservative, and an acid or alkali; And / or, the total mass percentage of the oil phase and rhamnolipids in the skin care lotion is 2%-80%, preferably 5%-40%; And / or, the rhamnolipin is a rhamnolipin with Rha-Rha-C10-C10 type as the main component, and the mass percentage of Rha-Rha-C10-C10 type in the rhamnolipin is 40% or more.

5. The skin lotion according to claim 4, characterized in that, The esters include at least one of monoesters, diesters, and polyesters; And / or, the hydrocarbon oils include at least one of squalane, squalene, white oil, hydrocarbon waxes, hydrogenated polyisobutylene, isododecane, and isohexadecane; And / or, the natural oils include at least one of meadowfoam seed oil, jojoba oil, sweet almond oil, camellia oil, coconut oil, macadamia nut oil, avocado oil, shea butter, cocoa seed butter, mango seed butter, grape seed oil, marula oil, Rosa damascena flower oil, sunflower seed oil, wild soybean oil, beeswax, ceresin wax, carnauba wax, and candelilla wax; And / or, the alkanol is a fatty alcohol of C12 or above; And / or, the fatty acid is a C12 or higher fatty acid; And / or, the silicone oil includes polydimethylsiloxane and its modified forms after grafting, block, or crosslinking.

6. The skin lotion according to claim 5, characterized in that, The esters include triglycerides, isononyl isononanoate, isopropyl myristate, and ethylhexyl palmitate. At least one of dibutyl ester, ester waxes, diisostearyl malate, triisostearyl citrate, and pentaerythritol tetrastearate; preferably, the triglyceride is obtained by esterification of fatty acids and glycerol, including at least one of caprylic / capric triglyceride, C10-C18 fatty acid triglyceride, triheptyl ester, and tris(2-hydroxymethyl)-2-ethylhexylene. And / or, the alkanols include at least one of cetearyl alcohol, behenyl alcohol, lauryl alcohol, myristyl alcohol, arachidyl alcohol, and beeswax alcohol; And / or, the fatty acid includes at least one of stearic acid, palmitic acid, and myristic acid; And / or, the silicone oil includes at least one of cyclopentasiloxane, 6-viscosity silicone oil, 100-viscosity silicone oil, 350-viscosity silicone oil, phenyl silicone oil, octyl silicone oil, and silicone elastomer.

7. The skin lotion according to any one of claims 4-6, characterized in that, The preservative includes at least one of organic acids, parabens, formaldehyde releasers, and alcohols, preferably at least one of phenoxyethanol, sodium benzoate, potassium sorbate, hexanediol, p-hydroxyacetophenone, caprylyl glycol, capryloyl hydroxamic acid, pentanediol, methylparaben, ethylparaben, and ethylhexylglycerin. And / or, the base includes at least one of potassium hydroxide, sodium hydroxide, triethanolamine, aminomethylpropanol, arginine, and ammonia; And / or, the acid includes at least one of citric acid, lactic acid, fruit acid, and salicylic acid; And / or, the aqueous phase may also include at least one of a humectant and a thickener.

8. The skin lotion according to claim 7, characterized in that, The moisturizer includes at least one of polyols, polysaccharides, polyethylene glycols, and natural factors, preferably at least one of glycerin, propylene glycol, butylene glycol, pentanediol, isopentyl glycol, hexanediol, sorbitol, xylitol, hyaluronic acid, sodium hyaluronate, fructooligosaccharides, trehalose, polyethylene glycol, sodium lactate, amino acids, betaine, pyrrolidone carboxylic acid and its salts, and urea. The thickener includes at least one of polyacrylic acid compounds, polysaccharides, polyurethanes, natural gums, and polyoxyethylene compounds, preferably at least one of carbomer, ammonium acryloyldimethyl taurate / VP copolymer, hydroxyethyl acrylate / sodium acryloyldimethyl taurate copolymer, acrylate / C10-30 alkanol acrylate cross-linked copolymer, polyacryloyldimethyl taurate, xanthan gum, sodium alginate, guar gum, sodium polyacrylate, sodium polyacrylate grafted starch, gellan gum, cellulose compounds, and polyacrylate cross-linked polymer-6.

9. A method for preparing a skin care lotion with rhamnolipid self-emulsification, characterized in that, include: Aqueous phase acquisition, preparation of aqueous phase compositions containing acid or alkali, or preparation of acid- and alkali-free aqueous phase compositions; Oil phase acquisition and preparation of oil phase compositions; Skin lotion is obtained by adding an acid- or alkali-containing aqueous phase composition to an oil phase composition; or by mixing an acid- and alkali-free aqueous phase composition with an oil phase composition to obtain an oil-water mixture, and then adding an acid or alkali to the oil-water mixture to obtain a skin lotion. The rhamnolipid is added to any step of the aqueous phase acquisition, oil phase acquisition, or skin lotion acquisition.

10. The preparation method according to claim 9, characterized in that, The oil phase temperature is 70℃-95℃; And / or, when the aqueous phase and the oil phase are mixed, the mixing is carried out under stirring conditions of 100 rpm-700 rpm or homogenization conditions of 3000 rpm-10000 rpm, and the temperature of the aqueous phase is greater than or equal to the temperature of the oil phase. After adding the raw materials, maintain the temperature at 60℃-70℃ and stir for 10-30 minutes at a stirring speed of 100rpm-700rpm. Then stir and cool down to room temperature.

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