Stable, low-viscosity oil-in-water emulsion for skin conditioning

Abstract

A novel cosmetic skin care composition is provided, comprising a low-viscosity oil-in-water emulsion that is stable despite a high oil content.The formulation of the present invention is suitable for application to all skin, and some embodiments described herein are configured to be particularly beneficial for hard-to-reach areas such as the scalp.A method of formulating said composition as a low-viscosity stable emulsion is also provided.The present invention relates generally to the field of personal care formulations for skin, and more particularly to a low-viscosity oil-in-water emulsion that is stable despite a high oil content.

Description

Technical Field

[0001] Field of the Invention The present invention generally relates to the field of personal care formulations for the skin, and more particularly to low-viscosity oil-in-water emulsions that are stable despite a high proportion of oil. The formulations of the present invention are suitable for application to all skin types, and some of the embodiments described herein are configured to be particularly beneficial for hard-to-reach areas such as the scalp. A method of formulating the composition as a low-viscosity stable emulsion is also provided.

Background Art

[0002] Background of the Invention Many types of products for providing moisture to the skin have been commonly used over the years. As the science of skin moisturization has evolved, the concept of moisturization using molecules widely known as natural moisturizing factors (NMFs), which are found naturally in nourished skin, has come to the forefront. NMFs are generally known as a wide range of basic units that exist naturally with respect to the skin. Examples of NMFs include various components such as amino acids, ceramides, phospholipids, saccharides, glycerin, hyaluronic acid, sodium pyrrolidone carboxylate (sodium PCA), urea, triglycerides, and fatty acids. <​​​​​Existing scalp care formulations are typically formulated to have a relatively high viscosity to maintain sufficient contact between the active ingredients and the scalp, and to prevent the formulation from running or dripping after application. They also typically contain active ingredients that are effective in controlling dandruff (e.g., zinc pyrithione or selenium sulfide). These are relatively unpleasant active ingredients that can be irritating to the scalp for some consumers. If dandruff is not present, there is little benefit in using scalp care formulations with such strongly active ingredients.

[0005] It is beneficial to provide scalp care formulations that nourish the sensitive skin of the scalp without using unpleasant active ingredients and that avoid the problems associated with excess product dripping during use. Furthermore, since scalp formulations are typically used sparingly by consumers, and only a small amount of product is needed for a single application, the product must withstand long-term storage and repeated use after opening. Therefore, stability is crucial for commercial marketability. With regard to scalp care formulations, it is beneficial to manufacture products that do not separate into their constituent oil and aqueous phases during the many phases of transport under potentially extreme and varied conditions of temperature, storage, retail, and use. [Overview of the project] [Means for solving the problem]

[0006] Summary of the Invention The skincare formulation of the present invention is formulated to have low viscosity, with a concentration similar to that of water. This characteristic promotes rapid absorption into the skin in areas such as the scalp, which in turn eliminates the need to make the formulation more concentrated.

[0007] It is further formulated as an oil-in-water emulsion with a high percentage of emollient, and the oil-in-water emulsion is remarkably stable despite the presence of such high levels of emollient. A particularly preferred emollient is squalane. Squalane is a moisturizing and beneficial hydrocarbon oil that is effective in addressing dry skin, especially dry scalp. It has a dry feel, absorbs quickly, and prevents the accumulation of any problematic residue on the scalp or hair.

[0008] A method for formulating the above composition is also provided, utilizing special equipment to reduce the particle size of the oil phase. Examples of such equipment that may be used include homogenizers, wet grinders, or microfluidizers. Microfluidizers are particularly effective for this application. Microfluidizers can be used for high-pressure homogenization to produce nanoemulsions by reducing the size of suspended solids and emulsions. In this case, the microfluidizer can be used to process the formulation of the present invention into a low-viscosity, stable emulsion. Furthermore, the use of a microfluidizer makes it possible to prepare the formulation of the present invention as an oil-in-water emulsion, which is more stable than a water-in-oil emulsion despite the high level of oil. The above method overcomes significant technical challenges by working in cooperation with a high percentage of oily components.

[0009] Therefore, in one aspect of the present invention, a personal care formulation is provided which consists of an oil-in-water emulsion containing a emollient in a high percentage of 15.00 to 20.00%, most preferably 15.00%.

[0010] In another aspect of the present invention, a personal care formulation is provided, comprising an oil-in-water emulsion containing hyaluronic acid, amino acids, and a natural moisturizing factor including sodium PCA.

[0011] In another aspect of the present invention, a formulation is provided which includes an oil-in-water emulsion having a viscosity close to that of water.

[0012] In a further aspect of the present invention, a formulation is provided that has excellent freeze-thaw stability despite being an oil-in-water emulsion with a high oil content.

[0013] In a further aspect of the present invention, a method is provided for formulating a personal care composition that provides a thin emulsion having a high concentration of a skin emollient and a viscosity similar to that of water.

[0014] In a further aspect of the present invention, the use of such personal care compositions for the treatment of skin or other areas requiring moisture, particularly dry skin, hair, eyelashes, eyebrows, nails, or scalp, is provided.

[0015] In a further aspect of the present invention, a process is provided for the non-therapeutic treatment of skin or other areas requiring moisture, particularly dry skin, hair, eyelashes, eyebrows, nails, or scalp, the process comprising applying the personal care composition of the present invention to a base layer.

[0016] Furthermore, as described herein, the emulsions obtained according to the present invention remain stable and homogeneous over long periods of time at various temperatures and under conditions of repeated freezing and thawing.

[0017] The present invention offers numerous advantages. The cosmetic composition of the present invention provides consumers with an easy-to-apply, leave-on personal care formulation containing a high level of emollient in addition to other NMFs (all of which help nourish the skin). The formulation is prepared as an oil-in-water emulsion and has low viscosity despite the high level of emollient. It does not tend to feel heavy on the scalp or hair or any base layer to which it is applied. The lower viscosity means that the formulation can be applied and rapidly absorbed by the scalp, and that the possibility of over-application of the product and subsequent dripping or running is reduced. The formulation is also highly stable over a range of incubation times at various temperatures. Thus, the present invention offers a beneficial balance between efficacy and ease of use, applicability, and stability. These and other aspects of the present invention will become apparent from the following description. [Brief explanation of the drawing]

[0018] [Figure 1] In the case of the formulations shown in Table 1, an overview of the core process of combining phases A, B, and C is also shown in Figure 1. [Modes for carrying out the invention]

[0019] Detailed description of the invention This specification provides a novel skincare formulation that is beneficial to all skin but particularly beneficial to the scalp, and constitutes a low viscosity formulation despite being formulated as an oil-in-water formulation with a high percentage of emollients. This results in a formulation that is less likely to be applied excessively to areas such as the scalp, and is rapidly absorbed upon application. The formulation also exhibits strong stability under a variety of extreme conditions, especially for oil-in-water emulsions with such high levels of oil.

[0020] Preferred embodiments of the formulations of the present invention also contain many NMFs, which are intended to mimic components found naturally in healthy and nourished skin. Since the NMFs provided in the sample formulations are mainly water-soluble components, they are distributed in the aqueous phase of the oil-in-water formulations.

[0021] A preferred skin softener for use in the present invention is squalane, which is a hydrogenated form of squalene found naturally in the skin. Squalane is advantageous for use in externally applied skin care formulations because its hydrogenated form is stable, whereas non-hydrogenated squalene tends to oxidize.

[0022] In a preferred embodiment of the above formulation, squalane is provided at a relatively high percentage up to 20.00% by weight, preferably up to 18.00% by weight, and most preferably up to 15.00% by weight. This is important because the above formulation is prepared as a low-viscosity stable oil-in-water formulation. Representative oil-in-water formulations with low viscosity require a lower percentage of skin softener. Skin softeners in the range of 5% to 8% or less are typical in such thin emulsions that have been proven to be stable. As described below, a 15% level of squalane in a significantly stable formulation requires further processing steps that are technically advanced to achieve. The inventors are unaware of any commercially available thin oil-in-water emulsions that achieve the level of stability described below for the formulations of the present invention while containing such a high percentage of oil.

[0023] Formulators who are required to include such high levels of oil typically have to prepare water-in-oil emulsions or use other complex methods of emulsification. However, the preparation of water-in-oil emulsions is not a preferred option, particularly for formulations used in areas such as the scalp. Water-in-oil emulsions give a heavier feel to the product. A common example is night cream, which tends to be greasy, heavy and oily-feeling. For other skin care products and particularly for products for the scalp, it is important that they have a lighter feel, as provided by an oil-in-water emulsion, and that they tend to accumulate less on the surface of the scalp and hair.

[0024] Embodiments of the present invention are described below and should not be construed as limiting.

[0025] Formulation method To formulate the compositions of the present invention, most industrial homogenization mixers ( "kettles") sized and configured to mix personal care formulations are suitable. The kettle should be equipped with standard features such as an internal sidewall scraper (also called a sweeper) that is controllable separately from, for example, a homogenization paddle.

[0026] The formulations of the present invention can be prepared in three separate core phases (phase A, phase B, and phase C), with additional ingredients as required (as described below) for some of the phases. All of the steps described below can be carried out in a room temperature environment. All amounts of each ingredient are provided as a percentage of the weight of the final formulation.

[0027] Phase A can first be prepared by adding water to a stainless steel kettle having a built-in side sweeper and homogenizing paddle. The amount of water is appropriate such that the final formulation contains 65–85% by weight of water. As observed in the preferred sample formulation N1, the resulting weight percentage of water in the final formulation after combining all of phases A, B, and C is 74.374884%. The amounts provided in the manufacturing protocol provided below are described with respect to sample formulation N1, but the same procedure may be used to prepare any of the sample formulations outlined in this application.

[0028] In Phase A, any number of water-soluble components containing NMF may be added to the water when used in the formulation. These components, when applied as part of the final formulation, help to nourish the scalp or skin. In the example described below, four separate water-soluble NMF-containing components are used and added together up to 6.53% by weight of the final formulation, but it is noted that up to 20.00% by weight of NMF-containing aqueous components may be used in total if a relatively large volume of water is provided, without exhibiting difficulty in solubility. Similarly, more or less NMF-containing components may be used.

[0029] When used, each aqueous NMF-containing component is added one at a time, with mixing initiated at a low speed after each addition to avoid foaming. The homogenizer speed range is generally shown below with respect to each stage of adding further components, but those skilled in the art can determine to adjust the speed depending on the component being added and the state of the mixture when it is stirred. Those skilled in the art will also recognize what is considered "high," "medium," or "low" speed depending on the model of homogenizer being used and can adapt the homogenization speed accordingly.

[0030] To prepare the sample formulations shown in Table 1 below, in Phase A, a modified hyaluronic acid-containing component consisting of hydrolyzed C12-13 alkylglyceryl hyaluronic acid (marketed by Kewpie Corporation under the name HYALO-REPAIR) is added to water in a kettle in an amount equivalent to 0.05% by weight of the final formulation. HYALO-REPAIR is marketed for cosmetic products because it promotes moisture retention and barrier function restoration. It is mixed into the water until the batch is colorless and clear, starting at a low speed to avoid foaming and operating a side sweeper during homogenization.

[0031] Next, an additional NMF-containing ingredient called PRODEW 500 is added. PRODEW 500 is marketed by Ajinomoto Corporation and contains NMF such as sodium PCA and many amino acids. It is advertised as a beneficial moisturizing ingredient for hair care and other cosmetic products. PRODEW 500 may be added in an amount equivalent to 5.00% by weight of the formulation and should be mixed slowly to facilitate dispersion within the batch. The batch is then mixed slowly with a side sweeper in operation until the batch becomes colorless and transparent.

[0032] Next, a third NMF-containing ingredient (a hair conditioning active ingredient marketed by CLR, called HYGROPLEX V) may be added. An amount equivalent to 1.00% of the final formulation may be added. This ingredient contains hexylene glycol, sugars, and amino acids. It is added slowly while operating a side sweeper during homogenization. Mixing is continued until the batch is colorless and clear.

[0033] Next, the final NMF-containing ingredient (PHYSIOGENYL PF, marketed by Solabias) can be added while operating the side sweeper, initially at a low speed and gradually increasing the homogenizer speed to avoid foam formation. This ingredient contains several salts of PCA and is advertised as promoting effective skin moisturization. It can be added in an amount equivalent to 0.48% by weight of the final formulation. Mixing should be carried out until the batch is colorless and clear.

[0034] After the final water-soluble NMF-containing component is incorporated, phase A should be mixed at a medium speed with respect to the side sweeper, and then continued at a faster speed, taking periodic samples of the mixture from the bottom of the kettle (also known as valve purging or bucket flipping) if necessary to ensure sufficient homogenization. Mixing should continue until phase A is homogeneous, clear, and colorless. The viscosity of the fully mixed phase A remains low, similar to that of water.

[0035] Next, phase B is mixed in a separate kettle. Phase B is a mixture made from hydrophobic or oil-phase-compatible components such as emollients, preservatives, and emulsifiers. In the following sample formulations, the emollient used is squalane in an amount equivalent to 15.00% by weight of the final formulation (NEOSSANCE squalane may be used). However, amounts of emollient up to 20.00% may also be used, although a somewhat smaller amount of emollient may not be completely emulsified, as will be further explained below. Squalane is used in preferred embodiments, but many other emollients suitable for personal care formulations may be used, whole or in part, instead of squalane (e.g., caprylic / capric triglyceride or coco caprylate).

[0036] At least one surfactant is also required to produce an emulsion. A wide range of surfactants (often also called emulsifiers) are available in this field. In a preferred embodiment, the inventors utilized a combination of two surfactants. The first, isoceteth-20 (BRIJ® IC20-70), sold by Croda, can also be added to phase B in an amount equivalent to 1.00% by weight of the final formulation. The second surfactant can also be used in the preferred formulations shown in Table 1 (FLUIDIFEEL EASY (lauryl glucoside, myristyl glucoside, and polyglyceryl-6-laurate)). This component is sold by Seppic. It can be incorporated into phase B in an amount equivalent to 2.00% by weight of the final formulation.

[0037] Many surfactants can be used as alternatives to BRIJ® IC20-70 and FLUIDIFEEL EASY. It is preferable to use surfactants that are liquid at room temperature so that no further steps are required to melt or solubilize them into the formulation. However, at low temperatures, even normally liquid surfactants such as FLUIDIFEEL EASY may crystallize. If this occurs, it can be heated and mixed until homogeneous.

[0038] A necessary component used in a preferred formulation is a preservative. In the example above, a certain amount of ISCAGUARD CPP (chlorphenesin and phenoxyethanol), sold by ISCA, is then added to Phase B in an amount equivalent to 1.00% of the final formulation. Amounts in the range of 0.90–1.1% are also effective. Many other preservatives for personal care formulations are also suitable for use in the present invention as alternatives to ISCAGUARD CPP.

[0039] To prepare Phase B, for the specific components mentioned above, it is preferable to prepare a premixture of BRIJ® IC20-70, FLUIDIFEEL EASY, and ISCAGUARD CPP before adding the final component, NEOSSANCE squalane. It should be gently mixed using only a side sweeper until homogeneous. If mixed vigorously, Phase B will exist as a translucent to clear, colorless liquid with a viscosity similar to that of water.

[0040] After both phases A and B are homogenized, the next step is to slowly and continuously add phase B to phase A while stirring at high speed using both a homogenizer and a side sweeper. Then, grinding is performed at a moderate frequency. Mixing and grinding under these conditions for approximately 5-10 minutes is appropriate. The resulting batch is emulsified and has a translucent to opaque white appearance with a viscosity similar to that of water.

[0041] Phase C is optional. If used, it may consist of a single component used to adjust the pH. A suitable component is PURAC ULTRAPURE 90, sold by Corbian, which consists of lactic acid and water. In the sample formulation, Phase C contains PURAC ULTRAPURE 90 in an amount equivalent to 0.075116% by weight, which is mixed with the combined Phases A and B, and mixed at high speed with respect to the homogenizer and medium speed with respect to the side sweeper, along with grinder recirculation if deemed necessary. Amounts of PURAC ULTRAPURE 90 in the range of 0.067 to 0.083 also work well in the formulation of the present invention. Similarly, many other pH-adjusting acids work well in the above formulation.

[0042] The above product now appears as a translucent to opaque thin white emulsion. If phase C is included, the above product should have a pH in the desired range of 4.00 to 5.00, which is suitable for skincare products.

[0043] Next, a longer mixing is performed to ensure that the batches containing phases A, B, and C (if used) are homogeneously mixed. The product is stirred for approximately 30 minutes using high speed for the homogenizer and medium speed for the side sweeper.

[0044] At this point, the above product should be further processed to reduce the particle size of the emulsion. There are several ways to perform such processing. For example, a standard mill suitable for cosmetic formulations can be used. There are many suppliers of such mills, for example, the colloid mill product line available from Probst & Class. There are also suitable ultrasonic generators available from Sonic Corporation.

[0045] The batch may also be processed using a microfluidizer (which is a high-pressure homogenizer used to perform micromixing of emulsions and dispersions). While gently mixing continues, the batch is extruded through the microfluidizer at a high pressure of 10,000–30,000 psi via a narrow pipe channel to minimize the particle size of the formulation. The most preferred pressure is 30,000 psi, if this setting is available in the equipment used, although the range of 10,000–25,000 psi still produces a satisfactory product. The microfluidizer used by the inventors with satisfactory results was the MICROFLUIDICS M110P V3 Microfluidizer Processor manufactured by Microfluidics Corp. (Westwood, MA). Other models of microfluidizers from MICROFLUIDICS and other suppliers may also be used to achieve the same results. The above microfluidizer should be set with the shortest recirculation loop possible and with a high flow rate to avoid any opportunity for product separation.

[0046] When using a microfluidizer, after the first pass, the batch may be processed through the microfluidizer a second, third, and subsequent times. The formulation is then complete. Since one pass is generally sufficient to obtain a stable formulation, processing the batch through the microfluidizer three times is not essential. However, two or more microfluidizations are recommended to ensure complete processing of the formulation. [Examples]

[0047] The sample formulations prepared using the above method are shown in Table 1. [Table 1-1] [Table 1-2]

[0048] After microfluidization, the resulting formulation is a translucent to opaque emulsion with a pH in the range of 4.0–5.0 and a viscosity close to that of water. Despite containing a large amount of emollient, the emulsion prepared according to the described example is thin, with an average viscosity of 5.26 centipoise (cP). In this context, the viscosity of water is 1 cP, the viscosity of a typical face cream is 255,000 cP, and the viscosity of a hand cream is 465,000 cP. Therefore, the viscosity of the above formulation is low and close to that of water. Viscosity measurements were performed using a BROOKFIELD DVEELVTJ0 digital viscometer at room temperature (25°C) under standard conditions, with the spindle and speed set to LVT 61 and 100 RPM. The results of 10 measurements of the N1 sample performed under the above conditions are shown in Table 1 below. [Table 2]

[0049] Further measurements of the formulations and batches of the present invention showed consistent viscosities of 4.0–8.0 cP under the above conditions, most frequently in the range of 4.5–6.0 cP.

[0050] Regarding density, the specific gravity of the obtained formulation is in the range of 0.95 to 1.05. After passing through a microfluidizer twice, the particle size in the emulsion has a DV50 (median of volume distribution) range equal to or greater than 100 to 300 nm. In other words, the DV50 is greater than or equal to 100 nm.

[0051] In the case of the formulations shown in Table 1, an overview of the core process of combining phases A, B, and C is also shown in Figure 1.

[0052] It should be noted that, depending on the amounts of emollients and surfactants used, some of the final formulations obtained may show signs of a small amount of oily phase that is not fully emulsified. The preferred formulations in Table 1 and others (Category A), as further detailed in Table 5 below, are fully emulsified, however, some formulations with larger amounts of emollients have been observed to have several visible oily phase droplets at the top of the emulsion, observed immediately after formulation (see Categories B and C). Oily phase droplets appearing at the top may be distinguished from a situation where the oily phase has separated from the aqueous phase, which occurs after the time of formulation and may be observed as an oily layer (this oily layer begins to form at the bottom of the emulsion and grows over time).

[0053] Even in formulations having oil droplets at the top, the emulsion remained stable over various periods, as described in the stability test results below.

[0054] Since users are accustomed to shaking cosmetic products before use to ensure a uniform distribution of components in the aliquot dispensed for a single use, the small amount of oil droplets that may appear on the above formulation does not pose a problem for commercial marketability. However, if a complete and perfectly homogeneous emulsion is desired, the amounts of emollients and surfactants should be selected within the range of Category A, as detailed below.

[0055] The formulations of the present invention may further contain additional components, provided that they are soluble in either phase A or phase B, as can be seen by those skilled in the art. Such additional components may include cosmetic ingredients that enhance or complement the skincare formulation. The term “cosmetic ingredient” is used herein to refer to a product applied to the body (e.g., skin, hair) to improve or enhance the skin. Accordingly, further cosmetic ingredients (e.g., conditioners, moisturizers, silicones, and sunscreens) may be included.Other examples of cosmetic ingredients include peptides; other amino acids; carbohydrates (e.g., ascorbyl glucoside, glucosyl hesperidin, and saccharide isomerate); proteins (e.g., collagen, elastin, and hydrolyzed lupine protein); lipids (e.g., ceramides, sphingoglycolipids, and phospholipids); vitamins (e.g., niacinamide, biotin, ascorbic acid, retinol, retinoic acid, and panthenol); benzyl alcohol; sterols (e.g., phytosterols, zaclosterol, and 7-dehydrocholesterol); glycols; glycolic acid; isocyclomone; allantoin; PEG; flavanoids (e.g., apigenin, heseperidin, and genistein); esters (e.g., methylsilanol mannuronate, butyl avocadoate, and jojoba esters); plant products (e.g., Tasmannia Examples of ingredients include, but are not limited to, Lanceolata fruit / leaf extracts, Curculigo Orchioides root extracts, and rose flora; keratolytic agents (e.g., salicylic acid); betaine; glutamate; xylitol; sorbitol; caffeine; menthol; menthyl lactate; zinc oxide; zinc carbonate; erythritol; glycerin; lactate; and bioengineered products (e.g., Pseudoalteromonas exopolysaccharides, Alteromonas ferment filtrate, sodium hyaluronate).

[0056] The formulations of the present invention may also contain vitamins and their derivatives (e.g., panthenol, ascorbic acid, niacinamide, tocopherol, etc.); anti-inflammatory components (e.g., allantoin, phytantriol, sphingosine, and bisabolol, etc.); other moisturizing components (e.g., trimethylglycine and polyglutamic acid, etc.); further antioxidants (e.g., flavonoids, xanthones, isoflavones, alpha-lipoic acid, etc.); and other anti-aging active substances (e.g., β-glucan, α-hydroxy acid, and β-hydroxy acid, etc.).

[0057] The above formulations may also contain fragrances (e.g., essential oils, plant extracts, or synthetic fragrances). Examples include vanilla, cucumber, aloe vera, almond, mango, coconut, melon, linalool, citronellol, cinnamal, limonene, geraniol, eugenol, lavender oil, rose flower extract, bergamot oil, ylang-ylang oil, lemon, lime, orange, tangerine, peppermint, spearmint, and eucalyptus.

[0058] As used herein, the term “about” refers to an amount in the range of 10% or less than 10% of the amount shown, and preferably an amount in the range of 5% or less than 5%, where such amount is either greater than or less than the amount shown.

[0059] The present invention comprises a low viscosity oil-in-water emulsion prepared by a method that includes further processing to reduce particle size, as a weight percentage of the final formulation. (a) an amount of 15.00 to 20.00%, more preferably about 15.00%, of an emollient; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) water; It is equivalent to a skincare formulation containing the following, however (a) to (c) must total 100%.

[0060] The present invention also provides the final formulation as a weight percentage. (a) an amount of 15.00 to 20.00%, more preferably about 15.00%, of an emollient; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) a water-soluble NMF-containing component in an amount of 0.05 to 20.00%, more preferably 0.05 to 10.00%; and (d) water; This corresponds to a skincare formulation containing an oil-in-water emulsion containing the following, however (a) to (d) must total 100%.

[0061] The present invention also provides the final formulation as a weight percentage. (a) an amount of 15.00 to 20.00%, more preferably about 15.00%, of an emollient; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) A water-soluble NMF-containing component in an amount of 0.05 to 20.00%, more preferably 0.05 to 10.00%; (d) Preservatives in an amount of 0.90-1.1%, preferably about 1.0%; and (e) water; This corresponds to a skincare formulation containing an oil-in-water emulsion containing the following, however (a) to (e) must total 100%.

[0062] The present invention also provides the final formulation as a weight percentage. (a) an amount of 15.00 to 20.00%, more preferably about 15.00%, of an emollient; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) A water-soluble NMF-containing component in an amount of 0.05 to 20.00%, more preferably 0.05 to 10.00%; (d) Preservatives in an amount of 0.90-1.1%, preferably about 1.0%; and (e) pH adjuster in an amount of 0.067-0.083%, preferably about 0.075%; and (f) water; This corresponds to a skincare formulation containing an oil-in-water emulsion containing the following, however (a) to (f) must total 100%.

[0063] The present invention also provides the final formulation as a weight percentage. (a) Approximately 15.00% of an emollient; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) Water-soluble NMF-containing components in an amount of approximately 6.53%; (d) a preservative in an amount of about 1.0%; and (e) pH adjuster in an amount of approximately 0.075%; and (f) an appropriate amount of water This corresponds to a skincare formulation containing an oil-in-water emulsion containing [the specified ingredient].

[0064] The present invention also provides the final formulation as a weight percentage. (a) Approximately 15.00% squalane; (b) One or more surfactants in an amount of 2.00 to 4.50%, more preferably 2.50 to 3.50%, and even more preferably about 3.00%; (c) A water-soluble NMF-containing component in a total amount of approximately 6.53%, selected from some or all of the following: HYALO-REPAIR; PRODEW 500, HYDROPLEX V, and PHYSIOGENYL PF; (d) a preservative in an amount of about 1.0%; and (e) pH adjuster in an amount of approximately 0.075%; and (f) an appropriate amount of water This corresponds to a skincare formulation containing an oil-in-water emulsion containing [the specified ingredient].

[0065] The present invention also corresponds to the above-mentioned formulation having high stability under various conditions of time and temperature.

[0066] The present invention also corresponds to the above-mentioned formulation having a pH in the range of 4.0 to 5.0.

[0067] The present invention also corresponds to the above-mentioned formulation having low viscosity and a viscosity close to that of water.

[0068] The present invention also corresponds to the above-mentioned formulation having a viscosity in the range of 4.5 to 8 centipoise, more preferably 5 to 7 centipoise.

[0069] The present invention also corresponds to a method for producing the above formulation using a process that includes means for reducing the particle size of the oil phase of the emulsion.

[0070] The present invention also corresponds to the above-mentioned formulation when prepared according to the method described herein.

[0071] The present invention also corresponds to the use of the above formulations for moisturizing the skin, hair, eyelashes, eyebrows, nails, and / or scalp.

[0072] The present invention also corresponds to the use of the above-mentioned formulation for moisturizing the scalp.

[0073] The formulation of the present invention is intended for use on cleansed skin by rubbing a small amount directly onto the skin. It is particularly suitable for use on the scalp, but can be used on any outer surface of the skin or hair.

[0074] viscosity As described above, the formulation of the present invention has a high percentage of emollient and is an oil-in-water emulsion. When using such a high percentage of emollient, it is typically required to produce a water-in-oil emulsion instead in order to produce a stable emulsion. As mentioned earlier, this is undesirable due to the heavier and oilier feel of water-in-oil emulsions. The inventors were able to achieve a highly stable emulsion through careful control of the surfactant-to-emollient ratio and by using further processing steps in the manufacturing process to reduce the particle size of the oil phase.

[0075] The fact that the above formulation is a dilute emulsion with a viscosity close to that of water is also a significant technological advancement. When emollients are included in such a high percentage, the resulting emulsion is generally thicker and denser and is usually required to take the form of a cream or gel.

[0076] As described above, the low viscosity of the emulsion is advantageous for facilitating the application of the formulation to hard-to-reach areas such as the scalp. Low viscosity means that the product can be applied appropriately in small volumes, is rapidly absorbed into the skin or scalp, and does not accumulate on the surface of the skin or scalp.

[0077] efficacy The above formulation was confirmed to be cosmetically acceptable in that the combination of its components is neither toxic nor incompatible and is suitable for use in contact with stratum corneum tissue. The above formulation also underwent clinical trials to determine its efficacy in skin moisturizing. Formulation N1, as shown in Table 1 above, was tested for its ability to reduce water evaporation from the skin surface using an internationally accepted standard transepidermal water loss (TEWL) test protocol. TEWL is a highly sensitive indicator of skin barrier integrity and is measured mechanically by evaporometry. TEWL refers to the total share of water lost from the dermis and epidermal tissues to the outside through the stratum corneum. A decrease in the integrity of skin barrier function is indicated by an increase in the level of TEWL, while an improvement in the skin barrier is indicated by a decrease in TEWL. To measure using the TEWL protocol, water evaporating from the skin can be measured using an evaporometer having a probe that is placed in contact with the skin surface and contains a sensor that detects changes in water vapor release.

[0078] The above TEWL test was performed on the scalps of 53 healthy volunteers aged 18-65 years, including samples taken from different races and hair types. TEWL was measured by the amount of water vapor released from the surface in g / h / m³. 2 The measurements were taken using an evaporometer that measures in units of 1.5L. The evaporometer used was the Tewameter TM Nano, manufactured by Courage-Khazaka GmbH in Germany.

[0079] Before commencing the study, subjects were instructed to wash their hair with a standard shampoo provided by the clinic for one week and not to use any other hair products. Time 0 (T0) TEWL measurements were then performed in an air-conditioned room under standardized conditions, after a 15-minute relaxation period for the subjects to avoid any abnormalities in sample collection due to sweating or stress. The subjects were then given a standard shampoo and conditioner to take home and were instructed to wash and condition their hair according to their usual schedule, apply a few drops of the formulation of the present invention to a clean, dry scalp daily, massage the product into the scalp for 30 seconds, and then leave the product on without rinsing to allow it to be absorbed.

[0080] The TEWL values ​​for each of the 53 subjects were also measured over a two-week period with a tolerance of ±2 days after daily use of the above product (T 2週間 ), and after 4 weeks of product use with a tolerance of ±2 days (T 4週間 The amount of product used by each subject was recorded by weighing a sample of the test product and comparing it to the weight of a full container of the product provided at the start of the test. All participants were found to have used similar amounts.

[0081] The measurement values ​​for all 53 subjects are shown in Table 3 below. [Table 3-1] [Table 3-2] [Table 3-3]

[0082] The average results across all subjects are shown in Table 4 below. [Table 4]

[0083] As these results show, there was a 15-20% (average 19.6%) reduction in transepidermal water loss from the scalp surface after two weeks of product use, and a 20-25% (average 23.1%) reduction after four weeks of product use. These results were confirmed to be statistically significant by applying Student's t-test with a 95% confidence interval. Therefore, it has been established that the formulation of the present invention is effective in moisturizing the scalp and reducing water evaporation from it.

[0084] Subjective comments from participants regarding the formulation of the present invention were also collected. 77.4% of participants felt satisfied or very satisfied with the product, and 75.5% of participants stated that their scalp felt moisturized after using the product. The majority of these participants stated that their scalp felt significantly moisturized after two weeks of use, while the remainder claimed that they felt moisturized immediately or after four weeks of use. Furthermore, 86.8% rated the product as easy to apply, and 79.2% stated that the product was fully absorbed within 30 seconds of application. Overall, comments regarding the usefulness and subjective effectiveness of the product were positive. The objective measures of product efficacy provided by the TEWL results above further support the effectiveness of the product as a scalp skin hydrator.

[0085] Further formulations In addition to the formulation (N1) in Table 1, nine further formulations differing in the amounts of emollients and surfactants were prepared according to the above manufacturing procedure (which included two microemulsifications). These further formulations were then immediately evaluated for their physical properties. As shown in Table 5 below, some formulations had complete incorporation of the oil phase into the emulsion (Category A), while others had varying amounts of visible oil droplets on top of the remaining components that were otherwise completely emulsified (Categories B and C). As previously stated, the presence of some oil droplets does not preclude the commercial use of the above formulations. The pH of all formulations was within the acceptable range of 4.0–5.0.

[0086] The above formulations can be categorized into three types: (A) fully emulsified; (B) with no small amount of oil phase incorporated (small droplets of oil, less than 1 mm in diameter, on the surface of the remaining components); and (C) with no moderate amount of oil phase incorporated (moderate droplets of oil, greater than 1 mm in diameter, on the surface of the remaining components). The above formulations are shown in Table 5 below. [Table 5a-1] [Table 5a-2] [Table 5b]

[0087] In the above examples, all concentrations are listed as weight percentages of the final formulation and may exclude auxiliary substances such as diluents or fillers. Thus, the listed formulations include the listed components and auxiliary substances that may be selected by those skilled in the art, depending on the physical and chemical properties of the remaining components selected for the composition.

[0088] Regarding physical properties, while the inventors were successful in formulating oil-in-water emulsions, it can be observed that, depending on the differences in the amounts of squalane and surfactant, in some cases (categories B and C), some excess oil was not incorporated into the emulsion.

[0089] The above formulations were also tested for stability as shown below.

[0090] stability Overall, the formulations of the present invention exhibited acceptable stability under a wide range of extreme temperature conditions, and in some cases, remarkable stability. This is another highly beneficial technical feature of the present invention. Typical emulsions, in particular oil-in-water emulsions containing such high percentages of emollients, inevitably separate during storage, especially at higher temperatures.

[0091] Detailed stability tests for Formulation N1 from Table 1 above were conducted over 18 weeks at various temperatures (25°C, 4°C, and 45°C) under incubation in a container representative of those used for the final retail product, as shown in Table 6 below. Sunlight exposure conditions were also tested against controls, as indicated. In all cases, the formulation maintained its physical properties and pH within an acceptable range. [Table 6]

[0092] As shown, formulation N1 maintained its properties, viscosity, and pH despite being subjected to extreme conditions of temperature and UV exposure. Notably, the emulsion did not separate into different layers, as is typical for emulsions over time. In particular, UV exposure and high temperatures of 45°C are likely to cause most commercially available emulsions to separate into constituent layers. Therefore, it is remarkable that the formulation of the present invention remained stable under these conditions over such a long period.

[0093] Maintaining stability under the above conditions during incubation at various temperatures and UV exposures indicates that the product has an excellent shelf life. For example, achieving stability at 45°C for 8 weeks indicates a shelf life of 1 year, achieving stability at 45°C for 10 weeks indicates a shelf life of 1.5 years, and achieving stability at 45°C for 18 weeks indicates a shelf life of 3 years. While 1 year of stability is not considered commercially viable, 1.5 years of stability is acceptable and reasonable. 3 years of stability is considered exceptional for a low-viscosity oil-in-water emulsion.

[0094] Therefore, the above results demonstrate that this formulation has a long shelf life, which is important for storage under transport and retail conditions.

[0095] Two further stability tests yielded similar results. The freeze-thaw test is intended to confirm whether the product can withstand the conditions it may encounter during product transport and warehouse storage. In the field, a very stable product can withstand at least two freeze-thaw cycles.

[0096] The above N1 formulation and other formulations described herein were subjected to five consecutive freeze-thaw cycles (where samples were frozen at -25°C for 24 hours, thawed at room temperature, and the cycle was repeated four more times). At the conclusion of these freeze-thaw cycles, the above samples were observed to remain white and opaque, with a watery viscosity and a pH in the range of 4.50–4.55. The above freeze-thaw test is a rigorous test for personal care emulsions, and many oil-in-water emulsions are expected to separate during this test after just one freeze-thaw cycle. The fact that N1 survived five freeze-thaw cycles is particularly remarkable.

[0097] Similarly, further tests known in industry as "crash stability" were performed on the above formulations. Samples were frozen at -25°C for 24 hours and then incubated in an oven at 45°C for 24 hours. This cycle was repeated three times, and the formulations were evaluated after each cycle. Even after three cycles, the N1 sample remained white and opaque, with a watery viscosity and a pH in the range of 4.50–4.55. Crash stability is considered an even more stringent test for personal care emulsions than the freeze-thaw test, and most oil-in-water emulsions are expected to separate after the first cycle. Surprisingly, however, formulation N1 and several others maintained their properties and viscosity after at least two crash stability cycles. This is also a result of exceptional stability. Overcoming the first crash stability cycle is considered good, and overcoming the second cycle indicates a very stable product. The fact that N1 overcame the third crash stability cycle indicates an extremely stable product.

[0098] Stability tests were also performed on the 10 additional formulations listed in Table 5 above. Components whose amounts remained constant across formulations (NMF-containing components, preservatives, and pH adjusters) are shown in total. The designation "stable" means that the formulation maintained its properties and viscosity—i.e., white opaque, odorless, watery viscosity, and pH in the range of 4.50–4.60. The formulations are characterized into two groups: I - highly stable; and II - not sufficiently stable. The results are shown below. [Table 7]

[0099] The formulations in Group I showed good stability results, with formulation N1 showing the strongest results. The other formulations N2-N7 were equally stable at the indicated incubation temperature, but they could not withstand the same number of freeze-thaw or disintegration stability cycles. Formulations N8-N10 did not show good stability when incubated or did not pass enough freeze-thaw or disintegration cycles to be considered highly stable.

[0100] overview Therefore, the present invention has been confirmed to provide a very stable oil-in-water emulsion with low viscosity. It is suitable and beneficial for application to all skin, but is particularly well suited for application to the scalp.

[0101] The methods described herein, in particular, for reducing the particle size of the above formulation and forming a thin emulsion using a microfluidizer, are novel and result in a highly stable formulation that maintains its viscosity over long storage periods.

[0102] While specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover all such changes and modifications that fall within the scope of the invention. In certain embodiments, for example, the following are provided: (Item 1) An oil-in-water emulsion comprising an aqueous phase and an oil phase, having a viscosity of 4.5 to 8 centipoise, wherein the oil-in-water emulsion comprises, by weight, one or more oils and one or more surfactants based on the total weight of the emulsion, and the ratio of total oil to total surfactants is in the range of 3.8 to 7.5:1. (Item 2) The emulsion described in item 1, wherein the ratio of total oil to total surfactant is in the range of 4.5 to 6.5:1. (Item 3) The emulsion described in item 1, wherein the ratio of total oil to total surfactant is 5:1. (Item 4) The emulsion described in item 1 has a viscosity in the range of 5 to 7 centipoise. (Item 5) An oil-in-water emulsion as described in item 1, further containing 1-20% by weight of natural moisturizing factors. (Item 6) The oil-in-water emulsion described in item 1, further comprising 1% by weight of one or more preservatives. (Item 7) An oil-in-water emulsion as described in item 1, further containing 0.05 to 0.1% by weight of acid. (Item 8) An oil-in-water emulsion as described in item 1, having a specific gravity of 0.95 to 1.05. (Item 9) An oil-in-water emulsion as described in item 1, having oil phase particles having a DV50 of 100-300 nm. (Item 10) An oil-in-water emulsion as described in item 1, having a pH of 4.0 to 5.0. (Item 11) The oil-in-water emulsion described in item 1, wherein one of the oils is squalane. (Item 12) The oil-in-water emulsion described in item 1, wherein the one or more surfactants are selected from the group comprising isoceteth-20 and lauryl glucoside, myristyl glucoside, and polyglyceryl-6-laurate. (Item 13) An oil-in-water emulsion as described in item 1, which is stable at 25°C for at least 18 weeks. (Item 14) An oil-in-water emulsion as described in item 1, which is stable at 4°C for at least 18 weeks. (Item 15) An oil-in-water emulsion as described in item 1, which is stable at 45°C for at least 18 weeks. (Item 16) An oil-in-water emulsion as described in item 1, which remains stable after at least 18 weeks of exposure to sunlight for 8-10 hours per day while incubated at 25°C. (Item 17) An oil-in-water emulsion as described in item 1, which is stable over at least two cycles of freezing at -25°C and thawing at 45°C. (Item 18) An oil-in-water emulsion as described in item 1, which is stable after 5 cycles of freezing at -25°C and thawing at 45°C. (Item 19) The oil-in-water emulsion described in item 1, which, when applied to the skin daily for two weeks, results in a 15-20% reduction in transepidermal water loss. (Item 20) The oil-in-water emulsion described in item 1, which, when applied to the skin daily for four weeks, results in a 20-25% reduction in transepidermal water loss. (Item 21) A method for producing an oil-in-water emulsion as described in item 1, wherein the method is: (a) Preparation of a first mixture of water-soluble components; (b) Preparation of a second mixture of oil-soluble components; (c) Incorporating the second mixture into the first mixture to produce an oil-in-water emulsion; and (d) Reducing the particle size of the oil phase by using one or more of the processes of wet grinding, sonication, or microemulsion. A method that includes. (Item 22) The process is a microemulsion, as described in item 21. (Item 23) The microemulsion is produced under a pressure of 10,000 to 30,000 psi, as described in item 22. (Item 24) The use of the method described in item 21 for formulating the oil-in-water emulsion described in item 1. (Item 25) Cosmetic or dermatological products containing oil-in-water emulsions as described in item 1. (Item 26) A leave-on product comprising an oil-in-water emulsion as described in item 1, wherein the product is a leave-on composition to be applied to and remain on the keratinized tissue. (Item 27) A process for the non-therapeutic treatment of keratinized tissue such as skin, nails, or hair, comprising applying the oil-in-water emulsion described in item 1 to the skin, nails, or hair. (Item 28) A method for stabilizing an oil-in-water emulsion as described in item 1, comprising treating the oil-in-water emulsion with one or more of a wet grinder, an ultrasonic generator, or a microfluidizer. (Item 29) The aforementioned processing is carried out using a microfluidizer, as described in item 28.

Claims

1. An oil-in-water emulsion for leave-on topical use on the scalp, having a viscosity of 4.5 to 8 mPa·s and a specific gravity of 0.95 to 1.05, wherein the oil-in-water emulsion comprises, by weight, 15 to 20% by weight of one or more oils selected from the group consisting of squalane, caprylic / capric triglyceride, coconut caprylate and mixtures thereof, and one or more surfactants, based on the total weight of the emulsion, with a total oil:total surfactant ratio in the range of 3.8 to 7.5:

1.

2. The oil-in-water emulsion according to claim 1, further comprising 1 to 20% by weight of natural moisturizing factors.

3. The oil-in-water emulsion according to claim 1, comprising oil phase particles having a DV50 of 100 to 300 nm.

4. The oil-in-water emulsion according to claim 1, which is stable at 25°C for at least 18 weeks.

5. The oil-in-water emulsion according to claim 1, which is stable at 4°C for at least 18 weeks.

6. The oil-in-water emulsion according to claim 1, which is stable at 45°C for at least 18 weeks.

7. The oil-in-water emulsion according to claim 1, which remains stable even after exposure to sunlight for 8 to 10 hours per day for at least 18 weeks while incubated at 25°C.

8. The oil-in-water emulsion according to claim 1, which is stable over at least two cycles of freezing at -25°C and thawing at 45°C.

9. The oil-in-water emulsion according to claim 1, which is stable after five cycles of freezing at -25°C and thawing at 45°C.

10. The oil-in-water emulsion according to claim 1, which, when applied to the skin daily for two weeks, results in a 15-20% reduction in transepidermal water loss.

11. The oil-in-water emulsion according to claim 1, which, when applied to the skin daily for four weeks, results in a 20-25% reduction in transepidermal water loss.

12. A method for producing an oil-in-water emulsion according to claim 1, wherein the method is: (a) Preparation of a first mixture of water-soluble components; (b) Preparation of a second mixture of oil-soluble components; (c) Incorporating the second mixture into the first mixture to produce an oil-in-water emulsion; and (d) Reducing the particle size of the oil phase by using one or more of the processes of wet grinding, sonication, or microemulsion. A method that includes.

13. The method according to claim 12, wherein the process is a microemulsion.

14. The method according to claim 13, wherein the microemulsion is formed under a pressure of 10,000 to 30,000 psi.

15. The use of the method according to claim 12 for formulating the oil-in-water emulsion described in claim 1.

16. A process for non-therapeutic treatment of keratinized tissue on the scalp, comprising applying the oil-in-water emulsion according to claim 1 to the scalp.

17. A method for stabilizing an oil-in-water emulsion according to claim 1, comprising treating the oil-in-water emulsion with one or more of a wet grinder, an ultrasonic generator, or a microfluidizer.

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