Stable low viscosity oil-in-water emulsions 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 THEINVENTION The present invention generally relates to the field of personal care formulations for skin, and more particularly to low-viscosity oil-in-water emulsions that are stable despite their high oil content.The formulations of the present invention are 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 for formulating said compositions as low-viscosity stable emulsions is also provided. [Background technology]

[0002] 2. Background of the Invention Many types of products for moisturizing skin have been commonly used for many years.As the science of skin moisturization evolves, the concept of moisturizing using molecules that are naturally found in nourished skin and are widely known as natural moisturizing factors (NMFs) has gained attention.NMFs are generally known as a wide range of naturally occurring building blocks for skin.NMFs include various components such as amino acids, ceramides, phospholipids, saccharides, glycerin, hyaluronic acid, sodium pyrrolidine carboxylate (sodium PCA), urea, triglycerides, and fatty acids.

[0003] A particularly neglected area of ​​skin is the scalp. The scalp skin is similar to the skin of other parts of the body, but it has more sebaceous and sweat glands and has a lower barrier function, resulting in a lower ability to maintain and replenish moisture. Therefore, the scalp is prone to moisture imbalance, which can often manifest as dandruff. However, even in the absence of dandruff, it is important to keep the scalp nourished and healthy. The scalp supports the health of hair follicles and the hair that grows from them.

[0004] Existing scalp care formulations are typically formulated to have a relatively high viscosity in order to maintain sufficient contact between active ingredients and scalp and to prevent the formulation from running or dripping after application.They also typically contain active ingredients that are effective for controlling dandruff, such as zinc pyrithione or selenium sulfide.These are relatively unpleasant active ingredients that may be irritating to the scalp for some consumers.In the absence of dandruff, there is little benefit to using scalp care formulations with such strong actives.

[0005] It is beneficial to provide scalp care formulations that nourish the sensitive skin of scalp without using unpleasant active ingredients and avoid the problems associated with excessive product dripping during use.In addition, scalp formulations are typically used sparingly by consumers, and only a small amount of product is required to be applied per use, so the product needs to withstand long-term storage and repeated use after opening.Therefore, stability is important for commercial marketability.For scalp care formulations, it is beneficial to produce products that do not separate into their component oil and water phases during the many phases of temperature, storage, retail, and transportation under potentially extreme and varied conditions of use. Summary of the Invention [Means for solving the problem]

[0006] Summary of the Invention The skin care formulations of the present invention are formulated to have a low viscosity, similar in thickness to that of water, this characteristic promotes rapid absorption into the skin in areas such as the scalp, which in turn eliminates the need for thicker formulations.

[0007] It is further formulated as an oil-in-water emulsion with a high percentage of emollients, said oil-in-water emulsion being surprisingly stable, even though the emollients are present at such high levels.A particularly preferred emollient is squalane.Squalane is a moisturizing, beneficial hydrocarbon oil that is effective in combating dry skin, particularly dry skin on the scalp.It has a dry feel, is quickly absorbed, and prevents any problematic build-up of residue on the scalp or hair.

[0008] Also provided is a method of formulating the composition, which utilizes special equipment to reduce the particle size of the oil phase. Examples of such equipment that can be used are homogenizers, wet mills, or microfluidizers. Microfluidizers are particularly effective for this application. Microfluidizers can be used for high pressure homogenization to create nanoemulsions by reducing the size of suspensions and emulsions. In this case, the microfluidizers can be used to process the formulations of the present invention into stable emulsions with low viscosity. Furthermore, the use of microfluidizers allows the formulations of the present invention to be prepared as stable oil-in-water emulsions rather than water-in-oil emulsions, despite high levels of oil. The method overcomes significant technical challenges by working with a high percentage of oily components.

[0009] Thus, in one aspect of the present invention, there is provided a personal care formulation comprising an oil-in-water emulsion containing a high percentage of emollient, between 15.00 and 20.00%, most preferably 15.00%.

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

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

[0012] In a further aspect of the present invention, formulations are provided which have excellent freeze-thaw stability, especially despite being oil-in-water emulsions with a high proportion of oil.

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

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

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

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

[0017] The present invention has many advantages. The cosmetic composition of the present invention provides consumers with an easy-to-apply leave-on personal care formulation that contains high levels of emollients in addition to other NMFs (all of which help to nourish the skin). The formulation is made as an oil-in-water emulsion and has low viscosity despite the high levels of emollients. It does not tend to feel heavy on the scalp or hair or any substrate to which it is applied. Lower viscosity means that the formulation can be applied and quickly absorbed by the scalp, making it less likely that the product will overapply and subsequently drip or run. The formulation is also highly stable over a range of incubation times at various temperatures. Thus, the present invention provides a beneficial balance between efficacy and ease of use, coverage, and stability. These and other aspects of the invention will become apparent from the following description. [Brief description of the drawings]

[0018] [Figure 1] An overview of the core process of combining Phases A, B, and C for the formulation of Table 1 is also shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Detailed Description of the Invention Provided herein is a novel skin care formulation that is beneficial for all skin, but especially beneficial for scalp, and constitutes a low viscosity formulation, even though it is formulated as an oil-in-water formulation with a high percentage of emollient.This results in a formulation that is unlikely to be overapplied to areas such as scalp, and is quickly absorbed when applied.The formulation also shows strong stability characteristics under various extreme conditions, especially for oil-in-water emulsions with such high oil levels.

[0020] Preferred embodiments of the formulations of the present invention also contain a number of NMFs, which are intended to mimic components naturally found in healthy and nourished skin. The NMFs provided in the sample formulation are primarily water-soluble components, and therefore distribute into the aqueous phase of the oil-in-water formulation.

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

[0022] In a preferred embodiment of the formulation, squalane is provided in 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 since the formulation is prepared as a stable oil-in-water formulation with low viscosity. Typical oil-in-water formulations with low viscosity require a lower percentage of emollient. An emollient in the range of 5% to 8% or less is typical for such thin emulsions that have proven stable. As described below, a 15% level for squalane in a significantly stable formulation requires additional technologically advanced processing steps to achieve. The inventors are not aware of any commercially available oil-in-water thin emulsions that contain such a high percentage of oil while achieving the level of stability described below for the formulations of the present invention.

[0023] Formulators who are required to include such high levels of oil are usually required to prepare water-in-oil emulsions or use other complicated methods of emulsion.However, preparing water-in-oil emulsions is not a good option, especially for formulations that are used in areas such as the scalp.Water-in-oil emulsions provide a heavier feel to the product.A common example is night creams, which tend to feel thick, heavy, and oily.For other skin care products and especially scalp products, it is important to provide a lighter feel and a lower tendency to accumulate on the scalp and hair surface, as provided by oil-in-water emulsions.

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

[0025] Formulation Method Most industrial homogenizing mixers ("kettle") sized and configured for mixing personal care formulations are suitable for formulating the compositions of the present invention. The kettle should be equipped with standard features such as, for example, an internal sidewall scraper (also called a sweeper) that is controllable separately from the homogenizing paddle.

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

[0027] Phase A may be prepared by first adding water to a stainless steel kettle with built-in side sweeper and homogenizing paddle. The amount of water is appropriate such that the final formulation will have water in the range of 65-85% by weight. As seen in 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 make any of the sample formulations outlined in this application.

[0028] In phase A, any number of water-soluble ingredients containing NMF can be added into the water when used in the formulation. These ingredients help to nourish the scalp or skin when applied as part of the final formulation. In the example described below, four separate water-soluble NMF-containing ingredients are used and added together to 6.53% by weight of the final formulation, but it is noted that if a relatively large volume of water is given, an amount of NMF-containing aqueous ingredients up to 20.00% by weight in total can be used and does not show solubility difficulties. Similarly, more or less NMF-containing ingredients can be used.

[0029] If used, each aqueous NMF-containing component is added one at a time, with mixing commencing at low speed after each addition to avoid foaming. Homogenizer speed ranges are generally given below for each stage of addition of additional components, but one skilled in the art can use judgement to adjust the speed depending on the components being added and the state of the mixture as it is stirred. One skilled in the art will also know what is considered a "high", "medium", or "low" speed depending on the model of homogenizer being used, and can adapt the speed of homogenization accordingly.

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

[0031] Next, an additional NMF-containing ingredient called PRODEW 500 is added. PRODEW 500 is sold by Ajinomoto Corporation and contains NMFs such as sodium PCA and many amino acids. It is promoted as a beneficial moisturizing ingredient for hair care and other beauty products. PRODEW 500 may be added in an amount equivalent to 5.00% by weight of the formulation and should be mixed at low speed to promote dispersion within the batch. The batch is mixed at low speed with the side sweeper running until the batch is colorless and clear.

[0032] The third NMF-containing ingredient (a hair conditioning active sold by CLR called HYGROPLEX V) may then 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 at a slow speed with the side sweeper running during homogenization. Mixing is performed until the batch is colorless and clear.

[0033] The final NMF-containing ingredient (PHYSIOGENYL PF sold by Solabia) may then be added with the side sweeper running, initially at a slow speed and eventually increasing the homogenizer speed while avoiding foaming. This ingredient contains several salts of PCA and is advertised as promoting effective moisturization of the skin. It may be added in an amount equivalent to 0.48% by weight of the final formulation. Mixing should be performed until the batch is colorless and clear.

[0034] After incorporation of the final water-soluble NMF-containing ingredient, Phase A should continue to be mixed at medium speed with the side sweeper and at a higher speed with periodic samples of the mixture taken from the bottom of the kettle (also known as valve purging or bucket flips) as needed to ensure adequate homogenization. Mixing should continue until Phase A appears uniform, clear and colorless. The viscosity of thoroughly mixed Phase A remains low and is similar to that of water.

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

[0036] At least one surfactant is also necessary to create the emulsion. A wide range of surfactants (often referred to as emulsifiers) are available in the art. 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 formulation 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 in place of BRIJ IC20-70 and FLUIDIFEEL EASY. It is preferable to use a surfactant that is liquid at room temperature, so that the additional step of dissolving or solubilizing the surfactant into the formulation is not required.However, at low temperatures, even normally liquid surfactants, such as FLUIDIFEEL EASY, can crystallize.When this occurs, it can be heated and mixed until homogeneous.

[0038] An optional ingredient used in the preferred formulation is a preservative. In the above example, an 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 ranging from 0.90 to 1.1% are also effective. Many other preservatives for personal care formulations are also suitable for use in the present invention in place of ISCAGUARD CPP.

[0039] To prepare Phase B, for the specific ingredients listed above, it is preferred to make a premix of BRIJ® IC20-70, FLUIDIFEEL EASY, and ISCAGUARD CPP before adding the final ingredient, NEOSSANCE Squalane. It should be mixed gently using a side sweeper only until homogenous. Phase B when mixed vigorously will exist as a translucent to clear colorless liquid with a viscosity similar to that of water.

[0040] After both Phase A and Phase B are homogenous, the next step is to slowly and continuously add Phase B to Phase A with continuous high speed agitation using both the homogenizer and side sweeper. Medium frequency milling then follows. Approximately 5-10 minutes of mixing and milling under these conditions is adequate. 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. When 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 into the combined phases A and B, and mixed at high speed for the homogenizer and medium speed for the side sweeper, with mill recirculation if deemed necessary. Amounts of PURAC ULTRAPURE 90 in the range of 0.067 to 0.083 also work well in the formulations of the present invention. Similarly, many other pH adjusting acids work well in the above formulations.

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

[0043] Further extended mixing is then performed to ensure that the batch containing Phase A, Phase B, and Phase C (if used) is homogenously mixed. Using high speed for the homogenizer and medium speed for the side sweeper, the product is agitated for approximately 30 minutes.

[0044] At this point, the product should be further processed to reduce the size of the emulsion particles. There are several means to carry out such processing. For example, a standard mill suitable for cosmetic formulations can be used. There are many sources 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 continuing to be gently mixed, the batch is pushed through the microfluidizer at high pressures of 10,000 to 30,000 psi through thin pipe channels to minimize particle size of the formulation. The most preferred pressure is 30,000 psi if this setting is available on the equipment being used, but a range of 10,000 to 25,000 psi still produces a satisfactory product. The microfluidizer used by the inventors with satisfactory results was a 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 microfluidizer should be set with as short a recirculation loop as is available and at a high flow rate to avoid any chance of product separation.

[0046] If a microfluidizer is used, after the first pass the batch may be processed through the microfluidizer a second, third, and so on. The formulation is then complete. It is not necessary to process the batch three times through the microfluidizer, as the first run is generally sufficient to result in a stable formulation. However, two or more microfluidizations are recommended to be absolutely sure of thorough processing of the formulation. EXAMPLES

[0047] 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 the inclusion of a large amount of emollient, the emulsion made according to the described example is thin, with an average viscosity of 5.26 centipoise (cP). For the purposes of this context, the viscosity of water is 1 cP, the viscosity of a representative face cream is 255,000 cP, and the viscosity of a hand cream is 465,000 cP. Thus, the viscosity of the formulation is low and close to that of water. Viscosity measurements were performed at standard conditions at room temperature (25°C) using a BROOKFIELD DVEEL VTJ0 digital viscometer with its spindle and speed set to LVT 61, 100 RPM. Ten measurements of the N1 sample performed under the above conditions are shown in Table 1 below. [Table 2]

[0049] Further measurements of formulations and batches of the present invention have shown consistent viscosities of 4.0-8.0 cP at the above conditions, and most frequently in the range of 4.5-6.0 cP.

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

[0051] An overview of the core process of combining Phases A, B, and C for the formulation of Table 1 is also shown in FIG.

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

[0053] Even in formulations with oil droplets on top, the emulsions still remained stable over various periods of time, as noted in the stability test results below.

[0054] Since users are accustomed to shaking cosmetic products before use to ensure uniform distribution of the components in the aliquot dispensed for one use, the small amount of oil droplets appearing on the formulation above is not a problem for commercial marketability. However, if a complete and completely homogeneous emulsion is desired, the amount of emollient and surfactant should be selected within the range of Category A, as detailed below.

[0055] The formulation of the present invention may further comprise additional ingredients, provided that they are soluble in either phase A or phase B, as can be ascertained by those skilled in the art. Such additional ingredients may comprise cosmetic ingredients that enhance or complement skin care formulations. The term "cosmetic ingredient" is used herein to refer to products that are applied to the body (e.g., skin, hair) to improve or enhance the skin. Thus, additional cosmetic ingredients (e.g., conditioner, moisturizer, silicone, sunscreen, etc.) may be included.Other examples of cosmetic ingredients include peptides; other amino acids; carbohydrates (e.g., ascorbyl glucoside, glucosyl hesperidin, and saccharide isomerates); proteins (e.g., collagen, elastin, and hydrolyzed lupine protein); lipids (e.g., ceramides, glycosphingolipids, and phospholipids); vitamins (e.g., niacinamide, biotin, ascorbic acid, retinol, retinoic acid, and panthenol); benzyl alcohol; sterols (e.g., phytosterols, pomegranate sterols, and 7-dehydrocholesterol); glycols; glycolic acid; iso cyclomone; allantoin; PEG; flavanoids (e.g., apigenin, heseperidin, and genistein); esters (e.g., methylsilanol mannuronate, butyl avocadoate, and jojoba esters); plant products (e.g., Tasmannia Lanceolata fruit / leaf extract, Curculigo Orchioides root extract, and rose flora); keratolytic agents (such as salicylic acid); betaine; glutamate; xylitol; sorbitol; caffeine; menthol; menthyl lactate; zinc oxide; zinc carbonate; erythritol; glycerin; lactate; and biotechnology products (such as Pseudoalteromonas exopolysaccharides, Alteromonas ferment filtrate, sodium hyaluronate).

[0056] The formulations of the invention may also contain vitamins and their derivatives (such as, for example, panthenol, ascorbic acid, niacinamide, tocopherol, etc.); anti-inflammatory ingredients (such as, for example, allantoin, phytantriol, sphingosine, and bisabolol); other moisturizing ingredients (such as, for example, trimethylglycine and polyglutamic acid); additional antioxidants (such as, for example, flavonoids, xanthones, isoflavones, alpha lipoic acid, etc.); and other anti-aging actives (such as, for example, β-glucans, alpha hydroxy acids, and beta hydroxy acids, etc.).

[0057] The formulations may also contain fragrances, such as 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 within 10% or less than 10%, and preferably within 5% or less than 5% of a stated amount, where said amount is either greater than or less than the stated amount.

[0059] The present invention includes low viscosity oil-in-water emulsions made by a process that involves further processing to reduce particle size, as a weight percentage of the final formulation. (a) an emollient in an amount of 15.00 to 20.00%, more preferably about 15.00%; (b) one or more surfactants in an amount of from 2.00 to 4.50%, more preferably from 2.50 to 3.50%, and even more preferably about 3.00%; (c) water; provided, however, that the total of (a) to (c) must amount to 100%.

[0060] The present invention also provides, as a weight percentage of the final formulation, (a) an emollient in an amount of 15.00 to 20.00%, more preferably about 15.00%; (b) one or more surfactants in an amount of from 2.00 to 4.50%, more preferably from 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; provided that the sum of (a) through (d) must equal 100%.

[0061] The present invention also provides, as a weight percentage of the final formulation, (a) an emollient in an amount of 15.00 to 20.00%, more preferably about 15.00%; (b) one or more surfactants in an amount of from 2.00 to 4.50%, more preferably from 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) a preservative in an amount of 0.90 to 1.1%, preferably about 1.0%; and (e) water; provided that the total of (a) through (e) must equal 100%.

[0062] The present invention also provides, as a weight percentage of the final formulation, (a) an emollient in an amount of 15.00 to 20.00%, more preferably about 15.00%; (b) one or more surfactants in an amount of from 2.00 to 4.50%, more preferably from 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) a preservative in an amount of 0.90 to 1.1%, preferably about 1.0%; and (e) a pH adjuster in an amount of 0.067 to 0.083%, preferably about 0.075%; and (f) water; provided that the sum of (a) through (f) must equal 100%.

[0063] The present invention also provides, as a weight percentage of the final formulation, (a) an emollient in an amount of about 15.00%; (b) one or more surfactants in an amount of from 2.00 to 4.50%, more preferably from 2.50 to 3.50%, and even more preferably about 3.00%; (c) a water-soluble NMF-containing component in an amount of about 6.53%; (d) a preservative in the amount of about 1.0%; and (e) a pH adjuster in an amount of about 0.075%; and (f) A suitable amount of water The present invention corresponds to a skin care formulation comprising an oil-in-water emulsion containing:

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

[0065] The present invention also corresponds to said formulations, which have high stability under various conditions of time and temperature.

[0066] The present invention also corresponds to the above preparation, the pH of which is in the range of 4.0 to 5.0.

[0067] The present invention also corresponds to said formulations having a low viscosity, close to the viscosity of water.

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

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

[0070] The present invention also corresponds to the above formulations when made according to the methods described herein.

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

[0072] The present invention also relates to the use of the above preparations for moisturizing the scalp.

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

[0074] viscosity As mentioned 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, in order to make a stable emulsion, typically, it is required to make a water-in-oil emulsion instead.As mentioned above, this is undesirable due to the heavier and more oily feel of water-in-oil emulsion.Through careful control of the ratio of surfactant to emollient and through using additional processing steps in the manufacturing process to reduce the particle size of the oil phase, the inventors have been able to achieve a very stable emulsion.

[0075] It is also a significant technological advancement that the formulation is a thin emulsion, with a viscosity approaching that of water. When such high percentages of emollients are included, the resulting emulsion is generally thicker and denser, usually requiring the formulation to take the form of a cream or gel.

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

[0077] efficacy The formulation was confirmed to be cosmetically acceptable in that the combination of components is suitable for use in contact with stratum corneum tissue without toxicity or incompatibility. The formulation was also subjected to clinical trials to determine its effectiveness in moisturizing the skin. Formulation N1 as shown in Table 1 above was tested for its ability to reduce water loss from the skin surface using the internationally accepted standard transepidermal water loss (TEWL) test protocol. TEWL is a highly sensitive indicator of skin barrier integrity, which is measured mechanically by evaporometry. TEWL refers to the total share of water lost from the dermal and epidermal tissues through the stratum corneum to the outside. A decrease in the integrity of the 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 with a probe placed in contact with the skin surface, which contains a sensor that detects changes in water vapor emission.

[0078] The TEWL test was performed on the scalp of 53 healthy volunteers between the ages of 18 and 65, including a sampling of different races and hair types. TEWL is calculated as the water vapor emitted from a surface in g / h / m 2 The evaporation was measured using an evaporation meter measuring in units The evaporation meter used was a Tewameter™ Nano manufactured by Courage-Khazaka GmbH, Germany.

[0079] Before starting the test, subjects are instructed to wash their hair with the standard shampoo provided by the clinic for one week and not to use other hair products.Then, time 0 (T0) TEWL measurement is carried out under standardized conditions in an air-conditioned room after a 15-minute relaxation period for subjects to avoid abnormality in sample collection caused by sweating or stress.Then, the subjects are given standard shampoo and conditioner to take home, wash and condition their hair according to their usual schedule, and apply a few drops of the formulation of the present invention to clean, dry scalp every day, massage the product into scalp for 30 seconds, and then leave the product to be absorbed without rinsing it off.

[0080] The TEWL values ​​for each of the 53 subjects were also measured after daily use of the product over a 2-week period with a tolerance of ±2 days (T 2週間 ), and after 4 weeks of product use with a tolerance of ±2 days (T 4週間 ) was measured. At the end of the study, 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 the full amount of product provided at the start of the study to record overall usage. All participants were found to have used similar amounts.

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

[0082] The results, averaged across all subjects, were as shown in Table 4 below. [Table 4]

[0083] As shown by these results, there was a 15-20% (average 19.6%) reduction in water loss from the scalp surface after 2 weeks of product use, and a 20-25% (average 23.1%) reduction in water loss from the scalp surface after 4 weeks of product use. These results were confirmed to be statistically significant by application of the Student's t-test at 95% confidence interval. It was therefore established that the formulation of the present invention is effective in moisturizing the scalp and reducing water loss therefrom.

[0084] Subjective comments from participants on 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 they felt their scalp was moisturized after using the product. The majority of these participants stated that they felt their scalp was significantly moisturized after two weeks of use, and the remainder claimed that they felt moisturized immediately or after four weeks of use. In addition, 86.8% rated the product as easy to apply, and 79.2% stated that the product was completely absorbed within 30 seconds of application. Overall, comments on the usefulness and subjective effectiveness of the product were positive. The objective measures of product efficacy as provided by the TEWL results further support the effectiveness of the product as a scalp skin hydrator.

[0085] Further formulations In addition to formulation (N1) in Table 1, nine additional formulations differing in the amount of emollients and surfactants were prepared according to the manufacturing procedure described above (which included two microemulsions). The additional formulations were then immediately evaluated for physical properties. As shown in Table 5 below, some formulations had complete incorporation of the oil phase into the emulsion (category A), whereas some had varying amounts of oil droplets visible on top of the remaining ingredients that were otherwise completely emulsified (categories B and C). As stated previously, the presence of some oil droplets does not preclude the formulation from being used commercially. The pH of all formulations was in the acceptable range of 4.0-5.0.

[0086] The formulations can be placed into three categories: (A) fully emulsified; (B) low oil phase not incorporated (small (<1 mm diameter) droplets of oil on the surface of the remaining ingredients); and (C) moderate oil phase not incorporated (moderate (>1 mm diameter) droplets of oil on the surface of the remaining ingredients). The 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 a percentage by weight of the final formulation and may exclude auxiliary substances such as diluents or fillers. Thus, the above listed formulations include the above listed components and auxiliary substances as may be selected by one of skill in the art depending on the physical and chemical properties of the remaining components selected for the composition.

[0088] With regard to physical properties, the inventors were able to succeed in formulating oil-in-water emulsions, although it can be seen that depending on the differences in the amounts of squalane and surfactants, in some cases (categories B and C) some amount of 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 have demonstrated acceptable and in some cases outstanding stability under a wide range of extreme temperature conditions, which is another highly beneficial technical feature of the present invention.Typical emulsions, especially oil-in-water emulsions containing such high percentages of emollients, will inevitably separate during storage, especially at higher temperatures.

[0091] Detailed stability studies on Formulation N1 of Table 1 above were conducted over 18 weeks at various temperatures (25° C., 4° C., and 45° C.) under incubation in containers representative of those used for the final product at retail, as shown in Table 6 below. Conditions of sunlight exposure were also tested against controls as indicated. In all cases, the formulations maintained their physical properties and pH within acceptable ranges. [Table 6]

[0092] As shown, formulation N1 maintained its properties, consistency, 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 of aged emulsions. In particular, UV exposure and high temperature conditions at 45°C are likely to cause most commercial emulsions to separate into component layers. Therefore, it is surprising that the formulation of the present invention remained stable under these conditions for such an extended period of time.

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

[0094] Thus, the above results demonstrate that this formulation has a long shelf life, which is important for it to withstand shipping and storage under retail conditions.

[0095] Two additional stability tests were performed with similar results. The freeze-thaw test is intended to determine whether the product can withstand conditions likely to be encountered during product shipping and warehouse storage. In the field, a highly stable product is one that can withstand at least two freeze-thaw cycles.

[0096] The 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 samples were observed to remain white and opaque, with a water-like consistency and a pH in the range of 4.50 to 4.55. The freeze-thaw test is a tough test for personal care emulsions, and many oil-in-water emulsions are expected to separate during this test after one freeze-thaw cycle. The fact that N1 in particular survived five freeze-thaw cycles is surprising.

[0097] Similarly, a further test known in the industry as "crash stability" was performed on the above formulations. Samples were frozen at -25°C for 24 hours and then incubated in a 45°C oven 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 water-like consistency and a pH in the range of 4.50-4.55. Disintegration stability is considered to be an even more severe test for personal care emulsions than the freeze-thaw test, and most oil-in-water emulsions are expected to separate after the first. However, surprisingly, formulations N1 and several others maintained their properties and consistency through at least two crash stability cycles. This is also a result of exceptional stability. Surviving the first crash of crash stability is considered good, surviving the second indicates a very stable product. The fact that N1 survived the third crash of crash stability indicates an extremely stable product.

[0098] Stability testing was also performed on 10 additional formulations as described in Table 5 above. Ingredients whose amounts remained constant between formulations (NMF-containing ingredients, preservatives, and pH adjusters) were listed in total. The designation "stable" means that the formulation maintained its characteristics and consistency - i.e., white opaque, odorless, water-like viscosity, and pH in the range of 4.50-4.60. The formulations were characterized into two groups: I - highly stable; and II - not sufficiently stable. The results are shown below. [Table 7]

[0099] The above 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 incubation temperatures shown, but they did not survive the same number of freeze-thaw or collapse stability cycles. N8-N10 did not show good stability when incubated or did not pass enough freeze-thaw or collapse cycles to be considered highly stable.

[0100] overview It has thus been determined that the present invention provides a highly stable oil-in-water emulsion having a low viscosity, which is suitable and beneficial for application to all skin types, but which is particularly well adapted for application to the scalp.

[0101] The methods described herein, particularly the method for reducing the particle size of the formulation and rendering it into a thin emulsion using a microfluidizer, are novel and result in a highly stable formulation that maintains its consistency over extended storage periods.

[0102] While particular embodiments of the present invention have been illustrated and described, it would be obvious 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. It is therefore intended in the appended claims to cover all such changes and modifications that are within the scope of this invention.

Claims

1. 1. An oil-in-water emulsion comprising an aqueous phase and an oil phase and having a viscosity of 4.5 to 8 centipoise, said oil-in-water emulsion comprising, by weight, based on the total weight of said emulsion, one or more oils and one or more surfactants, the ratio of total oil:total surfactant being in the range of 3.8 to 7.5:

1.

2. 2. The emulsion of claim 1, wherein the total oil:total surfactant ratio is in the range of 4.5 to 6.5:

1.

3. 2. The emulsion of claim 1, wherein the total oil:total surfactant ratio is 5:

1.

4. 2. The emulsion of claim 1, wherein the viscosity is in the range of 5 to 7 centipoise.

5. 2. An oil-in-water emulsion according to claim 1, further comprising 1-20% by weight of a natural moisturising factor.

6. 10. An oil-in-water emulsion according to claim 1, further comprising 1% by weight of one or more preservatives.

7. 10. The oil-in-water emulsion of claim 1 further comprising 0.05 to 0.1 wt. % of an acid.

8. 2. The oil-in-water emulsion of claim 1 having a specific gravity of from 0.95 to 1.

05.

9. 2. An oil-in-water emulsion according to claim 1 having oil phase particles with a DV50 of 100 to 300 nm.

10. 2. The oil-in-water emulsion of claim 1 having a pH of from 4.0 to 5.

0.

11. 2. The oil-in-water emulsion of claim 1, wherein one of the oils is squalane.

12. 2. The oil-in-water emulsion of claim 1, wherein the one or more surfactants are selected from the group comprising isoceteth-20 and lauryl glucoside, myristyl glucoside, and polyglyceryl-6-laurate.

13. 10. The oil-in-water emulsion of claim 1, which is stable at 25°C for at least 18 weeks.

14. 2. The oil-in-water emulsion of claim 1, which is stable at 4° C. for at least 18 weeks.

15. 10. The oil-in-water emulsion of claim 1, which is stable at 45°C for at least 18 weeks.

16. 2. The oil-in-water emulsion of claim 1, which is stable after exposure to sunlight for 8-10 hours per day for at least 18 weeks while incubated at 25°C.

17. 2. An 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.

18. 2. The oil-in-water emulsion of claim 1, which is stable after at least 5 cycles of freezing at -25°C and thawing at 45°C.

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

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

21. 10. A method for producing an oil-in-water emulsion according to claim 1, said method comprising: (a) preparing a first mixture of water-soluble components; (b) preparing a second mixture of oil-soluble components; (c) incorporating the second mixture into the first mixture to create an oil-in-water emulsion; and (d) reducing the size of the particles of the oil phase by using one or more of the following processes: wet milling, sonication, or microemulsion. The method includes:

22. 22. The method of claim 21, wherein the process is a microemulsion.

23. The method of claim 22, wherein the microemulsion is carried out under a pressure of 10,000 to 30,000 psi.

24. 22. Use of the method of claim 21 for formulating an oil-in-water emulsion according to claim 1.

25. A cosmetic or dermatological product comprising an oil-in-water emulsion according to claim 1.

26. 13. A leave-on product comprising the oil-in-water emulsion of claim 1, wherein said product is a leave-on composition for application to and remaining on keratinous tissue.

27. 13. A process for the non-therapeutic treatment of keratinous tissue such as skin, nails, or hair, comprising applying to said skin, nails, or hair an oil-in-water emulsion according to claim 1.

28. 13. A method of stabilizing the oil-in-water emulsion of claim 1, comprising treating the oil-in-water emulsion with one or more of a wet mill, an ultrasonicator, or a microfluidizer.

29. 30. The method of claim 28, wherein the processing is performed using a microfluidizer.

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