JP7778337B2 - oil-in-water emulsion - Google Patents

Description

The present invention relates to an oil-in-water emulsion that is highly stable even when it contains a large amount of oily ingredients.

Emulsions are used in creams and other products in the fields of cosmetics, pharmaceuticals, food, etc. Among emulsions, oil-in-water emulsions are often used in cosmetics because of the pleasant feel they have when applied to the skin.

In oil-in-water emulsions used as cosmetics, increasing the amount of oily ingredients can be expected to improve emollient effects and prevent skin dryness. Furthermore, when such oil-in-water emulsions are used in sunscreens, precipitation of UV absorbers and stickiness caused by UV absorbers can be suppressed, allowing for the incorporation of larger amounts of UV absorbers, or the squeaking of UV scattering agents can be suppressed, allowing for the incorporation of larger amounts of UV scattering agents, resulting in high UV protection.

However, generally, when a large amount of oil-based ingredients is blended into an oil-in-water emulsion, the amount of surfactant blended is increased to achieve emulsion stability, posing the problem of stickiness caused by the surfactant, which impairs the feel when used. On the other hand, if the amount of surfactant blended is reduced in such cases, there is the problem of the emulsion easily separating into a water layer and an oil layer. Therefore, research and development has been conducted on oil-in-water emulsions that contain large amounts of oil-based ingredients and have high emulsion stability. For example, Patent Document 1 discloses an oil-in-water emulsion cosmetic that contains, in addition to water and oil-based ingredients, phospholipids, glycerin, 1,3-butylene glycol, and a higher alcohol that is solid at 25°C.

Patent No. 5833810

However, the oil-in-water emulsion cosmetic described in Patent Document 1 requires the inclusion of glycerin and 1,3-butylene glycol in specific proportions, and the inclusion of a solid higher alcohol, limiting the range of products to which it can be applied. Furthermore, higher alcohols can cause undesirable sensations during use, such as a braking sensation, making the experience unsatisfactory. In other words, even in light of this patent document, there is still a lack of a sufficient supply of oil-in-water emulsions that are highly stable, have a pleasant experience during use, and are applicable to a wide range of products, even when they contain a large amount of oil-based ingredients. The present invention has been made to solve these problems, and aims to provide an oil-in-water emulsion that is highly stable, has a pleasant experience during use, and is applicable to a wide range of products, even when they contain a large amount of oil-based ingredients.

As a result of extensive research, the inventors have discovered that by combining a water-soluble polymer containing a sugar chain with a nonionic surfactant and/or an amphoteric surfactant, it is possible to produce a highly stable oil-in-water emulsion even if it contains a large amount of oily ingredients. Based on this finding, the inventors have completed the following inventions.

(1) The oil-in-water emulsion of the present invention contains the following components (a) to (d):
(a) a water-soluble polymer containing a sugar chain;
(b) nonionic surfactants and/or amphoteric surfactants;
(c) oily raw material,
(d) Water.

(2) The oil-in-water emulsion according to the present invention may contain (c) an oily ingredient in a proportion of more than 27.5% by mass and less than 80% by mass, based on 100% by mass of the oil-in-water emulsion.

(3) The oil-in-water emulsion according to the present invention may contain (b) a surfactant in a mass ratio of more than 0.0016 to 0.04 per 1 part of (c) the oily raw material.

(4) The oil-in-water emulsion according to the present invention may contain (a) a water-soluble polymer in a proportion of more than 0.4% by mass and less than 4% by mass, based on 100% by mass of the oil-in-water emulsion.

(5) The oil-in-water emulsion of the present invention may have a viscosity of 6000 mPa·s or more at 25°C, measured using a single cylindrical rotational viscometer with an M3 rotor at a rotation speed of 12 rpm for a measurement time of 1 minute.

(6) The oil-in-water emulsion of the present invention may be used in cosmetics.

According to the present invention, an oil-in-water emulsion having high emulsification stability can be obtained even when a large amount of oil-based ingredients are incorporated. According to the present invention, an oil-in-water emulsion having high viscosity stability and minimal viscosity reduction even when salt is incorporated can be obtained. The oil-in-water emulsion of the present invention requires only a small amount of surfactant even when a large amount of oil-based ingredients are incorporated, thereby reducing stickiness caused by surfactants, reduced water resistance of the applied emulsion, and skin irritation and safety concerns caused by surfactants. By incorporating a water-soluble polymer in a predetermined ratio into the oil-in-water emulsion of the present invention, an oil-in-water emulsion having low stickiness and excellent spreadability, comfort on the skin, and usability can be obtained even when a large amount of oil-based ingredients is incorporated.

When the oil-in-water emulsion of the present invention is applied to skin cosmetics or finishing cosmetics, it is possible to blend in a large amount of oily ingredients, making it possible to produce products with improved emollient effects and anti-drying effects for the skin. When the oil-in-water emulsion of the present invention is applied to hair cosmetics, it is possible to blend in a large amount of oily ingredients, making it possible to produce products that give hair a moist feel, manageability, and a smooth texture after use.

When the oil-in-water emulsion of the present invention is applied to sunscreen cosmetics, it is possible to incorporate a large amount of oil-based ingredients, which prevents precipitation of the UV absorber even when a large amount of UV absorber is incorporated, making it possible to produce a product with high emulsion stability. Similarly, because it is possible to incorporate a large amount of oil-based ingredients, it is possible to reduce the squeaky feeling caused by the UV scattering agent even when a large amount of UV scattering agent is incorporated, making it possible to produce a product with a refreshing, pleasant feel on application and in use.

1 is a table showing raw materials used in the present example. 1 is a table showing the composition and the evaluation results of emulsion stability for oil-in-water emulsions produced using various water-soluble polymers. 1 is a table showing the composition and the evaluation results of emulsion stability for oil-in-water emulsions produced by varying the blending amount of a water-soluble polymer. (I) is a table showing the evaluation items and scoring criteria of the sensory test, and (II) is a table showing the scoring results and the average values (evaluation scores) of the five panelists (A to B). 1 is a table showing the composition and the evaluation results of a sensory test for oil-in-water emulsions produced by varying the blending amount of a water-soluble polymer. 1 is a table showing the composition and the evaluation results of emulsion stability for oil-in-water emulsions produced by varying the amount of surfactant blended. 1 is a table showing the composition and emulsion stability evaluation results of oil-in-water emulsions produced using various oily raw materials. 1 is a table showing the composition and the evaluation results of emulsion stability for oil-in-water emulsions produced by varying the blending amount of oily raw material. 1 is a table showing the composition, viscosity, and emulsion stability evaluation results for oil-in-water emulsions produced by varying the blending amounts of a water-soluble polymer and an oily raw material.

The present invention is described in detail below.

An oil-in-water (O/W) emulsion is one in which oil is mixed with water or an aqueous solution, with the oil dispersed in the water or aqueous solution as fine droplets. Whether an emulsion is oil-in-water or water-in-oil can be determined, for example, by sprinkling a powdered dye onto the emulsion and observing how it spreads. Specifically, a powdered water-soluble dye (e.g., methylene blue) or oil-soluble dye (e.g., Sudan III) is sprinkled onto the emulsion. If the dye spreads when the former is sprinkled, but not when the latter is sprinkled, the emulsion can be determined to be an oil-in-water emulsion.

In the present invention, "emulsion stability" refers to the degree of change in state (mainly separation of the oil and aqueous layers) when an emulsion is stored for a certain period of time. In other words, "emulsion stable," "high emulsion stability," or "good emulsion stability" means that there is little or no change in state after a certain period of time has passed, or that it takes a long time for a change in state to occur. Conversely, "no emulsion stability," "low emulsion stability," or "poor emulsion stability" means that there is a large change in state after a certain period of time has passed, or that the storage period until a change in state occurs is short. Emulsion stability can be evaluated, for example, by placing an emulsion in a sealed container and storing it at a relatively high temperature of between room temperature and approximately 50°C for a certain period of time, and then observing its state visually or with a microscope.

In the present invention, "viscosity stability" refers to the degree of viscosity change when salt is added to an emulsion. In other words, "viscosity stable," "high viscosity stability," or "good viscosity stability" means that when comparing the viscosity of an emulsion with added salt with that of an emulsion without added salt, there is little or no difference in the viscosity values between the two. Conversely, "no viscosity stability," "low viscosity stability," or "poor viscosity stability" means that there is a large difference in the viscosity values between the two.

The oil-in-water emulsion of the present invention contains (a) a water-soluble polymer containing a sugar chain, (b) a nonionic surfactant and/or an amphoteric surfactant, (c) an oil-based raw material, and (d) water.

A "water-soluble polymer containing a sugar chain" refers to a molecule that has a large molecular weight and is soluble in water, and that contains a sugar chain or is composed solely of a sugar chain. Water-soluble polymers containing a sugar chain include nonionic, anionic, and cationic types, and any of these can be used in the present invention. Examples of water-soluble polymers containing a sugar chain include those that can be used in cosmetics, quasi-drugs, pharmaceuticals, and foods. Specific examples include hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl starch phosphate, guar gum, tamarind seed gum, polyquaternium-10, xanthan gum, agar, quince seed gum, locust bean gum, sclerotium gum, carrageenan, starch, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and gellan gum.

A single type of water-soluble polymer containing a glycan may be blended into the oil-in-water emulsion, or two or more types may be blended in combination. The blending amount can be set appropriately depending on the type of water-soluble polymer, the intended use of the emulsion, and the types and blending amounts of other ingredients such as (b), (c), and (d) above. For example, assuming the entire emulsion is 100, the lower limit is preferably more than 0.4% by mass, more preferably 0.5% by mass or more, and even more preferably 0.6% by mass or more, 0.7% by mass or more, 0.8% by mass or more, 0.9% by mass or more, or 1.0% by mass or more, from the standpoint of emulsion stability. Furthermore, from the viewpoint of achieving excellent spreadability, comfort on the skin, and usability, the upper limit is preferably less than 4.0% by mass, more preferably 3.9% by mass or less, 3.8% by mass or less, 3.7% by mass or less, 3.6% by mass or less, 3.5% by mass or less, 3.4% by mass or less, 3.3% by mass or less, 3.2% by mass or less, 3.1% by mass or less, or 3.0% by mass or less is more preferred, and even more preferably 2.9% by mass or less, 2.8% by mass or less, 2.7% by mass or less, 2.6% by mass or less, 2.5% by mass or less, 2.4% by mass or less, 2.3% by mass or less, 2.2% by mass or less, 2.1% by mass or less, or 2.0% by mass or less is even more preferred.

In the present invention, the "nonionic surfactant" can be one that can be used in cosmetics, quasi-drugs, pharmaceuticals, foods, etc. Examples of nonionic surfactants include polyoxyethylene fatty acid esters (such as PEG-10 stearate), polyoxyethylene glycerin fatty acid esters (such as PEG-15 glyceryl stearate), polyoxyethylene sorbitan fatty acid esters (such as polysorbate 80), polyoxyethylene hydrogenated castor oil (such as PEG-60 hydrogenated castor oil), polyoxyethylene castor oil (such as PEG-30 castor oil), polyoxyethylene sorbitol tetra fatty acid esters (such as sorbeth 30 tetraoleate), glycerin fatty acid esters (such as glyceryl stearate), and sorbitan fatty acid esters. Examples include esters (such as sorbitan stearate), polyglycerin fatty acid esters (such as polyglyceryl-10 stearate), sucrose fatty acid esters (such as sucrose distearate), alkyl polyglucosides (such as lauryl glucoside), polyoxyethylene cholesteryl ethers (such as cholestrol-10), polyoxyethylene phytosteryl ethers (such as PEG-20 phytosterol), polyoxyethylene alkyl ethers (such as steareth-2, steareth-4, steareth-20, steareth-21), and polyether-modified silicones (such as PEG-10 dimethicone).

In the present invention, the "amphoteric surfactant" can be any surfactant that can be used in cosmetics, quasi-drugs, pharmaceuticals, foods, etc. Examples of amphoteric surfactants include lecithin (soybean lecithin, egg yolk lecithin, soybean phospholipid, hydrogenated egg yolk lecithin, hydrogenated soybean lecithin, hydroxide lecithin, lysolecithin, etc.), sulfate ester salt type, sulfonate salt type, phosphate ester salt type, imidazoline type, betaine type, and amidoamine oxide type amphoteric surfactants. Of these, lecithin is particularly irritating to the skin and is highly safe. Therefore, when the emulsion of the present invention is used in products intended for use on the skin or living organisms, such as skin care cosmetics, it is preferable to use lecithin as the amphoteric surfactant.

One type of nonionic surfactant and amphoteric surfactant may be blended into the emulsion alone, or two or more types may be blended in combination. The amount of these surfactants blended can be set appropriately depending on the type of surfactant, the purpose of the emulsion, and the types and amounts of other ingredients such as (a), (c), and (d) above. However, as shown in the examples below, in the present invention, even though a large amount of oily ingredients is contained, a relatively small amount of surfactant can be used to obtain an emulsion with high emulsion stability.

From the viewpoint of emulsion stability, the specific amount of surfactant to be added is preferably greater than 0.0016 by mass per 1 part of oil-based raw material, and more preferably 0.0017 or more, 0.0018 or more, 0.0019 or more, or 0.002 or more. Furthermore, from the viewpoints of avoiding poor feel and usability due to stickiness and the like caused by the surfactant, reducing skin irritation, and mitigating safety concerns caused by the surfactant, the upper limit is preferably 0.08 or less by mass relative to 1 gram of oil-based raw material, more preferably 0.078 or less, 0.076 or less, 0.074 or less, 0.072 or less, 0.07 or less, 0.068 or less, 0.066 or less, 0.064 or less, 0.062 or less, or 0.06 or less, and even more preferably 0.058 or less, 0.056 or less, 0.054 or less, 0.052 or less, 0.05 or less, 0.048 or less, 0.046 or less, 0.044 or less, 0.042 or less, or 0.04 or less.

The term "oily raw material" refers to a substance that dissolves in oil but is insoluble in water. In the present invention, oily raw materials that can be used in cosmetics, quasi-drugs, pharmaceuticals, foods, etc. can be used. For example, oily raw materials can be divided into oils and fats, higher fatty acids, waxes, hydrocarbons, esters, higher alcohols, silicone oils, etc. based on their chemical structure, and any of these can be used. Furthermore, oily raw materials that are liquid, solid, or semi-solid (such as a paste) at room temperature can also be used. Furthermore, oily raw materials that function as ultraviolet absorbers can also be used.

For example, examples of fats and oils include horse oil, coconut oil, shea butter, shea butter oil, rice germ oil, olive fruit oil, camellia oil, grape seed oil, macadamia nut oil, castor oil, apricot oil, and triethylhexanoin. Examples of higher fatty acids include coconut oil fatty acid, behenic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid. Examples of waxes include jojoba seed oil, carnauba wax, candelilla wax, beeswax, and lanolin. Examples of hydrocarbons include olefin-based hydrocarbons such as hydrogenated polyisobutene, isododecane, and tetradecene, mineral oil (liquid paraffin), paraffin, petrolatum, ceresin, microcrystalline wax, and squalane. Examples of esters include Examples of the alkyl esters include stearyl isostearate, cetyl palmitate, ethylhexyl palmitate, isopropyl myristate, 2-octyldodecyl myristate, cetyl 2-ethylhexanoate, and diisostearyl malate. Examples of higher alcohols include cetyl alcohol, stearyl alcohol, isostearyl alcohol, and 2-octyldodecanol. Examples of silicone oils include straight silicone oils such as dimethicone, amino-modified silicone oils such as amodimethicone, alkyl-modified silicone oils such as stearyl dimethicone, polyether-modified silicone oils such as PEG-12 dimethicone, phenyl-modified silicones such as methylphenylpolysiloxane, and cyclic polysiloxanes such as cyclopentasiloxane. Examples of UV absorbers include ethylhexyl methoxycinnamate, octocrylene, polysilicone-15, homosalate, and ethylhexyl salicylate.

A single oil-based ingredient may be blended into the emulsion, or two or more may be blended in combination. The amount of oil-based ingredient blended can be set appropriately depending on the intended use of the emulsion, but from the standpoint of emulsion stability, assuming the entire emulsion to be 100, the lower limit is preferably more than 27.5% by mass, more preferably 28% by mass or more, 28.5% by mass or more, 29% by mass or more, 29.5% by mass or more, or 30% by mass or more, and even more preferably 31% by mass or more, 32% by mass or more, 33% by mass or more, 34% by mass or more, 35% by mass or more, 36% by mass or more, 37% by mass or more, 38% by mass or more, 39% by mass or more, or 40% by mass or more. The upper limit is preferably less than 80% by mass, more preferably 79.5% by mass or less or 79% by mass or less, and even more preferably 77.5% by mass or less, 77% by mass or less, 76.5% by mass or less, 76% by mass or less, 75.5% by mass or less, or 75% by mass or less.

The viscosity of the oil-in-water emulsion according to the present invention is preferably 6000 mPa·s or more when measured under the following conditions. Such a viscosity allows for high emulsion stability, as will be shown in the examples below. The viscosity of the emulsion can be measured according to "Japanese Pharmacopoeia, 17th Edition (Ministry of Health, Labour and Welfare Notification No. 64, March 7, 2016) 2.53 Viscosity Measurement Method, Method 2, Rotational Viscometer Method."
Viscosity measurement conditions: Apparatus: commercially available single-cylindrical rotational viscometer (Brookfield type viscometer), temperature: 25°C, measurement time: 1 minute, rotor: M3, rotation speed: 12 rpm.

The viscosity of the oil-in-water emulsion can be adjusted by the amount of water-soluble polymer and/or oil-based ingredient. That is, a second preferred amount of water-soluble polymer containing a sugar chain can be an amount at which the viscosity of the oil-in-water emulsion measured under the above conditions is 6000 mPa·s or greater. Similarly, a second preferred amount of oil-based ingredient can be an amount at which the viscosity of the oil-in-water emulsion measured under the above conditions is 6000 mPa·s or greater.

The emulsion of the present invention can be produced by mixing the above (a) to (d) in a conventional manner. More specifically, as shown in the examples described below, first, (a) a water-soluble polymer containing a sugar chain is dispersed in a dispersion medium (such as water or 1,3-butylene glycol) to obtain Dispersion A. Next, (c) a nonionic surfactant and/or amphoteric surfactant is dissolved in an oil-based raw material (b) while heating as necessary, depending on the type and form of the raw material. This is then added to (d) water and dispersed while heating as necessary to obtain Dispersion B. Next, an example of a production procedure is to add Dispersion A to Dispersion B while heating and stirring as necessary, and mix them.

The form of the oil-in-water emulsion of the present invention is not particularly limited, but it can be, for example, liquid, cream, or gel.

The oil-in-water emulsion of the present invention can contain ingredients other than the above (a) to (d), provided that the effects of the present invention are not impaired. Examples of such ingredients include solvents or dispersion media, polyhydric alcohols such as ethanol, glycerin, 1,3-butylene glycol, propylene glycol, dipropylene glycol, and pentylene glycol, sugars such as sorbitol, cationic surfactants, pH adjusters, colorants, animal and plant extracts, vitamins and their derivatives, whitening agents, anti-inflammatory agents, chelating agents, inorganic or organic salts, solubilizers, preservatives, disinfectants, moisturizers, antioxidants, humectants, UV absorbers, UV scattering agents, thickeners, fragrances, cationic polymers, refreshing agents, and cooling agents. These other ingredients can be added as needed during or after emulsion preparation.

The oil-in-water emulsion of the present invention can be used in cosmetics, foods, pharmaceuticals, quasi-drugs, and the like. Examples of cosmetics include those containing a large amount of oily ingredients, such as lotions (moisturizers, serums, etc.), creams, emulsions, sunscreens, sunscreens, cleansers, wash-off packs, massage products, body rinses, liquid foundations, hair styling products (hair creams, etc.), hair care products (hair treatments, hair packs, hair conditioners, etc.), scalp products (scalp treatments, etc.), hair coloring products (color rinses, hair manicures, etc.), and hair rinses. When used in these cosmetics, the above (a), (b), and (c) of the oil-in-water emulsion of the present invention are selected to suit the intended use of the product, and the emulsion is used as a base. Depending on the intended use of the product, fragrances, quality-preserving ingredients (preservatives, antioxidants, etc.), cosmetic agents (UV absorbers, vitamins, plant extracts, whitening agents, etc.), ionic surfactants, and the like can be added to produce the cosmetics.

The present invention will now be described based on various examples. Note that the technical scope of the present invention is not limited to the characteristics demonstrated in these examples. In the examples, "%" represents % by mass ((w/w)%) unless otherwise specified.

<Test Method> Unless otherwise specified, the tests were carried out according to the following methods.
(1) Raw Materials Used An oil-in-water emulsion was produced using the raw materials shown in FIG. 1 (all commercially available products).

(2) Preparation of oil-in-water emulsion An oil-in-water emulsion was prepared according to the following steps 1 to 6.
1. A water-soluble polymer was dispersed in a dispersion medium (a portion of purified water, approximately 4% of the entire emulsion) to obtain Dispersion A.
2. To the remaining purified water, phenoxyethanol was added to 0.35% and pentylene glycol to 1% (final concentrations in the emulsion).
3. While heating to about 65°C to about 80°C, the surfactant was added to the oil-based raw material and dissolved.
4. While heating to about 65°C to about 80°C, the oily raw material from 3 was added to the purified water from 2 and stirred to disperse, thereby obtaining Dispersion B.
5. Dispersion A was added to Dispersion B while stirring. After the addition was complete, the mixture was stirred for 10 minutes.
6. Allow to cool to room temperature, completing the manufacturing process.

(3) Evaluation of emulsion stability The emulsion was placed in a transparent, sealed container and left in an environment at 40°C or 50°C for one week to one month. Alternatively, the emulsion was left in an environment where temperature changes from -10°C to 40°C were repeated in a 24-hour cycle (temperature change cycle) for one month. After one week and one month, the appearance was visually observed and evaluated according to the following criteria.
◯: Remains as one layer (no or very little change in state).
△: Tendency to separate into two layers is observed.
×: Separated into two layers.
-: Not rated.

Example 1: Investigation of Types of Water-Soluble Polymers (1) Evaluation of Emulsion Stability Oil-in-water emulsions Nos. 1 to 8 were prepared using various water-soluble polymers, and their emulsion stability was evaluated. The water-soluble polymers used were hydroxyethyl cellulose, hydroxypropyl starch phosphate, guar gum (galactomannan), and tamarind seed gum, which are nonionic water-soluble polymers containing sugar chains; polyquaternium-10 (O-(2-hydroxy-3-(trimethylammonio)propyl)hydroxyethyl cellulose chloride), which are cationic water-soluble polymers containing sugar chains; xanthan gum and agar, which are anionic water-soluble polymers containing sugar chains; and hydrolyzed collagen, which is a protein or peptide. For guar gum, tamarind seed gum, polyquaternium-10, xanthan gum, and agar, purified water and/or 1,3-butylene glycol were used as the dispersion medium in an amount equivalent to approximately 4% by mass of the total emulsion. The compositions and evaluation results of Nos. 1 to 8 are shown in Figure 2. Steareth-2 and Steareth-21 were used in combination in a blending ratio that gave an HLB (Hydrophilic-Lipophilic Balance) of about 10.

As shown in Figure 2, No. 8 (hydrolyzed collagen) separated after one week of storage at 40°C, whereas No. 1 to No. 7 (nonionic, cationic, or anionic water-soluble polymers containing sugar chains) were all stable for more than one week at 40°C and for more than one month under temperature cycling. Furthermore, No. 1 and Nos. 3 to 6 were stable for more than one month at 50°C. These results demonstrate that the use of water-soluble polymers containing sugar chains can impart high emulsion stability to oil-in-water emulsions. Furthermore, it was also demonstrated that any water-soluble polymer containing sugar chains, whether nonionic, cationic, or anionic, can impart high emulsion stability to oil-in-water emulsions.

(2) Evaluation of Viscosity Stability Oil-in-water emulsions Nos. 1 and 2 were prepared using hydroxyethyl cellulose (a nonionic water-soluble polymer containing sugar chains) or carbomer (anionic water-soluble polymer containing no sugar chains) as the water-soluble polymer. Subsequently, sodium chloride (NaCl) was added to the emulsion to a final concentration of 0.5% or 1%, and the resulting mixture was mixed and the viscosity was measured. The viscosity measurement conditions were as follows: measuring device: VISCOMETER TVB-10M (Toki Sangyo Co., Ltd.), 25°C, measurement time: 1 minute, rotor: M3 (for No. 1 measurement) or M4 (for No. 2 measurement), and rotation speed: 3 rpm. The viscosity of the sample without added NaCl (NaCl concentration 0%) was set to 100%, and the viscosities of the samples with NaCl concentrations of 0.5% and 1% were converted to percentages, which were used as the viscosity change rate. Nos. The compositions of Nos. 1 and 2 (Steareth-2 and Steareth-21 were used in combination in a proportion such that the HLB was approximately 10), the viscosity measurement results (unit: millipascal seconds (mPa s) (centipoise; cps)), and the viscosity change rate (in parentheses) are shown in Table 1.

As shown in Table 1, the viscosity change rate for No. 2 (carbomer) was 32% when the NaCl concentration was 0.5% and 23% when it was 1.0%, showing a significant decrease in viscosity as the NaCl concentration increased. In contrast, the viscosity change rate for No. 1 (hydroxyethyl cellulose) was 96% when the NaCl concentration was 0.5% and 103% when it was 1.0%, remaining nearly constant regardless of the NaCl concentration. These results demonstrate that by using a water-soluble polymer containing a sugar chain, it is possible to obtain an oil-in-water emulsion with minimal viscosity change and high viscosity stability even when salt is added.

Example 2: Study of the amount and viscosity of the water-soluble polymer (1) Evaluation of emulsion stability Oil-in-water emulsions No. 1 to 6 were produced by varying the amount of water-soluble polymer (hydroxyethyl cellulose) from 0.1% to 1.0%, and the emulsion stability was evaluated. The compositions of Nos. 1 to 6 (steareth-2 and steareth-21 were used in combination in a ratio such that the HLB was approximately 10) and the evaluation results are shown in Figure 3.

As shown in Figure 3, No. 5 (hydroxyethyl cellulose 0.5%) to No. 6 (hydroxyethyl cellulose 1.0%) were stable for more than one week at 50°C and for more than one month under temperature cycles, and No. 6 (hydroxyethyl cellulose 1%) was stable for more than one month at 50°C. These results demonstrate that, from the perspective of achieving high emulsion stability, the amount of water-soluble polymer blended is preferably greater than 0.4%, more preferably 0.5% or more, and even more preferably 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, or 1.0% or more.

(2) Sensory Evaluation Oil-in-water emulsions Nos. 1 to 7 were prepared by varying the blending amount of water-soluble polymer (hydroxyethyl cellulose) from 0.5% to 6.0%, and a sensory test was conducted. Specifically, five panelists (A to B) rated the emulsions on a 5-point scale (absolute rating) from 1 to 5 for "ease of spreadability,""skincompatibility," and "usability (comfortability)" when applying and blending the emulsions to the skin. The average of the scores given by all panelists for each sample was calculated and rounded to one decimal place to obtain the rating score. Next, the average of the ratings for the three evaluation items was calculated for each sample, and an overall rating was performed based on the following criteria. The rating criteria and the rating results by each panelist are shown in Figure 4, and the compositions of Nos. 1 to 7 (steareth-2 and steareth-21 were used in combination in a blending ratio such that the HLB was approximately 10), the rating score, and the overall rating are shown in Figure 5.
<<Criteria for overall evaluation>>
◎: The average of the evaluation points for the three items is 3.0 or more. ○: The average of the evaluation points for the three items is 2.5 or more and less than 3.0. △: The average of the evaluation points for the three items is 2.0 or more and less than 2.5. ×: The average of the evaluation points for the three items is less than 2.0.

As shown in Figures 4 and 5, the overall evaluation was ◎ for No. 1 (hydroxyethyl cellulose 0.5%) to No. 3 (hydroxyethyl cellulose 2.0%), and ○ for No. 4 (hydroxyethyl cellulose 3.0%). These results reveal that, from the perspective of achieving excellent spreadability, comfort on the skin, and usability, the amount of water-soluble polymer blended is preferably less than 4.0%, more preferably 3.9% or less, 3.8% or less, 3.7% or less, 3.6% or less, 3.5% or less, 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, or 3.0% or less, and even more preferably 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, or 2.0% or less.

Example 3: Study of Surfactant Types (1) Comparison of Nonionic and Anionic Surfactants Oil-in-water emulsions Nos. 1 and 2 were produced using steareth-2 and steareth-21 (nonionic surfactants) (used in combination in a ratio such that the HLB was approximately 10) or sodium lauroyl aspartate (anionic surfactant) as the surfactant, and the emulsion stability was evaluated. The compositions of Nos. 1 and 2 and the evaluation results are shown in Table 2.

As shown in Table 2, No. 2 (sodium lauroyl aspartate) showed a tendency to separate when stored at 40°C and 50°C for one week, whereas No. 1 (steareth-2 and steareth-21) remained stable for more than one month at 50°C and during temperature cycles. These results demonstrate that the use of nonionic surfactants can impart high emulsion stability to oil-in-water emulsions.

(2) Comparison between nonionic surfactants and amphoteric surfactants Oil-in-water emulsions Nos. 1 and 2 were produced using steareth-2 and steareth-21 (nonionic surfactants) (used in combination in a ratio such that the HLB was approximately 10) or hydrogenated lecithin (amphoteric surfactant) as the surfactant, and the emulsion stability was evaluated. The compositions of Nos. 1 and 2 and the evaluation results are shown in Table 3.

As shown in Table 3, both No. 1 (steareth-2 and steareth-21) and No. 2 (hydrogenated lecithin) were stable for more than one week at 50°C and for more than one month under temperature cycling. These results demonstrate that the use of nonionic or amphoteric surfactants can impart high emulsion stability to oil-in-water emulsions.

(3) HLB Study Oil-in-water emulsions Nos. 1 and 2 were produced using steareth-2 and steareth-21 as surfactants, and the emulsion stability was evaluated. However, the mass ratio of the two was steareth-2:steareth-21 = 1.04:0.96 (blending ratio for an HLB of approximately 10) for No. 1, and 0.09:1.91 (blending ratio for an HLB of approximately 15) for No. 2. The required HLB for the oil-in-water emulsion of mineral oil used as the oil-based raw material is approximately 10. The compositions and evaluation results of Nos. 1 and 2 are shown in Table 4.

As shown in Table 4, both No. 1 (HLB approximately 10) and No. 2 (HLB approximately 15) were stable for more than one month at 50°C and under temperature cycles. This demonstrates that even when a surfactant that does not match the required HLB of the oil-based raw material (No. 2) is used, high emulsion stability can be imparted to oil-in-water emulsions. These results demonstrate that, in this invention, nonionic and amphoteric surfactants, regardless of type, can impart high emulsion stability to oil-in-water emulsions.

Example 4: Investigation of surfactant blend amount The blend amount of surfactants (steareth-2 and steareth-21) (used in combination at a blending ratio such that the HLB is approximately 10) was varied from 0.0002 to 0.01 by mass relative to 1 part of the oil-based raw material to produce oil-in-water emulsions Nos. 1 to 6, and the emulsion stability was evaluated. The compositions and evaluation results of Nos. 1 to 6 are shown in Figure 6.

As shown in Figure 6, No. 5 (oil-based raw material: surfactant = 1:0.002) to No. 6 (oil-based raw material: surfactant = 1:0.01) were stable for more than one month at 50°C and under temperature change cycles. These results reveal that, from the perspective of achieving high emulsion stability, the amount of surfactant blended is preferably greater than 0.0016 parts by mass per 1 part of oil-based raw material, and more preferably 0.0017 or more, 0.0018 or more, 0.0019 or more, or 0.002 or more.

Example 5: Study of the type of oil-based raw material Oil-in-water emulsions Nos. 1 to 7 were produced using various oil-based raw materials, and the emulsion stability was evaluated. The oil-based raw materials used were mineral oil (liquid paraffin) and petrolatum as hydrocarbons, ethylhexyl palmitate (2-ethylhexyl palmitate) as esters, dimethicone (methylpolysiloxane) as silicone oils, olive fruit oil as fats and oils, and jojoba seed oil and beeswax as waxes. The compositions of Nos. 1 to 7 (steareth-2 and steareth-21 were used in combination in a ratio such that the HLB was approximately 7 to 10) and the evaluation results are shown in Figure 7.

As shown in Figure 7, all of Nos. 1 to 7 were stable for more than one week at 50°C. Additionally, Nos. 1 to 6 were stable for more than one month at 50°C and after temperature cycles. These results demonstrate that the present invention can produce oil-in-water emulsions with high emulsion stability, regardless of the type of oil-based raw material.

Example 6: Investigation of the blending amount of oil-based raw material Oil-in-water emulsions Nos. 1 to 11 were produced by varying the blending amount of oil-based raw material (mineral oil) from 10% to 80%, and the emulsion stability was evaluated. The blending amount of surfactant (steareth-2 and steareth-21 used in combination at a blending ratio that gave an HLB of approximately 10) was set to a mass ratio of 0.04 to 1 part of the oil-based raw material. The compositions and evaluation results of Nos. 1 to 11 are shown in Figure 8.

As shown in Figure 8, No. 5 (30% mineral oil) was stable for more than one week at 40°C and for more than one month under temperature cycling. Additionally, No. 6 (40% mineral oil) to No. 10 (79% mineral oil) were all stable for more than one month at 50°C and under temperature cycling.

From these results, it was revealed that, from the viewpoint of achieving high emulsion stability, the lower limit of the amount of oil-based ingredients is preferably more than 27.5%, more preferably 28% or more, 28.5% or more, 29% or more, 29.5% or more, or 30% or more, and even more preferably 31% or more, 32% or more, 33% or more, 34% or more, 35% or more, 36% or more, 37% or more, 38% or more, 39% or more, or 40% or more. Furthermore, from the viewpoint of achieving high emulsion stability, it was revealed that the upper limit of the amount of oil-based ingredients is preferably less than 80%, and more preferably 79.9% or less, 79.8% or less, 79.7% or less, 79.6% or less, 79.5% or less, 79.4% or less, 79.3% or less, 79.2% or less, 79.1% or less, or 79% or less.

Example 7: Study on the viscosity of oil-in-water emulsions Oil-in-water emulsions Nos. 1 to 3 were produced by varying the amount of water-soluble polymer (hydroxyethyl cellulose) from 0.3% to 0.5%. Furthermore, oil-in-water emulsions Nos. 4 to 6 were produced by varying the amount of oil-based raw material (mineral oil) from 27.5% to 50%. The viscosities of these emulsions were measured by the method described in Example 1 (2). However, the rotation speed was changed from 3 rpm to 12 rpm. Furthermore, emulsion stability was evaluated after one week at 40°C and one month under temperature cycling. The compositions of Nos. 1 to 6 (steareth-2 and steareth-21 were used in combination in a ratio that resulted in an HLB of approximately 10) and the evaluation results are shown in Figure 9.

As shown in Figure 9, No. 1, No. 2, and No. 4 had viscosities of 3,470 mPa·s, 5,120 mPa·s, and 5,450 mPa·s, respectively, and exhibited low emulsion stability. In contrast, No. 3, No. 5, and No. 6 had viscosities of 6,870 mPa·s, 6,790 mPa·s, and 7,530 mPa·s, respectively, and exhibited high emulsion stability. In other words, it was revealed that an oil-in-water emulsion with a viscosity of 6,000 mPa·s exhibited high emulsion stability.

These results demonstrate that, from the perspective of achieving high emulsion stability, the viscosity of the oil-in-water emulsion is preferably 6000 mPa·s or higher at 25°C, as measured using a single-cylindrical rotational viscometer with an M3 rotor at a rotation speed of 12 rpm for a measurement time of 1 minute. Furthermore, from the perspective of achieving high emulsion stability, it is preferable to incorporate an amount of water-soluble polymer containing a sugar chain and/or oil-based raw material such that the viscosity of the oil-in-water emulsion measured under these conditions is 6000 mPa·s or higher.

Claims (4)

The following (a) to (d):
(a) a water-soluble polymer containing a sugar chain;
(b) at least one nonionic surfactant and/or amphoteric surfactant selected from the group consisting of polyoxyethylene fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene hydrogenated castor oil, glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, alkyl polyglucosides, polyoxyethylene cholesteryl ethers, polyoxyethylene phytosteryl ethers, polyoxyethylene alkyl ethers, polyether-modified silicones, and hydrogenated lecithins;
(c) at least one oily raw material selected from the group consisting of hydrocarbons, esters, silicone oils, fats and oils, and waxes;
(d) water;
The (a) water-soluble polymer is contained in an amount of more than 0.4% by mass and less than 4% by mass relative to 100% by mass of the oil-in-water emulsion,
The (c) oily raw material is contained in an amount of more than 27.5% by mass and less than 80% by mass relative to 100% by mass of the oil-in-water emulsion,
The oil- based raw material contains a nonionic surfactant and/or an amphoteric surfactant in a mass ratio of more than 0.0016 to 0.04,
The viscosity at 25°C measured using a single cylindrical rotational viscometer with an M3 rotor at a rotation speed of 12 rpm for a measurement time of 1 minute is 6000 mPa·s or more.
Oil-in-water emulsion (but does not contain higher alcohol) (excluding solids) . A cosmetic product containing the oil-in-water emulsion of claim 1. (a) a step of adding a water-soluble polymer containing a sugar chain to a dispersion medium to obtain a dispersion A;
(b) a step of dissolving a nonionic surfactant and/or an amphoteric surfactant in (c) at least one oily raw material selected from the group consisting of hydrocarbons, esters, silicone oils, fats and oils, and waxes , and (d) adding the resulting solution to water to obtain a dispersion B;
a step of adding the dispersion A to the dispersion B and mixing them to obtain an oil-in-water emulsion;
Including,
the oil-in-water emulsion contains the water-soluble polymer (a) in an amount of more than 0.4% by mass and less than 4% by mass relative to 100% by mass of the oil-in-water emulsion,
the oil-in-water emulsion contains the oily raw material (c) in an amount of more than 27.5% by mass and less than 80% by mass relative to 100% by mass of the oil-in-water emulsion,
The oil-in-water emulsion contains a nonionic surfactant and/or an amphoteric surfactant in a mass ratio of more than 0.0016 to 0.04 per 1 of the oil- based raw material.
A method for producing an oil-in-water emulsion (not containing higher alcohol) (excluding solids) . The nonionic surfactant and/or amphoteric surfactant is at least one selected from the group consisting of polyoxyethylene fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene hydrogenated castor oil, glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, alkyl polyglucosides, polyoxyethylene cholesteryl ethers, polyoxyethylene phytosteryl ethers, polyoxyethylene alkyl ethers, polyether-modified silicones, and hydrogenated lecithins ;
The method according to claim 3 .