JP7765897B2 - emulsifying composition - Google Patents

Description

The present invention relates to an emulsion composition. More specifically, the present invention relates to an emulsion composition that has excellent separation stability.

Emulsion compositions are advantageous in terms of efficacy and usability, and are widely used as topical compositions. Emulsion compositions come in a variety of forms, including those that use liquid crystals such as lamellar liquid crystals, reverse hexagonal liquid crystals, and cubic liquid crystals, and each of these forms a unique emulsion system.

Cubic liquid crystals are known to be highly viscous liquid crystals, and are beginning to attract attention from the perspective of the penetration and absorption of active ingredients (Non-Patent Documents 1 and 2).

Patrick T. Spicer, et. al. (2001), “Novel Process for Producing Cubic Liquid Crystalline Nanoparticles (Cubosomes)”, Langmuir, 17, 5748-5756. Jun Wan, (2018), Phytantriol-based lyotropic liquid crystal as a transdermal delivery system. European Journal of Pharmaceutical Sciences, 125 : 93-101.

However, techniques for improving the separation stability of cubic liquid crystal emulsion compositions have not been fully explored.

The present invention therefore aims to provide a formulation technology that improves the separation stability of cubic liquid crystal emulsion compositions.

After extensive research, the inventors discovered that a cubic liquid crystal emulsion composition with excellent separation stability can be obtained by combining an ether-based nonionic surfactant with a higher fatty acid. The present invention was completed through further research based on this finding.

That is, the present invention provides the following aspects.
Item 1. An emulsion composition containing (A) an ether-based nonionic surfactant and (B) a higher fatty acid.
Item 2. The emulsion composition according to Item 1, wherein the component (A) is a polyoxyalkylene alkyl ether, a polyoxyalkylene alkenyl ether, and/or a polyoxyalkylene steryl ether.
Item 3. The emulsion composition according to Item 1 or 2, wherein the component (A) is a polyoxyalkylene alkyl ether and a polyoxyalkylene alkenyl ether.
Item 4. The emulsion composition according to any one of Items 1 to 3, wherein the total HLB value of component (A) is 11 to 18.
Item 5. The emulsion composition according to any one of Items 1 to 4, wherein the content of the component (A) is 3 to 25 wt %.
Item 6. The emulsion composition according to any one of Items 1 to 5, wherein the component (B) has 14 or more carbon atoms.
Item 7. The emulsion composition according to any one of Items 1 to 6, wherein the content of the component (B) is 0.1 to 1 part by weight per 1 part by weight of the component (A).

The present invention provides a cubic liquid crystal emulsion composition with excellent separation stability.

The emulsion composition of the present invention is characterized by containing (A) an ether-based nonionic surfactant (hereinafter also referred to as "component (A)") and (B) a higher fatty acid (hereinafter also referred to as "component (B)"). The emulsion composition of the present invention is described in detail below.

(A) Ether-Based Nonionic Surfactant The emulsion composition of the present invention contains an ether-based nonionic surfactant as component (A). In the present invention, the ether-based nonionic surfactant refers to a nonionic surfactant having a structure in which a polyoxyalkylene group serving as a hydrophilic moiety and a hydrocarbon group serving as a hydrophobic moiety are ether-bonded.

Examples of the alkylene oxide in the polyoxyalkylene group include alkylene oxides having 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms, such as ethylene oxide, propylene oxide, and butylene oxide. These alkylene oxides may be contained alone or in combination in the ether-based nonionic surfactant molecule. The number of moles of these alkylene oxides added may be, for example, 5 to 40, and more preferably 7 to 36.

Specific examples of ether-based nonionic surfactants include polyoxyalkylene alkyl ethers (nonionic surfactants having a structure in which a polyoxyalkylene group and an alkyl group are ether-bonded), polyoxyalkylene alkenyl ethers (nonionic surfactants having a structure in which a polyoxyalkylene group and an alkenyl group are ether-bonded), and polyoxyalkylene steryl ethers (nonionic surfactants having a structure in which a polyoxyalkylene group and a steryl group are ether-bonded).

The alkyl group in the polyoxyalkylene alkyl ether may be a straight-chain or branched alkyl group having 10 to 24 carbon atoms. Specific examples of the alkyl group include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl (cetyl), heptadecyl, octadecyl (stearyl), nonadecyl, eicosyl, docosyl, tetracosyl, and decyltetradecyl. These polyoxyalkylene alkyl ethers may be used alone or in combination. Among these polyoxyalkylene alkyl ethers, from the viewpoint of further improving separation stability, preferred are linear alkyl groups having 12 to 22 carbon atoms (more preferably 14 to 20 carbon atoms, even more preferably 16 to 18 carbon atoms) and branched alkyl groups having 14 to 24 carbon atoms (more preferably 18 to 24 carbon atoms, even more preferably 22 to 24 carbon atoms). Preferred examples include hexadecyl (cetyl) groups, heptadecyl groups, octadecyl (stearyl) groups, and decyltetradecyl groups, and a more preferred example is octadecyl (stearyl) groups.

The alkenyl group in the polyoxyalkylene alkenyl ether may be a straight-chain or branched alkenyl group having 10 to 24 carbon atoms, preferably 12 to 22 carbon atoms, and more preferably 14 to 20 carbon atoms. Specific examples of the alkenyl group include decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl (oleyl), nonadecenyl, icosenyl, henicosenyl, docosenyl, tricosenyl, and tetracosenyl. These alkenyl groups have a double bond at any position. These polyoxyalkylene alkenyl ethers may be used alone or in combination. Among these polyoxyalkylene alkenyl ethers, from the viewpoint of further improving separation stability, linear alkenyl groups having 12 to 22 carbon atoms are preferred, and linear alkenyl groups having 16 to 20 carbon atoms are more preferred. Specific preferred examples include hexadecenyl, heptadecenyl, octadecenyl (oleyl), nonadecenyl, and icosenyl groups, and a more preferred example is octadecenyl (oleyl).

Examples of steryl groups in polyoxyalkylene steryl ethers include cholesteryl groups (cholesterol residues), cholestaryl groups (cholestanol residues), stigmasteryl groups (stigmasterol residues), β-sitosteryl groups (β-sitosterol residues), lanosteryl groups (lanosterol residues), ergosteryl groups (ergosterol residues), phytosteryl groups (phytosterol residues), and hydrogenated groups thereof. These polyoxyalkylene steryl ethers may be used alone or in combination. Among these polyoxyalkylene steryl ethers, phytosteryl groups (phytosterol residues) are preferred from the viewpoint of further improving separation stability.

In the present invention, component (A) may be one of the above-mentioned polyoxyalkylene alkyl ethers, polyoxyalkylene alkenyl ethers, and polyoxyalkylene steryl ethers, or a combination of two or more of them. Among the above-mentioned polyoxyalkylene alkyl ethers, polyoxyalkylene alkenyl ethers, and polyoxyalkylene steryl ethers, a combination of polyoxyalkylene alkyl ethers and polyoxyalkylene alkenyl ethers is preferred.

In the present invention, the total HLB value of component (A) is not particularly limited, but examples include 11 to 18. Here, the HLB value generally indicates the affinity of a surfactant for water and oil. In the present invention, the HLB value determined by the Griffin method is used. The total HLB value refers to the sum of the individual HLB values of all compounds used in component (A), multiplied by the weight percentage of each compound when the total weight of component (A) is taken as 1. For example, if component (A) contains only compound a, which has an HLB value of 15, the total HLB value is 15 (= 15 x 1). If component (A) contains compound a1, which has an HLB value of 10, and compound a2, which has an HLB value of 18, in a weight ratio of a1:a2 = 4:6, the total HLB value is 14.8 (= 10 x 0.4 + 18 x 0.6). From the perspective of further improving separation stability, the total HLB value of component (A) is preferably 12 to 16, more preferably 13 to 15, and even more preferably 13.8 to 14.5.

Particularly preferred examples of component (A) include polyoxyethylene (20) polyoxypropylene (6) decyltetradecyl ether, polyoxyethylene (30) polyoxypropylene (6) decyltetradecyl ether, polyoxyethylene (20) polyoxypropylene (4) cetyl ether, polyoxyethylene (20) stearyl ether, polyoxyethylene (20) oleyl ether, and polyoxyethylene (30) phytosterol; more preferably, polyoxyethylene (30) polyoxypropylene (6) decyltetradecyl ether, polyoxyethylene (20) polyoxypropylene (4) cetyl ether, polyoxyethylene (20) stearyl ether, and polyoxyethylene (20) oleyl ether; even more preferably, polyoxyethylene (20) stearyl ether and polyoxyethylene (20) oleyl ether.

In the emulsion composition of the present invention, the content of component (A) is not particularly limited, but may be, for example, 3 to 25% by weight. From the perspective of further improving separation stability, the content of (A) is preferably 9 to 25% by weight, more preferably 10 to 22% by weight, and even more preferably 12 to 15% by weight.

(B) Higher Fatty Acid The emulsion composition of the present invention contains a higher fatty acid as component (B). In the present invention, a higher fatty acid is a fatty acid having 12 or more carbon atoms.

The higher fatty acid may be either a straight-chain fatty acid or a branched fatty acid, and may be either a saturated fatty acid or an unsaturated fatty acid. Specific examples of component (B) include lauric acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, arachidic acid, mead acid, arachidonic acid, behenic acid, isopalmitic acid, isostearic acid, and isoarachidic acid, with preferred examples being isopalmitic acid, isostearic acid, and isoarachidic acid.

These higher fatty acids may be used alone or in combination.

Of the above higher fatty acids, from the viewpoint of further improving separation stability, higher fatty acids having preferably 14 or more carbon atoms, more preferably 16 or more carbon atoms, and even more preferably 18 or more carbon atoms are preferred. The upper limit of the carbon number of component (B) is, for example, 22 or less, preferably 20 or less, and more preferably 19 or less.

Furthermore, among the above-mentioned higher fatty acids, branched fatty acids and/or saturated fatty acids are preferred, and branched saturated fatty acids are more preferred, from the viewpoint of further improving separation stability.

Of the above higher fatty acids, preferred examples of component (B) used in the present invention include isostearic acid and isoarachic acid, and a particularly preferred example is isostearic acid.

In the emulsion composition of the present invention, the content of component (B) is not particularly limited, but may be, for example, 2 to 10% by weight. From the viewpoint of further improving separation stability, the content of (B) is preferably 3 to 8% by weight, and more preferably 4 to 6% by weight.

In the emulsion composition of the present invention, the content ratio of component (B) per 1 part by weight of component (A) is determined by the above-mentioned contents of each component. However, from the viewpoint of further improving separation stability, the content ratio of component (B) per 1 part by weight of component (A) is preferably 0.05 to 1 part by weight, more preferably 0.15 to 0.7 parts by weight, and even more preferably 0.3 to 0.5 parts by weight.

The emulsion composition of the present invention contains water as a base. The water content in the emulsion composition of the present invention is not particularly limited, but may be, for example, 41% by weight or more, preferably 42 to 85% by weight, more preferably 43 to 60% by weight, and even more preferably 44 to 55% by weight.

The emulsion composition of the present invention contains an oily base. As the oily base, any oily base that is used in emulsion compositions can be used without any particular limitation, but from the viewpoint of further improving separation stability, liquid oil is preferably used. Examples of liquid oils include liquid hydrocarbon oils such as liquid paraffin, squalene, and squalane; silicone oils such as dimethylpolysiloxane and methylphenylpolysiloxane; medium-chain fatty acid triglycerides such as triglycerides of fatty acids having from 6 to 12 carbon atoms (for example, vegetable oils such as camellia oil, soybean oil, cottonseed oil, sesame oil, safflower oil, corn oil, coconut oil, perilla oil, and castor oil; and synthetic oils such as 2-linoleoyl-1,3-dioctanoylglycerol); and ester oils such as cetyl ethylhexanoate, octyldodecyl myristate, glyceryl tri-2-ethylhexanoate (glycerin triisooctanoate), isopropyl myristate, and glyceryl divalamethoxycinnamate-monoethylhexanoate.

These liquid oils may be used alone or in combination of two or more. Among these liquid oils, liquid hydrocarbon oils and ester oils are preferred, from the viewpoint of further improving separation stability.

The content of the oily base in the emulsion composition of the present invention is not particularly limited, but may be, for example, 5 to 20% by weight, and more preferably 10 to 15% by weight.

The emulsion composition of the present invention may contain, as necessary, other components in addition to the above-mentioned components, to the extent that the effects of the present invention are not impaired, such as other surfactants (anionic surfactants, cationic surfactants, zwitterionic surfactants), thickeners, other aqueous bases (monohydric lower alcohols such as ethanol and isopropanol; polyhydric alcohols, etc.), buffers, chelating agents, antioxidants, stabilizers, preservatives, fragrances, freshening agents, dispersants, wetting agents, etc. Among these other components, anionic surfactants and polyhydric alcohols are preferred from the viewpoint of further improving separation stability.

Anionic surfactants include those having a phosphate group, a carboxyl group, or a sulfate group, and one or more of these may be used. Among these anionic surfactants, those having a phosphate group are preferred, from the viewpoint of further improving separation stability.

Examples of anionic surfactants having a phosphate group include polyoxyethylene (POE) alkyl ether phosphates or their salts, and monoalkyl phosphates or their salts. Examples of POE alkyl ether phosphates or their salts include POE lauryl ether phosphate, sodium POE oleyl ether phosphate, and sodium POE cetyl ether phosphate. Examples of monoalkyl phosphates or their salts include lauryl phosphate. These anionic surfactants having a phosphate group can be used alone or in combination of two or more.

When the emulsion composition of the present invention contains an anionic surfactant, the content of the anionic surfactant is, for example, 1 to 10% by weight, preferably 2 to 8% by weight, and more preferably 3 to 6% by weight.

Examples of polyhydric alcohols include glycerin, propylene glycol, and 1,3-butylene glycol, and one or more of these may be used. Among these polyhydric alcohols, glycerin and 1,3-butylene glycol are preferred from the viewpoint of further improving separation stability.

When the emulsion composition of the present invention contains a polyhydric alcohol, the content of the polyhydric alcohol is, for example, 4 to 20% by weight. From the viewpoint of further improving separation stability, the content of the polyhydric alcohol is preferably 6 to 15% by weight, and more preferably 8 to 12% by weight.

The form of the emulsion composition of the present invention is not particularly limited, and examples thereof include liquid, semi-solid (gel, paste), and solid forms. From the viewpoint of further enhancing the effect of improving the feeling of use, the formulation is more preferably in the form of a gel or paste.

The emulsion composition of the present invention forms cubic liquid crystals. The formation of cubic liquid crystals can be confirmed using a small-angle X-ray scattering device.

The emulsion type of the emulsion composition of the present invention may be either an oil-in-water emulsion or a water-in-oil emulsion, but is preferably an oil-in-water emulsion.

The emulsion composition of the present invention can be used as an external preparation such as a cosmetic, topical quasi-drug, or topical pharmaceutical. The product form of the external composition of the present invention is not particularly limited, but examples include lotions, creams, ointments, emulsions, gels, oils, liniments, and aerosols.

The emulsion composition of the present invention can generally be used externally. When used externally, the application site of the emulsion composition of the present invention is not particularly limited. However, due to the bioadhesiveness based on the high viscosity unique to cubic liquid crystals, it can be preferably applied to skin areas requiring protection and/or areas that come into contact with clothing and other wearable articles. Specific areas to which the emulsion composition of the present invention can be applied include, for example, the face, neck, chest, back, arms, elbows, hands, axillae, abdomen, vulva, buttocks, anus, legs, fingers, toes, and soles, with the vulva, buttocks, anus, etc. being preferred, and the vulva being particularly preferred.

The target populations for the emulsion composition of the present invention are not particularly limited, but preferred examples include newborns (up to 28 days after birth) who are prone to diaper rash; infants (28 days after birth and under 1 year old); toddlers (1 year old to preschool age); women who are prone to rashes caused by menstrual blood and/or vaginal secretions; and middle-aged people (approximately 45 to under 55 years old) and elderly people (55 years and older) who are prone to rashes caused by urine, menstrual blood, and/or vaginal secretions. Among these, particularly preferred target populations include middle-aged and elderly people (approximately 45 years old and older) whose skin (particularly the vulva) is prone to physical and/or chemical irritation due to contact with clothing and other articles of clothing, menstrual blood, vaginal secretions, sweat, etc.

Manufacturing Method of Emulsion Composition The emulsion composition of the present invention can be prepared by mixing the above-mentioned components (A) and (B), and other components to be blended as necessary, in the usual order in the desired amounts, in accordance with a conventional manufacturing method of an emulsion composition.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

The emulsion compositions shown in Tables 1 and 2 were prepared. First, predetermined amounts of oily bases (liquid paraffin, glycerin triisooctanoate, and sodium POE oleyl ether phosphate) were mixed, and then components (A) and (B) were added and mixed at 80°C to prepare an oily composition. Separately, predetermined amounts of aqueous bases (purified water, 1,3-butylene glycol, and glycerin) were mixed at 80°C to prepare an aqueous composition. These oily and aqueous compositions were mixed at 80°C and emulsified to prepare emulsion compositions. The resulting emulsion compositions were evaluated as follows.

<Confirmation of cubic liquid crystal formation>
The formation of cubic liquid crystals in each emulsion composition was confirmed using a small-angle X-ray scattering device. Specifically, each emulsion composition was irradiated with X-rays, and the scattered X-rays emitted from the emulsion were detected to obtain a peak chart. The obtained peak pattern was then compared with a peak pattern characteristic of cubic liquid crystals to confirm the formation of cubic liquid crystals in each emulsion composition.

<Separation stability>
100 g of each emulsion composition was filled into a mayonnaise bottle (140 mL) and stored in a dark place at 25°C for 6 months. After storage, the appearance of each emulsion composition was observed, and the degree of separation stability was rated on a 10-point scale using a visual analog scale (VAS), with 10 points representing a clear state with no separation observed (Example 1) and 1 point representing a state in which severe separation was observed and the mixture did not become uniform even after shaking (Comparative Example 1). A score of 5 or higher was considered to have the desired separation stability. The results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, it was found that the blending of components (A) and (B) results in the formation of cubic liquid crystals with excellent separation stability.

Prescription example

Each emulsion composition shown in Tables 3 and 4 was prepared, and the formation of cubic liquid crystals, separation stability, and usability were evaluated using the same methods as in the Examples. Cubic liquid crystals were formed in all emulsion compositions of Formulation Examples 1 to 15, and the desired separation stability was observed.

Claims (6)

(A) an ether-based nonionic surfactant , ( B) a higher fatty acid , and (C) a polyhydric alcohol ,
An emulsion composition , wherein the total HLB value of the component (A) is 13 to 14.5, and the content of the component (C) is 4 to 12 wt % . The emulsion composition according to claim 1, wherein component (A) is a polyoxyalkylene alkyl ether, a polyoxyalkylene alkenyl ether, and/or a polyoxyalkylene steryl ether. The emulsion composition according to claim 1 or 2, wherein component (A) is a polyoxyalkylene alkyl ether and a polyoxyalkylene alkenyl ether. 4. The emulsion composition according to claim 1 , wherein the content of the component (A) is 3 to 25% by weight. The emulsion composition according to any one of claims 1 to 4 , wherein the component (B) has 14 or more carbon atoms. 6. The emulsion composition according to claim 1, wherein the content of the component (B) is 0.1 to 1 part by weight per 1 part by weight of the component (A).