Method for manufacturing oil-in-water-in-oil emulsion composition

Abstract

The purpose of the present invention is to provide a new scheme for enabling simpler and quicker manufacturing of an oil-in-water-in-oil emulsion composition. The present invention provides a method for manufacturing an oil-in-water-in-oil emulsion composition, the method including the following process: a process for arranging at least a portion of a vibrating body in a mixed liquid that contains water and a hydrophobic substance and ultrasonically vibrating the vibrating body, thereby generating microbubbles from a gas supplied to the periphery of at least a portion of the vibrating body and stirring and mixing the water and the hydrophobic substance, and, as a result, forming an oil-in-water-in-oil emulsion composition.

Description

Method for producing oil-in-water emulsion composition

[0001] The present invention relates to a method for producing an oil-in-water-in-oil emulsion composition containing water and a hydrophobic substance.

[0002] An oil-in-water-in-oil emulsion composition is an emulsion composition in which an oil-in-water emulsion composition, in which a hydrophobic substance (discontinuous phase) is dispersed in water (continuous phase), is dispersed in a hydrophobic substance (continuous phase), and is currently widely used in various fields such as medicine, cosmetics, and food and beverages.

[0003] Patent Document 1 discloses an oil-in-water-in-oil emulsion composition in which an innermost oil phase containing milk fat is emulsified in an aqueous phase, and the aqueous phase is emulsified in an outermost oil phase, and describes that the composition is produced by a method including a first emulsification step of producing an oil-in-water primary emulsion by emulsifying a mixed liquid containing water and an oil that will become the innermost oil phase containing milk fat using a pressure homogenizer, and a second emulsification step of emulsifying the primary emulsion in an oil that will become the outermost oil phase.

[0004] Microbubbles (hereinafter referred to as "microbubbles") have a large surface area per unit volume and a long residence time in liquid, and therefore have good solubility properties. They are therefore widely used in a variety of fields, such as increasing the amount of dissolved oxygen in closed water bodies using oxygen microbubbles, sterilizing liquids using ozone microbubbles, using the acoustic properties of microbubbles as an ultrasound contrast agent, separation technology making use of the adsorption properties at the bubble interface, and using microbubbles as a core material for hollow microcapsules making use of the shape stability of microbubbles, which are less prone to local deformation.

[0005] Patent Document 2 describes that by supplying gas around a vibrating body placed in a liquid, the supplied gas is subjected to strong ultrasonic waves generated by the vibrating body, and a large amount of microbubbles can be generated from the gas-liquid interface or bubbles on the vibrating body.

[0006] JP 2019-170214 A JP 2011-50832 A

[0007] Conventionally, in order to form an oil-in-water-in-oil emulsion composition, at least two steps have been required: a first step of forming an oil-in-water primary emulsion composition by emulsifying an oil or fat that will become the innermost oil phase with water; and a second step of emulsifying the primary emulsion composition in an oil or fat that will become the outermost oil phase, as described in Patent Document 1. This makes the production process complicated. Therefore, there has been a strong demand for a new method that enables the formation of an oil-in-water-in-oil emulsion composition more simply and quickly.

[0008] Therefore, an object of the present invention is to provide a new method that enables an oil-in-water-in-oil emulsion composition to be produced more simply and quickly.

[0009] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that an oil-in-water-in-oil emulsion composition can be produced simply and quickly in one step by generating microbubbles in a mixture containing water and a hydrophobic substance using ultrasonic vibrations and then stirring and mixing the microbubbles. Furthermore, they have found that the oil-in-water-in-oil emulsion composition produced in this manner has excellent emulsion stability, similar to that of oil-in-water-in-oil emulsion compositions produced by conventional techniques.

[0010] The present invention is based on these novel findings and includes the following inventions. [1] A method for producing an oil-in-water-in-oil emulsion composition, comprising the following steps: placing at least a portion of a vibrator in a mixed liquid containing water and a hydrophobic substance, and ultrasonically vibrating the vibrator to generate microbubbles from a gas supplied around at least a portion of the vibrator, while stirring and mixing the water and the hydrophobic substance, thereby forming an oil-in-water-in-oil emulsion composition. [2] The method for producing [1], in which the vibrator is ultrasonically vibrated at a frequency of 10 kHz or more and an amplitude of 10 μm or more. [3] The method for producing [1] or [2], in which the hydrophobic substance is one or more selected from the group consisting of fats and oils, hydrophobic waxes, and hydrophobic resins. [4] The method for producing any of [1] to [3], in which the mixed liquid does not contain an emulsifier. This specification includes the contents of the specification and the like of Japanese Patent Application No. 2024-030913, filed on March 1, 2024, from which the present application claims priority. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

[0011] According to the present invention, a new method is provided that enables a simple and rapid production of an oil-in-water-in-oil emulsion composition that can be used for a variety of applications. Furthermore, according to the present invention, an oil-in-water-in-oil emulsion composition having excellent emulsion stability similar to that of oil-in-water-in-oil emulsion compositions produced by conventional techniques can be obtained.

[0012] Fig. 1 is a photograph of a microscopic observation showing a double emulsion structure in an oil-in-water-in-oil emulsion composition formed by applying ultrasonic vibrations to a mixture of water and a hydrophobic substance to generate microbubbles while stirring and mixing the water and the hydrophobic substance. Fig. 2 is a graph showing the results of measuring the weight over time of an oil-in-water-in-oil emulsion composition (embodied product) and an oil-in-water emulsion composition (comparison product) applied to an artificial skin sheet.

[0013] In the present invention, "microbubbles" refer to tiny bubbles with a diameter of 100 μm or less. Microbubbles are characterized by a larger specific surface area, a slower rising speed, and a higher internal pressure compared to bubbles with larger diameters.

[0014] In the present invention, "oil-in-water-in-oil emulsion composition" means an emulsion composition in which an oil-in-water (O / W) emulsion composition in which a hydrophobic substance (discontinuous phase) is dispersed in water (continuous phase) is dispersed in the hydrophobic substance (continuous phase). In this specification, "oil-in-water-in-oil" and "O / W / O" emulsion compositions both refer to emulsion compositions having the above structure, and these terms can be used interchangeably.

[0015] In the present invention, the term "hydrophobic substance" refers to any substance that is insoluble in water and capable of forming an oil-in-water emulsion composition together with water. The term is not particularly limited, but preferred examples include fats and oils, hydrophobic waxes, and hydrophobic resins. The hydrophobic substance may be any substance used alone, or different types of hydrophobic substances may be used in combination. For example, the hydrophobic substance may be one or more substances selected from the group consisting of fats and oils, hydrophobic waxes, and hydrophobic resins. An appropriate substance can be selected and used depending on the intended use of the O / W / O emulsion composition to be produced.

[0016] In the present invention, the term "oils and fats" refers to any oils and fats that are generally used in forming emulsion compositions, and both polar and non-polar oils and fats can be used.Examples of such oils and fats include vegetable-derived oils (e.g., canola oil, rapeseed oil, soybean oil, corn oil, cottonseed oil, peanut oil, sesame oil, rice oil, rice bran oil, camellia oil, safflower oil, olive oil, linseed oil, perilla oil, perilla oil, sunflower oil, palm oil, tea oil, coconut oil, avocado oil, kukui nut oil, grapeseed oil, cocoa butter, shea butter, coconut oil, wheat germ oil, almond oil, evening primrose oil, castor oil, hazelnut oil, macadamia nut oil, rosehip oil, grape oil, cacao oil, jojoba oil, palm kernel oil, etc.), isostearyl Alcohol, caprylic alcohol, lauryl alcohol, stearyl alcohol, 2-octadecyl alcohol, myristyl alcohol, cetyl alcohol, phytosterol, cholesterol, stearic acid, isostearic acid, capric acid, lanolinic acid, lauric acid, myristic acid, palmitic acid, behenic acid, linoleic acid, linolenic acid, glyceryl monostearate, glyceryl monopalmitate, glyceryl monobehenate, glyceryl monomyristate, glyceryl monolaurate, glyceryl monolanolate, monolinoleic acid Glyceryl, Glyceryl Monolinoleate, Glyceryl Monooleate, Glyceryl Triisostearate, Caprylic / Capric Triglyceride, Ethylhexyl Palmitate, Cetyl Ethylhexanoate, Isopropyl Myristate, Glycerol Tri-2-heptylundecanoate, Glycerol Tri-2-ethylhexanoate, 2-Heptylundecyl Palmitate, Di-2-heptylundecyl Adipate, Cetyl Isooctanoate, Trimethylolpropane-2-trimethylolheptylundecanoate, Propane Examples of the oils and fats that can be used include, but are not limited to, synthetic ester oils such as pentaerythritol-2-ethylhexanoate, pentaerythritol-2-heptylundecanoate, pentaerythritol-2-ethylhexanoate, cholesterol isostearate, diethyl phthalate, and dibutyl phthalate; animal-derived oils and fats such as beef tallow, mutton tallow, lard, fish oil, lanolin, squalene, squalane, butter, butter oil, lard, fat, shortening, margarine, and ghee; silicone oil; and their extremely hardened oils and fats (hydrogenated oils and fats), and interesterified oils and fats.

[0017] In the present invention, the term "hydrophobic wax" refers to natural hydrophobic waxes derived from plants, animals, petroleum, or minerals, and synthetic hydrophobic waxes. Examples of such hydrophobic waxes include beeswax, spermaceti wax, wool wax, Japan wax, rosin (pine resin), candelilla wax, carnauba wax, cacao butter, paraffin wax, microcrystalline wax, ceresin wax, petrolatum wax, ozokenit wax, polyethylene wax, oxidized polyethylene wax, Fischer-Tropsch wax, alcohol-modified wax, maleic acid-modified oxidized polyethylene wax, and amide wax, but are not limited thereto.

[0018] In the present invention, the term "hydrophobic resin" refers to a resin that does not have hydrophilic groups or has a small content of hydrophilic groups. It refers to a resin that is insoluble in polar solvents such as water. Examples of such hydrophobic resins include, but are not limited to, silicone resins (not hydrophilized), polyurethane resins, fluorine-containing resins, polyethylene resins, polypropylene resins, polyester resins, acrylic resins, polystyrene resins, polycarbonate resins, polyvinyl chloride resins, polysulfone resins, polyethersulfone resins, polyaramid resins, polyamide resins, polyether resins, polyacrylonitrile resins, polyetherimide resins, and copolymers of these polymers.

[0019] In the present invention, the hydrophobic substance may be in a solid or liquid form at room temperature. However, for ease of dissolution, a substance having a melting point of 80°C or less, preferably 60°C or less, more preferably 50°C or less, and even more preferably 40°C or less is preferred. Among these, a substance that is in a liquid or semi-liquid (sol-like, gel-like, etc.) state at least at room temperature (5 to 35°C, preferably 15 to 30°C) is particularly preferred. The hydrophobic substance may be used alone or in combination with different hydrophobic substances. An appropriate substance can be selected and used depending on the intended use of the O / W / O emulsion composition to be produced. For example, when the O / W / O emulsion composition to be produced is to be used in fields such as food and beverages, pharmaceuticals (including quasi-drugs), and cosmetics, highly safe animal- or plant-derived oils and fats, hydrophobic waxes, and hydrophobic resins that have been confirmed to be biocompatible or bioaffinity can be suitably used.

[0020] In the present invention, the O / W / O emulsion composition can be produced by a method comprising the following steps: placing at least a part of a vibrator in a mixed liquid containing water and a hydrophobic substance, and ultrasonically vibrating the vibrator to generate microbubbles from a gas supplied around at least a part of the vibrator, and stirring and mixing the water and the hydrophobic substance, thereby forming an O / W / O emulsion composition.

[0021] The vibrator and the means for supplying gas to the periphery of at least a portion of the vibrator can be any means capable of generating ultrasonic vibrations and microbubbles, and an appropriate one can be selected and used based on a conventionally known microbubble generator (Japanese Patent Laid-Open No. 2011-50832).

[0022] For example, the vibrator may be any vibrator capable of generating ultrasonic vibrations, and its shape is not particularly limited. It may be composed of only an ultrasonic vibrator, but a configuration in which a vibration transmitter is connected to the ultrasonic vibrator to amplify its amplitude is preferred. The shape of the vibration transmitter is not particularly limited, but a shape known as an amplitude amplification horn commonly used to amplify ultrasonic amplitude is desirable. One preferred form of the vibration transmitter is a stepped cylindrical shape. One end of the stepped cylindrical shape has a larger cross-sectional area than the other end, serving as the transducer connection surface to which the ultrasonic vibrator is connected, and the other end (having a relatively small cross-sectional area) serves as the ultrasonic radiation surface where the vibration generated by the ultrasonic vibrator is amplified. As long as it can transmit ultrasonic pressure vibrations, the vibration transmitter may be a structure consisting of a single component or a structure in which multiple components are connected by screws, adhesives, welding, or the like. The material used as the vibration transmitter is not limited, but known materials used as ultrasonic horn materials are desirable, such as titanium alloys, pure titanium, Ni-Cr steel, stainless steel, brass, Monel metal, and tool steel.

[0023] The surface roughness of the vibrator is not particularly limited, but in order to disturb the mixed liquid and generate more microbubbles, it is desirable that the surface of the vibrator that comes into contact with the gas-liquid interface formed between the supplied gas and the mixed liquid has an uneven shape with an arithmetic mean roughness Ra of 50 μm or more.

[0024] The ultrasonic vibrator is not particularly limited and can be appropriately selected from known ultrasonic vibrators. The frequency and amplitude of the ultrasonic waves generated by the ultrasonic vibrator can be controlled by an electric signal obtained by amplifying a signal of any frequency and waveform generated by a function generator using an amplifier.

[0025] The means for supplying the gas need only be able to supply gas into the mixed liquid within a range in which ultrasonic vibrations from the vibrator are effectively transmitted, and it is preferable that as large a proportion of the supplied gas as possible be brought into contact with the vibrator, but the means and shape thereof are not particularly limited.

[0026] For example, a desirable means for supplying gas is to provide the vibrator with a gas supply port, a gas discharge port, and a gas flow path connecting them, and to supply gas from a gas pressurizing means to the gas supply port and discharge the gas from a gas discharge port located in the mixed liquid. The gas discharge port is preferably located at a position where ultrasonic vibrations from the vibrator are efficiently transmitted to the discharged gas, and is preferably provided on the ultrasonic radiation surface, for example. It is particularly preferable to provide the gas discharge port on the ultrasonic radiation surface so that the depth direction of the liquid is perpendicular to the ultrasonic radiation surface and the gas is discharged in the depth direction of the mixed liquid.

[0027] The opening shape of the gas discharge port provided in the vibrating body is not limited, but a circular or rectangular shape that is easy to process, or a slit shape, gear shape, rotary saw shape, or the like that can make the perimeter longer than the perimeter of the area-equivalent circle are desirable, and a plurality of gas discharge ports may be provided. The size of the gas discharge port is not particularly limited, but it is preferable that at least one of the opening areas is 0.4 mm ２ More than 0.6 mm, preferably 0.6 mm ２ More preferably, 0.7 mm ２ More preferably, 0.75 mm or more ２ The upper limit is not particularly limited, but is 32 mm ２ Less than 31 mm, preferably ２ Less than 30 mm, more preferably ２ Less than 29 mm, more preferably ２ The vibration direction of the surface on which the gas release port is provided is not particularly limited, but vibration in a direction perpendicular to the surface on which the gas release port is provided is desirable so that the strongest ultrasonic waves are generated.

[0028] The shape of the gas flow path provided in the vibrating body is not particularly limited as long as it is a shape that allows gas to pass through, but in order to disturb the mixed liquid and generate more bubbles and microbubbles, it is desirable for the gas flow path immediately before the gas release port to have an expansion structure, a contraction structure, or a structure that combines expansion and contraction, and examples of such structures include a sudden contraction shape or an orifice shape, a sudden expansion shape or a bell-mouth shape, a female thread shape that combines expansion and contraction, and a fin shape.

[0029] The gas pressurizing means for supplying the gas is not particularly limited as long as it can supply the gas to the gas outlet, and examples thereof include a compressor, a diaphragm pump, a suction pump, a gear pump, a high-pressure cylinder, etc. Examples of the gas to be supplied include air, nitrogen, oxygen, carbon dioxide, ozone, etc., and are not particularly limited. The amount of gas supplied is not particularly limited, and can be 5 to 500 mL / min, preferably 10 to 200 mL / min, and more preferably 40 to 100 mL / min.

[0030] The supplied gas forms a gas-liquid interface with the mixed liquid, and the ultrasonic vibrations from the vibrator cause disturbances at the gas-liquid interface, causing the gas to separate and release bubbles or directly microbubbles. The released bubbles are further split by the strong ultrasonic waves generated from the vibrator or the ultrasonic wave emitting surface, generating a large amount of microbubbles.

[0031] In the present invention, microbubbles are generated by vibrating bubbles present in the mixed liquid with ultrasound, which disrupts a portion of the bubbles or the gas-liquid interface on the vibrator. The frequency and amplitude of the ultrasound used are appropriately selected from the range of 10 kHz or higher and 10 μm or higher. The frequency is preferably 15 kHz or higher, more preferably 20 kHz or higher. There is no particular upper limit to the frequency, but it is preferably 100 kHz or lower, more preferably 40 kHz or lower. For example, the frequency is preferably 15 kHz to 100 kHz, at which many known ultrasonic vibrators exist, and more preferably 20 kHz to 40 kHz, at which a large amplitude can be achieved. Furthermore, ultrasound may be applied continuously or in a burst mode, in which the generation and cessation of waves is repeated at a frequency equal to or lower than the applied ultrasonic frequency. The amplitude is preferably 20 μm or higher, more preferably 30 μm or higher, and even more preferably 40 μm or higher. The upper limit of the amplitude is not particularly limited, but is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less (for example, 60 μm or less, or 50 μm or less). For example, the amplitude is desirably 10 μm to 90 μm, preferably 20 μm to 80 μm, more preferably 30 μm to 70 μm, and even more preferably 40 μm to 70 μm.

[0032] In the present invention, when the hydrophobic substance is in a solid form, at least the hydrophobic substance is heated to a temperature equal to or higher than the melting point and melted into a liquid or semi-liquid (gel, sol, etc.) state, and then used in the mixed liquid.

[0033] In the mixed solution, the amount of water and the hydrophobic substance (in a liquid or semi-liquid state) can be any amount that allows the formation of an O / W / O emulsion composition, and can be appropriately selected depending on the intended use of the O / W / O emulsion composition to be produced, the type of hydrophobic substance to be used, etc. For example, in the mixed solution, the amount of water and the hydrophobic substance (in a liquid or semi-liquid state) can be appropriately selected from the following ranges in terms of volume ratio (water:hydrophobic substance) (total volume being 100), such as 5 to 90:95 to 10, preferably 10 to 90:90 to 10, for example, 10 to 90:90 to 10, 20 to 90:80 to 10, 30 to 90:70 to 10, 40 to 90:60 to 10, 50 to 90:50 to 10, etc.

[0034] If necessary, the water and / or hydrophobic substance in the mixture may further contain components (hereinafter referred to as "other components") typically used in the production of the intended use form of the O / W / O emulsion composition to be produced, in amounts appropriate for the desired use form, as long as the effects of the resulting O / W / O emulsion composition are not impaired. Examples of such other components include, but are not limited to, excipients, disintegrants, lubricants, binders, diluents, buffers, suspending agents, thickeners, preservatives, antibacterial agents, antiseptics, antioxidants, UV absorbers, colorants, pigments, dyes, pigments, lubricants, plasticizers, solvents, solubilizers, isotonicity agents, flavorings, fragrances, sweeteners, flavoring components, acidulants, seasonings, humectants, vitamins, surfactants, chelating agents, and organic solvents. Other components may be included in the water or hydrophobic substance depending on their hydrophilic, lipophilic, or hydrophobic properties.

[0035] The water and / or hydrophobic substance in the mixed liquid may further contain an emulsifier, if necessary. Emulsifiers commonly used in the production of emulsion compositions can be used, and can be appropriately selected depending on the intended use form of the O / W / O emulsion composition to be produced. Examples of emulsifiers that can be used in the present invention include, but are not limited to, glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters, organic acid monoglycerides, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyglycerin-modified silicone oils, lecithins, saponins, phosphoproteins, polyoxyethylene alkyl ethers, polyoxyethylene alkylamines, and alkyl alkanolamides.

[0036] Preferably, no emulsifier is used in the present invention. An O / W / O emulsion composition produced by subjecting a mixture containing water and a hydrophobic substance to ultrasonic vibrations and stirring and mixing with the generation of microbubbles can achieve excellent emulsion stability without the addition of an emulsifier.

[0037] In stirring and mixing the mixed liquid, at least a portion of the vibrator, preferably the ultrasonic wave emitting surface, may be positioned near the interface between water and the hydrophobic substance, although the position is not particularly limited as long as it can stir and mix the mixed liquid. By positioning at least a portion of the vibrator near the interface between water and the hydrophobic substance, ultrasonic vibrations from the vibrator are efficiently transmitted to the vicinity of the interface, allowing for efficient stirring and mixing of the water and the hydrophobic substance, and enabling efficient formation of an O / W / O emulsion composition. In the present invention, "near the interface" preferably means within ±10 mm, more preferably ±5 mm, of the interface between water and the hydrophobic substance.

[0038] The mixture may be stirred and mixed under heating as necessary. When the hydrophobic substance is in a solid form, the mixture can be converted into a liquid or semi-liquid state (gel, sol, etc.) by heating at a temperature equal to or higher than the melting point of the hydrophobic substance.

[0039] The produced O / W / O emulsion composition may be subjected to heat sterilization treatment, if necessary.

[0040] Furthermore, the produced O / W / O emulsion composition may be further subjected to drying means, if necessary. The drying means may be a conventionally known drying means, and the water content of the emulsion composition may be appropriately adjusted depending on the desired shape of the semi-solid / semi-liquid (gel, sol, etc.) or dried product. The obtained dried product may be further subjected to crushing, pulverization, or grinding treatment, if necessary, to obtain a powder, flakes, or the like. The emulsion composition obtained by drying means may be mixed and stirred with other components in the amounts described above, if necessary, and / or may be subjected to heat sterilization treatment.

[0041] The produced O / W / O emulsion composition can be used as a base in applications such as foods and beverages, cosmetics, topical medicines, pharmaceuticals (including quasi-drugs), chemicals, synthetic products, agricultural chemicals, toiletries, spray products, paints, industrial thin film materials, and surface-modifying materials, and can be provided in a form suitable for the intended application (for example, in the form of a predetermined product, etc.) The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0042] (1) Production of O / W / O type emulsion compositions Pure water and a hydrophobic substance were added to a 100 mL glass beaker according to the formulations in Tables 1 to 4 below, and the ultrasonic wave emitting surface of the vibrator was positioned near the interface between the pure water and the hydrophobic substance. Ultrasonic vibrations were applied at a vibration frequency of 20 kHz and an amplitude of 40 μm while supplying air at a flow rate of 100 mL / min, thereby generating microbubbles and stirring and mixing the pure water and the hydrophobic substance, thereby producing O / W / O type emulsion compositions.

[0043] The vibrator, the application of ultrasonic vibrations, and the supply of air were performed using a conventional method (see JP 2011-50832 A). That is, the ultrasonic vibrator was a Langevin type ultrasonic vibrator fastened with bolts, and the vibration transmitter was a stepped cylindrical horn made of titanium alloy with a large area portion having an outer diameter of 12 mm and a length of 45 mm, a small area portion having an outer diameter of 6 mm and a length of 64 mm, and a total length of 109 mm, with the end on the small area side being the ultrasonic radiation surface. The ultrasonic radiation surface had a diameter of 2.5 mm, an opening area of ​​19.6 mm, and a diameter of 2.5 mm. The diameter of the cylindrical horn was 2.5 mm. The opening area of ​​the cylindrical horn was 19.6 mm. ２ The device has a circular gas outlet, which is connected to a gas supply port provided in the cylindrical part on the large-area side of the cylindrical horn by a gas flow path provided inside the cylindrical horn, and gas is released in a direction perpendicular to the ultrasonic radiation surface, i.e., in the depth direction of the mixed liquid, and the gas outlet vibrates perpendicular to the ultrasonic radiation surface. The amount of each component in the table is shown as a volume ratio, with the total volume of pure water and hydrophobic substance being 100. The butter and beef tallow / pork fat were heated to 60°C in a hot water bath, melted, and made into liquid form.

[0044] (2) Evaluation of O / W / O emulsion compositions The O / W / O emulsion compositions prepared above were observed under a microscope to confirm the presence or absence of an O / W / O double emulsion structure, and their uniformity (presence or absence of separation) was also confirmed visually. The results of each evaluation are also shown in Tables 1 to 4 below.

[0045]

[0046]

[0047]

[0048]

[0049] The above results confirm that the hydrophobic substance used in the oil phase of an O / W / O type is not limited to a specific one, but a variety of substances can be used, and that the production method of the present invention makes it possible to produce an O / W / O type emulsion composition in a single step.

[0050] Depending on the type of hydrophobic substance or the blending ratio of water to hydrophobic substance, separation of two layers was observed even after stirring and mixing. In this case, the lower layer was an O / W emulsion composition and the upper layer was an O / W / O emulsion composition. Therefore, the target O / W / O emulsion composition could be recovered from the upper layer. Furthermore, when separation of the two layers was observed, it was confirmed that the ratio (volume ratio) of the lower layer roughly corresponded to the volume ratio of the blended water. Therefore, when separation of the two layers was observed, it was suggested that a smaller volume ratio of the blended water is preferable from the perspective of more efficient production of an O / W / O emulsion composition.

[0051] (3) Evaluation of the physical properties of the O / W / O type emulsion composition As a hydrophobic substance, a mixture of jojoba oil, shea butter, and beeswax in a weight ratio of 7:5:3 was used. 90 mL of this mixture and 10 mL of pure water were added to a 100 mL glass beaker, and the mixture was stirred and mixed to generate microbubbles in the same manner as described above in "(1) Production of O / W / O type emulsion composition." An O / W / O type emulsion composition was then prepared. The composition was then rapidly cooled in a freezer to obtain a creamy O / W / O type emulsion composition (hereinafter referred to as "embodied product"). As a control, 90 mL of the mixture of jojoba oil, shea butter, and beeswax and 10 mL of pure water were stirred and mixed at 2500 RPM using a high-speed disperser to prepare an oil-in-water (O / W) emulsion composition. The composition was then rapidly cooled in a freezer to obtain a creamy O / W type emulsion composition (hereinafter referred to as "comparison product").

[0052] 0.04 g of each of the test product and the comparative product was applied to an artificial skin sheet (4.5 cm ２ The weights of the test samples and the comparative samples on the sheet were measured over time.

[0053] The results of measuring the weights of the working product and the comparative product are shown in Figure 2. The weight of the working product remained unchanged at 0.04 g even after 3 hours, whereas the weight of the comparative product decreased after 2 hours and was reduced to half (0.02 g) after 3 hours. This result demonstrates that the O / W / O emulsion composition produced by the present invention can retain moisture for a long period of time, that the O / W / O emulsion composition can maintain its shape for a long period of time, and that it has excellent emulsion stability similar to that of oil-in-water-in-oil emulsion compositions produced by conventional technology.

[0054] The O / W / O type emulsion composition produced according to the present invention, which has such physical properties, can be suitably used as a base not only for cosmetics (e.g., lip balm, moisturizing cream, etc.) that are applied to the skin, etc., topical medicines, and medicines (including quasi-drugs), but also for various other applications such as foods and beverages, chemicals, synthetic products, agricultural chemicals, toiletries, spray products, paints, industrial thin film materials, and surface-modified materials (but is not limited to these).

[0055] According to the present invention, an oil-in-water-in-oil emulsion composition that can be used for a variety of applications can be produced simply and quickly, and it is expected that the present invention will contribute to various fields in which oil-in-water-in-oil emulsion compositions are used.

Claims

1. A method for producing an oil-in-water-in-oil emulsion composition, comprising the following steps: placing at least a portion of a vibrator in a mixed liquid containing water and a hydrophobic substance, and ultrasonically vibrating the vibrator to generate microbubbles from gas supplied around at least a portion of the vibrator, and stirring and mixing the water and the hydrophobic substance, thereby forming an oil-in-water-in-oil emulsion composition.

2. The manufacturing method according to claim 1, wherein the vibrating body is subjected to ultrasonic vibration at a frequency of 10 kHz or more and an amplitude of 10 μm or more.

3. The manufacturing method according to claim 1, wherein the hydrophobic substance is one or more selected from the group consisting of oils and fats, hydrophobic waxes, and hydrophobic resins.

4. The method of claim 1, wherein the mixture does not contain an emulsifier.

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