Solubilizer for hydrophobic substance, aqueous solution, and production method for aqueous solution

Abstract

This solubilizer for a hydrophobic substance is a solution that contains an alkali metal salt of a tocopherol phosphate ester and at least one type of solvent selected from among aqueous solvents and dihydric alcohols. The at least one type of solvent selected from among aqueous solvents and dihydric alcohols may be one or more types of solvents selected from among water, 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol.

Description

Solubilizer for hydrophobic substances, aqueous solution, and method for producing aqueous solution

[0001] The present invention relates to a solubilizer for a hydrophobic substance, an aqueous solution containing a hydrophobic substance dissolved therein, and a method for producing the aqueous solution. This application claims priority to Japanese Patent Application No. 2024-018837, filed February 9, 2024, the contents of which are incorporated herein by reference.

[0002] As a method for producing an aqueous solution in which a hydrophobic substance is dissolved, a method using a solubilizing agent is known.

[0003] For example, Patent Document 1 discloses a solubilization technique that can easily and stably solubilize poorly water-soluble substances in an aqueous solvent at a high concentration using a component that does not cause denaturation of proteins such as labeling enzymes. Patent Document 1 also discloses a solubilizer for poorly water-soluble substances that contains a betaine derivative and / or a tetraalkylammonium salt.

[0004] Furthermore, Patent Document 2 discloses a solubilizer that can solubilize oil-soluble substances in aqueous components with a small amount of use, thereby obtaining a cosmetic preparation that is stable over time and highly transparent. Patent Document 2 discloses a solubilizer that contains, as essential components, a polyoxyethylene polyoxypropylene alkyl ether, a polyoxyethylene glyceryl fatty acid ester, and an anionic surfactant.

[0005] JP 2018-158317 A JP 2023-113046 A JP 59-44375 A International Publication No. 1997 / 014705

[0006] The technique of producing an aqueous solution by dissolving a hydrophobic substance in an aqueous solution using a solubilizing agent is used in various industrial applications. Depending on the type of hydrophobic substance and aqueous solvent to be dissolved by the solubilizing agent, the application of the aqueous solution containing the dissolved hydrophobic substance, and the like, a more suitable solubilizing agent is desired.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solubilizing agent capable of dissolving a hydrophobic substance in an aqueous solution, etc. Another object of the present invention is to provide a production method for producing an aqueous solution in which a hydrophobic substance is dissolved, using the solubilizing agent of the present invention.

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that alkali metal salts of tocopheryl phosphate, which are amphiphilic vitamin E derivatives having both hydrophilic and lipophilic properties, can be suitably used as raw materials for solubilizing agents for hydrophobic substances, and have arrived at the present invention. Specifically, the present invention relates to the following:

[0009] [1] A solubilizer for hydrophobic substances, which is a solution containing an alkali metal salt of tocopheryl phosphate and at least one solvent selected from an aqueous solvent and a dihydric alcohol.

[0010] [2] The solubilizer for hydrophobic substances according to [1], wherein the at least one solvent selected from aqueous solvents and dihydric alcohols is one or more solvents selected from water, 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol.

[0011] [3] The solubilizer for hydrophobic substances according to [1], wherein the at least one solvent selected from the aqueous solvent and the dihydric alcohol is water.

[0012] [4] The solubilizer for hydrophobic substances according to [1], wherein the at least one solvent selected from aqueous solvents and dihydric alcohols is one or more solvents selected from 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol.

[0013] [5] The solubilizer for hydrophobic substances according to [1], wherein the at least one solvent selected from the group consisting of an aqueous solvent and a dihydric alcohol is 3-(hexyloxy)-1,2-propanediol. [6] The solubilizer for hydrophobic substances according to any one of [1] to [5], wherein the alkali metal salt of tocopheryl phosphate is a sodium salt of tocopheryl phosphate.

[0014] [7] The solubilizer for hydrophobic substances according to any one of [1] to [6], wherein the ratio of the mass of the at least one solvent selected from an aqueous solvent and a dihydric alcohol to the mass of the alkali metal salt of tocopheryl phosphate is 2 to 20. [8] The solubilizer for hydrophobic substances according to any one of [1] to [7], wherein the hydrophobic substance is at least one selected from a hydrocarbon compound having 5 to 20 carbon atoms, an ester compound having 5 to 20 carbon atoms, and a fatty acid having 6 to 30 carbon atoms.

[0015] [9] An aqueous solution comprising the solubilizer for hydrophobic substances according to any one of [1] to [8], the aqueous solvent, and a hydrophobic substance, wherein the concentration of the alkali metal salt of tocopheryl phosphate is 0.01 mmol / L to 500 mmol / L, and the hydrophobic substance is dissolved in the aqueous solvent.

[0016]

[10] A method for producing an aqueous solution, comprising: a 1-1 step of dissolving an alkali metal salt of tocopherol phosphate in an aqueous solvent to produce a solution containing the alkali metal salt of tocopherol phosphate; and a 1-2 step of mixing the solution containing the alkali metal salt of tocopherol phosphate with a hydrophobic substance to produce an aqueous solution in which the hydrophobic substance is dissolved in an amount by mass that is 0.01 to 0.20 times the mass of the alkali metal salt of tocopherol phosphate.

[0017]

[11] A method for producing an aqueous solution, comprising: Step 2-1 of dissolving an alkali metal salt of tocopherol phosphate in one or more dihydric alcohols selected from 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol to produce a solution containing the alkali metal salt of tocopherol phosphate; Step 2-2 of mixing the solution containing the alkali metal salt of tocopherol phosphate with a hydrophobic substance to dissolve the hydrophobic substance in the solution containing the alkali metal salt of tocopherol phosphate to produce a solute-dissolved solution; and Step 2-3 of mixing the solute-dissolved solution with an aqueous solvent to produce an aqueous solution in which the hydrophobic substance is dissolved.

[0018]

[12] The method for producing an aqueous solution according to

[10] or

[11] , wherein the amounts of the alkali metal salt of tocopherol phosphate and the aqueous solvent are adjusted so that the concentration of the alkali metal salt of tocopherol phosphate in the aqueous solution is 0.01 mmol / L to 500 mmol / L.

[0019] The solubilizer for hydrophobic substances according to an embodiment of the present invention contains an alkali metal salt of tocopherol phosphate and at least one solvent selected from aqueous solvents and dihydric alcohols, and can therefore be suitably used as a solubilizer for dissolving hydrophobic substances in aqueous solvents such as aqueous solutions.

[0020] The method for producing an aqueous solution according to an embodiment of the present invention includes a step of mixing a solution containing an alkali metal salt of tocopheryl phosphate with a hydrophobic substance, and therefore, the method for producing an aqueous solution according to an embodiment of the present invention can efficiently dissolve the hydrophobic substance in an aqueous solvent, thereby efficiently producing an aqueous solution in which the hydrophobic substance is dissolved.

[0021] Photographs of the aqueous solution produced in Example 1 (left) and the sample solution produced in Reference Example 1 (right). Graphs showing the relationship between the concentration of sodium salt of DL-α-tocopheryl phosphate (TPNa) in an aqueous solution, the concentration of sodium dodecyl sulfate (SDS) in an aqueous solution, and the maximum decane concentration that can be solubilized in the aqueous solution. Graphs showing the relationship between the concentration of sodium salt of DL-α-tocopheryl phosphate (TPNa) in an aqueous solution, the concentration of sodium dodecyl sulfate (SDS) in an aqueous solution, and the maximum dodecane concentration that can be solubilized in the aqueous solution. Photographs of the aqueous solution produced in Example 4. Graphs showing the relationship between the type of dihydric alcohol in an aqueous solution and the maximum decane concentration that can be solubilized in the aqueous solution. Graphs showing the relationship between the type of dihydric alcohol in an aqueous solution and the maximum dodecane concentration that can be solubilized in the aqueous solution.

[0022] The solubilizer for hydrophobic substances and the method for producing an aqueous solution of the present invention are described in detail below. However, the present invention is not limited to the following embodiments. [Solubilizer] The solubilizer for hydrophobic substances of this embodiment is a solution containing an alkali metal salt of tocopherol phosphate. The alkali metal salt of tocopherol phosphate has the property of dissolving the hydrophobic substance in an aqueous solution or the like when brought into contact with a hydrophobic substance in a dissolved state. The solubilizer for hydrophobic substances of this embodiment may contain only one type of alkali metal salt of tocopherol phosphate, or may contain two or more types.

[0023] The mechanism by which alkali metal salts of tocopherol phosphate exhibit the function of dissolving hydrophobic substances in aqueous solutions is unknown. However, aqueous solutions containing alkali metal salts of tocopherol phosphate at concentrations of 100 mmol / L or less exhibit spherical self-assembled structures consisting of bilayer membranes. It is believed that these characteristic properties of alkali metal salts of tocopherol phosphate may be related to the mechanism by which they exhibit the function of dissolving hydrophobic substances in aqueous solutions.

[0024] The tocopherol phosphate in the alkali metal salt of tocopherol phosphate contained in the solubilizing agent of this embodiment is a compound in which a phosphate group has been introduced into a hydroxy group of tocopherol. Tocopherol phosphates include α-tocopherol phosphate, β-tocopherol phosphate, γ-tocopherol phosphate, and δ-tocopherol phosphate. The tocopherol phosphate in the alkali metal salt of tocopherol phosphate contained in the solubilizing agent may be any of these tocopherol phosphates, preferably α-tocopherol phosphate or γ-tocopherol phosphate, and most preferably DL-α-tocopherol phosphate because it is widely used as a cosmetic raw material and is easily available.

[0025] The alkali metal salt of tocopherol phosphate is preferably a sodium salt and / or a potassium salt of tocopherol phosphate, and preferably includes a sodium salt. This is because, among alkali metal salts of tocopherol phosphate, the sodium salt has high solubility in water and can more efficiently dissolve hydrophobic substances in aqueous solvents. In addition, the sodium salt of tocopherol phosphate is in the form of a powder, making it easy to handle.

[0026] In this embodiment, it is most preferable to use the sodium salt of DL-α-tocopheryl phosphate as the alkali metal salt of tocopheryl phosphate. This is because it allows hydrophobic substances to be dissolved more efficiently in aqueous solvents. The sodium salt of DL-α-tocopheryl phosphate is commercially available from Resonac Corporation under the product name TPNa (registered trademark) (display name: sodium tocopheryl phosphate).

[0027] The method for producing the alkali metal tocopherol phosphate is not particularly limited. The alkali metal tocopherol phosphate can be produced using the production methods described in Patent Documents 3 and 4, for example.

[0028] When producing sodium α-tocopherol phosphate as an alkali metal salt of tocopherol phosphate, it can be produced, for example, by the production method shown below. First, tocopherol is dissolved in a solvent, and the dissolved tocopherol is reacted with a phosphorylating agent such as phosphorus oxychloride. After completion of the reaction, the resulting reaction product is appropriately purified to obtain tocopherol phosphate. Furthermore, the obtained tocopherol phosphate is neutralized with sodium hydroxide. Through the above steps, sodium α-tocopherol phosphate is obtained.

[0029] When potassium α-tocopherol phosphate is produced as the alkali metal salt of tocopherol phosphate, it can be produced by the same method as that for producing sodium α-tocopherol phosphate, except that potassium hydroxide is used instead of sodium hydroxide to neutralize the tocopherol phosphate.

[0030] The solubilizer for the hydrophobic substance of this embodiment may contain an alkali metal salt of tocopheryl phosphate, and can be obtained by dissolving the alkali metal salt of tocopheryl phosphate in a solvent.

[0031] The solvent for the alkali metal salt of tocopherol phosphate used as the solubilizer for the hydrophobic substance of this embodiment is at least one solvent selected from aqueous solvents and dihydric alcohols.

[0032] The dihydric alcohol may be 1,2-hexanediol, 1,2-pentanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-(hexyloxy)-1,2-propanediol, 3-(cyclohexyloxy)-1,2-propanediol, 3-(2-ethylhexyloxy)-1,2-propanediol, 3-(heptyloxy)-1,2-propanediol, or dipropylene glycol (a mixture of three isomers: 4-oxa-2,6-heptanediol, 2-(2-hydroxy-propoxy)-propan-1-ol, and 2-(2-hydroxy-1-methyl-ethoxy)-propan-1-ol). Among these, 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol are preferred, and 3-(hexyloxy)-1,2-propanediol is more preferred. Two or more of these solvents may be combined in any ratio and used as a mixed solvent.

[0033] Examples of aqueous solvents that can be used as a solvent for a solution containing an alkali metal salt of tocopheryl phosphate include pure water, an aqueous solution containing a water-soluble compound, and a mixed solvent of water and a water-soluble organic compound such as methanol, ethanol, or 1,3-butanediol. The amount of the water-soluble compound and / or the water-soluble organic compound contained in the aqueous solvent is preferably small enough not to impair the performance as a solubilizer for hydrophobic substances. For example, the amount used is 10% by mass or less. In addition to the above, known compounds used as dyes, fragrances, moisturizers, pharmaceuticals, etc. may also be used as water-soluble compounds contained in the aqueous solvent.

[0034] The solvent for the solution containing the alkali metal salt of tocopherol phosphate may be one or more solvents selected from 1,2-hexanediol, 1,2-pentanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-(hexyloxy)-1,2-propanediol, 3-(cyclohexyloxy)-1,2-propanediol, 3-(2-ethylhexyloxy)-1,2-propanediol, 3-(heptyloxy)-1,2-propanediol, and dipropylene glycol. When these solvents (hereinafter sometimes abbreviated as "dihydric alcohols for dissolving alkali metal salts of tocopherol phosphate") are used, they may be used alone or in combination, and can be appropriately selected depending on the type of hydrophobic compound to be solubilized. Among these solvents, 1,2-pentanediol is preferred because it has good solubility for alkali metal salts of tocopherol phosphate and has antiseptic properties. 3-(hexyloxy)-1,2-propanediol is also preferred because it can solubilize a large amount of hydrophobic substances. The use of these solvents is also preferred because it can shorten the time required to solubilize the hydrophobic substance. When these solvents are used, they may contain small amounts (e.g., 10% or less) of other compatible compounds, just as in the case of using aqueous solvents.

[0035] In some cases, water may be used in combination with one or more solvents selected from dihydric alcohols for dissolving alkali metal salts of tocopheryl phosphate. In this case, the mixing ratio can be adjusted appropriately depending on the purpose.

[0036] The content of the alkali salt of tocopherol phosphate contained in the solution containing the alkali metal salt of tocopherol phosphate is not particularly limited. It can be adjusted depending on the aqueous solution of the hydrophobic compound to be obtained. The concentration of the alkali salt of tocopherol phosphate in the aqueous solution obtained after solubilization of the hydrophobic compound may be, for example, 0.01 mmol / L to 500 mmol / L, preferably 0.01 mmol / L to 200 mmol / L, and can be appropriately determined depending on the type of solvent, the type and amount of the hydrophobic compound to be solubilized, etc. When the concentration of the alkali salt of tocopherol phosphate is 0.01 mmol / L or more, an aqueous solution of the hydrophobic compound can be obtained. When the concentration of the alkali salt of tocopherol phosphate is 500 mmol / L or less, the hydrophobic compound can be sufficiently solubilized.

[0037] The mass ratio of the at least one solvent selected from an aqueous solvent and a dihydric alcohol for dissolving an alkali metal salt of tocopherol phosphate to the mass of the alkali metal salt of tocopherol phosphate is preferably 2 to 20, more preferably 7 to 12. When the mass ratio is 2 or more, dissolving the alkali salt of tocopherol phosphate in an aqueous solvent and / or a dihydric alcohol for dissolving an alkali metal salt of tocopherol phosphate significantly improves the ability of the solubilizing agent to dissolve hydrophobic substances in aqueous solutions. When the mass ratio is 20 or less, the concentration of the alkali salt of tocopherol phosphate in the solubilizing agent is sufficiently high, resulting in a solubilizing agent that can fully exhibit its performance as a solubilizing agent.

[0038] [Method for Producing Aqueous Solution] Next, an example of a method for producing an aqueous solution according to this embodiment will be described. In the method for producing an aqueous solution according to this embodiment, an aqueous solution containing a dissolved hydrophobic substance is produced using the solubilizer for a hydrophobic substance according to this embodiment.

[0039] The hydrophobic substance dissolved using the hydrophobic substance solubilizer of this embodiment is one that does not dissolve in water by itself. Whether or not a substance is hydrophobic can be confirmed by adding a substance to be solubilized, whose hydrophobicity is unknown, to water, stirring, and checking whether it dissolves, and then measuring its solubility. The hydrophobic substance of this embodiment is a substance whose solubility in water at 25°C is 0.1% or less.

[0040] Examples of hydrophobic substances that can be dissolved using the solubilizing agent for hydrophobic substances of this embodiment include hydrocarbon compounds having 5 to 20 carbon atoms, ester compounds having 5 to 20 carbon atoms, and fatty acids having 6 to 30 carbon atoms. More specifically, examples of the hydrophobic substance include decane, dodecane, 7-methyloctyl 7-methyloctanoate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, dimethicone, decamethylcyclopentasiloxane, glyceryl tri-2-ethylhexanoate, caprylic / capric triglyceride, α-olefin oligomer, octyldodecyl myristate, methylphenylpolysiloxane, phytosteryl-behenyl-2-octyldodecyl N-lauroyl-L-glutamate, shea butter, sunflower seed oil, sweet almond oil, jojoba seed oil, coconut oil, olive oil, meadowfoam seed oil, argania spinosa kernel oil, macadamia nut oil, liquid paraffin, and squalane. The hydrophobic substance to be dissolved using the solubilizer of this embodiment may be a single substance or a mixture of two or more substances.

[0041] (First Production Method) The first production method includes a 1-1 step of dissolving an alkali metal salt of tocopherol phosphate in the above-mentioned aqueous solvent to produce a solution (aqueous solution) containing the alkali metal salt of tocopherol phosphate, and a 1-2 step of mixing the solution (aqueous solution) containing the alkali metal salt of tocopherol phosphate with a hydrophobic substance to produce an aqueous solution in which the hydrophobic substance is dissolved.

[0042] (Step 1-1) As a method for dissolving an alkali metal salt of tocopherol phosphate in an aqueous solvent, a known method can be used, for example, a method in which a powder of an alkali metal salt of tocopherol phosphate is mixed with water and stirred. The stirring method is not particularly limited, and examples thereof include manual stirring, a method using a vortex mixer, a method using ultrasonic irradiation, a method using a magnetic stirrer, a method using a planetary mixer, a vortex mixer, or a rotator rotor. The stirring time is not particularly limited, and can be, for example, 1 second to 10 hours.

[0043] (Step 1-2) Next, an aqueous solution containing an alkali metal salt of tocopherol phosphate is mixed with a hydrophobic substance to produce an aqueous solution containing the hydrophobic substance dissolved therein. A known method can be used to mix the solution containing the alkali metal salt of tocopherol phosphate with the hydrophobic substance. For example, a stirring method similar to the stirring method that can be used in the above-mentioned method of mixing and stirring an alkali metal salt of tocopherol phosphate with an aqueous solvent can be used. The stirring of the solution containing the alkali metal salt of tocopherol phosphate with the hydrophobic substance may be carried out continuously or intermittently. The stirring time is not particularly limited and can be, for example, 1 second to 500 hours.

[0044] The solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance are preferably mixed so that the content (concentration) of the alkali metal salt of tocopherol phosphate in the mixed solution (the aqueous solution obtained after solubilization of the hydrophobic compound) of the solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance is 0.01 mmol / L to 500 mmol / L, more preferably 0.5 mmol / L to 200 mmol / L. When the content of the alkali metal salt of tocopherol phosphate in the mixed solution is 0.01 mmol / L or more, the hydrophobic substance can be efficiently dissolved in the aqueous solution. When the content of the alkali metal salt of tocopherol phosphate in the mixed solution is 500 mmol / L or less, the alkali metal salt of tocopherol phosphate can be stably dissolved in the mixed solution. Therefore, the mixed solution can fully exhibit its performance as a solubilizer for the solution containing the alkali salt of tocopherol phosphate.

[0045] The solution containing the alkali salt of tocopherol phosphate and the hydrophobic substance are preferably mixed so that the content (by mass) of the hydrophobic substance in the mixed solution of the solution containing the alkali salt of tocopherol phosphate and the hydrophobic substance is 0.01 to 0.20 times, and more preferably 0.01 to 0.19 times, the mass of the alkali metal salt of tocopherol phosphate. When the content of the hydrophobic substance is 0.01 times or more the mass of the alkali metal salt of tocopherol phosphate, the effect of dissolving the hydrophobic substance in the aqueous solution using the method for producing an aqueous solution of this embodiment becomes more pronounced. When the content of the hydrophobic substance is 0.20 times or less the mass of the alkali metal salt of tocopherol phosphate, the hydrophobic substance can be efficiently and easily dissolved in the aqueous solution using the method for producing an aqueous solution of this embodiment.

[0046] The content of the hydrophobic substance contained in the aqueous solution produced by the first production method can be appropriately determined depending on the application of the aqueous solution. In this embodiment, the aqueous solution produced by the first production method may be diluted by mixing it with water, if necessary.

[0047] The aqueous solution produced by the first production method is a transparent solution in which a hydrophobic substance is dissolved. In this embodiment, the aqueous solution being a transparent solution in which a hydrophobic substance is dissolved (in other words, a "solubilized solution") means that the aqueous solution does not contain any separated hydrophobic substance and has a transmittance of 75% or more at a wavelength of 550 nm as measured by the method described below.

[0048] (Second Production Method) The second production method includes the steps of: Step 2-1 of dissolving an alkali metal salt of tocopherol phosphate in the dihydric alcohol for dissolving an alkali metal salt of tocopherol phosphate to produce a solution containing the alkali metal salt of tocopherol phosphate; Step 2-2 of mixing the solution containing the alkali metal salt of tocopherol phosphate with a hydrophobic substance to dissolve the hydrophobic substance in the solution containing the alkali metal salt of tocopherol phosphate to produce a solute-dissolved solution; and Step 2-3 of mixing the solute-dissolved solution with an aqueous solvent to produce an aqueous solution in which the hydrophobic substance is dissolved.

[0049] (Step 2-1) As a method for dissolving an alkali metal salt of tocopherol phosphate in a dihydric alcohol for dissolving an alkali metal salt of tocopherol phosphate, a known method can be used, and a method similar to the method that can be used in the above-mentioned method of mixing an alkali metal salt of tocopherol phosphate with an aqueous solvent and stirring can be used.

[0050] (Step 2-2) Next, the solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance are mixed to dissolve the hydrophobic substance in the solution containing the alkali metal salt of tocopherol phosphate, thereby producing a solute-dissolved solution. The method for mixing the solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance is not particularly limited, and for example, the same method as in Production Method 1 can be used. The solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance may be stirred continuously or intermittently.

[0051] In the second production method, as in the first production method, the solution containing the alkali metal salt of tocopherol phosphate and the hydrophobic substance are mixed so that the content (concentration) of the alkali metal salt of tocopherol phosphate in the aqueous solution obtained after solubilization of the hydrophobic compound is preferably 0.01 mmol / L to 500 mmol / L, more preferably 0.01 mmol / L to 200 mmol / L.

[0052] (Step 2-3) Next, the solute-dissolved solution obtained in Step 2-2 is mixed with an aqueous solvent. In the second production method, the mass of the hydrophobic substance that can be solubilized depends on the type of dihydric alcohol and the mass of the alkali metal salt of tocopherol phosphate. It is preferable to confirm in advance the mass of the hydrophobic substance that can be solubilized when each dihydric alcohol is used. It is preferable to mix the solute-dissolved solution with the aqueous solvent so that the content (mass) of the hydrophobic substance contained in the mixture of the solute-dissolved solution and the aqueous solvent is within the solubilizable range. This makes it possible to produce a transparent aqueous solution in which the hydrophobic substance is dissolved. The second production method may result in a greater mass of hydrophobic substance that can be solubilized in the aqueous solution than the first production method. Another advantage of Step 2-3 is that it takes a shorter time for the hydrophobic substance to dissolve than Step 1-2.

[0053] (Aqueous Solution) The aqueous solution contains the solubilizer for the hydrophobic substance, an aqueous solvent, and the hydrophobic substance, and the hydrophobic substance is dissolved in the aqueous solvent. The concentration of the alkali metal salt of tocopheryl phosphate is preferably 0.01 mmol / L to 500 mmol / L. This allows the hydrophobic compound to be sufficiently solubilized.

[0054] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0055] Example 1 Decane 1.598 g of DL-α-tocopheryl phosphate sodium salt (TPNa (registered trademark); manufactured by Resonac Corporation) was weighed into a 30 mL screw bottle, and purified water was added. The mixture was stirred with a Three-One Motor (registered trademark; manufactured by Shinto Scientific Co., Ltd.) to dissolve the solution. The total volume was then adjusted to 30 mL, yielding a 100 mmol / L aqueous solution of DL-α-tocopheryl phosphate sodium salt.

[0056] Next, the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate was mixed with 0.30 g of decane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), a hydrophobic substance, and the mixture was stirred for 10 seconds at 10°C using a vortex mixer (manufactured by Scientific Industries). Separated hydrophobic substances were present in the mixed solution after stirring. The mixed solution was then stored at 25°C for 24 hours and again stirred for 1 minute at 10°C using a vortex mixer. Subsequently, the operation of storing the solution at 25°C for 24 hours and the operation of stirring the solution at 10°C for 1 minute were alternately repeated six times to obtain an aqueous solution of Example 1 having a decane concentration of 1.0% by mass.

[0057] Figure 1 is a photograph of the aqueous solution produced in Example 1 (left) and the sample solution produced in Reference Example 1 (right). As shown in Figure 1, the aqueous solution obtained in Example 1 was transparent.

[0058] Next, to numerically express the transparency of the aqueous solution of Example 1, the transmittance of light with a wavelength of 550 nm was measured. That is, the aqueous solution of Example 1 was placed in a 30 mL glass vial, and the transmittance was measured using a spectroscopic petroleum product color tester OME7700 (manufactured by Nippon Denshoku Industries Co., Ltd.). As a result of measuring the aqueous solution of Example 1, the transmittance was found to be 99.7%. Therefore, it was confirmed that a 100 mmol / L aqueous solution of DL-α-tocopheryl phosphate sodium salt can be used as a solubilizing agent for hydrophobic substances.

[0059] Reference Example 1 A sample solution of Reference Example 1 having a decane concentration of 1.4 mass% was obtained in the same manner as in Example 1, except that the amount of decane was 0.42 g and the amount of 100 mmol / L aqueous solution of sodium salt of DL-α-tocopheryl phosphate was 29.58 g. The sample solution of Reference Example 1 did not become transparent. Note that the transmittance of the sample solution of Reference Example 1 was not measured.

[0060] As shown in Fig. 1 , when the aqueous solution obtained in Example 1 (solution on the left) is compared with the sample solution obtained in Reference Example 1 (solution on the right), the aqueous solution in Example 1 is transparent, whereas the sample solution in Reference Example 1 is opaque. The results shown in Fig. 1 reveal that an aqueous solution of sodium DL-α-tocopheryl phosphate can be used as a solubilizing agent for hydrophobic substances, but there is a limit to the amount of hydrophobic substance that can be solubilized.

[0061] Reference Example 2 A 100 mmol / L aqueous solution of sodium dodecyl sulfate (SDS; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was prepared using 0.865 g of sodium dodecyl sulfate (SDS) instead of the aqueous solution of sodium DL-α-tocopheryl phosphate. The aqueous solution of sodium dodecyl sulfate and decane were mixed in the same manner as in Example 1, except that this aqueous solution of sodium dodecyl sulfate was used as a solubilizing agent and the amount of decane mixed was changed.

[0062] As a result, it was confirmed that a clear aqueous solution could be obtained with a 100 mmol / L aqueous solution of sodium dodecyl sulfate (SDS) when the amount of decane in the aqueous solution was 0.2 mass% or less. This indicates that a solubilizer for hydrophobic substances consisting of a 100 mmol / L aqueous solution of the sodium salt of DL-α-tocopheryl phosphate can solubilize more hydrophobic substances than a 100 mmol / L aqueous solution of sodium dodecyl sulfate.

[0063] [Experiment 1] Aqueous solutions of the sodium salt of DL-α-tocopheryl phosphate were mixed with decane in the same manner as in Example 1 and Reference Example 1, except that the concentration of the sodium salt of DL-α-tocopheryl phosphate (TPNa) in the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate and the amount of decane to be mixed were varied, and the maximum amount of decane that could be solubilized was investigated. The results are shown in Figure 2.

[0064] In addition, the aqueous sodium dodecyl sulfate solution was mixed with decane in the same manner as in Reference Example 2, except that the concentration of sodium dodecyl sulfate (SDS) in the aqueous sodium dodecyl sulfate solution and the amount of decane mixed were varied, and the maximum decane concentration at which solubilization was possible was investigated. The results are shown in Figure 2.

[0065] FIG. 2 is a graph showing the relationship between the concentration of DL-α-tocopheryl phosphate sodium salt (TPNa) in an aqueous solution and the concentration of sodium dodecyl sulfate (SDS) in an aqueous solution, and the maximum concentration of decane that can be solubilized in the aqueous solution.

[0066] As shown in Figure 2, it was confirmed that an aqueous solution of the sodium salt of DL-α-tocopheryl phosphate can solubilize 0.01% by mass to 1.0% by mass of decane. It was also found that the amount of hydrophobic substance that can be solubilized by the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate depends on the amount of the sodium salt of DL-α-tocopheryl phosphate used. It was also confirmed that the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate can solubilize a larger amount of decane than an aqueous solution of sodium dodecyl sulfate.

[0067] Example 2, Experiment 2 Dodecane An aqueous solution of the sodium salt of DL-α-tocopheryl phosphate was mixed with dodecane in the same manner as in Example 1 and Reference Example 1, except that dodecane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of decane as the hydrophobic substance, and the concentration of the sodium salt of DL-α-tocopheryl phosphate (TPNa) in the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate and the amount of dodecane mixed were varied, and the maximum dodecane concentration at which solubilization was possible was investigated. The results are shown in Figure 3.

[0068] In addition, dodecane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the hydrophobic substance instead of decane, and the sodium dodecyl sulfate (SDS) concentration in the sodium dodecyl sulfate aqueous solution and the amount of dodecane mixed were varied, and the sodium dodecyl sulfate aqueous solution and dodecane were mixed in the same manner as in Reference Example 2, to determine the maximum amount of dodecane that could be solubilized in the aqueous solution. The results are shown in Figure 3.

[0069] FIG. 3 is a graph showing the relationship between the concentration of DL-α-tocopheryl phosphate sodium salt (TPNa) in an aqueous solution and the concentration of sodium dodecyl sulfate (SDS) in an aqueous solution, and the maximum solubilizable dodecane concentration.

[0070] As shown in Figure 3, dodecane could be solubilized using an aqueous solution of the sodium salt of DL-α-tocopheryl phosphate. As shown in Figures 2 and 3, the amount of dodecane that could be solubilized by the aqueous solution of the sodium salt of DL-α-tocopheryl phosphate was smaller than the amount that could solubilize decane. This indicates that the amount that can be solubilized by an aqueous solution of the sodium salt of DL-α-tocopheryl phosphate varies depending on the hydrophobic substance.

[0071] Furthermore, as shown in Figure 3, it was found that the amount of hydrophobic substance that can be solubilized by an aqueous solution of the sodium salt of DL-α-tocopheryl phosphate depends on the amount of the sodium salt of DL-α-tocopheryl phosphate used. Also, as shown in Figure 3, it was confirmed that an aqueous solution of the sodium salt of DL-α-tocopheryl phosphate can solubilize more dodecane than an aqueous solution of sodium dodecyl sulfate.

[0072] [Example in which no dihydric alcohol is contained and the concentration of the hydrophobic substance is 0.1% by mass] [Example 3] 0.1598 g of DL-α-tocopheryl phosphate sodium salt (TPNa (registered trademark); manufactured by Resonac Co., Ltd.) was weighed out into a 30 mL screw bottle, and 29.8102 g of pure water was added. The mixture was stirred with a three-one motor to dissolve the mixture, thereby obtaining a solution containing the alkali metal salt of tocopheryl phosphate.

[0073] Next, the solution containing the alkali metal salt of tocopherol phosphate was mixed with 0.03 g of decane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), a hydrophobic substance, and the mixture was stirred for 10 seconds at 10°C using a vortex mixer (manufactured by Scientific Industries). Separated hydrophobic substances were present in the mixed solution after stirring. The mixed solution was then stored at 25°C for 24 hours and again stirred for 1 minute at 10°C using a vortex mixer. Subsequently, the operation of storing at 25°C for 24 hours and the operation of stirring at 10°C for 1 minute were alternately repeated six times to obtain an aqueous solution of Example 3 containing 0.1% by mass of decane. The concentration of the alkali metal salt of tocopherol phosphate in the aqueous solution was 10 mmol / L. The ratio of the mass of the hydrophobic substance to the mass of the alkali metal salt of tocopherol phosphate was 0.188.

[0074] The aqueous solution of Example 3 thus obtained was visually observed. As a result, no separated hydrophobic substance was present in the aqueous solution of Example 3. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solution of Example 3 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 1.

[0075] [Example in which the dihydric alcohol is 1,2-pentanediol and the concentration of the hydrophobic substance is 0.10% by mass] [Example 4] 0.1598 g of sodium salt of DL-α-tocopheryl phosphate (TPNa (registered trademark); manufactured by Resonac Co., Ltd.) was weighed out into a 30 mL screw bottle, and 1.5 g of 1,2-pentanediol (trade name: Diol PD, manufactured by Kokyu Alcohol Kogyo Co., Ltd.), which is a dihydric alcohol, was added and dissolved by stirring with a stirring rod, thereby obtaining a solution containing an alkali metal salt of tocopheryl phosphate in which the mass of 1,2-pentanediol was 9.4 times the mass of TPNa.

[0076] Next, the solution containing the alkali metal salt of tocopherol phosphate was mixed with 0.03 g of decane (Fujifilm Wako Pure Chemical Industries, Ltd.), a hydrophobic substance, and stirred using a stirring rod to dissolve the solute, yielding a solute-dissolved solution. Next, the solute-dissolved solution was mixed with 28.3102 g of ultrapure water (MilliQ), an aqueous solvent, and stirred for 10 seconds at 10 using a vortex mixer (Scientific Industries, Inc.). The mixture was then stored at 25°C for 24 hours, yielding an aqueous solution of Example 4 with a decane concentration of 0.1% by mass. The amounts of each component are shown below. TPNa: 0.1598 g 1,2-pentanediol: 1.50 g Decane: 0.03 g Concentration of TPNa in aqueous solution: 10 mmol / L Concentration of hydrophobic substance (decane) in aqueous solution: 0.10 mass % Ratio of mass of dihydric alcohol (1,2-pentanediol) to mass of TPNa: 9.4 Ratio of mass of hydrophobic substance to mass of TPNa: 0.188

[0077] Figure 4 is a photograph of the aqueous solution prepared in Example 4. As shown in Figure 4, no separated hydrophobic substances were present in the aqueous solution prepared in Example 4. The transmittance of light with a wavelength of 550 nm was measured for the aqueous solution prepared in Example 4 in the same manner as for the aqueous solution prepared in Example 1. The results are shown in Table 1.

[0078] [Examples 5 to 12] Aqueous solutions of Examples 5 to 12 each having a hydrophobic substance concentration of 0.1% by mass were obtained in the same manner as in Example 4, except that 0.03 g of the hydrophobic substance shown below was used.

[0079] (Hydrophobic Substances) Example 5: Dodecane (trade name: Dodecane, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Example 6: 7-methyloctyl 7-methyloctanoate (trade name: Salacos 99, manufactured by Nisshin Oillio Co., Ltd.) Example 7: Cetyl 2-ethylhexanoate (trade name: NIKKOL CIO, manufactured by Nikko Chemicals Co., Ltd.) Example 8: 2-ethylhexyl palmitate (trade name: NIKKOL IOP, manufactured by Nikko Chemicals Co., Ltd.) Example 9: Dimethicone (viscosity 6 cs) (trade name: KF-96A-6 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 10: Dimethicone (viscosity 20 cs) (trade name: KF-96A-20 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 11: Decamethylcyclopentasiloxane (trade name: KF995, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 12: Glyceryl tri-2-ethylhexanoate (trade name: T.I.O., manufactured by Nisshin Oillio Co., Ltd.)

[0080] The aqueous solutions of Examples 5 to 12 thus obtained were each visually observed. As a result, no hydrophobic substances were present in any of the aqueous solutions. Furthermore, the transmittance of light at a wavelength of 550 nm was measured for the aqueous solutions produced in Examples 5 to 12 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 1.

[0081] Comparative Example 1 (TPNa concentration: 0 mmol / L) A sample solution of Comparative Example 1 was obtained in the same manner as in Example 4, except that 28.47 g of pure water and 1.5 g of 1,2-pentanediol were used instead of the solution containing the alkali metal salt of tocopheryl phosphate.

[0082] The sample solution produced in Comparative Example 1 appeared transparent, but it was confirmed that separated hydrophobic substances were present on the surface in the form of oil droplets. The transmittance of light with a wavelength of 550 nm was measured for the sample solution produced in Comparative Example 1 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 1.

[0083] Table 1 shows the types of hydrophobic substances used in Examples 3 to 12 and Comparative Example 1, the concentrations of the hydrophobic substances in the aqueous solutions, the transmittances of the aqueous solutions, and the presence or absence of separated hydrophobic substances in the aqueous solutions.

[0084]

[0085] As shown in Table 1, the aqueous solutions produced in Examples 3 to 12 all contained no separated hydrophobic substances and had a transmittance of 75% or more at a wavelength of 550 nm. That is, the aqueous solutions produced in Examples 3 to 12 were all transparent solutions in which the hydrophobic substances were dissolved in the aqueous solution. That is, the results of Examples 3 to 12 demonstrated that the solubilizing agent of the present invention can solubilize various types of hydrophobic compounds. Furthermore, as shown in Table 1, the aqueous solution produced in Comparative Example 1 contained separated hydrophobic substances and the hydrophobic substances were not dissolved in the aqueous solution.

[0086] [Example in which the dihydric alcohol is 1,2-hexanediol and the concentration of the hydrophobic substance is 0.10 mass%] [Example 13] An aqueous solution of Example 13, in which the concentration of decane was 0.10 mass%, was obtained in the same manner as in Example 4, except that 1.50 g of 1,2-hexanediol (trade name: Effisin HD, manufactured by Ashland Japan) was used instead of 1,2-pentanediol as the dihydric alcohol. The amounts of each component are as follows: TPNa: 0.1598 g, 1,2-hexanediol: 1.50 g, decane: 0.03 g, TPNa concentration in the aqueous solution: 10 mmol / L, hydrophobic substance (decane) concentration in the aqueous solution: 0.10 mass%, ratio of the mass of the dihydric alcohol (1,2-hexanediol) to the mass of TPNa: 9.4, and ratio of the mass of the hydrophobic substance to the mass of TPNa: 0.188.

[0087] [Examples 14 to 25] Aqueous solutions of Examples 14 to 25 each having a hydrophobic substance concentration of 0.10 mass% were obtained in the same manner as in Example 13, except that 0.03 g of the following hydrophobic substance was used instead of decane. (Hydrophobic substances) Example 14: Dodecane (trade name: Dodecane, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Example 15: 7-methyloctyl 7-methyloctanoate (trade name: Salacos 99, manufactured by Nisshin Oillio Co., Ltd.) Example 16: Cetyl 2-ethylhexanoate (trade name: NIKKOL CIO, manufactured by Nikko Chemicals Co., Ltd.) Example 17: 2-ethylhexyl palmitate (trade name: NIKKOL IOP, manufactured by Nikko Chemicals Co., Ltd.) Example 18: Dimethicone (viscosity 6 cs) (trade name: KF-96A-6 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 19: Dimethicone (viscosity 20 cs) (trade name: KF-96A-20 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 20: Decamethylcyclopentasiloxane (trade name: KF995, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 21: Glyceryl tri-2-ethylhexanoate (trade name: T.I.O., manufactured by Nisshin Oillio Co., Ltd.) Example 22: Liquid paraffin (trade name: MORESCO White P-70, manufactured by MORESCO Co., Ltd.) Example 23: Squalane (trade name: Vegetable squalane, manufactured by Kishimoto Tokushu Kanyu Kogyosho Co., Ltd.) Example 24: α-Olefin oligomer (trade name: NIKKOL Synthelan 4SP, manufactured by Nikko Chemicals Co., Ltd.) Example 25: Octyldodecyl myristate (trade name: NIKKOL ODM-100, manufactured by Nikko Chemicals Co., Ltd.)

[0088] [Comparative Example 2] (Concentration of TPNa: 0 mmol / L) Except for using 1.50 g of 1,2-hexanediol instead of 1,2-pentanediol as the dihydric alcohol, an aqueous solution of Comparative Example 2 was obtained in the same manner as Comparative Example 1. [Comparative Example 3] (Concentration of TPNa: 0 mmol / L) Except for using 0.03 g of dodecane instead of decane as the hydrophobic substance, an aqueous solution of Comparative Example 3 was obtained in the same manner as Comparative Example 2.

[0089] The aqueous solutions of Examples 13 to 25 and Comparative Examples 2 and 3 were each visually observed. As a result, in Examples 13 to 25, no separated hydrophobic substance was present in the aqueous solutions. On the other hand, in the aqueous solutions of Comparative Examples 2 and 3, separated hydrophobic substance was present. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solutions of Examples 13 to 25 and Comparative Examples 2 and 3 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 2. The aqueous solutions of Examples 13 to 25 were solutions in which the hydrophobic substance was solubilized, but the aqueous solutions of Comparative Examples 2 and 3 were not solutions in which the hydrophobic substance was solubilized.

[0090]

[0091] [Example in which the dihydric alcohol is 1,2-pentanediol and the concentration of the hydrophobic substance is 0.01% by mass] [Example 26] The aqueous solution of Example 26 was obtained in the same manner as in Example 4, except that the amount of DL-α-tocopherol phosphate sodium salt (TPNa), the amount of 1,2-pentanediol as the dihydric alcohol, and the amount of decane as the hydrophobic substance were each changed to 1 / 10. The amount of ultrapure water as the aqueous solvent was adjusted so that the total amount of the aqueous solution was 30.0 g. The amount of each component is shown below. TPNa: 0.0160 g 1,2-pentanediol: 0.15 g Decane: 0.003 g Concentration of TPNa in aqueous solution: 1.0 mmol / L Concentration of hydrophobic substance (decane) in aqueous solution: 0.01 mass % Ratio of mass of dihydric alcohol (1,2-pentanediol) to mass of TPNa: 9.4 Ratio of mass of hydrophobic substance (decane) to mass of TPNa: 0.188

[0092] Examples 27 to 41 Aqueous solutions containing the hydrophobic substance of Examples 27 to 41 at a concentration of 0.01% by mass were obtained in the same manner as in Example 26, except that 0.003 g of the hydrophobic substance shown in Table 3 was used instead of decane. The trade names and manufacturers of the hydrophobic substances of Examples 39 to 41 are shown below. (Hydrophobic Substances) Example 39: Methylphenylpolysiloxane (trade name: KF-54, manufactured by Shin-Etsu Chemical Co., Ltd.) Example 40: Macadamia nut oil (trade name: NIKKOL Macadamia Nut Oil, manufactured by Nikko Chemicals Co., Ltd.) Example 41: N-lauroyl-L-glutamic acid di(phytosteryl behenyl 2-octyldodecyl) (trade name: Eldew PS-306, manufactured by Ajinomoto Co., Inc.)

[0093] Comparative Example 4 (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 4 was obtained in the same manner as Comparative Example 1, except that the amount of 1,2-pentanediol, which is a dihydric alcohol, and the amount of decane, which is a hydrophobic substance, were each changed to 1 / 10. The amount of pure water, which is the aqueous solvent, was adjusted so that the total amount of the aqueous solution was 30.0 g. The amount of each component is shown below. 1,2-Pentanediol: 0.15 g Decane: 0.003 g Comparative Example 5 (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 5 was obtained in the same manner as Comparative Example 4, except that 0.003 g of dodecane was used instead of decane as the hydrophobic substance.

[0094] The aqueous solutions of Examples 26 to 41 and Comparative Examples 4 and 5 were each visually observed. As a result, in Examples 26 to 41, no separated hydrophobic substance was present in the aqueous solutions. On the other hand, in the aqueous solutions of Comparative Examples 4 and 5, separated hydrophobic substance was present. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solutions of Examples 26 to 41 and Comparative Examples 4 and 5 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 3. The aqueous solutions of Examples 26 to 41 were solutions in which the hydrophobic substance was solubilized, but the aqueous solutions of Comparative Examples 4 and 5 were not solutions in which the hydrophobic substance was solubilized.

[0095]

[0096] [Example in which the dihydric alcohol is 1,2-hexanediol and the concentration of the hydrophobic substance is 0.01 mass%] [Example 42] An aqueous solution of Example 42 having a decane concentration of 0.01 mass% was obtained in the same manner as in Example 26, except that 0.15 g of 1,2-hexanediol was used instead of 1,2-pentanediol as the dihydric alcohol.

[0097] [Examples 43 to 57] Aqueous solutions containing the hydrophobic substance of Examples 43 to 57 at a concentration of 0.01% by mass were obtained in the same manner as in Example 42, except that 0.003 g of a hydrophobic substance shown in Table 4 was used instead of decane. The trade name and manufacturer of the hydrophobic substance of Example 51 are shown below. (Hydrophobic Substance) Example 51: Olive oil (trade name: NIKKOL Olive Oil, manufactured by Nikko Chemicals Co., Ltd.)

[0098] [Comparative Example 6] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 2 was obtained in the same manner as in Comparative Example 4, except that 0.15 g of 1,2-hexanediol was used instead of 1,2-pentanediol as the dihydric alcohol. [Comparative Example 7] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 5 was obtained in the same manner as in Comparative Example 6, except that 0.003 g of dodecane was used instead of decane as the hydrophobic substance.

[0099] The aqueous solutions of Examples 42 to 57 and Comparative Examples 6 and 7 were each visually observed. As a result, in Examples 42 to 57, no separated hydrophobic substance was present in the aqueous solutions. On the other hand, in the aqueous solutions of Comparative Examples 6 and 7, separated hydrophobic substance was present. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solutions of Examples 42 to 57 and Comparative Examples 6 and 7 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 4. The aqueous solutions of Examples 42 to 57 were solutions in which the hydrophobic substance was solubilized, but the aqueous solutions of Comparative Examples 6 and 7 were not solutions in which the hydrophobic substance was solubilized.

[0100]

[0101] [Example in which the dihydric alcohol is 3-(hexyloxy)-1,2-propanediol and the concentration of the hydrophobic substance is 0.01% by mass] [Example 58] An aqueous solution of Example 58, having a decane concentration of 0.01% by mass, was obtained in the same manner as in Example 26, except that 0.15 g of 3-(hexyloxy)-1,2-propanediol (trade name: ADEKA NOL NHG, manufactured by ADEKA Corporation) was used instead of 1,2-pentanediol as the dihydric alcohol.

[0102] [Examples 59 to 74] Aqueous solutions of Examples 59 to 74 having a hydrophobic substance concentration of 0.01 mass% were obtained in the same manner as in Example 58, except that 0.003 g of a hydrophobic substance shown in Table 5 was used instead of decane.

[0103] [Comparative Example 8] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 8 was obtained in the same manner as Comparative Example 4, except that 0.15 g of 3-(hexyloxy)-1,2-propanediol was used instead of 1,2-pentanediol as the dihydric alcohol. [Comparative Example 9] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 9 was obtained in the same manner as Comparative Example 8, except that 0.003 g of dodecane was used instead of decane as the hydrophobic substance.

[0104] The aqueous solutions of Examples 58 to 74 and Comparative Examples 8 and 9 were each visually observed. As a result, in Examples 58 to 74, no separated hydrophobic substance was present in the aqueous solutions. On the other hand, in the aqueous solutions of Comparative Examples 8 and 9, separated hydrophobic substance was present. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solutions of Examples 58 to 74 and Comparative Examples 8 and 9 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 5. The aqueous solutions of Examples 58 to 74 were solutions in which the hydrophobic substance was solubilized, but the aqueous solutions of Comparative Examples 8 and 9 were not solutions in which the hydrophobic substance was solubilized.

[0105]

[0106] [Example in which the dihydric alcohol is 3-(cyclohexyloxy)-1,2-propanediol and the concentration of the hydrophobic substance is 0.01% by mass] [Example 75] An aqueous solution of Example 75, having a decane concentration of 0.01% by mass, was obtained in the same manner as in Example 26, except that 0.15 g of 3-(cyclohexyloxy)-1,2-propanediol (trade name: ADEKA NOL CHG, manufactured by ADEKA Corporation) was used instead of 1,2-pentanediol as the dihydric alcohol.

[0107] [Examples 76 to 90] Aqueous solutions of Examples 76 to 90 having a hydrophobic substance concentration of 0.01 mass% were obtained in the same manner as in Example 75, except that 0.003 g of a hydrophobic substance shown in Table 6 was used instead of decane.

[0108] [Comparative Example 10] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 10 was obtained in the same manner as in Comparative Example 4, except that 0.15 g of 3-(cyclohexyloxy)-1,2-propanediol was used instead of 1,2-pentanediol as the dihydric alcohol. [Comparative Example 11] (Concentration of TPNa: 0 mmol / L) An aqueous solution of Comparative Example 11 was obtained in the same manner as in Comparative Example 10, except that 0.003 g of dodecane was used instead of decane as the hydrophobic substance.

[0109] The aqueous solutions of Examples 75 to 90 and Comparative Examples 10 and 11 were each visually observed. As a result, in Examples 75 to 90, no separated hydrophobic substance was present in the aqueous solutions. On the other hand, in the aqueous solutions of Comparative Examples 10 and 11, separated hydrophobic substance was present. Furthermore, the transmittance of light with a wavelength of 550 nm was measured for the aqueous solutions of Examples 75 to 90 and Comparative Examples 10 and 11 in the same manner as for the aqueous solution produced in Example 1. The results are shown in Table 6. The aqueous solutions of Examples 57 to 90 were solutions in which the hydrophobic substance was solubilized, but the aqueous solutions of Comparative Examples 10 and 11 were not solutions in which the hydrophobic substance was solubilized.

[0110]

[0111] [Experiment 3] 1.5980 g of sodium salt of DL-α-tocopheryl phosphate (TPNa (registered trademark); manufactured by Resonac Corporation) and 3.1960 g of a dihydric alcohol shown in Table 7 were placed in a 30 mL screw bottle and dissolved by stirring with a stirring rod to obtain a solution containing an alkali metal salt of tocopheryl phosphate in which the mass of the dihydric alcohol was 2.0 times the mass of TPNa. Next, the solution containing the alkali metal salt of tocopheryl phosphate was mixed with various amounts of decane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), a hydrophobic substance, and the mixture was stirred with a stirring rod to obtain a solute-dissolved solution. Next, ultrapure water (MilliQ) was added to the solute-dissolved solution to a total amount of 30.0 g, and the mixture was mixed. The mixture was stirred for 10 seconds at 10 using a vortex mixer (Scientific Industries) and then stored at 25°C for 24 hours to obtain aqueous solutions with various decane concentrations. The TPNa concentration in the aqueous solutions was 100 mmol / L. As in Example 1, the presence of separated hydrophobic substances in the aqueous solutions was confirmed visually. The transmittance of light at a wavelength of 550 nm was also measured. Aqueous solutions that did not contain separated hydrophobic substances and had a transmittance of 75% or higher were determined to be "solubilized solutions," and the maximum decane concentration that could be solubilized was determined. The results are shown in Table 7 and Figure 5. In Table 7 and Figure 5, the maximum decane concentration at which the aqueous solution containing 100 mmol / L of TPNa can be solubilized without the dihydric alcohol shown in Figure 2 is shown under the heading "unblended." Table 7 also shows the transmittance of the aqueous solution containing the maximum decane concentration.

[0112]

[0113] [Experiment 4] The maximum solubilizable dodecane concentration was determined in the same manner as in Experiment 3, except that dodecane was used instead of decane as the hydrophobic substance. The results are shown in Table 8 and Figure 6. In Table 8 and Figure 6, the maximum solubilizable dodecane concentration in an aqueous solution containing no dihydric alcohol and having a TPNa concentration of 100 mmol / L, as shown in Figure 3, is shown under the heading "unblended." Table 8 also shows the transmittance of the aqueous solution containing the maximum dodecane concentration.

[0114]

[0115] 5 and 6 show that the maximum solubilizable decane and dodecane concentrations are higher when an aqueous solvent and a dihydric alcohol are included than when only an aqueous solvent is included. In particular, when 3-(hexyloxy)-1,2-propanediol is included as the dihydric alcohol, the maximum solubilizable decane and dodecane concentrations are highest.

[0116] The solubilizing agent of the present embodiment is suitably used in a process for producing an aqueous solution by dissolving a hydrophobic substance in an aqueous solution or the like using the solubilizing agent.

Claims

1. A solubilizer for hydrophobic substances, which is a solution containing an alkali metal salt of tocopherol phosphate and at least one solvent selected from an aqueous solvent and a dihydric alcohol.

2. The solubilizer for hydrophobic substances according to claim 1, wherein the at least one solvent selected from aqueous solvents and dihydric alcohols is one or more solvents selected from water, 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol.

3. The solubilizer for hydrophobic substances according to claim 1, wherein the at least one solvent selected from the group consisting of aqueous solvents and dihydric alcohols is water.

4. The solubilizer for hydrophobic substances according to claim 1, wherein the at least one solvent selected from aqueous solvents and dihydric alcohols is one or more solvents selected from 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol.

5. The solubilizer for hydrophobic substances according to claim 1, wherein the at least one solvent selected from aqueous solvents and dihydric alcohols is 3-(hexyloxy)-1,2-propanediol.

6. A solubilizer for hydrophobic substances according to any one of claims 1 to 5, wherein the alkali metal salt of tocopheryl phosphate is a sodium salt of tocopheryl phosphate.

7. The solubilizer for hydrophobic substances according to claim 1, wherein the ratio of the mass of the at least one solvent selected from the aqueous solvent and the dihydric alcohol to the mass of the alkali metal salt of tocopheryl phosphate is 2 to 20.

8. The solubilizer for hydrophobic substances according to claim 1, wherein the hydrophobic substance is at least one selected from the group consisting of hydrocarbon compounds having 5 to 20 carbon atoms, ester compounds having 5 to 20 carbon atoms, and fatty acids having 6 to 30 carbon atoms.

9. An aqueous solution comprising the solubilizer for hydrophobic substances according to claim 1, the aqueous solvent, and a hydrophobic substance, wherein the concentration of the alkali metal salt of tocopheryl phosphate is 0.01 mmol / L to 500 mmol / L, and the hydrophobic substance is dissolved in the aqueous solvent.

10. A method for producing an aqueous solution, comprising: Step 1-1 of dissolving an alkali metal salt of tocopheryl phosphate in an aqueous solvent to produce a solution containing the alkali metal salt of tocopheryl phosphate; and Step 1-2 of mixing the solution containing the alkali metal salt of tocopheryl phosphate with a hydrophobic substance to produce an aqueous solution in which the hydrophobic substance is dissolved in an amount by mass that is 0.01 to 0.20 times the mass of the alkali metal salt of tocopheryl phosphate.

11. A method for producing an aqueous solution, comprising: Step 2-1 of dissolving an alkali metal salt of tocopheryl phosphate in one or more dihydric alcohols selected from 1,2-hexanediol, 1,2-pentanediol, 3-(hexyloxy)-1,2-propanediol, and 3-(cyclohexyloxy)-1,2-propanediol to produce a solution containing the alkali metal salt of tocopheryl phosphate; Step 2-2 of mixing the solution containing the alkali metal salt of tocopheryl phosphate with a hydrophobic substance to dissolve the hydrophobic substance in the solution containing the alkali metal salt of tocopheryl phosphate to produce a solute-dissolved solution; and Step 2-3 of mixing the solute-dissolved solution with an aqueous solvent to produce an aqueous solution in which the hydrophobic substance is dissolved.

12. The method for producing an aqueous solution according to claim 10 or 11, wherein the amounts of the alkali metal salt of tocopherol phosphate and the aqueous solvent are adjusted so that the concentration of the alkali metal salt of tocopherol phosphate in the aqueous solution is 0.01 mmol / L to 500 mmol / L.

Images