JP7809791B2 - Gel sheets for cosmetic packs - Google Patents

Description

The present invention relates to a gel sheet for a cosmetic pack.

Hydrogel compositions containing water are known as topical preparations that are applied to the skin.

Patent Document 1 discloses an external patch comprising a sheet-like support and a gel base layered on one surface of the support, which is used by applying the gel base to the skin surface after heating. The gel base of the external patch is characterized in that it is an oil-droplet-containing gel that contains an oily component with a melting point of 35-47°C and a surfactant for dispersing the oil component as oil droplets in the hydrogel.

Patent Document 2 discloses a gel composition for application to the skin containing 1 to 25% by mass of a water-containing oil, 0.4 to 6% by mass of a phospholipid, 0.1 to 10% by mass of an acrylic acid-based polymer, 0.1 to 10% by mass of a water-soluble polysaccharide capable of forming a gel, and water.

Japanese Patent Application Publication No. 2020-7275 Japanese Patent Application Publication No. 2019-26562

The topical patch in Patent Document 1 is designed to provide effective warmth, and contains an oil component with a melting point of 35-47°C, which ensures sustained warmth. The oil component in the form of oil droplets does not seep out from the gel base.

The water-containing oil agent in Patent Document 2 migrates from the gel composition for skin application to the skin when the gel composition for skin application is applied to the skin, resulting in the moisturizing effect of the water-containing oil agent on the skin. However, the gel in Patent Document 2 uses a water-soluble polysaccharide as the backbone, and the oil agent is a water-containing oil agent. Patent Document 2 also uses a phospholipid as an emulsifier to mix the water-containing oil agent with water. However, there is no mention of the size of the oil droplets on the gel surface.

The present invention aims to provide a gel sheet for cosmetic packs that has small oil droplets on the surface of the gel sheet and has excellent long-lasting skin moisturizing effects, and a method for manufacturing the same.

The present invention encompasses the embodiments described below.
Item 1.
A gel sheet for a cosmetic pack, comprising a synthetic polymer having a network structure, an oil, an exudative, a moisturizing agent, and water, wherein the average diameter of the oil on the surface of the gel sheet is 5 μm or less.
Item 2.
Item 2. The gel sheet for a cosmetic pack according to Item 1, wherein the oil comprises one or more oils selected from the group consisting of hydrocarbons, waxes, and oils and fats.
Item 3.
Item 3. The gel sheet for cosmetic packs according to Item 1 or 2, wherein the gel sheet for cosmetic packs contains the exudative agent in an amount of 0.1 to 20% by mass.
Item 4.
Item 4. The gel sheet for a cosmetic pack according to any one of Items 1 to 3, wherein the exudative agent contains a nonionic water-soluble polymer.
Item 5.
Item 5. The gel sheet for cosmetic packs according to any one of Items 1 to 4, wherein the synthetic polymer having a network structure is a polymer of a polymerizable unsaturated monomer having an anionic functional group or a crosslinked product of a salt of such a polymer with a crosslinking agent.
Item 6.
Item 6. The gel sheet for a cosmetic pack according to any one of Items 1 to 5, further comprising a nonionic surfactant having an HLB value of 6 or less and a nonionic surfactant having an HLB value of 10 or more.
Section 7.
Item 7. The gel sheet for a cosmetic pack according to Item 6, wherein both the nonionic surfactant having an HLB value of 6 or less and the nonionic surfactant having an HLB value of 10 or more are polyglycerol fatty acid esters.
Section 8.
Item 8. The gel sheet for a cosmetic pack according to Item 6 or 7, comprising 0.5% by mass or more of the nonionic surfactant having an HLB value of 6 or less and 0.5% by mass or more of the nonionic surfactant having an HLB value of 10 or more.
Item 9.
Item 9. A method for producing the gel sheet for a cosmetic pack according to any one of items 1 to 8,
A method for producing a gel sheet for a cosmetic pack, comprising: a step of mixing an oil solution to which a nonionic surfactant having an HLB value of 6 or less has been added with water to which a nonionic surfactant having an HLB value of 10 or more has been added to prepare an emulsion; and a step of mixing a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an exuding agent, a wetting agent, a crosslinking agent, water, and the emulsion to form a gel composition having a network structure.

The present invention provides a gel sheet for cosmetic packs in which the oil droplet size on the surface of the gel sheet is small and the moisturizing effect is excellent and lasts long, as well as a method for manufacturing the same.

FIG. 1 is a plan view of a gel sheet for a cosmetic pack according to an embodiment of the present invention. FIG. 10 is a plan view of a gel sheet for a cosmetic pack according to another embodiment of the present invention. FIG. 10 is a plan view of a gel sheet for a cosmetic pack according to another embodiment of the present invention. FIG. 10 is a plan view of a gel sheet for a cosmetic pack according to another embodiment of the present invention. 1 is a graph showing the relationship between the HLB value of surfactants used in Examples and Comparative Examples and the stability of emulsions.

In this specification, the term "comprise" is a concept that encompasses "consist essentially of" and "consist only of."
In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.
In one aspect of the present invention, there is provided a gel sheet for a cosmetic pack, which comprises a synthetic polymer having a network structure, an oil, an exudative, a moisturizing agent, and water, and is characterized in that the average diameter of the oil on the surface of the gel sheet is 5 μm or less.

(Synthetic polymer with network structure)
The synthetic polymer having a network structure is not particularly limited as long as it can absorb at least water and form a gel. When the hydrogel is used for transdermal applications in the field of cosmetics, synthetic polymers acceptable in the field can be used. In particular, synthetic polymers with affinity for water are used. For example, the synthetic polymer having a network structure is a crosslinked product of a polymer or salt thereof of a polymerizable unsaturated monomer having an anionic functional group and a crosslinking agent.

Examples of polymers of polymerizable unsaturated monomers with anionic functional groups and their salts include polyacrylic acid, which is a polymer of acrylic acid having a carboxyl group as the functional group; polymethacrylic acid, which is a polymer of methacrylic acid having a carboxyl group as the functional group, and their respective sodium salts, potassium salts, and triethanolamine salts; and polymers of t-butylacrylamidosulfonic acid, which has a sulfonic acid group as the functional group, and their sodium salts and potassium salts. Sodium polyacrylate is preferably used as the polymer of a polymerizable unsaturated monomer with anionic functional groups or its salts. Using sodium polyacrylate as the backbone of a synthetic polymer with a network structure enables the exudation of a humectant from the hydrogel (and gel sheets for cosmetic packs) by an exudative agent, and simultaneously, the supply of oil on the gel surface to the skin, thereby inhibiting moisture evaporation from the skin.

The preferred content of the polymer or salt thereof of a polymerizable unsaturated monomer having an anionic functional group before crosslinking is 0.50 to 35% by mass in the gel sheet.

In addition, taking into consideration handleability during production, it is preferable that the weight average molecular weight of the polymer or salt thereof of a polymerizable unsaturated monomer having an anionic functional group before crosslinking with a crosslinking agent is in the range of 100,000 to 5,000,000.

Synthetic polymers with a network structure can be obtained by crosslinking a polymer of a polymerizable unsaturated monomer having an anionic functional group or its salt. That is, a synthetic polymer with a network structure can be obtained by mixing a polymer of a polymerizable unsaturated monomer having an anionic functional group or its salt with a crosslinking agent (for example, by adding a crosslinking agent to a polymer of a polymerizable unsaturated monomer having an anionic functional group or its salt), and then heating as necessary.

Examples of crosslinking agents include aluminum hydroxide, potassium alum, aluminum sulfate, aluminum glycinate, aluminum acetate, aluminum oxide, aluminum metasilicate, magnesium chloride, calcium hydroxide, calcium carbonate, magnesium aluminometasilicate, polyethyleneimine, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, triglycidyl isocyanurate, etc. These crosslinking agents can be used alone or in combination of two or more.

The preferred content of crosslinking agent in the gel sheet for cosmetic packs is 0.10 to 5.0% by mass.

(oil agent)
The oil used in the gel sheet for a cosmetic pack is not particularly limited as long as it is suitable as an oil component to be applied to the skin.

Preferably, the oil contains one or more selected from the group consisting of hydrocarbons, waxes, and oils and fats. When these oils are used, the oil exuded from the gel sheet for cosmetic packs adheres to the skin, inhibiting moisture evaporation from the skin and providing sustained skin moisturizing effects.

Specific preferred hydrocarbons include, but are not limited to, squalane, petrolatum, mineral oil, etc.

Preferred waxes include, but are not limited to, jojoba seed oil, beeswax, etc.

Preferred oils include, but are not limited to, vegetable oils such as olive oil, macadamia nut oil, argan oil, shea butter, coconut oil, and grapeseed oil, and animal oils such as horse oil.

The preferred oil content in the gel sheet for cosmetic packs is 0.10 to 10% by mass. A more preferred content is 1.0 to 8.0% by mass.

In terms of skin moisturizing effect, it is preferable that the content be 0.10% by mass or more. In terms of emulsion stability, it is preferable that the content be 10% by mass or less.

(exudative)
An exuding agent is an agent used to effectively exude the solution within the hydrogel of a gel sheet for cosmetic packs onto the surface of the hydrogel. It is also called a solution exudation promoter. For example, by incorporating a substance that is hydrophilic but also has a certain degree of hydrophobicity as an exuding agent, the solution or water within the hydrogel can be effectively expelled. The solution that exudes onto the hydrogel surface, i.e., the solution that exudes out of the gel sheet for cosmetic packs (bleed liquid), is transferred to the skin that comes into contact with the gel sheet for cosmetic packs.

Preferred exudants include non-ionic water-soluble polymers and electrolytes.

Some nonionic water-soluble polymers are hydrophilic yet have a certain degree of hydrophobicity, allowing for effective ejection of the solution or water contained in the hydrogel. Preferred nonionic water-soluble polymers include glycols such as polyethylene glycol, polypropylene glycol, and polyglycerin, and polymers of polyhydric alcohols. These nonionic water-soluble polymers can be used alone or in combination of two or more.

In particular, it is preferable to use a nonionic water-soluble polymer with a specific moisture absorption in the range of 2 to 55, assuming that the moisture absorption of glycerin is 100. Because the water retention capacity is insufficient, a specific moisture absorption of 2 or more is preferable in terms of good compatibility with the synthetic polymers that make up the hydrogel. A specific moisture absorption of 55 or less is preferable in order to prevent the water retention capacity of the nonionic water-soluble polymer from inhibiting the solution within the hydrogel from coming out to the hydrogel surface, thereby ensuring a moisturizing feel and moisturizing effect. An even more preferable range of specific moisture absorption is 20 to 45.

In addition, some electrolytes have the effect of tightening the hydrogel's network structure, allowing the solution within the hydrogel to seep out to the hydrogel's surface. Preferred electrolytes are those that are readily water-soluble and have a proven track record of use in cosmetics, etc., but neutral salts of strong acids and strong alkalis are preferred due to their solubility and minimal pH fluctuation. Examples of such electrolytes include sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate. These electrolytes can be used alone or in combination.

The preferred content of the exudative agent in the gel sheet for cosmetic packs is 0.10 to 20% by mass, more preferably 1.0 to 10% by mass. When the exudative agent is a non-ionic water-soluble polymer or electrolyte, the preferred content is also 0.10 to 20% by mass, more preferably 1.0 to 10% by mass, in the gel sheet for cosmetic packs.

The exuding agent content is preferably 0.10% by mass or more in terms of adhesion and exudation effect. Furthermore, the exuding agent content is preferably 20% by mass or less in terms of preventing dripping.

(wetting agent)
The gel sheet for a cosmetic pack contains a moisturizing agent.

Examples of humectants include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol (DPG), glycerin, diglycerin, isopropylene glycol, 1,3-butylene glycol (1,3-BG), sorbitol, malbitol, trehalose, raffinose, xylitol, mannitol, hyaluronic acid and its salts, various derivatives of trehalose and raffinose, trimethylglycine, cyclodextrin, glycols such as hyaluronic acid and its salts, polyhydric alcohols, and polysaccharides. These humectants can be used alone or in combination of two or more.

The preferred content of humectant in the gel sheet for cosmetic packs is 1.0 to 50% by weight.

(Nonionic surfactant)
The gel sheet for cosmetic packs may contain a nonionic surfactant for the purposes of increasing the stability of the emulsion when the oil is dispersed in water and making the average diameter of the oil on the surface of the gel sheet for cosmetic packs 5 μm or less.

The nonionic surfactant preferably includes a nonionic surfactant with an HLB value of 6 or less and a nonionic surfactant with an HLB value of 10 or more. As explained in the manufacturing method for gel sheets for cosmetic packs described below, using specific nonionic surfactants with different HLB values to disperse oil can stabilize the emulsion and control the average diameter of oil droplets on the gel surface to 5 μm or less.

The HLB value indicates the surfactant's affinity for water and oil, a parameter known as the lipophilic-lipophilic balance.

The HLB value can be easily determined using known calculation methods, such as the Griffin method, Davis method, Atlas method, and Kawakami method. In this specification, the HLB value can be calculated using the Atlas method using the following formula (1). The saponification value and neutralization value in formula (1) can be measured according to the method published in the 2003 edition of the Standard Methods for the Analysis of Fats, Oils, and Related Materials (established by the Japan Oil Chemists' Society), compiled by the Japan Oil Chemists' Society.

HLB=20(1-S/A)...(1)
S is the saponification number of the ester, and A is the neutralization number of the fatty acid.

The saponification value is the number of milligrams of potassium hydroxide consumed when 1 g of fatty acid ester of polyhydric alcohol is hydrolyzed with potassium hydroxide, and the neutralization value is the number of milligrams of potassium hydroxide required to neutralize 1 g of the constituent fatty acid of fatty acid ester of polyhydric alcohol.

The HLB values of known surfactants are well known, and those skilled in the art can appropriately select nonionic surfactants with an HLB value of 6 or less and nonionic surfactants with an HLB value of 10 or more.

Nonionic surfactants may be any nonionic surfactant with an HLB value of 6 or less or a nonionic surfactant with an HLB value of 10 or more, but are not limited thereto. Examples include sorbitan fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, polyethylene glycol fatty acid esters, sucrose fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene propylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil fatty acid esters, polyoxyethylene phytostanol ethers, polyoxyethylene phytosterose ethers, polyoxyethylene cholestanol ethers, polyoxyethylene cholesteryl ethers, polyoxyalkylene-modified organopolysiloxanes, and polyoxyalkylene-alkyl co-modified organopolysiloxanes. One or more selected from these may be used. Polyglycerin fatty acid esters are more preferred.

The nonionic surfactant with an HLB value of 6 or less may be any nonionic surfactant with an HLB value of 6 or less, such as polyglyceryl-2 oleate, polyglyceryl-4 stearate, polyglyceryl-2 stearate, polyglyceryl-2 isostearate, polyglyceryl-2 diisostearate, and polyglyceryl-2 triisostearate, but preferably polyglyceryl-2 oleate, polyglyceryl-4 isostearate, and polyglyceryl-2 diisostearate. The nonionic surfactant with an HLB value of 6 or less may be one type, or two or more types.

The nonionic surfactant with an HLB value of 10 or higher may be any nonionic surfactant with an HLB value of 10 or higher, such as polyglyceryl-4 laurate, polyglyceryl-6 laurate, polyglyceryl-10 laurate, polyglyceryl-6 myristate, polyglyceryl-10 myristate, polyglyceryl-10 palmitate, polyglyceryl-10 stearate, and polyglyceryl-10 diisostearate, with polyglyceryl-4 laurate, polyglyceryl-6 laurate, and polyglyceryl-10 laurate being preferred. The nonionic surfactant with an HLB value of 10 or higher may be one type, or two or more types.

Preferably, the gel sheet for cosmetic packs contains a nonionic surfactant with an HLB value of 6 or less and a nonionic surfactant with an HLB value of 10 or more, both of which are polyglycerol fatty acid esters. This configuration more effectively disperses the oil, stabilizes the emulsion, and controls the average diameter of the oil on the surface of the gel sheet for cosmetic packs to 5 μm or less.

The preferred content of nonionic surfactants with an HLB value of 6 or less in the gel sheet for cosmetic packs is 0.50 to 5.0% by mass.

The preferred content of nonionic surfactants with an HLB value of 10 or more in the gel sheet for cosmetic packs is 0.50 to 5.0% by mass.

It is more preferable that the content of nonionic surfactants with an HLB value of 6 or less in the gel sheet for cosmetic packs be 0.50 to 5.0% by mass, and the content of nonionic surfactants with an HLB value of 10 or more be 0.50 to 5.0% by mass, in terms of dispersing the oil, stabilizing the emulsion, and controlling the average diameter of the oil on the surface of the gel sheet for cosmetic packs to 5 μm or less.

In addition, the gel sheet for cosmetic packs may contain nonionic surfactants other than nonionic surfactants with an HLB value of 6 or less and nonionic surfactants with an HLB value of 10 or more.

(Thickener)
The gel sheet for a cosmetic pack may further contain a thickener for the purpose of increasing the viscosity of the hydrogel and the gel sheet for a cosmetic pack.

Preferred thickeners include polysaccharides and their derivatives, such as cellulose, guar gum, cationized guar gum, starch, xanthan gum, and hydroxypropyl guar gum. Hydroxypropyl guar gum is more preferred in terms of improving dripping, improving adhesion, and/or providing a moisturizing feeling after use.

Hydroxypropyl guar gum is a nonionic polymer obtained by replacing the hydroxyl groups with hydroxypropyl groups using guar gum, a natural water-soluble polymeric polysaccharide contained in the endosperm portion of the seeds of the legume guar, by reacting it with sodium hydroxide and propylene oxide.

Hydroxypropyl guar gum with a degree of substitution of hydroxypropyl groups of 0.4 to 1.2 is preferably used. More preferably, it is 0.6 to 1.0, which is even more effective.

The preferred content of thickener in the gel sheet for cosmetic packs is 0.050 to 3.0% by mass. A content of 0.050% by mass or more is preferred in terms of improving dripping, enhancing adhesion, and/or providing a moisturizing feeling after use, while a content of 3.0% by mass or less is preferred in terms of preventing the gel sheet from becoming too sticky due to increased viscosity.

When the thickener is hydroxypropyl guar gum, it is preferably present in the gel sheet for cosmetic packs at 0.050 to 3.0% by mass, more preferably 0.050 to 2.0% by mass, and most preferably 0.10 to 1.0% by mass.

(pH adjuster)
To adjust the pH to an optimum value for the action of the crosslinking agent and ensure crosslinking, the gel sheet for cosmetic packs may contain a pH adjuster such as an α-hydroxy acid such as tartaric acid, lactic acid, or glycolic acid, as well as various organic acids such as citric acid or inorganic acids such as hydrochloric acid. These pH adjusters may be used alone or in combination of two or more.

The preferred content of pH adjuster in the gel sheet for cosmetic packs is 0.10 to 10% by mass.

(water)
The total amount of water is preferably 45 to 97% by mass, more preferably 50 to 95% by mass, based on the gel sheet for a cosmetic pack.

The gel sheet for cosmetic packs according to an embodiment of the present invention may contain ingredients other than those listed above. Examples of such ingredients include preservatives, antioxidants, antibacterial agents, medicinal ingredients, sequestering agents, fragrances, and colorants. These ingredients are added to the extent that they do not impair the effects of the present invention.

In a gel sheet for cosmetic packs according to an embodiment of the present invention, the average diameter of the oil on the surface of the gel sheet is 5 μm or less. In this specification, the average diameter of oil droplets is defined as the average value of the diameters of 100 or more oil droplets on the surface of the gel sheet observed under an optical microscope. It is more preferable to define the average diameter of oil droplets as the average value of the diameters of 100 or more oil droplets observed under an optical microscope. While the average diameter of oil in conventional gel sheets for cosmetic packs is greater than 5 μm, the gel sheet for cosmetic packs according to an embodiment of the present invention has a smaller oil droplet size on the gel surface. The smaller oil droplet size allows the oil droplets on the surface of the gel sheet to exude efficiently, facilitating the delivery of the oil to the skin. The exudative agent exudes the humectant from the gel, and the oil on the gel surface is delivered to the skin in combination, suppressing moisture evaporation, thereby achieving sustained skin moisturizing effects.

An intermediate substrate may be embedded in the cosmetic pack gel sheet of an embodiment of the present invention along the in-plane direction.

It may be laminated with a substrate made of nonwoven or woven fabric, or a substrate made of nonwoven or woven fabric may be embedded. Here, the in-plane direction of the hydrogel refers to any direction within a plane perpendicular to the thickness direction of the hydrogel. The presence of an intermediate substrate leads to reinforcement of the hydrogel and improved shape retention when cutting. Specific embodiments of the intermediate substrate include nonwoven or woven fabric. Materials that can be used for nonwoven and woven fabrics include natural fibers such as cellulose, silk, and hemp, synthetic fibers such as polyester, nylon, rayon, polyethylene, polypropylene, and polyurethane, and blends thereof, and a binder may be used if necessary.

The manufacturing method for nonwoven fabrics is not particularly limited, but examples include dry and wet methods, spunbonding, meltblown, airlaid, chemical bonding, thermal bonding, needle punching, and hydroentangling. It is preferable to adopt a manufacturing method appropriate for the basis weight and material, and to ensure uniformity in basis weight for position control of the intermediate substrate. Woven fabrics are also not particularly limited, and can be selected as appropriate, such as plain weave, tricot, or Russell.

The basis weight of the woven or nonwoven fabric is not particularly limited as long as it is a basis weight that allows the desired physical properties of the intermediate substrate to be obtained, but is preferably 10 to 40 g/ ^m² , and more preferably 10 to 28 g/ ^m² . If the basis weight of the woven or nonwoven fabric is too small, it may be impossible to reinforce the gel sheet, or the unevenness in the basis weight may increase, causing the liquid permeability during gel sheet production to vary depending on the location, which may result in fluctuations in the position of the intermediate substrate. If the basis weight is too large, the intermediate substrate may become hard, which may impair the hydrogel's ability to conform to the skin or adversely affect its conductivity. Therefore, the basis weight is set appropriately while taking these factors into consideration.

If the thickness of the intermediate substrate is too thick, it may not be able to penetrate the liquid well, which may have a negative effect on conductivity. Conversely, if it is too thin, it may not be possible to reinforce the gel sheet, as is the case when the basis weight is too small, and the position of the intermediate substrate may fluctuate. Therefore, the thickness should be set appropriately taking these factors into consideration. It is preferably within the range of 0.050 mm to 2.0 mm. Furthermore, 0.050 mm to 0.50 mm is more preferable, and 0.080 mm to 0.30 mm is particularly preferable.

The thickness of the gel sheet for cosmetic packs of the present invention (including the thickness of the substrate if the gel sheet for cosmetic packs includes a substrate) may be uniform throughout or may vary in parts, but to ensure adhesion, transparency, and strength, a thickness of 0.10 to 3.0 mm is preferred, and 0.20 to 2.0 mm is more preferred. From the perspective of gel sheet strength, a thickness of 0.1 mm or more is preferred, and from the perspective of adhesion, so that the weight of the gel sheet does not become too heavy, 3.0 mm or less is preferred.

Gel sheets for cosmetic packs used in skin care are well known. Figure 1 shows gel sheets 10L and 10R for cosmetic packs, respectively, for use under the left and right eyes. Figure 2 shows gel sheet 20 for cosmetic packs, which is applied to the skin of the face. Figure 3 shows gel sheet 20U for cosmetic packs, sized to fit the upper half of the face. Figure 4 shows gel sheet 20L for cosmetic packs, sized to fit the lower half of the face.

The pair of cosmetic pack gel sheets 10L and 10R shown in Figure 1 are for use under the left and right eyes, respectively. Cosmetic pack gel sheet 10L has a roughly arc-shaped outline on the lower side in Figure 1 that fits the lower eyelid of the left eye, and is used by adhering it to the skin just below the left eye so that its outline fits the lower eyelid of the left eye. Cosmetic pack gel sheet 10R has a roughly arc-shaped outline on the upper side in Figure 1 that fits the lower eyelid of the right eye, and is used by adhering it to the skin just below the right eye so that its outline fits the lower eyelid of the right eye.

The shape of the cosmetic pack gel sheet to be applied to the face is not limited to the shape shown in Figure 1, but may also be a shape that fits the entire face, as shown in Figure 2. The cosmetic pack gel sheet 20 shown in Figure 2 is a full-face cosmetic pack gel sheet formed to fit the entire face, and is formed in the shape of a roughly circular sheet with two through-holes 22 in the areas corresponding to the eyes, a through-hole 23 in the area corresponding to the mouth, a slit 24 in the area corresponding to the nose, and a slit 25 in the area corresponding to the chin, and the positions of the through-holes 22, 23 and the slits 24, 25 are adjusted so that the gel sheet can be applied to the entire face, following the curves of the face.

Furthermore, the cosmetic pack gel sheet to be applied to the face may be a cosmetic pack gel sheet 20U sized to fit the upper half of the face as shown in FIG. 3, or a cosmetic pack gel sheet 20L sized to fit the lower half of the face as shown in FIG. 4. In this case, the cosmetic pack gel sheet 20U sized to fit the upper half of the face and the cosmetic pack gel sheet 20L sized to fit the lower half of the face may be used separately, or they may be used in combination to be applied to the entire face. Here, the size corresponding to the upper half of the face refers to a size that includes at least the forehead but does not include the chin or cheeks, and the size corresponding to the lower half of the face refers to a size that includes at least the chin and cheeks but does not include the forehead. In FIGS. 3 and 4, the same components as those in FIG. 2 are designated by the same reference numerals and will not be described again.

The gel sheet for a cosmetic pack according to the embodiment of the present invention may be a gel sheet for a cosmetic pack that is attached to a part of the body other than the face, for example, the surface of the hand.
In some embodiments, the gel sheet for a cosmetic pack according to the present invention does not include a gel composition for application to skin that contains 1 to 25% by mass of a water-containing oil, 0.4 to 6% by mass of a phospholipid, 0.1 to 10% by mass of an acrylic acid-based polymer, 0.1 to 10% by mass of a water-soluble polysaccharide capable of forming a gel, and water.

(Manufacturing method)
In another aspect of the present invention, there is provided a method for producing the gel sheet for a cosmetic pack, which includes the steps of: mixing an oil solution containing a nonionic surfactant having an HLB value of 6 or less with water containing a nonionic surfactant having an HLB value of 10 or more to prepare an emulsion; and mixing a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an exuding agent, a wetting agent, a crosslinking agent, water, and the emulsion to form a gel composition having a network structure.

First, an emulsion is prepared by mixing an oil solution containing a nonionic surfactant with an HLB value of 6 or less with water containing a nonionic surfactant with an HLB value of 10 or more. The nonionic surfactant with an HLB value of 6 or less and the nonionic surfactant with an HLB value of 10 or more are the same as those described above as components of the gel sheet for cosmetic packs.

When oil is mixed with water and dispersed using specific nonionic surfactants with different HLB values, the emulsion becomes stable.

Next, a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an exuding agent, a wetting agent, a crosslinking agent, water, and the above emulsion are mixed, and the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer is reacted with the crosslinking agent to obtain a gelled composition with a network structure.

Because the emulsion is stable, it also remains stable in the form of a slurry, which is a composition obtained by mixing the emulsion with a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an exuding agent, a crosslinking agent, a wetting agent, and water. Even when the slurry is gelled, the average diameter of the oil droplets on the gel surface can be controlled to 5 μm or less. A pH adjuster is preferably added to the slurry to adjust the pH to 4-7, promoting the reaction between the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer and the crosslinking agent.

When mixing the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, the exuding agent, the crosslinking agent, the wetting agent, water, and the emulsion, these components may be mixed all at once or separately. Preferably, to ensure uniform dispersion of the thickener within the hydrogel, the thickener is mixed with the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer and the wetting agent before gel formation. The exuding agent may be mixed with this mixture or added later. It is then preferable to add a crosslinking agent to the mixture to cause a reaction between the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer and the crosslinking agent. Other components are added as appropriate before gelation.

If only one type of nonionic surfactant with an HLB value of 6 or less or one type of nonionic surfactant with an HLB value of 10 or more is added, or only two types of nonionic surfactants with an HLB value of 6 or less, or only two types of nonionic surfactants with an HLB value of 10 or more, or only nonionic surfactants with an HLB value of more than 6 but less than 10, a stable emulsion cannot be formed and the oil droplet size on the gel surface will be larger than 5 μm.

In the manufacturing method of the gel sheet for the above-mentioned cosmetic pack, first, an emulsion is prepared by mixing an oil solution to which a nonionic surfactant with an HLB value of 6 or less has been added and water to which a nonionic surfactant with an HLB value of 10 or more has been added.

The ratio of nonionic surfactants with an HLB value of 6 or less to oil is preferably 0.1 to 0.5 by mass.

The ratio of nonionic surfactants with an HLB value of 10 or more to water is preferably 0.01 to 1 by mass.

Next, a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an optional thickener, a humectant, and water are mixed to prepare a mixed liquid.

The ratio of polymers of polymerizable unsaturated monomers having anionic functional groups or salts of such polymers, wetting agents, and water is preferably 0.5-35:1-50:45-97 by mass, more preferably 1-30:2-35:50-95, and even more preferably 2-25:3-30:55-90 by mass.

When a thickener is used, the ratio by mass of the polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, the thickener, the humectant, and water is preferably 0.5-35:0.05-3:1-50:45-97, more preferably 1-30:0.1-2:2-35:50-95, and even more preferably 2-25:0.2-1:3-30:55-90.

The exudative agent is preferably added to the gel sheet for cosmetic packs at a concentration of 0.10 to 20% by weight, more preferably 1.0 to 10% by weight.

The crosslinking agent is preferably added to the gel sheet for cosmetic packs at a concentration of 0.10 to 5.0% by weight.

The pH adjuster is added so that the pH of the mixed solution is between 4 and 7.

In a preferred embodiment, the ingredients are blended in the following amounts relative to the total amount of ingredients constituting the gel sheet for a cosmetic pack:
Oil: preferably 2 to 10% by mass
Nonionic surfactants with an HLB value of 6 or less: preferably 0.50 to 5.0% by mass
Nonionic surfactants with an HLB value of 10 or more: preferably 0.50 to 5.0% by mass
Polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt thereof: preferably 0.50 to 35% by mass
Thickener: preferably 0.050 to 3.0% by mass
Wetting agent: preferably 1.0 to 50% by mass
Exuding agent: preferably 0.10 to 20% by mass, more preferably 1.0 to 12% by mass, and even more preferably 1 to 10% by mass
Crosslinking agent: preferably 0.10 to 5.0% by mass, more preferably 0.50 to 2.0% by mass
pH adjuster: preferably 0.10 to 10% by mass
Water: preferably 45 to 97% by mass, more preferably 50 to 95% by mass

The hydrogel can be molded into a desired shape, such as a sheet, by pouring a gel composition containing the components that make up the gel sheet for a cosmetic pack into a container of the desired shape, such as a container with a bottom and a substantially rectangular cross section, and then crosslinking and/or hardening the composition. The shape of the hydrogel sheet can be any shape suited to the purpose, including, but not limited to, a substantially rectangular or circular shape.

When a gel sheet for a cosmetic pack includes an intermediate substrate, the manufacturing process for the gel sheet for a cosmetic pack is not particularly limited and can be modified depending on the hydrogel composition, the material and thickness of the intermediate substrate, etc. For example, a method of holding the intermediate substrate in the air while applying a certain amount of tension to it, holding the upper and lower sides of the intermediate substrate in the air, pouring a gel composition containing the various components onto the upper and lower sides of the intermediate substrate, and crosslinking and/or curing the mixture to form a sheet; a method of making two gel sheets with smooth surfaces and then sandwiching the intermediate substrate, which is being held under a certain amount of tension, between the gel sheets to form a composite; or a method of making a gel sheet with a smooth surface, placing the intermediate substrate on top of the gel sheet while applying a certain amount of tension, and pouring a gel composition containing the various components onto the intermediate substrate, and crosslinking and/or curing the mixture; etc. can be appropriately employed.

This configuration makes it possible to more effectively disperse the oil, stabilize the emulsion, and control the average diameter of the oil on the surface of the gel sheet for cosmetic packs to 5 μm or less, thereby producing gel sheets for cosmetic packs in which the oil droplet size of the oil on the surface of the gel sheet has an average diameter of 5 μm or less.

Examples and comparative examples of the present invention will be described below, but the present invention is not limited to these.
1. Production of gel sheets
Example 1
An emulsion was prepared by adding water containing a nonionic surfactant with an HLB value of 10 or greater to an oil solution containing a nonionic surfactant with an HLB value of 6 or less, with the composition (mass %) shown in Table 1, and stirring at 9,000 rpm with a homogenizer for 5 minutes. A thickener, a wetting agent, and an exuding agent were added to a polymer of a polymerizable unsaturated monomer having an anionic functional group or its salt, and the mixture was thoroughly kneaded until uniform. The emulsion, crosslinker, preservative, and water were added to this mixture and thoroughly dispersed to form a slurry. A pH adjuster was added to this slurry to make a total of 100 parts by mass, and the mixture was thoroughly kneaded and stirred.

Next, a nylon knit fabric (tricot half) with a basis weight of 17 g/ ^m2 was sandwiched between two 38 μm thick PET films (polyethylene terephthalate film) and 100 μm thick PET films as an intermediate substrate, and an appropriate amount of the composition was immediately poured into the center of the film after mixing to achieve an overall thickness of 1 mm, forming a sheet. The mixture was left as is for 24 hours, yielding a 1 mm thick gel sheet. This gel sheet was cut into the shape of a face and used as a sample for evaluation.

(Examples 2 to 10)
As shown in Tables 1 to 3, gel sheet samples of Examples 2 to 10 were produced in the same manner as in Example 1, except that the compositions for forming the gel sheets were changed.

(Comparative Example 1)
Unlike Examples 1 to 10, an emulsion was not prepared. Instead, a thickener, a wetting agent, a surfactant, and an oil were added to a polymer of a polymerizable unsaturated monomer having an anionic functional group or its salt, and then an exuding agent and water were added and thoroughly kneaded until uniform. A crosslinking agent, a preservative, and water were added to this mixture and thoroughly dispersed to form a slurry. A pH adjuster was added to this slurry to make a total of 100 parts by mass, and the mixture was thoroughly kneaded and stirred.

Gel sheet samples were then prepared in the same manner as in Example 1.

(Comparative Examples 2 to 3)
As shown in Table 1, gel sheet samples of Comparative Examples 2 and 3 were produced in the same manner as in Comparative Example 1, except that the composition for forming the gel sheet was changed.

(Comparative Examples 4 to 11)
As shown in Tables 2 and 3, gel sheet samples of Comparative Examples 4 to 11 were produced in the same manner as in Example 1, except that the compositions for forming the gel sheets were changed.

2. Measurement Method and Evaluation Criteria (1) Measurement Method of HLB Value The HLB value was calculated by the Atlas method according to the following formula (1): The saponification value and neutralization value in formula (1) were determined according to the method published in the 2003 edition of the Standard Methods for the Analysis of Fats, Oils and Related Materials (established by the Japan Oil Chemists' Society), compiled by the Japan Oil Chemists' Society.

HLB=20(1-S/A)...(1)
S: Saponification value of ester, A: Neutralization value of fatty acid The saponification value is the number of milligrams of potassium hydroxide consumed when 1 g of fatty acid ester of polyhydric alcohol is hydrolyzed with potassium hydroxide, and the neutralization value is the number of milligrams of potassium hydroxide required to neutralize 1 g of constituent fatty acid of fatty acid ester of polyhydric alcohol.

(2) Method for measuring the average diameter of oil droplets on the gel surface The average diameter of oil droplets was defined as the average value of the diameters of 100 oil droplets observed in image observation mode using a Keyence VK-X1000 shape analysis laser microscope with a 20x or 50x objective lens.

(3) Emulsion Stability The emulsions prepared in each of the Examples and Comparative Examples were left to stand for 24 hours and visually observed. If the emulsion did not separate after standing, it was rated as PASS, and if the emulsion separated after standing, it was rated as FAIL.

(4) Slurry Stability The slurries prepared in each of the Examples and Comparative Examples were left to stand for 24 hours and visually observed. If the oil in the slurry did not separate, it was judged as PASS, and if the oil in the slurry separated, it was judged as FAIL.

(5) Durability Gel packs cut into the shape of a face were worn on the faces of 10 female subjects for 20 minutes, and the condition of the skin 2 hours after the gel pack was removed was evaluated as follows in terms of whether or not the moisturizing effect was felt to be lasting.
A: The skin remains moisturized for a very long time.
B: Skin moisture is maintained.
C: Skin does not stay moisturized for long.
D: Skin does not stay moisturized.

3. Results The surfactants used in the preparation of the gel sheet samples of the Examples and Comparative Examples and their HLB values are shown in Table 4.

In the sample of Example 1, both the emulsion and the slurry were stable, and the average diameter of the oil droplets on the gel surface was 3.8 μm. Skin moisturization was very sustained.

In the sample of Example 2, the humectants were 1,3-BG and DPG, and the type and ratio of humectants were changed, but the emulsion and slurry were stable, the average diameter of the oil droplets on the gel surface was 2.1 μm, and skin moisture was maintained for a long time.

In the sample of Example 3, the oil was jojoba oil, but the emulsion and slurry were stable, the average diameter of the oil droplets on the gel surface was 4.2 μm, and skin moisture was sustained.

In the samples of Examples 4 to 7, even when surfactants with different HLB values were used or the type and combination of oils were changed, the emulsions and slurries remained stable, the average diameter of the oil droplets on the gel surface was 5 μm or less, and skin moisturization was sustained for a long time.

In the samples of Examples 8 to 10, even when different types of nonionic surfactants were used, such as those with an HLB value of 6 or less and those with an HLB value of 10 or more, the emulsion and slurry were stable, the average diameter of the oil droplets on the gel surface was 5 μm or less, and skin moisturization was very sustained.

In the sample of Comparative Example 1, the slurry was unstable and the oil separated. The average diameter of the oil droplets on the gel surface was larger than 5 μm, and moisture retention was not sustained.

In the samples of Comparative Examples 2 and 3, the wetting agents were 1,3-BG and DPG, and the type and ratio of wetting agents were changed. However, when a polymer of a polymerizable unsaturated monomer with an anionic functional group or its salt, a thickener, a wetting agent, a surfactant, and an oil were kneaded together without preparing an emulsion, the stability of the slurry was poor and the oil separated. The average diameter of the oil droplets on the gel surface was larger than 5 μm, and moisture retention was not sustained.

In Comparative Examples 4 to 6, even when an emulsion was prepared, if only one type of nonionic surfactant was used, the emulsion and slurry were unstable and the oil separated. The average diameter of the oil droplets on the gel surface was larger than 5 μm, and moisturizing properties were not sustained.

In Comparative Example 7, when a nonionic surfactant with an HLB value of greater than 6 but less than 10 and a nonionic surfactant with an HLB value of 6 or less were used, the emulsion and slurry stability was poor and the oil separated. The average diameter of the oil droplets on the gel surface was greater than 5 μm, and moisturizing was not sustained.

In Comparative Example 8, when a nonionic surfactant with an HLB value of greater than 6 but less than 10 and a nonionic surfactant with an HLB value of 10 or greater were used, the emulsion and slurry stability was poor and the oil separated. The average diameter of the oil droplets on the gel surface was greater than 5 μm, and moisturizing was not sustained.

In Comparative Examples 9 to 11, when only two nonionic surfactants with an HLB value of 10 or higher or only two nonionic surfactants with an HLB value of 6 or lower were used, the emulsion and slurry stability was poor and the oil separated. The average diameter of the oil droplets on the gel surface was larger than 5 μm, and moisturizing was not sustained. Furthermore, because the compositions of Comparative Examples 10 and 11 did not contain an exuding agent, the oil-containing solution could not effectively exude onto the gel surface, making it difficult for the oil to be delivered to the skin and resulting in poor moisturizing.

Furthermore, for the two types of nonionic surfactants used in producing the gel sheets of Examples 1, 4, 7-10 and Comparative Examples 7-11, the intersection of the HLB value of the nonionic surfactant with the lower HLB value on the vertical axis and the HLB value of the nonionic surfactant with the higher HLB value on the horizontal axis was plotted. As shown in Figure 5, it was shown that the emulsifier was stable when the two types of nonionic surfactants were within the range enclosed by the square (the range in which the HLB value of one nonionic surfactant was 6 or less and the HLB value of the other nonionic surfactant was 10 or more).

Claims (8)

A gel sheet for a cosmetic pack, comprising a synthetic polymer having a network structure, an oil, an exuding agent, a humectant, a nonionic surfactant having an HLB value of 6 or less, a nonionic surfactant having an HLB value of 10 or more, and water,
The exuding agent contains a nonionic water-soluble polymer and/or an electrolyte,
A gel sheet for a cosmetic pack, characterized in that the average diameter of the oil on the surface of the gel sheet is 5 μm or less. The gel sheet for cosmetic packs according to claim 1, wherein the oil contains one or more selected from the group consisting of hydrocarbons, waxes, and oils and fats. The gel sheet for cosmetic packs according to claim 1, wherein the exudative agent is contained in the gel sheet for cosmetic packs at 0.1 to 20% by mass. The gel sheet for a cosmetic pack according to claim 1, wherein the exudative agent contains a nonionic water-soluble polymer. The gel sheet for cosmetic packs according to claim 1, wherein the synthetic polymer having a network structure is a polymer of a polymerizable unsaturated monomer having an anionic functional group or a crosslinked product of a salt of such a polymer and a crosslinking agent. 6. The gel sheet for a cosmetic pack according to claim 1, wherein both the nonionic surfactant with an HLB value of 6 or less and the nonionic surfactant with an HLB value of 10 or more are polyglycerol fatty acid esters. 6. The gel sheet for a cosmetic pack according to any one of claims 1 to 5, comprising 0.5% by mass or more of a nonionic surfactant having an HLB value of 6 or less and 0.5% by mass or more of a nonionic surfactant having an HLB value of 10 or more . 6. A method for producing a gel sheet for a cosmetic pack according to any one of claims 1 to 5, comprising: a step of mixing an oil solution to which a nonionic surfactant having an HLB value of 6 or less has been added with water to which a nonionic surfactant having an HLB value of 10 or more has been added to prepare an emulsion; and a step of mixing a polymer of a polymerizable unsaturated monomer having an anionic functional group or a salt of such a polymer, an exuding agent, a wetting agent, a crosslinking agent, water, and the emulsion to form a gel composition having a network structure.