JP7767032B2 - Gel Composition - Google Patents

Description

The present invention relates to a gel composition, a topical skin preparation, and a method for forming a gel composition.

Gel compositions are widely used in various fields, such as pharmaceuticals, quasi-drugs, cosmetics, fragrances, paints, adhesives, binders, packaging materials, emulsifiers, suspending agents, water retention agents, surfactants, fiber treatment agents, and paper processing agents.
Techniques relating to gel compositions include those described in Patent Documents 1 and 2 below.

Patent Document 1 describes a pack cosmetic characterized by combining a first agent, a sol of a divalent metal lactate or chloride added to an aqueous polyvinyl alcohol solution, and a second agent, a sol of an aqueous solution of alginic acid sodium, potassium, or triethanolamine salt added to borax, to form a gel film of both the first and second agents. It describes how the pack cosmetic changes very little over time even when applied to the skin for long periods of time, the peeling time can be freely adjusted, and it can constantly maintain a state of absorbing moisture, making it an extremely effective pack cosmetic in terms of the physiological functions and cosmetic effects of the skin.

Patent Document 2 describes that a polyvinyl alcohol gel molding having a structure in which a polyvinyl alcohol polymer is crosslinked with a titanium chelate compound has excellent strength.
The polyvinyl alcohol-based gel moldings of Patent Document 2 are primarily intended for use as carriers for fixing microorganisms, water-retaining materials, cold insulators, filter materials, etc., and are not intended for use in the fields of cosmetics, perfumes, toiletries, pharmaceuticals, quasi-drugs, etc., or as gel-type skin care agents.

Furthermore, as a technique relating to a composition containing polyvinyl alcohol, for example, there is a technique described in Patent Document 3 below.
Patent Document 3 describes that an aqueous composition comprising (A) a modified polyvinyl alcohol containing 0.1 to 20 mol % of carboxy groups in the molecule and (B) a water-soluble aluminum compound, in which the solid content blending ratio (A)/(B) by weight is 100/0.01 to 100/50, exhibits a large increase in viscosity with evaporation of water and has remarkably excellent initial adhesive strength.
The aqueous composition of Patent Document 3 is primarily intended for use as a paper processing adhesive, woodworking adhesive, fiber treatment agent, binder, paint, etc., which are solidified by evaporating water, and is not intended for use in the fields of cosmetics, perfumes, toiletries, pharmaceuticals, quasi-drugs, etc., or as a gel-type skin care agent.

Japanese Unexamined Patent Publication No. 55-127311 Japanese Patent Application Laid-Open No. 2020-152869 Japanese Patent Application Publication No. 11-1595

According to the investigations of the present inventors, it has become clear that gel compositions containing an anionic polymer and an aluminum salt exhibit large fluctuations in viscosity during storage, and may not exhibit desirable gel properties after storage.
The present invention relates to a gel composition that exhibits favorable gel properties even after storage, an external skin preparation, and a method for forming the gel composition.

The inventors discovered that a gel composition containing (A) an anionic polymer, (B) an aluminum salt, (C) water, and sulfate ions has a viscosity that exhibits favorable gel properties even after storage, and thus completed the present invention.

That is, the present invention relates to the following [1] to [3].
[1] A gel composition comprising the following components (A) to (C) and sulfate ions:
(A) an anionic polymer; (B) an aluminum salt; and (C) water. [2] A topical skin preparation comprising the gel composition according to [1] above.
[3] A method for forming a gel composition, comprising the step of gelling by mixing the following components (A) to (C) and sulfate ions before use:
(A) an anionized polymer (B) an aluminum salt (C) water

The present invention provides a gel composition, a topical skin preparation, and a method for forming a gel composition that exhibits favorable gel properties even after storage.

[Gel composition]
The gel composition of the present invention is a gel composition containing the following components (A) to (C) and sulfate ions.
(A) an anionic polymer (B) an aluminum salt (C) water In the present invention, "comprising component X" is considered to be synonymous with "composed of component X."
The gel composition of the present invention may also be a gel composition containing the following components (A), (B'), and (C) and sulfate ions. The aluminum ions may be aluminum ions derived from the aluminum salt (B) or from other components, but are preferably aluminum ions derived from the aluminum salt (B).
(A) Anionized polymer (B') Aluminum ions (C) Water

The gel composition of the present invention may also be a gel composition prepared by mixing components (A) to (C) and sulfate ions before use.

The gel composition of the present invention exhibits favorable gel properties, including a viscosity within a favorable range after storage, good adhesion, and reduced stickiness. Because the gel composition of the present invention has good adhesion to the skin, it is preferably applied to the skin. Therefore, the gel composition of the present invention is particularly suitable for use as a topical skin preparation. A topical skin preparation of the present invention refers to a composition applied to the skin in the fields of cosmetics, toiletries, pharmaceuticals, quasi-drugs, etc.

The reason why the gel composition of the present invention has the above-described structure and thereby exhibits the effects of the present invention is not clear, but is presumed to be as follows.
The gel composition of the present invention contains an anionized polymer as component (A), an aluminum salt as component (B), water as component (C), and sulfate ions.
Component (A), which is an anionic polymer, and component (B), which is an aluminum salt, are capable of forming a crosslinked gel due to ionic interaction.
It is known that aluminum ions form various polynuclear ions under acidic conditions. Therefore, it is believed that in gel compositions containing aluminum salts as cross-linking components, the polynucleation of aluminum ions gradually progresses during storage, changing the cross-linking points of the gel composition, resulting in a change in viscosity over time. On the other hand, it is known that the formation rate of aluminum polynuclear ions increases in the presence of sulfate ions. Therefore, it is believed that the inclusion of sulfate ions controls the formation rate of aluminum polynuclear ions, making it possible to adjust the viscosity during storage and exhibiting desirable gel properties after storage.

<Component (A): Anionic Polymer>
The gel composition of the present invention contains an anionic polymer as component (A).
Component (A) is, for example, a polymer having an anionic group such as a sulfonic acid group, a sulfate group, a carboxy group, a phosphate group, or a phosphonic acid group, preferably a polymer having at least one anionic group selected from the group consisting of a sulfonic acid group and a carboxy group, and more preferably a polymer having a carboxy group.
Examples of anionic polymers include vinyl polymers having anionic groups, such as anionic polyvinyl alcohol, carboxyvinyl polymers, and (meth)acrylic acid/(meth)acrylic acid ester copolymers; and anionic polysaccharides, such as anionic cellulose.
From the viewpoint of further suppressing stickiness and further improving adhesion, component (A) is preferably an anionized polyvinyl alcohol, more preferably a polyvinyl alcohol having at least one anionic group selected from a sulfonic acid group and a carboxy group, and even more preferably a polyvinyl alcohol having a carboxy group.
In this specification, the term "anionic group" refers to an anionic group or a group that can be ionized to become an anionic group.

Examples of polyvinyl alcohols having carboxy groups include: (1) those obtained by graft polymerization or block polymerization of polyvinyl alcohol with an unsaturated monomer having a carboxy group; (2) those obtained by copolymerizing a vinyl ester compound with an unsaturated monomer having at least one selected from a carboxy group and a carboxylic acid ester group, followed by saponification; (3) those obtained by polymerizing a vinyl ester compound using a chain transfer agent having a carboxy group, followed by saponification; and (4) those obtained by reacting polyvinyl alcohol with a carboxylating agent.

Examples of the unsaturated monomer having a carboxyl group used in the above methods (1) and (2) and the unsaturated monomer having a carboxylic acid ester group used in method (2) include ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, etc.; ethylenically unsaturated dicarboxylic acid monoesters such as maleic acid monoalkyl esters, fumaric acid monoalkyl esters, itaconic acid monoalkyl esters, etc.; ethylenically unsaturated dicarboxylic acid diesters such as maleic acid dialkyl esters, fumaric acid dialkyl esters, itaconic acid dialkyl esters, etc.; ethylenically unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, etc.; unsaturated monocarboxylic acids such as (meth)acrylic acid; unsaturated monocarboxylic acid esters such as (meth)acrylic acid alkyl esters, etc. Furthermore, salts of the above compounds may be used as the unsaturated monomer having at least one selected from the group consisting of a carboxyl group and a carboxylic acid ester group.
These compounds may be used alone or in combination of two or more.

Examples of vinyl ester compounds used in the above methods (2) and (3) include vinyl acetate, vinyl formate, vinyl propionate, vinyl versatate, vinyl pivalate, etc. Among these, vinyl acetate is preferred from the viewpoints of reactivity during synthesis and easy availability.
These compounds may be used alone or in combination of two or more.

Examples of the carboxylating agent used in the above method (4) include carboxylic acid anhydrides such as succinic anhydride, maleic anhydride, acetic anhydride, trimellitic anhydride, phthalic anhydride, pyromellitic anhydride, glutaric anhydride, hydrogenated phthalic anhydride, and naphthalenedicarboxylic anhydride.
These may be used alone or in combination of two or more.

The amount of anionic groups in the anionized polyvinyl alcohol (the proportion derived from monomers having anionic groups) is preferably 0.1 mol % or more, more preferably 0.5 mol % or more, and even more preferably 1 mol % or more, from the viewpoint of further suppressing sticky feeling and improving water retention and gel strength, and is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 3 mol % or less, from the viewpoint of further improving adhesion and improving the amount of water supplied and the moisturizing feeling when applied to the skin.
The amount of anionic groups in the anionized polyvinyl alcohol can be determined by analyzing the anionized polyvinyl alcohol before saponification using ¹ H-NMR (solvent: CDCl ₃ ).

The saponification degree of the anionized polyvinyl alcohol is, from the viewpoint of further suppressing stickiness and improving water retention and gel strength, 90 mol% or more, more preferably 95 mol% or more, and even more preferably 98 mol% or more. The upper limit of the saponification degree is not particularly limited, but is, for example, 100.0 mol% or less, preferably 99.9 mol% or less, and more preferably 99.5 mol% or less.
The degree of saponification of the anionized polyvinyl alcohol is measured in accordance with JIS K6726:1994.

The degree of polymerization of the anionized polyvinyl alcohol is preferably 100 or more, more preferably 500 or more, and even more preferably 1,000 or more, from the viewpoint of further suppressing stickiness and improving water retention and gel strength, and is preferably 200,000 or less, more preferably 10,000 or less, and even more preferably 4,000 or less, from the viewpoint of further improving adhesion and improving flexibility and elongation.
The degree of polymerization of the anionized polyvinyl alcohol can be calculated from the relative viscosity of an aqueous solution of completely saponified polyvinyl alcohol to that of water (see JIS K6726:1994).

Specific examples of anionic polyvinyl alcohol include KL-118, KL-318, KL-506, KM-118, and KM-618 manufactured by Kuraray Co., Ltd.; Gohsenx CKS50, Gohsenx T-330H, Gohsenx T-330, and Gohsenx T-350 manufactured by Mitsubishi Chemical Corporation; and AP-17, AT-17, and AF-17 manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.

Component (A) may be used alone or in combination of two or more types.

The content of component (A) in the gel composition of the present invention is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and even more preferably 8.0% by mass or more, from the viewpoint of further suppressing stickiness and improving water retention and gel strength; and is preferably 30.0% by mass or less, more preferably 25.0% by mass or less, even more preferably 20.0% by mass or less, even more preferably 15.0% by mass or less, and even more preferably 13.0% by mass or less, from the viewpoint of further improving adhesion and improving flexibility and elongation.

<Component (B): Aluminum Salt>
The gel composition of the present invention contains an aluminum salt as component (B).
The aluminum salt is preferably water-soluble, and examples thereof include salts of aluminum with an inorganic acid selected from hydrochloric acid, nitric acid, sulfuric acid, etc., or an organic acid such as acetic acid.
Specific examples of aluminum salts include aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum potassium sulfate, etc. Among these, from the viewpoints of safety, availability, price, gel properties, etc., at least one selected from aluminum chloride, aluminum sulfate, and aluminum potassium sulfate is preferred, and at least one selected from aluminum chloride and aluminum sulfate is more preferred.

Component (B) may be used alone or in combination of two or more types.

From the viewpoint of further suppressing stickiness and improving water retention and gel strength, the content of component (B) in the gel composition of the present invention is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.10% by mass or more, even more preferably 0.20% by mass or more, even more preferably 0.25% by mass or more, and even more preferably 0.28% by mass or more; from the viewpoint of further improving adhesion and improving flexibility and elongation, the content is preferably 10.0% by mass or less, more preferably 5.0% by mass or less, even more preferably 2.0% by mass or less, even more preferably 1.0% by mass or less, even more preferably 0.80% by mass or less, even more preferably 0.60% by mass or less, and even more preferably 0.50% by mass or less.

<Component (C): Water>
The gel composition of the present invention contains water as component (C).
Examples of the water component (C) include deionized water, distilled water, highly purified water, and ultrapure water.

The content of component (C) in the gel composition of the present invention is preferably the amount remaining after excluding components (A), (B), and other components described below.
The content of component (C) in the gel composition of the present invention is preferably 65.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 75.0% by mass or more, even more preferably 80.0% by mass or more, and even more preferably 85.0% by mass or more, from the viewpoint of adjusting the viscosity of the gel composition to an appropriate level and from the viewpoint of improving the stability of the gel composition and the moisturizing feeling when applied to the skin; and from the same viewpoints, it is preferably 98.99% by mass or less, more preferably 98.0% by mass or less, even more preferably 96.0% by mass or less, even more preferably 94.0% by mass or less, and even more preferably 92.0% by mass or less.

<Sulfate ion>
The gel composition of the present invention contains sulfate ions.
The sulfate ion may be an ion derived from component (B), or may be an ion derived from a sulfate salt or sulfuric acid other than component (B). Examples of sulfate salts other than component (B) include sodium sulfate, potassium sulfate, magnesium sulfate, zinc sulfate, and iron sulfate.

<Ratio of each ingredient>
In the gel composition of the present invention, the molar ratio of sulfate ions to aluminum ions (SO ₄ ²⁻ /Al ³⁺ ) is preferably 0.08 or more, more preferably 0.09 or more, even more preferably 0.10 or more, even more preferably 0.11 or more, even more preferably 0.13 or more, and even more preferably 0.15 or more, from the viewpoint of adjusting the viscosity during storage, and is preferably 1.45 or less, more preferably 0.50 or less, even more preferably 0.45 or less, even more preferably 0.35 or less, even more preferably 0.27 or less, even more preferably 0.25 or less, even more preferably 0.23 or less, and even more preferably 0.20 or less, from the viewpoint of adjusting the viscosity during storage.
Here, the aluminum ions are usually ions derived from component (B).

In the gel composition of the present invention, the mass ratio of component (C) to component (A) ((C)/(A)) is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and even more preferably 4.0 or more, from the viewpoints of further improving adhesion, improving the amount of water supplied, and improving the moisturizing feeling when applied to the skin; and from the viewpoints of suppressing stickiness and improving water retention and gel strength, it is preferably 20.0 or less, more preferably 16.0 or less, even more preferably 14.0 or less, even more preferably 12.0 or less, and even more preferably 10.0 or less.

In the gel composition of the present invention, the mass ratio of component (B) to component (A) ((B)/(A)) is preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.010 or more, even more preferably 0.020 or more, and even more preferably 0.025 or more, from the viewpoints of further suppressing stickiness and improving water retention and gel strength; and is preferably 0.500 or less, more preferably 0.200 or less, even more preferably 0.120 or less, even more preferably 0.080 or less, even more preferably 0.060 or less, even more preferably 0.050 or less, and even more preferably 0.035 or less, from the viewpoints of further improving adhesion and improving flexibility and elongation.

<Other ingredients>
The gel composition of the present invention may contain other ingredients as appropriate within the scope of not impairing the object of the present invention.
Examples of other components include components commonly used in cosmetics, perfumes, toiletries, pharmaceuticals, quasi-drugs, etc.; sulfates other than component (B), etc.
Examples of ingredients commonly used in these products include polymers other than component (A), moisturizers, whitening agents, blood circulation promoters, anti-inflammatory agents, disinfectants, UV absorbers, colorants, preservatives, antioxidants, fragrances, pH adjusters, chelating agents, water-retaining agents, medicines, and alcohols.

<pH>
The pH of the gel composition of the present invention at 25°C is preferably 2.0 or higher, more preferably 2.5 or higher, even more preferably 2.8 or higher, even more preferably 3.0 or higher, even more preferably 3.6 or higher, and even more preferably 3.8 or higher, from the viewpoint of further suppressing stickiness and improving water retention and gel strength, and is preferably 6.5 or lower, more preferably 6.0 or lower, even more preferably 5.5 or lower, and even more preferably 5.0 or lower, from the viewpoint of further improving adhesion, improving flexibility and elongation, and improving the amount of water supplied and the moisturizing feeling when applied to the skin.
The pH of the gel composition of the present invention at 25° C. can be measured specifically by the method described in the Examples.

<Storage modulus and loss modulus>
The ratio (G''/G'(tan δ)) of the loss modulus G'' (25°C, frequency: 62.8 rad/s) to the storage modulus G' (25°C, frequency: 62.8 rad/s) of the gel composition of the present invention is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more, from the viewpoint of further improving adhesion and improving flexibility and elongation, and is preferably 1.0 or less, more preferably 0.80 or less, and even more preferably 0.70 or less, from the viewpoint of further suppressing stickiness and improving water retention and gel strength.

The storage modulus G' (25°C, frequency: 62.8 rad/s) of the gel composition of the present invention is preferably 100 Pa or more, more preferably 300 Pa or more, even more preferably 500 Pa or more, even more preferably 800 Pa or more, and even more preferably 1000 Pa or more, from the viewpoint of further suppressing stickiness and improving water retention and gel strength; and is preferably 50,000 Pa or less, more preferably 40,000 Pa or less, and even more preferably 30,000 Pa or less, from the viewpoint of further improving adhesion and improving flexibility and elongation.

The ratio (G"/G'(tan δ)) of the loss modulus G" (25°C, frequency: 0.135 rad/s) to the storage modulus G' (25°C, frequency: 0.135 rad/s) of the gel composition of the present invention is preferably 0.10 or more, more preferably 0.50 or more, even more preferably 0.80 or more, and even more preferably 1.0 or more, from the viewpoints of further improving adhesion and improving flexibility and elongation; and is preferably 10.0 or less, more preferably 5.0 or less, even more preferably 3.8 or less, even more preferably 3.2 or less, even more preferably 2.6 or less, and even more preferably 2.2 or less, from the viewpoints of further suppressing stickiness and improving water retention and gel strength.

The storage modulus G' (25°C, frequency: 0.135 rad/s) of the gel composition of the present invention is preferably 1 Pa or more, more preferably 5 Pa or more, even more preferably 10 Pa or more, even more preferably 15 Pa or more, and even more preferably 20 Pa or more, from the viewpoint of further suppressing stickiness and improving water retention and gel strength; and is preferably 10,000 Pa or less, more preferably 5,000 Pa or less, even more preferably 3,000 Pa or less, and even more preferably 2,000 Pa or less, from the viewpoint of further improving adhesion and improving flexibility and elongation.

The storage modulus G' and loss modulus G'' of the gel composition of the present invention can be measured using a rheometer (jig: diameter 25 mm, made of PP, plate: parallel plate, diameter 8 mm) under conditions of temperature: 25°C, frequency: 10 ^-3 to 10 ² rad/s, strain: within the linear region, and more specifically, can be measured by the method described below.
<Storage Modulus G′ and Loss Modulus G″ of Gel Composition>
The storage modulus G' and loss modulus G'' of the gel composition are measured using a rheometer under the following conditions.
Equipment: MRC302 (manufactured by Anton Paar)
Jig: PP25 (Diameter: 24.985 mm)
Plate: Lower Measuring Plate L-PP08/CTD, D: 8 mm for CTD450/600/1000
Temperature: 25℃
Frequency: 10 ^-3 to 10 ² rad/s
Distortion: Within the linear region (e.g., 1% distortion)
Based on the measurement profile obtained under the above measurement conditions, the physical properties of the storage modulus G' (frequency: 62.8 rad/s, 0.135 rad/s) and the loss modulus G'' (frequency: 62.8 rad/s, 0.135 rad/s) are obtained.

<Viscosity>
The viscosity (25°C, shear rate 0.1 s ^-1 ) of the gel composition of the present invention is preferably 300 Pa·s or more, more preferably 500 Pa·s or more, even more preferably 600 Pa·s or more, even more preferably 900 Pa·s or more, and even more preferably 1000 Pa·s or more, from the viewpoint of further suppressing stickiness, improving water retention and gel strength, and further improving storage stability; and from the viewpoint of further improving adhesion, flexibility, and elongation, the viscosity is preferably 15000 Pa·s or less, more preferably 10000 Pa·s or less, even more preferably 5000 Pa·s or less, even more preferably 4000 Pa·s or less, even more preferably 3000 Pa·s or less, and even more preferably 2000 Pa·s or less.
The viscosity of the gel composition of the present invention can be specifically measured by the method described in the Examples, and corresponds to the initial shear viscosity in the Examples.

<Manufacturing method>
The gel composition of the present invention can be produced, for example, by dissolving component (A) in water to prepare an aqueous solution (A), dissolving component (B) in water to prepare an aqueous solution (B), and mixing the obtained aqueous solution (A), aqueous solution (B), and, if necessary, a sulfate ion source such as sulfate or sulfuric acid, using a known stirring device or the like.

[External skin preparations]
The gel composition of the present invention can be suitably used for external skin preparations, that is, the external skin preparation of the present invention contains the above-mentioned gel composition of the present invention.
The topical skin preparation of the present invention is applied to the skin, preferably to any part of the body, such as the face, trunk, limbs, etc., other than the scalp, and can be freely pulled or spread during use. It adheres well to the skin, provides the user with a pleasant cool feeling and sensation of use, is not sticky, and is easily peeled off from the skin after use.
Even when the external skin preparation of the present invention is packed in a container that is easy to carry, such as a tube or a bag, it is easy to take out and is not left behind in the container.

The topical skin preparation of the present invention is a composition applied to the skin in the fields of cosmetics, perfumes, pharmaceuticals, quasi-drugs, etc., and is preferably a gel-type skin care preparation, more preferably a skin care mask, and even more preferably a skin care facial mask.

[Method of forming gel composition]
The method for forming a gel composition of the present invention is a method for forming a gel composition, which includes a step of mixing the following components (A) to (C) and sulfate ions prior to use to gel the composition:
(A) an anionic polymer (B) an aluminum salt (C) water According to the method for forming a gel composition of the present invention, a gel composition that exhibits favorable gel properties even after storage can be obtained. The reason why the gel composition obtained by the method for forming a gel composition of the present invention exhibits the effects of the present invention is not clear, but it is thought to be the same reason why the gel composition of the present invention exhibits the effects of the present invention as described above.
The components (A) to (C) and sulfate ions in the method for forming the gel composition of the present invention, as well as the preferred embodiments, preferred compositions, and preferred uses of the resulting gel composition are the same as those of the gel composition of the present invention described above.
The method for forming a gel composition of the present invention also includes a method for using a gel composition, which includes a step of gelling by mixing component (A), component (B), component (C), and sulfate ions before use.

[Other aspects]
The gel composition of the present invention can be used, for example, in the following manner. First, the gel composition is stretched to an appropriate size and then applied to the skin, or the gel composition is applied to the skin and then stretched to an appropriate size. Next, the gel composition is left on the skin for a certain period of time, preferably 1 minute to 8 hours, more preferably 5 minutes to 1 hour. Thereafter, the gel composition is peeled off from the skin. The gel composition can be easily peeled off, thereby achieving good skin care effects. Furthermore, the gel composition may be used while massaging, either directly with the hands or with a tool such as a sponge.

Furthermore, the present invention provides a method for moisturizing skin by applying the gel composition of the present invention to the skin.

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

[Preparation of gel composition]
Example 1
(1) Preparation of Anionized Polyvinyl Alcohol (PVA) Aqueous Solution To a 2 L vessel were added 150.0 g of anionized PVA (product name: Gohsenex (registered trademark) T-330H, manufactured by Mitsubishi Chemical Corporation, degree of polymerization = 2,000, degree of saponification > 99.0 mol%, carboxylic acid modified) and 1,213.6 g of ion-exchanged water, and the mixture was stirred at 90°C for 2 hours or more to obtain an 11 mass% anionized PVA aqueous solution.

(2) Preparation of an Aqueous Aluminum Salt Solution 10.0 g of aluminum chloride (III) hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 45.2 g of ion-exchanged water were added to a 100 mL container and stirred at 50° C. for 1 hour or more to obtain a 10 mass % aqueous aluminum chloride solution.
10.0 g of aluminum sulfate octadecahydrate (manufactured by SIGMA-ALDRICH) and 75.6 g of ion-exchanged water were added to a 100 mL container and stirred at 50° C. for 1 hour or more to obtain a 6% by mass aqueous aluminum sulfate solution.
29.0 g of the resulting 10% by mass aqueous aluminum chloride solution and 10.0 g of a 6% by mass aqueous aluminum sulfate solution were mixed to obtain an aqueous aluminum chloride/aluminum sulfate solution.

(3) Preparation of Gel Composition To a 100 mL container (dedicated for a hybrid mixer), 60.0 g of an 11% by mass anionic PVA aqueous solution prepared at 25°C and 2.18 g of the aluminum chloride/aluminum sulfate aqueous solution obtained in (2) above were added, and the mixture was stirred for 10 minutes (rotation conditions: revolution 2000 rpm/rotation 800 rpm, acceleration: 400 G) using a hybrid mixer (device name: HM-500, manufactured by Keyence Corporation) to obtain a gel composition.

Example 2
(1) Preparation of anionized PVA aqueous solution 25.0 g of anionized PVA (product name: Gohsenex (registered trademark) T-330H, manufactured by Mitsubishi Chemical Corporation) and 200.6 g of ion-exchanged water were added to a 500 mL container and stirred at 90°C for 2 hours or more to obtain an 11.08 mass% anionized PVA aqueous solution.
5.0 g of sodium sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 45.0 g of ion-exchanged water were added to a 50 mL container and stirred at room temperature for 30 minutes or more to obtain a 10 mass % aqueous sodium sulfate solution.
To the resulting 11.08% by mass anionized PVA aqueous solution, 1.81 g of a 10% by mass aqueous sodium sulfate solution was added, and the mixture was stirred at 50° C. for 1 hour or more to obtain an anionized PVA/sodium sulfate aqueous solution.

(2) Preparation of Aqueous Aluminum Salt Solution A 10% by mass aqueous aluminum chloride solution was obtained in the same manner as in Example 1.

(3) Preparation of gel composition A gel composition was obtained in the same manner as in Example 1, except that in (3) Preparation of gel composition in Example 1, "60.05 g of the anionized PVA/sodium sulfate aqueous solution obtained in (1) of Example 2 and 1.88 g of a 10 mass % aluminum chloride aqueous solution" were used instead of "60.0 g of an 11 mass % anionized PVA aqueous solution and 2.18 g of an aluminum chloride/aluminum sulfate aqueous solution."

Example 3
A gel composition was obtained in the same manner as in Example 1, except that in the (3) Preparation of the gel composition of Example 1, "2.24 g of an aqueous aluminum chloride/aluminum sulfate solution obtained by mixing 29.0 g of a 10 mass % aqueous aluminum chloride solution and 12.5 g of a 6 mass % aqueous aluminum sulfate solution" was used instead of "2.18 g of an aqueous aluminum chloride/aluminum sulfate solution."

Example 4
A gel composition was obtained in the same manner as in Example 1, except that in the (3) Preparation of the gel composition in Example 1, "2.11 g of an aqueous aluminum chloride/aluminum sulfate solution prepared by mixing 29.0 g of a 10 mass % aqueous aluminum chloride solution and 7.5 g of a 6 mass % aqueous aluminum sulfate solution" was used instead of "2.18 g of an aqueous aluminum chloride/aluminum sulfate solution."

Example 5
A gel composition was obtained in the same manner as in Example 1, except that in the (3) Preparation of the gel composition of Example 1, "2.04 g of an aqueous aluminum chloride/aluminum sulfate solution obtained by mixing 29.0 g of a 10 mass % aqueous aluminum chloride solution and 5.0 g of a 6 mass % aqueous aluminum sulfate solution" was used instead of "2.18 g of an aqueous aluminum chloride/aluminum sulfate solution."

Example 6
In the (3) Preparation of the gel composition of Example 1, a gel composition was obtained in the same manner as in Example 1, except that "2.30 g of an aqueous aluminum chloride/aluminum sulfate solution prepared by mixing 29.0 g of a 10% by mass aqueous aluminum chloride solution and 15.0 g of a 6% by mass aqueous aluminum sulfate solution" was used instead of "2.18 g of an aqueous aluminum chloride/aluminum sulfate solution."

Example 7
(1) Preparation of anionized PVA aqueous solution To a 500 mL container were added 25.0 g of anionized PVA (product name: Gohsenex (registered trademark) T-330H, manufactured by Mitsubishi Chemical Corporation) and 199.0 g of ion-exchanged water, and the mixture was stirred at 90°C for 2 hours or more to obtain a 11.16 mass% anionized PVA aqueous solution.
5.0 g of sodium sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 45.0 g of ion-exchanged water were added to a 50 mL container and stirred at room temperature for 30 minutes or more to obtain a 10 mass % aqueous sodium sulfate solution.
To the resulting 11.16% by mass anionized PVA aqueous solution, 3.60 g of a 10% by mass aqueous sodium sulfate solution was added, and the mixture was stirred at 50° C. for 1 hour or more to obtain an anionized PVA/sodium sulfate aqueous solution.

(2) Preparation of Aqueous Aluminum Salt Solution A 10% by mass aqueous aluminum chloride solution was obtained in the same manner as in Example 1.

(3) Preparation of gel composition A gel composition was obtained in the same manner as in Example 1, except that in (3) Preparation of gel composition in Example 1, "60.10 g of the anionized PVA/sodium sulfate aqueous solution obtained in (1) of Example 7 and 1.88 g of a 10 mass % aluminum chloride aqueous solution" were used instead of "60.0 g of an 11 mass % anionized PVA aqueous solution and 2.18 g of an aluminum chloride/aluminum sulfate aqueous solution."

Example 8
A gel composition was obtained in the same manner as in Example 1, except that in (3) Preparation of gel composition in Example 1, "5.45 g of aqueous aluminum chloride/aluminum sulfate solution" was used instead of "2.18 g of aqueous aluminum chloride/aluminum sulfate solution."

Example 9
(1) Preparation of anionized PVA aqueous solution 25.0 g of anionized PVA (product name: Gohsenex (registered trademark) T-330H, manufactured by Mitsubishi Chemical Corporation) and 195.3 g of ion-exchanged water were placed in a 500 mL container and stirred at 90°C for 2 hours or more to obtain an 11.35 mass% anionized PVA aqueous solution.
5.0 g of sodium sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 45.0 g of ion-exchanged water were added to a 50 mL container and stirred at room temperature for 30 minutes or more to obtain a 10 mass % aqueous sodium sulfate solution.
To the resulting 11.35% by mass anionized PVA aqueous solution, 7.50 g of a 10% by mass aqueous sodium sulfate solution was added, and the mixture was stirred at 50° C. for 1 hour or more to obtain an anionized PVA/sodium sulfate aqueous solution.

(2) Preparation of Aqueous Aluminum Salt Solution A 10% by mass aqueous aluminum chloride solution was obtained in the same manner as in Example 1.

(3) Preparation of gel composition A gel composition was obtained in the same manner as in Example 1, except that in (3) Preparation of gel composition in Example 1, "60.0 g of an 11% by mass anionized PVA aqueous solution and 2.18 g of an aluminum chloride/aluminum sulfate aqueous solution" were used instead of "60.21 g of the anionized PVA/sodium sulfate aqueous solution obtained in (1) of Example 9 and 1.88 g of a 10% by mass aluminum chloride aqueous solution."

Comparative Example 1
A gel composition was obtained in the same manner as in Example 1 (3) except that in the preparation of the gel composition in Example 1, "60.0 g of an 11% by mass anionized PVA aqueous solution, 1.88 g of a 10% by mass aluminum chloride aqueous solution" was used instead of "60.0 g of an 11% by mass anionized PVA aqueous solution, 2.18 g of an aluminum chloride/aluminum sulfate aqueous solution."

[Physical property measurement and evaluation]
The gel compositions obtained in the examples and comparative examples were subjected to the following physical property measurements and evaluations. The evaluation results are shown in Table 1. The amount of each component in Table 1 is shown as % by mass.

<Molar ratio of sulfate ions to aluminum ions (SO ₄ ²⁻ /Al ³⁺ )>
The content of each component in the gel composition was calculated assuming that all sulfate ions and aluminum ions were dissociated.

<pH of gel composition>
The gel composition was filled into a 100 mL container, and the pH of the gel composition at 25°C was measured by inserting a glass electrode (manufactured by Horiba Ltd., product name: 9681S-10D) into the gel composition at 25°C.

<Viscosity of gel composition>
The shear viscosity of the gel composition was measured using a rheometer under the following conditions. The shear viscosity was measured immediately after the preparation of the gel composition (also referred to as "initial shear viscosity") and after the gel composition was stored in an environment of 50°C for one week (also referred to as "shear viscosity after one week at 50°C").
Equipment: MRC302 (manufactured by Anton Paar)
Jig: CP25-2 (Diameter: 24.978 mm)
Plate: Lower Measuring Plate L-PP08/CTD, D: 8 mm for CTD450/600/1000
Temperature: 25℃
Shear rate: 0.1 ^s

From Table 1, it can be seen that the gel compositions of the examples have viscosities higher than 50 Pa·s and lower than 5,500 Pa·s after storage at 50°C for one week, which is within the range that exhibits favorable gel properties even after storage.
In addition, when the gel compositions of the Examples were applied to the back of the hand and the back of the hand was turned over at 180° to observe the state of dripping of the gel composition, none of the gel compositions of the Examples dripped off the back of the hand. Furthermore, when the surface of the applied gel composition on the back of the hand was touched with the hand, none of the gel compositions of the Examples felt sticky.
From these results, it can be seen that the gel compositions of the examples have good adhesion to the skin even after storage, are less sticky, and exhibit favorable gel properties.
That is, it can be seen that the present invention can provide a gel composition, an external skin preparation, and a method for forming a gel composition that exhibits favorable gel properties even after storage.

Claims (8)

A gel composition comprising the following components (A) to (C) and sulfate ions:
the molar ratio of the sulfate ions to the aluminum ions contained in the gel composition (SO ₄ ²⁻ /Al ³⁺ ) is 0.13 or more and 0.27 or less;
the mass ratio of the component (B) to the component (A) ((B)/(A)) is 0.020 or more and 0.050 or less,
The component (A) contains polyvinyl alcohol having a carboxy group.
Gel composition.
(A) an anionized polymer (B) an aluminum salt (C) water 2. The gel composition according to claim 1 , wherein the degree of saponification of the polyvinyl alcohol is 90 mol % or more. 3. The gel composition according to claim 1, wherein the component (B) is water-soluble. 4. The gel composition according to claim 1, wherein the mass ratio of the component (C) to the component (A) ((C)/(A)) is 1.0 or more and 20.0 or less. The gel composition according to any one of claims 1 to 4 , wherein the content of the component (A) is 1.0% by mass or more and 30.0% by mass or less. The gel composition according to any one of claims 1 to 5 , wherein the content of the component (B) is 0.01% by mass or more and 10.0% by mass or less. An external skin preparation comprising the gel composition according to any one of claims 1 to 6 . A method for forming a gel composition, comprising the step of gelling by mixing the following components (A) to (C) and sulfate ions before use:
the molar ratio of the sulfate ions to the aluminum ions contained in the gel composition (SO ₄ ²⁻ /Al ³⁺ ) is 0.13 or more and 0.27 or less;
the mass ratio of the component (B) to the component (A) ((B)/(A)) is 0.020 or more and 0.050 or less;
The component (A) contains polyvinyl alcohol having a carboxy group.
A method for forming a gel composition.
(A) an anionized polymer (B) an aluminum salt (C) water