Hydrogel

Abstract

The present application provides a hydrogel, wherein the following components (A), (B), and (C) are contained: (A) one polyvinyl alcohol or a combination of two or more polyvinyl alcohols, the average alcoholysis degree of which is 95.0 mol% or more and less than 98.2 mol%; (B) boric acid and / or a salt thereof; and (C) a non-ionic cellulose derivative.

Description

Technical Field

[0001] This invention relates to a hydrogel. Background Technology

[0002] In China, as the number of facial mask products increases, consumers are becoming more aware of the product category and are beginning to use facial masks as an essential part of their skincare routine.

[0003] Currently, sheet masks are the mainstream product on the market. Their advantage is strong moisturizing effect, but their disadvantages include poor fit and unpleasant user experience (the liquid is sticky). Next are various cream masks (such as lotion masks and mud masks), which also suffer from insufficient moisturizing effect and poor usability (requiring rinsing after use). Therefore, consumers urgently need sheet mask products that can address the problems of commercially available products while maintaining skincare functions.

[0004] Patent Document 1 discloses a hydrogel mask formed from polyvinyl alcohol and borax. However, this hydrogel mask has shortcomings in terms of stability, especially in terms of stability at high and low temperatures.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: JP55127311A Summary of the Invention

[0008] In view of the above, the purpose of this invention is to provide a hydrogel that not only ensures stability at room temperature, but also solves the stability problems at high and low temperatures, thereby facilitating the long-term preservation of the hydrogel at room temperature, high temperature, and low temperature.

[0009] The inventors have discovered that by mixing polyvinyl alcohol with a specific average degree of hydrolysis with boric acid and / or its salts, as well as nonionic cellulose derivatives in an aqueous solution to induce a gelation reaction, the resulting hydrogel possesses a gel network structure that remains stable not only at room temperature but also at high and low temperatures. This ensures the stability of the hydrogel during long-term storage at room temperature, as well as its stability during long-term storage at high and low temperatures.

[0010] This invention provides a hydrogel containing the following components (A), (B) and (C):

[0011] (A) One type of polyvinyl alcohol or a combination of two or more types of polyvinyl alcohol, with an average degree of alcoholysis of 95.0 mol% or more and less than 98.2 mol%;

[0012] (B) Boric acid and / or its salts; and

[0013] (C) Nonionic cellulose derivatives.

[0014] In addition, the present invention also provides the use of hydrogels as topical skin agents.

[0015] Furthermore, the present invention also provides a skin care method for applying the hydrogel of the present invention to the skin.

[0016] The hydrogel according to the present invention maintains a good morphology of its gel network structure and its gel viscosity within a suitable range, regardless of whether it is stored at room temperature or at high or low temperatures for a long period of time. As a result, the hydrogel maintains good hardness and extensibility and has excellent spreadability on the skin. Attached Figure Description

[0017] Figure 1 This is a graph showing the results of rheological tests on the hydrogel. Detailed Implementation

[0018] The hydrogel of the present invention, its preparation method, and its usage method are described in detail below.

[0019] <Hydrogel>

[0020] [Ingredients (A)]

[0021] The component (A) used in this invention is one type of polyvinyl alcohol or a combination of two or more polyvinyl alcohols, with an average degree of alcoholysis of 95.0 mol% or more and less than 98.2 mol%. The polyvinyl alcohol possesses at least the [-CH2CH(OH)-] group. m Polymers of (i.e., (C2H4O)) structural units, preferably substances represented by the following general formula (1).

[0022]

[0023] In the formula, m is the degree of polymerization of the structural unit (C2H4O), and n is the degree of polymerization of the structural unit (C4H6O2). (m+n) is 250 or more, preferably 400 or more, more preferably 500 or more; and 5000 or less, preferably 4000 or less, more preferably 1000 or less. That is, (m+n) is 250 to 5000, preferably 400 to 4000, more preferably 500 to 1000.

[0024] Furthermore, the degree of hydrolysis of polyvinyl alcohol is calculated using the following formula.

[0025] Degree of alcoholysis = m / (m+n) × 100 mol%

[0026] Component (A) can be a single polyvinyl alcohol or a combination of two or more polyvinyl alcohols. From the perspective of balancing the stability of the gel network structure at both high and low temperatures, it is acceptable as long as its average degree of alcoholysis is above 95.0 mol% and below 98.2 mol%. When component (A) is a single polyvinyl alcohol, the average degree of alcoholysis of component (A) is the degree of alcoholysis of that polyvinyl alcohol. When component (A) is a combination of two or more polyvinyl alcohols (hereinafter referred to as "polyvinyl alcohol 1", "polyvinyl alcohol 2", ..., "polyvinyl alcohol n", etc.), the average degree of alcoholysis of component (A) is calculated using the following formula.

[0027] When component (A) uses two types of polyvinyl alcohol,

[0028] Average degree of alcoholysis = [(mass of polyvinyl alcohol 1 × degree of alcoholysis of polyvinyl alcohol 1) + (mass of polyvinyl alcohol 2 × degree of alcoholysis of polyvinyl alcohol 2)] / (mass of polyvinyl alcohol 1 + mass of polyvinyl alcohol 2);

[0029] When component (A) uses N types of polyvinyl alcohol (N is an integer greater than 2),

[0030] Average degree of alcoholysis = [(mass of polyvinyl alcohol 1 × degree of alcoholysis of polyvinyl alcohol 1) + (mass of polyvinyl alcohol 2 × degree of alcoholysis of polyvinyl alcohol 2) + ... (mass of polyvinyl alcohol N × degree of alcoholysis of polyvinyl alcohol N)] / (mass of polyvinyl alcohol 1 + mass of polyvinyl alcohol 2 + ... mass of polyvinyl alcohol N).

[0031] Commercially available polyvinyl alcohols include Gohsenol EG-40C (86.5–89 mol%) (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Gohsenol EG-05C (86.5–89 mol%) (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), PVA-220S (87–89 mol%) (manufactured by KURARAY Co., Ltd.), PVA-205S (86.5–89 mol%) (manufactured by KURARAY Co., Ltd.), PVA-117 (98–99 mol%) (manufactured by KURARAY Co., Ltd.), and PVA-217S (87–89 mol%) (manufactured by KURARAY Co., Ltd.).

[0032] From the viewpoint of balancing the stability of the gel network structure at both high and low temperatures, in the hydrogel of the present invention, the total content of component (A) is 3% by mass or more and 10% by mass or less, preferably 5% by mass or less, and more preferably 4% by mass or less. Based on the above viewpoints, in the hydrogel of the present invention, the total content of component (A) is 3% by mass or more and 10% by mass or less, preferably 3% by mass or more and 5% by mass or less, and more preferably 3% by mass or more and 4% by mass or less.

[0033] [Ingredient (B)]

[0034] As a component (B) used in this invention, boric acid and / or its salts can be exemplified by boric acid, as well as alkali metal borates such as sodium borate, potassium borate, and ammonium borate. From the viewpoint of convenience, sodium borate is preferred. Commercially available products include BORAX manufactured by Wako Pure Chemical Industries, Ltd.

[0035] Boric acid (B(OH)3) accepts hydroxide ions (OH) produced by water ionization in water and undergoes coordination to form B(OH)4. - The protons H produced by the ionization of water + This makes the boric acid aqueous solution exhibit weak acidity.

[0036] B(OH)3 + H2O = [B(OH)4] - +H +

[0037] Borates mainly include tetraborate (M[B4O5(OH)4], where M is sodium, potassium, or ammonium) and pentaborate (M[B5O6(OH)4], where M is sodium, potassium, or ammonium). When borates dissolve in water to form aqueous borate solutions, the borate anions present in the aqueous solution mainly include [B(OH)4]. - [B3O3(OH)4] - [B4O5(OH)4] 2- [B5O6(OH)4] - In the form of, etc.

[0038] Component (B) can be used directly or dissolved in water as an aqueous solution. Furthermore, component (B) can be used alone or in combination of two or more. From the viewpoint of the extensibility of the hydrogel, in the hydrogel of the present invention, the content of component (B), calculated as borate, is 0.5% by mass or more, preferably 0.6% by mass or more, and 1.5% by mass or less, preferably 1.0% by mass or less. Considering the above points, in the hydrogel of the present invention, the content of component (B) is 0.5% by mass or more and 1.5% by mass or less, preferably 0.6% by mass or more and 1.0% by mass or less.

[0039] When an aqueous solution of component (A) polyvinyl alcohol is mixed with an aqueous solution of component (B) boric acid and / or its salt, a gelation reaction occurs, forming a water-insoluble complex with a gel network structure. In this gel network structure, polyvinyl alcohol forms the network structure, while component (B) boric acid and / or its salt act as a structural anchor at the intersections. This gel network structure allows the hydrogel to achieve appropriate hardness and extensibility, and it exhibits good long-term stability not only at room temperature but also at both high and low temperatures. Therefore, it can maintain its shape even when adhered to the skin for extended periods.

[0040] The structural formula of the gel network structure is shown below.

[0041]

[0042] The inventors of this invention have discovered that by adjusting the average number of OH structures in component (A), the average number of OH structures in component (B), and the ratio of the average number of OH structures in component (A) to the average number of OH structures in component (B) in the aqueous solution during the gelation reaction to a specific range, the resulting water-insoluble complex with a gel network structure can exhibit excellent stability at room temperature, high temperature, and low temperature, especially excellent long-term storage stability. Therefore, the hydrogel has suitable hardness and ductility at room temperature, high temperature, and low temperature, and exhibits excellent stability.

[0043] The average number of OH structures in component (A), considering the various structural units of component (A), can be roughly calculated using the following formula:

[0044] When component (A) uses N types of polyvinyl alcohols, and these N types of polyvinyl alcohols include the structural unit (C2H4O) and other structural units,

[0045] The average number of OH structures in component (A) = [average degree of alcoholysis × (mass of polyvinyl alcohol 1 + mass of polyvinyl alcohol 2 + ... mass of polyvinyl alcohol N)] / (average degree of alcoholysis × molecular weight of structural unit (C2H4O) + ... (1 - average degree of alcoholysis) × molecular weight of other structural units).

[0046] The average number of OH structures in component (B) can be roughly calculated using the following formula, taking into account the number of anionic forms that component (B) may exist in aqueous solution:

[0047] The average number of OH structures in component (B) = (mass of component (B) / molecular weight of component (B)) × number of anionic forms × 4.

[0048] Therefore, from the viewpoint of balancing the stability of the gel network structure at both high and low temperatures, the average number of OH structures in component (A) is preferably 0.07 or more, and more preferably 0.1 or less; the average number of OH structures in component (B) is preferably 0.04 or more, and more preferably 0.07 or less; and the ratio of the average number of OH structures in component (A) to the average number of OH structures in component (B) (average number of OH structures in component (A) / average number of OH structures in component (B)) is preferably 0.5 or more, and more preferably 2.5 or less.

[0049] [Ingredient (C)]

[0050] The component (C) of this invention is a nonionic cellulose derivative, which acts as a thickener. It is mainly used to absorb water from the hydrogel to increase its viscosity or impart thixotropy, thereby ensuring the stability of the hydrogel's gel network structure, especially its stability at high and low temperatures.

[0051] Examples of nonionic cellulose derivatives include alkyl celluloses such as methylcellulose and ethylcellulose; and hydroxyalkyl celluloses such as hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylethylcellulose. Among these, methylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose are preferred from the viewpoint of hydrogel stability, particularly stability at high and low temperatures.

[0052] As non-ionic cellulose derivatives, commercially available products include hydroxyethyl cellulose (e.g., Daicel FineChem: SE-850, Dow Chemical: Cellosize HEC QP-52000-H), hydroxyethyl methyl cellulose (AkzoNobel: STRUCTURE CELL 12000M), hydroxypropyl cellulose (e.g., Nippon Soda: HPC-H, HPC-M, HPC-L), hydroxypropyl methyl cellulose (e.g., Shin-Etsu Chemical: Metalose 60SH-4000, Metalose 90SH-4000), and methyl cellulose (e.g., Shin-Etsu Chemical: Metalose SM4000), etc.

[0053] Furthermore, as a component (C) nonionic cellulose derivative, from the viewpoint of taking into account the stability of the gel network structure of the hydrogel at both high and low temperatures, a molecular weight of 50,000 to 3,000,000 is preferred.

[0054] Component (C) can be used in one or more combinations. From the viewpoint of balancing the stability of the gel network structure of the hydrogel at both high and low temperatures, its content in the total composition is 0.05% by mass or more, preferably 0.2% by mass or more; and 2% by mass or less, preferably 1.5% by mass or less, more preferably 0.8% by mass or less. Based on the above viewpoints, in the hydrogel of the present invention, the content of component (C) is 0.05% by mass or more and 2% by mass or less, preferably 0.2% by mass or more and 1.5% by mass or less, more preferably 0.2% by mass or more and 0.8% by mass or less.

[0055] Furthermore, from the viewpoint of balancing the stability of the gel network structure of the hydrogel at both high and low temperatures, the mass ratio of the total content of component (A) to the content of component (C) [total content of component (A) / content of component (C)] is 1.5 to 25, preferably 2 to 10.

[0056] [Other ingredients]

[0057] In addition, in the hydrogel of the present invention, besides the above-mentioned components, other components commonly used in cosmetics may be used without affecting the effect of the present invention, such as moisturizers, polymers, whitening agents, blood circulation promoters, anti-inflammatory agents, bactericides, ultraviolet absorbers, colorants, preservatives, antioxidants, fragrances, pH adjusters, chelating agents, etc.

[0058] Examples of water used in this invention include deionized water, distilled water, high-purity water, and ultrapure water.

[0059] In the hydrogel of the present invention, the water content is the balance (adjusted to 100% by mass) excluding the above-mentioned components (A) to (C) and other components. Furthermore, from the viewpoint of balancing the stability of the gel network structure of the hydrogel at both high and low temperatures, the water content is preferably 85-95% by mass, more preferably 86-93.5% by mass.

[0060] <Preparation methods of hydrogels>

[0061] The method for manufacturing the hydrogel of the present invention can be exemplified by the following steps: dissolving component (A), component (C) and optional other components together in water to form an aqueous solution, dissolving component (B) in water to form an aqueous solution, then adding the aqueous solution of component (B) to the aqueous solutions of components (A), (C) and optional other components, stirring, and obtaining the hydrogel.

[0062] The hydrogel of the present invention has a viscosity of 600 Pa·s or higher, preferably 840 Pa·s or higher, and 8000 Pa·s or lower, preferably 5000 Pa·s or lower, at room temperature (25°C), high temperature (40°C), and low temperature (-5°C). If the viscosity is within this range, the hydrogel has good spreadability, is easy to store and use even in summer or winter, and is easy to spread on the skin.

[0063] The hydrogel of this invention is easy to remove even when filled into portable packaging such as tubes or bags, and will not leave any residue in the packaging.

[0064] The hydrogel of this invention is applied to the skin, preferably to any part of the body other than the scalp, such as the face, body, hands, and feet. It can be stretched and extended freely during use, providing excellent skin adhesion and a cooling and moisturizing sensation without stickiness. It is also easy to peel off the skin after use.

[0065] <How to use hydrogel>

[0066] In any case, the hydrogel of the present invention can be applied to the skin as a topical skin agent to achieve skin care. Specifically, in use, the hydrogel can be first stretched to an appropriate size and then applied to the skin; or, the hydrogel can be first applied to the skin and then stretched to an appropriate size, and then left on the skin for a period of time, preferably 1 minute to 8 hours, more preferably 5 minutes to 1 hour, and easily peeled off after use, thereby obtaining a good skin care effect. In addition, massage can be combined with the use of the hydrogel. Massage can be performed directly by hand or using tools such as a sponge.

[0067] Furthermore, the present invention provides a skin moisturizing method, wherein the hydrogel of the present invention is applied to the skin to moisturize the skin.

[0068] Preferred embodiments of the present invention are further disclosed below in relation to the embodiments described above.

[0069] <1> A hydrogel comprising the following components (A), (B) and (C):

[0070] (A) One type of polyvinyl alcohol or a combination of two or more types of polyvinyl alcohol, with an average degree of alcoholysis of 95.0 mol% or more and less than 98.2 mol%;

[0071] (B) Boric acid and / or its salts; and

[0072] (C) Nonionic cellulose derivatives.

[0073] <2> As mentioned above <1> The hydrogel of the present invention, wherein the total content of component (A) is 3% by mass or more and 10% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less; furthermore, the total content of component (A) in the hydrogel of the present invention is 3% by mass or more and 10% by mass or less, preferably 3% by mass or more and 5% by mass or less, more preferably 3% by mass or more and 4% by mass or less.

[0074] <3> As mentioned above <1> or <2> The hydrogel, wherein component (B) boric acid and / or its salts are selected from one or more of boric acid, sodium borate, potassium borate, and ammonium borate.

[0075] <4> As mentioned above <1> ~ <3> In any one of the hydrogels of the present invention, the content of component (B), calculated as borate, is 0.5% by mass or more, preferably 0.6% by mass or more, and 1.5% by mass or less, preferably 1.0% by mass or less; furthermore, in the hydrogel of the present invention, the content of component (B) is 0.5% by mass or more and 1.5% by mass or less, preferably 0.6% by mass or more and 1.0% by mass or less.

[0076] <5> As mentioned above <1> ~ <4> In any one of the hydrogels, the average number of OH structures in component (A) is preferably 0.07 or more, and more preferably 0.1 or less.

[0077] <6> As mentioned above <1> ~ <5> In any one of the hydrogels, the average number of OH structures in component (B) is preferably 0.04 or more, and more preferably 0.07 or less.

[0078] <7> As mentioned above <1> ~ <6> In any one of the hydrogels, the ratio of the average number of OH structures of component (A) to the average number of OH structures of component (B) (average number of OH structures of component (A) / average number of OH structures of component (B)) is preferably 0.5 or more, and preferably 2.5 or less.

[0079] <8> As mentioned above <1> ~ <7> In any one of the hydrogels, the component (C) nonionic cellulose derivative is selected from one or more of methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylethylcellulose, preferably selected from one or more of methylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose.

[0080] <9> As mentioned above <1> ~ <8> In any one of the hydrogels, the molecular weight of component (C) nonionic cellulose derivative is 50,000 to 3,000,000.

[0081] <10> As mentioned above <1> ~ <9> In any one of the hydrogels, the content of component (C) in the total composition is 0.05% by mass or more, preferably 0.2% by mass or more; and 2% by mass or less, preferably 1.5% by mass or less, more preferably 0.8% by mass or less; furthermore, in the hydrogel of the present invention, the content of component (C) is 0.05% by mass or more and 2% by mass or less, preferably 0.2% by mass or more and 1.5% by mass or less, more preferably 0.2% by mass or more and 0.8% by mass or less.

[0082] <11> As mentioned above <1> ~ <10> In any one of the hydrogels, the mass ratio of the total content of component (A) to the content of component (C) [total content of component (A) / content of component (C)] is 1.5 to 25, preferably 2 to 10.

[0083] <12> As mentioned above <1> ~ <11> In any one of the hydrogels, the water content is the balance (adjusted to 100% by mass) excluding the components (A) to (C) and other components. Furthermore, the water content is preferably 85-95% by mass, more preferably 86-93.5% by mass.

[0084] <13> As mentioned above <1> ~ <12> In any one of the hydrogels, when the hydrogel is stored at -5°C to 40°C, a rheological test is performed on the hydrogel. The elastic modulus G' curve and the viscous modulus G” curve of the hydrogel intersect within the range of 0.1 to 100 rad / s. Specifically, when the angular velocity is 0.1 to 0.3 rad / s, the elastic modulus of the hydrogel is less than the viscous modulus of the hydrogel, and when the angular velocity is 10 to 100 rad / s, the elastic modulus of the hydrogel is greater than the viscous modulus of the hydrogel.

[0085] <14> As mentioned above <1> ~ <13> The hydrogel described in any one of the following descriptions, wherein the viscosity of the hydrogel at -5°C to 40°C is 600 Pa·s or more, preferably 840 Pa·s or more, and 8000 Pa·s or less, preferably 5000 Pa·s or less, and more preferably 600 to 8000 Pa·s.

[0086] <15> The above <1> ~ <14> The use of the hydrogel described in any one of the following statements as a topical skin agent.

[0087] <16> A skin care method, wherein the above-mentioned <1> ~ <14> The hydrogel described in any one of these applications is applied to the skin.

[0088] Example

[0089] The present invention is further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Additionally, the amounts of each component are percentages by mass.

[0090] Examples 1-15, Comparative Examples 1-4

[0091] I. Manufacturing Method

[0092] According to the composition shown in Tables 1-4, components (A), (C) and other components are suspended in deionized water at room temperature and stirred in a water bath at above 80°C until completely dissolved. After cooling to room temperature, the evaporated water content is replenished, and then an aqueous solution of component (B) is added. The resulting mixture is stirred to allow component (A) and component (B) to undergo a gelation reaction to obtain a hydrogel.

[0093] II. Calculation Method

[0094] 1. Regarding ingredient (A)

[0095] In Tables 1-4, component (A) is composed of component (A1) polyvinyl alcohol 1 and component (A2) polyvinyl alcohol 2, wherein the degree of alcoholysis of component (A1) is 98.46 mol% and the degree of alcoholysis of component (A2) is 88 mol%. In addition, as structural units of component (A) (refer to the aforementioned general formula (1)), (C2H4O) has a molecular weight of 44 and (C4H6O2) has a molecular weight of 86.

[0096] (1) The formula for calculating the average degree of alcoholysis of component (A) is as follows:

[0097] Average degree of alcoholysis = [mass of A1 × degree of alcoholysis of A1 + mass of A2 × degree of alcoholysis of A2)] / (mass of A1 + mass of A2)

[0098] In the formula, the total content of component (A) (A1+A2) is the sum of the actual content of polyvinyl alcohol in each of its components (A1) and (A2).

[0099] (2) The formula for calculating the average number of OH structures in component (A) is as follows:

[0100] The average number of OH structures in component (A) = [average degree of alcoholysis × (mass of A1 + mass of A2)] / (average degree of alcoholysis × molecular weight of structural unit (C2H4O) + (1 - average degree of alcoholysis) × molecular weight of structural unit (C4H6O2)).

[0101] 2. Regarding ingredient (B)

[0102] Since component (B) used in Tables 1-4 is borax, namely sodium tetraborate decahydrate (which can be represented as Na2B4O7·10H2O or Na2[B4O5(OH)4]·8H2O), with a molecular weight of 381.37, when it dissolves in water, the borate anions present in the aqueous solution mainly include [B(OH)4]. - [B3O3(OH)4] - [B4O5(OH)4] 2- [B5O6(OH)4] - Therefore, the average number of OH structures in component (B) is calculated as follows:

[0103] The average number of OH structures in component (B) = (mass of component (B) / molecular weight of component (B)) × 4 × 4.

[0104] III. Evaluation Methods

[0105] Each hydrogel obtained was placed in a glass bottle and stored at room temperature (25°C) for 1 day, at high temperature (40°C) for 2 months, and at low temperature (-5°C) for 2 months, respectively. After being returned to room temperature, the viscosity of each was measured. The results are presented in Tables 1 to 4 as “25°C viscosity (after 1 day)”, “40°C viscosity (after 2 months)”, and “-5°C viscosity (after 2 months)”.

[0106] The viscosity was measured under the following conditions.

[0107] Viscometer: VISCOMETER TVB-10 (manufactured by TOKI SANGYO CO.,LTD)

[0108] Rotor No.: TF

[0109] Rotor speed: 2.5 rpm

[0110] Measurement time: 1 minute

[0111] Temperature 25℃ (after 1 day): After storing the glass bottle containing hydrogel in a constant temperature bath at 25℃±1℃ for 1 day, take it out and measure it immediately.

[0112] Temperature 40℃ (after 2 months): After storing the glass bottle containing hydrogel in a constant temperature bath at 40℃±1℃ for 2 months, remove it and restore it to room temperature (25℃) for measurement.

[0113] Temperature -5℃ (after 2 months): After storing the glass bottle containing hydrogel in a constant temperature bath at -5℃±1℃ for 2 months, remove it and restore it to room temperature (25℃) for measurement.

[0114] IV. Rheological Testing

[0115] Rheological tests were performed on the hydrogels of Examples 1-15. Figure 1 As shown, the rheological test used a frequency scanning mode, with the horizontal axis representing angular velocity and the vertical axis representing G' (elastic modulus) and G" (viscous modulus). The figure shows that when the elastic modulus G' curve is higher than the viscous modulus G" curve (i.e., G' > G"), the elastic modulus is dominant, exhibiting a gel state; when the elastic modulus G' curve is lower than the viscous modulus G" curve (i.e., G' < G"), the viscous modulus is dominant, exhibiting a fluid state; and when the elastic modulus G' curve and the viscous modulus G" curve intersect (i.e., G' = G"), the viscous modulus and elastic modulus values ​​are equal, representing the sol-gel transition point.

[0116] Table 1

[0117]

[0118] *The content of component (B) is calculated by converting the amount of borax (molecular weight: 381.37) into the amount of sodium borate (molecular weight: 201.22), expressed as sodium borate.

[0119] Table 2

[0120]

[0121] *The content of component (B) is calculated by converting the amount of borax (molecular weight: 381.37) into the amount of sodium borate (molecular weight: 201.22), expressed as sodium borate.

[0122] Table 3

[0123]

[0124] *The content of component (B) is calculated by converting the amount of borax (molecular weight: 381.37) into the amount of sodium borate (molecular weight: 201.22), expressed as sodium borate.

[0125] Table 4

[0126]

[0127] *The content of component (B) is calculated by converting the amount of borax (molecular weight: 381.37) into the amount of sodium borate (molecular weight: 201.22), expressed as sodium borate.

[0128] Furthermore, the components used in Examples 1 to 15 and Comparative Examples 1 to 4 described in Tables 1 to 4 above are shown in Table 5 below.

[0129] Table 5

[0130]

[0131] As can be clearly seen from Tables 1 to 4 above, the hydrogels obtained from Examples 1 to 15 all have suitable viscosity after being stored at room temperature for 1 day, at high temperature for 2 months, and at low temperature for 2 months, taking into account the storage stability at room temperature, high temperature, and low temperature.

[0132] In contrast, although the hydrogels of Comparative Examples 1 and 2 contain component (A), the average degree of alcoholysis of component (A) is outside the specific range of the present invention (95.0 mol% or more and less than 98.2 mol%). Specifically, the average degree of alcoholysis of Comparative Example 1 is lower than the lower limit of the specific range of the present invention, so after being stored at high temperature for 2 months, the hydrogel exhibits stratification and its viscosity cannot be detected, thus its storage stability at high temperature is poor. The average degree of alcoholysis of Comparative Example 2 is higher than the upper limit of the specific range of the present invention, so after being stored at low temperature for 2 months, its viscosity becomes very high, thus its storage stability at low temperature is poor.

[0133] The hydrogels of Comparative Examples 3 and 4, which do not contain the component (C) of the present invention, exhibited water exudation after being stored at low temperature for 2 months, making it impossible to detect their viscosity. Therefore, their storage stability at low temperature was poor.

Claims

1. A hydrogel, wherein, It contains the following ingredients (A), (B) and (C): (A) A combination of one or more polyvinyl alcohols, with an average degree of alcoholysis of 95.0 mol% or more and less than 98.2 mol%; (B) Boric acid and / or its salts; and (C) Nonionic cellulose derivatives Furthermore, the ratio of the average number of OH structures in component (A) to the average number of OH structures in component (B) is 0.994 or more and 2.022 or less, and the average number of OH structures in component (B) is 0.04 or more and 0.07 or less. In the hydrogel, the total content of component (A) is less than 10% by mass, the content of component (B) is more than 0.5% by mass and less than 1.5% by mass (calculated as borate), and the content of component (C) is 0.2% to 1.5% by mass. The viscosity of the hydrogel is 600~8000 Pa•s at -5℃~40℃.

2. The hydrogel according to claim 1, wherein, In the hydrogel, the total content of component (A) is less than 5% by mass.

3. The hydrogel according to claim 1 or 2, wherein, In the hydrogel, the total content of component (A) is 3% by mass or more.

4. The hydrogel according to claim 1 or 2, wherein, In the hydrogel, the content of component (B), calculated as borate, is 0.6% by mass or more and 1.0% by mass or less.

5. The hydrogel according to claim 1 or 2, wherein, The total content of component (A) is in a mass ratio of 1.5 to 25 relative to the content of component (C).

6. The hydrogel according to claim 1 or 2, wherein, The total content of component (A) is in a mass ratio of 2 to 10 to the content of component (C).

7. The hydrogel according to claim 1 or 2, wherein, Component (B) is selected from one or more of boric acid, sodium borate, potassium borate, and ammonium borate.

8. The hydrogel according to claim 1 or 2, wherein, Component (C) is one or more nonionic cellulose derivatives selected from methylcellulose, ethylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxyethyl methylcellulose, hydroxypropylcellulose, and hydroxyethyl ethylcellulose.

9. The hydrogel according to claim 1 or 2, wherein, Component (C) is a non-ionic cellulose derivative with a molecular weight of 50,000 to 3,000,000.

10. The hydrogel according to claim 1 or 2, wherein, The water content is 85-95% by mass.

11. The hydrogel according to claim 1 or 2, wherein, When the hydrogel was stored at -5℃ to 40℃, rheological tests were performed on it. The elastic modulus G' curve and the viscous modulus G” curve of the hydrogel intersected in the range of angular velocity from 0.1 to 100 rad / s. Specifically, when the angular velocity was 0.1 to 0.3 rad / s, the elastic modulus of the hydrogel was less than the viscous modulus of the hydrogel, and when the angular velocity was 10 to 100 rad / s, the elastic modulus of the hydrogel was greater than the viscous modulus of the hydrogel.

12. Use of the hydrogel according to any one of claims 1 to 11 as a topical skin agent.

13. A skin care method, wherein, Apply the hydrogel according to any one of claims 1 to 11 to the skin.

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