Particle-containing hydrogel

Abstract

The present invention addresses the problem of providing a hydrogel in which a large amount of volatile components can be stably dispersed and which has superior ability in releasing volatile components in a sustained manner.　Provided is a hydrogel containing porous resin particles and volatile components. The porous resin particles have a pore diameter of 5-30 nm and an oil absorption of 50-700 ml / 100 g. The mass ratio of the volatile components (A) to the porous resin particles (B) contained in the hydrogel is (A):(B)=1:1 to 1:4.

Description

[Technical Field]

[0001] The present invention relates to hydrogels. [Background technology]

[0002] Hydrogels are polymers with high affinity for water that swell in aqueous solvents. Hydrogels have various properties depending on their application, such as water absorption, swelling, moisture retention, adhesiveness, and electrical conductivity. These properties are utilized in a wide range of fields, including civil engineering, agriculture, food, medicine, cosmetics, and electricity.

[0003] For example, Patent Document 1 discloses a hydrogel that contains a polymer matrix and water and has a specific network structure.

[0004] Furthermore, while flavorings are sometimes used as additives in hydrogels, the use of menthol poses the problem that, because menthol is crystalline at room temperature, it is difficult to dissolve in the blend liquid used to prepare the hydrogel, and adding a large amount of menthol causes the blend liquid and the hydrogel prepared from the blend liquid to become cloudy. Patent Document 2 discloses a hydrogel containing 0.001 to 1% by mass of l-menthol, but adding more than 1% by mass of l-menthol causes the hydrogel to become cloudy, making it difficult to prepare a hydrogel with a high l-menthol content. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-150458 [Patent Document 2] Japanese Patent Publication No. 2021-147543 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a hydrogel that can stably disperse a large amount of a volatile component and has excellent sustained release properties for the volatile component. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors conducted extensive research and discovered that by encapsulating volatile components in porous resin particles and dispersing them in a hydrogel, it is possible to stably disperse a large amount of volatile components in the hydrogel and also achieve excellent sustained release properties for the volatile components.

[0008] The present invention has been completed based on these findings and includes the following broad aspects. [Section 1] A hydrogel comprising porous resin particles and a volatile component, The porous resin particles have a pore diameter of 5 to 30 nm and an oil absorption of 50 to 700 ml / 100 g, The mass ratio of the volatile component (A) to the porous resin particles (B) contained in the hydrogel is (A):(B) = 1:1 to 1:4 Hydrogel. [Section 2] Item 2. The hydrogel according to Item 1, wherein the porous resin particles are made of a monofunctional (meth)acrylic acid ester and a crosslinkable monomer. [Section 3] Item 3. The hydrogel according to Item 1 or 2, wherein the content of the volatile component is 0.5 to 5% by mass relative to 100% by mass of the hydrogel. [Section 4] 4. The hydrogel according to any one of items 1 to 3, wherein the volatile component is at least one selected from the group consisting of fragrances, spices, and essential oils. [Section 5] Item 5. The hydrogel according to any one of Items 1 to 4, comprising a polymer matrix, water, and a wetting agent. [Section 6] Item 6. The hydrogel according to Item 5, wherein the polymer matrix is ​​made of a copolymer of a monofunctional monomer having one ethylenically unsaturated group and a crosslinkable monomer. [Section 7] Item 7. The hydrogel according to Item 6, wherein the content of the structural unit derived from the monofunctional monomer is 10 to 40% by mass relative to 100% by mass of the hydrogel. [Section 8] Item 6 or 7, wherein the monofunctional monomer is at least one selected from the group consisting of (meth)acrylamide, (meth)acrylic acid, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, and tert-butylacrylamidosulfonic acid. [Section 9] Item 9. The hydrogel according to any one of Items 5 to 8, wherein the content of the humectant is 20 to 70% by mass relative to 100% by mass of the hydrogel. [Section 10] Item 10. The hydrogel according to any one of Items 1 to 9, which is used as a biological electrode in a monitoring device or a device for performing treatment using electrical stimulation, a return electrode for an electrosurgical instrument, an adhesive tape, or a wound dressing. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hydrogel that can stably disperse a large amount of a volatile component and has excellent sustained release properties for the volatile component. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1 is a schematic plan view of an embodiment of a gel sheet. [Figure 1B] 1B is a schematic cross-sectional view of the gel sheet of FIG. 1A taken along line 1B-1B. DETAILED DESCRIPTION OF THE INVENTION

[0011] As used herein, the singular forms (a, an, the, etc.) are intended to include both the singular and the plural unless otherwise expressly stated herein or clearly contradicted by context. 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 "~" means a numerical range that includes the numbers before and after "~" as the upper and lower limits.

[0012] As used herein, "(meth)acryl" refers to acryl, methacryl, or both. Thus, (meth)acrylamide and / or N,N-dimethyl(meth)acrylamide refers to (1) acrylamide, methacrylamide, or both, (2) N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, or both, or (3) both (1) and (2).

[0013] <Hydrogel> The hydrogel of the present invention is a hydrogel comprising porous resin particles and a volatile component, wherein the porous resin particles have a pore diameter of 5 to 30 nm and an oil absorption capacity of 50 to 700 ml / 100 g, and the mass ratio of (A) the volatile component to (B) the porous resin particles contained in the hydrogel is (A):(B) = 1:1 to 1:4.

[0014] In the hydrogel of the present invention, the porous resin particles and the volatile component are preferably contained in the hydrogel as volatile component-containing particles in which the volatile component is supported in the porous resin particles.

[0015] (Porous resin particles) The porous resin particles are not particularly limited as long as they have a porous structure, but are preferably water-insoluble. The water-insoluble nature of resin particles refers to the nature of the resin particles themselves being water-insoluble, as well as the nature of water-soluble acrylic resins, alginic acid resins, or amide resins being crosslinked to become water-insoluble. Here, "water-insoluble" refers to the nature of the particles not being dissolved, but being suspended and / or dispersed when added to water, at the visual level.

[0016] Examples of the porous resin particles include acrylic resins, alginic acid resins, amide resins, etc. Among these, porous resin particles made of acrylic resins are preferred.

[0017] Porous resin particles made of acrylic resin include porous resin particles made of a polymer of a monomer mixture, and the monomer mixture includes, as monomers, a monofunctional (meth)acrylic acid ester and a crosslinkable monomer.

[0018] Examples of the monofunctional (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, glycidyl (meth)acrylate, methoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, (meth) Examples of the monofunctional (meth)acrylic acid ester include butoxytriethylene glycol acrylate, methoxydipropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, N-vinyl-2-pyrrolidone (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and 2-hydroxy-3-phenyloxypropyl (meth)acrylate. These monofunctional (meth)acrylic acid esters may be used alone or in combination of two or more. The monofunctional (meth)acrylic acid ester used in the present invention is preferably a C1 to C4 (carbon number 1 to 4) alkyl ester of (meth)acrylic acid, and particularly preferably methyl methacrylate.

[0019] The content of the monofunctional (meth)acrylic acid ester in the monomer mixture is in the range of 1 to 50% by mass, preferably in the range of 10 to 50% by mass. When the content of the monofunctional (meth)acrylic acid ester in the monomer mixture is in the range of 1 to 50% by mass, the crosslinkable monomer can be contained in the monomer mixture in a sufficient amount, thereby imparting sufficient porosity to the porous resin particles, thereby increasing the specific surface area and reducing the bulk density of the porous resin particles.

[0020] As the crosslinkable monomer, a known crosslinkable monomer having two or more ethylenically unsaturated groups can be used.

[0021] Examples of the crosslinkable monomer include (meth)acrylic crosslinkable monomers such as ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl (meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; and vinyl crosslinkable monomers such as divinylbenzene, divinylnaphthalene, diallyl phthalate, and derivatives thereof. Among these, (meth)acrylic crosslinkable monomers are preferred, and ethylene glycol di(meth)acrylate is more preferred. These crosslinkable monomers may be used alone or in combination of two or more.

[0022] The content of the crosslinkable monomer in the monomer mixture is preferably in the range of 50 to 99% by mass, more preferably in the range of 50 to 90% by mass. When the content of the crosslinkable monomer in the monomer mixture is in the range of 50 to 99% by mass, the porous resin particles are provided with sufficient porosity, which increases the specific surface area and reduces the bulk density of the porous resin particles.

[0023] Furthermore, the monomer mixture may contain other monomers in addition to the monofunctional (meth)acrylic acid ester and the crosslinkable monomer, as long as they do not affect the specific surface area of ​​the porous resin particles of the present invention.

[0024] The pore diameter of the porous resin particles is 5 to 30 nm, preferably 10 to 20 nm. If the average pore diameter is less than 5 nm, the penetration of volatile components into the porous resin particles may be hindered. If the pore diameter is more than 30 nm, the release rate of volatile components from the porous resin particles may increase, potentially reducing the sustained release of the volatile components in the hydrogel. The pore diameter refers to the average pore diameter obtained from the nitrogen desorption isotherm using the BJH method. For example, the measurement method using the BJH method involves measuring the nitrogen desorption isotherm of the resin particles to be measured using a specific surface area / pore size distribution analyzer (Tristar II 3020, manufactured by Shimadzu Corporation), and calculating the pore diameter (average pore diameter) using the BJH method (Barrett, EP; Joyner, LG; Halenda, PP, J. Am. Chem. Soc. 73, 373 (1951)).

[0025] The oil absorption of the porous resin particles is 50 to 700 ml / 100 g, preferably 100 to 700 ml / 100 g. An oil absorption of 50 ml / 100 g or more is preferable because a large amount of volatile components can be supported in the porous resin particles. If the oil absorption exceeds 700 ml / 100 g, the porous resin particles will have many voids inside, which may make it difficult to ensure sufficient particle strength. The oil absorption can be measured based on the measurement method of JIS K 5101-13-2.

[0026] The pore volume of the porous resin particles is preferably 0.30 to 0.90 ml / g, and more preferably 0.40 to 0.70 ml / g. A pore volume of 0.30 ml / g or more is preferable because a large amount of volatile components can be supported in the porous resin particles. Furthermore, a pore volume of 0.90 ml / g or less is preferable because the particle strength of the porous resin particles does not decrease. In this specification, the pore volume refers to the pore volume per unit mass, and in the present invention, it means the pore volume obtained from the nitrogen desorption isotherm using the BJH method. As a measurement method using the BJH method, for example, the nitrogen desorption isotherm of the resin particles to be measured is measured using a specific surface area / pore distribution measuring device (Tristar II 3020, manufactured by Shimadzu Corporation), and the pore volume (cumulative pore volume) can be calculated based on the BJH method (Barrett, EP; Joyner, LG; Halenda, PP, J. Am. Chem. Soc. 73, 373 (1951)).

[0027] The specific surface area of ​​the porous resin particles is 50 to 300 m 2 / g, and 80 to 200m 2 / g. It is more preferable that the specific surface area is 50m 2 When the specific surface area is 300 m / g or more, the porous resin particles can absorb a large amount of volatile components, which is preferable. 2 / g or less is preferable because the particle strength of the porous resin particles does not decrease. In this specification, the specific surface area refers to the surface area per unit mass, and in the present invention, it refers to the specific surface area obtained by the BET method (N2). The measurement of the specific surface area by the BET method (N2) can be performed according to the BET method (nitrogen adsorption method) described in ISO 9277 1st Edition JIS Z 8830:2001. For example, the BET nitrogen adsorption isotherm of the resin particles to be measured can be measured using a specific surface area / pore distribution analyzer (Tristar II 3020, manufactured by Shimadzu Corporation), and the specific surface area can be calculated from the amount of nitrogen adsorption using the BET multipoint method.

[0028] The bulk density of the porous resin particles is preferably 0.20 to 0.70 g / ml, and more preferably 0.30 to 0.60 g / ml. A bulk density of 0.20 g / ml or more is preferable because the particle strength of the porous resin particles does not decrease. A bulk density of 0.70 g / ml or less is preferable because a large amount of volatile components can be supported in the porous resin particles. In this specification, bulk density refers to the packed apparent density measured using a powder tester PT-E model manufactured by Hosokawa Micron Corporation.

[0029] The volume-average particle diameter of the porous resin particles is preferably in the range of 0.50 to 100 μm, more preferably in the range of 1.0 to 50 μm, and particularly preferably in the range of 2.0 to 30 μm. When the diameter is within this range, the penetration of volatile components into the porous resin particles can be effectively achieved. The volume-average particle diameter is measured using a particle size distribution analyzer (Multisizer 4e (manufactured by Beckman Coulter)) by dispersing 0.1 g of resin particles in 10 ml of a 0.1% by mass aqueous solution of a nonionic surfactant. The volume-average particle diameter is calculated from the average value in the particle size distribution based on the volume of 100,000 particles.

[0030] The porous resin particles can be produced by suspension polymerizing a monomer mixture containing a monofunctional (meth)acrylic acid ester and a crosslinkable monomer in an aqueous medium in the presence of an organic solvent, and then removing the organic solvent.

[0031] The content of the porous resin particles in the hydrogel is preferably 0.50 to 10% by mass, and more preferably 1.0 to 6.0% by mass, relative to 100% by mass of the hydrogel. When the content of the porous resin particles is within the above range, it becomes possible to add a large amount of volatile components to the hydrogel without impairing the mechanical strength and flexibility of the hydrogel.

[0032] (volatile components) Examples of the volatile components include flavorings, spices, essential oils, etc., which can be used alone or in combination of two or more.

[0033] Examples of flavors and spices include citrus essential oils such as l-menthol, orange oil, lemon oil, grapefruit oil, lime oil, tangerine oil, lavender oil, mandarin oil, and pergamot oil; spice oils such as sage, rosemary, shiso, basil, ginger, and wasabi; oleoresins obtained by solvent extraction of these; aromatic plant oils such as coffee oil, roasted nut oils, and sesame oil; and natural or synthetic flavor compounds such as vanillin, maltol, linalool, graniol, citral, and limonene. From the viewpoint of effectiveness, l-menthol is preferred, and natural menthol, synthetic menthol, and menthol-containing essential oils such as peppermint oil, peppermint oil, and spearmint oil can be used alone or in combination.

[0034] Examples of essential oils include cypress essential oil, cypress essential oil, cedar essential oil, and pine essential oil.

[0035] The content of the volatile component in the hydrogel is preferably 0.50 to 5.0% by mass, more preferably 1.0 to 3.0% by mass, relative to 100% by mass of the hydrogel. A volatile component content of 0.50% by mass or more is preferable because a hydrogel with excellent sustained release properties of the volatile component can be obtained. A volatile component content of 5.0% by mass or less is preferable because the volatile component is less likely to precipitate in the hydrogel.

[0036] The volatile component can be optionally diluted with a solvent to form a solvent solution. The solvent is not particularly limited as long as it is uniformly miscible with the volatile component, but ester oil, silicone oil, hydrocarbon oil, wax, etc. are preferred. Commercially available products include Neolite 100P (manufactured by Kokyu Alcohol Kogyo Co., Ltd.) and KAK HL (manufactured by Kokyu Alcohol Kogyo Co., Ltd.).

[0037] When preparing a solvent solution containing a volatile component, it is preferable to prepare the solvent solution so that the concentration of the volatile component in the solvent solution is 20% by mass or more.

[0038] The content of the solvent in the hydrogel is preferably 0 to 5.0% by mass relative to 100% by mass of the hydrogel. By keeping the content of the solvent within the above range, a large amount of volatile components can be supported in the porous resin particles, and a hydrogel with excellent sustained release properties of the volatile components can be obtained, which is preferable.

[0039] (Method for preparing porous resin particles carrying volatile components (volatile component-containing particles)) Porous resin particles carrying a volatile component (volatile component-containing particles) can be obtained by mixing and stirring the volatile component or a solvent solution containing the volatile component with the porous resin particles. The stirring time is not particularly limited, but is generally about 0.50 to 12 hours.

[0040] In the present invention, the mass ratio ((A):(B)) of the volatile component (A) to the porous resin particles (B) in the volatile component-containing particles contained in the hydrogel is 1:1 to 1:4, and preferably 1:2 to 1:2.5. Within the above range, the volatile component can be supported in the porous particles, and a hydrogel with excellent sustained release of the volatile component can be obtained.

[0041] The hydrogel of the present invention preferably contains a polymer matrix, water, and a humectant.

[0042] (polymer matrix) The polymer matrix is ​​preferably contained in an amount of 10 to 40% by mass, more preferably 15 to 30% by mass, based on 100% by mass of the hydrogel. If the content is 10% by mass or more, the hydrogel has sufficient shape retention and is unlikely to be too soft or easily torn. If the content is 40% by mass or less, the flexibility of the hydrogel is unlikely to be impaired.

[0043] The polymer matrix is ​​not particularly limited as long as it can form a network structure and can absorb at least water to form a gel. For example, it can be formed from a copolymer of a monofunctional monomer having one ethylenically unsaturated group and a crosslinkable monomer.

[0044] (1) Monofunctional monomer The monofunctional monomer is not particularly limited as long as it has one ethylenically unsaturated group, but is preferably a water-soluble monomer. For example, the monofunctional monomer may be (meth)acrylamide, dialkyl (meth)acrylamides such as N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, alkyl (meth)acrylamides such as N-isopropyl (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide; hydroxyalkyl (meth)acrylamides such as N-hydroxyethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide; N-ethoxymethyl (meth)acrylamide, N-propoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, N-pentyl (meth)acrylamide, Examples of suitable alkoxyalkyl (meth)acrylamides include alkoxymethyl (meth)acrylamide, N-hexyloxymethyl (meth)acrylamide, N-heptoxymethyl (meth)acrylamide, N-octoxymethyl (meth)acrylamide, N-ethoxyethyl (meth)acrylamide, N-propoxyethyl (meth)acrylamide, and N-butoxyethyl (meth)acrylamide; cationic acrylamide compounds containing an amino group, such as N,N-dimethylaminopropyl (meth)acrylamide; sulfonic acid group-containing anionic monofunctional monomers or salts thereof, such as 4-acryloylmorpholine and tert-butylacrylamidosulfonic acid; diacetone (meth)acrylamide; (meth)acrylic acid or its salts; and derivatives thereof. Among these, at least one selected from the group consisting of (meth)acrylamide, N,N-dimethyl (meth)acrylamide, diacetone (meth)acrylamide, tert-butylacrylamidosulfonic acid and its salts, and (meth)acrylic acid and its salts is preferably used, but is not limited thereto. These monofunctional monomers may be used alone or in combination of two or more.

[0045] In addition to the above, the monofunctional monomer may optionally be a vinylamide-based monofunctional monomer such as N-vinylpyrrolidone, N-vinylacetamide, or N-vinylformamide; a nonionic monofunctional monomer such as allyl alcohol; a styrene-based monomer; etc. These monofunctional monomers may be used alone or in combination of two or more.

[0046] The content of the structural unit derived from the monofunctional monomer in the hydrogel is preferably in the range of 10 to 40% by mass, more preferably 15 to 35% by mass, based on 100% by mass of the hydrogel. The content of the structural unit derived from the monofunctional monomer within the above range is preferable from the viewpoints of the shapeability, adhesive strength, handleability, and flexibility of the hydrogel. A content of 10% by mass or more is unlikely to result in a decrease in shape stability due to a small amount of monofunctional monomer, and the cohesive strength and holding power of the hydrogel itself are not reduced, resulting in a hydrogel with appropriate adhesive strength. Furthermore, a content of 40% by mass or less is unlikely to result in a hydrogel with appropriate adhesive strength, and is unlikely to result in a loss of flexibility of the hydrogel.

[0047] (2) Crosslinkable monomer The crosslinkable monomer preferably has two or more polymerizable double bonds in its molecule. Examples of such crosslinkable monomers include polyfunctional (meth)acrylamides or (meth)acrylates such as N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)glycerin di(meth)acrylate, and (poly)glycerin tri(meth)acrylate, as well as tetraallyloxyethane and diallylammonium chloride. These may be used alone or in combination. The crosslinkable monomer having two or more polymerizable double bonds in its molecule may also be a polyglycerin derivative, which is a polyfunctional compound having two or more (meth)acryloyl groups or vinyl groups and a molecular weight of 400 or more, as described in Japanese Patent Publication No. 2803886.

[0048] The content of structural units derived from crosslinkable monomers in the hydrogel is preferably within the range of 0.010% by mass to 0.50% by mass, and more preferably 0.010% by mass to 0.10% by mass, relative to 100% by mass of the hydrogel. A content of structural units derived from crosslinkable monomers within the above range is preferable from the viewpoints of the shapeability, adhesive strength, handleability, and flexibility of the hydrogel. A content of 0.010% by mass or more reduces the risk of reduced shape stability due to low crosslink density, and also reduces the cohesive strength and the holding power of the hydrogel itself, resulting in a hydrogel with appropriate adhesive strength. Furthermore, there is also less risk of the gel sheet being difficult to handle, such as part of the gel material remaining on the adherend upon peeling. A content of 0.50% by mass or less reduces the risk of a hydrogel with appropriate adhesive strength and impairing the flexibility of the hydrogel.

[0049] (water) The water content of the hydrogel is not particularly limited, but is preferably 10 to 60% by mass, and more preferably 15 to 30% by mass, relative to 100% by mass of the hydrogel. If the water content is 10% by mass or more, the water content relative to the equilibrium water content of the hydrogel will not be too low, and there is little risk of deterioration (e.g., swelling) due to the hygroscopicity of the hydrogel. If the water content is 60% by mass or less, there is little risk of deterioration (e.g., shrinkage) due to drying of the hydrogel.

[0050] (wetting agent) The wetting agent is not particularly limited, and examples thereof include diols such as ethylene glycol, triethylene glycol, 1,6-hexanediol, 1,9-nonanediol, propylene glycol, and butanediol; trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol; polyhydric alcohol condensates such as polyethylene glycol, polypropylene glycol, and polyglycerin; polyhydric alcohol modified products such as polyoxyethylene glycerin; polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, and polyoxyethylene glycerin. Examples of suitable sugars include polyoxyethylene alkyl ethers such as ethylene methyl glucoside, polyoxypropylene lauryl ether, polyoxypropylene stearyl ether, polyoxypropylene isostearyl ether, and polyoxypropylene methyl glucoside; monosaccharides such as xylose, arabinose, glucose, galactose, and mannose; disaccharides such as sucrose, maltose, cellobiose, and lactose; oligosaccharides such as maltotriose; and polysaccharides such as xylan, starch, cellulose, chitin, and chitosan. Amino sugars derived from these sugars and their N-acetylated products are also applicable. Regardless of whether they are D- or L-isomers, two or more of these sugars may be used in combination.

[0051] Among humectants, it is preferable to use polyhydric alcohols that are liquid in the temperature range in which the hydrogel is used (for example, around 20°C when used indoors), and specifically, ethylene glycol, triethylene glycol, propylene glycol, polypropylene glycol, polyethylene glycol, polyglycerin, glycerin, etc. are suitable.

[0052] The content of the humectant in the hydrogel is not particularly limited, but is preferably in the range of 20 to 70% by mass, and more preferably in the range of 30 to 60% by mass, relative to 100% by mass of the hydrogel. A humectant content of 20% by mass or more provides the resulting hydrogel with moisturizing properties and inhibits water evaporation, improving the stability of the hydrogel over time. Furthermore, a humectant content of 70% by mass or less is preferred because it prevents the humectant from bleeding out from the surface of the hydrogel, thereby inhibiting a loss of adhesive strength due to bleeding out.

[0053] (electrolyte) The hydrogel may also optionally contain an electrolyte, which may impart electrical conductivity to the hydrogel.

[0054] When imparting conductivity to a hydrogel, the content of the electrolyte in the hydrogel is preferably 0.050 to 10% by mass, and more preferably 0.10 to 6.0% by mass, relative to 100% by mass of the hydrogel. An electrolyte content of 0.050% by mass or more is preferable because it reduces the impedance of the hydrogel sheet and improves conductivity. On the other hand, if the content of the electrolyte in the hydrogel is too high, it becomes difficult for the electrolyte to dissolve in the hydrogel, which may cause crystal precipitation within the gel or inhibit the dissolution of other components. Furthermore, the conductivity may plateau, and adding more electrolyte may no longer be beneficial from the perspective of imparting conductivity.

[0055] The electrolyte is not particularly limited, and examples thereof include alkali metal halides such as sodium halide (e.g., sodium chloride), lithium halide, and potassium halide; alkaline earth metal halides such as magnesium halide and calcium halide; and other metal halides. Furthermore, hypochlorite, chlorite, chlorate, perchlorate, sulfate, carbonate, nitrate, and phosphate salts of various metals are also suitable. Furthermore, inorganic salts such as ammonium salts and various complex salts are also suitable. Salts of monovalent organic carboxylic acids such as acetic acid, benzoic acid, and lactic acid; salts of polyvalent organic carboxylic acids such as tartaric acid; monovalent or divalent or higher salts of polyvalent carboxylic acids such as phthalic acid, succinic acid, adipic acid, and citric acid; metal salts of organic acids such as sulfonic acid and amino acids; and organic ammonium salts.

[0056] Furthermore, a base such as sodium hydroxide may be added to the hydrogel as appropriate for the purpose of adjusting the pH.

[0057] (additives) Furthermore, the hydrogel may optionally contain other additives, such as rust inhibitors, antifungal agents, antioxidants, dispersants, antifoaming agents, stabilizers, surfactants, colorants, etc.

[0058] (intermediate substrate) The hydrogel of the present invention may further comprise an intermediate substrate embedded in the in-plane direction. Here, the in-plane direction of the hydrogel refers to any direction within a plane perpendicular to the thickness direction of the hydrogel. The inclusion of the intermediate substrate leads to reinforcement of the hydrogel and improved shape retention when cutting. Note that a hydrogel with an intermediate substrate embedded in the in-plane direction can also be referred to interchangeably as a composite material comprising a hydrogel and an intermediate substrate embedded in the in-plane direction of the hydrogel.

[0059] The intermediate substrate is not particularly limited, and examples thereof include nonwoven fabric, woven fabric, paper, film, etc. The material of the intermediate substrate can be natural fibers such as cellulose, silk, hemp, etc., synthetic fibers such as polyester, nylon, rayon, polyethylene, polypropylene, polyurethane, etc., or a blend thereof, and optionally a binder may be used, and further, optionally colored.

[0060] The method for producing nonwoven fabrics is not particularly limited, but examples include dry method, wet method, spunbond method, meltblown method, airlaid method, chemical bond method, thermal bond method, needle punch method, and hydroentanglement method. It is preferable to adopt a manufacturing method appropriate for the basis weight, material, etc., and to avoid unevenness in the basis weight for position control of the intermediate substrate. The woven fabric is also not particularly limited, and can be selected appropriately, such as plain weave, tricot, or Russell.

[0061] The basis weight of the nonwoven fabric or woven fabric is not particularly limited as long as it can provide the desired physical properties as an intermediate substrate. For example, it is 10 to 100 g / m 2 It is preferable that the nonwoven fabric or woven fabric has a basis weight of 10 g / m 2 When the weight is 100 g / m or more, the gel sheet can be reinforced. 2 If the thickness is below this value, the intermediate substrate will not become too hard, and the conformability to the skin and electrical conductivity of the hydrogel will not be impaired.

[0062] The thickness of the intermediate substrate is appropriately set taking into consideration the fact that if it is too thick, the liquid permeability will be poor, and conversely, if it is too thin, it may not be possible to reinforce the gel sheet, as in the case where the basis weight is too small. Preferably, the thickness is within the range of 0.050 mm to 2.0 mm. Furthermore, it is more preferably 0.050 mm to 0.50 mm, and particularly preferably 0.080 mm to 0.30 mm.

[0063] The thickness of the hydrogel of the present invention is selected appropriately depending on the application, and is, for example, within the range of 0.20 mm to 2.0 mm. In a preferred embodiment, the thickness of the hydrogel of the present invention is 0.30 mm to 1.2 mm.

[0064] <Uses of hydrogel> The hydrogel of the present invention is capable of stably dispersing a large amount of volatile components and is excellent in sustained release of the volatile components.

[0065] The hydrogel of the present invention has excellent flexibility and water retention properties, and can therefore be used in a wide range of fields, including medicine, cosmetics, food, chemistry, civil engineering, agriculture, bioengineering, and sports. For example, it can be used as a bioelectrode hydrogel, a cooling gel, a cosmetic face mask, a cell culture medium, etc. Preferably, the hydrogel of the present invention can be used as a bioelectrode in a monitoring device or a device that performs treatment using electrical stimulation, a return electrode for an electrosurgical instrument, an adhesive tape, or a wound dressing.

[0066] <Hydrogel manufacturing method> The hydrogel according to an embodiment of the present invention is composed of a gel obtained by uniformly dispersing the above-mentioned materials other than water and a polymerization initiator in water, and polymerizing and crosslinking the resulting mixture by heating or irradiating with ultraviolet light, for example. The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator, and any known thermal polymerization initiator or photopolymerization initiator for polymerizing acrylic monomers can be used. The content of the polymerization initiator is not particularly limited, but is preferably 0.010% by mass or more and 1.0% by mass or less, relative to 100% by mass of the total amount of the resulting hydrogel (total amount of the above-mentioned mixture). Furthermore, when polymerization is performed by ultraviolet irradiation, the cumulative dose of ultraviolet light varies depending on the content of the polymerization initiator, and is, for example, 800 to 10,000 mJ / cm. 2 It is preferable that the range is 2000 to 10000 mJ / cm 2 In the present invention, the reaction rates of the non-crosslinkable monomer and the crosslinkable monomer can be appropriately adjusted by appropriately setting the amount of the polymerization initiator and the amount of ultraviolet irradiation.

[0067] The hydrogel of the above embodiment of the present invention can be molded into a desired shape, such as a sheet, by pouring the blended liquid into a container of a desired shape, such as a container with a bottom and a substantially rectangular cross section, and polymerizing it by heating, irradiating with ultraviolet light, or the like. The shape of the hydrogel molded into a sheet can be any shape depending on the purpose, and examples include, but are not limited to, a substantially rectangular shape, a substantially circular shape, and the like. Hereinafter, a sheet-shaped hydrogel will be referred to as a "hydrogel sheet" or simply as a "gel sheet."

[0068] The manufacturing process for a hydrogel sheet comprising an intermediate substrate is not particularly limited, and the detailed conditions vary depending on the hydrogel composition, the material, thickness, etc. of the intermediate substrate. For example, a method in which the intermediate substrate is held in the air under a certain level of tension so as to minimize deformation in the vertical direction of the intermediate substrate, a liquid blend is poured onto the upper and lower sides of the intermediate substrate, and polymerized by light irradiation or the like to form a sheet; a method in which two hydrogel sheets with smooth surfaces are prepared, and then the intermediate substrate, held under a certain level of tension, is sandwiched between these hydrogels to form a composite; or a method in which a hydrogel sheet with a smooth surface is prepared, an intermediate substrate is placed on top of the hydrogel under a certain level of tension, a monomer blend is poured onto the intermediate substrate, and further polymerized by light irradiation or the like; etc. can be appropriately employed. If such a manufacturing process is a continuous process, the intermediate substrate and / or hydrogel may be rolled, removed, and cut into appropriate sheets.

[0069] <Embodiments of Hydrogel Sheet> Fig. 1A shows a schematic plan view of one embodiment of a gel sheet, and Fig. 1B shows a cross-sectional view of the gel sheet of Fig. 1A taken along line 1B-1B. The gel sheet 1 comprises a hydrogel 2 of the present invention, and an intermediate substrate 3 is embedded along the in-plane direction of the hydrogel 2, the intermediate substrate 3 being a nonwoven fabric or a woven fabric. In this embodiment, a base film 4 is provided on one side of the gel sheet 1, and a top film 5 is provided on the back side of the side on which the base film 4 is provided; however, the base film 4 and the top film 5 may be omitted.

[0070] As the base film 4, for example, a resin film made of a resin such as polyester, polyolefin, polystyrene, or polyurethane, paper, or paper laminated with the above-mentioned resin film can be used.

[0071] The surface of the base film 4 that comes into contact with the gel sheet 1 is preferably subjected to a release treatment. Examples of the release treatment include silicone coating, and in particular, baked silicone coating that undergoes a crosslinking or curing reaction with heat or ultraviolet light is preferred. As the film to be subjected to the release treatment, biaxially stretched PET (polyethylene terephthalate) film, OPP (oriented polypropylene) film, etc. are particularly preferred.

[0072] The top film 5 can basically be made of the same material as the base film, but if the top film is to be polymerized by irradiating it with ultraviolet light or the like, it is preferable to select a film made of a material that does not block light so as not to interfere with photopolymerization. [Example]

[0073] The present invention will be explained in more detail using Production Examples and Examples, but the present invention is not limited to these Examples.

[0074] Example 1 1. Preparation of Volatile Component-containing Particles Using a stirring / mixing vessel, 1% by mass of the volatile component l-menthol was dissolved in 1% by mass of the solvent Neolite 100P (manufactured by Kokyu Alcohol Kogyo Co., Ltd.) as shown in Table 1 to obtain a solvent solution of the volatile component. The solvent solution was then mixed with a 100% ethanol solution prepared with reference to our patent no. 5812374, which had an average pore diameter of 18 nm, an oil absorption of 150 ml / 100 g, a pore volume of 0.40 ml / g, and a specific surface area of ​​80 m. 2 The mixture was gradually added to 2% by mass of particles A having parameters of 0.1g / g, bulk density of 0.40g / ml, and volume average particle diameter of 8µm, and after stirring, particles containing a volatile component were obtained.

[0075] 2. Preparation of the compound solution Using a stirring / mixing vessel, 20% by mass of acrylamide (AAM) as a monofunctional monomer, 0.040% by mass of N,N'-methylenebisacrylamide (MBAA) as a crosslinking monomer, 54.8% by mass of glycerin as a wetting agent, 18% by mass of ion-exchanged water, and 3.16% by mass of other additives including electrolytes, surfactants, dispersants, pH adjusters, preservatives, initiators, adhesives, and chelating agents were added as shown in Table 1, and the mixture was stirred until completely dissolved to obtain a monomer solution.The volatile component-containing particles prepared in step 1 were then added to the monomer solution, and the mixture was uniformly dispersed using a homomixer to obtain a blended solution.

[0076] 3. Hydrogel Fabrication Next, the obtained mixture was dropped onto a silicone-coated PET film (base film) having a thickness of 100 μm, and a nylon woven fabric and a silicone-coated PET film (top film) having a thickness of 38 μm were placed on top of the dropped mixture to uniformly spread the mixture and fix it to 0.90 mm. A metal halide lamp was used to apply an energy dose of 3000 mJ / cm to this mixture. 2 By irradiating the sheet with ultraviolet light at 1000 W / cm 2 , a hydrogel sheet having a thickness of 0.90 mm was obtained.

[0077] Examples 2 to 10 The hydrogels of Examples 2 to 10 were produced in the same manner as in Example 1, except that the mass % of each component was changed as shown in Table 1.

[0078] (Comparative Examples 1 to 4) The hydrogels of Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that the mass % of each component was changed as shown in Table 1. Note that in Comparative Examples 1, 2, and 4, the volatile components could not be stably dispersed and precipitated in the hydrogel, so the hydrogel could not be produced.

[0079] The components used in Examples 1 to 10 and Comparative Examples 1 to 4 are as follows: AAM: Acrylamide AA: Acrylic acid ·DMAA: N,N-dimethylacrylamide MBAA: N,N'-methylenebisacrylamide l-Menthol: Menthol JP COS (manufactured by Takasago International Corporation) Lavender oil: LAVENDER GEL SK F 2263 (manufactured by Inoue Fragrance Manufacturing Co., Ltd.) Citrus oil: Citrus Gel SK F 2264 (manufactured by Inoue Perfume Manufacturing Co., Ltd.) Neolite 100P: Isodecyl neopentanoate (manufactured by Kokyu Alcohol Kogyo Co., Ltd.) ·Particle A (porous resin particles): average pore diameter 18 nm, oil absorption 150 ml / 100 g, pore volume 0.40 ml / g, specific surface area 80 m 2 / g, bulk density 0.40g / ml, volume average particle size 8.0μm ·Particle B (porous resin particles): average pore diameter 13 nm, oil absorption 250 ml / 100 g, pore volume 0.70 ml / g, specific surface area 200 m 2 / g, bulk density 0.30g / ml, volume average particle size 8.0μm ·Particle C (porous resin particles): average pore diameter 18 nm, oil absorption 100 ml / 100 g, pore volume 0.40 ml / g, specific surface area 100 m 2 / g, bulk density 0.60g / ml, volume average particle size 20μm Particle D (non-porous resin particles): Volume average particle diameter 8.0 μm SB-700 (porous inorganic particles): porous silica particles, oil absorption capacity 400-700 ml / 100 g, average particle size 4.0-6.0 μm (manufactured by Miyoshi Kasei Co., Ltd.)

[0080] (Odor retention (sustained release) evaluation) After peeling the hydrogel from the PET film (base film), the odor of the gel surface was evaluated by five panelists trained in sensory testing after 10 seconds of exposure to the air, and a score was calculated. The PET film (base film) was then placed over the gel, and the same evaluation was repeated 20 times, with a score calculated each time. The average scores of the five panelists for the first, tenth, and twentieth times were calculated. The results are shown in Table 1. Score 1: Odorless Score 2: I peeled off the protective film and put my nose close to the gel surface and could smell a faint odor. Score 3: I noticed an odor when I removed the protective film. Score 4: A strong odor was detected when removing the protective film.

[0081] (result) In the hydrogels of Examples 1 to 10, a large amount of volatile components was stably dispersed, and the sustained release of the volatile components was excellent.

[0082] In the compositions of Comparative Examples 1, 2, and 4, the volatile components precipitated in the hydrogel, making it impossible to produce a hydrogel. In the hydrogel of Comparative Example 3, the odor of the volatile components rapidly decreased, resulting in poor sustained release.

[0083] [Table 1] [Explanation of symbols]

[0084] 1. Gel sheet 2...Hydrogel 3...Intermediate substrate 4...Base film 5...Top film

Claims

1. A hydrogel comprising porous resin particles, a volatile component, a polymer matrix, water, and a wetting agent, the porous resin particles have a pore diameter of 5 to 30 nm and an oil absorption of 50 to 700 ml / 100 g; the porous resin particles are composed of a monofunctional (meth)acrylic acid ester and a crosslinkable monomer, The mass ratio of the volatile component (A) to the porous resin particles (B) contained in the hydrogel is (A):(B)=1:1~1:4 Hydrogel.

2. The hydrogel according to claim 1, wherein the content of the volatile component is 0.5 to 5% by mass relative to 100% by mass of the hydrogel.

3. The hydrogel according to claim 1, wherein the volatile component is at least one selected from the group consisting of fragrances, spices, and essential oils.

4. 2. The hydrogel according to claim 1, wherein the polymer matrix comprises a copolymer of a monofunctional monomer having one ethylenically unsaturated group and a crosslinkable monomer.

5. The hydrogel according to claim 4, wherein the content of the structural unit derived from the monofunctional monomer is 10 to 40% by mass relative to 100% by mass of the hydrogel.

6. The hydrogel according to claim 4, wherein the monofunctional monomer is at least one selected from the group consisting of (meth)acrylamide, (meth)acrylic acid, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, and tert-butylacrylamidosulfonic acid.

7. 2. The hydrogel according to claim 1, wherein the content of the humectant is 20 to 70% by mass relative to 100% by mass of the hydrogel.

8. 2. The hydrogel according to claim 1, which is used as a biological electrode in a monitoring device or a device for performing treatment using electrical stimulation, a return electrode for an electrosurgical instrument, an adhesive tape, or a wound dressing.

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