Hydrogel

Abstract

The problem addressed by the present invention is to provide a hydrogel in which adhesion variability is suppressed while maintaining suitable adhesiveness to skin.　Provided are: a hydrogel including a hydrogel, and fibers dispersed within the hydrogel, wherein an intermediate substrate is not included in the hydrogel, adhesive force to a Bakelite plate is 1.0 to 10 N / 20mm, and the value of the coefficient of variation CV of adhesive force is less than 4.0; and a manufacturing method therefor.

Description

[Technical Field]

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

[0002] Hydrogels are suitably used as surgical tapes to be applied to living bodies, tapes for fixing various medical devices, pads for bioelectrodes to be applied to living bodies, electrocardiogram electrodes, industrial adhesive tapes for building materials, electronic materials, etc. These hydrogels are often embedded with intermediate substrates for the purposes of reinforcement and / or improving shape retention during cutting.

[0003] For example, Patent Document 1 discloses a gel sheet including an intermediate substrate embedded in a gel, in which the degree of waviness within the gel sheet in the intermediate substrate is set within a specific range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-97216 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional gel sheets containing intermediate substrates have sometimes had the problem of inconsistent adhesion to the skin, which can cause inconvenience such as the pad peeling off from the skin when used as a gel pad for an electrode.

[0006] The object of the present invention is to provide a hydrogel that maintains appropriate adhesion to the skin and processability and handling properties while suppressing variations in adhesion. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors conducted extensive research and discovered that by replacing the intermediate substrate with a composition that includes fibers, it is possible to suppress uneven adhesion while maintaining appropriate adhesion to the skin.

[0008] The present invention has been completed based on these findings and includes the following broad aspects. [Section 1] A hydrogel comprising a hydrogel and fibers dispersed in the hydrogel, The hydrogel does not contain an intermediate substrate, A hydrogel having an adhesive strength to a Bakelite plate of 1.0 to 10 N / 20 mm and a coefficient of variation (CV) of adhesive strength of less than 4.0. [Section 2] Item 1. The hydrogel according to Item 1, wherein the fiber includes at least dietary fiber. [Section 3] Item 3. The hydrogel according to Item 1 or 2, wherein the fibers include dietary fiber and polyolefin fiber. [Section 4] Item 4. The hydrogel according to Item 2 or 3, wherein the dietary fiber content is 0.20 to 2.0 mass % in terms of pure content. [Section 5] Item 5. The hydrogel according to any one of Items 2 to 4, wherein the dietary fiber has an average fiber diameter of 10 to 500 nm. [Section 6] Item 6. The hydrogel according to any one of Items 2 to 5, wherein the dietary fiber comprises cellulose. [Section 7] Item 4. The hydrogel according to Item 3, wherein the content of the polyolefin fiber is 0.20 to 2.0 mass % in terms of pure content. [Section 8] Item 8. The hydrogel according to any one of Items 3 to 7, wherein the polyolefin fibers have an average fiber length of 0.50 to 2.0 mm. [Section 9] Item 9. The hydrogel according to any one of items 1 to 8, having an adhesive strength to a Bakelite plate of 2.5 to 10 N / 20 mm. [Section 10] the hydrogel comprises a polymer matrix, water, and a humectant; Item 10. The hydrogel according to any one of items 1 to 9, wherein the polymer matrix is ​​a copolymer of at least one monofunctional monomer selected from the group consisting of (meth)acrylamide-based monomers and (meth)acrylic acid esters and a crosslinkable monomer. [Section 11] Item 11. The hydrogel according to any one of items 1 to 10, wherein the thickness of the hydrogel is 0.20 to 2.0 mm. [Section 12] Item 12. The hydrogel according to any one of items 1 to 11, having a storage modulus of 3,000 to 9,000 Pa. [Section 13] Item 13. A bioelectrode hydrogel used by being placed between an electrode made of a conductive material and a skin surface, the bioelectrode hydrogel comprising the hydrogel according to any one of Items 1 to 12. [Section 14] A method for producing the hydrogel according to any one of items 1 to 12, A polymerizable solution containing a monofunctional monomer, a crosslinkable monomer, fibers, water, a polymerization initiator, and a moisturizing agent, and having a crosslinkable monomer content of 0.010 to 0.050 mass %, has a peak intensity of 50 to 150 mW / cm 2 A method for producing a hydrogel, comprising the step of irradiating the hydrogel with ultraviolet light. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hydrogel that maintains appropriate adhesion to the skin and processability and handling properties while suppressing variations in adhesion. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] In this specification, (meth)acrylic means acrylic or methacrylic, and (meth)acrylate means acrylate or methacrylate.

[0012] <Hydrogel> The hydrogel of the present invention is a hydrogel containing a hydrogel and fibers dispersed in the hydrogel. The hydrogel of the present invention does not contain an intermediate substrate, and has an adhesive strength to a Bakelite plate of 1.0 to 10 N / 20 mm, and a coefficient of variation (CV) of the adhesive strength of less than 4.0.

[0013] The hydrogel of the present invention is a sheet-shaped hydrogel composition containing various hydrogel components and fibers. The components of the hydrogel composition used to form the hydrogel can be those used in known hydrogels. For example, the hydrogel composition may contain a polymer matrix, water, and a humectant. The hydrogel composition may also contain an electrolyte and one or more additives.

[0014] 1. Polymer matrix The polymer matrix is ​​preferably contained in an amount of 10 to 60% by mass, more preferably 13 to 40% by mass, and even more preferably 15 to 35% by mass, of 100% by mass of hydrogel (hereinafter, "100% by mass of hydrogel" may be alternatively referred to as 100% by mass of hydrogel composition). A content of 10% by mass or more is preferred because it increases the strength of the hydrogel and makes it easier to maintain the sheet shape. A content of 60% by mass or less is also preferred because it allows for the movement of ions within the hydrogel.

[0015] The polymer matrix can be formed from a copolymer of a monofunctional monomer having one ethylenically unsaturated group and a crosslinkable monomer.

[0016] 1-1. Monofunctional monomers The monofunctional monomer is not particularly limited as long as it has one ethylenically unsaturated group, but is preferably a water-soluble monomer, such as a (meth)acrylamide monomer or a (meth)acrylic acid ester.

[0017] Examples of the (meth)acrylamide monomer include (meth)acrylamide, N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide, N-alkyl(meth)acrylamides such as N-isopropyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide and N-propyl(meth)acrylamide, N-hydroxyalkyl(meth)acrylamides such as N-hydroxyethyl(meth)acrylamide and N-hydroxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide and N-propyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide and N-hydroxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-isopropyl ... Examples thereof include N-alkoxyalkyl(meth)acrylamides such as N-isobutoxymethyl(meth)acrylamide, N-pentoxymethyl(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; amino group-containing cationic acrylamide compounds such as dimethylaminopropyl(meth)acrylamide; sulfonic acid group-containing anionic monofunctional monomers or salts thereof such as 4-acryloylmorpholine and tert-butylacrylamidosulfonic acid; and derivatives thereof. Among these, at least one selected from the group consisting of (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, 4-acryloylmorpholine, tert-butylacrylamidosulfonic acid, and salts thereof is preferably used, but is not limited thereto.

[0018] Examples of the (meth)acrylic acid ester include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and (meth)acrylic acid esters. (Meth)acrylic acid alkyl esters such as 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-pentyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, tridecyl (meth)acrylate, and n-stearyl (meth)acrylate; alicyclic (meth)acrylic acid esters such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and 1-adamantyl (meth)acrylate. Examples of suitable (meth)acrylic acid esters include alkoxy group-containing (meth)acrylic acid esters such as 2-methoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylates such as methoxytriethylene glycol (meth)acrylate; hydroxyalkyl (meth)acrylates (in which an aryl group may be bonded to the hydroxyalkyl group via an ether bond) such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; glycerin mono(meth)acrylate; mono(meth)acrylic acid polyalkylene glycols such as polyethylene glycol mono(meth)acrylate and polyethylene glycol-polypropylene glycol copolymers; (meth)acrylic acid esters having an aromatic ring such as benzyl (meth)acrylate; and (meth)acrylic acid esters having a heterocyclic ring such as tetrahydrofurfuryl (meth)acrylate. These monofunctional monomers may be used alone or in combination of two or more.

[0019] In addition to the (meth)acrylamide-based monomers and (meth)acrylic acid esters, the monofunctional monomers that can be used optionally include (meth)acrylic acid or its salts, vinylamide-based monofunctional monomers such as vinylpyrrolidone, vinylacetamide, and vinylformamide, nonionic monofunctional monomers such as allyl alcohol, and styrene-based monomers. Each of these monofunctional monomers may be used alone, or two or more of them may be used in combination.

[0020] The content of the structural unit derived from the monofunctional monomer in the hydrogel is not particularly limited, but is preferably 8.5 to 60% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 35% by mass. A content of the structural unit derived from the monofunctional monomer within the above range is preferred from the viewpoint of the shape retention and flexibility of the hydrogel. When the content is 8.5% by mass or more, the hydrogel has sufficient shape retention and is unlikely to be too soft or prone to tearing. Furthermore, when the content is 60% by mass or less, the flexibility of the hydrogel is unlikely to be impaired, and this is preferred in that it allows ion movement within the hydrogel.

[0021] 1-2. Crosslinkable monomers 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 methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, glycerin di(meth)acrylate, and 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.

[0022] The content of structural units derived from crosslinkable monomers in the hydrogel is preferably within the range of 0.010 to 1.5% by mass, more preferably 0.010 to 0.30% by mass, and even more preferably 0.010 to 0.050% by mass. 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 concerns about 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 concern about the handling of the hydrogel being impaired, such as when part of the gel material remains on the adherend upon peeling. A content of 1.5% by mass or less reduces the risk of a loss of flexibility of the hydrogel, resulting in a hydrogel with appropriate adhesive strength.

[0023] 2.Water The water content of the hydrogel is not particularly limited, but is preferably 10 to 60% by mass, more preferably 10 to 45% by mass, and even more preferably 15 to 30% by mass. 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.

[0024] 3. Moisturizer The moisturizer 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; modified polyhydric alcohols such as polyoxyethylene glycerin; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, and polyoxyethylene methyl glucoside; and polyoxyalkylene alkyl ethers such as polyoxypropylene alkyl ethers such as polyoxypropylene lauryl ether, polyoxypropylene stearyl ether, polyoxypropylene isostearyl ether, and polyoxypropylene methyl glucoside.

[0025] Among moisturizers, it is preferable to use polyhydric alcohols that are liquid within the temperature range in which the hydrogel is used (for example, around 20°C when used indoors), and specific examples of suitable polyhydric alcohols include ethylene glycol, triethylene glycol, propylene glycol, polypropylene glycol, polyethylene glycol, polyglycerin, and glycerin.

[0026] The content of the humectant in the hydrogel is not particularly limited, but is preferably 20 to 70% by mass, and more preferably 25 to 65% by mass. 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 hydrogel surface and inhibits a decrease in adhesive strength due to bleeding out.

[0027] 4. Electrolytes The hydrogel may optionally contain an electrolyte, which may render the hydrogel electrically conductive.

[0028] When imparting conductivity to a hydrogel, the content of the electrolyte in the hydrogel is preferably 0.050 to 10% by mass, more preferably 0.10 to 6.0% by mass. An electrolyte content of 0.05% by mass or more is preferable because it reduces the impedance of the hydrogel and improves conductivity. Furthermore, while the impedance decreases as the electrolyte content increases, if the electrolyte content is too high, the impedance no longer decreases and it is wasteful in terms of cost. Therefore, from the perspective of balancing conductivity and cost, the electrolyte content is preferably 10% by mass or less.

[0029] 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.

[0030] Furthermore, a base such as sodium hydroxide may be added to the hydrogel as needed to adjust the pH.

[0031] 5. Additives Additionally, the hydrogel may optionally contain other additives, such as rust inhibitors, antifungal agents, antioxidants, antifoaming agents, stabilizers, surfactants, colorants, essential oils, and the like.

[0032] 6. Fiber The fibers contained in the hydrogel are not particularly limited as long as they can be dispersed in the hydrogel, and may be either hydrophilic or hydrophobic fibers, with hydrophilic fibers being preferred. The fibers can also be said to be dispersed in the hydrogel composition or hydrogel. It is also preferred that the fibers be uniformly dispersed in the hydrogel composition or hydrogel.

[0033] Examples of hydrophilic fibers include dietary fibers such as cellulose; artificial cellulose fibers such as rayon and acetate; and synthetic fibers such as hydrophilically treated polyolefin fibers, polyamides, and polyesters. These fibers may be used alone or in combination of two or more, but it is preferable to use a combination of two or more. Furthermore, it is preferable that the fiber contains at least dietary fiber, and it is more preferable that the fiber contains dietary fiber and polyolefin fiber.

[0034] The total fiber content is preferably 0.50 to 2.5% by mass, and more preferably 0.60 to 2.0% by mass, based on the pure content. A fiber content of 0.50% by mass or more is preferred because the hydrogel has good mechanical strength and hardness. A fiber content of 2.5% by mass or less is preferred because the hydrogel does not become too hard and has good flexibility.

[0035] Dietary Fiber The dietary fiber is not particularly limited as long as it can be added to the hydrogel. Examples of dietary fiber include cellulose, polydextrose, sodium alginate, inulin, carrageenan, hemicellulose, lignin, chitin, chitosan, pectin, etc. Commercially available products include EXILVA (manufactured by Borregaard), Helvacell AQ Plus (registered trademark), Fiberon (registered trademark), and Healthy Gum (registered trademark) (all manufactured by Sumitomo Pharma Food & Chemical Co., Ltd.). Cellulose is particularly preferred.

[0036] The cellulose is not particularly limited as long as it can be added to a hydrogel. Examples of cellulose include those derived from plant materials such as wood fiber (pulp), those in which some of the hydroxyl groups have been oxidized, and those chemically modified by etherification such as acylation or carboxymethylation, esterification, or other reactions. Cellulose can be obtained, for example, by subjecting a raw material to a suitable chemical treatment such as oxidation or etherification, followed by mechanical disintegration or other methods to form a fibrous cellulose.

[0037] The cellulose may include one or more of lignocellulose, cellulose nanofiber (CNF), cellulose nanocrystal (CNC), and microfibrillated cellulose (NFC). Lignocellulose is composed of cellulose, hemicellulose, and lignin. Cellulose nanofiber, cellulose nanocrystal, etc. are cellulose fibers contained in wood pulp, etc. that have been defibrated to the nano-size level. Microfibrillated cellulose contains cellulose microfibrils (single cellulose nanofibers), which are the basic skeletal material of plants.

[0038] The dietary fiber preferably has an average fiber diameter of 10 to 500 nm, more preferably 20 to 300 nm. An average fiber diameter of 10 nm or more is preferred because the hydrogel has good mechanical strength. Furthermore, an average fiber diameter of 500 nm or less is preferred because the interaction between the dietary fiber and the polymer matrix is ​​good, resulting in good mechanical strength. The average fiber diameter of dietary fiber can be measured by morphological observation using a scanning electron microscope, measuring the fiber diameters at any 10 or more points, and calculating the number average.

[0039] The average fiber length of the dietary fiber is not particularly limited, but is preferably 1.0 to 50 μm, more preferably 5.0 to 30 μm. An average fiber length of 1.0 μm or more is preferable because the mechanical strength of the hydrogel is improved and handling is facilitated. Furthermore, an average fiber length of 50 μm or less is preferable because the dispersibility of the dietary fiber in the hydrogel is improved. The average fiber length of the dietary fiber can be calculated by measuring the fiber length at any 10 or more points by morphological observation using a scanning electron microscope, and then calculating the number average.

[0040] The dietary fiber content is preferably 0.20 to 2.0% by mass, and more preferably 0.50 to 1.5% by mass, based on the pure content. A dietary fiber content of 0.20% by mass or more is preferred because the hydrogel has good mechanical strength and hardness. A dietary fiber content of 2.0% by mass or less is preferred because the hydrogel does not become too hard, has appropriate adhesiveness, and has good flexibility.

[0041] 6-2. Polyolefin fiber Examples of polyolefin fibers include polyethylene fibers and polypropylene fibers. Polyolefin fibers are preferably hydrophilized from the viewpoint of miscibility with hydrogels, dispersion stability, or miscibility and dispersion stability in hydrogels. The hydrophilization treatment is not particularly limited, but may be performed by applying a hydrophilizing agent such as a surfactant, or by surface modification using corona surface treatment or plus magic electricity treatment. Commercially available hydrophilized polyolefin fibers can be used, such as the SWP series (manufactured by Mitsui Chemicals, Inc.).

[0042] The polyolefin fibers preferably have an average fiber diameter of 1.0 to 60 μm, more preferably 5.0 to 30 μm. An average fiber diameter of 1.0 μm or more is preferred because the polyolefin fibers have rigidity and the hydrogel has good mechanical strength. Furthermore, an average fiber diameter of 60 μm or less is preferred because the interaction between the polyolefin fibers and the polymer matrix is ​​good, resulting in good mechanical strength. The average fiber diameter of polyolefin fibers can be measured by morphological observation using a scanning electron microscope, measuring the fiber diameters at any 10 or more points, and calculating the number average.

[0043] The polyolefin fibers preferably have an average fiber length of 0.50 to 2.0 mm, more preferably 0.90 to 1.5 mm. An average fiber length of 0.50 mm or more is preferable because the mechanical strength of the hydrogel is improved and handling is facilitated. Furthermore, a polyolefin fiber length of 2.0 mm or less is preferable because the polyolefin fibers are well dispersed in the hydrogel. The average fiber length of the polyolefin fibers can be calculated by measuring the lengths of multiple fibers (e.g., 10 or more) using an optical microscope and averaging the measured values.

[0044] The content of polyolefin fiber is preferably 0.20 to 2.0 mass% in terms of pure content, and more preferably 0.50 to 1.5 mass%. A polyolefin fiber content of 0.20 mass% or more is preferred because the mechanical strength and hardness of the hydrogel are good. A polyolefin fiber content of 2.0 mass% or less is preferred because the hydrogel is not too hard and has good flexibility.

[0045] <Hydrogel manufacturing method> The hydrogel of the present invention can be produced by a method including the following (Step 1) and (Step 2). (Step 1) A step of preparing a polymerization solution containing a monofunctional monomer, a crosslinkable monomer, fibers, water, a polymerization initiator, and a moisturizing agent. (Step 2) A step of polymerizing the polymerization solution.

[0046] (Process 1) This is a process for preparing a polymerization solution containing a monofunctional monomer, a crosslinkable monomer, fibers, water, a polymerization initiator, and a humectant. The above-mentioned materials can be used to prepare the polymerization solution. The polymerization solution is prepared by uniformly dispersing these materials.

[0047] As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator can be used, but it is preferable to use a photopolymerization initiator which shows little change in components before and after polymerization.

[0048] Examples of the photopolymerization initiator include 2-hydroxy-2-methyl-1-phenyl-propan-1-one (product name: Omnirad 1173, manufactured by IGM Resins BV), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Omnirad 184, manufactured by IGM Resins BV), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-propan-1-one (product name: Omnirad 2959, manufactured by IGM Resins BV), 2-methyl-1-[(methylthio)phenyl]-2-morpholinopropan-1-one (product name: Omnirad 907, manufactured by IGM Resins BV), and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (product name: Omnirad 369, manufactured by IGM Resins BV). The polymerization initiator may be used alone or in combination of two or more.

[0049] The amount of polymerization initiator used is preferably 0.010 to 3.0% by mass, and more preferably 0.050 to 1.0% by mass, relative to 100% by mass of the total of all monomers (monofunctional monomers and crosslinkable monomers). When the amount is 0.010% by mass or more, no unpolymerized monomers remain in the hydrogel, and when the amount is 3.0% by mass or less, there is no concern about odor and / or discoloration (yellowing) due to the remaining polymerization initiator after the polymerization reaction, which is preferable.

[0050] The preferred blending ratios of the components in the polymerization solution are as follows: Monofunctional monomer: 10 to 60% by mass, more preferably 15 to 35% by mass. Crosslinkable monomer: 0.010 to 1.5% by mass, more preferably 0.010 to 0.050% by mass. Fiber: 0.50 to 2.5 mass % as a pure content, more preferably 0.60 to 2.0 mass %. Water: 10 to 60% by mass, more preferably 15 to 30% by mass. · Moisturizer: 20 to 70% by mass, more preferably 25 to 65% by mass. Polymerization initiator: 0.010 to 3.0% by mass, more preferably 0.050 to 1.0% by mass. Electrolyte: 0.050 to 10% by mass, more preferably 0.1 to 6.0% by mass. Other ingredients: 0.50 to 2.0% by mass.

[0051] In the above, the fiber preferably includes dietary fiber. The blending ratio of dietary fiber is preferably 0.20 to 2.0 mass% in terms of pure content, more preferably 0.50 to 1.5 mass%. The fiber preferably includes polyolefin fiber. The blending ratio of polyolefin fiber is preferably 0.20 to 2.0 mass% in terms of pure content, more preferably 0.50 to 1.5 mass%.

[0052] The polymerization solution is prepared by thoroughly stirring the above components until they are uniformly dispersed. The temperature during stirring is preferably 20 to 40°C.

[0053] After preparation, the polymerization solution is optionally formed into a sheet before polymerization in (step 2). Examples of methods for forming the polymerization solution into a sheet include (a) a method of pouring the polymerization solution into a mold, (b) a method of pouring the polymerization solution between protective films and maintaining a constant thickness, and (c) a method of coating the polymerization solution onto a protective film. Method (a) has the advantage that a hydrogel of any shape can be obtained. Methods (b) and (c) have the advantage that a relatively thin hydrogel can be obtained.

[0054] As the protective film, 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.

[0055] The surface of the protective film that comes into contact with the polymerization solution or hydrogel is preferably subjected to a release treatment. Examples of the release treatment include silicone coating, and baked silicone coating, which undergoes a crosslinking or curing reaction with heat or ultraviolet light, is particularly preferred. Particularly preferred films to be subjected to the release treatment include biaxially stretched PET (polyethylene terephthalate) film and OPP (oriented polypropylene) film.

[0056] Furthermore, when the protective film is provided and then irradiated with ultraviolet light or the like to polymerize it in the following step (Step 2), it is preferable to select a film made of a material that does not block light so as not to interfere with photopolymerization.

[0057] (Process 2) A hydrogel can be obtained by polymerizing the polymerization solution by applying heat or irradiating with light. The conditions for applying heat and irradiating with light are not particularly limited as long as a hydrogel can be obtained, and general conditions can be used.

[0058] When polymerization is carried out by ultraviolet irradiation, the cumulative dose of ultraviolet light varies depending on the content of the polymerization initiator, but is, for example, 1000 mJ / cm 2 ~ 10000mJ / cm 2 It is preferable that the range is 2000 mJ / cm 2 ~10,000mJ / cm 2 It is more preferable that the peak intensity of the ultraviolet light is within the range of 30 mW / cm. 2 ~300mW / cm 2 It is preferable that the range is 50 mW / cm 2 ~150mW / cm 2 More preferably, it is in the range of 70 mW / cm 2 ~130mW / cm 2In the present invention, the reaction rates of the monofunctional monomer and the crosslinkable monomer can be appropriately adjusted by appropriately setting the amount of the polymerization initiator and the amount of ultraviolet irradiation.

[0059] <Physical properties of hydrogel> 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 to 2.0 mm. In a preferred embodiment, the thickness of the hydrogel of the present invention is 0.30 to 1.2 mm.

[0060] The adhesive strength of the hydrogel of the present invention to a Bakelite plate is 1.0 to 10 N / 20 mm, preferably 2.5 to 10 N / 20 mm, and more preferably 3.0 to 10 N / 20 mm. If the adhesive strength is less than 1.0 N / 20 mm, the hydrogel may fall off from the skin. If the adhesive strength is greater than 10 N / 20 mm, the adhesive strength to the skin may be too strong, causing pain and / or redness upon removal.

[0061] Furthermore, the coefficient of variation (CV) of the adhesive strength of the hydrogel of the present invention to a Bakelite plate is less than 4.0, preferably less than 3.8, and more preferably less than 3.5. The coefficient of variation (CV) can be used as an index of variation in adhesive strength. If the coefficient of variation is 4.0 or more, the adhesive strength will vary greatly, making it more likely that the hydrogel will partially lift and / or fall off from the skin during use.

[0062] In the present invention, the adhesive strength to a Bakelite plate and the coefficient of variation of the adhesive strength are measured by the following method.

[0063] The hydrogel was cut into 120 mm x 20 mm pieces, attached to a Bakelite plate, and pressed with a 2 kg pressure roller back and forth once to form a test specimen. A rheometer (Sun Scientific Co., Ltd., CR-500DX) was used for measurement, with an angle of 90 degrees and a speed of 300 mm / min. The stress values ​​(N / 20 mm) at predetermined peel points (30, 40, 50, 60, and 70 mm) from the measurement start point on the test specimen were taken as measurements, and the adhesive strength was calculated by averaging the measured values. The coefficient of variation (CV) was also calculated from the measured values ​​using the following formula: CV value (%) = (standard deviation x 100) / average value

[0064] The hydrogel of the present invention preferably has a storage modulus of 3000 Pa to 9000 Pa, more preferably 4000 Pa to 8000 Pa. The higher the storage modulus, the more elastic the hydrogel is and serves as an index of hardness. When the storage modulus is 3000 Pa or more, the hydrogel is not too soft and has good mechanical strength and handleability. When the storage modulus is 9000 Pa or less, the hydrogel is not too hard and has good handleability. In the present invention, the storage modulus is measured by the following method.

[0065] A viscoelasticity measuring device (Anton Paar, MR-102) is used as the measuring device, and viscoelasticity measurements are performed at 23°C and a frequency of 0.1 Hz with a strain of 1%. A 25φ gel piece is attached to a 25φ SUS parallel plate as a jig, and after pressing it up to a load point of 1 N, the storage modulus is calculated at 0.1 Hz.

[0066] In some embodiments, the hydrogel has excellent processability. When the fiber content is 0.50 to 2.5 mass% in terms of pure content, a hydrogel with excellent processability is obtained. When the dietary fiber content is 0.20 to 2.5 mass% in terms of pure content, a hydrogel with excellent processability is obtained. When the polyolefin fiber content is 0.20 to 2.0 mass% in terms of pure content, a hydrogel with excellent processability is obtained. When the dietary fiber content is 0.20 to 2.0 mass% in terms of pure content and the polyolefin fiber content is 0.20 to 2.0 mass% in terms of pure content, a hydrogel with excellent processability is obtained.

[0067] <Uses of hydrogel> The hydrogel of the present invention has no variation in adhesive strength and is therefore suitable for use in applications requiring uniform adhesiveness. For example, it can be used as a wound dressing, a bioadhesive, or a bioelectrode hydrogel. Preferably, the hydrogel of the above embodiment of the present invention can be used as a bioelectrode hydrogel that is placed between an electrode made of a conductive material and the skin surface.

[0068] In addition, the hydrogel of the present invention can be suitably used as a base material for transdermal absorbents by impregnating it with a drug; as an electrode material for industrial measurements, an industrial adhesive material, etc. in industrial applications; as a non-polarized electrode for electrical geological surveys in building materials applications, for example, by being placed on the surface of the ground or bedrock; as a conductive material for detecting damage to waterproof sheets used in waste disposal sites; and as a conductive adhesive material placed between a concrete structure and a metal anode in a method for cathodic protection of a concrete structure. [Example]

[0069] The present invention will be explained in more detail using Production Examples and Examples, but the present invention is not limited to these Examples.

[0070] Example 1 1. Preparation of Polymerization Solution Using a stirring / mixing vessel, 20% by weight of acrylamide (monofunctional monomer), 0.018% by weight of methylenebisacrylamide (crosslinking monomer), 0.50% by weight of microfibrillated cellulose (Exilva, P-01V, Borregaard) (distillation fiber), 0.50% by weight of polyethylene hyperbranched fiber (SWP, E790, Mitsui Chemicals) (polyolefin fiber), 18% by weight of ion-exchanged water, and 58% by weight of glycerin (humectant) were added and uniformly dispersed using a homomixer. Next, 2.0% by weight of sodium chloride (electrolyte), 0.982% by weight of citric acid, sodium benzoate, 0.13% by weight of a photoinitiator (Omnirad 2959, IGM Resins BV), and 0.982% by weight of a surfactant were added as additives, and the mixture was stirred until completely dissolved to obtain a polymerization solution.

[0071] 2. Hydrogel Fabrication The obtained polymerization solution was dropped onto a silicone-coated PET film and spread evenly by passing it through a certain clearance. Then, another silicone-coated PET film was placed on top of it, and the liquid was spread evenly and fixed to a thickness of 0.75 mm. A metal halide lamp was used to illuminate the film with a peak irradiance of 130 mW / cm. 2 , energy amount 3000mJ / cm 2 By irradiating the solution with ultraviolet light at 400 K, a hydrogel with a thickness of 0.75 mm was obtained.

[0072] (Examples 2 to 8, 10) Polymerization solutions were prepared in the same manner as in Example 1, except that the mass % of each component and the gel thickness were changed as shown in Table 1. Hydrogels were produced in the same manner as in Example 1 using each of these blended solutions.

[0073] Example 9 Using a stirring / mixing vessel, 14.4 mass% of acrylic acid as a monofunctional monomer, 9.6 mass% of tert-butylacrylamidosulfonic acid (TBAS), 0.018 mass% of methylenebisacrylamide as a cross-linking monomer, and 8.0 mass% of 50 mass% NaOH solution were added to adjust the pH to 4-5, as shown in Table 1. Subsequently, 0.50 mass% of pure microfibrillated cellulose (Exilva, P-01V, Borregaard) as dietary fiber, 0.50 mass% of pure polyethylene hyperbranched fiber (SWP, E790, Mitsui Chemicals, Inc.) as polyolefin fiber, 17.3 mass% of ion-exchanged water, and 46.7 mass% of glycerin as a humectant were added, and the mixture was uniformly dispersed using a homomixer. Next, 2.0% by mass of sodium chloride as an electrolyte and 0.982% by mass of other additives, including citric acid, sodium benzoate, a photopolymerization initiator, and a surfactant, were added and stirred until completely dissolved to obtain a polymerization solution. Using this polymerization solution, a hydrogel was produced in the same manner as in Example 1.

[0074] Example 11 Using a stirring / mixing vessel, 20% by weight of acrylamide as a monofunctional monomer, 0.018% by weight of methylenebisacrylamide as a crosslinking monomer, 0.50% by weight of citrus-derived dietary fiber (Helbacell AQ Plus, manufactured by Sumitomo Pharma Food & Chemical Co., Ltd.), 0.50% by weight of pure polyethylene hyperbranched fiber (SWP, E790, manufactured by Mitsui Chemicals, Inc.), 18% by weight of ion-exchanged water, and 58% by weight of glycerin as a humectant were added and uniformly dispersed using a homomixer. Next, 2.0% by weight of sodium chloride as an electrolyte, 0.982% by weight of other additives (citric acid, sodium benzoate, photopolymerization initiator (Omnirad 2959, manufactured by IGM Resins BV), and 0.13% by weight of surfactant were added and stirred until completely dissolved to obtain a polymerization solution. Hydrogels were produced using this polymerization solution as in Example 1.

[0075] (Examples 12 and 13) Polymerization solutions were prepared in the same manner as in Example 11, except that the mass % of each component and the gel thickness were changed as shown in Table 1. Hydrogels were produced in the same manner as in Example 1 using each of these blended solutions.

[0076] (Comparative Examples 1 to 4) Polymerization solutions were prepared in the same manner as in Example 1, except that the mass % of each component and the gel thickness were changed as shown in Table 2. Hydrogels were produced in the same manner as in Example 1 using each of these blended solutions.

[0077] However, in Comparative Example 1, the dispersibility was poor and phase separation occurred, so no hydrogel was produced and the sample was excluded from the evaluation.

[0078] (Comparative Example 5) 1. Preparation of Polymerization Solution Using a stirring / mixing vessel, 20% by weight of acrylamide as a monofunctional monomer, 0.018% by weight of methylenebisacrylamide as a crosslinking monomer, and 18% by weight of ion-exchanged water were mixed and stirred to dissolve uniformly. Then, 59.0% by weight of glycerin as a humectant was added and dispersed uniformly using a homomixer. Next, 2.0% by weight of sodium chloride as an electrolyte and 0.982% by weight of other additives (citric acid, sodium benzoate, photopolymerization initiator, and surfactant) were added and stirred until completely dissolved. The resulting mixture was stirred until uniform, yielding a polymerization solution.

[0079] 2. Hydrogel Fabrication The obtained polymerization solution was dropped onto a silicone-coated PET film, and the solution was spread evenly by passing through a certain clearance. An intermediate substrate (nonwoven fabric) was placed on top of it, and the compounded solution was dropped onto it. A silicone-coated PET film was placed on top of that, and the solution was spread evenly and fixed to a thickness of 0.75 mm. A metal halide lamp was used to illuminate the film with a peak irradiance of 130 mW / cm. 2 , energy amount 3000mJ / cm 2 By irradiating the solution with ultraviolet light at 400 K, a hydrogel with a thickness of 0.75 mm was obtained.

[0080] (Comparative Example 6) A polymerization solution was prepared in the same manner as in Comparative Example 5. Using this polymerization solution, a hydrogel was produced in the same manner as in Comparative Example 5, except that no intermediate substrate was used.

[0081] (Comparative Example 7) Using a stirring / mixing vessel, 14.4 wt% acrylic acid as a monofunctional monomer, 9.6 wt% tert-butylacrylamidosulfonic acid (TBAS), 0.018 wt% methylenebisacrylamide as a crosslinking monomer, and 8.0 wt% 50 wt% NaOH solution were added to adjust the pH to 4-5, as shown in Table 2. Subsequently, 17.3 wt% ion-exchanged water and 47.7 wt% glycerin as a humectant were added and stirred until completely dissolved. Next, 2.0 wt% sodium chloride as an electrolyte and 0.982 wt% total of citric acid, sodium benzoate, a photopolymerization initiator, and a surfactant as other additives were added and stirred until completely dissolved, yielding a polymerization solution. Using this polymerization solution, a hydrogel was produced in the same manner as in Example 1.

[0082] (Comparative Examples 8 to 10) Polymerization solutions were prepared in the same manner as in Example 11, except that the mass % of each component was changed as shown in Table 2. Hydrogels were produced in the same manner as in Example 11 using each of these blended solutions.

[0083] However, in Comparative Example 8, the dispersibility was poor and phase separation occurred, so no hydrogel was produced and the sample was excluded from the evaluation.

[0084] (Adhesion strength evaluation to Bakelite board) The hydrogel was cut into a 120 mm x 20 mm piece, and the PET film was peeled off to reveal the gel surface. A Bakelite plate was attached to the gel surface, and a 2 kg pressure roller was used to press the surface back and forth. A rheometer (Sun Scientific Co., Ltd., CR-500DX) was used for the measurement, with the measurement conditions being a 90° angle and a speed of 300 mm / min. The stress values ​​(N / 20 mm) at predetermined peeling points (30, 40, 50, 60, and 70 mm) from the starting point of the measurement were recorded as measurements. The adhesive strength was calculated from the average value of three test values ​​(15 points in total). The coefficient of variation (CV) was calculated from the three test values ​​(15 points in total) using the following formula, and this value was used as an index of the variation in the adhesive strength of the hydrogel. CV value (%) = (standard deviation x 100) / average value The measurement was carried out under an environment of temperature 23±5°C and humidity 55%±10%. The results are shown in Tables 1 and 2.

[0085] (Evaluation of handling) The hydrogel was cut into a piece of 120mm x 20mm, the PET film peeled off, and a SUS plate (SUS304 mirror finish) was attached to the gel surface, which was then pressed back and forth with a 2kg pressure roller to create a test specimen. When 15 trained panelists peeled the hydrogel, the gel was given an "A" if it could be peeled cleanly without stretching, a "B" if it was partially deformed but could be peeled cleanly, and a "C" if it stretched and could not be peeled cleanly. The results are shown in Tables 1 and 2.

[0086] (Evaluation of workability) To prepare 16 40 mm x 40 mm test pieces, a Thomson blade was inserted up to the interface between the PET film and hydrogel, cutting only the hydrogel without cutting the PET film. The test pieces were punched out with an 8 mm gap between each piece. The unnecessary hydrogel surrounding the blank area (margin) surrounding the punched test piece was then peeled off. If even one of the 16 test pieces peeled off when the blank area was peeled off, or if the cut surface of the test piece was rough when cut with the Thomson blade, the processability was rated "B" (poor). If all 16 test pieces remained clean, the processability was rated "A" (good). The results are shown in Tables 1 and 2.

[0087] (Evaluation of storage modulus) Using a viscoelasticity measuring device (Anton Paar, MR-102), viscoelasticity measurements were performed at 23°C and a frequency of 0.1 Hz with a strain of 1%. A 25φ gel piece was attached to a 25φ stainless steel parallel plate, and the plate was pressed against the plate until a load of 1 N was reached. The storage modulus was then calculated at 0.1 Hz. A higher storage modulus is an index of hardness, which indicates elasticity. The results are shown in Tables 1 and 2.

[0088] (liquid stability) After preparation, the polymerization solution was left to stand for one day, and the stability of the solution was confirmed visually. A uniformly dispersed solution was rated "A," a partially insufficiently dispersed solution was rated "B," and a completely phase-separated solution was rated "C." The results are shown in Tables 1 and 2.

[0089] (result) The hydrogels of Examples 1 to 13 had good adhesive strength, suppressed variations in adhesiveness, and were easy to handle and process. The polymerization solutions also had good stability.

[0090] In Comparative Example 1, the dispersibility (liquid stability) of the polymerization solution was poor, and phase separation occurred, making it impossible to produce a hydrogel. The hydrogels of Comparative Examples 2 and 10 had poor adhesive strength. The hydrogels of Comparative Examples 3 to 5, 7, and 9 had large variations in adhesive strength. The hydrogel of Comparative Example 6 contained neither fibers nor an intermediate substrate, and therefore had poor handleability. In Comparative Example 8, the dispersibility was poor, and phase separation occurred, so hydrogel production was not performed.

[0091] [Table 1]

[0092] [Table 2]

Claims

1. A hydrogel comprising a hydrogel and fibers dispersed in the hydrogel, The hydrogel does not contain an intermediate substrate, The fibers include dietary fibers and polyolefin fibers, the hydrogel comprises a polymer matrix, water, and a humectant; the polymer matrix is ​​a copolymer of at least one monofunctional monomer selected from the group consisting of (meth)acrylamide-based monomers and (meth)acrylic acid esters, and a crosslinkable monomer; the intermediate substrate is a nonwoven fabric, A hydrogel having an adhesive strength to a Bakelite plate of 1.0 to 10 N / 20 mm and a coefficient of variation (CV) value of the adhesive strength of less than 4.

0.

2. 2. The hydrogel according to claim 1, wherein the dietary fiber content is 0.20 to 2.0 mass% in terms of pure content.

3. 2. The hydrogel according to claim 1, wherein the dietary fiber has an average fiber diameter of 10 to 500 nm.

4. The hydrogel of claim 1 , wherein the dietary fiber comprises cellulose.

5. 2. The hydrogel according to claim 1, wherein the content of the polyolefin fiber is 0.20 to 2.0 mass% in terms of pure content.

6. 2. The hydrogel according to claim 1, wherein the polyolefin fibers have an average fiber length of 0.50 to 2.0 mm.

7. 2. The hydrogel according to claim 1, wherein the adhesive strength to a Bakelite plate is 2.5 to 10 N / 20 mm.

8. 2. The hydrogel according to claim 1, wherein the thickness of the hydrogel is 0.20 to 2.0 mm.

9. 2. The hydrogel according to claim 1, having a storage modulus of 3,000 to 9,000 Pa.

10. A bioelectrode hydrogel used by being placed between an electrode made of a conductive material and a skin surface, the bioelectrode hydrogel comprising the hydrogel according to claim 1.

11. A method for producing the hydrogel according to claim 1, A polymerizable solution containing a monofunctional monomer, a crosslinkable monomer, fibers, water, a polymerization initiator, and a moisturizing agent, and having a crosslinkable monomer content of 0.010 to 0.050 mass %, has a peak intensity of 50 to 150 mW / cm 2 A method for producing a hydrogel, comprising the step of irradiating the hydrogel with ultraviolet light.

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