JP5666859B2 - Adhesive hydrogel, composition for producing adhesive hydrogel, and gel sheet - Google Patents

Description

  The present invention relates to an adhesive hydrogel, a composition for producing an adhesive hydrogel, and a gel sheet. More specifically, the present invention relates to an adhesive hydrogel that can be suitably used as a raw material for biomedical electrodes, medical adhesives, cosmetics, quasi-drugs, industrial measurement electrodes, and the like, a composition for production thereof, It relates to the gel sheet containing.

  A hydrogel is basically a polymer having a high affinity with water swelled in an aqueous solvent. Hydrogel has various properties such as water absorption, swelling, adhesiveness, and conductivity. Utilizing these properties, it can be used in a wide range of fields such as civil engineering, architecture, food, medicine, cosmetics, and electricity. Has been.

  In recent years, EMS (Electrical Muscle Stimulation) for slimming and strength training has become widespread, and the opportunity to be used in ordinary homes has increased. When used in a general household, durability of an electrode pad to be affixed on the skin is required. That is, the adhesive gel used for the electrode pad is required to have an adhesive force that does not decrease even after pasting and peeling (hereinafter referred to as repeated adhesive force). When the adhesive force is repeatedly improved, there is a merit in using the electrode pad in the medical field that is originally used disposable.

  The main cause of the repeated decrease in adhesive strength is that when the gel is peeled from the skin, keratin that has fallen off from the skin surface adheres to the surface of the gel and the effective adhesive area decreases. From this point of view, as a technique for improving the adhesive force repeatedly, a technique for recovering the adhesive force by washing the adhesive surface soiled by several times of skin application with water is known (see Patent Document 1). Moreover, the technique which improves adhesiveness by using a predetermined amount of water-soluble polymer is known (refer patent document 2).

Japanese Patent No. 3437124 JP 2003-96431 A

  However, the hydrogel described in Patent Document 1 requires operations such as washing with water in order to recover the adhesive strength after repeated use. Therefore, when used at home, etc., the conditions described in the instruction manual, etc. must be observed for the cleaning method, drying method, etc. in order to reliably restore the adhesive strength. Such conditions may make the user feel cumbersome.

Hydrogel has a property of absorbing water when it comes into contact with water, and does not exhibit adhesive strength when absorbed. Therefore, for reuse, it is necessary to evaporate excess water under specified conditions and restore it to its original state. Moreover, when it contacts with water for a long time more than necessary, hydrogel will absorb water excessively and the restoration | recovery of a composition may become difficult.
Therefore, it cannot be said that the hydrogel of patent document 1 can enjoy the effect easily for all users.
On the other hand, although the technique of Patent Document 2 can improve the adhesive strength of hydrogel, it seems that there is room for improvement in terms of repeated adhesive strength.

  This invention makes it the subject to provide the adhesive hydrogel which has the outstanding repeating adhesive force, without accompanying special operations, such as washing | cleaning.

  As a result of intensive studies to solve the above problems, the inventors of the present invention contain polyvinyl pyrrolidone having a K value in a predetermined range in a predetermined ratio in a polymer matrix made of a copolymer of a predetermined monomer. It was found that the hydrogel made was excellent in repeated adhesive strength, and the present invention was reached.

  Thus, according to the present invention, there is provided an adhesive hydrogel comprising water, a polyhydric alcohol, and a polyvinyl pyrrolidone having a K value of 25 to 88 in the polymer matrix, wherein the polymer matrix comprises (meth) acrylic acid. , A derivative thereof, or a copolymer of a crosslinkable monomer and a vinyl monomer having 4 to 5 carbon atoms having two carboxyl groups and a polymerizable monomer mixture containing (meth) acrylamide or a derivative thereof, 2.5 to 22.5 parts by weight of the (meth) acrylic acid, a derivative thereof, or a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups with respect to 100 parts by weight of the hydrogel, the (meth) acrylamide Alternatively, an adhesive hydrogel comprising 2.5 to 22.5 parts by weight of a derivative thereof and 5 to 40 parts by weight of the polyvinyl pyrrolidone is provided. It is.

  Moreover, according to the present invention, there is provided a composition for producing an adhesive hydrogel used for producing the adhesive hydrogel described above, with respect to 100 parts by weight of the composition for producing an adhesive hydrogel, (Meth) acrylic acid, its derivative or 2.5 to 22.5 parts by weight of a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups and 2.5 to 22.5 parts by weight of (meth) acrylamide or its derivative Provided is a composition for producing an adhesive hydrogel comprising a polymerizable monomer mixture, a crosslinkable monomer, water, a polyhydric alcohol, and 5 to 40 parts by weight of a polyvinyl pyrrolidone having a K value of 25 to 88. Is done.

  Furthermore, according to this invention, the gel sheet characterized by including the said adhesive hydrogel is provided.

  The adhesive hydrogel according to the present invention is excellent in repeated adhesive strength. Therefore, products (such as electrode pads) using the hydrogel according to the present invention can withstand repeated use as compared with conventional products, so that the product life is long, economical, and resource saving is achieved. be able to.

  When polyhydric alcohol is selected from ethylene glycol, propylene glycol, butanediol, glycerin, pentaerythritol, sorbitol, polyethylene glycol, polypropylene glycol, polyglycerin, polyoxyethylene glycerin A hydrogel can be provided.

(Meth) acrylic acid, its derivatives or vinyl derivatives having 4 to 5 carbon atoms having two carboxyl groups are (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, (poly) ethylene glycol (meta ) Acrylate, (poly) propylene glycol (meth) acrylate or (poly) glycerin (meth) acrylate, and (meth) acrylamide or a derivative thereof is tertiary butyl acrylamide sulfonic acid (TBAS) or a salt thereof, N, N -Dimethylaminoethylacrylamide (DMAEAA) hydrochloride, N, N-dimethylaminopropylacrylamide (DMAPAA) hydrochloride, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl ( (Meth) acrylic Bromide, N, N- dimethyl (meth) acrylamide If, N, is selected N- diethyl (meth) acrylamide, from acryloyl morpholine can provide adhesive hydrogel having a more excellent repeated adhesion.
Moreover, when an adhesive hydrogel further contains 0.05-10 weight part electrolyte with respect to 100 weight part of adhesive hydrogel, the adhesive hydrogel provided with electroconductivity can be provided.

  The adhesive hydrogel according to the present invention (hereinafter, also simply referred to as “hydrogel” or “gel”) includes water, a polyhydric alcohol, and polyvinylpyrrolidone having a K value of 25 to 88 in a polymer matrix. The polymer matrix comprises (meth) acrylic acid, a derivative thereof, or a polymerizable monomer mixture containing a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups and (meth) acrylamide or a derivative thereof and a crosslinkable monomer. It is a copolymer with the body. In addition, (meth) acryl means acryl or methacryl.

(Polymer matrix)
The polymer matrix (hereinafter also referred to as “matrix”) is a polymerizable monomer containing (meth) acrylic acid, a derivative thereof or a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups and (meth) acrylamide or a derivative thereof. It is a copolymer of a monomer mixture and a crosslinkable monomer.
(1) Polymerizable monomer mixture (meth) acrylic acid, a derivative thereof, or a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups and (meth) acrylamide or a derivative thereof contained in the polymerizable monomer mixture are Since the polymerization reactivity is good, the residual monomer can be reduced. Moreover, the affinity with the other component in adhesive hydrogel is also favorable.

Examples of (meth) acrylic acid, derivatives thereof or vinyl derivatives having 4 to 5 carbon atoms having two carboxyl groups include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, (poly) ethylene glycol ( Examples include (meth) acrylate, (poly) propylene glycol (meth) acrylate, (poly) glycerin (meth) acrylate, and the like.
Here, (poly) ethylene means ethylene or polyethylene. Polyethylene means a structure having 2 to 10 ethylene units. (Poly) propylene and (poly) glycerin mean the same contents as (poly) ethylene.

  (Meth) acrylamide or a derivative thereof includes tertiary butylacrylamide sulfonic acid (TBAS) or a salt thereof, N, N-dimethylaminoethylacrylamide (DMAEAA) hydrochloride, N, N-dimethylaminopropylacrylamide (DMAPAA) hydrochloride Electrolyte acrylamide derivatives such as (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N- Non-electrolytic acrylamide derivatives such as diethyl (meth) acrylamide and acryloylmorpholine can be mentioned.

  (Meth) acrylic acid, a derivative thereof, or a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups is contained in an amount of 2.5 to 22.5 parts by weight based on 100 parts by weight of the adhesive hydrogel. Preferably, it is 5 to 22 parts by weight. If the amount contained is less than 2.5 parts by weight, the adhesive strength of the hydrogel may be reduced. On the other hand, if the amount exceeds 22.5 parts by weight, a large amount of residual monomer is generated, so that the post-treatment process becomes complicated, and the quality of the hydrogel obtained by the influence of the residual monomer may be deteriorated.

(Meth) acrylamide or a derivative thereof is contained in an amount of 2.5 to 22.5 parts by weight with respect to 100 parts by weight of the adhesive hydrogel. Preferably, it is 3 to 22 parts by weight. If the amount contained is less than 2.5 parts by weight, a large amount of residual monomer may be generated. On the other hand, if it exceeds 22.5 parts by weight, the tackiness of the hydrogel may be reduced.
Moreover, it is preferable that these (meth) acrylic acid, its derivative, or the C4-C5 vinyl derivative which has two carboxyl groups, and (meth) acrylamide or its derivative are water-soluble.

(2) Crosslinkable monomer As the crosslinkable monomer, one having two or more double bonds having polymerizability in the molecule is preferable. Specifically, methylene bis (meth) acrylamide, ethylene bis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin tri ( Examples include polyfunctional (meth) acrylamides such as (meth) acrylate or (meth) acrylates, tetraallyloxyethane, diallyl ammonium chloride, and the like. These may be used alone or in combination of two or more.

In addition, glycidyl (meth) having one or more polymerizable double bonds and one or more epoxy groups, hydroxyl groups, alkoxy groups, etc. as functional groups having crosslinkable reactivity by elimination reaction or ring-opening reaction Examples include acrylate and N-methylolacrylamide.
Furthermore, in the case of performing crosslinking with ions, a part of the ionic polymerizable monomer can have a function as a crosslinkable monomer.

  The ratio of the crosslinkable monomer in producing the polymer matrix varies depending on the polymerizable monomer species and the crosslinkable monomer species used, but is generally 0.01 to 100 parts by weight of the hydrogel. It is preferable that it is -0.5 weight part. More preferably, it is 0.05 to 0.25 parts by weight. When the ratio of the crosslinkable monomer is less than 0.01 parts by weight, the crosslink density is lowered and the shape stability of the gel becomes poor. May remain. In addition, when used for electrical measurement, there may be a case where the measured value is likely to fluctuate due to a variation in thickness. On the other hand, when the amount exceeds 0.5 parts by weight, the gel tends to be hard and brittle with almost no adhesive force.

(Polymer matrix content)
A polymer matrix is formed by polymerizing and crosslinking the polymerizable monomer and the crosslinkable monomer. The ratio of the polymer matrix contained in the adhesive hydrogel of the present invention is preferably 5 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the adhesive hydrogel. When the ratio of the polymer matrix in the adhesive hydrogel is less than 5 parts by weight, the matrix concentration in the resulting gel is too low, so the matrix can not be subjected to the solvent and is easy to bleed, and the gel has low waist strength. There is a case. On the other hand, if it exceeds 50 parts by weight, the exotherm during polymerization becomes too large, and the reaction may run away, resulting in boiling beyond the boiling point of the solvent. Moreover, when it boils, since a bubble mixes in a gel, a favorable gel may not be obtained.

(Polyhydric alcohol)
Examples of the polyhydric alcohol contained in the adhesive hydrogel of the present invention include diols such as ethylene glycol, propylene glycol, and butanediol, polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol, polyethylene glycol, polypropylene glycol, polyglycerin, and the like. And polyhydric alcohol modified products such as polyoxyethylene glycerin. These can be used alone or in combination of two or more.

  Among these polyhydric alcohols, it is preferable to use those which are liquid in a temperature range where hydrogel is actually used (for example, around 20 ° C. when used indoors). Examples of such polyhydric alcohols include ethylene glycol, propylene glycol, polyethylene glycol, polyglycerin, glycerin and the like.

  The content of the polyhydric alcohol is preferably 10 to 80 parts by weight with respect to 100 parts by weight of the hydrogel. More preferably, it is 20-70 weight part. When the content of the polyhydric alcohol is less than 10 parts by weight, the gel has poor moisture retention, water transpiration becomes remarkable, the gel is not stable over time, and lacks flexibility, thus imparting tackiness to the gel. May be difficult. On the other hand, if it exceeds 80 parts by weight, the polyhydric alcohol may bleed on the surface of the gel and the adhesive strength may be reduced. In addition, when preparing a blended solution of polyhydric alcohol, water, and polyvinylpyrrolidone, the viscosity becomes too high, handling may be poor, and dissolution may be difficult. Furthermore, bubbles may be mixed when the gel is formed, and an extra defoaming process may be required.

(Polyvinylpyrrolidone)
Polyvinylpyrrolidone is contained in an amount of 5 to 40 parts by weight with respect to 100 parts by weight of the hydrogel. Preferably, it is 5 to 30 parts by weight. If the content of polyvinyl pyrrolidone is less than 5 parts by weight, the adhesiveness may be lowered repeatedly. On the other hand, when the amount exceeds 40 parts by weight, the viscosity of the blended solution at the time of gel preparation becomes too high, the blended solution aggregates, and uniform dissolution becomes difficult, and a uniform gel may not be obtained. In addition, 100 weight part of hydrogel is the total of each addition amount of a polymerizable monomer, a crosslinkable monomer, water, a polyhydric alcohol, and polyvinylpyrrolidone.

  The K value of polyvinylpyrrolidone is 25-88. Preferably, it is 27-85. When the K value is less than 25, when a gel is applied to a living body and peeled off, the water-soluble polymer existing in the vicinity of the gel surface may remain on the skin surface, and uncomfortable feeling may remain. Furthermore, when the water-soluble polymer is raised at the interface between the gel adhesive surface and the object to be pasted, the adhesion may be hindered due to low molecular weight and lack of cohesion. On the other hand, if the K value exceeds 88, even if the amount of the water-soluble polymer to be added is a very small amount, the viscosity of the compounded liquid prepared when preparing the gel becomes too high, making uniform dissolution difficult. A uniform gel may not be obtained.

(water)
The content of water contained in the adhesive hydrogel is not particularly limited, but in order to optimize the finally obtained adhesive properties and electrical properties, the content is 10 to 50 parts by weight with respect to the entire adhesive hydrogel. It is preferable that it is a weight part. More preferably, it is 10 to 45 parts by weight. If the water content is less than 10 parts by weight, the moisture content with respect to the equilibrium moisture content of the gel is too small, so that the hygroscopicity becomes strong and the gel may deteriorate over time. On the other hand, if the amount exceeds 50 parts by weight, the difference from the equilibrium moisture content of the gel becomes large, so that the gel may shrink due to drying or the physical properties may change.

(Electrolytes)
The adhesive hydrogel may contain an electrolyte. By including an electrolyte, it is possible to obtain a conductive gel suitable for bioelectrode applications such as an electrocardiogram measurement electrode, a low-frequency treatment device electrode, and various earth electrodes. When used as such a bioelectrode application, the specific resistance of the adhesive hydrogel containing the electrolyte is preferably 0.1 to 10 kΩ · cm.

  A salt is mentioned as electrolyte contained in the adhesive hydrogel in this invention. Salts include sodium halide, potassium halide, magnesium halide, calcium halide, alkali metal halides, alkaline earth metal halides, other metal halides, various metals, hypochlorous acid, Chloric acid, chloric acid, perchlorate, sulfate, nitrate, phosphate, ammonium salts, inorganic salts such as various complex salts, monovalent organic carboxylates such as acetic acid, benzoic acid, lactic acid, tartaric acid, phthalates In addition to monovalent or divalent salts of polyvalent carboxylic acids such as acids, succinic acid, adipic acid and citric acid, metal salts of organic acids such as sulfonic acids and amino acids, and organic ammonium salts, poly (meth) Polymer electrolyte salts such as acrylic acid, polyvinyl sulfonic acid, polytertiary butyl acrylamide sulfonic acid, polyallylamine, and polyethyleneimine are listed. It is.

  The electrolyte may be insoluble during the preparation of the hydrogel, and may have a property of dissolving in the hydrogel over time, even if it is in a dispersed form during preparation of the mixture. Examples of such an electrolyte include silicates, aluminates, metal oxides, hydroxides, and the like.

  When the electroconductivity suitable for adhesive hydrogel is calculated | required, it is preferable that 0.05-10 weight part of electrolyte is contained with respect to 100 weight part of hydrogel. More preferably, it is 0.1 to 2 parts by weight. Hydrogel containing moisture originally has a characteristic as a dielectric, and has an electric capacity corresponding to the thickness of the gel and the area of the electrode element when the electrode is produced by combining with the electrode element. However, the impedance (Z) of the electrode is greatly influenced by the electrolyte concentration, particularly in the low frequency region below 1 kHz. When the content of the electrolyte is less than 0.05 parts by weight, the impedance becomes high and may not be suitable for conductive use. On the other hand, if it exceeds 10 parts by weight, it may be difficult to dissolve the electrolyte in the hydrogel, and crystal precipitation may occur inside the gel, or dissolution of other components may be hindered. In addition, the conductive performance reaches its peak, and it cannot be said that addition beyond this is beneficial from the viewpoint of imparting conductivity.

  The electrolyte may be used for purposes other than imparting conductivity to the hydrogel. For example, an acidic salt, a basic salt, or a polyfunctional salt may be added for the purpose of adjusting the pH of the hydrogel. In addition, an electrolyte may be added for the purpose of improving the moisture retention performance of the hydrogel and imparting antibacterial properties.

(Other additives)
Adhesive hydrogels include antiseptics, bactericides, rust inhibitors, antioxidants, stabilizers, fragrances, surfactants, colorants, anti-inflammatory agents, vitamins, whitening agents, etc. Medicinal ingredients may be added as appropriate.

(Exemplary method for obtaining adhesive hydrogel)
As a method for obtaining an adhesive hydrogel, for example, a polymerizable monomer, a crosslinkable monomer, water, a non-crosslinked water-soluble polymer and, if necessary, a polymerization initiator are dissolved or uniformly dispersed, and heated or heated. The method obtained by superposing | polymerizing by performing ultraviolet irradiation etc. is mentioned. It can also be obtained by impregnating a polymer matrix previously formed by a polymerization reaction with water or a non-crosslinked water-soluble polymer. In addition, a crosslinkable monomer or catalyst is added to a polymer blend obtained by dissolving or uniformly dispersing a linear polymer obtained by polymerizing only a polymerizable monomer, water, a non-crosslinked water-soluble polymer, and the like. It can also be obtained by a method of adding and reacting a linear polymer with a crosslinkable monomer to form a matrix.

  As a polymerization method for obtaining the hydrogel, general radical polymerization, redox polymerization, radiation polymerization and the like are possible in addition to photopolymerization. Among the various polymerization methods described above, photopolymerization by light irradiation is preferred because the production process is simple and very economical, and at the same time it is possible to obtain a gel having stable physical properties.

In photopolymerization, it is preferable to polymerize by irradiating with ultraviolet rays in the presence of a photopolymerizable initiator. The cumulative irradiation amount of ultraviolet rays is preferably 1000 mJ / cm ² or more. If ^{2000mJ / cm 2 ~10000mJ / cm 2} , since the amount of residual monomer in the gel can be reduced to 100ppm or less, more preferably. When the cumulative irradiation amount of ultraviolet rays is less than 1000 mJ / cm ² , the polymerization reaction may not proceed sufficiently. If it is too large, it is necessary to increase the size of the ultraviolet irradiation device, and unnecessary energy will be consumed. Furthermore, a separate process for removing the heat generated by ultraviolet irradiation is required, which may increase the manufacturing cost.

  The photopolymerizable initiator is not particularly limited as long as it is cleaved with ultraviolet rays or visible rays to generate radicals, and known ones can be used. Of these, α-hydroxyketone, α-aminoketone, benzylmethyl ketal, bisacylphosphine oxide, metallocene and the like are preferable.

  Specific examples of the photopolymerization initiator include 1- “4- (2-hydroxyethoxy) -phenyl” -2-hydroxy-2-methyl-propan-1-one (product name: Irgacure 2959, Ciba Specialty Chemicals) 2-hydroxy-2-methyl-1-phenyl-propan-1-one (product name: Darocur 1173, manufactured by Ciba Specialty Chemicals), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Irgacure 184) 2-methyl-1-“(methylthio) phenyl” -2-morpholinopropan-1-one (product name: Irgacure 907, manufactured by Ciba Specialty Chemicals), 2-benzyl- 2-Dimethylamino-1- (4-morpholinophenyl) -butane-1- Emissions (product name: Irgacure 369, manufactured by Ciba Specialty Chemicals), and the like. These may be used alone or in combination.

  The photopolymerization initiator is preferably added in an amount of 0.01 to 1 part by weight with respect to 100 parts by weight of the hydrogel in order to sufficiently perform the polymerization reaction and reduce the amount of residual monomer. More preferably, it is 0.05 to 0.5 part by weight. When the addition amount of the photopolymerization initiator is less than 0.01 parts by weight, the polymerization reaction may not sufficiently proceed. On the other hand, when the amount exceeds 1 part by weight, the hydrogel may be discolored (yellowed) or smelled by the residue of the polymerization initiator after the polymerization reaction.

(Example of adhesive hydrogel molding method (gel sheet))
Since the adhesive hydrogel is gelled by polymerizing and crosslinking a liquid compounded liquid, it can be appropriately shaped according to the application. For example, the said composition is dripped on base films, such as a resin film, and after dripping, a top film, such as a resin film, is spread on the upper surface, a composition is spread, and it controls to desired thickness. In this state, an adhesive hydrogel having a desired thickness can be obtained by polymerization and crosslinking by irradiation with light (ultraviolet rays) and / or heat.

  For example, when used as an adhesive, it may be formed into a gel sheet having a thickness of 0.01 mm to 2.0 mm. In that case, you may shape | mold into the gel sheet which provided the protective film in the single side | surface or both surfaces.

  The protective film for producing the gel sheet can be used as a separator or a support, and a known film may be used. Moreover, the preparation method of a gel sheet is not specifically limited, It can manufacture by a well-known method.

  As the base film, polyester, polyolefin, polystyrene, polyurethane, paper, paper laminated with a resin film, or the like can be used. The surface of the film that contacts the gel sheet is preferably subjected to a release treatment such as silicone coating.

  When the base film is used as a release paper, a film having a release treatment applied to the surface of a film such as polyester, polyolefin, polystyrene, paper, paper laminated with a resin film, or the like is preferably used. Biaxially stretched PET film, OPP and the like are particularly preferable. Examples of the mold release treatment method include a silicone coating, and a baking type silicone coating that is crosslinked and cured with heat or ultraviolet rays is particularly preferable.

  When the base film is used not as a release paper but as an adhesive packing material (backing material), it is preferable to use polyester, polyolefin, polystyrene, polyurethane or the like without releasing treatment. Of these, polyurethane films are particularly preferred because they are flexible and have water vapor permeability. In addition, since a polyurethane film is usually too soft and difficult to handle in the production process, it is preferable to laminate and use a polyolefin film or paper as a carrier film.

  It is preferable that a gel production | generation process is performed in the state which attached the carrier film to the base film. The top film may be basically made of the same material as the base film, but it is preferable to select a film that does not block light so as not to prevent photopolymerization. Moreover, it is preferable not to use the film used for the packing material (backing material) as the top film. In particular, when the film used for the packing material may be deteriorated by irradiation with ultraviolet rays or the like, it is not preferable because the film is located on the side directly irradiated with ultraviolet rays.

(Example of electrode pad using hydrogel and its manufacturing method)
Adhesive hydrogels have the property of adhering safely to the skin and the like. Moreover, electroconductivity can be easily provided by adding electrolyte arbitrarily. Therefore, it can be suitably used as an adhesive conductive part such as an electrode pad. An example of using the adhesive hydrogel of the present invention as an electrode pad will be described below.

  First, an adhesive hydrogel is laminated on one side of a conductive layer in which a conductive substance such as carbon is kneaded. Next, a non-conductive support is laminated on the surface opposite to the surface on which the hydrogel is laminated. A conductive material such as a copper wire is attached to the support so as to be in contact with the conductive layer, which serves as a terminal. Electricity can flow from the outside through the terminal to an external monitor or the like, and can become an adhesive conductive site where electricity can flow through the conductive layer and the hydrogel to the object to be applied.

  The conductive layer includes a carbon coat layer formed of a carbon paste using a polyester-based or polyurethane-based resin as a binder, a layer coated with a conductive ink containing a metal such as Ag / AgCl, carbon, etc., a metal foil on the resin film (Aluminum, stainless steel, Ag, etc.) or a layer laminated with a conductive film kneaded with carbon or the like is used. It is desirable for the conductive layer to have a strength that does not easily break when a force is applied from the outside, such as a tensile force. If it breaks easily, the conductive layer may be cut off during the production of the electrode, the electrode of the final product may be deformed due to stretching, and further, depending on the user's handling, the conductive layer in the electrode may break, causing burns, etc. There is a possibility of attracting. On the other hand, since it sticks to an uneven skin surface, flexibility is also required. It is necessary to select a conductive layer having physical properties that do not cause problems during use.

  In the case of a film in which a support and a conductive layer are laminated, the terminal is formed by providing a part of the film where the hydrogel is not laminated when laminating the adhesive hydrogel on the conductive layer. . Terminals (portions where no hydrogel is laminated) are sandwiched between clips and connected to lead wires.

  In the case of an electrode having a caulking structure, the electrode is not particularly limited as long as it has conductivity, but a snap terminal and a resin molded product in which a metal such as stainless steel or carbon is kneaded and a resin molded product are Ag / AgCl or the like. An element coated with metal, and the part of the sandwiched structure becomes a terminal and is connected to the outside.

  When using a metal wire, etc., the metal wire is partly sandwiched between the conductive layer and the support, and the portion that protrudes from the laminated portion of the conductive layer and the support is covered with a non-conductive resin or the like. The tip of the metal wire is connected to the outside by being connected to the lead wire.

(Repeated adhesive strength of gel sheet containing adhesive hydrogel)
The gel sheet and electrode pad obtained using the adhesive hydrogel have excellent repeated adhesive strength. Specifically, N1 is the initial adhesive strength (the force required for first peeling after sticking to an object), and the sticking and peeling are repeated to require the tenth adhesive strength (required for the tenth peeling). Force) is N10, the relationship between N1 and N2 is
0.85 <N10 / N1 <1
It becomes. When N10 / N1 is smaller than 0.85, the adhesive strength is remarkably reduced when repeatedly used, and therefore it is preferable to exceed 0.85. It is particularly preferred that it exceeds 0.90.

  Since the adhesive hydrogel according to the present invention has excellent repeated adhesive strength as described above, the gel sheet and electrode pad obtained using this hydrogel have excellent repeated adhesive that is not found in conventional products. Power and can prolong the product life. Therefore, it is expected to help save resources by reducing the frequency of single use.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

First, measurement methods and evaluation methods in Examples and Comparative Examples will be described.
(Measurement method of K value)
The K value in the present invention is a value obtained by expressing the size of the molecular weight by the Fikenscher method, and can be obtained by the following measurement method. When the K value is less than 20, the viscosity of a 5% (g / 100 ml) solution is measured, and when the K value is 20 or more, the viscosity of a 1% (g / 100 ml) solution is measured. Sample concentration is converted to dry matter. If the K value is 20 or more, 1.0 g of the sample is accurately measured, put into a 100 ml volumetric flask, add distilled water at room temperature, dissolve completely with shaking, add distilled water to make exactly 100 ml. To do. The sample solution is allowed to stand for 30 minutes in a thermostatic chamber (25 ± 0.2 ° C.) and then measured using an Ubbelohde viscometer. Measure the time for the solution to flow between the two markings. Measure several times and take the average value. In order to define the relative viscosity, the same is measured for distilled water. The two obtained flow times are corrected based on the Hagenbach-Couette correction value.
K value = {[300ClogZ + (C + 1.5ClogZ) 2] 1/2 + 1.5ClogZ-C} / (0.15C + 0.003C2) (1)
In the above formula (1), C represents the concentration of the sample (%: g / 100 ml), and Z represents the relative viscosity (ηrel) of the solution having the concentration C.
The relative viscosity ηrel is obtained from the following equation.
ηrel = (solution flow time) ÷ (water flow time) (2)

(Measurement method of adhesive strength)
A sample lined with a nonwoven fabric is cut into a strip of 20 mm × 100 mm, and this test piece is attached to a bakelite plate (paper bakelite, product number: PL113, manufactured by Sumitomo Bakelite Co., Ltd.) and set in a texture analyzer manufactured by Eiko Seiki Co., Ltd. Thereafter, the force at the time of peeling in the 90 ° direction at a speed of 300 mm / min according to JIS-Z0237 is defined as the adhesive strength.

(Measurement method of repeated adhesive strength: Skin 180 ° repeated adhesive strength)
A sample lined with a non-woven fabric is cut into a strip of 20 mm × 150 mm, and this test piece is applied to the skin on the inner side of the left arm, which has been lightly wiped with alcohol in advance. Two minutes after sticking, using Tensilon (Orientec Co., Ltd.), the value of the force required to peel the test piece in the 180 ° direction at a speed of 1000 mm / min is defined as the initial adhesive strength (N1). . Thereafter, the peeled test piece is affixed to the inner skin of the left arm and peeled off repeatedly, and the force value required for the 10th peeling (counting from the first peeling) is defined as N10. And the numerical value which remove | divided N10 by N1 is made into the adhesive force retention rate with respect to initial stage adhesive force. The measurement conditions are an atmosphere with a temperature of 23 ° C. and a humidity of 60%.

(Measurement method of specific resistance)
A sample lined with a nonwoven fabric is cut into a square of 20 mm × 200 mm, a stainless steel plate is bonded to both sides of the test piece, and the impedance when a current of 1 kHz, 10 Vp-p is passed between the stainless steel plates is measured. The specific resistance is calculated from the obtained impedance (I) and the area (S) and thickness (d) of the test piece by the following formula.
Specific resistance (Ω · cm) = I (Ω) ÷ d (cm) × S (cm ² )

Example 1
10 parts by weight of tertiary butyl acrylamide sulfonic acid and 15 parts by weight of acrylic acid as a polymerizable monomer, 0.06 parts by weight of N, N′-methylenebisacrylamide as a crosslinkable monomer, and 39.94 glycerin as a polyhydric alcohol. 10 parts by weight of polyvinyl pyrrolidone (Daiichi Kogyo Seiyaku Co., Ltd .: CLEASUS K30) having a K value of 29.2, 0.5 parts by weight of sodium chloride as an electrolyte, and 1- “4- (2” as an ultraviolet polymerization initiator -Hydroxyethoxy) -phenyl "-2-hydroxy-2-methyl-propan-1-one (product name: Irgacure 2959, manufactured by Ciba Specialty Chemicals) was stirred and dissolved to prepare a monomer compounding solution. did.

Then, this compounded liquid was adjusted to pH 4.0-5.0 with 50 wt% NaOH aqueous solution, and it adjusted so that the quantity of ion-exchange water might be 25 weight part. Next, the obtained monomer blend solution was irradiated with ultraviolet rays having an energy amount of 3000 mJ / cm ² using a metal halide lamp to obtain a sheet-like adhesive hydrogel having a thickness of 0.75 mm. The adhesive strength of this hydrogel was 1.6, the repeated adhesive strength (N10 / N1) was 0.90, and the specific resistance value was 2.7.

(Example 2)
A hydrogel was produced in the same manner as in Example 1 except that the amount of glycerin added was changed to 34.94 parts by weight and the amount of polyvinylpyrrolidone added was changed to 15 parts by weight. The adhesive strength of this hydrogel was 3.16, the repeated adhesive strength (N10 / N1) was 0.91, and the specific resistance value was 3.5.

Example 3
A hydrogel was prepared in the same manner as in Example 1 except that the amount of glycerin added was changed to 29.94 parts by weight and the amount of polyvinylpyrrolidone added was changed to 20 parts by weight. The adhesive strength of this hydrogel was 5.26, the repeated adhesive strength (N10 / N1) was 0.93, and the specific resistance value was 5.5.

Example 4
A hydrogel was produced in the same manner as in Example 1 except that the amount of tertiary butyl acrylamide sulfonic acid added was changed to 5 parts by weight and the amount of acrylic acid added was changed to 20 parts by weight. The adhesive strength of this hydrogel was 1.65, the repeated adhesive strength (N10 / N1) was 0.90, and the specific resistance value was 2.85.

(Example 5)
A hydrogel was produced in the same manner as in Example 1 except that the amount of tertiary butyl acrylamide sulfonic acid added was changed to 20 parts by weight and the amount of acrylic acid added was changed to 5 parts by weight. The adhesive strength of this hydrogel was 1.95, the repeated adhesive strength (N10 / N1) was 0.91, and the specific resistance value was 3.8.

(Example 6)
A hydrogel was produced in the same manner as in Example 1 except that the K value of polyvinylpyrrolidone was changed to 49.5. This hydrogel had an adhesive strength of 1.48, a repeated adhesive strength (N10 / N1) of 0.86, and a specific resistance value of 2.6.

(Comparative Example 1)
A hydrogel was produced in the same manner as in Example 1 except that the amount of glycerin added was changed to 49.69 parts by weight and the amount of polyvinylpyrrolidone added was changed to 0.25 parts by weight. The adhesive strength of this hydrogel was 1.22, the repeated adhesive strength (N10 / N1) was 0.65, and the specific resistance value was 2.5.

(Comparative Example 2)
A hydrogel was prepared in the same manner as in Example 1 except that the amount of glycerin added was changed to 5 parts by weight and the amount of polyvinylpyrrolidone added was changed to 45 parts by weight. However, since the monomer compound solution could not be produced without completely dissolving, the production of the hydrogel was abandoned.

(Comparative Example 3)
A hydrogel was prepared in the same manner as in Example 1 except that the amount of tertiary butyl acrylamide sulfonic acid added was changed to 25 parts by weight and no acrylic acid was added. The adhesive strength of this hydrogel was 1.18, the repeated adhesive strength (N10 / N1) was 0.81, and the specific resistance value was 2.5.

(Comparative Example 4)
In the same manner as in Example 1, except that the amount of tertiary butyl acrylamide sulfonic acid added was changed to 25 parts by weight, the amount of polyvinyl pyrrolidone added was changed to 0.25 parts by weight, and acrylic acid was not added. A hydrogel was prepared. The adhesive strength of this hydrogel was 1.55, the repeated adhesive strength (N10 / N1) was 0.61, and the specific resistance value was 2.4.

(Comparative Example 5)
A hydrogel was produced in the same manner as in Example 1 except that the K value of polyvinylpyrrolidone was changed to 94.2. However, since the monomer compound solution could not be produced without completely dissolving, the production of the hydrogel was abandoned.

(Comparative Example 6)
A hydrogel was produced in the same manner as in Example 1 except that the K value of polyvinylpyrrolidone was changed to 16.5. The adhesive strength of this hydrogel was 1.25, the repeated adhesive strength (N10 / N1) was 0.52, and the specific resistance value was 2.7.
Table 1 summarizes the amounts and results of the raw materials used in Examples 1 to 6 and Comparative Examples 1 to 6.

ＩＲ２９５９：１−「４−（２−ヒドロキシエトキシ）−フェニル」−２−ヒドロキシ−２−メチル−プロパン−１−オン（製品名：イルガキュア２９５９、チバスペシャリティーケミカルズ社製）

IR2959: 1- “4- (2-hydroxyethoxy) -phenyl” -2-hydroxy-2-methyl-propan-1-one (product name: Irgacure 2959, manufactured by Ciba Specialty Chemicals)

  As shown in Table 1, (meth) acrylic acid, a derivative thereof, or a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups, (meth) acrylamide or a derivative thereof, and polyvinylpyrrolidone are produced within the scope of the present invention. The tacky hydrogel was found to have excellent repeated tack.

Claims (6)

  An adhesive hydrogel comprising water, a polyhydric alcohol, and a polyvinyl pyrrolidone having a K value of 25 to 88 in a polymer matrix, wherein the polymer matrix has (meth) acrylic acid, a derivative thereof, or a carboxyl group. It is a copolymer of a polymerizable monomer mixture containing two vinyl derivatives having 4 to 5 carbon atoms and (meth) acrylamide or a derivative thereof and a crosslinkable monomer, and 100 parts by weight of the adhesive hydrogel On the other hand, 2.5 to 22.5 parts by weight of the (meth) acrylic acid, a derivative thereof or a vinyl derivative having 2 to 5 carbon atoms having 2 to 5 carbon atoms, and the (meth) acrylamide or a derivative thereof is 2.5. -22.5 parts by weight, 5 to 40 parts by weight of the polyvinyl pyrrolidone is contained.   The adhesive hydrogel according to claim 1, wherein the polyhydric alcohol is selected from ethylene glycol, propylene glycol, butanediol, glycerin, pentaerythritol, sorbitol, polyethylene glycol, polypropylene glycol, polyglycerin, and polyoxyethylene glycerin.   The (meth) acrylic acid, its derivatives, or vinyl derivatives having 4 to 5 carbon atoms having two carboxyl groups are (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, (poly) ethylene glycol ( Selected from (meth) acrylate, (poly) propylene glycol (meth) acrylate or (poly) glycerin (meth) acrylate, and the (meth) acrylamide or a derivative thereof is tertiary butyl acrylamide sulfonic acid (TBAS) or a salt thereof, N , N-dimethylaminoethylacrylamide (DMAEAA) hydrochloride, N, N-dimethylaminopropylacrylamide (DMAPAA) hydrochloride, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N- Propyl (meth) Acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, adhesive hydrogel according to claim 1 or 2 selected from acryloyl morpholine.   The adhesive hydrogel according to any one of claims 1 to 3, wherein the adhesive hydrogel further comprises 0.05 to 10 parts by weight of an electrolyte with respect to 100 parts by weight of the adhesive hydrogel.   It is a composition for adhesive hydrogel manufacture used for manufacture of the adhesive hydrogel as described in any one of Claims 1-4, Comprising: With respect to 100 weight part of said compositions for adhesive hydrogel manufacture , (Meth) acrylic acid, its derivative or 2.5 to 22.5 parts by weight of a vinyl derivative having 4 to 5 carbon atoms having two carboxyl groups and 2.5 to 22.5 parts by weight of (meth) acrylamide or its derivative A composition for producing an adhesive hydrogel, comprising a polymerizable monomer mixture, a crosslinkable monomer, water, a polyhydric alcohol, and 5 to 40 parts by weight of a polyvinyl pyrrolidone having a K value of 25 to 88.   A gel sheet comprising the adhesive hydrogel according to any one of claims 1 to 4.