JPWO2019188818A1 - Hydrogel - Google Patents

Abstract

To provide a hydrogel having excellent adhesiveness to an electrode element, having optimum adhesive strength to the skin surface, and having corrosion resistance to corrosion objects such as aluminum and tin used as an electrode element. With the goal. The hydrogel 1 has a laminated structure of the A layer 10 and the B layer 20, and the A layer 10 contains a monomer-derived component, water, a moisturizer and an electrolyte, and the chloride ion concentration in the A layer 10 is the above. It is 2.0% by weight or less with respect to water, and the B layer 20 contains a monomer-derived component, water, a moisturizing agent and an electrolyte, and has a pH of 3 to 7.

Description

The present invention relates to hydrogels. In particular, it relates to a hydrogel in a medical electrode used by being attached to a living body.

For electrodes of automatic external defibrillators (AEDs) or electrodes for electrosurgical scalpels, and for medical electrodes used for electrocardiogram measurement and treatment using electrical stimulation such as low frequency and medium frequency. , A hydrogel adhesive material (medical electrode hydrogel) is used for the part to be attached to the living body. This hydrogel is arranged between an electrode element composed of a conductive material and a skin surface, and carbon, various metals, Ag-AgCl (silver / silver chloride) and the like are used as the conductive material.

In particular, in a medical electrode used as a counter electrode, if carbon or a silver sheet (printed matter such as Ag-AgCl) is used for the electrode, the electric capacity is insufficient and the electrode cannot be used. On the other hand, an electrode composed of aluminum can be used as a ground for a high current body of an electric knife, but aluminum is corroded by long-term storage or heat storage, the electrode area is reduced, and some conductivity is reduced. There was something. One of the major causes of corrosion is the electrolyte (chloride ion) contained in the hydrogel.

On the other hand, in Patent Document 1, the electrode element is described in a biological electrode including a conductive gel, an electrode element, and a cable for electrically connecting a biological electrode and an external device. Disclosed are bioelectrodes, which are thin films formed using an Al alloy that is transparent to X-rays and has corrosion resistance to conductive gels.

Japanese Unexamined Patent Publication No. 2013-192818

In the biological electrode (medical electrode) of Patent Document 1, the corrosiveness is reduced by adding a component such as Mn to aluminum to form an alloy, but the unit price of the electrode is high and the production lot is large. , It is difficult to manufacture at low cost.

Further, in order to secure a long shelf life of the medical electrode, it has been attempted to make the electrode element thicker in consideration of corrosion due to oxidation of the electrode element. However, if the electrode element is made thicker, the flexibility of the medical electrode is increased. Is reduced and the contact with the skin is deteriorated. In that case, there is a concern that problems such as burns may occur during defibrillation in AED applications. In addition, there is a concern that the electric heating area will decrease and the risk of burns will increase in the counter electrode application as well.

Therefore, the present invention has excellent adhesiveness to the electrode element, has optimum adhesive force to the skin surface, and has corrosion resistance to corrosion objects such as aluminum and tin used as the electrode element. The purpose is to provide a gel.

The present inventors prepared a plurality of gels containing an inorganic salt containing chloride ions on the electrode element side and an inorganic salt containing chloride ions on the skin side, and laminated these gels to prepare the above-mentioned gels. He found that the problem could be solved and completed the invention. That is, the gist of the present invention is as follows.

(1) A hydrogel having a laminated structure of A layer and B layer.
The layer A contains a monomer-derived component, water, a moisturizer, and an electrolyte, and the chloride ion concentration in the layer A is 2.0% by weight or less with respect to the water.
The B layer contains a monomer-derived component, water, a moisturizer, and an electrolyte.
The hydrogel having a pH of 3-7.
(2) The hydrogel according to (1) above, wherein the amount of the electrolyte added to the layer A is 60 to 100% by weight based on the solubility in water at 20 ° C.
(3) The hydrogel according to (1) or (2) above, wherein the monomer-derived component in the A layer and the monomer-derived component in the B layer are the same compound.
(4) The hydrogel according to (3) above, wherein the monomer-derived component contains a (meth) acrylic monomer.
(5) The hydrogel according to any one of (1) to (4) above, wherein the moisturizer is a polyhydric alcohol.
(6) The adhesive strength of the A layer to aluminum is 2.5 N / 20 mm or more, and the adhesive strength of the B layer to the bakelite plate is 1.0 to 9.0 N / 20 mm. The hydrogel according to any one of 5).
(7) Described in any one of (1) to (6) above, wherein the impedance of the laminated body with the SUS plate at a frequency of 1 kHz is 20 to 500 Ω, and the impedance at a frequency of 10 Hz is 200 to 600 Ω. Hydrogel.
(8) The hydrogel according to any one of (1) to (7) above, wherein an intermediate base material is embedded along the in-plane direction of the hydrogel having a laminated structure.
(9) The hydrogel according to any one of (1) to (8) above, which is a medical electrode hydrogel used by arranging it between an electrode element made of a conductive material and a skin surface. The medical electrode hydrogel, wherein the A layer is a layer in contact with the electrode element, and the B layer is a layer in contact with the skin surface.
This specification includes the disclosure content of Japanese Patent Application No. 2018-068906, which is the basis of the priority of the present application.

The hydrogel of the present invention adopts a laminated structure of a layer A containing only a small amount of chloride ions and a layer B, and controls the pH within a specific range to keep the overall impedance in a good range. While maintaining it, it is possible to suppress the corrosion attack on the electrode element due to the components in the hydrogel. Therefore, it is possible to inexpensively supply a medical electrode having high electrode performance with excellent stability over time.

It is a figure which shows typically the cross section of one Embodiment of the medical electrode using the hydrogel which concerns on this invention.

Hereinafter, the present invention will be described in detail.
FIG. 1 shows a cross section of an embodiment of a medical electrode using a hydrogel according to the present invention. The hydrogel 1 in this embodiment is formed by laminating the A layer 10 and the B layer 20. Next, the compositions of the A layer 10 and the B layer 20 will be described.

The layer A 10 contains a monomer-derived component, water, a moisturizer, and an electrolyte. The chloride ion concentration in the layer A 10 is 2.0% by weight or less with respect to water.

(Monomer-derived component)
The monomer-derived component used in the A layer is contained in the state of a water-soluble polymer containing a crosslinked site by polymerization. The water-soluble polymer can be obtained by a copolymer of a non-crosslinkable monomer and a crosslinkable monomer. For example, a copolymer of a water-soluble (meth) acrylic monomer and a crosslinkable monomer having two or more alkenyl groups can be used.

Examples of the (meth) acrylic monomer include (meth) acrylamide, N-alkyl modified (meth) acrylamide, N, N-dialkyl modified (meth) acrylamide, (meth) acrylic acid, alkyl (meth) acrylate and the like (meth). An acrylic monomer can be exemplified. Moreover, a water-soluble monomer such as N-vinylamide can be exemplified.

Further, as the crosslinkable monomer having two or more alkenyl groups, a crosslinkable monomer such as polyfunctional acrylate and polyfunctional acrylamide can be exemplified.

The crosslinked water-soluble polymer can form a matrix of water-soluble polymers. That is, it is a composition containing a crosslinked water-soluble polymer composed of monomer-derived components, water, a moisturizer and an electrolyte, and the water, the moisturizer and the electrolyte are contained in the matrix of the water-soluble polymer. The contained hydrogel can be obtained.

Specific examples of the non-crosslinkable monomer as a monomer-derived component constituting the water-soluble polymer will be described in more detail. (Meta) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl ( Non-electrolyte acrylamide derivatives such as meta) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, acryloylmorpholin, tarsal butyl acrylamide sulfonic acid (TBAS) and / or salts thereof, N , N-dimethylaminoethylacrylamide (DMAEAA) hydrochloride, electrolyte-based acrylamide derivatives such as N, N-dimethylaminopropylacrylamide (DMAPAA) hydrochloride, (meth) acrylic acid, maleic acid, itaconic acid, sulfopropyl methacrylate (SPM) ) And / or salts thereof, electrolyte-based acrylic derivatives such as methacryloyloxyethyl trimethylammonium chloride (QDM), and non-electrolyte-based acrylic derivatives such as hydroxyethyl (meth) acrylate and polyethylene glycol (meth) acrylate.

Specific examples of the crosslinkable monomer include N, N'-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, glycerin tri (meth) acrylate and the like. In addition, in this specification, "(meth) acrylic" and "(meth) acrylate" mean "acrylic and methacrylic", "acrylate and methacrylate", respectively.

The content of the crosslinked water-soluble polymer in the layer A is such that the non-crosslinkable monomer and the crosslinkable monomer are uniformly dissolved when the compounding solution containing the non-crosslinkable monomer and the crosslinkable monomer is prepared. For example, it is not particularly limited. However, the crosslinked water-soluble polymer is preferably 15% by weight or more based on the total amount of the A layer in order to maintain the gel strength of the obtained gel body and enhance the shape retention and processability. It is more preferably 18% by weight or more.

In addition, a non-crosslinkable monomer is used to form a matrix of crosslinked water-soluble polymers. The non-crosslinkable monomer is mainly water-soluble and has sufficiently high solubility in water, particularly at room temperature. In the case of a liquid monomer, a monomer that dissolves in water at an arbitrary ratio is preferable. On the other hand, in addition to water and the monomer, it may be necessary to dissolve a moisturizer, an electrolyte, and, if necessary, an additive such as a polymerization initiator in the composition constituting the layer A. In this case, The concentration of the crosslinked water-soluble polymer is preferably set to 35% by weight or less, more preferably 30% by weight or less, based on the total amount of the A layer.

The content of the crosslinkable monomer with respect to the total amount of the A layer should be appropriately set according to the molecular weight, chemical and physical properties of the non-crosslinkable monomer or the crosslinkable monomer, but the retention of the obtained gel body In order to improve the properties, it is preferably set to 0.01% by weight or more, and more preferably 0.05% by weight or more. On the contrary, it is preferable to set it to 1.0% by weight or less because it is easier to obtain the initial tack when used as an adhesive material if it has flexibility to the extent that the shape retention is not impaired. It is more preferable to set it to 6.6% by weight or less.

As described above, since the non-crosslinkable monomer occupies most of the matrix, it is preferable that the non-crosslinkable monomer has high water solubility. Is preferably at least _{20 (g / 100mL-H 2} O) or more in for example solubility, more preferably not more _{50 (g / 100mL-H 2} O) or more, and most preferably 65 (g / 100mL-H ₂ O) That's all.

Since the crosslinkable monomer forms a part of the matrix, the hydrophilicity of the entire matrix is not impaired even if a water-soluble monomer is not necessarily used. As a method of dissolving a crosslinkable monomer having low water solubility in the compounding solution, for example, when the crosslinkable monomer is a liquid, there is a method of dissolving it in a non-crosslinkable monomer, and moisturizing a polyvalent alcohol or the like in addition to the non-crosslinkable monomer. There is also a method of dissolving it in an agent and adding it.

(Moisturizer)
The layer A contains a moisturizer in order to improve moisturizing property and plasticity. As the moisturizer, it is preferable to use a polyhydric alcohol. Examples of polyhydric alcohols include diols such as ethylene glycol, propylene glycol and butanediol, polyhydric alcohols such as glycerin, pentaerythritol and sorbitol, polyhydric alcohol condensates such as polyethylene glycol, polypropylene glycol and polyglycerin, and poly. Polyhydric alcohol variants such as oxyethylene glycerin can be used. The moisturizer is liquid at room temperature (preferably at 10 ° C or higher below freezing point), and more specifically, it is multivalent in liquid in the temperature range where the gel is actually used (for example, around 20 ° C when used indoors). It is preferable to use alcohol.

Since the layer A contains water, the water tends to evaporate and / or dry in a short time without a moisturizer, the plasticity is impaired, and the adhesiveness, particularly the initial tacking force, tends to be significantly reduced. Further, when the hydrogel of the present invention is used for a medical electrode, when water evaporates, the impedance of the electrode becomes high, and when the electrode exceeds a specific impedance, it becomes unusable. Therefore, the moisturizer prevents the water from evaporating more than a certain amount by adding it to the A layer, and at the same time, if the moisturizer is liquid at room temperature, the moisturizer itself also has a function as a plasticizer.

The concentration of the moisturizer in the A layer is preferably 35% by weight or more, more preferably 40% by weight or more, based on the total amount of the A layer in order to maintain moisturizing property and plasticity and to exhibit excellent stability. Is more preferable. The amount of this moisturizer is 70% by weight or less with respect to the total amount of the A layer in order to secure a certain level or more of the resin solid content in order to secure the waist strength and adhesive strength of the obtained gel body. It is preferably present, and more preferably 65% by weight or less.

(water)
The concentration of water contained in the A layer is 13% by weight or more in the compounding solution, that is, 13% by weight or more based on the total amount of the A layer in order to stably disperse the water-insoluble polymer having adhesiveness described later. It is preferably 18% by weight or more. Further, in order to suppress fluctuations in gel physical properties due to evaporation and drying and to stabilize gel physical properties, it is preferably 40% by weight or less, and more preferably 30% by weight or less, based on the total amount of the A layer. For example, when glycerin is used as a moisturizer, it has a property (moisturizing property) of retaining about 20 to about 40% by weight of its own weight in a relative humidity range of about 50% to 70%. Furthermore, as a result of the inventors preparing hydrogels containing various moisturizers and obtaining moisturizing properties at a relative humidity of 60%, for example, the moisturizing properties of glycerin are about 30% by weight, and that of sodium lactate is about 80% by weight. %Met.

As described above, the moisturizing property of the moisturizer depends on the relative humidity, and the moisturizing property of the hydrogel using the moisturizer also depends on the relative humidity. It is possible to control the moisturizing property of the gel at a constant humidity by using a combination of moisturizers having different moisturizing powers, but the relative humidity dependence is practically uncontrollable because it is a property peculiar to the moisturizer. .. Based on the above, a moisturizer with low moisturizing properties (ideally, it should be liquid at room temperature) is used at a high concentration, and the water content in the gel design is set low to moisturize the gel. Although it is possible to apparently reduce the relative humidity dependence of the sex, in the A layer, in order to stably disperse the water-insoluble polymer having adhesiveness, etc., the water content should be maintained above the above concentration. Is preferable.

(Electrolytes)
The A layer contains an electrolyte. As a result, conductivity is imparted to the gel material constituting the A layer. The electrolyte is not particularly limited, and for example, alkali metal halides such as sodium halide, lithium halide and potassium halide; alkaline earth metals halide such as magnesium halide and calcium halide; and other metal halides. And so on. Further, as the above-mentioned electrolyte, various metals such as hypochlorite, chlorite, chlorite, perchlorate, sulfate, carbonate, nitrate and phosphate are also preferably used. In addition, as the above electrolyte, inorganic salts such as ammonium salt and various complex salts; 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; phthalic acid, succinic acid and adipine. Monovalent or divalent or higher salts of polyvalent carboxylic acids such as acids and citric acids; metal salts of organic acids such as sulfonic acid and amino acids; organic ammonium salts and the like are also suitable. Any one of these electrolytes can be used alone or in combination of two or more.

However, the chloride ion concentration in the A layer needs to be 2.0% by weight or less with respect to the water contained in the A layer. It is preferably 1.0% by weight or less, more preferably 0.5% by weight or less. This makes it possible to suppress the corrosion of aluminum and tin used as the electrode element in contact with the A layer in the medical electrode. Since the chloride ion concentration is 2.0% by weight or less with respect to water, it is preferable to use salts that do not contain chloride ions as the electrolyte, and as specific examples, sulfates and carbonates of alkali metals such as sodium. Etc., sulfates and carbonates of alkaline earth metals such as magnesium can be mentioned. Particularly preferred are sodium sulfate and magnesium sulfate. However, salts containing chloride ions such as sodium chloride are not excluded in the A layer, and the chloride ion concentration is 2.0% by weight or less, and if necessary, together with the above sulfates and the like. Can be contained.

The amount of the electrolyte added to the layer A varies depending on the type of electrolyte, but is preferably 0.05 to 10% by weight, more preferably 2 to 6% by weight, based on the total amount of the layer A. The amount of the electrolyte added is preferably 60 to 100% by weight with respect to the solubility in water at 20 ° C. (the limit amount of the electrolyte dissolved in water in the layer A). More preferably, it is 80 to 100% by weight. If the electrolyte content is too low, the impedance will be high and the conductivity will be impaired. Further, the impedance decreases as the content of the electrolyte increases, but if the content of the electrolyte is too large, the amount of water required for dissolution increases, which is not preferable.
The solubility of the electrolyte in water at 20 ° C. in the present invention is 19.5 (g / 100 mL-H ₂ O) for sodium sulfate, 33.7 (g / 100 mL-H ₂ O) for magnesium sulfate, and chloride, respectively. Sodium is 35.89 (g / 100 mL-H ₂ O).

(Water-insoluble polymer)
A water-insoluble polymer having adhesiveness can be added to the A layer, if necessary. Examples of the water-insoluble polymer having adhesiveness include those obtained by polymerizing one or more hydrophobic monomers such as (meth) acrylic ester, vinyl acetate, and maleic acid ester. Specifically, it is a single or copolymer of a hydrophobic monomer such as isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, butyl (meth) acrylate, vinyl acetate, and dioctyl maleate. In addition to the above, any one or more of hydrophobic monomers such as ethylene, propylene, butylene, methyl (meth) acrylate and ethyl (meth) acrylate may be further copolymerized. It is also possible to use a silicone adhesive or a natural rubber-based or synthetic rubber-based adhesive. Among these, the acrylic ester copolymer has been repeatedly improved and is preferably used because of its high adhesiveness.

In order to disperse the water-insoluble polymer having adhesiveness in the layer A, it is preferable to use an emulsion in which the polymer is emulsified and dispersed. Generally, the solid content of the emulsion is 30-60% by weight, and most of the rest is water. For example, as an emulsion of an acrylic ester-based copolymer resin, a trade name "Polysol PSA SE-1730" manufactured by Showa High Polymer Co., Ltd., a trade name "Viniblanc ADH-1048" manufactured by Nisshin Chemical Industry Co., Ltd., etc. are preferably used. ..

The content of the water-insoluble polymer having adhesiveness in the A layer may be adjusted according to the effect expected for the final product, but in order to obtain good adhesiveness to the electrode element, the content of the total amount of the A layer may be adjusted. It is preferable to add 3% by weight or more. It is more preferably 5% by weight or more, and particularly preferably 8% by weight or more. A large amount may be added, but if the amount added is too large, the adhesive strength does not improve more than a certain value, and the conductivity of the hydrogel also decreases when used as a medical electrode hydrogel. It is preferable that the amount is 20% by weight or less based on the total amount of the A layer in consideration of the balance. It is more preferably 15% by weight or less, and particularly preferably 13% by weight or less.

Further, the water-insoluble polymer having adhesiveness is preferably a copolymer of the hydrophobic monomer and the hydrophilic monomer. Copolymerizing a hydrophilic monomer with a hydrophobic monomer has an advantage that the dispersion stability of a water-insoluble polymer is increased and the addition of a dispersant, a surfactant, or the like can be reduced.

When the water-insoluble polymer having adhesiveness is a copolymer of a hydrophobic monomer and a hydrophilic monomer, dispersion stabilization is performed when the copolymerization ratio of the hydrophilic monomer in the copolymer is 0.1% by weight or more. The effect of Further, when the copolymerization ratio is more than 5% by weight, it becomes difficult to produce the polymer, according to JP-A-2002-80809, JP-A-2003-336024, and JP-A-2003-335805. Have been described. Therefore, as the water-insoluble polymer, it is preferable to use a copolymer of a hydrophobic monomer and a hydrophilic monomer in which the copolymerization ratio of the hydrophilic monomer is 0.1 to 5% by weight.

Examples of the hydrophilic monomer include hydroxyethyl (meth) acrylate, polyethylene glycol (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and the like. N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, acryloylmorpholin, tertiary butylacrylamide sulfonic acid (TBAS) and / or a salt thereof, N, N-dimethylaminoethylacrylamide (DMAEAA) hydrochloric acid Salts, N, N-dimethylaminopropylacrylamide (DMAPAA) hydrochloride, (meth) acrylic acid, maleic acid, itaconic acid, sulfopropylmethacrylate (SPM) and / or salts thereof, methacryloyloxyethyltrimethylammonium chloride (QDM), etc. Water-soluble monomer of. Among these, it is desirable to contain a water-soluble monomer containing at least one carboxyl group, and in particular, (meth) acrylic acid and / or a salt thereof is a general-purpose monomer and is preferably used, and among them, alkyl acrylate. It is preferable to use an ester.

(Aphiphile polymer)
If necessary, the layer A in the hydrogel according to the present embodiment may contain an amphipathic polymer to impart good adhesion to an electrode element made of a conductive material. Further, by containing the amphipathic polymer and also including the water-insoluble polymer having adhesiveness, the dispersion stability of the water-insoluble polymer is improved. In particular, since the dispersion stability of the water-insoluble polymer becomes good at the time of preparing the compounding solution forming the A layer, a more uniform and high quality stability A layer of a good hydrogel can be obtained.

In the present invention, amphipathic means that it is soluble in at least a mixed solvent of organic solvent and water, and is preferably soluble in both water and a polar organic solvent. An example of a mixed solvent of an organic solvent and water is a mixed solvent of ethanol / water = 60/40. Therefore, the amphipathic polymer corresponds to a polymer that dissolves in a mixed solvent of ethanol / water = 60/40 at room temperature.

In the present embodiment, polyvinyl alcohol having a saponification degree of 50 to 98% can be used as the amphipathic polymer. If the degree of saponification is less than 50% or more than 98%, water solubilization becomes difficult, if not impossible, and the handleability during production is lowered. Regarding the degree of saponification of polyvinyl alcohol, a degree of saponification of 98% or more is referred to as complete saponification, about 98% to 80% is referred to as partial saponification, and less than that is referred to as low saponification. With regard to partial saponification, when distinguishing in more detail, those having a saponification degree of about 95% may be referred to as intermediate saponification, and those having a saponification degree of about 95% to 80% may be referred to as partial saponification. The degree of saponification is a percentage calculated by the following formula.
Degree of saponification = polyvinyl alcohol unit /
(Vinyl acetate unit + polyvinyl alcohol unit) x 100
* Calculate by substituting the amount of substance (number of moles) of each unit into the above formula.

Specific examples of polyvinyl alcohol with a degree of saponification of 50 to 98% include the product name "J Poval JMR-10M" of Japan Vam & Poval Co., Ltd. (65% degree of saponification) and the product name of Nippon Synthetic Chemical Industry Co., Ltd. "Gosefa". Immers LW-300 "(Kenification degree 53-60%), Denka Poval MP-10" (Kenka Poval MP-10), Nippon Vam & Poval Co., Ltd. product name "J Poval VP" -18 ”(88% degree of saponification) and the like.

Further, as the amphipathic polymer, a water-soluble polymer such as polyacrylic acid or a salt thereof may be contained. Examples of such a water-soluble polymer include a copolymer of acrylic acid and methacrylic acid, a polymer containing acrylamide of N-alkylsulfonic acid as a constituent unit, and the like. Any of these may be used alone, or a plurality of types may be used in combination. The copolymer of acrylic acid and methacrylic acid preferably has a copolymerization ratio (molar ratio) of acrylic acid and methacrylic acid of 9: 1 to 1: 9.

The copolymer of acrylic acid and methacrylic acid can be produced, for example, by a method such as radical polymerization, redox reaction, or light irradiation. As such a copolymer of acrylic acid and methacrylic acid, commercially available products such as Julimer AC-20H and AC-20L (trade name) manufactured by Toagosei Co., Ltd. and FL-200 (trade name) manufactured by Nippon Shokubai Co., Ltd. are available. It can also be used.

The weight average molecular weight of the polymer containing acrylamide N-alkylsulfonic acid as a constituent unit is not particularly limited, but in order to make the compounding solution easy to prepare and the obtained hydrogel to exhibit the optimum adhesive strength. It is preferably 7 million or less. Further, it is preferably 500,000 or more in order to obtain a cohesive gel.

The polymer containing acrylamide N-alkylsulfonic acid as a structural unit may be a copolymer with another polymer. Examples of the above-mentioned copolymers on the market include copolymers of acrylic acid and acrylamide N-alkylsulfonic acid. Specifically, a copolymer of acrylic acid and acrylamide methylpropane sulfonic acid (Alonbis AH-305 (trade name) manufactured by Toagosei Co., Ltd.) or the like can be used.

When the polymer containing acrylamide N-alkylsulfonate as a constituent unit is a copolymer with another polymer, the copolymerization ratio (molar ratio) is the polymer containing acrylamide N-alkylsulfonate: other polymer = 2. : 8 to 8: 2, more preferably 2: 8 to 5: 5.

The amount of the amphipathic polymer added to the layer A is preferably 0.05% by weight or more based on the total amount of the layer A in order to obtain the effect of improving the dispersion stability of the compounding solution by the addition. It is preferably 0.1% by weight or more. If the amount added is too large, the viscosity of the compounding solution increases, so it takes time for the bubbles mixed in during the preparation of the compounding solution to escape, and if the amount of electrolyte added is large, the water-insoluble polymer tends to aggregate. Tend. Therefore, the amount of the amphipathic polymer added is 5.0% by weight or less, preferably 4.0% by weight or less, based on the total amount of the A layer. In order to improve the dispersion stability, the effect can be sufficiently obtained with this amount of addition.

(PH adjuster)
The layer A is heated or light-irradiated with a compounding solution containing at least the monomers constituting the monomer-derived components, water, a moisturizer and an electrolyte, a water-insoluble polymer and an amphipathic polymer used as necessary, and a polymerization initiator. This can be obtained by subjecting it to a polymerization reaction. The pH of the obtained layer A is in the range of 3 to 7. Originally, when a water-soluble acrylic ester or acrylamide derivative, whether a monomer or a polymer, is stored in an alkaline aqueous solution, hydrolysis of an ester group or an amide group proceeds. On the contrary, even if the pH becomes too acidic, hydrolysis proceeds in the same manner. Therefore, by adjusting the pH to 3 to 7, the hydrolysis of the acrylic monomer can be suppressed, and the storage stability of the compounding solution and the long-term storage stability after gel formation are improved.

Since the pH of the hydrogel is adjusted to 3 to 7 in the layer A, a pH adjusting agent can be added as needed. The pH can be adjusted to 3 to 7 by adding a certain amount of mineral acid or organic acid to the compounding solution as a pH adjuster. In this case, it is preferable to use a polyfunctional mineral acid and / or an organic acid. Furthermore, it is preferable to use a mixture of the acid and its salt because pH buffering property is exhibited and the pH can be further stabilized.

Examples of the mineral acid include sulfuric acid, phosphoric acid, carbonic acid and the like. Examples of the organic acid include polyfunctional carboxylic acids such as citric acid, oxalic acid, malonic acid, succinic acid and tartaric acid. The amount of the mineral acid, the organic acid, and salts thereof, which are pH adjusters, is not particularly limited, and can be appropriately set according to the ability of the pH adjuster.

(Polymerization initiator)
The compounding solution may contain a photopolymerization initiator. The photopolymerization initiator is preferably one that is cleaved by ultraviolet rays or visible light to generate radicals, and examples thereof include α-hydroxyketone, α-aminoketone, benzylmethylketal, bisacylphosphine oxide, and metallocene. More specifically, 2-hydroxy-2-methyl-1-phenyl-propane-1-one (product name: DaroCure 1173, manufactured by Ciba Speciality Chemicals Co., Ltd.), 1-hydroxy-cyclohexyl-phenyl-ketone (product). Name: Irgacure 184, manufactured by Ciba Speciality Chemicals Co., Ltd., 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-propane-1-one (Product name: Irgacure 2959, Ciba) Specialty Chemicals Co., Ltd.), 2-Methyl-1-[(Methylthio) phenyl] -2-morpholinopropan-1-one (Product name: Irgacure 907, Cibas Specialty Chemicals Co., Ltd.), 2-Benzyl- 2-Dimethylamino-1- (4-morpholinophenyl) -butane-1-one (product name: Irgacure 369, manufactured by Ciba Speciality Chemicals Co., Ltd.), 2-Hyrodoxy-1- {4- [4- (2) -Hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1-one (product name: Irgacure 127, manufactured by Ciba Speciality Chemicals Co., Ltd.) and the like. These can be used alone or in combination of two or more.

The amount of the photopolymerization initiator added is preferably 0.01% by weight or more in 100% by weight of the pre-gelling compounding solution in order to sufficiently carry out the polymerization reaction and reduce residual monomers, and the photopolymerization initiator is started. It is preferably 1.0% by weight or less in order to prevent discoloration (yellowing) and odor due to the reaction residue of the agent. More preferably, it is 0.05 to 0.5% by weight.

(Surfactant)
When forming the A layer, a surfactant can be added to the compounding solution. Surfactants make it possible to reduce the tendency of aggregation of water-insoluble polymers and amphipathic polymers due to salting out. In particular, a surfactant having a polyoxyethylene alkyl ether sulfate group is preferable. In order to obtain the effect of adding these surfactants, it is preferable to add 0.1% by weight or more with respect to the compounding solution, and when the influence on adhesiveness and other performance is taken into consideration, the compounding solution It is preferably added in an amount of 2.0% by weight or less. The method of adding the surfactant is not particularly limited.

(Peroxide)
Further, if necessary, by adding at least 0.003% by weight of a peroxide to the compounding solution, it is possible to prevent yellowing of the gel after polymerization. It should be noted that even if 0.3% by weight or more is added to the compounding solution, not only does the yellowing prevention effect not cause a large difference, but also a large amount of peroxide remains in the gel, so that when used as a medical electrode, There is a high risk of corroding the conductive material that makes up the electrode element. Peroxides remaining in the gel are reduced by aging for a certain period of time after gel formation. Aging refers to accelerating the decomposition of peroxides and the like by allowing the gel to stand under constant temperature conditions. In order to promote the decomposition of peroxide, it is preferable to set the aging temperature to 30 ° C. or higher. In addition, if the aging temperature is too high, there is a risk that the gel matrix, etc. will decompose and deteriorate, and the protective film, etc. that will be attached to the gel will shrink, causing wrinkles and deformation. It is preferably set to 60 ° C. or lower. The most preferable aging temperature is 35 to 45 ° C.

Examples of the peroxide include hydrogen peroxide, sodium percarbonate, sodium perborate, peracetic acid, chlorine dioxide and the like. It is preferable that these peroxides are diluted with water to 10% or less before being added to the compounding solution. Also, once added to the formulation, the formulation should be used within 24 hours. If a long period of time has passed since the addition of these peroxides, the polymerization reaction may start and a gel may be formed unintentionally.

Subsequently, the composition of the B layer 20 to be laminated with the A layer 10 will be described. Like the A layer, the B layer contains at least a monomer-derived component, water, a moisturizer, and an electrolyte. The contents of the monomer-derived components, water, moisturizer and electrolyte in the B layer, and their addition amounts are the same as in the case of the A layer. However, in the B layer, there is no limitation on the electrolyte as in the A layer in which the chloride ion concentration is 2.0% by weight or less with respect to water, and even salts containing chloride ions such as sodium chloride 2 It can be blended in excess of 0.0% by weight. As a result, the impedance of the entire hydrogel in which the A layer and the B layer are laminated is adjusted, and it can be used as a medical electrode.

In layer B, components other than monomer-derived components, water, moisturizers and electrolytes, for example, water-insoluble polymers, amphipathic polymers, pH adjusters, surfactants, peroxides, etc. to be added as needed. Is the same as in the case of the A layer.

The pH of the entire hydrogel 1 including the A layer 10 and the B layer 20 is preferably in the range of 3 to 7, and particularly preferably 4 to 7. Originally, when a water-soluble acrylic ester or acrylamide derivative, whether a monomer or a polymer, is stored in an alkaline aqueous solution, hydrolysis of an ester group or an amide group proceeds. On the contrary, even if the pH becomes too acidic, hydrolysis proceeds in the same manner. Therefore, by adjusting the pH to 3 to 7, it becomes possible to suppress the hydrolysis of the acrylic monomer, and the long-term storage stability after gel formation is also improved. Further, by adjusting the pH of the entire hydrogel 1 to 3 to 7, it leads to prevention of corrosion of the electrode element and the like and reduction of irritation to the skin (pain, redness, etc.).

The optimum range of impedance of the entire hydrogel 1 including the A layer 10 and the B layer 20 varies depending on the type of medical electrode and is not particularly limited, but preferably, the frequency measured for the laminate with the SUS plate is 1 kHz. The impedance at 10 Hz is 20 to 500 Ω, and the impedance at a frequency of 10 Hz is 200 to 600 Ω. Within the above range, noise generated when used as a medical electrode can be reduced.

Here, a specific method for measuring impedance at a frequency of 1 kHz or 10 Hz is as follows. First, two sets of hydrogels to be measured with a SUS plate attached are prepared, and test pieces in which the gel portions are in contact with each other are prepared. Then, when an input voltage of 10 V, a resistance of 1 MΩ, and a current of 10 μA of 1 kHz to 10 Hz are applied to this test piece, the voltage applied between the SUS plates can be read with an oscilloscope, and the impedance can be obtained by the following formula (Ohm's law). it can.
｜ Z ｜ ＝ E / I
(| Z | is the impedance value (Ω) of the hydrogel, E is the voltage value (V) read by the oscilloscope, and I is the current applied to the test piece.)

Further, the monomer-derived component in the A layer and the monomer-derived component in the B layer may be different compounds or the same compound, but are preferably the same. As a result, the compositions of the A layer and the B layer are similar, and the adhesion between the layers can be further improved.

In the hydrogel according to the present embodiment, the content of water contained in the A layer and the B layer is determined by, for example, taking out a sample of the A layer or the B layer having a predetermined weight, drying the sample, and measuring the dry weight. Then, it can be determined by a method of calculating and determining the difference between the initial weight and the dry weight, or by a volumetric titration method, a coulometric titration method or the like using a Karl Fischer moisture measuring device.

Further, in the hydrogel according to the present embodiment, the content of the moisturizer contained in the layers A and B is not limited, but for example, means such as solvent extraction method and liquid chromatography (LC) can be used. Can be quantified using.

In the hydrogel 1 of the present embodiment, on the A layer 10 side, the chloride ion concentration is 2.0% by weight or less with respect to water, so that corrosion of aluminum or the like can be suppressed. Taking advantage of this feature, the hydrogel 1 of the present embodiment can be used as a medical electrode hydrogel by adhering the A layer 10 to the electrode element 30 made of a conductive material, as shown in FIG. In FIG. 1, a protective film 40 such as polyethylene terephthalate that has been further subjected to a mold release treatment is laminated on the B layer 20, and when used, the protective film 40 is peeled off and the B layer 20 side is attached to the skin. used.

The electrode 30 is formed by printing and coating a conductive ink containing a metal such as Ag, Ag / AgCl, carbon or the like on a resin film which is the surface base material 50 to form a conductive layer, or the surface base material 50 is used. It can be obtained by laminating a conductive film in which a metal foil (aluminum, stainless steel, Ag, tin, etc.) or carbon is kneaded onto a certain resin film to form a conductive layer.

The thickness of the resin film as the surface base material 50 is preferably about 5 μm to 150 μm. The material of the resin film is not particularly limited, but synthetic paper suitable for printing (polypropylene to which an inorganic filler is added), PET, OPP film and the like are preferable. Further, in order to improve the appearance, paper, non-woven fabric, and foam (polyethylene, polyethylene) are applied to the surface of the surface base material 50 opposite to the electrode 30 to the extent that cosmetic printing is not applied or the flexibility is not impaired. (Soft foam sheet such as vinyl acetate and polyurethane), a film or sheet such as polyurethane may be laminated.

Considering the use as a hydrogel for medical electrodes, etc., the specific adhesive strength of each of the A layer and the B layer is that the adhesive strength of the A layer to aluminum is 2.5 N / 20 mm or more, and the B layer. The adhesive strength to the bakelite plate is preferably 1.0 to 9.0 N / 20 mm. More preferably, the adhesive force of the A layer to aluminum is 7 to 15 N / 20 mm, and the adhesive force of the B layer to the bakelite plate is 1.5 to 8 N / 20 mm. Within this range, it is optimal as an adhesive force to the electrode 30 and the skin surface.

In the present invention, the adhesive strength to aluminum is measured as follows. First, the hydrogel is cut into 120 mm × 20 mm, an aluminum film (PET / aluminum (1N30) laminated product (manufactured by Totai Co., Ltd .; 9 μm)) is attached to the side of the A layer to be measured, and a 2 kg crimping roller is attached. It is reciprocated once and allowed to stand at room temperature for 1 day, and then a synthetic paper coated with an inorganic filler is attached to the surface of the hydrogel opposite to the side to which the aluminum film is attached to prepare a test piece. Subsequently, the surface on the aluminum film side is adhered to SUS using double-sided tape, the end of the hydrogel with synthetic paper is peeled off from the aluminum film, and JIS is used using a leometer (manufactured by Sun Scientific Co., Ltd., CR-500DX). -Z0237: Measure the stress value (N / 20 mm) at a predetermined peeling time (30, 40, 50, 60, 70 mm) from the measurement start point under the measurement conditions of 90 degrees and a speed of 300 mm / min according to 2009. The average value of the values of the three tests (15 points in total) is used as the adhesive strength to aluminum. The measurement shall be performed in an environment with a temperature of 23 ± 5 ° C. and a humidity of 55% ± 10%.

The adhesive strength to the bakelite plate is measured as follows. That is, a hydrogel is cut into a size of 120 mm × 20 mm, a bakelite plate is attached to the side of the B layer to be measured (the A layer when measuring the A layer), and a 2 kg crimping roller is reciprocated once to prepare a test piece. Then, using a rheometer (manufactured by Sun Scientific Co., Ltd., CR-500DX), the measurement conditions were set to an angle of 90 degrees and a speed of 300 mm / min according to JIS-Z0237: 2009, and a predetermined peeling point (30,) from the measurement start point. The stress value (N / 20 mm) at 40, 50, 60, 70 mm) is measured, and the average value of the values of the three tests (15 points in total) is used as the adhesive strength to the bakelite plate. The measurement shall be performed in an environment with a temperature of 23 ± 5 ° C. and a humidity of 55% ± 10%.

The thickness of each of the A layer 10 and the B layer 20 can be appropriately set in consideration of the application and the like. Specifically, the thickness of the A layer is 0.2 to 1.2 mm, the thickness of the B layer is 0.2 to 1.2 mm, and the ratio of the thickness of the A layer to the B layer is 1: 6 to 6. It is preferably 1: 1 and more preferably 1: 3 to 3: 1.

Further, as shown in FIG. 1, the intermediate base material 60 can be embedded in the hydrogel 1 along the in-plane direction of the hydrogel 1, if necessary. These intermediate base materials 60 are used to reinforce the gel and improve the shape retention during cutting. For example, when hydrogel 1 is distributed as an intermediate material for processing, these intermediate base materials are necessary for easy handling by a terminal processor. As the intermediate base material, a non-woven fabric or a woven fabric is preferably used. As the material of the non-woven fabric and the woven fabric, natural fibers such as cellulose, silk and linen, synthetic fibers such as polyester, nylon, rayon, polyethylene, polypropylene and polyurethane, or blends thereof can be used.

A semipermeable membrane is also preferably used as an intermediate base material. This semipermeable membrane is composed of cellophane, cellulose acetate, etc., and is more difficult for water and moisturizers to pass through than woven fabrics or non-woven fabrics. Therefore, the compositions of the A layer and the B layer at the time of production are maintained for a longer period of time. be able to.

If the thickness of the intermediate base material is too thick, the permeability of the liquid deteriorates, which may adversely affect the conductivity. On the contrary, if it is too thin, the hydrogel may be reinforced in the same manner as when the basis weight is too small. Since there is a possibility that it will not be possible, it will be set appropriately in consideration of these. It is preferably in the range of 0.02 to 2.0 mm. Further, it is more preferably 0.02 to 0.5 mm, and particularly preferably 0.03 to 0.3 mm.

The total thickness of the hydrogel in the present invention is preferably 0.4 to 2.4 mm, more preferably 0.6 to 1.5 mm, and preferably 0.7 to 1.0 mm. Especially preferable. The thickness of the hydrogel can be determined by measurement with a micrometer or the like.

Hydrogel 1 is produced by preparing a compounding solution containing necessary components for each of the A layer and the B layer, and sequentially polymerizing and laminating the compounding solution by heating or light irradiation. Can be done.

In the case of the A layer compounding solution, as an example, an emulsion of a water-insoluble polymer is added to a solution in which an amphipathic polymer previously dissolved in water is further diluted with water and uniformly stirred, if necessary. , Uniformly disperse. Next, a moisturizer is added and stirred until uniformly dispersed. This is referred to as [Liquid 1].

Then, the monomer is added to [Liquid 1] and stirred. Depending on the type of monomer, heat may be absorbed or heat may be generated during dissolution. Therefore, it is preferable to heat the monomer when it absorbs heat and cool it when it generates heat. When heating or cooling, the temperature of [Liquid 1] is preferably set to be in the range of 10 ° C to 50 ° C, and more preferably 20 ° C to 40 ° C. If the temperature is too low, it takes time to dissolve the monomer itself, especially in the case of a solid monomer, and it also takes time to dissolve the additive components other than the monomer. Depending on the components to be added, it may not dissolve if the temperature is too low. In addition, when the temperature drops extremely, emulsions and other polymer components may aggregate. In addition, if the temperature is too high, the emulsion may be poorly dispersed, or if a highly reactive component is contained, the reaction may start or run away, and the volatile components in the compounding solution may evaporate, as designed. In some cases, the compounding solution cannot be obtained.

The electrolyte is preferably added after the step of adding the monomer. When the electrolyte is added, the emulsion and other polymer components may aggregate due to salting out, but the effect of suppressing aggregation can be obtained by dissolving the monomer first. It is presumed that the monomer itself acts as a surfactant, but the detailed mechanism is unknown.

Next, a compounding solution is obtained by adding a necessary component other than the above and a polymerization initiator, stirring and mixing until all the components are completely dissolved.

The compounding solution of the B layer can also be prepared in the same manner as the compounding solution of the A layer. The procedure for preparing the mixed solution of the A layer and the B layer is not limited to the above procedure.

The storage of each compounding solution is not particularly limited as long as the emulsion to be added and other components are stable, but it is preferably stored in the range of 0 ° C to 50 ° C, and should be stored in the range of 20 ° C to 40 ° C. Is even more preferable.

The method for producing the hydrogel 1 is not particularly limited because detailed conditions differ depending on the composition of the A layer and the B layer, the material of the intermediate base material, the thickness, and the like. For example, when embedding an intermediate base material, the intermediate base material is held in the air with a certain amount of tension applied to the intermediate base material, and a monomer compounding solution is poured into the upper and lower sides of the intermediate base material. A method of polymerizing by light irradiation or the like to form a sheet, or an intermediate base material in which a sheet-like A layer and B layer gel material having a smooth surface is prepared and then held under a certain tension or more. Is sandwiched between these gel materials and composited, or a sheet-like A layer having a smooth surface is prepared, and a certain amount of tension or more is applied on the A layer as needed. A method or the like in which an intermediate base material is placed, a B-layer monomer compounding solution is poured onto the intermediate base material, and further polymerization is carried out by light irradiation or the like can be appropriately adopted. It is also possible to supply the hydrogel in a roll form and continuously carry out the above-mentioned manufacturing process.

Normally, the compounding solution of the B layer is first dropped onto a resin film or the like (base film), and the upper surface thereof is covered with a release-treated resin film or the like (top film) to spread the solution and control the thickness to a certain level. In this state, the compounding solution is polymerized and crosslinked by irradiation with heat or light (ultraviolet rays) to obtain a gel body having a certain thickness. As the base film, polyester, polyolefin, polystyrene, polyurethane, paper, paper laminated with a resin film, or the like can be used.

When the base film is used as the protective film 40, a film having a mold release treatment on the surface of polyester, polyolefin, polystyrene, paper, paper laminated with a resin film, or the like is preferably used. In particular, biaxially stretched PET film, OPP, and the like are preferable. Examples of the release treatment method include silicone coating, and in particular, a baking type silicone coating that is crosslinked and cured by heat or ultraviolet rays is preferable.

As the top film, it is basically possible to use the same material as the base film, but when gel is formed by light irradiation, it is necessary to select a material that does not block light.

After the gel is continuously polymerized and crosslinked, an intermediate base material is placed on the generated B layer as needed, and the compounding solution of the A layer is dropped onto the intermediate base material, and the top is further formed as in the case of the B layer. A hydrogel having a laminated structure of A layer and B layer can be obtained by covering with a film, spreading the liquid, and subjecting it to heat or light irradiation to polymerize and crosslink.

In addition, the compounding solution includes preservatives, bactericides, fungicides, rust inhibitors, antioxidants, stabilizers, fragrances, colorants, etc., as well as anti-inflammatory agents, vitamins, whitening agents, etc. Medicinal ingredients may be added as appropriate.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Example 1)
-Preparation of compounding solution for layer A As shown in Table 1, using a stirring / mixing container, acrylamide as a non-crosslinkable monomer and methylenebisacrylamide as a crosslinkable monomer were combined in an amount of 19.96% by weight, ion-exchanged water 17. After 93% by weight was mixed and stirred to uniformly dissolve, 57.69% by weight of glycerin was added as a moisturizing agent, and the mixture was stirred until uniform as described above. Next, sodium sulfate was 2.80% by weight as an electrolyte, sodium chloride was 0.61% by weight, and citric acid, sodium benzoate, a photopolymerization initiator, and a surfactant were combined as 0.31% by weight as other additives. It was added and stirred until completely dissolved. Finally, 0.70% by weight of an acrylic acid-methacrylic acid copolymer (Julimer AC-20H, manufactured by Toa Synthetic Co., Ltd.) was added as an amphipathic polymer, and the mixture was stirred until uniform to prepare a transparent compounding solution. Obtained.

-Adjustment of the compounding solution of layer B Using a stirring / mixing container, as shown in Table 1, 20.13% by weight of acrylamide as a non-crosslinking monomer and methylenebisacrylamide as a cross-linking monomer, ion-exchanged water 18. After 08% by weight was mixed and stirred to uniformly dissolve, 58.19% by weight of glycerin was added as a moisturizing agent, and the mixture was stirred until uniform as described above. Next, 0.70% by weight of sodium sulfate, 1.89% by weight of sodium chloride was added as an electrolyte, and 0.31% by weight of citric acid, sodium benzoate, a photoinitiator, and a surfactant were added as other additives. And stirred until completely dissolved. Finally, 0.70% by weight of Julimer AC-20H (manufactured by Toagosei Co., Ltd.) was added as an amphipathic polymer, and the mixture was stirred until uniform to obtain a transparent compounding solution.

-Manufacture of hydrogel By dropping the obtained compounding solution of layer B on a silicone-coated PET film and passing it through a certain clearance, the solution is spread evenly and the thickness becomes 0.5 mm. Fixed as. By irradiating this with ultraviolet rays at an energy amount of 500 mJ / cm ² using a metal halide lamp, a B layer having a thickness of 0.5 mm was obtained. An intermediate base material (nylon mesh) is placed on the obtained B layer, the compounding solution of the A layer is dropped onto the layer B, and a PET film coated with silicone is applied over the layer to spread the solution uniformly. , Fixed so that the thickness was 0.5 mm. It performs irradiation of infrared rays (total 3500mJ / cm ² for B layer) by using a metal halide lamp energy 3000 mJ / ^cm 2, to obtain a total thickness of 1.0mm hydrogel.

(Example 2)
The compounding liquids of the A layer and the B layer were prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 3)
The compounding solution of the layer A was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1.
Regarding the B layer, finally, as a water-insoluble polymer, an emulsion of an acrylic ester-based copolymer resin (solid content 50% by weight, trade name "Polysol PSA SE-1730", manufactured by Showa High Polymer Co., Ltd.) was added by 22.86 weight. % (Solid content 11.43% by weight, water 11.43% by weight), as an amphoteric polymer, polyvinyl with a saponification degree of 65% instead of the acrylic acid-methacrylic acid copolymer (Julimer AC-20H). Alcohol was added in an amount of 0.19% by weight, and the preparation was carried out in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1, to obtain a milky white compounding solution. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 4)
The weight% of each component of the A layer and the B layer was changed as shown in Table 1, and the B layer was replaced with an acrylic acid-methacrylic acid copolymer (Julimer AC-20H) as an amphipathic polymer. A compounding solution of the A layer and the B layer was prepared in the same manner as in Example 1 except that 2.87% by weight of polyvinyl alcohol having a saponification degree of 88% was added. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 5)
The compounding solution of the layer A was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1.
Regarding layer B, 1.09% by weight of acrylic acid-acrylamide methylpropanesulfonic acid copolymer (Aronbis AH-305X, manufactured by Toagosei Co., Ltd.) was added as an amphipathic polymer, and the weight% of each component is shown. A hydrogel was produced by preparing in the same manner as in Example 1 except that the changes were shown in 1.

(Example 6)
The compounding liquids of the A layer and the B layer were prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 7)
Regarding layer A, the weight% of each component was changed as shown in Table 1, and an emulsion of an acrylic ester-based copolymer resin (Polysol PSA SE-1730) as a water-insoluble polymer was added as a solid content in the compounding solution. .09% by weight was added, and 0.18% by weight of polyvinyl alcohol having a saponification degree of 88% was used as the amphoteric polymer in place of the acrylic acid-methacrylic acid copolymer (Julimer AC-20H). A compounding solution was prepared in the same manner as in Example 1 except that it was added. Regarding the layer B, a compounding solution was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 8)
For layer A, a compounding solution was prepared in the same manner as in Example 7 except that the weight% of each component was changed as shown in Table 1. For the B layer, 3.07% by weight of polyvinyl alcohol having a saponification degree of 65% was added as an amphipathic polymer in place of the acrylic acid-methacrylic acid copolymer (Julimer AC-20H), and each component was added. A compounding solution was prepared in the same manner as in Example 7 except that the weight% was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 9)
The compounding liquids of the A layer and the B layer were prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 10)
For layer A, a compounding solution was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. For the B layer, the weight% of each component was changed as shown in Table 1, and a compounding solution was prepared in the same manner as in Example 1 except that sodium sulfate was not added. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Example 11)
Regarding layer A, a compounding solution was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1 and magnesium sulfate was added in an amount of 4.80% by weight instead of sodium sulfate. .. Regarding the B layer, a compounding solution was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1 and 1.23% by weight of magnesium sulfate was added instead of sodium sulfate. .. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Actual comparison example 12)
The layer A was prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. For the B layer, the weight% of each component was changed as shown in Table 1, and a compounding solution was prepared in the same manner as in Example 1 except that sodium sulfate was not added. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Comparative Examples 1 to 6)
The compounding liquids of the A layer and the B layer were prepared in the same manner as in Example 1 except that the weight% of each component was changed as shown in Table 1. Using each of these compounding solutions, a hydrogel was produced in the same manner as in Example 1.

(Adhesive strength evaluation method)
For the obtained hydrogels of Examples 1 to 12 and Comparative Examples 1 to 6, the adhesive strengths of the A layer and the B layer to the bakelite plate, aluminum and the skin were measured. The evaluation method of each adhesive strength is as follows.

・ Adhesive strength evaluation (Bakelite board)
The hydrogel was cut into 120 mm × 20 mm, the PET film was peeled off, a bakelite plate was attached to the gel surface, and a 2 kg crimping roller was reciprocated once to obtain a test piece. A rheometer (CR-500DX manufactured by Sun Scientific Co., Ltd.) was used for the measurement, and the measurement conditions were an angle of 90 degrees and a speed of 300 mm / min according to JIS-Z0237; 2009. The stress value (N / 20 mm) at a predetermined peeling point (30, 40, 50, 60, 70 mm) is measured from the measurement start point, and the average value is calculated from the values of 3 tests (15 points in total), and this value is obtained. Was used as the adhesive strength of the hydrogel to the bakelite plate of the A layer or the B layer. The measurement was carried out in an environment of a temperature of 23 ± 5 ° C. and a humidity of 55% ± 10%.

・ Adhesive strength evaluation (skin)
The hydrogel was cut into 120 mm × 20 mm, and a synthetic paper coated with an inorganic filler was attached to the gel surface that appeared after peeling off the PET film in order to make a handle at the time of measurement, and used as a test piece. Then, 5 subjects (men and women in their 20s to 50s) were admitted to the measurement room in an environment of a temperature of 23 ± 5 ° C. and a humidity of 55% ± 10% 15 minutes before application. The test piece was attached to the inside of each subject's forearm with as little hair as possible, and maintained in that state for 30 minutes. A rheometer (manufactured by Sun Scientific Co., Ltd., CR-500DX) was used for the measurement, and the measurement conditions were an angle of 180 degrees and a speed of 1000 mm / min. The stress value (N / 20 mm) at a predetermined peeling point (30, 40, 50, 60, 70 mm) is measured from the measurement start point, and the average value is calculated from the values of the two tests (10 points in total), and this value is obtained. Was defined as the adhesive strength of the hydrogel layer B to the skin.

・ Adhesive strength evaluation (aluminum)
Cut out the hydrogel to 120 mm x 20 mm, peel off the PET film, attach an aluminum film (PET / aluminum (1N30) laminate (manufactured by Totai Co., Ltd .; 9 μm)) to the gel surface, and use a 2 kg crimping roller. After one round trip and crimping, it was allowed to stand at room temperature for one day. Then, a synthetic paper coated with an inorganic filler was attached to the other gel surface to make a handle for measurement, and used as a test piece. The surface on the aluminum film side was adhered to SUS using double-sided tape. Then, the end of the gel with the synthetic paper coated with the inorganic filler is peeled off from the aluminum film, and a rheometer (manufactured by Sun Scientific Co., Ltd., CR-500DX) is used for the measurement, and the measurement conditions are according to JIS-Z0237; 2009. Was performed at an angle of 90 degrees and a speed of 300 mm / min. The stress value (N / 20 mm) at a predetermined peeling point (30, 40, 50, 60, 70 mm) is measured from the measurement start point, and the average value is calculated from the values of 3 tests (15 points in total), and this value is obtained. Was defined as the adhesive strength of the Hydrogel A layer to aluminum. The measurement was carried out in an environment of a temperature of 23 ± 5 ° C. and a humidity of 55% ± 10%.

(Hydrogen ion concentration evaluation method)
The hydrogel was cut into a size of 20 × 20 mm, a drop of ion-exchanged water was dropped on the gel surface that appeared after peeling off the PET film, and a pH test paper (manufactured by Whatman Co., Ltd.) was allowed to stand on it. The degree of color change after 1 minute was visually judged.

(Impedance evaluation method)
The hydrogel was cut into 20 x 20 mm, the gel surface (layer A) that appeared after peeling off the PET film was attached to a 25 x 10 mm SUS304 (thickness 2 mm) to make another same one, and each PET film was made. The gel surfaces (layer B) that appeared after peeling off were bonded together to form a test piece. When an input voltage of 10 V, a resistor of 1 MΩ, and a current of 1 kHz and 10 Hz are applied to this test piece, the voltage applied between the SUS plates is read by an oscilloscope (Tektronix; TDS3014), and the impedance value is measured by the following formula (Ohm's law). Asked.
｜ Z ｜ ＝ E / I
| Z | is the impedance value (Ω), E is the voltage value (V) read by the oscilloscope, and I is the current 10 (μA) applied to the electrodes.

(Aluminum corrosiveness evaluation method)
The hydrogel was cut into 100 x 250 mm, the gel surface (layer A) that appeared after peeling off the PET film was attached to a PET / aluminum (1N30) laminate (manufactured by Totai Co., Ltd .; 9 μm), and ovened at 50 ° C for 10 days. The number of pinholes generated in the aluminum was visually confirmed. In Table 1, those in which no pinholes were observed are marked with ◯, those in which one pinhole was observed are marked with Δ, and those in which multiple pinholes were observed are marked with x.

(Method for evaluating solubility of compounding solution)
The appearance when the compounding solution was prepared was visually confirmed, and those in which the compound was uniformly dissolved were marked with ◯, and those in which insoluble components were observed were marked with x.
The above evaluation results are shown in Table 1.

As shown in Table 1, the hydrogels of Examples 1 to 12 in which the chloride ion concentration in the layer A is 2.0% by weight or less with respect to water and the pH is in the range of 3 to 7 are electrode elements. It was possible to prevent the corrosion of aluminum while having the optimum adhesive strength against aluminum and the skin surface. Further, the hydrogels of Examples 1 to 12 have a good impedance value, and as a hydrogel used for a medical electrode, they have excellent conductivity and can reduce noise.

On the other hand, the hydrogels of Comparative Examples 2 to 4 in which the chloride ion concentration in the layer A exceeded 2.0% by weight caused corrosion of the aluminum foil and were unsuitable as a hydrogel for a medical electrode. Further, the hydrogels of Comparative Examples 1 and 6 in which no electrolyte is added to both the A layer and the B layer or the B layer have high impedance, and the measurement accuracy may be low as the hydrogel of the medical electrode. Was the result.

1 Hydrogel 10 A layer 20 B layer 30 Electrode element 40 Protective film 50 Surface base material 60 Intermediate base material All publications, patents and patent applications cited herein are incorporated herein by reference in their entirety. To do.

Claims (9)

A hydrogel having a laminated structure of A layer and B layer.
The layer A contains a monomer-derived component, water, a moisturizer, and an electrolyte, and the chloride ion concentration in the layer A is 2.0% by weight or less with respect to the water.
The B layer contains a monomer-derived component, water, a moisturizer, and an electrolyte.
The hydrogel having a pH of 3-7. The hydrogel according to claim 1, wherein the amount of the electrolyte added to the layer A is 60 to 100% by weight based on the solubility in water at 20 ° C. The hydrogel according to claim 1 or 2, wherein the monomer-derived component in the A layer and the monomer-derived component in the B layer are the same compound. The hydrogel according to claim 3, wherein the monomer-derived component contains a (meth) acrylic monomer. The hydrogel according to any one of claims 1 to 4, wherein the moisturizer is a polyhydric alcohol. Any one of claims 1 to 5, wherein the adhesive force of the A layer to aluminum is 2.5 N / 20 mm or more, and the adhesive force of the B layer to the bakelite plate is 1.0 to 9.0 N / 20 mm. The hydrogel described in the section. The hydrogel according to any one of claims 1 to 6, wherein the impedance of the laminate with the SUS plate at a frequency of 1 kHz is 20 to 500 Ω, and the impedance at a frequency of 10 Hz is 200 to 600 Ω. The hydrogel according to any one of claims 1 to 7, wherein an intermediate base material is embedded along the in-plane direction of the hydrogel having a laminated structure. A medical electrode hydrogel used by being arranged between an electrode element made of a conductive material and a skin surface, which comprises the hydrogel according to any one of claims 1 to 8, and is the A layer. Is a layer in contact with the electrode element, and the B layer is a layer in contact with the skin surface. The medical electrode hydrogel.

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