JPH1095962A - Electroconductive adhesive composition, electroconductive pad obtained from the same composition and medical electrode using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, having stabilized adhesion characteristics and capable of preparing medical electrodes capable of withstanding repetitive uses by neutralizing a carboxyl group-containing acrylic polymer as a base polymer with a specific amine compound. SOLUTION: This composition comprises (A) an acrylic polymer, containing carboxyl groups neutralized with an alkanolamine and having 5,000-200,000 weight - average molecular weight, (B) a polyhydric alcohol, (C) water, (D) and electrolyte and (E) a glycidyl group-containing compound. The neutralization degree with the alkanolamine is preferably >=20mol% in the component A and the amount of the compounded component B is preferably regulated to 20-70wt.%. The moisture content of the component C is preferably 5-60wt.% in the composition. An electroconductive tacky pad can be prepared from the composition at 0.5-5mm thickness therein. Thereby, medical electrodes can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive pressure-sensitive adhesive composition and a medical electrode using the same, and more particularly to a method for relieving pain such as stiff shoulders and lower back pain by applying a low frequency weak current to a living body. Medical electrodes for therapeutic use, medical electrodes used for monitors such as electrocardiographs, electromyographs, and electroencephalographs that derive and measure weak currents in the body, earth electrodes used when using an electric scalpel, and hair removal The present invention relates to a medical electrode used for cosmetic applications such as treatment, a conductive pressure-sensitive adhesive composition which can be used for a conductive medium which needs conductivity in contact with a living body, and a medical electrode which can be used repeatedly. is there.

[0002]

2. Description of the Related Art Conventionally, a medical electrode which induces a blood flow by introducing an electric signal such as a weak current due to a low frequency or an electromagnetic wave due to a high frequency from the outside of a living body to promote a blood flow and a massage effect or the like is mainly used. Medical electrodes such as electrocardiographs, electroencephalographs, and electromyographs that take out and measure a weak current from a living body are known, and these electrodes are formed by laminating an electrode plate and a conductive adhesive layer. Is used.

[0003] Usually, a pressure-sensitive adhesive composition for forming the conductive pressure-sensitive adhesive layer comprises a water-soluble polymer represented by polyacrylic acid or sodium polyacrylate as a base polymer, to which water and an electrolyte are blended. A wet type is known.

On the other hand, medical electrodes using such a water-containing pressure-sensitive adhesive composition are roughly classified into a disposable type which is discarded after one or two uses and a repetitive type which is used several tens times. In the case of disposable medical electrodes,
The thickness of the pressure-sensitive adhesive layer is relatively thin, 200 μm or less, but in the repetitive type, the thickness of the pressure-sensitive adhesive layer is set to 500 μm or more in order to prevent the contained water from evaporating to increase the impedance. ing. further,
In the case of the repetitive type, the stratum corneum on the skin surface may peel off and transfer to the surface of the adhesive layer, and the adhesive strength may gradually decrease.Therefore, it is necessary to reduce the adhesive strength by blending a relatively large amount of a plasticizer. As a result, it is necessary to increase the thickness of the pressure-sensitive adhesive layer in order to maintain the necessary minimum skin adhesiveness.

[0005] As the above-mentioned disposable type medical electrode, there is one represented by JP-A-56-36939. This publication discloses a dry pressure-sensitive adhesive layer using a hydrophilic polymer containing a monomer unit containing at least 5 mol% of a carboxylate. However, the pressure-sensitive adhesive layer described in this publication does not substantially contain water, and absorbs (absorbs) moisture in the air in a short time to exhibit conductivity, and is not a crosslinked structure. That is, since the conductivity is developed by moisture absorption, the pressure-sensitive adhesive layer needs to be made as thin as possible for early conductivity development. In addition, since the pressure-sensitive adhesive layer is not a cross-linked structure, if the pressure-sensitive adhesive layer is thick, cohesive force is insufficient. Adhesion may be left on the skin surface. Therefore, it is clear that the medical electrode described in the publication is a disposable type having a thin adhesive layer.

In the present invention, a study was conducted to develop a medical electrode of a repetitive use type which is not a disposable type but has a low unit cost per use and is used for a long-time use. The characteristics include the following.

[0007] The exfoliated keratin is not transferred to the surface of the adhesive layer due to keratin damage to the skin, and the adhesive strength is not reduced. It is soft and has good wettability to the skin surface (adhesion to the skin surface). Minimize impedance changes due to fluctuations in water content.

As a method for satisfying the above characteristics, there is a method of blending a large amount of a softening agent such as a polyhydric alcohol and further partially cross-linking the pressure-sensitive adhesive layer. No., for example.

[0009]

Problems to be Solved by the Invention
No. 35706 discloses a medical electrode of a repetitive use type using an adhesive cross-linked hydrated gel made of a polyacrylic acid-based polymer cross-linked by a polyepoxide compound. Although this medical electrode satisfies the above-mentioned required characteristics, it is a water-containing type, so if it is used under conditions where the atmosphere is dry such as in winter or left for a long time,
As the contained water evaporates gradually and the impedance increases, the pressure-sensitive adhesive layer becomes hard, which may cause a decrease in adhesive strength and a decrease in skin adhesion. In particular, practically, a decrease in adhesiveness or skin adhesion causes an increase in contact resistance with the skin, and therefore, a conductive adhesive composition that does not change these properties even when water evaporates. Development is requested.

[0010]

The inventors of the present invention have repeatedly studied to provide a conductive pressure-sensitive adhesive composition satisfying the above characteristics and a medical electrode using the same. It has been found that the above-mentioned conventional problems can be solved by neutralizing with a specific amine compound using an acrylic polymer containing, and the present invention has been completed.

That is, the present invention provides a carboxyl group neutralized with an alkanolamine having a weight average molecular weight of 0.1.
50,000-200,000 acrylic polymer, polyhydric alcohol,
An object of the present invention is to provide a conductive pressure-sensitive adhesive composition comprising water, an electrolyte, and a glycidyl group-containing compound.

The present invention also provides a conductive pressure-sensitive adhesive pad formed by forming the above-mentioned conductive pressure-sensitive adhesive composition into a layer.

Further, the present invention provides a medical electrode comprising the above-mentioned conductive adhesive pad formed on one side of an electrode plate with a thickness of 0.5 to 5 mm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic polymer used in the conductive pressure-sensitive adhesive composition of the present invention is obtained by neutralizing a carboxyl group contained by using alkanolamine as a neutralizing agent. The carboxyl group-containing acrylic polymer that can be used can be obtained by copolymerizing a carboxyl group-containing monomer such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid alone or with another monomer. The monomer to be copolymerized is used for the purpose of imparting flexibility and adhesive properties to the adhesive layer. For example, (meth) acrylic acid ethyl ester, (meth) acrylic acid butyl ester, (meth) acrylic acid 2-hydroxyethyl ester, (Meth) acrylic acid esters such as (meth) acrylic acid polyethylene ester. When copolymerizing these monomers, it is necessary to adjust the obtained acrylic polymer to a range compatible with water or polyhydric alcohol, and practically 30% by weight or less in the obtained acrylic polymer. , Preferably 15% by weight or less.

In the present invention, the acrylic polymer has a weight average molecular weight of 0.5 to 200,000, preferably 1 to 15
Adjust to ten thousand. When the weight average molecular weight is less than 50,000, the molecular weight is too low to give sufficient cohesiveness to the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is inferior in shape retention and causes a phenomenon of adhesive residue on the skin surface. There is fear. On the other hand, when the weight average molecular weight exceeds 200,000, the solution viscosity increases, and a layer is formed (film formation).
Manufacturing problems such as difficulty are likely to occur.

Furthermore, in the present invention, it is important that the carboxyl group in the molecule of the acrylic polymer is neutralized with an alkanolamine. In other words, since the acrylic polymer before neutralization is strongly acidic in a water-containing state, when applied to the skin surface, skin irritation is strongly expressed,
It is necessary to adjust the pH to a weakly acidic to neutral region by neutralization. However, if only neutralization is used, sodium hydroxide or potassium hydroxide may be used, but when these neutralizing agents are used, since the carboxyl group is an alkali metal salt, the water content is When evaporated, the polymer tends to be hard and the tackiness tends to decrease.

On the other hand, surprisingly, the alkanolamines used in the present invention are less likely to cause the above-mentioned problems even if the water content is reduced, so that their adhesion is hardly reduced. It turned out. Thus, alkanolamines not only act as neutralizing agents,
It also acts as a stabilizer for the adhesive properties. Such alkanolamines include, for example, ethanolamine, diethanolamine, triethanolamine,
Or, a so-called monovalent alkanolamine such as a quaternary amine salt thereof may be used. Among them, it is preferable to use triethanolamine from the viewpoint of safety for a living body. Incidentally, a divalent or higher polyvalent amine such as polyethyleneimine or triethylenetetramine is not preferred because it rapidly reacts with a carboxyl group in the acrylic polymer to form a gel.

In the present invention, the degree of neutralization using an alkanolamine is at least 20 mol%, preferably 3 mol%.
When the content is 0 mol% or more, the pH of the pressure-sensitive adhesive composition of the present invention is in a weakly acidic to neutral range, which is preferable from the viewpoint of reducing skin irritation.

In the present invention, a polyhydric alcohol is added to the pressure-sensitive adhesive composition as a plasticizer. In other words, excellent flexibility is exhibited when a layer is formed by blending a polyhydric alcohol. Polyhydric alcohols also have good compatibility with the acrylic polymer and water. As such a polyhydric alcohol, for example, glycerin, polyglycerin, polyethylene glycol, polypropylene glycol, polyalkylene glycol and the like can be used. These may be used alone or in combination of two or more, and are desirably adjusted to be in the range of 20 to 70% by weight, preferably 30 to 60% by weight in the pressure-sensitive adhesive composition. If the compounding amount is less than 20% by weight, the water to be contained volatilizes less and is easy to dry,
In addition, there is a possibility that sufficient skin adhesion may not be obtained.
On the other hand, if it exceeds 70% by weight, the adhesive strength tends to decrease.

Further, in the present invention, water is contained in the pressure-sensitive adhesive composition in order to obtain a medical electrode of a repeated use type. The preferred water content is 5 to 5 in the pressure-sensitive adhesive composition.
It is in the range of 60% by weight, preferably 10 to 40% by weight. When the water content is less than 5% by weight, the electric resistance tends to increase, and when it exceeds 60% by weight, the adhesiveness becomes slightly inferior. It is preferable to adjust to.

Further, in the present invention, an electrolyte is blended in order to exhibit sufficient conductivity. Examples of the electrolyte that can be used include inorganic salts such as sodium chloride, potassium chloride, and lithium chloride. The electrolyte is preferably incorporated in the adhesive composition in a range of about 0.1 to 5% by weight.

The conductive pressure-sensitive adhesive composition of the present invention contains a glycidyl group-containing compound together with the above-mentioned components. The glycidyl group-containing compound is for externally cross-linking the acrylic polymer and forming a water-insoluble gel-like body by keeping polyhydric alcohol, water, and an electrolyte compatible in the obtained cross-linked structure. . Examples of such a glycidyl group-containing compound include compounds having at least two glycidyl groups in a molecule, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycerin diglycidyl ether. The compounding amount of the glycidyl group-containing compound is in the range of about 0.05 to 5 parts by weight, preferably 0.2 to 1 part by weight based on 100 parts by weight of the acrylic polymer.
If the amount is small, it is difficult to obtain a crosslinked structure having sufficient shape retention and water resistance, and if it is too large, the adhesiveness tends to decrease.

The conductive pressure-sensitive adhesive composition of the present invention contains the above components as essential components. If necessary, a crosslinking reaction accelerator such as a tertiary amine, an antioxidant, a light stabilizer, etc. In any amount.

By forming the conductive pressure-sensitive adhesive composition having the above structure into a layer, a conductive pressure-sensitive adhesive pad can be obtained. As a specific method for obtaining such a pad, for example, a solution containing the conductive pressure-sensitive adhesive composition, a uniform thickness on the treated surface of the separator subjected to a release treatment of the surface, or dried, The solution can be obtained by injecting and drying into a mold of any size whose inner surface has been release-treated.

In the present invention, a medical electrode can be obtained by forming the conductive adhesive pad on one side of an electrode plate with a thickness of 0.5 to 5 mm. The conductive adhesive pad in the medical electrode of the present invention is 0.5 to 5 mm, preferably 0.5 to 5 mm.
厚 み 3 mm in thickness range. If the thickness is too small, the effects of adsorption and desorption such as absorption (adsorption) of moisture in the atmosphere and reduced volatilization of moisture in the conductive adhesive pad will appear in a short time, resulting in an increase in the electrical resistance value or repeated Since the adhesive strength may be reduced by use, it is preferable to adjust the thickness to at least 0.5 mm or more.

As the electrode plate in the medical electrode of the present invention, a metal plate or a metal foil made of a metal such as aluminum, tin, silver, copper, nickel, or a metal plate or a metal foil made of an alloy such as nickel silver is used as it is. Or, or used as a conductive layer such as the above metal plate and metal foil, conductive paint, this is polyethylene terephthalate, polyethylene, polypropylene, ethylene / vinyl acetate copolymer, polyvinyl chloride,
A laminate formed on one side of a plastic film made of an insulating resin such as polyvinylidene chloride, an acrylic resin, a polyurethane resin, or the like can be given. The thickness of the electrode plate is preferably about 5 to 250 μm from the viewpoint of self-supporting property and handling (operability). When the electrode plate is a laminated plate, the conductive layer is preferably formed in the form of a foil or a vapor-deposited film. Therefore, it is usually preferable to use a metal layer having a thickness of 50 μm or less and a plastic film having a thickness of 2 to 200 μm. When the laminated plate is an electrode plate, when the thickness of the plastic film is thin, that is, when there is no rigidity, a fabric such as a nonwoven fabric or a woven fabric or a foam film can be appropriately laminated on the surface of the plastic film.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below and specifically described. Hereinafter, “parts” in the text means “parts by weight”.

Example 1 20 parts of polyacrylic acid (weight average molecular weight 100,000) was dispersed in 50 parts of glycerin, and 30 parts of water was added and dissolved by stirring. Thereafter, 20 parts of triethanolamine and 0.5 part of sodium chloride were added, and finally 0.4 part of triglycidyl isocyanate was added, and the mixture was sufficiently stirred and mixed. Acrylic acid neutralization degree 48
Mol%).

The obtained composition was applied to a release-treated surface of a polyethylene terephthalate separator having one surface subjected to a release treatment so as to have a thickness of 1 mm, and crosslinked to prepare a conductive adhesive pad. This pad was cut into a size of 50 mm × 50 mm, and its electric resistance was measured.
Ω. The electric resistance value of the conductive adhesive pad is
After separating the separator, sandwiching the front and back surfaces of the pad with a copper plate, sandwiching each copper plate with a metal cord, and applying an applied voltage of 1 with an LCR meter manufactured by Hewlett-Packard Company.
V, and the impedance was measured under the conditions of a measurement frequency of 1 kHz.

Comparative Example 1 20 parts of sodium polyacrylate was dispersed in 50 parts of glycerin, and 30 parts of water was added and dissolved by stirring. after that,
0.5 part of sodium chloride was added, and finally 0.4 part of triglycidyl isocyanate was added and sufficiently stirred and mixed to obtain a conductive pressure-sensitive adhesive composition.

The obtained composition was coated on a separator subjected to a release treatment in the same manner as in Example 1 and crosslinked to prepare a conductive adhesive pad having a thickness of 1 mm. This pad is 50mm x 50
It was cut into a size of mm and its electric resistance value was measured to be 25Ω.

The conductive pressure-sensitive adhesive pads obtained in Example 1 and Comparative Example 1 were laminated on one side of an electrode plate to form a 40 mm × 40
A medical electrode having a size of mm was produced. The electrode plate was a 75 μm-thick polyethylene terephthalate film having one surface coated with a conductive carbon paint at a thickness of 10 μm, and the conductive adhesive pad was laminated on the paint surface.

The separator was peeled off from the obtained medical electrode, the pressure-sensitive adhesive layer was exposed to the air, and left at 70 ° C. for 24 hours. The electric resistance value, shear stress and sensation before and after standing were measured by the following methods, and the results are shown in Table 1.
It was shown to.

<Electrical Resistance Value> After the separator was peeled off and the electrode plate was stuck on a copper plate, the terminal connection portion of the electrode plate and the copper plate were sandwiched by metal cords, respectively, and the applied voltage was measured with a Hewlett-Packard LCR meter. The impedance was measured under the conditions of 1 V and a measurement frequency of 1 kHz. In addition,
The electrode area was 50 mm × 50 mm.

<Shear stress> (Shear stress of electrode pad) The conductive adhesive pad is cut into a width of 20 mm x a length of 40 mm, and the thickness of the adhesive pad is measured with a sheet gauge. Next, the separator was removed and two file papers (20 mm
(Width x about 70 mm length) and are alternately stuck from the end of the adhesive pad in a sandwich shape, and are reciprocated once at a speed of about 50 mm / sec with a rubber roll having a load of 850 g. The crimped sample is sandwiched and set between the chucks of the rheometer, and the lower chuck is lowered at a speed of about 20 mm / min.
The stress at the time of 0% shift was measured.

<Sensitivity> A medical electrode obtained by using each of the examples and the comparative examples was attached to both of the electrodes, and a sensation test was performed by using a commercially available low-frequency treatment device. The evaluation was as follows. ：: An effect such as mom and tataku was obtained, and there was no discomfort such as tingling.

X: The effect of mom, tataku, etc. is hardly felt or tingling.

<Probe tack> Using a rheometer tester, a cylindrical probe having a diameter of 12 mm was brought into contact with the adhesive surface of the conductive adhesive pad by its own weight for 10 seconds, and then the probe was pulled up (separated). At this time, the peeling force (adhesive force) was measured.

[0039]

[Table 1]

As is clear from the results shown in Table 1, the moisture in the adhesive pad volatilizes (evaporates) in both the example product and the comparative example product, and the electric resistance value (impedance) increases.
The values of the shear stress and the probe tack varied less in the example product. As a result, the product of the example had good adhesion to the skin surface, so that a good result was obtained in the bodily sensation when used as a low-frequency therapeutic device.

[0041]

The conductive pressure-sensitive adhesive composition of the present invention uses an acrylic polymer containing a carboxyl group as a base polymer, neutralizes this polymer with a specific amine compound, and further removes water, polyhydric alcohol and electrolyte. Since it contains, the adhesive properties are stable even if the amount of water contained varies. Therefore, when a conductive pressure-sensitive adhesive pad is produced using the composition or a medical electrode is produced by laminating the pad on an electrode plate, it exhibits excellent properties that can withstand repeated use, which is not available in conventional products. Is obtained.

Claims (6)

[Claims] An alkanolamine-neutralized carboxyl group-containing acrylic polymer having a weight average molecular weight of 0.5 to 200,000, a polyhydric alcohol, water, an electrolyte, and a glycidyl group-containing compound. Conductive adhesive composition to be used. 2. The neutralization degree with an alkanolamine is 20.
The conductive pressure-sensitive adhesive composition according to claim 1, which is at least mol%. 3. The method according to claim 1, wherein the water content is 5 to 60% by weight.
The conductive pressure-sensitive adhesive composition as described in the above. 4. A conductive pressure-sensitive adhesive pad formed by forming the conductive pressure-sensitive adhesive composition according to claim 1 into a layer. 5. A medical electrode wherein the conductive adhesive pad according to claim 4 is formed on one surface of an electrode plate with a thickness of 0.5 to 5 mm. 6. The medical electrode according to claim 5, wherein the electrode plate has a conductive layer formed on one surface of a plastic film.