JPH03258239A - Conductive gel and electrode pad using the same - Google Patents

Abstract

PURPOSE:To obtain a conductive gel excellent in stickiness and shape retention by constituting the conductive gel so that a specific polyfunctional compound is contained in an amount of 2.0-35%. by wt. of a hydrophilic monomer and, further, water, a plasticizer, an electrolyte and a polymerization intiator are contained. CONSTITUTION:The main composition of a conductive gel consists of a hydrophilic polymer, a crosslinking agent, a plasticizer, and an electrolyte and, as the crosslinking agent, a polyfunctional compound with an MW of 400 or more having two or more (meth)acryloyl or vinyl groups is used and the conductive gel is obtained by irradiating a mixture consisting of the polyfunctional compound, the hydrophilic monomer, polyhydric alcohol, the electrolyte and a polymerization initiator with light or heating said mixture. As the hydrophilic monomer, there are vinyl ether, polyethylene glycol monoacrylate and the like and, as the electrolyte, there are lithium chloride, sodium chloride, potassium chloride and the like. As the plasticizer, glycerine and polyhydric alcohol such as glycols are used and a photosensitizer such as amines or a sulfur compound may be added in order to accelerate polymerization reaction. As a result, the conductive gel simultaneously satisfying both of stickiness and shape retention is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a conductive gel and an electrode pad using the same, and in particular, it is used for applying electrodes to the human body during treatment using a low frequency treatment device or electrocardiogram measurement. This invention relates to an electrode pad that can be reliably fixed to the skin and can be reused without leaving any residue on the skin after the pad is peeled off.

[Prior Art] In recent years, in the medical field, conductive hydrogels made by crosslinking hydrophilic polymers by some method have been disclosed or used as a substitute for conductive creams or pastes to improve the adhesion between the skin and electrodes. It is covered with cloth.

For example, Japanese Utility Model Publication No. 61-42564 discloses "polyacrylic acid or its salt and a polyepoxy compound," and JP-A-60-153839 discloses "a carboxyl group-containing polymer and a polyamine or polyepoxy compound." JP-A No. 62-8607 discloses polyammonium salts.
Publication No. 6 discloses "a polyurethane polyol prepolymer and a polyisocyanate prepolymer having an alkylene oxide chain." Note that these formulations contain polyhydric alcohols as plasticizers, electrolytes, and the like.

[Problems to be solved by the invention] However, the conductive gels with known compositions so far have
It is not necessarily the case that adhesive properties and gel shape retention properties are satisfied at the same time, and those with high shape retention properties have problems in wettability and adhesiveness to the skin.

For example, in the case of electrode pads for low-frequency therapy machines, if the adhesiveness is poor, there is a problem in that a lot of electrical noise is generated. In addition, since the shape retention of the conductive gel is insufficient, it is necessary to sandwich a mesh-like reinforcing carrier in the center of the conductive gel, or to sandwich the conductive gel between mesh-like reinforcing carriers. Therefore, there was a problem in that the manufacturing process became complicated. Another problem was that it was difficult to punch out with a die. An electrode pad in which a mesh-like carrier is sandwiched in the center of gel is disclosed in Japanese Patent Application Laid-open No. 58-1.
It is disclosed in Japanese Patent Publication No. 83137, Japanese Utility Model Publication No. 6CI-31682, and Japanese Patent Application Laid-open No. 116324/1983. The gel sandwiched between meshes was created in 1986-146.
It is disclosed in Japanese Patent No. 902.

Furthermore, in the case of an electrode in which a mesh-like carrier is sandwiched between conductive gels, if the carrier is not placed precisely in the center of the conductive gel, the adhesion strength tends to vary between the top and bottom surfaces of the electrode pad. There was a problem.

An object of the present invention is to solve the above-mentioned problems and provide a conductive gel with excellent adhesiveness and shape retention, and a carrier-free electrode pad using this gel.

[Means for Solving the Problems] In order to achieve such an object, the conductive gel of the present invention has a wood-philic monomer, two or more (meth)acryloyl groups or vinyl groups, and has a molecular weight of 4006) 2.0 to 35 wt% of the polyfunctional compound to the hydrophilic monomer
and further contains water, a plasticizer, an electrolyte, and a polymerization initiator.

In addition, the electrode pad of the present invention has a wood-philic monomer and two or more (meth)acryloyl groups or vinyl groups, and has a molecular weight of 4006). 35 wt%, and further contains water, a plasticizer, an electrolyte, and a polymerization initiator.

[Function] The main components of the ion conductive gel are a hydrophilic polymer, a crosslinker, a plasticizer, and an electrolyte. The present inventor uses the polyfunctional compound (having two or more (meth)acryloyl groups or vinyl groups and a molecular weight of 4006) as a crosslinking agent, and uses the polyfunctional compound, a wood-philic monomer, a polyhydric alcohol, an electrolyte, We have discovered that a gel obtained by irradiating or heating a mixture of water and a polymerization initiator has both good shape retention and adhesive properties.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

The raw materials for the conductive gel were mixed as shown below, and the conductive gel was produced according to the steps from (1) to (2).

Wood-loving Jozuma 20.0g Glycerin 60.0g Water 10.0g Potassium hydroxide 5.0g Lithium chloride 2.5g Photopolymerization initiator 0.1g Polyfunctional compound
Xg ■ Inject nitrogen gas into the liquid mixture obtained by mixing the above raw materials to drive out oxygen in the liquid.

■Pour the mixed solution into a vat lined with release film. The thickness of the conductive gel is adjusted by the amount of the mixed solution flowed at this time.

■Place a release film on the surface of the mixed solution.

(2) Irradiate the mixture with ultraviolet light for about 30 seconds through the release film to solidify it.

■Punch the prepared conductive gel into the desired shape (.

Various conductive gels were produced by the above-mentioned process by changing the combination of the hydrophilic monomer and the polyfunctional compound and the amount of the polyfunctional compound. Benzyl dimethyl ketal (trade name: Irgacure 651, manufactured by Ciba Geigy) was used as a photopolymerization initiator. Glycerin is a plasticizer.

Potassium hydroxide is a neutralizing agent, and when using acrylic acid as the wood-philic monomer, the neutralizing agent may or may not be used, but it is better to add it to adjust the pH of the mixed solution. Lithium chloride is an electrolyte.

The preparation of decaglycerol trimethacrylate used in the examples will be explained below.

Dissolve commercially available decaglycerin in dimethyl sulfoxide and add isocyanate ethyl methacrylate (
IEMA) was added at an arbitrary ratio and stirred for about 5 hours to introduce a methacryloyl group into decaglycerin. Next, the reaction solvent was distilled off to obtain decaglycerol trimethacrylate, which is a polyfunctional oil sesame. Although isocyanate ethyl methacrylate was used as the isocyanate monomer, any monomer that can introduce a (meth)acryloyl group or a vinyl group may be used.

The amount of the polyfunctional compound blended was varied from 1 to 5 g by using acrylic acid as the Daiichikyou L-L 2 diphilic monomer and decaglycerin trimethacrylate as the polyfunctional compound.

Example 1...1g Example 2...2g Example 3...3g Example 4...4g Example 5...5g Acrylamide, polyfunctional compound as decaglycerin trimethacrylate,
The blending amount of the polyfunctional compound was varied from 1 to 3 g.

Example 6...1g Example 7...2g Example 8...3g Contains amount of polyfunctional compound where the hydrophilic monomer is N-vinyl 2-pyrrolidone and the polyfunctional compound is decaglycerin trimethacrylate. was varied from 1 to 3 g.

Example 9...1g Example 10...2g Example 11...3g Loss of polyfunctional compound using acrylic acid as the l-mer hydrophilic monomer and polyethylene glycol 600 diacrylate as the polyfunctional compound The amount added was varied.

Example 12: 0.5g Example 13: 1.0g For comparison with Examples 1 to 13, conductive gels shown in Comparative Examples 1 to 12 were prepared.

A The wood-philic monomer was used as acrylic acid, the polyfunctional monomer was used as triglyceryl diacrylate, and the amount of the polyfunctional compound was varied from 0.1 to 1 g.

Comparative example 1...031g Comparative example 2...0.3g Comparative example 3...0.5g Comparative example 4...1.0g The compound was polyethylene glycol 200 diacrylate, and the amount of the polyfunctional compound was varied.

Comparative example 5...0.1g Comparative example 6...0.3g Comparative example 7...0.5g Comparative example 8...1. Og L1 inhibition-1, the hydrophilic monomer was acrylic acid, the polyfunctional compound was decaglycerin trimethacrylate, and the blending amount of the polyfunctional compound was varied.

Comparative example 9...0.3g Comparative example IO...8. Og L1 - Dan - H The wood-philic monomer was acrylic acid, the polyfunctional compound was polyethylene glycol 500 diacrylate, and the blending amount of the polyfunctional compound was varied.

Comparative example 11...0.1g Comparative example 12...0.3g Examples 2 and 3 were tested using a commercially available low frequency healing machine (manufactured by Tateishi Electric Co., Ltd., Elepuls HV-FO6). Electrical stimulation was obtained.

Tables 1 and 2 show the results of evaluating the adhesiveness and shape retention of the conductive gels produced in the above-mentioned Examples and Comparative Examples. Adhesiveness was evaluated by applying finger pressure to the conductive gel, and shape retention was evaluated by cutting the conductive gel into 4 cm long and 4 cm wide pieces and pasting them on the skin on the inside of the lower arm, and measuring the conductivity after peeling them off. Evaluation was made based on the shape of the gel.

Table 1 Table 2 Adhesion 0: Very strong adhesion O: Good adhesion △: Acceptable adhesion (but somewhat weak) Adhesive residue shape retention ○: Good shape retention △: Acceptable shape retention ×: Little or no shape retention As can be seen from Table 1, the conductive gels produced in Examples were It was possible to satisfy both tackiness and shape retention properties at the same time.Furthermore, it was possible to satisfy both tackiness and shape retention properties at the same time over a wide range of compounding amounts of the crosslinking agent.

On the other hand, in the comparative examples, it was not possible to obtain a product that satisfied both adhesion and shape retention properties at the same time.

For example, in Comparative Example 1-4, when the amount of triglycerin diacrylate, which is a crosslinking agent, is increased, the shape retention improves, but the tackiness is good when the amount of crosslinking agent is 0.3g. When the amount exceeds 0.5 g, the adhesive becomes almost non-sticky. Comparative Example 5-8 and Comparative Example 9-1
Similarly, in Example 2, there was a tendency that when the amount of crosslinking agent exceeded a certain level, the adhesiveness of the conductive gel almost disappeared. Outside the scope of this claim, for example, the molecular weight is 40
If the amount of the polyfunctional compound having 0 or more and 2 or more (meth)acryloyl or vinyl groups added is less than 2 wt% based on the wood-philic monomer (Comparative Example 9, 11, 12), sufficient protection can be obtained. Moldability cannot be obtained, and conversely, if it exceeds 35 wt%, there is almost no tackiness (Comparative Example 10)
.

In the above-mentioned examples, everything except the blended amount of the polyfunctional compound was constant, but it is not limited to this (as long as it is within the standard blended range).

In the above examples, decaglycerin trimethacrylate (molecular weight Mw + 1195) was used as the polyfunctional compound, but it is not limited to this. It may be glycerin poly(meth)acrylate or polyglycerin polyvinyl. As the hydrophilic monomer, vinyl ether polyethylene glycol monoacrylate, etc. may be used (but is not limited by the examples. Also, the polyglycerin used to synthesize the polyglycerin-derived polyfunctional compound may be an isomer). Good too.

The neutralizing agent is not limited to potassium hydroxide, and for example, sodium hydroxide or the like may be used. The electrolyte is not limited to lithium chloride; for example, sodium chloride, potassium chloride, lithium perchlorate, or the like may be used.

The plasticizer may be any material as long as it can plasticize the hydrophilic polymer and has a moisturizing effect; for example, polyhydric alcohols such as glycerin, pentaerythritol, and glycols are preferably used.

When using a photopolymerization initiator, in addition to the standard formulation, a photosensitizer such as amines, sulfur compounds, and nitrogen compounds may be added to promote the polymerization reaction. Additionally, synthetic, semi-synthetic or natural hydrophilic polymers such as polyvinylpyrrolidone, polyvinyl alcohol, hydroxyethyl cellulose, sodium alginate, pullulan, etc. may be added as film reinforcement agents to reinforce the conductive gel film. .

Furthermore, in order to further adjust the shape retention properties, lipophilic monomers such as acrylic acid, esters, or styrene may be copolymerized.

Although a photopolymerization initiator is used in the Examples and Comparative Examples, a thermal polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, and potassium persulfate may also be used. In addition, the initiator is selected depending on the composition of monomers and other components.

[Effect of the invention 1 As explained above, in the present invention, the molecular weight is 4
Since the conductive gel is prepared using a polyfunctional compound having 00 or more and two or more (meth)acryloyl groups or vinyl groups as a crosslinking agent, the conductive gel satisfies both adhesiveness and shape retention properties at the same time. It has the effect of being able to obtain

Claims (1)

[Scope of Claims] 1) Contains 2.0 to 35 wt% of a hydrophilic monomer and a polyfunctional compound having two or more (meth)acryloyl groups or vinyl groups and having a molecular weight of 400 or more based on the hydrophilic monomer. , further comprising water, a plasticizer, an electrolyte, and a polymerization initiator. 2) The conductive gel according to claim 1, wherein the polymerization initiator is a photopolymerization initiator. 3) The conductive gel according to claim 1, wherein the conductive gel further contains a film reinforcing agent. 4) The conductive gel according to claim 1, wherein the conductive gel further contains a lipophilic monomer. 5) The conductive gel according to claim 1, wherein the polyfunctional compound is a polyglycerin derivative. 6) The conductive gel according to claim 1, wherein the polyfunctional compound is a polyethylene glycol derivative. 7) Contains 1.0 to 35 wt% of a hydrophilic monomer and a polyfunctional compound having two or more (meth)acryloyl groups or vinyl groups and a molecular weight of 400 or more based on the hydrophilic monomer, and further includes water and a plasticizer. , an electrode pad comprising a conductive gel containing an electrolyte and a polymerization initiator.