JPH0146144B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to medical electrodes, and particularly to bioelectrodes that are attached to the skin. Conventionally, in detection applications such as electrocardiograms and electroencephalogram measurements, or current transmission or stimulation applications such as pain relief, so-called electrode pastes and hydrocarbon Gels have been used to apply conductive elements to the skin. Recently, as an alternative to these electrode pastes and hydrogels, flexible sheet-like bioelectrodes based on high molecular weight polysaccharides plasticized with polyhydric alcohols have already been proposed (U.S. Patent No.
4125110 specification, etc.). This electrode has ideal bio-skin compatibility due to its excellent PH buffering effect, antibacterial effect, water retention and water absorption ability, etc., as well as a certain degree of self-shape retention, good skin adhesion and conductivity. However, when used under high temperature, high humidity, or sweaty conditions such as in the summer, it loses its shape retention. The inventors of the present invention have discovered that the material has a serious drawback of being easily fluidized and deformed. Therefore, the main object of the present invention is to overcome the above-mentioned drawbacks of bioelectrodes mainly composed of high molecular weight polysaccharides, and to develop a novel bioelectrode with significantly improved shape retention that can withstand use under high temperature, high humidity and sweaty conditions. The purpose is to provide bioelectrodes. The problem of the above-mentioned improvement of the present invention is that in a bioelectrode based on a high molecular weight polysaccharide plasticized with a polyhydric alcohol, metals of divalent or higher valence that exhibit basicity in the presence of amphoteric or water. A water-soluble or slightly water-soluble oxide, hydroxide, or a weak acid salt thereof is added to the polysaccharide.
0.5 to 20 parts by weight per 100 parts by weight, preferably 1 to 10 parts by weight
This can be achieved very effectively by adding parts by weight. Here, the high molecular weight polysaccharide usually has a molecular weight of about 300,000 or more, more preferably about 300,000 or more.
Various high molecular weight polysaccharides having 1 million or more acidic groups such as carboxyl groups and carboxylic acid groups in their structures (hereinafter, polysaccharides having these acidic groups or acid groups in their structures are referred to as "acidic polysaccharides"). Examples of preferred examples include gum karaya, gum tragacanth, and gum xanthan. Particularly preferred is gum karaya, which has a relatively large amount of carboxyl groups and whose aqueous solution is acidic. and resinous polysaccharides such as gum tragacanth. Furthermore, if necessary, two or more types of polysaccharides may be appropriately mixed and used. Further, as the polyhydric alcohol, ethylene glycol and propylene glycol, which can soften and plasticize these polysaccharides, and particularly preferably glycerin are used. The blending ratio of both as a base material is usually 25 to 70% by weight of acidic polysaccharide, preferably 30 to 65% by weight, and 75 to 30% by weight of polyhydric alcohol, preferably 70 to 35% by weight. In addition, these base materials can usually be further mixed with a required amount of commonly used additives such as electrolyte and water in order to impart desired conductivity, pH value, etc. to the electrode. The invention is not particularly limited with respect to the type and amount of these commonly used additive aids. On the other hand, as the polyvalent metal oxide, hydroxide or salt, various polyvalent metal compounds that are amphoteric or exhibit alkalinity in the presence of water can be used as described above, but preferred ones include magnesium, Examples include oxides or hydroxides of calcium, barium, lead, zinc, iron, aluminum, or weak organic acid salts thereof such as lactate and citrate; particularly useful ones include MgO, ZnO, CaO, PbO. , Zn(OH) ₂ ,
Mg(OH) ₂ , Al(OH) ₃ , Ca(OH) ₂ , Ba(OH) ₂ ,
Iron citrate, etc. may be mentioned. Although the details of the mechanism of action of the reaction between these metal compounds and high molecular weight polysaccharides are not necessarily clear, as shown in the examples below, carboxyl groups,
A high molecular weight polysaccharide having acidic groups such as carboxylic acid groups or acid groups and swollen and plasticized by a polyhydric alcohol and a basic or amphoteric metal compound first undergo a kind of neutralization reaction, and finally It is presumed that the crosslinking reaction of polysaccharides by polyvalent metal ions is achieved, resulting in a marked improvement in the shape retention and elasticity of the product. In other words, the crosslinked structure of polysaccharides due to polyvalent metal ions cannot be created simply by providing a large amount of metal ions.
It can be said that it is effectively formed only on the premise of a preliminary reaction mechanism similar to acid/base neutralization reactions. In fact, according to the knowledge of the present inventors, even if a water-soluble neutral or acidic polyvalent metal salt is used, no significant improvement in the shape retention or elasticity of the target polysaccharide has been observed. It's something that didn't exist. In addition, the amount added is not particularly critical, but from a practical point of view it is 0.5 to 100 parts by weight of polysaccharide.
It is necessary that the amount is about 20 parts by weight, preferably about 1 to 10 parts by weight. Here, an example of a suitable formulation and standard composition range when using karaya gum as the polysaccharide and MgO as the metal oxide is as follows.

[Table] The electrode of the present invention having the above composition is usually prepared by uniformly mixing the base material component (and additive auxiliary agent) and the metal compound, and pressing the mixture at a pressure of 10 to 20 kg using a hot press heated to about 80°C. A flexible sheet-like product is obtained by heating and pressurizing at a pressure of /cm ³ for about 5 to 10 minutes. The electrode of the invention thus obtained can be used in sensing applications, for example, in the structure illustrated in the accompanying FIG. 1, while in stimulation or grounding applications, it can be used in the structure shown in FIG. 2. That is, in each figure, the electrode 1 of the present invention is electrically connected to the main body of the device and used by connecting conductive elements 2 and 4 made of metal or the like placed thereon to lead wires. Example 1 To a standard composition consisting of 45 g of karaya gum, 55 g of glycerin, 5 g of NaCl, and 5 g of saline (containing 25% NaCl), various metal compounds shown in Table 2 below were further blended to form a homogeneous mixture, which was then mixed with 80 g of
Pressure by hot press machine heated to 20 °C
A flexible sheet-like bioelectrode sample was manufactured by heating and pressing at Kg/cm ³ for 5 minutes.

【table】

[Table] 2 Standard composition: 50g of gum tragacanth, 40g of glycerin, 10g of ethylene glycol,
A sample was prepared as in Example 1 above, except that 5 g of NaCl and 7.5 g of water were used. 3. Standard composition: 25g of karaya gum, 20g of xanthan gum, 55g of glycerin, 5g of NaCl, and 10g of water.
A sample was produced in the same manner as in Example 1, except that a material consisting of: 4 A sample was produced in the same manner as in Example 1, except that the standard composition consisted of 30 g of karaya gum, 15 g of sodium alginate, 45 g of glycerin, and 3 g of NaCl. 5 (Comparative Example) For the standard composition of Example 1, 5.0g of each
CaSO ₄ , CaCl ₂ , borax, magnesium acetate,
A comparative sample was prepared by incorporating zinc acetate. Test Example Each sample obtained in Examples to Comparative Examples was left in a constant temperature and humidity chamber at a temperature of 35° C. and a humidity of 90% for 1 day and night, and immersed in water for 6 hours, and changes in shape and elasticity were observed and judged. As a result, it was found that each of the samples of Examples had little change in shape, maintained relatively good elasticity, and could withstand use under high temperature and high humidity conditions. On the other hand, in each sample of the comparative example, significant deformation or fluidization occurred in all tests.
It was confirmed that the additives did not contribute to improving shape retention. In addition, in the case of a sample prepared using only the standard composition of Example 1 as a control, it was also observed that the sheet fluidized and significantly deformed in all tests. As is clear from the above, the bioelectrode with improved shape retention according to the present invention inherits the above-mentioned advantageous properties of conventional polysaccharide electrodes, and has excellent properties that can withstand use under high temperature, high humidity, and sweaty conditions. It can be said that it has an extremely useful effect in practice of having moisture resistance and shape retention.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing how the bioelectrode of the present invention is used. 1... Bioelectrode, 2, 4... Conductive element, 3...
Insulation protection cover.

Claims (1)

[Scope of Claims] 1. In a bioelectrode based on a polysaccharide having a high molecular weight carboxyl group plasticized with a polyhydric alcohol, one or two types that are amphoteric or exhibit basicity in the presence of water. A bioelectrode with improved shape retention, characterized in that at least one polyvalent metal oxide or hydroxide is added. 2. The bioelectrode according to claim 1, wherein the base material comprises 30 to 65% by weight of a high molecular weight acidic polysaccharide and 70 to 35% by weight of polyhydric alcohol. 3. Claim 1, wherein the metal oxide or hydroxide is an oxide or hydroxide of a metal selected from the group consisting of magnesium, calcium, barium, zinc, iron, and aluminum. 2. The bioelectrode according to items 2 to 2. 4. The bioelectrode according to claims 1 and 2, wherein the metal salt is a metal salt of an organic weak acid.