JPH0376933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a biological electrode that is attached to the skin.

Traditionally, equipment and electricity have been used for detection applications such as electrocardiograms and brain wave measurements, stimulation or current transmission applications such as low frequency therapy and iontophoresis (iontophoresis), and grounding applications such as return electrodes for electric scalpels. In order to maintain electrical connection between a conductive element that is electrically connected to the skin of a living body, a so-called electrode paste or cream has been applied to the conductive element or the skin. Recently,
As an alternative to these electrode pastes and creams, various biological electrodes have been proposed that have self-shape retention, skin adhesion, and electrical conductivity.

For example, Japanese Patent Application Laid-open No. 52-95895, Japanese Patent Application Laid-open No. 55-81635.
Japanese Patent No. 56-36939, Japanese Patent No. 58-135506, etc. disclose various electrodes for application to the skin that are made of crosslinked or non-crosslinked polymers.

However, products based on these non-crosslinked polymers cannot be used for long-term monitoring applications such as Holter electrocardiographs or long-term iontophoresis applications, which have recently become increasingly important. It is difficult to maintain stable electrical connection due to flow deformation due to sweating, etc. On the other hand, in the case of products based on crosslinked polymers, most of them are directly crosslinked from monomers. Therefore, it may be difficult to avoid biological stimulation or toxicity due to residual monomers.

In view of the above, the main object of the present invention is to maintain good dimensional stability and electrical connection without flow deformation even in long-term use, and to be formed only from compositional elements that do not have any harmful effects on living organisms. The object of the present invention is to provide a novel biological electrode made of a base material.

The above object is achieved by the electrode of the present invention, the main component of which is a partially ester crosslinked reaction product of a carboxyl group-containing hydrophilic polymer and a polyhydric alcohol.

Hereinafter, the compositional elements, formulation and reaction conditions, mode of use, characteristics, etc. of the electrode of the present invention will be explained in more detail.

Carboxyl group-containing hydrophilic polymer Homopolymers or copolymers of monomers such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, citraconic acid, and hemicic acid, or these monomers and ethylene, propylene, butadiene, Isoprene, isobutene, alkyl vinyl ether (C ₁ - _{C 6} ), vinyl acetate, vinyl chloride, acrylamide, styrene,
Suitable examples include copolymers with various monomers having no carboxyl group, such as vinyl alcohol.

In this case, the average molecular weight of the polymer is preferably 10,000 or more, more preferably 100,000 or more, and the preferable proportion of the carboxyl group-containing monomer in the polymer is 5 mol % or more.

On the other hand, the carboxyl group in the polymer is an acid anhydride,
It may be in the form of a monovalent metal salt, an amine salt, or a quaternary ammonium salt, but in the case of a carboxylate, the pH of the polymer aqueous solution is generally preferably adjusted to 7 or less before being subjected to the reaction.

Polyhydric alcohol ethylene glycol, diethylene glycol,
Aliphatic glycols such as triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, butanediol, pentadiol, hexylene glycol, octylene glycol, glycerin, trimethylolpropane, hexane Polyols such as triol, polypropylene glycol, polyglycerin, polyvinyl alcohol and its derivatives, oligosaccharides containing monosaccharides to trisaccharides or polysaccharide hydrolysates, and various polyhydric alcohols in which part of the hydroxyl groups are phenolic hydroxyl groups. can be exemplified as suitable examples.

Incidentally, these polyhydric alcohols also have a function as a plasticizer as described below.

Formulation and reaction conditions The electrode of the present invention has a main component of the base material of 5 to 70% by weight, more preferably 10 to 50% by weight based on the entire base material.
from 1 to 95% by weight, more preferably 10% by weight with the aforementioned polymer of
Although it contains ~60% by weight of a partial ester crosslinking reaction product with the polyhydric alcohol, the following additional components may be further added thereto in order to further improve conductivity, adhesiveness, etc.

Electrolytes Various electrolytes such as NaCl, KCl, Na ₂ CO ₃ , potassium citrate, etc. may be included to increase conductivity.

Plasticizer The polyhydric alcohol may be used as it is as a plasticizer to improve the fluidity of the base material, but if necessary, a plasticizer such as a polyhydric alcohol may be further added and used.

Water Can be added to increase the conductivity and tackiness of the base material.

Tackifier Various types of adhesives can be added, but rosin-based hydrogenated resin adhesives such as Hercules ForaxAX and ABITOL, as well as adhesive emulsions such as vinyl acetate, acrylic, and polybdenum, may be used depending on their compatibility with the base material, etc. It can be said to be particularly useful in this respect.

Hydrophilic polymers Hydrophilic polysaccharide gums such as karaya gum, guar gum, pectin, gelatin, chitosan, carboxymethyl cellulose, polyvinyl alcohol,
Polydialkylaminoalkyl (meth)acrylate, polyvinylpyridinium halogen salt,
Any hydrophilic or water-soluble polymers such as polydiallylammonium halide salts, polyaminomethylacrylamide, polyvinylimidazoline, ionene polymers, cationic flocculants such as polyvinyltetraammonium halide salts can be used to improve the rheological properties of the base material. Can be added. That is, these water-soluble polymers are incorporated into the ester link and provide useful viscoelastic properties to the base material.

Monohydric Alcohols Aliphatic monohydric alcohols such as methanol, ethanol, propanol, isopropanol, butyl alcohol, sec-butanol, and 1-decanol can be added to adjust the hydrophilic/hydrophobic balance of the base material.

On the other hand, the electrode base material of the present invention can be easily prepared by subjecting the above-mentioned main components alone or a system in which various additives are mixed thereto to an ester crosslinking reaction at 50 to 100°C for 50 to 1 hour under acidic conditions. prepared. In this case, a mineral acid such as hydrochloric acid may be used as an acid catalyst for promoting the esterification reaction, as is well known.

Characteristics and usage mode The electrode base material of the present invention prepared as described above is as follows:
Although it is substantially water-insoluble, it has moderate water absorption and swelling properties, so it exhibits good dimensional stability even when used for long periods of time, and provides reliable electrical connection between the conductive element and the skin. In addition, extremely strong skin adhesion can be achieved without a tackifier, and a relatively large amount of water can be contained in the ester crosslinked network without deteriorating the overall viscoelastic properties, resulting in low impedance properties. It has advantages such as being able to retain an ionic drug at a desired concentration without containing impurity ions that are particularly undesirable as an electrode for iontophoresis.

As described above, the electrode base material of the present invention, which is substantially free of residual monomers that generally cause skin irritation, can have good biocompatibility.

On the other hand, the electrode base material of the present invention can be used, for example, in the structure illustrated in the attached FIG. 1 in sensing applications, while it can be used in the structure shown in FIG. 2 in stimulation or energization applications. That is, in each figure, the electrode base material 1 of the present invention is electrically connected to the main body of the device as a biological electrode by connecting conductive elements 2 and 4 made of metal or the like placed thereon to lead wires. Connected and used.

Although the above embodiment shows the simplest form, the present invention is not limited to this in any way, and may be used as a composite structure as shown in the attached FIG. 3, for example.

That is, in FIG. 3, the composite electrode includes a connecting terminal 5, a reinforcing insulating tape 6, a base material 7 of the present invention,
It consists of a nonwoven fabric or sponge 8 and an adhesive tape 9.

Furthermore, the base material of the present invention may be used by integrally impregnating reinforcing materials such as nonwoven fabrics, sponges, and paper materials.

Example An electrode base material was prepared by subjecting a mixture of Formulation Examples 1 to 6 below to a partial ester crosslinking reaction at 60°C for 15 hours. All of the obtained base materials were water-insoluble and finitely water-swellable, and also had suitable skin adhesion and low impedance characteristics (specific resistance: 0.8 to 10 kΩ·cm).

Formulation example 1 Poly(vinyl methyl ether/maleic anhydride) MW200,000...20 parts by weight Glycerin...20 10% saline solution...60 2 Poly(vinyl methyl ether/maleic anhydride) MW200,000...20 parts by weight Parts Glycerin...10 Polyethylene glycol...50 10% saline 50 3 Poly(vinyl methyl ether/maleic anhydride) MW200,000...20 parts by weight Polyglycerin*...20 10% saline 60 *Water, diglycerin, triglycerin mixture 4 Poly(vinyl methyl ether/maleic anhydride) MW200,000...30 parts by weight Sorbitol...30 10% saline solution...40 5 Poly(isoprene/maleic anhydride) M.
W.50,000...20 parts by weight Carboxymethyl cellulose...10 Glycerin...30 10% saline solution...10 6 Poly(isobutylene/maleic anhydride) M.
W.150,000...40 parts by weight Glycerin...55 10% saline solution...5

[Brief explanation of drawings]

FIGS. 1 to 3 are cross-sectional views showing how the biological electrode of the present invention is used. 1, 7... Electrode base material, 2, 4, 5... Conductive element, 3... Insulation protection cover.

Claims (1)

[Claims] 1. A biological electrode characterized in that the main component of the base material is a partially ester crosslinked reaction product of a carboxyl group-containing hydrophilic polymer and a polyhydric alcohol.