JPH08169985A - Thermoplastic conductive composition and electrode pad made thereof - Google Patents

Abstract

PURPOSE: To provide a thermoplastic conductive composition used to make e.g. an electrode pad which transmits an electrical signal from a living body to a medical diagnostic apparatus or to introduce e.g. low-frequency waves into a living body to alleviate or cure a pain and being excellent in adhesion to the skin, conductivity and workability in coating and to provide an electrode pad made thereof. CONSTITUTION: This composition essentially consists of a skeletal component used for forming a gel and comprising a rubbery elastomer comprising an epichlorohydrin polymer and a thermoplastic polymer, an ionic compound and a solvent for dissolving the ionic compound. The ionic compound is desirably a lithium salt such as lithium perchlorate. The solvents used desirably are nonvolatile liquids such as glycols such as ethylene glycol and polyethylene glycol, alkyl ethers and polyols.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a thermoplastic conductive composition,
And an electrode pad using the same.

[0002]

2. Description of the Related Art Conventionally, as an electrode to be used in contact with a living body, a weak current with a low frequency is introduced into the body to promote blood flow, and a massage effect is expected to relieve pain such as stiff shoulders and low back pain. Treatment electrodes, medical electrodes for measuring electrocardiograms and electromyograms by extracting weak currents inside the body, ground electrodes used when using an electric scalpel, cosmetics used for hair removal treatment, etc. Various electrodes such as electrodes are known.

For these electrodes, conductive electrode pads are used as a contact medium with the surface of the living body.
In general, water-soluble polymers such as sodium polyacrylate and polyvinyl alcohol, water-soluble gel type that contains ionic dissociating electrolyte such as sodium chloride and water as a conductive medium, and metal powder or carbon as an adhesive. A type containing conductive powder such as black is widely used.

However, since the former hydrous gel type electrode pad contains a relatively large amount of water, the water content in the gel tends to change due to the influence of atmospheric humidity,
An expensive sealing wrapping material is required to keep the water content constant. Furthermore, when applied for a long time, it absorbs sweat secreted from the living body and causes deterioration of characteristics such as a decrease in adhesive strength. Further, since the latter type of electrode pad requires a relatively large amount of conductive powder, the adhesive force is likely to decrease, and it is difficult to balance the electrical conductivity and the adhesive property.

Also in terms of manufacturing, in the former hydrogel type, a gel is formed by adding a crosslinking agent to a pad composition having a water-soluble polymer as a skeleton and then applying heat or ultraviolet irradiation, Although a method of performing gel formation by subjecting a pad composition containing a monomer for forming a water-soluble polymer to heating or ultraviolet irradiation is generally adopted,
There are problems that the added crosslinking agent has a short pot life and the solution viscosity becomes too high, resulting in poor coating film-forming property. Further, in the case of formation from a monomer, there is also a problem that skin irritation is exhibited by the residual monomer.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the conventional conductive composition used for the electrode pad, and exhibits excellent conductivity and tackiness. It is an object of the present invention to provide a conductive composition which is also excellent in coating workability.

A further object of the present invention is to provide an electrode pad using this composition.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors in order to achieve the above-mentioned object, as a result, an epichlorohydrin-based polymer was used as a skeleton component during gel formation, and a thermoplastic polymer was used in combination. It was found that a composition that solves the above-mentioned object can be obtained by using a rubber-like elastic body, and completed the present invention.

That is, the thermoplastic conductive composition of the present invention is
A rubber-like elastic body composed of an epichlorohydrin-based polymer and a thermoplastic polymer contains an ionic compound and a solvent capable of dissolving the ionic compound as essential components.

[0010] In a particularly preferred embodiment, the composition further comprises a tackifier, which has good adhesive properties when applied to a living body.

The electrode pad of the present invention is formed by molding the above thermoplastic conductive composition into a pad shape.

The epichlorohydrin-based polymer used in the present invention is easily and uniformly compatible with the ionic compound and the solvent described later, and can exhibit good conductivity. Examples of such epichlorohydrin-based polymer include epichlorohydrin rubber, epichlorohydrin / ethylene oxide copolymer rubber, epichlorohydrin / allyl glycidyl ether copolymer rubber, epichlorohydrin /
A rubbery polymer such as an ethylene oxide / allyl glycidyl ether copolymer rubber can be used.

The thermoplastic polymer used in combination with the epichlorohydrin-based polymer is, for example, styrene / isoprene / styrene copolymer, styrene / butadiene /
Styrene-based polymers such as styrene copolymers, styrene / ethylene-butylene / styrene copolymers, rubber like 1,2-polybutadiene, polyester-based polymers, olefin-based polymers, ethylene / vinyl acetate copolymers, etc. A polymer having elasticity can be used. The reason for using such a thermoplastic polymer in combination in the present invention is that when the epichlorohydrin-based polymer alone is formed into a film, shrinkage may occur, or adhesive residue may occur on the surface of the adhered skin due to insufficient cohesive force. However, such a problem can be solved by blending a thermoplastic polymer.

In the present invention, the blending ratio of the epichlorohydrin-based polymer and the thermoplastic polymer can be appropriately changed depending on the required degree of conductivity, moldability into an electrode pad, etc. In order to exert the properties, the blending ratio of the epichlorohydrin-based polymer is 40 to 95% by weight, preferably 40 to 7% by weight based on the total amount of the polymer.
It is preferable to set it in the range of 5% by weight. When the blending ratio of the epichlorohydrin-based polymer is less than 40% by weight, practically sufficient conductivity may not be obtained, and when it exceeds 95% by weight, the blending ratio of the thermoplastic polymer decreases. Therefore, it may not be possible to expect the improvement of the above-mentioned shrinkage and lack of cohesive force.

The blending ratio of the total amount of the above-mentioned two kinds of polymers in the finally obtained conductive composition is about 40% by weight or more in order to maintain appropriate shape retention and cohesiveness. It is preferably in the range of 50 to 80% by weight.

In the composition of the present invention, the ionic compound to be added for exhibiting conductivity is specifically a cation selected from alkali metals such as lithium, sodium, potassium and magnesium and alkaline earth metals. And a halogen ion such as chlorine ion or iodine ion, an anion such as perchlorate ion, thiocyanate ion, trifluoromethanesulfonate ion, or toluenesulfonate ion, and lithium stearylsulfonate. And organic salts such as quaternary ammonium salts, and ionic compounds such as quaternary ammonium salts. Among these ionic compounds, it is particularly preferable to use a lithium salt which has relatively low energy for ion dissociation and has high mobility in a solvent described later. Specific compounds include LiBr, LiI, LiClO ₄ , LiSCN, L
such as ICF ₃ SO ₃ and the like. The blending amount of the ionic compound can be arbitrarily changed depending on the kind and the blending amount of the rubber-like elastic body made of the polymer, the blending amount of the solvent described below, etc. 0.01 to 30 parts by weight per 100 parts by weight of the composition,
It is preferably set in the range of 5 to 20 parts by weight. When the amount of the ionic compound is less than 0.01 part by weight, the conductivity is poor, and when it exceeds 30 parts by weight, the amount of the ionic compound to be blended becomes equal to or higher than the saturated solubility and the compound is not completely dissolved.
It may be recrystallized after dissolution to cause a decrease in conductivity.

The solvent used in the present invention is one which dissolves the above ionic compound and can also be a solvent which dissolves the epichlorohydrin type polymer and the thermoplastic polymer. Further, it is preferable that it is difficult to volatilize at room temperature or under moderate heating, and the boiling point is 1
A material having a temperature of 80 ° C. or higher, preferably 250 ° C. or higher is used.
Examples of such solvents include polyhydric alcohols such as ethylene glycol and propylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyalkylene glycols such as polyethylene glycol dimethyl ether, and poly (oxyethylene-oxypropylene) alkyl. Alkyl ethers such as ethers, polyether polyols, polyester polyols, polycarbonate polyols, polyols such as polycaprolactone polyols, carbonic acid esters such as ethylene carbonate and propylene carbonate, cyclic esters such as caprolactone, sulfolane, dimethylimidazolidinone, etc. Heterocyclic compounds, polyhydric alcohol fatty acids such as glycol dicaprylate Ester, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. The blending amount of such a solvent is the type and blending amount of the rubber-like elastic body made of the polymer,
The amount of the ionic compound can be arbitrarily changed according to the type and amount of the ionic compound, but in order to exhibit excellent conductivity, it is preferable that the amount is large. However, when the compounding amount is increased, the cohesiveness is reduced when a molded body such as an electrode pad is seen.
It is desirable to adjust in the range of 0 to 75% by weight, and practically 20 to 60% by weight.

In the composition of the present invention, in addition to the above-mentioned essential components, a plasticizer or a softening agent which is generally used as a compatibilizing agent for the rubber-like elastic body and the solvent is contained in the composition. Can be added in an amount not exceeding 30% by weight. Specific examples thereof include vegetable oils such as olive oil and castor oil, mineral oils such as process oil, ester oils such as dibutyl phthalate, dioctyl phthalate, diethyl adipate, and isopropyl myristate.

Further, various rosin-based resins, terpene-based resins, petroleum-based resins, phenols are added to the composition of the present invention in order to improve the adhesiveness of the composition of the present invention when it is made into a molded article such as an electrode pad. A tackifier such as a resin, a xylene resin, a styrene resin, a coumarone indene resin, or a dicyclopentadiene resin can be added to the composition in an amount not exceeding 40% by weight.

As other optional components, various fillers, colorants such as pigments, antioxidants, ultraviolet absorbers and the like can be blended in optional amounts as required.

Next, an example of a method for obtaining the thermoplastic conductive composition and electrode pad of the present invention will be described below.

First, as a first method, an essential component consisting of an epichlorohydrin-based polymer and a thermoplastic polymer, an ionic compound and a solvent is blended with an optional component such as a tackifier, if necessary, The composition of the present invention, which is uniformly mixed with a kneader such as a kneader, is prepared. Then, the composition is formed into a sheet by an extruder or the like, or the composition is sandwiched between two separators,
The electrode pad of the present invention is produced by press-forming into a sheet shape with a press machine.

In the second method, the epichlorohydrin polymer and the thermoplastic polymer are dissolved in any organic solvent, and then an ionic compound or solvent is added, and various optional components are blended if necessary. , Preparing a homogeneous solution containing the composition of the present invention. Next, this solution is applied onto an arbitrary carrier such as a separator, and only the organic solvent is volatilized by heating to produce a sheet-shaped electrode pad of the present invention.

The former method is a practical method because the obtained pad can be made thicker and can be manufactured relatively inexpensively. In addition to the above, the electrode pad of the present invention can be obtained by applying a conductive paint to one surface of a plastic film such as a polyester film or a polyethylene film, depositing a metal film, or laminating a metal foil. It may have a structure in which an electrode pad having the above composition is formed on the conductive surface of the conductive support.

[0025]

EXAMPLES Hereinafter, the thermoplastic conductive composition of the present invention and the electrode pad using the same will be described in detail with reference to Examples. It is needless to say that the present invention is not limited to the following embodiments, and various applications can be made without departing from the technical idea of the present invention. In the following examples, parts and% mean parts by weight and% by weight.

Example 1 140 parts of 30 parts of epichlorohydrin rubber and 30 parts of ethylene / vinyl acetate copolymer (41% vinyl acetate content) were used.
Knead evenly with a kneader set to ℃, and add 8 parts of lithium perchlorate to dimethyl polyethylene glycol 4 beforehand.
Add the solution dissolved in 0 part little by little, and add 8 kneaders.
The temperature was set to 0 ° C. and the mixture was kneaded uniformly to obtain a conductive composition of the present invention.

Next, the obtained composition was sandwiched between two polyester separators and pressure-molded by a pressing machine set at a temperature of 80 ° C. to a thickness of 0.5 mm to obtain a sheet-like shape. An electrode pad was produced.

No shrinkage phenomenon was observed in the obtained sheet-like electrode pad, and the film-forming property was extremely good. Moreover, when the counter voltage and the counter impedance were measured as an electrode pad for electrocardiogram measurement, 1.2 mV and 0.9 k
It was Ω and had sufficient conductivity in practical use.

Example 2 30 parts of epichlorohydrin / ethylene oxide (1: 1) rubber and 30 parts of ethylene / vinyl acetate copolymer (vinyl acetate content 41%) were uniformly kneaded in a kneader set at 140 ° C. A solution prepared by previously dissolving 8 parts of lithium perchlorate in 40 parts of dimethyl polyethylene glycol was added little by little, and the kneader was set at a temperature of 80 ° C. to uniformly knead the mixture to obtain a conductive composition of the present invention.

Next, the composition thus obtained was sandwiched between two polyester separators and pressure-molded to a thickness of 0.5 mm by a pressing machine set at a temperature of 80 ° C. An electrode pad was produced.

No contraction phenomenon was observed in the obtained sheet-like electrode pad, and the film-forming property was extremely good. Moreover, when the counter voltage and the counter impedance were measured as an electrode pad for electrocardiogram measurement, it was 1.1 mV and 1.3 k.
It was Ω and had sufficient conductivity in practical use.

Example 3 35 parts of epichlorohydrin / ethylene oxide (1: 1) rubber and 35 parts of styrene / butadiene / styrene copolymer (styrene content 30%) rubber were uniformly kneaded in a kneader set at 140 ° C. A solution prepared by previously dissolving 6 parts of lithium trifluoromethanesulfonate in 30 parts of butyltriethylene glycol was added little by little, and the kneader was set at a temperature of 80 ° C. to uniformly knead the solution to obtain the conductive composition of the present invention. Obtained.

Next, the obtained composition was sandwiched between two polyester separators and pressure-molded to a thickness of 0.5 mm by a press machine set at a temperature of 80 ° C. to obtain a sheet-shaped product. An electrode pad was produced.

No contraction phenomenon was observed in the obtained sheet-like electrode pad, and the film-forming property was extremely good. Moreover, when the counter voltage and the counter impedance were measured as an electrode pad for measuring an electrocardiogram, 2.5 mV and 5.2 k were obtained.
It was Ω and had sufficient conductivity in practical use.

Example 4 30 parts of epichlorohydrin / ethylene oxide (1: 1) rubber and 30 parts of ethylene / vinyl acetate copolymer (vinyl acetate content 41%) were uniformly kneaded with a kneader set at 140 ° C., and further, 20 parts of an alicyclic saturated hydrocarbon resin (softening point 100 ° C.) as a tackifier was added and kneaded, and a solution prepared by previously dissolving 6 parts of lithium perchlorate in 30 parts of butyltriethylene glycol was added thereto. The mixture was added little by little, and the kneader was set at a temperature of 80 ° C. to uniformly knead the mixture to obtain a conductive composition of the present invention.

Next, the obtained composition was sandwiched between two polyester separators and pressure-molded by a pressing machine set at a temperature of 80 ° C. to a thickness of 0.5 mm to obtain a sheet-like shape. An electrode pad was produced.

No contraction phenomenon was observed in the obtained sheet-like electrode pad, and it was excellent in film-forming property and adhesiveness to human body. Moreover, when the counter voltage and the counter impedance were measured as an electrode pad for electrocardiogram measurement, it was 0.3 mV.
And 3.8 kΩ, which was practically sufficient conductivity.

Example 5 40 parts of epichlorohydrin / ethylene oxide (1: 1) rubber and 20 parts of ethylene / vinyl acetate copolymer (vinyl acetate content 41%) were uniformly kneaded with a kneader set at 140 ° C., and further, 20 parts of hydrogenated rosin (softening point 80 ° C.) as a tackifier is added and kneaded, to which a solution of 6 parts of lithium perchlorate dissolved in 30 parts of butyltriethylene glycol is added little by little. The kneader was set at a temperature of 80 ° C. and uniformly kneaded to obtain a conductive composition of the present invention.

Next, the obtained composition was sandwiched between two polyester separators and pressure-molded by a pressing machine set at a temperature of 80 ° C. to a thickness of 0.5 mm to obtain a sheet-like shape. An electrode pad was produced.

No contraction phenomenon was observed in the obtained sheet-like electrode pad, and it was excellent in film-forming property and adhesiveness to human body. Moreover, when the counter voltage and the counter impedance were measured as an electrode pad for electrocardiogram measurement, it was 0.3 mV.
And 2.9 kΩ, which was practically sufficient conductivity.

Comparative Example 1 70 parts of epichlorohydrin rubber was uniformly kneaded with a kneader set at 140 ° C., and 8 parts of lithium perchlorate was previously mixed therein.
A solution in which 40 parts of dimethyl polyethylene glycol was dissolved was added little by little, and the kneader was set at a temperature of 80 ° C. to uniformly knead the mixture to obtain a conductive composition.

Next, the obtained composition was sandwiched between two polyester separators and pressure-molded by a pressing machine set at a temperature of 80 ° C. to a thickness of 0.5 mm to obtain a sheet-like shape. An electrode pad was produced.

The obtained sheet-shaped electrode pad has a thickened peripheral portion due to a contraction phenomenon, and the voltage and impedance were measured as an electrode pad for electrocardiogram measurement.
It was 0.4 mV and 1.3 kΩ, and had practically sufficient conductivity.

Comparative Example 2 70 parts of styrene / butadiene / styrene copolymer (styrene content 30%) rubber was uniformly kneaded with a kneader set at 140 ° C., and 8 parts of lithium perchlorate was previously mixed with 40 parts of dimethyl polyethylene glycol 40. The dissolved solution was added little by little, and the kneader was set at a temperature of 80 ° C. to uniformly knead the mixture to obtain a conductive composition. This composition had a poor compatibility with dimethyl polyethylene glycol, and the bleeding phenomenon was immediately observed, so that it could not be practically used as an electrode pad.

The characteristics measured for the conductive compositions and the electrode pads prepared in the above Examples and Comparative Examples are summarized in Table 1 below.

[0046]

[Table 1]

<Test Method><FilmFormability> The presence or absence of shrinkage phenomenon when a film was formed by a pressure press was observed. ○: No shrinkage, ×: Shrinkage

<Countervoltage> ANSI / AMMI EC12
-The test method of 1983 was followed. (Electrode area: 2 cm x
3cm, electrode material: silver vapor deposition)

<Impedance> The same test method as that for the above-mentioned voltage was used.

<Cohesiveness> Thickness 1 mm, area 20 mm × 2
The electrode pad molded to 0 mm was placed on a flat plate and left standing at 40 ° C. for 24 hours, and it was observed whether or not it was flowing without shape retention. ○: No flow, ×: Flow started

<Tackiness> The tackiness of the molded electrode pad was examined by touching with a finger. ○: There is a sticky feeling, ×: There is no sticky feeling

[0052]

INDUSTRIAL APPLICABILITY As described above, the thermoplastic conductive composition of the present invention uses an epichlorohydrin-based polymer as a skeleton component during gel formation, and further uses a rubber-like elastic material in combination with a thermoplastic polymer. Therefore, it has an excellent balance of conductivity and adhesiveness, and also has excellent coating workability.

Further, since the electrode pad obtained from the conductive composition having such characteristics has excellent conductivity, it can be used as a therapeutic electrode, a medical electrode, a ground electrode,
It is useful as a pad for various electrodes such as a beauty electrode.

Claims (4)

[Claims] 1. A thermoplastic conductive material comprising a rubber-like elastic body composed of an epichlorohydrin polymer and a thermoplastic polymer, and an ionic compound and a solvent capable of dissolving the ionic compound as essential components. Composition. 2. The thermoplastic polymer composition according to claim 1, wherein the ionic compound is a lithium salt. 3. The thermoplastic conductive composition according to claim 1, further comprising a tackifier. 4. An electrode pad comprising the thermoplastic conductive composition according to claim 1.