JPH029074B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an ion conductive adhesive for biological electrodes, particularly for high-performance ECG (electrocardiogram), EEG (electroencephalogram), and EOG (electroencephalogram) for biological research, diagnosis, or biological treatment. The present invention relates to an ion conductive adhesive suitable for use as a dry bioelectrode material when taking an electrooculogram (electrooculogram), an electrode as a return electrode of an electric scalpel, a conductor of a low frequency treatment device, etc. (Prior Art) Conventionally, the following materials have been studied as electrically conductive adhesives, but each of them has various problems. For example, there are adhesives that have a conductive effect by mixing fine metal powder, carbon fibers, metal fibers, carbon powder, metal salts, etc. with an appropriate adhesive, but this method requires a fairly high mixing ratio of conductive solids. Therefore, the physical properties must be different from those of the adhesive itself. Also highly absorbent, hygroscopic resins (e.g. acrylic acid (salt) grafted starch,
There are hydrogels made of denatured polyvinyl alcohol (such as modified polyvinyl alcohol) in which metal salts are dissolved, but they are not practical because they have insufficient adhesion and disappear when the water evaporates. Furthermore, there are hydrogels made by absorbing water such as polyhydroxyethyl methacrylate (HEMA), which are made to have electrical conductivity, but such acrylic polymers are generally obtained by polymerizing monomers, and residual monomers are When used as a biological adhesive, toxicity to the human body remains a problem. In addition, in the case of forming a composite with an adhesive layer, there is also the problem that when polymerized on a substrate such as cloth, foam, or plastic, these substrates are attacked. In addition, bioelectrode materials include aluminum, gold, silver,
Thin plates of highly conductive metals such as platinum and copper have been used, but bioelectrode materials made of such metals have poor adhesion to the skin and are insufficient for detecting electrical signals from the skin. It was necessary to apply conductive jelly, cream, paste, etc. to the skin to improve contact between the electrode material and the skin, and to secure it with surgical tape or the like to prevent it from falling off. In this case, if you apply jelly, etc., the performance may deteriorate due to heat and sweat from the skin during use, and even if you try to remove the jelly, etc. after use, it may not be removed sufficiently and may remain. It was hot. Therefore, a dry type bioelectrode material as shown in FIG. 1 was developed, which does not require the application of such a conductive jelly or the like. That is, this bioelectrode material is AgCl-
A conductive adhesive 3 is provided on the back surface of a holder 2 that holds an Ag-based electrode connector 1. The conductive adhesive 3 is, for example, one in which a foam such as polyurethane is impregnated with a conductive liquid compound to enable detection of electrical signals from the skin.
Since this material simply carries an electrolyte sol containing water on the conductive part, it loses its conductivity when it dries, causing skin irritation due to the electrolyte, and the adhesion of the part corresponding to the conductive part to the skin. Due to its poor adhesion, it must be fixed to the skin with surgical tape or the like. On the other hand, products have been developed in which natural polymeric polysaccharide gums such as karaya gum are mixed with polyhydric alcohol, fine salt particles, fine metal particles, etc. in order to provide adhesion and adhesion. Because it uses natural polymeric polysaccharides, the quality may vary depending on the production lot, and since it is an ionic conductor that uses water as a medium, it may be affected by moisture and cause problems.
Furthermore, since it is difficult to absorb sweat from living bodies and cannot respond to changes in pH, allergies and bacteria are likely to occur during long-term use, which poses problems from a functional and hygienic perspective. In addition, fine particles of metals and salts mixed together form discontinuous conductive paths, which can lead to uneven electrolysis and cause noise.
Moreover, these contaminants change color during long-term storage and become brown and opaque, causing problems such as discomfort and disgust when they come into contact with the skin. (Objective of the Invention) The present invention has been made in view of the above circumstances, and aims to be flexible, have excellent adhesion to the skin, have excellent adhesion in itself, be transparent, and have good properties. An ionically conductive polymer that has good conductivity, eases sweating and skin effects, has a good tactile and familiar feel, and can be used continuously for a long period of time without discomfort or aversion for stable electrical detection. Our goal is to provide adhesives. (Means for achieving the object) In order to achieve the object, the ion conductive polymer adhesive of the present invention comprises a polyurethane polyol prepolymer having an alkylene oxide chain,
The gist of the present invention is that it is formed by reacting a polyurethane polyisocyanate prepolymer having an alkylene oxide chain, and contains an ionic compound. The polyurethane polyol prepolymer used in the present invention is, for example, a polyfunctional compound having a structure shown by the following structural formula (), and the polyurethane polyisocyanate prepolymer is a polyfunctional compound having a structure shown by, for example, the following structural formula () to (). In the molecular weight range, they are liquid at room temperature, and all have alkylene oxide chains in the main chain [structural formulas () to () (A), (B), (C), (D)]
]. In particular, polyurethane polyol prepolymer becomes a viscous resin liquid or solid at room temperature in a relatively high molecular weight range, and when it is reacted with polyurethane polyisocyanate prepolymer, it becomes a solid resin without stickiness, which achieves the purpose of the present invention. It's not something to achieve. In order to exhibit adhesiveness, the size of each alkylene oxide chain and the total molecular weight must be controlled as shown in the Examples. This alkylene oxide chain (A)(B)(C)
(D) is a linear or partially branched alkylene oxide polymer or a copolymer of different alkylene oxides, such as (-CH ₂ --O)- _o , (-CH ₂
―CH ₂ ―O―)― _o , (―CH ₂ ―CH ₂ ―CH ₂ ―CH ₂ ―
O) - _o ,

【formula】

[Formula] etc. (However, R is an alkyl group, an alicyclic compound, or an aromatic compound, (D) is an alkylene oxide chain, and l is an integer of 1 or 4) These prepolymers () to () are , reactive functional groups at the terminal or side chain (-OH group and -NCO
When this functional group reacts and forms a urethane bond, an adhesive penetrating polyurethane is formed. This polyurethane alkylene oxide chain (A)
Parts (B), (C), and (D) are in a state in which ionic compounds easily form complexes. Therefore, when an ionic compound is mixed, a complex or solid solution is formed mainly at this alkylene oxide chain, and when a potential is applied, it becomes ionic conduction and current flows, resulting in good electrical conductivity (approximately 10 ^{3 to 7} Ω). It comes to show. In addition, examples of ionic compounds to be mixed include sodium chloride, potassium chloride, lithium chloride, lithium perchlorate, ammonium chloride, potassium chlorate, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, ammonium sulfate, Inorganic salts such as potassium nitrate, sodium nitrate, sodium carbonate, lithium borofluoride, sodium thiocyanate, lithium trifluoromethanesulfonate,
Organic salts such as sodium acetate, sodium alginate, sodium polyacrylate, sodium ligninsulfonate, and sodium toluenesulfonate are used.
These may be used alone or in combination.
However, when used as an adhesive for bioelectrodes, one that does not affect the human body is selected. Such an ionic compound may be blended at the time of mixing the polyol prepolymer and the polyisocyanate prepolymer, or after the reaction, it may be impregnated as an aqueous or organic solution and the solvent may be removed by drying. Further, if necessary, it is desirable to blend a plasticizer such as dimethoxypolyethylene glycol, for example dimethoxytetraethylene glycol, with the ionic compound to modify the adhesive. When such a plasticizer is added, the hydrogen bonds in the alkylene oxide chain are broken, reducing crystallinity and increasing the space for absorbing ionic compounds, increasing the chance of complex formation with ionic compounds and improving conductivity. further improves. The reaction ratio of polyurethane polyol and polyurethane polyisocyanate can be controlled by the ratio of terminal functional groups, and is 1≦[OH]/
[NCO] must be 5. [OH]/
[NCO]<1 is unsuitable because unreacted -NCO remains and post-reaction occurs. Again [OH]/
If [NCO]>5, the segment having an OH group at the end will be excessive and elution by heat or solvent will occur, which is not preferable. The molecular weight range of the polyurethane polyol and polyurethane polyisocyanate constituting the adhesive material of the present invention varies widely depending on the type and molecular shape of the alkylene oxide and isocyanate, and whether the alkylene oxide is a homopolymer or a copolymer. , about 1,000 to 10,000 for polyurethane polyol, and about 500 to 10,000 for polyurethane polyisocyanate, but preferably in the range of about 1,400 to 6,000 and 1,000 to 6,000, respectively. When the ionic compound is dissolved and blended in polyurethane polyol etc., the amount is preferably 0.1 to 100 parts per 100 parts of polyurethane polyol etc.
It is 0.5 to 30 parts. If it is less than 0.1 part, a sufficient ionic conduction effect cannot be obtained, and if it exceeds 100 parts, it will be difficult to dissolve, and no significant effect can be expected from mixing the ionic compound. A catalyst such as dibutyltin dilaurate is used, and the amount of this catalyst is in the range of 0.1 to 5 parts, preferably 0.5 to 1 part, based on 100 parts of the polyurethane polyol prepolymer. As mentioned above, the ion conductive polymer adhesive of the present invention comprises a polyurethane polyol prepolymer,
polyurethane polyisocyanate prepolymer,
It can be obtained by mixing and reacting an ionic compound and preferably a plasticizer, or by mixing and reacting only the previous two components and then impregnating and drying the solution with an ionic compound, etc. In that case, the necessary Depending on the requirements, the above-mentioned mixture is applied onto a substrate such as cloth, paper, plastic sheet, foam, etc., reacted, and formed into an appropriate shape such as a sheet, disk, or mesh. Unlike monomers, the prepolymers used in this case are safe because they do not leave any unreacted materials, and they have a moderate viscosity, so they can penetrate into the bubbles or seams of foams, cloth, etc. during the reaction, and form the base material. It is possible to avoid troubles such as damage to the (Function and effect) Such an ion-conductive polymer adhesive contains ionic compounds and plasticizers mainly in the alkylene oxide chain portion of the interstitial polyurethane formed by the reaction of a polyurethane polyol prepolymer and a polyurethane polyisocyanate prepolymer. It has a structure in which an agent intervenes, and when a potential is applied to it,
Current flows through ionic conduction, and as shown in the measurement results of Examples described below, it exhibits good conductivity with a volume resistivity of about 10 ^{3 to 7} Ωcm. Moreover, since this adhesive is a reaction product of a solvent-free prepolymer, there is no adverse effect such as skin irritation due to solvents, and the prepolymer has an alkylene oxide chain as its main chain. By selecting the type of segment, the balance between hydrophilicity and hydrophobicity of the segment can be adjusted.
It is non-toxic and forms a gel-like material that has excellent adhesiveness, flexibility, and compatibility with the skin due to the urethane bond. Therefore, even if it is not fixed with surgical tape or the like, it will adhere tightly to the skin due to its excellent adhesiveness and will not fall off. Furthermore, since it is transparent, it does not cause discomfort or disgust. Next, examples will be given. (Example 1) A polyurethane polyol prepolymer in which the alkylene oxide chains (A), (B), and (C) in the structural formula [] have the configurations shown in Table 1 below, and a polyurethane polyisocyanate prepolymer (molecular weight:
1600, segment D: polypropylene glycol), an ionic compound (lithium perchlorate),
Plasticizer (dimethoxytetraethylene glycol)
and a catalyst (dibutyltin dilaurate) in the proportions shown in Table 1 below, and the mixture was reacted and cured at room temperature to form an ion conductive polymer adhesive test piece (No. 1).
~6) was obtained. Regarding this test piece, JIS K-
6911 Volume resistivity was measured using a method similar to Section 5-13, and tackiness was also examined. The results are shown in Table 1 below. Note that the segment (D) in this example has a molecular weight of 1000, and the prepolymer polyisocyanate prepolymer used contains a polyfunctional isocyanate with a low molecular weight during synthesis.

[Table] (Example 2) A polyurethane polyol prepolymer in which alkylene oxide chains (A), (B), and (C) in the above structural formula [] have the configurations shown in Table 2 below, and a polyurethane polyisocyanate prepolymer (Example 2) 1) and the catalyst (same as in Example 1) in the following 2nd example.
They were mixed in the proportions shown in the table and reacted and cured at room temperature to obtain three types of sheet pieces (Nos. 7 to 9). This sheet piece was added to solution (0.5mol/LiCO ₄ in ethanol), solution (0.5mol/LiCO _{4 in water/ethanol), solution (0.5mol/LiCO 4} in water/ethanol),
A test piece was prepared by immersing the sample in an aqueous solution of LiCO ₄ and drying it by leaving it at room temperature for a day and night, and then drying it under reduced pressure at 40°C for 2 hours. Regarding this test piece, JIS K-
6911 The volume resistivity was measured after immersion and after drying using a method similar to Section 5-13, and the results are shown in Table 3 below.

[Table] Copolymers of tyrene glycol and polypropylene glycol are shown. composition
The ratio is the molecular weight ratio of each segment.

[Table]
The ion conductive adhesive used in this example exhibited no cracking, bacterial growth, loss of transparency, or loss of adhesiveness over a long period of time. Conventional natural polysaccharide-based ion conductive adhesives for bioelectrodes (e.g. Karaya gum) exhibit a specific volume resistivity of 10 ⁴ to ^{10 7} Ωcm, and are susceptible to variations in quality, changes in performance due to the influence of moisture, etc. It has drawbacks such as easy growth of bacteria and discoloration. From the above results, the ion conductive polymer adhesive of the present invention exhibits conductivity that is sufficiently satisfactory for use in biological electrodes, and has good adhesive properties.According to actual electrocardiogram measurements, It can be seen that good results were obtained, and there was no change over time, and that the conventional problems were solved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a dry bioelectrode material. 1... Electrode connector, 2... Holding material, 3... Conductive adhesive.

Claims (1)

[Scope of Claims] 1. An ionic conductive product characterized in that it is made by reacting a polyurethane polyol prepolymer having an alkylene oxide chain with a polyurethane polyisocyanate prepolymer having an alkylene oxide chain, and contains an ionic compound. Polymer adhesive. 2 Claim 1 further contains a plasticizer
The ionically conductive polymer adhesive described in 2.