JP3539572B2 - Medical conductive media - Google Patents

Description

【００４５】
表１の結果から明らかなように、本発明の医療用導電性媒体は充分な導電性と凝集性を有し、しかも皮膚刺激性を有しないものである。また、粘着性については用いる汎用ポリマーであるアクリル系重合体の種類などによって適宜付与することができるものである。
【００４６】
また、有機溶媒として炭酸プロピレンを用いた本発明品と、エーテル系の有機溶媒を用いた従来品における電解質としての過塩素酸リチウムの添加量が導電性に及ぼす影響を、以下の実施例及び比較例にて調べた。
【００４７】
実施例５
実施例１にて用いたアクリル系重合体３５部に、炭酸プロピレン４０部、フタル酸ジブチル２５部を加えて均一に溶解撹拌したのち、過塩素酸リチウムを下記表２に示す部数添加、溶解し、均一な粘稠溶液とした。
【００４８】
次いで、この粘稠溶液にアルミニウムキレート０．３部を加えて撹拌したのち、この溶液を表面シリコーン処理を施したセパレータ上に乾燥後の厚みが０．３ｍｍとなるように塗布、乾燥して、本発明の医療用導電性媒体を得た。
【００４９】
比較例４および５
実施例１にて用いたアクリル系重合体３５部に、ポリエチレングリコールノニルフェニルエーテル（ＥＯ＝２）４０部（比較例４）、またはジブチルジエチレングリコール４０部（比較例５）を加え、さらにフタル酸ジブチル２５部を加えて均一に溶解撹拌したのち、過塩素酸リチウムを下記表２に示す部数添加、溶解し、均一な粘稠溶液とした。
【００５０】
次いで、この粘稠溶液にアルミニウムキレート０．３部を加えて撹拌したのち、この溶液を表面シリコーン処理を施したセパレータ上に乾燥後の厚みが０．３ｍｍとなるように塗布、乾燥して、医療用導電性媒体を得た。
【００５１】
【表２】

【００５２】
表２から明らかなように、炭酸プロピレンと、可塑剤や軟化剤を併用した本発明品では過塩素酸リチウムの量が微量でも低い抵抗値を示すが、エーテル系の有機溶媒を含有する従来品では、多量に含有させないと充分に抵抗値を下げることができないことが判る。
【００５３】
【発明の効果】
本発明の医療用導電性媒体は、以上のように汎用ポリマーとしてのアクリル系重合体に、有機溶媒としての炭酸プロピレンと、電解質としての特定の無機塩を相溶状態に含み、さらに可塑剤や軟化剤を配合した状態で架橋処理を施してゲル状媒体にしているので、インピーダンスが低く優れた導電性を発揮するものである。また、凝集性と粘着性のバランスにも優れ皮膚刺激性も小さいので、各種医療用電極や、治療電極などにおける生体面との接触媒体として有用なものである。[0001]
[Industrial applications]
The present invention relates to a conductive medium used for medical applications, and more particularly, to a medical conductive medium which is used as a contact medium in a living body electrode or the like for performing diagnosis or treatment by sticking to a body surface.
[0002]
[Prior art]
Conventionally, a biomedical electrode formed by forming a conductive medium layer on an electrode plate is a therapeutic electrode that is expected to promote a blood flow and a massage effect by applying a weak current such as a low frequency to a living body from an external device. Various types of electrodes have been developed, such as diagnostic electrodes used for electrocardiographs that take out and measure weak currents in the living body, ground electrodes used when using an electric scalpel, and electrodes used for cosmetic purposes such as hair loss. I have.
[0003]
The conductive medium functions as a contact medium between the electrode plate and the living body surface in such various electrodes, and requires appropriate skin adhesion and conductivity. As a conductive medium used for medical applications, a water-containing gel-like adhesive medium containing a water-soluble polymer such as sodium polyacrylate or polyvinyl alcohol as a base polymer, sodium chloride as an electrolyte, and further containing water is known. ing.
[0004]
However, such a water-containing adhesive medium is susceptible to the influence of the atmospheric humidity during storage and use, and moisture in the atmosphere and sweat from the skin surface adhere to the adhesive medium. There is a possibility that the moisture in the material may be desorbed and the adhesive property and the conductivity may fluctuate. Therefore, the fact is that the package is usually hermetically sealed even during storage using expensive packaging materials.
[0005]
On the other hand, a so-called non-aqueous adhesive medium has been proposed in order to solve the above-mentioned drawbacks of the water-containing conductive adhesive medium (see JP-A-3-267041). This adhesive medium has a three-dimensional crosslinked structure in which an alkyl acrylate having a long alkylene oxide chain and a dissociable functional group in a side chain is used as a base polymer and a low molecular dissociable salt is dissolved and contained as an electrolyte.
[0006]
However, since alkyl acrylate having an alkylene oxide long chain in the side chain is not a general-purpose polymer, its preparation is complicated. Further, in order to exhibit practical conductivity, it is necessary to contain a relatively large amount of a low-molecular dissociable salt.For example, when using lithium perchlorate described in Examples of the same publication, And more than 1 part by weight per 100 parts by weight of the base polymer. Such an adhesive medium containing a large amount of lithium perchlorate is excellent in conductivity, but has high irritation to the skin surface and easily causes rash and the like, which is not practically preferable.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a medical conductive medium that exhibits excellent conductivity and does not irritate the skin surface to be adhered in developing the non-aqueous type conductive medium. Is to do.
[0008]
[Means for Solving the Problems]
As a result of repeated studies to achieve the above object, the inventors of the present invention have found that a general-purpose acrylic polymer having alkyl (meth) acrylate as a main component monomer , propylene carbonate as a solvent , It has been found that the content of an inorganic salt as an electrolyte can be reduced by adding an agent and / or a softener, and the present invention has been completed.
[0009]
That is, the present invention relates to an acrylic polymer obtained by polymerizing at least 50% by weight of an alkyl (meth) acrylate having an alkyl group having 1 to 14 carbon atoms in an ester side chain (an acrylic polymer having an alkylene oxide long chain in a side chain). and excluding system polymer), medicine for the propylene carbonate, and a monohydric or inorganic salt comprising a divalent metal ion, and a plasticizer and / or softening agent, characterized in that the crosslinking treatment is applied To provide a conductive medium for use. In particular, when a lithium salt is used as the inorganic salt, the effect of the present invention is remarkably exhibited, which is a preferable embodiment.
[0010]
The acrylic polymer as the base polymer of the medical conductive medium in the present invention is freely compatible with propylene carbonate described below, and is for imparting appropriate skin adhesion if necessary. It is obtained by polymerizing at least 50% by weight, preferably 60 to 99% by weight of a (meth) acrylic acid alkyl ester having an alkyl group of the number 1 to 14 in the ester side chain as a main monomer. Specifically, it is an esterified product of an alkyl alcohol having 1 to 14 carbon atoms and acrylic acid or methacrylic acid, which may be used alone or in combination of two or more. It goes without saying that the alkyl group may be linear or branched. When the polymerization amount of the alkyl (meth) acrylate is less than 50% by weight, there is a possibility that sufficient skin adhesion may not be exhibited when tackiness is imparted as an adhesive medium.
[0011]
The acrylic polymer according to the present invention comprises, as a main component monomer, an alkyl (meth) acrylate having an alkyl group having 1 to 14 carbon atoms in the ester side chain as described above, and a monomer which can be copolymerized therewith. Those obtained by copolymerizing the body in an amount of 50% by weight or less, preferably 1 to 40% by weight can be used. By copolymerizing such a monomer, it is possible to impart cohesiveness to the obtained polymer and to impart a crosslinking point at the time of a crosslinking treatment described later. In addition, even when the acrylic polymer does not have a functional group serving as a reaction point at the time of crosslinking, a functional group serving as a crosslinking point can be provided by performing a known chemical modification such as hydrolysis treatment. A polymer using only the above-mentioned alkyl (meth) acrylate may be used.
[0012]
Examples of such copolymerizable monomers include carboxyl group-containing monomers such as (meth) acrylic acid, (anhydride) maleic acid, itaconic acid, crotonic acid, and fumaric acid, and (meth) acrylic acid 2 And hydroxyl group-containing monomers such as -hydroxyethyl ester and (meth) acrylic acid 2-hydroxypropyl ester, and functional monomers such as (meth) acrylamide and (meth) acrylic acid alkyl phosphate. In addition, as long as the compatibility with propylene carbonate is not impaired, an appropriate amount of (meth) acrylic acid alkyl ester having an alkyl group having 15 or more carbon atoms as a side chain may be polymerized.
[0013]
Propylene carbonate contained in the conductive medium of the present invention together with the acrylic polymer is an organic solvent that is hydrophilic and has a relatively high dielectric constant, and plays a very important role in the present invention. In other words, this propylene carbonate exhibits good conductivity by dissolving the inorganic salt contained as an electrolyte, and is compatible with the acrylic polymer to form a non-aqueous gel. It gives elasticity. In particular, by adding propylene carbonate , the amount of the inorganic salt added as an electrolyte can be reduced, so that it plays an important role in reducing skin irritation.
[0014]
If the content of such propylene carbonate is small, practical conductivity cannot be expected, and if it is too large, tackiness is reduced and cohesiveness is reduced, so 20 to 90% by weight, preferably 40 to 80% by weight. %.
[0015]
The inorganic salt contained as an electrolyte together with the propylene carbonate is an inorganic salt containing a monovalent alkali metal ion such as lithium ion or sodium ion or a divalent alkaline earth metal ion such as calcium as a cation component. On the other hand, examples of the anion component include a halogen ion such as a chloride ion, a bromine ion, and an iodine ion; a perchlorate ion; and an alkyl sulfonate ion. Of these, lithium salts are preferred from the viewpoint of conductivity, and in consideration of the solubility with propylene carbonate , lithium bromide, lithium iodide, lithium perchlorate, and lithium trifluorosulfonate are particularly preferred. When such an inorganic salt is contained in a large amount, it causes skin irritation when it comes into contact with the skin for a long time, so that it is in the range of 0.01 to 1% by weight, preferably 0.1 to 0.6% by weight. Preferably.
[0016]
Furthermore, in addition to the above-mentioned propylene carbonate and inorganic salt, a plasticizer and a softener are added to the medical conductive medium of the present invention . The compounding amount of such a plasticizer or softener can be compounded within a range of 40% by weight or less, preferably 5 to 30% by weight. Specifically, olive oil, vegetable oils such as castor oil, mineral oils such as process oils, dibutyl phthalate, dioctyl phthalate, diethyl adipate, ester oils such as isopropyl myristate and the like can be used. It is effective for improving the compatibility with propylene carbonate and improving the adhesive properties.
[0017]
As described above, the composition in which each component is blended is three-dimensionally cross-linked by performing a cross-linking treatment, and becomes a conductive gel. As a method of the crosslinking treatment, a crosslinking agent is blended and heated to chemically crosslink the acrylic polymer in a state containing propylene carbonate , or to irradiate radiation such as ultraviolet rays, electron beams, and γ rays to physically crosslink. There is a method of cross-linking an acrylic polymer in an effective manner.
[0018]
Examples of the crosslinking agent include diisocyanate compounds such as phenylene diisocyanate, 2,4-toluylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene dissocyanate, and hydrogenated products of 4,4-diphenylmethane diisocyanate, and polyethylene glycol diglycidyl ether. And compounds having at least two epoxy groups in the molecule, such as glycerin triglycidyl ether, and polyvalent metal organic compounds such as aluminum alcoholate and aluminum chelate. In the crosslinking reaction, the crosslinking reaction can be controlled using an organic tin catalyst such as dioctyltin dilaurate or a neutralizing agent such as sodium hydroxide or triethanolamine.
[0019]
Since the amount of such a cross-linking agent greatly affects the cohesiveness and adhesive properties of the obtained cross-linked product, it is usually set to 0.01 to 10% by weight, preferably 0.05 to 5% by weight. If the amount is less than 0.01% by weight, the crosslinking is not sufficient and the cohesiveness becomes insufficient, resulting in a gel having no shape retention. On the other hand, when the amount exceeds 10% by weight, propylene carbonate, which is a liquid component, tends to bleed, and the adhesive properties are reduced.
[0020]
On the other hand, in the case of crosslinking by irradiation with radiation such as electron beam or γ-ray, various peroxides such as benzoyl peroxide and lauroyl peroxide are added as necessary, and the irradiation dose is increased for the same reason as in the case of the crosslinking agent. Is adjusted to the range of 10 to 100 kGly, preferably 20 to 70 kGly. In the case of ultraviolet irradiation, light irradiation can be carried out in the presence of an ultraviolet radical initiator such as benzophenone or benzoylalkyl ether or various sensitizers.
[0021]
The medical conductive medium of the present invention obtained as described above is compatible with the acrylic polymer in a state where a specific inorganic salt is dissolved and dissociated in propylene carbonate, which is a solvent having a relatively high dielectric constant, as an electrolyte. It exhibits excellent conductivity by being further contained and retained, and further by being compounded with a plasticizer and a softener . Moreover, since the conductive medium has been subjected to the cross-linking treatment, it has not only excellent cohesiveness but also little irritation to the skin surface to be adhered.
[0022]
【Example】
Hereinafter, examples of the medical conductive medium of the present invention will be shown, and more specifically. It goes without saying that various applications can be made without departing from the technical idea of the present invention. In the following text, “part” means “part by weight”.
[0023]
Example 1
97 parts of n-butyl acrylate and 3 parts of methacrylic acid were copolymerized in toluene using azobisisobutyronitrile as a polymerization initiator. The weight average molecular weight (GLP method) of the obtained acrylic polymer was 570,000.
[0024]
After 30 parts of propylene carbonate and 30 parts of diethyl phthalate were added to 30 parts of the obtained acrylic polymer and uniformly dissolved and stirred, 0.2 part of lithium perchlorate was added and dissolved to obtain a uniform viscous solution. did.
[0025]
Next, 0.1 part of dioctyltin dilaurate and 0.5 part of carbodiimide-modified isocyanate were added to the viscous solution, and the mixture was stirred. After that, the solution was dried on a surface-treated silicone separator to a thickness of 0.3 mm. The resultant was coated and dried to obtain a medical conductive medium of the present invention.
[0026]
Example 2
To 40 parts of the acrylic polymer used in Example 1, 40 parts of propylene carbonate and 20 parts of dibutyl phthalate were added, and the mixture was uniformly dissolved and stirred. Then, 0.2 part of lithium perchlorate was added and dissolved, and the mixture was uniformly mixed. A viscous solution was obtained.
[0027]
Then, 0.1 part of dioctyltin dilaurate and 0.3 part of aluminum chelate are added to this viscous solution and stirred, and then the thickness of this solution after drying on a surface-treated separator is 0.3 mm. And then dried to obtain a medical conductive medium of the present invention.
[0028]
Example 3
70 parts of ethyl acrylate, 29 parts of 2-ethylhexyl acrylate, and 1 part of 2-hydroxymethyl acrylate were copolymerized in the same manner as in Example 1 to obtain an acrylic polymer. The weight average molecular weight was 420,000.
[0029]
To 35 parts of the obtained acrylic polymer, 45 parts of propylene carbonate and 20 parts of dibutyl phthalate were added and uniformly dissolved and stirred, and then 0.4 part of lithium iodide was added and dissolved to form a uniform viscous solution. .
[0030]
Next, 0.1 part of dioctyltin dilaurate and 0.5 part of carbodiimide-modified isocyanate were added to the viscous solution, and the mixture was stirred. After that, the solution was dried on a surface-treated silicone separator to a thickness of 0.3 mm. The resultant was coated and dried to obtain a medical conductive medium of the present invention.

[0031]
Example 4
To 35 parts of the acrylic polymer used in Example 1, 45 parts of propylene carbonate and 20 parts of dibutyl phthalate were added and uniformly dissolved and stirred. Then, 0.2 parts of lithium perchlorate and 0.1 parts of benzoyl peroxide were added. Was added and dissolved to obtain a uniform viscous solution.
[0032]
Next, the viscous solution was put into a petri dish to a depth of 0.3 mm, and after purging with nitrogen, irradiated with 60 kGly γ-ray to obtain a medical conductive medium of the present invention solidified in a gel state.
[0033]
Comparative Example 1
To 30 parts of the acrylic polymer used in Example 1, 40 parts of polyethylene glycol nonylphenyl ether (EO = 2) and 30 parts of dibutyl phthalate were added, and the mixture was uniformly dissolved and stirred. Was added and dissolved to obtain a uniform viscous solution.
[0034]
Next, after adding 0.3 parts of aluminum chelate to the viscous solution and stirring, the solution was applied on a surface-siliconized separator so that the thickness after drying was 0.3 mm, and dried, A medical conductive medium was obtained.
[0035]
Comparative Example 2
To 30 parts of the acrylic polymer used in Example 1, 40 parts of polyethylene glycol nonyl phenyl ether (EO = 2) and 30 parts of dibutyl phthalate were added and uniformly dissolved and stirred, and then 1 part of lithium perchlorate was added. Addition and dissolution resulted in a homogeneous viscous solution.
[0036]
Then, after adding 0.3 parts of aluminum chelate to the viscous solution and stirring, the solution was applied on a surface-siliconized separator so that the thickness after drying was 0.3 mm, and dried. A medical conductive medium was obtained.
[0037]
Comparative Example 3
To 30 parts of the acrylic polymer used in Example 1, 40 parts of dibutyldiethylene glycol and 30 parts of dibutyl phthalate were added, and the mixture was uniformly dissolved and stirred. Then, 0.2 part of lithium perchlorate was added and dissolved, and the mixture was uniformly dissolved. A viscous solution was obtained.
[0038]
Next, 0.1 part of dioctyltin dilaurate and 0.6 part of carbodiimide-modified isocyanate were added to the viscous solution, and the mixture was stirred. After that, the solution was dried on a surface-treated silicone separator to a thickness of 0.3 mm. The resultant was coated and dried to obtain a medical conductive medium.
[0039]
The conductivity, cohesion, adhesiveness, and skin irritation of the conductive media obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were measured or determined according to the following criteria. Shown in
[0040]
<Conductivity>
The conductive medium having a thickness of 0.3 mm obtained in each of Examples and Comparative Examples was cut into an area of 10 mm × 10 mm, sandwiched between copper plates from both sides, and an AC voltage of 1 kHz and 1 mV was applied using an LCR meter. In each case, the impedance was measured.
[0041]
<Cohesiveness>
The conductive medium having a thickness of 0.3 mm obtained in each of Examples and Comparative Examples was cut into an area of 20 mm × 20 mm, placed on a flat plate, and left at 40 ° C. for 24 hours to lose its shape (deformation). ) And run-off were observed. [○: good cohesiveness, ×: poor cohesiveness]
[0042]
<Tackiness>
The conductive medium having a thickness of 0.3 mm obtained in each of the examples and comparative examples was cut into an area of 20 mm x 20 mm, and the stickiness was determined by touching the medium. [○: Sufficient stickiness, Δ: Slightly sticky, ×: No sticky]
[0043]
<Skin irritation>
The conductive medium having a thickness of 0.3 mm obtained in each of the examples and comparative examples was cut into an area of 10 mm x 10 mm, which was adhered to the inner side of the upper arm, and the skin irritation after 8 hours was determined. When pain or itching occurred during the test, the test was interrupted to determine the stimulus state. [○: no irritation, Δ: weak irritation, ×: obvious irritation]
[0044]
[Table 1]

[0045]
As is clear from the results shown in Table 1, the medical conductive medium of the present invention has sufficient conductivity and cohesiveness, and has no skin irritation. In addition, the adhesiveness can be appropriately imparted depending on the type of an acrylic polymer which is a general-purpose polymer to be used.
[0046]
In addition, the effect of the amount of lithium perchlorate added as an electrolyte on the conductivity between the product of the present invention using propylene carbonate as the organic solvent and the conventional product using an ether-based organic solvent was evaluated by the following Examples and Comparative Examples. Investigated by example.
[0047]
Example 5
To 35 parts of the acrylic polymer used in Example 1, 40 parts of propylene carbonate and 25 parts of dibutyl phthalate were added and uniformly dissolved and stirred, and then lithium perchlorate was added and dissolved in the number of parts shown in Table 2 below. To give a homogeneous viscous solution.
[0048]
Then, after adding 0.3 parts of aluminum chelate to the viscous solution and stirring, the solution was applied on a surface-siliconized separator so that the thickness after drying was 0.3 mm, and dried. A medical conductive medium of the present invention was obtained.
[0049]
Comparative Examples 4 and 5
To 35 parts of the acrylic polymer used in Example 1, 40 parts of polyethylene glycol nonylphenyl ether (EO = 2) (Comparative Example 4) or 40 parts of dibutyldiethylene glycol (Comparative Example 5) were added, and further dibutyl phthalate was added. After adding 25 parts and uniformly dissolving and stirring, lithium perchlorate was added and dissolved in the number of parts shown in Table 2 below to obtain a uniform viscous solution.
[0050]
Then, after adding 0.3 parts of aluminum chelate to the viscous solution and stirring, the solution was applied on a surface-siliconized separator so that the thickness after drying was 0.3 mm, and dried. A medical conductive medium was obtained.
[0051]
[Table 2]

[0052]
As is clear from Table 2, the product of the present invention in which propylene carbonate is used in combination with a plasticizer and a softening agent shows a low resistance value even with a small amount of lithium perchlorate, but the conventional product containing an ether organic solvent. It can be seen that the resistance value cannot be sufficiently reduced unless a large amount is contained.
[0053]
【The invention's effect】
The medical conductive medium of the present invention contains an acrylic polymer as a general-purpose polymer as described above, propylene carbonate as an organic solvent, and a specific inorganic salt as an electrolyte in a compatible state, and further includes a plasticizer and Since the gelling medium is formed by performing a cross-linking treatment in a state in which the softening agent is blended, it has low impedance and exhibits excellent conductivity. In addition, since it has a good balance between cohesiveness and adhesiveness and low skin irritation, it is useful as a medium for contact with a living body surface in various medical electrodes, therapeutic electrodes and the like.

Claims (4)

Acrylic polymer obtained by polymerizing at least 50% by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms in an ester side chain ( excluding an acrylic polymer having a long alkylene oxide chain in a side chain) ) , Propylene carbonate, an inorganic salt composed of a monovalent or divalent metal ion, and a plasticizer and / or a softener, and subjected to a cross-linking treatment. The medical conductive medium according to claim 1, wherein the plasticizer and / or the softener is an ester oil. The medical conductive medium according to claim 1, wherein the inorganic salt is a lithium salt. 2. The medical conductive medium according to claim 1, wherein the crosslinking treatment is performed by blending a crosslinking agent or by irradiation with radiation.