JP5377380B2 - Electrode pad and manufacturing method thereof - Google Patents

Description

The present invention relates to an electrode pad and a manufacturing method thereof . More particularly, the present invention relates to an electrode pad including a polyurethane gel having improved strength and a method for manufacturing the same . The electrode pad of the present invention transmits an electrical signal from the human body surface to a recording device such as an electrocardiograph, an electroencephalograph, an electromyograph, or transmits an electrical signal from the device to the human body surface like a low frequency electrode. An electrode pad for interposing between the metal electrode surface of the device and the human skin surface and maintaining good mechanical and electrical connection between them, particularly an electrode pad suitable for suction type electrodes It can be used suitably.

Conventionally, this type of electrode pad has increasingly used a hydrophilic gel molded product using a gel-like polyurethane (polyurethane gel). However, there is a problem that during use, there are few hydrophilic gel molded products that have sufficient strength, retain moisture and maintain conductivity, and retain the flexibility of polyurethane gel, and must be replaced during use. there were.
JP-A-2004-43577 (Patent Document 1) reports an electrode pad that can solve the above problems. The above publication describes that an electrode pad with excellent performance can be obtained by using a specific plasticizer for the electrode pad.

JP 2004-43577 A

  The electrode pad described in the above publication has high moisture retention, excellent electrical conductivity, and excellent flexibility of the polyurethane gel. However, in order to prevent degradation due to deterioration during repeated use or deterioration during storage, further improvement in the strength of the polyurethane gel and the electrode pad has been desired.

Thus, according to the present invention, an electrode pad comprising a polyurethane gel obtained by gelling a mixture containing a hydrophilic polyurethane prepolymer and water, and an aqueous electrolyte solution ,
The hydrophilic polyurethane prepolymer comprises a polyisocyanate component and a polyol component;
The polyol component has at least one polyoxyalkylene chain containing an oxyethylene group,
The oxyethylene group accounts for 50 to 95% by weight of the total molecular weight of the polyoxyalkylene chain;
An electrode pad is provided in which the polyisocyanate component is contained in the hydrophilic polyurethane prepolymer in an amount of 15 to 25% by weight based on the total amount of the polyisocyanate component and the polyol component.
Further, according to the present invention, there is provided a method for producing the electrode pad , wherein the electrode pad is obtained by gelling a mixture containing the hydrophilic polyurethane prepolymer and water. The

According to the present invention, it is possible to provide a polyurethane gel having high moisture retention, excellent flexibility, and improved strength, and an electrode pad including the polyurethane gel.
The mixture further includes a plasticizer,
The plasticizer contains polyoxypropylated glycerin, polyoxypropylated sorbitol, polyalkylene glycol, oxyethylene group and oxypropylene, which contains oxyethylene group and oxypropylene group, of which oxypropylene group accounts for 60 to 90% by weight of the total molecular weight When the oxypropylene group is selected from the group consisting of monoethers of polyalkylene glycol and glycol diethers, wherein the oxypropylene group occupies 30 to 90% by weight of the total molecular weight of the polyoxyalkylene chain, In addition, a polyurethane gel with improved strength and excellent flexibility can be provided.

Furthermore, when the mixture further contains a polyoxyethylene polyoxypropylene block polymer as a surfactant, it is possible to provide a polyurethane gel having higher moisture retention, excellent flexibility, and improved strength.
In addition, when the electrode pad is obtained by gelling a mixture containing a hydrophilic polyurethane prepolymer and an aqueous electrolyte solution, the electrode pad has higher moisture retention, excellent conductivity and flexibility, and improved strength. Can provide.

The polyurethane gel of the present invention can be obtained by gelling a mixture containing a hydrophilic polyurethane prepolymer and water. Here, the hydrophilic polyurethane prepolymer contains a polyisocyanate component and a polyol component. The polyurethane gel can be formed by the urethane reaction of the polyisocyanate component and the polyol component.
(Hydrophilic polyurethane prepolymer)
(1) Polyisocyanate component As the polyisocyanate component, a component derived from a known polyisocyanate can be used. Examples of the polyisocyanate include methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate. These polyisocyanates may be used alone or in combination of two or more.

(2) Polyol component The polyol component has at least one polyoxyalkylene chain containing an oxyethylene group. The polyoxyalkylene chain includes an oxypropylene group, an oxybutylene group and the like in addition to the oxyethylene group. A polyoxyalkylene chain having a molecular weight of 500 to 3000 is preferably used. The polyoxyalkylene chain can be obtained, for example, by polymerizing at least one monomer such as ethylene oxide, propylene oxide, butylene oxide. Further, the polyoxyalkylene chain may partially contain units derived from other polyols such as heptanediol, hexanediol, and cyclohexanediol. Moreover, when using a copolymer as a polyoxyalkylene chain, the constitution of the copolymer may be a random copolymer or a block copolymer.

  Here, the oxyethylene group accounts for 50 to 95% by weight of the total molecular weight of the polyoxyalkylene chain. When the amount is less than 50% by weight, the dispersibility in water is deteriorated, and the formed gel may be separated. When it is more than 95% by weight, the gel becomes soft and the strength may be insufficient. A more preferable occupation ratio of the oxyethylene group is 60 to 80% by weight.

(3) Ratio of polyisocyanate component and polyol component The polyisocyanate component is contained in the hydrophilic polyurethane prepolymer in an amount of 15 to 25% by weight based on the total amount of the polyisocyanate component and the polyol component. When the content of the polyisocyanate component is less than 15% by weight, gelation becomes insufficient and the shape retention of the gel is deteriorated, so that the strength may be lowered. When the amount is more than 25% by weight, the strength may decrease (particularly, the strength may decrease with time). Here, the strength is not simply increased by increasing the content of the polyisocyanate component. The reason for this is considered to be that when the content is increased, the molecular weight between the cross-linking points of the polyisocyanate component and the polyol component is decreased, and as a result, the strength is decreased. The content of the polyisocyanate component is more preferably 17 to 23% by weight.

(water)
The water content is preferably 20 to 95% by weight with respect to the total of the polyurethane gel and water. When the water content is less than 20% by weight, the produced gel may become too hard to be adapted to the adherend. If it exceeds 95% by weight, a gel having sufficient strength may not be formed. A more preferable content is 50 to 80% by weight.
Moreover, it is preferable that the polyisocyanate component and water are contained in the mixture in a ratio of 0.04: 1 to 0.08: 1. By containing water in this proportion, a polyurethane gel having an improved appearance can be obtained. When the ratio of the polyisocyanate component is less than 0.04, not only the strength is lowered, but the gel may not be sufficiently hardened and molding may be difficult. When more than 0.08, the foaming at the time of gelation is intense, and the appearance of the gel may be deteriorated. A more desirable ratio is 0.05: 1 to 0.075: 1.

(Other ingredients)
(I) The mixture may further contain a plasticizer.
The plasticizer has a role of maintaining a good affinity between the hydrophilic polyurethane prepolymer and water. By including a plasticizer, moisture is not separated during gel formation, the desired shape is maintained, moisture retention during use is good, and flexibility of the gel can be ensured even when dried.

The plasticizer is not particularly limited, but has a polyoxyalkylene chain in the main skeleton, and the polyoxyalkylene chain is a polyalkylene glycol type oil mainly composed of oxyethylene and oxypropylene, and includes triol, diol, monool, And other polyols and types that do not contain hydroxyl groups. For example,
-Polyoxypropylated glycerin (average molecular weight is preferably 200-5000),
-Polyoxypropylated sorbitol (average molecular weight is preferably 300 to 5000),
A plasticizer containing two or more oxyalkylene chains (a) a polyalkylene glycol containing an oxyethylene group and an oxypropylene group, of which the oxypropylene group accounts for 60 to 90% by weight of the total molecular weight (average molecular weight is 200 to 6000 is preferred),
(B) a monoether of polyalkylene glycol containing an oxyethylene group and an oxypropylene group, wherein the oxypropylene group accounts for 30 to 90% by weight of the total molecular weight of the polyoxyalkylene chain (average molecular weight is preferably 200 to 4000), And glycol diethers.

The plasticizer containing two or more oxyalkylene chains may be a random copolymer or a block copolymer. One hydroxyl group of the monoether of polyalkylene glycol contained in the plasticizer (b) is, for example, ether-bonded to an alkyl group.
Specific examples of glycol diethers include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, diethylene glycol Examples include propylene glycol dimethyl ether and tripropylene glycol dimethyl ether.

  The content of the plasticizer in the mixture is preferably 5 to 30% by weight. When the content of the plasticizer is less than 5% by weight, the flexibility during drying is small and the polyurethane gel adherence may be insufficient. Moreover, when it exceeds 30 weight%, a polyurethane gel may become too soft and a shape may not be hold | maintained. A more preferable content is 10 to 20% by weight.

(Ii) The mixture may further contain a surfactant. The surfactant has an action of increasing the compatibility between the polyurethane prepolymer and water, and is effective in preventing water separation after gelation, stabilizing the electrolyte solution, and preventing self-adhesion of the generated gel.
Specific examples of the surfactant include oxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyethylene hydrogenated castor oil, and the like. Examples thereof include oxypropylene block polymers (average molecular weight is preferably about 1000 to 8000).

(Iii) The mixture may further contain a chain extender. A known material can be used as the chain extender. Examples thereof include diols such as ethylene glycol, propylene glycol, and butanediol, and diamines such as ethylenediamine, toluenediamine, and isophoronediamine.
(Iv) In the mixture, reaction suppression of acidic substances such as p-toluenesulfonic acid such as amines such as triethanolamine as a reaction accelerator for urethane prepolymer, sodium carbonate, sodium silicate and the like as other additives An agent, a gel reinforcing filler such as Aerosil, an antifungal agent such as Amical, and a coloring agent can be added.

(5) Gelation The mixture containing the hydrophilic polyurethane prepolymer becomes a polyurethane gel by gelation.
The content of the hydrophilic polyurethane prepolymer in the mixture is preferably 5 to 30% by weight. When the content of the hydrophilic polyurethane prepolymer is less than 5% by weight, a gel having sufficient strength may not be generated. On the other hand, if it exceeds 30% by weight, the gel may become too hard to fit the adherend. A more preferable content is 10 to 20% by weight.

Gelation is performed by stirring a mixed liquid containing a hydrophilic polyurethane prepolymer and water, a plasticizer, a surfactant, an electrolyte, a reaction accelerator, and the like so that each compound is uniformly mixed, and then, in a mold container or the like. It is made to gel by injecting, reacting (crosslinking) and aging while maintaining an appropriate temperature and humidity environment.
The reaction temperature is preferably 20 to 50 ° C. The reaction humidity is preferably 40 to 70% RH. Although reaction time is suitably adjusted according to a molding, it can be set as about 3 to 60 minutes. In the gelation, the reaction rate may be adjusted by adding treatments such as heating, cooling, and pH adjustment as necessary.
The thickness of the polyurethane gel is adjusted by spreading the mixture before the gelation is completed using, for example, an extruder, a doctor blade, or a roller, or filling a container with a predetermined thickness. it can.

(6) Polyurethane gel shape The shape of the polyurethane gel is not particularly limited, but is oval, circular, heart-shaped, semi-circular, semi-elliptical, square, rectangular, trapezoidal, triangular, shape along the application site, or these A combination etc. are mentioned. Moreover, if a convex part or a concave part is provided for the purpose of positioning or the like in the center part or the peripheral part of the gel sheet, or if a cut or cut-out part is provided according to the shape of the use site, the handling property of the gel sheet can be improved.

(Electrode pad)
The electrode pad includes a polyurethane gel and an aqueous electrolyte solution.
(1) Electrolyte aqueous solution The electrolyte aqueous solution contains water and an electrolyte.
As the electrolyte, normally used sodium chloride, potassium chloride and the like are suitable. The content of the electrolyte is preferably 0.1 to 5% by weight with respect to the total of the polyurethane gel and the aqueous electrolyte solution. When the electrolyte content is less than 0.1% by weight, desired conductivity may not be obtained. When it is more than 5% by weight, the electrolyte component may be deposited on the gel surface, resulting in poor appearance. A more preferable content is 0.2 to 2% by weight.
The water content is the same as the content described in the column of polyurethane gel.

(2) Formation method of electrode pad The formation method of the electrode pad can employ the same method as the formation method of the polyurethane gel except that the electrolyte solution is contained in the mixture for forming the polyurethane gel. In particular, the electrode pad is preferably formed by gelling a mixture containing a hydrophilic polyurethane prepolymer and an aqueous electrolyte solution. In this method, the moisture retention of the electrode pad can be further improved.

(3) Use of electrode pads Electrode pads can be used to transmit electrical signals from the human body surface to devices such as electrocardiographs, electroencephalographs, and electromyographs, or from devices such as low-frequency treatment devices. Can be suitably used for the purpose of maintaining good mechanical and electrical connection between the electrode and the human body surface by interposing between the electrode constituting the device and the human body surface. .

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. The measurement methods described in the examples are described below.
(Tensile strength)
A sample molded into a donut shape having an outer diameter of 22 mm, an inner diameter of 10 mm and a thickness of 8 mm was pulled with a Tensilon universal testing machine (manufactured by Orientec, Japan) at a temperature of 23 ° C., a humidity of 54%, and a test speed of 300 mm / min. The load when tearing is broken is taken as the tensile strength.
Further, the sample is put into a hot air dryer at 50 ° C., taken out after 240 hours, left in a room at 23 ± 2 ° C. and humidity 53 ± 3% for 24 hours, and then the tensile strength is measured in the same manner as described above. This measurement condition is a deterioration acceleration test and corresponds to a deterioration time of about one year when stored at 25 ° C.
From the strength after the heat treatment and the strength before the heat treatment, the strength retention rate is calculated using the following formula.
Formula: Maintenance ratio (%) = 100 × (strength after heat treatment) ÷ (strength before heat treatment)

Example 1
20 g of water, 5.5 g of polyoxypropylated glycerin (Sanyox GP-400 manufactured by Sanyo Chemical Industries, average molecular weight 400), polyoxyethylene polyoxypropylene block polymer (Epan 450 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., average molecular weight 2400) Add 0.17 g, Yottle DP-95 (antibacterial agent manufactured by Mitsui Chemicals) 0.0072 g and sodium chloride 0.15 g, and dissolve with stirring. 6.7 g of this aqueous solution and polyurethane prepolymer (prepolymer 660 manufactured by Aoki Oil & Fat Co., Ltd., methylene diphenyl diisocyanate (MDI): ethylene oxide (EO): propylene oxide (PO) = 23: 62: 15 (% by weight)) are mixed. Stir quickly and pour into a predetermined mold. The mold was held at a temperature of 25 ° C. and a humidity of 60% for 3 minutes, reacted and solidified, and then the gel was taken out of the mold, and further held at a temperature of 30 ° C. and a humidity of 45% for 5 minutes, reacted and aged. The obtained polyurethane gel was sealed in an aluminum laminated film bag.
The tensile strength of the obtained polyurethane gel was measured, and the results are shown in Table 1.

Example 2
A polyurethane gel was obtained in the same manner as in Example 1 except that the polyurethane prepolymer was replaced with one having MDI: EO: PO = 17: 66: 17 (weight%) (prepolymer 460 manufactured by Aoki Oil & Fat Co., Ltd.). The tensile strength of the obtained polyurethane gel was measured, and the results are shown in Table 1.
Example 3
A polyurethane gel was obtained in the same manner as in Example 1 except that the amount of the polyurethane prepolymer used was 5.9 g. The tensile strength of the obtained polyurethane gel was measured, and the results are shown in Table 1.
Example 4
A polyurethane gel was obtained in the same manner as in Example 2 except that the amount of the polyurethane prepolymer used was 5.9 g. The tensile strength of the obtained polyurethane gel was measured, and the results are shown in Table 1.

Comparative Example 1
A polyurethane gel was obtained in the same manner as in Example 1 except that the polyurethane prepolymer was replaced with one having MDI: EO: PO = 29: 53: 18 (wt%) (Hicell DN-70, manufactured by Toho Chemical Industry Co., Ltd.). . The tensile strength of the obtained polyurethane gel was measured, and the results are shown in Table 1.

  From Table 1, the polyurethane gel in which the polyisocyanate component is contained in the hydrophilic polyurethane prepolymer in an amount of 15 to 25% by weight based on the total amount of the polyisocyanate component and the polyol component has a good tensile strength maintenance rate. I understand that.

Claims (6)

An electrode pad comprising a polyurethane gel obtained by gelling a mixture containing a hydrophilic polyurethane prepolymer and water, and an electrolyte aqueous solution ,
The hydrophilic polyurethane prepolymer comprises a polyisocyanate component and a polyol component;
The polyol component has at least one polyoxyalkylene chain containing an oxyethylene group,
The oxyethylene group accounts for 50 to 95% by weight of the total molecular weight of the polyoxyalkylene chain;
The pad for electrodes , wherein the polyisocyanate component is contained in the hydrophilic polyurethane prepolymer in an amount of 15 to 25% by weight based on the total amount of the polyisocyanate component and the polyol component. The electrode pad according to claim 1, wherein the polyisocyanate component and water are contained in the mixture in a ratio of 0.04: 1 to 0.08: 1. The mixture further comprises a plasticizer;
The plasticizer includes polyoxypropylated glycerin, polyoxypropylated sorbitol, polyoxyalkylene glycol, oxyethylene group and oxyethylene group, wherein the oxypropylene group comprises 60 to 90% by weight of the total molecular weight. 3. The propylene group, wherein the oxypropylene group is selected from the group consisting of polyalkylene glycol monoethers and glycol diethers occupying 30 to 90% by weight of the total molecular weight of the polyoxyalkylene chain. Electrode pads . The electrode pad according to claim 1, wherein the mixture further contains a polyoxyethylene polyoxypropylene block polymer as a surfactant. The electrode pad according to any one of claims 1 to 4, wherein the electrode pad is obtained by gelling a mixture containing the hydrophilic polyurethane prepolymer and an aqueous electrolyte solution. A manufacturing method of the electrode pad according to any one of claims 1 to 5, mixture preparation of the electrode pads to obtain a polyurethane gel by gelling including said hydrophilic polyurethane prepolymer and water Method.