JP2003225217A - Silicone rubber composition for living body electrode and electrode for living body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicone rubber composition for a living body electrode which imparts a stable conductivity to an electrode composed thereof to be used on the surface of a human body or the like through formulating a specific amount of conductive carbon and an antistatic agent having a part containing metal ions in a molecule. <P>SOLUTION: This silicone rubber composition for living body electrode is characterized by comprising (A) 100 pts.wt. organopolysiloxane represented by average composition formula (1): R<SP>1</SP><SB>n</SB>SiO(<SB>4-n)/2</SB>(wherein R<SP>1</SP>is the same or different nonsubstituted or substituted monovalent hydrocarbon group; n is a positive number of 1.98-0.02) and having at least two unsaturated aliphatic groups in a molecule, (B) 1-100 pts.wt. conductive carbon, (C) 0.1-50 pts.wt. antistatic agent having a part containing metal ions in the molecule and (D) a curing agent having the amount which can cure the ingredient (A). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition for bioelectrodes, which provides a cured product which is stable in a conductive region and has a good surface conductive property even when contacted with human skin or the like. The present invention relates to a biomedical electrode.

[0002]

2. Description of the Related Art Electrodes used for electrocardiograms and the like are still made of metal in some cases. However, a conventional metal electrode using nickel silver or the like feels cold when it comes into contact with the skin,
It is not suitable for people with a bad heart, and if vacuum contact is made with the skin at the time of measurement, there is the problem that traces of the electrodes will remain on the contact area. In order to solve this, the development of a rubber electrode has been desired, but in the conventional conductive silicone rubber blended with carbon, electron conduction could not be obtained due to salt and water contained in sweat on the human body surface, When contacted with the skin under pressure, the resistance value varied and was not suitable for use. In addition, a conductive rubber made of polyurethane having a polar group and also having ion conductivity is easily affected by a natural environment (humidity, etc.) and has poor weather resistance, so that there is a problem in reliability during measurement.

Further, the inventor of the present invention has disclosed in Japanese Patent Laid-Open No. 2001-164
In JP-A-118, a semiconductive roll material suitable for a semiconductive roll material is proposed by using a conductive titanium oxide whisker in combination with an antistatic agent having a portion containing a metal ion in the molecule. There is no mention of application to.

The present invention has been made to improve the above circumstances, and a silicone rubber composition for a biomedical electrode that can be obtained by stabilizing the resistance value of the electrode on the surface of the human body and the like for a living body obtained by using the same. It is intended to provide an electrode.

[0005]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that carbon-containing conductive silicone rubber contains a portion containing a metal ion in its molecule. It has been found that by blending an antistatic agent having a property of giving a stable conductivity to silicone rubber, and being stable to the environment of the human body surface, it can be a material for bioelectrodes that can withstand long-term use. .

That is, 100 parts of organopolysiloxane represented by the following average composition formula (1) (part by weight, the same applies hereinafter)
And 1 to 100 parts of the conductive carbon of the component (B), and 0.1 to 50 parts of the antistatic agent having a part containing a metal ion in the molecule of the component (C) are blended. The rubber composition may be formed of an organic peroxide or an organohydrogenpolysiloxane / platinum-based catalyst alone,
It can also be cured with a combined system of organic peroxide and organohydrogenpolysiloxane / platinum-based catalyst, and the resulting molded product prevents the alteration of the electrical conductivity on the human body surface, resulting in a change in the resistance value of the material. Therefore, the present invention was found to be the most suitable as a material for a biomedical electrode, since it can withstand long-term use, and the present invention has been accomplished.

Accordingly, the present invention provides (A) the following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is not substituted or A substituted monovalent hydrocarbon group, n is a positive number of 1.98 to 2.02), and 100 parts by weight of organopolysiloxane having at least two aliphatic unsaturated groups in one molecule. (B) Conductive carbon 1 to 100 parts by weight (C) Antistatic agent having a part containing a metal ion in the molecule 0.1 to 50 parts by weight (D) Curing agent Amount capable of curing the above component (A). Provided is a silicone rubber composition for a biomedical electrode and a biomedical electrode characterized by containing the same.

The present invention will be described in more detail below. The organopolysiloxane of the component (A), which is the first essential component of the silicone rubber composition according to the present invention, is represented by the following average composition formula (1): It is an organopolysiloxane having at least two aliphatic unsaturated groups in the molecule. R ¹ _n SiO _{(4-n) / 2} (1) (In the formula, R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group, and n is 1.98 to 2.02. Is a positive number.)

In the above formula, R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a cycloalkyl group such as a cyclohexyl group, a vinyl group or an allyl group,
Alkenyl groups such as butenyl group and hexenyl group, aryl groups such as phenyl group and tolyl group, aralkyl groups such as benzyl group and phenylethyl group, or part or all of hydrogen atoms bonded to carbon atoms of these groups are halogen. An atom, a chloromethyl group substituted with a cyano group, a trifluoropropyl group, a cyanoethyl group and the like, which are the same or different and preferably have 1 to 10 carbon atoms, more preferably have 1 to 8 carbon atoms and are unsubstituted or substituted. It is a monovalent hydrocarbon group. In this case, R ¹ needs to have at least two aliphatic unsaturated groups (particularly alkenyl groups), but the content of aliphatic unsaturated groups in R ¹ is 0.001 to 20 mol. %, Particularly preferably 0.025 to 5 mol%. Also,
n is a positive number of 1.98 to 2.02. The organopolysiloxane of the above formula (1) is basically preferably linear, but may be one kind or a mixture of two or more kinds having different molecular structures. The aliphatic unsaturated group may be at the end of the molecular chain or in the middle of the molecular chain, but is preferably at least at the end of the molecular chain.

Further, the above-mentioned organopolysiloxane has an average degree of polymerization of 100 to 20,000, particularly 3,000 to 8,
It is preferably 000.

The conductive carbon as the component (B), which is the second essential component of the present invention, is carbon black that has been conventionally used, such as Denka Black (manufactured by Denki Kagaku Kogyo KK) or Ketjen Black ( (Ketjen Black International Co., Ltd.) and the like.

The amount of the component (B) added is preferably 1 to 100 parts, more preferably 10 to 90 parts, relative to 100 parts of the component (A) organopolysiloxane. If it is less than 1 part, the electric resistance intended by the present invention cannot be obtained, and if it exceeds 100 parts, the workability of the silicone rubber compound is greatly impaired.

The antistatic agent having a portion containing a metal ion in the molecule of the component (C) which is the third essential component of the present invention is
There is no particular limitation as long as it contains a metal ionic group in the molecule and has antistatic properties, but a polyether having a moiety containing the metal ionic group in the molecule is preferable. This is because the metal ion in the molecule develops conductivity, which complements the electron conduction of carbon, so it shows a certain resistance value even when the molded product is pressurized, and it also bleeds moderately and Stabilizes the electrical conductivity of silicone rubber even in the presence of sweat. Examples of metal ions include alkali metal ions and alkaline earth metal ions,
Particularly, lithium ion (Li ⁺ ) is preferable. Examples of commercially available products include US600 series (manufactured by Sanken Kako Co., Ltd.), Sanconol series (manufactured by Sanko Kasei Co., Ltd.) and the like. The addition amount is 0.1 to 50 parts with respect to 100 parts of the organopolysiloxane (A), and particularly 1
It is preferable to add 10 parts. When it is less than 0.1 part, the ionic conductivity effect is not sufficiently exhibited, and when it exceeds 50 parts, the processability of the silicone rubber is significantly impaired.

In the present invention, it is the fourth essential component (D).
As the component curing agent, a known organohydrogenpolysiloxane / platinum-based catalyst (curing agent for addition reaction) or an organic peroxide catalyst can be used.

As the platinum-based catalyst, known catalysts can be used, and specifically, platinum element simple substance, platinum compound, platinum complex, chloroplatinic acid, alcohol compound of chloroplatinic acid, aldehyde compound, ether compound, various olefins. And the complex are exemplified. The amount of the platinum-based catalyst added is preferably in the range of 1 to 2,000 ppm as platinum atom with respect to the organopolysiloxane of the component (A).

On the other hand, the organohydrogenpolysiloxane may be linear, branched or cyclic, but is preferably one represented by the following average composition formula (2).

H _b R ² _c SiO _{(4-bc) / 2} (2) (wherein R ² is the same as R ¹ and has ¹ to 10 carbon atoms, especially 1
Although it is an unsubstituted or substituted monovalent hydrocarbon group of to 8, those having no aliphatic unsaturated bond are preferable. b is 0 <b ≦
3 is a positive number, c is a positive number 0 ≦ c <3, and b + c is 0 <b +
c ≦ 3. )

This organohydrogenpolysiloxane preferably has a degree of polymerization of 300 or less, and is a diorganopolysiloxane having a terminal blocked with a dimethylhydrogensilyl group, a dimethylsiloxane unit and a methylhydrogensiloxane unit, and a terminal trimethylsiloxy group. A copolymer with a unit, a low-viscosity fluid composed of a dimethylhydrogensiloxane unit (H (CH ₃ ) ₂ SiO _0.5 unit) and a SiO ₂ unit, 1,3,5,7-tetrahydrogen-1,3,3. 5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1,5-dihydrogen-3,7- Examples of dihexyl-1,3,5,7-tetramethylcyclotetrasiloxane are .

The addition amount of the organohydrogenpolysiloxane as the curing agent is such that the hydrogen atom (Si) directly bonded to the silicon atom with respect to the aliphatic unsaturated group (particularly alkenyl group) of the organopolysiloxane of the component (A). It is desirable to use it in a ratio such that the (-H group) is 50 to 500 mol%.

Examples of the organic peroxide catalyst include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, and the like. 2,5-dimethyl-bis (2,2
5-t-butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate and the like can be mentioned. The addition amount of the organic peroxide catalyst is preferably 0.1 to 5 parts with respect to 100 parts of the organopolysiloxane as the component (A).

The silicone rubber composition according to the present invention includes
In addition to the above-mentioned essential components, a reinforcing silica powder may be added as an optional component as long as it does not impair the effects of the present invention. The reinforcing silica powder is added to obtain a silicone rubber having excellent mechanical strength, and for this purpose, the specific surface area is 50 m ² / g or more, preferably 100 to 400 m ² / g. is there. Specific surface area is 50m ² /
If it is less than g, the mechanical strength of the cured product may decrease. Examples of such reinforcing silica include fumed silica and precipitated silica, and those whose surface is made hydrophobic with chlorosilane or hexamethyldisilazane are also preferably used.

The amount of the reinforcing silica powder added is 5 to 70 with respect to 100 parts of the organopolysiloxane of the component (A).
Parts, especially 10 to 50 parts are preferable, and if it is less than 5 parts, the reinforcing effect cannot be obtained because the addition amount is too small, and if it exceeds 70 parts, the workability deteriorates and the mechanical strength decreases. There is a risk.

In the composition of the present invention, if necessary, other conductive materials such as conductive inorganic oxides (acicular conductive titanium oxide, conductive zinc oxide, etc.), silicone rubber powder as a filler, Fillers such as red iron oxide, ground quartz and calcium carbonate may be added.

Furthermore, an inorganic material for forming a sponge,
An organic foaming agent may be added. Examples of the foaming agent include azobisisobutyronitrile, dinitropentamethylenetetramine, benzenesulfone hydrazide, and azodicarbonamide. The addition amount thereof is preferably in the range of 1 to 10 parts per 100 parts of the silicone rubber compound. is there. Thus, by adding a foaming agent to the composition of the present invention, a sponge-like silicone rubber can be obtained.

Further, it is optional to add various additives such as a colorant and a heat resistance improver, a reaction control agent, a release agent or a dispersant for a filler to the composition of the present invention, if necessary. However, the diphenylsilanediol, various alkoxysilanes, carbon functional silanes, silanol group-containing low molecular weight siloxanes, etc. used as the filler dispersant should be added in a minimum amount so as not to impair the effects of the present invention. It is preferable to stop.

Further, in order to make the silicone rubber composition of the present invention flame-retardant and fire-resistant, a platinum-containing material, a platinum compound and titanium dioxide, platinum and manganese carbonate, platinum and γ-Fe.
Known additives such as ₂ O ₃ , ferrite, mica, glass fiber and glass flakes may be added.

The silicone rubber composition according to the present invention is prepared by uniformly mixing the above-mentioned components using a rubber kneader such as a two-roll, Banbury mixer, dough mixer (kneader), etc. It can be obtained by applying.

The thus obtained silicone rubber composition for a biomedical electrode can be molded into a shape required for a biomedical electrode by various molding methods such as mold pressure molding and extrusion molding. . The curing can be appropriately selected depending on the curing method and the thickness of the molded product, but usually 80
It can be carried out under the conditions of ~ 400 ° C for 10 seconds to 30 days.

The silicone rubber composition for a bioelectrode of the present invention has a volume resistivity of 1.0 Ω · c, especially when a cured product thereof is used.
By adjusting to m or less, it can be suitably used as a biomedical electrode.

[0030]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 and 2] Dimethylsiloxane unit 99.825 mol%, methylvinylsiloxane unit 0.
15 mol%, dimethylvinylsiloxane unit 0.025
100 parts by weight of rubber-like organopolysiloxane having an average degree of polymerization of about 5,000 and DENKA BLACK (manufactured by Denki Kagaku Kogyo KK) as conductive carbon
Part, Sanconol 20R (manufactured by Sanko Kasei Co., Ltd.) as an antistatic agent having a part containing lithium ions 6 parts and 1
Two parts were blended using a roll as shown in Table 1 to obtain a base compound.

To 100 parts of the above base compound, 2 parts of C-8A (manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a curing agent, and molded at 170 ° C./10 minutes in a mold having a thickness of 2 mm, and then 200 ° C. And treated for 4 hours to obtain a sheet. Next, this sheet was subjected to an electric resistance measuring device capable of arbitrarily changing the thickness between electrodes, and the resistance value at a compressibility of 10, 20, 30% was measured, and the resistance value stability was evaluated. The results are shown in Table 1.

[Comparative Example 1] As a comparative example, Table 1 also shows an example of Example 1 in which no antistatic agent was used.

[0034]

[Table 1]

From the results shown in Table 1, it was confirmed that the silicone rubber composition for a bioelectrode of the present invention gives a stable conductive region even under pressure.

[0036]

EFFECTS OF THE INVENTION The silicone rubber composition for a bioelectrode of the present invention contains a specific amount of conductive carbon and an antistatic agent having a portion containing a metal ion in the molecule. Stable conductivity is provided as an electrode used in the.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08K 3/24 C08L 71/00 Z C08L 71/00 83/07 83/07 A61B 5/04 300B F term ( Reference) 4C053 BB03 4F071 AA51 AA67 AB03 AE03 AE15 AF37 AH15 BA01 BB03 BB06 4J002 CH002 CH052 CP131 CP141 DA036 DA117 DD027 DE187 EC077 FD102 FD116 FD147 FD157 GQ00

Claims (2)

[Claims] (A) The following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted monovalent) Is a hydrocarbon group, and n is a positive number of 1.98 to 2.02) and has at least two aliphatic unsaturated groups in one molecule 100 parts by weight (B) conductivity Carbon 1 to 100 parts by weight (C) Antistatic agent having a part containing a metal ion in the molecule 0.1 to 50 parts by weight (D) Curing agent Containing an amount capable of curing the component (A). A silicone rubber composition for a biomedical electrode, comprising: 2. A biomedical electrode obtained by curing and molding the silicone rubber composition according to claim 1.