JPH0695442B2 - Conductive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive composition that can be applied to various electrodes in addition to an electrocardiographic electrode.

[Conventional technology]

In general, an electrode such as an electrocardiogram electrode is used by being attached to the skin of a human body using a conductive composition having rubber elasticity and adhesiveness. As such a conductive composition, a polymer electrolyte, a water-soluble polymer or a hydrophilic polymer containing an electrolyte is generally used as a conductive polymer, and is used in a hydrogel state. Such a conventional conductive composition, the main constituent of the water-containing gel is composed of the conductive polymer,
The conductive polymer is a polyelectrolyte, a water-soluble polymer or a hydrophilic polymer as described above. Therefore, the conventional conductive composition tends to lack affinity and tackiness for oily surfaces such as human skin. Further, as a drawback of the above water-soluble polymers and the like, there is also a tendency that the original shape is easily changed by swelling or dissolution with water, which causes troubles in storage, transportation and the like.

[Problems to be solved by the invention]

In order to solve such problems of affinity for an oily surface of a human body, adhesiveness, and deformation due to moisture, etc., carbon particles as a conductive substance are dispersed in a rubber component, thereby forming a conductive composition. The method of making was proposed. However, since this product does not have water, the electrical contact resistance with respect to the skin becomes high, and the electrical conductivity does not reach the desired range. It is also conceivable to disperse or emulsify the electrolyte with water in a continuous phase such as rubber, but even in this case, sufficient conductivity cannot be obtained and at the same time, the water easily bleeds out of the system. There are some difficulties and it is not practical.

The present invention has been made in view of such circumstances, and has a high affinity for oily surfaces such as a human body, its original shape does not easily change due to moisture and the like, and has high conductivity. The purpose is to provide a composition.

[Means for solving problems]

In order to achieve the above-mentioned object, the conductive composition of the present invention has bentonite particles which are in an integrated state by absorbing water distributed in a continuous phase mainly composed of a rubber component and an oil component. Therefore, the bentonite particles that absorb water are electrically contacted with each other to provide conductivity.

That is, unlike the conventional electrolyte polymer or a water-soluble polymer containing an electrolyte, this conductive composition has a continuous phase composed mainly of a rubber component and an oil component, and the continuous phase is simply moisturized. Are not dispersed or emulsified and exist, but are present in an integrated state by being absorbed by bentonite. Therefore, it does not cause bleeding or the like and has a high affinity for human skin. Moreover, due to the action of the above-mentioned hydrous bentonite particles, the electrical contact resistance with respect to the skin becomes low. As a result, in combination with the electrical contact between the bentonite particles, a high degree of conductivity is exhibited. Also,
The conductive composition of the present invention has a rubber component and an oil component as main components, and does not have a conventional water-soluble polymer or the like as a main component, so that swelling due to humidity and water does not occur, The initial shape can be maintained for a long time.

More specifically, in the conventional oil-soluble polymer-based hydrogel, water particles are emulsified in the form of a W / O type emulsion, whereas in the conductive composition of the present invention, water is absorbed by bentonite. In addition, the water-absorbed bentonite is present in the rubber-oil continuous phase rather than in the form of conventional emulsified particles, but usually as a relatively large granular lump in which fine particles are connected. It is presumed that a part of the lumps are exposed on the surface of the conductive composition, and the rest are connected inside the conductive composition to be distributed in an electrical contact state. Therefore, it is considered that the excellent effect as described above can be obtained.

In the present invention, the water-absorbed bentonite particles are
It is intended to include not only the original particles but also a lump formed by connecting the above-mentioned fine particles.

Such a conductive composition uses a rubber component and an oil component,
It can be obtained by using a tackifying component and the like as necessary.

Examples of the rubber component include ABA type teleblock copolymer elastomers. In this case, it is preferable that A block is made of a hard polymer of vinyl compound such as styrene and methylstyrene, and B block is made of a soft polymer of conjugated diene compound such as butadiene and isoprene. After that, natural rubber, isoprene rubber, etc. can also be used. These may be used alone or in combination.

Examples of the oil component used together with the rubber component include machine oil, cylinder oil, transformer oil, rosin oil and various vegetable oils such as liquid paraffin and salad oil.
These may be used alone or in combination. The amount of the oil component used is preferably set to about 100 parts based on 5 to 120 parts by weight of the rubber component (hereinafter abbreviated as “part”).

Examples of the tackifying component include rosin, modified rosin, petroleum resin, polyterpene resin, polybutene and liquid polyisobutylene. These may be used alone or in combination. Then, when used, it is preferable to set the usage amount within the range of 50 to 300 parts with respect to 100 parts of the rubber component.

An emulsifier is usually used together with the above components. As this emulsifier, nonionic surfactants and anionic surfactants are mainly used. Examples of the nonionic surfactants include polyethylene glycol oleyl ether, polyethylene glycol nonyl phenyl ether, and sorbitan monolaurate. Examples of the anionic surfactant include polyethylene glycol alkyl ether phosphoric acid and magnesium stearate,
Examples include aluminum, calcium and zinc. The amount of these emulsifiers used is 1 to 20 with respect to 100 parts of water.
It is preferable to set it within the range of the part.

Bentonite is used in the water-absorbing state together with the above components in the conductive composition of the present invention, which is a major feature. The bentonite is usually used in combination with water, and the water is 5 to 5% of the total amount of the conductive composition.
It is preferable to set it in the range of 70% by weight (hereinafter abbreviated as “%”) and to set bentonite in a ratio of 5 to 100 parts with respect to 100 parts of water.

The conductive composition of the present invention can be manufactured using the above-mentioned raw materials, for example, as follows. That is, the rubber component, the oil component, and the tackifying component are mixed at a predetermined ratio, and the mixture is heated to about 80 to 150 ° C. and dissolved. Next, an emulsifier or the like is added to this dissolved substance and mixed. On the other hand,
Water and bentonite are mixed at a temperature of 40 to 100 ° C to form an integrated state (water is absorbed by bentonite and coexists in the same phase), and this is added to the above mixture and mixed well. To do. In this way, the target conductive composition is obtained. This conductive composition is usually applied on a support such as a nonwoven fabric or a synthetic resin film for use.

In the conductive composition thus obtained, bentonite absorbs water and is in an integrated state, so that water is stably present even in a high water content state. Therefore, the phenomenon of decrease in adhesive strength due to surface bleeding of water does not occur.

Although the tackifier component is used in the above example, the use of the tackifier component is discontinued when the electrically conductive composition is used for applications that do not require tackiness.

〔The invention's effect〕

As described above, the conductive composition of the present invention comprises a rubber component,
Bentonite particles, which are in an integrated state by absorbing water, are distributed in an electrical contact state in the continuous phase containing oil as the main component, so that water is stable even in a highly hydrous gel state. In addition, it has high conductivity, has a good affinity for the skin, and does not deform due to moisture absorption. That is, the conductive composition of the present invention exhibits excellent characteristics not seen in the past due to the unique constitution not seen in the past.

Next, examples will be described together with comparative examples.

[Example 1] 100 parts of fluid paraffin having a viscosity of 170 cp (20 ° C), 80 parts of polyterpene resin (YS resin PX # 800, manufactured by Yasuhara Yushi Kogyo Co., Ltd.), styrene-butadiene-styrene tereblock elastomer (Califlex, manufactured by Shell Chemical Co., Ltd.) TR1101) 50 parts to 110
It melted by heating at ℃. Then, 10 parts of an emulsifier (Neugen EA80, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 5 parts of magnesium stearate were added to the above-mentioned dissolved substance. Then, while maintaining this at 80 to 90 ° C, a mixture of 60 parts of bentonite (pharmaceutical product) in 200 parts of water was added and dispersed in this mixture,
A desired hydrogel-like conductive composition was obtained.

Next, the conductive composition obtained as described above was spread on a polyester nonwoven fabric to a thickness of 1 mm to prepare a sample.

[Example 2] Fluid paraffin (Sumoil P-55, manufactured by Matsumura Oil Research Institute)
120 parts, styrene-isoprene-styrene tereblock elastomer (Cielflex TR110 manufactured by Shell Chemical Co., Ltd.)
7) 90 parts, petroleum resin (Arakawa Chemical Co., Alcon P-7
0) 150 parts was heated and dissolved at 120 ° C., and 20 parts of an emulsifier (Solgen S-40, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 5 parts of magnesium stearate were added and mixed. Next, set this to 80-90
While keeping the temperature at 0 ° C, a mixture of 60 parts of bentonite (Pharmacopoeia) in 300 parts of water was added and dispersed therein to obtain a target conductive composition.

The conductive composition obtained as described above was spread on a nonwoven fabric in the same manner as in Example 1 to prepare a sample.

[Comparative Example 1] Instead of bentonite, the same amount of precipitated calcium carbonate (pharmaceutical product) was used. A sample was prepared in the same manner as in Example 1 except for the above.

[Comparative Example 2] Precipitated calcium carbonate (pharmaceutical product) was used instead of bentonite. A sample was prepared in the same manner as in Example 2 except for the above.

The adhesive force and the change with time of the samples obtained as described above were measured. The results are shown in Table 1 below.

<< Adhesion test method >> Prepare a test piece with a width of 20 mm and a length of 250 mm, wash the phenol resin plate with acetone in advance, dry it thoroughly, and attach the test piece to the test plate wiped with a dry and clean cloth. , Using an 850g rubber roller, passing it twice at a speed of 300 mm / min, and 30 minutes later, using a Shipper type pendulum tensile tester, peeling by 180 ° peel at a speed of 300 mm / min. The load was measured.

From Table 1, it can be seen that although the Example product has a slightly inferior initial adhesive force as compared with the Comparative Example product, the adhesive force is rather increased over time, which is a remarkable contrast with the Comparative Example which is significantly decreased over time. Is doing. In addition, it can be seen that the comparative example product has a remarkably high electric resistance and a great difficulty in conductivity, whereas the example product has a remarkably low resistance value and is extremely rich in conductivity.

[Brief description of drawings]

The drawing is a time / weight reduction ratio curve diagram of the example product and the comparative example product. A: Example 1, B: Comparative example 1

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Konno 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denki Kogyo Co., Ltd. (72) Naonori Takahashi 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. Bentonite particles which are in a unified state by absorbing water are distributed in a continuous phase mainly composed of a rubber component and an oil component. A conductive composition, which is provided with electrical conductivity by mutual electrical contact. 2. The electrically conductive composition according to claim 1, wherein the continuous phase contains a tackifying component.