WO2018180190A1

WO2018180190A1 - Silver chloride coated particle

Info

Publication number: WO2018180190A1
Application number: PCT/JP2018/007980
Authority: WO
Inventors: 雅之登峠
Original assignee: タツタ電線株式会社
Priority date: 2017-03-30
Filing date: 2018-03-02
Publication date: 2018-10-04
Also published as: CN110366460A; KR20190130638A; JP6654164B2; JP2018168445A

Abstract

Provided is a silver chloride coated particle wherein the amount of silver used can be reduced while maintaining stable conductivity when used, for example, in a conductive paste constituting a bioelectrode. The particle has a dendrite shaped core having silver on at least part of the surface thereof, and a silver chloride coating layer formed from silver chloride covering at least part of the core surface.

Description

Silver chloride coated grains

The present invention relates to a silver chloride coated particle having at least a part of its surface coated with silver chloride, for example, a particle suitably used in place of silver chloride particles used for biomedical electrodes of medical devices. is there.

In a medical device that measures biological information such as an electrocardiogram, a silver-silver chloride electrode using silver and silver chloride is used as a living body electrode that comes into contact with the living body and receives an electrical signal from the living body. Such biomedical electrodes include those that are used repeatedly and those that are disposable. In particular, disposable biomedical electrodes reduce the amount of silver used due to demands for cost reduction and resource saving. Is required.

Therefore, as a disposable bioelectrode, for example, as shown in FIG. 1, silver particles 4 and silver chloride particles 6, which are spherical or flake-like particles, are formed on a surface of a conductive material 2 such as carbon. What applied the electrically conductive paste mix | blended with is used. The electrical signal in the living body is based on ionic conduction, and a conductive substance such as an electrolyte gel is interposed between the living body surface and the living body electrode 1 as necessary, so that the living body electrode 1 is directly or indirectly on the living body surface. The living body electrical signal can be transmitted to the living body electrode 1 by connecting to the living body electrode, and the silver chloride particles 6 on the living body electrode surface receiving the living body electrical signal are ionized into silver ions 5 and chloride ions 8. To do. Then, by transferring electrons 7 between the ionized silver ions 5 and the silver particles 4 existing as molecules, the electric signal is converted from ionic conduction to electric conduction, and is transmitted to the measuring instrument via the conductive material 2. Biological information can be transmitted.

However, the silver particles 4 and the silver chloride particles 6 are difficult to uniformly disperse in the conductive paste due to the difference in specific gravity and the high agglomeration property and hard disintegration property of the silver chloride particles 6. Therefore, in order to obtain stable electrical conductivity, the conventional biomedical electrode needs to contain 80 to 90% by mass or more of silver (including silver derived from silver chloride) in the conductive paste. There was room for further reduction.

Further, Patent Document 1 discloses particles in which the surface of spherical silver particles is changed to silver chloride by a chemical reaction, and describes that this is applied to a glucose detection sensor or a reference electrode.

However, when the present inventors tried to use these particles in place of silver chloride particles in a living body electrode, the conductivity may be insufficient, and the connection reliability between the living body electrode and the living body is lacking. It turned out that there was a problem.

WO1998003431A1

The present invention has been made in view of the above points. For example, when blended in a conductive paste constituting a biological electrode, the amount of silver used can be reduced while maintaining stable conductivity. An object of the present invention is to provide silver chloride-coated grains.

A silver chloride-coated particle according to the present invention has a dendrite-shaped core having silver on at least a part of the surface, and a silver chloride coating layer made of silver chloride that covers at least a part of the surface of the core. To do.

The core may be made of silver, an inner core containing at least one selected from the group consisting of gold, copper and nickel, and an outer core made of silver covering at least a part of the surface thereof It may have.

The silver chloride-coated particles may have an average particle size of 1 μm to 100 μm.

The silver chloride-coated particles may have a specific surface area of 0.5 to 5.0 m ² / g.

The silver chloride-coated particles may have a silver chloride content ratio (silver chloride / (silver + silver chloride)) in the total amount of silver and silver chloride of 5% by mass to 95% by mass.

The silver chloride-coated particles can be suitably used for a silver-silver chloride electrode.

According to the silver chloride-coated particles of the present invention, for example, when blended in a conductive paste constituting a biological electrode, it is possible to maintain stable conductivity even when the amount of silver blended in the paste is reduced. it can. Therefore, by using this, it is possible to provide a biological electrode that is cheaper and more reliable than the prior art.

It is a schematic diagram showing a conventional silver-silver chloride electrode obtained by applying a conductive paste to a conductive material. It is an electron micrograph (magnification: 10000 times) showing dendritic silver particles used as a core for silver chloride-coated particles according to an embodiment of the present invention. FIG. 2 is an electron micrograph (magnification: 10000 times) showing silver chloride-coated particles according to an embodiment of the present invention, the silver chloride-coated particles having 10% by mass of silver chloride on the surface of the core shown in FIG. 1. FIG. 2 is an electron micrograph (magnification: 10000 times) showing silver chloride-coated particles according to an embodiment of the present invention, the silver chloride-coated particles having 20% by mass of silver chloride on the surface of the core shown in FIG. 1. FIG. 2 is an electron micrograph (magnification: 10000 times) showing silver chloride-coated particles according to an embodiment of the present invention, the silver chloride-coated particles having 30% by mass of silver chloride on the surface of the core shown in FIG. 1. FIG. 2 is an electron micrograph (magnification: 10000 times) showing silver chloride-coated particles according to an embodiment of the present invention, the silver chloride-coated particles having 70% by mass of silver chloride on the surface of the core shown in FIG. 1. In an Example, it is a schematic diagram which shows the circuit used for the measurement of an impedance characteristic.

Hereinafter, embodiments of the present invention will be described more specifically.

A silver chloride-coated particle according to an embodiment of the present invention comprises a dendrite-shaped core having silver on at least a part of a surface thereof, and a silver chloride coating layer made of silver chloride that covers at least a part of the surface of the core. Shall have.

Here, the dendrite shape means a shape having one or more dendritic protrusions protruding from the particle surface. For example, as shown in the electron micrographs of FIGS. Or the thing of the shape formed in three dimensions is mentioned, However, It is not limited to these, Only the main branch without a branch may be sufficient.

The core has a dendrite shape and is not particularly limited as long as it has silver on at least a part of its surface, and may be made of silver, a metal other than silver, a metal compound, an inorganic compound, or It may contain an organic compound. Specifically, gold, copper, nickel, etc. are mentioned as metals other than silver. By using a dendrite-shaped core as the core, the shape of the silver chloride-coated particles can also be made dendritic.

Among the materials exemplified above, the core is preferably a core made of silver from the viewpoint of ease of manufacture and conductive stability. As such a dendrite-shaped silver particle, what was produced by the method of patent 4149364 can be used, for example.

Further, from the viewpoint of further reducing the amount of silver used, when the above-mentioned material other than silver is used for the core, the core is composed of an inner core made of the above-mentioned metal material other than silver and silver covering at least a part of the surface thereof. It can have an outer core. As such a core, for example, a core particle in which the surface of a dendrite-shaped metal particle serving as an inner core is coated with silver by a displacement plating coating method or a reduction plating coating method according to a conventional method can be used. For example, silver-coated copper powder prepared by the method described in JP2013-1917A and coated with silver on the surface of dendritic copper particles can be used.

The surface of the core may be entirely covered with a silver chloride coating layer, or a part of the surface may be covered with a silver chloride coating layer, and silver existing on the surface of the core may be partially exposed. .

The average particle diameter of the silver chloride-coated particles is not particularly limited, but for example, when used for a conductive paste, it is preferably 1 μm to 100 μm, and more preferably 3 μm to 10 μm. Here, the average particle diameter in this specification means a particle diameter (primary particle diameter) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction scattering method.

The specific surface area of the silver chloride-coated particles is not particularly limited. However, for example, when used for a conductive paste, it is preferably 0.5 to 5.0 m ² / g, and 1.0 to 2.0 m ² / g. It is more preferable that Here, in this specification, the specific surface area means that a measurement sample is put in a vacuum dryer, treated at room temperature for 2 hours, and then the sample is filled so that the cells are dense, and then the BET specific surface area measurement device is used. The measured value is set after performing pretreatment at a deaeration temperature of 40 ° C. for 60 minutes.

The content ratio of silver chloride in the total amount of silver and silver chloride in the silver chloride-coated particles (silver chloride / (silver + silver chloride)) is not particularly limited, but may be 5 to 95% by mass. The content is preferably 10% by mass to 70% by mass. Here, in this specification, the content (mass%) of silver chloride and silver in the silver chloride-coated particles is determined by using an apparatus capable of differential thermal analysis (DTA) or differential scanning calorimetry (DSC). The reagent or silver reagent and silver chloride-coated particles are measured under the conditions shown below, a DTA curve or DSC curve is obtained, and the value calculated from formula (1) or formula (2) from the peak area of the melting peak. . In addition, when the core of the silver chloride-coated particle is composed of an inner core such as gold, copper, or nickel and an outer core of a silver layer covering the surface as described above, it can be measured by the same method. . Moreover, when measuring silver content, it is desirable to use DSC for high temperature measurement.

<Silver chloride measurement conditions>
Sample amount: about 10mg
Temperature increase rate ... 10 ° C / min
Measurement temperature range: Room temperature to 500 ° C
Temperature conditions: After raising the temperature from room temperature to 480 ° C., the temperature is lowered to 350 ° C., and the temperature is raised again to 480 ° C.
Atmosphere: Nitrogen, flow rate: 150 ml / min
Sample container: Alumina (open type)
Standard material ... Al ₂ O ₃
Standard substance amount: approx. 10mg

<Formula 1>
Silver chloride content (mass%) in silver chloride coated particles = (peak area value of silver chloride per gram of silver chloride coated particles) / (peak area value of silver chloride per gram of silver chloride reagent) × 100 (1)

<Silver measurement conditions>
Sample amount: about 10mg
Temperature increase rate ... 10 ° C / min
Measurement temperature range: Room temperature to 1000 ° C
Temperature conditions: After raising the temperature from room temperature to 1000 ° C., the temperature is lowered to 800 ° C., and the temperature is raised again to 1000 ° C.
Atmosphere: Nitrogen, flow rate: 150 ml / min
Sample container: Alumina (open type)
Standard material ... Al ₂ O ₃
Standard substance amount: approx. 10mg

<Formula 2>
Silver content (mass%) in silver chloride-coated particles = (silver peak area value per gram of silver chloride-coated particles) / (silver peak area value per gram of silver reagent) × 100 (2)

The method for producing the silver chloride-coated particles of the present invention is not particularly limited, but silver existing on the surface of the dendrite-shaped core can be changed into silver chloride by a chemical reaction according to a conventional method. It can be produced by preparing silver particles and reacting them at room temperature in an aqueous sodium hypochlorite solution. At this time, by appropriately adjusting the reaction conditions such as the chemical concentration, the amount of silver chloride produced can be manipulated, and the mass ratio of silver to silver chloride in the silver chloride-coated particles can also be adjusted. Depending on the reaction conditions, silver chloride-coated grains may contain silver oxide, but this does not affect the effects of the present invention.

The silver chloride-coated particles thus obtained can be blended in, for example, a resin and used as a conductive paste. The obtained conductive paste can be used for a silver-silver chloride electrode, and can be suitably used for, for example, a biological electrode.

By using the silver chloride coated particles of the present invention as the metal particles to be blended in the conductive paste, stable conductivity can be maintained even when the amount of silver used is reduced. The mechanism of this effect is not clear, but can be estimated as follows.

First, the dendrite shape of the grains reduces the aggregation and difficulty of silver chloride, and also makes it difficult for sedimentation to occur in the conductive paste, thereby improving the dispersibility of silver chloride. . In addition, since the number of contacts between particles increases, it is considered that stable conductivity can be maintained even when the amount of silver used is reduced.

In addition, the dendritic shape increases the specific surface area of silver chloride that covers the surface of the grains. For example, when used as a biological electrode, the contact area with the electrolyte that is present between the living body when measuring biological information As the value increases, the responsiveness of the biomedical electrode becomes excellent.

Furthermore, by adopting a dendrite shape, it can be applied to a conductive material (corresponding to the conductive material 2 in FIG. 1) coated with a conductive paste containing the silver chloride-coated particles of the present invention or at the time of biological information measurement. Improves the connection reliability between the living body electrode and the living body by the dendritic protrusion of the silver chloride coated particles being pierced into the electrolyte layer such as an electrolyte gel or conductive adhesive interposed between the electrode and the living body. There is also an effect.

Examples of the present invention are shown below, but the present invention is not limited to the following examples. In the following, the content and the like are based on mass unless otherwise specified.

The detail of each component used by the Example and the comparative example is as follows.
Silver particles A: dendritic shape, manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size = 8.0 μm
Silver particle B: dendrite shape, manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size = 5.3 μm
Silica particles: “Silicia 710” manufactured by Fuji Silysia Chemical Ltd.
・ Polyester resin: “LP035” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.

<Preparation Example 1 of Silver Chloride Coated Particle>
As a reaction solution, a solution obtained by diluting a sodium hypochlorite solution having an effective chlorine concentration of 10% by mass 20 times was prepared. On the other hand, 10 g of the silver particles A were added to 20 g of ethanol, and stirred for 3 minutes at room temperature using an ultrasonic stirring device to prepare an ethanol dispersion slurry.

The obtained ethanol dispersion slurry was mixed with the reaction solution, and stirred at room temperature for 3 minutes using ultrasonic stirring. After stirring, the reaction solution and the particles were separated with a vacuum filtration device, and the particles were washed with purified water and ethanol. Thereafter, the particles were dried at room temperature in a vacuum desiccator to obtain silver chloride-coated silver particles (a) coated with silver chloride.

The resulting silver chloride-coated silver particles (a) had a silver chloride content of 21% by mass and a specific surface area of 1.10 m ² / g.

<Preparation example 2 of silver chloride coated particles>
A reaction solution prepared by diluting a sodium hypochlorite solution having an effective chlorine concentration of 10% by mass was used as a reaction solution, and the same procedure as in Production Example 1 was performed except that the silver particles B were used instead of the silver particles A. Silver chloride-coated silver particles (b) were obtained. The obtained silver chloride-coated silver particles (b) had a silver chloride content of 76% by mass and a specific surface area of 1.06 m ² / g.

<Production Example 3 of Silver Chloride Coated Particles>
Silver chloride-coated silver particles (c) were obtained in the same manner as in Production Example 1 except that the silver particles B were used in place of the silver particles A. The resulting silver chloride-coated silver particles (c) had a silver chloride content of 21% by mass and a specific surface area of 1.06 m ² / g.

<Production of electrode>
The silver chloride-coated particles obtained as described above are mixed with silver particles B, silica particles, and a polyester resin in accordance with the formulation (mass%) shown in Table 1, and diluted with methyl ethyl ketone (MEK) to obtain a conductive paste for electrodes. Prepared. On the silver vapor-deposited polyethylene terephthalate (PET) film, the electroconductive paste for electrodes was apply | coated using the applicator, and it was made to dry for 3 minutes in a 120 degreeC drying furnace. The thickness of the electrode layer was 30 μm. A biological electrode sample was prepared by laminating a conductive gel on the electrode layer.

<Evaluation methods>
Regarding the obtained biomedical electrode sample, a standard for disposable electrocardiogram electrodes (AAMI-EC12: Association of the Medical Instrumentation EC12) established by the American National Standards Institute (ANSI). The required impedance characteristics (ACZ: Alternating Current impedance, impedance is denoted as Z) were evaluated.

Specifically, the conductive gel of the biological electrode sample is bonded to form an electrode pair 12, and as shown in FIG. 7, the electrode pair 12, the resistor 10 connected in series, and the function generator 11 are connected in parallel. A circuit connected to the power source 9 was prepared, and the AC impedance was measured for each of the 12 electrode pairs 12, and the average value was obtained. The biomedical electrode in the above-mentioned standard has an average impedance value of 2 kΩ or less when applied not exceeding 10 Hz, 100 μAp-p (Ap-p: difference between the maximum current value and the minimum current value measured by alternating current). There must be.

The results are shown in Table 1. The conductive paste used in the conventional biomedical electrode contained 80 to 90% by mass or more of silver, whereas the dendrite according to the present invention. Even when the silver content in the conductive paste is greatly reduced to 33.6 to 63.7% by mass by using the silver chloride-coated particles having the shape, the impedance characteristics required as a biological electrode can be obtained. It was observed that it was obtained.

DESCRIPTION OF SYMBOLS 1 ... Silver-silver chloride electrode 2 ... Conductive material, such as carbon 3 ... Resin 4 ... Silver (Ag)
5 ... Silver ion (Ag ⁺ )
6. Silver chloride (AgCl)
7 ... electron (e ^-)
8 ... chloride ion (Cl ^-)
9 ... Power supply 10 ... Resistor 11 ... Function generator 12 ... Electrode pair of electrode samples bonded together

Claims

A dendrite-shaped core having silver on at least a part of the surface;
Silver chloride-coated particles having a silver chloride coating layer made of silver chloride that covers at least a part of the surface of the core.
The silver chloride-coated particle according to claim 1, wherein the core is made of silver.
The core has an inner core containing at least one selected from the group consisting of gold, copper, and nickel, and an outer core made of silver covering at least a part of the surface thereof. 2. Silver chloride-coated particles according to 1.
The silver chloride-coated particle according to any one of claims 1 to 3, wherein the average particle size is 1 µm to 100 µm.
The silver chloride-coated particle according to any one of claims 1 to 4, wherein the specific surface area is 0.5 to 5.0 m 2 / g.
6. The content ratio of silver chloride in the total amount of silver and silver chloride (silver chloride / (silver + silver chloride)) is 5% by mass to 95% by mass. 2. Silver chloride-coated particles according to item 1.
The silver chloride-coated particle according to any one of claims 1 to 6, which is used for a silver-silver chloride electrode.