JP3119446B2 - Electrode and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-efficiency ferrite electrode useful as an electrode for an alkali ion water purifier, or as an electrode for the recovery of heavy metals and precious metals in plating, electrodeposition coating and wastewater, and a method for producing the same. Things.

[0002]

2. Description of the Related Art Heretofore, as a ferrite electrode, a metal member such as copper, aluminum, titanium, brass, iron, galvanized iron, stainless steel or the like is conductively bonded to a ferrite hollow body having a pipe-shaped end closed. (Eg, epoxy resin or phenol resin containing silver (Japanese Utility Model Publication No. 56-40852)), a ferrite hollow body and a metal member inserted therein are bonded using solder or lead (Japanese Utility Model Application Publication No. No. 56-40855), a ferrite hollow body and iron inserted therein adhered with an epoxy resin containing lead, solder, silver or graphite (J.
-18044).

[0003] However, these ferrite electrodes have an advantage that the connection between the metal member and the ferrite can be easily performed, but have various drawbacks caused by the conductive adhesive. That is, the epoxy resin or phenolic resin-based conductive adhesive reduces the volume of the resin during the curing reaction at the time of bonding, so that a large number of voids are generated inside and a uniform bonding surface as a whole is obtained. Without forming, it becomes line bonding or point bonding, the bonding area is small, and the bonding strength is inevitably reduced. Then, at the time of energization, the current is concentrated on the narrow adhesive portion and local heating is performed, which causes damage or abnormal wear of this portion.

On the other hand, when bonding is performed using solder or lead, thermal expansion due to heat generation during energization causes stress due to a difference between the ferrite and ferrite. Since it cannot be relaxed, there is a disadvantage that the electrode is destroyed and cannot be used until the ferrite portion is completely consumed.

[0005] These disadvantages include low current densities, eg, 1
When used at a current density of 0 A / dm ² or less, there is not much problem, but a high current density, for example, 15 A / d 2
When used in m ² or more results in a significant decrease in pot life. Therefore, conventionally, the number of electrodes was increased,
This has been dealt with by increasing the size of the electrodes. However, there is a limitation that this cannot be done if space is not available.

[0006]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of the conventional ferrite electrode, allows the ferrite portion to be uniformly bonded to the power feeder, and has good conductivity and sufficient bonding. By obtaining strength, 15 A / dm ²
As described above, an object of the present invention is to provide a ferrite electrode that can be used stably for a long time even in a high current density region of 25 A / dm ² or more.

[0007]

Means for Solving the Problems The present inventors have made uniform the bonding between the ferrite portion of the ferrite electrode and the power supply, have a large bonding area, and sufficiently cope with heat generation during energization. As a result of intensive research to develop a ferrite electrode that does not cause breakage or abnormal wear, the volume of the ferrite part and the power supply body expands when bonded and adheres firmly with a wide contact area The present inventors have found that it is possible to use a conductive foamed plastic that can reduce the stress caused by heat generation at the time of energization, that is, a conductive foamed plastic, and have accomplished the present invention based on this finding.

That is, the present invention is characterized in that an electrically conductive foamed plastic is used as a binder in an electrode composed of a ferrite hollow cylinder, a power supply inserted therein, and a binder for bonding the two. To provide a ferrite electrode. According to the method of the present invention, the ferrite electrode is easily formed by inserting a power feeder into a ferrite hollow cylindrical body, filling a gap between the two with a plastic raw material containing a conductive fine powder and a foaming agent, and foaming. Can be manufactured.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ferrite electrode of the present invention differs from the conventional ferrite electrode only in that conductive foamed plastic is used as a binder, and all other components are the same as the conventional ferrite electrode. It can be. FIG. 1 is a longitudinal sectional view of one example of a ferrite electrode of the present invention, in which a power feeder 2 is inserted into a ferrite cylinder 1 and a gap between the two is filled with a conductive foamed plastic 3 to bond the two. doing. In this example, one end of the cylindrical body 1 is open and the other end is closed. However, if desired, the cylindrical body 1 may be formed in a shape in which both ends are open and the power feeder is penetrated.

The ferrite material forming the ferrite cylinder 1 in the present invention can be appropriately selected from the ferrite materials used in the conventional ferrite electrodes according to the purpose of use. As such a material, for example, 53 to 95 mol% of iron oxide in terms of Fe ₂ O ₃ and 47 to 5 mol% of manganese oxide in terms of MO (M is Mn, Ni, Co, Mg, Cu or Zn) , Nickel oxide, cobalt oxide, magnesium oxide, or zinc oxide having a spinel crystal structure. These have excellent electrodeposition strength, resistivity, and spalling strength, and are used as electrodes for alkali ion water purifiers, plating, electrodeposition coating, heavy metals in wastewater, and electrodes for recovery of precious metals. I have.

The ferrite cylinder 1 can be manufactured, for example, as follows. That is, F
e ₂ O ₃ 55-75 mol%, converted to the above-mentioned MO, and
After thoroughly mixing 25 mol% of a metal oxide, for example, nickel oxide or magnesium oxide in a ball mill, the mixture is heated in air at 800 to 1400 ° C. for 1 to 3 hours, cooled and pulverized to obtain a fine powder. I do. At this time, 55 to 75 mol% in terms of Fe ₂ O ₃ instead of the raw material Fe ₂ O ₃
Mixture and of Fe and FeO equivalent to, these and Fe ₂
Mixtures with O ₃ can be used, and instead of metal oxides, compounds which can be converted to these oxides by heating, for example carbonates, hydroxides or oxalates, can also be used.

Next, the fine powder thus obtained is formed into a predetermined cylindrical shape by pressure molding, extrusion molding, injection molding, cast molding, or the like.
After firing for ~ 12 hours, the mixture is gradually cooled to obtain a desired ferrite cylinder. The feeder to be inserted into the ferrite cylinder 1 thus obtained can be appropriately selected from the metals used as feeders for conventional ferrite electrodes according to the intended use. Such metals include, for example, copper, aluminum, titanium, brass,
There are iron, galvanized iron and stainless steel. These metals are generally used as rods such as round bars and square bars, thin wires, and their stranded wires.

Next, in the ferrite electrode of the present invention,
It is necessary to use a conductive foamed plastic as a binder for electrically connecting the ferrite cylinder and the power supply body and for firmly adhering them. This conductive foamed plastic is one in which conductive fine powder is uniformly dispersed in a matrix made of foamed plastic. The material of the foamed plastic constituting the matrix may be any of a thermoplastic plastic and a thermosetting plastic, and can be arbitrarily selected from those conventionally used as materials of the foamed plastic. Such plastics include, for example, ethylene, polypropylene, polystyrene, ABS resin, ethylene-vinyl acetate copolymer, polyethylene terephthalate, modified polyphenylene ether, polyamide, polycarbonate, polyurethane, and the like. Polyurethane is particularly preferred because it cures simultaneously with foaming and the cured product has appropriate physical properties as a binder for a ferrite electrode.

The conductive fine powder used for imparting conductivity to the binder by being dispersed in the matrix includes metal powders such as copper, silver, nickel and aluminum, and carbon-based powders such as carbon black and graphite. Although powder is used, silver powder or silver-plated copper powder is particularly preferable in that it has good oxidation resistance and provides high conductivity. These powders usually have a particle size of 10 to 100 μm, but any particle size can be used without particular limitation as long as it has been used to impart conductivity to plastics. This conductive fine powder,
50 to 90% by weight, preferably 60 to 80% by weight, based on the foamed plastic of the matrix. If the amount is smaller than this, sufficient conductivity cannot be obtained, and if the amount is larger than this, the adhesiveness decreases.

The porosity of the conductive foamed plastic in the present invention is preferably in the range of 10 to 50% based on the matrix capacity. When the porosity is larger than 50%, the conductivity becomes insufficient, and when the porosity is smaller than 10%, the filling rate becomes insufficient, and the adhesion decreases.

To manufacture a ferrite electrode according to the method of the present invention, a power feeder is inserted into a hollow ferrite cylinder, and a gap between the two is filled with a plastic raw material containing a conductive fine powder and a foaming agent. As plastic raw materials at this time, polyethylene, polypropylene, polystyrene, polyvinyl chloride, ethylene-vinyl acetate polymer, polyether,
For thermoplastics such as polyester,
These powders or condyles are used, and thermosetting plastics such as epoxide resins and phenolic resins use low molecular weight raw material components before curing. In the case of polyurethane, a raw material mixture of a polyisocyanate component and a polyol component or a mixture of a prepolymer and a chain extender is used.

The foaming agent added to the plastic raw material may be a gaseous, liquid, or solid physical foaming agent or a chemical foaming agent, but is easy to handle and easy to adjust the expansion ratio. To liquid or solid.

Examples of such solid foaming agents include inorganic foaming agents such as sodium bicarbonate, ammonium bicarbonate, ammonium carbonate, azide compounds, sodium borohydride, azo compounds, nitroso compounds, and sulfonyl hydrazides. Examples of the organic foaming agent and liquid foaming agents include aliphatic hydrocarbons such as pentane, butane, and hexane, and water.

These foaming agents have an expansion ratio of 1.1 to 1.
It is added to the plastic raw material in an amount sufficient to obtain a factor of five. Then, the plastic material containing the foaming agent in such a ratio and the above-mentioned conductive fine powder is filled into the gap between the ferrite cylinder and the power feeder in such an amount that the volume is completely filled at the time of heating and foaming. Next, when the ferrite cylinder filled with the binder and the feeder inserted therein are heated, the binder is melted or hardened, and at the same time foams and expands in volume, thereby causing the ferrite cylinder and the feeder to separate from each other. They are bonded together and electrically connected. As the heating temperature at this time, the melting temperature of the used plastic raw material, generally in the range of 150 to 300 ° C. is used. The heating time depends on the heating temperature, but is in the range of 1 to 10 hours.

[0020]

The ferrite electrode of the present invention uses a conductive binder which causes volume expansion due to foaming, so that the gap between the ferrite and the power feeder is completely filled with the conductive binder to provide uniform conductivity and sufficient conductivity. High adhesive strength. This apparently increases the cross-sectional area of the power supply body, so that the resistance value of the entire electrode can be reduced. Such effects are obtained when the feeder is made of a flexible and large surface area material, for example, a rod-shaped or pipe-shaped material is more than a linear material. Further, since the binder is in a foamed state even after curing, the stress at the time of energization generated between the power supply portion and the ferrite can be reduced, so that the ferrite electrode can be stably used for a long time.

[0021]

Next, the present invention will be described in more detail by way of examples.

EXAMPLE 1 Nine stranded wires 88 of a 2.3 mm diameter copper wire were placed on a ferrite cylinder having an outer diameter of 28 mm, an inner diameter of 12 mm, and a length of 900 mm.
100 g of a polyurethane adhesive containing 80% by weight of silver and 0.5% by weight of water [product code XA-664, manufactured by Fujikura Kasei Co., Ltd.]
And heated at 150 ° C. for 2 hours to cure. In this way, a ferrite electrode in which the power supply body and the ferrite cylinder were bonded and connected by the conductive foamed plastic having a porosity of 40% was obtained.

Comparative Example 1 Using the same ferrite cylinder and power feeder as in Example 1, a polyurethane adhesive containing 80% by weight of silver as a binder [Fujikura Kasei Co., Ltd. product name "Doteite D-75"]
3 "], a ferrite electrode was manufactured by filling 200 g, heating at 150 ° C. for 2 hours, and curing. In this ferrite electrode, voids are generated due to volume shrinkage after curing reaction in the binder part, and air taken in at the time of application of the binder remains as it is after bonding, so most of the bonding surface becomes a space, point bonding or line bonding It was in the state of.

Example 2 A copper round bar having a diameter of 15 mm and a length of 950 mm was inserted into a ferrite cylinder having an outer diameter of 28 mm, an inner diameter of 16 mm and a length of 900 mm, and was used in Example 1 for a gap between the cylinder and the round bar. 170 g of the same binder were charged. Then, this is 1
A ferrite electrode was manufactured by heating at 50 ° C. for 2 hours to cause foaming and curing. The binder used in this example had a specific resistance of about 0.5 Ωcm, showed uniform adhesion at the joint, and had a low resistance value. About the ferrite electrode thus obtained, ten points were selected at equal intervals in the length direction, and the resistance (Ω) between the feeder and the surface of the ferrite cylinder at those points was measured. Table 1 shows the results. Further, the ferrite cylinder and the copper round bar were twisted in opposite directions, and the torsional strength (kgf) when the bonded surface was peeled off was measured. In this example, the inner diameter of the ferrite cylinder was enlarged as compared with Example 1, so that the thickness of the cylinder could be reduced by 25%, and the cross-sectional area of the power supply could be approximately doubled. .

Comparative Example 2 Using the same binder as in Comparative Example 1, a ferrite electrode was produced in the same manner as in Example 2. With respect to the ferrite electrode thus obtained, ten points were selected in the same manner as in Example 2, and the resistance (Ω) was measured. Table 1 shows the results. Further, the adhesive strength (kgf) was measured in the same manner as in Example 2, and is shown in Table 2.

[0026]

[Table 1]

As can be seen from this table, the ferrite electrode bonded with the conductive foamed plastic has a resistance value of 2 to 9
While the variation is as small as Ω, the ferrite electrode bonded with non-foamed plastic has a resistance of 16 to 62
There was remarkable variation between 4Ω, and local ferrite consumption was observed at the lowest resistance part.

[0028]

[Table 2]

As is clear from this table, the bonding strength is significantly improved in the case of bonding with foamed plastic compared to the case of bonding with non-foamed plastic. That is,
The bonding strength of non-foamed plastic is 4 to 9 kgf, whereas the bonding strength of foamed plastic is 2 to 9 kgf.
09 to 375 kgf. This is because, in the case of non-foamed plastic, the ferrite and the power feeder are partially and non-uniformly bonded by dots and lines, whereas in the case of foamed plastic, the ferrite and the power supply are entirely and uniformly bonded by surface bonding. Because it is.

Example 3 A ferrite cylinder having an outer diameter of 28 mm, an inner diameter of 12 mm, and a length of 900 mm was prepared.
By inserting the same copper stranded wire as used in Example 1 into a 0 mm ferrite cylinder and bonding the same conductive foamed plastic as used in Example 1 as a binder, a ferrite electrode was formed. Two were produced.
Next, an electrolytic test was performed using these ferrite electrodes as anodes. At this time, the temperature rise inside the electrodes and the durability time until the electrodes were exhausted were determined. The electrolysis conditions at this time are as follows. Electrolyte: 1% nitric acid aqueous solution Current density: 30 A / dm ² Cathode: SUS Distance between electrodes: 30 mm

Comparative Example 3 Two ferrite electrodes were produced in the same manner as in Example 3, except that the conductive non-foamed plastic used in Comparative Example 1 was used instead of the conductive foamed plastic. Electrolytic tests were performed on these ferrite electrodes in the same manner as in Example 3, and the results are shown in Table 3.

[0032]

[Table 3]

As is clear from this table, the ferrite electrode of Example 3 generates a smaller amount of heat than the ferrite electrode of Comparative Example 3, so that the temperature rise inside the electrode is small. In addition, the ferrite electrode of Comparative Example 3 had non-uniform conductivity, and current was concentrated on a part of good conductivity, causing local heat generation, and damage was observed before the ferrite electrode was exhausted. Was.

Example 4 A copper round bar having a diameter of 10 mm and a length of 950 mm was inserted into a ferrite cylinder having an outer diameter of 28 mm, an inner diameter of 16 mm and a length of 900 mm, and a phenol resin containing 60% by weight of silver was inserted between the two. Tamura Kaken Co., Ltd., trade name "Alzelite VA"
-17 "], sodium hydrogen carbonate 0.3 as a foaming agent.
Then, 130 g of the mixture was added, and the mixture was gradually heated, and then heated at 120 ° C. for 5 hours to foam. Next, this was cooled to produce a ferrite electrode in which the ferrite and the power supply were bonded with a foamed plastic having a porosity of 40%. The ferrite electrode thus obtained was cut at a substantially central portion, and the state of the binder was observed. As a result, the bonding state was uniform and no void was observed.
The resistance between the surface of the ferrite cylinder and the feeder was in the range of 5 to 15Ω.

REFERENCE EXAMPLE Nine samples of ferrite electrodes were manufactured in the same manner as in Example 1, and the following reliability tests were performed. Table 4 shows the results. (1) Temperature cycle test One cycle of each of the samples maintained at -30 ° C and 70 ° C for 1 hour was regarded as one cycle, and the cycle was repeated five times. (2) Cold storage test Maintained at -20 ° C for 72 hours. (3) High temperature storage test Maintained at 85 ° C for 240 hours. Before and after the above test, the resistance between the terminal and the surface of the ferrite cylinder was measured with a tester, the current density using a 1M-sulfuric acid aqueous solution was measured at 40 A / dm ² , and the electrolysis consumption was measured for 720 hours. Later, cracks and chips were checked, and the confidentiality of the seal was examined. Table 4 shows the results.
Shown in

[0036]

[Table 4]

As is clear from this table, the ferrite electrode of the present invention has sufficient reliability even in a mounting test.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one example of a ferrite electrode of the present invention.

[Description of Signs] 1 Ferrite cylinder 2 Power feeder 3 Conductive foam plastic

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 17/10 C02F 1/46 C25C 3/12 C25D 13/00

Claims (5)

(57) [Claims] 1. An electrode comprising a hollow ferrite cylinder, a feeder inserted therein, and a binder for bonding the two, wherein a conductive foamed plastic is used as a binder. . 2. The ferrite electrode according to claim 1, wherein the conductive foamed plastic is a foamed plastic containing conductive fine powder. 3. The ferrite electrode according to claim 2, wherein the conductive fine powder is at least one selected from a metal powder and a carbon powder. 4. A power feeder is inserted into a ferrite hollow cylindrical body, a plastic material containing a conductive fine powder and a foaming agent is filled in a gap between the two, and then heated and melted or hardened, and foamed at the same time. A method for manufacturing a ferrite electrode, wherein a hollow ferrite cylinder and a power supply body are integrally bonded. 5. The method according to claim 4, wherein the plastic material is a polyurethane-forming material.