JP2002358968A - Alkaline dry battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance of an alkaline dry battery. SOLUTION: In the alkaline dry battery having a conductive membrane on the inner wall of a positive electrode can 14 that contacts the positive electrode mixture, the above conductive membrane is formed by powder electrostatic painting employing a conductive powder paint. Thereby, it enables to improve greatly the discharge characteristics, while keeping the performance equal to the conventional product employing a liquid conductive paint in the alkaline resistance and peeling properties of the conductive membrane. In particular, when the surface roughness of the conductive membrane is made 10 μm or more, improvement in the discharge characteristics is greatly remarkable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode can structure for a cylindrical alkaline dry battery, and more particularly, to a conductive film formed on the inner wall of the positive electrode can.

[0002]

2. Description of the Related Art Conventionally, a bottomed cylindrical positive electrode can also serving as a positive electrode terminal, a hollow cylindrical positive electrode mixture disposed in contact with the inner wall of the positive electrode can, and the positive electrode mixture via a separator Alkaline dry batteries with a gelled zinc negative electrode filled in the hollow part of the battery are known, and are mainly used for notebook computers and Cs because of their high capacity and excellent heavy load (strong discharge) characteristics.
It is widely used in portable electronic devices such as D, MD players and liquid crystal televisions.

Meanwhile, in the alkaline dry battery, the content ratio of manganese dioxide serving as a positive electrode mixture and a conductive agent (graphite powder) greatly affects contact resistance with a positive electrode can, and in particular, a high capacity manganese dioxide content is large. The battery of the above has a drawback that the heavy load characteristic is apt to be reduced during storage at a high temperature. For this reason, in a high-capacity alkaline battery, a nickel-plated steel plate is used as a positive electrode can, and a conductive coating containing graphite as a main component is formed on the inner wall surface to reduce the contact resistance between the positive electrode mixture and the positive electrode can. It has been reduced as much as possible, thereby improving the heavy load characteristics.

[0004] Conventionally, as a method of forming the conductive film, a liquid conductive paint mainly composed of graphite powder diluted with a low boiling point organic solvent is applied in a mist state by a spray gun or the like, and thereafter, A coating using a liquid paint, such as forming a cured film (conductive film) by evaporating and drying a solvent in a dryer, has been common.

[0005]

However, the formation of the conductive film by the liquid paint has a problem caused by the solvent of the conductive paint such as the following organic solvent and water.

That is, regarding organic solvents, there is a danger of flammable fire and the like, and odor, poisoning, air pollution, and other hygiene and environmental problems. There are problems with equipment and cleaning.
In addition, in the case of a liquid paint, there is a problem that management of solid content and viscosity adjustment is complicated, and a coating defect such as accumulation, flow, and dripping of the paint tends to occur at the time of forming a coating film.

SUMMARY OF THE INVENTION An object of the present invention is to provide an alkaline dry battery which can solve the above-mentioned problems associated with the conventional formation of a conductive film and can further improve battery performance.

[0008]

That is, according to the present invention, there is provided an alkaline dry battery having a conductive coating on an inner wall of a positive electrode can in contact with a positive electrode mixture, wherein the conductive coating is a conductive powder coating. It is characterized by being formed by powder electrostatic coating using a.

Further, the present invention according to claim 2 is characterized in that the surface roughness of the conductive film is 10 μm or more.

The so-called electrostatic powder coating means that a charged powder coating is sprayed toward a non-painted object (in the present invention, the inner wall of the positive electrode can) and applied to the non-painted object by the Coulomb force. This is a coating method for forming a cured film (a conductive film in the present invention) by drying. In this case, a triboelectric charging gun is used for charging the powder and spraying the charged powder. The conductive coating of the present invention by powder electrostatic coating has the same performance as that of the conventional liquid coating in terms of alkali resistance and peeling properties, and greatly improves discharge characteristics. In particular, when the surface roughness of the conductive film is 10 μm or more, the discharge characteristics are significantly improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an alkaline dry battery having a conductive coating formed on the inner wall of a positive electrode can in contact with a positive electrode mixture, wherein the conductive coating is formed by electrostatic powder coating using a conductive powder coating. Things. According to the present invention, in the formation of a conductive film using a conventional liquid conductive paint, organic solvents and water, etc., flammability caused by the solvent, odor, poisoning, air pollution, drainage equipment and other problems and paint Can be solved at once, and good results can be obtained in battery performance as described later.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a powder electrostatic coating apparatus used in the present invention. Reference numeral 1 denotes a frictional charging gun, and reference numeral 2 denotes a powder hopper provided with a paint tank 3. In the present apparatus, the powder paint 4a in the fuel tank 3 supplied from the paint supply port 13 is drawn out by the transport air of the injector 5, and is supplied to the frictional charging gun 1 via the powder hose 6 in a constant amount. Has become.

FIG. 2 shows the internal structure of the frictional charging gun 1. The triboelectric charging gun 1 has a cylindrical outer shell 7 and a powder passage 12 (charging portion) formed by a non-conductive tube (plastic tube 8) housed in the cylinder. Is provided with an air supply port 9 communicating with a pressurized air source (not shown), and a spray nozzle 1 for spraying a charged powder coating material at a downstream end.
1 is provided. The outer shell 7 is provided with a ground wire 10 for removing charges accumulated in the charging unit 12.

In the triboelectric charging gun 1 having the above-described structure, the conductive powder coating material 4 (mixture of graphite and a binder serving as an adhesive) supplied from the powder hopper 2 via the powder hose 6 has an upstream portion thereof. In the portion, the air is accelerated by the air flow ejected from the air supply port 9 and, as shown in FIG. The friction charging method is adopted. Then, the charged powder is sprayed from the spray nozzle 11 at the downstream end, and due to the Coulomb force, the charged powder is applied to the inner wall of the positive electrode can 14 which is a non-painted material (not shown, but the non-painted material is put in a painting booth). Coated and dried to form a conductive coating. Incidentally, in FIG.
When the powder coating comes into contact with the powder coating and the powder coating is positively charged, the non-conductive tube 8 side is charged with a negative charge of the opposite polarity,
The accumulated negative charges are sequentially removed to the GND via the ground line 10.

[Examples] Next, the following confirmation tests were conducted to confirm the effects of the present invention, and the performances of the present invention and conventional products were compared.

(1) Alkali resistance and peeling property test A positive electrode can of the present invention having a conductive coating formed by electrostatic powder coating, and a conventional positive electrode can using a liquid conductive paint (comparative example)
Were prepared, and their alkali resistance and peeling properties were investigated. Incidentally, as a paint for powder electrostatic coating, an average particle size of 8
A mixture of graphite with a binder and the like was used.
For the alkali resistance test, each positive electrode can was
It was immersed in a 40% KOH aqueous solution for 72 hours, and the state of the conductive film was observed. In addition, a peeling test was performed using a mending tape, and the peelability of the conductive film before and after immersion was examined.

According to this test, no abnormality such as swelling of the coating film due to the aqueous alkali solution was observed in both the present invention and the comparative example.
Further, since no peeling of the film was observed in the tape peeling test, it was confirmed that the positive electrode can according to the present invention maintained the same alkali resistance and peeling properties as those of the conventional product.

(2) Discharge Characteristics Alkaline dry batteries were prepared using three types of positive electrode cans, each having a different surface roughness of the conductive film, and the discharge characteristics were examined. The discharge test was carried out at 60 ° C.
The battery was stored for one day, and then the discharge duration was measured when the battery was continuously discharged to a final voltage of 0.9 V at a load of 1500 mA. Each test result is shown in Table 1 below as an index value when the initial performance (performance within one month after production) is set to 100.

[Table 1] Surface roughness (μm) of conductive film Continuous discharge performance Invention 1686 Invention 2 10 90 Invention 3 14 91 Comparative example 1 6 82 Comparative example 2 10 82 Comparative example 3 14 83 According to Table 1, it can be seen that the present invention has better discharge characteristics than the comparative example (conventional product). In particular, when the surface roughness of the conductive film was 10 μm or more, the improvement of the discharge characteristics was extremely remarkable, and it was confirmed that deterioration after storage was smaller as the roughness was larger.

[0020]

As described above, according to the present invention,
Since the conductive coating on the inner wall of the positive electrode can is formed by powder electrostatic coating, the discharge characteristics are greatly improved while maintaining the same performance as the conventional product using a liquid conductive paint in the alkali resistance and peeling properties of the conductive coating. Could be improved. In particular, when the surface roughness of the conductive film is 10 μm or more, the improvement of the discharge characteristics becomes extremely remarkable, and the deterioration after storage of the battery can be reduced as compared with the conventional product.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic configuration of a powder electrostatic coating apparatus.

FIG. 2 is a sectional view showing the internal structure of the triboelectric charging gun.

FIG. 3 is a diagram showing a charged state of a conductive powder coating material by a friction charging method.

[Explanation of symbols]

 4a, 4b Conductive powder coating 14 Positive electrode can

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA09 CC06 DD17 KK01 5H017 AA02 AS01 AS06 AS10 BB08 CC01 DD05 EE01 EE10 HH03 5H024 AA03 AA14 BB08 CC02 CC06 CC19 DD02 EE09 FF09 HH13 HH15

Claims (2)

[Claims] 1. An alkaline dry battery having a conductive coating on the inner wall of a positive electrode can in contact with a positive electrode mixture, wherein the conductive coating is formed by powder electrostatic coating using a conductive powder coating. Alkaline batteries. 2. The alkaline dry battery according to claim 1, wherein the surface roughness of the conductive film is 10 μm or more.