JPS622429B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an alkaline battery, and its purpose is to provide a method for manufacturing an alkaline battery with excellent leakage resistance. In general, in alkaline batteries such as button batteries, an anode mixture layer is inserted at the bottom of the anode can, a part of the electrolyte is further injected, and a separator layer is placed on top of the mixture layer. Next, the cathode terminal plate containing most of the cathode mixture and electrolyte is fitted into the opening of the anode can with a synthetic resin gasket having an inverted L-shaped cross section interposed, and then the upper part of the anode can is pushed inward. Manufactured by bending and sealing. In this way, in button-type alkaline batteries, there is a
In addition, in the cylindrical type, a gasket made of synthetic resin is interposed between the anode can and the cathode terminal plate, cathode lead rod, etc., to isolate the two electrodes and mechanically buffer them, making the inside of the battery liquid-tight. Manufactured by holding. However, this synthetic resin gasket tends to absorb moisture from the air or electrolyte before and after it is assembled into a battery, and as a result, as the moisture content inside the gasket increases, its repulsive stress gradually decreases. However, over time, the gasket loses its buffering ability, and the repulsive force decreases, especially in areas where the clamping force is concentrated between the cathode and anode cans, and the liquid tightness within the battery collapses from this area. This has the disadvantage of not only deteriorating battery characteristics but also damaging internal equipment due to electrolyte leakage. This tendency is particularly strong in hot and humid conditions, and has become a major problem in regions such as Japan, where people visit seasonally. In light of the above-mentioned circumstances, the inventors continued their intensive research and found that the above-mentioned tendency was observed when manufacturing an alkaline battery using a gasket made of a material with a particularly high saturated water content among gaskets made of synthetic resins. If we first elucidate the strong facts, and then in the subsequent research process, make the moisture content of a gasket molded from the above materials 0.0 to 0.3%, provide a packing layer on its surface that is more hydrophobic than the gasket, and then incorporate it into a battery. Since the water content of the gasket is low during assembly, good rebound stress is obtained, which allows for strong clamping.
Moreover, the hydrophobicity of the packing layer provided on the surface prevents the absorption of moisture after incorporation, so leakage of the electrolyte can be prevented for a long period of time, and this invention was completed based on the knowledge. That is, in this invention, when a gasket molded from polyamide resin is placed in the opening of the anode can to seal it and make the inside of the alkaline battery liquid-tight, the gasket is treated under low humidity conditions beforehand. This invention relates to a method for producing an alkaline battery, which is characterized by adjusting the water content of the gasket to 0.0 to 0.3%, and then providing a packing layer on the surface that is more hydrophobic than the gasket. The material for the gasket used in this invention is:
Of the synthetic resin materials that have large inherent stress and are used as gasket members, those with a saturated water content generally
The content is 0.1% or more, and specific examples thereof include polyamide resins such as nylon 6, nylon 66, nylon 610, nylon 11, and nylon 12. On the other hand, the saturated moisture content like polyethylene
Gaskets made of materials with a content of 0.1% or less are unsuitable because their water absorption is so small that the manufacturing method of the present invention is hardly effective. After molding such materials according to conventional methods, such as injection molding or punching, there is a method to adjust the moisture content of the gasket to 0.0 to 0.3%, for example, by absorbing moisture during cooling after molding. If it is a gasket that is
It is preferable to use the required method such as adjusting the moisture content to about 0.3%.In this case, if heat treatment is performed at the same time, the treatment time can be shortened, so it is usually recommended to perform the treatment under heat, but do not use too high a temperature. If added, the gasket may undergo thermal deterioration and its shape may change, so it is preferable to heat the gasket at a temperature of 90° C. or lower. However, in this invention, the processing method that prevents moisture absorption of the gasket by storing the gasket whose water content is almost 0 immediately after melt molding such as injection molding under low humidity conditions while cooling is the most effective method in terms of manufacturing steps. It can be used preferably. Here, low humidity conditions refer to conditions in which the almost completely dry gasket does not absorb moisture in the atmosphere, and is usually stored in a vacuum atmosphere of about 0 to 20 mmHg, in a closed system with a desiccant, or in a non-permeable Covering the gasket with a film such as aluminum foil,
Or conditions for combining these methods. The reason why the water content of the gasket is limited to 0.0 to 0.3% in this invention is because the water content and the repulsive stress at that water content generally differ depending on the members that make up the gasket. The leakage resistance effect of the alkaline battery obtained depends mainly on the characteristics of the components, but the water content is 0.0 to 0.3%.
If the moisture content is within the range of 100% and the moisture content is lower than the saturated moisture content, which is almost completely dry, any material will exhibit its best repulsive force over a long period of time against the clamping force when sealing the battery, and will prevent liquid leakage. This is because it can be effectively prevented. The packing material that is then applied to the gasket whose moisture content has been adjusted to form a packing layer may be one that is liquid at room temperature or one that is solid at room temperature. When applying to the gasket,
Not only those that are solid at room temperature but also those that are liquid at room temperature are usually applied as a solution dissolved in an appropriate solvent, and after this application, the packing layer is formed by drying and volatilizing the solvent. Stronger hydrophobicity than these packing gaskets,
Examples include pitch, aliphatic polyamide, rubber adhesive, and silicone oil. In addition to improving the adhesion between the gasket and the cathode current collector, this packing also functions as a moisture-proof film to prevent the gasket from absorbing moisture from the air during the alkaline battery assembly process. In order to manufacture an alkaline battery by incorporating a gasket with a packing layer and adjusting the moisture content into an alkaline battery, it is sufficient to follow a conventional method.For example, as shown in the drawing, a button type battery is manufactured. If available, an anode mixture layer 2 consisting of an anode active material such as Ag ₂ O, HgO, MnO ₂ and a conductive agent such as carbon or graphite is inserted into the bottom of the anode can 1 with a tapered cross section, and an alkali such as KOH is inserted. A portion of the electrolytic solution is injected, and a protective film such as a pump propylene, a separator such as cellophane, and an electrolytic solution holding layer made of a nonwoven fabric are sequentially placed on the upper surface of the mixture layer 2 to form a separator layer 3. A gasket with an L-shaped cross section, which has a packing layer 6 on its surface and has a moisture content adjusted to 0.0 to 0.3%, and has a cathode terminal plate 5 filled with a cathode agent 4 made of a mixture of zinc powder and mostly alkaline electrolyte. 7 is fitted into the opening of the anode can, and the upper end 8 of the anode can is bent inward and sealed to make the inside of the battery liquid-tight. As mentioned above, the method for manufacturing an alkaline battery according to the present invention reduces the water content by treating a gasket molded from polyamide resin under low humidity conditions.
By adjusting the concentration to 0.0 to 0.3% and installing a packing layer on the surface that is more hydrophobic than the gasket, the battery obtained by this method has a structure in which the bond between the anode can and the cathode can be maintained for a long period of time. The gasket repulses well against the strong compressive force during sealing, and the inside of the battery can be kept liquid-tight, causing no problems such as leakage, and the battery characteristics can function well. This is because batteries obtained by conventional methods absorb moisture in the air after gasket molding and are assembled into batteries with some loss of repulsion stress. This greatly improves the drawback that the gasket's repulsive stress deteriorates even further, eventually destroying the liquid tightness inside the battery and causing leakage of the electrolyte. Next, test examples of the present invention will be described, and the method of the present invention will be explained in detail. Nylon 610 is injection molded to form a gasket with an L-shaped cross section, and the gasket immediately after molding is
After storage at mmHg of 20 to 30℃, a solution of asphalt pitch (distillation residue of asphalt-based crude oil) dissolved in toluene is applied, and after this application is dried to evaporate the solvent, a packing layer with a thickness of 200 to 300μ is formed. was formed. When we measured the moisture content of the gasket just before battery assembly, it was 0.0% (Battery A), due to the difference in the vacuum condition.
Three types of batteries were obtained: 0.1% (Battery B) and 0.3% (Battery C). Then, it was stored for 20 hours and 200 days without any low humidity conditions.
A packing layer consisting of the same pitch was formed in the same manner as above on a gasket that had been stored in an atmosphere at a temperature of 20°C and a relative humidity of 65%, and the moisture content was measured. Two types of batteries were obtained: D) and 1.0% (Battery E). These five types of batteries were stored in an atmosphere at a temperature of 45°C and a relative humidity of 90%, and the number of batteries leaking out of 100 batteries of the same type was determined over time. The results are shown in the table below.

[Table] As is clear from the above results, the moisture content of the gasket obtained by the manufacturing method according to the present invention is 0.0.
It can be seen that the button-type alkaline battery coated with pitch adjusted to ~0.3% is a battery with excellent leakage resistance.

[Brief explanation of the drawing]

The drawing is a sectional view of a button-type alkaline battery obtained by the manufacturing method according to the present invention. 1... Anode can, 6... Packing layer, 7... Gasket.

Claims (1)

[Claims] 1 A gasket 7 molded from polyamide resin is placed in the opening of the anode can 1 to seal it and make the inside of the alkaline battery liquid-tight.
Before installing the gasket, the moisture content is adjusted to 0.0 to 0.3% by treatment under low humidity conditions, and then a packing layer 6, which is more hydrophobic than the gasket, is applied to the surface.
A method for producing an alkaline battery, comprising: