JPH0555979B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a non-grading dry battery, and more specifically, by improving the properties of a zinc can used as a negative electrode,
This invention relates to a dry battery that can be made battery-free without deteriorating its performance. <Prior art> A positive electrode mixture made by kneading a mixed powder mainly composed of manganese dioxide with an electrolytic solution such as a zinc chloride solution or an ammonium chloride solution is passed through a paper separator coated with a starch paste and dried. Dry batteries that are housed inside a can are in high demand because they are cheaper than alkaline batteries and the like. As zinc cans used in such dry batteries, those processed into a cylindrical shape with a bottom by a so-called impact extrusion method are widely used. However, in the above-mentioned impact extrusion method, for example, zinc pellets are punched out from a thickly rolled zinc plate and heated to about 150 to 200 degrees Celsius, then pressurized and impact-extruded in one step. Since zinc cans are made by this method, the internal crystal grains of the manufactured zinc cans have large distortions, and the zinc crystal grains are unevenly distributed. For this reason, the inner surface of the zinc can cannot be homogenized, the zinc can is likely to cause local discharge during storage or use, and the zinc can cannot be uniformly consumed and dissolved. In order to suppress this kind of local discharge in zinc cans and to improve battery performance by improving uneven consumption, current dry batteries, such as R20 type dry batteries, are made with mercury containing 3 to 5 mg of mercury per battery. processing.
Such starification treatment involves adding mercury, for example in the form of mercuric chloride (HgCl ₂ ), to the starch paste applied to the paper separator, or adding mercury to the electrolyte mixed in the positive electrode mixture. It is added in the same way. By this oxidation treatment, the properties of the inner surface of the zinc can in contact with the outer surface of the positive electrode mixture can be made homogeneous, and the above-mentioned deterioration in performance can be suppressed. <Problems to be Solved by the Invention> However, no matter what method of addition is used, if the dry battery is subjected to the oxidation treatment as described above, mercury will be contained in the dry cell, even if only in a trace amount. Nowadays, various environmental pollutions are becoming a problem, and there is a strong demand for dry batteries to be made battery-free. <Means for Solving the Problems> The dry battery of the present invention uses a zinc can annealed at 250 to 400°C. The reason why the temperature of the annealing treatment is set to the above range is as follows. That is, if the treatment temperature is lower than 250° C., the distortion of the crystal structure due to recrystallization of the crystal particles in the zinc can will not be removed and the crystal particles will not be uniform enough, and the desired effect will not be obtained. Also, the processing temperature
If the temperature is higher than 400°C, the zinc can will soften due to the temperature rise and will no longer be able to maintain its shape, resulting in a significant degree of shape change. Incidentally, the annealing time may be set to a level that allows sufficient recrystallization of the crystal grains depending on the annealing temperature, and may be appropriately set within a range of, for example, 10 minutes to 2 hours. <Function> By using the above annealing treatment, the crystal grains of the zinc can are recrystallized, the distortion of the structure is removed, and the zinc crystal grains are made uniform,
It is possible to effectively prevent local discharge of zinc cans and to consume the zinc cans uniformly without carrying out the above-mentioned drying treatment. <Example> Using a zinc can obtained by making cans from zinc pellets by impact extrusion, this zinc can was annealed at 375°C for 30 minutes, then put into a dilute hydrochloric acid solution, and the above annealing treatment removed zinc. A series of steps were performed to remove the oxidized layer formed on the surface of the can, followed by washing with water and drying. Using the zinc can made by this process, an R20 type non-tank dry battery (product A of the present invention) was produced as shown in the attached drawing. In this figure, 1 is a zinc can, 2 is a positive electrode mixture containing manganese dioxide as an active material, 3 is a synthetic resin upper sealing body placed at the opening of the zinc can, and 4 is press-fitted into the positive electrode mixture 2. A carbon rod, 5 a sealant, 6 a positive terminal plate, 7 a heat-shrinkable tube, and 8 a metal exterior can. Also,
After annealing at 250°C for 2 hours, an R20 type non-gradable dry battery (invention product A') was prepared in the same manner as inventive product A.
After assembling and further annealing at 225° C. for 2 hours, an R20 type non-gradable dry battery (comparative product B) was assembled in the same manner as product A of the present invention. Next, an R20 type non-grading dry cell (comparative product C) was made in the same manner except that a zinc can without the above-mentioned annealing treatment was used. similar
R20 type dry cell batteries (comparison product D) were each made. In addition, a zinc can that had been annealed at 375°C for 30 minutes in an inert gas atmosphere (for example, nitrogen gas atmosphere) was used, and the other conditions were the same as inventive product A. E) was created. Furthermore, if annealing treatment is performed in such an inert gas atmosphere, an oxide layer will not be formed on the surface of the zinc can after this treatment, and the oxide layer removal treatment as in the case of product A of the present invention described above is not required. Become. After manufacturing, these six types of dry batteries were tested at a temperature of 20
℃, discharge time when continuous discharge is performed with a discharge resistance of 2Ω (final voltage 0.9V), and when two intermittent discharges are performed for 30 minutes each day with a discharge resistance of 2Ω (final voltage 0.9V)
In addition, the discharge time (cutoff voltage 1.0V) when discharging intermittently for 4 hours a day with a discharge resistance of 10Ω is as shown in Table 1. Note that the results of the discharge experiments in Table 1 and Table 2 below are the average values of five batteries for each dry cell.

[Table] Also, for these six types of dry batteries, 1
Discharge time when continuous or intermittent discharge is performed under the same conditions after a year of storage, and
Table 2 shows the measurement results of the corrosion weight loss (mg) of zinc cans after one year of storage at room temperature. The weight of each zinc can at the time of manufacture was approximately 18 g, and the weight loss due to corrosion was shown as the average value of 50 batteries for each battery.

【table】

[Table] From Tables 1 and 2, all of the battery performances of the invention products A, A', and E are the same as those of the comparative product D, which has undergone amalgam treatment.
The corrosion weight loss after stocking was also kept as low as that of Comparative Product D, and it was verified that its performance was sufficient for practical use. It is clear that similar effects can be obtained even if the present invention is applied to dry batteries using zinc cans made by other can manufacturing methods, such as deep drawing. <Effects of the Invention> The dry cell of the present invention constructed as described above has the excellent effect of making the dry cell dry without substantially impairing the battery discharge performance and stock performance, and has an excellent industrial effect. has great utility value.

[Brief explanation of the drawing]

The accompanying drawings are sectional views of essential parts of the embodiment. 1... Zinc can, 2... Positive electrode mixture.

Claims (1)

[Scope of Claims] 1. A non-toxic dry battery characterized by using a zinc can annealed at 250 to 400°C. 2. The non-toxic dry battery according to claim 1, wherein the annealing treatment is performed in an inert gas atmosphere.