JPH0243307B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a paper-lined manganese dioxide dry battery in which an anode mixture containing an electrolyte is sealed in an anode can (zinc can) via a separator. Fig. 1 is a cross-sectional view showing the structure of a conventional dry battery and a dry battery according to the present invention. , a separator made of, for example, kraft paper, 3 a cup-shaped bottom paper provided at the bottom of the zinc can 1, 4 an anode mixture sealed in the zinc can 1 via the separator 2 and the bottom paper 3, and depolarized. The main components are manganese dioxide as an agent, acetylene black as a conductive material, and an aqueous solution of zinc chloride and ammonium chloride as an electrolyte. 5
is a carbon rod as an anode conductor inserted into the anode mixture 4, 6 is a cover paper that covers the anode mixture 4, and 7 is a cover paper 6
8 is a synthetic resin tube that covers the zinc can 1; 9 is a metal cap for the anode fitted to the upper end of the carbon rod 5; 10 is in contact with the bottom outer surface of the zinc can 1. A metal plate for a cathode, 11 is a metal outer can that tightens the metal cap 9 and the metal plate 10 via synthetic resin washers 12, 12, 13
is a synthetic resin sealing body provided inside the metal cap 9. In the conventional manufacturing method of a paper-lined manganese dioxide dry battery having such a structure, the inner peripheral surface of the zinc can 1 is covered with a separator 2, and then a bottom paper 3 is loaded on the bottom surface of the zinc can 1. On the other hand, as the anode mixture 4,
First, about two-thirds of the required amount of electrolyte is added to a mixture of electrolytic manganese dioxide, acetylene black, and a small amount of zinc oxide, and the mixture is kneaded to form a wet powder mixture. This mixture is aged and stored for 1 to 3 days to homogenize the electrolyte and to allow air to escape to increase the bulk density, and then the mixture is pressure-molded to produce a columnar mixture. After inserting this columnar mixture into the zinc can 1, about 1/3 of the remaining electrolyte was injected and permeated, and then a carbon rod 5 was press-fitted into the center of the columnar mixture and the zinc was passed through the separator 2. A dry battery was manufactured by making good contact between the can 1 and the anode mixture 4. The first drawback of the dry cell battery manufactured as described above is that a considerable amount of air remains in the mixture even after aging, which obstructs the movement of electrolyte and ions, reducing discharge performance, and expands after pressure molding. , cracks, weight variations, etc. occurred, and the discharge performance was unstable. The composition of the commonly used mixture is electrolytic manganese dioxide (specific gravity 4.4)
is 50% by weight, and acetylene black (specific gravity 2) is 9
% by weight, zinc oxide (specific gravity 5.5) is 0.3% by weight, electrolyte (specific gravity 1.25; aqueous solution of 25% by weight zinc chloride, 4% by weight ammonium chloride) is 40.7% by weight, and its true density, that is, no air is included. The density of the mixture in the unattached state is 2.063 g/cm ³ .
However, it is impossible to increase the true density of the anode mixture 4 in the actual finished product to 1.98 g/ ^cm3 , or 96% of the true density, using conventional methods, and even with the best conventional product.
It was about 1.96 g/cm ³ . This was due to incomplete degassing of the anode mixture 4, which was one of the causes of deterioration in discharge performance. The second drawback of the conventional product is that the distribution of the electrolyte in the anode mixture 4 is uneven and the utilization rate of manganese dioxide is poor, resulting in low discharge performance and large variations. In other words, in the conventional method, after inserting the columnar mixture into the zinc can 1, the remaining electrolyte is injected, so the electrolyte on the zinc can 1 side inevitably becomes excessive, and as a result, the electrolyte on the carbon rod 5 side becomes insufficient. Something like the above happens. The third drawback is that, as mentioned above, because the remaining electrolyte is injected, there is an excess of electrolyte at the shoulder of the anode mixture, so leakage accidents are likely to occur after the battery is assembled, especially under high temperature conditions. It is in. The fourth drawback is that when the electrolyte is injected, splashing of the electrolyte may occur, which may corrode the inner and outer surfaces of the zinc can 1, resulting in incomplete sealing of the sealant 7, and damage to the manufacturing machine. The reason is that it is not desirable because it contaminates the water. The fifth drawback is that productivity is poor, and the first is that the production line gets dirty when the electrolyte is injected, resulting in a decrease in work efficiency. The second problem is that storage space is required for the aging of the mixture, and the manufacturing process becomes complicated due to the storage amount and storage period. In order to improve these drawbacks, the present inventors have proposed the following manufacturing method. That is, by first mixing manganese dioxide and the conductive material with all the required electrolyte solution, eliminating the step of injecting the electrolyte solution in the middle, and by granulating the mixture containing the electrolyte solution while applying impact. The above-mentioned drawbacks are improved by releasing the air in the mixture and making the electrolyte uniform, and then crushing the granular mixture and sealing it in the cathode can 1. Next, the details will be explained. First, 84.5% by weight of electrolytic manganese dioxide, 15.0% by weight of acetylene black as a conductive material, and zinc oxide.
When 55 volumes of an electrolytic solution containing 71% water, 25% zinc chloride, and 4% ammonium chloride are added by weight to 100 volumes of 0.5% solid material and mixed and stirred, the water content becomes 25-30%.
% and a bulk density of 0.8 to 0.9 g/cc. In this case, the total amount of electrolyte added is different from the conventional method. The composition of this mixture is exactly the same as that of the conventional product. Figure 2 is a cutaway perspective view showing an example of a device for granulating this mixture while applying an impact.
1 is a pot-shaped container having a center tube 15 in the center, 16 is a high tension spring that supports the container 14, and 17 is a vibration motor. When the mixture prepared as described above is immediately put into the container 14 without aging and the motor 17 is operated, a high three-dimensional vibration is applied to the container 14, and the mixture is moved as shown by the arrow in the figure. Start rotating slowly and increase the diameter to 05-5mm in 4-8 minutes.
It is granulated into granules. This mixture is in container 14
The electrolyte is degassed and the electrolyte is homogenized by the impact caused by the collision of the electrolyte with the wall, the vibration given at that time, and the collision of the mixture. FIG. 3 is a cross-sectional view showing the process of filling the cathode can 1 with the granular mixture prepared as described above.
8b and a guide portion 18c,
The tip has a reduced shape that becomes thinner toward the guide 8c at the tip. 19 is a measuring section 18a
It is a piston that moves up and down inside the measuring section 18.
It is dimensioned to have a gap between it and a. 20
is a granular mixture. In this step, after pulling up the piston 19, a predetermined amount of the granular mixture 20 is added to the measuring part 18a, and the piston 19 is press-fitted into the measuring part 18a.
Pressure is applied to the granular mixture 20 in the filling jig 18. Since the filling jig 18 becomes thinner toward the tip, the granular mixture 20 under pressure is crushed while being pushed out to the tip. At the time of crushing, pressure is applied to the mixture and unnecessary air is discharged from the gap between the measuring part 18a and the piston 19, so that the mixture is sufficiently deaerated. The crushed mixture is further extruded by pressure to form the anode mixture 4.
A zinc can 1 loaded with a separator 2 and a bottom paper 3 is filled. At this time, the zinc can 1 is adapted to move downward as the piston 19 moves, and this movement is adjusted so that an appropriate pressure is applied to the filled anode mixture 4. Therefore, anode mixture 4
Contact with the separator 2 and penetration of the electrolyte into the separator 2 are uniformly performed. As mentioned above, the granule mixture 20 is mainly crushed in the crushing part 18b,
When exiting the guide portion 18c, the grain shape is not retained at all. When the filling of the anode mixture 4 is completed as described above, the lid paper 6 is inserted into the zinc can 1, and the carbon rod 5 is press-fitted into the anode mixture 4 through the hole provided in the center of the lid paper 6.
By press-fitting the carbon rod 5, the anode mixture 4 is further deaerated and its density increases, and the contact with the zinc can 1 through the separator 2 is improved, and the electrolyte permeates into the separator 2. It becomes complete. According to this manufacturing method, the granular mixture is crushed and deaerated by using the tapered filling jig 18, and is directly filled into the zinc can 1. It can be manufactured in fewer steps than when The density of the anode mixture 4 produced in this way is approximately
2.00g/cm ³ , the highest density of conventional products 1.96g/cm ³
An extremely high value was obtained compared to . These values are 97% and 95%, respectively, of the true density of 2.063 g/cm ³ determined from the above composition. However, in the above method, the mixture adheres to the inner wall of the container 14 during the granulation process, and shocks and vibrations are not sufficiently transmitted to the mixture, resulting in insufficient deaeration and large variations in the diameter of the granular mixture 20. Another disadvantage was that granulation took a long time. The purpose of this invention is to improve the above-mentioned drawbacks by mixing a small amount of tetrafluoroethylene resin into the mixture before granulation. The present inventors have studied various granulation accelerators that make it difficult for the mixture to adhere to the inner wall of the container 14 and that can produce a granular mixture 20 of uniform size. It has been found that it is effective to add a small amount of a superior tetrafluoroethylene resin to the mixture before granulation. That is, such a mixture is treated with the device shown in Figure 2 for 3 to 3 minutes.
As a result of applying high vibration for 5 minutes, the diameter is 0.5mm or more, 4.0mm
Bulk density: 0.95g/cc or more, 1.10g/cc or less,
A granule mixture 20 having a granule density of 1.95 g/cm ³ or more and 2.04 g/cm ³ or less was obtained. On the other hand, those without the addition of tetrafluoroethylene have a diameter of 4 to 8 minutes in granulation time.
0.5mm or more, 5.0mm or less, bulk density 0.90g/cc or more,
1.20g/cc or less, particle density 1.92g/ ^cm3 or more, 2.02
g/cm ³ or less. That is, compared to those without tetrafluoroethylene, those to which tetrafluoroethylene is added are better degassed, have less variation in the above-mentioned amounts, and require less granulation time. Furthermore, the density of the anode mixture 4 of a dry battery produced using the granular mixture 20 as described above in the process explained with reference to FIG. 3 is 1.99 g/cm ³ (96.5% of true density) or more without additives. , 2.03
g/cm ³ (98.4% of true density) or less,
2.02g/cm ³ for those containing tetrafluoroethylene
(97.9% of true density) or more, 2.04g/cm ³ (of true density
98.9%) or less. Next, an example will be explained. The conventional SUM-1 type dry battery A and the dry battery B, which had the same specifications but were manufactured by granulating for 6 minutes without adding tetrafluoroethylene, and the dry battery B, which also had the same specifications but with the addition of 0.005% by weight of tetrafluoroethylene. Tables 1 and 2 show the results of tests for discharge performance and leakage resistance of dry battery C manufactured by granulating the battery for 4 minutes.

【table】

[Table] Table 1 shows the average value and standard deviation of the discharge duration at 20°C for 10 samples of each sample immediately after manufacture. Dry battery B is significantly superior to conventional dry battery A. However, dry battery C had even better discharge performance, and the effect of tetrafluoroethylene was clearly recognized. Table 2 also shows 20 samples of 50 pieces for each sample immediately after production.
Number of leaks after 3 months with 2Ω load at °C,
The figures also show the number of leakages after 100 batteries were stored at 60°C for 3 months. Dry batteries B and C are clearly superior in leakage resistance, and the effect of ethylene tetrafluoride is also recognized. As mentioned above, the reason why dry batteries B and C are significantly superior to conventional dry battery A is due to the effects of complete degassing of the anode mixture 4 and uniform electrolyte distribution. However, it is obvious that the fourth and fifth drawbacks of the conventional method described above are eliminated since the injection of electrolyte and the aging of the mixture are not performed in the intermediate steps. Furthermore, dry cell C is even better than dry cell B because the mixture containing tetrafluoroethylene is less likely to adhere to the inner wall of the container 14 during granulation, so that deaeration is more complete. This is because the sizes of the agents 20 are uniform, and variations in the amount of the anode mixture 4 are reduced. Further, since the mixture is less likely to adhere to the container 14, work efficiency is also improved. As a result of various experiments and studies, it has been found that if the amount of tetrafluoroethylene in the anode mixture 4 is less than 0.0001% by weight, it is the same as when no additive is added, and the above-mentioned effects cannot be obtained. On the other hand, if the content is 0.02% by weight or more, it will impede the movement of ions during discharge of the dry cell, lowering the utilization rate of manganese dioxide and lowering the discharge performance, which is not preferred in practice. In other words, the amount of tetrafluoroethylene resin is 0.0001% by weight or more, 0.02% by weight in the anode mixture.
It is most effective when mixed in the following amounts. In addition, the granular mixture 20 has a diameter of 0.5 mm or more and 5.0 mm.
Hereinafter, it has become clear that the preferred ranges are a bulk density of 0.90 g/cc or more and 1.20 g/cc or less, and a granule density of 1.92 g/cm ³ or more. The reason is as follows. If the diameter is smaller than 0.5 mm, the degassing is insufficient, and the movement of the electrolyte to the cathode after manufacture and the movement of ions during operation are obstructed by air, resulting in poor discharge performance and large variations. Undesirable. On the other hand, if the diameter is 5.0 mm or more, the amount of the granular mixture 20 filled into the measuring part 18a of the filling jig 18 will vary, and as a result, the amount of the anode mixture 4 filled into the zinc can 1 will vary, which is preferable. do not have. If the bulk density is less than 0.90g/cc, granulation will be incomplete and degassing will be insufficient, resulting in poor discharge performance and large variations, as well as
The variation in the amount of anode mixture 4 filled into the battery becomes large, resulting in poor discharge performance and leakage resistance. On the other hand, when the bulk density is greater than 1.20 g/cc, the granulation becomes excessive, and at the same time, the free electrolyte oozes out onto the surface of the granules, and the diameter of the granules also increases considerably. For this reason, the flow of the granular mixture 20 becomes poor, and the measuring part 18
The variation in the granular mixture 20 supplemented to a becomes large. As a result, the variation in the anode mixture 4 filled in the zinc can 1 becomes large, which is undesirable and causes problems in the production of dry batteries. Furthermore, if the particle density is less than 1.92 g/cm ³ , deaeration is insufficient, resulting in low discharge performance and large variations. The granular mixture 20 to be filled into the filling jig 18 in this way is optimally one that meets the conditions described above. In the above example, the mixture was granulated using a three-dimensional high-vibration device as shown in Fig. 2, but if the device is capable of granulating while applying impact, other devices such as two-dimensional high-vibration device can be used. Similar effects can be obtained with devices such as devices. As explained above, this invention involves granulating a mixture of all the electrolyte and an appropriate amount of a solid material containing tetrafluoroethylene resin while applying an impact, and then turning the granular mixture into a shape with a reduced tip. By filling the filling jig with a predetermined amount, crushing it under pressure, and filling it directly into the cathode can, it can be granulated in a short time while being sufficiently degassed, and the density of the anode mixture can be reduced to 96% of the true density. % or more, it is possible to produce dry batteries with good degassing and uniform electrolyte distribution, greatly improved discharge performance and leakage resistance, and without injecting electrolyte or aging the mixture during the process. Therefore, the various drawbacks associated with these can be eliminated, and the effect of crushing the granular mixture and filling the mixture in one process can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a dry battery, and FIGS. 2 and 3 are a broken perspective view and a sectional view showing an embodiment of the manufacturing method of the present invention. In the figure, 1 is a cathode can, 4 is an anode mixture, and 20 is a granular mixture. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1 (a) Manganese dioxide, a conductive material, all required electrolytes, and a content of 0.0001% by weight or more and 0.02% by weight or less based on the entire anode mixture containing these. Step of mixing with tetrafluoroethylene resin (b) Step of granulating the granular mixture while applying impact to the mixture made in step (b) (c) Granules made in step (b) A method for producing a manganese dioxide dry battery, which includes a step of filling a filling jig with a reduced tip shape with a mixture, applying pressure in the direction of the tip to crush it, and filling the cathode can from the tip. 2 The granular mixture supplemented in the step (c) above has a diameter of 0.5
5.0 mm or more, bulk density 0.90 or more and 1.20 g/cc or less,
The method for producing a manganese dioxide dry battery according to claim 1, wherein the particle density is 1.92 g/cm ³ or more.