JPH0517807Y2 - - Google Patents

Description

[Detailed explanation of the idea]

<Industrial Application Field> This invention relates to the improvement of cylindrical alkaline batteries such as the LR14 type and LR20 type. <<Prior Art>> Conventionally, cylindrical alkaline batteries having the following internal structure are known. A positive electrode mixture press-molded into a cylindrical shape is placed in a bottomed cylindrical positive electrode can in close contact with the inner peripheral surface of the positive electrode can. A cylindrical separator is placed in close contact with the inner peripheral surface of this positive electrode mixture. The separator is
For example, it is made of polypropylene nonwoven fabric sheet rolled into a cylindrical shape, and has no bottom and is open. Therefore, the bottom surface of the positive electrode can is exposed at the lower end opening of the separator. A synthetic resin in a molten state is injected into the exposed bottom portion to form a synthetic resin layer that covers the lower opening edge of the separator and the central inner bottom of the positive electrode can inside the lower opening edge. After this synthetic resin layer is cured, the inner circumferential side of the separator is filled with a negative electrode. In this structure, the synthetic resin layer described above is for reliably insulating and separating the bottom surface of the positive electrode can and the negative electrode. A structure is also known in which a pre-formed resin plate is fitted into the opening at the lower end of the separator instead of a synthetic resin layer injected in a molten state and hardened. Compared to the resin plate fitting method, the method of injecting molten resin has better insulation sealing performance at the lower opening edge of the separator. There is also a structure in which the separator is made in the shape of a bag with a bottom and the above synthetic resin layer is not formed. This makes manufacturing the separator extremely troublesome. <<Problems to be solved by the invention>> As described above, the structure in which the synthetic resin layer is formed by injecting and curing molten resin can be said to be basically superior to other structures. However, in order to actually construct a battery with excellent performance, the resin material used for the synthetic resin layer must be appropriately selected. The resin material used for the synthetic resin layer is first desired to have sufficient resistance to alkaline electrolytes. In addition, if the flowability of the resin is poor when injecting it in a molten state, the molten resin will not spread evenly to the necessary parts of the inner bottom of the positive electrode can, causing pinholes and other problems to occur, resulting in leakage between the negative electrode and the positive electrode can. A route will be created. It is also desirable that the synthetic resin layer does not crack even when a battery stored at a low temperature of about -10° C. is dropped and subjected to impact. Furthermore, it is desirable that the synthetic resin layer does not soften and deform even if the battery is stored at a high temperature such as 80°C. In conventional batteries with the above structure, the synthetic resin layer is made of vinyl acetate or polyamide synthetic resin, which does not satisfy alkali resistance, fluidity, crack resistance at low temperatures, and heat resistance. Ta. In other words, vinyl acetate-based synthetic resin has excellent fluidity and is easy to manufacture, but it may be attacked by alkaline electrolyte after long-term storage, or cracks may occur in the resin layer when dropped at low temperatures, resulting in voltage degradation. Problems such as On the other hand, polyamide-based synthetic resins have excellent alkali resistance and crack resistance when dropped at low temperatures, but they have the disadvantage of having poor fluidity due to their high viscosity when melted, making them difficult to work with, and being expensive. . This invention was made in view of the conventional problems mentioned above, and its purpose was to form the synthetic resin layer described above with a resin material that has excellent alkali resistance, flowability, crack resistance at low temperatures, and heat resistance, The purpose of the present invention is to provide a cylindrical alkaline battery with excellent performance. 《Means for solving the problem》 Therefore, in this invention, the resin material for forming the synthetic resin layer mentioned above is a polyolefin-based heat-melting resin, and the hardness of the resin is in the range of 20 to 50/25 degrees Celsius. It was used. <<Function>> Polyolefin-based hot-melt resin has excellent alkali resistance and fluidity. Also, the penetration is 20 to 50/25
The above-mentioned resin at a temperature of -10°C does not become very hard even at a low temperature of about -10°C, and cracks are less likely to occur even if an impact is applied in that state. Furthermore, it does not soften much even at high temperatures of around 80°C, and almost no deformation is observed. <<Example>> FIG. 1 is a diagram showing the structure and manufacturing process of a cylindrical alkaline battery according to the present invention. As shown in FIG. 1A, first, a positive electrode mixture 4 press-molded into a cylindrical shape is loaded into a bottomed cylindrical positive electrode can 1 .
Next, a cylindrical separator 3 is loaded so as to be in close contact with the inner peripheral surface of the positive electrode mixture 4. Next, separator 3
An appropriate amount of molten synthetic resin (polyolefin-based heat-melting resin, penetration rate 20-50/25°C) is injected from a nozzle onto the bottom surface 1a of the positive electrode can 1 exposed at the lower end opening 3a of the separator. The resin evenly spreads over the lower end edge of 3 and the bottom surface 1a surrounded by it. When the molten resin 7 is hardened, it becomes a synthetic resin layer 70 shown in FIG. 1B. Next, the inner periphery of the separator 3 is filled with the negative electrode 2 . Then, the assembly of the sealing gasket 5, the negative terminal plate 6, and the current collector rod 8 is fitted from the upper opening of the positive electrode can 1 to seal the positive electrode can 1, and the opening edge of the positive electrode can 1 is caulked inward. As a specific example of the above-mentioned polyolefin-based hot-melt resin, one was used that uses an olefin-based polymer and synthetic rubber as a base elastomer, contains petroleum-based synthetic resin as a tackifying resin, and appropriate amounts of wax as a viscosity modifier. The general properties of this resin are shown in the table below.

[Table] Regarding alkali resistance, no problematic changes were observed even after 30 days of immersion in 45% KOH solution. Furthermore, no cracks occurred even at low temperatures of -20°C. <<Effects of the invention>> As explained in detail above, according to this invention, the synthetic resin layer that closes the opening at the lower end of the separator has excellent alkali resistance, low-temperature cracking resistance, and heat resistance. Since the flowability during injection is also good, the insulation separation performance between the positive electrode can and the negative electrode by the synthetic resin layer is extremely good and highly reliable.

[Brief explanation of the drawing]

FIG. 1A is a sectional view showing the manufacturing process of the cylindrical alkaline battery according to the present invention, and FIG. 1B is a sectional view of the completed cylindrical alkaline battery. 1...Positive electrode can, 1a...Bottom surface, 2...Negative electrode, 3
... Separator, 3a ... Lower end opening, 4 ... Positive electrode mixture, 7 ... Synthetic resin in molten state, 70 ... Cured synthetic resin layer.

Claims (1)

[Scope of utility model registration request] A cylindrical positive electrode can with a bottom, a cylindrical positive electrode mixture that is placed in close contact with the inner peripheral surface of the positive electrode can, a cylindrical separator that is placed in close contact with the inner peripheral surface of this positive electrode mixture, and this separator. A cylindrical alkaline battery comprising: a synthetic resin layer formed on the central inner bottom of the positive electrode can in a portion surrounded by the lower opening edge of the battery; and a negative electrode filled in the inner peripheral portion of the separator; The above synthetic resin layer is a cylindrical alkali resin layer made by injecting a polyolefin thermofusible resin in a molten state and hardening it, and having a hardness in the range of 20 to 50/25 degrees Celsius. battery.