JP2950574B2 - Immersion treatment method of carbon rod for manganese dry battery - Google Patents

Description

The present invention relates to a method of immersing a carbon rod for a manganese dry battery with improved high-temperature storability.

<Conventional technology> Since the carbon rod used as a current collector of a manganese dry battery is porous in itself, if the molded carbon rod is directly incorporated into the battery, air will flow into the battery through the carbon rod. And the corrosion of the positive electrode terminal plate due to the infiltration of the electrolyte solution.

Conventionally, in order to prevent such problems, a carbon rod is immersed in a molten paraffin wax immersion tank to impregnate a porous impregnant made of paraffin wax into the inside of the porous material and close the gap. Incorporated.

By the way, in recent years, manganese dry batteries have been required to have durability in high-temperature storage similar to that of electronic components, and as a guideline, durability from conventional storage at 45 ° C. to storage at 60 ° C. has been evaluated.

In addition, when stored at such a high temperature, there is a problem that the paraffin wax impregnated in the carbon rod is deteriorated by melting.

In order to solve this problem, paraffin wax is commercially available as a paraffin wax that can withstand high-temperature storage. For example, it has been considered that the use of a microwax having a melting point of 180 ° F. (84 ° C.) as the impregnating agent satisfies the above-described high-temperature storage performance.

<< Problems to be Solved by the Invention >> However, in the above-mentioned immersion treatment method, what is actually impregnated using the high melting point microwax is 60%.
When stored at ℃, internal resistance increases compared to the initial state,
In addition, deterioration of the sealing agent and the like have occurred.

The reason for this is that if the melting point of paraffin wax or microwax used as an impregnating agent is assumed to be 80 ° C., its low value of about 20 ° C. becomes the softening point, and when stored at 60 ° C., it is contained in the high melting point paraffin wax. It is presumed that the low molecular weight component melts and oozes out on the surface of the carbon rod, increasing the contact resistance between the positive electrode mixture and the carbon rod and deteriorating the sealing agent applied to the carbon rod. You.

The present invention has been made in view of the fact that, if the melting point of the impregnating agent is set to at least 90 ° C., it is possible to prevent the exudation of the impregnating agent components due to high-temperature storage, and the carbon for manganese dry batteries with improved high-temperature storage properties has been made. An object of the present invention is to provide a method of immersing a rod.

<< Means for Solving the Problems >> In order to achieve the above object, in the method of the present invention, as an impregnating agent, a molecular weight of 300 having normal paraffin as a main component is used.
Paraffin wax consisting of ~ 500 hydrocarbon compounds,
Alternatively, an impregnating composition comprising microwax consisting of a mixture of isoparaffin and cycloparaffinic hydrocarbon having a molecular weight of 35 to 60 as a main component, a binding polyolefin resin added thereto, and having a melting point of at least 90 ° C. or more was used. It is characterized by the following.

As the crystalline polyolefin-based resin in the impregnating composition used for the impregnation, crystalline polyethylene having a melting point of 107 ° C. or crystalline polypropylene having a softening point of 145 ° C. is used.

Then, this is mixed and dispersed in paraffin wax or microwax having the above-mentioned composition as a main component at a temperature of 150 to 160 ° C. to obtain an impregnating composition having a melting point of 90 ° C. or more.

The value of the melting point of 90 ° C. or higher generally means that the softening point of the wax is about 20 ° C. lower than the melting point as described above, and considering the storability at 60 ° C., the softening point is at least 70 ° C. It is a value set by paying attention to the fact that it should be set to about ° C.

By setting the melting point to 90 ° C. or higher, the amount of the crystalline polyolefin resin to be added is determined.

For example, when the resin is polyethylene, the added amount is 5 to 10%, and at most 15% (weight, the same applies hereinafter).

In other words, the reason for this limitation is that the amount of addition is lower than the lower limit of 5%.
%, The melting point becomes 90 ° C. or less, and the desired effect cannot be obtained.

Conversely, if it exceeds 15% of the upper limit, the melt viscosity becomes too high, and the impregnating property to the carbon rod decreases unless the impregnation temperature is set to a considerably high value or the time is not prolonged.

In the case where another crystalline polyolefin resin is used, the amount to be added is determined by setting the melting point to 90 ° C. or higher and considering the viscosity at the time of impregnation.

As the carbon rod, one obtained by kneading graphite, pitch, tar, or the like as a binder, extruding into a rod shape, firing, and then cutting to a predetermined size is used.

In this method of impregnating a carbon rod, the carbon rod is charged into an immersion tank filled with an impregnating agent comprising the composition, kept in a vacuum state, and kept at 150 ° C. in accordance with the melt viscosity of the impregnating agent. If the impregnating agent is impregnated to a saturated state, then it is pulled up, and the impregnating agent on the surface is removed by heating to obtain an impregnated carbon rod.

Thereafter, the manganese dry battery is completed by incorporating the carbon rod, which has been subjected to the above-described treatment, into the battery by a conventional method.

<< Operation >> Since the melting point of the impregnating agent is at least 90 ° C or more even when the manganese dry battery using the carbon rod obtained by the above treatment is stored at 60 ° C, its softening point is 70 ° C or more, Therefore, it can be presumed that the leaching of the low molecular weight component to the carbon rod surface at this storage temperature is prevented.

<< Effects of the Invention >> As described above, in the method of immersing a carbon rod for a manganese dry battery of the present invention, the carbon rod is impregnated with the above-described impregnating composition into a carbon rod under high-temperature storage at 60 ° C. It is possible to prevent an increase in internal resistance due to leaching of the impregnating agent onto the rod surface, deterioration of the sealing agent, and the like, and improve high-temperature storage performance.

<< Embodiment >> Next, an embodiment of the present invention will be described. However, the present invention is not limited to the following embodiments.

Examples Microwax with melting point 180 ° F (84 ° C) (molecules 35-60)
5% of crystalline polyethylene having a melting point of 130 ° C with respect to 95% of microwax in an immersion tank maintained at 150 ° C containing a mixture of isoparaffins and cycloparaffinic hydrocarbons) and uniformly dispersed and mixed. An impregnating composition was obtained. The melting point of the obtained impregnating composition was 105 ° C.

With the inside of this immersion tank evacuated, keep the temperature at 150 ° C, which is the optimum melt viscosity, and put the molded carbon rod,
It was impregnated to a saturated state by immersing for several minutes, then pulled up and heated at 140 to 150 ° C. to remove the excess impregnating agent adhering to the surface, thereby obtaining an impregnated carbon rod.

Thereafter, this was assembled into a battery by a conventional method to complete an R20 type (single) manganese dry battery.

Comparative Example A carbon rod was put into a vacuum immersion tank maintained at 150 ° C. containing microwax having a melting point of 180 ° F. (84 ° C.), which is the highest melting point of the conventional type, and impregnated to a saturated state. Thereafter, the impregnating agent on the surface was removed by pulling up and heating to obtain an impregnated carbon rod.

Thereafter, this was assembled into a battery by a conventional method to complete an R20 type (single) manganese dry battery.

Next, each of the dry batteries of the above Examples and Comparative Examples was 5
Continuous discharge performance after storage at 60 ° C for 20 days (load resistance 2Ω,
Comparing the cutoff voltage (0.9V), the average discharge time of the battery of the example was 310 minutes, while the comparative example (conventional product)
Had an average discharge time of 270 minutes, which was significantly lower.

Therefore, although the method of the present invention cannot be directly estimated as compared with the conventional method, it can be estimated that there is no seepage of the impregnating agent on the surface of the carbon rod, thereby reducing the increase in internal resistance.

Further, as a result of examining the short-circuit current after storing each of the above dry batteries at 20 ° C. for 20 days at 60 ° C. and then standing at room temperature for 3 months, the average short-circuit current of the example was 8.5 A, and the range was 7.8.
8.8 A, whereas the average short-circuit current of the comparative example was 7.3 A.
And the range was 7.0-7.5A.

Therefore, the short-circuit current value in the method of the present invention is larger than that of the conventional method, and it can be estimated that the degree of deterioration of the sealing agent due to leaching of the impregnating agent is reduced.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahide Takeshima 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (72) Inventor Nobuaki Watanabe 5-36-11 Shimbashi, Minato-ku, Tokyo (56) References JP-A-56-59452 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/06 H01M 2/06

Claims (1)

(57) [Claims] 1. A carbon rod constituting a positive electrode current collector is immersed in an immersion tank containing a molten impregnating agent, and the porous interior of the carbon rod is impregnated with the impregnating agent and then pulled up. A method for immersing a carbon rod for a manganese dry battery, comprising the step of removing an excess impregnating agent attached to the surface of the carbon rod, wherein the impregnating agent is composed of a hydrocarbon compound having a molecular weight of 300 to 500 and having normal paraffin as a main component. An impregnating composition consisting mainly of paraffin wax or microwax consisting of a mixture of isoparaffins and cycloparaffinic hydrocarbons having a molecular weight of 35 to 60, to which a crystalline polyolefin resin is added and whose melting point is set to at least 90 ° C. A method of immersing a carbon rod for a manganese dry battery, comprising: