JP3494775B2 - Zinc alloy powder for alkaline battery and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc alloy powder for alkaline batteries, which suppresses the generation of hydrogen gas and has improved battery characteristics, and a method for producing the same. More specifically, it relates to chromium which causes hydrogen gas generation. The purpose is to prevent the generation of hydrogen gas by controlling the nickel content to below a specified level.

[0002]

2. Description of the Related Art Conventionally, a zinc alloy powder for an alkaline battery, which is used as a negative electrode of an alkaline battery in which an electrolytic solution is an alkaline aqueous solution such as caustic potash, is produced from industrially obtained zinc such as electric zinc. It is manufactured by atomizing molten metal alloyed with a small amount of added metal by the atomizing method.

The zinc alloy powder thus obtained contains chromium, manganese, iron, cobalt, nickel, copper, silver, lead, cadmium and antimony as trace impurities detected in addition to the metal added as an alloy component. , Tin, etc. are contained, and it is well known that all of them promote corrosion of zinc and significantly increase the generation of hydrogen gas.

The reason why these trace impurities are contained is as follows. That is, the impurities that accompany the ore processed in the smelting process are not removed in the smelting process and remain in a very small amount, and further when these industrially produced zinc is used to produce zinc powder for batteries. In the manufacturing process, trace impurities are not removed, and conversely, there is a high possibility that trace amounts of impurities will be mixed in from the equipment and equipment used to contaminate the zinc powder for batteries.

This indicates that the trace impurities contained in zinc used as a raw material remain as unavoidable impurities in zinc powder for batteries almost as they are.

As a countermeasure against these problems, high-purity zinc containing a small amount of impurities can be used. For example, it is possible to select and use electric zinc having a low content of specific impurities, use purified zinc obtained by distilling and refining ordinary electric zinc as a raw material under atmospheric pressure or vacuum, or use electric zinc. Is to use re-electrorefined zinc as a consumable electrode.

In addition to high-purity zinc as a raw material, measures are taken not only for the purpose of suppressing contamination by equipment used in battery powder manufacturing processes, instrumental equipment, etc. Zinc powder can be produced.

One of the most basic means is the third
It is the addition of metal elements, and among those proposed as such effective addition elements, for example, aluminum, indium, bismuth, etc. are used, and the optimum value of the component amount selected from these and experimentally confirmed and optimized It is also possible to manufacture by selecting various combinations.

Further, hydrogen gas generation is suppressed by a method such as addition of a corrosion inhibitor (Inhibitor) to an alkaline battery, such as improvement of properties including zinc particle shape, particle size distribution, surface state, and physical properties, and the like. It was

[0010]

However, it is necessary to use zinc whose raw material has a specific impurity content regulated as described above, or to use zinc whose raw material zinc is purified to regulate the total amount of impurities. In that case, it is not enough to reduce the amount of gas generation, and it will increase the cost.In addition, in the improved technology by adding specific alloy components, there are numerous combinations and optimal combinations of components for alloy elements, To date, no zinc powder for batteries that is technically satisfactory has been produced.

The present invention has been made to solve the above-mentioned drawbacks, and has found that hydrogen gas generation can be significantly suppressed by reducing the mixing of specific impurities, and the present invention can be provided. .

[0012]

Means for Solving the Problems The inventors of the present invention have made earnest studies in accordance with this object, and as a result, hydrogen gas generation is controlled by controlling the addition amounts of chromium and nickel as impurities within a specific range. I found that I could control the amount.

That is, the first aspect of the present invention is that 0.001 to 0.1% by weight of aluminum and 0.001 of bismuth are used.
To 0.1% by weight, 0.001 to 0.1% by weight of indium, and 0.1 to 0.5% by weight of chromium, the present invention relates to a zinc alloy powder for alkaline batteries. .

The second aspect of the present invention is to add aluminum to 0.0
01-0.1% by weight, bismuth 0.001-0.1% by weight, indium 0.001-0.1% by weight,
The present invention relates to a zinc alloy powder for an alkaline battery, which is made of zinc containing 0.1 to 0.5 ppm by weight of nickel.

The third aspect of the present invention is to add aluminum to 0.0
01-0.1% by weight, bismuth 0.001-0.1% by weight, indium 0.001-0.1% by weight,
Also, zinc containing 0.1 to 0.5 ppm by weight of chromium melted at a temperature of 600 ° C. or lower is sprayed into a hopper coated with a heat-resistant resin that does not contain chromium on the inner surface to generate gas. The present invention relates to a method for producing a zinc alloy powder for an alkaline battery, which is characterized by using an alloy powder having a low content.

The fourth aspect of the present invention is to add aluminum to 0.0
01-0.1% by weight, bismuth 0.001-0.1% by weight, indium 0.001-0.1% by weight,
In addition, zinc containing 0.1 to 0.5 ppm by weight of nickel melted in a gas atmosphere at a temperature of 600 ° C. or lower,
The present invention relates to a method for producing a zinc alloy powder for an alkaline battery, which comprises spraying into a hopper having a nickel-free heat-resistant resin coated on its inner surface to obtain an alloy powder having a small amount of gas generation.

[0017]

In the past, efforts have been made to reduce the content of impurities in zinc alloys as much as possible, and the reduction has been made to some extent technically, but there are various problems as described above.

The inventors of the present invention diligently studied the influence of each impurity on the gas generation, and regarding the one in which iron was dealt with among these impurities, Japanese Patent Application No. 7-14130.
Patent application was filed as No. 2.

On the other hand, chromium and nickel as impurity elements are additive elements that constitute so-called stainless steel, which is often used as a corrosion resistant material, and it is common to use this material almost at locations where corrosion is disliked. .

As equipment for producing zinc powder for alkaline batteries, iron-based equipment will be cheap because of its robustness and heat resistance, but corrosion will proceed depending on the surrounding conditions.
Since it is possible that corroded iron rust peels off, or minute and minute metal pieces scraped due to wear etc. are mixed in the product, currently, when using it as an equipment structure, use stainless steel as much as possible. Is normal.

Although stainless steel is excellent in both corrosion resistance and heat resistance, it has the drawback that when it is mixed into a product due to wear or the like, it cannot be sorted by a magnetic separation machine in the middle of the manufacturing process. It will prompt the occurrence.

The inventors of the present invention have made improvements as far as possible in each device / equipment in the manufacturing process to prevent impurities from being mixed in as much as possible. However, with regard to chromium and nickel contained in trace amounts, except those contained in the raw materials. However, the cause of contamination as an impurity could not be identified and no countermeasure could be taken.

From these things, the present inventors considered the place where it comes into contact with metals such as chromium and nickel as the place where contamination can occur, and investigated the material and contact state of each device / equipment in the manufacturing process.

Referring to FIG. 1, the atomizing process in the manufacturing process is performed in the furnace 2 provided on the hopper 1,
The zinc alloy 3 melted at about 500 ° C. is held, the zinc alloy is made to flow down from the lower part of the furnace, and the high pressure gas 4 is injected to obtain zinc alloy powder of a predetermined size.
The hot zinc sprayed here is cooled to room temperature,
A part of it is cooled by keeping high temperature and colliding with a stainless steel hopper wall, and it reaches the bottom face 6 of the hopper while falling on the side face 5 of the hopper, or directly collides with the bottom face of the hopper and is deposited there. There is something that can be cooled.

In this step, the zinc alloy powder which is high temperature and semi-molten reacts with chromium and nickel, which are the constituent metals of the stainless steel forming the inner wall of the hopper, in a trace amount to form an intermetallic compound with zinc. It was found that the contents of chromium and nickel in zinc alloy increased. In particular, when the spray temperature was slightly high and the bottom of the hopper was thickly accumulated to store heat, the temperature was higher.

From these facts, in order to study the effects of chromium and nickel as alkaline battery powders, the present inventors have conducted a normal zinc atomization process on a molten zinc alloy in which chromium and nickel are directly added to a zinc alloy, to obtain a battery. A zinc powder for use was prepared, and a gas generation test was conducted for this powder. As shown in FIGS. 3 and 4, the degree of influence of gas generation could be grasped although the tendency was different.

As a result, it was found that these elements have a non-negligible effect on the alkaline zinc battery powder with respect to gas generation.

Therefore, while preventing mechanical mixing of stainless steel or the like, by preventing contamination due to reaction in the hopper and controlling the degree of influence of chromium or nickel on gas generation, alkaline powder zinc powder After confirming that the gas generation amount can be reduced, the present inventors achieved the object by improving the inner wall of the hopper and applying Teflon (registered trademark) as a heat resistant resin containing no chromium or nickel to the inner wall surface. I found what I got.

Further, in the present invention, a zinc alloy prepared by using industrially refined zinc that is usually used as a raw material, melting this zinc, and then adding aluminum, bismuth and indium as alloy components is used.

In this case, the addition amount range of aluminum is
0.001 to 0.1% by weight, the addition amount range of bismuth is preferably 0.001 to 0.1% by weight, and the addition amount range of indium is preferably 0.001 to 0.1% by weight. In this range, aluminum is By alloying with zinc, it shows the effect of smoothing the surface of the alloy powder particles, and indium has the effect of increasing the hydrogen overvoltage on the surface of the alloy powder and suppressing the gas generation due to corrosion during storage as a battery, while bismuth is Similarly, it has an effect of suppressing gas generation before and after discharge.

Normal atomization is performed with a molten zinc alloy in which these alloying elements are controlled within the above range, and the inner wall of the hopper is processed to prevent chromium and nickel from being mixed as impurities to obtain a desired zinc alloy powder. I decided to get it.

The present invention is described in detail below with reference to examples, but these ranges do not limit the present invention.

[0033]

Example 1 A desired powder was manufactured using the zinc alloy powder manufacturing apparatus shown in FIG. Zinc containing less than 0.5 ppm by weight of Cr is melted at about 500 ° C. in the furnace 2, and predetermined amounts of aluminum, bismuth and indium shown in Table 1 (Sample Nos. 1 to 4) are added to the zinc alloy. A molten metal was prepared, and the molten metal was atomized and sprayed into the hopper 1 to which Teflon (registered trademark) was joined to obtain a zinc alloy powder. With respect to the obtained zinc alloy powder, the chromium content and the gas generation amount were determined.

The gas generation amount measuring device shown in FIG. 2 was used for measuring the gas generation amount. In this case, first, the obtained zinc alloy powder was gelled, then incorporated into an LR6 type battery (cell) 11, discharged at 20 ° C. and 10 Ω for 48 hours, and then the cap 12 was placed in a thermostatic chamber 10 whose temperature was adjusted to 45 ° C. The current generation rate in the test tube 8 filled with the liquid paraffin 14 and sealed with the silicone rubber stopper 7 was read by the scale of the pipette and found, and these values are also shown in Table 1 together. .

[0035] As shown in Table 1, the content of chromium is 0.5 wtpp
m or less and having a specific composition. 1-4
In all of the zinc alloy powders, the gas generation rate is about 0.1 ml / cell · day or less, which is the limit value.

[0036]

[Comparative Example 1] The zinc alloy powders shown in Table 1 (Sample Nos. 6 to 13) were prepared in the same manner as in Examples by preparing zinc alloy melts containing predetermined amounts of aluminum, bismuth and indium, respectively. A zinc alloy powder was obtained by directly spraying onto the inner wall of a conventional stainless steel hopper.

Sample No. of the comparative example. With respect to the zinc alloy powders of 6 to 10, the content of chromium in the obtained zinc alloy powder exceeds 0.5 ppm by weight, so that hydrogen gas generation is suppressed even if the composition is within the range specified in the present invention. No effect is observed. Sample No. of the comparative example. The zinc alloy powders Nos. 11 to 13 have an effect of suppressing hydrogen gas generation because the composition thereof deviates from the range specified by the present invention even though the content of chromium is 0.5 ppm by weight or less. Absent.

[0038]

Example 2 A desired powder was manufactured using the zinc alloy powder manufacturing apparatus shown in FIG. Zinc containing less than 0.5 ppm by weight of Ni was melted in a furnace 2 at about 500 ° C., and predetermined amounts of aluminum, bismuth and indium shown in Table 2 (Sample Nos. 14 to 18) were added to the zinc alloy. A molten metal was prepared, and the molten metal was atomized and sprayed into the hopper 1 to which Teflon (registered trademark) was joined to obtain a zinc alloy powder. The nickel content and the gas generation amount of the obtained zinc alloy powder were determined.

The gas generation amount measuring apparatus shown in FIG. 2 was used for measuring the gas generation amount. In this case, first, the obtained zinc alloy powder was gelled, then incorporated into an LR6 type battery (cell) 11, discharged at 20 ° C. and 10 Ω for 48 hours, and then the cap 12 was placed in a thermostatic chamber 10 whose temperature was adjusted to 45 ° C. The current generating rod 13 was removed, the gas generation rate in the test tube 8 filled with liquid paraffin 14 and sealed with the silicone rubber stopper 7 was read with a scale of a pipette, and these values are also shown in Table 2. .

[0040]

[Table 2] As shown in Table 2, the nickel content is 0.5 weight pp
Sample No. having a specific composition of less than m. 14 ~
In all of the 18 zinc alloy powders, the gas generation rate is about 0.1 ml / cell · day or less, which is the limit value.

[0041]

[Comparative Example 2] The zinc alloy powders shown in Table 2 (Sample Nos. 19 to 26) were prepared by the same method as in Example 1 except that predetermined amounts of aluminum, bismuth and indium were added to the zinc alloy powders. A zinc alloy powder was obtained by directly spraying onto the inner wall of a conventional stainless steel hopper.

Sample No. of the comparative example. In the zinc alloy powders Nos. 19 to 23, the content of nickel in the obtained zinc alloy powder exceeds 0.5 ppm by weight, so that hydrogen gas generation is suppressed even if the composition is within the range specified in the present invention. No effect is observed. Sample No. of the comparative example. The zinc alloy powders of Nos. 24 to 26 have an effect of suppressing hydrogen gas generation because the composition deviates from the range defined by the present invention, even though the content of nickel is 0.5 ppm by weight or less. Absent.

[0043]

As described above, in the present invention, zinc alloy powder for alkaline batteries with a small amount of gas generation can be obtained by suppressing the mixing of the trace components of chromium and nickel in the manufacturing process, and it is possible to obtain the zinc alloy powder for a long time. It is possible to obtain effects such as providing a battery that can be used to the market.

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus for producing zinc alloy powder used in Examples.

FIG. 2 is a schematic diagram showing a measuring device for measuring a gas generation amount.

FIG. 3 is a diagram showing a relationship between a nickel content and a gas generation amount.

FIG. 4 is a diagram showing a relationship between a chromium content and a gas generation amount.

[Explanation of symbols]

1 hopper 2 furnaces 3 Zinc alloy 4 high pressure gas 5 Teflon (registered trademark) junction hopper inner wall 6 hopper bottom 7 Silicone rubber stopper 8 test tubes 9 pipettes 10 constant temperature bath 11 LR6 type battery 12 caps 13 Current collector 14 Liquid paraffin

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 5-166507 (JP, A) JP-A 3-61342 (JP, A) JP-A 61-116755 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 4/42 B22F 9/08

Claims (4)

(57) [Claims] 1. Aluminum is contained in an amount of 0.001 to 0.1% by weight, bismuth in an amount of 0.001 to 0.1% by weight, indium in an amount of 0.001 to 0.1% by weight, and chromium of 0.001 to 0.1% by weight .
A zinc alloy powder for an alkaline battery, which is composed of zinc in an amount of 1 to 0.5 ppm by weight . 2. The aluminum containing 0.001-0.1% by weight, bismuth 0.001-0.1% by weight, indium 0.001-0.1% by weight, nickel 0.1.
Zinc alloy powder for alkaline batteries, characterized in that the zinc alloy powder is contained in an amount of 0.5 to 0.5 ppm by weight . 3. Aluminum containing 0.001 to 0.1% by weight, bismuth 0.001 to 0.1% by weight, indium 0.001 to 0.1% by weight, and chromium 0.1 .
What melted zinc containing 1 to 0.5 ppm by weight at a temperature of 600 ° C. or lower was sprayed into a hopper coated with a heat-resistant resin that does not contain chromium on the inner surface to obtain an alloy powder with a small amount of gas generation. A method for producing a zinc alloy powder for an alkaline battery, comprising: 4. Aluminum is contained in an amount of 0.001 to 0.1% by weight, bismuth in an amount of 0.001 to 0.1% by weight, indium in an amount of 0.001 to 0.1% by weight, and nickel is included.
An alloy with a small amount of gas generated by melting zinc containing 0.1 to 0.5 weight ppm at a temperature of 600 ° C. or lower and spraying it inside a hopper coated with a heat-resistant resin that does not contain nickel. A method for producing a zinc alloy powder for an alkaline battery, which is a powder.