JPS6148562B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing zinc particles. especially,
This invention relates to the spheroidization of fine zinc powder with many flat or angular parts obtained by gas atomization.

Zinc powder is widely used for electrode plates in batteries and the like, and is produced by methods such as gas atomization and underwater dripping. For example, when zinc powder is produced by a gas atomization method, 40 to 325 meshes of zinc powder can be obtained.

When looking at the shape of these zinc powders under a microscope, some of them are spherical, but there are also grains with spherical parts and straight parts such as flat parts, corners, and projections. Zinc powder with such straight parts is
For example, when used as zinc powder for batteries,
There was a problem with poor weighing and accuracy. This is because zinc grains with straight parts wedge into other grains in the accumulated layer at the hopper outlet, reducing the fluidity of the zinc powder as a whole, thereby preventing it from flowing out smoothly from the hopper outlet. It is. In addition, when weighing before assembling the battery, the amount of zinc powder in the square of the measuring instrument is extremely uneven, and the measurement surface after scraping off the raised part with a leveling tool is very uneven. It fluctuated, and the required weighing accuracy could not be obtained. In battery electrode applications, the amount of zinc that makes up the electrode plate has a significant impact on its performance, and as batteries are increasingly required to have higher performance, it is desirable to measure zinc powder under a specified measurement accuracy. There is.

Metering accuracy is greatly improved by spheroidizing the individual particles of zinc powder so that they are neither flat nor elongated nor have sharp edges. This is because it avoids the above-mentioned problems of hopper flow and unevenness of the measuring surface of the square, and enables dense deposition.

Regarding the spheroidization of zinc powder, (a) it is possible to easily and efficiently spheroidize small zinc powders of 40 to 325, (b) it is suitable for mass production, and (c) it is spherical. Requirements such as not causing oxidation problems due to temperature rise of zinc powder during oxidation work are required. The present inventor made repeated trials using several devices such as a milling machine and a screw machine, but no satisfactory results were obtained.

As a result of further study, we found that extremely effective spheroidization was achieved by rotating a pair of pin disks with a large number of pins facing each other, and passing the zinc powder from the center through the rotating pins to the outer periphery. It was found that the effect was obtained. While passing through the group of rotating pins, the zinc powder is subjected to repeated impact and ablation effects, thereby achieving spheroidization in a short time. It is also possible to flow an inert gas to avoid raising the temperature of the zinc powder during treatment.

Thus, the present invention provides a pair of pin disks in which a large number of pins are planted at narrow intervals except for the central portion,
A pair of pin discs are arranged such that the pin radial position of one pin disc alternates with the pin radial position of the other pin disc, and the pins face each other in a staggered relationship, and at least one of them is rotated within the housing. Inject zinc powder in the central part between the pair of pin disks,
The present invention also provides a method for producing spheroidized zinc particles, characterized in that the spheroidized zinc particles released from the outer periphery of a pair of pin disks are recovered from a housing.

The present invention will be explained in detail below.

The zinc powder treated by the method of the present invention may be produced by any conventional method. For example, a typical example is the aforementioned gas atomization method in which molten zinc is blown off in the form of a spray and cooled in the air.
Regardless of the method, the produced zinc powder contains at least some particles having spherical portions and straight portions.

In the present invention, this straight section is treated by passing zinc powder through a device that has a pair of pin disks each having groups of pins facing each other alternately and rotates one or both of the pin disks.

FIG. 1 shows an example of the device, in which a pair of pin disks 1 and 1' are placed in a housing 10 so that at least one of them is driven to rotate. Pin board 1,
1' is, for example, a disc 2 in which a large number of pins 3 made of a hard material, each having a diameter of 3 to 5 mm and a length of 1 to 3 cm, are planted. The pin discs 1 and 1' are as shown in Figure 1.
The pins are alternately rotated relative to each other in a staggered relationship while facing each other. Therefore, the radial position of the pin row on one pin board must be different from the radial position of the pin row on the other pin board. Generally, the pins are arranged in 2 to 4 concentric rows as shown in Figure 2, and the concentric rows of pins on the other pin board are positioned in the center between the concentric rows of pins on one pin board. There is. Thus, the pin disks 1 and 1' in the opposed state form narrowly spaced passages by their pin groups. The passage spacing must be small enough to prevent the input zinc powder from passing through in an uninterfered manner. As long as the relative rotation of the pin disk is allowed, the pins may have any suitable arrangement pattern other than the illustrated concentric circular row distribution pattern.

The pin discs 1 and 1' are driven by a shaft, at least one of which is connected to a suitable motor. The pin disk and the shaft are connected by a flange 6. Zinc powder is introduced from the inlet 5 through the opening 7 in the flange 6 into the central part 8 of the disc. There is no pin planted in the center of the disc. The charged zinc powder introduced into the central space formed by the opposing pin discs is propelled around the outside by centrifugal force or by the gas flow action if a flow gas is used, and is propelled at high speed. It exits from the outer periphery of the pin plate through a narrow passage between rotating pin groups. While passing through a group of pins,
Zinc particles are subjected to repeated impact, abrasion and ablation actions, elongated grains are cut off at both ends, protrusions are cut off,
In addition, sharp corners become rounded and spherical.

The disk is rotated very rapidly, but the desired spheroidizing effect is achieved at 9000 rpm or more, preferably at 12000 rpm or more.

When the process was carried out at 9000 rpm, zinc powder having linear parts was mixed in the process, which was not preferable, but the effect was seen by repeating the process three times. In this case, the treatment time was approximately 1 minute per application of 1 kg, and the treatment was completed in an extremely short time.

In addition, in the case of 12000 rpm, the effect was quite high even if it was only passed once, and more than 80% of the straight sections were removed. Furthermore, 14000rpm
In this case, more than 90% of the straight parts were removed in one pass.

Zinc powder is susceptible to oxidation and when treated by this treatment method has a heat of 40 to 50° C. due to friction, so it is preferable to flow a cooling gas such as nitrogen gas.

The spheroidized zinc powder is recovered from the housing and separated from debris, fines, etc. in a bag filter.

The obtained zinc powder was placed in a battery container and the measurement accuracy was measured, and it became clear that there was very little variation.

By implementing the present invention as described above, the following effects are produced.

(1) Extremely fine particles such as zinc powder can be spheroidized continuously in a short period of several tens of seconds.

(2) By using zinc powder obtained by this method for button-type alkaline battery negative electrodes, etc., extremely high weighing accuracy can be achieved.

EXAMPLE 5 kg of zinc powder obtained by the spraying method was collected and introduced little by little into a spheroidizing device having opposing pin discs as shown in the figure.

The pin disk was rotated at 14,000 rpm, and zinc powder was introduced from the center of the pin disk, and N ₂ gas was blown into the pin to release the zinc powder inside the pin to the outer periphery of the pin, which was then collected by a bag.

The pins were arranged in three concentrically spaced rows on the pin board. 100 pin discs were arranged so that they interlocked with each other.

The zinc powder treated at 14,000 rpm contained more than 90% of the zinc powder without straight parts, and had high weighing accuracy. Processing time is 5 kg/5 kg
The process could be done in minutes.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view of an example of a spheroidizing apparatus according to the present invention, and FIG. 2 is a front view of one of the pin disks. 1, 1': Pin disk, 2: Disc, 3: Pin, 5:
Inlet, 7: Flange opening, 8: Center, 10:
housing.

Claims (1)

[Claims] 1 A pair of pin discs with a large number of pins planted at narrow intervals except in the center, where the pin radial position of one pin disc alternates with the pin radial position of the other pin disc, and the pins are staggered. At least one of the pair of pin disks facing each other is rotated in a housing, and zinc powder is introduced into the housing at the central portion between the pair of pin disks, and the zinc powder is discharged from the outer periphery of the pair of pin disks. 1. A method for producing spheroidized zinc particles, which comprises recovering spheroidized zinc particles from a housing.