JPH043250B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a method for making micro solid particles having various irregular shapes into spherical shapes, or at least improving the micro solid particles into rounded spherical particles. b. Prior Art Conventionally, fine powder has been spheroidized for the purpose of preventing solid particles from caking, improving dispersibility, and improving fluidity. Place it in a mold or ball mill type stirrer and leave it for a long time (generally several hours to several tens of hours)
This has been done by stirring and applying frictional and compressive forces to the particles that accompany the stirring. c Problems to be Solved by the Invention However, it takes several to ten hours to obtain the desired granular shape, which not only increases the size of the apparatus, but also increases the frictional and compressive forces generated during stirring. Because it acts uniformly on microparticles with different particle sizes, a considerable portion of the particles being processed into spherical shapes may be crushed (grinded), or conversely, flat particles may be produced, resulting in poor quality and processing efficiency. There was a big problem. d Means for solving the problems The present invention was made in view of the above circumstances, and
The problems of the prior art have been solved, and microscopic solid particles with different particle sizes and shapes as shown in Figure 4 (photograph) a can be produced by mechanical impact means and, if necessary, by thermal means as an auxiliary means. , for an extremely short period of time (several seconds ~
The present invention provides a method capable of producing uniformly rounded particles as shown in Fig. 4 (photograph) b within a few minutes.
A rotary disk surrounding an impact pin is arranged, and the airflow generated by the rotation of the impact pin is guided into the impact chamber.
The entire amount of amorphous fine solid particles with a particle size of 40 to 0.1 μm is repeatedly passed through the impact chamber along with the air flow, and the air flow is caused to flow along the impact pin and the outermost orbital surface of the impact pin, and is constant therewith. The rotary plate is rotated at a speed of 50 to 120 m/sec to the amorphous fine solid particles between the collision ring and the collision ring, which is arranged around a space of .
Give a mechanical blow while rotating at a circumferential speed of
The present invention provides a method for spheronizing fine solid particles, which is characterized by changing the shape of the amorphous solid particles into rounded spherical particles without crushing them. Typical powders that can be spheronized by the method of the present invention include organic substances such as epoxy powder, nylon powder, polyethylene powder, polystyrene powder, cellulose, and silk powder, and titanium oxide, which generally have a particle size of about 0.1 μm to 40 μm. , graphite, zinc powder, nickel, copper, lead, iron, and other inorganic substances and metals. However, without being limited to these materials, industries such as various chemical industries, electricity, magnetic materials industries, cosmetics, paints, printing inks, toners, coloring materials, textiles, pharmaceuticals, foods, rubber, plastics, and ceramics industries. It can be applied to various materials used in Here, if the particle size exceeds 40 μm, the particles tend to be easily crushed, which is not preferable. In addition, during so-called surface modification, in which microparticles different from the core particles are immobilized or film-formed on the surface of these particles using the various materials listed above as cores, the materials that serve as the cores are When the particles have an unstable shape (generally, the particle size is irregular), a spheroidization treatment can be performed simultaneously with the surface modification treatment. e Example First, an example of a powder impact device used to carry out the method of the present invention will be described in detail with reference to the drawings. 1 and 2 show an example in which a powder impact device is used as the impact type striking means. In the figure, 1 is a casing of a powder impacting device used to carry out the method of the present invention, 2 is a rear cover, 3 is a front cover, 4 is a rotary disk that rotates at high speed inside the casing 1, and 5 is a A plurality of impact pins are provided radially around the outer periphery of the rotary disk 4 at predetermined intervals, and are generally hammer-shaped or plate-shaped. Reference numeral 6 designates a rotating shaft that rotatably supports the rotary disk 4 within the casing 1, and 8 designates a collision ring disposed around the outermost orbital surface of the impact pin 5 with a certain space therebetween. , this uses various shapes of concave and convex type or circumferential flat plate type. 9 is an on-off valve for discharging spherical processing powder provided by cutting out a part of the collision ring; 10 is a valve shaft of the on-off valve 9;
11 is an actuator that operates the on-off valve 9 via the valve shaft 10; 13 has one end opening in a part of the inner wall of the collision ring 8; and the other end opening in the front cover 3 near the center of the rotary disk 4. 14 is a raw material hopper; 15 is a raw material hopper 1;
A chute for supplying raw materials connects 4 and the circulation circuit 13, 16 is a raw material measuring feeder, and 17 is a raw material storage tank. 18 is the outer periphery of the rotary disk 4 and the collision ring 8
A shock chamber 19 is provided between the circulation circuit 13 and
The circulation ports are shown respectively. 20 is a spherical processing powder discharge chute, 21 is a cyclone, 22 is a rotary valve, 23 is a bag filter, 24 is a rotary valve, 25 is an exhaust fan, and 31 is a powder impacting device used to carry out the method of the present invention. A timed control device for controlling the operation of each is shown. When carrying out the method of spheronizing fine powder according to the present invention using the above-mentioned apparatus, the following procedure is performed. First, the on-off valve 9 for discharging the spheronized powder is closed, and the rotating shaft 6 is driven by a driving means (not shown) while introducing inert gas into the apparatus as necessary. However, depending on the nature of the material to be spheronized, particles will not be crushed at 50 m/sec to 120 m/sec.
The rotary disk 4 is rotated at a circumferential speed in the range of m/sec.
At this time, as the impact pin 5 on the outer periphery of the rotary disk 4 rotates, a rapid airflow of air/inert gas is generated, and a fan effect based on the centrifugal force of this airflow causes the impact chamber 18 to
A circulating flow of air returning to the center of the rotary disk 4 is formed around the circulating circuit 13 of the circulating circuit 13 that opens to the rotary disk 4, that is, a completely self-circulating flow is formed. Moreover, the amount of circulating air per unit time that occurs at this time is significantly larger than the total volume of the shock chamber and circulation system, so an enormous number of airflow circulation cycles are formed in a short period of time. . In addition, when the circumferential speed of the rotary disk is less than 50 m/sec, the impact force and the number of circulations are small, and the processing takes time. Also, 120m/
If it exceeds sec, particles may be crushed,
Undesirable. Next, a certain amount of the powder to be processed is fed into the raw material hopper 14 by the metering feeder 16 in a short time. The powder to be treated passes from the raw material hopper 14 through the chute 15 and enters the shock chamber. The powder particles sent into the impact chamber 18 are momentarily impacted by a large number of impact pins 5 of the rotary disk 4 that rotates at high speed, and further collide with the surrounding impact ring 8 to be damaged. The treated powder is selectively subjected to a strong impact action. At the same time, the powder to be treated is circulated through the circulation circuit 13 along with the flow of the circulating glass, returns to the impact chamber 18, and is again subjected to the impact action. Such an impact operation is repeated many times in a short period of time, and the powder to be treated, which was irregularly shaped before the treatment, becomes rounded. This series of impact operations, that is, spheronization operations, is continued until the entire surface of the micropowder particles has a uniform spherical shape, or at least a considerable roundness, but compared to the total volume of the impact chamber and circulatory system. Since a large amount of gas (air and inert gas) circulates within the system, the powder to be treated that circulates together with the gas is subjected to a huge number of impacts in an extremely short period of time. Although it depends on the amount of treatment per batch, the time required for this spherical treatment is generally completed within an extremely short time of several seconds to several minutes, even including the time for supplying the powder to be treated. After the above-mentioned spheroidizing process is completed, the on-off valve 9 for discharging the spheroidized powder is moved to the position shown by the chain line and opened, and the spheroidized powder is discharged. This spheroidized powder is affected by the centrifugal force acting on itself (as long as the centrifugal force is acting on the processed powder, the discharge valve 9 may be placed in a different position) and the discharge valve 9 may be placed in a different position. It is discharged from the shock chamber 18 and the circulation circuit 13 in a short time (several seconds) by the suction force of the wind machine 25, and is discharged from the cyclone 21 and the circulation circuit 13 through the chute 20. After being guided to a powder collecting device such as a filter 23, the powder is collected and discharged to the outside of the system via rotary valves 22 and 24. After the spheronized powder is discharged, the on-off valve 9 is immediately closed, and a certain amount of the powder to be processed from the next time onwards is supplied to the shock chamber from the metering filter 16 again, and is spheronized through the same process. powder is produced one after another. Note that these series of batch spheroidizing operations are controlled and continued by a time control device 31 whose time limit is set in advance in relation to the operating time of related equipment. In addition, if it is necessary to use thermal treatment as an auxiliary during the spheronizing operation (for example, when it is necessary to soften the powder to be treated), the collision ring 8 and the circulation circuit 13 may have a jacket structure. , it is possible to set temperature conditions convenient for the spheroidization treatment of the powder to be treated through various heating mediums and coolants. In addition, in the powder impact device used to carry out the method of the present invention, auxiliary blades may be attached to the rotary disk 4 to further apply force to the circulating flow. That is, if the circulating air volume is increased, the number of times of circulation within a unit time increases, and therefore the number of collisions of powder particles also increases, so that the spheronization processing time can be shortened. Next, in the powder spheronization work carried out in the powder impacting device used to carry out the method of the present invention, it is necessary to prevent oxidative deterioration during the spheronization process of the powder to be processed, and to prevent ignition and explosion. The following describes the use of various inert gases such as nitrogen gas for this purpose. FIG. 3 shows a powder impact device according to the present invention,
An example using this inert gas will be shown. In the description of this embodiment, the same members as in the previous embodiment are designated by the same reference numerals, and the explanation thereof will be omitted. Third
In the figure, 26 is a raw material supply valve provided at the bottom of the raw material hopper 14, and 27 is a chute 1 for supplying raw materials.
5 is an inert gas supply valve opened, 28 is an inert gas supply source, and 29 is an inert gas supply path.
In this embodiment, the circulation circuit 13 is connected to the casing 1.
Shows how it is stored inside. When starting the operation, first, the raw material supply valve 26 is closed, the on-off valve 9 is opened, and then the inert gas supply valve 27 is opened to fill the shock chamber 18 and circulation circuit 13 with inert gas. The substitution of inert gas into the shock chamber and circulation circuit prior to the start of this spheronization process is usually completed within a few minutes. Next, after closing the on-off valve 9 and the supply valve 27 at the same time, the raw material supply valve 26 is immediately opened and the pre-calculated powder to be processed is passed through the chute 15 into the shock chamber 1.
Supply to 8. After supplying, the supply valve 26 is immediately returned to the closed state, and upon receiving this signal, the weighing feeder 16 measures and supplies the next powder to be processed to the raw material hopper 14. Thereafter, the powder to be treated is bombarded with an inert gas in the same manner as in the above embodiment, and the powder to be treated is spheroidized while being kept in sufficient contact with the inert gas while circulating through the circulation circuit 13. be done. Next, when the on-off valve 9 and the supply valve 27 are opened, the spheroidized powder is transferred from the shock chamber 18 and the circulation circuit 13 to the chute 2.
0 and at the same time shock chamber 18 and circulation circuit 1.
3 is replaced with a new inert gas. The discharged spherical powder is treated in the same manner as in the previous example. Thereafter, if the on-off valve 9 and the supply valve 27 are closed and the raw material supply valve 26 is opened, the next spheronizing operation will proceed. Note that this series of batch spheronization operations including supply and stop of inert gas are controlled and continued by the time control device 31 as in the previous embodiment. Next, a specific processing example will be shown below. The powder impact device shown in Fig. 1 was used, in which the outer diameter of the eight plate-type impact pins surrounding the rotary disk was 23 mm, and the diameter of the circulation circuit was 54.9 mm. Amorphous styrene resin powder pulverized products (Fig. 4 a) with an average particle diameter dp50 = 15 μm were subjected to spherical treatment under the treatment conditions shown in the table below as spherical treated powders.
A spherical powder with uniform roundness as shown in Figure b was obtained.

[Table] Calculated from the product and the internal volume of the circulation circuit.
Incidentally, the scanning electron micrographs of the powder before and after the spheroidization treatment obtained in the above execution number (T-3) are shown in the fourth column.
As shown in the figure. f. Effects of the Invention As described above, the feature of the method for granulating solid (powder) particles according to the present invention is that the method of granulating solid (powder) particles according to the present invention is characterized by utilizing a strong impact force on fine powder particles as an impact impact means. Therefore, with the fine powder particles completely dispersed in the gas phase within the device system, impact force can be applied to the entire surface of powder particles of different particle sizes and shapes without pulverizing the particles. The reason is that the magnitude of the impact force itself and the number of times of impact can be adjusted as desired. Therefore, it is possible to completely prevent adhesion of various micron-order fine powders that tend to agglomerate to each other, and at the same time, it is possible to apply just the right impact force to each of the fine powders. Particles with uniform roundness can be efficiently produced in a short time.

[Brief explanation of drawings]

FIG. 1 is a conceptual explanatory diagram systematically showing one embodiment of a powder impacting device used to carry out the method of the present invention, together with its front and rear devices, and FIG. 2 is a side view of FIG. 1. FIG. 3 is an explanatory diagram of another example in which an inert gas is used, and FIG. 4 is a scanning electron micrograph of the powder before and after the spheroidization treatment. Both b indicate 1000 times magnification.

Claims (1)

[Scope of Claims] 1. A rotary disk surrounding an impact pin is arranged in an impact chamber, and an air flow generated by the rotation of the impact pin is guided and circulated in the impact chamber, and together with the air flow, particles with a diameter of 40
The entire amount of amorphous fine solid particles of ~0.1 μm was repeatedly passed through the impact chamber, and the particles were placed around the impact pin along the outermost orbital surface of the impact pin and with a certain space therebetween. Between the collision ring and the amorphous fine solid particles, the rotary disk
While rotating at a circumferential speed of 50 to 120 m/sec, applying a mechanical blow to the amorphous solid particles without crushing them,
A method for spheronizing fine solid particles, which is characterized by changing the shape of the solid particles into rounded spherical particles. 2. The method for spheroidizing fine solid particles according to claim 1, characterized in that the particles are softened by heating as an auxiliary means. 3. The method for spheronizing fine solid particles according to claim 1 or 2, characterized in that the spheronizing treatment is carried out under an inert gas atmosphere.