JPH0747295A - Method for pulverizing method and device - Google Patents

Abstract

PURPOSE:To provide a method and a device for pulverizing resin of low melting point to produce fine particles and enabling throughput to be increased and necessary motive power to be reduced. CONSTITUTION:A pulverizer 10 is constituted of a rotor 12 rotated around an axial center in a hollow vessel 11, a stator 14 surrounding the circumference of the rotor, a low temperature device 16 for holding the inside of the hollow vessel at low temperature and a particle feeder 18 which supplies particles A for pulverizing together with gas being in a state of low temperature and decompression to the vicinity of the axial center of the rotor. Furthermore, the pulverizer 10 is constituted of a suction separating device 20 and a classification circuiting device 30. The suction separating device 20 sucks particles pulverized by collision together with gas to the outside of the hollow vessel and holds the inside of the hollow vessel in the state of decompression and separates the particles contained in the gas. The classification circulating device 30 classifies the separated particles into coarse grains L and fine particles S and mixes the coarse rains with particles for pulverizing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crushing method and apparatus, and more particularly to a high speed rotary crushing method and apparatus.

[0002]

2. Description of the Related Art Conventionally, an air jet mill and a high-speed rotary mill (high-speed rotary pulverizer) have been used for pulverizing a resin such as a toner for a copying machine. The air jet mill is capable of high-speed impact of 200 m / s or more and can produce relatively fine particles, but has a problem that it is not suitable for mass production because of its low processing capacity and large power requirements. On the other hand, the high-speed rotary mill is, as illustrated in FIG. 4, a rotor 2 that rotates around an axis in a hollow container 1.
And a stator 3 surrounding the rotor, the rotor 2 is rotated at high speed, the grinding particles 4 are supplied together with the gas near the axis of the rotor 2, and the particles are made to collide with the stator 3 by the rotation of the rotor 2. The particles crushed by collision are taken out together with the gas. The high-speed rotary mill is suitable for mass production because it has a high processing capacity and a small required power, but it is difficult to make the particle collision speed 150 m / s or more, and it is possible to produce only particles of about 8 to 10 μm. There was a point. Therefore, there has been a demand for a crushing device capable of efficiently producing finer particles (for example, 5 μm or less).

In order to meet such demands, a high-speed rotary crusher for crushing a casing while cooling it (Japanese Patent Publication No.
-100), a vacuum high-speed impact crusher for crushing in a decompressed vacuum chamber (JP-A-1-107854), and heat exchange between a liquid refrigerant of the crusher and an object to be crushed by an air stream at low temperature. A low-temperature airflow-type crushing device for airflow crushing (Japanese Patent Publication No. 1-16539) has been proposed.

[0004]

However, Japanese Patent Publication No. 64-64
In the No. 100 pulverizer, the particles are not sufficiently cooled even when the casing is cooled, and the viscosity of the air is increased by the cooling, so that the collision speed of the particles is reduced, and the particle size is about 8 to 10 μm as in the conventional case. Only fine particles could be produced. Further, the crushing apparatus of JP-A-1-107854 has a problem that it cannot be applied to the crushing of a resin having a low melting point such as a toner because the crushed object is heated by the crushing. Further, the low temperature air flow type pulverizer of Japanese Examined Patent Publication No. 1-16539 has a problem that the particle size is limited to about 8 to 10 μm and the required power is large.

The present invention was devised to solve such problems. That is, it is an object of the present invention to provide a pulverizing method and apparatus which can be applied to a resin having a low melting point, can produce fine particles, and can enhance processing capacity and reduce required power.

[0006]

According to the present invention, a hollow container is provided with a rotor that rotates about an axis and a stator that surrounds the rotor, and the hollow container is maintained at a low temperature and reduced pressure. Then, the rotor is rotated at a high speed, particles for grinding are supplied together with a gas in a low temperature and reduced pressure in the vicinity of the axial center of the rotor, the particles are made to collide with the stator by the rotation of the rotor, and the particles are ground by the collision. Is taken out of the hollow container together with the gas, the particles in the gas are classified into coarse particles and fine particles, and the classified coarse particles are mixed with the particles for crushing.

According to a preferred embodiment of the present invention, the peripheral speed of the rotor is 40 m / s or more, and the low temperature is -20.
C. or lower, and the reduced pressure is 300 torr or lower.
Furthermore, according to the present invention, a rotor that rotates about an axis in a hollow container, and a stator that surrounds the rotor,
A crusher consisting of a low temperature device for holding the hollow container at a low temperature, a particle supply device for supplying crushed particles together with a gas in a low temperature and reduced pressure in the vicinity of the axial center of the rotor, and particles crushed by collision Is suctioned with the gas to the outside of the hollow container to hold the inside of the hollow container in a depressurized state, and a suction separation device for separating the particles in the gas, and the separated particles are classified into coarse particles and fine particles. There is provided a crushing device including a classifying and circulating device for mixing the particles for crushing.

[0008]

According to the above-described method and apparatus of the present invention, the inside of the hollow container is kept at a low temperature and a reduced pressure, and the grinding particles are supplied together with the gas at a low temperature and a reduced pressure in the vicinity of the axis of the rotor that rotates at high speed. Therefore, the air resistance of the particles is reduced by the reduced pressure, the rotor can be rotated at a higher speed with a small required power, and the particles are prevented from escaping along with the air flow, and the decrease in the relative impact velocity can be reduced. In addition, the impact resistance of the resin can be reduced due to the low temperature. Therefore, a high-speed rotary pulverizer is used to remove particles at a higher speed (for example, 2
00 m / s or more), and the fine particles can be produced by this high-speed impact. Further, since it is pulverized at a low temperature, it can be applied to a resin having a low melting point. Furthermore, due to the reduction in air resistance, the processing capacity can be increased and the required power can be reduced more than ever before.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a crushing device according to the present invention. In this figure, the crusher is a crusher 10,
The suction / separation device 20 and the classification / circulation device 30 are included.
The crusher 10 includes a rotor 12 that rotates around an axis in a hollow container 11, and a stator 1 that surrounds the rotor 12.
4 and a low temperature device 16 for keeping the inside of the hollow container 12 at a low temperature
And a particle supply device 18 for supplying the particles A for grinding together with the gas in a low temperature and reduced pressure in the vicinity of the axis of the rotor 12. The low temperature device 16 includes, for example, a refrigerant jacket (not shown) provided in the hollow container 12 and a refrigerant supply device that supplies a refrigerant (for example, liquid nitrogen or liquefied carbon dioxide gas) to the jacket. The particle supply device 18 is composed of, for example, a sluice valve or a screw feeder, and is capable of supplying the grinding particles A to the inside while keeping the inside of the hollow container 12 in a depressurized state. The peripheral speed of the rotor 12 is 40 m / s or more, and the temperature of the hollow container 12 is preferably -20 ° C or less.

The suction separation device 20 sucks the particles crushed by collision with the gas to the outside of the hollow container 11 to keep the inside of the hollow container 11 in a depressurized state and separates the particles in the gas. There is. The suction separation device 20 includes a vacuum pump 21, a blower 22, a bag filter 23, and gate valves 24 and 25. In this embodiment, the suction separation device 2
0 is a suction separation line 26 for sucking particles together with gas to the outside of the hollow container 11 through a valve 24 by a vacuum pump 21 and separating the particles by a bag filter 23, and a blower 2
2, a particle supply line 28 for supplying the particles separated by the bag filter 23 via the valve 25 to the classification / circulation device 30. It is preferable that the suction separation line 26 and the particle supply line 28 are provided in two systems, respectively, which are alternately switched to enable continuous operation. Further, the capacity of the vacuum pump 21 is larger than the amount of gas supplied together with the particles by the particle supply device 18, and the volume inside the hollow container 12 is 300.
It is preferable to set it so that the pressure can be maintained at a reduced pressure of less than torr.

The classification / circulation device 30 classifies the separated particles into coarse particles L and fine particles S, and mixes the coarse particles L with the grinding particles A. The classification and circulation device 30 has a classification rotor (not shown) inside, and the high speed rotation of this rotor classifies the particles supplied from the suction separation device 20 into coarse particles L and fine particles S, and the classified coarse particles L with gas and crusher 2
0 to the particle supply device 18. Classification and circulation device 30 such that the average particle size of the fine particles S is, for example, 5 μm or less.
(For example, the number of rotations of the rotor) is set.

The crushing device shown in FIG. 1 is used as follows. First, the inside of the hollow container 11 is kept at a low temperature of −20 ° C. or less and a reduced pressure of 300 torr or less by the low temperature device 16 and the suction separation device 20, and the rotor 12 of the crusher 10 is rotated at a high speed of 40 m / s or more in peripheral speed. To do. Next, the particles A for grinding are supplied near the axis of the rotor 12 together with the gas in the low temperature and reduced pressure state, and the particles A are fed to the rotor 12
Is rotated to collide with the stator 14 and pulverize. Further, the particles separated by the collision are taken out of the hollow container 11 together with the gas by the suction separation device 20, and the particles in the gas are classified into the coarse particles L and the fine particles S by the classification and circulation device 30 to classify the coarse particles. L is mixed with the grinding particles A.

FIG. 2 is a diagram showing the relationship between the impact strength of various resins and the temperature. As is clear from this figure, the resin used for the toner of the copying machine generally has a low impact strength at a low temperature of 0 ° C. or lower, and remarkably lowers at −20 ° C. or lower. Therefore, by maintaining the inside of the hollow container 11 at a low temperature of −20 ° C. or less, fine particles can be easily manufactured. Further, the air density increases at low temperatures, but by maintaining the temperature at −20 ° C. or lower and the depressurized state at 300 torr or less, the air density can be reduced to ½ or less compared to normal temperature. Furthermore, in the same state, the viscosity of air is reduced by 20 to 30%. Therefore, by using a low temperature of −20 ° C. or less and a reduced pressure of 300 torr or less together, the air resistance of the particles is reduced by the reduced pressure, the rotor can be rotated at a higher speed with a small required power, and the relative movement between the particles and the rotor or the stator is reduced. It is possible to reduce the decrease in impact speed. Further, since it is pulverized at a low temperature, it can be applied to a resin having a low melting point.

FIG. 3 is a diagram showing the correction coefficient Ce of Cunningham in the resistance force F that the particles receive from the fluid. The resistance force F that a particle receives from a fluid is generally expressed by the following equation. ^{F = Cd · (πD 2/} 4) · (ρv 2/2) / Ce ··· ( Equation 1) In this equation, Cd is the drag coefficient, D is the particle diameter, [rho is the fluid density, v is the particle and the fluid Is the speed difference. When a low temperature of −20 ° C. or lower and a reduced pressure of 300 torr or less are used together, the correction coefficient Ce of Cunningham becomes larger than 1 and the fluid density ρ becomes smaller as shown in FIG. 3, so that when other factors are the same. The resistance force F that the particles receive from the fluid becomes synergistically small, and it becomes possible to cause the particles to collide with the stator at high speed. This makes it possible to produce finer particles than ever before.

[0015]

As described above, according to the method and apparatus of the present invention, the inside of the hollow container is kept at a low temperature and a reduced pressure, and the grinding particles are kept at a low temperature and a reduced pressure in the vicinity of the axis of the rotor rotating at a high speed. Since it is supplied together with the gas, the air resistance of the particles is reduced by the reduced pressure, the rotor can be rotated at a higher speed with a small required power, and the reduction in the relative impact speed between the particles and the rotor or the stator can be reduced. In addition, the impact resistance of the resin can be reduced due to the low temperature. Therefore, the particles can be made to collide with the stator or the rotor at a higher speed (for example, 200 m / s or more) than ever before by the high-speed rotary pulverizer, and fine particles can be produced by this high-speed impact.

Therefore, the crushing method and the crushing apparatus of the present invention can be applied to a resin having a low melting point, can produce fine particles, have an excellent effect that the processing capacity can be increased and the required power can be reduced. There is.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a crushing device according to the present invention.

FIG. 2 is a diagram showing the relationship between impact strength and temperature of various resins.

FIG. 3 is a diagram showing a correction coefficient Ce of Cunningham in a resistance force F that particles receive from a fluid.

FIG. 4 is a schematic view of a conventional high-speed rotary crushing device.

[Explanation of symbols]

 1 Hollow Container 2 Rotor 3 Stator 4 Grinding Particles 10 Grinder 12 Rotor 14 Stator 16 Low Temperature Device 18 Particle Feeder 20 Suction Separator 21 Vacuum Pump 22 Blower 23 Bag Filter 24, 25 Gate Valve 26 Suction Separation Line 28 Particle Supply Line 30 Classification circulation device A Particles for grinding L Coarse particles S Fine particles

Claims (3)

[Claims] 1. A hollow container is provided with a rotor rotating about an axis and a stator surrounding the rotor, the hollow container is kept at a low temperature and a reduced pressure, and the rotor is rotated at a high speed. Particles for grinding are supplied together with a gas in a low temperature and reduced pressure in the vicinity of the axial center of the rotor, the particles are made to collide with the stator by the rotation of the rotor, and the particles ground by collision are taken out of the hollow container together with the gas, A pulverization method, characterized in that particles in a gas are classified into coarse particles and fine particles, and the classified coarse particles are mixed into the particles for pulverization. 2. The peripheral speed of the rotor is 40 m / s or more, the low temperature is −20 ° C. or less, and the decompression is 300.
The pulverization method according to claim 1, wherein the pulverization method is not more than torr. 3. A rotor which rotates about an axis in a hollow container, a stator which surrounds the rotor, a low temperature device which keeps the inside of the hollow container at a low temperature, and a low temperature near the axis of the rotor. A pulverizer consisting of a particle supply device for supplying pulverizing particles together with a gas under reduced pressure, and the particles pulverized by collision are sucked together with the gas to the outside of the hollow container to hold the inside of the hollow container at a reduced pressure, A pulverizer comprising a suction separator for separating particles in the gas and a classifying circulation device for classifying the separated particles into coarse particles and fine particles and mixing the coarse particles with the particles for crushing.