JPH0824692A - Method and vessel for crushing - Google Patents

Abstract

PURPOSE:To manufacture simply a crushed product provided with a sharp grain size distribution in a short time even when a material to be crushed is a hard substance such as cubic boron nitride. CONSTITUTION:In the crushing method using a planetary mill in which a material to be crushed is fed into a crushing vessel having both of revolution axis and rotation axis in the vertical direction, and crushing is carried out by revolving the vessel, the crushing vessel is divided into two or three or more chambers by a mesh screen, and the material to be crushed and a crushing medium are fed into the above-referred one or two or more chambers, and crushing is carried out while varying the number of revolutions of the crushing vessel. The crushing vessel for a planetary mill is divided into two or three or more upper and lower chambers by the mesh screen. Further in the crushing method or the crushing vessel for the planetary mill, a tapered face or a curved face is formed at least on the bottom section inner face of a chamber into which the crushing medium is fed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding method and a grinding container by a planetary mill. INDUSTRIAL APPLICABILITY The present invention is suitably used in the field of producing powder with a specific particle size represented by, for example, abrasive grains and abrasives in high yield.

[0002]

2. Description of the Related Art A planetary mill in which a crushing container arranged at equal intervals on the revolution circle revolves and the container itself also revolves along with the revolving motion of a planetary mill is a function of high centrifugal acceleration generated in the crushing container. Has a higher crushing capacity than existing crushers. In addition, crushing is performed by subjecting the object to be crushed placed in the crushing container to impact and compression by the crushing medium. You can

[0003]

The main purpose of grinding with a planetary mill is to obtain finer powders and to grind harder substances. Among them, the former is being researched and put to practical use by optimizing the conditions in the conventional batch pulverization method and improving the efficiency by continuously feeding and recovering the material to be pulverized. 6
There is a continuous crushing type planetary ball mill disclosed in JP-A-3-278563. On the other hand, with regard to the latter, for example, grinding of high hardness substances such as abrasive grains and abrasives with a planetary mill is rarely performed. This is due to the following reasons.

That is, the abrasive grains and the abrasives are used by classifying the pulverized products into a predetermined grain size range. However, the actual demands are different from each other, so that the pulverization is in great demand. This is done so that as much milled product as the particle size can be recovered. However, in batch pulverization using a planetary mill, because of its high pulverizing ability, once pulverized to the target particle size is further pulverized (over-milled), the powder yield of the target particle size is increased. This is due to the decrease.

As a method for controlling the particle size of the crushed product, there is a continuous crushing method such as a ball mill or a vibration mill. This method is a method of continuously charging and recovering the object to be crushed during crushing, and by controlling the residence time of the object to be crushed in the crushing container, the powder having a particle size equal to or smaller than the target particle size before being overcrushed Is a method of separating. On the other hand, the planetary mill is difficult to achieve such continuation because the structure of the crusher is complicated. As an example of successful succession, Japanese Patent Application Laid-Open No. 63-27
Although there is a Japanese Patent No. 8563, this method uses an air stream to collect and separate the pulverized material, and therefore it is difficult to efficiently separate the pulverized product of several tens of μm to several hundreds of μm that is often used for abrasive grains and the like. is there.

[0006]

In order to prevent over-milling in a planetary mill, the present inventors need to carry out milling in an extremely short time to remove a milled product having a particle size equal to or smaller than a target grain size. Solving the above problems from the viewpoint that it is difficult to recover coarse particles in the conventional continuous crushing planetary ball mill, and that it is not industrial to collect and separate the crushed products one by one like batch crushing. In order to do so, various studies were conducted. As a result, the present invention has been completed by finding out the following matters.

(1) In order to separate a crushed product crushed to a particle size not more than the target in a crushing container of a planetary mill, a separate chamber for receiving the crushed product is provided inside the crushing container with a mesh screen. Some of the fallen milled product can be separated through a mesh screen.

(2) However, since the crushed product that cannot be separated as it is is over-crushed, in order to prevent it, if the rotation speed of the crushing container is reduced below a certain value, the drop is promoted and the separation proceeds. Can be made.

(3) If a taper surface or a curved surface is provided on at least the inner surface of the bottom of the room partitioned by the mesh screen and containing the grinding medium, the crushed product can be easily dropped and separated. Moreover, since the object to be crushed is dispersed over the entire side wall of the container when the crushing container starts to rotate, uniform crushing is possible.

That is, according to the present invention, in a pulverization method by a planetary mill in which an object to be pulverized is charged into a pulverization container in which both the revolution axis and the rotation axis are vertical, the pulverization container is rotated to perform pulverization. A crushing method characterized by partitioning into 2 or 3 or more rooms by a screen, charging an object to be crushed and a crushing medium into the 1 or 2 or more rooms and crushing while changing the rotation speed of the crushing container, and a container A crushing container for a planetary mill, characterized by being divided into two or more upper and lower chambers by a mesh screen. Further, in the above crushing method or the above crushing container for a planetary mill, a taper surface or a curved surface is provided at least on the inner surface of the bottom of the chamber in which the crushing medium is charged.

Explaining the present invention in more detail below, the greatest feature of the present invention is that the object to be crushed and the crushing medium are charged into one or more chambers partitioned by a mesh screen and the number of revolutions thereof is changed. Is to pulverize by a conventional pulverization method using a planetary mill to separate a pulverized product having a target particle size. Therefore, in carrying out the present invention, the conventional planetary mill can be used as it is without requiring any special modification or installation of auxiliary equipment in the crusher body. An example thereof is "P-5 type" manufactured by Fritsche.

However, in the present invention, since it is desirable to change the revolution speed of the crushing container by periodically changing the revolution speed of the crushing container during crushing, the crusher can freely change the revolution speed by an inverter or the like. It is desirable to have a mechanism that can do this. Further, in most of the ordinary planetary mills, the rotation speed of the crushing container is determined by the rotation speed, but the rotation speed and revolution speed may be independently adjusted.

The crushing container used in the present invention is divided into two or more chambers vertically by one or more mesh screens having the same or different openings so that the crushing container can be separated to a desired particle size. Has been. Preferably, it is divided into three or more rooms vertically by two or more mesh screens having different openings. Regarding the way of tensioning the mesh screen, it is desirable that the crushed product is in the horizontal direction because it is separated by natural fall, but it is not necessarily limited as long as the separation is performed, and it may be a conical shape, for example. good.

It is not necessary to make the size (volume) of each room divided into two or more rooms up and down different, but the powder having a small particle size is bulkier than the powder having a large particle size. Therefore, the room for accommodating the powder having a small particle size can be made larger in proportion to its bulkiness than the room for accommodating the powder having a large particle size.

Further, the shape of each room may be arbitrary, but as described above, in order to make the falling and separation of the crushed products easier and to carry out a more uniform crushing, at least the crushing medium-filled room It is preferable that the inner surface of the bottom portion is provided with a tapered surface or a curved surface. For example, when the grinding medium has a spherical shape, it is preferable to provide a curved surface having a radius of curvature equal to or larger than the radius of the grinding medium on the inner surface of the bottom so as to hit the entire side wall. It is not always necessary to provide a tapered surface or a curved surface on the inner surface of the bottom of the room where the grinding medium is not charged.

There is no particular restriction on the material of the mesh screen as long as there is no extreme change in the opening during separation. However, when the mesh screen is severely damaged by the grinding medium, the strength of the mesh screen itself can be increased by using, for example, a punched wire mesh, or the mesh screen can be prevented from coming into direct contact with the grinding medium. Reinforcing mesh with wide openings can be used. The material of the crushing container itself is not particularly limited, and chrome steel is used, for example.

Next, the crushing method of the present invention will be described. In the present invention, the crushing container having the above and below partitioned chambers is used as the crushing container of the planetary mill. The number of crushing containers is 1 or 2 or more, and they are mounted on the planetary mill at equal intervals. When the number of crushing containers is one, an equal weight figurine is attached at the diagonal position to balance the crushing containers.

The object to be crushed is placed in one or more chambers in which the crushing container is divided into two or more chambers. That is, in the present invention, the object to be crushed is usually left empty at a lowermost stage or a chamber at the lowermost stage and its vicinity as a dedicated chamber for recovering pulverized products, and is placed at an arbitrary upper position 1 or 2. The above-mentioned room, usually the uppermost room, is prepared, but it is not limited to this and all rooms can be prepared. In this case, the particle size composition of the pulverized material charged in each room may be the same or different, but the powder having the target particle size is present in the lowermost stage or the lowermost stage and the chambers in the vicinity thereof. Alternatively, a powder having a particle size slightly larger than the target particle size is charged together with the grinding medium, and the amount of the grinding medium is
It is also possible to produce a powder having a target particle size with a regular shape by adjusting the shape or size and performing chamfering with or without grinding.

In each room except the dedicated room for collecting crushing containers,
Usually, a grinding medium such as a steel ball is put in. The shape of the grinding medium is not limited to the spherical shape, and may be, for example, a cylindrical shape.
The particle size distribution of the crushed product can be adjusted by the type and size of the crushing medium, and the target particle size can be adjusted by opening the mesh screen. Two or more mesh screens used to form three or more rooms have fine mesh openings from the top to the bottom, and use mesh screens with meshes of the desired particle size at any location. It is preferable to set. In the present invention, since it is optimal to form the lowermost stage or the vicinity thereof as a dedicated collection chamber, the mesh screen opening for that purpose has the target particle size.

Separation of the crushed product utilizes natural fall due to the reduction or stop of the rotation speed associated with the reduction or stop of the revolution speed. Therefore, the shape itself of each room of the crush container is not specially devised. Although not necessary, it is preferable that at least the inner surface of the bottom of the chamber in which the grinding medium is charged is provided with a tapered surface or a curved surface. In addition, since basically the same crushing as batch crushing is performed during crushing, conditions such as the capacity of each room, the type of crushing medium, the amount of crushing medium, the amount of crushed material, and the rotation speed of the crushing container are generally recommended. It is possible to use the conditions as they are. For example, “Powder Engineering” Vol 25-5 p297-302 1
988, "Powder Engineering" Vol 25-9 p603-608.
The conditions are described in 1988.

The number of revolutions of the pulverization container and its change, the pulverization time and the time for changing the number of revolutions, which are necessary to separate the pulverized product having a particle size not larger than the target particle size, are determined by the kind of the object to be pulverized and the target particle It depends on the diameter. These conditions can be determined in advance by experiments.

For example, the target particle size is 150 to 200 μm.
When the alumina powder of No. 1 is manufactured using a planetary mill having a revolution diameter of 30 cm and a rotation speed of 3 times the revolution speed, the revolution speed is 100 to 700 rpm, and the revolution time of one revolution is 1
~ 10 seconds. Under these conditions, if you want to obtain a sharper particle size distribution, shorten the revolution time once.
In order to obtain a powder with a more uniform shape, the revolution speed is reduced. Further, when the target particle size is smaller than the above or when a substance harder than alumina, such as a cubic boron nitride sintered body is pulverized, the rotation time is about 2 to 5 times and the rotation number is Increase by about 20 to 50%.

In the present invention, when the target particle size is large, the separation in the crushing container is sufficiently performed by either dry or wet crushing method. If the target particle size is small,
Since the separation may be insufficient due to clogging of the mesh screen, it is desirable to use a dispersion medium such as water in that case.

The crushing method of the present invention is suitable for the production of powder in which the demand for relatively coarse particles is relatively large and the demand amount greatly differs depending on the particle size. Typical examples thereof are silicon carbide, alumina and boron carbide. , Cubic boron nitride, diamond and other abrasives and abrasives. The preferable range of the target particle size by the pulverizing method of the present invention is 50 μm or more, especially 1
It is at least 00 μm.

[0025]

In the present invention, during crushing, the object to be crushed existing on the side wall is crushed by the crushing medium by the centrifugal force as in the conventional batch crushing. In the present invention, since the crushing time is short, there is little opportunity for one particle to come into contact with the crushing medium, and the change in the particle size distribution of the entire object to be crushed due to crushing is only slightly shifted to the direction of smaller particle size, which does not result in over-milling. A milled product can be produced. If the rotation speed of the crushing container is reduced in such a state, the centrifugal force will decrease and the crushing medium and the object to be crushed will drop downward. It has the function of scraping and dispersing the crushed material. For this reason,
The pulverized product in a dispersed state can be easily separated into a lower chamber such as a dedicated collection chamber through a mesh screen, and a pulverized product having a target particle size or a particle size in the vicinity thereof can be efficiently obtained. it can.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 In order to produce alumina powder having a target particle size of 150 to 200 μm, a pulverizing container having a capacity of 500 ml (inner diameter 75 m
A mesh screen made of wire mesh having a mesh size of 205 μm was horizontally installed at almost the center of a (m. In the upper chamber (capacity 250 ml), 3 chrome steel balls with a diameter of 25.5 mm were used as grinding media, and an alumina abrasive "JIS R6" as the material to be ground.
001 # 18 "100g was put in, and the lower room was vacant.

This is a commercially available planetary mill (revolution diameter 30c
m, the number of revolutions of which is 3 times the number of revolutions) and the revolution axis and the rotation axis of the crushing container are both installed in the vertical direction, and after attaching a container of equal weight to that diagonal position, The operation of rotating at a revolution speed of 540 rpm for 5 seconds and then stopping was repeated. The time (grinding time) until the crushed material disappeared in the upper room by this repeated operation was measured. Table 1 shows the results.

Further, the pulverized product recovered in the lower exclusive chamber is treated with dilute hydrochloric acid to remove and dry the mixed iron powder and the like, and 5 g thereof is arbitrarily taken out to have a mesh diameter of 75 mm and openings 200 and 150. Vibration sieving was performed for 60 minutes using a 100, 50 μm electroformed sieve, and the sieve residue (weight) was measured to determine the particle size distribution. Table 1 shows the results.

Example 2 Example 1 except that a curved surface having a radius of curvature of 13 mm was provided on the inner surface of the bottom of the upper room partitioned by a mesh screen.
Grinding was carried out in the same manner as in.

Example 3 A cubic boron nitride sintered body was roughly crushed with a stamp mill, and then classified using a JIS standard mesh sieve to obtain "# 18".
100 g of a ground product having a particle size corresponding to the abrasive grains was separated.
Pulverization was performed in the same manner as in Example 1 except that this was used as the object to be pulverized.

Comparative Example 1 The crushing container has a capacity of 250 which is not divided by a mesh screen.
Pulverization was performed in the same manner as in Example 1 except that a milliliter pulverization container (cylindrical container having an inner diameter of 75 mm) was used. After crushing once (that is, revolution speed 540 rpm
After rotating for 5 seconds and then stopping), all the pulverized products were taken out from the pulverization container, and the pulverized products under 205 μm were separated using a 205 μm sieve. The 205 μm sieve residue was returned to the crushing container and crushed again under the above conditions. This operation was repeated until the 205 μm sieving residue remained. 20
The total time required for this crushing including the time for separating by a 5 μm sieve and the particle size distribution of the entire crushed product were measured. The results are shown in Table 1.

Comparative Example 2 Comparative Example 1 except that continuous pulverization was carried out until the 205 μm sieving residue was exhausted without pulverizing and separating each time.
Grinding was carried out in the same manner as in. The time required for this pulverization and the particle size distribution of the pulverized product were measured. The results are shown in Table 1.

[0034]

[Table 1]

The following can be seen from Table 1. In the conventional batch grinding (Comparative Example 2), the powder yield of the target particle size is 15%, but in Example 1 and Comparative Example 1, a high yield of 34% is achieved. However, in Comparative Example 1, the time required for grinding is extremely long. An effect equivalent to that of Example 1 is exerted also for pulverization of an extremely hard cubic boron nitride sintered body (Example 3). By providing a curved surface on the inner surface of the bottom of the chamber into which the grinding medium is charged, the separation is promoted, a yield equal to or higher than that in Example 1 is obtained, and the grinding time is shortened (Example 2).

[0036]

According to the present invention, a pulverized product having a sharp particle size distribution can be easily produced in a short time. Until now, since there were few pulverization methods for efficiently recovering only powder having a relatively large particle size, the present invention particularly contributes to the field of hard abrasive grains such as cubic boron nitride sintered bodies and abrasives. There is a lot to do.

Claims (4)

[Claims] 1. A pulverization method using a planetary mill in which an object to be pulverized is charged into a pulverization container in which both the revolution axis and the rotation axis are in the vertical direction, and the pulverization object is rotated to perform pulverization. A crushing method characterized by partitioning into three or more chambers, charging the object to be crushed and a crushing medium into one or more chambers, and crushing while changing the rotation speed of the crushing container. 2. A crushing container for a planetary mill, characterized in that the container is divided into two or more upper and lower chambers by a mesh screen. 3. The crushing method according to claim 1, wherein a tapered surface or a curved surface is provided at least on the inner surface of the bottom of the chamber in which the crushing medium is charged. 4. The crushing container for a planetary mill according to claim 2, wherein at least the inner surface of the bottom of the chamber in which the crushing medium is charged is provided with a tapered surface or a curved surface.