JP2002320921A - Classification method for fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a classification method for fine particles wherein a cylindrical screen classifier is used and there is not only less destruction of the screen but also it is high in classification yield of powdery bodies marked is adherence thus can also reduce a cost by shortening a working time. SOLUTION: In the fine particle classification method wherein the cylindrical screen classifier is used, this invention relates to a classification method wherein the diameter of a tapping ball used is >=15 mm and less than one-fifth the diameter of the cylindrical screen. In addition, the classification method limits the mass of the tapping ball being in the range of more than 0.2 and less than 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for classifying fine particles using a cylindrical screen classifier. More specifically, the present invention relates to a cylindrical screen classifier suitable for classifying fine particles which easily adhere to a screen due to static electricity and a method of classifying fine particles using a tapping ball.

[0002]

2. Description of the Related Art When classifying powders that do not like metal contamination such as high-purity silica used for electronic materials and semiconductors, for example, a cylindrical screen classifier manufactured by Turbo Kogyo Co., Ltd. using a synthetic fiber screen (trade name) A turbo screener is used. However, when classifying such a powder, there is a problem that the static electricity generated during the classification causes the powder to adhere to the screen and cause clogging, thereby lowering the classification yield.

In order to prevent clogging of the screen due to powder adhesion, Japanese Patent Application Laid-Open No. 3-131372 discloses that several to several tens of tapping balls (described as elastic balls) of several millimeters are charged. It has been proposed to install a blocking disc to prevent discharge from the outlet. Further, Japanese Patent Application Laid-Open No. 9-1074 proposes a method of bending the tip of a rotary wing and repelling the tapping ball in order to prevent the tapping ball from being biased near the outlet.

[0004]

However, Japanese Patent Application Laid-Open No. Hei 3-1
The use of a tapping ball of several millimeters described in Japanese Patent No. 31372 has a problem that the diameter of the tapping ball is so small that the tapping ball may be caught in the gap between the rotary wing and the screen and damage the screen.
Even in the method described in No. 4 in which the tip of the rotating blade is bent to prevent the tapping ball from being biased, the problem of the tapping ball getting stuck in the gap between the screen and the rotating blade is not improved. Also, if a tapping ball having a large diameter is used, the weight of the tapping ball will damage the screen and damage the screen. Therefore, if the rotational speed of the rotor of the cylindrical screen classifier was reduced to reduce the damage, a sufficient throughput could not be obtained. The present invention aims to solve these problems.

[0005]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above problems, and as a result, in a classifier using a cylindrical screen, the diameter of a tapping ball to be used is set to a specific range. The book found that tapping balls could be prevented from biting into the gap between the screen and the rotor, and that by setting the ball mass to a specific range, the screen could be prevented from being damaged and becoming easily broken due to fatigue damage. Completed the invention.

That is, the first invention of the present invention is characterized in that in a classifier using a cylindrical screen, the diameter of the tapping ball used is in the range of 15 mm or more and 1/5 or less of the diameter of the cylindrical screen. This is a method for classifying fine particles.

The second invention of the present invention is the method for classifying fine particles according to the first invention, wherein the mass of the tapping ball is in the range of 0.2 g or more and 6 g or less.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. The classifier using a cylindrical screen used in the present invention refers to a method in which the raw material powder 2 supplied from one end of the cylindrical screen 1 to the inside is pressed against the inner surface of the cylindrical screen by a rotating blade 3 rotating at high speed by a motor 9. Reference numeral 5 denotes an apparatus for performing classification by passing through the cylindrical screen 1 and discharging coarse particles 6 from an outlet 7. For example, a cylindrical screen classifier manufactured by Turbo Kogyo Co., Ltd. (trade name: Turbo Screener TS250 × 20
0) is used.

The aperture of the cylindrical screen is not particularly limited, but may be 10 μm to 500 μm. The material of the cylindrical screen is not particularly limited, but is preferably made of synthetic fiber, more preferably nylon, polypropylene,
It is made of polyethylene, polyester, and polyimide. Further, it is more preferable to use a synthetic fiber which has been subjected to antistatic processing.

As shown in FIG. 2, a tapping ball 4a,
One to five, preferably one to two, 4b are inserted inside the cylindrical screen. As the material of the tapping ball, a synthetic resin is used, and polypropylene, urethane and cellulose are preferred. Polypropylene and urethane balls are drilled through holes,
Further, a hollowed-out one can be used. Alternatively, it may be simply a hole. At this time, if the cut edge is sharp, it is preferable to use it after making it smooth with a file or the like. Ping-pong balls are inexpensive and preferable as cellulose balls.

The diameter of the tapping ball is 15 mm or more,
The diameter is preferably not more than 1/5 of the diameter of the cylindrical screen, and more preferably not less than 20 mm, and not more than 1 /
6 or less. If the diameter is less than 15 mm, the tapping ball may bite into the gap between the screen and the rotating blades.

The mass of the tapping ball is 0.2 g or more,
6 g or less, more preferably 0.2 g or more,
3 g or less. If the mass of the tapping ball is larger than 6 g, the screen will be damaged and damaged.
If it is less than 0.2 g, a sufficient tapping effect cannot be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to examples and comparative examples with reference to FIGS. As a classifier, a cylindrical screen classifier (Turbo Screener TS250 × 200) manufactured by Turbo Kogyo Co., Ltd. was used. The diameter of the cylindrical screen 1 used is 250 mm. The cylindrical screen 1 used polyester openings of 33 μm and 50 μm. The tapping ball was obtained by processing a commercially available synthetic resin ball. The raw material powder 2 used for classification has an average particle size of 1
0 μm silica. Silica is put into a hopper of a classifier, introduced into the classifier by a vibrating feeder, and classified. The classification yield was calculated by the following method. Classification yield (% by mass) = (1 pass fine particle mass (kg) +2
Pass fine particle mass (kg) + 3-pass fine particle mass (kg))
/ Mass of raw material silica powder (kg) × 100 Here, the first 1 of the raw material silica powder classified by the classifier
The first pass is called one pass, and after dividing into fine particles 5 that have passed through the cylindrical screen and coarse particles 6 that have not passed and that have been discharged from the outlet 7, the coarse particles 6 are again processed with a classifier in two passes. The treatment of the obtained coarse particles 6 with a classifier repeatedly is called three passes.

Example 1 A polypropylene ball having a diameter of 19.1 mm was drilled into three 6 mm holes on an XYZ axis to have a mass of 1.5 mm.
The g was used as a tapping ball. When the cut edge was sharp, it was used after making it smooth with a file. The number of rotations of the classifier was 800. The screen is aperture 3
3 μm was used. 100 kg of silica was classified to obtain a classification yield of 91% by mass. At this time, without the tapping ball, the classification yield was 37% by mass.

Example 2 A ping-pong ball made of cellulose having a diameter of 38 mm was used as a tapping ball. The mass is 2.5 g. The aperture of the screen is 33 μm. Classifier rotation speed is 1000
Rotation. Silica was classified into 150 kg and the classification yield was 97.
% By weight. At this time, without the tapping ball, the classification yield was 40% by mass.

Comparative Example 1 A urethane ball having a diameter of 7.9 mm and a mass of 0.3 g was used as a tapping ball. Classifier rotation speed is 100
Zero rotation was performed. The screen used had an opening of 33 μm.
The screen was torn when the silica was subjected to the 15 kg classification treatment during the 100 kg classification. As a result of inspecting the classifier, the screen was torn at the position where the tapping ball was bitten. In addition, dents were found on the rotor blades.

Comparative Example 2 A polypropylene ball having a diameter of 25.4 mm and a mass of 7.3 g was used as a tapping ball. The number of revolutions of the classifier was 700. The screen used had openings of 50 μm. 50 kg of silica was classified to obtain a classification yield of 83% by mass. After classification, the classifier was inspected to confirm a large number of scratches on the screen. It was in a state where it could not be used for classification.

Table 1 summarizes the results of Examples and Comparative Examples.

[Table 1]

[0019]

According to the method of the present invention, in the method of classifying fine particles using a cylindrical screen classifier, the breakage of the screen is reduced, and the classification yield of powder with remarkable adhesion can be improved.
Costs were reduced by shortening the work time. Also, reduced damage to the screen has made it possible to use it for a long time. This method uses powders that are easy to adhere with raw materials such as cosmetics, paints, fillers and special ceramics,
It is preferably used for classification.

[0020]

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical screen 2 Raw material powder 3 Rotor blade 4a, 4b Tapping ball 5 Fine particle 6 Coarse particle 7 Outlet 8 Casing 9 Motor

Claims (2)

[Claims] 1. A method for classifying fine particles using a cylindrical screen, wherein the diameter of a tapping ball used is 15
A method for sphering fine particles, wherein the diameter is in the range of not less than 1 mm and not more than 1/5 of the diameter of the cylindrical screen. 2. The method according to claim 1, wherein the mass of the tapping ball is in the range of 0.2 g or more and 6 g or less.