JPH0329461B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a classification method for classifying microparticles having a particle size of several μm to several tens of μm into the particle size (particle size) by a wet method. This article relates to a classification method using ultrasonic vibration in a wet method.

(Prior art and problems to be solved) There are two methods for classifying microparticles such as plastic spheres such as polymer beads and ceramic raw material powder: one is to classify the microparticles by their particle size itself, and the other is to classify the microparticles by their weight based on water or water. can be broadly divided into indirect classification methods that utilize properties such as resistance to air or kinetic energy. The former method is a classification method using a so-called sieve, and the latter method is a centrifugal separation method, a static sedimentation method using gravity, a classification method based on differences in particle flight distance, etc. However, since this latter method is an indirect classification method, it is inevitable that particulate matter other than the target product will be mixed in. Classification methods using a sieve include a dry method performed in the atmosphere and a wet method performed by suspending particles in a dispersion medium.
Classification using a wet sieve is the simplest method, and if the raw material particles are relatively large, it is easiest to use this method, but this method tends to cause fine particles to aggregate, resulting in classification due to clogging. There is a decrease in efficiency. The wet method has improved this point. In other words, the method involves dispersing fine particles in a dispersion liquid to eliminate surface charge on the particles to prevent particle agglomeration and sieve out the fine particles. However, for such fine particles, a sieve with a fine pore size is used. Therefore, even with this method, clogging occurs and the classification efficiency decreases over time. Therefore, a method has been proposed for classifying the dispersion by applying vibrations to the dispersion and causing the dispersion to pulsate (see Japanese Patent Laid-Open No. 131173/1983). This method is less likely to cause clogging and can be classified in a continuous manner, but it has the disadvantage that the classification efficiency is low because pulsation causes particles that have passed through the sieve to return to their original state.

The present inventor conducted various studies to improve these shortcomings and provide a new classification method. As a result, in the conventional method, the fine particles to be classified pass from above to below the mesh of the sieve, resulting in particles clogging the mesh. In order to improve this point, we used a wet method to classify particles accurately and efficiently by using ultrasonic vibration to pass the fine particles from below to above the mesh of the sieve. The purpose of the present invention is to provide a method for classifying microparticles of several micrometers to several tens of micrometers with high accuracy and high efficiency using a wet method using ultrasonic vibration.

(Means for Solving the Problems) That is, the present invention supplies a dispersion liquid in which microparticles are dispersed in a liquid to a dispersion tank equipped with a tube with a perforated plate attached to one end, and disperses the dispersion liquid. Ultrasonic vibration is applied to the dispersion liquid from the periphery of the tank, and microparticles having a particle diameter smaller than the pore diameter of the perforated plate are transferred from below the perforated plate through the holes into the tubular body. This is a method for classifying particles.

Therefore, the perforated plate in the present invention has a large number of fine holes, and a sieve having fine mesh is usually used. The pore diameter is appropriately selected, for example, in the range of several microns to several tens of microns, depending on the size of the particles to be classified. Further, the frequency of the vibrator used in this invention is usually about 15 to 50 kHz, but it can be changed as appropriate depending on the size of the particles to be classified.

Therefore, the present invention can be applied to various particles such as dyes, cosmetics, drugs, glass particles, ceramic particles, cement, etc., and various liquids including water can be used as the dispersion medium. The concentration of the dispersion liquid in which the particles are dispersed is not particularly limited, but is usually up to 20% by weight; if the concentration is too high, the particles tend to aggregate. When the concentration is high, it is preferable to use a dispersant, and the dispersant is a surfactant or the like that neutralizes the surface charge of the particles.

Next, the present invention will be specifically explained. 1st
The figure shows an apparatus used in the method of the present invention, which consists of three tanks: a stirring tank 1, a classification tank 2, and a sampling tank 3. Inside the classification tank, there is installed a tube body 5 in which a perforated plate 4 is attached to one end and a conduit 8 connected to a collection tank is inserted in the other end, and this classification tank is equipped with a medium 11 for transmitting sound waves. It is placed inside a filled ultrasonic cleaner 10. The stirring tank and the classification tank are connected by a conduit 7 via a liquid supply pump 6. A stirrer is provided in the stirring tank.
In operation, first, a dispersion medium is placed in a stirring tank, and raw material particles to be classified are added thereto and stirred to form a dispersion liquid. The dispersion liquid is sent to a classification tank in the ultrasonic cleaner by a liquid supply pump. The dispersion enters the interior of the tube through the holes in the perforated plate. At the same time, when an ultrasonic cleaner generates ultrasonic waves, the ultrasonic waves are transmitted to the dispersion liquid in the dispersion tank through the water that transmits the ultrasonic waves. Fine particles having a certain particle size migrate into the inside of the tube through the holes of the perforated plate. The fine particles that have migrated to the inside of the tube are sent together with the dispersion liquid to a collection tank by a suction pump, and particles of the desired particle size are collected and can be classified.

Next, one of the characteristics of the present invention is that the dispersion liquid moves upward from the bottom of the sieve, and this point will be explained using an experimental example.

Experimental Example 1 What is shown in FIG. 2 is the particle size distribution of glass microspheres before the classification experiment. In the classification experiment, this group of glass microspheres (hereinafter referred to as the original sample) is used after being dispersed in water. The perforated plate used had a mesh of 20 μm.

Experimental procedure Put 5g of the original sample into a beaker and mix with water to make a total of 2. This was dispersed by applying ultrasonic waves, and then uniformly dispersed using a stirrer to form a dispersion liquid, which was divided into two parts each. Place one side in a stirring tank and continue stirring. Next, turn on the ultrasonic cleaner to apply ultrasonic vibration to the water and classification tank. Activate the feed pump and suction pump. Dispersion liquid 1
After treating the water, water 1 was placed in the stirring tank, and the pump and ultrasonic cleaner were continued to operate until all of the water in water 1 disappeared.

The samples collected in the collection tank and those remaining in the classification tank were measured using a light transmission particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation).

Experimental example 2 (comparison) The same equipment was used, but the stirring tank and collection tank were replaced in order to inject the dispersion above the sieve, and the flow directions of pumps 6 and 9 were reversed from the previous experiment. The device was changed. Therefore, the dispersion liquid is injected from the stirring tank through the conduit 8 by the pump 9 from above the tube body, and the fine particles that have passed through the perforations of the perforated plate are guided by the pump 6 through the conduit 7 to the collection tank. Then, the remaining 1 of the dispersion used in the previous experiment
was placed in a stirring tank, the ultrasonic cleaner was activated, water 1 was added to the stirring tank, and the above operation was continued until all the water disappeared. The measurement was performed using a light transmission particle size analyzer (SA-CP3). FIG. 3 shows the particle size distribution in the sampling tank collected in Experimental Example 1, and FIG. 4 shows the particle size distribution of the particles that remained in the classification tank without being collected. Similarly, the particle size distribution in the sampling tank collected in Experimental Example 2 is shown in FIG. 5, and the particle size distribution of the particles remaining in the classification tank without being collected is shown in FIG. Comparing the amounts collected in these experiments is as follows.

Comparison of the amount collected in Experimental Examples 1 and 2 Experimental Example 1...Collected material (in the collection tank) 1.058g Experimental Example 2...〃 0.834g Considering these results, the particle size distribution of the collected materials in Experimental Examples 1 and 2 is The peak of 19 to 20 μm was observed to be larger in Experimental Example 1, and in SEM observation, Experimental Example 1 had a large proportion of particles around 20 μm. This is due to the use of a 20 μm mesh. In other words, this shows that passing the perforated plate from below rather than from above causes less clogging and allows more efficient classification. And it's more efficient than pulsation.

(Effects) As described above, the present invention applies ultrasonic vibrations to the sample-containing dispersion liquid to be classified and causes the dispersion liquid to pass from below to above the perforated plate, thereby allowing the dispersion liquid to fall from above. This has the effect of reducing the clogging of the eyelets and allowing the collection of fine particles of the desired particle size with high accuracy over a long period of time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the classification device used in the present invention,
Figure 2 is a particle size distribution diagram of sample particles used in the present invention before classification, Figures 3 and 4 are particle size distribution diagrams classified by Experimental Example 1, which is the classification method of the present invention, and Figure 5 The figure and FIG. 6 are particle size distribution diagrams classified according to Experimental Example 2, which is a comparative example. 1... Stirring tank, 2... Classification tank, 3... Collection tank, 4... Perforated plate, 5... Pipe body, 6... Liquid supply pump, 7, 8... Conduit, 9... Suction pump, 10... Ultrasonic cleaner, 11
...medium.

Claims (1)

[Claims] 1. A dispersion liquid in which microparticles are dispersed in a liquid is supplied to a classification tank equipped with a tube with a perforated plate attached to one end, and ultrasonic vibrations are applied to the dispersion liquid from around the classification tank to create a porous A method for classifying microparticles using ultrasonic waves, characterized in that microparticles having a particle size smaller than the pore diameter of the plate are moved from below the perforated plate through the holes into the tube body.