JPH11326177A - Method for judging shape of powder particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the degree of estrangement from the spherical shape of a powder particle by using a sieve with a sieve mesh with essentially the same diameter as the particle diameter of a sample grain being obtained by the light-scattering method for sifting the sample grain and by obtaining the ratio below or above the sieve. SOLUTION: For one of two parts of a sample powder divided in advance so that the grain size is not maldistributed, the distribution of the grain size is measured by the light scattering method using a laser diffraction particle meter according to, for example, the wet method and a particle diameter X of a point where the ratio of the amount of integrated particle from the smaller or larger particle diameter reaches n% (for example, 50%) is obtained. Then, a sieve with the sieve mesh with essentially the same diameter as the particle diameter X is used for sifting the other of the divided sample grains, thus obtaining the ratio below or above the sieve. Then, based on the ratio below or above the sieve, the degree of estrangement is judged from the spherical shape of the sample grain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the shape of a powder particle, which can easily determine the degree of deviation of the powder particle from a sphere.

[0002]

2. Description of the Related Art Coal charged in a coke oven, graphite used for battery materials, various fillers used for molding plastics and manufacturing paints, inks and cosmetics, powders used for sintering operations, In the field of handling powder such as dust, it is often necessary to grasp the shape of powder particles.

Conventionally, methods for measuring the shape of powder particles include:
The direct observation method using an optical microscope or an electron microscope is widely used. The light scattering method (irradiates the liquid or gas phase in which particles are dispersed with light, collects the reflected light from the particles, Measurement method) has also been adopted.

[0004] "General Research on Waste Treatment and Recycling Technology," a public document of the Planning and Coordination Bureau of the Environment Agency, "Techniques for detoxification and utilization technology of asbestos waste" in 63 (1991), 1990. The research entitled “Research” describes trends in asbestos waste countermeasures and technical countermeasures regarding problems. Among them, methods for analyzing asbestos from the topography include optical microscopy (collection). The number of fibers in each sample is counted using a phase contrast microscope, and asbestos is distinguished from other fibrous substances by using a biological microscope together. After smoothing and depositing carbon or gold, there is a method of counting the number of fibers by SEM) and a real-time method (a method using a fibrous aerosol monitor). Bets have been described.

"Pollution and Countermeasures, Vol. 25, No. 10 (1989)
The paper entitled "Measurement of Asbestos in the Atmosphere Using a Fibrous Aerosol Monitor" on pages 990 to 995 also provides a detailed description of a method using a fibrous aerosol monitor in comparison with optical microscopy.

Japanese Patent Publication No. 7-52151 discloses an automatic powder particle shape measuring apparatus utilizing the principle of capturing a powder particle image from two directions forming an angle of 6 to 10 degrees with respect to the powder particles. Have been. In the description of the prior art in this publication, an average particle size is conventionally given as a measurement value representing the powder particle shape, and a method for measuring the average particle size is an optical method such as a laser diffraction type particle size distribution measurement. It is described that there are a method for measuring directly from a two-dimensional image obtained using a scanning electron microscope or an optical microscope, a method for calculating from a specific surface area obtained by a specific surface area meter, and the like.

Japanese Patent Application Laid-Open No. 7-301593 discloses that a liquid phase or a gaseous phase in which particles are dispersed is irradiated with incident light, and the liquid phase or the gas phase is located at a small angle of 0 to 5 degrees ahead of the incident light. Or collect the scattered light transmitted through the gas phase, compare the intensity of the scattered light with the vertical component and the horizontal component, determine the spherical or non-spherical shape of the particle based on the intensity ratio, and calculate the particle size based on the sum of the intensity A method and apparatus for simultaneous measurement and determination of particle diameter and particle shape by forward small angle scattering are shown. In the description of the prior art in this publication, reference is also made to conventional microscopic observation methods and light scattering methods, and the problems of the conventional methods are also described.

[0008]

In the conventional microscopic observation method, the prior processing for preparing briquettes and the like is complicated, it takes time from sample acquisition to measurement, and it is difficult to take an average sample. In addition, there are various problems such as the fact that the measurement operation requires skill and that the determination is easily scattered by the measurer or the judge.

A conventional method for measuring the particle size distribution by the light scattering method is an improved method which can be evaluated even when the powder is non-spherical, especially the method disclosed in Japanese Patent Application Laid-Open No. 7-301593. There is a shape determination method. This method is spherical-
It is possible to determine non-spherical shapes in real time, which is effective for process control.However, since calibration curve data is required in advance, it is necessary to prepare a calibration curve for analytical tests that often handle unknown samples. Has to be considered.

Under such a background, the present invention provides a light scattering method without taking complicated means such as microscopic observation, and without taking the complicated means of creating a calibration curve as seen in the light scattering method. The object of the present invention is to provide a method for judging the shape of powder particles that can easily judge the degree of deviation of the powder particles from the sphere by utilizing the principles of both the sieving method and the sieving method. It is.

[0011]

Means for Solving the Problems The method for determining the shape of powder particles according to the present invention is as follows. Or, to determine the particle diameter X of the sample powder when the integrated particle amount from the larger one is n%. ・ Sieving the sample powder using a sieve having a sieve having substantially the same diameter as the particle diameter X By determining the ratio under the sieve or on the sieve, ・ Determining the degree of deviation from the spherical shape of the sample powder based on the ratio under the sieve or on the sieve at that time .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the present invention, the sample powder is divided into two parts so that the particle size distribution is not deviated, and a part thereof is used for measuring the particle size distribution by a light scattering method (for example, using a laser diffraction particle meter by a wet method). The other part is prepared for particle size distribution measurement using a sieve.

Next, the particle size distribution of the sample powder is measured by a light scattering method using a part of the powder (for example, in a laser diffraction particle meter by the wet method, about 0.5 g of the sample is placed in an appropriate dispersion medium). By measuring the particle size distribution by dispersing the sample powder), the particle size X at the integrated particle amount n% from the smaller or larger particle size of the sample powder is determined (for example, the median size is adopted, The particle diameter X at the point where the percentage of the integrated particle amount from the smaller particle diameter becomes 50% is determined).

FIG. 1 shows a structural diagram of a measuring section of a laser diffraction particle meter. In FIG. 1, (1) is a laser diode, (2)
Is a condenser lens, (3) is a spatial filter, (4) is a collimating lens, (5) is a flow cell, (6) is a Fourier transform lens, (7) is a concentric sensor, and (8) is a circulation tank.

Next, by using a sieve having a sieve having substantially the same diameter as the particle diameter X obtained above (for example, using a standard sieve having a sieve closest to the particle diameter X), By sieving the separated sample powder, the ratio under the sieve or on the sieve is determined.

After the ratio under the sieve or on the sieve is determined as described above, the degree of deviation of the sample powder from the sphere is determined based on the ratio at the time of the under sieve or on the sieve.

For the determination of the degree of divergence, for example, the degree of divergence defined by the equation: divergence (%) = 100 × (U−n) / n can be used. U in the formula
Is, for example,% under the sieve when sieved using a sieve having a sieve having substantially the same diameter as the particle diameter X obtained by the light scattering method. Further, n in the formula is, for example,% of the integrated particle amount from the smaller particle diameter of the particle diameter X obtained by the light scattering method.

The powder particles to which the shape determination method of the present invention can be applied include carbonaceous particles (coal, coke, graphite, etc.), earth and sand,
Any material can be used as long as it can be sieved, including iron ore, metal, plastics powder, inorganic or organic fillers and pigments, ceramics, asbestos, ceramic raw materials, dust, and the like.

<Function> In the present invention, a combination of particle size distribution measurement by a light scattering method and sieving of a sample powder by a sieve is performed.

FIG. 2 shows a principle diagram of a part for evaluating the particle diameter due to the difference in the method of measuring the particle size distribution.
1 is a principle diagram of a light scattering method, and (b) is a principle diagram of a sieving method using a sieve.

In the measurement of the particle size distribution by the light scattering method shown in FIG. 2A, the maximum diameter of the flaky or elongated particles is easily measured as the particle diameter of the particles. On the other hand, FIG.
The measurement of the particle size distribution by the screening method of (b) is based on the principle that the minimum diameter of the particle is measured as the particle diameter of the particle because the particle is sieved based on whether or not the particle passes through a certain sieve. I have.

Therefore, if the shape of the powder particles is close to spherical, the difference between the particle size obtained from the result measured by the light scattering method and the particle size when sieved using a sieve is small, The more the shape of the particles becomes flaky or elongated, the greater the difference between the particle sizes measured by the two methods.

Therefore, in the present invention, the particle size X of the sample powder when the integrated particle amount from the smaller or larger particle size is n% is determined by measuring the particle size distribution of the sample powder by the light scattering method. By sieving the sample powder using a sieve having a sieve having substantially the same diameter as the particle size X, the ratio under the sieve or the ratio on the sieve is determined, and the ratio under the sieve or the ratio on the sieve is n %, The powder particles are close to spherical, and it can be determined that the powder particles are farther from the spherical shape as the ratio under the sieve or the ratio on the sieve is farther from n%.

According to the method of the present invention based on the above principle, it is possible to judge in a short time, there is no individual difference in measurement and judgment, it is possible to make a quantitative judgment, and it is possible to grasp the average shape of a sample powder. , There are advantages.

[0026]

The present invention will be further described with reference to the following examples.

Examples 1 and 2 Sample A was made of mineral biotite particles, and sample B was made of synthetic phenol resin particles. One of the samples was divided in advance so that the particle size distribution was not biased. The particle size distribution was measured by a light scattering method using a laser diffraction particle meter based on the wet method. The results are shown in FIG. The horizontal axis is the particle diameter (μm) by the light scattering method, and the vertical axis is the percentage of the integrated particle amount from the smaller particle diameter at this time.

As shown in FIG. 3, the integrated particle amount 5 of the sample A measured by the light scattering method, for example, from the smaller particle diameter.
0% diameter (hereinafter abbreviated as median diameter) is 0.333mm (333μm)
It was found that the median diameter of sample B was 0.213 mm (213 μm).

Next, as a sieve having a sieve closest to the median diameter,
A 0.355 mm (355 μm) JIS standard test sieve for sample A and a 0.212 mm (212 μm) JIS standard sieve for sample B were selected. Then, using the selected sieve, the other half of the sample, which had been divided in advance so that the particle size distribution was not biased, was sieved. Met. From this result, it can be seen that the degree of deviation of the sample A from the sphere is remarkable, and that the sample B is quite close to the sphere.

In order to directly visually confirm the particle shapes of Sample A and Sample B, a briquette was prepared and observed under a microscope (magnification: 175 times, Sample A was long and thin, Sample B was rounded). ), The ratio of short axis diameter / long axis diameter was calculated by measuring the long axis diameter and short axis diameter of the powder particles. When the shape of the powder particles is spherical, the ratio of the minor axis diameter / major axis diameter is 1, and when the shape of the powder particles is flaky or elongated, it is smaller than 1. The ratio of the short axis diameter to the long axis diameter calculated based on the results of the above microscopic observation was 0.423 for sample A and 0.793 for sample B.

Examples 3 to 5 Coal particles were used as Samples C, D and E, and each of the samples which had been divided in advance so that the particle size distribution was not biased, was subjected to laser diffraction particles by the wet method. The particle size distribution was measured by a light scattering method using a meter. The median diameter by the light scattering method was 0.235 mm for sample C and 0.235 mm for sample D.
06 mm, and sample E was 0.199 mm.

The sieves closest to these median diameters were 0.250 mm for sample C and 0.250 mm for sample D and sample E.
A test sieve of JIS standard having a sieve of 0.212 mm was selected, and the other sample which had been divided in advance so that the particle size distribution was not biased was sieved. The sieving percentage of sample C is 61.7%, the sieving percentage of sample D
Was 53.9%, and the under-sieving% of Sample E was 53.0%.

When the degree of divergence from the sphere is defined by the equation: degree of divergence (%) = 100 × (U−n) / n, U of sample C, D and E (% under sieving by the sieving method) is Since 61.7, 53.9, and 53.0, and n (medium diameter by light scattering method) is 50, the divergence of sample C is 23.4%, the divergence of sample D is 7.8%, and the divergence of sample E is 6.0%. Becomes

On the other hand, Samples C, D and E were molded into briquettes, and the ratio of the short axis diameter to the long axis diameter of the powder particles was measured under a microscope (magnification: 50 to 100 times). ,
Values of 0.486, 0.596, and 0.680 were obtained in the order of D and E.

FIG. 4 shows the results obtained by plotting the above results by plotting the ratio of the minor axis diameter / major axis diameter by microscopic observation on the horizontal axis and the above-mentioned divergence on the vertical axis. FIG.
Thus, the smaller the ratio of the minor axis diameter / major axis diameter, that is, the more the sphere becomes flaky or elongated, the greater the degree of divergence determined according to the method of the present invention, and hence the method of the present invention. It can be seen that is an index that simply indicates the degree of deviation of the powder particles from the sphere.

[0036]

In the present invention, the particle size X of the sample powder is calculated by measuring the particle size distribution by the light scattering method, and the integrated particle amount from the smaller or larger particle size is n%. The sample powder is sieved using a sieve having a sieve having substantially the same diameter as the diameter X to determine the ratio under the sieve or on the sieve. The degree of deviation from the spherical shape of the body is determined.

Therefore, according to the method of the present invention, the following excellent effects can be obtained. The determination can be performed in a short time without requiring complicated preprocessing and means. For example, the time required from sample acquisition to particle shape discrimination can be reduced to about 1/12 that of a microscope observation method. -Since measurement and judgment do not require skill and there is no individual difference, an objective judgment can be made. Further, a progress record leading to the determination can be left. -The degree of deviation from the spherical shape can be quantitatively determined. Unlike the microscopy method for producing briquettes and the like, in the present invention, the sample powder used for the measurement can be collected and reused. In the microscope observation method, it is not known whether the particles entering the visual field have an average shape, but in the present invention, the average shape of the entire sample can be known.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a measurement unit of a laser diffraction particle meter.

FIGS. 2A and 2B are diagrams showing the principle of the evaluation part of the particle diameter according to the difference in the method of measuring the particle size distribution, wherein FIG. 2A shows the principle of the light scattering method, and FIG. 2B shows the principle of the screening method using a sieve. It is.

FIG. 3 is a diagram showing the results of measuring the particle size distribution of a sample A and a sample B by a light scattering method using a laser diffraction particle meter by a wet method.

FIG. 4 is a graph showing the relationship between the ratio of minor axis diameter / major axis diameter and the degree of deviation for samples C, D, and E.

[Explanation of symbols]

 (1)… laser diode, (2)… condenser lens, (3)… spatial filter, (4)… collimating lens, (5)… flow cell, (6)… Fourier transform lens, (7)… concentric sensor, (8)… Circulation tank

Claims (1)

[Claims] A particle size distribution of a sample powder is measured by a light scattering method using a part of the sample powder. Determining the diameter X, sieving the sample powder using a sieve having a sieve having substantially the same diameter as the particle diameter X to determine the ratio under or above the sieve, Alternatively, the degree of deviation of the sample powder from the spherical shape is determined based on the ratio on the sieve, and the shape of the powder particles is determined.