JP3552399B2 - Laser diffraction particle size distribution analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser diffraction type particle size distribution measuring device used for measuring the particle size of a sample having a relatively small concentration and a relatively high concentration.
[0002]
[Prior art]
In a laser diffraction type particle size distribution measuring device, particles suspended in a liquid are usually circulated through a laser beam irradiation position, or dried powder is dispersed by compressed air and blown into the laser beam, Measurement is performed. In the case of a small amount of sample, particles suspended in a liquid are placed in a glass box-shaped cell and fixed at the laser beam irradiation position.
[0003]
In the case of circulating particles suspended in liquid, a pump, pipes for liquid flow path, etc. are required, which complicates the configuration and causes sample particles to remain after measurement, causing errors in the next measurement or washing. Is troublesome.
[0004]
On the other hand, the method of dispersing particles with compressed air also requires a compressed air source, a dust collector that collects the dispersed particles, and the like. Not suitable for toxic substances. A box cell is simple to construct with a small amount of sample, but must be suspended in a liquid and requires dilution for laser beam transmission.
[0005]
In order to solve these drawbacks, a method has been used in which a sample is placed in an open cell, and a laser light source is disposed below the cell to measure the particle size distribution.
[0006]
Conventionally, in this type of laser diffraction type particle size distribution measurement, as shown in FIG. 4, a sample cell 101 containing a sample (sample) S is placed on an installation table 102 provided with a laser beam passage hole 102a, and Laser light is emitted from the installed laser light source 103, and is collimated by a collimator 104 into a parallel light beam having a predetermined cross-sectional area. After irradiating the diffracted / scattered light from above and condensing it with a condenser lens 106, the diffracted / scattered light is detected by a forward diffracted / scattered light sensor 107 such as a ring detector, and the particle size distribution of the sample S is measured.
[0007]
[Problems to be solved by the invention]
By the way, the above-described apparatus has a simple structure, and can easily wash and collect a measurement sample. However, when measuring the particle size distribution of a high-concentration sample such as a paste or a slurry, the occurrence of multiple scattered light is reduced. Therefore, it is necessary to make the thickness of the sample extremely thin with respect to the optical axis of the laser beam.
[0008]
However, in the above prior art, it is difficult to easily reduce the thickness of the sample layer because an open cell having an appropriate depth is used. The thickness was partially different, and the measurement data varied.
[0009]
The present invention has been made in order to solve the above-mentioned problems, and can easily form a thin sample layer regardless of the type of a dry or liquid measurement sample. An object of the present invention is to provide a laser diffraction type particle size distribution measuring apparatus capable of extremely reducing the occurrence of scattering and reducing errors in measurement data due to non-uniform thickness of a sample layer.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a laser diffraction type particle size distribution measuring apparatus according to the present invention comprises a sample cell containing a sample, a means for irradiating the sample cell with laser light, and a sample particle group obtained by irradiating the laser light. A laser diffraction type particle size distribution measuring apparatus provided with means for measuring the intensity distribution of diffraction / scattered light, wherein the sample cell has a concave portion having a depth substantially equal to the size of the sample particles in a translucent flat plate. Is formed.
[0011]
The particle size distribution is measured by irradiating the sample with laser light and measuring the intensity distribution of the resulting diffraction / scattered light. However, since the sample is placed in a sample cell having a depth approximately equal to the size of the sample particle, The sample can be easily set, and even when measuring a high-concentration sample, the transmission of laser light is guaranteed regardless of the type of the dry or liquid sample, and the occurrence of multiple scattering is extremely reduced. So that accurate measurements can be made.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 shows a sample cell in a laser diffraction type particle size distribution measuring apparatus according to the present invention.
FIG. 1A is a plan view of a cell, and FIG. 1B is a side view of the cell.
[0014]
Reference numeral 1 denotes a cell formed of a light-transmitting substance such as a flat glass, and 2 denotes a circular depression 2 (recess) provided in the cell 1. The recess 2 does not penetrate the cell 1 and has a certain thickness (about 1 mm) on the bottom surface. Then, the bottom surface of the depression 2 is optically polished so as not to cause scattering or the like due to the passage of the laser beam. The size of the bottom surface of the depression 2 is formed larger than the cross-sectional area of the laser beam. By the way, cells of various depths are prepared, and these cells are selected at the time of measurement according to the type of sample. In this case, the size of the particle is predicted in advance, and the depth of the depression 2 is slightly larger than the maximum particle diameter of the sample.
[0015]
In this case, if the sample is a suspension, the cell may be set at the irradiation position of the laser beam after setting the sample. However, if the sample is a dry powder, the cell is recessed as shown in FIG. After putting the dry powder 4 into the plate 2, the surface of the cell 1 must be flattened by scraping the surface of the cell 1 with the plate 3, or the plate must be pressed against the recess 2 of the cell 1 to flatten the surface. is there. By doing so, the thickness of the sample layer can be made uniform in each part, and the occurrence of multiple scattering can be suppressed because the particle layer does not have multiple layers.
[0016]
The shape of the depression 2 does not have to be circular, but the circular shape has no corners on the side surface and is more convenient for cleaning cells before and after sample measurement.
[0017]
Next, a method of measuring the particle size distribution using the cell in which the sample is set as described above will be described using the apparatus shown in FIG.
[0018]
The sample cell 1 in which the sample (sample) is placed as described above is placed on the mounting table 102 provided with the laser light passage hole 102a, and the laser light is emitted from the laser light source 103 installed below, and the collimator 104 emits the laser light. After being converted into a parallel light beam having a predetermined sectional area, the sample 101 is irradiated at right angles to the sample 101 via a collimator 104 and a transparent cover 105 for protecting the laser light source 103, and diffracted / scattered light emitted from above is collected by a condenser lens 106. After the light emission, the light is detected by a forward diffraction / scattered light sensor 107 such as a ring detector, and the particle size distribution of the sample S is measured.
[0019]
At the time of this measurement, when the sample is a suspension, it is desirable that the installation table 102 be provided with a horizontal adjustment mechanism so that the liquid level in the cell is particularly horizontal.
[0020]
In the above-described embodiment, the shape of the dent of the cell is such that the bottom surface is completely flat. However, the shape of the dent (recess) 6 may be spherical as shown in FIG. In this case, if the radius of curvature of the concave portion is extremely large, the bottom surface can be regarded as flat, processing by polishing is easier than making the bottom surface completely flat, and the depth of the depression is equal to the size of the particle, It can be easily processed to a depth very close to that, that is, about 10 μm.
[0021]
Furthermore, since the bottom surface is spherical, there is no corner portion formed by the bottom surface and the side surface perpendicular to the bottom surface as when the bottom surface is flat, and the sample particles do not accumulate. It gets even easier.
[0022]
Also, a thin cover glass without optical distortion may be placed on the recess of the planar cell, and if a sealant is put between the cover glass and the cell, a laser light source, a collimator, a cell, a lens, The present invention can also be used for a horizontal laser diffraction type particle size distribution measuring device in which a sensor is placed horizontally.
[0023]
【The invention's effect】
As described above, according to the present invention, since the concave portion is provided in the cell and the depth of the concave portion is made substantially the same as the size of the particles of the measurement sample, the type of the dry or liquid measurement sample can be determined. It is possible to easily create a thin sample layer, and to minimize the occurrence of multiple scattering, even for a sample with a high concentration, and to reduce errors in measurement data due to uneven thickness of the sample layer. .
[Brief description of the drawings]
FIG. 1 is a view showing a cell of a laser diffraction type particle size distribution measuring apparatus of the present invention.
FIG. 2 is a diagram showing an example of a method for setting a dry powder in a cell.
FIG. 3 is a diagram showing an example in which a dent having a different shape is provided in a cell.
FIG. 4 is a view showing a vertical laser diffraction type particle size distribution measuring device.

Claims (1)

A laser diffraction particle size distribution comprising a sample cell for accommodating a sample, a means for irradiating the sample cell with laser light, and a means for measuring the intensity distribution of diffraction / scattered light by the sample particle group obtained by the laser light irradiation In a measuring apparatus, the sample cell is formed by forming a concave portion having a depth substantially equal to the size of a sample particle on a light-transmitting flat plate-shaped plate, wherein a laser diffraction type particle size distribution measuring apparatus is used.

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