JP2003207438A - Particle diameter distribution measuring apparatus and method of defoaming for particle diameter distribution measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle diameter distribution measuring apparatus and a method of defoaming for the particle diameter distribution measuring apparatus capable of surely removing air bubbles accumulated in a circulatory system, and conducting accurate measurements in a laser diffraction/scattering particle diameter distribution measuring apparatus. <P>SOLUTION: The particle diameter distribution measuring apparatus 1 obtains a particle diameter distribution of a measuring object particles S by applying light L to a measuring object sample S' comprising measuring object particles S dispersed in a dispersion medium Lq, detecting an intensity distribution of scattered light Ls from the measuring object particles S, and calculating based on the intensity distribution. The apparatus 1 includes a function P for removing air bubbles mixed in the dispersion medium Lq by processes S1 to S3 including at least ultrasonic defoaming processes S2, S3 facilitating coalescence and elimination of the air bubbles contained in the dispersion medium Lq by using an ultrasonic oscillator 9 for resolving the aggregation of the measuring object particles S. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle size distribution measuring device for removing bubbles mixed in a sample liquid and a defoaming method for the particle size distribution measuring device.

[0002]

2. Description of the Related Art Conventionally, particles to be measured are put into a dispersion medium filled in a circulation system to generate a sample to be measured, and then light is irradiated while the sample to be measured is circulated to scatter from the sample to be measured. There is a particle size distribution measuring device that obtains the particle size distribution of particles to be measured by detecting the intensity distribution of light and performing calculation based on the detected intensity distribution of scattered light.

[0003]

However, in the above-described conventional apparatus, when the dispersion medium is injected into the circulation system and the dispersion medium is supplied to the flow cell by the circulation pump, bubbles are mixed in the dispersion medium, Bubbles were sometimes introduced into the flow cell. In such a case, unstable air bubbles cause light scattering and refraction, which may cause an error in the measurement value or make the measurement impossible. The term "air bubbles" in the present specification includes all the air masses that are substantially the same as or smaller than the particles to be measured and are sufficiently larger than the particles to be measured.

In particular, in order to prevent the agglomeration of particles to be measured having a small particle diameter, when a surface tension of the dispersion medium is reduced by adding a surfactant such as sodium hexametaphosphate to the dispersion medium, bubbles are less likely to break, When the circulation pump was operated to fill the circulation medium with the dispersion medium, a large amount of bubbles were mixed in the dispersion medium. Then, the bubbles that were included when performing a blank measurement that does not include the particles to be measured, the bubbles are bonded to each other at the time of the measurement that includes the particles to be measured have a large diameter, or are discharged to the outside of the flow cell, The state could change.

That is, when bubbles remain in the circulation system, the blank value increases due to scattered light from the bubbles during blank measurement,
When measuring the sample, these bubbles will collapse naturally,
By changing the scattered light intensity generated from the bubbles,
Accurate scattered light from the particles could not be obtained, and an accurate particle size distribution could not be obtained.

Therefore, the operator waits for a sufficient time until the bubbles in the circulation system disappear, or the operation of the circulation pump so that the bubbles in the circulation system are removed after the dispersion medium is injected into the circulation system. There was a case where the bubble removing operation was intermittently performed by, for example, stopping after operating for a certain time. However, since this bubble removal operation is performed depending on the experience of the operator, the reproducibility is poor, and the experience of the operator causes a large difference in the measurement results.

The present invention has been made in consideration of such circumstances, and in a laser diffraction / scattering type particle size distribution measuring apparatus, bubbles accumulated in a circulation system are surely removed,
An object of the present invention is to provide a particle size distribution measuring device and a defoaming method of the particle size distribution measuring device that can perform accurate measurement.

[0008]

The present invention has means for solving the above-mentioned problems as follows. That is, the particle size distribution measuring device of the first invention irradiates a measurement target sample in which the measurement target particles are dispersed in a dispersion medium with light, detects the intensity distribution of scattered light from the measurement target sample, and A particle size distribution measuring device for calculating the particle size distribution of particles to be measured by calculating based on the combination of bubbles contained in the dispersion medium using an ultrasonic oscillator for separating agglomeration of particles to be measured, and It is characterized in that it has a function of removing bubbles mixed in the dispersion medium by a defoaming treatment including at least an ultrasonic defoaming treatment that promotes discharge.

Therefore, since the ultrasonic defoaming treatment can effectively combine bubbles and eliminate them, even if the dispersion medium contains a surfactant, the bubbles contained in the dispersion medium can be removed in a short time. It can be discharged, and the particle size distribution measurement can be easily performed without the influence of bubbles.

Further, the particle size distribution measuring device of the second invention irradiates light on a sample to be measured in which particles to be measured are dispersed in a dispersion medium, and detects the intensity distribution of scattered light from the sample to be measured. , A particle size distribution measuring device for calculating the particle size distribution of particles to be measured by calculating based on this, and measuring scattered light intensity after performing a defoaming process for removing bubbles contained in a dispersion medium However, it has a function of judging the necessity of repeating the defoaming process based on the intensity of the scattered light.

Therefore, the number of repetitions of the defoaming process is judged based on the scattered light intensity used for measuring the particle size distribution, so that the particle size distribution measurement is adversely affected as compared with the case where the operator visually judges. It is possible to more accurately determine whether or not the bubbles are of a certain level. In addition, since the judgment criteria are always the same, regardless of the operator's experience, defoaming treatment can be reliably performed, and anyone can perform measurement with good reproducibility using any dispersion medium.

The scattered light intensity when the dispersion medium containing no bubbles is irradiated with light is stored in advance as a comparison value, and the scattered light intensity when the dispersion medium used for actual measurement is irradiated with the light is compared with the comparison value. Then, if it is necessary to repeat the defoaming process, and if the defoaming process is repeated until the scattered light intensity of the dispersion medium used for actual measurement falls within the allowable range for the comparison value, the inclusion of bubbles It is possible to make an accurate judgment for automatically repeating the defoaming process until is within a predetermined allowable range.

The defoaming treatment promotes the bonding of bubbles contained in the dispersion medium by using an ultrasonic oscillator for irradiating ultrasonic waves for separating the multiple bonds of the aggregated particles to be measured, and removes them. When the ultrasonic defoaming treatment is included, bubbles can be effectively bound and eliminated by this ultrasonic defoaming treatment, and since this ultrasonic defoaming treatment is repeated to the necessary minimum, a surfactant is mixed. Even with this dispersion medium, the bubbles contained in this dispersion medium can be discharged in a shorter time, and the particle size distribution measurement without the influence of bubbles can be performed quickly and easily.

The defoaming method of the particle size distribution measuring device of the third invention irradiates light on a sample to be measured in which particles to be measured are dispersed in a dispersion medium, and detects the intensity distribution of scattered light from the sample to be measured. Then, by calculating based on this, a defoaming method in a particle size distribution measuring apparatus for determining the particle size distribution of the particles to be measured, before performing a blank measurement with a dispersion medium,
A pump for circulating the sample to be measured is intermittently operated to discharge large bubbles, and an ultrasonic oscillator for separating agglomeration of particles to be measured is used to combine and discharge small bubbles contained in the dispersion medium. It is characterized in that a series of defoaming treatments are carried out to promote the binding and discharge of hidden bubbles contained in the dispersion medium by using the ultrasonic oscillator while rotating the pump.

The series of defoaming treatments can rapidly remove bubbles of various sizes contained in the dispersion medium. That is, the flow rate of the dispersion medium flowing in the circulation system is changed by operating the pump intermittently (to operate for a time required to complete one round of the circulation system or for a time longer than this, and to stop). Thus, large air bubbles and air lumps can be quickly discharged. Also, by combining small bubbles contained in the dispersion medium using an ultrasonic oscillator,
It is possible to combine small bubbles that could not be discharged by the pump discharge to grow into relatively large bubbles that are easy to discharge. Further, by encouraging the bonding of hidden bubbles contained in the dispersion medium by using the ultrasonic oscillator while rotating the pump, it is possible to easily discharge the bubbles that have become large due to the bonding.

In the defoaming method of the particle size distribution measuring apparatus of the fourth invention, the measurement target sample in which the measurement target particles are dispersed in a dispersion medium is irradiated with light, and the intensity distribution of scattered light from the measurement target sample is detected. Then, by calculating based on this, a defoaming method in a particle size distribution measuring apparatus for determining the particle size distribution of the particles to be measured, before performing a blank measurement with a dispersion medium,
After performing the defoaming treatment for removing bubbles contained in the dispersion medium, the scattered light intensity is measured, and the defoaming treatment is performed by determining whether or not the defoaming treatment is required to be repeated based on the scattered light intensity. The feature is that the process is repeated.

In the particle size distribution measuring device and the defoaming method of the particle size distribution measuring device, all the defoaming is performed by a software sequence, so that no new hardware configuration is required and the manufacturing cost can be suppressed. You can It is desirable that the speed of the pump for circulating the dispersion medium can be adjusted freely.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the particle size distribution measuring device 1 of the present invention will be described in detail below with reference to the drawings.
In FIG. 1, 2 is a measuring unit of the particle size distribution measuring apparatus 1, and 3 is an arithmetic processing unit which is connected to the measuring unit 2 and outputs a measurement result.

Reference numeral 4 denotes a liquid reservoir for mixing and stirring the particles S to be measured in a dispersion medium such as pure water, 5 denotes a centrifugal pump formed at the lower end of the liquid reservoir 4, and 6 denotes the centrifugal pump 5. A motor for rotating, 7 is a circulation passage for connecting the base end and the end to the discharge portion side and the suction portion side of the pump 5 at the lower end portion of the liquid reservoir 4, and 8 is provided in this circulation passage 7. A flow cell, 9 is an ultrasonic oscillator provided in the circulation passage 8, and 10 is an electromagnetic valve for discharging a liquid (a sample to be measured or the like) in the circulation passage 7. Further, each of the units 4 to 10 constitutes a circulation system 11 that circulates the measurement target sample S ′.

On the other hand, 12 is a He-Ne laser light source, and 13
Is a beam expander for expanding the diameter of the laser light from the light source 12, and 14 is a multi-channel detector for detecting scattered light by the sample S ′ to be measured in the flow cell 8. Therefore, the respective units 8 and 12 to 14 form an optical system 15.

A CPU 16 communicates with the arithmetic processing unit 3 to receive a command from the arithmetic processing unit 3 to control the measuring unit 2 as a whole and to output a measurement result to the arithmetic processing unit 3. , 17 are storage units for recording a simple program P that can be executed by the CPU 16.

The arithmetic processing unit 3 outputs the appropriate command to the measuring unit 2 to analyze the measurement result obtained and obtains the particle size distribution of the particles S to be measured, and the particle size distribution is displayed on the display unit 3a. Output. In addition, a command for appropriately controlling the circulation system 11 is output according to an instruction from the operator,
The obtained measurement results, particle size distribution, etc. are output to a printer or the like not shown in the figure, or recorded on an arbitrary recording medium.

The liquid reservoir 4 has an inlet for a dispersion medium Lq to be filled in the circulation system 11, particles S to be measured, and a dispersion promoter such as a surfactant Tw, and is measured by mixing these. It is configured to generate the target sample S ′. In the case of this example, a centrifugal pump 5 is formed at the lower end of the liquid reservoir 4, and the pump 5 is rotated by a motor 6 so that the sample S ′ to be measured is filled in the circulation flow path 7 and Circulate. The motor 6 has a variable rotation speed in 15 steps, for example. However, the present invention does not limit the configurations of the liquid reservoir 4, the pump 5, and the motor 6.

The cell 8 is made of a light-transmissive material such as glass so that the laser light L from the He-Ne laser light source 12 can pass through the sample S ′ to be measured in the cell 8 while circulating the sample S ′ to be measured. It is a configured flow cell.

The ultrasonic oscillator 9 is attached at an appropriate position in the circulation channel 7, and by irradiating the sample S ′ to be measured with ultrasonic waves, the particles S to be measured dispersed in the sample S ′ to be measured. Although it is intended to prevent agglomeration, in the present invention, the ultrasonic oscillator 9 is used to promote the bonding of bubbles contained in the dispersion medium Lq, and the bubbles are discharged (in the present invention, the bubbles are discharged to the dispersion medium Lq. It means the discharge of mixed bubbles and air layers, and is referred to as defoaming hereinafter).

The laser light source 12 is not limited to the He-Ne laser, but may be another light source such as a tungsten lamp or may use two or more light sources. In particular, since a tungsten lamp can measure even a smaller particle size, it is possible to measure a wide particle size range by using both a tungsten lamp and a He-Ne laser.

The detector 14 has a ring detector 14a formed in front of the traveling direction of the laser light L and a plurality of detectors 14b formed rearward from the side in the traveling direction of the laser light L. is doing. Therefore, the laser light L
The light quantity of the scattered light Ls can be detected for each angle from the front to the rear with respect to the traveling direction of. (In the following description, the detected value of the light amount for each scattering angle is represented as the output for each channel of the detector 14)

The CPU 16 is preferably a one-chip microcomputer that achieves energy saving, and rotates the motor 6 of the pump 5 and the ultrasonic oscillator 9
Is operated, and various programs P for inputting signals from each detector 14 are read from the storage unit 17 and executed.

When the particle size distribution of the particles S to be measured is measured using the particle size distribution measuring apparatus 1, first, at least the dispersion medium Lq such as water is circulated in the circulation system 1 prior to the blank measurement.
1 and filled with scattered light Ls in the absence of bubbles
Is detected for each channel, and the scattered light intensity of the light at this time is stored in advance as a comparison value.

The dispersion medium Lq used at this time is preferably the same as the dispersion medium Lq in which the particles S to be measured are dispersed, and when the surfactant Tw is used to measure the particle size distribution of the particles S to be measured, It is desirable that the surfactant Tw is also mixed in the dispersion medium Lq when storing it as a comparison value. This comparison value is measured and stored by the sample S to be measured.
The measurement is performed prior to the measurement of the particle size distribution, and is performed at the time of manufacturing the particle size distribution measuring device 1, and is preferably performed periodically.

When the particle size distribution of the particles S to be measured is measured, the dispersion medium Lq and the surfactant Tw are charged into the liquid reservoir 4 and the pump 5 is driven to disperse the surfactant Tw in the circulation system. The medium Lq is filled. At this time, although illustration is omitted, in the software for the particle size distribution measuring device on the arithmetic processing unit 3 side, a “foam removal” button is displayed at an appropriate position on the measurement screen for measurement on the display unit 3a. is doing. Then, when the operator operates this bubble removal button, the bubble removal command is output from the arithmetic processing unit 3 to the measurement unit 2.

A basic program P for controlling the measuring unit 2 as in this example is stored in the storage unit 17 on the measuring unit 2 side, and is executed by the CPU 16 on the measuring unit 2 side. Since it is configured as described above, the load on the arithmetic processing unit 3 side can be reduced, and the arithmetic processing unit 3 can concentrate on the analysis of scattered light intensity. However, the present invention limits this point. is not. That is, the CPU 16 on the measuring unit 2 side may control only a more basic operation, and the arithmetic processing unit 3 may execute the program P to instruct the measuring unit 2 to issue a command one by one.

In any case, since the program P executed by the particle size distribution measuring apparatus 1 is instructed to perform a series of defoaming procedures, the CPU 16 causes the pump 5 for moving the circulation system 11 and the inside of the circulation system 11 to operate. ON / OFF and the strength adjustment of the ultrasonic oscillator 9 provided in the can be performed based on a predetermined sequence.

FIG. 2 is a diagram showing an example of a series of defoaming processes instructed by the program P. The operation of the program P will be described below with reference to FIG. 2 together with FIG.

First, in S1, the rotation of the pump 5 is turned on and off intermittently.
This is a step of performing processing for turning off / on. More specifically, after the pump 5 is driven for a predetermined time such that the dispersion medium Lq can make one round in the circulation flow path 7 or longer, for example, for about 1 second, the upper portion is opened like the liquid reservoir 4. The pump 5 is stopped for about 1 second as a predetermined period of time during which bubbles located at the lower part of the existing portion are discharged by buoyancy.

Therefore, due to the intermittent operation of the pump 5, the large air accumulated in the intricate portion of the circulation passage 7 is degassed from the portion such as the liquid reservoir 4 whose upper end is open. Here, by intermittently turning ON / OFF the pump 5, it is possible to change the flow velocity of the dispersion medium Lq flowing in the circulation flow path 7, and thereby the circulation flow path 7
Even if there are some irregularities on the inner peripheral surface of the, it is possible to effectively deaerate a relatively large air pool.

Step S2 is a step in which the pump 5 is temporarily stopped and ultrasonic waves are emitted using the ultrasonic oscillator 9. That is, by irradiating the dispersion medium Lq that does not contain the measurement target particles S with the ultrasonic oscillator 9 that was originally provided to eliminate the aggregation of the measurement target particles S, the dispersion medium L
Bonding of bubbles mixed in q can be promoted. Therefore, the relatively large bubbles rise in a short time due to buoyancy and are discharged from the liquid reservoir 4 and the like.

Further, the irradiation of ultrasonic waves can be carried out at once for all the parts in the circulation flow path 7, and the bubbles located in the relatively complicated parts in the circulation flow path 7 are also attracted. Thus, the discharge can be promoted.

Step S3 is a step in which the pump 5 is rotated at a low speed, and ultrasonic waves are emitted while the dispersion medium Lq is slowly circulated. More specifically, the rotation speed of the pump 5 is set to 1
Expressed in 5 stages, while continuing to irradiate ultrasonic waves while rotating at a rotation speed of 2 to 3 steps (about 10 to 20% of the normal rotation speed), fine bubbles are combined by the action of ultrasonic waves and compared. Bubbles that have grown significantly larger can be easily discharged.

Here, by irradiating ultrasonic waves while rotating the pump 5 at a low speed, the dispersion medium Lq slowly circulates in the circulation system 11, while the bubbles that have grown greatly are opened at the upper ends of the liquid reservoir 4 and the like. You can degas from the part where it is. The rotational speed of the pump 5 is determined by the shape of the open portion of the liquid reservoir 4 and the like, the viscosity of the dispersion medium Lq, and the step S1.
It is determined by the buoyancy of bubbles, which is determined by the size of bubbles that cannot be discharged by the defoaming process.

Step S4 is executed at the time when the series of defoaming processing shown in steps S1 to S3 is completed, and the step of irradiating the cell 8 with the laser beam L and examining the scattered light information thereof. Is.

Step S5 is a step for confirming whether or not sufficient defoaming has been achieved by the series of defoaming processes described above. That is, in the scattered light detector 14, the scattered light intensity at the time when the series of defoaming processes S1 to S3 is completed is performed as the comparison value in a specific channel that is easily affected by the scattered light Ls due to the bubbles. When the intensity of scattered light stored in advance (intensity of scattered light in the absence of bubbles) is higher than a predetermined percentage, such as 10%, the series of defoaming processes S1 to S3 is further continued.

That is, the particle size distribution measuring device 1 of the present invention
Is the defoaming process for removing the bubbles contained in the dispersion medium Lq, and then the scattered light intensity is measured. Based on this scattered light intensity, the effects of the defoaming processes S1 to S3 and the dispersion medium Lq are included. Since it has the function of checking the amount of bubbles and judging the necessity of repetition, the defoaming process S is always performed on a fixed basis.
1 to S3 can be performed. That is, the reproducibility is improved.

Further, the pump 5 in step S1
The intermittent operation interval, the ultrasonic wave irradiation time in step S2, the ultrasonic wave irradiation time in step S3 while rotating the pump 5 at a low speed, and the rotation speed of the pump 5 are determined by the shape of the circulation system 11 and the dispersion medium Lq. The time required for the series of defoaming treatments S1 to S3 can be minimized by optimally setting it in accordance with the viscosity and the degree of difficulty in breaking bubbles due to the surfactant Tw (reduction rate of surface tension). That is, an effective defoaming process can be performed in the necessary minimum time.

In addition, although not described in detail in FIG. 2, the scattered light intensity measured after repeating the series of defoaming processes S1 to S3 a predetermined number of times or more is a predetermined value or more as compared with the comparison value. If it is high, the scattering is not due to bubbles but to the dirt of the cell, and therefore an error signal is output by an alarm or a display on the display unit 3a to notify the operator of the abnormality.

In this example, in order to determine whether or not the bubble removal is sufficient in step S5, the intensity of scattered light in a specific channel which is apt to receive the light scattered by bubbles is compared with a previously stored comparison value. However, the present invention is not limited to this point. That is, in step S4, a total value of scattered light intensities in a plurality of channels is obtained, and the total value is compared with the total value in the same channel of the comparison value to determine whether or not bubble removal is performed to an appropriate degree. You may do it.

Further, the scattered light intensity before the series of defoaming processes S1 to S3 may be compared with the scattered light intensity after the series of defoaming processes S1 to S3. In this case, in step S5, the amount of bubbles reduced by the defoaming processes S1 to S3 can be confirmed, and further defoaming process S1.
It can be used as a criterion for determining whether to execute 1 to S3, and it can also be determined whether the defoaming processes S1 to S3 are effective.

In any case, the particle size distribution measuring apparatus 1 of the present invention performs the series of defoaming treatment S1 before performing the blank measurement.
By performing ~ S3 a minimum number of times, the bubbles can be removed from the circulation system, and if bubbles remain in the circulation system, the blank value increases due to the scattered light from the bubbles during the blank measurement, and the blank value increases during the sample measurement. It is possible to prevent the situation in which the intensity of scattered light from the bubble decreases due to the automatic collapse of the bubble. That is, even if the dispersion medium Lq is apt to generate bubbles, particularly when the surfactant Tw is used, the accurate scattered light Ls from the particles can be measured very easily.

The influence of bubbles which is a problem in the particle size distribution measurement is preferably judged based on the measured value of the scattered light Ls used in the calculation of the particle size distribution, and the influence of the bubbles appears on the scattered light intensity. It is possible to confirm that there is no effect of air bubbles to the extent suitable for particle size distribution measurement.

[0050]

As described above, according to the particle size distribution measuring apparatus and the defoaming method of the particle size distribution measuring apparatus of the present invention,
The bubbles contained in the dispersion medium can be effectively defoamed, the generation of scattered light by the bubbles can be eliminated, and the scattered light by the particles can be accurately measured. In particular, by determining the influence of bubbles left in the circulation system with software and repeating the defoaming process, it is possible to perform highly accurate particle size distribution measurement regardless of who uses any dispersion medium.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a preferred example of a particle size distribution measuring device of the present invention.

FIG. 2 is a diagram showing an example of a defoaming method of the particle size distribution measuring device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Particle size distribution measuring apparatus, 9 ... Ultrasonic oscillator, Lq ... Dispersion medium, S ... Particles to be measured, S '... Sample to be measured, S1 to S
3 ... Defoaming treatment, S2, S3 ... Ultrasonic defoaming treatment, P (S
4, S5) ... A function for determining the necessity of repetition, L ... Laser light, Ls ... Scattered light.

Claims (6)

[Claims] 1. A measurement is performed by irradiating a sample to be measured, in which particles to be measured are dispersed in a dispersion medium, with light, detecting the intensity distribution of scattered light from the sample to be measured, and calculating based on this. A particle size distribution measuring device for obtaining a particle size distribution of target particles, which uses an ultrasonic oscillator for separating agglomeration of particles to be measured, which is an ultrasonic defoaming process for promoting bonding and discharge of bubbles contained in a dispersion medium. A particle size distribution measuring device having a function of removing bubbles mixed in a dispersion medium by a defoaming treatment containing at least. 2. A measurement is performed by irradiating a measurement target sample, which is obtained by dispersing particles to be measured in a dispersion medium, with light, detecting the intensity distribution of scattered light from the measurement target sample, and calculating based on this. A particle size distribution measuring device for obtaining a particle size distribution of target particles, wherein scattered light intensity is measured after performing a defoaming process for removing bubbles contained in a dispersion medium, and the desorption is performed based on the scattered light intensity. A particle size distribution measuring device having a function of judging the necessity of repeating foam treatment. 3. The scattered light intensity when a dispersion medium not containing bubbles is irradiated with light is stored in advance as a comparison value, and the scattered light intensity when the dispersion medium used for actual measurement is irradiated with the light and the comparison value. The defoaming treatment is repeated until the scattered light intensity of the dispersion medium to be actually measured falls within an allowable range with respect to the comparison value by comparing the above values to determine the necessity of repeating the defoaming treatment. Particle size distribution measuring device. 4. An ultrasonic wave in which the defoaming treatment promotes the bonding of bubbles contained in a dispersion medium by using an ultrasonic oscillator for irradiating ultrasonic waves for separating agglomeration of particles to be measured, thereby removing the bubbles. The particle size distribution measuring device according to claim 2, which comprises a defoaming treatment. 5. The measurement is carried out by irradiating a sample to be measured in which particles to be measured are dispersed in a dispersion medium with light, detecting the intensity distribution of scattered light from the sample to be measured, and calculating based on this. A defoaming method in a particle size distribution measuring apparatus for obtaining a particle size distribution of target particles, in which a large air bubble is generated by intermittently operating a pump for circulating a sample to be measured before performing a blank measurement with a dispersion medium. Discharge, promote the binding and discharge of small bubbles contained in the dispersion medium using an ultrasonic oscillator for separating the agglomeration of the particles to be measured, contained in the dispersion medium using the ultrasonic oscillator while rotating the pump. A defoaming method for a particle size distribution measuring apparatus, which comprises performing a series of defoaming treatments for promoting the binding and discharge of hidden bubbles. 6. The measurement is carried out by irradiating a sample to be measured, in which particles to be measured are dispersed in a dispersion medium, with light, detecting the intensity distribution of scattered light from the sample to be measured, and calculating based on this. A defoaming method in a particle size distribution measuring device for obtaining a particle size distribution of target particles, before performing a blank measurement with a dispersion medium, after performing a defoaming process to remove bubbles contained in the dispersion medium, scattered light A defoaming method for a particle size distribution measuring apparatus, characterized in that the defoaming treatment is repeated by measuring the intensity and determining whether or not the defoaming treatment needs to be repeated based on the scattered light intensity.