JP2011179836A - Device and method for measuring grain size distribution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for measuring grain size distribution, capable of accurately performing measurement, even suspension, where particles are dispersed into a solvent with high concentration, as it is without any dilution. <P>SOLUTION: In the grain size distribution measuring device, the suspension where particles are dispersed into a solvent is sealed into a measurement cell, the measurement cell is rotated around a rotary axis for precipitating the particles by centrifugal force, a change in the amount of light transmission in the precipitation process is measured in the precipitation course, and particle size distribution is measured from the change in the amount of light transmission. The grain size distribution measuring device includes: a measurement unit, where an area of a sample storage unit of the measurement cell in a section vertical to the rotary axis is set to be a storage unit sectional area, the measurement cell is disposed at a side close to the rotary axis, and the storage unit area is nearly constant; and a tapered unit disposed at a side remote from the rotary axis, where the storage unit area increases as the distance from the rotary axis increases. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a centrifugal sedimentation type particle size distribution measuring apparatus and a measuring method for measuring a particle sedimentation process in a centrifugal field as a change in light transmittance with time, and obtaining a particle size distribution, and in particular, particles are dispersed in a solvent at a high concentration. The present invention relates to a measuring apparatus and a measuring method suitable for measuring the particle size distribution of a material.

  In the field of electronic information materials, many pastes and slurry-like materials in which solid powder is dispersed in a solvent are used, and the particle size distribution is based on the workability when manufacturing the product and the machine after the product is made. It is recognized as an important factor because it affects properties and the like. In particular, in recent years, a large number of materials in which particles are dispersed at a high concentration have been developed, and with the development of these materials, it is evaluated whether these materials can sufficiently perform their functions, or when stable dispersibility cannot be achieved, In order to clarify the factors, there is a growing demand for measuring and evaluating the particle size distribution more accurately and quickly.

  One of the particle size distribution measuring methods is a centrifugal sedimentation method. (For example, patent document 1). FIG. 4 schematically shows a conventional particle size distribution measuring apparatus, and FIG. 3 shows a sectional view of a conventional general measurement cell. A sample in which particles are dispersed in a solvent is sealed in a measurement cell 2, and the measurement cell is set on a disk-shaped rotary rotor 4 in a particle size distribution measuring apparatus with a lid 3 attached. When centrifugal force is applied, the particles in the sample enclosed in the measurement cell 2 settle in the centrifugal force direction according to Stokes' law expressed by the following formula (1). In equation (1), v is the sedimentation velocity, d is the particle diameter (diameter), η is the solvent viscosity, σ is the particle density, ρ is the solvent density, r is the radius of rotation, and ω is the angular velocity.

  As is clear from the above formula (1), particles having a larger particle diameter d settle faster. When a sample in which particles having various particle diameters are dispersed in a solvent is precipitated in a centrifugal field, each particle is precipitated at a speed corresponding to the particle diameter according to the equation (1). The state is measured as a change in light transmittance at a certain distance by the light source 6 and the detector 7 shown in FIG. 4, and the absorbance is continuously calculated from the Lambert-Beer law expressed by the following equation (2). The particle size of each particle can be determined.

In the above formula (2), I ₀ is the intensity of incident light, I _l is the intensity of transmitted light, ε is the molar extinction coefficient, c is the molar concentration, and l is the thickness of the solvent through which light passes.

The above is an example of the particle size distribution calculation method based on the centrifugal sedimentation method, and there are several other variations, but because the measurement itself was based on the principle of measuring the light transmittance, it depends on the performance of the detector. Naturally there is a limit to the particle concentration. For example, when the detector is a CCD sensor, the accuracy that can be measured as a change in the amount of transmitted light is 0.1% with respect to 100% transmittance (3.0 in terms of optical density OD value) in consideration of variations in measured values. Therefore, a low transmission light region with a measurement accuracy of 0.1% or less cannot be detected by a CCD sensor detector. Therefore, when a sample with a high particle concentration is measured, the concentration of particles decreases by centrifugation, and the transmittance change can be measured only after the amount of transmitted light reaches 0.1% or more. As a result, the sedimentation of particles at the initial stage of centrifugation is overlooked, and an accurate particle size distribution cannot be obtained. In order to avoid this, conventionally, it has been necessary to perform complicated operations before measurement, such as carefully adjusting the sample concentration or diluting the sample so as to be within the range of the detector performance. In addition, operations such as sample preparation and dilution may change the particle size distribution, such as the state of particle aggregation, and it is necessary to consider whether or not there is an influence on the interpretation of the data. was there.

  On the other hand, when the particle concentration in the lower part of the measurement cell gradually increases with the sedimentation of the particles, the sedimentation rate becomes slow due to factors that inhibit the sedimentation of the particles such as collision between particles and upward flow of solvent. This is because the higher the concentration, the greater the effect. If the measured data is calculated as it is, an error that cannot be ignored is obtained. Conventionally, the sedimentation velocity with respect to the particle concentration is measured, and a correction formula is obtained from the result. However, if the composition and particles of the material are different, they do not match completely, and it is necessary to obtain a correction formula for each type, which is very inefficient.

JP-A-62-76431

  In the present invention, in view of the problems as described above, a particle size distribution that can be accurately measured as it is without dilution even in a suspension in which particles are dispersed at a high concentration in a solvent. An object is to provide a measuring apparatus and a particle size distribution measuring method.

In order to achieve the above object, the present invention provides the following measuring apparatus and measuring method.
(1) A suspension in which particles are dispersed in a solvent is sealed in a measurement cell, and the particles are settled by centrifugal force by rotating the measurement cell around a rotation axis, and the amount of transmitted light in the sedimentation process is changed. A particle size distribution measuring apparatus for measuring and obtaining a particle size distribution from the change in transmitted light amount, wherein the area of the sample storage portion of the measurement cell in a cross section perpendicular to the rotation axis is a storage portion cross-sectional area, and the measurement cell is A measuring unit disposed on the side closer to the rotation axis and having a substantially constant storage area, and a taper portion disposed on the side far from the rotation axis and having a larger storage area as the distance from the rotation axis increases. A particle size distribution measuring apparatus that has the same.
(2) The particle size distribution measuring apparatus according to claim 1, wherein the thickness of the sample storage part of the measurement cell in the measurement part is 0.1 to 1.0 mm.
(3) A suspension in which particles are dispersed in a solvent is sealed in a measurement cell, and the measurement cell is rotated around a rotation axis so that the particles are sedimented by centrifugal force. A particle size distribution measurement method for measuring and obtaining a particle size distribution from the transmitted light amount change, wherein the area of the sample storage portion of the measurement cell in a cross section perpendicular to the rotation axis is a storage portion cross-sectional area, as the measurement cell, A measuring unit that is disposed on the side closer to the rotation axis and has a substantially constant storage area, and a taper portion that is disposed on the side far from the rotation axis and increases in storage area as the distance from the rotation axis increases. The particle size distribution measurement is characterized in that the measurement is started in a state where the particle concentration of the suspension in the tapered portion is lower than the particle concentration of the suspension in the measuring portion. Method.

  According to the present invention, a suspension having a concentration higher than the ability of a detector that could not be measured by a conventional particle size distribution measuring apparatus can be measured as it is without dilution, and further, a high concentration can be measured. Therefore, since the obstruction factor generated by particle sedimentation that becomes larger as the value becomes smaller can be reduced, accurate measurement becomes possible. As a result, it is possible to accurately measure the particle size distribution even with a high-concentration suspension that changes the dispersibility by dilution.

It is the figure which represented typically an example of the particle size distribution measuring apparatus of this invention. It is sectional drawing of the measurement cell used by this invention. It is sectional drawing of the conventional general measurement cell. It is the figure which represented the conventional particle size distribution measuring apparatus typically. 3 is a weight-based particle size distribution curve obtained by the measurement of Example 2. FIG. 3 is a weight-based particle size distribution curve obtained by the measurement of Comparative Example 2. FIG.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an example of a particle size distribution measuring apparatus of the present invention.

  In FIG. 1, a measurement cell 1 that encloses a suspension in which particles are dispersed in a solvent, a rotary rotor 4 that sets the measurement cell 1, and a motor that drives the rotary rotor 4 are provided. The measurement cell 1 can be made of glass or resin depending on the sample. One surface sandwiched by the measurement cell 1 includes a light source 6 attached at a fixed distance from the center of rotation, and a collimating lens 8 for making the light from the light source 6 parallel light, and the other opposing surface. Are provided with a condensing lens 9 for condensing transmitted parallel light and a detector 7 for receiving the condensed light. The detector 7 is preferably a photoelectric conversion element such as a CCD sensor. In order to obtain the particle size distribution from the change in the amount of transmitted light, the detector preferably has a high light receiving sensitivity and a low pixel resolution, and more preferably has a gradation of 1024 gradations or more.

  The output signal from the detector 7 is taken into the arithmetic processing device via the image taking board, and the particle size distribution is calculated by the calculation.

  FIG. 2 shows a sectional view of the measuring cell 1 which is a characteristic part of the present invention. The measuring cell 1 according to the present invention has a measuring unit 1a having a substantially constant cross-sectional area of the receiving unit disposed on the side close to the rotating shaft and a distance from the rotating shaft disposed on the side far from the rotating shaft. Accordingly, the taper portion 1b is formed so that the cross-sectional area of the accommodating portion increases. In the present invention, the sample storage portion refers to a portion surrounded by the inner surface of the measurement cell in which the suspension used as a sample is stored, and the storage section cross-sectional area refers to the measurement in a cross section perpendicular to the rotation axis. It refers to the cross-sectional area of the cell sample storage. The shape of the cross section perpendicular to the rotation axis of the housing portion and the taper portion may be any of a rectangle, a square, a shape obtained by rounding the vicinity of the apex of these shapes, an ellipse, a circle, etc. Preferably, the suspension used for the measurement has a constant width and thickness of the suspension, or a shape in which the vicinity of the top of the rectangle is rounded.

  When measuring a sample with a high particle concentration, the particle concentration on the side far from the rotation axis of the measurement cell 1 gradually increases due to sedimentation of the particles due to centrifugal force. The particles become difficult to settle due to the influence. Moreover, the tendency is more remarkable as the particle concentration is higher. Therefore, accurate measurement cannot be performed only by using a cell having a thin measuring portion 1a. As a means for solving the problem, a taper portion 1b is provided on the side farther from the rotation axis of the measurement cell 1, and the taper portion 1b whose sectional area increases as the distance from the rotation axis increases. There is no problem if the shape of the tapered portion is such that the cross-sectional area of the storage portion increases as the distance from the rotation axis increases, and the dimensions of either the width direction or the thickness direction of the sample storage portion are satisfactory. May be a shape in which one becomes larger, a shape in which one becomes smaller and the other becomes larger, or a shape in which both become larger. In addition, the thickness or width of the sample storage portion does not necessarily have a shape that increases linearly, but a shape that increases linearly as shown in FIG. 2 is preferable.

  In the present invention, the transmitted light amount change is measured by the measuring unit 1a, and is not measured by the taber unit 1b. By providing the tapered portion 1b, the physical gap between the particles that have settled is widened, the collision and contact between the particles are reduced, and even if an upward flow occurs due to particle sedimentation, the inside of the tapered portion 1b By vortexing, the influence on the measurement unit 1a of the measurement cell 1 becomes small, and accurate measurement can be performed.

  Moreover, it is preferable that the thickness of the measurement part 1a exists in the range of 0.1-1.0 mm. In the present invention, the thickness of the measurement cell or the measurement part refers to the length of the accommodating part in the direction in which the light used for measurement is transmitted. When measurement is performed, the thickness of the suspension part through which the light used for measurement is transmitted. Corresponds to the length.

  The conventional general measurement cell 2 shown in FIG. 3 has a particle size distribution using a suspension having a low particle concentration and an OD value of less than 3.0 as a sample because the thickness of the measurement part is 3 mm or more. Can be measured relatively accurately. However, when the particle size distribution is measured using a suspension having a high particle concentration and an OD value of 3.0 or more as a sample, the amount of transmitted light is small at the beginning of the measurement, which is below the resolution of the detector, and the particles settle. Since it cannot be measured as a change in the amount of transmitted light, sedimentation of relatively large particles at the beginning of measurement is overlooked. On the other hand, when the measurement cell used in the present invention as shown in FIG. 2 is used, even a sample having a high particle concentration has a small OD value and a large amount of transmitted light because the thickness of the measurement part is small. The sedimentation of particles can be measured as a change in the amount of transmitted light, and measurement without oversight is possible. However, if the thickness of the measuring portion 1a is too thin, the influence of contact between the particles and the inner wall of the cell and friction increases, which may cause a calculation error. Therefore, the thickness of the measuring portion 1a is 0. It is preferable that it is in the range of 1 to 1.0 mm.

  Next, the particle size distribution measuring method of the present invention will be described. In the particle size distribution measuring method of the present invention, when the measurement is performed by enclosing the suspension in the measurement cell 1 of the present invention described above, the particle concentration of the suspension in the tapered portion 1b is the suspension in the measuring portion 1a. It is preferable to start the measurement in a state lower than the liquid particle concentration. Specifically, after enclosing only a suspension having a lower particle concentration than the suspension to be measured in the tapered portion 1b or a solvent that does not disperse the particles, the suspension to be measured is enclosed in the measuring portion 1a and measured. By starting the process, more effects can be obtained. By enclosing only a suspension or solvent having a particle concentration lower than that of the suspension to be measured in the tapered portion 1b, it becomes possible to suppress collision and contact between the particles, and further, the particle concentration can be suppressed to be low. It is possible to reduce the upward flow accompanying sedimentation. This effect can be obtained more effectively as the particle concentration of the suspension sealed in the tapered portion 1b is lower. Moreover, it is desirable that the solvent of the suspension sealed in the taper portion 1b (the solvent in the case where only the solvent is used) is the same solvent as the solvent of the sample sealed in the measurement unit. For example, if a solvent with a lower density or a higher solvent than the solvent of the sample to be sealed in the measurement unit is used, even if there are no particles, the sedimentation of particles is in an ideal state due to the influence of the density difference of the solvent, that is, There is a case in which a deviation from the state satisfying the above-described expression (1) occurs. When the taper portion 1b is filled with a low-density solvent or a suspension using a low-density solvent, the solvent itself floats, which may hinder particle sedimentation and prevent accurate measurement. In addition, when the tapered portion 1b is filled with a high-density solvent or a suspension using a high-density solvent, the speed is reduced when the particles settle in the region, and a layer with a high particle concentration is formed near the interface. In some cases, accurate measurement cannot be performed. However, there are many cases where some density difference between the solvents does not matter to some extent, and the influence changes depending on the density difference between the particles and the solvent, the concentration of the suspension, etc. is not.

  Hereinafter, the present invention will be described with reference to examples. In addition, this invention is not limited to an Example.

Example 1 and Comparative Example 1
FIG. 5 shows the result of measuring the particle size distribution of a sample in which the particle concentration is changed by the particle size distribution measuring apparatus of the present invention. Moreover, the measurement result in the conventional particle size distribution measuring apparatus is also shown as a comparative example.
In Example 1, a glass cell having the following dimensions was used as a measurement cell. It should be noted that the dimension in the direction in which the measurement light is transmitted is the thickness, the dimension in the direction of the rotation axis is the height, and the dimension in the direction perpendicular to both is the width.
・ External shape: Cube with a width of 12.5 mm, a thickness of 12.5 mm, and a height of 80 mm. ・ Sample storage part of the measurement part: a cube with a width of 10 mm, a thickness of 1 mm, and a height of 74 mm. A shape in which the accommodating cross section on the near side is a rectangle with a width of 10 mm and a thickness of 1 mm, a side far from the rotation axis is a rectangle with a width of 10 mm and a thickness of 9 mm, a height of 4 mm, and a taper angle of 45 °.

In Comparative Example 1, a cylindrical glass cell manufactured by Nippon Luft Co. having the following shape was used as a measurement cell.
-External shape: a cylinder with a diameter of 12.5 mm and a height of 84 mm-Sample storage part: a cylinder with a diameter of 10.0 mm and a height of 82.5 mm The measurement is performed with a commercially available particle size distribution / dispersion stability analyzer LumiSizer manufactured by Nippon Luft The measurement cell of the present invention and the conventional measurement cell were arranged. Centrifugation was performed at 500 rpm for 60 minutes, and the particle size distribution of all the obtained data was calculated in the Constant Position mode.

  As the particles, glass beads having a product display particle size of 22 μm (as catalog values, 10% particle diameter d10 was displayed as 18 μm, 50% particle diameter d50 as 22 μm, 90% particle diameter d90 as 26 μm) were used. As the solvent, a polymer resin dissolved in an organic solvent (viscosity: 20 Pa · s) was used. The suspension was mixed with the solvent so that the particles would be 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt% and 20 wt%, respectively, and at 20 ° C with vacuum degassing. Stir for 15 minutes to disperse.

  In Example 1, only the solvent was sealed in the taper portion, and the suspension was sealed in the measurement portion, and the particle size distribution was measured. In Comparative Example 1, the suspension was sealed in the measurement cell, and the particle size distribution was measured.

  Table 1 shows the measurement results for each measurement. In Table 1, d10, d50, and d90 indicate the 10% particle diameter, 50% particle diameter, and 90% particle diameter in the weight distribution curve, respectively. %, 50%, and 10%.

  In Example 1, a value close to the product display particle size (d50) was obtained for each particle concentration sample, and d10 and d90 were also substantially constant without depending on the particle concentration. In Example 1, a sample having a low particle concentration such as 0.5% by weight or 1.0% by weight has a value relatively close to the product display particle diameter, but a sample having a high particle concentration of 5% or more is obtained. It can be seen that the particle diameter of d50 gradually decreases. Similarly, as the particle concentration increases, d10 and d90 become values close to the particle diameter of d50, indicating that accurate measurement is not possible.

Example 2 and Comparative Example 2
The glass beads having a product display particle size of 22 μm and the glass beads having a product display particle size of 41 μm (d10 is 37 μm, d50 is 41 μm, d90 is 45 μm) used in Example 1 are in a mass ratio of 4: 1. A suspension in which an acrylic resin is dissolved in an organic solvent (viscosity: 20 Pa · s) and mixed to a particle concentration of 10% by weight and dispersed in the same manner as in Example 1 is used as a sample. It was. The particle size distribution was measured in the same manner as in Example 1 and Comparative Example 1.

  5 and 6 show the measurement results of Example 2 and Comparative Example 2. FIG. In Example 2, as shown in FIG. 5, a particle size distribution curve having two peaks in the vicinity of the product display particle size of each glass bead was obtained, but in Comparative Example 2, as shown in FIG. A particle size distribution curve having only one peak in the vicinity was obtained. From these results, it can be seen that the method using the suspension having a high concentration of 10% by weight cannot perform accurate measurement using the conventional technique, but according to the present invention, an accurate measurement result can be obtained.

DESCRIPTION OF SYMBOLS 1 Measurement cell 1a Measuring part 1b Tapered part 2 Measuring cell 3 Lid 4 Rotating rotor 5 Driving device 6 Light source 7 Detector 8 Collimating lens 9 Condensing lens

Claims (3)

A suspension in which particles are dispersed in a solvent is sealed in a measurement cell, the particles are sedimented by centrifugal force by rotating the measurement cell around a rotation axis, and the amount of transmitted light in the sedimentation process is measured, A particle size distribution measuring apparatus for obtaining a particle size distribution from the transmitted light amount change, wherein an area of a sample storage portion of the measurement cell in a cross section perpendicular to the rotation axis is a storage portion cross-sectional area, and the measurement cell is on the rotation axis It has a measuring part that is disposed on the near side and has a housing part area that is substantially constant, and a taper part that is disposed on the side far from the rotating shaft and increases in the housing part area as the distance from the rotating shaft increases. A particle size distribution measuring device. The particle size distribution measuring apparatus according to claim 1, wherein the thickness of the sample storage portion of the measurement cell in the measurement unit is 0.1 to 1.0 mm. A suspension in which particles are dispersed in a solvent is sealed in a measurement cell, the particles are sedimented by centrifugal force by rotating the measurement cell around a rotation axis, and the amount of transmitted light in the sedimentation process is measured, A particle size distribution measuring method for obtaining a particle size distribution from the transmitted light amount change, wherein the area of the sample storage portion of the measurement cell in a cross section perpendicular to the rotation axis is a storage section cross-sectional area, and the measurement cell is connected to the rotation shaft. A measuring cell having a measuring unit disposed on the near side and having a substantially constant housing area, and a tapered portion disposed on a side far from the rotating shaft and increasing in the housing area as the distance from the rotating shaft increases. The particle size distribution measuring method is characterized in that the measurement is started in a state where the particle concentration of the suspension in the tapered portion is lower than the particle concentration of the suspension in the measuring portion.

Images