JPH0437937B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to the dispersion state of light-scattering particles in a thin layer containing light-scattering particles at a high concentration to the extent that multiple scattering by the light-scattering particles occurs. , relates to a device for measuring average particle size.

[Background technology]

Conventional methods for measuring the particle size of particles in suspension include microscopy, sedimentation, and light scattering, but all of them require considerable dilution, and dilution may change the state of the particles or There are problems such as the amount of man-hours and time required.

In particular, although measurement of the dispersion state of pigment particles in paint liquid is important for quality evaluation in the paint manufacturing process, it is difficult to measure due to the above-mentioned problems, and a simple measurement method is desired. Ta.

As a method for measuring particle size based on the light scattering intensity distribution by particles, for example, the method described in Japanese Patent Application Laid-open No. 190248/1983 is known. However, this method cannot be applied unless the particle to be measured is a single particle, the particle size is the same, and the particle concentration is so dilute that multiple scattering by particles does not occur, and it does not suffer from the problems mentioned above. It's not a solution.

Therefore, the applicant has previously developed a method that can easily measure the dispersion state, that is, the particle size (average particle diameter) of light-scattering particles in highly concentrated suspensions such as paints, without dilution or with only slight dilution. It was done.

This method is based on the well-known principle that when light-scattering particles are irradiated with a parallel beam of light, the intensity of the scattered light depends on the particle diameter.
The intensity of a parallel beam of light transmitted through a thin layer of a highly concentrated suspension is
I ₂ , and when the intensity of the scattered light is I ₁ , the ratio of both I ₁ /
As shown by the solid line in Figure 1, I ₂ shows a good correspondence with the dispersion state of the suspension, that is, the particle size (average particle diameter), so by detecting this ratio I ₁ /I ₂ , the dispersion state This is to determine the particle size (average particle diameter). The reliability of this method was confirmed by the following experimental facts.

In order to understand the light scattering pattern of a liquid containing a high concentration of light scattering particles, paint liquids with different degrees of dispersion, or particle sizes (average particle diameter), are made into thin layers, and the forward scattering is measured using the apparatus shown in Figure 2a. Figure 2b shows the measured light intensity distribution of the light. In FIG. 2a, 1 is a light source such as a helium neon laser, 2 is a light flux adjusting means, 3 is a measured object consisting of a thin layer containing light scattering particles, and 4 is a photodetector as a light intensity distribution detecting means. be. The light emitted from the light source 1 is adjusted to a parallel light beam having a predetermined diameter by a light beam adjusting means 2 composed of a condenser lens, a pinhole, a collimator lens, etc., and is irradiated onto the object 3 to be measured. The object to be measured 3 is a highly concentrated suspension liquid and is housed between two glass plates (not shown).
The forward scattered light distribution due to the light scattering particles in the object to be measured 3 is measured by scanning the photodetector 4 in the direction of the arrow shown in the figure.

In Figure 2b, the light scattering particles are quinacridone red pigment, the pigment volume concentration is 9.4%, the sample thickness is 100 μm,
This is an example of measurement using a helium neon laser light source and a beam diameter of 10 mm. In the figure, A shows the forward scattered light intensity distribution of the sample at the initial stage of dispersion, B shows the sample with advanced dispersion, and C shows the forward scattered light intensity distribution of only the sample container, and normalized with the maximum intensity as 1. As is clear from Figure 2b, as the dispersion progresses, the intensity of the scattered light changes in the scattering angle range of 0.5 to 10 degrees around the irradiated light beam, and it is not useful as a practical evaluation scale for the degree of dispersion. It was found to be very useful.

By the way, in carrying out such a simple particle size measurement method, it is necessary to control the thickness of the thin layer of the highly concentrated suspension to be between several μm and about 0.1 mm. Therefore, in order to make the sample layer thinner,
Samples were placed in thin transparent cells of various thicknesses. However, in this case, the transparent cell must be cleaned and set for each measurement, which makes the operations for measurement and cleaning complicated, and therefore the measurement method cannot be automated. When it is necessary to measure various types of paints and the like using the same measuring device, it is particularly desirable to have a device that can be easily cleaned.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of these circumstances, it is an object of the present invention to provide a measuring device that can automate and carry out the above-mentioned simple particle size measuring method.

[Disclosure of the invention]

The inventors have conducted extensive research in an attempt to obtain a particle size measuring device that does not use a transparent cell, can be easily cleaned and measured, and can be automated. As a result, we succeeded in obtaining such a particle size measuring device and completed this invention.

In order to achieve the above object, the present invention comprises a passage through which a sample containing solid particles flows, a measuring part is provided in a part of the passage, and openings are provided at opposing positions on the wall of the measuring part. The formed tube and the light transmitting window sealed so that the sample does not enter are faced to one of the two openings, and a parallel light beam is irradiated from the light transmitting window toward the other opening. A generating means, a light transmitting window sealed to prevent the sample from entering is faced to the other opening, and a light receiving part is provided at the back of this light transmitting window, and parallel light coming from the own light transmitting window is provided. A light amount detection means for detecting transmitted light and scattered light by the light receiving section, and a seal for preventing the sample from leaking around each light transmission window and between each opening of the parallel light flux generation means and light amount detection means. The gist of the particle size measuring device is: a particle size measuring device comprising: a stop means; There is. The present invention will be described in detail below based on drawings showing embodiments.

FIG. 3 shows a particle size measuring device according to the present invention.
An example is shown. As shown in the figure, this particle size measuring device includes a tube 5, a parallel light beam generating means 6, and a light amount detecting means 7, respectively. The tube 5 has a passage 5a through which a sample containing solid particles flows,
Openings 8 and 9 are formed at opposing positions in the measuring section 5b of this passage 5a. The tube 5 is the measurement part 5
At position b, the openings 8 and 9 are close to each other, so that the cross section is elliptical and equally flat, and therefore, as shown in FIG. 4, the width D of the passage 5b is widened. The cross-sectional area is the same from one end to the other, and the inner circumferential surface of the tube is smooth, so that the flow state of the sample passing through the passage 5a does not change at any position in the passage 5a. be. Therefore, the sample flows smoothly and does not stagnate. As an example of a specific design, for example, both ends of the passage 5a are circular with a diameter of about 14 mm, and the thickness of the measuring part 5b (thickness in the direction connecting both openings 8 and 9) is about 6.5 mm. Measuring part 5b
The reason why the openings 8 and 9 are made flat is that the diameters of the openings 8 and 9 can be made large even if the cross-sectional area of the passage 5a is small.

The parallel light flux generating means 6 includes a cylinder (ride guide) 6c having a light transmitting window 6a at the tip and a lens 6b inside. The tip of the optical fiber 6d that guides the light is facing. Light transmission window 6a
is sealed with an optically smooth transparent solid, so that the sample passing through the passage 5a does not enter the inside of the cylinder 6c. This light transmitting window 6a faces the opening 8, and an O-ring is inserted between the two to prevent the sample from leaking around the window 6a and between the opening 8.
A is inserted. The parallel light beam generating means 6 is
The light emitted from the tip of the optical fiber 6d is passed through the lens 6d.
The parallel light beam is converted into a parallel light beam along the axial direction of the cylindrical body 6a, and the parallel light beam is irradiated toward the opening 9 from the light transmission window 6a. The cylindrical body 6c of the parallel light beam generating means 6 is inserted and fixed into a guard cylindrical body (inner light guide guard) 10 so that its tip slightly protrudes from the opening 8, and the guard cylindrical body 10 is inserted into another guard cylindrical body 10. It is inserted and fixed into the cylindrical body (outer light guide guard) 11. The guard cylinder 11 is placed in a cylinder 12 whose tip is fixed to the outer surface of the opening 8 and which is provided with a linear ball bearing 12a on the inner peripheral surface, so that its position can be varied in the front-rear direction (direction of irradiation of the parallel light beam). It is inserted and is moved back and forth by a driving means 13 such as an air cylinder attached to the rear end. Although the linear ball bearing 12a is used to smoothly move the guard cylinder 11, it is not necessarily required.
Threaded portion 11 provided at the rear of guard cylinder 11
A double nut type stopper 14 is screwed into the hole a, and a micro dial gauge 15 is attached to the stopper 14.

The light amount detection means 7 has a box (dark box) 7a fixed to the outer surface of the opening 9, a light transmitting window 16, and a light receiving section 17 consisting of a photo sensor. Box body 7
a is used to prevent the measurement value from being influenced by external light that hits the light receiving section 17. Here too, the light transmitting window 16
is sealed with an optically smooth transparent solid, and the passageway 5
The sample passing through a is prevented from entering the box body 7a. As shown in the figure, the light transmission window 16 is
An O-ring 9a is fitted around the opening 9 and between the opening 9 to prevent the sample from leaking.

As shown in the figure, the transparent solid 16a that seals the light transmission window 16 has a shape in which a disk with a small diameter is superimposed on a disk with a large diameter, and the disk with the small diameter is directed toward the passage 5a. The opening 9 has a large outer diameter and a small inner diameter. In this way, when the parallel light beam generating means 6 retreats, there is no risk that the liquid sample passing through the passage 5a will come off the light transmission window 16 due to its high viscosity. However, it does not necessarily have to be this way. A ring-shaped holding plate 18 made of Teflon or the like and a ring-shaped holding plate 19 made of stainless steel or the like are fixed to the tube 5 with screws 20 to hold the light transmitting window 16 and fix it in the opening 9. ing.

The front end surface of the parallel light beam generating means 6 (the transparent solid front surface of the light transmitting window 6a) and the transparent solid front surface of the light transmitting window 16 are as follows.
Both are made to have a high degree of parallelism at the μm level by polishing at the μm level, and in order to maintain such high parallelism, the light transmitting window 1
The mounting position of the transparent solid material sealing the window 16 can be finely adjusted by appropriately adjusting the tightening strength of screws 20 arranged symmetrically with respect to the center of the window 16.

As the transparent solid for sealing the light transmitting windows 6a and 16, it is preferable to use a material having high light transmittance, optical smoothness (no light scattering), and high hardness, such as optical glass or synthetic sapphire.

A narrow slit is formed between the light transmission windows 6a and 16, and the distance therebetween can be adjusted by moving the parallel light beam generating means 6 back and forth using the drive means 13. If the tip of the parallel light flux generating means 6 (light transmitting window 6a) strongly collides with the light transmitting window 16, the light transmitting window 6a or 16 will be damaged. A stopper 14 is used to maintain a predetermined distance between the two transmission windows 6a and 16.
The distance between the two light transmitting windows 6a and 16 can be read using a micro dial gauge 15.

The light receiving section 17 is arranged on the ceiling of the box body 7a, and as shown in FIG. 5, ring-shaped silicon photodiodes 17a with different radii...
They are arranged on the substrate 17b with the same center.
Grooves 17c are provided between each silicon photodiode 17a and on the outside of the outermost silicon photodiode 17a, and the silicon photodiodes 17a... are electrically isolated from each other. The center of the light receiving section 17 is aligned with the axis of the parallel light flux generating means 6, and the parallel transmitted light entering from the light transmission window 16 is received by a silicon photodiode in the central portion.
The scattered light is received by a silicon photodiode on the periphery. Each silicon photodiode 17a generates a current corresponding to the intensity of the received light, and these are connected to an amplifier 21 that amplifies the current corresponding to the intensity of scattered light and an amplifier 22 that amplifies the current corresponding to the intensity of parallel transmitted light. The signal is amplified, inputted to the arithmetic processing unit 23, and subjected to arithmetic processing.

This pigment particle size measuring device is used, for example, in the following manner.

As shown in FIG. 3, on both sides of the tube 5,
A tube 24 for sending the sample and a tube 25 for discharging the sample are connected. Then, the sample is poured into the passage 5a. This measuring device can measure both liquid and gas samples in which solid particles are dispersed, but in the case of liquid samples, the flow rate must be less than 500 mm/sec and the particles in the sample should not settle. It is better to speed it up. Next, the light transmitting window 6a is moved by the air cylinder 13, and both the light transmitting windows 6a, 16 are
Adjust the spacing between. As shown in FIG. 6, light 26 is transmitted from the tip of the optical fiber 6d to a lens 6.
This light 26 is converted into a parallel light beam 27 by the lens 6b, and this parallel light beam 27 is irradiated from the light transmission window 6a. The parallel light beam 27 hits the sample flowing between the light transmission windows 6a and 16, and is divided into parallel transmitted light 28 and scattered light 29 while passing through the sample. The parallel transmitted light 28 and the scattered light 29 are transmitted through the light transmission window 16.
The light passes through and hits the light receiving section 17. In the light receiving section 17, a current is generated in accordance with the light hitting the silicon photodiode 17a, so the amplifier 21,
22, and the ratio (I ₁ /I ₂ ) of the amount of scattered light I ₁ to the amount of parallel transmitted light I ₂ is obtained by an arithmetic processing unit. This ratio I ₁ /
I ₂ corresponds to the dispersion state of solid fine particles contained in the sample, that is, the particle size (average particle diameter).

When measuring a sample different from the previous one, use passage 5a.
Cleaning liquid such as solvent should be poured into the area. in this case,
With the parallel light beam generating means 6 retracted, the passage 5a
It is preferable to widen the measurement part 5b so that the cleaning liquid can flow smoothly.

As mentioned above, if the measuring device according to the present invention is used, measurement and cleaning can be easily performed, and it can also be automated and incorporated into paint manufacturing equipment, etc.

In the above embodiment, the parallel light flux generating means guides the light emitted from the external light source into the cylinder through an optical fiber, but it is not necessary to do so, and the light source may be placed inside the cylinder. The light emitted from the light beam may be applied directly or via a lens system to a lens for converting the light into a parallel beam of light. As in the embodiment, the light transmitting window of the light detecting means is fixed in position, and the light transmitting window of the parallel light beam generating means is variable in position, and by moving the latter light transmitting window, the distance between the two light transmitting windows can be changed. It is not necessarily necessary to adjust the Only the former light transmitting window may be variable in position, or both light transmitting windows may be variable in position. Instead of using a photo sensor equipped with a large number of ring-shaped silicon photodiodes as the light receiving section as in the embodiment, a photo sensor equipped with one silicon photodiode may be used and scanned.

In the parallel light beam generating means, if the transparent solid of the light transmitting window 6 is fixed to the cylindrical body as shown in FIGS. 7 and 8, there is no possibility of it coming off.
In FIG. 7, a groove 6e is provided on the inner circumferential surface of the tip end of the cylinder 6c, and the edge of the large diameter portion of a transparent solid 6g having a double disk shape of large and small diameters is fitted into this groove 6e. 8th
In the figure, a groove 6h is provided in the inner circumferential surface of the tip end of the cylinder 6c, and the edge of the truncated conical transparent solid 6i is fitted into the groove 6h. When fixing transparent solids, adhesive may be used if necessary. However, if the cylindrical body 6c is made of an elastic material, it may be simply fitted, and if the cylindrical body 6c is made of an inelastic material, the transparent solid 6c
It is preferable that the tip of the cylindrical body 6c is detachable at the grooves 6e and 6h so that the tubes 6e and 6i can be fitted into the grooves 6e and 6h.

Depending on the configuration of the light amount detection means, a large portion of the scattered light may be lost in the parallel transmitted light. In this case, the utilization rate of scattered light is not very good. In such a case, if a Fourier transform lens is placed in the light amount detection means and each of the scattered light and parallel transmitted light is condensed to a single point at the focal length, the utilization rate of the scattered light can be increased. be able to.

Next, the degree of dispersion of the paint liquid sampled in the pigment dispersion process in paint manufacturing, that is, a parameter representing the particle size of the pigment in the paint liquid (ratio of scattered light amount/parallel transmitted light amount), was calculated according to the present invention shown in FIG. The results of measurements using the embodiment of the measuring device will be described.

(Measurement 1) A dispersing paint liquid containing phthalocyanine green as a pigment was measured at dispersion times of 30 minutes, 50 minutes, and 80 minutes. spacing) of 25 μm,
It was decided to change the diameter to 50 μm and 100 μm and measure it three times each. Glass beads were used as a dispersion medium. The results are shown in Figure 9. Also, for comparison,
At each dispersion time, the grind gauge particle size was measured using method A of the methods using a grind gauge specified in JISK-5400. The measurement results are also shown in FIG. 9.
A method using a grind gauge is currently widely used in the paint industry as a method for measuring the particle size of dispersed pigment particles in a paint liquid. Method A is implemented as follows. Pour more sample into the two deep grooves of the grind gauge than it takes to fill the entire groove. Hold the upper part of the scraper near both ends with your fingertips, and place the cutting edge deep in the groove of the grind gauge so that it is perpendicular to the longitudinal direction of the groove, so that the center of the scraper is approximately perpendicular to the top surface of the grind gauge. to press against. While pressing the tip of the blade, pull it all at once in the direction of 0 on the scale at an even speed within 1 second. Observe the condition appearing on the surface of the sample squeezed into the two grooves from above within 5 seconds after pulling off the scraper, check the density of the distribution of crumbs, and read the scale. Repeat this test 5 to 6 times, discard values that differ by more than 1 scale, take only the approximate values for 3 times, and calculate the average value to the nearest 5 to 6.
Enter the number and round to the nearest tenth.

In FIG. 9, the symbols ○, △, and □ represent the measurement results when the thickness of the paint layer is 25 μm, 50 μm, and 100 μm, respectively, and ◇ represents the measurement result using the grind gauge method. The number 2 next to the symbol indicates that two measured values overlap.

As shown in Fig. 9, the particle size measurement results using the measuring device shown in Fig. 3 are reproducible, and regardless of the thickness of the paint layer, the parameter representing particle size in the measurement results with the grind gauge is the same as the dispersion time. It can be seen that it corresponds to the decrease in size over time.

(Measurement 2) The dispersed paint containing quinacridone purple as the pigment was measured at dispersion times of 30 minutes, 60 minutes, and 90 minutes. At each measurement time, the thickness of the measured paint layer was changed to 25 μm and 50 μm. In this case, glass beads were used as the dispersion medium. The results are shown in FIG.

In FIG. 10, the symbols ○ and △ represent the measurement results when the thickness of the paint layer was 25 μm and 50 μm, respectively.

From Figure 10, it can be seen that the particle size measurement results using the measuring device in Figure 3 are reproducible, and are consistent with the fact that the parameter representing particle size decreases with dispersion time regardless of the thickness of the paint layer. I know that there is.

〔Effect of the invention〕

Since the particle size measuring device according to the present invention is configured as described above, it is possible to automate and implement the simple particle size measuring method as described above.

In particular, as measurement samples, it is possible to easily handle samples with various particle concentrations, from those with dilute particle concentrations to those with high particle concentrations, such as high concentration suspensions such as paints. In other words, with conventional measuring equipment,
The measuring device according to the present invention replaces sample cells with different thicknesses (transparent cells containing the sample) depending on the particle concentration of the sample, but by changing the spacing between the light transmission windows, Therefore, it is possible to always easily set an appropriate measurement thickness for a sample of any particle concentration, and the efficiency of the measurement work can be improved. In addition, with conventional sample cells, it was necessary to clean the inside of the narrow transparent cell to remove remaining samples every time a test was completed, which was a very time-consuming process. For example, if a suitable cleaning solution is flowed into the tube that serves as the passage for the sample with the light transmitting windows widely spaced apart, cleaning can be done extremely easily and effectively, and the efficiency of the measurement work can also be improved in this respect. .

[Brief explanation of drawings]

Figure 1 is a graph showing the accuracy of the principle of the particle size measuring device according to the invention, Figure 2a is an explanatory diagram of the measuring device for measuring the state of light scattering by a sample layer containing light scattering particles, and Figure 2b is 2 is a graph showing the light scattering pattern determined by the device shown in FIG. 5 is a front view of the light receiving part of the same particle size measuring device, FIG. 6 is an explanatory diagram of the progress state of light in the same particle size measuring device, FIGS. 7 and 8 are explanatory diagrams of a method of fixing a transparent solid, FIG. 9 is a graph showing the results of particle size measurements using the particle size measuring device and grind gauge shown in FIG. 3, and FIG. 10 is a graph showing the results of particle size measurements using the particle size measuring device shown in FIG. 5...Pipe, 5a...Passage, 5b...Measurement part, 6
...Parallel light beam generating means, 6a...Light transmission window, 7...
...Light amount detection means, 8, 9...Aperture, 8a, 9a
...O-ring, 16...light transmission window, 17...light receiving section, 18, 19...pressing plate, 20...screw.

Claims (1)

[Scope of Claims] 1. A tube that constitutes a passage through which a sample containing solid fine particles flows, has a measuring section in a part thereof, and has openings formed at opposing positions in the wall of the measuring section; A light transmitting window sealed to prevent the sample from entering the opening faces one of the openings, and a parallel light flux generating means for irradiating a parallel light flux from the light transmitting window toward the other opening; A light transmitting window that is sealed so as not to be exposed faces the other opening, and a light receiving section is provided at the back of this light transmitting window, and the parallel transmitted light and scattered light that enters from the own light transmitting window are a light amount detection means for detecting each by a light receiving section; and a sealing means for preventing the sample from leaking around each light transmission window and between each opening of the parallel light flux generation means and the light amount detection means, respectively. A particle size measuring device comprising: a narrow slit-like space between the two light-transmitting windows, and the interval between the two light-transmitting windows is variable. 2. The light transmission window of the light amount detection means is fixed in position, the parallel light flux generation means is variable in position in the direction of irradiation of the parallel light flux, and the parallel light flux generation means is moved back and forth by a driving means attached thereto. A particle size measuring device according to claim 1. 3. The collimated beam generating means includes a cylindrical body having a light transmitting window at the tip and a lens inside, and the tip of an optical fiber that guides light from a light source faces the rear focal point of the lens. Particle size measuring device according to scope 1 or 2.