JP3274230B2 - Aggregated fine particle dispersion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dispersing aggregated fine particles, and more particularly, to a method for dispersing aggregated particles by accelerating airflow.

[0002]

2. Description of the Related Art In general, inorganic or organic fine particles such as ceramics are more likely to aggregate as the particle size becomes smaller. Therefore, several to several tens or more primary particles are aggregated to form an aggregate. There are many cases.

On the other hand, there is often a demand in various fields to disperse aggregated fine particles into primary particles,
For this purpose, for example, a large number of large-diameter beads are put into a container and stirred while supplying the aggregated fine particles, or a mechanical aggregate destruction method of supplying the aggregated fine particles to a rotating brush, or the aggregated fine particles are ejected to an ejector. A method of supplying and dispersing by acceleration in an air stream has been conventionally performed.

The present inventors have already reported that in the above-mentioned dispersion method in a gas stream, for example, fine particles having a diameter of about several μm can increase the dispersibility of aggregated particles by increasing the gas flow gas density. (Endo, Takasaka: Chemical Engineering Transactions, 1
8, p760 (1992)).

[0005]

However, in the mechanical dispersion method described above, there is a limit to the particle size of the object to be dispersed,
In addition, there is a limit to the suppression of contamination caused by a mechanical stirrer or the like. On the other hand, the dispersion method in an air stream has a lower limit on fine particles that can be dispersed, and is not necessarily effective for fine particles of 1 μm or less, for example.

In view of such problems of the conventional method, the present inventors have conducted intensive studies for the purpose of theoretical analysis of the fine particle dispersion mechanism and the development of more effective means required in practice. The present invention has been developed.

According to the present invention, in order to achieve the above object, the present invention described in each of the claims is completed, and one of its features is an object to be dispersed.
1.0 [mu] m and fine <br/> child aggregates of primary particle size of submicron diameter under diameter or less, 50.mu. this particulate aggregate is adhered to the surface
The mixture of the dispersion medium particles on m diameter or more, these microparticles
Accelerate the above mixture of agglomerates and dispersion media particles in a gas stream
In Rutokoro give dispersed primary particles of submicron size Te.

[0008] The present invention is, in the conventional method is particularly effective when the target aggregates of primary particle diameter of submicron size dispersion is difficult, fine is the submicron particulate
And particle aggregation (primary particles), can be used and distributed media particles of the dispersing medium particle e.g. 50μm~150μm size of about 100 [mu] m.

The fine particles to be dispersed include, for example, plastic particles, ceramic particles, calcium carbonate, alumina, polystyrene latex and the like.

The material of the dispersion medium particles is not particularly limited, but for example, ceramics and the like are preferably used, and glass beads can be particularly preferably used.

In the above configuration, as means for accelerating the dispersion medium particles in the air stream, for example, an ejector, a high-pressure vessel, or the like can be used. Air flow pressure is 0.5kg
/ Cm ^{2 to} 150 kg / cm ² can be used to carry out the present invention.

The reason why the above configuration is employed in the present invention is as follows. When the model shown and aggregated particles composed magnitude of two particles is placed instantaneously in a field of uniform flow in FIG. 1, the dispersion force F _d by the following equation acting between these different size particles Given by In this case, the small particle size is A and the large particle size is B.

[0013]

(Equation 1)

[0014] As a method wherein increasing the dispersion force F _d, consider the size d _VB of large particles B, and the influence of the dispersion effect due to the increase the density [rho _PB.

FIG. 2 shows a dispersion force F _d received from a fluid in which one PSL particle adheres to one glass bead (d _VB = 100 μm) (two particles having different diameters) assuming a test described later.
(A curve with a large slope) was obtained from the above equation, and the conditions regarding the fluid were as follows: P _f is the initial pressure of the nitrogen gas supplied to the ejector used in the test described later, and ρ _f is the critical pressure at the throat of the ejector. Is the density of the nitrogen gas reached. The curve with a small slope shows the Hamaker constant as A ₁₂
= 1.2 × 10 ⁻¹⁰ J and the interparticle distance of 0.4 nm, the PSL particles and glass beads (d _p2 = 10
0 pm). The Hamaker constant is an average value of literature values A ₁₁ = 1 × 10 ⁻¹⁹ J (PSL) and A ₂₂ = 1.5 ×
From 10 ^-19 J (SiO ₂ as glass), A ₁₂ = (A
₁₁ · A ₂₂ ) Calculated as ^1/2 . From this FIG. 2, the PSL
Between particles and glass beads, about one order of magnitude greater dispersion forces F _d acts compared to PSL particles together, although dispersion effects (particle size ≒ 105 .mu.m of PSL particles) at the maximum value of F _d is the highest, Even if the PSL particles have a diameter of about 0.5 μm, for example, P
₁ = _{1 to} 2 MPa, abs. It can be expected that it will easily separate from the glass particles to some degree.

Further, such glass beads and 0.5 μm
A mixture of fine particles having a diameter of about 100% is excellent in handleability, for example, in that flowability is good and quantitative supply is easy.

On the basis of these theoretical analysis and handling properties, in order to disperse fine particles, particularly of the order of submicron, which are to be dispersed, it is necessary to use dispersion medium particles having a larger particle diameter than the fine particles. Thus, the present invention was developed.

[0018]

EXAMPLE Using the apparatus shown in FIG. 3, a dispersion test of aggregated fine particles was performed. The apparatus shown in FIG.
A throat portion 11 facing the thin tube 2 so as to supply glass beads having fine particles adhered to the surface through a 2 mmφ) 2, and a taper provided so that the opening diameter gradually increases forward from the throat portion 11. An ejector 1 serving as a pressure gas inlet 13 to which a nitrogen gas cylinder 3 is connected by a gas pipe 4 so as to blow a pressure nitrogen gas into the throat 11 from around the back of the throat 11; The gas flow blown out from the tapered opening 12 of the ejector 1 is transported through a transport pipe 5 to a chamber 6 (capacity: 0.05 m ³ ), which is a sample collection container. The fine particles are allowed to settle by natural settling.

Using the above apparatus, a test was conducted as follows.

A thermo-hygrostat (temperature 298, K, humidity 40)
%), A PSL (polystyrene latex) particle suspension was dried for 48 hours, and monodispersed standard particles having a particle size of 0.305 μm and 0.493 μm (density 1.05 × 10 5
³ kg / m ³ ) and glass beads having a diameter of about 100 μm (density 2.4 × 10 ³ kg / m ³ ) were ^{combined with} 1 × 10 ⁻⁵ m
^In a closed glass container (not shown) of No. 3, a fixed amount (1.8 × 10 ⁵ , 3.5 PSL particles per glass bead)
× 10 ⁵ , 7.0 × 10 ⁵ , 3.5 × 10 ⁶ )
This was mixed by shaking and stirring to prepare a supply particle sample having PSL particles adhered to the surface of glass beads.

This sample is sucked into the negative pressure part of the throat part 11 of the apparatus of FIG. 3 through the thin tube 2 at about 10 mg / s, accelerated and dispersed by a high-speed nitrogen gas flow of the throat part 11, and then introduced into the chamber 6. After all the particles were deposited on the slide glass 7 by spontaneous sedimentation, the dispersion state of about 1000 particles was observed with an engineering microscope.

The test results are shown in FIG. 4 (PSL particle size:
493 μm) and FIG. 5 (PSL particle diameter: 0.305 μm)
m). In this figure, the vertical axis indicates the ratio of aggregates composed of N (N is a natural number) primary particles to the total number of particles (single particles and aggregated particles) after dispersion excluding glass beads, and the horizontal axis indicates The number ratio between the supplied PSL particles and the primary particles of the glass beads is shown.

As can be seen from the results of FIGS. 4 and 5,
When the glass beads were not added, the PSL particles were not so dispersed, but it was confirmed that the glass beads were added and the ratio of the added glass beads was increased, and the dispersing effect was improved. The nitrogen pressure is 1.1-2M
Pa, abs. It can be seen that about 85 to 90% of single particles are obtained.

In each case of the PSL particles having the above-mentioned particle diameters, the number ratio between the PSL particles and the glass beads for which the best dispersion results were obtained is as follows. It is about の of the case where it is assumed that the particles are attached, and the attachment state of the particles at this time is shown in the micrograph of FIG. 6 before (a) and after (b) after dispersion. As a result, the PSL particles are partially thinly attached to the surface of the glass beads before the dispersion, but almost all the PSL particles are dispersed after the dispersion.
It can be seen that the particles are separated.

The large-diameter glass beads have a terminal sedimentation velocity sufficiently higher than that of the PSL particles (0.5 m / s for the glass beads in the above example), and are easily classified from the fine particles such as the PSL particles. it can. For example, a method of passing through a sieve having openings slightly smaller than glass beads after dispersion, or a method of cyclone separation can be used.

[0026]

According to the present invention, there is an effect that most of fine particles, particularly submicron fine particles, can be dispersed to primary particles in a gas phase.

Further fine submicron, for example if the engaged mixed to the extent that covers one layer on the surface of the dispersing medium particles such as glass beads of 100μm extent, supply pressure of 1 to airflow acceleration Dispersion can be easily performed at about 2 Ma, and there is also an effect that excellent dispersibility can be obtained with a relatively simple configuration as a dispersing device.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing two large and small particle aggregates,

FIG. 2 is a diagram showing a dispersing force F _d received from a fluid by a glass bead to which PSL particles are adhered, obtained from an equation,

FIG. 3 is a schematic configuration diagram of an apparatus used for a dispersion test;

FIG. 4 shows the test results (PSL particles d _p1 = 0.49).
3 μm),

FIG. 5 shows the test results (PSL particles d _p1 = 0.30)
5 μm),

FIG. 6 is a diagram showing the adhesion state of PSL particles on the surface of glass beads before dispersion (a) and after dispersion (b).

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Murata 5-3-1 Tsurugaoka, Oi-machi, Iruma-gun, Saitama Prefecture Nisshin Flour Milling Co., Ltd., Research and Development Department, Production Technology Research Institute (56) References JP-A Sho 54- 37951 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 19/00 B07B 11/06

Claims (4)

(57) [Claims] 1. A which is an object to be distributed target 1.0 [mu] m diameter or less of a support
Aggregates of fine particles with a primary particle diameter of Bmicron diameter and these fine particles
A mixture of the dispersion medium particles having a diameter of 50 μm or more with the particle aggregate adhered to the surface thereof is mixed with the fine particle aggregate and the dispersion medium particle.
Of the above sub-micron diameter
Dispersion method of aggregated fine particles, wherein Rukoto give the following particle. 2. The method according to claim 1, wherein the dispersion medium flow is 50 μm.
dispersion method of aggregated fine particles, which is a m~150μm diameter. 3. The method of claim 2, dispersion method of aggregated fine particles, wherein the dispersion medium particles are glass beads. 4. In any of claims 1 to 3,
Dispersion method of aggregated fine particles, characterized in that means for the dispersing medium particles are accelerated in a gas stream is ejector.