JPH05337351A - Method for dispersing fine particles in liquid - Google Patents

Abstract

PURPOSE:To enhance the dispersibility of fine particles in a solution and to reduce the flocculation thereof by adding a substance capable of controlling the zeta potential of the fine particles in the solution to the solution in specific ratio. CONSTITUTION:The potential energy W between fine particles 1, 2 in a liquid is the sum of Van der Waals attraction VA and electrostatic repulsive force VR due to an electric double layer. Then, the peak of potential is made high to enhance dispersion or to reduce flocculation. Herein, a substance capable of controlling the zeta potential of fine particles in a solution such as alcohol or glycol is added to the solution in addition concn. of 10<-7>-25vol%. Whereupon, the surface potential of fine particles becomes high and electrostatic repulsive force is enhanced.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The dispersion method of the present invention is used in the production process of many materials such as electronic materials, magnetic materials, optical materials, and ceramics, in which fine particles of compounds containing inorganic or organic substances including various metals, alloys, and ceramics, In particular, the present invention relates to a method for producing ultrafine particles, and relates to a technique suitable for producing fine particles having good dispersion.

[0002]

2. Description of the Related Art In the manufacturing process of many materials such as electronic materials, magnetic materials, optical materials, and ceramics, the fine particles used as the raw material adjusting, crushing, kneading, mixing, and molding steps have a high concentration in the medium. It is suspended. Whether these fine particles are agglomerated or sufficiently dispersed has a great influence on the performance of the resulting material. Recently, there has been an increasing demand for using ultrafine particles of 1 μm or less, and there are cases where highly accurate control is required to eliminate aggregated particles in the slurry.

As a countermeasure against this, an ionic surfactant such as sodium dodecyl sulfate or a polymer additive such as polyethylene oxide is added. The means for dispersing fine particles using these is described in Chemistry of Dispersion / Emulsion Systems (1979), pages 269 to 273.

There is also a method of dispersing with physical energy such as ultrasonic waves. The means for dispersing is described in Ultrasonic Technical Handbook (1960), pages 1060 to 1070.

[0005]

In the conventional method in which an ionic surfactant is added and dispersed, as the concentration of ions in the liquid increases, the particles tend to agglomerate as they become smaller.
Therefore, it is considered that the conventional method is not suitable for dispersing ultrafine particles of 1 μm or less.

In the conventional method of adding a polymer additive to disperse the polymer additive, the polymer additive acts as a dispersant, but also acts as a coagulant depending on the concentration added, and it is difficult to adjust the optimum addition concentration of the dispersant. Therefore, it is considered that the conventional method is not suitable for dispersing ultrafine particles of 1 μm or less.

In the conventional method of dispersing particles with physical energy such as ultrasonic waves, the surface area of the particles becomes smaller as the particles become smaller, so that the physical energy required for each particle is small. On the contrary, when ultrasonic waves are irradiated for a long time, the particles conversely aggregate. Therefore, it is considered that it is difficult to disperse the particles by the conventional method.

In order to solve the above problems, an object of the present invention is to propose a technique for obtaining fine particles with good dispersion of ultrafine particles of compounds containing various metals, alloys, inorganic materials including ceramics or compounds containing organic materials and with little aggregation. Especially.

[0009]

The present invention provides a substance capable of controlling the zeta potential (surface potential) of fine particles in a solution,
The present invention relates to a method for dispersing fine particles in a liquid, which improves the dispersion or reduces aggregation of the fine particles in the solution when added to the solution.

FIG. 1 shows a basic conceptual diagram of the present invention. Figure 1
(A) shows the relationship between the distance (Å) between the particles and the potential energy- (W).
(B) is the electrostatic repulsion force due to the electric double layer formed by the surface charge 3 between the fine particles 1 and the fine particles 2, FIG.
(C) is a van der between the fine particles 1 and the fine particles 2.
It is a conceptual diagram which shows the attractive force by Waals force. As shown in FIG. 1, the potential energy −W between the fine particles 1 and the fine particles 2 in the liquid is van der Waals.
It is the sum (W = VA + VR) of two potentials, the attractive force (VA) due to the force and the electrostatic repulsive force (VR) due to the electric double layer, and it is considered that the particles are aggregated when the potential peaks are exceeded. Therefore, the present invention has been made paying attention to increasing the peak of this potential and increasing the surface potential (zeta potential) of the fine particles to improve the electrostatic repulsion force in order to improve dispersion or reduce aggregation. It is a thing. FIG. 2 shows the relationship between the time change of the particle concentration of the suspended fine particles after standing and the zeta potential of the fine particles. In FIG. 2, 4 is silicon (Si) particles etched by hydrofluoric acid (volume ratio of HF: H ₂ O = 1: 99).
Fine particles collected by a filter after soaking in the hydrofluoric acid. Hereinafter referred to as bare Si particles. ) 5 is untreated Si particles, 6
Are Fe particles. The zeta potential differs depending on the type of particles, and even the same Si particles have a zeta potential depending on the surface state.
The value of the electric potential is different, and the time variation of the particle concentration of fine particles is different. (Measurement of change in particle concentration over time is shown in Examples described later.) Therefore, it is considered that the dispersion of fine particles or the aggregation can be reduced by controlling the zeta potential.

Further, the zeta potential of the fine particles is generally negative, but in rare cases, both particles may be positive like alumina particles. Controlling the zeta potential means increasing its absolute value.

The present invention was made based on the finding that the zeta potential of fine particles can be controlled by adding a specific substance to a liquid.

Here, the relationship between the zeta potential and the sliding surface will be briefly described.

It is considered that when the fine particles move in the solution, several layers of liquid molecules are adsorbed and moved around the fine particles. At this time, the boundary surface between several layers of liquid molecules and the liquid around it is called a “sliding surface”, and the potential on this surface is related to the dispersion and aggregation of the fine particles as described above. (For the sliding surface, for example, Fumio Kitahara, "Chemistry of Dispersion / Emulsion System"
(Engineering Book 1979), page 102. )
On the other hand, since the zeta potential is measured by the electrophoresis method, the potential of this sliding surface is measured exactly. (Details of the method for measuring the zeta potential are shown in the examples described later.) In the present invention, alcohol, glycol, amine, amino alcohol is used as a substance capable of controlling the zeta potential, that is, the potential of the sliding surface. It has been found that it is effective to add substances such as phenol, aldehyde, organic acid, ester, ketone and nonionic surfactant to the liquid. In these substances, the charge distribution in the molecule is not uniform, some parts are slightly positive, some parts are slightly negative, and the total is zero. That is, these materials have dipole moments. It is considered that the non-uniformity of the charge distribution is the reason why the zeta potential of the fine particles or the like changes due to these substances. For example, when various alcohols are used, the value of the zeta potential is different, which can be explained semi-quantitatively by the heterogeneity of the charge distribution in the molecule as follows.

FIG. 3 and FIG. 4 show the charge distribution in the alcohol molecule and the zeta potential of the alcohol molecule adsorbed on the surface of the fine particles, which is obtained by theoretical calculation based on quantum mechanics. The adsorption state of each alcohol on the fine particles 1 is shown in FIG.
The case shown in FIG. 4 and the case shown in FIG. 4 can be considered. In the case shown in FIG. 3, assuming that the position of the sliding surface is the 3rd to 4th atoms from the surface of the fine particles 1, the larger the absolute value of the electric charge of the carbon atom near that position, the larger the absolute value of the zeta potential becomes. You can see that it is getting bigger. That is, when the alcohol is adsorbed,
It can be considered that the local distribution of charges existing in the vicinity of the 3rd to 4th atoms from the adsorption end affects the value of the zeta potential.

On the other hand, in the case shown in FIG. 4, the relationship between the position of an oxygen atom having a large negative charge and the sliding surface is different, and the closer the oxygen atom is to the sliding surface, the larger the absolute value of the zeta potential becomes. Can be considered Therefore, in each case, it is inferred that the magnitude of the zeta potential depends on the nonuniformity of the charge distribution in the alcohol molecule.

However, it is indispensable that a substance capable of controlling the zeta potential is adsorbed on the fine particles, and -O is present in one molecule.
It is a common point that they are substances having a hydrophilic group such as H, —CHO, —COOH, and —NH ₂ and a hydrophobic group composed of a hydrocarbon group, and this is considered to cause adsorption to fine particles.

All of the above substances that can control the zeta potential are substances that are difficult to ion dissociate. When a substance that easily dissociates into ions is added to the liquid, the concentration of ions in the liquid becomes high, and the fine particles easily aggregate. That is, even if the zeta potential is increased, the effect of dispersing the fine particles may not be sufficiently exhibited. Therefore, it is very preferable to use a substance that is difficult to dissociate into ions in order to realize the present invention.

Therefore, it can be understood that a substance which hardly dissociates into ions and has a hydrophilic group and a hydrophobic group in one molecule is effective for controlling the zeta potential. However, the effect of controlling the zeta potential differs depending on the balance between the charge distribution in the molecule and the slip surface. That is, 2 to 6 from the adsorption end of the substance to the fine particles
It can be easily understood that a substance in which the charge distribution of any one of the atoms or a plurality of atoms is negative is effective. Specifically, when those atoms have a large electronegativity such as oxygen atom, halogen atom and nitrogen atom, or the atomic group bonded to them is an electron emitting group or an atom having a large electronegativity. Is. It is also effective to combine a plurality of types of substances.

FIG. 5 is a conceptual diagram showing a state in which two or more kinds of nonionic surfactants or the like having different molecular lengths are adsorbed on the surface of fine particles. As shown in FIG. 5, CH ₃ —R—R—R—OH and CH ₃ —R having different molecular lengths are formed on the surface of the fine particles 1.
-R-OH (R is, - (CH ₂₎ when n- Arco -
Le, R is _{- (CH 2 CH 2 O)} m-, or - (CH ₂₎ n
- and - (CH ₂ CH ₂ O) is when a m- combination is a nonionic surfactant. n and m are integers of about 5 to 20. )
When is adsorbed, the molecular ends of the shorter molecules that are densely adsorbed become pseudo particle surfaces, that is, the sliding surfaces of the fine particles shift to the outside of the ends of the shorter molecules. The hydrophilic group of the longer molecule (including an oxygen atom having a high electronegativity) is located just near the sliding surface, which is an effective method for controlling the zeta potential.

FIG. 6 (a) is a conceptual diagram showing a state in which a nonionic surfactant and an alcohol having a relatively short molecular chain are adsorbed on the surface of the fine particles 1 when they are added in combination. .. 6 (b) and 6 (c) are conceptual diagrams showing a state in which, when a nonionic surfactant or the like and amino alcohol are added in combination, they are adsorbed on the surface of the fine particles 1. is there. 6 (a) to 6 (c), R is the same as in FIG. Thus, when a nonionic surfactant is used in combination with alcohol or amino alcohol, a low molecular weight alcohol or amino alcohol is added to the hydrophobic group portion of the nonionic surfactant or the like. It is considered that zeta potential changes due to adsorption. And
Depending on the type of fine particles, the amount of adsorption increases, so
The change in the data potential also becomes larger. Therefore, the effect of dispersing the fine particles is increased.

In addition to the above-mentioned glycols, those having a greater dispersion effect when combined with a nonionic surfactant or the like are
It is a substance having a hydrophilic group and a hydrophobic group in one molecule such as amine, aldehyde, organic acid, ester and ketone.

The addition concentration of the above-mentioned substance depends on the kind of the substance, but is generally 10 to ^{7 to} 25 v with respect to the solution.
ol%. Addition of 10 to ⁷ vol% or more is effective, and addition of more than 25 vol% is meaningless.

The optimum addition concentration range is 0.1 to 2.5 vol% in the case of alcohol, 10 to ⁷ to 10 to ¹ vol% in the case of amino alcohol, and 0.001 in the case of organic acid. ~
0.1vol%, 0.1-1.0v in case of aldehyde
ol%, and in the case of ketone, it is 0.1 to 2.0 vol%.

[0025]

According to the present invention, by adding a substance capable of controlling the zeta potential to a solution, the absolute value of the zeta potential of the fine particles in the solution is increased, and the absolute value of the zeta potential between the fine particles in the solution is increased. The electrostatic repulsion force of increases. As a result, the potential energy between the fine particles becomes high, and it becomes possible to improve the dispersion of the fine particles or reduce the agglomeration.

At the same time, there is an effect that it is possible to prevent the fine particles from being adhered to the wall surface of the container.

[0027]

EXAMPLES First, a method for measuring zeta potential will be described.

The zeta potential can be usually determined by electrophoresis. Electrophoresis is a phenomenon in which fine particles having a surface charge move when an electric field is applied to the liquid.By measuring the moving speed of the fine particles, the zeta potential of the fine particles, which is proportional to the moving speed, can be determined. You can ask.
In the present invention, LA manufactured by Pen Kem based on this principle is used.
The ZERO potential of the fine particles was measured with a SER ZEE ™ Model 501.

In order to confirm the effect of the present invention, polystyrene particles, Fe particles, Si particles and SiO ₂ particles were used. These particles are used simply because particles having a uniform particle size are easily available, and the effect of the present invention is not limited to these fine particles.

The polystyrene particles are The Dow C
Particle size 1-0.0 made by the chemical company
The one having a size of 38 μm was used. Fe particles, Si particles and Si
O ₂ particles having a particle diameter of 1 μm manufactured by Kojundo Chemical Co., Ltd. were used. There is a case where Si particles are not pretreated, and a case where bare Si particles used in the experiment after being etched in hydrofluoric acid having a volume ratio of HF: H ₂ O = 1: 99 for 1 minute.

It is considered that the value of the zeta potential does not depend on the particle size of the particles, and the measured data at the above particle size is 0.05 μm.
Even ultrafine particles of about m can be used as they are.

Example 1 The effect of controlling the zeta potential of a substance having a hydrophilic group and a hydrophobic group, which is difficult to dissociate into ions, is shown. A wide range of substances such as alcohols, aldehydes, organic acids, esters and ketones were found to have a zeta potential control effect. As an example of the added concentration and the effect of controlling the zeta potential, a case where ethanol is added to bare Si particles etched with hydrofluoric acid will be described.

FIG. 7 shows the relationship between the concentration of ethanol added and the change in the zeta potential of bare Si particles. Bare Si particles before the addition of ethanol were -33.2 mV, but 0.5 vo
It was possible to control the zeta potential of the Si particles to -47.3 mV by adding 1% of ethanol. (Although not shown in FIG. 7, it was effective up to the addition of about 25 vol% (20 wt%).) The addition concentration at which the value of the zeta potential becomes minimum differs depending on the substance, but substances other than ethanol The same result as in FIG. 7 was obtained. Table 1 and Table 2
Table 1 shows the addition concentration when the value of the zeta potential becomes minimum for various substances and the value of the zeta potential at that time.

[0034]

[Table 1]

[0035]

[Table 2]

(Example 2) With respect to amino alcohol, a larger effect was obtained with a smaller addition concentration.
Table 3 shows the change in zeta potential when various amino alcohols were added.

[0037]

[Table 3]

FIG. 8 shows the relationship between the addition concentration when 2-aminoethanol was added and the zeta potential of 1 μm polystyrene particles, and the addition concentration and the zeta potential when monoisopropanolamine was added. FIG. 9 shows the relationship of the cell potential. In the case of amino alcohol, the same substance as in Example 1 is used.
The value of the zeta potential rarely becomes minimum, and as shown in FIGS. 8 and 9, the absolute value of the zeta potential increased as the content was added.

Amino alcohol is 10 to ⁷ mol.
Addition of 1 / l (3 × 10 to ⁶ vol%) or more showed a sufficient effect for controlling the zeta potential.

Example 3 Table 4 shows changes in the zeta potential when an alcohol containing a halogen atom was added.

[0041]

[Table 4]

Hexafluoro-2-propanol and 1
It was found that H, 1H-pentafluoropropanol has an effect of greatly changing the zeta potential. It can be seen that both are more effective than the substances containing no halogen atom.

Example 4 Table 5 shows the change in zeta potential when a substance containing a nitrogen atom was added.

[0044]

[Table 5]

It was found that formamide and N-methylformamide have the effect of greatly changing the zeta potential. It can be seen that both are more effective than the substance containing no nitrogen atom.

(Example 5) _{(R :-( CH 2) n-,} n synthesizes a nonionic surfactant represented by an integer) of about 5 to 20, Ze -. Were studied data potential control effect. The results are shown in Table 6.

[0047]

[Table 6]

It has been found to be effective for many particles. Similar effects can be expected for surfactants having a similar structure.

(Example 6) Two kinds of nonionic surfactants I: CH ₃ (CH ₂ ) ₁₀ CH ₂ O (CH ₂ C) having different molecular lengths
H ₂ O) ₁₂ H and II: CH ₃ (CH ₂ ) ₁₄ CH ₂ O (CH ₂
CH ₂ O) ₁₄ H was synthesized, and the effect of controlling the zeta potential was investigated for these. The results are shown in Table 7.

[0050]

[Table 7]

It has been found to be effective for many particles. The same effect can be expected with a combination of surfactants having a similar structure.

Example 7 Nonionic Surfactant CH
₃ (CH ₂ ) ₁₀ CH ₂ O (CH ₂ CH ₂ O) ₁₂ H and alcohol
Table 8 shows an example in which the two are used in combination.

[0053]

[Table 8]

In particular, the effect of F is small when only alcohol is used.
It was found that e particles, Si particles, SiO ₂ particles, etc. also have a great effect. Of course, similar effects can be expected for alcohols other than ethanol.

Example 8 Table 9 shows an example of a combination of the synthesized nonionic surfactant CH ₃ (CH ₂ ) ₁₀ CH ₂ O (CH ₂ CH ₂ O) ₁₂ H and amino alcohol.

[0056]

[Table 9]

In particular, it was found that Fe particles, Si particles, SiO ₂ particles, etc., which have a small effect only with amino alcohol, have a great effect.

Example 9 The dispersion effect of fine particles according to the present invention was confirmed by the following procedure. As shown in FIG.
0.038 μm polystyrene particles were put into ultrapure water in a cylindrical glass tube (sedimentation tube) having a height of 30 cm to form a suspension, and the particle concentration was adjusted to 5 × 10 ¹¹ particles / cm ³ . )
Shake it and let it stand. It was found that the particle concentration of the suspension decreased with the standing time. The change over time in the particle concentration of polystyrene particles was measured from the light transmittance using a spectrophotometer. The light transmittance is shown as a comparative value when the light having a main wavelength of 420 nm emitted from the spectrophotometer is used, the transmittance of ultrapure water is set to 100, and the opaque material is set to 0. (As a dispersion evaluation method based on transmittance,
For example, Fumio Kitahara, "Chemistry of Dispersion / Emulsion Systems" (Engineering Book 1
979) p.129. ) After adding 3 × 10 to ⁵ vol% of 2-aminoethanol, the change of the particle concentration of polystyrene particles in the sedimentation tube with time was measured in the same manner. The result is shown at 14 in FIG. Almost no change was seen in particle concentration.

Also, the particle concentration did not change much when ethanol was added instead of 2-aminoethanol.

In each case, the dispersibility of the polystyrene particles is improved, and it is clear that the fining time is longer than that in the case where no additive is added.

Example 10 Next, the same dispersion confirmation experiment using polystyrene particles of 0.038 μm was conducted by adding hydrochloric acid to adjust the hydrogen ion concentration of the container. The relationship between the standing time at pH 3 and the particle concentration was the same as the result in ultrapure water and was the same as 13 in FIG. This is shown at 13 in FIG. That is, the particle concentration decreased with the standing time. However, as shown at 15 in FIG. 12, almost no change in particle concentration was observed by adding 3 × 10 to ⁵ vol% of 2-aminoethanol.

Example 11 Next, the same dispersion confirmation experiment was carried out using 0.2 μm polystyrene particles. However, hydrochloric acid was added to adjust the hydrogen ion concentration in the solution, and 0.2 μm polystyrene particles were easily aggregated (particle concentration was adjusted to 4 × 10 ¹² particles / cm ³ ).
When 2-aminoethanol was added in an amount of 3 × 10 to ⁵ % by volume, no change was observed in the particle concentration as shown in 17 of FIG. That is, it is shown that the addition of 2-aminoethanol can prevent the aggregation that has occurred at a certain pH. The particle concentration for each pH in FIG. 13 indicates the particle concentration after a standing time of 5 days.

Example 12 Next, the same dispersion confirmation experiment was conducted using polystyrene particles of 1 μm. 1 μm
Since the particles of No. 1 did not aggregate in ultrapure water, the experiment was conducted by adding hydrochloric acid to adjust the hydrogen ion concentration of the solution. As shown at 18 in FIG. 14, when the pH becomes higher than about pH 2 on the acidic side, the fine particles of 1 μm aggregate. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^{3. The} particle concentration for each pH in FIG. 14 indicates the particle concentration after 5 days of standing time.) 2- When 3 × 10 to ⁵ vol% of aminoethanol was added,
As shown in 19 of 4 above, the hydrogen ion concentration at which aggregation occurred changed. That is, it is shown that the addition of 2-aminoethanol can prevent the aggregation that has occurred at a certain pH, that is, the aggregation can be prevented even in a region having a higher acidity.

It should be noted that even if alkaline, it has a symmetrical effect, and by adding 2-aminoethanol, the region where aggregation occurs can be shifted to a more alkaline region.

(Example 13) Next, the particle diameter was 1 μm in ultrapure water.
m Si particles were suspended and the same dispersion confirmation experiment was performed. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^{3. The} particle concentration for each pH in FIG. 15 indicates the particle concentration after one day of standing time.) As shown by 20 in FIG. If the pH becomes higher than about 2.2 on the acidic side, 1μ
The m particles become aggregated.

Nonionic surfactant 10 used in Example 7
~ ⁷ mol / l and 2-aminoethanol 3 x 10 ~ ⁵ vo
When 1% was added, the hydrogen ion concentration at which aggregation occurred changed to a more acidic side as shown by 21 in FIG. That is, it was found that the addition of 2-aminoethanol can prevent the aggregation that has occurred at a certain pH.

Example 14 Next, the volume ratio of HF: H ₂ O was changed.
= 1:99 hydrofluoric acid was prepared to suspend bare Si particles having a particle diameter of 1 µm, and the same dispersion confirmation experiment was performed. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^3. )
As indicated by 22 in FIG. 16, it was found that the particle concentration decreased with standing time. Next, after adding 10 to ⁷ mol / l of the nonionic surfactant used in Example 7 and 3 × 10 to ⁵ vol% of 2-aminoethanol, a dispersion confirmation experiment was conducted in the same manner. The obtained result is also shown at 23 in FIG. Almost no aggregation was observed.

(Example 15) Next, the particle diameter was 1 μm in ultrapure water.
m SiO ₂ particles were suspended and the same dispersion confirmation experiment was conducted. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^{3. The} particle concentration for each pH in FIG. 17 indicates the particle concentration after one day of standing time.) As shown in 24 of FIG. When the acidic side becomes larger than about pH 2.2,
1 μm particles become aggregated. When the nonionic surfactant used in Example 7 (10 to ⁷ mol / l) and 2-aminoethanol (3 × 10 to ⁵ vol%) were added, the amount of 25 in FIG.
As shown in, the concentration of hydrogen ions causing aggregation changed to a more acidic side. That is, it was found that the addition of 2-aminoethanol can prevent the aggregation that has occurred at a certain pH.

(Example 16) Next, the particle size was 1 μm in ultrapure water.
Fe particles of m were suspended, and the same dispersion confirmation experiment was performed. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^{3. The} particle concentration for each pH in FIG. 18 indicates the particle concentration after a standing time of one day.) As shown in 26 of FIG. In particular, when the acidic side becomes larger than about pH 3, 1 μm particles are aggregated. The nonionic surfactant used in Example 7 (10 to ⁷ mol / l) and 2-aminoethanol were mixed with 3 ×.
When 10 to ⁵ vol% was added, the hydrogen ion concentration at which aggregation occurred changed as shown by 27 in FIG. That is,
It has been found that the addition of 2-aminoethanol can prevent the aggregation that has occurred at a certain pH.

Example 17 Next, the relationship between the concentration of 2-aminoethanol added and the dispersion effect was examined. 1 μm
The polystyrene particles of were suspended and the same dispersion confirmation experiment was performed. (The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ^{3. The} particle concentration for each pH in FIG. 19 shows the particle concentration after 5 days of standing time.) As shown in 28 of FIG. When the acidic side becomes larger than about pH 2.2,
1 μm particles become aggregated. 2-aminoethano
When 3 × 10 to ⁵ vol% of hydrogen was added, the hydrogen ion concentration at which aggregation occurred changed as indicated by 29 in FIG. Two
It was revealed that when the addition concentration of -aminoethanol was set to 3 x 10 to ³ vol, the hydrogen ion concentration at which agglomeration occurred was further reduced and the dispersion effect was further increased, as indicated by 30 in FIG. That is, 2-aminoethano-
It is considered that the absolute value of the zeta potential of the fine particles increased due to the increase in the addition concentration of the ruthenium, and the dispersion effect increased accordingly. Therefore, the same effect can be expected for other particles by increasing the addition concentration.

Example 18 Next, the volume ratio of HF: H₂O
= 1: 99 of hydrofluoric acid is prepared and S of particle diameter 1 μm is prepared.
The i particles were suspended, and the same dispersion confirmation experiment was performed.
(Particle concentration is 5 × 10 ¹³Pieces / cm³Adjusted to. ) In Figure 20
It can be seen that the particle concentration decreases with standing time as shown.
won. Next, the nonionic surfactant 1 used in Example 7
0 ~⁷mol / l and 1-vol% of m-aminophenol
After adding, the dispersion confirmation experiment was performed in the same manner, and was obtained.
The result is also shown at 32 in FIG. Almost no aggregation
I couldn't.

(Example 19) Next, in volume ratio, HF: H ₂ O was used.
= 1: 99 of hydrofluoric acid is prepared and S of particle diameter 1 μm is prepared.
The i particles were dispersed, and the same dispersion confirmation experiment was performed.
(The particle concentration was adjusted to 5 × 10 ¹³ particles / cm ³ ).
As shown in Fig. 1, it was found that the particle concentration decreased with the standing time. Next, after adding 10 to ⁷ mol / l of the nonionic surfactant used in Example 7 and 0.5 vol% of formamide, a dispersion confirmation experiment was conducted in the same manner, and the obtained results are also shown in FIG. Shown in. Almost no aggregation was observed. From the above dispersion confirmation experiment, it was demonstrated that the control of the zeta potential described in the present invention is effective in reducing the dispersion and aggregation of the fine particles.

(Embodiment 20) FIG. 22 shows an example of a distributed control system for carrying out the present invention. In FIG. 22, the suspension charged from the raw material charging unit 35 and the zeta potential control substance supplied from the zeta potential control substance storage unit 36 through the addition concentration control unit 37 are the stirring tank 38. It is sent to and mixed and dispersed to produce a ceramic raw material.

[0074]

EFFECTS OF THE INVENTION According to the present invention, since it is possible to improve the dispersion and aggregation of fine particles in a liquid, it is possible to produce fine particles having good fine particle dispersibility at a low cost in the process of producing a material. ..

The present invention can also be expected to be effective as an aggregating agent by combining the substance according to the present invention with fine particles.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a particle-particle distance and a potential energy according to the present invention.

FIG. 2 is a graph showing the relationship between the zeta potential of fine particles and the particle concentration.

FIG. 3 is a diagram showing the charge distribution of alcohol molecules adsorbed on the surface of fine particles and the potential on the sliding surface.

FIG. 4 is a diagram showing the charge distribution of alcohol molecules adsorbed on the surface of fine particles and the potential on the sliding surface.

FIG. 5 is a view showing nonionic surfactant molecules or alcohol molecules adsorbed on the surface of fine particles.

FIG. 6 (a), FIG. 6 (b) and FIG. 6 (c) are diagrams showing adsorbed states when a nonionic surfactant and alcohol are added in combination.

FIG. 7 is a diagram showing the relationship between the concentration of ethanol added and the zeta potential of bare Si particles.

FIG. 8 is a diagram showing the relationship between the added concentration of 2-aminoethanol and the zeta potential of polystyrene fine particles.

FIG. 9 is a graph showing the relationship between the zeta potential of fine particles and the concentration of monoisopropanolamine added.

FIG. 10 is a conceptual diagram showing a method for measuring a particle concentration change by a spectrophotometer.

FIG. 11 is a diagram showing a relationship between a standing time of a polystyrene particle suspension and a change in particle concentration.

FIG. 12 is a diagram showing a relationship between a standing time of a polystyrene particle suspension and a change in particle concentration.

FIG. 13 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 14 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 15 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 16 is a diagram showing a relationship between a standing time of a suspension of bare Si particles and a change in particle concentration.

FIG. 17 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 18 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 19 is a diagram showing a relationship between hydrogen ion concentration and particle concentration.

FIG. 20 is a diagram showing the relationship between the standing time of a suspension of Si particles and the change in particle concentration.

FIG. 21 is a diagram showing a relationship between a standing time of a suspension of Si particles and a change in particle concentration.

FIG. 22 is a diagram showing an example of a distributed control system according to the present invention.

[Explanation of symbols]

1 ... fine particles, 2 ... fine particles, 3 ... surface charge, 4 ... bare Si
Particles, 5 ... Si particles, 6 ... Fe particles, 7 ... Sliding surface, 8 ...
Suspension of fine particles, 9 ... Spectrophotometer laser irradiation part, 10 ...
Spectrophotometer laser light receiving part, 11 ... Laser light, 12 ... Sedimented fine particles, 13 ... In case of no addition, 14 ... In case of adding 2 × 10 to ⁵ vol% of 2-aminoethanol, 15 ... When 1 vol% of ethanol is added, 16 ... When no addition is added, 17 ... 2-Aminoethanol is added at 3 × 10 to ⁵ vol%
In the case of addition, 18 ... In the case of no addition, 19 ... In the case of adding 3 × 10 to ⁵ vol% of 2-aminoethanol, 20 ...
In the case of no addition, 21 ... Nonionic surfactant 10 to ⁷ mol
/ L and 2-aminoethanol added at 3 x 10 to ⁵ vol%, 22 ... no addition, 23 ... nonionic surfactant 10 to ⁷ mol / l and 2-amino ethanol at 3 x 1
If 0 to ⁵ vol% is added, 24 ... 25 without addition
... nonionic surfactant 10 ~ ⁷ mol / l and 2 aminoethanol - when added Le 3 × 10 ~ ⁵ vol%, when the 26 ... no additive, 27 ... non-ionic surfactant 10 ~ ⁷ mol /
1 and 2-aminoethanol were added in an amount of 3 × 10 to ⁵ vol%, 28 ... No addition was added, 29: 2-aminoethanol was added in an amount of 3 × 10 to ⁵ vol%, 30 ... -When adding 3 x 10 to ³ vol%
1 ... In case of no addition, 32 ... Nonionic surfactant 10 to ⁷ m
ol / l and 2 aminoethanol - Le 3 × 10 ~ ⁵ vol%
When added, 33 ... When not added, 34 ... Nonionic surfactant 10 to ⁷ mol / l and 2-aminoethanol 3
When adding 10 to ⁵ vol%, 35 ... Raw material charging part, 3
6 ... Zeta potential control substance storage section, 37 ... Addition concentration adjusting section, 38 ... Stirring tank, 39 ... Zeramix processing section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Osamu Oka, 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture

Claims (11)

[Claims] 1. A substance capable of controlling the zeta potential (surface potential) of fine particles in a solution is added to the solution in an amount of 10 to ^{7 to} 25 vo.
A method for dispersing fine particles in a liquid, which comprises improving the dispersion or reducing aggregation of the fine particles as an adsorbent in a solution by adding at an addition concentration within the range of 1%. 2. A substance capable of controlling the zeta potential of fine particles in a solution is a substance having a charge distribution in the molecule (dipole mode).
A substance having a ment). 3. The method for dispersing fine particles in a liquid according to claim 1, wherein the substance capable of controlling the zeta potential of the fine particles in the solution is a substance having a hydrophilic group and a hydrophobic group in one molecule. 4. The substance capable of controlling the zeta-potential of fine particles in a solution is composed of any one of 2 to 6 atoms from the end of the molecule, or a molecule having a negative charge distribution of a plurality of atoms. The method for dispersing fine particles in a liquid according to claim 1, which is a substance. 5. The method for dispersing fine particles in a liquid according to claim 1, wherein the substance capable of controlling the zeta potential of the fine particles in the solution is a substance which is difficult to dissociate into ions. 6. A substance having a hydrophilic group and a hydrophobic group in one molecule,
The method for dispersing fine particles in liquid according to claim 3, wherein the hydrophobic group is a substance in which some or all of hydrogen atoms are replaced with halogen atoms. 7. The method for dispersing fine particles in a liquid according to claim 1, wherein the substance capable of controlling the zeta potential of the fine particles in the solution is a substance having an amino group and a hydroxyl group in one molecule. 8. A substance having a hydrophilic group and a hydrophobic group in one molecule,
The method for dispersing fine particles in a liquid according to claim 3, wherein the hydrophobic group is a substance in which some or all of hydrogen atoms are replaced with nitrogen atoms. 9. The method for dispersing fine particles in a liquid according to claim 2, which is carried out by adding two or more kinds of substances having different molecular lengths. 10. The method for dispersing fine particles in a liquid according to claim 1, which is carried out by adding at least one nonionic surfactant and a substance having a hydrophilic group and a hydrophobic group in one molecule. 11. The method for dispersing fine particles in liquid according to claim 1, wherein the non-adsorbent is a compound containing an inorganic substance or an organic substance including various metals, alloys, and ceramics.