JPS62212202A - Inorganic oxide spherical fine particle and production thereof - Google Patents

Abstract

PURPOSE:Inorganic oxide monodispersed spherical fine particles, consisting of cesium salt of a heteropolyacid, having an almost spherical particle shape, specific average particle diameter and particle size distribution and smooth surface. CONSTITUTION:Inorganic oxide spherical fine particles which are monodispersed fine particles consisting of cesium salt of a heteropolyacid acid having the Keggin structure and smooth surface as well as the following morphological characteristics (a)-(c). (a) An almost spherical particle shape. (b) The average particle diameter is within the range of 0.01-0.3mum (not including 0.3mum). (c) The standard deviation value of the particle diameter is within the range of 1.0-2.0. The above-mentioned heteropolyacid is expressed by the formula (m is an integer of 3-7; n is a positive number determined by the constituent elements; X is at least one element selected from the group consisting of phosphorus, arsenic, silicon, germanium and boron; Z is at least one element which may contain vanadium to the range of 1/3 expressed in terms of atomic ratio and is selected from tungsten and molybdenum).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to novel inorganic oxide spherical fine particles and a method for producing the same. Specifically, fine particles made of a cesium salt of a heteropolyacid (a) have an almost perfect spherical shape; (
b) Average particle diameter is 0.01 μm to 0.3 μm (however, 0.01 μm to 0.3 μm
．． The present invention relates to monodispersed, smooth-surfaced inorganic oxide spherical fine particles having the following characteristics: ÷<C> standard deviation value of particle diameter is in the range of 1.0 to 2.0 (excluding 3 μm). Furthermore, in the production of the present invention, a homogeneous solution in which cesium and the element group that generates the heteropolyacid coexist is first heated with w.
The present invention relates to a method for producing inorganic oxide spherical fine particles having the above-mentioned characteristics by preparing a solution of 4 and then adjusting I)H of the solution to a range of 0.1 to 6.5.

In recent years, true spherical fine particles have become required in various fields such as electronics, electrical equipment, paints, textiles, plastics, polishing, and medicine, and fine particles made of various materials such as organic materials and non-embroidered materials have been researched and developed. However, the current situation is that they are not able to adequately respond to diverse needs. For example, fine particles mainly made of organic polymers generally have insufficient heat resistance, electrical conductivity, and thermal conductivity, while fine particles made of solid materials such as calcium sulfate, silica, and alumina generally have a wide particle size distribution and are prone to agglomeration. There are drawbacks such as.

In addition to the above-mentioned shape characteristics (a), (b), and (c), the inorganic oxide spherical fine particles disclosed in the present invention have
It has good dispersion in polar solvents such as water and alcohols.It has chemical resistance when dispersed and mixed in polyester resin, etc. ÷ It has heat resistance up to about 750℃ ÷ It has electrical conductivity and volume resistivity. It has characteristics such as a value in the range of 103 to 10 TΩ・α, and is also expected to have various specific physical properties such as chemical and electrical functions derived from the heteropolyacid structure, and is of industrial significance. It is something.

[Prior Art] Cesium salts of heteropolyacids having a Keggin structure have been known (Kagaku to Kogyo, Vol. 11, No. 4, p. 32).
2-0328 (1958), etc.).

Also, a solution of heteropolyacid (this solution exhibits strong acidity)
It is also known that when cesium ions are mixed with cesium ions, fine particle precipitates consisting of cesium salts of heteropolyacids are formed (Proceedings of the 49th Spring Annual Meeting of the Chemical Society of Japan, 1 p.3
7 (1984), etc.). However, until now, no literature has been found that describes the properties of the particles in detail, such as their shape.

The present inventors conducted a detailed study on the manufacturing method and the properties of fine particles for cesium salts of various heteropolyacids, and found that a fine particle manufacturing method using a conventionally known method (hereinafter referred to as cesium direct The mixing method (abbreviated as "mixing method") only resulted in non-uniform particle shapes and particle sizes. FIG. 2 attached hereto shows an example of an electron microscopic image of particles produced by a conventionally known method. However, the particle shape image shown in FIG. 2 is an example, and
Reaction conditions for the cesium direct mixing method (e.g. temperature,
depending on the addition time, etc.) or the type of heteropolyacid, etc.
Although the shape, particle size, etc. vary, it has not been possible to obtain inorganic oxide spherical fine particles having the characteristics disclosed in the present invention in any case.

[Problems to be Solved by the Invention] As mentioned above, the object of the present invention is to produce fine particles made of a cesium salt of a heteropolyacid, which cannot be achieved by conventionally known methods; , (b) within the specified average particle size range, and (c) to obtain inorganic oxide fine particles with novel characteristics in which the particle size distribution is kept within a certain range, and other purposes are as described above. The object of the present invention is to provide a new industrial method for producing inorganic oxide fine particles having new properties.

[Means for Solving the Problems] According to the findings of the present inventors, the reaction between heteropolyacid and cesium ions is very fast. Therefore, for example, when a cesium-containing solution is added to a solution of heteropolyacid, the addition At the same time, insoluble cesium heteropolyacid salt is precipitated, and as cesium is added, the amount of precipitation increases, and the cesium reacts until the value of C3+/heteropolyacid=3/1 (molar ratio). Then, the precipitates at various cesium addition levels are separated and
Linear diffraction analysis revealed that the precipitated particles at all stages were structurally cesium salts of heteropolyacids, but electron microscopic observation revealed that the particle shapes were nonuniform and the particle size distribution was wide. Therefore, after various studies, we found that the precipitation mechanisms of insoluble salts are: 1. Nucleation, 2. Nuclear growth, and 2. particle formation.
When considered separately in stages, in the cesium direct mixing method, the reaction rates of (1) and (2) are unbalanced and proceed concurrently, resulting in a polydisperse and non-uniform particle group with a wide particle size distribution. I came to the conclusion that no.

The present invention was discovered as a result of intensive studies in view of the problems in the prior art described in E. The specific strategy is: 1) First prepare a homogeneous solution in which cesium and the elements that can constitute a heteropolyacid coexist; By adjusting to pl-1, a cesium salt is produced together with a heteropolyacid. By the above-mentioned manufacturing method, for the first time, child-dispersible inorganic oxide spherical fine particles having the novel characteristics disclosed in the present invention as illustrated in the attached FIG. 1 were obtained.

[Work] The present invention will be specifically explained in detail below.

The inorganic oxide fine particles specified by the present invention have the following general formula (I) HmXZt 2O+a−nH2O(I) (where the formula (I
) where m is an integer from 3 to 7, n is a positive number determined by the constituent elements, X is at least one element selected from the group consisting of phosphorus, arsenic, silicon, germanium, and boron, and 2 is vanadium in atomic ratio. A cesium salt of a heteropolyacid having a Keggin structure, each representing at least one element selected from the group consisting of tungsten and molybdenum, which may be contained up to 1/3 of the cesium salt. is generally represented by the following general formula (I[).

H, LC8,,
is 2 to 3, a + b = ta (m is the same as in formula (I), and C represents O or a positive number, respectively) As a specific substance represented by general formula (II), for example, 12-tung cesium sulfate, 12-tungstohim mt-sium, 121 cesium silicate, 12
-tungst cesium germanate, 12-tungst l
Cesium acid, cesium 12-molybdophosphate, cesium 12-molybdoborate, 12-T::cesium ribdosilicate, cesium 12-molybdogermanate, cesium 12-molybdoborate, and H3PMOxWt 2-X0
411 ・n +12O. HsSi MoxWt
2-XO40・nl-12Q, Hs BMOxWt 2
-X04Q ・n H2O (x is an integer from 1 to 11), H4PMOI s Vt 040 -n H2O゜Hs PMO9V3 04 o on H2O゜1-1s PWt a V2O4 a ・n H2O
Examples include cesium salts of complex coordination heteropolyacids such as, but these are merely examples and are not limited to the above substances. When forming particles, it is naturally possible to form them from a mixture of cesium salts of the above-mentioned heteropolyacids, and the above general formula (I[) indicates the average composition in the particles.

"Smooth surface" as disclosed in the present invention means that the surface has no irregularities (uniform surface) as a result of electron microscope observation at 100,000 times magnification.Furthermore, "monodispersed" means that the particle size It means that the distribution is narrow and there are no aggregates.Also, "the particle shape is almost perfectly spherical" means that the major axis and minor axis of each particle of 100 particle groups within an arbitrary field of view in an electron microscope observation image of particles. This means that the ratio of the major axis to the minor axis is 1.10 or less for more than half of the particles.

Next, specific embodiments of the method of the present invention will be explained.

First, a group of elements (group A) (at least one element selected from phosphorus, arsenic, silicon, germanium, and boron) that can constitute the heteropolyacid in the first step of producing spherical fine particles disclosed in the present invention ) and group B (tungsten,
To prepare a homogeneous solution in which molybdenum is coexisting with at least one element selected from molybdenum (which may contain up to 1/3 of vanadium in atomic ratio) and cesium, for example, 12-tung When producing particles made of cesium strinate, a compound containing phosphorus as Group A, such as an inorganic phosphorus compound such as phosphoric acid, ammonium phosphate, or sodium phosphate, or an organic phosphorus compound such as triethyl phosphate, and tungsten as BRY. Uniformly dissolving tungsten-containing compounds such as ammonium acid, sodium tungstate, and tungsten oxide, inorganic cesium compounds such as cesium nitrate, cesium carbonate, cesium chloride, and cesium sulfate, or organic compounds such as cesium acetate as cesium compounds. Consisting of In this case, it is naturally possible to use compounds that share both groups, such as ammonium phosphotungstate. The same applies to compounds of group A and group B other than phosphorus and tungsten. In this case, the solvent may be water, ethanol, acetone, ethylene glycol, etc., as long as it dissolves the compound containing the above element group, but if it is difficult to dissolve, use appropriate means such as pH, temperature, and solvent selection to create a homogeneous solution. Good too. In this case, preferably liquid water is used as the solvent. In this case, homogeneous dissolution means that most of the compounds are dissolved, including the case where some inert substances coexist.

The addition ratio of group A, group B, and cesium is not particularly stipulated, but considering the yield of particle generation, the atomic ratio of group A, group B, and cesium is
Group: Cesium is preferably in the range of 1 to 6:12:0.3 to 5.

In addition, as a special case of the first step described above, the heteropolyacid is decomposed by adding a basic substance such as caustic soda to the solution of the heteropolyacid prepared in advance to make pl-1 1, and then the i-cesium compound is added. Naturally, methods for preparing a homogeneous solution are also included.

Further, for the purpose of reducing the particle size to 1, a small amount of fine particles such as silicic acid sol or a cesium salt of a heteropolyacid may be added or allowed to coexist as a single crystal nucleus material during or after the first stage preparation. In this case, the solution may become slightly cloudy due to the crystal nucleus material.

Next, in the second step, the l)H of the above-mentioned homogeneous solution is adjusted to heterogenize the element group that can constitute the heteropolyacid, and to precipitate it as a cesium salt. Preferred p in this case
The range of H varies depending on the constituent elements and reaction conditions such as temperature, but the pH is in the range of 0.1 to 6.5, more preferably in the range of 0.5 to 5.0. pH
If the pH is too low, the yield of particles will be poor, and if the pH is high, the time required for heterogenization will be long, which is undesirable. Various pH adjusting materials can be used in this case, including mineral acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as acetic acid and oxalic acid; and substances that decompose to produce acidic substances. Preferably, they are used in either gaseous, solid or liquid state. Further, when the elements in the pH moderation material are included in the above group A or group B, the addition of the pH adjusting material can also serve as the addition of part or all of group A or group B.

Although the reaction temperature is not particularly limited, it is preferably in the range of 10°C to 150°C, and the lower the temperature, the smaller the average particle diameter tends to be.

By the above-described production method, the particle size distribution, expressed as standard deviation value, was in the range of 1.0 to 2.0, and by applying more preferable conditions, it was possible to make it in the range of 1.0 to 1.5.

The following steps can then be included after the second step if desired. In addition, when the particles are obtained as a suspension, ionic impurities in the solution are removed using an ion exchanger such as an anion exchange resin and/or a cation exchange resin, and the particles are prepared as a powder. When obtained as a cesium salt, the particles formed of the cesium salt containing a heteropolyacid are separated by a conventional method such as centrifugation, filtration, and solvent distillation, and then the particles are optionally washed and dried. Further, when obtaining an anhydride of the particles, it can be calcined at a temperature of up to 750°C. No change was observed in the crystal structure, particle shape, distribution, etc. of any of the particles obtained by the method of the present invention, even when they were anhydrated. Therefore, it was confirmed that the inorganic oxide spherical fine particles disclosed in the present invention have heat resistance up to nearly 750° C., which is the melting point of cesium heteropolyacid.

The present invention will be explained in more detail below with reference to Examples.

However, the average particle diameter is 10% of any particle in a 1m electron microscope image.
The diameter of 0 particles was measured and the standard deviation value was determined using the following formula.

(However, Xi indicates the i-th particle size and n = 100.) Example 1 70 mL of water was placed in a 1 Jl glass round-bottomed flask equipped with a stirrer, thermometer, reflux condenser, pH measuring electrode, and dropping funnel.
0d, sodium tungstate (Na 2 WO4.
2H2O) 1400, sodium metasilicate (Na
After dissolving 15.1 g of 2 Si 03 ・9)-Iz O) in a uniform solution under stirring, cesium nitrate (c3NO3) was dissolved.
27. h, Si:W:C3=1.5:1
A homogeneous solution containing 2:4 (atomic ratio) was prepared. Next, the flask is heated to a temperature at which the solvent refluxes (
After the temperature was raised to 104°C), concentrated hydrochloric acid was added to the solution to adjust the PTL of the solution to 1.8. The solution was stirred at that temperature for 3 hours (1, ooOrpi), followed by a heteroization reaction to obtain a suspension. During that time, the pH of the solution was adjusted by adding hydrochloric acid. After the reaction, it was cooled to room temperature and centrifuged to separate the precipitate. The precipitated particles were washed with water twice, centrifuged twice, and then flushed with acetone. , air-dried to powder particles of 90%
g (referred to as sample A) was obtained.

In addition, Sample B was obtained by firing a portion of Sample A and (7) at 700° C. in an air atmosphere.

Structural formula based on X-ray diffraction and elemental analysis results of these particles,
Table 1 shows the measurement results of the particle surface condition, particle shape, average particle diameter, standard deviation value of particle diameter, etc., as measured by electron microscope IJlilJ observation at a magnification of 100,000 times.

Figure 1 also shows an electron microscope image of the sample FIB (100,000x,
The scale unit is 1.0 μm).

Comparative Example 1 12-Tungstocesium silicate grains - Reporting Example 1
Particles were manufactured using the same equipment as in Example 1 and the following manufacturing method except that the same weight ratio was used.

The pH of an aqueous solution consisting only of sodium tungstate and sodium metasilicate was adjusted to 1.8 with concentrated hydrochloric acid, and the solution was heated under reflux for 3 hours to carry out the heterogenization reaction. At this time, most of the raw material compounds are 12-tungstosilicic acid (H4S
It was confirmed by infrared analysis that it had been converted into a heteropolyacid (i t Wt 2O4G .nH2O). Next, the above heteropolyacid-containing solution was mixed with stirring (1,OOOrp
g+) An aqueous cesium nitrate solution was added to obtain a suspension. Thereafter, the same procedure as in Example 1 was carried out to obtain an air-dried sample and a sample of the fired particles at 01700°C. The results are shown in Table-1.

Furthermore, FIG. 2 shows a 1-filtration image of the sample under an electron microscope (100,000 times, scale unit: 1.0 μι).

Example 2 Example 1 except that ammonium tungstate was previously dissolved in an aqueous sodium hydroxide solution, and cerium carbonate and sium were added to obtain a homogeneous solution, and then the heteroization reaction was performed at room temperature. I did the same thing.

At this time, the composition in the homogeneous solution is P:W:C5=1:12:3
(atomic ratio). Table 1 shows the measurement results of the particles after firing at 500''C.

Comparative Example 2 Production of cesium phosphoric acid particles using the same equipment as in Example 1.
12O) was dissolved in water, and a stirring aqueous solution of cesium legate was added dropwise at room temperature to obtain a suspension. The final raw material addition composition at this time was P:W:Cs-1:12:3 (atomic ratio).

Table 1 shows the measurement results of the particles after firing at 500°C.

Example 3 Phosphormolybdic acid (H3Pt MOt2
O4 a -n H2O,n is approximately 4.1: Nippon Inorganic Chemical Industries) was added, and then pated with aqueous sodium hydroxide solution.
After adjusting H to 4.5, cesium nitrate was added to obtain a homogeneous aqueous solution. Thereafter, the flask was ice-cooled to maintain the liquid temperature at 5° C., and while stirring, a nitric acid aqueous solution was added to adjust the pH to 1.8. After the reaction was continued for 1 hour to obtain a suspension, the same procedure as in Example 1 was carried out to produce calcined powder particles treated at 500°C. The results are shown in Table-1.

Comparative Example 3 Production of cesium 12-molyphosphate fine particles Example 3
In , instead of preparing a homogeneous aqueous solution containing phosphorus, molybdenum and cesium, an aqueous phosphomolybdic acid solution (14 mfM%, pH 1,1) was maintained at 5° C. and stirred in Iir! A 10% by weight aqueous solution of cesium acid was added dropwise to obtain a suspension. Thereafter, the same procedure as in Example 1 was carried out to obtain a fired powder treated at 500°C.

The results are shown in Table-1.

Example 4 A powder calcined at 500°C was obtained in the same manner as in Example 1 except that molybdic acid (H2MO04.H2O) was used in place of sodium tungstate in Example 1 of 12-Molyc. -1.

Comparative Example 4 12-Molybdenum Caesium Fine Particles-1 Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that molybdic acid was used instead of sodium tungstate, and the results shown in Table 1 below were obtained.

Example 5 Moribana: 1st part.

Using the same equipment as in Example 1, molybdenum trioxide 72, O
g, vanadium pentoxide 12.1 g, phosphoric acid (85f [%
) 4.8 (l c15t and concentrated nitric acid 10d to water 80
The mixture was added to 0 d and heated under reflux with stirring for 24 hours to obtain a deep red solution. Insoluble matter in the solution was removed by filtration, and the solution was returned to the same reactor. Next, a 10% by weight aqueous sodium hydroxide solution was added at room temperature to adjust the pH to 4.5, and 32.1 tJ of cesium nitrate was added to prepare a homogeneous solution in WA. Add 20% Wii! to the above solution. Acid was added dropwise to adjust the pH of the solution to 1.8, causing a heteroization reaction.Brr4
I got some liquid. After that, the same procedure as in Example 1 was carried out, and the following table-1
I got the result.

Comparative example 5 Molybdovanatriate cesium fine particles.

In Example 5, the pH was adjusted to 4.5.
The procedure was repeated in the same manner, except that cesium sulfate was adjusted to 1.8 and cesium sulfate was added as a 10% by weight aqueous solution to obtain a direct suspension.

[Brief explanation of drawings]

Figure 1 is an electron microscope #A leap image showing the particle structure of sample B obtained by the method of Example 1, magnified 100,000 times, scale unit 1.
．． 0 μm), and FIG. 2 shows an electron microscope layer image (10 μm) showing the particle structure of the sample obtained by the method of Comparative Example 1.
10,000 times, scale unit 1.0μ■).

Claims (5)

[Claims] (1) Fine particles consisting of a cesium salt of a heteropolyacid having a Keggin structure, which are as follows (a), (b) and (c)
Monodispersed inorganic oxide spherical fine particles with a smooth surface that satisfy the following. (a) The particle shape is almost perfectly spherical. (b) Average particle diameter of 0.01 μm to 0.3 μm (however, 0.01 μm to 0.3 μm
．． (excluding 3 μm). (c) The standard deviation value of particle diameter is in the range of 1.0 to 2.0. (2) The heteropolyacid has the following general formula (I) HmXZ_1_2O_4_0・nH_2O(I) (However, in the general formula (I), m is an integer from 3 to 7, n is a positive number determined by the constituent elements, and X is At least one element selected from the group consisting of phosphorus, arsenic, silicon, germanium, and boron; Z is at least one element selected from the group consisting of tungsten and molybdenum, which may contain vanadium up to 1/3 in atomic ratio; each represents a kind of element)
Claim (1) characterized by:
The inorganic oxide spherical fine particles described above. (3) In the production of inorganic oxide spherical fine particles made of a cesium salt of a heteropolyacid having a Keggin structure, the pH of a homogeneous solution in which cesium and a group of elements capable of forming a heteropolyacid coexist is adjusted to a range of 0.1 to 6.5. 1. A method for producing monodispersed spherical inorganic oxide particles with a smooth surface, characterized by precipitating a cesium salt of a heteropolyacid by adjusting the conditions. (4) The element groups that generate heteropolyacids are Group A (at least one element selected from phosphorus, arsenic, silicon, germanium, and boron) and Group B (a group consisting of tungsten and molybdenum, which may contain vanadium). The method according to claim (3), characterized in that the method comprises at least one element selected from the following. (5) The method according to claim (3) or (4), characterized in that the pH of the homogeneous solution is adjusted to a range of 0.5 to 5.