JP6678041B2 - Fine barium carbonate particles - Google Patents

Description

  The present invention relates to fine barium carbonate particles and a method for producing the same.

  Barium carbonate is widely used as a raw material for electronic materials, in the manufacture of ferrite magnets, and as an additive for CRT glass. With the miniaturization of electronic devices, barium carbonate used for the above applications is required to have fine particles having a uniform composition.

  Barium carbonate is usually obtained by removing impurities from barium salts (barium hydroxide, barium chloride, barium nitrate, etc.) by recrystallization, filtration, etc., preparing an aqueous solution of the obtained barium salt, and then adding carbon dioxide gas to the aqueous barium salt solution. Or a solution of a water-soluble carbonate (ammonium carbonate, sodium carbonate, potassium carbonate, etc.) is mixed.

JP-A-2005-044744 JP-A-7-025611

However, the barium carbonate obtained by the conventional method has a problem that particles are easily aggregated, the shape is acicular, and the barium carbonate does not become a true sphere. That is, Patent Document 1 describes that spherical barium carbonate can be obtained by mixing a gluconic acid-based salt with a barium compound and reacting it with carbon dioxide or a water-soluble carbonate. However, the obtained barium carbonate particles were substantially spherical with a large aspect ratio, and true spherical particles were not obtained. In addition, Patent Document 2 describes that a reaction is performed in an excess state of a barium salt, and a carboxylic acid is added to suppress abnormal growth of barium carbonate particles to obtain fine particles. Were needle-like particles. As described above, in the prior art, a spherical shape, or even a spherical shape having a hollow structure, has not been reported. As described above, conventionally known barium carbonate particles do not have a true spherical shape or a hollow shape, and in the above-mentioned various applications, particularly in the case of a film-like or sheet-like shape, the filling property and the light weight ratio are sufficient. It was not satisfactory.
Accordingly, an object of the present invention is to provide fine spherical or hollow true spherical barium carbonate particles and a method for producing the same.

  Therefore, the present inventors have conducted various studies to obtain true spherical or hollow true spherical barium carbonate particles.As a result of spray pyrolysis of an organic acid barium solution, the particle diameter is small, and a true spherical or hollow true spherical particle is obtained. The present inventors have found that barium carbonate particles can be efficiently obtained, and have completed the present invention.

  That is, the present invention provides the following [1] to [4].

[1] Fine barium carbonate particles having an average circularity of 0.75 or more and an average particle size of 0.1 μm to 20 μm.
[2] A shell having a hollow chamber, the shell having a thickness of 1.5 to 27% of the average particle diameter, an apparent density of 0.4 to 4.5 g / cm ³ , and a hollow ratio of 10 to 90%. [1] Fine barium carbonate particles according to [1].
[3] The fine barium carbonate according to [1] or [2], wherein the bulk density is 0.1 to ² g / cm ³ , the compressive strength is 0.3 to 150 MPa, and the BET specific surface area is 0.1 to 35 m ² / g. particle.
[4] The method for producing fine barium carbonate particles according to any one of [1] to [3], wherein the barium organic acid salt solution is subjected to spray pyrolysis.

  Since the barium carbonate particles of the present invention have a small particle size and a true spherical shape with an average circularity of 0.75 or more, the filling property into a film or sheet shape is good. In the case of hollow particles, high filling properties and reduction in the weight of the filling can be improved.

3 shows an SEM image of barium carbonate particles. 3 shows an SEM image showing a cross section of barium carbonate particles. 3 shows an XRD image of barium carbonate particles.

The fine barium carbonate of the present invention is characterized in that the average circularity is 0.75 or more and the average particle size is 0.1 μm to 20 μm.
The shape of the fine barium carbonate particles of the present invention is substantially spherical, and the average circularity is 0.75 or more. The preferred average circularity is 0.8 or more. Such a shape is achieved by manufacturing by a spray pyrolysis method.

Here, the circularity is determined by measuring the projected area (A) and the perimeter (PM) of a particle from a scanning electron micrograph, and assuming that the area of a perfect circle with respect to the perimeter (PM) is (B), Circularity is expressed as A / B. Therefore, since the circumference and the area of a perfect circle having the same circumference as the circumference (PM) of the sample particle are PM = 2πr and B = πr ² , respectively, B = π × (PM / 2π) ² The circularity of the particles is calculated as circularity = A / B = A × 4π / (PM) ² . The circularity is measured for 100 particles, and the average value is used as the average circularity.

  The average particle size of the fine barium carbonate particles of the present invention is 0.1 μm to 20 μm, preferably 0.1 μm to 15 μm, and more preferably 0.5 μm to 10 μm. Hollow particles having an average particle diameter of less than 0.1 μm require the use of a special device such as ultrasonic irradiation, and if the average particle diameter exceeds 20 μm, a part of the particles may become an incomplete sphere, which is not preferable. The average particle size can be adjusted by adjusting the diameter of a fluid nozzle used for spraying. Here, the particle size can be measured by analysis with an electron microscope, and the average is JIS R 1629 “Method of measuring particle size distribution by laser diffraction / scattering method of fine ceramics raw material”, particle size distribution measuring apparatus by laser diffraction / scattering method Can be calculated by, for example, a micro truck (manufactured by Nikkiso Co., Ltd.).

  The particle size distribution (particle size distribution) of the fine barium carbonate particles of the present invention is as narrow as possible, and preferably 80% or more of the particles are within ± 5.0 μm of the average particle size, and 80% or more of the particles have an average particle size of Is more preferably ± 4.5 μm, and even more preferably 80% or more of the particles are within ± 4.0 μm of the average particle diameter.

  The barium carbonate microparticles of the present invention may have a hollow space from the viewpoint of imparting lightness, heat insulation, heat shielding, etc. It is preferable to have a shell, and the thickness of the shell is 1.5 to 27% of the average particle diameter. The hollow ratio is preferably 10 to 90%. It can be confirmed from the SEM image and the TEM image that the particles are hollow particles having a hollow chamber.

The thickness of the shell is preferably from 1.6 to 27%, more preferably from 1.7 to 20%, even more preferably from 1.7 to 17% of the average particle diameter from the viewpoints of strength, weight reduction and thermal conductivity. Further, the hollow ratio is preferably from 10 to 90%, more preferably from 20 to 90%, and still more preferably from 30 to 90%, from the viewpoint of strength, weight reduction, thermal conductivity and the like. The thickness of the shell can be measured from a TEM image. The shell thickness is measured for 50 particles, and the average value is used as the average film thickness. The hollow ratio is calculated as follows. The particles and the voids in the particles are assumed to be true spheres. Assuming that the particle diameter is (A) and the average film thickness determined from the SEM image or TEM image is (B), the radius of the void of the particle is expressed as A / 2-B. The volume of a perfect circle having the same volume as the sample particles is V ₁ = 4/3 × π × (A / 2) ² . The volume of the void is V ₂ = 4/3 × π × (A / 2−B) ² , and the hollow ratio of the particles can be calculated as the hollow ratio = V ₂ / V ₁ × 100.

The bulk density of the fine barium carbonate particle of the present invention, the strength, from the viewpoint of such weight reduction and thermal conductivity is preferably from 0.1-2 g / cm ^3, in the range of 0.15~2g / cm ³ Is more preferable, and further preferably 0.2 to 2 g / cm ³ . The bulk density can be measured by a measuring method according to JIS R 1628 "Method of measuring bulk density of fine ceramic powder", or a powder mechanical property measuring device such as a powder tester (manufactured by Hosokawa Micron Corporation).

Apparent density of the fine barium carbonate particle of the present invention, the strength, from the viewpoint of such weight reduction and thermal conductivity is preferably from 0.4~4.5g / cm ^3, with 0.5-4 g / cm ³ More preferably, it is more preferably 0.6 to ³ g / cm ³ . The apparent density can be measured by a measuring method according to JIS R 1620 “Method for measuring particle density of fine ceramic powder”, using an Acupic (made by Shimadzu Corporation) dry-type automatic densitometer.

  The barium carbonate particles of the present invention preferably have a compressive strength of 0.3 to 150 MPa, more preferably 1 to 150 MPa, and still more preferably 1 to 100 MPa. The compressive strength can be measured with an MCT-510 (manufactured by Shimadzu Corporation) micro compression tester.

BET specific surface area of the fine barium carbonate particle of the present invention is preferably from 0.1~35m ² / g, more preferably 0.1~16m ² / g, more preferably 0.1 to 10 m ² / g . The BET specific surface area can be measured by a measurement method according to JIS Z 8830 "Method for measuring specific surface area of powder (solid) by gas adsorption", using a flow soap II 2300 (manufactured by Shimadzu Corporation) BET specific surface area meter.

  The fine barium carbonate particles of the present invention can be produced by spray pyrolysis of a barium organic acid salt solution. Specifically, it can be produced by a spray pyrolysis method in which a barium salt solution of an organic acid is sprayed with a spray nozzle and pyrolyzed.

Examples of the barium salt of an organic acid used as a raw material include barium salts of organic carboxylic acids such as barium acetate and barium propionate. Here, the organic acid is preferably an organic carboxylic acid, particularly a fatty acid, and more preferably a C ₁ -C ₃₆ fatty acid. As the organic acid barium salt solution, an organic acid barium salt aqueous solution is preferable.

  The concentration of the organic acid barium salt in the organic acid barium salt solution is preferably from 0.01 to 2 M, more preferably from 0.01 to 1 M.

  It is preferable to spray the organic acid barium salt solution with a spray nozzle, particularly a two-fluid nozzle, from the viewpoints of adjustment of particle diameter and productivity. Here, the two-fluid nozzle method includes an internal mixing method in which air and an organic acid barium salt solution are mixed inside the nozzle, and an external mixing method in which air and the organic acid barium salt solution are mixed outside the nozzle. Can also be adopted.

  The sprayed mist is thermally decomposed by passing through a drying zone at 100 to 800 ° C. and then a pyrolysis zone at 900 to 1450 ° C. to become barium carbonate particles. The temperature of the drying zone is preferably from 100 to 800 ° C, more preferably from 200 to 800 ° C, in order to obtain particles having a high degree of circularity, since it is necessary to quickly dry the water in the particles. The outside of the mist is dried by this drying zone to form a barium organic acid film, and the internal liquid is dried starting therefrom, so that the particles are formed in a hollow shape.

  The temperature of the pyrolysis zone is preferably 900 ° C. or higher, and more preferably 1000 ° C. or higher, in order to maintain hollowness. From the viewpoint that barium organic acid is thermally decomposed into barium carbonate and barium carbonate is not converted into barium oxide, the temperature is preferably 1450 ° C. or lower, more preferably 1400 ° C. or lower. By proceeding the pyrolysis reaction at once in the pyrolysis zone, the hollow structure formed in the drying zone is strengthened, so that barium carbonate hollow particles having a thin shell partitioning the hollow chamber can be obtained.

  The obtained barium carbonate hollow particles can be adjusted in particle size by passing through a filter after cooling.

  Since the fine barium carbonate particles of the present invention have a true spherical shape or a hollow true spherical shape, the filling properties of the film or sheet are good, and the weight can be reduced. In the case of a hollow true sphere, properties such as heat insulation and heat insulation can be imparted because of its low thermal conductivity.

  Next, the present invention will be described in more detail with reference to examples.

Example 1
An aqueous barium acetate solution in which 0.1 mol of barium acetate was dissolved in 1 liter of distilled water was charged into a solution tank of a spray pyrolyzer. The charged aqueous solution was sprayed in a mist form through a two-fluid nozzle by a liquid sending pump, and passed through a drying zone (about 600 ° C.) and then a pyrolysis zone (about 1150 ° C.). Barium carbonate hollow particles were collected using a bag filter.
Table 1 shows the characteristics of the barium carbonate particles obtained under the temperature conditions of the drying zone of 600 ° C. and the thermal decomposition zone of 1150 ° C. FIG. 1 shows an SEM image of the particle, FIG. 2 shows an SEM image of a cross section of the particle, and FIG. 3 shows XRD.

Example 2
Even when the drying zone was set to 200 ° C. and the thermal decomposition zone was set to 1150 ° C., barium carbonate hollow particles having an average particle diameter of 0.96 μm and a circularity of 0.8 were obtained in the same manner as described above (Table 1).

Example 3
On the other hand, when the drying zone was 400 ° C. and the pyrolysis zone was 800 ° C., solid particles having an average particle diameter of 1.4 μm and a circularity of 0.79 were obtained (Table 1).

Claims (4)

Average circularity of 0.75 or more, an average particle diameter of Ri 0.1μm~20μm der has a shell having a hollow chamber, from 1.5 to 27% of an average particle diameter thickness of the shell, an apparent density of 0 Fine barium carbonate particles having a porosity of 0.4 to 4.5 g / cm ³ and a hollow ratio of 10 to 90% . Bulk density 0.1-2 g / cm ^3, compressive strength 0.3～150MPa, claim 1 Symbol placement of fine barium carbonate particle has a BET specific surface area of 0.1~35m ² / g. A method for producing fine barium carbonate particles having an average circularity of 0.75 or more and an average particle size of 0.1 μm to 20 μm, which comprises subjecting an organic acid barium salt solution to spray pyrolysis. The obtained fine barium carbonate particles have a shell having a hollow chamber, the thickness of the shell is 1.5 to 27% of the average particle diameter, and the apparent density is 0.4 to 4.5 g / cm. ^Three The method for producing fine barium carbonate particles according to claim 3, wherein the hollow ratio is 10 to 90%.