JPH0264016A - Zirconia-based hollow microspherical particle and production thereof - Google Patents

Abstract

PURPOSE:To obtain hollow microspherical particles, having a prescribed film thickness and particle diameter and excellent in fire resistance and heat insulating properties by spray-drying an aqueous sol of crystalline zirconia and/or X-ray diffractometrically amorphous zirconia and/or hydrated zirconia containing a water-soluble high polymer added thereto and calcining the resultant blend. CONSTITUTION:An aqueous sol of fine particles of crystalline zirconia having <=50Angstrom crystal diameter and/or X-ray diffractometrically amorphous zirconia and/or hydrated zirconia is prepared. A water-soluble high polymer is added to the above-mentioned aqueous sol and the resultant blend is spray-dried and calcined at >=500 deg.C temperature. Thereby, zirconia-based hollow microspherical particles, having the shell consisting of zirconia-based microcrystalline particles and having <5mum and >=10mum particle diameter are obtained.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to zirconia fine hollow spherical particles and a method for producing the same. [Prior art] As a method for producing micro hollow spherical particles of metal oxide,
A method is known in which the surface of a spherical particle serving as a core is coated with fine metal oxide particles using a binder, and then the core portion is removed by firing; a method in which the core is melted at high temperature and sprayed into the air is known. There is. In addition, Japanese Patent Publication No. 57-11004 discloses a method in which a surfactant is added to an inorganic material powder having sinterability, and the resultant foam-containing slurry is sprayed into hot air and dried. Also, in Japanese Patent Application Laid-Open No. 62-191426,
A translucent aqueous sol of monoclinic zirconia microcrystals obtained by hydrothermally treating an aqueous solution of zirconium salt at a temperature around 200°C for a long time is spray-dried to form a zirconia film with a film thickness of approximately 10 μm and a particle size of approximately 50 to 100 μm. A method for producing polycrystalline microhollow spherical particles is presented.

[Problems to be Solved by the Invention] However, in these methods, porous solid spheres are used. It is easy to produce depressed spheres, crushed particles, etc. that are not spherical, and it is difficult to obtain uniformly shaped hollow spherical particles. Furthermore, even if the obtained product has a hollow spherical shape, the shell is thick and the bulk specific gravity is large. An object of the present invention is to provide zirconia micro hollow spherical particles that have a spherical shape and have a thin and uniform shell thickness, and therefore have a small bulk specific gravity, which could not be produced using conventional techniques, and a method for producing the same. There is a particular thing. [Means for Solving the Problems] That is, the zirconia micro hollow spherical particles of the present invention have shells made of zirconia microcrystal particles and a film thickness of 5 μm.
The gist is that the particle size is less than m and the particle size is 10 μn1 or more. The zirconia material of the shell is preferably made of a high-strength cubic or tetragonal crystal in which a stabilizer such as calcia, magnesia, ittria, or ceria is dissolved. However, even if the microspheres are composed of monoclinic crystals containing a small amount of stabilizer or no stabilizer at all, the microspheres described above can be put to practical use. The above-mentioned zirconia fine hollow spherical particles of the present invention have Xt! iI A water-soluble polymer is added to an aqueous sol of fine particles of crystalline zirconia with a crystallite diameter of 50 Å or less and/or X-ray amorphous zirconia and/or hydrated zirconia, and spray-dried at 500°C. It can be manufactured by firing at a temperature above. In order to obtain the above-mentioned product whose shell is made of zirconia in which a stabilizer is dissolved, an aqueous sol containing a stabilizer source may be used as the above-mentioned aqueous sol. For example, calcium and magnesium. Aqueous solutions of salts such as yttrium and cerium; hydroxides or oxide fine particles of these elements may be included in the aqueous sol. If zirconia in an aqueous sol is used with an X-ray crystallite diameter of more than 50, only porous solid spheres or hollow spheres with a thick film can be obtained. The aqueous sol of the zirconia fine particles in the present invention is
For example, an aqueous solution of a water-soluble zirconium salt is heated to about 120°C.
Hydrolyze by heating at a temperature below (if the heating temperature is higher than the above range, the zirconia in the resulting aqueous sol will be larger than 50), or neutralize with ammonia etc. It can be obtained by Alternatively, a polyhydric carboxylic acid having 2 to 4 carboxylic acid groups in the molecule or a salt thereof is added to an aqueous solution of a water-soluble zirconium salt to perform hydrolysis by adding 0.5 mol or less per 1 gram atom of zirconium. (Unexamined Japanese Patent Publication No. 00-25
5622), it is possible to obtain an aqueous sol capable of producing sinterable iΩi, that is, hollow particles that are difficult to crush. When an aqueous solution of a stabilizer source salt is coexisted with an aqueous solution of the water-soluble zirconium salt and hydrolyzed or neutralized, an aqueous sol containing an aqueous solution of a stabilizer source salt can be obtained. Of course, after generating an aqueous sol, an aqueous solution of a salt as a stabilizer source, its oxide, etc. may be added. The aqueous sol obtained as described above usually has a low sol concentration, but is subjected to the following treatment either as it is or after 4-condensation. In addition, in order to avoid gelation during the next process of adding a water-soluble polymer, ammonia is usually added before the process to raise the pH to 7 or slightly higher. A water-soluble polymer is added to the aqueous sol thus obtained and spray-dried. If a water-soluble polymer is not added, depressions or solid spheres will occur, making it impossible to obtain uniformly spherical thin-film spherical particles. The water-soluble polymer used must be uniformly soluble in water and must not generate bubbles. A water-soluble polymer that meets these conditions maintains the gel produced by spray drying in a true spherical shape and exhibits a sufficient binder effect. Typical water-soluble polymers include polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyacrylic ester, polymethacrylic ester, and the like. In order to produce hollow spherical particles with a thin shell and a small bulk specific gravity, as mentioned above, it is desirable that the crystallite size of the zirconia particles in the aqueous sol that is the starting material be fine. The concentration of zirconia in the pond aqueous sol and the amount of water-soluble polymer added to the aqueous sol are also important. If the concentration of zirconia (ZrO,) in the aqueous sol is too high, spherical particles will not be obtained and the shape of the particles will vary greatly. On the other hand, if it is too low, very small spherical particles, powdery particles, solid particles, etc. are likely to be obtained. Its concentration is 35% by weight or less, especially 5~
A range of 30% by weight is preferred. In addition, if the amount of water-soluble polymer added to the aqueous sol is too large, the particles tend to stick together and form clumps, while if it is too small, the particles tend to become spherical and powdery. It is. Although the amount added varies depending on the type of water-soluble polymer, it is usually 5% by weight or more, particularly preferably in the range of 10 to 50% by weight, based on the zirconia in the aqueous sol. Spray drying may be performed using hot air at 100 to 200°C. Any method such as a nozzle method or a disk method can be used. The particle size of the hollow spherical particles obtained varies depending on conditions such as the zirconia concentration in the aqueous sol, the nozzle pressure during spray drying in the case of a nozzle method, and the rotation speed of the atomizer in the case of a disk method. 30
Particle sizes in the range ˜150 μm are obtained. The gel of hollow spherical particles obtained in this way has a bulk specific gravity in the range of about 0.2 to about 0.8, and is made of zirconia microcrystal particles with a particle size of 10 μm or more by firing at a temperature of 500°C or higher. Microscopic hollow spherical particles are obtained. If the stabilizer is MgO or CaO, for example, 7 mol% or more, Y, Q. In order to obtain hollow spherical particles consisting of tetragonal or cubic zirconia microcrystal particles containing 2 mol% or more of CeO2, or 8 mol% or more of CeO2, the hollow spherical particle gel obtained by spray drying is It is preferable to perform the firing in the range of 1500°C to about 1500°C. In this way, hollow spherical particles consisting of zirconia microcrystal particles having a crystal grain size of about 0.5 μm or less are obtained. Further, by firing within this range, sintering between particles progresses, and hollow spherical particles having a certain degree of strength can be obtained. When obtaining hollow spherical particles consisting of monoclinic zirconia microcrystal particles in which the content of the stabilizer does not meet the above value or does not contain the stabilizer, approximately 0.
It is preferable to perform the firing at a temperature in the range of 0°C to about 1200°C. This is because if the firing temperature exceeds 1200° C., there is a possibility of crushing depending on the cooling conditions after firing. The micro hollow spherical particles obtained as described above consist of a uniform thin shell with a thickness of less than 5 μm, usually about 2 μm to about 4 μm, a bulk specific gravity in the range of 0.3 to about 1.5, and a particle size of 10 μm.
It is in the range of μm or more and 150 μm. Hereinafter, the present invention will be explained by showing specific examples, but the present invention is not limited thereto. [Effects of the Invention] The zirconia microscopic hollow spherical particles of the present invention have a uniform and thin film thickness. Moreover, since it is made from zirconia, which has a high melting point and low thermal conductivity, it has excellent fire resistance and heat insulation properties.Therefore, the tetragonal and cubic crystals are expected to be used as fireproof and heat insulating materials. Ru. Furthermore, monoclinic crystals are suitable as fillers for cosmetics and other products that are used at relatively low temperatures. According to the method of the present invention, the above-mentioned zirconia fine hollow spherical particles can be easily produced. [Example] Example 1 Zirconium oxychloride octahydrate (reagent special grade purity 99.0
% or more) in water, and the concentration of zirconium Z r
An aqueous solution of about 300 g/D in terms of 02 was prepared. Yttrium oxide (reagent special grade purity 99.99) is added to this aqueous solution.
6 or more) dissolved in hydrochloric acid and water were added to prepare an aqueous solution containing 3 mol % of yttrium (calculated as Y2O) and having a zirconium concentration of approximately 50 g/D in terms of Z r 02. This aqueous solution was heated to 100°C for 60°C while stirring.
The mixture was heated and hydrolyzed by holding for a certain period of time. The hydrolysis rate at this time was about 95%. The obtained aqueous sol was a milky white opaque sol, and the crystallite size of the zirconia fine particles determined by X-ray diffraction was about 30. The aqueous sol was concentrated under reduced pressure and the pH was adjusted to about 7 by adding aqueous ammonia. Next, an aqueous solution of polyethylene glycol is added to adjust the concentration of zirconia Z.
An aqueous sol was prepared in which the content of polyethylene glycol was approximately 150 g/N in terms of r 02 and the content of polyethylene glycol was 20% by weight in terms of solids based on zirconia. This aqueous sol was supplied to a disc-type spray dryer and spray-dried. The rotational speed of the atomizer was about 10,000 rpm, and the hot air temperature was about 150°C. As a result, Kasahi City is approximately 0.
4. A gel of hollow spherical particles with an average particle diameter of about 60 μm was obtained. After degreasing this gel at about 500℃, it was heated to 1400℃ for 2 hours.
It was baked for a certain period of time. As a result, Kasahi city approximately 1.
0. Zirconia hollow spherical particles with a shell thickness of approximately 3 μm and a particle size of 50 μm were obtained. Photographs of its appearance and cross section taken with a scanning electron microscope are shown in FIGS. 1 and 2, respectively. Example 2 Zirconium oxychloride was dissolved in water to prepare an aqueous solution having a zirconium concentration of about 300 g/liter in terms of Z r 02. To this aqueous solution, an aqueous solution of yttrium oxide dissolved in hydrochloric acid, an aqueous solution of oxalic acid, and water were added to contain 3 mol% of yttrium in terms of y, o, and 0.05 mol of oxalic acid per 1 gram atom of zirconium. Contains zirconium with a degree of Z "02 equivalent of approximately 200 g/I
An aqueous solution of I was prepared. Pour this mixed aqueous solution into a glass container, and while stirring,
The mixture was heated at 00°C for 20 hours. As a result, a cloudy, opaque aqueous sol was obtained. The hydrolysis rate was about 90%. Aqueous ammonia was added to this aqueous sol to adjust the pH to about 7. x of the generated hydrated zirconia fine particles! ! The diffraction peaks were very broad and substantially amorphous. An aqueous solution of polyvinyl alcohol was added to this sol, and the concentration of zirconia was approximately 150 g/D in terms of Z r 02,
An aqueous sol containing about 25% by weight of polyvinyl alcohol solids based on zirconia was prepared. This aqueous sol was spray-dried to obtain a gel with hollow spherical particles having a bulk specific gravity of approximately 0.4. This gel was heated and degreased at approximately 500°C, and then heated to 1300°C.
It was held for 2 hours and fired. As a result, Kasahi City is approximately 0.
8. Average grain size of approximately 7, consisting of a uniform thin film with a shell thickness of approximately 3 μm.
Zirconia fine hollow spherical particles of 0 μm were obtained. Comparative Example 1 In the same manner as in Example 1, yttrium was replaced with Y2O. It contains 3 mol% in terms of conversion, and the concentration of zirconium is Z r
An aqueous solution having a concentration of about 50 f/N in terms of 02 was prepared. This aqueous solution was heated and hydrolyzed by holding it at 100° C. for 60 hours while stirring. Aqueous ammonia was added to the resulting aqueous sol to adjust the pH to about 7. Then, it was concentrated to dryness under reduced pressure and calcined at 800°C for 2 hours. The X-ray crystallite diameter of the obtained powder was about 200. Water was added to this powder and pulverized in a ball mill to prepare a slurry consisting of zirconia fine particles with a particle size of 0.5 μn1. Approximately 20 L [fW96] of polyethylene glycol was added to this slurry in terms of solid content based on zirconia, and the slurry was spray-dried in hot air. The obtained gel had a bulk specific gravity of about 0.9, and was heated and degreased at around 500°C and then fired at 1400°C for 2 hours. As a result, the particle size was 60 μm. Porous solid spheres with a bulk specific gravity of 2.3 were obtained, and no hollow spherical particles were obtained. 1 and 2 are scanning electron micrographs showing the zirconia hollow spherical particles obtained in Example 1 and the particle structure of their cross section, respectively. Special γ1 Applicant: Tosoh Corporation Comparative Example 2 Same as Example 1 except that polyethylene glycol was not added, and the concentration of zirconia was about 150 in terms of ZrO2.
An aqueous sol of g/R was prepared. This aqueous sol was prepared in Example 1.
It was spray-dried in hot air in the same manner as above. As a result, a gel with a bulk specific gravity of about 1.0 was obtained, and when it was held and fired at 1400°C for 2 hours, the particle size was 60 μm and the bulk specific gravity was 1.0.
9 porous solid spheres were obtained.

[Brief explanation of the drawing]

Claims (4)

[Claims] (1) The shell is made of zirconia microcrystal particles, the film thickness is less than 5 μm, and the grain size is 10 μm or more,
Zirconia micro hollow spherical particles. (2) The zirconia micro hollow spherical particles according to claim (1), wherein the zirconia shell contains a stabilizer. (3) A water-soluble polymer is added to an aqueous sol of fine particles of crystalline zirconia with an X-ray crystallite diameter of 50 Å or less and/or X-ray amorphous zirconia and/or hydrated zirconia, and spray-dried. and firing at a temperature of 500°C or higher. (4) The method for producing zirconia fine hollow spherical particles according to claim (3), wherein the aqueous sol contains a stabilizer source.