JP2001151509A - Spherical titanium oxide fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical high purity titanium oxide fine particle having excellent dispersibility and usable generally for an electronic material, an ultraviolet shielding material or a photocatalyst. SOLUTION: The spherical titanium oxide fine particle is obtained by the vapor phase reaction of titanium tetrachloride and has D1/D2 of 1.0-1.25 when the average particle diameter measured by SEM photography is expressed by D1 and the average particle diameter determined by BET specific surface area is expressed by D2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to spherical and high-purity titanium oxide fine particles which have excellent dispersibility and can be widely used for electronic materials, ultraviolet shielding materials or photocatalysts.

[0002]

2. Description of the Related Art Titanium oxide fine particles have long been used as white pigments, and in recent years have been widely used as constituent materials for capacitors and thermistors and as sintering materials used for electronic materials such as barium titanate raw materials. Further, since titanium oxide has a large refractive index in a wavelength region near visible light, light absorption hardly occurs in the visible light region. For this reason, recently, it has been widely used for materials such as cosmetics, medicines, and paints which require ultraviolet shielding. Furthermore, by irradiating the titanium oxide with light having energy equal to or greater than its band gap, the titanium oxide is excited, and electrons are generated in the conduction band and holes are generated in the valence band. Applications for photocatalytic reactions utilizing oxidizing power are being actively developed. The applications of this titanium oxide photocatalyst are very diverse, including generation of hydrogen by decomposition of water, exhaust gas treatment, air purification, deodorization, sterilization,
Numerous applications have been developed, such as antibacterial, water treatment, and contamination prevention for lighting equipment.

As described above, titanium oxides are used in a wide variety of applications. When titanium oxide fine particles are used in pigments, paints, sintered materials, and the like, they are often used by suspending and dispersing them in water or an organic solvent. In that case, the dispersibility of the titanium oxide fine particles in the solvent becomes a problem.

In particular, in titanium oxide for electronic materials, for example, barium titanate as a dielectric substance is prepared using titanium oxide and a barium compound such as barium carbonate as raw materials. At this time, the titanium oxide is suspended in a solvent. After being dispersed and mixed with a barium compound, it is sintered. Since the particle size of the prepared barium titanate mainly depends on the particle size of the raw material titanium oxide, in order to prepare finer particles, it is necessary to use the finer particle raw material titanium oxide, In order to respond to recent miniaturization of electronic materials, 1
Ultrafine titanium oxide particles of less than μm are required. However, as the titanium oxide becomes finer, the dispersibility in the solvent becomes worse, and when the titanium oxide is suspended in the solvent, agglomeration of the fine particles occurs. When barium titanate is prepared as described above, the fine titanium oxide Despite the use, the particle size increased conversely, and when sintered further, it did not react uniformly, and when the product was viewed at the molecular level, the dispersion of titanium and barium was uneven. As a result, the characteristics of the electronic material are adversely affected.

[0005] Further, in the ultraviolet shielding material, there is a problem that the agglutination of titanium oxide particles deteriorates the ultraviolet shielding characteristics.

[0006] Among the conventional methods for producing titanium oxide, a method called a gas phase oxidation method is a gas phase oxidation method in which titanium tetrachloride is oxidized by contacting it with oxygen in a gas phase, or a hydrogen gas or the like which burns to produce water. There is a so-called flame hydrolysis method in which a combustible gas and oxygen are supplied to a combustion burner to form a flame, into which titanium tetrachloride is introduced. For example, JP-A-6-340423 discloses a method capable of producing titanium oxide fine particles having a high rutile ratio and a primary particle diameter of 0.1 μm or less.
In the flame hydrolysis method of producing titanium oxide by hydrolysis of titanium tetrachloride by burning a mixed gas of titanium tetrachloride, hydrogen and oxygen in the gas phase, the titanium tetrachloride, hydrogen And a method of reacting oxygen and oxygen in a specific molar ratio.

Japanese Patent Application Laid-Open No. Hei 8-217654 discloses that a titanium compound is incorporated into a hydrogen-containing gas by a flame hydrolysis method, wherein the titanium compound is contained in a hydrogen-containing gas in an amount of 50 to 3 in terms of titanium dioxide.
Disclosed are crystalline titanium oxide fine particles for UV shielding cosmetics having an average particle size of 0.04 to 0.15 µm, supplied at a rate of 300 g / m ³ and flame-hydrolyzed at a temperature of 300 to 1500 ° C.

On the other hand, as a method for producing titanium oxide having a spherical shape, generally, for example, a method of hydrolyzing an organic titanium compound such as titanium tetraalkoxide or a method of hydrolyzing an aqueous solution of titanyl sulfate to obtain an obtained hydrous titanium oxide There is a method of firing titanium. For example, JP-A-5-1630
No. 22 discloses that titanyl sulfate is hydrolyzed at a temperature of 170 ° C. or higher and at a pressure higher than the saturated vapor pressure at the temperature to obtain hydrous titanium dioxide, and then the hydrous titanium dioxide is heated to 400 to 900 ° C. And a method of producing spherical anatase-type titanium dioxide by firing at a temperature of 0.1 g / m. Further, JP-A-8-333117 discloses an aqueous solution of titanyl sulfate containing 5.0 to 100 g / l of titanyl sulfate in terms of TiO ₂ and excess sulfuric acid in a molar ratio to titanium of 1.0 to 3.0. In addition, an equimolar or more urea is added to all the sulfate groups in the aqueous solution, heated to 85 ° C. or higher and the boiling point or lower, and the precipitated metatitanic acid particles are collected and fired at 650 to 850 ° C. A method for producing porous spherical anatase-type titanium oxide particles having a uniform particle size and a large specific surface area is disclosed.

Further, in order to solve the problem of dispersibility,
Attempts have been made to coat a hydrophobic substance which is inherently highly dispersible, such as silica or alumina, on the surface of titanium oxide particles. For example, Japanese Patent Application Laid-Open No. 5-281726 discloses that an aqueous solution of an aluminum basic salt is acidified with an acid. pH 10.5
A method is disclosed in which the mixture is adjusted to ２．０12.0, a titanium dioxide slurry is mixed with the mixture, and the mixture is neutralized with an acid to uniformly precipitate aluminum oxide hydrate on the surface of the titanium dioxide particles.

[0010]

However, the shape of the titanium oxide particles obtained by the conventional gas phase oxidation method of titanium tetrachloride such as the above-mentioned gas phase oxidation method or flame hydrolysis method is irregular. The specific surface area was larger than the particle diameter. Therefore, when suspended in a solvent for preparing an electronic material such as barium titanate, the dispersibility is very poor, and even when fine titanium oxide particles are used, there is a problem that the particles are aggregated. .

In the method of producing titanium oxide having a spherical shape, a method of hydrolyzing an organic titanium compound such as titanium tetraalkoxide is very expensive since titanium tetraalkoxide as a raw material is produced from titanium tetrachloride. However, there is a problem that the cost of the resulting titanium oxide is also increased. The method of producing titanium oxide by hydrolyzing titanyl sulfate to obtain hydrous titanium dioxide and then calcining it is necessary to separate and dry the hydrous titanium dioxide obtained in the liquid phase, and to further bake it, which requires a very complicated process. Yes, it also increases costs. Furthermore, when titanyl sulfate is used as a raw material, a sulfate group remains in the titanium oxide particles finally obtained, which adversely affects the properties of the sintered material, ultraviolet shielding material or photocatalyst, especially when used for electronic materials. .

Further, since components other than titanium oxide, such as coating of the surface of titanium oxide particles with a foreign substance, are used, the original characteristics of titanium oxide are changed, and in particular, the characteristics are adversely affected for electronic materials. Is difficult.

Accordingly, an object of the present invention is to provide spherical and high-purity titanium oxide fine particles having excellent dispersibility and low cost.

[0014]

Under such circumstances, the present inventors have conducted intensive studies and have found that titanium oxide fine particles in a method capable of producing titanium oxide at low cost, such as a gas phase reaction method of titanium tetrachloride. As a result of diligent research, they have found titanium oxide fine particles having excellent dispersibility, and suitable for a sintered material such as a spherical and high-purity electronic material, an ultraviolet shielding material, or a photocatalyst, and completed the present invention. Reached.

[0015] That is, the present invention relates to a gas phase of titanium tetrachloride.
The average particle size obtained from the reaction and measured from the SEM photograph is
D₁, The average particle size determined from the BET specific surface area is D_TwoMade
Time D ₁/ D_TwoIs 1.0 to 1.25
And spherical titanium oxide particles.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.
I do. The spherical titanium oxide fine particles of the present invention are
The average particle size measured is₁, Determined from the BET specific surface area
Average particle size is D _TwoD when₁/ D_TwoBut usually 1.0
~ 1.25, preferably 1.0 ~ 1.23, more preferably
Or 1.0 to 1.20.

The average particle diameter D ₂ obtained from the BET specific surface area in the above equation is an average particle diameter assuming that the particles are true spheres. As the value of D ₁ / D ₂ approaches 1, the particle shape becomes larger. Indicates that the particle is a true sphere, and that the particle surface is smooth and the pore volume inside the particle is small. Therefore, the titanium oxide fine particles of the present invention are more spherical than those obtained by the conventional gas phase method, have a smooth surface, and have a smaller pore volume. Thereby, since the specific surface area is small even with the same particle size, the cohesive force between the particles is small, and the dispersibility when suspended in a solvent is excellent. Furthermore, since the pore volume is small, shrinkage upon sintering is small and the sintering characteristics are excellent.

Generally, on the surface or inside of the titanium oxide particles after the reaction in the gas phase method, chlorine and chlorine content of hydrogen chloride are attached or adsorbed. The chlorine content in the titanium oxide, particularly when used in electronic materials, has an adverse effect on its properties, so it is necessary to remove it as much as possible. Usually, after titanium oxide fine particles are formed, steam treatment, heat treatment or alcohol treatment is performed. Depending on
This chlorine is removed. In the case of titanium oxide produced by the conventional gas phase method, the finer the particles, the larger the specific surface area of the particles, and as a result, the greater the amount of chlorine adsorbed on the particles, and it is not possible to remove chlorine to an acceptable level. It was difficult. On the other hand, the spherical titanium oxide fine particles of the present invention have a relatively smooth particle surface and a small pore volume, so that chlorine can be easily removed by the same method as the conventional one, as compared with the conventional titanium oxide particles. As a result, high-purity titanium oxide fine particles with less chlorine content can be produced.

The spherical titanium oxide fine particles of the present invention need not necessarily be perfectly spherical, but may be substantially spherical, may be elliptical or have irregularities on the particle surface, and have a circularity coefficient of 0.7 to 1.0. It is. The circularity coefficient is determined from the following equation (1) by image analysis of a SEM photograph. Circularity coefficient = 4πL ₁ / (L ₂ ) ² (1) (where L ₁ represents the projected area of the particle, and L ₂ represents the contour length of the projected particle).

The particle properties such as the particle diameter and specific surface area of the spherical titanium oxide fine particles of the present invention may be such that D ₁ / D ₂ and the circularity coefficient are within the above-mentioned specific ranges. can not but the average particle diameter D ₁ is preferably 0.01 to 5 [mu] m, more preferably 0.05 to 2
μm, more preferably 0.1 to 1 μm, and the specific surface area is preferably 0.5 to 100 m ² / g, more preferably 1 to 50 m ² / g, and still more preferably ² to 30 m ² / g.
In addition, the crystal type cannot be specified unconditionally, and may be adjusted according to the application. For example, a rutile type is preferable for a sintered material, a pigment or an ultraviolet shielding material, and the rutile ratio is usually 10 to 100%. On the other hand, an anatase type is preferable for photocatalysts.

Further, the titanium oxide fine particles of the present invention contain Fe, Al,
Si and Na are each less than 20 ppm, and C
l is less than 200 ppm. Desirably, each of Fe, Al, Si and Na contained in the titanium oxide fine particles is 1
It is less than 0 ppm and Cl is less than 100 ppm, more preferably less than 50 ppm. As described above, since the titanium oxide fine particles of the present invention are produced by a gas phase method, they do not contain or remain impurity elements such as titanium oxide obtained by a liquid phase method, and silica as in the prior art is used. Alternatively, it is a high-purity titanium oxide fine particle that has not been treated with other components such as surface coating of a hydrophobic substance such as alumina and contains almost no other components other than titanium oxide. When used as a material or a photocatalyst, excellent effects can be obtained without changing the original properties of titanium oxide.

The spherical titanium oxide fine particles of the present invention are obtained by a gas phase reaction of titanium tetrachloride. A flammable gas such as hydrogen gas or the like that generates water and oxygen are supplied to a combustion burner to form a flame, and the flame can be produced by a method such as a flame hydrolysis method in which titanium tetrachloride is introduced. Although the titanium oxide fine particles of the present invention are spherical, in order to form such spherical particles by a gas phase oxidation reaction, the reaction temperature at which the titanium oxide particles are formed is increased, and the particle generation reaction is performed more quickly. There is a need. Therefore, in the present invention, titanium tetrachloride is converted to oxygen or water (steam).
It is preferable to add hydrogen, propane, or the like during the oxidation reaction by contacting with hydrogen. Preferred combinations of raw material components include 1) titanium tetrachloride, oxygen and hydrogen, 2)
These are titanium tetrachloride, oxygen, hydrogen, and water, and these components are brought into contact to cause a gas phase reaction.

When the above-mentioned components are brought into contact with each other and reacted, the supply ratio of the above-mentioned components to the reaction section is as follows, assuming that each supply gas is in a standard state, and that 1 liter of titanium tetrachloride gas corresponds to 1 liter of oxygen. From 30 to 30, preferably from 2 to 20 l, particularly preferably from 4 to 10 l, from 0.1 to 10 l, preferably from 0.2 to 5 l, particularly preferably from 0.3 to 1.0 l of hydrogen and from 0 to 10 l of steam. 0.05 to 1.0 l, preferably 0.1 to 1.0 l
0.5 l.

The supply amount of each raw material gas varies depending on the reaction scale, the diameter of the nozzle for supplying each gas, and the like, and is appropriately set. It is desirable to set so that

In the gas phase oxidation reaction of titanium tetrachloride, if the concentration of titanium oxide fine particles generated in the reaction section is high, the particles grow and agglomerate due to collision of the particles, and the shape becomes irregular. turn into. Therefore, it is preferable that the concentration of the titanium oxide fine particles generated in the reaction section relative to the volume of the reaction section is as low as possible, and the reaction is performed in a more dilute state than the reaction conditions in the conventional gas phase reaction method. For this purpose, each of the above components to be supplied is diluted with an inert gas such as argon or nitrogen, supplied to a reaction section, and reacted. In particular, the titanium tetrachloride gas concentration and the partial pressure of each component in the reaction section are important in the reaction section, specifically in a flame in which titanium tetrachloride reacts with oxygen to generate titanium oxide, and these components are diluted. Supply as follows. At this time, the concentration of the titanium tetrachloride gas is usually preferably 20% by volume or less, more preferably 3 to 16% by volume, of the total gas amount supplied to the reaction section. In the total gas amount supplied to the reaction section, oxygen is 80% by volume or less, preferably 4% by volume.
0 to 70% by volume, and hydrogen is 20% by volume or less, preferably 3 to 10% by volume. Further, the concentration (partial pressure) of the inert gas component such as nitrogen gas for diluting these gas components in the total gas amount supplied to the reaction section is usually 0 to 5%.
It is 0% by volume, preferably 10 to 30% by volume.

It is desirable that titanium tetrachloride gas and oxygen among the above components are diluted with an inert gas such as nitrogen and supplied to the reaction section. The dilution ratio is based on the assumption that titanium tetrachloride is in a standard state. Then, 0.1 to 10 liters of inert gas, preferably 0.3 to 1 liters per 1 liter of titanium tetrachloride gas is used.
l. Further, the dilution ratio of oxygen is as follows.
l, preferably from 0.3 to 1 l.

As described above, titanium oxide fine particles are produced by reacting the respective components, and the titanium oxide fine particles produced in the reaction section are preferably cooled in order to prevent aggregation of the particles due to the reaction temperature. Usually, the produced titanium oxide fine particles are cooled by providing a cooling step after the reaction section. Specifically, a cooling section having a cooling jacket is provided after the reaction section. If the cooling section is not sufficient, it is desirable to insert the air or an inert gas such as nitrogen as a cooling gas after the reaction section (flame) to rapidly cool the generated titanium oxide fine particles. The cooling gas such as air or nitrogen inserted at this time is assumed to be in a standard state.
It is at least 1 l, preferably at least 3 l, particularly preferably at least 5 l.

An example of a specific process for producing the spherical titanium oxide fine particles of the present invention will be described below. First, liquid titanium tetrachloride is heated in advance, vaporized, diluted with nitrogen gas as required, and introduced into a reaction furnace. At this time, hydrogen gas is preliminarily mixed with titanium tetrachloride, or hydrogen gas is simultaneously introduced into the reactor separately from titanium tetrachloride. Simultaneously with the introduction of titanium tetrachloride, oxygen gas and / or steam is diluted with nitrogen gas, if necessary, and introduced into a reaction furnace to perform an oxidation reaction. The reaction temperature is usually 500 to 1200 ° C., preferably 80 ° C.
0 to 1100 ° C. In order to obtain the spherical titanium oxide fine particles of the present invention, it is desirable to carry out the oxidation reaction at such a relatively high temperature.

The titanium oxide fine particles are generated by the above oxidation reaction, and then the titanium oxide fine particles are cooled. Usually, a cooling tank equipped with a cooling jacket or the like is used, and at the same time, an inert gas such as air or nitrogen gas is brought into contact with the generated titanium oxide fine particles and rapidly cooled.

Thereafter, the generated titanium oxide fine particles are collected, and the chlorine gas remaining in the titanium oxide fine particles is subjected to heat treatment such as vacuum heating, heating in an air or nitrogen gas atmosphere, steam treatment, or contact treatment with alcohol. To obtain titanium oxide fine particles having a spherical degree of the present invention.

The spherical titanium oxide fine particles of the present invention can be used for all applications in which they are dispersed in a solvent such as a sintering material, a pigment, an ultraviolet shielding material or a photocatalyst, and are particularly effective for electronic materials such as capacitors. .

[0032]

The present invention will be more specifically described below with reference to examples and comparative examples. Note that this is merely an example and does not limit the present invention.

In the present specification, the average particle diameter (SEM diameter), circularity coefficient, specific surface area and impurities of titanium oxide fine particles were measured by the following methods. 1) Average particle diameter D ₁ : Fine particles are observed by an electron microscope (SEM), the SEM image is taken into an image analyzer (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), and the image is assumed to be a circle. The converted circle equivalent diameter was measured (number of analyzed particles: about 200). 2) Circularity coefficient: Measured from the above SEM image using an image analyzer V10 manufactured by Toyobo Co., Ltd. 3) BET specific surface area: measured by the BET method. 4) Average particle size D ₂ : The average particle size was calculated from the BET specific surface area and the true specific gravity of titanium oxide. 5) Quantification of impurities: Fe, Al, Si and Na components in titanium oxide: Measured by atomic absorption method. Cl component in titanium oxide: measured by an absorption spectrophotometry.

Example 1 Titanium oxide fine particles were prepared by a gas phase method in which titanium tetrachloride was contacted with oxygen and hydrogen in a gas phase and oxidized. First,
In a gas-phase reaction tube equipped with a multi-tube burner having an inner diameter of 400 mm, a mixed gas of titanium tetrachloride and hydrogen gas preheated and vaporized to about 800 ° C. is supplied to the multi-tube burner, and from another supply nozzle Oxygen gas preheated to 800 ° C. was supplied and oxidized at about 1000 ° C. in a gas phase reaction tube to generate titanium oxide fine particles. At this time, titanium tetrachloride was 60 l / min, hydrogen gas was 40 l / min, and oxygen gas was 3 l / min.
Each was fed at 80 l / min. Thereafter, air was inserted at a rate of 400 l / min from the bottom of the gas phase reaction tube to cool the generated titanium oxide fine particles. Thereafter, heat treatment was performed at 350 ° C. to 400 ° C. for 2 hours in a nitrogen atmosphere of the obtained titanium oxide fine particles. The average particle size D ₁ , circularity coefficient, specific surface area, average particle size D ₂ , D
Table 1 shows ₁ / D ₂ and the content of impurities.

Example 2 First, in a gas-phase reaction tube equipped with a multi-tube burner having an inner diameter of 400 mm at the top, a mixture of titanium tetrachloride, hydrogen gas, and nitrogen gas preheated and vaporized to about 800 ° C. in the multi-tube burner. Supply gas, while 800 ° C from another supply nozzle
Supply a pre-heated mixed gas of oxygen gas and nitrogen gas to
An oxidation reaction was performed at about 1000 ° C. in a gas-phase reaction tube to generate titanium oxide fine particles. At this time, the titanium tetrachloride mixed gas is supplied at a rate of 60 l / min of titanium tetrachloride, 40 l / min of hydrogen gas, 20 l / min of nitrogen gas, 500 l / min of an oxygen mixed gas composed of 380 l / min of oxygen and 120 l / min of nitrogen gas, respectively. did.
After that, air was supplied as cooling gas from the bottom of the gas-phase reaction tube.
At a rate of 00 l / min, the generated titanium oxide fine particles were cooled. Thereafter, heat treatment was performed at 350 ° C. to 400 ° C. for 2 hours in a nitrogen atmosphere of the obtained titanium oxide fine particles. Table 1 shows the average particle diameter D ₁ , the circularity coefficient, the specific surface area, the average particle diameters D ₂ , D ₁ / D _2, and the content of impurities of the spherical titanium oxide fine particles thus obtained.

Example 3 Titanium oxide fine particles were prepared in the same manner as in Example 2 except that air was inserted at 500 l / min as a cooling gas. Table 1 shows the average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameter D ₂ , D ₁ / D ₂ and the content of impurities of the obtained spherical titanium oxide fine particles. FIG. 1 shows an SEM photograph of the obtained spherical titanium oxide fine particles.

Example 4 Titanium oxide fine particles were prepared in the same manner as in Example 2 except that air was inserted at 800 l / min as a cooling gas. Table 1 shows the average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameter D ₂ , D ₁ / D ₂ and the content of impurities of the obtained spherical titanium oxide fine particles.

Embodiment 5 Instead of 500 l / min of oxygen mixed gas, 360 l / oxygen mixed gas consisting of 240 l / min of oxygen gas and 120 l / min of nitrogen gas was used.
The titanium oxide fine particles were prepared in the same manner as in Example 4 except that the amount of titanium oxide was used. The average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameters D ₂ , D _{1 of the} obtained spherical titanium oxide fine particles
Table 1 shows / D ₂ and the content of impurities.

Example 6 Titanium oxide fine particles were prepared in the same manner as in Example 4 except that the supply amount of titanium tetrachloride was 100 l / min and the titanium tetrachloride was not diluted with nitrogen gas. Table 1 shows the average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameter D ₂ , D ₁ / D ₂ and the content of impurities of the obtained spherical titanium oxide fine particles.

Comparative Example 1 Titanium oxide fine particles were prepared in the same manner as in Example 2 except that no hydrogen gas was used. Average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameter D of the obtained titanium oxide fine particles
Table 1 shows the contents of D ₂ , D ₁ / D ₂ and impurities. Also,
FIG. 2 shows an SEM photograph of the obtained titanium oxide fine particles.

Comparative Example 2 First, in a gas-phase reaction tube equipped with a multi-tube burner having an inner diameter of 400 mm at the top, titanium tetrachloride gas preheated to about 800 ° C. and vaporized was supplied to the multi-tube burner. Oxygen gas and water vapor preheated to 800 ° C. were supplied from a supply nozzle, and an oxidation reaction was performed at about 1000 ° C. in a gas phase reaction tube to generate titanium oxide fine particles. At this time, titanium tetrachloride was 200 l / min, oxygen gas was 380 l / min, and water vapor was 1 l / min.
Each was fed at 70 l / min. Thereafter, air was inserted at a rate of 100 l / min from the bottom of the gas phase reaction tube to cool the generated titanium oxide fine particles. Thereafter, heat treatment was performed at 350 ° C. to 400 ° C. for 2 hours in a nitrogen atmosphere of the obtained titanium oxide fine particles. The average particle diameter D ₁ , circularity coefficient, specific surface area, average particle diameter D ₂ , D ₁ / D of the titanium oxide fine particles thus obtained are described.
The content of D ₂ and impurities shown in Table 1.

[0042]

[Table 1] * "10>" in the table indicates that the content is less than 10 ppm.

[0043]

As described above, the titanium oxide fine particles of the present invention are different from the titanium oxide produced by the conventional gas phase method in that the average particle diameter measured from SEM photographs is D ₁ , and the average particle diameter determined from the BET specific surface area. High-purity titanium oxide fine particles having a spherical shape and a small amount of impurity components with a ratio of D ₁ / D ₂ of 1.0 to 1.25 when the diameter is D ₂ , and is used as an electronic material or a photocatalyst. It is effective for

[Brief description of the drawings]

FIG. 1 shows SE of titanium oxide fine particles prepared in Example 3.
It is an M photograph.

FIG. 2 shows SE of titanium oxide fine particles prepared in Comparative Example 1.
It is an M photograph.

Claims (6)

[Claims] 1. A method comprising the steps of:
D ₁ / D ₂ is 1 when the average particle size of the average particle diameter measured from M photographs obtained from D _1, BET specific surface area was D _2.
0 to 1.25, spherical titanium oxide fine particles. 2. The spherical titanium oxide fine particles according to claim 1, wherein a circularity coefficient represented by the following formula (1) is 0.7 to 1.0. Circularity coefficient = 4πL ₁ / (L ₂ ) ² (1) (where L ₁ represents the projected area of the particle, and L ₂ represents the contour length of the projected particle). 3. The spherical titanium oxide fine particles according to claim _{1, wherein the} average particle diameter D ₁ is 0.01 to 5 μm. 4. Fe contained in the titanium oxide fine particles,
The spherical titanium oxide fine particles according to any one of claims 1 to 3, wherein Al, Si and Na are each less than 20 ppm and Cl is less than 200 ppm. 5. In the gas phase reaction of the titanium tetrachloride,
2. The method according to claim 1, wherein the compound is produced by adding hydrogen.
5. The spherical titanium oxide fine particles according to any one of 4. 6. In the gas phase reaction of the titanium tetrachloride,
The spherical titanium oxide fine particles according to any one of claims 1 to 5, wherein the titanium tetrachloride gas concentration in the reaction section is manufactured under a condition of 20% by volume or less.