TWI522318B - Titanium oxide particles and methods for producing the same - Google Patents

Description

Titanium oxide particles and method of producing the same

The present invention relates to a titanium oxide particle, a method for producing the same, and a slurry, a dispersion, a composition, and a dielectric material comprising titanium oxide particles.

Titanium oxide is widely used in industrial applications. It has been widely used in photocatalysts, solar cells, dielectric materials, electrode materials for Li-ion batteries, etc., as a representative of cosmetics, ultraviolet shielding materials, and antimony rubber additives. use. Further, "titanium oxide" is described as titanium dioxide in Japanese Industrial Standards (JIS). However, since titanium oxide is widely used as a general name, it is abbreviated as titanium oxide in the present specification.

Recently, titanium oxide has attracted attention as a raw material for high-performance dielectric materials such as BaTiO ₃ . BaTiO ₃ can be obtained by the following reaction under heating.

BaCO ₃ +TiO ₂ → BaTiO ₃ +CO ₂

The above reaction is a solid phase reaction, in which BaCO _{3 is} first decomposed at a high temperature to form BaO, and BaO is referred to as a dispersed solid solution TiO ₂ particle to become BaTiO ₃ . Accordingly, the size of the BaTiO ₃ particles becomes the size of the TiO ₂ particles. In recent years, with the miniaturization of laminated ceramic capacitors, thinning of a dielectric layer has been a problem, and therefore, atomization and homogenization of BaTiO ₃ particles have become indispensable. Accordingly, in order to achieve uniformization, it is necessary to atomize and homogenize the TiO ₂ of the BaTiO ₃ raw material.

The method for producing titanium oxide generally has a liquid phase method of hydrolyzing titanium tetrachloride or titanium sulfate, and a gas phase method in which titanium tetrachloride is reacted with oxygen or water vapor at a high temperature.

Although the liquid phase method has an advantage that titanium oxide can be produced under relatively mild conditions, in order to obtain titanium oxide in a state of a sol or a slurry, when it is used in this state, there is a problem that the use is limited.

Further, in order to use the sol or the slurry as the titanium oxide particles, it is necessary to dry them, and after drying, the aggregation generally becomes intense. Such a highly condensed titanium oxide particle has a problem that the particle diameter becomes uneven. Further, when the titanium oxide particles are dispersed in a solvent, the dispersibility is also deteriorated. When the dispersibility is deteriorated, when the raw materials are mixed for the formation of the above-mentioned BaTiO ₃ , the titanium oxide particles are not sufficiently mixed with other raw materials, and the raw material components are biased, causing uneven growth during the reaction, resulting in poor performance such as low strength and quality. Variations, etc. Moreover, when the titanium oxide is pulverized and pulverized in order to improve the dispersibility, there is a problem that the abrasion of the treatment such as pulverization or the unevenness of the particle size distribution is caused.

In addition, in the gas phase method, titanium oxide is obtained as a powder, and in the gas phase method, since a solvent is not used, a problem enumerated in a liquid phase method is generated. Less questions. However, in the gas phase method, in order to use titanium tetrachloride in the raw material, the obtained titanium oxide particles have a problem of causing inclusion of Cl.

For example, when the titanium oxide particles containing the Cl are used as a raw material of BaTiO ₃ , BaO is formed by mixing the titanium oxide particles containing the Cl and BaCO ₃ and heating, and Cl reacts with the BaO to form BaCl ₂ . The resulting BaCl ₂ is melted to function as a flux, causing agglomeration of TiO ₂ particles or BaTiO ₃ particles. Further, the molten flux is easily localized, and aggregation is increased in the localized portion, and quality variation occurs between the other portions. When the particles are agglomerated, the crystals of the BaTiO ₃ particles grow to become abnormal particles, and the dielectric properties of BaTiO _{3 are} lowered. The above problem is caused by the fact that the presence or absence of Cl in the titanium oxide is likely to occur, so that the surface of the particles and the Cl inside the particles are all reduced.

Patent Document 1 describes a method for producing a low-halogen titanium oxide particle, which is characterized in that a titanium oxide particle having a low halogen content such as Cl is obtained by a vapor phase method, and a titanium halide gas is used in a gas phase. The coarse titanium oxide particles obtained by the hydrolysis or oxidation reaction are brought into contact with a mixed gas containing an alcohol and water vapor.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] WO09/017212

As described above, titanium oxide particles having a small Cl content and excellent uniformity and dispersibility are desired. However, the uniformity and dispersibility of the titanium oxide particles obtained by the liquid phase method are not good. Further, the titanium oxide particles obtained by the vapor phase method have a large Cl content. Further, the titanium oxide particles obtained by Patent Document 1 did not sufficiently reduce the Cl content.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a titanium oxide particle having a low Cl content and excellent uniformity and dispersibility, a method for producing the same, and a slurry and dispersion containing the titanium oxide. Body, composition and dielectric material.

As a result of intensive studies in view of the above-mentioned problems, the inventors of the present invention have found that the raw titanium oxide particles are produced by reacting a gas containing a specific amount of titanium tetrachloride and an inert gas and a gas containing a specific oxidizing gas. In the first step and the second step of dechlorinating the powder by the dry dechlorination method, titanium oxide particles having a small Cl content and excellent uniformity and dispersibility can be produced.

That is, the present invention provides the following [1] to [13].

[1] A method for producing titanium oxide particles, comprising: introducing a gas G1 containing titanium tetrachloride and an inert gas, and a gas G2 containing at least one of oxygen and water vapor and an inert gas into a reaction tube; The first step of producing the crude titanium oxide particles and the second step of dechlorinating the coarse titanium oxide particles by the dry dechlorination method, which is characterized by the total amount of inert gas introduced into the reaction tube of the first step ( Gas G1 and The total amount of inert gas in the gas G2 is 1 mA or more and 50 mA or less with respect to 1 mol of titanium tetrachloride, and the amount of inert gas in the gas G2 is 5 m with respect to 1 mol of the inert gas in the gas G1. the above.

[2] The method for producing titanium oxide particles according to [1], wherein in the first step, the gas G1 and the gas G2 are introduced into a reaction tube having a temperature of 900 ° C or higher and less than 1,200 ° C and reacted.

[3] The method for producing titanium oxide particles according to [1] or [2], wherein, in the first step, the total amount of oxygen and water vapor in the gas G2 is made with respect to 1 mol of titanium tetrachloride. The gas G1 and the gas G2 are introduced into the reaction tube in a manner of 1 mol or more and 50 mol or less.

[4] The method for producing a titanium oxide particle according to any one of [1] to [3] wherein, in the first step, the amount of the inert gas in the gas G1 is increased with respect to 1 mol of titanium tetrachloride. The gas G1 and the gas G2 are introduced into the reaction tube in a manner of less than 3 moles.

[5] A titanium oxide particle having a total Cl content a of 200 ppm by mass or less, characterized in that D ₉₀ /D ₅₀ determined by a laser diffraction scattering analysis method is defined as X, which is adsorbed by nitrogen gas. When the BET specific surface area measured by the BET method is Y (m ² /g), X/Y is 0.060 or less.

[6] The titanium oxide particle according to claim 5, wherein a surface Cl content (mass ppm) of the titanium oxide particle measured by a silver nitrate potential difference titration is subtracted from a total Cl content a (mass ppm) in the titanium oxide particle The content of the internal Cl content c of the obtained titanium oxide particles is 200 ppm by mass or less.

[7] The titanium oxide particles according to [5] or [6], wherein the BET specific surface area Y is from 20 to 200 m ² /g.

[8] The titanium oxide particles according to any one of [5] to [7] wherein the content of the titanium oxide is 99.9% by mass or more.

[9] The titanium oxide particles according to any one of [5] to [8], wherein the contents of Na, Al, S, Fe, Ni, Cr, Nb, and Zr are each 10 mass ppm or less, and Si and C are respectively The content is 100 ppm by mass or less.

[10] A slurry comprising the titanium oxide particles according to any one of [5] to [9].

[11] A dispersion comprising the titanium oxide particles according to any one of [5] to [9].

[12] A composition comprising the titanium oxide particles according to any one of [5] to [9].

[13] A dielectric material obtained by the titanium oxide particles according to any one of [5] to [9].

According to the present invention, it is possible to provide a titanium oxide particle having a small total Cl content a and excellent uniformity and dispersibility, a method for producing the same, and a slurry, a dispersion, a composition, and a dielectric material comprising the titanium oxide.

1‧‧‧Reaction tube

2‧‧‧Cooling tube

3‧‧‧ Cooling medium (air, nitrogen, water, etc.)

4‧‧‧ coarse titanium oxide particles

5‧‧‧Step 2

G1‧‧‧ gas G1

G2‧‧‧ gas G2

Z‧‧‧Reaction zone

Fig. 1 is a schematic view showing a suitable example of the first step of the method for producing titanium oxide particles of the present invention.

[Titanium oxide particles]

The titanium oxide particle of the present invention has a total Cl content a of 200 ppm by mass or less, D ₉₀ /D ₅₀ measured by a laser diffraction scattering analysis method as X, and a BET specific surface area measured by a BET method by nitrogen adsorption. In the case of Y (m ² /g), X/Y is a titanium oxide particle of 0.060 or less. The titanium oxide particles of the present invention have a small total a content of a, and are excellent in uniformity and dispersibility. The titanium oxide particles of the present invention can be suitably produced by the method for producing titanium oxide particles of the present invention to be described later.

The titanium oxide particles of the present invention have a total Cl content a of 200 ppm by mass or less.

The total Cl content a refers to the total content of Cl in the titanium oxide particles, which is dissolved by the addition of hydrofluoric acid to the titanium oxide, and the silver nitrate solution is dropped into the solution, and the silver nitrate potential difference titration method for measuring the potential difference is used. value.

When the total Cl content a exceeds 200 ppm by mass, when the titanium oxide particles are used as a raw material such as BaTiO ₃ , they become a flux (Flux) at the time of firing. The molten flux is easily localized, and the localized portion is coagulated and the quality is mutated with other portions. Further, when the particles are agglomerated, the crystals of the BaTiO ₃ particles grow to become abnormal particles, and the dielectric properties of BaTiO ₃ also decrease. From this viewpoint, the total Cl content a in the titanium oxide particles is preferably 180 ppm by mass or less, more preferably 150 ppm by mass or less, still more preferably 120 ppm by mass or less, still more preferably 100 ppm by mass or less. Further, it is more preferably 40 ppm or less. Further, 40 ppm is the measurement limit value of the measurement method.

The surface Cl content b is a Cl content on the surface of the titanium oxide particles, and from the same viewpoint, it is preferably 200 ppm by mass or less, more preferably 180 ppm by mass or less, still more preferably 150 ppm by mass or less, and still more It is preferably 120 ppm by mass or less, and more preferably 100 ppm by mass or less.

In the present invention, the surface Cl content b means a value measured by dispersing titanium oxide in water and dropping a silver nitrate solution in the solution, and measuring the potential difference by a silver nitrate potential difference titration method.

In the present measurement method, the lower limit of quantification is 40 ppm, and the case where the measured value is lower than the lower limit of quantification is set to be 0 ppm or more and less than 40 ppm.

Further, when a BaTiO ₃ layer or the like containing a titanium oxide particle containing Cl as a raw material is produced inside the particle, the Cl diffuses to the surface of the layer over time, causing a problem of corrosion and deterioration of the substrate on which the layer is formed. Further, Cl which is present inside the titanium oxide particles is difficult to remove by a simple de-Cl treatment such as washing with water or drying. Therefore, it is desirable not only to have Cl on the surface of the titanium oxide particles but also inside the particles.

From this point of view, the internal Cl content c is a Cl content c inside the titanium oxide particles, preferably 200 ppm by mass or less, more preferably 120 ppm by mass or less, still more preferably 100 ppm by mass or less.

Further, in the present invention, the internal Cl content c means the total Cl content a from the above (total content of Cl in the titanium oxide particles), minus (in the particle The Cl content of the surface) is the value of the surface Cl content b.

The titanium oxide particles of the present invention preferably have a content of Na, Al, S, Fe, Ni, Cr, Nb and Zr of 10 ppm by mass or less. Further, the titanium oxide particles of the present invention preferably have a content of Si and C of 100 ppm by mass or less. As described above, when the amount of impurities is small, when the titanium oxide particles are used as a raw material to obtain a dielectric, it is suppressed that the dielectric properties are deteriorated due to the presence of impurities. Further, when the titanium oxide particles are used in a photocatalyst or a solar cell, the transparency due to the coloring of Fe is prevented or suppressed, and the occurrence of lattice defects due to Al or S is prevented or suppressed. The performance of photocatalyst or solar cell is reduced.

The titanium oxide particles of the present invention preferably have a content of titanium oxide of 99.9% by mass or more, whereby the purity is improved, so that the influence by the above impurities is small. Further, the contents of such impurities and titanium oxide are determined by the measurement methods described in the examples.

The titanium oxide particles of the present invention have a D ₉₀ /D ₅₀ determined by a laser diffraction scattering analysis method as X, and a BET specific surface area measured by a BET method by nitrogen adsorption is determined to be Y (m ² /g). , X / Y is below 0.060.

In general, as the BET specific surface area Y particles are larger, the surface energy is more likely to aggregate and the particle diameter becomes uneven, and the value of X (D ₉₀ /D ₅₀ ) tends to increase. Dividing this value X(D ₉₀ /D ₅₀ ) by the value X/Y of the BET specific surface area Y can be used as an index for removing the uniformity of the influence of the BET specific surface area. It can be said that the smaller the value of X/Y, the uniformity The more excellent.

From the viewpoint of improving uniformity, the value of this X/Y is preferably It is 0.055 or less, more preferably 0.050 or less, still more preferably 0.045 or less, still more preferably 0.040 or less, still more preferably 0.035 or less.

In addition, in the measurement method of the particle size distribution of particles, by the "Ultrafine Particles Handbook" Saito Into six supervision, Fuji. In Techno System, p93, (1990), there are sedimentation method, microscopic method, laser diffraction scattering analysis method (light scattering method), direct counting method, etc., among which the particle size measured by the precipitation method and the direct counting method is Above 100 nm, it is not suitable for measuring the particle size distribution of fine particles having a particle diameter of 100 nm or less. Further, the microscopic method also has a measurement method in which the sample sample is sampled or the sample is processed beforehand, and it cannot be said that it is a preferable measurement method. In this regard, the laser diffraction scattering analysis method (light scattering method) can measure the particle diameter in the range of several nm to several μm , and is suitable for the measurement of fine particles. The order of measurement for the particle size distribution by the laser diffraction scattering analysis method (light scattering method) will be described below.

To 100 g of the titanium oxide particles, 100 ml of pure water and 100 μl of a 10% aqueous sodium hexametaphosphate solution were added, and ultrasonic irradiation (50 kHz, 100 W) was performed for 3 minutes. This slurry was placed in a laser diffraction type particle size distribution measuring apparatus (Shimadzu SALD 2000J), and the particle size distribution was measured. According to the measurement, D ₅₀ (particle diameter (μm) having a cumulative particle size of 50% in volume cumulative particle size distribution), D ₉₀ (particle diameter (μm) having a cumulative particle size of 90% in volume cumulative particle size distribution) was obtained. ), X (D ₉₀ / D ₅₀ ).

It is judged that the smaller the D ₉₀ value in the particle size distribution measured, the better the dispersibility with respect to the hydrophilic solvent, and the value of D ₉₀ is preferably 8 μm or less, more preferably 5 μm or less, still more preferably 3.5 μm or less. More preferably, it is 1 μm or less.

The above-mentioned value X (D ₉₀ /D ₅₀ ) of the titanium oxide particles of the present invention is 6.00 or less, preferably 5.50 or less, more preferably 5.00 or less, more preferably 5.00 or less, from the viewpoint of improving the uniformity of the titanium oxide particles. Below 2.00, it is more preferably 1.50 or less, further preferably 1.40 or less.

In addition, the BET specific surface area Y (m ² /g) of the titanium oxide particles of the present invention is preferably from 20 to 200 m ² /g from the viewpoint of obtaining titanium oxide particles having less impurities and excellent uniformity and dispersibility. , more preferably 20 ~ 190m ² / g, and still more preferably 20 ~ 150m ² / g, again more preferably 20 ~ 100m ² / g, again more preferably 20 ~ 50m ² / g.

Although the gold-red petrochemical rate of the titanium oxide particles of the present invention can be widely controlled, the ultraviolet shielding property or the photocatalytic activity is generally preferably rutile type, preferably 3 to 95%, more preferably 6~. 95%, more preferably 30 to 95%, and even more preferably 50 to 95%, and most preferably 50 to 90%.

Here, the term "red sap" refers to the content of rutile-type titanium oxide in titanium oxide.

[Slurry, dispersion, composition and dielectric material]

The slurry, the dispersion, the composition, and the dielectric material of the present invention comprise the titanium oxide particles described above. The slurry, dispersion, composition, and dielectric material of the present invention are suitable for photocatalytic use, solar cell use, dielectric use, and the like.

[Method for Producing Titanium Oxide Particles]

The method for producing titanium oxide particles of the present invention has a method of: containing tetrachlorine The first step of producing the crude titanium oxide particles and the crude titanium oxide by introducing a gas G1 of titanium and an inert gas, and a gas G2 containing at least one of oxygen and water vapor and an inert gas into the reaction tube a second step of dechlorination of the particles by a dry dechlorination method, wherein the total amount of the inert gas introduced into the reaction tube in the first step is 1 mol or more and 50 mol or less with respect to 1 mol of titanium tetrachloride. The method of producing the titanium oxide particles having a molar amount of 5 m or more with respect to the inert gas 1 mol in the gas G2.

According to the present invention, titanium oxide particles having a low total Cl content a and excellent uniformity and dispersibility can be obtained.

That is, when the titanium oxide particles are produced by a vapor phase method, when attempting to reduce the total Cl content a in the titanium oxide particles to sufficiently carry out the reaction, the sintering or aggregation of the particles is promoted, the specific surface area is lowered, and the uniformity of the particle diameter is reduced. The dispersion of particles. Further, when the reaction is insufficient, the total Cl content a in the titanium oxide particles increases.

The present inventors have found that the total amount of the inert gas introduced into the reaction tube by the first step is 1 mol or more and 50 mol or less with respect to titanium tetrachloride 1 and is inert in the gas G2. The amount of gas is set to 5 m or more with respect to 1 mol of the inert gas in the gas G1, and titanium oxide particles having a low Cl content and excellent uniformity and dispersibility can be obtained, and the present invention has been completed.

<Step 1>

In the first step, a gas containing titanium tetrachloride and an inert gas G1 and a gas G2 containing at least one of oxygen and water vapor and an inert gas are introduced into a reaction tube to carry out a reaction to produce coarse titanium oxide particles.

In the first step, the total amount of the inert gas introduced into the reaction tube, that is, the total amount of the inert gas in the gas G1 and the inert gas in the gas G2 is 1 mol or more relative to the titanium tetrachloride. And 50 m or less, and the amount of inert gas in the gas G2 is 5 m or more with respect to the inert gas 1 mol in the gas G1. Thereby, the effect of reducing the uniformity of the particle diameter a and improving the uniformity of the particle diameter and the dispersibility of the particles can be obtained.

(Total amount of inert gas introduced into the reaction tube)

The total amount of the inert gas introduced into the reaction tube is as described above, and is 1 mol or more and 50 mol or less with respect to 1 mol of titanium tetrachloride. When the total amount of the inert gas is less than the range, the density of the titanium oxide particles in the reaction zone is increased, and aggregation and sintering become easy. Here, the "reaction zone" refers to a region from the raw material merging portion by the introduction of the cooling air to the end of the reaction.

Further, when the inert gas is more than the above range, the reactivity of the raw material is lowered, the oxidation reaction of titanium tetrachloride cannot be completed, and the internal Cl content c inside the titanium oxide particles is increased, and as a result, the total Cl content a is increased. Therefore, in order to produce titanium oxide particles having a small total Cl content a, it is necessary to complete the oxidation reaction of titanium tetrachloride, and to suppress reaction conditions such as aggregation and sintering, and the total amount of inert gas introduced into the reaction tube relative to tetrachloroethylene. Titanium gas 1 mole, preferably 1 mole or more and 30 moles or less, more preferably 1 mole or more and 20 moles or less, more preferably 1 mole or more and 10 moles or less, and still more good It is 1 mole or more and 5 moles or less.

Fig. 1 is a schematic view showing a suitable embodiment of the first step.

First, the gas G1 and the gas G2 are introduced into the reaction tube 1. In this case, it is preferable that the reaction tube 1 is heated in advance so that the temperature in the reaction tube 1 after introduction of the gas G1 and the gas G2 in the reaction tube 1 is within a predetermined temperature range. The material gas (gas G1 and gas G2) is retained in the reaction tube 1 for a predetermined time. The inside of the reaction tube 1 becomes the reaction zone Z.

Next, as the cooling medium 3, the gas or water is introduced between the reaction tube 1 and the cooling tube 2, and the material gas is rapidly cooled, and the coarse titanium oxide particles 4 of the reaction product are discharged from the cooling tube 2 together with the cooling medium 3. Thereby, the coarse titanium oxide particles 4 can be suitably produced. The obtained coarse titanium oxide particles are sent to the second step 5.

(gas G1)

The gas G1 contains titanium tetrachloride and an inert gas.

In the gas G1, the content of the inert gas of 1 mol of titanium tetrachloride is preferably 0.1 mol or more, more preferably 0.5 mol, from the viewpoint of suppressing the particle diameter of the titanium oxide particles obtained. More preferably, it is more than 1 mole, and more preferably 1.5 moles or more, and still more preferably 2 moles or more. Further, from the viewpoint of promoting the reaction, it is preferably 50 m or less, more preferably 20 m or less, still more preferably 10 m or less, still more preferably 5 m or less, and further preferably 3 m. Below the ear.

Examples of the inert gas include nitrogen gas, helium gas, argon gas, and the like. From the economical point of view, it is preferably nitrogen. The total content of the titanium tetrachloride and the inert gas in the gas G1 is preferably 80 mol% or more from the viewpoint of obtaining a titanium oxide particle having a low total Cl content a and excellent uniformity and dispersibility. More preferably, it is 90% by mole or more, more preferably 95% by mole or more, and even more preferably 99% by mole or more.

(gas G2)

The gas G2 contains at least one of oxygen and water vapor and an inert gas.

In the gas G2, the content of the inert gas of 1 mol with respect to the total amount of oxygen and water vapor is preferably 0.1 mol or more and 50 mol or less. When the concentration is 50 mol or less, since the concentration of the raw material in the reaction tube is high, the reaction is promoted, and the total Cl content a and the internal Cl content c can be reduced. Further, when it is 0.1 mol or more, titanium oxide particles having a small internal Cl content c and a low total Cl content a can be obtained. From this point of view, the content of the inert gas of 1 mol with respect to the total amount of oxygen and water vapor is more preferably 0.1 mol or more and 30 mol or less, still more preferably 0.1 mol or more and 20 mol or less. More preferably, it is 0.1 mol or more and 10 mol or less, and further more preferably 0.1 mol or more and 5 mol or less.

Examples of the inert gas include nitrogen gas, helium gas, and argon gas. From the viewpoint of economy, nitrogen gas is preferred. Although the inert gas in the gas G2 may be the same as or different from the inert gas in the gas G1, it is preferably nitrogen gas from the viewpoint of economy.

Although the gas G2 may contain at least one of oxygen and water vapor, the viewpoint of obtaining a titanium oxide particle having a low Cl content and excellent uniformity and dispersibility is obtained. In terms of point, it is preferable to contain both.

From the same point of view, it is 1 mole relative to oxygen. The water vapor is preferably 1 mole or more, more preferably 4 moles or more, still more preferably 10 moles or more, still more preferably 30 moles or more, still more preferably 40 moles or more, and further preferably. It is 150 m or less, more preferably 100 m or less, even more preferably 80 m or less, and even more preferably 70 m or less, and further preferably 60 m or less.

The total content of the oxygen, the water vapor, and the inert gas in the gas G2 is preferably 80 mol% or more from the viewpoint of obtaining a titanium oxide particle having a low total Cl content a and excellent uniformity and dispersibility. More preferably, it is 90% by mole or more, more preferably 95% by mole or more, and even more preferably 99% by mole or more.

(Assignment of inert gas G1 and gas G2)

From the viewpoint of preventing the progress of the oxidation reaction and obtaining the titanium oxide particles having an internal Cl content c and a total Cl content a, the amount of the inert gas introduced into the gas G2 is 1 mol with respect to the inert gas introduced into the gas G1. 5 mol or more, preferably 10 mol or more, more preferably 20 m or more, still more preferably 30 m or more, and more preferably 100 m or less, more preferably 80 m or less, and then More preferably, it is 70 m or less, and even more preferably 60 m or less.

(The ratio of titanium tetrachloride to the total amount of oxygen and water vapor)

The total amount of oxygen and water vapor to the reaction tube, relative to titanium tetrachloride The introduction amount of the reaction tube is 1 mol, preferably 1 mol or more and 50 mol or less, more preferably 1 mol or more and 20 mol or less. When the introduction amount of oxygen and water vapor is increased, the number of fine particles which increase the number of nucleation of titanium oxide is easily obtained, but even if it exceeds 50 mol, the effect of increasing the number of nucleation is hardly obtained. The introduction amount of oxygen and water vapor does not affect the characteristics of titanium oxide even if it exceeds 50 mol, but the upper limit is set from the viewpoint of economy. Further, when it is 1 mol or more, titanium oxide having little oxygen deficiency and no coloration can be obtained.

(ratio of gas G1 to gas G2)

The introduction amount of the gas G2 to the reaction tube is preferably 1 mol or more and 50 mol or less, more preferably 1 mol or more and 20 mol or less with respect to the introduction amount of the gas G1 to the reaction tube. . When the amount of gas of the gas G2 is increased, the number of fine particles which increase the number of nucleation of titanium oxide is easily obtained, but even if it exceeds 50 m, the effect of increasing the number of nucleation is hardly obtained. Even if the gas G2 exceeds 50 mol, it does not affect the characteristics of titanium oxide, but the upper limit is set from the viewpoint of economy. Further, when it is 1 mol or more, titanium oxide having little oxygen deficiency and no coloration can be obtained.

(reaction temperature and reaction time)

The temperature in the reaction tube into which the gas G1 and the gas G2 are introduced is preferably 900 ° C or more and less than 1,200 ° C, more preferably 900 ° C or more and less than 1,100 ° C. By increasing the temperature inside the reaction tube, the reaction is completed simultaneously with the mixing, the uniform nucleation is enhanced, and the reaction zone can be narrowed. The temperature inside the reaction tube is When the temperature is 900 ° C or higher, the reaction proceeds well, and the internal Cl content c of the titanium oxide particles decreases. Further, when the temperature inside the reaction tube was less than 1,200 ° C, the growth of the particles was suppressed to obtain fine particles.

When the raw material gas is introduced into the reaction tube, the titanium oxide particles may be grown without rapid cooling, and the particles may be sintered. Therefore, the high temperature residence time of 900 ° C or more and less than 1,200 ° C is preferably 0.1 second or less, more preferably 0.03 second or less, still more preferably 0.02 second or less.

As means for rapid cooling, for example, a method of introducing a large amount of a gas such as cooling air or nitrogen into the reaction mixture, or a method of performing water spraying, or the like is suitable.

<Step 2>

In the second step, the coarse titanium oxide particles obtained in the first step are dechlorinated by a dry dechlorination method.

Here, the "dry dechlorination method" refers to heating a coarse titanium oxide particle in the presence of water vapor using a heating device such as a cylindrical rotary heating furnace, a hot air circulation type heating furnace, a flow drying furnace, or a stirring drying furnace. The method of removing Cl. This heating device is preferably a cylindrical rotary heating furnace.

Further, although the dechlorination method also has a wet dechlorination method, it is necessary to carry out the drying step, so that the titanium oxide particles are aggregated to reduce the dispersibility.

The dechlorination by the heating of the coarse titanium oxide particles is preferably such that the mass ratio of the water vapor to the coarse titanium oxide particles (=the mass of the water vapor/the mass of the coarse titanium oxide particles, the same applies hereinafter) is 0.01 or more. The titanium oxide particles are heated while being in contact with water vapor, more preferably 0.03 Above, it is more preferably 0.1 or more.

The dechlorination is carried out by subjecting Cl on the surface of the titanium oxide to substitution reaction with water in the vicinity of the particles or surface hydroxyl groups of adjacent particles. When Cl on the surface of the titanium oxide particles is substituted by water, the crystal grains cannot be dechlorinated when they are grown, but when they are substituted by the surface hydroxyl groups of the adjacent particles, the crystal grains are grown simultaneously with dechlorination. In other words, it is considered that the mass ratio of water vapor to titanium oxide is important for dechlorination while suppressing grain growth. However, when the mass ratio of water vapor to titanium oxide is 0.01 or more, the effect of suppressing grain growth is suppressed.

The heating temperature is preferably 200 ° C or more and 550 ° C or less, more preferably 400 ° C or more and 550 ° C or less. When it is 550 ° C or less, sintering of titanium oxide particles is suppressed, and grain growth is suppressed. When the heating temperature is 200 ° C or higher, the dechlorination efficiency can be improved.

The water vapor in contact with the titanium oxide is preferably used in combination with air. The air has a function of efficiently moving the separated Cl from the titanium oxide to the outside of the system. Further, the air containing water vapor is preferably heated at 200 ° C or more and 1,000 ° C or less.

[Examples]

Hereinafter, the examples and comparative examples will be specifically described, but the present invention is not limited thereto.

Further, the method for measuring the physical properties of titanium oxide particles is as follows.

(1) Gold-red petrochemical rate

The content of the rutile-type titanium oxide in the titanium oxide particles (the ratio of the rutile ratio) was measured by a powder X-ray diffraction method.

In other words, for the titanium oxide particles to be dried, "X'pertPRO" manufactured by PANalytical Co., Ltd. was used as a measuring device, a copper target was used, and a Cu-Kα1 line was used, with a tube voltage of 45 kV, a tube current of 40 mA, and a measurement range of 2θ = 10~. X-ray diffraction measurement was carried out under the conditions of 80 deg, sampling amplitude of 0.0167 deg, and scanning speed of 0.0192 deg/s.

The peak height (Hr) corresponding to the maximum peak of the rutile crystal, the peak height (Hb) corresponding to the maximum peak of the brookite crystal, and the peak height (Ha) of the maximum peak corresponding to the anatase crystal are obtained. The content of the rutile-type titanium oxide in the titanium oxide particles (the ratio of the rutile ratio) was determined by the following calculation formula.

Gold red petrochemical rate (%) = {Hr / (Ha + Hb + Hr)} × 100

(2) BET specific surface area Y

The BET specific surface area Y (m ² /g) of the titanium oxide particles was measured by a specific surface area measuring apparatus (model: Flow Sorb II, 2300) manufactured by Shimadzu Corporation.

(3) Total Cl content a

The total Cl content a in the titanium oxide particles was measured by a silver nitrate potential difference titration method.

That is, the titanium oxide particles are weighed. Secondly, by dissolving the titanium oxide particles by adding hydrofluoric acid to microwave irradiation, the solution is dissolved in silver nitrate. The liquid, by measuring the potential difference, finds the mass of chlorine in the solution. Further, the total Cl content a in the titanium oxide particles was calculated from the mass of the titanium oxide particles and the mass of chlorine in the solution.

(4) Surface Cl content b

The surface Cl content b in the titanium oxide particles was measured by a silver nitrate potential difference titration method.

That is, the titanium oxide particles are weighed. Next, by dispersing the titanium oxide particles in water and dropping a silver nitrate solution into the solution, the potential difference was measured to determine the mass of chlorine in the solution. Further, the surface Cl content b in the titanium oxide particles was calculated from the mass of the titanium oxide particles and the mass of chlorine in the solution.

(5) Internal Cl content c

From the total Cl content a obtained by the above (3) and (4), and by subtracting the surface Cl content b, the internal Cl content c was calculated.

(6) D ₅₀ , D ₉₀ , X (D ₉₀ /D ₅₀ ), and X/Y

To 100 g of the titanium oxide particles, 100 ml of pure water and 100 μl of a 10% aqueous sodium hexametaphosphate solution were added, and ultrasonic irradiation (50 kHz, 100 W) was performed for 3 minutes. This slurry was placed in a laser diffraction type particle size distribution measuring apparatus (SALD (registered trademark)-2000J) manufactured by Shimadzu Corporation, and the particle size distribution was measured. According to the measurement, D ₅₀ (particle diameter (μm) having a cumulative particle size of 50% in volume cumulative particle size distribution), D ₉₀ (particle diameter (μm) having a cumulative particle size of 90% in volume cumulative particle size distribution) was obtained. ), X (D ₉₀ / D ₅₀ ). Further, from the value of X and the BET specific surface area Y described above, X/Y is calculated.

(7) Content of titanium oxide in titanium oxide particles

The content of titanium oxide in the titanium oxide particles is determined by "100-total impurity concentration (% by mass)".

(8) Content of other impurities

The method of measuring impurities is as follows.

Fe: Atomic Absorption Method (Atom Absorption Meter Z-2300 by Hitachi Advanced Technology Co., Ltd.)

Al, Si: Fluorescence X-ray analysis (XRF) (Simultix10, manufactured by Rigaku Motor Co., Ltd.)

C, S: high frequency induction furnace combustion infrared absorption method

Na, Ni, Cr, Nb, Zr: Inductively coupled plasma mass spectrometry

Example 1 <Step 1>

Tetrachlorination of 8.3 Nm ³ /hr (N means standard state, the same below) of gaseous titanium tetrachloride (purity of titanium tetrachloride ≧ 99.99% by mass) diluted with 0.5 Nm ³ /hr of nitrogen gas A titanium diluent gas (gas G1), an oxidizing gas (gas G2) obtained by mixing 18 Nm ³ /hr of inert gas with 0.5 Nm ³ /hr of oxygen and 36 Nm ³ /hr of water vapor, and introducing it into a quartz glass reactor . The cooling air was introduced into the reaction tube so that the high-temperature residence time of 900 ° C or higher and less than 1,200 ° C was 0.02 seconds, and the coarse titanium oxide particles were collected in a Teflon bag filter. The amounts of various gases used are shown in Table 1.

<Step 2>

The obtained coarse titanium oxide particles were passed through a cylindrical rotary heating furnace, and the mass ratio of the water vapor to the coarse titanium oxide (mass of water vapor/mass of coarse titanium oxide particles) was 0.7, and de-Cl was performed at a heating temperature of 510 ° C. Titanium oxide particles were obtained, and various physical properties were measured. The measurement results are shown in Table 3.

Examples 2 to 7 and Comparative Examples 1 to 2

The first step was carried out in the same manner as in Example 1 except that the amount of gas in the first step and the high-temperature residence time were as shown in Table 1 or Table 2.

Next, the second step was carried out in the same manner as in Example 1 except that the mass ratio of the water of the second step to the coarse titanium oxide and the heating temperature were as shown in Table 1 or Table 2. The measurement results are shown in Table 3 or Table 4.

Comparative example 3

Titanium oxide particles are obtained by the production conditions described in JP-A-2007-314418. The details will be as follows.

The gaseous 11.8Nm ³ / hr of titanium tetrachloride diluted in 8Nm ³ / hr of titanium tetrachloride diluted gas inert gas, preheated at 900 ℃, mixing 8Nm ³ / hr of oxygen to 32Nm ³ / hr of The oxidizing gas of water vapor was preheated at 800 ° C and introduced into a reactor made of quartz glass. The cooling air was introduced into the reaction tube so that the high-temperature residence time of 800 ° C or more and less than 1,000 ° C was 0.01 second, and the fine particle-shaped titanium oxide particles were collected in a polytetrafluoroethylene bag filter.

The obtained titanium oxide particles were passed through a cylindrical rotary heating furnace, and de-Cl was carried out at a mass ratio of water to titanium oxide of 0.02 and a heating temperature of 450 ° C to obtain titanium oxide particles. The total Cl content a of the obtained titanium oxide particles had exceeded 200 ppm by mass, and X/Y was more than 0.060.

The gas amount is shown in Table 2, and the measurement results of the physical properties of the titanium oxide particles are shown in Table 4.

Comparative example 4

The titanium oxide particles were obtained in the same manner as in Comparative Example 3 except that the production conditions described in JP-A-2007-314418 and Table 2 were changed.

The gas amount is shown in Table 2, and the measurement results of the physical properties of the titanium oxide particles are shown in Table 4.

Comparative Example 5

The titanium oxide particles were obtained in the same manner as in Comparative Example 3 except that the production conditions described in JP-A-2011-57552 and Table 2 were changed.

The gas amount is shown in Table 2, and the measurement results of the physical properties of the titanium oxide particles are shown in Table 4.

Comparative Example 6

The oxidation was carried out in the same manner as in Comparative Example 3 except that the production conditions described in JP-A-10-25102, Table 2 were changed. Titanium particles.

The gas amount is shown in Table 2, and the measurement results of the physical properties of the titanium oxide particles are shown in Table 4.

Comparative Example 7

The titanium oxide particles were obtained in the same manner as in Comparative Example 3 except that the production conditions described in JP-A-2003-277057 and Table 2 were changed.

The gas amount is shown in Table 2, and the measurement results of the physical properties of the titanium oxide particles are shown in Table 4.

[Industrial availability]

According to the present invention, there is provided a vapor phase method of titanium oxide particles having less impurities and superior uniformity and dispersibility than conventional titanium oxide having the same BET specific surface area, and a process for producing the same. The titanium oxide of the present invention is suitable for photocatalytic use, solar cell use, dielectric use, etc., and does not require a disintegration step or the like as a powder, or an extremely slight device, and is industrially very valuable.

Claims (13)

A method for producing titanium oxide particles, comprising: introducing a gas G1 containing titanium tetrachloride and an inert gas, and a gas G2 containing at least one of oxygen and water vapor and an inert gas into a reaction tube and reacting the same; The first step of producing the coarse titanium oxide particles and the second step of dechlorinating the coarse titanium oxide particles by the dry dechlorination method, which is characterized in that the total amount of the inert gas introduced into the reaction tube of the first step (gas G1 and The total amount of inert gas in the gas G2 is 1 mA or more and 50 mA or less with respect to 1 mol of titanium tetrachloride, and the amount of inert gas in the gas G2 is 5 m with respect to 1 mol of the inert gas in the gas G1. the above. The method for producing titanium oxide particles according to claim 1, wherein in the first step, the gas G1 and the gas G2 are introduced into a reaction tube having a temperature of 900 ° C or higher and less than 1,200 ° C and reacted. The method for producing titanium oxide particles according to claim 1 or 2, wherein, in the first step, the total amount of oxygen and water vapor in the gas G2 is 1 mol or more with respect to 1 mol of titanium tetrachloride. The gas G1 and the gas G2 are introduced into the reaction tube in a manner of 50 mol or less. The method for producing a titanium oxide particle according to claim 1 or 2, wherein, in the first step, the amount of the inert gas in the gas G1 is less than 3 mol with respect to 1 mol of titanium tetrachloride. The gas G1 and the gas G2 are introduced into the reaction tube. A titanium oxide particle having a total Cl content a of 200 ppm by mass or less, characterized in that D ₉₀ /D ₅₀ determined by laser diffraction scattering analysis is defined as X, which is determined by a BET method by nitrogen adsorption When the BET specific surface area is Y (m ² /g), X/Y is 0.060 or less. The titanium oxide particle of claim 5, wherein the oxidation obtained by subtracting the surface Cl content b (mass ppm) of the titanium oxide particles by the silver nitrate potential difference titration is subtracted from the total Cl content a (mass ppm) of the titanium oxide particles. The internal Cl content c of the titanium particles is 200 ppm by mass or less. The titanium oxide particle of claim 5 or 6, wherein the BET specific surface area Y is from 20 to 200 m ² /g. The titanium oxide particles according to claim 5 or 6, wherein the content of the titanium oxide is 99.9% by mass or more. The titanium oxide particles according to claim 5 or 6, wherein the contents of Na, Al, S, Fe, Ni, Cr, Nb, and Zr are each 10 ppm by mass or less, and the contents of Si and C are each 100 ppm by mass or less. A slurry comprising the titanium oxide particles according to any one of claims 5 to 9. A dispersion comprising the titanium oxide particles according to any one of claims 5 to 9. A composition comprising the titanium oxide particles according to any one of claims 5 to 9. A dielectric material obtained by the titanium oxide particles according to any one of claims 5 to 9.