JP2008273832A - High purity titanium oxide and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high purity titanium dioxide which has excellent dispersibility and an average diameter within the range of 5-20 μm, and which is used in wide industrial fields, especially suitably used as a raw material for photocatalyst fine powder and ceramic moldings, in a flame fusion method by which titanium dioxide having excellent dispersibility can be obtained, and to provide a method for producing the same. <P>SOLUTION: Titanium dioxide made spherical in a short high temperature residence time is obtained by the flame fusion method using titanium dioxide obtained by a vapor phase method and having excellent dispersibility as a raw material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the method of obtaining spherical titanium dioxide by introducing titanium dioxide as a raw material into a high-temperature flame, the present invention has an average diameter in the range of 5 to 200 μm by laser particle size analysis, and Fe, Ni, Cr, The present invention relates to titanium dioxide with less impurities of Si, Al, Zr, S, and Cl and a method for producing the same.

  Titanium dioxide powders are widely used as white pigments, cosmetics, raw materials for dielectric barium titanate, photocatalysts, and the like. The reason why it is used as a white pigment / cosmetic is because of its excellent concealability and ultraviolet shielding ability. In order to sufficiently bring out such functions when used, it is required that titanium dioxide be a dispersion with very little aggregation. This is because when aggregated particles are present, not only the touch and smoothness are deteriorated, but also titanium dioxide is unevenly present on the skin, resulting in inferior UV shielding ability and uneven concealment. It is because it ends.

  When used as a raw material for dielectric barium titanate or other ceramic materials, it is usually passed through a process in which titanium dioxide is slurried with other components, mixed or pulverized, molded, and then sintered. It is. The reason for undergoing such a process is also to eliminate uneven distribution of raw material components in the sintered body. The uneven distribution of raw material components causes non-uniform growth of the structure during sintering, resulting in a decrease in strength or a defect in performance. Particle pores (closed pores or open pores) also cause unevenness of the structure, which causes a decrease in strength and performance of the sintered body. Aggregated particles often cause uneven distribution of the composition and are reduced by the mixing and pulverization process. However, in order to sufficiently reduce in practical use, a great deal of energy must be spent in the mixing and pulverization. Therefore, it is preferable that the raw material powder has a characteristic of being easily dispersed, that is, easily mixed with other components.

  In addition, the particle size is also a very important factor in eliminating the uneven distribution of a single component. In ceramics applications, multiple component powders having different particle size distributions may be mixed and molded and sintered. If a plurality of powders having different particle sizes can be easily dispersed, a homogenization step requiring large energy can be omitted. For example, a powder having a good dispersibility of 5 to 200 μm, which is often used in electronic materials-related ceramic raw materials and the like that strictly require a uniform composition of a sintered body, is very useful. Further, high purity may be required at the same time for powders that require such a uniform composition. This is because the function can be expected to be further improved by the high purity.

  Such a highly dispersible powder having high purity and no pores is preferable not only as a ceramic raw material but also as a rutile single crystal raw material used as a polarizer material for an optical isolator. The rutile single crystal is a Bernoulli method in which titanium dioxide powder is introduced into an oxyhydrogen flame to grow a single crystal, and a floating zone method in which a single crystal is grown by heating and melting the sample by collecting the light from the light source. and so on. In terms of powder characteristics, the purity and flowability of the powder are important in the former Bernoulli method, and the purity and moldability of the powder are important in the latter floating zone method. In general, fluidity is adjusted by granulation, but granulation is not necessary if the particle size is in the range of 5 to 200 μm as described above. Moreover, if it can disperse | distribute uniformly with the powder from which a particle size differs, moldability will also become favorable. Since rutile single crystals dislike coloring, high purity is required, and it is desirable that there are no vacancies in the particles that cause scattering of transmitted light.

  Next, the photocatalyst will be described. Titanium dioxide has the property of absorbing electrons with a wavelength of about 400 nm or less to excite electrons. When the generated electrons and holes reach the particle surface, they combine with oxygen and water to generate various radical species. This radical species mainly exhibits an oxidizing action, and oxidatively decomposes the substance adsorbed on the surface. This is the basic principle of the photocatalyst.

  In order to utilize the photocatalytic ability of titanium dioxide, it is necessary to support titanium dioxide on the surface of the structure to make it easy to adsorb substances. In general, titanium dioxide is often loaded on a structure using slurryed titanium dioxide as a raw material and dried. In the presence of aggregates, when dried or solidified, the aggregate composition is supported on the structure as it is, so that the film composition becomes non-uniform, and the transparency and smoothness of the film are impaired, resulting in a reduction in commercial value. is there. Moreover, in order to exhibit the photocatalytic ability, it is necessary to be exposed on the surface on which titanium dioxide is formed. The thickness of this film is generally several μm to several tens of μm when an organic binder is employed. Therefore, the photocatalytic particles having an average particle diameter of about 5 to 200 μm are highly likely to have a part of the particles on the film, and can fully exhibit the photocatalytic ability. Basically, titanium dioxide that is expected to have a photocatalytic activity is preferably highly pure. This is because the presence of impurities may reduce the photocatalytic ability. For example, Fe, Cl, and the like are impurities that are undesirable because they trap generated radicals.

  As described above, there is a demand for high-purity, void-free powders that have good dispersibility in a wide range of applications. Moreover, since there exists a suitable particle size according to a use, the technique which can manufacture arbitrary particle sizes is calculated | required.

  Titanium dioxide production methods are roughly classified into a gas phase method and a liquid phase method. The vapor phase method is a method in which titanium tetrachloride or the like is vaporized and reacted with an oxidizing gas such as oxygen or water vapor, and the liquid phase method is a method in which an aqueous solution such as titanyl sulfate is hydrolyzed. The gas phase method is far superior to the liquid phase method in terms of obtaining a powder having low aggregation.

  On the other hand, in the vapor phase method, it is very difficult to produce particles having an average particle size exceeding 2 μm. In terms of controllability of the particle size, the liquid phase method is easier to control the particle size over a wider range. However, in the liquid phase method, the concentration of generated particles and the concentration of nuclei in the reaction field are much higher than in the gas phase method. In addition, a solid-liquid separation / drying step is required, and liquid cross-linking between particles generated during solid-liquid separation causes aggregation during drying.

  Examples of the vapor phase method include hydrolyzing titanium tetrachloride in JP-A-6-340423 in a flame to obtain titanium dioxide having a high rutile content, and titanium tetrachloride in JP-A-7-316536. A method of hydrolyzing in a high temperature gas phase to obtain crystalline transparent titanium dioxide is known.

  However, even in these methods, it is difficult to produce a powder without agglomeration. Relatively low agglomeration, i.e., a monodisperse powder can be obtained by introducing titanium dioxide powder directly into a high-temperature flame and melting the powder at that high temperature to obtain titanium dioxide powder. These include a melting method, a method of introducing titanium tetrachloride gas or titanium alkoxide instead of titanium dioxide, and simultaneously producing and spheroidizing titanium dioxide, and a method of firing and pulverizing titanium dioxide as a raw material.

  The method disclosed in Japanese Patent Laid-Open No. 10-174864 is a typical example of a flame melting method using titanium dioxide as a raw material by introducing rutile type titanium dioxide powder into a high temperature flame to form anatase type titanium dioxide having photocatalytic activity. The method disclosed in Japanese Patent Application Laid-Open No. 2001-151509, which obtains spherical titanium dioxide by increasing the temperature by using hydrogen in the gas phase reaction of titanium tetrachloride, is a typical example of the method of simultaneously producing titanium dioxide and spheroidizing.

  The feature of the flame melting method is that the productivity of the fine powder is extremely low or the fine powder cannot be produced. The flame melting method is a technique in which raw material titanium dioxide is introduced into a flame, and titanium dioxide particles partially melted by heat are spheroidized by their surface tension. The titanium dioxide used as a raw material is a relatively coarse powder obtained by a liquid phase method. However, if a fine powder is to be obtained, it is necessary to use the fine powder as a raw material. However, if the raw material powder is a fine particle, the powder is agglomerated and the primary particles are small, so that they are easily melted, and the movement of the powder becomes active due to the turbulent flame flow. As a result, the chances of association with other particles increase, so that coarse particles increase and at the same time grain growth easily occurs, and the probability of taking air into the particles during the growth process also increases. When the raw material powder is large to some extent, it is also a feature that spherical particles having almost no pores and close to the raw material particle size can be obtained.

  On the other hand, the method of introducing titanium alkoxide, titanium tetrachloride, etc., which are raw materials, into a combustion flame and hydrolyzing it to obtain titanium dioxide requires a process from nucleation to grain growth in the combustion flame. Therefore, it is possible to increase the particle size to some extent by increasing the residence time at high temperatures, such as increasing the amount of flammable gas and lengthening the flame, but excessive equipment is required. In particular, when titanium tetrachloride is used as a raw material, the residence time of high-temperature chlorine gas or high-temperature hydrogen chloride gas is increased, which promotes corrosion of the reactor / equipment and makes it difficult to obtain a high-purity product. Therefore, in general, it is extremely difficult for such a method to grow primary particles to large particles exceeding 2 μm.

  From the above points, in the method using a flame, it is difficult to control the high temperature zone length and the residence time, and it is difficult to control the particle size and increase the purity. As a result, the particle size range of several μm to several hundred μm. It was difficult to obtain high purity titanium dioxide.

  The method by stationary firing is based on the premise that grains are grown, in other words, a method in which grains are grown by facilitating movement of atoms at a high temperature. At that time, atomic movement from the device material is unavoidable, and impurities are mixed. Further, in the case of stationary firing, pulverization after firing, that is, particle size adjustment is indispensable, and impurities from the pulverized media cannot be avoided. Fe, Cr, Ni, Al, Si, Zr, etc. are mentioned as a substance which is easy to mix by a stationary baking method.

  The problem to be solved in the present invention is a wide range of industrial applications in the flame melting method for obtaining titanium dioxide with good dispersibility, especially from several μm to several hundred μm suitable as a raw material for photocatalyst powders and ceramics. It is possible to obtain a titanium dioxide having a high purity and good dispersibility having an average diameter in the range of 5 and a production method thereof.

  In view of the above, the present invention has been made as a result of earnest research. The present inventors can easily spheroidize with a short high-temperature residence time by using titanium dioxide having a specific particle size with good dispersibility and a raw material obtained by a specific production method as a raw material titanium dioxide for a flame melting method. The present inventors have found a method for obtaining high-purity, non-porous titanium dioxide that is easy to control the particle size and has good dispersibility.

That is, the present invention relates to the following inventions (1) to (27).
(1) In titanium dioxide, the average particle diameter measured by a laser particle size analysis method is in the range of 5 to 200 μm, the purity as TiO 2 is 99.5% by mass or more, and Fe, Ni, Cr, Al And Zr are each 20 mass ppm or less, Si is 40 mass ppm or less, Cl is 0.05 mass% or less, and S is 50 mass ppm or less.
(2) Titanium dioxide according to item 1 above, wherein the density of titanium dioxide is 3.7 g / cm ³ or more.
(3) Titanium dioxide according to any one of the preceding items 1 to 2, wherein the titanium dioxide has photocatalytic activity.
(4) Titanium dioxide has the following formula (1)
Sphericality = (circumference of a circle having the same area as the projected area of the particle) / (length of the contour of the projected particle image) (1)
4. Titanium dioxide according to any one of items 1 to 3, which is a particle having a sphericity of 0.9 or more defined by

(5) In the method of obtaining spherical titanium dioxide by introducing raw material titanium dioxide into the flame, the raw material titanium dioxide introduced into the high-temperature flame formed by the combustible gas and the combustion-supporting gas oxidizes titanium tetrachloride. 5. The method for producing titanium dioxide as described in any one of 1 to 4 above, which is produced by a gas phase method in which high temperature oxidation is performed with a reactive gas.
(6) In the gas phase method in which the raw material titanium dioxide produces titanium dioxide by oxidizing titanium tetrachloride with an oxidizing gas, each of the gas containing titanium tetrachloride and the oxidizing gas is preheated to 500 ° C. or more, 6. The method for producing titanium dioxide as described in 5 above, wherein the titanium dioxide is obtained by reacting each of them by supplying them to a reaction tube at a flow rate of 10 m / sec or more.
(7) The method for producing titanium dioxide as described in (6) above, wherein the reaction is carried out by retaining a gas containing titanium tetrachloride and an oxidizing gas in a temperature region in the reaction tube exceeding 600 ° C. for a period of 3 seconds or less.
(8) The raw material titanium dioxide has a BET equivalent particle diameter of 7 to 500 nm, an average particle diameter of 0.4 to 10 μm measured by a laser particle size analysis method, Fe, Ni, Cr, Al and Zr, each 20 mass ppm or less, 8. The method for producing titanium dioxide as described in any one of 5 to 7 above, which is vapor phase titanium dioxide containing Si at 40 mass ppm or less, Cl at 1 mass% or less, and S at 200 mass ppm or less.
(9) Gas phase method dioxide in which the raw material titanium dioxide contains Fe, Ni, Cr, Al and Zr each of 20 mass ppm or less, Si 40 mass ppm or less, Cl 1 mass% or less, and S 200 mass ppm or less. Titanium gas phase method titanium dioxide having a BET equivalent particle diameter of 7 to 500 nm and an average particle diameter of 0.4 to 10 μm measured by a laser particle size analysis method, a BET equivalent particle diameter of 150 to 1000 nm and a laser particle size 8. The method for producing titanium dioxide as described in any one of 5 to 7 above, which is a mixed powder with vapor phase titanium dioxide having an average particle diameter of 0.5 to 20 μm measured by an analysis method .
(10) The method for producing titanium dioxide as described in any one of 5 to 9 above, wherein the raw material titanium dioxide is dispersed and transported by a carrier gas in a turbulent state having a Reynolds number of 10,000 or more in the pipe and introduced into the high-temperature flame. .
(11) The jet velocity of the nozzle of the raw material carrier gas is 8 Nm / sec (N means the standard state. Nm / sec is the flow rate (Nm ³ / sec) converted from the flow rate of the gas ejected from the nozzle to the standard state. The flow rate obtained by dividing by the area (m ² ) of the nozzle ejection port.) Or more, and the ejection flow rate of the burner nozzle of the combustible gas is 0.8 times to 4 times the nozzle ejection flow rate of the raw material carrier gas The oxidizing gas burner nozzle ejection flow rate is in the range of 1.3 to 11 times the raw material carrier gas nozzle ejection flow rate, and the oxidizing gas ejection flow rate is larger than the combustible gas ejection flow rate. The method for producing titanium dioxide according to 10 above.
(12) The flammable gas is any one of methane, ethane, propane, ethylene, propylene, acetylene, butane, LPG, hydrogen, carbon monoxide, or a mixed gas thereof. A method for producing titanium dioxide according to claim 1.
(13) The method for producing titanium dioxide according to any one of items 10 to 12, wherein the oxidizing gas contains 15% by volume or more and 100% by volume or less of oxygen.
(14) The method for producing titanium dioxide according to any one of items 10 to 13, wherein the raw material titanium dioxide is jetted together with the carrier gas from the upstream portion of the flame in the downstream direction of the combustion gas.

(15) An organic polymer composition comprising 0.01 to 80% by mass of the titanium dioxide according to any one of items 1 to 4 in the total mass of the composition.
(16) The organic polymer according to item 15 above, wherein the organic polymer of the organic polymer composition is at least one resin selected from the group consisting of synthetic thermoplastic resins, synthetic thermosetting resins, and natural resins. Composition.
(17) The organic polymer composition according to item 15 or 16, wherein the organic polymer composition is a compound.
(18) The organic polymer composition according to item 15 or 16, wherein the organic polymer composition is a master batch.
(19) A molded article obtained by molding the organic polymer composition as described in 15 or 16 above.
(20) A slurry comprising the titanium dioxide described in any one of (1) to (4) above.
(21) A coating agent comprising the titanium dioxide according to any one of items 1 to 4.
(22) A paint comprising the titanium dioxide described in any one of (1) to (4) above.
(23) A structure comprising the titanium dioxide according to any one of items 1 to 4 on a surface thereof.
(24) A titanium dioxide single crystal characterized by using the titanium dioxide according to any one of items 1 to 4 as a raw material.
(25) A ceramic molded body characterized by using the titanium dioxide according to any one of items 1 to 4 as a raw material.
(26) A dielectric material comprising the titanium dioxide described in any one of (1) to (4) above.
(27) A cosmetic comprising the titanium dioxide according to any one of items 1 to 4.

  The titanium dioxide of the present invention has an average diameter in the range of 5 μm to 200 μm, which is widely used industrially, and has high purity and excellent dispersibility. Therefore, it is used as an organic polymer composition, paint, cosmetics and the like. In particular, it can be used as a photocatalyst powder, ceramic molded body raw material, dielectric raw material, rutile single crystal raw material and the like. In the present invention, titanium dioxide having such dispersibility and high purity and a method for producing the same are provided.

Details of the present invention will be described below.
For example, ultrafine titanium dioxide having a BET equivalent particle diameter of 7 to 1,000 nm to be a raw material titanium dioxide can be obtained as follows.

  In the vapor phase method of producing titanium dioxide by oxidizing titanium tetrachloride with oxidizing gas at high temperature, the titanium tetrachloride-containing gas and oxidizing gas are preheated to 500 ° C or higher and supplied to the reaction tube, respectively. Let Here, the preheated gas containing titanium tetrachloride and the oxidizing gas are supplied to the reaction tube at a flow rate of 10 m / second or more, respectively. In addition, the preheated gas containing titanium tetrachloride and the oxidizing gas are allowed to react in a temperature region where the temperature in the reaction tube exceeds 600 ° C. for 3 seconds or less. In this production method, it is preferable that a gas containing preheated titanium tetrachloride and an oxidizing gas are supplied into the reaction tube to generate turbulence in the reaction tube.

  Further, the gas containing titanium tetrachloride and the oxidizing gas may be supplied into the reaction tube by a coaxial parallel flow nozzle. Moreover, the gas containing titanium tetrachloride can contain 10 to 100% of titanium tetrachloride.

  The characteristics of the vapor phase titanium dioxide obtained by the above production method will be described. Vapor phase titanium dioxide forms a chain structure in which primary particles are long and continuous with weak point bonds. This chain structure is formed in a reaction field where particles are formed, and is characteristic of a powder obtained by a vapor phase method. The length varies depending on the particle size of the primary particles. The powder obtained by the liquid phase method does not have such a chain structure, and is an aggregate in which primary particles gather together in a lump.

  According to the present invention, a powder having a BET-equivalent particle diameter in the range of 7 to 500 nm obtained by the vapor phase method and a powder in the range of 150 to 1000 nm are appropriately mixed or used alone as a raw material. Thus, it is possible to obtain titanium dioxide having an average particle diameter of 5 to 200 μm in an arbitrary range by a laser particle size analysis method. The product particle size can be controlled by changing the mixing ratio of the raw materials and adjusting the combustion flame. In order to obtain a product with a large particle size, the proportion of the raw material on the large particle size side may be increased.

  The fact that the powder obtained by the vapor phase method is suitable as the raw material of the present invention is largely due to this chain structure. The chain structure is considered to be a unit of aggregation in the gas phase method and a unit of movement in the air stream. In addition, since the primary particles have a chain-like shape, they are easily subjected to airflow resistance and easy to transport, and the powder is introduced into the flame in a state of being dispersed by the shearing force received from the airflow. In addition, the air accompanying the spheroidization easily escapes, and spherical particles that are close to the theoretical density, that is, have very few holes can be obtained.

The density of the titanium dioxide thus obtained is usually 3.7 g / cm ³ or more. Further, the titanium dioxide particles obtained in this way have the following formula (1)
Sphericality = (circumference of a circle having the same area as the projected area of the particle) / (length of the contour of the projected particle image) (1)
The sphericity defined by is usually 0.9 or more.

  When used in pigments, cosmetics, etc., particles having a high sphericity take advantage of the rolling property and become a powder excellent in touch and smoothness. When used as a ceramic raw material, it is possible not only to obtain a compact having a high density by appropriate blending, but also to have a high dispersibility and fluidity. Moreover, when using as fillers, such as resin, it becomes a powder excellent in filling property. Thus, the powder having a low degree of aggregation and a spherical shape is a very useful powder.

  The pipe diameter and flow velocity are determined so that the air flow for transporting the raw material titanium dioxide has a Reynolds number in the pipe of 10,000 or more, preferably 15,000 or more. It is possible to efficiently disperse the powder obtained by the vapor phase method with the Reynolds number in the pipe in this range.

  On the other hand, since the powder by the liquid phase method is agglomerated particles, the bulk density is large and the dispersibility is poor. Therefore, when the powder obtained by the liquid phase method is used as raw material titanium dioxide, a technique for dispersing it in an air flow is first required. In order to disperse the agglomerated powder having poor dispersibility, it is common to increase the carrier gas and increase the flow rate. However, in terms of powder characteristics, the resistance and shearing force received from the air current cannot be expected as the powder obtained by the vapor phase method. Therefore, it is necessary to make the flow velocity very high. However, if the amount of carrier gas is excessive, the temperature of the combustion flame is lowered due to the cooling effect. In addition, the shape of the flame is disturbed, and the temperature of the reaction zone is lowered more than necessary. In order to compensate for this, a method of reducing the amount of combustible gas is conceivable, but the high temperature zone becomes long and particle size control becomes difficult. Even if the powder is introduced into the reaction zone, it is a powder that is agglomerated so that it becomes a low-density powder with bubbles remaining inside the particles.

  It is considered that titanium dioxide produced by the vapor phase method introduced into the high temperature zone melts and contracts by receiving heat, and one chain structure forms one spherical particle. Since vapor phase titanium dioxide has small primary particles, it is easy to melt and spheroidize even at a relatively low temperature. Due to this feature, spherical titanium dioxide can be obtained even if the combustion amount of the flame gas is lowered.

  Normally, in a high-temperature flame, a plurality of spherical particles associate and grow to grow into large-diameter particles. However, the flame temperature is relatively low, and as described above, they are well dispersed in chain structure units. Therefore, it is difficult for the melted particles to associate and grow. As a result, a fine powder having a narrow particle size distribution width, that is, a sharp particle size distribution can be obtained.

  A powder having a wide particle size distribution is not preferable for use. For example, when used as a ceramic raw material, it leads directly to the non-uniformity of the structure after sintering and lowers the bending strength. In addition, as a resin filler for which high filling is desired, a sharper particle size distribution is preferable because the particle size is blended for higher filling.

  In order to avoid a wide particle size distribution, the high temperature zone should be as short as possible. As described above, the high temperature zone is a place for association and growth along with the spheroidization of particles. In order to obtain a particle size distribution as narrow as possible, it is desirable to set the temperature range so that spheroidization occurs and no association / growth occurs at the same time. However, since the reaction of the combustion zone and the grain growth are complicatedly related to the characteristics of the raw materials and the flame factors, it is very difficult to control in such a temperature range. In the present invention, the high temperature zone temperature is adjusted to be as low as possible by controlling the flow ratio of the flammable gas / oxidizing gas and the carrier gas, and the gas phase method dioxide having a small primary particle having a chain structure in the raw material powder. This problem was solved by using titanium.

  The greatest advantage of this method is that impurities can be reduced in addition to controlling the particle size distribution.

  The combustion flame is generally formed by a burner. Since the burner undergoes a rapid temperature change upon ignition, general ceramics as a heat-resistant material is unsuitable for apparatus components. Therefore, although metal materials are used as the device members, it is inevitable that impurities are mixed into the product due to wear of the members softened by the high temperature of the flame. However, by using a powder having the property of being easily transported by air flow, such as a powder obtained by a vapor phase method, the wear can be reduced and the flame is controlled at a low temperature, so the apparatus temperature is also lowered. Impurities due to wear are reduced.

Also, the shape of the burner is preferably such that the product purity does not decrease even when a metal member is used. The shape of the burner is preferably a coaxial triple tube structure. That is, the raw material titanium dioxide is passed through the innermost tube, and a carrier gas such as air or nitrogen that transports it, gas fuel gas such as LPG is provided outside the outer tube, and oxidizing gas such as oxygen or air is provided in the outermost tube. A structure that passes through. The flow velocity of the raw material carrier gas ejected from the burner nozzle is 8 Nm / second (N means the standard state. Nm / second is the flow rate (Nm ³ / second) obtained by converting the flow rate of the gas ejected from the nozzle into the standard state. The flow rate obtained by dividing by the area (m ² ) of the nozzle outlet is shown below. The same shall apply hereinafter.) Or more, preferably 8 Nm / second to 50 Nm / second, and the Reynolds number in the pipe is 10,000 or more, preferably Determines the pipe diameter to be 15,000 or more. Under this condition, the raw material powder can be sufficiently dispersed. The burner nozzle ejection flow rate of the combustible gas is set to be 0.8 to 4 times, preferably 0.9 to 3 times the innermost pipe, that is, the ejection flow rate of the raw material carrier gas. The burner nozzle ejection flow rate of the oxidizing gas is set in a range of 1.3 to 11 times, preferably 3 to 6 times the ejection flow rate of the raw material carrier gas. Thereby, the combustion flame shape suitable for obtaining the powder of the present invention can be maintained. Further, under this condition, Fe, Ni, Cr, Si, Al, and Zr are hardly mixed and can be made equal to the impurity level of the raw material. Therefore, it is preferable to use a raw material having as high a purity as possible.

Impurities such as Cl and S generate HCl, Cl ₂ , SO _{2 and the} like through a high temperature history during flame melting. When the material constituting the combustion zone is a stainless steel material, it is corroded by such a gas, and impurities such as Fe increase. Therefore, it is preferable that Cl and S in the raw material are low. For this reason, the purity of TiO ₂ as a raw material is 99.5% by mass or more, Fe, Ni, Cr, Al, and Zr are each 20 mass ppm or less, preferably 10 mass ppm or less, and Si is 40 masses. ppm or less, preferably 20 mass ppm or less, Cl is 1 mass% or less, preferably 0.2 mass% or less, and S is 200 mass ppm or less, preferably 100 mass ppm or less.

  The spherical titanium dioxide obtained in this way is collected by a bag filter or the like to obtain a product.

When the raw material titanium dioxide is used, the obtained titanium dioxide has a purity as TiO ₂ of 99.5% by mass or more, and Fe, Ni, Cr, Al, and Zr are each 20 ppm by mass or less. 1 mass ppm to 10 mass ppm, preferably 0.1 mass ppm to 10 mass ppm, and Si is 40 mass ppm or less, preferably 1 mass ppm to 20 mass ppm, more preferably 0.1 mass ppm. To 20 mass ppm, and Cl is 1 mass% or less, preferably 0.001 mass% to 0.2 mass%, more preferably 0.0001 mass% to 0.2 mass%, and S is 200 mass ppm or less. Preferably it becomes 1 mass ppm-100 mass ppm, More preferably, it becomes 0.1 mass ppm-100 mass ppm.

  A typical production apparatus for producing vapor phase titanium dioxide used as a raw material of the present invention is schematically shown in FIG. 1, and an example of a typical production apparatus for carrying out the present invention is schematically shown in FIG. Show. Hereinafter, a description will be given based on this figure.

  First, FIG. 1 will be described. 1 is a coaxial parallel flow nozzle, 2 is a preheater, 3 is a reaction tube, and 4 is a bag filter. Raw material titanium dioxide is produced according to this typical flow.

  Next, FIG. 2 will be described. Reference numeral 5 denotes a feeder and a hopper for quantitatively supplying vapor phase titanium dioxide as a raw material. The raw material supply amount is arbitrary, but it is necessary to increase the Reynolds number in the pipe of the carrier gas as the raw material particle size increases as the material is supplied in a large amount.

  6 is a carrier gas for transporting the raw material powder into the flame, and air, nitrogen gas or the like is used. The raw material titanium dioxide sent out by the raw material feeder 5 is dispersed and transported by this carrier gas and introduced into the flame. The carrier gas needs to be in a turbulent state due to the dispersion of the raw material powder, and the flow velocity and the pipe diameter are set so that the Reynolds number in the pipe is 10,000 or more, preferably 15,000 or more.

  7 is a combustible gas for creating a combustion flame, and basically any flammable gas can be used, but preferably methane, ethane, propane, ethylene, propylene, acetylene, butane, LPG, Either hydrogen, carbon monoxide, or a mixed gas thereof, preferably LPG is preferred. The jetting flow rate of the carrier gas is 8 Nm / second or more, and the burner nozzle jetting flow rate of the combustible gas is preferably 0.8 to 4 times.

  8 is a combustion-supporting gas (also referred to as an oxidizing gas). Any gas containing oxygen can be used as the oxidizing gas, but oxygen is preferred. The burner nozzle ejection flow rate of the oxidizing gas is in the range of 1.3 to 11 times, and the ejection flow rate of the oxidizing gas is preferably larger than the ejection flow rate of the combustible gas. Carrier gas, combustible gas, and combustion-supporting gas containing raw material powder are introduced into the combustion tube using a coaxial triple tube nozzle to form a flame. To stabilize the flame, a coaxial triple pipe is preferable. Furthermore, a carrier gas is used for the innermost pipe, an oxidizing gas is used for the outermost pipe, and a combustible gas is supplied to the pipe sandwiched between the two. Preferred for.

  A combustion flame is formed in the combustion tube 9. Since the temperature of the combustion tube changes abruptly, it is preferable to use a stainless steel tube equipped with a water cooling jacket. In general, ceramics are not preferred because they cannot withstand rapid temperature changes.

  The fine powder generated in the combustion tube is collected by the bag filter 10, and the product is collected by the product hopper 12. The combustion exhaust gas 11 is discharged out of the system.

  The titanium dioxide of the present invention can be used for applications such as photocatalyst materials, additives for resin products / rubber products / paper / paints / printing inks, cosmetics, ceramic products, electronic parts, and rutile single crystal raw materials. In particular, it can be preferably used for applications requiring dispersibility / fillability in a medium and high purity.

  The titanium dioxide of the present invention can be used as a composition by adding to an organic polymer, for example. Examples of the organic polymer include a synthetic thermoplastic resin, a synthetic thermosetting resin, and a natural resin. Specific examples of such an organic polymer include, for example, polyolefins such as polyethylene, polypropylene, and polystyrene, polyamides such as nylon 6, nylon 66, and aramid, polyesters such as polyethylene terephthalate and unsaturated polyester, polyvinyl chloride, and polyvinyl chloride. Vinylidene, polyethylene oxide, polyethylene glycol, silicone resin, polyvinyl alcohol, vinyl acetal resin, polyacetate, ABS resin, epoxy resin, vinyl acetate resin, cellulose, rayon and other cellulose derivatives, urethane resin, polycarbonate, urea resin, fluorine resin , Polyvinylidene fluoride, phenol resin, celluloid, chitin, starch sheet, acrylic resin, melamine resin, alkyd resin and the like.

  These organic polymer compositions containing the titanium dioxide of the present invention include, for example, a paint (coating composition), a compound (for example, the powder-containing resin composition), and a master for a molded article containing titanium dioxide at a high concentration. It can be used in the form of a batch. You may add additives, such as antioxidant, an anti-static agent, and a metal fatty acid salt, to an organic polymer composition.

  The concentration of the titanium dioxide of the present invention in the organic polymer composition is preferably 0.01 to 80% by mass, particularly preferably 1 to 50% by mass, based on the total mass of the composition.

  By molding such a polymer composition, a molded body having an ultraviolet shielding ability can be obtained. Examples of such a molded body include fibers, films, and plastic molded bodies.

  Moreover, after dispersing the titanium dioxide of the present invention in water or an organic solvent, a binder can be optionally added to form a coating agent. The binder material is not particularly limited, and may be an organic binder or an inorganic binder.

  As such a binder, for example, polyvinyl alcohol, melamine resin, urethane resin, celluloid, chitin, starch sheet, polyacrylamide, acrylamide, polyester such as unsaturated polyester, polyvinyl chloride, polyvinylidene chloride, polyethylene oxide, polyethylene glycol, Examples thereof include silicon resin, vinyl acetal resin, epoxy resin, vinyl acetate resin, urethane resin, urea resin, fluorine resin, polyvinylidene fluoride, and phenol resin. Further, as an inorganic binder, for example, zirconium oxychloride, zirconium zirconium chloride, zirconium nitrate, zirconium sulfate, zirconium acetate, zirconium carbonate such as ammonium carbonate, zirconium propionate, silicon compounds such as alkoxysilane, silicate, aluminum, Examples thereof include metal alkoxides of titanium.

  Moreover, the addition amount of the binder in the coating agent is preferably 0.01% by mass to 20% by mass, and particularly preferably 1% by mass to 10% by mass.

  When the content of the binder is 0.01% by mass or less, sufficient adhesion cannot be obtained after coating, and when it exceeds 20% by mass, problems such as thickening occur and it is economically disadvantageous.

  Furthermore, you may equip the surface of a structure with the titanium dioxide of this invention. Such a structure is not particularly limited, and may be composed of, for example, inorganic materials such as metal, concrete, glass, and ceramics, and composed of organic materials such as paper, plastic, wood, and leather. However, it may be a combination thereof. Examples of these include, for example, building materials, machines, vehicles, glass products, household appliances, agricultural materials, electronic equipment, tools, tableware, bath products, toilet products, furniture, clothing, fabric products, textiles, leather products, paper products, Examples include sports equipment, baskets, containers, glasses, signboards, piping, wiring, metal fittings, sanitary materials, and automobile goods.

  These methods provided on the surface are not particularly limited. For example, the organic polymer composition and the coating agent described above may be applied directly to the structure or already applied to the surface. You may apply | coat on the structure with a film | membrane. Furthermore, you may form another coating film on these.

  The present invention will be described using examples and comparative examples, but the present invention is not limited to these examples.

Example 1:
Gaseous titanium tetrachloride with a concentration of 100% is preheated to 1,000 ° C., and a mixed gas of 96% oxygen and 4% by volume of water vapor is preheated to 1,000 ° C., respectively, using a coaxial parallel flow nozzle, and a flow rate of 49 m / Second and 50 m / second. For production, an apparatus shown in FIG. 1 was used, and titanium tetrachloride gas was introduced into the inner tube. The flow rate in the tube at a reaction temperature of 1,630 ° C. was 8 m / sec as a calculated value. In addition, after reaction, cooling air is introduced into the reaction tube so that the high temperature residence time in the reaction tube is 0.1 seconds or less, and then the titanium dioxide powder produced using a polytetrafluoroethylene bag filter is collected. did.

  The obtained titanium dioxide powder had a BET equivalent particle size of 300 nm and an average particle size measured by a laser particle size analysis method of 0.6 μm. When Fe, Al, and Si were analyzed using Shimadzu Corporation plasma emission spectrometer ICPS-7500, they were 5 ppm, 3 ppm, and 15 ppm, respectively, and Cr, Ni, and Zr were detected ( 1 ppm by mass) or less. Moreover, it was 0.01 mass% when Cl was analyzed using Hiranuma Sangyo Co., Ltd. automatic titrator C-500. This titanium dioxide was used as a raw material titanium dioxide.

  Next, LPG and oxygen were ejected from the nozzle at a flow rate of 90 Nm / second and 200 Nm / second from the intermediate tube and the outermost tube of the coaxial triple tube, respectively, to form a combustion flame.

The raw material titanium dioxide was transported through the innermost tube together with air as a carrier gas at a supply rate of 6 kg / hour, and ejected from the nozzle. At this time, the nozzle ejection velocity of air was 40 Nm / second, and the Reynolds number in the piping to be conveyed was 43,000. The burned gas containing solids was sent to the bag filter to collect the powder. The powder thus obtained was white, and when particle size analysis was performed using a laser particle size analyzer SALD-2000J manufactured by Shimadzu Corporation, a spherical powder having an average particle size of 160 μm was obtained. . Moreover, when Fe was analyzed using Shimadzu Corporation plasma emission analyzer ICPS-7500, it was 8 ppm by mass, and Cr, Ni, Al, Si, and Zr were analyzed. The equivalence, Cr, Ni and Zr were all below the detection limit. Similarly, when S was analyzed, it was 6 ppm by mass. Moreover, it was 0.003 mass% when Cl was analyzed using Hiranuma Sangyo Co., Ltd. automatic titrator C-500. Further, the specific gravity of this powder was measured by the specific gravity bin method according to JIS Z 8807 and converted to obtain the density, which was 3.98 g / cm ³ . The sphericity was determined by photographing 300 to 500 particles of this powder with a scanning electron microscope and measuring this image with an image analyzer NIRECO LUZEX5000. No particles having a sphericity of 0.9 or less were observed, and the simple average sphericity was 0.95.

Example 2:
A gas consisting of 23% by volume of gaseous titanium tetrachloride and 77% by volume of nitrogen is preheated to 1,100 ° C., and an oxidizing gas consisting of 45% by volume of air and 55% by volume of water vapor is preheated to 1,000 ° C., respectively. Using parallel flow nozzles, they were introduced into the reaction tube at flow rates of 92 m / second and 97 m / second, respectively. A gas containing titanium tetrachloride was introduced into the inner tube. The flow rate in the tube at the reaction temperature of 1,250 ° C. was 13 m / sec as a calculated value. After the reaction, cooling air was introduced into the reaction tube so that the high-temperature residence time in the reaction tube was 0.2 seconds, and then titanium dioxide powder was collected using a polytetrafluoroethylene bag filter.

  The obtained titanium dioxide had a BET equivalent particle size of 10 nm and an average particle size measured by a laser particle size analysis method of 0.16 μm. Moreover, when Fe, Cr, Ni, Al, Si, and Zr were analyzed using Shimadzu Corporation plasma emission analyzer ICPS-7500, Fe was 3 mass ppm, Al was 3 mass ppm, and Si was 26 mass. ppm, and Cr, Ni, and Zr were all below the detection limit. Moreover, it was 0.8 mass% when Cl was analyzed using Hiranuma Sangyo Co., Ltd. automatic titrator C-500. This titanium dioxide was used as a raw material titanium dioxide.

  LPG and oxygen were ejected from the nozzle at the flow rates of 25 Nm / second and 105 Nm / second from the intermediate tube and the outermost tube of the coaxial triple tube, respectively, to form a combustion flame.

Next, the raw material titanium dioxide was transported in the innermost tube together with air as a carrier gas at a supply rate of 2 kg / hour and ejected from the nozzle. At this time, the nozzle nozzle flow velocity of air was 23 Nm / sec, and the Reynolds number in the transported piping was 23,000. The burned gas containing solids was sent to the bag filter to collect the powder. The powder thus obtained was white, and when a particle size analysis was performed using a laser type particle size analyzer SALD-2000J manufactured by Shimadzu Corporation, a spherical powder having an average particle size of 9 μm was obtained. . Moreover, when Fe, Cr, Ni, Al, Si, and Zr were analyzed using Shimadzu Corporation plasma emission analyzer ICPS-7500, Fe was 7 mass ppm, Al was 3 mass ppm, and Si was 26 mass. ppm, Cr, Ni, and Zr were all below the detection limit. Similarly, when S was analyzed, it was 5 ppm by mass. Moreover, it was 0.02 mass% when Cl was analyzed using Hiranuma Sangyo Co., Ltd. automatic titrator C-500. Further, when the density and sphericity of the powder were determined in the same manner as in Example 1, they were 3.75 g / cm ³ and 0.96.

Example 3:
LPG and oxygen were ejected from the nozzle at the flow rates of 45 Nm / second and 115 Nm / second from the intermediate tube and the outermost tube of the coaxial triple tube, respectively, to form a combustion flame.

Next, the raw material titanium dioxide having a BET equivalent particle diameter of 300 nm used in Example 1 and the raw material titanium dioxide having a BET equivalent particle diameter of 10 nm used in Example 2 were mixed at a mass ratio of 1: 1, and 3 kg / It was transported in the innermost pipe together with nitrogen as a carrier gas at a time supply speed, and was ejected from the nozzle. At this time, the flow rate of the nitrogen nozzle was 30 Nm / sec, and the Reynolds number in the transported pipe was 31,000. The burned gas containing solids was sent to the bag filter to collect the powder. The powder thus obtained was white, and when the particle size analysis was performed using a laser particle size analyzer SALD-2000J manufactured by Shimadzu Corporation, the average particle size was 90 μm. Moreover, when Fe was analyzed using Shimadzu Corporation plasma emission spectrometer ICPS-7500, it was 6 mass ppm, and S was 6 mass ppm. Similarly, when Cr, Ni, Al, Si, and Zr were analyzed, Al was 3 ppm by mass, Si was 20 ppm by mass, and Cr, Ni, and Zr were all below the detection limit. Moreover, it was 60 mass ppm when Cl was analyzed using the automatic titration apparatus C-500 by Hiranuma Sangyo Co., Ltd. Further, when the density and sphericity of the powder were determined in the same manner as in Example 1, they were 3.84 g / cm ³ and 0.92.

Example 4:
The powder obtained in Example 3, that is, 8 g of spherical titanium dioxide powder having an average particle diameter of 90 μm, was mixed in 76 g of pure water to obtain a slurry. A spherical titanium dioxide-containing coating agent A was prepared by adding 16 g of an acrylic silicon resin emulsion: SX8172 (A) -01 (manufactured by JSR Corporation) as a binder to the slurry.

  On the other hand, 8 g of powder obtained by mixing the raw material titanium dioxide having a BET equivalent particle diameter of 300 nm and the raw titanium dioxide having a BET equivalent particle diameter of 100 nm used in Example 3 in a mass ratio of 1: 1 is mixed with 76 g of pure water to form a slurry. Similarly, 16 g of acrylic silicon resin emulsion: SX8172 (A) -01 (manufactured by JSR Corporation) was added as a binder to prepare a titanium dioxide-containing coating agent B.

  Next, these two kinds of coating agents are impregnated into a polyester nonwoven fabric: Marix 10706 WTD (manufactured by Unitika Ltd.), squeezed with a roller, and then air-dried for 24 hours to apply a nonwoven fabric sample A (coating agent A containing spherical titanium dioxide). ) And a nonwoven fabric sample B (coating with titanium dioxide-containing coating agent B). The mass of the nonwoven fabric before and after coating was measured, and the amount of each titanium dioxide applied was calculated from the increase. The results are shown in Table 1.

Each non-woven fabric sample obtained above was sized 210 mm × 300 mm, raised in a tedlar bag (manufactured by GL Sciences, AAK-5: 5 L capacity), and filled with 5 L of dry air containing 60 volume ppm of hydrogen sulfide. . Then, black light: FL205. BL, 20W (manufactured by Hitachi, Ltd.) is irradiated with ultraviolet rays so that the nonwoven fabric sample has an ultraviolet intensity at 365 nm of 0.5 mW / cm ^2, and the concentration of hydrogen sulfide after 4 hours is detected by a detector tube: No. 4LL (stock) (Measured by Gastech). The results are shown in Table 1.

The above-mentioned nonwoven fabric sample was subjected to an accelerated exposure apparatus: Suntest CPS + (manufactured by ATLAS), and 50 mW / cm ² of light was applied to examine the coloring of the fibers after 24 hours. The results are shown in Table 1. From these results, it can be seen that the titanium dioxide powder obtained in the present invention is excellent as a photocatalyst.

Comparative Example 1:
An aqueous titanyl sulfate solution containing 200 g / l of TiO ₂ was heated to 80 ° C., and an aqueous NaOH solution was added dropwise to pH 4 with stirring, followed by aging at 80 ° C. for 30 minutes. This solution was added to a 0.4 wt% as TiO ₂ amount added aqueous solution of titanyl sulfate containing 200 g / l in the TiO _2. This was heated with stirring, boiled for 6 hours, and hydrolyzed. Thereafter, filtration and washing with water were performed, and the obtained solid was fired in an external heating rotary kiln. As a result, titanium dioxide having a BET equivalent particle size of 150 nm and an average particle size of 250 nm by laser particle size analysis was obtained.

  On the other hand, LPG and oxygen were ejected from the nozzle at a flow rate of 90 Nm / second and 210 Nm / second from the intermediate tube and the outermost tube of the coaxial triple tube, respectively, to form a combustion flame.

Next, titanium dioxide having a BET equivalent particle size of 150 nm obtained by the above liquid phase method and an average particle size of 250 nm by laser particle size analysis is conveyed at a supply rate of 3 kg / hour through an innermost tube together with air as a carrier gas. Erupted from. The liquid phase titanium dioxide contained 40 mass ppm of S and 10 mass ppm of Fe. At this time, the nozzle nozzle flow velocity of air was 60 Nm / sec, and the Reynolds number in the transported piping was 62,000. The burned gas containing solids was sent to the bag filter to collect the powder. The powder thus obtained was white, and when the particle size analysis was performed using a laser particle size analyzer SALD-2000J manufactured by Shimadzu Corporation, the average particle size was 310 μm. The particle shape also included irregularly shaped particles that appeared to have melted and fused together. When Fe was analyzed using Shimadzu Corporation plasma emission analyzer ICPS-7500, it was 350 mass ppm, and S was 35 mass ppm. Further, the density and sphericity of the powder were determined in the same manner as in Example 1, and found to be 3.52 g / cm ³ and 0.76.

Comparative Example 2:
An aqueous titanyl sulfate solution containing 200 g / l of TiO ₂ was heated to 80 ° C., and an aqueous NaOH solution was added dropwise to pH 4 while stirring, followed by aging at 80 ° C. for 30 minutes. This solution was added so as to be 1 wt% as TiO ₂ amount added aqueous solution of titanyl sulfate containing 200 g / l in the TiO _2. This was heated with stirring, boiled for 4 hours, and hydrolyzed. Thereafter, filtration and washing with water were performed, and the obtained solid was fired in an external heating rotary kiln. As a result, titanium dioxide having a BET equivalent particle size of 50 nm and an average particle size of 400 nm by laser particle size analysis was obtained.

  LPG and oxygen were ejected from the nozzle at the flow rates of 25 Nm / second and 105 Nm / second from the intermediate tube and the outermost tube of the coaxial triple tube, respectively, to form a combustion flame.

Next, titanium dioxide having a BET equivalent particle size of 50 nm obtained by the liquid phase method and an average particle size of 400 nm by the laser particle size analysis method is conveyed at a supply rate of 3 kg / hour through the innermost tube together with air as a carrier gas. Erupted from. At this time, the nozzle nozzle flow velocity of air was 40 Nm / second, and the Reynolds number in the transported piping was 46,000. The burned gas containing solids was sent to the bag filter to collect the powder. The powder thus obtained was white, and when the particle size analysis was performed using a laser particle size analyzer SALD-2000J manufactured by Shimadzu Corporation, the average particle size was 220 μm. Moreover, when Fe was analyzed using Shimadzu Corporation plasma emission analyzer ICPS-7500, it was 200 mass ppm, and S was 10 mass ppm. Further, when the density and sphericity of the powder were determined in the same manner as in Example 1, they were 3.32 g / cm ³ and 0.80.

Comparative Example 3:
Titanium dioxide having a BET-equivalent particle size of 300 nm and an average particle size of 0.6 μm by laser particle size analysis used in Example 1 was placed in a quartz container, and baked at 1100 ° C. for 48 hours in an electric furnace. This was pulverized in a mortar and subjected to particle size analysis using a laser particle size analyzer SALD-2000J manufactured by Shimadzu Corporation. As a result, a white powder having an average particle size of 20 μm was obtained. When this powder was analyzed using a plasma emission analyzer ICPS-7500 manufactured by Shimadzu Corporation, Fe was 10 ppm by mass and Si was 60 ppm by mass. Further, when the density and sphericity of the powder were determined in the same manner as in Example 1, they were 3.85 g / cm ³ and 0.88.

It is the schematic which shows typically an example of the reaction apparatus which enforces the manufacturing method of the raw material titanium dioxide used by this invention. It is the schematic which shows typically an example of the reaction apparatus which enforces the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coaxial parallel flow nozzle part 2 Preheater 3 Reaction tube 4 Bag filter 5 Raw material feeder & hopper 6 Raw material carrier gas 7 Combustible gas 8 Oxidizing gas 9 Combustion zone 10 Product collector 11 Exhaust gas 12 Product hopper

Claims (27)

In titanium dioxide, the average particle diameter measured by laser particle size analysis is in the range of 5 to 200 μm, the purity as TiO ₂ is 99.5% by mass or more, and Fe, Ni, Cr, Al and Zr Are each 20 mass ppm or less, Si is 40 mass ppm or less, Cl is 0.05 mass% or less, and S is 50 mass ppm or less. The titanium dioxide according to claim 1, wherein the density of titanium dioxide is 3.7 g / cm ³ or more.   The titanium dioxide according to any one of claims 1 to 2, wherein the titanium dioxide has a photocatalytic ability. Titanium dioxide has the following formula (1)
Sphericality = (circumference of a circle having the same area as the projected area of the particle) / (length of the contour of the projected particle image) (1)
The titanium dioxide according to any one of claims 1 to 3, which is a particle having a sphericity defined by (1) of 0.9 or more.   In the method of obtaining spherical titanium dioxide by introducing raw material titanium dioxide into the flame, the raw material titanium dioxide introduced into the high temperature flame formed by the combustible gas and the supporting gas is titanium tetrachloride as an oxidizing gas. The method for producing titanium dioxide according to any one of claims 1 to 4, wherein the titanium dioxide is produced by a vapor phase method in which oxidation is performed at a high temperature.   In the vapor phase method in which the raw material titanium dioxide produces titanium dioxide by oxidizing titanium tetrachloride with an oxidizing gas, the titanium tetrachloride-containing gas and the oxidizing gas are each preheated to 500 ° C. or more, and each flow rate is 10 m. 6. The method for producing titanium dioxide according to claim 5, wherein the titanium dioxide is obtained by reacting by supplying to a reaction tube at a rate of at least / sec.   The method for producing titanium dioxide according to claim 6, wherein the reaction is carried out by retaining a gas containing titanium tetrachloride and an oxidizing gas in a temperature region in the reaction tube exceeding 600 ° C for a period of 3 seconds or less.   The raw material titanium dioxide has a BET equivalent particle diameter of 7 to 500 nm, an average particle diameter of 0.4 to 10 μm measured by laser particle size analysis, Fe, Ni, Cr, Al and Zr are each 20 mass ppm or less, and Si is 40 The method for producing titanium dioxide according to any one of claims 5 to 7, wherein the titanium dioxide is vapor phase titanium dioxide containing not more than ppm by mass, not more than 1% by mass of Cl, and not more than 200 ppm by mass of S.   The raw material titanium dioxide is vapor phase titanium dioxide containing Fe, Ni, Cr, Al, and Zr, each of 20 mass ppm or less, Si 40 mass ppm or less, Cl 1 mass% or less, and S 200 mass ppm or less. The gas phase method titanium dioxide having a BET equivalent particle diameter of 7 to 500 nm and an average particle diameter of 0.4 to 10 μm measured by a laser particle size analysis method, and a BET equivalent particle diameter of 150 to 1000 nm and a laser particle size analysis method. The method for producing titanium dioxide according to any one of claims 5 to 7, which is a mixed powder with vapor phase titanium dioxide having an average particle diameter of 0.5 to 20 µm.   The method for producing titanium dioxide according to any one of claims 5 to 9, wherein the raw material titanium dioxide is dispersed and transported by a carrier gas in a turbulent state with a Reynolds number of 10,000 or more in the pipe and introduced into the high-temperature flame. The jet velocity of the nozzle of the raw material carrier gas is 8 Nm / sec (N means the standard state. Nm / sec is the flow rate (Nm ³ / sec) converted from the flow rate of the gas ejected from the nozzle to the standard state. The flow rate obtained by dividing by the area of the jet outlet (m ² ) is shown above.) The combustion flow rate of the burner nozzle of the combustible gas is 0.8 to 4 times the nozzle flow rate of the raw material carrier gas. The burner nozzle ejection flow rate of the oxidizing gas is in the range of 1.3 to 11 times the nozzle ejection flow rate of the raw material carrier gas, and the oxidizing gas ejection flow rate is greater than the combustible gas ejection flow rate. Item 11. A method for producing titanium dioxide according to Item 10.   The combustible gas is any one of methane, ethane, propane, ethylene, propylene, acetylene, butane, LPG, hydrogen, carbon monoxide, or a mixed gas thereof. The manufacturing method of the titanium dioxide as described in a term.   The method for producing titanium dioxide according to any one of claims 10 to 12, wherein the oxidizing gas contains 15% by volume to 100% by volume of oxygen.   The method for producing titanium dioxide according to any one of claims 10 to 13, wherein the raw material titanium dioxide is jetted together with the carrier gas from the upstream portion of the flame in the downstream direction of the combustion gas.   An organic polymer composition comprising 0.01% to 80% by mass of the titanium dioxide according to any one of claims 1 to 4 in the total mass of the composition.   The organic polymer composition according to claim 15, wherein the organic polymer of the organic polymer composition is at least one resin selected from the group consisting of a synthetic thermoplastic resin, a synthetic thermosetting resin, and a natural resin. .   The organic polymer composition according to claim 15 or 16, wherein the organic polymer composition is a compound.   The organic polymer composition according to claim 15 or 16, wherein the organic polymer composition is a master batch.   A molded article obtained by molding the organic polymer composition according to claim 15 or 16.   A slurry comprising the titanium dioxide according to any one of claims 1 to 4.   The coating agent characterized by including the titanium dioxide as described in any one of Claims 1 thru | or 4.   The coating material characterized by including the titanium dioxide as described in any one of Claims 1 thru | or 4.   A structure comprising the titanium dioxide according to any one of claims 1 to 4 on a surface.   Titanium dioxide single crystal characterized by using the titanium dioxide according to any one of claims 1 to 4 as a raw material.   A ceramic molded body comprising the titanium dioxide according to any one of claims 1 to 4 as a raw material.   A dielectric material comprising the titanium dioxide according to any one of claims 1 to 4.   Cosmetics containing the titanium dioxide as described in any one of Claims 1 thru | or 4.

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