Method for producing titanium dioxide powder

Abstract

This invention provides a method for producing titanium oxide powder that can effectively remove Cl. [Solution] The present invention provides a method for producing titanium oxide powder containing TiO2, comprising a heating step of heating raw material powder containing TiO2 and Cl inside a heating container to a temperature of 850°C to 880°C for 2 to 3 hours, wherein the heating container used is one which is provided with a communication section that allows gas to flow between the inside and outside of the heating container.

Description

[Technical Field]

[0001] This invention relates to a method for producing titanium dioxide powder. [Background technology]

[0002] Titanium dioxide powder containing the functional material TiO2 possesses high whiteness and opacity, exhibits catalytic activity upon light irradiation, and also combines excellent properties such as dispersibility, weather resistance, and chemical stability. For this reason, titanium dioxide powder is widely used not only as a white pigment and UV-blocking filler, which were its main applications, but also as a photocatalyst and in various other applications.

[0003] In recent years, the use of titanium oxide powder in electronic devices and components has been rapidly expanding. For example, barium titanate, which is derived from titanium oxide powder, is used as a ferroelectric material in multilayer ceramic capacitors (MLCCs) and positive temperature coefficient thermistors (PTC thermistors).

[0004] Titanium dioxide powder may be manufactured by a method known as the gas phase method, in which titanium halide gas is mixed with water vapor, oxygen gas, an inert gas, etc., in a gas phase and reacted to produce titanium dioxide. Furthermore, the titanium dioxide powder obtained by the gas phase method, etc., may be heated to a predetermined temperature before being used for the above-mentioned applications.

[0005] Regarding the heating of titanium oxide powder, for example, Patent Document 1 describes a firing container having an inner wall made of titanium or a titanium alloy, which has an open section, and the total area of ​​the open section and the volume of the firing container are given by the following formula (1): 0.005 ≤ A / B ≤ 0.2 (1) (wherein A is the total area of ​​the open section (cm²)). 2) indicates that B is the volume inside the firing container (cm³ 3 The present invention describes a method for producing metal oxides, characterized by firing in a firing container having a relationship represented by ). According to this "method for producing metal oxides," "According to the present invention, when firing a mixture of a metal oxide such as titanium oxide or its precursor with at least one or both of a sulfur compound or a nitrogen compound in a firing container, it is possible to provide a method for producing sulfur-containing metal oxides or nitrogen-containing metal oxides that allows for easy control of reactivity and enables mass production. Furthermore, according to the present invention, it is possible to provide a method for producing metal oxides in which there is no adhesion of fired product powder to the firing container, there is little discoloration of the firing container, and the firing container can be reused without empty firing." [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4841506 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, titanium dioxide powder may contain chlorine (Cl) due to factors such as its production by a gas-phase method. To effectively remove Cl from titanium dioxide powder, it is necessary to heat the powder to a relatively high temperature. However, there was a problem in that heating the titanium dioxide powder in a simple heating container did not adequately remove the Cl.

[0008] This invention aims to address these problems, and its objective is to provide a method for producing titanium oxide powder that can effectively remove Cl. [Means for solving the problem]

[0009] After diligent research, the inventor discovered that even when heated to a certain temperature, if the titanium dioxide powder is contained in a sealed container, the desorption of Cl from the titanium dioxide powder and the subsequent removal of Cl do not occur sufficiently.

[0010] The present invention relates to a method for producing titanium oxide powder, which is a method for producing titanium oxide powder containing TiO2, and includes a heating step of heating raw material powder containing TiO2 and Cl inside a heating container to a temperature of 850°C to 880°C for 2 to 3 hours, wherein the heating container used is a heating container provided with a communication section that allows gas to flow between the inside and outside of the heating container.

[0011] Here, the titanium dioxide powder that is used in the heating process before the heating process is referred to as "raw material powder" to distinguish it from the titanium dioxide powder that has been used after the heating process.

[0012] In the method for producing titanium oxide powder according to this invention, it is preferable that the heating container has a container body and a lid, and the communication portion includes a notch formed on the edge of the container body.

[0013] In this case, it is preferable that, in a side view of the container body, the notch has a trapezoidal shape in which the width gradually decreases towards the deeper side in the depth direction of the container body.

[0014] In this case, it is preferable that the container body has a rectangular shape in plan view, and that the notches are formed on each of the four edges of the container body.

[0015] Preferably, at least the inner surface of the heating container that comes into contact with the titanium oxide powder is made of a material containing at least one of aluminum oxide (Al2O3), magnesium oxide (MgO), and zirconium oxide (ZrO2).

[0016] In the heating step, it is preferable to heat the raw material powder while stacking a plurality of the heating containers each containing the raw material powder in the vertical direction.

[0017] In the heating step, it is preferable to heat the raw material powder while sucking the inside of the heating furnace in which the heating container is arranged.

[0018] In the method for producing titanium oxide powder of this invention, the raw material powder is granulated powder, the titanium oxide powder is sintered powder, and in the heating step, by heating the raw material powder, the constituent particles of the granules in the raw material powder may be sintered together.

Advantages of the Invention

[0019] According to the method for producing titanium oxide powder of this invention, Cl can be effectively removed.

Brief Description of the Drawings

[0020] [Figure 1] It is a perspective view showing an example of a container body and a lid of a heating container that can be used in the heating step of the method for producing titanium oxide powder according to one embodiment of this invention, in an open state. [Figure 2] It is a side view showing the container body and the lid of the heating container of FIG. 1 in a closed state. [Figure 3] It is a side view showing a state where a plurality of the heating containers of FIG. 1 are closed and stacked. [Figure 4] It is a graph showing the Cl content of the titanium oxide powder obtained in each test of the examples. [Figure 5] It is a schematic diagram showing the arrangement mode of the heating containers in the heating furnace of the examples.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of this invention will be described in detail. One embodiment of this invention provides a method for producing titanium oxide powder, which contains TiO2. This method includes a heating step in which raw material powder containing TiO2 (titanium dioxide) and Cl (chlorine) is heated in a heating container at a temperature of 850°C to 880°C for 2 to 3 hours. By setting the heating temperature to 850°C to 880°C and the heating time to 2 to 3 hours, Cl can be effectively removed from the titanium oxide powder.

[0022] In this process, a heating container is used to hold the raw material powder during the heating process. This heating container is equipped with a communication section that allows gas to flow between the inside and outside of the heating container. By using a heating container with such a communication section, during heating in the heating process, the Cl in the titanium oxide powder is easily detached from the titanium oxide powder and then discharged to the outside through the communication section, thus effectively removing the Cl.

[0023] The raw material powder typically contains mainly TiO2, but various materials containing Cl can be used. The following describes in detail, as an example, a case where granulated powder obtained by sequentially performing a reaction step and a granulation step using a gas-phase method is used as the raw material powder, but is not limited to this. For example, titanium oxide powder obtained in the reaction step but not granulated may be used as the raw material powder, and a heating step may be performed on it. Furthermore, this invention can also be applied to raw material powders containing Cl that are produced by methods other than the gas-phase method or obtained through purchase.

[0024] (Reaction process) In the reaction process, titanium chloride gas, such as titanium tetrachloride, and an oxidizing gas are preheated and then mixed in the reactor at a predetermined high temperature, bringing the titanium chloride gas into contact with the oxidizing gas. Hydrogen gas and / or an inert gas may also be supplied. More specifically, for example, the titanium chloride gas can be diluted by mixing it with an inert gas and then supplied into the reactor along with water vapor, and, if necessary, oxygen gas and hydrogen gas.

[0025] Examples of titanium chloride gases include titanium tetrachloride gas. Examples of oxidizing gases include oxygen gas and water vapor.

[0026] Inside the reactor, a product containing TiO2 is produced by the reaction of titanium chloride gas with oxygen gas and / or water vapor in the flame of a combustion burner. When titanium tetrachloride gas is used as the titanium chloride gas, this reaction is represented by the equations TiCl4 + O2 → TiO2 + 2Cl2 or TiCl4 + 2H2O → TiO2 + 4HCl. The reaction temperature can be any temperature at which TiO2 is produced, for example, 600°C to 1100°C. After that, the gas containing the product powder is cooled by contact with a cooling gas such as air, and the product powder is collected from there.

[0027] The resulting powder obtained from the reaction in the above-described reactor may contain Cl derived from titanium chloride gas, etc. Such Cl can be effectively removed in the heating step after the resulting powder has been granulated through the granulation process described later. While Cl in titanium oxide powder poses a risk of corrosion and damage to manufacturing equipment when manufacturing products using titanium oxide powder, in this embodiment, such a risk can be reduced because at least a portion of the Cl is removed in the heating step.

[0028] (granulation process) In the granulation process, the generated powder is mixed with water as a dispersion medium to form a slurry, and this slurry is used to granulate the generated powder by spray drying. As a result, multiple particles in the generated powder clump together to form granules, and a granulated powder containing these granules is obtained.

[0029] When preparing a slurry for spray drying, water is used as the dispersion medium to mix the generated powder. Using water as the dispersion medium suppresses contamination by components of organic solvents that might otherwise be present. The slurry may contain dispersion media other than water, but it is preferable that it contains substantially only water as the dispersion medium. The slurry may also contain substances other than the dispersion medium, but from the viewpoint of further increasing the purity of the titanium dioxide powder, it is preferable that it consists of the generated powder and water. Spray drying can be performed well even without adding other substances.

[0030] Examples of water used in preparing the slurry include tap water, industrial water, distilled water, purified water, ion-exchanged water, pure water, and ultrapure water. The mass ratio of water to the generated powder in the slurry is preferably 100% to 130%, more preferably 115% to 120%. If the amount of water is too much relative to the amount of generated powder, the particle size of the constituent particles of the granules after granulation may become small, and if the amount of water is too little, the particle size of the constituent particles of the granules after granulation may become large.

[0031] Various spray drying apparatuses can be used to spray dry the generated powder in a slurry. In one example of a spray drying apparatus, the slurry is supplied to a rotating disk inside the apparatus, causing droplets of slurry to be ejected into the surroundings by the rotation of the disk. At this time, the water in the droplets evaporates due to contact with hot air that is separately supplied around the disk, and as the droplets are dispersed, multiple particles of the generated powder contained in the droplets dry and solidify, forming granules of a size corresponding to the size of the droplets. If necessary, when granules exceeding a predetermined size are formed, the larger granules may be separated and dropped by their own weight from the airflow inside the spray drying apparatus. In this way, the generated powder is granulated, becoming a granulated powder containing granules of a predetermined size. In spray drying, the slurry is simply dried by being ejected as droplets, so it is unlikely that a significant amount of metal originating from the spray drying apparatus will be mixed into the granulated powder. The conditions for spray drying can be appropriately set considering the generated powder and the titanium oxide powder to be manufactured.

[0032] The granulated powder obtained by spray drying has a TAP density of 0.80 g / cm³. 3 ~1.20g / cm 3 Furthermore, 0.90 g / cm³ 3 ~1.10g / cm 3 This is preferable. If the TAP density of the granulated powder is too high, there is a possibility that fine particles may be mixed in, which may worsen the fluidity. If it is too low, there is a possibility that voids may be formed in the granulated powder, which may cause air bubbles to form in the product. The TAP density is measured in accordance with JIS R1628-1997 using a tap density meter, Tap Denser KYT-4000, manufactured by Seishin Corporation.

[0033] The granulated powder obtained in the granulation process can be used as a raw material powder in the heating process described below.

[0034] (Heating process) In the heating process, the raw material powder containing TiO2 and Cl is heated in a heating container to a temperature of 850°C to 880°C for 2 to 3 hours. This removes at least some of the Cl from the raw material powder, yielding titanium oxide powder. The presence of TiO2 in the raw material powder and titanium oxide powder can be confirmed by X-ray diffraction (XRD).

[0035] When granulated powder is used as a raw material, the particles constituting the granules in the granulated powder may sinter together, causing the granules to become sintered particles, and titanium oxide powder containing these sintered particles may be obtained.

[0036] If the heating temperature in the heating process is too low, there is a possibility that the desorption of Cl from the raw material powder will be insufficient, and there is a concern that the sintering of the constituent particles of the granules will not proceed when obtaining sintered powder. On the other hand, if the heating temperature is too high, there is a risk that the granulated powder will stick together. Also, if the heating time is too short, there is a concern that the desorption of Cl will not be sufficient, and there is a concern that the sintering of the constituent particles of the granules will not be completed when obtaining sintered powder. On the other hand, if the heating time is too long, the work efficiency may decrease. From this viewpoint, it is preferable that the heating temperature be 850°C to 880°C and the heating time be 2 to 3 hours.

[0037] Furthermore, in the heating process, in order to effectively remove Cl, the heating container used to heat the raw material powder should be equipped with a communication section that allows gas to flow between the inside and outside of the heating container. With a heating container that has a communication section, the Cl that detaches from the raw material powder during heating is discharged to the outside of the heating container, thereby promoting the removal of Cl from the raw material powder.

[0038] As an example, the heating container 1 shown in Figures 1 and 2 has a container body 2, such as a cylindrical container with a bottom, and a lid 3 that covers the opening 2a of the container body 2. The container body 2 and lid 3 of this heating container 1 are rectangular or square in plan view, but the shapes of the container body 2 and lid 3 can be changed as appropriate.

[0039] In this example, the container body 2 is composed of a side wall 2b that surrounds the titanium oxide powder placed inside, and a bottom wall 2c that seals the end of the side wall 2b opposite to the end on the axial side of the opening 2a (upper side in Figures 1 and 2) (lower side in Figures 1 and 2). The lid 3 shown is a flat plate that conforms to the shape of the container body 2 in a plan view. By covering the opening 2a of the container body 2 with the lid 3, the heating container 1 is closed.

[0040] In this heating container 1, as a communication part as described above, a notch 7 is provided on the edge 2d of the side wall 2b of the container body 2 on the side of the opening 2a, which is recessed from the edge 2d compared to the rest of the container. When the opening 2a of the container body 2 is covered with the lid 3, the notch 7 is located between the lid 3 and the edge 2d of the container body 2, as shown in Figure 2, and becomes a through hole that penetrates to the inside and outside of the heating container 1, functioning as a communication part that allows gas to flow between the inside and outside. In addition to or instead of providing the notch 7, other forms of communication parts, such as through holes formed in the side wall 2b, etc., can also be provided, although they are not shown in the illustration.

[0041] Using a heating container 1 with a notch 7 as a communication section is preferable because, since the notch 7 is formed on the edge 2d on the opening 2a side, the raw material powder placed inside is less likely to leak out from the notch 7, and as shown in Figure 3, even when the heating process is performed with multiple heating containers 1 stacked on top of each other, the flow of gas between the inside and outside through the notch 7 is ensured.

[0042] When the connecting portion is a notch 7, the notch 7 can be any shape, but it is particularly preferable that it has a trapezoidal shape in which the width (length in the left-right direction in Figures 1-3) gradually decreases towards the deeper side (downward side in Figures 1-3) in the depth direction of the container body 2, as shown in the figures. This improves the escape of detached Cl.

[0043] Furthermore, when the connecting portion is a notch 7 and the container body 2 has a rectangular shape in plan view, it is preferable that the notch 7 be formed on each of the four edges 2d corresponding to the four sides of the rectangle of the container body 2, as shown in the illustrated example. This allows the Cl detached from the raw material powder inside to be efficiently discharged to the outside through the four notches 7 on each of the four edges 2d.

[0044] In the heating container 1, it is preferable that at least the inner surface that can come into contact with the titanium oxide powder is made of a material containing at least one of aluminum oxide (Al2O3), magnesium oxide (MgO), and zirconium oxide (ZrO2). The inner surface of the heating container 1 may also contain other components in addition to the above at least one, such as silicon dioxide (SiO2), but it is more preferable that at least 50% by mass or more of the main material of the inner surface is at least one of aluminum oxide, magnesium oxide, and zirconium oxide. The content of at least one of aluminum oxide, magnesium oxide, and zirconium oxide in the inner surface is preferably 98% by mass or more, and more preferably 99% by mass or more.

[0045] Aluminum oxide, magnesium oxide, and zirconium oxide have relatively high thermal conductivity and tend to have a relatively low porosity. Therefore, when the heating container 1 is constructed from such materials, the raw material powder inside is easily heated effectively, and cracking is less likely to occur even when the heating container 1 is repeatedly used in the heating process, thus suppressing contamination. Aluminum oxide is particularly suitable from the viewpoint of suppressing contamination. In addition, aluminum oxide, magnesium oxide, and zirconium oxide also possess the required heat resistance. Metals or alloys such as titanium may not have sufficient heat resistance to the high temperatures they are exposed to in the heating process. Furthermore, not only the inner surface of the heating container 1 but also the entire container body 2 and lid 3 may be constructed from the above materials.

[0046] The thermal conductivity of the material containing at least one of aluminum oxide (Al2O3), magnesium oxide (MgO), and zirconium oxide (ZrO2) that constitutes at least the inner surface of the heating container 1 is preferably 2.8 W / mK to 32.0 W / mK. Furthermore, the porosity of the material is preferably 1% to 0.1%.

[0047] When performing the heating process using the heating container 1 as described above, put the raw material powder into each of the plurality of heating containers 1, stack them vertically as shown in FIG. 3 in a heating furnace (not shown), and heat the raw material powder inside each heating container 1 in that state.

[0048] Even when performing the heating process with a plurality of heating containers 1 stacked in this way, it is possible to discharge Cl detached from the raw material powder from the notch 7 provided at the edge 2d of the side wall 2b of the container body 2. Further, instead of putting the raw material powder into one large heating container 1, by heating the raw material powder in a state of being divided into each of the plurality of heating containers 1, heat can be more easily transferred to almost the entire raw material powder through each heating container 1, so that the removal of chlorine is performed more effectively. Although not shown, a stacked container group 11 composed of a plurality of heating containers 1 stacked in the vertical direction may be arranged in a plurality of sets on the side. However, in order to discharge Cl well from each communication part (such as the notch 7) of each heating container 1, it is desirable to position the stacked container groups 11 adjacent to each other on the side with a certain interval.

[0049] In the heating process, it is preferable to heat the raw material powder in the heating container 1 while sucking the inside of the heating furnace in which the heating container 1 is arranged. In this case, the inside of the heating furnace can be in a slightly reduced-pressure atmosphere compared to the atmosphere. Thereby, Cl detached from the raw material powder in the heating container 1 is more easily discharged from the inside of the heating container 1 to the outside through the communication part (such as the notch 7).

[0050] The titanium oxide powder obtained after the heating process, for example, when it is a sintered powder, the BET specific surface area is 5.0 m 2 / g to 10.0 m 2 / g, and further may be 6.0 m 2 / g to 9.0 m 2 / g. The raw material powder has a BET specific surface area of, for example, 10 m 2 / g to 100 m 2 / g, typically 20 m 2 / g to 40 m 2The result may be / g, and the granulated powder may be similar to that of the raw material powder. The BET specific surface area is measured by the BET method (gas adsorption method), and a fully automatic specific surface area measuring device (Macsorb®) manufactured by Mountec Co., Ltd. can be used.

[0051] In the case of sintered titanium oxide powder, raw material powder, and granulated powder, the TiO2 content may be approximately 99.99% by mass or higher, and even higher than 99.9% by mass. The TiO2 content can be measured by titration using ammonium iron(III) sulfate.

[0052] The content of metal impurities in titanium dioxide powder is preferably 5 ppm by mass or less, and more preferably 3 ppm by mass or less. Examples of metal impurities include Fe, Cr, Al, etc. If multiple types of metal impurities are present, the above content refers to the total content of those metal impurities. The presence of metal impurities is confirmed by ion exchange separation-ICP emission spectroscopy, and their content is measured by ion exchange separation-ICP emission spectroscopy.

[0053] The Cl content of titanium dioxide powder is preferably less than 0.001% by mass, and more preferably 0.0005% by mass or less. The Cl content is measured by silver nitrate titration, in which the Cl dissolved in the solution after dispersing titanium dioxide powder in an aqueous nitric acid solution is titrated with a silver nitrate standard solution. Specifically, 10.0 g of the sample and 5 mL of nitric acid (1+1) are placed in a 200 mL poly beaker with approximately 100 mL of water, and the sample is titrated using an automatic titrator (model: GT-200, manufactured by Nitto Seikou Analytech Co., Ltd.) with a silver nitrate standard solution (0.02 mol / L) (inflection point: 150 mV).

[0054] Furthermore, the carbon (C) content of the titanium dioxide powder is preferably 0.01% by mass or less, and more preferably 0.005% by mass or less. The carbon (C) content is measured by combustion-infrared absorption spectroscopy (measuring device: EMIA-920V2, manufactured by Horiba, Ltd.). The sulfur (S) content of the titanium dioxide powder is below the detection limit when measured by combustion-infrared absorption spectroscopy (measuring device: EMIA-920V2, manufactured by Horiba, Ltd.), and is substantially 0% by mass. In addition, the nitrogen (N) content of the titanium dioxide powder is less than the amount intentionally included.

[0055] The average circularity of titanium oxide powder as a sintered powder can be, for example, 0.85 to 0.95, typically 0.87 to 0.93. If the average circularity is too small, the fluidity will decrease, which may reduce the quantitative supply capacity. To measure the average circularity of titanium oxide powder, the particles are photographed using a microscope manufactured by Keyence Corporation, and the area and perimeter of each particle are determined. The perimeter of the particle is calculated from the ratio of the perimeter of a circle corresponding to the particle's area (area S = π × diameter D squared, and perimeter L = π × D) to the actual perimeter ((circumference of an equal-area circle) ÷ (perimeter)).

[0056] Titanium oxide powder, as a sintered powder, can be suitably used in prisms and other optical materials that utilize the high refractive index properties of TiO2, for example. In such applications, titanium oxide powder may be required to have a certain degree of fluidity, be resistant to scattering, and possess sufficient strength to withstand supply and transportation without damage. The titanium oxide powder described above can satisfy these requirements.

[0057] (Cl removal process) The heating container 1 used in the above heating process may have Cl (Cl) adhering to it, which has been detached from the raw material powder. To prevent the Cl adhering to the heating container 1 from causing an increase in the Cl content of the titanium oxide powder obtained in the next heating process using the heating container 1, it is preferable to perform a Cl removal process on the heating container 1 before using it in the next heating process.

[0058] In the Cl removal process, the heating container 1 can be heated to a temperature of 600°C or higher for 8 hours or more, without titanium oxide powder inside (e.g., empty heating). If the temperature is below 600°C and / or the heating time is less than 8 hours, there is a concern that the removal of Cl from the heating container 1 will be insufficient. The upper limit of the heating temperature at this time is not particularly limited as long as the heating container 1 can withstand it, but it may be set to, for example, 1000°C or lower. The heating time may also be set to 15 hours or less. [Examples]

[0059] Next, the method for producing titanium dioxide powder according to this invention was experimentally carried out and its effects were confirmed, which are described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0060] As shown in Figure 4, a series of tests were conducted to obtain titanium oxide powder (sintered powder) by heating raw material powder (granulated powder) containing TiO2 and Cl in a heating container. Here, the heating temperature was set to 850°C and the heating time to 2 hours. In each test, as shown in Figure 5, two sets of stacked containers, each consisting of three heating containers stacked vertically below the thermocouple, and four sets of stacked containers, each consisting of four heating containers stacked vertically, were arranged side by side in the heating furnace, for a total of 22 heating containers. Although not clear from Figure 5, each stacked container group was arranged in two rows in the depth direction of the figure. After heating, the titanium oxide powder was removed from the heating container, and its Cl content was measured using the method described above. The results are shown in Figure 4.

[0061] In tests No. 1 through 18, suction was not performed inside the heating furnace, but from test No. 19 onward, the raw material powder was heated while suction was performed inside the heating furnace.

[0062] Furthermore, from Test No. 21 onwards, the heating container for the raw material powder was changed. The heating container from Test No. 21 onwards has a rectangular (square) container body and lid in plan view, as shown in Figures 1 and 2, with notches formed on the four edges of the container body to serve as connecting parts. The external dimensions of this heating container are 150 mm × 150 mm × 50 mm, and the internal dimensions are 136 mm × 136 mm × 43 mm. In side view, the dimensions of the notches are 70 mm and 50 mm at the top and bottom, and 8 mm in height. The heating container used up to Test No. 20 is substantially the same as the heating container from Test No. 21 onwards, except that the container body does not have notches. In all tests, the raw material powder was placed to a height of 35 mm from the bottom surface of the container body.

[0063] Furthermore, from test No. 60 onwards, the heating container was preheated to 600°C for 1 hour before heating the raw material powder.

[0064] Figure 4 shows that changing the heating container to one with a notch significantly reduces the Cl content of the titanium oxide powder obtained after heating. Furthermore, Figure 4 also shows that suction within the heating furnace and pre-heating the heating container contribute to a further reduction in Cl content.

[0065] These results show that the titanium dioxide powder manufacturing method of this invention can effectively remove Cl. [Explanation of Symbols]

[0066] 1 Heating container 2. Container body 2a opening 2b side wall 2c bottom wall 2d edge 3 Lid 7 Notch 11. Stacked container group

Claims

1. TiO 2 A method for producing titanium dioxide powder containing, TiO 2 The process includes a heating step in which a raw material powder containing Cl is heated to a temperature of 850°C to 880°C inside a heating container for 2 to 3 hours. A method for producing titanium oxide powder, wherein the heating container is provided with a communication section that allows gas to flow between the inside and outside of the heating container.

2. The method for producing titanium oxide powder according to claim 1, wherein the heating container has a container body and a lid, and the communication portion includes a notch formed on the edge of the container body.

3. The method for producing titanium oxide powder according to claim 2, wherein, in a side view of the container body, the notch has a trapezoidal shape in which the width gradually decreases towards the deeper side in the depth direction of the container body.

4. A method for producing titanium oxide powder according to claim 2 or 3, wherein the container body has a rectangular shape in plan view, and the notches are formed on each of the four edges of the container body.

5. At least the inner surface of the heating container that comes into contact with the titanium oxide powder is made of aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO) and zirconium dioxide (ZrO) 2 A method for producing titanium dioxide powder according to any one of claims 1 to 3, comprising a material containing at least one of the following:

6. A method for producing titanium oxide powder according to any one of claims 1 to 3, wherein in the heating step, the raw material powder is heated with a plurality of heating containers, each containing the raw material powder, stacked vertically on top of each other.

7. A method for producing titanium oxide powder according to any one of claims 1 to 3, wherein the heating step involves heating the raw material powder while suction is applied to the inside of a heating furnace in which the heating container is located.

8. The raw material powder is granulated powder, and the titanium oxide powder is sintered powder. A method for producing titanium oxide powder according to any one of claims 1 to 3, wherein the heating step involves heating the raw material powder to sinter the constituent particles of the granules in the raw material powder.

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