Rutile type titanium oxide powder having large particle size and process for producing the same

Abstract

To provide a rutile type titanium oxide powder having a large particle diameter and containing rutile type titanium oxide particles having a polyhedral shape capable of further increasing a refractive index, and to provide a method for producing the same.SOLUTION: A large particle size rutile type titanium oxide powder comprising rutile type titanium oxide particles having a polyhedral shape and having a number average primary particle size of more than 10 μm and 100 μm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a large particle size rutile type titanium oxide powder and a method for producing the same. [Background technology]

[0002] Titanium dioxide has ultraviolet absorption capabilities, excellent photocatalytic activity, and a high refractive index, making it useful in a wide range of applications, including paints, cosmetics, environmental purification, and solar cells. Titanium dioxide crystal structures include anatase, rutile, and brookite, with the rutile type having a particularly high refractive index of 2.71. For this reason, rutile titanium dioxide is used in paints, films, cosmetics, pigments, and other applications where a high refractive index is required.

[0003] Depending on the application, rutile-type titanium dioxide in the form of flakes or fine particles and methods for producing the same have been proposed, as shown below.

[0004] For example, Patent Document 1 discloses a method for producing titanium dioxide, which comprises applying a solution of titanium alkoxide and an organic alkaline substance dissolved in an organic solvent to a smooth surface, hydrolyzing the coating, drying, peeling, and calcining the coating. It also discloses that this method produces transparent, flaky titanium oxide.

[0005] Patent Document 2 discloses a method for producing flaky titanium dioxide powder. The method involves heating and melting a mixed powder of titanium oxide powder and potassium carbonate powder (TiO2 / K2O molar ratio: 1.5 to 2.5), cooling the molten product to obtain a mass of fibrous potassium dititanate crystals, and using an acid aqueous solution as a treatment liquid to remove the K in the crystals. + It is shown that all of the ions are eluted and the fiber mass is subjected to a wet grinding process, and the powder recovered from the treatment solution is dehydrated and dried, and then calcined at approximately 500 to 1000°C. It is also shown that the obtained powder has a flaky shape, with a length of approximately 5 to 100 μm, a width of approximately 2 to 20 μm, a thickness of approximately 0.01 to 2 μm, and an aspect ratio of approximately 30 to 200 or more.

[0006] Patent Document 3 discloses a method for producing highly crystalline, spherical, monodisperse titanium dioxide particles having a particle size of 0.3 to 10 microns. The method involves melting a non-oxide raw material by heating with oxygen-containing plasma, while simultaneously inducing an oxidation reaction in the melt. Because the oxidation reaction is exothermic, there is a localized temperature rise in the vicinity of the melt, causing oxide droplets with particle sizes of 0.3 to 10 microns to scatter, and these droplets solidify to produce crystalline, spherical titanium dioxide powder.

[0007] Patent Document 4 describes a method for producing a powder having a primary particle size of 0.4 μm or more and 10 μm or less according to an SEM photograph, a BET specific surface area of ​​0.1 m 2 / g or more 5m 2 / g or less, and the value obtained by dividing the primary particle size by the particle size calculated from the BET specific surface area is 1 to 3, and the rutile-type titanium dioxide powder for use as a filler to be blended into glass paste is shown, which has few agglomerated particles.

[0008] Patent Document 5 discloses needle-shaped titanium oxide microparticles characterized by an average minor axis of 25 to 200 nm, an average major axis of 75 to 3000 nm, an average aspect ratio of 3 to 40, and a purity of 99% by weight or more. It also discloses a method for producing amorphous needle-shaped titanium oxide microparticles, which comprises adding titanium alkoxide to a solvent containing water and an alcohol containing at least methanol, followed by stirring or ultrasonic treatment, and a method for producing crystalline needle-shaped titanium oxide microparticles, which comprises heat-treating the amorphous needle-shaped titanium oxide microparticles. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 4-144918 [Patent Document 2] Japanese Patent Application Publication No. 7-157312 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-274851 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-239020 [Patent Document 5] Japanese Patent Application Laid-Open No. 2004-315356 Summary of the Invention [Problem to be solved by the invention]

[0010] In recent years, there has been a demand for relatively large rutile-type titanium oxide powders with a number-average primary particle size exceeding 10 μm, for example as fillers for mixing with resins, pigments, catalysts, or catalyst supports. In contrast, Patent Documents 1 and 2 relate to titanium dioxide having a flaky shape, and Patent Documents 3 to 5 relate to small titanium oxide particles with a particle size of 10 μm or less. None of these documents relate to relatively large rutile-type titanium oxide particles. Furthermore, these documents do not examine rutile-type titanium oxide particles with a large particle size and a shape that can further increase the refractive index.

[0011] The present disclosure has been made in view of the above circumstances, and its purpose is to provide a large-particle size rutile-type titanium dioxide powder containing polyhedral rutile-type titanium dioxide particles that can further increase the refractive index and having a number average primary particle size of more than 10 μm, and a method for producing the same. [Means for solving the problem]

[0012] Aspect 1 of the present invention is The large particle size rutile titanium oxide powder contains polyhedral rutile titanium oxide particles and has a number average primary particle size of more than 10 μm and not more than 100 μm.

[0013] Aspect 2 of the present invention is A method for producing the large particle size rutile type titanium oxide powder according to aspect 1, comprising: a mixing step of mixing one or more titanium oxide raw materials selected from titanium oxide and titanium compounds that become titanium oxide when heated at 800°C or higher with one or more additives selected from the group consisting of chlorides, sulfates, and phosphates to obtain a mixture; and a calcination step of calcining the mixture at 800°C or higher.

[0014] Aspect 3 of the present invention is Aspect 2 is a method for producing a large-particle size rutile-type titanium oxide powder, wherein the additive is at least one of sodium chloride and potassium chloride.

[0015] A fourth aspect of the present invention is In the method for producing a large-particle size rutile-type titanium oxide powder according to aspect 2 or 3, the proportion of the additive in the mixture is 15% by mass or more and 90% by mass or less.

[0016] A fifth aspect of the present invention is The large particle size rutile titanium dioxide powder according to aspect 1 is used as a filler for mixing with resin.

[0017] A sixth aspect of the present invention is The large particle size rutile titanium dioxide powder according to Aspect 1 is used as a pigment.

[0018] A seventh aspect of the present invention is The large particle size rutile titanium dioxide powder according to Aspect 1 is used as a catalyst and / or a catalyst support.

[0019] Aspect 8 of the present invention is A filler for mixing with resin, comprising the large particle size rutile titanium dioxide powder according to aspect 1.

[0020] A ninth aspect of the present invention is A pigment comprising the large particle size rutile titanium dioxide powder according to embodiment 1.

[0021] A tenth aspect of the present invention is A catalyst and / or catalyst support comprising the large particle size rutile titanium dioxide powder according to embodiment 1. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a large particle size rutile-type titanium oxide powder containing polyhedral rutile-type titanium oxide particles that can further increase the refractive index, and a method for producing the same. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is an X-ray diffraction pattern of titanium oxide of Example 1. [Figure 2A] FIG. 2 is a schematic diagram for explaining how to determine the number average primary particle diameter. [Figure 2B] FIG. 2 is another schematic explanatory diagram for explaining how to determine the number average primary particle diameter. [Figure 3] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 1 at 1000 magnifications. [Figure 4] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 2 at 1000 magnifications. [Figure 5] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 3 at 1000 magnifications. [Figure 6] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 4 at 1000 magnifications. [Figure 7] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 5 at 1000 magnifications. [Figure 8] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 6 at 1000 magnifications. [Figure 9] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 7 at 1000 magnifications. [Figure 10] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 8 at 1000 magnifications. [Figure 11] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 9 at 1000 magnifications. [Figure 12] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Example 10 at 1000 magnifications. [Figure 13] 1 is a scanning electron microscope (SEM) photograph of titanium oxide of Comparative Example 1 at 1000 magnifications. [Figure 14]1 is a scanning electron microscope (SEM) photograph of titanium oxide of Comparative Example 2 at 1000 magnifications. DETAILED DESCRIPTION OF THE INVENTION

[0024] The large particle size rutile-type titanium oxide powder according to this embodiment and its production method will be described below, but the present invention is not limited to these descriptions.

[0025] 1. Large particle size rutile titanium dioxide powder The large-particle-size rutile-type titanium oxide powder according to this embodiment contains polyhedral rutile-type titanium oxide particles and has a number-average primary particle diameter of more than 10 μm and not more than 100 μm. As mentioned above, in recent years, there has been a demand for relatively large rutile-type titanium oxide particles having a number-average primary particle diameter of more than 10 μm, for example, as a filler for resin mixing, a pigment, a catalyst, or a catalyst support. This size facilitates easy mixing with resins, for example, when used as a filler for resin mixing. On the other hand, if the number-average primary particle diameter is 10 μm or less, the interaction between particles becomes large, which can lead to increased viscosity and difficulty in mixing when used as a filler for resin mixing. The number-average primary particle diameter is preferably 12 μm or more, more preferably 15 μm or more, and even 20 μm or more, and can be 23 μm or more. On the other hand, if the number-average primary particle diameter exceeds 100 μm, problems such as unevenness on the surface of the resin being mixed can occur when used as a filler for resin mixing, for example, when mixed with a resin. Therefore, the number average primary particle size is 100 μm or less, and preferably 90 μm or less. The number average primary particle size can be determined by the method described in the Examples.

[0026] The large-particle-size rutile-type titanium oxide powder according to this embodiment contains polyhedral rutile-type titanium oxide particles as the titanium oxide particles that make up the powder. The greater the difference in refractive index, the greater the specular reflection of light. Therefore, particles with a higher refractive index have a higher specular reflectance. The polyhedral rutile-type titanium oxide particles of this embodiment are thought to take advantage of the high refractive index of rutile-type titanium oxide to increase the difference in refractive index, and as a result, to increase the specular reflectance.

[0027] As used herein, "polyhedral" particles refer to particles whose surface is composed of 6 to 30 planes, and in which all interior angles of each plane are within 180°. Polyhedral particles also include those with rounded corners, resulting in a rounded shape either entirely or partially. Polyhedral particles also include those with a broken shape, such as a crack or chip. That is, particles with a shape similar to a polyhedral particle, which is presumed to have been formed by the breakage of a polyhedral particle, are considered to be polyhedral particles. Polyhedral particles also include agglomerated particles formed by the aggregation of polyhedral particles.

[0028] When observing the SEM image of the large-particle size rutile-type titanium oxide powder described in the Examples below, for example, polyhedral rutile-type titanium oxide particles preferably account for 50 area % or more, more preferably 65 area % or more, and even more preferably 80 area % or more of the total rutile-type titanium oxide particles. Most preferably, the large-particle size rutile-type titanium oxide powder according to this embodiment is composed of polyhedral rutile-type titanium oxide particles (the proportion of polyhedral rutile-type titanium oxide particles to the total rutile-type titanium oxide particles is 100 area %).

[0029] The large particle size rutile titanium oxide powder may contain rutile titanium oxide particles that are not polyhedral, such as spherical, within the range that does not impair the effects of this embodiment. However, when observing, for example, an SEM image described in the Examples below, the area ratio of non-polyhedral rutile titanium oxide particles is preferably 50 area % or less, more preferably 35 area % or less, even more preferably 20 area % or less, and most preferably zero.

[0030] When observing the SEM image of the large-particle-size rutile titanium dioxide powder described later in the Examples, for example, the average aspect ratio (e.g., the average aspect ratio of 30 particles) calculated from the maximum length possible within the area enclosed by the periphery of a single particle (in the case of the particles illustrated schematically in FIG. 2A below, the periphery is the solid line) divided by the longest perpendicular length perpendicular to the maximum length can be, for example, 3.0 or less, or even 2.0 or less, or even 1.5 or less. A smaller aspect ratio is preferable because it is easier to mix with a resin when used, for example, as a filler for resin mixing.

[0031] The large-particle size rutile-type titanium dioxide powder according to this embodiment can be used in any suitable application, such as filler for resin mixing, pigment, catalyst, catalyst support, etc. This embodiment also includes filler for resin mixing, pigment, catalyst, and / or catalyst support that contain the large-particle size rutile-type titanium dioxide powder according to this embodiment. The large-particle size rutile-type titanium dioxide powder according to this embodiment, having a predetermined size and shape, can be easily mixed with resin, for example, when used as filler for resin mixing.

[0032] 2. Manufacturing method for large particle size rutile titanium dioxide powder The method for producing the large particle size rutile type titanium oxide powder according to this embodiment is as follows: a mixing step of mixing one or more titanium oxide raw materials selected from titanium oxide and titanium compounds that become titanium oxide when heated at 800°C or higher with one or more additives selected from the group consisting of chlorides, sulfates, and phosphates to obtain a mixture; and a firing step of firing the mixture at a temperature of 800° C. or higher. Each step will be described in detail below.

[0033] (Mixing process) The first step in the method for producing large-particle size rutile-type titanium oxide powder according to this embodiment includes a mixing step of mixing one or more titanium oxide raw materials selected from titanium oxide and titanium compounds that become titanium oxide when heated to 800°C or higher with one or more additives selected from the group consisting of chlorides, sulfates, and phosphates to obtain a mixture.

[0034] The raw material used in the method for producing large-particle size rutile-type titanium oxide powder is one or more titanium oxide raw materials selected from the group consisting of titanium oxide and titanium compounds that become titanium oxide when heated at 800°C or higher. Examples of titanium compounds that become titanium oxide when heated at 800°C or higher include one or more of titanyl sulfate and titanium hydroxide, which become titanium oxide when fired at 800°C or higher. The size of the titanium oxide raw material is not limited, and the median diameter (D50) or number average primary particle diameter can be, for example, 0.010 μm to 20 μm.

[0035] The additives to be mixed with the titanium oxide raw material must be compounds that do not form stable compounds with titanium oxide when fired at 800°C or higher, and that melt partially or completely at the firing temperature, dissolving the titanium oxide partially or completely. It is believed that titanium oxide dissolved in a specific additive can exhibit the effect of growing into a desired crystal structure by precipitating as the additive volatilizes.

[0036] Examples of compounds that can exhibit the above-mentioned effects include chlorides such as lithium chloride, sodium chloride, potassium chloride, calcium chloride, strontium chloride, and barium chloride; sulfates such as sodium sulfate, potassium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; and phosphates such as monosodium phosphate, disodium phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, calcium dihydrogen pyrophosphate, calcium pyrophosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, potassium pyrophosphate, potassium tripolyphosphate, and potassium metaphosphate. One or more of these can be used. From the standpoints of cost and easy availability, it is desirable to use at least one of sodium chloride and potassium chloride as the additive.

[0037] The mass ratio of the additive to the mixture, i.e., the ratio of the additive when the mixture is 100% by mass, is preferably 15% by mass or more and 90% by mass or less. A mass ratio of the additive of 15% by mass or more is preferred because the above-mentioned effects are easily achieved. The mass ratio of the additive is more preferably 20% by mass or more. Even if the mass ratio of the additive exceeds 90% by mass, it is possible to produce the desired large-particle rutile-type titanium dioxide powder, but this is not preferred from the standpoint of cost because the amount of additive increases, so the mass ratio of the additive is preferably 90% by mass or less.

[0038] The titanium oxide raw material and the additive may be mixed by either a wet method or a dry method. When mixed by a wet method, water or an organic solvent such as ethanol can be used. From the viewpoint of cost and labor saving, dry mixing is preferable.

[0039] (Firing process) The second step in the method for producing large-particle-size rutile-type titanium dioxide powder according to this embodiment includes a calcination step in which the mixture is calcined at 800°C or higher. The calcination step can be carried out using a box furnace, a pusher furnace, a roller hearth kiln, a rotary kiln, or the like. To increase the particle size of titanium dioxide by calcination, the calcination temperature should be 800°C or higher, preferably 900°C or higher, but not higher than 1400°C, or even not higher than 1200°C. The calcination time can be appropriately set depending on the amount of material to be processed. The calcination atmosphere can be an oxygen-containing atmosphere such as air. It is believed that the additives melt during the calcination step, dissolving the titanium dioxide raw material, and the additives volatilize during calcination, resulting in the precipitation and particle growth of polyhedral rutile-type titanium dioxide. After firing, the fired product is cooled and removed, but there is no need to perform rapid cooling such as removing the fired product to room temperature after heating is stopped. For example, the fired product may be cooled in the furnace after heating is stopped, and can be cooled at a rate of, for example, 30°C / hr to 200°C / hr.

[0040] The method for producing large-particle-size rutile-type titanium oxide powder according to this embodiment only needs to include the mixing step and the calcination step, and other steps are not limited. The method for producing large-particle-size rutile-type titanium oxide powder according to this embodiment may include a washing step as a third step, for example, after the calcination step. For washing in the washing step, ion-exchanged water, an aqueous acetic acid solution, a hydrochloric acid solution, an aqueous sulfuric acid solution, an aqueous nitric acid solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution, or an organic solvent such as ethanol, propanol, or acetone can be used. Washing using ion-exchanged water is preferred. [Example]

[0041] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the above-mentioned and below-mentioned aims, and all such modifications are included in the technical scope of the present invention.

[0042] 1. Sample Preparation [Example 1] 24 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 6 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was calcined by heating and holding at 1000°C for 5 hours. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0043] [Example 2] 21 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 9 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0044] [Example 3] 18 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 12 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0045] [Example 4] 15 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 15 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0046] [Example 5] 24 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 6 g of potassium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0047] [Example 6] 18 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 12 g of potassium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0048] [Example 7] 3 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 27 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 30 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0049] [Example 8] 25.5 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 4.5 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The mixture was heated in a box-type electric furnace at a rate of 150 °C per hour (150 °C / h) and then heated and held at 1000 °C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100 °C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered solid (residue) was collected and dried at 120 °C for 12 hours to obtain a titanium oxide powder sample.

[0050] [Example 9] 21 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 9 g of sodium sulfate were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 10 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0051] [Example 10] 18 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 12 g of potassium tripolyphosphate were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 10 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0052] [Comparative Example 1] 27 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 3 g of sodium chloride were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0053] Comparative Example 2 21 g of titanium oxide raw material with a number average primary particle diameter of 0.1 μm to 1 μm and 9 g of sodium carbonate were placed in a bag and mixed in the bag for 15 minutes to obtain a mixture. 10 g of the mixture was weighed out and placed in a crucible. The temperature was increased at a rate of 150°C per hour (150°C / h) in a box-type electric furnace, and the mixture was heated and held at 1000°C for 5 hours for calcination. After heating and holding, the mixture was allowed to cool naturally in the furnace, removed when it was below 100°C, and cooled to room temperature. The calcined powder was removed, placed in a beaker, and stirred in 400 mL of ion-exchanged water for 5 minutes to obtain a washed product. The washed product was then filtered for solid-liquid separation. The filtered product (residue) was collected and dried at 120°C for 12 hours to obtain a titanium oxide powder sample.

[0054] 2. Evaluation In this example, the evaluation items of identifying the titanium oxide crystalline phase by X-ray diffraction and measuring the number average primary particle size of the titanium oxide powder were carried out as follows.

[0055] (Identification of titanium oxide crystalline phases by X-ray diffraction) The prepared sample was placed on a measurement sample holder and set in a Rigaku X-ray diffractometer [MiniFlex]. Measurements were performed using Cu / Kα radiation, 30 kV / 15 mA, and a scanning range of 10° to 70°. The crystalline phase of titanium oxide was identified from the obtained X-ray diffraction pattern.

[0056] The diffraction pattern of the titanium oxide powder obtained by measuring it with an X-ray diffractometer is shown in Figure 1. The diffraction pattern in Figure 1 indicates that a rutile phase was obtained.

[0057] (Number average primary particle diameter) The obtained titanium oxide powder was photographed under a scanning electron microscope (SEM) at 300x magnification (field of view: approximately 430 μm × approximately 290 μm). The image analysis software [ImageJ] was used to determine the length of the longest side of the measured particle and the length of the longest side (proximal long side) originating from the end of this longest side. The method for determining these sides is explained using Figure 2A, which shows a schematic representation of the particle being measured on the photograph. The particle shown in Figure 2A is a particle in which four planes, a to d, are observed on the photograph. For this particle, the length of the "longest side of the measured particle" refers to the length of the longest side 1 of the solid lines indicating the particle's outline on the photograph. Furthermore, the longest side (proximal long side) originating from the ends 3A and 3B of this longest side 1 refers to side 2A. In other words, for the particle in Figure 2A, the lengths of two sides, side 1 and side 2A, are used to calculate the particle diameter. The particle diameter is calculated by multiplying the average value of these two sides by √2, i.e., by the formula: particle diameter = [(length of the longest side + length of the longest side starting from the longest side) / 2] × √2. Note that sides that do not form the outer periphery (for example, sides indicated by dashed lines in Figure 2A) are not used in calculating the particle diameter. Furthermore, as shown in Figure 2B, when the outer periphery of a particle is rectangular, the lengths of sides 2A and 2B starting from the longest side 1 are the same, so it is sufficient to use the length of either side 2A or 2B for the calculation. Note that according to the above measurement method, spherical particles that do not have sides are excluded from the measurement.

[0058] The particle diameters of 100 titanium oxide particles were measured in this manner, and the average value was calculated, which was designated as the number-average primary particle diameter. Regarding the particles in the photograph, those whose longest side 1 was greater than 1 pixel, which could be recognized by the image analysis software, were targeted; particles whose longest side 1 was less than 1 pixel were excluded from the measurement as noise. The number-average primary particle diameter of the titanium oxide powder determined for each example is shown in Table 1. In SEM images taken with a scanning electron microscope (SEM) at 300x magnification, the proportion of polyhedral rutile-type titanium oxide particles to the total rutile-type titanium oxide particles in Examples 1 to 10 was 50 area % or more, for example, 58 area % in Example 8.

[0059] 3 to 14 are scanning electron microscope (SEM) photographs at 1000 magnifications of the titanium oxide powders obtained in Examples 1 to 10 and Comparative Examples 1 and 2, respectively.

[0060] [Table 1]

[0061] Table 1 and Figures 3 to 14 reveal the following. In all of Examples 1 to 10, in which large-particle-size rutile-type titanium oxide powders of the present embodiment were obtained, large-particle-size rutile-type titanium oxide powders containing polyhedral rutile-type titanium oxide particles and having a number-average primary particle size of more than 10 μm and 100 μm or less were obtained. In contrast, in Comparative Example 1, in which a small amount of additive was used in the production process, irregular particles were obtained in which the particles were fused together, unlike the polyhedral shape of the particles in Examples 1 to 10, as shown in Figure 13. In Comparative Example 2, which was produced using a compound other than the additive specified in the present embodiment, the particles were significantly fused together, unlike the polyhedral shape of the particles in Examples 1 to 10, as shown in Figure 14, and were irregular particles that could hardly be called granular. [Industrial Applicability]

[0062] The large particle size rutile titanium oxide powder according to this embodiment can be used for any suitable purpose, for example, as a filler for mixing with resins, a pigment, a catalyst, a catalyst support, or the like.

Claims

1. A large particle size rutile titanium oxide powder containing polyhedral rutile titanium oxide particles and having a number average primary particle size of more than 10 μm and not more than 100 μm.

2. 2. A method for producing the large particle size rutile type titanium oxide powder according to claim 1, comprising: a mixing step of mixing one or more titanium oxide raw materials selected from titanium oxide and titanium compounds that become titanium oxide when heated to 800°C or higher with one or more additives selected from the group consisting of chlorides, sulfates, and phosphates to obtain a mixture; and a calcination step of calcining the mixture at 800°C or higher.

3. 3. The method for producing large-particle size rutile-type titanium oxide powder according to claim 2, wherein the additive is at least one of sodium chloride and potassium chloride.

4. 4. The method for producing large-particle size rutile-type titanium oxide powder according to claim 2, wherein the ratio of the additive to the mixture is 15% by mass or more and 90% by mass or less.

5. 2. The large particle size rutile type titanium dioxide powder according to claim 1, which is used as a filler for mixing with resin.

6. 2. The large particle size rutile type titanium dioxide powder according to claim 1, which is used as a pigment.

7. 2. The large-particle-size rutile-type titanium oxide powder according to claim 1, which is used as a catalyst and / or a catalyst support.

8. A filler for mixing with resin, comprising the large particle size rutile type titanium dioxide powder according to claim 1.

9. A pigment comprising the large particle size rutile type titanium dioxide powder according to claim 1.

10. A catalyst and / or catalyst support comprising the large particle size rutile type titanium oxide powder according to claim 1.

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