Titanium oxide particles, resin composition, and method for producing titanium oxide particles

Abstract

Provided are titanium oxide particles having excellent solar reflectance. The titanium oxide particles contain titanium dioxide, and a value calculated by standard deviation / average particle diameter × 100 of the titanium oxide particles is 30% or less. A method for producing titanium oxide particles includes a mixing step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to form a mixture, and a firing step of firing the mixture, wherein a molar ratio of Mo / M1 (where M1 represents Na and K) in the mixture is more than 0.5.

Description

[Technical Field]

[0001] The present invention relates to titanium oxide particles, a resin composition, and a method for producing titanium oxide particles. [Background technology]

[0002] Titanium oxide particles are widely used in a variety of fields, including inks, resin fillers, catalysts, catalyst carriers, adsorbents, photocatalysts, antibacterial agents, optical materials, cosmetic compounding ingredients, pigments, paints, fillers, and electronics materials. Patent Document 1 discloses rutile-type titanium oxide particles containing molybdenum, the titanium oxide particles having an average particle size of 0.1 to 100 μm.

[0003] Titanium oxide particles can scatter light in the visible and infrared regions and have an excellent ability to block infrared rays, which are the part of sunlight that is most easily converted into heat energy, and are therefore used in cosmetics, heat-shielding paints, etc. For example, in Patent Document 2, particulate titanium oxide having a primary particle size of 0.5 to 2.0 μm is used as a filler with heat-shielding properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-13954 [Patent Document 2] International Publication No. 2004 / 052786 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when titanium oxide particles are intended to be used to take advantage of their heat-shielding properties, there is still room for improvement in the heat-shielding performance of titanium oxide particles.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide titanium oxide particles having excellent solar reflectance. [Means for solving the problem]

[0007] (1) Titanium oxide particles containing titanium dioxide, Titanium oxide particles, wherein the value calculated by dividing the standard deviation of the titanium oxide particles by the average particle diameter x 100 is 30% or less. (2) The titanium oxide particles according to (1) above, wherein the average particle size of the titanium oxide particles is 0.1 to 10 μm. (3) The titanium dioxide particles according to (1) or (2), wherein the average crystallite size of the titanium dioxide determined from the peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement is 220 nm or more. (4) The titanium oxide particles according to any one of (1) to (3) above, which contain molybdenum. (5) The titanium dioxide particles according to any one of (1) to (4), wherein the titanium dioxide contains rutile titanium dioxide. (6) The titanium oxide particles according to any one of (1) to (5) above, which are used for a heat-shielding coating material. (7) A resin composition comprising a resin and the titanium oxide particles described in any one of (1) to (6). (8) The resin composition according to (7) above, which is a heat-shielding coating material. (9) A method for producing titanium oxide particles according to any one of (1) to (6), comprising the steps of: a mixing step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to form a mixture; A calcination step of calcining the mixture, A method for producing titanium oxide particles, wherein the molar ratio of Mo / M1 (M1 represents Na and K) in the mixture is greater than 0.5. (10) The mixing step is a step of mixing a titanium compound with a compound containing molybdenum and potassium or a compound containing molybdenum and sodium to obtain a mixture, the compound containing molybdenum and potassium is K2Mo2O7, The method for producing titanium oxide particles according to (9) above, wherein the compound containing molybdenum and sodium is Na2Mo2O7. [Effects of the Invention]

[0008] According to the present invention, titanium oxide particles having excellent solar reflectance can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an SEM image of titanium oxide particles of Example 1. [Figure 2] 1 is an SEM image of titanium oxide particles of Example 2. [Figure 3] 1 is an SEM image of titanium oxide particles of Example 3. [Figure 4] 1 is an SEM image of titanium oxide particles of Example 4. [Figure 5] 1 is an X-ray diffraction (XRD) pattern of titanium oxide particles of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the titanium oxide particles, resin composition, and method for producing titanium oxide particles of the present invention will be described.

[0011] <Titanium oxide particles> The titanium oxide particles of the embodiment are titanium oxide particles containing titanium dioxide, and the value calculated by dividing the standard deviation of the titanium oxide particles by the average particle diameter x 100 is 30% or less, preferably 2 to 30%, more preferably 5 to 25%, and even more preferably 10 to 25%. Titanium oxide particles that satisfy the above-mentioned upper limit value of standard deviation / average particle diameter×100 are excellent in solar reflectance.

[0012] The average particle size of the titanium oxide particles in the embodiment may be 0.1 μm or more, 0.5 μm or more, or 0.7 μm or more. The average particle size of the titanium oxide particles may be 10 μm or less, 7 μm or less, or 5 μm or less. Titanium oxide particles having an average particle size that satisfies the above numerical value have even more excellent solar reflectance.

[0013] An example of the range of the average particle diameter of the titanium oxide particles is 0.1 μm or more and 10 μm or less, 0.5 μm or more and 7 μm or less, or 0.7 μm or more and 5 μm or less.

[0014] In this specification, the average particle diameter of titanium oxide particles refers to the average value of the maximum distance between two points on the outline of the primary particle of 50 or more randomly selected titanium oxide particles, which are photographed with a scanning electron microscope (SEM) and observed in a two-dimensional image.

[0015] The median diameter D of the titanium oxide particles of the embodiment 50 The thickness may be 0.1 μm or more and 10 μm or less, 0.5 μm or more and 7 μm or less, or 0.7 μm or more and 5 μm or less.

[0016] The median diameter D50 of the titanium oxide particles of the embodiment is determined by measuring the particle size distribution of a sample powder in a dry state using a laser diffraction dry particle size distribution analyzer (for example, HELOS (H3355) & RODOS manufactured by Nippon Laser Co., Ltd.) under conditions of a dispersion pressure of 3 bar and a suction pressure of 90 mbar, and determining the particle diameter at the point where the volume cumulative % distribution curve intersects with the horizontal axis of 50% as D. 50 is calculated as follows.

[0017] The average crystallite size of titanium dioxide contained in the titanium oxide particles, determined from the peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement, is preferably 220 nm or more, more preferably 250 nm or more, and more preferably 300 nm or more. By including titanium dioxide having an average crystallite size equal to or larger than the above lower limit, the layer solar reflectance of the titanium oxide particles can be made even better.

[0018] The upper limit of the average crystallite size of the titanium dioxide determined from the peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement may be, for example, 700 nm or less, 650 nm or less, or 600 nm or less.

[0019] Examples of the range of the average crystallite size of the titanium dioxide determined from the peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement include 220 nm or more and 700 nm or less, 250 nm or more and 650 nm or less, and 300 nm or more and 600 nm or less.

[0020] The average crystallite size of the titanium oxide particles of the embodiment can be determined by the following measurement method.

[0021] [Crystallite size measurement] Measurements are performed using an X-ray diffractometer (e.g., SmartLab, manufactured by Rigaku Corporation), an ultra-high resolution spiral analyzer (CALSA) as the detector, and PDXL2 analysis software. The measurement method is the 2θ / θ method, and the average crystallite size of titanium dioxide is calculated using the Scherrer equation from the half-width of the peak appearing at 2θ = 27.5° ± 1.0° under the following measurement conditions. (Measurement conditions) Scan range: 2θ=10~70° step: 2θ=0.002° speed:2θ=0.05° / min βs=20rpm Soller / PSC: 2θ=2.5° short Soller: 2θ=2.5° Analysis software: PDXL2 Device specific width: None Peak shape: Automatic analysis using CALSA functions

[0022] The titanium oxide particles of the embodiment contain titanium dioxide (TiO2). The titanium oxide particles of the embodiment contain titanium dioxide (TiO2) in an amount of preferably 50 mass% or more, more preferably 50 to 99.9 mass%, more preferably 80 to 99.9 mass%, and even more preferably 90 to 99.8 mass%, based on the total mass (100 mass%) of the titanium oxide particles.

[0023] The content of titanium dioxide (TiO2) in the titanium oxide particles of the embodiment may be a value calculated by the following XRF analysis.

[0024] The titanium content in the titanium oxide particles of the embodiment, as determined by XRF analysis of the titanium oxide particles, may be 50 mass% or more, 50 to 99.9 mass%, 80 to 99.9 mass%, or 90 to 99.8 mass% in terms of TiO2 relative to 100 mass% of the total mass of the titanium oxide particles.

[0025] The content in terms of TiO2 refers to a value obtained from the amount of TiO2 obtained by converting the titanium content determined by XRF analysis of the titanium oxide particles using a calibration curve in terms of TiO2.

[0026] The titanium oxide particles of the embodiment may contain molybdenum. The titanium oxide particles of the embodiment may contain molybdenum derived from a molybdenum compound that may be used in the production method described below.

[0027] The state and amount of molybdenum that may be contained in the titanium oxide particles of the embodiment are not particularly limited, and it may be contained in the titanium oxide particles as molybdenum metal, molybdenum oxide, a partially reduced molybdenum compound, etc. Molybdenum is thought to be contained in the titanium oxide particles as MoO, but it may also be contained in the titanium oxide particles as MoO, MoO, etc. other than MoO.

[0028] The form in which molybdenum is contained is not particularly limited, and it may be contained in a form in which it adheres to the surface of the titanium oxide particles, in a form in which it is substituted as part of the crystal structure of the titanium oxide particles, in an amorphous state, or in a combination of these.

[0029] The molybdenum content in the titanium oxide particles of the embodiment, calculated as MoO3 relative to the total mass of the titanium oxide particles (100 mass%), determined by XRF analysis of the titanium oxide particles, may be 0.01 mass% or more, 0.01 to 25 mass%, 0.05 to 10 mass%, or 0.1 to 5 mass%.

[0030] The content in terms of MoO3 refers to a value obtained by converting the molybdenum content determined by XRF analysis of the titanium oxide particles into the amount of MoO3 using a calibration curve in terms of MoO3.

[0031] The titanium oxide particles of the embodiment may contain potassium and / or sodium. The titanium oxide particles of the embodiment may contain potassium and / or sodium derived from a potassium compound and / or a sodium compound that may be used in the production method described below.

[0032] The potassium and / or sodium content in the titanium oxide particles may be 5% by mass or less, or may be 0.01 to 5% by mass, in terms of the total content in terms of KO and NaO relative to 100% by mass of the total mass of the titanium oxide particles, as determined by XRF analysis of the titanium oxide particles.

[0033] The total content in terms of K2O and Na2O refers to the sum of the amount of K2O obtained by converting the potassium content determined by XRF analysis of the titanium oxide particles using a calibration curve in terms of K2O, and the amount of Na2O obtained by converting the sodium content determined by XRF analysis using a calibration curve in terms of Na2O. Note that the potassium content and / or sodium content in the titanium oxide particles may be zero.

[0034] The titanium content, molybdenum content, and potassium and / or sodium content in the titanium oxide particles can be freely combined.

[0035] An example of the particulate titanium oxide of the embodiment is a particulate titanium oxide having a titanium content of 50 to 99.9 mass % in terms of TiO2 and a molybdenum content of 0.01 to 25 mass % in terms of MoO3, relative to 100 mass % of the total mass of the particulate titanium oxide, as determined by XRF analysis of the particulate titanium oxide.

[0036] An example of the particulate titanium oxide of the embodiment is titanium oxide particles having a titanium content of 50 to 99.9 mass% in terms of TiO2, a molybdenum content of 0.01 to 25 mass% in terms of MoO3, and a total content of potassium and / or sodium of 0.01 to 5 mass% in terms of KO and Na2O, relative to 100 mass% of the total mass of the titanium oxide particles, as determined by XRF analysis of the particulate titanium oxide.

[0037] The crystal structure of titanium dioxide contained in the titanium oxide particles of the embodiment can be identified by the XRD pattern of the spectrum obtained in XRD analysis.

[0038] Titanium dioxide crystal structures include anatase, rutile, and brookite. In the titanium dioxide particles of the present embodiment, the titanium dioxide preferably contains rutile titanium dioxide. The rutile crystallization rate of the titanium dioxide is preferably 90% or more. Titanium oxide particles containing rutile titanium dioxide have a high refractive index and excellent infrared shielding ability, and therefore can be expected to have a high heat-shielding effect.

[0039] The manufacturing method of the embodiment described below provides excellent shape control according to the crystalline shape of the titanium oxide particles to be manufactured. The titanium oxide particles of the embodiment have a controlled crystalline shape and can have an idiomorphic shape such as a polyhedral shape or a substantially spherical shape. The shape may be a polyhedral shape that is substantially close to a sphere with flat surfaces, or a substantially spherical shape with smooth spherical surfaces. Titanium oxide particles having these shapes can be manufactured by the manufacturing method described below.

[0040] The titanium oxide particles of the embodiment have excellent solar reflectance. The titanium oxide particles of the embodiment have a solar reflectance R determined by the following [Infrared Reflection Evaluation]. * However, it may be 65% or more, may be 65 to 90%, or may be 68 to 80%.

[0041] [Infrared reflection evaluation] A glass substrate has a hole (approximately 2 cm in diameter) in the center for placing the sample. Titanium oxide particles, which are sample powder, are filled into the hole, and the surface of the sample powder is then covered with a cover plate made of quartz glass. Measure the absorption and reflectance spectra (200-2500 nm) of the sample powder using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (e.g., U-4100, Hitachi High-Tech Science Co., Ltd.) to obtain the reflectance in the NIR region (700-2500 nm). The measurement conditions are a scanning speed of 600 nm / min with an integrating sphere, a sampling interval of 2.00 nm, and a slit width of 5.00 nm. The obtained data is calculated as solar reflectance R using the following formula: * Convert to.

number

[0042] The titanium oxide particles of the embodiment have the above-mentioned excellent solar reflectance and can therefore be used as a heat-shielding agent. A composition containing the titanium oxide particles of the embodiment can be used as a coating agent for coating the surface of an article. The titanium oxide particles of the embodiment can be suitably used as a heat-shielding agent contained in a heat-shielding paint. The titanium oxide particles of the embodiment can be suitably used as titanium oxide particles for a heat-shielding paint.

[0043] The heat-shielding paint can be used by being applied to the surfaces of various articles, such as roofs, building exterior walls, and other building frameworks, road surfaces such as asphalt surfaces and concrete surfaces, vehicles such as trains and automobiles, airplanes, ships, electrical appliances, etc. The heat-shielding paint can be suitably used as a paint for road paving.

[0044] The heat-shielding coating material is preferably a resin composition containing a resin. The titanium oxide particles of the embodiment can be suitably used as a resin filler contained in the resin composition.

[0045] One embodiment of the present invention provides a resin composition containing a resin and titanium oxide particles, wherein the titanium oxide particles contain titanium dioxide and have a value of 30% or less as calculated by dividing the standard deviation by the average particle size x 100. The resin composition of this embodiment can be suitably used as the above-mentioned heat-shielding coating material.

[0046] The titanium oxide particles contained in the resin composition and the heat-shielding coating material may be the same as the titanium oxide particles in the embodiment described above.

[0047] Examples of the resin that may be contained in the above-mentioned resin composition and heat-shielding coating material include, but are not limited to, acrylic resin, urea resin, melamine resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, phenolic resin, acrylic silicone resin, polyvinyl chloride, polyvinyl acetate, alkyd resin, aminoalkyd resin, and fluororesin.

[0048] The resin composition and the heat-shielding coating material may further contain a solvent. Examples of the solvent include, but are not limited to, aromatic solvents such as toluene, xylene, and methoxybenzene; acetate ester solvents such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; propionate solvents such as ethoxyethyl propionate; alcohol solvents such as methanol, ethanol, propanol, n-butanol, and isobutanol; ether solvents such as butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol ethyl ether, and diethylene glycol dimethyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aliphatic hydrocarbon solvents such as hexane; nitrogen compound solvents such as N,N-dimethylformamide, γ-butyrolactam, N-methyl-2-pyrrolidone, aniline, and pyridine; lactone solvents such as γ-butyrolactone; carbamate esters such as a 48:52 mixture of methyl carbamate and ethyl carbamate; and water.

[0049] The resin composition and the heat-shielding coating material may further contain various additives, such as pigments (excluding the titanium oxide particles), dispersants, antifoaming agents, film-forming aids, fillers, paint auxiliary agents, drying agents, plasticizers, and / or auxiliary pigments.

[0050] The content of the titanium oxide particles of the embodiment relative to the total volume (100% by volume) of the resin composition is preferably 1 to 50% by volume in terms of solid content excluding the solvent.

[0051] As one embodiment of the present invention, a coating film of the resin composition of the embodiment and an article having the coating film can be provided. The coating film may be a coating film containing the resin composition of the embodiment, or may be a coating film made of the resin composition of the embodiment.

[0052] <Method for producing titanium oxide particles> The method for producing titanium oxide particles according to the embodiment includes (I) calcining a titanium compound in the presence of a molybdenum compound and a potassium compound and / or a sodium compound, or (II) calcining a titanium compound in the presence of a molybdenum compound.

[0053] The method for producing titanium oxide particles according to the embodiment may include a mixing step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to prepare a mixture, and a calcination step of calcining the mixture. The molar ratio of Mo / M1 (M1 represents Na and K) in the mixture in the mixing step may be greater than 0.5, may be 0.65 or more, may be 0.9 or more, or may be 1 or more.

[0054] According to a method for producing titanium oxide particles in which the molar ratio (Mo / M1) is greater than 0.5, the flux effect is improved and the average crystallite size of the titanium dioxide contained in the produced titanium oxide particles can be easily increased.

[0055] The molar ratio of Mo / M1 (M1 represents Na and K) in the mixture in the mixing step may be 3 or less, 2 or less, or 1.5 or less.

[0056] Examples of the numerical range of the molar ratio of Mo / M1 (M1 represents Na and K) in the mixture in the mixing step may be greater than 0.5 and less than or equal to 3, greater than or equal to 0.65 and less than or equal to 3, greater than or equal to 0.9 and less than or equal to 2, or greater than or equal to 1 and less than or equal to 1.5. When the mixture does not contain K, M1 may be only Na. When the mixture does not contain Na, M1 may be only K. When the mixture contains both Na and K, M1 may be the total amount of Na and K.

[0057] Regarding the amounts of the titanium compound and molybdenum compound used, in order to obtain the titanium oxide particles of the above embodiment with high efficiency, the molar ratio of titanium atoms in the mixture to molybdenum atoms in the molybdenum compound is preferably in the range of 0.5 to 50.0, more preferably in the range of 0.5 to 35.0, and particularly preferably in the range of 1.5 to 20.

[0058] In the case of the above-described production method (II), the molar ratio of titanium atoms in the mixture to molybdenum atoms in the molybdenum compound is preferably in the range of from 35.0 to 120.0, more preferably from 35.0 to 100.0, which is preferable from the viewpoint of the sheath-removal and washability of the resulting titanium oxide particles.

[0059] Here, at least a part of the molybdenum compound and potassium compound may be replaced with a compound containing molybdenum and potassium, such as potassium molybdate (e.g., KMo n O 3n+1 , n=1, 2, 3) can also be used. Similarly, at least a portion of the molybdenum compound and sodium compound can be replaced with a compound containing molybdenum and sodium, such as sodium molybdate (e.g., Na2Mo n O 3n+1 , x=1, 2, 3) can also be used. In particular, the use of Na2Mo2O7 or K2Mo2O7 has a high flux effect on crystal growth, and tends to easily improve the average crystallite size of titanium dioxide. A step of mixing a titanium compound with a compound containing molybdenum and potassium and / or sodium to prepare a mixture is also considered to be a step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to prepare a mixture.

[0060] [Mixing process] The mixing step is a step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to form a mixture.

[0061] The mixing state of the mixture is not particularly limited, and it is sufficient that the molybdenum compound and the potassium compound and / or sodium compound are present in the same space where they can act on the titanium compound, or that the molybdenum compound is present in the same space where they can act on the titanium compound. Specifically, they may be mixed in an unmixed state, or may be mixed by any of simple mixing of powders, mechanical mixing using a grinder or the like, or mixing using a mortar or the like, and may be mixed in a dry state or a wet state.

[0062] The above starting compounds will now be described.

[0063] (Titanium compounds) The titanium compound used as a raw material (hereinafter sometimes referred to as a precursor) is not particularly limited as long as it becomes titanium oxide upon heat treatment, and examples of titanium oxides that can be used include titanium chloride, titanium sulfate, metatitanic acid, amorphous titanium oxide, anatase titanium oxide, rutile titanium oxide, and mixed anatase and rutile titanium oxide. There are no particular limitations on the physical form, such as shape, particle size, and specific surface area, of the titanium compound used as a precursor.

[0064] The shape of the titanium oxide particles after calcination is hardly reflected by the shape of the precursor titanium compound, and therefore any shape, such as a sphere, an amorphous structure with an aspect (wire, fiber, ribbon, tube, etc.), or a sheet, can be suitably used.

[0065] Similarly, the particle size of the titanium oxide particles after firing is hardly affected by the particle size of the precursor titanium compound, so titanium compounds ranging from several nm to several hundred μm can be suitably used. Furthermore, the specific surface area of ​​the precursor titanium compound is not particularly limited, and any titanium compound can be suitably used.

[0066] The titanium compound precursor may consist solely of titanium compound, or may contain a small amount of a metal compound. For example, an aluminum compound, a silicon compound, a zinc compound, etc. may also be present. To efficiently form titanium oxide crystals using a molybdenum compound as a fluxing agent, the content of these metal compounds in the titanium compound precursor is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0067] The titanium compound precursor may also be a composite of a titanium compound and an organic compound. For example, an organic / inorganic composite obtained by modifying titanium oxide with an organic silane, or a titanium compound composite having a polymer adsorbed thereon, can also be suitably used. When using such a composite, there are no particular restrictions on the organic compound content, but in order to efficiently produce rutile-type titanium oxide particles having a substantially spherical idiomorphic shape, the organic compound content is preferably 60% by mass or less, and more preferably 30% by mass or less.

[0068] (Molybdenum compounds) Molybdenum-containing titanium oxide particles can be obtained by sintering the titanium compound in the presence of molybdenum, which is used as a fluxing agent. Molybdenum compounds include molybdenum oxide, which is formed by bonding molybdenum metal with oxygen and forming an anion (MO x n- (hereinafter, M represents a metal).

[0069] Acid anion (MO x n- ) is formed by bonding molybdenum metal with oxygen, and the compound containing the acid radical anion is not particularly limited as long as it is a compound that is converted to molybdenum oxide at or below the firing temperature. For example, molybdic acid, HPMo 12 O 40 , H3SiMo 12 O 40 , NH4Mo7O 12Among these, molybdenum oxide is preferably used from the viewpoint of cost. In this case, as titanium oxide particles are formed, molybdenum oxide sublimes, and most of it can be removed from the reaction system.

[0070] In addition, the molybdenum metal is bonded to oxygen to form an acid radical anion (MO x n- As the compound containing ), a metal molybdate that does not decompose at the firing temperature can also be used. For example, sodium molybdate, potassium molybdate, lithium molybdate, or a mixture of multiple molybdenum metal salts can be suitably used. For example, sodium molybdate, potassium molybdate, lithium molybdate, etc., which are soluble in water, are preferred because they can be easily removed by washing with water. A mixture of a molybdenum compound and a metal compound can also be used as the fluxing agent. In this case, the molybdenum compound and the metal compound are reacted by high-temperature firing to form a metal molybdate. The metal molybdate formed is not particularly limited as long as it can form titanium oxide particles as a fluxing agent.

[0071] For example, a compound containing molybdenum and potassium suitable as a fluxing agent can be produced during the firing process using a molybdenum compound and a potassium compound, which are cheaper and more readily available as raw materials. Here, the use of a molybdenum compound and a potassium compound as fluxing agents and the use of a compound containing molybdenum and potassium as fluxing agents are both collectively referred to as the use of a molybdenum compound and a potassium compound as fluxing agents, i.e., in the presence of a molybdenum compound and a potassium compound.

[0072] For example, a compound containing molybdenum and sodium suitable as a fluxing agent can be produced during the firing process using a molybdenum compound and a sodium compound, which are cheaper and more readily available as raw materials. Here, the use of a molybdenum compound and a sodium compound as fluxing agents and the use of a compound containing molybdenum and sodium as fluxing agents are both considered to be the use of a molybdenum compound and a sodium compound as fluxing agents, i.e., in the presence of a molybdenum compound and a sodium compound.

[0073] In addition, potassium molybdate (K2Mo n O 3n+1 , n=1 to 3) contains potassium and can therefore also function as a potassium compound, which will be described later.

[0074] Also, sodium molybdate (Na2Mo n O 3n+1 , n=1 to 3) contains sodium and can therefore function as a sodium compound, which will be described later.

[0075] The fluxing agent containing a molybdenum compound may consist solely of a molybdenum compound, or may contain other inorganic compounds. For example, it may contain a calcium compound, an iron compound, a silicon compound, etc. In order to efficiently form rutile-type titanium oxide particles using a molybdenum compound as a fluxing agent, the content of these inorganic compounds is preferably 20% by mass or less, and more preferably 10% by mass or less, based on the oxide.

[0076] The fluxing agent containing a molybdenum compound may also be a composite of a molybdenum compound and an organic compound. For example, an organic / inorganic composite obtained by modifying a molybdenum compound with an organic silane, or a molybdenum compound composite adsorbed with a polymer, can also be suitably used. When using such a composite, the organic compound content is not particularly limited, but in order to efficiently form rutile-type titanium dioxide particles, the organic compound content is preferably 60% by mass or less, and more preferably 30% by mass or less.

[0077] The above-mentioned molybdenum compounds may be used alone or in combination of two or more kinds.

[0078] (potassium compounds) The potassium compound is not particularly limited, but examples thereof include potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium bicarbonate, potassium acetate, potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, and potassium tungstate. In this case, the potassium compound includes isomers, as in the case of molybdenum compounds. Among these, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate, and potassium molybdate are preferably used, and potassium carbonate, potassium bicarbonate, potassium chloride, potassium sulfate, and potassium molybdate are more preferably used.

[0079] The potassium compounds described above may be used alone or in combination of two or more.

[0080] As described above, potassium molybdate contains molybdenum and can therefore also function as the molybdenum compound described above.

[0081] (sodium compounds) The sodium compound is not particularly limited, but examples thereof include sodium carbonate, sodium molybdate, sodium oxide, sodium sulfate, sodium hydroxide, sodium nitrate, sodium chloride, metallic sodium, etc. Among these, it is preferable to use sodium carbonate, sodium molybdate, sodium oxide, and sodium sulfate from the viewpoints of industrial availability and ease of handling.

[0082] The above-mentioned sodium compounds may be used alone or in combination of two or more kinds.

[0083] As described above, sodium molybdate contains molybdenum and can therefore also function as the molybdenum compound described above.

[0084] Although the molybdenum compound may be classified as a molybdenum compound in this manner, the molybdenum compound is at least one compound selected from the group consisting of molybdenum oxide, potassium molybdate, and sodium molybdate, It is preferable that the sodium compound is sodium carbonate or sodium molybdate, and the potassium compound is potassium carbonate or potassium molybdate.

[0085] The mixing step is a step of mixing a titanium compound with a compound containing molybdenum and potassium or a compound containing molybdenum and sodium to obtain a mixture, and it is more preferable that the compound containing molybdenum and potassium is K2Mo2O7 and the compound containing molybdenum and sodium is Na2Mo2O7.

[0086] [Firing process] The firing step is a step of firing the mixture. In this firing, when the firing temperature exceeds 700°C, the molybdenum compound functions as a fluxing agent, and efficiently works to form titanium oxide particles with a rutile crystallization rate of 90% or more.

[0087] The calcination temperature may be any temperature at which the desired titanium oxide particles are formed or higher, specifically, the maximum temperature may be in the range of 700 to 1400° C. In particular, to efficiently form titanium oxide particles having an average crystallite size of 220 nm or more determined from the peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement of titanium dioxide, calcination at a temperature of 800 to 1400° C. is more preferable, and calcination at a temperature of 800 to 1350° C. is even more preferable. In the case of production method (II), the firing temperature is more preferably 800 to 1400°C, even more preferably 800 to 1350°C, and most preferably 900 to 1100°C.

[0088] As for the firing time, it is preferable that the time required to raise the temperature to a predetermined firing temperature is in the range of 20 minutes to 10 hours, and that the time required to maintain the firing temperature is in the range of 5 minutes to 45 hours. In the case of production method (II), the time required for raising the temperature to the predetermined calcination temperature is preferably in the range of 20 minutes to 10 hours, and the time required for holding the calcination temperature is preferably in the range of 5 minutes to 45 hours, more preferably in the range of 15 minutes to 30 hours, and most preferably in the range of 2 to 7 hours.

[0089] The titanium oxide particles of the above embodiment can be easily obtained by selecting conditions such as a firing temperature of preferably 700 to 1400°C and a firing temperature holding time of 5 minutes to 45 hours, more preferably a firing temperature of 800 to 1400°C and a firing temperature holding time of 5 minutes to 45 hours, even more preferably a firing temperature of 800 to 1350°C and a firing temperature holding time of 10 minutes to 30 hours, and particularly preferably a firing temperature of 800 to 1350°C and a firing temperature holding time of 15 to 30 hours.

[0090] The firing atmosphere is not particularly limited, and firing can be carried out in an atmosphere of air or oxygen, or an inert atmosphere such as nitrogen or argon, but an air atmosphere is more preferable in terms of cost.

[0091] The calcination apparatus is not particularly limited, and a so-called calcination furnace can be used. The calcination furnace is preferably made of a material that does not react with the sublimated molybdenum oxide, and it is preferable to use a highly airtight calcination furnace so that the molybdenum oxide can be efficiently utilized.

[0092] According to the method for producing particulate titanium oxide of the embodiment, the particulate titanium oxide of the above embodiment can be produced. [Example]

[0093] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0094] <Analysis and Evaluation> The powders of each of the examples and comparative examples were used as samples to carry out the following measurements.

[0095] [Average particle size / standard deviation] The sample was photographed with a scanning electron microscope (SEM), and the particles observed in the two-dimensional image were analyzed. The maximum distance between two points on the outline of the primary particle of 50 or more randomly selected particles was taken as the particle diameter, and the average of these distances was taken as the average particle diameter. The standard deviation was determined based on the particle size data measured above, and the value of standard deviation / average particle size×100 was calculated.

[0096] [Crystalline phase analysis by X-ray diffraction (XRD)] The prepared sample was placed on a measurement sample holder with a depth of 0.5 mm, and a constant load was applied to fill it flat. The sample was then placed in a wide-angle X-ray diffraction (XRD) apparatus (Ultima IV, Rigaku Corporation) and measured using Cu / Kα radiation, 40 kV / 30 mA, a scan speed of 2 degrees / min, and a scan range of 10 to 70 degrees.

[0097] [Particle size distribution measurement] The particle size distribution of the sample powder was measured in a dry state using a laser diffraction dry particle size distribution analyzer (HELOS (H3355) & RODOS manufactured by Japan Laser Co., Ltd.) under the conditions of a dispersion pressure of 3 bar and a suction pressure of 90 mbar. The particle size at the point where the volume cumulative % distribution curve intersects with the horizontal axis at 50% was defined as D. 50 was requested as follows.

[0098] [Composition analysis by X-ray fluorescence (XRF)] Approximately 70 mg of the prepared sample was placed on filter paper and covered with PP film for composition analysis using an X-ray fluorescence (XRF) analyzer (Primus IV, manufactured by Rigaku Corporation). The amounts of various elements determined from the XRF analysis results were converted to the oxides listed in Table 2 (mass%) to calculate the percentage of the content of each oxide relative to 100% mass of the total sample.

[0099] [Crystallite size measurement] Measurements were performed using an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation) with CALSA as the detector and PDXL2 as the analysis software. The measurement method was the 2θ / θ method, and the average crystallite size of titanium dioxide was calculated using the Scherrer equation from the half-width of the peak appearing at 2θ = 27.5° ± 1.0° under the following measurement conditions. (Measurement conditions) Scan range: 2θ=10~70° step: 2θ=0.002° speed:2θ=0.05° / min βs=20rpm Soller / PSC: 2θ=2.5° short Soller: 2θ=2.5° Analysis software: PDXL2 Device specific width: None Peak shape: Automatic analysis using CALSA functions

[0100] [Infrared reflection evaluation] A glass substrate had a hole (diameter: about 2 cm) in the center for placing the sample, and the sample powder was filled into the hole. The surface of the sample powder was then covered with a cover plate made of quartz glass. The absorption and reflectance spectra (200–2500 nm) of the sample powder were measured using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (U-4100, Hitachi High-Tech Science Co., Ltd.) to obtain the reflectance in the NIR region (700–2500 nm). The measurement conditions were a scanning speed of 600 nm / min with an integrating sphere, a sampling interval of 2.00 nm, and a slit width of 5.00 nm. The obtained data is calculated as solar reflectance R using the following formula: * was converted to.

number

[0101] [ Crucible separation Evaluation The fired product was removed from the crucible, and the crucible releasability was evaluated based on the percentage of powder remaining on the crucible walls and bottom. The crucible releasability was calculated as the weight of the crucible (A), the weight of the crucible and powder after firing (B), and the weight of the crucible and powder after removal (C). A crucible releasability of less than 0.1 was evaluated as "Good," and a crucible releasability of 0.1 or more was evaluated as "Poor." Crucible separation property = (CA) / (BA)

[0102] <Production of potassium molybdate> [Manufacturing Example 1] 36.17 g of potassium carbonate (K2CO3) and 75.34 g of molybdenum oxide (MoO3) were mixed to obtain a mixture. The resulting mixture was placed in a crucible and fired in a muffle furnace at 700° C. for 5 hours. The temperature was increased at a rate of 5° C. / min. After the temperature was reduced to room temperature, the crucible was removed, and a powder of Production Example 1 was obtained. When this powder was subjected to XRD measurement, scattering peaks originating from K2Mo2O7 were confirmed, confirming the synthesis of K2Mo2O7.

[0103] <Production of titanium oxide particles> [Example 1] 20 g of titanium oxide (TiO2) and 20 g of potassium molybdate (K2Mo2O7) produced in Production Example 1 above were placed in a 100 mL polypropylene bottle and mixed and pulverized for 30 minutes using a paint shaker to obtain a mixture. The resulting mixture was further mixed uniformly in a mortar, then placed in a crucible and fired in a muffle furnace at 800°C for 24 hours. The temperature was increased at a rate of 5°C / min. After cooling to room temperature, the crucible was removed and a powder was obtained. The powder was then dispersed in 80 ml of pure water for 30 minutes, and then centrifuged at 5,000 rpm for 10 minutes, after which the supernatant was removed. This procedure was repeated four times. The obtained precipitate was dried at 80° C. for 24 hours and pulverized in a mortar to obtain a pale yellow powder of Example 1.

[0104] [Example 2] The yellow powder of Example 2 was obtained by the same procedure as in Example 1, except that 24.51 g of metatitanic acid (VK-P101, H2TiO3, manufactured by Xuan Cheng Jing Rui New Materials Co., Ltd.) was used instead of titanium oxide and the firing temperature was changed as shown in Table 1.

[0105] [Example 3] 20 g of titanium oxide (TiO2) and 0.6 g of molybdenum oxide (MoO3) were placed in a 100 mL polypropylene bottle, and mixed and pulverized for 30 minutes using a paint shaker to obtain a mixture. The resulting mixture was further mixed uniformly in a mortar, then placed in a crucible and fired in a muffle furnace at 1100°C for 5 hours. The temperature was increased at a rate of 5°C / min. After cooling to room temperature, the crucible was removed and a powder was obtained. The powder was then dispersed in 80 ml of pure water for 30 minutes, and then centrifuged at 5,000 rpm for 10 minutes, after which the supernatant was removed. This procedure was repeated four times. The obtained precipitate was dried at 80° C. for 24 hours and pulverized in a mortar to obtain a pale yellow powder of Example 3.

[0106] [Example 4] A pale yellow powder of Example 4 was obtained by the same procedure as in Example 3, except that 0.4 g of molybdenum oxide was used and the firing temperature was changed as shown in Table 1.

[0107] [Comparative Example 1] Commercially available titanium oxide particles (manufactured by Teika Corporation) were used as the powder of Comparative Example 1.

[0108] The synthesis conditions are shown in Table 1. "-" indicates that the corresponding compound was not used.

[0109] [Table 1]

[0110] <Result> SEM images of the powders obtained in Examples 1 to 4 above are shown in FIGS.

[0111] The results of each of the above evaluations are shown in Table 2. "ND" stands for not detected.

[0112] [Table 2]

[0113] The particle shapes of each example and comparative example, as determined from SEM images, are shown in Table 2. When particles of different shapes were found to be mixed, the representative shape (the shape most commonly observed) was shown.

[0114] The results of the XRD analysis of the sample of Example 1 are shown in Figure 5. A sharp scattering peak attributable to rutile titanium dioxide appeared, and no crystalline peaks other than those attributable to the rutile crystal structure were observed.

[0115] From the results of the SEM observation and XRD analysis described above, it was confirmed that the powder obtained in each example was titanium oxide particles containing molybdenum and rutile-type titanium dioxide.

[0116] The titanium oxide particles of Examples 1 to 4, which have a narrow particle size distribution, expressed as the value of standard deviation / average particle size×100, have a lower solar reflectance R * The value was high and the material had excellent heat-shielding properties.

[0117] Furthermore, the titanium dioxide particles of Examples 1 to 4 had a larger average crystallite size of 220 nm or more than that of the titanium dioxide particles of Comparative Example 1.

[0118] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to each embodiment, but is limited only by the scope of the claims.

Claims

1. Titanium oxide particles comprising titanium dioxide, Titanium oxide particles, wherein the value calculated by dividing the standard deviation of the titanium oxide particles by the average particle diameter x 100 is 5 to 25%.

2. 2. The titanium oxide particles according to claim 1, wherein the average particle size of the titanium oxide particles is 0.1 to 10 μm.

3. 3. The titanium oxide particles according to claim 1, wherein the titanium dioxide has an average crystallite size of 220 nm or more, determined from a peak at 2θ=27.5°±1.0° obtained by X-ray diffraction measurement.

4. 3. The titanium oxide particles according to claim 1, which contain molybdenum.

5. The titanium dioxide particles according to claim 1 or 2, wherein the titanium dioxide comprises rutile titanium dioxide.

6. 3. The titanium oxide particles according to claim 1, which are used for a heat-shielding coating material.

7. A resin composition comprising a resin and the titanium oxide particles according to claim 1 or 2.

8. The resin composition according to claim 7, which is a heat-shielding coating material.

9. 3. The method for producing titanium oxide particles according to claim 1 or 2, a mixing step of mixing a titanium compound, a molybdenum compound, and a potassium compound and / or a sodium compound to form a mixture; A calcination step of calcining the mixture, Mo / M1 in the mixture (M1 represents Na and K). ) is greater than 0.

5.

10. the mixing step is a step of mixing a titanium compound with a compound containing molybdenum and potassium or a compound containing molybdenum and sodium to obtain a mixture, The compound containing molybdenum and potassium is K ２ Mo ２ O ７ and The compound containing molybdenum and sodium is Na ２ Mo ２ O ７ The method for producing titanium oxide particles according to claim 9, wherein

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