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 the titanium oxide particles.

Background Art

[0002] Titanium oxide particles are widely used in the fields of inks, resin fillers, catalysts, catalyst carriers, adsorbents, photocatalysts, antibacterial agents, optical materials, cosmetic ingredients, pigments, paints, fillers, electronic materials, and the like. Patent Document 1 discloses rutile-type titanium oxide particles containing molybdenum, wherein the average particle diameter of the titanium oxide particles is 0.1 to 100 μm.

[0003] Titanium oxide particles can scatter light in the visible and infrared regions, and have excellent ability to shield infrared rays that are most easily converted into thermal energy in sunlight, and are used in cosmetics, heat shielding paints, and the like. For example, in Patent Document 2, particulate titanium oxide having a primary particle diameter of 0.5 to 2.0 μm is applied as a heat shielding property filler.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when attempting to apply titanium oxide particles by taking advantage of their heat shielding properties, there is still room for improvement in enhancing the heat shielding performance of the titanium oxide particles.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide titanium oxide particles having excellent solar reflectance.

Means for Solving the Problems

[0007] (1) Titanium oxide particles containing titanium dioxide, wherein the value calculated by standard deviation / average particle diameter × 100 of the titanium oxide particles is 30% or less, titanium oxide particles. (2) The titanium oxide particles according to (1) above, wherein the average particle diameter of the titanium oxide particles is 0.1 to 10 μm. (3) The titanium oxide particles according to (1) or (2) above, wherein the average crystallite size obtained from the peak of 2θ = 27.5° ± 1.0° obtained by X-ray diffraction measurement of the titanium dioxide is 220 nm or more. (4) Titanium oxide particles containing molybdenum, according to any one of (1) to (3) above. (5) The titanium oxide particles according to any one of (1) to (4) above, wherein the titanium dioxide contains rutile-type titanium dioxide. (6) The titanium oxide particles according to any one of (1) to (5) above, which are for heat-insulating paints. (7) A resin composition containing a resin and the titanium oxide particles according to any one of (1) to (6) above. (8) The resin composition according to (7) above, which is a heat-insulating paint. (9) A method for producing the titanium oxide particles according to any one of (1) to (6) above, wherein 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 firing step of firing the mixture, and a method for producing titanium oxide particles, wherein the molar ratio of Mo / M1 (where M1 represents Na and K) in the mixture is more 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 form a mixture, The compound containing molybdenum and potassium is K2Mo2O7, The compound containing molybdenum and sodium is Na2Mo2O7, and the method for producing titanium oxide particles according to the above (9).

Advantages of the Invention

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

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out 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 standard deviation / average particle diameter × 100 of the titanium oxide particles is 30% or less, preferably 2 to 30%, more preferably 5 to 25%, and even more preferably 10 to 25%. Titanium oxide particles satisfying a numerical value equal to or less than the upper limit value of the above standard deviation / average particle diameter × 100 are excellent in solar reflectance.

[0012] The average particle diameter of the titanium oxide particles in the embodiment may be 0.1 μm or more, may be 0.5 μm or more, and may be 0.7 μm or more. The average particle diameter of the titanium oxide particles may be 10 μm or less, may be 7 μm or less, and may be 5 μm or less. Titanium oxide particles with an average particle diameter satisfying the above numerical values are even more excellent in solar reflectance.

[0013] As an example of the numerical range of the above numerical values of the average particle diameter of the titanium oxide particles, it may be 0.1 μm or more and 10 μm or less, may be 0.5 μm or more and 7 μm or less, and may be 0.7 μm or more and 5 μm or less.

[0014] In this specification, the average particle diameter of titanium oxide particles means that titanium oxide particles are photographed with a scanning electron microscope (SEM), and for the titanium oxide particles confirmed on the two-dimensional image, among the distances between two points on the contour line of the primary particles of 50 or more randomly selected titanium oxide particles, the maximum length is taken as the particle diameter, and the average value thereof is adopted.

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

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

[0017] The average crystallite size obtained from the peak of 2θ = 27.5° ± 1.0° obtained by X-ray diffraction measurement of titanium dioxide contained in the titanium oxide particles is preferably 220 nm or 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 greater than the above lower limit value, the solar reflectance of the titanium oxide particle layer can be made even more excellent.

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

[0019] As an example of the numerical range of the above numerical value of the average crystallite size of the titanium dioxide obtained from the peak at 2θ = 27.5° ± 1.0° obtained by X-ray diffraction measurement, it may be 220 nm or more and 700 nm or less, may be 250 nm or more and 650 nm or less, or may be 300 nm or more and 600 nm or less.

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

[0021] [Measurement of Crystallite Size] Using an X-ray diffractometer (for example, SmartLab, manufactured by Rigaku Corporation), using an ultra-high resolution spiral analyzer (CALSA) as a detector, and using PDXL2 as analysis software, measurement is performed. The measurement method is the 2θ / θ method. Under the following measurement conditions, the average crystallite size of titanium dioxide is calculated using the Scherrer equation from the half-value width of the peak that appears at 2θ = 27.5° ± 1.0°. (Measurement Conditions) Scan range: 2θ = 10 to 70° Step: 2θ = 0.002° Speed: 2θ = 0.05° / min βs = 20 rpm Soller / PSC: 2θ = 2.5° short Soller: 2θ = 2.5° Analysis software: PDXL2 Device inherent width: None Peak shape: Automatic analysis using the CALSA function

[0022] The titanium oxide particles of the embodiment contain titanium dioxide (TiO2). It is preferable that the titanium oxide particles of the embodiment contain 50 mass% or more of titanium dioxide (TiO2) with respect to the total mass (100 mass%) of the titanium oxide particles, preferably contain 50 to 99.9 mass%, more preferably contain 80 to 99.9 mass%, and even more preferably contain 90 to 99.8 mass%.

[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 may be such that the content rate in terms of TiO2 conversion with respect to 100 mass% of the total mass of the titanium oxide particles, which is determined by subjecting the titanium oxide particles to XRF analysis, is 50 mass% or more, may be 50 to 99.9 mass%, may be 80 to 99.9 mass%, or may be 90 to 99.8 mass%.

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

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

[0027] The state of existence and amount of molybdenum that may be contained in the titanium oxide particles of the embodiment are not particularly limited, and in addition to molybdenum metal, molybdenum oxide, a molybdenum compound in which a part has been reduced, etc. may be contained in the titanium oxide particles. Molybdenum is considered to be contained in the titanium oxide particles as MoO3, but in addition to MoO3, it may also be contained in the titanium oxide particles as MoO2, MoO, etc.

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

[0029] In the titanium oxide particles of the embodiment, the molybdenum content may be such that the content rate in terms of MoO3 conversion with respect to 100% by mass of the total mass of the titanium oxide particles, which is determined by XRF analysis of the titanium oxide particles, is 0.01% by mass or more, may be 0.01 to 25% by mass, may be 0.05 to 10% by mass, or may be 0.1 to 5% by mass.

[0030] The content rate in terms of MoO3 conversion means a value obtained from the amount of MoO3 obtained by converting the molybdenum content determined by XRF analysis of the titanium oxide particles using a calibration curve in terms of MoO3 conversion.

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

[0032] In the titanium oxide particles, the total content rate in terms of K2O conversion and Na2O conversion with respect to 100% by mass of the total mass of the titanium oxide particles, which is determined by XRF analysis of the titanium oxide particles, may be 5% by mass or less, or may be 0.01 to 5% by mass.

[0033] The total content in terms of K2O conversion and Na2O conversion refers to the value obtained from 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 for K2O conversion and the amount of Na2O obtained by converting the sodium content determined by XRF analysis using a calibration curve for Na2O conversion. Note that the potassium content and / or sodium content in the titanium oxide particles may be 0.

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

[0035] As an example of the titanium oxide particles of the embodiment, titanium oxide particles can be exemplified in which the content rate of titanium in terms of TiO2 in the total mass of the titanium oxide particles determined by XRF analysis is 50 to 99.9% by mass, and the content rate of molybdenum in terms of MoO3 is 0.01 to 25% by mass.

[0036] As an example of the titanium oxide particles of the embodiment, titanium oxide particles can be exemplified in which the content rate of titanium in terms of TiO2 in the total mass of the titanium oxide particles determined by XRF analysis is 50 to 99.9% by mass, the content rate of molybdenum in terms of MoO3 is 0.01 to 25% by mass, and the total content rate in terms of K2O conversion and Na2O conversion of potassium and / or sodium is 0.01 to 5% by mass.

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

[0038] As crystal structures of titanium dioxide, there are anatase type, rutile type, and brookite type. It is preferable that the titanium oxide particles of the embodiment contain rutile type titanium dioxide as the titanium dioxide. The rutile crystallization rate of the titanium dioxide is preferably 90% or more. Titanium oxide particles containing rutile-type titanium dioxide have a high refractive index and excellent infrared shielding ability, so a high heat shielding effect can be expected.

[0039] According to the manufacturing method of the embodiment described later, it is excellent in shape control according to the crystal shape of the composition of the manufactured titanium oxide particles. The titanium oxide particles of the embodiment have a controlled crystal shape and can have a polyhedral shape or an idiomorphic shape such as a substantially spherical shape. As the shape, it may be a polyhedron that is substantially spherical with a flat surface, or a substantially spherical shape with a smooth spherical surface. Titanium oxide particles having these shapes can be manufactured by the manufacturing method described later.

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

[0041] [Infrared Reflection Evaluation] After filling the hole (about 2 cm in diameter) in the center of the glass substrate with the sample powder of titanium oxide particles, the surface of the sample powder is covered with a cover plate made of quartz glass. The absorption spectrum and reflection spectrum (200 to 2500 nm) of the sample powder are measured with a UV-Vis-NIR spectrophotometer (for example, U-4100, manufactured by Hitachi High-Technologies Corporation) to obtain the reflectance in the NIR region (700 to 2500 nm). The measurement conditions are a scanning speed of 600 nm / min, a sampling interval of 2.00 nm, and a slit width of 5.00 nm by attaching an integrating sphere. The obtained data is converted to the solar reflectance R using the following formula. * for conversion.

Equation

[0042] Since the titanium oxide particles of the embodiment have the above excellent solar reflectance, they can be used as a heat insulating agent. The 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 insulating agent contained in a heat insulating paint. The titanium oxide particles of the embodiment can be suitably used as titanium oxide particles for heat insulating paint.

[0043] The heat insulating paint can be used, for example, by applying it to the surface of building structures such as roofs and building exteriors; road surfaces such as asphalt surfaces and concrete surfaces; vehicles such as trains and automobiles; and various articles such as airplanes, ships, and electrical products. The heat insulating paint can be suitably used as a paint for road paving.

[0044] The heat insulating paint 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] As one embodiment of the present invention, a resin composition containing a resin and titanium oxide particles, wherein the titanium oxide particles contain titanium dioxide and the value calculated by standard deviation / average particle diameter × 100 is 30% or less, can be provided. The resin composition of the embodiment can be suitably used as the above heat insulating paint.

[0046] Examples of the titanium oxide particles contained in the above resin composition and heat insulating paint include the same ones as the titanium oxide particles of the embodiment described above.

[0047] Examples of the resin that may be contained in the above resin composition and heat insulating paint include, but are not limited to, acrylic resin, urea resin, melamine resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, phenol resin, acrylic silicone resin, polyvinyl chloride, polyvinyl acetate, alkyd resin, amino alkyd resin, fluororesin, etc.

[0048] The resin composition and the heat insulating paint may further contain a solvent. Examples of the solvent include aromatic solvents such as toluene, xylene, and methoxybenzene; acetate 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; water; and the like, and are not limited thereto.

[0049] The resin composition and the heat insulating paint may further contain various additives, such as pigments (excluding those corresponding to the titanium oxide particles), dispersants, antifoaming agents, film-forming aids, fillers, paint auxiliaries, driers, plasticizers, and / or auxiliary pigments.

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

[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 a coating film composed 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) firing a titanium compound in the presence of a molybdenum compound and a potassium compound and / or a sodium compound, or (II) firing 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 form a mixture, and a firing step of firing the mixture. The molar ratio of Mo / M1 (where 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, and may be 1 or more.

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

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

[0056] As an example of the numerical range of the molar ratio of Mo / M1 (where M1 represents Na and K) in the mixture in the mixing step, it may be greater than 0.5 and 3 or less, may be 0.65 or more and 3 or less, may be 0.9 or more and 2 or less, and may be 1 or more and 1.5 or less. 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] As for the amounts of the titanium compound and the molybdenum compound used, in order to obtain titanium oxide particles with high efficiency in the above-described embodiment, 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 production method of the above (II), the molar ratio of titanium atoms in the mixture to molybdenum atoms in the molybdenum compound is preferably in the range of more than 35.0 and 120.0 or less, and more preferably in the range of more than 35.0 and 100.0 or less. Being within the above range is preferable from the viewpoints of the looseness and washability of the obtained titanium oxide particles.

[0059] Here, instead of at least a part of the molybdenum compound and the potassium compound, a compound containing molybdenum and potassium such as potassium molybdate (for example, K2Mo n O 3n+1 , n = 1, 2, 3) can also be used. Similarly, instead of at least a part of the molybdenum compound and the sodium compound, a compound containing molybdenum and sodium such as sodium molybdate (for example, 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 the average crystallite size of titanium dioxide tends to be easily improved. The step of mixing a titanium compound and a compound containing molybdenum, potassium and / or sodium to form a mixture is also regarded as the step of mixing a titanium compound, a molybdenum compound, a potassium compound and / or a sodium compound to form a mixture.

[0060] [Mixing Step] The mixing step is a step of mixing a titanium compound, a molybdenum compound, 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 it can act on the titanium compound. Specifically, even in a state where they are not mixed, it may be any of simple mixing by mixing powders, mechanical mixing using a pulverizer or the like, mixing using a mortar or the like, etc., and may be mixing in a dry state or a wet state.

[0062] Hereinafter, the above raw material compounds will be described.

[0063] (Titanium compound) 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 by heat treatment. For example, titanium chloride, titanium sulfate, metatitanic acid, amorphous titanium oxide, anatase-type titanium oxide, rutile-type titanium oxide, a mixed-type titanium oxide of anatase type and rutile type, etc. can be used. Regarding the physical forms such as the shape, particle diameter, and specific surface area of the titanium compound as a precursor, there is no particular limitation.

[0064] Regarding the shape of the titanium oxide particles after firing, since the shape of the titanium compound as a precursor is hardly reflected, for example, any of spherical, amorphous, structured bodies with aspect (wire, fiber, ribbon, tube, etc.), sheet, etc. can be preferably used.

[0065] Similarly, regarding the particle diameter of the titanium oxide particles after firing, since the particle diameter of the titanium compound as a precursor is hardly reflected, titanium compounds from several nm to several hundred μm can be preferably used. Furthermore, the specific surface area of the titanium compound as a precursor is not particularly limited, and any titanium compound can be preferably used.

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

[0067] Also, the titanium compound as the precursor may be a composite of a titanium compound and an organic compound. For example, an organic / inorganic composite obtained by modifying titanium oxide using an organosilane, a titanium compound composite adsorbed with a polymer, etc. can also be preferably used. When using these composites, there is no particular limitation on the content rate of the organic compound, but in order to efficiently produce rutile-type titanium oxide particles having a substantially spherical automorphic shape, the content rate is preferably 60% by mass or less, and more preferably 30% by mass or less.

[0068] (Molybdenum compound) By sintering the titanium compound in the presence of molybdenum, titanium oxide particles containing molybdenum can be obtained. At this time, the molybdenum compound is used as a fluxing agent. The molybdenum compound may be molybdenum oxide or a compound containing an acid root anion (MO x n- ; hereinafter, M represents a metal).

[0069] The acid root anion (MO x n- ) is formed by the bonding of molybdenum metal with oxygen, and the compound containing the acid root anion is not particularly limited as long as it is a compound that converts to molybdenum oxide below the firing temperature. For example, molybdic acid, H3PMo 12 O 40 , H3SiMo 12 O 40 , NH4Mo7O 12etc. can be preferably used. Among these, considering the cost aspect, it is preferable to use molybdenum oxide. In this case, along with the formation of titanium oxide particles, molybdenum oxide sublimes and most of it can be removed from the reaction system.

[0070] Also, as the compound containing an acid radical anion (MO x n- ) formed by the combination of molybdenum metal and oxygen, 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 metal molybdates can be preferably used. For example, sodium molybdate, potassium molybdate, lithium molybdate, etc. that are soluble in water are preferable because they can be easily removed by water washing. As the fluxing agent, a mixture of a molybdenum compound and a metal compound can also be used. In this case, the molybdenum compound and the metal compound are reacted by high-temperature firing to form a metal molybdate. The formed metal molybdate is not particularly limited as long as it can form titanium oxide particles as the fluxing agent.

[0071] For example, a compound containing molybdenum and potassium, which is suitable as the fluxing agent, can be produced, for example, from a molybdenum compound and a potassium compound that are cheaper and more easily available during the firing process. Here, when using the molybdenum compound and the potassium compound as the fluxing agent, when using the compound containing molybdenum and potassium as the fluxing agent, and when using both together, that is, when using the molybdenum compound and the potassium compound as the fluxing agent, it is regarded as being in the presence of the molybdenum compound and the potassium compound.

[0072] For example, a compound containing molybdenum and sodium, which is suitable as a fluxing agent, can be produced during the firing process using, for example, a molybdenum compound and a sodium compound that are cheaper and more readily available as raw materials. Here, when using a molybdenum compound and a sodium compound as a fluxing agent, and when using a compound containing molybdenum and sodium as a fluxing agent, both cases are considered as using a molybdenum compound and a sodium compound as a fluxing agent, that is, in the presence of a molybdenum compound and a sodium compound.

[0073] Also, potassium molybdate (K2Mo n O 3n+1 , n = 1 to 3) contains potassium and thus may also have the function as a potassium compound described later.

[0074] Also, sodium molybdate (Na2Mo n O 3n+1 , n = 1 to 3) contains sodium and thus may also have the function as a sodium compound described later.

[0075] The fluxing agent containing a molybdenum compound may consist only of the 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, more preferably 10% by mass or less, based on the oxide.

[0076] In addition, the flux agent containing the molybdenum compound may be a complex of the molybdenum compound and an organic compound. For example, an organic / inorganic complex obtained by modifying a molybdenum compound with an organic silane, a molybdenum compound complex adsorbed with a polymer, etc. can also be preferably used. When using these complexes, the content of the organic compound is not particularly limited, but in order to efficiently form rutile-type titanium oxide particles, the 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.

[0078] (Potassium compound) The potassium compound is not particularly limited, and examples thereof include potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium acetate, potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, potassium tungstate, etc. At this time, similar to the case of the molybdenum compound, the potassium compound contains isomers. Among these, it is preferable to use potassium carbonate, potassium hydrogen carbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate, potassium molybdate, and more preferably potassium carbonate, potassium hydrogen carbonate, potassium chloride, potassium sulfate, potassium molybdate.

[0079] In addition, the above-mentioned potassium compounds may be used alone or in combination of two or more.

[0080] Also, similar to the above, since potassium molybdate contains molybdenum, it may also have the function as the above-mentioned molybdenum compound.

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

[0082] In addition, the above-mentioned sodium compounds may be used alone or in combination of two or more.

[0083] Further, in the same manner as described above, since sodium molybdate contains molybdenum, it may also have the function as the above-mentioned molybdenum compound.

[0084] Thus, although there may be overlapping notations as molybdenum compounds in classification, 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, potassium, or a compound containing molybdenum, sodium to form a mixture, and it is more preferable that the compound containing molybdenum, potassium is K2Mo2O7, and the compound containing molybdenum, sodium is Na2Mo2O7.

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

[0087] Regarding the firing temperature, it only needs to be equal to or higher than the temperature at which the target titanium oxide particles are formed. Specifically, the maximum temperature may be in the range of 700 to 1400 °C. In particular, for the formation of titanium oxide particles with an average crystallite size of 220 nm or more obtained from the peak of 2θ = 27.5° ± 1.0° obtained by X-ray diffraction measurement of titanium dioxide, firing at a temperature of 800 to 1400 °C is more preferable, and firing in the temperature range of 800 to 1350 °C is even more preferable. In the case of production method (II), the firing temperature is more preferably firing at 800 to 1400 °C, even more preferably firing in the temperature range of 800 to 1350 °C, and most preferably firing in the temperature range of 900 to 1100 °C.

[0088] Regarding the firing time, it is preferable to raise the temperature to a predetermined firing temperature in the range of 20 minutes to 10 hours and hold the temperature at the firing temperature for 5 minutes to 45 hours. In the case of production method (II), it is preferable to raise the temperature to a predetermined firing temperature in the range of 20 minutes to 10 hours and hold the temperature at the firing temperature for 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] Preferably, the firing temperature is 700 to 1400 °C and the firing temperature holding time is 5 minutes to 45 hours. More preferably, the firing temperature is 800 to 1400 °C and the firing temperature holding time is 5 minutes to 45 hours. Even more preferably, the firing temperature is 800 to 1350 °C and the firing temperature holding time is 10 minutes to 30 hours. Particularly preferably, by selecting the conditions of a firing temperature of 800 to 1350 °C and a firing temperature holding time of 15 to 30 hours, the titanium oxide particles of the above embodiments can be easily obtained.

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

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

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

Examples

[0093] Next, examples are shown to explain the present invention in more detail, but the present invention is not limited to the following examples.

[0094] <Analysis and Evaluation> Using the powders of each example and comparative example as samples, the following measurements were performed.

[0095] [Average Particle Diameter and Standard Deviation] The sample was photographed with a scanning electron microscope (SEM), and for the particles confirmed on the two-dimensional image, among the distances between two points on the contour line of the primary particles of 50 or more randomly selected particles, the maximum length was taken as the particle diameter, and the average value thereof was taken as the average particle diameter. Based on the particle diameter data measured above, the standard deviation was determined, and the value of standard deviation / average particle diameter × 100 was calculated.

[0096] [Analysis of Crystal Phase by X-ray Diffraction (XRD) Method] The prepared sample was placed in a measurement sample holder with a depth of 0.5 mm, filled under a certain load to make it flat, and then set in a wide-angle X-ray diffraction (XRD) apparatus (Ultima IV, manufactured by Rigaku Corporation), and measured under the conditions of Cu / Kα ray, 40 kV / 30 mA, scan speed 2 degrees / minute, and scan range 10 to 70 degrees.

[0097] [Particle Size Distribution Measurement] Using a laser diffraction dry particle size analyzer (HELOS (H3355) & RODOS, manufactured by Nippon Laser Co., Ltd.), the particle size distribution of the sample powder was measured dry 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 integration % distribution curve intersects the horizontal axis of 50% was determined as D 50 as follows.

[0098] [Composition analysis by X-ray fluorescence (XRF)] Using an X-ray fluorescence (XRF) analyzer (PrimusIV, manufactured by Rigaku Corporation), approximately 70 mg of the prepared sample was placed on a filter paper, covered with a PP film, and composition analysis was performed. The amounts of various elements obtained from the XRF analysis results were converted to oxides (mass %) in the oxides described in Table 2, and the ratios of the contents of various oxides to 100 mass % of the total mass of the sample were calculated.

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

[0100] [Infrared reflection evaluation] After filling the hole (diameter approximately 2 cm) in the center of a glass substrate with the sample powder, the surface of the sample powder was covered with a cover plate made of quartz glass. The absorption spectrum and reflection spectrum (200 - 2500 nm) of the sample powder were measured with a UV-Vis-NIR spectrophotometer (U-4100, manufactured by Hitachi High-Tech Science Corporation), and the reflectance in the NIR region (700 - 2500 nm) was obtained. The measurement conditions were a scanning speed of 600 nm / min, a sampling interval of 2.00 nm, and a slit width of 5.00 nm by means of an integrating sphere attachment. The obtained data was converted to the solar reflectance R using the following formula. * to. [Equation] Here, r(λ) is the spectral reflectance obtained from the experiment (Wm -2 ), and i(λ) is the spectral irradiance of sunlight obtained based on SJ / T10174 - 91 (Wm -2 nm -1 ).

[0101] [Evaluation of crucible release property] The fired product was taken out of the crucible, and the crucible release property was evaluated from the ratio of the amount of powder remaining on the wall and bottom surfaces of the crucible. The crucible release property 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). If the crucible release property was less than 0.1, it was evaluated as "〇", and if it was 0.1 or more, it was evaluated as "×". Crucible release property = (C - A) / (B - A)

[0102] [Production of potassium molybdate] [Production Example 1] 36.17 g of potassium carbonate (K2CO3) and 75.34 g of molybdenum trioxide (MoO3) were mixed to obtain a mixture. The obtained mixture was charged into a crucible and fired in a muffle furnace at 700 °C for 5 hours. The temperature was raised at a rate of 5 °C / min. After cooling to room temperature, the crucible was taken out to obtain the powder of Production Example 1. When XRD measurement was performed on this powder, scattering peaks derived from K2Mo2O7 were confirmed, and the synthesis of K2Mo2O7 was confirmed.

[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 charged into a 100 mL polypropylene bottle and mixed and pulverized for 30 minutes using a paint shaker to obtain a mixture. After further uniformly mixing the obtained mixture in a mortar, it was charged into a crucible and fired in a muffle furnace at 800 °C for 24 hours. The temperature was raised at 5 °C / min. After cooling to room temperature, the crucible was taken out to obtain a powder. Subsequently, the powder was dispersed in 80 ml of pure water for 30 minutes and then centrifuged at 5000 rpm for 10 minutes to remove the supernatant. This operation was repeated 4 times. The obtained precipitate was dried at 80 °C for 24 hours and pulverized in a mortar to obtain the pale yellow powder of Example 1.

[0104] [Example 2] 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, the yellow powder of Example 2 was obtained by the same operation as in Example 1.

[0105] [Example 3] 20 g of titanium oxide (TiO2) and 0.6 g of molybdenum oxide (MoO3) were charged into a 100 mL polypropylene bottle and mixed and pulverized for 30 minutes using a paint shaker to obtain a mixture. After further uniformly mixing the obtained mixture in a mortar, it was charged into a crucible and fired in a muffle furnace at 1100 °C for 5 hours. The temperature was raised at 5 °C / min. After cooling to room temperature, the crucible was taken out to obtain a powder. Subsequently, the powder was dispersed in 80 ml of pure water for 30 minutes and then centrifuged at 5000 rpm for 10 minutes to remove the supernatant. This operation was repeated 4 times. The obtained precipitate was dried at 80 °C for 24 hours and pulverized in a mortar to obtain the pale yellow powder of Example 3.

[0106] [Example 4] In Example 3, except that 0.4 g of molybdenum oxide was used and the firing temperature was changed as described in Table 1, the same operations as in Example 3 were carried out to obtain the pale yellow powder of Example 4.

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

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

[0109]

Table 1

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

[0111] The results of the above evaluations are shown in Table 2. "N.D." is an abbreviation for not detected, indicating non-detection.

[0112]

Table 2

[0113] Table 2 describes the shapes of the particles of each Example and Comparative Example, as determined from the SEM images. When particles of different shapes are observed to be mixed, the representative shape (the most frequently observed shape) is described.

[0114] The results of the XRD analysis of the sample of Example 1 are shown in FIG. 5. Sharp scattering peaks derived from rutile-type titanium dioxide appeared, and no crystal system peaks other than the rutile crystal structure were observed.

[0115] From the above results of SEM observation and XRD analysis, it was confirmed that the powders obtained in each Example were 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 represented by the value of standard deviation / average particle diameter × 100, have a higher value of solar reflectance R * than the titanium oxide particles of Comparative Example 1 and have excellent heat insulation properties.

[0117] In addition, the titanium oxide particles of Examples 1 to 4 had a larger average crystallite size of titanium dioxide, which was 220 nm or more, than the titanium oxide particles of Comparative Example 1.

[0118] Each configuration and their combinations, etc. in each embodiment are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the spirit of the present invention. Further, the present invention is not limited by each embodiment and is limited only by the scope of the claims.

Claims

1. Titanium oxide particles containing titanium dioxide, wherein the value calculated by standard deviation / average particle diameter × 100 of the titanium oxide particles is 30% or less, are titanium oxide particles.

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

3. The titanium oxide particles according to claim 1 or 2, wherein the average crystallite size of the titanium dioxide obtained 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 claim 1 or 2, containing molybdenum.

5. The titanium oxide particles according to claim 1 or 2, wherein the titanium dioxide contains rutile-type titanium dioxide.

6. The titanium oxide particles according to claim 1 or 2, which are for a heat insulating paint.

7. A resin composition containing 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 insulating paint.

9. A method for producing the titanium oxide particles according to claim 1 or 2, comprising 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 the molar ratio of Mo / M1 (where M1 represents Na and K) in the mixture is more than 0.5, is a method for producing titanium oxide particles.

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 form a mixture, ​ The compound containing the 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 the compound is as described above.

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