Dispersion of barium titanate particles and method for producing same

Abstract

To provide a dispersion of nano-sized barium titanate particles that can be mass-produced and has excellent dispersion stability, and to provide a method for producing the dispersion.SOLUTION: The production method comprises, in order, a first step of preparing a first solution by mixing a barium alkoxide, a titanium alkoxide, and an organic solvent having a hydroxyl group so that the atomic ratio of barium to titanium is 0.90 to 1.10, a second step of keeping the first solution at or below 15°C for at least 1 hour, a third step of preparing a third solution at or below 15°C by mixing the first solution obtained in the second step with a second solution containing water in a continuous reactor at or below 15°C, and a fourth step of heating the third solution to 60°C or above. In the dispersion of particles obtained by the production method, the average particle size of the particles (D50 particle size (A)) is 3 to 30 nm, D90 particle size (B) is 8 to 80 nm, the crystallite size (C) is 5 to 15 nm, and the ratio (A / C) is 0.3 to 5.0.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersion of barium titanate particles having excellent dispersion stability, and a method for producing the same. [Background technology]

[0002] Barium titanate (hereinafter referred to as BTO) is widely known as a high-dielectric material and is used in electronic device components such as multilayer ceramic capacitors. In recent years, as multilayer ceramic capacitors have become smaller and their capacitance has increased, the dielectric and electrode layers have become thinner. Nano-sized BTO particles with excellent dispersion stability are required as co-materials for these dielectric and electrode layers, and the ability to mass-produce these particles is also required.

[0003] Conventionally, a known method for producing nano-sized BTO particles involves adding a mixture of water and a polar solvent dropwise to barium and titanium alkoxides to hydrolyze the mixture, followed by heating and aging at 10°C or higher to obtain nano-sized BTO particles (see, for example, Patent Document 1). However, the dispersion stability of these particles is insufficient. Furthermore, this method is a so-called batch production method, making mass production difficult.

[0004] Another known method for continuously producing BTO particles is to carry out hydrolysis in a thin film fluid to continuously produce ceramic nanoparticles (see, for example, Patent Document 2). However, the dispersion stability of the BTO particles obtained by this method is also insufficient.

[0005] Meanwhile, the present applicant has disclosed a continuous production method using a micromixing chip (see Patent Document 3). Although this method can produce nano-sized BTO particles, the dispersion stability is insufficient. Furthermore, this method has the risk of clogging the flow channel with gel-like material during continuous production, making mass production difficult.

[0006] Furthermore, the present applicant has disclosed a method for producing BTO particles using an alkyl cellosolve solution of barium hydroxide (see Patent Document 4). Although this method makes it possible to produce nano-sized BTO particles inexpensively, the dispersion stability is insufficient. Furthermore, mass production is difficult, so the productivity is not sufficient. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-306691 [Patent Document 2] WO2009 / 008392 issue [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-172581 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-240904 Summary of the Invention [Problem to be solved by the invention]

[0008] The smaller the particle size of BTO particles, the more likely they are to aggregate, making it difficult to store conventional nano-sized BTO particle dispersions for long periods of time. This meant that they could not be uniformly dispersed when used as co-materials for dielectric layers and electrode layers. Therefore, there is a demand for nano-sized BTO particle dispersions with excellent dispersion stability. Furthermore, conventional manufacturing methods make mass production difficult. [Means for solving the problem]

[0009] Therefore, in order to solve such problems, a dispersion of BTO particles was prepared by the following manufacturing method.

[0010] First, barium alkoxide, titanium alkoxide, and an organic solvent having a hydroxyl group are mixed so that the atomic ratio of barium to titanium (Ba / Ti ratio) is 0.90 to 1.10 (first step). Next, the first solution obtained in the first step is maintained at 15°C or below for at least 1 hour (second step). Next, this first solution maintained at 15°C or below is mixed with a second solution containing water in a continuous reactor at 15°C or below (third step). Next, the third solution obtained in the third step is heated to 60°C or above (fourth step).

[0011] The dispersion of BTO particles prepared in this way was analyzed by dynamic light scattering. 50 Particle diameter (A) is 3 to 30 nm, D 90 The particle size (B) is 8 to 80 nm, and the crystallite size (C) is 5 to 15 nm. 50 The ratio of particle size to crystallite size (A / C) is 0.3 to 5.0. [Effects of the Invention]

[0012] According to the present invention, a dispersion of nano-sized BTO particles having excellent dispersion stability can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Method for producing dispersion of barium titanate particles] Hereinafter, a method for producing a dispersion (hereinafter, sometimes simply referred to as "dispersion") of barium titanate particles (hereinafter, sometimes simply referred to as "BTO particles" or "particles") according to the present invention will be described.

[0014] This production method includes the following steps, in order: a first step of preparing a first solution by mixing barium alkoxide, titanium alkoxide, and an organic solvent containing hydroxyl groups so that the atomic ratio of barium to titanium (Ba / Ti ratio) is 0.90 to 1.10; a second step of maintaining this first solution at 15°C or below for at least one hour; a third step of mixing the first solution obtained in the second step with a second solution containing water in a continuous reactor at 15°C or below; and a fourth step of heating the third solution obtained in the third step to 60°C or above. This results in a dispersion of nano-sized BTO particles with excellent dispersion stability. This production method also enables mass production.

[0015] Each step will be described below.

[0016] [First step] A first solution is prepared by mixing barium alkoxide, titanium alkoxide, and an organic solvent having a hydroxyl group.

[0017] The barium alkoxide and titanium alkoxide are mixed so that the atomic ratio of barium to titanium (Ba / Ti) in the first solution is 0.90 to 1.10. This atomic ratio range makes it possible to obtain BTO particles with a highly crystalline perovskite crystal structure. This atomic ratio is preferably 0.95 to 1.05, more preferably 0.98 to 1.02, and most preferably 1.00.

[0018] The organic solvent having a hydroxyl group is preferably mixed so that the total concentration of barium alkoxide and titanium alkoxide in the first solution is 0.5 to 10.0 mol / kg. If the total concentration is less than 0.5 mol / kg, productivity may decrease. Conversely, if it exceeds 10.0 mol / kg, the dispersion stability of the BTO particle dispersion may become insufficient. This total concentration is more preferably 1.0 to 8.0 mol / kg, and even more preferably 2.0 to 5.0 mol / kg.

[0019] In this step, it is preferable to avoid contact between the metal alkoxide and water. If at least one of the barium alkoxide and the titanium alkoxide is hydrolyzed with water, a dispersion of nano-sized BTO particles with high dispersion stability may not be obtained. Therefore, in preparing the first solution, it is preferable to not only avoid the inclusion of water, but also to pay attention to the atmosphere.

[0020] For example, the relative humidity when mixing barium alkoxide, titanium alkoxide, and an organic solvent having a hydroxyl group is preferably 50% or less. If the relative humidity is higher than 50%, these metal alkoxides may be hydrolyzed by moisture in the air, making it difficult to obtain nano-sized BTO particles. The relative humidity is more preferably 45% or less, even more preferably 30% or less, and particularly preferably 10% or less. Suitable methods for lowering the relative humidity include replacing the inside of a glove box or tank with nitrogen gas or dry air, reducing the pressure, or using silica gel or the like to adsorb moisture from the air.

[0021] In addition, as a means for reducing the influence of moisture in the air, it is also effective to use a container in which the contact area between the liquid surface and the air is small.

[0022] The barium alkoxide and titanium alkoxide to be used may be commercially available products, or products produced from compounds such as the respective metals, hydroxides, or halides by conventionally known methods may be used.

[0023] Examples of barium alkoxides include barium dimethoxide, barium diethoxide, barium dipropoxide, barium diisopropoxide, barium dibutoxide, barium diisobutoxide, etc. Examples of titanium alkoxides include titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium tetraisobutoxide, titanium tetrastearyl alkoxide, titanium tetrakis(2-ethyl-1-hexanolate), etc.

[0024] These may be used as a monomer or may be polymerized to some extent, such as an oligomer, and may be used alone or in combination of two or more.

[0025] Examples of organic solvents having a hydroxyl group include alcohols, phenols, glycols, glycol ethers, etc. Examples of alcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, etc. Examples of phenols include phenol, cresol, naphthol, etc. Examples of glycols include ethylene glycol and propylene glycol, etc. Examples of glycol ethers include diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, etc.

[0026] These may be used alone or in combination of two or more.

[0027] [Second process] The first solution obtained in the first step is kept at 15°C or below for at least one hour. This step suppresses the generation of gel-like material in the subsequent third step, improving productivity. It also improves the dispersion stability of the resulting particles. While the exact reason for this is unclear, it is believed that in the third step, the metal alkoxide in the first solution kept at 15°C or below is mixed uniformly at the molecular level with the water-containing solution while suppressing hydrolysis reactions.

[0028] If the temperature is higher than 15°C, the hydrolysis reaction in the third step may proceed, generating a gel-like substance and potentially clogging the flow path. This may require stopping the operation and cleaning the production line to ensure proper flow path maintenance, potentially reducing productivity. Furthermore, the dispersion stability of the resulting particles may be reduced. The lower limit of this temperature is not particularly set as long as the solution has fluidity, but it may be, for example, -40°C. This is because lowering the temperature below -40°C does not significantly improve the productivity or dispersion stability of the desired particles, but instead requires a more expensive cooling device, which affects production costs. The temperature of the solution is preferably -20 to 10°C, more preferably -20 to 5°C.

[0029] This first solution is preferably held at 15°C or below for 3 hours or longer. Although the exact reason for this is unknown, holding the solution for 3 hours or longer makes the solution homogeneous, which prevents the generation of gelatinous matter in the continuous reactor and the deterioration of the dispersion stability of the BTO particles in the subsequent third step. The longer the holding time, the better, with 12 hours or longer being preferable, and 24 hours or longer being even more preferable. There is no upper limit to the holding time, but holding the solution for more than 96 hours does not result in any significant improvement in the productivity or dispersion stability of the desired particles.

[0030] When maintaining the first solution at 15°C or below, it is preferable to avoid contact between the metal alkoxide and water, as in the first step. Here, contact with water includes contact with moisture in the air. Contact with water accelerates hydrolysis of the metal alkoxide in the first solution, and during mixing in the third step described below, gel-like material may form in the continuous reactor, potentially clogging the flow path and reducing productivity. Furthermore, the dispersion stability of the resulting dispersion may be reduced. Therefore, in the second step, the first solution may be fluidized by stirring or the like, but it is preferable to leave it undisturbed to reduce contact with moisture in the air. Furthermore, the second step is preferably carried out under the same relative humidity as the first step or under a lower relative humidity. More specifically, it is preferable to carry out the second step in a vacuum or in an atmosphere substituted with nitrogen gas or dry air, and it is preferable to use a hermetically sealed container.

[0031] [Third step] In the second step, the first solution, maintained at 15°C or below, is mixed with the second solution containing water to produce a third solution. A continuous reactor is used for this mixing. A continuous reactor can quantitatively mix and react the solutions at a constant ratio. In this way, the quantitative supply, mixing, reaction, and discharge of the solutions can be carried out continuously, thereby achieving stable quality and mass production of BTO particles. Examples of continuous reactors include a continuous flow microreactor, a forced thin film microreactor, and a line mixer.

[0032] Examples of continuous flow microreactors that can be used include the microreactor disclosed in Patent Document 3 by the present applicant and the stacked multi-channel reactor SMCR manufactured by Kobe Steel, Ltd. Examples of forced thin film microreactors that can be used include the ULREA series manufactured by M Technique Co., Ltd.

[0033] When the first solution and the second solution are mixed, the temperature of the reaction site (mixing temperature) is 15°C or lower. If the temperature of the reaction site is 15°C or lower, the generation of gel-like matter is suppressed. If the temperature of the reaction site is higher than this temperature, gel-like matter may be generated in the continuous reactor, clogging the flow path and reducing productivity. In addition, the temperature of the third solution may also exceed 15°C. As a result, the average particle size of the resulting dispersion may become too large and the dispersion stability may decrease. There is no particular lower limit for this temperature, but it is, for example, -40°C for the same reasons as for the first solution in the second step. The temperature of the reaction site is more preferably 10°C or lower, and even more preferably 5°C or lower.

[0034] If the mixing temperature of the first solution and the second solution is 15°C or less, the temperature of the third solution discharged from the continuous reactor can be easily kept at 15°C or less. If this temperature is higher than 15°C, a gel-like substance may be generated in the continuous reactor, clogging the flow path and reducing productivity. Furthermore, the average particle size of the particles in the resulting dispersion may become too large, and dispersion stability may be reduced. The lower limit of this temperature is not particularly set as long as the solution has fluidity, but is, for example, -40°C for the same reasons as for the first solution in the second step. The temperature of the discharged mixed solution is more preferably 10°C or less, and even more preferably 0 to 10°C.

[0035] The ratio of the total number of moles of barium alkoxide and titanium alkoxide contained in the first solution to the number of moles of water in the second solution (water / (barium alkoxide + titanium alkoxide)) is preferably 1 to 10. If the molar ratio is less than 1, hydrolysis of these metal alkoxides will be insufficient, making it difficult to obtain highly crystalline BTO particles. Conversely, if the molar ratio exceeds 10, gel-like matter may be generated in the continuous reactor, reducing productivity, the crystallite size of the particles in the resulting dispersion may become too large, and dispersion stability may be reduced. The molar ratio (water / (barium alkoxide + titanium alkoxide)) is more preferably 2 to 8, and even more preferably 3 to 6.

[0036] Here, the second solution is preferably a solution in which the mass ratio of water to alcohol (water / alcohol) is 0.05 to 1.00. If the mass ratio is within this range, a rapid hydrolysis reaction can be suppressed, and BTO particles with the desired crystallite size and average particle size can be obtained.

[0037] Even if the mass ratio is less than 0.05, it is unlikely that the crystallite size or average particle size can be adjusted to be any smaller. Rather, the concentration of the resulting third solution will be too low, which may result in a decrease in productivity. Conversely, if the mass ratio is higher than 1.00, the result will be essentially the same as if water were used directly. This may result in the formation of a gel-like substance in the continuous reactor, which may result in a decrease in productivity. Furthermore, the crystallite size or average particle size of the BTO particles may become too large.

[0038] The alcohol used is preferably a lower alcohol such as methanol, ethanol, propanol, isopropanol, or butanol. These may be used alone or in combination of two or more. The mixture may also contain organic solvents other than alcohol (e.g., glycols, glycol ethers, etc.), surfactants, dispersants, etc. The mass ratio of water to alcohol is more preferably 0.10 to 0.80, and even more preferably 0.30 to 0.60.

[0039] The liquid feed rate of the first solution is preferably 4 L / Hr or more. If it is less than 4 L / Hr, productivity at an industrial level is not sufficient. There is no particular upper limit to this liquid feed rate, but considering the capacity of the above-mentioned commercially available continuous reactor, it is, for example, 20 L / Hr. However, if a larger device is used for production or if multiple devices are arranged in parallel for production, it is thought that it may be possible to exceed 20 L / Hr.

[0040] In order to control the "temperature of the third solution discharged from the continuous reactor" and the "temperature of the reaction site," it is more preferable that the temperatures of the "first solution" and the "second solution" mixed in the continuous reactor are both 15°C or less. When the temperatures of these solutions are within this range, it is easy to keep the temperature of the third solution discharged from the continuous reactor at 15°C or less. If the temperatures of these solutions deviate from this temperature, the temperature of the reaction site may also deviate from the specified temperature, and the temperature of the third solution discharged from the continuous reactor may also deviate from the specified temperature. In this state, gel-like matter may form in the continuous reactor, clogging the flow path of the apparatus and reducing productivity. Furthermore, even if a dispersion is obtained, the average particle size of the particles may become too large or the dispersion stability may be reduced.

[0041] The temperatures of the "first solution" and the "second solution" may be the same or different. The lower limit of the temperature of these solutions is not particularly set as long as the solutions have fluidity, but is, for example, -40°C for the same reasons as for the first solution in the second step. The temperature of these solutions before being mixed in the continuous reactor is more preferably -20 to 10°C, and even more preferably -20 to 5°C.

[0042] [Fourth step] The third solution is heated to 60°C or higher. This heating promotes the hydrolysis reaction and dehydration condensation reaction of barium alkoxide and titanium alkoxide, resulting in a dispersion of nano-sized BTO particles with high dispersion stability. If the heating temperature is below 60°C, the dispersion stability may be reduced. There is no particular upper limit for the heating temperature, but it is, for example, 200°C. If the temperature exceeds 200°C, an expensive pressure-resistant container will be required, and the crystallinity and dispersion stability of the particles will not be further improved. The heating temperature is preferably 60 to 130°C, more preferably 70 to 100°C.

[0043] The heating time is preferably 2 hours or more. By heating for 2 hours or more, a dispersion liquid of BTO particles with high dispersion stability can be easily obtained. Here, if the heating time is less than 2 hours, sufficient crystallization may not be achieved or the dispersion stability may be reduced. The heating time is more preferably 12 hours or more, and even more preferably 24 hours or more.

[0044] [Other steps] The dispersion thus obtained may be subjected to a dispersion treatment, a washing treatment, a surface treatment, and a concentration adjustment treatment, as required.

[0045] If the aggregated particles are broken down by dispersion treatment, the particle size distribution will become sharper than before dispersion treatment, and D 50 Particle size and D 90 The dispersion treatment may be carried out by simple stirring, but may also be carried out using a conventional ultrasonic stirrer, homogenizer, homomixer, bead mill, or the like.

[0046] The dispersion can be washed to reduce particles and impurities (especially halogen elements) in the dispersion. Examples of washing methods include a conventionally known filtration washing method using an ultrafiltration membrane, an ion exchange method using an ion exchange resin, and a centrifugal washing method in which centrifugal sedimentation is performed to replace the supernatant.

[0047] The use of surface-treated particles improves the mixing stability with other components used in the high dielectric layer and electrode layer of the multilayer ceramic capacitor, and with the UV-curable resin or additives used in the high refractive index film. The surface treatment agent is not particularly limited as long as it is a conventionally known surface treatment agent that can be used for nano-sized metal oxide particles, and examples thereof include silane coupling agents, titanate coupling agents, surfactants, and organic acids.

[0048] The solids concentration of the dispersion is preferably 60% by mass or less. If this concentration is extremely low, the storage and transportation costs of the dispersion will increase, so the solids concentration may be increased by a concentration adjustment process. Conversely, if the solids concentration exceeds 60% by mass, the dispersion stability of the dispersion may be reduced. Furthermore, the dispersion stability of a coating solution using this dispersion may also be reduced. Methods for adjusting the solids concentration include, for example, concentrating the dispersion using an ultrafiltration membrane method, distillation, or reduced-pressure distillation, and diluting the dispersion by adding a solvent. Solvent substitution may also be performed simultaneously with concentrating or diluting the dispersion. Examples of solvents that can be used include water, alcohols, ketones, esters, glycols, glycol ethers, glycol ether acetates, monoterpene alcohols, etc., and can be selected appropriately depending on the application. These solvents are not particularly limited as long as they are conventionally known solvents. There is no particular lower limit for the solids concentration, but it is, for example, about 10% by mass. If a lower concentration is required, it can be achieved by diluting with an appropriate solvent. The solid content concentration of the dispersion is more preferably 20 to 60% by mass, and even more preferably 25 to 40% by mass.

[0049] [BTO particle dispersion] The dispersion of BTO particles of the present invention has an average particle diameter (D 50 Particle diameter (A) is 3 to 30 nm, D 90 Particle size (B) is 8-80 nm, crystallite size (C) is 5-15 nm, D 50 The ratio (A / C) of particle size (A) to crystallite size is 0.3 to 5.0. The crystalline structure of the particles can be confirmed by X-ray diffraction. Such a dispersion can be obtained by the above-mentioned production method.

[0050] where D 50 The particle size is the particle size at which the cumulative distribution of particles is 50%, D 90 The particle size refers to the particle size at which the cumulative particle distribution is 90%.

[0051] D 50If the particle size (A) is less than 3 nm, the dispersion stability may be reduced. Conversely, if it exceeds 30 nm, it may be difficult to disperse uniformly when used as a co-material for the electrode layer of a thin-film ceramic capacitor. Furthermore, when forming a high refractive index film, a transparent film may not be obtained. 50 The particle size is preferably 5 to 20 nm.

[0052] D 90 If the particle size (B) is less than 8 nm, the dispersion stability may be reduced. Conversely, if it exceeds 80 nm, it may be difficult to disperse uniformly when used as a co-material for the electrode layer of a thin-film ceramic capacitor. Furthermore, when forming a high refractive index film, a transparent film may not be obtained. 90 The particle size is preferably 15 to 50 nm.

[0053] If the crystallite diameter (C) is less than 5 nm, the dispersion stability is likely to be low, and the crystallinity may be insufficient, making it difficult to obtain a high dielectric constant. Conversely, if it exceeds 15 nm, it may be difficult to disperse uniformly when used as a co-material for the electrode layer of a thin-film ceramic capacitor. Furthermore, when forming a high refractive index film, it may be difficult to obtain a transparent coating. The crystallite diameter is preferably 7 to 12 nm.

[0054] A ratio (A / C) of less than 0.3 is difficult to obtain. Conversely, a ratio (A / C) of more than 5.0 indicates a high degree of particle aggregation in the dispersion, which may result in inability to uniformly disperse particles in the film. Therefore, when used as a co-material for an electrode layer, it may be difficult to achieve a uniform electrode layer, or the haze of the coating film may increase. The ratio (A / C) is preferably 0.3 to 3.0.

[0055] The content of halogen elements in the dispersion is preferably less than 500 ppm relative to the solid content of the dispersion. If the content is 500 ppm or more, when used as a co-material for the electrode layer of a multilayer ceramic capacitor, the capacitor may crack or deform. The content of halogen elements is more preferably less than 100 ppm. Here, halogen elements refer to F, Cl, Br, and I.

[0056] By keeping the solids concentration of the dispersion at 60% by mass or less, it is possible to prevent a decrease in the dispersion stability of the dispersion or coating liquid. The solids concentration is set taking into consideration the required particle blending amount and workability depending on the application, so there is no particular lower limit for the solids concentration, but in consideration of storage and transportation costs, it is about 10% by mass. If a lower concentration is required, it can be achieved by diluting with an appropriate solvent. The solids concentration of the dispersion is more preferably 20 to 50% by mass, and even more preferably 25 to 40% by mass.

[0057] Examples of solvents for this dispersion include water, alcohols, ketones, esters, glycols, glycol ethers, glycol ether acetates, and monoterpene alcohols, and can be selected appropriately depending on the application. By selecting the solvent, it is possible to improve the mixing stability with other components used in the high dielectric layer and electrode layer of a multilayer ceramic capacitor, as well as with the UV-curable resin and additives used in the high refractive index film. When changing the solvent, a known solvent substitution method can be used.

[0058] The dispersion of the present invention is also 50 The ratio (E / C) of the particle size (E) to the above-mentioned crystallite size (C) is preferably 0.3 to 7.0. 50 The particle diameter (E) was measured by dynamic light scattering after heating a dispersion liquid prepared by using ethanol as a solvent and adjusting the solid content concentration to 30% by mass at 50°C for 3 hours. 50 If the solvent type or solid content concentration of the original dispersion is different, the solvent is replaced with ethanol and the solid content concentration is adjusted to 30 mass % before evaluation.

[0059] Incidentally, the higher the solids concentration of a dispersion, and the greater the thermal history it is subjected to, the lower its stability tends to be. Here, this ratio (E / C) is a value determined by measuring a dispersion adjusted to a specific state as described above, and is one index of the dispersion stability of the dispersion. The lower this value, the better the dispersion stability.

[0060] Here, it is difficult to obtain a ratio (E / C) of less than 0.3. Conversely, if it is higher than 7.0, the dispersion stability is low, and there is a risk that the dispersion liquid cannot be stored for a long period of time or that it cannot be uniformly dispersed when used as a co-material for the electrode layer of a thin-film ceramic capacitor. The ratio (E / C) is more preferably 0.5 to 5.0.

[0061] Examples of the present invention will be described below.

[0062] [Example 1] [First step] Nitrogen gas was added to a 30 L tank, and the relative humidity was adjusted to 25%. 14.9 kg of ethylene glycol monomethyl ether was placed in the tank, and the temperature was adjusted to 25°C. While stirring, 6.6 kg of barium diethoxide was added over 5 minutes. Subsequently, 8.3 kg of titanium tetraisopropoxide was added over 10 minutes to prepare a first solution.

[0063] The properties of each step and the solution are shown in Tables 1 and 2 (the same applies to the following Examples and Comparative Examples).

[0064] [Second process] This first solution was transferred to a sealable container adjusted to a relative humidity of 25%. Nitrogen gas was sealed into the container so that the relative humidity after cooling would be 25% or less, and the container was cooled to -10°C while maintaining the seal and left to stand for 24 hours.

[0065] [Third step] A second solution was prepared by adding 3.8 kg of pure water to 9.0 kg of methanol with stirring and adjusting the temperature to 3°C. The first solution obtained in the second step was also adjusted to 3°C. Next, using the microreactor for micro-reactions described in Patent Document 3 as a continuous flow microreactor, the first solution was delivered at 5.0 L / Hr and the second solution at 2.4 L / Hr while maintaining the micromixing chip in the reaction field at 4°C, to prepare a third solution. Continuous operation was performed under these conditions for 6.4 hours, and the entire amount was delivered.

[0066] [Fourth step] This third solution was heated to 70° C. and maintained at this temperature for 24 hours to produce a dispersion of BTO particles according to the present invention.

[0067] Next, in order to evaluate the properties of this dispersion, the dispersion was concentrated using a rotary evaporator to a solid content concentration of 30% by mass.

[0068] The properties of this dispersion were measured by the following methods: The preparation conditions of the dispersion and the measurement results are shown in Tables 1 and 2 (the same applies to the following Examples and Comparative Examples).

[0069] (1)D 50 Particle size (A), D 90 Particle size (B) Using a particle size distribution analyzer (NANOTRAC-WAVEII manufactured by Microtrac-Bell) using dynamic light scattering, the D of particles in the dispersion was measured. 50 Particle size (A) and D 90 The particle diameter (B) was measured. The refractive index of the particles used in the measurement was 1.93 and the density was 6.00.

[0070] (2) Crystal structure and crystallite size (C) The dispersion was dried at 150°C for 1 hour, and the resulting powder was crushed in a mortar. The crystal structure was identified using an X-ray diffractometer (RINT1400 manufactured by Rigaku Denki Co., Ltd.). The half-width of the (110) peak near 2θ = 31.5° was measured, and the crystallite size was calculated using the Scherrer formula below.

[0071] D=κλ / βcosθ (In the formula, D is the crystallite diameter (Å), κ is the Scherrer constant, λ is the wavelength (Å), β is the half-width (dimensionless), and θ is the reflection angle (rad).)

[0072] (3) Solid content concentration 5 g of the dispersion was collected, precisely weighed into a porcelain crucible, and dried. Then, it was fired at 1000°C for 1 hour, cooled to room temperature in a desiccator containing a desiccant, and then precisely weighed again. The solid content was calculated from the mass of the ignition residue.

[0073] (4) Halogen elements The amount of halogen element in the dispersion was measured using an ICP emission spectrometer (Shimadzu Corporation, ICPS-8100) to determine the content of halogen element relative to the solid content in the dispersion.

[0074] (5) D after heat treatment 50 Particle size (E) 10 g of a dispersion liquid adjusted to a solid content of 30% by mass using ethanol as a solvent was placed in a sealed container and heated at 50°C for 3 hours. The dispersion liquid after heating was analyzed by dynamic light scattering in the same manner as described above. 50 The particle size (E) was measured, and the ratio (E / C) was calculated from this value (E) and the above-mentioned crystallite size (C).

[0075] (6) Possibility of mass production In this example, it was determined that mass production was possible when the third step could be operated continuously for 5 hours or more.

[0076] Third process continuous operation for 5 hours or more: Continuous operation of the third process is less than 5 hours: ×

[0077] [Example 2] The dispersion of BTO particles obtained in the same manner as in Example 1 was subjected to ultrasonic treatment for 30 minutes, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain an ethanol dispersion of BTO particles with a solid content concentration of 30 mass %.

[0078] [Example 3] 30 g of anion exchange resin (SA-20A manufactured by Mitsubishi Chemical) was added to 100 g of an ethanol dispersion of BTO particles obtained in the same manner as in Example 2. The mixture was stirred at room temperature for 30 minutes, and then the ion exchange resin was separated. Subsequently, 3 g of methyltrimethoxysilane was added as a surface treatment agent, and the mixture was stirred at 30°C for 18 hours. The mixture was then concentrated using an ultrafiltration membrane to obtain a dispersion of surface-treated BTO particles with a solid content of 30% by mass.

[0079] [Example 4] A first solution was prepared in the same manner as in Example 1, except that in the first step, the relative humidity was adjusted to 50% and 6.3 kg of barium diethoxide and 8.6 kg of titanium tetraisopropoxide were used.

[0080] In the second step, this first solution was transferred to a sealable container adjusted to a relative humidity of 50%. Nitrogen gas was sealed into the container so that the relative humidity after cooling would be 50% or less, and the container was cooled to 12°C while maintaining the seal and allowed to stand for 24 hours.

[0081] In the third step, 3.7 kg of pure water was added to 8.9 kg of methanol while stirring to prepare a second solution. Next, a third solution was prepared in the same manner as in Example 1, except that the temperature of this solution, the first solution obtained in the second step, and the temperature of the micromixing tip were adjusted to 15°C. Under these conditions, continuous operation was carried out for 6.4 hours, and the entire amount was transferred.

[0082] In the fourth step, except for using this third solution, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content concentration of 30 mass %.

[0083] [Example 5] A first solution was prepared in the same manner as in Example 1, except that 6.9 kg of barium diethoxide and 7.8 kg of titanium tetraisopropoxide were used in the first step.

[0084] In the second step, the same procedure as in Example 1 was carried out except that the temperature was cooled to -18°C and the mixture was allowed to stand for 3 hours.

[0085] In the third step, 3.7 kg of pure water was added to 8.9 kg of methanol while stirring to prepare a second solution. The temperature of this solution and the first solution obtained in the second step was adjusted to -18°C, and the temperature of the micromixing tip was set to -10°C. A third solution was prepared in the same manner as in Example 1. Under these conditions, continuous operation was performed for 6.3 hours, and the entire amount was transferred.

[0086] In the fourth step, the third solution was heated to 60°C and maintained at this temperature for 3 hours, but the procedure was the same as in Example 1 to produce a dispersion of BTO particles of the present invention. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content of 30% by mass.

[0087] [Example 6] A first solution was prepared in the same manner as in Example 1, except that in the first step, the relative humidity was adjusted to 10% and 10.8 kg of ethylene glycol monomethyl ether, 12.0 kg of barium diethoxide, and 14.7 kg of titanium tetraisopropoxide were used.

[0088] In the second step, this first solution was transferred to a sealable container adjusted to a relative humidity of 10%. Nitrogen gas was sealed into the container so that the relative humidity after cooling would be 10% or less, and the container was cooled to 0°C while maintaining the seal and allowed to stand for 96 hours.

[0089] In the third step, 6.8 kg of pure water was added to 16.1 kg of methanol while stirring to prepare the second solution, which was then adjusted to 8°C. The first solution obtained in the second step was also adjusted to 8°C. Next, using a ULREA SS-11 forced thin film reactor manufactured by M-Technique Co., Ltd., the temperature of the reaction field was maintained at 8°C, and the first solution was pumped at 5.0 L / Hr and the second solution at 3.4 L / Hr to prepare the third solution. Continuous operation was carried out under these conditions for 8.0 hours, and the entire amount was pumped.

[0090] In the fourth step, the third solution was placed in a pressure vessel and heated to 125°C. This temperature was maintained for 48 hours to produce a dispersion of BTO particles of the present invention. The dispersion was then concentrated using a rotary evaporator, and the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solids concentration of 30% by mass.

[0091] [Example 7] A first solution was prepared in the same manner as in Example 1, except that a 200 L tank was used and 105.0 kg of ethylene glycol monomethyl ether, 6.0 kg of barium diethoxide, and 7.5 kg of titanium tetraisopropoxide were used in the first step.

[0092] In the second step, the same procedure as in Example 1 was carried out except that the temperature was cooled to 7°C.

[0093] In the third step, 7.6 kg of pure water was added to 76.0 kg of methanol with stirring to prepare a second solution, which was then adjusted to 7°C. The first solution obtained in the second step was adjusted to 5°C. Next, while maintaining the temperature of the reaction site at 7°C, the first solution was pumped at 20.0 L / Hr and the second solution at 16.3 L / Hr to prepare a third solution. Continuous operation was performed under these conditions for 6.4 hours, and the entire amount was pumped.

[0094] In the fourth step, except that this third solution was used, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator to obtain a dispersion with a solid content concentration of 30 mass %.

[0095] [Comparative Example 1] A first solution was prepared in the same manner as in Example 1, except that 7.2 kg of barium diethoxide and 7.5 kg of titanium tetraisopropoxide were used in the first step.

[0096] Except for using this first solution in the second and third steps, a third solution was prepared in the same manner as in Example 1. Under these conditions, the production line became clogged (blocked) 4.2 hours after the start of operation of the third step, so after cleaning the production line, the liquid supply was resumed and operation was resumed.

[0097] In the fourth step, except for using this third solution, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content concentration of 30 mass %.

[0098] Comparative Example 2 A first solution was prepared in the same manner as in Example 1, except that in the first step, 14.7 kg of ethylene glycol monomethyl ether, 5.75 kg of barium diethoxide, and 9.0 kg of titanium tetraisopropoxide were used.

[0099] The second step was carried out in the same manner as in Example 1, except that this first solution was used.

[0100] In the third step, a second solution was prepared by adding 3.7 kg of pure water to 8.8 kg of methanol with stirring and adjusting the temperature to 3° C. Except for using this second solution, a third solution was prepared in the same manner as in Example 1. Under these conditions, the production line became clogged 3.1 hours after the start of operation, so the production line was cleaned and the liquid supply was resumed.

[0101] In the fourth step, except for using this third solution, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content concentration of 30 mass %.

[0102] Comparative Example 3 In the first step, the first solution was prepared in the same manner as in Example 1.

[0103] In the second step, this first solution was transferred to a sealable container adjusted to a relative humidity of 25%. Nitrogen gas was sealed into the container so that the relative humidity at 25°C was 25% or less, and the container was kept sealed and kept at 25°C for 24 hours.

[0104] In the third step, except that the first solution obtained in the second step was used, the third solution was prepared in the same manner as in Example 1. Under these conditions, the production line became clogged 4.2 hours after the start of operation, so the production line was cleaned and the liquid supply was resumed.

[0105] In the fourth step, except for using this third solution, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content concentration of 30 mass %.

[0106] Comparative Example 4 The first and second steps were carried out in the same manner as in Example 1.

[0107] In the third step, the third solution was prepared in the same manner as in Example 1, except that the second solution and the first solution were adjusted to 20° C. Under these conditions, the production line became clogged 2.0 hours after the start of operation, so the production line was cleaned and the liquid supply was resumed.

[0108] In the fourth step, except for using this third solution, a dispersion of BTO particles of the present invention was produced in the same manner as in Example 1. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane to obtain a dispersion with a solid content concentration of 30 mass %.

[0109] Comparative Example 5 A dispersion of BTO particles of the present invention was produced in the same manner as in Example 1, except that steps up to the third step were carried out, and in the fourth step, the third solution was heated to 50°C and maintained at this temperature for 12 hours. Next, the dispersion was concentrated using a rotary evaporator, and then the solvent was replaced with ethanol using an ultrafiltration membrane, yielding a dispersion with a solids concentration of 30% by mass.

[0110] [Table 1]

[0111] [Table 2]

Claims

1. a first step of mixing the barium alkoxide, the titanium alkoxide, and an organic solvent having a hydroxyl group in an atmosphere of a relative humidity of 50% or less so that the atomic ratio of barium to titanium (Ba / Ti ratio) is 0.90 to 1.10 and the total concentration of the barium alkoxide and the titanium alkoxide is 0.5 to 10.0 mol / kg; a second step of maintaining the first solution obtained in the first step at −40 to 12° C. for 3 hours or more; a third step of mixing the first solution obtained in the second step with a second solution containing water in a continuous reactor at 15°C or less; a fourth step of heating the third solution obtained in the third step to 60°C or higher; A method for producing a dispersion of barium titanate particles, comprising the steps of:

2. 2. The method for producing a dispersion liquid of barium titanate particles according to claim 1, wherein in the second step, the first solution is kept at −18 to 12° C. for 3 hours or more.

3. 2. The method for producing a dispersion liquid of barium titanate particles according to claim 1, wherein in the second step, the first solution is kept at −18 to 12° C. for 3 to 96 hours.

4. The method for producing a dispersion of barium titanate particles according to claim 1, characterized in that the molar ratio (water / (barium alkoxide + titanium alkoxide)) of the number of moles of water in the second solution (used in the third step) to the total number of moles of barium alkoxide and titanium alkoxide in the first solution is 1 to 10.

5. The method for producing a dispersion liquid of barium titanate particles according to claim 1, characterized in that the second solution contains alcohol, and the mass ratio of water to alcohol (water / alcohol) is 0.05 to 1.

00.

6. 2. The method for producing a dispersion liquid of barium titanate particles according to claim 1, wherein in the third step, the first solution is fed at a rate of 4 L / Hr or more.

7. 2. The method for producing a dispersion liquid of barium titanate particles according to claim 1, wherein the first solution and the second solution are at 15° C. or less in the third step.

8. 2. The method for producing a dispersion of barium titanate particles according to claim 1, wherein the solid content is adjusted to 20 to 60 mass % after the fourth step.

9. Dynamic light scattering of particles ５０ Particle diameter (A) is 3 to 30 nm, D ９０ The particle diameter (B) is 8 to 80 nm, the crystallite diameter (C) is 5 to 15 nm, and ５０ A dispersion of barium titanate particles having a particle size to crystallite size ratio (A / C) of 0.3 to 5.0, The solid content of the dispersion was adjusted to 30% by mass using ethanol as a solvent, and the dispersion was heated at 50°C for 3 hours. ５０ The ratio (E / C) of the particle size (E) to the crystallite size (C) is 0.3 to 7.0; A dispersion of barium titanate particles, characterized in that the content of halogen elements relative to the solid content in the dispersion is less than 500 ppm.

10. 10. The dispersion of barium titanate particles according to claim 9, wherein the solid content is 10 to 60% by mass.

Images