WO2020045164A1

WO2020045164A1 - Method for producing aqueous dispersion and organic solvent dispersion of zirconium oxide particles

Info

Publication number: WO2020045164A1
Application number: PCT/JP2019/032433
Authority: WO
Inventors: 考則森田
Original assignee: 堺化学工業株式会社
Priority date: 2018-08-27
Filing date: 2019-08-20
Publication date: 2020-03-05
Also published as: TW202019816A; JP2020033195A; JP6665901B2

Abstract

According to the present invention, a method for producing an aqueous zirconium oxide particle dispersion is provided, the method comprising: a step for reacting zirconium oxychloride with a basic substance to obtain a first water slurry containing zirconium oxide particles; a step in which the first water slurry is washed to obtain a second water slurry, 1 part by mole or more of an organic acid is added to the second water slurry with respect to 1 part by mole of zirconium to obtain a third water slurry having a chlorine ion content of less than 4000 ppm with respect to the weight of zirconium particles, and then hydrochloric acid is added to the third water slurry to obtain a fourth water slurry having a chlorine ion content of 4000-20000 ppm with respect to the weight of zirconium oxide particles; a step for hydrothermally treating the fourth water slurry to obtain a precursor of an aqueous zirconium oxide particle dispersion; and a fourth step in which the precursor of an aqueous zirconium oxide particle dispersion is washed by ultrafiltration to obtain an aqueous zirconium oxide particle dispersion having a chlorine ion content of 1500-7000 ppm with respect to the weight of zirconium oxide particles. The aqueous zirconium oxide particle dispersion thus obtained has excellent transparency and low viscosity even when containing a high concentration of fine zirconium oxide particles, and in particular, exhibits excellent long-term storage stability regardless of the ambient temperature.

Description

Method for producing aqueous dispersion and organic solvent dispersion of zirconium oxide particles

The present invention relates to a method for producing each of an aqueous dispersion and an organic solvent dispersion of zirconium oxide particles, and more specifically, has a low viscosity and high transparency while containing fine zirconium oxide particles at a high concentration, and has a long term. The present invention relates to a method for producing an aqueous dispersion of zirconium oxide particles and an organic solvent dispersion having excellent storage stability. The zirconium oxide particle dispersion obtained by the method of the present invention is useful for various uses in the optical field, particularly, as a material for an optical composite resin such as an LED sealing resin and an antireflection film.

Conventionally, inorganic oxide particle dispersions such as silica, alumina, zinc oxide, tin oxide, zirconia, titania, and the like have been used in various industrial fields, particularly, in the optical field, used to adjust the refractive index. ing. Above all, zirconium oxide has a high refractive index, and in recent years, various proposals have been made to use it as a highly functional resin or film which is compounded with a transparent resin or film to improve its refractive index.

For example, by adding zirconium oxide having a high refractive index to the sealing resin covering the LED, the refractive index of the sealing resin is increased, so that light emitted from the light emitter can be more efficiently extracted, and the luminance of the LED can be improved. Is known to improve.

Similarly, zirconium oxide is also used for the antireflection film on the display surface of a flat panel display (FPD) such as a liquid crystal display (LCD) and an electroluminescence display (EL). The antireflection film is a laminated film in which a low refractive index layer and a high refractive index layer are laminated, and a composite resin material in which zirconium oxide is dispersed in the high refractive index layer is used.

In the above-mentioned applications, when the primary particle diameter of the zirconium oxide and the secondary aggregation particle diameter in the resin are not sufficiently smaller than the wavelength of visible light (380 to 800 nm), the influence of the scattering by the zirconium oxide particles causes The necessary transparency cannot be obtained because the sealing resin and the antireflection film become cloudy. Therefore, there is a strong demand for the development of a highly transparent zirconium oxide particle dispersion in which zirconium oxide particles are dispersed as fine particles in a resin.

In recent years, various methods for obtaining zirconium oxide fine particles and dispersions thereof have been proposed in order to meet such demands. A typical method for obtaining a zirconium oxide particle dispersion utilizes zirconium hydroxide generated by alkali neutralization of a zirconium salt.For example, hydrochloric acid is added at a predetermined concentration to a slurry of zirconium hydroxide. A method of obtaining a dispersion of zirconium oxide particles by heating at a boiling temperature is known (see Patent Document 1). However, according to this method, the resulting zirconium oxide has an average particle diameter of 50 nm or more, so that the dispersion liquid does not have sufficient transparency.

An aqueous solution containing a zirconium salt is added to an aqueous solution of an alkali metal hydroxide heated to 60 ° C. or higher and neutralized, that is, reverse neutralized, filtered, washed, added with water, stirred, and acidified. There is also known a method of obtaining a zirconia dispersion by heating and stirring at a temperature of 80 to 100 ° C. (see Patent Document 2).

Further, in the presence of carboxylic acids such as malic acid, citric acid and tartaric acid, a zirconium salt is neutralized with an alkali in water to obtain a zirconium hydroxide gel, which is once washed, ripened, and ultrasonically oxidized. There is known a method of obtaining a dispersion of zirconium oxide particles by performing a hydrothermal treatment again in the presence of the carboxylic acid after sufficient dispersion by irradiation or the like (see Patent Document 3).

The zirconium salt is reacted with an alkali in water to obtain a slurry of zirconium oxide particles, which is then filtered, washed, and repulped, and the resulting slurry is added to 1 part by mole of zirconium in the slurry. A method for obtaining a highly transparent aqueous dispersion of zirconium oxide particles by washing the resulting aqueous dispersion of zirconium oxide particles after adding 1 mol part or more of an organic acid and performing a hydrothermal treatment at a temperature of 170 ° C. or higher is also proposed. (See Patent Document 4).

As the use of the zirconium oxide particle dispersion has been expanded and its use has increased, the demand for its long-term storage stability has been increasing. No description is given, and depending on the obtained aqueous dispersion, the long-term storage stability may actually be poor.

Stabilizers such as acetic acid, β-diketone, and salicylic acid are added to an aqueous dispersion of zirconium oxide particles together with an organic solvent, and the mixture is filtered, and water is replaced with an organic solvent. Although a solvent dispersion has been proposed (see Patent Document 5), it has not been clarified how much stability with time.

In particular, in relation to long-term storage stability, conventionally, the dispersion of known zirconium oxide nanoparticles is not sufficient long-term storage stability, to ensure long-term storage stability, or to prevent deterioration Usually, it is stored at a refrigeration temperature or a freezing temperature, and is returned to a normal temperature when used.

JP-A-5-24844 JP 2008-31023 A JP 2006-143535 A JP 2010-150066 A JP 2007-238422A

The present invention has been made in order to solve the above-described problems in the conventional zirconium oxide particle dispersion liquid, and even if it contains fine zirconium oxide particles at a high concentration, it has excellent transparency and low viscosity. In addition, an object of the present invention is to provide a method for producing an aqueous dispersion of zirconium oxide particles and an organic solvent dispersion, which are particularly excellent in storage stability over a long period of time.

In particular, the present invention relates to water of zirconium oxide nanoparticles having excellent long-term storage stability regardless of temperature, for example, in an environment without temperature control ranging from about 10 ° C. to about 40 ° C., and thus in an environment at room temperature. An object of the present invention is to provide a method for producing each of a dispersion and an organic solvent dispersion.

The inventor of the present invention started from a step of reacting zirconium oxychloride with a basic substance in alkaline water to obtain a first water slurry containing zirconium oxide particles. As a result of a detailed study on the method of leading to the above, starting from the first water slurry, the second and third water slurries of zirconium oxide particles obtained on the way, and in some cases, the aqueous dispersion By controlling the chlorine ion content with respect to the weight of the zirconium oxide particles in the given precursor optimally and finally setting the chloride ion content in a predetermined range, the zirconium oxide particles contain a high concentration of fine zirconium oxide particles. Zirconium oxide, which has excellent transparency and low viscosity, and in particular, has excellent storage stability over a long period of time in the above-mentioned sense. It has found that it is possible to obtain an aqueous dispersion and organic solvent dispersion of particles, and have reached the present invention.

According to the present invention, the following methods for producing an aqueous dispersion of zirconium oxide particles and an organic solvent dispersion are provided. Furthermore, according to the present invention, similarly, there are provided methods for producing an aqueous dispersion and an organic solvent dispersion of stabilized zirconium oxide particles, which are solid solutions containing a stabilizing element.

(1) Production of Zirconium Oxide Particle Aqueous Dispersion Reaction of zirconium oxychloride with a basic substance in water to obtain a first aqueous slurry containing zirconium oxide particles in a pH range of 9.6 to 11.0. One process,
(A) The first water slurry is filtered and washed, and then repulped in water to obtain a second water slurry containing the zirconium oxide particles. The second water slurry contains 1 mol part of zirconium. 1 mol part or more of an organic acid is added to obtain a third water slurry having a chlorine ion content of less than 4000 ppm based on the weight of the zirconium oxide particles, and then hydrochloric acid is added to the third water slurry to obtain a zirconium oxide particle. (B) obtaining a fourth water slurry having a chlorine ion content in the range of 4000 to 20,000 ppm with respect to the weight of (a), or (b) filtering and washing the first water slurry, followed by repulping in water to obtain the zirconium oxide. A second water slurry containing particles is obtained. Hydrochloric acid is added to the second water slurry so that the chlorine ion content with respect to the weight of the zirconium oxide particles is 400%. A third water slurry in the range of 0 to 20,000 ppm is obtained. Then, 1 mol part or more of organic acid is added to 1 mol part of zirconium to the third water slurry, and chlorine ion content based on the weight of zirconium oxide particles is added. A second step of obtaining a fourth water slurry having a rate in the range of 4000 to 20000 ppm;
A third step of hydrothermally treating the fourth aqueous slurry to obtain the zirconium oxide particle aqueous dispersion precursor, and washing the zirconium oxide particle aqueous dispersion precursor by ultrafiltration to obtain a zirconium oxide particle A method for producing an aqueous dispersion of zirconium oxide particles, comprising a fourth step of obtaining an aqueous dispersion of zirconium oxide particles having a chlorine ion content based on weight in the range of 1500 to 7000 ppm.

(2) Production of Stabilized Aqueous Dispersion of Zirconium Oxide Particles A salt of zirconium oxychloride and at least one stabilizing element selected from aluminum, magnesium, titanium and rare earth elements is reacted with a basic substance in water to form zirconium. And a first step of obtaining a first water slurry having a pH in the range of 9.6 to 11.0 containing particles of the coprecipitate of the stabilizing element.
(A) The first water slurry is filtered, washed with water, and then repulped in water to obtain a second water slurry containing particles of the coprecipitated zirconium and the stabilizing element. An organic acid is added to the slurry in an amount of 1 mol part or more based on 1 mol part of the total amount of zirconium and the stabilizing element, and the chlorine ion content is less than 4000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A third water slurry is obtained, and then hydrochloric acid is added to the third water slurry to obtain a fourth water slurry having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. Or (b) filtering and washing the first water slurry and then repulping in water to contain particles of the co-precipitate of the zirconium and the stabilizing element. A second water slurry is obtained, and hydrochloric acid is added to the second water slurry to form a third water having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A slurry is obtained, and then 1 mol part or more of an organic acid is added to 1 mol part of the total amount of zirconium and the stabilizing element to the third water slurry, and the total amount of zirconium and the stabilizing element in terms of oxide is added. A second step of obtaining a fourth water slurry having a chloride ion content based on weight in the range of 4000 to 20,000 ppm,
A third step of hydrothermally treating the fourth water slurry to obtain a stabilized zirconium oxide particle aqueous dispersion precursor which is a solid solution containing the stabilizing element, and the stabilized zirconium oxide particle aqueous dispersion precursor A fourth step of washing by ultrafiltration to obtain an aqueous dispersion of stabilized zirconium oxide particles having a chloride ion content in the range of 1500 to 7000 ppm based on the weight of the stabilized zirconium oxide particles. A method for producing a dispersion.

(3) Production of Zirconium Oxide Particle Organic Solvent Dispersion Water, which is a dispersion medium of the zirconium oxide particle aqueous dispersion obtained by the method described in (1) above, is replaced with an organic solvent, and the weight of the zirconium oxide particles is reduced. A method for producing an organic solvent dispersion of zirconium oxide particles, wherein the dispersion medium has a chlorine ion content in the range of 1500 to 7000 ppm with respect to the zirconium oxide particles, wherein the dispersion medium is the organic solvent.

(4) Production of Stabilized Zirconium Oxide Particle Organic Solvent Dispersion Water, which is the dispersion medium of the stabilized zirconium oxide particle aqueous dispersion obtained by the method described in (2) above, is replaced with an organic solvent to stabilize the dispersion. Production of a stabilized zirconium oxide particle organic solvent dispersion in which the dispersion medium is the above-mentioned organic solvent in which the chlorine ion content is in the range of 1500 to 7000 ppm based on the weight of the stabilized zirconium oxide particles. Method.

In the following, (stabilized) zirconium oxide particles mean zirconium oxide particles and / or stabilized zirconium oxide particles.

As described above, both the aqueous dispersion and the organic solvent dispersion of (stabilized) zirconium oxide particles obtained by the method of the present invention may contain fine (stabilized) zirconium oxide particles at a high concentration. It has high transparency and low viscosity, and has a viscosity increase of 20 mPa · s or less when stored at a temperature of 25 ° C. for 24 months, and is remarkably excellent in long-term storage stability.

According to a preferred embodiment of the present invention, regardless of the environmental temperature, especially under normal temperature environment, even when stored for 40 months or more, the viscosity is substantially the same as the viscosity immediately after production, long-term storage stability (Stabilized) aqueous dispersion and organic solvent dispersion of zirconium oxide particles can be obtained.

(1) First Method for Producing Aqueous Dispersion of Zirconium Oxide Particles In the production of an aqueous dispersion of zirconium oxide particles by the method of the present invention, as a first step, zirconium oxychloride is reacted with a basic substance in water. Then, a first water slurry containing the above zirconium oxide particles and having a pH in the range of 9.6 to 11.0 is obtained.

In the present invention, the temperature at which the zirconium oxychloride is reacted with the above basic substance in water is not particularly limited, but is usually in the range of 10 to 50 ° C, preferably 15 to 40 ° C. Range.

In the neutralization reaction when neutralizing zirconium oxychloride as an acid with a basic substance, the molar excess of the basic substance with respect to the acid, that is, the molar excess during alkali neutralization is usually 1.15 to 1 .5. The molar excess of the basic substance with respect to the acid will be described later.

Regarding the method of reacting zirconium oxychloride with the above basic substance in water, for example, a method of adding an aqueous solution of a basic substance to an aqueous solution of a zirconium oxychloride salt, a method of adding an aqueous solution of zirconium oxychloride to an aqueous solution of a basic substance, The zirconium chloride aqueous solution and the basic substance aqueous solution may be added in advance to a so-called filling solution placed in a precipitation reactor at the same time, but any method may be used. A simultaneous neutralization method in which the mixture is simultaneously added to a so-called filling solution placed in a reaction vessel is preferable.

アルカリ As the basic substance, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, ammonia, or the like is preferably used, but is not limited thereto. The basic substance is usually used as an aqueous solution.

The concentration of the aqueous zirconium oxychloride solution is preferably 2.4 mol / L or less, and the concentration of the basic substance aqueous solution is preferably 10 mol / L or less.

According to the present invention, in the first step, a first water slurry having a zirconium oxide particle concentration of usually 1 to 20% by weight is thus obtained. When the concentration of zirconium oxide particles in the first water slurry exceeds 20% by weight, such a first water slurry has a high viscosity, is difficult to stir, and has a chlorine ion content of the obtained zirconium oxide particles. Becomes uneven, and in the second step, washing becomes insufficient, and by using such a water slurry, an aqueous dispersion of zirconium oxide particles having the desired high transparency and low viscosity is obtained. Can not do. In particular, according to the present invention, the concentration of zirconium oxide particles in the first water slurry is preferably in the range of 1 to 10% by weight.

Second Step In the present invention, the second step is to filter and wash the first water slurry obtained in the first step, repulp it in water, and to prepare a second water slurry containing the zirconium oxide particles. An organic acid and hydrochloric acid are added to the second water slurry to obtain a water slurry (fourth water slurry) containing zirconium oxide particles having a chloride ion content in the range of 4000 to 20,000 ppm based on the weight of the zirconium oxide particles. This is the step of obtaining.

順序 In the second step, the order of adding the organic acid and hydrochloric acid may be the following method (a) of adding the organic acid first, or the following method (b) of adding hydrochloric acid first.

The method (a) is as follows.
(A) The first water slurry is filtered and washed, and then repulped in water to obtain a second water slurry containing the zirconium oxide particles. The second water slurry contains 1 mol part of zirconium. 1 mol part or more of an organic acid is added to obtain a third water slurry having a chlorine ion content of less than 4000 ppm based on the weight of the zirconium oxide particles, and then hydrochloric acid is added to the third water slurry to obtain a zirconium oxide particle. To obtain a fourth water slurry having a chlorine ion content in the range of 4000 to 20,000 ppm based on the weight of the water.

Method (b) is as follows.
(B) The first water slurry is filtered and washed, and then repulped in water to obtain a second water slurry containing the zirconium oxide particles. Hydrochloric acid is added to the second water slurry, and zirconium oxide is added. A chlorine water content based on the weight of the particles is in the range of 4,000 to 20,000 ppm). A third water slurry is obtained, and then the organic acid is added to the third water slurry in an amount of 1 mol part or more per 1 mol part of zirconium. And obtaining a fourth water slurry having a chlorine ion content in the range of 4000 to 20,000 ppm based on the weight of the zirconium oxide particles.

When the method (a) is used, 1 mol part or more of organic acid is added to 1 mol part of zirconium to the second water slurry, and the chlorine ion content with respect to the weight of the zirconium oxide particles is 3000 ppm or less. It is preferable to obtain a water slurry of No. 3 and particularly preferable to obtain a third water slurry of 2000 ppm or less.

In the first step, when the zirconium oxychloride and the basic substance are reacted in water to obtain a first water slurry containing zirconium oxide particles, a large amount of the basic substance is used with respect to the zirconium oxychloride. When the pH at the time of the reaction is higher than the above range, the obtained zirconium oxide particles occlude the internal substance in a large amount, and in the second step, the basic substance cannot be completely removed. The hydrochloric acid added in the third step is consumed for neutralization in the hydrothermal treatment in the fourth step, and as a result, an aqueous dispersion of zirconium oxide particles having a target chlorine ion content cannot be obtained.

On the other hand, in the first step, when the first water slurry containing zirconium oxide particles is obtained by reacting zirconium oxychloride and the above-mentioned basic substance in water, the amount of the above-mentioned basic substance with respect to zirconium oxychloride is reduced. When the pH at the time of the above reaction is lower than the above range, it is difficult to control the content of chloride ions that the obtained zirconium oxide particles occlude inside, and as a result, the chlorine ion content of The dispersion is large, and an aqueous dispersion of zirconium oxide particles having a stable chlorine ion content cannot be obtained.

When the first water slurry is filtered and washed, and then repulped in water to obtain a second water slurry containing zirconium oxide particles, the second water slurry has an electric conductivity of 500 μS / cm or less. Is preferred.

カリウム When zirconium oxychloride is neutralized in water with a basic substance such as potassium hydroxide, potassium chloride is by-produced. Therefore, when the by-product salt contained in the first water slurry obtained by reacting zirconium oxychloride with potassium hydroxide in water, that is, potassium chloride is not sufficiently removed, such Even if an organic acid is added to the water slurry and a hydrothermal treatment is performed, it is difficult to obtain a sufficient dispersing effect. Therefore, even if an ultrafiltration treatment is performed thereafter, a highly transparent aqueous dispersion of zirconium oxide particles cannot be obtained.

Further, in the present invention, the obtained first water slurry is filtered and washed, and the obtained cake is repulped in water to form a second water slurry. Stirring with a stirrer may be used as a water slurry, but if necessary, in addition to wet media dispersion such as a bead mill, ultrasonic irradiation, using means such as a high-pressure homogenizer, the above cake may be repulped in water. Good.

As described above, in the second step, an organic acid and hydrochloric acid are added to the second water slurry to form a water slurry containing zirconium oxide particles having a chloride ion content with respect to the weight of the zirconium oxide particles in a predetermined range. However, the hydrochloric acid also functions as a deflocculant, and the organic acid is also a deflocculant like hydrochloric acid (chloride ion), and the zirconium oxide particles in the obtained third water slurry are obtained. Are used for so-called acid deflocculation, in which the particles are dispersed by repulsively charging each other.

カルボン As the organic acid, preferably, a carboxylic acid or a hydroxycarboxylic acid is used. Specific examples of such organic acids include, for example, formic acid, acetic acid, monocarboxylic acids such as propionic acid, oxalic acid, malonic acid, succinic acid, fumaric acid, dicarboxylic acids such as maleic acid and higher polybasic acids Acids, lactic acid, malic acid, tartaric acid, citric acid, salts of hydroxycarboxylic acids such as gluconic acid and the like can be mentioned.

In addition, as described above, these organic acids are generally used in an amount of 1 mol part or more based on 1 mol part of zirconium in the third water slurry to be subjected to hydrothermal treatment. It is used in the range of mole parts, most preferably in the range of 1-3 mole parts. When the amount of the organic acid is less than 1 mol part per 1 mol part of zirconium in the third water slurry, not only the obtained aqueous dispersion of zirconium oxide particles is insufficient in transparency but also the viscosity May also be higher. On the other hand, if the amount of the organic acid exceeds 5 parts by mol with respect to 1 part by mol of zirconium in the third water slurry, there is no particular effect corresponding thereto and it is not economical.

The hydrochloric acid is not particularly limited, but a hydrochloric acid having a concentration of 40% or less is preferable.

Third Step According to the present invention, the fourth water slurry containing the organic acid thus obtained and having a chlorine ion content in the range of 4000 to 20,000 ppm based on the weight of the zirconium oxide particles is prepared in the third step. As a process, a hydrothermal treatment is performed at a temperature of 170 ° C. or higher to obtain a precursor of an aqueous dispersion of zirconium oxide particles.

As described above, the organic acid is a deflocculant, and according to the present invention, the fourth water slurry is treated under the harsh conditions of hydrothermal treatment in the presence of the deflocculant. The particles are peptized more effectively.

According to the present invention, the zirconium oxide particle concentration of the fourth water slurry subjected to the hydrothermal treatment is usually in the range of 1 to 20% by weight, and preferably in the range of 1 to 10% by weight. When the concentration of zirconium oxide particles in the fourth water slurry exceeds 20% by weight, the viscosity of the water slurry is high, which causes difficulty in hydrothermal treatment. In particular, according to the present invention, the concentration of zirconium oxide particles in the fourth water slurry is preferably in the range of 1 to 10% by weight.

水 The temperature of the hydrothermal treatment is usually 170 ° C. or higher, preferably a temperature of 170 ° C. to 230 ° C. When the temperature of the hydrothermal treatment is lower than 170 ° C., the obtained aqueous dispersion of zirconium oxide particles not only does not have sufficient transparency, but also contains sedimenting coarse aggregated particles and has a high viscosity. Sometimes.

The time of the hydrothermal treatment is usually 1 hour or more, preferably 3 hours or more. When the temperature of the hydrothermal treatment is shorter than 1 hour, not only the obtained aqueous dispersion of zirconium oxide particles does not have sufficient transparency, but also coarse sedimentable aggregated particles are generated, and the desired transparent An aqueous dispersion of zirconium oxide particles having high properties cannot be obtained. Although the time of the hydrothermal treatment may be lengthened, an effect corresponding to the time is not particularly obtained, so that usually 10 hours or less is sufficient.

Fourth Step Next, according to the present invention, the thus obtained aqueous dispersion precursor of zirconium oxide particles is washed by ultrafiltration as a fourth step, and the chlorine ion content with respect to the weight of the zirconium oxide particles is reduced. An aqueous dispersion of zirconium oxide particles having a zirconium oxide particle concentration in the range of 1500 to 7000 ppm, preferably 2000 to 5000 ppm, is usually in the range of 1 to 30% by weight. When the chloride ion concentration with respect to the weight of the zirconium oxide particles is less than 1500 ppm, the storage stability of the aqueous dispersion becomes poor. On the other hand, when the chloride ion concentration with respect to the weight of the zirconium oxide particles exceeds 7000 ppm, there is a risk of corrosion of the manufacturing equipment.

According to the present invention, the aqueous dispersion of zirconium oxide particles thus obtained can be concentrated, if necessary. This concentration can be achieved by means such as evaporation concentration using a rotary evaporator or concentration using ultrafiltration using an ultrafiltration membrane. The concentration means is not particularly limited, but is preferably concentrated by ultrafiltration using an ultrafiltration membrane.

Therefore, according to the present invention, the aqueous dispersion of zirconium oxide particles obtained by the above-mentioned hydrothermal treatment can be washed while being concentrated using an ultrafiltration membrane. That is, the aqueous dispersion of zirconium oxide particles is concentrated by ultrafiltration, and the obtained concentrate is diluted with water by adding water, washed, and the obtained water slurry is again ultrafiltered, and thus, The aqueous dispersion is subjected to ultrafiltration, and by repeating the concentration and dilution, the aqueous dispersion of zirconium oxide particles obtained by the hydrothermal treatment is concentrated and washed, and the remaining by-product salts are repeatedly removed with water. Thus, the aqueous dispersion of zirconium oxide particles can be concentrated to obtain an aqueous dispersion having an increased zirconium oxide concentration.

According to the present invention, an aqueous dispersion of zirconium oxide particles having a zirconium oxide particle concentration of 10 to 50% by weight, having low viscosity and high transparency, and having excellent long-term storage stability is thus obtained. Obtainable.

According to the present invention, the upper limit of the zirconium oxide particle concentration of the aqueous dispersion of zirconium oxide particles is usually 50% by weight, and preferably 40% by weight. This is because an aqueous dispersion having a zirconium oxide particle concentration exceeding 50% by weight has a high viscosity and eventually loses fluidity and gels.

Next, the production of an aqueous dispersion of stabilized zirconium oxide particles as a solid solution containing a stabilizing element by the method of the present invention will be described.

(2) Production of stabilized aqueous dispersion of zirconium oxide particles In order to obtain an aqueous dispersion of stabilized zirconium oxide particles by the first method according to the present invention, a method of producing the above-described aqueous dispersion of zirconium oxide particles is described. In place of the aqueous solution of zirconium oxychloride, the same treatment may be performed using an aqueous solution containing zirconium oxychloride and a salt of the above stabilizing element. Usually, the concentration of the salt of the stabilizing element in the aqueous solution is preferably 0.5 mol / L or less.

において In the present invention, the stabilizing element is preferably at least one selected from aluminum, magnesium, titanium and rare earth elements.

The salt of the stabilizing element is not particularly limited, but usually, a water-soluble salt such as chloride or nitrate is preferably used. For example, when the stabilizing element is aluminum, aluminum chloride is preferably used, and when the stabilizing element is yttrium, yttrium chloride is preferably used. In the present invention, the stabilizing element is generally used in a range of 1 to 20 mol% based on the zirconium element.

In the present invention, for example, in the neutralization reaction when neutralizing acids zirconium oxychloride and yttrium chloride with a basic substance, the molar excess of the basic substance with respect to the acid is usually 1.15 to 1.5. Is preferably within the range. The molar excess of the basic substance with respect to the acid will be described later.

According to the present invention, to obtain an aqueous dispersion of zirconium oxide particles, which is a solid solution containing the stabilizing element, in the same manner as in the case of obtaining the aqueous dispersion of zirconium oxide particles described above, first, an oxy Reacting a salt of zirconium chloride and the stabilizing element with a basic substance in water to form a first zirconium and a stabilizing element having a pH in the range of 9.6 to 11.0 containing particles of a coprecipitate of the stabilizing element; Obtain a water slurry.

Then, as a second step,
(A) The first water slurry is filtered, washed with water, and then repulped in water to obtain a second water slurry containing particles of the coprecipitated zirconium and the stabilizing element. An organic acid is added to the slurry in an amount of 1 mol part or more based on 1 mol part of the total amount of zirconium and the stabilizing element, and the chlorine ion content is less than 4000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A third water slurry is obtained, and then hydrochloric acid is added to the third water slurry to obtain a fourth water slurry having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. Or (b) filtering and washing the first water slurry and then repulping in water to contain particles of the co-precipitate of the zirconium and the stabilizing element. A second water slurry is obtained, and hydrochloric acid is added to the second water slurry to form a third water having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A slurry is obtained, and then 1 mol part or more of an organic acid is added to 1 mol part of the total amount of zirconium and the stabilizing element to the third water slurry, and the total amount of zirconium and the stabilizing element in terms of oxide is added. A fourth water slurry having a chloride ion content in the range of 4000 to 20,000 ppm by weight is obtained.

Next, as in the case of obtaining the aqueous dispersion of zirconium oxide particles described above, as a third step, the fourth water slurry is subjected to hydrothermal treatment to obtain a stabilized aqueous dispersion of zirconium oxide particles. As a fourth step, the precursor is subjected to an ultrafiltration treatment so that the chloride ion content with respect to the weight of the stabilized zirconium oxide particles is in the range of 1500 to 7000 ppm, preferably 2000 to 5000 ppm, and the zirconium oxide particle concentration is reduced. Usually, an aqueous dispersion of stabilized zirconium oxide particles in the range of 1 to 30% by weight is obtained.

Thus, the aqueous dispersion of stabilized zirconium oxide particles obtained by the method of the present invention has the same properties as the above-mentioned aqueous dispersion of zirconium oxide particles.

That is, when the (stabilized) zirconium oxide particle aqueous dispersion obtained by the method of the present invention has a (stabilized) zirconium oxide particle concentration of 30% by weight, the total light transmittance is 70% or more. In a particle size distribution measurement by a dynamic light scattering method, D50 having a particle diameter of 50% by volume on a volume basis is in a range of 1 to 20 nm, preferably 1 to 10 nm, and a viscosity at a temperature of 25 ° C. immediately after production is 20 mPa · s or less, preferably 10 mPa · s or less, compared to the viscosity at a temperature of 25 ° C. immediately after production, the increase in viscosity at a temperature of 25 ° C. after 24 months of production is 20 mPa · s or less, preferably Is 10 mPa · s or less.

According to a preferred embodiment of the method of the present invention, the aqueous dispersion of the (stabilized) zirconium oxide particles according to the present invention is not affected by the ambient temperature, in particular, not at a refrigeration or freezing temperature of 10 ° C. or lower, but at an ambient temperature. Even after storage for a long period of 40 months or more, an aqueous dispersion of stabilized zirconium oxide particles whose viscosity does not substantially change compared to immediately after production can be obtained.

Next, the production of the (stabilized) zirconium oxide particle organic solvent dispersion by the method of the present invention will be described.

(3) Production of (Stabilized) Organic Solvent Dispersion of Zirconium Oxide Particles According to the method of the present invention, an aqueous dispersion of (stabilized) zirconium oxide particles is passed through the first to fourth steps as described above. Get.

Therefore, according to the present invention, by replacing water, which is a dispersion medium of the aqueous dispersion of (stabilized) zirconium oxide particles, with an organic solvent, the organic solvent is used as a dispersion medium, and the (stabilized) zirconium oxide is dispersed. An organic solvent dispersion of (stabilized) zirconium oxide particles having a chloride ion content based on the weight of the particles in the range of 1500 to 7000 ppm, preferably 2000 to 5000 ppm can be obtained.

において In the present invention, the organic solvent is not particularly limited, but is preferably a water-miscible organic solvent. Such a water-miscible organic solvent is not particularly limited. Examples thereof include aliphatic alcohols such as methanol, ethanol and 2-propanol, aliphatic carboxylic esters such as ethyl acetate and methyl formate, and acetone. , Methyl ethyl ketone, aliphatic ketones such as methyl isobutyl ketone, polyhydric alcohols such as ethylene glycol and glycerin, and a mixture of two or more thereof, particularly preferably methanol, methyl ethyl ketone, methyl isobutyl ketone or Is a mixture of

According to the present invention, in order to replace water as a dispersion medium in an aqueous dispersion of (stabilized) zirconium oxide particles with an organic solvent, the aqueous dispersion is treated with a rotary evaporator to remove water, and then newly. An organic solvent is added, or the aqueous dispersion is subjected to ultrafiltration to remove water as a dispersion medium to obtain a slurry.The slurry is diluted with an organic solvent, and ultrafiltrated again. By repeating filtration and dilution, water, which is the initial dispersion medium, is replaced with an organic solvent, and a (stabilized) zirconium oxide particle organic solvent dispersion in which the dispersion medium is the organic solvent can be obtained.

Further, for example, (stabilized) zirconium oxide particles are obtained by replacing water as a dispersion medium in an aqueous dispersion of (stabilized) zirconium oxide particles with a water-miscible organic solvent and using the water-miscible organic solvent as a dispersion medium. After obtaining the organic solvent dispersion, the water-miscible organic solvent is further replaced with another organic solvent, and a new (stabilized) zirconium oxide particle organic solvent dispersion using the other organic solvent as a dispersion medium is formed. You can also get.

Such a (stabilized) zirconium oxide particle organic solvent dispersion obtained according to the present invention also has the same properties as the (stabilized) zirconium oxide particle aqueous dispersion described above, and has a low viscosity and high transparency. It has excellent long-term storage stability.

As described above, the (stabilized) aqueous dispersion of zirconium oxide particles and the organic solvent dispersion obtained by the method of the present invention may be further subjected to wet media dispersion such as a bead mill, ultrasonic irradiation, high pressure Dispersion treatment using a homogenizer or the like may be performed.

When the (stabilized) zirconium oxide particle aqueous dispersion and the organic solvent dispersion obtained by the above-described method of the present invention have a (stabilized) zirconium oxide particle concentration of 30% by weight, the total light transmittance is 70%. %, And the particle size distribution measured by a dynamic light scattering method has a particle diameter D50 of 50% by volume on a volume basis in the range of 1 to 20 nm, preferably 1 to 10 nm. The viscosity at 20 ° C. is 20 mPa · s or less, preferably 10 mPa · s or less, and the increase in viscosity at a temperature of 25 ° C. after 24 months of production is greater than the viscosity at a temperature of 25 ° C. immediately after the production. It is 20 mPa · s or less, preferably 10 mPa · s or less.

According to a preferred embodiment of the method of the present invention, both the aqueous dispersion and the organic solvent dispersion of the (stabilized) zirconium oxide particles obtained after storage for a long period of 40 months or more at room temperature are maintained. The viscosity is substantially unchanged compared to immediately after production.

As described above, according to the method of the present invention, even in an environment without temperature control, for example, from about 10 ° C. to about 40 ° C., and thus in a normal temperature environment, long-term storage stability can be achieved regardless of the environmental temperature. An aqueous dispersion and an organic solvent dispersion of zirconium oxide nanoparticles having excellent properties can be obtained.

Of course, the aqueous dispersion of the zirconium oxide particles and the organic solvent dispersion according to the present invention may be stored at a refrigerated temperature and then returned to room temperature during use, or may be stored in a frozen state, and then stored during use. Even after thawing to room temperature, there is no change or deterioration in its physical properties and stability.

In the following Examples and Comparative Examples, the ultrafiltration in the fourth step was performed using "Microza" manufactured by Asahi Kasei Chemicals Corporation, Model ACV-3010D (molecular weight cut off 13000) to produce an organic solvent dispersion. , Ultrafiltration when replacing water as a dispersion medium of an aqueous dispersion with an organic solvent was performed using "Microza" manufactured by Asahi Kasei Chemicals Corporation, Model ACP-1010D (molecular weight cut off 13000). .

In the following Examples and Comparative Examples, the particle size distribution, viscosity and total light transmittance of the (stabilized) zirconium oxide particle dispersion, and the chloride ion concentration of the (stabilized) zirconium oxide particle aqueous slurry or dispersion were as follows: Was measured as follows.
Particle Size Distribution D50, D90 and Dmax were measured using a dynamic light scattering particle size distribution analyzer (UPA-UT manufactured by Nikkiso Co., Ltd.). D50, D90 and Dmax are numerical values on a volume basis.
Viscosity The viscosity was measured with a tuning fork vibration type SV viscometer (SV-1A, manufactured by A & D Corp. (measured viscosity range: 0.3 to 1000 mPa · s)).
Using a total light transmittance haze meter (NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.), fill a cell with an optical path length of 10 mm with ion-exchanged water, perform standard calibration, and similarly fill the cell with the dispersion liquid. The total light transmittance was measured. In addition, when the total light transmittance was 50% or more, the dispersion and the dispersion precursor were regarded as transparent.
Chlorine ion concentration Silver nitrate was added to the obtained water slurry and dispersion using an automatic titrator (TS-2000 manufactured by Hiranuma Sangyo Co., Ltd.), and chloride ions were measured by precipitation titration.
Evaluation of long-term storage stability of dispersion A dispersion was manufactured, and when the amount of increase in viscosity when stored at a temperature of 25 ° C for 24 months was 20 mPa · s or less, “（” (for long-term storage stability) Excellent), a dispersion was produced, and when the viscosity increase when stored at a temperature of 25 ° C. for 24 months exceeded 20 mPa · s or when the gel was already gelled, “x” (long-term storage) Inferior in stability).

Example 1
(Production of Stabilized Aqueous Dispersion of Zirconium Oxide Particles (I-1))
First Step 900 L of a mixed aqueous solution of 0.6 mol / L zirconium oxychloride and 0.03 mol / L yttrium chloride was prepared. The mixed aqueous solution of zirconium oxychloride and yttrium chloride is poured into a precipitation reactor in which 1500 L of a 0.9 mol / L potassium hydroxide aqueous solution has been previously poured, and the zirconium oxychloride and yttrium chloride are coprecipitated by a so-called reverse neutralization reaction. Thus, a first water slurry containing particles of the coprecipitate of zirconium and yttrium was obtained. The pH of the obtained first water slurry was 10.

Second step The first water slurry is filtered, washed until the washing filtrate has an electric conductivity of 10 μS / cm or less, repulped again in pure water, and particles of the coprecipitated zirconium and yttrium particles. Was obtained. 42 kg of acetic acid (1.3 mol parts per 1 mol part of the total amount of zirconium and yttrium in the second water slurry) is added to the second water slurry, and the solid content is an oxide of zirconium and yttrium. 600 L of a third water slurry having a converted total weight of 7.5% by weight and a chlorine ion concentration of 8 ppm was obtained. In the third water slurry, the chlorine ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 110 ppm.

Next, 1 kg of 35% hydrochloric acid was added to the third water slurry to obtain a fourth water slurry having a chloride ion concentration of 580 ppm. In the fourth water slurry, the chlorine ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 7,730 ppm.

Third Step The fourth water slurry was subjected to hydrothermal treatment at 190 ° C. for 3 hours to obtain a transparent aqueous dispersion precursor of stabilized zirconium oxide particles.

Fourth step The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated with an ultrafiltration membrane, and the stabilized zirconium oxide particles have a concentration of 30.8% by weight and a concentration of 840 ppm of chloride ions. An aqueous dispersion (I-1) was obtained. In the aqueous dispersion, the chloride ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 2,730 ppm.

(Production of stabilized methanol dispersion of zirconium oxide particles (II-1))
10 kg of the above-mentioned aqueous dispersion of stabilized zirconium oxide particles (I-1) was concentrated using an ultrafiltration membrane, and methanol equivalent to the amount of the obtained filtrate was added to the concentrated dispersion thus obtained. By continuously and simultaneously performing the concentration of the dispersion and the dilution with methanol in parallel, the dispersion medium of the dispersion is converted from water while maintaining the stabilized zirconium oxide content in the dispersion at 30% by weight. The methanol was replaced with methanol to obtain a stabilized zirconium oxide particle methanol dispersion (II-1) having a stabilized zirconium oxide particle concentration of 30.8% by weight and a chlorine ion concentration of 810 ppm. At this time, the amount of methanol used for dilution was 90 L.

塩素 In the methanol dispersion of the stabilized zirconium oxide particles, the chlorine ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 2630 ppm.

Example 2
(Production of stabilized aqueous dispersion of zirconium oxide particles (I-2))
First Step 900 L of a mixed aqueous solution of 0.6 mol / L zirconium oxychloride and 0.03 mol / L yttrium chloride and 680 L of a 1.9 mol / L potassium hydroxide aqueous solution were prepared. The mixed aqueous solution of zirconium oxychloride and yttrium chloride and the aqueous potassium hydroxide solution are simultaneously poured into a precipitation reactor filled with 820 liters of pure water in advance, and the zirconium oxychloride and yttrium chloride are co-precipitated by simultaneous neutralization. And a first water slurry containing particles of the coprecipitate of yttrium. The pH of the resulting first water slurry was 10.2.

Second step The first water slurry is filtered, washed until the washing filtrate has an electric conductivity of 10 μS / cm or less, repulped in pure water, and contains particles of the coprecipitated zirconium and yttrium. A second water slurry was obtained. 42 kg of acetic acid (1.3 mol parts per 1 mol part of the total amount of zirconium and yttrium in the second water slurry) is added to the second water slurry, and the solid content is an oxide of zirconium and yttrium. 600 L of a third water slurry having a converted total weight of 7.5% by weight was obtained.

塩素 The third water slurry had a chlorine ion concentration of 3 ppm. In the third water slurry, the chloride ion content based on the total weight of zirconium and yttrium oxides calculated based on the chloride ion concentration was 40 ppm.

Next, 130 g of 35% hydrochloric acid was added to 60 L of the third water slurry to obtain a fourth water slurry having a chlorine ion concentration of 720 ppm. In the fourth water slurry, the chloride ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 9650 ppm.

Fourth step: The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated by an ultrafiltration membrane, and the stabilized zirconium oxide particles have a concentration of 30.4% by weight and a chlorine ion concentration of 1010 ppm. An aqueous dispersion (I-2) was obtained. In the aqueous dispersion, the chloride ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 3320 ppm.

Example 3
(Production of stabilized aqueous dispersion of zirconium oxide particles (I-3))
Second Step To 60 L of the third water slurry obtained in Example 2, 85 g of 35% hydrochloric acid was added to obtain a fourth water slurry having a chloride ion concentration of 480 ppm. In the fourth water slurry, the chloride ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 6420 ppm.

Fourth step The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated with an ultrafiltration membrane, and the stabilized zirconium oxide particles having a stabilized zirconium oxide concentration of 30.4% by weight and a chloride ion concentration of 670 ppm are obtained. Was obtained as an aqueous dispersion (I-3). In the aqueous dispersion, the chlorine ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 22,10 ppm.

Example 4
(Production of stabilized aqueous dispersion of zirconium oxide particles (I-4))
Second Step To 60 L of the third water slurry obtained in Example 2, 65 g of 35% hydrochloric acid was added to obtain a fourth water slurry having a chlorine ion concentration of 380 ppm. In the fourth water slurry, the chloride ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 5080 ppm.

Fourth step The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated with an ultrafiltration membrane, and the stabilized zirconium oxide particles having a stabilized zirconium oxide concentration of 30.0% by weight and a chloride ion concentration of 530 ppm are obtained. An aqueous dispersion (I-4) was obtained. In the aqueous dispersion, the chloride ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 1770 ppm.

Comparative Example 1
(Production of Stabilized Aqueous Dispersion of Zirconium Oxide Particles (I-5) as Comparative Example)
Second Step To 60 L of the third water slurry obtained in Example 2, 25 g of 35% hydrochloric acid was added to obtain a fourth water slurry having a chloride ion concentration of 140 ppm. In the fourth water slurry, the chlorine ion content based on the total weight of zirconium and yttrium oxide calculated based on the chloride ion concentration was 1,830 ppm.

Fourth step The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated with an ultrafiltration membrane, and the stabilized zirconium oxide particles having a concentration of 30.0% by weight of stabilized zirconium oxide and a concentration of 190 ppm of chloride ion are provided. Was obtained as an aqueous dispersion (I-5). In the aqueous dispersion, the chloride ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 640 ppm.

Comparative Example 2
(Production of Stabilized Aqueous Dispersion of Zirconium Oxide Particles (I-6) as Comparative Example)
Third Step The third water slurry obtained in Example 2 was subjected to hydrothermal treatment at 190 ° C. for 3 hours to obtain a transparent aqueous dispersion precursor of stabilized zirconium oxide particles.

Fourth step The transparent dispersion precursor of the stabilized zirconium oxide particles is washed and concentrated by an ultrafiltration membrane, and the stabilized zirconium oxide particles have a concentration of 30.7% by weight and a chlorine ion concentration of 3 ppm. Was obtained as an aqueous dispersion (I-6). In the aqueous dispersion, the chlorine ion content based on the weight of the stabilized zirconium oxide particles calculated based on the chloride ion concentration was 10 ppm.

Example 5
(Production of aqueous dispersion of zirconium oxide particles (I-7))
First Step 900 L of a 0.6 mol / L zirconium oxychloride aqueous solution and 680 L of a 1.9 mol / L potassium hydroxide aqueous solution were prepared. The zirconium oxychloride aqueous solution and the potassium hydroxide aqueous solution are simultaneously poured into a precipitation reactor filled with 820 L of pure water in advance, and the zirconium oxychloride is precipitated by simultaneous neutralization, so that the first water slurry containing zirconium oxide particles is formed. I got The pH of the obtained first water slurry was 10.

Second step The first water slurry is filtered, washed until the electric conductivity of the water washing filtrate becomes 10 μS / cm or less, then repulped to pure water again, and the second water containing the zirconium oxide particles is removed. A slurry was obtained. 42 kg of acetic acid (1.4 mol parts per 1 mol part of zirconium in the second water slurry) is added to the second water slurry, and the solid content is 7.5 wt% in terms of zirconium oxide. % Of a third water slurry was obtained.

塩素 The chlorine ion concentration of the third water slurry was 6 ppm. In the third water slurry, the chlorine ion content based on the weight of the zirconium oxide particles calculated based on the chloride ion concentration was 90 ppm.

Next, 1.8 kg of the 35% hydrochloric acid of the third water slurry was added to obtain a fourth water slurry having a chloride ion concentration of 1040 ppm. In the fourth water slurry, the chloride ion content based on the weight of the zirconium oxide particles calculated based on the chloride ion concentration was 13,800 ppm.

Third Step The fourth water slurry was subjected to a hydrothermal treatment at 190 ° C. for 3 hours to obtain a transparent aqueous dispersion precursor of zirconium oxide particles.

Fourth Step The precursor of the transparent aqueous dispersion of zirconium oxide particles is washed and concentrated with an ultrafiltration membrane, and the aqueous dispersion of zirconium oxide particles having a zirconium oxide particle concentration of 30.2% by weight and a chloride ion concentration of 1440 ppm ( I-7) was obtained. In this aqueous dispersion, the chloride ion content based on the weight of the zirconium oxide particles calculated based on the chloride ion concentration was 4790 ppm.

(Production of methanol dispersion of zirconium oxide particles (II-7))
10 kg of the aqueous dispersion of zirconium oxide particles (I-7) was concentrated using an ultrafiltration membrane, and methanol equivalent to the amount of the obtained filtrate was added to the concentrated dispersion thus obtained. By performing the concentration of the dispersion and the dilution with methanol continuously and simultaneously in parallel, the dispersion medium of the dispersion is replaced with methanol while maintaining the zirconium oxide particle concentration in the dispersion at 30% by weight. Thus, a methanol dispersion (II-7) of zirconium oxide particles having a concentration of zirconium oxide particles of 30.3% by weight and a chloride ion concentration of 1400 ppm was obtained. At this time, the amount of methanol used for dilution was 90 L. In the methanol dispersion, the chlorine ion content based on the weight of the zirconium oxide particles calculated based on the chloride ion concentration was 4610 ppm.

The methanol was removed from the methanol dispersion of the zirconium oxide particles obtained in Example 5, dried, and the zirconium oxide fine particles thus obtained were observed with a TEM (transmission electron microscope). The primary particle size was about 5 nm.

The methanol is removed from the stabilized zirconium oxide particle methanol dispersion, which is a solid solution containing yttrium, obtained in Examples 1 to 4 and Comparative Examples 1 and 2, and dried. Thus, the obtained stabilized zirconium oxide particle powder is obtained. When observed with a TEM (transmission electron microscope), the average primary particle diameter of the stabilized zirconium oxide particles was about 3 nm.

Table 1 shows the molar excess of alkali to acid when the (mixed) aqueous solution of zirconium oxychloride (and yttrium chloride) (acid) in the above Examples and Comparative Examples was neutralized with potassium hydroxide (alkali). Here, the molar excess is represented by the ratio of the molar amount of the alkali used in the neutralization reaction / the molar amount of the acid used.

The chemical formula of the neutralization reaction of zirconium oxychloride and yttrium chloride with potassium hydroxide is as follows.

ZrOCl ₂ + 2KOH → ZrO (OH) ₂ + 2KCl (1)
YCl ₃ + 3KOH → Y (OH) ₃ + 3KCl (2)
Therefore, the molar excess E of the alkali with respect to the acid can be obtained by the following equation.
E = K / (2Z + 3Y) (3)
Here, K represents the molar amount of potassium hydroxide used, Z represents the molar amount of zirconium oxychloride used, and Y represents the molar amount of yttrium chloride used.

In Examples 1 to 5 and Comparative Examples 1 and 2, the concentration of the aqueous potassium hydroxide solution used in the first step, the pH of the first water slurry obtained in the first step, and the pH of the third slurry obtained in the second step Ion concentration of the water slurry and the chlorine ion content (Cl / ZrO ₂ ) calculated based on the chlorine ion concentration, the fourth water slurry obtained in the second step (Examples 1 to 5 and Comparative Example 1) Table 1 shows the chloride ion concentration (Cl / ZrO ₂ ) calculated based on the chloride ion concentration and the chloride ion concentration. However, the chlorine ion content in Examples 1 to 4 and Comparative Examples 1 and 2 is the chlorine ion content with respect to the total weight of zirconium and yttrium as oxides. It is a chloride ion content with respect to weight.

In addition, the (stabilized) zirconium oxide particle concentration, pH, electric conductivity, particle size distribution, and total light transmission of the (stabilized) zirconium oxide particle aqueous dispersions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 described above. Ratio, chlorine ion content (Cl / ZrO ₂ ) with respect to the weight of the (stabilized) zirconium oxide particles, calculated based on the chlorine ion concentration and the chloride ion concentration, the viscosity at 25 ° C. and the water dispersion of the aqueous dispersion immediately after production. Table 2 shows the results of evaluating the long-term storage stability of the solution.

Further, the (stabilized) zirconium oxide calculated based on the concentration of the methanol dispersion of the zirconium oxide particles obtained in Examples 1 and 5, the particle size distribution, the total light transmittance, and the chloride ion concentration, as well as the chloride ion concentration. Table 3 shows the results of evaluation of chloride ion content (Cl / ZrO ₂ ), water content, viscosity at 25 ° C. immediately after production, viscosity after 7 days from production, and long-term storage stability with respect to the particles.

As shown in Examples 1 to 5, the aqueous dispersion of (stabilized) zirconium oxide particles obtained according to the method of the present invention has high transparency and low viscosity even if it contains fine zirconium oxide particles at a high concentration. In addition, the amount of increase in viscosity when stored at a temperature of 25 ° C. for 24 months is 20 mPa · s or less, and is extremely excellent in long-term storage stability. In particular, according to a preferred embodiment, even after storage for 40 months or more, the viscosity at 25 ° C. is substantially the same as immediately after production, and is extremely excellent in long-term storage stability.

Further, an organic solvent dispersion obtained by replacing water as a dispersion medium of the (stabilized) aqueous dispersion of zirconium oxide particles obtained according to the method of the present invention with an organic solvent is also an aqueous dispersion as shown in Table 3. Similarly to the above, even if it contains fine zirconium oxide particles at a high concentration, it has high transparency and low viscosity, and further, the viscosity increase amount when stored at a temperature of 25 ° C. for 24 months is 20 mPa · s or less. It is remarkably excellent in long-term storage stability. In particular, according to a preferred embodiment, even after storage for 40 months or more, its viscosity at 25 ° C. is substantially the same as immediately after production, and is extremely excellent in long-term storage stability.

Claims

A first step of reacting zirconium oxychloride with a basic substance in water to obtain a first water slurry containing zirconium oxide particles and having a pH in the range of 9.6 to 11.0;
(A) The first water slurry is filtered and washed, and then repulped in water to obtain a second water slurry containing the zirconium oxide particles. The second water slurry contains 1 mol part of zirconium. 1 mol part or more of an organic acid is added to obtain a third water slurry having a chlorine ion content of less than 4000 ppm based on the weight of the zirconium oxide particles, and then hydrochloric acid is added to the third water slurry to obtain a zirconium oxide particle. (B) obtaining a fourth water slurry having a chlorine ion content in the range of 4000 to 20,000 ppm with respect to the weight of (a), or (b) filtering and washing the first water slurry, followed by repulping in water to obtain the zirconium oxide. A second water slurry containing particles is obtained. Hydrochloric acid is added to the second water slurry so that the chlorine ion content with respect to the weight of the zirconium oxide particles is 400%. A third water slurry in the range of 0 to 20,000 ppm is obtained. Then, 1 mol part or more of organic acid is added to 1 mol part of zirconium to the third water slurry, and chlorine ion content based on the weight of zirconium oxide particles is added. A second step of obtaining a fourth water slurry having a rate in the range of 4000 to 20000 ppm;
A third step of hydrothermally treating the fourth aqueous slurry to obtain the zirconium oxide particle aqueous dispersion precursor, and washing the zirconium oxide particle aqueous dispersion precursor by ultrafiltration to obtain a zirconium oxide particle A method for producing an aqueous dispersion of zirconium oxide particles, comprising a fourth step of obtaining an aqueous dispersion of zirconium oxide particles having a chlorine ion content based on weight in the range of 1500 to 7000 ppm.
A salt of zirconium oxychloride and at least one stabilizing element selected from aluminum, magnesium, titanium and rare earth elements is reacted with a basic substance in water to contain particles of a coprecipitate of zirconium and the stabilizing element. a first step of obtaining a first water slurry having a pH in the range of 9.6 to 11.0;
(A) The first water slurry is filtered, washed with water, and then repulped in water to obtain a second water slurry containing particles of the coprecipitated zirconium and the stabilizing element. An organic acid is added to the slurry in an amount of 1 mol part or more based on 1 mol part of the total amount of zirconium and the stabilizing element, and the chlorine ion content is less than 4000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A third water slurry is obtained, and then hydrochloric acid is added to the third water slurry to obtain a fourth water slurry having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. Or (b) filtering and washing the first water slurry and then repulping in water to contain particles of the co-precipitate of the zirconium and the stabilizing element. A second water slurry is obtained, and hydrochloric acid is added to the second water slurry to form a third water having a chloride ion content in the range of 4000 to 20,000 ppm based on the total weight of zirconium and the stabilizing element in terms of oxide. A slurry is obtained, and then 1 mol part or more of an organic acid is added to the third water slurry with respect to 1 mol part of the total amount of zirconium and the stabilizing element, and a total of zirconium and the stabilizing element in terms of oxide is added. A second step of obtaining a fourth water slurry having a chloride ion content based on weight in the range of 4000 to 20,000 ppm,
A third step of hydrothermally treating the fourth water slurry to obtain a stabilized zirconium oxide particle aqueous dispersion precursor which is a solid solution containing the stabilizing element, and the stabilized zirconium oxide particle aqueous dispersion precursor A fourth step of washing by ultrafiltration to obtain an aqueous dispersion of stabilized zirconium oxide particles having a chloride ion content in the range of 1500 to 7000 ppm based on the weight of the stabilized zirconium oxide particles. A method for producing a dispersion.
Water as a dispersion medium of the aqueous dispersion of zirconium oxide particles obtained by the method according to claim 1 is replaced with an organic solvent, and the chlorine ion content relative to the weight of the zirconium oxide particles is in the range of 1500 to 7000 ppm. And a method for producing an organic solvent dispersion of zirconium oxide particles, wherein a dispersion medium of the organic solvent is a zirconium oxide particle whose dispersion medium is the above-mentioned organic solvent.
The water as a dispersion medium of the aqueous dispersion of stabilized zirconium oxide particles obtained by the method according to claim 2 is replaced with an organic solvent, and the chlorine ion content based on the weight of the stabilized zirconium oxide particles is 1500 to 7000 ppm. A method for producing a stabilized zirconium oxide particle organic solvent dispersion, wherein the dispersion medium is a stabilized zirconium oxide particle organic solvent dispersion in which the dispersion medium is the above-mentioned organic solvent.