JP2005179111A - Method for manufacturing zirconia sol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a zirconia sol of a colloid region having a uniform particle size distribution and excellent in stability. <P>SOLUTION: This manufacturing method comprises the following steps (a)-(d) and the sol in which fine zirconia particles whose average particle diameter is within a range of 5-100 nm are dispersed is manufactured; (a) a step of preparing a dispersion of a zirconium hydroxide gel by adding an aqueous alkali solution to an aqueous zirconium compound solution in the presence of a particle growth regulator, (b) a step of washing the zirconium hydroxide gel, (c) a step of hydrothermally treating a dispersion of the zirconium hydroxide gel in the presence of a particle growth regulator, (d) a step of washing the hydrothermally treated zirconium hydroxide gel. In the steps, the particle growth regulator is a carboxylic acid or a hydroxycarboxylic acid and the hydrothermal treatment is carried out within a temperature range of 100-250°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a colloidal zirconia sol having excellent stability.

Conventionally, colloidal particles such as silica, alumina, titania, zirconia, zinc oxide, antimony pentoxide, cerium oxide, tin oxide, silica-alumina, silica-zirconia, etc. are known, and to adjust the refractive index as an optical material It is blended and used for coatings.
For example, silica is used as a low refractive index material, alumina is used as a medium refractive index material, and titania, zirconia, and the like are used as high refractive index materials. At this time, although titania sol is excellent in that it has a high refractive index, there are problems in light resistance, weather resistance, and the like due to the dispersion stability, photocatalytic activity of titanium oxide depending on the usage and application. For this reason, it has been attempted to improve dispersion stability, light resistance, weather resistance, etc. by combining other components, such as silica components, but depending on the composite component, the refractive index can be lowered. In addition to this, it is difficult to completely suppress the photocatalytic activity, so that the light resistance, weather resistance, etc. may be insufficient.

On the other hand, zirconia sol has substantially no photocatalytic activity and is excellent in light resistance, weather resistance, etc. Conventionally, as a method for producing zirconia sol, an aqueous solution containing a water-soluble zirconium salt such as zirconium oxychloride is hydrolyzed. The method of making it known is known.
Further, JP-A-6-166519 (Patent Document 1) discloses that an aqueous solution containing a water-soluble zirconium salt is brought into contact with an anion exchange resin, and the anion of the zirconium salt is ion-exchanged with a hydroxyl ion. A method for producing a zirconia sol is described, in which a smooth gel-like substance is obtained, and the obtained gel-like substance is dispersed in water and an organic acid such as acetic acid is added.
JP-A-5-24844 (Patent Document 2) describes a method for producing a hydrated zirconia sol in which the acid concentration of a slurry-like mixture containing zirconium hydroxide and an acid is controlled and heat-treated, Examples of the acid include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, and organic acids such as acetic acid and citric acid.

However, as in Patent Document 1 or Patent Document 2, a zirconia sol is prepared by adding an organic acid or inorganic acid such as citric acid citric acid to a hydrolyzate such as zirconium hydroxide and a zirconium hydroxide gel. However, it was difficult to obtain a colloidal zirconia sol having a uniform particle size distribution and excellent stability.
JP-A-6-166519 JP-A-5-24844

  It is an object of the present invention to produce a colloidal zirconia sol having a uniform particle size distribution and excellent stability.

The present invention is a method for producing a sol in which zirconia fine particles having an average particle diameter in the range of 5 to 100 nm are dispersed, comprising the following steps (a) to (d).
(A) a step of preparing a dispersion of zirconium hydroxide gel by adding an alkaline aqueous solution to a zirconium compound aqueous solution in the presence of a particle growth regulator (b) a step of washing the zirconium hydroxide gel (c) particle growth A step of hydrothermally treating the dispersion of the zirconium hydroxide gel in the presence of a modifier (d) a step of washing the hydrothermally treated zirconium hydroxide gel

The zirconia fine particle-dispersed sol washed in the step (d) may be concentrated or diluted.
The particle growth regulator is preferably carboxylic acid or hydroxycarboxylic acid.
The hydrothermal treatment is preferably performed in a temperature range of 100 to 250 ° C.
In the step (b), the conductivity of the zirconium hydroxide gel dispersion is preferably 10 μS / cm or less, and in the step (d), the conductivity of the zirconia sol is preferably 200 μS / cm or less. .

  According to the present invention, it is possible to produce a zirconia sol having a relatively small particle size, a uniform particle size distribution, a non-aggregate, and excellent dispersibility and stability. Moreover, since this zirconia sol is excellent in transparency, light resistance, weather resistance, etc., it is suitable as a high refractive index material, a refractive index adjusting agent, etc. in optical materials.

Hereinafter, the manufacturing method of the zirconia sol of this invention is demonstrated in order of a process.
Step (a)
Zirconium compounds used in the present invention include zirconium chloride (ZrCl ₂ ), zirconium oxychloride (ZrOCl ₂ ), zirconium nitrate, zirconyl nitrate, zirconium sulfate, zirconium carbonate, zirconium acetate and the like, as well as zirconium alkoxides.
First, an aqueous solution of a zirconium compound is prepared. The concentration of the zirconium compound aqueous solution at this time is preferably in the range of 0.1 to 5% by weight, more preferably 0.2 to 3% by weight in terms of ZrO ₂ . When the concentration is less than 0.1% by weight, the yield and production efficiency are low. On the other hand, when the concentration exceeds 5% by weight, the particle size of the resulting zirconia sol tends to be non-uniform.

As the particle growth regulator used in the present invention, carboxylic acid, carboxylate, hydroxycarboxylic acid, or hydroxycarboxylate is used.
Specifically, monocarboxylic acids and monocarboxylic acid salts such as formic acid, acetic acid, succinic acid, acrylic acid (unsaturated carboxylic acid), gluconic acid, malic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid And polyvalent carboxylic acids such as sebacic acid, maleic acid, fumaric acid, and phthalic acid, and polyvalent carboxylic acid salts.
Further, α-lactic acid, β-lactic acid, γ-hydroxyvaleric acid, glyceric acid, tartaric acid, citric acid, tropic acid, hydroxycarboxylic acid and hydroxycarboxylate of benzylic acid can be mentioned.

  In the step (a), the particle growth regulator or the aqueous solution of the particle growth regulator is mixed with the zirconium compound aqueous solution. At this time, the molar ratio (Cm / Zm) between the number of moles of zirconium compound (Zm) and the number of moles of grain growth regulator (Cm) is in the range of 0.01 to 1, more preferably 0.1 to 0.5. Preferably there is. When the molar ratio is less than 0.01, a coarse zirconium hydroxide hydrogel is formed or a heterogeneous zirconium hydroxide hydrogel is formed. Therefore, it is obtained by hydrothermal treatment in the step (c) described later. The particle diameter of the zirconia sol to be obtained may not be uniform or the average particle diameter may not be 100 nm or less. On the other hand, even when the molar ratio exceeds 1, there is a problem that the particle size is not made uniform or the effect of suppressing the average particle size is not further improved, and the economy is lowered.

Next, an aqueous alkali compound solution is added to the zirconium compound aqueous solution containing the particle growth regulator while sufficiently stirring.
As the alkaline aqueous solution, a basic aqueous solution such as aqueous ammonia or organic amine can be used in addition to an aqueous alkali metal solution such as aqueous NaOH or KOH.
The aqueous alkali solution is added so that the zirconium compound aqueous solution has a pH of 3 to 12, more preferably 4 to 11. When the pH is less than 3, the hydrolysis of the zirconium compound may be insufficient, or washing in the step (b) described later may be difficult. On the other hand, even if the pH exceeds 12, the step described later ( Cleaning in b) may be difficult.
In addition, the temperature of the zirconium compound aqueous solution when adding the alkaline aqueous solution is not particularly limited, but it is usually preferably in the range of 10 to 50 ° C, more preferably 15 to 40 ° C.

Step (b)
Next, the produced dispersion of zirconium hydroxide hydrogel is washed.
The washing method is not particularly limited as long as it can remove cations, anions, or salts, and a conventionally known method can be adopted. For example, an ultrafiltration membrane method, a filtration separation method, a centrifugal filtration method, an ion Examples include the exchange resin method.
Among these, the ion exchange resin method is preferable because the ion concentration after washing can be effectively reduced. In this case, it is efficient to wash with an ion exchange resin method after washing with an ultrafiltration membrane method in advance. As the ion exchange resin, both ion exchange resins can be used, or a cation exchange resin and an anion exchange resin can be sequentially used.
The conductivity after washing is preferably 10 μS / cm or less, more preferably 5 μS / cm or less. When the electric conductivity after washing exceeds 10 μS / cm, the effect of the particle growth regulator cannot be obtained sufficiently, or the particle size distribution of the obtained zirconia sol tends to be non-uniform.
Further, the pH of the washed zirconium hydroxide hydrogel dispersion at this time is approximately in the range of 5-8.

Step (c)
Next, the zirconium hydroxide gel dispersion is hydrothermally treated in the presence of a particle growth regulator.
The concentration of the washed zirconium hydroxide hydrogel dispersion obtained in the step (b) is 0.1 to 20% by weight, more preferably 0.2 to 15% by weight, particularly 0.5 to 10% by weight in terms of ZrO _2. It is preferable to adjust to the range. When this concentration is less than 0.1% by weight, the particle size distribution becomes uniform, but the yield and production efficiency are lowered. On the other hand, if the concentration exceeds 20% by weight, aggregates may be formed in the resulting zirconia sol.

Thereafter, a particle growth regulator or an aqueous solution of the particle growth regulator is added to the zirconium hydroxide hydrogel dispersion. As the particle growth regulator, the same ones as described above can be used.
The amount of the particle growth regulator added at this time is determined by the molar ratio (Cmc / Zmc) between the number of moles of ZrO ₂ (Zmc) and the number of moles of grain growth regulator (Cmc) in the zirconium hydroxide hydrogel dispersion. , 0.05 to 0.8, and more preferably 0.1 to 0.5. When the molar ratio (Cmc / Zmc) is less than 0.05, aggregates may be generated in the silica sol, or it may be difficult to obtain a silica sol having an average particle size of 100 nm or less. On the other hand, if the molar ratio (Cmc / Zmc) exceeds 0.8, particle growth or crystallization is greatly suppressed, so that it takes a long time to grow to a desired particle diameter or crystallization is insufficient. For this reason, it may be difficult to obtain a zirconia sol having a desired refractive index or a desired particle size.

Next, the zirconium hydroxide hydrogel dispersion containing the particle growth regulator is heated with sufficient stirring and hydrothermally treated. It is preferable to disperse the aggregate of zirconium hydroxide hydrogel as much as possible by irradiating ultrasonic waves before or during the temperature rise.
When the aggregate of the zirconium hydroxide hydrogel is dispersed, coarse particles are not present in the obtained zirconia sol, and a zirconia sol having a more uniform particle size distribution tends to be obtained.
The hydrothermal treatment temperature is preferably in the range of 100 to 250 ° C, more preferably 120 to 200 ° C. When the temperature is lower than 100 ° C., it may take a long time for particle growth, or it may be difficult to obtain a zirconia sol having a desired refractive index or a desired particle size. On the other hand, even if the hydrothermal treatment temperature exceeds 250 ° C., the effect of further shortening the particle growth time is small, and in some cases, the particle size distribution may be non-uniform or coarse particles may be generated.
The hydrothermal treatment time is not particularly limited and is usually 0.5 to 12 hours, although it varies depending on the treatment temperature.

Step (d)
A zirconia sol is prepared by washing the hydrothermally treated zirconium hydroxide hydrogel dispersion obtained in step (c).
As a cleaning method in the step (d), an ultrafiltration membrane method is preferable in that an excess particle growth regulator can be removed. Further, if necessary, washing with an ion exchange resin can be performed before and / or after washing by the ultrafiltration membrane method. The ion exchange resin method is preferable because the ion concentration after washing can be effectively reduced.
The conductivity of the zirconia sol obtained here is preferably about 200 μS / cm or less. Moreover, it is preferable that the pH of a zirconia sol is about 3-5. When the conductivity and pH of the zirconia sol are in the above ranges, the zirconia sol is excellent in stability.

Step (e)
Although the zirconia sol obtained in the step (d) can be used as it is, it can be used after being concentrated or diluted depending on its use. As a method of concentration, a conventionally known method can be employed. For example, it may be concentrated by heating with a rotary evaporator or the like, or further concentrated under reduced pressure, or concentrated by an ultrafiltration membrane method. You can also.
The conductivity of the zirconia sol thus obtained is preferably 200 μS / cm or less, more preferably 100 μS / cm or less. Further, the pH of the zirconia sol at this time is approximately in the range of 3 to 5. When the conductivity and pH of the zirconia sol are in the above ranges, the zirconia sol is excellent in stability.

According to the method of the present invention, a sol in which zirconia fine particles having an average particle diameter of 5 to 100 nm, further 10 to 50 nm are dispersed is obtained. When the average particle diameter is less than 5 nm, the refractive index tends to decrease because of insufficient crystallization of zirconia.
A zirconia sol having an average particle diameter exceeding 100 nm can be obtained without using the method of the present invention. Moreover, even if it is obtained, the zirconia sol becomes cloudy or has low transparency, and there is a limit to applications.

In the present invention, the average particle diameter of the fine particles in the zirconia sol was photographed with a transmission electron micrograph (TEM), and the particle diameters of 50 particles were measured and averaged.
The fine particles in the zirconia sol obtained by the method of the present invention had a refractive index measured by the standard refractive index liquid method in the range of 1.7 to 2.2.

  The zirconia sol using water as a dispersion medium obtained in the present invention can be replaced with an organic solvent such as alcohol, glycol, ester, ether, ketone or the like as required to obtain an organozirconia sol. Such an organozirconia sol, for example, can be suitably used as an optical material for a refractive index adjuster of a hard coat film for a resin lens, an antireflection film, or the like.

Preparation of zirconia sol (1) 65.5 g of zirconium oxychloride octahydrate ( ZrOCl ₂ .8H ₂ O) was dissolved in 2432 g of pure water, and 5.5 g of malic acid (Cm / Zm = 0.2) was added thereto. Then, 313 g of a 10 wt% KOH aqueous solution was added to prepare a zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1 wt%). At this time, the pH of the dispersion was 10.5 and the temperature was 19 ° C.
Subsequently, it was washed by an ultrafiltration membrane method until the electric conductivity reached 280 μS / cm. Next, 95 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: SK1-BH) was added to the zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) for deionization. Next, after the cation exchange resin was separated, 50 g of an anion exchange resin (manufactured by Mitsubishi Chemical Corporation: SANUPC) was added for deionization. The conductivity of the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) thus obtained was 3.6 μS / cm and pH was 7.2.

Next, 197 g (Cmc / Zmc = 0.14) of a malic acid aqueous solution having a concentration of 2% by weight was added to the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration of 1% by weight), and ultrasonic waves were irradiated for 1 hour. After the dispersion treatment, the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 640 μS / cm and the pH was 2.53.
Next, 110 g of an anion exchange resin (manufactured by Mitsubishi Chemical Co., Ltd .: SANUPC) was added for deionization, followed by washing with an ultrafiltration membrane method while supplying 3750 g of pure water. At this time, the conductivity was 47 μS / cm, and the pH was 3.4. Thereafter, it was concentrated to prepare zirconia sol (1). In TEM observation of the obtained zirconia sol (1), coarse particles and fine particles were not observed. The average particle diameter, pH and conductivity of zirconia sol (1) were measured, and the results are shown in Table 1. The refractive index was measured by the following method, and the results are shown in Table 1.

Refractive index measurement (1) A zirconia sol is taken in an evaporator and the dispersion medium is evaporated.
(2) Dry at 120 ° C. to obtain a powder.
(3) A standard refractive index liquid having a known refractive index is dropped in the form of a few drops of glass substrate, and zirconia powder is mixed therewith.
(4) The operation of (3) is performed with various standard refractive index liquids, and the refractive index of the standard refractive index liquid when the mixed liquid becomes transparent is set as the refractive index of the zirconia particles.

Preparation of zirconia sol (2) A washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) was prepared in the same manner as in Example 1, and 141 g of malic acid aqueous solution (Cmc / Zmc = 2% by weight) was prepared. 0.10) was added and ultrasonic waves were applied for 1 hour to disperse the hydrogel, and then the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 620 μS / cm and the pH was 2.65.
Next, a zirconia sol (2) was prepared in the same manner as in Example 1. In TEM observation of the obtained zirconia sol (2), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (2) were measured, and the results are shown in Table 1.

Preparation of zirconia sol (3) A washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1 wt%) was prepared in the same manner as in Example 1, and 703 g (Cmc / Zmc = Cmc / Zmc = 2 wt% malic acid aqueous solution) was prepared. 0.550) was added and ultrasonic waves were applied for 1 hour to disperse the hydrogel, and then the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 680 μS / cm and the pH was 2.45.
Next, a zirconia sol (3) was prepared in the same manner as in Example 1. In TEM observation of the obtained zirconia sol (3), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (3) were measured, and the results are shown in Table 1.

Preparation of zirconia sol (4) In Example 1, a zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1 wt%) was prepared in the same manner except that 2.8 g of malic acid (Cm / Zm = 0.1) was added. Prepared. At this time, the pH of the dispersion was 10.5 and the temperature was 19 ° C.
Subsequently, washing with an ultrafiltration membrane method, deionization with a cation exchange resin, and deionization with an anion exchange resin were performed. The washed zirconium hydroxide hydrogel dispersion thus obtained (ZrO ₂ concentration 1% by weight) had an electric conductivity of 3.0 μS / cm and a pH of 7.0.
Thereafter, hydrothermal treatment was performed in the same manner as in Example 1. The zirconia sol obtained by hydrothermal treatment had an electric conductivity of 640 μS / cm and a pH of 2.60.
Subsequently, deionization with an anion exchange resin was performed, and the membrane was washed by an ultrafiltration membrane method. The electric conductivity at this time was 45 μS / cm, and the pH was 3.3. Then, it concentrated and the zirconia sol (4) was prepared. In TEM observation of the obtained zirconia sol (4), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (4) were measured, and the results are shown in Table 1.

Preparation of zirconia sol (5) In Example 1, except that 13.8 g of malic acid (Cm / Zm = 0.5) was added, a zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) was prepared. Prepared. At this time, the pH of the dispersion was 10.5 and the temperature was 20 ° C.
Subsequently, washing with an ultrafiltration membrane method, deionization with a cation exchange resin, and deionization with an anion exchange resin were performed. The washed zirconium hydroxide hydrogel dispersion thus obtained (ZrO ₂ concentration 1 wt%) had an electric conductivity of 10 μS / cm and a pH of 7.2.
Thereafter, hydrothermal treatment was performed in the same manner as in Example 1. The zirconia sol obtained by hydrothermal treatment had an electric conductivity of 680 μS / cm and a pH of 2.50.
Subsequently, deionization with an anion exchange resin was performed, and the membrane was washed by an ultrafiltration membrane method. At this time, the electric conductivity was 80 μS / cm and the pH was 3.0. Then, it concentrated and the zirconia sol (5) was prepared. In TEM observation of the obtained zirconia sol (5), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (5) were measured, and the results are shown in Table 1.

Preparation of zirconia sol (6) 65.5 g of zirconium oxychloride octahydrate ( ZrOCl ₂ .8H ₂ O) was dissolved in 2432 g of pure water, and 8.53 g of citric acid monohydrate (Cm / Zm = 0. 2) was added, and then 313 g of a 10 wt% KOH aqueous solution was added to prepare a zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1 wt%). At this time, the pH of the dispersion was 10.5 and the temperature was 19 ° C.
Subsequently, it was washed by an ultrafiltration membrane method until the electric conductivity reached 280 μS / cm. Next, 95 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: SK1-BH) was added to the zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) for deionization. Next, after the cation exchange resin was separated, 50 g of an anion exchange resin (manufactured by Mitsubishi Chemical Corporation: SANUPC) was added for deionization. The conductivity of the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) thus obtained was 3.6 μS / cm, and the pH was 7.0.

Next, 273 g of a 2% by weight aqueous citric acid solution (Cmc / Zmc = 0.14) was added to the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight), and ultrasonic waves were applied for 1 hour to irradiate the hydrogel. After the dispersion treatment, the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 660 μS / cm and the pH was 2.45.
Next, 110 g of an anion exchange resin (manufactured by Mitsubishi Chemical Co., Ltd .: SANUPC) was added for deionization, followed by washing with an ultrafiltration membrane method while supplying 3750 g of pure water. At this time, the electric conductivity was 55 μS / cm and the pH was 3.2. Thereafter, it was concentrated to prepare zirconia sol (6). In TEM observation of the obtained zirconia sol (6), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (6) were measured, and the results are shown in Table 1.

Preparation of zirconia sol (7) In 2432 g of pure water, 65.5 g of zirconium oxychloride octahydrate ( ZrOCl ₂ .8H ₂ O) was dissolved, to which 6 g of tartaric acid (Cm / Zm = 0.2) was added. Then, 313 g of a 10 wt% KOH aqueous solution was added to prepare a zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1 wt%). At this time, the pH of the dispersion was 10.5 and the temperature was 19 ° C.
Subsequently, it was washed by an ultrafiltration membrane method until the electric conductivity reached 280 μS / cm. Next, 95 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: SK1-BH) was added to the zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) for deionization. Next, after the cation exchange resin was separated, 50 g of an anion exchange resin (manufactured by Mitsubishi Chemical Corporation: SANUPC) was added for deionization. The conductivity of the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) thus obtained was 3.6 μS / cm, and the pH was 7.0.

Next, 213 g (Cmc / Zmc = 0.14) of a tartaric acid aqueous solution having a concentration of 2% by weight was added to the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration of 1% by weight), and ultrasonic waves were irradiated for 1 hour to disperse the hydrogel. After the treatment, the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 655 μS / cm and the pH was 2.50.
Next, 110 g of an anion exchange resin (manufactured by Mitsubishi Chemical Co., Ltd .: SANUPC) was added for deionization, followed by washing with an ultrafiltration membrane method while supplying 3750 g of pure water. At this time, the electric conductivity was 50 μS / cm and the pH was 3.3. Then, it concentrated and the zirconia sol (7) was prepared. In TEM observation of the obtained zirconia sol (7), coarse particles and fine particles were not observed. The average particle diameter, refractive index, pH and conductivity of zirconia sol (7) were measured, and the results are shown in Table 1.

Comparative Example 1

Preparation of zirconia sol (R1) Zirconium hydroxide hydrogel by adding 313 g of 10% by weight KOH aqueous solution to an aqueous solution of 65.5 g of zirconium oxychloride octahydrate ( ZrOCl ₂ .8H ₂ O) in 2432 g of pure water A dispersion (ZrO ₂ concentration 1% by weight) was prepared. At this time, the pH of the dispersion was 12.0, and the temperature was 20 ° C.
Subsequently, it was washed by an ultrafiltration membrane method until the electric conductivity reached 280 μS / cm. Next, 95 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: SK1-BH) was added to the zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) for deionization. Next, after the cation exchange resin was separated, 50 g of an anion exchange resin (manufactured by Mitsubishi Chemical Corporation: SANUPC) was added for deionization. The washed zirconium hydroxide hydrogel dispersion thus obtained (ZrO ₂ concentration 1% by weight) had an electric conductivity of 3.5 μS / cm and a pH of 7.3.

Next, the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) was irradiated with ultrasonic waves for 1 hour to disperse the hydrogel, then filled in an autoclave, and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 650 μS / cm and the pH was 2.65.
Next, 110 g of an anion exchange resin (manufactured by Mitsubishi Chemical Co., Ltd .: SANUPC) was added for deionization, followed by washing with an ultrafiltration membrane method while supplying 3750 g of pure water. At this time, the electric conductivity was 49 μS / cm and the pH was 3.5. Thereafter, it was concentrated to prepare zirconia sol (R1). In the TEM observation of the obtained zirconia sol (R1), it was secondary particles having an average particle diameter of 115 nm in which primary particles of about 40 nm were aggregated.
The average particle diameter, refractive index, pH and conductivity of zirconia sol (R1) were measured, and the results are shown in Table 1.

Comparative Example 2

Preparation of zirconia sol (R2) Zirconium hydroxide hydrogel was prepared by adding 313 g of 10 wt% KOH aqueous solution to an aqueous solution of 65.5 g of zirconium oxychloride octahydrate ( ZrOCl ₂ .8H ₂ O) in 2432 g of pure water. A dispersion (ZrO ₂ concentration 1% by weight) was prepared. At this time, the pH of the dispersion was 12.0, and the temperature was 20 ° C.
Subsequently, it was washed by an ultrafiltration membrane method until the electric conductivity reached 280 μS / cm. Next, 95 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: SK1-BH) was added to the zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration: 1% by weight) for deionization. Next, after the cation exchange resin was separated, 50 g of an anion exchange resin (manufactured by Mitsubishi Chemical Corporation: SANUPC) was added for deionization. The conductivity of the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration 1% by weight) thus obtained was 3.5 μS / cm and pH was 7.3.

Next, 197 g (Cmc / Zmc = 0.14) of a malic acid aqueous solution having a concentration of 2% by weight was added to the washed zirconium hydroxide hydrogel dispersion (ZrO ₂ concentration of 1% by weight), and ultrasonic waves were irradiated for 1 hour. After the dispersion treatment, the autoclave was filled and hydrothermally treated at 200 ° C. for 2 hours. A zirconia sol was obtained by hydrothermal treatment, but the conductivity was 650 μS / cm and the pH was 2.65.
Next, 110 g of an anion exchange resin (manufactured by Mitsubishi Chemical Co., Ltd .: SANUPC) was added for deionization, followed by washing with an ultrafiltration membrane method while supplying 3750 g of pure water. At this time, the electric conductivity was 50 μS / cm and the pH was 3.45. Thereafter, it was concentrated to prepare zirconia sol (R2). In the TEM observation of the obtained zirconia sol (R2), it was secondary particles having an average particle diameter of 105 nm in which primary particles of about 25 nm were aggregated.
The average particle diameter, refractive index, pH and conductivity of zirconia sol (R2) were measured, and the results are shown in Table 1.

Claims (6)

A method for producing a sol in which zirconia fine particles having an average particle diameter in the range of 5 to 100 nm are dispersed, comprising the following steps (a) to (d).
(A) a step of preparing a dispersion of zirconium hydroxide gel by adding an alkaline aqueous solution to a zirconium compound aqueous solution in the presence of a particle growth regulator (b) a step of washing the zirconium hydroxide gel (c) particle growth A step of hydrothermally treating the dispersion of the zirconium hydroxide gel in the presence of a modifier (d) a step of washing the hydrothermally treated zirconium hydroxide gel   The method for producing a zirconia sol according to claim 1, wherein the zirconia fine particle-dispersed sol after washing in the step (d) is concentrated or diluted.   The method for producing a zirconia sol according to claim 1 or 2, wherein the particle growth regulator is a carboxylic acid or a hydroxycarboxylic acid.   The method for producing a zirconia sol according to any one of claims 1 to 3, wherein the hydrothermal treatment is performed in a temperature range of 100 to 250 ° C.   The method for producing a zirconia sol according to any one of claims 1 to 4, wherein the conductivity of the zirconium hydroxide gel dispersion is set to 10 µS / cm or less in the step (b). The method for producing a zirconia sol according to any one of claims 1 to 5, wherein an electric conductivity of the zirconia sol is set to 200 µS / cm or less in the step (d).