JPH0791066B2 - Method for producing titanium oxide fine particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing titanium oxide fine particles, and more particularly to a method for producing monodispersed titanium oxide fine particles having high sphericity with high productivity.

[Conventional technology]

Conventionally, as a method for producing monodisperse titanium oxide fine particles with high sphericity and submicron order, the present inventors have
First, in the hydrolysis reaction of titanium alkoxide in alcohol, the concentration of titanium alkoxide in the reaction solution at the start of the reaction to 0.2 mol / or less, the amount of water is controlled to the equivalent or less required for the hydrolysis of titanium alkoxide, When colloidal particles of titanium oxide are formed, 0.5 weight times or more of the total amount of the reaction solution is added to the alcohol, and then the reaction solution is stirred to grow fine particles of titanium oxide, which results in monodisperse and highly sphericity oxidation. A method for producing titanium fine particles was proposed. (JP-A-62-91418).

In order to further improve the yield of titanium oxide fine particles in the above method, the present inventors have a titanium alkoxide concentration of 1.2 mol / in alcohol having a water content of 3 g / or less.
Dissolved in the following, to the resulting titanium alkoxide solution, to start the hydrolysis by adding an alcohol solution of water containing an equivalent amount of water required for the hydrolysis of the titanium alkoxide at a concentration of 100 g / or less, to start the hydrolysis of titanium oxide. When the colloidal particles are produced, an alcohol solution of water having a water concentration of 2 to 10 g / is added in an amount of 0.5 times by weight or more of the total amount of the reaction solution, and then the produced titanium oxide fine particles are grown. Has been proposed (JP-A-62-226814).

[Problems to be solved by the invention]

Both of the above two methods are methods in which the hydrolysis of the titanium alkoxide is performed in an extremely dilute system, and therefore it is necessary to repeatedly use the solvent alcohol after use in order to improve the industrial profitability. Dehydration was essential for repeated use of alcohol. However, for dehydration of alcohol, metals such as Na and Mg, silica gel,
Since the use of a water absorbing agent such as zeolite or the like or the rectification operation is required, it has been a cause of complicating the production process of the titanium oxide fine particles and reducing productivity and economic efficiency.

Therefore, the object of the present invention is that the dehydration treatment of the alcohol after use is not necessary and the alcohol can be reused as it is. Therefore, it is simple and highly productive and economical, and it is monodisperse and has high sphericity. It is to provide a method capable of manufacturing.

[Means for solving problems]

The present invention, as a solution to the above problems, a solution obtained by dissolving titanium alkoxide in an alcohol having a water content of 3 g / or less in a concentration of 2 to 5 mol /, and a water concentration of 6
Mix hydrous alcohol with g / or less so that the total water / titanium molar ratio is 2.5 or less, and when the reaction solution becomes cloudy, add hydrous alcohol with water concentration of 5 g / or less to the total amount of the reaction solution. A method for producing fine titanium oxide particles, which comprises the steps of adding 0.5 times by weight or more and making the total water / titanium molar ratio 4.4 or less, and then growing the fine titanium oxide particles produced by the cloudiness. Is.

According to the method of the present invention, after the nucleation of a certain amount of titanium oxide fine particles is generated, only the grain growth with these nuclei as the nuclei is promoted, and the subsequent nucleation is suppressed. Fine oxide particles are obtained.

The titanium oxide obtained here is generally a hydrate, but is simply referred to as “titanium oxide” in the present specification.

The titanium alkoxide solution used in the first step of the method of the present invention contains titanium alkoxide as a raw material in an amount of 2 to 5 mol using an alcohol having a water content of 3 g / or less as a solvent.
It is prepared by dissolving in a concentration of 1 /, preferably 3.5 to 4.5 mol /.

Examples of the titanium alkoxide used here include titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, etc., preferably titanium ethoxide, titanium propoxide, titanium butoxide. Alcohol used as a solvent is a good solvent of titanium alkoxide, and those having compatibility with water are suitable, and specific examples include methanol, ethanol, and methanol denatured alcohol (9: 1 mixture of ethanol-methanol). ),
Propanol and the like, preferably ethanol can be mentioned.

The alcohol used has a water content of 3 g / or less, preferably 2 g / or less. When the content of water exceeds 3 g /, a rapid hydrolysis reaction of titanium alkoxide occurs immediately after the raw material titanium alkoxide is dissolved in alcohol, and it becomes difficult to control the nucleation and particle growth of titanium oxide fine particles. Therefore, titanium oxide fine particles having high monodispersity cannot be obtained.

Since the concentration of the reaction product in the hydrolysis reaction of the titanium alkoxide is too low when the concentration of the titanium alkoxide is less than 2 mol /, when the concentration of the titanium alkoxide exceeds 5 mol /, the reaction in the hydrolysis reaction of the titanium alkoxide Since the concentration of the product becomes too high, it becomes difficult to control the nucleation and grain growth of titanium oxide fine particles, and it is not possible to obtain titanium oxide fine particles having high monodispersity.

In the first step of the present invention, the total amount of water / titanium (H ₂ O / Ti) is obtained by mixing the titanium alkoxide alcohol solution obtained as described above and a hydrous alcohol having a water concentration of 6 g / or less. The mixture is mixed so that the molar ratio thereof is 2.5 or less, preferably 1.8 to 2.2, and the hydrolysis reaction is started.

Here, the overall H ₂ O / Ti molar ratio is the ratio of the total number of moles of water in the alcohol solution of the mixed titanium alkoxide and water in the hydrous alcohol to the number of moles of the titanium alkoxide used. Say.

The water-containing alcohol has a water concentration of 6 g / or less, preferably 4.5 to 5.5 g /. The concentration of water in hydrous alcohol exceeds 6 g /, and the total H ₂ O / Ti molar ratio is
When it exceeds 2.5, the concentration of the reaction product in the hydrolysis reaction becomes too high, so that the uniformity of the particle diameter of the obtained titanium oxide fine particles is deteriorated, and the titanium oxide fine particles having high monodispersity cannot be obtained. If the amount of water required for the hydrolysis of the titanium alkoxide is too small, the yield will be low and the nucleation by hydrolysis will take time, resulting in non-uniform nucleation and impairing the monodispersity of the reaction product. It becomes easy and not preferable.

Next, in the second step, the titanium oxide colloidal particles are produced by the progress of the above-mentioned hydrolysis reaction, and when the particles become cloudy, the concentration of water is 5 g / or less, preferably 2.5 to 3.5. The reaction solution is diluted by adding g / hydrous alcohol to suppress nucleation and promote grain growth.
When the concentration of water in the hydrous alcohol added to dilute the reaction solution exceeds 5 g /, the content of water in the alcohol recovered by solid-liquid separation of titanium oxide fine particles is 3 g.
In order to reuse the recovered alcohol in the method of the present invention in excess of /, dehydration treatment is required, which makes it impossible to achieve simplification of the process and is disadvantageous in terms of economy and productivity. On the other hand, if it exceeds 5 g / titanium oxide fine particles are aggregated and the particle size distribution of the fine particles is likely to be polydispersed. If the concentration of water is too low, the yield of titanium oxide fine particles will be low, which is not preferable. The hydroalcohol to be added is for diluting the solution, and those exemplified for the above-mentioned hydrolysis can be used, but it may be different from the alcohol used at the time of hydrolysis.

Usually, after mixing the alcoholic solution of titanium alkoxide and the hydrous alcohol in the first step described above, white turbidity due to titanium oxide fine particles is observed when several tens of seconds have passed at room temperature. This cloudiness is due to the fact that the concentration of Ti (OH) ₄ produced by hydrolysis exceeds the critical saturation point and Ti (OH) ₄ becomes a precursor for nucleation to form titanium oxide nuclei by a condensation reaction and colloid particles. It is thought that it grew and became visible to the extent that it became. Therefore, by appropriately selecting the time until the addition of the hydroalcohol in the second step, the number of nuclei formed is controlled, and only those nuclei are grown to produce titanium oxide fine particles having an arbitrary particle size. It is possible.

The hydroalcohol is required to be 0.5 times by weight or more of the total amount of the reaction solution, preferably 0.8 to 1.5 times by weight.
The H ₂ O / Ti molar ratio is 4.4 or less, preferably 3.0 to 4.0. The total molar ratio of H ₂ O / Ti as used herein means the moles of the raw material titanium alkoxide used in the total moles of water in the alcohol and hydrous alcohol used in the first step and the second step. A ratio to a number.

The addition of this hydroalcohol suppresses the subsequent nucleation of titanium oxide, and the obtained particles have high monodispersity. When the amount of the hydrous alcohol added is less than 0.5 times by weight, the particles obtained have low monodispersity.
It is considered that this is because the concentration of Ti (OH) ₄ produced again reached the critical saturation point or higher and the precipitation of colloidal particles was restarted, resulting in the inclusion of finer particles. When the total H ₂ O / Ti molar ratio exceeds 4.4, the resulting titanium oxide fine particles are likely to be polydispersed.

In the method of the present invention, next, after stopping the new nucleation of colloidal particles by adding the hydrous alcohol,
Grain growth is preferably carried out while stirring the solution. This stirring is an operation for uniformly aggregating the nuclei generated by hydrolysis throughout the solution to prevent agglomeration of particles,
It is also performed by bringing the nuclei into contact with a fresh Ti (OH) ₄ solution to promote neospherical grain growth. The stirring method is not particularly limited, and may be, for example, an ordinary propeller-type stirrer,
It may be performed by ultrasonic waves.

The particle growth rate of titanium oxide is high until a certain time after the addition of the hydroalcohol, but becomes slower as the particles grow. Therefore, titanium oxide fine particles having different particle diameters can be obtained by appropriately selecting the time, and it is easy to control the particle diameter in the submicron order.

The titanium oxide fine particles having a desired particle size thus obtained are dispersed by ultrasonic waves in a dilute solution of ammonia water, a surfactant, or the like in order to prevent the particles from aggregating, followed by centrifugation or the like. Solid-liquid separation is carried out, and the particles are collected and dried by an appropriate method to obtain titanium oxide fine particles having high sphericity and monodispersity.

As described above, the alcohol recovered after the method of the present invention has a water content of 3 g / or less, and can be reused as it is in the process of the present invention without dehydration treatment.

The titanium oxide fine particles obtained by the method of the present invention are amorphous hydrates and usually crystallize at around 400 ° C., but if necessary, after dispersion treatment in water at 40 ° C. or higher and heat treatment, It is possible to obtain crystalline titanium oxide fine particles while maintaining monodispersibility and sphericity even at extremely low temperatures. For example, according to the dispersion treatment at 40 ℃, crystallization by heating at 120 ℃, 60
Crystallization occurs even at 80 ° C when dispersed at temperatures above ℃. When crystallized by heat treatment, the titanium oxide fine particles become porous, but at too high a temperature, the pores are fused and become fine particles. Therefore, it is preferable to properly use the conditions of this heat treatment depending on the use of titanium oxide.

The method of dispersion treatment is not particularly limited, and may be, for example, a stirrer or ultrasonic waves. This dispersion treatment may be carried out for a time such that the titanium oxide fine particles are sufficiently dispersed in water, and is not particularly limited.

The atmosphere for the heat treatment is not particularly limited, and may be any atmosphere such as air or oxygen.

The thus obtained sphericity and high monodispersity, the submicron-order titanium oxide fine particles are optimal as a raw material powder for sintered ceramics, and therefore, an electronic material such as barium titanate (BaTiO ₃ ), It is useful as a raw material titanium oxide such as lead zirconate titanate (PZT).

Moreover, it is optimal as a raw material for pigments, paints, catalyst carriers, gems, etc., because it is a fine particle powder with high monodispersity. Further, when it is used as a cosmetic product, since it is a fine particle having a high sphericity and a high monodispersity, it is easy to obtain a cosmetic product with a good rust. Further, since the specific surface area of the titanium oxide fine particles obtained by the method of the present invention is 100 to 150 m ² / g, the particle diameter is 100 to 150 A.
Can be inferred. This has a particle size most suitable for protecting the skin from ultraviolet rays, and can be suitably used as a raw material for cosmetics such as sunscreen cream and foundation.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Examples 1-5, Comparative Examples 1-2 Titanium isopropoxide Ti (OC ₃ H _{7) 4} ethanol dissolved in a concentration of 4.0 mol / (water content 2.0 g /) (A solution) 25 m
l for water concentrations of 4.0, 4.5, 5.0, 5.5, 6.0, 6.2 and 6.5
It was added to each 700 ml of water-containing ethanol (solution B) having g /.

When 30 to 90 seconds had passed after the addition, each solution became cloudy.

Immediately after visually confirming this white turbidity, 750 ml of ethanol (solution C) having a water concentration of 3.0 g / was added to each solution, and the solutions were stirred to grow titanium oxide fine particles. About 2
After a lapse of time, the reaction solution was subjected to a centrifugal separator to perform solid-liquid separation of titanium oxide fine particles and alcohol.

The obtained fine particles are stored in ammonia water at pH 10.5 at room temperature for 15
After ultrasonically dispersing for a minute, the mixture was centrifuged again. This dispersion treatment was repeated 3 times, the treatment liquid was decanted, and then vacuum dried at 80 ° C. for 16 hours.

Scanning electron microscope (SEM) of the obtained titanium oxide fine particles
A photograph was taken, and sphericity, monodispersity and particle size were evaluated according to the following criteria.

(1) Roundness I: Extremely high.

II: High.

III: Low.

(2) Particle size measurement method The particle size of 50 particles is randomly measured by SEM photograph,
A range of particle diameters in which 40 particles are included around the average particle diameters is obtained.

(3) Monodispersity Monodispersion: 70% or more of all measured particles have a mode diameter of ±
Included within 20%.

Almost monodisperse: 50 to 70% of all measured particles are contained within ± 20% of the mode diameter.

Polydispersity: Less than 50% of all measured particles have a mode diameter of ±
Included within 20%.

Further, it was found by X-ray diffraction that the dry powder of the titanium oxide fine particles was amorphous. Further, by differential thermal analysis (DTA-TG), X-ray diffraction and SEM observation, the fine particles were crystallized at around 400 ° C. and converted into anatase-type titanium oxide without changing the particle shape. It was found that the dry powder was a hydrate represented by TiO ₂ .1.5H ₂ O, because all the weight loss was thought to be due to dehydration. Based on this finding, the yield of titanium oxide fine particles with respect to the raw material alkoxide was calculated.

Further, the alcohol obtained by the solid-liquid separation,
After simple distillation to separate unreacted titanium alkoxide (including a reaction intermediate), the water content was measured by the Karl Fischer method.

The above results are shown in Table 1.

Examples 6 to 9 and Comparative Examples 3 to 4 As the liquid B, only 700 ml of hydrous ethanol having a water concentration of 5.0 g / was used, and as the liquid C, the water concentrations were 2.5 and 3.5, respectively.
Titanium oxide fine particles were produced in the same manner as in Example 1 except that 750 ml of ethanol, which was 4.0, 4.5, 5.2, and 6.0 g /, was used. The diameter and yield and the content of water in the recovered alcohol were measured.

The results are shown in Table 1.

Comparing the results of Examples 1 to 5 and Comparative Examples 1 and 2 shown in Table 1, the hydroalcohol used for hydrolysis (liquid B)
If the concentration of water in the mixture exceeds 6 g /, the sphericity and monodispersity of the titanium oxide fine particles obtained will decrease, and the overall H ₂ O / Ti molar ratio at the start of the hydrolysis reaction will be 2.5. It can be seen that the titanium oxide fine particles become polydispersed when the amount exceeds the limit.
Further, from the results of Examples 6 to 9 and Comparative Examples 3 to 4, when the concentration of water in the hydrous alcohol added for suppressing the nucleation of titanium oxide fine particles exceeds 5 g /, the titanium oxide fine particles obtained are Both sphericity and monodispersity decrease,
Furthermore, from the results of Comparative Example 4, it is found that the titanium oxide fine particles obtained are polydispersed when the total molar ratio of H ₂ O / Ti at the time of adding the hydrous alcohol exceeds 4.4.

〔The invention's effect〕

In the method of the present invention, the alcohol recovered after the production of the titanium oxide fine particles can be reused as it is in the step of the present invention without performing a regeneration treatment such as dehydration. Therefore, it is possible to produce titanium oxide fine particles having a high sphericity and a high degree of monodispersity and a particle size of submicron order with high productivity and high yield, and the method of the present invention is a production method having high industrial practicality. is there.

Claims (2)

[Claims] 1. A solution obtained by dissolving a titanium alkoxide in an alcohol having a water content of 3 g / or less at a concentration of 2 to 5 mol /, and a hydrous alcohol having a water concentration of 6 g / or less, as a whole. When the reaction solution becomes turbid, the hydrous alcohol containing water at a concentration of 5 g / or less than 0.5 weight times the total amount of the reaction solution and more than the total amount of water / titanium is mixed. A method for producing titanium oxide fine particles, which comprises the steps of adding so that the molar ratio is 4.4 or less, and then growing the titanium oxide fine particles generated by the cloudiness. 2. The method for producing titanium oxide fine particles according to claim 1, wherein amorphous titanium oxide fine particles obtained by growing the produced titanium oxide fine particles are used.
A production method comprising a step of performing dispersion treatment in water at a temperature of ℃ or higher, and then heat treatment.