Titanium oxide dispersion

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a titanium oxide dispersion having excellent dispersibility and which can be widely used for applications such as electronic materials such as crystalline ceramic powder, ultraviolet shielding materials, paints, cosmetics and photocatalysts.

【0002】

[Conventional technology]

Titanium oxide powder has been used as a white pigment for a long time, and in recent years, it has been widely used as a sintering material used for electronic materials such as a constituent material of capacitors and thermistors, and a raw material of crystalline ceramic powder such as barium titanate. Has been done. Further, since titanium oxide exhibits a large refractive index in the wavelength region near visible light, almost no light absorption occurs in the visible light region. For this reason, it has recently been widely used in materials such as cosmetics, pharmaceuticals, and paints that require UV shielding. Furthermore, by irradiating titanium oxide with light having an energy equal to or greater than its bandgap, titanium oxide is excited to generate electrons in the conduction band and holes in the conduction band. Applications for photocatalytic reactions that utilize oxidizing power are being actively developed. This titanium oxide photocatalyst has a wide variety of uses, such as hydrogen generation due to water decomposition, exhaust gas treatment, air purification, deodorization, sterilization, antibacterial, water treatment, and stain prevention for lighting equipment. Is being done.

【0003】

As described above, titanium oxide has a wide variety of uses, but when titanium oxide powder is used as a pigment, paint, sintered material, etc., it is often suspended and dispersed in water or an organic solvent, and in that case, it is oxidized. Dispersibility of titanium powder in a solvent becomes a problem. Specifically, after the titanium oxide powder is dispersed in a solvent, it aggregates and precipitates. In particular, when ultrafine titanium oxide of 1 μm or less is dispersed, there is a problem that the viscosity of the dispersion becomes high when the concentration of titanium oxide contained is increased.

【0004】

Further, in the titanium oxide sol for a photocatalyst, in order to prevent the aggregation of titanium oxide particles, the pH of the sol or the aqueous solution must be adjusted to the acidic side, and when forming the photocatalyst from the sol, the base material or application. Was limited. In the titanium oxide dispersion for the ultraviolet shielding material, there arises a problem that the ultraviolet shielding property deteriorates due to the aggregation of the titanium oxide particles.

【0005】

In titanium oxide for electronic materials, for example, barium titanate, which is a dielectric substance, is prepared using barium compounds such as titanium oxide and barium carbonate as raw materials. At this time, titanium oxide is suspended and dispersed in a solvent to form barium. After mixing with the compound, it is sintered. Since the particle size of barium titanate to be prepared mainly depends on the particle size of titanium oxide as a raw material, titanium oxide, which is a raw material of finer particles, must be used in order to prepare finer particles. In order to cope with the recent miniaturization of electronic materials, ultrafine titanium oxide of 1 μm or less is required. However, as titanium oxide is atomized, the dispersibility in the solvent deteriorates, and when suspended in the solvent, the fine particles aggregate with each other. When barium titanate is prepared as described above, the fine particles of titanium oxide are collected. On the contrary, when the particle size becomes large or when the product is sintered, it does not react uniformly, and when the product is viewed at the molecular level, the dispersion of titanium and barium is non-uniform. As a result, the properties as an electronic material are adversely affected.

【0006】

In order to solve the problem of dispersibility of titanium oxide powder as described above, it has been attempted to coat the surface of titanium oxide particles with a hydrophobic substance having originally high dispersibility such as silica and alumina. For example, in Japanese Patent Application Laid-Open No. 5-218126, the pH of an aqueous aluminum basic salt solution is adjusted to 10.5 to 12.0 with an acid, a titanium dioxide slurry is mixed with the aqueous solution, and then this is neutralized with an acid to form a surface of titanium dioxide particles. A method for uniformly precipitating aluminum oxide hydrate is disclosed. Further, Japanese Patent Application Laid-Open No. 7-257923 discloses an aqueous dispersion of titanium oxide using a condensed phosphate such as sodium hexametaphosphate as a dispersant.

【0007】

[Problems to be Solved by the Invention]

However, since the conventional method for improving the dispersibility of the titanium oxide powder as described above or the dispersion uses a component other than titanium oxide such as a coating with a foreign substance on the surface of the titanium oxide particles or a dispersant for a metal salt. , Titanium oxide is difficult to apply because it changes the original properties and adversely affects the properties of photocatalysts and electronic materials.

【0008】

Therefore, an object of the present invention is to provide a titanium oxide dispersion capable of uniform dispersion even when added at a high concentration without coating with a foreign substance and without using a metal salt dispersant. It is in.

【0009】

[Means for Solving the Invention]

In such a situation, as a result of diligent studies by the present inventors, if titanium oxide powder is added to the peroxotitanic acid-containing dispersion medium and dispersed by high-speed stirring, a uniform dispersion state is maintained even if the addition concentration is increased, and the viscosity is maintained. We have found that a highly dispersible titanium oxide dispersion that does not rise so much can be obtained, and that the titanium oxide powder can be uniformly dispersed in water in a neutral region, and the present invention has been completed. ..

【0010】

That is, the present invention provides a titanium oxide dispersion characterized in that titanium oxide powder is uniformly dispersed in a peroxotitanic acid-containing dispersion medium.

【0011】

The present invention also provides a titanium oxide film, which is characterized by being formed from the titanium oxide dispersion. Further, the present invention provides a method for producing a titanium oxide dispersion, which comprises adding titanium oxide powder to a peroxotitanium acid-containing dispersion medium and then stirring the dispersion to which the titanium oxide is added at high speed. It is to provide.

【0012】

BEST MODE FOR CARRYING OUT THE INVENTION

The titanium oxide used in the present invention can be produced by various methods. For example, (1) a method of hydrolyzing a titanium-containing solution such as titanyl sulfate or titanium sulfate, (2) a method of hydrolyzing an organic titanium compound such as titanium alkoxide, (3) a halogen such as titanium trichloride or titanium tetrachloride. A method of neutralizing or hydrolyzing an aqueous solution of titanium tetrachloride, (4) a vapor phase method in which titanium tetrachloride is contacted with oxygen in the gas phase to oxidize it, and (5) a flammable gas such as hydrogen gas that burns to generate water. And oxygen is supplied to the combustion burner to form a flame, and a method such as a flame hydrolysis method in which titanium tetrachloride is introduced into the flame can be mentioned. Of these, the dry method is preferable in that a titanium oxide powder having desired particle characteristics can be obtained at low cost.

【0013】

Among the above-mentioned methods for producing titanium oxide, as a method for obtaining higher-purity titanium oxide and lower-cost titanium oxide, titanium tetrachloride such as (4) vapor phase method or (5) flame hydrolysis method is used. Is preferable in the gas phase (titanium tetrachloride vapor phase oxidation method), and this method does not mix or remain impurity elements such as titanium oxide obtained by the liquid phase method, and other than titanium oxide. Since it is a high-purity titanium oxide powder containing almost no components, when it is used as an electronic material, an ultraviolet shielding material or a photocatalyst, the original characteristics of titanium oxide do not change and an excellent effect can be obtained.

【0014】

The production method of the titanium oxide powder produced by the vapor phase method of (4) will be specifically described. First, the liquid titanium tetrachloride is preheated, vaporized, and introduced into the reactor. Next, at the same time as the introduction of titanium tetrachloride, oxygen gas is introduced into the reactor to carry out an oxidation reaction. The oxidation reaction temperature is 500 to 1200 ° C, preferably 600 to 1100 ° C. Further, during the oxidation reaction, it is preferable to supply hydrogen gas or water vapor together with titanium tetrachloride and oxygen gas into the reaction furnace from the viewpoint of controlling the rutile formation rate. The titanium oxide powder is produced by the oxidation reaction, and then the titanium oxide powder is cooled. As a cooling method, a cooling tank provided with a cooling jacket or the like is usually used, and a method of cooling while contacting an inert gas such as nitrogen gas with the generated titanium oxide powder can be mentioned. Then, the cooled titanium oxide powder is collected, and the chlorine gas remaining in the titanium oxide powder is removed by heat treatment to obtain the titanium oxide powder. Examples of the heat treatment include vacuum heat treatment, heating in an air or nitrogen gas atmosphere, steam treatment, and the like. Further, if necessary, the produced titanium oxide may be classified. It is also preferable to pulverize or crush the titanium oxide thus obtained. As a crushing or crushing method, a vibration mill, a ball mill, a disc mill, a turbo mill, a tower mill, a paint shaker, a lightning crusher, a vibration crusher and the like are used.

【0015】

The particle properties such as the particle size and specific surface area of the titanium oxide powder used in the present invention are not particularly limited because they differ depending on the use of the titanium oxide dispersion, but the average particle size is preferably 0.01 to 5 μm, more preferably 0.01 to 5 μm. It is 0.05 to 2 μm, more preferably 0.1 to 1 μm, and the specific surface area is preferably 0.5 to 100 m.²/ g, more preferably 1-50m²/ g, more preferably 2-30m²/ g. For example, in the case of a photocatalyst and an electronic material, the titanium oxide powder is preferably as fine as possible from the viewpoint of enhancing the photocatalytic performance and maintaining the characteristics of the electronic material.

【0016】

In addition, the crystal type cannot be unequivocally specified and may be adjusted according to the intended use. For example, for sintered materials, pigments or UV shielding materials, the rutile type is preferable, and the rutileization rate is usually 10 to 100%. It is preferably 50 to 100%, while the anatase type is preferable for the photocatalyst, and the rutileization rate is 0 to 80%, preferably 0 to 50%.

【0017】

Further, in the titanium oxide used in the present invention, Fe, Al, Si and Na contained in the titanium oxide powder as impurities are each less than 20 ppm, preferably less than 10 ppm, and more preferably less than 5 ppm. In addition, Cl in the titanium oxide powder is less than 500 ppm, preferably less than 200 ppm, and more preferably less than 100 ppm. If impurities are contained in excess of the above range, the photocatalytic performance is deteriorated in the case of photocatalytic use, and it becomes a factor of deteriorating the electronic material characteristics in the case of electronic material use.

【0018】

The peroxotitanic acid used in the present invention is also called peroxytitanic acid or titanium peroxide, and its structure is H.₄TiO₅, Ti (OOH) (OH)₃Or TiO₃ 2H₂Indicated by O. Peroxotinic acid is usually treated as a yellow, tan or reddish brown transparent viscous aqueous solution (sol solution), and commercially available ones can be used. Examples of commercially available products include "PTA-85" and "PTA-170" (both are PTA aqueous solutions manufactured by Tanaka Transfer Co., Ltd.). It can also be prepared by a known method. For example, an aqueous solution of titanium tetrachloride is hydrolyzed with aqueous ammonia to produce a slurry containing titanium hydroxide, which is washed and then hydrogen peroxide is added. Obtain an aqueous solution of peroxytitanic acid.

【0019】

The dispersion medium containing peroxotitanic acid is not particularly limited, and examples thereof include water and alcohols such as methanol and ethanol, of which water is preferable. The dispersion medium can be used alone or in admixture of two or more. When the dispersion medium is water, a commercially available peroxotitanic acid aqueous solution can be used as it is. The blending ratio of peroxotitanic acid and the dispersion medium is appropriately determined depending on the type of the dispersion medium, the concentration of the titanium oxide powder added, and the use of the titanium oxide dispersion.

【0020】

As a method for uniformly dispersing the titanium oxide powder in the peroxotitanate-containing dispersion medium, a general method may be used. For example, the titanium oxide powder produced by the vapor phase oxidation method or the like is used as the peroxotitanate-containing dispersion medium. Add and disperse using means such as high-speed stirring and shaking with a homogenizer, Henschel mixer and super mixer, or use a crusher such as a vibration mill or ball mill to disperse the titanium oxide powder and peroxotitanic acid-containing dispersion medium. A method of wet pulverization can be mentioned, and among these, the method of high-speed stirring at 1000 to 15000 rpm is preferable because it can be efficiently performed in a short time. To add titanium oxide powder to the peroxotitanic acid-containing dispersion medium, it depends on the amount of titanium oxide powder added and the production capacity of the titanium oxide dispersion, but a small amount is added continuously or dividedly. Is desirable. The amount of titanium oxide powder added once per 100 ml of the peroxotitanic acid-containing dispersion medium is preferably 0.1 to 5 g, preferably 0.5 to 2 g, because a high-concentration uniform dispersion can be efficiently obtained. At the time of dispersion, in order to improve the dispersion efficiency, the peroxotitanic acid-containing dispersion medium may be heated. The heating temperature is room temperature to 100 ° C, preferably 30 to 80 ° C. When the peroxotitanic acid aqueous solution is heat-treated, the titanium oxide powder can be partially precipitated, and the concentration of the titanium oxide powder can be adjusted.

【0021】

The method of adding titanium oxide powder to the peroxotitanic acid-containing dispersion medium is not limited to this, and a method of simultaneously adding titanium oxide powder and peroxotitanic acid to the dispersion medium and stirring, or adding titanium oxide powder in advance. Examples thereof include a method of adding peroxotitanic acid to the dispersion medium and stirring the mixture. In the present invention, a method of adding titanium oxide powder to an aqueous solution of peroxotitanic acid and stirring it, a method of simultaneously adding and stirring peroxotitanium acid and titanium oxide powder to a dispersion medium, or adding peroxotitanic acid to a dispersion medium. After that, a method of adding titanium oxide powder and stirring is preferable.

【0022】

The ratio of peroxotitanic acid in the titanium oxide dispersion of the present invention is 1 to 100% by weight, preferably 5 to 80% by weight, and more preferably 10 to 50% by weight with respect to the titanium oxide powder. The concentration of the titanium oxide powder in the titanium oxide dispersion varies depending on the intended use and is arbitrary, but is 0.5 to 60% by weight, preferably 5 to 60% by weight, and more preferably 10 to 60% by weight. Since the titanium oxide dispersion of the present invention is extremely excellent in dispersibility of the titanium oxide powder, it can be contained in an amount of 50% by weight or more as the concentration of the titanium oxide powder. That is, in the titanium oxide dispersion of the present invention, even if the concentration of titanium oxide is increased, the viscosity of the dispersion itself does not increase so much, so that it is possible to prepare a high concentration titanium oxide dispersion that could not be achieved in the past. is there.

【0023】

In the titanium oxide dispersion of the present invention, in the case of an aqueous dispersion, the pH thereof can be arbitrarily adjusted depending on the intended use, but in the present invention, the pH is 5 to 10, preferably pH 6 to 8, particularly preferably pH 6.5 to 7.5. is there. Since the surface of the titanium oxide particles originally contains a hydroxyl group, the dispersibility is not good in the neutral region. Therefore, as described above, the conventional titanium oxide sol adjusts the pH to be acidic and improves the dispersibility. Therefore, when a titanium oxide film is formed by spraying titanium oxide sol on a base material to prepare a photocatalyst or an ultraviolet shielding material, a base material that corrodes under acid cannot be used, and its use is limited. However, the titanium oxide dispersion of the present invention exhibits extremely high dispersibility even in the neutral region as described above, and is therefore very effective as a photocatalyst or an ultraviolet shielding material.

【0024】

As described above, since the titanium oxide powder of the present invention has a high concentration and high dispersion of titanium oxide powder, it is used for forming a titanium oxide film such as a photocatalyst, a pigment, an ultraviolet shielding material such as a paint or a cosmetic, or titanium. It can be used for all purposes such as a raw material for crystalline ceramic powder such as barium acid acid, which is dispersed in a solvent. The titanium oxide film may be formed from the titanium oxide dispersion of the present invention by a known method. For example, a sprayer filled with the titanium oxide dispersion is used to spray the substrate in a desired amount, and then spraying the film into a desired amount. A method of drying or heat-treating at room temperature can be used.

【0025】

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the present specification, the dispersity of the titanium oxide dispersion, the particle size distribution in the titanium oxide dispersion, the amount of impurities in the titanium oxide powder, and the rutileization rate were measured by the methods shown below.

【0026】

(Dispersity A method) Put 5 g of titanium oxide powder and 45 ml of dispersion medium in a container, stir at a high speed of 10000 rpm with a homogenizer for 20 minutes at room temperature, disperse, and let stand at room temperature for 144 hours. Then, the supernatant is removed, only the precipitated titanium oxide powder is separated and dried, and the weight (g) thereof is measured, and this weight value is defined as the degree of dispersion. The smaller the value of the degree of dispersion, the better the dispersibility. (Dispersity B method) Put titanium oxide powder and a dispersion medium in a container, stir at a high speed of 10000 rpm with a homogenizer for 20 minutes at room temperature, disperse, and let stand at room temperature for 144 hours. Then, the dispersion is transferred from the container to a measuring cylinder and the appearance is visually observed. The evaluation is performed by indicating that the mark indicates almost no separation, and the × mark indicates that a large amount of separated and precipitated titanium oxide powder is observed.

【0027】

(Particle size distribution) Laser light scattering method The measurement was performed using a particle size measuring machine LA700 (manufactured by HORIBA, Ltd.).

【0028】

(Quantitative analysis of impurities) Fe, Al, Si and Na in titanium oxide powder were quantitatively analyzed by atomic absorption spectroscopy, and chlorine was measured by absorptiometry.

【0029】

(Rutilation rate) According to ASTM D 3720-84, the peak area (Ir) of the strongest diffraction line (plane index 110) of rutile-type crystalline titanium oxide and the strongest diffraction line (plane) of anatase-type crystalline titanium oxide in the X-ray diffraction pattern. The peak area (Ia) of the index 101) was calculated from the above formula.

【0030】

Example 1 Titanium oxide obtained by the vapor phase method, with an average particle size (BET diameter) of 0.03 μm and a specific surface area (BET) of 46 m.²0.5 g of titanium oxide powder with / g, rutileization rate of 33.3%, Fe, Al, Si and Na content of 10 ppm or less and chlorine content of 80 ppm in 45 ml (dispersion medium) of 0.85 wt% peroxotitanic acid aqueous solution. It was added in 10 portions each, stirred and dispersed to obtain a titanium oxide dispersion. This manufacturing method was carried out in accordance with the dispersion degree A method, and as a result, the dispersion degree was 0.5.

【0031】

Comparative example 1 A dispersion was obtained in the same manner as in Example 1 except that water was used instead of the 0.85% by weight peroxotitanic acid aqueous solution. The dispersity (method A) of this titanium oxide dispersion was 2.5.

【0032】

Comparative example 2 A dispersion was obtained in the same manner as in Example 1 except that a 0.27% by weight ammonium polyacrylate aqueous solution was used instead of the 0.85% by weight peroxotitanate aqueous solution. The dispersity (method A) of this titanium oxide dispersion was 1.1.

【0033】

Comparative example 3 A dispersion was obtained in the same manner as in Example 1 except that a 0.27% by weight sodium polyacrylate aqueous solution was used instead of the 0.85% by weight peroxotitanate aqueous solution. The dispersity (method A) of this titanium oxide dispersion was 4.8.

【0034】

Comparative example 4 A dispersion was obtained in the same manner as in Example 1 except that a poison-containing aqueous solution was used instead of the 0.85% by weight peroxotitanic acid aqueous solution. "Poise" is a surfactant manufactured by Kao, and the concentration added was 0.22% by weight. The dispersity (method A) of this titanium oxide dispersion was 1.0.

【0035】

The dispersion of Example 1 showed excellent dispersibility. Further, although the dispersions of Comparative Examples 2 and 4 have excellent dispersibility, they contain substances other than titanium oxide, and when they are used for a photocatalyst or an electronic material, their characteristics may be adversely affected.

【0036】

Example 2 5 g of the same titanium oxide powder used in Example 1 was added to 45 ml of a 0.85 wt% peroxotitanic acid aqueous solution in 10 divided doses of 0.5 g each, and the mixture was stirred at a high speed of 10000 rpm with a homogenizer for 20 minutes at room temperature. The mixture was dispersed to obtain a titanium oxide dispersion. The particle size distribution of this dispersion was measured and the results are shown in Table 1.

【0037】

Comparative example 5 A titanium oxide dispersion was obtained by the same method as in Example 2 except that water was used instead of the 0.85% by weight peroxotitanic acid aqueous solution. The particle size distribution of this dispersion was measured by the same method as in Example 2. The results are shown in Table 1.

【0038】

[table 1]

<img file="JP2001220141A_D0001.tif" />The particle size distributions D90, D50, and D10 indicate the integrated particle size of 90%, 50%, and 10% (μm), respectively.

【0039】

From Example 2 and Comparative Example 5, it is clear that D50 and D90 are smaller than the peroxotitanic acid-free dispersion of Comparative Example 5 and the titanium oxide powder is not aggregated in the particle size distribution by the laser light scattering method. is there.

【0040】

Examples 3 to 6 The same titanium oxide powder used in Example 1 was added to 45 ml of a peroxotitanic acid aqueous solution (dispersion medium) under the conditions shown in Table 2, and the powder was prepared by a method based on the dispersion degree B method, and the dispersion degree was evaluated. .. The results are shown in Table 2. However, the concentration of peroxotitanic acid was adjusted to a concentration of 20% by weight with respect to the titanium oxide powder. In Table 2, the values in parentheses indicate the mixing ratio of titanium oxide powder in the dispersion.

【0041】

Comparative Example 6 and Comparative Example 7 The procedure was the same as in Example 5 except that water (Comparative Example 6) and a 1% aqueous solution of ammonium polyacrylate (PAA) (Comparative Example 7) were used instead of the peroxotitanate aqueous solution. The results are shown in Table 2.

【0042】

[Table 2]

<img file="JP2001220141A_D0002.tif" />【0043】

[Effect of the invention]

As described above, the titanium oxide dispersion of the present invention is a highly dispersed titanium oxide dispersion unlike the conventional titanium oxide sol or titanium oxide dispersion, and therefore, it is a titanium oxide film such as a photocatalyst or an ultraviolet shielding material. It is effective for forming and as a raw material for crystalline ceramic powder such as barium titanate.