JP2000247638A - Production of liquid dispersion of crystalline titanium dioxide grains - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a liquid dispersion of crystalline titanium dioxide grains which is capable of forming a titanium dioxide coating film having good adhesion and a high density. SOLUTION: This production process comprises: adding a hydrogen peroxide aqueous solution to an aqueous solution of a titanium-containing raw material to form a peroxotitanium complex; thereafter adding a basic substance to the peroxotitanium complex to obtain a solution; allowing this solution to stand or heating the solution, to form a precipitate of a polymer of peroxotitanium hydrate; then removing at least dissolved components other than water from the titanium-containing raw material aqueous solution, from the precipitate; and thereafter heating the resulting precipitate in such a state that water is not separated, to >=70 deg.C and maintaining the precipitate at that temperature, to produce the objective crystalline titanium dioxide grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crystalline titanium oxide particle-dispersed liquid, and more particularly to a crystalline titanium oxide useful as a titanium oxide coating agent used for forming a titanium oxide film on a substrate. The present invention relates to a method for producing an oxide particle dispersion liquid.

[0002]

2. Description of the Related Art A titanium oxide film is formed by applying a titanium oxide powder slurry or an aqueous solution of titanium chloride or titanium sulfate to a substrate, followed by baking, or applying a sol prepared by hydrolysis of a metal alkoxide to the substrate. A sol-gel method of post-baking, a sputtering method of sputtering an oxide target in a high vacuum to form a film on a substrate, and a method of evaporating an organometallic compound or a halide and decomposing it in a heating furnace to form a film on the substrate. There are a CVD method, a plasma spraying method in which solid particles are melted in a plasma generated in the atmosphere, and the substrate surface is irradiated. Among them, a method using a coating liquid as a method for forming a titanium oxide film is said to be simple and highly practical.

[0003] The coating method using titanium oxide powder is simple, but it is difficult to obtain a dense and good-adhesion film, and the formation of a titanium oxide film generally requires a high synthesis temperature. It is necessary to use a heat-resistant substrate that can withstand
There are limitations on the types of substrates that can be applied. Further, in order to obtain a dispersion liquid of the fine particles of titanium oxide, an acid or a suitable organic dispersant is generally used, and there is a drawback that harmful halogen compounds and the like are generated by firing. Further, the method of applying and sintering an aqueous solution of titanium chloride or titanium sulfate generates harmful halogen compounds, and requires a sintering temperature of several hundred degrees or more.

[0004] Commercially available titanium oxide sols prepared by the sol-gel method can be applied and impregnated, can be coated over a large area, can be synthesized at low temperatures, and have many industrial advantages. However, titanium tetraisopropoxide and tetrabutyl titanate are available. Therefore, there is a problem that the raw material is expensive, and the raw material is chemically unstable, is easily affected by temperature control and atmosphere, and is difficult to handle. In addition, the sol-gel method requires heating at 400 ° C. or higher to remove by baking because it contains an acid or an organic substance in the raw material sol. There was a problem that it was easy.

In addition, the sol-gel method is complicated and requires the use of an organic solvent. The titanium oxide sol prepared by the sol-gel method contains an acid, an alkali or an organic substance, and causes corrosion of the material to be coated. There was a problem. Further, a temperature of 400 ° C. or more is required to decompose organic substances, and there is a drawback that harmful halides, nitrogen oxides, and the like are formed as byproducts during heating and firing.

As described above, it is difficult to produce a high-density crystalline titania film at a low temperature by the conventional method. In the sol-gel method which can be produced at a relatively low temperature, organic substances and acids are decomposed and eliminated by heat treatment. Is required, which also causes the porous body to be easily made porous. To produce a film having a high density, the heat treatment temperature had to be relatively high. There is also a drawback that these auxiliaries generate harmful substances such as nitrogen oxides and organic gases by heat treatment.

[0007] In contrast to such a method, when forming a titanium oxide film from peroxotitanium hydrate, it is known that a film having good characteristics can be formed at a relatively low temperature. Peroxotitanium hydrate is obtained by adding hydrogen peroxide solution directly to a solution of titanium tetrachloride, titanium sulfate, etc.
It is known to produce peroxotitanium hydrate ions, which condense and form in the form of solid precipitates. Further, peroxotitanium hydrate ions are generated as polynuclear ions containing two or more titanium atoms at a pH of 1 or more, and gradually condensed and precipitated at room temperature. Therefore, since it is difficult to use a titanium oxide coating agent at a pH of 1 or more, the types of substrates to which a strongly acidic coating agent having a pH of 1 or less can be applied are limited. In addition, there is also a problem that the contained halogen and sulfur generate harmful substances such as hydrogen halide and sulfur oxide by the heat treatment.

Further, in order to produce a high-purity titanium oxide film, a hydrogen peroxide solution is directly added to titanium hydride or alkoxytitanium to dissolve it,
That is, it has been proposed in Japanese Patent Application Laid-Open No. 62-252319 to produce a substance considered to be a peroxotitanium hydrate. However, these titanium raw materials are not stable, and have a drawback that a considerable exothermic reaction occurs when a hydrogen peroxide solution is applied, resulting in adverse effects such as thermal decomposition of the raw materials and products. Therefore, in the case of mass production, cooling cannot be performed sufficiently, so that the generated peroxotitanic acid polymerizes and becomes very thick, and in extreme cases, the particles grow to such an extent that light transmission is blocked. When it is used as a coating agent, it causes a decrease in adhesion and density of the film.

Further, a method for producing an aqueous solution considered to be a peroxotitanium hydrate described as titanyl ion hydrogen peroxide complex or titanic acid by adding aqueous hydrogen peroxide to a gel or sol of hydrous titanium oxide. Are disclosed in JP-A-63-35419 and JP-A-1-24222.
No. 0 publication. However, when hydrogen peroxide solution is added directly to titanium hydroxide, the peroxo-formation and solution formation occur at the same time, so the heat generation is large and it is necessary to sufficiently stir and cool, but when the production volume is large, the temperature adjustment becomes very difficult, If the cooling is not sufficient, there is a problem that the viscosity increases, condensation occurs, the polymer grows as particles, and the polymer sometimes becomes cloudy.

When a gel or sol of hydrous titanium oxide is prepared, a basic substance such as ammonia is added. However, precipitation of hydrous titanium oxide occurs instantaneously. Anions such as chloride ions are taken in and are easily adsorbed. In particular, the presence of anionic impurities such as chloride ions and sulfate ions promotes the condensation of peroxotitanium hydrate generated after the addition of aqueous hydrogen peroxide, and a transparent aqueous solution may not be obtained. Further, even if the hydrous titanium oxide is washed with distilled water, it is difficult to completely remove impurities, which has been a major problem for the stable production of peroxotitanium hydrate.

The present inventor has disclosed in Japanese Patent Application Laid-Open Nos. 9-71418 and 10-67516,
It has been proposed that by heating peroxotitanium hydrate, a coating agent on which anatase ultrafine particles are deposited can be obtained, and thereby it is possible to form a crystalline titania film having good adhesion. With these methods, it is possible to form a crystalline titania film having better adhesion than the conventional method. However, when the residual amount of cations such as ammonium ions is large, peroxotitanium hydrate When an aqueous solution of the product is heated to produce an anatase sol, peroxo groups are less likely to decompose, the size of the particles becomes larger, and when used as a coating agent, adhesion or density may be poor. Was.

[0012]

SUMMARY OF THE INVENTION The present invention solves the conventional problems and provides a new method for producing crystalline titanium oxide particles which is useful as a coating agent for forming a titanium oxide film. Is what you do. That is, when producing an aqueous solution of peroxotitanium hydrate with aqueous hydrogen peroxide, adhesion due to condensation due to thermal influence in the production process, or adhesion that occurs when used as a coating agent due to unnecessary growth of particles, etc. It is an object of the present invention to prevent a decrease in density, and to provide crystalline titanium oxide particles having good adhesion and capable of forming a titanium oxide coating film having a high density.

[0013]

According to the present invention, there is provided a method for producing crystalline titanium oxide particles, wherein a peroxotitanium complex is formed by adding aqueous hydrogen peroxide to a titanium-containing raw material aqueous solution, and then a basic substance is added. After forming a precipitate of a polymer of peroxotitanium hydrate by leaving or heating the obtained solution, water is separated after removing at least dissolved components other than water derived from the titanium-containing raw material aqueous solution. This is a method for producing a crystalline titanium oxide particle-dispersed liquid in which heating is performed at a temperature of 70 ° C. or higher without being performed. The method for producing a crystalline titanium oxide particle dispersed liquid according to the above, wherein dissolved components other than water derived from the basic substance added for hydrate formation are also removed. Wash with water to remove dissolved components,
Alternatively, it is a method for producing the above-mentioned crystalline titanium oxide particle dispersion liquid by an ion exchange reaction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention eliminates factors that promote condensation and the like in the production process of crystalline titanium oxide particles via peroxotitanium hydrate, and directly removes a hydrate in a precipitated state from a hydrate in a precipitated state. It has been found that crystalline particles having excellent characteristics can be obtained, and the present invention has been accomplished.

That is, the reaction product which promotes the condensation and the like in the reaction process or the impurity mixed in from the raw material is separated at an early stage to prevent the condensation and the like, and comprises the following steps. . (1) Step of Precipitating Polymer of Peroxotitanium Hydrate A soluble titanium compound such as titanium tetrachloride is diluted with water, and an appropriate amount of hydrogen peroxide solution is added to form a brown peroxo complex. Add a basic substance such as
An aqueous solution of yellow peroxotitanium hydrate is prepared, and this aqueous solution is left at room temperature or heated to precipitate and precipitate a polymer of peroxotitanium hydrate. (2) Step of removing ionic substances and impurities The liquid containing the precipitate of the polymer of peroxotitanium hydrate is washed, or subjected to treatment such as filtration and washing to remove ammonium ions contained in the liquid. Remove chlorine ions or impurities derived from raw materials. (3) Step of forming crystalline titanium oxide particles A precipitate of peroxotitanium hydrate from which ionic substances and impurities have been removed by a washing treatment is obtained at a temperature of 80 ° C. or more in the form of a slurry or a dispersion in which water is not separated. By heating at normal pressure or in an autoclave, crystalline titanium oxide particles are formed.

By forming the titanium oxide particles by the above steps, a crystalline titanium oxide particle can be formed, and a dispersion of the crystalline titanium oxide particles useful for forming a titanium oxide film having excellent characteristics at a low temperature. Can be obtained.

The soluble titanium compound used as a raw material in the method of the present invention includes titanium tetrachloride, titanium sulfate,
Titanium nitrate, alkoxytitanium and the like can be mentioned. Also, the amount of hydrogen peroxide solution to be added to the aqueous solution of the soluble titanium compound requires a molar ratio of hydrogen peroxide / titanium of 1 or more, and if it is less than that, the peroxo-formation is not completely completed. In addition, since some of the added hydrogen peroxide solution decomposes without participating in the reaction, it is preferable to add the hydrogen peroxide / titanium molar ratio in excess of 1.

When hydrogen peroxide solution is added to a soluble titanium-containing solution, peroxolation occurs almost instantaneously and the pH becomes 3
Below, it is mainly dissolved as a cation, and when the pH is 3 or more, it is mainly present as an anion of peroxotitanium hydrate. This is presumably because the higher the pH, the faster the condensation and the precipitation of the amorphous peroxotitanium hydrate polymer. Even when a basic substance is added, if the pH is low, the time required to precipitate a polymer of peroxotitanium hydrate increases, so it is preferable to add the basic substance until the pH becomes 3 or more, and more preferably It is better to adjust the pH to the neutral range. When a yellow precipitate is formed from the yellow transparent liquid of peroxotitanium hydrate formed by adding a basic substance, the precipitate may be left at room temperature, but the precipitation is promoted by heating. Can be. Stirring further accelerates precipitation.

In the step of removing ammonium ions and chloride ions contained in the liquid from the liquid containing the precipitate and impurities derived from the raw material, methods such as decantation, filtration and washing, and centrifugation, or ion exchange A method for removing ionic substances by applying a reaction or a reverse osmosis method can be used.

If the residual amount of impurities is large, it is desirable to sufficiently treat the aqueous solution of peroxotitanium hydrate which is finally obtained, since this adversely affects the stability and properties of the aqueous solution.
In particular, anions such as chloride ions are thought to promote the condensation of peroxotitanium hydrate, and if these are not sufficiently removed, they may not be completely transparent and may become cloudy. On the other hand, even if cations such as ammonium ions remain, a yellow transparent aqueous solution containing peroxotitanium hydrate can be obtained if the anions are sufficiently removed.

Next, the dispersion containing the precipitates or the mud is heated. The heating temperature is preferably 70 ° C. or higher. If the heating temperature is lower than 70 ° C., the formation of anatase crystalline titanium oxide particles is not sufficient. Further, the heating temperature is more preferably from 80 ° C to 2000 ° C. At 200 ° C. or higher, anatase precipitation occurs in a very short time, so that it is difficult to adjust the treatment time. Further, the heating time is preferably from 5 minutes to 20 hours. By heating in an autoclave, it becomes possible to produce crystalline titanium oxide particles in a short time. In autoclaving, 100 ° C
To 200 ° C.

In the treatment of the precipitate, when the precipitate is dried, the precipitate is dehydrated and solidified, which adversely affects the production process of the crystalline titanium oxide particle dispersion liquid. Therefore, it is necessary to prevent the precipitate from being dried. In the method of the present invention, when the precipitate is heated, a dispersion liquid of the particles is generated together with the generation of the crystalline particles.

Further, the crystalline titanium oxide particle-dispersed liquid of the present invention can form a crystalline titania film only by coating, and thus is useful as a coating agent for a material that cannot be subjected to heat treatment. Further, it can be used for various uses such as a protective film, a photocatalyst, and a material for preventing gas permeation of a synthetic resin film, and a material having a relatively high density and good adhesion can be obtained at a relatively low temperature.

The liquid in which the crystalline titanium oxide particles of the present invention are dispersed can be mixed with various kinds of solid fine particles and dispersed with an ultrasonic wave or a ball mill. It is also possible to form a composite in which another substance is supported or dispersed in a titanium film.
In addition, as a substrate to be applied, ceramics, ceramics,
It can be applied to any material that can withstand heat treatment according to the application, such as metals, plastics, fibers, building materials, etc.It can also perform surface treatment on the inside of porous bodies and powders. The titanium oxide coating agent produced by the present invention can be used in fields such as the production of protective coatings, photocatalytic films, ultraviolet cut coatings, colored coating films, dielectric films, film sensors, and titanium oxide sols for various material products.

[0025]

The present invention will be described below with reference to examples. Example 1 5 ml of a 60% aqueous solution of titanium tetrachloride in 500 ml of distilled water
20 ml of 30% aqueous hydrogen peroxide solution
Add stirring to produce a brown transparent liquid, and add
Methanol water (1: 9) was added dropwise to adjust the pH to 7, and the yellowish transparent
A light solution was made. Release the resulting solution at 25 ° C all day and night
And a yellow precipitate formed. This is filtered and washed
After purification, make up to about 150 ml with distilled water,
And 25 g each of anion exchange resin and 30
Leave for minutes to remove cationic and anionic substances
Was. As the cation exchange resin, organo Amberla
Ito IR120B (Na⁺1 hour with 2N hydrochloric acid
After treatment, wash⁺ Using the replacement type,
As an anion exchange resin, organo Amberlite
IRA410 (Cl ^- 1N sodium hydroxide
And then washed with OH^- Even if it was a substitution type
Was used.

The obtained liquid containing the yellow precipitate is 150 m
and heated at 100 ° C. for 5 hours while sealing in a glass container to produce a pale yellow translucent liquid. The powder obtained by drying the generated liquid was measured by an X-ray diffractometer (RAD-B, manufactured by Rigaku Corporation) using a copper target under the conditions of an acceleration voltage of 30 kV and a current of 15 mA, and the results are shown in FIG. Show. In FIG. 1, a peak indicating crystalline anatase was confirmed, and it was confirmed that crystalline anatase was present in the dried product of the pale yellow translucent liquid.
The crystallite diameter determined from the half width of the diffraction peak was 8 nm. Further, the generated liquid was applied on a slide glass, dried at 60 ° C., and subjected to heat treatment to obtain a titanium oxide film.

Example 2 5 ml of a 60% aqueous solution of titanium tetrachloride was added to 500 ml of distilled water.
20 ml of 30% aqueous hydrogen peroxide solution
The mixture was stirred to produce a brown transparent liquid, and aqueous ammonia (1: 9) was added dropwise to the solution to adjust the pH to 7, thereby producing a yellow transparent solution. The resulting solution was left overnight at 25 ° C. to produce a yellow precipitate. This was filtered and washed, made up to about 150 ml with distilled water, sealed in a glass container, and heated at 100 ° C. for 5 hours, except that Example 1 was used.
As a result, the same dispersion as in Example 1 containing anatase crystalline titanium oxide was obtained.

Example 3 5 ml of a 60% aqueous solution of titanium tetrachloride was added to 500 ml of distilled water.
20 ml of 30% aqueous hydrogen peroxide solution
The mixture was stirred to prepare a brown transparent liquid, and aqueous ammonia (1: 9) was added dropwise to the solution to adjust the pH to 7, a yellow transparent solution was prepared, and the solution was heated at 60 ° C. for 2 hours. And heated at 60 ° C. for 2 hours to make the liquid containing the yellow precipitate 150 ml, sealed in a glass container,
Heat at 12 ° C. for 12 hours to obtain a translucent yellow liquid. FIG. 2 shows the result of measuring the powder obtained by drying this liquid by X-ray diffraction.
Shown in In FIG. 2, a peak indicating crystalline anatase was confirmed, and it was confirmed that crystalline anatase was present in the pale yellow translucent liquid.

Comparative Example 1 5 ml of a 60% aqueous solution of titanium tetrachloride was added to 500 ml of distilled water.
20 ml of 30% aqueous hydrogen peroxide solution
In addition, stirring was performed to produce a brown transparent liquid, and aqueous ammonia (1: 9) was added dropwise to the solution to adjust the pH to 7, a yellow transparent solution was produced, and the solution was heated at 60 ° C. for 2 hours. The yellow precipitate was sufficiently filtered and washed. The liquid containing the yellow precipitate was made up to 150 ml, and sealed in a glass container.
Except for heating at 12 ° C. for 12 hours, the mixture was treated in the same manner as in Example 3 to obtain a yellow opaque liquid. FIG. 3 shows the result of measuring the powder obtained by drying this liquid by X-ray diffraction. In FIG. 3, no clear peak indicating the presence of a crystalline substance was observed, and it was confirmed that no crystalline anatase was present in this liquid.

[0030]

According to the production method of the present invention, the condensation of peroxotitanium hydrate can be easily suppressed, and anatase having a small particle size is directly dispersed from the precipitate of peroxotitanium hydrate. A crystalline titanium oxide particle can be obtained as a dispersion, and when used as a coating agent, a dense titanium oxide film can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the result of X-ray diffraction of a dried pale yellow translucent liquid obtained in one example of the present invention.

FIG. 2 is a diagram illustrating an X-ray diffraction result of a dried pale yellow translucent liquid obtained in another example of the present invention.

FIG. 3 is a diagram illustrating an X-ray diffraction result of a dried pale yellow opaque liquid obtained in Comparative Example of the present invention.

Claims (3)

[Claims] In a method for producing a crystalline titanium oxide particle dispersion liquid, a solution obtained by adding a hydrogen peroxide solution to a titanium-containing raw material aqueous solution to form a peroxotitanium complex and then adding a basic substance. After forming a precipitate of a polymer of peroxotitanium hydrate by leaving or heating, after removing at least dissolved components other than water derived from the titanium-containing raw material aqueous solution, 70 ° C or more without separating water A method for producing a crystalline titanium oxide particle-dispersed liquid, characterized by heating at a temperature of: 2. The method for producing a crystalline titanium oxide particle-dispersed liquid according to claim 1, wherein dissolved components other than water derived from the basic substance added for hydrate formation are also removed. 3. The method for producing a crystalline titanium oxide particle-dispersed liquid according to claim 1, wherein the removal of the dissolved component is carried out by washing with water or an ion exchange reaction.