JP3490012B2 - Method for producing crystalline titanium oxide particle dispersion liquid - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a crystalline titanium oxide particle-dispersed liquid, and particularly crystalline titanium 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-dispersed 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 and then baking it, or applying a sol prepared by hydrolysis of a metal alkoxide to the substrate. Post-baking sol-gel method, sputtering method in which oxide target is sputtered in high vacuum to form film on substrate, organometallic compound or halide is volatilized and decomposed in heating furnace to form film on substrate There are a CVD method, plasma spraying in which solid particles are melted in plasma generated in the atmosphere, and the surface of the substrate is irradiated with the plasma. Among them, the method of using a coating liquid as a method of forming a titanium oxide film is said to be simple and highly practical.

Although the coating method using titanium oxide powder is simple, it is difficult to obtain a dense and good adhesive film, and a titanium oxide film generally requires a high synthesis temperature. It is necessary to use a heat resistant substrate that can withstand,
There are restrictions 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 defect that harmful compounds such as halogen compounds are produced by firing. Further, the method of coating and firing an aqueous solution of titanium chloride, titanium sulfate or the like produces a harmful halogen compound and requires a firing temperature of several hundred degrees or more.

Commercially available titanium oxide sol prepared by the sol-gel method can be applied and impregnated, and can be coated on a large area and can be synthesized at low temperature, which has many industrial advantages, but titanium tetraisopropoxide and tetrabutyl titanate are available. Since it has to be synthesized by using such an organic metal, there is a problem that the raw material is expensive, and the raw material is chemically unstable and easily affected by temperature control and atmosphere and is difficult to handle. Further, the sol-gel method requires heating at 400 ° C. or higher to remove by burning because the raw material sol contains an acid or an organic substance, and is not suitable for a material that is easily attacked by an acid. There was a problem that it was easy.

In the sol-gel method, the steps are complicated, and an organic solvent must be used. Acids, alkalis, or organic substances are added to the titanium oxide sol produced by the sol-gel method, which causes corrosion of the material to be coated. There was a problem. Further, a temperature of 400 ° C. or higher is required for decomposing organic substances, and there is a drawback that harmful halides, nitrogen oxides, and the like are by-produced during heating and firing.

As described above, it is difficult to form a crystalline titania film having a high density at a low temperature by the conventional method, and the sol-gel method, which can be formed at a relatively low temperature, decomposes and eliminates an organic substance, an acid and the like by heat treatment. However, this also causes the porous layer to be easily made porous, and the heat treatment temperature had to be relatively high in order to form a film having a high density. In addition, there is a drawback that these auxiliary agents generate harmful substances such as nitrogen oxides and organic gas by heat treatment.

In contrast to such a method, when a titanium oxide film is formed from peroxotitanium hydrate, it is known that a film having good characteristics can be formed at a relatively low temperature. Peroxotitanium hydrate can be 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 ion is generated as a polynuclear ion containing two or more titanium atoms at a pH of 1 or more, and gradually condenses and precipitates at room temperature. Therefore, since it is difficult to use it as a titanium oxide coating agent having 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. Further, there is a problem that the contained halogen, sulfur, etc. generate harmful substances such as hydrogen halide, sulfur oxide, etc. by heat treatment.

Further, in order to produce a high-purity titanium oxide film, titanium hydrogen peroxide is obtained by directly adding hydrogen peroxide water to titanium hydride or alkoxy titanium to dissolve it.
That is, it has been proposed in JP-A-62-252319 to produce a substance considered to be peroxotitanium hydrate. However, these titanium raw materials are not stable, and have a drawback that a considerable exothermic reaction occurs when hydrogen peroxide solution is allowed to act, resulting in adverse effects such as thermal decomposition of the raw materials and products. Therefore, in the case of large-scale production, the peroxotitanic acid that is produced polymerizes and becomes extremely thick because it cannot be sufficiently cooled, and in extreme cases, particles grow to such an extent that light transmission is blocked. When it is used as a coating agent, it causes a decrease in the adhesion and density of the film.

Further, a method for producing an aqueous solution considered to be peroxotitanium hydrate described as titanyl ion hydrogen peroxide complex or titanic acid by adding hydrogen peroxide water to a gel or sol of hydrous titanium oxide. JP-A-63-35419 and JP-A-1-224422.
No. 0 publication. However, when hydrogen peroxide solution is directly added to titanium hydroxide, since peroxo oxidation and solution formation occur at the same time, a large amount of heat is generated and it is necessary to sufficiently stir and cool, but when the production amount increases, it becomes very difficult to control the temperature. If it cannot be cooled sufficiently, there is a problem that the viscosity increases, condensation occurs, the polymer grows as particles, and it may become cloudy.

In addition, when a gel or sol of hydrous titanium oxide is prepared, a basic substance such as ammonia is added, but since the hydrous titanium oxide precipitates instantaneously, cations such as ammonium ions which are impurities and Incorporates anions such as chlorine ions to facilitate adsorption. In particular, the presence of anionic impurities such as chlorine ions and sulfate ions accelerates the condensation of peroxotitanium hydrate formed after the addition of hydrogen peroxide solution, and a transparent aqueous solution may not be obtained in some cases. Further, it is difficult to completely remove impurities even if the hydrous titanium oxide is washed with distilled water, which is a big problem for stable production of peroxotitanium hydrate.

The inventor of the present invention discloses in Japanese Patent Laid-Open Nos. 9-71418 and 10-67516,
It is proposed that a coating agent in which anatase ultrafine particles are deposited can be obtained by heating peroxotitanium hydrate, and by this, a crystalline titania film having good adhesion can be formed. By these methods, it is possible to form a crystalline titania film having better adhesion than conventional methods. However, when the residual amount of cations such as ammonium ions is large, peroxotitanium hydrate is hydrated. When an anatase sol is produced by heating an aqueous solution of a substance, decomposition of the peroxo group is less likely to occur, the particle size becomes large, and the adhesiveness or density when used as a coating agent may be poor. It was

[0012]

DISCLOSURE OF THE INVENTION The present invention solves the conventional problems and provides a new method of producing crystalline titanium oxide particles, which is also useful as a coating agent for forming a titanium oxide film. To do. That is, when an aqueous solution of peroxotitanium hydrate is prepared with hydrogen peroxide solution, the adhesion and the adhesiveness caused when it is used as a coating agent due to condensation due to thermal influence in the manufacturing process, or excessive growth of particles, etc. It is an object to prevent a decrease in density, and an object is to obtain crystalline titanium oxide particles which have good adhesion and can form a titanium oxide coating film having a high density.

[0013]

The present invention provides a method for producing crystalline titanium oxide particles, wherein hydrogen peroxide is added to a titanium-containing raw material aqueous solution to form a peroxotitanium complex, and then a basic substance is added. After forming a precipitate of a polymer of peroxotitanium hydrate by allowing the solution obtained by leaving to stand, at least after removing dissolved components other than water derived from the titanium-containing raw material aqueous solution, water is not separated Is a method for producing a crystalline titanium oxide particle-dispersed liquid which is heated at a temperature of 70 ° C. or higher. The method for producing a crystalline titanium oxide particle-dispersed liquid as described above, wherein dissolved components other than water derived from the basic substance added for forming a hydrate is also removed. The method for producing a crystalline titanium oxide particle-dispersed liquid as described above, wherein the dissolved components are removed by washing with water or an ion exchange reaction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention eliminates a factor that promotes condensation and the like in the process of producing crystalline titanium oxide particles via peroxotitanium hydrate, and at the same time, directly removes the precipitated hydrate. It was found that crystalline particles having excellent characteristics can be obtained, and the present invention has been accomplished.

That is, the condensation product is prevented by early separating the reaction product, which is a factor that promotes the condensation product in the reaction process, or the impurities mixed in from the raw materials, and is composed of 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. Basic substance such as
An aqueous solution of yellow peroxotitanium hydrate is prepared, and the aqueous solution is left standing 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 peroxotitanium hydrate polymer is washed or subjected to treatments such as filtration and washing to remove ammonium ions and the like contained in the liquid. Remove chlorine ions or impurities derived from raw materials. (3) Step of forming crystalline titanium oxide particles At 80 ° C or higher, a precipitate of peroxotitanium hydrate from which ionic substances and impurities have been removed by a washing treatment does not separate water into a muddy substance or a dispersion liquid. The crystalline titanium oxide particles are formed by heating at normal pressure or in an autoclave.

A crystalline titanium oxide particle dispersion capable of forming crystalline titanium oxide particles by the above steps and useful for forming a titanium oxide film having excellent characteristics at low temperatures, etc. Can be obtained.

Soluble titanium compounds used as raw materials in the method of the present invention include titanium tetrachloride, titanium sulfate,
Examples thereof include titanium nitrate and alkoxytitanium. Further, the amount of hydrogen peroxide solution added to the aqueous solution of the soluble titanium compound needs to have a hydrogen peroxide / titanium molar ratio of 1 or more, and if the amount is less than that, the peroxo oxidation is not completely completed. Moreover, 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 the soluble titanium-containing solution, peroxidation occurs almost instantly, and the pH becomes 3 or less.
In the following, it is mainly dissolved as a cation, and when the pH is 3 or more, it mainly exists as an anion of peroxotitanium hydrate. It is considered that this is because the higher the pH, the faster the condensation and the precipitation of the amorphous peroxotitanium hydrate polymer. Even when the basic substance is added, it is preferable to add the basic substance until the pH becomes 3 or more, because the time for precipitating the polymer of peroxotitanium hydrate becomes long when the pH is low. It is better to adjust the pH to the neutral range. When a yellow precipitate is formed from a yellow transparent liquid of peroxotitanium hydrate formed by adding a basic substance, it may be left at room temperature, but it should be heated to promote precipitation. You can Precipitation is further accelerated with stirring.

In the step of removing ammonium ions and chlorine ions contained in the liquid or impurities derived from the raw material from the liquid containing the precipitate, a method such as decantation, filter washing, centrifugal separation, or ion exchange is performed. A method of removing an ionic substance by applying a reaction or reverse osmosis method can be used.

If the residual amount of impurities is large, the stability and properties of the finally obtained aqueous solution of peroxotitanium hydrate will be adversely affected, so it is desirable to treat it sufficiently.
In particular, anions such as chlorine ions are considered to promote condensation of peroxotitanium hydrate, and if these are not removed sufficiently, 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 by sufficiently removing the anions.

Next, the dispersion containing the precipitate or the mud is heat-treated. The heating temperature is preferably 70 ° C. or higher, and if the temperature is lower than 70 ° C., the production of crystalline titanium oxide particles of anatase is not sufficient. The heating temperature is more preferably 80 ° C to 200 ° C. At 200 ° C. or higher, the precipitation of anatase occurs in a very short time, making it difficult to adjust the treatment time.
The heating time is preferably 5 minutes to 20 hours. By heating in an autoclave, it becomes possible to produce crystalline titanium oxide particles in a short time. The autoclave treatment is preferably performed at 100 ° C to 200 ° C.

In the treatment of the precipitate, it is necessary to prevent dehydration and solidification of the precipitate when it is dried and adversely affect the production process of the crystalline titanium oxide particle-dispersed liquid. In the method of the present invention, when the precipitate is heated, a dispersion liquid of particles is formed together with the formation of crystalline particles.

Further, the crystalline titanium oxide particle-dispersed liquid of the present invention can form a crystalline titania film only by coating, so that it is useful as a coating agent for materials that cannot be heat-treated. Further, it can be used for various applications such as a protective film, a photocatalyst, and a gas permeation blocking material for 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 by ultrasonic waves, a ball mill, etc. Oxidation obtained by applying it and drying and firing. It is also possible to create a composite in which another substance is supported or dispersed in the titanium film.
In addition, as the substrate to be applied, ceramics, ceramics,
It can be applied to any material, such as metal, plastics, fibers, and building materials, as long as it can withstand heat treatment according to the application, and it can also be surface-treated inside the porous body or powder. The titanium oxide coating agent produced by the present invention can be used in fields such as production of protective coatings for various material products, photocatalyst coatings, ultraviolet cut coatings, colored coating coatings, dielectric coatings, membrane sensors, titanium oxide sols.

[0025]

EXAMPLES The present invention will be described below with reference to examples. Example 1 Titanium tetrachloride 60% aqueous solution 5 ml with distilled water 500 ml
20ml of 30% hydrogen peroxide solution to the diluted solution
Add and stir to make a brown transparent liquid, and add to this solution.
Water (1: 9) was added dropwise to adjust the pH to 7 and the yellow transparent
A bright solution was made. Release the resulting solution at 25 ° C overnight
Then, a yellow precipitate was formed. This is filtered and washed
After purification, make up to about 150 ml with distilled water and use cation exchange resin and
And anion exchange resin 25g each
Leave for a minute to remove cationic substances and anionic substances.
It was As a cation exchange resin, amber made by Organo
Ito IR120B (Na⁺Substitution type) with 2N hydrochloric acid for 1 hour
After processing, wash and⁺ Use the substitution type,
As anion exchange resin, Amberlite made by Organo
IRA410 (Cl ^- Substitution type) 1N sodium hydroxide
Treated for 1 hour, then washed and OH^- The replacement type
Was used.

The liquid containing the obtained yellow precipitate is set to 150 m.
When it was made 1 and sealed in a glass container and heated at 100 ° C. for 5 hours, a pale yellow translucent liquid was produced. The powder obtained by drying the generated liquid was measured by an X-ray diffractometer (RAD-B manufactured by Rigaku Denki) using a copper target under the measurement conditions of an acceleration voltage of 30 kV and a current of 15 mA, and the result is shown in FIG. Show. In FIG. 1, a peak showing 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. In addition, a titanium oxide film was obtained by applying the produced liquid on a slide glass, drying it at 60 ° C., and heating it.

Example 2 5 ml of 60% titanium tetrachloride aqueous solution was diluted with distilled water to 500 ml.
20ml of 30% hydrogen peroxide solution to the diluted solution
In addition, the mixture was stirred to prepare a brown transparent liquid, and aqueous ammonia (1: 9) was added dropwise to this solution to adjust the pH to 7 to prepare a yellow transparent solution. The obtained solution was left at 25 ° C. for a whole day and night to produce a yellow precipitate. This was filtered, washed, and 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.
When treated in the same manner as in Example 1, the same dispersion containing crystalline titanium oxide of anatase as in Example 1 was obtained.

Comparative Example 1 Titanium tetrachloride 60% aqueous solution 5 ml was distilled water 500 ml
20ml of 30% hydrogen peroxide solution to the diluted solution
The solution was stirred to prepare a brown transparent liquid, ammonia water (1: 9) was added dropwise to this solution to adjust the pH to 7, and a yellow transparent solution was prepared, which was heated at 60 ° C. for 2 hours to obtain The yellow precipitate was thoroughly filtered and washed. Make up the liquid containing this yellow precipitate to 150 ml and seal it in a glass container.
The mixture was heated at ℃ for 12 hours to obtain a yellow translucent liquid. The result of measuring the powder obtained by drying this liquid by X-ray diffraction is shown in FIG.
Shown in. Although a peak showing crystalline anatase was present in FIG. 2, the peak was smaller than that in FIG. 1 showing the example and the amount of crystalline anatase was insufficient as compared with the example.

Comparative Example 2 5 ml of 60% titanium tetrachloride aqueous solution was diluted with distilled water to 500 ml.
20ml of 30% hydrogen peroxide solution to the diluted solution
The solution was stirred to prepare a brown transparent liquid, ammonia water (1: 9) was added dropwise to this solution to adjust the pH to 7, and a yellow transparent solution was prepared, which was heated at 60 ° C. for 2 hours to obtain The yellow precipitate was thoroughly filtered and washed. The liquid containing this yellow precipitate is made up to 150 ml and sealed in a glass container.
A yellow opaque liquid was obtained by treating in the same manner as in Comparative Example 1 except that heating was performed at 12 ° C. for 12 hours. The result of measuring the powder obtained by drying this liquid by X-ray diffraction is shown in FIG. In FIG. 3, no clear peak indicating the presence of a crystalline substance was observed, and it was confirmed that crystalline anatase was not present in this liquid.

[0030]

EFFECTS OF THE INVENTION By the production method according to 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 dispersion of crystalline titanium oxide particles can be obtained, and when used as a coating agent, a dense titanium oxide film can be formed.

[Brief description of drawings]

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

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

Claims (3)

(57) [Claims] 1. A method for producing a crystalline titanium oxide particle-dispersed liquid, comprising: adding a hydrogen peroxide solution to a titanium-containing raw material aqueous solution to form a peroxotitanium complex, and then adding a basic substance to the solution. Is allowed to stand to form a polymer precipitate of peroxotitanium hydrate, and then at least the dissolved components other than water derived from the titanium-containing raw material aqueous solution are removed. A method for producing a crystalline titanium oxide particle-dispersed liquid, which comprises heating. 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 forming a hydrate are also removed. 3. The method for producing a crystalline titanium oxide particle-dispersed liquid according to claim 1 or 2, wherein the dissolved components are removed by washing with water or an ion exchange reaction.