JP2875993B2 - Anatase dispersion and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stable anatase dispersion which can be used for forming a protective film containing titanium oxide, a photocatalytic film and the like on a substrate.

[0002]

2. Description of the Related Art A titanium-containing material is applied to various materials such as glass, white porcelain, metal, building materials, plastics and the like, dried or baked at a low temperature to form a protective film made of titanium oxide, a photocatalyst, a dielectric film, and a semiconductor film. , An ultraviolet cut film, a colored coating and the like are formed.

[0003] As a method of forming a titanium oxide film, there is known a method in which a dispersion or the like containing fine particles of titanium oxide is applied, dried and fired.
For example, a method of coating and drying a dispersion prepared by a sol-gel method from a titanium alkoxide on a substrate, and a method of directly applying and drying a titanium alkoxide, followed by baking are known. In these methods, since an acid or an organic substance is contained, it is necessary to remove the organic substance by heating to a high temperature when firing the coating film. There is also a problem that the obtained coating film is likely to be a heterogeneous or porous film.

[0004] Also, a dispersion prepared from an aqueous solution of a titanium-containing compound must use an acid such as hydrochloric acid or an organic dispersant as a dispersant. Even in this case, if the dispersion is left at room temperature, the fine particles take several hours to several days. Gelation and aggregation occurred, and the stability was extremely poor.

[0005] Further, since it contains an acid, the material which can be applied is limited, and a harmful halogen compound is produced at the stage of firing. Furthermore, in order to obtain a dense film with good adhesion,
The sintering temperature needs to be several hundred degrees or more, and there is a limitation in the use for materials such as plastics, metal, low melting point glass, and building materials.

In order to solve these problems, a coating solution containing peroxopolytitanic acid dissolved or dispersed in water or the like as a matrix component has been proposed as a coating agent for forming a stable and easily baked film. Has been proposed in JP-A-7-286114. However, the titanium compound obtained from the coating solution disclosed in the present invention was not an anatase type titanium oxide, and a compound having photocatalytic activity and the like could not be obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a high dispersion stability in a liquid, and the drying and baking steps after application are easy.
It is possible to form a dense film with excellent catalytic activity,
An object of the present invention is to provide an anatase dispersion.

[0008]

SUMMARY OF THE INVENTION The present invention is an anatase dispersion in which anatase fine particles having a surface modified with a peroxo group are dispersed in water. Further, in the method for producing an anatase dispersion, a peroxide is added to a solution of titanium hydroxide or titanium oxide formed by precipitation from a titanium-containing liquid in water to form a peroxotitanium solution. The titanium solution is heated at 85 ° C to 200 ° C for 40 minutes.
This is a method for producing an anatase dispersion in which heat treatment is performed for a time period of 2 hours to 2 hours.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The anatase ultrafine particles of the present invention contain anatase ultrafine particles, and the surface of the anatase ultrafine particles is modified with a peroxo group. Since the repulsion between the particles acts due to the polarization of the group, it is considered that the particles exist stably for a long time without aggregation.

The anatase dispersion of the present invention has a particle size of 50 n.
m or less of fine anatase fine particles,
When the particle size of the anatase fine particles is larger than 50 nm, the effect of gravity acting on the fine particles becomes large, and the fine particles tend to settle. This anatase dispersion is very stable at room temperature, does not require any special auxiliary agent other than water as a solvent, and does not contain organic substances and halogens. Further, the anatase dispersion is almost neutral, and can be used for materials such as metals and building materials which are susceptible to corrosion by acids. Further, when a titanium oxide film is formed by coating on a substrate, there is a feature that the adhesion to the substrate is good and the densification is easy at a low temperature. Therefore, the anatase film can be formed at a lower temperature than before by only application drying or heat treatment,
A material that can sufficiently withstand practical use can be obtained only by drying.

The method for producing the anatase dispersion of the present invention will be described. The anatase dispersion liquid uses titanium hydroxide gel or a liquid in which ultrafine particles of finely pulverized titanium hydroxide, titanium oxide or the like are dispersed in water as a raw material of a titanium-containing substance. As the titanium hydroxide gel, a gel produced by a method of reacting an aqueous solution of an inorganic titanium compound such as titanium chloride or titanium sulfate with ammonia, sodium hydroxide or the like can be used.

Next, the dispersion of titanium hydroxide gel, titanium oxide, etc. is sufficiently washed with water until the substance used for the formation of the precipitate is no longer detected, and then hydrogen peroxide is added thereto and stirred to obtain a yellow peroxotitanic acid solution. The unreacted one of the added aqueous hydrogen peroxide is decomposed on standing. When the obtained yellow peroxotitanic acid solution is subjected to heat treatment at 85 ° C. to 200 ° C. for 40 hours to 2 hours, a crystal nucleus of an anatase having a peroxo group can be generated. The heating temperature is 95
C. to 100.degree. C., and the heating temperature is preferably 8 hours to 4 hours.

On the other hand, when the heating temperature is lower than 85 ° C. or when the heating time is shorter than 2 hours, a dispersion having anatase crystals cannot be obtained. In addition, when the heating temperature is higher than 200 ° C., the reaction rate becomes large, and it becomes difficult to adjust the rate of formation of the peroxo group-modified anatase dispersion from the peroxotitanic acid solution, and at high pressure. It is not preferable because processing equipment is required. When the heating time is 40 hours or more,
It is not preferable because the peroxo group is decomposed and the anatase fine particles are aggregated. By the above processing, several nm
A pale yellow translucent or opaque liquid containing crystallized anatase fine particles of 〜50 nm is obtained, and the peroxo group is modified on the anatase surface.

Since the anatase dispersion of the present invention contains only oxygen and hydrogen in addition to titanium, only water and oxygen are generated when it is denatured into titanium oxide by drying or calcination. In addition, it is not necessary to remove the carbon component and the halogen component, which cannot be avoided, and a crystalline anatase film having a relatively high density can be manufactured even at a lower temperature than in the past. Also, pH
Is neutral, so there is no need to consider problems such as effects on the human body during use and corrosion of the substrate. Furthermore, it has extremely high stability in the room temperature range and withstands long-term storage.

When the anatase dispersion is applied to a substrate, a surfactant or the like may be added in order to improve the wettability with the substrate. Further, a solution containing insoluble solid particles and a metal other than titanium can be mixed and used as a coating liquid suitable for various uses. When preparing an anatase film using the anatase dispersion of the present invention, it can be applied to any substrate such as ceramics, porcelain, metal, plastics, fibers, and building materials, depending on the intended use, and can be applied to the inside of a porous body or the surface of powder. It can also be used for processing purposes.

[0016]

The present invention will be further described below with reference to examples. Example 1 10 ml of a 60% by weight aqueous solution of titanium tetrachloride was added to 1 part of distilled water.
2.5 wt% ammonia water was added to the 2,000 ml solution.
Titanium hydroxide was precipitated by dropping 10 ml. The precipitate was separated by filtration, washed with distilled water, and distilled water was added to make 180 ml of the titanium hydroxide suspension.
0 ml was added and stirred. The mixture was left at 7 ° C. for 24 hours to decompose excess hydrogen peroxide solution,
ml were obtained. Next, the obtained liquid was heated at 100 ° C. for 6 hours to obtain a pale yellow translucent dispersion. Even if this liquid was left under normal temperature and normal pressure for 6 months, no change such as generation of precipitation or the like occurred. The pH was about 7 and neutral.

The obtained dispersion is diluted 100 times with water,
After dripping on a sample holding sheet mesh and drying, it was observed with a transmission electron microscope (JEM-2010, manufactured by JEOL Ltd.) at an acceleration voltage of 200 kV. FIG. 1 shows the obtained electron micrograph. FIG. 1A is a photograph showing the appearance of ultrafine anatase particles. FIG. 1 (B) is a photograph for explaining a crystal lattice image of an anatase crystal, and (101)
3 shows a lattice of a plane, which indicates that the crystal has a crystal structure without disorder of the crystal structure.

Further, a powder obtained by drying the anatase dispersion at room temperature is mixed with potassium bromide powder to form a tablet. / IR-53
00) by the transmission method, and the results are shown in FIG. As shown by the arrow, the absorption peak of the peroxo group was confirmed. The anatase dispersion was dried at room temperature, and the obtained powder was analyzed with an X-ray diffractometer (RAD-B manufactured by Rigaku Denki).
Was measured using a copper target under the conditions of an acceleration voltage of 30 kV and a current of 15 mA. The result is shown in FIG. An anatase peak is observed, and the thickness of the crystal is 10 nm from the half width of the peak of the (101) plane. From the above results, it was confirmed that the dispersion liquid of the present invention was obtained by dispersing fine particles of anatase crystal, and that a peroxo group was present on the surface of the anatase crystal.

Example 2 The liquid obtained in Example 1 was applied on a quartz substrate and heat-treated at various temperatures. The thickness of the obtained anatase membrane is about 0.5μ.
m. The density of the film was evaluated from the refractive index of the film, and the adhesion was evaluated from the tensile test of the film. Table 1 shows the physical properties of these films.

Table 1 Heat treatment temperature (° C.) Generated phase density (%) Adhesion strength (kg / cm ² ) Dry only Anatase 69> 100 100 Anatase 70> 100 200 Anatase 76 450 300 300 Anatase 84 597 400 Anatase 87> 700 500 Anatase 91 600 Anatase 93 In Table 1, “>” indicates that the adhesive strength is equal to or greater than the breaking strength because the resin for bonding the pulling jig was broken. From the above results, it was found that a dense anatase film can be formed with good adhesion.

Example 3 The liquid prepared in Example 1 was applied to a slide glass,
It dried at ℃, and produced a 0.5 μm-thick thin film. One drop of a 0.04 M silver nitrate aqueous solution was spread on the thin film and spread.
The W black light was irradiated from a distance of 3 cm. Since the portion to which the silver nitrate solution was applied turned blackish brown in about 5 minutes, it was confirmed that silver ions were reduced by the photocatalytic action of anatase, and metal silver was deposited. In addition, red ink (single spare ink manufactured by Pilot Corporation) diluted 20 times with water is applied on the same film, and similarly irradiated with ultraviolet light, the red ink is decomposed by photocatalysis, and the color is changed in 20 minutes. Disappeared.

COMPARATIVE EXAMPLE 1 A titanium-containing yellow liquid produced by treating with a hydrogen peroxide solution in the same manner as in Example 1 was heated at 80 ° C. for 1 hour, and the obtained liquid was applied to a slide glass. And dry with 0.
A thin film having a thickness of 5 μm was prepared, and the photocatalytic properties were measured using a silver nitrate aqueous solution and a red ink in the same manner as in Example 3. However, the color of silver nitrate did not change even after 60 minutes, and that of red ink after 120 minutes. However, there was almost no color fading.
Further, a powder obtained by drying the liquid at room temperature was measured under the same conditions as in Example 1, and the results are shown in FIG. Only an undulation showing an amorphous state, no anatase was formed.

[0023]

Industrial Applicability The anatase dispersion of the present invention is stable for a long period of time, and can produce an anatase film having a higher density and excellent adhesiveness at a lower temperature than conventional ones. And easy to handle, and can be applied on various substrates.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of anatase of one example of the present invention.

FIG. 2 is a diagram illustrating an infrared absorption spectrum of a dispersion according to an example of the present invention.

FIG. 3 is a diagram illustrating an X-ray diffraction test result of anatase of one example of the present invention.

FIG. 4 is a diagram illustrating an X-ray diffraction test result of a dispersion of a comparative example.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23C 30/00 C23C 30/00 C

Claims (2)

(57) [Claims] 1. An anatase dispersion, wherein anatase fine particles whose surface is modified with a peroxo group are dispersed in water. 2. A method for producing an anatase dispersion, comprising:
Titanium hydroxide formed by precipitation from a titanium-containing liquid, or a liquid in which titanium oxide is dispersed in water, a peroxide is added to form a peroxotitanium solution, and then the peroxotitanium solution is heated at 85 ° C to 200 ° C. , 4
A method for producing an anatase dispersion, wherein a heat treatment is performed for 0 to 2 hours.