JP2938376B2 - Liquid for forming titania film, titania film 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 method for producing a liquid for forming a titania film, characterized in that a hydrogen peroxide solution is applied to a titanium hydroxide gel prepared from a titanium solution and a basic solution for synthesis. The present invention relates to a method for producing a liquid containing titanium oxide synthesized by heat treatment at a temperature of not less than ° C., and a titania film characterized by being prepared by applying and drying or heating the liquid. The titania film of the present invention can be used in fields such as protective coatings of various materials, photocatalysts, ultraviolet cut coatings, and colored coatings.

[0002]

2. Description of the Related Art A titania 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 firing, or by applying a sol produced by hydrolysis of a metal alkoxide to the substrate, followed by firing. Sol-gel method,
A sputtering method in which an oxide target is sputtered in a high vacuum to form a film on a substrate, and a CV in which an organic metal or halide is volatilized and decomposed in an electric furnace to form a film on the substrate.
Method D includes plasma spraying in which solid particles are melted in plasma generated in the atmosphere and beaten to the substrate surface.

[0003]

The method of applying titanium oxide powder is simple, but it is difficult to obtain a dense and good-adhesion film, and the synthesis temperature is generally high, so that the type of the substrate is considerably limited. The method of applying and sintering an aqueous solution of titanium chloride or titanium sulfate generates a harmful halogen compound and requires a sintering temperature of several hundred degrees or more, and is not used in the above-mentioned industrial application fields.

[0004] Plasma spraying is a film forming method in which a solid is melted in plasma and is beaten to the surface of a substrate. The film forming rate is high, but a dense film is hardly obtained, and a uniform and highly adherent oxide film is produced. I couldn't do that.

[0005] Further, in the sputtering method, the CVD method, and the like, a good film cannot be obtained unless the pressure is reduced, and a reaction vessel capable of evacuating is required. There is a disadvantage that the substrate must be heated to several hundred degrees or more.

[0006] Commercial TiO2 sol produced by the sol-gel method can be applied and impregnated, can be coated over a large area, can be synthesized at low temperatures, and has many industrial advantages. However, titanium tetraisopropoxide, tetrabutyl titanate, etc. 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, and is not suitable for a material that is easily attacked by an acid, and easily becomes porous when baking at a low temperature. . In addition, the sol-gel method requires complicated steps and requires the use of harmful organic solvents. The TiO2 sol prepared by the sol-gel method contains an acid, alkali or organic substance, which requires a problem of corrosion of the material to be coated and a temperature (400 ° C. or higher) for eliminating the organic substance. There are drawbacks such as harmful halides and nitrogen oxides being formed as by-products.

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 formed at a relatively low temperature, it is necessary to decompose and eliminate organic substances, acids, and the like by heat treatment. Had to be relatively high. There is also a disadvantage that these auxiliaries generate harmful substances such as nitrogen oxides and organic gases by heat treatment. Even in the sol-gel method, which can be synthesized at a relatively low temperature, it is possible to obtain 0.1% by one application.
Only those having a thickness of about 1 to 0.3 μm could be formed with good adhesion.

[0008]

In order to solve the above-mentioned problems, in the present invention, a coating liquid for forming a titania film is synthesized by completely new means as follows. First, a titanium hydroxide gel called orthotitanic acid is precipitated from an aqueous solution of titanium chloride or titanium sulfate and an alkaline solution such as ammonia or caustic soda. Wash with water by decantation with water to separate the titanium hydroxide gel.
Further, by adding aqueous hydrogen peroxide to decompose and remove excess hydrogen peroxide, the yellow transparent viscous liquid of claim 1 can be obtained. This liquid is considered to contain peroxidized titanium hydroxide, as will be described later.
It is essentially different from O2 sol. On the other hand, claim 2
According to the invention, when the liquid of claim 1 is subjected to a heat treatment at 80 ° C. or higher, a liquid containing crystallized ultrafine particles of titanium oxide can be obtained. This liquid is essentially different from commercial TiO2 sols because it is neutral and free of substances other than titanium, oxygen and hydrogen. By coating and drying these two liquids on a substrate or performing heat treatment at a low temperature, a dense titania film having excellent adhesion can be formed. In addition, it is possible to form a titania film having a thickness of 1 μm or more with a single coating with good adhesion without peeling.

The raw material of titanium is desirably inexpensive and easy to handle, such as sulfates, chlorides, oxalates, and the like. The basic substance that causes precipitation of hydroxide is preferably aqueous ammonia, caustic soda, or the like. The salt by-produced by the reaction is desirably in a combination that forms stable and harmless sodium chloride, sodium sulfate or ammonium chloride. The concentration of the raw material solution is not particularly limited. The precipitation pH is about 2 and
It is desirable that impurities such as are not coprecipitated.

The precipitated titanium hydroxide (sometimes referred to as orthotitanic acid) is in a gel state polymerized by polymerization of OH and hydrogen bonds, and cannot be used as a coating solution for the titania film as it is. When hydrogen peroxide solution is added to this gel, a part of OH becomes a peroxide state and dissolves as peroxotitanate ion, or it becomes a kind of sol in which the polymer chain is divided into low molecules, and excess hydrogen peroxide is added. Is decomposed into water and oxygen and can be used as a viscous liquid for forming a titania film. Since this sol contains only oxygen and hydrogen in addition to titanium, only water and oxygen are generated when it is changed to titanium oxide by drying or baking, the carbon component necessary for the thermal decomposition method such as the sol-gel method or sulfate is used. It is not necessary to remove a halogen component, and a crystalline titania film having a relatively high density can be manufactured even at a lower temperature than in the past. Also, since the pH is neutral, there is no need to consider the effects on the human body during use and corrosion of the substrate. In addition, hydrogen peroxide acts not only as a sol agent but also as a stabilizer, and has extremely high stability in the room temperature range of the sol and withstands long-term storage. Further, when this liquid is heated to 80 ° C. or higher, it can be denatured to a liquid in which ultrafine particles of titanium oxide have been generated. If the temperature is lower than 80 ° C., crystallization of titania does not proceed sufficiently. A crystalline titania film can be formed at a lower temperature by coating and drying or heating, but a processing temperature of 200 ° C. or higher is required to improve the adhesion.

When a liquid for forming a titania film is applied to a substrate, an appropriate surfactant can be added in order to improve wettability with the substrate. However, the titania film-forming liquid that has not been subjected to heat treatment, when adding a solution containing other transition metal ions or Ag ions or a strong acid or alkali, liberates titanic acid from the titanium solution in the sol state, Care must be taken as gelation may occur.

The liquid for forming a titania film according to claim 1 is 20
An amorphous titania film slightly containing OH groups at a temperature lower than 0 ° C., 200
At a temperature of not less than ° C., a crystalline dense titania film can be produced. These films have excellent acid resistance and can be used for various corrosion-resistant coatings. Further, a titania film-forming liquid which has been subjected to heat treatment at 80 ° C. or higher can form a crystalline titania film only by being applied, and thus is useful as a coating material of a material which cannot be subjected to heat treatment. In such a method, a material having a relatively high density and good adhesion can be obtained at a relatively low temperature, which can be used for various uses such as a protective film and a photocatalyst.

[0013] The dried membrane is water-resistant but impregnable, and impregnated with another solution and baked to form a composite in which the titania film carries or disperses another substance. It is also possible.

The substrate can be coated on any material, such as ceramics, porcelain, metal, plastics, fibers, and building materials, which can withstand heat treatment according to the intended use. It is also possible to perform In particular, since it is neutral, titania coating of metal can be effectively performed.

[0015]

Example 1 5 cc of a 60% titanium tetrachloride solution as a raw material
To 500 cc of distilled water with ammonia water (1:
9) was added dropwise to precipitate titanium hydroxide. After washing with distilled water, 10 cc of a 30% aqueous solution of hydrogen peroxide was added and stirred to prepare 70 cc of a yellow viscous liquid (sol solution) containing titanium. Immediately after the addition of the hydrogen peroxide, oxygen was generated and foaming occurred, but after the excess hydrogen peroxide was decomposed, the foaming subsided, and there was no change even after 6 months at normal temperature and normal pressure. The pH was neutral at 6.4. Polished alumina was used as a substrate, immersed and dried in a sol solution, and then heat-treated at various temperatures. The thickness of the film obtained by one application is 1μ.
m. The physical properties of the obtained titania film are shown below. Heat treatment temperature (° C.) Generated phase density (%) Dry only Amorphous 100 Amorphous 200 Anatase 71 300 Anatase 72 400 Anatase 74 500 Anatase 85 600 Anatase 92 At 200 ° C. or higher, a dense crystalline titania film can be obtained with good adhesion. Was.

[0016]

Example 2 The liquid of Example 1 was used at 80 ° C., 100 ° C., 12
The properties of the sol solution heat-treated or autoclaved at 0 ° C., 160 ° C., and 200 ° C. for 6 hours are shown below. Heat treatment temperature (° C) Product phase 80 Anatase Light yellow translucent liquid 100 Anatase Light yellow translucent liquid 120 Anatase White opaque liquid 160 Anatase White opaque liquid 200 Anatase White opaque liquid Both neutral and crystallized titania A liquid containing (anatase type) was obtained. Polished alumina was immersed and dried in a liquid treated at 100 ° C., and then heat-treated at various temperatures. The physical properties of the obtained titania film are shown below. Heat treatment temperature (° C) Produced phase Density (%) Dry only Anatase 69 100 Anatase 70 200 Anatase 73 300 Anatase 75 400 Anatase 78 500 Anatase 87 600 Anatase 95 A crystalline titania film can be produced even at room temperature and has excellent adhesion. Was.

[00017]

Comparative Example 1 As a raw material, a liquid in which titanium hydroxide was dispersed in water (0.2 M, white opaque liquid, containing a dispersant) was used.
The polished alumina was immersed in the liquid and dried, and then heat-treated at various temperatures. The thickness of the film obtained by one application is 0.2μ
m. When the coating was thicker than that, the film was easily peeled off after drying. The physical properties of the obtained titania film are shown below. Heat treatment temperature (° C.) Generated phase density (%) Dry only Amorphous 100 Amorphous 200 Amorphous 300 Amorphous 400 Anatase 49 500 Anatase 60 600 Anatase 81 At 400 ° C. or higher, a crystalline titania film is obtained. The densification temperature required a higher temperature than the method of the present invention.

[0018]

Example 3 The sol solution of Example 1 and the titanium hydroxide of Comparative Example 1 were applied to an iron plate (99.9%), heat-treated at various temperatures, and immersed in a 0.1N nitric acid aqueous solution at room temperature for 1 hour. An acid resistance test was performed. The thickness is about 0.3 μm. The results are shown below. Heat treatment temperature (° C.) Film of Example 1 Film of Example 2 Film with titanium hydroxide Dry only Corrosion Corrosion 100 Partial corrosion Partial corrosion Corrosion 200 Good Good Corrosion 300 Good Good Corrosion 400 Good Good Partial corrosion 500 Good Good Good 600 good good good It was shown that the present invention could produce a titania film exhibiting acid resistance by heat treatment at a lower temperature.

[0019]

Example 4 The sol solution of Example 1 was applied to a slide glass and dried, immersed in a 0.04 N silver nitrate aqueous solution for 1 minute, washed with water and fired at 300 ° C. As a result, about 3 wt% of silver oxide
The resulting dense titania film was obtained. This coating can be used as a silver antimicrobial coating.

[0020]

Example 5 The sol solution of Example 1 and the titanium hydroxide of Comparative Example 1 were applied to a slide glass, heat-treated at various temperatures, immersed in a 100 ppm acetic acid solution, and irradiated with a 6 W ultraviolet lamp (1). ), An acetic acid decomposition test was performed and a photocatalytic activity test was performed. The thickness is about 0.3 μm. The results are shown below. Heat treatment temperature (° C.) Film of Example 1 Film of Example 2 Film with titanium hydroxide Dry only Inactive Inactive 100 Inactive Active Inactive 200 Active Active Inactive 300 Active Active Inactive 400 Active Active 500 Active Active Activity 600 Activity Activity Activity In the present invention, crystalline titania was generated by a lower temperature heat treatment, and thus a titania film exhibiting photocatalytic properties could be generated at a lower temperature.

[0021]

By using the method of the present invention, a stable titania film forming solution can be prepared, and a crystalline titania film having a relatively high density and excellent adhesion can be formed at a low temperature. Becomes Further, the liquid of the present invention is a conventional Ti
It is essentially different from O2 sol, and it does not produce harmful by-products by baking, it is neutral and easy to handle, and it can form a dense film of 1 μm or more in one application. There are many advantages above. Due to such advantages, problems such as stability of raw material liquid, pH, low-temperature synthesis, and the like, which have been a problem in producing an oxide film by a coating method, can be solved. Therefore, there are great industrial effects such as the application of photocatalytic activity to metal by titania coating which requires low-temperature coating and low-temperature titania coating to various materials.

Claims (4)

(57) [Claims] In a liquid for forming a titania film, a hydrogen peroxide solution is allowed to act on a titanium hydroxide gel prepared from an aqueous solution containing titanium and a basic substance, and then subjected to a heat treatment at 80 ° C. or higher or a heat treatment in an autoclave. 1. A liquid for forming a titania film, wherein titanium oxide fine particles comprising anatase are produced. 2. A method for producing a liquid for forming a titania film, wherein a hydrogen peroxide solution is allowed to act on a titanium hydroxide gel prepared from an aqueous solution containing titanium and a basic substance.
A method for producing a liquid for forming a titania film, characterized in that titanium oxide fine particles comprising anatase are generated by the above heat treatment or heat treatment in an autoclave. 3. A titania film obtained by subjecting a titanium hydroxide gel prepared from an aqueous solution containing titanium and a basic substance to a hydrogen peroxide solution, followed by heat treatment at 80 ° C. or higher or heat treatment in an autoclave. After applying or impregnating a liquid in which titanium oxide fine particles comprising anatase are dispersed,
A titania film produced by drying or heat treatment. 4. A method for forming a titania film, wherein a hydrogen peroxide solution is allowed to act on a titanium hydroxide gel prepared from an aqueous solution containing titanium and a basic substance, followed by heat treatment at 80 ° C. or higher or heat treatment in an autoclave. A method for forming a titania film, comprising applying or impregnating a substrate with a liquid in which titanium oxide fine particles of anatase obtained by the above method are dispersed, and then drying or heating the substrate.