JP2002285341A - Method for producing titanium material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a titanium material which exhibits the actions of deodorization, stain prevention, sterilization, clouding prevention, or the like, forming an anatase type titanium oxide layer having photocatalytic activity on the surface of a titanium base material of pure titanium or a titanium alloy by a simple method of wet surface treatment and heat treatment, and as a result imparting excellent adhesion with the titanium base material to the layer, and allowing the layer to continuously maintain photocatalytic activity over a long period. SOLUTION: The anatase type titanium oxide layer having photocatalytic activity can be formed on the surface of the titanium base material having photocatalytic activity by a simple method where the surface of the titanium base material is subjected to sulfuric acid water solution treatment, and titanyl sulfate is water-washed to form titanium hydroxide; and the oxide of phosphorous or the oxide of potassium is adsorbed on the titanium hydroxide, and after that, heating treatment is performed thereto at 300 to 800 deg.C in the air. In this way, excellent adhesion with the titanium base material is imparted to the layer, and its photocatalytic activity can be maintained over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a titanium material having functions such as deodorization, antifouling property, bactericidal action and antifogging by imparting photocatalytic activity to the surface of a titanium substrate.

[0002]

2. Description of the Related Art Conventionally, it is known that titanium oxide, iron oxide, zinc oxide and the like, which are metal oxides having semiconductor characteristics, have photocatalytic activity. It has been reported that these substances having photocatalytic activity exert effects such as deodorization, antifouling, sterilization, and antifogging. In particular, titanium oxide shows an effective catalytic activity by irradiating light of a specific wavelength in the ultraviolet region (380 nm or less), and deodorant, antifouling, sterilizing and removing by a strong oxidation reaction derived from the photocatalytic action. Because it exhibits anti-fog, etc., a very wide range of applied developments are being developed.

[0003] The crystal structures of titanium oxide include anatase type and rutile type which are tetragonal and brookite type which are orthorhombic, and only anatase type is caused by a specific wavelength in the ultraviolet region as described above. It has photocatalytic activity.

[0004] When anatase-type or brookite-type titanium oxide is heated at a temperature of 800 ° C or more, both of them are transformed into rutile-type crystals.

The photocatalytic activity of anatase type titanium oxide is as follows:
Hydroxyl radicals generated from water due to oxidizing power based on holes generated by photoexcitation with a wavelength of 380 nm or less, which deodorize, antifoul, and sterilize by oxidatively decomposing contaminants, especially organic compounds. Functions such as removal and anti-fog are exhibited.

[0006] As described above, anatase-type titanium oxide forms holes by photoexcitation, but also has a very strong reducing power based on the excited electrons, and reduces oxygen to form superoxide, thereby contaminating it. It also has the function of decomposing substances, especially organic compounds.

Taking advantage of such characteristics of titanium oxide, it is applied to members such as air purifiers, building materials and deodorizing refrigerators. Specifically, the surface of these members is composed of titanium oxide fine particles and a binder component. A coating is formed. As a method of forming the coating, a spray coating method, a dip coating method, a spin coating method, or the like is used.

However, in such a method for forming a film, since the concentration of the titanium oxide fine particles contained in the film is not uniform, the efficiency of exhibiting photocatalytic activity is low, and there is also a problem in the adhesion of the film. Therefore, there is a problem that it is easy to peel off, and it is difficult to continuously develop photocatalytic activity over a long period of time because the film is easily damaged when subjected to an external force such as cleaning.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to deodorize and prevent the odor caused by the photocatalytic activity of titanium oxide. It is an object of the present invention to provide a method for producing a titanium material that can exhibit effects such as soiling, sterilization, and antifogging more effectively and continuously for a long period of time.

[0010]

SUMMARY OF THE INVENTION In order to solve these problems, a method for producing a titanium material having photocatalytic activity according to the present invention comprises a titanium oxide containing anatase type titanium oxide on the surface of the titanium material. The gist is that a titanium material is immersed in an oxidizing aqueous solution to form a layer, a titanium hydroxide layer is formed, and then heated to form a titanium oxide layer by a dehydration reaction.

It goes without saying that the titanium base material can be applied not only to pure titanium but also to titanium alloys, for example, those containing titanium such as an alloy of titanium and aluminum and an alloy of titanium and vanadium.

In the above, an oxide layer containing anatase-type titanium oxide is formed on the surface of a titanium substrate, and titanium is used to prevent dislocation to rutile type having no photocatalytic activity. It is preferable that the surface of the base material contains either a phosphate oxide or a potassium oxide, and the photocatalytic activity of the titanium oxide obtained by this method is effective and can be continuously exerted over a long period of time. I can do it.

[0013] The heat treatment of the titanium base material on the surface of which the titanium oxide adsorbed the phosphorus oxide or the potassium oxide is performed at 300 to 800 ° C, more preferably 400 to 700 ° C, in the presence of oxygen in the atmosphere. It is desirable to carry out in the temperature range described above.

If the heating temperature of the titanium hydroxide is lower than 300 ° C., the dehydration reaction does not sufficiently occur, so that no titanium oxide is produced or even if the dehydration reaction occurs, only amorphous titanium oxide is produced. If the temperature is higher than ° C., the anatase-type crystal formed in the middle temperature region is transformed into a rutile-type crystal. Therefore, it is desirable to carry out the heat dehydration reaction in the above temperature range.

More preferably, the thickness of the oxide layer formed on the surface of the titanium substrate is 0.1 μm or more, and the content of anatase type contained in the oxide is 1% by volume or more. The photocatalytic activity can be reliably exhibited.

(Action) In general, titanium is excellent in corrosion resistance because a very dense and chemically stable titanium oxide film is formed on the surface thereof. By utilizing the properties of titanium and utilizing titanium oxide formed on the surface of titanium, it is possible to exhibit the same photocatalytic activity as that of the film-formed body comprising the titanium oxide fine particles and the binder also by the titanium oxide. In addition, in the titanium oxide produced by such a method, the adhesion of the titanium oxide layer to the titanium substrate is also good, and the problem of peeling of the film as described above is solved, and the titanium oxide can be easily formed. Can be done.

The inventors of the present invention have examined the factors that affect the photocatalytic activity, including the crystal structure of titanium oxide, in addition to the uniformity and thickness of the titanium oxide, and found that anatase was present in the oxide layer formed on the surface of the titanium material. A method for producing a titanium oxide layer having a type crystal structure was found.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation and effect of the present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples.

When an oxide layer is formed on the surface of a titanium substrate by a usual heat oxidation method, an amorphous or rutile type titanium oxide is formed. Such titanium oxide does not show photocatalytic activity, but the titanium material is converted to sulfuric acid. By treating with an aqueous solution, titanyl sulfate was formed, which was hydrolyzed to form titanium hydroxide, and then treated with an aqueous solution of phosphorus oxide or potassium oxide to adsorb those oxides to titanium hydroxide. A method of forming titanium oxide having an anatase crystal structure on the surface of a titanium material by post-heating treatment was found.

In order to exhibit excellent photocatalytic activity,
It is preferable that the oxide layer has a thickness of 0.1 μm or more and an anatase crystal structure of 1% by volume or more.

In order to efficiently produce anatase-type titanium oxide powder, it is necessary to adsorb phosphorus or potassium to titanium hydroxide in an oxide state to suppress the rearrangement reaction from anatase-type to rutile-type crystal structure. Well-known (by Manabu Seino, titanium oxide, Gihodo Publishing).

Therefore, in order to make the titanium substrate surface contain 1% by volume or more of an anatase type crystal structure having photocatalytic activity, the titanium oxide formed on the surface of the titanium substrate is heated and calcined to form the oxide layer. Both phosphorus and potassium are in the form of oxides, but are preferably contained at 0.1 atomic% or more in terms of atomic state.

In order to form a photocatalytically active oxide layer having a thickness of 0.1 μm or more on the surface of the titanium substrate, it is necessary to use
Treatment with a 10% aqueous sulfuric acid solution forms titanyl sulfate, which is hydrolyzed to titanium hydroxide, in the presence of oxygen in the air at 300 to 800 ° C, more preferably at 4 to 800 ° C.
Heat at 00-700 ° C for 10-60 minutes, and
After heating for 0 minutes, a titanium oxide layer of 0.5 μm or more is obtained.

In order to form an oxide layer having an optimal photocatalytic activity on the surface of the titanium substrate, the above-mentioned suitable temperature and suitable time are present in the heating stage, and the heating temperature is preferably at the suitable temperature, ie, 3 ° C.
When the temperature is lower than 00 ° C., dislocation from the amorphous oxide to the oxide containing the anatase crystal does not occur, and when the heating time is shorter than the preferable time of 10 minutes, the thickness of the oxide layer becomes zero. When the thickness is as thin as 0.1 μm or less, a required photocatalytic activity may not be exhibited. If the heating temperature is raised above the suitable temperature of 800 ° C., a rearrangement reaction from the anatase type to the rutile type may occur, and the photocatalytic activity may not be able to be exhibited. Hereinafter, embodiments to which the present invention is specifically applied will be described.

[0025]

(Example 1) Industrial pure titanium plate (99.5)
%) Was degreased with a 10% aqueous solution of caustic soda, washed with a mixed solution of an equal amount of 10% hydrofluoric acid and 10% nitric acid, thoroughly washed with water, and dried. Next, titanyl sulfate was generated on the surface of the titanium material by immersing the pure titanium plate in a 10% aqueous sulfuric acid solution. A titanium hydroxide layer was formed on the surface of the titanium material by hydrolyzing the titanyl sulfate on the surface of the titanium material generated by such a method using pure water.

The phosphoric acid component was adsorbed in the titanium hydroxide on the surface of the titanium material by immersing the titanium hydroxide layer formed on the surface of the titanium substrate in a 10% phosphoric acid aqueous solution.

After the phosphoric acid component was adsorbed on the titanium hydroxide layer on the surface of the titanium substrate, it was dried. Thereafter, an oxide layer containing anatase-type titanium oxide can be generated by performing a heat treatment at 500 ° C. for 60 minutes in an air atmosphere,
The thickness of the oxide layer was about 0.3 μm.

The light of the titanium material on which the above oxide layer is formed
To confirm the catalytic activity, immerse in an aqueous potassium iodide solution.
Cough, black light with high UV intensity (3mW /
cm ^Two) To confirm iodine generation
As a result, the anatase crystal structure contains 1.2% by volume.
It was confirmed that an oxide layer was formed.

In order to evaluate the adhesion of the titanium material on which the oxide layer was formed, a 180 ° bending test was performed to evaluate the adhesion of the oxide layer. The properties of the oxide layer were very excellent, and the oxide layer did not peel off even when the surface of the oxide layer was subjected to sliding treatment with a tortoise shell.

(Example 2) Titanium hydroxide was formed on the surface of a titanium substrate in the same manner as in Example 1, then treated with a 10% aqueous solution of potassium hydroxide to adsorb potassium oxide, and then dried. . Thereafter, at 600 ° C. in the air atmosphere, 60
By performing the heat treatment for one minute, an oxide layer containing anatase-type titanium oxide could be formed, and the thickness of the oxide layer was about 0.5 μm.

As in Example 1, in order to confirm the photocatalytic activity of the titanium material on which the titanium oxide layer was formed,
By immersing in an aqueous solution of potassium iodide and irradiating with black light (3 mW / cm ² ) having a high ultraviolet intensity to confirm the generation of iodine, the oxidation containing 2.0% by volume of the anatase crystal structure was confirmed. It was confirmed that the material layer was formed.

The above-mentioned adhesion test and sliding test of the oxide layer were carried out in the same manner as in Example 1, but no peeling of the oxide layer was observed in any of the tests.

Example 3 Titanium alloy plate (Ti: 94)
%, Al: 6%) in the same manner as in Example 1 to form a titanium hydroxide having phosphorus oxide adsorbed on the surface of the alloy.
By heating at 60 ° C. for 60 minutes, an oxide layer containing anatase type titanium oxide could be formed, and the oxide layer was about 0.3 μm. In addition, it was confirmed that an anatase type crystal structure was contained at 1.2% by volume using an aqueous solution of potassium iodide.

The adhesion test and the sliding test of the oxide layer were carried out in the same manner as in Example 1, but no peeling of the oxide layer was observed in any of the tests.

Comparative Example 1 Pure titanium plate for industrial use (99.5)
%) Was degreased with a 10% aqueous solution of caustic soda.
After washing with a mixed solution of hydrofluoric acid and nitric acid in the same manner as described above, the plate was sufficiently washed with water and dried. Next, the pure titanium plate was treated with a 10% aqueous sulfuric acid solution to produce titanyl sulfate on the surface of the titanium substrate. Titanyl sulfate on the surface of the titanium substrate produced by such a method was hydrolyzed using pure water to form a titanium hydroxide layer on the surface of the titanium substrate.

By subjecting the obtained titanium substrate having the titanium hydroxide layer to a heat treatment at 500 ° C. for 60 minutes in an air atmosphere, an oxide layer containing titanium oxide can be formed. Was about 0.2 μm.

In order to confirm the presence or absence of photocatalytic activity of the titanium substrate on which the above oxide layer was formed, the titanium substrate was immersed in an aqueous solution of potassium iodide and exposed to a black light (3
mW / cm ² ), but no iodine was found, indicating that the anatase crystal structure was not formed in the oxide layer.

The reason why the anatase-type crystal structure was not formed in this manner is considered to be that phosphorus oxide or potassium oxide was not adsorbed on the titanium oxide layer as shown in Examples 1 to 3. .

(Comparative Example 2) Pure titanium plate for industrial use (99.5)
%) Was degreased with a 10% aqueous solution of caustic soda.
Washed with a mixed solution of hydrofluoric acid and nitric acid in the same manner as described above, and then sufficiently washed with water and dried. Using an aqueous dispersion of anatase-type titanium oxide in the form of a white powder prepared from titanium isopropoxide and hydrogen peroxide, the solution was applied to the titanium plate at 110 ° C.
For 30 minutes. When the photocatalytic activity of this oxide layer was confirmed in the same manner as in Example 1, it was confirmed that the oxide layer was an anatase type crystal having oxidizing power. When this oxide layer was subjected to an adhesion test by a 180 ° bending test, a peeling phenomenon of the oxide layer was observed, and a sliding test was performed using a turtle child skelet, and the oxide layer was partially peeled from the titanium plate. Was observed.

As described above, in the coated substrate formed by coating the titanium plate with the titanium oxide dispersion, it was found that the oxide layer was peeled from the titanium plate.

[0041]

According to the present invention, an oxide layer containing titanium oxide having an anatase type crystal structure on the surface of a titanium substrate is heated by washing with an aqueous sulfuric acid solution, pure water, adsorbing phosphorus oxide or potassium oxide. By forming it by a simple method such as treatment, it gives excellent photocatalytic activity and also has excellent adhesion to the substrate. It can be effectively used as a precious metal such as a watch having an effect of anti-fogging and the like and an environmental component such as an air conditioner.

Continued on the front page F-term (reference) 4G069 AA03 AA08 BA04A BA04B BA48A BB01C BB05C BB10C BB14C BC03C BC50C CA11 CA17 DA05 EA08 EB15Y EC22X EC22Y FA01 FA03 FB14 FB18 FB34 FC02 FC04 FC07 4K022 AA02AA33

Claims (3)

[Claims] 1. a step of immersing a titanium substrate in an aqueous sulfuric acid solution to produce titanyl sulfate on the surface of the titanium substrate;
A step of hydrolyzing the titanyl sulfate to produce titanium hydroxide, and a step of immersing the titanium hydroxide in a phosphoric acid aqueous solution or a potassium hydroxide aqueous solution to adsorb phosphate or potassium oxide to the titanium hydroxide. And a step of heat-treating the titanium hydroxide to which the phosphorus oxide or potassium oxide is adsorbed to form a titanium oxide layer on the surface of the titanium base material. 2. A heat treatment temperature in a step of heat-treating the titanium hydroxide to form titanium oxide, which is in a range of 300 ° C. or more to 800 ° C. or less.
3. The method for producing a titanium material according to item 1. 3. The method according to claim 1, wherein the titanium oxide layer is an anatase-type titanium oxide layer having photocatalytic activity.