JP2003320257A - Article for purifying environment and sol-gel production method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a photocatalyst film having a sufficient water-absorption capability as compared with an anatase film and carrying out photolysis in the entire inner and outer region of the film by decreasing the light reflectance and increasing the effective quantity of light. <P>SOLUTION: The article for purifying environments comprises a silica gel film 6 which is formed on the surface of an article 2 to be brought into contact with the environments and which has a large number of fine pores 14 communicating with the environments and a large number of photocatalyst particles 8 which are dispersed and fixed in the surface and the inside of the silica gel film 6 and carry out the photolysis of polluting substances in the environments. The photocatalyst particles 8 exposed to the surface and the fine pores of the silica gel film 5 can highly efficiently decompose polluting substances in the environments. Photocatalyst particles 8 are evenly dispersed in a sol solution, applied to the article 2, and aged at a normal temperature to form a photocatalyst-silica gel film 4. The photocatalyst-silica gel film 4 formed at a normal temperature adsorbs a large quantity of water, has a refractive index approximately the same as that of glass, and is highly light transmissive. Rutile particles 8a bearing ultrafine metal particles 8b may be used for the photocatalyst particles. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an environmental purification article that photolyzes pollutants in the environment by means of a photocatalyst, and more specifically, a silica gel membrane having a large number of pores communicating with the environment is formed on the surface of the article. A sol-gel is formed at room temperature, and a large number of photocatalyst particles such as ultrafine metal particle-supported photocatalyst particles are uniformly dispersed and fixed on the surface and inside of the silica gel film, and contaminants in the environment are adsorbed by the pores of the silica gel film. The present invention relates to an environment-purifying article that can efficiently decompose pollutants in the environment by photocatalyst particles by positively utilizing the high translucency and high hydrophilicity of a silica gel film, and a method for producing a sol-gel thereof.

[0002]

2. Description of the Related Art Generally, titanium dioxide is classified into anatase type and rutile type due to the difference in crystal structure. Of these, titanium dioxide that can be used as a photocatalyst is anatase type (hereinafter referred to as anatase), and rutile type (hereinafter referred to as rutile) is usually considered to have extremely low photocatalytic efficiency.

The use of anatase as a photocatalyst begins with the technology of photodecomposing water to produce hydrogen. At present, anatase is placed in a refrigerator or an air purifier to irradiate it with ultraviolet rays to decompose a bad odor in the refrigerator or room. It has been expanded to include uses. As a method of fixing anatase, a method of applying anatase to a substrate or applying it into the pores of a honeycomb body is known.

Next, a sol-gel technique for forming a transparent anatase film on the surface of glass or tile has been established because it is necessary to increase the light receiving area in order to increase the efficiency of photocatalytic decomposition. That is, an anatase sol film is formed starting from titanium ethoxide, and this anatase sol film is grown to an anatase gel film while being heated. Finally, the anatase gel film is heated at a temperature of several hundreds of degrees Celsius or more to be uniformly transparent. A method has been developed to form a simple anatase film.

This anatase film forming technique was first applied to toilet floor tiles and toilet pottery products, and a system for photodecomposing malodorous organic substances adhering to the tiles and pottery with ultraviolet rays has been put into practical use. Furthermore, an anatase film is formed on the surface of the window glass to prevent the window glass from becoming dirty, and an anatase film is formed on the transparent glass of the light source for illumination in the tunnel to keep the transparent glass clean at all times. It is being held.

[0006]

However, the following problems have been pointed out for the above anatase film. FIG. 14 is a structural diagram of a conventional anatase film 70. In order to prevent the anatase film 70 from peeling off from the substrate surface such as tiles, it is necessary to form the anatase film 70 densely, and finally the anatase film is heated at a temperature of several hundreds of degrees Celsius. Of course, depending on the heating temperature, the crystallinity of the anatase film 70 is high.
Are drawn to form a single crystal film.

FIG. 15 is an explanatory view of dehydration by heating in the conventional anatase film 70. Since the valence of Ti is tetravalent, the Ti atom on the surface has one dangling bond (unbonded hand), and a hydroxyl group which is a decomposition product of water is usually bonded to this dangling bond. . Also, O
One hydrogen atom, which is a decomposition product of water, is bound to. Since this bonding layer is a layer in which water is chemically bonded, the chemically adsorbed water layer 2
It is called 2a.

However, since the conventional anatase film 70 is finally heated at several 100 ° C., the chemically adsorbed water layer 22
OH and H of a are desorbed by heat, and the chemically adsorbed water and the physically adsorbed water are evaporated and hardly remain. If the heating temperature is 600 ° C. or higher, two dangling bonds of Ti bond with O, and the dangling bonds may disappear from the surface. If the dangling bond disappears in this way, even if water molecules approach the surface,
You can no longer combine.

The disappearance of water molecules from the surface rapidly reduces the photocatalytic efficiency of anatase. The reason can be understood from the principle of photocatalysis of titanium oxide. When ultraviolet rays hit anatase, electrons and holes are generated, and the electrons convert O ₂ into O ₂
^The holes are reduced to ⁻ and OH becomes OH ⁻ (hydroxyl radical).
O ₂ ⁻ and OH · can move on the anatase surface to decompose organic substances.

Since the hydroxyl radicals are supplied from the water molecules on the anatase surface, the hydroxyl radicals are not generated when the water adsorbed on the anatase surface disappears. Since hydroxyl radicals support half of the photocatalytic efficiency, the loss of adsorbed water causes the photocatalytic efficiency to drop sharply. In particular, those of the optical resolving power of OH · is O ₂ in recent years of research ^- are said to be more powerful than.

FIG. 16 is an explanatory diagram of a decrease in light transmittance in the anatase film 70 of the conventional plate-shaped article 30. An anatase film 70 is formed on the surface of the plate-shaped article 30.
Now, when the light L enters the anatase film 70, a part of the light is reflected by the anatase film surface 70a with the reflectance R, and the remaining light is transmitted through the anatase film 70 to perform a photolytic action. The light reflected by the surface 30a of the plate-like article is again reflected by the surface 70a of the anatase film with the same reflectance R as described above.

As the reflectance R increases, the anatase film 7
Since the transmitted light intensity to 0 decreases, it is expected that the photolysis efficiency in the anatase film 70 will naturally decrease accordingly. This reflectance R is Fresnel's reflection formula R = {(n ₁
It can be calculated by −n ₂ ) / (n ₁ + n ₂ )} ² . n ₁ is the absolute refractive index of the atmosphere, and n ₂ is the absolute refractive index of the anatase film 70.

Substituting n ₁ = 1 and n ₂ = 2.52,
Since R = 0.19, it can be seen that when anatase is used as a photocatalyst, 19% of the light L is discarded by reflection and does not contribute to photolysis. Therefore, as long as an anatase film is used as a photocatalyst, 19% of light has a drawback that it does not contribute to photodecomposition in principle.

FIG. 17 is an explanatory view of a decrease in light transmittance in the anatase film 70 of the conventional light source article 40. The light source article 40 represents a fluorescent lamp, and includes a phosphor layer 44 on the inner surface side of a glass tube 42 and an anatase film 70 on the outer surface side.

The ultraviolet rays generated by the discharge of the hollow portion 46 excite the phosphor layer 44 to generate fluorescence. Phosphor layer 44
The light L emitted in (1) passes through the glass tube 42 and the anatase film 70 and is emitted into the atmosphere.

The light L is reflected by the surface 42a of the glass tube and the surface 70a of the anatase film, but photolysis is performed by the anatase film 70.
Therefore, if the reflection on the surface 42a of the glass tube is large, the efficiency of photolysis is reduced.

The reflectance R of the glass tube surface 42a is
Refractive index n of tube 42₁And the refractive index n of the anatase film 70_TwoTo
It can be calculated using the Fresnel reflection formula. n₁= 1.5
And n _Two= 2.52 gives R = 0.064.
It Therefore, about 6% of the fluorescence does not contribute to photolysis.
I understand.

Thus, the anatase film 7 is used as a photocatalyst.
When 0 is used, there is a serious drawback that the adsorbed water disappears by the final heating of the sol-gel film, and the dangling bond disappears by the further heating at a high temperature so that the water adsorption becomes impossible. Further, it has been found that there is a defect peculiar to anatase that the light reflectance R increases due to the large refractive index of anatase, and the photolysis efficiency decreases due to a decrease in the effective light amount.

Therefore, it is an object of the present invention to stop using an anatase film as a photocatalytic film formed on the surface of an article, and replace the anatase film with sufficient adsorbed water and at the same time reduce the light reflectance. By providing a photocatalyst film capable of photodecomposing on the entire surface and inside of the film by increasing the effective light amount by providing a product for environmental purification having a markedly improved environmental purification function and a manufacturing method thereof. Is.

[0020]

The present invention has been made to solve the above-mentioned problems, and the first invention thereof is to form a silica gel film on the surface of an article which comes into contact with the environment. It has a large number of pores communicating with the inside thereof, and the photocatalyst particles are uniformly dispersed and fixed on the surface and inside of this silica gel membrane to constitute an environmental purification article. Since the silica gel film has an extremely highly hydrophilic surface, it is possible to supply hydroxyl ions by the adsorbed water that is always present on the surface, and it is possible to decompose pollutants with high efficiency by generating hydroxyl radicals. Further, the refractive index of the silica gel film is almost the same as that of glass, and the reflectance on the surface of the silica gel film is significantly lower than that of anatase, and almost all light can be used for photocatalytic decomposition. Furthermore, since the photocatalyst particles are uniformly dispersed on the surface and inside of the silica gel film, the photocatalyst particles are exposed on the surface and the pores of the silica gel film, and the contaminants adsorbed inside the pores are more effective by the neighboring photocatalyst particles. Can be decomposed.

The second invention uses a metal ultrafine particle-supporting photocatalyst in which at least metal ultrafine particles are supported on the surface of rutile-type titanium dioxide particles as the photocatalyst particles. Therefore, not only ultraviolet rays but also blue visible light is caused by the gap energy characteristic of rutile. Can also be used for photolysis, and can be photolyzed by sunlight as well as UV lamps. Further, by supporting the ultrafine metal particles, the electrons generated in rutile can be efficiently transferred to the surface of the ultrafine metal particles by the quantum effect, and the pollutants can be decomposed with high efficiency.

A third invention is to prepare a silanol solution by adding silicon alkoxide and water to alcohol, and to hold this silanol solution at room temperature to grow innumerable silica sol particles by hydrolysis and polycondensation reaction. To form a silica sol liquid, and the silica sol liquid and photocatalyst powder are added to a suitable solvent and mixed and aged at room temperature to form a photocatalytic silica sol liquid, so that the photocatalyst particles can be uniformly dispersed in the silica sol liquid. it can. When this photocatalyst silica sol liquid is applied to the surface of an article to form a photocatalyst silica sol film, photocatalyst particles can be uniformly dispersed on the surface and inside of the photocatalyst silica sol film. Further, since the photocatalytic silica sol film is aged to the photocatalytic silica gel film while keeping this article at room temperature, a large amount of chemically adsorbed water and physically adsorbed water are present on the surface of the silica gel film due to the operation at room temperature in all steps. Provided is an article for environmental purification, which can surely secure the photocatalytic decomposition power of a silica gel film due to the formation of radicals.

In the fourth aspect of the present invention, since the photocatalysts carrying metal ultrafine particles in which at least metal ultrafine particles are carried on the surfaces of rutile type titanium dioxide particles are used as photocatalyst particles, the photocatalyst particles carrying ultrafine metal particles are provided on the surface of the article for environmental purification. It is possible to form a silica gel film in which is uniformly dispersed and fixed, and by rutile, not only ultraviolet rays but also blue visible light can be used for photolysis, and not only ultraviolet rays but also sunlight can be photolyzed.
Also, because it carries ultrafine metal particles, its quantum effect
Provided is a method for producing a sol-gel for an environmental purification article that is capable of rapidly decomposing pollutants.

In the fifth invention, a light source, a shade of a light source, a building, a structure, an inorganic fiber, or an inorganic fiber product can be used as an article, and various kinds can be obtained by forming a photocatalytic silica gel film on the surface of these articles. A high added value of photolytic power can be added to the ordinary value of an article.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that when the photocatalyst particles carrying ultrafine metal particles are supported on the surface of the adsorbent, the adsorbent adsorbs pollutant particles in the environment on the surface, The idea was that the photocatalyst supporting ultrafine metal particles could be strongly decomposed by photocatalyst.

First, an invention using activated carbon fiber as an adsorbent was made, and this was disclosed as Japanese Patent Laid-Open No. 11-47611. However, forming a fabric from activated carbon fiber,
There has been a problem that a technique for housing this cloth in an article or attaching it to the surface is required, and the activated carbon fiber is black and does not transmit light.

Next, the adsorbent is sharpened to ensure transparency.
We carefully examined high-performance porous glass as a transparent adsorbent.
The invention to be introduced has been made, and is disclosed in JP-A-11-262672.
Published as an issue. This porous glass is made of high-silicate glass
It is formed as an intermediate product of_TwoA small amount of
B_TwoO_ThreeAnd Al_TwoO_ThreeAnd Na_TwoBorosilicate by adding O
Glass, heat-treated to make SiO_TwoInsoluble phase consisting of
And B_TwoO_ThreeAnd Al_TwoO _ThreeAnd Na_TwoDivided into soluble phase consisting of O
Make them share. When the soluble phase is eluted by acid treatment, the soluble phase
Porous glass having spaces as continuous pores is completed.

Porous glass is good as a transparent adsorbent having pores, but since the surface-adsorbed water is completely evaporated due to the melting treatment, it is difficult to generate hydroxyl radicals on the surface and pores. Become. Moreover, in order to prevent alteration of the photocatalyst due to the melting treatment, there is only a method of attaching the ultrafine metal particle-supported photocatalyst particles to the surface of the porous glass by post-treatment. Therefore, although the photocatalyst particles supporting ultrafine metal particles can be attached to the surface of the porous glass film, they cannot be uniformly dispersed inside the pores. That is, since the ultrafine metal particle-supported photocatalyst particles do not exist inside the porous glass film, the contaminants adsorbed in the pores are hard to be decomposed, and the photocatalytic force is reduced accordingly.

The present invention succeeds in overcoming all of the above-mentioned drawbacks by using a silica gel film instead of the porous glass film. The silica sol-gel method is a known method, but the present invention is greatly different from the conventional silica sol-gel method in the following points.

First, in the present invention, since the photocatalyst particles are mixed and dispersed at the stage of the silica sol liquid to form a film on the surface of the article, the photocatalyst particles can be uniformly dispersed inside and on the surface of the silica gel film. Therefore, the photocatalyst particles are uniformly dispersed and exposed on both the surface of the silica gel film and the pores inside.

Contaminants are adsorbed from the surface, but not only adhere to the surface but are adsorbed in the numerous pores inside. For the pollutants adsorbed in the pores, the photocatalyst particles dispersed inside exert the photolytic action, and for the contaminants adsorbed on the surface, the photocatalyst particles on the surface exert the photolytic action. , Comprehensively efficient photolysis can be realized.

Secondly, in the known silica sol-gel method, the dried silica gel film is finally heated at several 100 ° C. to perform the vitrification treatment. In the present invention, since the sol-gel process is all performed in a normal temperature atmosphere and no heat treatment is performed, a large amount of adsorbed water remains on the surface and pores of the silica gel membrane. Due to the presence of this adsorbed water, hydroxyl radicals are effectively generated, and the photolysis process proceeds efficiently.

The silica gel film of the present invention is hardened and dried at room temperature, that is, at room temperature. The silica gel film obtained has a hardness such that it cannot be peeled off even when scratched with a pencil lead of 6H. With a hardness of this level, there is no problem in practical use, and it can withstand normal use as an environmental purification article.

Embodiments of the environmental purification article and the sol-gel manufacturing method thereof according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view for schematically explaining the environmental purification article according to the present invention. Article 2 is photocatalytic silica gel film 4
Represents all the goods that are formed, regardless of real estate or real estate. For example, glass tubes of light sources, shades of light sources, outer wall surfaces and roofs of buildings, tiles and ceramics, outer and inner surfaces of various products, piers and outer walls of bridges and highways, inorganic fibers, or inorganic fiber products, and other photocatalysts. All articles whose surface is not decomposed by are included in the article of the present invention. In general, articles made of organic materials such as plastics are photolyzed over a long period of time, but since there is no effect of photolysis for a short period of time, in such a case, the organic articles are also used. Included in the inventive article.

A photocatalyst silica gel film 4 is formed on the article surface 2a, and a large number of photocatalyst particles 8 are uniformly dispersed and fixed on the surface and inside of the silica gel film 6.

When the silanol solution to be described later is hydrolyzed, Si (OH) ₄ is formed, and Si (OH) ₄ is further formed through polycondensation.
The silica sol primary particles 10 are formed by the formation of O ₂ and the mutual coupling of SiO ₂ . The silica sol primary particles 10 are bonded to each other over time to form silica sol secondary particles 12 surrounded by a dotted line.

Although the silica sol primary particles 10 have small primary particle pores (not shown), the silica sol secondary particles 12 also have secondary particle pores 12a.
When the silica sol secondary particles 12 are bonded to each other to form a network, innumerable pores 14 are formed.
4 is a complicated and complicated environment (for example, air or liquid)
Is in communication with. Environmental contaminants and harmful substances are adsorbed on the pores 14 and the surface of the photocatalyst silica gel film.

In the silica sol-gel method used in the present invention, the heat treatment is not performed and the aging is performed at room temperature (room temperature), so that the secondary particle pores 12a and the pores 14 are formed relatively large. Therefore, a large amount of contaminants and harmful substances can be adsorbed in the secondary particle pores 12a and pores 14.
Further, since no heat treatment is carried out, a large amount of water necessary for the photocatalytic decomposition is adsorbed on the membrane surface 18 and the surfaces of the pores 14, and the hydroxyl radical formed by the decomposition of this water molecule makes the photocatalyst more efficient. Decomposition can be done.

The surface 18 of the photocatalytic silica gel film 4 has a large number of film surface recesses 16, and the pores 14 and the film surface recesses 16 are formed.
Innumerable photocatalyst particles 8 are dispersed and fixed in other fine spaces. Since the photocatalyst particles 8 are put into the silica sol liquid and uniformly mixed, the photocatalyst particles 8 are uniformly dispersed in the silica gel film 6. Due to this uniform dispersion, it can be seen that the photocatalyst particles 8 are predominantly present in the silica gel film 6 more than in the silica gel film surface 18. Therefore, in the present invention, the photocatalytic decomposition inside the silica gel film 6 plays an important role.

The pollutant particles in the environment are the pores 14 and the surface 1.
Adsorbed on 8. In addition, the photocatalyst silica gel film 4 is
When light is irradiated through the product 2, the photocatalyst particles cause
O_Two ⁻And OH. Are formed and these O_Two ⁻Or OH
Adsorbed contaminant particles that have moved through the pores 14 and the membrane surface 18
Decompose the child.

As the photocatalyst particles 8, ultrafine metal particle-supported photocatalyst particles which the present inventors have already disclosed in JP-A-10-146531 are suitable. In FIG. 1, the photocatalyst particles carrying the ultrafine metal particles are shown as photocatalyst particles 8. One or more ultrafine metal particles 8 are added to the rutile particles 8a.
The state in which b is carried is shown.

The ultrafine metal particles 8b are metal particles having a particle size of about 1 to 5 nm, and are firmly bonded to the rutile particles 8a. The rutile particles 8a are metal oxide semiconductors having a gap energy of 3.05 eV, and of course ultraviolet rays,
It is also characterized by being excited by blue visible light.

The ultrafine metal particles 8b have a particle size of 1 to 5 nm
Since it is minute, the rutile particles 8a and the ultrafine metal particles 8b are
The wave function is considered to be in a quantum resonant tunneling state
To be When these rutile particles are exposed to light, they are excited by light.
Electrons and holes are generated by the
Immediately transferred to the ultrafine metal particles 8b by _Two
O_Two ⁻Reduce to. At the same time, holes are rutile particles 8a.
On the surface of⁻Is oxidized to produce OH. like this
And the effective O for effective photolysis_Two ⁻When
OH. Can be generated.

If the photocatalyst particles 8 are dispersed in the pores 14, the produced O ₂ ⁻ and OH · move through the pores 14 and the polluted organic substances adsorbed in the pores 14 are removed. It decomposes one after another. Therefore, in the present invention, by combining the photocatalyst particles 8 with the silica sol-gel method, the photocatalyst particles 8 have been successfully dispersed in the silica gel film 6.

FIG. 2 is a process chart showing a method for producing a sol-gel for an environmental purification article according to the present invention. In step m1, the silanol solution is adjusted. The silanol solution is prepared by mixing silicon alkoxide, water for hydrolysis, alcohol for preparing a homogeneous solution, and acid for reaction catalyst.

The silicon alkoxide is represented by the general formula of Si (OR) _n , and R may be an alkyl group. For example, Si
_(OC 2 _{H 5) 4:} tetraethoxysilane (ethyl silicate) and Si (OCH _{3) 4:} tetramethoxysilane (methyl silicate) and the like can be used. Further, alcohol as a solvent includes, for example, methanol and ethanol,
As the acid for the catalyst, hydrochloric acid, nitric acid, sulfuric acid, acetic acid, hydrofluoric acid, etc. can be used.

In step m2, the silanol solution is left to age at room temperature for 24 hours. As a result, a silica sol liquid is formed at m3. This reaction process is a two-step reaction, and the first-step reaction is the following hydrolysis. nSi (OC ₂ H ₅ ) ₄ +4 nH ₂ O → nSi (OH) ₄ +
4nC ₂ H ₅ OH

The second stage reaction is a polycondensation reaction of Si (OH) ₄ represented by the following formula. The nSi (OH) ₄ → nSiO ₂ + 2nH ₂ O SiO ₂ molecules are bonded to each other to form silica sol particles. The silica sol particles are considered to be silica sol primary particles 10.

At m4, the photocatalyst powder is added to the silica sol liquid, and the mixture is stirred at m5 for 12 hours or more with a ball mill. By applying a ball mill, silica sol particles with a uniform particle size can be formed, and a photocatalytic silica sol liquid is formed (m
6) Can be done. The silica sol particles at this stage are considered to be silica sol secondary particles 12.

At m7, the photocatalytic silica sol liquid is formed into a film on the surface of the article. Various methods such as a dipping method, a spin coating method, a brush method, and a printing method can be adopted as the film forming method. The dipping method is efficient with a light source such as a fluorescent lamp, and after pulling up, spin drying (m8) for about 5 minutes to remove excess silica sol liquid. As a result, a photocatalytic silica sol film can be formed (m9) on the surface of the article.

The photocatalytic silica sol film-formed article 12
Aging the photocatalytic silica sol film by leaving it at room temperature for a period of time (m
10) Then, a film structure is formed while silica sol particles form a network with each other, and the hardness is increased while being gradually dried to form a photocatalytic silica gel film (m11).

Finally, the residual hydrochloric acid used as a catalyst is washed with water (m12) and removed to complete a photocatalytic silica gel membrane (m13). The silica gel film at this stage is the photocatalytic silica gel film 4 shown in FIG. The photocatalyst silica gel film 4 is formed by uniformly dispersing and fixing photocatalyst particles 8 in a silica gel film 6. If an acid is not used as a catalyst in the silanol solution, the m12 washing step is unnecessary.

FIG. 3 is a particle growth state diagram in the silica sol-gel process according to the present invention. The silica sol-gel method starts with a silanol solution 20 and uses silica sol primary particles 10
The photocatalyst particles 8 are introduced at the stage where the particles are formed.

When the silica sol liquid containing the photocatalyst is mixed and aged while being agitated, the secondary particles of the silica sol 12 are formed, and the photocatalyst particles 8 are dispersed in the meantime. Further, while forming a network, the photocatalyst silica gel film 4 in which the photocatalyst particles 8 are uniformly dispersed in the silica gel film 6 is completed.

FIG. 4 is a schematic plan view of the photocatalytic silica gel film 4. The photocatalyst silica gel film 4 has a large number of film surface recesses 1
6 are scattered, and photocatalyst particles 8 are uniformly dispersed in these film surface concave portions 16. As the photocatalyst particles 8, ultrafine metal particles-supported photocatalyst particles in which ultrafine metal particles 8b are supported on rutile particles 8a are used.

FIG. 5 is an explanatory view of adsorbed water on the surface of the photocatalytic silica gel film according to the present invention. Since the silica sol-gel method of the present invention is characterized in that all steps are processed at room temperature, a large amount of adsorbed water is present on the surface of the photocatalytic silica gel film 4.

Water molecule is H⁺And OH⁻Dissociates into OH⁻Is
Bonded to Si, H⁺Binds to O, and this chemical bond layer becomes
The adsorbed water layer 22a is formed. Next, this OH⁻And H⁺
To H _TwoPhysically adsorbed water layer where O is bonded one after another by hydrogen bond
22b is formed. Therefore, the photocatalytic silica gel of the present invention
Since a large amount of water molecules exist in the membrane 4, it is necessary for the photocatalyst.
Hydroxyl radicals are abundantly formed.

FIG. 6 is a sectional view for explaining light transmission in the plate-like article according to the present invention. The article 2 includes all articles used for photocatalyst, and the article having a plate shape among them is referred to as a plate article 30. The photocatalytic silica gel film 4 is formed on the surface of the plate-shaped article 30. The photocatalyst silica gel film 4 is formed by dispersing photocatalyst particles 8 in a silica gel film 6. Since the plate-like article 30 has no light transmitting property, it is irradiated with light from the surface of the photocatalytic silica gel film 4.

Innumerable pores 14 are formed in the silica gel film 6, and the photocatalyst particles 8 are distributed so as to be exposed in the pores 14. When the light L is irradiated, a part of the light is reflected by the surface 18 of the photocatalyst silica gel film, and the remaining light is transmitted through the photocatalyst silica gel film 4 to decompose the polluted organic substance adsorbed in the pores 14. The light that reaches the surface is partially reflected again by the photocatalytic silica gel film 4 and passes through the environment.

The reflectance R of the light L is the Fresnel reflection formula R =
It is calculated by {(n ₁ −n ₂ ) / (n ₁ + n ₂ )} ² . Atmospheric refractive index n ₁ = 1 and photocatalytic silica gel film refractive index n ₂ =
Using 1.5 (substantially the same as glass), R = 0.04. In other words, it can be understood that 96% of the light L can be transmitted through the photocatalytic silica gel film 4 and photodecomposed, which is far better than 81% of the anatase film. The reason for this is that silica gel films have a small index of refraction that is about the same as glass.

FIG. 7 is a sectional view for explaining light transmission in the light source article according to the present invention. In this embodiment, the article 2
A light source such as a fluorescent lamp or a lamp is used as the light source, and the photocatalytic silica gel film 4 is formed on the surface of the glass tube for light irradiation of the light source.

In the light source article 40, the fluorescent film 44 is formed on the inner surface of the glass tube 42 having the hollow portion 46.
A photocatalytic silica gel film 4 is formed on the outer surface of 2.
When a voltage is applied to an electrode (not shown), fluorescence is emitted from the fluorescent film 44 by the ultraviolet rays generated by the discharge of the hollow portion 46.

The light L emitted from the fluorescent film 44 is emitted to the environment via the glass tube 42 and the photocatalytic silica gel film 4. The light L is partly reflected by the glass tube surface 42a, and the remaining light is transmitted through the photocatalytic silica gel film 4 to perform a photocatalytic reaction.

The light reflectance R by the glass tube surface 42a is also calculated by the Fresnel reflection formula. Since the refractive index n ₁ of the glass tube 42 is about 1.5 and the refractive index n ₂ of the photocatalytic silica gel film 4 is also about 1.5, the reflectance R = 0 from n ₁ −n ₂ = 0. That is, it can be seen that 100% of the light L is transmitted inside the photocatalytic silica gel film 4.

Inside and on the surface of the photocatalytic silica gel film 4,
The organic contaminants adsorbed in the pores 14 are photocatalytically decomposed,
Then, the light is emitted from the photocatalytic silica gel film surface 18 to the environment. Reflectance R by photocatalytic silica gel film surface 18
Is R = 0.04 from the refractive index n ₁ = 1.5 of the silica gel film and the refractive index n ₂ = 1 of the atmosphere, but this 4% of the reflected light returns to the photocatalytic silica gel film 4 again. There is no loss due to photolysis.

[0067]

EXAMPLES [Example 1: Photocatalytic effect of plate-like article having photocatalyst silica gel film formed thereon] FIG. 8 shows a plate-like article 3 according to the present invention.
It is a test device figure which confirms the photocatalytic effect of 0. The closed container 50 is an acrylic desiccator having a volume of 17.5 liters, and a sample of 150 mm × 100 mm is horizontally placed in the closed container 50. This sample is a plate-shaped article 30.
The photocatalytic silica gel film 4 is formed on the surface of the.
5% by weight of photocatalyst particles in rutile particles with an average particle size of 20 nm
Of Pt is carried.

As the plate-like article 30, three types were selected: a ceramic-treated aluminum plate, a white color steel plate, and a surface-treated aluminum plate with NaOH. Two 6 W lamps 54 were placed 3 cm apart directly above the sample. This lamp 54 is a type FL6BL ultraviolet lamp manufactured by Toshiba, and its ultraviolet intensity is 1.26 mW / cm ² at a wavelength of 365 nm.

Add 1 part of acetaldehyde into the closed container 50.
Gas was injected into the container at a concentration of 00 ppm and circulated by the circulation fan 52, the gas in the container was sampled with time, and the concentration was measured by a gas chromatograph.

FIG. 9 is a time course diagram of acetaldehyde concentration when a plate-like article is used. All of the three types of plate-shaped articles had an initial concentration of 100 ppm (t = 0), but with the passage of time, the ceramic coating plate decomposed at the highest speed, the second was a white color steel plate, and the third was a NaOH-treated aluminum plate. Became.

The decomposition rate constant k is 2.94 (1 / h) for the ceramic coating and 2.13 for the white color steel plate,
It became 1.46 for the aluminum plate treated with NaOH. Therefore, the ceramic coated plate is considered to be the most suitable as the material property.

Example 2 Photocatalytic Effect of Light Source Lamp Formed with Photocatalytic Silica Gel Film FIG. 10 is a test apparatus diagram for confirming the photocatalytic effect of the light source article 40 according to the present invention. In the sealed container 50, the photocatalytic silica gel film 4 is placed in the glass tube 4.
Two light source articles 40 each having a film formed on its outer surface are arranged.

The light source article 40 was a cold cathode tube, and the photocatalyst silica gel film 4 was sol-gel formed on this surface by a dipping method. The light source article 40 was a cold cathode tube, and three types of cold cathode tubes were prepared. The first is a photocatalyst silica gel film formed in one layer, the second is a photocatalyst silica gel film formed in two layers,
The third and third are three layers of photocatalytic silica gel film.

FIG. 11 is a time chart of acetaldehyde concentration and carbon dioxide concentration when the light source article 40 is used.
The temperature was adjusted to 20 ° C., the relative humidity was adjusted to 60%, and the initial concentration was adjusted to 40 ppm (t = 0). Other than (1), t =
Although it is less than 40 ppm at 0, it indicates that the space concentration is lowered because acetaldehyde is adsorbed on the photocatalytic silica gel film.

With respect to the decomposition of acetaldehyde, the third coating had the highest decomposition rate, followed by the second coating and the first coating. Decomposition rate constant is 5.12.
(1 / h), the second coating was 3.21 (1 / h), and the first coating was 1.97 (1 / h). Contrary to the decrease in acetaldehyde concentration, the carbon dioxide concentration gradually increases. However, with respect to the carbon dioxide concentration, the second coating is the highest, and the sequence is not always clear between the first coating and the third coating. This seems to be a problem in the method of measuring carbon dioxide concentration.

[Example 3: Photocatalytic effect of glass fiber product formed with photocatalytic silica gel film] FIG. 12 is a test apparatus diagram for confirming the photocatalytic effect of the glass fiber product article 60 according to the present invention. The test conditions are almost the same as in Example 1, and the different points will be described. The lamp 55 is a white fluorescent lamp (made by Toshiba,
Type FL6N), the amount of light is 0.02m at a wavelength of 365nm
W / cm ² and 1.2 mW / cm ² at a wavelength of 405 nm.

The glass fiber product article 60 is a woven fabric made of glass fiber, model H201-C2150 is 550 ° C.
It means that it is a product for roll blinds that has been baked for 40 minutes to remove surface impurities. The photocatalyst silica gel film 4 was formed on the glass fiber product article 60 by the dipping method. Three types of weight ratios of the photocatalytic silica gel film 4 to the glass fiber product article 60 were prepared: 1.4%, 6.0%, and 11.2%.

FIG. 13 is a time course diagram of the acetaldehyde concentration when the glass fiber product article 60 is used. The acetaldehyde concentration was measured by gas chromatography every 30 minutes, and the measurement was continued for 180 minutes. The larger the weight of the photocatalyst, the faster the decomposition rate, and the decomposition rate constant is 11.2%.
At 0.89 (1 / h) and 6.0% at 0.53 (1 /
h), 1.4% was found to be 0.13 (1 / h).

The present invention is not limited to the above embodiments, and various modifications, design changes, etc. within the technical scope of the present invention are included in the technical scope thereof. Needless to say.

[0080]

According to the first invention, a silica gel film having a large number of pores communicating with the environment inside is formed on the surface of an article, and photocatalyst particles are uniformly dispersed and fixed on the surface and inside of the silica gel film. Therefore, the extremely hydrophilic surface of the silica gel film supplies sufficient water for photodecomposition, and the pollutants can be decomposed with high efficiency due to the high oxidizing power of the hydroxyl radicals produced in large quantities. . Moreover, the refractive index of the silica gel film is almost the same as that of glass, and the refractive index is similar to that of air, water, and organic solvents, and the light reflectance on the surface of the silica gel film in contact with the environment such as air and liquid is extremely small. Has the characteristic that almost all of the above can be utilized for photolysis. Furthermore, since the photocatalyst particles are uniformly dispersed on the surface and inside of the silica gel film, the photocatalyst particles are exposed on the surface of the silica gel film and innumerable pores, and the contaminants adsorbed inside the pores are separated from the photocatalyst particles in the vicinity. Can be effectively decomposed.

According to the second invention, the photocatalyst carrying ultrafine metal particles in which at least ultrafine metal particles are carried on the surface of rutile type titanium dioxide particles is used as the photocatalyst particles.
Due to the gap energy characteristic of rutile, not only ultraviolet rays but also blue visible light can be used for photolysis. Similar to ultraviolet lamps, white fluorescent lamps and sunlight can also be used for photolysis, and various commercially available light sources can be used. Further, since the ultrafine metal particles are firmly supported on the rutile particles, the electrons generated in the rutile by photoexcitation can be immediately transferred to the surface of the ultrafine metal particles by the quantum resonance tunneling effect, and a large amount of O ₂ ⁻ can generate pollutants. Highly efficient decomposition can be realized.

According to the third invention, since the silica sol liquid and the photocatalyst powder are added to an appropriate solvent and mixed and aged at room temperature to form a photocatalytic silica sol liquid, the photocatalyst particles are uniformly dispersed in the silica sol liquid. It When this photocatalytic silica sol liquid is applied to the surface of an article to form a photocatalytic silica sol film, photocatalyst particles can be uniformly dispersed on the surface and inside of the photocatalytic silica sol film. Furthermore, since the photocatalytic silica sol film is aged to the photocatalytic silica gel film by keeping this article at room temperature, a large amount of chemically adsorbed water or physically adsorbed water exists on the surface and pores of the silica gel film due to the room temperature operation of all steps. To do. Moreover, since numerous photocatalyst powders are uniformly dispersed and exposed on the surface and pores of the silica gel film, the photocatalyst powder and water coexist in the vicinity of each other, and due to the high translucency of the silica gel film, the hydroxide A large amount of radicals are generated, and it is possible to manufacture an environmental purification article that retains a high photolytic power.

According to the fourth aspect of the present invention, since the photocatalysts carrying ultrafine metal particles in which at least ultrafine metal particles are carried on the surface of rutile type titanium dioxide particles are used as photocatalyst particles,
Due to the gap energy characteristics of rutile, it is possible to utilize ultraviolet light and blue visible light as decomposed light.
You can use sunlight and many other types of light sources on the market.
Further, since the ultrafine metal particles is a composite photocatalyst particles firmly supported on rutile particles, since electrons generated resulting in rutile can be immediately transferred to the metal ultrafine particles surface by the quantum resonant tunneling effect, O ₂ ^- large amounts of High efficiency decomposition of pollutants can be realized by the generation.

According to the fifth invention, the article is a light source,
Light shades, buildings, structures, inorganic fibers, or inorganic fiber products can be used, and by simply forming a photocatalytic silica gel film on the surface of these products, a high added value of photolytic power can be added to the ordinary use value of various products. Can be added to contribute to the creation of new industries.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an environmental purification article according to the present invention.

FIG. 2 is a process drawing showing a method for manufacturing an environmental purification article according to the present invention.

FIG. 3 is a particle growth state diagram in the silica sol-gel process according to the present invention.

FIG. 4 is a schematic plan view of a photocatalytic silica gel film 4.

FIG. 5 is an explanatory view of adsorbed water on the surface of the photocatalytic silica gel film according to the present invention.

FIG. 6 is a cross-sectional view illustrating light transmission in the plate-like article according to the present invention.

FIG. 7 is a cross-sectional view illustrating light transmission in a light source article according to the present invention.

FIG. 8 is a test device diagram for confirming the photocatalytic effect of the plate-shaped article 30 according to the present invention.

FIG. 9 is a time course diagram of acetaldehyde concentration when the plate-shaped article 30 according to the present invention is used.

FIG. 10 is a diagram of a test apparatus for confirming the photocatalytic effect of the light source article 40 according to the present invention.

FIG. 11 is a time course diagram of acetaldehyde concentration and carbon dioxide concentration when the light source article 40 according to the present invention is used.

FIG. 12 is a test device diagram for confirming the photocatalytic effect of the glass fiber product article 60 according to the present invention.

FIG. 13 is a time course diagram of acetaldehyde concentration when the glass fiber product article 60 according to the present invention is used.

FIG. 14 is a structural diagram of a conventional anatase film 70.

FIG. 15 is an explanatory diagram of dehydration by heating in the conventional anatase film 70.

FIG. 16 is an explanatory diagram of a decrease in light transmittance in the anatase film 70 of the conventional plate-shaped article 30.

FIG. 17 is an explanatory diagram of a decrease in light transmittance in the anatase film 70 of the conventional light source article 40.

[Explanation of reference numerals] 2 is an article, 2a is an article surface, 4 is a photocatalytic silica gel film,
6 is a silica gel film, 8 is photocatalyst particles, 8a is rutile particles, 8b is ultrafine metal particles, 10 is silica sol primary particles,
12 is silica sol secondary particles, 12a is secondary particle pores, 1
4 is a pore, 16 is a recess on the membrane surface, 18 is a photocatalyst silica gel membrane surface (silica gel membrane surface), 20 is a silanol solution,
22a is a chemically adsorbed water layer, 22b is a physically adsorbed water layer, 30 is a plate-like article, 30a is a plate-like article surface, 40 is a light source article, 4
2 is a glass tube, 42a is a glass tube surface, 44 is a fluorescent film,
46 is a hollow part, 50 is a sealed container, 52 is a circulation fan,
54 and 55 are lamps, 70 is an anatase film, and 70a is an anatase film surface.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Kenji Oshita             2-7-19 Nishi, Saito-ku, Osaka-shi, Osaka               Within Daiken Chemical Industry Co., Ltd. (72) Inventor Takeshi Nishi             2-7-19 Nishi, Saito-ku, Osaka-shi, Osaka               Within Daiken Chemical Industry Co., Ltd. (72) Inventor Akio Harada             2-7-19 Nishi, Saito-ku, Osaka-shi, Osaka               Within Daiken Chemical Industry Co., Ltd. F-term (reference) 4G069 AA02 AA03 AA08 BA02A                       BA02B BA04A BA04B BA13A                       BA13B BA14A BA14B BA17                       BA38 BA48A BB02A BB02B                       BC75A BC75B CA17 EA09                       EA11 FA03 FA04 FA06 FB08                       FB15

Claims (5)

[Claims] 1. An article prepared for photodegrading pollutants in the environment, a silica gel film formed on the surface of the article in contact with the environment, and the silica gel film is provided with a large number of fine particles that communicate with the environment. It is composed of photocatalyst particles that have pores inside and are dispersed and fixed on the surface and inside of this silica gel membrane to decompose pollutants in the environment. Contamination in the environment is caused by the photocatalyst exposed on the surface and pores of the silica gel membrane. An environmental purification article characterized by decomposing substances. 2. The environmental purification article according to claim 1, wherein the photocatalyst particles are ultrafine metal particle-supported photocatalysts in which at least ultrafine metal particles are supported on the surfaces of rutile-type titanium dioxide particles. 3. A silica sol liquid is prepared by adding silicon alkoxide and water to alcohol to prepare a silanol solution, and maintaining this silanol solution at room temperature to grow innumerable silica sol particles by hydrolysis and polycondensation reaction. The silica sol liquid and the photocatalyst powder are added to a suitable solvent and mixed and aged at room temperature to form a photocatalytic silica sol liquid, and the photocatalytic silica sol liquid is applied to the surface of an article to form a photocatalytic silica sol film. A method for producing a sol-gel for an environmental purification article, characterized in that the article is kept at room temperature and the photocatalytic silica sol film is aged and dried to a photocatalytic silica gel film. 4. The method for producing a sol-gel for an environmental purification article according to claim 3, wherein the photocatalyst powder is a photocatalyst carrying ultrafine metal particles having at least ultrafine metal particles supported on the surface of rutile-type titanium dioxide particles. 5. The method for producing a sol-gel for an environmental purification article according to claim 3, wherein the article is a light source, a shade of a light source, a building, a structure, an inorganic fiber, or an inorganic fiber product.