JP2001038220A - Photocatalyst and functional base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand the surface area of a substrate and to almost equally activate a photocatalytic function layer by using a pair of reticulated members comprising Al or an alloy thereof and the substrate, which has a nonwoven fabric comprising Al or an alloy thereof, held between them and forming the photocatalytic function layer on the surface of the substrate. SOLUTION: A photocatalyst element 1 is constituted by forming a photocatalytic function layer 5 on the surface (both surfaces) of a substrate 2 wherein a nonwoven fabric 40 made of a metal is held between a pair of reticulated members 30, 30. The substrate 2 is constituted by interposing fibers (laminate) comprising Al or an alloy thereof between the reticulated members 30, 30 formed from Al or an alloy thereof and subsequently pressing (rolling) the same from both surfaces to hold the nonwoven fabric 40 made of a metal formed by the entanglement of metal fibers between both reticulated members 30, 30. As each of the reticulated members 30, for example, an expanded metal is used. The photocatalytic function layer 5 is formed by bonding a sol. soln. having a photocatalyst semiconductor, for example, TiO2 mixed therewith to the surface of the substrate 2 by spraying or dipping and drying the sol. soln. layer before baking the same at predetermined temp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst for oxidatively decomposing an organic compound or an inorganic compound suspended in a gas or a liquid (referred to as a fluid), and a functional substrate using the same.

[0002]

2. Description of the Related Art As petrochemical products increase, complex pollution of harmful organic compounds inside and outside a living environment has become a problem. As a means for solving this, there is a purification method using oxidative decomposition by a photocatalytic semiconductor.

For example, there is a method in which a photocatalytic semiconductor is carried on the surface of a gas constituting an apparatus or equipment, and the harmful organic substance is brought into contact with the photocatalytic semiconductor by placing the apparatus or equipment in a fluid in which the harmful organic substance floats. is there. In this case, in order to achieve a high photocatalytic function, it is necessary that the surface area of the photocatalytic function layer is large and that the photocatalytic semiconductor is sufficiently activated by an electromagnetic wave having an excitation wavelength.

Therefore, various proposals have conventionally been made with respect to a technique for increasing the surface area of the substrate and a technique for forming a photocatalytic layer (see, for example, JP-A-5-309267 and JP-A-8-196903). ).

[0005]

However, these methods merely increase the surface area and increase the area of the photocatalyst functional layer, but the activation rate by the electromagnetic wave of the excitation wavelength is low, or the fluid and the photocatalyst semiconductor cannot be separated. There are disadvantages such as poor contact efficiency. In addition, in order to form a device or an appliance, it is preferable that the substrate supporting the photocatalytic semiconductor can be formed by pressing such as press working, or has flexibility that can be rounded or bent. In particular, no inorganic base material has such a condition, and the range in which the photocatalyst can be used is narrow.

Accordingly, it is an object of the present invention to provide a photocatalyst which can increase the surface area of a substrate, activate a photocatalytic functional layer formed on the surface thereof almost uniformly, and increase the contact efficiency between a fluid and a photocatalytic semiconductor. An object of the present invention is to provide a body and a functional base material using the same.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method for producing a substrate comprising a pair of mesh members made of Al or an alloy thereof and a non-woven fabric made of Al or an alloy thereof held therebetween. And a technical means of forming a photocatalytic functional layer on the surface of the substrate. In the present invention, for example, expanded metal is used as the mesh member, and the nonwoven fabric can be formed by pressing Al fibers between a pair of expanded metals. Further, the photocatalyst of the present invention can be used as a functional base material having both a photocatalytic function and a silencing function.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a photocatalyst according to one embodiment of the present invention. In the figure, 1 is a photocatalyst, 2 is a substrate, 3
Reference numeral 0 denotes a mesh member, reference numeral 40 denotes a metal nonwoven fabric, and reference numeral 5 denotes a photocatalytic functional layer (indicated by a chain line). The photocatalyst 1 has a photocatalyst functional layer 5 on the surface (both surfaces) of a base 2 holding a metal nonwoven fabric 40 between a pair of mesh members 30, 30. The base 2 is made of a mesh member 30 formed of Al or an alloy thereof.
A fiber (laminate) made of the same metal material as described above is interposed between the metal fibers 30 and then pressed (rolled) from both sides to form a metal nonwoven fabric 40 formed by entanglement of metal fibers.
Is held. As the mesh member, FIG.
As shown in (1), for example, an expanded metal (a metal sheet having a large number of cuts, and the cuts are pulled in a substantially perpendicular direction to form a net) can be used.
３3 mm is preferred. The size of the hole (diamond) is 3 on the long hole side.
It is preferable that the short hole side has a range of 2 to 10 mm.
The mesh of the pair of mesh members may be the same or different. As the fiber made of Al or its alloy, a short fiber having a wire diameter of 10 to 200 μm and a length of several mm to several tens mm can be used, and a long fiber of several tens cm or more can also be used. The thickness of the photocatalyst formed in this way may be 1 mm or more from the viewpoint of the noise reduction effect, but is preferably 10 mm or less, more preferably 1 mm or less for weight reduction.
５5 mm.

The photocatalytic function layer 5 is formed by applying a sol solution mixed with a photoconductive semiconductor such as TiO _{2 to} the surface of the substrate by spraying or dipping and drying the sol solution.
It can be formed by baking at a temperature of less than 500C to less than 500C. If amorphous titanium peroxide or titanium oxide is mixed in the sol in a titanium weight ratio (dry amount) of 1: 1 or 1: 5 in addition to the photocatalyst semiconductor, the photocatalyst semiconductor is produced at a relatively low temperature. The particles can be firmly supported.

[0010] Further, P for supplementing functions such as fungicide sterilization.
t, Ag, Rh, RuO ₂ , Nb, Cu, Sn, NiO
Of zeolite, silica (silicon dioxide), alumina, zinc oxide, magnesium oxide, rutile type titanium oxide, zirconium phosphate, etc. One or more kinds of inorganic materials, various types of activated carbon, porous phenol resins and melamine resins can be mixed.

The photocatalyst layer may be formed after the surface of the substrate is sprayed with a protective material such as an aqueous solution of titanium peroxide to perform a base treatment for forming a protective film. In any case, if the film is formed in advance with an aqueous solution of titanium peroxide, the adhesion and spreadability of the TiO ₂ sol solution are improved, so that it is easy to get wet, and the photo functional layer is uniformly and widely formed on the surface of the substrate. can do. Titanium peroxide aqueous solution has excellent spreadability even when the substrate is metal such as stainless steel.
It is effective to apply the _two sol liquids widely and uniformly. Although the aqueous solution of titanium peroxide also functions as a binder, it does not include a ceramic-based composition and has good compatibility with metals, so the photocatalytic functional layer formed on the surface of the substrate may cause the substrate to flex or vibrate. Is less likely to peel off.

Other photocatalytic semiconductors include ZnO, SrT
iO₃, CdS, CdO, CaP, InP, In
₂O₃, CaAs, BaTiO₃, K₂NbO₃, Fe
₂O₃, Ta₂O₅, WO₃, SaO₂, Bi₂O₃,
NiO, Cu₂O, SiC, SiO ₂, MoS₂, Mo
S₃, InPb, RuO₂, CeO₂and so on. this
Titanium oxide TiO2₂(Anatase type) is inexpensive and characteristic
Is stable and harmless to the human body.
Best.

The catalytic function of the photocatalytic semiconductor is such that when the semiconductor is irradiated with an excitation wavelength (electromagnetic wave of excitation wavelength, ultraviolet region in the case of TiO ₂ ) of a band gap equal to or greater than that of a semiconductor such as a metal oxide, electron cleavage occurs in the semiconductor. OH on the surface
It generates active radical hydroxyl groups and active oxygen of-and O _2- and decomposes organic compounds in contact with them by oxidation or reduction. Thereby, a bad smell and oil stain can be cleaned. In addition, bacteria and viruses can be killed (sterilized) by the same function.

According to the structure of the present invention, the surface area of the photocatalytic functional layer is large, and the electromagnetic wave of the excitation wavelength irradiated from the outside easily reaches the particles deep in the photocatalytic functional layer.
The photocatalytic function layer is activated in a wide range. In addition, since the fluid passing through such a laminated structure portion is reflected on the wall of the laminated structure, or enters the concave portion and temporarily stays, there are many chances that the organic matter floating in the fluid comes into contact with the photocatalytic semiconductor. . Therefore, the photocatalyst has high performance.

[0015] In addition, such a photocatalyst may have a sound-absorbing (sound-absorbing, sound-insulating) function, a visual shielding function, or a wave-eliminating or foam-eliminating function when the fluid is in a liquid phase, as well as a cleaning function, depending on the usage. Can be. The silencing is, for example, a case where the photocatalyst is used as a partition wall that separates a roadway and a human road on a road.
When the substrate is made of a metal non-woven fabric at the same time as x is decomposed and removed, sound waves are guided to a complicated internal space of the metal non-woven fabric formed by entanglement of metal fibers, and the transmitted energy is absorbed. The visual blocking function is a function of blocking the passage of light, so that the photocatalyst can be used as a partition or the like. Furthermore, wave extinction is analogous to the absorption of sound waves. The wave of the liquid makes the opportunity of contact between the organic compound floating in the liquid and the photocatalytic semiconductor non-uniform, but the fluid temporarily stops in the internal space of the metal non-woven fabric due to the above-mentioned metal non-woven fabric, and the contact with the photo-semiconductor is caused. The contact chance becomes almost uniform.

In addition, the photocatalyst of the present invention can be used for a base or a filter of an air conditioner or an exhaust gas treatment device, an indoor wall plate for a toilet or a building, an algae-proof aquarium wall, a swimming pool wall, and the like.

[0017]

EXAMPLES Example of Production of Photocatalyst (Example 1) As a substrate, an Al fiber having a diameter of 90 to 140 μm, a length of 10 mm to 150 mm, and a surface density of 1650 g / m ² was used. Rolled aluminum rolling metal with a thickness of 0.4mm and a mesh size of 4mm x 8mm and a thickness of 0.6mm by roller rolling to smooth out irregularities and sandwich it between two expanded metals with a flat surface. These were rolled and rolled to a thickness of 1.6 mm.

Next, as a photocatalyst functional material, an aqueous solution of amorphous titanium oxide (0.84 w%): aqueous solution of anatase titanium oxide (0.84 w%) is mixed at a ratio of 3: 7, and the mixture is added to the surface of the substrate. 9g / 25cm ² (wet state)
Spray. After drying at room temperature, heating and drying (3
(00 ° C. × 1 hr) to obtain a photocatalyst.

(Example 2) The coating amount of the photocatalytic functional material was set to 3.
A photocatalyst was prepared under the same conditions as in Example 1 except that the photocatalyst was changed to 8 g / 25 cm ² .

Comparative Example 1 An anatase type titanium oxide aqueous solution (0.84%): colloidal silica aqueous solution (0.84%) was mixed at a weight ratio of 3: 1 as a photocatalytic functional material. Spraying onto the surface of the substrate (application amount 2.9 g /
25cm ² ) also dried at room temperature and then dried by heating (300 ℃ × 1h)
To obtain a photocatalyst.

Comparative Example 2 An anatase-type titanium oxide aqueous solution (0.84 wt /%): colloidal silica aqueous solution (0.84 wt%) was mixed at a weight ratio of 2: 1 as a photocatalytic functional material. (2.9 g / 25 cm ² ), dried at room temperature, and then dried by heating (300 g).
C. x 1 h) to obtain a photocatalyst.

Next, the photocatalysts of the above Examples and Comparative Examples were measured for their ability to remove nitrogen oxides (NOx) by the following method, and the results are shown in Table 1. The photocatalyst was set in a glass container, and 0.5 liter /
NOx gas was introduced at a flow rate of 1 minute, and ultraviolet light having a wavelength of 485 nm and an output of 1.0 mW / cm ² was irradiated.
The gas concentration (A), the concentration of NOx gas at the time of ultraviolet irradiation (B), and the concentration of NOx gas after 5 minutes from the irradiation of ultraviolet light (C) were measured, and the NOx removal rate ｛AB / A × 100
(%) Or AC / A × 100 (%)} was calculated.

[0023]

[Table 1]

From Table 1, it can be seen that in Comparative Examples 1 and 2, the NOx removal rate during ultraviolet irradiation was only about 71% and about 82%, and in Comparative Example 1 in particular, NOx was removed 5 minutes after the ultraviolet irradiation.
It can be seen that the removal rate has dropped to about 59%. In contrast to Comparative Examples 1 and 2, in Examples 1 and 2, the NOx removal rate at the time of irradiation with ultraviolet light exceeded 90%, and a high NOx removal rate of about 86% even 5 minutes after irradiation with ultraviolet light. It was confirmed that it maintained.

[0025]

According to the present invention, the photocatalyst body has many voids and irregularities in the surface layer, the photocatalytic functional layer has a large area, a large oxidizing / reducing power, and the organic compound floating in the fluid and the photocatalytic function. The photocatalyst with high performance has many opportunities to contact with the layer. In particular, since it has a structure in which a metal nonwoven fabric is held between a pair of mesh members, a photocatalyst having a large noise reduction effect and high contaminant removal performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a photocatalyst according to another embodiment of the present invention.

FIG. 2 is a schematic diagram showing a surface of a base.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photocatalyst body, 2 base materials, 30 mesh members, 40 nonwoven fabric made of metal, 5 photocatalytic functional layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shiro Ogata 1-1-1 Hatagaya, Shibuya-ku, Tokyo Kobayashi Building 6F (72) Inventor Toru Morimoto 3-58-2 Wakamiya, Ichikawa-shi, Chiba

Claims (3)

[Claims] 1. A substrate having a pair of mesh members made of Al or an alloy thereof, a non-woven fabric made of Al or an alloy thereof held between the members, and a photocatalytic functional layer formed on the surface of the substrate. Photocatalyst. 2. The photocatalyst according to claim 1, wherein the mesh member is an expanded metal, and the nonwoven fabric is formed by pressing Al fibers between a pair of expanded metals. 3. A functional substrate comprising the photocatalyst according to claim 1 and having both a photocatalytic function and a silencing function.