JP2004121371A - Member and element for cleaning air - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cleaning member which can be manufactured easily and is excellent in air cleaning ability and from which a photocatalyst does not readily fall when the member is carried or used after the photocatalyst is once caused to deposit on the member. <P>SOLUTION: This air cleaning member does not substantially make air pass therethrough and at least one surface of the base material of this member is coated with particles having uneven surfaces and, in addition, particulates working as a photocatalyst and caused to deposit. When the member is constituted in this way, the photocatalyst can be caused to deposit easily and firmly. In addition, since the effective contacting surface area and contacting time between the photocatalyst and air can be increased, the air cleaning ability of this member can be improved significantly. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air cleaning member and an air cleaning element using the same. More specifically, the air cleaning member of the present invention has a high convenience that the photocatalyst can be easily carried in the manufacturing process, and the air has a large effective surface area of the photocatalyst with respect to the air to be treated. Since it has not only a cleaning ability but also a moldability and a shape retaining property, it is useful as a member of an air cleaning device or the like.
[0002]
[Prior art]
Photocatalysts such as titanium oxide do not have a breakthrough life like adsorbents, maintain their activity for a long time, and can decompose and sterilize harmful substances and odorous substances in the air. Widely used in
[0003]
For example, in an air purification unit and the like described in Patent Document 1, an air filter carrying a photocatalyst is used as a constituent member, and in an air purifier disclosed in Patent Document 2, a photocatalyst is carried on a honeycomb structure. Even if the light to be irradiated is not constant, it is designed so that at least a part of the light is irradiated.
[0004]
However, any of these members is a mechanism for purifying by passing air, so that the contact time between air and the photocatalyst is short, and the air cleaning ability is not sufficient. Further, such a short contact time is also due to a small effective contact surface area between the photocatalyst carried on an air filter or the like and air.
[0005]
Such a problem of air purifying ability is important in treating exhaust gas generated from industrial equipment containing a large amount of harmful substances and odorous substances. Further, even when the air cleaning member is used at home, if the air cleaning ability is low, sick house syndrome or the like cannot be sufficiently prevented.
[0006]
Patent Document 1 also discloses that an undercoat layer is formed of silica or alumina and a photocatalyst is supported thereon, but the undercoat layer cannot be formed to such an extent that the air filter is clogged. Therefore, it is not possible to carry a sufficient amount of photocatalyst to exhibit satisfactory air purifying ability.
[0007]
Furthermore, these prior arts have poor moldability and shape retention because the photocatalyst is carried on fibers or the like, and cannot be used as the main skeleton of an air cleaning device or the like.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-325444 (Claim 1 etc.)
[Patent Document 2]
JP 2001-79070 A (Claim 1 etc.)
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and an object of the present invention is to enable the photocatalyst to be easily supported in the manufacturing process, and the photocatalyst once supported to be transported or used. It does not fall off easily and can also enjoy moldability and shape retention, and furthermore, has an extremely large effective contact surface area between the photocatalyst and air and a long contact time, so that it can exhibit excellent air cleaning ability. An object of the present invention is to provide an air cleaning member.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have conducted intensive research on conditions that can increase the contact area between air and photocatalyst and lengthen the contact time, and first adhered particles having surface irregularities to the substrate. If a photocatalyst is supported on the photocatalyst, the production is extremely easy and the retention of the photocatalyst is improved, so that the contact area between the photocatalyst and the air is greatly increased. The present inventors have found that a member having an excellent air cleaning ability can be obtained if the structure does not allow the air to pass through.
[0011]
That is, the air purifying member according to the present invention is a member for purifying air, in which at least one surface of a substrate is coated with particles having surface irregularities, and fine particles having a photocatalytic action are supported. And is substantially impermeable to air.
[0012]
The average particle size of the “particles having surface irregularities” is preferably about 7 μm to about 500 μm. Further, as the type, at least one selected from the group consisting of fused alumina, silicon carbide, zirconia, and emery can be suitably used.
[0013]
The average particle diameter of the “fine particles having a photocatalytic action” is preferably about 30 nm or less, and titanium oxide can be suitably used as the material. Further, the crystal structure of titanium oxide is preferably an anatase type.
[0014]
The air purifying element of the present invention includes the air purifying member and the light source as constituent elements, and the air purifying member is arranged at a position that comes into contact with the airflow and receives light irradiation from the light source. I do.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The greatest feature of the air cleaning member according to the present invention is that the air cleaning ability is very excellent because the contact area between the air and the photocatalyst is large and the contact time can be lengthened. Even if not used, it is very easy to carry the photocatalyst fine particles, and the fine particles once carried are not easily dropped off. That is, in the present invention, by adopting the above constitutional requirements, a conventional air cleaning member having insufficient air purifying ability has been improved and air purifying ability has been significantly improved.
[0016]
Hereinafter, embodiments of the present invention exhibiting such features and effects thereof will be described in detail.
[0017]
The air cleaning member of the present invention is formed by coating at least one surface of a substrate with particles having surface irregularities and carrying fine particles having a photocatalytic action.
[0018]
As the "substrate" to be used, paper, cloth, metal, wood and the like can be used without particular limitation. That is, there is no particular limitation as long as the particles can be coated. However, it is preferable to use a “base material” that has plasticity and can be freely processed. Conventional products use an air filter that allows air to permeate, so they have poor moldability and do not have shape retention even when molding is possible. Since the degree is large, it can be applied to all devices for purifying air, such as an air purifying device. In this case, the material and its thickness may be selected according to the purpose, but paper, cloth or metal is used, and its thickness is preferably about 50 μm to about 900 μm. This is because such a “base material” has moldability and shape retention, and can be processed. The processing may be performed after supporting the fine particles, may be performed after coating the particles, and may further support the fine particles, or may be performed after the processing, and then coated with the particles to further support the fine particles. .
[0019]
The main function and effect of the “particles having surface irregularities” to be coated on the base material is to facilitate the loading of fine particles having a photocatalytic action, and to allow the fine particles to be present in the pores and recesses present on the surface of the particles and in the gaps between the particles. The purpose is to prevent falling off by carrying. In other words, by coating the substrate with the “particles having surface irregularities”, the photocatalyst fine particles can be easily supported without being used without using a binder, and can be easily prevented from falling off. It is possible to avoid a decrease in the area of contact with air due to being buried in the space. Therefore, as the “particles having surface irregularities”, those which are easily coated on a substrate, and which are covered with fine irregularities so as to be able to carry fine particles, or porous are used.
[0020]
Examples of such “particles having surface irregularities” include, for example, fused alumina, alumina, silicon carbide, zirconia, garnet, emery, diamond, garnet, silica, diatomaceous earth, iron oxide, chromium oxide, calcined alumina, boron carbide , Tungsten carbide, calcined dolomite, tourmaline, silica, aluminum, platinum, iron, copper, zeolite, and the like. One selected from these may be used alone, or two or more may be appropriately combined. Can be used. Of these, fused alumina, silicon carbide, zirconia and emery are inexpensive and highly convenient at the time of production. In addition, iron oxide, chromium oxide, aluminum, platinum, and copper have an effect of increasing the catalytic activity when using titanium oxide as a photocatalyst. Furthermore, tourmaline and zeolites themselves have a deodorizing function.
[0021]
The average particle size of the “particles having surface irregularities” is preferably from about 7 μm to about 500 μm. If it is less than about 7 μm, the supporting ability of the fine particles having a photocatalytic action tends to be insufficient, and if it exceeds about 500 μm, it tends to fall off the substrate, which makes it impossible to support the photocatalytic fine particles. Therefore, the average particle size is more preferably about 10 μm or more and about 100 μm or less.
[0022]
The method for producing such “particles having irregularities” can be a general known method without particular limitation.For example, after mechanically pulverizing the raw material, the particle size is determined by sieving or the degree of floating / sedimentation in water. Can be prepared by adjusting
[0023]
As a method of coating particles having surface irregularities on the substrate, a general method can be used as long as the surface irregularities of the particles on which the fine particles are to be supported and the gaps between the particles remain. For example, there is a method in which an adhesive is spread thinly on a substrate, and particles are adhered on the adhesive to cover the adhesive. In this case, examples of the adhesive include resins such as glue and water-resistant resin. Further, as a substrate coated with particles having surface irregularities, for example, a commercially available sandpaper can be used as it is, and the photocatalyst fine particles can be supported on the sandpaper.
[0024]
By irradiating light, harmful substances such as aldehydes in the air are decomposed and removed, substances causing odors are adsorbed and decomposed, and sterilization / sterilization and antifouling effects are achieved by irradiating light. Use something that can be demonstrated. Specifically, transition metals and their oxides can be used as photocatalysts, such as titanium oxide, zinc oxide, tungsten oxide, cadmium oxide, indium oxide, silver oxide, manganese oxide, iron oxide, tin oxide, and vanadium oxide. , Niobium oxide and the like. Among them, titanium oxide can be suitably used. This is because titanium oxide is hardly deteriorated and can not only exert a catalyst semipermanently but also can be used safely. Further, there are two types of crystal structures of titanium oxide, that is, rutile type and anatase type, and anatase type is preferably used from the viewpoint of photocatalytic activity.
[0025]
The average particle diameter of the “fine particles having a photocatalytic action” is preferably about 30 nm or less, more preferably 20 nm or less. This is because the particles are likely to be carried in the concave portions or holes existing on the surface of the “particles having surface irregularities”, and when the thickness exceeds about 30 nm, the photocatalytic activity may be insufficient. A preferred lower limit of the average particle size is 5 nm. If it is less than this, unnecessarily fine particles tend to fall off from the air cleaning member. Further, fine particles within the above range are easily aggregated by moisture, and have an effect that they are easily supported while maintaining sufficient activity.
[0026]
In order to obtain “fine particles having a photocatalytic action” having a preferable particle size, for example, a liquid phase method or a gas phase method can be used. Here, the liquid phase method is a method of firing the precipitate generated by hydrolyzing the raw material, and the gas phase method is a method of burning the raw material with oxygen at a high temperature.
[0027]
The air purifying member of the present invention is substantially impermeable to air. Conventional air purifying members used in air purifiers, etc., have a photocatalyst carried on a filter that passes air, so the contact time between the air and the photocatalyst is short, and the air must be sufficiently purified. Can not. On the other hand, the air purifying member of the present invention substantially does not allow air to pass therethrough. Therefore, if the member is arranged along the airflow, the contact time with air becomes longer, and sufficient air cleaning can be achieved. Further, since there is no need to consider clogging or the like in the air filter, it is possible to carry a sufficient amount of the photocatalyst. In addition, in order to satisfy the requirement, it is general to use a material that is substantially impermeable to air as the base material.
[0028]
By employing the configuration of the present invention, the loading of the fine particles having a photocatalytic action can be performed very easily without using a binder. The method for supporting the fine particles having a photocatalytic action on a substrate coated with particles having surface irregularities is not particularly limited, but a general method can be used. For example, the fine particles are directly applied (rubbed) on the substrate coated with the particles, or the slurry is dried in advance, and then rubbed on the substrate coated with the particles. Alternatively, it is possible to employ a very simple method of dipping the base material coated with the particles into a fine particle slurry and drying, and then removing extra fine particles adhered thereto.
[0029]
FIG. 1 is a schematic view of the air cleaning member manufactured as described above. As shown in the figure, the “fine particles having a photocatalytic action” 3 are carried on the irregularities on the surface of the “particles having surface irregularities” 2 and the gaps between the particles, and therefore do not easily fall off. In addition, since the area where the “fine particles having a photocatalytic action” comes into contact with air becomes very large, the air cleaning member according to the present invention enjoys excellent air cleaning ability.
[0030]
FIG. 2 shows an example of an air cleaning element using the air cleaning member according to the present invention. In the element, an air cleaning member 5 of the present invention is installed along the inner surface of the casing part 4, and a light source 6 for activating a photocatalyst is disposed therein. Since the air introduced into the element moves along the member 5 without passing through the member 5, the air can sufficiently come into contact with the photocatalyst carried on the surface, so that harmful components and odor components in the air are reduced. Decomposed efficiently. The light source used here may be one capable of exhibiting the catalytic ability of the photocatalyst, and an optimal light source may be selected according to the type of the photocatalyst. For example, when light to be irradiated does not leak outside, an ultraviolet lamp capable of maximizing the catalytic activity of the photocatalyst can be used.
[0031]
In the case of processing a large amount of exhaust gas generated from an industrial facility or the like, by stacking a large number of elements as shown in FIG. 3, for example, it is possible to adapt to the processing of a large amount of exhaust gas containing harmful components. It is also possible to In the case of treating a large amount of exhaust gas or the like, more efficient treatment can be performed by supporting fine particles having a photocatalytic action on both surfaces of the substrate.
[0032]
Of course, the scope of the present invention is not limited by the above drawings. For example, in addition to the above, if the air purifying member of the present invention is installed as wallpaper or the like of a portion to be irradiated with sunlight or room light, the harmful components and the like in the air are constantly decomposed, so that sick house syndrome Can be prevented.
[0033]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples, but the scope of the present invention is not limited thereto.
[0034]
(Example 1) Preparation of an air cleaning member A 10 cm square sandpaper (waterproof paper # 320, manufactured by KOKUYO Co., Ltd.) to which silicon carbide having an average particle size of 80 µm was adhered was coated with titanium oxide having an average particle size of 7 nm ( (Ishihara Sangyo Co., Ltd., ST-01) After the fine powder was made into a slurry, the dried powder was rubbed evenly, and excess titanium oxide was shaken off to produce an air cleaning member.
[0035]
(Test Example 1) Air cleaning ability test A 10 cm square air cleaning member prepared in Example 1 was installed in a closed metal container having a capacity of 7.5 L, and the surface of the test member was irradiated with ultraviolet rays. An ultraviolet germicidal lamp (wavelength: 254 nm) was set at a position 6 cm away from the top.
[0036]
A suitable amount of acetaldehyde was charged into the sealed container, and the mixture was allowed to stand for 30 minutes without turning on the ultraviolet germicidal lamp. Then, the germicidal lamp was turned on (point 0 in FIG. 4), and the acetaldehyde concentration was measured by gas chromatography. Was measured.
[0037]
In addition, similar tests were performed using the following conventional products having a photocatalyst supported on a filter as comparative examples.
[0038]
A-Glass fiber woven filter (O-System Co., Ltd.)
B-Honeycomb filter ("Aqualajit" of Mitsubishi Paper Mills, Ltd.)
C-porous metal filter ("TiOMET" of Hitachi Metals, Ltd.)
D-Titanium Oxide Thermal Spray Filter (Kinki High Energy Processing Technology Laboratory)
E-crystal titanium oxide filter (manufactured by Kobe Steel Ltd.)
Further, when no air cleaning member was provided as a control, the same measurement was performed. The results are shown as a graph in FIG.
[0039]
According to the results of FIG. 4, it was revealed that the conventional product in which the photocatalyst was supported on the air filter did not always have sufficient air cleaning ability. The reason why the concentration of acetaldehyde is reduced even before the ultraviolet lamp is turned on is considered to be caused by the trapping in the holes of the respective materials.
[0040]
Even after the ultraviolet lamp is turned on, the inclination is hardly changed except for E. That is, it can be seen that the air cleaning ability of the conventional product depends on the compound adsorption ability of the material, and the characteristics of the photocatalyst are hardly exhibited. In addition, even if E has some photocatalytic effect, the air cleaning ability is not sufficient. It should be noted that although only the acetaldehyde concentration alone indicates that the product B has an excellent air cleaning ability, the decrease in the concentration is almost completed before the ultraviolet lamp is turned on, and the photocatalyst hardly acts. This means that if the adsorbing capacity is saturated, no more air purifying ability can be expected anymore, and no sustained effect can be expected.
[0041]
On the other hand, according to Example 1, the air purifying member of the present invention can be manufactured by carrying a photocatalyst very easily, and according to the results of FIG. It has been found that harmful substances can be almost completely decomposed, and that the harmful substances can be reduced to several ppm after 60 minutes. This is because despite the fact that the member of the present invention coats the “substrate” with “particles having irregularities” and carries the “photocatalyst fine particles” thereon, it can easily carry the “photocatalyst fine particles”. It can be considered that a large amount of the "photocatalyst fine particles" can be firmly supported, and the surface area of contact with air is very large because there is no need to use a binder. Further, since the air cleaning ability of the product of the present invention does not depend on the ability of the material to adsorb harmful substances, it is possible to constantly and semipermanently exhibit its properties.
[0042]
【The invention's effect】
The air purifying member of the present invention can easily carry a photocatalyst in its manufacturing process, and the once-supported photocatalyst does not easily fall off during transportation or use. The effective contact surface area with air is very large, the contact time can be prolonged, and it has excellent air cleaning ability. Further, since the air purifying element of the present invention can effectively exert the effects of the air purifying member as it is, it can be applied to the treatment of a large amount of harmful exhaust gas generated from industrial equipment and the like. It is very useful as a part of an air purifier or the like.
[Brief description of the drawings]
FIG. 1 is a schematic view of an air cleaning member according to the present invention. FIG. 2 is a schematic view of an air cleaning element using the air cleaning member according to the present invention. FIG. Schematic diagram of the air cleaning element used [Figure 4] Graph showing the results of the air cleaning ability test [Explanation of reference numerals]
1: Base material 2: Particles having surface irregularities 3: Fine particles having photocatalytic action 4: Casing portions 5, 8: Air cleaning members 6, 9 of the present invention: Light sources 7, 10: Air flow

Claims (7)

A member for purifying air, in which at least one surface of the substrate is coated with particles having surface irregularities, and fine particles having a photocatalytic action are carried, and substantially do not pass air. A member for air purification characterized by the following. The air cleaning member according to claim 1, wherein the particles having the surface irregularities have an average particle size of about 7 µm to about 500 µm. The air cleaning member according to claim 1, wherein the particles having surface irregularities are at least one selected from the group consisting of fused alumina, silicon carbide, zirconia, and emery. The air cleaning member according to any one of claims 1 to 3, wherein the photocatalytic fine particles have an average particle size of about 30 nm or less. The air cleaning member according to any one of claims 1 to 4, wherein the fine particles having a photocatalytic action are titanium oxide. The air cleaning member according to claim 5, wherein the titanium oxide has an anatase-type crystal structure. An element for purifying air, comprising the air purifying member according to any one of claims 1 to 6 and a light source as components, wherein the air cleaning member comes into contact with an air current and emits light from the light source. An air cleaning element, which is arranged at a site to be irradiated.

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