JP2002355299A - Air cleaning filter using photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air cleaning filter using a photocatalyst. SOLUTION: This air cleaning filter uses functional powder with photocatalytic action. The structure of the carrier itself is simplified as an absorptive material. A photocatalyst which can be prolonged in catalytic activity time after shading, easily available at low cost, and can effectively absorb and remove toxic gas, bacteria, odor, etc., is used. Functional powder with photocatalytic action is carried by activated charcoal fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter used for a commercial or industrial air purifier, and more particularly to an air purifying filter having a function of decomposing organic gas components or bacteria in a gas phase by light irradiation. .

[0002]

2. Description of the Related Art In recent years, COx gas emitted from vehicles such as diesel vehicles and gasoline vehicles or various factories into the atmosphere,
Exhaust gas such as NOx gas and HC gas, formaldehyde contained in building materials and adhesives, etc. Solvents and other harmful or odorous components in the factory Air containing organic substances in waste gas and garbage incineration plants and factories Dioxins and germs, etc., which are emitted from the environment, pollute the environment of homes, offices, factories, nature, etc., and are cited as a major problem as a cause of destroying the living environment.

[0003] As means for adsorbing and removing such organic gas components, harmful gases, bacteria, odors and the like in the gas phase, regenerated cellulose supported on honeycomb, porous ceramics, glass fiber or metal fiber or carbon fiber, wood pulp, etc. ,
Granular, powder or fibrous activated carbon materials and zeolites made from raw materials such as sawdust, coconut palm, coal, phenol, and synthetic fibers are used. These materials are effective to some extent as materials for removing such harmful substances.
However, when the particle size or the fiber size of the conventional granular, powder or fibrous activated carbon material is large, the surface area is small, and there is a problem that the adsorption effect is small accordingly. As a method of increasing the adsorption effect, it is conceivable to make the activated carbon finer and to increase the outer surface area. For example, in the case of removing organic substances by adsorption, the higher the contact efficiency with the gas, that is, the finer the activated carbon and the larger the external surface area, the higher the efficiency.

[0004] However, fine activated carbon has problems in that it is poor in handleability and flows out during ventilation. Conventional fibrous activated carbon can be densely filled to form a compact, but the strength of the compact at this time is weak, and there are problems such as pressure fluctuations and clogging during use. Not a way. Since the above-mentioned problems of activated carbon are caused by the shape and properties of the activated carbon itself, it has been proposed to specify the size of the activated carbon particles and further to combine the activated carbon with fibrous activated carbon or reinforcing fibers made of synthetic resin. In order to improve the adsorption capacity and processability of activated carbon fibers, it is important to use a high-purity, controlled fiber material. However, such a method has problems that not only the structure becomes complicated and the manufacturing cost increases, but also that the quality is not constant. The above problems are limited by the nature and shape of the activated carbon itself. Unless this is solved, it is necessary to obtain an effective means to effectively and inexpensively adsorb and remove organic substances, bacteria, odors and the like in the gas phase. There is a problem that can not be.

On the other hand, a method of removing harmful substances using a photocatalyst has been studied. For example, a woven fabric of glass fiber is immersed in a solution comprising titanium oxide and an organic resin, dried and fired to carry a photocatalyst on the glass fiber. Examples of the carrier include honeycombs and porous ceramics, and examples thereof include glass fibers, synthetic fibers, natural fibers, recycled fibers, metal fibers such as stainless steel, alumina fibers, and carbon fibers. As the functional powder having a photocatalytic action, in addition to the titanium oxide (TiO ₂ ),
ZnO, Fe ₂ O ₃ , CdS, CdSe, SrTiO ₃
And the like.

The above-mentioned functional powder having photocatalytic action is
It is effective as a means for decomposing and removing organic gas components, harmful gases, bacteria, odors and the like in the gas phase. In addition, the functional powder having a photocatalytic action is hydrophilic, and enters under a harmful substance (dirt) captured by water, causing the dirt to naturally flow down,
Alternatively, it has a feature of having a self-cleaning function of removing the same by decomposing it into carbon dioxide and water. However, in order to remove harmful substances in the gas phase by using such a functional powder having photocatalytic action, it is necessary to have a complicated structure, which requires a large space and requires constant light irradiation. Energy cost problem. From the above, even when using activated carbon fiber, or when using a functional powder having a photocatalytic action, at present, there is no effective method for solving the above problems. is there.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to use a functional powder having a photocatalytic action, to simplify the structure by using a carrier itself as an adsorbent, and to prolong the catalytic activation time even after shading. It is an object of the present invention to provide an air purifying filter using a photocatalyst which can be easily obtained at low cost and can effectively adsorb and remove harmful gases, bacteria, odors and the like.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that the above problems can be solved by selecting a carrier suitable for a functional powder having a photocatalytic action. Thus, the present invention has been completed. That is, the present invention provides: An air purifying filter using a photocatalyst, wherein a functional powder having a photocatalytic action is supported on activated carbon fibers. 2. 2. The air purifying filter using a photocatalyst according to the above 1, wherein the functional powder having a photocatalytic action is coated with a different kind of oxide powder for preventing oxidative decomposition of the activated carbon fiber. Is provided.

[0009]

DETAILED DESCRIPTION OF THE INVENTION As activated carbon fibers, long fibers are effective, but short fibers can also be used. In particular, a material that does not cause clogging during long-term use is desirable. The production of the activated carbon fiber is not particularly limited. For example, the specific gravity produced by heat-treating petroleum cracked residual oil is 1.24, and the softening point is 261 °.
C, a fiber obtained by melt-spinning an optically isotropic pitch having an aromatic hydrocarbon fraction fa of 0.54 into a fiber can be used. This fiber is introduced into an air heating furnace, and 300 °
C to infusibilize it, and heat it to 50 C in a nitrogen stream.
The temperature is raised to 0 ° C., carbonization is performed to obtain carbon fibers, activation treatment is performed in 950 ° C. propane gas combustion exhaust gas, and treatment is performed in nitrogen to obtain activated carbon fibers (Patent No. 29)
67389). In addition, activated carbon fibers can also be obtained by using coal tar, natural fibers or synthetic fibers as raw materials.

[0010] The activated carbon fibers produced as described above are provided with TiO ₂ , ZnO, Fe ₂ O ₃ , CdS, and CdS.
e. Coating a functional powder having photocatalytic action such as SrTiO ₃ . Particularly, titanium oxide (TiO ₂ ) is preferable. When using this titanium oxide, the particle size is 0.001 to 50 μm, preferably 0.01 to 50 μm.
It is desirable to use a 10 μm powder. As a binder at the time of coating, melamine resin, epoxy resin, fluororesin, polyolefin resin, vinyl resin, polytetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-perfluoroalkoxyethylene A copolymer resin or the like can be used. When the air purifying filter is to be maintained for a long period of time, a material that is not eroded by the oxidizing action of titanium oxide is desirable.

The above-described photocatalytic titanium oxide or the like machine
Functional powder oxidizes activated carbon fiber during long-term use
Photocatalytic action of the titanium oxide etc.
Of oxidative decomposition of activated carbon fiber with functional powder having
SiO₂, WO₃, SnO ₂Of different oxide powders such as
Is desirable. This activates carbon
Fiber degradation can be prevented. This SiO₂Different oxides such as
Powder coating is performed, for example, by the mechanofusion method.
Can be performed, but using other coatings
good. This SiO₂Coating of different oxide powders such as
The effect that the layer can also prevent deterioration due to oxidation of the binder
There is also.

The air purification filter using the photocatalyst produced as described above has, on the one hand, the carrier itself made of activated carbon fiber effectively adsorbs and removes harmful gases, bacteria, odors and the like, and on the other hand, has a photocatalytic action. As a structure in which the function by oxidative decomposition is kept waiting by using the functional powder, a complex function of effectively decomposing, adsorbing and removing harmful gases, bacteria, odors and the like can be provided. In addition, the functional powder having a photocatalytic action is hydrophilic, and enters under a harmful substance (dirt) captured by water to allow the dirt to flow down naturally and to remove the dirt by decomposing it into carbon dioxide and water. It has the feature of having a self-cleaning function. As a result, the structure of the air purifying filter is simplified, the function of the air purifying filter can be maintained even after shading, and the air purifying filter can be obtained at low cost.

[0013]

EXAMPLES AND COMPARATIVE EXAMPLES Next, examples in which various substances are adsorbed using the air purifying filter having the decomposition and adsorption performance of the present invention will be described. Note that the present embodiment is for easy understanding, and does not limit the scope of the present invention.

(Example 1) A fiber obtained by heat-spinning an optically isotropic pitch produced by heat-treating a cracked residual oil of petroleum is used, and the fiber is heated to 300 ° C in an air heating furnace. Raise the temperature to make it infusibilized, and put it in a nitrogen stream at 500 °
C and carbonized to carbon fiber, and further 95
Perform activation treatment in propane gas combustion exhaust gas at 0 ° C,
Felt-like activated carbon fibers (fiber diameter: 5 to 30 μm) which were treated in nitrogen to obtain activated carbon fibers were used. Titanium oxide having a particle diameter of 7 nm was used as a functional powder having a photocatalytic action, and 40 wt% of titanium oxide powder was mixed and stirred in a dispersion of polytetrafluoroethylene resin with water. The activated carbon fiber was immersed in the dispersion containing the titanium oxide powder, pulled up, and dried to remove water. Thereafter, firing was performed at 380 ° C. for 10 minutes to obtain an activated carbon fiber coated with a polytetrafluoroethylene resin and titanium oxide. The activated carbon fiber supporting the titanium oxide powder having the photocatalytic action is put in a glass container, a certain amount of polysiloxane is put in the container, and at the same time, the activated carbon fiber is irradiated with ultraviolet rays (310 to 400 nm) from a light source (black light). did. Then, the gas was extracted from the container every predetermined time, and the concentration was measured by gas chromatography. Table 1 shows the results.

(Example 2) The activated carbon fiber produced in the same manner as in Example 1 was used. Similarly, the activated carbon fiber was immersed in a dispersion containing titanium oxide powder and then pulled up. Dry to remove moisture. Thereafter, firing was performed at 380 ° C. for 10 minutes to obtain an activated carbon fiber coated with a polytetrafluoroethylene resin and titanium oxide. The activated carbon fiber carrying the titanium oxide powder having a photocatalytic action was placed in a glass container, a certain amount of polysiloxane was placed in the container, and simultaneously, the activated carbon fiber was irradiated with ultraviolet rays from a light source. However, ultraviolet irradiation was performed only in the first half, and ultraviolet irradiation was not performed for the remaining 40 minutes. Then, the gas was extracted from the container every predetermined time, and the concentration was measured by gas chromatography. Table 1 shows the results.

Example 3 An active material produced in the same manner as in Example 1
Carbon fiber was used. Functional powder having photocatalytic action
asParticle size 7nmUsing titanium oxide
To prevent oxidative decomposition of activated carbon fiber₂The mechano
Coating was performed by a fusion method. This SiO₂
Was coated with titanium oxide in the same manner as in Example 1.
Dispersion of tetrafluoroethylene resin with water
40 wt% of titanium oxide powder was mixed and stirred. Soshi
The dispersion containing the titanium oxide powder
In, the active carbon fiber is immersed, then pulled up and dried
Water was removed. Then bake at 380 ° C for 10 minutes
Polytetrafluoroethylene resin and SiO₂The coat
Carbon fiber coated with titanium oxide having a coating layer
I got This titanium oxide powder having photocatalytic action is supported
Activated carbon fiber in a glass container
Add a certain amount of polysiloxane and simultaneously convert to activated carbon fiber
Ultraviolet light was irradiated from a light source. And every time a certain time elapses
Extract gas from the container and use gas chromatography
The concentration was measured. As a result, decomposition and adsorption of harmful gas components
The performance was similar to that of Example 1 shown in Table 1 in a short time.
However, the ability to decompose and adsorb activated carbon fibers for a longer period of time
Investigation revealed that SiO₂Acid with a coating layer of
The activated carbon fiber coated with titanium oxide is made of SiO ₂No
Effect is longer than that without
It was found that the deterioration of the fiber was small.

(Comparative Example 1) The above-mentioned activated carbon fiber was immersed in a dispersion containing titanium oxide powder in the same manner as in Example 1, and then pulled up, and dried. To remove water. After this, 3
It was baked at 80 ° C. for 10 minutes to obtain a carbon fiber coated with a polytetrafluoroethylene resin and titanium oxide. The carbon fiber supporting the titanium oxide powder having a photocatalytic action was placed in a glass container, a certain amount of polysiloxane was placed in the container, and the carbon fiber was simultaneously irradiated with ultraviolet rays from a light source.
Then, the gas was extracted from the container every predetermined time, and the concentration was measured by gas chromatography. Table 1 shows the results.

[0018]

[Table 1]

In the tests in the above Examples and Comparative Examples, the activated carbon fibers coated with titanium oxide photocatalyst of the present example showed greater removal of harmful gases than the titanium oxide photocatalyst coated with simple carbon fibers. The effect was shown. As described above, the ability to adsorb low-molecular gaseous gases indicates that various dangerous molecules in the environment can also be adsorbed. This is because, on the one hand, the activated carbon fiber carrier itself effectively absorbs and removes harmful gases, bacteria, odors and the like, and on the other hand, the harmful gases,
This is considered to be due to the combined effect of effectively decomposing and removing bacteria and odors. Furthermore, the one in which titanium oxide photocatalyst is directly coated on activated carbon fiber may be slightly degraded by oxidative decomposition due to active oxygen generated by the photocatalyst when used for a long period of time. This is a problem that can be easily solved by coating the SiO ₂ to be prevented. From the above, the air purifying filter using the photocatalyst of the present invention can be used for exhaust gas such as COx gas, NOx gas, HC gas, etc., which are emitted into the atmosphere from vehicles such as diesel vehicles and gasoline vehicles or various factories, building materials and adhesives. Hazardous components in air and waste gas containing solvent and other harmful components or malodorous components in the factory, such as formaldehyde, etc., acetaldehyde in the odor of tobacco, dioxin discharged from garbage incineration plants and factories, etc. It has antibacterial properties and a dust-collecting effect by absorbing mold and capturing mold and bacteria.

[0020]

The air purifying filter using the photocatalyst of the present invention is capable of efficiently removing factors that pollute the environment of homes, offices, factories, nature, etc. and destroy the living environment as an air purifying filter. Further, the air purifying filter has the excellent features that the structure of the air purifying filter can be simplified, the function of the air purifying filter can be maintained even after shading, and that it can be obtained at low cost.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/86 B01J 35/02 J B01J 35/02 B01D 53/36 JG F term (Reference) 4C080 AA07 BB02 BB05 CC02 HH05 JJ05 KK02 LL02 LL10 MM01 MM02 NN05 4D019 AA01 BA03 BB03 BC07 CB04 4D048 AA17 AB03 BA05X BA06X BA07X BA41X BB08 CD05 EA01 4G069 AA03 AA03 AA08 BA02B BA04B BA08A BA18A BAEBA18BA22

Claims (2)

[Claims] 1. An air purifying filter using a photocatalyst, wherein a functional powder having a photocatalytic action is supported on activated carbon fibers. 2. An air purifying filter using a photocatalyst according to claim 1, wherein the functional powder having a photocatalytic action is coated with a different kind of oxide powder for preventing oxidative decomposition of activated carbon fibers. .