JP2000042320A - Functional filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently maintain the contact between a photocatalyst and a fluid to be treated and to sufficiently develop the photocatalytic activity of the photocatalyst by using a metal long fiber aggregate in a web state as the base body of a filter and applying the photocatalyst on the aggregate. SOLUTION: The base body of this functional filter consists of a metal long fiber aggregate in a web state. The metal long fiber which constitutes the metal long fiber aggregate in the web state is a long and thin fiber of metal such as stainless steel, brass, copper, aluminum, nickel, titanium, tantalum, or the other and its diameter is preferably about 50 to 100 μm. As for a photocatalyst, one kind or a combination of two or more kinds of metal compd. semiconductor particles such as titanium oxide, zinc oxide, tungsten oxide, iron oxide and strontium titanate can be used. These particles show the photocatalytic function when being irradiated with light at a wavelength having higher energy than the band gap of the photocatalyst. Especially, titanium oxide is preferably used because it has high photocatalytic function and is chemically stable and harmless.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an excellent antifouling function,
The present invention relates to a photocatalyst-coated functional filter that has a deodorizing function, an antibacterial function, a harmful component removing function, and is excellent in environmental amenities.

[0002]

2. Description of the Related Art Conventionally, as a functional filter for the purpose of antifouling, deodorizing, antibacterial, and removing harmful components of gases and liquids, a filter in which activated carbon is wrapped in a nonwoven fabric or a net, and a layer in which activated carbon is filled in layers. For example, such a functional filter is frequently used as a deodorizing filter in an air conditioner or the like. Paper, such as paper,
Organic fibers such as non-woven fabrics and wire mesh are generally used.

In recent years, photocatalysts have been used to decompose dirt, deodorize,
Various uses have been proposed for use in imparting various functions such as antibacterial, harmful component decomposition, air purification, and the like, and studies have been made on the use of photocatalysts in filters for the purpose of imparting the above-mentioned various functions. However, there has not yet been proposed a photocatalyst-based filter that has been satisfactorily and sufficiently provided with the above-mentioned various functions. In other words, needless to say, the photocatalyst cannot show its photodegradation activity unless it is irradiated with light, so if the filter is made two-dimensionally thin so that the photocatalyst can be easily irradiated with light, the photocatalyst and The contact with the fluid to be treated becomes insufficient, and the above functions are not sufficiently imparted to the filter. On the other hand, if the filter has a three-dimensional thickness in order to ensure sufficient contact between the filter and the fluid to be treated, light generally does not easily reach the three-dimensional thickness direction, and the photocatalytic activity of the photocatalyst is sufficient. And the above functions are not sufficiently imparted to the filter. As described above, in the use of a photocatalyst for a filter, the problem of ensuring sufficient contact between the fluid to be treated and the filter and the problem of sufficiently irradiating the photocatalyst to sufficiently exert its photocatalytic activity are contradictory. This conflicting issue has not yet been resolved.

[0004]

DISCLOSURE OF THE INVENTION In view of the above-mentioned conventional circumstances, an object of the present invention is to provide a photocatalyst with which the fluid to be treated is sufficiently contacted, and that the photocatalyst activity of the photocatalyst is sufficiently exhibited to provide an excellent protection. It is an object of the present invention to provide a photocatalyst-coated functional filter having various functions such as a soiling function, a deodorizing function, an antibacterial function, a harmful component removing function, and an air purifying function.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, using a web-like metal continuous fiber aggregate as a base of a filter and coating it with a photocatalyst, the object has been achieved. The present invention has been completed by finding out what can be achieved. That is, the functional filter according to the present invention is characterized in that a web-like metal long fiber aggregate is coated with a photocatalyst. In the present invention, since the base of the filter is a web-like aggregate made of long metal fibers, unlike the case where the base is made of an organic material, it is not decomposed by the photocatalytic function and is nonflammable. It can be used in an environment where there is a high risk of fire such as a kitchen. In addition, since there is also reflection of light by long metal fibers, even if the filter has a three-dimensional thickness, light can reach the three-dimensional thickness direction, ensuring sufficient contact between the photocatalyst and the fluid to be treated. In addition, the photocatalyst activity of the photocatalyst can be sufficiently exhibited.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The base of the functional filter of the present invention is a web-like metal continuous fiber aggregate. Here, the web shape of the web-shaped metal long fiber aggregate means that the fibers are in a mat shape,
It refers to a state of being gathered in a cotton-like or net-like shape, or being woven into a cloth-like or sheet-like shape. The thickness of the web-like metal continuous fiber aggregate can be appropriately selected as needed, but generally, 10 to 100 mm is appropriate. The long metal fibers constituting the web-shaped long metal fiber aggregate are elongated fibers of stainless steel, brass, copper, aluminum, nickel, titanium, tantalum or other metals, and preferably have a diameter of 50 to 100 μm. Also,
Various cross-sectional shapes such as a rectangular shape, a circular shape, and a star shape can be used. Among them, fibers having a rectangular cross section are bonded to each other because the faces of the fibers and the corners are in contact with each other. And the photocatalyst is coated on a flat surface, so that the photocatalyst is more easily supported. As a method for producing long metal fibers, conventionally known methods such as a method of drawing can be used. Among them, a method of winding a thin metal sheet of a material into a coil shape and cutting it thinly with an appropriate cutting tool from the end face thereof. Is preferably used because a fiber having a rectangular cross section can be obtained and mass production can be performed at low cost. An example of such a metal long fiber is Bekinit (trade name) manufactured by Bekinit Co., Ltd.

The photocatalyst used in the functional filter of the present invention is a particle that exhibits a photocatalytic function when irradiated with light having a wavelength having energy equal to or greater than the band gap, such as titanium oxide, zinc oxide, tungsten oxide, iron oxide, and titanium oxide. Known metal compound semiconductor particles such as strontium acid can be used alone or in combination of two or more. In particular, titanium oxide which has a high photocatalytic function, is chemically stable, and is harmless is preferably used. Further, the inside of the particles of the photocatalyst as described above and / or
Or, as a second component, V, Fe, Co,
It is preferable to include at least one metal and / or metal compound selected from Ni, Cu, Zn, Ru, Rh, Pd, Ag, Pt and Au, since a higher photocatalytic function is exhibited. Examples of the metal compound used as the second component include oxides, hydroxides, oxyhydroxides, sulfates, halides, nitrates, and metal ions. In addition, the content of the second component can be appropriately selected as needed, such as the type of the second component used. Further, the above-mentioned photocatalyst can also remove harmful components such as acetaldehyde and ethylene gas.

An example of a method for producing titanium oxide preferably used as a photocatalyst in the present invention is as follows. That is, (a) a method in which a titanium compound such as titanyl sulfate, titanium chloride, or titanium alkoxide is heated and hydrolyzed in the presence of seeds for nucleation as necessary.
(B) a method of adding an alkali to a titanium compound such as titanyl sulfate, titanium chloride or titanium alkoxide in the presence of seeds for nucleation as necessary to neutralize the compound; Phase oxidation method,
(D) Known methods such as a method of calcining or hydrothermally treating the titanium oxide obtained by the method (a) or (b) above, particularly the titanium oxide obtained by the method (a) or 100 ° C. Titanium oxide obtained by hydrothermal treatment at the above temperature is preferable because of its high photocatalytic function. Also,
Titanium oxide used as a photocatalyst in the present invention includes, in addition to titanium oxide, those commonly referred to as hydrous titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide, etc. May be either an anatase type or a rutile type, but the anatase type is more preferably used because of its higher photocatalytic function. Furthermore, in order to make the inside and / or the surface of the photocatalyst particles contain the metal and / or metal compound of the second component as described above, the metal and / or the metal compound is added during the production of the photocatalyst particles. Then, a method of adding the metal and / or the metal compound after producing the photocatalyst particles, adsorbing the resultant, and heating or reducing it as necessary can be used.

The method for forming the functional filter of the present invention, that is, the method for coating the web-like metal long fiber aggregate with a photocatalyst is not particularly limited, and may be appropriately selected as necessary. Can be. For example, the method itself is conventionally known in general as a method for coating a substrate with a photocatalyst, and (a) a coating composition containing a photocatalyst is applied to a web-like metal long fiber aggregate, and the coating film is formed. Curing method, (b)
A method in which a coating agent composition is applied to a web-like metal long-fiber assembly, a photocatalyst is sprayed on the coating film, and the coating film is cured. (C) A pressure-sensitive adhesive liquid is applied to the web-like metal long-fiber assembly. Then, a method of dispersing and adhering a photocatalyst onto the coating film of the pressure-sensitive adhesive liquid and then curing the mixture can be appropriately selected and adopted.

[0010] The present inventors have also found that the following method is suitable as a method for forming the functional filter of the present invention with respect to the method for forming the functional filter of the present invention. One preferable method is a composition comprising (a) an organopolysiloxane as a main component, an organosiloxane having a functional side chain as a cross-linking agent, and a curing catalyst, which are blended in a web-like metal long fiber aggregate;
A catalyst comprising (b) a composition in which a high heat solvent is blended with ceramic particles, (c) an organic solvent solution of perhydropolysilazane, and (d) a low molecular weight glycidyl ether type epoxy resin in the presence of a metal oxide powder. And react
Using a coating composition containing a photocatalyst blended with a specific film-forming component selected from the prepared prepolymer,
It is a method of painting it and curing the coating. A coating agent composition in which a photocatalyst is blended with these specific film-forming components has been devised by the present inventors, and is a novel coating agent composition according to the invention separately filed in a patent application (filed on July 14, 1998). The use of these coating agent compositions can suppress a decrease in the activity of the photocatalyst, maintain a high catalytic activity inherent to the photocatalyst, form a photocatalyst-containing coating, and have a robust photocatalyst of any thickness. The excellent effect that the containing film can be easily formed is obtained.

As another method of constructing the functional filter of the present invention, a coating composition containing one of the above-mentioned (a) to (d) as a film-forming component is used. It is also possible to use a method in which a metal long fiber aggregate is applied, a photocatalyst is sprayed on the coating film, and the coating film is cured.

As described above, one of the specific film-forming components used in the coating composition is an organopolysiloxane as a main component, and an organosiloxane having a functional side chain as a crosslinking agent and a curing catalyst. (Hereinafter abbreviated as "organopolysiloxane composition"). In this organopolysiloxane composition, the organopolysiloxane as a main component preferably has a methyl group or a phenyl group. As the crosslinking agent, an organosiloxane having a functional side chain such as an alkoxy group, an acyloxy group, and an oxime group is preferable. As the curing catalyst, an organic compound containing a metal such as Zn, Al, Co, and Sn and a halogen are preferable. The organopolysiloxane composition preferably contains a silicon component in an amount of 40% or more in terms of SiO ₂ , and does not contain a solvent, water or a hydroxyl group. Also,
The organopolysiloxane composition cures even when heated at low temperature or dried at room temperature to form a hard ceramic coating having excellent adhesion. Further, the curing mechanism is such that the functional group of the organopolysiloxane of the main agent is first hydrolyzed by moisture in the air to be changed to a hydroxyl group, and then the hydroxyl group of the organopolysiloxane is converted to the hydroxyl group of the crosslinking agent organosiloxane. It is considered that a functional group is attacked and a dealcoholization reaction is caused by the action of a curing catalyst to form a cured polysiloxane as a polymer compound having a three-dimensional structure. It becomes a metal alkoxy condensate by the so-called sol-gel method. Examples of such organopolysiloxane compositions include heatless glass (HEA) sold by Homer Technology Co., Ltd.
TLS GLASS) (trade name).
If necessary, the organopolysiloxane composition may be, for example, a silicone resin having an intermediate structure between inorganic and organic in which a siloxane bond has a three-dimensionally extended network structure and one methyl group bonded to a silicon atom. Other formulations, such as microparticles, can also be added. Examples of the silicone resin having an intermediate structure between inorganic and organic include Tospearl (trade name) sold by Toshiba Silicone Co., Ltd.

Another one of the film-forming components is, as described above, a composition comprising a ceramic particle and a solvent for high heat. Examples of the solvent for high heat in this composition include:
Examples thereof include alcohol solvents such as butanol and isopropanol. Examples of ceramic particles include:
Ceramic particles such as alumina, aluminum, zirconia, fused silica, pearlite, and mullite can be used, and the particle size can be appropriately selected as necessary. In general, several to several tens of μm is appropriate. The high heat solvent is preferably used in such a manner that the specific gravity becomes about 2 to 3 in the entire film formation product. As an example of a composition in which a solvent for high heat is blended with the ceramic particles, Red Proof (trade name) manufactured by Athen Co., Ltd. and the like can be mentioned.

Still another one of the film-forming components is a solution of perhydropolysilazane in an organic solvent as described above. Perhydropolysilazane has a structural formula of [SiH _a N
_Hb ] _n (where a is 1 to 3 and b is 0 or 1). This perhydropolysilazane can be synthesized, for example, by forming a complex of dichlorosilane and pyridine in a solvent (pyridine complex method) to obtain a relatively high molecular weight oligomer having a small number of low molecular weight cyclic substances. it can. Although the actual molecular structure is complex, it is an oligomer having a number average molecular weight of several thousand containing many irregular cyclic parts. This perhydropolysilazane is converted into ceramics by firing after coating on the surface of the substrate, and is converted into silica glass (SiO ₂ ) when fired in air or an atmosphere similar thereto. Examples of the organic solvent include aromatic hydrocarbon solvents such as benzene, toluene, and xylene, among which xylene is preferably used. The concentration of perhydropolysilazane in the organic solvent solution can be appropriately selected as needed. However, if the concentration is high, it becomes syrupy and poor in workability, so that it is in a range having an appropriate viscosity. Examples of such perhydropolysilazane include Tonen polysilazane (trade name) manufactured by Tonen Corporation. Further, a filler such as magnesium oxide and silicon carbide can be added to the organic solvent solution of perhydropolysilazane, if necessary.

Still another one of the film-forming components is
As described above, this is a prepolymer prepared by reacting a low molecular weight glycidyl ether type epoxy resin using a catalyst in the presence of a metal oxide powder. This prepolymer can be obtained by the following production method, for example, according to the description of Examples 1 to 5 in International Publication No. WO090 / 08168. First, a low molecular weight glycidyl ether type epoxy resin and a catalyst are charged into a reaction vessel and reacted under heating. Next, the metal oxide powder is charged into the reaction vessel, heating is continued while stirring, and after a required time, the reaction is terminated to obtain a prepolymer. Examples of the low-molecular-weight glycidyl ether type epoxy resin used in the production of the prepolymer include diglycidyl ether of resorcinol, and diglycidyl ether of bisphenol A. As the catalyst, 2-ethyl-4
-Methylimidazole, 2-methylimidazole, 4-
Methyl imidazole and the like can be mentioned. further,
The metal oxide powder is not particularly limited, but silica powder, alumina powder, and magnesia powder are preferably used. Further, as an example of the prepolymer, Seraprotex (trade name) manufactured by Nikko Co., Ltd. can be mentioned.

In the case of a method in which a photocatalyst is blended with a coating agent composition containing the above-mentioned specific film-forming component to apply the coating, the amount of the photocatalyst cannot be determined unconditionally depending on the kind of the film-forming component used. , Generally a film-forming component 10
233 to 10 parts by weight to 0 parts by weight is appropriate. When adjusting the coating composition, any one of the above-mentioned various film-forming components and the photocatalyst are appropriately mixed using a known mixing means such as a Henschel mixer, an open roll mixer, or a Banbury mixer. Can be. In this preparation, an additive such as a titanium oxide-based dispersant can be added as needed, depending on the type of the film-forming component used.

In the method of applying a coating composition containing the above-mentioned specific film-forming component, spraying a photocatalyst on the coating film and curing the coating film, the amount of the photocatalyst to be sprayed is required. Depending on the condition, the photocatalyst can be appropriately selected as long as the photocatalyst spreads uniformly over the entire surface.

The coating agent composition is easily applied to a web-like metal continuous fiber aggregate to a desired thickness by a known coating method such as a dipping coating method, a spray coating method, a roll coating method, and a brush coating method. be able to.
Further, in the case where the web-like metal long fiber aggregate is in danger of exuding a harmful substance to the photocatalyst, a barrier is previously formed on the web-like metal long fiber aggregate before applying the specific coating agent composition. It is desirable to provide. Examples of the barrier provided in advance include a silica coating formed by a so-called sol-gel method.
That is, tetraalkoxysilane, which is a precursor of amorphous silica, is diluted with alcohol, water and a hydrolysis accelerator are added thereto to prepare a mixed solution, and the mixed solution is applied to the surface of a substrate to form a coating of amorphous silica. Is formed. The tetraalkoxysilane used at this time includes tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, and the like, and the alcohol includes methanol, ethanol, n-propanol, isopropanol, and the like. Examples of the hydrolysis accelerator include inorganic and organic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, acetic acid, and oxalic acid, and inorganic and organic bases such as sodium hydroxide, potassium hydroxide, and alkylamine. .

The conditions for curing the coating film of the above-mentioned specific coating agent composition applied to the web-like continuous metal fiber aggregate can be appropriately selected according to the kind of the film-forming component used, and the like. When the components are (a) and (b), the temperature is from room temperature to 120 ° C. for 1 to 24 hours, when (c) is 100 to 600 ° C. for 1 hour, and when (d) is 80 ° C., 4 hours. The holding is appropriate, and the curing can be performed by a conventionally known method. It is generally preferred that the cured film is pre-irradiated with light to remove stains and the like. The irradiation light amount and irradiation time at that time are not particularly limited as long as they can remove dirt and the like. This pre-irradiation removes dirt and the like on the surface of the coating film, and finely roughens the film. In particular, in the case of a method in which a photocatalyst is previously blended with a coating composition and applied, the photocatalyst is partially removed. And increase the activity.

Another method suitable for constructing the functional filter of the present invention is to apply a silicone pressure-sensitive adhesive liquid to a web-like metal continuous fiber aggregate, to cure the liquid, and to apply the pressure-sensitive adhesive liquid on a coating film. This is a method in which a photocatalyst is sprayed and adhered to the substrate. According to these methods, an excellent effect is obtained in that the photocatalyst is present on the surface, so that the catalytic activity is kept high, and that dust and the like adhere to the adhesive surface and are easily removed.

As the silicone pressure-sensitive adhesive liquid used in the above-mentioned another preferable method, a known silicone pressure-sensitive adhesive such as an addition-reaction-type silicone pressure-sensitive adhesive or a peroxide-curable silicone pressure-sensitive adhesive can be used. . Examples of the addition reaction type silicone adhesive include SD4560 (trade name) manufactured by Dow Corning Toray Silicone Co., Ltd. and Shin-Etsu Silicone X-40- manufactured by Shin-Etsu Chemical Co., Ltd.
3068 (product name). Examples of the peroxide-curable silicone pressure-sensitive adhesive include SH4280 (trade name) manufactured by Dow Corning Toray Silicone Co., Ltd. and Shin-Etsu Silicone KR-10 manufactured by Shin-Etsu Chemical Co., Ltd.
1-10 (trade name) and the like.

In the above method, the amount of the photocatalyst sprayed on the coating film in the method in which a silicone pressure-sensitive adhesive liquid is applied in advance and the photocatalyst is sprayed and adhered on the coating film is appropriately selected as necessary. In general, it is sufficient if the photocatalyst uniformly spreads over the entire surface. In addition, the silicone adhesive liquid is applied to the web-like metal long fiber aggregate in the same manner as the method using the specific coating agent composition described above, such as a dipping coating method, a spray coating method, a roll coating method, and a brush coating method. And other known coating methods. In addition, the curing of the coating film of the silicone pressure-sensitive adhesive liquid sprayed with the photocatalyst or the coating film of the mixture of the silicone pressure-sensitive adhesive liquid and the photocatalyst is generally 80 to 80%.
It is appropriate to hold at 120 ° C. for 1 to 5 minutes. Further, these curing can be performed by a conventionally known method.

The filter produced by the above method has excellent antifouling function, deodorizing function, antibacterial function, harmful component removing function,
It is used as a functional filter having various functions such as an air purification function, and is specifically suitable for a filter installed in a ventilation duct of a kitchen or a filter for an air conditioner.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Example 1 Heatless glass GS600A1 (sold by Homer Technology Co., Ltd .; trade name; a composition containing an organopolysiloxane as a main component, an organosiloxane having a functional side chain as a crosslinking agent, and a curing catalyst) 10
0 parts by weight and 100 parts by weight of a powdery titanium oxide photocatalyst (ST-01, manufactured by Ishihara Techno Co., Ltd .; X-ray particle size = 7 nm) were mixed by a ball mill to prepare a coating agent composition. This coating composition was wound into a coil of a stainless steel thin plate having a thickness of 120 μm to form a coil having a width of 500 μm.
m, made of stainless steel filaments obtained by cutting
A web-like stainless steel long fiber aggregate (3 g / 500 ml) having a thickness of 40 mm, a width of 120 mm and a thickness of 15 mm is applied by dipping coating so as to have a thickness of 200 μm, and kept at 120 ° C. for 2 hours in a curing furnace. The coating film of the coating composition was cured to obtain a target filter.

The obtained filter was subjected to an ammonia decomposition test. This ammonia decomposition test was performed by the following method. That is, a transparent sealed reaction vessel (with an internal volume of 3
l), a test sample is placed therein, and a gas to be measured is charged into the reaction vessel such that the atmosphere in the reaction vessel has a predetermined gas concentration to be measured, and a black light [8 W × 2 (0.5
mW / cm ² )], and at the same time, the atmosphere in the reaction vessel is circulated between the reaction vessel and the pipe-shaped circulation path by a circulation pump (2 l / min), and a detector for the gas to be measured is placed in the circulation path. The measurement was carried out by measuring the change over time in the concentration of the gas to be measured in the circulating atmosphere. FIG. 1 is a graph showing the measurement results of the ammonia gas concentration. In FIG. 1, a plot plotted with ◆ is a plot of the ammonia gas concentration when light irradiation was not performed, and a plot plotted with ■ is a plot of the ammonia gas concentration after the start of light irradiation.

Example 2 A silicone pressure-sensitive adhesive liquid (X-40-3068, manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to a web-like stainless steel filament aggregate similar to that used in Example 1 by a dipping coating method. It is applied to a thickness of 50 μm, and 3 g of a photocatalyst is sprayed onto the coating film by spraying, and the coating is held at 120 ° C. for 2 minutes in a curing furnace to cure the silicone adhesive liquid coating film. I got An acetaldehyde (odor component of tobacco) decomposition test was performed on the obtained filter. This acetaldehyde decomposition test was performed in the same manner as in the ammonia decomposition test of Example 1, except that acetaldehyde was used as the measurement target gas instead of ammonia. FIG. 2 is a graph showing the measurement results of the acetaldehyde gas concentration. The plotting method in FIG. 2 is the same as that in FIG.

[0027]

According to the present invention, the base of the filter is a web-like aggregate of metal long fibers, and light is reflected by the metal long fibers. Can reach the three-dimensional thickness direction, so that the contact between the photocatalyst and the fluid to be treated can be sufficiently ensured, and the photocatalytic activity of the photocatalyst can be sufficiently exhibited, so that an excellent antifouling function, deodorizing function, Provided is a functional filter coated with a photocatalyst, having various functions such as an antibacterial function, a harmful component removing function, and an air purifying function.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of an ammonia decomposition test in Example 1.

FIG. 2 is a graph showing the results of an acetaldehyde decomposition test in Example 2.

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Claims (8)

[Claims] 1. A functional filter comprising a web-like aggregate of long metal fibers coated with a photocatalyst. 2. The functional filter according to claim 1, wherein the long metal fibers forming the web-shaped aggregate are manufactured by cutting a coil-shaped thin metal plate at an end face thereof. 3. The functional filter according to claim 1, wherein the photocatalyst is at least one selected from titanium oxide, zinc oxide, tungsten oxide, iron oxide, and strontium titanate. 4. The photocatalyst coating on the web-like metal long-fiber assembly is performed by applying a coating composition containing a photocatalyst to the web-like metal long-fiber assembly and curing the coating film. Item 4. The functional filter according to any one of Items 1 to 3. 5. The coating of a photocatalyst on a web-like metal long-fiber assembly by applying a coating agent composition to the web-like metal long-fiber assembly, spraying the photocatalyst on the coating film, and curing the coating film. The functional filter according to any one of claims 1 to 3, wherein the functional filter is made. 6. The functional filter according to claim 4, wherein the film-forming component of the coating agent composition is one selected from the following (a) to (d). (A) A composition comprising an organopolysiloxane as a main component, an organosiloxane having a functional side chain as a crosslinking agent, and a curing catalyst. (B) A composition in which a high heat solvent is blended with ceramic particles. (C) An organic solvent solution of perhydropolysilazane. (D) A prepolymer prepared by reacting a low molecular weight glycidyl ether type epoxy resin with a catalyst in the presence of a metal oxide powder. 7. A method for coating a web-like metal long fiber aggregate with a photocatalyst, comprising applying an adhesive liquid to the web-like metal long fiber aggregate, curing the liquid, and spraying the photocatalyst onto the coating film of the adhesive liquid. The functional filter according to any one of claims 1 to 3, wherein the functional filter is made to adhere. 8. The functional filter according to claim 7, wherein the pressure-sensitive adhesive liquid is a silicone pressure-sensitive adhesive liquid.