Photocatalyst support board

The present invention relates to a photocatalyst-supporting board that supports photocatalyst particles, mainly fine particles of titanium oxide, and is suitable for environmental purification and deodorization of air, or environmental purification of water.

Fine particle titanium oxide is known as a substance that has a catalytic action on metals and metal oxides, and particularly acts as a catalytic action by irradiation with light, so-called photocatalyst, and the photocatalytic action of this fine particle titanium oxide is the oxidation of organic substances and microorganisms. It has been noted that it has remarkable effects such as growth suppression and death.

However, it is extremely difficult to use fine particle titanium oxide in the form of a single particle. This is because if fine particles of titanium oxide are used in the form of simple particles in the air, they will scatter, and if they are used in water, they will be immediately dispersed in water, which has the drawback of deteriorating the environment. Moreover, there arises a problem that scattered or dispersed particles cannot be easily recovered. Therefore, in order to utilize the fine particle titanium oxide, it is necessary to process it into an arbitrary shaped object that does not scatter or disperse.

Therefore, a method of modeling by mixing fine particle titanium oxide with cement or gypsum has been proposed. In addition, when fine particle titanium oxide is mixed with a general organic compound, the organic compound itself decomposes and deteriorates due to the oxidizing action of fine particle titanium oxide. Therefore, a specific persistent organic compound is used, and fine particles are used together with a binder. A method of mixing titanium oxide for modeling, or a method of covering a part of the surface of the fine particle titanium oxide with silica or the like so that the fine particle titanium oxide and the organic compound do not come into direct contact with each other has been proposed.<patcit num="1"><text>Japanese Patent Application Laid-Open No. 6-315614</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 6-256540</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 7-171408</text></patcit><patcit num="4"><text>Japanese Patent Application Laid-Open No. 9-290165</text></patcit><patcit num="5"><text>Japanese Patent Application Laid-Open No. 10-225640</text></patcit><nplcit num="1"><text>"Forefront of Photocatalyst Business" edited by Koji Takeuchi and Koji Shijuku, Kogyo Chosakai, published on November 8, 2001</text></nplcit><nplcit num="2"><text>Akira Fujishima, Kazuhito Hashimoto, Toshiya Watanabe "Mechanism of Photocatalyst" Nihon Jitsugyo Publishing Co., Ltd. February 10, 2003</text></nplcit>

<p> However, the modeled object by the modeling method according to these proposals has a problem in that the photocatalytic action per surface area of the fine particle titanium oxide is not sufficiently exhibited. That is, according to these modeling methods, the fine particle titanium oxide is buried in the modeled object in order to give strength to the modeled object or to cover the particle surface of the fine particle titanium oxide with a substance such as silica. Since it is not sufficiently exposed on the surface of the particle, the photocatalytic action may be reduced.</p><p> Further, since polytetrafluoroethylene (hereinafter, simply referred to as "PTFE") is not affected by the photocatalytic action, a method of modeling using a mixed powder of this PTFE and fine particle titanium oxide is adopted. However, in order to fully exert the photocatalytic action, the content of fine particle titanium oxide must be increased, and conversely, the content of PTFE decreases. There is a drawback that the formability is significantly reduced and it easily collapses even if it is modeled.</p><p> Therefore, the present inventor has considered to support and model fine particle titanium oxide by the supporting effect of stirring PTFE to fibrilize. However, it was concluded that due to the low content of PTFE, fine particles of titanium oxide could not be sufficiently supported and would easily disintegrate. Therefore, the present inventor further establishes a method in which a mixed powder of fine particle titanium oxide and PTFE is stirred to form PTFE, and then press-molded and sintered at the melting point of PTFE (about 350 ° C) to fix the fibril. I thought. However, it was concluded that the modeled object could not be obtained with appropriate strength due to the low content of PTFE, and that it would still be in a fragile state.</p><p> It is known that when the content of PTFE is about 50% by weight, sufficient formability can be obtained by the method of sintering PTFE and fixing fibrils as described above. However, when the content of PTFE is increased in this way for modeling, the PTFE covers the surface of titanium oxide too much, and the PTFE inhibits the contact between titanium oxide and gas or liquid, so that the photocatalytic action is significantly reduced. There is a drawback that it ends up.</p><p> Therefore, the present inventor has conducted extensive research, and in view of the above problems, the photocatalytic action of the fine particle titanium oxide is maximized by containing a large amount of the fine particle titanium oxide, and the strength is sufficient as a modeled object. We have developed a photocatalyst-supporting board equipped with.</p>

<p> The photocatalyst-supporting board according to the present invention is formed by adhering a mixed powder mainly composed of photocatalyst particles and PTFE particles to a metal porous plate having a large number of pores so as to close the pores, and the front and back surfaces thereof. It is characterized in that both sides are photocatalytic surfaces.</p><p> Further, with respect to the above-mentioned photocatalyst-supporting board, a mixed powder obtained by mixing and stirring photocatalyst particles and fibrillated PTFE particles to fibrillate the PTFE particles is applied to a metal porous plate having a large number of pores. After filling and pressurizing so that the particles are closed, the particles may be heat-treated at a temperature equal to or higher than the melting point of PTFE to be sintered.</p><p> Further, the photocatalyst particles may be 75% by weight or more, the PTFE particles may be 25% by weight or less, the photocatalyst particles may be anatase-type titanium oxide, and the specific surface area of the anatase-type titanium oxide may be 100 m.²It may be more than / g, preferably 200m²It may be / g or more. Compared to rutile-type titanium oxide, anatase-type titanium oxide has a large photocatalytic action, and since the particle size is small, it has a large specific surface area per gram. It is most suitable as a photocatalyst particle used for a photocatalyst carrying board.</p><p> The photocatalyst-supporting board according to the present invention is mainly composed of photocatalyst particles and PTFE particles, and other substances may be mixed as long as it is necessary or depending on the purpose.</p><p> Furthermore, the above-mentioned metal perforated plate has a thickness of 0.4 mm to 3 mm, and the area of one hole of the metal perforated plate is 4 mm.²~ 100mm²This is preferable in that a photocatalytic substance such as titanium oxide can be efficiently used for photocatalytic action, and the mixed powder is sufficiently supported on a metal porous plate to maintain the strength of the photocatalyst-supporting board. As this perforated metal plate, there are various types such as an expanded metal mesh having a square or hexagonal hole shape, a grid-like wire mesh formed by crossing metal wires, or a punched metal plate having a circular or rectangular hole shape. Metal perforated plate can be adopted.</p><p> Further, a reinforcing frame may be arranged around the metal perforated plate, and if the reinforcing frame is arranged, the metal perforated plate can be prevented from being deformed by stress such as bending. It is possible to prevent the mixed powder adhering to the portion from falling off. Furthermore, the reinforcing frames arranged around the metal perforated plate are configured to have a connecting structure that can be joined to each other in a two-dimensional or three-dimensional manner so that they can be connected in a plane like laying tiles, or in a cubic shape. It may be possible to connect and assemble in three dimensions.</p><p> Furthermore, both or one of the metal perforated plate and the reinforcing frame may be made of aluminum or stainless steel, and in the case of aluminum, it is easy to process and lightweight, and it is in contact with a liquid for a long period of time. When it is in the air, it may be treated with alumite to prevent corrosion. Further, in the case of stainless steel, it has an advantage of excellent durability because it has corrosion resistance and is sturdy. The material of both or one of the metal perforated plate and the reinforcing frame is not limited to the above, and various materials such as nickel-plated iron may be used. Further, as the material of the reinforcing frame, various materials such as synthetic resin and ceramic may be appropriately selected depending on the implementation status of the photocatalyst-supporting board according to the present invention.</p><p> Further, the above-mentioned photocatalyst-supporting board may be dedicated to purifying the atmospheric environment or deodorizing the atmosphere. In either case, the mixed powder supported on the photocatalyst-supporting board does not scatter in the air, which is preferable. Is. Furthermore, the photocatalyst-supported board has a coefficient of neutralization rate of ammonia in the atmosphere of 2.3 × 10.²¹Pieces / m²-It is desirable that the time is longer than that, and in this case, a photocatalyst-supporting board dedicated to the atmosphere can be obtained, which can exert an extremely excellent effect of photocatalytic action.</p><p> Further, the above-mentioned photocatalyst-supporting board may be dedicated to purifying the environment of freshwater or seawater, or may be dedicated to purifying freshwater or seawater for breeding or viewing organisms in freshwater or seawater. It is suitable because the mixed powder supported on the photocatalyst-supported board does not disperse in water. Furthermore, the photocatalyst-supported board has an ammonia neutralization rate coefficient of 7.5 × 10 in water.²⁰Pieces / m²-It is desirable that the time is longer than that, and in this case, a photocatalyst-supporting board dedicated to water that can exert an extremely excellent photocatalytic effect can be obtained.</p>

<p> By constructing the photocatalyst-supporting board according to the present invention as described above, it is possible to maximize the photocatalytic action of the fine particle titanium oxide by containing a large amount of fine particle titanium oxide, and to have sufficient strength as a modeled object. A photocatalyst-supporting board suitable for practical use was obtained.</p>

The best mode for carrying out the invention will be described below.

Hereinafter, examples of the photocatalyst carrying board according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view with a partially enlarged view of the expanded metal used for producing the photocatalyst carrying board according to the first embodiment, and FIG. 2 is a metal in which a rubber sponge sheet and a rubber sheet are superposed on the expanded metal filled with the mixed powder. It is a schematic cross-sectional view showing a state of being pressure-molded by a vertical pressurizing die made of the same product, and FIG. 3 is a partially cutaway perspective view of a finished product of the photocatalyst carrying board according to the first embodiment with a partially enlarged view. , FIG. 4 is a cross-sectional view of a finished product of the photocatalyst carrying board according to the first embodiment.

(Preparation of mixed powder) Anatase type titanium oxide powder 90g (manufactured by TAYCA Corporation, product number; AMT100, specifications according to the company's catalog: crystalline form; anatase, specific surface area; 260m²/ G, average particle size; 6 nm) and 10 g of fibrillated PTFE powder (manufactured by Daikin Industries, Ltd., product number; fine powder F104) in a mixer (manufactured by SUNBEAM-OSTER, PHOENIX BLENDER-KB-1). The mixed powder was stirred at a constant temperature of 50 ° C. at a rotation speed of 16800 rpm for 2 minutes to prepare a mixed powder A.

(Preparation of unfired photocatalyst-supported board) As shown in Fig. 1, the thickness is 1.55 mm and the area of one hole is 15 mm.²Aluminum Expanded Metal E (Kansai Iron Works Co., Ltd., Kantetsu Expanded Metal 4 mm (distance between centers in the short mesh direction) x 8 mm (distance between centers in the long mesh direction) x 0.8 mm (plate thickness) x 0.8 mm ( As shown in FIG. 2, the mixed powder A is filled in the step size)) so that the hole e of the expanded metal E is closed. Then, a rubber sponge sheet S having a thickness of 2 mm is superposed on the portion e'filled with the mixed powder A at least in the expanded metal E, and a rubber sheet G having a thickness of 1 mm is superposed on both the upper and lower outer sides thereof. 50kg / cm from the outside with a metal push die P for vertical pressurization²Press-molded with. The unfired product of the photocatalyst-supported board produced by using the mixed powder A is referred to as board A. When the board A produced here was immersed in a water tank, the water tank immediately became cloudy and titanium oxide particles flowed out.

(Preparation of photocatalyst-supported board) Therefore, the above board A is heat-treated for 10 minutes in an electric furnace heated to 370 ° C, which is slightly higher than the melting point of PTFE, and fired. A finished product of the photocatalyst-supported board L was obtained by fitting it so as to be sandwiched between the stainless steel reinforcing frame F of 11 cm and 10 cm square. This finished product is shown in FIGS. 3 and 4. An inner groove f that can be held by the board A is formed on the inner surface of the reinforcing frame F. Concavo-convex f'that can be joined to other reinforcing frames is formed on the outer side surface, and it is possible to connect in a plane like laying tiles or to connect in a cubic shape three-dimensionally and assemble. ing. The finished photocatalyst-supported board produced using the mixed powder A is referred to as board AH. Even if this board AH was immersed in the water tank, the water tank did not become cloudy.

A flowchart of the manufacturing process of this embodiment is shown in FIG.

(Preparation of mixed powder) Anatase type titanium oxide powder 80g (manufactured by TAYCA Corporation, product number; AMT100, specifications according to the company's catalog: crystalline form; anatase, specific surface area; 260m²/ G, average particle size; 6 nm) and 20 g of fibriltable PTFE powder (manufactured by Daikin Industries, Ltd., product number; fine powder F104) in a mixer (manufactured by SUNBEAM-OSTER, PHOENIX BLENDER-KB-1). The mixed powder was stirred at a constant temperature of 50 ° C. at a rotation speed of 16800 rpm for 2 minutes to prepare a mixed powder B.

(Preparation of unfired photocatalyst-supported board) Thickness 1.55 mm, area of one opening 15 mm²Aluminum expanded metal (manufactured by Kansai Iron Works Co., Ltd., Kantetsu expanded metal 4 mm (distance between centers in the short mesh direction) x 8 mm (distance between centers in the long mesh direction) x 0.8 mm (plate thickness) x 0.8 mm (incremented) The width)) is filled with the mixed powder B so as to close the pores of the expanded metal. Then, a rubber sponge sheet having a thickness of 2 mm is layered from above and below on the portion of the expanded metal filled with the mixed powder B, and a rubber sheet having a thickness of 1 mm is layered on both the upper and lower outer sides thereof. 50kg / cm by vertical pressurizing die²Press-molded with. The unfired product of the photocatalyst-supported board produced by using the mixed powder B is referred to as board B. When the board B produced here was immersed in a water tank, the water tank immediately became cloudy and titanium oxide particles flowed out.

(Preparation of photocatalyst-supported board) Therefore, the above board B was heat-treated for 10 minutes in an electric furnace heated to 370 ° C, which slightly exceeds the melting point of PTFE, and fired. , The finished product of the photocatalyst-supported board was obtained by fitting it so as to be sandwiched between the stainless steel reinforcing frames of 10 cm square. A groove that allows the board B to be narrowed is formed on the inner surface of the reinforcing frame. The outer side surface is formed with irregularities that can be joined to other reinforcing frames, so that tiles can be connected in a plane like laying down tiles, or can be assembled in a cubic shape by three-dimensionally connecting them. .. The finished photocatalyst-supported board produced using the mixed powder B is referred to as board BH. Even if this board BH was immersed in the water tank, the water tank did not become cloudy.

[Comparative example 1]

In Example 1 above, 90 g of titanium oxide powder and 10 g of PTFE powder were mixed to prepare a photocatalyst-supported board, but in Comparative Example 1, the photocatalyst-supported board was prepared by changing to 60 g of titanium oxide powder and 40 g of PTFE powder. It is a thing.

That is, titanium oxide powder 60 g (manufactured by TAYCA Corporation, product number; AMT100, specifications according to the company's catalog: crystalline form; anatas, specific surface area; 260 m²Using / g, average particle size; 6 nm) and 40 g of fibriltable PTFE powder (manufactured by Daikin Industries, Ltd., product number; fine powder F104), by the same production method as the production of the mixed powder shown in Example 1. Prepare mixed powder C. Using this mixed powder C, a photocatalyst-supported board unfired product is produced by the same production method as in the production of the photocatalyst-supported board unfired product shown in Example 1, and this is referred to as board C. Then, using this board C, a photocatalyst-supported board is manufactured by the same manufacturing method as that of the photocatalyst-supported board shown in Example 1, and this is referred to as a board CH.

[Comparative example 2]

In Example 1 above, 90 g of titanium oxide powder and 10 g of PTFE powder were mixed to prepare a photocatalyst-supported board, but in Comparative Example 2, the photocatalyst-supported board was prepared by changing to 30 g of titanium oxide powder and 70 g of PTFE powder. It is a thing.

That is, titanium oxide powder 30 g (manufactured by TAYCA Corporation, product number; AMT100, specifications according to the company's catalog: crystalline form; anatas, specific surface area; 260 m²Using / g, average particle size; 6 nm) and 70 g of fibriltable PTFE powder (manufactured by Daikin Industries, Ltd., product number; fine powder F104), by the same production method as the production of the mixed powder shown in Example 1. Prepare mixed powder C. Using this mixed powder C, a photocatalyst-supported board unfired product is produced by the same production method as in the production of the photocatalyst-supported board unfired product shown in Example 1, and this is referred to as board D. Then, using this board D, a photocatalyst-supported board is manufactured by the same manufacturing method as that of the photocatalyst-supported board shown in Example 1, and this is referred to as a board DH.

Table 1 shows the weights of the components of the mixed powder A and the mixed powder B prepared in the above example and the mixed powder C and the mixed powder D prepared in the comparative example.

<tables num="1"><img file="JP2005254185A_D0001.tif" /></tables>

[Comparison test]

The boards AH and BH in the above examples, and the boards CH and DH in the comparative examples were tested to measure the time required for ammonia to neutralize in air and water as follows, and the boards in the examples were tested. AH and board BH neutralized ammonia in a short time, demonstrating that the photocatalytic action is remarkable.

As a reference for comparison, about 70 g of commercially available photocatalyst ceramic balls (sold by Otsuka Filtration Tank Research Institute, photocatalyst / special ceramic, trade name "Strica", one spherical shape with a diameter of about 6.6 mm) are spread in about 10 cm square. The same measurement was performed using the same material. Furthermore, only ammonia was injected as a reference, and the change over time of ammonia was confirmed.

[Ammonia neutralization test in air]

-Test method Board AH, board BH, board CH and board DH are stored in polypropylene, colorless and transparent airtight container with lid (11.5 cm square, height 3 cm), and Lithomas test paper (manufactured by Advantech Toyo Co., Ltd .; width 9 mm). ) Is cut into a nearly square shape and placed on the corners and center of each board. Then, using a pipette, 0.05 ml of an aqueous solution of ammonia having a concentration of 28% (weight calibrated by a chemical balance was 0.047 g) was injected into one corner of each container, and the time required for the lithomas test paper to reach neutralization was measured.

Measurement environment On a sunny day in May, measurement started at 10 am in Osaka and ended 24 hours later. The measurements were taken in direct sunlight during the day and under fluorescent light from about 6 pm after sunset to about 6 am after sunrise the next morning.

-Confirmation method The PH value is determined by comparing the color displayed on the Lithomas test paper with the standard color specified on the Lithomas test paper. Further, in an intermediate state in comparison with the standard color, for example, when the color displayed on the Lithomas test paper is an intermediate color between the standard colors of PH7 and PH8, the larger value, that is, PH8 is adopted. Furthermore, when it was judged to be PH7, it was confirmed that it was odorless.

Table 2 shows the measurement results of each board. The powder weight is the weight of each mixed powder used to form each board. The ammonia neutralization rate coefficient is the rate at which ammonia reaches neutralization, and is the value obtained by dividing the number of molecules of ammonia under a certain concentration by the product of both surface areas of the photocatalyst-supporting board and the time required for neutralization. is there. The number of molecules of ammonia in the neutralization test is 0.047 g (weight of aqueous ammonia solution) x 28% (concentration) ÷ 17 g (weight of ammonia per mole) x 6 x 10.²³(Avogadro's number) = 4.6 × 10²⁰(2 significant digits). This number of molecules is 0.02 m on both surface areas of the photocatalyst-supported board.²The ammonia neutralization rate coefficient is calculated by dividing by the product of the time required for neutralization.

<tables num="2"><img file="JP2005254185A_D0002.tif" /></tables>

[Evaluation]

From the above test results, it was confirmed that the ammonia in PH11 reached neutralization in the gas in the container containing the board AH within 1 hour from the start of the test, and the photocatalytic action of the board AH was remarkably exhibited. In addition, it was confirmed that the gas in the container containing the board BH was neutralized in 5 hours, and that the photocatalytic action of the board BH was sufficiently exhibited. On the other hand, the gas in the container containing the board CH finally reached neutralization in 24 hours, confirming that the photocatalytic action of the board CH was not sufficient. It was also confirmed that the gas in the container containing the board DH and the ceramic balls did not reach neutralization even after 24 hours, and its practicality as a photocatalyst was low. Based on the above results, the ammonia neutralization rate coefficient of the photocatalyst-supported board was 2.3 × 10.²¹Pieces / m²-If it is longer than the time, it has been demonstrated that a photocatalyst-supporting board dedicated to the atmosphere that can exert an extremely excellent photocatalytic effect can be obtained, and the content of photocatalyst particles in the mixed powder used for manufacturing the photocatalyst-supporting board has been determined. This can be achieved by reducing the content of PTFE to 75% or more and the content of PTFE to 25% or less. The reference did not change the pH of the gas in the container even after 24 hours, which confirmed that the test method was accurate and the measurement results were reliable.

[Ammonia neutralization test in water]

-Test method Put 200 ml of water in the same container used in the above "Neutralization test of ammonia in air", and use a pipette to make an aqueous solution of ammonia with a concentration of 28% 0.05 ml (calibrated with a chemical balance). After injecting 0.047 g), the board AH, board BH, board CH and board DH are stored in each container, and one drop of water injected from each container is collected at regular intervals and dropped on the Lithomas test paper. Then, the change in PH was measured.

Measurement environment On a sunny day in May, measurement started at 10 am in Osaka and ended 48 hours later. During the daytime, the measurements were taken outdoors, avoiding direct sunlight, under fluorescent light from about 6 pm after sunset to about 6 am after sunrise the next morning.

The confirmation method is the same as the confirmation method in the above-mentioned "Ammonia neutralization test in air".

The measurement results are shown in Table 3. The weight of the powder used to form each board is the same as the weight of the powder in the above-mentioned "Ammonia neutralization test in air". The ammonia neutralization rate coefficient is calculated by the method described in "Ammonia Neutralization Test in Air".

<tables num="3"><img file="JP2005254185A_D0003.tif" /></tables>

[Evaluation]

From the above test results, it was confirmed that the ammonia in PH11 reached neutralization in the liquid in the container containing the board AH within 5 hours from the start of the test, and the photocatalytic action of the board AH was remarkable. In addition, the liquid in the container containing the board BH was neutralized in 24 hours, and it was confirmed that the board BH also had a sufficient photocatalytic action. On the other hand, the liquid in the container containing the board CH finally reached neutralization in 48 hours, confirming that the photocatalytic action of the board CH was not sufficient. It was also confirmed that the air in the container containing the board DH and the ceramic balls did not reach neutralization even after 48 hours, and the practicality as a photocatalyst was low. Based on the above results, the ammonia neutralization rate coefficient of the photocatalyst-supported board was 7.5 × 10.²⁰Pieces / m²-When the time is longer than that, it has been demonstrated that a photocatalyst-supporting board exclusively for water that can exert an extremely excellent photocatalytic effect can be obtained, and the content of photocatalyst particles in the mixed powder used for manufacturing the photocatalyst-supporting board is 75. This can be achieved by reducing the content of PTFE to 25% or more. The reference did not change the pH of the liquid in the container even after 24 hours, which confirmed that the test method was accurate and the measurement results were reliable.

When the photocatalyst-supported board according to the present invention is used, the deodorizing and purifying effects of liquids and gases are remarkable, and the board has sufficient strength. Therefore, it has high industrial utility value.

<figref num="1">It is a perspective view with a partially enlarged view of the expanded metal used for manufacturing the photocatalyst carrying board which concerns on Example 1. FIG.</figref><figref num="2">It is a schematic cross-sectional view which shows the state in which the rubber sponge sheet and the rubber sheet are superposed on the expanded metal filled with the mixed powder, and pressure-molded by the metal push die for vertical pressurization.</figref><figref num="3">It is a partially cutaway perspective view with a partially enlarged view of the finished product of the photocatalyst carrying board according to the first embodiment.</figref><figref num="4">It is sectional drawing of the finished product of the photocatalyst carrying board which concerns on Example 1. FIG.</figref><figref num="5">It is a flowchart which shows the manufacturing process of the photocatalyst-supporting board which concerns on Example 1.</figref>

Code description

A Mixed powder E Expanded metal e Hole e' Part filled with mixed powder S Rubber sponge sheet G Rubber sheet P Metal top and bottom Pressurizing die F Reinforcing frame f Inner groove f' Joinable unevenness L Photocatalyst supporting board