JP2002071298A - Photocatalytic heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic heat exchanger excellent in antibacterial performance, an excellent hydrophilic performance and deodorizing performance and not having silica odor. SOLUTION: The photocatalytic heat exchanger is characterized in that a fin 21 surface of the heat exchanger is coated with a photocatalyst 32, an inorganic antibacterial agent 33 and an organic binder 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for an air conditioner, and more particularly to a photocatalytic heat exchanger for a home and automobile air conditioner, which simultaneously realizes a deodorizing function and prevention of bacterial growth on heat exchanger fins. About.

[0002]

2. Description of the Related Art Activated carbon, ozone, noble metal-based oxidation catalysts, and the like have been used for deodorization in conventional air conditioners. However, in either method, it is necessary to install the air conditioner at a position that does not obstruct the flow path of the air flowing into and out of the heat exchanger so as not to obstruct the cooling and heating functions inherent to the air conditioner. For this reason, the contact area with the odorous gas is small, and at present, sufficient deodorizing performance cannot be obtained.

As a method for solving the above-mentioned problem, there has been proposed a photocatalytic heat exchanger in which a titanium oxide powder as a photocatalyst is formed on an aluminum fin of a heat exchanger together with a silica-based inorganic binder (Japanese Patent Application Laid-Open No. Hei 8-8). No. 296992). Specifically, as shown in FIG. 4, a corrosion-resistant coating 42 and a coating 45 composed of titanium oxide fine particles 43 and a silica-based inorganic binder 44 are sequentially formed on the surface of the main body portion 41 of the aluminum fin. 4
By irradiating the ultraviolet light 3 with the ultraviolet light, deodorization is performed by decomposition of the odor gas contacted by the photocatalytic action generated on the surface of the titanium oxide fine particles 43. That is, since the heat exchanger having a large contact area with the odor gas is coated with the photocatalyst, excellent deodorizing performance can be obtained as compared with a conventional deodorizing method using a noble metal-based oxidation catalyst or the like.

Further, since the photocatalytic action of titanium oxide also has an antibacterial effect, the photocatalytic heat exchanger having the above-mentioned structure has a feature that it has antibacterial performance in addition to deodorization and hydrophilicity.

[0005]

However, in the above-described photocatalytic heat exchanger, the photocatalytic action on the surface of the aluminum fin is an effect that appears only when the ultraviolet lamp is irradiated. That is, there is a defect that bacteria cannot be prevented from growing on the surface of the aluminum fin that is not or hardly hit by ultraviolet light from the lamp. Furthermore, since a silica-based inorganic substance is used for the binder, an unpleasant cement odor is generated immediately after the start of the cooling / heating operation. In order to solve this problem, it is effective to use an organic binder. However, when an organic binder is used, the photocatalytic action of titanium oxide not only decomposes the odorous gas that has come into contact, but also decomposes the organic binder. However, there is also a problem that the particles are peeled off.

An object of the present invention is to provide a photocatalyst heat exchanger having an antibacterial performance in addition to an excellent deodorizing function in an air conditioner for home use or automobile use. With the goal.

[0007]

In order to achieve the above object, a photocatalyst heat exchanger according to the present invention comprises a fin surface made of a heat conductive metal material coated with a photocatalyst, an inorganic antibacterial agent and an organic binder. It is characterized by being.

As described above, in addition to the photocatalyst, an inorganic antibacterial agent is coated on the fin surface together with the organic binder, so that excellent antibacterial performance can be obtained even on the fin surface where light is hardly exposed. Moreover, since an organic binder is used, it is possible to eliminate the generation of unpleasant cement odor when a silica-based inorganic binder is used.

A second aspect of the present invention is characterized in that the photocatalyst according to the first aspect of the present invention uses, as the photocatalyst having fine pores on the surface of titanium oxide particles, a photocatalytic particle coated with an inert ceramic film. . This prevents direct contact between the titanium oxide and the organic binder, so that the organic binder can be prevented from decomposing and deteriorating due to the photocatalytic action of the titanium oxide during ultraviolet light irradiation.

Here, the heat conductive metal material is preferably aluminum or an aluminum alloy.

The invention of claim 3 is characterized in that, in the invention of claim 1, the organic binder is a polymer compound having hydrophilicity. The binder has a hydrophilic structure because the photocatalyst particles used have a structure in which the surface of the titanium oxide particles is coated with an inert ceramic film as a photocatalyst having fine pores. This is because the decrease in the superhydrophilicity effect on the surface of the photocatalyst particles as compared with the case where it is used is compensated for by the hydrophilicity of the binder.

At this time, the polymer compound having hydrophilicity is preferably a polymer containing (meth) acrylic acid or vinyl alcohol as a polymerized unit, a cellulose compound, or a mixture thereof.

According to a third aspect of the present invention, in the first aspect, the inorganic antibacterial agent comprises a silica gel carrying a thiosulfatosilver complex and at least a part of the surface of the silica gel coated with a hydrolyzate of tetraalkoxysilane. Silver silica gel antibacterial agent.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 is a schematic side view of the inside of an indoor unit of an air conditioner using the photocatalytic heat exchanger of the present invention, FIG. 2 is a perspective view of the photocatalytic heat exchanger of the present invention, and FIG. 3 is an aluminum fin of the photocatalytic heat exchanger of the present invention. FIG.

As shown in FIG. 1, a photocatalytic heat exchanger 12, an ultraviolet lamp (15 W; peak wavelength 365 nm) 13, and a blower 14 are provided in the indoor unit 11. As shown in FIG. 2, the photocatalyst heat exchanger 12 has a structure in which a large number of aluminum fins 21 are attached in parallel at regular intervals to a metal pipe 22 which is a passage for a refrigerant. As shown in FIG. 3, the aluminum fins 21 are made of a photocatalyst particle 32 formed by coating a surface of a main body 31 made of aluminum with an inert ceramic film as a photocatalyst having fine pores on the surface of titanium oxide particles. And a coating 35 composed of silver silica gel-based antibacterial agent particles 33 containing a thiosulfatosilver complex and an organic binder 34.

Here, in the indoor unit 11,
As shown by the arrow, the indoor air passes through the photocatalytic heat exchanger 12 from above the indoor unit 11 and further passes through the blower 14.
After passing through, the air is discharged from the lower part of the indoor unit 11 into the room. Further, by turning on the ultraviolet lamp 13, the odor gas contained in the room air in contact with the photocatalyst particles 23 in the coating 25 formed on the surface of the aluminum fin 21 of the photocatalyst heat exchanger 12 is decomposed by photocatalysis. It is deodorized. Further, since the organic binder 34 has hydrophilicity, it is possible to prevent water droplets from being formed on the surface of the aluminum fins 21 and to prevent the problem that the floor is blown into the room from the blow-out opening and the floor is wet.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The photocatalyst heat exchanger of the present invention will be described below together with its manufacturing method.

(Example) As an aluminum fin material, an aluminum plate (material: 1330, thickness: 0.1 mm, temper: H26) which had been degreased and washed in advance was used. The photocatalyst powder is a powder obtained by coating the surface of anatase-type titanium oxide particles having a particle size of about 40 nm with porous alumina having pores of 10 nm (for example, Patent Publication: No. 2).
No. 945926), and polyvinyl alcohol, which is a polymer compound having hydrophilicity, was used as the binder. In addition, silver silica gel antibacterial particles (particle diameter: about 0.4 μm) were used as the inorganic antibacterial agent.

Here, a method for producing the silver silica gel antibacterial agent will be described. 100 parts by weight of a water-soluble silver salt such as silver acetate is added to and dissolved in water containing no chlorine, and 450 parts by weight of a mixture of sodium sulfite and sodium bisulfite and 300 parts by weight of sodium thiosulfate are sequentially and stirred. Mix and dissolve to obtain an aqueous silver complex solution. The weight of sodium thiosulfate is given as the weight of its hydrate, Na ₂ S ₂ O ₃ .5H ₂ O. Next, 100 parts by weight of a silica gel powder having an average particle size of 3 μm dried at 180 ° C. for 2 hours or more are mixed with the above-mentioned aqueous solution of silver thiosulfato complex so as to become 2 parts by weight as a silver component. Next, the solvent and the water absorbed in the silica gel are promptly removed. This is pulverized to a predetermined particle size (about 0.4 μm) to obtain silica gel carrying an antibacterial material. As a coating material, 100 parts by weight of the antibacterial material-supporting silica gel is dispersed in a solution obtained by diluting 100 parts by weight of tetraethoxysilane with 100 parts by weight of ethyl alcohol, and at least a part of the surface of the silica gel is coated.
Then, this is dried to obtain a silver silica gel antibacterial agent.

The above-mentioned titanium oxide photocatalyst powder coated with porous alumina and a silver silica gel antibacterial agent are applied on aluminum fins together with a polyvinyl alcohol as a hydrophilic organic binder at 200 ° C.
For 30 seconds to form a photocatalytic film having a thickness of 1 μm on the aluminum fins. Then, the fin material was pressed using a volatile press oil to form fins having a predetermined shape. Further, after assembling the fins with a tube for a refrigerant, the pressurized press oil was degreased by heating and drying at a predetermined temperature to produce a photocatalyst heat exchanger A.

Comparative Example Next, as a comparative example, anatase-type titanium oxide particles (ST-01, Ishihara Sangyo) having a particle size of about 7 nm were used as a photocatalyst powder, and a silica-based inorganic material was used as a binder. After the application, it was dried by heating at 150 ° C. for 30 minutes to form a photocatalytic film having a thickness of 1 μm. Then, similarly to the above-described method, the photocatalytic heat exchanger B
Was prepared.

(Experiment 1) The photocatalyst heat exchanger A of the present invention described above.
A part of the fins of the photocatalyst heat exchanger B of the comparative example was cut out (size: 10 mm × 10 mm), and after preparing each sample, the antibacterial properties of these samples were evaluated. A specific evaluation method is to prepare three sterilized glass Petri dishes, put each sample thoroughly washed with alcohol in each Petri dish, put them in a constant temperature bath maintained at a temperature of 35% at a humidity of 90%, and remove E. coli. The same amount (approximately 1 × 10 ⁵ cells / ml) was dropped on each of the above samples and kept for 18 hours, and then the amount of E. coli on each sample was measured. In addition, a 5W fluorescent lamp is installed in the above constant temperature vessel,
The sample in the petri dish is irradiated with light.

As a result, when irradiation with a fluorescent lamp was performed, the number of E. coli in the comparative photocatalytic heat exchanger B was about 1 × 1.
0 whereas only up to ³ cells / ml not reduced, it was found that reduced to about 100 in the photocatalyst heat exchanger A of the present invention. When the fluorescent lamp was not irradiated, the number of E. coli in the comparative photocatalytic heat exchanger B was about 9 × 1.
0 up to ⁴ / ml while only decreased and it is observed that is reduced to about 5 × 10 ² cells / ml in photocatalytic heat exchanger A of the present invention.

As described above, the photocatalytic heat exchanger of the present invention
In particular, it had excellent antibacterial performance even without light irradiation.

(Experiment 2) The obtained photocatalytic heat exchanger A and photocatalytic heat exchanger B were evaluated for odor. The odor was evaluated by a panelist after performing a breath blow. As a result, the photocatalyst heat exchanger B of the present invention felt a rather strong odor, while the photocatalyst heat exchanger A of the present invention hardly felt it.

(Experiment 3) Next, the indoor unit of an air conditioner using the photocatalytic heat exchanger A of the present invention and the indoor unit of the air conditioner using the photocatalytic heat exchanger B of the comparative example (both in FIG. 1)
The deodorizing performance was evaluated by the following structure. The specific evaluation method is as follows: an indoor unit of an air conditioner using the photocatalyst heat exchanger A and the photocatalyst heat exchanger B;
m, width 4 m, depth 4 m, placed in an airtight laboratory (filled with 15 ppm concentration of acetaldehyde) at room temperature 28 ° C., set the temperature at 20 ° C., and keep the humidity at 40% while cooling. The operation was performed, and the photocatalytic decomposition performance of acetaldehyde was measured. In addition, the drain hose of the dehumidified dew condensation water which is usually taken out of the room was guided into a plastic tank provided in the airtight laboratory in order to ensure the airtightness of the laboratory.

As a result, in the indoor unit of the air conditioner using the comparative photocatalytic heat exchanger B, the concentration of acetaldehyde after about 30 minutes was 8 ppm, and 3 ppm after 1 hour. In the photocatalyst heat exchanger A of the present invention, the concentration of acetaldehyde after about 30 minutes was 8 ppm, and was 3 ppm after 1 hour. That is, it was found that the photocatalyst heat exchanger A of the present invention had excellent deodorizing properties as in the case of the conventional photocatalyst heat exchanger B.

(Experiment 4) Further, with respect to the obtained photocatalyst heat exchanger A and photocatalyst heat exchanger B, a part of the fin was cut out (size: 5 mm square) to prepare each sample.
The hydrophilicity was evaluated by measuring the contact angles of water drops of these samples. The hydrophilicity was evaluated by irradiating each sample for 10 minutes at an irradiation distance of 25 cm using a fluorescent lamp light source (15 W; peak wavelength 365 nm) in the ultraviolet region.
After a certain period of time, 1 microliter of ultrapure water (μ
1) is dropped, and the contact angle of ultrapure water is measured using a contact angle meter.

As a result, the contact angle of the fins in the photocatalytic heat exchanger A of the present invention was 8 ° immediately after the start of elapsed time measurement, 11 ° after 12 hours, and 12 ° after 36 hours. The contact angle of the fins in the comparative photocatalytic heat exchanger B was 7 ° immediately after the start of the elapsed time measurement, 12 ° after 12 hours, and 14 ° after 36 hours.

From the above results, the photocatalytic heat exchange A of the present invention
Was found to have the same level of hydrophilicity as the conventional photocatalytic heat exchanger B.

From the results of Experiment 1 and Experiment 2,
The photocatalyst heat exchanger A of the present invention is different from the conventional photocatalyst heat exchanger B
It can be seen that it has excellent antibacterial performance and solves the problem of cement odor of the conventional photocatalytic heat exchanger as compared with the conventional method. In addition, the results of Experiments 3 and 4 show that they have the same deodorizing performance and hydrophilic properties as those of the conventional photocatalytic heat exchanger.

In the photocatalyst particles of the embodiment of the present invention, alumina was used as the photocatalytically inactive ceramic film having fine pores coated on the surface of the titanium oxide particles. However, the present invention is not limited to this. Similar results were obtained with titanium oxide, zirconium oxide, silicon oxide, magnesium oxide and calcium oxide.

In the examples of the present invention, polyvinyl alcohol was used as the organic binder. However, the present invention is not limited to this. For example, a polymer containing (meth) acrylic acid or vinyl alcohol as a polymerization unit, a cellulose compound, or a polymer thereof may be used. In the case of a mixture of the above, similar results were obtained. Specifically, poly (meth) acrylic acid, a copolymer of poly (meth) acrylic acid and polyvinyl acetate, a copolymer of poly (meth) acrylic acid and polyvinyl alcohol, and poly (meth) acrylic acid Cellulose copolymer,
Copolymer of poly (meth) acrylic acid and starch, poly (meth) acrylamide, poly (meth) acrylamidomethylpropanesulfonic acid, copolymer of (meth) acrylic acid and polyamide, polyvinyl alcohol, polyvinyl acetate It is a partially saponified product and a cellulosic resin.

In the embodiment of the present invention, the photocatalyst film is formed directly on the fins of aluminum or the like. However, the present invention is not limited to this. A chromate treatment layer is provided on the aluminum fins as a corrosion-resistant film. The same effect was obtained in the configuration in which the photocatalytic film was formed thereon.

[0035]

As is apparent from the above description, the photocatalyst heat exchanger of the present invention has a structure in which the fin surface of the heat exchanger is coated with a photocatalyst, an inorganic antibacterial agent and an organic binder. As compared with the case where the titanium oxide particles are coated with the silica-based inorganic binder, not only are excellent deodorizing performance and hydrophilic performance, but also no generation of cement odor, and further excellent antibacterial performance.

[Brief description of the drawings]

FIG. 1 is a schematic side view of the interior of an indoor unit of an air conditioner using the photocatalytic heat exchanger of the present invention.

FIG. 2 is a perspective view of the photocatalytic heat exchanger of the present invention.

FIG. 3 is a cross-sectional view of the aluminum fin of the present invention.

FIG. 4 is a cross-sectional view of a conventional photocatalytic heat exchanger.

[Explanation of symbols]

Reference Signs List 11 Indoor unit of air conditioner 12 Photocatalytic heat exchanger 13 Ultraviolet lamp 14 Blower 21 Aluminum fin with photocatalytic coating 22 Metallic pipe 31 Aluminum fin 32 The surface was coated with an inert alumina film as a photocatalyst having fine pores Photocatalyst particles 33 Inorganic antibacterial agent (silver silica gel antibacterial agent particles) 34 Organic binder (polyvinyl alcohol) 35 Photocatalytic coating 41 Aluminum fin 42 Titanium oxide particles 43 Silica-based inorganic binder 44 Photocatalytic coating

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B01J 37/02 301 F25B 39/00 P F24F 1/00 F28F 13/18 B F25B 39/00 B01D 53/36 H F28F 13 / 18 F24F 1/00 371Z (72) Inventor Toshioka Toshioka 1006 Kazuma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 3L051 BC03 BC05 BC10 4C080 AA07 AA10 BB02 BB05 CC01 HH05 JJ04 KK08 LL10 MM02Q17 4D048 AA22 AB01 AB03 BA03X BA07X BB03 BC07 CC33 CC34 CC42 EA01 4G069 AA03 AA08 AA09 BA01B BA04A BA04B BA04C BA17 BA48A BA48C CA01 CA07 CA10 CA17 DA06 EC22Y EE01 EE07 FA04 FB23

Claims (4)

[Claims] 1. A photocatalytic heat exchanger, wherein a fin surface made of a heat conductive metal material is coated with a photocatalyst, an inorganic antibacterial agent and an organic binder. 2. The photocatalyst heat exchanger according to claim 1, wherein the photocatalyst is a particle in which titanium oxide particles are coated with an inert ceramic film as a photocatalyst having fine pores on the surface. 3. The photocatalytic heat exchanger according to claim 1, wherein the organic binder is a polymer compound having hydrophilicity. 4. The method according to claim 1, wherein the inorganic antibacterial agent is a silver silica gel antibacterial agent obtained by supporting a thiosulfatosilver complex on silica gel and coating at least a part of the surface of the silica gel with a hydrolyzate of tetraalkoxysilane. The photocatalyst heat exchanger according to claim 1, characterized in that: