JPH10227532A - Transparent cover for solar heat collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain water repellency of a surface for a long period by forming a substantially clear surface layer containing a photocatalyst particles, water repellent silicone and a material to prevent the occurrence of hydrophilicity due to photo excitation of the photocatalyst of the water repellent silicone. SOLUTION: A transparent surface layer is formed on the surface of a transparent cover 10. The surface layer contains photocatalyst particles, silicone, and a material to prevent the occurrence of hydrophilicity due to photo excitation of a photocatalyst, such as silicone, cobalt, or a cobalt compound. By containing the material, preventing the occurrence of hydrophility due to photo excitation of the photocatalyst, such as cobalt or a cobalt compound, in the surface layer, the occurrence of hydrophilicity of silicone due to photo excitation of the photocatalyst is prevented. Further, since the photocatalyst is contained, fouling adhered with lapse of the time is decomposed based on an oxidation decomposable property of the photocatalyst. This constitution permanently maintains water repellency of the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar heat collector such as a solar water heater, and more particularly, to a transparent cover of a solar heat collector which is resistant to contamination.

[0002]

2. Description of the Related Art The heat collector of a solar heat collector is covered by a transparent cover. Japanese Industrial Standards stipulates that the transparent cover of a solar heat collector is made of polycarbonate, glass (plain glass,
Float glass, polished glass, or tempered glass),
It is recommended to be formed of glass fiber reinforced polyester or a material having the same or better quality (JI
S, A4111).

[0003]

During long-term use, the transparent cover of the solar heat collector is contaminated with dust, and the light transmittance and, consequently, the heat collection efficiency are reduced. In recent years, stains on the transparent cover have become remarkable due to environmental pollution. Therefore, it is desirable to clean the transparent cover of the solar collector periodically or as needed. However, since the solar heat collector is installed on the roof, its cover is not easy to clean. Therefore, a transparent cover of a solar heat collector to which dirt is less likely to adhere is desired.

As a method for preventing the adhesion of dirt, it is known that it is better to impart water repellency to the surface of a substrate. As one of the methods, there is a method of forming a surface layer made of a water-repellent silicone on a substrate surface. However, with this structure, the contact angle with water is reduced to about 70 ° due to the adhesion of dirt over time, and the effect of water repellency is not maintained. Therefore, as another method for solving the above-mentioned problem, there is a method of forming a surface layer comprising a photocatalyst and a water-repellent silicone on the surface of a substrate. According to this method, it is possible to decompose the adhered dirt over time based on the oxidative decomposability of the photocatalyst. However, in this configuration, when exposed to sunlight outdoors, the silicone is hydrophilized by photoexcitation of the photocatalyst, so that the water repellency of the surface cannot be maintained. In view of the above circumstances, the present invention provides a transparent cover of a solar heat collector that can maintain the water repellency of the surface for a long period of time, and thus provides a transparent cover of a solar heat collector that is difficult to adhere to for a long period of time. The purpose is to do.

[0005]

According to the present invention, in order to solve the above-mentioned problems, photocatalyst particles, water-repellent silicone, and hydrophilicity of the water-repellent silicone by photoexcitation of the photocatalyst are provided on a transparent cover surface. A substantially transparent surface layer containing a substance for preventing the formation of a photocatalyst, or a substantially transparent layer containing photocatalyst particles and a water-repellent silicone on the surface of the transparent cover. A transparent cover for the solar heat collector, wherein a substance for preventing the water-repellent silicone from becoming hydrophilic by photoexcitation of the photocatalyst is fixed to at least a part of the surface of the layer. -Is provided. Preventing the silicon from becoming hydrophilic by photoexcitation of the photocatalyst by making the surface layer contain a substance such as cobalt or a cobalt compound for preventing the photocatalyst from becoming hydrophilic by photoexcitation. Can be. In addition, since the photocatalyst is contained, it is possible to decompose the dirt adhering with time based on the oxidative decomposability of the photocatalyst. Therefore, the water repellency of the surface can be maintained permanently, and a transparent cover of the solar heat collector to which dirt hardly adheres for a long time can be provided.

[0006]

FIG. 1 shows an embodiment of a solar heat collector according to the present invention. The solar heat collector 10 is a natural circulation type,
A plurality of heat collectors 12 and a hot water tank 14 are provided, and the heat collectors 12 are covered with a transparent cover 16. In the illustrated embodiment, the solar heat collector 10 is of a natural circulation type, but the present invention can also be applied to a free standing type solar heat collector. On the surface of the transparent cover 16, a transparent surface layer 18 is formed. In one embodiment, as shown in FIG. 2, photocatalyst particles, silicon, and a photocatalyst such as cobalt or a cobalt compound are used. Contains a substance for preventing hydrophilization due to light excitation. In another embodiment, as shown in FIG. 3, a layer containing photocatalyst particles and a water-repellent silicone is formed, and at least a part of the surface of the layer is coated with a water-repellent silicon such as cobalt or a cobalt compound. A substance for preventing the photocatalyst from becoming hydrophilic by photoexcitation is fixed. An intermediate layer made of silica, silicon, acrylic silicon or the like may be provided between the transparent cover 16 and the surface layer 18.

A photocatalyst has an energy greater than the energy gap between the conduction band and the valence band of the crystal.
A substance capable of generating conduction electrons and holes by excitation of electrons in the valence band (photoexcitation) when irradiated with light (excitation light) having a short wavelength (excitation light).
Oxides such as zeta-type titanium oxide, zinc oxide, tin oxide, ferric oxide, bismuth trioxide, tungsten trioxide and strontium titanate can be suitably used. As a light source used for photoexcitation of the photocatalyst, sunlight can be used.

The silicone has an average composition formula R _p SiO _{(4-p) / 2} (where R is a functional group comprising one or more monovalent organic groups, or a monovalent organic group) A resin represented by the following formula: X is an alkoxy group or a halogen atom, and p is a number satisfying 0 <p <2. Is available.

As the cobalt compound, cobalt alloy, cobalt oxide, cobalt chloride, cobalt sulfate, cobalt iodide, cobalt bromide, cobalt acetate, cobalt chlorate, cobalt nitrate and the like can be suitably used.

The thickness of the surface layer is preferably set to 0.4 μm or less. Then, cloudiness due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. More preferably, the thickness of the surface layer is 0.2 μm or less. Then, it is possible to prevent the surface layer from being colored by light interference. Also, the thinner the surface layer, the better its transparency. Further, when the film thickness is reduced, the wear resistance of the surface layer is improved.

A metal such as Ag, Cu and Zn can be added to the surface layer. The surface layer to which the metal is added can kill bacteria and fungi attached to the surface even in a dark place.

Pt, Pd, Ru, Rh, I
A platinum group metal such as r or Os can be added.
The surface layer to which the metal is added can enhance the redox activity of the photocatalyst, and can improve the decomposability of organic contaminants and the decomposability of harmful gases and odors.

Next, a surface layer containing photocatalyst particles, water-repellent silicone, and a substance for preventing the water-repellent silicone from becoming hydrophilic by photoexcitation of the photocatalyst is formed on the surface of the substrate. The method of manufacturing the water-repellent member described above will be described. The production method in this case is basically based on applying a coating composition on the surface of a substrate and curing the coating composition.

Here, the coating composition contains a precursor of silicon as an essential component of a substance for preventing photocatalytic particles, cobalt or a cobalt compound or the like from becoming hydrophilic by photoexcitation of a photocatalyst. Solvents such as ethanol and propanol, catalysts that promote hydrolysis of silicone precursors such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid and maleic acid, and basic compounds such as tributylamine and hexylamine Silicon compounds such as acidic compounds such as aluminum, aluminum triisopropoxide and tetraisopropyl titanate;
And a surfactant for improving the dispersibility of the coating liquid such as a silane coupling agent.

As cobalt or a cobalt compound, a water-soluble cobalt compound is preferably used. As the water-soluble cobalt compound, for example, cobalt chloride, cobalt sulfate, cobalt iodide, cobalt bromide, cobalt acetate, cobalt chlorate, cobalt nitrate and the like can be suitably used.

[0016] Here silicone - The precursor emissions in the average composition formula _{R p SiX q O (4-} pq) / 2 ( wherein, R consists of one or more organic groups monovalent functional X or a functional group comprising two or more selected from a monovalent organic group and a hydrogen group, X is an alkoxy group or a halogen atom, and p and q are 0 <p <2, 0 <
a film-forming element composed of a siloxane represented by the following formula: q <4) or a general formula R _p SiX _4-p (where R is one or more monovalent organic groups) Wherein X is an alkoxy group or a halogen atom, and p is 1 or 2. A film-forming element comprising a hydrolyzable silane derivative to be
Can be suitably used.

Here, as the coating film forming element comprising the hydrolyzable silane derivative, methyltrimethoxysilane,
Methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltributoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, Phenyltributoxysilane,
Dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldipropoxysilane, diethyldibutoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenyl Methyldipropoxysilane, phenylmethyldibutoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltributoxysilane, γ-glycoxydoxypropyltrimethoxysilane, γ -Acryloxypropyltrimethoxysilane and the like can be suitably used.

The film-forming element composed of the siloxane includes a partial hydrolysis and dehydration-condensation polymerization of the hydrolyzable silane derivative, or a partial hydrolyzate of the hydrolyzable silane derivative, tetramethoxysilane, tetraethoxysilane and tetraethoxysilane. It can be produced by dehydration polycondensation with a partial hydrolyzate such as silane, tetrapropoxysilane, tetrabutoxysilane, diethoxydimethoxysilane and the like.

The coating method of the coating composition includes spray coating, dip coating, flow coating, spin coating, roll coating, brush coating, and sponge. A method such as coating can be suitably used. As a curing method, it can be carried out by polymerizing by heat treatment, standing at room temperature, ultraviolet irradiation, or the like.

Next, a layer containing photocatalyst particles and a water-repellent silicone is formed on the surface of the base material, and at least a part of the surface of the layer is formed by photoexcitation of the photocatalyst by the water-repellent silicone. A method for manufacturing a water-repellent member to which a substance for preventing hydrophilicity is fixed will be described. The production method in this case is basically based on the photo-excitation of a photocatalyst such as cobalt or a cobalt compound after coating and curing a coating composition containing photocatalyst particles and a water-repellent silicone precursor. By applying a solution containing a substance for preventing hydrophilization and fixing the solution to the surface.

Here, the coating composition has photocatalyst particles and a precursor of a water-repellent silicone as essential components, and in addition, a solvent such as water, ethanol, propanol, hydrochloric acid, nitric acid, and the like. Catalysts that promote the hydrolysis of silica precursors such as sulfuric acid, acetic acid and maleic acid, basic compounds such as tributylamine and hexylamine, and acidic compounds such as aluminum triisopropoxide and tetraisopropyl titanate Such as a catalyst for curing a precursor of silica,
A surfactant such as a silane coupling agent for improving the dispersibility of the coating liquid may be added.

[0022] Here silicone - The precursor emissions in the average composition formula _{R p SiX q O (4-} pq) / 2 ( wherein, R consists of one or more organic groups monovalent functional X or a functional group comprising two or more selected from a monovalent organic group and a hydrogen group, X is an alkoxy group or a halogen atom, and p and q are 0 <p <2, 0 <
a film-forming element composed of a siloxane represented by the following formula: q <4) or a general formula R _p SiX _4-p (where R is one or more monovalent organic groups) Wherein X is an alkoxy group or a halogen atom, and p is 1 or 2. A film-forming element comprising a hydrolyzable silane derivative to be
Can be suitably used.

Here, as the coating film forming element comprising the hydrolyzable silane derivative, methyltrimethoxysilane,
Methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltributoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, Phenyltributoxysilane,
Dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldipropoxysilane, diethyldibutoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenyl Methyldipropoxysilane, phenylmethyldibutoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltributoxysilane, γ-glycoxydoxypropyltrimethoxysilane, γ -Acryloxypropyltrimethoxysilane and the like can be suitably used.

The film-forming element composed of the siloxane includes partial hydrolysis and dehydration condensation polymerization of the hydrolyzable silane derivative, or partial hydrolyzate of the hydrolyzable silane derivative, tetramethoxysilane, tetraethoxysilane, and the like. It can be produced by dehydration polycondensation with a partial hydrolyzate such as silane, tetrapropoxysilane, tetrabutoxysilane, diethoxydimethoxysilane and the like.

The coating method of the above coating composition includes spray coating, dip coating, flow coating, spin coating, roll coating, brush coating, and sponge. A method such as coating can be suitably used. As a curing method, it can be carried out by polymerizing by heat treatment, standing at room temperature, ultraviolet irradiation, or the like.

The method of applying a solution containing a substance for preventing the photocatalyst such as cobalt or a cobalt compound from being hydrophilized by photoexcitation and fixing it on the surface includes, for example, cobalt chloride, cobalt sulfate, cobalt iodide, bromide, and the like. cobalt,
Spray coating method, dip coating method, flow coating method, spin coating method, roll coating method, brushing water-soluble cobalt compounds such as cobalt acetate, cobalt chlorate and cobalt nitrate Coating, sponge coating, etc., photoreduction, heat treatment, alcohol
This is performed by fixing by a method such as reduction using a sacrificial oxidizing agent such as toluene.

[0027]

【Example】

Reference example. Anatase type titanium oxide sol (Nissan Chemical, TA
-15, nitric acid peptized type, pH = 1), silica sol (Nippon Synthetic Rubber, Glasca A solution, pH = 4), methyltrimethoxysilane (Nippon Synthetic Rubber, Glasca B solution) and ethanol are mixed. The coating liquid obtained by stirring for 2 to 3 hours was applied on a 5 × 10 cm square glazed tile base material (TOTOKIKI, AB02E11) by spray coating.
A heat treatment was performed at 200 ° C. for 15 minutes to obtain a # 1 sample having a surface layer formed of 11 parts by weight of anatase type titanium oxide particles, 6 parts by weight of silica, and 5 parts by weight of silicone. The contact angle of the # 1 sample with water was 92 °. Here, the contact angle with water was evaluated using a contact angle measuring device (Kyowa Interface Science, CA-X150) by the contact angle with water 30 seconds after a water droplet was dropped from the micro syringe. Next, the surface of the # 1 sample was irradiated for one day with an ultraviolet illuminance of 0.3 mW / cm ² using an ultraviolet light source (Sankyo Electric, Black Light Blue (BLB) fluorescent lamp) to obtain a # 2 sample. As a result, the contact angle with water of the # 2 sample was hydrophilized to 0 °. Next, # 1 sample and #
One sample was irradiated with a mercury lamp at an ultraviolet irradiance of 22.8 mW / cm ² for 2 hours, and the surface of each of the # 3 samples obtained was subjected to Raman spectroscopic analysis. As a result, a peak of methyl group observed on the surface of sample # 1 was not observed in sample # 3, but a peak of hydroxyl group was observed instead. From the above,
It can be seen that the organic group bonded to the silicon atom in the silicon molecule on the surface of the film by the photoexcitation of the anatase type titanium oxide which is a photocatalyst is replaced by a hydroxyl group and becomes hydrophilic.

Embodiment 1 FIG. Anatase type titanium oxide sol (Nissan Chemical, TA-15, peptized nitrate, pH = 1),
Silica sol (Nippon Synthetic Rubber, Glasca A solution, pH = 4)
And methyltrimethoxysilane (Nippon Synthetic Rubber, Glasca B solution), cobalt chloride hexahydrate, and ethanol, and stirred for 2-3 hours. After coating with an acrylic silicon-based primer by a coating method, it is further applied onto a polycarbonate board base material further coated with a silicone-based hard coat,
Heat treated at 110 ° C. for 30 minutes to form a surface layer comprising 11 parts by weight of anatase type titanium oxide particles, 6 parts by weight of silica, 5 parts by weight of silicone, and 0.2 parts by weight of cobalt.
Four samples were obtained. The contact angle of the # 4 sample with water was 97 °. Here, the contact angle with water was evaluated using a contact angle measuring device (Kyowa Interface Science, CA-X150) by the contact angle with water 30 seconds after a water droplet was dropped from the micro syringe. Next, the surface of the sample # 4 was treated with an ultraviolet light source (Sankyo Electric, Black Light Blue (BLB) fluorescent lamp) at 0.3 mW /
Irradiation was performed for 1 day at an ultraviolet illuminance of cm ² to obtain a # 5 sample. As a result, the contact angle of the # 5 sample with water was still 95 °, maintaining water repellency. Therefore, it can be understood from the above that the hydrophilicity of the silicon on the surface of the coating film due to the photoexcitation of the anatase type titanium oxide as a photocatalyst is inhibited by cobalt. This is considered because the substitution of the hydroxyl group for the organic group bonded to the silicon atom in the silicon molecule on the surface of the coating is inhibited by cobalt.

Embodiment 2 FIG. Anatase type titanium oxide sol (Nissan Chemical, TA-15, peptized nitrate, pH = 1),
Silica sol (Nippon Synthetic Rubber, Glasca A solution, pH = 4)
And methyltrimethoxysilane (Nippon Synthetic Rubber, Glasca B solution) and ethanol were mixed, and the coating solution obtained by stirring for 2 to 3 hours was applied by spray coating.
Polycarbonate coated with an acrylic silicon-based primer and then further coated with a silicone-based hardcoat
The composition was applied on a substrate of a bone plate and heat-treated at 110 ° C. for 30 minutes to obtain 11 parts by weight of anatase type titanium oxide particles and silica 6
A surface layer consisting of 5 parts by weight of silicone and 5 parts by weight of silicon was formed. Further, a cobalt metal concentration of 50 μmol / g is further added.
After applying 0.3 g of an aqueous solution of cobalt chloride hexahydrate, the mixture was irradiated with ultraviolet light having an illuminance of 0.4 mW / cm ² for 10 minutes using an ultraviolet light source (Sankyo Electric Co., Ltd., Black Light Bull (BLB) fluorescent lamp). Cobalt was fixed on the substrate to obtain a # 6 sample. The contact angle of the # 6 sample with water was 96 °. Here, the contact angle with water is measured using a contact angle measuring instrument (Kyowa Interface Science, CA
-X150), and evaluated by the contact angle with water 30 seconds after a water drop was dropped from the micro syringe. Then # 6
The sample surface was irradiated with ultraviolet light of 0.3 mW / cm ² for one day using an ultraviolet light source (Sankyo Electric, Black Light Blue (BLB) fluorescent lamp) to obtain a # 7 sample. as a result,
The contact angle with water of the # 7 sample was still 94 °, maintaining water repellency. Therefore, it can be understood from the above that the hydrophilicity of the silicon on the surface of the coating film due to the photoexcitation of the anatase type titanium oxide as a photocatalyst is inhibited by cobalt. This is considered because the substitution of the hydroxyl group for the organic group bonded to the silicon atom in the silicon molecule on the surface of the coating is inhibited by cobalt.

Embodiment 3 FIG. The # 5 sample, the # 7 sample, and a polytetrafluoroethylene plate for comparison were placed under the roofed part of the building as shown in FIG. 3 and left for 4 months. As a result, stains were observed on the polytetrafluoroethylene plate, whereas no stains were observed on the # 5 and # 7 samples.

[0031]

According to the present invention, the transparent cover of the solar heat collector is provided.
A substantially transparent surface layer containing, on a transparent cover surface, photocatalyst particles, a water-repellent silicone, and a substance for preventing the water-repellent silicone from becoming hydrophilic by photoexcitation of the photocatalyst. Or a substantially transparent layer containing photocatalyst particles and water-repellent silicone is formed on the surface of the transparent cover, and at least a part of the surface of the layer has the repellent layer. By fixing a substance for preventing the hydrophilicity of the aqueous silicone by photoexcitation of the photocatalyst, the surface of the member can maintain water repellency for a long period of time and a solar heat capable of preventing water droplet adhesion for a long period of time. It is possible to provide a transparent cover of the heat collector.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a solar heat collector of the present invention.

FIG. 2 is a diagram showing a surface structure of a transparent cover of the solar heat collector of the present invention.

FIG. 3 is a view showing another surface structure of the transparent cover of the solar heat collector of the present invention.

[Explanation of symbols]

 10: Solar heat collector 12: Heat collector 14: Hot water tank 16: Transparent cover 18: Transparent surface layer

Claims (3)

[Claims] 1. A transparent cover of a solar heat collector, wherein a photocatalyst particle and a water-repellent silicone are provided on a surface of the transparent cover.
A substantially transparent surface layer containing a water-repellent silicone and a substance for preventing the water-repellent silicone from becoming hydrophilic by photoexcitation of the photocatalyst. Cover. 2. A transparent cover of a solar heat collector, wherein a substantially transparent layer containing photocatalyst particles and a water-repellent silicone is formed on a surface of the transparent cover, and further comprising the layer. A transparent cover for a solar heat collector, wherein a substance for preventing hydrophilicity of the water-repellent silicone by photoexcitation of the photocatalyst is fixed to at least a part of the surface. 3. The transparent cover of a solar heat collector according to claim 1, wherein the substance for preventing the photocatalyst from becoming hydrophilic due to photoexcitation is cobalt or a cobalt compound.