JPH09228331A - Self-cleaning guard fens, and cleaning method of guard fens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To wash away the sediment or contaminant adhered to a surface layer by rain and self-clean a guard fens base by forming the surface layer containing a photocatalytic oxide particle on the surface of the guard fens base. SOLUTION: A surface layer containing a photocatalytic oxide such as titanium oxide is formed on the surface of a guard fens base for guard rail, guard pipe or the like, and the surface layer is made highly hydrophilic by the optical excitation of the photocatalyst to wash away the sediment or contaminant adhered to the surface layer by rain. When the outermost surface is formed of a general organic oxide, the same effect can be provided by the action of the photocatalyst. When either one of silica, solid acid and silicone is combined with the photocatalytic oxide, hydrophilic property is further improved, and hydrophilic property of 10 deg. or less in terms of contact angle with water can be exhibited. When the guard fens base is formed of a steel plate, an intermediate layer is provided to prevent the reduction in hydrophilic speed by inclusion of either atom of Fe, Ni, and Co to the surface layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a guard fence capable of self-cleaning (self-cleaning) by rainfall and a self-cleaning method thereof.

[0002]

2. Description of the Related Art A guard fence is used for the purpose of preventing a traveling vehicle from leaving a road, a traveling lane or a bridge, and protecting a pedestrian walking on a sidewalk from a traveling vehicle traveling in an adjacent lane. There are three types of guard fences: guard rails, guard cables, and guard pipes. Of these, guardrails have the highest versatility, but guardrails are used mainly for urban areas in sidewalk applications. Aluminum plates, steel plates, stainless steel plates, titanium plates, etc. are used for the guard fence.

[0003]

The guard fence is contaminated by soot in exhaust gas, tire abrasion powder, and dust soared from the road surface or the ground. If the guard fence becomes dark and dirty, it gives an unpleasant impression and the landscape is damaged. An object of the present invention is to provide a guard fence that can be self-cleaned by rainfall and a method of self-cleaning by rainfall.

[0004]

SUMMARY OF THE INVENTION The present invention is based on the discovery that, in a member having a surface layer containing a photocatalyst formed thereon, when the photocatalyst is photoexcited, the surface of the member is highly hydrophilized. This phenomenon is considered to proceed by the following mechanism. That is, when the photocatalyst is irradiated with light having an energy larger than the energy gap between the valence band upper end and the conduction band lower end of the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. The action of either or both of them probably imparts polarity to the surface and collects polar components such as water and hydroxyl groups. Then, one or both of conduction electrons and holes and the above-mentioned polar component cooperate with each other to cut off a chemical bond between the surface and the contaminant chemically adsorbed on the surface, and to cause a chemical adsorbed water on the surface. Is adsorbed, and a physically adsorbed water layer is formed thereon. Further, once the surface of the member is highly hydrophilized, the hydrophilicity of the surface is maintained for a certain period even if the member is kept in a dark place.

The present invention provides a self-cleaning guard fence having a surface layer containing substantially transparent photocatalytic oxide particles on the surface of a guard fence substrate. By providing a surface layer containing photocatalytic oxide particles, the surface of the surface layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst, and the guard fence surface, when exposed to rainfall, deposits and / or deposits. The contaminants will be washed away by the raindrops.

In a preferred embodiment of the present invention, the surface layer further contains silica. By containing silica, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when held in a dark place is improved. The reason seems to be related to the ability of silica to store water in its structure.

In a preferred embodiment of the present invention, the surface layer further contains a solid acid. When the solid acid is contained, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when kept in a dark place is improved. The reason is that when the surface layer contains a solid acid, the polarity of the surface is extremely large regardless of the presence or absence of light, so that water molecules, which are polar molecules, are selectively adsorbed over hydrophobic molecules. Easy to make. Therefore, a stable physically adsorbed water layer is easily formed, and even if the layer is kept in a dark place, the hydrophilicity of the surface can be maintained at a high level for a considerably long period.

In a preferred embodiment of the present invention, the surface layer further contains silicone.
By containing silicone, by photoexcitation of the photocatalyst, at least a part of the organic group bonded to the silicon atom in the silicone is replaced with a hydroxyl group, and a physically adsorbed water layer is formed on the organic group, so that the surface is It exhibits a high degree of hydrophilicity close to a water wetting angle of 0 °, and improves the hydrophilicity maintaining ability when kept in a dark place.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a specific structure of the present invention will be described. On the surface of the guard fence in the present invention, as shown in FIG. 1 or 2, a layer containing a photocatalytic (crystalline) oxide or the like is formed on the surface of the base material. By taking such a surface structure, the surface of the guard fence is
It becomes highly hydrophilic in response to photoexcitation of the photocatalyst.
As a result, the deposits and / or contaminants attached to the surface of the surface layer due to rainfall are washed away by the raindrops.

In FIG. 1, the surface layer consists only of photocatalytic oxide particles. In this case, since the photocatalyst is made of an oxide, the oxide shows hydrophilicity in a state where the pollutant in the environment is not adsorbed, so that the photoexcited action is to eliminate the pollutant to form an adsorbed water layer. Thus, it is easy to exhibit hydrophilicity and a uniform water film can be formed. In FIG. 2, M represents a metal element. Therefore, in the case of FIG. 2, the outermost surface is made of a general inorganic oxide. Also in this case, since the oxide shows hydrophilicity in the state where the pollutant in the environment is not adsorbed, the pollutant is excluded by the photoexcitation action of the photocatalytic oxide mixed in the surface layer in addition to the above inorganic oxide. By forming the adsorbed water layer, a uniform water film can be formed.

As the guard fence base material to which the present invention can be applied, an aluminum plate, a steel plate, a stainless plate, a titanium plate or the like can be used. Here, when the guard fence base material is a base material containing any atom of Fe, Ni, Co such as a steel plate or a stainless steel plate, the base material and the surface layer are used to form the surface layer on the base material. It is better to provide an intermediate layer between them. F
This is because if one of the atoms e, Ni, or Co is mixed in the surface layer, the hydrophilization rate will decrease.

A photocatalyst is a photocatalyst of an electron in the valence band when it is irradiated with light (excitation light) having an energy (that is, a short wavelength) larger than the energy gap between the conduction band and the valence band of the crystal. Excitation (photoexcitation) refers to a substance capable of generating conduction electrons and holes, and the photocatalytic titanium oxide refers to crystalline titanium oxide such as anatase type titanium oxide and rutile type titanium oxide. Here, the light source used for photoexcitation of the photocatalyst is exposed to the sun during the day, so sunlight can be used. Also, at night, road lighting or running vehicle lighting can be used as a light source. In order for the surface of the base material to be highly hydrophilic by the photoexcitation of the photocatalyst, the illuminance of the excitation light may be 0.001 mW / cm ² or more,
It is preferably 0.01 mW / cm ² or more, and 0. 1 mW
/ Cm ² or more is more preferable.

The thickness of the surface layer containing the photocatalytic titanium oxide is preferably 0.4 μm or less. Then, white turbidity due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. Furthermore, it is more preferable that the thickness of the surface layer containing the photocatalytic titanium oxide be 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. The surface of the surface layer may be further provided with a wear-resistant or corrosion-resistant protective layer capable of being made hydrophilic and other functional films.

A metal such as Ag, Cu, or 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.

The surface layer has pt, Pd, Ru, R
A platinum group metal such as h, Ir, Os can be added. The surface layer to which the metal is added can enhance the oxidation-reduction activity of the photocatalyst and improve the deodorizing and purifying action and the like. In addition, when a solid acid is added in addition to the photocatalyst, the acidity of the solid acid is improved by the addition of a platinum group metal, so that the hydrophilicity is also improved, and the formation of a water film on the attached water is further promoted. The hydrophilicity when the excitation light is not irradiated to the photocatalyst for a long period of time is also improved. Mo may be added to the surface layer. Also in this case, since the acidity of the solid acid is improved by the addition, the hydrophilicity-maintaining property is also improved, and the formation of a water film of the attached water is further promoted, and the hydrophilicity-maintaining property when the photocatalyst is not irradiated with the excitation light for a certain period of time. Also improves.

The term "hydrophilic" refers to the property of being easily conformed when water is dropped on the surface, and generally refers to a state where the water wetting angle is less than 90 °. The term “high hydrophilicity” in the present invention refers to a property that is highly compatible when water is dropped on the surface, and more specifically, a state where the water wetting angle is about 10 ° or less. In particular, as disclosed in PCT / JP96 / 00734, the water wetting angle is preferably 10 ° or less, more preferably 5 ° or less, as disclosed in PCT / JP96 / 00734.

The solid acid in the present invention includes sulfuric acid carrying Al.
₂ O ₃ , sulfuric acid supported TiO ₂ , sulfuric acid supported ZrO ₂ , sulfuric acid supported SnO ₂ , sulfuric acid supported Fe ₂ O ₃ , sulfuric acid supported SiO ₂ ,
Sulfuric acid supporting HfO ₂ , TiO ₂ / WO ₃ , WO ₃ / SnO
₂ , WO ₃ / ZrO ₂ , WO ₃ / Fe ₂ O ₃ , SiO _{2
· Al 2 O 3, TiO 2} / SiO 2, TiO 2 / Al 2
O ₃ , TiO ₂ / ZrO _{2 and the} like can be preferably used.

Next, a method for forming the surface layer will be described. First, the production method in the case where the surface layer is composed of only the photocatalytic oxide will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, there are roughly three methods. One method is a sol coating and firing method, the other method is an organic titanate method, and the other method is an electron beam evaporation method. (1) Sol-coating and firing method Anatase-type titanium oxide sol is applied to the surface of a substrate by a method such as spray coating, dip coating, flow coating, spin coating, or roll coating, and then fired. (2) Organic titanate method Titanium alkoxide (tetraethoxy titanium, tetramethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, etc.), titanium acetate, titanium chelate, etc. are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.). , After diluting with a non-aqueous solvent such as alcohol (ethanol, propanol, butanol, etc.), while partially or completely proceeding the hydrolysis, the mixture is spray-coated, dip-coated, Apply by methods such as flow coating method, spin coating method, roll coating method,
dry. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Electron beam evaporation method An amorphous titanium oxide layer is formed on the surface of a substrate by irradiating a titanium oxide target with an electron beam. After that, firing at a temperature higher than the crystallization temperature of anatase,
Phase transition of amorphous titanium oxide to anatase titanium oxide.

Next, the case where the surface layer is composed of a photocatalytic oxide and silica will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, for example, there are the following three methods. One method is a sol coating and firing method, the other is an organic titanate method, and the other is a tetrafunctional silane method. (1) Sol coating and baking method A mixture of anatase-type titanium oxide sol and silica sol is applied to the substrate surface by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method, and a roll coating method, and then fired. I do. (2) Organic titanate method Titanium alkoxides (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, and other organic titanates are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) and silica sol. Add alcohol (ethanol,
After diluting with a non-aqueous solvent such as propanol, butanol, etc., and then allowing the hydrolysis to proceed partially or completely, the mixture is spray-coated, dip-coated, flow-coated,
It is applied by a method such as spin coating or roll coating and dried. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Tetrafunctional silane method A mixture of tetraalkoxysilane (tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.) and anatase type titanium oxide sol is spray-coated or dip-coated on the surface of a substrate. , A flow coating method, a spin coating method, a roll coating method, or the like, and if necessary, hydrolyzing to form silanol, and then silanol is subjected to dehydration condensation polymerization by a method such as heating.

Next, the case where the surface layer is composed of a photocatalytic oxide and a solid acid will be described by taking as an example the case where the photocatalyst is anatase type titanium oxide and the solid acid is TiO ₂ / WO ₃ . In this case, a method of mixing an ammonia solution of tungstic acid and an anatase-type titanium oxide sol and, if necessary, diluting the mixture with a diluting liquid (water, ethanol, etc.) on the surface of the base material by spray coating, dip coating, or the like. It is applied by a method such as a flow coating method, a spin coating method, and a roll coating method, and is baked. Other methods include electron beam evaporation and hydrolysis and dehydration polycondensation of organic titanates such as titanium alkoxide, titanium acetate, and titanium chelate to form an amorphous titanium oxide film, and then tungstic acid is applied, and then amorphous. Heat treatment is performed at a temperature at which titanium oxide is crystallized and a TiO ₂ / WO ₃ composite oxide is formed.

Next, the case where the surface layer is composed of a photocatalytic oxide and silicone will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. The method in this case is to mix a coating composed of uncured or partially cured silicone or a precursor of silicone and anatase type titanium oxide sol, and hydrolyze the precursor of silicone as needed, and then mix the mixture. Is applied to the surface of the substrate by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method and a roll coating method, and the hydrolyzate of the silicone precursor is dehydrated and polycondensed by a method such as heating. Then, a surface layer composed of anatase type titanium oxide particles and silicone is formed. In the formed surface layer, at least a part of the organic group bonded to the silicon atom in the silicone molecule is replaced with a hydroxyl group by photoexcitation of the anatase type titanium oxide by irradiation with light including ultraviolet rays, and further thereon. A physisorbed water layer is formed and exhibits a high degree of hydrophilicity. Here, the precursor of silicone includes methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, ethyltripropoxysilane, and phenyl. Trimethoxysilane,
Phenyltriethoxysilane, phenyltributoxysilane, phenyltripropoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldibutoxysilane, diethyldi Propoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenylmethyldibutoxysilane, phenylmethyldipropoxysilane, γ-glycidoxypropyltrimethoxysilane, and their hydrolysates and their mixtures are preferably used. it can.

[0022]

【Example】

Example 1 3 parts by weight of silica sol (Nippon Synthetic Rubber, Glasca A liquid, solid content 20% by weight, pH = 4) was mixed on the surface of a 10 cm square aluminum plate, and then methyltrimethoxysilane (Nippon Synthetic Rubber, Glasca B was added. Liquid) 1 part by weight and ethanol were added, and the mixture was further stirred for 2 hours, and a coating liquid was prepared by partially subjecting methyltrimethoxysilane to a hydrolysis reaction and a dehydration polycondensation reaction. After applying this coating liquid by a flow coating method, it was heated at 150 ° C. for 30 minutes to form a base coat layer on the surface of the aluminum plate. Next, 56 parts by weight of anatase-type titanium oxide sol (Nissan Chemical Co., Ltd., TA-15, solid content 15% by weight, nitric acid deflocculation type, pH = 1) and silica sol (Nippon Synthetic Rubber, Glasca A liquid, solid content 20% by weight). , P
H = 4) After mixing 33 parts by weight, 11 parts by weight of methyltrimethoxysilane (Nippon Synthetic Rubber, Liquid Glasco B) and ethanol were added, and the mixture was further stirred for 2 hours to partially hydrolyze methyltrimethoxysilane. And a dehydration polycondensation reaction to prepare a coating liquid. This coating liquid was applied to the surface of the base coat layer by a flow coating method, and then heated at 150 ° C. for 30 minutes to form a surface layer. Next, the surface coated with the coating liquid was irradiated with ultraviolet rays for about 3 days at an ultraviolet illuminance of 0.5 mW / cm ² using an ultraviolet light source ((Sankyo Denki, Black Light Blue (BLB) fluorescent lamp), and then # 1. A sample was obtained.For comparison, an aluminum plate # 2 sample was also prepared. Water droplets were dropped on the # 1 sample and the # 2 sample, and the contact angle with water was measured. Using a contact angle measuring device (Kyowa Interface Science, CA-X150), the contact angle with water 30 seconds after dropping was evaluated, and as a result, the contact angle with water of the # 2 sample was as high as 50 °. In contrast, the # 1 sample showed a high degree of hydrophilicity with a contact angle with water of 0 °.

Next, the # 1 sample and the # 2 sample were installed outdoors and examined for self-cleaning property by rainfall.
The self-cleaning property by rainfall was tested as follows. That is, the outdoor stain acceleration test device shown in FIGS. 3 and 4 was installed on the roof of a building located in Chigasaki City. With reference to FIGS. 3 and 4, the apparatus includes an inclined sample support surface 22 supported by a frame 20 for mounting a sample 24. A roof 26 inclined forward is fixed to the top of the frame. The roof is made of a corrugated plastic plate, and the collected rain flows down in a streak on the surface of the sample 24 attached to the sample support surface 22. The # 1 sample was attached to the sample support surface 22 of this device and exposed to weather conditions for one month from June 12, 1995. During the rainy season, it rained frequently. When observed one month later, no stain was observed. The state was examined by the change in color difference of the most contaminated part before and after mounting the acceleration test device. Here, the color difference is a color difference meter (Tokyo Denshoku)
According to Japanese Industrial Standards (JIS) H0201, Δ
Checked using the E * designation. As a result, the color difference change is 0.8
And was very small.

Example 2 3 parts by weight of silica sol (Nippon Synthetic Rubber, Glasca A liquid, solid content 20% by weight, pH = 4) was mixed on the surface of a 10 cm square stainless plate, and then methyltrimethoxysilane (Nippon Synthetic Rubber) , Glasca B solution) and ethanol were added, and the mixture was further stirred for 2 hours, and methyltrimethoxysilane was partially subjected to a hydrolysis reaction and a dehydration polycondensation reaction to prepare a coating solution. After applying this coating liquid by a flow coating method, it was heated at 150 ° C. for 30 minutes to form a base coat layer on the surface of the stainless steel plate. Next, anatase type titanium oxide sol (NISSAN CHEMICAL, TA-15, solid content 15
% By weight, nitric acid peptization type, pH = 1) 56 parts by weight, and silica sol (Japan Synthetic Rubber, Glask A liquid, solid content 20% by weight, pH = 4) 33 parts by weight are mixed, and then methyltrimethoxysilane (Japan 11 parts by weight of synthetic rubber (Glasca solution B) and ethanol were added, and the mixture was further stirred for 2 hours, and methyltrimethoxysilane was partially subjected to a hydrolysis reaction and a dehydration polycondensation reaction to prepare a coating solution. This coating liquid was applied to the surface of the base coat layer by a flow coating method, and then heated at 150 ° C. for 30 minutes to form a surface layer. Next, 0.5 mW / cm ² was applied to the surface coated with the coating liquid by using an ultraviolet light source ((Sankyo Denki, Black Light Blue (BLB) fluorescent lamp).
The sample was irradiated with ultraviolet rays at a UV illuminance of 3 days for about 3 days to obtain a # 3 sample. A stainless plate # 4 sample was also prepared for comparison. #
Water droplets were dropped on the 3 samples and the # 4 sample, and the contact angle with water was measured. As a result, the contact angle with water of the # 4 sample was 60.
While the contact angle with water was 0 °, the sample # 3 showed a high degree of hydrophilicity.

Next, the # 3 sample was placed outdoors and examined for self-cleaning property by rainfall. The self-cleaning property by rainfall was tested as follows. That is, the outdoor stain acceleration test device shown in FIGS. 3 and 4 was installed on the roof of a building located in Chigasaki City. With reference to FIGS. 3 and 4, the apparatus includes an inclined sample support surface 22 supported by a frame 20 for mounting a sample 24. A roof 26 inclined forward is fixed to the top of the frame. The roof is made of a corrugated plastic plate, and the collected rain flows down in a streak on the surface of the sample 24 attached to the sample support surface 22. Attach the # 3 sample to the sample support surface 22 of this device, 199
It was exposed to weather conditions for one month from June 12, 1993. During the rainy season, it rained frequently. When observed one month later, no stain was observed. The state was examined by the change in color difference of the most contaminated part before and after mounting the acceleration test device. Here, the color difference was examined using a color difference meter (Tokyo Denshoku) according to the Japanese Industrial Standards (JIS) H0201 and using ΔE * display. As a result, the change in color difference was 0.9, which was very small.

Example 3 A 10 cm square stainless steel plate was used to prepare a 3.5 wt% tetraethoxysilane solution (diluent:
24 minutes per minute after immersion in ethanol and hydrolysis catalyst: hydrochloric acid
It was pulled up at a speed of cm, and the solution was applied to the surface of the stainless plate by the dip coating method and dried.
Through the steps so far, tetraethoxysilane was hydrolyzed to generate silanol groups, and then the silanol groups were subjected to dehydration polycondensation to form a thin film containing amorphous silica as a main component on the surface. Next, after dipping in a tetraethoxy titanium solution (diluent: ethanol, hydrolysis catalyst: hydrochloric acid) with a concentration of 3.5% by weight, the solution is pulled up at a rate of 24 cm / min, and the solution is dip-coated to the surface of the stainless steel plate. And then dried to obtain # 5 sample. Through the steps up to this point, tetraethoxy titanium was hydrolyzed to generate a hydroxyl group, and then the hydroxyl group was dehydrated and polycondensed to form a thin film containing amorphous titanium oxide as a main component on the surface. Next, the # 5 sample surface was subjected to corona discharge treatment (Kasuga Denki) using a wire electrode as an electrode, the gap between the electrode tip and the sample surface was 2 mm, the voltage was 26 kV, the frequency was 39 kHz, and the sample feed rate was 4.2 m / min. Under the conditions, dealkylation treatment was performed by high-frequency corona discharge treatment.
Next, after dipping the # 5 sample surface in a 1 wt% tungstic acid solution (solvent: ammonia water), the sample was pulled up at a rate of 24 cm / min, and the solution was dip-coated.
It was applied on the surface and baked at 500 ° C. to obtain a # 6 sample. By firing, the amorphous titanium oxide was crystallized to produce anatase titanium oxide. Next, after leaving this # 6 sample in a dark place for several days, the surface of the sample was irradiated with ultraviolet rays at a UV illuminance of 0.5 mW / cm ² for about 1 hour using a BLB fluorescent lamp to obtain a # 7 sample. It was For comparison, a # 8 sample in which a 10 cm square stainless plate was left in the dark for several days was also prepared.
First, water drops were dropped on the # 7 sample and the # 8 sample, and the state after the drop was observed and the contact angle with water was measured. as a result#
When water droplets were dropped on the surface of the 7 samples from the microsyringe, it was observed that the water droplets spread uniformly on the surface of the sample in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the case of the # 8 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface but did not reach a uniform water film shape. The contact angle with water after 30 seconds is 6
It was 0 °. Further, the # 8 sample was left in the dark for 2 days thereafter to obtain a # 9 sample. And for # 9 sample,
Similarly, the contact angle with water was measured by a contact angle measuring device. As a result, when water droplets were dropped onto the sample surface from the microsyringe on the # 9 sample, it was observed that the water droplets spread uniformly on the sample surface in the form of a water film, similarly to the # 7 sample. The contact angle with water was maintained at about 1 °.

Next, oleic acid was applied to the surface of the # 7 sample, and each sample was immersed in water filled in a water tank while keeping the sample surface in a horizontal posture. As a result, the oleic acid became round and separated from the surface by light rubbing.

Next, 1 part by weight of hydrophobic carbon black,
A slurry was prepared by suspending a powder mixture consisting of 1 part by weight of hydrophilic carbon black in water at a concentration of 1.05 g / liter. 150 ml of the above slurry was made to flow down on a # 7 sample inclined at 45 degrees and dried for 15 minutes, then 150 ml of distilled water was made to flow down and dried for 15 minutes, and this cycle was repeated 25 times. The change in color difference before and after the test was measured using a color difference meter (Tokyo Denshoku). The color difference was evaluated according to Japanese Industrial Standards (JIS) H0201 using ΔE * notation. As a result, the change in color difference of the # 7 sample before and after the test was 0.
There was almost no change from 4.

[0029]

According to the present invention, the surface of the guard fence substrate is provided with a surface layer containing photocatalytic oxide particles, whereby the surface of the surface layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst. As a result, the surface of the surface layer is self-cleaned by the rainfall.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface structure of a guard fence according to the present invention.

FIG. 2 is a diagram showing another surface structure of the guard fence according to the present invention.

FIG. 3 is a front view of an outdoor dirt acceleration test apparatus according to an embodiment of the present invention.

FIG. 4 is a side view of an outdoor dirt acceleration test device according to an embodiment of the present invention.

Claims (10)

[Claims] 1. A surface of a guard fence substrate is provided with a surface layer containing photocatalytic oxide particles, the surface of the layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst, and the surface of the guard fence is A self-cleaning guard fence that allows deposited deposits and / or contaminants to be washed away by raindrops when exposed to rainfall. 2. The self-cleaning guard fence according to claim 1, wherein the surface layer further contains silica. 3. The self-cleaning guard fence according to claim 1, wherein the surface layer further contains a solid acid. 4. The self-cleaning guard fence according to claim 1, wherein the surface layer further contains silicone. 5. The surface of the surface layer exhibits hydrophilicity of 10 ° or less in terms of contact angle with water in response to photoexcitation of the photocatalytic oxide. The self-cleaning guard fence described in 1 to 4. 6. The method according to claim 1, wherein a protective layer capable of being made hydrophilic is further provided on the surface of the surface layer.
The self-cleaning guard fence according to item 5. 7. The guard fence base material is made of steel or stainless steel, and an intermediate layer is provided between the guard fence base material and the surface layer. Self-cleaning guard fence. 8. The self-cleaning guard fence according to claim 1, wherein the guard fence base material is a guard rail base material. 9. The self-cleaning guard fence according to claim 1, wherein the guard fence base material is a guard pipe base material. 10. A step of preparing the guard fence according to claim 1, a step of arranging the guard fence outdoors,
Photoexciting a photocatalyst contained in the surface layer to make the surface of the surface layer hydrophilic, deposits and / or contaminants attached to the surface of the surface layer by exposing the substrate to rainfall A method of self-cleaning the guard fence, which comprises the step of rinsing off with raindrops.