JPH09228073A - Water-repelelnt member and method for preventing coating of snow and ice using the member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a water-repellent member capable of maintaining water repellency over a long period at the time of forming a water-repellent coating film on the member surface by forming a layer contg. a photocatalyst grain and an electron-capture metal as the substrate layer of the water-repellent coating film. SOLUTION: When a water-repellent coating film (having >=20μm average surface roughness) is formed on the surface of a member, a layer (having >=100nm thickness) contg. a photocatalyst grain and an electron-capture metal is formed as the substrate layer of the coating film. Meanwhile, titanium oxide is most preferably used as the photocatalyst grain, Ag, Cu, Pt, Pd, Ru, etc., are used as the electron-capture metal, and the thickness of the water-repellent layer is controlled so that UV reaches the substrate layer. Consequently, the component such as a contaminant depositing on the water-repellent coating film surface deteriorating the water repellency is decomposed and removed by the oxidationreduction reaction of the photocatalyst grain, and a high water repellent effect is maintained over a long period.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a member having a water-repellent coating formed on its surface.

[0002]

2. Description of the Related Art For example, members installed outdoors such as power transmission lines, antennas and roofs are easily damaged by rain, snow and ice. For example, when water drops adhere to the power transmission line, the water drops form a downward conical shape, which facilitates discharge and leads to power transmission loss. In winter, the water drops droop in a icy manner, and the tip is sharpened to further increase the discharge amount. In addition, if snow and ice adhere to the antenna, the electric field intensity decreases, which deteriorates the quality of communication or causes communication failure. Furthermore, if ice and snow adhere to members installed outdoors such as power transmission lines, antennas, roofs, etc., due to their weight, for example, cutting of power transmission lines, collapse of steel towers, bending of antennas, deformation of roofs, and leakage of rain will occur. .

Further, even some members used indoors must avoid the attachment of water droplets.

As a proposal for eliminating the above-mentioned disadvantage caused by the adhesion of water droplets and the like, it has been proposed to make the characteristics of the member surface extremely water-repellent or hydrophilic (1994.8. 17 Nihon Keizai Shimbun evening edition).
In this article, polytetrafluoroethylene is mentioned as a material that exhibits water repellency, and aluminum fluoride is mentioned as a material that exhibits hydrophilicity. In addition to this, many water-repellent and hydrophilic paints are commercially available.

When water repellency is imparted to the surface of a member, water droplets move around on the surface of the member. For this reason, it has been found that water droplets are less likely to adhere, and that water droplets are less likely to adhere to snow and ice.

[0006]

As described above, when the water repellent coating is formed on the surface of the member, the contact angle with water is sufficiently large, and the damage caused by water droplets, snow or ice can be prevented. However, due to the attachment of dirt over time, the effect of water repellency diminishes, and water drops, snow, ice, etc. attach, resulting in power transmission loss, communication failure, rain leak, and the like.

[0007]

The present inventors have made the present invention by paying attention to the fact that photocatalyst particles such as titanium oxide have a function of decomposing stains and malodorous components by a redox reaction. Incidentally, the photocatalyst particles such as titanium oxide have a redox action as well as a hydrophilizing action recently found by the present inventors, but the present invention utilizes the redox reaction.

When the photocatalyst particles are irradiated with ultraviolet rays or the like, an electron-hole pair is generated by photoexcitation when the photocatalyst particles are irradiated with ultraviolet rays, and among these, the electrons reduce surface oxygen and superoxide ions ( O ₂ ^-) to generate the hole is to oxidize the surface hydroxyl groups hydroxyl radical (· O
H), and these highly reactive active species (O
₂ ^- by redox reaction and · OH) is that of degrading substance attached to the surface.

That is, the water-repellent member according to the present invention has a water-repellent coating formed on the surface thereof, and further a layer containing photocatalyst particles and an electron-trapping metal is formed as an underlayer of the water-repellent coating. The thickness of the underlayer is preferably 100 nm or more, and the thickness of the water-repellent coating is such that ultraviolet rays can reach the underlayer. As the electron-trapping metal, A
g, Cu, Pt, Pd, Ru, Ir, Os, Au, Fe, Ni, C
o etc. are suitable.

The above-mentioned water repellency is maintained by decomposing substances adhering to the surface of the water repellent coating. The mechanism will be described based on the following (Chemical formula 1).

[0011]

Embedded image

Namely, the diffusion into the surface resulting in rate-limiting of, much trouble generated electrons (e ^-) and holes (h ^·) is reverts in recombination reactions to ultraviolet (hv), the reaction proceeds Disappear. Therefore, in the present invention, the photocatalyst particles (Ti
A O ₂₎ of the other, is added an electron trapping metal, electrons produced by these metals (e ^-) and electron (e out of the hole (h ^{·) -} supplemented), resulting as a hole an excess of (h ^·). Then, it recombination reaction hardly occurs, a hole (h ^·) is able to diffuse to the surface, soil components are decomposed.

Further, when the water repellency of the surface becomes high, it becomes difficult for the liquid to permeate, and the anchor effect and the fastener effect are small, so that the water droplets (snow,
The adhesion can be reduced by reducing the area of ice. To reduce the contact area,
The surface average roughness Ra of the water-repellent coating may be increased, and in practice Ra is preferably 20 μm or more.

In another water repellent member according to the present invention, a water repellent coating having photocatalyst particles dispersed is formed on the surface, and the average surface roughness Ra of this water repellent coating is set to 20 μm or more.
In this water repellent member, since the photocatalyst particles are directly exposed to the outside air, addition of an electron-trapping metal is not essential, but not all photocatalyst particles are exposed to the outside air. It is preferred to add a scavenging metal.

Further, in the method for preventing icing and snow formation according to the present invention, the water repellent member is provided at a place outdoors that receives sunlight and rainfall.

Titanium oxide is most preferred as the photocatalyst particles, but in addition to this, ZnO, SnO ₂ , SrTiO ₃ ,
Examples thereof include metal oxides such as WO ₃ , Bi ₂ O ₃ and Fe ₂ O ₃ .

As an example of the method for forming the base layer containing photocatalyst particles, titania (titanium oxide) will be described. Amorphous titania is formed, silica-containing titania is coated, tin oxide-containing titania is coated, and titania-containing silicone coating is prepared. Application and the like can be mentioned.

The formation of amorphous titania is a method in which the surface to be coated is first coated with amorphous titania and then fired to cause a phase change to crystalline titania, and either of the following methods can be adopted. . (1) Hydrolysis and dehydration condensation polymerization of an organic titanium compound An alkoxide of titanium, for example, tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, or a hydrochloride such as hydrochloric acid or ethylamine After adding a decomposition inhibitor and diluting with an alcohol such as ethanol or propanol, the mixture is applied after partially or completely promoting the hydrolysis, and then the mixture is applied, and the temperature is from room temperature to 200 ° C. And dry. By drying, the hydrolysis of the alkoxide of titanium is completed to form titanium hydroxide, and a layer of amorphous titania is formed by dehydration-condensation polymerization of titanium hydroxide. Instead of titanium alkoxide,
Other organic titanium compounds such as titanium chelates or titanium acetate may be used. (2) Formation of amorphous titania by inorganic titanium compound Inorganic titanium compound such as TiCl ₄ or Ti (S
Hydrolysis and dehydration polycondensation are performed by applying an acidic aqueous solution of O ₄ ) ₂ and drying at a temperature of 100 to 200 ° C.
Form a layer of amorphous titania. Or it may form a layer of amorphous titania on the surface to be coated by chemical vapor deposition of TiCl _4. (3) Formation of amorphous titania by sputtering A target of metal titanium is irradiated with an electron beam in an oxidizing atmosphere to form a layer of amorphous titania on the surface to be coated.

Application of silica-containing titania is to form a layer of a mixture of titania and silica on the surface to be coated. The ratio of silica to the total of titania and silica is 5 to 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. The following method can be employed for forming the surface layer made of silica-containing titania. (1) A suspension containing particles of anatase type or rutile type titania and particles of silica is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Based on a mixture of a precursor of amorphous silica (for example, tetraalkoxysilane such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc.) and crystalline titania sol After applying to the surface of the material and hydrolyzing it as necessary to form silanol, heating at a temperature of about 100 ° C. or more and subjecting the silanol to dehydration polycondensation, the titania is bound with amorphous silica. Obtained surface layer (photocatalytic coating). In particular, if the dehydration condensation polymerization of silanol is performed at a temperature of about 200 ° C. or higher, the degree of polymerization of silanol can be increased, and the alkali resistance performance of the photocatalytic coating can be improved. (3) Dispersing silica particles in a solution of amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) Is applied to the surface of the base material, and the titanium compound is cooled to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which silica particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate. (4) Amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) in a solution of amorphous titania precursor (For example, tetraalkoxysilanes such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc., silanols which are hydrolysates thereof, or polysiloxanes having an average molecular weight of 3000 or less) And apply to the surface of the substrate. Next, these precursors are subjected to hydrolysis and dehydration condensation polymerization to form a thin film composed of a mixture of amorphous titania and amorphous silica. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The application of titania containing tin oxide is to form a layer of a mixture of titania and tin oxide on the surface to be coated. The ratio of tin oxide to the total of titania and tin oxide is 1 to 95 mol%, preferably 1 to 50 mol%. The following method can be adopted as a method for forming a surface layer made of titania mixed with tin oxide. (1) A suspension containing particles of anatase type or rutile type titania and particles of tin oxide is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Dispersion of tin oxide particles in a solution of a precursor of amorphous titania (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) The resulting suspension is applied to the surface of the substrate, and the titanium compound is heated to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which tin oxide particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The titania-containing silicone paint is applied by using a paint in which titania (photocatalyst particles) is dispersed in a film-forming element made of uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. . This method has the advantages that the coating film-forming element can be cured at a relatively low temperature, can be applied as many times as necessary, and can exhibit a photocatalytic effect even in sunlight. The following resins can be used as the resin. Methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltrit-butoxysilane, ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, Ethyltriisopropoxysilane, ethyltri-t-butoxysilane, n-propyltrichlorosilane, n-propyltribromosilane, n-
Propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltriisopropoxysilane, n
-Propyltri-t-butoxysilane, n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-hexyltriisopropoxysilane, n-
Hexyltri-t-butoxysilane, n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n
-Decyltriisopropoxysilane, n-decyltri-t
-Butoxysilane, n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-octadecyltrit-butoxysilane, phenyltrichloro Silane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltri-t-butoxysilane, tetrachlorosilane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane , Tetrabutoxysilane, dimethoxydiethoxysilane, dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxy Silane, diphenyl dichlorosilane, diphenyl bromine, diphenyldimethoxysilane, diphenyldiethoxysilane, phenylmethyl dichlorosilane, phenyl methyl dibromo silane,
Phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, triethoxyhydrosilane, tribromohydrosilane, trimethoxyhydrosilane, isopropoxyhydrosilane, tri-t-butoxyhydrosilane, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane Silane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane, trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane, tri Fluoropropyltri-t-butoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxy Cypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri-t-butoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldi Ethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-
Methacryloxypropyltri-t-butoxysilane, γ
-Aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltrit-butoxysilane , Γ-
Mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltrit-
Butoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and their partial hydrolysates or mixtures thereof can be used. .

[0022]

1 shows a specific example of a water repellent member according to the present invention, in which (a) is a perspective view of a power transmission line,
2B is a perspective view of the antenna, FIG. 2C is a perspective view of the roof material, and FIG. 2 is a cross-sectional view of the water repellent member, but the present invention is not limited to these members.

Specific examples will be described below. (Example 1) Anatase-type titania sol (Nissan Kagaku T
A-15) and an aqueous solution of copper acetate are mixed and diluted with ethanol, and then trimethoxymethylsilane (Nippon Synthetic Rubber)
Glasca B solution) was added to prepare a titania-containing coating composition. The composition of the coating composition was 100 parts by weight of trimethoxymethylsilane, 100 parts by weight of titania, and copper acetate was 2 parts by weight in terms of copper. This coating composition is applied to the surface of a single-wire coated cord, heated to 150 ° C. and cured to form an underlayer, on which polytetrafluoroethylene fine particle dispersion (Daikin Polyflon TF) is formed.
E) was very thinly impregnated and coated and baked to form a polytetrafluoroethylene film as a water-repellent film on the underlayer. Then, for the obtained member, BL
UV light was irradiated for 5 days using a B fluorescent lamp at an illuminance of 0.5 mW / cm ² .

(Evaluation 1) 2.5 m of the coated cord having the above-mentioned underlayer and water-repellent coating was suspended between two columns. In addition, as a comparative example, a normal cord having no underlayer and water-repellent coating formed thereon was suspended in parallel with the coated cord having the underlayer and water-repellent coating formed thereon. Then, watering the whole of these cords with a watering shower. As a result, innumerable water droplets were attached downward on the cord of the comparative example, whereas no water droplet was attached on the cord of the example.

(Example 2) A Yagi-type antenna for a television, which was cut out to a length of 30 cm, was prepared, and the coating composition prepared in Example 1 was applied to this and cured by heating to 150 ° C. An underlayer was formed, and a polytetrafluoroethylene film was formed as a water-repellent film on the underlayer in the same manner as in Example 1. Then, the obtained member was irradiated with ultraviolet rays for 5 days with an illuminance of 0.5 mW / cm ² using a BLB fluorescent lamp.

(Evaluation 2) A part of the antenna on which the underlayer and the water-repellent coating were formed was immersed in a water tank. As a comparative example, part of the antenna on which the underlayer and the water-repellent coating were not formed was immersed in a water tank. Next, these examples and comparative examples were pulled up horizontally and held horizontally, and the state of water droplet adhesion was observed. In the comparative example, it was observed that 10 or more water droplets were hanging. On the other hand, in the example, the adhesion of water droplets was not recognized.

(Example 3) A solution obtained by impregnating a dispersion liquid of polytetrafluoroethylene (PTFE) with 40 wt% of photocatalytic titanium oxide (Ishihara Sangyo ST41) was impregnated to a melting point (327 ° C) or higher. Heat it up
A film was prepared by casting in a viscous fluid state. A roofing material was produced by adhering this to a steel plate.

(Evaluation 3) When the above roofing material was exposed in the field for 3 weeks, the PTFE film to which titanium oxide was not added had its water repellency deteriorated due to dirt, and water droplets adhered when wetted with water. With the addition of titanium oxide photocatalyst,
When it was wet with water, the water repellency was maintained and water droplets fell off.

[0029]

As described above, according to the present invention, not only the water-repellent coating is formed on the surface of the member, but also a layer containing photocatalyst particles and an electron-trapping metal is formed as an underlayer of the water-repellent coating. , A component that inhibits water repellency such as dirt adhered to the surface of a water repellent coating by an oxidation-reduction reaction caused by the photocatalyst particles simply by being installed in an environment where light having an energy higher than the bandgap energy of the photocatalyst particles such as ultraviolet rays is irradiated. Can be decomposed and removed, and a high water-repellent effect can be maintained for a long period of time.

[Brief description of drawings]

1A is a perspective view of a power transmission line as a water repellent member according to the present invention, FIG. 1B is a perspective view of an antenna as a water repellent member according to the present invention, and FIG. 1C is a water repellent member according to the present invention. Perspective view of roofing material

FIG. 2 is an enlarged sectional view of a water repellent member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Senkoku 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Kikai Co., Ltd. (72) Toshiya Watanabe Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka 2-1-1 1-1 Totoki Co., Ltd. (72) Inventor Atsushi Kitamura 2-1-1 1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture

Claims (5)

[Claims] 1. A water-repellent member having a water-repellent coating formed on the surface thereof, wherein a layer containing photocatalyst particles and an electron-trapping metal is formed as an underlayer of the water-repellent coating. . 2. The water repellent member according to claim 1, wherein
A water-repellent member, wherein the average surface roughness Ra of the water-repellent coating film is 20 μm or more. 3. A water repellent member having a water repellent coating in which photocatalyst particles are dispersed formed on the surface thereof, wherein the surface average roughness Ra of the water repellent coating is 20 μm or more. 4. The water repellent member according to claim 3,
A water-repellent member, wherein the water-repellent coating contains an electron-trapping metal. 5. A method for preventing snow accretion using a water-repellent member, characterized in that the water-repellent member according to any one of claims 1 to 4 is provided in a place outdoors that receives sunlight and rainfall. .