JP3648848B2 - Road marking with excellent visibility, its construction method and self-cleaning method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a road marking, a construction method thereof, and a self-cleaning method.
[0002]
[Prior art]
The road markings are blended with colored pigments to ensure daytime visibility. Further, retroreflectors such as glass beads are scattered and fixed on the surface of the road markings, and the nighttime visibility is guaranteed by retroreflecting the light of the vehicle headlight.
[0003]
[Problems to be solved by the invention]
Road markings are soiled by combustion products in exhaust gas, tire wear powder and urban dust, and the visibility in the daytime decreases as the soil becomes dirty. Similarly, the retroreflective glass beads on the surface are also soiled and the retroreflectiveness is lowered, so that the nighttime visibility is lowered due to the soiling. Therefore, the road markings must be updated regularly, but the construction requires not only a large amount of money and labor, but also traffic regulations.
[0004]
An object of the present invention is to provide a road marking capable of exhibiting excellent day and night visibility over a long period of time, a construction method thereof, and a self-cleaning method of the road marking.
[0005]
[Means for Solving the Problems]
The inventor has discovered that photoexcitation of the photocatalyst results in a highly hydrophilic surface of the photocatalyst. When photocatalytic titania is photoexcited with ultraviolet rays, it is surprising that the surface becomes highly hydrophilic so that the contact angle with water is 10 ° or less, more specifically 5 ° or less, especially about 0 °. Was discovered.
[0006]
The present invention is based on this discovery. In one aspect of the present invention, the road marking surface and / or retroreflective glass beads are coated with a transparent layer containing a semiconductor photocatalyst. The photocatalyst is illuminated by the sun during the day and is photoexcited by sunlight. With photoexcitation, the surface of the photocatalyst-containing layer is highly hydrophilized. Once highly hydrophilized, the surface hydrophilicity persists even at night.
[0007]
Hydrophobic substances such as combustion products in exhaust gas, tire wear powder, and urban dust are less likely to adhere to the hydrophilic surface. In addition, road markings are sometimes exposed to rainfall. Since the superhydrophilic surface has a greater affinity for water than for hydrophobic substances such as combustion products, dirt adhering to the surface can be easily released from the surface by rainwater and washed away by rainwater each time it rains. The surface is self-cleaning. In this way, the surface of the road marking is kept clean, so that excellent visibility is exhibited throughout the day and night.
[0008]
Road markings can be constructed in various ways. In one aspect, an uncured road marking paint is applied to the road surface, and after the retroreflective glass beads are spread on the paint, the paint is cured, and then the surface of the coating film and the glass beads contains a photocatalyst. Cover with layers. In this case, the photocatalyst-containing layer is preferably formed of a silicone layer in which photocatalyst particles are dispersed. When the photocatalyst is photoexcited, at least a part of the organic group bonded to the silicon atom of the silicone molecule is substituted with a hydroxyl group by the photocatalytic action, and a superhydrophilic silicone derivative is formed on the surface of the silicone layer.
[0009]
In other embodiments, retroreflective glass beads pre-coated with a transparent layer containing a semiconductor photocatalyst can be used. In this case, an uncured road marking paint is applied to the road surface, and glass beads are spread on the paint to cure the paint. This method can be easily constructed by a conventional road marking construction machine.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a first embodiment of the road marking according to the present invention. The road marking 10 is composed of a coating film 12 formed of a road marking paint and a number of retroreflective glass beads 14 scattered and fixed on the surface thereof. The road marking paint is, for example, a mixture of an aggregate such as calcium carbonate or a color pigment in a thermoplastic resin.
[0011]
The glass beads 14 have an average particle diameter of about 600 μm, and the surface thereof is coated with a semiconductor photocatalyst layer 16 having a thickness of about 1 μm or less, preferably about 0.5 μm.
As the photocatalyst, titania (TiO ₂ ) is most preferable. Titania is harmless, chemically stable, and available at low cost. Either anatase-type titania or rutile-type titania can be used. It is considered that when photocatalytic titania is photoexcited by ultraviolet rays, water is chemically adsorbed on the surface in the form of hydroxyl groups (OH ⁻ ) by photocatalysis, and as a result, the surface becomes superhydrophilic. Other photocatalysts which can be used include metal oxides such as _{ZnO, SnO 2, SrTiO 3,} WO 3, Bi 2 O 3, Fe 2 O 3. Since these metal oxides, like titania, contain metal elements and oxygen on the surface, it is thought that surface hydroxyl groups (OH ⁻ ) should be adsorbed.
[0012]
When the photocatalyst is titania, the photocatalyst layer 16 can be formed by dip-coating titania sol on the glass beads 14 and baking at a temperature of 300 ° C. or higher and lower than the softening point of the glass. In order to prevent alkali network modifying ions such as sodium in the glass from diffusing from the glass into the photocatalyst layer during firing, it is preferable to previously coat the glass beads 14 with an intermediate layer such as silica. In addition, it is preferable to add about 20% of SiO ₂ or SnO ₂ to titania. In this way, the surface of the photocatalyst layer 16 can be made superhydrophilic so that the contact angle with water becomes 0 ° during photoexcitation.
[0013]
The road marking 10 can be constructed with a conventional spray construction machine (not shown). A road marking paint made of a thermoplastic resin is melted in a melting pot, applied to the road surface in a desired pattern, and after the glass beads 14 coated with the photocatalyst layer 16 are dispersed, the paint is cured.
[0014]
After construction of the road marking 10, the photocatalyst layer 16 of the glass beads 14 is photoexcited by sunlight in the daytime, and the surface of the photocatalyst layer 16 is hydrophilized so that the contact angle with water is 10 ° or less, particularly about 0 °. Is done. Once hydrophilized, the surface hydrophilicity persists at night.
[0015]
Hydrophobic substances such as combustion products in exhaust gas, tire wear powder, and urban dust are less likely to adhere to such highly hydrophilic surfaces. In addition, since the contact angle of inorganic substances such as mud and soil with water is 20 ° to 50 °, the photocatalyst layer 16 that has been superhydrophilicized to such an extent that the contact angle with water becomes about 0 ° is mud. Inorganic dust such as soil and dirt is difficult to adhere.
[0016]
The road marking 10 is occasionally exposed to rainfall. Since the affinity of the superhydrophilic photocatalyst layer 16 for water is larger than the affinity for hydrophobic substances such as combustion products, the dirt deposited on the surface of the photocatalyst layer 16 is released from the surface by rainwater, Washed away by rainwater each time. Thus, the surface of the photocatalyst layer 16 of the glass beads 14 is self-cleaned.
[0017]
FIG. 2 shows a second embodiment of the road marking according to the present invention. Similar to the first embodiment, the road marking 10 is composed of a coating film 12 made of a road marking paint and retroreflective glass beads 14 dispersed and fixed on the surface thereof. In this embodiment, the photocatalyst layer 18 is uniformly coated on the surfaces of the coating film 12 and the glass beads 14.
[0018]
The photocatalyst layer 18 is a paint in which particles of photocatalyst such as titania are dispersed in a ratio of 50% by weight or less in a film-forming element made of uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. The coating composition can be uniformly applied to the surface of the road marking 10, and the coating film forming element can be cured.
[0019]
The coating film forming element of this coating composition includes methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltri-t-butoxysilane; ethyltrichlorosilane, ethyltrichlorosilane. Bromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltri-t-butoxysilane; n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxy Silane, n-propyltriisopropoxysilane, n-propyltri-t-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyl Riethoxysilane, n-hexyltriisopropoxysilane, n-hexyltri-t-butoxysilane; n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-decyl Triisopropoxysilane, n-decyltri-t-butoxysilane; n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n- Octadecyltri-t-butoxysilane; phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltri-t-butoxy Silane: Tetrachlorosilane, Tetrabromosilane, Tetramethoxysilane, Tetraethoxysilane, Tetrabutoxysilane, Dimethoxydiethoxysilane; Dimethyldichlorosilane, Dimethyldibromosilane, Dimethyldimethoxysilane, Dimethyldiethoxysilane; Diphenyldichlorosilane , Diphenyldibromosilane, diphenyldimethoxysilane, diphenyldiethoxysilane; phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, trimethyl Ethoxyhydrosilane, triisopropoxyhydrosilane, tri-t-butoxyhydrosilane; vinyltrichlorosilane, vinyl Tribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane; trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltri Ethoxysilane, trifluoropropyltriisopropoxysilane, trifluoropropyltri-t-butoxysilane; γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane , Γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri-t-butoxysilane; Liloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ -Methacryloxypropyltri-t-butoxysilane; gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropyltriisosilane Propoxysilane, γ-aminopropyltri-t-butoxysilane; γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ -Mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ) Ethyltriethoxysilane; and partial hydrolysates thereof; and mixtures thereof.
[0020]
This road marking can be constructed by the spray construction machine shown in FIG. This construction machine is mounted on the construction vehicle 20, and the road marking paint is melted by the melting pot 22 and applied to the road surface by the rotating gear roll 24. The glass beads 14 accommodated in the tank 26 are spread on the road marking paint by a spreader 28. Finally, the photocatalyst-containing silicone paint stored in the paint tank 30 is applied by the rotating gear roll 32. As the silicone is cured, a photocatalyst-containing silicone layer 18 is formed.
[0021]
When the photocatalyst-containing silicone layer 18 is photoexcited by sunlight, the organic groups bonded to the silicon atoms of the silicone molecules are replaced with hydroxyl groups by the photocatalytic action of the photocatalyst, and the surface of the photocatalyst-containing silicone layer 18 has a contact angle with water. Is superhydrophilic to an extent of about 0 °.
[0022]
In this second embodiment, the photocatalyst layer 18 is coated not only on the glass beads 14 but also on the road marking coating film 12, so that the dirt on the road marking coating film 12 is prevented and the visibility of the road marking is improved. To do.
[0023]
The superhydrophilic phenomenon by the photocatalyst can be realized by a photocatalytic action weaker than the photooxidation action by the photocatalyst. Therefore, in order to prevent the road marking coating film 12 from being deteriorated by the photocatalyst, it is preferable to weaken the photooxidation action of the photocatalyst. For this purpose, the film thickness of the photocatalyst-containing silicone layer 18 is preferably 0.1 μm or less. Moreover, if it is such a film thickness, the abrasion resistance of the photocatalyst layer 18 can be improved. Alternatively, the photocatalytic activity of the photocatalyst can be increased by adding one or more of alkali metal, alkaline earth metal, alumina, silica, zirconia, antimony oxide, amorphous titania, and hydrous titania to the photocatalyst-containing silicone layer 18. Can be suppressed. Furthermore, another layer made of silicone or the like may be provided between the road marking coating film 12 and the photocatalyst-containing silicone layer 18 to prevent deterioration of the road marking coating film 12.
[0024]
Example 1
86 parts by weight of ethanol, 6 parts by weight of tetraethoxysilane Si (OC ₂ H ₅ ) ₄ (Wako Pure Chemical), 6 parts by weight of pure water, and 2 parts by weight of 36% hydrochloric acid as a hydrolysis inhibitor for tetraethoxysilane In addition, mixing was performed to prepare a silica coating solution. Since the solution generated heat by mixing, the mixture was allowed to cool for about 1 hour. This solution was applied to the surface of a 10 cm square soda lime glass plate by a flow coating method and dried at a temperature of 80 ° C. Along with drying, tetraethoxysilane was first hydrolyzed to become silanol Si (OH) ₄ , and then an amorphous silica thin film was formed on the surface of the glass plate by dehydration condensation polymerization of silanol.
[0025]
Next, 0.1 part by weight of 36% hydrochloric acid as a hydrolysis inhibitor was added to a mixture of 1 part by weight of tetraethoxytitanium Ti (OC ₂ H ₅ ) ₄ (Merck) and 9 parts by weight of ethanol to obtain a titania coating solution. This solution was applied to the surface of the glass plate by a flow coating method in dry air. The coating amount was 45 μg / cm ² in terms of titania. Since the hydrolysis rate of tetraethoxytitanium was extremely fast, a part of tetraethoxytitanium was hydrolyzed at the coating stage, and titanium hydroxide Ti (OH) ₄ began to be produced.
[0026]
Next, the glass plate is kept at a temperature of about 150 ° C. for 1 to 10 minutes to complete the hydrolysis of tetraethoxytitanium, and the produced titanium hydroxide is subjected to dehydration condensation polymerization to form amorphous titania. Generated. Thus, a glass plate in which amorphous titania was coated on amorphous silica was obtained. This glass plate was baked at a temperature of 500 ° C. to convert amorphous titania into anatase titania.
[0027]
After leaving this sample in a dark place for several days, using a 20 W black light blue (BLB) fluorescent lamp (Sankyo Electric, FL20BLB), an ultraviolet illuminance (anatase-type titania band) of 0.5 mW / cm ^{2 on} the surface of the sample. A sample of # 1 was obtained by irradiating ultraviolet rays for about 1 hour at an illuminance of ultraviolet rays having energy higher than the gap energy. For comparison, a glass plate without a titania coating was prepared and used as a sample # 2.
[0028]
The contact angle between the # 1 sample and the water of the # 2 sample was measured with a contact angle measuring device (manufactured by Kyowa Interface Science Co., Ltd., model CA-X150). The detection limit of the low angle side of this contact angle measuring device was 1 °. The contact angle was measured 30 seconds after a water droplet was dropped from the microsyringe onto the sample surface. The reading of the measuring instrument with respect to water on the surface of # 1 sample was 0 °, indicating super hydrophilicity. In contrast, the contact angle of the # 2 sample with water was 30 to 40 °.
[0029]
When oleic acid was applied to the surface of this glass plate and the glass plate was immersed in water filled in a water tank while maintaining the glass plate surface in a horizontal position, the oleic acid curled up into oil droplets, and the surface of the glass plate Was released from and surfaced.
[0030]
Example 2
In this example, a 10 cm square aluminum substrate was used as the base material. In order to smooth the surface of the substrate, it was previously coated with a silicone layer. For this reason, the liquid A (silica sol) and the liquid B (trimethoxymethylsilane) of the paint composition “Glaska” of Japanese synthetic rubber are mixed so that the weight ratio of the liquid A and the liquid B is 3: 1. The mixed solution was applied to an aluminum substrate and cured at a temperature of 150 ° C. to obtain a plurality of aluminum substrates (# 1 sample) covered with a 3 μm-thick silicone base coat.
[0031]
The # 1 sample was then coated with a titania-containing paint. More specifically, anatase-type titania sol (Nissan Chemical, TA-15) and the above-mentioned “Glaska” solution A (silica sol) are mixed, diluted with ethanol, and further added with the above-mentioned “Glaska” solution B. The composition for preparation was prepared. The composition of this coating composition was 39 parts by weight of silica, 97 parts by weight of trimethoxymethylsilane, and 87 parts by weight of titania.
This coating composition was applied to the surface of sample # 1 and cured at a temperature of 150 ° C. to form a topcoat in which anatase-type titania particles were dispersed in a silicone coating film, thereby obtaining sample # 2.
[0032]
Next, the # 2 sample was irradiated with ultraviolet rays at an illuminance of 0.5 mW / cm ² for 5 days using a BLB fluorescent lamp to obtain a # 3 sample. When the contact angle between the surface of the sample and water was measured with a contact angle measuring device (ERMA, model GI-1000, low angle detection limit 3 °), the contact angle reading was less than 3 °. The contact angle of sample # 2 before UV irradiation was measured and found to be 70 °. The contact angle of # 1 sample was measured and found to be 90 °. Furthermore, the # 1 sample was irradiated with ultraviolet rays for 5 days under the same conditions as the # 2 sample, and the contact angle was measured. The contact angle was 85 °.
[0033]
From this, it can be seen that when the photocatalyst is contained in silicone and the photocatalyst is photoexcited, the silicone coating is highly hydrophilized. It is considered that the organic group bonded to the silicon atom of the silicone molecule is replaced with a hydroxyl group by photocatalysis and a hydrophilic silicone derivative is formed on the surface.
[0034]
【The invention's effect】
According to the present invention, dirt is prevented from adhering to the road marking, and the dirt adhering to the surface is washed away by rainwater every rain, and the surface of the road marking is self-cleaned. Can be improved.
In addition, since the road marking according to the present invention exhibits excellent visibility over a long period of time, the frequency of updating the road marking can be minimized, and the cost and labor of road maintenance can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic enlarged sectional view of a first embodiment of a road marking according to the present invention.
FIG. 2 is a schematic enlarged sectional view of a second embodiment of the road marking according to the present invention.
FIG. 3 is a schematic view of a road marking construction machine.
[Explanation of symbols]
10: Road marking 12: Road marking coating 14: Retroreflective glass beads 16, 18: Photocatalyst containing layer

Claims (6)

In the road marking in which the retroreflector is partially embedded in the road marking coating, the surfaces of the retroreflector and the road marking coating are covered with a transparent layer containing a semiconductor photocatalyst, and the photocatalyst is sunlight. The surface of the photocatalyst-containing layer is hydrophilized as it is photoexcited by the road surface, so that dirt adhered to the surface is washed away by rainwater when the road marking is exposed to rain. Sign. The photocatalyst-containing layer is formed of a silicone layer in which photocatalyst particles are dispersed, and the surface of the silicone layer is a silicone in which an organic group bonded to a silicon atom of a silicone molecule is at least partially substituted with a hydroxyl group by the action of a photocatalyst. The road marking according to claim 1 formed of a derivative. In the road marking in which the retroreflector is partially embedded in the road marking coating film, the retroreflector is covered with a transparent layer containing a semiconductor photocatalyst, and the photocatalyst is photoexcited as the photocatalyst is photoexcited by sunlight. A road marking characterized in that the surface of the containing layer is hydrophilized so that the dirt adhered to the surface of the retroreflector is washed away by rainwater when the road marking is exposed to rain. An uncured road marking paint is applied to the road surface, retroreflective glass beads are spread on the paint, and the paint is cured to form a road marking paint film and glass beads on the paint film. A road marking construction method comprising fixing and coating the surface of the coating film and glass beads with a transparent layer containing a semiconductor photocatalyst. An uncured road marking paint is applied to the road surface, retroreflective glass beads coated with a transparent layer containing a semiconductor photocatalyst are sprayed on the paint, and the paint is cured to form a road marking coating film. A road marking construction method comprising forming and fixing glass beads to the coating film. The surface of the road marking in which the retroreflector is embedded is coated with a transparent layer containing a semiconductor photocatalyst, and the photocatalyst is exposed to sunlight and photoexcited to hydrophilize the surface of the layer, thereby exposing the road marking to rainfall. A self-cleaning method for pavement marking comprising washing off dirt adhering to the surface with rain water.

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