JP2001139891A - Coating agent and coating technique for forming photocatalytic functional surface on organic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the conventional problems that a substrate of which the surface can be directly coated with photocatalytic titanium oxide is limited to a nonoxidizable inorganic substance such as a ceramic and that a substrate with an organic surface can not be used. SOLUTION: The addition of calcium alginate to a composite substance containing photocatalytic titanium oxide enables the titanium oxide to be enclosed in the meshes of a net and fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst having and maintaining a photocatalytic function of antifouling, deodorizing and sterilizing irrespective of the quality of a substrate surface.

[0002]

2. Description of the Related Art Photocatalytic titanium oxide is most used as a photocatalyst because of its chemical stability that it is not attacked by most acids, bases and organic solvents. Zinc oxide has a similar energy band structure. Are reported to have high activity as photocatalysts. However, zinc oxide causes a photodissolution phenomenon when irradiated with light in an aqueous solution. hydrochloric acid,
It has the property of easily dissolving with acids such as nitric acid and cannot be used with confidence. Metal sulfides and metal chalcogenides can use visible light, but, like zinc oxide, when used as a photocatalyst in water, are known to dissolve in water as metal ions and have toxicity. Therefore, it has been confirmed that the photocatalytic titanium oxide does not cause poisoning and has no carcinogenicity, and it can be said that this is also an excellent substance in this respect.

[0003] Irradiation of light (ultraviolet light) to photocatalytic titanium oxide generates holes, which react with water and oxygen to generate O.
H radicals are generated. These OH radicals have much stronger oxidizing power than chlorine and ozone, which are widely used for disinfection of water, and have carbon-carbon bonds (83 kcal / mol) and carbon-hydrogen bonds (83 kcal / mol) in molecules constituting organic substances. 99k
cal / mol), carbon-nitrogen bond (73 kcal / m
ol), carbon-oxygen bond (84 kcal / mol), oxygen-hydrogen bond (111 kcal / mol), and nitrogen-hydrogen bond (93 kcal / mol), the energy of OH radical is 120 kcal / mo.
It is thought that these bonds can be easily cleaved and decomposed because they are much larger than 1. By this action, chemical substances in the air such as various harmful chemical substances and malodorous substances dissolved in water can be easily decomposed and made harmless.

[0004]

The objects to which this photocatalytic titanium oxide can be directly applied to the surface of the substrate are limited to inorganic substances such as ceramics which do not undergo an oxidation reaction, and the surface of the substrate is an organic substance. Not applicable in case of

As described above, even if the photocatalytic titanium oxide has excellent antifouling, deodorizing, sterilizing, and other effects, it cannot be applied to the case where the substrate surface is an organic substance. Therefore, an object of the present invention is to provide a method capable of incorporating and fixing photocatalytic titanium oxide by adding calcium alginate, which is an organic polymer compound having a three-dimensional structure.

[0006]

SUMMARY OF THE INVENTION The present invention is a photocatalytic functional surface forming means which does not require a protective layer even if the substrate surface is an organic substance, wherein calcium alginate is added to a composite containing photocatalytic titanium oxide. By adding, it is possible to immobilize the photocatalytic titanium oxide by wrapping it in a mesh,
Without causing any harm to the surface of the organic base material, it oxidizes and oxidizes harmful substances such as dirt, smell, fungi, etc., organic substances, compounds, and nitrogen oxides in contact with the photocatalytic titanium oxide.
Based on the discovery of decomposition.

[0007] When photocatalytic titanium oxide receives light (ultraviolet light) having a wavelength of about 400 nm or less, the valence band electrons are excited into the conduction band due to the characteristics of the n-type semiconductor, and thus take a positive charge. Holes and negatively charged electrons are generated. The + and-charges combine with water and oxygen in the air to form hydroxyl radicals and other organic substances, compounds, nitrogen oxides, etc., such as stains, odors, fungi, etc. due to a stronger oxidative decomposition power than ozone or chlorine. Remove harmful substances.

Examples of the organic polymer compound having a three-dimensional structure include calcium alginate, alginic acid, sodium alginate, magnesium alginate, ammonium alginate, propylene glycol alginate, alginate fiber, and PAA, PVA, NIPA.
M, PVA-PAA and the like. Alginic acid is obtained as a highly viscous precipitate by treating a dried seaweed sodium carbonate extract with acid. Commercially available alginic acid is the sodium salt, which gradually dissolves in water like a glue and produces an extremely viscous liquid. Metal salts other than alkali metals do not dissolve in water.
It is used for the production of stabilizers for viscous foods such as ice cream and cheese, as well as pastes for printing and finishing, adhesive binders, fining agents and lubricants. In addition, polymer gel is "a polymer and a swollen body having a three-dimensional network structure insoluble in any solvent."
It is defined as Therefore, as important conditions for being a polymer gel, a polymer and a crosslinked structure are required. In particular, the crosslinked structure can be said to be an essential condition for distinguishing between the gel state and the liquid state. Depending on the type of the crosslinked structure, the method for producing the gel can be roughly classified into whether the crosslink point is a covalent bond or an intermolecular bond. Further, the former may be a case where a cross-linking point is formed at the time of synthesis or a case where post-cross-linking is performed, and the latter may be formed by a hydrogen bond, an electrostatic bond, a hydrophobic bond, or a complex reaction.

Calcium alginate is used for ceramics,
Inorganic base materials such as concrete, glass, and metals tend to have poor fixation power, so it is preferable to form the base layer with a colorful organic paint in view of the landscape. The surface becomes an organic substance, and concerns about immobilization power are eliminated. Further, a method of forming a surface layer with a photocatalytic surface-forming coating agent obtained by adding calcium alginate and a transition metal to a composite containing photocatalytic titanium oxide thereon is desired.

An oxidation reaction of photocatalytic titanium oxide, which is energized by photoexcitation and takes on energy and decomposes organic substances and the like one after another, is not promoted unless a reduction reaction functions. Therefore, in order to activate the exchange of electrons at the time of redox, it is preferable to charge transition metals such as platinum and copper to the composite containing photocatalytic titanium oxide, and the oxidative decomposition ability can be enhanced. However, an organic base material is often used for the surface of the base material, and when the photocatalytic titanium oxide is directly supported, the surface is oxidized and decomposed. Thus, it is preferable to cover the surface with the photocatalytic titanium oxide with an organic polymer compound such as calcium alginate. Therefore, it has the effect of preventing oxidative decomposition of the surface of the substrate employing an organic substance and decomposing organic substances, compounds and nitrogen oxides which come into contact with the photocatalytic titanium oxide.

[0011] The above composite includes Pt, Pd, Rh, R
platinum group metals such as u, Os, Ir, and Ag, Cu,
A metal such as Zn can be added. In the layer to which the metal is added, the oxidation-reduction activity of the photocatalyst is activated, so that actions such as antibacterial and deodorizing are promoted.

A surface layer formed by a photocatalytic functional surface forming coating agent obtained by adding calcium alginate to a composite containing photocatalytic titanium oxide and a surface layer formed by a photocatalytic functional surface forming coating agent charged with transition metals. The layer thickness may be 1 nm or more and 1 mm or less, preferably 0.1 μm to 1.0 μm.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION There are many materials suitable for forming the photocatalytic function surface of the present invention, including interior and exterior materials of buildings, including furniture and lighting, but specifically, siding materials, tiles, and the like. Glass, sash, screen door, shutter, gate, carport, solarium, veranda handrail, roofing material,
Building sash, painted steel plate, aluminum panel, stone, floor, wall, ceiling, shoji, tatami, sink, toilet, closet, mirror stand,
There are sideboards, beds, sliding doors and lighting equipment. For roads, there are tunnel interior boards, tunnel lighting, road signs, road signs, road information boards, road lighting, soundproof walls, guard fences, road decorative boards, road reflectors, elevated roads, etc. In terms of vehicles, there are Shinkansen trains, trains, buses, trucks, passenger cars, light vans, airplanes, rockets, gondolaes in amusement parks, gondolaes in ropeways, motorcycles, snowmobiles, and ships such as passenger ships, cargo ships, fishing boats, and submarines. In addition, there are bridges, monitoring towers, TV towers, parking lots, steel towers, tents, arcades in shopping streets, guide boards, notice boards, advertising towers, etc. in structures and structures, and the surface of the base material can be irradiated with light and air Or if it is in contact with water, the effect can be expected,
There are countless things that add a purifying function. or,
The substrate and the shape are not particularly limited, and the surface may be painted, painted, or written on the surface. For example, iron, cast iron, non-ferrous metal, resin, cement, tile, ceramic,
Plastic, concrete, glass, ceramic, fiber,
It may be wood, stone or paper, etc., or a combination or laminate thereof.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Embodiment 1 FIG. After diluting the coating solution containing photocatalytic titanium oxide (ST-K03, Ishihara Sangyo) 30 times with isopropyl alcohol, it is calcium alginate (Wako Pure Chemical), which is an organic polymer compound, and transition metals. Copper nitrate (Wako Pure Chemical Industries) was added to obtain a photocatalytic functional surface forming coating agent. This photocatalytic surface-forming coating agent is coated on a pet film (5.5 cm × 5.
A 0.5 μm surface layer was formed on the surface of a 5 cm PANAC using a turbine type ultra-low pressure coater (Polymer 9000L type). The photocatalytic surface forming coated PET film is used as an antibacterial sample,
Unprocessed pet film (5.5cm × 5.5cm ・ PA
NAC) was brought to the Japan Food Sanitation Association as an unprocessed sample, and an antibacterial effect test was requested. Test Method 1) Test strain Enterohemorrhagic Escherichia coli O157, Staphylococcus aureus MRSA 2) Preparation of bacterial solution
After culturing for 8 hours, the mixture was diluted 500-fold with sterile purified water, and pH7.
The bacterial solution was adjusted to 0 ± 0.2. (Bacteria count: about 1
0 ⁶ cfu / ml) 3) Operation Each of the antibacterial processed test piece (3 pieces) and the blank non-processed test piece (3 pieces) was put into a sterile chalet, and 0.2 ml of the bacterial solution was inoculated on the test surface. After covering with a cover film and covering the top, the temperature was 35 ° C and the humidity was 99
%, And stored for 24 hours under the condition of irradiation with a fluorescent lamp at 500 lux. After storage (three each), the bacteria adhering to the coated film were washed out with 10 ml of SCDLP broth medium, cultured in SA medium at 35 ° C. for 48 hours, the number of bacteria was measured, and the average value was shown. For the control plot, 0.2 bacterial solution was added to 6 sterile chalets.
ml, inoculated with a covering film, and capped. The three chalets were stored for 24 hours under conditions of a temperature of 35 ° C., a humidity of 99%, and a fluorescent lamp irradiation of 500 lux. Immediately after inoculation and after storage for 24 hours, the bacteria adhering to each of the coated films were washed out with 10 ml of SCDLP broth medium, cultured in SA medium at 35 ° C. for 48 hours, and the number of bacteria was measured, and the average value was shown.

Example 2, Okura flame-retardant plywood (5.5 ×
1235 × 2440 (Okura Kogyo) was subjected to clear coating with an aqueous acrylic emulsion (Kitakawa Seisakusho) to form a base layer. Further, a coating solution containing photocatalytic titanium oxide (ST-K03, Ishihara Sangyo) was diluted 30-fold with isopropyl alcohol, and then calcium alginate (Wako Pure Chemical), an organic polymer compound, and a transition metal Copper nitrate (Wako Pure Chemical Industries, Ltd.) was added to obtain a photocatalytic functional surface-forming coating agent. This photocatalytic function surface forming coating agent was spray-coated on the right half of the substrate surface with a turbine type ultra-low pressure coating machine (Volume 9000L type) to obtain a 0.5 μm surface layer. This spray coating method does not require a compressor, and is 0.3 kg / cm ² , 40
It is composed of a combination of a turbine and a gun that generates ultra-low pressure air with a performance of 00 l / min. Incidentally, the coating rate is 80% to 90%, which is an environment-friendly coating machine.
After the photocatalytic function surface formation coating was completed, it was installed on the roof of our company, and the change in the contamination status in the photocatalytic function untreated / left half photocatalytic function treated / right half was observed. Table 1 shows the results.

[Table 1]

[0016]

The coating agent and the coating technique for forming a photocatalytic surface on the organic substrate of the present invention are not limited to materials such as organic substances, inorganic substances, organic / inorganic hybrid substances, and metallic substances. Photocatalytic titanium oxide can be carried on the surface of the base material, and dirt, odor, fungi, and other organic substances, compounds, and the like contacted with the photocatalytic titanium oxide.
The function of oxidizing and decomposing nitrogen oxides can be maintained permanently.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a first embodiment according to the present invention.

FIG. 2 is a diagram showing an embodiment of a second embodiment according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 base material 2 surface 3 photocatalytic titanium oxide 4 calcium alginate 5 transition metal 6 surface layer 11 base material 12 surface 13 aqueous acrylic emulsion 14 underlayer 15 photocatalytic titanium oxide 16 calcium alginate 17 transition metal 18 surface layer

Claims (4)

[Claims] 1. A coating agent and a coating for forming a photocatalytic functional surface on an organic substrate, wherein a surface layer is formed by a coating agent obtained by adding calcium alginate to a composite containing photocatalytic titanium oxide. Technology. 2. An undercoat layer is formed on the surface of a base material with an organic paint, and a surface layer is formed on the base layer with a coating agent obtained by adding calcium alginate to a composite containing a photocatalytic titanium oxide. A coating agent and a coating technique for forming a photocatalytic functional surface on an organic substrate. 3. A coating agent for forming a photocatalytic functional surface on an organic substrate according to claim 1, wherein the composite containing photocatalytic titanium oxide is charged with a transition metal. Painting technology. 4. The film thickness of a surface layer formed by a coating agent obtained by adding calcium alginate to a composite containing a photocatalytic titanium oxide is 1 nm or more and 1 mm or less. And coating technology for forming photocatalytic functional surfaces on organic substrates.