JP2005199261A - Photocatalyst composite material, coating composition comprising photocatalyst and self-cleaning type coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst composite material capable of heightening the organic material decomposing activity of a coating film formed by water paint when the photocatalyst composite material is blended with the water paint, suppressing the deterioration of the coating film and easily forming the coating film, and also to provide a coating composition comprising photocatalyst with high organic material decomposing activity and capable of easily forming a deterioration-suppressed coating film. <P>SOLUTION: This photocatalyst composite material 10 has a hollow particle 11 and a photocatalyst 12 carried at least by a part of the surface of the hollow particle 11 and its density is less than 1 g/cm<SP>3</SP>. In the photocatalyst composite material 10 according to this invention, it is preferable that a porous layer 13 made up of a porous body is formed at least on a part of the surface. The coating composition comprising photocatalyst contains the above photocatalyst composite material 10, a binder resin and the water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photocatalyst composite material blended in a composition using water as a solvent, such as an aqueous paint. The present invention also relates to a coating composition containing a photocatalyst and a coating film having self-cleaning properties.

A photocatalyst is activated by light and can decompose organic substances. Taking advantage of this property, it has been studied to apply and develop a photocatalyst in the field of building exteriors (see, for example, Patent Document 1). For example, an exterior coating film having a photocatalytic function may be formed by blending a photocatalyst with an aqueous paint in which a binder is dispersed in water and coating the paint on a base material such as a wall material. In the coating film for exteriors containing this photocatalyst, dirt (organic matter) adhering to the surface can be decomposed by the photocatalyst, and since the hydrophilic photocatalyst is exposed on the surface of the coating film, the oil is difficult to adhere. Demonstrate. Therefore, the exterior coating film containing the photocatalyst has a self-cleaning property that removes dirt by itself.
In addition, as a construction method at the time of forming the coating film for exterior, there is a case where a substrate is placed horizontally in a painting factory and is painted.
Japanese Patent Laid-Open No. 2002-14389

However, when a water-based paint containing a general photocatalyst is simply applied to a substrate, most of the photocatalyst is not exposed on the surface and is embedded in the coating film. A photocatalyst that is buried inside the coating film and receives only a small amount of light has a low organic matter decomposing activity. Therefore, when an aqueous paint containing a photocatalyst was simply applied to a substrate, the organic matter decomposing activity was low. Therefore, the self-cleaning property of the coating film was insufficient.
Moreover, since the photocatalyst buried in the coating film has a slight organic substance decomposing activity, the organic binder was decomposed. Therefore, when there is much photocatalyst amount inside a coating film, there existed a problem that a coating film deteriorated.

As a countermeasure, a method of reducing the film thickness of the coating film to 10 μm or less is considered. If the coating film thickness is reduced, the amount of photocatalyst on the surface of the coating film increases, the organic matter decomposition activity can be increased, and at the same time, the amount of photocatalyst inside the coating film decreases, so the decomposition of the binder inside the coating film is suppressed. Deterioration of the coating film can be suppressed. However, it is not easy to stably form a thin coating film having a thickness of 10 μm or less on the substrate, and the workability is low.
The present invention has been made in view of the above circumstances, and when blended in an aqueous paint, the organic matter decomposing activity of the paint film formed with the aqueous paint can be increased, and the deterioration of the paint film can be suppressed. It aims at providing the photocatalyst composite material which can form a coating film easily.
Another object of the present invention is to provide a photocatalyst-containing coating composition that can easily form a coating film having high organic matter decomposition activity and suppressed deterioration.
It is another object of the present invention to provide a self-cleaning coating film that has a high organic matter decomposing activity and has suppressed deterioration.

The photocatalyst composite material of the present invention has hollow particles and a photocatalyst supported on at least a part of the surface of the hollow particles, and has a density of less than 1 g / cm ³ .
In the photocatalyst composite material of the present invention, a porous layer made of a porous material is preferably formed on at least a part of the surface.
The photocatalyst-containing coating composition of the present invention contains the above-described photocatalyst composite material, a binder resin, and water.
The self-cleaning coating film of the present invention is formed by coating the above-described photocatalyst-containing coating composition.

Since the photocatalyst composite material of the present invention floats on water, when it is blended in an aqueous paint, the photocatalyst concentration of the coating surface layer formed with the aqueous paint can be increased. Therefore, while the amount of the photocatalyst buried in the coating film is reduced, the exposed photocatalyst is increased, so that the organic matter decomposition activity is increased. Therefore, the self-cleaning property is sufficiently exhibited. Moreover, the decomposition degradation of a binder can be suppressed and deterioration of a coating film is suppressed. Moreover, since a general coating method can be applied, a coating film can be easily formed.
The photocatalyst-containing coating composition of the present invention can easily form a coating film having high organic matter decomposing activity and suppressed deterioration.
The self-cleaning coating film of the present invention has high organic matter decomposing activity, and its deterioration is suppressed.

(Photocatalyst composite material)
One embodiment of the photocatalyst composite material of the present invention will be described with reference to FIG. The photocatalyst composite material 10 of this embodiment has a hollow particle 11 and a photocatalyst 12 supported on a part of the surface of the hollow particle 11.

Here, examples of the hollow particles 11 include hollow beads, and examples of the hollow beads include organic materials such as urethane resin beads, silicone rubber beads, and acrylic resin beads, and inorganic materials such as glass beads. Is mentioned.
Since the hollow particles 11 are hollow and have a low density, the density of the photocatalyst composite material 10 can be easily reduced to less than 1 g / cm ³ by supporting the photocatalyst on the hollow particles 11.
The particle diameter of the hollow particles is 1-1000 μm, preferably 1-100 μm, more preferably 1-50 μm.

The photocatalyst 12 is activated by light such as ultraviolet light or visible light, and decomposes an organic substance. Examples thereof include an anatase-type titanium oxide catalyst.
Furthermore, the surface of an anatase-type titanium oxide catalyst having silica, alumina, silica-alumina or the like adhered for controlling the activity can also be used.

This photocatalytic composite material 10 has a density of less than 1 g / cm ³ . When the density is less than 1 g / cm ³ , the photocatalytic composite material 10 comes to float on water. When the density exceeds 1 g / cm ³ , the photocatalyst is submerged in water. Therefore, when the photocatalyst composite material is blended with an aqueous coating material and a coating film is formed using the aqueous coating material, the photocatalyst buried inside the coating film Will increase.
In order to make the density less than 1 g / cm ³ , the density of the hollow particles, the type of the photocatalyst, the supported amount, etc. may be appropriately selected.

Next, the manufacturing method of a photocatalyst composite material is demonstrated.
The method for producing the photocatalyst composite material varies depending on the material of the hollow particles.
When the hollow particles are inorganic such as glass beads, it is preferable to employ a chemical catalyst supporting method as a method for supporting the photocatalyst on the surface of the hollow particles. If the chemical catalyst loading method is adopted, even if the inorganic hollow particles have weak shell strength, the photocatalyst can be loaded without being destroyed.
Examples of the chemical catalyst supporting method include a method in which amorphous titanium oxide is attached to the surface of the hollow particles by a sol-gel method, and this is fired to generate anatase-type titanium oxide. Hereinafter, an example of a method for producing a photocatalyst composite material by attaching titanium oxide to the surface of the hollow particles by the sol-gel method and baking the titanium oxide will be described.

First, a solvent is charged into a reaction vessel, and while stirring, hollow particles and titanium alkoxide are sequentially and sequentially added so as not to mix water as much as possible to prepare a mixed solution. Here, as a solvent, alcohol similar to the alkoxy group of titanium alkoxide is preferable.
Next, a solvent mixture composed of pure water and a solvent is added little by little to the mixture to generate titania gel (amorphous titanium oxide) on the surface of the hollow particles. The stirring at that time may be performed at such a speed that the hollow particles are uniformly dispersed in the reaction vessel.
After sufficiently stirring, the stirring is stopped, and the liquid containing hollow particles to which amorphous titanium oxide is adhered is decanted several times by suction filtration. The cleaning liquid used for decantation is preferably the same as the above solvent. In addition, when water is used as the cleaning liquid, unreacted titania sol may react rapidly, making it impossible to produce a desired photocatalyst composite material.

Next, after drying to remove the solvent, firing is performed to obtain a final photocatalyst composite material. In this firing, firing conditions such as firing temperature, firing time, and temperature raising time are not particularly limited as long as amorphous titanium oxide is changed to anatase type.
Before firing, it is preferable to confirm that the hollow particles to which amorphous titanium oxide is adhered are dispersed in water and float in water. When it did not float on water, the conditions were not appropriate, and it was considered that the hollow particles were broken or the amount of titanium oxide attached to the hollow particles was too much.
Further, in the above catalyst loading method, the amount of amorphous titanium oxide produced on the surface of the hollow particles depends on the concentration of each of the hollow particles, titanium alkoxide and water, and the stirring speed, so depending on the purpose, the hollow particles, titanium alkoxide, Each concentration of water and the stirring speed are appropriately selected.

When the hollow particles are organic such as resin beads, it is preferable to employ a mechanical catalyst supporting method as a method of supporting the photocatalyst on the surface of the hollow particles. If it is a mechanical catalyst carrying method, a baking process can be skipped and manufacture will be simplified.
As a specific method for supporting a mechanical catalyst, there is a method in which hollow particles and anatase-type titanium oxide (photocatalyst) are collided with a mixer such as a ball mill, and these are fixed.
The organic hollow particles can adopt the mechanical catalyst supporting method because the organic hollow particles have a low glass transition temperature and can be easily controlled to have a desired particle diameter.

Examples of the method for fixing the organic hollow particles and titanium oxide using a mixer include a dry fixing method and a wet fixing method.
An example of the dry fixing method will be described. First, organic hollow particles, a photocatalyst, and a medium are sequentially put into a container. Here, the medium is a stirrer that stirs the contents during mixing, and has a mechanical strength larger than that of the organic hollow particles. Next, after sealing the container, the container is rotated and vibrated using a shaker so that the photocatalyst collides with the organic hollow particles and is buried.
After sufficiently stirring, the rotation and vibration are stopped, and filtration is performed using a filter screen that is opened to the extent that the media does not pass through, and the media is removed to obtain a photocatalyst composite material in which the photocatalyst is fixed to the organic hollow particles.
In the dry fixing method, the amount of the photocatalyst fixed to the hollow particles depends on the concentration of the hollow particles, the photocatalyst, and the medium in the container, the rotational vibration speed and the rotational vibration time at the time of mixing. Select as appropriate.

Next, an example of the wet fixing method will be described. First, a solvent, organic hollow particles, a photocatalyst, and a medium are sequentially put into a container, and an antifoaming agent and a pigment dispersant are added as necessary. Here, a solvent that does not dissolve the organic hollow particles is selected as the solvent. Next, the container is stirred while keeping the temperature inside the container constant to make the container uniform. Thereafter, the stirring speed is increased so that the photocatalyst collides with the organic hollow particles and is buried.
After sufficiently stirring, stirring is stopped, and decantation is performed a plurality of times by suction filtration to obtain a photocatalyst composite material in which the photocatalyst is fixed to the organic hollow particles. The cleaning liquid used for decantation is the same as the above solvent.
In the wet fixing method, the amount of the photocatalyst fixed to the hollow particles depends on the concentration of the hollow particles, the photocatalyst, and the medium in the container, the stirring speed at the time of mixing, and the stirring time. select.

  Also in the fixing method, it is preferable to confirm that the obtained photocatalyst composite material is dispersed in water and floats in water. If it did not float on water, the fixing conditions were not appropriate, and it was considered that the hollow particles were broken or that the amount of titanium oxide fixed to the hollow particles was too much.

The photocatalyst composite material described above has hollow particles and a photocatalyst supported on a part of the surface of the hollow particles, and has a true density of less than 1.0 g / cm ³ , so it floats on water. Therefore, when this photocatalyst composite material is mix | blended with an aqueous coating material and a coating film is formed on the base material set | placed horizontally using this aqueous coating material, the photocatalyst density | concentration of a coating-film surface layer can be made high. Therefore, the amount of the photocatalyst buried in the coating film is reduced and the exposed photocatalyst is increased, so that the organic matter decomposition activity is increased. Therefore, the self-cleaning property is sufficiently exhibited.
Moreover, as a result of the amount of the photocatalyst buried in the coating film being reduced, the degradation of the binder can be suppressed, and the deterioration of the coating film can be suppressed.
In addition, since a general coating method may be applied without applying a special coating method such as thinning the coating film, the coating film can be easily formed.

Note that the photocatalyst composite material of the present invention is not limited to the above-described embodiment example. For example, the photocatalyst is supported on a part of the surface of the hollow particles, but if the true density does not exceed 1 g / cm ³ , the photocatalyst composite material is hollow. A photocatalyst may be supported on the entire surface of the particles. However, in order to make the true density less than 1 g / cm ³ , it is better to support the photocatalyst on a part of the hollow particle surface.

Moreover, as shown in FIG. 2, the photocatalyst composite material of this invention may have the porous layer 13 formed in the surface. However, the porous layer 13 is formed so as not to block light to the photocatalyst 12. If the photocatalyst 12 is completely covered with the porous layer, the light to the photocatalyst is blocked and the photocatalytic activity is not exhibited.
Here, the porous layer 13 is a layer made of a porous body. Since the porous body can adsorb a large amount of organic matter, if a porous layer is formed on the photocatalyst composite material, the organic matter can be adsorbed while not exposed to light such as at night and without exhibiting the organic matter decomposition activity. The organic matter adsorbed on the porous layer 13 is decomposed by the photocatalyst during the day when the light hits it. Therefore, by forming the porous layer 13, the amount of organic matter can be increased.
The porous body forming the porous layer 13 is not particularly limited as long as it is porous, and examples thereof include apatite.

(Photocatalyst-containing coating composition)
Next, the photocatalyst-containing coating composition of the present invention will be described.
The photocatalyst-containing coating composition of the present invention is a water-based paint containing the photocatalyst composite material, a binder resin, and water.
The binder resin is not particularly limited. For example, polyester (saturated polyester, unsaturated polyester), melamine resin, phenol resin, polyamide, ketone resin, epoxy resin, urethane resin, acrylic resin, ethylene-vinyl acetate copolymer, styrene -An acrylate copolymer, an acrylate copolymer, a vinyl acetate-acrylic copolymer, an acrylic-silicone copolymer, etc. are mentioned.
Further, since the activity of the photocatalyst is inhibited when the binder resin is opaque, the binder resin is preferably transparent.

In this photocatalyst-containing coating composition, the photocatalyst composite material is preferably contained in the range of 5 to 25% by mass with respect to the binder resin. When the content of the photocatalyst composite material is less than 5% by mass with respect to the binder resin, the self-cleaning property of the coating film formed from this coating composition may be insufficient. Moreover, even if it contains more than 25 mass% with respect to binder resin, self-cleaning property does not become high according to the quantity, a coating film becomes easy to be broken, and only raises cost.
Moreover, in a photocatalyst containing coating composition, it is preferable that binder resin is contained in 5-45 mass%. When the content of the binder resin is less than 5% by mass, the function as the binder is hardly exhibited, and for example, cracks are likely to occur on the coating film surface. On the other hand, if it exceeds 45 mass%, the binder action is saturated and not only disadvantageous in cost, but also the drying process after coating tends to take too much time.

The viscosity of the photocatalyst-containing coating composition is preferably 0.1 to 5.0 Pa · s, preferably 0.5 to 3.0 Pa · s, depending on the base material, the coating method, and the performance to be secured. Is more preferable, and 1.0 to 2.0 Pa · s is particularly preferable. If the viscosity of the photocatalyst-containing coating composition is less than 0.5 Pa · s, sagging tends to occur during coating, and if it exceeds 5.0 Pa · s, the photocatalyst composite material may not float. In addition, the viscosity here is a viscosity by the Brookfield method (viscosity by a B-type viscometer).
Further, in this photocatalyst-containing coating composition, the photocatalyst composite material floats and is unevenly distributed at the top, so it is necessary to make it uniform by stirring or the like during coating, but the viscosity is 0.1 to 5.0 Pa · If it is s, it is easy to make it uniform. On the other hand, when the viscosity is less than 0.1 Pa · s, the photocatalyst composite material tends to be unevenly distributed immediately after the stirring is stopped, and when it is more than 5.0 Pa · s, the stirring time until it becomes uniform tends to be longer.
In order to adjust to a preferable viscosity, when the viscosity is too high, water is appropriately added to lower the viscosity. On the other hand, when the viscosity is too low, an appropriate water-soluble thickener is added to increase the viscosity. Examples of the water-soluble thickener include carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylate, vinyl / maleic acid copolymer, polyether, polyether urethane, colloidal silica, and the like.

(Self-cleaning coating film)
The self-cleaning coating film of the present invention is formed by coating the above-described photocatalyst-containing coating composition. Examples of the substrate on which the photocatalyst-containing coating composition is coated include building boards such as concrete board, asbestos cement board, hard board, gypsum board, asbestos perlite board, calcium silicate board, ABS resin, styrene resin, Plastic moldings such as acrylic resin, vinyl chloride resin, melamine resin and polyester resin, metals such as iron plate, aluminum plate, tin plate and tin plate, a wide range of materials such as wood, synthetic wood glass, ceramic molding, etc. Is mentioned. An undercoat layer may be formed on these substrates in order to smooth the surface.
The coating method is not particularly limited, and examples thereof include spray coating, roll coating, shower coating, dip coating, and brush coating. Among these, spray coating is preferable from the viewpoint of workability. In painting, in order to ensure that the photocatalyst composite material is unevenly distributed on the surface side, it is preferable to place the base material horizontally in a painting factory.
In addition, coatings, especially exterior coatings, are not formed by painting at the construction site, but are transported to the construction site after being formed on the substrate in the painting factory, from the viewpoint of quality and workability. There are many cases. When painting in a coating factory, the substrate is often placed horizontally, so it is common to form a coating on the horizontally placed substrate.

Since the self-cleaning coating film described above is formed by applying the above-described photocatalyst-containing coating composition, the photocatalytic composite material that floats in water with a true density of less than 1.0 g / cm ³ is formed on the surface side. It is unevenly distributed (see FIG. 5). Therefore, since the amount of photocatalyst buried in the coating film is small and the exposed photocatalyst is large, the organic matter decomposition activity is high. Further, since the amount of the photocatalyst buried in the coating film is small, the decomposition degradation of the binder is suppressed, and the degradation is suppressed.

<Examples 1 to 7: Method for producing photocatalytic composite material using glass beads>
In a beaker, isopropyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., sometimes referred to as IPA) is charged, and while stirring this, glass beads (Cell Star SX-39, manufactured by Tokai Kogyo Co., Ltd., average particle) 40 μm in diameter) and titania sol (Origatix TA-10 manufactured by Matsumoto Pharmaceutical Co., Ltd.) were sequentially added in the amounts shown in Table 1 to prepare a mixed solution.

Next, a solvent mixture composed of pure water and isopropyl alcohol solvent in the ratio shown in Table 1 was added little by little to the above mixture to produce titania gel (amorphous titanium oxide) on the glass bead surface. After 6 hours of reaction and sufficient stirring, the stirring was stopped and the liquid containing glass beads with amorphous titanium oxide adhered was decanted several times by suction filtration. Isopropyl alcohol was used as a cleaning liquid during decantation.
Subsequently, after drying and removing isopropyl alcohol, it baked at 500 degreeC for 2 hours, the amorphous titanium oxide was changed into the anatase type crystal, and the photocatalyst composite material was obtained. In addition, before baking, it confirmed that the hollow particle to which the amorphous titanium oxide adhered was disperse | distributed in water, and floated on water.

  The obtained photocatalytic composite material was analyzed using a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDS), a fluorescent X-ray analyzer, and an X-ray diffractometer (XRD). The presence or absence of production, the presence or absence of titanium oxide supported on glass beads, etc. were confirmed. The results are shown in Table 2.

(SEM, EDS)
The particle surfaces before and after supporting titanium oxide were observed with an SEM (manufactured by JEOL Ltd., magnification: 3000 times). When the surface of the particles is “wrinkled skin”, it indicates that titanium oxide is adhered. In the case of “smooth”, it indicates that titanium oxide is not attached. FIG. 3 shows an electron micrograph of the surface of the particles having titanium oxide attached to form a “skin skin”, and FIG. 4 shows an electron micrograph of the glass bead surface.
Moreover, the component of the part of "Yuzu skin-like" was analyzed in EDS (made by Oxford Instruments). In addition, although EDS can confirm the presence or absence of the titanium oxide production | generation on a glass bead, since the measurement precision is inadequate, it measured with the following fluorescence X-rays about the titanium oxide production amount.
(Fluorescent X-ray)
About 10 g of the photocatalytic composite material was filled in the cell, and the amount of titanium oxide in the entire photocatalytic composite material was determined using a fluorescent X-ray analyzer. From the obtained amount of titanium oxide (mol%), the amount of titanium relative to silicon (Si) forming glass beads was determined.
<XRD>
XRD (manufactured by Rigaku Corporation) was used to confirm whether or not the titanium oxide adhered on the glass beads was an anatase type crystal exhibiting a photocatalytic effect.

(Evaluation of organic matter decomposition activity)
The organic substance decomposition activity of the obtained photocatalyst composite material was evaluated by the decomposition of methylene blue.
First, 25 ml of 20 ppm methylene blue aqueous solution was put into a 50 ml sample bottle, and a photocatalyst composite material sample was added thereto so that its concentration was 2% by mass to obtain a sample solution. Next, while stirring the sample solution with a magnetic stirrer, black light (wavelength: 365 nm) was irradiated with an intensity of 1.0 mW / cm ² for 3 hours, and the color of the sample solution after irradiation was visually determined. In the case of having an organic substance decomposing activity, methylene blue is decomposed and the color of the sample solution changes from blue to colorless and transparent.
The determination is as follows.
A: Colorless and transparent B: Dilute blue C: Blue D: Dense blue (color of methylene blue aqueous solution)

<Examples 8 and 9: Method for producing photocatalyst composite material using acrylic resin hollow beads (wet fixing method)>
In a double wall stainless steel container, pure water, acrylic resin hollow beads (M-610 manufactured by Matsumoto Yushi Co., Ltd.), titanium oxide (anatase type titanium oxide W-10 manufactured by Ishihara Sangyo Co., Ltd.), defoaming An agent (San Nopco Co., Ltd. SN deformer 399) and media (zirconia beads, diameter 1 mm) were sequentially added in the amounts shown in Table 4 to prepare a mixed solution.

Next, the titanium oxide collides with the acrylic resin hollow beads. The titanium oxide is fixed to the acrylic resin hollow beads by stirring for 0.5 hour at a stirring speed enough to embed titanium oxide in the hollow beads. It was. At that time, hot water of 40 ° C. was circulated between the walls of the double wall to keep the temperature of the mixed liquid inside thereof constant. Then, stirring was stopped and decantation was performed several times by suction filtration. Pure water was used as a cleaning liquid during decantation.
After drying, the hollow particles with titanium oxide adhered were dispersed in water and confirmed to float in water.
The obtained photocatalyst composite material was analyzed using a scanning electron microscope (SEM) and a fluorescent X-ray analyzer, and the presence / absence of adhesion of anatase-type titanium oxide to the hollow beads was confirmed. The results are shown in Table 5. Moreover, it shows in Table 6 about the evaluation result of organic substance decomposition | disassembly activity.

<Examples 10 and 11: Method for producing photocatalyst composite material using acrylic resin hollow beads (dry fixing method)>
Acrylic resin hollow beads (M-610 manufactured by Matsumoto Yushi Co., Ltd.), titanium oxide (anatase type titanium oxide W-10 manufactured by Ishihara Sangyo Co., Ltd.), media (zirconia beads, diameter 1 mm) in a plastic container Were sequentially added in the amounts shown in Table 7, and the container was sealed.

Next, the titanium oxide collides with the acrylic resin hollow beads, and the titanium oxide is made of acrylic resin by rotating and vibrating the container using a shaker to such an extent that the titanium oxide is buried in the hollow beads by the collision. Fixed to hollow beads. After shaking for 10 minutes, the medium was separated from the beads (photocatalyst composite material) to which titanium oxide was fixed by filtering through a filter screen opened to such an extent that the medium did not pass. Next, it was confirmed that the hollow particles to which titanium oxide was adhered were dispersed in water and floated in water.
The obtained photocatalyst composite material was analyzed using a scanning electron microscope (SEM) and a fluorescent X-ray analyzer, and the presence / absence of adhesion of anatase-type titanium oxide to the hollow beads was confirmed. The results are shown in Table 8. Moreover, it shows in Table 9 about the evaluation result of organic substance decomposition | disassembly activity.

The materials of Examples 1 to 11 were photocatalyst composite materials in which anatase-type titanium oxide as a photocatalyst was supported on glass beads as hollow particles or hollow beads made of acrylic resin, and had organic substance decomposition activity. Moreover, these photocatalyst composite materials floated on water. When a water-based paint containing such a photocatalytic composite material is used and a coating film is formed on a horizontally placed substrate by a general coating method, the resulting coating film exhibits sufficient self-cleaning properties. At the same time, deterioration is suppressed.
The materials of Reference Examples 1 to 3 were hollow particles themselves and did not have organic substance decomposition activity.

<Example 12: Photocatalyst-containing coating composition and coating film>
Photocatalyst composite material and binder resin of Example 2 with the composition shown in Table 10 (Polydurex G-651 manufactured by Asahi Kasei Chemicals Corporation, water-based acrylic silicone, emulsion, solid content 42%) and antifoaming agent (BYK-023 manufactured by BYK Chemie) And water were mixed to prepare a photocatalyst-containing coating composition. Next, an aluminum plate on which an undercoat layer (undercoat paint; acrylic / urethane solvent-type paint) is formed is placed horizontally on the floor so that the coating amount of the photocatalyst-containing paint composition is 500 g / m ² on the undercoat layer. Spray painted. And it dried for 2 weeks at 23 degreeC and 50% of relative humidity, and formed the coating film. The obtained coating film was evaluated as follows. The evaluation results are shown in Table 11.

(Weatherability)
A 2000-hour weather resistance test was conducted using a sunshine weather meter (manufactured by Suga Test Instruments Co., Ltd.). Then, gloss and color difference (ΔE) before and after the test (0 hour) and after the test (after 2000 hours) were measured. The color difference was measured using an SM color computer (SM-7-IS-2B type) manufactured by Suga Test Instruments. The smaller the gloss retention ({(gloss before test−gloss after test) / gloss before test} × 100), the greater ΔE, the lower the weather resistance.
(Photocatalytic activity)
A 100ppm methylene blue solution is spray-coated on the surface of the coating so that the color difference (ΔE) before and after coating is about 15, dried in a dark place at 23 ° C and 50% relative humidity for 3 hours, then black Light (wavelength; 365 nm) was irradiated at an intensity of 1.0 mW / cm ² for a maximum of 5 hours. In that case, the color difference of the coating-film surface for every hour was measured. And based on the measured color difference, the decolorization rate was calculated | required and it was set as the parameter | index of methylene blue decomposition | disassembly. The decolorization rate is obtained from the following equation.
Decolorization rate (%) = {(ΔE ₀ −ΔE _n ) / ΔE ₀ } × 100 (%)
Here, ΔE ₀ is the color difference of the coating film surface before the black light irradiation, and ΔE _n is the color difference of the coating film surface when the black light is irradiated for n hours.

<Example 13, Reference Example 4>
A coating film in Example 13 was obtained in the same manner as Example 12 except that the photocatalyst composite material of Example 4 was used.
A coating film in Reference Example 4 was obtained in the same manner as in Example 12 except that the photocatalyst composite material of Reference Example 1 was used.
These coating films were also evaluated in the same manner as in Example 12. Reference Example 4 is a blank test.

  In the coating films of Examples 12 and 13 containing the photocatalytic composite material of claim 1 of the present application, as shown in the cross-sectional photograph of FIG. 5, the photocatalytic composite material was unevenly distributed on the surface. As a result, despite showing high photocatalytic activity, the weather resistance was within an acceptable range, and deterioration was suppressed.

  The photocatalyst composite material of the present invention is suitably blended in a water-based paint for building exteriors.

It is sectional drawing which shows one embodiment of the photocatalyst composite material of this invention. It is sectional drawing which shows the other embodiment example of the photocatalyst composite material of this invention. It is an electron micrograph of the photocatalyst composite material surface. It is an electron micrograph of the glass bead surface. It is the photograph which image | photographed the cross section of an example of the self-cleaning coating film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photocatalyst composite material 11 Hollow particle 12 Photocatalyst 13 Porous layer

Claims (4)

A photocatalyst composite material comprising hollow particles and a photocatalyst supported on at least a part of the surface of the hollow particles, wherein the density is less than 1 g / cm ³ .   The photocatalyst composite material according to claim 1, wherein a porous layer made of a porous material is formed on at least a part of the surface.   A photocatalyst-containing coating composition comprising the photocatalyst composite material according to claim 1, a binder resin, and water. A self-cleaning coating film formed by coating the photocatalyst-containing coating composition according to claim 3.

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