JP2006008902A - Photocatalytic coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalytic coating composition excellent in soil resistance. <P>SOLUTION: The photocatalytic coating composition consists of apatite-coated titanium dioxide fine particles and reactive silica fine particles with a weight average molecular weight of 1,000±200, comprising a siloxane compound expressed by formula (1): SiO<SB>a</SB>(OH)<SB>b</SB>(OR<SP>1</SP>)<SB>c</SB>(OR<SP>2</SP>)<SB>d</SB>(wherein, 0.8≤a≤1.6; 0.3≤b≤1.3; 0.2≤c+d≤1.9; b=4-(2a+c+d); R<SP>1</SP>is a methyl group or an ethyl group; and R<SP>2</SP>is a group different from R<SP>1</SP>) or a hydrolysis condensate of a tetraalkoxy silane expressed by formula (2): Si(OR<SP>1</SP>)<SB>4</SB>(wherein, R<SP>1</SP>is a methyl group or an ethyl group). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photocatalytic coating composition, and more particularly to a photocatalytic coating composition containing apatite-coated titanium oxide fine particles as a photocatalyst.

  Titanium oxide photocatalyst can decompose organic substances and bacteria by ultraviolet rays contained in electric light and sunlight, so it is antifouling, sick house measures, hospital infection prevention, deodorization, antibacterial and antifungal, air purification, water treatment, self-cleaning It is used in the environmental field for such purposes. When titanium oxide is kneaded into fibers or plastics, the fibers and plastics are decomposed by photocatalytic action, so they are used in a form that is coated with a porous film such as silica or coated with apatite on the surface. . In particular, apatite-coated titanium oxide, in which the surface of titanium oxide is coated with apatite, can improve the decomposition efficiency of organic matter and bacteria due to the adsorption performance of apatite.

  One of the uses of apatite-coated titanium oxide is antifouling paint, which has already been widely used. For example, a sol-gel method using alkoxysilane or silicate is generally used to impart a binder function and use as a paint. However, with such a method, the bonding strength of the coating film is excellent, but if the film thickness is increased too much, it breaks and there is a problem that it is not suitable for construction on a rough surface. Therefore, it has been necessary to apply the coating composition in a very dilute state with a solid content of 0.1 to 2%. In addition, when silica fine particles are used as a binder, since there are few silanol groups present on the surface of the fine particles, there is a problem that the bonding strength of the coating film is small, and after construction, the apatite-coated titanium oxide can be easily peeled off by wind and rain. It was.

  Further, as a binder of the coating material, at least one functional group that contains a silicone acrylic resin (for example, see Patent Document 1) and a silicon atom bonded to a hydroxyl group or a hydrolyzable group and can be crosslinked by forming a siloxane bond. It has been proposed to use an organic polymer (see, for example, Patent Document 2). However, since these binders having an organic group are highly hydrophobic, there is a problem that dust or the like tends to adhere to the coating film, and the antifouling effect is impaired.

JP 2001-64583 A JP 2002-47418 A

  The objective of this invention is providing the photocatalyst coating composition excellent in the antifouling effect.

The present invention provides apatite-coated titanium oxide fine particles, formula (1):
SiO _a (OH) _b (OR ¹ ) _c (OR ² ) _d (1)
(In the formula, 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3, 0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d), R ¹ is a methyl group or an ethyl group , R ² is an organic group different from R ¹ ) or a formula (2):
Si (OR ¹ ) ₄ (2)
(Wherein R ¹ is a methyl or ethyl group), a photocatalytic coating composition comprising a reactive silica fine particle having a weight average molecular weight of 1000 ± 200, comprising a hydrolyzed condensate of tetraalkoxysilane, and an aqueous solvent Related to things.

  The reactive silica fine particles have the formula (3):

(Wherein, n is an integer of 2 to 8) and is preferably obtained by adding water and a catalyst to methyl silicate.

  The average particle diameter of the reactive silica fine particles is preferably 9 ± 3 nm.

  According to the present invention, the use of reactive silica fine particles having a silanol group consisting of a substantially complete inorganic compound as a binder for apatite-coated titanium oxide fine particles increases the hydrophilicity of the coating film and provides excellent antifouling properties. An effect can be obtained. In addition, compared to the case of using alkoxysilane or silicate, it is applied at a relatively high concentration without the risk of cracking when applied thickly even on construction surfaces with large irregularities such as during repairs. be able to. Further, since the surface of the fine particles has many silanol groups, the bonding force is large, and the apatite-coated titanium oxide fine particles are not easily peeled off by rain or the like after the construction.

The photocatalytic coating composition of the present invention comprises apatite-coated titanium oxide fine particles, formula (1):
SiO _a (OH) _b (OR ¹ ) _c (OR ² ) _d (1)
(In the formula, 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3, 0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d), R ¹ is a methyl group or an ethyl group , R ² is an organic group different from R ¹ ) or a formula (2):
Si (OR ¹ ) ₄ (2)
(Wherein R ¹ is a hydrolyzed condensate of tetraalkoxysilane represented by the formula ( ¹ ), consisting of reactive silica fine particles having a weight average molecular weight of 1000 ± 200 and an aqueous solvent.

  Apatite-coated titanium oxide fine particles are obtained by precipitating apatite on the surface of titanium oxide by immersing titanium oxide in an aqueous solution in which calcium ions, phosphate ions, etc. are dissolved, and heating and stirring. The surface has a form in which apatite is coated with a confetti shape (see Japanese Patent Application Laid-Open No. 10-244166).

  Titanium oxide (titanium dioxide) includes rutile, brookite, and anatase type titanium oxides depending on the crystal structure. However, anatase type titanium oxide is available because it has a high photocatalytic activity and can have any particle size. preferable.

  The coating amount of apatite is preferably 5 parts by weight or more, more preferably 10 parts by weight or more with respect to 100 parts by weight of titanium oxide. If the apatite coating amount is less than 5 parts by weight, not only the apatite adsorption ability is inferior, but it becomes impossible to take in harmful substances and contaminants floating in the space or in the vicinity of the catalyst and move them to the titanium oxide particle surface. When no light is irradiated, the adsorbed harmful substance is re-desorbed, and as a result, the photocatalytic activity tends to be insufficiently developed. Moreover, the coating amount of apatite is preferably 20 parts by weight or less, more preferably 15 parts by weight or less with respect to 100 parts by weight of titanium oxide. If the coating amount of apatite exceeds 20 parts by weight, the surface of the titanium oxide particles will be completely covered with the apatite crystals, so that the substance intended for decomposition cannot move to the titanium oxide surface, resulting in photocatalytic activity. There is a tendency for expression to be insufficient.

  The average primary particle diameter of the apatite-coated titanium oxide fine particles is preferably 10 nm or more, more preferably 30 nm or more. If the average primary particle diameter of the apatite-coated titanium oxide fine particles is less than 10 nm, it becomes easy to re-agglomerate after the dispersion treatment up to the primary particles by the homogenizer as the first stage of paint production, and as a result, the particle diameter after adjustment of the paint Therefore, the specific surface area is reduced and the catalytic activity is lowered. The average primary particle size of the apatite-coated titanium oxide fine particles is preferably 250 nm or less, more preferably 100 nm or less. If the average primary particle diameter of the apatite-coated titanium oxide fine particles exceeds 250 nm, the final coating is colored white, which tends to cause uneven coating and requires transparency such as glass. It tends to be unsuitable for objects to be coated. In addition, as the particle diameter increases, the sedimentation rate of the apatite-coated titanium oxide fine particles in the paint increases, and thus the storage stability of the paint tends to be inferior.

  The content of the apatite-coated titanium oxide fine particles in the solid content of the paint is preferably 5% by weight or more, more preferably 25% by weight or more. If the content of the apatite-coated titanium oxide fine particles is less than 5% by weight, the area occupied by the apatite-coated titanium oxide fine particles on the surface of the dried coating film is not sufficient, and it is necessary to laminate many times to obtain the desired photocatalytic effect. There is a tendency. Further, the content of the apatite-coated titanium oxide fine particles in the solid content of the paint is preferably 75% by weight or less, more preferably 50% by weight or less. When the content of the apatite-coated titanium oxide fine particles exceeds 75% by weight, the binder content is too small, and thus the apatite-coated titanium oxide fine particles tend to lack a bonding force or an adhesion force to the base material. . Originally, the photocatalytic reaction is a reaction on the surface of the coating film where ultraviolet rays are directly incident, and the apatite-coated titanium oxide existing on the surface acts effectively, but the titanium oxide inside the coating film is effective for this reaction. Therefore, even if the solid content of the apatite-coated titanium oxide exceeds 50% by weight, the effect as a photocatalyst is hardly improved and the cost tends to increase as a result.

  Although it does not specifically limit as a manufacturing method of the reactive silica fine particle which has a silanol group, It is preferable to consist of the hydrolysis condensate of the alkoxysilane obtained by adding water to alkoxysilane or its oligomer, and aging. As the alkoxysilane, tetraalkoxysilane is preferable, and tetramethoxysilane is particularly preferable because it is excellent in hydrolytic condensation and can provide a high-quality coating film.

As a method for producing reactive silica fine particles having a silanol group, the above formula (1):
SiO _a (OH) _b (OR ¹ ) _c (OR ² ) _d (1)
(In the formula, 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3, 0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d), R ¹ is a methyl group or an ethyl group , R ² is an organic group different from R ¹ ), there is a method of adding water to the siloxane compound and aging, but there is no particular limitation.

The siloxane compound of the formula (1) is obtained by, for example, hydrolyzing and condensing an alkoxysilane represented by Si (OR ¹ ) ₄ (R ¹ is a methyl group or an ethyl group) to obtain the formula (3):

(Wherein n is an integer of 2 to 8), and subsequently in the presence of water, an alcohol represented by R ² OH is added to obtain an OH group in the oligomer simultaneously with transesterification. be able to.

  Here, in the said Formula (1), when a is less than 0.8, it exists in the tendency for the hardened | cured material obtained by hardening to become opaque. On the other hand, when a is larger than 1.6, the viscosity of the coating solution is high and unstable and tends to gel. When b is less than 0.3, the boiling water resistance of the coating film is inferior when formed into a coating film, and when it is greater than 1.3, the cured product obtained by curing tends to be opaque. When c + d is less than 0.2, when formed into a coating film, it is inferior in boiling water, and when it is greater than 1.9, the cured product obtained by curing tends to be opaque.

In the formula (1), R ¹ is a methyl group or an ethyl group. In the case of a methyl group, the cured product has excellent physical properties such as hardness and chemical resistance. R ² is an organic group different from R ¹ , preferably an organic group that can be transesterified with R ¹ , for example, an ethyl group, an isopropyl group, a butyl group, a 1-methoxy-2-ethyl group, 1 - ethoxy-2-propyl group, 1-methoxy-2-propyl, 2-methoxyethyl group, 2-ethoxyethyl _{group, C 2 H 5 OC 2 H} 4 OC 2 H 4 -, CH 3 C 2 H 4 OC ₂ H ₄ —, C ₂ H ₅ OC ₂ H ₄ —, CH ₃ OC ₂ H ₄ — and the like.

  As a method for producing reactive silica fine particles having a silanol group, in particular, the formula (4):

(Wherein n is an integer of 2 to 8), the method of adding water and a catalyst to the methyl silicate not only facilitates dealcoholization in the hydrolytic condensation step, but also the silanol group in the aqueous medium. It is preferable from the viewpoint of stability.

  Aging is performed by stirring at 5 to 50 ° C. for 1 to 24 hours after completion of the reaction.

  Aging can be carried out in the presence of an organic solvent such as alcohol. By aging in the presence of an organic solvent, the storage stability of reactive silica fine particles having a silanol group can be enhanced.

  The aging can be performed in the presence of a catalyst as necessary.

  Examples of the catalyst include organic amines such as N-methyldiethanolamine and triethylamine, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid, acetic acid, formic acid, p-toluenesulfonic acid, benzoic acid, phthalic acid, maleic acid and propion. Organic acids such as acids and oxalic acids, alkaline catalysts such as potassium hydroxide, sodium hydroxide, calcium hydroxide, and ammonia water, organic tin compounds such as organic metals, metal alkoxides, dibutyltin laurate, dibutyltin octate, and dibutyltin diacetate Aluminum tris (acetylacetonate), titanium tetrakis (acetylacetonate), titanium bis (isopropoxy) bis (acetylacetonate), zirconium tetrakis (acetylacetonate), zirconium bis (butoxy) Bis (acetylacetonate), metal chelate compounds such as zirconium bis (Isopuropukishi) bis (acetylacetonate), boron butoxide, boron compounds such as boric acid. Of these, organic amines are preferred because they can be formed quickly after application and a tough coating can be obtained. They also act as catalysts for hydrolysis of alkoxysilyl groups, and also serve as condensation catalysts for silanol groups during drying. A metal chelate compound is preferable from the viewpoint of availability.

  The reactive silica fine particles having a silanol group obtained as described above preferably have an average particle size of 1 nm or more, more preferably 6 nm or more. When the average particle size is less than 1 nm, the number of reactive silica fine particles contained in the unit volume increases, so that in the drying process after coating, the coating film becomes too dense and cracks are likely to occur, Since the interaction with the titanium oxide particles becomes large, gelation may occur during storage of the paint. The average particle size of the reactive silica fine particles is, for example, 20 nm or less, preferably 15 nm or less, more preferably 12 nm or less. If the average particle diameter exceeds 20 nm, the silanol groups of one reactive silica fine particle are reduced, resulting in lack of reactivity such as adhesion to the substrate and imparting a binder function to the titanium oxide particles. It is unsuitable as a resin that constitutes.

  Moreover, the reactive silica fine particle which has a silanol group has the weight average molecular weight measured by gel permeation chromatography (GPC), for example, 1000 +/- 200 in standard polystyrene conversion. When the weight average molecular weight exceeds 1200, the particle diameter of the generated reactive fine particles increases, and the coating solution tends to become cloudy, and the reactivity and storage stability tend to decrease. On the other hand, when the weight average molecular weight is less than 800, hydrolysis and condensation reaction is not sufficient, and low molecular weight oligomers are included, so that the hydrophilicity as a binder tends to be lowered.

  As described above, the reactive silica fine particle having a silanol group has a very small average particle diameter relative to its molecular weight, and is a unique form of silica having an ultra-dense structure.

  Therefore, the reactive silica fine particles have many silanol groups on the surface of the fine particles.

  Examples of commercially available reactive silica fine particles having a silanol group include MSH-4 manufactured by Mitsubishi Chemical Corporation.

  In the present invention, the reactive silica fine particles having a silanol group function as a binder for the coating material. When reactive silica fine particles with silanol groups are used, they are thickly applied even to construction surfaces with large irregularities, such as when renovating, compared to when using alkoxysilanes and silicates that are commonly used at present. Sometimes there is no risk of cracking and it can be applied at a relatively high concentration. In addition, since the reactive silica fine particles having silanol groups have many silanol groups on the surface, the apatite-coated titanium oxide fine particles are not easily removed due to wind and rain after construction.

  Further, the reactive silica fine particles having a silanol group can form a colorless and transparent coating film and are present as fine particles in the coating film, so that the catalytic performance thereof is not buried in the apatite-coated titanium oxide fine particles. Will not be disturbed.

  Furthermore, the reactive silica fine particles having a silanol group are made of a substantially complete inorganic compound unlike a binder such as a silicone acrylic resin, and further have a large number of silanol groups on the surface. High antifouling effect can be achieved.

  The content of reactive silica fine particles having a silanol group is preferably 0.5% by weight or more, more preferably 3% by weight or more. When the content of the reactive silica fine particles is less than 0.5% by weight, the binding strength as a binder for constituting the coating material is inferior, and physical properties required for the coating film, such as water resistance and scratch resistance, are lacking. Tend to be. In addition, during the storage of the paint, the sedimentation of particles occurs at an early stage, so that the storage stability tends to be lacking.

  The content of the reactive silica fine particles is preferably 20% by weight or less, more preferably 10% by weight or less. When the content of the reactive silica fine particles exceeds 20% by weight, the area occupied by the silica fine particles on the coating film surface becomes too large, and as a result, the abundance of the apatite-coated titanium oxide on the coating film surface becomes insufficient. It tends to be lacking in effectiveness. Moreover, in order to apply to the stability in the paint, the primary particles are aggregated. As a result, the average particle diameter of the reactive fine particles is increased, and the binding force as a binder tends to be inferior.

  The aqueous solvent refers to a solvent containing water as a main component and contains 30% by weight or more of water. In addition, for the purpose of improving coating workability and appearance, an organic solvent that is compatible with water such as alcohol, ether, glycol ether and the like can be included, and is not particularly limited.

  The photocatalyst coating material of the present invention further comprises a dispersion stabilizer, a surfactant, an antifoaming agent, a plasticizer, an antioxidant, an ultraviolet absorber, a light stabilizer, a fragrance, a curing agent, a pH adjuster, and an anti-rust agent as necessary. An additive such as an agent, a fungicide, or a film-forming agent can be contained in such an amount that the hydrophilicity at the initial stage of the coating film formation is not lowered.

  The photocatalyst coating composition of the present invention comprises the apatec-coated titanium oxide fine particles and the reactive silica fine particles having silanol groups, a sand mill, a homogenizer, a ball mill, a roll mill, a paint shaker, an ultrasonic disperser, a blade-type stirrer, a magnetic stirrer, It can be produced by dispersing in an aqueous solvent using a high-speed disperser, an emulsifier or the like. In particular, at a high rotational speed of 10,000 rpm or higher, it is possible to disperse to the target particle size by a relatively short time of processing, and there is no contamination that was a disadvantage of a disperser using a dispersion medium. Therefore, the dispersion treatment with a homogenizer is preferable not only in the production of the paint but also in the physical properties.

  The solid content concentration of the photocatalyst coating composition of the present invention is preferably 3% by weight or more, more preferably 6% by weight or more. If the solid content concentration is less than 3% by weight, the titanium oxide does not take a share at the time of coating production, and it tends to take more time than necessary to disperse to the primary particles, which is not preferable. The solid content concentration of the photocatalyst coating composition is preferably 20% by weight or less, more preferably 10% by weight or less. If the solid content concentration exceeds 20% by weight, the titanium oxide particles are likely to re-aggregate during storage of the paint, resulting in a large particle size of the titanium oxide in the coating film, resulting in a decrease in the photocatalytic function. There is a fear. Moreover, in the coating of the solid content concentration of 3 to 20% by weight, the photocatalyst coating is applied several times to increase the surface presence ratio of the photocatalyst. However, the solid content concentration of the photocatalyst coating composition is 20% by weight. In the case of exceeding the above, the target coating thickness is reached by one application, and as a result, the surface abundance ratio of the photocatalyst is lowered, and the catalytic function tends not to be exhibited well.

  The photocatalyst coating composition of the present invention can be applied to the surface of a substrate and then dried or cured to form a coating film. Application methods include brush coating, sponge coating, spray coating, roll coating, flow coating, spin coating, dip coating, and the like. Drying or curing can be performed by standing at room temperature, forced drying, heating, ultraviolet irradiation, or the like.

  The photocatalyst coating composition of the present invention is applied to wallpaper, curtains, concrete, window glass and the like on the inner surface (inner wall, ceiling, floor) of a building structure.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these.

Example 1
1000 g of Apatec slurry (7-8% aqueous suspension of apatite-coated titanium oxide fine particles having an average particle size of 660 nm) manufactured by Marutake Sangyo Co., Ltd. was filtered through a 150-mesh filter paper. To the filtrate, 2.5 g of Nopco SN-5040 manufactured by San Nopco Co., Ltd. was added as a dispersion stabilizer, and dispersed with a homogenizer at 10000 rpm for 2 minutes. The solution was filtered again with 150 mesh filter paper to obtain a treatment liquid. The average particle diameter of the titanium oxide fine particles in the obtained treatment liquid was 231 nm.

  To 500 g of the treatment liquid, 210 g of MSH-4 (reactive silica fine particles having a silanol group, average particle diameter of 7.9 nm) manufactured by Mitsubishi Chemical Corporation and 340 g of water were added, and the mixture was stirred at 100 rpm for 3 minutes at a low speed. After that, it was filtered through a 150 mesh filter paper, and the filtrate was used as a paint. The obtained coating material was 3.2 wt% titanium, 16 wt% aqueous solvent, and 6.8 wt% solid content. In addition, the average particle diameter was measured using the dynamic light scattering type particle size distribution measuring apparatus (Horiba Ltd. make, LB-550). The characteristics of MSH-4 manufactured by Mitsubishi Chemical Corporation are as follows.

Appearance: Colorless transparent liquid Structure:

(Wherein n is an integer of 2 to 8) Hydrolyzed condensate obtained by catalyzing an organic amine of methyl silicate Active component (silica conversion content): 16%
Main solvent: water / methanol (35% by weight of water)
Viscosity: 2.0 ± 1.0 mPa · s
Density: 0.90 ± 0.05 g / cm ³
Average particle size: 7.9 nm
Weight average molecular weight: 1000

  Using a 1 mil applicator, a paint was applied to an acrylic plate whose surface was polished with # 200 water-resistant paper so that the film thickness when wet was 25 μm. Thereafter, it was dried at room temperature for 1 week to obtain a test specimen.

Comparative Example 1
Example 1 except that 67 g of Mitsubishi Rayon Co., Ltd. MX-2919 (45% suspension of acrylic resin, average particle size 129 nm) and 433 g of water were used instead of MSH-4 manufactured by Mitsubishi Chemical Co., Ltd. The coating material was adjusted in the same manner as described above to prepare a test specimen.

Comparative Example 2
In place of MSH-4 manufactured by Mitsubishi Chemical Co., Ltd., 75 g of water-based Glasca XW-305 (40% aqueous suspension of silicon hybrid acrylic resin, average particle size 87 nm) manufactured by JSR Co., Ltd. and 1.5 g of butyl cellosolve A coating was prepared in the same manner as in Example 1 except that a mixture of 423 g of water was used, and a test specimen was prepared.

Example 2
Same as Example 1 except that 60 g of Mitsubishi Chemical Corporation MSH-4, 50 g and MX-2919 (Mitsubishi Rayon Co., Ltd.) MX-2919 (average particle size 129 nm) and water 390 g were added to the treatment liquid of Example 1. A test specimen was prepared by the method described above.

(Surface analysis)
Carbon was vapor-deposited on the surface of the test body, and a surface composition image and a secondary electron image in the vertical direction were taken using a scanning electron microscope (manufactured by JEOL Ltd.). The results are shown in FIGS. The carbon deposition was performed by using SC-701C manufactured by Sanyu Electronics Co., Ltd. so that the carbon had a thickness of about 15 nm. The scanning electron micrograph was taken under the conditions of an acceleration voltage of 15 kV and a magnification of 1000 times in the composition image (reflected electron image). In the secondary electron image, the acceleration voltage was 5 kV and the magnification was 5000 times.

  FIG. 1 is a composition image 1 of the paint specimen obtained in Example 1, FIG. 2 is a secondary electron image 2 of the paint specimen obtained in Example 1, and FIG. 3 is a paint test obtained in Comparative Example 1. 4 is a secondary electron image 2 of the paint specimen obtained in Comparative Example 1, FIG. 5 is a composition image 1 of the paint specimen obtained in Comparative Example 2, and FIG. FIG. 7 is a composition image 1 of the paint test specimen obtained in Comparative Example 3, and FIG. 8 is a secondary electron image of the paint test specimen obtained in Comparative Example 3. 2 is shown. As a result, as shown in the composition image 1 of FIG. 1 and the secondary electron image 2 of FIG. 2, in Example 1, the composition considered to be fine particles of titanium oxide was uniformly dispersed in the surface layer, and the surface layer It was found that the particles were exposed well and the coating surface was dense. As shown in composition image 1 in FIGS. 3 and 5, in Comparative Examples 1 and 2, it is considered that a titanium component having a large particle diameter and a titanium component having a small particle diameter coexist. Moreover, it can be seen from the secondary electron image 2 in FIG. 6 that in Comparative Example 2, the exposure of titanium oxide on the coating film surface is reduced. In Example 2, fine particles of titanium oxide are uniformly dispersed from composition image 1 in FIG. 7, and the exposed state to the surface layer is also good. From secondary electron images 2 in FIGS. It turns out that it exists in a coating-film surface layer.

(Composition analysis)
Carbon was vapor-deposited on the surface of the test body, and surface atom quantification was performed using X-ray microanalysis (JXA-8900M manufactured by JEOL Ltd.). The obtained results are shown in Table 1.

  From Table 1, in Example 1, compared with Comparative Example 1 and 2, since there are many composition ratios of the oxygen atom of a coating-film surface, and a silicon atom, a silanol group exists in the coating-film surface and hydrophilicity is improved. I understand that. Also, the composition ratio of phosphorus atoms and calcium atoms is larger than that of the comparative example, and since these are atoms derived from calcium phosphate, apatite coating or free phosphate is applied to the coating surface layer. It suggests that it exists. The composition ratio of titanium atoms is 15.30% in Example 1, which is a result showing that apatite-coated titanium oxide fine particles are present in a large number on the coating surface layer. Also in Example 2, the composition ratio of atoms derived from calcium phosphate and titanium atoms is larger than that of the comparative example, and it can be seen that there are many apatite-coated titanium oxide fine particles on the surface of the coating film.

(Hydrophilicity at the initial stage of coating formation)
Using a Iwata spray gun W-100-101G, the coating composition of Example 1 and Comparative Examples 1 to 3 on a glass plate for testing 1 mm (manufactured by Coating Star Industry Co., Ltd.) under conditions of a pressure of 5 kg / cm ² . The test specimen was coated with a dry coating thickness of 10 μm.

  Using a contact angle measuring device (CA-X150, manufactured by Kyowa Interface Chemical Co., Ltd.), the contact angle with the ion exchange water on the surface of the specimen was measured.

  The results were 0 ° in Example 1, 16 ° in Example 2, and 43 ° and 60 ° in Comparative Examples 1 and 2, respectively. This result shows that the initial hydrophilicity in Examples 1 and 2 is excellent.

It is a composition image of the coating material test body obtained in Example 1 photographed using a scanning electron microscope. It is the secondary electron image of the coating material test body obtained in Example 1 image | photographed using the scanning electron microscope. It is a composition image of the paint test body obtained in Comparative Example 1, which was taken using a scanning electron microscope. It is a secondary electron image of the coating material test body obtained by the comparative example 1 image | photographed using the scanning electron microscope. It is a composition image of the coating material test body obtained by the comparative example 2 image | photographed using the scanning electron microscope. It is a secondary electron image of the coating material test body obtained by the comparative example 2 image | photographed using the scanning electron microscope. It is a composition image of the paint test body obtained in Example 2 photographed using a scanning electron microscope. It is the secondary electron image of the coating material test body obtained in Example 2 image | photographed using the scanning electron microscope.

Explanation of symbols

1 Composition image 2 Secondary electron image

Claims (3)

Apatite-coated titanium oxide fine particles, formula (1):
SiO _a (OH) _b (OR ¹ ) _c (OR ² ) _d (1)
(In the formula, 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3, 0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d), R ¹ is a methyl group or an ethyl group , R ² is an organic group different from R ¹ ) or a formula (2):
Si (OR ¹ ) ₄ (2)
A photocatalytic coating composition comprising a reactive silica fine particle having a weight average molecular weight of 1000 ± 200 and a water-based solvent comprising a hydrolyzed condensate of tetraalkoxysilane represented by the formula (wherein R ¹ is a methyl group or an ethyl group) object. The reactive silica fine particles have the formula (3):
The photocatalyst coating composition according to claim 1, wherein the photocatalyst coating composition is obtained by adding water and a catalyst to methyl silicate represented by the formula (wherein n is an integer of 2 to 8). The photocatalyst coating composition according to claim 1 or 2, wherein the reactive silica fine particles have an average particle size of 9 ± 3 nm.