JPH10176140A - Photocatalyst coating composition and photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photocatalyst coating compsn. having an excellent photocatalytic function and to prepare a photocatalyst using the same. SOLUTION: This photocatalyst coating compsn. is composed mainly of a partial hydrolyzate of a silane compd. and a photocatalyst particle. In this case, an acid or an alkali is added to enhance the degree of condensation of the partial hydrolyzate of the silane compd., thereby increasing the viscosity to a value which is 2 to 20 times larger than the initial viscosity. The photocatalyst is prepd. by coating a substrate with the compsn., drying the coating, and curing the dried coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to plastics,
For photocatalytic coatings that exhibit photocatalytic effects such as antifouling performance, deodorizing performance, and contaminant removal performance in environmental air by being fixed to the surface of wood, metals, ceramics, and their painted products. The present invention relates to a composition and a photocatalyst body on which the photocatalyst coating composition is fixed.

[0002]

2. Description of the Related Art A photocatalyst is a substance that exhibits a photocatalytic function when irradiated with light having a wavelength having energy equal to or greater than its band gap.
Tungsten oxide, iron oxide, strontium titanate,
It refers to a known metal compound semiconductor powder such as cadmium sulfide or cadmium selenide. When these substances are irradiated with light having a wavelength having energy equal to or greater than the band gap, photoexcitation generates electrons in the conduction band and holes in the valence band. Among the electron-hole pairs generated by these light irradiations, the high reducing power of the electrons and the high oxidizing power of the holes are used for the decomposition of organic substances and the decomposition of water. In order to use these properties for environmental purification such as decomposing and removing harmful substances and odorous substances, it is necessary to immobilize the catalyst powder on the surface of the substrate, and various studies have been made.

[0003] JP-A-7-171408 proposes a photocatalyst in which photocatalyst particles are adhered to a substrate via a hardly decomposable binder.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. 7-1
The point of the photocatalyst body described in JP-A-71408 is that the photocatalyst powder is fixed to the substrate using a hardly decomposable binder that is hardly decomposed and deteriorated by the photocatalyst particles as a binder. No mention is made of the effect of the type and structure of the adhesive on the photocatalytic performance.

In view of such circumstances, the present inventors have conducted intensive studies on the effects of the type and structure of the coating composition on photocatalytic performance in a photocatalyst coating composition containing photocatalyst particles. Increase the degree of condensation of the partial hydrolyzate to increase the viscosity to 2
By increasing the ratio by up to 20 times, it was found that the photocatalyst obtained by using the same exhibited excellent photocatalytic performance, and the present invention was completed.

[0006]

That is, the present invention provides a photocatalyst coating composition containing a partial hydrolyzate of a silane compound and a photocatalyst particle as main components to increase the degree of condensation of the partial hydrolyzate of the silane compound. A photocatalyst coating composition characterized by having a viscosity 2 to 20 times the initial viscosity of the composition, and a photocatalyst obtained by applying the composition onto a substrate, drying and curing the composition. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The silane compound in the present invention is represented by the following general formula:

Embedded image (wherein, X is an alkyl group, an amino group, an epoxy group, methacryloxy group or mercapto group, Y is an alkoxy group or chlorine atom, n represents an integer of 0~4) X _n SiY _4-n in It is a compound shown.

The silane compound includes, for example, methyltrichlorosilane, tetrachlorosilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrisilane. Examples include methoxysilane, tetramethoxysilane, tetraethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, and the like.

The partial hydrolyzate of the silane compound is obtained by hydrolyzing the silane compound in a mixed solvent such as water and alcohol in the presence of an acid.

From the viewpoint of the photocatalytic performance of the photocatalyst obtained by applying the photocatalyst coating composition, as well as the weather resistance, hot water resistance, abrasion resistance, etc., a partially hydrolyzed silane compound represented by the following general formula:

A partial hydrolyzate of tetraalkoxysilane represented by the formula: Si (OR ¹ ) ₄ (wherein R ¹ represents an alkyl group having 1 to 4 carbon atoms) and a compound represented by the general formula:

Embedded image R ² _n Si (OR ³⁾ in _4-n (wherein, R ² is a hydrocarbon group having 1 to 6 carbon atoms, R ³ is an alkyl group having 1 to 4 carbon atoms, n represents 1 to 3 A mixture of partial hydrolysates of the silane compound represented by the following general formula:
A co-partial hydrolyzate with a silane compound represented by Chemical formula 6 is preferable.

That is, for example, a partial hydrolyzate of tetraalkoxysilane such as tetramethoxysilane and tetraethoxysilane and trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane A mixture of a partial hydrolyzate of an alkylalkoxysilane such as silane or a co-partial hydrolyzate of a tetraalkylsilane and an alkylalkoxysilane is preferably used.

These partial hydrolysates can be obtained by separately or mixing a silane compound represented by the above general formula (5) and a silane compound represented by the above general formula (6), for example, in a mixed solvent such as water and alcohol. It is obtained by hydrolysis in the presence of an acid.

The ratio of the partial hydrolyzate of the silane compound represented by the general formula (5) and the partial hydrolyzate of the silane compound represented by the general formula (6) is determined by the ratio of the partial hydrolyzate of the silane compound represented by the general formula (5). Is converted to SiO ₂ , and the partial hydrolyzate of the silane compound represented by the general formula (6) is converted to R ²
It is preferable that the weight ratio is 5/95 to 95/5 in terms of _n SiO _{(4-n) / 2} (R ² and n are the same as above). If the partial hydrolyzate of the silane compound represented by the general formula (5) exceeds 95% by weight, the flexibility of the coating film deteriorates and cracks are likely to occur. On the other hand, if the hydrolyzate is less than 5% by weight, the abrasion resistance decreases.

The partial hydrolyzate of these silane compounds is dissolved in a solvent to form a composition. As the solvent, alcohols, ketones, esters, cellosolves, ethers, halides, carboxylic acids, aromatic compounds, and the like can be used, and the selection depends on factors such as the base material used and the evaporation rate. And is widely mixed with the components of the coating composition. In particular, lower alcohols (eg, methanol, ethanol, propanol, butanol), lower alkyl carboxylic acids (eg, formic acid, acetic acid, propionic acid), aromatic compounds (eg, toluene, xylene), esters (eg, ethyl acetate, Butyl acetate) and cellosolves (eg,
It is preferable to use methyl cellosolve, butyl cellosolve) alone or in combination. The amount of solvent used is
It can be selected in an appropriate amount according to the required thickness and coating method of the coating film, and further the dispersion state at the time of photocatalyst particle dispersion, but the concentration of the partial hydrolyzate of the silane compound in the composition is 5 to 35% by weight. % [X _n SiO _{(4-n) / 2} (X and n are the same as those described above);
When the silane compound is used, SiO ₂ and R ² _n
SiO.sub. _{(4-n) / 2} ].

In the present invention, a composition obtained by dissolving a partial hydrolyzate of a silane compound as a main component in a solvent is used so that the viscosity of the partial hydrolyzate is 2 to 20 times the initial viscosity of the composition. Must be enhanced. Increasing the degree of condensation of the partial hydrolyzate may be performed after dispersing the photocatalyst particles described below in the composition, or may be performed before dispersing the photocatalyst particles, and then dispersing the photocatalyst particles. Good.

Increasing the degree of condensation of the partial hydrolyzate is
For a composition containing a partial hydrolyzate of a silane compound as a main component, a small amount of an acid or an alkali is added, and by heating if necessary, the viscosity becomes 2 to 20 times the initial viscosity of the composition. As described above, the condensation of the partial hydrolyzate of the silane compound proceeds to increase the degree of condensation. When the viscosity is less than twice the initial viscosity of the composition, the photocatalytic performance of the obtained photocatalytic coating composition is insufficiently improved, and
If it exceeds 0 times, it is unsuitable from the viewpoint of the performance of the obtained coating film and the handling of the composition for photocatalytic coating.

As described above, the photocatalyst particles in the present invention are particles that exhibit a photocatalytic function when irradiated with light having a wavelength having energy equal to or greater than the band gap (shown in Table 1 below). Known metal compound semiconductors such as zinc oxide, tungsten oxide, iron oxide, strontium titanate, cadmium sulfide, and cadmium selenide can be used alone or in combination of two or more. Among these photocatalyst particles, titanium oxide which is excellent in transparency and durability and is harmless is preferably used.

[0018]

[Table 1]

A metal or a metal compound such as vanadium, copper, palladium, silver, platinum, or gold may be contained inside or on the surface of the photocatalyst particles for the purpose of enhancing the photocatalytic function.

Further, an adsorbent may be used together with the photocatalyst particles, and it is preferable to use the photocatalyst particles and the adsorbent together in order to improve the deodorizing performance and the performance of removing pollutants in the ambient air. As the adsorbent, a carbon-based adsorbent such as activated carbon, a zeolite-based adsorbent, a molecular sieve, a metal oxide-based adsorbent, a chelate resin, and the like are preferable.

The amount of the photocatalyst particles in the composition for photocatalyst coating in the present invention is a value converted into a partial hydrolyzate of the photocatalyst particles and a silane compound (X _n SiO _{(4-n) / 2).} And when the silane compound of formula (6) is used, the total amount of SiO ₂ and R ² _n SiO _{(4-n) / 2} ] is preferably 5 to 70% by weight. If the particle amount is less than 5% by weight, the photocatalytic performance is not sufficient, and if it exceeds 70% by weight, the adhesion of the composition to the substrate is unfavorably deteriorated.

Photocatalyst particles can be dispersed in the composition by adding the photocatalyst particles to the composition, stirring and dispersing using a homomixer, a magnet stirrer, or the like, dispersing using a ball mill, a sand mill, an attritor, or the like. This is performed by dispersing using, for example. The photocatalyst particles are added and dispersed in a particle form, a sol form, or the like.

The composition for photocatalyst coating of the present invention comprises:
The composition is applied on a substrate, heated and dried at a temperature of 70 ° C. or more, and cured to form a coating film having high hardness, which is fixed on the substrate to give a photocatalyst. Acids such as hydrochloric acid, phosphoric acid, toluenesulfonic acid, organic amines, metal salts of organic carboxylic acids,
Hardening accelerators such as metal thiocyanates, metal borates, and organotin compounds can be added to the composition.
Further, it is also possible to add a surfactant for the purpose of preventing repelling of a coating film and pinholes.

Further, for the purpose of imparting flexibility to the composition of the present invention, for example, a copolymer of (meth) acrylates described in JP-B-53-45222 may be added. An ultraviolet absorber, an antistatic agent and the like may be added.

The composition of the present invention can be applied to a substrate by any conventional method such as spray coating, dip coating, roll coating and the like.

The thickness of the formed coating film varies depending on the type and amount of the photocatalyst particles, the viscosity of the photocatalyst coating composition, and the like, but the thickness is preferably about 0.1 to 30 μm. If too thin, the amount of photocatalyst particles will decrease,
Antifouling performance and deodorant performance due to photocatalysis are reduced,
If the thickness is too large, there is a fear that the coating film is cracked or the like, which is not preferable.

When the photocatalyst having the photocatalyst coating composition of the present invention immobilized on a substrate is irradiated with light having a wavelength having an energy equal to or greater than the band gap of the photocatalyst particles, the dirt attached to the surface of the photocatalyst is reduced. Decompose substances,
Pollutants such as malodorous substances and nitrogen oxides present near the photocatalyst can be removed by oxidation or decomposition. As the light source, for example, sunlight, a fluorescent lamp, a black light, a mercury lamp, or the like is used.

[0028]

The photocatalyst in which the composition for photocatalyst coating of the present invention is immobilized on a substrate has an excellent photocatalytic function, and can decompose dirt attached to the surface of the photocatalyst,
It is effective in removing pollutants such as malodorous substances and nitrogen oxides existing near the photocatalyst by oxidation and decomposition.

[0029]

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. Example 1 A hydrolysis vessel equipped with a reflux condenser was charged with 7.7 g of isopropyl alcohol, 33.5 g of tetraethoxysilane, and 64.0 g of methyltriethoxysilane, mixed and dissolved, and further 24.8 g of a 0.003 N hydrochloric acid aqueous solution. Was added thereto, and the solution was refluxed for 2 hours while stirring to carry out cohydrolysis. After the reaction, the mixture was cooled to room temperature to obtain a co-partial hydrolyzate solution. The resulting solution was 11.9% by weight of tetraethoxysilane partial hydrolyzate in terms of SiO ₂ , and CH ₃ SiO
Methyltriethoxysilane partial hydrolyzate 2 in _1.5 conversion
6.0% by weight.

The co-partial hydrolyzate solution 65 prepared above
35 parts by weight of n-butanol was added to parts by weight to obtain composition A. SiO ₂ and CH ₃ S in the composition A
The weight of the partial hydrolyzate in terms of iO _1.5 is 16.9% by weight.
Met. The viscosity of composition A (all viscosities described below were measured at room temperature using a B-type viscometer) was 3.0.
cp.

Next, an aqueous 0.1 N sodium hydroxide solution was added to 30 g of the composition A (the amount of addition was 0.01 to 10%).
0.3 ml), the degree of condensation of partial hydrolysis is increased, and composition B (viscosity: 14.1 cp), composition C (viscosity: 19.3 cp), and composition D (viscosity: 47.3 cp)
I got

To 100 parts by weight of the above composition B, 4.7 parts by weight of ST-01 (photocatalytic titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd.) was added and stirred and dispersed as a photocatalyst particle to obtain a photocatalyst coating composition. . The content of the photocatalyst particles in the photocatalyst coating composition is determined by a partial hydrolyzate of the photocatalyst particles and a silane compound (SiO ₂ and CH ₃ S).
(a value converted to iO _1.5 ).

This photocatalyst coating composition was added in an amount of 0.3
After coating on an aluminum plate with a thickness of 75 cm ^{2 by} a dipping method (pulling speed: 10 cm / min), 100 ° C.
And dried for 2 hours to obtain a photocatalyst. The photocatalyst was placed in a glass container of about 3 liters, and then a standard gas of nitric oxide was injected and sealed. Next, the surface of the sample was irradiated with black light so that the ultraviolet intensity (260 to 400 nm) was 1.3 mW / cm ^2, and NOx in the container was
The gas concentration was measured over time with a NOx detector tube (11 L, manufactured by Gastech). Table 2 shows the results.

Example 2 To 100 parts by weight of the composition C obtained in Example 1, 4.7 parts by weight of ST-01 (photocatalytic titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd.) were added as photocatalyst particles, followed by stirring and dispersion. A coating composition was obtained. The content of the photocatalyst particles in the photocatalyst coating composition is determined by the partial hydrolyzate of the photocatalyst particles and the silane compound (SiO ₂ and CH ₃ SiO
(Converted to _1.5 ) and 22% by weight. Thereafter, a photocatalyst was prepared in the same manner as in Example 1,
Ox gas concentration was measured. Table 2 shows the results.

Example 3 To 100 parts by weight of the composition C obtained in the same manner as in Example 1 was added 16.9 parts by weight of ST-01 (photocatalytic titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd.) as photocatalyst particles, followed by stirring and dispersion. Thus, a composition for photocatalyst coating was obtained. The content of the photocatalyst particles in the composition for photocatalyst coating was 50% based on the total amount of the photocatalyst particles and the partial hydrolyzate of the silane compound (values converted into SiO ₂ and CH ₃ SiO _1.5 ).
% By weight. Hereinafter, a photocatalyst was prepared in the same manner as in Example 1, and the NOx gas concentration was measured. Table 2 shows the results
Shown in

Example 4 To 100 parts by weight of the composition D obtained in Example 1, 4.7 parts by weight of ST-01 (photocatalyst titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd.) was added and stirred and dispersed. A coating composition was obtained. The content of the photocatalyst particles in the photocatalyst coating composition is determined by the partial hydrolyzate of the photocatalyst particles and the silane compound (SiO ₂ and CH ₃ SiO
(Converted to _1.5 ) and 22% by weight. Thereafter, a photocatalyst was prepared in the same manner as in Example 1,
Ox gas concentration was measured. Table 2 shows the results.

Comparative Example 1 To 100 parts by weight of the composition A obtained in the same manner as in Example 1, 4.7 parts by weight of ST-01 (photocatalytic titanium oxide particles manufactured by Ishihara Sangyo) were added as photocatalyst particles, followed by stirring and dispersion. Thus, a composition for photocatalyst coating was obtained. The content of the photocatalyst particles in the photocatalyst coating composition is determined by the partial hydrolyzate (SiO ₂ and C
(Converted to H ₃ SiO _1.5 ). Hereinafter, a photocatalyst was prepared in the same manner as in Example 1, and the NOx gas concentration was measured. Table 2 shows the results.

[0038]

[Table 2]

Claims (11)

[Claims] 1. A photocatalyst coating composition containing a partial hydrolyzate of a silane compound and photocatalyst particles as main components to increase the degree of condensation of the partial hydrolyzate of the silane compound to 2 to 20 times the initial viscosity. A composition for photocatalyst coating, wherein the composition is doubled. 2. After making the viscosity 2 to 20 times the initial viscosity,
The composition according to claim 1, wherein the photocatalyst particles are dispersed. 3. The composition according to claim 1, wherein the viscosity is made 2 to 20 times the initial viscosity after dispersing the photocatalyst particles. Partially hydrolyzed wherein the silane compound has the general formula of 1 ## STR1 X _n SiY _4-n (wherein, X is an alkyl group, an amino group, an epoxy group, methacryloxy group or mercapto group, Y Is an alkoxy group or a chlorine atom, and n represents an integer of 0 to 4). Tetra partial hydrolyzate wherein the silane compound has the general formula of 2 ## STR2 ## Si (OR ¹⁾ ₄ where (wherein, R ¹ represents an alkyl group having 1 to 4 carbon atoms) represented by R ² _n Si (OR ³ ) _{4 -n} (where R ² is a hydrocarbon group having 1 to 6 carbon atoms, and R ³ is an alkyl group having 1 to 4 carbon atoms) , N represents an integer of from 1 to 3), and / or a mixture of the respective partial hydrolysates. 6. A tetraalkoxy compound represented by the general formula:
The weight ratio of the silane to the compound represented by the general formula 3 is
Each SiO_TwoAnd R^TwoSiO_{(4-n) / 2}(R ^TwoAnd n are
5/95 to 95/5
Item 6. The composition according to Item 5. 7. The method according to claim 1, wherein the concentration of the partial hydrolyzate of the silane compound is 5 to 35% by weight in terms of X _n SiO _{(4-n) / 2} (X and n are the same as above). Composition. 8. The amount of the photocatalyst particles is 5 to 70% by weight based on the total of the photocatalyst particles and the partial hydrolyzate of the silane compound (converted to X _n SiO _{(4-n) / 2} ). A composition as described. 9. The composition according to claim 1, wherein the photocatalyst particles are titanium oxide particles. 10. The composition according to claim 1, wherein an acid or an alkali is added to increase the degree of condensation of a partial hydrolyzate of the silane compound. 11. Applying the composition according to claim 1 on a substrate,
Dry and cured photocatalyst.