WO2001021716A1

WO2001021716A1 - PHOTOCATALYST COATING MATERIAL FOR NOx REMOVAL AND METHOD OF FORMING COATING FILM OF THE SAME

Info

Publication number: WO2001021716A1
Application number: PCT/JP2000/006327
Authority: WO
Inventors: Kazuhiko Mori; Mitsuru Nakamura; Masanobu Tanaka
Original assignee: Nihon Parkerizing Co., Ltd.
Priority date: 1999-09-17
Filing date: 2000-09-14
Publication date: 2001-03-29
Also published as: AU7314500A; JP2001081412A

Abstract

A photocatalyst coating material for NOx removal which is capable of forming a film having satisfactory film properties, satisfactory NOx-removing ability, and long-term durability of the catalytic performance. To a mixture of 40,000 parts by weight of titanium dioxide and 1,000 to 40,000 parts by weight of a binder is added 1 to 200 parts by weight of a promotor metal-containing additive comprising a water-soluble palladium and/or platinum compound. According to need, an alcohol solution of 200 to 20,000 parts by weight of an alkoxysilane is further added. Thus, a water-based coating material is prepared. A coating fluid comprising this coating material is applied to a substrate. The coating is dried by heating either directly or after having been irradiated with ultraviolet having a wavelength shorter than 400 nm to precipitate palladium and/or platinum metal in a high concentration in a surface layer of the coating. Thus, a photocatalyst coating film for NOx removal is formed.

Description

Specification

Technical Field

The present invention relates to a photocatalytic coating material that exhibits functionality using light, particularly to a titanium dioxide photocatalytic coating material used for purifying NOx, and a method for forming a photocatalytic coating film. More specifically, the present invention is applied to exterior building materials such as road guard rails, sound barriers, building exterior walls, sidewalk panels, and poles to remove atmospheric NOx. TECHNICAL FIELD The present invention relates to a photocatalyst paint for purifying NOx and a method for forming a photocatalyst coating film, the main purpose of which is to purify NOx. Background art

Ceramic coatings that have better heat resistance and abrasion resistance than conventional organic coatings include alkali metal silicates, phosphates, silica sols, and the like. Types such as metal oxides are known.

These paints have the characteristics of inorganic paints, such as excellent heat resistance and abrasion resistance, but in recent years they have given ceramic coatings new functions. Attempts have been made to use metal oxide-based materials.

Among various ceramic materials, titanium oxide can exhibit an excellent photocatalytic effect, and exerts a high oxidizing power upon irradiation with ultraviolet rays.

In recent years, attempts to utilize this effect for environmental purification have been actively studied. Particular, the method of removing the N 0 and N 0 ₂ of which NO x gases with a titanium dioxide emissions photocatalyst from the oxidized to nitric acid in the atmosphere, It is recognized that there is no need for power or equipment, and that it has practical effects.

However, the titanium dioxide photocatalyst has the problem that the selection range of the binder is limited because most of the organic binder is decomposed by its catalytic activity. Further, in order to improve the gas decomposability, it is necessary that the coating film has air permeability, and its particle size is 1/10 to 1/10 as compared with ordinary pigments. Since it is an ultrafine particle of / 100, it is very difficult to form a good coating film in physical properties such as hardness and adhesion.

Further, the decomposition of N Ox gas is NO is oxidation to N 0 ₃ via the NO _2, in the coating film composed only of titanium dioxide emissions and by Nda, the oxidation rate from N 02 to N 0 ₃ for slow, is 1 Z 2 ~ l / 4 of N 0 being subjected to the oxidation without being oxidized only to N_〇 _2, Therefore toxic N 0 ₂ concentrations human body, and the arc increases rather There is a big problem that there are many. In addition, even if it shows good NOx decomposability in the early stage, there is also a problem that the NOx removing performance is remarkably deteriorated by long-term outdoor use.

As a means for solving these problems, a method of using a photocatalyst to which activated carbon is added for forming a coating film is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 6-31614. Further, a method of supporting ruthenium on titanium dioxide is disclosed in Patent Publication No. 2566361. However, even these improved methods are not yet sufficient in terms of durability and heat resistance to withstand long-term use, and as a result, paints and coatings that have practicality and durability Is not yet offered

Disclosure of the invention The present invention, the conventionally of the NO x purifying photocatalytic titanium oxide emissions paints and coatings has have to solve the above problems, by-product less of N 0 _2, high have the NO x purification rate is obtained, The present invention also provides a highly practical photocatalytic coating for NOx purification and a method for forming a photocatalytic coating film, which has high adhesion and hardness that can withstand use as an exterior material, and maintains these performances for a long time. Things.

In order to solve the above-mentioned problems, the present inventors first added various metal compounds to photocatalytic titanium dioxide and examined the effect on NOx decomposability. Titanium dioxide light, prepared by dissolving a small amount of a Pd or Pt compound complex in a catalyst and a binder, for example, a dispersion of silica particles, and adding an alkoxysilane as needed. It was found that the properties of the paint film and the NO x removal were significantly improved in the produced paint.

In addition, as a result of testing N〇X decomposability of titanium dioxide photocatalysts with different particle sizes, NOx removal performance was found to be higher when ultrafine anatase-type photocatalyst particles with a smaller particle size of 5 to 7ηπι were used. Although slightly improved, the hardness of the coating film was not sufficient, and it was confirmed that the particle diameter of the photocatalyst was preferably in the range of 10 to 40 nra.

Next, the present inventors studied a method of applying the NOx purifying photocatalytic coating material, and irradiated the coating with ultraviolet light during the coating and drying, whereby Pd and Pt were deposited. The present invention was completed by confirming that NOx decomposability was improved even when the amount of these metals was small. That is, the photocatalytic paint for purifying N〇x of the present invention (1) is composed of 4000 parts by weight of titanium dioxide and 1 to 200 parts by weight of a water-soluble Pd compound and a water-soluble compound in water. At least one kind of catalyst-enhancing metal-containing additive selected from the acidic Pt compounds, and 100 to 400 parts by weight of a binder. is there. The NOx purifying photocatalyst paint (2) of the present invention comprises, in water, 4000 parts by weight of titanium dioxide, and 100000 to 400 parts by weight of an inorganic binder. An A agent comprising 1 to 200 parts by weight of at least one catalyst-enhancing metal-containing additive selected from a water-soluble Pd compound and a water-soluble Pt compound; It is characterized by comprising a B agent containing 200 parts by weight of alkoxysilane and a liquid alcohol capable of dissolving the alkoxysilane.

In each of the NOx purification photocatalyst paints (1) and (2) of the present invention, the titanium dioxide preferably has an average particle diameter of 10 to 4.0 nra.

In the method (1) for forming a NOx purifying photocatalytic coating film of the present invention, a coating liquid containing the NOx purifying photocatalytic coating of the present invention is applied to a substrate surface to form a coating liquid layer. The coating liquid layer is dried by heating.

In the method (2) for forming a NOx purifying photocatalytic coating film of the present invention, a coating liquid containing the NOx purifying photocatalytic coating of the present invention is applied to a substrate surface to form a coating liquid layer. The coating liquid layer is irradiated with light containing ultraviolet light having a wavelength of less than 400 nm before drying, and then the coating liquid layer is heated and dried, whereby at least one of Pd and Pt is reduced. It is a feature of the present invention to form a coating film having a surface portion on which a catalyst-strengthening metal composed of a seed is concentrated. BEST MODE FOR CARRYING OUT THE INVENTION

The details of the present invention will be described below.

The NOx purifying photocatalyst paint (1) of the present invention is obtained by dissolving 40000 parts by weight of titanium dioxide and 1 to 200 parts by weight, preferably 5 to 50 parts by weight in water. Water-soluble Pd compounds and water-soluble Pt compounds It contains at least one kind of catalyst-reinforced metal-containing additive and 100 to 400 parts by weight, preferably 500 to 2000 parts by weight of a binder. . The titanium dioxide used in the present invention is not particularly limited, but those which are crystallized into an anatase type or a rutile type having high photocatalytic activity are preferable. A more preferred average particle size is from 10 to 40 nm, more preferably from 12 to 30 nm.

These titanium dioxide particles are obtained by a dry method by burning titanium tetrachloride, or by hydrolyzing titanium tetrachloride or titanium sulfate, or by hydrolyzing titanium alkoxide or acetyl acetonate. It is preferable to use a powder produced by a warm method by decomposition in water using a homomixer or the like.

There is no particular limitation on the water-soluble Pd compound and the water-soluble Pt compound, but palladium chloride or platinum chloride may be used.However, the pH of Pd or Pt, such as a chloroammine complex, may be used. It is more preferable to use a complex compound of Pd or Pt near neutrality and a chelate compound of Pd or Pt. It is permissible that some of these compounds are adsorbed on the surface of the titanium dioxide particles in the titanium dioxide dispersion or precipitated on the surface of the titanium dioxide particles.

If the amount of these water-soluble compounds of Pd or Pt is less than 1 part by weight with respect to 4000 parts by weight of titanium dioxide, the N 0 X removal rate of the resulting coating film is insufficient. This is not preferred because the deterioration of the catalyst with time increases, and when it exceeds 200 parts by weight, the paint becomes expensive, which is not preferred.

The binder contained in the paint of the present invention is not particularly limited, but water-based sol, alcohol-based sol, alumina sol, zeolite, smectite, etc. may be used. Is preferred. Of these, use smectites or zeolite which are excellent in N 02 adsorption effect This is the most preferred. It is preferable that the blending amount of the binder is 100 to 400 parts by weight based on 4000 parts by weight of titanium dioxide. If the amount is less than 1000 parts by weight, the adhesion of the resulting coating film will be reduced. If it exceeds 40000 parts by weight, the content of titanium dioxide will be too low, and It is not preferable because the effect is insufficient. It is preferable that the photocatalytic paint for purifying N Ox of the present invention is produced and stored in two liquids of agent A and agent B, mixed and reacted before use, and then applied. In the composition of both solutions when divided into two solutions, as the A agent, 4000 parts by weight of titanium dioxide in water and 5.0000 to 400 parts by weight, preferably 100 parts by weight Selected from 0.000 to 300 parts by weight of inorganic binder and 1 to 200 parts by weight, preferably 10 to 50 parts by weight of water-soluble Pd and water-soluble Pt compound And at least one kind of catalyst-enhancing metal-containing additive. The total solid content is preferably dispersed in water so as to have a concentration of 5 to 50%, and is necessary for controlling the reaction rate with the alkoxysilane contained in the agent B. It is more preferable to adjust the pH to 3 to 5 or 8 to 9 by adding a small amount of a pH adjuster such as an acid or an alkali as necessary.

Further, as the agent B, 200 to 200 parts by weight of alkoxysilane relative to 40000 parts by weight of titanium dioxide, and an amount capable of dissolving the alkoxysilane are used. Contains alcohol. The types of alkoxysilanes include methyltrialkoxysilane, ethyltrialkoxysilane, and phenyltriethoxysilane, and among these, methyltrialkoxysilane is the most preferred. It is most preferable to use it, and a part of this may be replaced with tetraalkoxysilane or a partial hydrolyzate thereof.

The mixing ratio of the A agent and the B agent is such that the amount of the alkoxysilane is 200 to 2000 parts by weight, preferably 40.0 parts by weight of titanium dioxide. It should be 2000 to 1000 parts by weight. A range of 400 to 100 parts by weight is more preferred. The liquid alcohol that dissolves the alkoxysilane is preferably selected from lower alcohols such as methanol, ethanol, and isopropyl alcohol. Alkoxysilane reduces and precipitates Pd or Pt ions, so even if the amount of these metals added is extremely small relative to the amount of titanium dioxide, the effect of removing NOx can be significantly improved. Can be. If the amount of alkoxysilane is less than 200 parts by weight relative to 400 parts by weight of titanium dioxide, the hardness of the resulting coating film is insufficient, which is preferred. Exceeding 0.000 parts by weight is not preferred because the NO x removal rate of the resulting coating film is reduced.

In the method (1) for forming a coating film using the NOx purifying photocatalytic paint (1) or (2) of the present invention, the NOx purifying photocatalytic paint (1) or (2) is used as a substrate. A coating liquid layer is formed by applying the composition to the surface, and the coating liquid layer is heated and dried to form a coating film. In the coating film forming method (2) of the present invention, a coating solution containing the NOx purifying photocatalytic coating material (1) or (2) is applied to the surface of the substrate, and the ultraviolet light having a wavelength of less than 400 nm is dried before drying. Irradiation is performed on the coating liquid layer to form a Pd or Pt concentrated layer on the coating film surface.

As a result of this treatment, at least one kind of Pd and Pt of the catalyst-reinforced metal precipitates on the surface of the coating solution where ultraviolet light can easily reach, and the distribution of the catalyst-reinforced metal on the surface is concentrated. However, a high effect can be obtained even by adding a small amount of metal. It is not preferable that the light having a wavelength of less than 40 O nm does not exist because the above-mentioned effect by light irradiation cannot be obtained. The drying by heating in the method (1) or (2) of the present invention is preferably carried out at 80 to 400 ° C, more preferably at 150 to 250 ° C. The heating drying time can be set appropriately according to the heating drying temperature. However, it is generally 1 to 30 minutes. Example

The present invention will be described specifically with reference to the following examples, but the present invention is not limited by these examples.

Examples 1 to 8 and Comparative Examples 1 to 4

In Examples 1 to 8 and Comparative Examples 1 to 4, the following materials were used.

(1) Carbon dioxide

In Comparative Examples 1 to 2, Examples 1 to 4, and Examples 7 to 8, P—25 (anayuichi + rutile, particle size: 20 nra, manufactured by Nippon Aerosil Co., Ltd.) was used as titanium dioxide. ) It was used. In other comparative examples and examples, ST-01 (anatase: particle size: 7 nm) manufactured by Ishihara Sangyo Co., Ltd. was used. About 200 g of titanium dioxide was mixed with 800 ml of water, and this mixture was dispersed with a homomixer.

(2) Pd compound and Pt compound

Palladium chloride or platinum chloride was dissolved in water, and this solution was neutralized with ammonia water to obtain a chlorammine pd or Pt complex solution, which was added to a titanium dioxide dispersion.

(3) Inorganic binder

In Comparative Examples 1 to 3, Examples 2 to 3, and Example 7, a water-based silica sol (Snowtex N) manufactured by Nissan Chemical Industries, Ltd. was used. In Comparative Example 4, Example 5, and Example 8, aluminum sol (alumina sol 200) manufactured by Nissan Chemical Industries, Ltd. was used. In Examples 4 and 6, a smectite (Rabonite XGL manufactured by Nippon Silica Co., Ltd.) was used.

(4) Preparation of coating solution

Pd aqueous solution or Pt compound aqueous solution and inorganic binder It was added to the aqueous dispersion of titanium fluoride to obtain Agent A, and methyltrimethoxysilane was used separately as alkoxysilane, which was quadrupled (weight) with isoprono and ノール anol. The diluted solution was used as agent B. Both AB agents were mixed, the pH of the mixed solution was adjusted to 4 to 5 with acetic acid, and the mixture was aged for 1 hour to prepare a coating solution having the composition shown in Table 1.

Table 1 shows the composition of the coating solution composed of a mixture of the A agent and the B agent of the photocatalytic coating used in each of Comparative Examples 1 to 4 and Examples 1 to 8. The total solids concentration in each coating solution was 35% by weight.

In Comparative Example 1, Comparative Example 3, Example 1, Example 4, and Example 7, the aluminum primer was coated with a silicone primer and dried at 80 ° C. The photocatalyst coating liquid of the present invention was applied. In Comparative Example 2, Examples 2 to 3, and Examples 5 to 6 and Example 8, a plate obtained by applying a silicone primer to a plate coated with powdered polyester on a zinc-plated steel plate was used.

The test piece was applied with the prepared coating solution (solid content: 35) using a spray gun so that the film thickness became about 10 m.

Drying was performed at 150 ° C. for 10 minutes in a drying oven. In the actual施例7-8, dried at 0. 7 mW / cm ² intensity black click Lai Bok (wavelength 3 6 5 nm) to 1 0 minutes irradiated after 1 5 0 ° C after application .

Evaluation of coating film performance was performed according to the following test methods and evaluation criteria. The results are shown in Table 1.

(1) Hardness of coating film

The hardness of the dried coating film was measured with a pencil for JIS-K540 drawing test.

(2) Adhesion

Adhesion of coating film JIS-K540 The adhesion of the coating film was determined according to the adhesion test. A film that did not peel at all was judged as pass (〇), and a film that was peeled was judged as unacceptable (X).

(3) N Ox removal rate

A 10 cm square test piece was placed in a pyrex glass measuring cell, and 1 ppm of NO gas was continuously passed at a flow rate of 1.2 L / min. In this case, continuously irradiated with ultraviolet rays with a wavelength of 3 6 5 nm from the upper glass windows black Cry Bok, the N 0 and N 0 ₂ concentration through the cell gas Shimadzu atmospheric N Ox gas analysis equipment It was measured and the N〇 X removal rate was calculated. (4) Outdoor exposure test

To confirm whether the performance could be maintained even when used outdoors for a long period of time, a 6-month outdoor exposure test was performed, and the performance after exposure was tested.

Electrified N N x Composition and depainting performance of Kakawa photocatalytic paint

As is clear from the results of the test evaluation of the photocatalytic paints for N〇X purification in Comparative Examples 1 to 4 and Examples 1 to 8 shown in Table 1, the composition of the titanium oxide coating solution having a composition outside the scope of the present invention. In Comparative Examples 1 to 4 in which was used, the coating film appearance, adhesion, hydrophilicity, and photocatalytic properties were all unsatisfactory. On the other hand, in Examples 1 to 8 using the titanium oxide paint and the method for forming a titanium oxide coating film of the present invention, good coating film appearance, adhesion, hydrophilicity, and photocatalytic performance were obtained. Industrial applicability

According to the photocatalytic paint for NOx purification and the method for forming a coating film of the present invention, "good coating film properties" and "NOx purification rate", which were not compatible with each other, and " As a result, a highly practical coating film can be obtained as a N〇x purification material. In particular, N 塗布 x is emitted from tobacco and heating equipment when applied to the exterior of buildings, such as urban areas, intersections and their surroundings, where NOx concentration is high, or applied indoors to walls and ceilings. It has a wide range of uses, such as removal, and is of great practical value as a living environment measure.

Claims

The scope of the claims

1. In water, 40000 parts by weight of titanium dioxide and 1 to 200 parts by weight of metal, at least one selected from the group consisting of water-soluble Pd compounds and water-soluble Pt compounds A photocatalytic paint for purifying N〇x, comprising: a catalyst-reinforced metal-containing additive; and 100 to 400 parts by weight of a binder.

2.000 parts by weight of titanium dioxide, 100 to 400 parts by weight of an inorganic binder, and 1 to 200 parts by weight of a water-soluble Pd compound and A agent containing at least one catalyst selected from water-soluble Pt compounds and a reinforcing metal-containing additive, and 200 to 200 parts by weight of alkoxysilane and this alkoxysilane are dissolved. A NOx purifying photocatalytic paint, comprising a B agent containing an obtainable amount of liquid alcohol.

3. The photocatalytic paint for purifying NOx according to claim 1 or 2, wherein the titanium dioxide has an average particle size of 10 to 40 nm.

4. The coating liquid containing the N〇x purification photocatalytic coating according to any one of claims 1 to 3 is applied to the surface of the base material to form a coating liquid layer, and this coating is performed. A method for forming a photocatalytic coating film for NOx purification, characterized by heating and drying a liquid layer.

5. A coating liquid containing the NOx purification photocatalytic coating according to any one of claims 1 to 3 is applied to a substrate surface to form a coating liquid layer. Before drying the layer, the layer is irradiated with light containing an ultraviolet ray having a wavelength of less than 40 nm, and then the coating liquid layer is dried by heating, whereby at least one of Pd and Pt is reduced. A method for forming a NOx purifying photocatalytic coating film, comprising forming a coating film having a surface portion on which a catalyst-reinforced metal comprising a seed is concentrated.