JP2002256222A - Cured coating film holding photo-oxidation catalyst with high warm water resistance - Google Patents

Abstract

(57) [Problem] To provide an aqueous coating composition and a cured coating film which form a fluorine-based cured coating film having high temperature resistance despite being cured at room temperature. SOLUTION: Photooxidation catalyst particles, organic solvent-soluble fluororesin, and flaky silica particles composed of flaky silica secondary particles formed from flaky silica flake primary particles are dispersed in an aqueous medium. Is prepared, applied to a substrate, and dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cured coating film formed on the surface of a substrate and holding a photo-oxidation catalyst such as titanium oxide. It relates to a system cured coating film.

[0002]

2. Description of the Related Art In recent years, photo-oxidation catalyst particles such as titanium oxide have a high environmental purification ability capable of strongly decomposing and treating various environmental pollutants such as water pollutants and air pollutants at normal temperature and pressure. It has been noted that since it was found to be a potential one, it could be a powerful key in addressing increasingly serious environmental issues, and it is well known that there are active studies in various places for practical use .

[0003] In practical use, first,
It is essential to immobilize the finely divided catalyst particles on various substrates, and various immobilization methods such as a sol-gel firing method, an immobilization method using a porous substance, a kneading method, and a deposition method have been proposed. . Above all, a method of dispersing the catalyst particles in a highly durable resin to form a coating (hereinafter, sometimes referred to as a photocatalytic coating) is that the coating can be fixed at a low temperature without the need to bake, It is expected to be a method that can be applied to various structures because it has features such as being able to strongly fix the catalyst without fear and being applicable to a wide range of base materials.

As a binder for the photocatalytic paint, an inorganic binder may be used, but an organic resin having high oxidation resistance, particularly a fluororesin, is most preferred. As the fluororesin, for example, an alternating copolymer of a polymerized unit based on fluoroethylene and a polymerized unit based on alkyl vinyl ether (usually a solvent (Referred to as melt-type fluororesin).

[0005] Originally, photooxidation catalysts were used to decompose environmental pollutants.
As is clear from the fact that the first idea to apply to the treatment was proposed in the field of wastewater treatment, one of the major uses of the photooxidation catalyst is in the purification of industrial wastewater. The water pollutants targeted here include organic phosphorus compounds, nitrogen-containing compounds, cyanide compounds, coloring substances, organochlorine compounds, crude oil, etc., but in the case of wastewater, waves, water streams,
Since mechanical force due to water pressure or the like is applied to the coating film, it is required that the film has a higher strength so as to withstand water pressure or the like than when used in the atmosphere.

Further, the temperature of the waste water to be treated is not always at the room temperature level, and often exceeds, for example, 50 ° C. Especially in the case of industrial wastewater, if the temperature of the wastewater is high, heat recovery may be performed from the wastewater for the purpose of energy saving, and it is estimated that the temperature level of the wastewater after heat recovery is often around 60 ° C. Is done.

As described above, in the case of treating industrial wastewater, a cured film having a photooxidation catalytic action (hereinafter, sometimes referred to as a photocatalyst film) is a high-strength film. At the same time, it is desirable for the strength to have a warm water resistance of about 60 ° C.

Conventionally, for example, in a photocatalytic paint using an organic solvent-soluble fluororesin as a binder for anatase type titanium oxide particles, in order to improve the strength of the coating film,
It has been proposed to add silica or the like as a filler to the fluororesin (see, for example,
363, JP-A-11-1659 and the like. ).

However, according to the study of the present inventors, in a photocatalytic paint to which the above silica or the like is added as a filler, the fluorine-based paint composition is applied to a substrate,
The cured coating film obtained by drying at room temperature is easily peeled off from the cured coating film in hot water resistance (for example, immersion treatment in hot water at 60 ° C. for 7 days), and good durability is obtained. Not found. It is possible to impart such warm water resistance by improving the hardness of the coating film by heating the above photocatalytic coating material at 100 ° C. or higher after forming the coating film. Regardless of the piece level, it is extremely difficult to actually apply it on a large-area substrate at the site of a wastewater treatment facility or the like and heat-treat and cure it.
Not practical.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cured coating film formed on the surface of a substrate and holding a photo-oxidation catalyst such as titanium oxide. There is no need to heat and cure in the above, just by leaving it at room temperature as it is, it cures quickly, and
An object of the present invention is to provide a fluorine-based aqueous coating composition capable of forming a fluorine-based cured coating film having high warm water resistance despite curing at room temperature, and a cured coating film thus formed.

[0011]

That is, according to the present invention, the following inventions are provided. (1) A room temperature-curable fluorine-based cured coating film formed on the surface of a base material and holding a photo-oxidation catalyst, wherein a binder component in the cured coating film is an organic solvent-soluble fluororesin. And flaky silica particles having a laminar structure composed of leaf-like silica secondary particles formed by laminating a plurality of flaky silica primary particles in which the flake primary particles are oriented in parallel with respect to each other. Wherein the content of the photo-oxidation catalyst in the cured coating film is 50 to 70% by mass and the binder component is 50 to 30% by mass. (Hereinafter sometimes referred to as a fluorine-based cured coating film of the present invention or a cured coating film of the present invention).

(2) A fluorine-based aqueous coating composition for forming a room temperature-curable cured coating film holding a photo-oxidation catalyst on the surface of a substrate, wherein the photo-oxidation catalyst particles and an organic solvent-soluble fluorine Resin, and flaky silica particles having a layered structure of flaky silica secondary particles in which flaky primary particles of flaky silica are mutually oriented in parallel with each other and formed by stacking a plurality of flakes, The photo-oxidation catalyst is dispersed in an aqueous medium as a component, and the photo-oxidation catalyst accounts for 50 to 70% by mass of the solid component.
0 to 30% by mass of a fluorinated aqueous coating composition (hereinafter, may be referred to as a fluorinated aqueous coating composition of the present invention or an aqueous coating composition of the present invention).

(3) A fluorine-based cured coating film holding a photooxidation catalyst having high water resistance, wherein the fluorine-based aqueous coating composition according to (2) is applied on a substrate and dried. Formation method.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

(Photo-oxidation catalyst particles) Light used in the present invention
As the oxidation catalyst, those known per se may be used.
TiO_Two, ZnO, SrTiO_Three, WO_Three, SnO_Two, Nb
_TwoO_Five, ZrO_Two, Bi_TwoO _Three, NiO, Cu_TwoO, Si
O_Two, RuO_Two, CeO_Two, BaTiO_Three, K_TwoNbO_Three, T
a_TwoO_Three, Fe_TwoO_Three, CdS, InP, MOS_Two, Zn
Examples include S, CdSe, and GaAs. Above all, touch
Highly solvent-active, chemically stable and non-toxic
Titanium dioxide (TiO_Two) Is most preferred. Titanium dioxide
As a catalyst, a rutile type can be used.
Highly active, anatase-type titanium dioxide particles are preferred.
New The average particle diameter is 5 to 200 nm,
Preferably, the thickness is 10 to 100 nm. Photo-oxidation
Anatase-type titanium dioxide for catalysts is commercially available from various companies.
Powders or sols are suitable for the purpose.
A shift can also be used suitably.

(Organic Solvent-Soluble Fluororesin) In the present invention, an organic solvent-soluble fluororesin is used as a main binder component of the photooxidation catalyst particles.

The organic solvent-soluble fluororesin used in the present invention (hereinafter referred to as the solvent-soluble fluororesin in the present invention or simply referred to as the fluororesin in the present invention) mainly comprises a fluoroolefin, Was copolymerized with a copolymer component for making the solvent soluble (alkyl vinyl ether, alkyl vinyl ester, hydroxyl group-containing unsaturated ether, hydroxyl group-containing unsaturated ester, epoxy group-containing unsaturated ether, hydrolyzable silyl compound, etc.). It is most preferable to use the photo-oxidation catalyst because it is durable to the photo-oxidation catalyst as described above.

Examples of the fluoroolefin include tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, vinylidene fluoride, vinyl fluoride, hexafluoropropylene,
Examples thereof include trifluoropropylene, hexafluoroisobutene and perfluorovinyl ether, and particularly preferred are tetrafluoroethylene and chlorotrifluoroethylene.

Examples of the alkyl vinyl ether include ethyl vinyl ether, butyl vinyl ether, and cyclohexyl vinyl ether. Examples of the alkyl vinyl ester include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caprylate, vinyl caproate, and laurin. Vinyl acid, vinyl palmitate, vinyl versatate, vinyl stearate and the like.

Examples of the hydroxyl group-containing unsaturated ether include hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, cyclohexane dimethanol monovinyl ether, hydroxyethyl isopropenyl ether, hydroxybutyl isopropenyl ether, and propylene glycol monoallyl ether. Examples of the saturated ester include vinyl hydroxybutanoate, vinyl hydroxyoctanoate, isopropenyl hydroxybutanoate, hydroxyethyl crotonate, and the like.

Examples of the unsaturated ether containing an epoxy group include glycidyl allyl ether, glycidyl vinyl ether, 1-allyloxybutene oxide, and 1-vinyloxybutene oxide. The hydrolyzable silyl compound is vinyltrimethoxysilane. , Vinyltriethoxysilane, vinyloxypropyltrimethoxysilane,
Allyltrimethoxysilane and the like can be mentioned.

The above-mentioned copolymer components can be used alone or as a mixture of two or more, and other copolymerizable monomers can be added as long as the characteristics of the fluororesin are not impaired. . For example, olefins such as ethylene, propylene and isobutylene, (meth) acrylates such as ethyl acrylate, methyl acrylate, ethyl methacrylate and methyl methacrylate, vinyl acetate, vinyl butyrate, vinyl pivalate and vinyl benzoate And chloroolefins such as vinyl chloride and vinylidene chloride.

The content ratio of the polymerized unit based on the fluoroolefin in the solvent-soluble fluororesin is preferably from 20 to 80 mol%. This content ratio is 20 mol%
When the amount is less than the above, the weather resistance decreases, and when it exceeds 80 mol%, the solvent solubility decreases. Further, the number average molecular weight of the fluororesin is preferably about 2,000 to 100,000.

The solvent-soluble fluororesin in the present invention can be produced by a usual radical polymerization method. As the polymerization form, basically, bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization are possible, but a fluorine-based aqueous coating composition for forming a fluorine-based cured coating film of the present invention is prepared. In this case, it must be a room temperature curing type, and as described below, the secondary particles of foliar silica, which is another binder to be mixed therewith, are preferably prepared as a water slurry. Most preferably, the emulsion polymerization is carried out in an aqueous medium in which the fluororesin is obtained as an aqueous emulsion.

The polymerization temperature depends on the type of polymerization initiator, but is usually about 10 to 120 ° C., and the reaction pressure is 0.1.
About 10 MPa. As the polymerization initiator, potassium persulfate, hydrogen peroxide, or a redox initiator composed of these and sodium hydrogen sulfite, sodium thiosulfate, disuccinic peroxide, monosuccinic peroxide, etc., based on the charged monomer amount 0.02-0.
About 6% by mass is used. Here, the aqueous medium is
In addition to using water alone, it means that it may contain a part of an organic solvent mainly composed of water, such as methanol, isopropanol, methyl cellosolve, or butyl cellosolve, which is water-soluble and has an affinity for a fluororesin, if desired.

The concentration of the fluororesin of the present invention obtained as described above in terms of solid content in the aqueous emulsion is as follows:
About 6 to 60% by mass is preferable. The aqueous emulsion contains a dispersant, a film-forming aid, a surfactant, an antifoaming agent,
Leveling agent, antistatic agent, plasticizer, crosslinking agent, curing agent,
A curing accelerator, a pigment and the like can be added.

As the curing agent, when the copolymerization component contains a hydroxyl group such as a hydroxyl group-containing unsaturated ether or unsaturated ester, a polyvalent isocyanate such as hexamethylene diisocyanate; Resins, urea resins, etc. are used, and in the case of epoxy group-containing unsaturated ethers, polyamine and phthalic anhydride are used.
In the case of a hydrolyzable silyl compound, butylamine, dibutyltin laurate, trichloroacetic acid and the like are used.

In the present invention, the mixing of the aqueous emulsion of the fluororesin with the above-mentioned dispersant and curing agent is carried out by using a mixer such as a ball mill, a sand mill, a paint shaker, a jet mill, a kneader, and a three-roll mill, which is used for ordinary coating. can do. In addition, as the aqueous emulsion of the fluororesin, for example, those commercially available as Lumiflon EF4200 (trade name, manufactured by Asahi Glass Co., Ltd.) can be used.

In some cases, instead of or together with the fluororesin, an acrylic silicone resin having a certain level of durability against the photooxidation catalyst can be used alone or in combination.

(Scaly silica particles) In the present invention,
As another binder component of the photo-oxidation catalyst particles, flaky silica particles are used together with the solvent-soluble fluororesin.

The flaky silica particles are silica having a novel particle morphology proposed by the present inventors,
The flaky primary particles of the flaky silica are substantially composed of the secondary particles of the flaky silica, which are formed by laminating a plurality of laminated primary particles in parallel with each other, and having a layer structure independent of each other. Silica particles.

The average particle size of the particles is not particularly limited.
It is about 1 to 20 μm, preferably about 0.01 to 10 μm, and more preferably about 0.1 to 10 μm. Here, as a method of measuring the average particle diameter, a laser diffraction / scattering type particle size measuring device (for example, model LA-920, manufactured by Horiba, Ltd.) and a dynamic light scattering type particle size distribution measuring device (for example, manufactured by Horiba, Ltd.
LB-500) or a Coulter counter (for example, MA-II type, manufactured by Coulter Electronics Co., Ltd.) or the like, which is appropriately applied according to the range of the particle diameter.

The silica secondary particles are formed by overlapping scale-like primary particles, but the primary particles cannot be identified by a scanning electron microscope (hereinafter abbreviated as SEM). This is because only the leaf-like secondary particles in which a plurality of sheets are overlapped with their planes oriented in parallel can be identified. When observed using a transmission electron microscope (hereinafter abbreviated as TEM), the electron beam is The primary particles, which are ultrathin flake particles that partially transmit, can be identified. In addition,
The bonding between the layers of the primary particles is extremely strong, and it is difficult to separate and isolate the flake-like primary particles, which are constituent units thereof, one by one from the leaf-like secondary particles by ordinary means. It is.

The foliar silica secondary particles used in the present invention are:
It can be obtained by crushing tertiary aggregate particles of silica (tertiary particles) by a specific method proposed by the present inventors.

Here, the silica tertiary aggregate particles can be preferably produced by the method proposed by the present inventors (see, for example, JP-A-2000-72432).

That is, using silica hydrogel and sodium silicate or sodium hydroxide and water as raw materials,
The hydrothermal treatment is carried out at a temperature of about 160 to 200 ° C. to produce tertiary aggregate particles of flaky silica mainly composed of silica-X or silica-Y in a slurry state.

The silica hydrogel is prepared by introducing, for example, an aqueous solution of an alkali silicate and an aqueous solution of a mineral acid into separate containers provided with outlets through separate inlets and instantaneously mixing them.
A silica sol is produced by immediately releasing the silica sol from the discharge port into a gaseous medium such as air, and gelling in the air while drawing a parabola.

The tertiary silica aggregate particles obtained in the form of a water slurry in this manner are subjected to a specific mechanical method proposed by the present inventors (hereinafter, sometimes referred to as a mechanical crushing method). (For example, Japanese Patent Application No. 11-351182, Japanese Patent Application 2000)
See -206264. ). That is, a water slurry of the tertiary aggregate particles (solid concentration 1 to 3)
(30% by mass) is crushed into secondary particles of foliar silica by means of a wet bead mill or the like of a system of mechanically high-speed stirring using a pulverizing medium, whereby secondary particles of foliar silica are obtained as a water slurry. .

The basic physical properties of the foliar silica secondary particles used in the present invention are as follows. The SiO ₂ purity of the silica in the silica secondary particles is 99.0% by mass or more. The pH is 6.0 to 8.0, and the spectrum of X-ray diffraction is ASTM (American Society
for Testing and Materials) (hereinafter simply referred to as an ASTM card) No. 16-
2θ corresponding to 0380 = 2θ corresponding to Silica-X and / or ASTM card number 31-1233 characterized by major peaks at 4.9 °, 26.0 °, and 28.3 °.
Silica consisting of silica-Y characterized by main peaks at 5.6 °, 25.8 ° and 28.3 °. As peaks other than the above, peaks such as ASTM card numbers 31-1234 and 37-0386 are observed for silica-X, and ASTM card numbers 35-63 and 25-1332 are observed for silica-Y. is there.

Regarding the particle diameter, a Coulter counter (manufactured by Coulter Electronics Co., Ltd., MA-II
Average particle size of 1 to 10 μm by a laser diffraction / scattering type particle size distribution measuring device (Horiba Seisakusho, L
A-920 type), the average particle size is 0.01 to 10 μm.
m.

When the pore distribution of the silica secondary particles was measured by the BET method (trade name: Bellsorp-28, manufactured by Nippon Bell Co., Ltd.), the pore volume was 0.05 to 0.15 ml / g.
The specific surface area is 30 to 80 m ² / g, and the oil absorption (JI
SK5101) is 100 to 150 ml / 100 g.

From the pore distribution curve, the silica secondary particles have a pore diameter of 2 to 6 nm, especially 3.5 to 4.0.
A sharp large peak is observed around nm. This indicates that the voids formed between the flakes are remarkably present as mesopore regions (pores having a diameter of 2 to 50 nm between micro and macro pores).

The silica (not heat-treated at room temperature)
iO ₂ ) has an infrared absorption spectrum (FT-IR) of 36
Silica having a silanol group having one absorption band at each of 00 to 3700 cm ^-1 and 3400 to 3500 cm ^-1 .

The amount of silanol groups per specific surface area by the BET method is determined by the so-called heating weight method.
Using the numerical value W (% by mass) of the difference in decrease in mass in the equilibrium from heating at 1200 ° C. to heating at 1200 ° C. and the numerical value SA (m ² / g) of the BET specific surface area, (W × 11
11.1) / SA = SiOH The amount of silanol groups per specific surface area determined by the BET method based on the formula of SiOH (μmol / m ² ) has a large value of 50 to 70 μmol / m ² (of silica gel). Several times).

By having such a high-density silanol group, the silica secondary particles used in the present invention can be easily subjected to chemical modification, and a coating film formed from the silica secondary particles can be used. By performing heat treatment at about 400 to 600 ° C., a silanol group can be condensed or reacted to improve the strength of the coating film.

The heat resistance of the foliar silica secondary particles used in the present invention is 500 to 100 in an air atmosphere.
After heating at 0 ° C. for 1 hour, changes in the morphology and dimensions of the particles were observed by SEM, but no particular change was observed.

The saturated solubility of the silica in an aqueous acid solution and aqueous alkali solution at 20 ° C. is low. That is, the dissolved SiO ₂ concentration is 0.008% by mass for a 10% by mass aqueous HCl solution, and 0.1% for ion-exchanged water.
For a 006 mass%, 5 mass% NaOH aqueous solution,
It is 0.79% by mass with respect to 0.55% by mass and 10% by mass of NaOH aqueous solution, indicating that it has small solubility in both acids and alkalis and has acid resistance and alkali resistance. In particular, it has a very small solubility in an aqueous alkali solution as compared with silica gel or colloidal silica, indicating that it has alkali resistance.

The water slurry of the secondary particles of foliar silica used in the present invention is different from conventional silica gel, colloidal silica and the like, as described by the present inventors (for example,
See Japanese Patent Application No. 11-351182. ), Any film formation when applied alone to the surface of a substrate such as metal, plastic, glass, ceramics, wood, cement hardened material, stone, paper, leather, etc. and dried, or further heat-treated if desired Without using an auxiliary agent or the like, it has a remarkable self-film-forming property (coating function) by itself, and has an extremely characteristic property of forming a tough cured coating film. This is due to the unique scaly shape having, in the process of drying the coating applied to the substrate surface, by the scaly particles overlapping each other parallel to the substrate and engaging each other Inferred.

In the present invention, the scaly silica particles are most preferably silica, which is collectively referred to as so-called lamellar polysilicic acid or a metal salt thereof. Here, the layered polysilicic acid refers to a polysilicic acid having a silicate layer structure whose basic structural unit is composed of only SiO ₄ tetrahedron.

The above-mentioned silica-X and silica-Y
Was originally reported by A. Heydemann and BAMitsyuk et al. And was called by them, but in later years,
It has been found that these actually correspond to a kind of what is generally called layered polysilicic acid or a salt thereof.

The layered polysilicic acid or a salt thereof is, for example, silica-X, silica-Y, kenyaite, magadiite, macatite, islayite, kanemite, octosilicate, and the like. It is a general term for an H-type in which an alkali metal or the like in an acid salt is ion-exchanged with hydrogen ions, or a salt-type such as an alkali metal salt before the acid treatment. In the present invention, the layered polysilicic acid means both the H type and the salt type such as an alkali metal.

In the present invention, both the alkali metal salt type layered polysilicate and the alkali metal salt type layered polysilicate can be used. In the present invention, the H-type layered polysilicic acid is more suitable in the present invention because the pH of the salt is highly alkaline and the pH of the H-type layered polysilicic acid is close to neutral.

The H-type layered polysilicic acid that can be preferably used is measured by a titration method using sulfuric acid, hydrochloric acid, sodium hydroxide, an aqueous solution of sodium chloride or the like as a titrant (for example, see JP-A-60-161319). Acidity (expressed in millimoles of titratable H ⁺ ions per mole of SiO ₂ ) of 0.01-70 mmol H 2
⁺ / Mol SiO ₂ is preferable, and 0.01 to 50
Mmol H ⁺ / mol SiO ₂ is more preferred,
Most preferred is about 20 mmol H ⁺ / mol SiO ₂ .

On the other hand, when the sodium remaining in the layered polysilicate is measured and expressed in terms of mass ppm of sodium per unit mass in terms of SiO ₂ , the sodium per mass in terms of SiO ₂ is about 1-27000 ppm. Is preferably about 1 to 20,000 ppm, and most preferably about 1 to 8000 ppm.

The above-mentioned layered polysilicic acid is usually a tertiary silica aggregate particle having a gap formed by irregularly overlapping scale-like particles (actually, secondary particles obtained by laminating primary particles of ultra-thin flakes). Therefore, in a water slurry state,
By applying the mechanical disintegration method previously proposed by the present inventor, secondary particles of foliar silica can be obtained in a similar manner and can be used preferably. In addition, among the foliar silica secondary particles obtained from the layered polysilicic acid, silica-X, silica-Y, H
Kenyaite, H-type magadiite and the like are most suitable for use in the present invention.

(Blending Composition of Fluorine-Based Aqueous Coating Composition) The above-mentioned photo-oxidation catalyst particles, an organic solvent-soluble fluororesin,
And flaky silica particles having a layered structure of flaky silica secondary particles in which flaky primary particles of flaky silica are oriented in parallel with each other and a plurality of flaky silica particles are formed as a solid component. By dispersing in a water-based medium, a fluorine-based water-based coating composition of the present invention for forming a room temperature-curable cured coating film holding a photo-oxidation catalyst on a substrate surface is obtained.

The content of the photo-oxidation catalyst in the aqueous coating composition of the present invention is 50 to 70% by mass in the solid component, and the total amount of the fluororesin and the flaky silica particles is 50 to 70%.
30% by mass. If the content of the photo-oxidation catalyst is less than 50% by mass, the photo-oxidation catalyst function in the case of forming a cured coating film is not sufficiently exhibited, and if it exceeds 70% by mass, the strength of the cured coating film becomes weak and the hot water resistance becomes poor. Lower.

The mass ratio of the fluororesin to the flaky silica particles is preferably from 0.2 to 3.0, and more preferably from 0.5 to 2.0. When the proportion of the fluororesin is less than 0.2, the cured coating film has insufficient warm water resistance, and when it exceeds 3.0, the catalytic function of the cured coating film is reduced.

The aqueous fluorinated coating composition of the present invention is prepared by mixing a photo-oxidation catalyst particle, an aqueous emulsion of a fluororesin and an aqueous slurry of secondary particles of foliar silica with a suitable mixer, and uniformly dispersing the aqueous slurry. It is obtained by making it into a composition in a shape. Generally, an organic polymer substance such as a fluororesin in an aqueous emulsion state is highly pH-dependent with respect to the stability of the emulsion state. Therefore, an aqueous emulsion of the organic polymer substance and a water slurry of secondary particles of foliar silica are used. Are mixed as they are, p
When H changes, the aqueous emulsion state of the organic polymer substance becomes unstable or in an extreme case, the aqueous emulsion state may be broken and gelled. Therefore, in such a case, the pH of the aqueous slurry of the foliar silica secondary particles is adjusted in advance so as to substantially match the pH of the aqueous emulsion of the fluororesin.
After the adjustment, it is preferable to mix both.

The aqueous medium in the present invention includes
As described above, water may be used alone, but methanol, which is water-soluble and has an affinity for the fluororesin, if desired,
An organic solvent such as isopropanol, methyl cellosolve, and butyl cellosolve may be partially contained.

The means for mixing the water slurry or the like is not particularly limited, and a stirring device having stirring blades, a wet disperser such as a bead mill using dispersed beads, and the like can be applied. In addition, the ball mill, sand mill, paint seeker, jet mill, kneader, and the like used when preparing the aqueous emulsion of the fluororesin as described above,
Three rolls or the like can also be used.

(Method of Forming Cured Coating Film) The aqueous coating composition of the present invention prepared as described above is coated on a substrate and dried to hold a photooxidation catalyst having high warm water resistance. The cured fluorine-based coating film of the present invention is formed.

The substrate is not particularly limited, and examples thereof include metal, plastic, glass, ceramics, wood, hardened cement, stone, paper, and leather. The coating film obtained from this aqueous coating composition is basically characterized by being a cold-setting type, and as shown in Examples below, has high warm water resistance irrespective of being a cold-setting type Things. The drying time is usually about 10 to 75 hours, preferably about 20 to 50 hours. In some cases, the addition of heat treatment or the like is not excluded.

The base material is, for example, a stainless steel base material,
In the case of a metal substrate such as an aluminum substrate, the surface of the substrate on which a cured coating film is to be formed is preferably subjected to a roughening treatment in advance. As means for the surface roughening treatment, means usually employed for forming fine irregularities and / or scratches on the surface of the base material can be applied, and is not particularly limited.
It is preferably performed by a known surface roughening treatment such as a sand blast treatment, a sand cloth treatment, a chemical polishing treatment, and an electrolytic polishing treatment. These surface roughening means are appropriately selected according to the type of the target substrate and the desired degree of surface roughness.

The maximum height (Ry) of the surface roughness of the roughened substrate is 1 to 100 μm, preferably 1 to 50 μm.
m, more preferably about 1 to 30 μm.

Here, the maximum height Ry (Rmax) of the surface roughness
Is also displayed. ) Is JISB0601-1994
Measured with a surface roughness meter, as specified by
Extract only the reference length from the roughness curve of the surface of the target substrate (target surface) in the direction of the average line, and measure the distance between the peak line and the bottom line of the extracted portion in the direction of the vertical magnification of the roughness curve This is indicated in μm.

The water-based coating composition of the present invention is applied to the surface-roughened material to form a coating film. The surface is then cleaned by a conventional method such as degreasing after the surface-roughening treatment. Preferably, a treatment is performed. It should be noted that the surface roughening treatment of the base material can be similarly performed on the base material other than the metal.

If the surface of the base material has not been roughened, the heat treatment after coating is performed at a sufficiently high temperature (for example, 50 ° C.).
(0 ° C.), only a cured coating film that does not withstand the hot water resistance test evaluation may be obtained. Further, the undercoating film or the intermediate coating film may be formed on the surface of the substrate, and then the aqueous coating composition of the present invention may be applied.

The means for applying the aqueous coating composition of the present invention to the surface of a substrate is not particularly limited, and may be, for example, brush coating, bar coating, roll coating, spray coating, or the like.
Means used for coating general paints such as electrostatic coating and dip coating can be used.

The cured coating film of the present invention holding the photo-oxidation catalyst formed on the substrate surface as described above corresponds to the binder component in the cured coating film according to the composition of the aqueous coating composition. But,
Organic solvent-soluble fluororesin and flaky silica flakes 1
And the flake-like silica particles having a particle structure of a laminated structure composed of a plurality of flaky silica secondary particles formed by stacking a plurality of secondary particles in which planes are oriented parallel to each other, and the cured coating The content of the photo-oxidation catalyst in the film is 50
And the binder component is 50 to 3% by mass.
0% by mass. Similarly, the mass ratio of the fluororesin to the flaky silica particles is preferably from 0.2 to 3.0, and more preferably from 0.5 to 2.
0.

[0071]

One of the features of the fluorine-based cured coating film of the present invention holding a photooxidation catalyst is that the coating film contains secondary particles of foliar silica in addition to the fluororesin.
The foliar silica secondary particles are created by the present inventors, but as described above, because they have a unique laminar structure particle shape, they are entangled with each other on the base material, and are oriented to overlap. It has a remarkable coating film forming function by itself. That is, from the aqueous slurry of the foliar silica secondary particles, a strong self-film-forming property that a strong silica coating can be formed on a substrate without using any binder and only by drying at room temperature. Things. In this respect, it is essentially different from known silica particles such as silica gel which does not have any film forming properties and which is conventionally compounded as a filler in a fluorine-based cured coating film.

In the present invention, the strength of the obtained fluororesin coating film is drastically increased by blending the foliar silica secondary particles having such a strong self-forming property into the aqueous coating composition containing the fluororesin. It is considered that the coating film can be improved to form a coating film having high warm water resistance.

Further, since the foliar silica secondary particles have a scale-like particle shape, the external surface area per unit mass of the particles is extremely large. Can be uniformly and highly dispersed. Moreover, since the leaf-like silica secondary particles are porous, a gas-permeable and / or liquid-permeable structure can be formed in the cured coating film obtained due to the porous structure. The wastewater containing water pollutants and the atmosphere containing air pollutants are introduced into the porous structure, and come into contact with the photo-oxidation catalyst carried on the silica secondary particles, and are suitably oxidized and decomposed. You can do it.

Since the fluorine-based cured coating film of the present invention holding the photooxidation catalyst is a coating film having high temperature resistance, it is suitable not only for treatment of normal temperature wastewater but also for treatment of water pollutants in warm wastewater. Can be applied to Also, of course,
Coating which holds the optical oxidation catalyst, as treatment material of the NO _x such as air pollutants, exposed roadside sound insulating wall, such as a highway, wallboard, paving materials, bridges, to the elements of the outer wall or the like of a building or the like structure It can be suitably used in places and places with high temperature and high humidity.

[0075]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. In the following Examples and Comparative Examples, the surface roughness of the substrate was measured by a surface roughness meter (Sumittest 402, manufactured by Mitutoyo Corporation) in accordance with JIS B0601-1994.

Similarly, the hot water resistance test of the cured coating film
Evaluation was performed by the following method. That is, a test piece having a cured coating film prepared by a method described below is hung with a thread in a water bath holding ion-exchanged water at 60 ° C., and a 100 mm long portion of the test piece is immersed to a depth of about 60 mm. The state of the cured film after one week has passed is compared with the first cured film before immersion in warm water by visual observation.
It was tested whether a change was observed.

[Synthesis Example 1] (Production of tertiary aggregated silica particles using hydrogel as starting material) A silica hydrogel as a starting material was prepared as follows using sodium silicate as an alkali source. SiO ₂ / N
a ₂ O = 3.0 (molar ratio), 2,000 ml / min of an aqueous solution of sodium silicate having an SiO ₂ concentration of 21.0% by mass
And a sulfuric acid aqueous solution having a sulfuric acid concentration of 20.0% by mass are introduced into a container provided with a discharge port through separate inlets, and are mixed instantaneously and uniformly. Was adjusted to 7.5 to 8.0, and the silica sol solution uniformly mixed was continuously discharged into the air from the discharge port. The released liquid became spherical droplets in the air, and gelled in the air while flying in a parabola for about 1 second. At the drop point, leave an aging tank filled with water,
Dropped here and aged.

After aging, the pH was adjusted to 6, and the mixture was sufficiently washed with water to obtain a silica hydrogel. The obtained silica hydrogel particles have a spherical particle shape and an average particle diameter of 6
mm. SiO ₂ in the silica hydrogel particles
The mass ratio of water to mass was 4.55 times, and the residual sodium in the silica hydrogel particles was 110 ppm.
Met.

The above silica hydrogel particles were roughly pulverized to an average particle diameter of 2.5 mm using a double roll crusher and used in the next hydrothermal treatment step.

In a 50000 ml autoclave (electrically heated, with anchor-type stirring blades), the total Si in the system was
The silica hydrogel having a particle diameter of 2.5 mm (SiO ₂ 18% by mass) so that the O ₂ / Na ₂ O molar ratio is 12.0.
23.7 kg and sodium silicate aqueous solution (SiO ₂ 2
8.75% by mass, 9.3% by mass of Na ₂ O, SiO ₂ / N
5.5 kg of a ₂ O = 3.17 (molar ratio) was added, and 10.7 kg of ion-exchanged water was added thereto, and a hydrothermal treatment was performed at 185 ° C. for 8 hours while stirring at 50 rpm. The total silica concentration in the system was 15% by mass as SiO ₂ .

The slurry after the hydrothermal treatment was subjected to filtration water washing using a filter cloth type vertical centrifugal separator (model TU-18, manufactured by Toko Kikai Co., Ltd.) to give a solid water content of 69.7% by mass (solid content concentration). 3
0.3% by mass) of a silica wet cake.

[0082] Water is added to the above wet cake and repulped.
After a slurry of silica having a SiO ₂ concentration of 7.0% by mass was formed, a medium fluidized bed dryer (Okawara Seisakusho Co., Ltd., SFD-M)
4. INI type) and dried at a hot air temperature of 300 ° C.
6 kg of dry fine powder was obtained.

The product phase of the resulting fine powder was identified by powder X-ray diffraction spectrum. As a result, X-ray diffraction spectra of 2θ = 4.9 ° and 26.0 ° corresponding to ASTM card No. 16-0380 were obtained. In addition to the main peak of silica-X, which is characterized by the main peak, peaks corresponding to ASTM card numbers 31-1234 and 37-0386 were observed.

When the morphology of the formed particles was observed by TEM, it was observed that the scale-shaped flake primary particles were oriented parallel to each other between the planes, and that a plurality of sheets overlapped to form leaf-like silica secondary particles. Was.

On the other hand, when the morphology of the formed particles was observed by SEM, the primary particles could not be identified, and were observed as if the secondary particles of foliar silica were primary particles. The shape of the leaf-like particles was scaly, and it was observed that the tertiary silica aggregate particles having a large number of gaps (voids or pockets) were irregularly overlapped and formed. This is the silica tertiary aggregate particle in the present invention.

The leaf-like particles (TEM) observed by SEM
The average thickness of the part corresponding to the secondary particles) is 0.06 μm
On the other hand, the average maximum length of the plate with respect to the thickness is 5.4.
In μm, the aspect ratio was 90, the average minimum length of the plate was 1.6 μm, and the aspect ratio was 27.

The average particle diameter of this fine powder (silica tertiary aggregate particles) was measured using a Coulter counter (MA-II type, manufactured by Coulter Electronics Co., Ltd., aperture tube diameter: 5).
When measured using 0 μm (same in the following synthesis examples), it was 6.1 μm.

[Synthesis Example 2] (Production of tertiary aggregated silica particles using hydrogel as starting material) A silica hydrogel as a starting material was prepared as follows using NaOH as an alkali source. SiO ₂ / Na ₂ O =
A sodium silicate aqueous solution having a concentration of 3.0 (molar ratio) and an SiO ₂ concentration of 21.0 mass% and a sulfuric acid aqueous solution having a sulfuric acid concentration of 20.0 mass% were separately placed in a container provided with a discharge port. The liquid introduced from the inlet is instantaneously mixed uniformly, and the pH of the liquid discharged into the air from the outlet is 7.5 to 7.5.
The flow rate ratio of the two liquids was adjusted so as to be 8.0, and the uniformly mixed silica sol liquid was continuously discharged into the air from the discharge port. The released liquid became spherical droplets in the air, and gelled in the air while flying in a parabola for about 1 second. An aging tank filled with water was placed at the dropping point, and the ripening tank was dropped and ripened.

After aging, the pH was adjusted to 6, and the mixture was sufficiently washed with water to obtain a silica hydrogel. The obtained silica hydrogel particles have a spherical particle shape and an average particle diameter of 6
mm. SiO ₂ in the silica hydrogel particles
The mass ratio of water to mass is 4.38 times, and the residual sodium in the silica hydrogel particles is 112 ppm.
Met.

The above silica hydrogel particles were roughly pulverized to an average particle diameter of 2.5 mm using a double roll crusher and used in the next hydrothermal treatment step.

In a 5000 ml autoclave (electrically heated, with anchor-type stirring blades), the total SiO 2 in the system was added.
2688 g of the above silica hydrogel having a particle diameter of 2.5 mm (18.6% by mass of SiO ₂ ) and an aqueous solution of sodium hydroxide (NaOH) so that the molar ratio of ₂ / Na ₂ O is 11.0.
126 g of 48.5% by mass), 1186 g of ion-exchanged water was added thereto, and 0.5 g of a seed crystal was added thereto.
Hydrothermal treatment was performed at 180 ° C. for 12 hours while stirring at rpm. The total silica concentration in the system was 12.5 as SiO _2.
% By mass.

The slurry after the hydrothermal treatment was subjected to filtration water washing using a filter cloth type vertical centrifugal separator (manufactured by Toko Kikai Co., Ltd., TU-18 type), and the solid water content was 66.7% by mass (solid content concentration). 3
(3.3% by mass) of silica was obtained.

Water was added to the wet cake and repulped.
After a slurry of silica having a SiO ₂ concentration of 7.0% by mass was formed, a medium fluidized bed dryer (Okawara Seisakusho Co., Ltd., SFD-M)
INI type) and dried at a hot air temperature of 300 ° C.
8 g of a dry fine powder were obtained.

The generated fine powder was identified by a powder X-ray diffraction spectrum to identify the generated phase.
ASTM card number 31-
In addition to the main peak of silica-Y characterized by main peaks of 2θ = 5.6 ° and 25.8 ° corresponding to 1233, AST
Peaks corresponding to M card numbers 35-63 and 25-1332 were observed.

When the morphology of the formed particles was observed with a TEM, it was observed that the scale-shaped flake primary particles were oriented parallel to each other in planes, and a plurality of sheets were overlapped to form leaf-like silica secondary particles. Was.

On the other hand, when the form of the formed particles was observed by SEM, the primary particles could not be identified, and were observed as if the secondary particles of foliar silica were primary particles. The shape of the leaf-like particles was scaly, and it was observed that the tertiary silica aggregate particles having a large number of gaps (voids or pockets) were irregularly overlapped and formed.

The leaf-like particles (T
In EM, the average thickness of the portion corresponding to the secondary particles) is 0.07
For μm, the average maximum length of the plate for that thickness is:
At 6.0 μm, the aspect ratio was 86, the average minimum length of the plate was 1.8 μm, and the aspect ratio was 26.

The average particle diameter of the fine powder was determined by using a Coulter Counter (manufactured by Coulter Electronics, MA
-II) was 6.5 μm.

[Synthesis Example 3] (Production of secondary particles of slurry-like foliar silica from wet cake of Synthesis Example 1) 1000 g of wet cake after filtration and washing with a centrifuge shown in Synthesis Example 1 (solids concentration: 30.3% by mass)
020 g was added and repulped to prepare a silica slurry having a solid content of 15% by mass. In this slurry state, the average particle size measured by a Coulter counter is 7.2 μm,
The viscosity measured by a B-type viscometer was 0.010 Pa · s.

Next, this slurry was mixed with a medium stirring bead mill (Dynomill KD, manufactured by Shinmaru Enterprises Co., Ltd.).
L-PILOT A type (vessel capacity: 1.4 L, diameter: 0.5 mm, filled with 80% zirconia beads: 80%)) is passed once at a shaft rotation speed of 3,400 rpm at a flow rate of 30 L / h to crush and disperse silica tertiary aggregate particles. Was performed.

The average particle size of the fine particles in the slurry after crushing and dispersing measured by a Coulter counter was 1.6 μm. The viscosity of the slurry was measured with a B-type viscometer and found to be 0.13 Pa · s. The pH of this slurry was 6.4.

[0102] Further, the water of the slurry was evaporated to dryness, it was analyzed silica and sodium in the dried solid sodium of SiO ₂ unit mass standards, 73
It was 0 ppm.

Next, in order to examine the physical properties of the dried leaf-like silica secondary particles close to the state of the fine particles in the slurry, a dry powder was obtained by the following method.

Since the slurry has a peculiar property that it is extremely easily coagulated by drying, in order to obtain a monodispersed dry powder, a water slurry having a very low concentration is dried while preventing coagulation. There is a need.

That is, the slurry (solid concentration 15
Water), and the slurry concentration was adjusted to a solid concentration of 0.3% by mass.

Using a small spray dryer (GA32 type, manufactured by Yamato Scientific Co., Ltd.), the slurry was supplied at a slurry supply rate of 1.7 ml / min and a spray pressure of 0.3 MPa.
(G), spray drying was performed at a hot air temperature of 130 ° C. to obtain a dry fine powder.

The average particle size of the obtained dried fine powder as measured by a Coulter counter was 1.9 μm. When this fine powder was observed by SEM, the silica tertiary aggregate particles were:
Substantially not recognized, and it was found that this was substantially composed of the foliar silica secondary particles in the present invention.

The product phase was identified by powder X-ray diffraction spectrum in consideration of this fine powder. As the X-ray diffraction spectrum, 2θ = 4.9 ° and 26.0 corresponding to ASTM card No. 16-0380. In addition to the main peak of silica-X, which is characterized by the main peak of ゜, peaks corresponding to ASTM card numbers 31-1234 and 37-0386 were recognized, and it was confirmed that the peaks were the same as before the pulverization.

When the morphology of the formed particles was observed by TEM, it was found that the scale-like flake primary particles were oriented parallel to each other between the planes, and a plurality of the flake-like primary particles were overlapped to form the leaf-like silica secondary particles of the present invention. Was observed.

Further, this fine powder was embedded in an epoxy resin, and an ultra-thin section was prepared with an ultramicrotome.
When observed at M, the thickness of the primary particles was 1 to 10 nm.
It turned out to be extremely thin.

The fine powder had a pore volume of 0.12 ml / g and a specific surface area of 65 m ² / g by a BET method pore distribution measuring device (Bellsoap 28 type, manufactured by Nippon Bell Co., Ltd.).
In the pore distribution curve, a sharp large peak in the mesopore region was observed around 3.6 nm.

In the measurement of infrared absorption spectrum (FT-IR510, manufactured by Nicole Japan) of the fine powder, 3600 to 3700 cm ^-1 and 3400 to 3500 c
A silanol group having one absorption band was observed at m ^-1 .

The amount of the silanol group (SiOH) is
From the difference between the loss on drying at 120 ° C. for 2 hours and the loss on heating at 1200 ° C. for 3 hours (W mass%), silanol groups per unit mass of silica (SiOH) = W × 111.
According to a calculation formula of 1.1 (μmol / g), 36
It was 50 μmol / g, which was a large value of 56.2 μmol / m ² per specific surface area according to the BET method.

The heat resistance was measured under air atmosphere at 500
At ~ 1000 ° C, no particular change was observed by observation with a scanning electron microscope.

20 for acid aqueous solution and alkali aqueous solution
For saturated solubility at 0 ° C., the dissolved SiO ₂ concentration is 1
0.008% by mass with respect to 0% by mass HCl aqueous solution,
0.006% by mass, 5% by mass with respect to ion-exchanged water
The content was 0.55% by mass with respect to the NaOH aqueous solution and 0.79% by mass with respect to the 10% by mass NaOH aqueous solution. Particularly with respect to alkali resistance, for example, the solubility was very small as compared with silica gel (in the case of silica gel, the solubility was 6 even in a 3% by mass NaOH aqueous solution.
5% by mass. ).

[Synthesis Example 4] (Production of secondary particles of slurry-like foliar silica from wet cake of Synthesis Example 2) Synthesis Example 3 using wet cake after filtration and washing with a centrifuge shown in Synthesis Example 2 In the same manner as described above, a medium stirring bead mill (manufactured by Shinmaru Enterprises Co., Ltd., Dynomill KD
L-PILOT A type (vessel capacity: 1.4 L, diameter: 0.5 mm, filled with 80% zirconia beads: 80%)) is passed once at a shaft rotation speed of 3,400 rpm at a flow rate of 30 L / h to crush and disperse silica tertiary aggregate particles. And a water slurry of foliar silica secondary particles having a solid content of 15% by mass was obtained.

The average particle size of the fine particles in the slurry after the crushing and dispersing was 1.7 μm by a Coulter counter. The viscosity of this slurry was measured with a B-type viscometer, and was 0.11 Pa · s. The pH of this slurry was 6.4.

[0118] Further, the water of the slurry was evaporated to dryness, it was analyzed silica and sodium in the dried solid sodium of SiO ₂ unit mass standards, 75
It was 0 ppm.

Example 1 (1) Anatase-type titanium dioxide (trade name: STS-21, manufactured by Ishihara Sangyo Co., Ltd., average particle diameter: 0.02 μm) was 3.8.
g, 3.23 g of an aqueous emulsion of an organic solvent-soluble fluororesin (manufactured by Asahi Glass Co., Ltd., trade name: Lumiflon FE4200, solid content concentration: 49% by mass, pH 7.6), Synthesis Example 3
An aqueous sodium hydroxide solution was added to 6.3 g of a water slurry of foliar silica secondary particles to adjust the pH of the foliar silica secondary particle slurry (average particle diameter 1.6 μm (Coulter Electronics Co., Ltd., Coulter Counter MA-II).
The value measured by the mold (same in the following Examples and Comparative Examples), the solid content concentration of 15% by mass, and the pH of 8.5) were 6.3.
g, and 17.2 g of ion-exchanged water were mixed with a small medium bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL A type (the same in the following examples and comparative examples)). The dispersion was dispersed to obtain a water-based slurry aqueous fluorine-based coating composition having a solid content concentration of 18.2% by mass for forming a cured coating film (in terms of solid content, titanium oxide fine particles: fluororesin: leaf-like silica secondary particles) = 60: 25: 15).

(2) Next, a stainless steel plate (50 mm × 100 mm × 1.5 m
m) was prepared, and the surface of the stainless steel plate was subjected to sand cloth polishing using a sand cloth of cross number AA-240 in accordance with JIS K5400, followed by further degreasing treatment (the processing solvent was xylene: isopropyl alcohol). = 1: 1 mixture).

The surface roughness of the stainless steel plate polished with the sand cloth was observed with a scanning electron microscope.
It is observed that a large number of fine irregularities and scratches are formed, and the maximum height Ry of the surface roughness of the surface is 3.
It was 0 μm.

(3) Next, a bar coater coating method (JI
SK5400), using a # 40 bar coater (manufactured by Eto Kikai Co., Ltd.), the above-mentioned fluorine-based water-based paint was applied to one surface of the above-mentioned stainless steel plate, and dried at room temperature for 24 hours to obtain a test piece. The amount applied to the test piece was about 16.
It was 5 g / m ² . This cured coating film was a uniform and smooth cured coating film.

Further, in measuring the hot water resistance of the cured coating film, a polyester adhesive tape was used to cover the uncoated surface, which is the back surface of the test piece, to the end of the coated surface. , And subjected to a warm water resistance test. As a result of the hot water resistance test, it was confirmed that no change was observed in the cured coating film.

Example 2 (1) 3.8 g of anatase-type titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., trade name: STS-21, average particle size 0.02 μm);
Aqueous emulsion of fluororesin soluble in organic solvent (Lumiflon FE4200, manufactured by Asahi Glass Co., Ltd., solid content 4
9% by mass, pH 7.6) and 2.58 g of a water slurry of the secondary particles of foliar silica in Synthesis Example 3 to which 8.4 g of an aqueous sodium hydroxide solution was added to adjust the pH of the secondary particle slurry of foliar silica (average). Particle size 1.6 μm, solid content concentration 15
% By mass, pH 8.5), and 8.4 g of ion-exchanged water.
The slurry obtained by mixing 4.0 g was highly dispersed using a small-size medium bead mill, and a water-slurry fluorine-based aqueous coating composition having a solid content concentration of 17.4% by mass for forming a cured coating film was obtained. Obtained (in terms of solid content mass, titanium oxide fine particles:
Fluororesin: foliar silica secondary particles = 60: 20: 2
0).

(2) Next, a stainless steel plate (50 mm × 100 mm × 1.5 m
m) was prepared, and the surface of the stainless steel plate was subjected to sand cloth polishing and then degreased in the same manner as in Example 1 (the processing solvent used was a xylene: isopropyl alcohol = 1: 1 mixed solution).

The surface roughness of the sand-polished stainless steel plate was observed with a scanning electron microscope.
It is observed that a large number of fine irregularities and scratches are formed, and the maximum height Ry of the surface roughness of the surface is 3.
It was 0 μm.

(3) Next, the above-mentioned fluorine-based aqueous coating composition was applied to one surface of the above stainless steel plate by a bar coater coating method in the same manner as in Example 1, and dried at room temperature for 48 hours to obtain a test piece. . The amount applied to the test piece was about 16.4 g / m ² in terms of solid content. This cured coating,
The cured film was uniform and smooth.

A warm water resistance test was carried out in the same manner as in Example 1. As a result, it was confirmed that no change was observed in the cured coating film.

Example 3 (1) Anatase type titanium dioxide (Ishihara Sangyo Co., trade name S
3.8 g of TS-21, average particle diameter 0.02 μm), an aqueous emulsion of an organic solvent-soluble fluororesin (trade name: Lumiflon FE4200, manufactured by Asahi Glass Co., Ltd., solid content concentration 49)
Mass%, pH 7.6), and aqueous sodium hydroxide solution was added to 10.5 g of a water slurry of the secondary particles of foliar silica in Synthesis Example 3 to adjust the pH of the secondary particle slurry of foliar silica (average particles). 1.6 μm diameter, solids concentration 15
% By mass, pH 8.5) and 15.0 g of ion-exchanged water were highly dispersed using a small-size medium bead mill, and the solid content concentration for forming a cured coating film was 17%. A water-slurry-based fluorine-based water-based coating composition of 0.6% by mass was obtained (in terms of solid content, titanium oxide fine particles: fluororesin: leaf-like silica secondary particles = 60: 15: 2).
5).

(2) Next, a stainless steel plate (50 mm × 100 mm × 1.5 m
m) was prepared and polished with sand cloth in the same manner as in Example 1, and then further degreased (using a mixed solvent of xylene: isopropyl alcohol = 1: 1).

When the roughness of the surface of the stainless steel plate polished with the sand cloth was observed with a scanning electron microscope,
It is observed that a large number of fine irregularities and scratches are formed, and the maximum height Ry of the surface roughness of the surface is 3.
It was 0 μm.

(3) Next, the above-mentioned fluorine-based aqueous coating composition was applied to one surface of the above stainless steel plate by a bar coater coating method in the same manner as in Example 1, and dried at room temperature for 72 hours to obtain a test piece. . The amount applied to the test piece was about 16.6 g / m ² in terms of solid content. This cured coating,
The cured film was uniform and smooth.

A hot water resistance test was conducted in the same manner as in Example 1. As a result, it was confirmed that no change was observed in the cured coating film.

Example 4 (1) 3.8 g of anatase-type titanium dioxide (trade name: STS-21, manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.02 μm);
Aqueous emulsion of fluororesin soluble in organic solvent (Lumiflon FE4200, manufactured by Asahi Glass Co., Ltd., solid content 4
9% by mass, pH 7.6) and 3.23 g of a water slurry of secondary silica particles in Synthesis Example 4 to which a sodium hydroxide aqueous solution was added to adjust the pH of the secondary silica slurry particles (average). Particle size 1.6 μm, solid content concentration 15
Mass%, pH 8.5) 6.3 g, and ion-exchanged water 1
The slurry obtained by mixing 5.7 g with 5.7 g was highly dispersed using a small-size medium bead mill, and a water-slurry fluorine-based aqueous coating composition having a solids concentration of 17.9% by mass for forming a cured coating film was obtained. Obtained (in terms of solid content mass, titanium oxide fine particles:
Fluororesin: foliar silica secondary particles = 60: 25: 1
5).

(2) Next, a stainless steel plate (50 mm × 100 mm × 1.5 m
m) was prepared and polished with sand cloth in the same manner as in Example 1, and then further degreased (using a mixed solvent of xylene: isopropyl alcohol = 1: 1).

The surface roughness of the stainless steel plate polished with the sand cloth was observed with a scanning electron microscope.
It is observed that a large number of fine irregularities and scratches are formed, and the maximum height Ry of the surface roughness of the surface is 3.
It was 0 μm.

(3) Next, the above-mentioned fluorine-based aqueous coating composition was applied to one surface of the above stainless steel plate by a bar coater coating method in the same manner as in Example 1, and dried at room temperature for 24 hours to obtain a test piece. . The amount applied to the test piece was about 16.2 g / m ² in terms of solid content. This cured coating,
The cured film was uniform and smooth.

A hot water resistance test was conducted in the same manner as in Example 1. As a result, it was confirmed that no change was observed in the cured coating film.

Comparative Example 1 (1) Anatase type titanium dioxide (trade name: STS-21, manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.02 μm) was 3.8.
g, 3.23 g of an aqueous emulsion of an organic solvent-soluble fluororesin (manufactured by Asahi Glass Co., Ltd., trade name: Lumiflon FE4200, solid content concentration: 49% by mass, pH 7.6), fine powdered silica gel (manufactured by Dokai Chemical Industry Co., Ltd., average) Water and an aqueous sodium hydroxide solution were added to a particle diameter of 3 μm, a pore volume of 0.35 ml / g, and a specific surface area of 600 m ² / g) to adjust the pH of the finely divided silica gel slurry (average particle diameter: 3 μm, solid content: 15% by mass) , PH 8.5) and 6.3 g of ion-exchanged water, and the resulting slurry was highly dispersed using a small-size medium bead mill, and the solid content concentration for forming a cured coating film was 18.2. By weight, a water-based fluorinated aqueous coating composition was obtained (in terms of solid content, titanium oxide fine particles: fluororesin: finely divided silica gel = 60: 25: 1).
5).

(2) Next, a stainless steel plate (50 mm × 100 mm × 1.5 m
m) was prepared and polished with sand cloth in the same manner as in Example 1, and then further degreased (using a mixed solvent of xylene: isopropyl alcohol = 1: 1).

The surface roughness of the sand-polished stainless steel plate was observed with a scanning electron microscope.
It is observed that a large number of fine irregularities and scratches are formed, and the maximum height Ry of the surface roughness of the surface is 3.
It was 0 μm.

(3) Subsequently, the above-mentioned fluorine-based aqueous coating composition was applied to one surface of the above stainless steel plate by a bar coater coating method in the same manner as in Example 1, and dried at room temperature for 24 hours to obtain a test piece. . The amount applied to the test piece was about 16.5 g / m ² in terms of solid content.

A hot water resistance test was carried out in the same manner as in Example 1. As a result, the cured coating film was all peeled off in less than one day. That is, it was confirmed that the cured coating film had very poor warm water resistance.

[0144]

According to the present invention, a fluorine-based cured coating film holding a photo-oxidation catalyst such as titanium oxide is coated on a substrate with a fluorine-based aqueous coating composition as a photocatalyst coating, and then heat-cured at, for example, 100 ° C. or more. It is a room-temperature-curing type that can be quickly cured by simply leaving it to stand at room temperature without the necessity. As described above, since the cured coating film is a coating film having high temperature resistance regardless of whether it is a room temperature curing type coating film, it can be used not only for treatment of room temperature wastewater but also for treatment of water pollutants in warm wastewater. Can also be suitably applied. Further, it can be suitably used in the process of air pollutants such as NO _x by coating the wall surface exposed to wind and rain sound insulating wall, such as highway roadside.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Atsushi Fujii, Inventor 13-1 Kitaminato-machi, Wakamatsu-ku, Kitakyushu-shi, Fukuoka Prefecture (72) Inventor Eiichi Ono Kitaminato-cho, Wakamatsu-ku, Fukuoka No. 13-1 Dokai Chemical Co., Ltd. F term (reference) 4D075 CA38 EA23 EB16 4J038 CD091 CD101 CD111 GA02 GA03 GA07 GA15 HA066 HA216 HA446 JA19 JA20 JA21 KA04 KA06 KA15 KA20 MA08 MA10 NA04 NA12 NA18 PA18 PB05 PC02 PC03 PC06 PC08 PC08 PC10

Claims (11)

[Claims] 1. A room temperature curing type fluorine-based cured coating film formed on a substrate surface and holding a photo-oxidation catalyst, wherein the binder component in the cured coating film is an organic solvent-soluble fluorine-based coating film. The resin and the flaky silica particles having a laminar structure composed of a plurality of leaf-like silica secondary particles formed by laminating a plurality of flake primary particles in which the flake primary particles of a flaky silica are oriented parallel to each other are substantially formed from And the content of the photooxidation catalyst in the cured coating film is 50 to 70% by mass, and
A fluorine-based cured coating film holding a photooxidation catalyst having high warm water resistance, wherein the binder component is 50 to 30% by mass. 2. The cured coating film according to claim 1, wherein a mass ratio of the fluororesin to the flaky silica particles in the binder is 0.2 to 3.0. 3. The cured coating film according to claim 1, wherein the foliar silica secondary particles are layered polysilicic acid. 4. The curing method according to claim 1, wherein the secondary particles of the foliated silica are silica whose main peak in X-ray diffraction analysis corresponds to silica-X and / or silica-Y. Coatings. 5. The cured coating film according to claim 1, wherein the photo-oxidation catalyst is titanium oxide fine particles. 6. A fluorine-based water-based coating composition for forming a room temperature-curable cured coating film holding a photo-oxidation catalyst on a substrate surface, comprising a photo-oxidation catalyst particle and an organic solvent-soluble fluororesin. And flaky silica 2 in which primary particles of flaky silica are oriented in parallel with each other and a plurality of flakes are formed.
Scaly silica particles having a particle structure of a laminated structure composed of the following particles are dispersed in an aqueous medium as a solid component, and the photooxidation catalyst is 50 to 70% by mass of the solid component, And flaky silica particles are 50
A water-based fluorinated coating composition characterized by being in an amount of from 30 to 30% by mass. 7. The fluorine-based aqueous coating composition according to claim 6, wherein the mass ratio of the fluororesin to the flaky silica particles is from 0.2 to 3.0. 8. The fluorine-based aqueous coating composition according to claim 6, wherein the secondary particles of the foliated silica are layered polysilicic acid. 9. The fluorine according to claim 6, wherein the secondary particles of the foliar silica are silica whose main peak in X-ray diffraction analysis corresponds to silica-X and / or silica-Y. Aqueous paint composition. 10. The fluorine-based aqueous coating composition according to claim 6, wherein the photooxidation catalyst is titanium oxide fine particles. 11. Fluorine holding a photooxidation catalyst having high water resistance, wherein the fluorine-based aqueous coating composition according to any one of claims 6 to 10 is applied on a substrate and dried. Method of forming a system cured coating film.