JP2004285349A - Coating agent and forming method of porous film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent forming a coating film having porosity, and to provide a forming method of the porous film. <P>SOLUTION: In the coating agent comprising (A) a coating film forming component, (B) a filler, (C) a porosity forming agent, and (D) an organic solvent, the porosity forming agent (C) is a sulfate. The forming method of the porous film comprises coating a substrate with the coating agent, drying them, and then eluting water-soluble matter in an obtained coating film. Desirably, the coating film forming component (A) comprises a polyorganosiloxane resin, and the filler (B) contains titanium oxide having optical catalytic activity as at least a part of the component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating agent containing a porosifying agent and a method for forming a porous film using the same.

Conventionally, there is a method of adsorbing a gas or a liquid substance to a coating film by increasing the surface area of the coating film. As methods for increasing the surface area of the coating film, for example, (1) a method of forming irregularities on the coating film surface by using spray dust, and (2) a fine crack on the coating film by utilizing the curing shrinkage of the coating film. And (3) a method of dispersing water-soluble resin fine particles in a water-insoluble coating film and immersing the coating film in water to form pores in the coating film.

  The method (1) is inferior in stain resistance and physical properties of the coating film because the surface of the coating film is rough, the method (2) is inferior in physical properties and durability of the coating film, and the method (3). The method is that when using pigments, etc., the difference in specific gravity between the pigment and the water-soluble resin particles is large, so that the water-soluble resin particles are not uniformly dispersed in the coating film, and the water-soluble resin particles are deformed or broken during spray coating Therefore, there are problems that stable particles are not dispersed in the coating film, that wastewater treatment is troublesome, and that the cost increases.

  As a method for solving such a problem, Patent Document 1 discloses that a water-soluble inorganic salt particle in a coating film is eluted by immersing a coating film formed from a coating material to form a porous uniform hole in the coating film. A method of forming is described. However, in this method, depending on the type of the water-soluble inorganic salt particles, the storage stability of the coating is insufficient, and the formed coating film is easily affected by humidity, and causes metal corrosion when applied to a metal surface. There was something.

JP 2001-179173 A

  An object of the present invention is to provide a coating agent that forms a coating film that has good storage stability in a paint state and is not easily affected by humidity, and a method for forming a porous film using the coating agent. is there.

The present inventors have conducted intensive studies to solve the above-described problems, and as a result, by using a specific compound as a porosifying agent, the storage stability in a paint state is good, and the influence of humidity and the like is good. The present inventors have found that porous and uniform pores can be formed in the coating film irrespective of this, and have reached the present invention.
That is, the present invention
1. A coating agent containing (A) a film-forming component, (B) a filler, (C) a porogen, and (D) an organic solvent, wherein the porogen (C) is a sulfate. A coating agent characterized by being
2. The coating composition according to claim 1, wherein the film-forming component (A) contains a polyorganosiloxane resin.
3. The coating agent according to item 1 or 2, wherein the filler (B) contains titanium oxide having photocatalytic activity as at least a part of its component.
4. The coating according to any one of Items 1 to 3, wherein the porosifying agent (C) is a compound having a melting point of 200 ° C. or higher and a solubility of 30 g or more in 100 g of water at 25 ° C. Agent,
5. The coating agent according to any one of items 1 to 4, wherein the organic solvent (D) contains at least 80% by weight of a hydrophobic organic solvent,
6. A porous film, characterized in that a coating material according to any one of items 1 to 5 is applied to a substrate, and after drying, a water-soluble substance in the obtained coating film is eluted. Forming method,
7.6 An article having a porous membrane formed by the method according to item 6,
About.

  The coating agent of the present invention can be easily produced regardless of the on-site environment and the like, and is excellent in pigment dispersibility and storage stability. Since the porous film formed from the coating agent has a good appearance and a large surface area, its function can be increased only by mixing a small amount of a functional substance. For example, when titanium oxide or the like having photocatalytic activity is contained, performances such as decomposing pollutants in the air can be efficiently exhibited.

  Hereinafter, the present invention will be described in detail.

  In the present invention, as the resin component contained in the film-forming component (A), a resin conventionally used in the field of coating can be used, and a non-crosslinking type and a crosslinking type (self-crosslinking type or external crosslinking by a curing agent) can be used. Type). Further, it is desirable that the coating film formed from the resin does not dissolve in water.

  As the non-crosslinked type, for example, acrylic resin, polyester resin, polyurethane resin, alkyd resin, cellulose resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, nylon, ABS resin, polycarbonate resin, epoxy resin, phenol resin, fluorine resin, silicone resin and the like can be mentioned. These resins can be used alone or in combination of two or more. Further, these resins may be two or more kinds of modified resins.

  Examples of the crosslinking type include amino-curable acrylic resin, amino-curable polyester resin, (block) polyisocyanate-curable acrylic resin, (block) polyisocyanate-curable polyester resin, (block) polyisocyanate-curable epoxy resin, and anhydrous. Examples include acid-curable epoxy resins, polyacid-curable epoxy resins, polyorganosiloxane resins, oxidation-curable alkyd resins, and active energy ray-curable resins. These resins can be used alone or in combination of two or more.

  In the present invention, when the coating material contains titanium oxide having photocatalytic activity as a filler (B) described later, the film forming component ( A) preferably contains a polyorganosiloxane resin as a resin component.

  As the polyorganosiloxane resin suitable in the present invention, for example, a resin obtained by subjecting an alkoxysilane mixture containing 5 to 95% by weight of a tetraalkoxysilane to a condensation reaction can be exemplified. If the amount of the tetraalkoxysilane is less than 5% by weight, the storage stability of the coating agent may be insufficient, while if it exceeds 95% by weight, the finish of the formed coating film may be insufficient.

  Examples of the tetraalkoxysilane include, for example, an organosilane compound in which a substituent bonded to a silicon atom is the same or different and is an alkoxy group having 1 to 6 carbon atoms, and specific examples thereof include tetramethoxysilane and tetramethoxysilane. Examples include ethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, and low condensates thereof. Here, the low condensate means an oligomer having a degree of polymerization of 10 or less.

  More preferably, the polyorganosiloxane resin contains 5-95% by weight, preferably 20-80% by weight of tetraalkoxysilane, and 5-95% by weight, preferably 20-80% by weight of trialkoxysilane. Examples of the resin include a resin obtained by subjecting an alkoxysilane mixture to a condensation reaction.

  Examples of the trialkoxysilane include, for example, an organosilane compound having the same or different alkoxy group as a substituent bonded to a silicon atom and having 1 to 6 carbon atoms. Specifically, methyltrimethoxysilane , Methyltriethoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriphenoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriphenoxysilane and low condensates thereof And a trialkoxysilane having an alkyl group of 6.

  In addition, the alkoxysilane mixture includes dialkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, and methylethyldiethoxysilane, and trimethylmethoxysilane, trimethylethoxysilane, triphenylmethoxysilane, and dimethylethylethoxysilane. Etc. and low condensates thereof.

  In condensing the above alkoxysilane mixture, for example, the mixture is reacted under stirring at about 20 to 100 ° C. for about 30 minutes to about 10 hours in the presence of an organic solvent and an acid. Inorganic bases such as monoethylamine, diethylamine, triethylamine, etc., ammonia and the like can be added to raise the pH of the system to 7 or more to allow the condensation reaction to proceed. After completion of the reaction, it can be produced by removing residual water by distillation, azeotropic distillation, or the like.

  The weight average molecular weight of the polyorganosiloxane resin produced as described above is in the range of 1,000 to 6,000, preferably 2,000 to 4,000, from the viewpoint of the coating film properties, curability, and thick coating property of the formed coating film. It is desirable. In addition, in this specification, a weight average molecular weight is the value which converted the weight average molecular weight measured by the gel permeation chromatography based on the weight average molecular weight of polystyrene.

  The composition obtained as described above can be a three-dimensional condensate, and has a sufficient function as a coating film forming component. At this time, the curability can be further improved by adding a base catalyst such as tetramethylammonium hydroxide or tributylamine or an organic metal catalyst. Examples of the organometallic catalyst include organic tin compounds such as diacetyltin diacetate, dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, diacetyltin dioctoate, tin octylate, dibutyltin diacetate, and dibutyltin dioctylate; aluminum trimethoxide Organic aluminum compounds such as aluminum trisacetylacetonate, aluminum tri-n-butoxide, aluminum tris (acetylacetone), aluminum tris (acetoacetateethyl), aluminum diisopropoxy (acetoacetateethyl), aluminum acetylacetonate; titanium tetrakis (Ethylene glycol monomethyl ether), titanium tetrakis (ethylene glycol monoethyl ether), titani Organic titanium compounds such as uranium tetrakis (ethylene glycol monobutyl ether) and tetra-normal butyl titanate; zirconium tetrakis (ethylene glycol monomethyl ether), zirconium tetrakis (ethylene glycol monoethyl ether), zirconium tetrakis (ethylene glycol monobutyl ether), zirconium normal propyl Organic zirconium compounds such as zirconium normal butyrate and zirconium tetrakis (acetylacetonate); organic zinc compounds such as zinc naphthenate; organic cobalt compounds such as cobalt octylate and cobalt naphthenate; Among them, organoaluminum compounds are preferred.

  As the filler (B) used in the present invention, any conventionally used pigments such as coloring pigments, extender pigments, anticorrosion pigments, metal pigments and the like can be used without any particular limitation. Examples of the coloring pigment include white pigments such as titanium dioxide, zinc white, lead white, basic lead sulfate, lead sulfate, lithopone, zinc sulfide, and antimony white; red pigments such as redwood; blue pigments such as phthalocyanine blue; And green pigments such as green.

  Examples of extenders include barita powder, precipitated barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, satin white, mica powder, and the like. . Examples of the rust preventive pigment include calcium plumbate and zinc phosphate. Examples of the metal powder pigment and the metal luster pigment include aluminum powder, bronze powder, copper powder, tin powder, lead powder, zinc powder, iron phosphide, and the like.

  In the present invention, it is desirable that the filler (B) contains titanium oxide having photocatalytic activity as at least a part of its components.

  Titanium oxide, which has photocatalytic activity, is excited by absorbing light such as sunlight and artificial illumination light to generate holes and OH radicals, which exhibit a strong oxidizing effect, and contaminate the air. Is a compound that can be decomposed. According to the compound, it is possible to oxidize nitrogen oxides in the air to change to nitric acid and chemically change them to nitrogen and water, and to oxidize sulfur oxides in the air to change to sulfuric acid. It is known that it can be done. As the titanium oxide having photocatalytic activity, conventionally known ones can be used without particular limitation as long as they can absorb ultraviolet light and / or visible light and exhibit a photocatalytic action. For example, anatase-type titanium oxide, Vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, rhenium, osmium, palladium, platinum, iridium, niobium, molybdenum, tungsten, etc. Can be used.

  The present invention is characterized by using a sulfate as the porosifying agent (C). In the present invention, powdery anhydrous sulfate is particularly preferred from the viewpoints of pigment dispersibility, porosity of the formed coating film, and the like. The sulfate is preferably a compound having a melting point of 200 ° C. or higher, preferably 300 ° C. or higher, and soluble in 100 g of water at 25 ° C. in a range of 30 g or higher, preferably 30 to 85 g.

  In the sulfate, examples of positive ions that form a salt with sulfate ions include magnesium, aluminum, calcium, sodium, potassium, and ammonium. Specific examples of the porosifying agent (C) include ammonium sulfate, aluminum sulfate, and the like. Magnesium sulfate and the like are particularly preferred.

  The above-mentioned porosifying agent (C) includes, in addition to sulfates, bromides such as sodium bromide, ammonium bromide and potassium bromide; chlorides such as ammonium chloride, sodium chloride and potassium chloride; sodium fluoride, ammonium fluoride, A fluoride such as potassium fluoride can be used in combination.

  In the coating composition of the present invention, the filler (B) is 1 to 300% by weight, preferably 5 to 80% by weight, based on the solid content of the film forming component (A) of the coating composition, and the porosifying agent (C) Is in the range of 5 to 100% by weight, preferably 10 to 80% by weight.

  The organic solvent (D) contained in the coating composition of the present invention is not particularly limited, but includes, for example, hexane, heptane, octane, toluene, xylene (o-, m-, p-), petroleum naphtha and the like. Hydrocarbon solvents; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate; methanol, ethanol, n- Alcohol solvents such as butanol, secondary butanol, tert-butyl alcohol, isobutyl alcohol, pentanol, n-hexanol, cyclohexanol, 2-ethylhexanol, n-octanol, benzyl alcohol, hexylene glycol; Lofran, ethylene glycol monobutyl ether, ethylene glycol monotert-butyl ether, ethylene glycol monohexyl ether, 2-ethylhexyl glycol, 2-butoxyethanol, ether solvents such as diethylene glycol monobutyl ether; and the like; Can be used in combination.

  In the present invention, since the storage stability and the pigment dispersibility of the coating agent are good, a hydrophobic organic solvent among the above solvents is contained in the organic solvent (D) in an amount of 80% by weight or more, preferably 85% by weight or more. Desirably, it exists within the range. The hydrophobic organic solvent is preferably a hydrophobic organic solvent which exhibits a solubility of water of 10% by weight or less, preferably 5% by weight or less in an organic solvent at 20 ° C.

  Examples of the hydrophobic organic solvent include hydrocarbon solvents such as hexane, heptane, octane, toluene, xylene (o-, m-, p-) and petroleum naphtha; ketone solvents such as methyl isobutyl ketone, isophorone and cyclohexanone. Solvents: ester solvents such as ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate; n-butanol, secondary butanol, tert-butyl alcohol, isobutyl alcohol, pentanol, n-hexanol, cyclohexanol, 2-ethyl Alcohol solvents such as hexanol, n-octanol, benzyl alcohol, and hexylene glycol; and the like, and these may be used alone or in combination of two or more.

  The coating composition of the present invention may further contain a dye, a fluidity regulator, a thickener, a curing catalyst, an ultraviolet absorber, a light stabilizer, a heat stabilizer, an initiator, and other fillers, if necessary, in addition to the above. (Eg, silica balloons, organic cross-linked resin particles, etc.), other resins, plasticizers, and the like.

  The coating composition of the present invention can be produced, for example, by mixing the components containing the above-mentioned film-forming component (A), filler (B), porogen (C) and organic solvent (D). As the mixing machine, a pigment dispersing machine conventionally used in paint production such as a disper, a pebble ball mill, a small dispersing machine (paint shaker), a sand mill, and a three-roller can be used without any particular limitation.

  Although the viscosity of the coating composition of the present invention obtained as described above is not particularly limited, it is preferable that the viscosity be in the range of 100 to 4000 mPa · s, preferably 300 to 2000 mPa · s. This is preferable from the viewpoint of uniform formability and suitability for thick coating. In this specification, the viscosity refers to a value obtained by adjusting a sample to 25 ° C. and measuring with a Brookfield viscometer.

  The method for forming a porous film according to the present invention is characterized in that a coating material obtained as described above is applied to a base material, and after drying, a water-soluble substance in the obtained coating film is eluted. This is a method of forming a porous film.

  As the base material, a metal such as aluminum, an inorganic material such as concrete or glass, an organic material such as plastic, wood, fiber, and a coating film, and a combination thereof can be used. In addition, it can be applied not only to a plate or the like, but also to a substrate processed into various shapes.

  The coating can be performed by a conventionally known coating method such as spray coating, roller coating, brush coating, bar coater coating, and dip coating. The coating film thickness (dry) is usually 5 to 1000 μm. Preferably, the thickness is in the range of 10 to 500 μm.

  Drying or curing conditions can be appropriately selected according to the type of the coating material and the type of the organic solvent. Specifically, for example, at room temperature, a range of 1 hour to 7 days, preferably 2 hours to 1 day is suitable. In the case of heating, for example, a range of 1 minute to 24 hours, preferably 10 minutes to 5 hours at a temperature of 50 to 200 ° C. is suitable.

  The obtained coating film can be made porous by eluting the porosifying agent (C) in the coating film with water. The elution can be performed by spraying water directly on the coating film, or by immersing the coating film in water. Further, by exposing the coated base material outdoors, it is possible to gradually elute the porosifying agent (C) from the coating film due to rain or the like. Further, the water used for the elution may contain, if necessary, an adjusting agent for controlling the dissolution of the porosifying agent (C), such as an alkali compound, an acidic compound and a solvent.

For example, the porous film formed by the method of the present invention can be measured for its porosity by the following formula.
Porosity ratio (%) = {(weight of coating film before making porous−weight of coating film after making porous) / weight of coating film before making porous} × 100
According to the method of the present invention, the porosity can be in the range of about 2 to 50%, preferably about 4 to 45%. Further, the degree of porosity can be confirmed by observing a cross section of the coating film under a microscope.

Examples will be described.
The present invention will be described in detail with reference to examples. The invention is not limited to the embodiments provided.

Production Example 1 of Coating Agent
The following raw materials are charged into an enamel container, mixed by disperser stirring and pre-kneaded, and then dispersed by a small disperser (paint shaker) using a glass bead as a dispersion media, and a coating agent having a viscosity of 453 mPa · s ( N-1) was prepared.
Composition of coating agent (N-1) "Acridic A-180" (Note 1) 222 g
"JR-600A" (Note 2) 100g
40 g of anhydrous magnesium sulfate (Note 3)
40 g of ethyl acetate
(Note 1) "Acridic A-180": trade name, manufactured by Dainippon Ink Industries, Ltd., solvent-type acrylic resin having an average molecular weight of 80,000, solvent: toluene, solid content 45%
(Note 2) "JR-600A": trade name, manufactured by Teica Co., Ltd., rutile-type titanium oxide (note 3) anhydrous magnesium sulfate: manufactured by Wako Pure Chemical Industries, solubility 36 g in 100 g of water at 25 ° C, melting point 1185 ° C, powdery .

Example 2
The following materials were charged into an enamel container, mixed by disperser stirring, and pre-kneaded. Thereafter, using a glass bead as a dispersion medium, dispersion was carried out with a small disperser (paint shaker), and a coating agent (N-2) was used. A base paint was manufactured. Thereafter, aluminum trisacetylacetonate as a reaction catalyst was mixed with the base paint so that the amount of aluminum trisacetylacetonate was 1% by weight based on the resin solid content of the base paint, and a coating agent having a viscosity of 480 mPa · s was used. (N-2) was obtained.
200g of polyorganosiloxane resin varnish (Note 4) for base coating composition for coating agent (N-2)
"ST-01" (Note 5) 100g
40 g of anhydrous magnesium sulfate
30 g of ethyl acetate
(Note 4) Average molecular weight 3000, solvent: ethyl acetate, solid content 50%
After adding 62 g of tetraethoxysilane, 125 g of methyltriethoxysilane and 187 g of ethyl acetate to the reaction vessel and heating the contents to 80 ° C. while stirring, 30 g of 0.2N hydrochloric acid was added and reacted at 80 ° C. for 10 hours. I let it. Next, 30 g of triethylamine is added to the reaction product to raise the pH to 7 or more, and a condensation reaction is performed at 80 ° C. for 2 hours. Thereafter, 100 g of ethyl acetate is added and the temperature is raised to 120 ° C., and the nonvolatile content becomes 50% Solvent removal was performed to obtain the resin having a weight average molecular weight of 3000 and a solid content of 50%.
(Note 5) “ST-01”: trade name, manufactured by Ishihara Sangyo Co., Ltd., an anatase-type titanium oxide having photocatalytic activity.
The following raw materials are charged into an enamel container, mixed by disperser stirring, and pre-kneaded. Thereafter, using a glass bead as a dispersion medium, dispersion is performed with a small disperser (paint shaker) to obtain a coating agent (N-3). A base paint was manufactured. Thereafter, aluminum trisacetylacetonate as a reaction catalyst was mixed with the base paint so that the amount of aluminum trisacetylacetonate was 1% by weight based on the resin solid content of the base paint, and a coating agent having a viscosity of 470 mPa · s was used. (N-3) was obtained.
200g of polyorganosiloxane resin varnish (Note 4) for base coating composition for coating agent (N-3)
"ST-01" (Note 5) 100g
40 g of anhydrous aluminum sulfate (Note 6)
30 g of ethyl acetate
(Note 6) Anhydrous aluminum sulfate: melting point 770 ° C., solubility 38 g in water 100 g at 25 ° C., powdered
The following raw materials are charged into an enamel container, mixed by disperser stirring, and pre-kneaded. Thereafter, using a glass bead as a dispersion medium, dispersion is performed with a small disperser (paint shaker) to obtain a coating agent (N-3). A base paint was manufactured. Thereafter, aluminum trisacetylacetonate as a reaction catalyst was mixed with the base paint so that the amount of aluminum trisacetylacetonate was 1% by weight based on the resin solid content of the base paint, and a coating agent having a viscosity of 420 mPa · s was used. (N-4) was obtained.
Base coating composition for coating agent (N-4) Polyorganosiloxane resin varnish (Note 4) 200 g
"ST-01" (Note 5) 100g
40 g of anhydrous magnesium sulfate
Ethylene glycol monobutyl ether (hydrophilic organic solvent)
30g.

Comparative Example 1
A coating agent (S-1) having a viscosity of 420 mPa · s was produced in the same manner as in Example 1 except that the composition was changed as follows.
Composition of coating agent (S-1) "Acridic A-180" (Note 1) 222 g
"JR-600A" (Note 2) 100g
40 g of anhydrous calcium chloride (Note 7)
40 g of ethyl acetate
(Note 7) Anhydrous calcium chloride; melting point 82 g in 100 g of water at 772 ° C. and 25 ° C.
Comparative Example 2
A coating agent (S-2) having a viscosity of 480 mPa · s was produced in the same manner as in Example 1 except that the composition was changed as follows.
Composition of coating agent (S-2) "Acridic A-180" (Note 1) 222 g
"JR-600A" (Note 2) 100g
20 g of ethyl acetate
Comparative Example 3
A coating agent (S-3) having a viscosity of 446 mPa · s was prepared in the same manner as in Example 2 except that the composition of the base paint was changed as follows.
Composition of base paint for coating agent (S-3) Polyorganosiloxane resin varnish (Note 4) 200 g
"ST-01" (Note 5) 100g
40 g of anhydrous calcium chloride (Note 7)
30 g of ethyl acetate
Comparative Example 4
A coating agent (S-4) having a viscosity of 480 mPa · s was prepared in the same manner as in Example 2 except that the composition of the base paint was changed as follows.
Composition of base paint for coating agent (S-4) Polyorganosiloxane resin varnish (Note 4) 200 g
"ST-100" (Note 5) 100g
60 g of ethyl acetate.

Formation of Porous Film Each of the coating materials prepared in Example 1 and Comparative Examples 1-2 was diluted with ethyl acetate, spray-coated on an aluminum plate and a tin plate, and dried at 80 ° C. for 1 hour. A 30 μm thick coating was obtained. Similarly, in Examples 2 to 4 and Comparative Examples 3 and 4, the base paint and the reaction catalyst were mixed at the above weight ratio, diluted with ethyl acetate, spray-coated on an aluminum plate and a tin plate, and heated at 160 ° C. for 30 minutes. After drying for 30 minutes, a coated film having a dry film thickness of 30 μm was obtained. Next, the coated panel was immersed in water at 20 ° C. for 24 hours, and then drained and dried at 80 ° C. for 30 minutes to form a porous film. Then, the performance evaluation of the porous coated panel and the storage test of the undiluted coating solution were performed. Table 1 shows the results.

Evaluation method (* 1) Appearance: Visual inspection of the coating film of each coated panel (material: aluminum plate) that was made porous by immersion in water, and found that the coating film was abnormal (Butsu, cissing, dent, crack, peeling, blister, discoloration) ) Was evaluated.
◎: excellent, ○: good, ○ △: slightly poor, Δ: poor, ×: extremely poor (* 2) Metal corrosion resistance: Moisture resistance of porous painted panels (material: tin plate) The test piece was put into a test machine (50 ° C., 95% RH) and tested for 8 hours. The degree of rusting of the coating film after the test was evaluated.
：: excellent, ○: good, ○ △: slightly rusted, Δ: rusted, ×: markedly rusted.
(* 3) Porosity of the coating film: The porosity of the coating film was calculated from the above formula and compared (material: aluminum plate).
(* 4) Surface area of coating film: The surface area of each of the porous coated panels (material: aluminum plate) was measured using a specific surface area / pore distribution measuring device (BET adsorption method). It was expressed as a magnification relative to the surface area of the coating film before making it porous.

(* 5) Pigment dispersibility: Dispersion was performed with a small disperser (paint shaker), and the difficulty of dispersibility was evaluated from the dispersion time and the degree of dispersion.
：: excellent, ：: good, ○ △: slightly poor, Δ: poor, ×: extremely poor (* 6) state: The state of each coating agent (absence, sedimentation, presence or absence of varnish floating) was visually inspected. .
：: excellent, ○: good, ○ △: slightly poor, Δ: poor, ×: extremely poor (* 7) Storage test of coating stock solution: each coating for 2 months at 5 ° C and 20 ° C Was subjected to a storage test. After storage, the state (gelation, butting, sedimentation, presence / absence of varnish floating) and viscosity change were examined. Further, the coating agent after storage is diluted with ethyl acetate, spray-coated on an aluminum plate, dried at 80 ° C. for 1 hour, and the state of the coated film after drying (bubbles, cissing, dents, cracks, peeling, blistering, discoloration) Was evaluated.
：: excellent, ○: good, ○ △: slightly poor, Δ: poor, ×: extremely poor

Claims (7)

A coating agent containing (A) a film-forming component, (B) a filler, (C) a porogen, and (D) an organic solvent, wherein the porogen (C) is a sulfate. A coating agent characterized by the following. The coating composition according to claim 1, wherein the film-forming component (A) contains a polyorganosiloxane resin. 3. The coating composition according to claim 1, wherein the filler (B) contains titanium oxide having photocatalytic activity as at least a part of its component. The coating agent according to any one of claims 1 to 3, wherein the porosifying agent (C) is a compound having a melting point of 200 ° C or more and being soluble in 30 g or more in 100 g of water at 25 ° C. The coating agent according to any one of claims 1 to 4, wherein the organic solvent (D) contains at least 80% by weight of a hydrophobic organic solvent. 6. Forming a porous film, comprising applying the coating agent according to any one of claims 1 to 5 to a base material, drying the coating material, and elute water-soluble substances in the obtained coating film. Method. An article having a porous film formed by the method according to claim 6.