JP2018044030A - Aqueous clear coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous clear coating composition capable of forming a coated film which has excellent antifouling properties and can impart a matte effect, and to provide a method for forming a coated film.SOLUTION: An air-drying type aqueous clear coating composition contains acrylic resin emulsion (A), silica fine particles (B) and a glossiness modifier (C) having an amount of water absorption of 0.8 g/g or more, where an amount of the glossiness modifier (C) contained in the aqueous clear coating composition is 1-60 pts.mass with respect to 100 pts.mass of a resin solid content of the acrylic resin emulsion (A), a 60° glossiness value of a dry coated film with a film thickness of 50 μm is 85 or less, and a water contact angle is 60° or less.SELECTED DRAWING: None

Description

  The present invention relates to an air-drying aqueous clear coating composition and a coating film forming method using the same.

  In recent years, awareness of reducing environmental impact has increased, and replacement with environmentally conscious products is required. In the paint field, for example, it is required to reduce the amount of organic solvent used, and such a request can be satisfied by using an aqueous paint composition.

  For example, in the fields of buildings, building exterior materials, and the like, a coating film that is formed from a water-based coating composition and exhibits stain resistance is required. Patent Document 1 (Patent No. 4673224) discloses a polymer (I) containing a hydrolyzable silyl group-containing radical polymer unit, colloidal silica (II) having an average particle diameter of 60 nm, and a specific surfactant (III). An aqueous coating material is disclosed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2010-77357) discloses (A) an aqueous resin dispersion obtained by polymerizing an α, β-ethylenically unsaturated monomer, and (B) an amide group, amino group, hydroxyl group. A water-soluble resin composition comprising an amphiphilic polymer having at least one functional group selected from a group as a hydrophilic part and having a hydrophobic part, and (C) colloidal silica dispersed in an aqueous medium. A paint composition is disclosed.

  Thus, an aqueous coating composition containing an aqueous resin dispersion and colloidal silica is used in order to provide stain resistance to the coating film. In the drying process of these water-based coating compositions, the colloidal silica moves to the surface of the coating film, thereby forming a hydrophilic surface and obtaining a coating film having stain resistance, for example, rain-stain stain resistance.

Japanese Patent No. 4673224 JP 2010-77357 A

In the fields of buildings, building exterior materials, and the like, various conditions are required in addition to the above-described contamination resistance, depending on the appearance required for the object to be coated.
For example, what has a matte effect is requested | required in external appearances, such as a building exterior material. For example, a clear coating having a matte effect may be applied on the design coating film in order to faithfully reproduce the color, gloss, etc. of the desired appearance. In order to satisfy such a requirement, generally, fine particles capable of diffusing light are added to an aqueous coating composition or an aqueous coating composition. However, if the blending amount of the fine particles capable of diffusing light is increased in order to obtain a matting effect (in order to reduce the gloss value), the hydrophilicity of the coating film is often impaired. As a result, the contamination resistance of the coating film surface is lowered.

  For this reason, a coating film having excellent stain resistance and a matting effect, for example, a clear coating, is required, and in particular, an aqueous clear coating composition capable of forming such a clear coating in consideration of the environment. Is required.

  An object of this invention is to provide the water-based clear coating composition which can form the coating film which has the outstanding antifouling property and can bring out the matting effect in view of the said present condition. Furthermore, this invention aims at providing the formation method of the coating film using the water-based coating composition which has such a characteristic.

In order to solve the above problems, the present invention provides the following aspects.
[1] An air-drying aqueous clear coating composition comprising an acrylic resin emulsion (A), silica fine particles (B), and a gloss modifier (C) having a water absorption of 0.8 g / g or more,
The 60 ° gloss value of the dry coating film having a thickness of 50 μm of the water-based clear coating composition is 85 or less, and the water contact angle is 60 ° or less.
A naturally dry aqueous clear coating composition.
[2] The average particle size of the silica fine particles (B) is in the range of 0.5 to 60 nm, and the average particle size of the gloss modifier (C) is in the range of 0.5 to 60 μm. ] The air-drying clear coating composition according to claim 1.
[3] The gloss modifier (C) is one or more selected from the group consisting of silica, talc, organic beads, calcium carbonate, kaolin, barium sulfate, mica and diatomaceous earth, [1] or [1] [2] The air-drying clear coating composition according to [2].
[4] The natural drying type according to any one of [1] to [3], wherein the gloss adjusting agent (C) is one or more selected from the group consisting of silica, talc and organic beads. Aqueous clear coating composition.
[5] The gloss adjusting agent (C) includes at least one selected from the group consisting of silica and talc, and organic beads, and includes a total addition amount of silica and talc and a total addition amount of organic beads. Ratio ((silica + talc) / organic beads)
Is an air-drying clear coating composition according to any one of [1] to [4], wherein 0.07 to 2.0.
[6] The amount of the silica fine particles (B) contained in the aqueous clear coating composition is 0.5 to 25 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). The air-drying clear coating composition according to any one of 1] to [5].
[7] The amount of the gloss modifier (C) contained in the aqueous clear coating composition is 1 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). [1] The air-drying clear coating composition according to any one of [6].
[8] A method for forming a coating film comprising a step of coating the object to be coated with the air-drying aqueous clear coating composition according to any one of [1] to [7] and air-drying.

  The air-drying clear coating composition of the present invention is an aqueous composition, can reduce the amount of organic solvent used, and can reduce the environmental burden. Furthermore, it has both excellent antifouling properties and matte properties.

Hereinafter, the process that led to the completion of the present invention will be described.
For example, in the case of an aqueous coating composition, the inventors have paid attention to the fact that the use of fine particles capable of diffusing light to obtain a matting effect impairs the hydrophilicity of the formed coating film. Although not limited to a specific theory, such a phenomenon can occur by adding a fine particle capable of diffusing light to suppress the migration of colloidal silica that can contribute to contamination resistance to the coating surface. I thought it was a thing.

  Thus, as a result of intensive studies, the present inventors have found that a coating formed by using an aqueous clear coating composition containing an acrylic resin emulsion (A), silica fine particles (B), and a specific gloss modifier (C). The present inventors have found that the film has a matte effect and antifouling property and completed the present invention.

More specifically, the present invention relates to an air-drying aqueous clear coating comprising an acrylic resin emulsion (A), silica fine particles (B), and a gloss modifier (C) having a water absorption of 0.8 g / g or more. A composition comprising:
The 60 ° gloss value of the dry coating film having a thickness of 50 μm of the water-based clear coating composition is 85 or less, and the water contact angle is 60 ° or less.
The present invention relates to a naturally dry type aqueous clear coating composition.

  In the present invention, the water absorption amount of the gloss adjusting agent (C) is 0.8 g / g or more, preferably 0.8 to 10.0 g / g, specifically 0.8 to 6.0 g / g. The gloss adjusting agent (C) having a larger water absorption is less likely to be familiar with water, indicating that its surface is more hydrophobic. By having such a range of water absorption, the interaction between the gloss adjusting agent (C) having a hydrophobic surface and the silica fine particles (B), for example, colloidal silica, is reduced, and colloidal silica during coating film drying. Is difficult to prevent from moving to the surface.

  Thus, by using the silica fine particles (B) and the gloss modifier (C) of the present invention, the formed coating film can have a matte effect and an antifouling property. This is not limited to a specific theory, but by using the gloss modifier (C) according to the present invention, the silica fine particles contained in the natural dry aqueous clear coating composition ( B), for example, since colloidal silica is promoted to migrate to the surface of the coating film or is not inhibited from migrating to the surface, hydrophilicity of the coating film surface is improved, excellent antifouling properties are provided, and gloss The matting effect brought about by the adjusting agent (C) is expressed, and it is presumed that the coating film can have a matting effect and an antifouling property.

  On the other hand, if the water absorption is less than 0.8 g / g, the water contact angle of the coating film becomes high, and problems such as the antifouling property not being exhibited may occur.

  For example, when a plurality of types of gloss adjusting agents (C) are used, the water absorption amount of all the gloss adjusting agents (C) is preferably within the scope of the present invention. Thereby, for example, it is possible to balance gloss (matte effect) and antifouling property. For example, when two kinds of gloss adjusting agents (C) are used, one uses a gloss adjusting agent (C) showing a high water absorption amount, and the other uses a gloss adjusting agent (C) showing a lower water absorption amount. Thereby, compared with the case where a single gloss adjusting agent (C) is used, the gloss can be further lowered, and the antifouling property can be improved.

  Here, in the present invention, the amount of water absorption refers to the “oil absorption amount” described in the method of JIS K5101-13-1, and “purified linseed oil” is replaced with water, for example, ion-exchanged water, purified water, or the like. The measured value. Moreover, when the amount of water absorption becomes higher, the surface of the gloss adjusting agent (C) becomes hydrophobic, and the interaction with the silica fine particles (B) is reduced. Thereby, for example, colloidal silica can be transferred to the surface of the coating film, a hydrophilic surface is formed on the coating film, and a coating film excellent in stain resistance, for example, rain-stain stain resistance can be obtained.

In an embodiment, the amount of the gloss modifier (C) contained in the aqueous clear coating composition is 1 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). Preferably, it is 5-40 mass parts, for example, 5-30 mass parts. By using the gloss adjusting agent (C) in such a range, the antifouling property can be more effectively brought about, and in addition, a desired gloss (matte property) can be led. For example, when the object to be coated has various appearances, a coating film having a uniform film thickness can be formed according to a desired appearance, for example, a surface having a smooth surface or a surface having irregularities. Dirty, lower haze, etc. can be shown.
Further, loss of continuity of the resin binder can be reduced, and film characteristics such as film strength and transparency can be maintained.

In the present invention, the 60 ° gloss value of the dry coating film having a film thickness of 50 μm of the aqueous clear coating composition is 85 or less, preferably 60 or less, for example 40 or less.
When the 60 ° gloss value of the dried coating film is within such a range, a desired matting effect can be obtained. The aqueous coating composition of the present invention can be applied to an article having various surface forms, and in addition, a desired matting effect can be obtained. For example, when the aqueous coating composition of the present invention is applied to an object having a smooth surface, the 60 ° gloss value of the coating film is preferably 40 or less. In addition, for example, when the aqueous clear coating composition of the present invention is applied to the surface of a stone-like coating film having a stone-like appearance, the 60 ° gloss value of the coating film may be 30 or less. preferable.
In the present invention, the 60 ° gloss value is obtained by applying the aqueous clear coating composition of the present invention to a glass plate so as to have a thickness of 50 μm and drying it at room temperature for 1 day. It is the value which measured on 60 degree gloss.

In the present invention, the water contact angle of the dry coating film having a film thickness of 50 μm in the aqueous clear coating composition is, for example, 60 ° or less, preferably 50 ° or less, for example, 40 ° or less.
When the water contact angle of the dried coating film is within such a range, it can have excellent antifouling properties. For example, when the surface of the object to be coated is smooth, the water contact angle of the coating film is preferably 50 ° or less, and the coating film has unevenness on the coating film surface, for example, the surface of a stone-like coating film When the aqueous clear coating composition of the present invention is applied, the water contact angle of the coating film is preferably 50 ° or less.
By having a water contact angle in such a range, good antifouling properties can be exhibited not only on a smooth coating film surface but also on an uneven coating film surface.
In the present invention, the water contact angle is determined by applying the aqueous clear coating composition of the present invention to a glass plate to a thickness of 50 μm, drying at room temperature for 1 day, and using a contact angle meter to drop 4 μl of water droplets. Is dropped onto the coating film, and the water contact angle after 20 seconds is measured.

  Here, in the air-drying clear coating composition of the present invention, the “air-drying type” means, for example, without heating to a high temperature of about 50 ° C. or higher without performing forced drying when forming the coating film, or It means a composition capable of forming a coating film without using far infrared rays, near infrared rays, a heat gun or the like. For example, an air-drying water-based clear coating composition is a composition that can form a coating film by standing in a temperature atmosphere of 40 ° C. or lower.

(About each component)
The present invention is an air-drying aqueous clear coating composition comprising an acrylic resin emulsion (A), silica fine particles (B), and a gloss modifier (C) having a water absorption of 0.8 g / g or more. Below, each component which can be used in this invention is illustrated.

(Acrylic resin emulsion (A))
The acrylic resin emulsion (A) contained in the aqueous clear coating of the present invention is a film forming resin component. An acrylic resin emulsion (A) may be used independently and may use 2 or more types together.

  In a certain aspect, as an acrylic resin emulsion (A), the acrylic resin emulsion comprised from the below-mentioned monomer may be used, an acrylic silicone resin emulsion may be used, and these may be used together. Moreover, you may use combining each emulsion in multiple types.

  The acrylic resin emulsion (A) can be prepared by emulsion polymerization of a polymerizable monomer in an aqueous medium. As a polymerizable monomer used for the preparation of the acrylic resin emulsion (A), for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n- Butyl (meth) acrylate, i-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, n-hexyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc. 1 to 1 carbon Alkyl (meth) acrylates having an alkyl group;

  Cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and pt-butylcyclohexyl (meth) acrylate;

  Hydroxyl group-containing radical polymerizable monomers such as 2-hydroxyethyl (meth) acrylate, 2- (3-) hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate;

  Hydroxypolyethylene oxide mono (meth) acrylate, hydroxypolypropyleneoxide mono (meth) acrylate, hydroxy (polyethyleneoxide-polypropyleneoxide) mono (meth) acrylate, hydroxy (polyethyleneoxide-propyleneoxide) mono (meth) acrylate, hydroxy (polyethyleneoxide -Polytetramethylene oxide) mono (meth) acrylate, hydroxy (polyethylene oxide-tetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetra Methylene oxide) mono (meth) acrylate, methoxypolyethylene oxide mono (meth) ) Acrylate, Lauroxy polyethylene oxide mono (meth) acrylate, stearoxy polyethylene oxide mono (meth) acrylate, allyloxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polypropylene oxide mono (meta) ) Polyalkylene oxide group-containing (meth) acrylates such as acrylate, octoxy (polyethylene oxide-polypropylene oxide) mono (meth) acrylate, nonylphenoxy (polyethylene oxide-propylene oxide) mono (meth) acrylate;

  Aminoalkyl (meth) acrylates such as 2-aminoethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, 2-aminopropyl (meth) acrylate, 2-butylaminoethyl (meth) acrylate;

  Amide group-containing polymerizable monomers such as (meth) acrylamide, N-methylolacrylamide, N-butoxymethyl (meth) acrylamide;

  Multifunctional (meth) acrylates such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and many such as triallyl cyanurate Functional allyl compounds;

  Vinylsilanes such as vinylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldichlorosilane, vinyltrichlorosilane; γ-acryloyloxyethylmethyldimethoxysilane, γ-acryloyloxyethyltrimethoxysilane, γ-acryloyloxy Ethyltriethoxysilane, γ-acryloyloxypropylmethyldimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, γ-acryloyloxypropyltriethoxysilane, γ-acryloyloxyethylmethyldichlorosilane, γ-acryloyloxyethyltrichlorosilane, γ -Acryloyloxya such as acryloyloxypropylmethyldichlorosilane, γ-acryloyloxypropyltrichlorosilane, etc. Kill silanes: γ-methacryloyloxyethylmethyldimethoxysilane, γ-methacryloyloxyethyltrimethoxysilane, γ-methacryloyloxyethyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ- Methacryloyloxyalkylsilanes such as methacryloyloxypropyltriethoxysilane, γ-methacryloyloxyethylmethyldichlorosilane, γ-methacryloyloxyethyltrichlorosilane, γ-methacryloyloxypropylmethyldichlorosilane, γ-methacryloyloxypropyltrichlorosilane;

  2- (2′-hydroxy-5 ′-(meth) acryloxyethylphenyl) -2H-benzotriazole, 1- (meth) acryloyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1 -(Meth) acryloyl-4-methoxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-amino-4-cyano-2,2,6,6-tetramethylpiperidine, etc. UV resistant group-containing (meth) acrylate;

  Dimethylaminoethyl (meth) acrylate methyl chloride salt, allyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, phenyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, tetrahydrofurfuryl ( Other (meth) acrylic monomers such as meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate;

  Carbonyls based on aldehyde groups or keto groups such as acrolein, diacetone acrylamide, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, pivalin aldehyde, diacetone (meth) acrylate, acetonitrile acrylate, acetoacetoxyethyl (meth) acrylate Group-containing monomers;

  Aromatic vinyl monomers such as styrene, methylstyrene, chlorostyrene, methoxystyrene;

  (Meth) acrylic acid, itaconic acid, fumaric acid, maleic acid, half esters thereof, 2- (meth) acryloxyethyl phthalic acid, 2- (meth) acryloxyethyl hexahydrophthalic acid, etc. body;

  Of oxirane group-containing radical polymerizable monomers such as glycidyl (meth) acrylate and ethylenically unsaturated amides such as N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide and N-methoxymethyl (meth) acrylamide Examples include self-crosslinkable functional group-containing radical polymerizable monomers such as alkylol and alkoxyalkyl compounds.

  In some embodiments, the monomer mixture is selected from the group consisting of methyl methacrylate, 2-ethylhexyl acrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, triallyl cyanurate, n-butyl methacrylate, acrylic acid and diacetone acrylamide. A combination of at least two of these may be used.

  Examples of the method for producing the acrylic resin emulsion (A) according to the present invention include a method of diluting with water after emulsion polymerization or solution polymerization, a method of diluting with water after solution polymerization and desolvation, and the acrylic resin emulsion obtained by these methods. It is preferable to use (A), and it is more preferable to use an acrylic resin emulsion (A) obtained by emulsion polymerization.

  In order to obtain an emulsion by an emulsion polymerization method, for example, a known method such as a method in which a radical polymerizable monomer mixture is supplied into a polymerization system in the presence of a surfactant and polymerization is performed with a radical polymerization initiator. Can be used.

  As the initiator, those generally used for radical polymerization can be used. Specific examples thereof include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, azobisisobutyronitrile, 2, 2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2 -Oil-soluble azo compounds such as phenylazo-4-methoxy-2,4-dimethylvaleronitrile and 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl ] Propionamide}, 2,2′-azobis {2-methyl-N- [2- (1-hydroxyethyl)] propionamide}, 2,2′-azobis {2-methyl N- [2- (1-hydroxybutyl)] propionamide}, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] and its salts, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] and salts thereof, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] and salts thereof, 2 , 2'-azobis (1-imino-1-pyrrolidino-2-methylpropane) and its salts, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] Propane} and its salts, 2,2′-azobis (2-methylpropionamidine) and its salts, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] and its Organic peroxidation such as water-soluble azo compounds such as salts, benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate Things etc. are mentioned. These initiators can be used alone or as a mixture of two or more. When acceleration of the polymerization rate and low temperature polymerization at 70 ° C. or lower are desired, for example, 2,2′-azobis [2- (2-imidazoline-2- It is advantageous to use a water-soluble azo compound such as yl) propane] or a salt thereof, or a reducing agent such as sodium bisulfite, ferrous sulfate, ascorbate, or longalite in combination with a radical polymerization catalyst.

  The addition amount of the radical polymerization initiator is usually in the range of 0.01 to 10% by weight with respect to the total amount of the radical polymerizable monomer. A range of 05 to 5% by weight is preferred.

  When adjusting the molecular weight of the resin component of the acrylic resin emulsion (A), as a molecular weight modifier, n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, n-hexyl mercaptan, etc. Mercaptans; halogen compounds such as carbon tetrachloride and ethylene bromide; and the use of a known chain transfer agent such as α-methylstyrene dimer can be used for the adjustment. Usually, it is 1 weight% or less with respect to the whole quantity of a radically polymerizable monomer.

  Moreover, it is preferable that an acrylic resin emulsion (A) contains 0.1-10 mass parts of surfactant with respect to a total of 100 mass parts of resin solid content of an acrylic resin emulsion (A). When the surfactant is present in an amount of 0.1 part by mass or more, the storage stability of the acrylic resin emulsion (A) is improved, and when emulsion polymerization is performed in the presence of the surfactant, the stability during polymerization is also improved. Further, by setting the surfactant to 10 parts by mass or less, it is possible to maintain the stability over time without impairing the water resistance. A more preferable content is 0.5 to 8 parts by mass.

  Examples of the surfactant include various known anionic, cationic or nonionic surfactants, and polymer emulsifiers. A so-called reactive emulsifier having an ethylenically unsaturated bond in the surfactant component can also be used.

  The emulsion obtained by the emulsion polymerization method has a stability of the system by adjusting the pH of the system to neutral to weakly alkaline, that is, in the range of about pH 6.5 to 10.0 by adding a basic compound after polymerization. Can be increased. Examples of the basic compound include ammonia, triethylamine, propylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, 1-amino-2-propanol, 2 -Amino-1-propanol, 2-amino-2-methyl-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylaminoethanol , Ethoxypropylamine, aminobenzyl alcohol, morpholine, sodium hydroxide, potassium hydroxide and the like.

In an embodiment, an acrylic silicone resin emulsion can be used as the acrylic resin emulsion (A) according to the present invention. The acrylic silicone resin is, for example, a resin having a block made of the above-mentioned monomer constituting an acrylic resin and a block made of a repeating unit constituting a silicone resin. For example, a silane compound is polymerized by a conventional method to synthesize a polymer (silicone resin) having a siloxane bond in the main skeleton, and then the above acrylic component (monomer) is graft-polymerized to the polymer by a conventional method. Or can be produced by bonding acrylic resin by a conventional method.
The silicone resin is not particularly limited. For example, a silicone resin having an unsaturated double bond in the molecular structure, such as an alkyd-modified silicone resin, may be used for graft polymerization of an acrylic component. May use a monomer other than the acrylic component.
Further, a catalyst may be added to promote the reaction between the acrylic component or the acrylic resin and the silicone resin. Here, the catalyst is not particularly limited. For example, in addition to metal alkoxides (for example, titanium isopropoxide), metal acylates and metal chelates made of titanium, aluminum, etc., tin compounds, hydrochloric acid, phosphorus Examples include acids such as acid compounds and carboxyl group-containing compounds, bases such as ammonium, and salts thereof.
Here, a hydroxyl group can be introduced into the acrylic silicone resin by using a hydroxyl group-containing silane compound or by using a hydroxyl group-containing monomer for an acrylic component or a monomer other than the acrylic component. In addition, a commercial item can be used conveniently for the hydroxyl-containing acrylic silicone resin which can be utilized for the coating composition of this invention.

(Silica fine particles (B))
The silica fine particles (B) according to the present invention have an average particle diameter in the range of 0.5 to 60 nm, for example, in the range of 1.0 to 60 nm. The average particle size is preferably less than 40 nm, for example less than 20 nm. In a certain embodiment, the lower limit of the average particle diameter of the silica fine particles (B) is, for example, 0.5 nm, and preferably 1.0 nm.
In one embodiment, two or more kinds of silica fine particles (B) included within the scope of the present invention may be used. For example, silica fine particles (B) having an average particle diameter in the range of 1 to 15 nm and silica fine particles (B) having an average particle diameter in the range of 30 to 60 nm may be used in combination.

  The average particle diameter of the silica fine particles (B) can be determined, for example, by observation using a transmission electron microscope (TEM). For example, when using commercially available silica fine particles as the silica fine particles (B), the average particle diameter measured by the manufacturer may be adopted.

In the present invention, as silica fine particles (B), for example, wet silica fine particles, specifically, precipitated silica, gel silica (silica gel), and colloidal silica can be used. It is preferable to use colloidal silica as the silica fine particles (B). For example, when the particle size of colloidal silica is 60 nm or less, colloidal silica is likely to float on the surface of the coating film during film formation. In the coating surface layer, the colloidal silica is formed into a film so as to close the gap between the polymer particles of the coating component and to cover the polymer particles, and the polymer and colloidal silica, or colloidal silica are chemically bonded. Alternatively, it can physically adsorb and be present on the surface of the coating film, so that high stain resistance is exhibited.
On the other hand, when the average particle diameter of colloidal silica exceeds 60 nm, light striking the coating film surface or transmitted light is diffusely reflected, which may cause problems such as whitening of the coating film.

In the present invention, the amount of the silica fine particles (B) contained in the aqueous clear coating composition is 0.5 to 25 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A), preferably 1 to 20 parts by mass, for example 3 to 10 parts by mass. By using the silica fine particles (B) in such a range, the colloidal silica floats on the surface of the coating film at the time of film formation, and the colloidal silica closely fills the gaps between the polymer particles of the coating component. The polymer and colloidal silica, or colloidal silica can be chemically bonded or physically adsorbed to be present on the surface of the coating film, thereby exhibiting high contamination resistance. Further, for example, when the content of the silica fine particles is increased within the scope of the present invention, better antifouling property and lower gloss can be brought about.
On the other hand, if the content of the silica fine particles (B) is less than 0.5 parts by mass, the amount of silica exposed on the surface of the coating film decreases, and the desired water contact angle / contamination resistance may not be obtained. Moreover, if the content of the silica fine particles (B) exceeds 25 parts by mass, haze may increase.
In addition, when using several types of silica fine particles (B), it sets suitably so that the total amount may become the said range.

As the colloidal silica, a commercially available product can be used, which may be one using water as a dispersion medium or one using an organic solvent as a dispersion medium.
For example, as an aqueous colloidal silica showing acidity, trade names: Snowtex OXS (SiO ₂ solid content 10%), Snowtex OS (SiO ₂ solid content 20%), Snowtex O (SiO ₂ solid content 20%), Snowtex O-40 (SiO ₂ solid content 40%), Snowtex OL (SiO ₂ solid content 20%), Snowtex OUP (SiO ₂ solid content 15%) (the above is made by Nissan Chemical Industries, Ltd.), Adelite AT-20Q (Asahi Denka Kogyo Co., Ltd., SiO ₂ solid content 20%), Cataloid SN (Catalyst Kasei Kogyo Co., Ltd., SiO ₂ solid content 20%), Silica Doll-20A (Nippon Chemical Industry Co., Ltd.) Product, SiO ₂ solid content 20%), silica dol-20GA (manufactured by Nippon Chemical Industry Co., Ltd., SiO ₂ solid content 20%), and the like.
Examples of the aqueous colloidal silica showing alkalinity include, for example, trade names: Snowtex XS (SiO ₂ solid content 20%), Snowtex 20 (SiO ₂ solid content 20%), Snowtex 30 (SiO ₂ solid content 30%), Snowtex 40 (SiO ₂ solid content 40%), Snowtex 50 (SiO ₂ solid content 50%), Snowtex C (SiO ₂ solid content 20%), Snowtex N (SiO ₂ solid content 20%), Snowtex NS (SiO ₂ solid content 20%), Snowtex S (SiO ₂ solid content 30%), Snowtex CM (SiO ₂ solid content 30%), Snowtex UP (SiO ₂ solid content 20%), Snowtex 20L ( SiO ₂ solid content 20%), Snowtex 30L (SiO ₂ solid content 30%), Snowtex XL (SiO 2 ₍₂ solid content 40%), (the above is manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20 (SiO ₂ solid content 20%), Adelite AT-20N (SiO ₂ solid content 20%), Adelite AT-20A ( SiO ₂ solid content 20%), Adelite AT-30, Adelite AT-40, Adelite AT-50, Adelite AT-30A, Adelite AT-300, Adelite AT-300S (above manufactured by Asahi Denka Kogyo Co., Ltd.), Cataloid S-20L (SiO ₂ solid content 20%), Cataloid S-20H (SiO ₂ solid content 20%) Cataloid S-30L (SiO ₂ solid content 30%), Cataloid S-30H (SiO ₂ solid content 30%), Cataloid SI-30 (SiO ₂ solid content 30%), Cataloid SI-40 (SiO ₂ solid content 40%), Cataloid SI-50 (Si O ₂ solid content 47%), Cataloid SI-350 (SiO ₂ solid content 30%), Cataloid SI-500 (SiO ₂ solid content 20%), Cataloid SI-45P (SiO ₂ solid content 40%), Cataloid SI- 80P (SiO ₂ solid content: 40%), Cataloid SA (SiO ₂ solid content: 30%), Cataloid SC-30 (SiO ₂ solid content: 30%) (the above is made by Catalyst Chemical Industry Co., Ltd.), Silica Dole-20 ( SiO ₂ 20% solids), silica Doll -30 (SiO ₂ solid content of 30%), silica Doll -40 (SiO ₂ solid content of 40%), silica Doll -30S (SiO ₂ solid content of 30%), silica Doll - 20Al (SiO ₂ solid content of 20%), silica Doll -20A (SiO ₂ solid content of 20%), silica Doll 20B (SiO ₂ solid content of 20%), silica Doll 20G (SiO ₂ solid content of 20%), silica Doll -20GA (SiO ₂ 20% solids), ammonium silicate (SiO ₂ solid content of 40%) (all manufactured by the Nippon Chemical Industrial Co., Ltd.) and the like.
Examples of the cationic colloidal silica include Snowtex AK (Nissan Chemical Industry Co., Ltd., SiO ₂ solid content 19%), Silica Doll-20P (Nippon Chemical Industry Co., Ltd., SiO ₂ solid content 20%) and the like. It is done.
In the present invention, these colloidal silicas can be used alone or in combination of two or more.

(Gloss modifier (C))
As described above, the gloss adjusting agent (C) according to the present invention has a water absorption of 0.8 g / g or more, preferably a water absorption of 0.8 to 10.0 g / g, specifically 0.8. 8 to 6.0 g / g.

The average particle diameter of the gloss adjusting agent (C) according to the present invention is in the range of 0.5 to 60 μm, preferably 1.0 to 50 μm, for example 5 to 30 μm. When the average particle diameter exceeds 60 μm, the gloss modifier (C) may be exposed on the surface of the coating film, and the smoothness of the coating film may be lost and the appearance of the coating film may be deteriorated.
In addition, the measurement of the average particle diameter of a glossiness modifier (C) can be measured using the laser diffraction and a scattering method (The particle size distribution measuring apparatus LS13320BECKMANCOULTER company make), for example. Specifically, the average particle diameter can be measured using a sample in which 10 g of 0.2% sodium hexametaphosphate aqueous solution is added to 0.1 g of the gloss modifier (C) and dispersed for 10 minutes by an ultrasonic cleaner.

In the present invention, the total amount of the gloss adjusting agent (C) contained in the aqueous clear coating composition is 1 to 60 parts by mass, preferably 1 to 100 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). 50 parts by mass, for example 1 to 40 parts by mass. In a certain aspect, the total amount of a glossiness modifier (C) is 5-30 mass parts. By using the gloss adjusting agent (C) within such a range, a matte effect is brought about on the coating film. Furthermore, since the colloidal silica is not promoted or suppressed from floating on the surface of the coating film during film formation, the antifouling property of the coating film is not impaired.
On the other hand, if the total amount of the gloss adjusting agent (C) is less than 1 part by mass, the desired gloss adjusting effect cannot be obtained. When it is 60 or more, the transparency of the coating film is lowered, or the continuity of the coating film is lowered and the coating film strength is lowered.
In addition, when using multiple types of gloss adjusting agents (C), it sets suitably so that the total amount may become the said range.

The gloss adjusting agent (C) preferably has a refractive index close to that of the acrylic resin emulsion (A). By having such a relationship, the transparency of the coating film formed from the aqueous clear coating composition of the present invention can be ensured.
For example, when the acrylic resin emulsion (A) has a refractive index of 1.49 to 1.53, the gloss adjusting agent (C) has a refractive index of 1.40 to 1.70, preferably 1.40 to 1.60. Can range.
On the other hand, when the refractive index of the gloss adjusting agent (C) is far from the refractive index of the acrylic resin emulsion (A), the coating film becomes cloudy and the transparency is lowered.

Examples of the gloss modifier (C) include inorganic gloss modifiers and organic gloss modifiers. For example, silica, talc, calcium carbonate, kaolin, barium sulfate, diatomaceous earth, and mica can be used as the inorganic gloss modifier. In one embodiment, it is preferable to use at least one selected from silica, talc, and mixtures thereof.
In one embodiment, silica and talc having a high water absorption may be used. For example, silica having a water absorption of 2.0 to 6.0 g / g can be used, and talc is 1.10. Those having a water absorption of ˜4.00 g / g can be used. By using at least one selected from silica, talc, and a mixture thereof, a coating film having low gloss and a lower water contact angle can be formed.

  As the organic gloss modifier, for example, organic beads, specifically, at least one selected from the group consisting of polymethyl methacrylate, polystyrene, urea resin, polyacrylonitrile, polyethylene and the like may be used. Such organic beads may be commercially available, Art Pearl Series (manufactured by Negami Industrial Co., Ltd.), Tuftic AR Series (manufactured by Toyobo Co., Ltd.), Chemisnow Series (manufactured by Soken Chemical Co., Ltd.), Techpolymer Series (made by Sekisui Plastics Co., Ltd.) and the like.

  In one embodiment, an inorganic gloss modifier and an organic gloss modifier can be used in combination. Gloss and haze can be balanced by using an inorganic gloss modifier and an organic gloss modifier in combination. For example, a combination of at least one selected from the group consisting of silica and talc and organic beads is preferable.

Although not limited to a specific theory, the use of an inorganic gloss modifier, such as silica or talc, tends to increase the matting effect, and the use thereof frequently tends to increase haze (turbidity). On the other hand, organic beads are less prone to haze than silica but tend to be less glossy. Therefore, there is an advantage that both gloss and haze can be designed in a more preferable range by combining an inorganic gloss modifier, such as silica or talc, and organic beads.
The haze can be measured, for example, using a haze meter NDH2000 (manufactured by Nippon Denshoku Co., Ltd.) using a coating film (on a glass plate) as a test specimen.

  When the gloss adjusting agent (C) includes at least one selected from the group consisting of silica and talc and organic beads, the ratio of the total addition amount of silica and talc and the total addition amount of organic beads (( Silica + talc) / organic beads) is 0.07 to 2.0, preferably 0.1 to 1.0, and in some embodiments 0.3 to 0.8, for example 0.3 to 0. .6. By combining silica and / or talc and organic beads within such a range, a balance between gloss and haze can be obtained, and furthermore, a coating film having good antifouling properties can be obtained. Specifically, for example, the gloss, haze, and antifouling properties required as a clear coating for objects to be coated and coatings having various surface forms can be obtained more effectively.

  In one embodiment, the relationship of ((silica + talc) / organic beads) is 0.07 or more and less than 1. By having such a relationship, it is possible to maintain excellent antifouling properties while further reducing gloss and / or haze.

(Other ingredients)
The clear coating composition of the present invention is usually used in the range of 10 to 80% by mass of the solid content. In addition, various pigments, antifoaming agents, pigment dispersants, leveling agents, anti-sagging agents, matting agents, UV absorbers, antioxidants, heat resistance improvers, slips are used to develop high performance coating materials. May contain various additives such as additives, preservatives, plasticizers, film-forming aids, and may be used in combination with other emulsion resins, water-soluble resins, viscosity control agents, and curing agents such as melamines. Good.

As film-forming aids, those usually used in water-based paints can be used, for example, linear, branched or cyclic aliphatic alcohols having 5 to 10 carbon atoms, alcohols containing aromatic groups. Represented by the general formula HO— (CH ₂ CHXO) n—R ₁ (R ₁ ; linear or branched alkyl group having 1 to 10 carbon atoms, X: hydrogen or methyl group, n ≦ 5 integer) poly) ethylene glycol or (poly) monoethers and propylene glycol, the general formula _{R 2 COO- (CH 2 CHXO)} n-R 3 (R 2, R 3: 1 to 10 carbons straight chain or branched (Poly) ethylene glycol ether ester or (poly) propylene glycol ether ester represented by alkyl group, X: hydrogen or methyl group, n ≦ 5), aromatic organic solvent such as toluene and xylene Agent, mono- or diisobutyrate of 2,2,4-trimethyl-1,3-pentanediol, diester compounds such as diisobutyl adipate, fatty acid esters such as 2-hydroxypropyl oleate, 3-methoxybutanol, 3 -Methoxybutanol acetate, 3-methyl-3-methoxybutanol, 3-methyl-3-methoxybutanol acetate and the like.

  As the thickening agent, a thickening agent usually used in water-based paints such as an alkali swelling thickener, a polyether-based associative thickener, and hydroxyethyl cellulose can be used.

  As the antifoaming agent, antifoaming agents usually used for water-based paints such as silicon-based, mineral oil-based, and hydrocarbon-based can be used.

(Coating)
About the coating film formed with the aqueous clear coating composition of this invention, the 60 degree gloss value of the dry coating film whose film thickness is 50 micrometers is 85 or less, Preferably it is 60 or less, for example, 40 or less.
Moreover, the water contact angle of the dry coating film with a film thickness of 50 μm is 60 ° or less, preferably 50 ° or less, for example 40 ° or less.

  The haze of the coating film formed by the aqueous clear coating composition of the present invention can be 95 or less, preferably 80 or less. Moreover, the coating film formed with the aqueous clear coating composition of the present invention exhibits excellent stain resistance.

(Coating film forming method)
This invention also provides the coating-film formation method including the process of apply | coating the natural-drying type | formula aqueous clear coating composition mentioned above to a to-be-coated article, and air-drying.

  In order to form a coating film on the surface of an object to be coated, for example, various coating methods such as a spray coating method, a roller coating method, a bar coating method, an air knife coating method, a brush coating method, and a dipping method can be appropriately selected. . The aqueous clear coating composition is applied so that the dry film thickness after coating is 10 to 100 μm, preferably 20 to 50 μm.

  The method for forming a coating film of the present invention includes a step of naturally drying the applied aqueous clear coating composition. For example, the natural dry type aqueous clear coating composition has a temperature atmosphere of 40 ° C. or less, for example, 1 A coating film can be formed by standing for 1 week from time.

The aqueous clear coating composition of the present invention is not particularly limited in the position where the coating film is formed, and can be formed into a coated product by forming a film on various articles (for convenience, referred to as an object to be coated). Examples of such objects to be coated include cement mortar, slate board, gypsum board, extruded board, foamable concrete, metal, glass, porcelain tile, asphalt, wood, waterproof rubber material, plastic, calcium silicate base material, etc. The coating film formed from the aqueous clear coating composition of the present invention can be positioned as the surface finish of these various objects to be coated. For example, the water-based clear coating composition of the present invention can be suitably used for outer walls of buildings such as iron structures such as bridges, detached houses, apartments, and commercial facilities.
In a certain aspect, the said to-be-coated article may be formed with a desired coating film, for example, an exterior coating film such as a stone-like coating film, a waterproof coating film, and the like. In such embodiments, the aqueous clear coating composition of the present invention can be applied over a variety of coatings.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

[Production Example 1] Production of acrylic resin emulsion (1) A flask equipped with a stirrer, a reflux condenser, a temperature control device, and a dropping pump was charged with deionized water and the first monomer mixture, and the internal temperature of the flask was adjusted to 40. After raising the temperature to 0 ° C., the following reducing agent aqueous solution and first initiator aqueous solution were added. After confirming the peak top temperature due to the polymerization exotherm, the internal temperature of the flask was maintained at 75 ° C. Table 1 shows specific components and addition amounts in each mixture.

  Subsequently, 0.5 hours after adding the reducing agent aqueous solution, the second monomer mixture was added dropwise over 2.75 hours. Moreover, the 2nd initiator aqueous solution was dripped in parallel over 3 hours from the dripping pump different from a 2nd monomer mixture. Table 2 shows specific components and addition amounts in each mixture.

  After maintaining at 75 ° C. for 1 hour, the resulting dispersion was cooled to room temperature, 1.45 parts of 28% ammonia water, 0.7 parts of adipic acid dihydrazide, 5.0 parts of Neucor 707SF, and Emulgen 1150S 1.7 parts of -60 was added to obtain an acrylic resin emulsion (1). The solid content was 46%.

[Production Example 2] Production of acrylic silicone resin emulsion (2) First, an aqueous polyorganosiloxane polymer dispersion (SiEm) was prepared.
The raw material compositions shown in Table 3 were premixed with a homomixer and emulsified with a pressure homogenizer at a pressure of 200 kg / cm ² to obtain a pre-emulsion.
Next, water (90 parts) and dodecylbenzenesulfonic acid (10 parts) were charged into a flask equipped with a stirrer, a reflux condenser, a temperature controller and a dropping pump, and the internal temperature of the flask was kept at 85 ° C. with stirring. The pre-emulsion was added dropwise over 4 hours. After completion of the dropwise addition, the polymerization is further allowed to proceed for 1 hour, the resulting polyorganosiloxane copolymer dispersion is cooled, and the following sodium hydroxide aqueous solution is added to obtain a polyorganosiloxane copolymer aqueous dispersion (SiEm). Prepared. The solid content of the SiEm was 18% by mass.

Next, an acrylic silicone resin emulsion (2) was produced.
The above-mentioned SiEm, deionized water, and the first monomer mixture were charged into a flask equipped with a stirrer, a reflux condenser, a temperature controller, and a dropping pump, and the temperature of the flask was raised to 40 ° C. An aqueous solution and a first aqueous initiator solution were added. After confirming the peak top temperature due to the polymerization exotherm, the internal temperature of the flask was maintained at 75 ° C. Table 4 shows specific components and addition amounts in each mixture.

  Subsequently, 0.5 hours after adding the reducing agent aqueous solution, the second monomer mixture was added dropwise over 2.75 hours. Moreover, the 2nd initiator aqueous solution was dripped in parallel over 3 hours from the dripping pump different from a 2nd monomer mixture. Table 5 shows specific components and addition amounts in each mixture.

  After maintaining at 75 ° C. for 1 hour, the resulting dispersion was cooled to room temperature, 1.45 parts of 28% ammonia water, 0.7 parts of adipic acid dihydrazide, 5.0 parts of Neucor 707SF, and Emulgen 1150S 1.7 parts of -60 (trade name, manufactured by Kao Corporation) was added to obtain an acrylic resin emulsion (2). The solid content was 46%.

Example 1
Raw materials having the blending amounts shown in Table 6 were mixed with stirring with a disper to prepare an aqueous clear coating composition. Table 7 shows the blending amounts of the silica fine particles (B) and the gloss modifier (C) with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion.

(Examples 2 to 43, Comparative Examples 1 to 5)
Acrylic resin emulsion (A), silica fine particles (B), and gloss modifier (C) were blended in the proportions shown in Table 7 or Table 8, and aqueous clear coating compositions according to Examples and Comparative Examples were prepared. In Example 41, for the coating film formation used for the coating film property evaluation described later, the aqueous clear coating composition was dried at a temperature of 40 ° C. after coating to form a coating film.

(Gloss measurement)
The coating composition in each example and comparative example was coated on a glass plate (thickness 2 mm) using a 6MIL applicator and dried at room temperature for 1 day, and then the glass plate was placed on the black portion of the black and white opaque paper. , 60 ° gloss was measured. For the measurement, MULTI GLOSS 268 PLUS (manufactured by KONICA MINOLTA) was used. The obtained results are shown in Table 7 or Table 8. The lower the gloss value, the more matte effect was obtained.

(Measurement of water contact angle)
The coating composition in each Example and Comparative Example was applied on a glass plate using a 6MIL applicator and dried at room temperature for 1 day.
Using a contact angle meter Drop Master 500 (manufactured by Kyowa Interface Chemical Co., Ltd.), 4 μl of water droplets were dropped on the coating film, and the water contact angle after 20 seconds was measured. The obtained results are shown in Table 7 or Table 8. The smaller the water contact angle, the better the water wettability of the coating film surface, and the effect of facilitating washing away the adhering contaminants with water due to rain.

(Transparency evaluation of coating film)
Haze was measured using a haze meter NDH2000 (manufactured by Nippon Denshoku Co., Ltd.) using the same coating film (on a glass plate) used for gloss measurement as a test specimen. The obtained results are shown in Table 7 or Table 8. The effect that the transparency of a coating film is so high that a haze value is small is acquired.

(Contamination resistance evaluation)
Preparation of contaminated liquid: A contaminated liquid was prepared by suspending 1% each of hydrophobic carbon black (Mitsubishi Carbon Black # 20, manufactured by Mitsubishi Chemical Corporation) and hydrophilic carbon black (FW200, manufactured by Orion Engineered Carbons) in water.

Preparation of test plate: A white glossy water-based emulsion paint was applied to an aluminum plate with a 6 mil applicator and dried at room temperature for 1 day. Next, the paints of Examples and Comparative Examples were brushed and dried at room temperature for 7 days so that the solid application amount was 50 g / m ² . Then, it cut | disconnected to 10x5 cm and used for the contamination | pollution resistance test.

  Contamination resistance test: The above-mentioned test piece was coated with the contamination liquid 20 times with a brush and then dried at room temperature for 3 hours. Thereafter, it was washed twice with a brush under running water and dried at room temperature for 3 hours.

Evaluation of stain resistance: The hue (ΔL) after the test was measured based on the test piece before the stain resistance test. (Color difference meter CR-400, manufactured by KONICA MINOLTA)
The obtained results are shown in Table 7 or Table 8. The smaller the stain resistance value (absolute value), the better the stain resistance.

Thus, according to the air drying type clear coating composition which concerns on this invention, it can form the coating film which has the outstanding antifouling property and can bring out the matting effect. Furthermore, according to the air-drying clear coating composition according to the present invention, it is possible to obtain a coating film excellent in antifouling property, matting effect and haze value balance. For example, the water contact angle measured on a glass plate may be 5 to 10 ° higher than when the water contact angle is measured on a white enamel coating film.
On the other hand, the coating film formed from the aqueous clear coating composition according to the comparative example cannot have both a matte effect and an antifouling property.

  INDUSTRIAL APPLICABILITY The present invention can provide an air-drying aqueous clear coating composition that can form a coating film that has excellent antifouling properties and can provide a matting effect. Furthermore, this invention can provide the formation method of the coating film using the aqueous coating material composition which has such a characteristic. Such a water-based clear coating composition can be suitably used for outer walls of buildings such as iron structures such as bridges, detached houses, apartments, and commercial facilities.

Claims (8)

An air-drying aqueous clear coating composition comprising an acrylic resin emulsion (A), silica fine particles (B), and a gloss modifier (C) having a water absorption of 0.8 g / g or more,
A naturally-drying aqueous clear coating composition having a 60 ° gloss value of 85 or less and a water contact angle of 60 ° or less of a dry coating film having a film thickness of 50 μm. The average particle size of the silica fine particles (B) is in the range of 0.5 to 60 nm,
2. The air-drying clear coating composition according to claim 1, wherein the gloss adjusting agent (C) has an average particle size in the range of 0.5 to 60 μm.   The glossiness modifier (C) is one or more selected from the group consisting of silica, talc, organic beads, calcium carbonate, kaolin, barium sulfate, mica, and diatomaceous earth, according to claim 1 or 2. A naturally dry aqueous clear coating composition.   The air drying clear coating composition according to any one of claims 1 to 3, wherein the gloss adjusting agent (C) is one or more selected from the group consisting of silica, talc and organic beads. object. The gloss modifier (C) includes at least one selected from the group consisting of silica and talc and organic beads, and the ratio of the total addition amount of silica and talc and the total addition amount of organic beads (( Silica + Talc) / Organic beads)
The air-drying clear coating composition according to any one of claims 1 to 4, wherein is 0.07 to 2.0.   The amount of the silica fine particles (B) contained in the aqueous clear coating composition is 0.5 to 25 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). 6. The air-drying clear coating composition according to any one of 5 above.   The amount of the gloss modifier (C) contained in the aqueous clear coating composition is 1 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic resin emulsion (A). 7. The air-drying clear coating composition according to any one of 6 above.   The coating-film formation method including the process of apply | coating the natural-drying type water-based clear coating composition of any one of Claims 1-7 to a to-be-coated article, and air-drying.