JP2012021107A - Aqueous two-part clear coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous two-part clear coating composition suitable for forming a clear coating film having good polishing workability even under forced drying conditions and excellent in finished appearance after polishing.SOLUTION: The aqueous two-part clear coating composition comprises an acrylic resin emulsion (I) prepared by dispersing in water an acrylic resin obtained by polymerizing polymerizable unsaturated monomer components having mutually different compositions separately in multiple stages in the presence of an organic solvent, and a curing agent (II) containing a polyisocyanate component (c1) having an acid radical, wherein a polymerizable unsaturated monomer component (A) as one of the above monomer components comprises an epoxy group-containing monomer (a1), a hydroxyl group-containing monomer (a2) and other monomers (a3), and a polymerizable unsaturated monomer component (B) as the other of the above monomer components comprises a carboxyl group-containing monomer (b1), a hydroxyl group-containing monomer (b2) and other monomers (b3).

Description

  The present invention relates to an aqueous two-part clear coating composition.

  In recent years, environmental pollution and effects on the human body have been taken into account, and the number of cases in which water-based paints are used instead of solvent-based paints has increased considerably.

  For example, the outer plate portion of an automobile body is generally coated with a multilayer coating film composed of an undercoating film, an intermediate coating film, a top coating film, and a clear coating film for the purpose of providing corrosion protection and aesthetics. Among these coating films, the base coating composition, the intermediate coating composition, and the top coating composition that form the base coating film, the intermediate coating film, and the top coating film are being made water-based. With regard to the clear coating composition, it is difficult to achieve the same performance and finished appearance as the solvent-based clear coating composition, and the development thereof is required.

  For example, the present applicant has proposed an aqueous clear coating composition containing a hydroxyl group- and acid group-containing particulate resin aqueous dispersion and a crosslinking agent in Patent Document 1 and exhibiting a specific viscosity.

  Patent Document 2 discloses an acrylic polyol aqueous dispersion obtained by water-dispersing a specific acrylic polyol obtained by polymerization including solution polymerization for producing a core and solution polymerization for producing a shell, and sulfonic acid. An aqueous two-component curable composition containing a curing agent containing a polyisocyanate having a group is disclosed.

  According to the water-based clear coating composition described in these patent documents, it is possible to form a clear coating film having excellent smoothness and gloss and having no appearance of coating surface abnormalities such as wax, The clear coating film is obtained by high-temperature baking of so-called two-coat one-bake, which is an advantageous condition in terms of finish and physical properties of the coating film.

  By the way, also in the field of automobile repair coating, water-based paints are required from the viewpoint of improving the environment at repair sites.

  Because automobile bodies are equipped with parts that are sensitive to high temperatures such as gasoline tanks, electrical equipment, and computers, repair coatings cannot be baked at high temperatures when repairing automobile bodies and are forced under relatively mild conditions. It is common to perform drying.

  Also, at the repair site, the top coat clear coating is completely removed to match the finished appearance so that the repair coating is indistinguishable from the unrepaired part, and to remove dust and dirt adhering to the repair coating. Polishing with a compound or the like is usually performed before drying.

  In this way, the water-based clear paint composition used for automobile repair coating has a finish similar to that of the solvent-based clear paint composition under forced drying conditions that do not affect parts in the automobile body. In addition, the coating film is required to have excellent polishing workability.

  However, as described above, it is difficult to design a heat-curable water-based clear coating composition that has excellent coating film properties and excellent finished appearance, as described above, and the coating composition described in Patent Documents 1 and 2 above. However, although it is effective with respect to abnormal coating surfaces of clear coatings such as armpits, sacks, etc., there is still room for improvement with respect to the polishing workability of the clear coating film dried under milder conditions and the finish after polishing.

WO2007 / 013684 pamphlet JP 2009-212244 A

  An object of the present invention is to provide a two-component water-based clear coating composition that is suitable for forming a clear coating film having good polishing workability even under forced drying conditions and having an excellent finished appearance after polishing.

As a result of intensive studies on the above-mentioned problems, the present inventors have obtained by polymerizing a polymerizable unsaturated monomer (A) having a specific composition and a polymerizable unsaturated monomer (B) having a specific composition in multiple stages. An aqueous two-component composition containing an acrylic resin emulsion obtained by dispersing an acrylic resin in water and a curing agent containing a specific polyisocyanate component can form a clear coating film excellent in polishing workability and finish. And reached the present invention.
That is, the present invention
1. An aqueous two-component clear coating composition comprising an acrylic resin emulsion (I) and a curing agent (II), wherein the acrylic resin emulsion (I) has a different composition in the presence of an organic solvent. A polymerizable unsaturated monomer component (A) that is obtained by water-dispersing an acrylic resin obtained by polymerizing a monomer component in multiple stages,
Epoxy group-containing polymerizable unsaturated monomer (a1),
A polymerizable unsaturated monomer component (B) containing a hydroxyl group-containing polymerizable unsaturated monomer (a2) and another polymerizable unsaturated monomer (a3) and used in at least one other stage of polymerization,
Carboxyl group-containing polymerizable unsaturated monomer (b1),
Comprising a hydroxyl group-containing polymerizable unsaturated monomer (b2) and other polymerizable unsaturated monomers (b3),
The aqueous two-component clear coating composition, wherein the curing agent (II) contains a polyisocyanate component (c1) having an acid group.
2. 1 item | term in which the other polymerizable unsaturated monomer (a4) which is a copolymerization component of a polymerizable unsaturated monomer component (A) contains the methacrylate which has a C3-C4 alkyl group as a part of the component. The aqueous two-component clear coating composition according to claim,
3. The other polymerizable unsaturated monomer (a4), which is a copolymerization component of the polymerizable unsaturated monomer component (A), includes a polymerizable unsaturated monomer having an isobornyl group as a part of the component. The aqueous two-component clear coating composition according to claim,
4). Polymerizability having a methacryloyl group in which the content of methacrylate having 3 to 4 carbon atoms is in the range of 20 to 65% by mass in all polymerizable unsaturated monomers used for the production of acrylic resin emulsion (I) The aqueous two-component clear coating composition according to any one of items 1 to 3, wherein the content of the unsaturated monomer is in the range of 30 to 90% by mass,
5. Any one of Items 1 to 4, wherein the amount of the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A) is in the range of 3 to 30 mol. Or an aqueous two-component clear coating composition according to claim 1,
6). The aqueous 2 according to any one of 1 to 5, wherein the curing agent (II) further comprises a polyisocyanate component (c2) other than the (c1) in addition to the polyisocyanate component (c1) having an acid group. Liquid-type clear paint composition,
7). The aqueous 2 liquid according to any one of 1 to 6, wherein the curing agent (II) further comprises an organic solvent having a solubility in 100 g of water of 10 g or less in addition to the polyisocyanate component (c1) having an acid group. Type clear paint composition,
About.

  According to the aqueous two-component clear coating composition of the present invention, since the storage stability of the acrylic resin emulsion is very good, the composition of a plurality of polymerizable unsaturated monomer components used in the production of the acrylic resin emulsion is reduced. It has the advantage that it can be designed widely. By combining the emulsion with a polyisocyanate component having an acid group, a clear coating film excellent in polishing workability and finish after polishing can be formed even under forced drying conditions. Moreover, according to this invention, the miscibility of an acrylic resin emulsion and a hardening | curing agent is very favorable, and a clear coating film with a transparent feeling can be formed.

Acrylic resin emulsion (I);
The acrylic resin emulsion (I) used in the aqueous two-component clear coating composition of the present invention is obtained by polymerizing polymerizable unsaturated monomer components having different compositions in multiple stages in the presence of an organic solvent. It is an emulsion obtained by water-dispersing the obtained acrylic resin.

As the polymerizable unsaturated monomer component (A) in at least one stage for producing the acrylic resin, an epoxy group-containing polymerizable unsaturated monomer (a1),
It contains a hydroxyl group-containing polymerizable unsaturated monomer (a2) and other polymerizable unsaturated monomers (a3).

  In the present invention, the epoxy group-containing polymerizable unsaturated monomer (a1) is reacted with a carboxyl group contained in the polymerizable unsaturated monomer component (B) described later, and a copolymer of the polymerizable unsaturated monomer component (A) A monomer used for grafting a copolymer of the polymerizable unsaturated monomer component (B) to further improve the water dispersion stability of the acrylic resin emulsion (I), such as glycidyl (meth) acrylate, β -Methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether, etc. These can be used alone or in combination of two or more It can be used.

  The hydroxyl group-containing polymerizable polymerizable unsaturated monomer (a2) is used to introduce a hydroxyl group for reacting with the curing agent (II) described later into the acrylic resin emulsion (I), and to disperse the acrylic resin emulsion (I) in water. Monomers that are copolymerized to contribute to the properties, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. A monoesterified product of (meth) acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms; a ε-caprolactone modified product of a monoesterified product of the (meth) acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms; Examples include allyl alcohol, which can be used alone or in combination of two or more. .

  The other polymerizable unsaturated monomer (a3) is a polymerizable unsaturated monomer other than the monomer (a1) and the monomer (a2), and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl. (Meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meta ) Acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl acrylate (trade name, manufactured by Osaka Organic Chemical Co., Ltd.), cyclohexyl (Meta) ak Rate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, alkyl or cycloalkyl (meth) acrylate such as tricyclodecanyl (meth) acrylate; isobornyl (meth) acrylate, etc. Polymerizable unsaturated monomer having an isobornyl group; Polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; Polymerizable unsaturated monomer having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate Saturated monomer; aromatic ring-containing polymerizable unsaturated monomer such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, Vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltriisopropoxysilane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) Acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane, γ- (meth) acryloyloxypropyltri-n-propoxysilane, γ- (meth) acryloyloxypropyltriisopropoxysilane, vinyltri Polymerizable unsaturated monomers having hydrolyzable silyl groups such as acetoxysilane, β- (meth) acryloyloxyethyltrimethoxysilane; perfluorobutylethyl (meth) acrylate, perfluoroio Perfluoroalkyl (meth) acrylates such as tilethyl (meth) acrylate; polymerizable unsaturated monomers having a fluorinated alkyl group such as fluoroolefin; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. Vinyl compounds; phosphate group-containing polymerizable unsaturated monomers such as 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; (meth) acrylic Carboxyl group-containing polymerizable unsaturated monomers such as acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate; (meth) acrylonitrile, (meth) acrylamide, Nitrogen-containing polymerizable unsaturated monomers such as ethylene bis (meth) acrylamide, ethylenebis (meth) acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl (meth) acrylate and amines; allyl (meth) Polymerizable unsaturated monomers having at least two polymerizable unsaturated groups in one molecule such as acrylate and 1,6-hexanediol di (meth) acrylate; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl ( Meth) acrylate, allyl sulfonic acid, 4-styrene sulfonic acid and the like; polymerizable unsaturated monomers having a sulfonic acid group such as sodium salt and ammonium salt of these sulfonic acids; maleic anhydride, itaconic anhydride, citraconic anhydride, etc. Heavy with acid anhydride groups Sex unsaturated monomers, and these may be used alone or in combination.

  In the present invention, the other polymerizable unsaturated monomer (a3) preferably includes a methacrylate having an alkyl group having 3 to 4 carbon atoms as a part of the component from the viewpoint of the abrasiveness of the clear coating film. ing.

  Examples of the methacrylate having an alkyl group having 3 to 4 carbon atoms in the present invention include n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, tert-butyl methacrylate, and the like. Can be used alone or in combination of two or more.

  The amount thereof used is suitably 10% by mass or more, preferably 50% by mass or more, more preferably 60 to 95% by mass in the other polymerizable unsaturated monomer (a3).

  In addition, in the other polymerizable unsaturated monomer (a3), it is particularly preferable that the clear coating film has an abrasive property of a clear coating film that contains both n-butyl methacrylate and i-butyl methacrylate as methacrylates having an alkyl group having 3 to 4 carbon atoms. Desirable in terms. The preferred use ratio when both are included is suitably in the range of 95/5 to 5/95, particularly 10/90 to 50/50, in terms of mass ratio of n-butyl methacrylate / i-butyl methacrylate.

  The other polymerizable unsaturated monomer (a3) preferably contains a polymerizable unsaturated monomer having an isobornyl group as a part of the component from the viewpoint of the abrasiveness of the clear coating film.

  Examples of the isobornyl group-containing polymerizable unsaturated monomer include isobornyl (meth) acrylate, and can be used alone or in combination.

  When the isobornyl group-containing polymerizable unsaturated monomer is used, the use amount thereof is in the range of 1 to 50% by mass, preferably 5 to 20% by mass in the other polymerizable unsaturated monomer (a3). This is suitable from the point of abrasiveness of the clear coating film.

  In the present invention, the acrylic resin for producing the acrylic resin emulsion (I) has a polymerizable unsaturated monomer component (B) as a copolymer component in addition to the polymerizable unsaturated monomer component (A).

Such polymerizable unsaturated monomer component (B) is:
Carboxyl group-containing polymerizable unsaturated monomer (b1),
It comprises a hydroxyl group-containing polymerizable unsaturated monomer (b2) and other polymerizable unsaturated monomers (b3).

  As the carboxyl group-containing polymerizable unsaturated monomer (b1), an aqueous dispersion group is introduced into the acrylic resin emulsion (I) and reacted with an epoxy group contained in the copolymer of the polymerizable unsaturated monomer component (A). It is also a monomer used to introduce a functional group to be used, and specifically includes (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, etc., and these may be used alone or in combination of two or more. Can be used.

  The hydroxyl group-containing polymerizable unsaturated monomer (b2) is the same as the compounds listed in the hydroxyl group-containing polymerizable unsaturated monomer (a2), and can be used alone or in combination of two or more thereof. .

  The other polymerizable unsaturated monomer (b3) is a polymerizable unsaturated monomer other than the monomer (b1) and the monomer (b2), and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl. (Meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meta ) Acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methyl Alkyl or cycloalkyl (meth) acrylate such as hexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecanyl (meth) acrylate; isobornyl group such as isobornyl (meth) acrylate A polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; a polymerizable unsaturated monomer having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate; Aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene, etc .; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate Phosphoric acid group-containing polymerizable unsaturated monomers such as 2-acryloyloxypropyl acid phosphate and 2-methacryloyloxypropyl acid phosphate; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid Polymerizable unsaturated monomers having sulfonic acid groups such as sodium salts and ammonium salts of these sulfonic acids; polymerization having acid anhydride groups such as maleic anhydride, itaconic anhydride and citraconic anhydride Unsaturated monomers, etc .; vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltriisopropoxysilane, γ- (meth) a Liloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane, γ- (meth) Polymerizability having hydrolyzable silyl groups such as acryloyloxypropyltri-n-propoxysilane, γ- (meth) acryloyloxypropyltriisopropoxysilane, vinyltriacetoxysilane, β- (meth) acryloyloxyethyltrimethoxysilane Unsaturated monomer; perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; fluorinated alkyl group such as fluoroolefin Polymerizable unsaturated monomers; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylonitrile, (meth) acrylamide, methylenebis (meth) acrylamide, ethylenebis (meth) Nitrogen-containing polymerizable unsaturated monomers such as acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl (meth) acrylate and amines; allyl (meth) acrylate, 1,6-hexanediol di (meth) ) Polymerizable unsaturated monomers having at least two polymerizable unsaturated groups in one molecule such as acrylate, and the like can be used, and these can be used alone or in combination of two or more.

  In addition, the other polymerizable unsaturated monomer (b3) contains a methacrylate having a C3-4 alkyl group as a part of the component from the viewpoint of finish after the clear coating film is polished. Is suitable.

  The methacrylate having an alkyl group having 3 to 4 carbon atoms can be appropriately selected from the compounds listed in the description of the other polymerizable monomer (a3), and can be used as another polymerizable unsaturated monomer. The content in (b3) is 10% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and the total amount of the monomer (b3) is an alkyl group having 3 to 4 carbon atoms. A methacrylate having

  In this invention, content of the methacrylate which has a C3-C4 alkyl group is 20-65 mass% in the all polymerizable unsaturated monomer used for manufacture of acrylic resin emulsion (I), Preferably it is 40. It is within the range of ˜60% by mass, and the total content of polymerizable unsaturated monomers having a methacryloyl group is within the range of 30 to 90% by mass, preferably within the range of 50 to 80% by mass. This is desirable from the viewpoint of the finish and polishing workability of the coating film formed from the coating composition, and the finish after the polishing work.

  In the present specification, examples of the polymerizable unsaturated monomer having a methacryloyl group include compounds having a methacryloyl group in the molecule, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n -Butyl methacrylate, i-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, tridecyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, methyl cyclohexyl methacrylate, t -Butylcyclohexyl methacrylate, cyclododecyl methacrylate, tricyclodecanyl methacrylate Alkyl or cycloalkyl methacrylate such as acrylate; methacrylate having an isobornyl group such as isobornyl methacrylate; methacrylate having an adamantyl group such as adamantyl methacrylate; methacrylate having a cyclodecenyl group such as tricyclodecenyl methacrylate; methacrylic acid; benzyl methacrylate Gamma-methacryloyloxypropyltrimethoxysilane, gamma-methacryloyloxypropylmethyldimethoxysilane, gamma-methacryloyloxypropyltriethoxysilane, gamma-methacryloyloxypropylmethyldiethoxysilane, gamma-methacryloyloxypropyltri-n-propoxysilane , Γ-methacryloyloxypropyltriisopropoxysilane, β-methacryloyloxyethyl Methacrylates having alkoxysilyl groups such as rutrimethoxysilane; perfluoroalkyl methacrylates such as perfluorobutylethyl methacrylate and perfluorooctylethyl methacrylate; phosphate groups such as 2-methacryloyloxyethyl acid phosphate and 2-methacryloyloxypropyl acid phosphate Containing methacrylate; monoesterified product of methacrylic acid such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, etc. and a dihydric alcohol having 2 to 8 carbon atoms; Ε-caprolactone modified product of monoesterified product with dihydric alcohol having 2 to 8 carbon atoms; methacrylonitrile, methacrylamide, Tylene bismethacrylamide, ethylenebismethacrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl methacrylate and amines; polymerizable unsaturated groups such as allyl methacrylate and 1,6-hexanediol dimethacrylate Methacrylates having at least two per molecule; epoxy groups such as glycidyl methacrylate, β-methylglycidyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexylethyl methacrylate, 3,4-epoxycyclohexylpropyl methacrylate Contains methacrylate; 2-sulfoethyl methacrylate and its sodium salt and ammonium salt.

In the acrylic resin emulsion (I), the use ratio of the monomers (a1) to (a3) in the polymerizable unsaturated monomer component (A) can be appropriately adjusted as long as it is within the scope of the present invention.
The monomer (a1) is 0.1 to 40% by mass, preferably 0.5 to 25% by mass,
The monomer (a2) is 15 to 54.9% by mass, preferably 20 to 44.5% by mass,
The monomer (a3) is 45 to 84.9% by mass, preferably 55 to 79.5% by mass,
Can be within the range of

Moreover, the use ratio of these monomers (b1) to (b3) in the polymerizable unsaturated monomer component (B) can be appropriately adjusted as long as it is within the scope of the present invention.
Monomer (b1) is 5 to 60% by mass, preferably 10 to 50% by mass,
The monomer (b2) is 20 to 75% by mass, preferably 25 to 65% by mass,
The monomer (b3) is 20 to 75% by mass, preferably 25 to 65% by mass,
Can be within the range of

  Further, in these polymerizable unsaturated monomer components (A) and (B), the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A). From the viewpoint of the storage stability of the acrylic resin emulsion (I), the finish of the clear coating film, and the polishing properties, the amount is adjusted to be in the range of 3 to 30 mol, particularly 6 to 20 mol. Is suitable.

  In the present invention, the use ratio of the polymerizable unsaturated monomer components (A) and (B) is 60/40 to 95/5, particularly 70/30 to 90, in terms of mass ratio of monomer component (A) / monomer component (B). / 10 is suitable from the viewpoint of the water dispersion stability of the acrylic resin emulsion (I) and the finish of the clear coating film.

  The polymerization of the polymerizable unsaturated monomer components (A) and (B) is not particularly limited. For example, the polymerizable unsaturated monomer component (A) is dropped while heating in the presence of an organic solvent. The resulting acrylic resin emulsion (I) is dispersed in water by polymerizing and polymerizing the polymerizable unsaturated monomer component (B) dropwise into the copolymer solution of the polymerizable unsaturated monomer component (A). This is desirable because it tends to be excellent in stability and storage stability.

  Moreover, you may add suitably the polymerization by polymerizable unsaturated monomer components other than the said polymerizable unsaturated monomer component (A) and (B) as needed.

  The reaction temperature for polymerizing the monomers (A) and (B) is usually in the range of about 60 to about 200 ° C., preferably about 70 to about 160 ° C., and the reaction time is usually about 10 hours or less, preferably about 0.5 to about 6 hours.

  In said reaction, it is preferable to add a polymerization initiator suitably. Examples of such polymerization initiators include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, di-tert-amyl peroxide, and t-butyl. Organic peroxides such as peroxy-2-ethylhexanoate, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyro Nitrile, azobis (2,4-dimethylvaleronitrile), azobis (2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobuta Acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], azobis {2-methyl-N- [2- (1-hydroxy Butyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate, sodium persulfate, and the like.

  These polymerization catalysts may be used alone or in combination of two or more. Moreover, there is no problem even if the kind and amount of the polymerization initiator are different during the polymerization of the polymerizable unsaturated monomer component (A) and the polymerizable unsaturated monomer component (B).

  The blending amount of the polymerization initiator is 0.01 to 20 parts by weight, particularly 0.1 to 15 parts by weight, more particularly 0.3 to 10 parts by weight based on 100 parts by weight of the polymerizable unsaturated monomer used at that stage. The range of parts by mass is preferable from the viewpoint of water dispersion stability of the resulting acrylic resin emulsion (I).

  The polymerization is usually carried out in the presence of an organic solvent. The selection of the organic solvent can be appropriately performed in consideration of the polymerization temperature, ease of handling during emulsion production, and long-term storage stability of the resulting aqueous dispersion.

  An organic solvent can also be added when the acrylic resin is dispersed in water.

  As the organic solvent, alcohol solvents, cellosolve solvents, carbitol solvents and the like are preferable. Specifically, for example, alcohol solvents such as n-butanol; ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol mono n-butyl ether, Examples thereof include cellosolve solvents such as dipropylene glycol monomethyl ether and dipropylene glycol mono n-butyl ether; carbitol solvents such as diethylene glycol monobutyl ether and diethylene glycol monoethyl ether.

  Further, as the organic solvent, an inert organic solvent that is not mixed with water other than the above can also be used as long as it does not hinder the water dispersion stability of the acrylic resin emulsion (I). Examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as methyl ethyl ketone and cyclohexanone.

  The acrylic resin obtained as described above has a weight average molecular weight within the range of 5,000 to 100,000, particularly 10,000 to 50,000, more particularly 10,000 to 30,000. It is suitable from the viewpoints of the water dispersion stability of the resin emulsion (I), the finish of the clear coating film, smoothness, abrasiveness, and the like.

  In this specification, the weight average molecular weight of the acrylic resin is “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) as a gel permeation chromatograph, and “TSKgel G4000HXL” is used as a column. A total of four “TSKgel G3000HXL” and one “TSKgel G2000HXL” (trade name, all manufactured by Tosoh Corporation) were used, a differential refractometer was used as a detector, a mobile phase; tetrahydrofuran, Measurement can be performed under the conditions of measurement temperature: 40 ° C., flow rate: 1 mL / min.

  In the present invention, the acrylic resin emulsion (I) can be obtained by dispersing the acrylic resin in water.

  As a method of water dispersion, some or all of anionic groups such as carboxyl groups contained in the acrylic resin are neutralized with a basic compound and dispersed in water, or in an aqueous medium containing a basic compound. It is also possible to add and disperse the acrylic resin.

  Examples of the basic compounds for neutralization include ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, triethylamine, tributylamine, Examples thereof include organic amines such as dimethylethanolamine and diethylenetriamine; alkali metal hydroxides such as caustic soda and caustic potash; 0.1 to 1.5 equivalents, preferably 0.5 to the carboxyl group in the acrylic resin. It is appropriate to use ˜1.2 equivalents.

  The acrylic resin emulsion (I) obtained as described above is a core-shell type acrylic emulsion having a copolymer of a polymerizable unsaturated monomer component (A) as a core and a polymerizable unsaturated monomer component (B) as a shell. The average particle diameter can be within a range of 0.05 to 1.0 μm, preferably 0.08 to 0.8 μm.

  In this specification, the average particle size is diluted with a submicron particle analyzer N4 (trade name, manufactured by Beckman Coulter, Inc., particle size distribution measuring device) to a concentration suitable for measurement with deionized water, The value measured at room temperature (about 20 ° C.).

  Further, the hydroxyl value per solid content of the acrylic resin emulsion (I) is in the range of 70 to 170 mgKOH / g, particularly 80 to 130 mgKOH / g, more particularly 100 to 120 mgKOH / g, and the acid value per solid content is 5 to 5. If it is in the range of 50 mgKOH / g, especially 20 to 35 mgKOH / g, more particularly 20 to 30 mgKOH / g, it is suitable from the viewpoint of the finish of the clear coating film to be formed, the polishability, the finish after polishing work, etc. Yes.

  The coating form of the aqueous two-component clear coating composition of the present invention can be a two-component composition in which the main component containing the acrylic resin emulsion (I) and the curing agent (II) described below are mixed immediately before use.

  The ratio of the acrylic resin emulsion (I) resin solid content in the total resin solid content contained in the main agent can be 60% by mass or more, particularly 80 to 100% by mass.

  In addition to the acrylic resin emulsion (I), the main agent is required to include a modifying resin, an antifoaming agent, a thickening agent, an ultraviolet absorber, a light stabilizer, a surface conditioner, an organic solvent, and the like as necessary. It can be included depending on the purpose.

Curing agent (II);
In the present invention, the above acrylic resin emulsion (I) is combined with a curing agent (II) containing a polyisocyanate component (c1) having an acid group, so that it can be polished in addition to various performances such as curability and weather resistance. An excellent film can be formed even under mild drying conditions.

  The polyisocyanate component (c1) having an acid group is a compound having an acid group and an isocyanate group. For example, a polyisocyanate is a compound having both a functional group reactive with an isocyanate group and an acid group in the molecule. It can be prepared by reacting.

  Examples of the polyisocyanate for adjusting the polyisocyanate component (c1) having an acid group include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cyclic aliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate. Aromatic diisocyanates such as tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4 , 6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate and the like, such as a polyisocyanate compound having three or more isocyanate groups. Organic polyisocyanate itself, or an adduct of each of these organic polyisocyanates with polyhydric alcohol, low molecular weight polyester resin or water, or the above-mentioned cyclized polymer of each organic polyisocyanate, and further, an isocyanate / biuret body Etc. Of these, aliphatic diisocyanates are preferred.

  Examples of the acid group possessed by the compound for reacting with the polyisocyanate include a carboxyl group, a phosphoric acid group, and a sulfonic acid group, and examples of the active hydrogen group include a hydroxyl group and an amino group.

  The polyisocyanate component (c1) having an acid group may have a polyether chain in addition to the acid group.

  In the present invention, the curing agent (II) further contains a polyisocyanate component (c2) other than (c1) in addition to the polyisocyanate component (c1) having an acid group. Suitable from the point of sex.

  As said polyisocyanate component (c2), what is conventionally used for an organic solvent type coating material can be used without a restriction | limiting, For example, the polyisocyanate which does not have an acid group or a nonionic group can be mentioned. Aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; Cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; Aromatic diisocyanates such as tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate Triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2; ´ Addition of organic polyisocyanate itself, such as a polyisocyanate compound having three or more isocyanate groups such as 5,5'-tetraisocyanate, or each of these organic polyisocyanates and a polyhydric alcohol, a low molecular weight polyester resin or water. Or cyclized polymers of the respective organic polyisocyanates described above, and isocyanate / biuret bodies, etc., can be used alone or in combination of two or more. Among them, cyclized polymers, particularly cyclized polymers of aliphatic diisocyanates are suitable.

  Examples of the polyisocyanate component (c2) include nonionic polyether-modified polyisocyanates obtained by modifying polyisocyanates as listed in the description of the component (c1) with a polyether compound.

  When the polyisocyanate component (c2) is used in combination, the use ratio of the polyisocyanate component (c1) having an acid group and the polyisocyanate component (c2) is (c2) in the total mass of (c1) and (c2). From the viewpoint of the water resistance of the clear coating film and the miscibility with the acrylic resin emulsion (I), it is suitable that it is in the range of 10% by mass or more, preferably 40 to 80% by mass.

  In the present invention, the curing agent (II) contains the polyisocyanate component (c1) as an essential component, and optionally includes a polyisocyanate component (c2). It can mix | blend suitably.

  Among these, as the organic solvent, it is possible to use an organic solvent having a solubility in 100 g of water at 25 ° C. of 10 g or less, preferably in the range of 0.1 to 8 g. The curing agent (II) and the acrylic resin emulsion ( It is suitable from the viewpoint of miscibility with the main agent containing I).

  Such organic solvents include isobutyl acetate, butyl acetate, isoamyl acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, methyl methoxybutyl acetate, methoxypropyl acetate, ethyl ethoxypropionate, nitropropane, methyl isobutyl ketone, methyl amyl. Examples thereof include ketones, oxohexyl acetate, dimethyl glutarate, dimethyl succinate, and dimethyl adipate. These can be used alone or in combination of two or more.

  Among the organic solvents, it is preferable that the boiling point is 100 ° C. or higher, particularly 110 ° C. to 250 ° C.

  From the viewpoint of miscibility with the main agent and storage stability of the curing agent, the organic solvent is preferably used in the range of 20 to 200% by mass, particularly 50 to 150% by mass, based on the solid content of the curing agent (II). ing.

Aqueous two-component clear coating composition The aqueous two-component clear coating composition of the present invention is mixed as needed by mixing the main component containing the acrylic resin emulsion (I) and the curing agent (II) immediately before use. And can be painted.

  As a compounding quantity of the said hardening | curing agent (II), the isocyanate equivalent of hardening | curing agent (II) is 0.5-3 equivalent normally with respect to 1 equivalent of hydroxyl groups normally contained in the said acrylic resin emulsion (I). It is preferably used within the range of 0 to 2.5 equivalents, more particularly 1.2 to 2.2 equivalents.

  The paint can be applied to the surface of various base materials, such as metals such as iron and aluminum; inorganic base materials such as slate plates and PC plates; organic base materials such as plastics; Can be mentioned. These coated surfaces may be coated with a water-based or solvent-type paint.

  Examples of the coating method of the aqueous two-component coating composition of the present invention include air spray coating, airless spray coating, electrostatic coating, brush coating, roller coating, lysing gun, universal gun, dipping, roll coater, curtain flow coater, Examples thereof include a roller curtain coater and a die coater. The roller curtain coater and the die coater can be selected as appropriate according to the use of the base material and the like, and may be applied a plurality of times.

  As a dry film thickness, it is 1-500 micrometers, for example, Preferably it can be in the range of 10-100 micrometers.

  The paint of the present invention can form a coating film excellent in finish and polish even under forced drying conditions, but the drying method of the formed coating film is not particularly limited and is baked or dried at room temperature. Of course, there is no problem even if it is done.

  Here, baking drying, forced drying, and room temperature drying are not strictly distinguished, but for example, drying atmosphere temperature is 100 to 200 ° C., particularly 120 to 180 ° C., baking drying is 40 ° C. or more and less than 100 ° C. In particular, the condition of 50 ° C. to 90 ° C. can be forced drying, and the condition of less than 50 ° C., particularly 40 ° C. or less can be room temperature drying.

  Moreover, when using this coating material for repair coatings, such as a motor vehicle, the repair clear film formed may be grind | polished as needed after repair coating. Examples of the polishing method include a method of polishing the repair clear coating film with water-resistant abrasive paper, and then polishing the polished surface sequentially with a compound for rough polishing and a compound for final polishing. It is possible to obtain a repair clear coating film that is excellent and has no noticeable difference in appearance from the unrepaired portion.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. In the following examples, “part” and “%” mean “part by mass” and “% by mass”, respectively.
≪Manufacture of acrylic polyol aqueous dispersion≫
Production Example 1
50 parts of propylene glycol monopropyl ether was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120 ° C. under a nitrogen stream while stirring. When the temperature reached 120 ° C., the following mixed solution 1 was added dropwise over 4 hours, and after completion of the addition, the temperature was maintained at 120 ° C. for 1 hour.
≪Mixed solution 1≫
5 parts of styrene,
13 parts of n-butyl methacrylate,
i-butyl methacrylate 31.5 parts,
2-ethylhexyl acrylate 5 parts,
10 parts of isobornyl acrylate,
20 parts of 2-hydroxyethyl methacrylate,
0.5 part of glycidyl methacrylate,
1.5 parts of t-butylperoxy-2-ethylhexanoate.
Subsequently, while the temperature of 120 ° C. was maintained, the following mixed solution 2 was added dropwise to the flask over 1 hour, and after completion of the addition, the mixture was maintained at 120 ° C. for 1.5 hours to obtain an acrylic polyol solution.
≪Mixed solution 2≫
6 parts i-butyl methacrylate,
6 parts 2-hydroxyethyl methacrylate,
3 parts acrylic acid,
0.3 parts of t-butylperoxy-2-ethylhexanoate.
The resin solid content of the obtained acrylic polyol solution was 77.5%, and the weight average molecular weight was 15000. Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the solid content became 85%. This was cooled to 95 ° C., 2.41 parts of dimethylethanolamine was added, and the mixture was stirred for 30 minutes. Further, deionized water was added dropwise over 2 hours with stirring so that the resin solid content was 45%, and the acid value per resin solid content was 21.4 mgKOH / g, and the hydroxyl value per resin solid content was 112 mgKOH / g. Acrylic polyol aqueous dispersion No1 having an average particle size of 0.12 μm was obtained.

Production Examples 2 to 14 and Production Example 16
An acrylic polyol aqueous dispersion was obtained in the same manner as in Production Example 1 except that the contents and blending amounts in Production Example 1 were as shown in Table 1 below.

Production Example 15 of Acrylic Polyol Water Dispersion Obtained by One-Step Polymerization 15
50 parts of propylene glycol monopropyl ether was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120 ° C. under a nitrogen stream while stirring. When the temperature reached 120 ° C., the following mixed solution was added dropwise over 4 hours, and after completion of the addition, the temperature was maintained at 120 ° C. for 1 hour.
≪Mixed solution≫
5 parts of styrene,
13 parts of n-butyl methacrylate,
37.5 parts of i-butyl methacrylate,
5.5 parts of 2-ethylhexyl acrylate,
10 parts of isobornyl acrylate,
26.0 parts 2-hydroxyethyl methacrylate,
3 parts acrylic acid,
1.8 parts of t-butylperoxy-2-ethylhexanoate,
Subsequently, a solution prepared by dissolving 0.5 part of t-butylperoxy-2-ethylhexanoate in 5 parts of propylene glycol monopropyl ether was dropped over 1 hour while maintaining the temperature of 120 ° C. Further, after completion of dropping, the mixture was kept at 120 ° C. for 1.5 hours to obtain an acrylic polyol solution. The obtained acrylic polyol had a resin solid content of 74.3 mass% and a weight average molecular weight of 20000.

Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the solid content became 85%. This was cooled to 95 ° C., 2.41 parts of dimethylethanolamine was added, and the mixture was stirred for 30 minutes. Furthermore, 100 parts of deionized water was added dropwise over 2 hours with stirring to adjust the resin solid content to 45%, but it was extremely high viscosity and difficult to handle. When deionized water was further added, the resin solid content was 20%, the viscosity became 2000 cps, and it became possible to handle it as an aqueous dispersion.
(*) Storage stability test About each acrylic polyol aqueous dispersion obtained by the said manufacture example, the storage stability test was done according to the following test method.
Storage stability: 800 g of each aqueous dispersion was placed in a glass bottle having a capacity of about 1 L and stored in a constant temperature room at 40 ° C. for 120 days. Then, it returned to room temperature, the state in a container was observed visually, and the following reference | standard evaluated. The results are shown in Table 1.
(Double-circle): Generation | occurrence | production of a sediment and a viscosity change are not recognized at all.
○: Sediment generation and a slight change in viscosity are observed, but return to the original state by stirring.
(Triangle | delta): Generation | occurrence | production of sediment and a viscosity change are recognized.
X: Significant generation of sediment and / or significant viscosity change is observed.

≪Manufacture of aqueous clear paint composition≫
Example 1
In the container, the acrylic polyol aqueous dispersion No. 1 obtained in Production Example 1 was used. No. 1 715 parts (solid content 322 parts), curing agent No. 1 194 parts (solid content 97 parts) of No. 1 was added and stirred and mixed with deionized water so that the solid content was 35% to obtain an aqueous clear coating composition.

Examples 2-18 and Comparative Examples 1-3
In Example 1 above, an aqueous clear coating composition was obtained in the same manner as Example 1 except that the formulation was as shown in Table 2 below.
In addition, emulsion No. whose solid content is 20%. For No. 15, no deionized water was added.

Hardener No. 1: "Baihijoule XP2655" (trade name, manufactured by Sumika Bayer, HMDI polyisocyanate having a sulfonic acid group, NCO content 21%) and ethylene glycol monobutyl acetate (boiling point 192 ° C, 25 ° C with respect to 100 g of water) Dissolved amount 1.1 g) 50 parts containing curing agent No. 2: "Baihijoule XP2655" (trade name, manufactured by Sumika Bayer, HMDI polyisocyanate having a sulfonic acid group, NCO content 21%) 25 parts, "Desmodur N3900" (trade name, manufactured by Sumika Bayer, organic Solvent-soluble HMDI nurate polyisocyanate NCO content 24%), 25 parts and 50 parts of ethylene glycol monobutyl acetate (boiling point 192 ° C., dissolved in 1.1 g of water at 25 ° C. 1.1 g) 3: “Baihijoule XP2655” (trade name, manufactured by Sumika Bayer, HMDI polyisocyanate having a sulfonic acid group, NCO content (21%) 35 parts, “Desmodur N3900” (trade name, manufactured by Sumika Bayer, Curing agent No. 4 containing 15 parts of organic solvent-soluble HMDI nurate polyisocyanate NCO content, 15 parts and 50 parts of ethylene glycol monobutyl acetate (boiling point 192 ° C., dissolved in 100 g of water at 25 ° C., 1.1 g): "Baihijur 304" (trade name, manufactured by Sumika Bayer, HMDI polyisocyanate having nonionic hydrophilic group, water-dispersible polyisocyanate, NCO content 18%) and ethylene glycol monobutyl acetate (boiling point 192 ° C, 25 50 g of water dissolved in 100 g of water at a temperature of 1.1 g)

≪Preparation and evaluation of test plate≫
(* 1) Finishing property Each aqueous clear coating composition obtained above was spray-coated on a polypropylene plate so that the dry film thickness was 50 μm. Next, it was dried at 80 ° C. for 30 minutes using an electric hot air drier, and allowed to stand for 1 day to prepare a test coated plate. Then, the surface state was visually observed and evaluated according to the following criteria.
A: Level with very good smoothness,
○: Smooth and good level,
Δ: Slightly at least one of swell, gloss, and chili skin is seen, a slightly problematic level,
X: At least one of swell, gloss, and chili skin is remarkably problematic.
(* 2) “Letan WB Eco Base 411 Special Black” (trade name, water-based paint for repairing automobiles manufactured by Kansai Paint Co., Ltd.) is spray-coated on the abrasive electrodeposition plate to a dry film thickness of 15 μm. Each aqueous clear coating composition obtained was spray-coated at 20 ° C. under a dry film thickness of 50 μm. Thereafter, the test plate was kept horizontally for 20 minutes, then dried at 80 ° C. for 30 minutes using an electric hot air dryer, and cooled to room temperature to prepare a test plate. Each test plate was water-polished using # 2000 water-resistant abrasive paper, and then polished for 60 seconds using a coarse polishing compound on a rough polishing buff, and the degree of removal of paper scratches by the water-resistant abrasive paper was visually evaluated. Further, the finishing buff was polished for 60 seconds using the finishing compound, the buffing scratches were removed, and the finished gloss was visually determined.
(2-1) How to remove paper scratches ◎: No paper scratches,
○: Almost no paper scratches
Δ: Some paper scratches remain
X: Paper scratches remain remarkably.
(2-2) Finished gloss ◎: Gloss is very good.
○: Good gloss,
Δ: Gloss slightly decreased,
X: Gloss is greatly reduced.
(* 3) Miscibility Each acrylic resin emulsion and each curing agent were blended in a container in the combination shown in Table 2 so as to be an equal amount, and the paint state after stirring with a spatula was evaluated.
A: The paint state after stirring the spatula is very good.
○: The paint state after stirring the spatula is good.
Δ: After stirring the spatula, a partially uneven state is observed.
X: It is difficult to homogenize with spatula stirring.
(* 4) Water resistance Each test coated plate obtained in the above abrasiveness test was evaluated for the appearance of the coating film after being immersed in warm water at 40 ° C for 4 days.
A: No change before and after immersion
○: Slight shine is observed compared to before immersion, but at a practical level,
Δ: Some coating film defects such as blisters are observed,
X: Remarkable coating film defects such as swelling.

Claims (7)

An aqueous two-component clear coating composition comprising an acrylic resin emulsion (I) and a curing agent (II), wherein the acrylic resin emulsion (I) has a different composition in the presence of an organic solvent. A polymerizable unsaturated monomer component (A) that is obtained by water-dispersing an acrylic resin obtained by polymerizing a monomer component in multiple stages,
Epoxy group-containing polymerizable unsaturated monomer (a1),
A polymerizable unsaturated monomer component (B) containing a hydroxyl group-containing polymerizable unsaturated monomer (a2) and another polymerizable unsaturated monomer (a3) and used in at least one other stage of polymerization,
Carboxyl group-containing polymerizable unsaturated monomer (b1),
Comprising a hydroxyl group-containing polymerizable unsaturated monomer (b2) and other polymerizable unsaturated monomers (b3),
The aqueous two-component clear coating composition, wherein the curing agent (II) contains a polyisocyanate component (c1) having an acid group. The other polymerizable unsaturated monomer (a4) which is a copolymerization component of the polymerizable unsaturated monomer component (A) contains a methacrylate having an alkyl group having 3 to 4 carbon atoms as a part of the component. An aqueous two-component clear coating composition as described in 1. The other polymerizable unsaturated monomer (a4) which is a copolymerization component of the polymerizable unsaturated monomer component (A) contains a polymerizable unsaturated monomer having an isobornyl group as a part of the component. The aqueous two-component clear coating composition as described. Polymerizability having a methacryloyl group in which the content of methacrylate having 3 to 4 carbon atoms is in the range of 20 to 65% by mass in all polymerizable unsaturated monomers used for the production of acrylic resin emulsion (I) The aqueous two-component clear coating composition according to any one of claims 1 to 3, wherein the content of the unsaturated monomer is in the range of 30 to 90% by mass. The amount of the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A) is in the range of 3 to 30 mol. 2. An aqueous two-component clear coating composition according to item 1. The aqueous 2 according to any one of claims 1 to 5, wherein the curing agent (II) further comprises a polyisocyanate component (c2) other than the (c1) in addition to the polyisocyanate component (c1) having an acid group. Liquid clear paint composition. The aqueous two-component solution according to any one of claims 1 to 6, wherein the curing agent (II) further comprises an organic solvent having a solubility in 100 g of water of 10 g or less in addition to the polyisocyanate component (c1) having an acid group. Type clear paint composition.