JP2013221041A - Water-based coating composition and method for forming multilayer coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based coating composition and a method for forming a multilayer coating film, for forming a multilayer coating film excellent in smoothness, image clarity, flip-flop property, adhesiveness and water resistance.SOLUTION: A water-based coating composition comprises acrylic resin particles (A), a hydroxyl group-containing resin (B), a crosslinking agent (C), a viscosity controlling agent (D) and a pigment (E). The acrylic resin particles (A) have a core-shell structure, in which a core part is crosslinked; and the acrylic resin particles include 3 to 70 pts.mass of a polymerizable unsaturated monomer (a1) having a hydrocarbon group with 4 or more carbon atoms. The viscosity controlling agent (D) comprises 5 to 50 pts.mass of a polymerizable unsaturated monomer (d1) having a weight average molecular weight of 100,000 or more and a polyoxyalkylene chain, 5 to 90 pts.mass of a hydrophilic functional group-containing polymerizable unsaturated monomer (d2), and 5 to 90 pts.mass of other polymerizable unsaturated monomers (d3). A method for forming a multilayer coating film is also disclosed.

Description

  The present invention relates to an aqueous coating composition and a method for forming a multilayer coating film characterized by containing acrylic resin particles, a hydroxyl group-containing resin, a crosslinking agent, a viscosity modifier, and a pigment.

  In general, a coating method for coating an object requiring excellent appearance such as an automobile body or an automobile part is performed by atomizing a paint from the viewpoint of the appearance of the formed coating film, production efficiency, and the like. Specific examples of such a coating method include spray coating and rotary atomization coating.

  In the case of coating by atomizing the paint, the paint used is generally low in viscosity when spraying, rotating atomization, etc., and the smaller paint particles are formed, which makes smoothness smooth. It is preferable because an excellent coating film is formed. On the other hand, after the coating material is applied to the object, the coating viscosity is relatively high, and it is difficult for the upper layer and / or the lower layer to be mixed with the coating material. It is preferable because a film is formed and the coating film is less likely to sag on the vertical surface of the object. In addition, when the paint is a base paint containing a bright pigment such as an aluminum pigment, if the paint viscosity is high after the paint is applied to an object, the bright pigment in the paint is difficult to move and the orientation is Since it becomes difficult to disturb, it is possible to form a coating film having excellent glitter. Note that a coating film with excellent glitter generally has a remarkable change in brightness due to the observation angle when the coating film is observed at different angles, and the glitter pigment is relatively contained in the coating film. A coating film that exists uniformly and has almost no metallic unevenness. Further, as described above, the fact that the change in brightness depending on the observation angle is remarkable is generally said to have high flip-flop properties.

  For the reasons described above, the viscosity is low when the shear rate is high as in atomization, and the viscosity is high when the shear rate is low such as when the paint is left standing or applied. It is preferable because a coating film having excellent properties (pigment sedimentation property or color separation property) and an excellent appearance can be formed. That is, it is preferable that the coating material has a viscosity that decreases as the shear rate increases.

  By the way, conventionally, as a method of forming a multilayer coating film in an automobile body or an automobile part, primer coating (intermediate coating) is applied to an object to be coated (such as a steel plate or plastic coated with electrodeposition) → heat curing → base coating A method of forming a multilayer coating film by a three-coat two-bake method in which coating, clear coating, and heat curing are sequentially employed is widely employed.

  In general, the 3-coat 2-bake method is employed when a so-called metallic-colored coating film is formed using a base paint containing a bright pigment.

  On the other hand, in recent years, from the viewpoint of shortening the line process and saving energy, the heat curing process or primer coating process after primer coating has been omitted, and primer coating → base coating → clear coating → heat curing are sequentially performed. A three-coat one-bake method and a two-coat one-bake method (in which a preheating (preheating) step may be applied after the coating is applied) are sequentially studied. Among these, from the viewpoint of suppressing environmental pollution due to volatilization of organic solvents, a 3-coat 1-bake method and a 2-coat 1-bake method using a water-based paint as a base paint are particularly required.

  However, when the 3-coat 1-bake method or the 2-coat 1-bake method is used, the smoothness and sharpness of the coating film formed by mixing between the aqueous base paint and the primer paint and / or the aqueous base paint and the clear paint are obtained. In some cases, deterioration of the property and flip-flop property may occur, which has been a problem.

  As a means for increasing the viscosity when the shear rate after coating is low in the aqueous base coating material and suppressing the mixed layer, a method of blending an associative viscosity modifier in the coating material can be mentioned. The associative viscosity modifier generally has a hydrophilic part and a hydrophobic part in one molecule. In the aqueous coating material, the hydrophilic part contributes to the stability in an aqueous solution, and the hydrophobic part is an aqueous coating material. It is a viscosity modifier that forms a network structure by adsorbing on the surface of pigments and acrylic / emulsion particles blended in it, or by associating hydrophobic parts with each other, and effectively increases the viscosity. . In order to increase the thickening effect due to the association, the acrylic emulsion particles preferably contain a hydrophobic monomer.

  The associative viscosity modifier usually forms a network structure by hydrophobic interaction and develops viscosity. On the other hand, when a large shear force is applied, the hydrophobic interaction and the network structure collapse, and the viscosity decreases. For this reason, the water-based paint containing the associative viscosity modifier has a viscosity characteristic in which the viscosity decreases as the shear rate increases.

  In general, the aqueous base coating material may contain a surfactant in order to disperse a hydrophobic resin component in water. Moreover, when a water-soluble resin, an additive, or a pigment dispersion paste is contained, the contained hydrophilic organic solvent may be brought into the aqueous paint.

  However, when an associative viscosity modifier is used in an aqueous base paint containing the surfactant and / or hydrophilic organic solvent, the viscosity due to the associative viscosity modifier becomes difficult to develop, and the formed coating film Since smoothness, sharpness, and flip-flop properties may deteriorate, it has been a problem. Specifically, when the viscosity when the water-based base coating is applied to an object to be coated is low, a mixed layer is formed between the upper layer and / or the lower layer, and the formed coating film is smooth. When the paint is applied, the glittering pigment in the paint moves and the orientation of the glittering pigment becomes irregular. In some cases, the plasticity may be lowered or metallic unevenness may occur. On the other hand, by increasing the content of the associative viscosity modifier in the water-based paint, when increasing the viscosity when applied, the viscosity when the shear rate is high also increases, and when the paint is atomized Since the coating particle becomes large, the smoothness of the formed coating film may be inferior.

  Patent Document 1 discloses that a viscosity control agent comprising a hydrophobic part and a hydrophilic part obtained by hydrophobizing a hydrophilic polymer and / or obtained by hydrophobizing a hydrophobic polymer is an aqueous solution. The concentration dependence of the viscosity of the dispersion can be reduced. Furthermore, the water-based paint using the viscosity control agent exhibits stable flow properties regardless of changes in the coating conditions, particularly temperature and humidity conditions, and is stable. In particular, it is described that a coating film having a good finish can be obtained. However, in some cases, the viscosity control agent has insufficient viscosity. In particular, when the viscosity control agent is used in a paint containing a surfactant and / or a hydrophilic organic solvent, sufficient viscosity cannot be obtained, and the formed coating film has sharpness and flip-flop properties. There was a tendency to decrease or metallic unevenness to occur.

Patent Document 2 describes that a urethane-based viscosity modifier having a specific structure is a thickener / viscosity modifier excellent in thickening and thixotropic properties. The thixotropic property is the above-described viscosity characteristic in which the viscosity decreases as the shear rate increases. However, the urethane-based viscosity modifier sometimes has insufficient viscosity expression. In particular, when the urethane-based viscosity modifier is used in a paint containing a surfactant and / or a hydrophilic organic solvent, sufficient viscosity cannot be obtained, and the clarity of the formed coating film and the flip-flop There was a tendency for the property to deteriorate or metallic unevenness to occur.
In Patent Document 3, an intermediate coating film is formed in a three-coat one-bake coating film forming method in which an intermediate coating film, a base coating film, and a clear coating film are sequentially formed on a substrate by wet-on-wet. The base coating material for forming the intermediate coating material and the base coating film contains an amide group-containing acrylic resin and a crosslinking agent, and the crosslinking agent contained in the intermediate coating material is an aliphatic isocyanate-based active methylene. A method for forming a coating film comprising a block isocyanate is described. When the aliphatic isocyanate-based active methylene block isocyanate, which is the cross-linking agent, has an average functional group number greater than 3, the amide group-containing acrylic resin exhibits a viscosity control effect, and 3 coats 1 Fatigue and reversal at the interface between each coating layer when controlled by the bake method is controlled, and the curing of the intermediate coating starts before the base coating and clear coating, providing sufficient flowability. It can be ensured, and since the surface concealing property against rough skin of the electrodeposition coating film is excellent, a multi-layer coating film having excellent finished appearance and excellent coating film properties, particularly chipping resistance can be obtained. Is described. However, the storage stability of the active methylene block isocyanate in the paint is poor, and there are cases where the smoothness and sharpness are lowered, and the adhesion and water resistance are lowered due to insufficient curing.
Patent Document 4 discloses a second water-based paint for forming a multilayer coating film by sequentially applying a first water-based paint, a second water-based paint, and a clear paint on a substrate by wet-on-wet. Emulsion particles comprising a copolymer of vinyl polymerizable monomers including a polyfunctional vinyl monomer, (b) an amide group-containing water-soluble acrylic resin, (c) a urethane emulsion, and (d) a crosslinking agent. Due to the internal cross-linking structure, even when the coating is performed wet-on-wet, the infiltration of the clear coating component into the lower layer coating film is suppressed, so that the mixed layer with the upper layer coating film is controlled. As a result, it is possible to reduce the energy, and a multilayer coating film having excellent appearance and water resistance can be obtained. The second water-based paint includes (b) an amide group-containing water-soluble acrylic resin, and (c) a urethane emulsion. And (d) It is described that the storage stability is excellent due to the inclusion of the crosslinking agent. However, the smoothness, sharpness, and flip-flop properties of the formed coating due to the mixed layer may be reduced between the intermediate coating and the aqueous base coating and / or the aqueous base coating and the clear coating, and the heating temperature may be low. As a result, water resistance may be lowered due to insufficient curing.

JP 2000-1662 A JP 2002-69430 A Japanese Patent Laid-Open No. 2002-153806 JP 2007-297545 A

  The present invention provides an aqueous coating composition having a high viscosity expression and a viscosity characteristic in which the viscosity decreases with an increase in shear rate. In particular, the aqueous coating composition is used as an aqueous base coating composition. Excellent in smoothness, sharpness, flip-flop property, adhesion and water resistance when coating with 3 coat 1 bake method or 2 coat 1 bake method, and heating and curing each layer simultaneously to form multi-layer coating film An aqueous coating composition capable of forming a multilayer coating film, a method for forming a multilayer coating film using the aqueous coating composition, and an article coated with the aqueous coating composition are provided. This is the issue.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have now obtained an acrylic resin particle, a hydroxyl group-containing resin, a crosslinking agent, a viscosity modifier and a pigment in an aqueous coating composition containing the acrylic resin. The particle has a core-shell structure in which the core is crosslinked, and the acrylic resin particle (A) is composed of a polymerizable unsaturated monomer having a hydrocarbon group having 4 or more carbon atoms, and the weight average of the hydroxyl group-containing resin A polymerizable unsaturated monomer having a molecular weight of 1,000 or more and less than 100,000, the viscosity modifier having a polyoxyalkylene group, a hydrophilic functional group-containing polymerizable unsaturated monomer having no polyoxyalkylene group, and others A water-based coating composition comprising: a polymerizable unsaturated monomer, wherein the viscosity modifier has a weight average molecular weight of 100,000 or more. Multi-layer coating with excellent smoothness, sharpness, flip-flop properties, adhesion and water resistance when three or two layers are applied as a composition and each layer is simultaneously heat-cured to form a multilayer coating film. It was found that a film was formed.

That is, the present invention provides an aqueous coating composition containing the following acrylic resin particles, a hydroxyl group-containing resin, a crosslinking agent, a viscosity modifier and a pigment, a coating film forming method using the aqueous coating composition, and the aqueous coating composition. An article in which an object is painted is provided.

Item 1. In the aqueous coating composition containing the acrylic resin particles (A), the hydroxyl group-containing resin (B), the crosslinking agent (C), the viscosity modifier (D) and the pigment (E),
The acrylic resin particles (A) have a core-shell structure with a mass ratio of 10/90 to 90/10, the core part is cross-linked, and the polymerizable unsaturated constituting the acrylic resin particles (A) The amount of the polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms is 3 to 70 parts by mass with respect to 100 parts by mass of the total amount of monomers. Yes,
The hydroxyl group-containing resin (B) has a weight average molecular weight of 1,000 or more and less than 100,000,
The viscosity modifier (D) has a weight average molecular weight of 100,000 or more, and a polymerizable unsaturated monomer (d1) 5 to 50 having a polyoxyalkylene chain with respect to 100 parts by mass of the total monomer constituting the viscosity modifier (D). Hydrophilic material having no at least one polyoxyalkylene chain selected from parts by mass, N-vinyl-2-pyrrolidone, N-substituted (meth) acrylamide, hydroxyl group-containing polymerizable unsaturated monomer and acid group-containing polymerizable unsaturated monomer 5 to 90 parts by mass of polymerizable functional group-containing polymerizable unsaturated monomer (d2), 5 to 90 parts by mass of other polymerizable unsaturated monomer (d3),
A water-based paint composition characterized by the above.
Item 2. Item 2. The aqueous coating composition according to Item 1, wherein the crosslinking agent (C) is a block polyisocyanate compound.
Item 3. The blocked polyisocyanate compound is at least one of the blocked isocyanate groups represented by the following general formula (I)

[In the formula (I), R ¹ , R ² , R ⁴ and R ⁵ each independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ is a straight chain having 1 to 12 carbon atoms. Or a branched alkylene group is represented. ],
Blocked isocyanate group represented by the following general formula (II)

[In formula (II), R ² , R ³ , R ⁴ and R ⁵ are the same as above. ],
And a blocked isocyanate group represented by the following general formula (III)

Wherein ^{(III), R 2, R} 3, R 4 and ^{R 5} are as defined above, ^{R 6} represents a hydrocarbon group having 1 to 12 carbon atoms. ]
Item 3. The aqueous coating composition according to Item 2, which contains an active methylene type blocked polyisocyanate compound (CB) having at least one type of blocked isocyanate group selected from the group consisting of:
Item 4. Item 4. The aqueous coating composition according to Item 3, wherein, in the general formula (I), R ¹ is an isopropyl group.
Item 5. Item 5. The water-based coating composition according to any one of Items 3 and 4, wherein, in the general formula (III), R ⁶ is an isopropyl group.
Item 6. The active methylene type block polyisocyanate compound (CB) is represented by the following general formula (IV)

[In Formula (IV), R < ¹ > is the same as the above, and may be the same as or different from each other. ]
An active methylene type blocked polyisocyanate compound (cb3-1) having a blocked isocyanate group represented by the formula (II) and a secondary alcohol (cb4) represented by the following general formula (VI)

[In the formula (VI), R ² , R ³ , R ⁴ and R ⁵ are the same as described above. ]
Item 5. The aqueous coating composition according to Item 3 or 4, which is obtained by reacting
Item 7. The active methylene type block polyisocyanate compound (CB) is represented by the following general formula (V)

[In formula (V), R ⁶ is the same as described above, and R ⁷ represents a hydrocarbon group having 1 to 12 carbon atoms. ]
Any one of Items 3 or 5 obtained by reacting an active methylene type blocked polyisocyanate compound (cb3-2) having a blocked isocyanate group represented by the formula (II) with a secondary alcohol (cb4) represented by the general formula (VI) The water-based paint composition according to claim 1.
Item 8. Item 8. The aqueous coating composition according to any one of Items 2 to 7, wherein the block polyisocyanate compound is a block polyisocyanate compound having a hydrophilic group.
Item 9. The viscosity-controlling agent (D), the hydrophilic functional group-containing polymerizable unsaturated monomer (d2) having no polyoxyalkylene chain, contains (meth) acrylic acid as at least one kind thereof, and the viscosity-controlling agent Item 9. The aqueous coating composition according to any one of Items 1 to 8, wherein the acid value of (D) is 50 to 600 mgKOH / g.
Item 10. The other polymerizable unsaturated monomer (d3) constituting the viscosity modifier (D) is a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 3 or more carbon atoms as at least one kind thereof. Item 10. The aqueous coating composition according to any one of Items 1 to 9, which comprises a polymerizable unsaturated monomer.
Item 11. Step 1-1: A step of applying a primer coating composition (X) on an object to form a primer coating film,
Step 1-2: A step of applying a water-based base coating composition (Y) on the uncured primer coating formed in Step 1-1 to form a base coating,
Step 1-3: A step of applying a clear coating composition (Z) on the uncured base coating formed in Step 1-2 to form a clear coating, and Step 1-4: Step 1 Including the step of simultaneously heat-curing the uncured primer coating, the uncured base coating, and the uncured clear coating formed in 1 to 1-3, wherein the aqueous base coating composition (Y) is Item 11. A method for forming a multilayer coating film, which is the aqueous coating composition according to any one of items 1 to 10.
Item 12. Step 2-1: a step of coating a water-based base coating composition (Y) on an object to form a base coating film;
Step 2-2: A step of applying a clear coating composition (Z) on the uncured base coating film formed in Step 2-1, to form a clear coating film, and Step 2-3: Step 2- Including the step of simultaneously heat-curing the uncured base coating film and the uncured clear coating film formed in 1-2, wherein the aqueous base coating composition (Y) is any one of Items 1 to 10 above. A method for forming a multilayer coating film, which is the water-based coating composition according to Item.
Item 13. Item 13. The method for forming a multilayer coating film according to any one of Items 11 or 12, wherein the clear coating composition (Z) contains a hydroxyl group-containing resin and a polyisocyanate compound.
Item 14. The method for forming a multilayer coating film according to any one of Items 11 to 13, wherein the heat curing temperature is 70 to 140 ° C.
Item 15. Item having a multilayer coating film formed by the multilayer coating film forming method according to any one of Items 11 to 14.

  The water-based coating composition of the present invention has a viscosity characteristic in which the viscosity is high and the viscosity decreases with increasing shear rate. In particular, when the aqueous coating composition is applied in three or two layers as an aqueous base coating composition, and each layer is simultaneously heated and cured to form a multilayer coating film, smoothness, sharpness, flip-flop properties, A multilayer coating film excellent in adhesion and water resistance can be formed.

  Hereinafter, the water-based coating composition of the present invention will be described in detail.

Aqueous coating composition The aqueous coating composition of the present invention contains acrylic resin particles (A), a hydroxyl group-containing resin (B), a crosslinking agent (C), a viscosity modifier (D), and a pigment (E).

Acrylic resin particles (A)
The acrylic resin particles (A) used in the aqueous coating composition of the present invention have a core-shell structure produced by two-stage polymerization in an aqueous medium, and the copolymer (I) constituting the core part. The ratio of copolymer (II) which comprises a shell part is a core-shell type acrylic resin particle (A) which exists in the range of about 10 / 90-90 / 10 by solid content mass ratio.

Polymerizable unsaturated monomer (a) constituting acrylic resin particles (A)
The polymerizable unsaturated monomer (a) constituting the acrylic resin particles (A) has 4 or more carbon atoms with respect to 100 parts by mass of the total amount of polymerizable unsaturated monomers constituting the acrylic resin particles (A). There is no particular limitation except that the polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group is contained in an amount of 3 to 70 parts by mass. The compounds having a polymerizable unsaturated group (a1) to (a5) can be preferably used.

In the present specification, the polymerizable unsaturated group means an unsaturated group capable of radical polymerization. Examples of the polymerizable unsaturated group include a vinyl group and a (meth) acryloyl group.
"(Meth) acrylate" is "acrylate or methacrylate", "(meth) acrylic acid" is "acrylic acid or methacrylic acid", "(meth) acryloyl" is "acryloyl or methacryloyl", "(meth) acrylamide" Means “acrylamide or methacrylamide”, respectively.

Polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms
A polymerizable unsaturated monomer having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms excludes a monomer having a hydrophilic group such as a hydroxyl group-containing polymerizable unsaturated monomer. . Specific examples of the monomer include n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2- Ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, alkyl or cycloalkyl (meth) acrylates such as t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate and tricyclodecanyl (meth) acrylate; isobornyl (meth) acrylate Polymerizable unsaturated compounds having an isobornyl group such as relate; Polymerizable unsaturated compounds having an adamantyl group such as adamantyl (meth) acrylate; Aromatic rings such as benzyl (meth) acrylate, styrene, α-methylstyrene and vinyltoluene Examples thereof include polymerizable unsaturated monomers.

Polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule
Specific examples of the polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule include, for example, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1,1,1-trishydroxymethylethanedi (meth) Acrylate, 1,1,1-tris hydroxymethyl ethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, divinylbenzene and the like.

Hydroxyl-containing polymerizable unsaturated monomer (a3)
Specific examples of the hydroxyl group-containing polymerizable unsaturated monomer include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. A monoesterified product of (meth) acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms, and a ε-caprolactone modified product of a monoesterified product of the (meth) acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms N-hydroxymethyl (meth) acrylamide, allyl alcohol, (meth) acrylate having a polyoxyalkylene chain whose molecular end is a hydroxyl group, and the like.

Carboxyl group-containing polymerizable unsaturated monomer (a4)
Specific examples of the carboxyl group-containing polymerizable unsaturated monomer include (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, and the like.

Polymerizable unsaturated monomers (a5) other than (a1) to (a4)
Examples of the polymerizable unsaturated monomer other than (a1) to (a4) include 3 or less carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and the like. Alkyl (meth) acrylate; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Nitrogen-containing polymerizable unsaturated monomers not containing a urethane bond such as an adduct of acrylamide, glycidyl (meth) acrylate and amines; reaction product of hydroxyl group-containing compound with isocyanate group-containing polymerizable unsaturated monomer or hydroxyl group-containing polymerization Containing unsaturated unsaturated monomers and isocyanate groups Polymerizable unsaturated monomer having urethane bond such as reaction product with compound; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxy Epoxy group-containing polymerizable unsaturated monomers such as cyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group ; 2-acrylamido-2-methylpropane sulfonic acid, 2-sulfoethyl (meth) acrylate, allyl sulfonic acid, 4-styrene sulfonic acid, etc., polymerization having sulfonic acid groups such as sodium salt and ammonium salt of these sulfonic acids Unsaturated monomers; alkoxy such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane Polymerizable unsaturated monomers having a silyl group; perfluoroalkyl (meth) acrylates such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; polymerizable monomers having a fluorinated alkyl group such as fluoroolefin A saturated monomer; a polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group; a (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group.
These are not particularly limited and can be suitably used as long as they can be copolymerized with other polymerizable unsaturated monomers as the polymerizable unsaturated monomers constituting the acrylic resin particles (A).

Core copolymer (I)
The core copolymer (I) constituting the acrylic resin particles (A) of the present invention is a copolymer characterized by having a crosslinked structure. As a method for making the core copolymer (I) into a crosslinked structure, crosslinking is performed by copolymerizing a monomer containing a polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule. In addition, the polymerizable unsaturated monomer that reacts with each other, such as an isocyanate group-containing polymerizable unsaturated monomer and a hydroxyl group-containing polymerizable unsaturated monomer, or a glycidyl group-containing polymerizable unsaturated monomer and a carboxyl group-containing polymerizable unsaturated monomer. Crosslinking may be performed by copolymerizing a monomer component containing a saturated monomer, but it is more preferable to crosslink using a polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule. .

  The polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule has a function of imparting a crosslinked structure to the core copolymer (I), and the polymerizable unsaturated group Among the polymerizable unsaturated monomers exemplified as the polymerizable unsaturated monomer (a2) having two or more in a molecule, one can be suitably used alone, or two or more can be used in combination. Methylene bis (meth) acrylamide, allyl (meth) acrylate, and ethylene glycol di (meth) acrylate are preferably used in view of the viscosity of the paint and the coating film performance.

  The use ratio of the polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule can be appropriately determined according to the degree of crosslinking of the core copolymer (I). , Preferably about 0.3 to 10 parts by mass, more preferably about 0.5 to 5 parts by mass, based on the total mass of the monomers constituting the core copolymer (I). More preferably, it is about 8 to 3 parts by mass.

  As the copolymer component of the core copolymer (I), in addition to the polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule, the hydrocarbon having 4 or more carbon atoms. Polymerizable unsaturated monomer having a group (a1), a hydroxyl group-containing polymerizable unsaturated monomer (a3), a carboxyl group-containing polymerizable unsaturated monomer (a4) and polymerizable unsaturated monomers other than (a1) to (a4) Among the polymerizable unsaturated monomers exemplified in (a5), one kind can be suitably used alone, or two or more kinds can be used in combination.

Shell copolymer (II)
The shell part copolymer (II) constituting the acrylic resin particles (A) of the present invention includes a hydroxyl group-containing polymerizable unsaturated monomer (a3) and a carboxyl group-containing polymerizable unsaturated monomer as components of the copolymer. It is preferable to contain (a4).
Further, from the viewpoint of smoothness and sharpness of the resulting coating film, the polymerizable unsaturated monomer (a2) having two or more polymerizable unsaturated groups in one molecule is not used, and the copolymer (II ) Is preferably uncrosslinked.
The hydroxyl group-containing polymerizable unsaturated monomer (a3) improves the water resistance of the coating film by introducing a hydroxyl group that undergoes a crosslinking reaction with the crosslinking agent (C) into the resulting acrylic resin particles (A). It has a function of improving the stability of acrylic resin particles in an aqueous medium. Among the polymerizable unsaturated monomers exemplified as the hydroxyl group-containing polymerizable unsaturated monomer (a3), it can be suitably used singly or in combination of two or more, but 2-hydroxyethyl (meth) acrylate 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are preferably used, and 2-hydroxyethyl (meth) acrylate is more preferably used.

  The carboxyl group-containing polymerizable unsaturated monomer (a4) has a function of improving the stability of the obtained acrylic resin particles in an aqueous medium. Among the polymerizable unsaturated monomers exemplified as the carboxyl group-containing polymerizable unsaturated monomer (a4), one kind can be suitably used alone, or two or more kinds can be used in combination, but (meth) acrylic acid is used. It is preferable.

  The polymerizable unsaturated monomer used as the monomer for the shell copolymer (II) is not particularly limited, and other polymerizable unsaturated monomers may be used as the polymerizable unsaturated monomer constituting the shell copolymer (II). Any material that can be copolymerized with a monomer can be preferably used. For example, it can be suitably used from the polymerizable unsaturated monomers exemplified as the polymerizable unsaturated monomer (a5) other than the above (a1) to (a4) as necessary. These monomers can be used individually by 1 type or in combination of 2 or more types.

  The hydroxyl value of the acrylic resin particles (A) is preferably about 5 to 200 mgKOH / g, from the viewpoint of excellent stability of the acrylic resin particles in an aqueous medium and water resistance of the obtained coating film, and preferably 10 to 150 mgKOH / g. More preferably, it is about g, and it is still more preferable that it is about 20-100 mgKOH / g.

  The acid value of the acrylic resin particles (A) is preferably about 5 to 100 mgKOH / g, and preferably 10 to 80 mgKOH / g from the viewpoint of excellent stability of the acrylic resin in an aqueous medium and excellent water resistance of the obtained coating film. More preferably, it is about 15-50 mgKOH / g.

  The acrylic resin particles (A) of the present invention contain the linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms as a constituent component of the core part and / or shell part copolymer. It contains a polymerizable unsaturated monomer (a1). One of the polymerizable unsaturated monomers exemplified as the polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms is used alone. , Or a combination of two or more, can be used preferably, but n-butyl (meth) acrylate, i-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and styrene are preferably used.

Acrylic resin particles obtained by copolymerizing the above-mentioned polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms are blended in the aqueous coating composition of the present invention. Thus, a base coating film having a lower polarity is obtained, and when the lower layer is an uncured aqueous primer coating composition, a mixed layer with the primer coating film is suppressed. In addition, by developing a hydrophobic interaction with the viscosity modifier (D), it becomes an aqueous coating composition having excellent thixotropic properties, and has a smooth coating, sharpness, and flip-flop properties. Is obtained.
The proportion of the polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms depends on the smoothness and sharpness of the resulting multilayer coating film. From the viewpoint of properties, it is preferably about 3 to 70 parts by weight, more preferably about 15 to 65 parts by weight, based on the total weight of the monomers constituting the acrylic resin particles (A), more preferably 30 to 60 parts. More preferably, it is about part by mass.

  The ratio of the core part copolymer (I) / shell part copolymer (II) in the core-shell type acrylic resin particles (A) is 10/90 in terms of solid content mass ratio from the viewpoint of improving the glossiness of the coating film. It is preferably about ˜90 / 10, more preferably about 50/50 to 85/15, and still more preferably about 65/35 to 80/20.

Emulsion polymerization for preparing an emulsion of the core copolymer (I) can be performed by a conventionally known method. For example, it can be carried out by emulsion polymerization of the monomer mixture using a polymerization initiator in the presence of an emulsifier.
As the emulsifier, an anionic emulsifier and a nonionic emulsifier are suitable. Examples of the anionic emulsifier include sodium salts and ammonium salts such as alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid. Nonionic emulsifiers include, for example, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene Examples include ethylene octyl phenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate It is done.
Also, a polyoxyalkylene group-containing anionic emulsifier having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule; an anionic group and radically polymerizable unsaturated in one molecule It is also possible to use reactive anionic emulsifiers having groups. Of these, it is preferable to use a reactive anionic emulsifier.
Examples of the reactive anionic emulsifier include sodium salts of sulfonic acid compounds having radically polymerizable unsaturated groups such as allyl groups, methallyl groups, (meth) acryloyl groups, propenyl groups, butenyl groups, and ammonium salts of the sulfonic acid compounds. Etc. Among these, an ammonium salt of a sulfonic acid compound having a radically polymerizable unsaturated group is preferable because the resulting coating film has excellent water resistance. Examples of the commercially available ammonium salt of the sulfonic acid compound include “Latemul S-180A” (trade name, manufactured by Kao Corporation).
Of the ammonium salts of sulfonic acid compounds having radically polymerizable unsaturated groups, ammonium salts of sulfonic acid compounds having radically polymerizable unsaturated groups and polyoxyalkylene groups are more preferred. As a commercial item of the ammonium salt of the sulfonic acid compound having the radical polymerizable unsaturated group and the polyoxyalkylene group, for example, “AQUALON KH-10” (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), “SR” -1025A "(trade name, manufactured by ADEKA Corporation).
The amount of the emulsifier used is preferably about 0.1 to 15% by mass, more preferably about 0.5 to 10% by mass, and about 1 to 5% by mass based on the total amount of all monomers used. Further preferred.
Examples of the polymerization initiator include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butyl peroxylaurate, and tert-butyl peroxy. Organic peroxides such as isopropyl carbonate, tert-butyl peroxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobis (2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2-hydroxy) Cyethyl) -propionamide], azo compounds such as azobis {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate, sodium persulfate, etc. Is mentioned. These polymerization initiators can be used singly or in combination of two or more. Moreover, it is good also as a redox initiator by using together with reducing agents, such as saccharide | sugar, sodium formaldehyde sulfoxylate, and an iron complex, as needed to the said polymerization initiator.
In general, the amount of the polymerization initiator used is preferably about 0.1 to 5% by mass, more preferably about 0.2 to 3% by mass, based on the total mass of all monomers used. The method for adding the polymerization initiator is not particularly limited, and can be appropriately selected according to the type and amount thereof. For example, it may be previously contained in the monomer mixture or the aqueous medium, or may be added all at once during the polymerization, or may be added dropwise.
The core-shell type acrylic resin particles (A) are obtained by adding the polymerizable unsaturated monomer mixture of the shell part to the emulsion of the core part copolymer (I) obtained as described above, and further polymerizing the mixture. It can be obtained by forming (II).
The monomer mixture forming the shell copolymer (II) can appropriately contain components such as the polymerization initiator, chain transfer agent, reducing agent, and emulsifier, if necessary. The monomer mixture can be dropped as it is, but it is desirable to drop the monomer mixture as a monomer emulsion obtained by dispersing the monomer mixture in an aqueous medium. In this case, the particle size of the monomer emulsion is not particularly limited.
As a polymerization method of the monomer mixture for forming the shell copolymer (II), for example, the monomer mixture or an emulsion thereof is dripped in a batch or gradually, and an emulsion of the core copolymer (I) is obtained. And a method of heating to an appropriate temperature while stirring.
The acrylic resin particles (A) thus obtained are water-dispersible in a core-shell type multilayer structure, and can generally have an average particle size in the range of about 10 to 1,000 nm, particularly about 20 to 500 nm. .

In this specification, the average particle diameter of the acrylic resin particles (A) is a value measured at 20 ° C. after diluting with deionized water by a conventional method using a submicron particle size distribution measuring device. As the submicron particle size distribution measuring device, for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.
In order to improve the mechanical stability of the acrylic resin particles (A), it is desirable to neutralize acid groups such as carboxyl groups of the acrylic resin particles with a neutralizing agent. The neutralizing agent is not particularly limited as long as it can neutralize an acid group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, 2- (dimethylamino) ethanol, 2-amino-2-methyl- Examples include 1-propanol, triethylamine, and aqueous ammonia. These neutralizing agents are desirably used in such an amount that the pH of the aqueous dispersion of the acrylic resin particles (A) after neutralization is about 6.5 to 9.0.

  The acrylic resin particle (A) of the present invention has a core-shell structure in which a core part is cross-linked, and is a linear, branched or cyclic saturated or unsaturated carbonization having a strong hydrophobicity of 4 or more carbon atoms. It contains a polymerizable unsaturated monomer (a1) having a hydrogen group.

Even when the water-based coating composition of the present invention containing the acrylic resin particles (A) is applied as a base coating composition by wet-on-wet, by containing crosslinked particles having strong hydrophobicity, the upper layer and / or the lower layer And the mixed layer is suppressed.
In addition, since the acrylic resin particles (A) have strong hydrophobicity, due to hydrophobic interaction with the associative viscosity modifier (including the viscosity modifier (D)), the viscosity is highly expressed, and It has the viscosity characteristic that the viscosity decreases with increasing shear rate. Accordingly, the atomization at the time of coating is good and the viscosity at the time of coating is high, so that the mixed layer is suppressed, and the orientation of the glitter pigment and the appearance of the coating film are improved.
By these effects, a multilayer coating film excellent in smoothness, sharpness, flip-flop properties and water resistance can be formed.

Hydroxyl-containing resin (B)
The hydroxyl group-containing resin (B) used in the aqueous coating composition of the present invention has at least one hydroxyl group in one molecule and has a weight average molecular weight of 1,000 or more and less than 100,000. It is a resin containing a hydrophilic functional group such as a group. Specific examples include a polyester resin, a water-soluble acrylic resin, a urethane resin, a polyether resin, and a polycarbonate resin. Among these, the hydroxyl group-containing polyester resin (B1), the hydroxyl group-containing water-soluble acrylic resin (B2), and the hydroxyl group-containing urethane resin (B3) are preferable, and the hydroxyl group-containing polyester resin (B1) and the hydroxyl group-containing water-soluble acrylic resin (B2) are preferable. Particularly preferred.

  In addition, the number average molecular weight or the weight average molecular weight in this specification is the number average molecular weight or the weight average of polystyrene measured by a gel permeation chromatograph (manufactured by Tosoh Corporation, “HLC8120GPC”). It is a value converted based on the molecular weight. In this measurement, the columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (all trade names, Tosoh Corporation) The measurement conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow rate 1 mL / min, detector RI were used.

Hydroxyl-containing polyester resin (B1)
The said hydroxyl-containing polyester resin (B1) can be manufactured by esterification reaction or transesterification with a polybasic acid component and a polyhydric alcohol component, for example. Specifically, for example, the equivalent ratio (COOH / OH) of the carboxyl group in the polybasic acid component and the hydroxyl group in the polyhydric alcohol component is less than 1, and the esterification reaction is performed in a state where there are more hydroxyl groups than carboxyl groups. Can be manufactured.

  The acid value of the hydroxyl group-containing polyester resin can be adjusted by, for example, performing the esterification reaction while tracking the acid value, and ending the esterification reaction when the target acid value is reached. it can.

  The polybasic acid component is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, tetrahydro Polybasic acids such as phthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid and pyromellitic acid; anhydrides of these polybasic acids; lower alkyl esterified products of these polybasic acids, etc. These may be used alone or in combination of two or more.

  The polyhydric alcohol component is a compound having two or more hydroxyl groups in one molecule, such as ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol. Α-glycol such as 2,3-butylene glycol, 1,2-hexanediol, 1,2-dihydroxycyclohexane, 3-ethoxypropane-1,2-diol, 3-phenoxypropane-1,2-diol -Neolyl glycol, 2-methyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propane All, 2-phenoxypropane-1,3-diol, 2-methyl-2-phenylpropane-1,3-diol, 1,3-propylene glycol, 1,3-butylene glycol, 2-ethyl-1,3- Octanediol, 1,3-dihydroxycyclohexane, 1,4-butanediol, 1,4-dihydroxycyclohexane, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 3-methyl-1 , 5-pentanediol, 1,4-dimethylolcyclohexane, tricyclodecane dimethanol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (this is hydroxypivalin) Acid ester of neopentyl glycol), bisphenol A, bis Phenol F, bis (4-hydroxyhexyl) -2,2-propane, bis (4-hydroxyhexyl) methane, 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8, 10-tetraoxaspiro [5,5] undecane, diethylene glycol, triethylene glycol, glycerol, diglycerol, triglycerol, pentaerythritol, dipentaerythritol, sorbitol, mannitol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, And tris (2-hydroxyethyl) isocyanurate. These can be used alone or in combination of two or more.

  The esterification or transesterification reaction of the polybasic acid component and the polyhydric alcohol component can be carried out by a known method. For example, the polybasic acid component and the polyhydric alcohol component are overlapped at a temperature of about 180 to 250 ° C. It can be obtained by condensation.

  The hydroxyl group-containing polyester resin can be modified with a fatty acid, a monoepoxy compound or the like during the preparation of the polyester resin or after the esterification reaction. Examples of the fatty acid include coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor An oil fatty acid, safflower oil fatty acid, etc. are mentioned, As said monoepoxy compound, "Cardura E10P" (a brand name, the Japan Epoxy Resin company make, the glycidyl ester of a synthetic hyperbranched fatty acid) etc. are mentioned, for example.

  The hydroxyl group-containing polyester resin has an acid value of 50 mgKOH / g or less, preferably 10 to 40 mgKOH / g, more preferably 15 to 35 mgKOH / g, and a number average molecular weight of 500 from the viewpoint of smoothness of the resulting coating film. It is suitable to be in the range of from 10,000 to 10,000, preferably from 700 to 5,000, more preferably from 1,000 to 2,000. From the viewpoint of curability, the hydroxyl value is preferably in the range of 10 to 200 mgKOH / g, preferably 30 to 180 mgKOH / g, and more preferably 50 to 165 mgKOH / g.

Hydroxyl group-containing water-soluble acrylic resin (B2)
The hydroxyl group-containing water-soluble acrylic resin (B2) can be produced by (co) polymerizing a polymerizable unsaturated monomer component containing a hydroxyl group-containing polymerizable unsaturated monomer under normal conditions such as solution polymerization.
From the viewpoint of smoothness of the resulting coating film, the acid value is 60 mgKOH / g or less, preferably 1 to 50 mgKOH / g, more preferably 5 to 40 mgKOH / g, and the weight average molecular weight is 1,000 or more and less than 100,000. Preferably, it is within the range of 3,000 or more and less than 80,000, more preferably 5,000 or more and less than 60,000. From the viewpoint of curability, the hydroxyl value is 20 to 200 mgKOH / g, preferably 30 to 180 mgKOH / g, and more preferably 50 to 165 mgKOH / g.

  The hydroxyl group-containing water-soluble acrylic resin (B2) has a hydroxyl group-containing polymerizable unsaturated monomer and a hydrophilic functional group-containing polymerizable unsaturated monomer as constituent components and is in a dissolved state (transparent) in an aqueous medium. The core-shell type acrylic resin particles (A) in a dispersed state are clearly distinguished from each other.

  The hydroxyl group-containing polymerizable unsaturated monomer is a compound having at least one hydroxyl group and one polymerizable unsaturated bond in one molecule, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meta ) Monoesterified product of (meth) acrylic acid such as acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and dihydric alcohol having 2 to 8 carbon atoms, and (meth) acrylic acid Ε-caprolactone modified product of monoesterified product with dihydric alcohol having 2 to 8 carbon atoms, allyl alcohol, (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end, and the like. Two or more types can be used in combination.

The hydrophilic functional group-containing polymerizable unsaturated monomer is a compound having one or more hydrophilic functional groups and polymerizable unsaturated bonds in one molecule, such as N-substituted (meth) acrylamide, polyoxyalkylene. Examples thereof include a chain-containing (meth) acrylate and / or an acid group-containing (meth) acrylate, and these can be used alone or in combination of two or more.
Of these, acid group-containing polymerizable unsaturated monomers are preferable, and (meth) acrylic acid, maleic acid, phosphoric acid group-containing polymerizable unsaturated monomers, and sulfonic acid-containing polymerizable unsaturated monomers are more preferable.
Moreover, the said acid group can be neutralized with a neutralizing agent as needed. The neutralizing agent is not particularly limited as long as it can neutralize an acid group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, 2- (dimethylamino) ethanol, 2-amino-2-methyl- Examples include 1-propanol, triethylamine, and aqueous ammonia.

  Examples of other polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer and the hydrophilic functional group-containing polymerizable unsaturated monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n- Propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) 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 Industry Co., Ltd.) , Cyclohexyl (meta Alkyl, cycloalkyl (meth) acrylates such as acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (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; Vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene; Vinyltrimethoxysilane, vinyltri Polymerization having alkoxysilyl groups such as ethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane Saturated monomer; Perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; Polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; Maleimide group Polymerizable unsaturated monomer having a photopolymerizable functional group; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) ) Nitrogen-containing polymerizable unsaturated monomers such as acrylamide, dimethylaminoethyl (meth) acrylate, adducts of glycidyl (meth) acrylate and amines; having a polyoxyethylene chain whose molecular terminal is an alkoxy group ( (Meth) acrylate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4 Addition reaction of hydroxybenzophenones such as-(3-methacryloyloxy-2-hydroxypropoxy) benzophenone and 2,2'-dihydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone with glycidyl (meth) acrylate A polymerizable unsaturated monomer having an ultraviolet absorbing group such as a product or 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole; 4- (meth) acryloyloxy-1,2 , 2,6 -Pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1 -(Meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6 , 6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-croto Polymerizable unsaturated monomers having UV stabilizing performance such as noyloxy-2,2,6,6-tetramethylpiperidine; acrolein, dye Polymerization having a carbonyl group such as acetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone) Unsaturated unsaturated monomer compounds and the like, and these can be used alone or in combination of two or more.

Hydroxyl-containing polyurethane resin (B3)
The hydroxyl group-containing polyurethane resin (B3) is selected from, for example, at least one diisocyanate compound selected from an aliphatic diisocyanate compound, an alicyclic diisocyanate compound and an aromatic diisocyanate compound, a polyether polyol, a polyester polyol, and a polycarbonate polyol. The thing formed by making it react with at least 1 sort (s) of polyol compound can be mentioned.

  Specifically, for example, at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates, at least one diol selected from polyether diols, polyester diols and polycarbonate diols, low molecular weight polyhydroxy compounds and dimethylol. A urethane prepolymer is produced by reacting an alkanoic acid, neutralized with a tertiary amine, emulsified and dispersed in water, and if necessary, contains a chain extender such as polyamine, a crosslinking agent, a terminator, etc. Examples thereof include a mixture obtained by mixing with an aqueous medium and reacting until the isocyanate group is substantially eliminated. By the above method, a self-emulsifying type polyurethane resin having an average particle diameter of 0.001 to 3 μm can be usually obtained.

Cross-linking agent (C)
The crosslinking agent (C) reacts with a crosslinkable functional group such as a hydroxyl group, a carboxyl group, and an epoxy group in the acrylic resin particles (A) and / or the hydroxyl group-containing resin (B) to form the aqueous coating composition of the present invention. Is a compound capable of curing. Examples of the crosslinking agent (C) include amino resins, polyisocyanate compounds, block polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, and carbodiimide group-containing compounds. Especially, the block polyisocyanate compound and amino resin which can react with a hydroxyl group are preferable from a water-resistant and storage viewpoint of the coating film obtained. These can be used alone or in combination of two or more.

Block Polyisocyanate Compound The block polyisocyanate compound is not particularly limited, and can be synthesized using a normal polyisocyanate compound and a blocking agent.

The polyisocyanate compound is obtained using the following diisocyanate as a main raw material.
Diisocyanates are aliphatic and / or alicyclic diisocyanates. Aliphatic diisocyanates having 4 to 30 carbon atoms are preferred, and alicyclic diisocyanates having 8 to 30 carbon atoms are preferred. For example, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1 , 6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, etc. Can be mentioned. Among these, 1,6-hexamethylene diisocyanate or isophorone diisocyanate is preferable from the viewpoint of weather resistance and / or industrial availability, and these may be used alone or in combination.

  The polyisocyanate compound has about 2 to 20 isocyanate groups in one molecule and forms, for example, biuret bond, urea bond, isocyanurate bond, uretdione bond, urethane bond, allophanate bond, oxadiazine trione bond, etc. 2-20-mer oligomer of diisocyanate produced by the process.

  As the blocking agent used for blocking the isocyanate group of the polyisocyanate compound, known ones can be used. For example, active methylene, phenol, alcohol, mercaptan, acid amide, imide, Amine, imidazole, urea, carbamate, imine, oxime, sulfite compounds and the like can be suitably used.

  Moreover, the said block polyisocyanate compound is a block polyisocyanate compound which has a hydrophilic group from a viewpoint of the storage stability and sclerosis | hardenability of water-based coating composition, and the smoothness and sharpness of the multilayer coating film formed. Is preferred.

  Examples of the block polyisocyanate compound having a hydrophilic group include an active hydrogen-containing compound having a nonionic hydrophilic group, an active hydrogen-containing compound having an anionic hydrophilic group, and an active hydrogen-containing compound having a cationic hydrophilic group. It can be obtained by using an active hydrogen-containing compound having a hydrophilic group.

  The active hydrogen-containing compound having a hydrophilic group is preferably an active hydrogen-containing compound having a nonionic hydrophilic group, more preferably polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether and polyethylene glycol, and polyethylene glycol monomethyl ether. Is more preferable.

  Moreover, as a block polyisocyanate compound, an active methylene type block polyisocyanate compound (CB) can be used conveniently.

Active methylene type block polyisocyanate compound (CB)
The blocked polyisocyanate compound (CB) is a blocked isocyanate group represented by the following general formula (I)

[In the formula (I), R ¹ , R ² , R ⁴ and R ⁵ independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ is a straight chain having 1 to 12 carbon atoms or Represents a branched alkylene group. ],
Blocked isocyanate group represented by the following general formula (II)

[In formula (II), R ² , R ³ , R ⁴ and R ⁵ are the same as above. ]
And a blocked isocyanate group represented by the following general formula (III)

Wherein ^{(III), R 2, R} 3, R 4 and ^{R 5} are as defined above, ^{R 6} represents a hydrocarbon group having 1 to 12 carbon atoms. ]
An active methylene type blocked polyisocyanate compound having at least one type of blocked isocyanate group selected from:

  As a synthesis method of the above active methylene type block polyisocyanate compound (CB), for example, an active methylene compound (cb2) is reacted with an isocyanate group in a polyisocyanate compound (cb1) having two or more isocyanate groups in one molecule. To obtain an active methylene type block polyisocyanate compound (cb3) and then reacting the resulting active methylene type block polyisocyanate compound (cb3) with a secondary alcohol (cb4), an active methylene compound ( There is a method obtained by reacting a reaction product of cb2) and secondary alcohol (cb4) with an isocyanate group in the polyisocyanate compound (cb1), and the former method is particularly preferred.

Polyisocyanate compound (cb1)
The polyisocyanate compound (cb1) is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, And polyisocyanate derivatives.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3. -Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate); 2 , 6-Diisocyanatohexanoic acid 2-isocyanatoethyl, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,6 1-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl Examples thereof include aliphatic triisocyanates such as octane.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name) : Isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis (isocyanato) Methyl) cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylenebis (4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), alicyclic diisocyanate such as norbornane diisocyanate 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2 .1) Heptane, 2- (3-isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5- Di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) ) Heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanate) Toethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3 An alicyclic triisocyanate such as -isocyanatopropyl) -bicyclo (2.2.1) heptane can be used.

  Examples of the araliphatic polyisocyanate include methylene bis (4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω′-diisocyanato- Aromatic aliphatic diisocyanates such as 1,4-diethylbenzene, 1,3- or 1,4-bis (1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; 1,3 And araliphatic triisocyanates such as 5-triisocyanatomethylbenzene.

  Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4- TDI), 2,6-tolylene diisocyanate (common name: 2,6-TDI) or mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate; triphenylmethane-4 , 4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and the like; 4,4′-diphenylmethane-2,2 ′ , 5,5'-tetraisocyanate and other aromatics Mention may be made of the tiger isocyanate.

  Examples of the polyisocyanate derivatives include dimer, trimer, biuret, allophanate, uretdione, uretoimine, isocyanurate, oxadiazine trione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI). And Crude TDI.

  The above polyisocyanates and derivatives thereof may be used alone or in combination of two or more. Of these polyisocyanates, as the polyisocyanate compound (cb1), since the resulting active methylene type block polyisocyanate compound (CB) is less likely to yellow when heated, aliphatic diisocyanates and alicyclics are used. Diisocyanates and their derivatives are preferred. Of these, aliphatic diisocyanates and derivatives thereof are more preferable from the viewpoint of improving the flexibility of the formed coating film.

  Moreover, as said polyisocyanate compound (cb1), you may use the prepolymer formed by making the said polyisocyanate and its derivative (s), and the compound which can react with this polyisocyanate react on an isocyanate group excess condition. Examples of the compound capable of reacting with the polyisocyanate include compounds having an active hydrogen group such as a hydroxyl group and an amino group. Specifically, for example, polyhydric alcohol, low molecular weight polyester resin, amine, water, etc. Can be used.

  The polyisocyanate compound (cb1) is a polymer of an isocyanate group-containing polymerizable unsaturated monomer or a polymerizable unsaturated monomer other than the isocyanate group-containing polymerizable unsaturated monomer and the isocyanate group-containing polymerizable unsaturated monomer. A copolymer with a monomer may be used.

  The polyisocyanate compound (cb1) is a number from the viewpoint of the reactivity of the obtained active methylene block polyisocyanate compound (CB) and the compatibility between the active methylene block polyisocyanate compound (CB) and other coating components. The average molecular weight is preferably in the range of 300 to 20,000, more preferably in the range of 400 to 8,000, and still more preferably in the range of 500 to 2,000.

  The polyisocyanate compound (cb1) is used from the viewpoint of the reactivity of the obtained active methylene block polyisocyanate compound (CB) and the compatibility between the active methylene block polyisocyanate compound (CB) and other coating components. The average number of isocyanate functional groups in one molecule is preferably in the range of 2 to 100. As a minimum, 3 is more preferable from a viewpoint of improving the reactivity of the active methylene type block polyisocyanate compound (CB) obtained. The upper limit is more preferably 20 from the viewpoint of preventing gelation during the production of the active methylene type block polyisocyanate compound (CB).

Active methylene compound (cb2)
Examples of the active methylene compound (cb2) that blocks the isocyanate group in the polyisocyanate compound (cb1) include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-malonate. Butyl, diisobutyl malonate, di-sec-butyl malonate, di-t-butyl malonate, di-n-pentyl malonate, di-n-hexyl malonate, di (2-ethylhexyl) malonate, methyl isopropyl malonate, malonic acid Such as ethyl isopropyl, methyl n-butyl malonate, ethyl n-butyl malonate, methyl isobutyl malonate, ethyl isobutyl malonate, methyl sec-butyl malonate, ethyl sec-butyl malonate, diphenyl malonate and dibenzyl malonate Malonic acid diester, ace Methyl acetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, t-butyl acetoacetate, n-pentyl acetoacetate, n-hexyl acetoacetate Acetoacetate such as 2-ethylhexyl acetoacetate, phenyl acetoacetate and benzyl acetoacetate, methyl isobutyrylacetate, ethyl isobutyrylacetate, n-propyl isobutyrylacetate, isopropyl isobutyrylacetate, n-butyl isobutyrylacetate, isobutyl isobutylylacetate, isobutyrylacetate sec-butyl, t-butyl isobutyryl acetate, n-pentyl isobutyryl acetate, n-hexyl isobutyryl acetate, 2-ethylhexyl isobutyryl acetate, phenyl isobutyryl acetate and iso Isobutyryl acetates such as styryl benzyl acetate and the like, which may be used alone or in combination.

  Among them, from the viewpoint of smoothness and sharpness of the formed multilayer coating film, the active methylene compound (cb2) is dimethyl malonate, diethyl malonate, diisopropyl malonate, methyl acetoacetate, ethyl acetoacetate, isobutyryl. It is preferably at least one compound selected from the group consisting of methyl acetate and ethyl isobutyryl acetate, and more preferably at least one compound selected from the group consisting of diisopropyl malonate, methyl isobutyryl acetate and ethyl isobutyryl acetate. preferable. Among them, diisopropyl malonate is used from the viewpoint of smoothness and sharpness of the formed multilayer coating film, reactivity of the obtained active methylene type block polyisocyanate compound (CB) and storage stability of the aqueous coating composition. More preferably it is.

  For the blocking reaction of the isocyanate group with the active methylene compound (cb2), a reaction catalyst can be used as necessary. Examples of the reaction catalyst include metal hydroxide, metal alkoxide, metal carboxylate, metal acetyl acetylate, hydroxide of onium salt, onium carboxylate, metal salt of active methylene compound, onium salt of active methylene compound, aminosilanes Basic compounds such as amines and phosphines are preferred. Of these, ammonium salts, phosphonium salts, and sulfonium salts are preferred as onium salts. The amount of the reaction catalyst used is usually preferably in the range of 10 to 10,000 ppm, based on the total solid mass of the polyisocyanate compound (cb1) and the active methylene compound (cb2). More preferably, it is in the range of 000 ppm.

  The blocking reaction of the isocyanate group with the active methylene compound (cb2) can be performed at 0 to 150 ° C., and a solvent may be used. In this case, the solvent is preferably an aprotic solvent, and particularly preferably an ester, ether, N-alkylamide, ketone or the like. If the reaction proceeds as intended, an acid component may be added to neutralize the basic compound as a catalyst and stop the reaction.

  In the blocking reaction of the isocyanate group with the active methylene compound (cb2), the amount of the active methylene compound (cb2) used is not particularly limited, but is 0.1% with respect to 1 mol of the isocyanate group in the polyisocyanate compound (cb1). It is suitable to use -3 mol, preferably 0.2-2 mol. In addition, the active methylene compound that has not reacted with the isocyanate group in the polyisocyanate compound (cb1) can be removed after completion of the blocking reaction.

  In addition to the active methylene compound (cb2), for example, alcohol, phenol, oxime, amine, acid amide, imidazole, pyridine, mercaptan and the like blocking agents may be used in combination.

  Further, some of the isocyanate groups in the polyisocyanate compound (cb1) may be reacted with an active hydrogen-containing compound. By reacting some of the isocyanate groups in the polyisocyanate compound (cb1) with an active hydrogen-containing compound, for example, the storage stability of the resulting active methylene type block polyisocyanate compound (CB) is improved, the active methylene It is possible to adjust the compatibility between the mold block polyisocyanate compound (CB) and other coating components and to improve the flexibility of the formed coating film.

  When some of the isocyanate groups in the polyisocyanate compound (cb1) are reacted with the active hydrogen-containing compound, the reaction of the polyisocyanate compound (cb1), the active methylene compound (cb2) and the active hydrogen-containing compound The order is not particularly limited. Specifically, a method in which a part of the isocyanate group in the polyisocyanate compound (cb1) is blocked with an active methylene compound (cb2) and then the remaining isocyanate group is reacted with an active hydrogen-containing compound, polyisocyanate compound (cb1) A method of reacting an active hydrogen-containing compound with a part of the isocyanate group in the mixture and then blocking the remaining isocyanate group with the active methylene compound (cb2) and an active methylene compound (cb2) on the isocyanate group in the polyisocyanate compound (cb1) ) And an active hydrogen-containing compound are reacted at the same time.

  Examples of the active hydrogen-containing compound include a hydroxyl group-containing compound and an amino group-containing compound.

  Examples of the hydroxyl group-containing compound include propanol, butanol, pentanol, hexanol, heptanol, 2-ethyl-1-hexanol, octanol, nonanol, decanol, tridecanol, stearyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol. , Polyethylene glycol (propylene glycol), polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, polyethylene glycol (propylene glycol) monoalkyl ether, trimethylolpropane and the like. These may be used alone or in combination of two or more. be able to. In the present specification, “polyethylene glycol (propylene glycol)” means a copolymer of ethylene glycol and propylene glycol, and includes both a block copolymer and a random copolymer.

  Especially, it is preferable that the said hydroxyl-containing compound is a monohydric alcohol from a viewpoint of suppressing the viscosity increase of the active methylene type block polyisocyanate compound (CB) obtained. Examples of the monohydric alcohol include propanol, butanol, pentanol, hexanol, heptanol, 2-ethyl-1-hexanol, octanol, nonanol, decanol, tridecanol, stearyl alcohol, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl. Examples include ether, polyethylene glycol (propylene glycol) monoalkyl ether, and the like. These can be used alone or in combination of two or more.

  Examples of the amino group-containing compound include butylamine, octylamine, stearylamine, dibutylamine, dioctylamine, dicyclohexylamine, dilaurylamine, α- (aminoalkyl) -ω-alkoxypolyoxyethylene (oxypropylene). , Hexamethylenediamine, diethylenetriamine, polyoxypropylene-α, ω-diamine (as commercial products, for example, “Jeffamine D-400” manufactured by Huntsman, etc.) can be used, and these can be used alone or Two or more types can be used in combination.

  Especially, it is preferable that the said amino group containing compound is a monovalent amine from a viewpoint of suppressing the viscosity increase of the active methylene type block polyisocyanate compound (CB) obtained. Examples of the monovalent amine include butylamine, octylamine, stearylamine, dibutylamine, dioctylamine, dicyclohexylamine, dilaurylamine, α- (aminoalkyl) -ω-alkoxypolyoxyethylene (oxypropylene), and the like. These may be used alone or in combination of two or more.

  When some of the isocyanate groups in the polyisocyanate compound (cb1) are reacted with the active hydrogen-containing compound, the storage stability and curability of the aqueous coating composition, and the smoothness, freshness of the formed multilayer coating film, From the viewpoints of film quality and water resistance, the reaction ratio between the polyisocyanate compound (cb1) and the active hydrogen-containing compound is based on 1 mole of isocyanate groups in the polyisocyanate compound (cb1). The number of moles of hydrogen is preferably in the range of 0.03 to 0.6 mole. As an upper limit, 0.4 is more preferable from the viewpoint of curability of the aqueous coating composition and water resistance of the multilayer coating film to be formed, and 0.3 is more preferable. The lower limit is more preferably 0.04, and even more preferably 0.05, from the viewpoint of the storage stability of the aqueous coating composition and the smoothness and sharpness of the formed multilayer coating film.

  The active methylene type block polyisocyanate compound (CB) has an activity having a hydrophilic group from the viewpoints of storage stability and curability of the aqueous coating composition and smoothness and sharpness of the formed multilayer coating film. A methylene type block polyisocyanate compound (CB ′) is preferred.

  The active methylene type block polyisocyanate compound (CB ′) having a hydrophilic group can be obtained, for example, by using an active hydrogen-containing compound having a hydrophilic group as the active hydrogen-containing compound.

  Examples of the active hydrogen-containing compound having a hydrophilic group include an active hydrogen-containing compound having a nonionic hydrophilic group, an active hydrogen-containing compound having an anionic hydrophilic group, and an active hydrogen-containing compound having a cationic hydrophilic group. These can be used alone or in combination of two or more. Especially, since the reaction which blocks the isocyanate group in the said polyisocyanate compound (cb1) by the said active methylene compound (cb2) is hard to be inhibited, it is preferable to use the active hydrogen containing compound which has a nonionic hydrophilic group. .

  As the active hydrogen-containing compound having a nonionic hydrophilic group, for example, an active hydrogen-containing compound having a polyoxyalkylene group can be suitably used. As said polyoxyalkylene group, a polyoxyethylene group, a polyoxypropylene group, a polyoxyethylene (oxypropylene) group etc. are mentioned, for example, These can be used individually or in combination of 2 or more types. Of these, active hydrogen-containing compounds having a polyoxyethylene group are preferred from the viewpoint of storage stability of the aqueous coating composition.

  The active hydrogen-containing compound having a polyoxyethylene group is 3 or more, preferably 5 to 100, more preferably from the viewpoint of the storage stability of the aqueous coating composition and the water resistance of the multilayer coating film to be formed. Preferably has 8 to 45 consecutive oxyethylene groups.

  Moreover, the active hydrogen containing compound which has the said polyoxyethylene group may contain oxyalkylene groups other than an oxyethylene group other than the continuous oxyethylene group. Examples of the oxyalkylene group other than the oxyethylene group include an oxypropylene group, an oxybutylene group, and an oxystyrene group. The molar ratio of the oxyethylene group in the oxyalkylene group in the active hydrogen-containing compound having a polyoxyethylene group is within the range of 20 to 100 mol% from the viewpoint of the storage stability of the aqueous coating composition. Preferably, it is in the range of 50 to 100 mol%. When the molar ratio of the oxyethylene group in the oxyalkylene group is less than 20 mol%, imparting hydrophilicity may be insufficient, and the storage stability of the aqueous coating composition may be lowered.

  Further, the active hydrogen-containing compound having a nonionic hydrophilic group has a number average molecular weight in the range of 200 to 2,000 from the viewpoint of storage stability of the aqueous coating composition and water resistance of the formed multilayer coating film. It is preferable to be within. The lower limit of the number average molecular weight is more preferably 300 and even more preferably 400 from the viewpoint of storage stability of the aqueous coating composition. As an upper limit, 1,500 is more preferable from the viewpoint of water resistance of the multilayer coating film to be formed, and 1,200 is more preferable.

  Examples of the active hydrogen-containing compound having a nonionic hydrophilic group include polyethylene glycol monoalkyl ethers (also known as ω-alkoxypolyoxyethylene) such as polyethylene glycol monomethyl ether and polyethylene glycol monoethyl ether, polypropylene glycol monomethyl ether, and Polypropylene glycol monoalkyl ethers such as polypropylene glycol monoethyl ether (also known as ω-alkoxypolyoxypropylene), ω-alkoxypolyoxyethylene (oxypropylene), ω-alkoxypolyoxyethylene (oxypropylene), etc. Oxyethylene (oxypropylene), polyethylene glycol (propylene glycol) monomethyl ether, polyethylene glycol Poly (ethylene glycol) (propylene glycol) monoalkyl ether such as ru (propylene glycol) monoethyl ether, polyethylene glycol, polypropylene glycol, polyethylene glycol (propylene glycol), α- (aminoalkyl) -ω-alkoxypolyoxyethylene, α- ( Aminoalkyl) -ω-alkoxypolyoxypropylene, α- (aminoalkyl) -ω-alkoxypolyoxyethylene (oxypropylene) and the like can be mentioned, and these can be used alone or in combination of two or more. Of these, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether and polyethylene glycol are preferable, and polyethylene glycol monomethyl ether is more preferable.

  Moreover, as a commercial item of the said polyethyleneglycol monomethyl ether, for example, "UNIOX M-400", "UNIOX M-550", "UNIOX M-1000", "UNIOX M-" made by NOF CORPORATION 2000 "and the like. Examples of the commercially available polyethylene glycol include “PEG # 200”, “PEG # 300”, “PEG # 400”, “PEG # 600”, “PEG # 1000”, “ PEG # 1500 "," PEG # 1540 "," PEG # 2000 "and the like.

  Examples of the active hydrogen-containing compound having an anionic hydrophilic group include an active hydrogen-containing compound having a carboxyl group, an active hydrogen-containing compound having a sulfonic acid group, an active hydrogen-containing compound having a phosphate group, and neutralization thereof. A salt etc. are mentioned, These can be used individually or in combination of 2 or more types. Especially, the active hydrogen containing compound which has a carboxyl group can be used suitably from a compatible viewpoint with the active methylene type block polyisocyanate compound (CB) and other coating component obtained.

  A part or all of the acid groups in the active hydrogen-containing compound having an anionic hydrophilic group are inhibited from blocking the isocyanate group in the polyisocyanate compound (cb1) with the active methylene compound (cb2). Since it becomes difficult, it is preferable to be neutralized with a basic compound.

  The neutralization of the acid group in the active hydrogen-containing compound having an anionic group may be performed before the reaction between the active hydrogen-containing compound having the anionic group and the polyisocyanate compound (cb1) or after the reaction. May be.

  Examples of the basic compound include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and barium hydroxide; metal alkoxides; ammonia; ethylamine, propyl First, such as amine, butylamine, benzylamine, monoethanolamine, 2,2-dimethyl-3-amino-1-propanol, 2-aminopropanol, 2-amino-2-methyl-1-propanol, 3-aminopropanol Secondary monoamines such as diethylamine, diethanolamine, di-n-propanolamine, di-isopropanolamine, N-methylethanolamine, N-ethylethanolamine; dimethylethanolamine, trimethylamine, triethylamine, Tertiary monoamines such as isopropylamine, methyldiethanolamine, 2- (dimethylamino) ethanol; polyamines such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, and the like. It can be used in combination of more than one species. The basic compound is used in an amount of usually 0.1 to 1.5 equivalents, preferably 0.2 to 1.2 equivalents, based on the anionic group in the active hydrogen-containing compound having an anionic group. can do.

  Examples of the active hydrogen-containing compound having a carboxyl group include monohydroxycarboxylic acids such as glycolic acid, lactic acid, hydroxypivalic acid, malic acid and citric acid, 2,2-dimethylolacetic acid, 2,2-dimethylollactic acid, , 2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, dimethylolheptanoic acid, dimethylolnonanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid and other dihydroxycarboxylic acids, these dihydroxycarboxylic acids Examples include acid lactone ring-opening adducts, glycine, 1-carboxy-1,5-pentylenediamine, dihydroxybenzoic acid, 3,5-diaminobenzoic acid, lysine, and arginine.

  Examples of the active hydrogen-containing compound having a sulfonic acid group include 2-amino-1-ethanesulfonic acid, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, and 1,3-phenylenediamine. -4,6-disulfonic acid, diaminobutanesulfonic acid, 3,6-diamino-2-toluenesulfonic acid, 2,4-diamino-5-toluenesulfonic acid, 2- (cyclohexylamino) -ethanesulfonic acid, 3- (Cyclohexylamino) -propanesulfonic acid and the like.

  Examples of the active hydrogen-containing compound having a phosphoric acid group include 2,3-dihydroxypropylphenyl phosphate, hydroxyalkylphosphonic acid, aminoalkylphosphonic acid and the like.

  When some of the isocyanate groups in the polyisocyanate compound (cb1) are reacted with the active hydrogen-containing compound having the hydrophilic group, the storage stability and curability of the aqueous coating composition, and the formed multilayer coating film From the viewpoints of smoothness, sharpness and water resistance, the reaction ratio between the polyisocyanate compound (cb1) and the active hydrogen-containing compound having a hydrophilic group is based on 1 mole of isocyanate groups in the polyisocyanate compound (cb1). The number of moles of active hydrogen in the active hydrogen-containing compound is preferably in the range of 0.03 to 0.6 mole. As an upper limit, 0.4 is more preferable from the viewpoint of curability of the aqueous coating composition and water resistance of the multilayer coating film to be formed, and 0.3 is more preferable. The lower limit is more preferably 0.04, and even more preferably 0.05, from the viewpoint of the storage stability of the aqueous coating composition and the smoothness and sharpness of the formed multilayer coating film.

  The active methylene type block polyisocyanate compound (CB) can be imparted with water dispersibility by mixing with a surfactant in advance. In this case, from the viewpoint of the stability of the coating material, the surfactant is preferably a nonionic surfactant and / or an anionic surfactant.

Active methylene type block polyisocyanate compound (cb3)
The active methylene type block polyisocyanate compound (cb3) is obtained by reacting the polyisocyanate compound (cb1) having two or more isocyanate groups in one molecule with the active methylene compound (cb2). A part or all of the isocyanate groups therein are compounds blocked with an active methylene compound (cb2).

  Among them, the active methylene type block polyisocyanate compound (cb3) is represented by the following general formula (IV).

[In Formula (IV), R ¹ independently represents a hydrocarbon group having 1 to 12 carbon atoms, and may be the same or different from each other. ]
An active methylene-type blocked polyisocyanate compound (cb3-1) having a blocked isocyanate group represented by formula (V):

Wherein (V), ^{R 6} and ^{R 7} independently represent a hydrocarbon group having 1 to 12 carbon atoms. ]
It is preferable that it is at least one of the active methylene type | mold block polyisocyanate compounds (cb3-2) which have the block isocyanate group shown by these.

Active methylene type block polyisocyanate compound (cb3-1)
The active methylene type block polyisocyanate compound (cb3-1) is an active methylene type block polyisocyanate compound having a blocked isocyanate group represented by the general formula (IV).

Among these, as the active methylene compound (cb2), which is one of the raw materials of the active methylene type block polyisocyanate compound, an active methylene compound that can be produced relatively easily can be used, and therefore, R ¹ has 1 to 1 carbon atoms. 3 alkyl groups are preferred. Among these, from the viewpoint of improving the compatibility between the obtained block polyisocyanate compound (CB) and other paint components, it is preferably an alkyl group having 2 or 3 carbon atoms, and the storage stability and formation of the aqueous paint composition. The isopropyl group is more preferable from the viewpoint of smoothness and sharpness of the multilayer coating film.

  The active methylene block polyisocyanate compound (cb3-1) can be obtained, for example, by reacting the polyisocyanate compound (cb1) with a dialkyl malonate having a hydrocarbon group having 1 to 12 carbon atoms. .

  Examples of the dialkyl malonate include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, disec-butyl malonate, and di-t malonate. -Butyl, di-n-pentyl malonate, di-n-hexyl malonate, di (2-ethylhexyl) malonate and the like can be mentioned, and these can be used alone or in combination of two or more. Of these, dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-sec-butyl malonate, and di-t-butyl malonate are preferred. Diethyl acid, di-n-propyl malonate, and diisopropyl malonate are more preferable, and diisopropyl malonate is more preferable.

Active methylene type block polyisocyanate compound (cb3-2)
The active methylene type block polyisocyanate compound (cb3-2) is an active methylene type block polyisocyanate compound having a blocked isocyanate group represented by the general formula (V).

Among them, as the active methylene compound (cb2), which is one of the raw materials of the active methylene type block polyisocyanate compound, an active methylene compound that can be produced relatively easily can be used, so that R ⁶ and R ⁷ are carbon. It is preferable that it is a C1-C3 alkyl group. Among these, from the viewpoint of improving the compatibility between the obtained active methylene type block polyisocyanate compound (CB) and other coating components, the alkyl group having 2 or 3 carbon atoms is preferable, and the storage stability of the aquatic coating composition is preferred. From the viewpoints of the properties, smoothness of the multilayer coating film, and sharpness, it is more preferable that it is an isopropyl group.

  The active methylene type block polyisocyanate compound (cb3-2) may be prepared by, for example, reacting the polyisocyanate compound (cb1) with an acetoacetic acid ester having a hydrocarbon group having 1 to 12 carbon atoms or a polyisocyanate compound (cb1). ) And an isobutyryl acetate ester having a hydrocarbon group having 1 to 12 carbon atoms. Especially, it is preferable to obtain by making the said polyisocyanate compound (cb1) react with the isobutyryl acetate ester which has a C1-C12 hydrocarbon group.

  Examples of the isobutyryl acetate include, for example, methyl isobutyryl acetate, ethyl isobutyryl acetate, n-propyl isobutyryl acetate, isopropyl isobutyryl acetate, n-butyl isobutylyl acetate, isobutyl isobutylyl acetate, sec-butyl isobutyryl acetate, t-butyl isobutyryl acetate, isobutyryl Examples include n-pentyl acetate, n-hexyl isobutyryl acetate, 2-ethylhexyl isobutyryl acetate, phenyl isobutyryl acetate, benzyl isobutyryl acetate and the like, and these can be used alone or in combination of two or more. Of these, methyl isobutyryl acetate, ethyl isobutyryl acetate and isopropyl isobutyryl acetate are preferred.

  Examples of the acetoacetate ester include methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, and t-butyl acetoacetate. , N-pentyl acetoacetate, n-hexyl acetoacetate, 2-ethylhexyl acetoacetate, phenyl acetoacetate, benzyl acetoacetate and the like, and these can be used alone or in combination of two or more. Of these, methyl acetoacetate, ethyl acetoacetate and isopropyl acetoacetate are preferred.

  The active methylene type block polyisocyanate compound (cb3) is obtained by reacting a polyisocyanate compound (cb1) having two or more isocyanate groups in one molecule, an active methylene compound (cb2) and the active hydrogen-containing compound. The obtained compound may be sufficient. Specifically, for example, by using an active hydrogen-containing compound having the polyoxyalkylene group as the active hydrogen-containing compound, a part of the isocyanate group in the polyisocyanate compound (cb1) is converted into an active methylene compound (cb2). ) And an active methylene type blocked polyisocyanate compound in which a part or all of other isocyanate groups are reacted with an active hydrogen-containing compound having a polyoxyalkylene group.

Secondary alcohol (cb4)
In the present invention, the block polyisocyanate compound (CB) includes, for example, the active methylene type block polyisocyanate compound (cb3) and a secondary alcohol (cb4) represented by the following general formula (VI):

[In Formula (VI), R ² , R ⁴ and R ⁵ independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ represents a linear or branched group having 1 to 12 carbon atoms. Represents an alkylene group. ]
Can be obtained by reacting.

The secondary alcohol (cb4) is a compound represented by the above general formula (VI). Among them, the active methylene-type blocked polyisocyanate compound (cb3) from the viewpoint of enhancing the reactivity with the secondary alcohol (cb4), R ² is preferably a methyl group. Further, when R ³ , R ⁴ and R ⁵ each have a large number of carbon atoms, the polarity of the resulting active methylene type block polyisocyanate compound (CB) may be reduced, and the compatibility with other paint components may be reduced. Therefore, R ³ is preferably an alkylene group having 1 to ³ carbon atoms, and R ⁴ and R ⁵ are preferably methyl groups.

  Examples of the secondary alcohol (cb4) include 4-methyl-2-pentanol, 5-methyl-2-hexanol, 6-methyl-2-heptanol, 7-methyl-2-octanol, and the like. Can be used alone or in combination of two or more. Among these, when part or all of the unreacted secondary alcohol (cb4) is distilled off after the reaction of the block polyisocyanate compound (cb3) and the secondary alcohol (cb4), the secondary alcohol (cb4 ) Is relatively easy, 4-methyl-2-pentanol having a relatively low boiling point is more preferable.

  Specifically, the active methylene type block polyisocyanate compound (CB) is, for example, the following general formula (IV) described in the description of the active methylene type block polyisocyanate compound (cb3).

[In Formula (IV), R ¹ independently represents a hydrocarbon group having 1 to 12 carbon atoms, and may be the same or different. ]
It can obtain by making the active methylene type block polyisocyanate compound (cb3-1) which has the block isocyanate group shown by said, and the said secondary alcohol (cb4) react.

In this case, at least one of R ¹ in the blocked isocyanate group in the active methylene type blocked polyisocyanate compound (cb3-1) is represented by the following general formula (VII)

[In Formula (VII), R ² , R ⁴ and R ⁵ independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ represents a linear or branched group having 1 to 12 carbon atoms. Represents an alkylene group. ]
It is substituted with a group represented by

  In this case, the obtained active methylene type block polyisocyanate compound (CB) is a blocked isocyanate group represented by the following general formula (I).

[In the formula (I), R ¹ , R ² , R ⁴ and R ⁵ independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ is a straight chain having 1 to 12 carbon atoms or Represents a branched alkylene group. ]
Here, in formula (I), R ¹ is more preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms, and particularly preferably a hydrocarbon group having 2 to 3 carbon atoms. preferable.
Or a blocked isocyanate group represented by the following general formula (II)

[In formula (II), R ² , R ³ , R ⁴ and R ⁵ are the same as above. ]
Have

The reaction of the active methylene type blocked polyisocyanate compound (cb3-1) and the secondary alcohol (cb4) is performed, for example, by at least one of R ¹ in the blocked isocyanate group in the active methylene type block polyisocyanate compound (cb3-1). The method is not particularly limited as long as it can be substituted with the group represented by the general formula (VII). In particular, by heating and reducing pressure, a part or all of the alcohol derived from at least one of R ^{1 in} the active methylene type block polyisocyanate compound (cb3-1) is distilled off to promote the reaction. A method of obtaining an active methylene type blocked polyisocyanate compound (CB) having a blocked isocyanate group represented by the general formula (I) or (II) is preferred.

  As the above production method, specifically, the pressure is reduced as necessary at a temperature of 20 to 150 ° C., preferably 75 to 95 ° C., and 5 minutes to 20 hours, preferably 10 minutes to 10 hours. It is appropriate to remove some or all of the alcohol. If the temperature is too low, the exchange reaction of the alkoxy group in the active methylene block polyisocyanate compound (cb3-1) is slowed down and the production efficiency is lowered. On the other hand, if it is too high, the active methylene block polyisocyanate compound ( CB) is not desirable because degradation and deterioration of CB) become severe and curability may be lowered.

  The active methylene type block polyisocyanate compound (CB) is represented by the following general formula (V) described in the description of the active methylene type block polyisocyanate compound (cb3).

Wherein (V), ^{R 6} and ^{R 7} independently represent a hydrocarbon group having 1 to 12 carbon atoms. ]
It can obtain by making the active methylene type block polyisocyanate compound (cb3-2) which has the block isocyanate group shown by, and the said secondary alcohol (cb4) react.

In this case, R ⁷ in the blocked isocyanate group in the active methylene type blocked polyisocyanate compound (cb3-2) is represented by the following general formula (VII)

[In Formula (VII), R ² , R ⁴ and R ⁵ independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ represents a linear or branched group having 1 to 12 carbon atoms. Represents an alkylene group. ]
It is substituted with a group represented by

  In this case, the obtained active methylene type blocked polyisocyanate compound (CB) is a blocked isocyanate group represented by the following general formula (III):

Wherein ^{(III), R 2, R} 3, R 4 and ^{R 5} are as defined above, ^{R 6} represents a hydrocarbon group having 1 to 12 carbon atoms. ]
Have

The reaction of the active methylene type blocked polyisocyanate compound (cb3-2) and the secondary alcohol (cb4) may be performed, for example, by converting R ⁷ in the blocked isocyanate group in the active methylene type block polyisocyanate compound (cb3-2) to the above general The technique is not particularly limited as long as it can be substituted with the group represented by formula (VII). In particular, by heating and reducing pressure, the alcohol derived from R ⁷ in the active methylene type block polyisocyanate compound (cb3-2) is partly or entirely distilled out of the system to promote the reaction. A method for obtaining an active methylene type blocked polyisocyanate compound (CB) having a blocked isocyanate group represented by the formula (III) is preferred.

  As the above production method, specifically, the pressure is reduced as necessary at a temperature of 20 to 150 ° C., preferably 75 to 95 ° C., and 5 minutes to 20 hours, preferably 10 minutes to 10 hours. It is appropriate to remove some or all of the alcohol. If the temperature is too low, the exchange reaction of the alkoxy group in the active methylene type block polyisocyanate compound (cb3-2) is slowed to reduce the production efficiency. On the other hand, if the temperature is too high, the active methylene type block polyisocyanate compound ( CB) is not desirable because degradation and deterioration of CB) may become severe and the curability may be lowered.

  In addition, in the production of the active methylene type block polyisocyanate compound (CB), the blending ratio of the active methylene type block polyisocyanate compound (cb3) and the secondary alcohol (cb4) is the active methylene type block polyisocyanate compound (CB) obtained. ), And the secondary alcohol (cb4) is within the range of 5 to 500 parts by mass based on 100 parts by mass of the solid content of the active methylene type block polyisocyanate compound (cb3). Preferably, it is in the range of 10 to 200 parts by mass. If it is less than 5 mass parts, the reaction rate of an active methylene type block polyisocyanate compound (cb3) and secondary alcohol (cb4) may be too slow. Moreover, when it exceeds 500 mass parts, the density | concentration of the active methylene type block polyisocyanate compound (CB) produced | generated may become low too much, and manufacturing efficiency may fall.

  In the reaction of the active methylene block polyisocyanate compound (cb3) and the secondary alcohol (cb4), the active methylene block polyisocyanate is used to adjust the molecular weight of the active methylene block polyisocyanate compound (CB). The removal operation may be performed after adding the polyfunctional hydroxyl group-containing compound to the compound (cb3) and the secondary alcohol (cb4).

  The number average molecular weight of the block polyisocyanate compound (CB) is 600 from the viewpoints of compatibility with other paint components, smoothness of the formed multilayer coating film, sharpness, water resistance, chipping resistance, and the like. It is preferable to be within the range of ˜30,000. The upper limit of the number average molecular weight is more preferably 10,000, and even more preferably 5,000, from the viewpoints of compatibility with other coating components and the smoothness and sharpness of the formed multilayer coating film. The lower limit is more preferably 900 and more preferably 1,000 from the viewpoint of water resistance and chipping resistance of the multilayer coating film to be formed.

  The multilayer coating film formed using the water-based coating composition containing the active methylene type block polyisocyanate compound (CB) has good smoothness, sharpness and water resistance, and has a low temperature (70 ° C to 120 ° C). Less than 2). The smoothness and sharpness are good because the active methylene type block polyisocyanate compound (CB) has a hydrocarbon group having a specific branched structure, so that the uncured primer coated with an aqueous primer coating composition is used. It is inferred that when the aqueous coating composition (aqueous base coating composition) is applied on the coating film, a mixed layer between both coating films is suppressed. Moreover, since the active methylene type block polyisocyanate compound (CB ′) having a hydrophilic group has particularly high storage stability in some cases, the curability and water resistance are good even after long-term storage.

As the amino resin amino resin, a partially methylolated amino resin or a completely methylolated amino resin obtained by a reaction between an amino component and an aldehyde component can be used. Examples of the amino component include melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and the like. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, and the like.

  Moreover, what methylated the methylol group of the said methylolated amino resin partially or completely with suitable alcohol can also be used. Examples of the alcohol used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2 ethyl butanol, and 2-ethyl hexanol.

  As the amino resin, a melamine resin is preferable. In particular, methyl ether melamine resins in which methylol groups of partially or fully methylolated melamine resins are partially or completely etherified with methyl alcohol, methylol groups of partially or fully methylolated melamine resins are partially or completely with butyl alcohol. Preference is given to butyl etherified melamine resins which have been etherified, and methyl-butyl mixed etherified melamine resins in which the methylol groups of the partially or fully methylolated melamine resin are partially or completely etherified with methyl alcohol and butyl alcohol.

  The melamine resin preferably has a weight average molecular weight of 400 to 6,000, more preferably 500 to 4,000, and more preferably 600 to 3, from the viewpoint of excellent water resistance of the resulting coating film. More preferably, it is 000.

  A commercially available product can be used as the melamine resin. Examples of commercially available product names include “Cymel 202”, “Cymel 203”, “Cymel 238”, “Cymel 251”, “Cymel 303”, “Cymel 323”, “Cymel 324”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 385”, “Cymel 1156”, “Cymel 1158”, “Cymel 1116”, “Cymel 1130” (above, made by Nippon Cytec Industries, Inc.), “Uban 120”, “ “Uban 20HS”, “Uban 20SE60”, “Uban 2021”, “Uban 2028”, “Uban 28-60” (manufactured by Mitsui Chemicals, Inc.), and the like.

Viscosity modifier (D)
The viscosity modifier (D) used in the aqueous coating composition of the present invention is 5 to 50 parts by weight of a polymerizable unsaturated monomer (d1) having a polyoxyalkylene chain, N-vinyl-2-pyrrolidone, N-substituted ( Hydrophilic functional group-containing polymerizable unsaturated monomer (d2) 5 having no at least one polyoxyalkylene chain selected from meth) acrylamide, a hydroxyl group-containing polymerizable unsaturated monomer and an acid group-containing polymerizable unsaturated monomer It can be produced by (co) polymerizing ˜90 parts by weight and 5 to 90 parts by weight of other polymerizable unsaturated monomers (d3) under ordinary conditions.

  The weight average molecular weight of the viscosity modifier is 100,000 or more, preferably 100,000 to 1,000,000, more preferably 200,000 to 850,000, and more particularly, from the viewpoint of the viscosity of the resulting aqueous paint. Preferably it is in the range of 300,000 to 750,000.

  The viscosity modifier (D) contains a polymerizable unsaturated monomer (d1) having a polyoxyalkylene chain and a hydrophilic functional group-containing polymerizable unsaturated monomer (d2) having no polyoxyalkylene chain, Since it is dissolved (transparent) in the aqueous medium, it is clearly distinguished from the acrylic resin particles (A) that are dispersed in the aqueous medium. Further, it is clearly distinguished from the hydroxyl group-containing water-soluble acrylic resin (B2) from the range of the weight average molecular weight.

  The polymerizable unsaturated monomer (d1) having a polyoxyalkylene chain is a monomer containing a polyoxyalkylene chain and a polymerizable unsaturated group in one molecule.

  Examples of the polyoxyalkylene chain include a polyoxyethylene chain, a polyoxypropylene chain, a chain composed of a polyoxyethylene block and a polyoxypropylene block, and a chain formed by randomly bonding polyoxyethylene and polyoxypropylene. These polyoxyalkylene chains generally have a molecular weight in the range of about 100 to 5,000, preferably about 200 to 4,000, more preferably about 300 to 3,000. It is.

Representative examples of the polymerizable unsaturated monomer having a polyoxyalkylene chain include, for example, the following general formula (VIII)
^{CH2 = C (-R 8) -C} (= O) -O- (CH (-R 9) -CH (-R 10) -O) n-R 11
(Wherein R ^{8 to} R ¹⁰ are H or CH 3, R ¹¹ is H or a hydrocarbon group having 1 to 18 carbon atoms, and n is an integer of 1 to 100). Mention may be made of monomers.

  Specific examples of the polymerizable unsaturated monomer (d1) having a polyoxyalkylene chain include, for example, tetraethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, ethoxytetraethylene glycol (meth) acrylate, n -Butoxytriethylene glycol (meth) acrylate, n-butoxytetraethylene glycol (meth) acrylate, tetrapropylene glycol (meth) acrylate, methoxytetrapyrene glycol (meth) acrylate, ethoxytetrapropylene glycol (meth) acrylate, n- Butoxytetrapropylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, Reethylene (propylene) glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, methoxypolyethylene (propylene) glycol (meta ) Acrylate, ethoxypolyethylene (propylene) glycol (meth) acrylate, and the like. These may be used alone or in combination of two or more. In the present specification, “polyethylene (propylene) glycol” means a copolymer of ethylene glycol and propylene glycol, and includes both a block copolymer and a random copolymer.

  Among these, polyethylene glycol (meth) acrylate, polyethylene (propylene) glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypolyethylene (propylene) glycol from the viewpoint of smoothness and sharpness of the formed coating film (Meth) acrylate is preferable, and polyethylene glycol (meth) acrylate and methoxypolyethylene glycol (meth) acrylate are more preferable.

  Examples of the hydrophilic functional group-containing polymerizable unsaturated monomer (d2) having no polyoxyalkylene chain include N-vinyl-2-pyrrolidone, N-substituted (meth) acrylamide, a hydroxyl group-containing polymerizable unsaturated monomer, and an acid. The group-containing polymerizable unsaturated monomer can be suitably used alone or in combination of two or more, but a hydroxyl group-containing polymerizable unsaturated monomer and / or an acid group-containing polymerizable unsaturated monomer is preferable, and an acid group As the polymerizable unsaturated monomer, (meth) acrylic acid is preferable.

  When the viscosity modifier (D) contains an acid group-containing polymerizable unsaturated monomer as a constituent component, the acid value of the viscosity modifier (D) is usually 50 to 600 mgKOH from the viewpoint of the viscosity of the aqueous coating composition. / G, more preferably 100 to 500 mgKOH / g, still more preferably 150 to 450 mgKOH / g, and still more preferably 200 to 400 mgKOH / g.

  Examples of the N-substituted (meth) acrylamide include N-methyl acrylamide, N-methyl methacrylamide, N-methylol acrylamide butyl ether, N-methylol methacrylamide butyl ether, N-ethyl acrylamide, N-ethyl methacrylamide, N- n-propylacrylamide, Nn-propylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-cyclopropylacrylamide, N-cyclopropylmethacrylamide, diacetoneacrylamide, diacetonemethacrylamide, N-hydroxymethyl Acrylamide, N-hydroxymethyl methacrylamide, N-hydroxyethyl acrylamide, N-hydroxyethyl methacrylamide, N, N- Methyl acrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N-methyl, N-ethylacrylamide, N-methyl, N-ethylmethacrylamide, N, N-dimethyl Aminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, N-methylol acrylamide methyl ether, N-methylol methacrylamide methyl ether, N-methylol acrylamide ethyl ether, N-methylol methacrylamide ethyl ether, N-methylol acrylamide propyl ether , N-methylol methacrylamide propyl ether, acryloyl morpholine, methacryloyl morpholine and the like. It can be used in combination on.

  Among these, Nn-propyl acrylamide, Nn-propyl methacrylamide, N-isopropyl acrylamide, N-isopropyl methacrylamide, N-hydroxyethyl acrylamide from the viewpoint of smoothness and sharpness of the formed coating film , N-hydroxyethylmethacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide are preferred, N, N-dimethylacrylamide, N, N -More preferred is dimethylmethacrylamide.

  Examples of the hydroxyl group-containing polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Monoesterified product of (meth) acrylic acid and C2-C8 dihydric alcohol, ε-caprolactone modified product of monoesterified product of (meth) acrylic acid and C2-C8 dihydric alcohol, etc. Examples thereof include a hydroxyl group-containing (meth) acrylate having no polyoxyalkylene chain, and these can be used alone or in combination of two or more.

  Examples of the acid group-containing polymerizable unsaturated monomer include carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate; 2-acrylamido-2-methylpropane Polymerizable unsaturated monomers having a sulfonic acid group such as sulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid, 4-styrenesulfonic acid; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2 -Phosphoric acid group-containing polymerizable unsaturated monomers such as acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate, etc., and these may be used alone or in combination of two or more. It can be.

  Moreover, the said acid group can be neutralized with a neutralizing agent as needed. The neutralizing agent is not particularly limited as long as it can neutralize an acid group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, 2- (dimethylamino) ethanol, 2-amino-2-methyl- Examples include 1-propanol, triethylamine, and aqueous ammonia.

  Other polymerizable unsaturated monomers (d3) include the above-mentioned polymerizable unsaturated monomer (d1) having a polyoxyalkylene chain and a hydrophilic functional group-containing polymerizable unsaturated monomer (d2) having no polyoxyalkylene chain. There is no particular limitation as long as it is a polymerizable unsaturated monomer that can be copolymerized with, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n- Butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, Tridecyl (meth) acrylate, lauryl (meth) ac Rate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate -An alkyl or cycloalkyl (meth) acrylate such as cyclododecyl (meth) acrylate; a polymerizable unsaturated monomer having an isobornyl group such as isobornyl (meth) acrylate; an adamantyl group such as adamantyl (meth) acrylate Polymerizable unsaturated monomers; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloylo Polymerizable unsaturated monomers having an alkoxysilyl group such as cypropyltrimethoxysilane and γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate and other pars Fluoroalkyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone, ethylene, butadiene, chloroprene , Vinyl compounds such as vinyl propionate and vinyl acetate; (meth) acrylates having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) Benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy- Addition reaction product of hydroxybenzophenones such as 4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone and glycidyl (meth) acrylate, or 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl)- Polymerizable unsaturated monomers having an ultraviolet absorbing group such as 2H-benzotriazole; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2, 2,6,6-tetramethylpiperi 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetra Methylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethyl Polymerization having UV stabilization performance such as piperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine Unsaturated monomers; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, pho Examples thereof include polymerizable unsaturated monomer compounds having a carbonyl group such as lumilstyrol, a vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone).

  These can be used alone or in combination of two or more. From the viewpoint of the viscosity of the resulting aqueous coating composition, at least one other polymerizable unsaturated monomer (d3) is a straight chain having 3 or more carbon atoms. It is preferable to contain a polymerizable unsaturated monomer having a chain, branched or cyclic saturated or unsaturated hydrocarbon group, and the content thereof is 100 parts by mass of the total amount of the other polymerizable unsaturated monomer (d3). It is more preferable to contain 34 parts by mass or more based on

  Examples of the polymerizable unsaturated monomer having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 3 or more carbon atoms include styrene, propyl (meth) acrylate, butyl (meth) acrylate, 2 -At least one selected from ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and isobornyl (meth) acrylate is preferable. Styrene, butyl (meth) acrylate, 2-ethylhexyl ( More preferably, it is at least one selected from (meth) acrylates.

Pigment (E)
Examples of the pigment (E) used in the aqueous coating composition of the present invention include a color pigment, a glitter pigment, an extender pigment, and the like, and may contain at least one of a color pigment and a glitter pigment. preferable. These can be used alone or in combination of two or more, but it is particularly preferable to contain at least one kind of volatile pigment.

  Examples of the bright pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide and iron oxide, and titanium oxide and iron oxide. And mica, glass flakes, and hologram pigments. Among these, aluminum, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide are preferably used, and aluminum is particularly preferably used. The aluminum pigment includes non-leafing aluminum and leafing aluminum, and any of them can be used. The above luster pigments can be used alone or in combination of two or more.

When the water-based coating composition contains the above-mentioned glittering pigment, the content of the glittering pigment is a resin solid content of 100 mass in which the acrylic resin particles (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C) are combined. It is suitable that it is 1-50 mass parts normally on the basis of a part, Preferably it is 2-30 mass parts, More preferably, it exists in the range of 3-20 mass parts.
Examples of the coloring pigment include titanium oxide, zinc white, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, and perylene pigment. , Dioxazine pigments, diketopyrrolopyrrole pigments, and the like.

  When the water-based coating composition contains the above-described color pigment, the content of the color pigment is 100 parts by mass of a resin solid content in which the acrylic resin particles (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C) are combined. As a standard, it is suitable that it is usually in the range of 1 to 150 parts by mass, preferably 3 to 130 parts by mass, and more preferably 5 to 110 parts by mass.

  Examples of the extender pigment include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white.

  When the aqueous coating composition of the present invention contains the above extender pigment, the content of the extender pigment is a resin solid content obtained by totaling the acrylic resin particles (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C). Based on 100 parts by mass, it is usually 1 to 200 parts by mass, preferably 2 to 100 parts by mass, and more preferably 3 to 50 parts by mass.

Composition and preparation method of aqueous coating composition In the aqueous coating composition of the present invention, the contents of the acrylic resin particles (A), the hydroxyl group-containing resin (B), the crosslinking agent (C) and the viscosity modifier (D) are acrylic. The resin particles (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C) can be contained in an amount within the range described below on the basis of 100 parts by mass of the resin solid content.
Acrylic resin particles (A): 1 to 90 parts by weight, preferably 5 to 80 parts by weight, more preferably 10 to 70 parts by weight,
Hydroxyl group-containing resin (B): 1 to 90 parts by mass, preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass,
Crosslinking agent (C): 5 to 60 parts by mass, preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass,
Viscosity modifier (D): 0.1-4.9 parts by mass, preferably 0.4-3.5 parts by mass, more preferably 0.7-2.5 parts by mass.

  The water-based paint composition is a term that is contrasted with the organic solvent-type paint composition, and generally, a film-forming resin, a pigment, and the like are dispersed in water or a medium mainly composed of water (aqueous medium). And / or a dissolved coating composition. The water content in the aqueous coating composition of the present invention is preferably 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass.

  The solid concentration of the aqueous coating composition of the present invention is generally within the range of 10 to 60% by mass, preferably 15 to 50% by mass, and more preferably 20 to 40% by mass.

  In the present specification, “solid content” of paints, resins, and the like means non-volatile components remaining after drying at 110 ° C. for 1 hour. For example, the solid content of the coating means a non-volatile component such as a base resin, a crosslinking agent, or a pigment contained in the coating that remains after drying at 110 ° C. for 1 hour. Therefore, the solid content concentration of the paint is determined by measuring the paint in a heat-resistant container such as an aluminum foil cup, spreading the paint on the bottom of the container, drying at 110 ° C. for 1 hour, and the mass of the paint component remaining after drying. Can be calculated by determining the ratio of the mass of the paint component remaining after drying to the total mass of the paint before drying.

The water-based coating composition of the present invention preferably further contains a hydrophobic organic solvent from the viewpoint of improving the smoothness of the formed coating film, the sharpness, and the resistance to cracking.
The hydrophobic organic solvent is desirably an organic solvent having a mass dissolved in 100 g of water at 20 ° C. of 10 g or less, preferably 5 g or less, more preferably 1 g or less. Examples of the organic solvent include hydrocarbon solvents such as rubber volatile oil, mineral spirit, toluene, xylene, and solvent naphtha; 1-hexanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-hexanol, Decanol, benzyl alcohol, ethylene glycol mono-2-ethylhexyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol mono-n-butyl ether, propylene glycol mono-2-ethylhexyl ether, propylene Alcohol solvents such as glycol monophenyl ether; S such as n-butyl acetate, isobutyl acetate, isoamyl acetate, methyl amyl acetate, ethylene glycol monobutyl ether Le solvents; methyl isobutyl ketone, may be mentioned cyclohexanone, ethyl n- amyl ketone solvents such as diisobutyl ketone. These can be used alone or in combination of two or more.

  When the water-based coating composition of the present invention contains the hydrophobic solvent, the content thereof is a resin solid content of 100 mass obtained by adding the acrylic resin particles (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C). In general, it is preferably in the range of 2 to 100 parts by weight, particularly 5 to 80 parts by weight, more particularly 8 to 60 parts by weight, based on parts.

  Moreover, the aqueous coating composition of this invention can contain a hydrophilic organic solvent as needed. Examples of the hydrophilic organic solvent include ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether and the like.

  The aqueous coating composition of the present invention comprises acrylic resin particles (A), a hydroxyl group-containing resin (B), a crosslinking agent (C), a viscosity modifier (D) and a pigment (E), and if necessary, hydrophobic An organic solvent, a hydrophilic organic solvent, and other coating additives can be prepared by mixing and dispersing in an aqueous medium by a method known per se. Examples of the paint additive include a curing catalyst, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, a surface conditioner, and an anti-settling agent.

In the water-based coating composition of the present invention, if necessary, another viscosity modifier can be used in combination with the viscosity modifier (D).
Examples of viscosity modifiers other than the viscosity modifier (D) include inorganic viscosity modifiers such as silicates, metal silicates, montmorillonites, colloidal alumina; and fibrin derivatives such as carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose. Systemic viscosity modifiers: Protein-based viscosity modifiers such as casein, sodium caseinate, and ammonium caseinate; Alginate-based viscosity modifiers such as sodium alginate; Polyvinyl-based viscosity modifiers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyvinylbenzyl ether copolymers Agents; polyether-based viscosity modifiers such as pluronic polyethers, polyether dialkyl esters, polyether dialkyl ethers, polyether epoxy modified products; partial esters of vinyl methyl ether-maleic anhydride copolymer Maleic anhydride copolymer viscosity modifier; polyamide-based rheology control agents such as polyamide amine salts. These viscosity modifiers can be used in combination with the viscosity modifier (D) as necessary.

The aqueous paint composition of the present invention has a high viscosity development property, and in particular, when the aqueous paint composition contains a surfactant and / or a hydrophilic solvent, the viscosity is exhibited, and as a result, the finish of the multilayer coating film is achieved. The following can be considered as reasons for improving the performance and flip-flop performance.
1. Due to the hydrophilic functional group of the viscosity modifier (D) contained in the aqueous coating composition of the present invention, a network structure is formed by hydrogen bonds with other resins, and high viscosity is expressed.
2. Since the acrylic resin particles (A) of the present invention have a strongly hydrophobic monomer, hydrophobic association with the hydrophobic part of the viscosity modifier (D) occurs, and a network structure is formed to exhibit high viscosity.
3. Since the viscosity modifier (D) has a weight average molecular weight of 100,000 or more and a relatively large volume, the network structure is not affected by the surfactant and / or the hydrophilic solvent and is stably high. Viscosity develops.

The multilayer coating film forming method of the present invention The multilayer coating film forming method using the aqueous coating composition of the present invention is a method I in which a multilayer coating film is formed by a 3-coat 1-bake system, or a 2-coat 1-bake system. Any of the methods II for forming a multilayer coating film can be suitably used.

Method I
Specifically, the first multilayer coating film forming method (Method I) of the present invention is a multilayer film comprising a primer coating film, a base coating film, and a clear coating film on an object to be coated such as an automobile body or an automobile part. It can be suitably used when the coating film is formed by the 3-coat 1-bake method.
In this case, the multilayer coating film can be formed according to the following steps 1-1 to 1-4.

Following steps 1-1 to 1-4:
Step 1-1: A step of applying a primer coating composition (X) to an article to form a primer coating film,
Step 1-2: A step of coating the aqueous base coating composition (Y) on the uncured primer coating to form a base coating.
Step 1-3: A step of applying a clear paint (Z) on the uncured base coating to form a clear coating, and Step 1-4: the uncured primer coating, uncured A method for forming a multilayer coating film, wherein the aqueous base coating composition (Y) is the aqueous coating composition of the present invention in the step of sequentially heating and curing the base coating film and the uncured clear coating film simultaneously.

Step 1-1
In the first multilayer coating film forming method (Method I) of the present invention, first, a primer coating composition (X) is applied onto an object to be coated.

In the method for forming a multi-layer coating film of the present invention, the object to be coated with the primer coating composition (X) is not particularly limited. For example, automobiles such as passenger cars, trucks, motorcycles, buses, etc. Examples of the outer plate portion of the vehicle body; automobile parts such as bumpers; and the outer plate portion of home electric products such as mobile phones and audio devices. Of these, the outer plate portion of the automobile body and the automobile parts are preferable.

  The material of these objects to be coated is not particularly limited. For example, iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, zinc alloy (Zn—Al, Zn—Ni, Zn— Fe, etc.) Metal materials such as plated steel; polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc. Plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials such as paper and cloth. Of these, metal materials and plastic materials are preferred.

  The object to be coated may be a metal surface of the metal material or a vehicle body formed from the metal material, and may be subjected to surface treatment such as phosphate treatment, chromate treatment, complex oxide treatment, A coating film may be formed thereon.

  As an object to be coated, a surface treatment is applied to the substrate as necessary, and an undercoat film is formed thereon, for example, a vehicle body in which an undercoat film is formed by an electrodeposition paint It may be.

  The article to be coated may be obtained by subjecting the plastic surface of the plastic material or an automobile part or the like molded therefrom to a surface treatment as necessary. Further, a combination of a plastic material and a metal material may be used.

Primer paint composition (X)
As the primer coating composition (X) used in the method for forming a multilayer coating film of the present invention, a known intermediate coating or a primer coating for plastic can be used. Specifically, for example, a coating composition containing a film-forming resin, a crosslinking agent, a color pigment, an extender pigment, a bright pigment, a conductive pigment and a solvent can be suitably used. Further, the primer coating composition ( X) is a paint additive such as an ultraviolet absorber, a light stabilizer, a curing catalyst, a plasticizer, an adhesion-imparting agent, a compatibilizer, an antifoaming agent, a viscosity modifier, a rust inhibitor, and a surface modifier, as necessary. Can be appropriately contained.

  Examples of the film-forming resin include acrylic resin, polyester resin, alkyd resin, urethane resin, polyolefin resin, and the like, and preferably contains a hydroxyl group. These can be used alone or in combination of two or more.

  The primer coating composition (X) may be crosslinked by blending a crosslinking agent, or may be substantially uncrosslinked without blending a crosslinking agent. Moreover, you may make it bridge | crosslink by the penetration of the crosslinking agent contained in the upper layer coating film. As a crosslinking agent, a melamine resin, a polyisocyanate compound, a blocked polyisocyanate compound, etc. can be used conveniently, for example.

  As the primer coating composition, either an organic solvent-type coating composition or an aqueous coating composition may be used, but an aqueous coating composition is preferably used.

  The primer coating composition (X) can be applied by a known method, for example, air spray coating, airless spray coating, rotary atomization coating, and the like. Also good. The coating film thickness of the primer coating composition (X) is usually preferably about 3 to 40 μm, more preferably about 5 to 30 μm, and still more preferably about 7 to 20 μm as a cured film thickness.

Step 1-2
Next, on the coating film of the primer coating composition (X) formed in Step 1-1 described above (hereinafter sometimes referred to as “primer coating film”), it is the aqueous coating composition of the present invention. The aqueous base coating composition (Y) is applied.

  The primer coating film can be subjected to preheating (preliminary drying), air blowing, etc. under heating conditions in which the coating film is not substantially cured before the aqueous base coating composition (Y) is applied. In the present invention, the cured coating film is a cured and dried state defined in JIS K 5600-1-1, that is, the center of the coating surface is strongly sandwiched between the thumb and index finger, and the coating surface has a dent due to fingerprints. The coating film does not stick, the movement of the coating film is not felt, and the center of the coating surface is rapidly and repeatedly rubbed with a fingertip so that the coating surface is not rubbed. On the other hand, an uncured coating film is a state in which the coating film has not reached the above-mentioned cured and dried state, and includes a finger-touch dried state and a semi-cured dried state defined in JIS K 5600-1-1.

  The preheating temperature is preferably 40 to 100 ° C, more preferably 50 to 90 ° C, and still more preferably 60 ° C or more and less than 80 ° C. The preheating time is preferably 30 seconds to 15 minutes, more preferably 1 to 10 minutes, and even more preferably 2 to 5 minutes. Moreover, the said air blow can be normally performed by spraying the air heated to the normal temperature or the temperature of 25-80 degreeC on the coating surface of the to-be-coated article for 30 seconds-15 minutes.

  From the viewpoint of improving the smoothness and sharpness of the multilayer coating film to be formed and suppressing the armpit, the primer coating film may be preheated as necessary before applying the aqueous base coating composition (Y). It is preferable to adjust so that the solid content of the coating film is usually in the range of 60 to 100% by mass, particularly 80 to 100% by mass, and more particularly 90 to 100% by mass by performing air blow or the like.

Here, the solid content of the coating film can be measured by the following method:
First, the primer coating composition (X) is coated on the object to be coated, and at the same time, the primer coating composition (X) is coated on the aluminum foil whose mass (W1) has been measured in advance. Subsequently, after the coating, the aluminum foil that has been preheated or the like is collected immediately before the aqueous base coating composition (Y) is coated, and its mass (W2) is measured. Next, the recovered aluminum foil is dried at 110 ° C. for 60 minutes and allowed to cool to room temperature in a desiccator, and then the mass (W3) of the aluminum foil is measured, and the solid content is determined according to the following formula.
Solid content (mass%) = {(W3-W1) / (W2-W1)} × 100
The water-based base coating composition (Y) can be applied on the substrate by a method known per se, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, etc. Alternatively, electrostatic application may be performed. Of these, methods such as air spray coating and rotary atomization coating are preferred.

  The coating film thickness of the aqueous base coating composition (Y) is usually 3 to 50 μm, preferably 5 to 35 μm, and more preferably 10 to 20 μm as a cured film thickness.

Step 1-3
In the first multilayer coating film forming method (Method I) of the present invention, a coating film (hereinafter referred to as “base coating film”) of the aqueous base coating composition (Y) formed in the above step 1-2. A clear coating composition (Z).

  From the viewpoint of preventing the occurrence of coating film defects such as armpits, before applying the clear coating composition (Z), the base coating should be preheated (pre-dried) and air blown under heating conditions that do not substantially cure the coating. Etc. are preferably performed. The preheating temperature is preferably 40 to 100 ° C, more preferably 50 to 90 ° C, and still more preferably 60 ° C to less than 80 ° C. The preheating time is preferably 30 seconds to 15 minutes, more preferably 1 to 10 minutes, and further preferably 2 to 5 minutes. Moreover, the said air blow can be normally performed by spraying the air heated to the normal temperature or the temperature of 25-80 degreeC on the coating surface of the to-be-coated article for 30 seconds-15 minutes.

  Before applying the clear coating composition (Z), the base coating film is subjected to the above preheating, air blowing, or the like as necessary, so that the solid content of the coating film is usually 60 to 100% by mass, particularly 80%. It is preferable to adjust so that it may become in the range of -100 mass%, and especially 90-100 mass%.

  As the clear coating composition (Z), any thermosetting clear coating composition known per se for coating automobile bodies, automobile parts or household electrical appliances can be used. For example, a base resin having a crosslinkable functional group and an organic solvent-type thermosetting paint, a water-based thermosetting paint, a thermosetting powder paint, and a thermosetting powder slurry paint containing a crosslinking agent can be used. However, an organic solvent type thermosetting paint is more preferable.

  Examples of the crosslinkable functional group possessed by the base resin include a carboxyl group, a hydroxyl group, an epoxy group, a silanol group, an alkoxysilyl group, and a reactive unsaturated group. Examples of the base resin include acrylic resin, polyester resin, alkyd resin, urethane resin, epoxy resin, and fluorine resin. Examples of the crosslinking agent include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl group-containing compounds, carboxyl group-containing resins, epoxy group-containing resins, and epoxy group-containing compounds.

  As the combination of the base resin / crosslinking agent in the clear coating composition (Z), carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / polyisocyanate compound, hydroxyl group-containing resin / blocked polyisocyanate compound, hydroxyl group-containing resin / Melamine resin and the like are preferable.

  The clear coating composition (Z) may be a one-pack type paint or a multi-part paint such as a two-pack type urethane resin paint, but at a relatively low temperature (70 ° C. to 120 ° C.). In the case of heat curing at a temperature of less than 0 ° C., a one-pack type urethane resin paint using a blocked polyisocyanate compound as a crosslinking agent or a two-pack type urethane resin paint using a polyisocyanate compound as a crosslinking agent is suitable.

  If necessary, the clear coating composition (Z) can contain a coloring pigment, a bright pigment, a dye, etc. to such an extent that the transparency is not impaired. An agent, an antifoaming agent, a viscosity adjusting agent, a rust preventive agent, a surface adjusting agent and the like can be appropriately contained.

  The clear coating composition (Z) is applied to the coating surface of the aqueous base coating composition (Y) by a method known per se, for example, air spray coating, airless spray coating, rotary atomization coating, etc. Electrostatic application may be performed during painting. The clear coating composition (Z) can be applied such that it has a cured film thickness of usually 10 to 80 μm, preferably 15 to 60 μm, more preferably 20 to 50 μm.

  In addition, after application of the clear coating composition (Z), an interval of about 1 to 60 minutes can be provided at room temperature or preheating can be performed at a temperature of 40 to 80 ° C. for 1 to 60 minutes as necessary. .

Step 1-4
In the first multilayer coating film forming method (Method I) of the present invention, the uncured primer coating film, the uncured base coating film and the uncured base coating film formed in Steps 1-1 to 1-3 described above. The cured clear coating is simultaneously cured by heating.

  Curing of the primer coating film, base coating film and clear coating film can be carried out by a normal coating film baking means, for example, hot air heating, infrared heating, high-frequency heating or the like.

  The heating temperature is preferably from 70 ° C to 140 ° C, more preferably from 70 to 120 ° C, and even more preferably from 80 to 100 ° C, from the viewpoint of energy saving and / or heat resistance of the substrate.

  The heating time is preferably 10 to 60 minutes, and more preferably 15 to 40 minutes. By this heating, a multilayer coating film composed of three layers of a primer coating film, a base coating film, and a clear coating film can be simultaneously cured.

  In Method I, the coating film thickness of the primer coating composition (X) is preferably a cured film thickness, usually within the range of 3 to 40 μm, particularly 5 to 30 μm, and more particularly 7 to 20 μm. The coating thickness of the aqueous base coating composition (Y) is preferably 3 to 50 μm, particularly preferably 5 to 35 μm, more preferably 10 to 20 μm as a cured film thickness. Further, the coating film thickness of the clear coating composition (Z) is a cured film thickness and is usually within the range of 10 to 80 μm, particularly 15 to 60 μm, and more particularly 20 to 50 μm.

Method II
Specifically, the second method for forming a multilayer coating film (Method II) of the present invention is to be applied to an object such as an automobile body or an automobile part described in the first method for forming a multilayer coating film (Method I). In addition, it can be suitably used when a multi-layer coating film comprising a base coating film and a clear coating film is formed by a 2-coat 1-bake method.
Formation of the multilayer coating film in this case can be performed according to the following steps 2-1 to 2-3.

Following steps 2-1 to 2-3:
Step 2-1: a step of applying a water-based base coating composition (Y) to an object to form a base coating film,
Step 2-2: A step of coating the clear coating composition (Z) on the uncured base coating to form a clear coating; and Step 2-3: the uncured base coating and A method for forming a multilayer coating film, wherein the aqueous base coating composition (Y) is the aqueous coating composition of the present invention in the step of sequentially heating and curing the uncured clear coating film simultaneously.

Step 2-1
In the second multilayer coating film forming method (Method II) of the present invention, first, the aqueous coating composition of the present invention described in Step 1-2 above the article to be coated described in Step 1-1. An aqueous base coating composition (Y) is applied.

Step 2-2
Next, the clear coating composition (Z) described in the above step 1-3 is applied onto the base coating film of the aqueous base coating composition (Y) formed in the above step 2-1.

Step 2-3
The uncured base coating film and the uncured clear coating film formed in the above-described steps 2-1 to 2-2 are simultaneously heat-cured.
Heat curing of the base coating film and the clear coating film can be performed by the method described in the step 1-4.

  In addition, after applying the paint in step 2-1 and / or step 2-2, if necessary, an interval of about 1 to 60 minutes at room temperature or a heating condition in which the coating film does not substantially harden ( For example, preheating (preheating) or air blowing can be performed at a temperature of 40 to 80 ° C. for 1 to 60 minutes.

  In Method II, the coating thickness of the aqueous base coating composition (Y) is preferably in the range of usually 3 to 50 μm, particularly 5 to 35 μm, more particularly 10 to 20 μm as the cured film thickness. Further, the coating film thickness of the clear coating composition (Z) is a cured film thickness and is usually within the range of 10 to 80 μm, particularly 15 to 60 μm, and more particularly 20 to 50 μm.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples. “Part” and “%” are based on mass. Moreover, the film thickness of a coating film is based on a cured coating film.

Production and Production Example 1 of Hydroxyl-Containing Acrylic Resin (AC) for Primer Paint Composition 1
To a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and water separator, 60 parts of ethylene glycol monobutyl ether and 15 parts of isobutyl alcohol were added and heated to 110 ° C. in a nitrogen stream. When the temperature reached 110 ° C., a mixture of 10 parts of styrene, 48 parts of methyl methacrylate, 26 parts of n-butyl acrylate, 10 parts of 2-hydroxyethyl methacrylate, 6 parts of acrylic acid and 1 part of azobisisobutyronitrile was added dropwise over 3 hours. did. After completion of the addition, the mixture was aged at 110 ° C. for 30 minutes, and a mixture of 1 part of azobisisobutyronitrile and 15 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour. Further, after aging at 110 ° C. for 1 hour, the mixture was cooled, neutralized with dimethylaminoethanol, and deionized water was added to obtain a hydroxyl group-containing acrylic resin (AC). The obtained hydroxyl group-containing acrylic resin had a solid content of 50%.

Production and production example 2 of hydroxyl group-containing polyester resin (PE) for primer coating composition
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of 1,2-cyclohexanedicarboxylic acid anhydride and adipine After charging 120 parts of acid and raising the temperature from 160 ° C. to 230 ° C. over 3 hours, the resulting condensed water was distilled off with a water separator and subjected to a condensation reaction at 230 ° C. for 4 hours. Subsequently, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added, reacted at 170 ° C. for 30 minutes, diluted with ethylene glycol monobutyl ether, solid content A hydroxyl group-containing polyester resin (PE) having a concentration of 70% was obtained. The obtained hydroxyl group-containing polyester resin had an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, and a number average molecular weight of 1,400.

Production and production example 3 of active methylene type block polyisocyanate compound (CB)
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, “Sumidule N-3300” (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene) Diisocyanate-derived isocyanurate structure-containing polyisocyanate, solid content of about 100%, isocyanate group content of 21.8%) 480 parts, ethyl acetate 150 parts and diisopropyl malonate 365 parts, while stirring under a nitrogen stream, sodium 4 parts of 28% methanol solution of methoxide was added and stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.07 mol / Kg. To this was added 870 parts of 4-methyl-2-pentanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 120 parts of 4-methyl-2-pentanol was further removed. Was added to obtain 1400 parts of an active methylene type block polyisocyanate compound solution (CB-1). The removal solvent simple trap contained 183 parts of isopropanol. The obtained active methylene type block polyisocyanate compound solution (CB-1) had a solid concentration of about 60%.

Production Example 4
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate, 330 parts of diisopropyl malonate And 27 parts of isopropyl acetoacetate were added, and 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, followed by stirring at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.08 mol / Kg. To this was added 870 parts of 4-methyl-2-pentanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 120 parts of 4-methyl-2-pentanol was further removed. Was added to obtain 1390 parts of an active methylene block polyisocyanate compound solution (CB-2). The removal solvent simple trap contained 173 parts of isopropanol. The obtained active methylene type block polyisocyanate compound solution (CB-2) had a solid content concentration of about 60%.

Production Example 5
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate, 280 parts of diethyl malonate Then, 30 parts of ethyl isobutyryl acetate was added, and 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, followed by stirring at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.08 mol / Kg. To this was added 870 parts of 4-methyl-2-pentanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 120 parts of 4-methyl-2-pentanol was further removed. Was added to obtain 1350 parts of an active methylene block polyisocyanate compound solution (CB-3). The removal solvent simple trap contained 133 parts of ethanol. The obtained active methylene type block polyisocyanate compound solution (CB-3) had a solid concentration of about 60%.

Production Example 6
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen introducing tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 360 parts of diisopropyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added with stirring under a nitrogen stream and stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.07 mol / Kg. To this was added 990 parts of 5-methyl-2-hexanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 120 parts of 5-methyl-2-hexanol was further removed. Was added to obtain 1400 parts of an active methylene type block polyisocyanate compound solution (CB-4). The removal solvent simple trap contained 180 parts of isopropanol. The obtained active methylene type block polyisocyanate compound solution (CB-4) had a solid concentration of about 60%.

Production Example 7
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 450 parts of “Duranate TPA-100”, 150 parts of ethyl acetate and 360 parts of diisopropyl malonate were added. While stirring under a nitrogen stream, 4 parts of a 28% methanol solution of sodium methoxide was added and stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.07 mol / Kg. To this was added 1110 parts of 6-methyl-2-heptanol, the solvent was distilled off under reduced pressure for 6 hours while maintaining the temperature of the system at 80 to 85 ° C., and 120 parts of 6-methyl-2-heptanol was further added. In addition, 1430 parts of an active methylene type block polyisocyanate compound solution (CB-5) was obtained. The removal solvent simple trap contained 170 parts of isopropanol. The obtained active methylene type block polyisocyanate compound solution (CB-5) had a solid content concentration of about 60%.

Production Example 8
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 360 parts of “Sumidule N-3300”, “Uniox M-550” (Nippon Oil) 60 parts of polyethylene glycol monomethyl ether, average molecular weight of about 550) and 0.2 part of 2,6-di-tert-butyl-4-methylphenol were mixed and mixed well at 130 ° C. under a nitrogen stream. Heated for hours. Next, 110 parts of ethyl acetate and 252 parts of diisopropyl malonate were charged, and 3 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, followed by stirring at 65 ° C. for 8 hours. The isocyanate content in the obtained resin solution was 0.12 mol / Kg. To this was added 683 parts of 4-methyl-2-pentanol, and the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 80 to 85 ° C. to obtain an active methylene block polyisocyanate compound solution (CB- 6) 1010 parts were obtained. The removal solvent simple trap contained 95 parts of isopropanol. The obtained active methylene type block polyisocyanate compound solution (CB-6) had a solid concentration of about 60%.

Production Example 9
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen introducing tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 310 parts of diethyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, and the mixture was stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.06 mol / Kg. To this was added 630 parts of n-butanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 90 parts of n-butanol was further added. 1270 parts of a type block polyisocyanate compound solution (CB-7) were obtained. The removal solvent simple trap contained 100 parts of ethanol. The obtained active methylene type block polyisocyanate compound solution (CB-7) had a solid concentration of about 60%.

Production Example 10
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen introducing tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 310 parts of diethyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, and the mixture was stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.06 mol / Kg. To this was added 630 parts of 2-butanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 90 parts of 2-butanol was further added to form active methylene. 1250 parts of a type block polyisocyanate compound solution (CB-8) were obtained. The removal solvent simple trap contained 70 parts of ethanol. The obtained active methylene type block polyisocyanate compound solution (CB-8) had a solid content concentration of about 60%.

Production Example 11
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen introducing tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 310 parts of diethyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, and the mixture was stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.06 mol / Kg. To this was added 1110 parts of 2-ethyl-1-hexanol, the solvent was distilled off under reduced pressure for 6 hours while maintaining the temperature of the system at 80 to 85 ° C., and 2-ethyl-1-hexanol was further removed. 120 parts were added to obtain 1410 parts of an active methylene type block polyisocyanate compound solution (CB-9). The removal solvent simple trap contained 130 parts of ethanol. The obtained active methylene type block polyisocyanate compound solution (CB-9) had a solid concentration of about 60%.

Production Example 12
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen introducing tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 310 parts of diethyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, and the mixture was stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.06 mol / Kg. To this was added 1000 parts of propylene glycol monopropyl ether, the solvent was distilled off under reduced pressure for 3 hours while maintaining the system temperature at 90 to 95 ° C., and 120 parts of propylene glycol monopropyl ether was further added. As a result, 1380 parts of an active methylene block polyisocyanate compound solution (CB-10) were obtained. The removal solvent simple trap contained 125 parts of ethanol. The obtained active methylene type block polyisocyanate compound solution (CB-10) had a solid concentration of about 60%.

Production and production example 13 of pigment dispersion
In a stirring and mixing container, 42.9 parts (30 parts solids) of a hydroxyl group-containing polyester resin (PE) for the primer coating composition obtained in Production Example 2 and “JR-806” (trade name, manufactured by Teika, rutile type dioxide) Titanium) 110 parts, “Ketjen Black EC600J” (trade name, manufactured by Lion, conductive carbon) 10 parts and deionized water 137.1 parts, and further, 2- (dimethylamino) ethanol was added, The pH was adjusted to 8.0. Next, the obtained mixed liquid is put in a wide-mouth glass bottle, glass beads having a diameter of about 1.3 mmφ are added as a dispersion medium and sealed, and dispersed for 4 hours with a paint shaker to obtain a pigment dispersion (P-1). Obtained.

Production and production example 14 of primer coating composition (X)
30 parts of a hydroxyl group-containing acrylic resin (AC) for primer coating composition obtained in Production Example 1 (15 parts of solid content), 50 parts of “Takelac WS5000” (15 parts of solid content) (trade name, manufactured by Mitsui Takeda Chemical Co., polyurethane) Dispersion, self-crosslinking type containing silanol group, solid content 30%), "Supercron E-403" 133.3 parts (solid content 40 parts) (trade name, Nippon Paper Industries Co., Ltd., water dispersion of chlorinated polypropylene , Resin chlorine content 15%, solid content 30%) and 300 parts of the pigment dispersion (P-1) obtained in Production Example 13 were uniformly mixed. Further, “ACRYSOL ASE-60” Ford at 20 ° C. at pH 8.0, solid content concentration 45%, with addition of ANDHAAS, polyacrylic acid viscosity modifier), 2- (dimethylamino) ethanol and deionized water Cup No. A primer coating composition (X-1) having a viscosity of 40 according to 4 was obtained.

Production Example 15
10 parts of hydroxyl group-containing acrylic resin (AC) for primer coating composition obtained in Production Example 1 (5 parts of solid content), 16.7 parts of “Duranate MFK60X” (10 parts of solid content) (trade name, manufactured by Asahi Kasei Corporation) , Active methylene type block polyisocyanate compound, solid content 60%), “Takelac WS5000” 50 parts (solid content 15 parts) (trade name, manufactured by Mitsui Takeda Chemical Co., Ltd., polyurethane dispersion, silanol group-containing self-crosslinking type, solid 30%), "Supercron E-403" 133.3 parts (solid content 40 parts) (trade name, manufactured by Nippon Paper Industries Co., Ltd., water dispersion of chlorinated polypropylene, resin chlorine content 15%, solid content 30 %) And 300 parts of the pigment dispersion (P-1) obtained in Production Example 13 were mixed uniformly, and “ACRYSOL ASE-60” (trade name, Rohm and Haas) Manufactured by Ford Cup No. 2 at 20 ° C., pH 8.0, solid content concentration 45%, with addition of 2- (dimethylamino) ethanol and deionized water. A primer coating composition (X-2) having a viscosity of 40 according to 4 was obtained.

Production and production example 16 of acrylic resin particles (A)
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube and dropping device, 120 parts of deionized water and “ADEKA rear soap SR-1025” (trade name, manufactured by ADEKA, emulsifier, effective Ingredient 25%) 0.8 parts was charged, stirred and mixed in a nitrogen stream, and heated to 80 ° C.
Next, 5% of the total amount of the monomer emulsion for core part below and 2.5 parts of a 6% ammonium persulfate aqueous solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remainder of the monomer emulsion for core part was dropped into a reaction vessel maintained at the same temperature over 3 hours, and aging was performed for 1 hour after the completion of the dropping. Next, the following monomer emulsion for shell part was added dropwise over 1 hour and aged for 1 hour, and then cooled to 30 ° C. while gradually adding 3.8 parts of 5% 2- (dimethylamino) ethanol aqueous solution to the reaction vessel. Then, the mixture was discharged while being filtered through a 100 mesh nylon cloth to obtain an acrylic resin particle aqueous dispersion (A-1) having an average particle diameter of 100 nm and a solid content of 30%. The obtained acrylic resin particles had an acid value of 17.2 mgKOH / g and a hydroxyl value of 27.2 mgKOH / g.

  Monomer emulsion for core part: 54 parts of deionized water, 3.1 parts of “ADEKA rear soap SR-1025”, 1 part of allyl methacrylate, 10 parts of styrene, 35 parts of n-butyl acrylate, 10 parts of methyl methacrylate, 20 parts of ethyl acrylate And 1 part of 2-hydroxyethyl methacrylate were mixed and stirred to obtain a monomer emulsion for the core part.

  Monomer emulsion for shell part: 50 parts of deionized water, 1.8 parts of “ADEKA rear soap SR-1025”, 0.04 part of 6% ammonium persulfate aqueous solution, 3 parts of styrene, 6 parts of n-butyl acrylate, 2-hydroxy A monomer emulsion for a shell part was obtained by mixing and stirring 5.3 parts of ethyl methacrylate, 2.6 parts of methacrylic acid, 3 parts of ethyl acrylate, and 3.1 parts of methyl methacrylate.

Production Examples 17-20
Acrylic resin particle aqueous dispersions (A-2) to (A-5) were obtained in the same manner as in Production Example 16 except that the composition shown in Table 1 below was used.

  Table 1 shows the raw material composition (parts), solid content (%), acid value (mgKOH / g) and hydroxyl value (mgKOH / g) of the acrylic resin particle aqueous dispersions (A-2) to (A-5). Show.

The abbreviations in Table 1 have the following meanings.
St: Styrene,
AMA: Allyl methacrylate,
nBA: n-butyl methacrylate,
MMA: methyl methacrylate,
EA: ethyl acrylate,
HEMA: 2-hydroxyethyl methacrylate,
MAAc: Methacrylic acid
Production Production Example 21 of Hydroxyl-Containing Polyester Resin (B1-1) 21
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator was charged with 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 146 parts of hexahydrophthalic anhydride and 139 parts of adipic acid. The temperature was raised between 160 ° C. and 230 ° C. over 3 hours, and then a condensation reaction was performed at 230 ° C. for 4 hours. Next, in order to add a carboxyl group to the obtained condensation reaction product, 28.8 parts of trimellitic anhydride was further added, reacted at 170 ° C. for 30 minutes, and then diluted with 2-ethyl-1-hexanol. A hydroxyl group-containing polyester resin solution (B1-1) having a solid content concentration of 70% was obtained. The obtained polyester resin had an acid value of 45 mgKOH / g, a hydroxyl value of 100 mgKOH / g, a solid content concentration of 70%, and a number average molecular weight of 2,500.

Production and Production Example 22 for Bright Pigment Dispersion Liquid (AL)
In a stirring and mixing container, 19 parts of aluminum pigment paste “GX-180A” (trade name, manufactured by Asahi Kasei Metals Co., Ltd., metal content: 74%), 34.8 parts of 2-ethyl-1-hexanol, resin solution containing a phosphate group (B2-1) (Note 1) 8 parts and 2- (dimethylamino) ethanol 0.2 part were uniformly mixed to obtain a bright pigment dispersion (AL).
(Note 1) Hydroxyl group-containing acrylic resin (B2-1): 27.5 parts of methoxypropanol and 27.5 of isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device. Part of the mixed solvent, heated to 110 ° C., 25 parts of styrene, 27.5 parts of n-butyl methacrylate, “isostearyl acrylate” (trade name, Osaka Organic Chemical Industries, Ltd., branched higher alkyl acrylate) 20 parts, 7.5 parts of 4-hydroxybutyl acrylate, 15 parts of a phosphoric acid group-containing polymerizable unsaturated monomer (Note 2), 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol, t-butylperoxyoctano 121.5 parts of a mixture consisting of 4 parts of ate is added to the above mixed solvent over 4 hours, and t-butyl peroxide is added. A mixture of Shiokutanoeto 0.5 parts of isopropanol 20 parts was added dropwise for 1 hour. Thereafter, the mixture was stirred and aged for 1 hour to obtain a hydroxyl group-containing acrylic resin (B2-1) having a solid content concentration of 50%. The acid value due to the phosphoric acid group of this resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.
(Note 2) Phosphoric acid group-containing polymerizable unsaturated monomer: 57.5 parts monobutyl phosphoric acid and 41 parts isobutanol were added to a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen introducing tube and a dropping device. The mixture was heated to 90 ° C., 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, and the mixture was further aged and stirred for 1 hour. Thereafter, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable unsaturated monomer solution having a solid content concentration of 50%. The acid value due to the phosphate group of the obtained monomer was 285 mgKOH / g.

Manufacture and production example 23 of viscosity modifier (D)
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen gas inlet tube and two dropping devices, “MPEG1000MA” (trade name, manufactured by Evonik Degussa Japan, R ⁸ in the above general formula (VIII) Is a methyl group, R ⁹ is a hydrogen atom, R ¹⁰ is a hydrogen atom, R ¹¹ is a methyl group, n is 21, methoxypolyethylene glycol monomethacrylate having a molecular weight of about 1,000), 10 parts ethylene glycol monobutyl ether 35 Part and 30 parts of diethylene glycol monoethyl ether acetate were heated to 85 ° C. while nitrogen gas was blown into the liquid. Next, in a reaction vessel maintained at the same temperature, a mixed solution consisting of 5 parts of styrene, 10 parts of methyl methacrylate, 35 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl methacrylate and 35 parts of methacrylic acid, and “Perbutyl O” (Trade name, manufactured by NOF Corporation, polymerization initiator, tert-butyl peroxy-2-ethylhexanoate) 0.13 part and a mixed solution consisting of 20 parts of ethylene glycol monobutyl ether, respectively, over 5 hours, simultaneously The solution was dropped into the reaction vessel, and after completion of the dropping, aging was performed by stirring at the same temperature for 2 hours. Then, in a reaction vessel maintained at the same temperature, a mixed solution consisting of 0.3 part of 2,2′-azobis (2,4-dimethylvaleronitrile) and 15 parts of ethylene glycol monobutyl ether was dropped over 1 hour, After completion of the dropwise addition, the mixture was aged by stirring for 2 hours at the same temperature. Next, 5 parts of 2- (dimethylamino) ethanol and ethylene glycol monobutyl ether were added and cooled to 30 ° C. to obtain a viscosity modifier solution (D-1) having a solid content of 20%. The viscosity modifier obtained had a weight average molecular weight of 330,000 and an acid value of 228 mgKOH / g.

Production Examples 24-33
Except for the formulation shown in Table 2 below, synthesis was performed in the same manner as in Production Example 23 to obtain viscosity modifier solutions (D-2) to (D-11) having a solid content of 20%.

  Table 2 below shows the raw material composition (parts), acid value, and weight average molecular weight of the viscosity modifier solutions (D-1) to (D-11). In addition, all the monomer compounding amounts in the table are the values of the monomer component amounts.

The abbreviations in Table 2 have the following meanings.
MPEG2000MA: Trade name, manufactured by Evonik Degussa Japan, R ⁸ in the above general formula (VIII) is a methyl group, R ⁹ is a hydrogen atom, R ¹⁰ is a hydrogen atom, R ¹¹ is a methyl group, n is 45, and the molecular weight is Methoxypolyethylene glycol monomethacrylate DMAA: N, N-dimethylacrylamide which is about 2,000
Production Example 1 of Aqueous Base Coating Composition (Y)
Acrylic resin particle aqueous dispersion (A-1) obtained in Production Example 16 133.3 parts (solid content 40 parts), hydroxyl group-containing polyester resin solution (B1-1) obtained in Production Example 21 42.9 parts (solid) 30 parts), a hydroxyl group-containing polyurethane resin solution "Yukot UX-5210" (trade name, polycarbonate-based aqueous polyurethane resin, Sanyo Chemical Industries, solid content 32%) 12.5 parts (solid content 4 parts), 36.7 parts of active methylene type block polyisocyanate compound solution (CB-1) obtained in Production Example 3 (solid content 22 parts), 62 parts of glitter pigment dispersion (AL) obtained in Production Example 22 and 2-ethyl -10 parts of hexanol were mixed uniformly, and further 5 parts (D-1) of the viscosity modifier solution obtained in Production Example 23 (1 part of solid content), 2- (dimethylamino) ethanol and deionized water were added. In addition, pH 8. A solid concentration of 25%, Ford cup No. at 20 ° C. An aqueous base coating composition (Y-1) having a viscosity of 40 according to 4 was obtained.

Examples 2-20, Comparative Examples 1-7
Aqueous base coating compositions (Y-2) to (Y-27) were obtained in the same manner as in Example 1 except that the formulation shown in Table 3 below was used. In addition, all the compounding quantities in a table | surface are solid content.

Test plate preparation Example 21
The primer coating composition (X-1) obtained in Production Example 14 was spray-coated on a degreased polypropylene plate (PP plate) to a cured film thickness of 15 μm to form a primer coating film. After standing for 3 minutes and preheating at 60 ° C. for 3 minutes, the aqueous base coating composition (Y-1) obtained in Example 1 was applied on the uncured primer coating film to a cured film thickness of 15 μm. The base coating film was formed by spray coating. After standing for 5 minutes and preheating at 60 ° C. for 5 minutes, “Soflex # 520 Clear” (trade name, polyisocyanate, manufactured by Kansai Paint Co., Ltd.) was applied as a clear coating composition on the uncured base coating film. A compound-containing two-component acrylic urethane-based organic solvent-type clear coating (hereinafter sometimes referred to as “clear coating composition (Z-1)”) was spray-coated to a cured film thickness of 35 μm to form a clear coating film. . After leaving it for 7 minutes, it heated at 80 degreeC for 30 minutes, the said primer coating film, the base coating film, and the clear coating film were hardened simultaneously, and the test board was produced.

Examples 22-40, Comparative Examples 8-14
In Example 21, the aqueous base coating composition (Y-1) obtained in Example 1 is changed to any of the aqueous base coating compositions (Y-2) to (Y-20) shown in Table 4 below. A test plate was produced in the same manner as in Example 21 except for the above.

Examples 41-44
In Example 21, the primer coating composition (X-1), the clear coating composition (Z-1), and / or the baking temperature of 80 ° C., the primer coating composition (X-2) and the clear coating shown in Table 4 below. Composition (Z-2) ("Magiclon TC-71" (trade name, manufactured by Kansai Paint Co., Ltd., a thermosetting clear coating composition containing a hydroxyl group-containing acrylic resin and a melamine resin, hereinafter referred to as "Z-2") And / or a test plate was prepared in the same manner as in Example 21 except that the baking temperature was changed to any of 70 ° C. to 115 ° C.

Example 45
A thermosetting epoxy resin-based cationic electrodeposition coating (trade name “Electron GT-10”, manufactured by Kansai Paint Co., Ltd.) is electrodeposited onto a cold-rolled steel sheet treated with zinc phosphate so as to have a film thickness of 20 μm. 170 It was cured by heating at 0 ° C. for 30 minutes. Next, a primer paint (trade name “TP-65-5”, manufactured by Kansai Paint Co., Ltd., polyester resin / amino resin organic solvent type paint composition) is electrostatically applied on the electrodeposition coating film so as to have a film thickness of 20 μm. After applying using a rotary atomizing coater and leaving it for 5 minutes, preheating was performed at 80 ° C. for 5 minutes. Subsequently, after setting for 7 minutes, the aqueous base coating composition (Y-1) obtained in Example 1 was spray-coated on the uncured primer coating so as to have a cured film thickness of 15 μm. Formed. After standing for 5 minutes and preheating at 60 ° C. for 5 minutes, the clear coating composition (Z-1) was spray-coated on the uncured base coating film so that the cured film thickness was 35 μm. A coating film was formed. After leaving it for 7 minutes, it heated at 115 degreeC for 30 minutes, the said primer coating film, the base coating film, and the clear coating film were hardened simultaneously, and the test board was produced.

Comparative Example 15
The test was conducted in the same manner as in Example 45 except that the aqueous coating composition (Y-1) obtained in Example 1 was changed to the aqueous coating composition (Y-21) shown in Table 4 below. A plate was made.

Example 46
A thermosetting epoxy resin-based cationic electrodeposition coating (trade name “Electron GT-10”, manufactured by Kansai Paint Co., Ltd.) is electrodeposited onto a cold-rolled steel sheet treated with zinc phosphate so as to have a film thickness of 20 μm. 170 It was cured by heating at 0 ° C. for 30 minutes. Subsequently, the aqueous base coating composition (Y-1) obtained in Example 1 was spray-coated on the electrodeposition coating film so as to have a cured film thickness of 15 μm to form a base coating film. After standing for 5 minutes and preheating at 60 ° C. for 5 minutes, the clear coating composition (Z-1) was spray-coated on the uncured base coating film so that the cured film thickness was 35 μm. A coating film was formed. After leaving it for 7 minutes, it heated at 80 degreeC for 30 minutes, the said primer coating film, the base coating film, and the clear coating film were hardened simultaneously, and the test board was produced.

Comparative Example 16
Example 46 is the same as Example 46 except that the aqueous base coating composition (Y-1) obtained in Example 1 is changed to the aqueous base coating composition (Y-21) shown in Table 4 below. A test plate was prepared.

Evaluation Test Using the test plates obtained in Examples 21 to 46 and Comparative Examples 8 to 16, the evaluation was performed by the following test method. The evaluation results are shown in Table 4 below.

(Test method)
Smoothness: The test plate was evaluated using the Wc value measured by “Wave Scan DOI” (trade name, manufactured by BYK Gardner). It shows that the smoothness of a coating surface is so high that Wc value is small.

  Sharpness: The test plate was evaluated using a Wa value measured by “Wave Scan DOI” (trade name, manufactured by BYK Gardner). The smaller the Wa value, the higher the clearness of the paint surface.

Water resistance adhesion: After immersing the test plate in warm water at 40 ° C. for 240 hours, pulling it up and drying at 20 ° C. for 12 hours, the multi-layer coating film of the test plate is cut into a grid shape with a cutter so as to reach the substrate, Make 100 2mm x 2mm gobangs. Then, the adhesive cellophane tape was stuck on the surface, and the remaining state of the goby eye coating after the tape was rapidly peeled off at 20 ° C. was examined.
(Double-circle): 100 galvanic coatings remain | survive and the small edge of a coating film does not arise in the edge of a cutting of a cutter.
◯: 100 gobanged paint films remain, but small edges of the paint film are formed at the edge of the cutter.
(Triangle | delta): 90-99 pieces of gobang eyes coating films remain | survive.
X: The remaining number of gobang eye coats is 89 or less.

Flip-flop property: For each test plate, the L value (lightness) at a light receiving angle of 15 degrees and a light receiving angle of 110 degrees was measured using a multi-angle spectrocolorimeter MA-68 (trade name, manufactured by X-Rite). The FF value was determined by the following formula.
FF value = L value with a light receiving angle of 15 degrees / L value with a light receiving angle of 110 degrees.
The larger the FF value, the larger the change in the L value (brightness) depending on the observation angle (light receiving angle), indicating that the flip-flop property is excellent.

Claims (15)

In the aqueous coating composition containing the acrylic resin particles (A), the hydroxyl group-containing resin (B), the crosslinking agent (C), the viscosity modifier (D) and the pigment (E),
The acrylic resin particles (A) have a core-shell structure with a mass ratio of 10/90 to 90/10, the core part is cross-linked, and the polymerizable unsaturated constituting the acrylic resin particles (A) The amount of the polymerizable unsaturated monomer (a1) having a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 4 or more carbon atoms is 3 to 70 parts by mass with respect to 100 parts by mass of the total amount of monomers. Yes,
The hydroxyl group-containing resin (B) has a weight average molecular weight of 1,000 or more and less than 100,000,
The viscosity modifier (D) has a weight average molecular weight of 100,000 or more, and a polymerizable unsaturated monomer (d1) 5 to 50 having a polyoxyalkylene chain with respect to 100 parts by mass of the total monomer constituting the viscosity modifier (D). Hydrophilic material having no at least one polyoxyalkylene chain selected from parts by mass, N-vinyl-2-pyrrolidone, N-substituted (meth) acrylamide, hydroxyl group-containing polymerizable unsaturated monomer and acid group-containing polymerizable unsaturated monomer 5 to 90 parts by mass of polymerizable functional group-containing polymerizable unsaturated monomer (d2), 5 to 90 parts by mass of other polymerizable unsaturated monomer (d3),
A water-based paint composition characterized by the above.   The aqueous coating composition according to claim 1, wherein the crosslinking agent (C) is a block polyisocyanate compound. The blocked polyisocyanate compound is at least one of the blocked isocyanate groups represented by the following general formula (I)

[In the formula (I), R ¹ , R ² , R ⁴ and R ⁵ each independently represent a hydrocarbon group having 1 to 12 carbon atoms, and R ³ is a straight chain having 1 to 12 carbon atoms. Or a branched alkylene group is represented. ],
Blocked isocyanate group represented by the following general formula (II)

[In formula (II), R ² , R ³ , R ⁴ and R ⁵ are the same as above. ],
And a blocked isocyanate group represented by the following general formula (III)

Wherein ^{(III), R 2, R} 3, R 4 and ^{R 5} are as defined above, ^{R 6} represents a hydrocarbon group having 1 to 12 carbon atoms. ]
The water-based paint composition according to claim 2, comprising an active methylene type blocked polyisocyanate compound (CB) having at least one type of blocked isocyanate group selected from the group consisting of: The water-based coating composition according to claim 3, wherein, in the general formula (I), R ¹ is an isopropyl group. The water-based coating composition according to any one of claims 3 and 4, wherein in the general formula (III), R ⁶ is an isopropyl group. The active methylene type block polyisocyanate compound (CB) is represented by the following general formula (IV)

[In Formula (IV), R < ¹ > is the same as the above, and may be the same as or different from each other. ]
An active methylene type blocked polyisocyanate compound (cb3-1) having a blocked isocyanate group represented by the formula (II) and a secondary alcohol (cb4) represented by the following general formula (VI)

[In the formula (VI), R ² , R ³ , R ⁴ and R ⁵ are the same as described above. ]
The water-based coating composition according to claim 3 or 4, which is obtained by reacting The active methylene type block polyisocyanate compound (CB) is represented by the following general formula (V)

[In formula (V), R ⁶ is the same as described above, and R ⁷ represents a hydrocarbon group having 1 to 12 carbon atoms. ]
The active methylene type block polyisocyanate compound (cb3-2) having a blocked isocyanate group represented by the formula (VI) and the secondary alcohol (cb4) represented by the general formula (VI) are obtained. The water-based paint composition according to claim 1.   The aqueous coating composition according to any one of claims 2 to 7, wherein the block polyisocyanate compound is a block polyisocyanate compound having a hydrophilic group.   The viscosity-controlling agent (D), the hydrophilic functional group-containing polymerizable unsaturated monomer (d2) having no polyoxyalkylene chain, contains (meth) acrylic acid as at least one kind thereof, and the viscosity-controlling agent The acid value of (D) is 50-600 mgKOH / g, The water-based coating composition of any one of Claims 1-8 characterized by the above-mentioned.   The other polymerizable unsaturated monomer (d3) constituting the viscosity modifier (D) is a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 3 or more carbon atoms as at least one kind thereof. The water-based paint composition according to any one of claims 1 to 9, further comprising a polymerizable unsaturated monomer. Step 1-1: A step of applying a primer coating composition (X) on an object to form a primer coating film,
Step 1-2: A step of applying a water-based base coating composition (Y) on the uncured primer coating formed in Step 1-1 to form a base coating,
Step 1-3: A step of applying a clear coating composition (Z) on the uncured base coating formed in Step 1-2 to form a clear coating, and Step 1-4: Step 1 The aqueous base coating composition (Y) comprises a step of simultaneously heating and curing the uncured primer coating, the uncured base coating, and the uncured clear coating formed in 1 to 1-3, Item 11. A method for forming a multilayer coating film, which is the aqueous coating composition according to any one of items 1 to 10. Step 2-1: a step of coating a water-based base coating composition (Y) on an object to form a base coating film;
Step 2-2: A step of applying a clear coating composition (Z) on the uncured base coating film formed in Step 2-1, to form a clear coating film, and Step 2-3: Step 2- It includes the step of simultaneously heat-curing the uncured base coating film and the uncured clear coating film formed in 1-2, and the aqueous base coating composition (Y) is any one of claims 1 to 10. A method for forming a multilayer coating film, which is the water-based coating composition according to Item.   The method for forming a multilayer coating film according to any one of claims 11 and 12, wherein the clear coating composition (Z) contains a hydroxyl group-containing resin and a polyisocyanate compound.   The method for forming a multilayer coating film according to any one of claims 11 to 13, wherein the heat curing temperature is 70 to 140 ° C.   The article | item which has the multilayer coating film formed by the multilayer coating-film formation method of any one of Claims 11-14.