JP5804661B2 - Water-based paint composition - Google Patents

Description

  The present invention relates to an aqueous coating composition and a method for forming a coating film using the aqueous coating composition.

  Conventionally, as a method of forming a coating film on an automobile body, an electrodeposition coating is applied to an object to be coated, and after heat-curing, an intermediate coating is applied, bake-cured, a base coat is applied, a preheat (preheating) is applied, and a clear coating is applied. Widely adopted is a method of forming a multi-layer coating by a 3-coat 2-bake method in which coating → baking and curing are sequentially performed, and a 2-coat 2-bake method in which intermediate coating is applied, baking and curing, top coating is applied, and baking and curing are sequentially performed. ing.

  In general, the 3-coat 2-bake method is used when a so-called metallic-colored coating film is formed using a base coat paint containing a bright pigment, and the 2-coat 2-bake method contains a color pigment. This is used when a so-called solid color coating such as white or black is formed using a top coating.

  On the other hand, in recent years, from the viewpoint of energy saving, the baking and curing process after coating of the intermediate coating is omitted, and the coating of the intermediate coating → preheating (preheating) → base coating coating → preheating (preheating) → clear coating A 3-coat 1-bake method in which coating → baking and curing are sequentially performed, and a 2-coat 1-bake method in which coating of intermediate coating is applied → preheating (preheating) → coating of a top coating → baking and curing are studied.

  Among these, from the viewpoint of suppressing environmental pollution due to volatilization of organic solvents, the above-mentioned 3-coat 1-bake method and 2-coat 1-bake method using water-based paints as the above-mentioned intermediate paint, base coat paint, and top coat paint are particularly required.

  However, a water-soluble or water-dispersible resin is used in the 3-coat 1-bake method using the water-based intermediate paint and the water-based base coat paint and the 2-coat 1-bake method using the water-based intermediate paint and the water-based top coat paint. Reduces the water resistance of the formed coating film due to, and decreases the smoothness and sharpness of the formed coating film due to the interlayer between the aqueous intermediate coating and the aqueous base coating, or between the aqueous intermediate coating and the aqueous top coating. It may have occurred and has been regarded as an issue.

  For example, Patent Document 1 uses a thermosetting aqueous intermediate coating (A), a thermosetting aqueous base coat (B), and a thermosetting clear coat coating (C), and the aqueous intermediate coating (A) and the aqueous coating. In the method in which the base coat (B) is applied by a wet-on-wet method, the neutralization value of the base resin of the aqueous intermediate coating material (A) is 10 to 40 mg KOH / g, and the base resin of the aqueous base coat coating material (B) is It is described that the finished appearance such as gloss and clearness does not deteriorate when the sum is increased by 10 to 20 more than that of the water-based paint (A). However, the multilayer coating film obtained by the coating method may have insufficient smoothness and water resistance.

  Patent Document 2 discloses that an intermediate coating film is formed by an aqueous intermediate coating, a metallic base coating by a water-based metallic base coating, and a clear coating by a clear coating on a substrate on which an electrodeposition coating is formed. In the coating film forming method, the aqueous intermediate coating is obtained by emulsion polymerization of an amide group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer, an amide group having a particle size of 0.01 to 1.0 μm It is described that in the case of containing an aqueous dispersion of contained acrylic resin particles, conformity and inversion at the interface between coating film layers are controlled, and a laminated coating film having a high appearance can be formed. However, the multilayer coating film obtained by the coating film forming method sometimes has insufficient smoothness.

  Patent Document 3 includes (1) a step of providing an object on which an electrodeposition coating film is formed; (2) an intermediate coating film by applying an aqueous intermediate coating on the electrodeposition coating film. A step of forming; (3) a step of forming a base coating and a clear coating by sequentially applying a water-based base coating and a clear coating on the intermediate coating without wet curing the intermediate coating; (4) a step of baking and curing the intermediate coating film, the base coating film and the clear coating film at the same time; wherein the aqueous intermediate coating composition contains a specific acrylic resin emulsion and urethane resin emulsion. In addition, when the intermediate coating film formed by the aqueous intermediate coating material has a specific water absorption rate and water elution rate, a mixed phase between the intermediate coating film and the base coating film is effectively prevented, and surface smoothness is achieved. Forms an excellent multilayer coating film It has been described that can. However, even in the multilayer coating film obtained by the multilayer coating film forming method, sufficient smoothness and sharpness may not be obtained.

  Patent Document 4 includes at least one monomer selected from (meth) acrylic acid alkyl esters as an intermediate coating material in the 3-coat 1-bake method, and further, if necessary, a styrene monomer, (meth) acrylonitrile. And a monomer (a) containing at least one monomer selected from the group consisting of (meth) acrylamide, an acid group-containing polymerizable unsaturated monomer (b), a hydroxyl group-containing polymerizable unsaturated monomer (c), and a crosslinkable monomer ( d) is a copolymer resin emulsion obtained by emulsion polymerization, wherein the resin has a glass transition temperature of −50 ° C. to 20 ° C., an acid value of 2 to 60 mgKOH / g, and a hydroxyl value of 10 to 120 mgKOH / g. When an aqueous intermediate coating composition containing a polymer resin emulsion and a curing agent is used, It is described that since the curing reactivity of the lugeon and the curing agent is increased, a multilayer coating film having good chipping resistance and water resistance and a good finished appearance can be formed. However, even in the multilayer coating film obtained by the multilayer coating film forming method, sufficient smoothness and sharpness may not be obtained.

JP-A-8-290102 JP 2001-205175 A JP 2004-358462 A WO2004 / 061025

  An object of the present invention is to provide an aqueous coating composition and a coating film forming method capable of forming a coating film excellent in smoothness, sharpness, water resistance and chipping resistance.

  Another object of the present invention is to form a multilayer coating film by recoating a water-based paint, thereby suppressing the intermixing between the water-based paints, thereby achieving smoothness, sharpness, water resistance and chipping resistance. Excellent aqueous coating composition and film forming method for forming a multi-layer coating film excellent in smoothness and sharpness without applying preheating (preheating) after coating the aqueous coating composition. Another object of the present invention is to provide an aqueous coating composition and a method for forming a coating film that can form a multilayer coating film.

  As a result of intensive studies to achieve the above object, the present inventors have found that an aqueous coating composition containing specific crosslinked resin particles can achieve the above object, and have completed the present invention.

The present invention provides the following aqueous coating composition and a method for forming a coating film using the aqueous coating composition.
1. (A) an aqueous film-forming resin, (B) a curing agent, and (C) a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and a polymerizable unsaturated group It consists of a polymerizable unsaturated monomer (c-2) having one in one molecule, and is polymerizable based on the total amount of the polymerizable unsaturated monomer (c-1) and the polymerizable unsaturated monomer (c-2). The core part of copolymer (I) obtained by copolymerizing the monomer component, wherein the proportion of unsaturated monomer (c-1) used is in the range of 0.1 to 20% by mass, and urea group-containing polymerization A core composed of a shell portion of a copolymer (II) obtained by copolymerizing a monomer component comprising a polymerizable unsaturated monomer (c-3) and another polymerizable unsaturated monomer (c-4) Containing cross-linked resin particles having a shell-type multilayer structure The aqueous coating composition according to claim.
2. Item 2. The aqueous coating composition according to Item 1, wherein the aqueous film-forming resin (A) is a hydroxyl group-containing acrylic resin (A1) and / or a hydroxyl group-containing polyester resin (A2).
3. The urea group-containing polymerizable unsaturated monomer (c-3) is at least one polymerizable unsaturated monomer selected from polymerizable unsaturated monomers having a urea group selected from an ethylurea group, a propylurea group, and a butylurea group. Item 3. The aqueous coating composition according to Item 1 or 2.
4). Item 4. The aqueous coating composition according to any one of Items 1 to 3, wherein the other polymerizable unsaturated monomer (c-4) contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part thereof.
5. Solid content mass ratio of copolymer (I) and copolymer (II) is (solid content mass of copolymer (I)) / (solid content mass of copolymer (II)) = 10 / 90- Item 5. The aqueous coating composition according to any one of Items 1 to 4, which is within a range of 95/5.
6). Item 6. The aqueous coating composition according to any one of Items 1 to 5, wherein the average particle size of the crosslinked resin particles (C) is in the range of 10 nm to 500 nm.
7). The mixing ratio of the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C) is aqueous based on the total of 100 parts by mass of the aqueous film-forming resin (A) and the curing agent (B). Item 1-6, wherein the film-forming resin (A) is 60 to 95 parts by mass, the curing agent (B) is 5 to 40 parts by mass, and the crosslinked resin particles (C) are 1 to 100 parts by mass. The water-based paint composition described in 1.
8). Furthermore, the water-based coating composition of any one of said claim | item 1-7 containing a hydrophobic solvent (F).
9. 9. An article coated with the aqueous coating composition according to any one of items 1 to 8.
10. (A) an aqueous film-forming resin, (B) a curing agent, and (C) a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and a polymerizable unsaturated group Containing one polymerizable unsaturated monomer (c-2) in one molecule,
Based on the total amount of the polymerizable unsaturated monomer (c-1) and the polymerizable unsaturated monomer (c-2), the use ratio of the polymerizable unsaturated monomer (c-1) is 0.1 to 20% by mass. In the emulsion containing the copolymer (I) obtained by emulsion polymerization of the monomer mixture within the range, the urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomers (c- An aqueous coating composition comprising crosslinked resin particles comprising a copolymer (II) obtained by adding a monomer mixture containing 4) and further emulsion polymerization.

  According to the aqueous coating composition of the present invention, a multilayer coating film excellent in smoothness, sharpness, water resistance and chipping resistance can be formed. In addition, according to the method for forming a coating film of the present invention, a multilayer coating film excellent in smoothness, sharpness, water resistance and chipping resistance is formed when a multilayer coating film is formed by recoating an aqueous paint. Can be formed. Furthermore, according to the method for forming a coating film of the present invention, when a multilayer coating film is formed by repeatedly applying a water-based paint, without performing preheating (preheating) after coating the water-based paint composition, A multilayer coating film excellent in smoothness and sharpness can be formed.

  Hereinafter, the aqueous coating composition and the coating film forming method of the present invention will be described in more detail.

  The aqueous coating composition of the present invention (hereinafter sometimes abbreviated as “present coating”) includes (A) an aqueous film-forming resin, (B) a curing agent, and (C) one molecule of a polymerizable unsaturated group. By copolymerizing a monomer component consisting of a polymerizable unsaturated monomer (c-1) having two or more in it and a polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule Obtained by copolymerizing a core component of the copolymer (I) obtained and a monomer component comprising a urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomer (c-4). It contains crosslinked resin particles having a core / shell type multilayer structure composed of a shell portion of the copolymer (II) to be produced.

Water-based film-forming resin (A)
In the aqueous coating composition of the present invention, (A) the aqueous film-forming resin is one excluding the following (C) crosslinked resin particles.
As the water-based film-forming resin (A), a water-soluble or water-dispersible film-forming resin known per se that has been conventionally used in water-based paints can be used. As a kind of resin, an acrylic resin, a polyester resin, an alkyd resin, a polyurethane resin etc. are mentioned, for example. The aqueous film-forming resin (A) preferably has a crosslinkable functional group such as a hydroxyl group, a carboxyl group, or an epoxy group.

  As the aqueous film-forming resin (A), it is preferable to use a hydroxyl group-containing acrylic resin (A1) and / or a hydroxyl group-containing polyester resin (A2).

  Moreover, it is more preferable to use together a hydroxyl-containing acrylic resin (A1) and a hydroxyl-containing polyester resin (A2) from a viewpoint of the smoothness of a coating film, and the improvement of sharpness. As a ratio in the case of using together, based on the total amount of the hydroxyl group-containing acrylic resin (A1) and the hydroxyl group-containing polyester resin (A2), the former is about 10 to 90% by mass, particularly about 20 to 80% by mass, and the latter Is preferably about 90 to 10% by mass, particularly about 80 to 20% by mass.

  When the aqueous film-forming resin (A) has a hydroxyl group, the hydroxyl value is preferably 1 to 300 mgKOH / g, more preferably 2 to 250 mgKOH / g, and 5 to 180 mgKOH / g. Is more preferable. When the resin (A) has an acid group such as a carboxyl group, the acid value is preferably 1 to 200 mgKOH / g, more preferably 2 to 150 mgKOH / g, and 5 to 80 mgKOH / g. More preferably.

Hydroxyl group-containing acrylic resin (A1)
The hydroxyl group-containing acrylic resin (A1) is usually prepared by a method known per se, such as an organic compound containing a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer. It can be produced by copolymerization by a method such as a solution polymerization method in a solvent or an emulsion polymerization method in water.

  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 ( Monoesterified product of (meth) acrylic acid such as (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms; the (meth) acrylic acid Ε-caprolactone modified product of monoesterified product of C 2 and C 8 dihydric alcohol; N-hydroxymethyl (meth) acrylamide; allyl alcohol, and further having a polyoxyethylene chain whose molecular terminal is a hydroxyl group (meta ) Acrylate and the like.

  In the present specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylic acid” means “acrylic acid or methacrylic acid”. “(Meth) acryloyl” means “acryloyl or methacryloyl”. “(Meth) acrylamide” means “acrylamide or methacrylamide”.

Moreover, the other polymerizable unsaturated monomer copolymerizable with the said hydroxyl-containing polymerizable unsaturated monomer can be suitably selected and used according to the characteristic desired for a hydroxyl-containing acrylic resin (A1). Specific examples of the monomer are listed in (i) to (xix). These can be used alone or in combination of two or more.
(I) alkyl or cycloalkyl (meth) acrylate: 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, n-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, t-butylcyclohexyl (meth) a Relate, cyclododecyl (meth) acrylate, tricyclodecanyl (meth) acrylate.
(Ii) Polymerizable unsaturated monomer having an isobornyl group: isobornyl (meth) acrylate and the like.
(Iii) Polymerizable unsaturated monomer having an adamantyl group: adamantyl (meth) acrylate and the like.
(Iv) Polymerizable unsaturated monomer having a tricyclodecenyl group: tricyclodecenyl (meth) acrylate and the like.
(V) Aromatic ring-containing polymerizable unsaturated monomers: benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene and the like.
(Vi) Polymerizable unsaturated monomer having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) Acryloyloxypropyltriethoxysilane and the like.
(Vii) Polymerizable unsaturated monomer having a fluorinated alkyl group: perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; fluoroolefin and the like.
(Viii) A polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group.
(Ix) Vinyl compound: N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate and the like.
(X) Phosphoric acid group-containing polymerizable unsaturated monomer: 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate, and the like.
(Xi) Carboxy group-containing polymerizable unsaturated monomer: (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate and the like.
(Xii) Nitrogen-containing polymerizable unsaturated monomer: (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylamino Propyl (meth) acrylamide, methylene bis (meth) acrylamide, ethylene bis (meth) acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl (meth) acrylate and amines.
(Xiii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like.
(Xiv) Epoxy group-containing polymerizable unsaturated monomer: glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether and the like.
(Xv) (meth) acrylate having a polyoxyethylene chain whose molecular end is an alkoxy group.
(Xvi) polymerizable unsaturated monomer having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc .; sodium salt of these sulfonic acids And ammonium salts.
(Xvii) polymerizable unsaturated monomer having an ultraviolet-absorbing functional group: 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxy) Propoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole and the like.
(Xviii) Light-stable polymerizable unsaturated monomer: 4- (meth) acryloyloxy-1,2,2,6,6-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-crotonoyloxy-2,2,6 - tetramethylpiperidine and the like.
(Xix) polymerizable unsaturated monomer having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrol, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone) , Vinyl ethyl ketone, vinyl butyl ketone) and the like.

  In addition, as the hydroxyl group-containing acrylic resin (A1), as a part thereof, a so-called urethane-modified acrylic resin obtained by extending a polyisocyanate compound to a part of the hydroxyl group in the resin by a urethanization reaction to increase the molecular weight is used in combination. May be.

  The hydroxyl value of the hydroxyl group-containing acrylic resin (A1) is in the range of 1 to 200 mgKOH / g, preferably 2 to 100 mgKOH / g, more preferably 5 to 60 mgKOH / g, from the viewpoint of water resistance of the resulting coating film. Preferably it is.

  Further, the acid value of the hydroxyl group-containing acrylic resin (A1) is from 1 to 200 mgKOH / g, preferably from 2 to 150 mgKOH / g, more preferably from 5 to 200 mgKOH / g, from the viewpoints of storage stability and water resistance of the resulting coating film. It is preferable to be within the range of 80 mgKOH / g.

  The hydroxyl group-containing acrylic resin (A1) has a weight average molecular weight of 2,000 to 5,000,000, preferably 100,000 to 2,000,000 from the viewpoints of the appearance and water resistance of the resulting coating film. It is preferable to be within the range of 000.

In this specification, the number average molecular weight and the weight average molecular weight are values obtained by converting the number average molecular weight and the weight average molecular weight measured using a gel permeation chromatograph (GPC) on the basis of the molecular weight of standard polystyrene.
Hydroxyl-containing polyester resin (A2)
In the aqueous coating composition of the present invention, the smoothness of the resulting coating film can be improved by using the hydroxyl group-containing polyester resin (A2) as the aqueous film-forming resin (A).

  The hydroxyl group-containing polyester resin (A2) can be usually produced by an esterification reaction or an ester exchange reaction between an acid component and an alcohol component.

  As said acid component, the compound normally used as an acid component can be used at the time of manufacture of a polyester resin. Examples of the acid component include an aliphatic polybasic acid, an alicyclic polybasic acid, an aromatic polybasic acid, and the like.

  The aliphatic polybasic acid is generally an aliphatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound. Examples of the aliphatic polybasic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, octadecanedioic acid, and citric acid. Aliphatic polyvalent carboxylic acid; anhydride of the aliphatic polyvalent carboxylic acid; esterified product of lower alkyl having about 1 to 4 carbon atoms of the aliphatic polyvalent carboxylic acid. The said aliphatic polybasic acid can be used individually by 1 type or in combination of 2 or more types.

  The alicyclic polybasic acid is generally a compound having one or more alicyclic structures and two or more carboxyl groups in one molecule, an acid anhydride of the compound, and an esterified product of the compound. The alicyclic structure is mainly a 4- to 6-membered ring structure. Examples of the alicyclic polybasic acid include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl- Alicyclic polycarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid; An anhydride of an alicyclic polyvalent carboxylic acid; an esterified product of a lower alkyl having about 1 to 4 carbon atoms of the alicyclic polyvalent carboxylic acid. The said alicyclic polybasic acid can be used individually by 1 type or in combination of 2 or more types.

  The aromatic polybasic acid is generally an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and an esterified product of the aromatic compound, for example, phthalic acid , Isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid and other aromatic polycarboxylic acids; anhydrides of the aromatic polycarboxylic acids; aromatics Examples thereof include esterified products of lower alkyl having about 1 to 4 carbon atoms of polyvalent carboxylic acid. The said aromatic polybasic acid can be used individually by 1 type or in combination of 2 or more types.

  Moreover, acid components other than the said aliphatic polybasic acid, alicyclic polybasic acid, and aromatic polybasic acid can also be used. Such acid component is not particularly limited, for example, 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, Fatty acids such as castor oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane Examples thereof include monocarboxylic acids such as acid and 10-phenyloctadecanoic acid; hydroxycarboxylic acids such as lactic acid, 3-hydroxybutanoic acid, and 3-hydroxy-4-ethoxybenzoic acid. These acid components can be used alone or in combination of two or more.

  As said alcohol component, the polyhydric alcohol which has a 2 or more hydroxyl group in 1 molecule can be used conveniently. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3 -Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentane 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, water Dihydric alcohols such as hydrogenated bisphenol A, hydrogenated bisphenol F and dimethylolpropionic acid; polylactone diols obtained by adding lactones such as ε-caprolactone to these dihydric alcohols; ester diols such as bis (hydroxyethyl) terephthalate Polyether diols such as alkylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polybutylene glycol; glycerin, trimethylol ethane, trimethylol propane, diglycerin, Trihydric or higher alcohols such as liglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl) isocyanuric acid, sorbitol, mannitol; -Polylactone polyols to which lactones such as caprolactone are added.

  Moreover, alcohol components other than the said polyhydric alcohol can also be used. The alcohol component is not particularly limited, and examples thereof include monoalcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, stearyl alcohol, and 2-phenoxyethanol; propylene oxide, butylene oxide, “Cardura E10” (trade name, HEXION Specialty) Examples include alcohol compounds obtained by reacting monoepoxy compounds such as Chemicals, Inc. (glycidyl esters of synthetic highly branched saturated fatty acids) and acids.

  The manufacturing method of a hydroxyl-containing polyester resin (A2) is not specifically limited, It can carry out in accordance with a normal method. For example, the acid component and the alcohol component are heated in a nitrogen stream at about 150 to 250 ° C. for about 5 to 10 hours, and a method of performing esterification reaction or transesterification reaction of the acid component and alcohol component is performed. A containing polyester resin can be produced.

  When the acid component and the alcohol component are esterified or transesterified, they may be added to the reaction vessel at one time, or one or both may be added in several portions. . First, after synthesizing a hydroxyl group-containing polyester resin, the resulting hydroxyl group-containing polyester resin may be reacted with an acid anhydride to be half-esterified to obtain a carboxyl group- and hydroxyl group-containing polyester resin. First, after synthesizing a carboxyl group-containing polyester resin, the alcohol component may be added to obtain a hydroxyl group-containing polyester resin.

  In the esterification or transesterification reaction, as a catalyst for promoting the reaction, dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, tetraisopropyl A catalyst known per se, such as titanate, can be used.

  The hydroxyl group-containing polyester resin (A2) can be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound or the like during or after the preparation of the resin.

  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 Oil fatty acid, safflower oil fatty acid and the like can be mentioned, and as the above-mentioned monoepoxy compound, for example, “Cardura E10” (trade name, manufactured by HEXION Specialty Chemicals, glycidyl ester of synthetic highly branched saturated fatty acid) is preferably used. it can.

  Examples of the polyisocyanate compound include aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, and methylcyclohexane-2. , 6-diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), alicyclic diisocyanates such as 1,3- (isocyanatomethyl) cyclohexane; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate Organic polyisocyanates such as polyisocyanates having 3 or more valences such as lysine triisocyanate An adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin, water, etc .; a cyclized polymer (for example, isocyanurate) of each of these organic polyisocyanates, a biuret type adduct Etc. These polyisocyanate compounds can be used individually by 1 type or in mixture of 2 or more types.

The hydroxyl group-containing polyester resin (A2) preferably has a hydroxyl value of 10 to 300 mgKOH / g, more preferably 30 to 250 mgKOH / g, and still more preferably 50 to 180 mgKOH / g. When the hydroxyl group-containing polyester resin (A2) further has a carboxyl group, the acid value is preferably 1 to 200 mgKOH / g, more preferably 15 to 100 mgKOH / g, and 20 to 60 mgKOH / g. More preferably, it is g. The number average molecular weight of the hydroxyl group-containing polyester resin (A2) is preferably 500 to 50,000, more preferably 1,000 to 30,000, and 1,200 to 10,000. Is more preferable.
Examples of the polyurethane resin include a reaction of at least one diol selected from aliphatic and / or alicyclic diisocyanate, polyether diol, polyester diol, and polycarbonate diol, a low molecular weight polyhydroxy compound, and dimethanol alkanoic acid. A urethane prepolymer is prepared, neutralized with a tertiary amine, emulsified and dispersed in water, and then mixed with an aqueous medium containing a chain extender such as polyamine, a crosslinking agent and / or a terminating agent as necessary. And what is made to react until an isocyanate group is substantially lose | eliminated can be mentioned. By the above method, a self-emulsifying type polyurethane resin having an average particle diameter of about 1 nm to 3000 nm can be usually obtained. Moreover, as a commercial item of the said polyurethane resin, "you coat UX-5000", "you coat UX-8100" (a brand name, the Sanyo Chemical Industries make) etc. can be mentioned, for example.

Curing agent (B)
The curing agent (B) is a compound capable of curing the composition of the present invention by reacting with a crosslinkable functional group such as a hydroxyl group, a carboxyl group, and an epoxy group in the aqueous film-forming resin (A). Examples of the curing agent (B) include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, carbodiimide group-containing compounds, and the like. Among these, from the viewpoint of water resistance of the resulting coating film, amino resins that can react with hydroxyl groups, blocked polyisocyanates, and carbodiimide group-containing compounds that can react with carboxyl groups are preferred, and amino resins are particularly preferred. A hardening | curing agent (B) can be used individually by 1 type or in combination of 2 or more types.

  As said amino resin, the partial methylolation amino resin obtained by reaction of an amino component and an aldehyde component, or a complete methylolation amino resin 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, and benzaldehyde.

  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, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethyl-1-butanol, and 2-ethyl-1. -Hexanol etc. are mentioned.

  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. Preferred is a methyl-butyl mixed etherified melamine resin in which the methylol group of a partially or completely methylolated melamine resin is partially or completely etherified with methyl alcohol and butyl alcohol. Etherified melamine resins are more preferred. Moreover, imino group containing melamine resin is preferable.

  The melamine resin preferably has a weight average molecular weight of 400 to 6,000, more preferably 500 to 4,000, and still more preferably 600 to 3,000.

  A commercially available product can be used as the melamine resin. Examples of commercially available product names include “Cymel 202”, “Cymel 203”, “Cymel 204”, “Cymel 211”, “Cymel 238”, “Cymel 250”, “Cymel 303”, “Cymel 323”, “Cymel 324”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 385”, “Cymel 1156”, “Cymel 1158”, “Cymel 1116”, “Cymel 1130” , "Uban 120", "Uban 20HS", "Uban 20SE60", "Uban 2021", "Uban 2028", "Uban 28-60" (above, Mitsui Chemicals).

  When a melamine resin is used as the curing agent (B), sulfonic acids such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid; salts of these sulfonic acids with amine compounds; It can be used as a catalyst.

  The blocked polyisocyanate compound is a compound obtained by blocking an isocyanate group of a polyisocyanate compound having at least two isocyanate groups in one molecule with a blocking agent.

  Examples of the polyisocyanate compound having at least two isocyanate groups in one molecule include aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; hydrogenated xylylene diisocyanate, cyclohexylene Cycloaliphatic diisocyanates such as diisocyanate and isophorone diisocyanate; Aromatic diisocyanates such as tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate; 2-isocyanato Ethyl-2,6-diisocyanatocaproate, 3-i Trivalent or higher organic polyisocyanate compounds such as cyanatomethyl-1,6-hexamethylene diisocyanate and 4-isocyanatomethyl-1,8-octamethylene diisocyanate (commonly known as triaminononane triisocyanate); 2 of these polyisocyanate compounds A polymer or a trimer (biuret, isocyanurate, etc.); a prepolymer obtained by subjecting these polyisocyanate compound and polyhydric alcohol, low molecular weight polyester resin or water to urethanization under an excess of isocyanate groups. .

  Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; ε-caprolactam, δ-valero Lactams such as lactam, γ-butyrolactam, β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Ethers such as propylene glycol monomethyl ether and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, di Alcohols such as acetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; oximes such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; dimethyl malonate, malon Active methylenes such as diethyl acetate, ethyl acetoacetate, methyl acetoacetate, acetylacetone; butyl mercaptan, Mercaptans such as t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol; acetanilide, acetanisid, acetolide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide Acid amides such as benzamide; imides such as succinimide, phthalic acid imide, and maleic acid imide; diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenyl Amines such as amines; Imidazoles such as imidazole and 2-ethylimidazole; urea, thiourea, ethyleneurea, ethylene Ureas such as lenthiourea and diphenylurea; Carbamates such as phenyl N-phenylcarbamate; Imines such as ethyleneimine and propyleneimine; Sulphites such as sodium bisulfite and potassium bisulfite; Azole compounds Etc. Examples of the azole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3, Pyrazole or pyrazole derivatives such as 5-dimethylpyrazole and 3-methyl-5-phenylpyrazole; Imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole and 2-phenylimidazole; 2-methylimidazoline And imidazoline derivatives such as 2-phenylimidazoline.

  Among them, preferred blocking agents include oxime blocking agents, active methylene blocking agents, pyrazoles or pyrazole derivatives.

  In addition, as the blocking agent, hydroxycarboxylic acids having one or more hydroxyl groups and one or more carboxyl groups, such as hydroxypivalic acid and dimethylolpropionic acid, can be used. In particular, a blocked polyisocyanate compound in which an isocyanate group is blocked using the hydroxycarboxylic acid and then the carboxyl group of the hydroxycarboxylic acid is neutralized to impart water dispersibility can be suitably used.

  As said carbodiimide group containing compound, what made the carbon dioxide reaction of the isocyanate groups of the said polyisocyanate compound can be used, for example. A commercial item can be used as this carbodiimide group containing compound. Commercially available product names include, for example, “Carbodilite V-02”, “Carbodilite V-02-L2”, “Carbodilite V-04”, “Carbodilite E-01”, “Carbodilite E-02” (all Nisshinbo And product names).

  The blending ratio of the water-based film-forming resin (A) and the curing agent (B) in the water-based coating composition of the present invention is 60 to 95% by mass, preferably 65 to 90% by mass based on the total amount of both. %, More preferably 70 to 90% by mass, the latter being 5 to 40% by mass, preferably 10 to 35% by mass, and more preferably 10 to 30% by mass. From the viewpoint of improving chipping resistance, it is preferable.

  When the aqueous coating composition of the present invention contains the hydroxyl group-containing acrylic resin (A1) as at least one of the aqueous film-forming resins (A), the blending amount of the hydroxyl group-containing acrylic resin (A1) Based on the total amount of the conductive resin (A) and the curing agent (B), it is preferably 2 to 80% by mass, more preferably 10 to 60% by mass, and 20 to 50% by mass. Further preferred.

  When the aqueous coating composition of the present invention contains the hydroxyl group-containing polyester resin (A2) as at least one kind of the aqueous film-forming resin (A), the compounding amount of the hydroxyl group-containing polyester resin (A2) is aqueous. Based on the total amount of the film-forming resin (A) and the curing agent (B), it is preferably 2 to 80% by mass, more preferably 5 to 60% by mass, and 10 to 50% by mass. Is more preferable.

Crosslinked resin particles (C)
The crosslinked resin particles (C) are a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and a polymerizable unsaturated group having one polymerizable unsaturated group in one molecule. Core part of copolymer (I) obtained by copolymerizing monomer component comprising monomer (c-2), urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomers It is a crosslinked resin particle having a core / shell type multilayer structure composed of a shell portion of a copolymer (II) obtained by copolymerizing a monomer component comprising (c-4).

  Examples of the polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in the molecule used as the monomer for the copolymer (I) include allyl (meth) acrylate, ethylene glycol di (meta) ) 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- Lithhydroxymethylethane di (meth) acrylate, 1,1,1-trishydroxymethylethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, Examples include divinylbenzene, methylene bisacrylamide, and ethylene bisacrylamide. These monomers can be used individually by 1 type or in combination of 2 or more types.

  Examples of the polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups per molecule include allyl (meth) acrylate, ethylene glycol di (meth) acrylate, and 1,4-butane. Diol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 1,6-hexanediol di (meth) acrylate can be preferably used.

  The use ratio of the polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule is one molecule of polymerizable unsaturated groups from the viewpoint of improving the stability of the resulting paint. Preferably based on the total amount of the polymerizable unsaturated monomer (c-1) having two or more in it and the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule, it is preferably 0 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and particularly preferably 1 to 5% by mass.

As the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule used as a monomer for the copolymer (I),
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, n-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, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, trisyl Rodekaniru (meth) alkyl or cycloalkyl acrylates such as (meth) acrylate;
Polymerizable unsaturated monomers having an isobornyl group such as isobornyl (meth) acrylate;
Polymerizable unsaturated monomers having an adamantyl group such as adamantyl (meth) acrylate;
Polymerizable unsaturated monomers having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate;
Aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene;
Polymerization having alkoxysilyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane Unsaturated monomers;
Perfluoroalkyl (meth) acrylates such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate;
A polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin;
A polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group;
Vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate and vinyl acetate;
(Meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and 2 having 2 to 8 carbon atoms Monoesterified product with monohydric alcohol, ε-caprolactone modified product of monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms, N-hydroxymethyl (meth) acrylamide, allyl alcohol, molecule A hydroxyl group-containing polymerizable unsaturated monomer such as (meth) acrylate having a polyoxyethylene chain whose terminal is a hydroxyl group;
Carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate;
(Meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, glycidyl (meth) acrylate Nitrogen-containing polymerizable unsaturated monomers such as adducts of amines with amines;
Glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate Epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether;
And (meth) acrylate having a polyoxyethylene chain whose molecular end is an alkoxy group. These monomers can be used individually by 1 type or in combination of 2 or more type according to the performance requested | required of crosslinked resin particle (C).

  The polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group per molecule has at least a part of carbon atoms of 1 to 3, particularly, from the viewpoint of improving the stability of the resulting coating. A polymerizable unsaturated monomer having an alkyl group having 1 or 2 carbon atoms can be contained.

  Examples of the polymerizable unsaturated monomer having an alkyl group having 1 or 2 carbon atoms include methyl (meth) acrylate and ethyl (meth) acrylate. These monomers can be used individually by 1 type or in combination of 2 or more types.

  In addition, as the polymerizable unsaturated monomer having an alkyl group having 1 or 2 carbon atoms, it is preferable to use methyl methacrylate and / or ethyl methacrylate from the viewpoint of improving the stability of the paint, and methyl methacrylate is preferably used. More preferred.

  The polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule is substantially free of the following urea group-containing polymerizable unsaturated monomer (c-3). Is preferable, but a proportion of the copolymer (I) monomer is smaller than the proportion of the urea group-containing polymerizable unsaturated monomer (c-3) contained in the total copolymer (II) monomer. It can contain as.

  When the following urea group-containing polymerizable unsaturated monomer (c-3) is used as the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule, the urea group-containing polymerizable property is used. The proportion of the unsaturated monomer (c-3) used is preferably less than 10% by weight, more preferably less than 5% by weight, even more preferably 2% by weight, based on the total amount of the monomers for the copolymer (I). Is less than.

  The urea group-containing polymerizable unsaturated monomer (c-3) used as the monomer for the copolymer (II) is a polymerizable unsaturated monomer having a urea group (urea bonding group (—NH—CO—NH—)). .

  The urea group (urea bonding group) can form a pseudo-crosslinked structure due to hydrogen bonding in the coated film after the solvent such as water is volatilized, and can exhibit the effect of increasing the viscosity of the coated film.

  The urethane group (—NHCO—) and the amide group have one hydrogen atom bonded to the nitrogen atom, whereas the urea group has two hydrogen atoms bonded to the nitrogen atom, Since the number of bonding points increases, the pseudo-crosslinked structure by hydrogen bonding becomes denser than the urethane group and amide group, and a high viscosity increasing effect can be exhibited.

  Although it will not specifically limit if it is a polymerizable unsaturated monomer containing a urea group, For example, as a urea group containing polymerizable unsaturated monomer (c-3), an amine compound is added to a polymerizable unsaturated monomer containing an isocyanate group. The monomer obtained by making it react can be mention | raise | lifted.

  Examples of the polymerizable unsaturated monomer containing an isocyanate group include 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate, and the like, and also contain a hydroxyl group. Examples include adducts of a polymerizable unsaturated monomer and diisocyanate.

  Examples of the polymerizable unsaturated monomer containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Glycol (meth) acrylates such as allyl alcohol, polyallyl monoallyl ether, and the like.

  Examples of the diisocyanate include alicyclic, aromatic group-containing aliphatic or aromatic diisocyanate compounds. Further, isocyanurate of a diisocyanate compound (triisocyanate of diisocyanate) can also be used.

  Examples of the diisocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, undecane diisocyanate- (1,11), lysine ester diisocyanate, cyclohexane-1,3- and 1, 4-diisocyanate, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (IPDI), 4,4′-diisocyanatodicyclodicyclomethane, ω, ω′-dipropyl ether diisocyanate, thio Dipropyl diisocyanate, cyclohexyl-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,5-dimethyl-2,4-bis (isocyanatomethyl) , 1,5-trimethyl-2,4-bis (ω-isocyanatoethyl) -benzene, 1,3,5-trimethyl-2,4-bis (isocyanatomethyl) benzene, 1,3,5-triethyl -2,4-bis (isocyanatomethyl) benzene, dicyclohexyldimethylmethane-4,4'-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate and diphenylmethane-4,4'-diisocyanate .

  2,4-diisocyanatotoluene and / or 2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenylmethane and 1,4-diisocyanatoisopropylbenzene, cyclohexyl-1,4-diisocyanate, Aromatic diisocyanates such as toluene diisocyanate and hexamethylene diisocyanate can also be used. Furthermore, mixtures of these compounds can also be used.

  Examples of the isocyanurate of the diisocyanate compound include the above-described diisocyanate trimers. The isocyanate may be a diisocyanate or a mixture of trimers.

  Examples of amine compounds that react with polymerizable unsaturated monomers containing isocyanate groups to form urea groups include primary amines and secondary amines. Of these, primary amines can be preferably used.

  As primary amines, amines having one or more primary amino groups and one or more ethers and / or hydroxyl groups can also be used, for example ethanolamine, 6-aminohexanol, p-methoxybenzylamine, Methoxypropylamine, 3,4-dimethoxyphenylethylamine, 2,5-dimethoxyaniline, furfurylamine, tetrahydrofurfurylamine, benzylamine, ethylamine, propylamine (n-propylamine, isopropylamine), butylamine (n-butylamine, sec-butylamine, tert-butylamine), n-pentylamine, 1-methylbutylamine, 1-ethylpropylamine, 2-ethylbutylamine, hexylamine, octylamine, decylamine, stearyl Min, cyclohexylamine, aniline, primary amines such as hexamethylene diamine. The amine compounds can be used as a mixture.

  As the amine compound, ethylamine, propylamine, and butylamine are preferable from the viewpoint of improving water resistance.

  The reaction of the polymerizable unsaturated monomer containing an isocyanate group with an amine compound is carried out by the equivalent ratio of the isocyanate group present in the polymerizable unsaturated monomer containing an isocyanate group and the active hydrogen present in the amine compound ( The active hydrogen / isocyanate group present in the amine compound) is 0.5 to 2, preferably 0.7 to 1.5, more preferably 0.8 to 1.2. The method can be used.

  In particular, in the reaction of the polymerizable unsaturated monomer containing the isocyanate group with the amine compound, generally, either the polymerizable unsaturated monomer containing the isocyanate group or the amine compound is more than the stoichiometric amount. For example, the ratio of the number of amino groups of the amine compound to the number of isocyanate groups of the polymerizable unsaturated monomer containing an isocyanate group should be 0.7 to 1.5, preferably 0.9 to 1.1. Can do.

  The reaction between the polymerizable unsaturated monomer containing an isocyanate group and the amine compound can be carried out by a known method by mixing the two and raising the temperature as desired. This reaction is desirably performed at a temperature of 10 to 70 ° C, preferably 20 to 50 ° C. In general, the reaction components can be mixed by a known method, but it is usually desirable to add a polymerizable unsaturated monomer containing an isocyanate group to the amine compound, and this addition is performed in several stages as desired. Can do. In general, this reaction can be carried out in the presence of a solvent such as an aliphatic hydrocarbon such as acetone, methyl isobutyl ketone, benzene, toluene, xylene, tetrahydrofuran, or petroleum ether.

The use ratio of the above-mentioned urea group-containing polymerizable unsaturated monomer (c-3) is a urea group-containing one having one polymerizable unsaturated group in one molecule from the viewpoint of smoothness and sharpness of the resulting coating film. Based on the total amount of the polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomer (c-4), 5 to 70% by mass, particularly 10 to 60% by mass, more particularly 15 to 50% by mass. Even more particularly, it is preferable to be within the range of 15 to 40% by mass.
The other polymerizable unsaturated monomer (c-4) used as the monomer for the copolymer (II) is a monomer other than the urea group-containing polymerizable unsaturated monomer (c-3), for example, polymerizable unsaturated Among the polymerizable unsaturated monomers (c-2) having one group per molecule, those other than those having a urea group can be used.

  As the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule (excluding those having a urea group), those exemplified for the copolymer (I) monomer are the same. In addition, acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (eg, vinyl methyl ketone, vinyl ethyl ketone) Carbonyl group-containing polymerizable unsaturated monomers such as vinyl butyl ketone) can also be used. These monomers can be used alone or in combination of two or more.

  The other polymerizable unsaturated monomer (c-4) used as the copolymer (II) monomer preferably contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part thereof.

  The hydroxyl group-containing polymerizable unsaturated monomer improves the water resistance and the like of the coating film by incorporating a hydroxyl group that undergoes a crosslinking reaction with the curing agent (B) into the resulting crosslinked resin particle (C). C) has a function of improving stability in an aqueous medium.

  Examples of the hydroxyl group-containing polymerizable unsaturated monomer include the hydroxyl group exemplified by the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group per molecule of the copolymer (I) monomer. A polymerizable unsaturated monomer is mentioned. These monomers can be used alone or in combination of two or more.

  Among the hydroxyl group-containing polymerizable unsaturated monomers, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are particularly preferable. Can be used for

  When the hydroxyl group-containing polymerizable unsaturated monomer is contained as the other polymerizable unsaturated monomer (c-4), the proportion of the hydroxyl group-containing polymerizable unsaturated monomer used is stable in the aqueous medium of the crosslinked resin particles (C). From the viewpoint of excellent properties and chipping resistance of the resulting coating film, the total amount of urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomer (c-4) is 1 to It is preferably 30% by mass, more preferably 3 to 25% by mass, and even more preferably 5 to 20% by mass.

  The other polymerizable unsaturated monomer (c-4) preferably contains a carboxyl group-containing polymerizable unsaturated monomer as at least a part thereof.

  Examples of the carboxyl group-containing polymerizable unsaturated monomer include, for example, carboxyls exemplified in the polymerizable unsaturated monomer (c-2) having one polymerizable unsaturated group in one molecule of the copolymer (I) monomer. And group-containing polymerizable unsaturated monomers. These monomers can be used alone or in combination of two or more.

  Among them, acrylic acid and / or methacrylic acid can be preferably used as the carboxyl group-containing polymerizable unsaturated monomer.

  When the carboxyl group-containing polymerizable unsaturated monomer is contained as the other polymerizable unsaturated monomer (c-4), the proportion of the carboxyl group-containing polymerizable unsaturated monomer used in the aqueous medium of the crosslinked resin particles (C) From the viewpoint of excellent stability in the case, it is 1 to 30% by mass based on the total amount of the urea group-containing polymerizable unsaturated monomer (c-3) and the other polymerizable unsaturated monomer (c-4). Preferably, it is 3-25 mass%, More preferably, it is 5-20 mass%.

  Moreover, it is preferable that the said other polymerizable unsaturated monomer (c-4) contains the alkyl or cycloalkyl (meth) acrylate which has a C4-C22 alkyl group as at least one part.

  Examples of the alkyl or cycloalkyl (meth) acrylate having an alkyl group having 4 to 22 carbon atoms include n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) ) Acrylate, 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, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, isobornyl ( Data) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate. These monomers can be used alone or in combination of two or more.

  As the alkyl or cycloalkyl (meth) acrylate having an alkyl group having 4 to 22 carbon atoms, an alkyl (meth) acrylate having an alkyl group having 4 to 8 carbon atoms can be preferably used.

  When other polymerizable unsaturated monomer (c-4) contains an alkyl or cycloalkyl (meth) acrylate having an alkyl group having 4 to 22 carbon atoms, an alkyl or cyclohexane having an alkyl group having 4 to 22 carbon atoms The proportion of alkyl (meth) acrylate used is the total of the urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomers (c-4) from the viewpoint of coating workability such as sagging resistance. Based on the amount, it is preferably 1 to 80% by mass, more preferably 3 to 60% by mass, and still more preferably 5 to 50% by mass.

  Moreover, it is preferable that the said other polymerizable unsaturated monomer (c-4) contains the alkyl (meth) acrylate which has a C1-C3 alkyl group as at least one part.

  Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and iso-propyl (meth) acrylate. It is done. These monomers can be used alone or in combination of two or more.

  As the alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms, from the viewpoint of improving the stability of the obtained paint, among them, methyl methacrylate and / or ethyl methacrylate can be preferably used. Methyl methacrylate can be more preferably used.

  When the other polymerizable unsaturated monomer (c-4) contains an alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms, the alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms The use ratio is preferably 1 to 80% by mass based on the total amount of the urea group-containing polymerizable unsaturated monomer (c-3) and the other polymerizable unsaturated monomer (c-4). More preferably, it is 60 mass%, and it is still more preferable that it is 5-50 mass%.

  Furthermore, as another polymerizable unsaturated monomer (c-4) used as a monomer for the copolymer (II), a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule is used. ) Can be used. As the polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule, those exemplified for the copolymer (I) monomer can be similarly used. These monomers can be used alone or in combination of two or more.

  From the viewpoint of improving the smoothness of the coating film, the ratio of the copolymer (I) / copolymer (II) in the crosslinked resin particles (C) is 10/95 to 95/5 in terms of solid content mass ratio. Preferably, it is 50/50 to 90/10, more preferably 65/35 to 85/15.

  The crosslinked resin particles (C) preferably have a hydroxyl value of 1 to 50 mgKOH / g, more preferably 2 to 30 mgKOH / g, from the viewpoint of excellent chipping resistance of the resulting coating film. More preferably, it is 20 mgKOH / g.

  The crosslinked resin particles (C) preferably have an acid value of 2 to 50 mgKOH / g, more preferably 5 to 40 mgKOH / g, from the viewpoint of excellent smoothness of the coating film and stability of the paint. Preferably, it is 10-30 mgKOH / g.

  Crosslinked resin particles (C) are, for example, polymerizable having a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and one polymerizable unsaturated group in one molecule. In an emulsion containing the copolymer (I) obtained by emulsion polymerization of a monomer mixture containing an unsaturated monomer (c-2), a urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable properties It can be obtained by adding a monomer mixture containing an unsaturated monomer (c-4) and further preparing a copolymer (II) obtained by emulsion polymerization.

  The emulsion polymerization for preparing the emulsion of the copolymer (I) can be performed by a conventionally known method such as a seed polymerization method or a mini-emulsion polymerization method. For example, using a polymerization initiator in the presence of an emulsifier. This can be done by emulsion polymerization of the monomer mixture.

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 octyl Phenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan mono Teareto, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, and the like.
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, or the anionic group and polymerizable unsaturated in one molecule Reactive anionic emulsifiers having groups may be used.

  The amount of the emulsifier used is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1 to 5% by mass, based on the total amount of all monomers used.

  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-hydro 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 monomer mixture may contain a chain transfer agent for the purpose of adjusting the molecular weight of the resulting crosslinked resin particles (C). Examples of the chain transfer agent include compounds having a mercapto group. Specific examples include lauryl mercaptan, t-dodecyl mercaptan, octyl mercaptan, 2-ethylhexyl thioglycolate, 2-methyl-5-tert-butylthio. Examples include phenol, mercaptoethanol, thioglycerol, mercaptoacetic acid (thioglycolic acid), mercaptopropionate, n-octyl-3-mercaptopropionate, and the like. When the chain transfer agent is used, the amount used is generally 0.05 to 10% by weight, particularly 0.1 to 5% by weight, based on the total amount of all monomers used. It is.

  Furthermore, an organic solvent such as a long-chain saturated hydrocarbon solvent such as hexadecane or a long-chain alcohol solvent such as hexadecanol may be blended with the monomer mixture as necessary.

  Crosslinked resin particle (C) contains urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomer (c-4) in the emulsion of copolymer (I) obtained above. Can be obtained by adding the monomer mixture to be further polymerized to form the copolymer (II).

  The monomer mixture that forms the copolymer (II) can appropriately contain components such as the emulsifier, the polymerization initiator, the reducing agent, and the chain transfer agent, 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 method for polymerizing the monomer mixture forming the copolymer (II), for example, the monomer mixture or an emulsion thereof is added all at once or gradually, and added to the emulsion of the copolymer (I). A method of heating to an appropriate temperature while stirring can be mentioned.

  The crosslinked resin particles (C) thus obtained are usually one polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and one polymerizable unsaturated group in one molecule. A copolymer (I) of a monomer mixture composed of a polymerizable unsaturated monomer (c-2) having a core part, and a urea group-containing polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomers (c -4) has a multilayer structure in which the monomer mixture copolymer (II) is a shell part.

  Further, the crosslinked resin particles (C) may be formed of a polymerizable unsaturated monomer (one or more) that forms another resin layer between the step of obtaining the copolymer (I) and the step of obtaining the copolymer (II). It is good also as a crosslinked resin particle which consists of a 3 layer or more layer by adding the process of supplying an emulsion polymerization by supplying 2 or more types of mixtures.

  In the present invention, the “shell part” of the crosslinked resin particles (C) means a polymer layer present in the outermost layer of the resin particles, and the “core part” means a polymer layer of the resin particle inner layer excluding the shell part. The “core / shell type structure” means a structure having the core part and the shell part. The core / shell type structure is generally a layer structure in which the core part is completely covered with the shell part. However, depending on the mass ratio of the core part and the shell part, the monomer amount of the shell part may be a layer structure. May not be sufficient to form In such a case, it is not necessary to have a complete layer structure as described above, and a structure in which a part of the core part is covered with the shell part, or a component of the shell part in part of the core part. The polymerizable unsaturated monomer may be graft polymerized. Further, the concept of the multilayer structure in the core / shell structure is similarly applied to the case where the multilayer structure is formed in the core portion in the crosslinked resin particle (C) of the present invention.

  The crosslinked resin particles (C) can have an average particle diameter generally in the range of 10 to 500 nm, preferably 30 to 300 nm, particularly preferably 50 to 200 nm.

  In the present specification, the average particle diameter of the crosslinked resin particles (C) is a value measured at 20 ° C. after diluting with deionized water by a conventional method using a submicron particle size distribution measuring apparatus. As the submicron particle size distribution measuring device, for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.

  When the crosslinked resin particle (C) has an acidic group such as a carboxyl group, the acidic group is neutralized with a neutralizing agent in order to improve the mechanical stability of the particle of the crosslinked resin particle (C). It is desirable. The neutralizing agent is not particularly limited as long as it can neutralize acidic groups. 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 crosslinked resin particles (C) after neutralization becomes about 4.0 to 9.0.

Aqueous paint composition The aqueous paint composition of the present invention is a paint composition containing the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C).

  The mixing ratio of the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C) in the aqueous coating composition of the present invention is the sum of the aqueous film-forming resin (A) and the curing agent (B). It is preferable to be within the following range based on 100 parts by mass.

Aqueous film-forming resin (A): 60 to 95 parts by mass, preferably 65 to 90 parts by mass, more preferably 70 to 90 parts by mass,
Curing agent (B): 5 to 40 parts by mass, preferably 10 to 35 parts by mass, more preferably 10 to 30 parts by mass,
Crosslinked resin particles (C): 1 to 100 parts by mass, preferably 3 to 50 parts by mass, and more preferably 5 to 40 parts by mass.

  The reason why a coating film excellent in smoothness, sharpness, and water resistance can be formed by using the aqueous coating composition of the present invention is not clear, but the crosslinked resin particles (C) in the coating composition are core parts. By having a cross-linked structure, the shape of the resin particles is stably maintained in a relatively uniform state, so that smoothness is improved, and water to the multilayer coating film formed by the cross-linked structure is improved. It is presumed that water resistance is improved because permeation is suppressed.

  Furthermore, the cross-linked resin particles (C) have a urea group in the shell portion, so that a pseudo-crosslinked structure due to hydrogen bonding is denser than a urethane group, an amide group, etc., and a high viscosity increasing effect is exhibited in the coated film. Therefore, it is presumed that the layering between the two coating films when the water-based paint is applied onto the coating film is suppressed and the sharpness is improved.

  The aqueous coating composition of the present invention preferably further contains a pigment (D). Examples of the pigment (D) include a color pigment, an extender pigment, and a glitter pigment, and the pigment (D) can be used alone or in combination of two or more.

  When the aqueous coating composition of the present invention contains the pigment (D), the blending amount of the pigment (D) depends on the aqueous film-forming resin (A) and curing agent (B in the aqueous coating composition of the present invention. ) And the total of 100 parts by mass of the crosslinked resin particles (C), generally 1 to 200 parts by mass, preferably 20 to 150 parts by mass, and more preferably 50 to 120 parts by mass.

  Examples of the colored pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, and perylene pigment. Of these, titanium oxide and carbon black can be preferably used.

  When the water-based paint composition of the present invention contains the above-mentioned color pigment, the amount of the color pigment blended is the water-based film-forming resin (A), the curing agent (B), and the crosslinked resin in the water-based paint composition of the present invention Based on the total 100 parts by mass of the particles (C), it can be in the range of usually 1 to 120 parts by mass, preferably 3 to 100 parts by mass, and more preferably 5 to 90 parts by mass.

  Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. Among them, it is preferable to use barium sulfate and / or talc.

  In particular, the extender pigment may contain barium sulfate having an average primary particle diameter of 1 μm or less, more preferably barium sulfate having an average primary particle diameter in the range of 0.01 to 0.8 μm. An excellent multi-layer coating film having excellent appearance with high flip-flop properties and little metallic unevenness when using a paint containing a bright pigment as an aqueous base coat paint (aqueous second colored paint (Y)) Therefore, it is preferable.

  The average primary particle diameter of barium sulfate in the present invention is a value obtained by observing barium sulfate with a scanning electron microscope and averaging the maximum diameters of 20 barium sulfates on a straight line drawn randomly on an electron micrograph. It is.

  When the aqueous paint composition of the present invention contains the extender pigment, the amount of the extender pigment is such that the aqueous film-forming resin (A), the curing agent (B), and the cross-linked resin in the aqueous paint composition of the present invention. Based on the total 100 parts by mass of the particles (C), it can be in the range of usually 1 to 120 parts by mass, preferably 5 to 100 parts by mass, and more preferably 10 to 80 parts by mass.

  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, titanium oxide and iron oxide. Mention may be made of coated mica, glass flakes, hologram pigments and the like. These bright pigments can be used alone or in combination of two or more. The aluminum pigment includes non-leafing aluminum and leafing aluminum, and any of them can be used.

  When the aqueous coating composition of the present invention contains the above-mentioned glittering pigment, the blending amount of the glittering pigment is such that the aqueous film-forming resin (A), the curing agent (B) and the aqueous coating composition in the aqueous coating composition of the present invention are mixed. Based on the total of 100 parts by mass of the cross-linked resin particles (C), it is usually 1 to 50 parts by mass, preferably 2 to 30 parts by mass, and more preferably 3 to 20 parts by mass.

Oligomer (E)
The water-based coating composition of the present invention has a water tolerance of 10 or more, preferably 20 or more, more preferably 50 or more, and a number average molecular weight of 200 to 200, from the viewpoint of improving the smoothness of the coated surface of the multilayer coating film. It can further contain 1500, preferably 300 to 1000, more preferably 400 to 1000 oligomer compounds (excluding the acrylic resin (A)).

Specific examples include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, and etherified products thereof.
Among these, it is preferable to use a hydroxyl group-containing oligomer, particularly polyoxypropylene glyceryl ether.

  Examples of commercially available products include GP400, GP600, and GP1000 (manufactured by Sanyo Kasei Co., Ltd.).

  In the present invention, the water tolerance for the oligomer is a value obtained by the following measurement.

  The water tolerance of the oligomer was measured by the following method. Take 5.0 g of sample (oligomer) in a 200 ml beaker with a diameter of 5 cm and dilute with 50 ml of acetone. The sample solution is set to 20 ° C., a newspaper printed with No. 4 type is placed under the bottom of the beaker, and deionized water is dropped while stirring with a magnetic stirrer. At this time, water tolerance is defined as the maximum dripping amount (ml) of deionized water at the limit at which the No. 4 type of newspaper placed under the bottom of the beaker can be seen through from the top of the beaker. A larger water tolerance value means that the oligomer is more hydrophilic.

  When the aqueous coating composition of the present invention contains the oligomer (E), the blending amount thereof is 100 mass of the total solid content of the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C). The amount is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and still more preferably 5 to 15 parts by mass with respect to parts.

  The water-based coating composition of the present invention preferably further contains a hydrophobic solvent (F) from the viewpoint of improving workability such as sagging and armpits.

  The hydrophobic solvent (F) 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 glycol monophenyl ether, etc. Alcohol solvents; ester solvents such as n-butyl acetate, isobutyl acetate, isoamyl acetate, methyl amyl acetate, and ethylene glycol monobutyl ether Methyl isobutyl ketone, cyclohexanone, ethyl n- amyl ketone solvents such as diisobutyl ketone. These can be used individually by 1 type or in combination of 2 or more types.

  As the hydrophobic solvent (F), an alcohol-based hydrophobic solvent is preferably used. Among these, alcohol-based hydrophobic solvents having 7 to 14 carbon atoms are preferable, such as 1-octanol, 2-octanol, 2-ethyl-1-hexanol, ethylene glycol mono-2-ethylhexyl ether, propylene glycol mono n-butyl ether, dipropylene. More preferred is at least one alcohol-based hydrophobic solvent selected from the group consisting of glycol mono n-butyl ether.

  When the aqueous coating composition of the present invention contains a hydrophobic solvent (F), the blending amount thereof is the total solid content of the aqueous film-forming resin (A), the curing agent (B) and the crosslinked resin particles (C). The amount is preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, and still more preferably 8 to 30 parts by mass with respect to 100 parts by mass.

  In addition, the aqueous coating composition of the present invention further includes the following general formula (1) from the viewpoint of improving the smoothness and sharpness of the resulting coating film.

[Wherein, R ¹ and R ² independently represent a hydrocarbon group having 4 to 18 carbon atoms, R ³ represents an alkylene group having 2 to 4 carbon atoms, m represents an integer of 3 to 25, A plurality of R ³ may be the same or different. ]
The diester compound (G) represented by these can be contained.

As said hydrocarbon group, a C5-C11 alkyl group is preferable, a C5-C9 alkyl group is more preferable, and a C6-C8 alkyl group is further more preferable. In particular, when R ¹ and R ² are branched alkyl groups having 6 to 8 carbon atoms, smoothness excellent in the formed coating film even when the paint is applied after storage for a relatively long period of time. And sharpness can be imparted.

  The diester compound (G) can be obtained, for example, by esterifying a polyoxyalkylene glycol having two terminal hydroxyl groups and a monocarboxylic acid having a hydrocarbon group having 4 to 18 carbon atoms.

  Examples of the polyoxyalkylene glycol include polyethylene glycol, polypropylene glycol, a copolymer of polyethylene and propylene glycol, and polybutylene glycol. Among these, it is particularly preferable to use polyethylene glycol. These polyoxyalkylene glycols generally have a number average molecular weight of 100 to 1,200, preferably 150 to 600, and more preferably 200 to 400.

  Examples of the monocarboxylic acid having a hydrocarbon group having 4 to 18 carbon atoms include pentanoic acid, hexanoic acid, 2-ethylbutanoic acid, 3-methylpentanoic acid, benzoic acid, cyclohexanecarboxylic acid, heptanoic acid, 2 -Ethylpentanoic acid, 3-ethylpentanoic acid, octanoic acid, 2-ethylhexanoic acid, 4-ethylhexanoic acid, nonanoic acid, 2-ethylheptanoic acid, decanoic acid, 2-ethyloctanoic acid, 4-ethyloctanoic acid, Examples include dodecanoic acid, hexadecanoic acid, and octadecanoic acid. Among them, hexanoic acid, heptanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, octanoic acid, 2-ethylhexanoic acid, 4-ethylhexanoic acid, nonanoic acid, 2-ethylheptanoic acid, decanoic acid, 2- Monocarboxylic acids having an alkyl group having 5 to 9 carbon atoms such as ethyloctanoic acid and 4-ethyloctanoic acid are preferred, and heptanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, octanoic acid, 2-ethylhexanoic acid Monocarboxylic acids having an alkyl group having 6 to 8 carbon atoms such as 4-ethylhexanoic acid, nonanoic acid, 2-ethylheptanoic acid, etc. are more preferable, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-ethylhexane Monocarboxylic acids having a branched alkyl group having 6 to 8 carbon atoms such as acid, 4-ethylhexanoic acid and 2-ethylheptanoic acid are more preferred. There.

  The diesterification reaction between the polyoxyalkylene glycol and the monocarboxylic acid having a hydrocarbon group having 4 to 18 carbon atoms can be carried out by a method known per se. The polyoxyalkylene glycol and the monocarboxylic acid having a hydrocarbon group having 4 to 18 carbon atoms can be used alone or in combination of two or more. The molecular weight of the obtained diester compound (G) is 320 to 1,400, preferably 450 to 1,000, more preferably 500 to 800, and particularly preferably 500 to 700.

  When the aqueous coating composition of the present invention contains the diester compound (G), the blending amount thereof is the total solid content of the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C). It is preferable that it is 1-30 mass parts with respect to a mass part, It is more preferable that it is 3-20 mass parts, It is still more preferable that it is 5-15 mass parts.

  Moreover, the aqueous coating composition of the present invention comprises, if necessary, a thickener, a curing catalyst, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, an organic solvent other than the hydrophobic solvent (F), It can contain paint additives such as surface conditioners and anti-settling agents.

  Examples of the thickener include inorganic thickeners such as silicate, metal silicate, montmorillonite, colloidal alumina; copolymer of (meth) acrylic acid and (meth) acrylic ester, poly Polyacrylic acid thickeners such as sodium acrylate; one molecule has a hydrophilic part and a hydrophobic part. In an aqueous medium, the hydrophobic part is adsorbed on the surface of pigments and emulsion particles in the paint. Or an associative thickener that effectively exhibits a thickening action by associating the hydrophobic parts; a fibrin derivative-based thickener such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose; casein, sodium caseinate Protein thickeners such as ammonium caseinate; Alginic acid thickeners such as sodium alginate; Polyvinyl alcohol, Polyvinyl pyrrole Polyvinyl thickeners such as styrene, polyvinyl benzyl ether copolymer; polyether thickeners such as pluronic polyether, polyether dialkyl ester, polyether dialkyl ether, polyether epoxy modified product; vinyl methyl ether-anhydrous maleic Examples thereof include maleic anhydride copolymer thickeners such as partial esters of acid copolymers; and polyamide thickeners such as polyamide amine salts. These thickeners can be used alone or in combination of two or more.

  A commercial item can be used as said polyacrylic acid type | system | group thickener. Commercially available product names include, for example, “Primal ASE-60”, “Primal TT-615”, “Primal RM-5” manufactured by Rohm and Haas, “SN thickener 613”, “SN thickener 618” manufactured by San Nopco. ”,“ SN thickener 630 ”,“ SN thickener 634 ”,“ SN thickener 636 ”, and the like. A commercial product can be used as the associative thickener. As commercial names of commercial products, for example, “UH-420”, “UH-450”, “UH-462”, “UH-472”, “UH-540”, “UH-752”, “UH-752”, “ “UH-756VF”, “UH-814N”, “Primal RM-8W”, “Primal RM-825”, “Primal RM-2020NPR”, “Primal RM-12W”, “Primal RM-12W” manufactured by Rohm and Haas. "SN thickener 612", "SN thickener 621N", "SN thickener 625N", "SN thickener 627N", "SN thickener 660T" manufactured by San Nopco.

  As the above-mentioned thickener, it is preferable to use a polyacrylic acid-based thickener and / or an associative thickener, more preferably an associative thickener, having a hydrophobic group at the terminal, and a molecular chain It is more preferable to use a urethane associative thickener containing a urethane bond therein. A commercially available product can be used as the urethane associative thickener. As commercial names of commercial products, for example, “UH-420”, “UH-462”, “UH-472”, “UH-540”, “UH-752”, “UH-756VF” manufactured by ADEKA, “ UH-814N ”,“ SN thickener 612 ”,“ SN thickener 621N ”,“ SN thickener 625N ”,“ SN thickener 627N ”,“ SN thickener 660T ”, etc. manufactured by San Nopco.

  Moreover, when the aqueous coating composition of this invention contains the said thickener, the compounding quantity of this thickener is aqueous film forming resin (A), hardening | curing agent (B), and crosslinked resin particle (C). The total solid content is 100 to 10 parts by mass, preferably 0.01 to 10 parts by mass, more preferably 0.05 to 3 parts by mass, and still more preferably 0.1 to 2 parts by mass. preferable.

Preparation of aqueous coating composition The aqueous coating composition of the present invention comprises an aqueous film-forming resin (A), a curing agent (B), crosslinked resin particles (C), and, if necessary, a pigment (D), The oligomer (E), the hydrophobic solvent (F), the diester compound (G) and other additives for coating can be prepared by mixing and dispersing in an aqueous medium by a known method. As the aqueous medium, deionized water or a mixture of deionized water and a hydrophilic organic solvent can be used. Examples of the hydrophilic organic solvent include propylene glycol monomethyl ether.

  The solid content concentration of the aqueous coating composition of the present invention is usually preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and still more preferably 35 to 60% by mass.

Method for Forming Coating Film The aqueous coating composition of the present invention can form a coating film excellent in smoothness, sharpness, water resistance and chipping resistance by coating on various objects to be coated. Among them, it is possible to use the aqueous coating composition of the present invention as an aqueous coating for forming a lower layer coating in a multilayer coating forming method in which an aqueous coating is applied repeatedly. Smoothness, sharpness, water resistance and chipping resistance This is particularly preferable because a multilayer coating film having excellent properties can be formed. Furthermore, when using as a water-based paint for forming a lower layer coating film in a method for forming a multi-layer paint film in which a water-based paint is applied repeatedly, after applying the water-based paint composition of the present invention, the water-based paint is applied without preheating (preheating) or the like. Even if it is repeatedly applied, a multilayer coating film excellent in smoothness and sharpness can be formed, which is particularly preferable.

The article to be coated to which the aqueous coating composition of the present invention is applied is not particularly limited. Examples of the article to be coated include an outer plate portion of an automobile body such as a passenger car, a truck, a motorcycle, and a bus; an automobile component; an outer plate portion of a household electric product such as a mobile phone and an audio device. 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, metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel; polyethylene resin, polypropylene resin, acrylonitrile- Butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin and other plastic materials such as various FRPs; glass, cement, concrete and other inorganic materials; wood And fiber materials such as paper and cloth. Of these, metal materials and plastic materials are preferred.

  In addition, surface treatments such as phosphate treatment, chromate treatment, complex oxide treatment, etc. on metal surfaces such as automobile body skins, household electrical appliances, and metal base materials such as steel plates constituting these products May be given. Further, the article to be coated may be one in which an undercoat film and / or an intermediate coat film is formed on the metal surface. Among them, a vehicle body in which an undercoat film is formed with an electrodeposition paint is preferable, and a vehicle body in which an undercoat film is formed with a cationic electrodeposition paint is particularly preferable.

Coating method The coating method of the aqueous coating composition of the present invention is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, and the like. A film can be formed. Of these, methods such as air spray coating and rotary atomization coating are preferred. When applying, electrostatic application may be applied as necessary.

  The coating amount of the aqueous coating composition of the present invention is preferably an amount that is usually about 5 to 70 μm, preferably about 10 to 50 μm, more preferably about 20 to 40 μm as the cured film thickness.

  The wet coating film can be cured by applying the coating composition of the present invention to an object to be coated and then heating it. Heating can be performed by a known heating means. For example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be used. The heating temperature is preferably about 80 to 180 ° C, more preferably about 100 to 170 ° C, and still more preferably about 120 to 160 ° C. The heating time is not particularly limited, but is usually preferably about 10 to 60 minutes, more preferably about 20 to 40 minutes.

  After the application of the aqueous coating composition of the present invention, before performing the above heat curing, from the viewpoint of preventing the occurrence of coating film defects such as armpits, preheating, air blowing, etc. under heating conditions in which the coating film is not substantially cured. However, from the viewpoint of shortening the coating process, heat curing can also be performed without performing preheating, air blowing, or the like. The preheating temperature is preferably about 40 to 100 ° C, more preferably about 50 to 90 ° C, and still more preferably about 60 to 80 ° C. The preheating time is preferably about 30 seconds to 15 minutes, more preferably about 1 to 10 minutes, and further preferably about 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 about 25 to 80 degreeC on the coating surface of the to-be-coated article for about 30 seconds to 15 minutes.

  The aqueous coating composition of the present invention is used for forming an intermediate coating film when a multilayer coating film comprising an intermediate coating film and a top coating film is formed on an object such as an automobile body by a 2-coat 1-bake method. Can be preferably used. The coating film formation method in this case can be performed according to the following method I.

Method I
(1) A step of applying an aqueous coating composition of the present invention to an article to form an intermediate coating film;
(2) A step of applying a water-based top coat onto the uncured intermediate coating film to form a top coating film, and (3) Heat curing of the uncured intermediate coating film and the uncured top coating film at the same time. The coating-film formation method including the process to make.

  The object to be coated in the above method I is preferably an automobile body or the like on which an undercoat film is formed by a cationic electrodeposition paint. In the present specification, the uncured coating includes a touch-dried coating and a semi-cured coating.

  When the aqueous coating composition of the present invention is applied by the 2-coat 1-bake method of Method I, the coating film thickness is preferably about 5 to 60 μm, more preferably about 10 to 50 μm, more preferably 15 More preferably, it is about ˜40 μm. The coating thickness of the water-based top coating is preferably about 10 to 80 μm, more preferably about 15 to 60 μm, and still more preferably about 20 to 50 μm as the cured film thickness.

  In Method I, after the application of the aqueous paint composition of the present invention, from the viewpoint of preventing the occurrence of coating film defects such as armpits, preheating, air blowing, etc. are performed under heating conditions in which the coating film is not substantially cured. However, from the viewpoint of shortening the coating process, it is preferable to omit the steps such as preheating and air blowing. The preheating temperature is preferably about 40 to 100 ° C, more preferably about 50 to 90 ° C, and still more preferably about 60 to 80 ° C. The preheating time is preferably about 30 seconds to 15 minutes, more preferably about 1 to 10 minutes, and further preferably about 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 about 25 to 80 degreeC on the coating surface of the to-be-coated article for about 30 seconds to 15 minutes.

  In addition, after the application of the water-based top coating material, the preheating, air blowing, or the like can be performed under heating conditions in which the coating film is not substantially cured.

  The heat curing of both the uncured intermediate coating film and the uncured top coating film can be performed by the known heating means described above. The heating temperature is preferably about 80 to 180 ° C, more preferably about 100 to 170 ° C, and still more preferably about 120 to 160 ° C. The heating time is preferably about 10 to 60 minutes, and more preferably about 20 to 40 minutes. By this heating, both the intermediate coating film and the top coating film can be cured simultaneously.

  The water-based top coating used in the above method I is generally intended to give an excellent appearance to the object to be coated, and any known thermosetting water-based top coating for coating automobile bodies or the like. Can also be used. For example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, or an epoxy resin having a crosslinkable functional group such as a carboxyl group and a hydroxyl group, and a polyisocyanate compound, a melamine resin, and a urea resin that may be blocked It is possible to use a resin component made of a curing agent such as a resin component dissolved or dispersed in water together with a pigment and other additives. Especially, the thermosetting water-based paint which uses the said hydroxyl-containing acrylic resin (A1) and / or a hydroxyl-containing polyester resin (A2) as base resin, and uses a melamine resin as a hardening | curing agent can be used suitably.

Moreover, as said pigment, the said color pigment, extender pigment, luster pigment, etc. can be used. Especially, it is preferable that a water-based top coat contains a color pigment as at least 1 sort (s) of the said pigment.
Examples of the color pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline exemplified in the description of the aqueous coating composition of the present invention. Examples thereof include pigments, selenium pigments, and perylene pigments.

  When the water-based top coating contains the above-mentioned color pigment, the amount of the color pigment is usually 1 to 120 parts by weight, preferably 3 to 100 parts by weight, based on 100 parts by weight of the resin solid content in the water-based top coating. More preferably, it is in the range of 5 to 90 parts by mass.

  In addition, the water-based top coating is a normal paint such as a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent, if necessary. The additive for use can be contained alone or in combination of two or more.

  The aqueous coating composition of the present invention is used when a multilayer coating film comprising an intermediate coating film, a base coating film and a clear coating film is formed on an object such as an automobile body by a 3-coat 1-bake method. It can be suitably used for forming an intermediate coating film. The coating film formation method in this case can be performed according to the following method II.

Method II
(1) A step of applying an aqueous coating composition of the present invention to an article to form an intermediate coating film;
(2) forming a base coat film by applying an aqueous base coat paint on the uncured intermediate coat film;
(3) a step of applying a clear coat paint on the uncured base coat film to form a clear coat film; and (4) the uncured intermediate coat film, the uncured base coat film and the uncured film. A method for forming a multilayer coating film comprising a step of simultaneously heating and curing a clearcoat coating film.

  As the article to be coated in the above method II, an automobile body or the like in which an undercoat film is formed by a cationic electrodeposition paint is preferable.

  In Method II, the coating film thickness of the aqueous coating composition of the present invention is usually preferably about 5 to 60 μm, more preferably about 10 to 50 μm, and still more preferably about 15 to 40 μm as a cured film thickness. The coating thickness of the aqueous base coat paint is preferably about 5 to 30 μm, more preferably about 8 to 25 μm, and still more preferably about 10 to 20 μm as the cured film thickness. In addition, the coating thickness of the clear coat paint is usually preferably about 10 to 80 μm, more preferably about 15 to 60 μm, and still more preferably about 20 to 50 μm as a cured film thickness.

  In Method II, after the application of the aqueous coating composition of the present invention, from the viewpoint of preventing the occurrence of coating film defects such as armpits, preheating, air blowing, etc. are performed under heating conditions in which the coating film is not substantially cured. However, from the viewpoint of shortening the coating process, it is preferable to omit the steps such as preheating and air blowing. The preheating temperature is preferably about 40 to 100 ° C, more preferably about 50 to 90 ° C, and still more preferably about 60 to 80 ° C. The preheating time is preferably about 30 seconds to 15 minutes, more preferably about 1 to 10 minutes, and further preferably about 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 about 25 to 80 degreeC on the coating surface of the to-be-coated article for about 30 seconds to 15 minutes.

  In addition, the preheating, air blowing, and the like can be performed even after application of the aqueous base coat paint.

  Further, even after the clear coat paint is applied, if necessary, an interval of about 1 to 60 minutes can be provided at room temperature, or preheating can be performed at about 40 to 80 ° C. for about 1 to 60 minutes.

  Heat curing of the three-layer coating film including the uncured intermediate coating film, the uncured base coat film, and the uncured clear coat film can be performed by the known heating means described above. The heating temperature is preferably about 80 to 180 ° C, more preferably about 100 to 170 ° C, and still more preferably about 120 to 160 ° C. The heating time is preferably about 10 to 60 minutes, and more preferably about 20 to 40 minutes. By this heating, the three-layer coating film of the intermediate coating film, the base coating film and the clear coating film can be simultaneously cured.

  As the water-based base coat paint used in the above-mentioned method II, any known thermosetting water-based base coat paint for painting automobile bodies can be used. For example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, or an epoxy resin having a crosslinkable functional group such as a carboxyl group and a hydroxyl group, and a polyisocyanate compound, a melamine resin, and a urea resin that may be blocked It is possible to use a resin component made of a curing agent such as a resin component dissolved or dispersed in water together with a pigment and other additives. Especially, the thermosetting water-based paint which uses the said hydroxyl-containing acrylic resin (A1) and / or a hydroxyl-containing polyester resin (A2) as base resin, and uses a melamine resin as a hardening | curing agent can be used suitably.

Moreover, as said pigment, the said color pigment, extender pigment, luster pigment, etc. can be used. Among these, it is preferable that the aqueous base coat paint contains a glitter pigment as at least one of the above pigments.
Examples of the bright pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, titanium oxide, and iron oxide exemplified in the description of the aqueous coating composition of the present invention. And mica coated with aluminum oxide, titanium oxide and iron oxide, glass flakes, hologram pigments and the like. 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 above luster pigments can be used alone or in combination of two or more.

  The glitter pigment is preferably flake shaped. Further, as the glitter pigment, those having a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.0001 to 5 μm, particularly 0.001 to 2 μm are suitable.

  When the aqueous base coat paint contains the above-mentioned glitter pigment, the blending amount of the glitter pigment is usually 1 to 50 parts by mass, preferably 2 to 30 parts, based on 100 parts by mass of the resin solid content in the aqueous base coat paint. It is suitable that it is in the range of 3 parts by mass, more preferably 3-20 parts by mass.

  The aqueous base coat paint preferably contains the hydrophobic solvent (F).

  As the hydrophobic solvent (F), an alcohol-based hydrophobic solvent is preferably used from the viewpoint of excellent glitter of the resulting coating film. Among them, alcohol-based hydrophobic solvents having 7 to 14 carbon atoms such as 1-octanol, 2-octanol, 2-ethyl-1-hexanol, ethylene glycol mono-2-ethylhexyl ether, propylene glycol mono n-butyl ether, dipropylene More preferred is at least one alcohol-based hydrophobic solvent selected from the group consisting of glycol mono n-butyl ether.

  When the aqueous base coat paint contains a hydrophobic solvent (F), the blending amount thereof is 2 to 2 based on 100 parts by mass of the resin solid content in the aqueous base coat paint from the viewpoint of excellent glossiness of the obtained coating film. It is suitable that it is in the range of 70 parts by mass, preferably 11 to 60 parts by mass, more preferably 16 to 50 parts by mass.

  In addition, the water-based base coat paint is a normal paint such as a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent, if necessary. The additive for use can be contained alone or in combination of two or more.

  As the clear coat paint used in the method II, any of known thermosetting clear coat paints for painting automobile bodies can be used. Examples thereof include an organic solvent-type thermosetting coating composition, a water-based thermosetting coating composition, and a powder thermosetting coating composition containing a base resin having a crosslinkable functional group and a crosslinking agent.

  Examples of the crosslinkable functional group possessed by the base resin include a carboxyl group, a hydroxyl group, an epoxy group, and a silanol 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 a combination of the base resin / crosslinking agent of the clear coat paint, a carboxyl group-containing resin / epoxy group-containing resin, a hydroxyl group-containing resin / polyisocyanate compound, a hydroxyl group-containing resin / blocked polyisocyanate compound, a hydroxyl group-containing resin / melamine resin, etc. preferable.

  The clear coat paint composition may be a one-component paint or a multi-component paint such as a two-component urethane resin paint.

  In addition, the clear coat paint can contain a color pigment, a bright pigment, a dye, etc. as long as it does not impair the transparency, if necessary, and an extender pigment, an ultraviolet absorber, a light stabilizer, an extinguisher. A foaming agent, a thickener, a rust inhibitor, a surface conditioner, and the like can be appropriately contained.

  In the above methods I and II, the water-based top coating material, the water-based base coating material, and the clear coating material can be applied by a known method such as air spray coating, airless spray coating, or rotary atomization coating.

  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.

Production of hydroxyl-containing acrylic resin (A1)
Production Example 1
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device was charged with 30 parts of propylene glycol monopropyl ether, heated to 85 ° C., 10 parts of styrene, 30 parts of methyl methacrylate, 15 parts of 2-ethylhexyl acrylate, 11.5 parts of n-butyl acrylate, 30 parts of hydroxyethyl acrylate, 3.5 parts of acrylic acid, 10 parts of propylene glycol monopropyl ether and 2,2′-azobis (2,4-dimethylvalero Nitrile) 2 parts of the mixture was added dropwise over 4 hours, and aged for 1 hour after completion of the addition. Thereafter, a mixture of 5 parts of propylene glycol monopropyl ether and 1 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was added dropwise to the flask over 1 hour, followed by aging for 1 hour after completion of the addition. Further, 3.03 parts of 2- (dimethylamino) ethanol was added, and deionized water was gradually added to obtain a hydroxyl group-containing acrylic resin (A1-1) solution having a solid content concentration of 40%. The resulting hydroxyl group-containing acrylic resin had an acid value of 27 mgKOH / g, a hydroxyl value of 145 mgKOH / g, and a weight average molecular weight of about 60,000.

Production Example 2
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device was charged with 130 parts of deionized water and 0.52 part of “AQUALON KH-10”, and stirred and mixed in a nitrogen stream. The temperature was raised to 80 ° C. Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion (1) was dripped in the reaction container hold | maintained at the same temperature over 3 hours, and it age | cure | ripened for 1 hour after completion | finish of dripping. Thereafter, the following monomer emulsion (2) was added dropwise over 1 hour, and after aging for 1 hour, the mixture was cooled to 30 ° C. while gradually adding 40 parts of 5% dimethylethanolamine aqueous solution to the reaction vessel, and 100 mesh nylon It was discharged while being filtered with a cloth, and the average particle size was 100 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter), diluted with deionized water and measured at 20 ° C.), solid. A hydroxyl group-containing acrylic resin (A1-2) dispersion having a partial concentration of 30% was obtained. The obtained acrylic resin had an acid value of 33 mgKOH / g and a hydroxyl value of 25 mgKOH / g.

  Monomer emulsion (1): 42 parts of deionized water, 0.72 part of “AQUALON KH-10”, 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 parts of ethyl acrylate and 21 parts of n-butyl acrylate was mixed and stirred to obtain a monomer emulsion (1).

  Monomer emulsion (2): 18 parts of deionized water, 0.31 part of "Aqualon KH-10", 0.03 part of ammonium persulfate, 5.1 parts of methacrylic acid, 5.1 parts of 2-hydroxyethyl acrylate, styrene 3 Part, 6 parts of methyl methacrylate, 1.8 parts of ethyl acrylate and 9 parts of n-butyl acrylate were mixed and stirred to obtain a monomer emulsion (2).

Production and production example 3 of hydroxyl group-containing polyester resin (A2)
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 142 parts of isophthalic acid, 313 parts of adipic acid, 59 parts of methylpentanediol, 220 parts of trimethylolpropane and 228 parts of butylethylpropanediol Was heated from 160 ° C. to 230 ° C. over 3 hours, and then the condensed water thus formed was kept at 230 ° C. while being distilled off with a water separator, and reacted until the acid value was 3 mgKOH / g or less. It was. To this reaction product, 38 parts of trimellitic anhydride was added, and after 30 minutes of addition reaction at 170 ° C., the reaction product was cooled to 50 ° C. or less, and 2- (dimethylamino) ethanol was added in an equivalent amount to the acid group. After neutralization, deionized water was gradually added to obtain a hydroxyl group-containing polyester resin (A2-1) solution having a solid concentration of 45% and a pH of 6.3. The resulting hydroxyl group-containing polyester resin had an acid value of 35 mgKOH / g, a hydroxyl value of 164 mgKOH / g, and a number average molecular weight of 1600.

Production Example 4
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, 126 parts of hexahydrophthalic anhydride and 120 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. Subsequently, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added and reacted at 170 ° C. for 30 minutes, and then 2-ethyl-1-hexanol (20 ° C. Is diluted with 100 g of water (0.1 g), cooled to 50 ° C. or less, and 2- (dimethylamino) ethanol is added in an equivalent amount with respect to the acid groups to neutralize the solid content to 70. % Hydroxyl group-containing polyester resin (A2-2) solution was obtained. The obtained polyester resin had an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, a solid content concentration of 70%, and a weight average molecular weight of 6,400.

Production of crosslinked resin particles (C) Synthesis of urea group-containing polymerizable unsaturated monomer (c-3) Production Example 5
A four-necked flask equipped with a stirrer, thermometer, drying tube and dropping funnel was charged with 40 parts of tetrahydrofuran and 52.9 parts of 2-methacryloyloxyethyl isocyanate, and the temperature was lowered to 15 ° C. Subsequently, 37 parts of a 37.8% methanol solution of ethylamine was added dropwise over 1 hour while maintaining the temperature at 20 ° C. or lower while stirring, and the mixture was further maintained at room temperature for 2 hours with stirring. Thereafter, the temperature was raised to 60 ° C. and the solvent was removed under reduced pressure to obtain an ethylurea group-containing polymerizable unsaturated monomer (c-3-1) (active ingredient 100%).

Production Example 6
In Production Example 5, 52.9 parts of 2-methacryloyloxyethyl isocyanate is 51.2 parts, 37 parts of a 37.8% methanol solution of ethylamine is 24.1 parts of butylamine, and the temperature at the time of dropping is maintained at 35 ° C. Except for this, synthesis was carried out in the same manner as in Production Example 5 to obtain a butylurea group-containing polymerizable unsaturated monomer (c-3-2) (active ingredient 100%).

Production Example 7
In Production Example 5, 52.9 parts of 2-methacryloyloxyethyl isocyanate was 51.2 parts, 37 parts of a 37.8% methanol solution of ethylamine was 19.5 parts of isopropylamine, and the temperature at the time of dropping was maintained at 35 ° C. Except that, the synthesis was carried out in the same manner as in Production Example 5 to obtain an isopropylurea group-containing polymerizable unsaturated monomer (c-3-3) (active ingredient 100%).

Production Example 8
A four-necked flask equipped with a stirrer, thermometer, drying tube, air introduction tube and dropping funnel was charged with 42.9 parts of 2-hydroxyethyl methacrylate and 0.039 parts of p-methoxyphenol, and 20 ml of dry air per minute. Then, the temperature was raised to 60 ° C., 66.6 parts of isophorone diisocyanate was added, stirred for 2 hours, further heated to 80 ° C. and reacted for 1 hour. Thereafter, the temperature was lowered to 10 ° C., 50 parts of tetrahydrofuran was added, and 19.7 parts of butylamine was added dropwise over 1 hour while maintaining the temperature not exceeding 20 ° C. Thereafter, the temperature was raised to 60 ° C. and the solvent was removed under reduced pressure to obtain a butylurea group-containing polymerizable unsaturated monomer (c-3-4) (active ingredient 100%).

Production of crosslinked resin particles (C) Production Example 9
A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen introducing tube and a dropping device, 130 parts of deionized water, “Aqualon KH-10” (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyoxy 0.52 part of ethylene alkyl ether sulfate ester ammonium salt (active ingredient 97%) was charged, mixed with stirring in a nitrogen stream, and heated to 80 ° C.

  Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes.

  Then, the remaining monomer emulsion (1) was dripped in the reaction container hold | maintained at the same temperature over 3 hours, and it age | cure | ripened for 1 hour after completion | finish of dripping.

  Thereafter, the following monomer emulsion (2) was added dropwise over 1 hour, and after aging for 1 hour, the mixture was cooled to 30 ° C. while gradually adding 40 parts of a 5% 2- (dimethylamino) ethanol aqueous solution to the reaction vessel, Cross-linked resin particles having an average particle size of 138 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter), diluted with deionized water and measured at 20 ° C.), solid content concentration of 30% (C-1) A dispersion was obtained. The obtained crosslinked resin particles had a hydroxyl value of 9.4 mgKOH / g and an acid value of 14.3 mgKOH / g.

Monomer emulsion (1): 46.2 parts of deionized water, 0.79 part of “AQUALON KH-10”, 10.0 parts of n-butyl acrylate, 52.4 parts of methyl methacrylate, 11.6 parts of ethyl acrylate and ethylene A monomer emulsion (1) was obtained by mixing and stirring 3.08 parts of glycol dimethacrylate. (Total 77 parts of core monomer)
Monomer emulsion (2): 13.8 parts of deionized water, 0.24 part of “AQUALON KH-10”, 0.03 part of ammonium persulfate, ethylurea group-containing polymerizable unsaturated monomer (c-3-1) 9 parts, 2.99 parts of styrene, 4.37 parts of n-butyl acrylate, 4.37 parts of methyl methacrylate, 2.19 parts of 2-hydroxyethyl methacrylate and 2.19 parts of methacrylic acid are mixed and stirred to obtain a monomer emulsion. (2) was obtained. (Shell monomer total 23 parts)
Production Examples 10 to 34
Dispersions of crosslinked resin particles (C-2) to (C-26) in the same manner as in Production Example 9 except that the composition of the monomer emulsions (1) and (2) is changed as shown in Table 1 below. Got. Table 1 below shows the solid content concentration, acid value, hydroxyl value, and average particle size of the dispersions of the obtained crosslinked resin particles (C-2) to (C-26) together with Production Example 9.

Production Example 1 of water-based coating composition
25 parts of a hydroxyl group-containing acrylic resin (A1-1) solution obtained in Production Example 1 (resin solid content: 10 parts), “JR-806” (trade name, manufactured by Teica, rutile titanium dioxide), “Carbon MA” -100 "(trade name, manufactured by Mitsubishi Chemical Corporation, carbon black), 1 part," Variace B-35 "(trade name, manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder, average primary particle size 0.5 µm)," MICRO ACE S-3 "(trade name, manufactured by Nippon Talc Co., Ltd., talc powder, average primary particle size 4.8 μm) 3 parts and 46 parts of deionized water were mixed and adjusted to pH 8.0 with 2- (dimethylamino) ethanol. After adjustment, the mixture was dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste.

Next, 150 parts of the obtained pigment dispersion paste (10 parts of resin solid content), 83.3 parts of the hydroxyl group-containing acrylic resin (A1-2) dispersion obtained in Production Example 2 (25 parts of resin solid content), Production Example 33.3 parts of the hydroxyl group-containing polyester resin (A2-1) solution obtained in 3 (resin solid content 15 parts), 66.7 parts of the crosslinked resin particle (C-1) dispersion obtained in Production Example 9 (resin solid content) 20 parts), melamine resin (B-1) (methyl-butyl mixed etherified melamine resin, solid content 80%, weight average molecular weight 800) 37.5 parts (resin solid content 30 parts), and 2-ethyl-1- Ten parts of hexanol (mass dissolved in 100 g of water at 20 ° C .: 0.1 g) were mixed uniformly.
Next, “UH-752” (trade name, manufactured by ADEKA, urethane associative thickener), 2- (dimethylamino) ethanol and deionized water were added to the obtained mixture, pH 8.0, solid content Ford Cup No. 48 at a concentration of 48% and 20 ° C. A water-based coating composition (X-1) having a viscosity of 30 according to 4 was obtained.

Examples 2-33, Comparative Examples 1-6
In Example 1, the Ford Cup No. at pH 8.0 and 20 ° C. was used in the same manner as in Example 1 except that the formulation was as shown in Table 2 below. Aqueous coating compositions (X-2) to (X-33) and (X-36) to (X-41) having a viscosity of 30 according to 4 were obtained.

Example 34
25 parts of the hydroxyl group-containing acrylic resin (A1-1) solution obtained in Production Example 1 (10 parts of resin solid content), 60 parts of “JR-806”, 1 part of “Carbon MA-100”, “Variace B-35” 15 Part, 3 parts of “MICRO ACE S-3” and 46 parts of deionized water, adjusted to pH 8.0 with 2- (dimethylamino) ethanol, and then dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste It was.

  Next, 150 parts of the obtained pigment dispersion paste (10 parts of resin solid content), 83.3 parts of the hydroxyl group-containing acrylic resin (A1-2) dispersion obtained in Production Example 2 (25 parts of resin solid content), Production Example 33.3 parts of the hydroxyl group-containing polyester resin (A2-1) solution obtained in 3 (resin solid content 15 parts), 66.7 parts of the crosslinked resin particle (C-1) dispersion obtained in Production Example 9 (resin solid content) 20 parts), 37.5 parts of melamine resin (B-1) (30 parts of resin solids), and 10 parts of 2-ethyl-1-hexanol were uniformly mixed.

  Next, “Primal ASE-60” (trade name, manufactured by Rohm and Haas, polyacrylic acid-based thickener), 2- (dimethylamino) ethanol, and deionized water were added to the obtained mixture, and the pH was adjusted to 8. Ford Cup No. 0 and 20 ° C. An aqueous coating composition (X-34) having a viscosity of 30 according to 4 was obtained.

Example 35
25 parts of the hydroxyl group-containing acrylic resin (A1-1) solution obtained in Production Example 1 (10 parts of resin solid content), 60 parts of “JR-806”, 1 part of “Carbon MA-100”, “Variace B-35” 15 Part, 3 parts of “MICRO ACE S-3” and 46 parts of deionized water, adjusted to pH 8.0 with 2- (dimethylamino) ethanol, and then dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste It was.

  Next, 150 parts of the obtained pigment dispersion paste (10 parts of resin solid content), 83.3 parts of the hydroxyl group-containing acrylic resin (A1-2) dispersion obtained in Production Example 2 (25 parts of resin solid content), Production Example 33.3 parts of the hydroxyl group-containing polyester resin (A2-1) solution obtained in 3 (resin solid content 15 parts), 66.7 parts of the crosslinked resin particle (C-1) dispersion obtained in Production Example 9 (resin solid content) 20 parts), 37.5 parts of melamine resin (B-1) (30 parts of resin solids), and 10 parts of 2-ethyl-1-hexanol were uniformly mixed.

  Then, 2- (dimethylamino) ethanol and deionized water were added to the resulting mixture, and the Ford Cup No. 6 at pH 8.0 and 20 ° C was added. A water-based coating composition (X-35) having a viscosity of 30 according to 4 was obtained.

(Note 1) SPARWITE W-5HB: trade name, manufactured by Wilber Ellis, barium sulfate powder, average primary particle size 1.6 μm
(Note 2) U-coat UX-8100: trade name, manufactured by Sanyo Chemical Industries, urethane emulsion, solid content 35%
(Note 3) Melamine resin (B-2): imino group-containing methyl etherified melamine resin, solid content 80%, weight average molecular weight 800
(Note 4) Bihijoule VPLS2310: trade name, manufactured by Sumika Bayer Urethane Co., Ltd., blocked polyisocyanate compound, solid content 38%
(Note 5) Ethylene glycol mono n-butyl ether: Infinitely soluble in 100 g of water at 20 ° C. (Note 6) GP600: trade name, manufactured by Sanyo Chemical Industries, polyoxypropylene glycerin ether (molecular weight 600), water tolerance 100 or more (Note 7) Diester compound (F-1): Diester compound of polyoxyethylene glycol and 2-ethylhexanoic acid. In the general formula (1), R ¹ and R ² are 2-ethylheptyl groups, R ³ is an ethylene group, and m is 7. Molecular weight 578.

Production and Production Example 35 of Polyester Resin for Aqueous Topcoat and Aqueous Basecoat Paint
Hydroxyl-containing polyester in the same manner as in Production Example 4, except that 2-ethyl-1-hexanol as a diluent solvent is changed to ethylene glycol mono-n-butyl ether (mass dissolved in 100 g of water at 20 ° C .: infinite). A resin (A2-3) solution was obtained.

Production Example of Pigment Dispersion Paste for Water-Based Top Coating Production Example 36
25 parts of the hydroxyl group-containing acrylic resin (A1-1) solution obtained in Production Example 1 (resin solid content 10 parts), 60 parts of JR-806 and 35 parts of deionized water were mixed, and the pH was adjusted to 8 with 2- (dimethylamino) ethanol. After adjusting to 0.0, the mixture was dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste.

Production Example of Bright Pigment Dispersion for Aqueous Basecoat Paint Production Example 37
In a stirring and mixing container, 19 parts of an aluminum pigment paste “GX-180A” (made by Asahi Kasei Metals Co., Ltd., metal content 74%), 35 parts of 2-ethyl-1-hexanol, a phosphate group-containing resin solution (Note 8) 8 And 0.2 part of 2- (dimethylamino) ethanol were uniformly mixed to obtain a bright pigment dispersion (P1).

  (Note 8) Phosphate group-containing resin solution: Mixing 27.5 parts of methoxypropanol and 27.5 parts of isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device Add solvent, heat to 110 ° C., 25 parts styrene, 27.5 parts n-butyl methacrylate, 20 parts “isostearyl acrylate” (trade name, branched organic alkyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.), 4-hydroxy 7.5 parts of butyl acrylate, 15 parts of phosphoric acid group-containing polymerizable monomer (Note 9), 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol, 4 parts of t-butyl peroxyoctanoate 121.5 parts of the mixture is added to the above mixed solvent over 4 hours, and t-butyl peroxyoctanoate 0 The consisting of 5 parts of isopropanol 20 parts mixture was added dropwise for 1 hour. Thereafter, the mixture was aged and stirred for 1 hour to obtain a phosphate group-containing resin solution having a solid 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 9) Phosphoric acid group-containing polymerizable monomer: put 57.5 parts monobutyl phosphoric acid and 41 parts isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device, After raising the temperature 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 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.

Production Example 38
A bright pigment dispersion (P2) was obtained in the same manner as in Production Example 37 except that 35 parts of 2-ethyl-1-hexanol was changed to 35 parts of ethylene glycol mono n-butyl ether.

Production and production example 39 of water-based top coating
Hydroxyl-containing acrylic resin (A1-2) dispersion 100 parts obtained in Production Example 2 (resin solid content 30 parts), hydroxyl-containing polyester resin (A2-2) solution 42.9 parts obtained in Production Example 4 (resin solids) 30 parts), 120 parts of pigment dispersion paste obtained in Production Example 36 (10 parts of resin solids), 35 parts of 2-ethyl-1-hexanol and “Cymel 325” (trade name, manufactured by Nippon Cytec Industries, Inc., melamine resin) , 80% solid content) 37.5 parts (solid resin content 30 parts) was uniformly mixed, and further, “Primal ASE-60”, 2- (dimethylamino) ethanol and deionized water were added to adjust the pH to 8.0. Ford cup no. An aqueous top coat (Y-1) having a viscosity of 30 according to 4 was obtained.

Production and production example 40 of water-based base coat paint
Hydroxyl-containing acrylic resin (A1-2) dispersion 100 parts obtained in Production Example 2 (resin solid content 30 parts), hydroxyl-containing polyester resin (A2-2) solution 57.1 parts obtained in Production Example 4 (resin solids) 40 parts), 62.2 parts of the glitter pigment dispersion (P1) obtained in Production Example 37 (4 parts of resin solids) and 37.5 parts of “Cymel 325” (30 parts of resin solids) were uniformly mixed. In addition, “Primal ASE-60”, 2- (dimethylamino) ethanol and deionized water were added to adjust the pH of 8.0, solid content concentration 25%, Ford Cup No. 20 at 20 ° C. An aqueous base coat paint (Y-2) having a viscosity of 40 seconds according to 4 was obtained.

Production Example 41
Hydroxyl-containing acrylic resin (A1-2) dispersion 100 parts obtained in Production Example 2 (resin solid content 30 parts), hydroxyl-containing polyester resin (A2-3) solution 57.1 parts obtained in Production Example 35 (resin solids) 40 parts), 62.2 parts of the glitter pigment dispersion (P2) obtained in Production Example 38 (4 parts of resin solids) and 37.5 parts of “Cymel 325” (30 parts of resin solids) were uniformly mixed. In addition, “Primal ASE-60”, 2- (dimethylamino) ethanol and deionized water were added to adjust the pH of 8.0, solid content concentration 25%, Ford Cup No. 20 at 20 ° C. An aqueous base coat paint (Y-3) having a viscosity of 40 seconds according to 4 was obtained.

Coating Film Formation Methods Aqueous Coating Compositions (X-1) to (X-41) Obtained in Examples 1 to 35 and Comparative Examples 1 to 6, Aqueous Top Coating Paint (Y-1) Obtained in Production Example 39 and Production Using the water-based base coat paints (Y-2) to (Y-3) obtained in Examples 40 to 41, test plates were produced as follows and subjected to an evaluation test.

(Preparation of test article)
"Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) is electrodeposited onto a cold-rolled steel sheet that has been subjected to zinc phosphate chemical conversion treatment to a dry film thickness of 20 μm, at 170 ° C. It was cured by heating for 30 minutes to obtain a test article.

Example 36
The aqueous coating composition (X-1) obtained in Example 1 was electrostatically applied to the test object to be cured to a cured film thickness of 20 μm using a rotary atomizing electrostatic coating machine. An intermediate coating film was formed. After standing for 3 minutes, the water-based top coating (Y-1) obtained in Production Example 39 is applied to the uncured intermediate coating film using a rotary atomizing electrostatic coating machine so that the cured film thickness becomes 35 μm. A top coat film was formed by electrostatic coating. After leaving for 3 minutes, preheating was performed at 80 ° C. for 3 minutes, followed by heating at 140 ° C. for 30 minutes to simultaneously cure the intermediate coating film and the top coating film to prepare a test coated plate.

Examples 37-70, Comparative Examples 7-12
In Example 36, except that the aqueous coating composition (X-1) obtained in Example 1 is any one of the aqueous coating compositions (X-2) to (X-41) shown in Table 3 below. A test plate was produced in the same manner as in Example 36.

Example 71
The aqueous coating composition (X-1) obtained in Example 1 was electrostatically applied to the test object so as to have a cured film thickness of 20 μm using a rotary atomizing electrostatic coating machine. An intermediate coating film was formed. After standing for 3 minutes, the aqueous base coat paint (Y-2) obtained in Production Example 40 is applied on the uncured intermediate coating film to a cured film thickness of 15 μm using a rotary atomizing electrostatic coater. A base coat film was formed by electrostatic coating. After standing for 3 minutes and preheating at 80 ° C. for 3 minutes, “Magiclon KINO-1210” (trade name, manufactured by Kansai Paint Co., Ltd., acrylic resin-based solvent-based clear coating, An acid epoxy curable type (hereinafter sometimes referred to as “clear paint (Z-1)”) was electrostatically applied to a cured film thickness of 35 μm to form a clear coat film. After leaving it for 7 minutes, it was heated at 140 ° C. for 30 minutes to simultaneously cure the intermediate coating film, base coat film and clear coat film, and a test coating plate was prepared.

Examples 72-106, Comparative Examples 13-18
In Example 71, the water-based coating composition (X-1) obtained in Example 1 was changed to any one of the water-based coating compositions (X-2) to (X-41) shown in Table 4 below. A test coated plate was produced in the same manner as in Example 71 except that the aqueous base coat paint (Y-2) obtained in Example 40 was changed to the aqueous base coat paint (Y-2) or (Y-3) shown in Table 4. .

Evaluation Test Each of the test coated plates obtained in Examples 36 to 106 and Comparative Examples 7 to 18 was evaluated by the following test method. The evaluation results are shown in Tables 3 and 4 below.

(Test method)
Smoothness: Evaluated using a Wc value measured by “Wave Scan DOI” (trade name, manufactured by BYK Gardner). The Wc value is an index of the amplitude of the surface roughness having a wavelength of about 1 to 3 mm, and the smaller the measured value, the higher the smoothness of the coated surface.

  Vividness: Evaluated using a Wa value measured by “Wave Scan DOI” (trade name, manufactured by BYK Gardner). The Wa value is an index of the amplitude of the surface roughness having a wavelength of about 0.1 to 0.3 mm, and the smaller the measured value, the higher the clearness of the coated surface.

Water resistance (adhesion): The test plate is immersed in warm water of 40 ° C. for 240 hours, pulled up, dried at 20 ° C. for 12 hours, and then the multilayer coating film of the test plate is cut into a lattice shape with a cutter so as to reach the substrate. Make 100 goby eyes 2mm x 2mm in size. 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.
◎: 100 galvanic coatings remain, and no small chipping of the coating occurs at the edge of the cutter cut ◯: 100 galvanic coatings remain, but the coating is small at the cutting edge of the cutter △: 90 to 99 pieces of the Gobang eye coat remain ×: The number of remaining Goban eye coats is 89 or less.
Chipping resistance: A test plate was placed on a specimen holder of a stepping stone testing machine JA-400 (chipping test apparatus) manufactured by Suga Test Instruments Co., Ltd., and at −20 ° C., a distance of 30 cm from 0.392 MPa (4 kgf / cm ² ) 50 g of granite crushed stone with a particle size of 7 was collided with the test plate at an angle of 45 degrees by compressed air of ² ). Thereafter, the obtained test plate is washed with water, dried, and a cloth adhesive tape (manufactured by Nichiban Co., Ltd.) is applied to the coated surface. After peeling it off, the degree of scratches on the coating film is visually observed. And evaluated according to the following criteria.
◎: Scratch size is very small, electrodeposition surface or base steel plate is not exposed ○: Scratch size is small, electrodeposition surface or base steel plate is not exposed △: Scratch size is Although it is small, the electrodeposited surface and the base steel plate are exposed. X: The size of the scratch is considerably large, and the base steel plate is also exposed greatly.

Claims (10)

(A) an aqueous film-forming resin, (B) a curing agent, and (C) a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and a polymerizable unsaturated group It consists of a polymerizable unsaturated monomer (c-2) having one in one molecule, and is polymerizable based on the total amount of the polymerizable unsaturated monomer (c-1) and the polymerizable unsaturated monomer (c-2). The core part of copolymer (I) obtained by copolymerizing the monomer component, wherein the proportion of unsaturated monomer (c-1) used is in the range of 0.1 to 20% by mass, and urea group-containing polymerization A core composed of a shell portion of a copolymer (II) obtained by copolymerizing a monomer component comprising a polymerizable unsaturated monomer (c-3) and another polymerizable unsaturated monomer (c-4) Containing cross-linked resin particles having a shell-type multilayer structure The aqueous coating composition according to claim. The aqueous coating composition according to claim 1, wherein the aqueous film-forming resin (A) is a hydroxyl group-containing acrylic resin (A1) and / or a hydroxyl group-containing polyester resin (A2). The urea group-containing polymerizable unsaturated monomer (c-3) is at least one polymerizable unsaturated monomer selected from polymerizable unsaturated monomers having a urea group selected from an ethylurea group, a propylurea group, and a butylurea group. The water-based coating composition according to claim 1 or 2. The aqueous coating composition according to any one of claims 1 to 3, wherein the other polymerizable unsaturated monomer (c-4) contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part thereof. Solid content mass ratio of copolymer (I) and copolymer (II) is (solid content mass of copolymer (I)) / (solid content mass of copolymer (II)) = 10 / 90- It is in the range of 95/5, The water-based coating composition of any one of Claims 1-4. The water-based coating composition according to any one of claims 1 to 5, wherein the average particle size of the crosslinked resin particles (C) is in the range of 10 nm to 500 nm. The mixing ratio of the aqueous film-forming resin (A), the curing agent (B), and the crosslinked resin particles (C) is aqueous based on the total of 100 parts by mass of the aqueous film-forming resin (A) and the curing agent (B). The film-forming resin (A) is 60 to 95 parts by mass, the curing agent (B) is 5 to 40 parts by mass, and the crosslinked resin particles (C) are 1 to 100 parts by mass. The water-based paint composition described in 1. Furthermore, the water-based coating composition of any one of Claims 1-7 containing a hydrophobic solvent (F). An article coated with the aqueous coating composition according to any one of claims 1 to 8. (A) an aqueous film-forming resin, (B) a curing agent, and (C) a polymerizable unsaturated monomer (c-1) having two or more polymerizable unsaturated groups in one molecule and a polymerizable unsaturated group Polymerizable based on the total amount of polymerizable unsaturated monomer (c-1) and polymerizable unsaturated monomer (c-2), which contains one polymerizable unsaturated monomer (c-2) per molecule In the emulsion containing the copolymer (I) obtained by emulsion polymerization of the monomer mixture, the use ratio of the polymerizable unsaturated monomer (c-1) is in the range of 0.1 to 20% by mass. It comprises a copolymer (II) obtained by adding a monomer mixture containing a polymerizable unsaturated monomer (c-3) and other polymerizable unsaturated monomer (c-4) and further emulsion polymerization. Water-based coating characterized by containing crosslinked resin particles Composition.