JP2013212482A - Multilayered coating film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered coating film forming method capable of providing a multilayered coating film which has superior rapid curability at low temperature, has superior chipping resistance and finished appearances.SOLUTION: There is provided a multilayered coating film forming method of simultaneously baking and curing a multilayered coating film obtained by sequentially applying an aqueous first coloring paint (X), an aqueous second coloring paint (Y) and a clear paint (Z) onto a coating object. The aqueous first coloring paint (X) contains (A) an aqueous film forming resin, (B) a curing agent and (C) resin particles that are obtained by polymerizing monomer components containing a urea group-containing polymerizable unsaturated monomer (c1). The clear paint (Z) contains (K) a hydroxyl group-containing acrylic resin, (L) a polyisocyanate compound and (M) an organic metal catalyst comprising (M1) a metal compound of a specific metal and (M2) an amidine compound.

Description

  The present invention relates to a multilayer coating film forming method and a coated article capable of obtaining a multilayer coating film having excellent curability at low temperature and in a short time, chipping resistance and finished appearance.

In recent years, in the painting of industrial products in addition to automobile bodies, development for shortening the bake-hardening process and reducing the process has been actively conducted from the viewpoint of energy saving and reduction of environmental load.
Conventionally, as a method of forming a coating film on an automobile body, an electrodeposition coating is applied to an object to be coated, followed by heat curing, followed by intermediate coating coating → heat curing → base coating coating → preheating (preheating) → clear coating. There are a wide variety of methods for forming multi-layer coatings using the 3-coat 2-bake method in which coating is sequentially applied and heat-cured, and the 2-coat 2-bake method in which intermediate coating is applied, heat-curing, top-coating is applied, and heat-curing is sequentially performed. Has been done.

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

  In recent years, from the viewpoint of energy saving, the heat curing process after painting of the intermediate coating is omitted, and the coating of the intermediate coating is applied → preheating (preheating) → base coating is applied → preheating (preheating) → clear coating is applied → heating A 3-coat 1-bake system in which curing is performed sequentially and a 2-coat 1-bake system in which intermediate coating is applied, preheated (preliminary heating), top coating is applied, and heat-cured are sequentially 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 coating, base coating, and top coating are particularly required. .

  In shortening the bake-hardening process, there is an increasing demand for lowering the temperature and shortening the curing process. In the multi-layer coating film forming method for satisfying such a requirement for low-temperature and short-time curing, as a coating composition, in consideration of cost, a hydroxyl group-containing resin is cured using a polyisocyanate compound as a crosslinking agent. / Isocyanate group cross-linking paints are considered to be promising and have been studied.

  However, in the prior art, shortening of the curing time is insufficient in improving the curability at a low temperature in a short time, and it is difficult to satisfy the high-quality finished appearance required particularly in automobile painting.

  Patent Document 1 includes, as essential components, a pyrazole block polyisocyanate compound containing two or more tertiary isocyanate groups blocked with a pyrazole compound in one molecule and a hydroxyl group-containing resin having a specific hydroxyl value and a weight average molecular weight. The coating composition characterized by containing and the coating-film formation method using this coating composition are indicated. However, the coating film forming method using this coating composition has insufficient curability under short-time conditions.

  Patent Document 2 contains a polyol (A1), a polyether polyol (B), and a solvent (C), and the paint resin composition mainly characterized in that the polyol (A1) has a ring structure; ) A curable coating composition containing a polyisocyanate compound, and a curable coating composition characterized in that the curable coating composition further contains a metal organic compound and an acidic substance.

  However, this coating composition is excellent in low-temperature and short-time curability in an embodiment containing the metal organic compound and acidic substance, but has insufficient pot life, and coating film formation using the coating composition The finished appearance of the multilayer coating film obtained by the method may be insufficient.

  In addition, in the multi-layer coating film, the intermediate coating film which is the lower layer coating film of the clear coating film, the base coat film is generally used a coating composition using a hydroxyl-containing resin and a melamine resin as a crosslinking agent, As described above, in the multilayer coating film of low-temperature short-time curing in which the heat-curing step after coating the intermediate coating is omitted, the curability under low-temperature short-time conditions becomes insufficient, so that the resulting multi-layer coating is obtained. In some cases, the film hardness and chipping resistance were insufficient.

JP 2005-225907 A JP 2002-97412 A

  An object of the present invention is to provide a method for forming a multilayer coating film capable of obtaining a multilayer coating film having excellent curability, chipping resistance and finished appearance at a low temperature in a short time.

As a result of earnest research to solve the above problems, the present inventors,
In the method for forming a multilayer coating film, in which a water-based first colored paint, a water-based second colored paint, and a clear paint are sequentially applied on an object to be coated,
As an aqueous first colored paint,
(A) Aqueous film-forming resin, (B) curing agent, and (C) a urea group-containing polymerizable unsaturated monomer (c1) having one polymerizable unsaturated group in one molecule and other polymerizable unsaturated compounds A paint containing resin particles obtained by copolymerizing the monomer (c2),
As a clear paint,
According to the method for forming a multilayer coating film, comprising using a coating material containing an organic metal catalyst comprising a hydroxyl group-containing acrylic resin and a polyisocyanate compound having a specific hydroxyl value range, and a metal compound and an amidine compound having a specific range. The inventors have found that the object can be achieved, and have completed the present invention.

That is, the present invention
To the article to be coated, the following steps (1) to (4),
Step (1): A step of forming the first colored coating film by coating the aqueous first colored paint (X),
Step (2): A step of forming a second colored coating film by applying an aqueous second colored coating material (Y) on the first colored coating film formed in the step (1).
Step (3): a step of applying a clear paint (Z) on the second colored coating film formed in the step (2) to form a clear coating film, and a step (4): the step (1). A method for forming a multilayer coating film in which the first colored coating film, the second colored coating film and the clear coating film formed in (3) are simultaneously baked and cured,
The aqueous first colored paint (X) comprises (A) an aqueous film-forming resin, (B) a curing agent, and (C) a urea group-containing polymerizable unsaturated group having one polymerizable unsaturated group per molecule. A paint containing resin particles obtained by copolymerizing the monomer (c1) and other polymerizable unsaturated monomer (c2),
The clear paint (Z) is
(K) a hydroxyl group-containing acrylic resin having a hydroxyl value of 85 to 215 mgKOH / g,
(L) a polyisocyanate compound, and
(M) (M1) A metal compound in which the metal is one selected from the group consisting of zinc, tin, zirconium, bismuth, lead, cobalt, manganese, titanium, aluminum and molybdenum, and (M2) an organic metal comprising an amidine compound The present invention provides a method for forming a multilayer coating film characterized by being a paint containing a catalyst.

  Resin particles obtained by copolymerizing urea group-containing polymerizable unsaturated monomer (c1) and other polymerizable unsaturated monomer (c2) in the water-based first colored paint in the multilayer coating film forming method of the present invention Therefore, the sclerosis | hardenability and physical property of a 1st colored coating film improve by the hydrogen bond and sclerosis | hardenability improvement effect by the urea group which this particle | grain has. In addition, the hydrogen bond due to the urea group brings about the effect of developing the viscosity of the first colored coating film, the mixing with the second colored coating film during coating is suppressed, and the finished appearance of the multilayer coating film due to the mixing layer is reduced. Can be suppressed.

  Furthermore, since the clear paint contains an organometallic catalyst composed of a specific range of metal compounds and amidine compounds as a catalyst for the crosslinking reaction between the hydroxyl group-containing resin and the polyisocyanate compound, it can be cured at a low temperature and in a short time. It is excellent in performance and can satisfy both pot life.

  This is presumably because the organometallic catalyst forms a complex structure in which the amidine compound is coordinated with the metal compound. This amidine compound is sterically hindered, and this amidine compound is coordinated. While the structure is in use, the catalytic activity of the urethanization reaction inherent to the metal compound (metal ion) can be suppressed, so that the pot life is also excellent.

  In addition, since the amidine compound dissociates at a relatively low temperature, the coordinated amidine compound is detached when the low dissociation temperature is reached, the metal compound is regenerated, and the urethane inherent in the metal compound (metal ion) It is considered that a coating composition having excellent curability at a low temperature in a short time can be obtained by the action of the catalytic activity of the conversion reaction.

  By these synergistic effects, it is considered that a multilayer coating film excellent in curability, chipping resistance and finished appearance can be obtained.

  As described above, according to the multilayer coating film forming method of the present invention, there is provided a multilayer coating film forming method capable of obtaining a multilayer coating film having excellent curability, chipping resistance and finished appearance at a low temperature in a short time. It is possible to produce an effect that.

  Hereinafter, the multilayer coating film forming method of the present invention (hereinafter sometimes referred to as “the present method”) will be described in detail.

The multilayer coating film forming method of the present invention is a multilayer coating film forming method in which an aqueous first colored paint, an aqueous second colored paint, and a clear paint are sequentially applied to an object.
As an aqueous first colored paint,
(A) Aqueous film-forming resin, (B) curing agent, and (C) a urea group-containing polymerizable unsaturated monomer (c1) having one polymerizable unsaturated group in one molecule and other polymerizable unsaturated compounds A paint containing resin particles obtained by copolymerizing the monomer (c2),
As a clear paint,
A method for forming a multilayer coating film, comprising using a coating material containing a hydroxyl group-containing acrylic resin and a polyisocyanate compound having a specific hydroxyl value range, and an organometallic catalyst comprising a specific range of metal compound and amidine compound.

The coated material to which the present method is applied is not particularly limited. For example, a cold-rolled steel plate, a galvanized steel plate, a zinc alloy-plated steel plate, a stainless steel plate, a tin-plated steel plate, etc., aluminum Metal substrates such as plates and aluminum alloy plates; various plastic materials. Moreover, the vehicle body and components of various vehicles, such as a motor vehicle, a two-wheeled vehicle, and a container formed by these, may be sufficient.

  Moreover, as a to-be-coated object, surface treatments, such as a phosphate process, a chromate process, complex oxide process, may be given to the metal surface of the said metal base material or a vehicle body. Furthermore, as the object to be coated, a primer coating film is applied to a plastic material such as a bumper, in which an undercoating film and / or an intermediate coating film such as various electrodeposition coatings is formed on the metal base material, the vehicle body, etc. It may be formed.

Process (1)
In the multilayer coating film forming method of the present invention, first, the aqueous first colored paint (X) is applied. Water-based first colored paint (X)
The aqueous first colored paint (X) comprises (A) an aqueous film-forming resin, (B) a curing agent, and (C) a urea group-containing polymerizable unsaturated monomer having one polymerizable unsaturated group per molecule. It is a paint containing resin particles obtained by copolymerizing (c1) and other polymerizable unsaturated monomer (c2).

Aqueous film-forming resin (A)
In the aqueous first colored paint (X), the (A) aqueous film-forming resin is one excluding the following (C) 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.

  Moreover, 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.

  The hydroxyl group-containing acrylic resin (A1) is, as a part thereof, a so-called urethane-modified acrylic resin obtained by extending a polyisocyanate compound to a part of hydroxyl groups in the resin by a urethanization reaction to increase the molecular weight. Also good.

  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 the present specification, the number average molecular weight and the weight average molecular weight are values calculated from the chromatogram measured by gel permeation chromatography (GPC) based on the molecular weight of standard polystyrene. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI

Hydroxyl-containing polyester resin (A2)
By using the hydroxyl group-containing polyester resin (A2) as the aqueous film-forming resin (A) in the aqueous first colored paint (X), the smoothness of the resulting coating film can be improved.

  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 that can cure 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; 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 former is 60 to 95% by mass, preferably 65 to 90%, based on the total amount of the aqueous film-forming resin (A) and the curing agent (B) in the aqueous first colored paint (X). The smoothness of the coating film is such that the mass is 70% by mass, more preferably 70 to 90% by mass, and the latter is 5 to 40% by mass, preferably 10 to 35% by mass, and more preferably 10 to 30% by mass. And from the viewpoint of improving chipping resistance.

  When the aqueous first colored paint (X) contains the hydroxyl group-containing acrylic resin (A1) as at least one kind of the aqueous film-forming resin (A), the blending amount of the hydroxyl group-containing acrylic resin (A1) Based on the total amount of the forming 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. Is more preferable.

  Further, when the aqueous first colored paint (X) 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: Based on the total amount of the aqueous 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. More preferably.

Resin particles (C)
The resin particle (C) is obtained by copolymerizing a urea group-containing polymerizable unsaturated monomer (c1) having one polymerizable unsaturated group in one molecule and another polymerizable unsaturated monomer (c2). Resin particles.

  The urea group-containing polymerizable unsaturated monomer (c1) 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. As the urea group, an ethylurea group, a propylurea group, and a butylurea group are preferable.

  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 does not specifically limit as a urea group containing polymerizable unsaturated monomer (c1), For example, the monomer obtained by making an amine compound react with the polymerizable unsaturated monomer containing an isocyanate group 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.

  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) Benzene, 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, diphenylmethane-4,4'-diisocyanate and the like. .

  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.

  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 urea group-containing polymerizable unsaturated monomer (c1) is selected from the viewpoints of curability and chipping resistance of the resulting coating film, and the urea group-containing polymerizable unsaturated monomer (c1) and other polymerizable unsaturated monomers. Based on the total amount of monomers (c2), it is preferred to be in the range of 5 to 70% by weight, in particular 10 to 60% by weight, more particularly 15 to 50% by weight, even more particularly 15 to 40% by weight. .

  The other polymerizable unsaturated monomer (c2) is a monomer other than the urea group-containing polymerizable unsaturated monomer (c1).

Examples of the other polymerizable unsaturated monomer (c2) include, for example, methyl (meth) acrylate and ethyl as the polymerizable unsaturated monomer (c2-1) having one polymerizable unsaturated group in one molecule. (Meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meta ) 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- butyl cyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, alkyl or cycloalkyl (meth) acrylates such as tricyclodecanyl (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;
(Meth) acrylate having a polyoxyethylene chain whose molecular end is an alkoxy group;
Carbonyl groups such as acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone) Examples thereof include a polymerizable unsaturated monomer.

  These monomers can be used individually by 1 type or in combination of 2 or more type according to the performance requested | required of the resin particle (C).

  Furthermore, as the other polymerizable unsaturated monomer (c2), a polymerizable unsaturated monomer (c2-2) having two or more polymerizable unsaturated groups in one molecule can be used.

As the polymerizable unsaturated monomer (c2) having two or more polymerizable unsaturated groups in one molecule,
For example, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (Meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra ( (Meth) acrylate, glycerol di (meth) acrylate, 1,1,1-trishydroxymethylethane di (meth) acrylate, 1,1,1-trishydroxymethylethanetri (meth) acrylate 1,1,1-tris hydroxymethyl propane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, divinyl benzene, methylene bisacrylamide, ethylene bisacrylamide or the like exemplified. These monomers can be used alone or in combination of two or more.

  Examples of the polymerizable unsaturated monomer (c2-2) having two or more polymerizable unsaturated groups in one 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.

  In the case of using a polymerizable unsaturated monomer (c2-2) having two or more polymerizable unsaturated groups in one molecule, the use ratio thereof contains a urea group from the viewpoint of improving the stability of the resulting paint. Based on the total amount of the polymerizable unsaturated monomer (c1) and the other polymerizable unsaturated monomer (c2), preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably. Is preferably in the range of 1 to 5 mass%.

  It is preferable that the other polymerizable unsaturated monomer (c2) 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 obtained resin particles (C), and the resin particles (C). It has the function of improving the stability in an aqueous medium.

  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

  In the case of containing a hydroxyl group-containing polymerizable unsaturated monomer as the other polymerizable unsaturated monomer (c2), the proportion of the hydroxyl group-containing polymerizable unsaturated monomer used depends on the stability of the resin particles (C) in the aqueous medium. From the viewpoint of excellent chipping resistance of the resulting coating film, it is 1 to 30% by mass based on the total amount of the urea group-containing polymerizable unsaturated monomer (c1) and the other polymerizable unsaturated monomer (c2). Preferably, it is 3-25 mass%, More preferably, it is 5-20 mass%.

  The other polymerizable unsaturated monomer (c2) preferably contains a carboxyl group-containing polymerizable unsaturated monomer as at least a part thereof.

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

  Moreover, it is preferable that the said other polymerizable unsaturated monomer (c2) 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 ( Alkyl (meth) acrylates such as meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) ) Acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, cycloalkyl (meth) acrylates such as 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.

  In addition, from the viewpoints of hardness and chipping resistance, cycloalkyl (meth) acrylate having an alkyl group having 4 to 22 carbon atoms can be particularly preferably used.

  When other polymerizable unsaturated monomer (c2) contains an alkyl or cycloalkyl (meth) acrylate having an alkyl group having 4 to 22 carbon atoms, an alkyl or cycloalkyl having an alkyl group having 4 to 22 carbon atoms ( The use ratio of the (meth) acrylate is preferably 1 to 80% by mass based on the total amount of the urea group-containing polymerizable unsaturated monomer (c1) and the other polymerizable unsaturated monomer (c2). More preferably, it is 60 mass%, and it is still more preferable that it is 5-50 mass%.

  Moreover, the said other polymerizable unsaturated monomer (c2) has a C1-C3, especially C1-C2 alkyl group as at least one part from a viewpoint of the stability improvement of the coating material obtained. It is preferable to contain an alkyl (meth) acrylate.

  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 (c2) contains an alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms, the proportion of the alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms is used. Is preferably 1 to 80% by mass, and 3 to 60% by mass based on the total amount of the urea group-containing polymerizable unsaturated monomer (c1) and the other polymerizable unsaturated monomer (c2). Is more preferable, and it is still more preferable that it is 5-50 mass%.

  The resin particles (C) have different resin compositions in the central portion (core) and the outer shell portion (shell) from the viewpoint of controlling the particle structure, such as cross-linking structure and uneven distribution of functional groups in the particles. What has a core shell structure can be used conveniently.

  When the resin particles (C) have a core-shell structure, the core / shell ratio is preferably 10/90 to 95/5 in terms of solid content mass ratio, from the viewpoint of increasing the core ratio, The ratio is more preferably 50/50 to 90/10, and still more preferably 65/35 to 85/15.

When the resin particles (C) have a core-shell structure, the glass transition temperature (Tg ₁ ) of the central portion (core portion) is −65 to −10 ° C., preferably −60 to −20 ° C., more preferably It is suitable to be in the range of −50 to −20 ° C.

The glass transition temperature (Tg ₂ ) of the outer shell portion (shell) is −50 to 150 ° C., preferably −5 to 120 ° C., more preferably 10 to 110 ° C. is there.

Further, Tg ₂ is greater than the Tg _1, and the difference between the Tg ₂ and Tg ₁ is, 5 to 200 ° C., preferably suitably be 30 to 180 ° C., more preferably in the range of 50 to 160 ° C. .

  In this specification, the glass transition temperature Tg (absolute temperature) is a value calculated by the following equation.

1 / Tg = W ₁ / T ₁ + W ₂ / T ₂ +... W _n / T _n
[Wherein W ₁ , W ₂ ,..., W _n are mass fractions of each monomer, and T ₁ , T _2, ..., T _n are glass transition temperatures (absolute temperatures) of homopolymers of each monomer] is there. ]
In addition, the glass transition temperature of the homopolymer of each monomer is POLYMER HANDBOOK Fourth Edition, J. MoI. Brandrup, E .; h. Immergut, E .; A. The glass transition temperature of a monomer not described in the literature, which is a value according to Grulk ed. (1999), was synthesized such that a homopolymer of the monomer had a weight average molecular weight of about 50,000, and its glass transition temperature. Is the value measured by differential scanning thermal analysis.

  The 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 and the like of the resulting multilayer coating film. More preferably, it is -20 mgKOH / g.

  The 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. More preferably, it is 10-30 mgKOH / g.

  The resin particles (C) can be obtained, for example, by emulsion polymerization of a monomer mixture containing a urea group-containing polymerizable unsaturated monomer (c1) and another polymerizable unsaturated monomer (c2).

  The emulsion polymerization can be performed by a conventionally known method such as a seed polymerization method or a miniemulsion polymerization method. For example, the emulsion polymerization can be performed by emulsion polymerization of a monomer mixture using a polymerization initiator in the presence of an emulsifier. it can.

  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.

  Moreover, the monomer mixture may contain a chain transfer agent for the purpose of adjusting the molecular weight of the resulting 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.

  In order to obtain the core-shell structure resin particles (C), for example, monomer mixtures having different compositions can be prepared, and each can be synthesized by performing a polymerization reaction in multiple stages.

  In the aqueous first colored paint (X), the “shell part” of the resin particle (C) means a polymer layer present in the outermost layer of the resin particle, and the “core part” is a resin particle excluding the shell part. This means an inner polymer layer, and the “core / shell 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. In addition, 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 resin particles (C) of the water-based first colored paint (X).

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

  In this specification, the average particle diameter of the 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 resin particle (C) has an acidic group such as a carboxyl group, it is desirable to neutralize the acidic group with a neutralizing agent in order to improve the mechanical stability of the resin particle (C). 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 preferably used in such an amount that the pH of the aqueous dispersion of the resin particles (C) after neutralization becomes about 4.0 to 9.0.

Water-based first colored paint (X)
The aqueous first colored paint (X) is a paint composition containing the aqueous film-forming resin (A), the curing agent (B), and the resin particles (C).

  The mixing ratio of the aqueous film-forming resin (A), the curing agent (B), and the resin particles (C) in the aqueous first colored paint (X) 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 94 parts by mass, preferably 65 to 87 parts by mass, more preferably 70 to 85 parts by mass,
Curing agent (B): 5-39 parts by mass, preferably 10-32 parts by mass, more preferably 10-25 parts by mass,
Resin particles (C): 1 to 35 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass.

  The aqueous first colored paint (X) can usually contain the pigment (D) as a colorant. Examples of the pigment (D) include coloring pigments, extender pigments, and luster pigments. The pigments (D) can be used alone or in combination of two or more.

  When the aqueous first colored paint (X) contains the pigment (D), the blending amount of the pigment (D) is the aqueous film-forming resin (A) and the curing agent in the aqueous first colored paint (X). Generally, it can be in the range of 1 to 200 parts by weight, preferably 20 to 150 parts by weight, more preferably 50 to 120 parts by weight, based on the total of 100 parts by weight of (B) and the resin particles (C).

  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 aqueous first colored paint (X) contains the above-mentioned colored pigment, the amount of the colored pigment is such that the aqueous film-forming resin (A), the curing agent (B) and the aqueous first colored paint (X) Based on the total 100 parts by mass of the resin 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 multilayer coating film having an excellent appearance with high flip-flop properties and little metallic unevenness when using a paint containing a luster pigment as an excellent water-based second colored paint (Y) (aqueous base coat paint) Therefore, it is preferable.

In this specification, the average primary particle diameter of barium sulfate is the average of the maximum diameters of 20 barium sulfates on a straight line obtained by observing barium sulfate with a scanning electron microscope and randomly drawing on an electron micrograph. It is the value.
When the aqueous first colored paint (X) 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 aqueous first colored paint (X) Based on the total 100 parts by mass of the resin 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 water-based first colored paint (X) contains the glitter pigment, the blending amount of the glitter pigment is the water-based film-forming resin (A) and the curing agent (B in the water-based first colored paint (X). ) And resin particles (C) in a total amount of 100 parts by mass, 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 first colored paint (X) 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 from the viewpoint of improving the smoothness of the coating surface of the multilayer coating film. To 1500, preferably 300 to 1000, more preferably 400 to 1000 oligomer compounds (excluding the aqueous film-forming 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 this specification, 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 first colored paint (X) 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 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.

  In addition, the water-based first colored paint (X) is a thickener, a curing catalyst, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent, etc., if necessary. The paint additive can be contained.

  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 water-based 1st coloring coating material (X) contains the said thickener, the compounding quantity of this thickener is aqueous film forming resin (A), hardening | curing agent (B), and 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 first colored paint (X) The aqueous first colored paint (X) comprises an aqueous film-forming resin (A), a curing agent (B), resin particles (C), and, if necessary, a pigment. (D), oligomer (E), and other coating additives 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 first colored paint (X) is usually preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and still more preferably 35 to 60% by mass. .

Step (2)
An aqueous second colored paint (Y) is applied on the first colored coating film formed as described above.

  From the viewpoint of suppression of coating film defects such as armpits and sagging and smoothness of the obtained coating film, the aqueous second colored coating material (Y) has a solid content of 70 to 70%. It is suitable to carry out while being in the range of 100% by weight, preferably 80-100% by weight, more preferably 90-100% by weight.

  The solid content of the first colored coating film can be adjusted by, for example, preheating (preheating), air blowing, or the like before applying the aqueous second colored paint (Y).

  The preheating is usually performed by directly or indirectly heating the coated object in a drying furnace at a temperature of about 50 to about 110 ° C., preferably about 60 to about 80 ° C. for about 1 to 30 minutes. Can be performed.

  Moreover, the said air blow can be normally performed by spraying the air heated at the normal temperature or the temperature of about 25 degreeC-about 80 degreeC on the coating surface of the to-be-coated article.

  Moreover, the solid content of the first colored coating film can be measured, for example, by the following method.

First, the water-based first colored paint (X) is applied on the aluminum foil whose mass (W ₁ ) has been measured in advance simultaneously with the object to be coated. Subsequently, after the coating, the aluminum foil that has been preheated as necessary is collected immediately before the aqueous second colored paint (Y) is applied, and the mass (W ₂ ) is measured. Next, the recovered aluminum foil is dried at 110 ° C. for 60 minutes, and allowed to cool to room temperature in a desiccator. Then, the mass (W ₃ ) of the aluminum foil is measured, and the solid content is determined according to the following formula.

Solid content (mass%) = {(W ₃ −W ₁ ) / (W ₂ −W ₁ )} × 100
Water-based second colored paint (Y)
As the water-based second colored paint (Y) used in the method for forming a multilayer coating film of the present invention, for example, those known per se that are usually used in the coating of automobile bodies can be used.

  The aqueous second colored paint (Y) can be generally prepared by mixing and dispersing a base resin, a crosslinking agent, a pigment and the like in an aqueous medium.

  As the base resin, for example, a resin containing a carboxyl group and a hydroxyl group is preferably used. Examples of the base resin include acrylic resin, polyester resin, polyether resin, polycarbonate resin, and polyurethane resin.

  It is preferable that the carboxyl group and the carboxyl group in the hydroxyl group-containing resin are neutralized. The neutralization is preferably performed using a basic substance before mixing with a crosslinking agent or the like.

  Examples of basic substances used for neutralization include ammonia; primary monoamines such as ethylamine, propylamine, butylamine, benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, and 3-aminopropanol; Secondary monoamines such as diethylamine, diethanolamine, di-n- or diisopropanolamine, N-methylethanolamine, N-ethylethanolamine; N, N-dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine, etc. And tertiary amines such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, and other polyamines. These may be used alone or in combination of two or more thereof.

  The amount of the basic substance used for neutralization is usually in the range of 0.1 to 1.5 equivalents, particularly 0.3 to 1.2 equivalents, based on the carboxyl group and the carboxyl group in the hydroxyl group-containing resin. It is preferable that

  The base resin preferably has an acid value in the range of usually 10 to 150 mgKOH / g, particularly 30 to 100 mgKOH / g, from the viewpoint of water dispersibility and the like. In addition, the base resin preferably has a hydroxyl value in the range of usually 10 to 150 mgKOH / g, particularly 30 to 100 mgKOH / g, from the viewpoint of curability and the like.

  In addition, the base resin is usually a number average within the range of 3000 to 100,000, particularly 5000 to 50000 in the acrylic resin, and usually 500 to 50000, particularly 3000 to 30000 in the polyester resin from the viewpoint of weather resistance and the like. It preferably has a molecular weight.

  When a carboxyl group- and hydroxyl group-containing acrylic resin is used as the base resin, a carboxyl group- and hydroxyl group-containing acrylic resin produced by emulsion polymerization in the presence of a dispersion stabilizer can also be used.

  In the case of the acrylic resin produced by the emulsion polymerization, those having a number average molecular weight in the range of usually 100,000 or more, particularly 200000 to 2000000 are preferable.

  Examples of the dispersion stabilizer used in the emulsion polymerization include nonionic surfactants and anionic surfactants, and aqueous resins such as acrylic resins having an acid value of about 10 to 150 mgKOH / g and a number average molecular weight of about 5000 to 30000. Can be preferably used.

  The emulsion polymerization can be carried out by a method known per se.

  As the base resin, among them, an acrylic emulsion produced by a multistage polymerization method using a carboxyl group-containing unsaturated monomer as a copolymerization component can obtain an aqueous second colored paint (Y) excellent in coating workability. Therefore, it is preferable. That is, first, a polymerization reaction is carried out using a monomer mixture having a composition containing no or almost no carboxyl group-containing unsaturated monomer (usually 3% by mass or less in all monomers), and then containing a carboxyl group-containing unsaturated monomer ( The acrylic emulsion obtained by carrying out the polymerization reaction using a monomer mixture having a composition of 5 to 30% by mass in the total monomers usually has a viscosity developing effect by neutralization with a basic substance, This is preferable because an aqueous second colored paint (Y) excellent in coating workability such as sagging property can be obtained.

  As a crosslinking agent, at least 1 sort (s) chosen from the crosslinking agent which can react with a hydroxyl group, such as a melamine resin, a block polyisocyanate compound, a water dispersible block polyisocyanate compound, can be used, for example.

  The blending ratio of the base resin and the crosslinking agent in the aqueous second colored paint (Y) is generally 60 to 100% by weight, particularly 65 to 95% by weight, more particularly 70%, based on the total solid content of both components. It is preferred that the content of .about.90% by mass and the crosslinking agent is generally in the range of 0 to 40% by mass, particularly 5 to 35% by mass, more particularly 10 to 30% by mass.

  The pigment is not particularly limited, and for example, inorganic and organic pigments, extender pigments, glitter pigments, and the like can be preferably used. Examples of the color pigment include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, Examples include perylene pigments. Examples of the extender pigment include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white. Examples of the bright pigment include aluminum powder, mica powder, and mica powder coated with titanium oxide.

  The amount of the pigment blended is generally in the range of 0.1 to 200% by mass, particularly 1 to 100% by mass, based on the total solid content of the base resin and the crosslinking agent.

  For the aqueous second colored paint (Y), if necessary, a curing catalyst, a dispersant, an anti-settling agent, an antifoaming agent, a thickening agent, an ultraviolet absorber, a light stabilizer, a surface conditioner, an antioxidant Etc. can be used as appropriate.

  The non-volatile concentration during application of the aqueous second colored paint (Y) is usually preferably 15 to 65% by mass, and the single coating film can be an opaque or transparent solid or metallic coating film. In this specification, an opaque coating means a coating having a light transmittance of less than 5% in a cured coating of 20 μm of a coating alone, and a transparent coating means a light beam in the cured coating of 20 μm. It means a coating film having a transmittance of 5% or more.

  The water-based second colored paint (Y) has an appropriate viscosity, for example, a value when measured at 20 ° C. and a rotation speed of 60 rpm using a B-type viscometer, usually 200 to 800 cps (centipoise), preferably Is adjusted to 400 to 600 cps (centipoise), for example, air spray, airless spray, rotary atomizing coating or the like is applied electrostatically as necessary, and the film thickness based on the cured coating film is generally 5 The coating can be performed to have a thickness of ˜30 μm, particularly 10 to 25 μm.

  In this method, the aqueous second colored paint (Y) is applied on the first colored coating film, and then the clear paint (Z) is applied. Prior to the application of the clear paint (Z), if necessary, You may pre-dry the 2nd colored coating film obtained by apply | coating water-based 2nd colored paint (Y) at the temperature of about 50-100 degreeC.

  By this preliminary drying, the volatile components in the second colored coating film can be volatilized to some extent.

  Since the coating film is dried and solidified to some extent by the preliminary drying, the solvent, the low-molecular resin component, and the like contained in the coating film when the clear paint (Z) is applied onto the second colored coating film Even if it penetrates and diffuses into the colored coating film, it can suppress the decrease in viscosity of the second colored coating film, can suppress the reflow of the metallic pigment when using the metallic pigment, etc. Can be prevented.

Process (3)
As described above, the clear paint (Z) is applied onto the aqueous second colored coating film formed by the second colored paint (Y).

Clear paint (Z)
The clear paint (Z) is a clear paint containing a hydroxyl group-containing acrylic resin (K), a polyisocyanate compound (L), and an organometallic catalyst (M) composed of a metal compound (M1) and an amidine compound (M2).

Hydroxyl group-containing acrylic resin (K)
The hydroxyl group-containing acrylic resin (K) can be produced by copolymerizing monomer components composed of (k1) a hydroxyl group-containing polymerizable unsaturated monomer and (k2) other polymerizable unsaturated monomers by a conventional method.

  The hydroxyl group-containing polymerizable unsaturated monomer (k1) is a compound having one hydroxyl group and one polymerizable unsaturated bond in each molecule.

  Examples of the hydroxyl group-containing polymerizable unsaturated monomer (k1) include a secondary hydroxyl group-containing polymerizable unsaturated monomer (k1-1) and a hydroxyl group (excluding secondary hydroxyl group) -containing polymerizable unsaturated monomer (k1-2). Can do.

  Examples of the secondary hydroxyl group-containing polymerizable unsaturated monomer (k1-1) include ester moieties such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl (meth) acrylate. A polymerizable unsaturated monomer having a secondary hydroxyl group having 2 to 8, particularly 3 to 6, more particularly 3 or 4 carbon atoms of the alkyl group; (meth) acrylic acid and an epoxy group-containing compound (for example, Cardura E10, trade name) And adducts with Hexion Specialty Chemical Co., Ltd., neodecanoic acid glycidyl ester). Among these, 2-hydroxypropyl (meth) acrylate is particularly preferable.

The monomer (k1-1) can be used alone or in combination of two or more.
The hydroxyl group (excluding secondary hydroxyl group) -containing polymerizable unsaturated monomer (k1-2) is a compound having one hydroxyl group (excluding secondary hydroxyl group) and one polymerizable unsaturated bond in one molecule.

  Examples of the monomer include (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate, and a dihydric alcohol having 2 to 10 carbon atoms. And monoesterified products (excluding those having secondary hydroxyl groups); hydroxyl group-containing monomers modified by ring-opening polymerization reaction of ε-caprolactone (excluding those having secondary hydroxyl groups), and the like.

  As the hydroxyl group-containing monomer modified by ring-opening polymerization reaction of ε-caprolactone, a commercially available product can be used. Examples of commercially available products include “Placcel FA-1”, “Placcel FA-2”, “ Plaxel FA-3, Plaxel FA-4, Plaxel FA-5, Plaxel FM-1, Plaxel FM-2, Plaxel FM-3, Plaxel FM-4, Plaxel FM-5 "(all of which are trade names manufactured by Daicel Chemical Industries, Ltd.).

  The said monomer (k1-2) can be used by 1 type or in combination of 2 or more types.

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”.
The other polymerizable unsaturated monomer (k2) is a monomer other than the hydroxyl group-containing polymerizable unsaturated monomer (k1), specifically, a compound having one polymerizable unsaturated bond in one molecule. is there. Specific examples of the unsaturated monomer (k2) are listed in the following (1) to (7).

(1) Acid group-containing polymerizable unsaturated monomer The acid group-containing polymerizable unsaturated monomer is a compound having one acid group and one polymerizable unsaturated bond in each molecule. Examples of the monomer include carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride; sulfonic acid group-containing monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate; 2 Acidic phosphoric acid such as-(meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3-chloropropyl acid phosphate, 2-methacryloyloxyethylphenyl phosphate Examples include ester monomers. These can be used alone or in combination of two or more. When the acid group-containing polymerizable unsaturated monomer is used, the acrylic resin (A) preferably has an acid value of about 0.5 to 30 mgKOH / g, particularly about 1 to 20 mgKOH / g.

(2) Esterified product of acrylic acid or methacrylic acid and C1-C20 monohydric alcohol Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl acrylate, n- Butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, stearyl (meth) acrylate, iso Stearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) Examples include acrylate and isobornyl (meth) acrylate.

Of the esterified product of acrylic acid or methacrylic acid and a monohydric alcohol having 1 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 20 carbon atoms is selected from the viewpoint of improving the finished appearance and achieving both coating film hardness. The polymerizable unsaturated monomer (k2-1) to be contained can be preferably used.
Typical examples of the alicyclic hydrocarbon group having 6 to 20 carbon atoms include a cyclohexyl group, a cyclooctyl group, a cyclododecyl group, an isobornyl group, an adamantyl group, and a tricyclodecanyl group.

  Specific examples of the unsaturated monomer (k2-1) include, for example, cyclohexyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4-ethylcyclohexylmethyl (meth) acrylate, and 4-methoxycyclohexylmethyl (meth). Cycloalkyl (meth) acrylates such as acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate; isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl ( Examples include bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers such as (meth) acrylate, 3,5-dimethyladamantyl (meth) acrylate, and 3-tetracyclododecyl (meth) acrylate. It is possible.

  When the unsaturated monomer (k2-1) is used, the blending ratio is within the range of 10 to 60% by mass, particularly 15 to 50% by mass, more particularly 20 to 45% by mass, based on the total amount of the monomer components. Preferably there is.

(3) Alkoxysilyl group-containing polymerizable unsaturated monomer Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane, methacryloxyethyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxy Examples thereof include propyltrimethoxysilane, acryloxypropyltriethoxysilane, methacryloxypropyltriethoxysilane, vinyltris (β-methoxyethoxy) silane and the like. Among these, preferred alkoxysilyl group-containing polymerizable unsaturated monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

  By using an alkoxysilyl group-containing polymerizable unsaturated monomer as a constituent component, in addition to the crosslinking bond between a hydroxyl group and an isocyanate group, a condensation reaction between alkoxylyl groups and a crosslinking bond between the alkoxysilyl group and the hydroxyl group are generated. Therefore, curability can be improved.

  When an alkoxysilyl group-containing polymerizable unsaturated monomer is used as a constituent component, the blending ratio is preferably in the range of 1 to 20% by mass, particularly 1 to 10% by mass, based on the total amount of monomer components.

(4) Aromatic vinyl monomer Specific examples include styrene, α-methylstyrene, vinyltoluene and the like.

  By using an aromatic polymerizable unsaturated monomer as a constituent component, the glass transition temperature of the resulting resin is increased, and a hydrophobic coating film having a high refractive index can be obtained. The effect of improving the finished appearance can be obtained.

  When an aromatic polymerizable unsaturated monomer is used as a constituent component, the blending ratio is preferably 3 to 40% by mass, particularly 5 to 30% by mass, based on the total amount of monomer components.

(5) Glycidyl group-containing polymerizable unsaturated monomer The glycidyl group-containing polymerizable unsaturated monomer is a compound having one glycidyl group and one polymerizable unsaturated bond in one molecule, specifically, glycidyl acrylate. And glycidyl methacrylate.

(6) Polymerizable unsaturated bond-containing nitrogen atom-containing compound For example, acrylamide, methacrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetone Examples include acrylamide, N, N-dimethylaminoethyl (meth) acrylate, vinyl pyridine, vinyl imidazole, acrylonitrile, methacrylonitrile and the like.

(7) Other vinyl compounds For example, vinyl acetate, vinyl propionate, vinyl chloride, versatic acid vinyl ester and the like can be mentioned. Examples of the versatic acid vinyl ester include “Veoba 9” and “Veoba 10” (trade names, manufactured by Japan Epoxy Resin Co., Ltd.), which are commercially available products.

  As the other polymerizable unsaturated monomer (k2), the monomers represented by the above (1) to (7) may be used alone or in combination of two or more.

  The weight average molecular weight of the hydroxyl group-containing acrylic resin (K) is preferably about 2000 to 50000, particularly about 5000 to 30000, from the viewpoint of the finished appearance and curability of the coating film.

  The glass transition temperature of the hydroxyl group-containing acrylic resin (K) is preferably about −10 to 30 ° C., more preferably about −5 to 20 ° C., from the viewpoint of the curability of the coating film and the finished appearance.

  Secondary hydroxyl group-containing polymerizable unsaturated monomer (k1-1) out of the total amount of hydroxyl group-containing polymerizable unsaturated monomer (k1) in hydroxyl group-containing acrylic resin (K) from the viewpoint of improving the finished appearance of the coating film and pot life. It is preferable to contain 50-100 mass%, and it is more preferable to contain 80-100 mass%.

  In addition, the hydroxyl value of the hydroxyl group-containing acrylic resin (K) is 85 to 215 mgKOH / g, and is preferably in the range of 100 to 200 mgKOH / g, particularly 120 to 200 mgKOH / g, from the viewpoints of curability and finished appearance. preferable.

  The mixing ratio of the hydroxyl group-containing polymerizable unsaturated monomer (k1) and the other polymerizable unsaturated monomer (k2) is determined based on the total monomer amount from the viewpoint of curability and the finished appearance of the cured coating film. The unsaturated monomer (k1) is preferably about 20 to 50% by mass, more preferably about 30 to 45% by mass, and the other unsaturated monomer (k2) is preferably about 50 to 80% by mass, more preferably It is about 55-70 mass%.

The acid value of the hydroxyl group-containing acrylic resin (K) is preferably about 0.5 to 30 mgKOH / g, particularly about 1 to 20 mgKOH / g, from the viewpoint of curability of the coating composition.
A hydroxyl group-containing acrylic resin (K) can be obtained by copolymerizing the monomer mixture comprising the polymerizable unsaturated monomers (k1) and (k2).

  The copolymerization method for copolymerizing the monomer mixture to obtain the hydroxyl group-containing acrylic resin (K) is not particularly limited, and a known copolymerization method can be used. Among them, a solution polymerization method in which polymerization is performed in the presence of a polymerization initiator can be preferably used.

  Examples of the organic solvent used in the solution polymerization method include aromatic solvents such as toluene, xylene, and Swazol 1000 (trade name, high-boiling petroleum solvent) manufactured by Cosmo Oil; ethyl acetate, butyl acetate, 3 -Ester solvents such as methoxybutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, propyl propionate, butyl propionate, ethoxy ethyl Pionate can be mentioned.

  These organic solvents can be used singly or in combination of two or more, but it is preferable to use a high boiling ester solvent or ketone solvent from the viewpoint of the solubility of the acrylic resin. In addition, aromatic solvents having higher boiling points can be suitably used in combination.

  Examples of the polymerization initiator that can be used for copolymerization of the hydroxyl group-containing acrylic resin (K) include 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, and di-t-amyl. Examples thereof include radical polymerization initiators known per se such as peroxide, t-butyl peroctoate, and 2,2′-azobis (2-methylbutyronitrile).

  A hydroxyl-containing acrylic resin (K) can be used individually or in combination of 2 or more types.

  Resins other than the hydroxyl group-containing acrylic resin (K) can be used together as necessary. Specifically, for example, an acrylic resin other than the hydroxyl group-containing acrylic resin (K), a polyester resin, a polyether resin, a polyurethane resin, and the like can be mentioned. Preferred examples include a hydroxyl group-containing polyester resin and a hydroxyl group-containing polyurethane resin. be able to.

  The hydroxyl group-containing polyester resin can be produced by an ordinary method, for example, by an esterification reaction of a polybasic acid and a polyhydric alcohol. The polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexa And hydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and their anhydrides. The polyhydric alcohol contains two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3 -Propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxy Diols such as valinic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, etc. , And trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, and the like, and 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylol Examples thereof include hydroxycarboxylic acids such as pentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid.

  In addition, α-olefin epoxides such as propylene oxide and butylene oxide, monoepoxy compounds such as Cardura E10 (manufactured by Japan Epoxy Resin Co., Ltd., trade name, glycidyl ester of synthetic hyperbranched saturated fatty acid) and the like are reacted with acids, and these are reacted. A compound may be introduced into the polyester resin.

When introducing a carboxyl group into a polyester resin, for example, it can be introduced by adding an acid anhydride to a hydroxyl group-containing polyester and half-esterifying it.
The hydroxyl value of the hydroxyl group-containing polyester resin is preferably 85 to 250 mgKOH / g, more preferably 100 to 220 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyester resin is preferably 2500 to 40000, more preferably 5000 to 30000.

  Examples of the hydroxyl group-containing polyurethane resin include a hydroxyl group-containing polyurethane resin obtained by reacting a polyol and a polyisocyanate.

  Examples of the polyol include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and hexamethylene glycol, and trihydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol. Can do. Examples of the high molecular weight material include polyether polyol, polyester polyol, acrylic polyol, and epoxy polyol. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of the polyester polyol include alcohols such as the above divalent alcohols, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, and dibasic acids such as adipic acid, azelaic acid, and sebacic acid. Lactone-based ring-opening polymer polyol such as polycaprolactone, polycarbonate diol, and the like. Moreover, for example, carboxyl group-containing polyols such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid can also be used.

  Examples of the polyisocyanate to be reacted with the above polyol include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; and burette type addition of these polyisocyanates. Product, isocyanurate cycloadduct; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) Alicyclic diisocyanates such as di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate And burette type adducts, isocyanurate cycloadducts of these polyisocyanates; xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5- Naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, (m- or p-) phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl- Aromatic diisos such as 4,4'-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate) And burette-type adducts, isocyanurate cycloadducts of these polyisocyanates; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2, Polyisocyanates having three or more isocyanate groups in one molecule such as 4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate; and And polyisocyanate burette type adducts, isocyanurate ring adducts, and the like.

  The hydroxyl value of the hydroxyl group-containing polyurethane resin is preferably from 85 to 250 mgKOH / g, more preferably from 100 to 220 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyurethane resin is preferably 2500 to 40000, more preferably 5000 to 30000. The glass transition temperature of the hydroxyl group-containing polyurethane resin is preferably in the range of −40 ° C. to 85 ° C., more preferably in the range of −30 ° C. to 80 ° C.

  When a resin other than the above hydroxyl group-containing acrylic resin (K) (more specifically, a polyester resin, a polyether resin, a polyurethane resin, etc.) is used in combination, the resin other than the hydroxyl group-containing acrylic resin (K) is a hydroxyl group-containing acrylic. Preferably it exists in the range of 10-50 mass% with respect to solid content total amount of resin (K).

Polyisocyanate compound (L)
The polyisocyanate compound (L) is a curing agent for the clear paint (Z), and is a compound having two or more isocyanate groups in one molecule. Examples of the polyisocyanate compound (L) include those known for polyurethane production, such as aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates. Can do.

  Specific examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2- Fats such as butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, 2,6-diisocyanatomethylcaproate, lysine diisocyanate Lysine ester triisocyanate, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 3,6 tri diisocyanatohexane, and aliphatic triisocyanate such as 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: Isophorone diisocyanate), 4,4′-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane ( Common name: hydrogenated xylylene diisocyanate) or mixtures thereof, alicyclic diisocyanates such as norbornane diisocyanate, for example, 1,3,5-triisocyanatocyclohexane, 1,3, -Trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2,6 -Di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5 -(2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl -3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatotop Pyr) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, etc. And alicyclic triisocyanate.

  Examples of the araliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω′-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis ( 1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof, for example, an araliphatic triisocyanate such as 1,3,5-triisocyanatomethylbenzene Etc.

  Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4′- or 4,4′-diphenylmethane diisocyanate or a mixture thereof. 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, for example, triphenylmethane-4,4 ′, 4 '' '-Triisocyanate, aromatic triisocyanate such as 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, for example, 4,4'-diphenylmethane-2,2', 5 , 5'-Tetri And aromatic tetraisocyanates such as cyanate.

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

  Among the above, hexamethylene diisocyanate (hereinafter sometimes referred to as HMDI), isophorone diisocyanate (hereinafter sometimes referred to as IPDI), and derivatives thereof can be particularly suitably used because of industrial availability.

  The said polyisocyanate compound can be used individually or in combination of 2 or more types.

  In the polyisocyanate compound (L), the viscosity at 25 ° C. is preferably 200 to 4000 mPa · s, more preferably 250 to 3000 mPa · s, and still more preferably 300 to 2000 mPa · s from the viewpoints of curability and finished appearance. s. If the viscosity is less than 200 mPa · s, the clear coating film and, further, the resulting multilayer coating film may have reduced curability. Moreover, when it exceeds 4000 mPa · s, the finished appearance of the obtained multilayer coating film may be deteriorated.

  As the polyisocyanate compound (L), those containing a dimer or higher dimer of the diisocyanate compound can be suitably used from the viewpoint of low temperature short time curability and finished appearance.

  When the polyisocyanate compound (L) contains a dimer or higher multimer as described above, the content of the isocyanurate trimer is particularly 30 to 70 masses based on the total amount of the polyisocyanate compound. %, Particularly 40 to 70% by mass, more particularly 50 to 70% by mass, and the content of uretdione dimer is 3 to 30% by mass, particularly 5 to 25% by mass, more particularly 8 to 20% by mass, and other 3 A polymer having a content of a multimer of a monomer or more in a range of 0 to 67% by mass, particularly 5 to 55% by mass, and more particularly 10 to 42% by mass can be preferably used.

  In the above, the isocyanurate trimer is a polyisocyanate having an isocyanurate group consisting of three molecules of a diisocyanate monomer, and the uretdione dimer is a polyisocyanate having a uretdione group consisting of two molecules of a diisocyanate monomer. .

  The polyisocyanate compound preferably contains no unreacted diisocyanate monomer, and the residual diisocyanate monomer concentration is preferably 1% by mass or less, and more preferably 0.5% by mass or less.

Organometallic catalyst (M)
The organometallic catalyst (M) is a catalyst composed of a metal compound (M1) and an amidine compound (M2).

  By using the metal compound (M1) and the amidine compound (M2) in combination, it is excellent in curability at a low temperature and in a short time, has a good finished appearance of the coating film to be formed, and is a pot as a two-component paint Life can be maintained sufficiently.

  This is because the catalyst composed of the metal compound (M1) and the amidine compound (M2) forms a complex structure, and the amidine compound serves as a blocking agent. After the dissociation of the compound, the catalytic ability with excellent low-temperature curability inherent to the metal compound becomes active, so that it is possible to achieve both the curability of the clear paint (Z) in a short time and the pot life. I think that is due to.

  The metal compound (M1) is a metal compound in which the metal is one selected from the group consisting of zinc, tin, zirconium, bismuth, lead, cobalt, manganese, titanium, aluminum, and molybdenum. A compound, an acetylacetone metal complex, etc. can be mentioned. In particular, a carboxylic acid metal salt compound can be preferably used.

  Specific examples of the carboxylic acid metal salt compound include compounds represented by the following formula (1).

(RCO ₂ ) _n M (1)
(In the formula, M is a metal selected from the group consisting of Zn, Sn, Zr, Bi, Pb, Co, Mn, Ti, Al and Mo, and R is an alkyl group having 1 to 30 carbon atoms and 1 carbon atom. Represents an aralkyl group or an alkylaryl group of ˜30, and n is an integer having a value of 1 or more and 4 or less)
More specifically, for example, 2-ethylhexanoic acid metal salt, acetic acid metal salt, naphthenic acid metal salt, octanoic acid metal salt, stearic acid metal salt, neodecanoic acid metal salt, oleic acid metal salt and the like can be mentioned. .

  Because of its excellent catalytic activity and industrial availability, manganese octylate, tin octylate, cobalt octylate, titanium octylate, aluminum octylate, zinc octylate, zirconium octylate, bismuth octylate, or lead octylate Can be preferably used.

The amidine compound (M2) is an organic compound having a structure represented by R ¹ —C (═NR ² ) —NR ³ R ⁴ . This structure has a structure in which a carbon (C) atom has one nitrogen atom as a double bond and one nitrogen atom as a single bond.

In the structural formula R ¹ —C (═NR ² ) —NR ³ R ⁴ (1),
R ¹ is a hydrogen atom, an optionally substituted organic group bonded to a carbon atom, or an amine group, and specifically, an optionally substituted hydrocarbyl group or an etherified hydroxyl group. Can be mentioned.

R ² and R ³ are independently of each other an organic group bonded to a hydrogen atom or a carbon atom, or a heterocyclic ring having a structure bonded to each other (having one or more heteroatoms, or one or more heterocycles). Having a bonded double ring with atoms).

R ⁴ is a hydrogen atom, an optionally substituted organic group bonded to a carbon atom, an optionally etherified hydroxyl group, or preferably an optionally substituted hydrocarbyl group having 8 or more carbon atoms. be able to.

When R ¹ or R ⁴ is an organic group, they may be, for example, those having 1 to 40 carbon atoms or polymer groups having a molecular weight of, for example, 500 to 50,000.

The groups represented by R ¹ , R ² , R ³ , and R ⁴ can each independently contain an alcoholic hydroxyl group as a substituent.

An amidine compound represented by the structural formula R ¹ —C (═NR ² ) —NR ³ R ⁴ (1), in which R ² and R ³ are not bonded, specifically includes N′— Cyclohexyl-N, N-dimethylformamidine, N′-methyl-N, N-di-n-butylacetamidine, N′-octadecyl-N, N-dimethylformamidine, N′-cyclohexyl-N, N-dimethyl Valeroamidine, 1-methyl-2-cyclohexyliminopyrrolidine, 3-butyl-3,4,5,6-tetrahydropyrimidine, N- (hexyliminomethyl) morpholine, N- (α- (decyliminoethyl) ethyl) pyrrolidine N'-decyl-N, N-dimethylformamidine, N'-dodecyl-N, N-dimethylformamidine, N'-cyclohexyl-N, N-acetamidine and the like be able to.

Further, as the amidine compound, R ² -R ³ forms a 5- to 7-membered ring containing two nitrogen atoms in the amidine structure, and one of R ¹ -R ³ or R ¹ -R ⁴ is Amidine compounds having a structure in which a 5- to 9-membered ring is formed by one nitrogen atom and a plurality of carbon atoms in the amidine structure are also included in the amidine compound (M2).

  Specific examples of amidine compounds having such a structure include 1,5-diazabicyclo (4.3.0) on-5-ene and 1,8-diazabicyclo (5.4.0) undec-7. Ene, 1,4-diazabicyclo (3.3.0) oct-4-ene, 2-methyl-1,5-diazabicyclo (4.3.0) on-5-ene, 2,7,8-trimethyl- 1,5-diazabicyclo (4.3.0) on-5-ene, 2-butyl-1,5-diazabicyclo (4.3.0) on-5-ene, 1,9-diazabicyclo (6.5. 0) Tridec-8-ene and the like can be mentioned.

In addition, as an amidine compound, a heterocyclic compound having a structure in which R ² and R ^{3 in} the structural formula R ¹ —C (═NR ² ) —NR ³ R ⁴ (1) are bonded, such as imidazoline and imidazole. , Tetrahydropyrimidine, dihydropyrimidine, and pyrimidine ring-containing compounds.

  The imidazole compound is generally represented by the following structural formula.

In the above, R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom, alkyl group or substituted alkyl group, hydroxyalkyl group, allyl group, aralkyl group, cycloalkyl group, heterocyclic ring, Mention may be made of ether groups, thioether groups, halogens, —N (R) ₂ , polyethylene polyamines, nitro groups, keto groups, ester groups, carbonamido groups, and alkyl substituents of these functional groups.

  Specific examples of the imidazole compound include N- (2-hydroxyethyl) imidazole, N- (3-aminopropyl) imidazole, 4- (hydroxymethyl) imidazole, 1- (tert-butoxycarbonyl) imidazole, imidazole- 4-propionic acid, 4-carboxyimidazole, 1-butylimidazole, 1-methylimidazole, 2-methyl-4-imidazolecarboxylic acid, 4-formylimidazole, 1- (ethoxycarbonyl) imidazole, propylene oxide and imidazole and 2- Reaction product with methylimidazole, 1-trimethylsilylimidazole, 4- (hydroxymethyl) imidazole hydrochloride, copolymer of 1-chloro-2,3-epoxypropane and imidazole, 1 (p-toluenesulfonyl) imidazole, 1, 1-carbonylbisimidazole, 1- ( -Cyanoethyl) -2-ethyl-4-methylimidazole, 2-phenyl-2-imidazoline pyromellitate, 4- (hydroxymethyl) imidazole picrate, 2-propenoic acid and 4,5-dihydro-2-nonyl- Disodium salt of 1H-imidazole-1-ethanol and 2-heptyl-4,5-dihydro-1H-imidazole-1-ethanol, 1- (cyanoethyl) -2-undecylimidazole trimellitate, 1- (2- Hydroxypropyl) imidazole formate, sodium imidazole salt, silver imidazole salt and the like.

  The above amidine compounds can be used alone or in combination of two or more.

  Specifically, in the clear paint (Z), the organometallic catalyst (M) is a metal complex, and for example, the complex contains 1 mol of a carboxylic acid metal salt and 2 mol of an amidine compound in a solvent such as methanol. It can manufacture by heating with.

In the above production, a metal complex can be prepared by holding at about 50 ° C. for about 2 hours until a transparent solution is obtained. The clear solution is filtered and dried.
The molar ratio of the amidine compound (M2) to the metal compound (M1) (the ratio of the number of moles of (M2) / the number of moles of (M1)) is 1.3 to 8.0, particularly 1.6 to 5. It is preferably 0, more particularly in the range of 1.8 to 4.0.

  When the molar ratio is out of the range of 1.3 to 8.0, any of the low-temperature short-time curability, pot life, and finished appearance may be insufficient.

  The amount of the component (M) is 0.05 to 5% by mass, particularly 0.1%, based on the total amount of the component (K) and the component (L), from the viewpoints of low-temperature short-time curability, pot life, and finished appearance. It is preferable to be within a range of ˜4 mass%, more particularly within a range of 0.3 to 3 mass%.

  If it is less than 0.05% by mass, the low-temperature short-time curability may be insufficient. Moreover, when it exceeds 5 mass%, the finished appearance of the clear coating film obtained and also the multilayer coating film may become insufficient.

  The organometallic catalyst (M) can also be used after being dissolved in a solvent. Although the solvent is not particularly limited, for example, alcohols such as ethylene glycol, diethylene glycol, dipropylene glycol, propylene glycol, butanediol, hydrocarbons such as toluene, xylene, mineral terpenes, mineral spirits, ethyl acetate, Esters such as butyl acetate, methyl glycol acetate and cellosolve acetate, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, glycol ethers such as ethyl 3-ethoxypropionate and 3-methoxybutyl acetate, N, N-dimethylformamide , Organic solvents of amides such as N, N-dimethylacetamide, β-diketones such as acetylacetone and fluorinated substituents thereof, ketoesters such as methyl acetoacetate and ethyl acetoacetate It can be exemplified solvents of the kind or the like.

  In the clear paint (Z), in addition to the organometallic catalyst (M), a catalyst other than the organometallic catalyst (M) can be used as necessary.

  The catalyst other than the organometallic catalyst (M) is not particularly limited as long as it is a conventionally known organometallic as a catalyst for polyurethane production. Specifically, stannous diacetate, stannous dioctoate, Examples thereof include organic tin catalysts such as stannous dioleate, stannous dilaurate, dibutyltin oxide, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, and dioctyltin dilaurate. Of these, stannous dioctate and dibutyltin dilaurate are preferred.

  In the clear paint (Z), from the viewpoints of low-temperature short-time curability, the finished appearance of the resulting coating film, and the water resistance and acid resistance of the cured coating film, the isocyanate group in the polyisocyanate compound (L) and the hydroxyl group-containing acrylic The equivalent ratio (NCO / OH) with the hydroxyl group in the resin (K) is 0.8 to 1.8, preferably 0.8 to 1.6, more preferably 0.8 to 1.4. It is.

  The glass transition temperature (Tg) of the clear coating film formed by the clear coating (Z) is preferably about 80 to 120 ° C. from the viewpoint of improving the finished appearance of the clear coating film and further the multilayer coating film. Preferably it exists in the range of about 90-110 degreeC.

  In addition, in this invention, the glass transition temperature (Tg) of a coating film is the value calculated | required by the dynamic viscoelasticity measurement about the cured coating film.

  The dynamic viscoelasticity was measured under conditions of a temperature rising rate of 3 ° C./min, a temperature range of 20 to 200 ° C., and a frequency of 11 Hz. The glass transition temperature (Tg ° C.) of the coating film is a temperature at which the value of tan δ shows a maximum value in this measurement. As the dynamic viscoelasticity measuring device, FT Leospectra DVE-V4 (manufactured by Rheology, trade name, dynamic viscoelasticity measuring device) was used.

The other component clear coating (Z) is a coating composition containing a hydroxyl group-containing acrylic resin (K), a polyisocyanate compound (L) and an organometallic catalyst (M) as essential components, and usually contains an organic solvent. Further, if necessary, it can contain additives for paints usually used in the field of paints such as pigments, pigment dispersants, leveling agents, rheology control agents, ultraviolet absorbers, light stabilizers, plasticizers and the like.

As the pigment, it can be used without particular limitation, for example, titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, Colored pigments such as isoindoline pigments, selenium pigments, perylene pigments; body pigments such as talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, alumina why; aluminum powder, mica powder, titanium oxide Examples thereof include metallic pigments such as coated mica powder.

  These pigments described above can be used alone or in combination of two or more. The pigment content varies depending on the type, but is usually 0 to 200% by mass, preferably about 1 to 100% by mass, based on the total solid content of the (K) component, (L) component and (M) component. .

  Moreover, although content of a coloring pigment changes with the kinds, it is 0-150 mass% normally with respect to the solid content total amount of (K) component, (L) component, and (M) component, Preferably it is 1-100 mass%. Degree.

  The pigment content is preferably in a range that does not impair the transparency of the coating film obtained from the clear paint (Z).

  As the ultraviolet absorber, conventionally known ones can be used, and examples thereof include ultraviolet absorbers such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers.

  The content of the UV absorber in the clear paint (Z) is usually 0 to 10% by mass, particularly 0.2 to 5% by mass, more particularly 0.3 to 2% by mass, based on the total amount of resin solids. It is preferable from the viewpoint of weather resistance and yellowing resistance.

  A conventionally well-known thing can be used as a light stabilizer, For example, a hindered amine light stabilizer can be mention | raise | lifted.

  The content of the light stabilizer in the clear paint (Z) is usually 0 to 10% by mass, particularly 0.2 to 5% by mass, more particularly 0.3 to 2% by mass, based on the total amount of resin solids. It is preferable from the viewpoint of weather resistance and yellowing resistance.

  From the viewpoint of storage stability, the clear paint (Z) is preferably a two-component paint in which the hydroxyl group-containing acrylic resin (K) and organometallic catalyst (M) are separated from the polyisocyanate compound (L). It is preferable to use a mixture of the two immediately before.

Coating method of clear coating (Z) The coating method of clear coating (Z) is not particularly limited. For example, wet coating is applied by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, etc. Can be formed. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating is particularly preferred. The coating amount of the clear paint (Z) is usually set to an amount that provides a cured film thickness of about 10 to 50 μm, preferably about 20 to 40 μm.

  When air spray coating, airless spray coating, and rotary atomization coating are performed, the viscosity of the clear coating (Z) is adjusted to a viscosity range suitable for the coating, usually Ford Cup #No. In a 4-viscosity meter, it is preferable to adjust appropriately using a solvent such as an organic solvent so that a viscosity range of about 15 to 60 seconds is obtained at 20 ° C.

Process (4)
A multi-layer coating film composed of three layers of the first colored coating film, the second colored coating film and the clear coating film formed as described above can be obtained by, for example, using a normal coating film baking means. It can be performed by hot air heating, infrared heating, high-frequency heating or the like.

  The heating and holding temperature (keep temperature) is excellent in curability at a low temperature, and is therefore preferably in the range of 60 to 120 ° C, particularly 70 to 110 ° C, and more particularly 80 to 100 ° C. The heating and holding time (keep time) is preferably within the range of 5 to 15 minutes, particularly 5 to 12 minutes, more particularly 5 to 10 minutes, because this method is excellent in curability in a short time. ing.

  You may perform preliminary drying at the temperature of about 50-100 degreeC as needed before performing the said heat curing.

The multilayer coating film forming method of the present invention can obtain a multilayer coating film excellent in curability, chipping resistance and finished appearance at low temperature and in a short time. The multilayer coating film forming method of the present invention is an industrial product. It can be suitably used as a general method for forming a multilayer coating film. This method can be particularly suitably used as a method for forming a multilayer coating film for automobiles.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the following, “part” and “%” are both based on mass, and the film thickness of the coating film is based on the cured coating film.

Production of water-based first colored paint (X)
Production and production example 1 of hydroxyl group-containing acrylic resin (A1)
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, and a weight average molecular weight of 6,400.

Production of resin particles (C)
Synthesis production example 5 of a urea group-containing polymerizable unsaturated monomer (c1)
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 (c1-1) (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 (c1-2) (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 (c1-3) (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. Then, the temperature was raised to 60 ° C. and the solvent was removed under reduced pressure to obtain a butylurea group-containing polymerizable unsaturated monomer (c1-4) (active ingredient 100%).

Production and production example 9 of crosslinked resin particles (C)
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. 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, Inc.) and diluted with deionized water and measured at 20 ° C.) 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, 6.9 parts of ethylurea group-containing polymerizable unsaturated monomer (c1-1) , 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, and the monomer emulsion (2 ) (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.

  In addition, the crosslinked resin particles (C-25) and (C-26) of Production Examples 33 and 34 are for comparative examples.

Production Example 35
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) and 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) were uniformly mixed.

  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. An aqueous first colored paint (X-1) having a viscosity of 30 according to 4 was obtained.

Production Examples 36 to 69 and 72 to 75
In Production Example 35, the Ford Cup No. at pH 8.0 and 20 ° C. was prepared in the same manner as in Production Example 35 except that the formulation was as shown in Table 2 below. The water-based first colored paints (X-2) to (X-35) and (X-38) to (X-41) having a viscosity of 30 according to 4 were obtained.
The water-based first colored paints (X-38) to (X-41) in Production Examples 72 to 75 are for comparative examples.

Production Example 70
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) and 37.5 parts of melamine resin (B-1) (30 parts of resin solids) were mixed uniformly.

  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 first colored paint (X-36) having a viscosity of 30 according to 4 was obtained.

Production Example 71
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) and 37.5 parts of melamine resin (B-1) (30 parts of resin solids) were mixed uniformly.

  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. An aqueous first colored paint (X-37) 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) GP600: trade name, manufactured by Sanyo Kasei Co., Ltd., polyoxypropylene glycerol ether (molecular weight 600), water tolerance is 100 or more (Note 6) Diester compound: diester compound of polyoxyethylene glycol and 2-ethylhexanoic acid. In the general formula (1), R1 and R2 are 2-ethylheptyl groups, R3 is an ethylene group, and m is 7. Molecular weight 578.
The hydrophobic solvent 2-ethyl-1-hexanol in Table 2 has a mass of 0.1 g dissolved in 100 g of water at 20 ° C.

Manufacture of water-based second colored paint (Y)
Production and production example 76 of polyester resin for aqueous second colored paint (Y)
Solid content concentration was the same as in Production Example 4 except that 2-ethyl-1-hexanol as a diluent solvent was changed to ethylene glycol mono-n-butyl ether (mass dissolved in 100 g of water at 20 ° C .: infinite). A hydroxyl group-containing polyester resin (A2-3) solution of 70% was obtained.

Production and production example 77 of glitter pigment dispersion for aqueous second colored paint (Y) 77
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 78
A bright pigment dispersion (P2) was obtained in the same manner as in Production Example 77 except that 35 parts of 2-ethyl-1-hexanol was changed to 35 parts of ethylene glycol mono n-butyl ether.

Production Example 79
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 77 (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 Ford Cup No. 20 at 20 ° C. An aqueous second colored paint (Y-1) (aqueous base coat paint 1) having a viscosity of 40 according to 4 was obtained.

Production Example 80
Hydroxyl group-containing acrylic resin (A1-2) dispersion 100 parts obtained in Production Example 2 (resin solid content 30 parts), hydroxyl group-containing polyester resin (A2-3) solution 57.1 parts obtained in Production Example 76 (resin solids) 40 parts), 62.2 parts of the glitter pigment dispersion (P2) obtained in Production Example 78 (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 Ford Cup No. 20 at 20 ° C. An aqueous second colored paint (Y-2) (aqueous base coat paint 2) having a viscosity of 4 and a viscosity of 40 seconds was obtained.

Manufacture of clear paint (Z)
Production and production examples 81-92 of hydroxyl group-containing acrylic resins
31 parts of ethoxyethyl propionate was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 155 ° C. under nitrogen gas flow. After reaching 155 ° C., the flow of nitrogen gas was stopped, and a monomer mixture composed of a monomer and a polymerization initiator shown in Table 3 below was dropped over 4 hours. Next, after aging for 2 hours while ventilating nitrogen gas at 155 ° C., the mixture was cooled to 100 ° C. and diluted with 32.5 parts of butyl acetate, whereby a hydroxyl group-containing acrylic resin (K-1) having a solid content of 60% was obtained. To (K-12). The mass solid content concentration (%) and the resin property value of the obtained hydroxyl group-containing acrylic resin are shown in Table 3 below.

  The glass transition temperature (° C.) in Table 3 was calculated by the following formula.

1 / Tg (K) = (W1 / T1) + (W2 / T2) +
Tg (° C.) = Tg (K) -273
In each formula, W1, W2,... Represent the respective mass fractions of the monomers used for copolymerization, and T1, T2,... Represent the Tg (K) of the homopolymer of each monomer. The Tg (° C.) of the homopolymer of each monomer used in the above calculation is the value shown in the right column of the monomer name in Table 1.

  The hydroxyl group-containing acrylic resins (K-11) to (K-12) are resins for comparative examples.

Production and production example 93 of organometallic catalyst
A reactor equipped with a stirrer, a cooler, a temperature controller, a nitrogen inlet tube and a dropping funnel was added to 47 parts of ethyl-3-ethoxypropionate, Nikka octix zinc (* 1) (zinc octylate, Nippon Chemical Industry Co., Ltd.) Made, zinc content 8 mass%) was charged 81.6 parts, the inside of the reaction vessel was replaced with nitrogen and heated to 50 ° C. Next, 16.4 parts of 1-methylimidazole was added dropwise with stirring, and the temperature was maintained at 50 ° C. for 2 hours after the completion of the addition to complete the reaction. The obtained organometallic catalyst (M-1) was a transparent liquid having a zinc content of 4.5% by mass.

Production Examples 94 to 107
With the composition shown in Table 4 below, in the same manner as in Production Example 93, organometallic catalysts (M-2) to (M-15) were obtained.

  In addition, the molar ratio and mass metal concentration (%) of amidine compound (M2) / metal compound (M1) of organometallic catalysts (M-1) to (M-15) are shown in Table 4 below. The organometallic catalyst (M-15) is a catalyst for a comparative example.

  (* 1) to (* 10) in Table 2 are as follows.

Nikka Octics Zinc (* 1): Trade name, zinc octylate, zinc content 8%, manufactured by Nippon Chemical Industry Co., Ltd.
Nikka Octix Tin (* 2): trade name, tin octylate, tin content 28%, manufactured by Nippon Chemical Industry Co., Ltd.
Nikka Octix Lead (* 3): Trade name, lead octylate, lead content 24%, manufactured by Nippon Chemical Industry Co., Ltd.
K-KAT 348 (* 4): trade name, bismuth octylate, bismuth content 25%, manufactured by King Industries.
Nikka Octix Cobalt (* 5): trade name, cobalt octylate, cobalt content 8%, manufactured by Nippon Chemical Industry Co., Ltd.
Nikka Octix Manganese (* 6): trade name, manganese octylate, manganese content 8%, manufactured by Nippon Chemical Industry Co., Ltd.
Zinc naphthenate (* 7): 10.1% zinc content, manufactured by Tokyo Chemical Industry Co., Ltd.
Acetylacetone zinc (* 8): 25% zinc content, manufactured by Showa Chemical Co., Ltd.
DBN (* 9): 1,5-diazabicyclo [4.3.0] non-5-ene DBU (* 10): 1,8-diazabicyclo [5.4.0] undec-7-ene

Production Examples 108-145
Using the hydroxyl group-containing acrylic resin obtained in Production Examples 81 to 92, the organometallic catalyst obtained in Production Examples 93 to 107 and the raw materials described in Table 5 below, a blade type was prepared according to the formulation shown in Table 5 below. The mixture was stirred and mixed using a stirrer to prepare a clear paint (Z-1) to (Z-38). In addition, the mixing | blending of the clear coating material (Z) shown in Table 5 is solid content mass ratio of each component.
Clear paints (Z-36) to (Z-38) are for comparative examples.

  The polyisocyanate compounds (L-1) to (L-8) in Table 3 have the following meanings.

  Polyisocyanate compound (L-1): Polyisocyanate compound composed of hexamethylene diisocyanate, the composition ratio of the multimer is 53% for the isocyanurate trimer, and 47% for the multimer other than the trimer. Solid content 100%, NCO content 21.8%, viscosity is 3000 mPa · s at 25 ° C.

  Polyisocyanate compound (L-2): Polyisocyanate compound composed of hexamethylene diisocyanate, the composition ratio of multimers is 63% for isocyanurate trimers, 12% for uretdione dimers, and more than other trimers Body is 25%. The solid content is 100%, the NCO content is 21.8%, and the viscosity is 500 mPa · s at 25 ° C.

  Polyisocyanate compound (L-3): polyisocyanate compound composed of hexamethylene diisocyanate, multimer composition ratio is 45% for isocyanurate trimer, 25% for uretdione dimer, more than other trimers Body is 30%. Solid content 100%, NCO content 21.8%, viscosity 340 mPa · s at 25 ° C.

  Polyisocyanate compound (L-4): Polyisocyanate compound comprising hexamethylene diisocyanate, the composition ratio of the multimer is 27% for isocyanurate trimer, 37% for uretdione dimer, and more than other trimers Body is 36%. Solid content 100%, NCO content 21.8%, viscosity is 180 mPa · s at 25 ° C.

  Polyisocyanate compound (L-5): N3200, trade name, manufactured by Bayer AG, hexamethylene diisocyanate burette, solid content 100%, NCO content 23.0%, viscosity at 2500C is 2500 mPas.

  Polyisocyanate compound (L-6): XP2580, trade name, manufactured by Bayer AG, allophanate of hexamethylene diisocyanate, solid content 100%, NCO content 19.5%, viscosity is 450 mPa · s at 25 ° C.

  Polyisocyanate compound (L-7): Z4470, trade name, manufactured by Bayer, isocyanurate of isophorone diisocyanate, solid content 70%, NCO content 11.9%, viscosity is 600 mPa · s at 25 ° C.

  Polyisocyanate compound (L-8): N3800, trade name, manufactured by Bayer, isocyanurate of hexamethylene diisocyanate, solid content 100%, NCO content 11.0%, viscosity at 6000 mPa · s.

The clear paints (Z-1) to (Z-38) obtained in the above production examples 108 to 145 were added with butyl acetate to obtain Ford Cup #No. 4 was adjusted to a viscosity of 25 seconds at 20 ° C.
In addition, the pot life was measured for the viscosity at 20 ° C. at the beginning, 4 hours and 6 hours after the Ford Cup #No. 4 was used for evaluation. The gelled material is described as a gel. The measurement results are also shown in Table 5.

Multi-layer coating method (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.

(Multilayer coating film forming method 1)
Example 1
Electrostatic coating of the water-based first colored paint (X-1) obtained in Production Example 35 on the test object using a rotary atomizing electrostatic coater so as to have a cured film thickness of 20 μm. The first colored coating film was formed. After standing for 3 minutes, preheating was performed at 80 ° C. for 3 minutes.

  Next, the water-based second colored paint (Y-1) obtained in Production Example 79 is cured on the uncured first colored coating film using a rotary atomizing electrostatic coater to a cured film thickness of 15 μm. Thus, electrostatic coating was performed to form a second colored coating film.

  After standing for 5 minutes and preheating at 80 ° C. for 3 minutes, on the uncured second colored coating film, the clear coating (Z-1) prepared in Production Example 108 and viscosity-adjusted was cured to 35 μm. Electrostatic coating was performed to form a clear coating film.

  By standing at room temperature for 7 minutes and then heating at 100 ° C. for 7 minutes (keep time of coating plate temperature of 100 ° C.) to simultaneously cure the first colored coating film, second colored coating film and clear coating film A test coated plate was prepared.

Examples 2-38, Comparative Examples 1-4
In Example 1, the aqueous first colored paint (X-1) obtained in Production Example 35 was changed to any of the first aqueous colored paints (X-2) to (X-41) shown in Table 6 below. A test coated plate in the same manner as in Example 1 except that the water-based second colored paint (Y-1) obtained in Production Example 79 is the water-based base coat paint (Y-1) or (Y-2) shown in Table 6. Was made.

  About each test coating board obtained by the said Examples 1-38 and Comparative Examples 1-4, the following Knoop hardness, chipping resistance, and the finishing appearance test were done. The evaluation results are also shown in Table 6.

  Knoop Hardness: Each test plate was allowed to stand in a constant temperature room at 20 ° C. for 24 hours, and “Tucon hardness” was measured with TUKON (manufactured by American Chain & Cable Company, micro hardness tester).

  TU-CON hardness, also known as Knoop Hardness Number (KHN), expresses the hardness of the coating film that is read from the size of the diamond-shaped indentation that occurs when a square pyramid diamond indenter is pushed into the test surface of the material with a constant test load. The larger the value, the higher the hardness.

  Finished appearance: BYK “Wave-Scan” which is an apparatus that optically scans the light / dark pattern of the light on the coating film surface of each test plate and analyzes the contrast (strength) of the reflected light. A long wavelength value measured at 1000 μm and a short wavelength value measured at a wavelength region of 100 to 600 μm were determined, and each was evaluated as a parameter of the finished skin. These are the dispersion values of the measured light intensity. The smaller the value, the better the finished skin (smoothness of the painted surface).

  The test results are shown in Table 3 below together with the paint formulation.

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.

(Multilayer coating film forming method 2)
Example 39
Electrostatic coating of the water-based first colored paint (X-1) obtained in Production Example 35 on the test object using a rotary atomizing electrostatic coater so as to have a cured film thickness of 20 μm. The first colored coating film was formed. After standing for 3 minutes, preheating was performed at 80 ° C. for 3 minutes.

  Next, the water-based second colored paint (Y-1) obtained in Production Example 79 is cured on the uncured first colored coating film using a rotary atomizing electrostatic coater to a cured film thickness of 15 μm. Thus, electrostatic coating was performed to form a second colored coating film.

  After standing for 5 minutes and preheating at 80 ° C. for 3 minutes, on the uncured second colored coating film, the clear coating (Z-1) prepared in Production Example 108 and viscosity-adjusted was cured to 35 μm. Electrostatic coating was performed to form a clear coating film.

  By standing at room temperature for 7 minutes and then heating at 100 ° C. for 7 minutes (keep time of coating plate temperature of 100 ° C.) to simultaneously cure the first colored coating film, second colored coating film and clear coating film A test coated plate was prepared.

Examples 40-73, Comparative Examples 5-7
In Example 39, except that the clear paint (Z-1) produced and viscous in Production Example 108 was changed to any of the clear paints (Z-2) to (Z-38) shown in Table 7 below. A test coated plate was produced in the same manner as in Example 39.

  About each test coating board obtained by the said Examples 39-73 and Comparative Examples 5-7, it tested the Knoop hardness, chipping resistance, and finishing appearance similarly to the said multilayer coating-film formation method part 2, and also the following The NCO reaction rate was also measured. The evaluation results are also shown in Table 7.

NCO reaction rate: FT-IR equipment “FT / IR-420” (manufactured by JASCO), just after paint blending and viscosity adjustment, by liquid film method, and after heat curing (100 ° C. for 7 minutes) Was evaluated by measuring the surface of the test plate by the ATR method. The isocyanate peak (1690 cm ⁻¹ ) intensity and the isocyanurate peak (2271 cm ⁻¹ ) intensity were calculated, and the ratio of these was calculated to determine the NCO reaction rate.

NCO reaction rate (%) = 100-NCO residual rate (%)
NCO residual ratio (%) = (Isocyanate peak intensity after heat curing / isosinurate peak intensity) / (Isocyanate peak intensity immediately after blending of paint / isosinurate peak intensity) × 100

Claims (10)

To the article to be coated, the following steps (1) to (4),
Step (1): A step of forming the first colored coating film by coating the aqueous first colored paint (X),
Step (2): A step of forming a second colored coating film by applying an aqueous second colored coating material (Y) on the first colored coating film formed in the step (1).
Step (3): a step of applying a clear paint (Z) on the second colored coating film formed in the step (2) to form a clear coating film, and a step (4): the step (1). A method for forming a multilayer coating film in which the first colored coating film, the second colored coating film and the clear coating film formed in (3) are simultaneously baked and cured,
The aqueous first colored paint (X) comprises (A) an aqueous film-forming resin, (B) a curing agent, and (C) a urea group-containing polymerizable unsaturated group having one polymerizable unsaturated group per molecule. A paint containing resin particles obtained by copolymerizing the monomer (c1) and other polymerizable unsaturated monomer (c2),
The clear paint (Z) is
(K) a hydroxyl group-containing acrylic resin having a hydroxyl value of 85 to 215 mgKOH / g,
(L) a polyisocyanate compound, and
(M) (M1) A metal compound in which the metal is one selected from the group consisting of zinc, tin, zirconium, bismuth, lead, cobalt, manganese, titanium, aluminum and molybdenum, and (M2) an organic metal comprising an amidine compound A method for forming a multilayer coating film, which is a paint containing a catalyst.   The method for forming a multilayer coating film 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 (c1) having one polymerizable unsaturated group in one molecule is selected from polymerizable unsaturated monomers having a urea group selected from an ethylurea group, a propylurea group, and a butylurea group. The method for forming a multilayer coating film according to claim 1, which is at least one polymerizable unsaturated monomer.   The multilayer coating film forming method according to any one of claims 1 to 3, wherein the other polymerizable unsaturated monomer (c2) contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part thereof.   The method of forming a multilayer coating film according to any one of claims 1 to 4, wherein the resin particles (C) have a core / shell type structure.   The mass ratio of the core part and the shell part is in a range of (total mass of monomers constituting the core part) / (total mass of monomers constituting the shell part) = 10/90 to 95/5. The multilayer coating film forming method as described.   Of the total amount of the hydroxyl group-containing polymerizable unsaturated monomer (k1), which is a constituent monomer component of the hydroxyl group-containing acrylic resin (K), the content of the secondary hydroxyl group-containing polymerizable unsaturated monomer (k1-1) is 50 to 100 mass. The method for forming a multilayer coating film according to any one of claims 1 to 6.   As other polymerizable unsaturated monomer (k2) which is a constituent monomer component of the hydroxyl group-containing acrylic resin (K), an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (k2-1) having 6 to 20 carbon atoms is contained. The method for forming a multilayer coating film according to any one of claims 1 to 7.   The method for forming a multilayer coating film according to any one of claims 1 to 8, wherein the metal compound (M1) is a carboxylic acid metal salt compound.   An article comprising a multilayer coating film formed by the multilayer coating film forming method according to any one of claims 1 to 9.