JP5950392B2 - Water-based paint composition - Google Patents

Description

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

  In recent years, from the viewpoint of protecting the global environment, paints having a low volatile organic matter content (VOC) are required, and switching from solvent-based paints to water-based paints is being promoted.

  Here, the problems associated with the aqueousization of paints are that the pigments used in paints are generally hydrophobic and difficult to wet with water, and the pigment dispersion resins conventionally used in solvent-type colored paints are For example, the solubility in water is low and the dispersion stability in an aqueous medium is poor. Therefore, in designing the pigment dispersion resin in the water-based paint, it is important to satisfy both the wettability of the pigment and the dispersion stability of the pigment dispersion resin in the aqueous medium.

  With regard to the wettability of the pigment, it is said that it is advantageous that the resin for dispersing the pigment has a low viscosity and a low molecular weight. It is said that it is advantageous to have good solubility in the phase (aqueous medium). In addition, regarding the wettability of the pigment dispersion resin to the pigment surface and the adsorption to the pigment due to the interaction between the hydrophobic part of the pigment surface and the hydrophobic part of the pigment dispersion resin, the wettability of the pigment and the dispersion of the pigment dispersion resin Both stability is considered to be involved.

  From the above viewpoint, development of pigment dispersion resins and auxiliaries for water-based paints or water-based inks has been carried out. For example, in Patent Document 1, a monomer mixture containing an acidic functional group-containing polymerizable unsaturated monomer such as (meth) acrylic acid as part of the monomer component is polymerized as a pigment dispersion resin. It has been proposed to use a linear anionic polymer having an acidic functional group.

  Patent Document 2, Patent Document 3 and Patent Document 4 disclose a graft copolymer obtained by copolymerizing a carboxyl group-containing macromonomer as a pigment dispersion resin.

  Further, Patent Document 5, Patent Document 6 and Patent Document 7 disclose the use of a nonionic surfactant having a polyoxyalkylene chain as a pigment dispersant.

  Patent Document 8 and Patent Document 9 are copolymers having a polymerizable unsaturated monomer containing an ionic functional group and a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain as a copolymerization component. A pigment dispersing resin is disclosed.

  Furthermore, Patent Document 10 discloses a polymerizable unsaturated monomer having a polyoxyalkylene chain, a hydroxyl group-containing polymerizable unsaturated monomer having no polyoxyalkylene chain, a polymerizable unsaturated monomer having a cationic functional group, and the like. An aqueous coating composition using a pigment dispersion resin which is a copolymer as a copolymer component is disclosed.

JP 50-154328 A JP-A-1-182304 JP 7-316240 A Japanese National Patent Publication No. 10-502097 JP-A-9-255728 Japanese Patent Laid-Open No. 9-267034 Japanese Patent Publication No.8-19201 WO02 / 31010 Publication JP 2003-12744 A WO08 / 013290

  However, the pigment dispersion resin disclosed in Patent Document 1 is a dispersion-stabilizing pigment dispersion because the linear anionic polymer having an acidic functional group has high solubility in an aqueous medium. In addition, there is a problem that the dispersion formed using the dispersion is extremely high in viscosity and difficult to handle.

  In addition, the pigment dispersion resins disclosed in Patent Document 2, Patent Document 3 and Patent Document 4 are such that the graft copolymer obtained by copolymerizing a carboxyl group-containing macromonomer has a hydrophobic polymer trunk portion. And the branch part is hydrophilic, it is excellent in stabilizing the dispersion of the pigment. However, the pigment dispersion formed using the graft copolymer has a high viscosity and will be used in the future in terms of cost and VOC. From the viewpoint of reduction, since the pigment dispersion having a higher pigment concentration is required, the above graft copolymer is never satisfactory.

  Further, the nonionic surfactants disclosed in Patent Document 5, Patent Document 6 and Patent Document 7 can exist stably in the aqueous pigment dispersion, but the adsorptivity to the pigment is insufficient. In particular, the let-down stability is poor and the finished appearance of the coating film tends to be inferior.

  In addition, by using the pigment dispersing resin disclosed in Patent Document 8 and Patent Document 9, an aqueous pigment having a low viscosity, excellent color developability and excellent finished appearance of the coating film even at a high pigment concentration. A dispersion can be obtained. However, at present, in the top coating for automobile painting, not only the coating performance such as high durability, acid resistance, car wash scratch resistance, chipping resistance, etc., but also smoothness, transparency, color development, etc. The finished appearance of the coating film is required. In that respect, the above-mentioned resin for dispersing pigments may not have sufficient color developability and smoothness of the coating film obtained, and particularly when black pigments such as carbon black are dispersed, jet blackness (particularly pigments out of color developability). When it is a black pigment, it may be called jet black).

  Furthermore, the aqueous coating composition disclosed in Patent Document 10 is obtained because the cationic functional group of the pigment dispersing resin has a relatively short chain, so that the adsorptivity to the pigment is insufficient. There was a tendency for the color development and smoothness of the coating to be inferior.

  The present invention has been made in consideration of these points, and an object thereof is to obtain an aqueous coating composition excellent in the finished appearance of a coating film such as color developability, jetness and smoothness.

  As a result of intensive studies to achieve the above object, the present inventors have found that a water-based coating composition containing a specific copolymer, a specific acrylic resin, and a pigment has a color developing property, jet blackness and smoothness. The present invention was completed by finding that a coating film excellent in finished appearance such as properties was formed.

That is, the present invention provides the following aqueous coating composition, a method for forming a multilayer coating film using the aqueous coating composition, and an article coated with the aqueous coating composition.
Item 1.
(A) (a) a polymerizable unsaturated monomer having a cationic functional group represented by general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by general formula (2), (b ) A polymerizable unsaturated monomer having a polyoxyalkylene chain, and (c) a copolymer of another polymerizable unsaturated monomer,
A water-based paint composition comprising (B) a pigment, and (C) an acid group and a hydroxyl group-containing acrylic resin.

General formula (1)

[Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms]

General formula (2)

［式中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^４は炭素数６〜１０のアルキレン基を表し、Ｒ^３は水素原子または炭素数１〜３のアルキル基を表す］
項２．
ポリオキシアルキレン鎖を有する重合性不飽和モノマー（ｂ）が一般式（３）

[Wherein, R ¹ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 6 to 10 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms]
Item 2.
The polymerizable unsaturated monomer (b) having a polyoxyalkylene chain is represented by the general formula (3)

[Wherein R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁷ represents an alkylene group having 2 to 4 carbon atoms, and m represents 3 to 3 Represents an integer of 150, and the m oxyalkylene units (R ⁷ O) may be the same as or different from each other]
Item 4. The aqueous coating composition according to Item 1, which is a compound represented by the formula:
Item 3.
Item 3. The aqueous coating composition according to Item 1 or 2, wherein the other polymerizable unsaturated monomer (c) contains a hydroxyl group-containing polymerizable unsaturated monomer (c1) having no polyoxyalkylene chain.
Item 4.
Copolymer (A) is based on the total amount of monomers (a) to (c),
3 to 35% by mass of a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (2) (a)
5-40% by mass of a polymerizable unsaturated monomer (b) having a polyoxyalkylene chain,
And other polymerizable unsaturated monomer (c) 25-92 mass%
Item 4. The water-based coating composition according to any one of Items 1 to 3, which is obtained by copolymerization.
Item 5.
Item 5. The aqueous coating composition according to any one of Items 1 to 4, wherein the acid value of the acid group- and hydroxyl group-containing acrylic resin (C) is 1 to 50 mgKOH / g.
Item 6.
Item 6. The aqueous coating composition according to any one of Items 1 to 5, further comprising a melamine resin.
Item 7.
Item 7. The aqueous coating composition according to any one of Items 1 to 6, further comprising a hydroxyl group-containing polyester resin.
Item 8.
8. An article coated with the aqueous coating composition according to any one of items 1 to 7.
Item 9.
The aqueous coating composition according to any one of the above items 1 to 7 is applied on an object to be coated, and a clear coating is formed on the resulting uncured coating to form a clear coating, followed by heating. And a method for forming a multilayer coating film, wherein both coating films are cured simultaneously.
Item 10.
An article coated by the method for forming a multilayer coating film according to Item 9.

  According to the aqueous coating composition of the present invention, it is possible to form a coating film having excellent finished appearance such as color developability, jetness and smoothness.

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

  The aqueous coating composition of the present invention comprises a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (2). (A), a polymerizable unsaturated monomer (b) having a polyoxyalkylene chain, a copolymer (A) of other polymerizable unsaturated monomer (c), a pigment (B), and an acid group- and hydroxyl group-containing acrylic Resin (C) is contained.

More specifically, the aqueous coating composition of the present invention uses the copolymer (A) as a pigment dispersion resin and is mixed with the pigment (B) to obtain an aqueous pigment dispersion (D). It is preferably an aqueous coating composition obtained by mixing the aqueous pigment dispersion (D) with the acid group- and hydroxyl group-containing acrylic resin (C).
Copolymer (A)
The copolymer (A) is a polymerizable unsaturated monomer having a cationic functional group represented by the following general formula (1) and / or a polymerizable unsaturated group having a cationic functional group represented by the general formula (2). It is a copolymer of a saturated monomer (a), a polymerizable unsaturated monomer (b) having a polyoxyalkylene chain, and other polymerizable unsaturated monomers (c). The polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or the polymerizable unsaturated monomer having a cationic functional group represented by the general formula (2) (a) is hereinafter referred to as “ "Monomer (a)" may be abbreviated.

Monomer (a)
A polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (2) (a) is added to the copolymer. It is a monomer component for introducing a relatively long-chain secondary or tertiary amino group.

Here, the polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) (sometimes abbreviated as “monomer (a-1)”) is as follows.
General formula (1)

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

In particular, R ^{3 in} the formula is preferably a methyl group from the viewpoint of ease of synthesis and easy availability of materials.

Further, R ² in the formula is preferably a butylene group and a hexylene group from the viewpoint of obtaining a water-based coating composition excellent in the finished appearance of the coating film such as color developability, jet blackness, and smoothness.

On the other hand, polymerizable unsaturated monomers having a cationic functional group represented by the general formula (2) (sometimes abbreviated as “monomer (a-2)”) are as follows.
General formula (2)

In the general formula (2), R ¹ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 6 to 10 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

In particular, R ^{3 in} the formula is preferably a methyl group from the viewpoint of ease of synthesis and easy availability of materials.

Further, R ⁴ in the formula is preferably a hexylene group and an octylene group from the viewpoint of obtaining a water-based coating composition excellent in the finished appearance of the coating film such as color developability, jet blackness, and smoothness.

Preparation Method of Monomer (a) The preparation method of the monomer (a) includes the preparation method of the polymerizable unsaturated monomer (a-1) having a cationic functional group represented by the general formula (1) and the general formula (2). And a method for preparing a polymerizable unsaturated monomer (a-2) having a cationic functional group, as described above.

Preparation Method of Monomer (a-1) The polymerizable unsaturated monomer (a-1) having a cationic functional group represented by the general formula (1) is a compound having a (meth) acryloyl group and an isocyanate group (hereinafter, “ By reacting with an amine compound having a primary hydroxyl group at the terminal and having an alkyl chain (hereinafter sometimes abbreviated as “amine compound 1”). Can be obtained.

  Examples of the unsaturated isocyanate compound include 2-acryloyloxyethyl isocyanate and 2-methacryloyloxyethyl isocyanate.

  As a commercially available product of the 2-acryloyloxyethyl isocyanate, “Karenz AOI” (trade name, manufactured by Showa Denko KK) can be mentioned, and as a commercially available product of the 2-methacryloyloxyethyl isocyanate, “Karenz MOI” ( Trade name, manufactured by Showa Denko KK).

  Examples of the amine compound 1 include an amine compound having a primary hydroxyl group at a terminal and a linear alkyl chain having 1 to 6 carbon atoms, and having a primary hydroxyl group at a terminal and a main chain having 1 carbon atom. Any amine compound having a branched alkyl chain of ˜6 can be used without limitation.

Specifically, for example, N-methylaminomethanol, N-methylaminoethanol, N-methylaminopropanol (3-methylamino-1-propanol, 1-methylamino-2-propanol), N-methylaminobutanol (4 -Methylamino-1-butanol, 2-methylamino-isobutyl alcohol, etc.), N-methylaminopentanol (5-methylamino-1-pentanol, 4-methylamino-2-methyl-1-butanol, etc.), N-methylaminohexanol (6-methylamino-1-hexanol, 5-methylamino-3-methyl-1-pentanol, 4-methylamino-2,2-dimethyl-1-butanol, etc.), N-methylamino Heptanol (such as 5-methylamino-3,3-dimethyl-1-pentanol), N-methyl Amino octanol (6-methyl-2-ethyl-1-hexanol, etc.) and the like of N- methyl amino alcohol compound;
N, N-dimethylaminomethanol, N, N-dimethylaminoethanol, N, N-dimethylaminopropanol (3-dimethylamino-1-propanol, 1-dimethylamino-2-propanol), N, N-dimethylaminobutanol (4-dimethylamino-1-butanol, 2-dimethylamino-isobutyl alcohol, etc.), N, N-dimethylaminopentanol (5-dimethylamino-1-pentanol, 4-dimethylamino-2-methyl-1- Butanol, etc.), N, N-dimethylaminohexanol (6-dimethylamino-1-hexanol, 5-dimethylamino-3-methyl-1-pentanol, 4-dimethylamino-2,2-dimethyl-1-butanol, etc. ), N, N-dimethylaminoheptanol (5-dimethylamino-3, - dimethyl-1-pentanol, etc.), N, N-dimethylamino-octanol (6-dimethylamino-2-ethyl-1-hexanol, etc.), such as N, N-dimethyl amino alcohol compound; and the like.

  Among these compounds, the amine compound 1 has a primary hydroxyl group at the terminal and has 1 to 6 carbon atoms from the viewpoint of obtaining an aqueous coating composition having excellent finished appearance of the coating film such as color developability, jet blackness, and smoothness. Amine compounds having a linear alkyl chain are preferred, and among them, N, N-dimethylaminoethanol, 4-dimethylamino-1-butanol and 6-dimethylamino-1-hexanol are particularly preferred.

  The reaction between the unsaturated isocyanate compound and the amine compound 1 can be performed by a method known per se. For example, the unsaturated isocyanate is stirred in a solution of the amine compound containing a catalyst such as di-n-butyltin (IV) dilaurate and a polymerization inhibitor such as p-methoxyphenol at room temperature or under heating. It can be carried out by charging the compound.

  The amount of the unsaturated isocyanate compound and amine compound 1 used in that case is preferably 0.5 to 2.0 equivalents, more preferably the isocyanate group in the unsaturated isocyanate compound with respect to 1 equivalent of the hydroxyl group in the amine compound. Is adjusted to 0.7 to 1.5 equivalents, particularly preferably 0.8 to 1.2 equivalents. When the amount of the unsaturated isocyanate compound used is less than 0.5 equivalent, the yield of the polymerizable unsaturated monomer (a-1) having a cationic functional group represented by the general formula (1) is low, When it exceeds 2.0 equivalents, the unreacted unsaturated isocyanate compound remains, and the storage stability of the resulting aqueous coating composition may be lowered.

Preparation method of monomer (a-2) The polymerizable unsaturated monomer (a-2) having a cationic functional group represented by the general formula (2) is composed of a compound having a (meth) acryloyl group and a primary hydroxyl group at the terminal. And an amine compound having an alkyl chain (hereinafter sometimes abbreviated as “amine compound 2”).

  Examples of the compound having the (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. Of these, methyl (meth) acrylate is preferred from the viewpoint of reactivity.

  Examples of the amine compound 2 include an amine compound having a primary hydroxyl group at a terminal and a linear alkyl chain having 6 to 10 carbon atoms, and having a primary hydroxyl group at a terminal and a main chain having 6 carbon atoms. Any amine compound having a branched alkyl chain of 10 to 10 can be used without limitation.

Specifically, for example,
N-methylaminohexanol (6-methylamino-1-hexanol, 5-methylamino-3-methyl-1-pentanol, 4-methylamino-2,2-dimethyl-1-butanol, etc.), N-methylamino Heptanol (7-methylamino-1-heptanol, 5-methylamino-3,3-dimethyl-1-pentanol, etc.), N-methylaminooctanol (8-methylamino-1-octanol, 6-methylamino-) N-methyl such as 2-ethyl-1-hexanol), N-methylaminononanol (9-methylamino-1-nonanol etc.), N-methylamino-decanol (10-methylamino-1-decanol etc.) Amino alcohol compounds;
N, N-dimethylaminohexanol (6-dimethylamino-1-hexanol, 5-dimethylamino-3-methyl-1-pentanol, 4-dimethylamino-2,2-dimethyl-1-butanol, etc.), N, N-dimethylaminoheptanol (7-dimethylamino-1-heptanol, 5-dimethylamino-3,3-dimethyl-1-pentanol, etc.), N, N-dimethylaminooctanol (8-dimethylamino-1-octanol) 6-dimethylamino-2-ethyl-1-hexanol), N, N-dimethylamino-nonanol (9-dimethylamino-1-nonanol etc.), N, N-dimethylamino-decanol (10-dimethylamino-). N, N-dimethylamino alcohol compounds such as 1-decanol).

  Among these, as the amine compound 2, it has a primary hydroxyl group at the terminal and has 6 to 10 carbon atoms from the viewpoint of obtaining a water-based coating composition excellent in the finished appearance of the coating film such as color developability, jet blackness, and smoothness. Amine compounds having a linear alkyl chain are preferred, and among them, 6-dimethylamino-1-hexanol and 8-dimethylamino-1-octanol are particularly preferred.

  The reaction of the compound having a (meth) acryloyl group and the amine compound 2 can be carried out by a method known per se, for example, by transesterification. The amount of the compound having a (meth) acryloyl group and the amine compound 2 used here is preferably a compound having a (meth) acryloyl group with respect to 1 equivalent of a hydroxyl group in the amine compound. The amount is adjusted to be equivalent, more preferably 0.95 to 1.15 equivalent, and particularly preferably 0.9 to 1.1 equivalent. When the amount of the compound having a (meth) acryloyl group is less than 0.8 equivalent, the yield of the polymerizable unsaturated monomer (a-2) having the cationic functional group represented by the general formula (1) is low and obtained. If the coating film is inferior in color developability and smoothness, and exceeds 1.2 equivalents, the compound having an unreacted (meth) acryloyl group remains, and the storage stability of the resulting aqueous coating composition may decrease. is there.

  In the present specification, “(meth) acryloyl” is a general term for acryloyl and methacryloyl.

  The monomer (a) is generally from 3 to 35 mass%, particularly from 5 to 33, based on the total amount of the monomers (a) to (c), from the viewpoints of color developability, jetness, smoothness and the like of the formed coating film. It is preferable to use within a range of mass%, more particularly 7 to 30 mass%.

Polymerizable unsaturated monomer having polyoxyalkylene chain (b)
The polymerizable unsaturated monomer (b) having a polyoxyalkylene chain (hereinafter sometimes abbreviated as “monomer (b)”) is a monomer component for imparting hydrophilicity to the formed copolymer. Yes, it is a monomer containing a polyoxyalkylene chain and a polymerizable unsaturated group in one molecule.

  Examples of the polyoxyalkylene chain include a polyoxyethylene chain, a polyoxypropylene chain, a chain composed of a polyoxyethylene block and a polyoxypropylene block, and these polyoxyalkylene chains are generally 200-5. It is preferred to have a molecular weight in the range of 1,000, in particular 250 to 3,500, more particularly 300 to 2,500.

  Representative examples of the polymerizable unsaturated monomer (b) having a polyoxyalkylene chain include, for example, the general formula (3)

[Wherein, R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁷ represents an alkylene group having 2 to 4 carbon atoms which may be branched. , M represents an integer of 3 to 150, preferably 10 to 80, more preferably 25 to 50, and the m oxyalkylene units (R ⁷ O) may be the same as or different from each other. ]
The compound shown by can be mentioned.

  Specific examples of the compound of formula (3) include, for example, tetraethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, ethoxytetraethylene glycol (meth) acrylate, and n-butoxytetraethylene glycol (meth) acrylate. , Tetrapropylene glycol (meth) acrylate, methoxytetrapyrene glycol (meth) acrylate, ethoxytetrapropylene glycol (meth) acrylate, n-butoxytetrapropylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meta ) Acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate Etc. can be mentioned, which may be used either alone or in combination of two or more. Of these, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate and ethoxypolyethylene glycol (meth) acrylate are preferred, and methoxypolyethylene glycol (meth) acrylate and ethoxypolyethylene glycol (meth) acrylate are preferred. Is particularly preferred.

  In the present specification, “(meth) acrylate” is a general term for acrylate and methacrylate.

  The monomer (b) preferably has a molecular weight in the range of generally 200 to 7,000, particularly 500 to 3,000, more particularly 1,200 to 2,500.

  The monomer (b) is generally 5 to 40% by mass, particularly 7 to 35, based on the total amount of the monomers (a) to (c), from the viewpoint of color developability, jetness and smoothness of the formed coating film. It is preferable to use within a range of 10% by mass, more particularly 10 to 30% by mass.

Other polymerizable unsaturated monomer (c)
The other polymerizable unsaturated monomer (c) includes polymerizable unsaturated monomers other than the monomers (a) and (b) that can be copolymerized with the monomers (a) and (b).

Examples of other polymerizable unsaturated monomer (c) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and n-butyl (meth) acrylate. , I-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), etc. Alkyl (meth) ac Rate;
A polymerizable unsaturated monomer having a cycloalkyl group such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate;
Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers such as isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate and adamantyl (meth) acrylate;
Oxetane ring-containing (meth) acrylates such as 3-ethyl-3- (meth) acryloyloxymethyl oxetane, 3-methyl-3- (meth) acryloyloxymethyl oxetane, 3-butyl-3- (meth) acryloyloxymethyl oxetane ;
Examples thereof include vinyl aromatic compounds such as styrene, α-methylstyrene, and vinyl toluene; (meth) acrylonitrile, (meth) acrylamide, vinyl acetate, and the like, and these can be used alone or in combination of two or more.

  The other polymerizable unsaturated monomer (c) is generally 25 to 92 mass based on the total amount of the monomers (a) to (c) from the viewpoints of color developability, jetness and smoothness of the formed coating film. %, Particularly 32 to 88% by mass, more particularly 40 to 83% by mass.

  In particular, the other polymerizable unsaturated monomer (c) includes a hydroxyl group-containing polymerizable unsaturated monomer (c1) having no polyoxyalkylene chain, from the viewpoints of color developability, jetness and water resistance of the formed coating film. It is preferable to have. The hydroxyl group-containing polymerizable unsaturated monomer (c1) having no polyoxyalkylene chain (hereinafter sometimes abbreviated as “monomer (c1)”) is a polymerizable compound containing at least one hydroxyl group in one molecule. It is an unsaturated monomer and is a polymerizable unsaturated monomer other than the polymerizable unsaturated monomer (b) having a polyoxyalkylene chain.

  Examples of the hydroxyl group-containing polymerizable unsaturated monomer (c1) having no polyoxyalkylene chain include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl ( Monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms such as (meth) acrylate and 4-hydroxybutyl (meth) acrylate; (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms And ε-caprolactone modified products of monoester compounds, such as allyl alcohol, which can be used alone or in combination of two or more.

  As the monomer (c1), 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable, Of these, 4-hydroxybutyl (meth) acrylate is particularly preferable.

  The monomer (c1) is generally from 5 to 40% by mass, particularly from 7 to 35%, based on the total amount of the monomers (a) to (c), from the viewpoints of color development, jetness and smoothness of the formed coating film. It is preferable to use within a range of 10% by mass, more particularly 10 to 30% by mass.

  In particular, the other polymerizable unsaturated monomer (c) preferably contains an alkyl (meth) acrylate from the viewpoint of the color developability, jetness and smoothness of the formed coating film. Especially, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) Acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl ( It may contain an alkyl group-containing polymerizable unsaturated monomer having 4 or more carbon atoms such as (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and methylcyclohexyl (meth) acrylate. Is applied, it is preferable to contain the Among even more particularly of 4 to 8 carbon atoms the alkyl group-containing polymerizable unsaturated monomer. When the other polymerizable unsaturated monomer (c) contains the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms, the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms is a monomer ( It is suitable to use in the range of generally 10 to 40% by mass, particularly 15 to 35% by mass, more particularly 20 to 30% by mass, based on the total amount of a) to (c).

  In particular, the other polymerizable unsaturated monomer (c) preferably contains a vinyl aromatic compound from the viewpoint of the color developability, jetness and smoothness of the formed coating film. When the other polymerizable unsaturated monomer (c) contains a vinyl aromatic compound, the vinyl aromatic compound is generally 1 to 30% by mass, especially 3 based on the total amount of the monomers (a) to (c). It is preferable to use within the range of ˜25% by mass, more particularly 5˜20% by mass.

Copolymer (A)
The copolymer (A) is a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or a polymerization having a cationic functional group represented by the general formula (2). It can be obtained by copolymerizing the polymerizable unsaturated monomer (a), the polymerizable unsaturated monomer (b) having a polyoxyalkylene chain, and other polymerizable unsaturated monomers (c).

  The proportion of the monomers (a) to (c) used in the copolymerization is not strictly limited, and can be changed according to the physical properties desired for the copolymer to be formed.

  The copolymerization of the monomers (a) to (c) can be carried out by a method known per se, for example, a solution polymerization method in an organic solvent, an emulsion polymerization method in water, etc. Legal is preferred. As the copolymerization method by the solution polymerization method, for example, a mixture of monomers (a) to (c) and a radical polymerization initiator is dissolved or dispersed in an organic solvent, and usually 1 at a temperature of about 80 ° C. to about 200 ° C. A method of heating and polymerizing while stirring for about 10 hours can be mentioned.

  Examples of organic solvents that can be used for copolymerization include hydrocarbon solvents such as heptane, toluene, xylene, octane, mineral spirits; ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol mono Ester solvents such as butyl ether acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol and isobutanol; n-butyl ether; Ether solvents such as dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether; SWAZOL 310 manufactured by Cosmo Oil Co., Ltd. Wazoru 1000, and the like aromatic petroleum solvents such as Swasol 1500. These organic solvents can be used alone or in combination of two or more. The said organic solvent can be used in the ratio which will be normally 400 mass parts or less with respect to the total amount of monomer (a)-(c).

  Examples of the radical polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; 1,1-bis (tert-butylperoxy) -3 Peroxyketals such as 1,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate; cumene hydroperoxide Hydroperoxides such as 2,5-dimethylhexane-2,5-dihydroperoxide; 1,3-bis (tert-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5 -Di (tert-butyl pero C) Dialkyl peroxides such as hexane, diisopropylbenzene peroxide, tert-butylcumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide; Peroxycarbonates such as bis (tert-butylcyclohexyl) peroxydicarbonate; peroxyesters such as tert-butylperoxybenzoate and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane Organic peroxide polymerization initiator: 2,2′-azobisisobutyronitrile, 1,1-azobis (cyclohexane-1-carbonitrile), azocumene 2,2′-azobismethylvaleronitrile And azo polymerization initiators such as 4,4'-azobis (4-cyanovaleric acid). Although the usage-amount of these radical polymerization initiators is not specifically limited, It is 0.1-15 mass parts normally with respect to a total of 100 mass parts of monomer (a)-(c), Especially 0.3-10. It is desirable to be within the range of parts by mass.

  In the above polymerization reaction, the method of adding the monomer component and the polymerization initiator is not particularly limited, but the polymerization initiator is divided and dropped in several times from the initial polymerization to the late polymerization rather than charging all at the initial polymerization. It is preferable from the viewpoints of temperature control in the polymerization reaction and suppression of formation of unnecessary cross-linked products such as gelled products.

  The molecular weight of the copolymer (A) thus obtained is not particularly limited, but from the viewpoint of water dispersibility and the smoothness of the formed coating film, it is generally a weight average molecular weight of 5,000 to 5,000. It is preferable to be within the range of 100,000, particularly 8,000 to 70,000, more particularly 10,000 to 50,000.

  In this specification, the number average molecular weight and the weight average molecular weight are the retention time (retention capacity) measured using a gel permeation chromatograph (GPC) and the retention time of a standard polystyrene with a known molecular weight measured under the same conditions. (Retention capacity) is a value obtained by converting to the molecular weight of polystyrene. Specifically, “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) is used as the gel permeation chromatograph apparatus, and one “TSKgel G4000HXL”, two “TSKgel G3000HXL”, and A total of four “TSKgel G2000HXL” (trade name, all manufactured by Tosoh Corporation) were used, a differential refractometer was used as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: It is a value obtained by measuring under the condition of 1 mL / min.

  The copolymer (A) usually has a hydroxyl value in the range of 0 to 150 mgKOH / g, particularly 30 to 100 mgKOH / g, more particularly 50 to 90 mgKOH / g, from the viewpoint of water resistance of the formed coating film. Is preferred.

  The copolymer (A) preferably has an amine value in the range of generally 3 to 100 mgKOH / g, particularly 10 to 80 mgKOH / g, more particularly 15 to 60 mgKOH / g, from the viewpoint of color development and smoothness. is there.

  The copolymer (A) can be neutralized with an acidic neutralizer to make it water-dispersible or water-soluble. Examples of the acidic neutralizer include phosphoric acid, sulfonic acid, formic acid, acetic acid, propionic acid, n-butanoic acid, n-pentanoic acid, n-hexanoic acid, lactic acid, malic acid, and citric acid. Of these, lactic acid can be preferably used. The acidic neutralizing agents can be used alone or in combination of two or more.

  The copolymer (A) produced as described above, in the aqueous coating composition of the present invention, particularly when used as an aqueous pigment dispersion as a pigment dispersion resin, Both dispersion stabilization can be achieved. Since the monomer (a) component constituting the pigment dispersion resin has a relatively long-chain cationic functional group, the mobility of the functional group is improved, so that the pigment dispersion resin adsorbs to the pigment (B). In particular, it can work advantageously both in improving the adsorptivity to an inorganic color pigment that has been subjected to an oxidation treatment such as carbon black and in improving the dispersion stability of the resin.

  The monomer (b) component contributes to the improvement of the solubility of the pigment dispersion resin in the continuous phase (aqueous medium), and can particularly advantageously work to improve the dispersion stability of the pigment dispersion resin.

  Therefore, if the copolymer (A) is used as a pigment dispersion resin, an aqueous pigment dispersion (D) in which the pigment is uniformly dispersed can be obtained. Furthermore, when the aqueous pigment dispersion (D) is applied to the aqueous coating composition of the present invention, since the pigment is uniformly dispersed, a coating film excellent in color development and smoothness can be obtained.

  Moreover, in the aqueous coating composition of the present invention, the excellent adsorption efficiency of the copolymer (A) and the pigment (B) is to reduce the free cationic functional groups present in the aqueous coating composition. Contribute. And this prevents the thickening of the aqueous coating composition resulting from the interaction between the cationic functional group of the copolymer (A) and the acid group and the acid group of the hydroxyl group-containing acrylic resin (C), Helps improve the smoothness of the resulting coating.

  Furthermore, when a curing agent having reactivity with a hydroxyl group is used in combination, the curing agent reacts with the hydroxyl group contained in the aqueous coating composition, and the coating film obtained by the aqueous coating composition of the present invention becomes a crosslinked coating film. It helps to improve the water resistance of the coating film.

  The blending amount of the copolymer (A) in the aqueous coating composition of the present invention is preferably about 1 to 50 parts by mass, based on 100 parts by mass of the resin solid content in the aqueous coating composition. The amount is more preferably about part by mass, and further preferably about 3 to 30 parts by mass.

Aqueous pigment dispersion (D)
The aqueous pigment dispersion (D) includes the above-described copolymer (A), the pigment (B), an aqueous medium, and, if necessary, a dispersion aid, a basic neutralizer, and other additives. It can be prepared by blending. Moreover, you may use together other copolymers other than the said copolymer (A) as resin for pigment dispersion.

Pigment (B)
Examples of the pigment (B) include aluminum powder, copper powder, nickel powder, stainless steel powder, chromium powder, mica-like iron oxide, acid value titanium-coated mica powder, iron oxide-coated mica powder, and glittering graphite. Pigments: Organic red pigments such as pink EB, azo and quinacridone, organic blue pigments such as cyanine blue and cyanine green, organic yellow pigments such as benzimidazolone, isoindoline and quinophthalone; titanium oxide, Examples thereof include titanium yellow, bengara, carbon black, yellow lead, iron oxide, and inorganic coloring pigments such as various fired pigments. Further, extender pigments may be included. Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. Among them, barium sulfate and / or talc are preferably used. These pigments (B) may be subjected to a known surface treatment such as acid / base treatment, coupling agent treatment, plasma treatment, oxidation / reduction treatment and the like. Of these, inorganic color pigments that have been subjected to oxidation treatment such as carbon black are particularly suitable.

  The blending ratio of these pigments (B) is not particularly limited, but is usually 10 to 3,000 parts by weight, particularly 15 to 2,000 parts by weight, more particularly 100 parts by weight of the resin for pigment dispersion. It is preferable that it exists in the range of 15-1500 mass parts from the surface of pigment dispersibility, dispersion stability, the coloring power of the aqueous pigment dispersion (D) obtained, etc.

  Examples of the aqueous medium include water or a water-organic solvent mixed solution obtained by dissolving an organic solvent such as a water-soluble organic solvent in water. Examples of the organic solvent used here include methyl alcohol, ethyl alcohol, isopropyl alcohol, propylene glycol monopropyl ether, ethylene glycol monoble ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono Water-soluble organic solvents such as butyl ether, tripropylene glycol monomethyl ether, and 3-methyl 3-methoxybutanol; hardly soluble or insoluble organic solvents such as xylene, toluene, cyclohexanone, hexane, and pentane. These organic solvents can be used alone or in combination of two or more. As the organic solvent, those mainly composed of a water-soluble organic solvent are suitable. The mixing ratio of water and the organic solvent is not particularly limited, but the content of the organic solvent is desirably 50% by mass or less, particularly 35% by mass or less of the mixed solution. The mixing ratio of the aqueous medium is not particularly limited, but is usually 50 to 1,500 parts by weight, particularly 80 to 1,000 parts by weight, more particularly 100 to 500 parts by weight, per 100 parts by weight of the pigment dispersion resin. It is preferable that it is within the range of the parts in terms of viscosity at the time of pigment dispersion, pigment dispersibility, dispersion stability and production efficiency.

  Other copolymers used as necessary include, for example, a carboxyl group-containing polymerizable unsaturated monomer such as (meth) acrylic acid and a hydroxyl group-containing polymerizable unsaturated monomer such as 2-hydroxyethyl (meth) acrylate. And acrylic resins obtained by copolymerizing with other polymerizable unsaturated monomers in the presence of a radical polymerization initiator. The acrylic resin has a weight average molecular weight of about 2,000 to 150,000, particularly 5,000 to 100,000, an acid value of 5 to 150 mgKOH / g, particularly 15 to 100 mgKOH / g, and a hydroxyl value of 10 to 160 mgKOH. / G, particularly those in the range of 30 to 120 mg KOH / g are preferred.

  When another copolymer is used in combination, the proportion of the copolymer (A) used as the pigment dispersing resin and the other copolymer (solid content) is usually 100 parts by mass of the copolymer (A). The range of 1 to 80 parts by weight, particularly 10 to 50 parts by weight, of other copolymers is appropriate.

  The basic neutralizing agent is used to neutralize the copolymer used as a pigment dispersing resin when it has a carboxyl group, and to make the copolymer water-soluble or water-dispersed. Specific examples thereof include, for example, inorganic bases such as ammonium hydroxide, sodium hydroxide, potassium hydroxide; aminomethylpropanol, aminoethylpropanol, dimethylethanolamine, triethylamine, diethylethanolamine, dimethylaminopropanol, amino Mention may be made of amines such as methylpropanol. The blending amount of these basic neutralizing agents is about the amount necessary for water-soluble or water-dispersing the copolymer used as the pigment-dispersing resin, and usually the carboxyl group in the pigment-dispersing resin. The ratio is such that the neutralization equivalent is 0.3 to 1.5, particularly 0.4 to 1.3.

  Examples of the dispersion aid used as necessary include Disper BYK-182 and Disper BYK-180 manufactured by BYK-Chemie, Solsperse 12000 and Solsperse 27000 manufactured by Abycia, and other additives. , Antifoaming agents, antiseptics, rust inhibitors, plasticizers and the like. In consideration of the dispersibility of the pigment, the stability of the paste, the let-down stability, and the coating film performance, these blending amounts are preferably 50 parts or less with respect to 100 parts by mass of the copolymer (A). .

The aqueous pigment dispersion (D) can be prepared by uniformly mixing and dispersing the above-described components using a dispersing machine such as a paint shaker, sand mill, ball mill, LMZ mill, DCP pearl mill, and the like. it can.
Aqueous paint composition The aqueous paint composition of the present invention is prepared by mixing the aqueous pigment dispersion (D) prepared as described above with the acid group- and hydroxyl group-containing acrylic resin (C), so that it is stable in an aqueous medium. It can be obtained by dispersing it in

Acid group and hydroxyl group-containing acrylic resin (C)
The acid group- and hydroxyl group-containing acrylic resin (C) is used as one of the film-forming resins in the aqueous coating composition of the present invention.

  Examples of the acid group and hydroxyl group-containing acrylic resin (C) include a hydroxyl group-containing polymerizable unsaturated monomer, an acid group-containing polymerizable unsaturated monomer, and the hydroxyl group-containing polymerizable unsaturated monomer and the acid group-containing polymerizable unsaturated monomer. To produce other polymerizable unsaturated monomers copolymerizable with the copolymer by a method known per se, for example, a solution polymerization method in an organic solvent, an emulsion polymerization method in water, or the like. Can do.

  The hydroxyl group-containing polymerizable unsaturated monomer is a compound having at least one hydroxyl group and one polymerizable unsaturated bond in one molecule. As the hydroxyl group-containing polymerizable unsaturated monomer, for example, it can be appropriately selected from the monomer components (b) and (c1) described in the description of the copolymer (A). These can be used alone or in combination of two or more.

The acid group-containing polymerizable unsaturated monomer is a compound having at least one acid group and one polymerizable unsaturated bond in one molecule. As the acid group-containing polymerizable unsaturated monomer, for example,
Carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate;
Polymerizable unsaturated monomers having a sulfonic acid group such as 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, styrenesulfonic acid sodium salt, sulfoethyl methacrylate and its sodium salt and ammonium salt;
Examples thereof include polymerizable unsaturated monomers having a phosphoric acid group such as 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, and 2-methacryloyloxypropyl acid phosphate. These can be used alone or in combination of two or more.

Examples of other polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer and the acid group-containing polymerizable unsaturated monomer include:
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-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl ( Alkyl (meth) acrylates such as (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.);
A polymerizable unsaturated monomer having a cycloalkyl group such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate;
Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers such as isobornyl (meth) acrylate and adamantyl (meth) acrylate;
Vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene;
Polymerization having alkoxysilyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane Unsaturated monomer; perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; maleimide group Polymerizable unsaturated monomers having a photopolymerizable functional group such as N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate and the like; (meth) acrylonitrile , Nitrogen-containing polymerizable unsaturated monomers such as (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, adducts of glycidyl (meth) acrylate and amines; 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, etc. An epoxy group-containing polymerizable unsaturated monomer; a (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy Benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy- Polymerizable unsaturated monomers having UV-absorbing functional groups such as 4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone and 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole 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-tetramethylpipe Gin, 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- UV-stable polymerizable unsaturated monomers such as 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, 4-7 Vinyl alkyl ketones having 1 carbon atom (eg vinyl methyl keto , Vinyl ethyl ketone, include such polymerizable unsaturated monomer compound having a carbonyl group such as vinyl butyl ketone), which can be used either alone or in combination of two or more.

The proportion of the hydroxyl group-containing polymerizable unsaturated monomer used in the production of the acid group and hydroxyl group-containing acrylic resin (C) is preferably about 1 to 50% by mass, based on the total amount of monomer components, and 2 to 40%. About 3 mass% is more preferable, and about 3-30 mass% is further more preferable.

  The use ratio of the acid group-containing polymerizable unsaturated monomer in producing the acid group and hydroxyl group-containing acrylic resin (C) is preferably about 0.05 to 15% by mass based on the total amount of the monomer components, About 0.2-8 mass% is more preferable, and about 0.5-6 mass% is further more preferable.

The acid group and hydroxyl group-containing acrylic resin (C) preferably has a hydroxyl value of about 0.1 to 200 mgKOH / g, and about 2 to 150 mgKOH / g, from the viewpoint of water resistance of the resulting coating film. More preferably, it is more preferably about 5 to 100 mgKOH / g.

  The acid group and hydroxyl group-containing acrylic resin (C) has an acid value of 1 to 50 mgKOH / from the viewpoint of storage stability of the paint, color development of the resulting coating film, jet blackness, smoothness, water resistance, and the like. It is preferably about g, more preferably about 3 to 40 mgKOH / g, and still more preferably about 5 to 30 mgKOH / g.

  The acid group and hydroxyl group-containing acrylic resin (C) preferably has an alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms from the viewpoint of color developability, jetness, smoothness and the like of the resulting coating film. . The acid group and hydroxyl group-containing acrylic resin (C) having the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms is, for example, the same as the hydroxyl group-containing polymerizable unsaturated monomer and the acid group-containing polymerizable unsaturated monomer. Examples of other polymerizable unsaturated monomers that can be polymerized include n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, and n-hexyl. C4-C8, such as (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, etc. It is possible to produce by using an alkyl group-containing polymerizable unsaturated monomer. Kill.

  The use ratio of the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms is preferably about 5 to 30% by mass, more preferably about 10 to 25% by mass based on the total amount of the monomer components, and 15 to 15%. About 20% by mass is more preferable.

  The acid group and hydroxyl group-containing acrylic resin (C) preferably has an amide group. The acid group and hydroxyl group-containing acrylic resin (C) having an amide group is, for example, one kind of the other hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomer copolymerizable with the acid group-containing polymerizable unsaturated monomer. As, it can manufacture by using amide group containing polymerizable unsaturated monomers, such as (meth) acrylamide and N, N-dimethylaminopropyl (meth) acrylamide.

  The acid group and hydroxyl group-containing acrylic resin (C) is a water-dispersible acid group and hydroxyl group-containing acrylic having a core-shell type multilayer structure from the viewpoint of improving the smoothness and glitter of the coating film to be formed. It is preferably a resin (hereinafter referred to as “core / shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1)”).

  In the aqueous coating composition of the present invention, the core / shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1) is used alone, or the core / shell type water-dispersible acid group and hydroxyl group-containing acrylic resin ( It is preferable to use C-1) in combination with a water-soluble acid group-containing and hydroxyl group-containing acrylic resin (C-2).

As the core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1), one molecule of polymerizable unsaturated group is used from the viewpoint of improving the color developability, jetness and smoothness of the coating film to be formed. A core part which is a copolymer (I) having a polymerizable unsaturated monomer having two or more in the polymer and a polymerizable unsaturated monomer having one polymerizable unsaturated group in one molecule as a copolymerization component;
Copolymers comprising a hydroxyl group-containing polymerizable unsaturated monomer, an acid group-containing polymerizable unsaturated monomer, an alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms, and other polymerizable unsaturated monomers (II And a shell / shell type water-dispersible acid group and a hydroxyl group-containing acrylic resin (C-1-1).

  Examples of the polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule that can be used as the monomer for the core copolymer (I) include allyl (meth) acrylate, ethylene glycol di (meta) ) Acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,4-butanediol di ( (Meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1, , 1-trishydroxymethylethane di (meth) acrylate, 1,1,1-trishydroxymethylethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, Examples include diallyl terephthalate, divinylbenzene, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide. These monomers can be used alone or in combination of two or more.

  The polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule has a function of imparting a crosslinked structure to the core copolymer (I). The proportion of the polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule can be appropriately determined according to the degree of crosslinking of the core copolymer (I). Based on the total mass of monomers constituting I), it is preferably about 0.1 to 30% by mass, more preferably about 0.5 to 10% by mass, and about 1 to 7% by mass. Is more preferable.

  Examples of the polymerizable unsaturated monomer having two or more polymerizable unsaturated groups per molecule include allyl (meth) acrylate, ethylene glycol di (meta) from the viewpoint of suppressing metallic unevenness of the resulting coating film. ) Acrylate, methylene bis (meth) acrylamide, ethylene bis (meth) acrylamide and the like are preferably used. The amount used in the case of using this amide group-containing monomer is a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule and a polymerizable having one polymerizable unsaturated group in one molecule. Based on the total amount of unsaturated monomers, it is preferably about 0.1 to 25% by mass, more preferably about 0.5 to 8% by mass, and further about 1 to 4% by mass. preferable.

  The polymerizable unsaturated monomer having one polymerizable unsaturated group in one molecule that can be used as the monomer for the core copolymer (I) has two or more polymerizable unsaturated groups in one molecule. It is a polymerizable unsaturated monomer copolymerizable with a polymerizable unsaturated monomer.

  Specific examples of the polymerizable unsaturated monomer having one polymerizable unsaturated group per molecule include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl ( (Meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (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 (Meta) a Alkylate or cycloalkyl (meth) acrylate such as relate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecanyl (meth) acrylate; isobornyl (meth) acrylate, Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers such as adamantyl (meth) acrylate; polymerizable unsaturated monomers having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate; benzyl (meta ) Aromatic ring-containing polymerizable unsaturated monomers such as acrylate, styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloylio Polymerizable unsaturated monomers having an alkoxysilyl group such as cypropyltrimethoxysilane and γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate and other pars Fluoroalkyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone, ethylene, butadiene, chloroprene , Vinyl compounds such as vinyl propionate and vinyl acetate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl ( Ε- of monoesterified product of (meth) acrylic acid such as (meth) acrylate and dihydric alcohol having 2 to 8 carbon atoms, monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms Hydroxyl-containing polymerizable unsaturated monomers such as caprolactone-modified, N-hydroxymethyl (meth) acrylamide, allyl alcohol, (meth) acrylate having a polyoxyethylene chain whose molecular terminal is a hydroxyl group; (meth) acrylic acid, malee Carboxyl group-containing polymerizable unsaturated monomers such as 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) Nitrogen-containing polymerizable unsaturated monomers such as acrylamide, adducts of glycidyl (meth) acrylate and amines; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate , 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and other epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether; a polyoxyethylene chain having an alkoxy group at the molecular end (Meth) acrylate etc. which have this. These monomers can be used alone or in combination of two or more depending on the performance required for the core-shell type water-dispersible acid group and the hydroxyl group-containing acrylic resin (C-1-1).

  The use ratio of the polymerizable unsaturated monomer having one polymerizable unsaturated group per molecule is about 70 to 99.9% by mass on the basis of the total mass of monomers constituting the core part (I). Is more preferable, about 90-99.5 mass% is more preferable, and it is still more preferable that it is about 93-99 mass%.

  A hydroxyl group-containing polymerizable unsaturated monomer that can be used as a monomer for the shell copolymer (II) is a water-resistant acrylic resin by introducing a hydroxyl group that undergoes a crosslinking reaction with a curing agent into the resulting water-dispersible acrylic resin. Etc., and the function of improving the stability of the water-dispersible acrylic resin in an aqueous medium. Examples of the hydroxyl group-containing polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like ( Monoesterified product of (meth) acrylic acid and C2-C8 dihydric alcohol; ε-caprolactone modified product of monoesterified product of (meth) acrylic acid and C2-C8 dihydric alcohol; N- Examples thereof include hydroxymethyl (meth) acrylamide, allyl alcohol, and (meth) acrylate having a polyoxyethylene chain whose molecular end is a hydroxyl group. These monomers can be used alone or in combination of two or more. As the hydroxyl group-containing polymerizable unsaturated monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or the like is used. preferable.

  The use ratio of the above-mentioned hydroxyl group-containing polymerizable unsaturated monomer depends on the stability of the core-shell type water-dispersible acid group and the hydroxyl group-containing acrylic resin (C-1-1) in the aqueous medium and the water resistance of the coating film obtained. From the viewpoint of superiority, it is preferably about 1 to 40% by mass, more preferably about 4 to 25% by mass, and more preferably 7 to 19%, based on the total mass of monomers constituting the shell copolymer (II). More preferably, it is about mass%.

Examples of the acid group-containing polymerizable unsaturated monomer that can be used as the monomer for the shell copolymer (II) include carboxyl groups such as (meth) acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate. Polymerizable unsaturated monomers;
Polymerizable unsaturated monomers having a sulfonic acid group such as 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, styrenesulfonic acid sodium salt, sulfoethyl methacrylate and its sodium salt and ammonium salt;
Examples thereof include polymerizable unsaturated monomers having a phosphoric acid group such as 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, and 2-methacryloyloxypropyl acid phosphate. These can be used alone or in combination of two or more.

  The acid group-containing polymerizable unsaturated monomer preferably contains a carboxyl group-containing polymerizable unsaturated monomer. As the carboxyl group-containing polymerizable unsaturated monomer, it is particularly preferable to use acrylic acid and / or methacrylic acid. In the aqueous medium of the core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) obtained by including the carboxyl group-containing polymerizable unsaturated monomer as the other polymerizable unsaturated monomer It is possible to ensure the stability in

  When the above carboxyl group-containing polymerizable unsaturated monomer is used, the use ratio is the stability of the core-shell type water-dispersible acid group and the hydroxyl group-containing acrylic resin (C-1-1) in an aqueous medium and the coating obtained. From the viewpoint of excellent water resistance of the film, it is preferably about 1 to 30% by mass, more preferably about 5 to 25% by mass, based on the total mass of monomers constituting the shell copolymer (II). Preferably, it is about 7-19 mass%.

The alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms that can be used as the monomer for the shell copolymer (II) is a linear, branched or cyclic saturated or unsaturated alkyl having 4 to 8 carbon atoms. It is a polymerizable unsaturated monomer having a saturated hydrocarbon group. As the monomer, for example,
n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n- Polymerizable unsaturated monomers having a linear or branched saturated alkyl group such as octyl (meth) acrylate and 2-ethylhexyl (meth) acrylate;
A polymerizable unsaturated monomer having a cyclic saturated alkyl group such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, ethylcyclohexyl (meth) acrylate;
And polymerizable unsaturated monomers having a cyclic unsaturated alkyl group such as styrene, α-methylstyrene, and vinyl toluene. These monomers can be used alone or in combination of two or more.

  In addition, from the viewpoint of improving the color developability, jet blackness and smoothness of the resulting coating film, the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms has a linear or branched saturated alkyl group. It is preferable to use a polymerizable unsaturated monomer and / or a polymerizable unsaturated monomer having a cyclic unsaturated alkyl group. In particular, a polymerizable unsaturated monomer having a saturated alkyl group having 4 carbon atoms is preferred, and n-butyl (meth) acrylate and n-pentyl (meth) acrylate are more preferred.

  The proportion of the C4-C8 alkyl group-containing polymerizable unsaturated monomer used depends on the stability of the core-shell type water-dispersible acid group and the hydroxyl group-containing acrylic resin (C-1-1) in an aqueous medium. From the viewpoint of excellent water resistance of the resulting coating film, it is preferably about 30 to 80% by mass, and preferably about 40 to 70% by mass, based on the total mass of monomers constituting the shell copolymer (II). Is more preferable, and it is still more preferable that it is about 45-65 mass%.

Other polymerizable unsaturated monomers that can be used as the monomer for the shell copolymer (II) include polymerizable groups other than the hydroxyl group-containing polymerizable unsaturated monomer and the alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms. Unsaturated monomer. As the said monomer, it can select from the monomer enumerated with the said acid group and hydroxyl-containing acrylic resin (C) suitably, and can be used. For example,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) Alkyl (meth) acrylates having 1 to 3 carbon atoms or 9 or more carbon atoms such as acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.);
polymerizable unsaturated monomers having a cycloalkyl group having 9 or more carbon atoms, such as t-butylcyclohexyl (meth) acrylate and cyclododecyl (meth) acrylate;
Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers such as isobornyl (meth) acrylate and adamantyl (meth) acrylate;
Polymerization having alkoxysilyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane Unsaturated monomer; perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; maleimide group Polymerizable unsaturated monomers having a photopolymerizable functional group such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, and the like; methylene bis (meth) a Including acrylamide, ethylenebis (meth) acrylamide, (meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, adducts of glycidyl (meth) acrylate and amines Nitrogen polymerizable unsaturated monomer: glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4- Epoxy group-containing polymerizable unsaturated monomers such as epoxycyclohexylpropyl (meth) acrylate and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; -Hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2'-dihydroxy-4- (3-methacryloyl) Oxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H— Polymerizable unsaturated monomer having an ultraviolet absorbing functional group such as benzotriazole; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2 , 6,6-tetramethylpiperidine, 4- Ano-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- UV-stable polymerizable unsaturated monomers such as crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine; acrolein, Diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, Examples thereof include polymerizable unsaturated monomer compounds having a carbonyl group such as vinyl alkyl ketones having ˜7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone). It can be used in combination of more than one species.

  The proportion of other polymerizable unsaturated monomer used as the monomer for the shell part copolymer (II) is about 0 to 68% by mass based on the total mass of the monomers constituting the shell part copolymer (II). Is more preferable, about 0-51 mass% is more preferable, and it is still more preferable that it is about 0-41 mass%.

  Moreover, as another polymerizable unsaturated monomer used as a monomer for the shell copolymer (II), polymerization having two or more polymerizable unsaturated groups in one molecule from the viewpoint of improving the appearance of the obtained coating film. It is preferable that the copolymer (II) is an uncrosslinked type without using a polymerizable unsaturated monomer.

  The ratio of copolymer (I) / copolymer (II) in the core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) is determined from the viewpoint of improving the appearance of the coating film. The mass ratio is preferably about 10/90 to 90/10, more preferably about 50/50 to 85/15, and still more preferably about 65/35 to 80/20.

  The core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) preferably has a hydroxyl value of about 1 to 70 mgKOH / g from the viewpoint of excellent water resistance of the resulting coating film. More preferably, it is about 2 to 50 mgKOH / g, and further preferably about 5 to 30 mgKOH / g.

  The core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) has an acid value of 1 from the viewpoint of excellent storage stability of the coating composition and water resistance of the resulting coating film. It is preferably about ˜50 mg KOH / g, more preferably about 3 to 40 mg KOH / g, and still more preferably about 5 to 30 mg KOH / g.

  The core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) includes a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule, and a polymerizable unsaturated group. After emulsion polymerization of a monomer mixture composed of one polymerizable unsaturated monomer per molecule to obtain an emulsion of the core copolymer (I), a hydroxyl group-containing polymerizable unsaturated monomer, acid A monomer mixture comprising a group-containing polymerizable unsaturated monomer, an alkyl group-containing polymerizable unsaturated monomer having 4 to 8 carbon atoms, and other polymerizable unsaturated monomers is added, and emulsion polymerization is performed to obtain a shell copolymer ( Obtained by preparing II).

  Emulsion polymerization for preparing an emulsion of the core copolymer (I) can be performed by a conventionally known method. For example, it can be carried out by emulsion polymerization of the monomer mixture using a polymerization initiator in the presence of an emulsifier.

  As the emulsifier, an anionic emulsifier, a nonionic emulsifier and the like are suitable. Examples of the anionic emulsifier include sodium salts and ammonium salts such as alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid. Examples of nonionic emulsifiers include polyoxyethylene oleyl ether and polyoxyethylene lauryl ether. Moreover, a polyoxyalkylene group-containing anionic emulsifier; a reactive anionic emulsifier having an anionic group and a radically polymerizable unsaturated group in one molecule can also be used.

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

  Examples of the polymerization initiator include azo compounds and persulfates. 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 a reducing agent together with the said polymerization initiator as needed.

  In general, the amount of the polymerization initiator used is preferably about 0.1 to 5% by mass, more preferably about 0.2 to 3% by mass, based on the total mass of all monomers used. The method for adding the polymerization initiator is not particularly limited, and can be appropriately selected according to the type and amount thereof. For example, it may be previously contained in the monomer mixture or the aqueous medium, or may be added all at once during the polymerization, or may be added dropwise.

  The core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) is a hydroxyl group-containing polymerizable unsaturated monomer and acid group-containing emulsion in the core copolymer (I) obtained above. A monomer mixture comprising a polymerizable unsaturated monomer, a C4-C8 alkyl group-containing polymerizable unsaturated monomer, and other polymerizable unsaturated monomers is added and further polymerized to form a shell copolymer (II). Can be obtained.

  The monomer mixture forming the shell copolymer (II) can appropriately contain components such as the polymerization initiator, chain transfer agent, reducing agent, and emulsifier, if necessary. The monomer mixture can be dropped as it is, but it is desirable to drop the monomer mixture as a monomer emulsion obtained by dispersing the monomer mixture in an aqueous medium. In this case, the particle size of the monomer emulsion is not particularly limited.

  As a polymerization method of the monomer mixture for forming the shell copolymer (II), for example, the monomer mixture or an emulsion thereof is dripped in a batch or gradually, and an emulsion of the core copolymer (I) is obtained. And a method of heating to an appropriate temperature while stirring.

  The thus obtained core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) comprises a polymerizable unsaturated monomer and polymerizable unsaturated group having two or more polymerizable unsaturated groups in one molecule. A copolymer (I) of a monomer mixture composed of a polymerizable unsaturated monomer having one group in one molecule is used as a core part, a hydroxyl group-containing polymerizable unsaturated monomer, an acid group-containing polymerizable unsaturated monomer, and a carbon number of 4 It has a multilayer structure in which the shell (II) is a copolymer (II) of a monomer mixture comprising -8 alkyl group-containing polymerizable unsaturated monomers and other polymerizable unsaturated monomers.

The thus obtained core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) generally has an average particle size in the range of about 10 to 1,000 nm, particularly about 20 to 500 nm. it can.
In this specification, the average particle size of the core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1) is diluted with deionized water by a conventional method using a submicron particle size distribution analyzer. And then measured at 20 ° C. As the submicron particle size distribution measuring device, for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.

  In order to improve the mechanical stability of the particles of the core-shell type water-dispersible acid group and hydroxyl group-containing acrylic resin (C-1-1), the water-dispersible acrylic resin has an acid group such as a carboxyl group. It is desirable to neutralize with a compatibilizer. The neutralizing agent is not particularly limited as long as it can neutralize an acid group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, 2- (dimethylamino) ethanol, 2-amino-2-methyl- Examples include 1-propanol, triethylamine, and aqueous ammonia. These neutralizing agents are desirably used in such an amount that the pH of the aqueous dispersion of the water-dispersible acrylic resin after neutralization is about 6.5 to 9.0.

  As the acid group and hydroxyl group-containing acrylic resin (C), an acid group and hydroxyl group-containing acrylic resin (C) modified with a polyester and / or polyurethane resin can also be used.

  The blending amount of the acid group and hydroxyl group-containing acrylic resin (C) in the aqueous coating composition of the present invention is preferably about 2 to 70 parts by mass based on 100 parts by mass of the resin solid content in the aqueous coating composition. 10 to 55 parts by mass, more preferably about 15 to 45 parts by mass.

Film-forming resin other than acid group and hydroxyl group-containing acrylic resin (C) The aqueous coating composition of the present invention uses a film-forming resin other than acid group and hydroxyl group-containing acrylic resin (C) as required. Can do.

  As the film-forming resin other than the acid group- and hydroxyl group-containing acrylic resin (C), a known water-soluble or water-dispersible film-forming resin which has been used as a binder component of water-based paints has been used. Can do. Examples of the resin include acrylic resin, polyester resin, alkyd resin, polyurethane resin and the like, and these can be used alone or in combination of two or more. The film-forming resin preferably has a functional group such as a hydroxyl group, a carboxyl group, or an epoxy group, and particularly preferably a hydroxyl group-containing resin.

  In the present invention, the copolymer (A) used as a pigment dispersion resin in the aqueous pigment dispersion (D) is not included in the film-forming resin.

  The aqueous coating composition of the present invention may further contain a curing agent described later. When the aqueous coating composition of the present invention contains a curing agent, the film-forming resin other than the acid group and hydroxyl group-containing acrylic resin (C) usually has a functional group such as a hydroxyl group, a carboxyl group, and an epoxy group. A resin that can form a cured film by reacting with the curing agent is used. Examples of the resin include acrylic resins other than acid group- and hydroxyl group-containing acrylic resins (C), polyester resins, alkyd resins, polyurethane resins, and the like.

  Among these, the resin is preferably a hydroxyl group-containing resin, and more preferably a hydroxyl group-containing polyester resin. In addition, it is more preferable to use the acid group and hydroxyl group-containing acrylic resin (C) and the hydroxyl group-containing polyester resin in combination from the viewpoint of improving the smoothness and glossiness (flip-flop property) of the coating film. Moreover, as a ratio in the case of using together, based on the total amount of an acid group and a hydroxyl-containing acrylic resin (C) and a hydroxyl-containing polyester resin, the former is about 20-80 mass%, especially about 30-70 mass%. The latter is preferably about 80 to 20% by mass, particularly about 70 to 30% by mass.

  When the film-forming resin other than the acid group and hydroxyl group-containing acrylic resin (C) has an acid group such as a carboxyl group, the acid value is preferably about 5 to 150 mgKOH / g, and 10 to 100 mgKOH / g. More preferably, it is about 15-80 mgKOH / g. When the film-forming resin other than the acid group and hydroxyl group-containing acrylic resin (C) has a hydroxyl group, the hydroxyl value is preferably about 1 to 200 mgKOH / g, and about 2 to 180 mgKOH / g. Is more preferable, and it is still more preferable that it is about 5-170 mgKOH / g.

Hydroxyl-Containing Polyester Resin In the aqueous coating composition of the present invention, coating performance such as smoothness of the resulting coating can be improved by using a hydroxyl-containing polyester resin as the film-forming resin.

  The hydroxyl group-containing polyester resin 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 above aliphatic polybasic acids can be used alone or in combination of two or more.

  As the aliphatic polybasic acid, it is particularly preferable to use adipic acid and / or adipic anhydride from the viewpoint of the smoothness of the resulting coating film.

  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 or in combination of 2 or more types.

  As said alicyclic polybasic acid, from a smoothness viewpoint of the coating film obtained, 1, 2- cyclohexane dicarboxylic acid, 1, 2- cyclohexane dicarboxylic acid anhydride, 1, 3- cyclohexane dicarboxylic acid, 1, 4 -Cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic anhydride are preferably used, among which 1,2-cyclohexanedicarboxylic acid and / or 1,2 -More preferred is the use of cyclohexanedicarboxylic anhydride.

  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 aromatic polybasic acids can be used alone or in combination of two or more.

  As the aromatic polybasic acid, it is preferable to use phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, or trimellitic anhydride.

  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 and hydrogenated bisphenol F; polylactone diols obtained by adding lactones such as ε-caprolactone to these dihydric alcohols; ester diols such as bis (hydroxyethyl) terephthalate; alkylenes of bisphenol A Oxide adducts, polyether diols such as polyethylene glycol, polypropylene glycol, polybutylene glycol; glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6- Trivalent or higher alcohols such as hexanetriol, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl) isocyanuric acid, sorbitol, mannitol; lactones such as ε-caprolactone are added to these trivalent or higher alcohols And polylactone polyols.

  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 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. . Moreover, 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. Moreover, after synthesizing a carboxyl group-containing polyester resin, the above 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 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 alone or in admixture of two or more.

  In addition, as the hydroxyl group-containing polyester resin, from the viewpoint of excellent smoothness and water resistance of the resulting coating film, the content of the alicyclic polybasic acid in the raw acid component is based on the total amount of the acid component. What is about 20-100 mol% is preferable, What is about 25-95 mol% is more preferable, What is about 30-90 mol% is still more preferable. In particular, the alicyclic polybasic acid is preferably 1,2-cyclohexanedicarboxylic acid and / or 1,2-cyclohexanedicarboxylic anhydride from the viewpoint of excellent smoothness of the resulting coating film.

  The hydroxyl group-containing polyester resin preferably has a hydroxyl value of about 1 to 200 mgKOH / g, more preferably about 2 to 180 mgKOH / g, and still more preferably about 5 to 170 mgKOH / g. Further, when the hydroxyl group-containing polyester resin further has a carboxyl group, the acid value thereof is preferably about 5 to 150 mgKOH / g, more preferably about 10 to 100 mgKOH / g, and 15 to 80 mgKOH / g. More preferably, it is about. The number average molecular weight of the hydroxyl group-containing polyester resin is preferably about 500 to 50,000, more preferably about 1,000 to 30,000, and about 1,200 to 10,000. Is more preferable.

  As the hydroxyl group-containing polyester resin, a hydroxyl group-containing polyester resin modified with a polyurethane resin can also be used.

  When the aqueous coating composition according to the present invention contains a hydroxyl group-containing polyester resin, the amount of the hydroxyl group-containing polyester resin is about 2 to 70 parts by mass based on 100 parts by mass of the resin solid content in the aqueous coating composition. It is preferably about 10 to 55 parts by mass, and more preferably about 20 to 45 parts by mass.

Curing agent The curing agent used as necessary reacts with the functional group such as hydroxyl group, carboxyl group, epoxy group, etc. in the copolymer (A) and the film-forming resin, and the aqueous coating composition of the present invention. Is a compound capable of curing. Examples of the curing agent include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, carbodiimide group-containing compounds, and the like. Of these, amino resins that can react with hydroxyl groups, blocked polyisocyanate compounds, and carbodiimide group-containing compounds that can react with carboxyl groups are preferred, and amino resins are particularly preferred. A hardening | curing agent can be used individually 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-ethylbutanol, 2-ethylhexanol and the like. .

  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.

  The melamine resin preferably has a weight average molecular weight of about 400 to 6,000, more preferably about 800 to 5,000, and still more preferably about 1,000 to 4,000. Most preferably, it is about 1,200 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 238”, “Cymel 251”, “Cymel 303”, “Cymel 323”, “Cymel 324”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 385”, “Cymel 1156”, “Cymel 1158”, “Cymel 1116”, “Cymel 1130” (above, made by Nippon Cytec Industries, Inc.), “Uban 120”, “ “Uban 20HS”, “Uban 20SE60”, “Uban 2021”, “Uban 2028”, “Uban 28-60” (manufactured by Mitsui Chemicals, Inc.), and the like.

  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 blocking agent include oximes, phenols, alcohols, lactams, mercaptans, and the like.

  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, cyclohexane. Cycloaliphatic diisocyanates such as silylene diisocyanate and isophorone diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate; 2-isocyanate Natoethyl-2,6-diisocyanatocaproate, 3 Trivalent or higher organic polyisocyanate compounds such as isocyanatomethyl-1,6-hexamethylene diisocyanate and 4-isocyanatomethyl-1,8-octamethylene diisocyanate (common name: triaminononane triisocyanate); these polyisocyanate compounds And dimers or trimers of the following: a prepolymer obtained by subjecting these polyisocyanate compound and polyhydric alcohol, low molecular weight polyester resin or water to a urethanization reaction under an excess of isocyanate groups.

  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. As the carbodiimide group-containing compound, it is preferable to use a polycarbodiimide compound having at least two carbodiimide groups in one molecule.

  As said polycarbodiimide compound, it is preferable to use a water-soluble or water-dispersible polycarbodiimide compound from viewpoints, such as smoothness of the coating film obtained. As the water-soluble or water-dispersible polycarbodiimide compound, any polycarbodiimide compound that can be stably dissolved or dispersed in an aqueous medium can be used without particular limitation.

  Specific examples of the water-soluble polycarbodiimide compound include “Carbodilite SV-02”, “Carbodilite V-02”, “Carbodilite V-02-L2”, and “Carbodilite V-04” (all manufactured by Nisshinbo Co., Ltd.). , Product name), etc. can be used. Moreover, as said water dispersible polycarbodiimide compound, "Carbodilite E-01", "Carbodilite E-02" (all are the Nisshinbo Co., Ltd. make, brand name) etc. can be used, for example.

  The said polycarbodiimide compound can be used individually or in combination of 2 or more types, respectively.

  In the water-based coating composition according to the present invention, the blending ratio of the film-forming resin and the curing agent is from 30 to 95 based on the total amount of both from the viewpoint of improving the smoothness and water resistance of the coating film. About 50% by mass, preferably about 50 to 90% by mass, more preferably about 60 to 80% by mass, the latter being about 5 to 70% by mass, preferably about 10 to 50% by mass, more preferably 20 to 40% by mass. It is preferable that it is about.

  The aqueous medium can be appropriately selected from the aqueous media described in the description of the aqueous pigment dispersion of the present invention.

  In the aqueous coating composition of the present invention, if necessary, a curing catalyst, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a thickener, a rust inhibitor, a plasticizer, an organic solvent, a surface conditioner, An anti-settling agent or the like can be appropriately contained.

When the polyisocyanate compound which may be blocked as a curing agent is used as the curing catalyst, organometallic catalysts such as dibutyltin diacetate, dibutyltin dioctate and dibutyltin dilaurate; amines such as triethylamine and diethanolamine In the case of using an amino resin such as a melamine resin as a curing agent, a sulfonic acid compound such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, or a sulfonic acid thereof. An amine neutralized product of the compound can be preferably used.

  Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, cyanoacrylate-based, salicylate-based, and oxalic acid anilide-based compounds.

  Examples of the ultraviolet stabilizer include hindered amine compounds.

  The substrate to which the water-based coating composition of the present invention can be applied is not particularly limited. For example, iron, aluminum, brass, copper plate, stainless steel plate, tin plate, galvanized steel plate, alloyed zinc (Zn- Al, Zn-Ni, Zn-Fe, etc.) Metal materials such as plated steel sheets; polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, Resins such as epoxy resins and various plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials (paper, cloth, etc.), among others, metal materials and plastic materials Is preferred.

  In addition, the article to which the water-based coating composition of the present invention can be applied is not particularly limited, but includes an outer plate part of an automobile body such as a passenger car, a truck, a motorcycle, and a bus; an automobile part; An outer plate portion of a household electric product can be used, and among them, an outer plate portion of an automobile body and an automobile part are preferable.

  Further, the object to be coated may be one in which a surface treatment such as a phosphate treatment, a chromate treatment or a complex oxide treatment is performed on a metal surface such as the metal material or a vehicle body formed from the metal material. Furthermore, the object to be coated may be one in which an undercoat film and / or an intermediate coat film such as various electrodeposition paints are formed on the metal base material or the vehicle body. The undercoat and / or intermediate coat may be heat-cured or uncured.

  The coating method of the aqueous coating composition of the present invention is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, and the like. A film can be formed. These coating methods may be electrostatically applied as necessary. Of these, air spray coating and rotary atomization coating are preferred. The coating amount of the water-based coating composition is usually 5 to 70 μm, preferably about 10 to 50 μm as a cured film thickness.

  The wet coating film is cured by applying the aqueous coating composition of the present invention to an object to be coated and then heating. Heating can be performed by a heating means known per se. For example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be used. The heating temperature is usually within the range of about 80 to about 180 ° C, preferably about 100 to about 170 ° C, more preferably about 120 to about 160 ° C. The heating time is not particularly limited, but is usually 10 to 40 minutes, preferably about 15 to 30 minutes.

  The aqueous paint composition of the present invention can be used as a colored paint composition (including metallic paint and interference color paint) in which various pigments such as a color pigment, a metallic pigment, and an interference color pigment are blended. Among them, it can be suitably used as a paint for automobiles. As an aqueous base coat paint in a coating method in which a water-based base coat paint containing a glitter pigment and / or a color pigment is applied on an object to be coated, and then a clear paint is applied. It can be preferably used.

  When the aqueous coating composition of the present invention is used as an aqueous base coat coating, for example, the aqueous coating composition of the present invention is applied on a coating object that has been subjected to electrodeposition coating and / or intermediate coating to form a coating. Without coating the film, a clear coating is applied on the uncured coating, and then the uncured coating and the clear coating are heated and cured at the same time to form a multi-layer coating. It can be shown. The uncured coating includes a touch-dried coating and a semi-cured drying coating.

  When the aqueous coating composition of the present invention is applied by a 2-coat 1-bake method, the aqueous coating composition has a cured film thickness of usually 5 to 40 μm, preferably 10 to 30 μm, more preferably 10 to 20 μm. The clear coating can be applied so that the cured film thickness is usually in the range of 10 to 80 μm, preferably 15 to 60 μm.

  Moreover, when forming a multilayer coating film by said 2 coat 1 baking system, from a viewpoint of preventing generation | occurrence | production of coating-film defects, such as a repellency, a coating film is substantially after the application of the aqueous coating composition of this invention. It is preferable to perform preheating (preliminary heating), air blowing, etc. under heating conditions that do not harden. The preheating can be performed usually at a temperature of about 40 to about 100 ° C, preferably about 50 to about 90 ° C, more preferably about 60 to about 80 ° C, and the preheating time is usually 30 seconds to 15 minutes, Preferably it is 1-10 minutes, More preferably, it can be about 2-5 minutes. The air blow can be usually performed by blowing air heated to a normal temperature or a temperature of about 25 to about 80 ° C. on the coated surface of the object to be coated. In addition, after application of the clear paint, an interval of about 1 to 60 minutes, preferably about 3 to 20 minutes at room temperature, or a preheating at a temperature of about 40 to about 80 ° C. for about 1 to 60 minutes, if necessary. The coating can then be heat cured.

  The aqueous coating composition and the clear coating can be carried out by the above-mentioned heating means known per se, usually about 80 to about 180 ° C., preferably about 100 to about 170 ° C., more preferably about 120 to about 160 ° C. It is suitable to heat both coatings at the same temperature for 10 to 40 minutes, preferably 15 to 30 minutes.

  Further, the water-based coating composition of the present invention comprises applying an intermediate coating on an object to be coated, applying a base coating on the uncured intermediate coating without curing the coating, By a 3-coat 1-bake method in which a clear coating is applied on the uncured base coat without curing the coating, and three layers of the intermediate coating, base coating and clear coating are heated and cured simultaneously. In the multilayer coating film forming method, it can be suitably used as an intermediate coating material and / or a base coating material.

  When the aqueous coating composition of the present invention is applied by the above-mentioned three-coat one-bake method, the intermediate coating is preferably applied so that the cured film thickness is usually in the range of 10 to 60 μm, preferably 20 to 40 μm. The base coat paint is preferably applied so that the cured film thickness is usually in the range of 5 to 40 μm, preferably 10 to 30 μm, more preferably 10 to 20 μm, and the clear paint is a cured film thickness. In general, it is preferable that the coating is performed so as to be within a range of 10 to 80 μm, preferably 15 to 60 μm.

  In addition, when the aqueous coating composition of the present invention is used as an intermediate coating and / or base coating, preheating (preheating) under heating conditions in which the coating film is not substantially cured after application of the aqueous coating composition, Air blow or the like may be performed. The preheating can be performed usually at a temperature of about 40 to about 100 ° C, preferably about 50 to about 90 ° C, more preferably about 60 to about 80 ° C, and the preheating time is usually 30 seconds to 15 minutes, Preferably it is 1-10 minutes, More preferably, it can be about 2-5 minutes. The air blow can be usually performed by blowing air heated to a normal temperature or a temperature of about 25 to about 80 ° C. on the coated surface of the object to be coated. In addition, after the application of the clear paint, an interval of 1 to 60 minutes, preferably 3 to 20 minutes is provided at room temperature as necessary, or preheating is performed at a temperature of about 40 to about 80 ° C. for about 1 to 60 minutes. The coating can then be heat cured.

  Curing of the coating film can be carried out by the above-mentioned heating means known per se, usually at a temperature of about 80 to about 180 ° C., preferably about 100 to about 170 ° C., more preferably about 120 to about 160 ° C. It is suitable to cure the three-layer coating film simultaneously by heating for about 40 minutes, preferably about 15-30 minutes.

  By using the aqueous coating composition of the present invention, a coating film excellent in coating film performance and appearance can be formed. Therefore, the aqueous coating composition of the present invention can be suitably used as an automotive coating material.

  When the aqueous coating composition of the present invention is used as an intermediate coating, a thermosetting base coating known per se can be used as the base coating, specifically, for example, an alkyd resin, a polyester resin, A coating material containing a base resin such as an acrylic resin or a urethane resin and a curing agent such as an amino resin, a polyisocyanate compound, a block polyisocyanate compound, or a carbodiimide group-containing compound can be used. As the base coat paint, from the viewpoint of environmental problems, resource saving, etc., a high solid type paint or water-based paint with a small amount of organic solvent used can be suitably used.

  When the aqueous paint composition of the present invention is used as a base coat paint, a known thermosetting intermediate coat paint can be used as the intermediate coat paint. Specifically, for example, an alkyd resin or a polyester resin can be used. A coating material comprising a base resin such as an acrylic resin or a urethane resin and a curing agent such as an amino resin, a polyisocyanate compound, a block polyisocyanate compound, or a carbodiimide group-containing compound can be used. As the intermediate coating material, from the viewpoint of environmental problems and resource saving, a high solid type coating material, a water-based coating material, a powder coating material, etc. with a small amount of organic solvent used can be suitably used.

  In addition, as the clear paint, for example, a known paint that is usually used in the painting of automobile bodies can be used. Specifically, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, an epoxy resin, or a fluororesin having a crosslinkable functional group such as a hydroxyl group, a carboxyl group, an epoxy group, or a silanol group, and a melamine resin, Urea resin, optionally blocked polyisocyanate compound, carboxyl group-containing compound or resin, epoxy group-containing compound or resin-containing organic solvent-based thermosetting paint, aqueous thermosetting paint, Examples thereof include thermosetting powder coatings. Among these, a thermosetting paint containing a carboxyl group-containing resin and an epoxy group-containing resin and a thermosetting paint containing a hydroxyl group-containing resin and a polyisocyanate compound which may be blocked are suitable.

  Further, the form of the clear coating composition is not particularly limited, and may be any form such as an organic solvent type, a non-aqueous dispersion type, an aqueous solution type, an aqueous dispersion (slurry) type, a high solid type, and a powder type. Can be used.

  If necessary, the clear paint may contain coloring pigments, glitter pigments, dyes and the like to such an extent that the transparency of the formed coating film is not hindered. An agent, a light stabilizer, an antifoaming agent, a thickener, a rust inhibitor, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent and the like can be appropriately contained.

  Hereinafter, the present invention will be described more specifically with reference to examples. The scope of the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively, unless otherwise specified. Moreover, the film thickness of a coating film is based on a cured coating film.

Synthesis of monomer component (a) Production Example 1
77.6 parts of 2-methacryloyloxyethyl isocyanate and 0.06 parts of p-methoxyphenol were added to a four-necked reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, an air introduction tube and a dropping device. . Next, 37.6 parts of dimethylaminomethanol was added dropwise over 1 hour while agitating dry air in the reaction vessel and keeping the temperature at 30 ° C. or lower while stirring. After completion of dropping, the mixture was aged by stirring at 30 ° C. for 2 hours to obtain a polymerizable unsaturated monomer (a1) having an active ingredient of 100%. The monomer is a monomer in which R ² is a methylene group and R ³ is a methyl group in the general formula (1).
Production Example 2
77.6 parts of 2-methacryloyloxyethyl isocyanate and 0.06 parts of p-methoxyphenol were added to a four-necked reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, an air introduction tube and a dropping device. . Next, 44.6 parts of 2- (dimethylamino) ethanol was added dropwise over 1 hour while agitating dry air in the reaction vessel and keeping the temperature at 30 ° C. or lower while stirring. After completion of dropping, the mixture was aged by stirring at 30 ° C. for 2 hours to obtain a polymerizable unsaturated monomer (a2) having 100% of the active ingredient. This monomer is a monomer in which R ² is an ethylene group and R ³ is a methyl group in the general formula (1).
Production Example 3
77.6 parts of 2-methacryloyloxyethyl isocyanate and 0.07 part of p-methoxyphenol were added to a four-necked reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, an air introduction tube and a dropping device. . Next, 58.6 parts of 4-dimethylamino-1-butanol was added dropwise over 1 hour while agitating dry air in the reaction vessel and keeping the temperature at 30 ° C. or lower while stirring. After completion of dropping, the mixture was aged by stirring at 30 ° C. for 2 hours to obtain a polymerizable unsaturated monomer (a3) having 100% active ingredient. The monomer is a monomer in which R ² is a butylene group and R ³ is a methyl group in the general formula (1).
Production Example 4
77.6 parts of 2-methacryloyloxyethyl isocyanate and 0.08 part of p-methoxyphenol were added to a four-necked reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, an air introduction tube and a dropping device. . Next, 72.6 parts of 6-dimethylamino-1-hexanol was added dropwise over 1 hour while agitating dry air in the reaction vessel and keeping the temperature at 30 ° C. or lower while stirring. After completion of dropping, the mixture was aged by stirring at 30 ° C. for 2 hours to obtain a polymerizable unsaturated monomer (a4) having 100% of the active ingredient. The monomer is a monomer in which R ² is a hexylene group and R ³ is a methyl group in the general formula (1).
Production Example 5
To a four-necked reaction vessel equipped with a thermometer, thermostat, stirrer and air inlet tube, 252 parts of methyl methacrylate, 159.7 parts of 6-dimethylamino-1-hexanol and 3.99 parts of phenothiazine were added, and the mixture was The reaction was carried out at 95 degrees for 1 hour with stirring. Next, the reaction mixture was cooled to 90 ° C., 1.73 parts of di-n-butyltin oxide was added, and the mixture was reacted at 90 to 115 ° C. for 6 hours. Meanwhile, the reaction was carried out while removing the azeotrope. After the reaction, the pressure in the reactor was gradually reduced to obtain a polymerizable unsaturated monomer (a5) having an active ingredient of 100%. The monomer is a monomer in which R ⁴ is a hexylene group and R ³ is a methyl group in the general formula (2).
Production Example 6
In a four-necked reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, air inlet tube and dropping device, 252 parts of methyl methacrylate, 190.6 parts of 8-dimethylamino-1-octanol and phenothiazine 77 parts were added, and the mixture was reacted at 95 ° C. for 1 hour while stirring. Next, the reaction mixture was cooled to 90 ° C., 1.73 parts of di-n-butyltin oxide was added, and the mixture was reacted at 90 to 115 ° C. for 6 hours. Meanwhile, the reaction was carried out while removing the azeotrope. After the reaction, the pressure in the reactor was gradually reduced to obtain a polymerizable unsaturated monomer (a6) having an active ingredient of 100%. The monomer is a monomer in which R ⁴ is an octylene group and R ³ is a methyl group in the general formula (2).
Production Example 7
In a four-necked reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, air inlet tube and dropping device, 252 parts of methyl methacrylate, 128.9 parts of 4-dimethylamino-1-butanol and phenothiazine 22 parts were added, and the mixture was reacted at 95 ° C. for 1 hour while stirring. Next, the reaction mixture was cooled to 90 ° C., 1.73 parts of di-n-butyltin oxide was added, and the mixture was reacted at 90 to 115 ° C. for 6 hours. Meanwhile, the reaction was carried out while removing the azeotrope. After the reaction, the pressure in the reactor was gradually reduced to obtain a polymerizable unsaturated monomer (a7) having 100% active ingredient. The monomer is a monomer in which R ⁴ is a butylene group and R ³ is a methyl group in the general formula (2).
Production Example 8
77.6 parts of 2-methacryloyloxyethyl isocyanate and 0.08 part of p-methoxyphenol were added to a four-necked reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, an air introduction tube and a dropping device. . Next, 86.7 parts of 8-dimethylamino-1-octanol was added dropwise over 1 hour while agitating dry air in the reaction vessel and keeping the temperature at 30 ° C. or lower while stirring. After completion of dropping, the mixture was aged at 30 ° C. for 2 hours to obtain a polymerizable unsaturated monomer (a8) having an active ingredient of 100%. The monomer is a monomer in which R ² is an octylene group and R ³ is a methyl group in the general formula (1).

Production of copolymer (A) Production Example 9
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 15 parts of propylene glycol monomethyl ether and 25 parts of propylene glycol monobutyl ether, and heated and stirred to maintain at 110 ° C. Among them, 14.8 parts of the monomer (a1) obtained in Production Example 1, “NF biisomer S20W” (trade name, manufactured by Degussa, R ⁵ in the general formula (3) is a methyl group, and R ⁶ is a methyl group. Group, R ⁷ is ethylene group, m is 45, methoxypolyethylene glycol monomethacrylate having a molecular weight of about 2,000, 50% water diluted product) 40 parts (solid content 20 parts), 2-hydroxyethyl acrylate 10 parts , 27.6 parts of methyl methacrylate, 27.6 parts of n-butyl acrylate, 1 part of azobisisobutyronitrile and 20 parts of propylene glycol monomethyl ether were added dropwise over 3 hours. After completion of the dropwise addition, the mixture was aged at 110 ° C. for 30 minutes, and then an additional catalyst mixture composed of 15 parts of propylene glycol monomethyl ether and 0.5 part of azobisisobutyronitrile was added dropwise over 1 hour. Further, the mixture was aged at 110 ° C. for 1 hour and then cooled to obtain a copolymer (A1) having a solid content of 50%.
Production Examples 10-29
In Production Example 9, copolymers (A2) to (A15) and (AC1) to (AC6) were obtained in the same manner as in Production Example 9 except that the component composition and the blending ratio are as shown in Table 1 below. It was. The solid content, amine value, hydroxyl value and weight average molecular weight of the obtained copolymer are shown in Table 1 below. In addition, the amount of each polymerizable unsaturated monomer in the following Table 1 is a solid content.

(Note 1) MPEG1000: trade name, manufactured by Degussa, R ⁵ in the general formula (3) is a methyl group, R ⁶ is a methyl group, R ⁷ is an ethylene group, m is 21, and the molecular weight is about 1,000. Methoxypolyethylene glycol monomethacrylate that is above.
(Note 2) Dimethylaminoethyl methacrylate (Note 3) Dimethylaminopropylacrylamide
Aqueous pigment dispersion:
Production and production example 30 of aqueous pigment dispersion (D)
In a stirring and mixing container, 200 parts of the copolymer (A1) obtained in Production Example 9 (100 parts of solid content), 60 parts of “Raven5000UIII” (trade name, manufactured by Columbian Carbon Co., Ltd., carbon black pigment) and 750 deionized water. A portion was added and mixed uniformly. Next, the obtained mixed liquid was put into a wide-mouth glass bottle having a capacity of 225 cc, and zirconia beads having a diameter of about 0.5 mmφ were added as a dispersion medium and sealed, and dispersed in a paint shaker for 5 hours to form an aqueous pigment dispersion (D1). Got.

Production Examples 31-58
In Production Example 30, aqueous pigment dispersions (D2) to (D21) and (DC1) to (DC8) were obtained in the same manner as in Production Example 30, except that the composition was as shown in Table 2 below.

In the case of using the copolymers (AC5) and (AC6), since the pigment could not be dispersed, the subsequent evaluation was not performed.
(* 4) Cyanine Blue 5206: manufactured by Dainichi Seika Kogyo Co., Ltd., trade name, organic blue pigment (* 5) S # 12000: manufactured by Avicia, wetting and dispersing agent, trade name "Solsperse 12000"
(Note 6) RT355D: BASF Corporation organic red pigment, trade name “Shinkasha Magenta RT355D”

Water-based paint composition:
Synthesis of film-forming resin
Synthetic production example 59 of acid group- and hydroxyl group-containing acrylic resin (C)
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device, 128 parts of deionized water, “ADEKA rear soap SR-1025” (trade name, manufactured by ADEKA, emulsifier, active ingredient 25 %) 2 parts were charged, stirred and mixed in a nitrogen stream, and heated to 80 ° C.

  Next, 1% of the total amount of the following monomer emulsion for core part and 5.3 parts of 6% ammonium persulfate aqueous solution were introduced into the reaction vessel and kept at 80 ° C. for 15 minutes. Thereafter, the remainder of the monomer emulsion for the core part was dropped into a reaction vessel maintained at the same temperature over 3 hours, and aging was performed for 1 hour after completion of the dropping. Next, the following monomer emulsion for shell part was added dropwise over 1 hour, and after aging for 1 hour, it was cooled to 30 ° C. while gradually adding 40 parts of 5% 2- (dimethylamino) ethanol aqueous solution to the reaction vessel, The product was discharged while being filtered through a 100-mesh nylon cloth to obtain an acid group and hydroxyl group-containing acrylic resin (C1) having an average particle size of 100 nm, a solid content of 30%, an acid value of 0.5 mgKOH / g, and a hydroxyl value of 25 mgKOH / g.

  Monomer emulsion for core part: 40 parts of deionized water, 2.8 parts of “ADEKA rear soap SR-1025”, 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 of ethyl acrylate The monomer emulsion for the core part was obtained by mixing and stirring the part and 21 parts of n-butyl acrylate.

  Monomer emulsion for shell part: 17 parts of deionized water, 1.2 parts of “ADEKA rear soap SR-1025”, 0.03 part of ammonium persulfate, 3 parts of styrene, 5.1 parts of 2-hydroxyethyl acrylate, 0 part of methacrylic acid .1 part, 5 parts of methyl methacrylate, 1.8 parts of ethyl acrylate and 15 parts of n-butyl acrylate were mixed and stirred to obtain a monomer emulsion for shell part.

Production Examples 60-70
In Production Example 59, aqueous pigment dispersions (C2) to (C10), (CC1) and (CC2) were obtained in the same manner as in Production Example 59 except that the composition was as shown in Table 3 below.

Production Production Example 71 of Hydroxyl-Containing Polyester Resin 71
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of 1,2-cyclohexanedicarboxylic acid anhydride and adipine 120 parts of acid was charged, and the temperature was raised from 160 ° C. to 230 ° C. over 3 hours, followed by a condensation reaction at 230 ° C. for 4 hours. Subsequently, in order to introduce a carboxyl group into the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was added and reacted at 170 ° C. for 30 minutes, and then 2-ethyl-1-hexanol (20 Diluted with 100 g of water at 0.1 ° C. at a temperature of 0.1 g), a hydroxyl group-containing polyester resin solution having a solid content of 70%, an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, and a number average molecular weight of 1,400 (E1) was obtained.

Production of aqueous coating composition Example 1
In the stirring and mixing container, 84.2 parts of the aqueous pigment dispersion (D1) obtained in Production Example 30, 168 parts of the acid group and hydroxyl group-containing acrylic resin (C4) obtained in Production Example 62, and the hydroxyl group containing obtained in Production Example 71 26.2 parts of polyester resin (E1), 41.7 parts of melamine resin (F1) (methyl-butyl mixed etherified melamine resin, solid content 60%, weight average molecular weight 2,000), and mixed uniformly, Furthermore, “Primal ASE-60” (trade name, manufactured by Rohm and Haas, polyacrylic acid-based thickener), 2- (dimethylamino) ethanol and deionized water were added to adjust pH to 8.0, solid content of 25%, Ford Cup No. 20 at 20 ° C. An aqueous coating composition (X1) having a viscosity of 50 according to 4 was obtained.

Examples 2-30 and Comparative Examples 1-10
In Example 1, the Ford Cup No. at pH 8.0, solid content of 25%, 20 ° C. was prepared in the same manner as in Example 1 except that the formulation was as shown in Table 4 below. Water-based paint compositions (X2) to (X30) and (XC1) to (XC10) having a viscosity of 50 according to 4 were obtained. Subsequently, each water-based paint composition was subjected to a performance test based on the following test method. The results are also shown in Table 4.
Performance test About each water-based coating composition obtained in the said Examples 1-30 and Comparative Examples 1-10, the performance test was done based on the following test method.

Preparation method of test coating film "ELECRON GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin based cationic electrodeposition coating) on a cold-rolled steel sheet treated with zinc phosphate so that the cured film thickness is 20 μm. Electrodeposition coating was performed and cured by heating at 170 ° C. for 30 minutes to prepare a cured electrodeposition coating film. Next, an intermediate coating “WP-503T” (trade name, manufactured by Kansai Paint Co., Ltd., polyester resin-based aqueous intermediate coating) is applied onto the cured electrodeposition coating film using a rotary atomizing bell-type coating machine. The film was electrostatically coated to a thickness of 20 μm, allowed to stand for 3 minutes, then preheated at 80 ° C. for 3 minutes to obtain a test coating.

  On the test object, each aqueous coating composition obtained in the above Examples and Comparative Examples was applied to a cured film thickness of 15 μm using a rotary atomizing bell type coating machine. After standing for a minute, preheating was performed at 80 ° C. for 3 minutes. Next, Magiclon KINO-1210 (trade name, manufactured by Kansai Paint Co., Ltd., acrylic resin-based solvent-type clear coating) was applied on the uncured coating surface so as to have a cured film thickness of 35 μm. A test plate was prepared by heating at 30 ° C. for 30 minutes to simultaneously cure the three-layer coating film.

Test Method The smoothness and color developability of each test coating film were evaluated as follows. The test results are shown in Table 4 below.

Smoothness:
Evaluation was performed using the Wb value measured by “Wave Scan DOI” (trade name, manufactured by BYK Gardner). It shows that the smoothness of a coating surface is so high that a measured value is small.

Color development:
For the above-mentioned coating film, “MA-68II” (trade name, manufactured by X-Rite, multi-angle spectrocolorimeter) was used. The L * value (L * 45) was measured for the light in the direction perpendicular to the measurement target surface (light received at an angle of 45 ° with respect to the regular reflection light) among the reflected light irradiated with the light D65. The aqueous paint compositions (X25) to (X30) and (XC7) to (XC10), which are paint compositions other than black, were evaluated for color developability with a value of L * 45. In addition to the L * 45 value, the aqueous coating compositions (X1) to (X24) and (XC1) to (XC6), which are black coating compositions, were irradiated with standard light D65 from angles of 25 ° and 75 °. Time L * values (L * 25 and L * 75, respectively) were measured and evaluated as the sum of three values. The lower the measured value, the better the color developability.

Claims (7)

(A) (a) a polymerizable unsaturated monomer having a cationic functional group represented by general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by general formula (2), (b A copolymer obtained by copolymerizing a polymerizable unsaturated monomer having a polyoxyalkylene chain, and (c) another polymerizable unsaturated monomer by a solution polymerization method in an organic solvent,
(B) a pigment, and (C) a method for producing an aqueous coating composition containing an acid group and a hydroxyl group-containing acrylic resin ,
The copolymer (A) and the pigment (B) are mixed to obtain an aqueous pigment dispersion (D), and the aqueous pigment dispersion (D) is mixed with an acid group- and hydroxyl group-containing acrylic resin (C). A method for producing a water-based coating composition characterized by the above.
General formula (1)

[Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms]
General formula (2)

[Wherein, R ¹ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 6 to 10 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms] The polymerizable unsaturated monomer (b) having a polyoxyalkylene chain is represented by the general formula (3)

[Wherein R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁷ represents an alkylene group having 2 to 4 carbon atoms, and m represents 3 to 3 Represents an integer of 150, and the m oxyalkylene units (R ⁷ O) may be the same as or different from each other]
The method for producing an aqueous coating composition according to claim 1, wherein the compound is represented by the formula:   The method for producing an aqueous coating composition according to claim 1 or 2, wherein the other polymerizable unsaturated monomer (c) contains a hydroxyl group-containing polymerizable unsaturated monomer (c1) having no polyoxyalkylene chain. Copolymer (A) is based on the total amount of monomers (a) to (c),
3 to 35% by mass of a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (1) and / or a polymerizable unsaturated monomer having a cationic functional group represented by the general formula (2) (a)
5-40% by mass of a polymerizable unsaturated monomer (b) having a polyoxyalkylene chain,
And other polymerizable unsaturated monomer (c) 25-92 mass%
The method for producing an aqueous coating composition according to any one of claims 1 to 3, wherein the aqueous coating composition is obtained by copolymerization of   The method for producing an aqueous coating composition according to any one of claims 1 to 4, wherein the acid value of the acid group- and hydroxyl group-containing acrylic resin (C) is 1 to 50 mgKOH / g.   Furthermore, the manufacturing method of the water-based coating composition of any one of Claim 1 thru | or 5 containing a melamine resin.   The method for producing an aqueous coating composition according to any one of claims 1 to 6, further comprising a hydroxyl group-containing polyester resin.