JP2002155232A - Aqueous paint composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating composition excellent in retort resistance, workability, adhesion, and hardness as a coating for the outer surface of a metal can or a drawn can coated with a polyester film. And SOLUTION: An acrylic copolymer (a) obtained by copolymerizing the following (1) to (4) at a specific copolymerization ratio (a) is 30 to 85% by weight, and an aqueous amino resin (b) is 15 to 70% by weight. (A total amount of the acrylic copolymer (a) and the aqueous amino resin is 100% by weight). (1) α, β-monoethylenically unsaturated carboxylic acid,
(2) a (meth) acrylate monomer having a basic alkylamino group at the terminal, (3) N-alkoxymethyl (meth) acrylamide, (4) the above (1),
(Meth) acrylate monomers and / or vinyl monomers copolymerizable with (2) and (3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based paint composition, and more particularly to a water-based paint composition most suitable for the outer surface of a metal can or a polyester film-coated draw can.
More specifically, the present invention relates to an aqueous coating composition having excellent workability, adhesion, retort resistance, and hardness.

[0002]

2. Description of the Related Art The outer surfaces of beverage cans containing various drinks such as coffee, black tea, green tea, oolong tea, various juices and beer, and food cans containing food (hereinafter, both are referred to as beverage cans, etc.) It is coated with a coating that prevents corrosion of the can material, enhances aesthetic commercial value, and withstands a heat treatment step during food sterilization. Among the conventional paints provided for coating, the aqueous paints include a water-based paint of an aqueous dispersion type using a surfactant or an acid value of 20 (mg).
A water-soluble type water-based paint using a resin of KOH / g or more has been used, but it is difficult to balance retort treatment (pressure steam) at 125 ° C or more with workability, adhesion, and hardness. there were.

[0003] Means for solving the above-mentioned problems include an acrylic copolymer obtained by copolymerizing N-alkoxyacrylamide as disclosed in JP-A-5-202270 and JP-A-3-72577. Water-based coating compositions have been proposed.

[0004] In recent years, beverage cans having the following forms made of aluminum or steel have become mainstream. That is, a two-piece can (D) consisting of two parts, a bottomed cylindrical member integrally formed with a can body and a can bottom and a can lid
I) and a drawn can coated with a polyester film in which a polyester film is bonded to both sides of a metal material. In the case of DI cans, use DI (Draw and Ironi)
ng) After processing and trimming to make a cylindrical shape with a bottom, first, a printing ink layer is formed on the outer surface side, a top coat is applied on the printing ink layer, and then the outer surface side is finished. Then, a coating is applied to the inner surface side, and through a necking process and a flange process, a can body that can be provided to the content filling step is formed. On the other hand, in the case of a drawn can coated with a polyester film, a polyester film is stuck on both sides of a coil-shaped metal material, and after drawing it into a cylindrical shape with a bottom, a printing ink layer is formed on the outer surface side. A top coat is applied on top of the layer, and finally DI
Through a necking process and a flange forming process in the same manner as the can, a can body that can be provided to the content filling process is formed.

As can be seen from the above differences in the manufacturing process,
The baking conditions when the top coat is applied in the DI can and the polyester film-coated drawn can are different. That is,
In the case of DI cans, the baking of the inner coating film is added as a post-bake after the baking of the top coat itself. As a result, a sufficient amount of heat is given in total, and the baking is performed twice, so that the second baking strengthens the coating film on the outer surface and also alleviates the distortion of the coating film. This is a baking condition advantageous for satisfying retort properties and processing adhesion.

On the other hand, in the case of a drawn can coated with a polyester film, since the heat of baking of the inner surface coating cannot be used, it is necessary to sufficiently cure the coating with the heat of one baking. As a means for improving the curability, an acrylic copolymer having a higher copolymerization ratio of N-acrylmethyl (meth) acrylamide, which is a self-reactive acrylic monomer, may be used, or a curing agent may be used for the acrylic copolymer. It is conceivable to increase the amount of the amino resin used as the resin or to increase the amount of the acid catalyst which is a curing catalyst for the acrylic copolymer and the amino resin. However, although the curability itself can be improved by any of the methods, the curing strain of the coating film increases, and as a result, the retort resistance and the processing adhesion are not satisfied. By the way, in order to reduce the resources of the lid and, as a result, to reduce the cost of the entire can body, the mouth (opening) of the member of the can body after the coating film has been formed has hitherto been formed from the center of the can body. Processing (reduced diameter) to make it slightly thinner, DI
In recent years, cans have been increasingly required to be reduced in diameter. In the case of DI cans, baking conditions are more favorable for satisfying retort resistance and processing adhesion than those of polyester film coated drawn cans. The diameter of the can body is the same as that of the conventional can, but the mouth of the can must be processed to be thinner. . However, with the conventional coating materials, a coating film that satisfies both retort resistance and high processing adhesion cannot be formed.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above situation, and has excellent retort resistance, workability, adhesion and hardness as a paint for the outer surface of a metal can or a polyester film-coated draw can. It is an object of the present invention to provide a water-based coating composition.

[0008]

A coating composition containing an acrylic resin obtained by copolymerizing N-alkoxymethyl (meth) acrylamide as an essential component and an amino resin is prepared by using an acid catalyst. Acrylamide self-condenses, and the acrylamide reacts with the amino resin to cure. The present inventors have conducted intensive research, and as a result,
In such a reaction mechanism, by incorporating a basic component that inhibits the catalytic effect of the acid catalyst in the acrylic copolymer, without impairing the curability, the curing distortion is small and excellent in processability, The present inventors have found a coating composition capable of forming a coating film having excellent retort resistance, adhesion and hardness, and have completed the present invention. That is, the first invention provides the following (1)
Acrylic copolymer (a) 3 obtained by copolymerizing (4) to (4)
0 to 85% by weight, and an aqueous amino resin (b) 15 to 7
An aqueous coating composition containing 0% by weight (provided that the total amount of the acrylic copolymer (a) and the aqueous amino resin is 100% by weight). (1) 1 to 15% by weight of α, β-monoethylenically unsaturated carboxylic acid (2) 0.5 to 10% by weight of (meth) acrylate monomer having a basic alkylamino group at the terminal (3) N- Alkoxymethyl (meth) acrylamide 15 to 60% by weight (4) 10 to 70% by weight of (meth) acrylate monomers and / or vinyl monomers copolymerizable with the above (1), (2) and (3)

A second invention is that the amino resin is a benzoguanamine resin partially etherified with an alcohol, and is an amino resin having 0.5 to 2.0 imino groups per one benzoguanamine nucleus. A feature of the water-based coating composition according to the first aspect of the invention.

[0010] A third invention is a coated article characterized by being coated with the aqueous coating composition according to the first or second invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The α, β-monoethylenically unsaturated carboxylic acid (1) used in the copolymerization of the acrylic copolymer (a) used in the present invention is a source of the carboxylic acid, and is obtained after the copolymerization. It functions to make the acrylic copolymer (a) aqueous (water-soluble or water-dispersible) by neutralizing the carboxylic acid with a basic compound. α, β-
Examples of the monoethylenically unsaturated carboxylic acid (1) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid, with acrylic acid and methacrylic acid being particularly preferred. It is important to use the α, β-ethylenically unsaturated carboxylic acid (1) in obtaining the acrylic copolymer (a) in an amount of 1 to 15% by weight, and preferably 4 to 7% by weight. If it is less than 1% by weight, it is difficult to make the acrylic copolymer (a) aqueous, and if it exceeds 15% by weight, the water resistance of the coating film is poor.

[0012] The (meth) acrylate monomer (2) having a basic alkylamino group at the terminal is partially cured in the vicinity of the basic alkylamino group in the process of forming a coating film as described above. In addition, the coating film as a whole has a function of alleviating curing distortion without impairing curability and improving workability. The basic alkylamino group is represented by the following general formula (1).

[0013]

Embedded image

Specific examples of the (meth) acrylate monomer (2) having an alkylamino group include:
Examples include dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dibutylaminoethyl acrylate, and the like. When nitrogen of an alkylamino group is bonded to an alkyl group as described above, it forms an atomic group that gives basicity, and when bonded to an acyl group (RO-), the basicity is weakened and almost neutral. Becomes When the (meth) acrylate monomer (2) having a basic alkylamino group at the terminal is used for obtaining the acrylic copolymer (a), 0.5 to
It is important to use 10% by weight, and it is preferable to use 1 to 5% by weight. If the amount is less than 0.5% by weight, the effect of inhibiting the acid catalyst is small, and the effect of suppressing the curing strain is small. Therefore, the effect of improving the processability cannot be expected. Insufficient curing occurs and the coating film hardness decreases.

N-alkoxymethyl (meth) acrylamide (3) is obtained by reacting (meth) acrylamide with formalin to obtain N-methylol (meth) acrylamide. And alcohol. The alcohol used here is methanol,
Ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, n-amyl alcohol, isoamyl alcohol, 2-methyl-1-
Butanol, cyclohexanol, n-hexanol,
2-heptanol, 3-heptanol, n-heptanol, 2-ethylbutanol, n-octanol, 2-octanol, 2-ethylhexanol, nonanol, n
Alkyl alcohols such as decanol and undecanol, ethyl cellosolve, butyl cellosolve, methyl cellosolve, hexyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, 3-methoxy-butanol, 3-methyl-3-methoxybutanol,
Cellosolve or carbitol alcohols such as ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoisobutyl ether, methyl glycol, methyl diglycol, methyl propylene glycol, propyl propylene glycol, and isopropyl glycol; ethylene glycol and diethylene glycol And the like, but an alkyl alcohol is preferable, and an alcohol having 4 or less carbon atoms in the alkyl group is preferable. Specifically, N-methoxymethyl (meth) acrylamide,
N-ethoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide and the like can be mentioned.
These monomers (3) are the acrylic copolymer (a)
It is important to use 15 to 60% by weight when obtaining, and it is preferable to use 30 to 50% by weight. If it is less than 15% by weight, the retort resistance and hardness of the coating film are reduced, and
If the content exceeds 0% by weight, not only gelation during the reaction is liable to occur, but also if a copolymer is obtained without gelation, the processability of the coating film is reduced when the copolymer is used.

The (meth) acrylate monomer and / or vinyl monomer copolymerizable with the above (1) to (3) and used in obtaining the acrylic copolymer (a) include the above (19 to (3) Any monomer can be used as long as it can be copolymerized with the monomer of (1), and the former includes methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethyl acrylate, and cyclohexyl (meth).
Alkyl (meth) acrylates such as acrylate and stearyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and caprolactan-modified acrylate (manufactured by Daicel Chemical Industries, Ltd., trade name “Placcel FA-1, And hydroxyl group-containing monomers such as PLACCEL FA-3 ").
As the latter, aromatic vinyl monomers such as styrene and vinyl toluene, and vinyl carboxylate monomers such as vinyl acetate can be used.

The acrylic copolymer (a) can be obtained by ordinary solution polymerization, and a mixture of the above-mentioned monomers (1) to (4) is treated with benzoyl peroxide, t-
Peroxides such as butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, or 2,
Radical polymerization is carried out using an azo compound such as 2 'azobisisobutylnitrile as a catalyst. Examples of the organic solvent used for polymerization include isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, n-amyl alcohol, alcohol solvents such as isoamyl alcohol, butyl cellosolve, hexyl cellosolve, butyl carbitol, methyl glycol, methyl propylene glycol,
Cellosolves such as propylpropylene glycol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, and ethylene glycol monomethyl ether are exemplified.

The acrylic copolymer (a) has a number average molecular weight of 1500 to 5000 and a weight average molecular weight of 5000
~ 30,000, acid value 10 ~ 150 (mgKOH / g),
The hydroxyl value is preferably 0 to 150 (mgKOH / g), the glass transition temperature is preferably 0 to 80 ° C, and the number average molecular weight is 20.
00-4000, weight average molecular weight 7000-1500
0, acid value 30-70 (mgKOH / g), hydroxyl value 0
60 (mgKOH / g), glass transition temperature 20-60 ° C
Is more preferable.

To the resulting acrylic copolymer (a) solution, a volatile base such as ammonia or an organic amine is added together with water, or a volatile base such as ammonia or an organic amine is added and then water is added. By neutralizing all or part of the carboxylic acid in the copolymer (a), the acrylic copolymer (a) can be dissolved or dispersed in an aqueous medium. The volatile base preferably has a boiling point of 400 ° C. or lower. Examples of the organic amine include monoethanolamine, dimethylamine, diethylamine, triethylamine, triethanolamine, diethylethanolamine, and dimethylethanolamine.

Next, the aqueous amino resin (b) used in the present invention will be described. An aqueous amino resin is an amino resin that can be dissolved or dispersed in an aqueous medium, and includes benzoguanamine, melamine, spiroganamin,
Compounds such as acetoguanamine and phthalovanamin, which are formed by adding formaldehyde to some or all of the amino groups and then condensed to form a methylol and then condensed to have a high molecular weight. It is etherified to Among them, benzoguanamine resin is preferred. The benzoguanamine resin is obtained by condensing a methylol compound obtained by subjecting a part or all of the amino groups in benzoguanamine to addition reaction with formaldehyde, or by partially or wholly etherifying the methylol group of the methylol compound with an alcohol. It is more preferable that the benzoguanamine nucleus has 0.5 to 2.0 imino groups. When the number of imino groups is 2.0 or more, the stability with time as a coating is poor, and when the number is 0.5 or less, curing reactivity is poor. Specific examples include methyl etherified benzoguanamine and butyl etherified benzoguanamine. Examples of alcohols used for etherifying a methylol group include n-propyl alcohol, in addition to methanol and butanol.
Alkyl alcohols such as isopropyl alcohol, ethanol, isobutyl alcohol, s-butyl alcohol, t-butyl alcohol, butyl cellosolve, hexyl cellosolve, butyl carbitol, and 3-methyl-3-
Cellosolves such as methoxybutanol, 3-methoxybutanol, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, and methyl propylene glycol are also mentioned, and these may be used as a mixture.

The aqueous coating composition of the present invention has a total amount of the acrylic copolymer (a) and the aqueous amino resin (b) of 10
The acrylic copolymer (a) is added in an amount of 30 to 85% in 0% by weight.
%, An aqueous amino resin in an amount of 15 to 70% by weight, and an acrylic copolymer (a) in an amount of 40 to 70% by weight;
It is preferable to contain 30 to 60% by weight of the aqueous amino resin. When the content of the acrylic copolymer (a) exceeds 85% by weight and the content of the aqueous amino resin is less than 15% by weight, the retort resistance and hardness of the coating film become insufficient. On the other hand, when the acrylic copolymer (a) is less than 30% by weight and the aqueous amino resin exceeds 70% by weight, the processability of the coating film is reduced.

The aqueous coating composition of the present invention contains an acid catalyst or an amine-blocked product thereof, for example, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, etc., as an acrylic copolymer ( 0.05 to 4 parts by weight can be added to 100 parts by weight in total of a) and the aqueous amino resin (b). Further, conventionally known leveling agents, defoaming agents, and lubricants such as WAX can be added as needed. In addition, using a known disperser such as a sand mill and a disper, titanium oxide,
A pigment such as an aluminum pigment or quinacridone and the acrylic copolymer (a) may be kneaded to form a coating.

In the aqueous coating composition of the present invention, other commonly used water-soluble resins and water-dispersible resins, for example, polyester resins, polyether polyol resins,
It is also possible to use a polyester polyol resin, a maleated fatty acid, a resin of an ethylene oxide or propylene oxyside adduct of bisphenol A, or an epoxy resin in which a glycidyl group of an epoxy resin is added with an amine, phosphoric acid or the like. It is also possible to use a compound having an isocyanate group as a curing aid, and use active methylene, MEK oxime, blocked isocyanate having ε-caprolactam as a blocking agent, unblocked isocyanate, and MEK oxime-based aqueous isocyanate. It is also possible.

The aqueous coating composition of the present invention can be applied to various substrates by known means such as roll coating, spraying and brushing. For example, electroplated tin steel sheet,
The aqueous coating composition of the present invention is applied to an aluminum steel sheet, a stainless steel sheet, or a laminated steel sheet obtained by laminating a polyester film such as polyethylene terephthalate or polybutylene terephthalate on these metal sheets, and heated and cured to obtain a coated product. . In particular, the coating composition of the present invention is suitable for coating and coating the outer surface of a beverage can or the outer surface of a polyester film-coated metal can for beverage.

[0025]

The present invention will be described below with reference to examples. In the examples, “parts” and “%” represent parts by weight and% by weight, respectively. Production Example 1 (Production of Aqueous Dispersion of Acrylic Copolymer a-1) Ethylene glycol monoisopropyl ether 100 was placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a dropping tank, and a nitrogen gas blowing tube. Then, while stirring and maintaining the temperature at 105 ° C. while introducing nitrogen gas, a solution prepared by dissolving 5 parts of benzoyl peroxide in a monomer mixture having the following mixing ratio was added dropwise from a dropping tank over 3 hours. Methacrylic acid: 5% Dimethylaminoethyl acrylate: 4% (trade name: "Light Ester DM" Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) N-methoxymethyl acrylamide: 25% Methyl methacrylate: 20% Butyl acrylate: 51% Then 105 The reaction was carried out for 1 hour while maintaining the temperature at 0 ° C., 1 part of benzoyl peroxide was added, and the reaction was further carried out for 1 hour to complete the reaction. The solvent was removed under reduced pressure at 100 ° C. until ethylene glycol monoisopropyl ether had a nonvolatile content of 80%. Thereafter, 5.2 parts of dimethylethanolamine and water were added.
An aqueous dispersion of the acrylic copolymer a-1 having a solid content of 50% was obtained.

Production Examples 2 to 14 (acrylic copolymer a-2
Production of Aqueous Dispersion of No. 14 to 14) Aqueous acrylic copolymer a-2 having a solid content of 50% was similarly polymerized according to Production Example 1 with the monomer composition shown in Table 1.
To 11 and 13 were obtained. Incidentally, a-12 gelled during the synthesis.

Production Example 15 (Production of benzoguanamine resin b-1) Benzoguanamine 18 was placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a dropping tank, and a nitrogen gas blowing tube.
7 parts, 281 parts of 80% paraformaldehyde, and 320 parts of methanol were charged, and a 25% sodium hydroxide solution was added.
After adding 7 parts, the mixture was heated at 60 ° C. for 3 hours. Then 60%
A nitric acid solution was charged until the solution reached pH 3.5, and the reaction was continued for 4 hours. After completion of the reaction, the mixture was neutralized with a 25% sodium hydroxide solution, and then methanol water was removed under reduced pressure at 70 ° C. or lower. After filtration under reduced pressure, ethylene glycol monoisopropyl ether was added, and the solid content was reduced to 75%.
Of benzoguanamine resin b-1 was prepared. The number of imino groups and methylol groups per benzoguanamine nucleus is N
Table 2 shows the results of analysis and calculation by MR.

Production Examples 16 to 19 (benzoguanamine resin
Production of b-2 to 5) According to Production Example 15, benzoguanamine, paraformaldehyde and methanol shown in Table 2 were reacted to obtain benzoguanamine resins b-2 to 5. Table 2 shows the result of NMR analysis and calculation of the number of imino groups and methylol groups per benzoguanamine nucleus.

Examples 1 to 12 and Comparative Examples 1 to 7 After mixing the components according to the formulation (solid content) shown in Table 3, ethylene glycol monoisopropyl ether and water were added to reduce the amount of the organic solvent in the paint to 15%. %, Solid content 40
%. To this, 0.3% of an amine salt of paratoluenesulfonic acid and 0.3% of a silicone-based leveling agent were added to obtain an aqueous coating composition.

Table 4 shows the results of examining the stability of the coating compositions and the physical properties of the coating films prepared in Examples and Comparative Examples. Each test method is as follows. [Paint Stability] The state of gelation and separation of the resin in the paint when the paint was stored at room temperature for 2 months or more was evaluated by visual observation. Evaluation: no problem for 2 months or more (◎), no problem for 2 months (）), separation within 2 months (△), gelation within 2 months, thickening (×)

[Coating physical property test] The coating was applied to a polyester film-coated squeeze can by roll coating, so that the coating thickness after drying was 4 to 5 µm, and baked in a gas oven at an ambient temperature of 220 ° C for 1 minute. Was. Next, the painted can was opened and the one that was flattened was evaluated as a test painted plate. -Retort resistance test The coated plate was subjected to a pressure steam treatment (retort treatment) at 130C for 30 minutes, and then the whitening state of the coating film was visually evaluated. Evaluation (whitening area): 0% (◎), 0 to less than 2% (○) 2 to 10% (△), 10% or more (×)

Processability test The coated plate was punched into a cap shape having a diameter of 2.5 cm and a height of 0.5 to 2.0 cm (at intervals of 0.5 cm). It was visually evaluated with a loupe. Evaluation (crack height): 2 cm or more (◎), 2 cm (○) 1.5 cm (△), 1 cm or less (×)

○ Working adhesion (untreated, after retort treatment) A cross cut was made with a cutter knife on the processed part of the cap made at a height of 2 cm for the above workability test, and a cellophane tape was adhered. The peeled area of the coating film after peeling was visually evaluated. Separately, a cross cut was made in the cap processed part similarly prepared in the same manner.
After the retort treatment for 5 minutes, the peeling area of the coating film with the cellophane tape was similarly visually evaluated. Evaluation (peeled area): 0% (◎), 0 to less than 1% (○) 1 or more to less than 5% (△), 5 or more to (x)

○ Hardness in hot water After the coated plate was immersed in hot water at 80 ° C for 30 minutes, the pencil hardness was measured in the hot water at 80 ° C. Evaluation: F or higher (◎), HB (○), B
(△), 2B or less (×)

○ Scratch resistance After the coated plate was retorted at 130 ° C. for 30 minutes, a diamond needle having a diameter of 250 μm with a load of 100 g was brought into contact with the coating film and reciprocated at a speed of 600 mm / min. The number of reciprocations up to the mark was evaluated as abrasion resistance. Evaluation (number of reciprocations): 150 or more (（), 100 or more to less than 150 (○) 50 or more to less than 100 (△), less than 50 (×)

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

The aqueous coating composition of the present invention has excellent stability and reacts with an acid catalyst system.
Contains an acrylic copolymer (a) obtained by copolymerizing acrylamide, a (meth) acrylate having a basic alkylamino group that inhibits the catalytic effect of an acid catalyst, and an aqueous amino resin (b) By doing so, it is possible to suppress the curing distortion of the coating film without impairing the curability, and to provide a coating film having excellent workability, excellent retort resistance, excellent scratch resistance, and high hardness. In particular, it has become possible to provide a coating composition suitable for a drawn can coated with a polyester film and a DI can whose diameter has been reduced.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C09D 133/02 C09D 133/02 133/14 133/14 161/20 161/20 F-term (Reference) 4D075 CA02 CA13 DB04 DB07 DB40 DC42 EA07 EB22 EB32 4J038 CG091 CG092 CG141 CG142 CG171 CG172 CH201 CH202 CJ031 CJ032 CJ101 CJ102 DA171 DA172 GA02 GA03 GA06 GA09 MA08 MA10 NA11 NA12 NA14 NA24 NA25 NA26 PA19 PB04A02 PC08 AB08 A AL09P AM21Q BA04Q BA31S CA06 JA01

Claims (3)

[Claims] 1. An acrylic copolymer (a) obtained by copolymerizing the following (1) to (4): 30 to 85% by weight, and an aqueous amino resin (b): 15 to 70% by weight. A characteristic aqueous coating composition (provided that the total amount of the acrylic copolymer (a) and the aqueous amino resin is 100% by weight). (1) 1 to 15% by weight of α, β-monoethylenically unsaturated carboxylic acid (2) 0.5 to 10% by weight of (meth) acrylate monomer having a basic alkylamino group at the terminal (3) N- Alkoxymethyl (meth) acrylamide 15 to 60% by weight (4) 10 to 70% by weight of (meth) acrylate monomer and / or vinyl monomer copolymerizable with the above (1), (2) and (3) 2. The amino resin is a benzoguanamine resin partially etherified with an alcohol, and is an amino resin having 0.5 to 2.0 imino groups per benzoguanamine nucleus. Item 7. An aqueous coating composition according to Item 1. 3. A coated article which is coated with the aqueous coating composition according to claim 1 or 2.