KR100867730B1 - Water-based coating composition - Google Patents

Abstract

An object of this invention is to provide the coating composition for cans which can form the coating film excellent in bending workability, water whitening resistance, and flavor property.

0.1-20 mass parts of resol-type phenol resins (B) and the acrylic resin (C) of the acid value 100-500 mgKOH / g which have the following characteristics with respect to 100 mass parts of acrylic resin modified epoxy resins (A) 0.1- 20 mass parts is contained, and the said resin (A) and the said resin (C) are disperse | distributed stably in an aqueous medium, The aqueous coating composition characterized by the above-mentioned.

ACRYLIC RESIN (C): As an essential component, the vinyl copolymer chain | strand (1) which makes an acidic radical containing radically polymerizable monomer a monomer component, and the vinyl copolymer chain which makes a carboxyl group-containing radically polymerizable monomer a monomer component as an essential component (2 )

Description

Waterborne Coating Composition {WATER-BASED COATING COMPOSITION}

1 is a cross-sectional view of a coating film in which a polymer crosslinked fine particle (D) is blended in a coating to form an island-in-the-sea structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for cans useful for coating constituent members of food cans such as beverages and fruits, and metal cans such as lids. The resulting coating film has excellent balance between bending workability, whitening resistance, acid adhesion, and flavor. Can be formed.

Background Art Conventionally, can coating compositions for cans, such as can inner and outer surfaces, can lids, and the like, which have coating properties such as processability, adhesiveness and corrosion resistance, have been developed.

Conventionally, in an aqueous resin dispersion containing an acrylic acid (D) containing monobasic acid as an essential component with respect to an acrylic modified epoxy resin and containing 40% or more of an acrylic monomer component having a glass transition point of 0 ° C. or less. The invention which concerns on is known (patent document 1).

In addition, emulsion resins having an acid value of 150 to 450 mg KOH / g and a number average molecular weight of 2,000 to 50,000 formed by emulsion polymerization of an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a carboxyl group-containing epoxy resin and a carboxyl group-containing acrylic resin are present in the aqueous medium. The aqueous coating composition characterized by being disperse | distributed is known (patent document 2).

In addition, an aqueous coating composition containing an acrylic resin modified epoxy resin (A), a resol type phenol resin (B), and at least one adhesive imparting resin (C) selected from a polyester resin and a polyvinyl butyral resin is It is known (patent document 3).

In addition, the carboxyl group-containing acrylic resin and acid number 180 which have an acid value of 10-135 mgKOH / g, a glass transition temperature (Tg) of -20-20 degreeC, and a weight average molecular weight of 10,000-200,000 are some of the epoxy groups in an epoxy resin. A water-based coating composition is known, which contains a basic compound and an aqueous medium of an acrylic modified epoxy resin obtained by reacting with a part of the carboxyl group in a carboxyl group-containing acrylic resin of ˜450 mgKOH / g (Patent Document 4).

In addition, by dispersing the core shell fine particles in an aqueous resin composition obtained by dispersing the particulate self-emulsifying epoxy resin in an aqueous medium, the coating material for cans excellent in adhesion and processability, and the core shell fine particles (island) present in the coating film There is an invention in which the adhesion and workability of the coating film are improved in consideration of mutual adhesion between the portions (sea) where the fine particulate self-emulsifying epoxy resin is polymerized (Patent Document 5).

In addition, the aqueous coating composition containing an acrylic resin modified epoxy resin, a resol-type phenol resin, and a styrene copolymer rubber is known (patent document 6). However, the coating film obtained by coating the coating material of patent documents 1-6 is not satisfactory in the whole of bending workability, water whitening resistance, acid tightness resistance, flavor property, etc.

[Patent Document 1] Japanese Patent Application Laid-Open No. 8-302275

[Patent Document 2] Japanese Patent Application Laid-Open No. 9-227824

[Patent Document 3] Japanese Patent Application Laid-Open No. 11-343456

[Patent Document 4] Japanese Patent Publication No. 2005-187679

[Patent Document 5] Japanese Patent Application Laid-Open No. 9-67543

[Patent Document 6] Japanese Patent Application Laid-Open No. 11-263938

An object of the present invention is to find a coating composition for cans that can form a coating film excellent in bending workability, whitening resistance, and flavor.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, it discovered that the said subject can be solved by mix | blending a resol type phenol resin (B) and specific acrylic resin (C) with respect to an acrylic resin modified epoxy resin (A). Thus, the present invention has been completed. That is, this invention provides the following aqueous coating composition and coating composition for cans.

[1] Acrylic resin (C) 0.1 with 100 parts by mass of acrylic resin-modified epoxy resin (A), 0.1 to 20 parts by mass of resol-type phenolic resin (B), and an acid value of 100 to 500 mgKOH / g having the following characteristics: It is made to disperse -20 mass parts in an aqueous medium, The aqueous coating composition characterized by the above-mentioned.

Acrylic resin (C): Contains vinyl copolymer chain (1) which consists of at least 1 radically polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid group containing radically polymerizable monomer, and methacrylic acid It has a vinyl copolymer chain (2) which makes a monomer component into a component.

[2] The acrylic resin (C) is 10 to 60% by mass of at least one radical polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid or a phosphoric acid group-containing radical polymerizable monomer and other radical polymerizable unsaturated monomers ( 1) The vinyl copolymer resin (c1) which makes 40-90 mass% a monomer component, 10-60 mass% of methacrylic acid, and 40-90 mass% of other radically polymerizable unsaturated monomers (2) as a monomer component The aqueous coating composition as described in said [1] which is a polymer formed by making vinyl copolymer resin (c2) and the low molecular weight compound (c3) which has two or more complementary reactive groups reactive with an acidic group and a carboxyl group react in 1 molecule.

[3] vinyl copolymer resin (c1), vinyl copolymer resin (c2) and low molecular weight compound (c3) constituting acrylic resin (C); vinyl copolymer resin (c1) and vinyl copolymer resin (c2) Vinyl copolymer resin (c1) / vinyl copolymer resin (c2) = 60 / 40-95 / 5 (mass%) based on the total solid content of the, and [vinyl copolymer resin (c1) + vinyl copolymer Resin (c2)] / low molecular weight compound (c3) = 100 / 0.1-100/20 (mass part), It makes it react, The aqueous coating composition as described in said [2] characterized by the above-mentioned.

[4] The above-mentioned low molecular weight compound (c3) is at least one selected from epoxy resins having 180 to 5,000 epoxy equivalents, resol type phenol resins and polycarbodiimide compounds having two or more epoxy groups in one molecule. Or the aqueous coating composition described in [3].

[5] The aqueous coating composition according to the above [4], wherein the low molecular weight compound (c3) is an epoxy equivalent of 200 to 1,000 epoxy resin having two or more epoxy groups in one molecule.

[6] The resin or bisphenol type epoxy resin obtained by esterifying an acrylic resin modified epoxy resin (A) with a bisphenol type epoxy resin (a1) having a number average molecular weight of 2,000 to 35,000 and a carboxyl group-containing acrylic resin (a2) ( The aqueous coating composition in any one of said [1]-[5] which is resin formed by graft-polymerizing the polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer (a3) in a1).

[7] 1 to 50 parts by mass of the anionic polymer cross-linked fine particles (D) having the following characteristics, based on 100 parts by mass of the acrylic resin-modified epoxy resin (A), above-mentioned [1] to [6] The aqueous coating composition in any one of].

Anionic polymer crosslinked microparticles | fine-particles (D): 2-30 mass% of carboxyl group-containing radically polymerizable monomers (d1), 2-30 mass% of polyvinyl compounds (d2), and other radically polymerizable unsaturated monomers in presence of water. (d3) It consists of the polymer of the acid value 10-100 mgKOH / g manufactured by superposing | polymerizing-reacting the radically polymerizable unsaturated monomer component which consists of 40-96 mass%.

[8] A paint composition for cans, wherein the water-based coating composition according to any one of the above [1] to [7] is coated on the can body.

Below, the coating composition for cans of this invention is demonstrated.

[Can coating composition]

Acrylic resin modified epoxy resin (A):

The acrylic resin modified epoxy resin (A) may be either of the following resins (1) and (2).

Resin (1): Bisphenol type epoxy resin (a1) (hereinafter may be abbreviated as "epoxy resin (a1)") and carboxyl group-containing acrylic resin (a2) (hereinafter abbreviated as "acrylic resin (a2)") It may be a resin formed by ester addition). In the resin (1), the ester addition reaction can be easily carried out by heating the epoxy resin (a1) and the acrylic resin (a2), for example, in the presence of an esterification catalyst in an organic solvent solution.

Resin (2): It is resin formed by graft-polymerizing the polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer (a3) to bisphenol-type epoxy resin (a1). In resin (2), a polymerizable unsaturated monomer component can be graft-polymerized to epoxy resin (a1), for example in presence of radical generators, such as benzoyl peroxide, in an organic solvent.

As the bisphenol type epoxy resin (a1) used in the resin (1) and the resin (2), for example, epicrohydrin and bisphenol are condensed to high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary. A resin obtained by condensing a resin, epichlorohydrin and bisphenol in the presence of a catalyst such as an alkali catalyst to form a low molecular weight epoxy resin and carrying out a heavy addition reaction of the low molecular weight epoxy resin and bisphenol, and these obtained resins Or any of the epoxy ester resins formed by making a dibasic acid react with the said low molecular weight epoxy resin may be sufficient.

As said bisphenol, bis (4-hydroxyphenyl) methane [bisphenol F], 1, 1-bis (4-hydroxyphenyl) ethane, 2, 2-bis (4-hydroxyphenyl) propane [bisphenol A], 2 , 2-bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2 -Propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, bis (2- Hydroxy naphthyl) methane etc. are mentioned, Especially, bisphenol A and bisphenol F are used preferably. The said bisphenols can be used individually by 1 type or in mixture of 2 or more types.

As a dibasic acid used for manufacture of the said epoxy ester resin, following formula (1)

HOOC- (CH ₂ ) _n -COOH ... (1)

(In the formula, n is an integer of 1 to 12.) The compound represented by is preferably used, specifically, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecaneic acid, hexahydrophthalic acid, etc. It can be illustrated.

As a commercial item of an epoxy resin (a1), for example, Epicoat 1007 (epoxy equivalent approximately 1,700, number average molecular weight (note 1) approximately 2,900), epicoat 1009 (epoxy equivalent approximately 3,500, number) made in Japan epoxy resin Co., Ltd. Average molecular weight about 3,750), epicoat 1010 (epoxy equivalent about 4,500, number average molecular weight about 5,500); Araldite AER6099 (epoxy equivalent about 3,500, number average molecular weight about 3,800) by Asahi Chiba Corporation; And Mitsui Chemical Co., Ltd. Epomic R-309 (epoxy equivalent about 3,500, number average molecular weight about 3,800), etc. are mentioned.

(Note 1) Number average molecular weight: Performed according to JIS K 0124-83, using a TSKGEL4000H _XL + G3000H _XL + G2500H _XL + G2000H _XL (manufactured by Tosoh Corp.) at a flow rate of 1.0 ml / min at a separation column It calculated | required by calculation from the analytical curve of the chromatogram obtained by RI refractometer and polystyrene using tetrahydrofuran for GPC for eluent.

Especially as an epoxy resin (a1), the number average molecular weights are 2,000-35,000, Preferably it is 4,000-30,000, The epoxy film obtained is a bisphenol-type epoxy resin which is 1,000-12,000, Preferably it is the range of 3,000-10,000. It is preferred in the corrosion resistance of.

In the said resin (1), since the carboxyl group in an acrylic resin (a2) ester-adds reaction to the epoxy group in an epoxy resin (a1) at the time of ester addition reaction, an epoxy group is needed in an epoxy resin (a1), per molecule of epoxy resin An epoxy group is 0.5-2 average, Preferably it exists in the range of 0.5-1.6. On the other hand, in (2), since the graft reaction occurs by hydrogen extraction of the epoxy resin main chain and the graft polymerization reaction proceeds, the epoxy group does not have to be substantially present in the epoxy resin (a1).

Acrylic resin (a2) used in resin (1) is copolymer resin which uses a carboxyl group-containing polymerizable unsaturated monomer (a3) and other polymerizable unsaturated monomer (a4) as a monomer component.

As said carboxyl group-containing polymerizable unsaturated monomer (a3), monomers, such as (meth) acrylic acid, maleic acid, crotonic acid, itaconic acid, fumaric acid, are mentioned, for example, These can be used individually or in combination of 2 or more types.

The other polymerizable unsaturated monomer (a4) may be a monomer copolymerizable with the carboxyl group-containing polymerizable unsaturated monomer (a3), and can be appropriately selected and used according to the required performance. For example, styrene, vinyltoluene, 2- Aromatic vinyl monomers such as methyl styrene, t-butyl styrene and chlor styrene; Methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-, i- or t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl acrylate Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-, i- or t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, C1-C18 alkyl ester or cycloalkyl ester of acrylic acid or methacrylic acid, such as octyl methacrylate, decyl methacrylate, lauryl methacrylate, and cyclohexyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3- C ₂ to C ₈ hydroxyalkyl esters of acrylic acid or methacrylic acid such as hydroxypropyl methacrylate and hydroxybutyl methacrylate; N-substituted acrylamides such as N-metholacrylamide, N-butoxymethylacrylamide, N-methoxymethylacrylamide, N-metholol methacrylamide, and N-butoxymethylmethacrylamide or N- 1 type, or 2 or more types of mixtures, such as a substituted methacrylamide type monomer, are mentioned.

Especially as this other polymerizable unsaturated monomer (a4), the mixture of styrene and ethyl acrylate is especially preferable, The constituent mass ratio of styrene / ethyl acrylate is 99.9 / 0.1-40 / 60, Furthermore, it exists in the range of 99 / 1-50 / 50. Is suitable.

The carboxyl group-containing acrylic resin (a2) is not particularly limited in the constituent ratio and type of the monomer, but in general, the carboxyl group-containing radical polymerizable unsaturated monomer is preferably 15 to 80% by mass, particularly 20 to 60% by mass, and other polymerization It is preferable that it is 85-20 mass%, especially 80-40 mass% of a sex unsaturated monomer (a4).

Preparation of a carboxyl group-containing acrylic resin (a2) can be easily performed by carrying out solution polymerization reaction of the said monomer composition, for example in presence of a polymerization initiator in the organic solvent. The carboxyl group-containing acrylic resin (a2) preferably has a resin acid value in the range of 100 to 400 mgKOH / g and a number average molecular weight (see Note 1) of 5,000 to 100,000.

The reaction can be carried out by a conventionally known method, for example, blending an esterification catalyst in a uniform organic solvent solution of epoxy resin (a1) and acrylic resin (a2), until substantially all of the epoxy groups are consumed, Usually, it can carry out by making it react for about 1 to 6 hours at 60-130 degreeC reaction temperature. As said esterification catalyst, tertiary amines, such as triethylamine and dimethylethanolamine, quaternary salt compounds, such as triphenylphosphine, etc. are mentioned, for example, Tertiary amines are preferable.

Solid content concentration in the reaction system of an epoxy resin (a1) and an acrylic resin (a2) is not specifically limited as long as the reaction system exists in the viscosity range in which reaction does not interfere. Moreover, when using an esterification catalyst at the time of ester addition reaction, it is good to use the usage-amount normally in the range of 0.1-1 equivalent with respect to 1 equivalent of epoxy groups in an epoxy resin (a1).

Although it does not restrict | limit especially as content ratio of an epoxy resin (a1) and an acrylic resin (a2), Usually, it is preferable that epoxy resin (a1) is 60-90 mass%, especially 70-85 mass%, and acrylic resin (a2) It is preferable that it is 15-30 mass%, especially 20 mass%.

When an acrylic resin modified epoxy resin (A) is resin by the said resin (2), the polymerizable unsaturated monomer component which graft-polymerizes to an epoxy resin (a1) is a carboxyl group-containing acrylic resin (a2) in the said resin (1). The polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer (a3) which is a monomer component used for manufacture of the ()) is mentioned. Moreover, the said component may further contain the other polymerizable unsaturated monomer (a4) used by resin (1).

Graft polymerization reaction in the said resin (2) can be performed by a conventionally well-known method, For example, a radical generator and a polymerizable unsaturated monomer in the organic solvent solution of the epoxy resin (a1) heated at 80-150 degreeC. It can carry out by adding a uniform mixed solution of components gradually and holding it for about 1 to 10 hours at the same temperature. Examples of the radical generator include azobisisobutylonitrile, benzoyl peroxide, t-butylperbenzoyloctanoate, t-butylperoxy-2-ethylhexanoate, and the like.

As an organic solvent at the time of preparing the said resin (1) and resin (2), the polymerizable unsaturated monomer component containing an epoxy resin (a1), an acrylic resin (a2), or a carboxyl group-containing polymerizable unsaturated monomer (a3) is melt | dissolved. In addition, conventionally well-known thing can be used as long as it is an organic solvent which does not interfere with formation of an emulsion when neutralizing and aqueous-forming an acrylic resin modified epoxy resin (A) which is these reaction products.

Specific examples of the organic solvent include isopropanol, butyl alcohol, 2-hydroxy-4-methylpentane, 2-ethylhexyl alcohol, cyclohexanol, ethylene glycol, diethylene glycol, 1,3-butylene glycol, ethylene glycol monoethyl Ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and the like.

The acrylic resin modified epoxy resin (A) obtained by the said resin (1) or resin (2) has a carboxyl group, and it is water whose resin acid value exists in the range of 10-160 mgKOH / g, and also 20-100 mgKOH / g. It is preferable from a viewpoint of acidity, coating film performance, etc.

An acrylic resin modified epoxy resin (A) can disperse | distribute in an aqueous medium by neutralizing at least one part of the carboxyl groups in resin with a basic compound.

As a basic compound used for neutralization of the said carboxyl group, amines and ammonia are used preferably. Representative examples of the amines include alkylamines such as trimethylamine, triethylamine and tributylamine; Alkanolamines such as dimethylethanolamine, diethanolamine and aminomethylpropanol; Cyclic amines, such as morpholine, are mentioned. Although the neutralization degree of an acrylic resin modified epoxy resin (A) is not specifically limited, It is preferable that it is the range of 0.1-2.0 equivalent neutralization normally with respect to the carboxyl group in resin (A).

The aqueous medium may be only water, but may be a mixture of water and an organic solvent. As this organic solvent, all conventionally well-known things can be used and what was illustrated as the organic solvent which can be used at the time of the said acrylic resin modified epoxy resin (A) manufacture can be used preferably. It is preferable that the quantity of the organic solvent in the coating composition for cans of this invention is 20 mass% or less with respect to resin solid content of the coating composition for cans from a viewpoint of environmental protection.

In order to neutralize and disperse | distribute an acrylic resin modified epoxy resin (A) in an aqueous medium, it is good to follow a conventional method, For example, an acrylic resin modified epoxy resin (A) is added gradually in an aqueous medium containing the basic compound which is a neutralizing agent, under stirring. After neutralizing an acrylic resin modified epoxy resin (A) with a basic compound, the method of adding an aqueous medium to this neutralization under stirring, or adding this neutralization in an aqueous medium, etc. are mentioned.

<Resol type phenol resin (B)>

Although it is the resol type phenol resin (B) used for the coating composition for cans of this invention, it acts as a crosslinking agent of an acrylic resin modified epoxy resin (A) and an acrylic resin (C), Phenols, such as phenol and bisphenol A, formaldehyde, etc. Phenols obtained by condensation reaction of aldehydes in the presence of a reaction catalyst to introduce a methirol group, and alkyl etherification of a portion of the introduced methirol group with an alcohol having 6 or less carbon atoms.

The resol type phenol resin (B) has a number average molecular weight (Note 1) in the range of 200 to 2,000, preferably in the range of 300 to 1,200, and the average number of methirol groups per nucleus of benzene is 0.3 to 3.0, preferably Is in the range of 0.5 to 3.0, more preferably 0.7 to 3.0. By using the said resol type phenol resin, the coating film excellent in coating-film performance, such as adhesiveness, can be formed.

In the coating composition for cans of the present invention, the resol-type phenol resin (B) is in the range of 0.1 to 20 parts by mass, and preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid content of the acrylic resin modified epoxy resin (A). Do. Moreover, you may contain surfactant, an antifoamer, a pigment, a wax, a fragrance | flavor, etc. suitably as needed.

<Acrylic resin (C)>

The coating composition for cans of the present invention has particularly good acid adhesion resistance by blending acrylic resin (C), and the resulting coating film contributes to forming a coating film excellent in bending workability, whitening resistance, corrosion resistance and flavor resistance.

Acrylic resin (C) contains the vinyl copolymer chain (1) which consists of at least 1 radically polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid group containing radically polymerizable monomer, and methacrylic acid It has a vinyl copolymer chain (2) which makes a monomer component to be a component.

* Vinyl copolymer chain (1):

The vinyl copolymer chain (1) is preferably 10 to 60 mass% of at least one radically polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid group-containing radical polymerizable monomer, preferably 20 to 55 mass %, More preferably, it is 30-50 mass%, 40-90 mass% of other radically polymerizable unsaturated monomers (1), Preferably 45-80 mass%, More preferably, 50-70 mass% is a monomer component. The mixture (1) to be used is a vinyl copolymer resin (c1) obtained by a radical polymerization reaction in a suitable solvent.

If at least one radically polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid or phosphoric acid group-containing radical polymerizable monomer is less than 10% by mass, the adhesiveness is lowered, and if it exceeds 60% by mass, water resistance may be impaired.

2-acrylamide-2-methylpropanesulfonic acid is mentioned as a sulfonic acid group containing radically polymerizable monomer. Mono (2-hydroxyethyl methacrylate) phosphate is mentioned as a phosphoric acid group containing radically polymerizable monomer.

Acrylic acid is mentioned as an acrylic acid group containing radically polymerizable monomer, and itaconic acid is mentioned as an itaconic acid group containing radically polymerizable monomer.

As another radically polymerizable unsaturated monomer (1), For example, vinyl aromatic compounds, such as styrene, (alpha) -methylstyrene, vinyltoluene, p-chlorstyrene, and vinylpyridine;

For example, C ₂ to C ₈ hydroxides of acrylic acid or methacrylic acid such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Hydroxyl group-containing radically polymerizable unsaturated monomers such as oxyalkyl (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate; These hydroxyl-containing radically polymerizable unsaturated monomers and β-propiolactone, dimethyl propiolactone, butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprylolactone, γ-laurylolatone, ε-capro Reactants with lactone compounds, such as lactone and 6-caprolactone, etc., For example, Fraxel FM-1, Fraxel FM-2, Fraxel FM-3, Fraxel FA-1, Fraxel FA-2, Fraxel FA-3 ( As mentioned above, brand name Daicel Kagaku Corporation make, caprolactone modified (meth) acrylic-acid hydroxyester), etc .;

For example methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) ; acrylate, cyclohexyl (meth) acrylate such as (meth) such as C ₁ ~ C ₁₈ alkyl or cycloalkyl esters of acrylic acids.

For example, N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- Methyl-N- (2-hydroxyethyl) (meth) acrylamide, N-ethyl-N- (2-hydroxyethyl) (meth) acrylamide, N-methyl-N- (2-hydroxypropyl) ( Meta) acrylamide, N-methyl-N- (3-hydroxypropyl) (meth) acrylamide, N-ethyl-N- (2-hydroxypropyl) (meth) acrylamide, N-ethyl-N- ( 3-hydroxypropyl) (meth) acrylamide, N, N-di- (2-hydroxyethyl) (meth) acrylamide, N, N-di- (2-hydroxypropyl) (meth) acrylamide, etc. Nitrogen-containing radical polymerizable unsaturated monomers;

For example, vinyl trimethoxy silane, vinyl methyl dimethoxy silane, vinyl diethyl methoxy silane, vinyl triethoxy silane, vinyl methyl diethoxy silane vinyl dimethyl ethoxy silane, vinyl tripropoxy silane, vinyl methyl dipropoxy Silane, vinyl dimethyl propoxysilane, γ- (meth) acryloyloxypropyl trimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyldimethylmethoxysilane, etc. ; An alkoxysilyl group-containing radical polymerizable unsaturated monomer; Divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol Di (meth) acrylate, 1,4-butanediol diacrylate, glycerin di (meth) acrylate, glycerin tri (meth) acrylate, trimetholpropanedi (methane) acrylate, trimetholpropane tree (meth) ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, neopentyl glycol diacrylate, 1 , 6-hexanedioldiacrylate, glycerolaryloxydi (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanedi (meth) acrylate, 1,1,1-tris (hydroxymethyl Ethane (Meth) are vinyl compounds such as acrylates; Etc. can be mentioned.

In the production of vinyl copolymer resin (c1), at least one radical polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid group-containing radical polymerizable monomer and other radical polymerizable unsaturated monomers (1) are contained. The radical polymerization reaction by the mixture (1) to be performed is performed using a suitable solvent in the presence of a polymerization initiator. The reaction temperature is usually about 60 to 200 ° C, preferably about 70 to 160 ° C, and the reaction time is usually about 10 hours or less, preferably about 0.5 to about 6 hours.

As said polymerization initiator, azobisisobutylonitrile (AIBN) and t-butylperoxy-2 ethylhexanoate (perbutyl O) can be used, and the compounding quantity is 0.05-3 mass% with respect to the total of the mixture (1). to be.

As said solvent, For example, Hydrocarbon type, such as toluene, xylene, cyclohexane, n-hexane; Esters such as methyl acetate, ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone; Amide systems such as dimethylformamide and dimethylacetamide; Alcohols such as methanol, ethanol, n-propanol and iso-propanol; Or a mixture thereof.

Vinyl copolymer chain (2):

Vinyl copolymer chain (2) is 10-60 mass% of methacrylic acid, Preferably it is 15-55 mass%, More preferably, 20-50 mass%, 40-90 mass of other radically polymerizable unsaturated monomers (2) %, Preferably it is 45-80 mass%, More preferably, it is preferable that the mixture (2) which makes 50-75 mass% a monomer component is vinyl copolymer resin (c2) obtained by a radical polymerization reaction in a suitable solvent. Do. When methacrylic acid is less than 10 mass%, adhesiveness falls, and when it exceeds 60 mass%, there exists a possibility that water resistance may be impaired. As another radically polymerizable unsaturated monomer (2), 1 or more types of other radically polymerizable unsaturated monomers like those used for the vinyl copolymer chain (1) can be selected and used.

The vinyl copolymer chain (2) is characterized by not using at least one radical polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or phosphoric acid group-containing radical polymerizable monomer used in the vinyl copolymer chain (1). .

Although the vinyl copolymer resin (c2) is produced, the radical polymerization reaction by the mixture (2) containing methacrylic acid and other radical polymerizable unsaturated monomers (2) is carried out using a suitable solvent in the presence of a polymerization initiator. The reaction temperature is usually in the range of about 60 to 200 ° C, preferably about 70 to 160 ° C, and the reaction time is usually about 10 hours or less, preferably about 0.5 to about 6 hours. As said polymerization initiator and a solvent, the same solvent as what was used for the vinyl copolymer chain (1) can be selected suitably, and can be used.

In manufacturing acrylic resin (C), after synthesize | combining vinyl copolymer resin (c1), it can obtain by the method of making vinyl copolymer resin (c2) react.

More preferably, vinyl copolymer resin (c2) is added and stirred to vinyl copolymer resin (c1), the low molecular weight compound (c3) mentioned later is added, and acrylic resin (C) is obtained.

Low molecular weight compound (c3):

The acrylic resin (C) contains a low molecular weight compound (c3) having two or more complementary reactive groups in one molecule which have reactivity with an acid group and a carboxyl group in the presence of a vinyl copolymer resin (c1) and a vinyl copolymer resin (c2). It is preferable that it is a polymer obtained by making it react.

As the low molecular weight compound (c3), at least one selected from an epoxy equivalent of 180 to 5,000, preferably 200 to 1000 epoxy resin, a resol-type phenol resin and a polycarbodiimide compound having two or more epoxy groups in one molecule Can be used.

As a commercial item of an epoxy resin, Epicoat 828 (epoxy equivalent about 180, number average molecular weight about 360, epicoat 834 (epoxy equivalent about 235, number average molecular weight about 470), epicoat by Japan epoxy resin Co., Ltd. make, for example) 1007 (epoxy equivalent approximately 1,700, number average molecular weight approximately 2,900), epicoat 1009 (epoxy equivalent approximately 3,500, number average molecular weight approximately 3,750), epicot 1010 (epoxy equivalent approximately 4,500, number average molecular weight approximately 5,500); Asahi Chiba company make Araldite AER6099 (epoxy equivalent about 3,500, number average molecular weight about 3,800), Mitsui Chemical Co., Ltd. Epomic R-309 (epoxy equivalent about 3,500, number average molecular weight about 3,800), etc. are mentioned.

Among these, as an epoxy resin, Epicoat 828 and Epicoat 834 are also preferable at the point of the reaction efficiency of vinyl copolymer resin (c1) and vinyl copolymer resin (c2).

As a resol type phenol resin, the same thing as a resol type phenol resin (B) can be used, For example, a commercial item can mention Shonol BKS377 (made by Showa Co., Ltd.).

As a polycarbodiimide compound, it can obtain by making a polyisocyanate compound react in presence of a carbodi imidation catalyst in an inert solvent. Moreover, a dicarbodiimide compound like dicyclohexyl carbodiimide can also be used as a polycarbodiimide compound.

As a polyisocyanate compound, tolylene diisocyanate, xylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, bis (isocyanate methyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone, for example. Low molecular weight active hydrogens such as ethylene glycol, propylene glycol, trimetholpropane, hexanetriol, etc. in an excess amount of aromatic, alicyclic or aliphatic diisocyanate compounds such as diisocyanate and their isocyanurates, and these isocyanate compounds The terminal isocyanate containing compound obtained by making a containing compound react is mentioned.

As an inert solvent, For example, aromatic hydrocarbon solvents, such as toluene and xylene; Ketone solvents such as acetone and methyl ethyl ketone; Ether solvents such as dioxane; In addition, solvents, such as dimethylformamide, can be used. Various catalysts can be used as the catalyst for promoting the carbodiimide formation of the polyisocyanate compound, but 1-phenyl-2-phosphorene-1-oxide, 3-methyl-1-phenyl-2-phosphorene-1-oxide, 1 -Phenyl-2-phosphorene-1-sulfide, 1-ethyl-2-phosphorene-1-oxide, 1-ethyl-3-methyl-2-phosphorene-1-oxide, or isomers corresponding thereto, 3 -Phosphorenes are good. The catalyst amount can be used within the range of 0.01 to 1% by weight based on the total amount of the polyisocyanate compound. As a commercial item, Nissinbo Corporation, a carbodilite (trademark) series, for example, carbodilite V-02, carbodilite V-04, etc. are mentioned.

In manufacture of acrylic resin (C), reaction temperature in the radical polymerization reaction which uses the above-mentioned vinyl copolymer resin (c1), vinyl copolymer resin (c2), and a low molecular weight compound (c3) is normally About 60-200 degreeC, Preferably it is about 70-160 degreeC, More preferably, it is the range of 100-130 degreeC, and reaction time is about 10 hours or less normally, Preferably it is about 0.5 to about 6 hours. Thereafter, the mixture is diluted with an organic solvent such as propylene glycol n-propyl ether and cooled to obtain an acrylic resin (C).

As a reaction ratio of vinyl copolymer resin (c1), vinyl copolymer resin (c2), and a low molecular weight compound (c3), vinyl copolymer resin (c1), vinyl copolymer resin (c2), and a low molecular weight compound (c3) On the basis of the total solid content of the vinyl copolymer resin (c1) and the vinyl copolymer resin (c2), vinyl copolymer resin (c1) / vinyl copolymer resin (c2) = 60/40 to 95/5 (mass% ), Preferably it is 75/25-85/15 (mass%), and [Vinyl copolymer resin (c1) + vinyl copolymer resin (c2)] / low molecular weight compound (c3) = 100 / 0.1-100 / 20 (mass part), Preferably it is 100 / 2-100 / 10 (mass part), It is characterized by the above-mentioned. By setting it as the compounding ratio of this range, the film excellent in adhesiveness and corrosion resistance is obtained.

The acrylic resin (C) thus obtained has an acid value of 100 to 500 mgKOH / g, preferably 200 to 480 mgKOH / g, more preferably 300 to 450 mgKOH / g. The number average molecular weight is 1,000 to 25,000, preferably 2,000 to 20,000, and more preferably 3,000 to 10,000.

As for the coating composition for cans in this invention, 0.1-20 mass parts of acrylic resin (C) with respect to 100 mass parts of acrylic resin modified epoxy resins (A) obtained by the above, Preferably 1-10 mass parts, More preferably, Can contain 2-5 mass parts.

<Anionic Polymer Crosslinked Fine Particles (D)>

The coating composition for cans of this invention can further mix | blend anionic polymer crosslinked microparticles | fine-particles (D). The anionic polymer crosslinked fine particles (D) consist of a polymer obtained from a radical polymerizable unsaturated monomer composed of a carboxyl group-containing radical polymerizable monomer (d1), a polyvinyl compound (d2) and other radical polymerizable unsaturated monomers (d3). Here, content of each radically polymerizable unsaturated monomer is 2-30 mass% of carboxyl group-containing radically polymerizable monomer (d1) with respect to the total solid content of the radically polymerizable monomer comprised, Preferably 5-15 mass%, a polyvinyl compound (d2) 2-30 mass%, Preferably 5-15 mass%, 40-96 mass% of other radically polymerizable unsaturated monomers (d3), Preferably it is 70-90 mass%.

If the carboxyl group-containing radically polymerizable monomer (d1) is less than 2% by mass, the water dispersibility may be insufficient, and if it exceeds 30% by mass, the corrosion resistance may be impaired. If the polyvinyl compound (d2) is less than 2% by mass, the water whitening resistance is insufficient, and if it exceeds 30% by mass, the particle diameter becomes large, which is not preferable. Moreover, the following anionic polymer crosslinked microparticles | fine-particles (D1) or anionic polymer crosslinked microparticles | fine-particles (D2) are mentioned as an example of anionic polymer crosslinked microparticles | fine-particles (D).

* Anionic polymer crosslinked fine particles (D1):

5 mass% or less of a carboxyl group-containing radically polymerizable monomer (d1), Preferably it is 3 mass%, 4-35 mass% of polyvinyl compounds (d2), Preferably 10-25 mass%, and other radically polymerizable unsaturated monomers (d31) The mixture 3 of radically polymerizable monomers containing 60 to 96 mass%, preferably 75 to 90 mass% is subjected to the emulsion polymerization in the first step in the presence of water to obtain an aqueous dispersion (I).

Next, 10-35 mass% of carboxyl group-containing radically polymerizable monomer (d1), Preferably 15-25 mass% and 65-90 mass% of other radically polymerizable unsaturated monomers (d32), Preferably 75-85 mass% The mixture (4) of the radically polymerizable monomer containing is subjected to the second step emulsion polymerization in the presence of the water dispersion (I) and water to obtain anionic polymer crosslinked fine particles (D1).

As a carboxyl group-containing radically polymerizable monomer (d1) used for the mixture (3), monomers, such as (meth) acrylic acid, maleic acid, crotonic acid, itaconic acid, fumaric acid, are mentioned, for example, These are single or 2 types or more Can be used in combination.

Examples of the polyvinyl compound (d2) include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate. , 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol diacrylate, glycerin di (meth) acrylate, glycerin tri (meth) acrylate, trimetholpropanedi (meth) acrylate , Trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, Neopentylglycol diacrylate, 1,6-hexanedioldiacrylate, glycerolaryloxydi (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanedi (meth) acrylate, 1,1 ,One Tris (hydroxymethyl) ethane tri (meth) acrylate, etc. are mentioned, These can be selected suitably from these, and can be used.

As a polyvinyl compound (d2), the adduct which reacts the epoxy resin of epoxy equivalent 180-1,000 which has two or more epoxy groups in a molecule | numerator, and methacrylic acid and / or acrylic acid can also be used. Specifically, 0.5 to 0.98 mol, preferably 0.65 to 0.95 mol, and more preferably 0.75 to 0.9 mol of methacrylic acid and / or acrylic acid are used at a reaction temperature of 60 to 150 ° C with respect to 1 mol of the functional group in the epoxy resin. 10 minutes-180 minutes of addition products obtained by addition reaction.

As another radically polymerizable unsaturated monomer (d31), For example, Vinyl aromatic compounds, such as styrene, (alpha) -methylstyrene, vinyltoluene, p-chlorstyrene, and vinylpyridine; For example, C ₂ to C ₈ hydroxides of acrylic acid or methacrylic acid such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Hydroxyl group-containing radically polymerizable unsaturated monomers such as oxyalkyl (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and polybutylene glycol mono (meth) acrylate; These hydroxyl-containing radically polymerizable unsaturated monomers and β-propiolactone, dimethyl propiolactone, butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprylolactone, γ-laurylolatone, ε-capro Reactants of lactone compounds such as lactone and δ-caprolactone, and the like, for example, Fraxel FM-1, Fraxel FM-2, Fraxel FM-3, Fraxel FA-1, Fraxel FA-2, Fraxel FA-3 (above, Brand names, manufactured by Daicel Kagaku Co., caprolactone-modified (meth) acrylic acid hydroxyesters); For example methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylates, such as cyclohexyl (meth) acrylate such as (meth) C ₁ ~ C ₁₈ alkyl or cycloalkyl esters of acrylic acids; For example, N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- Methyl-N- (2-hydroxyethyl) (meth) acrylamide, N-ethyl-N- (2-hydroxyethyl) (meth) acrylamide, N-methyl-N- (2-hydroxypropyl) ( Meta) acrylamide, N-methyl-N- (3-hydroxypropyl) (meth) acrylamide, N-ethyl-N- (2-hydroxypropyl) (meth) acrylamide, N-ethyl-N- ( 3-hydroxypropyl) (meth) acrylamide, N, N-di- (2-hydroxyethyl) (meth) acrylamide, N, N-di- (2-hydroxypropyl) (meth) acrylamide, etc. Nitrogen-containing radical polymerizable unsaturated monomers; For example, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxy Silane, vinyl dimethyl propoxysilane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyldimethylmeth Oxysilane, etc .; An alkoxysilyl group-containing radical polymerizable unsaturated monomer; Can be mentioned.

A mixture (3) of a radically polymerizable monomer containing a carboxyl group-containing radically polymerizable monomer (d1), a polyvinyl compound (d2) and other radically polymerizable unsaturated monomers (d31) is subjected to an emulsion polymerization reaction using an emulsifier to obtain moisture. The body (I) can be manufactured. The reaction temperature at that time is usually in the range of about 60 to 90 ° C, preferably about 75 to 85 ° C, and the reaction time is usually about 10 hours or less, preferably about 0.5 to about 6 hours.

Subsequently, in the presence of the water dispersion (I), the mixture (4), and water, the emulsion polymerization after the second step is performed using an emulsifier and a polymerization initiator. The carboxyl group-containing radically polymerizable monomer (d1) used for the mixture (4) can select and use at least 1 type or more of the same monomers used for the mixture (3).

As another radically polymerizable unsaturated monomer (d32) used for the mixture (4), at least 1 sort (s) or more among the polyvinyl compound (d2) and other radically polymerizable unsaturated monomer (d31) used for the 1st step of polymerization reaction. Can be selected and used.

In addition, as a mass ratio of the water dispersion (I) and the mixture (4) at the time of using for manufacture of anionic polymer crosslinked microparticles | fine-particles (D1), based on the total amount of each mixture, water dispersion (I) / mixture (4) = 50 / 50-90/10 (mass ratio), Preferably it can adjust within the range of 70/30 (mass ratio)-85/15 (mass ratio).

As a polymerization initiator, ammonium persulfate, potassium persulfate, and sodium persulfate can be used, The compounding quantity is 0.05-3 mass%, Preferably 0.1-1.0 mass% is good.

Moreover, as an emulsifier used in the emulsion polymerization reaction of a 1st step and the emulsion polymerization reaction after a 2nd step, sodium salts and ammonium salts, such as an alkyl sulfonic acid, an alkylbenzene sulfonic acid, and alkyl phosphoric acid, are mentioned, for example. Moreover, the nonionic anionic emulsifier which has these anionic groups and nonionic groups, such as polyoxyethylene or polyoxypropylene chain, in 1 molecule, and the reactive anionic emulsifier which has these anionic groups and a polymerizable unsaturated group in 1 molecule; Can be mentioned.

Specifically, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether , Polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate Nonionic emulsifiers; Amphoteric ionic emulsifiers such as dimethyl alkyl betaines, dimethyl alkyl lauryl betaines and alkyl glycines; Can be mentioned.

As a concentration of the said emulsifier, 0.1-20 mass% with respect to the total amount of the monomer which comprises the mixture 3 or 4 is preferable, for the coating film performance also about 0.5-10 mass%. The polymerization reaction after the first and second stages can be carried out usually in water at a temperature of about 60 to 95 ° C., preferably at about 75 to 85 ° C. for about 1 to 5 hours, preferably about 2 to 4 hours. .

The obtained anionic polymer crosslinked fine particles (D1) have an acid value of 1 to 100 mgKOH / g, preferably 20 to 80 mgKOH / g, more preferably 40 to 75 mgKOH / g, average particle diameter (Note 2). Is 0.01 to 0.5 µm, preferably 0.1 to 0.35 µm, and more preferably 0.10 to 0.25 µm. This range is preferable in order to form a coating film excellent in drawing / ironing molding processability and water whitening resistance.

(Note 2) Average particle size: Dilute the sample to a concentration suitable for measurement in deionized water in submicron particle analyzer N4 (trade name, manufactured by Beckman Coulter, Inc.) and measured at room temperature (about 20 ° C). did.

* Anionic polymer crosslinked fine particles (D2):

First, 20-60 mass% of carboxyl group-containing radically polymerizable monomer (d1), Preferably 35-55 mass%, and 40-80 mass% of other radically polymerizable unsaturated monomers (d33), Preferably 45-65 mass The polymer (I) is obtained by carrying out radical polymerization reaction of the mixture (5) of the radically polymerizable monomer containing%. Next, 4-33 mass% of polyvinyl compounds (d2), Preferably 10-25 mass%, and 67-96 mass% of other radically polymerizable unsaturated monomers (d34), Preferably 75-90 mass% are contained The mixture 6 of radically polymerizable monomers is subjected to emulsion polymerization in the presence of the polymer (I) and water to obtain anionic polymer crosslinked fine particles (D2).

Regarding the production of the polymer (I), as the carboxyl group-containing radical polymerizable monomer (d1) used in the mixture (5), the same carboxyl group-containing radical polymerizable monomer (d1) as used for the preparation of the anionic polymer crosslinked fine particle (D1) is used. It can be used, For example, monomers, such as (meth) acrylic acid, maleic acid, crotonic acid, itaconic acid, fumaric acid, are mentioned, These can be used individually or in combination of 2 or more types.

As another radically polymerizable unsaturated monomer (d33), at least 1 type or more can be suitably selected from the polyvinyl compound (d2) used for manufacture of anionic polymer crosslinked microparticles | fine-particles (D1), and another radically polymerizable unsaturated monomer (d31), Can be used.

The radical polymerization reaction using the mixture (5) is carried out in a suitable solvent using a polymerization initiator at a temperature of about 90 to about 170 ° C, preferably about 100 to about 150 ° C, for about 1 to 5 hours, preferably 2 to 4 hours. It can be performed to a degree and polymer (I) can be obtained.

As a solvent used for the said reaction, For example, Hydrocarbon type, such as toluene, xylene, cyclohexane, n-hexane; Esters such as methyl acetate, ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone; Amide systems such as dimethylformamide and dimethylacetamide; Alcohols such as methanol, ethanol, n-propanol and iso-propanol; Or a mixture thereof.

As the polymerization initiator, azobisisobromononitrile (AIBN), t-butylperoxy-2-ethylhexanoate (perbutyl O), or the like can be used.

Next, 4-33 mass% of polyvinyl compounds (d2), Preferably 5-25 mass% and other radically polymerizable unsaturated monomer (d34) 67-96 mass%, Preferably it contains 60-90 mass% Is an emulsion polymerization reaction in the presence of the polymer (I) and water using the mixture (6).

As said polyvinyl compound (d2), 1 or more types of monomers used for manufacture of anionic polymer crosslinked microparticles | fine-particles (D1) can be selected and used. As another radically polymerizable unsaturated monomer (d34), at least 1 type or more can be selected suitably from another radically polymerizable unsaturated monomer (d31) and a carboxyl group-containing radically polymerizable monomer (d1).

In the reaction, polymerization initiators such as ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutyronitrile (AIBN) and t-butylperoxy-2-ethylhexanoate (perbutylO), and redox system It is also possible to use an initiator.

In addition, as a mass ratio of the polymer (I) and the mixture (6) at the time of using for manufacture of anionic polymer crosslinked microparticles | fine-particles (D2), polymer (I) / mixture (6) = 25/75 based on the total amount of each mixture -85/15 (mass ratio), Preferably it can adjust within the range of 60/40 (mass ratio)-80/20 (mass ratio).

As a density | concentration of the said polymerization initiator, it is 0.05-3 mass% with respect to the total amount of the monomer which comprises the mixture (6) or polymer (I), Preferably it is 0.1-10 mass%.

As a density | concentration of the said emulsifier, 0.3-3 mass% with respect to the total amount of the monomer which comprises the mixture 6 or polymer (I), Preferably about 0.5-2 mass% is also preferable for coating film performance. Moreover, if conditions are selected, granulation in the absence of an emulsifier is also possible.

In addition, in the presence of polymer (I) and water, the reaction temperature in the emulsion polymerization reaction using the mixture (6) is usually in the range of about 60 to 95 ° C, preferably about 75 to 85 ° C, and the reaction The time is usually about 10 hours or less, preferably about 0.5 to about 6 hours.

The obtained anionic polymer crosslinked microparticles | fine-particles (D2) have an acid value of 10-120 mgKOH / g, Preferably it is 30-100 mgKOH / g, More preferably, it is 50-90 mgKOH / g. The average particle diameter (Note 2) is 0.05-1.0 micrometer, Preferably it is 0.10-0.50 micrometer, More preferably, it is 0.10-0.30 micrometer. This range is preferable in order to form a coating film excellent in drawing / ironing molding processability and water whitening resistance.

In the coating composition for cans of the present invention, the anionic polymer crosslinked fine particles (D1) or anionic polymer crosslinked fine particles (D2) described above are further blended in the paint, whereby the coating film excellent in the balance between bending workability, whitening resistance, and flavor properties is obtained. Obtained.

The compounding quantity of the anionic polymer crosslinked microparticles | fine-particles (D1) or anionic polymer crosslinked microparticles | fine-particles (D2) mix | blended in this can coating composition is 1-50 mass parts per 100 mass parts of acrylic resin modified epoxy resins (A), Preferably it is 5-30 Range of parts by mass I am suitable. If it is less than 1 part by mass, it is ineffective for the improvement of coating performance such as bending workability, whitening resistance, and flavor, and if it exceeds 50 parts by mass, not only the coating stability is impaired but also the coating performance is not very effective.

The coating composition for cans of the present invention can be applied to various substrates. For example, an untreated or surface treated metal plate such as an aluminum plate, a steel plate, a didcjf plate, and a primer such as an epoxy or vinyl type are coated on these metal plates. The thing which processed these metal plates, such as a metal plate, with a can etc. is mentioned.

As a method of coating the coating composition for cans of this invention on a base material, various well-known methods, for example, roll coater coating, spray coating, immersion coating, electrodeposition coating, etc. are applicable. Among them, roll coater coating or spray coating is preferable. Although coating thickness may be suitably selected according to a use, about 3-20 micrometers is preferable normally. As dry conditions of a coated coating film, it is good to exist in the range for 10 second-30 minutes normally at 200-280 degreeC preferably on the conditions which reach | attain maximum raw material temperature of 120-300 degreeC normally.

Moreover, the coating film cross section obtained by apply | coating the coating composition for cans of this invention is a sea-island structure of the island part of 0.01-0.5 micrometer in diameter, Preferably it is 0.05-0.35 micrometer, More preferably, it is 0.08-0.15 micrometer. It is considered to form (refer FIG. 1), and it is thought that it contributes to the improvement of bending workability by forming such a sea island structure.

<Example>

The present invention will be described more specifically by way of examples. Hereinafter, "part" and "%" mean "mass part" and "mass%", respectively.

[Production (Manufacturing Examples 1-3) of Acrylic Resin Modified Epoxy Resin (A)]

Preparation Example 1 Preparation of Epoxy Resin Solution (a1)

Into a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, 558 parts of Epicoat 828EL (Note 3), 329 parts of bisphenol A, and 0.6 parts of tetrabutylammonium bromide were added, and the reaction was carried out at 160 ° C under a nitrogen stream. The reaction was followed by an epoxy equivalent and allowed to react for about 5 hours to obtain a bisphenol A type epoxy resin having a number average molecular weight of about 11,000 and an epoxy equivalent of about 8,000.

Note 3: Epicoat 828EL: Japan Epoxy Resin Co., Ltd., bisphenol A epoxy resin, epoxy equivalent approximately 190, molecular weight approximately 350

* Preparation Example 2: Preparation of carboxyl group-containing acrylic resin solution (a2)

Into a four-necked flask equipped with a reflux tube, a thermometer, a dropping lot, and a stirrer, 882 parts of n-butanol were added, `` 180 parts of methacrylic acid, 240 parts of styrene, 180 parts of ethyl acrylate, t-butylperoxy-2-ethylhexano 18 parts of "is heated to 100 degreeC under nitrogen stream, and it is dripped for about 3 hours from the dropping lot, and stirring is continued for 2 hours at the same temperature after dripping, and it cools then, and acrylic resin of 40% of solid content A solution was obtained. The obtained resin (solid content) had a resin acid value of 196 mgKOH / g and a number average molecular weight of about 19,000.

Preparation Example 3 Preparation of Acrylic Modified Epoxy Resin Dispersion (A)

In a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, 80 parts of bisphenol-A epoxy resin obtained in Production Example 1 (solid content), 50 parts of 40% acrylic resin solution obtained in Production Example 2 (20 parts solid), and diethylene After adding 33 parts of glycol monobutyl ether and heating and dissolving at 100 degreeC, after adding 2 parts of N, N- dimethylamino ethanol and reacting for about 2 hours, 3 parts of N, N- dimethylamino ethanol were added and reaction for 20 minutes. Continued. Then, 165 parts of deionized water was dripped over 1 hour, and water dispersion was performed, and the acrylic modified epoxy resin dispersion of the acid value 34 mgKOH / 9 and solid content 30% was obtained.

[Production of Resol-type Phenolic Resin (B)]

Preparation Example 4 Preparation of Resol-type Phenolic Resin Solution

In a four-necked flask equipped with a reflux tube, a thermometer and a stirrer, 188 parts of phenol and 324 parts of 37% formaldehyde aqueous solution were placed in the flask, and the contents were heated to 50 ° C. to uniformly dissolve the contents. Next, zinc acetate was added and mixed to adjust the pH in the system to 5.0, and then heated to 90 ° C to carry out the reaction for 5 hours. Subsequently, it cooled to 50 degreeC, the aqueous 32% calcium hydroxide dispersion was added slowly, pH was adjusted to 8.5, and reaction was performed at 50 degreeC for 4 hours.

After the reaction was completed, the pH was adjusted to 4.5 in 20% hydrochloric acid, and then the resin powder was extracted with a mixed solvent of xylene / n-butanol / cyclohexane = 1/2/1 (mass ratio) to remove the catalyst and the neutralized salt. Then, azeotropic dehydration was carried out under reduced pressure to obtain a pale yellow and transparent resol type phenol resin solution having a solid content of 60%.

[Production of Acrylic Resin (C) (Manufacturing Examples 5-10)]

* Preparation Example 5

70 parts of propylene glycol n-propyl ethers were put into the reaction container provided with the thermometer, the thermostat, the stirrer, the reflux cooler, and the dripping apparatus, and it stirred and mixed in nitrogen stream, and heated up at 100 degreeC.

Thereafter, a monomer mixture (20 parts of methyl methacrylate, 30 parts of 2-ethylhexyl acrylate, 50 parts of acrylic acid) and a polymerization initiator solution (8 parts of t-butylperoxy-2-ethylhexanoate, propylene glycol n- 50 parts of mixed solution of propyl ether) was added dropwise into the reactor with a metering pump over 4 hours, and aged for 0.5 hours after completion of dropping. Then, the polymerization initiator solution (0.5 parts of t-butylperoxy-2-ethylhexanoate and 30 parts of propylene glycol n-propyl ether mixtures) was dripped at 0.5 hour, and aging was carried out for 2 hours. Then, it cooled to 60 degreeC, filtered and discharged with 100 mesh nylon cross, and obtained acrylic resin (c1) of 40% of solid content, the acid value 390 mgKOH / g, and number average molecular weight 4,000. Resin (c2) (note 4) was added at 100 degreeC in the said acrylic resin (c1).

Note 4 Resin (c2)

70 parts of propylene glycol n-propyl ethers were put into the reaction container provided with the thermometer, the thermostat, the stirrer, the reflux cooler, and the dripping apparatus, and it stirred and mixed in nitrogen stream, and heated up at 100 degreeC. Thereafter, a monomer mixture (50 parts of methacrylic acid, 30 parts of ethyl acrylate, 20 parts of styrene), a polymerization initiator solution (8 parts of t-butylperoxy-2-ethylhexanoate, and 50 parts of propylene glycol n-propyl ether) The mixed solution) was added dropwise into the reactor with a metering pump over 4 hours, and aged for 0.5 hours after completion of dropping. Subsequently, the polymerization initiator solution (0.5 part of t-butylperoxy-2-ethylhexanoate and 30 parts of propylene glycol n-propyl ether mixtures) was dripped at 0.5 hour, and aged for 2 hours. Then, it cooled to 60 degreeC, filtered and discharged with 100 mesh nylon cross, and obtained resin (c2) of 40% of solid content, the acid value of 326 mgKOH / g, and number average molecular weight 4,000.

Next, 5 parts of Epicoat 834 (equivalent to Japan epoxy resin company, an epoxy resin, and a low molecular weight compound (c3)) was added, and the mixture was heated to 130 ° C and aged for 3 hours. Thereafter, the mixture was diluted with propylene glycol n-propyl ether, cooled to 60 ° C, filtered and discharged with 100 mesh nylon cross to obtain an acrylic resin No. 1 having a solid content of 40% and an acid value of 347 mgKOH / g.

* Production example 6 ~ 10

Acrylic resins No. 2 to No. 6 were obtained by the method similar to the manufacture example 5 except making the monomer to be used the compounding content of Table 1.

* 5: Shonool BKS-377F: manufactured by Showa Kobun-shi, trade name, resol type phenol resin, solid content 50%

* Comparative Production Example 1 (according to Japanese Patent Application Laid-Open No. 8-302275)

70 parts of propylene glycol n-propyl ethers were put into the reaction container provided with the thermometer, the thermostat, the stirrer, the reflux cooler, and the dripping apparatus, and it stirred and mixed in nitrogen stream, and heated up at 100 degreeC.

Thereafter, a monomer mixture (10 parts of acrylic acid, 40 parts of methyl methacrylate, 50 parts of ethyl acrylate), a polymerization initiator solution (8 parts of t-butylperoxy-2-ethylhexanoate, and propylene glycol n-propyl ether 50 Negative mixed liquid) was added dropwise into the reactor with a metering pump over 4 hours, and aged for 0.5 hour after completion of dropping. Subsequently, the polymerization initiator solution (0.5 part of t-butylperoxy-2-ethylhexanoate and 30 parts of propylene glycol n-propyl ether mixtures) was dripped at 0.5 hour, and aged for 2 hours. Thereafter, the mixture was cooled to 60 ° C, filtered and discharged with a 100 mesh nylon cross to obtain an acrylic resin No. 7 having a solid content of 40%, an acid value of 78 mgKOH / g, and a number average molecular weight of 3,500.

Comparative Example 2

70 parts of propylene glycol n-propyl ethers were put into the reaction container provided with the thermometer, the thermostat, the stirrer, the reflux cooler, and the dripping apparatus, and it stirred and mixed in nitrogen stream, and heated up at 100 degreeC.

Thereafter, a monomer mixture (50 parts of acrylic acid, 20 parts of methyl methacrylate, 30 parts of ethyl acrylate), a polymerization initiator solution (8 parts of t-butylperoxy-2-ethylhexanoate, and propylene glycol n-propyl ether 50 Negative mixed liquid) was added dropwise into the reactor with a metering pump over 4 hours, and aged for 0.5 hour after completion of dropping. Subsequently, the polymerization initiator solution (0.5 part of t-butylperoxy-2-ethylhexanoate and 30 parts of propylene glycol n-propyl ether mixtures) was dripped at 0.5 hour, and aged for 2 hours. Then, it cooled to 60 degreeC, filtered and discharged with 100 mesh nylon cross, and obtained the acrylic resin of 40% of solid content, the acid value 390 mgKOH / g, and number average molecular weight 4,000 (resin (c1)). Next, Resin (c2) (Note 4) obtained by carrying out similarly to manufacture example 5 in the said reaction container was added at 100 degreeC.

Next, 5 parts of Epicoat 834 (equivalent to Japan epoxy resin company, an epoxy resin, and a low molecular weight compound (c3)) was added, and the mixture was heated to 130 ° C and aged for 3 hours. Thereafter, the mixture was diluted with propylene glycol n-propyl ether, cooled to 60 ° C, filtered and discharged with a 100 mesh nylon cross to obtain an acrylic resin No. 8 having a solid content of 40%, an acid value of 330 mgKOH / g, and a number average molecular weight of 4,500. Got it.

Comparative Preparation Examples 3-6

Acrylic resins No. 9-No. 12 were obtained by the method similar to the comparative manufacture example 2 except making the monomer to be used the compounding content of Table 2.

* 5: Shonool BKS-377F: Showa Kobunshi Co., Ltd., a brand name, a resol type phenol resin

[Production of Anionic Polymer Crosslinked Fine Particles (D)]

Preparation Example 11 Preparation of Anionic Polymer Crosslinked Fine Particles (D1)

150 parts of deionized water and 0.5 parts (solid content) of "Newcol 562SF" (Note 6) were added to a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux cooler, and a dropping device, and stirred and mixed in a nitrogen stream to raise the temperature to 85 ° C. did.

Subsequently, 1% of the following "monomer mixture 1" and 5.2 parts of "2% ammonium persulfate aqueous solution" were introduced into the reaction vessel and kept at 85 ° C for 20 minutes. Thereafter, the remaining monomer emulsion and the aqueous ammonium persulfate solution were added dropwise into the reactor with a metering pump over 3 hours, and aged for 2 hours after completion of dropping. It cooled to 30 degreeC, and it filtered and discharged by 100 mesh nylon cross, and obtained the anionic polymer crosslinked microparticles (D1) of 0.1 micrometer of average particle diameters (note2), 25% of solid content, and acid value 65 mgKOH / g.

Monomer Mixture 1

135 deionized water

Styrene part 30

50 parts of ethyl acrylate

10 parts methacrylic acid

Ethylene glycol dimethacrylate 10 parts

`` Newcol 562SF '' (Note 6) 1 copy (solid)

`` 2% Ammonium Persulfate Aqueous Solution ''

0.2 part ammonium persulfate

10 parts deionized water

* 6 Newcol 562SF: Nippon Yukazai Co., Ltd., brand name, polyoxyethylene alkyl benzene sulfonate ammonium, active ingredient 60%

Preparation Example 12 Preparation of Anionic Polymer Crosslinked Fine Particles (D2)

95 parts of ethylene glycol monohexyl ether and 32 parts of n-butanol were put into the reaction container provided with the thermometer, the thermostat, the stirrer, the reflux cooler, and the dropping apparatus, and it stirred and mixed in nitrogen stream, and heated up at 100 degreeC.

Subsequently, a monomer mixture (50 parts of methacrylic acid, 45 parts of styrene, 5 parts of ethyl acrylate) and a polymerization initiator (2 parts of perbutylO, 10 parts of n-butanol) were added dropwise at the same time over 3 hours. And aged for 30 minutes. Thereafter, a polymerization initiator solution (0.4 parts of perbutylO, 10 parts of n-butanol) was added dropwise for 30 minutes, aged for 2 hours, and then diluted with 63 parts of n-butanol to obtain a solid content of 32%, an acid value of 326 mgKOH / mg, and a weight. Polymer No. 1 having an average molecular weight of 37,000 was obtained.

Subsequently, after neutralizing 25 parts (solid content) of the polymer No. 1 with 3.88 parts of dimethylethanolamine in a reaction vessel provided with a thermometer, a thermostat, a stirrer, and a reflux condenser, 250 parts of deionized water was added after stirring for 15 minutes. .

Then, below 30 degreeC, the following "monomer mixture" was added to deionized water to make an emulsion, and it was dripped in the reaction container over about 1 hour. Subsequently, after heating up to 85 degreeC and dripping the polymerization initiator aqueous solution (0.2 part of ammonium persulfate, 22 parts of deionized water) in nitrogen atmosphere, it aged for 2 hours. Thereafter, the mixture was cooled to 30 ° C, filtered through a 100-mesh nylon cross, discharged, and adjusted with deionized water to obtain anionic polymer crosslinked fine particles (D2) having a solid content of 20%. The anionic polymer crosslinked fine particles (D2) had an acid value of 82 mgKOH / g and an average particle diameter of 0.18 µm.

Monomer mixture

Deionized Water 75 parts

7.5 parts of ethylene glycol dimethacrylate

Ethylacrylate 37.5 parts

Styrene part 30

6) Newcol 562SF 0.75

Example 1 Preparation of Paint Composition for Cans

Acrylic part obtained in Production Example 5, in which neutral part equimolar amount of acid was previously neutralized with 1.7 parts (solid content) of a resol-type phenolic resin solution and 100 parts (solid content) of an acrylic modified epoxy resin dispersion having a solid content of 30% obtained in Production Example 3. After adding 5 parts (solid content) of resin No. 1 and stirring for about 30 minutes, deionized water was added gradually and adjusted, and the coating material No. 1 for cans of 25% of solid content was obtained.

Examples 2-9

Except having set it as the compounding content of Table 3, the coating materials No. 2-10 for cans of 25% of solid content were obtained by the method similar to Example 1.

Comparative Example 1

Obtained in Comparative Preparation Example 1, in which 1.7 parts (solid content) of the resol-type phenol resin solution was neutralized in advance with 100 parts (solid content) of the acrylic modified epoxy resin dispersion having a solid content of 30% obtained in Preparation Example 3, and the equimolar amount of acid was previously neutralized with dimethylethanolamine. After adding 5 parts (solid content) of acrylic resin No. 7, and stirring for about 30 minutes, deionized water was added gradually and adjusted, and the coating material No. 11 for cans of 25% of solid content was obtained.

Comparative Example 2-10

Except having set it as the compounding content of Table 4, the coating materials No.12-No.20 of 25% of solid content were obtained by the method similar to the comparative example 1.

* Production of trial

The coating for each can coating obtained in the above Examples and Comparative Examples is spray-coated to a # 5182 aluminum plate having a phosphoric acid chromate treatment so as to have a dry coating thickness of 10 μm, and baked and cured at 200 ° C. for 3 minutes. I made a plate. The performance test was done according to the following test method.

(7) Coating film cross section observation (μm): When the cross section of the coating film cut out of the test plate was observed with a scanning electron microscope (magnification of 5000 times), the structure could be confirmed, and it could be recognized in an area range of 10 μm × 10 μm. The average value (micrometer) of the width | variety (long diameter) of the longitudinal direction in 30 circular or elliptical drawing parts was calculated | required.

Note 8) T-Band Bending Processability:

After cutting the test plate 5 cm in the rolling direction and 4 cm in the vertical direction, a thickness of 0.26 was used between the bent portions of the test plate with the lower side folded twice using a special bending type DuPont impact tester in a room at 20 ° C. 2 mm of aluminum plate was inserted into the tester, and a weight of 1 kg iron having a flat contact surface was dropped at a height of 50 cm to impact the bent portion, and then energized for 6 seconds at an applied voltage of 6.5 V at the bent end portion. A current value of 20 mm in width at the bent tip was measured and evaluated according to the following criteria.

◎ less than 20㎃

○ is more than 20㎃ and less than 40㎃

△ is more than 40㎃ and less than 80㎃

× is 80㎃ or more.

Note 9) Retort adhesion of T-band bending part:

After cutting the test plate 5 cm in the rolling direction and 4 cm in the vertical direction, using a special bending type DuPont impact tester in a room at 20 ° C., the thickness was 0.26 between the bent portions of the test plate with the bottom folded twice. Two pieces of aluminum plate of mm were put into the tester, and a weight of 1 kg of iron having a flat contact surface was dropped at a height of 50 cm to give an impact to the bent portion, and then the test piece was placed in water at 125 ° C. for 30 minutes in an autoclave. Immerse. Thereafter, the water was wiped off, the processed portion was subjected to a peeling test with a cello tape, the site was energized with an applied voltage of 6.5 V, and a current value of 20 mm in width at the bent tip was measured and evaluated according to the following criteria.

◎ less than 20㎃

○ is more than 20㎃ and less than 40㎃

△ is more than 40㎃ and less than 80㎃

× is 80㎃ or more.

Note 10) Retort Whitening

The test plate was immersed in water, and the whitening state of the coating film processed at 125 degreeC for 30 minutes in the autoclave was evaluated by the following reference | standard.

◎ whitening is not confirmed at all,

○ very little whitening is confirmed,

△ whitening is confirmed a little,

× whitening is remarkably confirmed.

Note 11) Acid resistance

The test plate was immersed in an aqueous solution of 0.5% citric acid and malic acid, and treated at 125 ° C. for 30 minutes in an autoclave, and then the state was visually observed and evaluated according to the following criteria.

◎ deterioration is not confirmed at all,

(Circle) a peeling and swelling are confirmed slightly.

(Triangle | delta) is swollen and peeling is confirmed in the whole.

X is a swelling whole surface, peeling whole surface, or a weakening of a coating film is remarkable.

(12) Corrosion resistance after processing

The test piece was prepared in the same manner as the above-described T-band processing test, and the bent work was immersed in a mixed aqueous solution in which citric acid, malic acid, and sodium chloride were dissolved in 1%, respectively, and stored at 40 ° C. for 2 weeks. Was visually observed and evaluated by the following criteria.

◎ corrosion is not confirmed.

○ Corrosion is confirmed a little.

(Triangle | delta) is considerably corroded.

X is marked by corrosion.

(13) Flavor Castle

Each test plate was added to 30 mg / l of d-limonene (fragrance) in deionized water, and immersed at 35 ° C for 1 month in a solution dispersed in 1 g / l of S-1170 (manufactured by Mitsubishi Chemical Corporation, sucrose fatty acid ester). Saved. After storage, in order to measure d-limonene (fragrance) sorbed to the coating film, it was extracted by dipping in diethyl ether for 20 degreeC-1 week, and the extracted d-limonene (fragrance) was measured by gas chromatography, Evaluated by reference.

○ The extracted d-limonene (fragrance) is less than 0.6 mg per 120 mg of the coating film weight.

(Triangle | delta) shows that the extracted d-limonene (fragrance | flavor) is 0.6 mg or more per 120 mg of coating film weight, and is less than 1.6 mg.

X is 1.6 mg or more of 120-mg weight of extracted d-limonene (flavor).

According to the present invention, the bending workability, the whitening resistance, and the acid adhesion resistance are improved, so that a metal can having a coating film having excellent contents corrosion resistance and excellent flavor is obtained.

Claims (8)

100-20 mass parts of acrylic resin modified epoxy resins (A), 0.1-20 mass parts of resol-type phenol resins (B), and 0.1-20 mass of acrylic resin (C) of the acid value 100-500 mgKOH / g which has the following characteristics An aqueous coating composition, wherein the part is dispersed in an aqueous medium. ACRYLIC RESIN (C): Contains vinyl copolymer chain | strand (1) which consists of at least 1 type of radically polymerizable monomer selected from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid group containing radically polymerizable monomer, and methacrylic acid Has a vinyl copolymer chain (2) having a monomer component as a constituent component, 10-60 mass% of 1 or more types of radically polymerizable monomers chosen from acrylic acid, itaconic acid, sulfonic acid, or a phosphoric acid-containing radically polymerizable monomer, and 40-90 mass% of other radically polymerizable unsaturated monomers (1) as monomer components Vinyl copolymer resin (c1); Vinyl copolymer resin (c2) which makes 10-60 mass% of methacrylic acid and 40-90 mass% of other radically polymerizable unsaturated monomers (2) a monomer component; And A polymer formed by reacting a low molecular weight compound (c3) having two or more complementary reactive groups reactive with an acid group and a carboxyl group in one molecule.] delete The vinyl copolymer resin (c1), the vinyl copolymer resin (c2) and the low molecular weight compound (c3) constituting the acrylic resin (C) according to claim 1, wherein the vinyl copolymer resin (c1) and the vinyl copolymer resin Vinyl copolymer resin (c1) / vinyl copolymer resin (c2) = 60/40-95/5 (mass%) based on the total solid content of (c2), and it is [Vinyl copolymer resin (c1) + Vinyl copolymer resin (c2)] / low molecular weight compound (c3) = 100 / 0.1-100/20 (mass part), The aqueous coating composition characterized by the above-mentioned. The low molecular weight compound (c3) according to claim 1 or 3, wherein the low molecular weight compound (c3) is selected from an epoxy resin, a resol-type phenol resin, and a polycarbodiimide compound having an epoxy equivalent of 180 to 5,000 having two or more epoxy groups in one molecule. It is paper-like, The aqueous coating composition characterized by the above-mentioned. The water-based coating composition according to claim 4, wherein the low molecular weight compound (c3) is an epoxy equivalent of 200 to 1,000 epoxy resin having two or more epoxy groups in one molecule. The resin according to claim 1 or 3, wherein the acrylic resin modified epoxy resin (A) is formed by esterifying a bisphenol-type epoxy resin (a1) having a number average molecular weight of 2,000 to 35,000 and a carboxyl group-containing acrylic resin (a2). Or a resin obtained by graft polymerization of a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer (a3) to the bisphenol type epoxy resin (a1). 4-50 mass parts of anionic polymer crosslinked microparticles | fine-particles (D) which have the following characteristics further are contained with respect to 100 mass parts of acrylic resin modified epoxy resins (A). Aqueous coating compositions. [Anionic polymer crosslinked fine particle (D): 2-30 mass% of carboxyl group-containing radically polymerizable monomers (d1), 2-30 mass% of polyvinyl compounds (d2), and other radically polymerizable unsaturated in presence of water. It consists of the polymer of the acid value 10-100 mgKOH / g manufactured by superposing | polymerizing-reacting the radically polymerizable unsaturated monomer component which consists of 40-96 mass% of monomers (d3).] The coating composition for cans which aims at which the aqueous coating composition of Claim 1 or 3 is apply | coated to a can body.

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