JPH09278848A - Water-based coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based coating composition capable of forming a coating film excellent in dent resistance, flavor preservation, adaptability to retorting, tight adhesion, slip properties, corrosion resistance, processability, etc. SOLUTION: The composition comprises a dispersion in an aqueous medium of a resin obtained by emulsion-polymerizing an ethylenic monomer in the presence of an aqueous dispersion of a modified epoxy resin in which 55-90% of the epoxy groups have been converted to groups each having a polymerizable unsaturated group through reaction with a polymerizable unsaturated carboxylated monomer and at least part of the remaining epoxy groups have undergone esterification with a carboxylated acrylic resin. The modified epoxy resin contains carboxyl groups in an amount sufficient to enable the resin to self-disperse in water upon neutralization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel water-based coating composition, and more specifically, it is suitable for coating the inner surface of a can, and in particular, when it is applied to the inner surface of a steel can, it is perforated due to internal corrosion caused at an external impact location. The present invention relates to a novel water-based coating composition capable of forming a coating film that is less likely to occur.

[0002]

2. Description of the Related Art Conventionally, a carboxyl group-containing modified epoxy resin has been known as a vehicle component of an aqueous resin paint used for coating food cans and beverage cans. For example, a self-emulsifying emulsion paint obtained by esterifying a carboxyl group-containing acrylic resin and an epoxy resin disclosed in JP-A-55-3481 and JP-A-53-12.
Self-emulsifying emulsion paint obtained by graft-polymerizing a polymerizable unsaturated monomer containing a carboxyl group-containing polymerizable unsaturated monomer onto the epoxy resin disclosed in Japanese Patent Publication No. 85
JP-A-58-198513 and JP-A-60-106.
There is known a self-emulsifying emulsion paint obtained by polymerizing a reaction product of an epoxy resin and (meth) acrylic acid disclosed in Japanese Patent Publication No. 805 and a polymerizable unsaturated monomer. However, these emulsion paints are inferior in internal corrosion resistance (hereinafter referred to as “dent resistance”), workability, flavor resistance, etc. against the occurrence of puncture due to corrosion occurring at the external impact location in the emulsion paint coating can. There was a flaw.

Further, Japanese Patent Publication No. 4-12309 discloses that
An ionic polymer having a carboxyl group and a hydroxy ester group and having no unreacted epoxy group, which is obtained by reacting an epoxy resin with a carboxyl group-containing resin, and an ethylenically unsaturated monomer in an aqueous dispersion of the ionic polymer. An aqueous coating composition containing a polymerized copolymer and a neutralizing agent is disclosed. Furthermore, special table flat 3-500
Japanese Patent No. 785 discloses that the epoxy group in the epoxy resin is 5
A polymerizable unsaturated group-containing modified epoxy resin obtained by reacting 50% with a carboxyl group-containing ethylenically unsaturated monomer,
Terpolymerized with a tertiary amine, a carboxyl group-containing acrylic resin that is reacted with residual epoxy groups of the polymerizable unsaturated group-containing modified epoxy resin, and a polymerizable unsaturated group of the polymerizable unsaturated group-containing modified epoxy resin A reaction product of an addition-polymerizable monomer, and an addition polymer which is formed by the above-mentioned copolymerization but is not copolymerized with the polymerizable unsaturated group of the polymerizable unsaturated group-containing modified epoxy resin. Aqueous coating compositions are disclosed.

However, a coating film formed from the coating composition of Japanese Patent Publication No. 4-12309 or the coating composition of Japanese Patent Publication No. 3-500785 has inferior slipperiness, and further the coating film after retort treatment Since it is liable to be whitened or dyed with coffee, the retort resistance is poor and the flavor resistance is poor.

[0005]

The object of the present invention is to form a coating film excellent in dent resistance, flavor resistance, retort resistance, adhesion, slipperiness, corrosion resistance, workability, etc. The present invention is to provide a water-based coating composition suitable as.

[0006]

As a result of earnest research, the present inventor has found that the above object can be achieved by an aqueous paint containing a specific emulsion resin, and has completed the present invention.

That is, in the present invention, 55% to 90% of the epoxy groups of the [A] epoxy resin react with the carboxyl group-containing polymerizable unsaturated monomer to form a portion having a polymerizable unsaturated group, and the remaining Of at least a part of the epoxy group of the esterification reaction with a carboxyl group-containing acrylic resin, water of a modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group in an amount sufficient for self-dispersion in water by neutralization The present invention relates to a water-based coating composition, characterized in that an emulsion resin obtained by emulsion-polymerizing an ethylenically unsaturated monomer in the presence of a dispersion liquid is dispersed in an aqueous medium.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the emulsion resin which is the component [A] is an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group. It is an emulsion resin obtained by emulsion polymerization of a monomer.

In the modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group, 55% to 90% of the epoxy groups of the epoxy resin react with the carboxyl group-containing polymerizable unsaturated monomer to form a polymerizable unsaturated group. It has a sufficient amount of carboxyl groups so that at least a part of the remaining epoxy groups undergoes an esterification reaction with a carboxyl group-containing acrylic resin and can be self-dispersed in water in a neutralized form. is there.

The epoxy resin used in the production of the above modified epoxy resin is a resin having one or more epoxy groups in one molecule, and is composed of a polyphenol compound having two or more phenolic hydroxyl groups in one molecule and epichlorohydrin. Reaction products are generally preferred.

Specific examples of the above polyphenol compound include 2,2'-bis (4-hydroxyphenyl) propane (hereinafter sometimes referred to as "bisphenol A"), halogenated bisphenol A and bis (4-hydroxy). Phenyl) methane (hereinafter sometimes referred to as "bisphenol F"), 2,2'-bis (4-hydroxyphenyl) butyl, bis (4-hydroxyphenyl) sulfone (hereinafter sometimes referred to as "bisphenol S"),
Examples thereof include resorcinol, tetrahydroxyethane, phenol, and a novolac-type polyfunctional phenol that is condensed with cresol and formalin. Of these,
Bisphenol A and bisphenol F are preferred,
It may be a mixture of both.

Further, the epoxy resin may be an epoxy ester resin in which a reaction product of the polyphenol compound and epichlorohydrin is further combined with a dibasic acid.

Here, the dibasic acid has the general formula

[0014]

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(Wherein n represents an integer of 1 to 12), specifically, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid and hexahydro. Phthalic acid and the like can be preferably used.

Specific examples of such epoxy resin include, for example, Epicoat 1004 (epoxy equivalent of about 900, number average molecular weight about 1,400) manufactured by Shell Chemical Co., Epicoat 1007 (epoxy equivalent of about 1,700, number average molecular weight of about 1400). 2,900), Epicoat 1009 (epoxy equivalent of about 3,500, number average molecular weight about 3,750), Epicoat 1010 (epoxy equivalent of about 4,500, number average molecular weight about 5,500) and the like.

The above epoxy resin has a number average molecular weight of 2,
It is preferably in the range of 000 to 25,000 from the viewpoint of the balance of workability and corrosion resistance. Further, the epoxy resin preferably has an epoxy equivalent of 2,200 to 5,000.

The carboxyl group-containing polymerizable unsaturated monomer used for introducing the polymerizable unsaturated group by reacting with the epoxy group of the epoxy resin is acrylic acid,
Unsaturated monobasic acids such as methacrylic acid and crotonic acid; unsaturated fatty acids such as oleic acid and linolenic acid; maleic acid,
Examples thereof include monoesters of unsaturated dibasic acids such as itaconic acid and fumaric acid.

Further, as the carboxyl group-containing acrylic resin to be esterified with at least a part of the remaining epoxy groups of the above epoxy resin, at least a carboxyl group-containing radically polymerizable unsaturated monomer such as the following (i) group is used. A polymerization method such as emulsion polymerization, solution polymerization, bulk polymerization, etc., in addition to one type or a monomer of the (i) group and a radically polymerizable unsaturated monomer such as the following (ii) group which is copolymerizable therewith The acrylic resin obtained by polymerization can be exemplified by

(I) α, β-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and crotonic acid.

(Ii) 2-hydroxyethyl acrylate,
1 to 1 carbon atoms of acrylic acid or methacrylic acid such as 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate
8 hydroxyalkyl esters; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-
Butyl methacrylate, cyclohexyl acrylate,
Alkyl or cycloalkyl ester of 1 to 24 carbon atoms of acrylic acid or methacrylic acid such as cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, decyl acrylate, etc. Acrylamide, methacrylamide, N-methyl acrylamide, N-ethyl methacrylamide, diacetone acrylamide, N-methylol acrylamide, N
-Acrylic or methacrylic amides such as methylol methacrylamide, N-methoxymethyl acrylamide, N-butoxymethyl acrylamide, etc. or derivatives thereof; aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene; vinyl propionate , Vinyl acetate, acrylonitrile, methacrylonitrile, vinyl pivalate, Veova monomer (manufactured by Shell Chemical Co.) and the like.

Examples of preferable combinations of the above-mentioned unsaturated monomers include, for example, (a) methyl methacrylate /
2-ethylhexyl acrylate / acrylic acid, (b) styrene / methyl methacrylate / ethyl acrylate / methacrylic acid, (c) styrene / ethyl acrylate / methacrylic acid, (d) methyl methacrylate / ethyl acrylate / acrylic acid Etc.

The acid value of the solid content of the acrylic resin containing a carboxyl group should be in the range of 150 to 450 mgKOH / g so that the stability in an aqueous medium, the retort resistance of the resulting coating film, the flavor resistance, etc. From the viewpoint of

From the viewpoint of coating performance and coating workability, the weight average molecular weight of the carboxyl group-containing acrylic resin (styrene conversion value by GPC, the same applies hereinafter) is in the range of 5,000 to 100,000. ,preferable.

The reaction between the epoxy resin, the carboxyl group-containing polymerizable unsaturated monomer and the carboxyl group-containing acrylic resin is carried out by (1) reacting the epoxy resin with the carboxyl group-containing polymerizable unsaturated monomer, and then Either a method of reacting the residual epoxy group with a carboxyl group-containing acrylic resin or a method of (2) simultaneously reacting an epoxy resin, a carboxyl group-containing polymerizable unsaturated monomer, and a carboxyl group-containing acrylic resin may be used.

In the above method (1), the reaction between the epoxy resin and the carboxyl group-containing polymerizable unsaturated monomer is usually carried out by an esterification reaction in an organic solvent in the presence of an esterification catalyst such as an amine. It can be carried out. Then, a carboxyl group-containing acrylic resin is added to this reaction product, and the reaction can be carried out in an organic solvent in the presence of an esterification catalyst such as a tertiary amine. In the method (1), the reaction between the epoxy resin and the carboxyl group-containing polymerizable unsaturated monomer
An amount of the carboxyl group-containing polymerizable unsaturated monomer corresponding to 55 to 90%, preferably 55 to 80%, of the equivalent of the epoxy groups in the epoxy resin is used, and 55 of the epoxy groups is used.
~ 90%, preferably 55-80% esterified or 4
A quaternary salt is introduced to introduce a polymerizable unsaturated group into the epoxy resin.

In the above method (2), in order to simultaneously react the epoxy resin, the carboxyl group-containing polymerizable unsaturated monomer and the carboxyl group-containing acrylic resin, esterification of a tertiary amine or the like is usually carried out in an organic solvent. It can be carried out by subjecting these three members to an esterification reaction in the presence of a catalyst. In the method (2),
The amount of the carboxyl group-containing polymerizable unsaturated monomer used is
The amount corresponds to 55 to 90%, preferably 55 to 80%, of the equivalent weight of the epoxy group in the epoxy resin.

In the above methods (1) and (2), the amount of the carboxyl group-containing acrylic resin used can be arbitrarily selected according to the desired physical properties and the like, but normally, the carboxyl group-containing acrylic resin / epoxy resin solid is used. 5/95 to 90/10, more preferably 10/90 to 50/5 by weight ratio
It is preferable to be within the range of 0.

The reaction between the epoxy resin and the carboxyl group-containing polymerizable unsaturated monomer in the above method (1), the esterification reaction between this reaction product and the carboxyl group-containing acrylic resin, and 3 in the above method (2) In any of the above esterification reactions, when a tertiary amine is used as an esterification catalyst, the tertiary amine is added in an amount of 0.2 with respect to the equivalent amount of the epoxy groups in the epoxy resin.
0.5 to 5 equivalents, preferably 1 to 3 equivalents at 40 to 200 ° C., preferably 60 to 150 ° C.
It can be performed by holding for about 6 hours.

A modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group is obtained by the above reaction (1) or (2). In the above reaction (1) or (2), a carboxyl group-containing acrylic resin is obtained. In the esterification reaction of the carboxyl group in the medium or carboxyl group-containing polymerizable unsaturated monomer with the epoxy group in the epoxy resin, in the carboxyl group-containing acrylic resin or in the carboxyl group-containing polymerizable unsaturated monomer and the epoxy resin It is considered that both the quaternary ammonium chloride reaction of the epoxy group and the tertiary amine are simultaneously performed. In the above reaction (1) or (2), if the amount of the tertiary amine used is increased, the proportion of the quaternary ammonium chloride reaction tends to increase.

As the tertiary amine for promoting the esterification reaction in the above (1) and (2), for example, dimethylethanolamine, dimethylbenzylamine, triethanolamine, monomethyldiethanolamine, morpholine and the like can be used. preferable. The usage is
A range of 1 to 20% by weight is suitable based on the total solid content of the carboxyl group-containing acrylic resin or the carboxyl group-containing polymerizable unsaturated monomer and the epoxy resin.

The modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group obtained by the methods (1) and (2) above has a polymerizable unsaturated group of 0.04 to 0.45.
Equivalent / kg resin, preferably 0.10-0.3 equivalent / k
g resin, epoxy equivalent of 2,000 or more, preferably 2,
500-50,000, acid value 10-400mgKOH /
It is preferred to have g resin, preferably 30-150 mg KOH / g resin.

In the present invention, the emulsion resin [A]
Can be obtained by emulsion-polymerizing an ethylenically unsaturated monomer in the presence of an aqueous dispersion of the modified epoxy resin obtained as described above.

In order to disperse the modified epoxy resin in water to form an aqueous dispersion, for example, the modified epoxy resin obtained by the above method (1) or (2) is mixed with water and, if necessary, an amine. A neutralizer may be added and stirred.

As the above-mentioned neutralizing agent, those known per se can be used, and preferred specific examples include, for example, the general formula R ₁ R ₂ R ₃ N (in the formula, R ₁ , R ₂ and R ₃ are respectively A linear or branched lower alkyl group which may have a hydroxyl group), N-methylpyrrolidine,
At least one selected from the group consisting of N-methylmorpholine, pyridine, N-methylpyrrole, N-methylpiperidine, ammonia, and a mixture of any of these is included. Specific examples of the compound represented by the above general formula R ₁ R ₂ R ₃ N include trimethylamine, dimethylethanolamine (dimethylaminoethanol), methyldiethanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl-3. -Hydroxy-1-propylamine, dimethylbenzylamine, dimethyl-2-hydroxy-1-propylamine, diethylmethylamine, dimethyl-1-hydroxy-2-propylamine, and mixtures of any of these. it can. Of these, particularly preferred are triethylamine, dimethylethanolamine and the like.

The ethylenically unsaturated monomer used in the emulsion polymerization is a carboxyl group exemplified as the above (i) group, which forms a carboxyl group-containing acrylic resin that is reacted with an epoxy resin to obtain the modified epoxy resin. Group-containing radically polymerizable unsaturated monomers and the radically polymerizable unsaturated monomers exemplified as the group (ii) can be mentioned. Among them, at least one monomer selected from an alkyl ester of acrylic acid or methacrylic acid having 1 to 24 carbon atoms and styrene is preferable.

In the emulsion polymerization, the weight ratio of the modified epoxy resin to the ethylenically unsaturated monomer is 95/5 to 50/50, preferably 95/5 to 65, in terms of the former / the latter ratio.
It is preferably in the range of / 35.

The polymerization conditions in the above emulsion polymerization will differ depending on the monomer species and the polymerization initiator species used, but the reaction temperature is usually in the range of about 30 ° C. to about 100 ° C., and the polymerization time is 30 minutes to 10 hours. Is the range. The solid content concentration of the dispersion liquid of the emulsion resin [A] obtained by emulsion polymerization is not particularly limited, but is usually 15 to 15.
A solids concentration of 60% by weight is preferred.

In the water-based coating composition of the present invention, from the viewpoint of further improving retort resistance, slipperiness and the like, in addition to the emulsion resin [A], [B] a carboxyl group-containing acrylic resin and an epoxy resin are further added. At least one resin selected from a graft resin (b) obtained by graft-polymerizing a polymerizable unsaturated monomer containing a carboxyl group-containing polymerizable unsaturated monomer to an adduct resin (a) obtained by reacting It is preferable to disperse a carboxyl group-containing modified epoxy resin in an aqueous medium.

From the viewpoint of processability of the coating film, the modified epoxy resin [B] preferably has an epoxy equivalent of 2,000 or more, and more preferably in the range of 2,500 to 50,000. The acid value is preferably 10 to 400 mgKOH / g resin, and more preferably 30 to 150 mgKOH / g resin, from the viewpoints of resin stability and water resistance.

The epoxy resin used for producing the above-mentioned adduct resin (a) and graft resin (b) is used for forming an aqueous dispersion of the modified epoxy resin used for producing the emulsion resin [A]. As the epoxy resin to be used, those exemplified can be mentioned.

The carboxyl group-containing acrylic resin used in the production of the adduct resin (a) includes a carboxyl group-containing acrylic resin which is reacted with an epoxy resin to obtain the modified epoxy resin used in the production of the emulsion resin [A]. The resins exemplified as the acrylic resin can be mentioned.

The adduct resin (a) can be obtained by reacting an epoxy resin and a carboxyl group-containing acrylic resin in, for example, an organic solvent in the presence of a tertiary amine. In this reaction, mainly in the presence of a tertiary amine, an esterification reaction between a carboxyl group in a carboxyl group-containing acrylic resin and an epoxy group in an epoxy resin, and a carboxyl group in a carboxyl group-containing acrylic resin and an epoxy resin It is considered that both the quaternary ammonium chloride reaction of the epoxy group and the tertiary amine therein is carried out at the same time. In this reaction, the ratio of the carboxyl group-containing acrylic resin and the epoxy resin can be arbitrarily selected according to the desired physical properties of the modified epoxy resin to be formed, etc., but is usually the sum of the carboxyl group-containing acrylic resin and the epoxy resin. Based on the weight, the carboxyl group-containing acrylic resin is 5 to 90% by weight, especially 1
The range of 0 to 50% by weight and the range of 10 to 95% by weight of the epoxy resin, especially 50 to 90% by weight, are preferable.

As the tertiary amine that promotes the above reaction, for example, dimethylethanolamine, dimethylbenzylamine, triethanolamine, monomethyldiethanolamine, morpholine, etc. are preferably used, and the amount thereof is a carboxyl group-containing group. A range of 1 to 20% by weight is suitable based on the total solid content of the acrylic resin and the epoxy resin.

The reaction temperature and time of the above carboxyl group-containing acrylic resin and epoxy resin vary depending on the type of resin, the type of solvent, etc., but the reaction temperature is generally 40.
-200 ° C, especially 60-150 ° C, reaction time 0.5-6
It is preferably within the range of time.

The graft resin (b) is obtained by graft-polymerizing a polymerizable unsaturated monomer containing a carboxyl group-containing polymerizable unsaturated monomer onto an epoxy resin, for example, in the presence of a free radical generator in an organic solvent. Obtainable.

As the carboxyl group-containing polymerizable unsaturated monomer, there is formed a carboxyl group-containing acrylic resin which is reacted with an epoxy resin to obtain the modified epoxy resin used in the production of the emulsion resin [A] (i). Examples thereof include the carboxyl group-containing radically polymerizable unsaturated monomer exemplified.

In the polymerizable unsaturated monomer containing the carboxyl group-containing polymerizable unsaturated monomer, the polymerizable unsaturated monomer other than the carboxyl group-containing polymerizable unsaturated monomer is used in the production of the emulsion resin [A]. Radical-polymerizable unsaturated monomers exemplified as the group (ii) for forming a carboxyl group-containing acrylic resin that is reacted with an epoxy resin to obtain the modified epoxy resin can be mentioned.

Examples of free radical generators usable in the above graft polymerization reaction include benzoyl peroxide, perbutyl octate, t-butyl hydroperoxide, azobisisobutyronitrile, azobisisovaleronitrile, 2,2'-azobis (2-
Aminopropane) hydrochloride and the like can be used, and these can be generally used in a ratio of 0.5 to 20 parts by weight with respect to 100 parts by weight of the total amount of the epoxy resin and the polymerizable unsaturated monomer.

The composition ratio of the epoxy resin and the polymerizable unsaturated monomer in the graft polymerization is not strictly limited, but generally, the epoxy resin is contained in an amount of 10 to 95 parts by weight based on the total weight of the both components. %, Especially 50 to 90% by weight, polymerizable unsaturated monomer 90 to 5% by weight, especially 50
The range of 10 to 10% by weight is preferable.

The graft polymerization reaction is preferably carried out in an organic solvent system capable of dissolving or dispersing the epoxy resin, the polymerizable unsaturated monomer, the polymer formed from the polymerizable unsaturated monomer, the graft polymer and the like. .

The monomer composition in the graft polymerization can be arbitrarily selected depending on the properties required for the final paint and cured coating film. For example, by incorporating a carboxyl group-containing polymerizable unsaturated monomer into the graft polymerization monomer composition, it can react with unreacted epoxy resin and become water-based, resulting in stability of the paint and film-forming property during curing. Etc. can be improved.

The reaction conditions such as temperature and time during the graft polymerization are not special, and the conditions known per se can be used. This graft polymerization is considered to be due to the hydrogen abstraction reaction in the presence of the initiator.

It is considered that the graft reaction point is hydrogen bonded to the tertiary carbon in the epoxy resin skeleton (hydrogen on the carbon to which the secondary hydroxyl group is bonded).

The modified epoxy resin [B] is usually made into a water dispersion and then mixed with the emulsion resin [A]. The water-dispersed product of the modified epoxy resin [B] is obtained by dispersing the modified epoxy resin [B] as it is in an aqueous medium, or by neutralizing it with a basic compound or the like and then dissolving or dispersing it in the aqueous medium. ,Obtainable.

As the basic compound of the neutralizing agent, for example,
Examples thereof include those exemplified as the neutralizing agent used as needed when preparing an aqueous dispersion of a modified epoxy resin used in the production of the emulsion resin [A].

Neutralization is usually preferably carried out at a neutralization equivalent of 0.1 to 1.2. When neutralized in this way, the modified epoxy resin [B] can be made into a self-emulsifying type, and it is not necessary to use an emulsifier, a dispersant, or the like together in order to dissolve or disperse it in an aqueous medium.

As the modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group for producing the emulsion resin [A] and the organic solvent used when producing the modified epoxy resin [B], these are used. Resin and raw materials (resin, monomer) used for producing these resins can be dissolved or dispersed, and functional groups contained in these resins or raw materials (for example, carboxyl group, epoxy group, Those which are substantially inert to vinyl groups) are used.

As the organic solvent, various types of solvents can be used, but alcohol-based organic solvents are particularly preferable. For example, isopropanol, n-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. Examples thereof include monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether and the like.

Among these, particularly, a hydrophobic organic solvent such as n-butyl alcohol is soluble in the carboxyl group-containing acrylic resin, reduces the viscosity of the system, and serves as an auxiliary solvent for water-dispersing the acrylic resin. It is preferable to use this because it works.

In addition to the above alcoholic organic solvents, for example, aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl isobutyl ketone and methyl ethyl ketone. The low boiling point organic solvent can be used in combination. When used in combination, total organic solvent 1
It is preferably used in an amount of about 50 parts by weight or less in 00 parts by weight.

In the composition of the present invention, the emulsion resin [A] is used as an essential component, and if necessary, the carboxyl group-containing modified epoxy resin [B] is mixed and used. As long as the emulsion resin [A] is used, the compounding ratio of the emulsion resin [A] and the modified epoxy resin [B] is not particularly limited, but the former / the latter solid content weight ratio is 5/95 to. 95/5, 5 / 95-
It is preferably in the range of 70/30.

The composition of the present invention comprises the above emulsion resin [A] and optionally a carboxyl group-containing modified epoxy resin [B] stably dispersed in an aqueous medium. , A neutralizing agent, an organic solvent, a curing agent, and other organic resins can also be added. The solid content of the composition of the present invention is usually about 10 to 50% by weight, preferably about 15 to 35% by weight.

Here, examples of the aqueous medium include water, a mixed liquid of water and an organic solvent, and the like. Examples of the neutralizing agent include basic compounds and the like used as necessary in the production of the emulsion resin [A]. Examples of the organic solvent include the same organic solvents as those used for producing the modified epoxy resin [B]. Also,
Examples of the curing agent include urea resins, melamine resins, phenol resins and the like, their methylol compounds, and cross-linking agents such as their alkyl ether compounds, which are water-soluble or hydrophobic. Is also good. Furthermore,
Examples of the organic resin include polyester resin, polybutadiene and its modified resin, vinyl chloride-vinyl acetate-copolymer resin and the like.

As the above curing agent, a phenol resin is particularly suitable. As such a phenol resin, a resol type phenol-formaldehyde resin is preferable. The resol-type phenol-formaldehyde resin is a bisphenol alone or 1 mol of bisphenol and 1 mol of phenols and p-substituted monohydric phenol mixed at a ratio of 1 mol or less and formaldehyde of 4.0 to 4.0.
It can be obtained by carrying out a condensation reaction with 6.0 mol in the presence of a catalyst such as an alkali metal hydroxide.

The above bisphenols have the general formula

[0067]

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(Wherein R represents a divalent aliphatic hydrocarbon group having 1 to 4 carbon atoms), and
Specifically, for example, 2,2′-bis (4-hydroxyphenyl) propane (“bisphenol A”), bis (4
-Hydroxyphenyl) methane ("bisphenol F"), bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, and the like, among which bisphenol A is preferred. Is.

Examples of the p-substituted monohydric phenol include p-cresol, p-tert-butylphenol, p-ethylphenol, p-tert-amylphenol, p-nonylphenol, p-phenylphenol, p- Examples thereof include cyclohexylphenol.

When the p-substituted monohydric phenol is mixed with the bisphenol, the amount of the p-substituted monohydric phenol used is 1 mol or less, preferably 0.3 to 0.6 mol, per 1 mol of the bisphenol. It is good to set the degree. p-
When the amount of the substituted monohydric phenol used exceeds 1 mol, the flavor resistance of the paint for the inner surface of the can is impaired when the obtained phenol-formaldehyde resin is used as a curing agent, which is unsuitable.

The above-mentioned resol-type phenol-formaldehyde resin is preferably obtained by subjecting the above-mentioned phenols and formaldehyde to a condensation reaction in the presence of a catalyst such as an alkali metal hydroxide. It is preferable to use formaldehyde in an amount in the range of 4.0 to 6.0 mol per mole, which is more than the theoretical active hydrogen atom of the phenols.
When the blending amount of formaldehyde with respect to the phenols is less than 4.0 mol, the obtained resol-type phenol.
When formaldehyde resin is used as a curing agent in a paint for the inner surface of a can, it is inferior in flavor resistance. On the contrary, when the amount of formaldehyde compounded with respect to the phenols exceeds 6.0 mols, the resulting resole-type phenol-formaldehyde resin is used as a curing agent, the water resistance of the coating composition is deteriorated, and the flavor resistance is improved. Will be inferior to

In the water-based coating composition of the present invention, the amount of the resol-type phenol / formaldehyde resin to be blended is
The obtained coating composition is 20 parts by weight or less, and further 3 to 10 parts by weight based on 100 parts by weight of the total solid content of the emulsion resin [A] and the carboxyl group-containing modified epoxy resin [B]. It is preferable from the viewpoints of processability and flavor resistance of the film.

In the water-based coating composition of the present invention, if necessary, additives for coating such as a lubricant, an anti-agglomeration agent and a fluidity adjusting agent, a pigment and the like may be appropriately blended.

Specific examples of the lubricant include vegetable wax, animal wax, mineral wax, petroleum wax, fatty acid ester wax and the like.

Examples of plant waxes include carnauba wax, cotton wax, and wax. Animal waxes include lanolin wax, gallow wax, and beeswax. Petroleum waxes include paraffin wax, microcrystalline wax, and wax. Examples include petrolatum, mineral waxes include ozokerite and montan wax, and petroleum waxes include polyethylene wax.

Examples of the above fatty acid ester waxes include fatty acid sucrose ester and esterified products of polyglycerin ether and fatty acid.

Examples of the fatty acid sucrose ester include monoesters, diesters and triesters in which at least one of the eight hydroxyl groups present in sucrose disclosed in JP-A-6-293865 is esterified with a fatty acid. Mention may be made of the above polyesters or mixtures of these esters.

The esterification product of polyglycerin ether and fatty acid is, for example, an esterification product of polyglycerin ether which is a 4- to 12-mer of glycerin and fatty acid disclosed in JP-A-7-138501. The one in which 1/3 or more of the hydroxyl groups in the polyglycerin ether are esterified can be mentioned.

The fatty acid in the esterification product of fatty acid sucrose ester and polyglycerin ether and fatty acid is preferably saturated or unsaturated fatty acid having 11 to 23 carbon atoms, and specific examples thereof include lauric acid, oleic acid, myristic acid and palmitic acid. , Stearic acid, behenic acid and the like.

Among these lubricants, the melting point is 25-100.
It is preferable to use a wax having a temperature of 0 ° C. (more preferably 50 to 90 ° C.), such as carnauba wax, lanolin wax, paraffin wax, and fatty acid ester wax. These waxes may be in any form such as emulsion type, dispersion type and dissolution type.

By adding a lubricant to the water-based coating composition of the present invention, the surface of the coating film obtained from this composition can be imparted with slipperiness, the frictional resistance of the coating surface can be reduced, and the moldability can be improved. And the corrosion resistance and flavor retention after processing are also improved.

In the composition of the present invention, the compounding amount of the lubricant is not particularly limited, but is usually 15 with respect to the coating solid content.
It is preferably blended in an amount of not more than 10% by weight, more preferably 0.05 to 10% by weight.

The aqueous coating composition of the present invention can be applied to various substrates. For example, the composition of the present invention is particularly useful in the can manufacturing industry that uses mainly metal cans (often cylindrical), which are manufactured from aluminum, tin-free steel, electrolytic tin plates, rolled plates and the like. It can be used preferably. The cans used for packaging and shipping food, beer and other beverages are mainly three-piece or two-piece punching and ironing (D &
It is of the type I). Cans made from three-piece (body, lid and bottom) can be roll coated prior to forming the metal sheet into a can or can be spray coated after partial forming. D & I type cans, in which a metal sheet is stamped to produce a closed end cylinder, are generally spray coated.
The composition of the present invention generally has a composition of about 90-
A coating can be formed by drying at a temperature of 330 ° C. for about 5 seconds to about 30 minutes.

[0084]

EXAMPLES Hereinafter, Production Examples, Examples and Comparative Examples will be given,
The present invention will be described more specifically. In each example, "part" and "%" are based on weight.

Production Example 1 Production of Acrylic Resin Solution Containing Carboxyl Group A four-necked flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen inlet was charged with 542 parts of ethylene glycol monobutyl ether and heated to 93 ° C. It was kept heated.
Next, a mixed solution of 325 parts of methacrylic acid, 150 parts of styrene, 25 parts of ethyl acrylate and 30 parts of t-butylperoxy-2-ethylhexanoate and a polymerization initiator was maintained at 93 ° C. from the dropping funnel. The resulting mixture was added dropwise to the flask over 3 hours. After dropping, 100
The mixture was heated to ℃ and kept for 1 hour for aging. Then cool and add 595 parts of ethylene glycol monobutyl ether,
A carboxyl group-containing acrylic resin solution (1) having a solid content of about 30% was obtained. The obtained resin has a resin acid value of 425 mgK.
It had an OH / g resin, weight average molecular weight of about 10,000.

Production Example 2 Production of carboxyl group-containing acrylic resin solution 1365 parts of n-butanol was placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen inlet, and heated to 93 ° C. Held Next, methacrylic acid 67
A flask in which a mixed solution of 5 parts, 712 parts of styrene, 113 parts of ethyl acrylate and 52.5 parts of t-butylperoxy-2-ethylhexanoate and a polymerization initiator was held at 93 ° C. from a dropping funnel. It was dripped in over 3 hours. After dripping, heat to 100 ℃ and
Hold for time and mature. Then t-butylperoxy-
7.5 parts of 2-ethylhexanoate and n-butanol 4
A mixed solution with 5 parts was added dropwise over 30 minutes, and the mixture was kept for 2 hours for aging. Then, 600 parts of ethylene glycol monobutyl ether and 1430 parts of n-butanol were added to obtain a carboxyl group-containing acrylic resin solution (2) having a solid content of about 30%. The obtained resin has a resin acid value of 293 m.
It had a gKOH / g resin and a weight average molecular weight of about 30,000.

Production Example 3 Production of acrylic resin solution containing carboxyl group 1470 parts of n-butanol was placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen inlet, and heated to 100 ° C. Held Then methacrylic acid 4
50 parts, styrene 450 parts, ethyl acrylate 600
Part and a mixed solution of 30 parts of t-butylperoxy-2-ethylhexanoate and a polymerization initiator were added dropwise from a dropping funnel into the flask maintained at 100 ° C. over 3 hours. After completion of dropping, the mixture was kept at 100 ° C. for 1 hour for aging. Then, 750 parts of ethylene glycol monobutyl ether was added to obtain a carboxyl group-containing acrylic resin solution (3) having a solid content of about 40%. The resulting resin had a resin acid value of 198 mg KOH / g resin and a weight average molecular weight of about 60,000.

Production Example 4 Production of Polymerizable Unsaturated Group- and Carboxyl Group-Containing Modified Epoxy Resin "XAC-6109" (manufactured by Asahi Ciba, epoxy resin, epoxy equivalent 2,650, number average molecular weight 1)
2,800, solid content 100%) 233 parts and carboxyl group-containing acrylic resin solution (1) 203 parts having a solid content of about 30% obtained in Production Example 1 were charged, and after heating to 80 ° C. to uniformly dissolve At the same temperature, 4.4 parts of methacrylic acid was added, 11.8 parts of deionized water was added dropwise over 30 minutes, and then 15.9 parts of dimethylethanolamine were added to obtain 1
The mixture was stirred for a time to carry out an esterification reaction. Then, 725 parts of deionized water was added over 1 hour to obtain a modified epoxy resin solution (X-1) having a solid content of about 25%. The obtained resin had a polymerizable unsaturated group introduced into 58% of the epoxy groups of the epoxy resin, had an epoxy group residual rate of 0%, and had a resin acid value of 79 mgKOH / g.

Production Example 5 Production of Polymerizable Unsaturated Group- and Carboxyl Group-Containing Modified Epoxy Resin 233 parts of "XAC-6109" and the carboxyl group-containing acrylic resin solution having a solid content of about 30% obtained in Production Example 1 (1) 203 parts were charged, heated to 80 ° C. and uniformly dissolved, then 5.9 parts methacrylic acid was added at the same temperature, and 11.8 parts deionized water was added dropwise over 30 minutes,
Then, 15.9 parts of dimethylethanolamine was added and stirred for 1 hour to carry out an esterification reaction. Then, 730 parts of deionized water was added over 1 hour to obtain a modified epoxy resin solution (X-2) having a solid content of about 25%. The obtained resin had a polymerizable unsaturated group introduced into 78% of the epoxy groups of the epoxy resin, had an epoxy group residual rate of 0%, and had a resin acid value of 82 mgKOH / g.

Production Example 6 Production of Polymerizable Unsaturated Group- and Carboxyl Group-Containing Modified Epoxy Resin 233 parts of "XAC-6109" and a carboxyl group-containing acrylic resin solution having a solid content of about 30% obtained in Production Example 2 (2) After charging 203 parts and heating to 90 ° C. to dissolve uniformly, 4.4 parts of methacrylic acid was added at the same temperature, and 11.8 parts of deionized water was added dropwise over 30 minutes,
Then, 12.8 parts of dimethylethanolamine was added and stirred for 1 hour to carry out an esterification reaction. Then, 730 parts of deionized water was added over 1 hour to obtain a modified epoxy resin solution (X-3) having a solid content of about 25%. The obtained resin had a polymerizable unsaturated group introduced into 58% of the epoxy groups of the epoxy resin, had an epoxy group residual rate of 0%, and had a resin acid value of 53 mgKOH / g.

Production Example 7 Production of Polymerizable Unsaturated Group- and Carboxyl Group-Containing Modified Epoxy Resin 207 parts of "XAC-6109" and a carboxyl group-containing acrylic resin solution having a solid content of about 40% obtained in Production Example 3 were placed in a reaction vessel. (3) After charging 222 parts and heating to 100 ° C. to dissolve uniformly, 3.9 parts of methacrylic acid was added at the same temperature, 11.8 parts of deionized water was added dropwise over 30 minutes, and then, Dimethyl ethanolamine (12.8 parts) was added, and the mixture was stirred for 1 hour to carry out an esterification reaction. Then, 743 parts of deionized water was added over 1 hour to obtain a solid content of about 25
% Modified epoxy resin solution (X-4) was obtained. The obtained resin has a polymerizable unsaturated group introduced into 58% of the epoxy groups of the epoxy resin, and the residual rate of the epoxy group is 0.
%, Resin acid value 52 mgKOH / g.

Production Example 8 Production of Polymerizable Unsaturated Group- and Carboxyl Group-Containing Modified Epoxy Resin In a reaction vessel, Epicoat 828EL (manufactured by Yuka Shell Epoxy Co., bisphenol A type epoxy resin, epoxy equivalent 190, number average molecular weight 380) ) 880 parts, 492 parts of bisphenol A, 1.23 parts of tetraethylammonium bromide and 152 parts of methyl isobutyl ketone were charged and heated to 140 ° C. under a nitrogen stream and reacted for about 4 hours to obtain an epoxy resin solution. The epoxy resin obtained had an epoxy equivalent of 3,700 and a number average molecular weight of 17,000.
Had 0. Then, 807 parts of the carboxyl group-containing acrylic resin solution (1) having a solid content of about 30% obtained in Production Example 1 was charged into the obtained epoxy resin solution, heated to 90 ° C. to be uniformly dissolved, and then at the same temperature. Methacrylic acid 19.3
Parts were added, 58.3 parts of deionized water was added dropwise over 30 minutes, then 69.5 parts of dimethylethanolamine were added and stirred for 1 hour to carry out the esterification reaction. Then, 4050 parts of deionized water was added over 1 hour to obtain a modified epoxy resin solution (X-5) having a solid content of about 25%. The resin obtained is 60% of the epoxy groups of the epoxy resin.
Had a polymerizable unsaturated group introduced therein, and had an epoxy group residual rate of 0% and a resin acid value of 56 mgKOH / g.

Production Example 9 Production of Comparative Epoxy Resin Containing Polymerizable Unsaturated Group and Carboxyl Group for Comparison 233 parts of "XAC-6109" and a carboxyl group having a solid content of about 30% obtained in Production Example 1 were contained. 203 parts of acrylic resin solution (1) was charged, heated to 80 ° C. and uniformly dissolved, then 3.0 parts of methacrylic acid was added at the same temperature, and 11.8 parts of deionized water was added dropwise over 30 minutes. Then
Then, 15.9 parts of dimethylethanolamine was added and stirred for 1 hour to carry out an esterification reaction. Then, 716 parts of deionized water was added over 1 hour to obtain a modified epoxy resin solution (X-6) having a solid content of about 25%. The obtained resin had a polymerizable unsaturated group introduced into 40% of the epoxy groups of the epoxy resin, had an epoxy group residual rate of 0%, and had a resin acid value of 76 mgKOH / g.

Production Example 10 Production of polymerizable unsaturated group- and carboxyl group-containing modified epoxy resin for comparison In a reaction vessel, Epicoat 1004 (produced by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent of about 900, 153 parts of number average molecular weight 1,400) and 32 parts of ethylene glycol monobutyl ether were charged and heated to 130 ° C. under a nitrogen stream to give 0.03 part of tetramethylammonium chloride, 4.3 parts of methacrylic acid and butylated hydroxytoluene 0. Add .02 parts,
The reaction was performed for about 4 hours. Then, a carboxyl group-containing acrylic resin solution (2) 3 having a solid content of about 30% obtained in Production Example 2
After charging 10 parts and heating to 90 ° C. to dissolve uniformly, 29.1 parts of deionized water was added dropwise at the same temperature over 30 minutes, and then 14.6 parts of dimethylethanolamine was added for 1 hour. The esterification reaction was carried out with stirring. Then, 290 parts of deionized water was added over 1 hour to obtain a solid content of about 3
A 0% modified epoxy resin solution (X-7) was obtained. The obtained resin has a polymerizable unsaturated group introduced into 33% of the epoxy groups of the epoxy resin, and the residual rate of the epoxy group is 0.
%, Resin acid value 86 mg KOH / g.

Production Example 11 Production of carboxyl group-containing modified epoxy resin 194 parts of "XAC-6109" and 188 parts of the carboxyl group-containing acrylic resin solution (1) having a solid content of about 30% obtained in Production Example 1 were placed in a reaction vessel. After charging, heating to 80 ° C. to dissolve uniformly, 12.6 parts of deionized water was added to 3 at the same temperature.
The mixture was added dropwise over 0 minutes, 12.5 parts of dimethylethanolamine was added, and the mixture was stirred for 1 hour to carry out an esterification reaction. Then, 593 parts of deionized water was added over 1 hour to obtain a modified epoxy resin aqueous dispersion (B-1) which was an adduct resin (a) having a solid content of about 25%. The obtained resin is
It had an epoxy group residual rate of 0% and a resin acid value of 79 mgKOH / g.

Production Example 12 Production of Modified Epoxy Resin Containing Carboxyl Group In a reaction vessel, 880 parts of Epicoat 828EL (manufactured by Yuka Shell Epoxy Co., bisphenol A type epoxy resin, epoxy equivalent 190, number average molecular weight 380), bisphenol A Was charged with 1.23 parts of tetraethylammonium bromide and 152 parts of methyl isobutyl ketone, and the mixture was heated to 140 ° C. under a nitrogen stream and reacted for about 4 hours to obtain an epoxy resin solution. The epoxy resin obtained had an epoxy equivalent of 3,700 and a number average molecular weight of 17,000.
Had 0. Then, 807 parts of a carboxyl group-containing acrylic resin solution (1) having a solid content of about 30% obtained in Production Example 1 was charged into the obtained epoxy resin solution, heated to 90 ° C. and uniformly dissolved, and then at the same temperature. Deionized water (58.3 parts) was added dropwise over 30 minutes, then 69.5 parts of dimethylethanolamine was added and stirred for 1 hour to carry out an esterification reaction. Then, 4,000 parts of deionized water was added over 1 hour to obtain a modified epoxy resin aqueous dispersion (B-2) which was an adduct resin (a) having a solid content of about 25%. The obtained resin has an epoxy group residual rate of 0% and a resin acid value of 51 mg KO.
It had H / g.

Production Example 13 Production of Modified Epoxy Resin Containing Carboxyl Group In a reaction vessel, 200 parts of "XAC-6109", 108 parts of ethylene glycol monobutyl ether and 129 parts of n-butanol were charged and uniformly heated by heating to 118 ° C. Then, at the same temperature, 30 parts of methacrylic acid and 15 parts of styrene are added.
Part, 5 parts of ethyl acrylate, and 4 parts of a wetted product of benzoyl peroxide having a solid content of 75% were added dropwise over 2 hours, and the reaction was terminated at the same temperature when the epoxy equivalent reached 3,500. Cooled down. Further, 36 parts of dimethylethanolamine and 473 parts of deionized water were added and stirred at 60 ° C. to obtain a modified epoxy resin aqueous dispersion (B-3) which was a graft resin (b) having a solid content of about 25%. The obtained resin had an epoxy group residual ratio of 90% of the epoxy resin and a resin acid value of 75 mgKOH / g.

Production Example 14 Production of Emulsion Resin (A) 280 parts of modified epoxy resin solution (X-1) having a solid content of about 25% obtained in Production Example 4 and 90 parts of deionized water were placed in a reaction vessel.
18 parts of styrene, 12 parts of n-butyl acrylate and t
-Built in 0.17 part of butyl hydroperoxide,
It was heated to 70 ° C. under a nitrogen stream and ammonium persulfate was added to 0.
Add 28 parts and react at the same temperature for 2 hours to obtain a solid content of about 2
A 5% aqueous emulsion resin dispersion (A-1) was obtained.

Production Example 15 Production of Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution (X-2 obtained in Production Example 5 was used. Was carried out in the same manner as in Production Example 14 except that (1) was used to obtain an emulsion resin aqueous dispersion (A-2) having a solid content of about 25%.

Production Example 16 Production of Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution (X-3 obtained in Production Example 6 was used. Was performed in the same manner as in Production Example 14 to obtain an emulsion resin aqueous dispersion (A-3) having a solid content of about 25%.

Production Example 17 Production of Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution (X-4 obtained in Production Example 7 was used. Was performed in the same manner as in Production Example 14 to obtain an emulsion resin aqueous dispersion (A-4) having a solid content of about 25%.

Production Example 18 Production of Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution (X-5 obtained in Production Example 8 was used. Was performed in the same manner as in Production Example 14 to obtain an emulsion resin aqueous dispersion (A-5) having a solid content of about 25%.

Production Example 19 Production of Emulsion Resin (A) In a reaction vessel, 360 parts of modified epoxy resin solution (X-1) having a solid content of about 25% obtained in Production Example 4 and 30 parts of deionized water,
6 parts of styrene, 4 parts of n-butyl acrylate and 0.17 part of t-butyl hydroperoxide were charged and heated to 70 ° C. under a nitrogen stream to give ammonium persulfate 0.28.
Part and add to react at the same temperature for 2 hours, solid content about 25%
A water-based emulsion resin dispersion (A-6) was obtained.

Production Example 20 Production of Comparative Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution obtained in Production Example 9 ( X-6) was used in the same manner as in Production Example 14 to obtain an emulsion resin aqueous dispersion (A-7) having a solid content of about 25%.

Production Example 21 Production of Comparative Emulsion Resin (A) 224.6 parts of modified epoxy resin solution (X-7) having a solid content of about 25% obtained in Production Example 10 and dimethylethanolamine 1 were placed in a reaction vessel. 0.4 parts, deionized water 276.8 parts, styrene 6 parts and t-butyl hydroperoxide 0.2.
2 parts were charged, the mixture was heated to 70 ° C. under a nitrogen stream, 0.37 part of ammonium persulfate was added, and the mixture was reacted at the same temperature for 2 hours to give an emulsion resin aqueous dispersion (A-) having a solid content of about 25%.
8) was obtained.

Production Example 22 Production of Comparative Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution obtained in Production Example 11 ( The same procedure as in Production Example 14 except that B-1) was used to obtain an emulsion resin aqueous dispersion (A-9) having a solid content of about 25%.

Production Example 23 Production of Comparative Emulsion Resin (A) In Production Example 14, instead of the modified epoxy resin solution (X-1) obtained in Production Example 4, the modified epoxy resin solution obtained in Production Example 12 ( The same procedure as in Production Example 14 except that B-2) was used to obtain an aqueous dispersion of emulsion resin (A-10) having a solid content of about 25%.

Production Example 24 Production of Phenol Resin Solution 100 parts of bisphenol A, 178 parts of 37% aqueous formaldehyde solution and 1 part of caustic soda were added, and after reacting at 60 ° C. for 3 hours, the mixture was thoroughly washed with an aqueous solution of phosphoric acid to adjust the pH to 6
I made it. Then, 30 parts of n-butanol was added and dehydration was performed under reduced pressure at 50 ° C. for 3 hours. Again, n-butanol was added and the resin solution was filtered to obtain a phenol resin solution (P-1) having a solid content of 60% and a viscosity Y (Gardner foam viscometer, 25 ° C.).

Example 1 Production of Aqueous Coating Composition 40 parts of the emulsion resin aqueous dispersion (A-1) obtained in Production Example 14 and the modified epoxy resin aqueous dispersion (B obtained in Production Example 11 (B -1) 360 parts, 8 parts of the phenol resin solution (P-1) obtained in Production Example 24, "Mychem 16
0 "(Carnauba wax dispersion, 10% solid content, manufactured by Michael Man Chemicals) and 111 parts deionized water were added and stirred to obtain a stable aqueous coating composition having a solid content of about 20%.

Examples 2 to 10 and Comparative Examples 1 to 4 Production of Aqueous Coating Composition In Example 1, the emulsion resin aqueous dispersion, the carboxyl group-containing modified epoxy resin aqueous dispersion, the phenol resin solution, and the composition of the wax are mixed. As shown in Table 1 below, except that the amount of deionized water is adjusted so that the solid content is about 20%, and the solid content is about 20%.
A stable aqueous coating composition was obtained.

[0111]

[Table 1]

The amounts in Table 1 are parts by weight of solids.

Next, each aqueous coating composition obtained in Examples 1 to 10 and Comparative Examples 1 to 4 was applied to the inner surface of a steel 2-piece can having an internal capacity of 350 ml by a dry coating film of 150 to 170 mg per can. Spray evenly to achieve a weight of 200
A first coating film was formed by drying at 0 ° C. for about 2 minutes. On this coating film, the same aqueous coating composition was applied under the same conditions as the formation condition of the first coating film and dried to form a second coating film.
The weight of the total coating film on the inner surface of one can was 300 to 340 mg. The following coating film performance tests were performed on the obtained coated cans.

Flavor resistance: 340 ml of tap water treated with activated carbon was filled in the can of the test paint can, and the can was tightened to 100.
After sterilizing treatment at ℃ for 30 minutes, after storing at 37 ℃ for 3 months,
A flavor test was conducted according to the following evaluation criteria.

⊚ indicates no change, ∘ indicates a slight change, Δ indicates a slight change, × indicates a remarkable change,
Shown respectively.

Hygienic property: 340 ml of ion-exchanged water was filled in the can of the test paint can and wound, and after treatment at 125 ° C. for 30 minutes, potassium permanganate was added according to the test method described in the Food Sanitation Law. The hygiene was evaluated based on the consumption amount (ppm).

⊚: 0 ppm or more and less than 2 ppm, ◯: 2 ppm or more but less than 5 ppm, Δ: 5 ppm or more but less than 10 ppm, ×: 1
0 ppm or more is shown respectively.

Acid resistance: The body of the test paint can is cut open, and the end surface of the coated plate is repair-painted to form a test piece. The test piece is dipped in a 10% hydrochloric acid aqueous solution and dipped at 20 ° C. for 1 week. The coating film was visually evaluated according to the following criteria.

⊚ indicates no abnormality, ∘ indicates slight whitening, Δ indicates slight whitening, and x indicates marked whitening.

Retort resistance: The body of the test paint can was cut open, and the coating film of the test piece with the end face of the coated plate repair-coated was cross-cut and then immersed in boiling water at 125 ° C for 30 minutes, and then the coating film was cooled to room temperature. After drying, the appearance and adhesion of the coating film were evaluated according to the following criteria.

With respect to the appearance of the coating film, the degree of whitening of the coating film was visually evaluated. ⊚ indicates no change, and × indicates whitening. The adhesion of the coating film was evaluated by the coating surface after the cellophane adhesive tape was attached to the cross-cut coating surface and strongly peeled off. ◎ means no peeling, ○ means very slight peeling
Δ indicates slight peeling, and × indicates remarkable peeling.

Sliding property: The body of the test paint can was cut open, and the cut test piece was cut, and the test piece was cut by Swing Albert Instrument C.
o.) Egan slip tester model (Egan
The friction coefficient of the coating film was measured by Slip Tester Model) No.225-3.

Dent resistance: The body of the test paint can was cut open, the end surface of the coated plate was repair-painted, and the outer surface was covered with a nylon film to give a test piece. A wedge having a load of 500 g was struck from the outer coating film side of this test piece from a height of 30 cm to give an external impact. This test piece was placed in a glass bottle filled with an aqueous solution of 3% sodium chloride and 3% citric acid and sealed. After storing this glass bottle at 50 ° C. for 14 weeks, the iron ion concentration (ppm) in the aqueous solution was measured by the atomic absorption method and evaluated according to the following criteria.

⊚ indicates less than 0.5 ppm, ∘ indicates 0.5 ppm or more and less than 2 ppm, Δ indicates 2 ppm or more and less than 5 ppm, and x indicates 5 ppm or more.

Impact processability: The body of the test paint can was cut open and cut into a size of 40 mm × 50 mm to give a test piece. With the coating side of this test piece facing outward, the test piece was folded in two so that the length of the bent part was 40 mm, and a 0.23 mm thick tin-free steel was placed between the two folded test pieces. Scissors two pieces, drop a load of 3 kg from a height of 42 cm to the bending part, energize the bending tip for 6.5 V × 6 seconds, measure the current value (mA) of the processed part 2 cm width, the following criteria It was evaluated by.

⊚ indicates less than 1 mA, ∘ indicates 1 mA or more and less than 3 mA, Δ indicates 3 mA or more and less than 10 mA, and x indicates 10 mA or more.

The results of each test are shown in Table 2.

[0128]

[Table 2]

[0129]

The aqueous coating composition of the present invention comprises emulsion-polymerizing an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a modified epoxy resin containing a specific polymerizable unsaturated group and a carboxyl group. An emulsion resin [A], and, if necessary, a carboxyl group-containing modified epoxy resin [B],
Is a water-based coating composition stably dispersed in an aqueous medium, and in the production of the emulsion resin [A], 55 to 5 of the epoxy groups in the epoxy resin is used as the modified epoxy resin.
Since a polymer having a polymerizable unsaturated group introduced into a high proportion of 90% is used and the ethylenically unsaturated monomer is emulsion polymerized in the presence of an aqueous dispersion of this modified epoxy resin, ethylene is used. The unsaturated unsaturated monomer reacts with the polymerizable unsaturated group in the epoxy resin, and the polymer of the ethylenically unsaturated monomer is highly graft-bonded with the epoxy resin.

Since the water-based coating composition of the present invention contains the above-mentioned emulsion resin [A] as an essential component, the dent resistance, flavor resistance, retort resistance, adhesion, slipperiness, corrosion resistance, workability, etc. An excellent coating film can be formed. The water-based coating composition of the present invention can form a coating film exhibiting excellent properties, particularly for can coating, especially for can inner surface coating.

Claims (11)

[Claims] 1. 55% of epoxy groups of [A] epoxy resin
About 90% is a site having a polymerizable unsaturated group by reacting with a carboxyl group-containing polymerizable unsaturated monomer, and at least a part of the remaining epoxy group is esterified with a carboxyl group-containing acrylic resin. , Emulsion-polymerizing an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group in an amount sufficient for self-dispersion in water by neutralization. An aqueous coating composition comprising an emulsion resin dispersed in an aqueous medium. 2. The aqueous coating composition according to claim 1, wherein the epoxy resin in the emulsion resin [A] has an epoxy equivalent of 2,200 to 5,000 and a number average molecular weight of 2,000 to 25,000. 3. The carboxyl group-containing acrylic resin in the emulsion resin [A] has an acid value of 150 to 450 mgK.
OH / g resin, weight average molecular weight of 5,000 to 100,0
The water-based coating composition according to claim 1 or 2, which is a resin having 00. 4. A modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group in the emulsion resin [A] is a polymerizable unsaturated group 0.04 to 0.45 equivalent / kg resin and an epoxy equivalent of 2,000 or more. , Acid value 10-400m
It has gKOH / g resin, It is characterized by the above-mentioned.
The water-based coating composition according to any one of 3 above. 5. The emulsion resin [A] has a modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group and an ethylenically unsaturated monomer in a weight ratio of 95/5 to the former / the latter. The aqueous coating composition according to claim 1, which is an emulsion resin obtained by emulsion polymerization at 50/50. 6. An ethylenically unsaturated monomer used for emulsion polymerization of an emulsion resin [A] is at least one kind of monomer selected from an alkyl ester of acrylic acid or methacrylic acid having 1 to 24 carbon atoms and styrene. The aqueous coating composition according to claim 1, which is a body. 7. The emulsion resin [A] comprises a mixture of an epoxy resin, a carboxyl group-containing polymerizable unsaturated monomer, a carboxyl group-containing acrylic resin, and a tertiary amine as 1 part.
In the presence of an aqueous dispersion of a modified epoxy resin containing a polymerizable unsaturated group and a carboxyl group in an amount sufficient to self-disperse in water by neutralization, which is obtained by reacting at a temperature of 20 ° C. or less, ethylenic The aqueous coating composition according to claim 1, which is an emulsion resin obtained by emulsion-polymerizing a saturated monomer. 8. An addition resin (a) obtained by reacting a [B] carboxyl group-containing acrylic resin and an epoxy resin in addition to the emulsion resin [A] and an epoxy resin, and a carboxyl group-containing polymerizable unsaturated monomer. The carboxyl group-containing modified epoxy resin, which is at least one resin selected from the graft resins (b) obtained by graft-polymerizing a polymerizable unsaturated monomer containing carboxylic acid, is dispersed in an aqueous medium. Aqueous coating composition. 9. A carboxyl group-containing modified epoxy resin [B] has an epoxy equivalent of 2,000 or more and an acid value of 10 to 4.
The water-based coating composition according to claim 8, which comprises 00 mg KOH / g resin. 10. The compounding ratio of the emulsion resin [A] and the carboxyl group-containing modified epoxy resin [B] is 5/95 to 95/5 in terms of the former / latter solid content weight ratio.
The water-based coating composition according to 1. 11. The aqueous coating composition according to claim 1, further comprising a curing agent in the aqueous coating composition.