JP5502272B2 - Water-based paint composition - Google Patents

Description

  The present invention relates to an acrylic resin-modified epoxy resin-based aqueous coating composition, and in particular, an aqueous coating composition that can form a coating film excellent in processability, adhesion, and corrosion resistance, and that is suitable for can coating, especially for can lid coating. The present invention relates to a composition and a method for forming a coating film on a metal plate using the aqueous coating composition.

  Conventionally, organic solvent-based vinyl chloride sol paints are often used as paints for can lids because they can form coating films with excellent processability. There is an urgent need to make the paint for lids water-based.

  Conventionally, as a water-based paint for the inner surface of a can, a paint obtained by appropriately combining or reacting an epoxy resin, an acrylic resin, and a phenol resin is mainly used. When these water-based paints are used for can lid coating, the resulting coating film is generally hard and has processability, adhesion to a substrate, and corrosion resistance compared to a coating film from a vinyl chloride sol paint for can lids. In addition, there is a problem that when the tab of the can lid is opened, the coating film remains and the film resistance is poor.

  Various methods for solving these problems have been proposed. For example, Patent Document 1 discloses water-dispersed fine particles having an outer portion formed of a carboxyl group-containing self-emulsifying epoxy resin derived from a bisphenol F-type epoxy resin and a core portion formed of a conjugated diene resin. An aqueous resin composition for metal coating containing a resin has been proposed. Patent Document 2 proposes an aqueous paint in which a carboxyl group-containing acrylic resin-modified epoxy resin having an aromatic polymer epoxy resin having a number average molecular weight of 9,000 or more as an essential component is dispersed in water. Further, Patent Document 3 proposes an aqueous coating composition in which a specific resol type phenol resin and a styrene copolymer rubber are blended with an acrylic resin-modified epoxy resin.

  However, in any of the proposed compositions, the obtained coating film has not yet been put into practical use because the balance of workability, adhesion to a substrate, corrosion resistance, and film resistance is not sufficient.

  The object of the present invention is to provide a water-based paint having no problems as described above, capable of forming a coating film excellent in processability, adhesion to a substrate, corrosion resistance and film resistance, and suitable for use as a can lid. Is to get.

JP-A-5-9431 JP-A-7-138523 Japanese Patent Application Laid-Open No. 11-263939

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by an aqueous paint containing an acrylic resin-modified epoxy resin and specific water-dispersible acrylic polymer particles having a high molecular weight and a very low degree of crosslinking. As a result, the present invention has been completed.

Thus, according to the present invention, “1. (A) acrylic resin-modified epoxy resin and (B) carboxyl group-containing polymerizable unsaturated monomer 0.1 to 15 based on 100 parts by mass of the resin (A)”. And a monomer comprising 85 to 99.9% by weight of a polymerizable unsaturated monomer selected from monoesterified products of acrylic acid or methacrylic acid and a monohydric alcohol having 1 to 4 carbon atoms and styrene. Radical polymerization initiator which is a poorly water-soluble azo compound having a solubility in water at 25 ° C. of 0.01 to 1.0% by mass relative to the total mass of the saturated monomer and 3% by mass or less, and the polymerizable unsaturated monomer A copolymer obtained by emulsion polymerization in the presence of 1.5 to 6% by mass of a dispersion stabilizer with respect to the total mass of the acid, having an acid value of 3 to 35 mgKOH / g and a weight average molecular weight of 300,000 or more so Ri and mass concentration 1.35% of 1,4-dioxane and the absorbance values Ru der 0.2 Water-dispersible acrylic polymer particles at a wavelength of 330nm by spectrophotometer with a liquid as a solvent 0.5 A water-based coating composition containing ˜30 parts by mass.

2. The acrylic resin-modified epoxy resin (A) is obtained by esterifying the bisphenol type epoxy resin (a) and the carboxyl group-containing acrylic resin (b), or the bisphenol type epoxy resin (a) is not polymerized with a carboxyl group. Item 2. The aqueous coating composition according to Item 1, which is an acrylic resin-modified epoxy resin obtained by graft polymerization of a polymerizable unsaturated monomer component containing a saturated monomer.
3. Item 3. The aqueous coating composition according to Item 1 or 2, wherein the water-dispersible acrylic polymer particles (B) have a weight average molecular weight of 300,000 to 10,000,000.

4). Water-dispersible acrylic polymer particles (B) are in one molecule,
What is obtained by emulsion polymerization in the presence of a reactive emulsifier having a polyoxyethylene group and a polymerizable unsaturated group represented by — (CH ₂ CH ₂ O) _n — (where n is an integer of 5 to 60) The aqueous coating composition according to any one of Items 1 to 3, which is

5. Furthermore, as a crosslinking agent (C), the water-based coating composition as described in any one of said claim | item 1-4 containing at least 1 sort (s) of a phenol resin and an amino resin,
6). The water-based coating composition according to any one of Items 1 to 5, wherein the solid content of the component (C) is 0 to 15% by mass, based on 100 parts by mass of the resin solid content of the component (A).
7). 7. A coating film forming method, wherein the aqueous coating composition according to any one of items 1 to 6 is roll-coated on a metal plate and baked and cured. Is provided.

  The water-based coating composition of the present invention is a spectrophotometer using a liquid in which 1,4-dioxane having a weight average molecular weight of 300,000 or more and a mass concentration of 1.35% is used as a solvent in an acrylic resin-modified epoxy resin. The water-dispersible acrylic polymer particles having a high molecular weight and a very low degree of crosslinking are blended with an absorbance value at a wavelength of 330 nm of 0.2 or less. With this specific formulation, it was possible to form a coating film with excellent coating performance such as processability, adhesion to a substrate, processability, water resistance, corrosion resistance, hygiene and film resistance. Among the cans for painting the inner and outer surfaces of the can, it can be suitably used as a can lid.

  Below, the water-based coating composition of this invention is demonstrated in detail. First, each component of the water-based coating composition of this invention is demonstrated.

Acrylic resin modified epoxy resin (A)
The acrylic resin-modified epoxy resin that is the component (A) of the composition of the present invention is an epoxy resin modified with an acrylic resin, and suitable specific examples include, for example, the following (I) and (II). it can.
(I) Bisphenol type epoxy resin (a) [hereinafter sometimes abbreviated as “epoxy resin (a)”] and carboxyl group-containing acrylic resin (b) [hereinafter abbreviated as “acrylic resin (b)”) A resin obtained by an ester addition reaction with
(II) A resin obtained by graft polymerization of a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer to a bisphenol type epoxy resin (a).

  In the above (I), the epoxy resin (a) and the acrylic resin (b) can be easily subjected to an ester addition reaction by heating, for example, in an organic solvent solution in the presence of an esterification catalyst.

  In the above (II), for example, a polymerizable unsaturated monomer component can be graft-polymerized to the epoxy resin (a) in the presence of a radical generator such as benzoyl peroxide in an organic solvent.

  As the bisphenol type epoxy resin (a) used in the above (I) and (II), for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary. A resin obtained by condensing epichlorohydrin and bisphenol, if necessary, in the presence of a catalyst such as an alkali catalyst to form a low molecular weight epoxy resin, and subjecting this low molecular weight epoxy resin and bisphenol to a polyaddition reaction And any of epoxy resins obtained by reacting these obtained resins or the low molecular weight epoxy resin with a dibasic acid.

  Examples of the bisphenol include 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-hydroxynaphthyl) methane and the like can be mentioned among others. Bisphenol A and bisphenol F are preferably used . The bisphenols can be used alone or as a mixture of two or more.

As the dibasic acid used for the production of the epoxy ester resin, the following formula HOOC- (CH2) n-COOH
(Wherein, n is an integer of 1 to 12) is preferably used, and specifically, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexa Examples include hydrophthalic acid.

  Commercially available products of the bisphenol type epoxy resin (a) include, for example, Epicoat 1007 (epoxy equivalent of about 1,700, number average molecular weight of about 2,900), Epicoat 1009 (epoxy equivalent of about 3,500, manufactured by Japan Epoxy Resin Co., Ltd. , Number average molecular weight of about 3,750), Epicoat 1010 (epoxy equivalent of about 4,500, number average molecular weight of about 5,500); Araldite AER6099 (epoxy equivalent of about 3,500, number average molecular weight of about 3) manufactured by Asahi Ciba , 800); and Epomic R-309 (epoxy equivalent of about 3,500, number average molecular weight of about 3,800) manufactured by Mitsui Chemicals, Inc., and the like.

The bisphenol type epoxy resin (a) has a number average molecular weight of 2,000 to 35,000, preferably 4,000 to 30,000, and an epoxy equivalent of 1,000 to 12,000, preferably 3. It is suitable from the point of workability, corrosion resistance, etc. of the coating film obtained that it is a bisphenol type epoxy resin in the range of 10,000 to 10,000.
In the present specification, the number average molecular weight of resins other than the water-dispersible acrylic polymer particles (B) described later was calculated from the chromatogram measured by gel permeation chromatography based on the number average molecular weight of standard polystyrene. Value. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI

  In the above (I), since the carboxyl group in the acrylic resin (b) undergoes an ester addition reaction with the epoxy group in the epoxy resin (a) during the ester addition reaction, an epoxy group is present in the epoxy resin (a). The average number of epoxy groups per molecule of epoxy resin is 0.5 to 2, preferably 0.5 to 1.6. On the other hand, in the above (II), since the grafting reaction is caused by hydrogen abstraction of the epoxy resin main chain and the graft polymerization reaction proceeds, the epoxy resin (a) may be substantially free of epoxy groups.

  The carboxyl group-containing acrylic resin (b) used in the above (1) is a copolymer resin having a carboxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer as monomer components.

  Examples of the carboxyl group-containing polymerizable unsaturated monomer include one or a mixture of two or more of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc., among which methacrylic acid Are preferably used.

  The other polymerizable unsaturated monomer that is the monomer component of the carboxyl group-containing acrylic resin (b) may be any monomer that can be copolymerized with the carboxyl group-containing polymerizable unsaturated monomer, depending on the required performance. For example, aromatic vinyl monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, chlorostyrene; methyl acrylate, ethyl acrylate, acrylic N-propyl acid, isopropyl acrylate, n-, i- or t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl acrylate, methacryl Acid methyl, ethyl methacrylate, methacrylic acid n-propyl Acrylic acid or methacrylic acid such as pill, isopropyl methacrylate, n-, i- or t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate C1-C18 alkyl ester or cycloalkyl ester of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3- C2-C8 hydroxyalkyl esters of acrylic acid or methacrylic acid such as hydroxypropyl methacrylate, hydroxybutyl methacrylate; N-methyl 1 type or 2 types of N-substituted acrylamide type or N-substituted methacrylamide type monomers such as acrylamide, N-butoxymethyl acrylamide, N-methoxymethyl acrylamide, N-methylol methacrylamide, N-butoxymethyl methacrylamide The mixture of the above can be mentioned. As the other polymerizable unsaturated monomer, a mixture of styrene and ethyl acrylate is particularly preferable, and a constitutional mass ratio of styrene / ethyl acrylate is 99.9 / 0.1 to 40/60, more preferably 99/1 to It is suitable to be in the range of 50/50.

  The carboxyl group-containing acrylic resin (b) is not particularly limited in the constitutional ratio and type of the monomer, but usually the carboxyl group-containing polymerizable unsaturated monomer is 15 to 60% by mass, particularly 20 to 50% by mass. It is preferable that the other polymerizable unsaturated monomer is 85 to 40% by mass, particularly 80 to 50% by mass.

  The carboxyl group-containing acrylic resin (b) can be easily prepared, for example, by solution polymerization of the above monomer composition in an organic solvent in the presence of a polymerization initiator. The acrylic resin (b) preferably has a resin acid value of 100 to 400 and a number average molecular weight of 5,000 to 100,000.

  In the ester addition reaction in (I), the blending ratio of the epoxy resin (b) and the carboxyl group-containing acrylic resin (b) is such that the equivalent of the carboxyl group is excessive relative to the equivalent of the epoxy group. The ratio may be appropriately selected according to the coating workability and the coating film performance, but the former: the latter is usually 6: 4 to 9: 1 in terms of the solid mass ratio of the epoxy resin (a) and the acrylic resin (b). Furthermore, it is preferable to be within the range of 7: 3 to 9: 1.

  The ester addition reaction can be carried out by a conventionally known method. For example, an esterification catalyst is blended in a uniform organic solvent solution of the epoxy resin (a) and the acrylic resin (b), so that an epoxy group is substantially added. Until all of the above is consumed, the reaction can usually be carried out at a reaction temperature of 60 to 130 ° C. for about 1 to 6 hours. Examples of the esterification catalyst include tertiary amines such as triethylamine and dimethylethanolamine, and quaternary salt compounds such as triphenylphosphine. Among them, tertiary amines are preferable. is there.

  The solid content concentration in the reaction system of the epoxy resin (a) and the acrylic resin (b) is not particularly limited as long as the reaction system is within a viscosity range that does not hinder the reaction. Moreover, when using an esterification catalyst at the time of carrying out ester addition reaction, the usage-amount is normally used in the range of 0.1-1 equivalent with respect to 1 equivalent of epoxy groups in an epoxy resin (b). Is good.

  When the acrylic resin-modified epoxy resin (A) is a resin according to the above (II), the polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer to be graft-polymerized to the epoxy resin (a) is The carboxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers, which are monomer components used in the production of the carboxyl group-containing acrylic resin (b) in FIG.

  In the reaction (II), the use ratio of the epoxy resin (a) and the polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer is not particularly limited, but usually the former: The latter ratio is preferably in the range of 95 to 70% by mass: 5 to 30% by mass. In this case, the carboxyl group-containing polymerizable unsaturated monomer is preferably blended in an amount of 20 to 80% by mass in the total polymerizable unsaturated monomer. The amount of the radical generator used in the graft polymerization reaction is usually in the range of 3 to 15% by mass with respect to the polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer.

  The graft polymerization reaction in the above (II) can be carried out by a conventionally known method. For example, a radical generator and a polymerizable unsaturated are contained in an organic solvent solution of the epoxy resin (a) heated to 80 to 150 ° C. It can be carried out by gradually adding a uniform mixed solution with the monomer component and maintaining the same temperature for about 1 to 10 hours. Examples of the radical generator include azobisisobutyronitrile, benzoyl peroxide, t-butyl perbenzoyl octanoate, t-butyl peroxy-2-ethylhexanoate, and the like.

  Examples of the organic solvent used in the ester addition reaction in the above (I) and the graft polymerization reaction in the above (II) include an epoxy resin (a) and an acrylic resin (b) or a carboxyl group-containing polymerizable unsaturated monomer. An organic solvent that dissolves a polymerizable unsaturated monomer component containing aldehyde and does not hinder the formation of an emulsion when the reaction product, the acrylic resin-modified epoxy resin (A), is neutralized and made aqueous As long as it is, a conventionally well-known thing can be used.

  As the organic solvent, alcohol solvents, ethylene glycol monoalkyl ether solvents, and diethylene glycol monoalkyl ether solvents are preferable. 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 Examples include glycol monobutyl ether and diethylene glycol monomethyl ether. As the organic solvent, organic solvents that are difficult to mix with water other than those described above can be used as long as they do not hinder the stability of the carboxyl group-containing reaction product (A) in the aqueous medium. Examples thereof include aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, and the like.

  The acrylic resin-modified epoxy resin (A) obtained by the above (I) or (II) has a carboxyl group and has a resin acid value in the range of 10 to 160, more preferably in the range of 20 to 100. From the viewpoint of coating film performance and the like, it is preferable.

  The acrylic resin-modified epoxy resin (A) can be dispersed in an aqueous medium by neutralizing at least a part of the carboxyl groups in the resin with a basic compound. As the basic compound used for neutralization of the carboxyl group, amines and ammonia are preferably used. Representative examples of the amines include alkylamines such as trimethylamine, triethylamine, and tributylamine; alkanolamines such as dimethylethanolamine, diethanolamine, and aminomethylpropanol; and cyclic amines such as morpholine. The degree of neutralization of the acrylic resin-modified epoxy resin (A) is not particularly limited, but is usually in the range of 0.1 to 2.0 equivalent neutralization with respect to the carboxyl group in the resin (A). Is preferred.

  The aqueous medium may be only water, but may be a mixture of water and an organic solvent. As this organic solvent, any conventionally known organic solvent can be used as long as it is an organic solvent that can be mixed with water without affecting the stability of the acrylic resin-modified epoxy resin (A) in an aqueous medium. What was mentioned as an organic solvent which can be used in the case of acrylic resin modified epoxy resin (A) manufacture can be used conveniently. The amount of the organic solvent in the aqueous coating composition of the present invention is preferably in the range of 20% by mass or less from the viewpoint of environmental protection.

  In order to neutralize and disperse the acrylic resin-modified epoxy resin (A) in an aqueous medium, a conventional method may be used. For example, an acrylic resin modified with stirring in an aqueous medium containing a basic compound as a neutralizing agent. A method of gradually adding the epoxy resin (A), neutralizing the acrylic resin-modified epoxy resin (A) with a basic compound, and then adding an aqueous medium to the neutralized product with stirring or neutralizing the neutralized product Examples thereof include a method of adding a product into an aqueous medium.

Water dispersible acrylic polymer particles (B)
The aqueous coating composition of the present invention contains specific water-dispersible acrylic polymer particles as the component (B) in addition to the neutralized acrylic resin-modified epoxy resin (A).

  The water-dispersible acrylic polymer particles (B) have an absorbance at a wavelength of 330 nm by a spectrophotometer using 1,4-dioxane having a weight average molecular weight of 300,000 or more and a mass concentration of 1.35% as a solvent. Water-dispersible acrylic polymer particles having a value of 0.2 or less. The lower the absorbance value, the higher the transparency when a liquid using 1,4-dioxane as a solvent is obtained, and the polymer particles have a lower degree of crosslinking. The water-dispersible acrylic polymer particles (B) are characterized in that the absorbance value obtained by the absorbance measurement is 0.2 or less and the transparency is extremely high. In addition, in this specification, the liquid which uses 1, 4- dioxane as a solvent includes both the solution and dispersion liquid which use 1, 4- dioxane as a solvent.

For example, the water-dispersible acrylic polymer particles (B) are obtained by subjecting a polymerizable unsaturated monomer typified by a vinyl monomer to emulsion polymerization using a radical polymerization initiator in the presence of a dispersion stabilizer such as a surfactant. Can be obtained by:

  As the polymerizable unsaturated monomer to be emulsion-polymerized, carboxyl group-containing polymerizable unsaturated monomer (M-1) and other polymerizable unsaturated monomers having one or more polymerizable unsaturated groups in one molecule (M- 2) and, if necessary, a polyvinyl compound (M-3) having two or more polymerizable unsaturated groups in one molecule can be used.

  The carboxyl group-containing polymerizable unsaturated monomer (M-1) is a compound having one or more carboxyl groups and one polymerizable unsaturated group in one molecule, and water-dispersible acrylic polymer particles (B ) Is a monomer for introducing a carboxyl group, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid. Furthermore, acid anhydrides of these compounds, monocarboxylic acids obtained by half-esterification of the acid anhydrides, and the like are also included in the monomer (M-1). These carboxyl group-containing polymerizable unsaturated monomers can be used alone or in combination of two or more.

  As the carboxyl group-containing polymerizable unsaturated monomer (M-1), acrylic acid or methacrylic acid is generally used, but methacrylic acid is preferably used from the viewpoint of coating performance such as water resistance. Can do. When acrylic acid is used, since acrylic acid has a higher degree of dissociation in water than methacrylic acid, carboxyl groups in the produced polymer particles are likely to be localized on the particle surface. On the other hand, when methacrylic acid is used, the carboxyl groups are more likely to be uniformly distributed inside the particles than when acrylic acid is used. For this reason, when methacrylic acid is used, the carboxyl groups that are hydrophilic groups are uniformly distributed inside the particles when used as a coating film, compared to the case where acrylic acid is used. It is estimated that the water resistance (whitening resistance) is improved.

  The other polymerizable unsaturated monomer (M-2) is a compound having one polymerizable unsaturated group in one molecule other than the monomer (M-1). Specific examples thereof are as follows (1) ) To (9).

(1) Monoesterified product of acrylic acid or methacrylic acid and monohydric alcohol having 1 to 20 carbon atoms: for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, etc .;
(2) Aromatic vinyl monomers: for example, styrene, α-methylstyrene, vinyltoluene and the like;
(3) Glycidyl group-containing vinyl monomer: a compound having one or more glycidyl groups and one polymerizable unsaturated bond in a molecule, specifically, glycidyl acrylate, glycidyl methacrylate, etc .;
(4) Nitrogen-containing alkyl (C1-20) (meth) acrylate: for example, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, etc .;
(5) Polymerizable unsaturated group-containing amide compound: a compound having one or more amide groups and one polymerizable unsaturated bond in one molecule, such as acrylamide, methacrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, diacetone acrylamide, etc .;
(6) Hydroxyl-containing polymerizable unsaturated monomer: A compound having one or more hydroxyl groups and one polymerizable unsaturated group in one molecule, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3 Hydroxyl group-containing acrylate monomers such as hydroxypropyl acrylate and 4-hydroxybutyl acrylate, acrylic acid or methacrylic acid such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate and the number of carbon atoms Monoesterified product of 2 to 10 dihydric alcohols; N-methylolacrylamide, N-methylolmethacrylamide and the like;
(7) Polymerizable unsaturated group-containing nitrile compound: for example, acrylonitrile, methacrylonitrile, etc .;
(8) Diene compounds: for example, butadiene, isoprene and the like;
(9) Vinyl compound: For example, vinyl acetate, vinyl propionate, vinyl chloride and the like.

  These other polymerizable unsaturated monomers (M-2) can be used alone or in combination of two or more.

  The polyvinyl compound (M-3) is a compound having two or more polymerizable unsaturated groups in one molecule, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate. Examples include methacrylate, 1,6-hexanediol diacrylate, allyl methacrylate, allyl acrylate, divinylbenzene, trimethylolpropane triacrylate, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide. In addition, the said diene type compound is not contained in a polyvinyl compound (M-4). These polyvinyl compounds can be used alone or in combination of two or more.

The blending ratio of the polymerizable unsaturated monomer in the water-dispersible acrylic polymer particles (B) is as follows based on the total amount of the polymerizable unsaturated monomer.
Carboxyl group-containing polymerizable unsaturated monomer (M-1): 0.1 to 15% by mass, preferably 3 to 10% by mass,
Other polymerizable unsaturated monomer (M-2): 85-99.9% by mass, preferably 90-97% by mass,
Polyvinyl compound (M-3): 0 to 1% by mass, preferably 0 to 0.3% by mass.

The carboxyl group-containing polymerizable unsaturated monomer (M-1) is 0.1 to 15% by mass from the viewpoint of water dispersibility and water resistance of the polymer particles. Polyvinyl compound (M-3) is used as necessary, but the water-dispersible acrylic polymer particles having a high transparency, that is, a very low degree of crosslinking, in which the absorbance value is 0.2 or less. From the viewpoint of, it is preferable to make it extremely small even when used.
Examples of the dispersion stabilizer used in emulsion polymerization of the polymerizable unsaturated monomer include an anionic emulsifier, a nonionic emulsifier, and an amphoteric ion emulsifier. Specifically, examples of the anionic emulsifier include fatty acids, alkyl sulfate esters, alkylbenzene sulfonates, and alkyl phosphates. Nonionic emulsifiers include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl amines, alkyl alkanolamides, and the like. Can do. Examples of the zwitterionic emulsifier include alkylbedine.

  In addition, as a dispersion stabilizer, the copolymerization property in the emulsion polymerization reaction of the vinyl monomer that forms the water-dispersible acrylic polymer particles, the dispersion stability of the water-dispersible acrylic polymer particles in the paint, and obtained by the paint A reactive emulsifier can be particularly preferably used from the viewpoint of coating film performance such as water resistance of the coating film and reduction of residual monomer for environmental measures. The reactive emulsifier is an emulsifier having radical reactivity with a vinyl monomer, in other words, a surfactant having a polymerizable unsaturated group in one molecule.

  Specific examples of reactive emulsifiers include Eleminol JS-1, Eleminol JS-2 (manufactured by Sanyo Chemical Co., Ltd.), S-120, S-180A, S-180, Latem PD-104, Latem PD-420, Latem PD- 430S, Latemul PD-450 (manufactured by Kao Corporation), Aqualon HS-10, Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria soap SE-10N, Adekaria soap SE-20N, Adekaria soap SR-1025 ADEKA rear soap ER-10, ADEKA rear soap ER-20, ADEKA rear soap ER-30, ADEKA rear soap ER-40 (manufactured by Asahi Denka Co., Ltd.), ANTOX MS-60 (manufactured by Nippon Emulsifier Co., Ltd.) and the like. it can.

Among the reactive emulsifiers, as a particularly preferable one, — (CH ₂ CH ₂ O) _n — (wherein n is an integer of 5 to 60, preferably 10 to 55, more preferably 20 to 45, in one molecule. And a reactive emulsifier having a polyoxyethylene group and a polymerizable unsaturated group. Specific examples of the particularly preferable reactive emulsifier include Adequaria soap ER-30, Adequaria soap ER-40, Latemul PD-450, and the like.

  The water-dispersible acrylic polymer particles synthesized using the reactive emulsifier having a polyoxyethylene group and a polymerizable unsaturated group are polyoxyethylene particles having the reactive emulsifier in the main chain of the water-dispersible acrylic polymer particles. Since it has a structure in which ethylene groups are grafted in branches, in the coating liquid state as a coating composition, it acts as a dispersion stabilizer on other resin components in the coating composition, and an uncured coating film Since it acts as a compatibilizer with other resin components in the state, it is particularly preferable as the water-dispersible acrylic polymer particles (B) of the coating composition of the present invention. The above dispersion stabilizers such as emulsifiers can be used alone or in combination of two or more in the emulsion polymerization reaction.

  The amount of the dispersion stabilizer used in the emulsion polymerization of the water-dispersible acrylic polymer particles (B) is 0.1 to 10% by mass, particularly 1 to 7.5, based on the total amount of the polymerizable unsaturated monomer. It is preferably in the range of mass%, more particularly 1.5-6 mass%.

  Examples of the radical polymerization initiator used in emulsion polymerization of the water-dispersible acrylic polymer particles (B) include peroxides represented by ammonium persulfate, potassium persulfate, ammonium peroxide, and the like. And a so-called redox initiator, 2,2′-azobisisobutyronitrile, 4,4′-azobis (4-), which is a combination of a reducing agent such as sodium bisulfite, sodium thiosulfate, Rongalite, and ascorbic acid. And azo compounds such as 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide]. Of these, azo compounds are preferred.

  Of the azo compounds, a poorly water-soluble azo compound having a solubility in water of 25 ° C. of 3% by mass or less is preferable. Specific examples of such azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2,4-dimethylvalero. Nitrile, 1,1′-azobis (1-cyclohexane-1-carbonitrile), 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2′-azobis [ 2- (2-imidazolin-2-yl) propane], dimethyl-2,2′-azobisisobutyrate and the like, and in particular, 2,2′-azobisisobutyronitrile, 2,2 ′ -Azobis [2- (2-imidazolin-2-yl) propane] and dimethyl-2,2'-azobisisobutyrate are preferable from the viewpoint of increasing the molecular weight.

  The amount of the radical polymerization initiator is usually 0.01 to 5.0% by mass, preferably 0.01 to 1.0%, based on the total weight of the polymerizable unsaturated monomers forming the water-dispersible acrylic polymer particles. It is suitable to be in the mass% range. Further, the concentration of the polymerizable unsaturated monomer in the emulsion polymerization reaction system is usually 0.1 to 60% by mass, preferably 0.5 to 50% by mass.

The reaction temperature during emulsion polymerization varies depending on the radical polymerization initiator used, but is usually 40 to 100 ° C, preferably 50 to 90 ° C, and more preferably 60 to 80 ° C.
The reaction time is usually 3 to 24 hours, preferably 5 to 20 hours, and more preferably 7 to 16 hours.

  The water-dispersible acrylic polymer particles (B) may have a normal uniform structure or a multilayer structure such as a core / shell structure. Specifically, the water-dispersible acrylic polymer particles having a core / shell structure are, for example, a polymerizable unsaturated monomer component that initially contains no or almost no carboxyl group-containing polymerizable unsaturated monomer (M-1). Can be obtained by emulsion polymerization and then emulsion polymerization by adding a polymerizable unsaturated monomer component containing a large amount of carboxyl group-containing polymerizable unsaturated monomer (M-1).

  When combining the core part and the shell part, for example, allyl acrylate, allyl methacrylate, etc. are contained in the first polymerizable unsaturated monomer component, and allyl acrylate, allyl methacrylate, etc. remaining on the surface of the core part are included. It can be carried out by copolymerizing a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer (M-1) with an unreacted polymerizable unsaturated bond (allyl group).

  The water-dispersible acrylic polymer particles are 0.5 to 120 mg KOH / g, preferably 0.5 to 80 mg KOH / g, more preferably 3 to 3, from the viewpoint of storage stability and water resistance of the resulting coating film. It can have an acid value in the range of 35 mg KOH / g.

  Furthermore, the water-dispersible acrylic polymer particles (B) are in the range of 10 to 500 nm, preferably 20 to 300 nm, more preferably 40 to 200 nm, from the viewpoint of dispersion stability of the particles and smoothness when used as a coating film. It is suitable to have an average particle size within.

  In the present specification, the average particle size of the water-dispersible acrylic polymer particles is a value measured at 20 ° C. after dilution with deionized water by a conventional method using a submicron particle size distribution measuring device. As the submicron particle size distribution measuring device, for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.

  The weight-average molecular weight of the water-dispersible acrylic polymer particles (B) is from the viewpoint of coating stability such as storage stability, processability of the resulting coating film, adhesion to the substrate, corrosion resistance, film resistance, etc. It is 300,000 or more, preferably 300,000 to 10 million, more preferably 80 to 5 million.

  The weight average molecular weight of the water-dispersible acrylic polymer particles (B) can be determined by a static light scattering method. Specifically, a value can be obtained by using a multi-angle light scattering detector and creating a Jim plot or the like. Or it can obtain by creating a Debye plot etc. by the SEC-MALLS method which connected the multi-angle light scattering detector to the size exclusion chromatograph.

  In the present specification, the weight average molecular weight is measured by the SEC-MALLS method.

In general, for molecular weight measurement by the light scattering method, the following basic formula of light scattering (1)
Kc / R (θ) = 1 / MwP (θ) + 2A ₂ c + (1)
R (θ) = Reduction intensity of scattered light (Rayleigh coefficient) at angle θ
c = sample concentration
Mw = weight average molecular weight
A ₂ = second virial coefficient
K = optical parameter
P (θ) = Angle scattering function is used, but the weight average molecular weight of the present invention is the same as that in the above formula (1) as in the SEC-MALLS method in which a multi-angle light scattering detector is connected to a size exclusion chromatograph. A value obtained from an expression ignoring the second and subsequent terms, which is the product of the 2 virial coefficient and the sample concentration.
In this specification, including measurement in the production examples described later, in this specification, DAWN DSP Laser Photometer (manufactured by Wyatt Technology Co.) is used as a detector, and two “KF-806L” are used as columns, “KF-802”. 1 (both manufactured by Shodex, trade name), a total of three, solvent: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, sample concentration: 0.1% by mass To do.
The sample was prepared by drying an emulsion of the water-dispersible acrylic polymer particles (B) at room temperature, adding the dried polymer particles to tetrahydrofuran so that the solid content concentration becomes 2.5% by mass, and room temperature for 2 hours. The solution was dissolved in At the time of measurement, tetrahydrofuran was further diluted to a concentration of 0.1% by mass and filtered through a membrane filter having a pore size of 1 μm as a measurement sample.
The absorbance of the water-dispersible acrylic polymer particles using 1,4-dioxane as a solvent is 1 after the emulsion of water-dispersible acrylic polymer particles is dried at room temperature and then using 1,4-dioxane as the solvent. Using a spectrophotometer as a sample, the absorbance was measured under the condition of wavelength of 330 nm, and the measured value was divided by the cell length (in cm). It was determined by taking the absorbance. As a spectrophotometer, U-4100 (manufactured by HITACHI) was used. The liquid using 1,4-dioxane as a solvent is intended to dissolve dried polymer particles at room temperature for 2 hours, and includes both solutions and dispersions.

  The water-dispersible acrylic polymer particles (B) have an absorbance value at a wavelength of 330 nm measured by a spectrophotometer using a liquid containing 1.35% by mass of 1,4-dioxane as a solvent. From the viewpoint, it is 0.2 or less, preferably 0.15 or less, more preferably 0.1 or less.

  The water-dispersible acrylic polymer particles (B) are preferably neutralized with a basic compound. As a neutralizing agent for water-dispersible acrylic polymer particles (B), ammonia or a water-soluble amino compound such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropyl Amine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, diethanolamine, morpholine, etc. are preferably used. can do.

Cross-linking agent (C)
In order to improve curability, this invention composition can contain the crosslinking agent (C) which has the reactivity with the functional group in the said (A) component or (B) component as needed. In the component (A) and the component (B), a hydroxyl group, a carboxyl group and the like can exist as a functional group. When having reactivity with these functional groups, a phenol resin or an amino resin can be used as the crosslinking agent (C). Can be contained.

  Examples of the phenol resin include a resol type phenol resin in which a methylol group is introduced by a condensation reaction of phenols such as phenol and bisphenol A and aldehydes such as formaldehyde in the presence of a reaction catalyst. it can. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Further, those obtained by etherifying at least part of the methylol group of the resin with an alcohol having 1 to 8 carbon atoms such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, and the like can also be used. The resol type phenol resin has a number average molecular weight of 200 to 2,000, preferably 300 to 1,200, and an average number of methylol groups per benzene nucleus of 0.3 to 3.0. The number is preferably within the range of 0.5 to 3.0, more preferably 0.7 to 3.0.

  Examples of the amino resin used as the crosslinking agent (C) include methylolated amino resins obtained by reacting amino components such as melamine, urea, benzoguanamine, spiroguanamine, dicyandiamide and the aldehyde. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Further, those obtained by etherifying at least part of the methylol group of the resin with an alcohol having 1 to 8 carbon atoms such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, and the like can also be used.

Aqueous paint composition In the aqueous paint composition of the present invention, the blending ratio of the water-dispersible acrylic polymer particles (B) and the crosslinking agent (C) is based on 100 parts by mass of the acrylic resin-modified epoxy resin (A). The solid content is preferably within the following range.
(B) component: 0.5-30 mass%, Preferably 3-20 mass%,
(C) component: 0-15 mass%, Preferably it is 0-8 mass%.

  In the aqueous coating composition of the present invention, the acrylic resin-modified epoxy resin (A) is neutralized and dispersed in an aqueous medium. In the composition, water-dispersible acrylic polymer particles (B) and, if necessary, It contains a cross-linking agent (C), but for the purposes of improving paintability, coating film performance and coating beauty, preventing damage to the coating film during processing and transportation, and improving odor. Furthermore, a surfactant, an antifoaming agent, a pigment, a wax, a fragrance and the like may be appropriately contained as necessary. Although the solid content concentration of the aqueous coating composition of the present invention is not particularly limited, it is usually used in the range of 20 to 45% by weight.

  The water-based paint composition of the present invention can be applied to various base materials, for example, metals such as tinplate, aluminum, tin-free steel, iron, zinc, copper, galvanized steel sheet, alloy-plated steel sheet, and these metals. Chemically treated metal plates that have undergone surface treatment such as phosphate treatment and chromate treatment, metal plates that are coated with an epoxy or vinyl primer on these metal plates, and these metal plates are processed into cans. Can be mentioned. The coating film obtained from the composition of the present invention is excellent in processability, adhesion to a substrate, processability, water resistance, corrosion resistance and hygiene, and when applied to a can lid, the resistance when opening a tab. Excellent film residue.

  Various known methods such as roll coater coating, spray coating, dip coating, and electrodeposition coating can be applied as a method of coating the aqueous coating composition of the present invention on the substrate. Of these, roll coater coating is preferred. The coating thickness may be appropriately selected depending on the use, but is usually preferably about 3 to 20 μm. The drying conditions of the coated film are usually preferably 10 seconds to 30 minutes under the condition that the maximum material reaching temperature is 120 to 300 ° C., and in the case of roll coater coating, 10 to 50 seconds at 200 to 280 ° C. More preferably within the range of seconds.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples and comparative examples. Unless otherwise specified, “parts” and “%” mean “parts by mass” and “% by mass”, respectively.

Production Example 1 Production of Carboxyl Group-Containing Acrylic Resin Solution 400 parts of butanol was weighed into a four-necked flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen inlet. Next, 174 parts of methacrylic acid, 87 parts of styrene, 29 parts of ethyl acrylate, and 14.5 parts of benzoyl peroxide (75% water-wet product) were weighed in a beaker, well mixed and stirred to prepare a premix. The temperature of butanol in the flask was heated to 105 ° C., and the premix was added dropwise at this temperature over 3 hours from the dropping funnel. The copolymerization reaction was completed by maintaining the same temperature for another 2 hours. Next, 290 parts of 2-butoxyethanol was added to obtain a carboxyl group-containing acrylic resin solution (hereinafter referred to as “acrylic resin solution a”) having a viscosity of 370 centipoise, a resin acid value of 390, and a solid content concentration of 30%.

Production Example 2 Production of Epoxy Resin Solution Epicoat 828 (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent of about 190, viscosity of about 130 poise, 25 ° C.) 505 parts, bisphenol A 286 parts, tri-n-butylamine 0.5 part and methyl When 88 parts of isobutyl ketone was placed in a reaction vessel and heated to 135 ° C. under a nitrogen stream, the contents generated heat up to 180 ° C. This was cooled to 160 ° C. and reacted for about 3 hours to give an epoxy equivalent of 4000 and a solution viscosity (Gardner-Holt viscosity of a butyl carbitol solution with a resin content of 40% at 25 ° C.) 90% epoxy resin solution (hereinafter “ Epoxy resin solution b-1 ") was obtained.

Production Example 3
165 parts Epicoat 828, Epicoat 806H (Japan Epoxy Resin, bisphenol F type epoxy resin, epoxy equivalent of about 170, molecular weight of about 320) 579 parts Bisphenol F 410 parts, tetrabutylammonium bromide 0.6 parts and methyl isobutyl ketone 88 The portion was placed in a reaction vessel and reacted at 160 ° C. under a nitrogen stream. The reaction was monitored by epoxy equivalent and reacted for about 6 hours to obtain a 90% bisphenol A / F copolymer type epoxy resin solution b-2 having a number average molecular weight of about 8,000 and an epoxy equivalent of about 6,500.

Production Example 4 Production and Combination of Acrylic Resin Modified Epoxy Resin Aqueous Dispersion (1) Acrylic Resin Solution a 165 parts (2) Epoxy Resin Solution b-1 312 parts (3) n-Butanol 86 parts (4) 2-Butoxy Ethanol 47 parts (5) Deionized water 3.2 parts (6) Dimethylaminoethanol 5.3 parts (7) Dimethylaminoethanol 9.5 parts (8) Deionized water 372 parts Of the above (1) to (8) The total is 1000 copies.

  Said (1)-(4) was put into reaction container, and it heated at 115 degreeC under nitrogen stream, and dissolved the resin component. After dissolution, the mixture was cooled to 105 ° C., added in the order of (5) to (6), and held at 105 ° C. for 3 hours. The reaction product has an acrylic resin / epoxy resin solid mass ratio of 15/85. The reaction was followed by measuring the acid value, with an acid value of 51 at the end of the reaction. Next, after 3 hours, (7) is added, and then (8) is added over 30 minutes to disperse in water to obtain an acrylic resin-modified epoxy resin aqueous dispersion a-1 having a solid content of about 33%. Obtained.

Production Example 5
In Production Example 4, the same procedure as in Production Example 4 was carried out except that epoxy resin b-2 was used instead of epoxy resin solution b-1, and an acrylic resin-modified epoxy resin aqueous dispersion a-2 having a solid content of about 33%. Got.

Production Example 6
Compound epoxy resin solution b-1 80 parts n-butanol 28 parts diethylene glycol monobutyl ether 33 parts methacrylic acid 12 parts styrene 6 parts ethyl acrylate 2 parts benzoyl peroxide 2 parts dimethylaminoethanol 5 parts deionized water 135 parts 1) to (3) were added and heated to 115 ° C. under a nitrogen stream to dissolve the resin. After dissolution, the mixture of (4) to (6) was dropped from the dropping funnel over 1 hour while maintaining 115 ° C., and the reaction was carried out for about 2 hours while maintaining the same temperature. Subsequently, it cooled to 105 degreeC, (8) was added, and after stirring for 5 minutes, the temperature of the system was set to 70 degreeC and the said (9) was added gradually and water dispersion was performed. Furthermore, excess solvent was removed by distillation under reduced pressure to obtain an aqueous dispersion a-3 of an acrylic resin-modified epoxy resin having a solid content of about 33%.

Production Example 7 Production of water dispersion of water-dispersible acrylic polymer particles 85 parts of deionized water was charged into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, and stirred and mixed in a nitrogen stream. The temperature was raised to 75 ° C. Next, 3% of the total amount of the following monomer and initiator emulsion (Note 1) and 10 parts of a 0.5% aqueous solution of ammonium persulfate were introduced into the reaction vessel and held at 75 ° C. for 2 hours. Thereafter, the emulsion of the remaining monomer and initiator was dropped into the reaction vessel over 5 hours, and aging was performed for 6 hours after the completion of the dropping. Then, it cooled to 30 degreeC and adjusted so that solid content concentration might be 40% and pH might be 6.8 using 5.0% dimethylethanolamine aqueous solution and deionized water. Next, the solution was discharged while being filtered through a 200 mesh nylon cloth to obtain an aqueous dispersion of water-dispersible acrylic resin 1 having a solid content of 40%. The obtained water-dispersible acrylic resin 1 was diluted with deionized water and measured at 20 ° C. using an average particle diameter of 140 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter, Inc.). ), Acid value 10 mg KOH / g.

  (Note 1) Emulsion of monomer and initiator: 55 parts deionized water, 3.0 parts dodecylbenzenesulfonic acid amine salt emulsifier, 28.5 parts styrene, 70 parts ethyl acrylate, 1.5 parts methacrylic acid, 2 , 2′-azobis [2- (2-imidazolin-2-yl) propane] was mixed and stirred to obtain an emulsion of a monomer and an initiator.

Production Examples 8-14
Synthesis was performed in the same manner as in Production Example 7 except that the composition of the emulsion of the monomer and the initiator was as shown in Table 1 below, and aqueous dispersions of water-dispersible acrylic polymer particles 2 to 8 were obtained. Table 1 below shows the weight average molecular weight, absorbance, average particle size, acid value, and solid content concentration of the water-dispersible acrylic resins 1 to 8 obtained in combination with Production Example 7.

製造例１５
還流管、温度計、撹拌機を装着した四つ口フラスコに、フェノール１８８部、３７％ホルムアルデヒド水溶液３２４部をフラスコに仕込み、５０℃に加熱し内容物を均一に溶解した。次に、酢酸亜鉛を添加、混合して系内のｐＨを５．０に調整した後、９０℃に加熱し５時間反応を行った。ついで５０℃に冷却し、３２％水酸化カルシウム水分散液をゆっくり添加しｐＨを８．５に調整した後、５０℃で４時間反応を行った。反応終了後、２０％塩酸でｐＨを４．５に調整した後、キシレン／ｎ−ブタノール＝1／１（質量比）の混合溶剤で樹脂分の抽出を行い、触媒、中和塩を除去し、ついで減圧下で共沸脱水し、固形分６０％のフェノール樹脂溶液を得た。得られた樹脂（固形分）は、数平均分子量約３２０で、ベンゼン核１核当り、平均メチロール基数１．３個、平均アルコキシメチル基数０．２個を有していた。

Production Example 15
A four-necked flask equipped with a reflux tube, a thermometer, and a stirrer was charged with 188 parts of phenol and 324 parts of a 37% aqueous formaldehyde solution, and 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. and reacted for 5 hours. Next, the mixture was cooled to 50 ° C., and a 32% calcium hydroxide aqueous dispersion was slowly added to adjust the pH to 8.5, followed by reaction at 50 ° C. for 4 hours. After completion of the reaction, the pH is adjusted to 4.5 with 20% hydrochloric acid, and then the resin is extracted with a mixed solvent of xylene / n-butanol = 1/1 (mass ratio) to remove the catalyst and neutralized salt. Then, azeotropic dehydration was performed under reduced pressure to obtain a phenol resin solution having a solid content of 60%. The obtained resin (solid content) had a number average molecular weight of about 320 and an average number of methylol groups of 1.3 and an average number of alkoxymethyl groups of 0.2 per benzene nucleus.

Example 1
In a container, 857.6 parts of an aqueous dispersion of an acrylic resin-modified epoxy resin having a solid content of 33% obtained in Production Example 3, 107.0 parts of deionized water, and an aqueous dispersion of 40% solid content obtained in Production Example 9 21.2 parts of an aqueous dispersion of a water-soluble acrylic resin 3 and 14.2 parts of a resol type phenolic resin solution with a solid content of 60% obtained in Production Example 15 are uniformly mixed to obtain an aqueous coating composition with a solid content of 30%. It was.

Examples 2 to 10 and 12 to 15 , Reference Example 11 and Comparative Examples 1 to 4
Each aqueous coating composition was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 below was used. The compounding amount in Table 2 is a display by solid content.

  Various tests were performed on each of the water-based coating compositions obtained in the above Examples and Comparative Examples. The test method was performed according to the following method. The test results are shown in Table 2 below.

Test method Preparation of test coated plate: The aqueous coating composition obtained in each example was applied to an aluminum plate having a thickness of 0.3 mm with a bar coater so that the dry coating weight was 120 mg / 100 cm ^2, and the coating was performed at 100 ° C. for 2 minutes. After setting, a test plate was obtained by baking for 30 seconds under the conditions of an atmospheric temperature of 280 ° C. and a wind speed of 25 m / min so that the maximum material temperature reached 260 ° C. with a dryer. About this test board, it used for each test of adhesiveness of a coating film, boiling water resistance, workability, MEK extraction rate, and corrosion resistance. Further, potassium permanganate was prepared in the same manner as in the preparation of the above test plate except that an aluminum foil having a thickness of 0.1 mm was used instead of the aluminum plate having a thickness of 0.3 mm and the atmospheric temperature of the dryer was 275 ° C. A test plate for consumption test was obtained.

Adhesiveness of the coating film: Using a knife on the coating film surface of the test coating plate, 11 vertical and horizontal cuts of about 1.5 mm in width are put in a goblet shape. A cellophane adhesive tape having a width of 24 mm is closely attached, and the adhesiveness of the gobang eyes when strongly peeled is observed.
○: No peeling at all Δ: Some peeling ×: Remarkable peeling Water resistance: Boiling water resistance: After immersing the test coating plate in boiling water at about 100 ° C. for 30 minutes, the appearance of the coating film is visually evaluated according to the following criteria, and the coating plate after the test Adhesion is determined by the same evaluation method as in the above adhesion test.
(Appearance of coating film)
A: No abnormality such as whitening, blistering or peeling is observed.
○: Slight whitening is observed, but no swelling or peeling is observed.
Δ: Fair whitening is observed, but no swelling or peeling is observed.
X: Significant whitening, swelling, or peeling is observed.

Workability: In a room at 20 ° C, using a special goby-fold type DuPont impact tester, a 0.3 mm thick aluminum plate was sandwiched between the bent portions of the test coating plate with the bottom folded in two. Set the instrument in a bowl, drop a 3 kg weight of iron with a flat contact surface from a height of 50 cm to give impact to the bent part, and then energize the bent tip with an applied voltage of 6.5 V for 6 seconds. The current value (mA) of the bent tip portion 20 mm width is measured.
○: Less than 5 mA Δ: 5 mA or more and less than 15 mA X: 15 mA or more Potassium permanganate consumption: Water pipe treated with activated carbon per 1 cm of coating area, coated on 0.1 mm thick aluminum foil Put it in a heat-resistant glass bottle filled with the treated water so that the water becomes 1 cc, cover it, and sterilize at 125 ° C for 30 minutes, then test the method described in the Food Sanitation Law for the liquid contents (Ministry of Health and Welfare No. 434) According to the above, consumption of potassium permanganate was measured. Consumption is expressed in ppm.

MEK extraction residue ratio: The test coated plate was cut into a size of 10 cm × 10 cm, the ratio of the application area and methyl ethyl ketone (MEK) amount is set to be ^{1 cm} 2/1 cc, it was immersed in methyl ethyl ketone of boiling, Extract with boiling methyl ethyl ketone for 1 hour. The ratio of the remaining amount of extraction to the coating weight before processing of the test coating plate is expressed as a percentage.

Corrosion resistance: A can lid that had been made into a test plate using a lid press was filled with an aqueous solution in which 2 parts of malic acid, 2 parts of citric acid and 2 parts of salt were dissolved in 100 parts of deionized water. After being wound around the can body and stored for 14 days in a room at 50 ° C. with the coating surface of the test coating plate that has been made into a lid immersed in the contents, the can is opened, the state of the can lid is observed, and the following criteria are observed: Evaluated.
○: No abnormality is observed in the can lid.
Δ: Slight rust is observed on the can lid.
X: Remarkably rust is observed on the can lid.

Claims (7)

(A) Acrylic resin-modified epoxy resin, and (B) 0.1 to 15% by mass of a carboxyl group-containing polymerizable unsaturated monomer based on 100 parts by mass of the resin (A), and acrylic acid or methacrylic acid and carbon A monomer composed of 85 to 99.9% by mass of a polymerizable unsaturated monomer selected from monoesterified products with monohydric alcohols of 1 to 4 and styrene is 0.01% with respect to the total mass of the polymerizable unsaturated monomer. 1.5 to 6% by weight of a radical polymerization initiator which is a poorly water-soluble azo compound having a solubility in water at 25 ° C. of 3% by weight or less and 1.0 to 6% by weight based on the total weight of the polymerizable unsaturated monomers A copolymer obtained by emulsion polymerization in the presence of a mass% dispersion stabilizer, having an acid value of 3 to 35 mg KOH / g, a weight average molecular weight of 300,000 or more, and a mass concentration of 1.35%. 1 The value of absorbance at a wavelength of 330 nm 4-dioxane by spectrophotometer with a liquid as a solvent is characterized by containing Ru der 0.2 Water-dispersible acrylic polymer particles 0.5 to 30 parts by weight Water-based paint composition.
The acrylic resin-modified epoxy resin (A) is obtained by esterifying the bisphenol type epoxy resin (a) and the carboxyl group-containing acrylic resin (b), or the bisphenol type epoxy resin (a) is not polymerized with a carboxyl group. The water-based coating composition according to claim 1, which is an acrylic resin-modified epoxy resin obtained by graft polymerization of a polymerizable unsaturated monomer component containing a saturated monomer. The water-based coating composition according to claim 1 or 2, wherein the water-dispersible acrylic polymer particles (B) have a weight average molecular weight of 300,000 to 10,000,000. Water-dispersible acrylic polymer particles (B) are in one molecule,
What is obtained by emulsion polymerization in the presence of a reactive emulsifier having a polyoxyethylene group and a polymerizable unsaturated group represented by — (CH ₂ CH ₂ O) _n — (where n is an integer of 5 to 60) The water-based coating composition according to any one of claims 1 to 3. Furthermore, the aqueous coating composition as described in any one of Claims 1-4 which contains at least 1 sort (s) of a phenol resin and an amino resin as a crosslinking agent (C). The aqueous coating composition according to any one of claims 1 to 5, wherein the solid content of the component (C) is 0 to 15% by mass based on 100 parts by mass of the resin solid content of the component (A). A water-based coating composition according to any one of claims 1 to 6 is roll-coated on a metal plate and baked and cured.