JP2001354898A - Water-based coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based coating composition capable of forming a coated film excellent in processability in severe processing, corrosion resistance and resistance to leaving of a film, and also excellent in properties such as adhesion, retorting resistance, scratch resistance, hygiene and flavor-keeping properties. SOLUTION: This water-based coating composition is obtained by reacting an epoxy resin (A) and a carboxyl-containing acrylic resin (B), and neutralizing and dispersing the acryl-modified epoxy resin in an aqueous medium. The epoxy resin (A) consists essentially of at least one kind of resin selected from a composite bisphenol-type epoxy resin (a) obtained by reacting three components of a bisphenol-A type diglycidyl ether epoxy resin, bisphenol-F type diglycidyl ether epoxy resin and bisphenol F, and a modified resin (b) of the composite bisphenol type epoxy resin, and has 4,000-30,000 number average molecular weight and 3,000-15,000 epoxy equivalent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous coating composition,
Above all, the aqueous coating composition for the inner surface of a can that is useful for coating the inner surface of a edible can, especially has excellent workability, abrasion resistance, corrosion resistance, corrosion resistance and residual film resistance in the lid-forming process of the can lid, as well as adhesion, The present invention relates to an aqueous coating composition capable of forming a coating film having excellent properties such as retort properties, hygiene properties, and flavor properties.

[0002]

2. Description of the Related Art In recent years, paints for can inner surfaces have been
Water-based paints have begun to be widely used in terms of work hygiene, environmental protection measures, and fire safety.
These can inner coatings are described, for example, in JP-B-63-4193.
No. 4, JP-B-59-37026 and JP-A-6-370.
JP-A-329974 and the like mainly disclose a water-based paint containing an esterification reaction product of an epoxy resin and a carboxyl group-containing acrylic resin as a resin component.

When these conventional water-based paints are to be applied to can lids such as easy open ends, Japanese Patent Application Laid-Open No. 9-16998 discloses a method for forming a coating film that can withstand severe processing. Methods such as using a high molecular weight epoxy resin as shown are being performed.

[0004] However, although this method is certainly effective in improving workability, it does not satisfy the required performances by itself, and its resistance due to the decrease in the adhesion of the coating film to the material is reduced. There is a disadvantage that the feathering property is inferior, and a high molecular weight epoxy resin obtained by blending mainly with a bisphenol A skeleton is very difficult to handle due to its extremely high viscosity and is inferior in workability.

It is an object of the present invention to provide excellent workability, corrosion resistance, and film remnant resistance to severe processing such as can lid manufacturing, as well as adhesion, retort resistance, abrasion resistance, hygiene, and flavor. It is an object of the present invention to provide an aqueous coating composition capable of forming a coating film excellent in performance required for a coating film for a can inner surface such as the above.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, as an epoxy resin, a high-molecular-weight bisphenol A skeleton and a bisphenol F skeleton substantially consisting of specific raw materials have been used. Aqueous coating obtained by neutralizing an acrylic modified epoxy resin obtained by reacting the above epoxy resin with a carboxyl group-containing acrylic resin using a composite bisphenol-type epoxy resin having at least one and / or a modified resin thereof, and dispersing the same in an aqueous medium. Depending on the composition
The inventors have found that the above objects can be achieved, and have completed the present invention.

That is, the present invention relates to an aqueous coating composition obtained by neutralizing an acrylic modified epoxy resin obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) and dispersing it in an aqueous medium. The epoxy resin (A) is obtained by reacting a bisphenol A type diglycidyl ether epoxy resin, a bisphenol F type diglycidyl ether epoxy resin and bisphenol F in one molecule, and a bisphenol A skeleton and a bisphenol F skeleton in one molecule. And a resin composed essentially of at least one resin selected from the group consisting of a composite bisphenol type epoxy resin (a) and a modified resin (b) of the composite bisphenol type epoxy resin, and having a number average molecular weight of 4,000 to 30,000.
0 and an epoxy equivalent of 3,000 to 15,
000 in the range of 000.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the present invention comprises an aqueous solution obtained by neutralizing an acrylic modified epoxy resin obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) and dispersing the same in an aqueous medium. It is a coating composition. The epoxy resin (A) and the carboxyl group-containing acrylic resin (B) used for the production of the acrylic-modified epoxy resin are as follows.

Epoxy resin (A) The epoxy resin (A) is a bisphenol A skeleton in one molecule obtained by reacting a bisphenol A type diglycidyl ether epoxy resin, a bisphenol F type diglycidyl ether epoxy resin and bisphenol F. It can be substantially composed of at least one resin selected from a composite bisphenol-type epoxy resin (a) having a bisphenol F skeleton and a modified resin (b) of the composite bisphenol-type epoxy resin.

As the bisphenol A type diglycidyl ether epoxy resin used for the production of the above-mentioned composite bisphenol type epoxy resin (a), those having a relatively low epoxy equivalent are generally used.
Those having a thickness of from 0 to about 2,000 are suitable, and examples of commercially available products include Epicoat 8 manufactured by Yuka Shell Epoxy.
28EL, Epicoat 1001, Epicoat 1004,
Epicoat 1007: Araldite AE manufactured by Asahi Ciba
R250, Araldite AER260, Araldite A
ER6071, Araldite AER6004, Araldite AER6007; EPOMIC R14 manufactured by Mitsui Chemicals, Inc.
0, EPOMIC R301, EPOMIC R304, EPOMIC R307, Adeka Resin EP-410 manufactured by Asahi Denka Co., Ltd.
0 and Adeka Resin EP-5100.

As the bisphenol F type diglycidyl ether epoxy resin used in the production of the above-mentioned composite bisphenol type epoxy resin (a), a resin having a relatively low epoxy equivalent is generally used, and an epoxy equivalent of about 140 to about 2 is used. 2,000 are suitable, and examples of commercially available products include Epicoat 807 and Epicoat 806H manufactured by Yuka Shell Epoxy, Epomic R-114 manufactured by Mitsui Petrochemical, and Adeka Resin EP- manufactured by Asahi Denka.
4900, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.
(S), and Epototo YDF-170 of Toto Kasei.

The bisphenol A type diglycidyl ether epoxy resin, the bisphenol F type diglycidyl ether epoxy resin, and bisphenol F are subjected to an addition reaction to form a composite bisphenol type epoxy resin (a) which is a reaction product of the three components. ) Can be obtained.

The ratio of the bisphenol A skeleton to the bisphenol F skeleton in the composite bisphenol type epoxy resin (a) is not particularly limited, but the equivalent ratio of (A skeleton / F skeleton) in one molecule is not limited. , On average 10 / 90-60 / 40, preferably 20 / 80-5
It is preferable that the ratio is in the range of 0/50 from the viewpoint of the balance of performance such as adhesion, corrosion resistance and workability of the obtained coating film.

Composite bisphenol type epoxy resin (a)
Is not particularly limited, but has a number average molecular weight of 4,000 to 30,000, preferably 6,000 to 3,
In the range of 3,000 and the epoxy equivalent is 3,000.
~ 12,000, preferably 5,000 ~ 12,000
Those in the range are suitably used from the viewpoints of dispersion stability in an aqueous medium, processability and hygiene of the obtained coating film.

The modified bisphenol-type epoxy resin modified resin (b) is a bisphenol A-type diglycidyl ether epoxy resin or a bisphenol F-type diglycidyl which is a raw material for producing the composite bisphenol-type epoxy resin (a). It can be obtained by modifying a complex bisphenol type epoxy resin obtained by an addition reaction using three components of an ether epoxy resin and bisphenol F, for example, with a modifier such as dibasic acid. In this case, the complex bisphenol type epoxy resin to be reacted with the dibasic acid has a number average molecular weight of 2,000.
-10,000 and an epoxy equivalent of 1,500
Those within the range of ８8,000 can be suitably used. In addition, the dibasic acid includes a general formula HO
A compound represented by OC— (CH ₂ ) _n —COOH ( _{where n} represents an integer of 1 to 12), specifically, succinic acid;
Adipic acid, pimelic acid, azelaic acid, sebacic acid,
Dodecanedioic acid or hexahydrophthalic acid can be used,
In particular, adipic acid can be suitably used.

The modified bisphenol-type epoxy resin modified resin (b) is prepared by subjecting a mixture of the composite bisphenol-type epoxy resin and a dibasic acid to an esterification catalyst such as tri-n-butylamine or an organic solvent. It can be obtained by performing the reaction at a reaction temperature of about 120 to 180 ° C for about 1 to 4 hours.

The modified resin (b) of the above-mentioned composite bisphenol type epoxy resin is obtained because the dibasic acid molecular chain introduced into the molecule of the epoxy resin acts as a plastic component and can improve the adhesion. It can be said that it is advantageous for improving the workability and corrosion resistance of the coating film.

Carboxyl group-containing acrylic resin (B) In the present invention, a carboxyl group-containing acrylic resin (B) (hereinafter referred to as "acryl resin") used for producing an acryl-modified epoxy resin by reacting with the above-mentioned epoxy resin (A). (Sometimes abbreviated as “(B)”) is an acrylic copolymer containing a polymerizable unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, itaconic acid or fumaric acid as an essential monomer component. This copolymer has a resin acid value of 1
It is preferable that it is in the range of 30 to 500 mgKOH / g from the viewpoints of stability in an aqueous medium, workability of a coating film obtained, retort resistance, flavor properties and the like.

Other monomer components other than the polymerizable unsaturated carboxylic acid used for the polymerization of the acrylic resin (B) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, stearyl (meth) acrylate, Cetyl (meta)
C1-C15 alkyl esters of acrylic acid or methacrylic acid such as acrylate; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, and vinyltoluene; Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyamyl (meth) acrylate and hydroxyhexyl (meth) acrylate; and hydroxyethyl (meth) ) A hydroxyl-containing caprolactone-modified alkyl (meth) obtained by subjecting 1 to 5 moles of ε-caprolactone to a ring-opening addition reaction with respect to 1 mole of a hydroxyalkyl (meth) acrylate such as an acrylate. A) a hydroxyl group-containing polymerizable unsaturated monomer such as acrylate; acrylamide, methacrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-
n-propoxymethyl (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, Nn-
Butoxymethyl (meth) acrylamide, N-sec-
Butoxymethyl (meth) acrylamide, N-tert
Acrylamide monomers such as butoxymethyl (meth) acrylamide; and acrylonitrile, methacrylonitrile, vinyl acetate, ethylene, butadiene and the like.

The acrylic resin (B) is prepared by mixing a monomer mixture of the polymerizable unsaturated carboxylic acid with the other monomer components in an organic solvent, for example, in the presence of a radical polymerization initiator or a chain transfer agent. 1 to 10 at ~ 150 ° C
It can be obtained by heating and copolymerizing for about an hour. As the polymerization initiator, an organic peroxide type, an azo type, or the like is used. In the case of the organic peroxide type, benzoyl peroxide, t-butylperoxy 2-ethylhexanoate, di-t-butyl peroxide, Examples include t-butyl peroxybenzoate and t-amyl peroxy 2-ethylhexanoate, and azo-based compounds include, for example, azobisisobutyronitrile and azobisdimethylvaleronitrile. Examples of the chain transfer agent include α-methylstyrene dimer and mercaptans. The molecular weight of the acrylic resin (B) is not particularly limited, but is usually a number average molecular weight of 1,500 to 10,
It is preferably in the range of 000, more preferably 2,000 to 80,000.

The reaction between the epoxy resin (A) and the carboxyl group-containing acrylic resin (B) is carried out, for example, by an esterification catalyst such as triethylamine in an organic solvent.
In the presence of tertiary amines such as dimethylethanolamine and quaternary salt compounds such as triphenylphosphine,
It can be performed by heating at about 80 to 120 ° C. for about 0.5 to 8 hours to perform esterification, whereby an acrylic-modified epoxy resin can be obtained.

The mixing ratio of the epoxy resin (A) and the acrylic resin (B) in the above reaction may be appropriately selected according to the coating workability and coating film performance. Usually 60/40 to 90/1 in terms of solids weight ratio.
0, more preferably in the range of 70/30 to 90/10.

The acrylic-modified epoxy resin obtained by the above esterification reaction has an acid value of 15 to 100 mg KOH.
/ G is preferable in terms of dispersion stability in an aqueous medium, water resistance of the obtained coating film, and the like, and it is substantially free of an epoxy group from the viewpoint of storage stability. preferable.

The acrylic-modified epoxy resin is neutralized and dispersed in an aqueous medium. As the neutralizing agent used for neutralization, amines and ammonia are preferably used. Representative examples of the above amines include, for example, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, morpholine and the like. Among them, triethylamine and dimethylethanolamine are particularly preferable. The degree of neutralization of the acrylic-modified epoxy resin is not particularly limited, but is preferably in the range of usually 0.3 to 2.0 equivalent neutralization with respect to the carboxyl group in the resin.

The aqueous medium in which the acrylic-modified epoxy resin is dispersed may be water alone or a mixture of water and an organic solvent. As the organic solvent, any conventionally known organic solvent can be used as long as it is an organic solvent that does not affect the stability of the acrylic-modified epoxy resin in an aqueous medium and is miscible with water. As the organic solvent, alcohol solvents, cellosolve solvents, carbitol solvents and the like are preferable. Specific examples of the organic solvent include alcohol solvents such as n-butanol; cellosolve solvents such as ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; diethylene glycol monoethyl ether and the like. And carbitol solvents. In addition, as the organic solvent, an inert organic solvent that is not mixed with water other than the above can be used within a range that does not hinder the stability of the acrylic-modified epoxy resin in an aqueous medium. Examples thereof include aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, and ketones such as methyl ethyl ketone. The amount of the organic solvent in the aqueous coating composition of the present invention is desirably 50% by weight or less in an aqueous medium from the viewpoint of environmental protection and the like.

The acrylic-modified epoxy resin can be neutralized and dispersed in an aqueous medium by a conventional method. For example, the acrylic-modified epoxy resin is gradually added to an aqueous medium containing a neutralizing agent while stirring. After neutralizing the acrylic-modified epoxy resin with a neutralizing agent, the aqueous medium may be added to the neutralized product under stirring, or a method of adding the neutralized product to the aqueous medium. it can.

The aqueous coating composition of the present invention may comprise only an aqueous resin composition in which an acrylic-modified epoxy resin is neutralized and dispersed in an aqueous medium. For the purpose of preventing scratches at the time of transportation and transportation, improving odor, etc., in this aqueous resin composition, if necessary, a crosslinking agent resin such as a resol type phenol resin, a novolak type phenol resin, a melamine resin, a benzoguanamine resin, A surfactant, a wax, an antifoaming agent, a pigment, a fragrance and the like may be appropriately added.

The aqueous coating composition of the present invention can be applied to various substrates, for example, untreated or surface-treated metal plates such as aluminum plate, tin-free steel, tin plate, and the like, and these metal plates. And a coated metal plate obtained by processing these metal plates and the coated metal plate into cans, and the like.

As a method for applying the aqueous coating composition of the present invention to a substrate, various known methods, for example, coating methods such as roll coater coating, spray coating, dip coating and electrodeposition coating can be applied. Roll coater coating is preferred.
The thickness of the coating film of the aqueous coating composition of the present invention may be appropriately selected depending on the intended use, and usually, a dry film thickness of about 3 to 20 μm is appropriate. Drying conditions of the applied coating film are usually 5 seconds to 30 minutes under the condition that the maximum temperature of the material reaches 150 to 300 ° C., and further 200 to 280 ° C.
Is preferably in the range of 10 seconds to 50 seconds.

[0030]

The present invention will be described below in detail with reference to production examples, examples and comparative examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively. Production Example 1 Production of composite bisphenol type epoxy resin (a-1) (1) Epicoat 828EL (Note 1) 165 parts (2) Epicoat 806H (Note 2) 579 parts (3) Bisphenol F 410 parts (4) Tetrabutylammonium 0.6 part of bromide The above (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C under a nitrogen stream. The reaction was followed by an epoxy equivalent and reacted for about 6 hours to obtain a complex bisphenol-type epoxy resin (a-1) having a number average molecular weight of about 8,000 and an epoxy equivalent of about 6,500. (Note 1) Epicoat 828EL: Bisphenol A type epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd., having an epoxy equivalent of about 187 and a molecular weight of about 350. (Note 2) Epicoat 806H: Bisphenol F type epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd., having an epoxy equivalent of about 170 and a molecular weight of about 320.

Production Example 2 Production of Composite Bisphenol Epoxy Resin (a-2) (1) Epicoat 828EL 381 parts (2) Epicoat 806H 369 parts (3) Bisphenol F 401 parts (4) Tetrabutylammonium bromide 0.9 part The above (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C. for about 7 hours under a nitrogen stream to obtain a number average molecular weight of about 14,000 and an epoxy resin. A bisphenol A / F copolymer type epoxy resin having an equivalent weight of about 6,200 was obtained. Further, (5) and (6) were charged and reacted for about 2 hours to obtain a number average molecular weight of about 2
A composite bisphenol-type epoxy resin (a-2) having an epoxy equivalent of about 11,000 was obtained at 000.

Production Example 3 Production of Composite Bisphenol Epoxy Resin (a-3) (1) Epicoat 828EL 493 parts (2) Epicoat 806H 262 parts (3) Bisphenol F 395 parts (4) Tetrabutylammonium bromide 0.9 part The above-mentioned (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C. for about 8 hours under a nitrogen stream to obtain a number average molecular weight of about 19,000 and an epoxy resin. A complex bisphenol-type epoxy resin (a-3) having an equivalent weight of about 6,200 was obtained.

Production Example 4 Production of Composite Bisphenol Epoxy Resin (a-4) (1) Epicoat 828EL 576 parts (2) Epicoat 806H 183 parts (3) Bisphenol F 392 parts (4) Tetrabutylammonium bromide 0.9 part The above (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C. for about 7 hours under a nitrogen stream to obtain a number average molecular weight of about 16,000, A composite bisphenol-type epoxy resin (a-4) having an equivalent weight of about 5,800 was obtained.

Production Example 5 Production of Modified Resin (b-1) of Composite Bisphenol Epoxy Resin (1) Epicoat 828EL 177 parts (2) Epicoat 806H 623 parts (3) Bisphenol F 441 parts (4) Tetrabutylammonium bromide 0 6.6 parts (5) Adipic acid 6.4 parts (6) Tri-n-butylamine 0.5 part The above (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer. The reaction was carried out at 160 ° C. for about 4 hours under a nitrogen stream to obtain a bisphenol F type epoxy resin having a number average molecular weight of about 8,000 and an epoxy equivalent of about 6,000. Further, (5) and (6) were charged and reacted for about 2 hours to obtain a number average molecular weight of about 13,000,
A modified resin (b-1) of a complex bisphenol-type epoxy resin having an epoxy equivalent of about 10,000 was obtained.

Production Example 6 Production of Modified Resin (b-2) of Composite Bisphenol Epoxy Resin (1) Epicoat 828EL 177 parts (2) Epicoat 806H 623 parts (3) Bisphenol F 441 parts (4) Tetrabutylammonium bromide 0 .9 parts (5) Adipic acid 6.0 parts (6) Tri-n-butylamine 0.5 parts The above (1) to (4) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer. The reaction was carried out at 160 ° C. for about 8 hours in a nitrogen stream to obtain a bisphenol F type epoxy resin having a number average molecular weight of about 9,000 and an epoxy equivalent of about 6,000. Further, (5) and (6) were charged and reacted for about 2 hours to obtain a number average molecular weight of about 20,000,
A modified resin (b-2) of a composite bisphenol-type epoxy resin having an epoxy equivalent of about 11,000 was obtained.

Production Example 7 Production of composite bisphenol type epoxy resin (c-1) (for comparison) (1) Epicoat 828EL 170 parts (2) Epicoat 806H 636 parts (3) Bisphenol F 404 parts (4) Tetrabutylammonium bromide 0.6 parts The above (1) to (3) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C. under a nitrogen stream. The reaction was followed by an epoxy equivalent and reacted for about 4 hours to obtain a complex bisphenol type epoxy resin (c-1) having a number average molecular weight of about 3,000 and an epoxy equivalent of about 2,000.

Production Example 8 Production of bisphenol F type epoxy resin (c-2) (for comparison) (1) Epicoat 806H 800 parts (2) Bisphenol F 448 parts (3) Tetrabutylammonium bromide 0.6 part Reflux cooling tube The above (1) to (3) were charged into a four-necked flask equipped with a thermometer and a stirrer, and reacted at 160 ° C. under a nitrogen stream. The reaction was followed by an epoxy equivalent and reacted for about 6 hours to obtain a bisphenol F type epoxy resin (c-2) having a number average molecular weight of about 8,000 and an epoxy equivalent of about 7,000.

Production Example 9 Production of composite bisphenol type epoxy resin (c-3) (for comparison) (1) Epicoat 828EL 786 parts (2) Bisphenol F 262 parts (3) Bisphenol A 200 parts (4) Tetrabutylammonium bromide 0.6 parts The above (1) to (3) were charged into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 ° C. under a nitrogen stream. The reaction was followed by an epoxy equivalent and reacted for about 5 hours to obtain a composite bisphenol type epoxy resin (c-3) having a number average molecular weight of about 12,000 and an epoxy equivalent of about 13,000.

Production Example 10 Production of Carboxyl Group-Containing Acrylic Resin (B-1) (1) n-butanol 1096 parts (2) methacrylic acid 210 parts (3) styrene 180 parts (4) ethyl acrylate 210 parts (5) 18 parts of t-butyl peroxy 2-ethylhexanoate The above (1) was charged into a four-necked flask equipped with a reflux condenser, a thermometer, a monomer flow controller, and a stirrer, and heated to 100 ° C. under a nitrogen stream. , (2) to (5) were added dropwise over about 3 hours, and after the addition, stirring was continued at the same temperature for 2 hours, and then cooled to room temperature, and an acrylic resin solution (B- 1) was obtained. The obtained resin (solid content) had an acid value of 228 mgKOH / g and a number average molecular weight of about 15,000.
Had a zero.

Production Example 11 Production of Phenol Resin Solution (P-1) (1) p-cresol 108 parts (2) 37% aqueous formaldehyde solution 216 parts (3) 25% aqueous sodium hydroxide solution 160 parts Reflux cooling tube, thermometer The above (1) to (3) were charged into a four-necked flask equipped with a stirrer, reacted at 50 ° C. for 2 hours in a nitrogen stream, heated to 100 ° C., and further reacted at 100 ° C. for 1 hour. , After neutralization with hydrochloric acid, n-butanol /
Extraction was performed with a mixed solvent of xylene = 1/1 to obtain a 60% phenol resin solution (P-1). The average number of methylols per molecule of the obtained resin was 1.9.

Example 1 (1) 85 parts of the complex bisphenol-type epoxy resin (a-1) obtained in Production Example 1 (2) 42.9 parts of the acrylic resin solution (B-1) obtained in Production Example 10 ) 55.6 parts of diethylene glycol monobutyl ether (4) 3.7 parts of N, N-dimethylaminoethanol (5) 218 parts of deionized water (6) 2 parts of the phenol resin solution (P-1) obtained in Production Example 11 The above (1) to (3) were charged into a four-necked flask equipped with a cooling pipe, a thermometer, and a stirrer, heated to 100 ° C. and dissolved, and then (4) was added. The reaction was performed for 0.5 hours to obtain an acrylic-modified epoxy resin solution having a resin acid value of 25 mgKOH / g. When the temperature of this resin solution is 7
The temperature was adjusted to 0 ° C., and (5) was gradually added to carry out aqueous dispersion. Then, the mixture was concentrated under reduced pressure to remove excess solvent, and the solid content was reduced to about 3%.
A 0% aqueous dispersion was obtained. (6) was added to this aqueous dispersion and stirred for about 30 minutes to obtain an aqueous coating composition having a solid content of about 30%.

Examples 2 to 6 and Comparative Examples 1 to 4 The procedure of Example 1 was repeated, except that the type and amount of the epoxy resin were as shown in Table 1 below. Of each of the aqueous coating compositions was obtained.

(Note) in Table 1 has the following meanings.

(Note 3) Epicoat 1007: a bisphenol A type epoxy resin having a number average molecular weight of about 2,900 and an epoxy equivalent of about 2,000, manufactured by Yuka Shell Epoxy.

Various tests were carried out on the aqueous coating compositions obtained in the above Examples and Comparative Examples by the following methods.

Preparation of Test Plate Each aqueous coating composition obtained in each of the Examples and Comparative Examples was prepared using a plate having a thickness of 0.
Roll coating is performed on a 27 mm aluminum plate (aluminum 5182 material) so that the dry coating weight is about 120 mg / 100 cm ² (about 10 μm in dry film thickness), and it passes through a conveyor-conveying hot-air drying furnace and is baked. Into a test plate. The baking condition is the maximum temperature of the material reaching 240 ° C,
The conditions were such that the passage time in the furnace was 20 seconds.

With respect to the obtained test plate, each test of workability, corrosion resistance in a processed portion, residual film resistance, adhesion, retort resistance, flavor and hygiene was performed according to the following test methods.
The results of these tests are shown in Table 1 below.

Test Method Workability: A 0.3 mm thick aluminum plate was used between the bent parts of a test plate whose lower part was folded in two using a special goby fold type Dupont impact tester so that the coating surface was on the outside. 1
Hold the sheet, set it on the tester, and make the contact surface flat with a thickness of 1kg
After dropping an iron weight from a height of 50 cm to give an impact to the bent portion, a current value (mA) of 2 mm width at the bent tip portion when a voltage of 6.5 V is passed through the bent tip portion for 6 seconds Was measured, and the measured values were evaluated according to the following criteria. ◎: Current value less than 0.5 mA, ○: Current value of 0.5 mA or more and less than 1.0 mA, Δ: Current value of 1.0 mA or more and less than 5.0 mA, ×: Current value of 5.0 mA or more.

Scratch resistance: A scratch test needle was placed on a test plate, and the coated plate was moved at a constant speed while applying a constant load, and evaluation was performed in the state of a scratch. ◎: No scratches other than the needle contact portion, no cracks and peeling of the coating film around the scratches. ○: Cracking and peeling of the coating film around the needle contacting portion. △: Around the needle contacting portion. X: Cracking and peeling of the coating film are remarkably observed around the needle contact portion.

Processed part corrosion resistance: An aqueous solution prepared by dissolving 2 parts of malic acid, 2 parts of citric acid and 2 parts of sodium chloride in 100 parts of deionized water was prepared by subjecting a test plate to lid making using a lid press machine. And stored at 50 ° C. for 5 days in a state where the coating surface of the lid-formed test plate is immersed in the contents. After storage, the can was cut open and the state of the coating film was observed. The evaluation was performed according to the following criteria. ：: No change was observed in the can lid, ○: No rust was observed in the can lid, but very slight change was observed, Δ: Slight rust was observed in the can lid, ×: Significant rust on the can lid Is recognized.

Residual film resistance (feathering resistance): A lid made of a test plate using a lid press machine was deionized to remove 2 parts of malic acid, 2 parts of citric acid and 2 parts of salt. Water 10
Immerse in an aqueous solution dissolved in 0 parts and leave at 50 ° C. for 5 days. After removing the can lid and washing with deionized water, the can lid is immersed in boiling water of 100 ° C. for 30 minutes, and the opening of the lid is lifted upward with the coating surface facing down. Then, the peeling width of the coating film from the opening end was evaluated according to the following criteria. ◎: The maximum peel width of the coating film is less than 0.2 mm, ○: The maximum peel width of the coating film is 0.2 mm or more and less than 0.5 mm, and Δ: The maximum peel width of the coating film is 0.5 mm or more and 1.0 mm. Less than, ×: The maximum peel width of the coating film is 1.0 mm or more.

Adhesion: Eleven cuts each having a width of about 1.5 mm and a length and width of 11 mm were cut in a grid on the coating surface of the test plate using a knife, and a cellophane adhesive having a width of 24 mm was attached to the grid. The tape was brought into close contact with the tape, and the degree of peeling of the coating film at the cross section when the tape was instantaneously peeled was observed. The evaluation was performed according to the following criteria. ：: No peeling was observed at all, ：: Very slight peeling was observed, Δ: Extremely peeling was observed, ×: Remarkable peeling was observed.

Retort resistance: The test plate was immersed in water and treated in an autoclave at 125 ° C. for 30 minutes to evaluate the whitening state of the coating film according to the following criteria. ：: no whitening was observed at all; ○: very slight whitening was observed; Δ: slight whitening was observed; ×: significant whitening was observed.

Flavor (flavor retention): Application area of test plate: Place test plate in heat-resistant glass bottle such that tap water treated with activated carbon has a ratio of 2 cm ² : 1 cc, cover, and autoclave After sterilizing at 125 ° C. for 30 minutes in the container, a flavor test of the content liquid is performed. ◎: No change was observed at all, ：: Very slight change was observed, Δ: A considerable change was observed, ×: A remarkable change was observed.

Hygiene: A test plate and tap water treated with activated carbon were put into a heat-resistant glass bottle at a ratio of 1 cc of the tap water treated with activated carbon to 1 cm ² of the test plate, and the lid was closed. And 30 minutes at 125 ° C in an autoclave.
After treating for 1 minute, the liquid content after the treatment was evaluated for hygiene based on the consumption amount (ppm) of potassium permanganate according to the test method described in the Food Sanitation Law. ：: consumption amount is less than 1 ppm, ：: consumption amount is 1 ppm or more and less than 3 ppm, Δ: consumption amount is 3 ppm or more and less than 10 ppm, and X: consumption amount is 10 ppm or more.

[0056]

[Table 1]

[0057]

The main feature of the present invention is that at least one resin selected from high-molecular-weight composite bisphenol-type epoxy resins and modified resins of composite bisphenol-type epoxy resins is used as the epoxy resin (A). Thus, the composition of the present invention can achieve various advantages as described below. Since the composite bisphenol type epoxy resin contains a bisphenol F skeleton, it has a lower glass transition temperature than the bisphenol A type epoxy resin and acts as a soft component, improving the adhesion of the coating film, and thus the corrosion resistance and workability. A coating film having excellent scratch resistance, retort resistance and hygiene can be formed. And it is easy to handle due to the softening effect in the synthesis operation.

Further, in the composition of the present invention,
JP-A-199827 can omit the mixing step of bisphenol A type epoxy resin and bisphenol F type epoxy resin, further reduce the amount of solvent used for facilitating mixing, and omit the reduced pressure removing step. But the effect can be expected.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Reijiro Nishida 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa F-term in Kansai Paint Co., Ltd. 4J038 DB451 KA03 MA08 NA11 NA12 NA14 PB04 PC02

Claims (4)

[Claims] An aqueous coating composition comprising an acrylic modified epoxy resin obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B), which is neutralized and dispersed in an aqueous medium. The epoxy resin (A) has a bisphenol A skeleton and a bisphenol F skeleton in one molecule obtained by reacting bisphenol A type diglycidyl ether epoxy resin, bisphenol F type diglycidyl ether epoxy resin and bisphenol F in one molecule. It consists essentially of at least one resin selected from the group consisting of a bisphenol-type epoxy resin (a) and a modified resin of the composite bisphenol-type epoxy resin (b), and has a number average molecular weight in the range of 4,000 to 30,000. And the epoxy equivalent is in the range of 3,000 to 15,000. Aqueous coating composition. 2. An epoxy resin (A) having a number average molecular weight of 2,000 to 12,000 and an epoxy equivalent of 1,5.
2. A modified epoxy resin obtained by modifying a base epoxy resin which is a complex bisphenol type epoxy resin having a bisphenol A skeleton and a bisphenol F skeleton in one molecule of from 8,000 to 8,000 with a dibasic acid. Aqueous coating composition. 3. The acryl-modified epoxy resin is obtained by mixing the epoxy resin (A) and the carboxyl group-containing acrylic resin (B) in a solid content ratio of (A) / (B) of 60/4.
The aqueous coating composition according to claim 1 or 2, which is reacted at a mixing ratio of 0 to 90/10. 4. The method according to claim 1, further comprising a curing agent.
The aqueous coating composition according to any one of the above.