JPH06329974A - Water-base coating composition - Google Patents

Abstract

PURPOSE:To provide a water-base coating compsn. which exhibits excellent surface finish and antifoaming properties in roll coating work and can form a coating film with excellent properties. CONSTITUTION:The coating compsn. is a water-base dispersion obtd. by neutralizing and dispersing an acrylic-modified epoxy resin (A) and a carboxylated acrylic resin (B) in a wt. ratio of solid content of the former to the latter of (99:1)-(80:20). Resin A is obtd. by reacting a bisphenol epoxy resin (a) having an epoxy equivalent of 8,000-18,000 and a number average mol.wt. of 2,500-10,000 with a high-acid-value acrylic resin (b). Resin B has an SP value lower than that of resin b by 0.05-1.00.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a very good finish on the coated surface and excellent foam suppression / defoaming properties in roll coating work, and also has excellent flavor, hygiene, adhesion, processability and retort resistance. The present invention relates to an aqueous coating composition capable of forming a coating film having good performance and a coating film forming method using the same.

[0002]

2. Description of the Related Art Conventionally, in paints for cans, epoxy resins, which are materials excellent in corrosion resistance, workability, flavor retention, etc., have been mainly used as binders for solvent-based paints. On the other hand, even in water-based paints for cans, it is desired to use an epoxy resin as a binder due to its excellent characteristics, and various uses thereof have been proposed. Among them, the paint suitable for the inner surface of the can is
A composition in which an epoxy resin is mainly modified with a high acid value acrylic resin, the carboxyl groups in the resulting modified epoxy resin are neutralized with ammonia or amine, and the resulting resin is dispersed in water. For example, JP-A-53-1228
In the publication, a radical-generating catalyst such as benzoyl peroxide is used, and an acrylic monomer containing a carboxyl group-containing monomer is graft-polymerized on the main chain of an epoxy resin, and the resulting graft resin is treated with a basic compound such as ammonia or amine. A method of using and dispersing in water is disclosed. Further, JP-A-55-3481 and JP-A-5-3481.
In JP-A-5-3482, a high acid value acrylic resin which has been polymerized in advance with a radical generating catalyst such as benzoyl peroxide and an epoxy resin are subjected to an ester addition reaction under an esterification catalyst, and a carboxyl group in the obtained adduct is disclosed. A composition is disclosed in which the group is neutralized with a basic compound such as ammonia or amine and the resulting compound is dispersed in water.

Among these resin components, the epoxy resin component incorporated in the resin gives excellent adhesion to the coating material, and the acrylic resin component incorporated in the resin is aqueous in the form of ammonium salt or amine salt. Since it imparts self-emulsifying property in a diluent, it is easy to disperse in an aqueous diluent, has excellent adhesion to the metal for a can, and can form a coating film with corrosion resistance for cans. It is an excellent binder for paints.

However, when roll coating work is carried out using these water-based paints as paints for cans, foaming is severe especially in the circulation process of the paints, and many fine bubbles are transferred when the paints are applied to the object to be coated. I will end up. Therefore, there is a problem that pinholes, blisters, etc. occur in the baked coating film, the finish of the coating surface is significantly impaired, and the base surface cannot be sufficiently covered. Further, these water-based paints have a problem that they show structural viscosity and, when roll-painted, the surface smoothness is poor and high gloss cannot be obtained.

[0005]

As a result of intensive studies to solve the above problems in water-based paints, the present inventors have found that a specific acrylic modified epoxy resin and a solubility parameter (SP value) are constant. A water-based coating composition obtained by neutralizing a carboxyl group-containing acrylic resin set in the range to form an aqueous dispersion is excellent in foam suppression and defoaming properties during roll coating work, and has a coating surface with good finish. They have found that they can be formed and have completed the present invention.

That is, the present invention is as follows. Epoxy equivalent 8,
000 to 18,000 and number average molecular weight of 2,500 to 1 by gel permeation chromatography
Bisphenol type epoxy resin (a) which is 10,000
And an acrylic-modified epoxy resin (A) obtained by reacting a high acid value acrylic resin (b) with an SP value of 0.05 to 1.00 lower than the solubility parameter (SP value) of the resin (b). Solid content weight in which the carboxyl group-containing acrylic resin (B) is neutralized to form an aqueous dispersion, and the mixing ratio of the resin (A) and the resin (B) is (A) / (B) The water-based coating composition is characterized by having a ratio of 99/1 to 80/20.

The present invention also relates to 2. Item 1 wherein the mixing ratio of the bisphenol type epoxy resin (a) and the high acid value acrylic resin (b) in the reaction is 50/50 to 95/5 in terms of solid content weight ratio of (a) / (b). The above-mentioned water-based coating composition is provided.

Further, the present invention relates to 3. A water-based coating composition according to item 1 or 2 above, which contains a curing agent in addition to the acrylic modified epoxy resin (A) and the carboxyl group-containing acrylic resin (B).

The present invention also relates to 4. Item 1, 2 or 3 above
The present invention provides a method for forming a coating film, which comprises roll-coating a water-based coating composition as described above on a metal plate and then baking it.

[0010]

In the composition of the present invention, the epoxy resin (a) used for producing the acrylic modified epoxy resin (A) is
Epoxy equivalent is 8,000 to 18,000, preferably 9,000 to 14,000 and number average molecular weight by gel permeation chromatography is 2,500 to 2,500.
Any bisphenol type epoxy resin having a range of 10,000, preferably 3,000 to 9,000 can be used without particular limitation. This epoxy resin (a)
Is an esterification catalyst of a bisphenol type epoxy resin having a relatively low epoxy equivalent and a bisphenol compound, for example, tetraethylammonium bromide (TE
ABr) or a solvent in the presence of a reaction temperature of about 120-180
It can be obtained by carrying out the reaction for about 2 to 10 hours until the epoxy equivalent of the resin becomes 8,000 to 18,000 at ℃.

As the bisphenol type epoxy resin having a relatively low epoxy equivalent, the epoxy equivalent is about 140 to
Generally about 4,000, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, and these epoxy resins and acrylic acid, methacrylic acid, polycarboxylic acid or acid anhydride thereof. , A modified epoxy resin obtained by reacting a fatty acid, a polyether polyol, a polyester polyol, a polyamidoamine, a lactone, or the like.

Examples of commercially available bisphenol type epoxy resins having relatively low epoxy equivalents are Epicoat 828L and Epicoat 8 manufactured by Yuka Shell Epoxy Co., Ltd.
07P, Epicoat 1001, Epicoat 1004, Epicoat 1007, manufactured by Ciba-Geigy Araldite GY250, Araldite GY260, Araldite 6084, Araldite 7097, Araldite 609.
7, Epomic R130, Epomic R140, Epomic R302, Epomic R3 manufactured by Mitsui Petrochemical Industry Co., Ltd.
04, Epomic R307 and the like.

As the bisphenol compound which is reacted with the bisphenol type epoxy resin having a relatively low epoxy equivalent to obtain the epoxy resin (a), for example, bis (4-hydroxyphenyl) -2,2-propane,
4,4'-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -methane, bis- (4-hydroxyphenyl) -1,1-isobutane, bis (4 -Hydroxy-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,
1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone and the like can be mentioned.

High acid value acrylic resin (b) in the present invention
Is a high acid value acrylic copolymer containing a polymerizable unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid as an essential monomer component. The resin acid value of this copolymer is preferably 130 to 500, more preferably 200 to 400. When the acid value of the acrylic resin (b) is less than 130, the solvent resistance of the resulting coating film is lowered, and the flavor property tends to be deteriorated in the can inner surface application. On the other hand, if the acid value exceeds 500, the viscosity of the reaction system during the acrylic resin polymerization or the production of the acrylic modified epoxy resin tends to be extremely high, and the water resistance of the resulting coating film tends to be poor, and it is particularly used for can applications. In that case, whitening is likely to occur in the coating film after boiling.

Other monomer components other than the polymerizable unsaturated carboxylic acid used in the polymerization of the acrylic resin (b) are, for example, styrene, vinyltoluene and 2-
Styrene-based monomers such as methylstyrene, t-butylstyrene and chlorostyrene; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate,
Acrylic esters such as isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n methacrylate
-Butyl, isobutyl methacrylate, n-methacrylic acid
Methacrylic acid esters such as amyl, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate; acrylic acid 2
-Hydroxyethyl, hydroxypropyl acrylate,
Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate and hydroxypropyl methacrylate; N-
Examples thereof include N-substituted (meth) acrylic monomers such as methylol (meth) acrylamide and N-butoxymethyl (meth) acrylamide, and one or more of these can be selected. When used for cans, styrene and ethyl acrylate are particularly preferable among the above-mentioned other monomer components.

The acrylic resin (b) is a monomer mixture of the polymerizable unsaturated carboxylic acid and the other monomer components, for example, an organic solvent and azobisisobutyronitrile, benzoyl peroxide, t-butyl perbenzoyl. It can be obtained by heating and copolymerizing at 80 to 150 ° C. for about 1 to 10 hours in the presence of a radical polymerization initiator such as octanoate. The molecular weight of the acrylic resin (b) is not particularly limited, but a number average molecular weight of 1,500 to 40,000 is preferable,
More preferably, it is in the range of 2,000 to 20,000.

In the present invention, in order to obtain an acrylic-modified epoxy resin by reacting the bisphenol type epoxy resin (a) with the high acid value acrylic resin (b), both are treated with an esterification catalyst such as amine or ammonia. The reaction may be carried out by heating in the presence or absence of a solvent or in the presence or absence of a solvent. The performance of the resin obtained varies depending on the type and amount of catalyst. Usually, the amount of the catalyst is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the resin solid content used in the reaction.

As the solvent that can be used in the reaction,
For example, methoxypropanol, ethylene glycol monobutyl ether, n-butanol and the like can be mentioned, which is a good solvent for both the epoxy resin (a), the acrylic resin (b) and the reaction product acrylic modified epoxy resin (A). Some are preferred. When the esterification catalyst is used, the reaction temperature is appropriately about 80 to 120 ° C, and when the catalyst is not used, about 120 to 160 ° C is suitable. The progress of the reaction can be followed by using a generally known method for measuring an acid value, and the reaction is usually completed in 1 to 8 hours.

The mixing ratio of the bisphenol type epoxy resin (a) and the high acid value acrylic resin (b) used in the above esterification reaction may be appropriately selected depending on the coating workability and coating film performance, but it is usually The solid content ratio of (a) / (b) is 50.
The range of / 50 to 95/5 is preferable and 65/35 to 90 /
The range of 10 is more preferable. The acrylic modified epoxy resin (A) obtained by the above esterification reaction preferably has a number average molecular weight of 6,000 to 200,000 and an acid value of 20 to 140, and preferably has substantially no epoxy group. .

In the composition of the present invention, the carboxyl group-containing acrylic resin (B) used together with the acrylic modified epoxy resin (A) is a polymer of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and the like. It is an acrylic copolymer containing an unsaturated carboxylic acid as an essential monomer component. This copolymer may have an SP value which is 0.05 to 1.00 lower than the solubility parameter (SP value) of the high acid value acrylic resin (b) used in the production of the acrylic modified epoxy resin (A). It is necessary and it is preferable to have an SP value that is 0.10 to 0.50 lower. In either case where the value obtained by subtracting the SP value of the carboxyl group-containing acrylic resin (B) from the SP value of the high acid value acrylic resin (b) is less than 0.05 or more than 1.00, The water-based paint is not practical because it has insufficient foam suppression and defoaming properties.

In the present invention, the "solubility parameter (SP value)" of the acrylic resin is a value calculated by the following formula.

[Equation 1] δ: SP value of acrylic resin copolymerized from n kinds of acrylic monomers δ _i : SP value of acrylic monomer i component [(cal / cm ³ )
^0.5 ] Φ _i : Weight fraction of acrylic monomer i component where δ _i is KLHoy, Journal of Paint Technology, 42
[541], p76, Feb. From 1970. For example, the SP value of methacrylic acid is 13.11 and that of styrene is 9.
35 and ethyl acrylate are 8.81.

Other monomer components other than the polymerizable unsaturated carboxylic acid used for polymerizing the acrylic resin (B) are, for example, styrene, vinyltoluene, 2-
Styrene-based monomers such as methylstyrene, t-butylstyrene and chlorostyrene; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate,
Acrylic esters such as isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n methacrylate
-Butyl, isobutyl methacrylate, n-methacrylic acid
Methacrylic acid esters such as amyl, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate; acrylic acid 2
-Hydroxyethyl, hydroxypropyl acrylate,
Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate and hydroxypropyl methacrylate; N-
Examples thereof include N-substituted (meth) acrylic monomers such as methylol (meth) acrylamide and N-butoxymethyl (meth) acrylamide, and one or more of these can be selected. When used for cans, styrene and ethyl acrylate are particularly preferable among the above-mentioned other monomer components.

The acrylic resin (B) is a monomer mixture of the polymerizable unsaturated carboxylic acid and the other monomer components, for example, an organic solvent and azobisisobutyronitrile, benzoyl peroxide, t-butylperbenzoyl. It can be obtained by heating and copolymerizing at 80 to 150 ° C. for about 1 to 10 hours in the presence of a radical polymerization initiator such as octanoate. The molecular weight of the acrylic resin (B) is not particularly limited, but a number average molecular weight of 1,500 to 40,000 is preferable,
It is preferably in the range of 2,000 to 20,000. The resin acid value is 130 to 350, and further 160 to
A range of 320 is preferred.

In the aqueous coating composition of the present invention, the acrylic modified epoxy resin (A) and the carboxyl group-containing acrylic resin (B) are neutralized and dispersed in an aqueous medium (part of which may be dissolved). ) And form an aqueous dispersion. The order of neutralizing and water-dispersing the resin is not particularly limited, and the resin (A) and the resin (B) may be mixed and then neutralized and water-dispersed. The resin (B) may be neutralized and then mixed, and then water-dispersed. Alternatively, the resin (A) may be neutralized and water-dispersed before the neutralization product or neutralization of the resin (B), A water dispersion may be added.

The method of neutralizing the resin and dispersing it in an aqueous medium is, for example, a method of neutralizing the resin with a neutralizing agent and adding the neutralized product to water to disperse it. And a method of dispersing the resin in water containing a neutralizing agent, and a method of adding water containing a neutralizing agent to the resin to disperse the resin. In any case, the neutralized product of the resin (A) is stably dispersed in water, and the neutralized product of the resin (B) is stably dispersed in water or solubilized to form a stable aqueous dispersion. I wish I had it. The above resin (A)
The neutralization equivalent of the resin (B) is usually 0.5 to 1 with respect to 1 equivalent of the carboxyl group in the resin (A) and the resin (B) from the viewpoints of dispersibility of the resin, storage stability and odor. It is preferably in the range of 1.4 equivalents.

As the basic compound used for neutralizing the above-mentioned carboxyl group, conventionally known compounds can be widely used as long as they are generally used for neutralizing the carboxyl group,
For example, arbitrary primary amine, secondary amine, tertiary amine, monofunctional quaternary ammonium salt and the like can be mentioned. More specifically, methylamine, ethylamine, n-propylamine, isopropylamine, n-hexylamine,
Monoethanolamine, propanolamine, benzylamine, dimethylamine, dibutylamine, dihexylamine, methylethanolamine, diethanolamine, triethylamine, dimethylethanolamine, diethylethanolamine, dimethylcyclohexylamine, triethanolamine, tributylamine, dimethyl n-butylamine , Tripropylamine, γ-picoline, tetrahexyl ammonium hydroxide, morpholine, ammonia and the like.

The proportion of the acrylic modified epoxy resin (A) and the carboxyl group-containing acrylic resin (B) in the neutralization and water dispersion of the above resin is 99 (A) / (B) solid content weight ratio. / 1 to 80/20, and further 98/2 to
It is preferably 85/15. Above (A) / (B)
If the ratio is greater than 99/1, sufficient defoaming and defoaming properties cannot be obtained, and the smoothness of the coated surface during roll coating is poor, while the ratio (A) / (B) is less than 80/20. When it becomes smaller, the coating film obtained has poor processability and flavor properties and is not practical.

As described above, the emulsion obtained by neutralizing the resin (A) and the resin (B) and dispersing them in water can be used as it is. However, if necessary, the emulsion may be desolvated to remove the solvent. it can.

The water-based coating composition of the present invention may consist only of an emulsion obtained by neutralizing the resin (A) and the resin (B) and dispersing them in water, but if necessary, a phenol resin or melamine. Resins, benzoguanamine resins, urea resins and other curing agents, other aqueous anion resins, pigments, paint additives such as defoaming agents and leveling agents, etc. may be contained. The solid content concentration of the aqueous coating composition of the present invention is not particularly limited, but it is usually used in the range of 20 to 50% by weight. The aqueous coating composition thus obtained is extremely stable and does not undergo changes such as precipitation, separation and thickening even after several months in a storage test at a temperature of 30 ° C.

The water-based coating composition of the present invention contains metals such as tin plate, aluminum, tin-free steel, iron, zinc, copper, galvanized steel sheet and alloy-plated steel sheet, and these metals are subjected to phosphate treatment or chromate treatment. It can be applied to chemical conversion treated metal, wood, plastics, concrete, etc. The coating thickness may be appropriately selected depending on the application, but is usually 3 to 20 μm, and roll coating
It can be applied by spray coating, brush coating, roller coating, or the like. The coating film is usually dried at 120 to 28
It can be performed at 0 ° C. for about 10 seconds to about 30 minutes.

The water-based coating composition of the present invention is particularly suitable for roll coating, and when roll coating for can applications, the coating viscosity is usually 40 to 90 seconds (Ford Cup #
(4, measurement temperature 25 ℃), the dry film thickness is about 3 to about 8
It is roll-coated on a metal plate such as tin, aluminum, tin-free steel, etc., so that the maximum temperature reaches about 140-260 ℃ for about 10 seconds.
Bake for 20 minutes.

[0032]

The water-based coating composition of the present invention neutralizes and disperses in water an acrylic-modified epoxy resin using an epoxy resin having a specific epoxy equivalent and a molecular weight and a carboxyl group-containing acrylic resin having a specific SP value. Various combinations of these resins exhibit various coating film properties, a foam suppressing effect, a defoaming promoting effect, and a structural viscosity decreasing effect. As a result, even during roll coat painting work, foaming during paint circulation is extremely reduced, the amount of foam in the paint is reduced, transfer of fine bubbles to the coating plate is reduced, and the transferred bubbles are easily erased and baked. The dried coating surface is not adversely affected, and a coating film having good smoothness and gloss can be obtained. Thus, the finish of the coated surface and the coverage of the underlying surface are excellent, and the flavor, hygiene, adhesiveness, workability,
A coating film having good retort resistance can be formed.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples. Hereinafter, "parts" and "%" are based on weight.

Preparation Example 1 Preparation of bisphenol type epoxy resin (a-1) (1) Epicoat 828EL (Note 1) 1,000 parts (2) Bis (4-hydroxyphenyl) -methane 551 parts (3) Tetraethylammonium bromide 0.2 parts A four-necked flask equipped with a reflux tube, a thermometer, and a stirrer was charged with (1) to (3), and the reaction was carried out at 140 ° C under a nitrogen stream. The reaction is epoxy equivalent and 40% solution viscosity (25 ℃
Followed by Gardner-Holt viscosity of 40% solid content butyl carbitol solution in the above, and reacted for about 4 hours to obtain epoxy equivalent 10,000, 40% solution viscosity Z ₅ , number average molecular weight (gel permeation chromatography). A bisphenol type epoxy resin (a-1) of 7,800 was obtained by a graph. (Note 1) Epicoat 828EL: manufactured by Yuka Shell Epoxy Co., bisphenol A type epoxy resin, epoxy equivalent of about 186 to 187, molecular weight of about 350.

Production Example 2 Preparation of bisphenol type epoxy resin (a-2) (1) Epicoat 828EL 1,000 parts (2) Bis (4-hydroxyphenyl) -methane 563 parts (3) Tetraethylammonium bromide 0.2 parts (1) to (3) were charged in a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, and the reaction was carried out at 140 ° C under a nitrogen stream. The reaction was traced with epoxy equivalent and viscosity of 40% solution, and by reacting for about 4 hours, epoxy equivalent was 9.00
A bisphenol type epoxy resin (a-2) having a 0,40% solution viscosity Z ₄ and a number average molecular weight of 3,800 was obtained.

Preparation Example 3 Preparation of bisphenol type epoxy resin (a-3) (1) Epicoat 828EL 1,000 parts (2) Bis (4-hydroxyphenyl) -methane 561 parts (3) Tetraethylammonium bromide 0.2 parts (1) to (3) were charged in a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, and the reaction was carried out at 140 ° C under a nitrogen stream. The reaction is monitored by the epoxy equivalent and the viscosity of 40% solution, and the epoxy equivalent of 16.0 is obtained by reacting for about 6 hours.
A bisphenol type epoxy resin (a-3) having a solution viscosity of 00, 40% solution Z ₅ , and a number average molecular weight of 7,000 was obtained.

Production Example 4 Preparation of high acid value acrylic resin (b-1) (1) methoxypropanol 580 parts (2) methacrylic acid 160 parts (3) styrene 232 parts (4) ethyl acrylate 8 parts (5) benzoyl Peroxide 20 parts A four-necked flask equipped with a reflux tube, a thermometer, a monomer flow rate controller, and a stirrer was charged with 20% of the mixture of (2) to (5) and (1) in the flask, and under a nitrogen stream. The mixture is heated to 95 ° C. and the rest of the mixture of (2) to (5) is added dropwise over about 3 hours. After completion of the addition, stirring is continued at the same temperature for 2 hours, then cooled to room temperature and solid content is about 41%. Acrylic resin (b-1) solution of was obtained. The obtained resin (solid content) has an acid value of 261, an SP value of 10.84, and a number average molecular weight of about 7,80.
It was 0.

Production Example 5 Preparation of high acid value acrylic resin (b-2) (1) methoxypropanol 580 parts (2) methacrylic acid 160 parts (3) styrene 160 parts (4) ethyl acrylate 80 parts (5) benzoyl Peroxide 20 parts A four-necked flask equipped with a reflux tube, a thermometer, a monomer flow rate controller, and a stirrer was charged with 20% of the mixture of (2) to (5) and (1) in the flask, and under a nitrogen stream. The mixture was heated to 95 ° C. and the rest of the mixture of (2) to (5) was added dropwise over about 3 hours. After the addition was completed, stirring was continued for 2 hours at the same temperature, and then the mixture was cooled to room temperature and solid content was about 40%. An acrylic resin (b-2) solution of was obtained. The obtained resin (solid content) has an acid value of 261, an SP value of 10.75 and a number average molecular weight of about 8,20.
It was 0.

Production Example 6 Synthesis of Acrylic Modified Epoxy Resin (A-1) Solution and Emulsion Using It (1) Epoxy Resin (a-1) 80 Parts Obtained in Production Example 1 (2) Obtained in Production Example 4 Acrylic resin (b-1) solution 50 parts (3) Methoxypropanol 69.8 parts (4) Diethylene glycol mono n-butyl ether 16.5 parts (5) Dimethylethanolamine 0.2 parts (6) Fenodur PR401 (Note 2) ) 14.7 parts (7) Aqueous ammonia solution (concentration 25%) 7.6 parts (8) Deionized water 192.4 parts

A four-necked flask equipped with a reflux tube, a thermometer, and a stirrer was charged with (1) to (4), heated to 100 ° C. to dissolve them, and then (5) was added to maintain the temperature. The reaction was performed for 6 hours to obtain an acrylic modified epoxy resin (A-1) solution. This reaction was confirmed by measuring the acid value of the resin. The acid value of the obtained resin (solid content) was 49, and the number average molecular weight was about 8,900. The resin (A
-1) The temperature of the solution was adjusted to 60 ° C., (6) was added and mixed uniformly, (7) was added to neutralize the resin, and (8) was gradually added to perform water dispersion. Then, the solution was concentrated under reduced pressure to remove an excess solvent to obtain an emulsion. The solid content of the obtained emulsion was 40.2%, and deionized water was added to obtain a resin emulsion (E-1) having a solid content of 40%. (Note 2) Fenodur PR401: Hoechst Co., resol type phenol resin solution, solid content about 68%.

Production Example 7 Synthesis of Acrylic Modified Epoxy Resin (A-2) Solution and Emulsion Using the Same In Production Example 6, instead of the acrylic resin (b-1) solution, the acrylic resin (b) obtained in Production Example 5 was used. -2) Acrylic-modified epoxy resin (A-2) solution and an emulsion using the same were obtained in the same manner as in Production Example 6 except that the solution was used. The solid content of the emulsion after desolvation was 40.
5% and deionized water was added to obtain a resin emulsion (E-2) having a solid content of 40%.

Production Example 8 Synthesis of Acrylic Modified Epoxy Resin (A-3) Solution and Emulsion Using the Same In Production Example 6, instead of the epoxy resin (a-1), the epoxy resin (a- The procedure of Production Example 6 was repeated except that 2) was used to obtain an acrylic modified epoxy resin (A-3) solution and an emulsion using the same. The solid content of the emulsion after desolvation was 41.2%, and deionized water was added to obtain a resin emulsion (E-3) having a solid content of 40%.

Production Example 9 Synthesis of Acrylic Modified Epoxy Resin (A-4) Solution and Emulsion Using the Same In Production Example 6, instead of the epoxy resin (a-1), the epoxy resin (a- The procedure of Production Example 6 was repeated except that 3) was used to obtain an acrylic modified epoxy resin (A-4) solution and an emulsion using the same. The solid content of the emulsion after desolvation was 40.9%, and deionized water was added to obtain a resin emulsion (E-4) having a solid content of 40%.

Production Example 10 Preparation of Acrylic Resin (B-1) Solution Containing Carboxyl Group (1) methoxypropanol 580 parts (2) methacrylic acid 120 parts (3) styrene 240 parts (4) ethyl acrylate 40 parts (5) Benzoyl peroxide 20 parts A four-necked flask equipped with a reflux tube, a thermometer, a monomer flow rate controller, and a stirrer was charged with 20% of the mixture of (2) to (5) and (1) in the flask, and a nitrogen stream was introduced. The mixture is heated to 95 ° C. below and the rest of the mixture of (2) to (5) is added dropwise over about 3 hours. After completion of the addition, stirring is continued for 2 hours at the same temperature, and the mixture is cooled to room temperature and solid content is about 40%. Acrylic resin (B
-1) A solution was obtained. The obtained resin (solid content) has an acid value of 19
6, the SP value was 10.42, and the number average molecular weight was about 6,900.

Production Example 11 Preparation of Acrylic Resin (B-2) Solution Containing Carboxyl Group (1) Methoxypropanol 585 parts (2) Methacrylic acid 140 parts (3) Styrene 180 parts (4) Ethyl acrylate 80 parts (5) Benzoyl peroxide 15 parts 20% of the mixture of (2) to (5) and (1) were charged into a four-necked flask equipped with a reflux tube, a thermometer, a monomer flow rate controller, and a stirrer, and a nitrogen stream was introduced. 105 ° C below
The mixture is heated to (3) and the rest of the mixture of (2) to (5) is added dropwise over about 3 hours. After completion of the addition, stirring is continued for 2 hours at the same temperature, and the mixture is cooled to room temperature and the acrylic resin has a solid content of about 40%. (B
-2) A solution was obtained. The resulting resin (solid content) has an acid value of 22.
8, SP value was 10.56, and number average molecular weight was about 7,900.

Preparation Example 12 Preparation of Acrylic Resin Containing Carboxyl Group (B-3) [For Comparative Example] (1) Methoxypropanol 580 parts (2) Methacrylic acid 220 parts (3) Styrene 160 parts (4) Ethyl acrylate 20 Parts (5) benzoyl peroxide 20 parts 20% of the mixture of (2) to (5) and (1) in a flask equipped with a reflux tube, a thermometer, a monomer flow rate controller, and a stirrer. After charging, the mixture was heated to 95 ° C. under a nitrogen stream and the rest of the mixture of (2) to (5) was added dropwise over about 3 hours. After completion of the addition, stirring was continued at the same temperature for 2 hours and cooled to room temperature to solidify. About 40% of acrylic resin (B
-3) A solution was obtained. The obtained resin (solid content) has an acid value of 35.
9, SP value was 11.39, and number average molecular weight was about 7,000.

Production Example 13 Synthesis of acrylic modified epoxy resin (A-5) and emulsion using the same (for comparative example) (1) Epicoat 1009 (Note 3) 80 parts (2) Acrylic resin obtained in Production Example 4 (B-1) Solution 50 parts (3) Methoxypropanol 69.8 parts (4) Diethylene glycol mono n-butyl ether 16.5 parts (5) Dimethylethanolamine 0.2 parts (6) Fenodur PR401 14.7 parts (7) ) Ammonia aqueous solution (25% concentration) 7.6 parts (8) Deionized water 192.4 parts

A four-necked flask equipped with a reflux tube, a thermometer, and a stirrer was charged with (1) to (4), heated to 100 ° C. to dissolve them, and then (5) was added to maintain this temperature. The reaction was carried out for 3 hours to obtain an acrylic modified epoxy resin (A-5) solution. This reaction was confirmed by measuring the acid value of the resin. The acid value of the obtained resin (solid content) was 45, and the number average molecular weight was about 25,000. The temperature of the resin solution obtained above was set to 60 ° C., (6) was added and mixed uniformly,
(7) was added to neutralize the resin, and (8) was gradually added to disperse it in water. Then, the solution is concentrated under reduced pressure to remove excess solvent, and the acrylic modified epoxy resin emulsion (E-
5) was obtained. The solid content of the obtained emulsion is 40.0.
%Met. (Note 3) Epicoat 1009: manufactured by Yuka Shell Epoxy Co., bisphenol A type epoxy resin, epoxy equivalent of about 2,600, number average molecular weight of about 3,800.

Preparation of Aqueous Coating Composition Example 1 (1) Acrylic resin (B-1) solution obtained in Preparation Example 1 12.5 parts (2) Aqueous ammonia solution (concentration 25%) 1.4 parts (3) Deionized water 11.1 parts (4) 261.3 parts of resin emulsion (E-1) obtained in Production Example 6 (5) Deionized water 35.8 parts Put (1) in a container and add (2). Add well and stir well,
Furthermore, (3) was gradually added to obtain an aqueous liquid having a solid content of 20%. Put (4) in another container, and stir it above (1).
~ (3) mixture of aqueous solution is gradually added, and then (5) is added to adjust the viscosity to 75 to 80 seconds (Ford Cup #
4, the measurement temperature was adjusted to 25 ° C.) to obtain an aqueous coating composition.

Examples 2 to 8 and Comparative Examples 1 to 4 In Example 1, the amount of (2) aqueous ammonia solution (concentration 25%) relative to 100 parts of the total resin solid content is shown in Table 1 below.
And (1) acrylic resin (B) and (4)
Same as Example 1 except that the amount of the resin emulsion (E) and the acrylic modified epoxy resin (A) / carboxyl group-containing acrylic resin (B) are blended so that the solid content weight ratio is the ratio shown in Table 1 below. I went to. Note that (1)-
The amount of deionized water (3) is adjusted so that the solid content of the aqueous liquid which is the mixture of (3) is 20%, and the viscosity of the finally obtained aqueous coating composition is 75 to 80 seconds (Ford cup). (4) The amount of deionized water was adjusted so that the measurement temperature was 25 ° C.), and each aqueous coating composition was obtained in the same manner as in Example 1.

[0051]

[Table 1]

Each of the aqueous coating compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 4 was coated on a tin-free steel plate or 100 μm aluminum foil so that the dry film thickness was about 6 μm. The coated plate was obtained by baking at 10 ° C for 10 minutes. Tests of workability, retort resistance, and adhesion were performed on a coated plate formed by coating on a tin-free steel plate. In addition, hygiene and flavor tests were carried out on a coated plate coated on aluminum foil. Further, roll coating suitability of each aqueous coating composition, foam suppression / defoaming property, flow characteristics,
Storage stability was also tested. The test results are shown in Table 2 below.

Each of the above tests was conducted according to the following test methods. Processability: Fold the coated plate in two with the coating film on the outside,
Place two tin-free steel plates between the folded test pieces.
After the sheet is sandwiched and bent for 2T, 6.
The current value (mA) in the width of the processed portion of 2 cm was measured when a voltage of 5 V was applied for 6 seconds. The smaller the value, the better the workability. Retort resistance: The coated plate is immersed in water and treated in an autoclave at 125 ° C. for 30 minutes to determine the whitening state of the coating film. ○: No whitening, ×: Remarkably whitening

Adhesion: 2 coated plates (150 mm x 5.0 m)
Nylon film is sandwiched between the coated surface of m) and the surface to be adhered, and this is heated at 200 ° C for 60 seconds and then 200 ° C.
A test piece was prepared by pressing nylon for 30 seconds to fuse both coating films to each other. Next, the T-peel adhesive strength of this test piece was measured by a tensile tester (Shimadzu Autograph AGS-500A).
Was measured at a tension rate of 200 mm / min and a temperature of 20 ° C. The value was an average value of 5 times. Those having a T-peel adhesive strength of more than 3 kg / 5 mm were rated as ◯ and those having a T-peel adhesive strength of 3 kg / 5 mm or less were rated as x.

Hygiene: A test panel coated on 100 μm aluminum foil was placed in a heat-resistant glass bottle so that the ratio of coating area: tap water treated with activated carbon was 1 cm ² : 1 cc, and the lid was closed and autoclaved. Was treated at 125 ° C. for 30 minutes, and the content liquid was measured according to the test method described in the Food Sanitation Law (Ministry of Health and Welfare No. 434). Consumption is expressed in ppm. Flavor: A test panel coated with 100 μm aluminum foil was applied and the ratio of coating area: activated carbon treated tap water was 2 cm.
Put in a heat-resistant glass bottle so that the ratio becomes ² : 1 cc, cover with a lid, and treat in an autoclave at 125 ° C. for 30 minutes to carry out a flavor test of the content liquid. The case where no change was observed is marked as ○. When the flavor property is inferior and it is not practical, it is marked with x.

Roll coating suitability: The coating was circulated for 30 minutes at 35 to 40 ° C. with a natural roll coater, and then the film thickness after baking on tin-free steel (TFS) was 5
It was coated so as to have a thickness of about 7 μm and baked at 200 ° C. for 10 minutes. The degree of bubbles in the coating after circulating for 30 minutes, the degree of pinholes on the coated surface, the degree of blistering, the smoothness of the coated surface, and the degree of gloss were visually evaluated. Degree of bubbles in paint ○: Slight, △: Slightly high, ×: Quite high Pinhole / blister on the coated surface ○: Good with no pinholes or blisters, △: Small amount of pinholes or blisters, ×: Pinhole And blister occur considerably. Smoothness of coated surface / gloss ○: Good, ×: Poor

Foam suppression / defoaming property: 160 cc of water-based paint as a sample was put in a 1,000 cc graduated cylinder, and air was added to the paint through a glass ball filter using an air pump.
It was fed at a rate of 00 cc / min, and the foaming amount after feeding air for 5 minutes and the defoaming rate after the feeding was stopped were measured. It is shown that the smaller the amount of foaming, the better, and the larger the defoaming rate, the better.

Flowability: Using a B-type viscometer, the rotor No. 1 at 6 rpm and rotor no. 3, the viscosity at 60 rpm was measured, and the ratio TI value viscosity (6 rpm) / viscosity (60 rpm) was calculated to determine the flow characteristics. The closer the TI value is to 1.0, the closer it is to Newtonian. Storage stability: Put 100 cc of the test water-based paint in a glass wide-mouthed bottle with an internal capacity of 100 cc, seal it tightly, store it in a constant temperature bath at 50 ° C for 1 month, and then open it for inspection. The viscosity of the water-based paint and the particle size of the dispersed particles were investigated, and the change in state was comprehensively compared with that before storage. ◯: No change observed, Δ: slightly changed, ×: markedly changed

[0059]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Morita 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Ichiro Yoshihara 4-1-1, Higashi-Hachiman, Hiratsuka, Kanagawa West Paint Co., Ltd.

Claims (4)

[Claims] 1. Epoxy equivalent of 8,000 to 18,000
And an acrylic-modified epoxy resin (A) obtained by reacting a bisphenol type epoxy resin (a) having a number average molecular weight of 2,500 to 10,000 by gel permeation chromatography with a high acid value acrylic resin (b) , Solubility parameter (SP value) of the resin (b)
A carboxyl group-containing acrylic resin (B) having an SP value lower than that of 0.05 to 1.00 is neutralized to form an aqueous dispersion, and the resin (A) and the resin (B) are blended. 99% to 80 in terms of solid content weight ratio of (A) / (B)
/ 20, The water-based paint composition characterized by the above-mentioned. 2. The reaction ratio between the bisphenol type epoxy resin (a) and the high acid value acrylic resin (b) is 50/50 to 9 in terms of the solid content weight ratio of (a) / (b).
The aqueous coating composition according to claim 1, which is 5/5. 3. The water-based coating composition according to claim 1, which contains a curing agent in addition to the acrylic modified epoxy resin (A) and the carboxyl group-containing acrylic resin (B). 4. A method of forming a coating film, which comprises roll-coating the aqueous coating composition according to claim 1, 2 or 3 on a metal plate, and then baking it.