KR20010111628A - Aqueous Coating Compositions - Google Patents

Abstract

The present invention provides an aqueous coating composition capable of forming a coating film having excellent processability, corrosion resistance, and film resistance to difficult processing, and excellent performance in adhesion, retort resistance, scratch resistance, hygiene, and flavor.

An acrylic coating epoxy composition obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) is neutralized and dispersed in an aqueous medium, wherein the epoxy resin (A) is a bisphenol A diglycidyl ether epoxy. At least 1 sort (s) chosen from the composite bisphenol-type epoxy resin (a) obtained by making three components of resin, the bisphenol F diglycidyl ether epoxy resin, and bisphenol F react, and the modified resin (b) of the said composite bisphenol-type epoxy resin It is made of resin and relates to an aqueous coating composition having a number average molecular weight of 4,000 to 30,000 and an epoxy equivalent of 3,000 to 15,000.

Description

Aqueous Coating Compositions

The present invention relates to an aqueous coating composition, in particular a can inner surface aqueous coating composition useful for coating the inner surface of an edible can, and particularly excellent in processability, scratch resistance, corrosion resistance, and film resistance in lid manufacturing processing of can lids. The present invention relates to an aqueous coating composition capable of forming a coating film excellent in performances such as adhesion, retort resistance, hygiene, and flavor.

Conventional Technology and its Challenges

Background Art In recent years, can paints have been widely used in terms of work hygiene, environmental preservation measures, and fire safety. Such can inner coating is mainly composed of an esterification reaction product of an epoxy resin and a carboxyl group-containing acrylic resin, for example, in JP-A-63-41934, JP-A-59-37026, and JP-A-6-329974. It is disclosed as an aqueous paint.

In the case where the conventional water-based paint is to be applied to a can lid such as an easy open end, it is disclosed in Japanese Patent Application Laid-Open No. 9-16998 in order to form a coating film that can withstand difficult processing. The method of using the same high molecular weight epoxy resin is performed.

However, although this method is certainly effective in improving workability, it is not satisfactorily satisfied with various required performances, and has a drawback in that it is inferior in paging resistance due to a decrease in adhesion of the coating film to the material, and also bisphenol. Since the high molecular weight epoxy resin obtained by formulation centering on A skeleton is very high viscosity, handling is difficult and workability is inferior.

An object of the present invention is excellent in processability, corrosion resistance, film resistance to difficult processing, such as the lid manufacturing process of the can lid, and further required for can inner coating film such as adhesion, retort resistance, scratch resistance, hygiene, flavor It is an object to provide an aqueous coating composition capable of forming a coating film having excellent performance.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve the said subject, the present inventors used composite bisphenol-type epoxy resin and / or its modified resin which have a high molecular weight bisphenol A frame | skeleton and bisphenol F frame | skeleton which consist of a specific raw material as an epoxy resin. The present invention was accomplished by discovering that the above-described object can be achieved by an aqueous coating composition obtained by reacting the above-mentioned epoxy resin with a carboxyl group-containing acrylic resin by neutralizing and dispersing it in an aqueous medium.

That is, the present invention is an aqueous coating composition in which an acrylic modified epoxy resin obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) is neutralized and dispersed in an aqueous medium, wherein the epoxy resin (A) is a bisphenol A-type di A compound bisphenol-type epoxy resin (a) obtained by reacting a glycidyl ether epoxy resin, a bisphenol F type diglycidyl ether epoxy resin, and three components of bisphenol F, having a bisphenol A skeleton and a bisphenol F skeleton in one molecule, and It is composed of at least one resin selected from the modified resin (b) of the composite bisphenol-type epoxy resin, the number average molecular weight is in the range of 4,000 to 30,000 and the epoxy equivalent is in the range of 3,000 to 15,000 To provide a coating composition.

The composition of the present invention is an aqueous coating composition in which an acrylic modified epoxy resin obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) is neutralized and dispersed in an aqueous medium.

The epoxy resin (A) and carboxyl group-containing acrylic resin (B) used for manufacture of the said acrylic modified epoxy resin are as follows.

Epoxy Resin (A)

The epoxy resin (A) has a bisphenol A skeleton and a bisphenol F skeleton in one molecule obtained by reacting three components of a bisphenol A diglycidyl ether epoxy resin, a bisphenol F diglycidyl ether epoxy resin, and a bisphenol F. It may consist of at least one resin selected from the composite bisphenol-type epoxy resin (a) and the modified resin (b) of the composite bisphenol-type epoxy resin.

As the bisphenol A diglycidyl ether epoxy resin used in the production of the composite bisphenol-type epoxy resin (a), a relatively small epoxy equivalent is generally used, and an epoxy equivalent of about 140 to about 2,000 is suitable, and a commercially available product thereof. Examples include Epicoat 828 EL, Epicoat 1001, Epicoat 1004, and Epicoat 1007 available from Eucashell Epoxy; Araldite AER250, Araldite AER260, Araldite AER6071, Araldite AER6004, Araldite AER6007 from Asahi Chivasa; Examples thereof include Epomic R140, Epomic R301, Epomic R304, Epomic R307, and Adeka Resin EP-4100 and Adeka Resin EP-5100, manufactured by Mitsui Chemicals.

As the bisphenol F-type diglycidyl ether epoxy resin used in the production of the composite bisphenol-type epoxy resin (a), a relatively small epoxy equivalent is generally used, and an epoxy equivalent of about 140 to about 2,000 is suitable. Commercially available products include, for example, Epicoat 807, Epicoat 806H manufactured by Yucca Shell Epoxy Co., Epomic R-114 manufactured by Mitsui Sekiyu Chemical Co., Ltd., Adecar Resin EP-4900 manufactured by Asahi Denka Co., Ltd. Clone 830 (S), Edoto YDF-170 by Toto Kasei, etc. are mentioned.

The compound bisphenol-type epoxy resin (a) which is the reaction product of the said three components is obtained by addition-reacting three components of the said bisphenol A diglycidyl ether epoxy resin, the said bisphenol F diglycidyl ether epoxy resin, and the bisphenol F. Can be.

Although the ratio of the bisphenol A frame | skeleton and bisphenol F frame | skeleton in the said composite bisphenol-type epoxy resin (a) is not specifically limited, The equivalence ratio of (A frame | skeleton / F frame | skeleton) in one molecule averages 10/90-60/40, Preferably, what exists in the range of 20/80-50/50 is suitable from a viewpoint of the performance balance, such as adhesiveness, corrosion resistance, and workability of the coating film obtained.

The composite bisphenol type epoxy resin (a) is not particularly limited, but the number average molecular weight is in the range of 4,000 to 30,000, preferably 6,000 to 30,000, and the epoxy equivalent is in the range of 3,000 to 12,000, preferably 5,000 to 12,000. It is suitably used from a viewpoint of dispersion stability in an aqueous medium, processability or hygiene of the coating film obtained, and the like.

The modified resin (b) of the composite bisphenol-type epoxy resin is the bisphenol A diglycidyl ether epoxy resin and the bisphenol F-type diglycidyl ether, which are raw materials when the composite bisphenol-type epoxy resin (a) is produced. The composite bisphenol-type epoxy resin obtained by addition-reacting using the three components of an epoxy resin and bisphenol F can be obtained by denaturing with modifiers, such as a dibasic acid, for example. In this case, as the composite bisphenol type epoxy resin reacted with dibasic acid, those having a number average molecular weight of 2,000 to 10,000 and an epoxy equivalent in the range of 1,500 to 8,000 can be suitably used. As the dibasic acid, a compound represented by the general formula HOOC- (CH ₂ ) n -COOH (wherein n represents an integer of 1 to 12), specifically, succinic acid, adipic acid, pimeric acid, and azela. Phosphoric acid, sebacic acid, dodecane diacid, etc., or hexahydrophthalic acid, etc. can be used, and adipic acid can be used especially suitably.

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

The modified resin (b) of the composite bisphenol-type epoxy resin is advantageous in improving the processability or corrosion resistance of the coating film obtained because the dibasic acid molecular chain introduced into the molecule of the epoxy resin acts as a plastic component to improve the adhesion. can do.

Carboxyl group-containing acrylic resin (B)

The carboxyl group-containing acrylic resin (B) (hereinafter may be abbreviated as "acrylic resin (B)") used in the present invention to react with the epoxy resin (A) to produce an acrylic modified epoxy resin is acrylic acid or methacrylic acid. It is an acrylic copolymer which makes polymerizable unsaturated carboxylic acids, such as maleic acid, itaconic acid, and fumaric acid, an essential monomer component. It is preferable that this copolymer exists in the range of 130-500 mgKOH / g resin acid value from a viewpoint of stability in an aqueous medium, processability of the coating film obtained, retort resistance, flavor, etc.

As another monomer component other than the polymerizable unsaturated carboxylic acid used for superposition | polymerization of the said acrylic resin (B), 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 Alkyl esters having 1 to 15 carbon atoms of acrylic acid or methacrylic acid, such as stearyl (meth) acrylate and cetyl (meth) acrylate; Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; Aromatic vinyl monomers such as styrene, α-methylstyrene, and vinyltoluene; Hydroxy, such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyamyl (meth) acrylate, and hydroxyhexyl (meth) acrylate Caprolactone which has a hydroxyl group obtained by ring-opening addition reaction of 1-5 mol of (epsilon) -caprolactone with respect to 1 mol of hydroxyalkyl (meth) acrylates, such as alkyl (meth) acrylate and hydroxyethyl (meth) acrylate. Hydroxyl group-containing polymerizable unsaturated monomers such as modified alkyl (meth) acrylates; Acrylamide, methacrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, Nn-propoxymethyl (meth) acrylamide, N-isopropoxymethyl (meth) acryl Acrylamide monomers such as amide, Nn-butoxymethyl (meth) acrylamide, N-sec-butoxymethyl (meth) acrylamide, and N-tert-butoxymethyl (meth) acrylamide; Acrylonitrile, methacrylonitrile, vinyl acetate, ethylene, butadiene, etc. are mentioned.

The said acrylic resin (B) heats the monomer mixture of the said polymerizable unsaturated carboxylic acid and the said other monomer component, for example for 1 to 10 hours at 80-150 degreeC in presence of a radical polymerization initiator or a chain transfer agent in organic solvent, for example. Can be obtained by copolymerization. As the polymerization initiator, organic peroxides, azo or the like are used. In organic peroxides, benzoyl peroxide, t-butylperoxy 2-ethylhexanoate, di-butyl peroxide, t-butylperoxybenzoate, t-amyl peroxy 2-ethylhexanoate, etc. are mentioned, for example, azobisisobutyronitrile, azobisdimethylvaleronitrile, etc. are mentioned in an azo system. (Alpha) -methylstyrene dimer, mercaptans, etc. are mentioned as said chain transfer agent. Although the molecular weight of an acrylic resin (B) is not specifically limited, Usually, it is preferable to exist in the range of the number average molecular weights 1,500-100,000, and also 2,000-80,000.

The reaction between the epoxy resin (A) and the carboxyl group-containing acrylic resin (B) is, for example, an esterification catalyst in a organic solvent, for example, tertiary amines such as triethylamine, dimethylethanolamine or triphenylphosphine. It can be performed by heating and esterifying about 80 to 120 degreeC about 0.5 to 8 hours in presence of the quaternary salt compound of this, and acrylic modified epoxy resin can be obtained by this.

The mixing ratio of the epoxy resin (A) and the acrylic resin (B) in the above reaction can be appropriately selected depending on the coating workability or the coating film performance, but is usually 60 / in terms of the solid content weight of the resin (A) / resin (B). It is preferable to exist in the range of 40-90 / 10, Furthermore, 70 / 30-90 / 10.

It is preferable that the acrylic modified epoxy resin obtained by the said esterification reaction exists in the range of acid value 15-100 mgKOH / g from a viewpoint of dispersion stability in an aqueous medium, the water resistance of the coating film obtained, etc., and does not have an epoxy group substantially. It is preferable from a storage stability point of view.

The acrylic modified epoxy resin is neutralized and dispersed in an aqueous medium. As the neutralizing agent used for neutralization, amines or ammonia are suitably used. Representative examples of the amines include triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, and the like. Especially, triethylamine and dimethylethanolamine are suitable. Although the degree of neutralization of an acrylic modified epoxy resin is not specifically limited, It is preferable that it is the range of 0.3-2.0 equivalent neutralization normally with respect to the carboxyl group in resin.

The aqueous medium capable of dispersing the acrylic modified epoxy resin may be only water, or may be a mixture of water and an organic solvent. As such an organic solvent, any conventionally known solvent can be used as long as it is an organic solvent which can be mixed with water that does not interfere with the stability of the acrylic modified epoxy resin in the aqueous medium. The organic solvent is preferably an alcohol solvent, a cellosolve solvent, a carbitol solvent, or the like. As a specific example of this organic solvent, 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; Carbitol solvents such as diethylene glycol monoethyl ether; and the like. Moreover, as an organic solvent, the inert organic solvent which is not mixed with water of that excepting the above can also be used in the range which does not interfere with the stability in the aqueous medium of acrylic modified epoxy resin, As such an organic solvent, For example, aromatics, such as toluene and xylene Hydrocarbons, Ester, such as ethyl acetate and butyl acetate, Ketone, such as methyl ethyl ketone, are mentioned. The amount of the organic solvent in the aqueous coating composition of the present invention is preferably in the range of 50% by weight or less in the aqueous medium from the viewpoint of environmental protection and the like.

In order to neutralize and disperse an acrylic modified epoxy resin in an aqueous medium, a conventional method can be followed, for example, a method of slowly adding an acrylic modified epoxy resin under stirring in an aqueous medium containing a neutralizing agent, and neutralizing an acrylic modified epoxy resin with a neutralizing agent. After that, a method of adding an aqueous medium to the neutralized product or adding the neutralized product to the aqueous medium under stirring is mentioned.

Although the aqueous coating composition of this invention may consist only of the aqueous resin composition in which the acrylic modified epoxy resin was neutralized and disperse | distributed in the aqueous medium, it aims at improving coating film performance or paintability, preventing scratches at the time of processing or transport, and improving odor. In addition, crosslinking agent resins, such as a resol type phenol resin, a novolak-type phenol resin, melamine resin, and benzoguanamine resin, surfactant, a wax, an antifoamer, a pigment, a fragrance, etc. are suitably added to this aqueous resin composition as needed. good.

The aqueous coating composition of this invention can be applied to various base materials, For example, untreated or surface-treated metal plates, such as an aluminum plate, tin free steel, a tinplate, and primers, such as an epoxy type and a vinyl type, to these metal plates. The coated metal plate etc. which apply | coated and the molded metal plate which processed this metal plate or the coated metal plate etc. to a can etc. are mentioned.

As a method of coating the aqueous coating composition of the present invention on a substrate, various known methods, for example, a coating method such as roll coater coating, spray coating, immersion coating or electrodeposition coating, can be applied, and among them, roll coater coating is preferable. . Although the coating thickness of the aqueous coating composition of this invention can be suitably selected according to a use, Usually, the range which becomes about 3-20 micrometers in a dry coating film thickness is suitable. As drying conditions of the coated coating film, the range for 10 second-50 second is preferable at the conditions which will normally reach | attain maximum raw material temperature 150-300 degreeC, and also 200-280 degreeC at 200-280 degreeC.

Hereinafter, the present invention will be described in detail with reference to Production Examples, Examples and Comparative Examples. Hereinafter, "part" and "%" shall mean "weight part" and "weight%."

Preparation Example 1

Preparation of Composite Bisphenol-type Epoxy Resin (a-1)

(1) Epicoat 828 EL (Note 1) 165 parts

(2) 579 parts of epicoat 806H (note 2)

(3) Bisphenol F 410 parts

(4) tetrabutylammonium bromide 0.6part

The said (1)-(4) was put into the four neck flask equipped with the reflux cooling tube, the thermometer, and the stirrer, and reaction was performed at 160 degreeC under nitrogen stream. Reaction was tracked by epoxy equivalent and reacted for about 6 hours, and the composite bisphenol-type epoxy resin (a-1) of the number average molecular weight about 8,000 and epoxy equivalent about 6,5OO was obtained.

(Note 1) Epicoat 828 EL: It has a Euca-Shell epoxy company make, bisphenol-A epoxy resin, epoxy equivalent about 187, and molecular weight about 350.

(Note 2) Epicoat 806 H: It has a Euca shell epoxy company product, a bisphenol F-type epoxy resin, an epoxy equivalent of about 170, and a molecular weight of about 320.

Preparation Example 2

Preparation of Composite Bisphenol-type Epoxy Resin (a-2)

(1) Epicoat 828 EL part 381

(2) Epicoat 806 H 369 parts

(3) Bisphenol F 401 parts

(4) 0.9 parts of tetrabutylammonium bromide

Bisphenol A having a number average molecular weight of about 14,000 and an epoxy equivalent of about 6,200 was added to the four-necked flask equipped with a reflux condenser, thermometer, and stirrer, and reacted for about 7 hours at 160 ° C under a nitrogen stream. A / F copolymerized epoxy resin was obtained. (5) and (6) were put again, and it was made to react for about 2 hours, and the composite bisphenol-type epoxy resin (a-2) of the number average molecular weight about 20,000 and epoxy equivalent about 11,000 was obtained.

Preparation Example 3

Preparation of Composite Bisphenol-type Epoxy Resin (a-3)

(1) Epicoat 828 EL 493 Part

(2) Epicoat 806 H 262 parts

(3) Bisphenol F 395 parts

(4) 0.9 parts of tetrabutylammonium bromide

(1) to (4) were put into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted for about 8 hours at 160 ° C. under a nitrogen stream to carry out a compound bisphenol having a number average molecular weight of about 19,000 and an epoxy equivalent of about 6,200. A type epoxy resin (a-3) was obtained.

Preparation Example 4

Preparation of Composite Bisphenol-type Epoxy Resin (a-4)

(1) Epicoat 828 EL part 576

(2) 183 Epicoat 806 H

(3) bisphenol F 392 parts

(4) 0.9 parts of tetrabutylammonium bromide

(1) to (4) were put into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted for about 7 hours at 160 ° C. under a nitrogen stream to carry out a compound bisphenol having a number average molecular weight of about 16,000 and an epoxy equivalent of about 5,800. A type epoxy resin (a-4) was obtained.

Preparation Example 5

Preparation of Modified Resin (b-1) of Composite Bisphenol-type Epoxy Resin

(1) Epicoat 828 EL part 177

(2) Epicoat 806 H 623 part

(3) bisphenol F 441 parts

(4) tetrabutylammonium bromide 0.6part

(5) adipic acid 6.4part

(6) trin-butylamine0.5part

(1) to (4) were put into a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at 160 DEG C for about 4 hours under a stream of nitrogen to give a number average molecular weight of about 8,000 and an epoxy equivalent of about 6,000 bisphenol F A type epoxy resin was obtained. (5) and (6) were put again, and it was made to react for about 2 hours, and the modified resin (b-1) of the composite bisphenol-type epoxy resin of the number average molecular weight about 13,000 and epoxy equivalent about 10,000 was obtained.

Preparation Example 6

Preparation of Modified Resin (b-2) of Composite Bisphenol-type Epoxy Resin

(1) Epicoat 828 EL part 177

(2) Epicoat 806 H 623 part

(3) bisphenol F 441 parts

(4) 0.9 parts of tetrabutylammonium bromide

(5) adipic acid 6.0part

(6) trin-butylamine0.5part

(1) to (4) were added to a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and the reaction was carried out at 160 ° C. for about 8 hours under a stream of nitrogen to give a number average molecular weight of about 9,000 and an epoxy equivalent of about 6,000 bisphenol F A type epoxy resin was obtained. (5) and (6) were put again, and it was made to react for about 2 hours, and the modified resin (b-2) of the composite bisphenol-type epoxy resin of the number average molecular weight about 20,000 and epoxy equivalent about 11,000 was obtained.

Preparation Example 7

Preparation of composite bisphenol-type epoxy resin (c-1) (for comparison)

(1) Epicoat 828 EL 170 parts

(2) Epicoat 806 H 636 Part

(3) Bisphenol F 404 parts

(4) tetrabutylammonium bromide 0.6part

The said (1)-(3) was put into the four neck flask equipped with the reflux cooling tube, the thermometer, and the stirrer, and reaction was performed at 160 degreeC under nitrogen stream. The reaction was traced by epoxy equivalent and reacted for about 4 hours to obtain a composite bisphenol-type epoxy resin (c-1) having a number average molecular weight of about 3,000 and an epoxy equivalent of about 2,000.

Preparation Example 8

Preparation of bisphenol F type epoxy resin (c-2) (for comparison)

(1) Epicoat 806 H 800 parts

(2) Bisphenol F 448 parts

(3) tetrabutylammonium bromide 0.6part

The said (1)-(3) was put into the four neck flask equipped with the reflux cooling tube, the thermometer, and the stirrer, and reaction was performed at 160 degreeC under nitrogen stream. The reaction was tracked by 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.

Preparation Example 9

Preparation of composite bisphenol-type epoxy resin (c-3) (for comparison)

(1) Epicoat 828 EL 786 Part

(2) bisphenol 262 parts

(3) 200 parts of bisphenol A

(4) tetrabutylammonium bromide 0.6part

The said (1)-(3) was put into the four neck flask equipped with the reflux cooling tube, the thermometer, and the stirrer, and reaction was performed at 160 degreeC under nitrogen stream. The reaction was traced by 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.

Preparation Example 10

Preparation of carboxyl group-containing acrylic resin (B-1)

(1) 1096 parts of n-butanol

(2) 210 parts of methacrylic acid

(3) 180 parts of styrene

(4) 210 parts of ethyl acrylate

(5) t-butylperoxy2-ethylhexanoate 18 parts

(1) was added to a four-necked flask equipped with a reflux condenser, a thermometer, a monomer flow regulator, and a stirrer, and heated to 100 ° C. under a nitrogen stream, and the mixture of (2) to (5) was added dropwise over about 3 hours. After the addition, the mixture was stirred at the same temperature again for 2 hours, and then cooled to room temperature to obtain an acrylic resin solution (B-1) having a solid content of about 35%. The obtained resin (solid content) had an acid value of 228 mgKOH / g and a number average molecular weight of about 15,000.

Preparation Example 11

Preparation of Phenolic Resin Solution (P-1) (1)

(1) 108 parts of p-cresol

(2) 216 parts of 37% aqueous formaldehyde solution

(3) 160 parts of 25% sodium hydroxide aqueous solution

Put the above (1) to (3) in a four-necked flask equipped with a reflux condenser, a thermometer, a stirrer and reacted for 2 hours at 50 ℃ under a nitrogen stream, and then heated up to 100 ℃ and reacted again at 100 ℃ for 1 hour After neutralization, the mixture was extracted with a mixed solvent of n-butanol / xylene = 1/1 to obtain a 60% phenol resin solution (P-1). The average methylol number per molecule of obtained resin was 1.9.

Example 1

(1) 85 parts of the composite bisphenol-type epoxy resin (a-1) obtained in Production Example 1

(2) 42.9 parts of acrylic resin solution (B-1) obtained in Production Example 10

(3) 55.6 parts of diethylene glycol monobutyl ether

(4) N, N-dimethylaminoethanol 3.7 parts

(5) 218 parts of deionized water

(6) 2 parts of phenol resin solution (P-1) obtained in Production Example 11.

(1) to (3) were added to a four-necked flask equipped with a reflux condenser, a thermometer, and a stirrer, and heated to 100 ° C. to dissolve. It carried out and obtained the acrylic modified epoxy resin solution of 25 mgKOH / g of resin acid value. The temperature of this resin solution was 70 degreeC, (5) was added gradually, and water dispersion was performed. Subsequently, concentration was carried out under reduced pressure to remove excess solvent, thereby obtaining an aqueous dispersion having a solid content of about 30%. (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 2-6 and Comparative Examples 1-4

In Example 1, except having performed the kind and quantity of an epoxy resin as Table 1 which mentions later, the same operation as Example 1 was performed, and each aqueous coating composition of about 30% of solid content was obtained.

Note in Table 1 has the following meaning.

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

Various tests were done with the following method about the aqueous coating composition obtained by each said Example and the comparative example.

Create a trial

Each aqueous coating composition obtained in Examples and Comparative Examples was coated with a roll coater such that the dry coating film weight was about 120 mg / 100 cm 2 (about 10 μm in dry film thickness) on an aluminum plate (aluminum 5182 material) having a plate thickness of 0.27 mm. It carried out, it passed through the inside of a conveyer conveyance type hot air drying furnace, and baked and it was set as the test plate. Baking conditions were made into the conditions of the material reaching maximum temperature of 240 degreeC, and the furnace passage time 20 second.

The test plates obtained were each tested for workability, processed part corrosion resistance, film resistance, adhesion, retort resistance, flavor, and hygiene according to the following test method. The test results are shown in Table 1 later.

Test Methods

Processability: Using a special laxative bending type DuPont impact tester, a sheet of 0.3 mm thick aluminum sheet is inserted between the bent portions of the test plate folded in two so that the coated film surface becomes the outer side, and the contact surface is flat 1 kg in thickness. After dropping the weight of iron at 50 cm and giving an impact to the bend, measure the current value (mA) of the bend end 2 mm width when passing the voltage of 6.5 V through the bend end for 6 seconds. The measurement was evaluated based on the following criteria.

◎: current value is less than 0.5 mA,

○: current value is 0.5 mA or more and less than 0.1 mA,

(Triangle | delta): Current value is 1.0 mA or more and less than 5.0 mA,

X: current value is 5.0 mA or more

Scratch resistance test: After placing a needle for a scratch test on a test plate, the coating plate was moved at a constant speed while applying a constant load, and evaluation was performed in the state of a scratch.

(Double-circle): There is no wound other than a needle contact part, and the crack and peeling of a coating film are not found around a wound.

O: A slight crack or peeling of the coating film was found around the needle contact area,

(Triangle | delta): The crack and peeling of a coating film were found around the needle contact part considerably.

X: The crack and peeling of a coating film were found notably around a needle contact part.

Process part corrosion resistance: Using a lid making press machine, the can lid, which is made of a test plate, is wound on a can body filled with an aqueous solution in which 2 parts of malic acid, 2 parts of citric acid and 2 parts of salt are dissolved in 100 parts of deionized water. Store at 50 ° C for 5 days with the coating surface of the test plate immersed in the contents. This can was cut and the state of the coating film was observed. Evaluation was performed according to the following criteria.

◎: No change was found in the can lid

O: Rust was found on the lid of the compartment, but only a slight change was found.

△: slight rust was found on the can lid;

X: Significant rust was found in the can lid.

Resistant to membrane (pessing resistance): The lid of the test plate was manufactured using a lid making press, and the lid was immersed in an aqueous solution of 2 parts of malic acid, 2 parts of citric acid, and 2 parts of saline in 100 parts of deionized water, followed by 5 days at 50 ° C. Neglect the liver. Thereafter, the can lid was taken out and washed with deionized water, and the can lid was immersed in boiling water at 100 ° C. for 30 minutes, and then the opening of the lid was pulled upward to open the coating film surface downward, and then the opening was opened. The peeling width of the coating film from the edge part was evaluated based on the following criteria.

◎: maximum peeling width of the coating film is less than 0.2 mm,

O: The maximum peeling width of the coating film is 0.2 mm or more and less than 0.5 mm,

(Triangle | delta): The largest peeling width of a coating film is 0.5 mm or more and less than 1.0 mm,

X: The maximum peeling width of the coating film is 1.0 mm or more.

Adhesiveness: When using a knife on the coated film surface of the test plate, 11 sheaths each having a width of about 1.5 mm in length and width were formed in the shape of a checkerboard, and the cellophane adhesive tape having a width of 24 mm was closely attached to the checkerboard and peeled off instantaneously. The peeling degree of the checkerboard coating film was observed. Evaluation was performed according to the following criteria.

◎: no peeling was found at all,

O: Very little peeling is found,

Δ: significant peeling was found;

X: Remarkable peeling was found.

Retort resistance: The whitening state of the coating film which was immersed in water for 30 minutes at 125 degreeC in the autoclave was evaluated based on the following reference | standard.

◎: no whitening was found at all,

O: very little whitening is found,

△: slightly whitening is found,

×: Whitening was found remarkably.

Flavorability (flavor retention): Application area of the test plate: The test plate was put in a heat-resistant glass bottle so that the tap water treated with activated carbon had a ratio of 2 cm 2: 1 cc and covered with a lid and sterilized at 125 ° C. for 30 minutes in an autoclave. After that, a flavor test of the contents is performed.

◎: no change found at all,

O: very little change is found,

△: significant change was found,

X: A remarkable change was found.

Hygiene: The test and activated carbon-treated tap water are placed in a heat-resistant glass bottle at a rate such that the amount of activated carbon-treated tap water is 1 cc with respect to the coating area of 1 cm 2, and the lid is covered and treated at 125 ° C. for 30 minutes in an autoclave. The hygienicity was evaluated based on the consumption amount (ppm) of potassium permanganate in accordance with the test method described in the Food Sanitation Act, with respect to the treated solution.

◎: consumption is less than 1 ppm,

O: 1 ppm or more and less than 3 ppm,

(Triangle | delta): Consumption 3 ppm or more and less than 10 ppm,

X: consumption is 10 ppm or more.

The main feature of the present invention is the use of at least one resin selected from a high molecular weight composite bisphenol type epoxy resin and a modified bisphenol type epoxy resin as the epoxy resin (A). In this way, the composition of this invention can achieve various advantages as described below.

Since the composite bisphenol-type epoxy resin contains the bisphenol F frame | skeleton, since it has a low glass transition temperature and acts as a soft component compared with bisphenol-A epoxy resin, it is excellent in adhesiveness of a coating film, Furthermore, corrosion resistance and workability are improved, and it is abrasion resistance, It is possible to form a coating film having good retort resistance and hygiene. And it is easy to handle by the effect of soft nitriding even in synthetic work.

In the composition of the present invention, the mixing step of the bisphenol A epoxy resin and the bisphenol F type epoxy resin described in Japanese Patent Application Laid-Open No. 11-199827 can be omitted, and the amount of solvent used to facilitate the mixing can be omitted, and the pressure reduction removal step can be omitted. In addition, the effect can be expected.

Claims (4)

An acrylic coating epoxy composition obtained by reacting an epoxy resin (A) with a carboxyl group-containing acrylic resin (B) is neutralized and dispersed in an aqueous medium, wherein the epoxy resin (A) is a bisphenol A diglycidyl ether epoxy. A compound bisphenol-type epoxy resin (a) having the bisphenol A skeleton and the bisphenol F skeleton in one molecule, obtained by reacting a resin, a bisphenol F-type diglycidyl ether epoxy resin and a bisphenol F component, and the compound bisphenol-type epoxy An aqueous coating composition comprising at least one resin selected from modified resin (b) of the resin, wherein the number average molecular weight is in the range of 4,000 to 30,000 and the epoxy equivalent is in the range of 3,000 to 15,000. The base epoxy resin according to claim 1, wherein the epoxy resin (A) is a composite bisphenol-type epoxy resin having a bisphenol A skeleton and a bisphenol F skeleton in one molecule having a number average molecular weight of 2,000 to 12,000 and an epoxy equivalent of 1,500 to 8,000. An aqueous coating composition which is a modified epoxy resin modified with water. The compounding ratio according to claim 1 or 2, wherein the acrylic modified epoxy resin is an epoxy resin (A) and a carboxyl group-containing acrylic resin (B) of 60/40 to 90/10 in terms of a solid content weight ratio of (A) / (B). An aqueous coating composition obtained by reacting with a. The aqueous coating composition according to any one of claims 1 to 3, further comprising a curing agent.