JPH06228497A - Water-based coating composition - Google Patents

Abstract

PURPOSE:To obtain a composition, excellent in flavor retaining properties, processability, corrosion resistance and adhesion and useful for inner surfaces of cans, etc., by dispersing a specific carboxyl group-containing reactional product and a specified resol type phenol.formaldehyde resin in a specified proportion in an aqueous medium. CONSTITUTION:The composition is obtained by dispersing (A) 100 pts.wt. carboxyl group-containing reactional product composed of an aromatic epoxy resin and a carboxyl group-containing acrylic resin and (B) 1-50 pts.wt. resol type phenol.formaldehyde resin, prepared by reacting phenols with aldehydes, containing >=50wt.% compound of the formula [R1 is H or 1-12C alkyl; R2 and R3 are H or methylol; R4 is H or 1-2C alkyl; (n) is >=4] and having 1.0-2.0 average number of methylol groups in one molecule in an aqueous medium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aqueous coating composition. More specifically, the present invention relates to an aqueous coating composition which can be applied to a metal material directly or on a base coating material to form a coating film excellent in flavor retention and processability.

[0002]

2. Description of the Related Art Conventionally, an epoxy resin, which is a material excellent in corrosion resistance, processability, flavor retention, etc., has been mainly used as a binder for solvent-based paints in paints for cans. On the other hand, various water-based paints for cans have been proposed to use an epoxy resin as a binder due to its excellent characteristics. Among them, a paint suitable for the inner surface of a can is a composition mainly obtained by modifying an epoxy resin with a high acid value acrylic resin, neutralizing an excess carboxyl group with ammonia or amine, and dispersing this in water. For example, in JP-A-53-1228, a radical generating catalyst such as benzoyl peroxide is used to graft-polymerize an acrylic monomer containing a carboxyl group-containing monomer onto the main chain of an epoxy resin,
A method of dispersing in water using a basic compound such as ammonia or amine is disclosed. In addition, JP-A-55-34
No. 81 and JP-A-55-3482, a high acid value acrylic resin previously polymerized with a radical generating catalyst such as benzoyl peroxide and an epoxy resin are subjected to an ester addition reaction under an esterification catalyst. A composition is disclosed in which an excess carboxyl group of the obtained adduct is neutralized with a basic compound such as ammonia or amine and the resulting compound is dispersed in water.

Thus, the water-dispersible epoxy resin obtained by the above technique is insufficient in curing itself in the usual drying process of the paint for the inner surface of the can, and is inferior in adhesive strength to the metal, so that it has both functions. Amino resin and phenol resin are used in combination as a material for improving the temperature.

For example, JP-A-61-250023 discloses a combination of an acrylic resin containing a monobasic carboxylic acid monomer and an aromatic epoxy resin, and a phenol having 3 or 4 methylol groups per bisphenol molecule. A dispersion prepared by dispersing a resin-containing phenol resin in an aqueous medium in the presence of ammonia or an amine is disclosed, and JP-A-61-268864 discloses a monobasic carboxylic acid monomer. A precondensation product of a binder of an acrylic resin and an aromatic epoxy resin containing and a phenol resin containing a phenol resin having 3 or 4 methylol groups per bisphenol molecule in the presence of ammonia or amine in an aqueous medium. Dispersions dispersed therein are disclosed. However, all of the dispersions described in these publications have insufficient processability, and thus the dispersions are used as water-based paints for cans and have high processability such as easy-open lids, especially Steion tab lids. It is difficult to use for the required application.

[0005]

In view of the present situation, the present inventors can form a coating film which is excellent in flavor retention and processability, and is also excellent in corrosion resistance, adhesion, hygiene and the like. As a result of intensive studies to develop a water-based coating composition for inner surfaces, it was found that the intended purpose of the present invention can be achieved by using the following specific resol type phenol-formaldehyde resin as an essential component. The present invention has been completed based on such findings.

That is, according to the present invention, 100 parts by weight of a carboxyl group-containing reaction product comprising (A) an aromatic epoxy resin and a carboxyl group-containing acrylic resin, and (B) phenols and aldehydes After reaction, the following general formula [1]

[0007]

[Chemical 2]

(Wherein R ₁ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, R ₂ and R ₃ are hydrogen atoms or a methylol group, provided that R ₂ and R ₃ are hydrogen atoms at the same time. R ₄ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms.
Represents an integer of 4 or more. 1) 50 parts by weight or more of the compound represented by the formula (1), and 1 to 50 parts by weight of a resole type phenol-formaldehyde resin having an average number of methylol groups per molecule of 1.0 to 2.0 are dispersed in an aqueous medium. A water-based coating composition is provided.

In the present invention, the carboxyl group-containing reaction product composed of the aromatic epoxy resin as the component (A) and the carboxyl group-containing acrylic resin can be prepared, for example, by the following method. (I) A method of subjecting an aromatic epoxy resin and a carboxyl group-containing acrylic resin to an ester addition reaction in an organic solvent solution in the presence of a tertiary amine. (II) A method in which the radical polymerizable unsaturated monomer is graft-polymerized with an aromatic epoxy resin in the presence of a radical generator such as benzoyl peroxide in an organic solvent solution.

The aromatic epoxy resin used for producing the carboxyl group-containing reaction product is, for example, one obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of an alkali catalyst, and epichlorohydrin and bisphenol with an alkali catalyst. In addition to those obtained by polycondensing a low molecular weight epoxy resin in the presence of, and subjecting this low molecular weight epoxy resin and bisphenol to a polyaddition reaction, an epoxy ester resin in which a dibasic acid is combined may be used. . Examples of the dibasic acid of the general formula HOOC- (CH ₂₎ (wherein, n. Represents an integer of 1 to 12) _n -COOH compound represented by, specifically, succinic acid, adipic acid, Pimelic acid,
Azelaic acid, sebacic acid, dodecanedioic acid and the like, hexahydrophthalic acid and the like are preferably used. As the bisphenol, bisphenol A and bisphenol F are preferably used, or a mixture of both may be used.

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

The number of epoxy groups per molecule of the epoxy resin is not particularly limited, and is appropriately selected depending on the reaction form with the carboxyl group-containing acrylic resin described below. That is, when the reaction form is an ester reaction, the average number of epoxy groups per molecule of the epoxy resin is 0.
The number is preferably 5 to 2, preferably 0.5 to 1.6. Further, when the reaction form is a graft reaction of an acrylic monomer containing a carboxyl group-containing acrylic monomer by hydrogen abstraction of the epoxy resin main chain, the epoxy group may not substantially exist in the epoxy resin.

The number average molecular weight of the epoxy resin is usually about 1,400 to 8,000, preferably 2,
It is about 900 to 7,000. When the number average molecular weight of the epoxy resin is less than 1,400, low molecular components due to the epoxy resin are eluted into the contents of the can during the sterilization process, which tends to be unfavorable for hygiene. On the contrary, when the number average molecular weight of the epoxy resin is more than 8,000, the viscosity becomes too high during the reaction with the acrylic resin or the acrylic monomer, and stable emulsification tends to be difficult.

In the above (1) esterification reaction for obtaining a carboxyl group-containing reaction product, the carboxyl group-containing acrylic resin is a carboxyl group-containing radically polymerizable unsaturated monomer such as the following (a) group. An acrylic resin obtained by (co) polymerizing at least one and optionally a radically polymerizable unsaturated monomer such as the group (b) which is copolymerizable therewith can be exemplified.

(A) α, β-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid and the like. (B) A hydroxyalkyl ester having 1 to 8 carbon atoms of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate; methyl acrylate, methyl methacrylate, Ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2
-Ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, decyl acrylate, etc. Acrylic acid or methacrylic acid having 1 to 24 carbon atoms alkyl or cycloalkyl ester; acrylamide; Methacrylamide, N-methyl acrylamide, N-ethyl methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-
Functional acrylic or methacrylamide derivatives such as methylolmethacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide, etc .; Aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, etc .; Vinyl acetate, propionic acid. Vinyl monomers such as vinyl, acrylonitrile, methacrylonitrile, vinyl propionate, vinyl pivalate and Veova monomer (manufactured by Shell Chemical Co.).

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

The carboxyl group-containing acrylic resin can be easily prepared by, for example, a solution polymerization method using the above-mentioned unsaturated monomer in the presence of an initiator for radical polymerization. The number average molecular weight of the carboxyl group-containing acrylic resin is usually about 5,000 to 100,000,
Moreover, the acid value is preferably in the range of about 50 to 500 in terms of resin solid content.

The tertiary amine used in the ester addition reaction of the above (1) is a compound represented by the general formula R ⁵ R ⁶ R ⁷ N (wherein R ⁵ and R ⁶ are 1 to 10 carbon atoms bonded to the nitrogen atom). Amines represented by two substituted or unsubstituted monovalent alkyl groups, R ⁷ represents a substituted or unsubstituted monovalent alkyl group having 1 to 4 carbon atoms bonded to a nitrogen atom), for example, Triethylamine, dimethylethanolamine (dimethylaminoethanol), methyldiethanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl-3-hydroxy-1-propylamine, dimethylbenzylamine,
Dimethyl-2-hydroxy-1-propylamine, diethylmethylamine, dimethyl-1-hydroxy-2-propylamine, etc. Others N-methylpyrrolidine, N-methylmorpholine, pyridine, N-methylpyrrole, N-
Examples include methylpiperidine and the like, and these may be used alone or in combination of two or more. Among these, trimethylamine and dimethylethanolamine are particularly preferable.

In the above ester addition reaction, the solid content concentration of the aromatic epoxy resin and the carboxyl group-containing acrylic resin to be used is not particularly limited, and it is desirable to be in the range having the optimum viscosity of these resins. Further, it is appropriate that the tertiary amine is usually used in the range of 0.1 to 1 equivalent with respect to the epoxy group of the aromatic epoxy resin.

The above ester addition reaction can be carried out by a conventionally known method, for example, after uniformly mixing an organic solvent solution of an aromatic epoxy resin and an organic solvent solution of a carboxyl group-containing acrylic resin, The reaction can be carried out in the presence of the aqueous tertiary amine solution at a reaction temperature of usually 60 to 130 ° C. for about 1 to 6 hours until the epoxy groups are substantially consumed.

The radically polymerizable unsaturated monomer used in the graft polymerization reaction of (2) above for obtaining the carboxyl group-containing reaction product is a carboxyl group-containing acrylic resin in the ester addition reaction of (1) above. The same as the unsaturated monomers of the (a) group and the (b) group constituting the above can be mentioned.

In the above graft polymerization reaction, the ratio of the aromatic epoxy resin to the radically polymerizable unsaturated monomer used is not particularly limited, but usually the former: the latter = 9.
5 to 70% by weight: 5 to 30% by weight is preferable. In this case, the carboxyl group-containing radically polymerizable unsaturated monomer is preferably used in an amount of 20 to 80% by weight based on the total radically polymerizable monomers. Further, the radical generator is preferably used in an amount of usually 3 to 15% by weight based on the radically polymerizable unsaturated monomer.

The above-mentioned graft polymerization reaction can be carried out by a conventionally known method, for example, radical polymerization property obtained by uniformly mixing a radical generator with an organic solvent solution of an aromatic epoxy resin heated at 80 to 150 ° C. The unsaturated monomer may be added for 1 to 3 hours, and the same temperature may be maintained for 1 to 3 hours.

As the organic solvent used in the above ester addition reaction and graft polymerization reaction, an aromatic epoxy resin and a carboxyl group-containing acrylic resin are dissolved and the carboxylate of the reaction product of these resins is diluted with water. Any conventionally known organic solvent can be used as long as it is an organic solvent that can be mixed with water and does not hinder the formation of an emulsion.

The organic solvent is preferably an alcohol solvent, a cellosolve solvent or a carbitol solvent. Specific examples of such organic solvent include isopropanol, butyl alcohol, and 2-hydroxy-4-.
Methyl pentane, 2-ethylhexyl alcohol, cyclohexanol, ethylene glycol, diethylene glycol, 1,3-butylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and the like can be mentioned. Further, it is also possible to use an inert organic solvent which is not mixed with water other than the above, and as such an organic solvent, for example, toluene, aromatic hydrocarbons such as xylene, ethyl acetate, esters such as butyl acetate, acetone, Examples include ketones such as methyl ethyl ketone.

In the present invention, the reaction product which is the above-mentioned component (A) is water-dispersed by neutralizing at least a part of the carboxyl groups in the product with a basic compound. The resin acid value of the reaction product which is the component (A) is 30 to 100.
From the viewpoint of water dispersibility, coating film performance, etc.

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, any primary amine, secondary amine and the like. Examples include primary amines, tertiary amines, monofunctional quaternary ammonium salts, and the like. More specifically, methylamine, ethylamine, n-propylamine, isopropylamine, n-hexylamine,
Monoethanolamine, propanolamine, benzylamine, dimethylamine, dibutylamine, dihexylamine, methylethanolamine, diethanolamine, triethylamine, diethylethanolamine, dimethylcyclohexylamine, triethanolamine,
Examples thereof include tributylamine, dimethyl n-butylamine, tripropylamine, γ-picoline and tetrahexyl ammonium hydroxide. The amount of the neutralizing agent used is usually 0.1 with respect to the carboxyl group in the reaction product.
It is preferable to use it at a neutralization equivalent of ˜2. The treatment with the neutralizing agent can also be performed by a conventionally known method.

In the present invention, the resol type phenol / formaldehyde resin (hereinafter referred to as "phenol resin") used as the component (B) is obtained by reacting phenols and aldehydes, and is represented by the following general formula [1]. It is a phenol resin containing 50% by weight or more of the represented compound and having an average number of methylol groups per molecule of 1.0 to 2.0.

[0029]

[Chemical 3]

(Wherein R ₁ , R ₂ , R ₃ , R ₄ and n
Has the same meaning as above. )

[0031]

The phenolic resin as the component (B) is a high molecular weight compound represented by the above formula [1] in which the total number of methylol groups of R ₂ and R ₃ is 1 or 2, and n is 4 or more. 50% by weight or more, preferably 60% by weight or more,
Moreover, it is a characteristic that it is a low methylol compound with an average number of methylol per molecule being 1.0 to 2.0. When the average number of methylol groups per molecule of phenol resin exceeds 2.0, the crosslink density becomes high and the processability deteriorates.
If the number is less than 0, the amount of the phenol resin having no methylol group increases and it becomes ineffective as a curing agent, and the phenol resin is eluted in the sterilization process in the can application, which is not preferable for hygiene. The average number of methylol groups in one molecule in the above phenol / formaldehyde resin is 1.5 to
It is more preferably 2.0.

Further, since the phenolic resin as the component (B) has a small number of methylol groups as functional groups, the number of n in the above formula [1] has an important meaning, and the number of molecules of n less than 4 is When the number is 50% or more, the curability tends to be poor, and the phenol resin is eluted during the sterilization treatment step, which is not preferable in terms of hygiene. Although the upper limit of n is not particularly limited, it is usually from the viewpoint of viscosity and compatibility with the component (A).
The average number of n is preferably 8 or less.

In the above formula [1], the alkyl group having 1 to 12 carbon atoms represented by R ₁ is methyl group, ethyl group,
Examples thereof include a propyl group, a butyl group, a 2-ethylhexyl group and a lauryl group. Further, examples of the alkyl group having 1 to 2 carbon atoms represented by R ₄ include a methyl group and an ethyl group.

The phenol resin used as the component (B) in the present invention is produced, for example, by reacting a phenol with formaldehyde in a known reaction medium, preferably an aqueous medium, in the presence of a basic catalyst. .

Examples of phenols include bisphenols such as bisphenol A and bisphenol F, and trifunctional phenols such as phenol.
Further, a bifunctional mononuclear phenol such as p-cresol or p-tert-butylphenol may be used in combination with the bisphenol or the trifunctional mononuclear phenol. Examples of aldehydes include formalin and paraformaldehyde, and among them, formalin is preferable. The ratio of the phenols to the aldehydes used is usually about 0.3 to 2.5 mol, preferably about 0.5 to 2.0 mol per mol of the former.

As the basic catalyst, any of the basic catalysts conventionally used for the production of resol type phenol-formaldehyde resin can be used, but in order to obtain the phenol resin which can exert the intended effect of the present invention. It is preferable to use an alkali metal hydroxide, an alkaline earth metal hydroxide or an amine as a catalyst. Specific examples of the basic catalyst include, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like as alkali metal hydroxides, and magnesium hydroxide, barium hydroxide and the like as alkaline earth metal hydroxides. Examples of amines include triethylamine and the like.

In the case of an alkali metal hydroxide, the amount of the basic catalyst to be present in the reaction medium is usually 0.01 to 1.0 mol, preferably 0.05 to 1.0 mol, based on 1 mol of phenol. The amount is preferably about 1.0 mol, and in the case of an alkaline earth metal hydroxide, it is usually about 0.01 to 2.0 mol, preferably 0.05 per mol of phenol.
˜1.0 mol, and in the case of amines, it is usually about 0.1-0.5 mol, preferably about 0.05-0.1 mol, per mol of phenol. Is good.

The reaction conditions of the phenols and the aldehydes are not particularly limited and may be appropriately selected from a wide range, but generally 50 to 90 ° C., preferably 60 to 70 ° C. for 1 to 8 hours. The heating may be carried out for about 2 to 3 hours. The phenol resin thus produced is isolated and purified from the reaction mixture by a means known per se.

The aqueous coating composition of the present invention comprises the above component (A) and component (B) dispersed in an aqueous medium. The mixing ratio of the component (A) and the component (B) is
1 to 50 parts by weight of the latter for 100 parts by weight of the former,
It is preferably 2 to 20 parts by weight. When the amount of the component (B) is less than 1 part by weight, the hardness of the coating film formed from the composition is not sufficient, and corrosion resistance, water resistance and gel fraction tend to decrease. On the other hand, when the amount of the component (B) is more than 50 parts by weight, the hardness of the coating film is excessively increased, the workability is deteriorated, and the hygienic property tends to be poor. In the present invention, the resin solid content concentration in the composition is not particularly limited, but is usually about 1
It is suitable to add the above-mentioned components (A) and (B) so that the amount is in the range of 5 to 40% by weight.

The aqueous coating composition of the present invention may contain an organic solvent, but the amount thereof is preferably 20% by weight or less from the viewpoint of environmental pollution. Further, the composition of the present invention may be optionally blended with additives which are generally used, such as an anti-aggregation agent, a flow control agent and a pigment.

The aqueous coating composition of the present invention can be applied to various substrates by various techniques known in the art. For example, the compositions of the present invention can be used in the can manufacturing industry, which primarily uses metal cans made of aluminum, chin-free steel, rolled electric field tin plates, and the like.

The cans used to package and ship food, coffee, beer and other beverages are primarily of the three-piece or two-piece stamping and ironing (D & I) type. Three-piece (main body,
Cans made from lids and bottoms) can be roll coated prior to forming the metal sheet into a can, or can be spray coated after partial forming.
D & I type cans, in which a metal sheet is stamped to form a closed end cylinder, are generally spray coated. The lid is typically roll coated. After the coating, it is generally dried at a temperature of about 90 to 330 ° C. for about 5 seconds to about 30 minutes.

[0043]

EFFECT OF THE INVENTION The aqueous coating composition of the present invention is capable of forming a coating film having excellent flavor retention and processability as well as excellent corrosion resistance, adhesion and hygiene.

[0044]

EXAMPLES The present invention will be further clarified with reference to the following examples. Incidentally, in the following, simply, “part” and “%” mean “part by weight” and “% by weight”, respectively.

<Production of Acrylic Resin Solution Containing Carboxyl Group> Production Example 1 400 parts of butanol were weighed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen inlet. Next, 174 parts of methacrylic acid, 87 parts of styrene, 29 parts of ethyl acrylate, and 14.5 parts of benzoyl peroxide (75% water-wet product) were weighed in a beaker and thoroughly mixed and stirred to prepare a preliminary mixture. The temperature of butanol in the flask was heated to 105 ° C., at which temperature the premix was added dropwise from the dropping funnel over 3 hours. The temperature was maintained for another 2 hours to complete the copolymerization reaction. Then add 290 parts of 2-butoxyethanol,
Viscosity 370 centipoise, resin acid value 390, solid content 30
% Acrylic resin solution A containing a carboxyl group was obtained.

<Production of Epoxy Resin Solution> Production Example 2 Epicoat 828 (Epoxy resin manufactured by Yuka Shell Co., epoxy equivalent 190, viscosity about 130 poise, 25 ° C.) 50
5 parts, 286 parts of bisphenol A, 0.5 parts of tri-n-butylamine and 88 parts of methyl isobutyl ketone were placed in a reaction vessel and heated to 135 ° C. under a nitrogen stream,
The contents exothermed to 180 ° C. This product was cooled to 160 ° C and reacted for about 3 hours to give an epoxy value of 0.02.
5. Solution viscosity (Gardner-Holt viscosity of butyl carbitol solution with 40% resin content at 25 ° C) 90% of Z ₂
Epoxy resin solution B was obtained.

Production Example 3 Epicoat 807 (Epoxy resin manufactured by Yuka Shell Co., epoxy equivalent about 170, viscosity about 130 poise, 25 ° C.) 46
When 2 parts, 274 parts of bisphenol F, 0.5 part of tri-n-butylamine and 82 parts of methyl isobutyl ketone were placed in a reaction vessel and heated to 135 ° C. under a nitrogen stream,
The contents exothermed to 180 ° C. This product was cooled to 160 ° C and reacted for about 3 hours to give an epoxy value of 0.02.
4. Solution viscosity (Gardner-Holt viscosity in butyl carbitol solution of 40% resin content at 25 ° C) 90% of Z ₂
Epoxy resin solution C was obtained.

<Production of Phenol Resin Solution> Production Example 4 228 parts of bisphenol A, 216 parts of 37% aqueous formaldehyde solution and 2 parts of caustic soda were charged into a reaction kettle equipped with a stirrer and a reflux condenser, and the temperature was raised to 100 ° C. for 4 hours. It was made to react. Then, 2.45 parts of sulfuric acid was added to this, and further n
-228 parts of butanol was added, and azeotropic dehydration was performed by heating at a reduced pressure of 650 mmHg. After reducing the pressure to 80%, it was diluted to 60% with n-butanol to obtain a phenol resin solution D. When the obtained resin was analyzed by gel permeation chromatography (hereinafter abbreviated as "GPC"),
In the formula [1], n = 1 is 20% and n = 3 is 15
%, N = 5 is 10%, n is 7 or more and 55% is the ratio of the number of each molecule, and the average number of methylol per molecule is 1.
It was eight.

Production Example 5 108 parts of p-cresol, 216 parts of 37% aqueous formaldehyde solution and 160 parts of 25% aqueous sodium hydroxide solution were placed in a flask and reacted at 50 ° C. for 2 hours, then 10
The temperature was raised to 0 ° C., the reaction was further performed at 100 ° C. for 1 hour, the mixture was neutralized with hydrochloric acid, and then extracted with a mixed solvent of n-butanol / xylene = 1/1 to obtain a 60% phenol resin solution E. As a result of GPC analysis of the obtained resin, n = 0 in the formula [1] was 6%, n = 1 was 12%, n = 2 was 9%, and n was 2%.
= 3 is 9% and n is 4 or more and 64% is the ratio of the number of each molecule, and the average number of methylol per molecule was 1.9.

Production Example 6 A phenol resin solution F having a solid content of 60% was obtained in the same manner as in Production Example 4 except that the reaction time was changed from 4 hours to 6 hours. As a result of analyzing the obtained resin by GPC, n = 1 in the above formula [1] was 18%,
= 3 is 8%, n = 5 is 10%, and n is 7 or more is 64
%, And the average number of methylol per molecule was 2.0.

Production Example 7 (for comparison) In Production Example 4, the reaction temperature was changed from 100 ° C. to 60 ° C., and the reaction time was changed from 4 hours to 3 hours. A phenol resin solution G was obtained. As a result of GPC analysis of the obtained resin, n = 1 in the formula [1] was 39%, and n = 3 was 27%,
When n was 5 or more, the ratio of the number of each molecule was 34%, and the average number of methylol per molecule was 1.8.

Production Example 8 (for comparison) 228 parts of bisphenol A, 486 parts of 37% aqueous formaldehyde solution and 70 parts of caustic soda were charged into a reaction kettle equipped with a stirrer and a reflux condenser, and the temperature was raised to 60 ° C. and the reaction was carried out for 3 hours. . Then, 2.45 parts of sulfuric acid was added to this, and further n
-228 parts of butanol was added, and azeotropic dehydration was performed by heating at a reduced pressure of 650 mmHg. After reducing the pressure to 80%, dilute it to 60% with n-butanol and add bisphenol A.
Trimethylol body 30% and tetramethylol body 40
% Phenolic resin solution H was obtained. In the obtained resin, the average number of methylol groups per unit of bisphenol A was 3.0.

Production Example 9 (for comparison) 228 parts of bisphenol A, 37% aqueous formaldehyde solution 24.3 were placed in a reaction kettle equipped with a stirrer and a reflux condenser.
Part, 97.7 parts of water and 2 parts of caustic soda are charged, and the temperature is 60 ° C.
The temperature was raised to 3, and the reaction was performed for 3 hours. Then add sulfuric acid 2.45
228 parts of n-butanol was added, and the mixture was heated at a reduced pressure of 650 mmHg for azeotropic dehydration. After reducing the pressure to 80%, dilute it to 60% solids with n-butanol,
A phenol resin solution I containing 20% of a bisphenol A monomethylol body and 80% of a non-methylolated bisphenol A as main components was obtained. In the obtained resin, the average number of methylol groups per unit of bisphenol A was 0.2.

<Production of Aqueous Coating Composition> Example 1 Formulation (1) Acrylic resin solution A 150 parts (2) Epoxy resin solution B 283 parts (3) n-Butanol 86 parts (4) 2-Butoxyethanol 47 Parts (5) deionized water 3.2 parts (6) dimethylaminoethanol 5.3 parts (7) dimethylaminoethanol 9.5 parts (8) phenolic resin solution D 150 parts (9) deionized water 566 parts total 1 , 300 copies

The above-mentioned (1) to (4) were placed in a reaction vessel and heated to 115 ° C. under a nitrogen stream to dissolve the resin component. After dissolution, the mixture was cooled to 105 ° C, added in the order of (5) to (6), and kept at 105 ° C for 3 hours. The reaction product has an acrylic resin / epoxy resin solid content weight ratio of 15/85. The reaction was monitored by measuring the acid value, and the acid value was 51 at the end point of the reaction. Then after 3 hours add (7) and add 5
After 8 minutes (8) was added and hot blended at 105 ° C. for 30 minutes. Then, (9) was added over 30 minutes to obtain a stable aqueous paint having a solid content of 30%.

Example 2 An aqueous coating material was obtained in the same manner as in Example 1 except that the phenol resin solution E was used in the same amount in place of the phenol resin solution D.

Example 3 An aqueous coating material was obtained in the same manner as in Example 1 except that the same amount of the epoxy resin solution C was used instead of the epoxy resin solution B.

Example 4 Formulation (1) Epoxy resin solution B 283 parts (2) n-butanol 121 parts (3) 2-butoxyethanol 117 parts (4) Methacrylic acid 27 parts (5) Styrene 13.5 parts (6) ) Ethyl acrylate 4.5 parts (7) Benzoyl peroxide 3 parts (8) Dimethylaminoethanol 14.8 parts (9) Phenolic resin solution F 150 parts (10) Deionized water 566.2 parts Total 1,300 parts Put the above (1) to (3) in a reaction vessel, and under a nitrogen stream,
The resin component was dissolved by heating to 15 ° C. Then, the mixture of (4) to (7) was added dropwise over 1 hour, and further 115
The reaction was carried out at 0 ° C for 2 hours. Then cool to 105 ° C,
(8) was added, 5 minutes later, (9) was added, and hot blending was performed at 105 ° C. for 30 minutes. After that, (10) was added over 30 minutes to obtain a stable aqueous paint having a solid content of 30%.

Comparative Example 1 An aqueous paint was obtained in the same manner as in Example 1 except that the phenol resin solution D was not used.

Comparative Example 2 Cymel 115 was used instead of 150 parts of phenol resin solution D.
An aqueous paint was obtained in the same manner as in Example 1 except that 90 parts of 6 (melamine formaldehyde resin, manufactured by American Cyanamide) was used.

Comparative Example 3 An aqueous coating material was obtained in the same manner as in Example 1 except that the same amount of the phenol resin solution G was used instead of the phenol resin solution D.

Comparative Example 4 An aqueous coating material was obtained in the same manner as in Example 1 except that the phenol resin solution H was used in the same amount instead of the phenol resin solution D.

Comparative Example 5 An aqueous coating material was obtained in the same manner as in Example 1 except that the phenol resin solution I was used in the same amount instead of the phenol resin solution D.

Each of the water-based paints obtained in the above Examples and Comparative Examples was tested for adhesion of coating film, boiling water resistance, processability, flavor of water extract, and stability of paint over time. The test method was as follows.
The test results are shown in Table 1 below.

Test method Preparation of test coated plate: An aluminum plate having a thickness of 0.3 mm was coated with a bar coater so that the dry coating film weight was 120 mg / 100 cm ^2, and after setting at 100 ° C. for 2 minutes,
A test plate was obtained by baking in a dryer for 30 seconds at an ambient temperature of 280 ° C. and a wind speed of 25 m / min so that the maximum temperature reached by the material was 260 ° C. Adhesion, boiling water resistance,
It was subjected to each workability test. A water extract flavor was prepared in the same manner as the above test plate except that 0.1 mm thick aluminum foil was used instead of the 0.3 mm thick aluminum plate and the atmosphere temperature of the dryer was 275 ° C. A test plate for a sex test was obtained.

Adhesion: A knife is used to make eleven cuts each having a width of about 1.5 mm in the vertical and horizontal directions on the coating surface of the test coated plate. A cellophane adhesive tape with a width of 24 mm is adhered, and the adhesiveness of the eye area when strongly peeled off is observed. ◯: No peeling at all Δ: Slight peeling was observed ×: Significant peeling was observed Boiling water resistance: The test coated plate was immersed in boiling water at 100 ° C. for 30 minutes, and then the coating film was peeled with cellophane adhesive tape to obtain the same adhesion test as above. Judge by the evaluation method. ◯: No peeling at all △: Slight peeling off ×: Significant peeling off

Workability: In a room at 20 ° C., using a special goby folding type DuPont impact tester, two 0.3 mm thick aluminum plates were placed between the bent parts of the test coated plate with the lower part folded in two. It is sandwiched, set in a tester, and the contact surface is flat with a thickness of 1 kg.
After dropping the iron weight of 50cm from the height of 50cm and giving an impact to the bent part, the bending tip is energized for 6 seconds with an applied voltage of 6.5V, and the bending tip 2mm wide current value (mA) To measure. ○: Less than 1mA △: 1mA or more and less than 10mA ×: 10mA or more

Flavorability of water extract: A test piece coated with an aluminum foil having a thickness of 0.1 mm was treated with activated carbon so that the amount of tap water treated with activated carbon was 1 ml per 1 cm ^{2 of} coating area. Put it in a glass bottle, cover it with 125
After sterilization at 30 ° C. for 30 minutes, a flavor test of the content liquid is performed. ◯: No change was observed at all △: Slightly changed ×: Remarkably changed

Stability of paint over time: water-based paint to be tested 10
Put 0 ml in a glass wide-mouthed bottle with an internal volume of 100 ml, seal it, store it in a constant temperature bath at 50 ° C for 1 month, and then open and inspect it to see if the liquid surface has skin, the viscosity of water-based paint, and dispersed particles. The average particle size of is investigated and the change in state is comprehensively compared with that before storage. ◯: Almost no change Δ: Slight change x: Significant change

[0070]

[Table 1]

Claims (1)

[Claims] 1. A reaction product comprising 100 parts by weight of a carboxyl group-containing reaction product composed of (A) an aromatic epoxy resin and a carboxyl group-containing acrylic resin, and (B) a phenol and an aldehyde. General formula [1] (In the formula, R ₁ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, R ₂ and R ₃ are hydrogen atoms or a methylol group, provided that R ₂ and R ₃ are not hydrogen atoms at the same time, R ₄ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and n represents an integer of 4 or more) in an amount of 50% by weight or more, and The average number of methylol groups is 1.0 to 2.
An aqueous coating composition comprising 1 to 50 parts by weight of 0 resol type phenol-formaldehyde resin dispersed in an aqueous medium.