JPH01217023A - Coating composition for can - Google Patents

Abstract

PURPOSE:To provide the present composition capable of giving coating films of excellent boiling after resistance and processability, comprising a water-based product from a copolymer obtained from a specific polyhydroxyether macromonomer, an ethylenic unsaturated carboxylic acid and another vinyl monomer. CONSTITUTION:The objective composition comprising a water-based product from a copolymer obtained from (A) 10-90wt.% of an epoxy group-free polyhydroxyether macromonomer produced by addition reaction between (i) an epoxy resin with a number-average molecular weight of 2,900-29,000 having in one molecule 0.6-1.5 epoxy groups on average and (ii) an ethylenic unsaturated carboxylic acid, (B) 5-80wt.% of an ethylenic unsaturated carboxylic acid and (C) 5-85wt.% of another vinyl monomer. The component (i) is pref. a bisphenol F-type epoxy resin.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to a polyhydroxyether macromonomer (A) having substantially no epoxy groups, a polymerizable unsaturated acid monomer (B), and other vinyl monomers ( The present invention relates to a can coating composition which is an aqueous copolymer containing C) as an essential monomer component, and is useful for can interior applications such as food cans and beverage cans.

(Prior art) Conventionally, can interior paints contain a large amount of organic solvents, which is not only undesirable from an environmental hygiene and fire safety standpoint, but also because it is necessary to maintain an appropriate coating viscosity, it is impossible to convert the resin into polymer silicide, which results in low molecular weight paints. There were various problems such as a decrease in flakiness due to the ingredients. In order to solve these problems, water-based can interior paints are being developed in this field. Conventionally, water-based can inner surface paints include, for example, self-emulsifying emulsion paints prepared by esterifying acidic copolymers and epoxy resins in the presence of tertiary amines, as disclosed in Japanese Patent Application Laid-Open No. 55-3481. Decrease in corrosion resistance due to graded products,
Due to the polymer-11r1 reaction, a large amount of organic solvent is required for stable synthesis, and as a result, there are problems such as non-hazardous material compatibility paints are not applicable, and ■ JP-A-53-12
Publication No. 85 discloses a self-emulsifying emulsion paint in which a vinyl monomer containing a polymerizable undistributed hydrochloric acid monomer is graft-polymerized to an epoxy resin using a benzoyl peroxide catalyst. Since the acrylic resin is synthesized using a reaction system with a large amount of catalyst, there is a problem that the molecular weight of the acrylic resin is small and the flavor is poor. In addition, (1) JP-A-58-198513 and (1) JP-A-60-106805 disclose that (a) a compound obtained by reacting an epoxy resin with methacrylic acid, (b) acrylic acid or methacrylic acid, and (b) acrylic acid or methacrylic acid; A self-emulsifying emulsion paint is disclosed in which a polymerizable monomer consisting of (a) an aromatic vinyl monomer and (d) an alkyl ester of an α,β-ethylenically unsaturated carboxylic acid is reacted. However, since this paint uses (1) an epoxy resin with a high average functional group dust as the epoxy resin component, it is difficult to manufacture because gelation and thickening may occur during the copolymerization reaction.

(2) In the copolymerization reaction of monomer components (a) to (d), the reaction proceeds between the epoxy group derived from component (a) and the carboxyl group derived from component (b), so that the system It becomes viscous and has a high molecular weight, making it difficult to make it aqueous. (3) In the process of neutralizing the copolymer with a tertiary amine to make it aqueous, if the copolymer is neutralized with a tertiary amine in the presence of a carboxyl group and an epoxy group, the epoxy group converts into a quaternary ammonium salt. The resulting quaternary ammonium salt accelerates the reaction between the remaining epoxy groups and carboxyl groups, resulting in poor paint storage stability.

(4) The coating film thus obtained has poor water resistance, adhesion to materials, etc. because it contains a quaternary ammonium salt. (5) If, for example, a primary or secondary amine is used as the neutralizing agent, the system will thicken and cannot be made aqueous.

There were problems such as.

(Problem B to be Solved by the Invention) The present invention has been made for the purpose of solving the above-mentioned problems and providing a coating composition that forms a coating film suitable for the inner surface of a can.

(Means for Solving the Problems) As a result of various studies on methods for overcoming such conventional problems, the present inventor found that an average of 0.6 to 1.
Number average molecular weight 2,900-2 with 5 epoxy groups
It is obtained by addition reaction of 9,000 epoxy resin and ethylenically unsaturated carboxylic acid. Polyhydroxyether macromonomer (A
) 10 to 90% by weight, ethylenically unsaturated carboxylic acid (B
) 5 to 80% by weight and 5 to 85% by weight of a vinyl monomer (C) other than the above (A) and (B) as monomer components. Regarding.

The copolymer component of the coating composition of the present invention is a copolymer obtained by copolymerizing a polyhydroxyether macromonomer (A), an ethylenically unsaturated carboxylic acid (B), and a vinyl monomer (C).

The polyhydroxyether macromonomer (A) is composed of an epoxy resin having a number average molecular weight of 2,900 to 29,000 and having an average of 0.6 to 1.5 epoxy groups in one molecule and an ethylenically unsaturated carboxylic acid. It is obtained by addition reaction.

Specifically, as the epoxy resin, bisphenol such as bisphenol A or bisphenol F and shrimp halohydrin are used as an alkali, usually 0.6 to 1.5 mol of bisphenol, preferably 0.8 to 1.5 mol, per 1 mol of shrimp helohydrin. 1.2 mol of the mixture is continued to react in the presence of an alkali metal catalyst or alkaline earth metal catalyst until the reaction product has a number average molecular weight in the range of 2.900 to 29.000, or the above A low molecular weight condensate having two epoxy groups in one molecule obtained by reacting bisphenol and shrimp halohydrin in the presence of the above catalyst is used as a starting material, and usually 0.5 bisphenol is added per mole of the low molecular weight condensate. ~1.5 mol, preferably 0.8~
It is obtained by continuing the reaction with a mixture containing 1.2 mol in the presence of a catalyst until the number average molecular weight of the reaction product is in the range of 2,900 to 29,000.
Examples of the former catalyst include alkali metal or alkaline earth metal catalysts such as sodium hydroxide, potassium hydroxide, thirium hydroxide, barium hydroxide, calcium hydroxide, sodium carbonate, and calcium carbonate; In addition to the above, examples include n-butylamine, tri-n-butylamine, triethanolamine, piperidine, calcium carbonate, calcium chloride, and quaternary ammonium salts.

As mentioned above, the epoxy resin used in the present invention has an average of 0.6 to 1.5 particles per molecule, preferably 0.8 to 1.2 particles per molecule.
Number average molecular weight 2,900-29 with epoxy groups
,000. Preferably, it has an OOR range of 3.700 to 9,000. If the number of epoxy groups is less than 0.6, there will be a large amount of unreacted epoxy resin component chemically bonded to the copolymer, making it difficult to make it water-soluble and its storage properties will be poor, which is not preferable. If the number exceeds .5, the content of the divinyl compound increases in the reaction with ethylenically unsaturated carboxylic acid in the next step, which may cause gelation and thickening of the system during the copolymerization reaction, which is not preferable.

Also, if the number average molecular weight is less than 2.900, boiling water resistance,
The result is a coating film with poor corrosion resistance, processability, flavor retention, etc., and on the other hand, if the number average molecular weight is greater than 30,000, water dispersion becomes difficult, which is not preferable.

1- Among the epoxy resins mentioned above, when bisphenol F type epoxy resin is used, the resin can be made soft because it has H as the main skeleton, and it has excellent adhesive strength even when polymerized to silicide, so it has no flavor. retention, processability,
This is advantageous because a coating with excellent boiling water resistance is formed.

The ethylenically unsaturated carboxylic acid used by reacting with the epoxy resin to obtain the polyhydroxyether macromonomer (A) is a compound having one radically polymerizable unsaturated group and one carboxyl group in one molecule. Preferred specific examples include acrylic acid,
Methacrylic acid, 2-carboxyethyl acrylate, 2
-carboxyethyl methacrylate, 2-carboxypropyl methacrylate, and the like.

Polyhydroxyether macromonomer (
A) is produced by a commonly known production method 1, for example, by esterifying an epoxy resin and an ethylenically unsaturated carboxylic acid in the presence of a catalyst (e.g. tri-n-butylamine, tetraethylammonium bromide, dibutyltin oxide, etc.), usually at a concentration of 50 to 200%. While controlling the epoxy value of the reactants at the reaction temperature of ℃, the epoxy value is usually 0.01 or less, preferably 0.
．． This can be carried out by continuing the reaction until the temperature reaches 005 or less. The blending ratio of the epoxy resin and ethylenically unsaturated carboxylic acid is such that no epoxy group remains in the reaction product, that is, the ratio of the ethylenically unsaturated carboxylic acid to the epoxy group in the epoxy resin is approximately 1 mole or more. It is necessary to do so. If the epoxy value is greater than 0.01, the storage stability of the water-based paint composition will deteriorate, and the water resistance, adhesion, and flavor properties (consumption amount of potassium permanganate) will deteriorate.
etc. are also not preferred because they result in inferior coating films.

The ethylenically unsaturated carboxylic acid (B) copolymerized with the polyhydroxyether macromonomer (A) imparts a water-soluble or water-dispersible group to the copolymer. Ethylenically unsaturated carboxylic acids similar to those used in the production of macromonomers can be used.

The vinyl monomer (C) to be copolymerized with the polyhydroxyether macromonomer (A) and the ethylenically unsaturated carboxylic acid (B) can be appropriately selected depending on the required performance. Specifically, for example, ■ Hydroxy alkyl esters of acrylic acid or methacrylic acid having 1 to 8 carbon atoms, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, etc.: ■ Methyl Acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, i-butyl acrylate, i-butyl methacrylate, tert-
Butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate.

Alkyl or cycloacrylic acid or methacrylic acid having 1 to 24 carbon atoms, such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, decyl acrylate, etc. Alkyl ester; ■ Acrylamide, methacrylamide, N-methylacrylamide, N-ethylmethacrylamide, diacetone acrylamide, N-methylolacrylamide, N
- functional acrylic or methacrylamides such as methylolmethacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide; ■ styrene, vinyltoluene, vinyl propionate;
α-methylstyrene, vinyl acetate, acrylonitrile,
Examples include vinyl monomers such as methacrylonitrile, vinyl propionate, vinyl pivalate, and beoba monomer (Shell Chemical Products).

As these vinyl monomer (C) components, boiling water resistance,
It is preferable to use alkyl or cycloalkyl esters of acrylic acid or methacrylic acid having 1 to 4 carbon atoms, styrene, etc. because they form a coating film with good flavor retention properties.

Copolymerization of a vinyl monomer component to a polyhydroxyether macromer: This copolymerization reaction method is not particularly limited, but for example, an ethylenic polymer is added to a solution of a polyhydroxyether macromer (A) in an organic solvent under heating, usually at 40 to 180°C. One example is a method of copolymerizing the saturated carboxylic acid (B) and the vinyl monomer (C) while dropping them, but the present invention is not limited to this method in any way, and other methods known per se can be used.

In the copolymerization reaction, the composition ratio of the monomer components is 10 to 90%, preferably 50 to 90% of the polyhydroxyether macromonomer (A), based on the total weight of the monomer components.
0%, ethylenically unsaturated carboxylic acid (B) 5-80%,
Preferably 30-70%, vinyl monomer (C) 5-8
5%, preferably in the range of 30-75%. If the proportion of polyhydroxyether macromonomer (A) is less than 10%, the coating film will have poor adhesion to materials, boiling water resistance, corrosion resistance, flavor retention, flavor properties, processability, etc.; If the ratio of the components exceeds 90%, water dispersion becomes difficult, and even if water dispersion is carried out, the particle size of the paint is large and storage stability is poor, and the film formation property is also poor, resulting in an undesirable ethylenic non-containing film. Saturated carboxylic acid (
If the proportion of B) is less than 5%, water dispersion becomes difficult and the coating film has poor adhesion to the material.
) If the ratio of the component is more than 80%, the coating film will have poor boiling water resistance, corrosion resistance, etc. Further, it is preferable that the amount is adjusted within the range of 100%.

The organic solvent used in the copolymerization reaction quickly dissolves monomers such as polyhydroxy macromer (A), ethylenically unsaturated carboxylic acid (B), vinyl monomer (C), and their copolymers, and further Solvents with excellent miscibility with water are preferred. Examples of these organic solvents include the following formula % formula % (3) [In each of the above formulas, R1 is an alkyl group having 1 to 12 carbon atoms, R2 is 1m of alkyl groups having 1 to 6 carbon atoms is 1 to
is an integer of 6] alcohol-based solvents, cellosolve-based solvents, and calpitol-based solvents. Specific examples of such organic solvents include inpropatol, butyl alcohol, 2-hydroxy-4-methylpentane, 2-ethylhexyl alcohol, cyclohe-r-+mer, ethylene glycol,
diethylene glycol, 1,3-butylene gelicol,
Examples include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol 7-methyl ether, and the like.

In addition, inert organic solvents that are not miscible with water other than those mentioned above can also be used, and such organic solvents include, for example, aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; acetone, These include ketones such as methyl ethyl ketone. These organic solvents are preferably those that can be removed by residence under normal pressure or reduced pressure after producing the copolymer or water-based paint. 50% by weight or less, preferably 40% by weight
It can be adjusted to the following range.

The copolymerization reaction between the polyhydroxyether macromer (A), ethylenically unsaturated carboxylic acid, and vinyl monomer component is preferably carried out in the presence of a polymerization catalyst, and examples of the polymerization catalyst include benzoyl peroxide, perbutyl offtate, and t. -butyl hydroperoxide, azobisisobutyronitrile, azobishereronitrile, 2,2'-azobis(2-aminopropane) hydrochloride, etc., and these are generally 0.5 parts by weight per 100 parts by weight of the vinyl monomer component. It can be used in a ratio of 2 parts to 10-fold ω.

In the uninvented coating composition, a coating film with excellent performance can be formed using the above copolymer alone, but by mixing the copolymer with a crosslinking agent such as urea resin, melamine resin, or phenol resin, it is possible to form a coating film with excellent performance by using the copolymer alone. When coated and heated, it crosslinks and hardens, forming a coating III with excellent performance such as high boiling water resistance and processability.

The coating composition of the present invention can be made into a water-based coating by neutralizing the carboxyl groups in the copolymer with a basic compound neutralizing agent and dissolving or dispersing it in water.

As the basic compound of the neutralizing agent, those known per se can be used, and preferred specific examples include -maximum R3R
4R1N (in the formula, R3 and R4 are 1 in the alkyl moiety)
or substituted or unsubstituted m containing 2 carbon atoms
and R6 is a substituted or unsubstituted monovalent alkyl group containing 1 to 4 carbon atoms), N-methylpyrrolidine, N-methylmorpholine, pyridine, N-methyl At least one selected from the group consisting of pyrrole, N-methylpiperidine, and mixtures thereof. Some examples of R3R4R5N include: trimethylamine,
Dimethylethanolamine (dimethylaminoethanol), methyljetanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl-3-hydroxy-1-propylamine, dimethylbenzylamine, dimethyl-2-hydroxy-1-propyl Amines, diethylmethylamine, dimethyl-1-hydroxy-2-propylamine and mixtures thereof.

Most preferably trimethylamine or dimethylethanolamine is used.

Neutralization is preferably carried out at a neutralization equivalent of 0.1 to 2.

When the coating composition of the present invention is used for the inner surface of a can, the coating composition is applied to the surface of a metal material for a can,
The formed coating is then baked. Metal materials for cans include aluminum plates, steel plates, plated steel plates whose surfaces are plated with zinc, chromium, tin, aluminum, etc., or chemically treated steel plates whose surfaces are coated with chromic acid, iron phosphate, or zinc phosphate. Treated steel plates etc. can be used. In addition, as a means for applying it to the surface of the metal material for cans, for example, roll coating, spray coating, brush coating, spraying, painting, dipping, etc. can be used. The amount of application is usually 5 to 30. It seems that the range is sufficient. The baking of the paint film is generally about 150 to 220 degrees.
C1 preferably about 30-600 at about 180-200°C
seconds, preferably about 60 to 300 seconds.

(Effects of the Invention) As described above, the coating composition of the present invention contains a polyhydroxy macromonomer (A), an ethylenically unsaturated carboxylic acid (B), and a vinyl monomer (C) other than (A) and (B) in a specific composition ratio. Since the copolymer obtained by the copolymerization reaction is used as the main vehicle component, it has the following remarkable effects.

(1) Since an epoxy resin with a low average functional dust content is used as the epoxy resin component, there is little generation of divinyl monomer and there is no risk of gelation or thickening during the copolymerization reaction.

(2) Polyhydroxy macromonomer (A) t.

Since there is substantially no epoxy group in the component, there is no reaction with the ethylenically unsaturated carboxylic acid component (B), and the copolymerization reaction can be carried out without gelation or thickening.

(3) When the copolymer is neutralized with a neutralizing agent and water is removed and dispersed, a water-insoluble polyhydroxy macromonomer (A) is formed.
The component is the particle component, and the ethylenically unsaturated carboxylic acid (B)
Since a water dispersion is formed using the water dispersion stabilizer component, a large amount of organic solvent is not required for water dispersion, and a water dispersion with a low organic solvent content can be obtained, as well as a low organic solvent content. Therefore, it has excellent storage stability.

(4) Since the water dispersion does not contain a quaternary ammonium salt in the copolymer, it has excellent storage stability and can form a coating film with excellent boiling water resistance, adhesion to materials, flavor properties, etc. .

Next, the present invention will be explained in more detail with reference to Examples. In the examples, "1 part" and "%" are both based on weight.

Production example of polyhydroxyether macromonomer Polyhydroxyether macromonomer (IIL) Ebiko) 828 (epoxy resin manufactured by Yuka Shell Co., Ltd., number average molecular weight 380, epoxy equivalent weight 187) 500 parts, bisphenol A 288 parts (manufactured by Mitsui Toatsu Co., Ltd.) ), 0.5 parts of tri-n-butylamine, and 88 parts of butyl cellosolve were placed in a reaction vessel and heated to 135°C under a nitrogen stream, causing the contents to generate heat to 180°C. This product was cooled to 160°C and reacted for about 3 hours, resulting in a solid content of 90%, an epoxy value of 0.020 (measured by the hydrochloric acid-potassium iodide method, hereinafter the same meaning will be used), and an epoxy equivalent of 5,000. , number average molecular weight 5,500 (GPC measurement, hereinafter the same meaning is shown), number of epoxy groups in one molecule 1.10, and solution viscosity (fat content 40% at 25 ° C., Gardner-Holdt viscosity of butyl calpitol solution, The same meanings are shown below)
Z6 epoxy resin was obtained.

Next, 266 parts of the above 90% epoxy resin solution (solid content 2
40 parts), methacrylic acid 4.2 parts, butyl cellosolve 7
Add 8 parts of TEABr (tetraethylammonium bromide) and 0.25 parts of TEABr (tetraethylammonium bromide) to the reaction vessel and heat to 120 parts under nitrogen stream.
The reaction was carried out at ℃ for 6 hours. The resulting polyhydroxyether macromono? -(a) has an acid value of 1.0 and an epoxy value of 0.0
It was 02.

Polyhydroxyether macromonomer (b) Epoxy resin of polyhydroxyether macromonomer (a) ■
Epoxy resin ■ was obtained in the same manner as in the production of epoxy resin ■, except that 288 parts of bisphenol A used in step 2 was changed to 286 parts of bisphenol A. Next, the epoxy resin (
Polyhydroxyether macromonomer (b) was obtained by carrying out a reaction using polyhydroxyether macromonomer (b) using the composition shown in Table 1 and the synthesis conditions for polyhydroxyether (a).

Polyhydroxyether macromonomer (C) Epoxy resin of polyhydroxyether macromonomer (a)■
Epoxy resin ■ was obtained in the same manner as in the production of epoxy resin ■, except that 288 parts of bisphenol A used in step 2 was changed to 282 parts of bisphenol (a). Next, using the epoxy resin ■, the formulation and polyester resin shown in Table 1 were prepared. The reaction was carried out under the synthesis conditions of hydroxyether (a) to obtain polyhydroxyether macromonomer (C).

Polyhydroxyether macromonomer (d) Polyhydroxyether macromonomer (a) was blended and reacted for 7 hours under the conditions to obtain an epoxy resin (2).Next, using the epoxy resin (2), the formulation shown in Table 1 was prepared, and the poly The reaction was carried out under the synthesis conditions of hydroxyether (a) to obtain polyhydroxyether macromonomer 〇.

Polyhydroxyether macromonomer (e) Epoxy resin of polyhydroxyether macromonomer (a)■
Epoxy resin (2) was obtained in the same manner as in the method for producing epoxy resin (2) except that the 288 parts of bisphenol A used in (2) was changed to 297 parts.

Next, using the epoxy resin (1), a reaction was carried out under the formulation and synthesis conditions for polyhydroxyether (a) shown in Table 1 to obtain polyhydroxyether macromonomer (e).

Polyhydroxyether macromonomer (f) Epoxy resin of polyhydroxyether macromonomer (a) ■
Epoxy resin (2) was obtained in the same manner as in the method for producing epoxy resin (2) except that the 288 parts of bisphenol A used in (2) was changed to 292 parts.

Next, a reaction was carried out using the epoxy resin (D) under the formulation and synthesis conditions for polyhydroxyether (a) shown in Table 1 to obtain polyhydroxyether macromonomer (f).

Polyhydroxyether macromonomer (g) Epicote 807 (epoxy resin manufactured by Yuka Shell Co., Ltd.) Epoxy equivalent weight 173 500 parts, bisphenol F 296 parts (manufactured by Honshu Kagaku Kogyo Co., Ltd.), tri-n-butylamine 0.5 part and butyl cellosolve 88 parts were reacted. Place it in a container and place it under a nitrogen stream.
When heated to 35°C, the contents generated heat to 180°C.

This was cooled to 160°C and reacted for about 3 hours to obtain an epoxy resin (Enoki).
The reaction was carried out under the synthesis conditions of a) to obtain polyhydroxyether macromonomer (g).

Polyhydroxyether macromonomer (h) Epoxy resin of polyhydroxyether macromonomer (a) ■
Epoxy resin 0 was obtained in the same manner as in the production of epoxy resin (2) except that 288 parts of bisphenol A used in step 1 was changed to 305 parts.Next, the epoxy resin (2) was used to prepare the formulation shown in Table 1 and polyhydroxy ether (a ), the reaction was carried out under the synthesis conditions of polyhydroxyether macromonomer (
h) was obtained.

Polyhydroxyether macromonomer (i) Epoxy resin of polyhydroxyether macromonomer (a) ■
Epoxy resin (2) was obtained in the same manner as in the production of epoxy resin (2) except that the 288 parts of bisphenol A used in (2) was changed to 290 parts.

Next, a reaction was carried out using epoxy resin (1) under the formulation and synthesis conditions for polyhydroxyether (a) shown in Table 1 to obtain polyhydroxyether macromonomer (i).

Polyhydroxyether macromonomer (j) Reaction was carried out for 1 hour and 30 minutes under the blending conditions of polyhydroxyether macromonomer (e) to obtain epoxy resin. A reaction was carried out under the synthesis conditions of hydroxyether (a) to obtain polyhydroxyether macromonomer (j).

Polyhydroxyether macromonomer (k) Polyhydroxyether macromonomer (ID
Oita.

Copolymer production example Copolymer I (2) Butyl cellosolve 137 parts (3
) Methacrylic acid 36 parts (4) Styrene 18 parts (5) Ethyl acrylate 6 parts 650 parts Put (7) into a reaction vessel and heat to 100°C under a nitrogen stream. The mixture was added dropwise over a period of 3 hours and maintained at the same temperature for 2 hours to obtain copolymer (2).

Copolymers 1 to XX Copolymers II-XX were produced using the same method as Copolymer I using the formulations shown in Table 2.

Example 1-14 The above copolymer I-XIV was held at lOO''C, and dimethylaminoethanol was added at a neutralization equivalent (0, 6) per carboxyl group of the copolymer, and stirred for about 10 minutes. Thereafter, 5 parts of Cymel 1156 (American Cyanamid Company, trade name, butyl etherified melamine) was added to 100 parts of the copolymer (solid content), and stirring was continued for 30 minutes at the same temperature. Ionized water was added dropwise over about 1 hour to obtain the coating composition of Example 1-14.

Example 15 Example 15 was carried out using the same formulation and manufacturing method as in Example 1 except that the above copolymer I was used and Cymel 1156 was not used.
A coating composition was obtained.

Comparative Examples 1 to 6 Coating compositions of Comparative Examples 1 to 6 were obtained using the above-mentioned copolymerization process to XX and using the same formulation and manufacturing method as in Example 1.

Comparative Example 7 (2) Butyl cellosolve 239 parts (3
) n-Butanol 107 parts (4) Methacrylic acid 36 parts (5) Styrene 18 parts (6) Ethyl acrylate 6 parts To the reaction vessel (1) (
2) (3) was added and heated to 115°C under a nitrogen stream to dissolve the resin component.

Then, the mixture of (4) to (7) was heated to 311 parts 1 at 115°C.
The mixture was added dropwise over time and maintained at the same temperature for 2 hours to obtain a grafted epoxy resin. A coating composition of Comparative Example 7 was obtained using the epoxy resin and the same formulation and manufacturing method as in Example 1.

Comparative Example 8 0267 parts of epoxy resin used in the production of polyhydroxyether macromonomer (f), 26 parts of butyl cellosolve
A grafted epoxy resin was obtained using the same composition and conditions as in Comparative Example 7 except that the amount was changed to 6 parts. A coating composition of Comparative Example 8 was obtained using the epoxy resin and the same formulation and manufacturing method as in Example 1.

The properties of the coating compositions obtained in the above Examples and Comparative Examples are summarized in Table 3.

Storage test A 500 cc mayonnaise bottle was filled with about 80% of the paints of Examples and Comparative Examples, and after being left at 30°C for 2 months, the appearance and viscosity of the paints were measured. The appearance of the paint was evaluated as follows.

■ Absolutely no abnormality 0 Slight decrease in viscosity Δ Sediment present Samples were prepared by spray painting uniformly to form a film and then drying at a temperature range of 200° C. for about 2 minutes. These results are summarized in Table 3.

Various test methods (1) Degree of metal exposure Inject 1% saline solution containing 0.3% of 2504 surfactant into each prototype with inner surface coating by spray painting and baking process, and measure the amount of current applied after 4 seconds under 6V milliampere (mA)
Displayed in

(2) ′! ! : Adhesion: Adhesive film: Approximately 1 using the coating surface
．． Make 11 vertical and horizontal cuts in the goban with a width of 5 am. Observe the adhesion of the mouth of the gopan when a 24-inch wide cellophane adhesive tape is adhered and strongly peeled off.O No peeling at all Δ Slight peeling × Significant peeling (3) Boiling water resistance: Underwater at 100℃ for 30 minutes After treatment, the coating film is evaluated visually and by peeling off a cellophane adhesive tape using the same evaluation as (2) adhesion.

(4) Flavor retention In various test cans, tap water treated with activated carbon was heated at 250 rms.
Fill it with l and tighten it to 100'C! - After 30 minutes of sterilization, the samples were stored at 37°C for 3 months and a flavor test was conducted.

0 No change at all Δ Slight change × Significant change (5) Potassium permanganate consumption: Fill the inner-coated can with 250 d of ion-exchanged water, tighten the seam, and heat at 60℃-30
The samples were treated at 100° C. for 30 minutes and measured according to the test method described in the Food Sanitation Law. The consumption amount is expressed in ppm.

(6) #Corrosion Evaluation Various test cans were filled with 10% pine juice at 98°C with hot par 2 sealing, and after being stored at 37°C for 6 months, an opening test was conducted to observe the state of internal corrosion.

0 No corrosion Δ Slight corrosion × Significant corrosion (7) Workability: Using a special fold-type DuPont impact tester, place a sample folded in half at the bottom, and place a sample of iron weighing 1 kg with a flat contact surface. The length of the crack in the paint film at the bent portion when the weight was dropped from a height of 50 cm was measured.

0 to 10 layers・・・・・・O mark 10~2oII layer・・・Δmark 20 mm or more... Indicated by an X mark.

Claims (1)

[Claims] 1. Addition of an epoxy resin having a number average molecular weight of 2,900 to 29,000 and having an average of 0.6 to 1.5 epoxy groups in one molecule and an ethylenically unsaturated carboxylic acid. 10 to 90% by weight of the polyhydroxyether macromonomer (A) which is obtained by the reaction and which has substantially no epoxy groups, 5 to 80% by weight of the ethylenically unsaturated carboxylic acid (B), and the above (A) and (B). ) Vinyl monomers other than (C) 5-8
A can coating composition characterized in that it is an aqueous copolymer containing 5% by weight of a monomer component. 2. The can coating composition according to item 1, wherein the epoxy resin is a bisphenol F type epoxy resin.