JPH08325513A - Coating material composition - Google Patents

Abstract

PURPOSE: To obtain a coating material composition, capable of forming a coating film excellent in balance between deep drawing processability and hardness, adhesion, sanitary properties and alcohol resistance and suitable for especially an inner surface of a can. CONSTITUTION: This coating material composition for an inner surface of a can contains (a) 100 pts.wt. polyester resin having 10,000-100,000 number-average molecular weight, 10-120 deg.C static glass transition temperature, 1-15mg KOH/g hydroxyl value and <=10 acid value, (b) 1-20 pts.wt. epoxy resin having <=1,000 molecular weight and (c) 1-20 pts.wt. amino resin as resin components. Furthermore, a coated metallic can having a film for the inner surface of the can is obtained by forming a cured coating film of the coating material composition on the inner surface of the can. The coating film has 40-90 deg.C glass transition temperature without recognizing the peeling of the film at 40% Erichsen deep drawing ratio in the coated metallic can after extracting the film with a 20% aqueous solution of ethanol and <=2% maximum absorption coefficient of ultraviolet rays within the range of 200-300nm wavelength in an extract solution after the extraction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating composition having an excellent balance between deep drawing workability and hardness and capable of forming a coating film having excellent adhesion, hygiene and alcohol resistance, and is particularly suitable for the inner surface of a can. And a coated metal can having a cured coating film of the coating composition on the inner surface of the can.

[0002]

2. Description of the Related Art Conventionally, as paints for can inner / outer surfaces, lid inner / outer surfaces, and cap inner / outer surfaces which require high workability, amino-alkyd resins, amino-polyester resins, vinyl-amino resins, vinylorgano Resin-based paints such as sol are used.

However, a coating film obtained from an amino-alkyd resin- or amino-polyester resin-based coating material has a difficulty in balancing deep-drawing processability and hardness, and is a vinyl-amino resin or vinyl-organosol resin. A coating film obtained from a paint of a type has problems in hygiene and alcohol resistance when used on the inner surface of a can.

Therefore, the inventors of the present invention can form a coating film having an excellent balance between deep drawing workability and hardness, excellent adhesion, hygiene and alcohol resistance, and can be used on the inner surface of a can. As a result of earnest research to obtain the above, the present invention has been completed by finding that the above object can be achieved by a coating obtained by mixing a specific polyester resin as a resin component with a predetermined amount of a liquid epoxy resin and an amino resin.

[0005]

That is, the present invention is as follows.
(A) Number average molecular weight 10,000 to 100,000, static glass transition temperature 10 to 120 ° C., hydroxyl value 1 to 15 mg
Containing 1 to 20 parts by weight of (b) epoxy resin having a molecular weight of 1,000 or less and (c) 1 to 20 parts by weight of amino resin as resin components with respect to 100 parts by weight of polyester resin having KOH / g and an acid value of 10 or less A coating composition is provided. The present invention also relates to 2. The present invention provides the coating composition for the inner surface of a can according to the above item 1.

The present invention further relates to 3. A coated metal can obtained by forming a cured coating film of the coating composition according to the above item 1 on the inner surface of a metal can, the coating film having a glass transition temperature of 40 to 90 ° C., and an amount of a 20% ethanol aqueous solution. And the ratio of the coating area on the inner surface of the can to 100 ml / 100 cm ² ,
In the coated metal can after the coating film was extracted with a 20% aqueous ethanol solution at 100 ° C. for 60 minutes under pressure, peeling of the coating film was not observed at an Erichsen deep drawing ratio of 40%, and the extraction liquid after the extraction To provide a coated metal can having a coating film for the inner surface of the can having a maximum absorptance of ultraviolet rays in the wavelength range of 200 to 300 nm of 2% or less.

[0007]

The polyester resin which is the component (a) in the composition of the present invention is a hydroxyl group-containing polyester resin, and is an oil-free polyester resin, an oil-modified alkyd resin, or a modified product of these resins, for example, a urethane-modified polyester. It may be any of resin, urethane-modified alkyd resin, epoxy-modified polyester resin, epoxy-modified alkyd resin and the like.

The above oil-free polyester resin is mainly an esterified product of a polybasic acid and a polyhydric alcohol.
Examples of polybasic acids include adipic acid, isophthalic acid,
Examples thereof include terephthalic acid, sebacic acid, maleic acid, fumaric acid and trimellitic acid. These polybasic acids can be used alone or in admixture of two or more. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, trimethylolethane, trimethylolpropane, 1,4-butanediol, neopentyl glycol and the like. These polyhydric alcohols can be used alone or in admixture of two or more. The esterification reaction of both components can be performed by a known method.

The above oil-free polyester resin can also be obtained by performing a transesterification reaction using a lower alkyl ester of a polybasic acid (such as methyl ester or ethyl ester) instead of the polybasic acid in the above esterification reaction. be able to. The transesterification reaction of both components can be performed by a known method.

The alkyd resin is obtained by reacting an oil fatty acid by a known method in addition to the acid component and alcohol component of the oil-free polyester resin, and examples of the oil fatty acid include coconut oil fatty acid and soybean oil fatty acid. , Linseed oil fatty acid, safflower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, tung oil fatty acid and the like.

The urethane-modified polyester resin is the above-mentioned oil-free polyester resin, or an oil-free polyester resin obtained by reacting an acid component and an alcohol component in the production of the above oil-free polyester resin is known as a polyisocyanate compound. It was made to react by the method. The urethane-modified alkyd resin is obtained by reacting the above alkyd resin or an alkyd resin obtained by reacting each component during the production of the above alkyd resin with a polyisocyanate compound by a known method. Examples of the polyisocyanate compound used in producing the urethane-modified polyester resin and the urethane-modified alkyd resin include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′- Methylene bis (cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene and the like can be mentioned.

The epoxy-modified polyester is obtained by reacting the oil-free polyester resin or the oil-free polyester resin obtained by reacting the acid component and the alcohol component in the production of the oil-free polyester resin with an epoxy compound by a known method. It is a thing. The epoxy-modified alkyd resin is a resin obtained by reacting the alkyd resin or an alkyd resin obtained by reacting each component in the production of the alkyd resin with a polyisocyanate compound by a known method.

Epoxy compounds used in the production of epoxy-modified polyester resin and epoxy-modified alkyd resin include butyl glycidyl ether, octyl glycidyl ether, glycidyl laurate, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol. Aliphatics such as diglycidyl ether, polypropylene glycol diglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, hexanediol diglycidyl ether, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, diglycerin tetraglycidyl ether Epoxy compound; dicyclopentadiene dioxide, epoxy cyclo Alicyclic epoxy compounds such as cyclohexene carboxylic acid ethylene glycol diester; polyphenol compound and an epoxy compound obtained by reaction between epichlorohydrin, diglycidyl phthalate,
Examples thereof include aromatic or heterocyclic epoxy compounds such as triglycidyl isocyanurate.

Examples of the polyphenol compound which can be used for producing the epoxy compound obtained by the reaction of the above polyphenol compound and epichlorohydrin include, for example, bis (4-hydroxyphenyl) -2,2-propane, 4,
4'-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2 -Propane,
Bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl)-
1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolac, cresol novolac and the like can be mentioned.

Commercially available epoxy compounds obtained by the reaction of a polyphenol compound and epichlorohydrin are, for example, Epicoat 100 manufactured by Shell Chemical Co.
1, 1, 1004, 1007 and the like.

The above polyester resin has a number average molecular weight of 10,000 to 100,000, a glass transition temperature of 10 to 120 ° C., and a hydroxyl value of 1 from the viewpoint of processability of the obtained coating film, coating film hardness, alcohol resistance and the like. ~ 15mgKOH / g, acid value 10 or less, number average molecular weight 15,
000-40,000, glass transition temperature (Tg point) 40
It is preferable that the hydroxyl value is 3 to 10 mgKOH / g and the acid value is 5 or less. If the number average molecular weight is less than 10,000, the processability is poor. On the other hand, if the number average molecular weight is more than 100,000, the viscosity of the obtained coating composition becomes high and handling becomes difficult. Tg
If the point is less than 10 ° C, the hardness of the obtained coating film will be low, while if it exceeds 120 ° C, the processability of the obtained coating film will be deteriorated. If the hydroxyl value and the acid value are out of the above ranges, the workability and hardness cannot be balanced.

In the present invention, the glass transition temperature (Tg)
Is measured by differential thermal analysis (DSC), and the number average molecular weight is measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene.

The epoxy resin which is the component (b) in the composition of the present invention has a molecular weight of 1,000 or less and has at least one, preferably two or more epoxy groups in the molecule, and has an epoxy equivalent of Is preferably in the range of 100 to 500.

Examples of the epoxy resin (b) include various epoxy resins such as bisphenol A type, bisphenol F type and novolac type, and specific examples thereof include Epicoat 828, Epicoat 834, Epicoat 1001, Epicoat 154 [. Above, all manufactured by Yuka Shell Epoxy Co., Ltd.], Araldite 502, Araldite 6005 [all above manufactured by Ciba], Dow 33
2, Dow 331 [The above are all manufactured by Dow Chemical Co.]
And so on.

The amino resin which is the component (c) in the composition of the present invention includes amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine, dicyandiamide and formaldehyde, paraformaldehyde, acetaldehyde,
Methylolated amino resins obtained by reaction with aldehyde components such as benzaldehyde are mentioned. The methylol group of this methylolated amino resin has 1 carbon atom.
Those which are etherified with lower alcohols of 6 are also included in the above amino resins.

Examples of the amino resin include a methyl etherified melamine resin obtained by etherifying a part or all of the methylol groups of a methylolated melamine resin with methyl alcohol, a butyl etherified melamine resin butyl etherified with butyl alcohol, or a methyl alcohol. A mixed etherified melamine resin of methyl ether and butyl ether etherified by both butyl alcohol is preferred. As the butyl alcohol, isobutyl alcohol and n-butyl alcohol are preferable.

Specific examples of the above melamine resin include, for example, U-Van 20SE, 225 [above, all manufactured by Mitsui Toatsu Co., Ltd.], Super Beckamine J820-60, L-117-60, L-109. -65, 47-50
Butyl etherified melamine resins such as 8-60, L-118-60, G821-60 (all manufactured by Dainippon Ink and Chemicals, Inc.); Cymel 300, 30
3, the same 325, the same 327, the same 350, the same 730, the same 73
6, 738 (all manufactured by Mitsui Cytec Co., Ltd.), melan 522, 523 (all manufactured by Hitachi Chemical Co., Ltd.),
Nikarac MS001, MX430, MX650
[Sanwa Chemical Co., Ltd.], Sumimar M-55, M
-100, the same M-40S [Sumitomo Chemical Co., Ltd.], Regimin 740, the same 747 (all manufactured by Monsanto Co., Ltd.) and other methyl etherified melamine resins; Cymel 232, the same 2
66, the same XV-514, the same 1130 [all are manufactured by Mitsui Cytec Co., Ltd.], Nicarak MX500, the same MX60.
0, the same MS95 [all manufactured by Sanwa Chemical Co., Ltd.], Regimin 753, the same 755 [all manufactured by Monsanto],
Examples thereof include a mixed etherified melamine resin of methyl ether and butyl ether such as Sumimar M-66B (produced by Sumitomo Chemical Co., Ltd.).

In the composition of the present invention, the mixing ratio of the polyester resin (a), the epoxy resin (b) and the amino resin (c) is (b), (c) based on 100 parts by weight of the polyester resin (a). The ratio of each component is within the following range in terms of solid content ratio.

Epoxy resin (b): 1 to 20 parts by weight, preferably 5 to 15 parts by weight, amino resin (c): 1 to 20 parts by weight, preferably 3 to 1
0 parts by weight.

When the compounding amount of the epoxy resin (b) is less than 1 part by weight with respect to 100 parts by weight of the polyester resin (a), the adhesiveness of the coating film obtained is insufficient, and Erichsen after extraction with 20% ethanol water is used. Deep drawing causes peeling on the side surface of the coating film. On the other hand, when the blending amount exceeds 20% by weight, the amount of the resulting coating film extracted with 20% ethanol water increases and the hygienic property deteriorates.

When the amount of the amino resin (c) is less than 1 part by weight based on 100 parts by weight of the polyester resin (a),
If the content of the compounding amount exceeds 20% by weight, the processability of the obtained coating film is lowered and the coating film obtained is extracted with 20% ethanol water. Later Erichsen deep drawing causes peeling of the coating film on the side surface.

The form of the composition of the present invention is not particularly limited, but it is usually one in which the above components (a), (b) and (c) are dissolved or dispersed in an organic solvent. Examples of the organic solvent include (a), (b),
(C) An organic solvent capable of dissolving or dispersing each component is used. As a specific example, for example, toluene,
Aromatic hydrocarbon solvents such as xylene, ketone solvents such as cyclohexanone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, alcohol solvents such as ethanol and butanol, ethylene glycol monoethyl ether, ethylene glycol mono Examples thereof include ether alcohol solvents such as butyl ether, and these can be used alone or in admixture of two or more.

In addition to the above-mentioned components, the composition of the present invention may contain known coloring pigments for coating materials; extender pigments; additives such as defoaming agents and coating surface adjusting agents; and curing catalysts.

The composition of the present invention can be applied onto a metal plate or the inner surface of a can obtained by processing the metal plate and baked to form a coating film suitable for the inner surface of the can.

Examples of the metal plate include beverage cans, cans for canning,
Any metal plate can be used as long as it can be used for the lid and the cap, and examples thereof include an aluminum plate, a tin-free steel plate, and a tin plate.

The composition of the present invention can be coated by a known coating method such as roll coater coating or spray coating. The coating film thickness is not particularly limited, but the dry film thickness is 3 to 18 μm, and Is preferably in the range of 3 to 10 μm. The baking condition of the coating film is usually about 90 to
It is about 5 seconds to about 30 minutes at a temperature of 330 ° C.

As described above, the cured coating film from the composition of the present invention can be formed on the inner and outer surfaces of a metal plate, a can, a lid or a cap which is a processed metal plate. The composition of the present invention is particularly suitable for the inner surface of a can, and the coating film on the inner surface of a can obtained from the composition of the present invention has a glass transition temperature of 40 to 90 ° C., and the amount of 20% ethanol aqueous solution and the coating area Ratio is 10
The coated metal can after the coating film was extracted with a 20% aqueous solution of ethanol at a rate of 0 ml / 100 cm ² at 100 ° C. for 60 minutes under pressure, and the coating film peeled at an Erichsen deep drawing ratio of 40%. The maximum absorption rate of ultraviolet rays in the wavelength range of 200 to 300 nm in the extract after the extraction was 2
% Or less is preferable. When used for the inner surface of a can, it is preferable to appropriately adjust the composition of the composition of the present invention so that the cured coating film obtained from the composition of the present invention satisfies the above conditions.

[0033]

EFFECTS OF THE INVENTION The composition of the present invention can form a coating film having an excellent balance between deep drawing workability and hardness and excellent adhesion, hygiene and alcohol resistance. Suitable as a paint for the inside and outside of the cap. The cured coating film of the composition of the present invention has a glass transition temperature of 40 to 90 ° C., and the coated metal can after extraction of the coating film with a 20% aqueous ethanol solution has the Erichsen deep drawing ratio of 40%. No peeling was observed, and the maximum absorption rate of ultraviolet rays in the wavelength range of 200 to 300 nm in the extract after the extraction was 2%.
It is particularly suitable for the inner surface of a can as it can be:

[0034]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the following, "parts" and "%" are based on weight.

Production of Polyester Resin Solution Production Example 1 49.8 parts of terephthalic acid, 49.8 parts of isophthalic acid, 34.4 parts of hexahydroterephthalic acid, 28.adipic acid.
Charge 5 parts, neopentyl glycol 99.8 parts, trimethylolpropane 6.8 parts and polycondensation catalyst, heat,
Stirring is carried out while removing the water produced, and the esterification reaction is carried out.
A resin having an acid value of 1.0 and a Tg point of 60 ° C. was obtained. The obtained resin is methyl ethyl ketone / cyclohexanone = 50 /
A polyester resin solution A having a solid content of 30% was obtained by diluting with a mixed solvent of 50.

Production Example 2 37.7 parts of phthalic acid, 66.4 parts of isophthalic acid, 46.2 parts of hexahydrophthalic acid, 6.7 parts of trimellitic acid,
Charge 12.4 parts of ethylene glycol, 78.8 parts of neopentyl glycol, 6.8 parts of trimethylolpropane, and a polycondensation catalyst, heat and stir them to carry out an esterification reaction while removing water produced, and a number average molecular weight. 15,000
0, hydroxyl value 5.0 mgKOH / g, acid value 2.0, Tg point 80
A resin of ℃ was obtained. The obtained resin is methyl ethyl ketone /
Diluted with a mixed solvent of cyclohexanone = 50/50 to obtain a polyester resin solution B having a solid content of 30%.

Production Example 3 Polyester resin "TP-220" manufactured by Nippon Gosei Co., Ltd.
(Number average molecular weight 16,000, hydroxyl value 7.0 mgKOH / g
, Acid value 1 or less, Tg point 70 ° C.) was diluted with a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 to obtain a polyester resin solution C having a solid content of 30%.

Production Example 4 Polyester resin "Byron 10" manufactured by Toyobo Co., Ltd.
3 "(number average molecular weight 22,000, hydroxyl value 5 mgKOH / g
, Acid value 2 or less, Tg point 45 ° C.) was diluted with a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 to obtain a polyester resin solution D having a solid content of 30%.

Production Example 5 (for comparison) A polyester resin "Unitika Elitel UE-3300" manufactured by Unitika Ltd. (number average molecular weight 8,000, hydroxyl value 18 mgKOH / g, acid value 1 or less, Tg point 45 ° C.) was used. Diluted with a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 to obtain a polyester resin solution E having a solid content of 30%.

Production Example 6 (for comparison) Polyester resin "Unitika Elitel UE-3230" manufactured by Unitika Ltd. (number average molecular weight 20,000,
A hydroxyl value of 5.0 mgKOH / g, an acid value of 1 or less, and a Tg point of 3 ° C.) were diluted with a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 to obtain a polyester resin solution F having a solid content of 30%.

Production Example 7 (for comparison) Arakawa Chemical Co., Ltd. polyester resin "Arachid KA"
-1027 U "(number average molecular weight 10,000, hydroxyl value 20 mgKOH / g, acid value 3, Tg point 15 ° C) is diluted with a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 to obtain a polyester resin solution G having a solid content of 30%. Got

Using the polyester resin solutions having a solid content of 30% obtained in the above Production Examples 1 to 7, coating materials of Examples and Comparative Examples were obtained.

Example 1 A solid content of 3 was obtained by uniformly stirring the following composition in a container.
0% paint was obtained.

[0044] (* 1) Cymel 303: Mitsui Cytec Co., Ltd., methyl etherified melamine resin, solid content about 100%.

(* 2) Epicoat 828: manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin, molecular weight about 350, epoxy equivalent about 190.

(* 3) Solvesso 100: A high boiling aromatic hydrocarbon solvent manufactured by Esso Oil Co., Ltd.

(* 4) Nacure 5225: (Nakeure 5225) Dodecylbenzenesulfonic acid type curing catalyst manufactured by King Industries, Inc., USA.

Example 2 A solid content of 3 was obtained by uniformly stirring the following composition in a container.
0% paint was obtained.

[0049] (* 5) Epicoat 154: Yuka Shell Epoxy Co., Ltd.
Made, phenol novolac type epoxy resin, molecular weight about 5
00, epoxy equivalent of about 174.

Example 3 A solid content of 3 was obtained by uniformly stirring the following composition in a container.
0% paint was obtained.

[0051] (* 6) Cymel 325: Mitsui Cytec Co., Ltd., methyl etherified melamine resin, solid content about 80%.

Example 4 A coating material having a solid content of 30% was obtained in the same manner as in Example 3 except that 0.5 part of Nacure 5225 was added as a curing catalyst to the composition.

Example 5 A solid content of 3 was obtained by uniformly stirring the following composition in a container.
0% paint was obtained.

[0054] (* 7) 50% Epicoat 1001: manufactured by Yuka Shell Epoxy Co., Ltd., "Epicoat 1001" (bisphenol A type epoxy resin, molecular weight about 900, epoxy equivalent about 4)
90) dissolved in methyl ethyl ketone to give a solid content of 50%
Solution of.

Example 6 Stir evenly with the above composition in a container to obtain a solid content of 30.
% Paint obtained.

Comparative Example 1 Stir evenly with the above composition in a container to obtain a solid content of 30.
% Paint obtained.

Comparative Example 2 Stir evenly with the above composition in a container to obtain a solid content of 30.
% Paint obtained.

Comparative Example 3 Stir evenly with the above composition in a container to obtain a solid content of 30.
% Paint obtained.

Comparative Example 4 50% Epicoat 10 prepared by dissolving 7.5 parts of Epicoat 1004 (* 8) in 7.5 parts of cyclohexanone in place of 7.5 parts of Epicoat 154 in Example 2.
15 parts of 04 solution and 2 parts of Solvesso 100
A coating material having a solid content of 30% was obtained in the same manner as in Example 2 except that the amount was changed from 4.5 parts to 17 parts.

(* 8) Epicoat 1004: Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.
Molecular weight about 1400, epoxy equivalent about 950.

Comparative Example 5 A coating material having a solid content of 30% was obtained in the same manner as in Example 2 except that the polyester resin solution G was used in place of the polyester resin solution B.

Preparation of Test Coated Plates The coating materials obtained in the above Examples and Comparative Examples were coated with 0.25 mm thick #
A 5052 aluminum plate was coated so that the dry film thickness was 12 μm, and baked for 30 seconds with hot air having a wind speed of 18 m / sec and a maximum material arrival temperature (PMT) of 270 ° C. to obtain a test coated plate. The following tests were conducted on the obtained test coated plates. The test results are shown in Table 1 below. (1) Appearance of coating film: The appearance of the coating film of the test coated plate was visually observed.
Those with no abnormalities were marked with a circle.

(2) Adhesion: JIS K-5400
According to 8.5.2 (1990) cross-cut tape method, 100 squares of 1.5 mm x 1.5 mm are created on the coating surface of the test coated plate, and the adhesive cellophane tape on the surface is attached. The state of the coating film on the square portion after the rapid peeling was evaluated.

◯: No peeling was observed Δ: Slight peeling was observed ×: Significant peeling was observed.

(3) Deep drawing workability: Using a deep drawing machine having a drawing ratio of 40%, a cross-cut was made on the side surface of the test coated plate to carry out deep drawing work. Then, immersion treatment was performed in a 20% ethanol aqueous solution under pressure at 100 ° C. for 60 minutes. The state of peeling of the coating film on the processed side surface before and after the dipping treatment was visually observed. The evaluation was performed according to the following criteria. ◯: No peeling was observed Δ: Slight peeling was observed ×: Significant peeling was observed.

(4) Coating hardness: JI was applied to the coating on the test coated plate.
A pencil scratch test specified in SK-5400 84.2 (1990) was performed. The evaluation was performed by the yabure method.

(5) Hygiene: By a dipping treatment when a test coated plate having a coating area of 100 cm ² was dipped in 100 cc of 20% ethanol aqueous solution under pressure at 100 ° C. for 60 minutes. The coating film weight loss (%) was measured. In addition, the absorption rate of ultraviolet rays having a wavelength of 200 to 300 nm of the extract after the immersion treatment is measured by Hitachi Ltd., U-3200 Spectro Photom.
It was measured with an eter (spectrophotometer), and the maximum value of the absorption rate was described.

[0068]

[Table 1]

Claims (4)

[Claims] 1. (a) Number average molecular weight 10,000 to 10
20,000, static glass transition temperature 10 to 120 ° C., hydroxyl value 1 to 15 mgKOH / g, acid value 10 or less per 100 parts by weight of polyester resin (b) molecular weight 1,000 or less epoxy resin 1 to 20 Parts by weight and (c) amino resin 1
A coating composition containing 20 to 20 parts by weight as a resin component. 2. The amino resin (c) is at least one selected from a methyl etherified melamine resin, a butyl etherified melamine resin, and a mixed etherified melamine resin of methyl ether and butyl ether. The coating composition described. 3. The coating composition for an inner surface of a can according to claim 1 or 2. 4. A coated metal can having a cured coating film of the coating composition according to claim 1 or 2 formed on the inner surface of a metal can, the coating film having a glass transition temperature of 40 to 90 ° C. And the ratio of the amount of 20% aqueous ethanol solution to the coating area is 10
The coated metal can after the coating film was extracted with a 20% aqueous solution of ethanol at a rate of 0 ml / 100 cm ² at 100 ° C. for 60 minutes under pressure, and the coating film peeled at an Erichsen deep drawing ratio of 40%. The maximum absorption rate of ultraviolet rays in the wavelength range of 200 to 300 nm in the extract after the extraction was 2
% Or less, a coated metal can having a coating film for the inner surface of the can.