KR0178804B1 - Powder coating composition - Google Patents

Abstract

The present invention provides a bisphenol-type epoxy resin having a melting point of 50 to 150 DEG C and an epoxy equivalent of 600 to 3,000, an acid component having a melting point of 50 to 180 DEG C and an acid value of 40 to 550, and a (C) chloride Cans containing at least one curing catalyst selected from the group consisting of choline and organic carboxylic acid metal salts, wherein the equivalent ratio of epoxy groups in the resin (A): acid groups in the acid component (B) is 2: 1 to 1: 2 A powder coating composition.

Description

Cans Powder Coating Composition

The present invention provides a powder coating composition used to form a film on a can surface, more specifically a powder coating capable of producing a coating composition suitable for forming a film on the inner surface of a can by selecting a starting material. To a composition.

The can coating composition has been coated on metal cans such as food cans, beverage cans and the like to prevent metal elution and can corrosion. The coating composition used is generally a liquid coating composition prepared by dissolving or dispersing a resin such as an epoxy resin or a vinyl chloride resin in a solvent.

Recently, in the use of the liquid coating composition, the organic solvent contained in the liquid coating composition is volatilized to the atmosphere causing air pollution, and the organic solvent remaining in the coated film on the inner surface of the can is transferred to the can contents causing problems. As a result, the transition to pollution-free and solvent-free coating compositions has been accelerated.

Conventional powder coating compositions are used in terms of hygiene, where starting materials are not suitable for application to the inner surfaces of food and beverage cans, and the film surface for can production by the short time curing process required at can manufacturing line speed and other steps. Because of the impossibility of obtaining coated films with good smoothness, corrosion resistance and processability, development of powder coating compositions suitable for can inner coating compositions in direct contact with foods and beverages was needed.

A first object of the present invention is a can powder coating composition capable of forming a coated film having excellent appearance, adhesion, processability, water resistance, curability, corrosion resistance, and flavor retention on a can base material in a short curing process. To provide.

It is a second object of the present invention to provide a can powder coating composition which is capable of selecting a starting material to form a coated film free of residual solvents and without hygiene issues even when the can inner surface is in direct contact with food and beverage.

A third object of the present invention is a can powder coating composition which is free from foaming at the time of curing and can produce a composition capable of reducing residual stress in the case of corrective coating of side seam portions to form a coated film having excellent properties. To provide.

It is a fourth object of the present invention to provide can powder coating compositions which do not cause pollution problems due to volatilization of organic solvents in coating.

That is, this invention is a bisphenol-type epoxy resin with (A) melting | fusing point 50-150 degreeC, epoxy equivalent 600-3,000, (B) acid component whose melting | fusing point is 50-180 degreeC, and acid value 40-550, and (C (C) containing at least one curing catalyst selected from the group consisting of choline chloride and organic carboxylic acid metal salts, wherein the equivalent ratio of epoxy groups in the resin (A): acid groups in the acid component (B) is 2: 1 to 1: 2. An in can powder coating composition is provided.

In a first embodiment, the bisphenol type epoxy resin (A) is at least one epoxy resin selected from the group consisting of bisphenol A type epoxy resins and bisphenol F type epoxy resins.

In a second embodiment, the bisphenol-type epoxy resin (A) is at least one epoxy resin selected from the group consisting of dimer acid-modified bisphenol A-type epoxy resins and dimer acid-modified bisphenol F-type epoxy resins.

The acid component (B) is preferably an organic acid component containing, as a main component, at least one ester compound selected from the group consisting of acid anhydride group-containing ester compounds represented by the following formula [1] or [2]:

Wherein R ¹ is a divalent alkylene group having 2 to 6 carbon atoms, R ² is a trivalent saturated hydrocarbon group having 2 to 6 carbon atoms, and X is a hydrogen atom or trimellitic anhydride represented by the following formula [3]: Residues, provided that at least one of the Xs in each formula is a trimellitic anhydride residue:

In addition to the bisphenol type epoxy resin (A), the acid component (B), and the curing catalyst (C), the can powder coating composition of the present invention preferably contains (D) fine silica.

In another aspect, the present invention provides a method for coating the inner surface of a two-piece can, the method comprises the step of coating and then curing the can powder coating composition on the inner surface of the two-piece can, the powder coating composition is bisphenol-type epoxy Resin (A), an acid component (B), a curing catalyst (C) and preferably finely divided silica (D), wherein the bisphenol type epoxy resin (A) is a bisphenol A type epoxy resin and a bisphenol F type epoxy resin. At least one epoxy resin selected from the group consisting of:

In addition, the present invention provides a method for coating a can body welded portion of the inner surface of the can, the method comprises the step of coating the can powder coating composition on the can body welded portion of the inner surface of the can, and then curing the powder coating composition A bisphenol type epoxy resin (A), an acid component (B), a curing catalyst (C) and preferably finely divided silica (D), wherein the bisphenol type epoxy resin (A) is a dimer acid-modified bisphenol A type At least one epoxy resin selected from the group consisting of epoxy resins and dimer acid-modified bisphenol F-type epoxy resins.

Melting point of the bisphenol-type epoxy resin (A) in the composition of the present invention is 50 to 150 ℃, preferably 80 to 120 ℃, the equivalent is 600 to 3,000, preferably 900 to 2,000.

Resin (A) can be prepared by reacting epihalohydrin, bisphenol and, if necessary, modifying agents such as saturated aliphatic monocarboxylic acids, dibasic acids, polymerized fatty acids and the like. If the melting point of the resin (A) is less than 50 ° C., blocking of the powder coating composition may occur during storage. On the other hand, when the melting point is more than 150 ℃ thermal fluidity during the heat curing of the powder coating composition is poor to obtain a smooth coating film. When the epoxy equivalent of the resin (A) is less than 600, the blocking resistance during storage becomes poor, whereas when the epoxy equivalent of the resin (A) exceeds 3,000, the thermal fluidity of the powder coating composition and the corrosion resistance of the resulting coating film during the thermal curing are undesirable. Is reduced. Epihalohydrin is preferably epichlorohydrin.

Examples of bisphenols include bis (4-hydroxyphenyl) methane (ie bisphenol F), 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane (ie Bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, (ie bisphenol B), bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-t- Butyl-phenyl) -2,2-propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4-dihydroxy Benzophenone etc. are mentioned. Among these, bisphenol A and bisphenol F are preferable from the viewpoint of hygiene for use on the inner surface of the can.

Among the modifiers that can be used in the preparation of bisphenol type epoxy resins, dimer acids such as polymerized fatty acids are preferred in view of the processability of the coated film from which they are produced.

Dimer acids are prepared by dimerizing unsaturated higher fatty acids such as refined vegetable oil fatty acids obtained from dry and semi-dry oils. Unsaturated fatty acids are mainly C ₁₈ unsaturated fatty acids such as linoleic acid, linolenic acid, oleic acid and the like. Dimer acids contain predominantly dimers of such unsaturated fatty acids, but may also include other oligomers such as trimers and monomeric fatty acids.

It is known that the chemical structure of the dimer acid may vary depending on the type of monomeric fatty acid and the polymerization method, but is represented by the following structural formulas [4], [5] and [6]:

Wherein R ³ is CH ₃ (CH ₂ ) ₄ —, R ⁴ is — (CH ₂ ) ₇ COOH, and R ⁵ is CH ₃ (CH ₂ ) ₇ . All of the dimer acids represented by the above structural formulas can be used as modifiers.

Examples of commercially available resins of unmodified resins in bisphenol-type epoxy resins (A) include Epikote 1002, Epikote 1003, Epikote 1004 and Epikote 1007 (each manufactured by Yuka Shell Epoxy Co., Ltd.). Brand name of one product), Epicl on 1050, Epiclon 3050, Epiclon 4050, and Epiclon 7050 (each brand name manufactured by Dainippon Ink Chemicals, Inc.), Epo Tohto YDF-2004 (trade name of a product manufactured by Tototo Kasei Co., Ltd.).

In bisphenol-type epoxy resins in the present compositions, dimer acid-modified bisphenol-type epoxy resins are generally relatively low molecular weight bisphenol-type epoxy resins such as Epikote 828 (trade name available from Yucca Shell Epoxy Company Limited), Epikote 1001, It is prepared by the reaction of a dimer acid such as Epikote 1002, Epikote 1003, Epikote 1004 and the like, but is also prepared by (1) dimer acid, (2) condensate of bisphenol and epihalohydrin and (3) bisphenol. Can be.

The dimer acid modification degree in the dimer acid-modified bisphenol type epoxy resin is preferably 1 to 50% by weight, in particular 10 to 30% by weight, based on the modified epoxy resin.

In the composition of the present invention, the acid component (B) is a component that functions as a curing agent for a bisphenol-type epoxy resin (A), and has a melting point of 50 to 180 ° C. and an acid value of 40 to 550, respectively. It contains one or more compounds selected from as a main component, it can be prepared by the reaction of a polybasic acid component, a polyhydric alcohol component, and monobasic acid and monohydric alcohol, if necessary. Polyester compounds include diester oligomers, tri- or more polyester oligomers, and polyester resins.

Examples of the polybasic acid component constituting the acid component (B) include adipic acid, fumaric acid, maleic acid, maleic anhydride, phthalin, phthalic anhydride, isophthalic acid, terephthalic acid, sebacic acid, trimellitic acid, trimellitic anhydride, Dimer acids; and the like. These may be used only by 1 type or in mixture of 2 or more types.

Examples of the polyhydric alcohol component constituting the acid component (B) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, neofeltyl glycol, 1,6 -Dinucleic acid diol, diethylene glycol, triethylene glycol, crimethylol ethane, trimethylol propane, glycerin, pentaerythritol, sorbitol, mannitol, α-methylglucoside and the like. These may be used alone or in combination of two or more thereof.

Examples of the monobasic acid which is an optional component constituting the acid component (B) include benzoic acid, t-butyl benzoic acid, abidic acid and the like. Examples of the monohydric alcohol which is an optional component constituting the acid component (B) include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol and the like.

The acid component (B) is obtained by esterifying each component in the presence of a reaction catalyst such as dibutyltin oxide, hydroxybutyltin oxide, monobutyltin tris- (2-ethylhexanoate) or the like according to a conventional method. Can be. In view of hygiene, the reaction catalyst may be preferably used in an amount of less than 0.2% by weight based on the total amount of both the acid and the alcohol constituting the acid component (B). The acid component (B) may have a molecular weight of 160 to 10,000, preferably 400 to 6,000.

The acid component (B) preferably includes an organic acid component containing, as a main component, the acid anhydride group-containing ester compound represented by the general formula [1] or [2].

Specific examples of the divalent alkylene group represented by R ¹ in the acid anhydride group-containing ester compound represented by the general formula [1] and having 2 to 6 carbon atoms include ethylene, 1,2-propylene, trimethylene, and ethyl. Groups such as ethylene, tetramethylene, hexamethylene and the like.

The acid anhydride group-containing ester compound represented by the general formula [1] may be an esterification reaction product between alkylene glycol having 2 to 6 carbon atoms and trimellitic anhydride, for example, 2 of alkylene glycol A compound obtained by esterifying one hydroxyl group of one hydroxyl group with trimellitic anhydride, wherein each of the two hydroxyl groups of a compound having one acid anhydride group and an alkylene glycol and trimellitic anhydride is esterified As the obtained compound, there is a compound having two acid anhydride groups.

Examples of alkylene glycols having 2 to 6 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol Etc. Of these, ethylene glycol is particularly preferred.

Specific examples of the trivalent hydrocarbon group represented by R ² in the acid anhydride group-containing ester compound represented by the general formula [2] having 2 to 6 carbon atoms include 1,2,3-propanetriyl, 1, And groups such as 2,3-butanetriyl and 1,2,6-hexanetriyl.

The acid anhydride group-containing ester compound represented by the general formula [2] may be an esterification reaction product of a trihydric alcohol having 2 to 6 carbon atoms with trimellitic anhydride, and examples thereof include a hydroxide of a trihydric alcohol. Compounds obtained by esterifying each of one hydroxyl group, two hydroxyl groups, or three hydroxyl groups of three hydroxyl groups and a carboxyl group of trimellitic anhydride, that is, a compound having one acid anhydride group, two acids There are compounds with anhydride groups and compounds with three acid anhydride groups.

Examples of trihydric alcohols having 2 to 6 carbon atoms include glycerin, 1,2,3-butanetriol, 1,1,1-trimethylol propane, 1,2,6--hexanetriol, and the like. . Of these, glycerin is particularly preferred.

The organic acid component of the present invention contains the acid anhydride group-containing ester compound represented by the above general formula [1] or [2] as a main component, but other organic acids, such as 50% by weight or less of the organic acid component, preferably May contain an organic acid free of ester groups in a content of 30% by weight. An example of an organic acid without an ester group is trimellitic anhydride, which is an unreacted reactant when the acid anhydride group-containing ester compound is prepared by an esterification reaction between alkylene glycol or trihydric alcohol and trimellitic anhydride. Remaining as.

The acid component (B) preferably contains a compound in which R ¹ is an ethylene group and has two acid anhydride groups in an amount of at least 60% by weight of the acid component (B) in view of the balance between curability and processability of the coated film. Do.

The choline chloride or organic carboxylic acid metal salt having the formula [HOCH ₂ CH ₂ N (CH ₃ ) ₃ ⁺ Cl ^- constituting the component (C) of the composition of the present invention is the bisphenol-type epoxy resin (A) and the acid, respectively. It acts as a curing catalyst for the reaction between component (B). The curing catalyst in the powder coating composition of the present invention needs to meet the following requirements. That is, in the case of a curing catalyst, the reaction rate between the epoxy resin (A) and the acid component (B) needs to be kept at a low value while each component of the coating composition is usually melt mixed at 50 to 160 ° C., but at high temperatures. It is necessary to obtain a reaction rate such that curing by curing and short time curing, that is, curing under conditions of 160 to 350 ° C. and 7 to 180 seconds, is sufficient, and a reaction rate that hardly occurs during storage at room temperature. have. When applied to the inner surface of the can, it should not remain in the coated film in direct contact with food or beverages and should not cause hygiene problems.

Preferred as the organic carboxylic acid metal salt constituting the component (C) are metal salts of fatty acids having 5 or more carbon atoms. Specific examples thereof include tin 2-ethylhexanoate, zinc 2-ethylhexanoate, tin laurate, lithium stearate, and the like. Of these, 2-ethylhexanoic acid tin is preferable.

In the composition of the present invention, the mixing ratio of the bisphenol-type epoxy resin (A) and the acid component (B) is an equivalent ratio of the epoxy group in the resin (A) to the acid group in the acid component (B) is 2: 1 to 1: 2, preferably 1.3 The range is 1: 1 to 1: 1.6. When it is out of the said range, hardenability will become inadequate, and adhesiveness to a can body, workability, water resistance, corrosion resistance, flavor preservation, etc. are undesirably reduced. The equivalent of the acid group in the acid component (B) is calculated such that 1 mole of the acid anhydride group corresponds to 2 equivalents, and 1 mole of the carboxyl group corresponds to 1 equivalent.

Although the mixing ratio of choline chloride or organic carboxylic acid metal salt constituting component (C) in the composition of the present invention is not particularly limited, it is usually the total amount of bisphenol type epoxy resin (A) and acid component (B). Per 100 parts by weight, the catalytic effect and the smoothness and water resistance of the resulting coating film are in the range of 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight.

The composition of the present invention is mainly composed of bisphenol-type epoxy resin (A), acid component (B) and choline chloride or organic carboxylic acid metal salt as component (C), but if necessary, known film surface modifiers, solid waxes and colorings. It may contain a small amount of a pigment, an extender pigment, a modified resin having a melting point of 50 to 150 ° C. It is sometimes advantageous to add finely divided silica as an extender pigment to improve the flowability of the coating composition powder.

The mixing ratio of finely divided silica is preferably in the range of 0.1 to 5.0 parts by weight per 100 parts by weight, which is the total amount of the resin (A) and the acid component (B).

The powder coating compositions of the present invention comprise, for example, kneading machines or extruders under temperature and time conditions at which viscosity increase and gelling will not occur, i.e. for 3 to 60 seconds at 50 to 160 ° C. Each component may be melt mixed, then cooled, ground and sieved to obtain a powder coating composition having the desired particle distribution.

The particle size of the powder coating composition is preferably in the range of 1 to 80 mu m.

Examples of the metal material constituting the can for coating the powder coating composition of the present invention include untreated steel sheet, tin plate steel sheet, zinc plate steel sheet, chrome plate steel sheet, phosphate treated steel sheet, chromic acid treated steel sheet, untreated aluminum Sheets, chromic acid treated aluminum sheets, and the like. The method of coating the coating composition of the present invention on a metal material is carried out by, for example, an electrolytic coating followed by heat curing at about 160 to 350 ° C. for about 7 to 180 seconds and drying to form a cured coating film. can do.

The powder coating composition of the present invention can be used to coat both the inner and outer surfaces of the can. Examples of coating on both the inner and outer surfaces of the can include coating on the inner and outer surfaces of two and three piece cans, coating on the metal sheet constituting the can body and can lid, cutting and amounting the coated metal sheet. Repairing coatings of can body welds or side joints on the inner surface of the can formed by folding and welding the ends.

By using at least one resin selected from the group consisting of bisphenol A type epoxy resins and bisphenol F type epoxy resins as bisphenol type epoxy resins (A), starting materials without sanitary problems with good can inner coating properties and processing properties can be obtained. And a composition suitable for coating the inner surface of a two piece can.

The powder coating composition of the present invention has a cured film thickness in the range of 2 to 20 μm in the general area of the can inner surface and the can outer surface, and in the repair coating of the side seams so as to sufficiently coat the difference due to welding. It may be coated to have a range of 30 to 100㎛.

For side seam repair coatings, use of a composition capable of reducing residual stresses due to thick films, i.e. dimer acid modified bisphenol A epoxy resins and dimer acid modifieds, for example as bisphenol type epoxy resins (A) It is preferable to use at least one epoxy resin selected from the group consisting of the bisphenol F-type epoxy resins.

The present invention provides a can powder coating composition capable of forming a coating film having excellent properties in film appearance, adhesion, processability, curability, corrosion resistance, and flavor preservation on a can substrate by a short curing time.

The present invention provides a can powder coating composition capable of forming a coating film free of residual solvents and without hygiene problems even by direct contact with food and beverages as the can inner film by selecting a starting material.

The present invention provides a can powder coating composition capable of forming a coating film having excellent properties by preparing a composition which has no foaming action upon curing and can reduce residual stress in the case of repair coatings on side seams.

The present invention provides a can powder coating composition which does not cause a problem of environmental pollution due to volatilization of an organic solvent during coating.

The present invention will be described in more detail based on the following Examples and Comparative Examples, where parts and percentages are by weight.

Preparation of Dimer Acid-Modified Epoxy Resins:

[Manufacture Example 1-3]

Epikote 828EL (available from Yucca Shell Epoxy Company Limited. Bisphenol A liquid epoxy resin, epoxy equivalent: about 190), bisphenol A and dimer acid are formulated as shown in Table 1, followed by the addition of a catalyst and nitrogen atmosphere Under heating at 150 ° C., maintained at that temperature, and reacted until the acid value decreased to near zero to give each dimer acid-modified epoxy resin.

[Preparation of Can Powder Coating Composition]

Example 1

100 parts of Epikote 1004 (trade name) Yuka Shell Epoxy Company, a bisphenol A epoxy resin having a melting point of 97 ° C. and a melting point of 97 ° C., represented by E1004 in Tables 2 and 3), Rikacid TMEG 200 (New A brand name of a product sold by Japan Chemical Co., Ltd. (New Japan Chemical Co., Ltd.), wherein R in the general formula (I) An organic acid component containing 95% or more of an acid anhydride group-containing ester compound which is an ethylene group, and both X are trimellitic anhydride residues and an esterification reaction between trimellitic anhydride having an acid value of about 547 and ethylene glycol In Tables 2 and 3 below, 11 parts of TMEG, 1 part of choline chloride, 1 part of MODAFLOW (trade name of surface conditioner sold by Monsanto Co., Ltd.) and Carplex FPS 500 A mixture of 0.4 parts (trade name of the finely divided silica sold by Shionogi & Co., Ltd., Shionogi Co. Ltd., represented by FPS 500 in Tables 2 and 3 below) was dry mixed and then a bus Ko-kneader (Buss Ko) -Kneader) melt mixed in PR 46 (Buss Co., Ltd (trade name, Swiss)), cooled, pulverized and sieved to have a particle distribution of 5 to 60 μm and an average particle size A powder coating composition having a group of about 30 μm was obtained.

[Examples 2 to 12 and Comparative Examples 1 to 6]

The experiment was conducted in the same manner as in Example 1 except that the preparation of starting materials shown in Table 2 was used to obtain each powder coating composition having a particle distribution of 5 to 60 µm and an average particle size of about 30 µm. Obtained.

[Examples 13 to 20 and Comparative Examples 7 to 12]

The preparations of the starting materials shown in Table 3 were used, and the experiments were carried out in the same manner as in Example 1 except that a grinder and a sieve sorter were used, with a particle distribution of 1 to 30 μm and an average particle size of about 15 μm. After each powder coating composition was obtained, it was used to prepare each powder coating composition.

Example 21

Instead of 1 part of choline chloride, 0.2 parts of tin-2-ethylhexanoate was used, and the experiment was carried out in the same manner as in Example 1 except that Carplex FPS 500 was used in 0.5 parts instead of 0.4 parts, and the particle distribution was 5 to 60. Each powder coating composition was obtained having a mean particle size of about 30 μm.

[Examples 22 to 32 and Comparative Examples 13 to 18]

The experiments were conducted in the same manner as in Example 21, except that the preparations of the starting materials shown in Table 4 were used to obtain respective powder coating compositions having a particle distribution of 5 to 60 μm and an average particle size of about 30 μm. It was.

[Examples 33 to 40 and Comparative Examples 19 to 24]

Experiments were carried out in the same manner as in Example 21, except that the preparation of starting materials shown in Table 5 was used, except that a grinder and a screen sorter were used, with a particle distribution of 1 to 30 μm and an average particle size of about 15 μm. Each powder coating composition was obtained and then used to prepare each powder coating composition.

In Tables 2 to 5, (Note 1) to (Note 6) are as follows:

(Note 1) YDF2004: Bisphenol F type epoxy resin having an epoxy equivalent weight of about 1,000 and a melting point of 85 DEG C (available under the trade name Epo Tohto YDF2004 from Toto Kasei Co., Ltd.).

(Note 2) TMTA-C: R in the general formula (2) About 40% of an acid anhydride group-containing ester compound that is an esterification reaction product wherein is an 1,2,3-propanetriyl group and two of the three X are trimellitic anhydride residues; About 28% of said acid anhydride group-containing ester compound wherein in Formula (2) X is all trimellitic anhydride residues; And an organic acid component containing about 23% of trimellitic anhydride (total acid value = about 530) (commercially available under the trade name Rikacid TMTA-C from New Japan Chemical Company, Limited).

(Note 3) HT3380: In the general formula (1), R A substantial amount of said acid anhydride group-containing ester compound which is an ethylene group, and two X's are both trimellitic anhydride residues, and the acid anhydride wherein one of the two X's in the general formula (1) is a trimellitic anhydride residue. Trace amount of group-containing ester compound; In formula (2), R The anhydride group-containing ester compound wherein is 1,2,3-propane triyl group; And an organic acid component containing trimellitic anhydride (total acid value = about 550) (available under the trade name HARDENER HT3380 from Ciba-Geigy Company, Limited).

(Note 4) E1001: Bisphenol A type epoxy resin having an epoxy equivalent weight of about 475 and a melting point of about 70 ° C (commercially available under the trade name Epikote 1001 from Yucca Shell Epoxy Company, Limited).

(Note 5) CC314: A polyester resin having a melting point of about 100 DEG C and an acid value of 70 (commercially available under the trade name CRYLCOAT314 from US UCB Co., Ltd.).

(Note 6) GV340: Polyester resin with melting point of about 126 ° C and acid value of about 34 (commercially available under the trade name U-PICA COAT GV340 from Japan U-pica Co., Ltd.) .

[Performance test]

The following preparation method for the purpose of testing whether the powder coating compositions obtained in Examples 1 to 12 and 21 to 32 and Comparative Examples 1 to 6 and 13 to 18 are suitable for repair coating on the side seam of the can inner surface. A test plate coated according to (1) was prepared.

[Method for Manufacturing Coated Test Plate (1)]

Each powder coating composition obtained in Examples 1 to 12 and 21 to 32 and Comparative Examples 1 to 6 and 13 to 16 was electrostatically coated on a # 25 tin plate to give a dry film of about 45 μm thick, followed by 240 Curing at 15 ° C. for 15 seconds yielded each coated test plate.

For the purpose of testing whether the powder coating compositions obtained in Examples 13-20 and 33-40 and Comparative Examples 7-12 and 19-24 are suitable for coating on the inner surface of the body of a two-piece can, A test plate coated according to 2) was prepared.

[Coated Test Plate Manufacturing Method (2)]

Each powder coating composition obtained in Examples 13 to 20 and 33 to 40 and Comparative Examples 7 to 12 and 19 to 24 was electrostatically coated on # 25 tin plate so that the thickness of the dry film was about 15 μm, followed by 215 Heat curing at 60 ° C. for 60 seconds yielded each coated test plate.

According to the production method (1) and (2) of the coated test plate, after producing each coated test plate, according to the following test method, film appearance, gel fraction, processability, water resistance of the processing part, water resistance of the general part, The adhesion after the adhesion and water resistance test was tested.

[Test method]

Film appearance

The appearance of the film was visually observed. The appearance of the film was evaluated according to the following criteria.

(Circle): The coated surface is smooth overall, and foaming is not observed at all.

(Triangle | delta): A little uneven site | part is observed in the whole coated surface, and small foaming is observed.

X: Some uneven | corrugated site | part is observed all over the coated surface, and big foaming is observed.

Gel fraction

After placing the weighted coated test plate in a flask, the methyl ethyl ketone was added so that the ratio of methyl ethyl ketone (ml): coated area of the coated test plate (cm 2) was 100 ml: 100 cm 3, and heated to reflux. After extraction for 1 hour, the coated test plate was collected, dried at 120 ° C. for 30 minutes, cooled to room temperature, and the weight of W was measured. The weight of the tin plate before coating the coating composition was W, and the gel fraction (%) was determined in the following manner.

Gel fraction = {(W ₃ -W ₁ ) / (W ₂ -W ₁ )} × 100 (%)

Machinability

A coated test plate, folded so that the coated surface is the outer surface, is placed on the bottom of a specially folded DuPont impact tester, and 1 kg of iron having a smooth contact surface is dropped at a height of 50 cm, causing cracks on the film in the folded portion. The length of was measured. The following manufacturing characteristics were evaluated.

◎: less than 5 mm

○: less than 5 to 10 mm

△: 10 to less than 20mm

×: 20 mm or more

Water resistance of the processing part

The coated test plate tested for workability was immersed in hot water at 125 ° C. for 35 minutes in an autoclave, and then the length of the resulting crack was measured. Evaluation was carried out in the same manner as in the above workability test.

Water resistance (general part)

The coated test plate was immersed in deionized water, then treated in an autoclave with pressurized boiling water at 125 ° C. for 35 minutes and the bleaching degree of the film was measured. The film was evaluated as follows.

◎: Coated film is not bleached at all

○: The coated film is slightly bleached

△: coated film is slightly bleached

×: Coated film is heavily bleached

Adhesion

The coated film of the coated test plate was cut into squares by cutting 11 times in length and width at about 1.5 mm intervals using a knife. After the adhesive cellophane tape having a width of 24 mm was brought into close contact with the square film, the tape was strongly peeled off, and the adhesion characteristics of the square film were observed. The evaluation was as follows.

○: does not peel at all

△: slightly peeled off

×: remarkably peeled off

Adhesion after water resistance test

The coated test plate was immersed in deionized water and then treated in autoclave for 35 minutes with pressurized boiling water at 125 ° C., and the knife was cut 11 times in length and width at approximately 1.5 mm intervals to form a square. . After the adhesive cellophane tape having a width of 24 mm was brought into close contact with the square film, the tape was strongly peeled off to observe the adhesion characteristics of the square film and evaluated as in the adhesion test.

Preparation of can bodies for testing corrosion resistance and flavor preservation:

Preparation of the can body with a repair coating on the side seam of the can inner surface:

A solution-type epoxy-phenolic resin coating composition for use on the inner surface of the can is coated on a # 25 tin plate so that the dry film has a thickness of 5 μm (except for the extra edge for welding), followed by heat curing. A cured film was obtained.

After the resulting coated tin plate was welded with a can body for use in a three piece can, each powder coating composition obtained in Examples 1-12 and 21-32 and Comparative Examples 1-6 and 13-18 was subjected to a thickness. Electrostatically coated on the welded area on the inner surface of the resultant welded can body having a dry film having a dry film having a thickness of about 45 μm and a coating width of about 15 mm, and heat cured at 240 ° C. for 15 seconds to obtain a can body having a repair coating. It was.

[Production of Can Body of 2 Piece Cans]

Each powder coating composition obtained in Examples 13-20 and 33-40, Comparative Examples 7-12 and 19-24 was electrostatically coated on the inner surface of a 250 ml steel two-piece can to give a dry film thickness of about 15 μm. After heat curing at 215 ° C. for 60 seconds, a can body of two cans was obtained.

The following liquid samples were loaded into the can body and the can body of the two-piece cans respectively with the repair coating, followed by rolling and molding to perform the following corrosion resistance and flavor preservation tests.

In the case of a can body with a repair coating, the top and bottom caps were rolled and molded, and in the case of a can body of two piece cans, only the top cap was rolled and molded.

Corrosion resistance

The can body and the two-piece can body with the repair coating at 98 ° C. were filled with 10% fine juice, rolled and molded, respectively, stored at 37 ° C. for 6 months, and then the can was opened to corrode the inner surface. Was examined. The evaluation was as follows.

○: no corrosion at all

△: slightly corroded

×: markedly corroded

Flavor preservation

Into the can body and the two-piece can body of the repair coating, 250 ml of water prepared by treating tap water with activated carbon, rolled and sterilized for 30 minutes at 125 ℃, and then stored at 37 ℃ for 6 months , Flavor test was performed. The evaluation was as follows.

○: no change

△: slightly changed

×: significantly changed

Claims (5)

(A) has a melting point of 50 to 150 ° C. and an epoxy equivalent of 600 to 3000, and at least one is selected from the group consisting of dimer acid-modified bisphenol A type epoxy resins and dimer acid-modified bisphenol F type epoxy resins; An acid component selected from the group consisting of a bisphenol type epoxy resin selected from the group consisting of (B) a melting point of 50 to 180 ° C. and an acid value of 40 to 550, and at least one of a parent compound and a polyester compound, and (C) chloride Equivalent ratio of the epoxy group in the said resin (A): the acidic group in the said acid component (B) is 2: 1-1: 2, and the said acid contains one or more hardening catalyst selected from the group which consists of choline and an organic carboxylic acid metal salt. Component (B) is included in the range of 8 to 92 parts by weight per 100 parts by weight of the resin (A), and the curing catalyst (C) is 0.01 to 5 parts by weight per 100 parts by weight of the total amount of the resin (A) and the acid component (B). With range Can powder coating composition included. The acid component (B) according to claim 1, wherein the acid component (B) is an organic acid component containing, as a main component, at least one ester compound selected from the group consisting of acid anhydride group-containing ester compounds represented by the following formula [1] or [2]: Coating composition: Wherein R¹ is a divalent alkylene group having 2 to 6 carbon atoms, R ² is a trivalent saturated hydrocarbon group having 2 to 6 carbon atoms, X is a hydrogen atom or trimellitic anhydride represented by the following formula [3]: And at least one of the Xs is a trimellitic anhydride residue. The coating composition according to claim 1, wherein the coating composition contains (D) fine silica in addition to the bisphenol type epoxy resin (A), the acid component (B), and the curing catalyst (C). A method of coating an inner surface of a two-piece can, comprising coating and then curing the can powder coating composition of claim 1 on an inner surface of the two-piece can. A method of coating a can body weld on an inner surface of a can, comprising coating and then curing the can powder coating composition of claim 1 on a can body weld on an inner surface of a can.