GB2290544A

GB2290544A - Powder coating composition

Info

Publication number: GB2290544A
Application number: GB9512858A
Authority: GB
Inventors: Shingo Harada; Keiji Inomata; Ichiro Yoshihara
Original assignee: Kansai Paint Co Ltd
Current assignee: Kansai Paint Co Ltd
Priority date: 1994-06-23
Filing date: 1995-06-23
Publication date: 1996-01-03
Anticipated expiration: 2015-06-23
Also published as: KR0178804B1; KR960001056A; GB2290544B; GB9512858D0; TW291492B

Abstract

A can powder coating composition contains (A) a bisphenol based epoxy resin having a melting point of 50 to 150 DEG C and an epoxy equivalent of 600 to 3,000, (B) an acid component having a melting point of 50 to 180 DEG C and an acid value of 40 to 550, and (C) at least one curing catalyst selected from the group consisting of choline chloride and organic carboxylic acid metal salt, an equivalent ratio of an epoxy group in the resin (A) to an acid group in the acid component (B) being in the range of from 2:1 to 1:2. Resin (A) may be a dimer acid - modified bisphenol A based epoxy resin or a dimer acid - modified bisphenol F based epoxy resin. (B) may be an ester component containing an acid anhydride group. Suitable salts (C) include tin, zinc and lithium salts e.g. tin 2-ethylhexanoate.

Description

Powder Coating Composition The present invention relates to a powder coating composition, e.g. for forming a film onto the surface of a can. It preferably relates to a powder coating composition capable of making a coating composition suitable for forming a film onto a can internal surface by selecting starting materials.

A can coating composition has been coated onto a metal can such as food cans, beverage cans and the like for the purpose of preventing metal eluation and can corrosion. The coating composition to be used may generally include a liquid coating composition prepared by dissolving or dispersing a resin such as epoxy resin, vinyl chloride resin or the like into a solvent.

Recently, since the use of the above liquid coating composition causes problems such as the organic solvent contained in the liquid coating composition volatilizing into atmosphere, resulting in atmospheric pollution, and migration of the organic solvent remaining within the coated film in the can internal surface into can contents causing hygiene problems, switching over to an environmental pollution free and solvent-free coating composition has been accelerated.

Since a conventional powder coating composition is such that starting materials unsuitable to be applied onto an internal surface of food can and beverage can from hygienic point of view are used, and further that it is impossible to obtain a coated film having good properties in smoothness of film surface, corrosion resistance and fabrication properties for can making by a short time curing process required from a can making line speed and from other steps, development of a powder coating composition suitable for a can internal surface coating composition which contacts directly with foods and beverages has been demanded.

Preferred embodiments of the invention may enable one to provide one or more of the following: a can powder coating composition which is capable of forming a coated film having excellent properties in film appearance, adhesion properties, fabricating properties, water resistance, curing properties, corrosion resistance, resistance to off flavor onto a can base material by a short time curing process; a can powder coating composition which is capable of forming a coated film which is free of residual solvent and is free of hygienic problem, even if directly contacted with food and beverage as a can internal film, by selecting starting materials.

a can powder coating composition which is capable of forming a coated film having excellent properties by preparing such a composition as to be free of foaming on curing and to be able to reduce residual stress in the case of repair coating on a side seam area; a can power coating composition which does not cause problems of environmental pollution due to volatilization of organic solvent on coating.

The present invention provides a powder coating composition containing (A) a bisphenol based epoxy resin having a melting point of 50 to isOt and an epoxy equivalent of 600 to 3,000, (B) an acid component having a melting point of 50 to 180t and an acid value of 40 to 550, and (C) at least one curing catalyst selected from the group consisting of choline chloride and organic carboxylic acid metal salt, an equivalent ratio of an epoxy group in the resin (A) to an acid group in the acid component (B) being in the range of from 2:1 to 1:2.

The bisphenol based epoxy resin (A) as a first embodiment is at least one epoxy resin selected from the group consisting of bisphenol A based epoxy resin and bisphenol F based epoxy resin.

The bisphenol based epoxy resin (A) as a second embodiment is at least one epoxy resin selected from the group consisting of a dimer acid-modified bisphenol A based epoxy resin and a dimer acid-modified bisphenol F based epoxy resin.

The acid component (B) is preferably an organic acid component containing, as a major 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]: X - 0 R 1 - I:13 or

where R' is a bivalent alkylene group having 2 to 6 carbon atoms, R2 is a trivalent saturated hydrocarbon group having 2 to 6 carbon atoms, X is hydrogen atom or trimellitic anhydride residual group represented by the following formula [3]:

provided at least one of Xs is the trimellitic anhydride residual group.

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

The present invention also provides a method of coating a two piece can internal surface, which method comprises coating a can powder coating onto an internal surface of the two piece can, followed by curing, said can powder coating composition containing the bisphenol based epoxy resin (A), the acid component (B), the curing catalyst (C), and preferably the finely powdered silica (D), said bisphenol based epoxy resin (A) being at least one epoxy resin selected from the group consisting of bisphenol A based epoxy resin and bisphenol F based epoxy resin.

The present invention also provides a method of coating a can body welded area of a can internal surface, which method comprises coating a can powder coating composition onto the can body welded area of the can internal surface, followed by curing, said can powder coating composition containing the bisphenol based epoxy resin (A), the acid component (B), the curing catalyst (C), and preferably the finely powdered silica (D), said bisphenol based epoxy resin (A) being at least one epoxy resin selected from the group consisting of a dimer acid-modified bisphenol A based epoxy resin and a dimer acid-modified bisphenol F based epoxy resin.

Detailed Description of the Invention: The bisphenol based epoxy resin (A) in the composition of the present invention has a melting point of 50 to 150t , preferably 80 to 120t and an epoxy equivalent of 600 to 3,000, preferably 900 to 2,000.

The resin (A) may be prepared by reacting epihalohydrin, bisphenol and, if needed, a modifier such as saturated aliphatic monocarboxylic acid, dibasic acid, polymerized fatty acid or the like. When the melting point of the resin (A) is lower than SOt, blocking of a powder coating composition may take place during storage. On the other hand, when higher than 150 t, I thermal flowability of the powder coating composition on heat curing becomes poor, resulting in making it impossible to obtain a smooth coated film.

When the epoxy equivalent of the resin (A) is less than 600, anti-blocking properties during storage becomes poor. On the other hand more than 3,000, thermal flowability of the powder coating composition on heat curing and corrosion resistance of the resulting coated film are undesirably reduced. The epihalohydrin may preferably include epichlorohydrin.

Examples of the bisphenols may include bis(4hydroxyphenyl)methane i.e., bisphenol F, l,l-bis(4- hydroxyphenyl)ethane, 2,2-bis (4-hydroxyphenyl)propane i.e., bisphenol A, 2,2-bis(4-hydroxyphenyl)butane, i.e., bisphenol B, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4hydroxy-tert-butyl-phenyl)-2,2-propane, p- (4- hydroxyphenyl)phenol, oxybis(4-hydroxyphenyl), sulfonylbis(4-hydroxyphenyl), 4,41 -dihydroxybenzophenone and the like. Of these, bisphenol A and bisphenol F are preferred to be used in the can internal surface from hygienic point of view.

Of the modifiers which may be used in the preparation of the bisphenol based epoxy resin, a dimer acid as a polymerized fatty acid is preferred from the standpoint of fabricating properties of the resulting The dimer acid may be one prepared by dimerizing an unsaturated higher fatty acid such as purified vegetable oil fatty acid obtainable from drying oils and semidrying oils. The unsaturated fatty acid may mainly include C18 unsaturated fatty acid, for example, linoleic acid, linolenic acid, oleic acid, etc. The dimer acid mainly contains the dimer of the above unsaturated fatty acid, but may contain other oligomers such as trimer, and monomeric fatty acid.

The chemical structure of the dimer acid may vary depending on the kind of monomeric fatty acid and polymerization process used, but is generally to be represented by one or more of the following formulas [4], (5], and [6]:

where R3 is CH3(CH2)t-, R4 is -(CH2)7COOH, and R5 is CH3(CH2)7-. The dimer acidsrepresented by the above formulas may all be used as the modifier.

Examples of commercially available products of unmodified resins among bisphenol based epoxy resin (A) may include Epikote 1002, Epikote 1003, Epikote 1004 and Epikote 1007 (trade name, marketed by Yuka Shell Epoxy Co., Ltd. respectively), Epiclon 1050, Epiclon 3050, Epiclon 4050, and Epiclon 7050 (trade name marketed by Dainippon Ink & Chemicals, Inc.

respectively), Epo Tohto YDF-2004 (trade name, marketed by Tohto Kasei Co., Ltd.), and the like.

Of the bisphenol based epoxy resin in the composition of the present invention, the dimer acidmodified bisphenol based epoxy resin may generally be prepared by reacting relatively lower molecular weight bisphenol based epoxy resin such as Epikote 828 (trade name, marketed by Yuka Shell Epoxy Co. Ltd.), Epikote 1001, Epikote 1002, Epikote 1003, Epikote 1004, etc.

with dimer acid, but may also be prepared by reacting (1) a dimer acid, (2) a condensate of bisphenol with epihalohydrin, and (3) bisphenol.

A dimer acid modification degree in the dimer acid-modified bisphenol based epoxy resin is preferably in the range of from 1 to 50% by weight, particularly 10 to 30% by weight on the basis of the modified epoxy resin.

The acid component (B) in the composition of the present invention is a component to act as a curing agent for the bisphenol based epoxy resin (A) and contains, as a major component, at least one selected from the group consisting of monoester compound and polyester compound having a melting point of 50 to 180t and an acid value of 40 to 550 respectively, and may be prepared by reacting a polybasic acid component, a polyhydric alcohol, and, if needed, monobasic acid and monohydric alcohol. The polyester compound may include diester oligomer, tri- or higher poly-ester oligomer, and polyester resin.

Examples of the polybasic acid component constituting the acid component (B) may include adipic acid, fumaric acid, maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, sebacic acid, trimellitic acid, trimellitic anhydride, dimer acid, and the like. These may be used alone or in combination.

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

Examples of the monobasic acid optionally constituting the acid component (B) may include benzoic acid, t-butyl benzoic acid, abietic acid and the like.

Examples of the monohydric alcohol optionally constituting the acid component (B) may include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and the like.

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

The acid component (B) preferably include an organic acid component containing, as a major component, the acid anhydride group-containing ester compounds represented by the above formula [1] or [2].

Specific examples of bivalent alkylene group having 2 to 6 carbon atoms and represented by R1 in the acid anhydride group-containing -ester compound represented by the above formula [1] may include groups such as ethylene, 1,2-propylene, trimethylene, ethylethylene, tetramethylene, hexamethylene and the like.

The acid anhydride group-containing ester compound represented by the above formula [1] may be an esterified product between alkylene glycol having 2 to 6 carbon atoms and trimellitic anhydride, and may include a compound obtained by esterifying between one hydroxyl group of two hydroxyl groups in the alkylene glycol and trimellitic anhydride and having one acid anhydride group, and a compound obtained by esterifying between two hydroxyl groups in the alkylene glycol and trimellitic anhydride respectively and having two acid anhydride groups.

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

Specific examples of trivalent hydrocarbon group having 2 to 6 carbon atoms and represented by R2 in the acid anhydride group-containing ester compound represented by the above formula [2] may include groups such as 1,2,3-propanetriyl, 1,2,3-butanetriyl, 1,2,6- hexanetriyl and the like.

The acid anhydride group-containing ester compound represented by the above formula [2] may be an esterified product between trihydric alcohol having 2 to 6 carbon atoms and trimellitic anhydride, and may include compounds obtained by esterifying between one hydroxyl group, two hydroxyl groups or three hydroxyl groups of three hydroxyl groups of the trihydric alcohol and carboxyl group of trimellitic anhydride .respectively, that is, compounds having one acid anhydride group, compounds having two acid anhydride groups and compounds having three acid anhydride groups.

Examples of the trihydric alcohol having 2 to 6 carbon atoms may 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 above organic acid component of the present invention contains, as a major component, the acid anhydride group-containing ester compound represented by the above formula [1] or [2], but may contain other organic acid, for example, an ester group-free organic acid in an amount of 50y by weight or less, preferably 30y by weight in the organic acid component. An example of the ester group-free organic acid may include trimellitic anhydride, which remains as an unreacted reactant in the case where the acid anhydride groupcontaining ester compound is prepared by the esterification reaction between alkylene glycol or trihydric alcohol and trimellitic anhydride.

The acid component (B) is most preferably one containing such a compound that Rl is ethylene group and it has two acid anhydride groups, in an amount of 60% by weight or more in the acid component (B) from a standpoint of balance between curing properties and fabricating properties of the coated film.

Choline chloride having a chemical formula: tHOCH2CH2N(CH3 )3 ]+ Cl- or organic carboxylic acid metal salt constituting the component (C) in the composition of the present invention respectively acts as a curing catalyst of the reaction between the above bisphenol based epoxy- resin (A) and the above acid component (B).

It is necessary for the curing catalyst in the powder coating composition of the present invention to satisfy the following requirements. That is, it is necessary for the curing catalyst that a reaction rate between the epoxy resin (A) and the acid component (B) is at a low level during the respective components of the coating composition are melt blended usually at 50 to 160t, but such a reaction rate that curing by high temperature and short period of time curing, i.e., usually under the conditions of 160 to 35out and 7 to 180 seconds takes place satisfactorily, is obtained, and that such a reaction rate that a curing reaction hardly takes place during storage at room temperature, is obtained.When applied to the can internal surface, no hygienic problem is caused by remaining in the coated film directly contacting with food or beverage.

The organic carboxylic acid metal salt constituting the component (C) preferably include metal salts of fatty acid having 5 or more carbon atoms.

Specific examples thereof may include tin 2ethylhexanoate, zinc 2-ethylhexanoate, tin laurate, lithium stearate and the like. Of these, tin 2 ethylhexanoate is preferred.

A mixing ratio of the bisphenol based epoxy resin (A) and the acid component (B) in the composition of the present invention is such that an equivalent ratio of an epoxy group in the resin (A) to an acid group in the acid component (B) is in the range of from 2:1 to 1:2, preferably 1.3:1 to 1:1.6. When outside the above range, curing properties becomes unsatisfactory, and adhesion to the can body, fabricating propertes, water resistance, corrosion resistance, resistance to off flavor, etc. are undesirably reduced. The equivalent of the acid group in the acid component (B) is calculated as such that one mole of acid anhydride group corresponds to 2 equivalents, and one mole of carboxyl group corresponds to one equivalent.

A mixing ratio of the choline chloride or the organic corboxylic acid metal salt constituting the component (C) in the composition of the present invention may not particularly be limited, but is usually in the range of 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight from the standpoints of catalyst effect, and smoothness and water resistance of the resulting coated film, per 100 parts by weight of a total amount of the bisphenol based epoxy resin (A) and the acid component (B).

The composition of the present invention may essentially consist of the bisphenol based epoxy resin (A), the acid component (B) and the choline chloride or organic carboxylic acid metal salt as the component (C), but, if needed, may contain in a small amount known film surface modifier, solid waxes, color pigments, extender pigments, modified resins having a melting point of 50 to 150t , and the like. Addition of finely powdered silica as the extender pigment may advantageously improve flowability of the coating composition powder.

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

The powder coating composition of the present invention may be prepared, for example, by a process which comprises melt blending respective components constituting the composition of the present invention by use of a kneader or extruder under such temperature and time conditions that thickening and gelation may not take place, usually at 50 to 160t for 3 to 60 seconds, followed by cooling, grinding, and screening to obtain a powder coating composition having an intended particle distribution.

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

Examples of metal material constituting a can to coat the powder coating composition of the present invention may include untreated steel sheet, tin plated steel sheet, zinc plated steel sheet, chrome plated steel sheet, phosphate treated steel sheet, chromic acid treated steel sheet, untreated aluminum sheet, chromic acid treated aluminum sheet and the like. Coating of the coating composition of the present invention onto the metal material may be carried out, for example, by the electrostatic coating process, followed by heat curing at about 160 to 350t for about 7 to 180 seconds, and drying to form a cured coated film.

The powder coating composition of the present invention may be used for coating onto both can internal surface and can external surface.

Examples of coating onto can internal surface and can external surface, may include coating onto both internal surface and external surface of two piece can and three piece can, coating onto a metal sheet constituting a can body and can cap, repair coating of a can body welded area or side seam area on the can internal surface, which is formed by cutting a coated metal sheet, folding both ends, and welding, and the like.

Use of at least one resin selected from the group consisting of bisphenol A based epoxy resin and bisphenol F based epoxy resin as the bisphenol based epoxy resin (A) makes it possible to provide hygienic problem-free starting materials, along with good can internal surface coating properties and good fabricating properties, and makes it possible to obtain a composition suitable for coating the internal surface of two piece can.

The powder coating composition of the present invention may be coated as such that a cured film thickness is in the range of 2 to 2film in the general area of the can internal surface and can external surface, and is in the range of 30 to 100g m on repair coating of the side seam area to sufficiently coat a difference in level due to welding.

It is preferred for the repair coating of the side seam area to use a composition capable of reducing residual stress due to thick film, that is, to use, for example, at least one epoxy resin selected from the group consisting of dimer acid modified bisphenol A based epoxy resin and dimer acid modified bisphenol F based epoxy resin as the bisphenol based epoxy resin (A).

The present invention provides a can powder coating composition which is capable of forming a coated film having excellent properties in film appearance, adhesion properties, fabricating properties, curing properties, corrosion resistance, resistance to off flavor onto a can base material by a short time curing process.

The present invention provides a can powder coating composition which is capable of forming a coated film which is free of residual solvent and is free of hygienic problem, even if directly contacted with food and beverage as a can internal film, by selecting starting materials.

The present invention provides a can powder coating composition which is capable of forming a coated film having excellent properties by preparing such a composition as to be free of foaming on curing and to be able to reduce residual stress in the case of repair coating on a side seam area.

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

The present invention will be explained more in detail by the following Examples and Comparative Examples, in which part and "%" are represented by weight.

Preparation of dimer acid-modified epoxy resin: Preparation Examples 1-3 Epikote 828EL (marketed by Yuka Shell Epoxy Co., Ltd., bisphenol A based liquid epoxy resin, epoxy equivalent: about 190), bisphenol A and dimer acid were formulated as shown in Table 1, followed by adding a catalyst, heating at 150 C under nitrogen atmosphere, and keeping at that temperature and reacting until an acid value is reduced to substantially zero to obtain respective dimer acid-modified epoxy resins. Table 1

Formulation of starting materials (part) Dimer acid-modified epoxy resin Epikote 828EL Bisphenol A Dimer acid* Epoxy equivalent Melting point Abbreviation ( C) of product Preparation 56.5 18.5 25.0 about 1400 about 80 Dimer 1400 Example 1 Preparation 58.0 23.3 18.7 about 1800 about 100 Dimer 1800 Example 2 Preparation 59.3 23.2 17.5 about 1900 about 105 Dimer 1900 Example 3 * The dimer acid is a product prepared by dimerizing unsaturated higher fatty acids mainly consisting of C18 unsaturated fatty acids (purified vegetable oil faty acid) and has a composition containing 0.1% by weight or less of a monomer component, about 87% by weight of a dimer component and about 13% by weight of a trimer component, an acid value of 195 mg KOH/g and a viscosity of 6100 cst/25 C.

Preparation of Can Powder Coating Composition Example 1 A mixture of 100 parts of Epikote 1004 (trade name, marketed by Yuka Shell Epoxy Co., Ltd., bisphenol A based epoxy resin having an epoxy equivalent of about 920 and a melting point of 97t, in the following Tables 2 and 3 referred to as Use1004), 11 parts of Rikacid TMEG 200 (trade name, marketed by New Japan Chemical Co., Ltd., an organic acid component containing 95% or more of an acid anhydride groupcontaining ester compound which is such an esterification product between ethylene glycol and trimellitic anhydride that in the above formula [1], R is ethylene group, and both Xs are trimellitic anhydride residual group, acid value: about 547, in the following Tables 2 and 3, referred to as "TMEG 200"), one part of choline chloride, one part of MODAFLOW (trade name, marketed by Monsanto Co., Ltd., surface control agent), and 0.4 part of Carplex FPS 500 (trade name, marketed by Shionogi & Co., Ltd., finely powdered silica, in the following Tables 2 and 3, referred to as "FPS 500") was dry blended, followed by melt blending in Buss Ko-Kneader PR46 (trade name, marketed by BUSS Co., Ltd., Switzerland), cooling, grinding and screening to obtain a powder coating composition having a particle distribution of 5 to 60 A m and a mean particle size of about 30 m.

Examples 2-12 and Comparative Examples 1-6 Experiments were carried out in the same manner as in Example 1 except that formulations of starting materials were as shown in the following Table 2 to obtain respective powder coating compositions having a particle distribution of 5 to 60 m and a mean particle size of about 30 m.

Examples 13-20 and Comparative Examples 7-12 Experiments were carried out in the same manner as in Example 1 except that formulations of starting materials were as shown in the following Table 3, and that such grinder and screen classifier as to obtain a powder coating composition having a particle distribution of 1 to 30 m and a mean particle size of about 15 m were used to prepare respective powder coating compositions.

Example 21 Experiments were carried out in the same manner as in Example 1 except that 0.2 part of tin 2ethylhexanoate in place of one part of choline chloride was used and that 0.5 part of Carplex FPS500 in place of 0.4 part thereof was used to obtain respective powder coating compositions having a particle size distribution of 5 to 60 m and a mean particle size of about 30 m.

Examples 22-32 and Comparative Examples 13-18 Experiments were carried out in the same manner as in Example 21 except that formulations of starting materials were as shown in the following Table 4 to obtain respective powder coating compositions having a particle distribution of 5 to 60 m m and a mean particle size of about 30 m.

Examples 33-40 and Comparative Examples 19-24 Experiments were carried out in the same manner as in Example 21 except that formulations of starting materials were as shown in the following Table 5, and that such grinder and screen classifier as to obtain a powder coating composition having a particle distribution of 1 to 30 m m and a mean particle size of about 15iem were used to prepare respective powder coating compositions.

In Tables 2 to 5, (Note 1) to (Note 6) are as follows (Note 1) YDF2004: Bisphenol F based epoxy resin, marketed by Tohto Kasei Co., Ltd., Trade name flEpo Tohto YDF2004", Epoxy equivalent: about 1,000, melting point: 85 t.

(Note 2) TMTA-C: Trade name: Rikacid TMTA-C, marketed by New Japan Chemical Co., Ltd., a total acid value: about 530, an organic acid component containing about 40% of an acid anhydride group-containing ester compound which is such an esterification reaction product that R2 in the above formula [2] is 1,2,3-propanetriyl group, and that two Xs of three Xs are trimellitic anhydride residual group, about 28% of such an acid anhydride group-oontaining ester compound that three Xs in the above formula (2) are all trimellitic anhydride residual group, and about 23% of trimellitic anhydride.

(Note 3) HT3380: Trade name: UHARDENER HT3380", marketed by Ciba Geigy Co., Ltd., Total acid value: about 550, An organic acid component containing a major amount of such an acid anhydride group-containing ester compound that R1 in the above formula [1] is ethylene group, and two Xs are both trimellitic anhydride residual group, and a small amount of such an acid anhydride groupcontaining ester compound that one of two Xs in the above formula (1] is trimellitic anhydride residual group, such an acid anhydride group-containing ester compound that R2 in the above formula [2] is 1,2,3propanetriyl group, and trimellitic anhydride respectively.

(Note 4) E1001: Trade name: "Epikote 1001n, marketed by Yuka Shell Epoxy Co., Ltd., Bisphenol A based epoxy resin having an epoxy equivalent of about 475 and a melting point of about 70t.

(Note 5) CC314: Trade name: "CRYLCOAT 314", marketed by UCB Co., Ltd., U.S.A., Polyester resin having a melting point of about 100t and an acid value of about 70.

(Note 6) GV340: Trade name: "U-PICA COAT GV340", marketed by Japan U-pica Co., Ltd., Polyester resin having a melting point of about 126t and an acid value of about 34.

Performance Test Coated test plates were prepared according to the following preparation method (1) for the purpose of testing application properties of powder coating compositions obtained in Examples 1-12 and 21-32, and Comparative Examples 1-6 and 13-18 to repair coating onto the side seam area in the can internal surface.

Preparation method (1) of coated test plates Respective powder coating compositions obtained in Examples 1-12 and 21-32, and Comparative Examples 1-6 and 13-16 were subjected to electrostatic coating onto a &num;25 tinplate to be a dry film thickness of about 45 icm, followed by heat curing at 240 C for 15 seconds to obtain respective coated test plates.

Coated test plates were prepared according to the following preparation method (2) for the purpose of testing application properties of powder coating compositions obtaiiied in Examples 13-20 and 33-40, and Comparative Examples 7-12 and 19-24 to coating onto a can body internal surface of two piece can, etc.

Preparation method (2) of coated test plates Respective powder coating compositions obtained in Examples 13-20 and 33-40, and Comparative Examples 712 and 19-24 were subjected to electrostatic coating onto a &num;25 tinplate to be a dry film thickness of about 15, m, followed by heat curing at 215"C for 60 seconds to obtain respective coated test plates.

Respective coated test plates obtained by the preparation methods (1) and (2) of the coated test plate were tested on film appearance, gel fraction, fabricating properties, water resistance of fabricated part, water resistance of general area, adhesion properties and adhesion properties after water resistance test according to the following test methods.

Test Methods Film Appearance: Observations on the surface of the film are made by the naked eye. Evaluations are made according to the following criteria.

o : Coated surface is wholly smooth, and no foaming is observed.

A : Some unevenness is observed all over the coated surface, and small foams are observed.

X : Some unevenness is observed all over the coated surface, and large foams are observed.

Gel Fraction A coated test plate having a weight of W2 was placed into a flask, followed by adding methyl ethyl ketone in such an amount that a ratio of methyl ethyl ketone (ml) ) to coated area (cm) of the coated test plate is lOOwE to 100CD!, carrying out extraction for one hour under heat refluxing, removing the coated test plate, drying at 120 C for 30 minutes, cooling down to room temperature, and measuring a weight of W3.Taking a weight of the tinplate prior to coating a coating composition as W1, gel fraction (%) was determined by the following equation: Gel fraction= {(W3-W1)/(W2-W1)} X 100(%) Fabricating Properties: Coated test plates folded in two with the coated surface outside are placed at the bottom of a specially folded Du Pont impact tester, and a 1kg iron weight having a smooth contacting surface is allowed to fall down from a height of 50cm to measure length of cracks developed on the film in the folded part. Evaluation of fabricating properties is carried out as follows.

Qo : Less than 5mm 0: 5 to less than 1Omm A : 10 to less than 20mm x: 20 mm or more Water Resistance of Fabricated Part The coated test plates, which have been subjected to the fabricating properties test, were dipped into a hot water at 125"C in an autoclave for 35 minutes, followed by removing, and measuring length of cracks developed. Evaluation was carried out in the same manner as in the above fabricating properties test.

Water Resistance (general area) The coated test plates are dipped into deionized water, followed by subjecting to a pressurized boiling water treatment at 125t for 35 minutes in an autoclave, and measuring a degree of whitening of the coated film.

Evaluation was made as follows.

: : No whitening of the coated film is observed.

o : Slight whitening of the coated film is observed.

A: Some whitening of the coated film is observed.

X : Serious whitening of the coated film is observed.

Adhesion Properties: Squares are formed by effecting 11 cuts in length and width at about 1.5mm intervals on a coated film of the coated test plate by use of a knife. An adhesive cellophane tape having a width of 24mm is adhered to the squares, followed by strongly peeling the tape to observe the adhesion properties of the squares.

Evaluation was made as follows.

o : No peeling is observed.

A : Some peelings are observed.

X : Marked peelings are observed.

Adhesion Properties After Water Resistance Test The coated test plates are dipped into deionized water, followed by subjecting to a pressurized boiling water treatment at 125t for 35 minutes in an autoclave, and forming squares by effecting 11 cuts in length and width at about 1.5mm intervals on a film by (ft) use of a knife. An adhesive cellophane tape having a width of 24 mm is adhered to the squares, followed by strongly peeling the tape to observe the adhesion properties of the squares and to evaluate as in the above adhesion properties test.

Preparation of Can Body for Corrosion Resistance and Resistance to off flavor Tests: Preparation of Can Body With Repair Coating onto Side Seam Area in the Can Internal Surface: A solution type epoxy-phenol resin coating composition for use in the can internal surface was coated to be a dry film thickness of Siam onto a &num;25 tinplate except for an extra margin for welding, followed by heat curing to obtain a cured film.

The resulting coated tinplate was welded with a can body for use in a three piece can, followed by subjecting respective powder coating compositions obtained in Examples 1-12 and 21-32, and Comparative Examples 1-6 and 13-18 to electrostatic coating onto a welded area on the internal surface of the resulting welded can body with a dry film thickness of about 45 pm m and a coating width of about 15 mm, and heat curing at 2404C for 15 seconds to obtain a can body with repair coating.

Preparation of Can Body of Two Piece Can Respective powder coating compositions obtained in Examples 13-20 and 33-40, and Comparative Examples 7-12 and 19-24 were subjected to electrostatic coating onto an internal surface of a 250sQ steel two piece can to be a dry film thickness of about 15 m, followed by heat curing at 21sot for 60 seconds to obtain a can body of the two piece can.

The above can body with repair coating and the above can body of two piece can were charged with the following liquid samples respectively, followed by rolling and molding to be subjected to the following corrosion resistance and flavor retention properties tests. In the case of the can body with repair coating, both upper and lower caps were rolled and molded, and in the case of the can body of two piece can, the upper cap was rolled and molded.

Corrosion Resistance The can body with repair coating and the can body of two piece can were hot packed with a 10% pine juice at 98t to be rolled and molded respectively, followed by storing at 37t for 6 months, opening the can, and examining corrosion on the internal surface.

Evaluation was made as follows.

o : No corrosion is observed.

A : Corrosion is slightly observed.

x: Remarkable corrosion is observed.

Resistance to off flavor The can body with repair coating and the can body of two piece can were charged with 250d of water prepared by treating tap water with active carbon and rolled to be sterilized at 125"C for 30 minutes, followed by being stored at 37c for 6 months and by being subjected to flavor test. Evaluation was made as follows.

o : No change is observed.

#: Some changes are observed.

X : Marked changes are observed.

Table 2

Examples eq o - --l o omoo o oo oo oo E1004 100 100 100 100 -- (Note 1) 100 100 Diner 1400 100 100 100 100 - oo -s 1900 o oN 0 0 0 8 0 o TMEG200 11 1.3 11 2.2 11 2.2 8 1.6 11 o S~S TgTA-c (Note t 9.7 8.8 8.8 11 6.4 HT3380 (Note 3) 11 11 o m anhydride Choline chloride 1 1 1 1 1 0.5 1 1.5 1 1 1 1 MODAFLOW 1 1 1 1 1 1 1 1 1 1 1 1 0 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Epoxy group/Acid group 1.0 1.0 1.0 o 1.0 Ot 0 00 00 0.7 0.7 O0 Vlrtt- ratio) Film appearance o c U%~o 0 0N out 0 0 0 0 0 O0 Gel fraction (%) 95 92 90 95 95 94 93 92 91 93 92 95 m o eqe: 0 0 0 0 0o 0 0 0 o, resistance of 0 0 0 0 0 0 0 0 0 0 0 0 E U%4 F Water resistance eo ~ 0 0 04 tO O 00 00 O0 (general area) Test items Adhesion properties 0 0 0 0 0 0 0 0 0 0 0 0 1 t o Adhesion ~~o' O 0 0 0 0 0 0 0 0 0 O 0 after water resistance test ;;t resistance 0 0 0 0 0 0 0 0 0 0 0 0 t ~ ~ ~~o' to off 0 0 00 00 O0 flavor Powder flowability 0 = ~~o' ~ 0 O 00 0 00 00 O0 o storage 0 0 0 0 0 0 0 0 0 0 0 0 . ntS O es ~o ~~o ~ 0N 00 0 00 O0 O0 o 0 ~ ~~o' ~ O en 00 0 00 00 O0 ~ e 4 o ~ n h h O o C > > e tf) tD P. e) O X h v X &commat; - &commat; < t ; , O 04 0 h fz tq Cq O -{ z O O C h h C D o & h X O = bO O O O ~I :1 C ~I C ,1 t vI C G G h f S ho o o 4L o o ex X &commat; < X o H 4 Q 4 ~ ~ O ~i ~ bOl F 4 h 4) h O 0 3 C X t O O tt O ~{ C a O P AS h O O h h h h :t O h h e ~1 X O I h ~I h UE tQ h O UX O ~ Cl I : h O n tE O 0 - 4 oh a) 30 O acx Ez cz:zz s X c: > c < : 4 O a;o X X ffi gl h X &commat;,≈ < Y ~I 4 o X &commat; O Ew Table 2 (cont.)

1 2 8 4 5 8 El 004 100 100 100 c3u (Note 1) Diner 1400 100 100 El 001 (Note 4) 100 m =s o TVEG200 25 5 21.5 3.3 materials TVTA-C (Note 2) 13.2 11T3380 (Note 3) Trimellitic anhydride 7 4.5 s cc O x x X X o o X < o ~ 1 1 1 1 1 1 FPS500 0.4 0.4 0.4 0.4 0.4 0.4 Epoxy group/Acid group 1.0 0.45 2.2 1.0 1.0 0.45 (equivalent ratio) U1 appearance =t A 0 0 A Gel fraction x 94 99 51 97 93 99 uZ properties x x K A K K Water resistance of X K K K K K x part 4Z ~ ~ h . 4 VJ Test items Adhesion < - d K A < < A < o z o o properties K K A K K K after water resistance test Corrosion resistance A A K A A A Resistance to off 0 K A A 0 K s =It O N ~ .

Powder storage 0 A 0 K 0 A properties ~e w X c 4 n h h O h v 0 9 SP D C C > > C ,1 > D 4) 4Z 4 $ : c .a 4X e 0s o o o h h tn O I Z Z Z Z O h C C ffi 4 4 > h ss ffi h aX &commat; D tD O ~. h~I ffi 0 4Z e a = = O = X X < O el 41) 0 O ~I e O o bD El h e) h h D'1 X h O 4 0 h é h o Dk E o Ed d o a X o H H D 4) D 4 C s X h X11 3 5 O i > < a iii < = s e d -a < X h tDX O 4 h X : &commat; O &commat; Table 3

Examples - --- oe E1004 100 - o X 100 0000 c\l O ,,I El 001 (Note 4) u\ TV.E0200 11 1.3 8.5 1.7 11 materials TTA-C (Note 2) 9.7 6.8 8.5 HT3380 (Note 3) 11 8.5 Trimellitic anhydride 0 MODAFLON 1 1 1 1 1 1 1 1 FPS500 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Epoxy group/Acid w F (equivalent 900000000 Film appearance 0 00 -c0 0 Gel fraction ('6) 98 96 95 97 97 93 94 98 F o F ~~e oF 0Foo 0 Q, O 0 0 0 0 O0 Water resistance of ~ 0 0 0 0 0 0 0 UI part Water -- ----- m ~ > x area) Test items 00QO properties 0 0 0 0 0 0 0 0 O properties 0 0 0 0 0 0 0 0 after water resistance test t resistance O 0 0 0 0 0 0 0 - g ~ ~~0 to off 0 0 0 0 o o o 0 ~ ~ Powder flowability 0 0 ≈ 0 0 Powder storage 0 o " 0 0 0 0 0 0 0 0 8 0 n o ~ ~~e ~ 0000 0 00 00 O0 .0 e c e ~ ^~ 43 v eo ffi o :t tZJ n h ~ h O e X e 4z c > .

g O ~ h v 0 W 4 X tD tD > . e % o e e 43 4zç ç v Z Z X h h Ct t tD tD ~I D hD O w o ~ = C h O txz sn . Wq ec h h h h X 3 h o o H Zo b Z 04 45 ha4 e S Oc o n e O O O ~I C a O P h O O v h h h h O fi U S) É X 0m gI E h o e ffi é h e > a e ffi 0 {30 fflEstO~I ODbJ2 O v ~I ~I D 4JD 4Z C 54Z h tl} 3 3 0 3a i w > SS X < e X = X > < X ~ o o h s: :~ x e &commat; o ~~ b Table 3 (cont.)

ur Examples 7 8 9 10 11 12 El o 100 100 100 Dimer 1800 a x o a El m (Note w O Starting O Epoxy group/Acid group 1.0 0.45 2.2 1.0 1.0 0.45 ~ ~ Film appearance 0 A A 0 0 A Gel fraction (,') 96 99 55 94 99 Fabricating properties o x x A x x X ~ X X ~ Water resistance ----- ---- 0 0 Ea h Test items 4 O properties x x x < < x < x x after water resistance test 1 resistance A A x A A A t t flavor o Q x x O x x Q x Q d o cu Powder storage 0 A 0 x 0 A s o ~ O > ~~= ~ o ç o o X a o o o O UX X D O O t ,l ~ C X ~% oS~-d 4Z 0 d O t esl m) h ~ h O X e tD 4 C :4 Ç X X > e O & X h X 9 4 &commat; = t ç " O 0 0 h h a {Q O I O O O C ~{ O v~ h C h C ~I e X X 2 Z Z h h C 0 ffi ffi h X O D bO ç vv O C 4 h O O X 4t O ~I 0.4Z h O t!1 tO X tD h h h h 3 h o s C fd c +e ,4 c oe nze e o ola o 4 0 o e e 4 a: 0 a o 4 C O H 4 ] ~s > hI v 0 4 X tYI C C O C X X ~ ~ O ~I tss O tSJ td h h O 0 3 &commat; 1 45 O tD O ~I C < 10 P h O O t1 v h h h h t h ~ Cvl I e tD ~l lS O a o +, o ,1 h r/l aa h O tO O e e X O dJ O e l ct: n E ~{ ee 1n t1 CX E h X h tl) til tlZ h H P t t D.

O E O a: I o a X o cr H H D 4 D 4s C C 4Z al h la 3 :r o ~ .rt ~ F h C O to < : O -1 e fd -a a o 6 o e < o o h kl=fd Ez C):X :S X e:s X 3qz ; &commat; C) C h &commat;d > W 4 o X h e O 4N g nF 13 X Es Table 4

Examples 21 22 23 24 25 26 27 28 29 30 31 32 E1004 100 100 100 100 '1DF2004 (Note U Q 100 Diner 1400 100 100 100 100 Dimer 1900 100 100 ~ ow O TMEG200 11 1.3 11 11 2.2 8 10 0e O eq ~o O TMTA-C o o 2) 9.7 8.8 ~ (Note t ST 80 ~.

eq u t i" 1 1 1 1 1 1 1 1 1 1 1 1 cu 0.5 0.5 1.0 0.5 O 0.5 O O O O O o o (equivalent ratio) Film 090000 0 u 0 0 0 0 0 0 0 00QO Gel fraction (%) 93 92 F tl} Properties O 0 ≈ O O O O O O O O O O ~ ~ Water resistance of ~ 0 ≈ ≈ ≈ ≈ 0 0 0 0 (d part Water t0 O ~ 0~0 ≈ ≈ 0 ≈ 0 ≈ ≈ 0 0 0 0 0 ~ area) 000 o properties O 0 0 O s e o O O o0 after water resistance test o resistance 0 0 0 0 0 0 0 0 0 0 0 0 O to off o O 0 0 0 0 0 0 0 0 0 0 000 flowability Q 0 0 0 0 0 0 0 0 0 0 0 Powder C*l 0 0 0 uw o o dc O 0 0 8 0 0 0 0 8 0 o cq ue O evi ~ ~ 0~0 ~ O n O O o O O O O O O e o C X ~ ~^ &commat; &commat; v IX a o ~ eq uw ~ f O e e e 4Z c > l O O O h &commat; I Yl X 4v e e e c % c e e 45 4) 4 4) 5 tU d; O 0 4 b 0 h h 90 til O ~I Z vv X h td C 45 D, 41 h D tC oOoO ,P. o e é bO ee ga a ffi g h hC 4t a e &commat; S: Fe H O. O &commat; e 4] e bO C C O C v e =t ~ ~ I Cl 0 m D ttl h h O 0 3 X &commat; g < h h h t O h h CJ I =1 CQ W 0 XI E o é h é é e a &commat; h Ul g aa a & BR< O W E e az c a tQ o G ~I ~I D &commat; D 4) C C 4) fi h Ul tt 3 3 0 ~0+ : -IOG < : a a cs sso a o ee o o h swacz Ez Es- Ò k. x 4Z G tD < o e 4X h X 4X o: W Ez Table 4 (cont.)

- - - OQ=t El -: o 100 x x x x x x x o o - 100 El 001 (Note 4) 100 Starting TMEG2OO 25 5 21.5 materials CC314 (Note 5) 126 GV340 (Note 6) 179 118 Tin 2-ethylhexanoate d x x o O 1.0 0 'O x 1 1 1 1 1 ~ ~ < t O Fabricating properties o e c X a ~ Water resistance x 0 x A x x ca k Test items Adhesion < A x A A QQ )c Oc0 properties A x A x A x after water resistance test Corrosion resistance x A x x x x cu to Iat 9 o dd d x x x O x x Q x &commat; a ~ flowability C C ~ storage ~ A 0 x 0 0 OUN O e F ~~ O w x x x a a x x O o ~ ~^ 4v 4t o o m o -t U%4O O h O a a e4 C o 4z a a a c w cb a e 4X O O O X O v 2 c h $~I oe ha a al o < a Z Z e h C 0 0l 0&commat; h ffi O tCl ~S ~v C C 4Z h O O a 4 > O P. :n C h < CM e t a C 0e v a h a 3 ho t s3 0R a a 40Z tR bO C C C H &commat; a ~ o e o Wt ffi h h O 0 3 4 =t h ~ 71 t O evl X O s I h O O Z 10 h é a h o e o u ~ t e u :s E h e h a a a a X h l > O E O ts to X c a en o H H D 4 S C 4Z tn h t0 3 3 0 ~ < ~ F0 > E XX s e Ex U ::UK 3 t ea cz mZ ffi ffi o C < > 4Z h 4 0F 4 4 X X Z E Es Table 5

o o Starting TWEG2OO TTA-C (Note 2) materials CC31 (Note 5) 87 0 30 87 Tin 2-ethylhexanoate 0.2 0.2 1.0 0.2 0.2 1.0 O 1.0 MODAFLOW 1 1 1 1 1 1 1 FPS5OO 0.5 0.5 1.0 0.5 0.5 0.6 0.8 Epoxy group/Acid group 1.0 1.0 1.0 O O O o O m o m cco c File appearance 0 0 0 0 0 0 0 0 Gel > so (%) N 96 89 95 92 87 85 89 r) properties 0 0 0 0 o O 0 0 0 o O 0 Water resistance of 0 0 0 0 0 0 0 0 E ~ .

Water resistance 0 0 0 0 0 0 0 0 W m cmc (general 0 0 8 0 o Adhesion properties 0 0 0 0 0 0 0 0 after water resistance test Corrosion resistance Q O 0 0 0 O O O O to off 0 0 0 0 0 0 0 0 flavor (3 flowability 0 0 O Powder storage 0 0 0 Q O 0 0 0 o 0 o e o ~ 0~0 ~ o m O O O O O O O o O o~ 4X 4Z v ~ c evl 1 t11 h O e e e 4 c > W a a o a a a &commat; 4) 4Z 4Z 43 a O O &commat; O h h ttl tll O ~I ~v Se h 3 C ffi 4 oD a he a $ ~I O&commat;J h O bgl XS Yl a h h h h 3 h s ol 9 a 4Z C -e Z 9 A D84 C 4 é 4J a h ol 0s 0 4Z a 45 e tss c c o c q ~ Oo O e o O tlD &commat; h aI h O 0 3 u 4a h ; h h -t h el I -t ev o t~1 v v h 0 tQ h O a O e e e o a cs c ~ < : tn = E h E1 h a a a a 4 h 1 t sa O E SIX C) CoCq o a H oel D - C a é aH 2 azo E"E D E XDi s~ X = SX 3 < < h O zqs X ffi ffi 2 C b: 4 JJ h X ~I h a o 4) 4 &commat;0 X s zQ E Table 5 (cont.)

3 e m rc N P01 b y ta 3 w 10 11 12 E1004 100 100 100 m,g p yarp" a r z 0zo3 wwm 100 El 001 (Note m O e e < c o 100 " " "" E9 8 " m cb 3 o IP 3 X 3 e (D w 0 9 O 5 O W N0 X a v 3 25 cF Qq 00 5 b D O O fi e b CC314 ^&num;~ 169 98 GV34O (o o o 1 30 3 a 179 92 Tin O Z N N O e 3 em 0.2 1.0 1.0 1.0 ODAFLOW W 1 F 1 1 1 D O N w OWUI r O 1.5 0.5 W p FW y e s o (D DD 1 ;;I o Fabricating properties fabricated part Water resistance x A x A x x IU O D items Adhesion o A x A x A x nlu properties A x A A A x after water resistance test 1 resistance x x x A x x Resistance to off x x A A x x tn N v Powder flowability Oo . fD o b x o D D D D D D O O ~ ,o. &commat; o o tn o tss oO xx p x xxfflo -w N o O x x x x x D P D ' r o ~ wn ~

Claims

CLAIMS 1. A powder coating composition containing (A) a bisphenol based epoxy resin having a melting point of 50 to 1 50G and an epoxy equivalent of 600 to 3,000, (B) an acid component having a melting point of 50 to 1 80it and an acid value of 40 to 550, and (C) at least one curing catalyst selected from the group consisting of choline chloride and organic carboxylic acid metal salt, an equivalent ratio of an epoxy group in the resin (A) to an acid group in the acid component (B) being in the range of from 2:1 to 1:2.
2. A coating composition as claimed in claim 1, wherein said bisphenol based epoxy resin (A) is at least one epoxy resin selected from the group consisting of bisphenol A based epoxy resin and bisphenol F based epoxy resin.
3. A coating composition as claimed in claim 1, wherein said bisphenol based epoxy resin (A) is at least one epoxy resin selected from the group consisting of a dimer acid-modified bisphenol A based epoxy resin and a dimer acid-modified bisphenol F based epoxy resin.
4. A coating composition as claimed in claim 1,2 or 3 wherein said acid component (B) is an organic acid component containing, as a major component, at least one ester compound selected from the group consisting of acid anhydride group-containing ester compounds represented by the following formula [I ] or .E2]:

where R' is a bivalent alkylene group having 2 to 6 carbon atoms, R2 is a trivalent saturated hydrocarbon group having 2 to 6 carbon atoms, X is hydrogen atom or trimellitic anhydride residual group represented by the following formula [3):

provided at least one of Xs is the trimellitic anhydride residual group.
5. A coating composition as claimed in any preceding claim wherein said coating composition, in addition to the bisphenol based epoxy resin (A), the acid component (B) and the curing catalyst (C), contains (D) a finely powdered silica.
6. A powder coating composition substantially as herein described with reference to and as exemplified in the examples herein, excluding those examples designated 'Comparative Examples'.
7. A method of coating a two piece can internal surface, which method comprises coating the powder coating composition of claim 2, or claim 4 or claim 5 as appendant on claim 2, onto an internal surface of a two piece can, followed by curing.
8. A method of coating a can body welded area of a can internal surface, which method comprises coating a powder coating composition of claim 3, or claim 4 or claim 5 as appendant on claim 3 onto the can body welded area of the can internal surfce, followed by curing.
9. A method of coating substantially as herein described with reference to and as exemplified in the examples herein, excluding those examples designated 'Comparative Examples'.