JP5116784B2 - Coating composition and method for producing painted metal can - Google Patents

Description

  The present invention can be cured by using ultraviolet irradiation and post-heating in combination, and is excellent in coating performance such as processability, adhesion, hardness, scratch resistance, etc., especially in coating appearance, retort resistance, hardness in hot water. The present invention relates to a coating composition capable of forming an excellent coating film, and a method for producing a coated metal can using the composition.

  Conventionally, as an ultraviolet curable coating composition, a cationic polymerizable coating containing a cationic polymerizable compound having an epoxy group or a vinyl group and a cationic polymerization initiator that generates a cation by ultraviolet irradiation, and a radical polymerizable unsaturated group are included. Radical polymerization type paints containing a radical polymerizable compound having a radical polymerization initiator that generates radicals upon irradiation with ultraviolet rays are known.

  However, the radical polymerization type paint has a characteristic that the curing speed is relatively fast, but the adhesion to the material and processability are insufficient, and there is an inhibition of curing by oxygen, so the surface curability is inferior, In particular, there is a problem in that equipment such as nitrogen sealing is required for use in a thin film (2 to 8 μm).

  On the other hand, cationic polymerization paints have advantages such as better adhesion to materials and processability compared to radical polymerization paints, and they do not require equipment such as nitrogen encapsulation, but they have a curing speed. Since it is slow, the coating film performance, particularly the coating film appearance, retort resistance, and hardness in hot water are insufficient.

  Therefore, the present inventors can cure by combining ultraviolet irradiation with a thin film and heating after irradiation without requiring facilities such as nitrogen sealing, and coating properties such as workability, adhesion, hardness, and scratch resistance. With the aim of obtaining a coating composition that can form a coating film excellent in film performance, particularly excellent in coating film appearance, retort resistance, and hardness in hot water, particularly suitable for can coatings. I did research.

  As a result, this time, a paint in which a predetermined amount of a compound having a t-butyl ester group and a glycidyl group in one molecule or in a different molecule and a cationic polymerization initiator is mixed with the cationic polymerizable binder component is irradiated with ultraviolet rays. By heating, the cation generated by ultraviolet irradiation is used as a catalyst, the t-butyl ester group is decomposed, isobutene is eliminated, a free carboxyl group is generated, and the generated carboxyl group is a glycidyl group in the compound. It has been found that a coating film excellent in coating film appearance, retort resistance, hardness in hot water, and the like can be obtained by reacting with and crosslinking to complete the present invention.

  Thus, the present invention relates to (A) 1 to 60 parts by weight of a t-butyl ester group-containing compound and (C) a glycidyl group-containing compound with respect to 100 parts by weight of the cationic polymerizable binder component not containing glycidyl group. The present invention provides a coating composition comprising 1 to 60 parts by weight and (E) 0.01 to 20 parts by weight of a cationic polymerization initiator that generates cations by ultraviolet irradiation.

The present invention also relates to (A) 1 to 70 parts by weight of a compound having at least one t-butyl ester group and glycidyl group, and (E) ultraviolet rays, relative to 100 parts by weight of (A) the cationic polymerizable binder component. A coating composition comprising 0.01 to 20 parts by weight of a cationic polymerization initiator that generates cations by irradiation is provided.

  In addition, the present invention is characterized in that the coating composition is applied to a metal plate, a resin film laminated metal plate or a metal can obtained by molding these metal plates, irradiated with ultraviolet rays, and then heated and cured. A method for producing a coated metal can is provided.

  The coating composition of the present invention contains a cationically polymerizable binder component (A), a t-butyl ester group-containing compound (B), and a glycidyl group-containing compound (C) as a film-forming resin component, or cationically polymerizable. It contains a binder component (A) and a compound (D) containing a t-butyl ester group and a glycidyl group as a film-forming resin component, and facilities such as nitrogen sealing in the presence of a cationic polymerization initiator (E) Can be cured by cationic polymerization efficiently even by irradiation with a low dose of ultraviolet light and heating after irradiation, and processability, adhesion, hardness, scratch resistance, and coating film appearance even in thin films A coating film excellent in coating film performance such as retort resistance and hardness in hot water can be formed. The coating composition of the present invention can be suitably used particularly as an ultraviolet curable coating for the outer surface of the can.

  The composition of the present invention is a coating composition which can be cured by causing cationic polymerization by ultraviolet irradiation and heating, and the first composition of the present invention includes the following (A), (B), (C) and (E). The composition according to the present invention is a composition having the following components (A), (D) and (E) as essential components. Below, each component in this invention composition is demonstrated.

Cationic polymerizable binder component containing no glycidyl group (A)
The cationic polymerizable binder component (A) is a cationic polymerizable compound that can be cured by cation polymerization by ultraviolet irradiation and does not contain a glycidyl group. For example, the following (A), (B) , (C), (d), and (e).

  (A) Epoxy compound not containing glycidyl group: This epoxy compound is a compound having one or more epoxy groups other than glycidyl group in one molecule, and has an epoxy equivalent of 70 to 5,000, preferably 80 to 3,000. Can be preferably used.

  Representative examples of the epoxy compound (a) include, for example, dicyclopentadiene dioxide, (3,4-epoxycyclohexyl) methyl-3,4-epoxycyclohexanecarboxylate, bis (2,3-epoxycyclopentyl) ether, bis ( 3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, (3,4-epoxy-6-methylcyclohexyl) methyl-3,4-epoxy-6-methylcyclohexane Carboxylate, bis (3,4-epoxycyclohexylmethyl) acetal, bis (3,4-epoxycyclohexyl) ether of ethylene glycol, 3,4-epoxycyclohexanecarboxylic acid diester of ethylene glycol, (3,4-epoxy Cyclohexyl) methyl alcohol, (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-ethyl-3- (3,4-epoxycyclohexylmethyl) oxymethyloxetane, Epolide GT300 (manufactured by Daicel Chemical Industries, Ltd., trade name) Trifunctional alicyclic epoxy resin), Epolide GT400 (manufactured by Daicel Chemical Industries, Ltd., trade name, tetrafunctional alicyclic epoxy resin), EHPE (manufactured by Daicel Chemical Industries, Ltd., trade name, polyfunctional alicyclic) Formula epoxy resin), the following formula

(Co) polymerization of alicyclic epoxy group-containing ethylenically unsaturated monomers such as 3,4-epoxycyclohexylmethyl (meth) acrylate and other polymerizable unsaturated monomers as required. And alicyclic epoxy group-containing epoxy compounds such as alicyclic epoxy group-containing (co) polymers.

Other polymerizable unsaturated monomers used to produce the alicyclic epoxy group-containing copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl ( (Meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate _C1-24 alkyl (meth) acrylates such as stearyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxy Monoesterified product of polyhydric alcohol and acrylic acid or methacrylic acid such as sibutyl (meth) acrylate and polyethylene glycol mono (meth) acrylate; ε-caprolactone in monoesterified product of polyhydric alcohol and acrylic acid or methacrylic acid Hydroxyl group-containing monomers such as compounds obtained by ring-opening polymerization; carboxyl group-containing polymerizable unsaturated monomers such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride; N, N-dimethylaminoethyl (meth) acrylate, N, Aminoalkyl (meth) acrylates such as N-diethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate; acrylamide, methacrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N (Meth) acrylamide or a derivative thereof such as diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-methylolacrylamide, N-methylolacrylamide methyl ether, N-methylolacrylamide butyl ether; 3-acryloyloxy Methyl-3-ethyloxetane, 3-methacryloyloxymethyl-3-ethyloxetane, hydroxyl group-containing oxetane (for example, 3-ethyl-3-hydroxymethyloxetane, etc.) reacts with the hydroxyl group and is substantially free from oxetane ring. Unsaturated monomers (for example 2-iso A compound having an oxetane ring and an ethylenically unsaturated group in the molecule such as a compound obtained by reacting cyanatoethyl (meth) acrylate, m-isopropenyl-α, α-dimethylbenzyl isocyanate, methyl (meth) acrylate, etc. Styrene, acrylonitrile, methacrylonitrile, vinyl acetate and the like. These compounds can be used alone or in combination of two or more. In the present invention, “(meth) acrylate” means acrylate or methacrylate, and “(meth) acrylamide” means acrylamide or methacrylamide.

  (B) Vinyl compounds: compounds having a vinyl group, for example, aromatic vinyl compounds such as styrene, methylstyrene, p-chloromethylstyrene, vinyltoluene; n-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether Substituted or unsubstituted alkyl vinyl ethers such as: allyl vinyl ether, ethenyl vinyl ether, alkenyl vinyl ethers such as 1-methyl-2-propenyl vinyl ether; allyl vinyl ethers such as phenyl vinyl ether and p-methoxyphenyl vinyl ether; butanediol divinyl ether , Alkyl divinyl ethers such as triethylene glycol divinyl ether and cyclohexanediol divinyl ether; 1,4- Aralkyl divinyl ethers such as zendimethanol divinyl ether, Nm-chlorophenyldiethanolamine divinyl ether, m-phenylenebis (ethylene glycol) divinyl ether; aryl divinyl ethers such as hydroquinone divinyl ether and resorcinol divinyl ether; N-vinylcarbazole And cationically polymerizable nitrogen-containing compounds such as N-vinylpyrrolidone.

(C) Bicycloorthoester compound; for example, 1-phenyl-4-ethyl-2,6,
Examples include 7-trioxabicyclo- [2,2,2] -octane and 1-ethyl-4hydroxymethyl-2,6,7-trioxabicyclo- [2,2,2] -octane.

  (D) Spiro orthocarbonate compound; for example, 1,5,7,11-tetraoxaspiro- [5,5] -undecane, 3,9-dibenzyl-1,5,7,11-tetraoxaspiro- [5 , 5] -undecane, 1,4,6-trioxaspiro- [4,4] -nonane, 2-methyl-1,4,6-trioxaspiro- [4,4] -nonane, 1,4, And 6-trioxaspiro- [4,5] -decane.

  (E) Oxetane compound: Formula (1) below

In the molecule, for example, a compound represented by the following general formula (2) or (3) can be exemplified.

(In the above formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms, and R ³ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkylene group, a hydroxyalkyl group, or an alkyl group having 2 to 10 carbon atoms. An alkoxyalkyl group optionally substituted with a hydroxyl group, an aryl group optionally substituted with a hydroxyl group having 7 to 12 carbon atoms, an aralkyl group, an aryloxyalkyl group),

(In the above formula, two R ^{1 s} are the same or different and have the same meaning as described above, and R ⁴ represents an alkylene group having 1 to 6 carbon atoms, a cycloalkylene group, a phenylene group, a xylylene group, or 4 carbon atoms. Represents 30 to 30 polyalkyleneoxy groups).

Representative examples of the oxetane compound represented by the general formula (2) include 3-ethyl-3-methoxymethyl oxetane, 3-ethyl-3-ethoxymethyl oxetane, 3-ethyl-3-butoxymethyl oxetane, 3- Ethyl-3-hexyloxymethyloxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-allyloxymethyloxetane, 3-ethyl-3- (2'- Hydroxyethyl) oxymethyloxetane, 3-ethyl-3- (2'-hydroxy-3'-phenoxypropyl) oxymethyloxetane, 3-ethyl-3- (2'-hydroxy-3'-butoxypropyl) oxymethyloxetane 3-ethyl-3- [2 ′-(2 ″ -ethoxyethyl) oxymethyl] oxy Cetane, 3-ethyl-3- (2′-butoxyethyl) oxymethyloxetane, 3-ethyl-3-benzyloxymethyloxetane, 3-ethyl-3- (p-tert-butylbenzyloxymethyl) oxetane, etc. be able to.

As a typical example of the oxetane compound represented by the general formula (3), in the general formula (2), both R ¹ are both ethyl groups, and R ⁴ is methylene, ethylene, propylene, butylene, cyclohexylene. , Phenylene, xylylene group, poly (ethyleneoxy) group, and poly (propyleneoxy) group.

  As the oxetane compound, in addition to the compounds represented by the general formulas (2) and (3), for example, a compound having bis (3-ethyloxetanyl-3-methyl) oxide or a polymerizable unsaturated group and an oxetane ring [For example, the copolymer which has an oxetane ring formed by copolymerizing with other polymerizable unsaturated monomers can be mentioned, using [3-ethyl-3- (acryloyloxymethyl) oxetane] as one monomer component. .

  As the other polymerizable unsaturated monomer used for the above-mentioned copolymerization, other polymerizable unsaturated monomer (excluding a compound having an oxetane ring) used for producing the alicyclic epoxy group-containing copolymer. The same can be used.

  As the cationic polymerizable binder component (A), an epoxy compound (a) and an oxetane compound (e) are suitable, and among them, an alicyclic epoxy group-containing copolymer is easy to adjust viscosity and curability. It is suitable in terms of coating film performance. The alicyclic epoxy group-containing copolymer has an alicyclic epoxy group of 0.7 to 6.4 mol / kg, preferably 2.0 to 5.0 mol / kg in 1 kg of the copolymer. It is appropriate to have a concentration range, and it is appropriate that the number average molecular weight is in the range of 3,000 to 50,000.

Compound (B) having t-butyl ester group
The component (B) in the composition of the present invention is a compound having one or more, preferably two or more t-butyl ester groups in one molecule, and also includes a resin. An ester group is a compound that can generate a free carboxyl group by eliminating isobutene.

  Examples of the compound (B) having a t-butyl ester group include diphenolic acid-t-butoxycarbonylmethyl esters, bis-t-butoxycarbonylmethylthymolphthalein, trisphenol t-butoxycarbonate, t-butoxy. Ethylenic aromatic compounds having a carbonylamino group, etc .; also containing a homopolymer of t-butyl acrylate or t-butyl methacrylate, or t-butyl acrylate or t-butyl methacrylate and other polymerizable unsaturated groups as described below Examples thereof include a copolymer with a monomer.

Examples of other polymerizable unsaturated group-containing monomers constituting the copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) ) acrylates, alkyl or cycloalkyl esters of C ₁ -C ₂₄ (meth) acrylic acid such as cyclohexyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxy C ₂ -C ₈ hydroxyalkyl esters of (meth) acrylic acid such as butyl (meth) acrylate; (meth) formed by ring-opening addition of ε- caprolactone C ₂ -C ₈ hydroxyalkyl esters of acrylic acid ε- Caprolactone-modified (meth) acrylic acid esthetic Carboxyl group-containing unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid and maleic acid; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N Aminoalkyl (meth) acrylates such as N, diethylaminopropyl (meth) acrylate; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene; perfluorobutylethyl (meth) acrylate, perfluoroisononylethyl (meta ) Fluorine-containing unsaturated monomers such as acrylate; Polymerizable amides such as (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol (meth) acrylamide butyl ether; Polymerizability such as acrylonitrile and methacrylonitrile Toryls: cyclohexenyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, ε-caprolactone modified tetrahydrofurfuryl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, dicyclopentenyl (meth) ) Acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( (Meth) acrylate, 2-hydroxy-3-butoxypropyl (meth) acrylate, monohydroxyethyl (meth) acrylate phthalate And "Aronix M110" (trade name, paracumylphenol / ethylene oxide modified acrylate), acryloylmorpholine, N-vinyl-2-pyrrolidone and the like.

  The copolymer has a t-butyl ester group content of 0.7 mol / kg to 6.4 mol / kg, preferably 2.0 mol / kg to 5.0 mol / kg in 1 kg of the copolymer. It is appropriate to have a concentration range, and it is appropriate that the number average molecular weight is in the range of 3,000 to 50,000.

Glycidyl group-containing compound (C)
Component (C) in the composition of the present invention is a compound having 1 or more, preferably 2 or more glycidyl groups in one molecule, and also includes a resin. In compound (C), the glycidyl group in component (C) reacts with a free carboxyl group produced by elimination of isobutene from the t-butyl ester group in compound (B) using a cation as a catalyst. And can be crosslinked.

  Specific examples of the compound having one or more glycidyl groups in one molecule include, for example, glycidyl ether compounds such as diglycidyl ether, 2-glycidylphenyl glycidyl ether, and 2,6-diglycidylphenyl glycidyl ether; vinylcyclohexene dioxide , Glycidyl group such as lemonene dioxide and alicyclic epoxy group-containing compounds; bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin; glycidyl (meth) acrylate, methyl glycidyl ( Examples include (co) polymers of glycidyl group-containing polymerizable unsaturated monomers such as (meth) acrylate and allyl glycidyl ether, and other polymerizable unsaturated monomers as necessary.

As the other polymerizable unsaturated monomer constituting the copolymer that can be the component (C), other compounds in the case where the compound (B) having a t-butyl ester group is a copolymer are available. The monomer similar to a polymerizable unsaturated monomer can be mentioned. This copolymer has a concentration range of 0.7 mol / kg to 6.4 mol / kg, preferably 2.0 mol / kg to 5.0 mol / kg of glycidyl groups in 1 kg of the copolymer. The number average molecular weight is suitably in the range of 3,000 to 50,000.

Compound (D) containing t-butyl ester group and glycidyl group
The compound containing a t-butyl ester group and a glycidyl group, which is the component (D) of the composition of the present invention, is a compound having one or more t-butyl ester groups and one or more glycidyl groups in one molecule. Resins are also included. Since the compound (D) has a free carboxyl group and a glycidyl group which are generated by detaching isobutene from the t-butyl ester group by a cation, the compound (D) is reacted with the generated carboxyl group and the glycidyl group. Self-crosslinking with comrade.

  Examples of the compound (D) include a copolymer having t-butyl (meth) acrylate, glycidyl (meth) acrylate and, if necessary, other polymerizable unsaturated monomers as constituent monomer components. . As said other polymerizable unsaturated monomer, the monomer similar to another polymerizable unsaturated monomer in case the compound (B) which has the said t-butyl ester group is a copolymer can be mentioned.

  The copolymer has a concentration range of 0.7 mol / kg to 6.4 mol / kg, preferably 2.0 mol / kg to 5.0 mol / kg of glycidyl group in 1 kg of the copolymer. It is appropriate to have a t-butyl ester group in the concentration range of 0.7 mol / kg to 6.4 mol / kg, preferably 2.0 mol / kg to 5.0 mol / kg. The number average molecular weight is suitably in the range of 3,000 to 50,000.

Cationic polymerization initiator (E)
The cationic polymerization initiator which is the component (E) of the composition of the present invention is a compound that generates cations by irradiation with active energy rays such as ultraviolet rays. For example, compounds represented by the following formulas (4) to (20) Can be mentioned.

_{^{Ar 2 I + · X - (}} 4)
(In the formula, Ar represents an aryl group such as a phenyl group, and X ⁻ represents BF ₄ ⁻ , PF ₆ ⁻ , SbF ₅ (OH) ⁻ , SbF ₆ ⁻ or AsF ₆ ⁻ or the following formula)

Represents a group represented by
_{^{Ar 3 S + · X - (}} 5)
(Wherein Ar and X ⁻ have the same meaning as above)

(In the formula, R ⁵ represents an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, n represents an integer of 0 to 3, and X ⁻ has the same meaning as described above.)

(In the formula, Y ⁻ represents PF ₆ ⁻ , SbF ₆ ⁻ , SbF ₅ (OH) ⁻ or AsF ₆ ⁻ ).

Wherein X ⁻ has the same meaning as described above.

Wherein X ⁻ has the same meaning as described above.

Wherein X ⁻ has the same meaning as described above.

(Wherein R ⁶ is an aralkyl group having 7 to 15 carbon atoms or an alkenyl group having 3 to 9 carbon atoms, R ⁷ is a hydrocarbon group or hydroxyphenyl group having 1 to 7 carbon atoms, and R ⁸ is an oxygen atom. Or an alkyl group having 1 to 5 carbon atoms which may contain a sulfur atom, and X ⁻ has the same meaning as described above.

(Wherein R ⁹ and R ¹⁰ each independently represents an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms)

(Wherein R ⁹ and R ¹⁰ have the same meaning as above)

Commercially available products of the cationic polymerization initiator (E) include, for example, Silakia UVI-6970, UVI-6974, UVI-6990 (all of which are manufactured by Union Carbide, Inc.), Irgacure 261, 264 (and above, either Ciba Specialty Chemicals), CIT-1682 (Nippon Soda Co., Ltd.), BBI-102 (Midori Chemical Co., Ltd.), Adekaoptomer SP-150, SP-170 (all above) Asahi Denka Co., Ltd.).

UV-curable coating composition of the present invention The first invention composition of the present invention comprises the binder component (A), a compound (B) having a t-butyl ester group, a glycidyl group-containing compound (C) and a cationic polymerization initiator. It is a composition having (E) as an essential component. Moreover, the 2nd invention composition of this invention is a composition which has the said binder component (A), the compound (D) containing a t-butyl ester group, and a glycidyl group, and a cationic polymerization initiator (E) as an essential component. .

  In the first invention composition of the present invention, the amount of the t-butyl ester group-containing copolymer (B) is 1 to 60 parts by weight, preferably 3 to 100 parts by weight of the cationic polymerizable binder (A). It is suitable that it is in the range of 40 parts by weight, more preferably 5 to 20 parts by weight. When the amount of the component (B) is less than 1 part by weight, the hardness in the hot water, the adhesion, and the coating film hardness of the coating film heated and cured after the ultraviolet irradiation are liable to decrease, while the amount of the component (B) is 60 When the amount exceeds parts by weight, the curability of the coating film after irradiation is inferior, particularly in the case of irradiation with a low dose of ultraviolet rays, and poor workability due to a decrease in coating film hardness tends to occur.

  In the first invention composition of the present invention, the amount of the glycidyl group-containing compound (C) is 1 to 60 parts by weight, preferably 3 to 40 parts by weight, based on 100 parts by weight of the cationic polymerizable binder (A). Preferably it is in the range of 5 to 20 parts by weight. When the amount of the component (C) is less than 1 part by weight, the hardness in the hot water, the adhesion, and the coating film hardness of the coating film heated and cured after the ultraviolet irradiation are liable to decrease, while the amount of the component (C) When the amount exceeds 60 parts by weight, a ring-opening addition reaction between glycidyl groups occurs, so that the retort resistance of the coating film, the hardness in hot water, and the like tend to decrease.

  In the first invention composition of the present invention, the total of the t-butyl ester group-containing copolymer (B) and the glycidyl group-containing compound (C) is 100 parts by weight of the cationic polymerizable binder (A). 70 parts by weight or less, preferably 61 parts by weight or less, and more preferably 40 parts by weight or less, such as hardness, adhesion, coating film hardness, curability, etc. From the viewpoint of

  1st invention composition of this invention WHEREIN: The quantity of cationic polymerization initiator (E) is 0.01-20 weight with respect to 100 weight part of total solid content of (A), (B) and (C) component. Parts, preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, such as UV irradiation, coating film hardness after heating, coating film appearance (non-yellowing), weather resistance, etc. Appropriate from a point.

  In the second invention composition of the present invention, the amount of the compound (D) containing a t-butyl ester group and a glycidyl group is preferably 1 to 70 parts by weight, preferably 100 parts by weight of the cationic polymerizable binder (A). Is in the range of 3-40 parts by weight, more preferably in the range of 5-20 parts by weight, the hardness in water, adhesion, coating film hardness, and low irradiation amount of the coating film heated and cured after UV irradiation From the viewpoints of coating film curability, coating film hardness, retort resistance, and the like in heat curing after UV irradiation.

  Moreover, in the 2nd invention composition of this invention, the quantity of cationic polymerization initiator (E) is 0.01-20 weight part with respect to 100 weight part of total solid content of (A) and (D) component, Preferably in the range of 0.1 to 10 parts by weight, more preferably in the range of 1 to 5 parts by weight from the viewpoints of ultraviolet irradiation, coating film hardness after heating, coating film appearance (non-yellowing), weather resistance, etc. Is appropriate.

  In addition to the components (A), (B), (C) and (E), the first invention composition of the present invention comprises a compound containing a t-butyl ester group and a glycidyl group as necessary (D ) Can be contained. The content of the compound (D) is a quantitative range in which the total solid content of the components (B), (C) and (D) is 70 parts by weight or less with respect to 100 parts by weight of the component (A).

  In addition to the components (A), (D) and (E), the second invention composition of the present invention contains a t-butyl ester group-containing copolymer (B) and / or a glycidyl group, if necessary. A compound (C) can be contained. The content of the copolymer (B) and the compound (C) is such that the total solid content of the components (B), (C) and (D) is 70 parts by weight or less with respect to 100 parts by weight of the component (A). Is a quantitative range.

  Each of the first invention composition and the second invention composition of the present invention may further contain a color pigment, an extender pigment such as silica, a wax, a coating surface adjusting agent, and the like, if necessary.

  The coating composition of the present invention (the first invention composition and the second invention composition) can be prepared by mixing the components described above and stirring the mixture so as to obtain a uniform coating composition. For example, each component is mixed, heated at room temperature or if necessary (for example, about 50 ° C.), and stirred for about 10 minutes until uniform with a stirrer such as a dissolver. Can do.

  The coating composition of the present invention can be cured by coating an object to be coated, irradiating the coating film with ultraviolet rays, and heating after the irradiation. When the coating film contains a solvent, after coating, the solvent is removed by heating or the like, and then ultraviolet rays are irradiated. When the coating film of the coating composition of the present invention is irradiated with ultraviolet rays, cationic polymerization of the cationic polymerizable binder component (A) occurs, and at the same time, the t-butyl ester group in the component (B) or (D) is decomposed and isobutene is decomposed. Is eliminated to form a free carboxyl group. Next, by heating, the generated free carboxyl group reacts with the glycidyl group in the component (C) or the component (D), and the curing further proceeds to form a coating film excellent in coating film performance.

  The coating composition of the present invention is not particularly limited, but is particularly suitable for coating for metal cans. In this case, the coating material may be tin, aluminum, tin-free steel, iron. Metal plates such as zinc, copper, galvanized steel plates, alloy-plated steel plates of zinc and other metals (this metal plates may be subjected to chemical conversion treatment such as zinc phosphate treatment or chromate treatment); Resin film laminated metal plate in which polyester resin such as polyethylene terephthalate, polyolefin resin such as polyethylene or polypropylene, polyamide resin, epoxy resin, polyvinyl chloride, etc. are laminated on metal plate; these metal plates were molded A metal can etc. can be mentioned.

  In the coating composition of the present invention, the coating film thickness is not particularly limited, and can be appropriately selected depending on the application. In the case of a metal can application, the dry coating thickness is usually about 2 to 20 μm, preferably Can be in the range of about 2-8 μm. The composition of the present invention can be applied by methods such as roll coating, spray coating, brush coating, bar coating, roller coating, screen printing, and rotary printing.

  After coating, when the coating film contains a solvent, the solvent is usually removed by heating or the like and then irradiated with ultraviolet rays. The ultraviolet irradiation conditions can be appropriately changed according to the type of coated composition, film thickness, and the like. As a wavelength of the ultraviolet rays to be irradiated, a range of 200 to 450 nm is usually appropriate, and an irradiation source having a highly sensitive wavelength can be appropriately selected and used depending on the type of the photoinitiator.

Examples of the ultraviolet irradiation source include a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a carbon arc, a metal halide lamp, and sunlight. Irradiation condition to the coating film, usually, with light having a wavelength of about 200 to 450 nm, from about 10 to about 3000 mJ / cm ² is the amount of irradiation, it can be particularly carried out within the scope of 50~1000mJ / cm ^2.

  The coating film from the coating composition of the present invention can be cured by heating after irradiation with ultraviolet rays. The heating conditions should just be the conditions which can react the carboxyl group and glycidyl group in a coating film, for example, 100-250 degreeC, Preferably it is 120-230 degreeC for 1 minute-1 hour, Preferably it is 5- A heating condition of about 30 minutes is appropriate.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to an Example. Hereinafter, “parts” and “%” are based on weight unless otherwise specified.

Production Examples for Acrylic Resin Solutions Production Examples 1 to 4
In a four-necked flask, 58 parts of toluene and 30 parts of propylene glycol monomethyl ether were blended, and the mixed solution of monomers and polymerization initiator shown in Table 1 below was mixed with nitrogen while being heated and maintained at 108 ° C. It was dropped at a constant rate over 4 hours under an air stream. 30 minutes after the completion of the dropping of the above mixed solution, a mixed solution of 8 parts of toluene and 0.3 part of 2,2′-azobis (2-methylbutyronitrile) was dropped at a constant rate over 30 minutes under a nitrogen stream. did. After completion of dropping, the mixture was kept at the same temperature for about 2 hours, and then cooled to room temperature to obtain each acrylic resin solution. Production Example 4 is for a comparative example. Combine the glass transition temperature by DSC (Differential Scanning Thermal Analysis) measurement of the resin solid content of each acrylic resin solution obtained, the number average molecular weight by GPC (gel permeation chromatography) measurement, and the number of functional groups in one molecule. Table 1 shows.

Production Examples 5-8
In 206 parts of each acrylic resin solution obtained in the above Production Examples 1 to 4, (3,4-epoxycyclohexyl) methyl-3,4-epoxycyclohexanecarboxylate (hereinafter sometimes abbreviated as “epoxy compound A”). By adding 100 parts and distilling off the solvent component under reduced pressure, each resin liquid of acrylic resin / epoxy compound A = 50/50 containing substantially no solvent was obtained.

Examples 1-7 and Comparative Examples 1-4
A composition having the composition shown in Table 3 below was kept at 50 ° C. in a room where light was shielded and stirred for 20 minutes using a stirrer to obtain a uniform coating composition.

  (註) in Table 3 has the following meanings.

(* 1) Oxetane compound: 3-ethyl-3-hydroxymethyloxetane,
(* 2) Epicoat 828EL: manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin,
(* 3) Denarex R-45EPI: manufactured by Nagase Chemical Industries, epoxidized polybutadiene resin,
(* 4) Cyracure UVI-6990: manufactured by Union Carbide, photocationic polymerization initiator having antimonate anion (SbF ₆ ⁻ ), active ingredient 50%,
(* 5) Cyracure UVI-6974: manufactured by Union Carbide, photocationic polymerization initiator having antimonate anion (SbF ₆ ⁻ ), active ingredient 50%,
(* 6) Nacure 5225: manufactured by King Industries, USA, heat latent acid generator, active ingredient 25%,
(* 7) Paintad M: Silicon wax manufactured by Dow Corning.

  The storage stability test of each coating composition obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was also performed. The test results are shown in Table 3 below.

Preparation of test coated plate Each coating composition obtained in Examples 1 to 7 and Comparative Examples 3 to 4 having good storage stability was used as a tin-free steel plate (TFS) having a thickness of 0.20 mm, and a thickness. It coated so that the dry film thickness might be set to 5 micrometers on the PET steel plate which heat-pressed the 12-micrometer-thick homo PET (polyethylene terephthalate) sheet | seat on the 0.20 mm tin-free steel board. A high pressure mercury lamp (160 W / cm) was used for the coated plate obtained, and after irradiation with ultraviolet rays at a distance of 15 cm from the painted plate under the condition that the energy dose was 80 mJ / cm ² , baking was performed at 210 ° C. for 1 minute. The finished coated plate was used as a test coated plate.

  Each of the obtained test coated plates was tested based on the following test method. These test results are shown in Table 3 below.

Test Method Pencil Hardness: A pencil scratch test specified in JISK-5400 8.4.2 (1990) was performed on the coating film of the test coating plate in a room at 20 ° C. Evaluation was carried out by the blurring method.

Hardness in hot water: After immersing the test coated plate in hot water at 80 ° C. for 5 minutes, the coated plate is immersed in hot water,
The pencil scratch test prescribed | regulated to JISK-5400 8.4.2 (1990) was done. Evaluation was carried out by the blurring method.

  Coating state after retort treatment: The test coating plate is submerged in deionized water, and blisters generated on the coating after hydrothermal treatment at 125 ° C for 30 minutes in a pressure cooker, depending on the degree of peeling of the coating. Evaluation was based on criteria.

A: Neither generation of blisters nor peeling of the coating film is observed at all. ○: Slight fine blisters are observed but peeling of the coating film is not observed. Peeling is not recognized x: Blister generation is remarkable and peeling of the coating film is recognized.

  Storage stability: The coating composition was sealed in a 100 ml glass container and then stored in a thermostatic chamber at 40 ° C. for 30 days. The paint state before and after storage was confirmed. ○ indicates that there is no increase in viscosity.

Claims (3)

  (A) 1 to 70 parts by weight of a compound each having at least one t-butyl ester group and glycidyl group with respect to 100 parts by weight of a cationic polymerizable binder component not containing a glycidyl group, and (E) ultraviolet rays A coating composition characterized by containing 0.01 to 20 parts by weight of a cationic polymerization initiator that generates cations upon irradiation and does not contain a carboxyl group-containing resin.   Compound (D) is a glycidyl group-containing polymerizable unsaturated monomer 10-90 parts by weight, a t-butyl ester group-containing polymerizable unsaturated monomer 10-90 parts by weight, and other polymerizable unsaturated monomers 0-80 parts by weight. The coating composition according to claim 1, which is a copolymer.   The coating composition according to claim 1 or 2 is applied to a metal plate, a resin film laminated metal plate or a metal can obtained by molding these metal plates, irradiated with ultraviolet rays, and then heated and cured. To make painted metal cans.