JPH10212343A - Ultraviolet-curable can coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultraviolet-curable coating compsn. which is suitable for can coating and forms a coating film excellent in external appearance, fabricability, adhesiveness, hardness, slipperiness retention after retorting, and hardness in warm water. SOLUTION: This compsn. contains 100 pts.wt. compsn. comprising 10-90wt.% compd. (A) having an alicyclic epoxy group in the molecule and 90-10wt.% compd. (B) having an oxetane ring in the molecule, 1-50 pts.wt. copolymer (C) formed from a glycidylated polymerizable unsatd. monomer and another polymerizable unsatd. monomer and having at least one glycidyl group in the molecule and a glass transition point of 30 deg.C or higher, and 0.1-20 pts.wt. cationic polymn. initiator generating a cation when exposed to ultraviolet rays. A coated metal can is produced by applying the compsn. and irradiating it with ultraviolet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent coating properties such as processability, adhesion, hardness, and scratch resistance, which can be cured by ultraviolet irradiation. In particular, coating appearance, retort resistance, hardness in hot water The present invention relates to a UV-curable can coating composition capable of forming a coating film having excellent lubricity retention after retort treatment, and a method for producing a coated metal can using the composition.

[0002]

2. Description of the Related Art
UV-curable coating compositions include cationically polymerizable compounds having a cationically polymerizable compound having an epoxy group or a vinyl group and a cationically polymerizable initiator that generates cations upon irradiation with ultraviolet light, and a radical having a radically polymerizable unsaturated group. Radical polymerization type paints and the like containing a polymerizable compound and 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,
Insufficient adhesion to materials and workability, and hardening due to oxygen, resulting in poor surface curability. In particular, when using thin films (2 to 8μ), equipment such as nitrogen sealing is required. There is a problem that is. On the other hand, cationic polymerization type coatings have better adhesiveness to materials and workability than radical polymerization type coatings, and have the advantage that they do not require equipment such as nitrogen encapsulation. Is slow, so that there is a problem that the coating film performance, especially the coating film appearance and the retort resistance are insufficient.

[0003] In addition, all polymerization systems have a low irradiation dose (100
(mJ / cm ² ), there is a problem that the curability is insufficient.

[0004]

Accordingly, the present inventors have developed a thin film that can be cured by irradiating ultraviolet rays with a low irradiation amount without the need for facilities such as nitrogen filling, and have been required as a paint for cans. Excellent paint film performance such as processability, adhesion, hardness, scratch resistance, especially paint film appearance, retort resistance,
UV-curing type that can form a coating film with excellent lubricity retention of the coating film after retort treatment, and can form a coating film with excellent hardness in hot water after heating after UV irradiation For the purpose of obtaining a coating composition, diligent research was conducted. As a result, the present inventors have found that the above object can be achieved by mixing a predetermined amount of an alicyclic epoxy compound, an oxetane ring-containing compound, a copolymer containing a glycidyl group, and a cationic polymerization initiator. Thus, the present invention has been completed.

That is, the present invention relates to (A) 10 to 90 parts by weight of a compound having an alicyclic epoxy group in a molecule, and (B) 10 to 9 parts by weight of a compound having an oxetane ring in a molecule.
0% by weight and 100 parts by weight of the total of the compounds (A) and (B), (C) a copolymer of a glycidyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer, Copolymer having at least one glycidyl group in the molecule and having a glass transition temperature of 30 ° C. or higher
A UV-curable can coating composition comprising: 0 parts by weight and (D) 0.01 to 20 parts by weight of a cationic polymerization initiator which generates cations upon irradiation with ultraviolet rays.

The present invention also provides a coating composition for an ultraviolet-curable can described above on a metal plate, a resin film-laminated metal plate or a metal can formed by molding these metal plates, and is cured by irradiating ultraviolet rays. It is intended to provide a method for producing a coated metal can characterized by the above.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the present invention is a coating composition which can be cured by causing cationic polymerization by irradiation with ultraviolet rays. Each component in this composition will be described below.

Compound having an alicyclic epoxy group in the molecule
(A) Compound (A) having an alicyclic epoxy group in the molecule [hereinafter sometimes abbreviated as “epoxy compound (A)”]
Can be used without particular limitation as long as it is a compound having one or more, preferably 1 to 2 alicyclic epoxy groups in the molecule, and specific examples thereof include dicyclopentadienedioxide, limonene dioxide, Di (3,4-epoxycyclohexyl) adipate, (3,4-epoxycyclohexyl) methyl-3,4-epoxycyclohexanecarboxylate, (3,4-epoxy-6-methylcyclohexyl) methyl-3,4-epoxy- 6-
Methylcyclohexanecarboxylate, ethylene-
Examples thereof include 1,2-di (3,4-epoxycyclohexanecarboxylic acid) esters and compounds represented by the following formulas (1) to (3). These compounds can be used alone or in combination of two or more.

[0009]

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In the formula, R ¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have an epoxy group or an acyl group having 1 to 12 carbon atoms which may have an epoxy group. R ² represents an alkylene group having 1 to 6 carbon atoms, n represents an integer of 0 to 15,

[0011]

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In the formula, two R ³ are the same or different and each represents an alkylene group having 1 to 6 carbon atoms, and m is 0
Represents an integer of ~ 25,

[0013]

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In the formula, R ⁴ represents an alkylene group having 1 to 6 carbon atoms, and three R ^{5 s} are the same or different and each represent an alkyl group having 1 to 4 carbon atoms.

In the above formula (1), the alkyl group represented by R ¹ is linear, branched or cyclic, and specific examples thereof include methyl, ethyl, n- or i-propyl, and n-alkyl. , I- or t-butyl, octyl, cyclohexyl group and the like. Specific examples of the alkyl group having an epoxy group include a 3,4-epoxycyclohexylmethyl group. The acyl group that R ¹ can represent is a group of the formula RCO wherein R is a hydrogen atom or an alkyl, alkenyl, cycloalkyl, aryl,
Represents an organic group such as aralkyl), and specific examples thereof include formyl, acetyl, propionyl, butyroyl, octanoyl, lauroyl, acryloyl, methacryloyl, and benzoyl. Specific examples of the acyl group having an epoxy group Examples thereof include a 3,4-epoxycyclohexanecarbonyl group. The alkylene group represented by R ² is linear, branched or cyclic, and specific examples thereof include methylene, ethylene, 1,2- or 1,3-propylene, butylene, cyclohexylene and the like. be able to.

As a typical example of the compound represented by the above formula (1), when n is 0, 3,4-
Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexylmethyl alcohol, di (3,4-epoxycyclohexylmethyl) Ether, etc., and n is an integer of 1 to 15, preferably 1 to 6, and n is any integer of 1 to 15, and R ¹ is a hydrogen atom and R ² Is a methylene group, when R ¹ is a 3,4-epoxycyclohexanecarbonyl group and R ² is a methylene group, when R ¹ is an acryloyl group and R ² is a methylene group,
And compounds in which R ¹ is a methacryloyl group and R ² is a methylene group.

In the above formula (2), the alkylene group represented by R ³ is linear, branched or cyclic, and specific examples thereof include methylene, ethylene, 1,2- or 1,3-propylene. , Butylene and cyclohexylene groups. Thus, as a typical example of the compound represented by the formula (2), a compound in which all two R ³ are 1,2-ethylene groups and m is an integer of 0 to 25 is mentioned. Can be.

In the above formula (3), the alkylene group represented by R ⁴ is linear, branched or cyclic, and specific examples thereof include methylene, ethylene, 1,2- or 1,3-propylene. , Butylene and cyclohexylene groups. A typical example of the compound represented by the formula (3) is a compound in which R ⁴ is ethylene and all three R ⁵ are methyl groups, and R ⁴ is 1,2- or 1-. , 3-propylene group, and all ^three R ³ are methyl groups.

Among the compounds having an alicyclic epoxy group in the molecule described above, particularly preferred compounds are 3,4.
-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl alcohol, 3,4-epoxycyclohexylethyltrimethoxysilane or the following formula

[0020]

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Compounds represented by the following formulas can be mentioned.

Compound having an oxetane ring in the molecule
(B) Compound (B) used in the coating composition of the present invention
Is an oxetane ring capable of undergoing ring-opening polymerization by ultraviolet irradiation in the presence of a cationic polymerization initiator.

[0023]

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Is a compound having at least one, preferably 1 to 15, and more preferably 1 to 4 in one molecule (hereinafter referred to as an oxetane compound). Specifically, for example, the following formula (4) And the compounds represented by the following formulas (10), (11) and (12).

[0025]

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In the above formula (4), R⁶Is a hydrogen atom,
A fluorine atom, a straight-chain or branched-chain having 1 to 6 carbon atoms
Or a cyclic alkyl group (for example, methyl, ethyl, n-
Or i-propyl, n-, i- or t-butyl
, Pentyl, hexyl, cyclohexyl, etc.), charcoal
A linear or branched fluoroalkyl having 1 to 6 atoms
Kill group (for example, monofluoromethyl, difluoromethyl
Trifluoromethyl, 2,2,2-trifluoroe
Chill, perfluoroethyl, perfluoropropyl, pa
-Fluorobutyl, perfluorohexyl group, etc.)
Ryl group, aryl group (for example, phenyl, naphthyl,
An aralkyl group (e.g.,
Such as a jyl or phenethyl group), a furyl group or a thienyl group.
Represents; R ⁷Has a valence corresponding to the value of p and hydrogen
Z represents an atom or an organic group having 1 to 4 valences;
P represents an integer of 1 to 4;

The monovalent to tetravalent organic group represented by R ⁷ may have at least one kind of heteroatom selected from O, S, N and F and / or a siloxane bond. Examples thereof include 1 to 30 linear, branched or cyclic 1 to 4 valent hydrocarbon groups.

More specifically, examples of the monovalent group represented by R ⁷ include a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms (for example, methyl, ethyl, n- Or i-propyl, n-, i- or t
-Butyl, pentyl, hexyl, cyclohexyl group, etc.), a linear or branched alkoxyalkyl group having 1 to 6 carbon atoms (eg, methoxyethyl, ethoxyethyl, butoxyethyl, ethoxymethyl group, etc.), 1 carbon atom To 6 linear or branched fluoroalkyl groups (e.g., monofluoromethyl, difluoromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, Fluorohexyl group, etc., allyl group, aryl group (eg, phenyl, naphthyl, tolyl, xylyl group, etc.), aralkyl group (eg, benzyl, phenethyl group, etc.), furyl group, thienyl group, epoxy-containing group (eg, glycidyl) , 3,4-epoxycyclohexylmethyl And the like), and the like.

The divalent group represented by R ⁷ includes, for example, a linear, branched or cyclic alkylene group (particularly methylene, ethylene, 1,2- or 1,3-propylene, butylene) , An alkylene group having 1 to 15 carbon atoms such as a cyclohexylene group), a poly (alkyleneoxy) group having 4 to 30, preferably 4 to 8 carbon atoms (for example, poly (ethyleneoxy), poly (propyleneoxy) Group), phenylene group, xylylene group, the following formulas (5) and (6)

[0030]

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Wherein R ⁸ is O, S, CH ₂ , NH, S
O, SO ₂ , C (CF ₃ ) ₂ or C (CH ₃ ) ₂ ;

[0032]

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In the formula, R ⁹ represents an alkylene group having 1 to 6 carbon atoms, an arylene group or a direct bond, a carbon atom having an alkylene group and an alkylene group bonded by a (poly) siloxane chain. Number 2 to 30, preferably 2
Group 6 (for example, the alkylene group is an ethylene or propylene group, and the molecular weight of the (poly) siloxane chain is 130
To 15,000, especially 130 to 500, preferably those represented by the following formula (7)).

[0034]

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In the formula, k represents an integer of 1 to 6, and 1 represents 2
Or 3.

Further, as the tri- or tetravalent group which R ⁷ can represent, for example, the following formulas (8) to (11)

[0037]

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In the formula, R ¹⁰ represents an alkyl group having 1 to 6 carbon atoms, for example, an ethyl group.

[0039]

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In the formula, four R ¹¹ are the same or different and each represents an alkylene group having 1 to 6 carbon atoms, for example, an ethylene group.

[0041]

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[0042] wherein two R ¹² are identical or different, each represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, Represents a furyl group or a thienyl group,
And the like.

Of the monovalent to tetravalent organic groups which R ⁷ can represent, monovalent or divalent groups are preferred (ie, p is 1
Or 2 is preferable), among which alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, and hexyl; allyl groups; glycidyl groups; vinyl groups; and carbon atoms such as ethoxyethyl and methoxyethyl 1 to 6 alkoxyalkyl groups; benzyl group; methylene, ethylene,
1 carbon atom such as propylene, butylene and hexylene
An alkylene group of 1 to 6; a p-xylylene group;

[0044]

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The group represented by is preferred.

In the above formula (4), R ⁶ is preferably a hydrogen atom; an alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl and hexyl; an allyl group. A hydrogen atom, a methyl group and an ethyl group are preferred.

Among the compounds (B) having at least one oxetane ring in the molecule, (B-1) a compound having at least one, preferably one each of an oxetane ring and a hydroxyl group in the molecule, and (B-1) -2) A compound having at least two oxetane rings or an oxetane ring and an epoxy group in a molecule is preferable.

The oxetane compound (B-1) is, for example, a compound of the above formula (4) in which p is 1 and R ⁷ is a hydrogen atom, particularly represented by the following formula (4-1). Compounds can be mentioned.

[0049]

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In the formula, R ⁶¹ is a hydrogen atom, a fluorine atom,
A linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched fluoroalkyl group having 1 to 6 carbon atoms or an allyl group.

As a typical example of the compound represented by the formula (4-1), a compound represented by the formula (4-1) when R ⁶¹ is an ethyl group:
Can be mentioned.

Among the oxetane compounds (B-2), compounds having at least two oxetane rings in the molecule (hereinafter referred to as polyoxetane compounds) include:
When p is an integer of 2 to 4, the compound of the formula (4) may be mentioned, and among them, the compound represented by the following formula (4-2) is preferable.

[0053]

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In the formula, R ⁶¹ has the same meaning as described above,
⁷¹ represents a divalent to tetravalent organic group defined for R ⁷ in the formula (4), and q represents an integer of 2 to 4.

As a typical example of the compound represented by the above formula (4-2), R ⁶¹ is an ethyl group and R ⁷¹ is 1,4
A tetramethylene group, a dodecamethylene group, an o-, m- or p-xylylene group, or a group represented by the above formula (6) wherein R ⁹ is an ethylene group or a group represented by the above formula (7) -2).

As the polyoxetane compound, in addition to the compound represented by the above formula (4-2), the following formula (1)
Compounds represented by 2), (13) and (14) can be mentioned.

[0057]

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In the formula, two R ⁶¹ are the same or different and have the same meanings as described above, and an ethyl group is particularly preferred.

[0059]

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In the formula, s represents an integer of 25 to 200.

Further, the oxetane compound (B-2)
Of which has an oxetane ring and an epoxy group in the molecule (hereinafter referred to as epoxy-containing oxetane compound)
Represents one oxetane ring and one epoxy group in the molecule.
Includes compounds having a molecular weight of preferably less than 1000, and specifically includes, for example, a compound represented by the following formula (15).

[0062]

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In the formula, R ¹³ represents an epoxy group-containing group;
R ⁶¹ has the same meaning as described above.

A typical example of the epoxy-containing oxetane compound is a compound in the above formula (15) in which R ⁶¹ is an ethyl group and R ¹³ is a glycidyl group or a 3,4-epoxycyclohexylmethyl group. .

The oxetane compound (B) described above is
Each can be used alone, or two or more can be used in combination. In particular, it is preferable to use the compound (B-1) and the compound (B-2) in combination. The amount of each of the oxetane compounds (B-1) and (B-2) used in combination is the above-mentioned epoxy compound (A) and oxetane compound (B-1).
And the oxetane compound (B-1) in an amount of 5 to 60 parts by weight,
Preferably 5 to 40 parts by weight, more preferably 10 to 3 parts by weight.
0 parts by weight, and 5-6 oxetane compound (B-2)
0 parts by weight, preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight.

At least one glycidyl group in the molecule
The copolymer (C) used in the coating composition of the present invention is a copolymer having at least one glycidyl group in the molecule. For example, the copolymer (C) is a glycidyl group-containing polymerizable unsaturated monomer. (Hereinafter may be abbreviated as "glycidyl monomer") and, if necessary, other polymerizable unsaturated monomers copolymerizable with these monomers (hereinafter may be abbreviated as "other monomers"). Can be obtained by copolymerizing

The copolymer (C) needs to have a glass transition temperature of 30 ° C. or more from the viewpoint of hardness in hot water (hardness of the coating film in hot water), and particularly in the range of 50 ° C. to 135 ° C. Is preferred.

As the glycidyl monomer, any polymerizable unsaturated monomer containing a glycidyl group can be used without any particular limitation. Typical examples thereof include glycidyl acrylate, glycidyl methacrylate, methyl glycidyl acrylate, and methyl glycidyl methacrylate. , Allyl glycidyl ether, vinyl glycidyl ether and the like. Of these,
Glycidyl acrylate and glycidyl methacrylate are preferably used.

The other monomer copolymerizable with the glycidyl monomer is a monomer which is appropriately used as needed according to the intended performance of the obtained copolymer (C). Examples of the monomer include methyl acrylate and methyl acrylate. Methyl methacrylate, ethyl acrylate, ethyl methacrylate, n
-, I- or t-butyl acrylate, n-, i- or t-butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate,
C1-C24 alkyl or cycloalkyl esters of acrylic acid or methacrylic acid such as octyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate; 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate or the like, a hydroxyalkyl ester having 1 to 8 carbon atoms of acrylic acid or methacrylic acid; acrylic acid, Α, β-ethylenically unsaturated carboxylic acids such as methacrylic acid, maleic acid, itaconic acid, crotonic acid; acrylamide, methacrylamide, N-methylacrylamide, N-ethylmethacrylamide, diacetoneacrylamide, N-methylolacrylamide;
Acrylamide or methacrylamide such as N-methylol methacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide or derivatives thereof; aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; vinyl propionate; Vinyl acetate, acrylonitrile, methacrylonitrile, vinyl pivalate, beoba monomer (manufactured by Shell Chemical Co., vinyl ester of branched fatty acid), Silaprene F
M0711, FM0721, FM0725 (or more,
All of them include other vinyl monomers such as polydimethylsiloxane macromonomer having a methacryloyl group at the end and manufactured by Chisso Corporation. Of these monomers, styrene and methyl methacrylate are particularly preferred.

The copolymer (C) is prepared by subjecting a monomer component composed of the above-mentioned glycidyl monomer and, if necessary, other monomer to solution polymerization, bulk polymerization, emulsion polymerization in the presence or absence of a radical polymerization initiator, for example. , Suspension polymerization or the like, and can be obtained by polymerization using a polymerization method known per se. The copolymer (C) has a number average molecular weight of generally from 1,000 to 100,000, especially from 2,000 to 50,000.
Preferably it is in the range of 000.

The proportion of each monomer component in the polymerization of the copolymer (C) is preferably within the following range based on 100 parts by weight of the total amount of the monomer components.

Glycidyl monomer: 10 to 100 parts by weight, preferably 20 to 80 parts by weight Other monomer: 0 to 90 parts by weight, preferably 20
~ 80 parts by weight.

In the copolymer (C), the concentration of the glycidyl group is generally from 0.1 to 7.0 equivalents / kg, especially from 0.2 to 7.0 equivalents / kg.
It is preferably in the range of ~ 5.0 equivalents / kg.

In the polymerization of the copolymer (C), by using a polydimethylsiloxane macromonomer such as Silaplane FM0721 as another monomer, the leveling property of the obtained coating film and the coating film after retort treatment can be obtained. Lubricity can be improved.

Cationic polymerization initiator (D) Cationic polymerization initiator (D) used in the present invention
Is a compound that generates a cation by ultraviolet irradiation to initiate polymerization, and for example, the following formulas (I) to (XV)
And hexafluoroantimonate salts, pentafluorohydroxyantimonate salts, hexafluorophosphate salts, hexafluoroarsenate salts and other cationic polymerization initiators.

[0076] _{^{Ar 2 I + · X - (}} I) wherein, Ar represents an aryl group such as phenyl group,
X ^- is _{^{PF 6 -, SbF 6 -,}} AsF 6 - or B (C ₆ F ₅₎ represented by the following formula ₄ ^- represents a

[0077]

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[0078] _{^{Ar 3 S + · X - (}} II) wherein, Ar and X ^- is the same as defined above,

[0079]

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In the formula, R ²⁰ represents an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms;
Represents an integer of 3, and X ⁻ has the same meaning as described above;

[0081]

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Where Y ⁻ is PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻
Or SbF ₅ (OH) ^—

[0083]

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In the formula, X ⁻ has the same meaning as described above.

[0085]

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In the formula, X ⁻ has the same meaning as described above.

[0087]

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In the formula, X ⁻ has the same meaning as described above.

[0089]

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In the formula, R ²¹ represents an aralkyl group having 7 to 15 carbon atoms or an alkenyl group having 3 to 9 carbon atoms;
R ²² represents a hydrocarbon group or a hydroxyphenyl group having 1 to 7 carbon atoms, R ²³ represents an oxygen atom or an alkyl group having 1 to 5 carbon atoms which may contain a sulfur atom, X ^- is Having the above meaning,

[0091]

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In the formula, R ²⁴ and R ²⁵ each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms.

[0093]

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Wherein R ²⁴ and R ²⁵ have the same meaning as above

[0095]

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As the cationic polymerization initiator (C), commercially available products can be used. Examples of the commercially available products include Cyracure UVI-6970, UVI-6974, and UCI
VI-6990 (all, manufactured by Union Carbide of the United States), Irgacure 264 (manufactured by Ciba-Geigy),
CIT-1682 (manufactured by Nippon Soda Co., Ltd.) and the like can be mentioned.

Among the cationic polymerization initiators described above,
From the viewpoints of toxicity, versatility, and the like, a compound having a hexafluorophosphate anion (PF ₆ ⁻ ) is preferable.

In the coating composition of the present invention, in addition to the essential components (A), (B), (C) and (D), if necessary, a lubricity-imparting agent; a sensitizer; Pigments and dyes such as coloring pigments and extenders that do not significantly inhibit curing; modified resins such as polyol resins, phenolic resins, acrylic resins, polyester resins, polyolefin resins, epoxy resins, and epoxidized polybutadiene resins; organic resin fine particles A solvent or the like can be blended.

The above-mentioned lubricity imparting agent is compounded for the purpose of improving the lubricity of the obtained coating film.
Examples include waxes such as fatty acid ester wax, which is an esterified product of a polyol compound and a fatty acid, silicon-based wax, fluorine-based wax, polyolefin wax, animal-based wax, and plant-based wax.

The polyol compound used as a raw material of the fatty acid ester wax includes ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexane. Diol, glycerin, di- or higher polyglycerin, trimethylolpropane, pentaerythritol, dipentaerythritol and the like can be mentioned. Of these, polyol compounds having three or more hydroxyl groups in one molecule are preferable, and polyglycerin, trimethylolpropane, and pentaerythritol are particularly preferable.

The fatty acid used as another raw material of the fatty acid ester wax may be a saturated or unsaturated fatty acid, and is preferably a fatty acid having 6 to 32 carbon atoms. Specific examples of suitable fatty acids include caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachiic acid,
Saturated fatty acids such as behenic acid, cerotic acid, montanic acid, and melicic acid; caproleic acid, undecylenic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, eleostearic acid, setreic acid, erucic acid, licanoic acid, ricinoleic acid And unsaturated fatty acids such as arachidonic acid.

As the fatty acid ester wax, a wax in which at least 1/3 of the number of hydroxyl groups of the above polyol compound is esterified with a fatty acid is preferable.

Examples of the silicone wax include B
YK-300, BYK-320, BYK-330 [all manufactured by BYK Chemie (Big Chemie)]
Silwet L-77, Shilwet L-720, Silwet L-7602 [Nippon Unicar Co., Ltd.
Paintad 29, Paintad 32, Paintad M (both manufactured by Dow Corning) and Shin-Etsu Silicone KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.). -1MG, shamrock wax SST-3,
Shamrock wax fluoroslip 231 [or more,
Shamrock Chemicals Co., Ltd.], POLYFLUO
(Polyfluo) 120, 150, and 400 (Micro Powders).

Examples of the polyolefin wax include shamrock wax S-394 and shamrock wax S-395 (all manufactured by Shamrock Chemicals), Hoechst wax PE-520, and Hoechst wax PE-521 (all manufactured by Hoechst) ], Mitsui High Wax [manufactured by Mitsui Petrochemical Industry Co., Ltd.], and the like.
Examples of the animal wax include lanolin and beeswax, and examples of the plant wax include carnauba wax and water wax.

The lubricating agents described above can be used alone or in combination of two or more. The compounding amount of the lubricity-imparting agent is determined by the epoxy compound (A)
To 10 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the total amount of oxetane compound (B) and oxetane compound (B). it can.

Among the above lubricity-imparting agents, silicone-based wax has excellent lubricity-imparting property after coating is cured and before retort treatment, and fatty acid ester wax is excellent in lubrication-imparting property after painting is cured and after retort treatment. ing. Therefore, it is preferable to mix at least one selected from a silicone wax and a fatty acid ester wax. Above all, when the silicone-based wax is used in an amount of 0.01 to 5 parts by weight and the fatty acid ester wax is used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of the epoxy compound (A) and the oxetane compound (B), A coating film having excellent lubricity before and after retort treatment can be obtained.

The sensitizer is added for the purpose of further improving the curability by ultraviolet rays, and examples thereof include pyrene, perylene, acridine orange, thioxanthone, 2-chlorothioxanthone, and benzoflavin. . The compounding amount of this sensitizer is a total amount of the epoxy compound (A) and the oxetane compound (B) of 10
0 parts by weight or less, usually 10 parts by weight or less, preferably 3 parts by weight
Used within the range of parts by weight or less.

When a modified resin is blended, the modified resin is usually added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of the epoxy compound (A) and the oxetane compound (B).
It is preferably used in an amount of 0 parts by weight, particularly 5 to 20 parts by weight. Among the modified resins, epoxidized polybutadiene resin is particularly effective for improving the processability and adhesion of the coating film.

The organic resin fine particles have a particle size of 5
Organic resin fine particles in the range of 0 to 500 nm are preferable,
For example, acrylic resin fine particles whose inside is three-dimensionally crosslinked can be used. Organic resin fine particles include those obtained by pulverizing an organic polymer into fine particles; drying and pulverizing polymer fine particles obtained by emulsion polymerization in water in the presence of an emulsifier; Dry and pulverized polymer fine particles obtained by dispersion polymerization in a solvent can be used. By blending the organic resin fine particles with the coating composition of the present invention, the adhesion and processability of the coating film can be improved. When the organic resin fine particles are compounded, the compounding amounts of the organic resin fine particles are the epoxy compound (A) and the oxetane compound (B).
Is preferably 0.1 to 50 parts by weight, particularly preferably 1 to 10 parts by weight, based on 100 parts by weight of the total amount of

Coating Composition The coating composition of the present invention is obtained by mixing the above-mentioned components,
It can be prepared by stirring to obtain a uniform coating composition. For example, it can be prepared by mixing the components, heating if necessary (for example, about 50 ° C.), and stirring with a stirrer such as a dissolver until the mixture becomes uniform, for example, for about 10 minutes.

The proportions of the epoxy compound (A), oxetane compound (B), copolymer (C) and cationic polymerization initiator (D) can be as follows.

That is, the compound (A) is used in an amount of 10 to 90 parts by weight, preferably 20 to 70 parts by weight, in such a ratio that the total amount of the epoxy compound (A) and the oxetane compound (B) is 100 parts by weight. More preferably, 30 to 6
0 parts by weight, and 10 to 90 parts by weight of the compound (B), preferably 30 to 80 parts by weight, more preferably 40 to 7 parts by weight.
It can be used within the range of 0 parts by weight. When the amount of the epoxy compound (A) is less than 10 parts by weight in the total amount of 100 parts by weight, the hardness and adhesion of the obtained coating film are poor, while the amount of the epoxy compound (A) is 90 parts by weight. If the ratio exceeds the above range, the curability and retort resistance of the coating film due to irradiation with a low irradiation amount of ultraviolet light tend to be inferior.

The copolymer (C) is used in an amount of 1 to 50 parts by weight, preferably 100 parts by weight of the total amount of the epoxy compound (A) and the oxetane compound (B). It can be in the range of 3 to 30 parts by weight, more preferably 5 to 20 parts by weight. When the amount of the copolymer (C) is less than 1 part by weight, the hardness of the coating film after heating in post-heating at the time of ultraviolet irradiation at a low irradiation amount, the adhesion of the coating film, the coating film hardness, etc., decrease. On the other hand, when the amount of the copolymer (C) exceeds 50 parts by weight, the curability by ultraviolet irradiation at a low irradiation amount is particularly poor, and the hardness and retort resistance of the coating film tend to decrease.

The amount of the cationic polymerization initiator (D) used is the same as that of the epoxy compound (A) and the oxetane compound (B).
The cationic polymerization initiator (D) is used in an amount of 0.01 to 20 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of
0 parts by weight, more preferably 1 to 5 parts by weight.

The ultraviolet-curable can coating composition of the present invention comprises:
UV curable, tin, aluminum, tin-free steel, iron, zinc, copper, galvanized steel,
Metal plates molded into metal cans such as alloy-plated steel plates of zinc and other metals (this metal plate may be subjected to a chemical conversion treatment such as zinc phosphate treatment or chromate treatment); these metal plates Polyester resins such as polyethylene terephthalate, polyolefin resins such as polyethylene and polypropylene, polyamide resins, epoxy resins,
A resin film-laminated metal plate obtained by laminating a resin film such as polyvinyl chloride; or a metal can molded from such a metal plate can be coated and irradiated with ultraviolet rays to form a cured coating film. The thickness of the coating film can be appropriately selected depending on the application, but is generally in the range of about 2 to 20 μm, preferably about 2 to 8 μm as a dry coating film thickness.

The UV-curable can coating composition of the present invention comprises:
For example, roll coat painting, spray painting, brush painting,
It can be applied by a coating method such as bar coating, roller coating, and silk screen printing. If the coating contains a solvent, after coating, after removing the solvent by heating, etc., the coating is cured by ultraviolet irradiation,
Irradiation conditions can be appropriately changed according to the type and thickness of the coated coating composition. The wavelength of the ultraviolet light to be irradiated is usually appropriately in the range of 200 to 600 nm, and an irradiation source having a wavelength with high sensitivity can be appropriately selected and used depending on the kind of the cationic polymerization initiator. .

Examples of the ultraviolet irradiation source include a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a carbon arc, a metal halide lamp, and sunlight. Irradiation conditions for the coating film are usually 10 doses.
１，1,000 mJ / cm ² , especially 50-500 mJ / c
m ² is suitable.

After the irradiation with ultraviolet rays, the coating film may be heated, if necessary. By heating, unreacted substances in the coating film can be reduced, and curability of the coating film by irradiation with ultraviolet rays and distortion of the coating film caused by molding can be reduced. In some cases, this heating can improve the hardness and adhesion of the coating film. The heating is usually 150 to 25.
The reaction can be performed at an atmosphere temperature of 0 ° C. for 1 to 30 minutes.

[0119]

The ultraviolet-curable can coating composition of the present invention contains an epoxy compound (A), an oxetane compound (B) and a copolymer (C) as a film-forming resin component, In the presence of a polymerization initiator, it can be efficiently cured by cationic polymerization even with a low dose of UV irradiation without the need for equipment such as nitrogen encapsulation, and is required as a paint for cans even in thin films. Excellent coating properties such as processability, adhesion, hardness, and scratch resistance, as well as coating appearance, hardness in hot water, retort resistance,
It is possible to form a coating film having excellent lubricity retention after retort treatment. Therefore, the coating composition of the present invention is particularly suitable as a coating for the outer surface of a can.

[0120]

The present invention will be described more specifically with reference to the following examples. The “parts” and “%” are based on weight.

At least one glycidyl group in the molecule
Production Example 1 of Copolymer (C) to be Prepared Toluene 500 was placed in a flask equipped with a stirrer and a cooler.
The resulting mixture was heated to 95 ° C. while stirring. Then, while maintaining the same temperature, a mixture in which 125 parts of glycidyl methacrylate, 375 parts of styrene and 50 parts of 2,2'-azobisisobutyronitrile were previously mixed and dissolved was added dropwise over 4 hours, and polymerization was carried out. After that, toluene was removed by distillation under reduced pressure to obtain a copolymer (C). The obtained copolymer (C) had a number average molecular weight of about 3,000, a glycidyl group concentration of 1.8 equivalents / kg, and a glass transition temperature (Tg).
Had a temperature of 85 ° C.

Production Examples 2 to 9 Various copolymers were obtained in the same manner as in Production Example 1 except that the composition of the mixture to be dropped was as shown in Table 1 below. The number average molecular weight, glycidyl group concentration and glass transition temperature (Tg) of the obtained copolymer are shown in Table 1 below. The copolymers obtained in Production Examples 7 and 8 are comparative copolymers. The amounts of each component in Table 1 are expressed in parts by weight.

[0123]

[Table 1]

(Note) in Table 1 has the following meanings.

(Note 1) FM0711: manufactured by Chisso Corporation, trade name “Silaplane FM0711”, methacrylate having a polydimethylsiloxane chain, molecular weight of about 1,
000.

(Note 2) AIBN: 2,2'-azobisisobutyronitrile.

Example 1 60 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (denoted as "Compound A-1" in Table 2), 3-ethyl-3-hydroxymethyloxetane ( In Table 2, "Compound B-1-
1)), R ⁶¹ in the above formula (12)
Are all ethyl groups (in Table 2, denoted as “Compound B-2-1”), 20 parts, the copolymer (C) obtained in Production Example 1, 10 parts, Cyracure UVI-6990 (US , Union carbide Corporation, PF ₆ ^- cationic photopolymerization initiator) 6 parts of a polymerization degree of 10 of decaglycerol ether (1 molecule is a polyglycerol to the hydroxyl group of 12 with
And 1 part of a fatty acid ester wax obtained by reacting 1 mol of
(Silicon wax manufactured by Dow Corning Co.) was mixed in an amount of 0.2 part, and the mixture was stirred at 50 ° C. for 20 minutes to obtain an ultraviolet-curable can coating composition.

Examples 2 to 16 and Comparative Examples 1 to 6 The same operations as in Example 1 were carried out except for using the formulations shown in Table 2 below to obtain each UV-curable can coating composition.

[0129]

[Table 2]

[0130]

[Table 3]

(Note) in Table 2 has the following meanings.

(Note 3) DECH: a compound having two alicyclic epoxy groups represented by the following formula in the molecule.

[0133]

Embedded image

(Note 4) GOX: 3-ethyl-3- (glycidyloxymethyl) -oxetane, represented by the following formula.

[0135]

Embedded image

(N represents the number of 3 on average) (Note 5) R-45EPI: trade name “Denalex R-45EPI” manufactured by Nagase Kasei Kogyo Co., Ltd., epoxidized polybutadiene resin.

(Note 6) CKM-1634: a resol-type phenolic resin manufactured by Showa Polymer Co., Ltd. (Note 7) Organic resin fine particles b: An aqueous dispersion of polymer fine particles produced by the following production method is placed on a stainless steel vat, and the solid resin dried in an electric hot air dryer at 60 ° C. is pulverized. Organic resin fine particles having an average particle diameter of 80 nm.

Production Method In a flask, 3540 parts of deionized water and 51 parts of "Eleminol JS-2" (a 39% aqueous solution of a sulfosuccinic allyl group-containing anionic reactive emulsifier) manufactured by Sanyo Chemical Industries, Ltd. were mixed. The temperature was raised to 90 ° C. while stirring. To this, 2,2'-azobis [2-methyl-N-
(2-hydroxyethyl) -propionamide] 12.
20% of a polymerization initiator aqueous solution obtained by dissolving 5 parts in 500 parts of deionized water was added. Then 5% of a monomer mixture of 470 parts of styrene, 470 parts of n-butyl acrylate and 60 parts of 1,6-hexanediol diacrylate were added. Then, after further stirring for 30 minutes, the dropping of the remaining monomer mixture and aqueous solution of the polymerization initiator was started. The dropping of the monomer mixture was performed in 3 hours, and the dropping of the polymerization initiator aqueous solution was performed in 3.5 hours, during which the polymerization temperature was 90 ° C.
Held. After the dropping of the aqueous polymerization initiator solution, the temperature was maintained at 90 ° C. for 30 minutes and then cooled to room temperature to obtain an aqueous dispersion of polymer fine particles having a solid content of about 20% and three-dimensionally cross-linked inside.

Preparation of Test Coated Plate Each of the coating compositions obtained in the above Examples and Comparative Examples was prepared to have a thickness of 0.1 mm
12μ thick tin free steel plate (TFS) of 20mm and tin free steel plate of 0.20mm thickness
m homo PET (polyethylene terephthalate) sheet is thermocompressed to a PET steel sheet with a dry film thickness of 5 μm each.
And apply UV light to a high pressure mercury lamp (160
(W / cm) from the distance of 15 cm from the coated plate so that the energy dose was 80 mJ / cm ^2, and the coating film was cured to obtain a test coated plate.

A test was performed on each of the obtained test coated plates based on the following test method. All tests were conducted for 20
C.

Test Method Pencil hardness : JIS K-5400 was applied to the coating film of the test coated plate.
The test was performed by a pencil scratch test specified in 8.4.2 (1990). The evaluation was performed by the tearing method.

Impact resistance (DuPont type) : JIS K-5
400 8.3.2 (1990), using a Dupont impact tester on the test coated plate from the opposite side of the coating surface under the conditions of 3/8 inch diameter of hammer, 500 g of falling weight load, and 50 cm of falling weight height. Impact processing was performed, the processed part was observed with a microscope, and evaluated according to the following criteria.

◎: No cracks or peeling of the coating film were observed at all. ○: Slight cracks were observed, but no peeling of the coating film was observed. Δ: A considerable crack was observed, but no peeling of the coating film was observed. ×: Adhesion with peeling of coating film observed: JIS K-5400 8.5.2 (199
0) According to the cross cut tape method, 1.
One hundred squares of 5 mm × 1.5 mm were prepared, an adhesive cellophane tape was stuck on the surface thereof, and the state of the squares after rapid peeling was evaluated according to the following criteria.

◎: No peeling was observed at all ○: Slight margins were removed from the squares Δ: Slight peeling was observed in addition to the margins of the squares ×: Hardness in hot water at which significant peeling was observed: Test coated plate After heating at 200 ° C for 1 minute, 8
It was immersed in warm water at 0 ° C. for 10 minutes, and the pencil hardness was measured in warm water at 80 ° C. Evaluation is JIS K-5400
4.2 (1990).

The leveling properties of the coating compositions obtained in the above Examples and Comparative Examples were tested according to the following method.

Leveling property : Each coating composition was applied on a PET steel sheet by a roll coating method (natural coating) so as to have a dry film thickness of 5 μm. The appearance of the coated surface when cured by irradiation with ultraviolet rays was visually evaluated. The evaluation was performed according to the following criteria.

◎: Rolled surface is not seen on the coated surface and excellent in smoothness. ：: Slightly rolled on the coated surface but good in smoothness. ：: Rolled on the coated surface. ×: Smoothness is considerably poor. ×: Rolls are remarkably observed on the coated surface, and the smoothness is extremely poor.

Smoothness retention of coating film after retort treatment : Each test coated plate obtained by forming a coating film of each coating material of each of Examples and Comparative Examples on a PET steel plate was heated at 200 ° C. for 1 minute, and then heated for 12 minutes.
The coefficient of kinetic friction of the coating film after being immersed in hot water at 5 ° C. for 30 minutes and subjected to pressure sterilization (retort treatment) and the test coated plate before being subjected to pressure sterilization after heating at 200 ° C. for 1 minute Was measured, and the ratio of (dynamic friction coefficient of coating film after pressure sterilization / dynamic friction coefficient of coating film without pressure sterilization treatment) was calculated. The smaller the ratio, the better the lubricity of the coating film after the retort treatment.

Test Results The results of the above test are shown in Table 3 below.

[0150]

[Table 4]

[0151]

[Table 5]

Claims (11)

[Claims] (A) 10 to 90 parts by weight of a compound having an alicyclic epoxy group in a molecule, and (B) 10 to 90 parts by weight of a compound having an oxetane ring in a molecule; For 100 parts by weight of the total amount of B),
(C) a copolymer of a glycidyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer, having at least one glycidyl group in the molecule and having a glass transition temperature of 30 ° C. or higher. A UV-curable can coating composition comprising 1 to 50 parts by weight of a coalescent and (D) 0.01 to 20 parts by weight of a cationic polymerization initiator which generates cations upon irradiation with ultraviolet light. 2. A compound (B) having an oxetane ring in the molecule, (B-1) a compound having at least one oxetane ring and at least one hydroxyl group in the molecule, and (B-
2) at least one compound selected from the group consisting of compounds having at least two oxetane rings in the molecule or having an oxetane ring and an epoxy group;
The coating composition according to any one of the preceding claims. 3. The coating composition according to claim 2, wherein the compound (B) having an oxetane ring in the molecule is a combination of the compound (B-1) and the compound (B-2). 4. The compound (B-1) is added to the compound (B-1) based on 100 parts by weight of the total of the compounds (A) and (B).
The coating composition according to claim 3, comprising 5 to 60 parts by weight and 5 to 60 parts by weight of the compound (B-2). 5. The coating composition according to claim 1, wherein the other polymerizable unsaturated monomer in the copolymer (C) is styrene and / or methyl methacrylate. 6. The coating composition according to claim 1, further comprising 0.01 to 10 parts by weight of a lubricity imparting agent based on 100 parts by weight of the total of compounds (A) and (B). 7. The coating composition according to claim 6, wherein the lubricity imparting agent is at least one selected from a fatty acid ester wax which is an esterified product of a polyol compound and a fatty acid, and a silicone wax. 8. The coating composition according to claim 1, further comprising 0.1 to 30 parts by weight of a phenolic resin based on 100 parts by weight of the total of compounds (A) and (B). 9. The method according to claim 1, further comprising 0.1 to 50 parts by weight of the epoxidized polybutadiene resin based on 100 parts by weight of the total amount of the compounds (A) and (B). The coating composition according to any one of the preceding claims. 10. The method according to claim 1, further comprising 0.1 to 50 parts by weight of the resin fine particles based on 100 parts by weight of the total amount of the compounds (A) and (B). The coating composition according to any one of the preceding claims. 11. The coating composition for an ultraviolet-curable can according to claim 1, applied to a metal plate, a resin film-laminated metal plate or a metal can formed by molding these metal plates, and cured by irradiating ultraviolet rays. A method for producing a coated metal can, characterized by the following.