JPH09143396A - Ultraviolet-curable resin composition for coating metallic can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-curable resin composition useful as a coating agent which can form a coating film excellent in adhesion to metallic cans or drawn metallic cans coated with a polyester film, processability, heat resistance and hardness. SOLUTION: This ultraviolet-curable resin composition for coating metallic cans comprises a radical-polymerizable compound, a non-radical-polymerizable compound having a glass transition point of 40 deg.C or above and a radical photopolymerization initiator and has a viscosity of 50-1,000cP at 25 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition which is cured by ultraviolet irradiation, and more particularly to an ultraviolet curable resin composition which is useful as a coating agent for metal cans and polyester film-coated drawn metal cans.

[0002]

2. Description of the Related Art Various resin systems have been studied as a curable resin composition which does not contain an organic solvent which is one of the causes of air pollution. One of them is UV curable resin. As the ultraviolet curable resin, an acrylic resin as a radical polymerization type, an unsaturated polyester resin,
Polyene-thiol resin, cationic polymerization type epoxy resin, vinyl ether resin and the like are known.
Vinyl ether resins are also known as radical polymerization types. These resin compositions are used as coating agents, printing inks, adhesives and the like.

The radical polymerization type using an acrylic resin is, for example, a photocurable resin composition mainly composed of a reactive oligomer and norbornyl (meth) acrylate (JP-A-7-2962) and a reactive diluting monomer. As a photocurable resin composition using 4-t-butylcyclohexyl (meth) acrylate as a compound (JP-A-7-18037), JP-A-7-157668 discloses an unsaturated group-containing compound and a vinyl ether compound. The radiation curable resin composition used is disclosed.

Furthermore, an active energy ray-curable resin composition using a pentaerythritol-based acrylate and a non-radical-polymerizable resin having a softening point of 30 ° C. or higher (JP-A-7-1)
1166) and the like are disclosed.

A metal can made of aluminum or steel or a polyester film-coated squeezed metal can (a polyester film-coated squeezed metal can is formed by laminating a polyethylene terephthalate film on a metal plate of aluminum or steel and squeezing it into a cylindrical type having a capacity of 200 cc to 500 cc After being coated with a coating agent, the neck-in processing for the lid winding part and the diamond cutting processing for the body of the can (the square pyramid-shaped irregularities are added) are applied. After being filled, the retort treatment (hot water treatment at 130 ° C. for 30 minutes) for sterilizing the contents is performed. Therefore,
Such coating materials are required to have various high-level properties (adhesion of cured coating film, workability, retort resistance, etc.) and high-speed curing properties. Moreover, since the resin composition for coating a metal can is coated at a high speed of 100 m / min or more and a beautiful coating surface is required, the resin composition for coating a metal can has a flow and leveling capable of supporting high-speed coating. Goodness is required. However, conventional acrylic resins have insufficient flow, leveling, adhesion, processability, and retort resistance,
It was not satisfactory as a coating agent for metal cans and polyester film coated drawn metal cans. In order to improve the flow and leveling, addition of a non-reactive organic solvent has been considered, but it is against the flow of the ultraviolet curable resin composition aiming not to contain the organic solvent. Is.

[0006]

The object of the present invention is to have excellent adhesion to metal cans and polyester film-coated drawn metal cans, workability, heat resistance, and coating hardness, and
An object of the present invention is to provide an ultraviolet-curable resin composition that does not contain a non-reactive organic solvent and is useful as a coating material that can be applied at high speed.

[0007]

That is, the first invention is a radically polymerizable compound (A) having a glass transition point of 40.
A non-radical-polymerizable compound (B) having a temperature of not less than 150 ° C and not more than 150 ° C,
And a photoradical polymerization initiator (C), and a viscosity at 25 ° C. of 50 to 1000 cps, which is an ultraviolet-curable resin composition for coating a metal can. The second invention is a non-radical polymerization. First, the number average molecular weight of the organic compound (B) is 500 or more and 5000 or less.
An ultraviolet-curable resin composition for coating a metal can according to the invention, further comprising a non-radical polymerizable compound (B).
Is a ketone formaldehyde resin, which is the ultraviolet-curable resin composition for coating a metal can according to any one of the first and second inventions. Further, a fourth invention is the ultraviolet-curable resin composition for coating a metal can according to any one of the first invention to the third invention, which contains a pigment (D), and a fifth invention. Is an ultraviolet-curable resin composition for coating a metal can according to any one of the first to fourth inventions, characterized in that it covers a polyester film-covered drawn metal can.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The radical-polymerizable compound (A) used in the present invention represents a reactive oligomer having a radical-polymerizable unsaturated double bond in the molecule and a reactive diluting monomer. Examples of the reactive oligomer include polyester (meth) acrylate obtained by reaction of saturated or unsaturated polycarboxylic acid with alkyl polyol and (meth) acrylic acid, and reaction of epoxy resin with (meth) acrylic acid. Epoxy poly (meth) acrylate, urethane poly (meth) acrylate obtained by the reaction of polyol, polyisocyanate and hydroxyl group-containing (meth) acrylate, and polysiloxane poly (poly (siloxane) obtained by the reaction of polysiloxane and (meth) acrylic acid. Examples thereof include (meth) acrylates and polyamide poly (meth) acrylates obtained by reacting polyamide with (meth) acrylic acid. Among them, particularly preferable oligomers as a coating agent for metal cans are polyester (meth) acrylate and epoxy poly (meth) acrylate.

The reactive diluent monomer of the present invention is 1
A functional substance, a bifunctional, a trifunctional, a tetrafunctional or higher can be appropriately selected, and a liquid substance having a viscosity at 25 ° C. of 500 cps or less is preferable. Among the reactive diluting monomers, monofunctional ones include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate and propyl (meth) acrylate, and (meth) acrylates of alkylene oxide adducts of alkylphenols. (Meth) acrylate-based monofunctional diluents such as, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate,

Monofunctional vinyl ether type diluents such as chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, glycidyl vinyl ether, glycidyl ethyl vinyl ether, hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether and phenylethyl vinyl ether can be mentioned.

As the bifunctional (meth) acrylate diluent, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butylene glycol di ( (Meth) acrylate, bisphenol A alkylene oxide di (meth) acrylate, bisphenol F
Examples thereof include alkylene oxide di (meth) acrylate.

Examples of the bifunctional vinyl ether diluent include diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclohexane dimethylol divinyl ether and 1,6-hexane divinyl ether.

Among the reactive diluting monomers, (meth) acrylate-based trifunctional ones include trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate and glycerin tri (meth) acrylate. ,

Examples of the (meth) acrylate-based tetrafunctional or higher-functional diluent monomer include ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol alkylene oxide tetra (meth) acrylate, and dipentaerythritol hexa (meth). ) Acrylate and the like,

Examples of trifunctional or higher functional vinyl ether-based diluting monomers include trimethylolpropane trivinyl ether and polyester polyvinyl ether.

The non-radical-polymerizable compound (B) used in the present invention means a compound inactive to radical polymerization. Since it is inactive against radical polymerization, it can suppress or alleviate curing strain during radical polymerization and maintain or improve the adhesion of the coating film. The glass transition temperature (hereinafter abbreviated as Tg) of these non-radical polymerizable compounds (B) is 40 ° C. or higher and 150 ° C. or lower. Glass transition temperature 40
If the temperature is below ℃, the heat resistance of the coating film will be poor, and the hardness of the coating film will be insufficient, and it will not be put to practical use for metal cans. Glass transition temperature is 15
If the temperature is higher than 0 ° C, the coating becomes brittle and the workability is poor.
The number average molecular weight (hereinafter abbreviated as Mn) of these non-radical polymerizable compounds (B) is preferably 500 or more and 5000 or less. If the number average molecular weight is less than 500, the adhesion to the metal can and the polyester film-coated drawn metal can will be insufficient, and if the number average molecular weight is more than 5000, the viscosity as a coating agent will increase and coating will be difficult.

Specific examples of the non-radical polymerizable compound (B) used in the present invention include ketone formaldehyde resin, xylene formaldehyde resin, epoxy resin, polyester resin and terpene resin.

The ketone formaldehyde resin is synthesized by addition condensation of aromatic and / or aliphatic ketone and formaldehyde, and its hydrogenated product or isocyanate modified product can be used. For example, Synthetic resin AP manufactured by Huls
(Tg: 51 ° C., Mn: 780), Synthetic
resin SK (Tg: 83 ° C, Mn: 800), S
synthetic resin BL1201 (Tg:
124 ° C., Mn: 1800) and the like.

A xylene-formaldehyde resin synthesized by addition condensation of meta-xylene and formaldehyde and a derivative thereof modified with mesitylene or phenol are also suitably used. For example, Nikanol Resin HP-120 (Tg: 76. 8 ° C, Mn: 130
0), Nikanol Resin HP-100 (Tg: 67.5)
C, Mn: 1200), Nikanol Resin GHP-16
0 (Tg: 114 ° C., Mn: 1500) and the like.

As the epoxy resin, bisphenol A
And / or a bisphenol-type epoxy resin obtained by addition polymerization of bisphenol F and epichlorohydrin. Examples of the bisphenol A-type resin include Epicoat 1004 (Tg: 53) manufactured by Yuka Shell Epoxy Co., Ltd.
C, Mn: 1400), Epicoat 1007 (Tg: 6)
9 ° C., Mn: 2900), Epicoat 1009 (Tg:
79 ° C., Mn: 3800), as a bisphenol F type, Epicoat 4004P (Tg: 43 ° C., Mn: 163)
0), Epicoat 4007P (Tg: 59 ° C., Mn: 3)
166), Epicoat 4009P (Tg: 62 ° C., M
n: 4100), Epicoat 4010P (Tg: 63)
C., Mn: 4640) and the like.

The polyester resin is preferably a linear saturated polyester obtained by a condensation reaction of a polybasic acid and a polyhydric alcohol. For example, Byron 2 made by Toyobo
20 (Tg: 53 ° C., Mn: 2000 to 3000) and the like.

The terpene-based resin is a general term for resins made from turpentine oil obtained from raw pine resin, kraft pulp and pine chips, for example CLE manufactured by Yasuhara Chemical Co.
ARON P-125 (Tg: 68 ° C, Mn: 700)
Or YS RESIN TO-125 (Tg: 64 ° C,
Mn: 800) and the like.

In addition, melamine formaldehyde resin, benzoguanamine formaldehyde resin, phenol formaldehyde resin, epoxy resin, terpene resin, rosin resin, acrylic resin, urethane resin, etc. can be used as long as the condition of Tg: 40 to 150 ° C. is satisfied. They can be used alone or in combination as appropriate.

The mixing ratio of the radical-polymerizable compound (A) and the non-radical-polymerizable compound (B) is A / B = 95/5 to
40/60 is preferable, and more preferably A / B = 80
/ 20 to 60/40. If the amount of the non-radical polymerizable compound is less than 5 parts, the adhesiveness and heat resistance will deteriorate, and
If it exceeds 0 parts, the curability tends to deteriorate.

The photo-radical polymerization initiator (C) used in the present invention can be arbitrarily selected from known ones and used alone or in appropriate combination. Specific examples thereof include hydrogen abstraction type photopolymerization initiators such as benzophenone, methyl orthobenzoylbenzoate, diethylthioxanthone, and isopropylthioxanthone, benzoin ether, benzyldimethylketal, α-hydroxyalkylphenone, α-aminoalkylphenone, and acylphosphine. Examples thereof include intramolecular cleavage type photopolymerization initiators such as fin oxide.

It is important that the viscosity of the ultraviolet curable resin composition for coating a metal can of the present invention is 50 to 1000 cps. That is, if the viscosity is less than 50 cps, mist is generated or paint sags during high-speed coating, and if it exceeds 1000 cps, flow and leveling are poor and a smooth and beautiful coated surface cannot be obtained. Therefore, it is important that the viscosity is 50 to 1000 cps.

The ultraviolet-curable resin composition for coating a metal can of the present invention is used as a clear top coat paint or a size coat paint on the outer surface of a metal can or a polyester film-coated drawn metal can without adding a pigment (D). By using or by blending the pigment (D), it can be used as a white coat paint. As the pigment (D),
Examples thereof include titanium oxide, barium sulfate, phthalocyanine blue, benzidine yellow, watching red, carbon black, etc. When used as a white coat paint, titanium dioxide is preferable. Can also be used.

The ultraviolet curable resin composition for coating a metal can of the present invention further comprises a sensitizer, a thermal polymerization catalyst, a thermal polymerization inhibitor, a surfactant, a slip agent, an antifoaming agent, etc., depending on the purpose. Can be blended.

The ultraviolet-curable resin composition for coating a metal can of the present invention is applied to the surface of a metal can made of aluminum or steel and a polyester film-coated drawn metal can. As a coating method, roll coating, gravure coating, gravure offset coating, curtain flow coating, reverse coating, screen printing, spray coating, dipping and the like can be used.

A light source for photocuring the ultraviolet-curable resin composition for coating a metal can of the present invention is usually 200
A light source containing light in the range of up to 500 nm, for example, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a gallium lamp, a xenon lamp, a carbon arc lamp or the like can be used. In addition, these light sources, infrared, far infrared, hot air,
It is also possible to use heat by high frequency heating or the like together.

[0031]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto. In the examples, parts and% mean parts by weight and% by weight, respectively.

[0032]

Example 1 Bisphenol A type epoxy acrylate 60 parts (Ebecryl EB600 manufactured by Daicel UCB) Ketone formaldehyde resin (Tg: 51 ° C., MW: 780) 20 parts (Synthetic resin AP manufactured by Huls) 1-Hydroxycyclohexylphenyl 5 parts of ketone (Irgacure 184 manufactured by Ciba-Geigy) 20 parts of chloroethyl vinyl ether were mixed and stirred to prepare a paint 1. A material obtained by laminating a 100 μm PET film on a tin-free steel plate with a thickness of 300 μm (hereinafter referred to as “PET
/ TFS ") PET film and thickness 30
A film thickness of 10 μm each on a 0 μm aluminum plate
And apply under high pressure mercury lamp of 80W / cm for 1
It was passed at a speed of 0 m / min to obtain a cured coating film.

[0033]

Example 2 A resin having Tg: 83 ° C. and MW: 800 (S manufactured by Hüls) was added to the ketone formaldehyde resin of Example 1.
The mixture was mixed in the same manner as in Example 1 except that the synthetic resin SK was used, and 100 parts of titanium oxide (Taipaque CR-58 manufactured by Ishihara Sangyo Co., Ltd.) was further added to disperse the pigment to prepare a paint. Using this paint, a cured coating film was obtained in the same manner as in Example 1.

Examples 3 to 4 and Comparative Examples 1 to 4 In Examples 3 to 4 and Comparative Examples 1 to 4, coating materials were prepared with the compounding ratios shown in Tables 1 and 2, and the same method as in Example 1 was used. The coating was applied to obtain a cured coating film.

The viscosities of the coating materials obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and the adhesion, processability and heat resistance of the cured coating film,
The coating film hardness was evaluated by the method described below. The results are shown in Tables 1 to 3.

Viscosity: The viscosity at 25 ° C. was measured using a B type viscometer.

Adhesion: A cellophane tape peeling test was conducted based on JIS K5400, and the number of crosses where the coating film did not peel off per 100 crosses was displayed.

Workability: 1 using a DuPont impact tester
A test was performed with a 1/2 inch rod, a load of 500 g, and a height of 50 cm, and the state of the coating film was visually evaluated. ◎ No abnormality ○ Cracks were found in 1/4 of the test marks △ Cracks were found in 1/2 of the test marks × Cracks were generated on the entire surface

Heat resistance: The coating film subjected to the DuPont impact test was heat-treated at 200 ° C. for 1 minute, and the degree of peeling of the coating film was visually evaluated. ◎ No abnormality ○ Peeling of coating film was observed in 1/4 of the test traces △ Peeling of coating film was observed in 1/2 of the test traces × Peeling of coating film occurred on the entire surface

Coating hardness: Pencil hardness was measured according to JIS K5400.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

According to the present invention, high-speed coating is possible without containing a non-reactive organic solvent that causes air pollution,
Further, it is cured by irradiation with ultraviolet rays, and has good adhesion to metal cans and polyester film coated squeezed metal cans, workability,
An ultraviolet curable resin composition for coating a metal can having excellent heat resistance and coating film hardness was obtained.

Claims (5)

[Claims] 1. A radical-polymerizable compound (A), a non-radical-polymerizable compound (B) having a glass transition point of 40 ° C. or higher and 150 ° C. or lower, and a photo-radical polymerization initiator (C),
An ultraviolet curable resin composition for coating a metal can, which has a viscosity at 25 ° C. of 50 to 1000 cps. 2. The ultraviolet-curable resin composition for coating metal cans according to claim 1, wherein the number-average molecular weight of the non-radical-polymerizable compound (B) is 500 or more and 5000 or less. 3. The ultraviolet-curable resin composition for coating a metal can according to claim 1, wherein the non-radical-polymerizable compound (B) is a ketone formaldehyde resin. 4. The ultraviolet-curable resin composition for coating a metal can according to claim 1, which further comprises a pigment (D). 5. The ultraviolet-curable resin composition for coating a metal can according to claim 1, which coats a polyester film-coated drawn metal can.