JPH09143398A - Ultraviolet-curable resin composition and coating agent containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating resin compsn. which forms a coating film excellent in adhesion to a metal can, processibility, heat resistance, and hardness by compounding a free-radical-polymerizable (meth)acrylate compd., a non-free- radical-polymerizable compd., a pigment, and a specific photopolymn. initiator. SOLUTION: This ultraviolet-curable resin compsn. is obtd. by compounding a free-radical-polymerizable acrylate and/or methacrylate compd. (A) (e.g. a reactive oligomer or a reactive diluent monomer having at least one free-radical- polymerizable group such as CH2 =CHCOO- or CH2 =CCH3 COO- in the molecule), a non-free-radical-polymerizable compd. (B) having a glass transition point of 40-150 deg.C and a number average mol.wt. of 500-5,000 in a wt. ratio to ingredient A of (5:95)-(60:40), a pigment (C) in an amt. of 5-150wt.% of the sum of ingredients A and B, and an acylphosphine oxide photopolymn. initiator (D) in an amt. of 1-20wt.% of the sum of ingredients A and B.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art When an ultraviolet-curable composition containing a pigment is irradiated with ultraviolet rays to be cured, fine wrinkles in the form of wrinkles may be generated on the surface. It is considered that this phenomenon is caused by the fact that the pigment hinders the transmission of ultraviolet rays, so that only the surface layer is cured and the inside of the coating film is in an uncured state, and fine wrinkles in the form of wrinkles are generated.

As a method for solving these phenomena, a method of limiting the molecular weight and the number of double bonds of the radically polymerizable compound or reducing the pigment content as in JP-A-48-54135. There is. Alternatively, JP-A-54
-19897, JP-A-55-94, JP-A-55-28741 and the like, using a special ultraviolet irradiation device, or increasing the irradiation intensity of ultraviolet rays,
A method of slowing the line speed of ultraviolet irradiation is being used.

However, if the molecular weight of the radically polymerizable compound or the number of double bonds is limited, sufficient coating film physical properties cannot be obtained, and if the pigment content is reduced or the coating film is thinned, a sufficient coating film appearance is obtained. Not only is not obtained, but it is also insufficient in terms of resistance. Furthermore, using a special UV irradiation device, increasing the intensity of UV irradiation, or slowing the line speed may require new equipment investment, increase utility costs, or reduce production efficiency. However, it has a drawback that the production cost becomes high.

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. However, it was almost impossible to satisfy both the high-level characteristics and the high-speed curing property with the conventional technology.

[0006]

The object of the present invention is to have excellent adhesion, workability, heat resistance and coating film hardness to metal cans and polyester film-coated drawn metal cans, as well as high speed and internal curability. An excellent ultraviolet curable resin composition useful as a coating agent is provided.

[0007]

[Means for Solving the Problems] That is, the first invention is a radical-polymerizable acrylate and / or methacrylate compound (A), a non-radical-polymerizable compound (B),
An ultraviolet-curable resin composition comprising a pigment (C) and an acylphosphine oxide-based photopolymerization initiator (D). The second invention comprises a vinyl ether compound (E). The ultraviolet curable resin composition according to the first aspect of the invention, further characterized in that the non-radical polymerizable compound (B) is a ketone formaldehyde resin. The ultraviolet-curable resin composition according to any one of inventions 2 and 3. Further, a fourth invention is a coating agent comprising the ultraviolet curable resin composition according to any one of the first to third inventions, and the fifth invention is a coating for a metal can. The coating agent according to the fourth invention, characterized in that
The invention described in (4) is a coating agent according to the fourth invention, characterized in that it coats a polyester film-coated drawn metal can.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The radically polymerizable acrylate and / or methacrylate compound (A) used in the present invention is a radically polymerizable CH ₂ ═CHCO in the molecule.
Is a O- and CH ₂ = reactive with CCH ₃ COO- 1 or more oligomers and reactive diluent monomers. Examples of reactive oligomers include polyester (meth) acrylates obtained by reaction of saturated or unsaturated polycarboxylic acids with alkyl polyols and (meth) acrylic acid,
Epoxy poly (meth) acrylate obtained by reaction of epoxy resin and (meth) acrylic acid, urethane poly (meth) acrylate obtained by reaction of polyol, polyisocyanate and hydroxyl group-containing (meth) acrylate, polysiloxane and (meth ) Polysiloxane poly (meth) acrylate obtained by reaction with acrylic acid, polyamide poly (meth) acrylate obtained by reaction with polyamide (meth) acrylic acid, and the like. Among these, polyester (meth) acrylate and epoxy poly (meth) acrylate are particularly preferable as the coating agent for the metal can.

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. , Cyclohexyl (meth) acrylate, benzyl (meth) acrylate and the like.

Among the reactive diluting monomers, bifunctional ones include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butylene glycol. Examples thereof include di (meth) acrylate, bisphenol A alkylene oxide di (meth) acrylate, and bisphenol F alkylene oxide di (meth) acrylate.

Among the reactive diluting monomers, trifunctional ones include trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate and the like.
Examples of tetrafunctional or higher functional groups include ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol alkylene oxide tetra (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.

The non-radical polymerizable compound (B) used in the present invention means a compound which is inactive to radical polymerization. Since it is inactive against radical polymerization, it can suppress and alleviate curing strain during radical polymerization and maintain and improve the adhesion of the coating film. Glass transition temperature of these non-radical polymerizable compounds (B) (hereinafter abbreviated as Tg)
Is preferably 40 ° C. or higher and 150 ° C. or lower. When the glass transition temperature is 40 ° C or lower, the heat resistance of the coating film is poor,
If the retort treatment causes blisters, or if the glass transition temperature is 150 ° C. or higher, the coating film becomes brittle and the workability tends to be 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 500 or less, the adhesion to metal cans and polyester film-coated drawn metal cans tends to be insufficient.
When it is 0 or more, the viscosity of the coating agent increases, and it may be difficult to coat the metal can or the like.

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

The ketone formaldehyde resin is synthesized by addition condensation of aromatic and / or aliphatic ketone with formaldehyde, and its hydrogenated form or isocyanate modified form 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) manufactured by Mitsubishi Kasei Co., Ltd. 0.8 ° C, Mn: 13
00), Nikanol Resin HP-100 (Tg: 67.
5 ° C, Mn: 1200), Nikanol Resin GHP-1
60 (Tg: 114 ° C., Mn: 1500) and the like.

The epoxy resin is bisphenol A.
And / or a bisphenol type epoxy resin obtained by addition polymerization of bisphenol F and epichlorohydrin. Examples of the bisphenol A type include Epicoat 1004 (Tg: 53 ° C., manufactured by Yuka Shell Epoxy Co., Ltd.).
Mn: 1400), Epicoat 1007 (Tg: 69)
C, Mn: 2900), Epicoat 1009 (Tg: 7)
9 ° C., Mn: 3800), and as a bisphenol F type, Epicoat 4004P (Tg: 43 ° C., Mn: 16)
30), Epicor 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 220 (Tg: 53 ° C., Mn: 2000 to 3000) manufactured by Toyobo Co., Ltd. may be mentioned.

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 CL manufactured by Yasuhara Chemical Co.
EARON P-125 (Tg: 68 ° C., Mn: 70
0) and YS RESIN TO-125 (Tg: 64
C, Mn: 800).

In addition, melamine formaldehyde resin, benzoguanamine formaldehyde resin, phenol formaldehyde resin, epoxy resin, terpene resin, rosin resin, acrylic resin, urethane resin, etc. may be used alone or appropriately as long as they satisfy the condition of non-radical polymerizability. It can be used in combination.

The mixing ratio of the radical-polymerizable acrylate and / or methacrylate compound (A) and the non-radical-polymerizable compound (B) is preferably A / B = 95 / 5-40 / 60, more preferably A / B = 80 / 20-60 / 4
0. When the amount of the non-radical-polymerizable compound (B) is less than 5 parts, the adhesion and heat resistance tend to deteriorate,
If it exceeds 60 parts, the curability tends to deteriorate.

Examples of the pigment (C) used in the present invention include titanium oxide, carbon black, barium sulfate, phthalocyanine blue, benzidine yellow, and watching red. Further, aluminum powder, aluminum paste, zinc powder and the like are also used as pigments. These pigments (C) are used in an amount of 5 parts per 100 parts of the total amount of the radically polymerizable acrylate and / or methacrylate compound (A) and the non-radical polymerizable compound (B).
~ 150 parts can be blended, preferably 20-120.

The acylphosphine oxide photopolymerization initiator (D) used in the present invention has an absorption region even in a long wavelength region of 400 nm or more. Therefore, it has sufficient curability even in a system containing a pigment, which has an absorption range only in a short wavelength range and does not cure with other photo-radical polymerization initiators, and has excellent internal curability of the coating film. is there.

Specific examples of the acylphosphine oxide photopolymerization initiator (D) include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,2,6-trimethylbenzoyl-diphenylphosphine oxide.
A monofunctional initiator having only one photocleavage point in one molecule, such as 6-dichlorobenzoyl-diphenylphosphine oxide, and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl. Pentylphosphine oxide, bis (2,6 dichlorobenzoyl) -4
-Propylphenylphosphine oxide, bis (2,6dichlorobenzoyl) -2,5 dimethylphenylphosphine oxide, etc. are bifunctional initiators having two photocleavage points in one molecule. .

Such a photo-radical polymerization initiator (D) is
1 to 2 per 100 parts by weight of the total amount of the radical-polymerizable acrylate and / or methacrylic compound (A), the non-radical-polymerizable compound (B) and the vinyl ether compound (C).
0 parts can be added.

In the present invention, by using the acylphosphine oxide photopolymerization initiator (D), rapid internal curability in a pigment-containing system, which has been difficult in the past, is excellent, and a non-radical polymerizable compound (B By using (1) as an essential component, it is possible to suppress a large curing strain that tends to occur in a system having excellent curability, and to provide excellent adhesion, processability and the like.

The vinyl ether compound (E) used in the present invention has a vinyl ether group represented by CH ₂ ═CH—O—C, and the compound having such a functional group has cationic polymerizability and radical polymerization. It is also a compound having properties. Such vinyl ether compound (E)
Examples of the compound include various compounds. However, when a polyfunctional compound having two or more vinyl ether groups is used, curing strain may occur, resulting in poor adhesion. Therefore, it is preferable to use a monofunctional compound. It is preferable to have a Cl group, an OH group, a phenyl group or a glycidyl group from the viewpoint of excellent adhesion to a substrate, and a Cl group or a glycidyl group is most desirable from the viewpoint of adhesion to a polyester film.

Examples of such vinyl ether compound (E) include chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether,
Examples thereof include hydroxy-el vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, glycidyl vinyl ether, glycidyl ethyl vinyl ether and phenyl ethyl vinyl ether.

Radical-polymerizable acrylate and / or methacrylate compounds and non-radical-polymerizable compounds (A +
The mixing ratio of B) and vinyl ether compound (E) is (A
+ B) / E = 95/5 to 10/90, more preferably,
(A + B) / E = 80/20 to 30/70.

The photocurable coating composition of the present invention comprises a sensitizer, a thermal polymerization catalyst, a thermal polymerization inhibitor, a surfactant, a slip agent, an antifoaming agent, a reactive or non-reactive diluent depending on the purpose. Agents and the like can be added.

The ultraviolet-curable resin composition of the present invention is preferably used as a coating agent for aluminum or steel metal cans and polyester film-coated drawn metal cans. Terephthalate, polyethylene, polypropylene, nylon,
It is also applied to the surface of plastic films such as vinyl chloride, vinylidene chloride, and polycarbonate, and plastic molded products. As a coating method, roll coat,
It can be applied by a gravure coat, a gravure offset coat, a curtain flow coat, a reverse coat, a screen printing, a spray coating and a dipping method.

As the light source for photocuring the ultraviolet type coating composition of the present invention and the coating agent containing the same, a light source containing light in the range of 200 to 450 nm is usually used, for example, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide. A 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,
It is also possible to use heat by hot air, high frequency heating, or the like.

[0033]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0034]

Example 1 Bisphenol A type epoxy acrylate 50 parts (Ebecryl EB600 manufactured by Daicel UCB) Triethylene glycol diacrylate 30 parts Ketone formaldehyde resin (Tg: 83 ° C., Mn: 800) 20 parts (Synthetic resin manufactured by Huls) SK) 2,4,6-Trimethylbenzoyldiphenylphosphine oxide 5 parts Rutile type titanium oxide 100 parts (Taipaque CR-58 manufactured by Ishihara Sangyo Co., Ltd.) were mixed and dispersed in a sand mill for 1 hour to prepare coating material 1.

Examples 2 to 4 and Comparative Examples 1 to 3 In Examples 2 to 4, coating materials were prepared according to the compounding ratios shown in Table 1, and in Comparative Examples 1 to 3, coating materials were prepared according to the compounding ratios shown in Table 1. It was made.

The coating materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were laminated on a tin-free steel plate having a thickness of 300 μm and a PET film having a thickness of 100 μm (hereinafter referred to as “PET / TFS”). Abbreviated) on a PET film and an aluminum plate with a thickness of 300 μm, each having a thickness of 10 μm.
It was passed under a metal halide lamp of m at a speed of 40 m / min to obtain a cured coating film. The adhesion, processability, heat resistance, and coating film hardness of the obtained cured coating film were evaluated by the methods described below, and the curability of each coating material was evaluated. Table 3 shows the results.
Shown in

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 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 are observed in 1/4 of the test trace. △ Cracks are observed in 1/2 of the test mark. × Cracks were generated on the entire surface of the test mark.

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 the coating film is observed in 1/4 of the test trace. △ Peeling of the coating film is observed in 1/2 of the test trace. × Coating peeling occurred on the entire surface of the test trace.

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

Curable: 160 W / cm for the coated plate
Was passed under the metal halide lamp of No. 3 at a speed of 40 m / min, the curability was evaluated by the number of passages until the coating was cured, and the surface state of the coating at that time was observed.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

Industrial Applicability According to the present invention, a coating composition can be obtained which is cured at high speed by irradiation with ultraviolet rays to the inside and is excellent in adhesion to metal cans and polyester film-coated drawn metal cans, workability, heat resistance and coating film hardness. It was

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Claims (6)

[Claims] 1. A radical-polymerizable acrylate and / or methacrylate compound (A), a non-radical-polymerizable compound (B), a pigment (C), and an acylphosphine oxide-based photopolymerization initiator (D). An ultraviolet curable resin composition comprising: 2. The ultraviolet-curable resin composition according to claim 1, which contains a vinyl ether compound (E). 3. The ultraviolet curable resin composition according to claim 1, wherein the non-radical polymerizable compound (B) is a ketone formaldehyde resin. 4. A coating material comprising the ultraviolet curable resin composition according to any one of claims 1 to 3. 5. The coating agent according to claim 4, which coats a metal can. 6. The coating agent according to claim 4, which coats a polyester film-coated drawn metal can.