JP2002212509A - Ultraviolet light-curable coating composition containing aluminum and coated article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet light-curable coating composition which controls the dissolution of stearic acid of a leafing type surface-treating agent and can form coating films scarcely changing the masking appearance and the bright appearance. SOLUTION: The ultraviolet light-curable coating composition is characterized by comprising (A) aluminum pigment subjected to a surface treatment using stearic acid, (B) an ultraviolet light-polymerizable substance, (C) a photopolymerization initiator, and (D) stearic acid in an amount of 0.1 to 10 pts.wt. per 100 pts.wt. of the total amount of the components (A), (B) and (C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet-curable coating composition which imparts aesthetic and commercial value with a metallic-like glitter. More specifically, the present invention relates to an ultraviolet-curable coating composition which imparts glitter by containing a leafing-type aluminum pigment, and which has excellent storage stability over time by adding stearic acid. . As a main field of application, particularly, it is suitably used as a coating agent for metals, plastics and plastic film-coated metals, and is extremely useful as a base coat paint composition for beverage cans and food cans (hereinafter referred to as beverage cans and the like) containing beverages or foods. It is highly practical.

[0002]

2. Description of the Related Art The outer surface of a beverage can or the like is coated with a coating film of a base coat paint composition containing titanium oxide or aluminum as a pigment in order to prevent corrosion of the can base material and enhance aesthetic commercial value. Conventionally, these coating films have been formed by applying an organic solvent type paint such as an epoxy / amino resin, an acrylic / amino resin, or a polyester / amino resin with a roll coat and baking and curing. However, since these paints volatilize a large amount of solvent at the time of baking, a special recovery device is required to prevent air pollution. Therefore, recently, various water-based paints that do not easily cause air pollution and do not require a special recovery device have been proposed. However, even in this water-based paint, 20
Since it requires a high temperature of 0 ° C or more and a baking time in minutes,
Improvements are desired in terms of energy cost and productivity, as well as equipment space.

[0003] In order to solve these problems, ultraviolet curable coating compositions have been actively studied. The UV-curable coating composition is free of solvent and thus has no risk of air pollution, and has many advantages such as energy cost and productivity because a cured coating film can be obtained by UV irradiation. However, UV-curable coating compositions containing titanium oxide or aluminum as a pigment have the necessary UV-curing properties because the pigment absorbs or reflects the UV rays and prevents the UV rays from reaching the interior of the coating. Difficult to get.
For this reason, the necessary ultraviolet curability is obtained while keeping the pigment concentration low. On the other hand, if the pigment concentration is kept low, the hiding feeling of the coating film is impaired, so that adjustment is often made at the expense of either one.

When an aluminum pigment is contained, it is preferable to use a so-called leafing type aluminum pigment paste in which aluminum particles are easily oriented on the outermost surface of the coating film in order to obtain a hiding feeling at a low pigment concentration.
Such leafing type aluminum pigments are
The surfaces of the aluminum particles have been treated with stearic acid. However, an ultraviolet-polymerizable monomer generally used as a constituent material of an ultraviolet-curable resin composition dissolves stearic acid, which is a leafing-type surface treatment agent. As a result, even if a leafing type aluminum pigment is used, the dissolution of stearic acid proceeds with time in the resin composition, the aluminum pigment no longer forms the outermost surface of the coating film, and only a coating film with a reduced concealing feeling and glitter is obtained. Can not be.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultraviolet curable resin capable of suppressing the dissolution of stearic acid as a surface treating agent of the leafing type and forming a coating film with little change in concealing feeling and glitter. It is to provide a composition.
The present invention also provides a UV-curable paint containing an aluminum pigment for forming a coating by applying it to the surface of a metal, plastic, plastic film-coated metal can or bottle or the like containing a beverage or food. It is intended to provide a composition.

[0006]

That is, the first invention comprises an aluminum pigment (A) surface-treated with stearic acid, an ultraviolet-polymerizable substance (B), and a photoinitiator (C). (A) + (B) + (C) = 100 parts by weight, an ultraviolet curable coating composition containing an aluminum pigment, characterized by containing 0.1 to 10 parts by weight of stearic acid (D), A second invention is the coating composition according to the first invention, wherein the ultraviolet polymerizable substance (B) is a cationic polymerizable substance and the photoinitiator (C) is a cationic photoinitiator. The third invention is the coating composition according to the first or second invention, wherein the coating composition is coated with at least one selected from the group consisting of a metal, a plastic, and a metal coated with a plastic film.

According to a fourth aspect, there is provided an article to be coated on which a base material is coated with the coating composition according to the first or second aspect.
The invention according to the fourth aspect is the substrate according to the fourth aspect, wherein the substrate is at least one selected from the group consisting of a metal, a plastic, and a metal coated with a plastic film. The substrate according to the fifth aspect, wherein the substrate is a can or a bottle.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The ultraviolet-curable coating composition of the present invention is mainly used as a base coat. By blending aluminum as a pigment, it is used as a silver base coat. As the aluminum pigment (A), a paste obtained by converting aluminum powder into a paste with mineral spirit, solvent naphtha, or the like is suitably used. The aluminum pigment (A) is obtained by treating the surface with stearic acid, and preferably has a scale shape. Those having a size of about 5 to 20 μm are preferred. In addition, the aluminum pigment (A) is 5 to 5% when the total amount of the ultraviolet polymerizable substance (B) and the photoinitiator (C) described later, (A) + (B) + (C) = 100 wt%, Preferably, it is 30% by weight.
If it is less than 5% by weight, the hiding feeling of the coating film tends to be insufficient, and
If the amount is higher than the weight percentage, it is difficult to obtain ultraviolet curability.

The ultraviolet-polymerizable substance (B) used in the present invention includes a radical-polymerizable substance and a cationic-polymerizable substance. It is preferable to use a cationic polymerizable substance because the radical polymerizable substance easily inhibits the orientation of the aluminum pigment to the outermost surface of the coating film. As the cationic polymerizable substance, compounds such as an epoxy compound, a vinyl ether compound, an oxetane compound, a furan compound, a lactone compound, an oxazoline compound, a styrene derivative, and a cyclic siloxane compound can be used. More preferably, an epoxy compound or an oxetane compound is mainly used.
Examples of the epoxy compound include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, o-, m-, p-cresol novolak epoxy resin, phenol novolak epoxy resin, and alicyclic epoxy resin. is there. Examples of the oxetane compound include 3-ethyl-3-hydroxymethyloxetane, oxetanecarboxylic acid, hexyloxetane, oxetane methacrylate, benzyloxetane, allyloxetane, xylylene oxetane, and 3-ethyl-3.
-Phenoxymethyloxetane, 3-ethyl-3- (2
-Ethylhexyloxymethyl) oxetane, bis (3-
Ethyl-3-oxetanylmethyl) ether and the like.

When a radical polymerizable substance is used as the ultraviolet polymerizable substance (B), a radical photoinitiator may be used as the photoinitiator (C) and the ultraviolet polymerizable substance (B) may be used.
When a cationically polymerizable compound is used, it is preferable to use a cationic photoinitiator also as the photoinitiator (C). Examples of the cationic photoinitiator include aryldiazonium salts (for example, P-33 manufactured by Asahi Denka Kogyo), aryliodonium salts (for example, FC-509 manufactured by 3M, 2074 manufactured by Rhone Poulin), and arylsulfonium salts (Union. Carbide's Cyracure UVI-69
74, UVI-6970, UVI-6990, UVI-
6950, SP-150, SP-17 manufactured by Asahi Denka Kogyo Co., Ltd.
0, San-Aid SI-110L, SI manufactured by Sanshin Chemical Industry Co., Ltd.
-180L, SI-100L, CI-28 manufactured by Nippon Soda Co., Ltd.
55) Allene-ion complex (CG-2 manufactured by Ciba-Geigy)
4-61). The photoinitiator (C) is a total of 1 of the aluminum pigment (A) and the ultraviolet polymerizable substance (B).
It is desirable that the compounding be carried out within a range of 1 to 10 parts by weight based on 00 parts by weight. If it is less than 1%, the irradiation time of ultraviolet rays required for curing becomes long, and the productivity is poor. If it exceeds 10%, the cured coating film tends to be brittle. Further, a photosensitizer can be used in combination. In this case, the photosensitizer desirably has a hydrogen extracting effect, and preferably has a characteristic absorption in a long wavelength region of ultraviolet light, for example, a long wavelength region of 300 nm or more. For example, ITX, QTX, CPTX, and DTX from the KAYACURE series (manufactured by Nippon Kayaku Co., Ltd.)
ETX-S, Adeka Optomer SP-100 (manufactured by Asahi Denka Kogyo KK) and the like.

Stearic acid (D) is a so-called leafing type aluminum pigment surface-treated with stearic acid (A), a UV-polymerizable substance (B), and a photoinitiator (C) in a total amount of 100 parts by weight. And 0.1-10
It is important that the compounding be performed within the range of parts by weight. 0.1
If the amount is less than parts by weight, dissolution of stearic acid as a surface treating agent cannot be suppressed. If the amount is more than 10 parts by weight, the cured coating film tends to be brittle.

The ultraviolet-curable coating composition of the present invention is preferably applied (painted / cured) to metals, plastics, and plastic-coated metals, but can also be applied to substrates such as paper, wood, and glass. Examples of the metal include steel, aluminum, and the like. As the plastic, polyethylene, polypropylene, polyethylene terephthalate, nylon, vinyl chloride, vinylidene chloride, polycarbonate and the like are used. Plastic film-coated metal is a metal plate made of steel, aluminum, etc., made of polyethylene, polypropylene, polyethylene terephthalate,
It is made by laminating plastic films such as nylon, vinyl chloride, vinylidene chloride and polycarbonate. Preferably, the metal, plastic, plastic-coated metal is a can or a bottle. The UV-curable coating composition of the present invention may be applied to a plate-shaped substrate (painting / curing) and then formed into a can or a bottle, or may be applied in advance to a can- or bottle-shaped substrate. Is also good. The plate shape may be a relatively short sheet shape, a relatively long roll shape, or a flat plate shape.
In addition, the can shape is a two-piece, three-piece, with or without bottom and lid.
Regardless of the piece, it refers to a shape having a cylindrical curved surface. These cans or bottles are mainly used as containers for storing foods and beverages such as soft drinks, coffee drinks, alcoholic drinks, black tea, and oolong tea.

The method for applying the ultraviolet-curable coating composition of the present invention includes a method such as roll coating, gravure coating, gravure offset coating, curtain flow coating, reverse coating, screen printing, spray coating, and dip coating. You. The light source for photocuring the ultraviolet-curable coating composition of the present invention usually has a wavelength of 20.
A light source including light in the range of 0 to 500 nm, for example, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a gallium lamp,
Xenon lamps, carbon arc lamps and the like can be used. Further, these light sources may be used in combination with heat generated by infrared rays, far infrared rays, hot air, high-frequency heating, or the like.

The ultraviolet-curable resin composition of the present invention may contain, if necessary, other conventional components such as organic or inorganic pigments, extender pigments, dyes, resins, organic solvents, dispersing aids, as long as the purpose is not impaired. And coating additives such as leveling agents, anti-cratering agents, surfactants, defoamers, slip agents, UV absorbers, reactive or non-reactive diluents. Examples of the resin include epoxy, polyester, acrylic, and urethane.

[0015]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, “parts” represents “parts by weight” and “%” represents “% by weight”. The materials used are as follows. (A) Leafing type aluminum pigment surface-treated with stearic acid (solid content = 70%, compounding solvent = mineral spirit) (A ′) Non-leafing type aluminum pigment not surface-treated with stearic acid (solid content = 70%,
(Blended solvent = mineral spirit) (B) Cationic polymerizable substance having an alicyclic epoxy group (Siracure UVR-6110, manufactured by UCC) (C) Cationic photoinitiator (Siracure UVI-699)
0, manufactured by UCC) (D) Stearic acid

Examples 1 to 3 and Comparative Examples 1 to 3 According to the formulation shown in Table 1, the above (B) and (C) were dissolved and mixed, and then (A) or (A ') was added and stirred sufficiently. ,afterwards,
(D) was added thereto and sufficiently stirred again to obtain an ultraviolet-curable coating composition.

1. Lightness index L A white base coat containing titanium oxide was applied to a tin-free steel plate, and the ultraviolet-curable coating compositions of Examples 1 to 3 and Comparative Examples 1 to 4 were coated on a cured substrate.
After storing at 0 ° C. for a predetermined period, the coating amount is 60 mg / dm 2.
² so that it becomes a fusion V-valve (2
(40 W / cm) at a conveyor speed of 40 m / min and irradiated with ultraviolet rays to obtain a test sample plate. About the obtained sample plate, based on JIS Z8722,
The lightness index L was measured. Since the base material was colored white with the white base coat, the higher the hiding sensation with the aluminum pigment, the lower the value of the lightness index L. Figure 1 shows the results
Shown in

2. Pencil hardness A white base coat containing titanium oxide is applied to a tin-free steel plate, and the ultraviolet-curable coating compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 2 are immediately applied on a cured substrate. The coating was performed so as to have a coating film amount of 60 mg / dm ² , and passed under a V valve (240 W / cm) manufactured by Fusion Co., Ltd. at a conveyor speed of 40 m / min, and irradiated with ultraviolet rays to obtain a test sample plate. The pencil hardness of the obtained sample plate after 5 to 10 seconds from the irradiation of ultraviolet rays was measured according to JIS.
It was measured according to K5400. Shows the maximum hardness at which the paint film will not peel off at room temperature with Mitsubishi pencil "Uni".

[0019]

[Table 1]

[0020]

According to the present invention, it has a sufficiently practical ultraviolet curability and coating film properties, and particularly, a plastic bottle,
When coating a metal can coated with a plastic film, a coating agent useful as a coating material for an ultraviolet-curable base coat can be provided.

[0021]

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the number of storage days and the lightness index L of a coating film when each coating material is stored at 40 ° C.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 25/34 B65D 25/34 B C09D 5/00 C09D 5/00 Z 7/12 7/12 F term ( 3E062 AA04 AA09 AB02 AB14 AC02 AC03 JA08 JB23 JC04 4D075 DA13 DB01 DB31 EA21 EC10 4J038 DB061 DB071 DB161 DB261 DD021 DF021 DJ001 DL031 FA041 FA061 HA066 JA13 JA38 JB16 JC17 JC38 KA03 KA08 PC08 KA03 KA08 PC08

Claims (6)

[Claims] 1. An aluminum pigment (A) surface-treated with stearic acid, an ultraviolet polymerizable substance (B), and a photoinitiator (C), wherein (A) + (B) + (C) = 100. An aluminum-containing ultraviolet-curable coating composition comprising 0.1 to 10 parts by weight of stearic acid (D), when expressed as parts by weight. 2. The coating composition according to claim 1, wherein the ultraviolet polymerizable substance (B) is a cationic polymerizable substance, and the photoinitiator (C) is a cationic photoinitiator. 3. At least one selected from the group consisting of metal, plastic, and plastic film-coated metal
3. The coating composition according to claim 1, wherein the coating composition is coated with a seed. 4. An article to be coated comprising a substrate coated with the coating composition according to claim 1 or 2. 5. The substrate according to claim 4, wherein the substrate is at least one selected from the group consisting of a metal, a plastic, and a metal coated with a plastic film. 6. The substrate according to claim 5, wherein the substrate is a can or a bottle.