JP2003221554A - Aluminum-containing UV-curable coating composition and substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet curable resin composition which is excellent in curability and concealability, has low thixotropy, and is excellent in coatability. SOLUTION: It contains an aluminum pigment (A) surface-treated with stearic acid, an ultraviolet polymerizable substance (B), an epoxidized vegetable oil (C) and a photoinitiator (D), and (A) +
(B) + (C) + (D) = 100% by weight of an epoxidized vegetable oil (C) in an amount of 1 to 10% by weight.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultraviolet-curable coating composition which imparts an aesthetic commercial value to an object by means of a metallic-like luster, and mainly comprises a base coat and aluminum as a pigment. Used as. More specifically, in a UV-curable coating composition that imparts a glittering feeling by containing a so-called leafing type aluminum pigment, an UV-curable coating composition having excellent high-speed paintability and adhesion by adding an epoxidized vegetable oil. It relates to a coating composition. It is particularly useful as a coating agent for metals, plastics, and plastic film-coated metals, and has extremely high practicality as a base coat coating composition for beverage cans and food cans (hereinafter referred to as beverage cans, etc.) containing beverages or foods. is there.

[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 coating 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 are roll-coated with organic solvent type paints such as epoxy / amino resin, acrylic / amino resin, polyester / amino resin, etc.
It has been formed by 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 are unlikely to cause air pollution and do not require a special recovery device have been proposed.

However, even water-based paints require a high temperature of 200 ° C. or higher and a baking time in minutes, and therefore improvements are desired in terms of energy cost, productivity, and equipment space.

In order to solve these problems, UV-curable coating compositions have been actively studied. The UV-curable coating composition is solvent-free, so there is no risk of air pollution, and a cured coating film can be obtained by UV irradiation, which has many advantages such as energy cost and productivity. However, the UV-curable coating composition containing titanium oxide or aluminum as a pigment should be sufficiently UV-cured because the pigment absorbs UV rays or reflects UV rays and prevents the UV rays from reaching the inside of the coating film. Is difficult.

Therefore, the pigment concentration is suppressed to a low level, and ultraviolet rays are sufficiently cured. However, on the other hand, if the pigment concentration is kept low, the hiding feeling of the coating film is impaired. Therefore, it is often the case that either the curability or the hiding property is sacrificed for adjustment.

In a UV-curable coating composition containing an aluminum pigment, there is a method of using a so-called leafing type aluminum pigment surface-treated with stearic acid as a method of not sacrificing both curability and hiding power. . When using a so-called leafing type aluminum pigment surface-treated with stearic acid,
It is possible to obtain the required hiding feeling and UV curability at a relatively low pigment concentration.

However, the UV polymerizable monomer generally used as a constituent material of the UV curable resin composition is
The affinity with the aluminum pigment surface-treated with stearic acid is poor, and it is difficult to obtain a uniformly dispersed state. As a result, when using an aluminum pigment surface-treated with stearic acid to ensure curability and hiding power,
A coating composition having high thixotropy is likely to be obtained, and it has been difficult to secure high-speed coating property. Further, since the aluminum pigment surface-treated with stearic acid has a poor affinity with the UV-polymerizable monomer as described above, the UV-curable resin composition is liable to be separated from the constituent material, and the UV irradiation A phenomenon occurs in which aluminum particles are detached from the subsequent cured coating film. As a result, when an object to be coated coated with a cured coating film formed from the ultraviolet curable coating composition is transported, aluminum particles are separated from the coating film, causing contamination of the transportation facility and coating film defects.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultraviolet curable resin composition which has excellent curability and hiding power, low thixotropy, and excellent coatability.

[0010]

That is, the first invention is to provide an aluminum pigment (A) surface-treated with stearic acid, a UV-polymerizable substance (B), an epoxidized vegetable oil (C) and a photoinitiator ( D), containing (A) + (B) +
(C) + (D) = 100% by weight, and 1 to 10% by weight of epoxidized vegetable oil (C) is contained, which is an aluminum-containing UV-curable coating composition, and the second invention is The ultraviolet polymerizable substance (B) is a cationic polymerizable substance, and the photoinitiator (D) is a cationic photoinitiator, which is the coating composition according to the first invention, and the third invention is The coating composition according to the first or second invention, which is coated with at least one selected from the group consisting of a metal, a plastic, and a plastic film-coated metal.

A fourth aspect of the present invention is an article to be coated, which is obtained by coating a base material with the coating composition according to the first or second aspect of the invention.
The invention of No. 4 is the article to be coated according to the fourth invention, characterized in that the substrate is at least one selected from the group consisting of metals, plastics, and plastic film-coated metals, and the sixth invention is The substrate is a can or a bottle, which is the article to be coated according to the fifth invention.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum pigment (A) contained in the ultraviolet-curable coating composition of the present invention for imparting a metallic-like brilliance has a surface treated with stearic acid, The scale-like one is preferable. The average particle size is
The size is preferably about 5 to 20 μm. In addition, a paste made of mineral spirit, solvent naphtha or the like is preferably used. Further, the aluminum pigment (A) is a total of (A) +, which will be described later, a UV-polymerizable substance (B), an epoxidized vegetable oil (C) and a photoinitiator (D).
When (B) + (C) + (D) = 100% by weight, 5
It is preferably about 30% by weight. This is because if it is less than 5% by weight, the hiding feeling of the coating film tends to be insufficient, and if it is more than 30% by weight, it is difficult to obtain ultraviolet curability.

The UV-polymerizable substance (B) used in the present invention includes a radical-polymerizable substance and a cation-polymerizable substance. As the radically polymerizable substance, it is preferable to use a cationically polymerizable substance because it tends to hinder the orientation of the aluminum pigment on the outermost surface of the coating film.

As the cationically polymerizable substance, compounds such as epoxy compounds, vinyl ether compounds, oxetane compounds, furan compounds, lactone compounds, oxazoline compounds, styrene derivatives and cyclic siloxane compounds can be used. More preferably, an epoxy compound or an oxetane compound is mainly used.

The epoxy compound is an epoxy compound other than the epoxidized vegetable oil described below, and is bisphenol A.
Type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, o-, m-,
Examples thereof include p-cresol novolac type epoxy compounds, phenol novolac type epoxy compounds, and alicyclic epoxy compounds, and the following alicyclic epoxy compounds are preferably used.

[0016]

[Chemical 1]

[0017]

[Chemical 2]

[0018]

[Chemical 3]

As the oxetane compound, 3-ethyl-
3-hydroxymethyl oxetane, oxetane carboxylic acid, hexyl oxetane, oxetane methacrylate,
Benzyl oxetane, allyl oxetane, xylylene dioxetane, 3-ethyl-3-phenoxymethyl oxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, bis (3-ethyl-3-oxetanylmethyl) ether, etc. is there.

It is important that the epoxidized vegetable oil (C) has a vegetable oil portion and an epoxy portion. That is, an aluminum pigment (A) whose surface is treated with stearic acid by having an affinity for the vegetable oil portion with the aluminum pigment (A) obtained by surface treatment with stearic acid and an affinity for the epoxy portion with the ultraviolet polymerizable substance (B). Since the affinity with the ultraviolet polymerizable substance (B) can be improved, a uniform dispersion state can be obtained. As a result, it is possible to obtain a coating composition having reduced thixotropy and exhibiting fluidity excellent in high-speed coating property.

Further, since the epoxy portion of the epoxidized vegetable oil (C) has cationic polymerizability, when a cationic polymerizable material is used as the ultraviolet polymerizable material (B), it is incorporated into the cationic polymerization and the coating after curing is applied. The detachment of the aluminum pigment from the film is further suppressed, and the contamination of the transport facility and the coating film defect can be improved.

As a typical method for producing the epoxidized vegetable oil (C), a method of epoxidizing the vegetable oil using peracetic acid or hydrogen peroxide obtained by air-oxidizing acetaldehyde as an oxidizing agent is generally used. . The vegetable oil portion includes soybean oil, linseed oil, sunflower oil, rice bran oil, tall oil and the like.

The epoxidized vegetable oil (C) is a so-called leafing type aluminum pigment (A) surface-treated with stearic acid, an ultraviolet polymerizable substance (B), an epoxidized vegetable oil (C), and a photoinitiator (to be described later) ( D) total 1
It is important that the compounding amount be within the range of 1 to 10% by weight in 00% by weight. If the amount is less than 1 part by weight, the affinity between the aluminum pigment (A) formed by surface treatment with stearic acid and the UV-polymerizable substance (B) cannot be obtained, so that the thixotropic property of the obtained coating composition becomes high, It is difficult to secure high-speed paintability. If it exceeds 10 parts by weight, the cured coating film becomes brittle.

Next, the photoinitiator (D) used in the present invention will be described. When a radical polymerizable substance is used as the UV polymerizable substance (B), a radical photoinitiator is also used as the photoinitiator (D), and a cationic polymerizable substance is used as the UV polymerizable substance (B). In this case, it is preferable to use a cationic photoinitiator as the photoinitiator (D).

As the cationic photoinitiator, an aryl diazonium salt (for example, P-33 manufactured by Asahi Denka Co., Ltd.), an aryl iodonium salt (for example, FC-509 manufactured by 3M Co.,
Rhone-Poulin's 2074), Aryl sulfonium salt (Union Carbide's Cyracure UVI-)
6974, UVI-6970, UVI-6990, UV
I-6950, Asahi Denka Kogyo's SP-150, SP-1
70, San-Aid SI-110L, S manufactured by Sanshin Chemical Industry Co., Ltd.
I-180L, SI-100L, Nippon Soda CI-2
855) Allene-ion complex (CG-made by Ciba-Geigy)
24-61) and the like.

The photoinitiator (D) is blended within a range of 1 to 10 parts by weight with respect to a total of 100 parts by weight of the aluminum pigment (A), the ultraviolet polymerizable substance (B) and the epoxidized vegetable oil (C). It is desirable to be done. If it is less than 1 part, the irradiation time of ultraviolet rays required for curing becomes long and the productivity is poor. 1
If it exceeds 0 parts, the cured coating film tends to become brittle.

The coating composition of the present invention may further contain a photosensitizer. In this case, the photosensitizer is preferably one having a hydrogen abstracting action, and one having a characteristic absorption in a long wavelength region of ultraviolet rays, for example, a long wavelength region of 300 nm or more is suitable. For example, ITX, QTX, CPTX, D from KAYACURE series (manufactured by Nippon Kayaku Co., Ltd.)
ETX-S, ADEKA OPTOMER SP-100 (manufactured by Asahi Denka Co., Ltd.) and the like can be mentioned.

The UV-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 and aluminum. As the plastic, polyethylene, polypropylene, polyethylene terephthalate, nylon, vinyl chloride, vinylidene chloride, polycarbonate or the like is used. Plastic film coated metal means polyethylene, polypropylene, polyethylene terephthalate, metal plate such as steel or aluminum,
It is a laminate of plastic films such as nylon, vinyl chloride, vinylidene chloride, and polycarbonate.

The metal, plastic, plastic-coated metal is preferably a can or bottle. The UV-curable coating composition of the present invention may be applied (painted / cured) to a plate-shaped substrate and then formed into a can or bottle, or may be applied to a can-shaped or bottle-shaped substrate in advance. 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 with or without a bottom and a lid.
Regardless of piece or piece, it means a shape having a cylindrical curved surface. These cans or bottles are mainly used as containers for storing food and drink such as soft drinks, coffee drinks, alcoholic drinks, black tea and oolong tea.

As a method for coating the ultraviolet-curable coating composition of the present invention, roll coating, gravure coating, gravure offset coating, curtain flow coating, reverse coating, screen printing, spray coating, dip coating and the like are used. It

The light source for photo-curing the ultraviolet-curable coating composition of the present invention usually has a wavelength of 200 to 50.
A light source containing light in the range of 0 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. or,
Heat from infrared rays, far infrared rays, hot air, high frequency heating, etc. may be used in combination with these light sources.

The ultraviolet-curable resin composition of the present invention contains other conventional components, if necessary, such as organic or inorganic pigments, extender pigments, dyes, resins, organic solvents, dispersion aids, as long as the purpose is not impaired. , A leveling agent, an anti-crater agent, a surfactant, an antifoaming agent, a slipping agent, an ultraviolet absorber, a reactive or non-reactive diluent, and the like can be added to the coating composition. Examples of the resin include epoxy, polyester, acrylic and urethane.

[0033]

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, "part" means "part by weight" and "%" means "% 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) (B) Cationic polymerizable substance having alicyclic epoxy group (Cyracure UVR-6110, UCC) (C) Epoxidized soybean oil (D) Cationic photoinitiator (Syracure UVI-699)
0, made by UCC)

Examples 1 to 3, Comparative Examples 1 and 2 According to the formulations shown in Table 1, (B) and (C) above were dissolved and mixed, then (A) was added and sufficiently stirred, and then (D) ) Was added and the mixture was sufficiently stirred again to obtain an ultraviolet-curable coating composition. Examples 1 to 3 and Comparative Example 1 on polyethylene terephthalate
And the ultraviolet-curable coating composition obtained in 2
Painted to 0 mg / dm ² , and under a Fusion D valve (240 W / cm), conveyer speed 40 m /
Ultraviolet irradiation was carried out by passing it at a speed of min to obtain a test sample plate.

1. Thixo coefficient For each coating composition, the viscosity at 1 rpm and 10 rpm rotation speeds was measured using a rotational viscometer, and the thixo coefficient (viscosity at 1 rpm / 10 viscosity at 10 rpm) was determined. 2. Adhesion Using each test sample plate, in accordance with JIS K5400,
Each coating film was scratched in a rugged pattern, and then the detachment of aluminum particles was observed by a cellophane tape peeling test. ⊚: No detachment of aluminum pigment. ◯: The aluminum pigment was slightly detached. Δ: Removal of aluminum pigment having an area ratio of 50% or more and less than 100 ×: Removal of aluminum pigment having an area ratio of 100% 3. Pencil Hardness The pencil hardness of the obtained sample plate after 5 to 10 seconds of ultraviolet irradiation was measured according to JIS K5400. Displays the maximum hardness at which the coating film does not peel off with the Mitsubishi pencil "Uni" at room temperature.

[0036]

[Table 1]

[0037]

EFFECT OF THE INVENTION According to the present invention, it has sufficiently practical UV curability and coating film properties, and particularly plastic bottles,
In the case of coating a plastic film-coated metal can, a coating agent useful as an ultraviolet-curable base coat paint can be provided.

Claims (6)

[Claims] 1. An aluminum pigment (A) surface-treated with stearic acid, a UV-polymerizable substance (B), an epoxidized vegetable oil (C) and a photoinitiator (D), and (A) +
(B) + (C) + (D) = 100 wt%, epoxidized vegetable oil (C) is contained in 1 to 10 wt%, an aluminum-containing UV-curable coating composition. 2. The coating composition according to claim 1, wherein the UV-polymerizable substance (B) is a cationically polymerizable substance and the photoinitiator (D) is a cationic photoinitiator. 3. At least one selected from the group consisting of metals, plastics, and plastic film-coated metals.
The coating composition according to claim 1 or 2, which is coated with a seed. 4. An article to be coated, which comprises a substrate coated with the coating composition according to claim 1 or 2. 5. The article to be coated according to claim 4, wherein the substrate is at least one selected from the group consisting of metals, plastics, and plastic film-coated metals. 6. The article to be coated according to claim 5, wherein the substrate is a can or a bottle.