JPH0820741A - Ink composition for metal printing and coating method using the same - Google Patents

Abstract

(57) [Summary] [Object] To provide an ink for metal printing, which does not reduce the suitability for an aqueous overprint varnish, does not volatilize a solvent during baking, and has a coating film having excellent water resistance. In an ink composition for metal printing mainly composed of a pigment, a binder resin and a solvent, the solvent is a liquid at room temperature and has a molecular weight of 4500 or less and comprises the following (1) and (2) An ink composition for metal printing, wherein the ink composition for metal printing contains 3 to 50% by weight of at least one reactive solvent selected from the group. (1) A polyester polyol obtained by reacting a polyhydric alcohol component containing a branched alkanediol and a dicarboxylic acid component. (2) Poly (β-methyl-δ-valerolactone) polyol obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight polyhydric alcohol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ink composition for metal printing and a method for using the same. More specifically, the metal printing ink is printed on the metal surface, and the aqueous overprint varnish is wet-coated on the ink film immediately after printing,
The present invention relates to an ink composition for metal printing, which is preferably used in a coating method for heat curing.

[0002]

2. Description of the Related Art Conventionally, a binder such as an alkyd resin, a polyester resin, or an epoxy resin has been used for printing the outer surface of a metal material such as a zinc-plated or tin-plated iron plate, an aluminum plate, or a metal can made of these metal materials. Ink compositions for metal printing have been used which contain a resin and an organic solvent such as mineral oil or higher alcohol as a main vehicle component.

Further, overprinting is generally carried out on these printed surfaces in order to improve the adhesion, bending resistance, impact resistance and abrasion resistance of the ink coating film. This overprint varnish is a solvent type overprint consisting of a binder resin such as alkyd resin, polyester resin, acrylic resin and epoxy resin, a curing agent such as melamine resin and benzoguanamine resin, and an organic solvent such as mineral oil and cellosolve. Varnishes were widely used.

Printing of metal cans has been performed as follows.

1) The ink is printed on the outer surface of the can using an offset printing machine, a dry offset printing machine, or the like. 2) Immediately after printing, a coater or the like is used to apply the overprint varnish on the ink coating film in a wet-on-wet manner. 3) Perform primary baking at 150 to 280 ° C. 4) Apply the inner paint by spraying on the inner surface of the can. 5) Secondary baking is performed at 150 to 230 ° C.

However, in recent years, in the field of metal printing, there is a movement from solvent type overprint varnish to water type in view of problems of air pollution due to solvent, hygiene and safety in printing work environment. Is becoming noticeable.

However, when a water-based overprint varnish is applied to the ink coating film of the conventional ink composition for metal printing, repelling of the water-based overprint varnish, penetration of the water-based overprint varnish into the ink film, etc. A phenomenon occurs, and as a result, there is a problem that the gloss of the coating film or the adhesion of the coating film is remarkably deteriorated.

Therefore, it has been required that the ink for metal printing also has excellent coating suitability (suitability for water-based overprint varnish) for water-based overprint varnish.

As a method for improving the suitability of such an aqueous overprint varnish, an ink composition for metal printing using glycol, glycol monoether, glycol monoester or the like in at least a part of the solvent of the printing ink (special JP-A-54-22331) has been proposed.

Further, Japanese Patent Publication No. 5-75031 discloses that
Use of an alkylene glycol-based solvent having 4 to 8 carbon atoms
Japanese Patent Publication No. 5-40791 discloses use of a polyoxyalkylene glycol-based solvent, and Japanese Patent Publication No. 5-40792 discloses use of a polyoxyalkylene alkyl ether-based solvent. The use of an ethylene oxide adduct and / or a propylene oxide adduct of bisphenol A is disclosed in Japanese Patent Application Laid-Open No. 5-1 / 1993.
56195 proposes the use of an organic solvent having an aromatic ring.

However, although the organic solvent used in the ink composition for metal printing is effective in improving the suitability of the aqueous overprint varnish of the ink composition for metal printing, when the solvent is volatile, There was a problem of air pollution due to solvent volatilization at the time of baking, or when the solvent remained in the coating film by reaction, there was a problem that the water resistance of the coating film obtained was decreased because the residual solvent was hydrophilic. .

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art.
In a coating method in which a water-based overprint varnish is wet-coated on an ink film immediately after printing and heat-cured, the reactivity of the reactive solvent of the ink composition for metal printing and the water-based overcoat is not reduced during baking without lowering the suitability of the water-based overprint varnish. Provided is a metal printing ink composition in which a curing agent in a print varnish or an ink composition for metal printing reacts and remains in a coating film so that a solvent is not volatilized and the coating film obtained has good water resistance. The purpose is to

[0013]

That is, the present invention provides an ink composition for metal printing mainly composed of a pigment, a binder resin and a solvent, which is a liquid at room temperature and has a molecular weight of 4500 or less. And at least one reactive solvent selected from the group consisting of (1) and (2) below in an amount of 3 to 50% by weight in the ink composition for metal printing. .

(1) A polyester polyol obtained by reacting a polyhydric alcohol component containing a branched alkanediol with a dicarboxylic acid component.

(2) Poly (β-methyl-δ-valerolactone) polyol obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight polyhydric alcohol.

Further, the present invention relates to the ink composition for metal printing, wherein the ink composition for metal printing further contains a curing agent.

Further, according to the present invention, the polyester polyol in the ink composition for metal printing is obtained by reacting a polyhydric alcohol component containing 3-methyl-1,5-pentanediol with adipic acid. The present invention relates to an ink composition for metal printing, which is a polyol.

In the present invention, the ink composition for metal printing is used to print on a metal surface, and an aqueous overprint varnish containing a curing agent is applied onto the ink film in a state where the ink is not dried. The present invention relates to a coating method characterized by heat curing.

[0019]

FUNCTION AND EXAMPLES The ink composition for metal printing of the present invention will be described in detail below.

First, the reactive solvent that can be used in the ink composition for metal printing of the present invention is a liquid at the following room temperature and has a molecular weight (weight average molecular weight, the same applies hereinafter) of 4500 or less, preferably 500 to 2000. It is a polyol compound.

(1) Polyester polyol obtained by reacting a polyhydric alcohol component containing a branched alkanediol and a dicarboxylic acid component. Specifically, 1,4-pentanediol, 2,5-hexanediol, 3- Methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-methyl-1,8-octanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-
One or more branched alkanediols such as 1,3-propanediol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol and neopentyl glycol, and if necessary, A polyhydric alcohol component consisting of one or more polyhydric alcohols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane and glycerin; Examples thereof include polyester polyols obtained by reacting with one or more dicarboxylic acid components such as adipic acid, sebacic acid, azelaic acid, maleic acid, fumaric acid, glutaric acid, succinic acid, isophthalic acid, and terephthalic acid. . When the branched alkanediol and other polyhydric alcohol are used in combination, the content of the other polyhydric alcohol is preferably 50% by weight or less in the total polyhydric alcohol component.

(2) Poly (β-methyl-δ-valerolactone) polyol obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight polyhydric alcohol. Specifically, ethylene glycol and butanediol. , Glycerin and the like, preferably a polyol obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight polyhydric alcohol having a molecular weight of 300 or less.

The above polyol compounds may be used alone or in combination of two or more.

Among these, from the viewpoint of the fluidity of the polyol,
The polyol of (2) above and 3-methyl-1,5-
A polyester polyol obtained by reacting a polyhydric alcohol component containing pentanediol with adipic acid can be preferably used.

If the molecular weight of the reactive solvent exceeds 4000, the viscosity of the reactive solvent increases, the fluidity of the ink decreases, and the printability decreases, which is not preferable.

The amount of the specific reactive solvent used in the present invention is 3 to 50% by weight in the ink composition for metal printing. If the amount of the reactive solvent used in the present invention is less than the above range, the desired effect cannot be obtained, while if it exceeds the above range, the viscosity decreases and misting increases, the amount of the reactive solvent used increases. Causes a problem that printability is deteriorated.

In addition, in the ink composition for metal printing of the present invention, from the viewpoint of volatilization of the solvent and water resistance of the resulting coating film, the solvent should be composed of only the reactive solvent specified in the present invention. However, in the range where the volatilization of the solvent is allowed, and the water resistance of the resulting coating film is not reduced, conventionally used glycols, glycol monoalkyl ethers, high-boiling petroleum solvents, alkylbenzene, A solvent such as an aromatic solvent such as biphenyl ether can be used in combination.

Next, as the binder resin which can be used in the ink composition for metal printing of the present invention, various resins conventionally used as the binder resin of the ink composition for metal printing can be used. For example, resins such as long oil long alkyd resin, short oil long alkyd resin, oil free alkyd resin, various modified polyester resins, or epoxy ester resins can be used, and if necessary, vinyl modified alkyd resin, rosin, or fatty acid modified A phenol resin or a maleic acid resin can be used in combination.

Examples of the curing agent include amino resins such as melamine resin and benzoguanamine resin. When the curing agent contains an excessive amount of amino resin in the aqueous overprint varnish, it is not necessary to include it in the metal printing ink composition, but when the amino resin in the aqueous overprint varnish is small, In addition, in order to improve the water resistance of the resulting coating film, it is necessary to include it in the ink composition for metal printing.

As the colorant, a usual inorganic or organic pigment or dye can be used. Further, if necessary, additives such as wax can be used.

To produce the ink composition for metal printing of the present invention from the above-mentioned various materials, binder resins 10 to 6 are used.
It can be produced by an ordinary method by mixing 0% by weight, 5 to 60% by weight of colorant, 3 to 50% by weight of solvent, and 0 to 30% by weight of curing agent. When the water resistance of the coating film is improved, the amount of the curing agent is preferably 3 to 30% by weight.

As the water-based overprint varnish to be applied on the ink composition for metal printing, those conventionally used can be used, and specifically, water-based acrylic resin, water-based polyester resin, water-based alkyd. resin,
A water-based epoxy resin, or a modified resin of two or more of these may be used as a binder and an amino resin as a curing agent may be used in combination.

When printing on the surface of a metal material using the above-mentioned ink composition for metal printing and the aqueous overprint varnish, first, the ink composition for metal printing is usually dried by a dry offset printing machine, an offset printing machine or the like. Perform printing, overcoat the water-based overprint varnish with a coater etc. in a state where the ink does not dry,
After that, baking is performed at 150 to 280 ° C. for several seconds to several minutes.

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto.

[Synthesis Example 1] 200 parts by weight of soybean oil fatty acid,
100 parts by weight of trimethylolpropane, 160 parts by weight of neopentyl glycol, 130 parts by weight of adipic acid, and 175 parts by weight of isophthalic acid are esterified by a conventional method,
A liquid long oil length alkyd resin having an acid value of 9.0 and an oil length of 26% was obtained (referred to as resin 1).

[Synthesis Example 2] Neopentyl glycol 17
0 parts by weight, 110 parts by weight of trimethylolpropane, 170 parts by weight of adipic acid, and 200 parts by weight of isophthalic acid were esterified by a conventional method to obtain a liquid oil-free alkyd resin having an acid value of 17.0 (referred to as resin 2). ).

[Vehicle Production Examples 1 to 9] Vehicles were produced according to Table 1 using the resins obtained in Synthesis Example 1 and Synthesis Example 2, respectively.

[0038]

[Table 1]

[Examples 1 to 6 and Comparative Examples 1 to 3] Vehicle Using each of the vehicles obtained in the production examples, 30 parts by weight of the vehicle and 50 parts by weight of titanium oxide were dispersed in a kneaded meat by a conventional method, and then cured. 10 parts by weight of melamine resin Cymel 303 (manufactured by Mitsui Cyanamid Co., Ltd.) as an agent,
According to Table 2, 10 parts by weight of each solvent was added to prepare an ink composition for metal printing.

[0040]

[Table 2]

[Printing Test] Examples 1 to 6 and Comparative Example 1
The volatility of each of the ink compositions for metal printing obtained in Nos. 3 to 3 was evaluated, and each of these ink compositions for metal printing was used to dry about 30 parts in an aluminum 2-piece can by a dry offset method.
Printing with a coating film amount (solid content) of mg / 100 cm ² and using a roll coater with an aqueous acrylamino-based overprint varnish in a wet state in which the ink does not dry after printing, a solid content of about 60 mg / 100 cm ² Overprint on the entire surface with the amount of coating film, then 200 ℃ /
After baking for 2 minutes, the paintability and the water resistance of the coating film were evaluated. The evaluation results are shown in Table 3.

[Test Method] (1) Paintability (suitability for water-based overcoat print varnish) The water-based overcoat print varnish applied on the coating film of the ink composition for metal printing was visually inspected for repellency and entrapment. It was evaluated as 2, which has no problem at all, and 1 which repels and has a tendency to entangle.

(2) Water resistance (coating hardness) The test piece obtained in the above printing test was immersed in warm water at 85 ° C. for 30 minutes, and then, in the warm water, scratches on the coating film according to the pencil hardness test method. Then, the hardness of the pencil with the scratch on the coating film was determined as the hardness of the coating film to evaluate the water resistance.

(3) VOC measurement 2.0 g of each of the inks obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was weighed on an aluminum dish and added to a small amount of methyl ethyl ketone to dissolve. Then, it is left at room temperature to evaporate methyl ethyl ketone, and its weight is set to A. next,
The aluminum dish containing the sample is left to stand at 105 ± 5 ° C./3 hr, the weight is measured, and the weight is designated as B. The weight of the aluminum dish is C. The VOC value represented by the following formula was determined and the volatility was evaluated. VOC = {(A−B) / (A−C)} × 100

[0045]

[Table 3]

[0046]

The metal printing ink composition using the reactive solvent specified in the present invention has a specific reactive solvent of the present invention and an aqueous overprint varnish of the present invention during baking without deteriorating the suitability for the aqueous overprint varnish. Since the curing agent in the ink composition for metal printing reacts and remains in the coating film, the solvent does not volatilize and the resulting coating film has good water resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehiko Shintani 1-23-37 Edobori, Nishi-ku, Osaka Sakata Inx Co., Ltd.

Claims (4)

[Claims] 1. An ink composition for metal printing mainly composed of a pigment, a binder resin and a solvent, wherein the solvent is a liquid at room temperature and has a molecular weight of 4500 or less. An ink composition for metal printing, wherein the ink composition for metal printing contains 3 to 50% by weight of at least one reactive solvent selected from the group consisting of: (1) A polyester polyol obtained by reacting a polyhydric alcohol component containing a branched alkanediol and a dicarboxylic acid component. (2) Poly (β-methyl-δ-valerolactone) polyol obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight polyhydric alcohol. 2. The ink composition for metal printing according to claim 1, further comprising a curing agent. 3. The metal printing according to claim 1, wherein the polyester polyol is a polyester polyol obtained by reacting a polyhydric alcohol component containing 3-methyl-1,5-pentanediol with adipic acid. Ink composition. 4. An aqueous overprint varnish containing a curing agent is coated with an ink by printing on a metal surface using the ink composition for metal printing according to claim 1, 2 or 3 and the ink is not dried. A coating method, which comprises applying the composition on top and curing it by heating.