US-12624232-B2 - Metal printing ink composition

Abstract

An ink composition for printing on metal including a coloring pigment, resins, and a solvent is employed, wherein the ink composition contains a rosin-modified resin having an acid value of 10 to 400 mg KOH/g as at least part of the resins, and the solvent contains at least one compound selected from the group consisting of compounds represented by general formula (1): wherein each A is independently an alkylene group having 2 to 4 carbon atoms that may have a branch structure, R is an alkyl group having 1 to 13 carbon atoms that may have a branch structure and/or a ring structure, and n is an integer of 2 to 6.

Inventors

• Takayuki Furuya
• Takashi Araki

Assignees

• SAKATA INX CORPORATION

Dates

Publication Date

20260512

Application Date

20211028

Priority Date

20201130

Claims (6)

1. 1 . An ink composition for printing on metal including a coloring pigment, resins, and a solvent, wherein the ink composition has a viscosity of 10 to 70 Pa·s measured with a Laray viscometer at 25° C.; wherein the ink composition contains a rosin-modified resin having an acid value of 10 to 400 mg KOH/g as at least part of the resins, and the solvent contains at least one compound selected from the group consisting of compounds represented by the following formula (1): wherein each A is independently an alkylene group having 2 to 4 carbon atoms that may have a branch structure, R is an alkyl group having 1 to 13 carbon atoms that may have a branch structure and/or a ring structure, and n is an integer of 2 to 6.
2. 2 . The ink composition for printing on metal according to claim 1 , wherein the rosin-modified resin is in the form of a gelled varnish together with the solvent and a di- or higher valent metal alkoxy compound in the ink composition.
3. 3 . The ink composition for printing on metal according to claim 1 , wherein the solvent is 20 mass % or more of the entire ink composition.
4. 4 . The ink composition for printing on metal according to claim 1 , wherein the rosin-modified resin contains a portion in the structure thereof derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride.
5. 5 . The ink composition for printing on metal according to claim 1 , wherein the ink composition further contains an alkyd resin.
6. 6 . The ink composition for printing on metal according to claim 5 , wherein the alkyd resin is a coconut oil-modified alkyd resin.

Description

TECHNICAL FIELD The present invention relates to an ink composition for printing onto metal material. BACKGROUND ART In a printing process onto the outer surfaces of metal materials, such as zinc-coated or tin-coated iron plates, aluminum plates, or metal cans made of these metal materials, ink compositions for printing onto metal materials (thereafter, also referred to as “printing on metal”) have been used which contain binder resins, such as alkyd resins, polyester resins, and epoxy resins, and mineral oils or organic solvents, such as higher alcohols, as main vehicle ingredients. In addition, overprint varnishes are generally coated on such printed surfaces in order to improve various properties, such as adhesiveness, flexural resistance, impact resistance, and abrasion resistance, of the coated ink film. Widely used examples of such overprint varnishes are solvent-type varnishes, which are composed of binder resins, such as alkyd resins, polyester resins, acrylic resins, and epoxy resins, curing agents, such as melamine resins and benzoguanamine resins, and solvents, such as mineral oils and cellosolve-based organic solvents. In the printing process onto the outer surface of a metal material, after printing using ink with an offset printing machine or a dry offset printing machine, the overprint varnish was applied on the ink film in a wet-on-wet manner with a coater, followed by baking at 150 to 280° C. In recent years, from the viewpoints of air pollution caused by solvents as well as hygiene and safety in work environments for printing, water-based overprint varnishes have been generally used in place of the conventional solvent-type overprint varnishes also in the field of printing on metal. However, in the case that water-based overprint varnishes are applied onto the ink film composed of a conventional ink composition for printing on metal, various phenomena occur such as repellency of the water-based overprint varnish and penetration of the water-based overprint varnish into the ink film, resulting in a remarkable reduction in print qualities, such as gloss or adhesion of the coated film. Accordingly, the ink compositions have been required to have superior suitability for water-based overprint varnishes. In order to improve the suitability of ink for such water-based overprint varnishes, several methods have been proposed. For example, PTL 1 discloses the use of a solvent containing alkylene glycol having 4 to 8 carbon atoms, PTL 2 discloses the use of a polyoxyalkylene glycol-based solvent, PTL 3 discloses the use of a polyoxyalkylene alkyl ether-based organic solvent, and PTL 4 discloses the use of a polyoxyalkylene alkyl ester-based solvent. Such organic solvents employed in ink compositions are effective in an improvement in suitability of the ink compositions for water-based overprint varnishes; however, the flowability of the ink compositions are often insufficient and misting tends to occur during printing, resulting in remaining room for improvements in such properties. In the case that the flowability of ink compositions for printing on metal and the misting during printing are intended to be improved, a low-polarity solvent such as high-boiling point aromatic hydrocarbon may be used, for example, as disclosed in embodiments of PTL 5. For the purpose of a further reduction in environmental load, water-based overprint varnish products with reduced amounts of solvent ingredients to the utmost limit are commercially available at present, however, such water-based overprint varnishes may cause a drawback in repellency to the ink composition having the low-polarity solvent. CITATION LIST Patent Literatures PTL1: JP H5-75031BPTL2: JP H5-40791BPTL3: JP H5-40792BPTL4: JP 564-60670APTL5: JP 2009-249435A BRIEF DESCRIPTION OF THE INVENTION Problems to be Solved As described above, a trade-off relationship holds between an improvement in the flowability of the ink composition or misting during printing and a reduction in repellency of the overprint varnish during application, which means that satisfactoriness at one side leads to unsatisfactoriness at the other side. An object of the present invention, which has been completed in view of such circumstances, is to provide an ink composition for printing on metal which has superior properties in terms of a reduction in repellency and improvements in flowability and misting even when a water-based overprint varnish containing reduced amounts of solvent ingredients is applied onto the printed surface with the ink composition. Means to Solve Problems The present inventors have made intensive studies, found that the use of an ink composition containing both a rosin-modified resin with an acid value of 10 to 400 mg KOH/g as at least part of the resins contained in the ink composition and polyoxyalkylene alkyl ether-based solvent represented by general formula (1) can solve the drawback described above, and completed the present invention. In particular,