Metallic printing ink composition and metallic printed matter

Abstract

To provide an ink composition for metal printing which has good ink adhesion to plates and substrates, and is excellent in on-machine stability, film properties and productivity. [Solution] A metal printing ink composition containing a resin, a pigment, a solvent, and a dispersant, wherein the solvent contains a paraffinic solvent and / or a naphthenic solvent, and the dispersant is a basic dispersant. A metal printed product having a printed layer made of the metal printing ink composition provided on a metal medium, and an overprint layer made of an overprint varnish provided on the printed layer. A method for producing a metal printed product, which includes dry offset printing or offset printing the metal printing ink composition on a metal medium to form a printed layer, and then applying an overprint varnish on the printed layer to form the overprint layer.

Description

[Technical Field]

[0001] The present invention relates to an ink composition for metallic printing. More specifically, the present invention relates to an ink composition for metallic printing that exhibits good ink adhesion to plates and substrates, and is also excellent in on-press stability, film properties, and productivity, and to a metallic printed product using the ink. [Background technology]

[0002] Metal containers are used in a wide variety of applications, including beverage containers, general-purpose cans, and candy cans. Metal containers are primarily manufactured using two methods. One method involves printing and painting a sheet metal plate, followed by cutting, welding, and other processes to create the desired can body. The other method involves punching a metal plate, ironing it, and then forming it into a cylindrical shape with a bottom, and then printing and painting the body of the can. The latter method is specifically called a seamless can.

[0003] The surface of a metal container is printed with an ink composition for metal printing, and various designs, ingredient labels, etc. are provided. When printing on a metal container, printing ink is supplied from an ink fountain, transferred to the image area of ​​the plate via multiple rolls, and then transferred from the plate to a blanket, after which it is printed on the metal substrate. Metal printing employs a lithographic offset method or a dry offset method using a resin relief plate.

[0004] When printing using the offset or dry offset method, the ink exists on the rolls, plate, and substrate of the printing press in a thin film of just a few microns. Therefore, it is important for printing ink compositions to have stable fluidity and on-press stability, and to have good ink adhesion to the plate, blanket, and substrate in order to develop sufficient color even in a thin film and reproduce the desired design.

[0005] For example, Patent Document 1 describes a metal printing technology that suppresses thickening of image lines and dots by using an alkyd resin adjusted to a predetermined weight-average molecular weight, number-average molecular weight, and molecular weight distribution. Patent Document 2 also describes a metal printing technology that achieves excellent jet-black color and design reproducibility by using an alkyd resin containing a specific fatty acid and combined with the fatty acid in a specific ratio and amount. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7220523 [Patent Document 2] Patent No. 7284896 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides an ink composition for metallic printing which has good ink receptivity, on-press stability and film properties, and is also excellent in productivity, and a metallic printed product using the ink. [Means for solving the problem]

[0008] As a result of extensive research into the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by using the ink for metal printing described below, and have thus achieved the present invention.

[0009] That is, the present invention relates to an ink composition for metal printing comprising a resin, a pigment, a solvent, and a dispersant, wherein the solvent comprises a paraffinic solvent and / or a naphthenic solvent, and the dispersant comprises a basic dispersant.

[0010] The present invention also relates to an ink composition for metal printing, wherein the resin is an alkyd resin containing 40 to 60% by mass of structural units derived from fatty acids.

[0011] The present invention also relates to an ink composition for metal printing, wherein the resin is an alkyd resin containing 45 to 60% by mass of structural units derived from fatty acids and having a weight-average molecular weight of 8,000 or more.

[0012] The present invention further relates to an ink composition for metal printing, wherein the pigment is an organic pigment.

[0013] The present invention further relates to an ink composition for metal printing, wherein the resin is an alkyd resin containing structural units derived from isophthalic acid.

[0014] The present invention further relates to an ink composition for metal printing, wherein the content of the dispersant in the ink composition is 0.2 to 5 mass %.

[0015] The present invention further relates to an ink composition for metal printing, in which the total content of the paraffinic solvent and the naphthenic solvent is 20 to 100 mass % of the total solvent content.

[0016] The present invention further relates to a metallic print having a printed layer made of an ink composition for metallic printing on a metal medium, and an overprint layer provided on the printed layer.

[0017] Furthermore, the present invention relates to a method for producing a metallic printed item, which comprises forming a printed layer on a metal medium by dry offset printing or offset printing of an ink composition for metallic printing, and then applying an overprint varnish onto the printed layer to form an overprint layer. [Effects of the Invention]

[0018] According to the present invention, it is now possible to provide an ink composition for metallic printing that has excellent printability, such as ink receptivity and on-press stability, and also has good film properties and productivity, as well as metallic printed products using the same. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes in detail embodiments of the present invention. Note that the embodiments and explanations of the requirements described are examples of embodiments of the present invention, and can be implemented with appropriate modifications within the scope of the present invention.

[0020] (Ink composition for metal printing) The ink composition for metal printing of this embodiment (hereinafter also referred to as the ink composition) contains a resin, a pigment, a solvent, and a dispersant as essential components. By including a paraffinic solvent and / or a naphthenic solvent as the solvent and a basic dispersant as the dispersant, it is possible to obtain an ink composition for metal printing that has excellent printability, such as ink receptivity and on-press stability, as well as good film properties and productivity. Each component is described below.

[0021] <Dispersant> The dispersant contained in the ink composition of this embodiment includes a basic dispersant. By incorporating a basic dispersant, the ink composition has good ink receptivity, and is also excellent in on-machine stability and productivity.

[0022] The dispersant has a site for adsorption to the pigment and a site for dispersion stabilization. Examples of polar groups that the dispersant has include acidic groups, basic groups, and other functional groups. A basic dispersant is a dispersant in which the amount of basic groups is greater than the amount of acidic groups. Examples of basic groups include primary amino groups, secondary amino groups, tertiary amino groups, ammonium groups, imino groups, and nitrogen-containing heterocyclic groups. The use of a basic dispersant not only allows the ink composition to exhibit dispersion stability and fluidity, but also improves the affinity between the resin, solvent, and pigment, increasing adhesion and resulting in good ink receptivity, as well as excellent on-press stability and productivity.

[0023] The basic dispersant may have either a straight chain structure called a single structure or a comb structure having side chains on the main chain skeleton.

[0024] The amine value of the basic dispersant is preferably 5 to 150 mgKOH / g, and more preferably 8 to 100 mgKOH / g. When the amine value of the basic dispersant is in the above range, the ink composition has excellent ink receptivity. Here, the amine value of the basic dispersant refers to the amine value per 1 g of basic dispersant solids, and refers to the value calculated by potentiometric titration using a 0.1 N aqueous hydrochloric acid solution to determine the amount of hydrochloric acid required to neutralize the basic groups in the dispersant, and then converting the amount into an equivalent amount of potassium hydroxide.

[0025] Examples of commercially available basic dispersants include Solsperse 11200, Solsperse 13240, Solsperse 13650, Solsperse 13940, Solsperse 20000, Solsperse 24000, Solsperse 32000, Solsperse 33000, Solsperse 35200, and Solsperse 39000 manufactured by The Lubrizol Corporation; Ajisper PB821, Ajisper PB822, Ajisper PB824, and Ajisper PB881 manufactured by Ajinomoto Fine-Techno Co., Ltd.; and DISPERBYK-108, DISPERBYK-109, DISPERBYK-161, DISPERBYK-164, DISPERBYK-182, DISPERBYK-2008, and DISPERBYK-2022 manufactured by BYK Japan Co., Ltd. These may be used alone or in combination of two or more.

[0026] The content of the basic dispersant in the ink composition is preferably 0.2 to 5 mass %, more preferably 0.5 to 4 mass %, and even more preferably 0.5 to 2 mass %. When the content of the basic dispersant is within the above range, the ink composition exhibits good ink receptivity and is also excellent in on-machine stability, film properties, and productivity.

[0027] <Solvent> The ink composition of this embodiment contains a paraffinic hydrocarbon and / or naphthenic hydrocarbon as a solvent. By blending a paraffinic hydrocarbon and / or naphthenic hydrocarbon, affinity with the basic dispersant described above is improved, and the ink composition has excellent ink receptivity, on-press stability, and productivity.

[0028] The paraffinic hydrocarbon is not particularly limited. Paraffinic hydrocarbons include linear normal paraffins and branched isoparaffins, such as normal heptane, normal octane, normal nonane, isoheptane, isooctane, isononane, isodecane, and trimethylpentane.

[0029] The naphthenic hydrocarbons are not particularly limited, but include cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, and the like.

[0030] Examples of commercially available paraffinic hydrocarbons include IP Solvent 1620, IP Solvent 2028, and IP Solvent 2835 manufactured by Idemitsu Kosan Co., Ltd., D-SOL280 and D-SOL300 manufactured by Mitsubishi Shoji Chemical Co., Ltd., NS Clean 200, NS Clean 220, and NS Clean 230 manufactured by ENEOS Corporation, and NAS-5H manufactured by NOF Corporation. Examples of commercially available naphthenic hydrocarbons include Teclean N-20, Teclean N-22, Naphtesol 160, Naphtesol 200, and Naphtesol 220 manufactured by ENEOS Corporation, and EXXSOL D80, EXXSOL D110, and EXXSOL D130 manufactured by ExxonMobil Corporation. Commercially available mixed solvents of paraffinic hydrocarbons and naphthenic hydrocarbons include SPCN-80 manufactured by SPC Japan, and AF Solvent No. 5, AF Solvent No. 6, and AF Solvent No. 7 manufactured by Nippon Petrochemical Co., Ltd. These may be used alone or in combination of two or more.

[0031] The total content of paraffinic hydrocarbons and naphthenic hydrocarbons in the ink composition is preferably 10 to 55 mass %, more preferably 15 to 45 mass %. When the contents of paraffinic hydrocarbons and naphthenic hydrocarbons are within the above ranges, the ink composition exhibits good ink receptivity and excellent on-press stability.

[0032] Of the total solvent content, the combined content of paraffinic hydrocarbons and naphthenic hydrocarbons is preferably 20 to 100 mass%, more preferably 40 to 100 mass%, and even more preferably 70 to 100 mass%. When the combined content of paraffinic hydrocarbons and naphthenic hydrocarbons is within the above range, the ink composition has excellent ink receptivity.

[0033] The content of the solvent is not particularly limited. For example, the content of the solvent in the ink composition is preferably 10 to 60% by mass or more, and more preferably 15 to 50% by mass or more. When the content of the solvent is within the above range, the ink composition can be easily adjusted to an ink tack value that shows good printability in metal printing.

[0034] <Resin> The resin of the present embodiment is not particularly limited. Examples of the resin include polyester resin, petroleum resin, epoxy resin, ketone resin, rosin-modified phenolic resin, melamine resin, and benzoguanamine resin. Among these, the resin is preferably a polyester resin and / or a petroleum resin, and among polyester resins, an alkyd resin is more preferable. These resins may be used alone or in combination of two or more.

[0035] Alkyd resins exhibit good compatibility with solvents and basic dispersants, and when an overprint layer is formed on an ink layer made of an ink composition, they ensure suitability for overprint varnish, provide pigment dispersion stability, impart ink viscoelasticity suitable for printing, and provide excellent ink transferability to metal printing media.

[0036] The alkyd resin is not particularly limited. One example is an alkyd resin having a backbone made of a condensate of a polybasic acid and a polyhydric alcohol and modified with a fatty acid. The alkyd resin of this embodiment may be a resin modified with a fatty acid or a hydrogenated fatty acid, an oil or a hydrogenated oil, a monobasic acid, or the like. This allows the resin to contain structural units derived from fatty acids.

[0037] The oils and fatty acids include linseed oil, tung oil, safflower oil, soybean oil, tall oil, rice bran oil, palm oil, castor oil, dehydrated castor oil, sunflower oil, coconut oil, the fatty acids of these oils, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, eleostearic acid, 12-hydroxystearic acid, etc. The oils and fatty acids may be used in combination.

[0038] The content of fatty acid-derived structural units in the alkyd resin is preferably 40 to 60 mass %, more preferably 45 to 60 mass %, of the alkyd resin. When the content of fatty acid-derived structural units is within the above range, the alkyd resin has excellent compatibility with paraffinic hydrocarbons and / or naphthenic hydrocarbons and basic dispersants, and exhibits good ink receptivity, on-machine stability, and productivity.

[0039] Furthermore, a portion of the fatty acids may be replaced with a monobasic acid other than fatty acids. As other monobasic acids, benzoic acid, pt-butylbenzoic acid, abietic acid, 12-hydroxystearic acid, etc. may be used in combination.

[0040] Examples of polybasic acids include aromatic dibasic acids such as phthalic anhydride, isophthalic acid, and terephthalic acid, alicyclic dibasic acids such as tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and 1,4-cyclohexanedicarboxylic acid, aliphatic dibasic acids such as succinic anhydride, maleic anhydride, himic anhydride, adipic acid, sebacic acid, azelaic acid, and fumaric acid, and polybasic acids such as trimellitic anhydride and methylcyclohexene tricarboxylic anhydride. Polybasic acids may be used in combination.

[0041] The alkyd resin of the present invention is preferably an alkyd resin containing structural units derived from isophthalic acid. When the polybasic acid is an isophthalic acid component, the resulting alkyd resin has good ink receptivity, and even when the printed layer is thick, the ink composition maintains good film properties.

[0042] The polyhydric alcohol includes dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,6-hexanediol, bisphenol A, and hydrogenated bisphenol A; trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and tris(2-hydroxyethyl)isocyanurate; and tetrahydric or higher alcohols such as pentaerythritol and dipentaerythritol. Polyhydric alcohols may be used in combination.

[0043] The styrene-equivalent weight-average molecular weight of the alkyd resin is preferably 8,000 or more and 40,000 or less. When the weight-average molecular weight of the resin is within the above range, the compatibility with the solvent is excellent, and the on-machine stability and transferability are good. Furthermore, even when the ink composition has excellent ink receptivity and the printed layer is thick, the ink composition maintains good coating properties. In this embodiment, the weight-average molecular weight is a value measured by gel permeation chromatography (GPC).

[0044] The resin of this embodiment is preferably an alkyd resin containing 45 to 60% by mass of structural units derived from fatty acids and having a weight average molecular weight of at least 8000. This results in excellent ink receptivity and film physical properties.

[0045] The method for producing an alkyd resin is not particularly limited. Examples of methods for producing an alkyd resin include known methods such as the transesterification method using oil as a raw material and the fatty acid method using fatty acids as a raw material. For example, the fatty acid, polybasic acid, and polyhydric alcohol described above are charged together with xylene into a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, and the mixture is heated to 240°C with stirring under a nitrogen atmosphere to carry out an esterification reaction. After confirming that the desired acid value has been reached, the reaction is terminated to obtain an alkyd resin.

[0046] The polyester resin (excluding alkyd resins) is not particularly limited. For example, the polyester resin is a condensation product of a polybasic acid and a polyhydric alcohol, and is a polyester resin obtained by reacting a polybasic acid with a polyhydric alcohol using a known esterification reaction.

[0047] Polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, and triethylene glycol. Dihydric alcohols such as dipropylene glycol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, isosorbide, bisphenol A, and hydrogenated bisphenol A; trihydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, and 1,2,4-butanetriol; and trihydric or higher alcohols such as sorbitol and pentaerythritol. Polyhydric alcohols may be used in combination.

[0048] Examples of polybasic acids include aromatic dibasic acids such as phthalic acid, phthalic anhydride, isophthalic acid, and terephthalic acid; alicyclic dibasic acids such as tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, and 1,4-cyclohexanedicarboxylic acid; aliphatic dibasic acids such as oxalic acid, malonic acid, succinic acid, succinic anhydride, maleic anhydride, himic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and fumaric acid; and polybasic acids such as trimellitic anhydride and methylcyclohexene tricarboxylic anhydride. Monobasic acids may also be used in combination. Examples of monobasic acids include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, linoleic acid, and benzoic acid.

[0049] The content of the resin in the ink composition is not particularly limited as long as it can be adjusted to a predetermined ink tack value suitable for metal printing. For example, the content of the resin in the ink composition is preferably 20 to 60% by mass or more, and more preferably 30 to 50% by mass or more. By keeping the content of the resin within the above range, the ink composition maintains its printability, such as transferability and misting resistance, and also exhibits excellent coating film properties.

[0050] <Pigments> The pigment of the present embodiment is not particularly limited, and any known inorganic or organic pigment for printing ink can be used alone or in combination.

[0051] The inorganic pigments and organic pigments preferably have heat resistance, light resistance, and retort resistance. Inorganic pigments include titanium oxide, silica, carbon black, etc. Organic pigments include phthalocyanine pigments, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, quinophthalone pigments, etc.

[0052] The pigment of the present invention is preferably an organic pigment, which provides the ink composition with good ink receptivity and excellent productivity.

[0053] The content of the pigment in the ink composition is adjusted as appropriate depending on the type and purpose. For example, the content of the pigment in the ink composition is preferably 10 to 60% by mass or more, and more preferably 15 to 45% by mass or more. When the content of the pigment is within the above range, the ink composition has excellent printability such as on-press stability, good coloring power and hiding power, and is also excellent in productivity and dispersion stability.

[0054] <Other ingredients> In addition to the components described above, the ink composition of this embodiment may contain additives that are typically added to ink compositions, such as extender pigments, driers, acid catalysts, waxes, viscosity modifiers, and storage stabilizers.

[0055] <How to adjust printing ink> The method for preparing the ink composition of the present embodiment is not particularly limited. For example, the ink composition can be prepared by a conventional method using a three-roll mill, a ball mill, a bead mill, or the like.

[0056] The form of the ink composition of this embodiment varies depending on the type and content of resin, pigment, solvent, and additives. For example, the tack value is preferably 4 to 12, and more preferably 5 to 10. Here, the tack value is the value measured using a digital incometer (manufactured by Toyo Seiki Seisakusho, Ltd.) with 1.31 cc of ink, at a room temperature of 25°C, a roller temperature of 30°C, and a rotation speed of 400 rpm for 1 minute. A tack value within the above range provides excellent agglomeration resistance and misting resistance.

[0057] The flow value is preferably 25 to 50, and more preferably 30 to 45. Here, the flow value indicates the value measured using a horizontal plate viscometer (spread meter, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) at room temperature of 25°C and after 60 seconds, as the spread diameter value (unit: mm). When the flow value is in the above range, good transferability is exhibited.

[0058] <Metal Printing Method> The printing method for the ink composition of this embodiment is not particularly limited, and can be appropriately selected from dry offset methods using resin relief plates or waterless lithographic plates, and offset methods using water-based lithographic plates. The film thickness of the ink composition is optional, but should be in the range of 0.5 to 6 μm. By ensuring that the film thickness of the ink composition is within the above range, a metallic printed product can be obtained that exhibits excellent on-press stability and misting resistance, as well as good coloring power and hiding power. The resulting metallic printed product also has excellent film properties.

[0059] Furthermore, examples of metal printing media on which the ink composition of the present embodiment is printed include, but are not limited to, aluminum plates, steel plates, and coated plates obtained by laminating these with polyester films, etc. These substrates may be subjected to chemical conversion treatment, plating treatment, or base coating such as size coating, white coating, or silver coating.

[0060] The method for coating a substrate according to this embodiment includes the steps of providing a printed layer on the substrate using an ink composition, applying an overprint varnish to the printed layer, and then curing the printed layer. The printed / coated article of the present invention comprises, on a substrate, a printed layer formed using a printing ink composition and an overprint layer formed using an overprint varnish. The curing step is preferably heat curing, and the heating conditions are not particularly limited. For example, the first baking step involves heating at a temperature of 180°C to 300°C for approximately 3 to 90 seconds, and the second baking step involves heating at a temperature of 180°C to 300°C for approximately 30 to 150 seconds.

[0061] The overprint varnish is preferably a thermosetting one, and any conventionally known overprint varnish for metal containers can be used without any particular limitation. Examples include polyester-melamine, polyester-epoxy-melamine, and polyester-acrylic-melamine varnishes. The overprint varnish may be either water-based or solvent-based. [Example]

[0062] The present invention will be described below based on examples and comparative examples, but the present invention is not limited to these examples. Note that the numbers in the tables below are based on mass.

[0063] Details of the raw materials used and the synthesis method are as follows.

[0064] <Dispersant> Solsperse 13940 (basic, amine value: 91 mg KOH / g, manufactured by Lubrizol) Solsperse 20000 (basic, amine value: 32 mg KOH / g, manufactured by Lubrizol) Ajisper PB821 (basic, amine value: 10 mg KOH / g, manufactured by Ajinomoto Fine-Techno Co., Ltd.) Solsperse 36000 (acidic, manufactured by Lubrizol) Ajisper PN411 (acidic, manufactured by Ajinomoto Fine-Techno Co., Ltd.)

[0065] <Solvent> AF Solvent No. 4 (paraffinic hydrocarbons and naphthenic hydrocarbons, manufactured by Nippon Petrochemicals) AF Solvent No. 6 (paraffinic hydrocarbons and naphthenic hydrocarbons, manufactured by Nippon Petrochemicals) D-sol300 (paraffinic hydrocarbon, manufactured by Mitsubishi Corporation Chemicals) EXXSOLD110 (naphthenic hydrocarbon, manufactured by ExxonMobil) LAB (Linear Alkyl Benzene, Mitsui & Co., Ltd.) Sannix PP400 (propylene glycol, manufactured by Sanyo Chemical Industries, Ltd.)

[0066] <Resin> The resin was synthesized as follows, and the composition is shown in Table 1. (Synthesis of alkyd resin) Resin 1 45 parts of coconut oil fatty acid, 31 parts of isophthalic acid, 17 parts of pentaerythritol, 17 parts of trimethylolpropane, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain an alkyd resin with a weight-average molecular weight of 12,000 and a number-average molecular weight of 3,000. The amount of dehydration was 10 parts. Resin 2 50 parts of coconut oil fatty acid, 27.5 parts of isophthalic acid, 16 parts of pentaerythritol, 16 parts of trimethylolpropane, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain an alkyd resin with a weight-average molecular weight of 9,200 and a number-average molecular weight of 2,500. The amount of dehydration was 9.5 parts. Resin 3 55 parts of coconut oil fatty acid, 23 parts of isophthalic acid, 15.5 parts of pentaerythritol, 15.5 parts of trimethylolpropane, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain an alkyd resin with a weight-average molecular weight of 8,000 and a number-average molecular weight of 2,200. The amount of dehydration was 9 parts. Resin 4 65 parts of coconut oil fatty acid, 15.5 parts of isophthalic acid, 14 parts of pentaerythritol, 14 parts of trimethylolpropane, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain an alkyd resin with a weight-average molecular weight of 5,000 and a number-average molecular weight of 2,100. The amount of dehydration was 7 parts. Resin 5 55 parts of coconut oil fatty acid, 21 parts of phthalic anhydride, 15.5 parts of pentaerythritol, 15.5 parts of trimethylolpropane, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain an alkyd resin with a weight-average molecular weight of 3,500 and a number-average molecular weight of 2,000. The amount of dehydration was 7 parts.

[0067] (Synthesis of polyester resin) Resin 6 40 parts of tetrahydrophthalic anhydride, 52 parts of hydrogenated bisphenol A, and 13 parts of pentaerythritol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at a temperature of 220 to 230°C while circulating xylol under a nitrogen stream. After the reaction was completed, the xylol was distilled off at 240°C to obtain a polyester resin with a weight-average molecular weight of 8,500 and a number-average molecular weight of 2,500. The amount of dehydration was 5 parts. Resin 7 40 parts of tetrahydrophthalic anhydride, 52 parts of hydrogenated bisphenol A, and 13 parts of trimethylolpropane were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at a temperature of 220 to 230°C while circulating xylol under a nitrogen stream. After the reaction was completed, the xylol was distilled off at 240°C to obtain a polyester resin with a weight average molecular weight of 4,700 and a number average molecular weight of 1,600. The amount of dehydration was 5 parts.

[0068] [Table 1]

[0069] <Pigments> LIONOL BLUE FG-7351 (Phthalocyanine Blue 15:3, manufactured by Toyo Color Co., Ltd.) MA-77 (carbon black, manufactured by Mitsubishi Chemical Corporation)

[0070] The ink compositions of Examples 1 to 17 and Comparative Examples 1 to 5 were evaluated in the following manner, and the results are shown in Table 2.

[0071] [Table 2]

[0072] <Ink receptivity> Using a high-speed printability tester (PM904PT manufactured by SMT Corporation), 500 mg of each ink composition of the Examples and Comparative Examples was supplied and homogenized, then transferred onto a test rubber roll and then onto an aluminum plate at a printing speed of 8 m / s. The weight of the ink composition applied to the aluminum plate was evaluated. (Evaluation criteria) A: The mass change of the aluminum plate before and after printing is 150 mg or more. B: The change in mass of the aluminum plate before and after printing is 100 mg or more and less than 150 mg. C: The change in mass of the aluminum plate before and after printing is 50 mg or more and less than 100 mg. D: The mass change of the aluminum plate before and after printing is less than 50 mg. The practical evaluations are A, B and C.

[0073] <On-board stability> 1.31 cc of the ink compositions of the Examples and Comparative Examples was evenly placed on the rubber roll of a digital ink meter (manufactured by Toyo Seiki Seisakusho, Ltd.), and the time until the tack value reached its maximum was measured at 40°C and 1200 rpm to evaluate the on-press stability. Note that the longer the time until the maximum value is reached, the more suppressed is the release of solvent from the ink, and the less change there is in the fluidity and viscosity of the ink on the ink roller or blanket, which can be said to be the more excellent the on-press stability. (Evaluation criteria) A: It reaches its maximum value after 30 minutes. B: The maximum value is reached between 20 and 30 minutes. C: The maximum value is reached between 10 and 20 minutes. D: Reaches maximum value in less than 10 minutes. The practical evaluations are A, B and C.

[0074] <Film properties> Test panels were prepared using the ink compositions of the examples and comparative examples. Using an RI tester (manufactured by Kokubo Precision Co., Ltd.) and a four-section roll, 0.1 cc of the ink composition was spread on an aluminum plate, and the solvent-based overprint varnish was applied to the aluminum plate using a simple roll coater until the solid content of the solvent-based overprint varnish was 50 mg to 60 mg / 100 cm. 2 The coating was applied wet-on-wet onto the printed ink layer so that the coating was cured by heating in an electric oven. The baking and drying conditions were as follows: the first baking was performed by maintaining the test panel at 200°C for 30 seconds, and then the second baking was performed by maintaining the test panel at 200°C for 120 seconds. The pencil hardness of the prepared test panel was evaluated in accordance with JISK 5600-5-4 using a pencil hardness test pencil (manufactured by Mitsubishi Pencil Co., Ltd.) at room temperature of 25°C. (Evaluation criteria) A: Pencil hardness of 3H or higher. B: Pencil hardness is H or higher and 2H or lower. C: Pencil hardness is HB or higher and F or lower. D: Pencil hardness is B or less. The practical evaluations are A, B and C.

[0075] <Productivity> 1 kg of the raw materials for the ink compositions of the Examples and Comparative Examples was placed in a container, subjected to vibration stirring for 10 minutes, and then dispersed using a three-roll mill SDY-300 (manufactured by Buhler Co., Ltd.) set at a temperature of 50°C. The dispersion state of the ink composition after passing through the rolls was measured using a dispersed particle size measuring device (grind meter) in accordance with JIS K5600-2-5. The number of roll passes required to reduce the particle size to 5.0 microns or less was evaluated. (Evaluation criteria) A: The number of times the roll is passed through is less than three. B: The number of times the roll is passed through is 3 or more but less than 5 times. C: The number of times the roll is passed is 5 or more but less than 7 times. D: The number of times the roll is passed through is 7 or more. The practical evaluations are A, B and C.

[0076] The formulations of the examples and comparative examples are as follows: (Examples 1 to 17) The composition includes a resin, a pigment, a solvent, and a dispersant, wherein the solvent includes a paraffinic solvent and / or a naphthenic solvent, and the dispersant is a basic dispersant. (Comparative Examples 1 to 3) The difference from the compositions of the examples is that no basic dispersant is contained. (Comparative Examples 4 and 5) The difference from the compositions of the examples is that paraffinic hydrocarbons and / or naphthenic hydrocarbons are not included.

Claims

1. An ink composition for metal printing comprising a resin, a pigment, a solvent, and a dispersant, wherein the solvent comprises a paraffinic solvent and / or a naphthenic solvent, and the dispersant comprises a basic dispersant.

2. 2. The ink composition for metal printing according to claim 1, wherein the resin is an alkyd resin containing 40 to 60% by mass of structural units derived from fatty acids.

3. 2. The ink composition for metal printing according to claim 1, wherein the resin is an alkyd resin containing 45 to 60% by mass of structural units derived from fatty acids and having a weight average molecular weight of 8,000 or more.

4. 2. The ink composition for metal printing according to claim 1, wherein the pigment is an organic pigment.

5. 2. The ink composition for metal printing according to claim 1, wherein the resin is an alkyd resin containing structural units derived from isophthalic acid.

6. 2. The ink composition for metal printing according to claim 1, wherein the content of the dispersant in the ink composition is 0.2 to 5% by mass.

7. 2. The ink composition for metal printing according to claim 1, wherein the total content of the paraffinic solvent and the naphthenic solvent is 20 to 100 mass % of the total content of the solvents.

8. A metallic printed product having a printed layer formed on a metal medium and comprising the metallic printing ink composition according to any one of claims 1 to 7, and an overprint layer formed on the printed layer and comprising an overprint varnish.

9. A method for producing a metal printed item, comprising: forming a printed layer on a metal medium by dry offset printing or offset printing the ink composition for metal printing according to any one of claims 1 to 7; and applying an overprint varnish onto the printed layer to form an overprint layer.

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