Metallic printing ink composition and metallic print

Abstract

To provide an ink composition for metal printing which has good ink adhesion to a plate or a substrate, and is also excellent in on-press stability, film properties and productivity. [Solution] 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 is a basic dispersant. A metal printed product having a printed layer made of the ink composition for metal printing 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, comprising dry offset printing or offset printing the ink composition for metal printing on a metal medium to form a printed layer, and 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 metal printing. More specifically, the present invention relates to an ink composition for metal printing that has good ink adhesion to plates and substrates and is also excellent in on-press stability, film properties, and productivity, and to a metal 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 mainly manufactured by two methods. One method involves printing and painting a sheet-like metal plate, which is then cut, welded, and other processes to create the desired can body. The other method involves punching out a metal plate, processing it through processes such as ironing 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] On the surface of a metal container, a metal printing ink composition is printed, and various designs, ingredient indications, 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 surface via multiple rolls, and then transferred from the plate to a blanket, and then 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 as a thin film of several μm. Therefore, it is important that the printing ink composition has stable fluidity and on-press stability, and that it has 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 uses an alkyd resin adjusted to a predetermined weight average molecular weight, number average molecular weight, and molecular weight distribution to suppress thickening of image lines and dots. Patent Document 2 describes a metal printing technology that uses an alkyd resin that contains a specific fatty acid and is combined with the fatty acid in a specific ratio and amount to achieve excellent jet blackness and design reproducibility. [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 matter using the ink. [Means for solving the problem]

[0008] As a result of extensive research into the above problems, the inventors have discovered that the above problems can be solved by using the ink for metal printing described below, and have thus completed 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, in which 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 a structural unit 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 combined content of the paraffinic solvent and the naphthenic solvent is 20 to 100 mass % based on 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 metallic medium, and an overprint layer provided on the printed layer.

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

[0018] According to the present invention described above, it is now possible to provide an ink composition for metallic printing which has excellent printability such as ink receptivity and on-machine stability, and which also has good film properties and productivity, and a metallic printed product using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail. Note that the embodiment or description of the requirements described is an example of an embodiment of the present invention, and appropriate modifications can be made 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 paraffin-based solvent and / or a naphthene-based solvent as the solvent and including a basic dispersant as the dispersant, it is possible to obtain an ink composition for metal printing that is excellent in printability such as ink adhesion and on-machine stability, and also has good film properties and productivity. Each component will be described below.

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

[0022] The dispersant has an adsorption site to the pigment and a dispersion stabilizing site. In addition, examples of polar groups that the dispersant has include acidic groups, basic groups, and other functional groups, and a basic dispersant refers to 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. By using a basic dispersant, the ink composition not only exhibits dispersion stability and fluidity, but also improves the affinity of the resin, solvent, and pigment, and increases adhesion, resulting in good ink adhesion, and excellent on-machine stability and productivity.

[0023] The basic dispersant may have either a straight-chain structure called a single form or a comb-type structure having a side chain in the main chain.

[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 adhesion. Here, the amine value of the basic dispersant represents the amine value per 1 g of solid content of the basic dispersant, and refers to a value converted into an equivalent amount of potassium hydroxide after determining the amount of hydrochloric acid required to neutralize the basic groups in the dispersant by potentiometric titration using a 0.1 N aqueous hydrochloric acid solution.

[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 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-Chemie Japan Co., Ltd. These may be used alone or in combination of two or more kinds.

[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%. By having the content of the basic dispersant in 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 the present embodiment contains paraffinic hydrocarbons and / or naphthenic hydrocarbons as a solvent. By blending paraffinic hydrocarbons and / or naphthenic hydrocarbons, affinity with the basic dispersant described above is improved, and the ink composition has excellent ink adhesion, on-machine 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] Examples of naphthenic hydrocarbons include, but are not limited to, 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 Teclain N-20, Teclain 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 / 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 content of paraffinic hydrocarbons and naphthenic hydrocarbons is within the above range, the ink composition exhibits good ink receptivity and excellent on-machine stability.

[0032] In the total content of the solvents, the proportion of the total content of the paraffinic hydrocarbons and the naphthenic hydrocarbons is preferably 20 to 100 mass%, more preferably 40 to 100 mass%, and even more preferably 70 to 100 mass%. When the proportion of the total content of the paraffinic hydrocarbons and the 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. By having the content of the solvent 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. For example, the resin may be a polyester resin, a petroleum resin, an epoxy resin, a ketone resin, a rosin-modified phenolic resin, a melamine resin, a benzoguanamine resin, etc. Among these, the resin is preferably a polyester resin and / or a petroleum resin, and among the polyester resins, an alkyd resin is more preferable. These resins may be used alone or in combination of two or more kinds.

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

[0036] The alkyd resin is not particularly limited. One example is an alkyd resin having a skeleton of a condensate of a polybasic acid and a polyhydric alcohol and modified with a fatty acid. The alkyd resin of the present embodiment may be a resin modified with a fatty acid or a hydrogenated fatty acid, an oil or a hydrogenated oil, a monovalent acid, or the like. This allows the resin to have a structural unit derived from a fatty acid.

[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, linoleic acid, ricinoleic acid, eleostearic acid, 12-hydroxystearic acid, etc. The oils and fatty acids may be used in combination.

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

[0039] In addition, a part of the fatty acid may be changed to a monobasic acid other than fatty acid. As the other monobasic acid, benzoic acid, pt-butylbenzoic acid, abietic acid, 12-hydroxystearic acid, etc. can be used in combination.

[0040] The polybasic acid includes 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 a structural unit derived from isophthalic acid. Since the polybasic acid is an isophthalic acid component, the resulting alkyd resin has good ink-receiving properties, and even when the printed layer becomes 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 to 40,000. When the weight average molecular weight of the resin is within the above range, the compatibility with the solvent is excellent, and the stability on the machine and the transferability are good. In addition, even when the ink composition has excellent ink adhesion 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 provides excellent ink receptivity and film physical properties.

[0045] The method for producing the alkyd resin is not particularly limited. For example, the method for producing the alkyd resin is a known method such as an ester exchange method using oil as a raw material, or a fatty acid method using fatty acid as a raw material. As an example, the above-mentioned fatty acid, polybasic acid, and polyhydric alcohol are charged together with xylene in a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, and the temperature is raised to 240° C. while stirring under a nitrogen atmosphere to carry out an esterification reaction. After confirming that the acid value is an arbitrary value, 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. , dipropylene glycol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, isosorbide, bisphenol A, hydrogenated bisphenol A, and other dihydric alcohols, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, and other trihydric or higher alcohols, such as sorbitol and pentaerythritol. Polyhydric alcohols may be used in combination.

[0048] The polybasic acid may be an aromatic dibasic acid such as phthalic acid, phthalic anhydride, isophthalic acid, or terephthalic acid; an alicyclic dibasic acid such as tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, or 1,4-cyclohexanedicarboxylic acid; an aliphatic dibasic acid such as oxalic acid, malonic acid, succinic acid anhydride, maleic anhydride, hymic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, or fumaric acid; or a polybasic acid such as trimellitic anhydride or methylcyclohexene tricarboxylic anhydride. A monobasic acid may also be used in combination. Examples of the monobasic acid include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic 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. It is sufficient to adjust the ink tack value to a predetermined 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, more preferably 30 to 50% by mass or more. By having the content of the resin in the above range, the ink composition maintains the performance in terms of printability, such as transferability and misting resistance, and is also excellent in the coating film properties.

[0050] <Pigments> The pigment of the present embodiment is not particularly limited. Known inorganic or organic pigments for printing inks can be used alone or in combination.

[0051] The inorganic pigment and the organic pigment are preferably those having heat resistance, light resistance, and retort resistance. The inorganic pigment is titanium oxide, silica, carbon black, etc. The organic pigment is phthalocyanine pigment, azo pigment, quinacridone pigment, diketopyrrolopyrrole pigment, quinophthalone pigment, etc.

[0052] The pigment of the present invention is preferably an organic pigment. When the pigment is an organic pigment, the ink composition has good ink receptivity and is also excellent in productivity.

[0053] The content of the pigment in the ink composition is appropriately adjusted 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, more preferably 15 to 45% by mass or more. By having the content of the pigment within the above range, the ink composition has excellent printability such as on-machine stability, good coloring power and hiding power, and is also excellent in productivity and dispersion stability.

[0054] <Other ingredients> In addition to the above components, the ink composition of the present embodiment may contain additives that are typically added to ink compositions, such as extender pigments, dryers, 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 the resin, pigment, solvent, and additives. As an example, the tack value is preferably 4 to 12, and more preferably 5 to 10. Here, the tack value is a value measured by using a digital incometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and rotating the ink for 1 minute under the conditions of 1.31 cc of ink, room temperature of 25°C, roller temperature of 30°C, and rotation speed of 400 rpm. When the tack value is in the above range, the ink has 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 print manufacturing method> The printing method of the ink composition of this embodiment is not particularly limited, and can be appropriately selected from a dry offset method using a resin letterpress or a waterless lithographic plate, and an offset method using a water-based lithographic plate. The film thickness of the ink composition is arbitrary, but may be in the range of 0.5 to 6 μm. By setting the film thickness of the ink composition in the above range, a metal print that is excellent in on-machine stability and misting resistance, and exhibits good coloring power and hiding power can be obtained. In addition, the film properties of the obtained metal print are also excellent.

[0059] In addition, 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, and size coating, white coating, silver coating, etc. as base coating.

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

[0061] The overprint varnish is preferably a thermosetting one, and any conventionally known metal container overprint varnish can be used without any particular limitation. For example, polyester-melamine, polyester-epoxy-melamine, polyester-acrylic-melamine varnishes can be used. The overprint varnish can be either water-based or solvent-based. EXAMPLES

[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 mgKOH / g, manufactured by Lubrizol) Solsperse 20000 (basic, amine value: 32 mgKOH / g, manufactured by Lubrizol) AJISPER PB821 (basic, amine value: 10mgKOH / 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 and naphthenic hydrocarbons, manufactured by Nippon Petrochemicals) AF Solvent No. 6 (Paraffinic and naphthenic hydrocarbons, manufactured by Nippon Petrochemicals) D-sol300 (Paraffinic hydrocarbon, manufactured by Mitsubishi Corporation Chemical Co., Ltd.) EXXSOLD110 (naphthenic hydrocarbon, manufactured by ExxonMobil) ·LAB (Linear Alkylbenzene, 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-necked flask equipped with a stirrer, and esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, 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-necked flask equipped with a stirrer, and esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, 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-necked flask equipped with a stirrer, and esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, 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-necked flask equipped with a stirrer, and esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, 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-necked flask equipped with a stirrer, and esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, 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-necked flask equipped with a stirrer, and an esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream. After the reaction was completed, 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-necked flask equipped with a stirrer, and an esterification reaction was carried out at a temperature of 220°C to 230°C while circulating xylol under a nitrogen stream. After the reaction was completed, 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 adhesion> Using a high-speed printability tester (PM904PT manufactured by SMT Co., Ltd.), 500 mg of the ink compositions of the examples and comparative examples were fed and homogenized, then transferred to a test rubber roll, and then transferred to 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 change in mass 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 change in mass 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 inkometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the time until the tack value reached its maximum was measured under conditions of 40°C and 1200 rpm, to evaluate the on-press stability. Note that the longer the time it takes to reach its maximum value, the more suppressed the release of the solvent from the ink, and the less change 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 Seimitsu Co., Ltd.) and a four-part 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 so that the solid content of the solvent-based overprint varnish was 50 mg to 60 mg / 100 cm. 2 The coating was applied onto the printed ink layer by a wet-on-wet method so that the coating was cured by heating in an electric oven. The baking and drying conditions were as follows: the first baking step was performed by maintaining the test panel at 200°C for 30 seconds, and then the second baking step was performed by maintaining the test panel at 200°C for 120 seconds. The pencil hardness of the test panel was evaluated in accordance with JISK 5600-5-4 using a pencil for pencil hardness testing (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 lower. The practical evaluations are A, B, and C.

[0075] <Productivity> The raw materials of 1 kg of the ink compositions of the examples and comparative examples were placed in a container, and after vibration stirring for 10 minutes, the ink compositions were 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) according to JIS K5600-2-5. The number of roll passes at which the particle size became 5.0 microns or less was evaluated. (Evaluation Criteria) A: The roll has been passed through less than three times. B: The number of times the roll is passed 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 roll is passed through 7 times 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, 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 offset ink composition for metal printing comprising a resin, a pigment, a solvent, and a dispersant, The resin comprises an alkyd resin and / or a polyester resin, the solvent contains a paraffinic solvent and / or a naphthenic solvent, and the total content of the paraffinic solvent and the naphthenic solvent is 20 to 100 mass% based on the total content of the solvents; The offset ink composition for metal printing, wherein the dispersant comprises a basic dispersant, and the content of the dispersant in the offset ink composition is 0.2 to 5 mass %.

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

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

6. A metal print comprising a printing layer formed on a metal medium and comprising the offset ink composition for metal printing according to any one of claims 1 to 5, and an overprint layer formed on the printing layer and comprising a varnish for overprinting.

7. A method for producing a metal printed product, comprising: forming a printed layer on a metal medium by dry offset printing or offset printing the offset ink composition for metal printing according to any one of claims 1 to 5; and applying an overprint varnish onto the printed layer to form an overprint layer.

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