Ink composition for printing on metal

Abstract

[Problem] To provide an ink composition for printing on metal, said ink being satisfactory in all of misting suppression during printing, transferability during high-speed printing, and impact resistance after retort processing. [Solution] The aforementioned problem is solved by an ink composition for printing on metal, said ink containing a coloring pigment, a resin, and a solvent, wherein bentonite that is an extender pigment and a rosin-modified resin that has a softening point of at least 105°C are combined.

Description

Ink composition for metal printing

[0001] This invention relates to an ink composition for metal printing.

[0002] For printing on the metal exteriors of metal materials, such as galvanized or tinned iron sheets, aluminum sheets, or metal cans made from these metal materials, metal printing ink compositions are used, which primarily consist of binder resins such as alkyd resin, polyester resin, or epoxy resin, and organic solvents such as mineral oil or higher alcohols as vehicle components.

[0003] Furthermore, these printed surfaces are generally coated with overprint varnish to improve the adhesion, bending resistance, impact resistance, and abrasion resistance of the ink film. These overprint varnishes are widely used, and are solvent-based types consisting of binder resins such as alkyd resin, polyester resin, acrylic resin, and epoxy resin, hardeners such as melamine resin and benzoguanamine resin, and organic solvents such as mineral oil and cellosolve.

[0004] For printing on the metal exterior, ink is printed using an offset printing press, dry offset printing press, etc., and then an overprint varnish is applied to the ink film wet-on-wet using a coater, etc., and then baked at 150 to 280°C.

[0005] However, in recent years, due to concerns about air pollution caused by solvents and hygiene and safety in the printing work environment, it has become common practice in the field of metal printing to use water-based overprint varnishes instead of the solvent-based ones that were traditionally used. However, when water-based overprint varnish is applied to an ink film of a conventional metal printing ink composition, phenomena such as the water-based overprint varnish being repelled or penetrating into the ink film occur, resulting in a significant decrease in the quality of the coating, such as gloss or adhesion. Therefore, ink compositions have been required to have excellent compatibility with water-based overprint varnishes.

[0006] As a method to improve the suitability of such ink compositions for water-based overprint varnish, for example, Patent Document 1 proposes the use of alkylene glycol-based solvents with 4 to 8 carbon atoms, Patent Document 2 proposes the use of polyoxyalkylene glycol-based solvents, Patent Document 3 proposes the use of polyoxyalkylene alkyl ether-based organic solvents, and Patent Document 4 proposes the use of polyoxyalkylene alkyl ester-based solvents. While these organic solvents used in ink compositions are effective in improving the suitability of the ink composition for water-based overprint varnish, there was room for improvement in terms of factors such as the tendency to cause misting during printing.

[0007] Furthermore, in recent years, efforts have been made to increase the printing speed in metal printing in order to improve productivity. From the perspective of meeting these increased printing speeds, there is a growing demand for ink compositions with good transferability during printing.

[0008] Furthermore, depending on the application of the metal printed material, it may undergo retort processing for sterilization purposes, such as pressurization and heating with steam or hot water at 100°C or higher, as seen in two-piece and three-piece cans used for beverages like coffee and tea, or canned goods. Such processing can weaken the printed film of the metal printed material, significantly reducing its impact resistance, which is the ability to maintain the printed film when the printed surface is subjected to impact.

[0009] Against this backdrop, in order to improve properties such as transferability and impact resistance after retort processing, for example, Patent Documents 5 and 6 propose the use of specific carbon blacks and alkyd resins in combination, or the use of specific alkyd resins in combination with rosin-modified resins. However, from the viewpoint of satisfying all of the following: suppression of misting during printing, transferability during high-speed printing, and impact resistance after retort processing, there is room for further improvement. It should be noted that although these patent documents mention the use of rosin-modified resins, neither of them has considered rosin-modified resins with a weight-average molecular weight of less than 1,000, and the influence of the softening point of the rosin-modified resin has not been considered at all.

[0010] Japanese Patent Publication No. 5-75031, Japanese Patent Publication No. 5-40791, Japanese Patent Publication No. 5-40792, Japanese Patent Publication No. 64-60670, Japanese Patent No. 7494370, International Publication WO2024 / 224848

[0011] The present invention has been made in view of the above circumstances, and aims to provide a metal printing ink composition that can satisfy all of the following: suppression of misting during printing, transferability during high-speed printing, and impact resistance after retort processing.

[0012] The inventors of the present invention have conducted extensive research to solve the above problems and have found that the above problems can be solved by combining bentonite, a type of extender pigment, with a rosin-modified resin having a softening point of 105°C or higher, in a metal printing ink composition containing a coloring pigment, an extender pigment, a resin, and a solvent. The present invention is based on this finding and provides the following.

[0013] (1) The present invention relates to a metal printing ink composition comprising a coloring pigment, a resin, bentonite, and a solvent, characterized in that at least a portion of the resin comprises a rosin-modified resin having a softening point of 105°C or higher.

[0014] (2) The present invention is also a metal printing ink composition according to item (1), wherein the weight-average molecular weight of the rosin-modified resin is 1,000 or more.

[0015] (3) The present invention is a metal printing ink composition according to item (1) or (2), further characterized by containing silica.

[0016] (4) The present invention is also a metal printing ink composition as described in item (3), wherein the silica is hydrophobic treated silica.

[0017] (5) The present invention is also a metal printing ink composition according to any one of items (1) to (4), wherein the bentonite is organically modified bentonite.

[0018] (6) The present invention also relates to a metal printing ink composition according to any one of items (1) to (5), wherein the coloring pigment is carbon black.

[0019] (7) The present invention is also a metal printing ink composition as described in item (6), wherein the carbon black is acidic carbon black.

[0020] (8) The present invention is a metal printing ink composition according to any one of items (1) to (7), characterized in that it contains at least one selected from the group consisting of compounds represented by the following general formula (1) as the solvent. (In the above general formula (1), each A is independently a C2-C4 alkylene group which may have branching, R is a hydrogen atom or a C1-C13 alkyl group which may have branching and / or cyclic structures, and n is an integer from 2 to 25.)

[0021] (9) The present invention also relates to a solvent whose solubility parameter (sp value) is 10.00 (cal / cm³). ３ ) １／２ The metal printing ink composition described in item (8) is less than [amount missing].

[0022] (10) The present invention is also a metal printing ink composition according to any one of items (1) to (9), further comprising an alkyd resin as the resin.

[0023] (11) The present invention is also a metal printing ink composition according to item (10), characterized in that the alkyd resin satisfies the following conditions (A) to (C): (A) It is a condensation polymer of a polyhydric alcohol and a monohydric and / or polyhydric carboxylic acid, and the equivalent number of the polyhydric alcohol to the carboxylic acid (OH / COOH ratio) is 1.10 to 1.31 (B) The acid value is 4.0 to 8.9 mgKOH / g (C) The fatty acid modification amount is 46.0% by mass or more

[0024] (12) The present invention also relates to the metal printing ink composition according to item (10) or (11), wherein the weight-average molecular weight of the alkyd resin is less than 15,000.

[0025] (13) The present invention also relates to a metal printing ink composition according to any one of items (10) to (12), wherein the alkyd resin comprises a neopentyl glycol skeleton and a pentaerythritol skeleton.

[0026] (14) The present invention further provides the ink composition for metal printing according to item (11), wherein the carboxylic acid comprises isophthalic acid.

[0027] (15) The present invention further provides the ink composition for metal printing according to item (11) or (14), wherein the carboxylic acid comprises lauric acid, and the skeleton portion derived from lauric acid in the alkyd resin is 30% by mass or more.

[0028] (16) The present invention further provides the ink composition for metal printing according to any one of items (10) to (15), wherein the alkyd resin has an acid value of 4.0 to 8.0 mgKOH / g.

[0029] According to the present invention, there is provided an ink composition for metal printing that can satisfy all of the suppression of misting occurrence during printing, transferability during high-speed printing, and impact resistance after retort treatment.

[0030] Hereinafter, one embodiment of the ink composition for metal printing of the present invention will be described. It should be noted that the present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications within the scope of the present invention.

[0031] The ink composition for metal printing of the present invention (hereinafter appropriately abbreviated as "the ink composition of the present invention") is for metal printing, and is preferably applied to printing by a so-called dry offset printing method using a relief printing plate as the printing plate, or an offset printing method using a planographic printing plate as the printing plate, but can be applied to all printing methods commonly used in metal printing. In addition, since the ink composition of the present invention has excellent transferability during printing, it can favorably cope with high-speed printing which has been widely performed in recent years. Furthermore, since the printed film formed by baking treatment after printing with the ink composition of the present invention has good impact resistance even after being subjected to retort treatment, the ink composition of the present invention is of course applicable to general metal printed matters, and is also preferably applied to printing on metals that require retort treatment, such as two-piece cans and three-piece cans used for beverages such as coffee and tea, and canned foods.

[0032] The ink composition of the present invention comprises a color pigment, a resin, bentonite and a solvent, and is characterized by containing a rosin-modified resin having a softening point of 105°C or higher as at least part of the resin. Hereinafter, each component will be described.

[0033] [Resin] The ink composition of the present invention contains a rosin-modified resin having a softening point of 105°C or higher as an essential component. By containing such a rosin-modified resin, the transferability of the ink composition during printing is improved, and the impact resistance of the printed film after retort treatment can be made favorable. According to studies by the present inventors, it has been confirmed that the inclusion of the rosin-modified resin in the ink composition increases the solvent retention capacity of the ink composition on the printing press, and it is presumed that this maintains the viscosity of the ink composition during printing and improves the transferability. Further, regarding the softening point of the rosin-modified resin, the present inventors have for the first time found that there is a boundary point around 105°C from the viewpoint of achieving favorable impact resistance after retort treatment, and the use of a rosin-modified resin having a softening point above this temperature was effective. Therefore, in the present invention, a rosin-modified resin having a softening point of 105°C or higher is used. The softening point of the rosin-modified resin is preferably 110°C or higher, more preferably 115°C or higher, and even more preferably 120°C or higher.

[0034] The rosin-modified resin is a resin prepared using rosin as one of the raw materials. Rosin contains resin acids such as abietic acid, parastric acid, isopimaric acid, and levopimaric acid as a mixture, and these resin acids contain hydrophilic and chemically active carboxy groups, some of which have conjugated double bonds. Therefore, various rosin-modified resins have been prepared by, for example, combining polyhydric alcohols or polycarboxylic acids for polycondensation, adding resol which is a phenol condensate to the benzene ring contained in the rosin skeleton, or causing a Diels-Alder reaction with dienophiles such as maleic anhydride and maleic acid to add a maleic acid or maleic anhydride skeleton. Various such rosin-modified resins are commercially available, and it is also possible to obtain and use them.

[0035] Examples of rosin-modified resins include rosin ester resins, polymerized rosin ester resins, maleated rosin, fumarated rosin resins, rosin-modified maleic acid resins, rosin-modified fumaric acid resins, rosin-modified phenolic resins, rosin-modified alkyd resins, and rosin-modified polyester resins. In the present invention, any of these rosin-modified resins may be used, but among them, rosin ester resins are preferably used. Furthermore, the weight-average molecular weight of the rosin-modified resin is preferably about 1,000 to 10,000, more preferably about 1,000 to 5,000, and even more preferably about 1,000 to 3,000. If the weight-average molecular weight of the rosin-modified resin is 1,000 or more, the transferability of the ink composition during printing is improved, and the impact resistance of the printed film after retort treatment is improved, which is preferable.

[0036] The weight-average molecular weight of the resin in this invention can be measured by gel permeation chromatography (GPC). As an example, a Waters Acquity APC (Waters Corporation) was used as the GPC instrument, and ACQUITY APC XT 45 1.7 μm 4.6 × 150 mm, ACQUITY APC XT 200 2.5 μm 4.6 × 75 mm, and ACQUITY APC XT 900 2.5 μm 4.6 × 75 mm (Waters Corporation) were used as columns. Under the conditions of tetrahydrofuran as the mobile phase, column temperature 40°C, flow rate 0.8 ml / min, RI detector, sample injection concentration 10 mg / 5 ml, and injection volume 10 microliters, chromatography was performed, and the value obtained as the weight-average molecular weight in polystyrene terms can be cited.

[0037] In the present invention, it is preferable to use a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or more. By including such a high hydroxyl value rosin-modified resin in the ink composition of the present invention, the transferability of the ink composition during printing can be further improved. In addition, as the polarity of the composition itself increases, the affinity for water-based OP varnish, which is also highly polar, increases, and the effect of suppressing repellency even when applied wet-on-wet is also achieved. The hydroxyl value of the rosin-modified resin is more preferably 15 mg KOH / g or more, and even more preferably 20 mg KOH / g or more. Furthermore, there is no particular upper limit to the hydroxyl value of the rosin-modified resin, but as an example, it is about 200 mg KOH / g, preferably about 150 mg KOH / g, and more preferably about 100 mg KOH / g.

[0038] Furthermore, although not particularly limited, the acid value of the rosin-modified resin is preferably 100 mg KOH / g or less. Having an acid value of 100 mg KOH / g or less is preferable because it allows for both suppression of repelling when water-based OP varnish is applied wet-on-wet and suppression of printability such as misting and foil buildup. More preferably, the acid value of the rosin-modified resin is 80 mg KOH / g or less, and even more preferably 50 mg KOH / g or less.

[0039] The rosin-modified resin is used in a varnish state, which is dissolved or dispersed by heating with a solvent as described later. The rosin-modified resin may be used as a dissolved varnish, which remains dissolved or dispersed in the solvent, or, when preparing the varnish, a divalent or higher metal alkoxy compound may be added as a gelling agent to the dissolved varnish obtained by dissolving the resin, and the varnish may be used in a gelled varnish state. Among these, it is preferable to prepare a dissolved varnish from the rosin-modified resin and use it in the preparation of the ink composition, as this improves the transferability of the ink composition during printing. Furthermore, by preparing a gelled varnish from the rosin-modified resin and using it in the preparation of the ink composition, appropriate viscoelasticity is imparted to the ink composition, improving fluidity and reducing misting, as well as forming a tougher cured film.

[0040] The content of rosin-modified resin in the ink composition is preferably 3 to 50% by mass of the total composition, more preferably 4 to 25% by mass of the total composition, and even more preferably 5 to 20% by mass of the total composition.

[0041] The ink composition of the present invention may contain other resins in addition to the rosin-modified resin described above. Such resins are not particularly limited to those previously used in the preparation of ink compositions for metal printing, and examples include alkyd resins, polyester resins, petroleum resins, epoxy resins, ketone resins, amino resins, benzoguanamine resins, and the like. These resins may be used individually in combination with the rosin-modified resin, or two or more may be used in combination with the rosin-modified resin. Among these resins, it is preferable to use alkyd resin in combination with the rosin-modified resin. Next, alkyd resins will be described.

[0042] Alkyd resins are condensation polymers of polyhydric alcohols and monohydric and / or polyhydric carboxylic acids, and are a type of polyester. However, they can also be prepared by condensation polymerization with animal and vegetable oils and / or their fatty acids. In this case, the animal and vegetable oils are transesterified with the polyhydric alcohols to form fatty acids, which are then incorporated into the structure of the alkyd resin. The proportion of fatty acids derived from animal and vegetable oils in the alkyd resin is called the fatty acid modification amount (i.e., oil length), and in the present invention, a fatty acid modification amount of 46% by mass or more is preferred for the alkyd resin. A fatty acid modification amount of 46% by mass or more in the alkyd resin is preferable because it improves the high-speed transfer properties of the ink composition during printing. Note that oil-free alkyd resins that do not contain fatty acid components from animal and vegetable oils may also be used.

[0043] The alkyd resin used in the ink composition of the present invention is preferably one having a neopentyl glycol skeleton and a pentaerythritol skeleton in its molecule. Using an alkyd resin with such a skeleton is preferable because it can improve the impact resistance of the printed film after retort treatment. Such an alkyd resin is prepared using neopentyl glycol and pentaerythritol as polyhydric alcohols. In this case, other polyhydric alcohols may also be used in addition to neopentyl glycol and pentaerythritol.

[0044] Alkyd resins having a neopentyl glycol skeleton and a pentaerythritol skeleton in their molecules can be obtained, for example, as a condensed polymer of an acid component consisting of a fatty acid and / or a polycarboxylic acid (i.e., monovalent and / or polycarboxylic acid) and a polyhydric alcohol containing at least neopentyl glycol and pentaerythritol. Next, a method for preparing such alkyd resins will be described.

[0045] Fatty acids are obtained by hydrolyzing natural oils and fats such as vegetable oils and animal oils, and since they have one carboxyl group, they can form esters with polyhydric alcohols, as described later. In other words, fatty acids are monocarboxylic acids. By introducing such fatty acids into alkyd resins, the transferability of ink compositions using them can be improved, and the proportion of biomass-derived components can be increased. From this viewpoint, it is preferable to use an amount of fatty acid such that the fatty acid modification amount, which is the ratio of the mass of the fatty acid portion to the total mass of the resin (mass%), is 46.0% by mass or more. Furthermore, by setting this fatty acid modification amount to 46.0% by mass or more, it is possible to obtain the further effect of improving the impact resistance of the printed film after retort treatment. As a fatty acid, coconut oil fatty acid is preferred. Coconut oil fatty acid is rich in lauric acid, and this lauric acid provides a desirable effect. From this viewpoint, it is preferable that lauric acid is included in 30% by mass or more of the total amount of monohydric and / or polycarboxylic acids when preparing the alkyd resin. Various types of fatty acids can be used, and these can be used individually or in combination of two or more types.

[0046] Polycarboxylic acids are compounds having multiple carboxyl groups and are components used for condensation polymerization with polyhydric alcohols, which will be described later, to increase their molecular weight. Examples of such polycarboxylic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, trimellitic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexendicarboxylic acid, 1,4-cyclohexendicarboxylic acid, hexahydrophthalic anhydride, 5-sodiosulfoisophthalic acid, fumaric acid, benzoic acid, tert-butylbenzoic acid, tetrahydrophthalic anhydride, maleic anhydride, succinic acid, succinic anhydride, sebacic acid, azelaic acid, tetrabromophthalic anhydride, methylhymic anhydride, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, trimellitic anhydride, and methylcyclohexendicarboxylic acid anhydride. Among these, isophthalic acid, phthalic acid, phthalic anhydride, trimellitic acid, etc., are preferred, with isophthalic acid being more preferred. These polycarboxylic acids can be used individually or in combination of two or more.

[0047] Polyhydric alcohols form esters with the above-mentioned acidic components (i.e., monohydric and / or polyhydric carboxylic acids), thereby increasing the molecular weight of these components. Polyhydric alcohols can be any compound that has been used in the synthesis of alkyd resins, and examples include compounds having two or more hydroxyl groups.

[0048] Examples of such compounds include, in addition to the aforementioned pentaerythritol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, 1,3-butanediol, neopentyl glycol, spiroglycol, dioxane glycol, adamantanediol, 3-methyl-1,5-pentanediol, methyloctanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 2-methylpropane-1,3-diol, and 1,7-hepta Examples include diols, 1,8-octanediol, 1,9-nonanediol, 2,4-diethyl-1,5-pentanediol, ethylene oxide-modified compounds of difunctional phenols such as bisphenol A, propylene oxide-modified compounds of difunctional phenols such as bisphenol A, ethylene oxide-propylene oxide copolymer-modified compounds of bisphenol A, copolymer polyether polyols of ethylene oxide and propylene oxide, polycarbonate diols, adamantanediol, polyether diols, polyester diols, and polycaprolactone diols. These can be used individually or in combination of two or more.

[0049] To prepare alkyd resins, one method involves charging these acidic components and polyhydric alcohols into a reaction vessel, introducing an inert gas such as nitrogen gas, adding a small amount of solvent such as xylene, and heating the mixture. This allows for condensation polymerization while removing the water through azeotropic reaction with the condensed water. Alternatively, by using the condensation polymerization reaction of these acidic components and polyhydric alcohols as the first step, and then performing condensation polymerization in the second step using a polycarboxylic acid with three or more functions, such as trimellitic acid, an alkyd resin with a high degree of crosslinking and a tough cured film can be obtained. The reaction temperature can be around 170 to 250°C, and the reaction time can be around 5 to 25 hours, but is not particularly limited. The end of the reaction can be determined by monitoring the acid value of the reaction mixture as the reaction time progresses. That is, the reaction should be considered complete when the decrease in the acid value of the reaction mixture due to condensation polymerization stops. The condensation polymerization reaction can be carried out in a shorter time by distilling off the water produced by condensation polymerization or by using a reaction catalyst. Examples of reaction catalysts include tetrabutylzirconate, monobutyltin oxide, zirconium naphthate, and tetrabutyl titanate.

[0050] Furthermore, regarding the ratio of the acid component to the polyhydric alcohol used in the preparation of the alkyd resin, it is preferable to determine the equivalent ratio (OH / COOH ratio) of the polyhydric alcohol to the monohydric and / or polyhydric carboxylic acid, which is the acid component, so that it is 1.10 to 1.31. That is, the acid component, which is the monohydric and / or polyhydric carboxylic acid, may consist of multiple types of carboxylic acids with different numbers of carboxyl groups in their molecules, and the polyhydric alcohol may also consist of multiple types of polyhydric alcohols with different numbers of hydroxyl groups in their molecules. However, it is preferable that the total amount of hydroxyl groups in the polyhydric alcohol be 1.10 to 1.31 times the total amount of carboxyl groups in the acid component, more preferably 1.15 to 1.31 times, and even more preferably 1.20 to 1.31 times. By setting the equivalent ratio within this range, it is possible to improve the impact resistance of the printed film after retort treatment, and it is also preferable because it is possible to suppress undesirable gelation when preparing the alkyd resin.

[0051] Furthermore, the acid value of the alkyd resin is preferably 4.0 to 8.9 mg KOH / g, and more preferably 4.0 to 8.0 mg KOH / g. Setting the acid value of the alkyd resin within this range is preferable because it allows for good impact resistance of the printed film after retort treatment. To adjust the acid value of the alkyd resin, the change in the acid value of the reactants should be monitored during the condensation polymerization, and the condensation polymerization reaction should be terminated when the acid value of the reactants reaches the target acid value.

[0052] The weight-average molecular weight of the alkyd resin is not particularly limited, but it is preferably 3,000 or more and less than 20,000, and preferably 5,000 or more and less than 15,000. Among these, a weight-average molecular weight of less than 15,000 for the alkyd resin is preferred because it allows for a viscosity suitable for printing when used as an ink composition.

[0053] The content of alkyd resin in the ink composition is preferably 10 to 40% by mass relative to the total composition, and more preferably 20 to 40% by mass relative to the total composition.

[0054] [Solvent] The solvent used in the ink composition of the present invention can be any solvent that has been used in the field of metal printing inks, without any particular limitations. Examples of such solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, alkylbenzenes, polyalkylene glycols, and polyalkylene glycol alkyl ethers, all with a boiling point range of about 230 to 400°C. Among these, at least one selected from the group consisting of compounds represented by the following general formula (1) can be preferably used. Furthermore, the solubility parameter (sp value) of the solvent is 10.00 (cal / cm³). ３ ) １／２ Preferably, the solubility parameter (sp value) is less than 10.00 (cal / cm³). ３ ) １／２less than, and at least one solvent selected from the group consisting of compounds represented by the following general formula (1) is also referred to as a specific solvent. The sp value of the specific solvent is 9.80 (cal / cm ３ ) １／２ or less, which is cited as a more preferable example. Further, the lower limit of the sp value of the specific solvent is preferably 8.50 (cal / cm ３ ) １／２ or so, more preferably 9.00 (cal / cm ３ ) １／２ or so. The specific solvent having such an sp value can also be regarded as a polyalkylene glycol or polyalkylene glycol monoalkyl ether having hydrophobic properties.

[0055]

[0056] In the above general formula (1, each A is independently an optionally branched alkylene group having 2 to 4 carbon atoms. Examples of such an alkylene group include an ethylene group [-(CH ２ ) ２ -], a propylene group [-CH ２ (CH ３ )-CH ２ -, or -CH ２ CH ２ (CH ３ )-], a trimethylene group [-(CH ２ ) ３ -], an isopropylidene group [-C(CH ３ ) ２ -] and the like. Among these, a propylene group is preferably cited. In this case, the divalent group represented by AO in the general formula (1) is an oxypropylene group.

[0057] In the above general formula (1), R is a hydrogen atom or a C1-C13 alkyl group which may have a branched and / or cyclic structure. This alkyl group may be an aliphatic group or an alicyclic group. Examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, 2-ethylhexyl, octyl, decyl, and cyclohexyl groups. When R is an alkyl group, the compound represented by general formula (1) becomes a polyalkylene glycol monoalkyl ether, and when R is a hydrogen atom, the compound represented by general formula (1) becomes a polyalkylene glycol.

[0058] In the above general formula (1), n ​​is an integer between 2 and 25. When n is 2 or greater, it is preferable to ensure a sufficient boiling point for the specific solvent to provide stability to the ink composition on the printing press, and when n is 25 or less, a suitable viscosity for the solvent in the ink composition can be achieved.

[0059] Examples of compounds represented by the above general formula (1) include dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monooctyl ether, dipropylene glycol tridecyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monodecyl ether, tetrapropylene glycol monohexyl ether, pentapropylene glycol monobutyl ether, hexapropylene glycol monomethyl ether, polypropylene glycol monobutyl ether, and polypropylene glycol.

[0060] In the present invention, the sp value used is that calculated by the Fedros method (see reference: R.F. Fedros, Polym. Eng. Sci., 14(2) 147 (1974)).

[0061] The solvent content in the ink composition of the present invention is preferably 10 to 50% by mass of the total composition, and more preferably 20 to 45% by mass of the total composition. Furthermore, it is preferable that the content of a specific solvent within the solvent is 15 to 40% by mass of the total composition, and preferably that all of the solvent in the composition is the specific solvent. The inclusion of such a specific solvent in the ink composition of the present invention is preferable because it reduces misting during printing.

[0062] [Bentonite] The ink composition of the present invention contains bentonite. Bentonite is a clay whose main component is montmorillonite, a clay mineral, and various types are commercially available. According to the inventors' studies, adding bentonite to a metal printing ink composition can reduce the occurrence of misting during printing. A commercially available product called benton clay is also made of bentonite and can of course be used in the present invention. Among these bentonites, organically modified bentonite is particularly preferred in the ink composition of the present invention. Organically modified bentonite, also called organic bentonite, is obtained by reacting bentonite with an organic substance such as an anionic polymer or quaternary ammonium salt to modify its surface. Various types of such organically modified bentonite are commercially available, and one example is the CRAYTONE APA series manufactured by BIC Chemie Japan Co., Ltd.

[0063] The bentonite content in the ink composition is 0.1 to 4% by mass relative to the total composition. A content of 0.1% by mass or more effectively suppresses misting and yellowing when used in white inks, while a content of 4% by mass or less suppresses the reduction in gloss and yellowing associated with excessive bentonite addition when used in white inks. Preferably, the bentonite content in the ink composition is 0.4 to 3.6% by mass, and more preferably 1 to 3.0% by mass, relative to the total composition.

[0064] [Coloring Pigments] Coloring pigments are components that impart coloring power to the ink composition. Examples of coloring pigments include organic and / or inorganic pigments that have been conventionally used in printing ink compositions, without any particular limitations. Needless to say, in this invention, white pigments used to give whiteness to the ink composition are also treated as coloring pigments.

[0065] Examples of such coloring pigments include Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 15, 16, 17, 24, 32, 34, 35, 36, 37, 41, 42, 43, 49, 53, 55, 60, 61, 62, 63, 65, 73, 74, 75, 77, 81, 83, 87, 93, 94, 95, 97, 98, 99, 100, 101, 104, 105, 106, 108, 109, 110, 111, 113, 114, 116, 117, 119, 120, 123, 124, 126, 127, 128, 129, 130, 133, 138, 139, 150, 151, 152, 153, 154, 155, 165, 167, 168, 169, 170, 172, 173, 174, 175, 176, 179, 180, 181, 182, 183, 184, 185, 191, 193, 194, 199, 205, 206, 209, 212, 213, 214, 215, 219; Pigment Orange 1, 2, 3, 4, 5, 13, 15, 16, 17, 19, 20, 21, 24, 31, 34, 36, 38, 40, 43, 46, 48, 49, 51, 60, 61, 62, 64, 65, 66, 67, 68, 69, 71 ,72,73,74,81; Pigment Red 1,2,3,4,5,6,7,8,9,10,11,12,14,15,16,17,18,21,22,23,31,32,38,41,48,48:1,48:2,48:3,48:4,48:5,49,52,52:1,52:2,53:1,54,57:1,58,60:1,63,64:1,68,81:1,83,88,89,95,101,104,105,108,112,114,119,122,123,136,144,146,147,149,150,164,166,1 68, 169, 170, 171, 172, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 187, 188, 190, 193, 194, 200, 202, 206, 207, 208, 209, 210, 211, 213, 214, 216, 220, 220, 221, 224, 226, 237, 238, 239, 242, 245, 247, 248, 251, 253, 254, 255, 256, 257, 258, 260, 262, 263, 264, 266, 268, 269, 270, 271, 272, 279;Pigment Violet 1, 2, 3, 3:1, 3:3, 5:1, 13, 15, 16, 17, 19, 23, 25, 27, 29, 31, 32, 36, 37, 38, 42, 50; Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 15:6, 16, 17:1, 24, 24:1, 25, 26, 27, 28, 29, 36, 56, 60, 61, 62, 63, 75, 79, 80; Pigment Examples of pigments include: Green 1, 4, 7, 8, 10, 15, 17, 26, 36, 50; Pigment Brown 5, 6, 23, 24, 25, 32, 41, 42; Pigment Black 1, 6, 7, 9, 10, 11, 20, 26, 28, 31, 32, 34; Pigment White 1, 2, 4, 5, 6, 7, 11, 12, 18, 19, 21, 22, 23, 26, 27, 28, etc., as well as glass flakes, pearl pigments, hollow particles, etc. Of the above, glass flakes, pearl pigments, and hollow particles may not generally be treated as coloring pigments, but in this invention, pigments that produce some kind of optical effect are also treated as coloring pigments. Among these, from the perspective of color reproducibility, coating strength, and printability, the following are recommended: Pigment Yellow 13, Pigment Yellow 17, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 139, Pigment Yellow 180, Pigment Yellow 185, Pigment Orange 13, Pigment Orange 16, Pigment Orange 43, Pigment Orange 64, Pigment Red 48:1, Pigment Red 48:2, Pigment Red Preferred pigments include 48:3, Pigment Red 48:4, Pigment Red 53:1, Pigment Red 122, Pigment Red 166, Pigment Red 185, Pigment Red 254, Pigment Red 264, Pigment Violet 23, Pigment Violet 32, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:6, Pigment Green 7, Pigment Black 7, Pigment White 6, etc. Furthermore, in this invention, metal powder pigments used to impart metallic colors such as gold and silver to the ink composition are also treated as coloring pigments. Examples of such metal powder pigments include aluminum flakes, gold powder, bronze powder, and aluminum paste obtained by processing aluminum powder into a paste.

[0066] Of the above-mentioned coloring pigments, pigment blacks 6 and 7 correspond to carbon black. In the ink composition of the present invention, the inclusion of a rosin-modified resin with a softening point of 105°C or higher enhances transferability during printing and impact resistance after retort processing, and this effect is particularly pronounced when carbon black is used as the coloring pigment. From this viewpoint, carbon black can be preferred as the coloring pigment used in the present invention, and acidic carbon black is more preferred among them.

[0067] The amount of coloring pigment added is typically 5 to 50% by mass of the total ink composition, but is not particularly limited. When preparing a yellow ink composition using yellow pigment, a magenta ink composition using magenta pigment, a cyan ink composition using cyan pigment, or a black ink composition using black pigment, it is also possible to use other colored pigments or add other colored ink compositions as complementary colors.

[0068] [Other Components] The ink composition of the present invention may optionally contain other components such as alkanolamines, known curing agents, pigment dispersants, waxes, silica particles, stabilizers, etc.

[0069] By using alkanolamines, the occurrence of misting during printing can be reduced. Examples of alkanolamines include triethanolamine, dibutylethanolamine, methyldiethanolamine, methylethanolamine, and ethyldiethanolamine. When using alkanolamines, their content in the total ink composition is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and even more preferably 0.1 to 1.5% by mass.

[0070] For example, amino resins such as melamine resin and benzoguanamine resin can be used as curing agents.

[0071] Silica particles are SiO ２These are commercially available as powders, and are readily available in various forms, including those that are untreated, hydrophilic (after hydrophilic treatment), or hydrophobic (after hydrophobic treatment). Among these silica particles, hydrophobic silica is particularly preferred in the present invention. The silica particle content in the ink composition is preferably 1 to 8% by mass, and more preferably 2 to 5% by mass.

[0072] The ink composition of the present invention is prepared by mixing the above-mentioned components and using a conventional method with a roll mill, ball mill, bead mill, etc. The viscosity of the ink composition is exemplified by a value of 10 to 70 Pa·s at 25°C measured with a Raleigh viscometer, but is not particularly limited.

[0073] The metal to be printed using the ink composition of the present invention is not particularly limited, but examples include galvanized or tinned iron sheets, aluminum sheets, or metal cans made from these metal materials.

[0074] The ink compositions of the present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0075] [Preparation of Alkyd Resin Varnish 1] 7.5 parts by mass of neopentyl glycol, 7.5 parts by mass of pentaerythritol, 16.2 parts by mass of coconut oil fatty acid, and 16 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 20 mg KOH / g, thereby esterifying to obtain alkyd resin 1. 22.0 parts by mass of polyoxypropylene monobutyl ether was added to this alkyd resin 1 to obtain alkyd resin varnish 1. The fatty acid modification amount of alkyd resin 1 was 38% by mass, and the weight-average molecular weight was 9,330. The number of moles of PO (oxypropylene) groups added to the above polyoxypropylene monobutyl ether (i.e., the value of n in the above general formula (1)) was 5 to 6. The sp value of the above polyoxypropylene monobutyl ether by the Fedros method was 9.42 (cal / cm³). ３ ) １／２Therefore, the number of polyhydric alcohols relative to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 1 was 1.33.

[0076] [Preparation of Alkyd Resin Varnish 2] 7.5 parts by mass of neopentyl glycol, 7.5 parts by mass of pentaerythritol, 16.2 parts by mass of coconut oil fatty acid, 14.0 parts by mass of isophthalic acid, and 2.0 parts by mass of trimellitic anhydride were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 20 mg KOH / g, thereby esterifying to obtain alkyd resin 2. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 2 to obtain alkyd resin varnish 2. The fatty acid modification amount of alkyd resin 2 was 38% by mass, and the weight-average molecular weight was 11,665. In addition, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 2 was 1.33.

[0077] [Preparation of Alkyd Resin Varnish 3] 6.70 parts by mass of neopentyl glycol, 8.07 parts by mass of pentaerythritol, 22.50 parts by mass of coconut oil fatty acid, and 15.05 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 7.5 mg KOH / g, thereby esterifying to obtain alkyd resin 3. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 3 to obtain alkyd resin varnish 3. The fatty acid modification amount of alkyd resin 3 was 47.5% by mass, and the weight-average molecular weight was 12,589. Furthermore, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) during the preparation of alkyd resin 3 was 1.29.

[0078] [Preparation of Alkyd Resin Varnish 4] 6.70 parts by mass of neopentyl glycol, 8.07 parts by mass of pentaerythritol, 24.30 parts by mass of coconut oil fatty acid, and 14.37 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 7.5 mg KOH / g, thereby esterifying to obtain alkyd resin 4. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 4 to obtain alkyd resin varnish 4. The fatty acid modification amount of alkyd resin 4 was 50.0% by mass, and the weight-average molecular weight was 6,793. In addition, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 4 was 1.29.

[0079] [Preparation of Alkyd Resin Varnish 5] 6.70 parts by mass of neopentyl glycol, 8.07 parts by mass of pentaerythritol, 22.95 parts by mass of coconut oil fatty acid, and 15.63 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 7.5 mg KOH / g, thereby esterifying to obtain alkyd resin 5. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 5 to obtain alkyd resin varnish 5. The fatty acid modification amount of alkyd resin 5 was 47.5% by mass, and the weight-average molecular weight was 14,378. In addition, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 5 was 1.25.

[0080] [Preparation of Alkyd Resin Varnish 6] 6.70 parts by mass of neopentyl glycol, 8.07 parts by mass of pentaerythritol, 24.70 parts by mass of coconut oil fatty acid, and 14.97 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 7.5 mg KOH / g, thereby esterifying to obtain alkyd resin 6. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 6 to obtain alkyd resin varnish 6. The fatty acid modification amount of alkyd resin 6 was 50.0% by mass, and the weight-average molecular weight was 12,044. In addition, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 6 was 1.25.

[0081] [Preparation of Alkyd Resin Varnish 7] 6.70 parts by mass of neopentyl glycol, 8.07 parts by mass of pentaerythritol, 25.30 parts by mass of coconut oil fatty acid, and 15.76 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere according to a conventional method until the acid value of the mixture reached 7.5 mg KOH / g, thereby esterifying to obtain alkyd resin 7. 21.8 parts by mass of the above polyoxypropylene monobutyl ether were added to this alkyd resin 7 to obtain alkyd resin varnish 7. The fatty acid modification amount of alkyd resin 7 was 50.0% by mass, and the weight-average molecular weight was 17,339. In addition, the equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) when preparing alkyd resin 7 was 1.20.

[0082] [Preparation of Rosin-Modified Resin Varnish 1] Parts by mass of rosin ester resin (softening point 120-130°C, weight-average molecular weight 1,152, acid value less than 10 mgKOH / g) and 35.9 parts by mass of the above polyoxypropylene monobutyl ether were heated at 130°C for 1 hour to dissolve them and obtain rosin-modified resin varnish 1.

[0083] [Preparation of Rosin-Modified Resin Varnish 2] A polymerized rosin ester resin (softening point 130-140°C, weight-average molecular weight 1,486, acid value less than 10 mg KOH / g) was varnished using the same procedure as for the preparation of Rosin-Modified Resin Varnish 1 to obtain Rosin-Modified Resin Varnish 2.

[0084] [Preparation of Rosin-Modified Resin Varnish 3] A polymerized rosin ester resin (softening point of 165°C or higher, weight-average molecular weight of 1,870, acid value of 10-25 mgKOH / g) was varnished using the same procedure as for the preparation of Rosin-Modified Resin Varnish 1 to obtain Rosin-Modified Resin Varnish 3.

[0085] [Preparation of Rosin-Modified Resin Varnish 4] Rosin ester resin (softening point 94-104°C, weight-average molecular weight 744, acid value 10-20 mgKOH / g) was varnished using the same procedure as for the preparation of Rosin-Modified Resin Varnish 1 above to obtain Rosin-Modified Resin Varnish 4.

[0086] [Preparation of Ink Compositions] The ink compositions of the examples and comparative examples were prepared according to the formulations listed in Tables 1 to 3. The numerical values ​​for each formulation listed in Tables 1 to 3 are in parts by mass. When preparing the ink compositions, each component was mixed and then kneaded in a roll mill heated to 40°C. When evaluating the ink compositions of the examples and comparative examples, the above polyoxypropylene monobutyl ether was added so that the viscosity at 25°C was 20,000 to 30,000 mPa·s. In Tables 1-3, "carbon black" refers to acidic carbon black with an average primary particle size of 24 nm and a DBP oil absorption of 53-63 mL / 100 g; "bentonite" refers to CLAYTONE APA (Benton Clay), a product manufactured by BIC Chemie Japan Co., Ltd.; "silica" refers to surface-hydrophobic silica particles (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.); "solvent" refers to the polyoxypropylene monobutyl ether described above; the value in the "acid value" column is the acid value of the alkyd resin contained in the alkyd resin varnish used to prepare the ink; the value in the "fatty acid modification amount" column is the amount of fatty acid modification in the alkyd resin contained in the alkyd resin varnish used to prepare the ink; and the value in the "equivalent ratio" column is the number of equivalents (OH / COOH ratio) of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids when preparing the alkyd resin contained in the alkyd resin varnish used to prepare the ink.

[0087] [Evaluation of High-Speed ​​Transfer Properties] For each of the ink compositions in the examples and comparative examples, 0.1 cc of the ink composition was spread on a 50 μm thick aluminum substrate using a high-speed color spreader "PM-900PT" (manufactured by Mitsui Electric Seiki Co., Ltd.) at a printing pressure of 90 kgf and a spreading speed of 9 m / s. The obtained spreads were evaluated according to the following criteria. The evaluation results are shown in the "High-Speed ​​Transfer Properties" column of Tables 1 to 3. ○: No streaking observed at all △: Streaking observed in less than 50% of the transfer area ×: Streaking observed in 50% or more of the transfer area, indicating poor quality

[0088] [Evaluation of Misting Amount] For each example and comparative example ink composition, 2.6 cc of the ink composition was taken and applied to the rotating roller of an Incomometer, leveled evenly, and then rotated at 1200 rpm for 3 minutes. During this time, a blank sheet of paper was placed under the roller, and the amount of ink composition adhering to its surface due to misting was compared. The measurement was performed while keeping the roller at 40°C. The change in mass of the blank sheet of paper before and after measurement was determined and defined as the misting amount (mg). A larger change in the mass of the blank sheet of paper before and after measurement indicates a greater amount of ink composition scattering, so a smaller value indicates a better result. Based on the calculated misting amount (mg), the following criteria were used for evaluation. The evaluation results are shown in the "Misting" column of Tables 1 to 3. ○: Misting amount was less than 7 mg △: Misting amount was 7 mg or more and less than 13 mg ×: Misting amount was 13 mg or more

[0089] [Evaluation of impact resistance after retort treatment] For each example and comparative example, 0.2 cc of the ink composition was spread onto a 50 μm thick aluminum substrate using an RI color spreader to obtain a colored product. Then, a retort overprint varnish (manufactured by AkzoNobel) was applied to the colored surface of the colored product using a No. 0.4 bar coater (Meyer bar), and the product was held in an oven at 240°C for 2 minutes to obtain a retort sample. Subsequently, the retort sample was retorted using an autoclave (high-pressure steam sterilizer, HG-50 manufactured by Hirayama Seisakusho Co., Ltd.) at 125°C for 30 minutes to obtain a retort-treated product. The retort-treated samples were subjected to impact at four locations on the opposite side of the colored surface using a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name H-50), under the conditions of impact core diameter: 1 / 4Φ (6.35 mm), weight: 300 g, and weight drop height: 50 mm. The degree of peeling of the coating on the colored surface was evaluated according to the following criteria. The results are shown in the "Impact Resistance after Retorting" column of Tables 1-3. ◎: In all four locations, the coating did not peel off at the points of contact with the impact core. Subsequently, scratching the areas that had contact with the impact core did not cause damage. ○: In all four locations, the coating did not peel off at the points of contact with the impact core, but subsequent scratching of the areas that had contact with the impact core caused damage. ×: In one or more of the four locations, at least a portion of the coating peeled off at the points of contact with the impact core, exposing the aluminum substrate.

[0090]

[0091]

[0092]

[0093] As is clear from Tables 1 to 3, it can be seen that by combining a rosin-modified resin with a softening point of 105°C or higher and bentonite to create a metal printing ink composition, good ink transferability during printing, impact resistance after retorting, and misting amount are all achieved. On the other hand, in Comparative Example 1, which used a rosin-modified resin with a softening point of less than 105°C, the impact resistance after retorting was unusable for practical purposes, in Comparative Example 3, which did not contain bentonite, a large amount of misting occurred, and in Comparative Example 2, which did not contain a rosin-modified resin, the impact resistance after retorting was unusable for practical purposes, and the rapid transfer properties were also poor.

[0094] Furthermore, the ink compositions of Examples 9 to 13, which included an alkyd resin prepared with an acid value of 4.0 to 8.9 mg KOH / g, a fatty acid modification amount of 46.0% by mass or more, and an equivalent number of polyhydric alcohols to monohydric and / or polyhydric carboxylic acids (OH / COOH ratio) of 1.10 to 1.31, tended to show even better impact resistance after retorting compared to the ink compositions of Examples 1 to 8, which used alkyd resins that did not meet these conditions.

Claims

1. A metal printing ink composition comprising a coloring pigment, a resin, bentonite, and a solvent, characterized in that at least a portion of the resin contains a rosin-modified resin having a softening point of 105°C or higher.

2. The metal printing ink composition according to claim 1, wherein the weight-average molecular weight of the rosin-modified resin is 1,000 or more.

3. The metal printing ink composition according to claim 1 or 2, further characterized by containing silica.

4. The metal printing ink composition according to claim 3, wherein the silica is hydrophobic treated silica.

5. The metal printing ink composition according to any one of claims 1 to 4, wherein the bentonite is organically modified bentonite.

6. The metal printing ink composition according to any one of claims 1 to 5, wherein the coloring pigment is carbon black.

7. The metal printing ink composition according to claim 6, wherein the carbon black is acidic carbon black.

8. The metal printing ink composition according to any one of claims 1 to 7, characterized in that the solvent comprises at least one selected from the group consisting of compounds represented by the following general formula (1). (In the above general formula (1), each A is independently a C2-C4 alkylene group which may have branching, R is a hydrogen atom or a C1-C13 alkyl group which may have branching and / or cyclic structures, and n is an integer from 2 to 25.) 9. The solubility parameter (sp value) of the solvent is 10.00 (cal / cm³). ３ ) １／２ The metal printing ink composition according to claim 8, wherein the amount is less than [amount missing].

10. The metal printing ink composition according to any one of claims 1 to 9, further comprising an alkyd resin as the resin.

11. The metal printing ink composition according to 10, characterized in that the alkyd resin satisfies the following conditions (A) to (C): (A) It is a condensed polymer of a polyhydric alcohol and a monohydric and / or polyhydric carboxylic acid, and the equivalent number of the polyhydric alcohol to the carboxylic acid (OH / COOH ratio) is 1.10 to 1.31; (B) The acid value is 4.0 to 8.9 mgKOH / g; (C) The fatty acid modification amount is 46.0% by mass or more.

12. The metal printing ink composition according to claim 10 or 11, wherein the weight-average molecular weight of the alkyd resin is less than 15,000.

13. The metal printing ink composition according to any one of claims 10 to 12, wherein the alkyd resin comprises a neopentyl glycol skeleton and a pentaerythritol skeleton.

14. The metal printing ink composition according to claim 11, comprising isophthalic acid as the carboxylic acid.

15. The metal printing ink composition according to claim 11 or 14, wherein the carboxylic acid comprises lauric acid, and the lauric acid-derived skeleton portion in the alkyd resin is 30% by mass or more.

16. The metal printing ink composition according to any one of claims 10 to 15, wherein the acid value of the alkyd resin is 4.0 to 8.0 mg KOH / g.

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