Ink composition for metal printing

Abstract

The technical problem of the present invention is to provide an ink composition for metal printing, which does not extremely increase the oil degree of an alkyd resin and can obtain good transferability during printing. The technical problem is solved by using an ink composition for metal printing comprising a coloring pigment, a resin, and a solvent, the ink composition for metal printing comprising, as at least a part of the resin, a rosin-modified resin having a hydroxyl value of 10 mgKOH / g or more, and at least one compound selected from the group consisting of compounds represented by general formula (1) is contained as the solvent. In general formula (1), each A independently represents an alkylene group having 2-4 carbon atoms and optionally having a branched chain, R represents an alkyl group having 1-13 carbon atoms and optionally having a branched chain and / or a ring structure, and n represents an integer of 2-8.

Description

Technical Field

[0001] This invention relates to ink compositions for metal printing. Background Technology

[0002] In printing on the outer metal surface of metal raw materials, such as galvanized or tin-plated iron sheets, aluminum sheets, or metal cans made from these metal raw materials, a metal printing ink composition is used, with adhesive resins such as alkyd resins, polyester resins, and epoxy resins, and organic solvents such as mineral oils or higher alcohols as the main carrier components.

[0003] In addition, to improve the adhesion, bending resistance, impact resistance, and abrasion resistance of the ink coating, an overprint varnish is usually applied to these printed surfaces. These overprint varnishes are widely used solvent-based, consisting of adhesive resins such as alkyd resins, polyester resins, acrylic resins, and epoxy resins, curing agents such as melamine resins and benzoguanamine resins, and organic solvents such as mineral oils and solvent solvents.

[0004] Furthermore, when printing on the metal outer surface, after printing the ink using offset printing machines, dry offset printing machines, etc., a coating machine is used to apply a clear varnish to the ink film in a wet-on-wet manner, and then it is baked at 150~280℃.

[0005] However, in recent years, due to concerns about air pollution caused by solvents, hygiene in printing environments, and safety, water-based varnishes are generally no longer used in the field of metal printing. However, when water-based varnishes are applied to the ink film of conventional metal printing ink compositions, phenomena such as shrinkage and cracking of the water-based varnish and its penetration into the ink film occur. As a result, the quality of the coating, such as gloss and adhesion, is significantly reduced. Therefore, ink compositions are required to have excellent compatibility with water-based varnishes.

[0006] As methods to improve the adaptability of ink compositions to water-based overprinting varnishes, for example, Patent Document 1 proposes the use of alkylene glycol solvents with 4 to 8 carbon atoms, Patent Document 2 proposes the use of polyoxyalkylene glycol solvents, Patent Document 3 proposes the use of polyoxyalkylene alkyl ether organic solvents, and Patent Document 4 proposes the use of polyoxyalkylene alkyl ester solvents. While the organic solvents used in these ink compositions are effective in improving the adaptability of the ink compositions to water-based overprinting varnishes, there is room for improvement in aspects such as insufficient flowability of the ink compositions or splattering during printing.

[0007] In cases where it is desired to improve the flowability of ink compositions for metal printing and reduce ink splattering during printing, methods using low-polarity solvents such as high-boiling-point aromatic hydrocarbons are employed, as described in the embodiment of Patent Document 5. However, recently, water-based overprinting varnishes with solvent content reduced to the limit have been circulated with the aim of further reducing environmental impact. When using such overprinting varnishes, ink compositions using low-polarity solvents also suffer from shrinkage and cracking problems.

[0008] Furthermore, in recent years, high-speed printing has been achieved in metal printing to improve productivity. From the perspective of coping with this high-speed printing, the transferability of ink compositions has become important. Moreover, increasing the oil content of the alkyd resin contained in the ink composition is effective from the viewpoint of ensuring the transferability of the ink composition. However, ink compositions containing alkyd resins with high oil content have poor compatibility with water-based varnishes as described above, easily leading to shrinkage and cracking of the water-based varnish on the surface of the printed ink composition. In other words, the trade-off between increasing oil content based on transferability and adaptability to water-based varnish coating has become one of the technical problems.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Publication No. 5-75031

[0012] Patent Document 2: Japanese Patent Publication No. 5-40791

[0013] Patent Document 3: Japanese Patent Publication No. 5-40792

[0014] Patent Document 4: Japanese Patent Application Publication No. 64-60670

[0015] Patent Document 5: Japanese Patent Application Publication No. 2009-249435 Summary of the Invention

[0016] The technical problem solved by the invention

[0017] The present invention was made in view of the following situation, and its object is to provide an ink composition for metal printing that does not excessively increase the oiliness of alkyd resin and can achieve good transferability during printing.

[0018] Technical means to solve the problem

[0019] The inventors conducted repeated and in-depth research to solve the aforementioned technical problem, and as a result, discovered that the technical problem was solved by using an ink composition comprising at least a portion of a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or higher, which is a component of the resin included in the ink composition, and a polyoxyalkylene alkyl ether solvent represented by the following general formula (1), thereby completing the present invention. Specifically, the present invention provides the following contents.

[0020] (1) This invention relates to a metal printing ink composition, which is a metal printing ink composition comprising coloring pigments, resins, and solvents, wherein,

[0021] The metal printing ink composition comprises at least a portion of a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or higher, and comprises at least one compound selected from the following general formula (1) as the solvent.

[0022] [Chemical Formula 1]

[0023] ,

[0024] In the general formula (1), each A is independently an alkylene group with 2 to 4 carbon atoms that has a branched chain, R is an alkyl group with 1 to 13 carbon atoms that has a branched chain and / or ring structure, and n is an integer from 2 to 8.

[0025] (2) Furthermore, the metal printing ink composition of the present invention according to claim (1) further comprises:

[0026] 1-8% by mass of hydrophilic silica particles.

[0027] (3) Furthermore, the present invention relates to the metal printing ink composition according to claim (1) or (2), wherein,

[0028] The acid value of the rosin-modified resin is below 100 mg KOH / g.

[0029] (4) Furthermore, the present invention comprises a metal printing ink composition according to any one of claims (1) to (3), wherein,

[0030] When 70g of the rosin-modified resin was dissolved in 30g of tripropylene glycol monobutyl ether heated to 130°C and stirred for 60 minutes, a varnish with a hexane tolerance exceeding 50g / 5g, as determined by the following steps, was obtained.

[0031] Steps: After the dissolved varnish has cooled to room temperature, collect 5g into a beaker. While maintaining the liquid temperature in the beaker at 25°C, add small amounts of n-hexane to the dissolved varnish in the beaker while stirring. Calculate the mass (g) of n-hexane required until the liquid in the beaker begins to turn cloudy. Set the mass (g) of n-hexane calculated in this way as the n-hexane tolerance (g / 5g).

[0032] (5) Furthermore, the present invention comprises a metal printing ink composition according to any one of claims (1) to (4), wherein,

[0033] The rosin-modified resin is a rosin ester resin.

[0034] Invention Effects

[0035] According to the present invention, a metal printing ink composition can be provided that does not excessively increase the oiliness of alkyd resin and can achieve good transferability during printing. Detailed Implementation

[0036] The following describes one embodiment of the metal printing ink composition of the present invention. It should be noted that the present invention is not limited to the following embodiment, and appropriate modifications can be made within the scope of the present invention.

[0037] The ink composition of the present invention is used for metal printing, preferably in so-called dry offset printing using letterpress as the printing plate and offset printing using planographic as the printing plate, and can be applied to all printing methods commonly used in metal printing. Furthermore, even when a water-based overprint varnish (OP varnish) is applied immediately after printing using the ink composition, shrinkage and cracking of the applied OP varnish can be suppressed. Therefore, it is also preferably used in two-piece can printing using such printing and coating methods, and is also preferably used in three-piece can printing. According to the ink composition of the present invention, good transferability can be maintained, for example, even when the pigment content must be set high, as in white ink compositions. Furthermore, according to the ink composition of the present invention, good transferability during printing can be obtained without drastically increasing the oil content of the alkyd resin. Therefore, even when using a water-based OP varnish with reduced solvent content in a wet-on-wet process, printing that balances shrinkage and cracking suppression with good transferability during printing can be performed.

[0038] The ink composition of the present invention is a metal printing ink composition comprising a coloring pigment, a resin, and a solvent. The metal printing ink composition comprises at least a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or higher as a portion of the resin, and comprises at least one compound selected from the compounds shown in general formula (1) as the solvent. The components are described below.

[0039] [Resin]

[0040] The ink composition of the present invention comprises, as at least a portion, a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or higher. The ink composition of the present invention is achieved by including such a high-hydroxyl-value rosin-modified resin, which improves the transferability of the ink composition during printing. Furthermore, it is believed that by including such a rosin-modified resin in the ink composition of the present invention, the composition itself becomes more polar, resulting in increased affinity for similarly highly polar water-based OP varnishes, thus inhibiting shrinkage and cracking even when applied in a wet-on-wet manner.

[0041] Rosin-modified resins refer to resins prepared using rosin as one of the raw materials. Rosin contains a mixture of resin acids such as abietic acid, longleaf abietic acid, isopyric acid, and L-piperidine. These resin acids contain hydrophilic and chemically active carboxyl groups, some of which possess conjugated double bonds. Therefore, various rosin-modified resins can be prepared by combining polyols and polyacids for condensation polymerization, or by adding phenolic resins as condensates of phenol to the benzene rings contained in the rosin skeleton, or by reacting with maleic anhydride and maleic acid as dienophiles through a Diels-Alder reaction to form maleic acid and maleic anhydride skeletons. Such rosin-modified resins are commercially available and can be obtained and used.

[0042] Examples of rosin-modified resins include rosin ester resins, maleic rosin, fumaric 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 this invention, any rosin-modified resin can be used, but rosin ester resins are preferred.

[0043] The hydroxyl value of the rosin-modified resin is 10 mg KOH / g or more, preferably 15 mg KOH / g or more, and more preferably 20 mg KOH / g or more. Furthermore, there is no particular limitation on the upper limit of the hydroxyl value of the rosin-modified resin; as an example, approximately 200 mg KOH / g can be cited, preferably approximately 150 mg KOH / g, and more preferably approximately 100 mg KOH / g.

[0044] Furthermore, without particular limitation, an acid value of 100 mg KOH / g or less is preferably selected as the acid value of the rosin-modified resin. By setting the acid value of the rosin-modified resin to 100 mg KOH / g or less, printability can be achieved by simultaneously suppressing shrinkage and cracking during wet-on-wet application of water-based OP varnishes, as well as suppressing ink splatter and backing away; therefore, this is preferred. An acid value of 80 mg KOH / g or less is more preferred as the acid value of the rosin-modified resin, and an acid value of 50 mg KOH / g or less is even more preferred.

[0045] Rosin-modified resin is used to form a varnish by being dissolved or dispersed by heating with a solvent described below. Rosin-modified resin can be used as a dissolved varnish dissolved or dispersed in a solvent, or it can be used to form a gelled varnish by adding a divalent or higher metal alkoxy compound as a gelling agent to the dissolved varnish obtained by dissolving the resin during varnish preparation. It is preferred that a dissolved varnish prepared from rosin-modified resin be used in the preparation of ink compositions to improve the transferability of the ink composition during printing. Furthermore, by preparing a gelled varnish from rosin-modified resin and using it in the preparation of ink compositions, a suitable viscoelasticity is imparted to the ink composition, resulting in improved flowability and reduced ink splattering; additionally, a more robust cured coating can be formed.

[0046] The preferred content of rosin-modified resin in the ink composition is 5 to 50% by mass relative to the whole composition, more preferably 5 to 25% by mass relative to the whole composition, and even more preferably 7 to 20% by mass relative to the whole composition.

[0047] The ink composition of the present invention preferably includes an alkyd resin in addition to the rosin-modified resin. Alkyd resin is a condensation polymer of a polyol and a polyacid, and is a type of polyester. Alternatively, it can be prepared by polycondensation with animal and vegetable oils and / or their fatty acids. In this case, the animal and vegetable oils undergo transesterification with the polyol to become 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 oil content. For the alkyd resin used in the present invention, an oil content of 20-50% by mass is preferably given. It should be noted that oil-free alkyd resins, which do not contain fatty acid components derived from animal and vegetable oils, can also be used.

[0048] Various alkyd resins can be used as the alkyd resin in this invention, with coconut oil-modified alkyd resin being preferred. By using a coconut oil-modified alkyd resin as the alkyd resin, the dispersion stability of the ink composition becomes good; furthermore, it is preferred from the perspective of obtaining a good color tone with high transparency.

[0049] As such an alkyd resin, an alkyd resin having a phthalic acid backbone prepared by using orthophthalic acid as a polybasic acid is preferred. By using such an alkyd resin, the transferability of the ink is improved, and furthermore, the whiteness of white ink can be enhanced.

[0050] The content of alkyd resin in the ink composition is preferably 10 to 40% by mass relative to the whole composition, more preferably 10 to 30% by mass relative to the whole composition, and even more preferably 15 to 25% by mass.

[0051] In the ink composition of the present invention, in addition to the rosin-modified resin and alkyd resin, resins conventionally used for preparing ink compositions for metal printing can also be used in combination. That is, depending on the required performance such as printability and coating physical properties, various known resins compatible with the rosin-modified resin and alkyd resin can be used alone or in combination. Examples of such resins include polyester resins, petroleum resins, epoxy resins, ketone resins, amino resins, and benzoguanamine resins.

[0052] [solvent]

[0053] The ink composition of the present invention comprises at least one of the compounds selected from those shown in general formula (1) below as a solvent. Hereinafter, at least one solvent selected from the compounds shown in general formula (1) below will be referred to as a specific solvent.

[0054] [Chemical Formula 2]

[0055] ,

[0056] In the general formula (1), each A is independently determined and is optionally an alkylene group with 2 to 4 carbon atoms having a branched chain. Examples of such alkylene groups include ethylene [-(CH2)2-], propylene [-CH2(CH3)-CH2- or -CH2CH2(CH3)-], trimethylene [-(CH2)3-], isopropylene [-C(CH3)2-], etc.

[0057] In the general formula (1), R is an alkyl group with 1 to 13 carbon atoms, optionally having a branched chain and / or a ring structure. It should be noted that the alkyl group can be either an aliphatic group or an alicyclic group. Examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, 2-ethylhexyl, octyl, decyl, cyclohexyl, etc.

[0058] In the general formula (1), n ​​is an integer from 2 to 8. By making n 2 or more, it is possible to ensure a sufficient boiling point of the specific solvent that imparts stability to the ink composition on the printing press. Therefore, it is preferable to make n 8 or less, so that a viscosity preferred as a solvent for the ink composition can be formed.

[0059] Examples of compounds represented by the 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, and hexapropylene glycol monomethyl ether.

[0060] The content of the specific solvent in the ink composition of the present invention is preferably 5 to 40% by mass relative to the total composition, and more preferably 10% to 30% by mass relative to the total composition. By making the content of the specific solvent 5% or more by mass relative to the total composition, the compatibility of the rosin-modified resin in the ink composition can be improved, and shrinkage cracking can be effectively suppressed when water-based OP varnish is applied in a wet-on-wet manner after printing, which is therefore preferred.

[0061] Here, regarding the rosin-modified resin, it is preferable that when 70g of it is dissolved in 30g of tripropylene glycol monobutyl ether heated to 130°C and stirred for 60 minutes, a varnish with a hexane tolerance exceeding 50g / 5g is obtained. It should be noted that the determination of hexane tolerance, as described below, does not require particularly much effort, and therefore this selection process does not require excessive trial and error. By using a rosin-modified resin that meets these conditions, the compatibility of the rosin-modified resin in the ink composition can be improved, further enhancing the transferability of the ink composition in printing. Furthermore, the tripropylene glycol monobutyl ether refers to an ether of tripropylene glycol and butanol polymerized from 3 molecules of propylene oxide, and is one of the specific solvents used in this invention.

[0062] Next, the method for determining the hexane tolerance of the resin in this invention will be described. First, 70g of rosin-modified resin, the test object, is prepared and dissolved in 30g of tripropylene glycol monobutyl ether heated to 130°C for 60 minutes to prepare a dissolving varnish. After the obtained dissolving varnish is cooled to room temperature, 5g is collected into a beaker. While maintaining the liquid temperature in the beaker at 25°C, hexane is added to the dissolving varnish in the beaker in small amounts while stirring. The mass (g) of hexane required for the liquid in the beaker to begin to turn cloudy is calculated. The calculated mass (g) of hexane is the hexane tolerance (g / 5g). It should be noted that this determination is so sensitive that turbidity begins immediately upon adding only 1 drop of hexane to the solution just before it is about to turn cloudy. Therefore, the measurement error caused by the deviation in the judgment of turbidity due to different testers is not particularly problematic.

[0063] [Coloring Pigment]

[0064] Coloring pigments are components used to impart coloring power to ink compositions. Organic and / or inorganic pigments that have been used in printing ink compositions can be cited as examples of coloring pigments without particular limitation.

[0065] Examples of such coloring pigments include yellow pigments such as diazo yellow (pigment yellow 12, pigment yellow 13, pigment yellow 17, pigment yellow 1) and Hansa yellow; magenta pigments such as Brilliant Carmine 6B, Lake Red C, and Watchung Red; cyan pigments such as phthalocyanine blue, phthalocyanine green, and basic blue; black pigments such as carbon black; white pigments such as titanium dioxide; and fluorescent pigments. Furthermore, metallic powder pigments used to impart metallic colors such as gold and silver to ink compositions are also treated as coloring pigments in this invention. Examples of such metallic powder pigments include gold powder, bronze powder, aluminum paste made from aluminum powder, and mica powder.

[0066] The amount of coloring pigment added can be, for example, about 5 to 50% by mass relative to the total ink composition, without particular limitation. It should be noted that 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, other colors of pigment may be used in combination as complementary colors, or other colors of ink compositions may be added.

[0067] [Other ingredients]

[0068] In the ink composition of the present invention, other components may include known curing agents, pigment dispersants, solvents other than the specific solvent, waxes, silica particles, stabilizers, etc., as needed.

[0069] As a curing agent, amino resins such as melamine resin and benzoguanamine resin can be used.

[0070] Other solvents besides the specific solvent mentioned above include, for example, aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons such as alkylbenzenes, and higher alcohols with boiling points in the range of about 230 to 400°C.

[0071] Silica particles are commercially available in the form of SiO2 powder. In particular, hydrophilic silica particles (untreated or hydrophilized) and hydrophobic silica particles (hydrophobicated) are readily available. Among these silica particles, hydrophilic silica particles are preferred in the ink composition of the present invention. Using hydrophilic silica particles improves the transferability of the ink composition during printing and enhances the flowability of the ink composition, thus making it preferable. The preferred content of silica particles in the ink composition is 1 to 8% by mass, and more preferably 2 to 5% by mass.

[0072] The ink composition of the present invention can be prepared by mixing various components such as coloring pigments, resins, and solvents containing specific solvents, and using conventional methods such as roller mills, ball mills, and bead mills. As for the viscosity of the ink composition, an example value obtained using a Larrey viscometer at 25°C is 10 to 70 Pa·s, but there is no particular limitation.

[0073] The metal used for printing in the ink composition of the present invention is not particularly limited, and examples include galvanized or tin-plated iron plates, aluminum plates, or metal cans formed from these metal raw materials.

[0074] In addition, as a water-based OP varnish applied to the ink composition after printing, a commonly used water-based OP varnish can be used. Specifically, examples include water-based OP varnishes that use water-based acrylic resins, water-based polyester resins, water-based alkyd resins, water-based epoxy resins, or two or more of their modified resins as binders, and combine them with amino resins as curing agents.

[0075] When printing on the surface of a metal raw material using an ink composition and a water-based OP varnish, firstly, the ink composition of the present invention is used to print using a dry offset printing press, offset printing press, or the like. While the ink composition is not dry (wet-on-wet), an outer coating of water-based OP varnish is applied using a coating machine or the like. Then, it is baked at 150~280°C for several seconds to several minutes.

[0076] Example

[0077] The ink compositions of the present invention will be described in more detail below by way of examples, but the present invention is not limited to any of the examples below.

[0078] [Synthesis of alkyd resins]

[0079] A first-stage esterification was performed by reacting 5.98 parts by weight of neopentyl glycol, 8.53 parts by weight of pentaerythritol, 10.10 parts by weight of coconut oil fatty acids, 11.95 parts by weight of isophthalic acid, and 2.48 parts by weight of terephthalic acid at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mg KOH / g. Then, 0.70 parts by weight of trimellitic anhydride was added, and the mixture was heated at 165°C for 30 minutes under a nitrogen atmosphere for a second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain an alkyd resin with a weight-average molecular weight of 15303 and a number-average molecular weight of 1484. An alkyd resin varnish was prepared by adding 21.8 parts by weight of tripropylene glycol monobutyl ether (which is equivalent to the specific solvent mentioned above) and 2.0 parts by weight of triethanolamine to this alkyd resin.

[0080] [Preparation of Varnish 1]

[0081] 61.6 parts by weight of rosin ester resin (hydroxyl value 40-50 mgKOH / g, acid value 10-20 mgKOH / g, weight average molecular weight 744, number average molecular weight 701) and 35.9 parts by weight of tripropylene glycol monobutyl ether were heated at 130°C for 1 hour to dissolve them. Then, 2.5 parts by weight of ethyl aluminum diisopropyl acetoacetate were added, and the mixture was heated at 130°C for 30 minutes to obtain varnish 1. Varnish 1 is a gelled varnish containing rosin ester resin (hydroxyl value 40-50 mgKOH / g). It should be noted that the hexane tolerance of the rosin ester resin used in the preparation of varnish 1 was determined according to the steps given in this invention, and the result was 50. <g / 5g。

[0082] [Preparation of Varnish 2]

[0083] 63.2 parts by weight of rosin ester resin (hydroxyl value 20-30 mgKOH / g, acid value <10 mgKOH / g, weight average molecular weight 632, number average molecular weight 565) and 36.8 parts by weight of tripropylene glycol monobutyl ether were heated at 130°C for 1 hour to dissolve them, yielding varnish 2. Varnish 2 is a dissolved varnish containing rosin ester resin (hydroxyl value 20-30 mgKOH / g). It should be noted that the hexane tolerance of the rosin ester resin used in the preparation of varnish 2 was determined according to the steps given in this invention, and the result was 50. <g / 5g。

[0084] [Preparation of Varnish 3]

[0085] 61.4 parts by weight of the same rosin ester resin (hydroxyl value 20~30 mgKOH / g, acid value <10 mgKOH / g, weight average molecular weight 632, number average molecular weight 565) used in the preparation of varnish 2 and 35.7 parts by weight of tripropylene glycol monobutyl ether were heated at 130°C for 1 hour to dissolve them. Then, 2.9 parts by weight of ethyl aluminum diisopropyl acetoacetate were added, and the mixture was heated at 130°C for 30 minutes to obtain varnish 3. Varnish 3 is a gelled varnish prepared using the same rosin ester used in the preparation of varnish 2.

[0086] [Preparation of Varnish 4]

[0087] 61.4 parts by weight of maleic rosin resin (hydroxyl value ≈ 0 mg KOH / g, acid value 220 ≤ mg KOH / g, weight average molecular weight 877, number average molecular weight 766) and 35.5 parts by weight of tripropylene glycol monobutyl ether were heated at 130°C for 1 hour to dissolve them. Then, 3.1 parts by weight of ethyl aluminum diisopropyl acetoacetate were added, and the mixture was heated at 130°C for 30 minutes to obtain varnish 4. Varnish 4 is a gelled varnish containing maleic rosin resin (hydroxyl value ≈ 0 mg KOH / g). It should be noted that the hexane tolerance of the maleic rosin resin used in the preparation of varnish 4, calculated according to the steps given in this invention, is 4.9 g / 5 g.

[0088] [Examples 1-6, Comparative Example 1]

[0089] The components were mixed according to the formulations in Table 1, and the resulting mixtures were kneaded using a three-roll mill to prepare the ink compositions of Examples 1-6 and Comparative Example 1. It should be noted that in Table 1, "white pigment" is titanium dioxide, "hydrophobic silica" is surface-treated hydrophobic silica particles (manufactured by AEROSIL Co., Ltd., Japan, product name AEROSIL R972), "hydrophilic silica" is surface-untreated silica particles (manufactured by TOKUYAMA Co., Ltd., product name REOLOSIL CP102), "clay" is organo-affinity bentonite (manufactured by BYK Co., Ltd., product name CRAYTONE-APA), and "specific solvent" is tripropylene glycol monobutyl ether. Furthermore, the values ​​for each formulation amount in Table 1 refer to parts by mass.

[0090] [Liquidity Assessment]

[0091] For each ink composition of Examples 1-6 and Comparative Example 1, the slope measured using a spreader at 25°C according to JIS K5101-6-1:2004 is recorded in the "Slope" column of Table 1. It should be noted that a larger slope value means higher fluidity of the ink composition.

[0092] [Transferable]

[0093] For each ink composition of Examples 1-6 and Comparative Example 1, the transferability was evaluated in the following order. First, 0.15 cc of the ink composition was spread on a rubber blanket (AIR TACK FS, Kinyo Co., Ltd.) using a RI tester (manufactured by Meisei Corporation) with a 4-segment roller. After 10 or 20 minutes, an aluminum plate intended for printing was attached to the spread rubber blanket. While applying pressure, the transferability of the ink composition was visually assessed to determine whether the spread ink composition was transferred to the aluminum plate and the extent of the transfer. The evaluation criteria are as follows, and the results are shown in the "Transferability Evaluation" column of Table 1.

[0094] ○: It also transfers well after being left for 20 minutes.

[0095] △~○: The transfer was slightly insufficient after 20 minutes, but transferred well after 10 minutes.

[0096] △: No transfer occurred after 20 minutes, but a good transfer occurred after 10 minutes.

[0097] ×: No transfer occurred even after 10 minutes.

[0098] [Table 1]

[0099] ,

[0100] Comparing the ink compositions of Examples 1-6 with the ink composition of Comparative Example 1, it can be seen that by combining a rosin-modified resin having the hydroxyl value given by the present invention with a specific solvent, the transferability of the ink composition can be improved without changing the oiliness of the alkyd resin. Furthermore, comparing Examples 1 and 2, it can be seen that the ink composition using hydrophilic silica particles can maintain flowability to a higher degree compared to the ink composition using hydrophobic silica particles.

Claims

1. A metal printing ink composition, comprising a coloring pigment, a resin, and a solvent, wherein, The metal printing ink composition comprises at least a portion of a rosin-modified resin with a hydroxyl value of 10 mg KOH / g or higher, and comprises at least one compound selected from the following general formula (1) as the solvent. [Chemical Formula 1] ， In the general formula (1), each A is independently an alkylene group with 2 to 4 carbon atoms that has a branched chain, R is an alkyl group with 1 to 13 carbon atoms that has a branched chain and / or ring structure, and n is an integer from 2 to 8.

2. The ink composition for metal printing according to claim 1, further comprising: 1-8% by mass of hydrophilic silica particles.

3. The ink composition for metal printing according to claim 1 or 2, wherein, The acid value of the rosin-modified resin is below 100 mg KOH / g.

4. The ink composition for metal printing according to any one of claims 1 to 3, wherein, When 70g of the rosin-modified resin was dissolved in 30g of tripropylene glycol monobutyl ether heated to 130°C and stirred for 60 minutes, a varnish with a hexane tolerance exceeding 50g / 5g, as determined by the following steps, was obtained. Steps: After the dissolved varnish has cooled to room temperature, collect 5g into a beaker. While maintaining the liquid temperature in the beaker at 25°C, add small amounts of n-hexane to the dissolved varnish in the beaker while stirring. Calculate the mass (g) of n-hexane required until the liquid in the beaker begins to turn cloudy. Set the mass (g) of n-hexane calculated in this way as the n-hexane tolerance (g / 5g).

5. The ink composition for metal printing according to any one of claims 1 to 4, wherein, The rosin-modified resin is a rosin ester resin.

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