Metal printing ink composition

Abstract

To provide a metal printing ink composition which can reduce occurrence of misting during printing and also can maintain good impact resistance even after a metal printed matter after printing is subjected to retort treatment.SOLUTION: A metal printing ink composition should be used comprising carbon black, a resin, and a solvent. The carbon black is neutral carbon black. The solvent has a solubility parameter (sp value) of less than 10.0 (cal / cm3)1 / 2. The composition comprises at least one selected from the group consisting of compounds represented by the general formula (1) in the figure. In the general formula (1), each A is independently a C2-4 alkylene group that may be branched, R is a C1-13 alkyl group that may have a branched and / or cyclic structure, and n is an integer from 2 to 8.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] For printing on the outer surface of metal materials, such as galvanized or tinned iron sheets, aluminum plates, or metal cans made of these metal materials, an ink composition for metal printing mainly composed of a binder resin such as an alkyd resin, a polyester resin, or an epoxy resin and an organic solvent such as mineral oil or a higher alcohol as a main vehicle component is used.

[0003] Also, on these printed surfaces, in order to improve the adhesion, flex resistance, impact resistance, abrasion resistance, etc. of the ink coating film, coating by overprint varnish is generally performed. As these overprint varnishes, solvent-type ones composed of a binder resin such as an alkyd resin, a polyester resin, an acrylic resin, or an epoxy resin, a curing agent such as a melamine resin or a benzoguanamine resin, and an organic solvent such as mineral oil or a cellosolve type have been widely used.

[0004] And when printing on the outer surface of metal, after printing the ink using an offset printing machine, a dry offset printing machine, etc., the overprint varnish is applied wet-on-wet on the ink film using a coater, etc., and then baking is performed at 150 to 280°C.

[0005] However, in recent years, due to the problem of air pollution caused by solvents and the hygiene or safety aspects in the printing work environment, in the field of metal printing, it has become common to adopt water-based overprint varnishes instead of the conventionally used solvent-type overprint varnishes. However, when a water-based overprint varnish is applied onto the ink coating film of a conventional ink composition for metal printing, problems such as repulsion of the water-based overprint varnish and penetration of the water-based overprint varnish into the ink film occur. As a result, there has been a problem that the quality such as gloss or adhesion of the coating film is significantly deteriorated. Therefore, it has been required that the ink composition also has excellent suitability for water-based overprint varnishes.

[0006] As a method for improving the suitability for such water-based overprint varnishes, for example, Patent Document 1 proposes the use of an alkylene glycol-based solvent having 4 to 8 carbon atoms, Patent Document 2 proposes the use of a polyoxyalkylene glycol-based solvent, Patent Document 3 proposes the use of a polyoxyalkylene alkyl ether-based organic solvent, and Patent Document 4 proposes the use of a polyoxyalkylene alkyl ester-based solvent, respectively. The organic solvents used in these ink compositions are effective in improving the suitability of the ink composition for water-based overprint varnishes, but there is still room for improvement in terms of being prone to misting during printing.

[0007] Also, depending on the use of metal printed matter, for example, retort treatment, that is, pressurization and heat treatment with steam or hot water at 100°C or higher, may be performed for the purpose of sterilization, etc., such as in two-piece cans or three-piece cans used for beverages such as coffee and tea and canned goods. When such treatment is performed, the printed film of the metal printed matter becomes vulnerable, and the impact resistance, which is the performance of maintaining the printed film when an impact is applied to the printed surface, may be significantly reduced.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a metal printing ink composition capable of reducing the occurrence of misting during printing and maintaining good impact resistance even after the printed metal product has been subjected to retort processing.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the present inventors have found that in a black ink using carbon black as a coloring pigment, particularly by using neutral carbon black and a hydrophobic solvent having a solubility parameter (sp value) of less than 10.00 (cal / cm 3 ) 1 / 2 the above problems can be solved, and the present invention has been completed. Specifically, the present invention provides the following.

[0011] (1) The present invention is a metal printing ink composition containing carbon black, a resin, and a solvent, wherein the carbon black contains neutral carbon black, and the solvent has a solubility parameter (sp value) of less than 10.00 (cal / cm 3 ) 1 / 2 and contains at least one selected from the group consisting of compounds represented by the following general formula (1).

Chemical Formula

[0012] (2) The present invention also relates to the ink composition for metal printing according to item (1), having a viscosity at 25°C of 10 to 70 Pa·s as measured by a falling ball viscometer.

[0013] (3) The present invention also relates to the ink composition for metal printing according to item (1) or (2), wherein the resin is an alkyd resin.

[0014] (4) The present invention also relates to the ink composition for metal printing according to item (3), wherein the mass average molecular weight of the alkyd resin is less than 10,000.

[0015] (5) The present invention also relates to the ink composition for metal printing according to item (3) or (4), wherein the alkyd resin has a pentaerythritol skeleton.

[0016] (6) The present invention also relates to the ink composition for metal printing according to any one of items (1) to (5), wherein the divalent group represented by AO in the general formula (1) is an oxypropylene group.

[0017] (7) The present invention also relates to the ink composition for metal printing according to any one of items (1) to (6), further containing an alkanolamine.

[0018] (8) The present invention also relates to the ink composition for metal printing according to any one of items (1) to (7), further containing a rosin-modified resin.

Advantages of the Invention

[0019] According to the present invention, there is provided an ink composition for metal printing which can reduce the occurrence of misting during printing and maintain good impact resistance even after the printed metal product has been subjected to retort processing.

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the ink composition for metal printing of the present invention will be described. Note that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the present invention.

[0021] 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 plate as a printing plate or an offset printing method using a lithographic plate as a printing plate. However, it can be applied to all printing methods generally used in metal printing. Further, in the ink composition of the present invention, the occurrence of misting during printing is suppressed, and the occurrence of stains around the printing machine due to minute ink droplets generated during printing is suppressed. Furthermore, the printed film formed by baking after printing with the ink composition of the present invention has good impact resistance even after being subjected to retort treatment. Therefore, the ink composition of the present invention is preferably applied not only to general metal prints but also 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.

[0022] The ink composition of the present invention comprises carbon black, a resin and a solvent, and is characterized in that it contains a particularly neutral carbon black and a glycol monoether solvent represented by the general formula (1) having a specific solubility parameter (sp value) as the solvent. Hereinafter, each component will be described.

[0023] [Carbon Black] The ink composition of the present invention contains carbon black as a coloring pigment. Various commercially available carbon blacks exhibit acidity, neutrality, or alkalinity depending on the difference in their surface functional groups. In the present invention, particularly neutral carbon black is used. The neutral carbon black in the present invention refers to a carbon black having a pH in the range of 6.0 or more and 9.5 or less. The reason for using such neutral carbon black in the present invention is that, according to the findings of the present inventors, by using neutral carbon black instead of acidic carbon black that has been used in ink compositions for metal printing, the impact resistance of the ink film formed on the metal after retort treatment can be improved.

[0024] The pH of carbon black is determined by measuring a mixture of carbon black and distilled water with a glass electrode pH meter. Specifically, 1 g of the carbon black to be measured is added to 20 mL of distilled water (pH 7.0) from which carbonic acid has been removed, and mixed with a magnetic stirrer to prepare an aqueous suspension. The pH is measured at 25 °C using a glass electrode (German Industrial Standard DIN ISO 787 / 9).

[0025] The addition amount of carbon black is exemplified as about 5 to 50% by mass with respect to the whole ink composition, but is not particularly limited. In addition to carbon black, pigments of other colors or ink compositions of other colors may be added to the ink composition as complementary colors.

[0026] [Resin] Examples of the resin used in the ink composition of the present invention include those that have been used in ink compositions for metal printing without particular limitation. Among these resins, alkyd resin is preferably used in the ink composition of the present invention. Further, a rosin-modified resin may be combined with the alkyd resin and used. Next, these resins will be described.

[0027] An alkyd resin is a polycondensate of a polyhydric alcohol and a polybasic acid and is a type of polyester. However, it can also be prepared by performing polycondensation with vegetable oils and fats and / or their fatty acids in addition to these. At this time, the vegetable oils and fats are transesterified with the polyhydric alcohol to become fatty acids and are incorporated into the structure of the alkyd resin. The ratio derived from the fatty acids of the vegetable oils and fats in the alkyd resin is called the oil length, and the oil length of the alkyd resin used in the present invention is preferably 20 to 50% by mass. Note that an oil-free alkyd, which is an alkyd resin that does not contain the fatty acid component of vegetable oils and fats, may be used.

[0028] As the alkyd resin used in the present invention, those having a pentaerythritol skeleton in the molecule are preferably mentioned. By using an alkyd resin having such a skeleton, it is possible to improve the impact resistance after retort treatment in the printed film, which is preferable. Such an alkyd resin is prepared by using pentaerythritol as the polyhydric alcohol. Note that the alkyd resin used in the present invention may be prepared by using other polyhydric alcohols in addition to pentaerythritol.

[0029] An alkyd resin having a pentaerythritol skeleton in the molecule can be obtained, for example, as a polycondensate of an acid component composed of a fatty acid and a polybasic acid and a polyhydric alcohol containing at least pentaerythritol. Next, a method for preparing such an alkyd resin will be described.

[0030] Fatty acids are obtained by hydrolyzing natural oils and fats such as vegetable oils and animal oils. Since they have one carboxy group, they can form esters with polyhydric alcohols described below. By introducing such fatty acids into alkyd resins, the transferability of ink compositions using them can be enhanced, or the proportion of biomass-derived components can be increased. From such a viewpoint, it is preferable to use a fatty acid in an amount such that the oil length, which is the ratio (mass %) of the mass of the fatty acid portion to the mass of the entire resin, is about 20 to 50 mass %. As such a fatty acid, coconut oil is preferably mentioned. Note that various fatty acids can be mentioned, and these can be used alone or in combination of two or more.

[0031] Polybasic acids are compounds having a plurality of carboxy groups and are components for polycondensing with polyhydric alcohols described below to increase the molecular weight. Examples of such polybasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, trimellitic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexenedicarboxylic acid, 1,4-cyclohexenedicarboxylic acid, hexahydrophthalic anhydride, 5-sodium sulfoisophthalic acid, fumaric acid, benzoic acid, tert-butylbenzoic acid, tetrahydrophthalic anhydride, maleic anhydride, succinic acid, succinic anhydride, fumaric acid, sebacic acid, azelaic acid, tetrabromophthalic anhydride, methyl hymic anhydride, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, trimellitic anhydride, methylcyclohexenedicarboxylic anhydride, and the like. Among these, phthalic acid or phthalic anhydride is preferably mentioned. These polybasic acids can be used alone or in combination of two or more.

[0032] Polyhydric alcohols form esters with the above acid components and increase the molecular weight of these components. As polyhydric alcohols, those that have been used for the synthesis of alkyd resins so far can be used without limitation, and compounds having two or more hydroxyl groups are mentioned.

[0033] Examples of such compounds include, in addition to the above-mentioned 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-methyl-1,3-propanediol, hexamethylene glycol, octylene glycol, 9-nonanediol, 2,4-diethyl-1,5-pentanediol, ethylene oxide-modified compounds of bifunctional phenols such as bisphenol A, propylene oxide-modified compounds of bifunctional 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 diol, adamantanediol, polyether diol, polyester diol, polycaprolactone diol, etc. These can be used alone or in combination of two or more.

[0034] To prepare an alkyd resin, a small amount of a solvent such as xylene is added to a reaction kettle charged with these acid components and polyhydric alcohol, and heating is carried out while flowing an inert gas such as nitrogen gas, and polycondensation is carried out while removing water by azeotroping with condensed water. A method can be mentioned. Further, taking the polycondensation reaction of these acid components and polyhydric alcohol as the first stage, and as the second stage, polycondensation is carried out using a polybasic acid having three or more functional groups such as trimellitic acid, so that an alkyd resin that gives a highly crosslinked and tough cured film can also be obtained. The reaction temperature can be about 170 to 250 ° C, and the reaction time can be about 5 to 25 hours, but it is not particularly limited. The completion of the reaction can be determined by monitoring the acid value of the reaction mixture according to the passage of the reaction time. That is, the reaction may be terminated when the decrease in the acid value of the reaction mixture accompanying polycondensation stops. The polycondensation reaction can be carried out in a shorter time by distilling the water generated by polycondensation out of the system or using a reaction catalyst. Examples of the reaction catalyst include tetrabutyl zirconate, monobutyltin oxide (monobutyltin oxide), zirconium naphthate, tetrabutyl titanate, and the like.

[0035] The mass average molecular weight of the alkyd resin can preferably be less than 10,000, more preferably 8,500 or less, and even more preferably 7,000 or less. As described above, in the present invention, by using neutral carbon black, the impact resistance after retort treatment of the ink film formed on the metal can be improved. By using such a relatively low molecular weight alkyd resin, this impact resistance can be further improved, which is preferable.

[0036] The weight average molecular weight of the resin in the present invention can be measured by gel permeation chromatography (GPC). As an example, Waters Acquity APC (Waters) is used as the GPC apparatus, and ACQUITY APC XT 45 1.7μm 4.6×150mm, ACQUITY APC XT 200 2.5μm 4.6×75mm, and ACQUITY APC XT 900 2.5μm 4.6×75mm (Waters) are used as columns, respectively. Chromatography is performed under the conditions of using tetrahydrofuran as the mobile phase, a column temperature of 40°C, a flow rate of 0.8 milliliters / minute, an RI detector, a sample injection concentration of 10 milligrams / 5 milliliters, and an injection volume of 10 microliters, and the value obtained as the weight average molecular weight in terms of polystyrene can be cited.

[0037] The content of the alkyd resin in the ink composition is preferably 10 to 40% by mass, more preferably 20 to 40% by mass, based on the total composition.

[0038] The rosin-modified resin is a resin prepared using rosin as one of the raw materials. Rosin contains resin acids such as abietic acid, palustric acid, isopimaric acid, and levopimaric acid as a mixture. These resin acids contain hydrophilic and chemically active carboxyl groups, and some of them have conjugated double bonds. Therefore, various rosin-modified resins are prepared by, for example, combining polyhydric alcohols and polybasic acids for polycondensation, adding resole, which is a condensate of phenol, to the benzene ring contained in the rosin skeleton, or causing a Diels-Alder reaction with maleic anhydride or maleic acid, which is a dienophile, to add a maleic acid or maleic anhydride skeleton. Such rosin-modified resins are commercially available in various types, and it is also possible to obtain and use them.

[0039] Examples of the rosin-modified resin include rosin ester resin, maleated rosin, fumarated rosin resin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, rosin-modified phenol resin, rosin-modified alkyd resin, rosin-modified polyester resin, and the like. In the present invention, any rosin-modified resin may be used, but among them, rosin ester resin is preferably used.

[0040] As the rosin-modified resin used in the present invention, those having a hydroxyl value of 10 mgKOH / g or more are preferably used. When the ink composition of the present invention contains such a rosin-modified resin having a high hydroxyl value, 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 the highly polar aqueous OP varnish also increases, and the effect of suppressing repelling even when it is applied wet-on-wet is also achieved. The hydroxyl value of the rosin-modified resin is more preferably 15 mgKOH / g or more, and even more preferably 20 mgKOH / g or more. The upper limit of the hydroxyl value of the rosin-modified resin is not particularly limited, but for example, about 200 mgKOH / g can be mentioned, preferably about 150 mgKOH / g, and more preferably about 100 mgKOH / g.

[0041] Although not particularly limited, the acid value of the rosin-modified resin is preferably 100 mgKOH / g or less. When the acid value of the rosin-modified resin is 100 mgKOH / g or less, it is preferable because it can achieve both suppression of repelling when the aqueous OP varnish is applied wet-on-wet and printing suitability such as suppression of misting and overflowing. The acid value of the rosin-modified resin is more preferably 80 mgKOH / g or less, and even more preferably 50 mgKOH / g or less.

[0042] The rosin-modified resin is used in a state where it is dissolved or dispersed by heating together with a solvent described later to form a varnish. The rosin-modified resin may be used as a dissolved varnish that 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 it may be used in a state of being a gelled varnish. Among these, it is preferable to prepare a dissolved varnish from the rosin-modified resin and use this for the preparation of the ink composition, because the transferability of the ink composition during printing can be improved. Further, by preparing a gelled varnish from the rosin-modified resin and using this for the preparation of the ink composition, appropriate viscoelasticity can be imparted to the ink composition, fluidity can be improved and misting can be reduced, and a stronger and tougher cured film can be formed.

[0043] As the content of the rosin-modified resin in the ink composition, 5 to 50% by mass is preferably mentioned with respect to the whole composition, 5 to 25% by mass is more preferably mentioned with respect to the whole composition, and 7 to 20% by mass is even more preferably mentioned with respect to the whole composition.

[0044] In addition to the above-mentioned alkyd resin and rosin-modified resin, the ink composition of the present invention can also be used in combination with resins conventionally used for the preparation of metal printing ink compositions. That is, according to the required performance such as printing suitability and coating film physical properties, known resins compatible with the above-mentioned alkyd resin rosin-modified resin can be used alone or in a mixture of two or more. Examples of such resins include polyester resins, petroleum resins, epoxy resins, ketone resins, amino resins, benzoguanamine resins, and the like.

[0045] [Solvent] As the solvent used in the ink composition of the present invention, those that have been used in the field of inks for metal printing can be listed without particular limitation. Examples of such solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, alkylbenzenes, polyalkylene glycols, etc. having a boiling point range of about 230 to 400 °C. Among these, the ink composition of the present invention has a solubility parameter (sp value) of less than 10.00 (cal / cm 3 ) 1 / 2 and contains at least one selected from the group consisting of compounds represented by the following general formula (1) as essential. Hereinafter, the solvent having a solubility parameter (sp value) of less than 10.00 (cal / cm 3 ) 1 / 2 and at least one selected from the group consisting of compounds represented by the following general formula (1) is also called a specific solvent. The sp value of the specific solvent is preferably less than 9.80 (cal / cm 3 ) 1 / 2 . Further, the lower limit value of the sp value of the specific solvent is preferably about 8.50 (cal / cm 3 ) 1 / 2 , and more preferably about 9.00 (cal / cm 3 ) 1 / 2 . The specific solvent having such an sp value can also be called a polyalkylene glycol monoalkyl ether having hydrophobic properties. The reason for using such a specific solvent having hydrophobic properties in the present invention is that, instead of alkylbenzene-based solvents and hydrophilic polyalkylene glycol monoalkyl ether-based solvents that have been widely used in the field of ink compositions for metal printing, by using a hydrophobic polyalkylene glycol monoalkyl ether (i.e., a specific solvent), the occurrence of misting during printing can be significantly reduced, according to the findings of the present inventors.

[0046]

Chemical formula

[0047] In the general formula (1) above, each A is independently an alkylene group having 2 to 4 carbon atoms which may have a branch. Examples of such alkylene groups 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 mentioned. In this case, the divalent group represented by AO in the general formula (1) is an oxypropylene group.

[0048] In the general formula (1) above, R is an alkyl group having 1 to 13 carbon atoms which may have a branch and / or a ring structure. Note that this alkyl group may be an alicyclic group as well as an aliphatic group. Examples of such alkyl groups include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, a 2-ethylhexyl group, an octyl group, a decyl group, a cyclohexyl group, and the like.

[0049] In the general formula (1) above, n is an integer of 2 to 8. When n is 2 or more, it is preferable because a sufficient boiling point of a specific solvent can be ensured to impart stability of the ink composition on the printing machine. When n is 8 or less, a preferable viscosity can be achieved as the solvent of the ink composition.

[0050] Examples of the compound 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, hexapropylene glycol monomethyl ether, and the like.

[0051] In addition, as the sp value in the present invention, the value calculated by the Fedros method is used (see the literature: R.F. Fedros, Polym. Eng. Sci., 14(2) 147 (1974)).

[0052] The content of the solvent in the ink composition of the present invention is preferably 10 to 50% by mass, more preferably 20 to 45% by mass, based on the whole composition. Among the solvents, the content of the specific solvent is preferably 15 to 40% by mass based on the whole composition, and it is preferable that all of the solvents in the composition are the specific solvent.

[0053] The ink composition of the present invention preferably contains an alkanolamine in addition to the above components. By containing an alkanolamine in the ink composition of the present invention, it is possible to improve both the reduction of misting during printing and the impact resistance after retort treatment in the printed film.

[0054] Examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, ethylmonoethanolamine, n-butylmonoethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, and the like. Among these, triethanolamine is preferably mentioned.

[0055] As the content of the alkanolamine in the ink composition of the present invention, 0.1 to 3% by mass is preferably cited with respect to the whole composition, and 0.1 to 1 part by mass is more preferably cited.

[0056] In the ink composition of the present invention, as other components, known curing agents; pigment dispersants; waxes; extender pigments such as silica particles, calcium carbonate, bentonite clay, kaolin, talc, etc.; stabilizers, etc. can be added as necessary.

[0057] As the curing agent, for example, amino resins such as melamine resins and benzoguanamine resins can be used.

[0058] Silica particles are those commercially available as powders of SiO 2 and it is possible to easily obtain those that are not particularly surface-treated or are hydrophilic ones subjected to hydrophilization treatment, hydrophobic ones subjected to hydrophobic treatment, etc. Among these silica particles, in the ink composition of the present invention, hydrophobic silica particles are preferably used. By using hydrophobic silica particles, the transferability of the ink composition during printing can be made better, and the fluidity of the ink composition can be increased, which is preferable. As the content of the silica particles in the ink composition, 0.5 to 15% by mass is preferably cited, and 1 to 5% by mass is more preferably cited.

[0059] The ink composition of the present invention can be prepared by mixing the above-described respective components by a conventional method using a roll mill, a ball mill, a bead mill, etc. As the viscosity of the ink composition, the value at 25 ° C. measured by a La Rheometer can be exemplified as 10 to 70 Pa·s, but it is not particularly limited.

[0060] The metal for metal printing in the ink composition of the present invention is not particularly limited, and examples include galvanized or tinned iron plates, aluminum plates, or metal cans made of these metal materials.

Examples

[0061] Hereinafter, the ink composition of the present invention will be described in more detail by showing examples, but the present invention is not limited to the following examples at all.

[0062] [Preparation of Alkyd Resin Varnish 1] 5.98 parts by mass of neopentyl glycol, 8.53 parts by mass of pentaerythritol, 11.00 parts by mass of coconut oil fatty acid, 7.30 parts by mass of isophthalic acid and 6.50 parts by mass of phthalic anhydride were reacted at 220 ° C. under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g to perform the first-stage esterification. Then, 0.70 part by mass of trimellitic anhydride was added and heated at 165 ° C. for 30 minutes under a nitrogen atmosphere to perform the second-stage esterification. These esterification reactions were carried out according to a conventional method to obtain an alkyd resin 1 having a mass average molecular weight of 4,376 and a number average molecular weight of 1,995. To this alkyd resin 1, 15.0 parts by mass of tripropylene glycol monobutyl ether was added to obtain alkyd resin varnish 1. The sp value of this tripropylene glycol monobutyl ether is 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0063] [Preparation of Alkyd Resin Varnish 2] 5.00 parts by mass of neopentyl glycol, 9.18 parts by mass of pentaerythritol, 11.00 parts by mass of coconut oil fatty acid, 7.30 parts by mass of isophthalic acid and 6.50 parts by mass of phthalic anhydride were reacted at 220 ° C. under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g to perform the first-stage esterification. Then, 0.70 part by mass of trimellitic anhydride was added and heated at 165 ° C. for 30 minutes under a nitrogen atmosphere to perform the second-stage esterification. These esterification reactions were carried out according to a conventional method to obtain an alkyd resin 2 having a mass average molecular weight of 4,764 and a number average molecular weight of 2,348. To this alkyd resin 2, 10.0 parts by mass of tripropylene glycol monobutyl ether was added to obtain alkyd resin varnish 2. The sp value of this tripropylene glycol monobutyl ether is 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0064] [Preparation of Alkyd Resin Varnish 3] 5.00 parts by mass of neopentyl glycol, 10.80 parts by mass of trimethylolpropane, 11.00 parts by mass of coconut oil fatty acid, 7.30 parts by mass of isophthalic acid, and 6.50 parts by mass of phthalic anhydride were reacted at 220 °C under a nitrogen atmosphere until the acid value of the mixture reached 7 mg KOH / g to perform the first-stage esterification. Then, 0.70 part by mass of trimellitic anhydride was added, and the mixture was heated at 165 °C for 30 minutes under a nitrogen atmosphere to perform the second-stage esterification. These esterification reactions were carried out according to a conventional method to obtain an alkyd resin 3 having a mass average molecular weight of 2,785 and a number average molecular weight of 1,639. To this alkyd resin 3, 10.0 parts by mass of tripropylene glycol monobutyl ether was added to obtain alkyd resin varnish 3. The sp value of this tripropylene glycol monobutyl ether is 9.73 (cal / cm 3 ) 1 / 2 and it corresponds to the specific solvent in the present invention.

[0065] [Preparation of Alkyd Resin Varnish 4] 5.98 parts by mass of neopentyl glycol, 8.53 parts by mass of pentaerythritol, 10.10 parts by mass of coconut oil fatty acid, 11.95 parts by mass of isophthalic acid, and 2.48 parts by mass of terephthalic acid were reacted at 220 °C under a nitrogen atmosphere until the acid value of the mixture reached 7 mg KOH / g to perform the first-stage esterification. Then, 0.70 part by mass of trimellitic anhydride was added, and the mixture was heated at 165 °C for 30 minutes under a nitrogen atmosphere to perform the second-stage esterification. These esterification reactions were carried out according to a conventional method to obtain an alkyd resin 4 having a mass average molecular weight of 6,049 and a number average molecular weight of 2,591. To this alkyd resin 4, 21.8 parts by mass of tripropylene glycol monobutyl ether was added to obtain alkyd resin varnish 4. The sp value of this tripropylene glycol monobutyl ether is 9.73 (cal / cm 3 ) 1 / 2 and it corresponds to the specific solvent in the present invention.

[0066] [Preparation of Alkyd Resin Varnish 5] To the alkyd resin 2 obtained in the procedure for preparing the above alkyd resin varnish 2, triethylene glycol monobutyl ether was added in place of tripropylene glycol monobutyl ether to obtain alkyd resin varnish 5. The sp value of this triethylene glycol monobutyl ether is 10.32 (cal / cm 3 ) 1 / 2 and it does not correspond to the specific solvent in the present invention.

[0067] [Preparation of alkyd resin varnish 6] To the alkyd resin 2 obtained in the procedure for preparing the above alkyd resin varnish 2, pentapropylene glycol monobutyl ether was added in place of tripropylene glycol monobutyl ether to obtain alkyd resin varnish 6. The sp value of pentapropylene glycol monobutyl ether is 9.42 (cal / cm 3 ) 1 / 2 and it corresponds to the specific solvent in the present invention.

[0068] [Preparation of alkyd resin varnish 7] To the alkyd resin 2 obtained in the procedure for preparing the above alkyd resin varnish 2, tetrapropylene glycol mono-2-ethylhexyl ether was added in place of tripropylene glycol monobutyl ether to obtain alkyd resin varnish 7. The sp value of tetrapropylene glycol mono-2-ethylhexyl ether is 9.32 (cal / cm 3 ) 1 / 2 and it corresponds to the specific solvent in the present invention.

[0069] [Preparation of rosin-modified resin varnish 1] 63.2 parts by mass of a rosin ester resin (hydroxyl value 20 to 30 mgKOH / g, acid value < 10 mgKOH / g, mass average molecular weight 632, number average molecular weight 565) and 35.9 parts by mass of tripropylene glycol monobutyl ether were heated at 130°C for 1 hour to dissolve them, and rosin-modified resin varnish 1 was obtained. The sp value of this tripropylene glycol monobutyl ether is 9.73 (cal / cm 3 )1 / 2 It is applicable to the specific solvent in the present invention.

[0070] [Preparation of Rosin-Modified Resin Varnish 2] Rosin-modified resin varnish 2 was obtained in the same procedure as the preparation of the above rosin-modified resin varnish 1, except that triethylene glycol monobutyl ether was used instead of tripropylene glycol monobutyl ether. The sp value of this triethylene glycol monobutyl ether is 10.32 (cal / cm 3 ) 1 / 2 It does not correspond to the specific solvent in the present invention.

[0071] [Preparation of Rosin-Modified Resin Varnish 3] Rosin-modified resin varnish 3 was obtained in the same procedure as the preparation of the above rosin-modified resin varnish 1, except that pentapropylene glycol monobutyl ether was used instead of tripropylene glycol monobutyl ether. The sp value of this pentapropylene glycol monobutyl ether is 9.42 (cal / cm 3 ) 1 / 2 It is applicable to the specific solvent in the present invention.

[0072] [Preparation of Rosin-Modified Resin Varnish 4] Rosin-modified resin varnish 4 was obtained in the same procedure as the preparation of the above rosin-modified resin varnish 1, except that tetrapropylene glycol mono-2-ethylhexyl ether was used instead of tripropylene glycol monobutyl ether. The sp value of this tetrapropylene glycol mono-2-ethylhexyl ether is 9.32 (cal / cm 3 ) 1 / 2 It is applicable to the specific solvent in the present invention.

[0073] [Examples 1 to 12, Comparative Examples 1 to 3] The respective components were mixed according to the formulations in Tables 1 to 3, and the resulting mixtures were kneaded using a three-roll mill to prepare the ink compositions of Examples 1 to 12 and Comparative Examples 1 to 3. In Tables 1 to 3, "Neutral CB1" is HIBLACK 200L manufactured by Orion Engineered Carbons (neutral carbon black, primary particle size 28 nm, DBP absorption 62 ml / 100 g, pH 8.0), "Neutral CB2" is ELFTEX 415 manufactured by Cabot Corporation (neutral carbon black, primary particle size 25 nm, DBP absorption 55 ml / 100 g, pH 6.0 or more and 8.0 or less), "Neutral CB3" is Regal 250R manufactured by Cabot Corporation (neutral carbon black, primary particle size 34 nm, DBP absorption 48 ml / 100 g, pH 6.0 or more and 8.0 or less), "Neutral CB4" is Regal 350R manufactured by Cabot Corporation (neutral carbon black, primary particle size 48 nm, DBP absorption 46 ml / 100 g, pH 6.0 or more and 8.0 or less), "Acidic CB1" is Mitsubishi Carbon Black MA7 manufactured by Mitsubishi Chemical Corporation (acidic carbon black, primary particle size 24 nm, DBP absorption 66 ml / 100 g, pH 3.0), and "Acidic CB2" is Mogul E manufactured by Cabot Corporation (acidic carbon black, primary particle size 48 nm, DBP absorption 49 ml / 100 g, pH 2.5). Also, in Tables 1 to 3, "Specific Solvent 1" is tripropylene glycol monobutyl ether (sp value 9.73 (cal / cm 3 ) 1 / 2 ), "Specific Solvent 2" is pentapropylene glycol monobutyl ether (sp value 9.42 (cal / cm 3 ) 1 / 2 ), "Specific Solvent 3" is tetrapropylene glycol mono-2-ethylhexyl ether (sp value 9.32 (cal / cm 3 ) 1 / 2 ), "Non-Specific Solvent" is triethylene glycol monobutyl ether (sp value 10.32 (cal / cm 3 ) 1 / 2 ), and "Silica" is surface-hydrophobized silica particles (manufactured by Nippon Aerosil Co., Ltd., product name Aerosil R972). The numerical values of the respective compounding amounts in Tables 1 to 3 are all in parts by mass.

[0074] [Misting Amount Evaluation] For each of the ink compositions of the examples and comparative examples, 2.6 cc of the ink composition was taken and applied to the rotating roller of the inkometer to make it uniform, and then rotated at 1200 rpm for 3 minutes. During this time, a white paper was placed under the roller, and the amount of the ink composition adhering to the surface due to misting was compared. The measurement was carried out while keeping the roller at 40°C. The mass change of the white paper before and after the measurement was determined, and this was taken as the misting amount (mg). The larger the mass change of the white paper before and after the measurement, the larger the amount of scattering of the ink composition. Therefore, the smaller this value, the better the result. Based on the calculated misting amount (mg), the evaluation was carried out according to the following criteria. The evaluation results are shown in the "Misting" column of Tables 1 to 3. ○: The misting amount was less than 5 mg △: The misting amount was 5 mg or more and less than 10 mg ×: The misting amount was 10 mg or more

[0075] [Impact Resistance Evaluation after Retort Treatment] For each of the examples and comparative examples, 0.2 cc of the ink composition was applied using an RI color developing machine onto an aluminum substrate with a thickness of 50 μm to obtain a color developed product. Then, for the color developed surface of the color developed product, an overprint varnish for retort (manufactured by AkzoNobel) was applied using a No. 0.4 bar coater (Mayer bar), and held in an oven at 240°C for 2 minutes to obtain a retort sample. Then, the retort sample was subjected to a retort treatment using an autoclave (high-pressure steam sterilizer, HG-50 manufactured by Hirayama Seisakusho Co., Ltd.) under the conditions of 125°C for 30 minutes to obtain a retort-treated product. The obtained retort-treated product was subjected to impact on 4 locations from the opposite side of the color developed surface under the conditions of a striker diameter: 1 / 4Φ (6.35 mm), weight: 300 g, and weight drop height: 50 mm using a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name H-50), and the degree of peeling of the coating film on the color developed surface side was evaluated according to the following criteria. The results are shown in the "Impact Resistance after Retort" column of Tables 1 to 3. ○: For all 4 locations, the coating film at the location in contact with the striker did not peel off ×: For one or more of the four locations, at least a part of the coating film at the location in contact with the firing pin has peeled off, and the aluminum base material is exposed.

[0076]

Table 1

[0077]

Table 2

[0078]

Table 3

[0079] As is clear from Tables 1 to 3, it can be understood that by combining neutral carbon black with a specific solvent that satisfies a predetermined solubility parameter to form an ink composition for metal printing, the misting suitability and the impact resistance after retort become good.

Claims

1. A metal printing ink composition comprising carbon black, a resin and a solvent, The carbon black includes neutral carbon black, The resin contains an alkyd resin having a pentaerythritol skeleton or a neopentyl glycol skeleton and a mass average molecular weight of less than 10,000 in an amount of 10 to 40% by mass based on the entire composition, The solvent has a solubility parameter (sp value) of 10.00 (cal / cm ３ ) １／２ and containing at least one compound selected from the group consisting of compounds represented by the following general formula (1): 【Chemistry 1】 (In the above general formula (1), each A is independently an alkylene group having 2 to 4 carbon atoms which may have a branch, R is an alkyl group having 1 to 13 carbon atoms which may have a branched and / or cyclic structure, and n is an integer of 2 to 8.)

2. 2. The ink composition for metal printing according to claim 1, which has a viscosity of 10 to 70 Pa·s at 25° C. as measured by a Raleigh viscometer.

3. 2. The ink composition for metal printing according to claim 1, wherein the divalent group represented by AO in formula (1) is an oxypropylene group.

4. 2. The ink composition for metal printing according to claim 1, further comprising an alkanolamine.

5. 2. The ink composition for metal printing according to claim 1, further comprising a rosin-modified resin.

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