Metal printing ink composition

Abstract

To provide an ink composition for metal printing which reduces the occurrence of misting during printing and enables a printed metal print to maintain good impact resistance even after being subjected to retort treatment. The ink composition for metal printing contains carbon black, a resin, and a solvent, and the carbon black contains neutral carbon black, and the solvent contains a solubility parameter (sp value) of 10.0 (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): In general formula (1), each A is independently an alkylene group having 2 to 4 carbon atoms which may be branched, 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 from 2 to 8. TIFF0007638424000007.tif12157

Description

[Technical field]

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

[0002] For printing on the outer metal surfaces of metal materials, such as galvanized or tinned iron sheets, aluminum sheets, or metal cans made from these metal materials, ink compositions for metal printing are used which contain, as the main vehicle components, binder resins such as alkyd resins, polyester resins, and epoxy resins, and organic solvents such as mineral oils or higher alcohols.

[0003] Moreover, these printing surfaces are generally coated with an overprint varnish to improve the adhesion of the ink coating, bending resistance, impact resistance, abrasion resistance, etc. The most widely used overprint varnishes are solvent-based varnishes that contain binder resins such as alkyd resins, polyester resins, acrylic resins, and epoxy resins, hardeners such as melamine resins and benzoguanamine resins, and organic solvents such as mineral oils and cellosolves.

[0004] When printing on the outer metal surface, ink is printed using an offset printing machine, dry offset printing machine, etc., and then an overprint varnish is applied wet-on-wet onto the ink coating using a coater, etc., and then baked at 150 to 280°C.

[0005] However, in recent years, due to the problem of air pollution caused by solvents and the hygienic and safety aspects of the printing work environment, it has become common to adopt water-based overprint varnishes in the field of metal printing instead of the solvent-based overprint varnishes that have been used in the past. However, when a water-based overprint varnish is applied onto an ink coating film of a conventional ink composition for metal printing, there are problems such as the repelling of the water-based overprint varnish and the penetration of the water-based overprint varnish into the ink film, resulting in a significant decrease in the quality of the coating film, such as gloss or adhesion. Therefore, there has been a demand for ink compositions to have excellent suitability for water-based overprint varnishes.

[0006] As methods for improving suitability for such aqueous overprint varnish, 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. These organic solvents used in ink compositions are effective in improving the suitability of the ink composition for aqueous overprint varnish, but there is room for improvement in that they tend to cause misting during printing, for example.

[0007] Depending on the application of the metal printed material, for example, two-piece and three-piece cans used for beverages such as coffee and tea, and canned goods, may be subjected to retort treatment, i.e., pressurization and heat treatment with steam or hot water at 100°C or higher, for the purpose of sterilization, etc. Such treatment may weaken the printing film of the metal printed material, and the impact resistance, which is the ability to maintain the printing film when an impact is applied to the printed surface, may be significantly reduced. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 5-75031 [Patent Document 2] Special Publication No. 5-40791 [Patent Document 3] Special Publication No. 5-40792 [Patent Document 4] Japanese Patent Publication No. 64-60670 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide an ink composition for metal printing which reduces the occurrence of misting during printing and enables the metal print to maintain good impact resistance even after being subjected to retort treatment after printing. [Means for solving the problem]

[0010] As a result of intensive research conducted by the present inventors to solve the above problems, it has been found that, in a black ink containing carbon black as a coloring pigment, a carbon black having a solubility parameter (sp value) of 10.00 (cal / cm 3 ) 1 / 2 The present invention has been completed based on the discovery that the above problems can be solved by using a hydrophobic solvent having a viscosity of less than 100 nm.

[0011] (1) The present invention relates to an ink composition for metal printing, comprising carbon black, a resin, and a solvent, the carbon black comprising neutral carbon black, the resin comprising 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 relative to the entire composition, and the solvent comprising an alkyd resin having 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): It also contains rosin ester resin. The present invention relates to an ink composition for metal printing, comprising: [ka] (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.)

[0015] ( 2 In the present invention, the divalent group represented by AO in the general formula (1) is an oxypropylene group. Section (1) The ink composition for metal printing is as described above.

[0016] ( 3 The present invention further relates to a composition (1) containing an alkanolamine. or (2) The ink composition for metal printing is as described above. Effect of the Invention

[0018] According to the present invention, there is provided an ink composition for metal printing which reduces the occurrence of misting during printing and which can maintain good impact resistance of the printed metal print even after it is subjected to retort treatment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, one 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 embodiment, and can be practiced by making appropriate modifications within the scope of the present invention.

[0020] 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 the so-called dry offset printing method using a relief plate as a printing plate, or the offset printing method using a lithographic plate as a printing plate, but can be applied to all printing methods commonly used in metal printing. In addition, the ink composition of the present invention suppresses the occurrence of misting during printing, and suppresses the occurrence of stains around the printing machine due to minute ink droplets generated during printing. Furthermore, the printing film formed by baking treatment after printing with the ink composition of the present invention has good impact resistance even after retort treatment, so the ink composition of the present invention is not only applied to general metal printed matter, but 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 goods.

[0021] The ink composition of the present invention comprises carbon black, a resin and a solvent, and is characterized in that the carbon black is particularly neutral and the solvent is a glycol monoether solvent having a specific solubility parameter (sp value) and represented by general formula (1). Each component will be described below.

[0022] [Carbon black] The ink composition of the present invention contains carbon black as a color pigment. Various types of carbon black that are acidic, neutral, or alkaline depending on the surface functional group are commercially available, and neutral carbon black is particularly used in the present invention. Note that neutral carbon black in the present invention refers to carbon black with a pH range of 6.0 to 9.5. The reason for using such neutral carbon black in the present invention is based on the discovery by the present inventors that the impact resistance of the ink film formed on the metal after retort treatment can be improved by using neutral carbon black instead of the acidic carbon black that has been used in ink compositions for metal printing.

[0023] The pH of carbon black can be 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 decarbonated distilled water (pH 7.0), mixed with a magnetic stirrer to prepare an aqueous suspension, and the pH is measured at 25°C with a glass electrode (German Industrial Standard DIN ISO 787 / 9).

[0024] The amount of carbon black added is, for example, about 5 to 50 mass % based on the total amount of the 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.

[0025] [resin] The resin used in the ink composition of the present invention may be any resin that has been used in ink compositions for metal printing. Among these resins, an alkyd resin is preferably used in the ink composition of the present invention. The alkyd resin may also be used in combination with a rosin-modified resin. These resins will now be described.

[0026] Alkyd resins are condensation polymers of polyhydric alcohols and polybasic acids, and are a type of polyester, but 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 alcohol to become fatty acids, which are 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 oil length, and the oil length of the alkyd resin used in the present invention is preferably 20 to 50 mass%. Note that oil-free alkyds, which are alkyd resins that do not contain fatty acid components from animal and vegetable oils, may also be used.

[0027] The alkyd resin used in the present invention is preferably one having a pentaerythritol skeleton in the molecule. By using an alkyd resin having such a skeleton, it is preferable to improve the impact resistance of the printing film after retort treatment. Such an alkyd resin is prepared using pentaerythritol as a polyhydric alcohol. The alkyd resin used in the present invention may be prepared using other polyhydric alcohols in addition to pentaerythritol.

[0028] An alkyd resin having a pentaerythritol skeleton in the molecule can be obtained, for example, as a condensation polymer of an acid component consisting 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.

[0029] Fatty acids are obtained by hydrolysis of natural fats and oils such as vegetable oils and animal oils, and have one carboxyl group, so that they can form esters with polyhydric alcohols, which will be described later. By introducing such fatty acids into alkyd resins, it is possible to improve the transferability of the ink composition using the alkyd resin and to increase the ratio of biomass-derived components. From this 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 used. Various types of fatty acids can be mentioned, and these can be used alone or in combination of two or more.

[0030] The polybasic acid is a compound having a plurality of carboxy groups, and is a component for polycondensation with the polyhydric alcohol described later to obtain a high 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-sodiosulfoisophthalic acid, fumaric acid, benzoic acid, tert-butylbenzoic acid, tetrahydrophthalic anhydride, maleic anhydride, succinic acid, succinic anhydride, fumaric acid, sebacic acid, azelaic acid, tetrabromophthalic anhydride, methylhimic anhydride, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, trimellitic anhydride, and methylcyclohexenedicarboxylic anhydride. Among these, phthalic acid or phthalic anhydride is preferably used. These polybasic acids may be used alone or in combination of two or more kinds.

[0031] The polyhydric alcohol forms an ester with the above-mentioned acid component, and increases the molecular weight of these components. As the polyhydric alcohol, any of those that have been used in the synthesis of alkyd resins can be used without limitation, and examples of such polyhydric alcohol include compounds having two or more hydroxyl groups.

[0032] In addition to the above-mentioned pentaerythritol, such compounds include 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, hexamethionyl glycol, and the like. Examples of the polyether polyol include ethylene 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 and propylene oxide copolymer modified compounds of bisphenol A, copolymer polyether polyols of ethylene oxide and propylene oxide, polycarbonate diols, adamantane diols, polyether diols, polyester diols, polycaprolactone diols, etc. These may be used alone or in combination of two or more.

[0033] To prepare an alkyd resin, a method can be mentioned in which a reaction vessel containing these acid components and polyhydric alcohol is charged with an inert gas such as nitrogen gas, a small amount of a solvent such as xylene is added, and the mixture is heated to remove water by azeotropy with the condensed water. In addition, an alkyd resin that provides a highly crosslinked and tough cured coating can be obtained by performing a polycondensation reaction of these acid components and polyhydric alcohol as the first step, and performing a polycondensation reaction using a polybasic acid having three or more functional groups such as trimellitic acid as the second step. The reaction temperature can be about 170 to 250°C, and the reaction time can be about 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 elapses. That is, the reaction can be completed when the decrease in the acid value of the reaction mixture accompanying the polycondensation stops. The polycondensation reaction can be performed in a shorter time by distilling the water generated by the polycondensation out of the system or by using a reaction catalyst. Examples of the reaction catalyst include tetrabutyl zirconate, monobutyltin oxide, zirconium naphthate, and tetrabutyl titanate.

[0034] The mass average molecular weight of the alkyd resin is preferably less than 10,000, more preferably not more than 8,500, and even more preferably not more than 7,000. As described above, in the present invention, the impact resistance of the ink film formed on the metal after retort treatment can be improved by using neutral carbon black, and it is preferable to use such an alkyd resin having a relatively low molecular weight because the impact resistance can be further improved.

[0035] The mass average molecular weight of the resin in the present invention can be measured by gel permeation chromatography (GPC).As an example, the value can be obtained as the mass average molecular weight converted into polystyrene by performing chromatography using Waters Acquity APC (Waters) as a GPC device, 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) as columns, tetrahydrofuran as a mobile phase, column temperature 40℃, flow rate 0.8mL / min, RI detector, sample injection concentration 10mg / 5mL, and injection amount 10μL.

[0036] The content of the alkyd resin in the ink composition is preferably from 10 to 40 mass % relative to the entire composition, and more preferably from 20 to 40 mass % relative to the entire composition.

[0037] Rosin-modified resins are resins prepared using rosin as one of the raw materials. Rosin contains a mixture of resin acids such as abietic acid, palustric acid, isopimaric acid, and levopimaric acid, and these resin acids contain hydrophilic and chemically active carboxyl groups, some of which have conjugated double bonds. Therefore, various rosin-modified resins are prepared by combining polyhydric alcohols and polybasic acids and polycondensing them, adding resol, which is a condensate of phenol, to the benzene ring contained in the rosin skeleton, or by carrying out a Diels-Alder reaction with maleic anhydride or maleic acid, which are dienophiles, to add maleic acid or maleic anhydride skeletons. Various types of such rosin-modified resins are commercially available, and it is also possible to obtain and use them.

[0038] Examples of the rosin modified resin include rosin ester resin, maleic rosin, fumarated rosin resin, rosin modified maleic acid resin, rosin modified fumaric acid resin, rosin modified phenolic resin, rosin modified alkyd resin, rosin modified polyester resin, etc. In the present invention, any of the rosin modified resins may be used, but among these, rosin ester resins are preferably used.

[0039] The rosin-modified resin used in the present invention is preferably one having a hydroxyl value of 10 mgKOH / g or more. By including such a rosin-modified resin having a high hydroxyl value in the ink composition of the present invention, the transferability of the ink composition during printing can be improved, and the polarity of the composition itself becomes high, so that the affinity with the aqueous OP varnish, which also has a high polarity, is increased, and even if the ink composition is applied wet-on-wet, repelling is suppressed. 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 an example is about 200 mgKOH / g, preferably about 150 mgKOH / g, and more preferably about 100 mgKOH / g.

[0040] Although not particularly limited, the acid value of the rosin-modified resin is preferably 100 mgKOH / g or less. The acid value of the rosin-modified resin is preferably 100 mgKOH / g or less, since it is possible to suppress repelling when the aqueous OP varnish is applied wet-on-wet, and to achieve printability such as suppressing misting and bubbly. 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.

[0041] The rosin-modified resin is used in a state in which 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 in a state in which it is dissolved or dispersed in a solvent, or may be used in a state in which a divalent or higher metal alkoxy compound is added as a gelling agent to the dissolved varnish obtained by dissolving the resin when preparing the varnish, and the resin is used in a gelled varnish. Among these, it is preferable to prepare a dissolved varnish from the rosin-modified resin and use this to prepare the ink composition, since this can improve the transferability of the ink composition during printing. In addition, by preparing a gelled varnish from the rosin-modified resin and using this to prepare the ink composition, the ink composition is given an appropriate viscoelasticity, which can improve the flowability and reduce misting, and can form a tougher cured coating.

[0042] The content of the rosin-modified resin in the ink composition is preferably 5 to 50 mass% relative to the entire composition, more preferably 5 to 25 mass% relative to the entire composition, and even more preferably 7 to 20 mass% relative to the entire composition.

[0043] In addition to the above alkyd resin or rosin-modified resin, the ink composition of the present invention can also contain resins that have been used in the preparation of conventional ink compositions for metal printing. That is, depending on the required performance such as printability and coating film properties, known resins that are compatible with the above alkyd resin or rosin-modified 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.

[0044] [solvent] The solvent used in the ink composition of the present invention can be any solvent that has been used in the field of ink for metal printing, without any particular limitation. Examples of such solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, alkylbenzenes, polyalkylene glycols, etc., each of which has a boiling point range of about 230 to 400°C. The ink composition of the present invention is preferably a solvent having a solubility parameter (sp value) of 10.00 (cal / cm 3 ) 1 / 2 and essentially contains at least one selected from the group consisting of compounds represented by the following general formula (1): 3 ) 1 / 2 The specific solvent is at least one solvent selected from the group consisting of compounds represented by the following general formula (1) and having an sp value of 9.80 (cal / cm 3 ) 1 / 2 The lower limit of the sp value in the specific solvent is preferably 8.50 (cal / cm 3 ) 1 / 2 The preferred range is 9.00 (cal / cm 3 ) 1 / 2 It is more preferable to mention the degree. A specific solvent having such an sp value can also be said to be a polyalkylene glycol monoalkyl ether having hydrophobic properties. The reason for using such a specific solvent having hydrophobic properties in the present invention is based on the finding of the present inventors that the occurrence of misting during printing can be significantly reduced by using a hydrophobic polyalkylene glycol monoalkyl ether (i.e., a specific solvent) instead of an alkylbenzene-based solvent or a hydrophilic polyalkylene glycol monoalkyl ether-based solvent, which have been widely used in the field of ink compositions for metal printing.

[0045] [ka]

[0046] In the above general formula (1), 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 [-(CH2)2-], a propylene group [-CH2(CH3)-CH2- or -CH2CH2(CH3)-], a trimethylene group [-(CH2)3-], and an isopropylidene group [-C(CH3)2-]. Among these, a propylene group is preferred. In this case, the divalent group represented by AO in general formula (1) is an oxypropylene group.

[0047] In the above general formula (1), R is an alkyl group having 1 to 13 carbon atoms, which may have a branched and / or cyclic structure. This alkyl group may be not only an aliphatic group but also an alicyclic group. Examples of such an alkyl group 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, and a cyclohexyl group.

[0048] In the above general formula (1), n ​​is an integer of 2 to 8. When n is 2 or more, a sufficient boiling point of the specific solvent can be secured to provide stability to the ink composition on a printing machine, which is preferable, and when n is 8 or less, a viscosity suitable for the solvent of the ink composition can be achieved.

[0049] Examples of the compound 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, and hexapropylene glycol monomethyl ether.

[0050] In the present invention, the sp value is calculated by the Fedros method (see the literature: RF Fedros, Polym. Eng. Sci., 14(2)147(1974)).

[0051] 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 entire composition. Among the solvents, the content of the specific solvent is preferably 15 to 40% by mass, based on the entire composition, and it is preferable that all of the solvents in the composition are the specific solvent.

[0052] The ink composition of the present invention preferably contains an alkanolamine in addition to the above-mentioned components. By containing an alkanolamine in the ink composition of the present invention, it is possible to reduce misting during printing and improve the impact resistance of the printed film after retort treatment.

[0053] Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, ethylmonoethanolamine, n-butylmonoethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, etc. Among these, triethanolamine is preferred.

[0054] The content of the alkanolamine in the ink composition of the present invention is preferably from 0.1 to 3 mass %, and more preferably from 0.1 to 1 part by mass, based on the entire composition.

[0055] Other components that can be added to the ink composition of the present invention, as necessary, include known hardeners; pigment dispersants; waxes; extender pigments such as silica particles, calcium carbonate, benton clay, kaolin, and talc; stabilizers, and the like.

[0056] As the curing agent, for example, an amino resin such as a melamine resin or a benzoguanamine resin can be used.

[0057] Silica particles are commercially available as SiO2 powder, and are easily available in the form of hydrophilic particles that have not been surface-treated or that have been hydrophilized, or hydrophobic particles that have been hydrophobized. Among these silica particles, hydrophobic silica particles are preferably used in the ink composition of the present invention. By using hydrophobic silica particles, the transferability of the ink composition during printing can be improved, and the fluidity of the ink composition can be increased, which is preferable. The content of silica particles in the ink composition is preferably 0.5 to 15% by mass, and more preferably 1 to 5% by mass.

[0058] The ink composition of the present invention can be prepared by mixing the above-mentioned components and using a conventional method, such as a roll mill, a ball mill, a bead mill, etc. The viscosity of the ink composition is, for example, 10 to 70 Pa s at 25°C as measured by a Raleigh viscometer, but is not particularly limited.

[0059] The metal for metal printing in the ink composition of the present invention is not particularly limited, but examples thereof include galvanized or tinned iron plate, aluminum plate, and metal cans made of these metal materials. EXAMPLES

[0060] The ink composition of the present invention will be explained in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0061] [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 of esterification, and then 0.70 parts by mass of trimellitic anhydride was added and heated at 165°C for 30 minutes under a nitrogen atmosphere to perform the second stage of esterification. These esterification reactions were carried out according to a conventional method to obtain alkyd resin 1 having a mass average molecular weight of 4,376 and a number average molecular weight of 1,995. 15.0 parts by mass of tripropylene glycol monobutyl ether was added to this alkyd resin 1 to obtain alkyd resin varnish 1. The sp value of this tripropylene glycol monobutyl ether was 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0062] [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 of esterification, and then 0.70 parts by mass of trimellitic anhydride was added and heated at 165°C for 30 minutes under a nitrogen atmosphere to perform the second stage of 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. 10.0 parts by mass of tripropylene glycol monobutyl ether was added to this alkyd resin 2 to obtain an alkyd resin varnish 2. The sp value of this tripropylene glycol monobutyl ether was 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0063] [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 under a nitrogen atmosphere at 220°C until the acid value of the mixture reached 7 mgKOH / g to perform the first stage of esterification, and then 0.70 parts by mass of trimellitic anhydride was added and heated at 165°C for 30 minutes under a nitrogen atmosphere to perform the second stage of 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. 10.0 parts by mass of tripropylene glycol monobutyl ether was added to this alkyd resin 3 to obtain an alkyd resin varnish 3. The sp value of this tripropylene glycol monobutyl ether was 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0064] [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 mgKOH / g to perform the first stage of esterification, and then 0.70 parts by mass of trimellitic anhydride was added and heated at 165°C for 30 minutes under a nitrogen atmosphere to perform the second stage of esterification. These esterification reactions were carried out according to a conventional method to obtain alkyd resin 4 having a mass average molecular weight of 6,049 and a number average molecular weight of 2,591. 21.8 parts by mass of tripropylene glycol monobutyl ether was added to this alkyd resin 4 to obtain alkyd resin varnish 4. The sp value of this tripropylene glycol monobutyl ether was 9.73 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0065] [Preparation of alkyd resin varnish 5] To the alkyd resin 2 obtained by the procedure for preparing the alkyd resin varnish 2, triethylene glycol monobutyl ether was added in place of tripropylene glycol monobutyl ether to obtain an alkyd resin varnish 5. The sp value of this triethylene glycol monobutyl ether was 10.32 (cal / cm 3 ) 1 / 2 and does not fall under the category of the specific solvent in the present invention.

[0066] [Preparation of alkyd resin varnish 6] To the alkyd resin 2 obtained by the procedure for preparing the alkyd resin varnish 2, pentapropylene glycol monobutyl ether was added in place of tripropylene glycol monobutyl ether to obtain an alkyd resin varnish 6. The sp value of pentapropylene glycol monobutyl ether is 9.42 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0067] [Preparation of alkyd resin varnish 7] To the alkyd resin 2 obtained by the procedure for preparing the alkyd resin varnish 2, tetrapropylene glycol mono-2-ethylhexyl ether was added in place of tripropylene glycol monobutyl ether to obtain an alkyd resin varnish 7. The sp value of tetrapropylene glycol mono-2-ethylhexyl ether is 9.32 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0068] [Preparation of rosin-modified resin varnish 1] 63.2 parts by mass of rosin ester resin (hydroxyl value 20-30 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, to obtain rosin modified resin varnish 1. The sp value of this tripropylene glycol monobutyl ether was 9.73 (cal / cm 3 ) 1 / 2and corresponds to the specific solvent in the present invention.

[0069] [Preparation of rosin-modified resin varnish 2] A rosin-modified resin varnish 2 was obtained in the same manner as in the preparation of the 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 was 10.32 (cal / cm 3 ) 1 / 2 and does not fall under the category of the specific solvent in the present invention.

[0070] [Preparation of rosin-modified resin varnish 3] A rosin-modified resin varnish 3 was obtained in the same manner as in the preparation of the 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 was 9.42 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0071] [Preparation of rosin-modified resin varnish 4] Rosin-modified resin varnish 4 was obtained in the same manner as in the preparation of 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 was 9.32 (cal / cm 3 ) 1 / 2 and corresponds to the specific solvent in the present invention.

[0072] [Examples 1 to 12, Comparative Examples 1 to 3] Each of the ink compositions of Examples 1 to 12 and Comparative Examples 1 to 3 was prepared by mixing the components according to the formulations in Tables 1 to 3 and kneading the resulting mixtures in a three-roll mill. In addition, in Tables 1 to 3, "Neutral CB1" is HIBLACK200L (neutral carbon black, primary particle size 28 nm, DBP oil amount 62 ml / 100 g, pH 8.0) manufactured by Orion Engineered Carbons, "Neutral CB2" is ELFTEX415 (neutral carbon black, primary particle size 25 nm, DBP oil amount 55 ml / 100 g, pH 6.0 to 8.0) manufactured by Cabot Corporation, and "Neutral CB3" is Regal250R (neutral carbon black, primary particle size 34nm, DBP oil amount 48ml / 100g, pH 6.0 to 8.0), "neutral CB4" is Regal350R (neutral carbon black, primary particle diameter 48nm, DBP oil amount 46ml / 100g, pH 6.0 to 8.0) manufactured by Cabot Corporation, "acidic CB1" is Mitsubishi carbon black MA7 (acidic carbon black, primary particle diameter 24nm, DBP oil amount 66ml / 100g, pH 3.0) manufactured by Mitsubishi Chemical Corporation, and "acidic CB2" is Mogul E (acidic carbon black, primary particle diameter 48nm, DBP oil amount 49ml / 100g, pH 2.5) manufactured by Cabot Corporation. In addition, in Tables 1 to 3, "specific solvent 1" is tripropylene glycol monobutyl ether (sp value 9.73 (cal / cm 3 ) 1 / 2 ), and "specific solvent 2" is pentapropylene glycol monobutyl ether (sp value 9.42 (cal / cm 3 ) 1 / 2 ), and "specific solvent 3" is tetrapropylene glycol mono-2-ethylhexyl ether (sp value is 9.32 (cal / cm 3 ) 1 / 2 ), and the "non-specific solvent" is triethylene glycol monobutyl ether (sp value 10.32 (cal / cm 3 ) 1 / 2 ) and "silica" refers to silica particles with a hydrophobic surface (manufactured by Nippon Aerosil Co., Ltd., product name Aerosil R972). The numerical values ​​of each blend amount in Tables 1 to 3 are all parts by mass.

[0073] [Misting amount evaluation] For each of the ink compositions of the Examples and Comparative Examples, 2.6 cc of the ink composition was applied to the rotating roller of the ink meter and uniformly spread, 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 the ink composition adhering to the surface by misting was compared. The measurement was performed with the roller kept at 40°C. The change in mass of the blank sheet before and after the measurement was calculated, and this was taken as the misting amount (mg). The larger the change in mass of the blank sheet before and after the measurement, the greater the amount of the ink composition scattered, so the smaller this value, the better the result. Based on the calculated misting amount (mg), evaluation was performed according to the following criteria. The evaluation results are shown in the "misting" column of Tables 1 to 3. ○: The amount of misting was less than 5 mg. △: The amount of misting was 5mg or more and less than 10mg. ×: The amount of misting was 10 mg or more.

[0074] [Impact resistance evaluation after retort processing] For each of the Examples and Comparative Examples, 0.2 cc of the ink composition was spread on an aluminum substrate having a thickness of 50 μm using an RI spreader to obtain a spread product. Then, a retort overprint varnish (manufactured by AkzoNobel) was applied to the spread surface of the spread product using a No. 0.4 bar coater (Meyer bar), and the product was kept in an oven at 240° C. for 2 minutes to obtain a retort sample. Then, 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 product was subjected to impacts at four points from the opposite side of the painted surface using a DuPont impact tester (Toyo Seiki Seisakusho Co., Ltd., product name H-50) under the following conditions: impact point diameter: 1 / 4Φ (6.35 mm), weight: 300 g, weight drop height: 50 mm, and the degree of peeling of the coating film on the painted surface was evaluated according to the following criteria. The results are shown in the "Impact resistance after retort" column in Tables 1 to 3. ○: In all four locations, the coating did not peel off where it came into contact with the core. ×: At least a part of the coating film at the part that came into contact with the striking core was peeled off, exposing the aluminum base material at one or more of the four parts.

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3]

[0078] As is clear from Tables 1 to 3, by combining neutral carbon black with a specific solvent that satisfies a predetermined solubility parameter to form an ink composition for metal printing, it is understood that the misting suitability and impact resistance after retort are improved.

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 selected from the group consisting of compounds represented by the following general formula (1): The ink composition for metal printing further comprises a rosin ester resin. 【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, wherein the divalent group represented by AO in formula (1) is an oxypropylene group.

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

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