Set of ink composition for metal printing and aqueous overprint varnish, and ink composition for metal printing

Abstract

[Problem] To provide: an ink composition for metal printing which, even when an aqueous overprint varnish having an organic solvent content of less than 10 mass% is applied in a wet-on-wet manner onto an ink coating film in an application amount of 30 mg / dm2 or less, can suppress the occurrence of cissing of the varnish on the ink coating film and the deterioration in strength of the coating film; and a set of the ink composition and an overprint varnish. [Solution] An ink composition for metal printing which comprises a coloring pigment, an alkyd resin and a solvent is used, the ink composition for metal printing being characterized in that the solvent includes at least one compound selected from the group consisting of compounds represented by general formula (1) and the alkyd resin is a fatty acid-modified alkyd resin having a fatty acid modification amount of 25-50 mass%. In general formula (1), As each independently represent a C2-4 alkylene group that may be branched, R represents a C1-13 alkyl group that may have a branched and / or cyclic structure, and n is an integer of 2-8.

Description

Set of ink composition for metal printing and water-based overprint varnish, and ink composition for metal printing

[0001] 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, metal printing ink compositions are used, the main vehicle components of which are binder resins such as alkyd resins, polyester resins, and epoxy resins, and organic solvents such as mineral oils or higher alcohols.

[0002] Furthermore, these printed surfaces are generally coated with an overprint varnish to improve the adhesion, bending resistance, impact resistance, abrasion resistance, etc. 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.

[0003] When printing on the outer surface of a metal, ink is printed using an offset printing machine, dry offset printing machine, or the like, and then an overprint varnish is applied wet-on-wet onto the ink coating using a coater, or the like, and then baked at 150 to 280°C.

[0004] However, in recent years, due to concerns about air pollution caused by solvents and concerns about hygiene and safety in the printing environment, it has become common to use water-based overprint varnishes rather than the traditional solvent-based ones, even in the field of metal printing. However, even water-based overprint varnishes do not contain any solvents; they contain a hydrophilic organic solvent in combination with water. These hydrophilic organic solvents are typically recovered and burned during thermal drying after application. Therefore, from the perspective of reducing carbon dioxide emissions, even water-based overprint varnishes require a reduction in the amount of organic solvent contained in the overprint varnish or the amount of overprint varnish applied. However, using overprint varnishes with reduced organic solvent content or reducing the amount of overprint varnish applied can lead to problems such as varnish repellency on the ink coating and reduced coating strength due to uneven application.

[0005] As improvements to ink compositions for suppressing cissing of aqueous overprint varnish on ink coating films, various proposals have been made, for example, in Patent Documents 1 to 4. However, in the test examples of the ink compositions proposed in these documents, the amount of varnish applied was always at a normal level of 50 to 60 mg / dm ２ The range of the organic solvents used in the varnish composition was unclear, and the amount of organic solvents used in the varnish composition was unknown.

[0006] JP-A-2009-249435 JP-A-6-25583 Patent No. 7353551 Patent No. 7368674

[0007] The present invention has been made in view of the above circumstances, and provides a method for manufacturing a water-based overprint varnish having an organic solvent content of less than 10% by mass, applied in an amount of 30 mg / dm ２ The present invention aims to provide an ink composition for metal printing that can suppress varnish cissing on the ink coating and a decrease in coating film strength even when applied wet-on-wet as described below, and a set of such an ink composition for metal printing and an overprint varnish. In the present invention, the application amount of the overprint varnish (mg / dm ２) is the unit area (1 dm ２ The solid mass of the overprint varnish applied per 1000 sq. m. (i.e., mass after drying) is used.

[0008] A smaller amount of organic solvent contained in the aqueous overprint varnish leads to a correspondingly larger amount of water contained in the aqueous overprint varnish. Furthermore, a larger amount of water contained in the aqueous overprint varnish leads to a higher surface tension of the aqueous overprint varnish, which makes it more likely to cause cissing and uneven application when applied wet-on-wet to an ink coating. Meanwhile, when considering the amount of water to be applied to the aqueous overprint varnish, the greater the amount applied in wet-on-wet application, the less likely cissing and uneven application occurs. Therefore, reducing the amount of organic solvent contained in the aqueous overprint varnish and reducing the application amount can be said to be a very strict condition that makes cissing and uneven application more likely to occur. To overcome such strict conditions, the present inventors reviewed the formulation of the ink composition that serves as the base for the aqueous overprint varnish, and by using a solvent selected from the group consisting of compounds represented by the following general formula (1) as the solvent in the ink composition and a fatty acid-modified alkyd resin with a fatty acid modification content of 25 to 50% by mass as the resin, it was possible to produce an aqueous overprint varnish with an organic solvent content of less than 10% by mass at an application amount of 30 mg / dm ２ It has been found that even when wet-on-wet coating is performed as described below, it is possible to suppress the reduction in coating film strength due to varnish cissing on the ink coating film and uneven application. The present invention is based on this finding and provides the following.

[0009] (1) The present invention is an ink composition for metal printing comprising a color pigment, an alkyd resin, and a solvent, characterized in that the solvent comprises at least one compound selected from the group consisting of compounds represented by the following general formula (1), and the alkyd resin is a fatty acid-modified alkyd resin, and the amount of fatty acid modification is 25 to 50 mass%. (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.)

[0010] (2) Furthermore, the present invention provides a compound in which A in the above general formula (1) is an ethylene group (—CH ２ CH ２ -) or propylene group (-CH(CH ３ ) CH ２ - or -CH ２ -CH(CH ３ )-) is the ink composition for metal printing according to (1).

[0011] (3) The present invention also provides an ink composition for metal printing according to item (1) or (2), characterized in that the ink composition is used for undercoating printing for applying an aqueous overprint varnish having an organic solvent content of less than 10% by mass.

[0012] (4) The present invention also provides the ink composition for metal printing according to any one of (1) to (3), wherein the content of aromatic compounds in the solvent is less than 10% by mass.

[0013] (5) The present invention also provides the ink composition for metal printing according to any one of (1) to (4), further comprising a rosin-modified resin.

[0014] (6) The present invention also relates to a set comprising an ink composition for metal printing and an aqueous overprint varnish, wherein the ink composition for metal printing comprises a color pigment, an alkyd resin, and a solvent A, and the solvent A comprises at least one selected from the group consisting of compounds represented by the following general formula (1), the alkyd resin is a fatty acid-modified alkyd resin, and the amount of fatty acid modification is 25 to 50 mass %, and the content of organic solvents contained in the aqueous overprint varnish is less than 10 mass % relative to the total amount of the aqueous overprint varnish. (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] (7) The present invention also provides a compound in which A in the above general formula (1) is an ethylene group (—CH ２ CH ２ -) or propylene group (-CH(CH ３ ) CH ２ - or -CH ２ -CH(CH ３ )-) is a set according to item (6).

[0016] (8) The present invention also relates to the set according to item (6) or (7), wherein the content of aromatic compounds in the solvent A is less than 10% by mass.

[0017] (9) The present invention also relates to the set according to any one of items (6) to (8), wherein the ink composition for metal printing further contains a rosin-modified resin.

[0018] According to the present invention, an aqueous overprint varnish containing less than 10% by mass of organic solvent is applied in an amount of 30 mg / dm ２ Provided below is an ink composition for metal printing that can suppress varnish cissing on the ink coating and a decrease in coating strength even when applied wet-on-wet, and a set of such an ink composition for metal printing and an aqueous overprint varnish.

[0019] Hereinafter, one embodiment of the ink composition for metal printing of the present invention and one embodiment of a set of the ink composition for metal printing and an aqueous overprint varnish will be described. The present invention is not limited to the following embodiment, and can be practiced with appropriate modifications within the scope of the present invention. The aqueous overprint varnish is an overprint varnish containing a combination of a hydrophilic organic solvent and water as the solvent, as described above. In this specification, the overprint varnish will be abbreviated as OP varnish as appropriate.

[0020] <Ink Composition for Metal Printing> First, one embodiment of the ink composition for metal printing of the present invention will be described. 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 the printing plate or the offset printing method using a lithographic plate as the printing plate, but can be applied to all printing methods commonly used in metal printing. Furthermore, the ink composition of the present invention can suppress cissing and uneven application of an aqueous OP varnish applied wet-on-wet immediately after printing with the ink composition, and therefore can be preferably applied not only to two-piece can printing, which employs such printing and application methods, but also to three-piece can printing. In particular, the ink composition of the present invention can be applied to an aqueous OP varnish containing less than 10% by mass of organic solvent at a coating amount of 30 mg / dm ２ This has the great advantage that repelling and uneven coating are suppressed even when coating at temperatures below 100°C. This significantly reduces the amount of carbon dioxide emitted from the organic solvents contained in the water-based OP varnish during printing.

[0021] The ink composition of the present invention is a metal printing ink composition containing a color pigment, an alkyd resin, and a solvent, characterized in that the solvent contains at least one compound selected from the group consisting of compounds represented by general formula (1) above, and the alkyd resin is a fatty acid-modified alkyd resin with a fatty acid modification content of 25 to 50% by mass. In addition to these components, the ink composition of the present invention can also contain a rosin-modified resin as another resin. Each component will be described below.

[0022] [Alkyd Resin] The ink composition of the present invention contains a fatty acid-modified alkyd resin, the fatty acid modification content of which is 25 to 50% by mass. Hereinafter, the fatty acid-modified alkyd resin will also be referred to simply as alkyd resin. Alkyd resins are condensation polymers of polyhydric alcohols and polybasic acids, a type of polyester. However, fatty acid-modified alkyd resins can be synthesized by condensation polymerization with vegetable oils and / or fatty acids. That is, by adding a monobasic fatty acid to the condensation polymer during the formation of the alkyd resin, the fatty acid is incorporated into the alkyd resin structure, thereby synthesizing the fatty acid-modified alkyd resin. Furthermore, by adding a vegetable oil during the formation of the condensation polymer, the vegetable oil undergoes ester exchange with the polyhydric alcohol to form a fatty acid, which is then incorporated into the alkyd resin structure as a fatty acid, thereby synthesizing the fatty acid-modified alkyd resin. The proportion of fatty acid-derived components in the alkyd resin is referred to as the fatty acid modification content. The fatty acid modification content of the alkyd resin used in the present invention is 25 to 50% by mass. A fatty acid modification amount of 25% by mass or more is preferred because it allows the ink composition to maintain good transferability during printing, and a fatty acid modification amount of 50% by mass or less can suppress cissing and coating unevenness when a water-based OP varnish with a low organic solvent content is applied wet-on-wet to the ink coating surface with a small application amount, and can also reduce misting during printing.More preferably, the fatty acid modification amount of the alkyd resin is 25 to 45% by mass.

[0023] Fatty acids are obtained by hydrolyzing natural fats and oils such as vegetable oils and animal oils, and because they have one carboxyl group, they can form esters with the polyhydric alcohols described below. Examples of fatty acids include fatty acids such as linseed oil, tung oil, safflower oil, soybean oil, tall oil, rice bran oil, palm oil, castor oil, dehydrated castor oil, sunflower oil, and coconut oil, as well as caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, eleostearic acid, and 12-hydroxystearic acid. Among these, coconut oil fatty acids are preferred. These fatty acids can be used alone or in combination of two or more. Furthermore, the above-mentioned vegetable oils can be used together with or in place of the fatty acids.

[0024] The polybasic acid is a compound having multiple carboxy groups and is a component for polycondensation with a polyhydric alcohol (described later) 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-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. Of these, preferred examples include isophthalic acid, phthalic acid, phthalic anhydride, trimellitic anhydride, etc. These polybasic acids may be used alone or in combination of two or more.

[0025] The polyhydric alcohol forms an ester with the above-mentioned fatty acid or polybasic acid, thereby increasing 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 thereof include compounds having two or more hydroxyl groups.

[0026] Such compounds include pentaerythritol, trimethylolpropane, glycerin, 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, and 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- and propylene oxide-copolymerized compounds of bisphenol A, copolymerized 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.

[0027] To prepare an alkyd resin, a reaction vessel containing a polybasic acid, a polyhydric alcohol, and a fatty acid and / or a vegetable oil is charged with a small amount of a solvent such as xylene, and the mixture is heated while an inert gas such as nitrogen gas is introduced. The mixture is then azeotropically distilled with the condensed water to remove the water, resulting in condensation polymerization. Alternatively, this condensation polymerization reaction can be used as the first step, followed by condensation polymerization using a trifunctional or higher polybasic acid such as trimellitic acid in the second step to obtain an alkyd resin that provides a highly crosslinked, tough cured coating. The reaction temperature can be approximately 170 to 250°C, and the reaction time can be approximately 5 to 25 hours, but is not particularly limited. The completion of the reaction can be determined by monitoring the acid value of the reaction mixture over time. That is, the reaction is considered complete when the decrease in the acid value of the reaction mixture accompanying the condensation polymerization stops. The condensation polymerization reaction can be carried out in a shorter time by distilling the water generated by the condensation polymerization 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.

[0028] The content of the alkyd resin in the ink composition is preferably 20 to 70 mass % based on the total mass of the composition, and more preferably 30 to 60 mass % based on the total mass of the composition. The alkyd resin may be used in the form of a varnish obtained by dissolving it in a solvent described below.

[0029] [Rosin-Modified Resin] In addition to the alkyd resin, other resins may also be used in the ink composition of the present invention. A preferred example of such a resin is a rosin-modified resin. A rosin-modified resin is a resin 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. These resin acids contain hydrophilic and chemically active carboxyl groups, and some also contain conjugated double bonds. Therefore, various rosin-modified resins have been prepared by condensation polymerization of a combination of polyhydric alcohols and polybasic acids, adding a resole (a phenol condensate) to the benzene ring contained in the rosin skeleton, or performing a Diels-Alder reaction with dienophiles such as maleic anhydride or maleic acid to add a maleic acid or maleic anhydride skeleton. Various rosin-modified resins are commercially available, and they can be obtained and used. By using a rosin-modified resin in the ink composition of the present invention, it is possible to suppress the occurrence of misting during printing and also to increase the biomass content in the ink composition without impairing various required performances.

[0030] Examples of rosin-modified resins include rosin ester resins, maleated rosin, fumarated rosin resins, rosin-modified maleic acid resins, rosin-modified fumaric acid resins, rosin-modified phenolic resins, rosin-modified alkyd resins, rosin-modified polyester resins, etc. In the present invention, any of the rosin-modified resins may be used, but among these, rosin ester resins are preferably used.

[0031] Furthermore, it is preferable to use a rosin-modified resin with a hydroxyl value of 10 mgKOH / g or more. By including such a rosin-modified resin with a high hydroxyl value in the ink composition of the present invention, the transferability of the ink composition during printing can be further improved. Furthermore, as the polarity of the composition itself increases, the affinity with aqueous OP varnishes, which also have high polarity, is enhanced, and even when the ink composition is applied wet-on-wet, repelling and uneven application can be 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.

[0032] Furthermore, although not particularly limited, the acid value of the rosin-modified resin is preferably 100 mgKOH / g or less. Having an acid value of 100 mgKOH / g or less is preferable because it can achieve both suppression of repelling and uneven application when the aqueous OP varnish is applied wet-on-wet, and printability such as suppression of misting and blotting. 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.

[0033] The rosin-modified resin is used in the form of a varnish obtained by heating with a solvent described below to dissolve or disperse it. The rosin-modified resin may be used as a dissolved varnish in which it remains dissolved or dispersed in a solvent, or may be used in the form of a gelled varnish obtained by dissolving the resin in the varnish during preparation by adding a divalent or higher metal alkoxy compound as a gelling agent to the dissolved varnish. Among these, preparing a dissolved varnish from the rosin-modified resin and using it to prepare an ink composition is preferred, as it can improve the transferability of the ink composition during printing. Furthermore, preparing a gelled varnish from the rosin-modified resin and using it to prepare an ink composition can impart appropriate viscoelasticity to the ink composition, thereby improving flowability and reducing misting, and also forming a tougher cured coating.

[0034] The content of the rosin-modified resin in the ink composition is preferably 1 to 20 mass% relative to the total composition, more preferably 1 to 15 mass% relative to the total composition, and even more preferably 2 to 10 mass% relative to the total composition.

[0035] In addition to the alkyd resins and rosin-modified resins described above, the ink composition of the present invention can also contain resins that have been used in the preparation of ink compositions for metal printing. That is, known resins can be used alone or in combination of two or more depending on the required performance, such as printability and coating properties. Examples of such resins include polyester resins, petroleum resins, epoxy resins, ketone resins, amino resins, and benzoguanamine resins.

[0036] [Solvent] The ink composition of the present invention contains at least one solvent selected from the group consisting of compounds represented by the following general formula (1): Hereinafter, the at least one solvent selected from the group consisting of compounds represented by the following general formula (1) will also be referred to as a specific solvent.

[0037]

[0038] In the general formula (1), each A is independently determined and is an alkylene group having 2 to 4 carbon atoms, which may be branched. Examples of such an alkylene group include an ethylene group [—(CH ２ ) ２ -], propylene group [-CH ２ (CH ３ )-CH ２ - or -CH ２ CH ２ (CH ３ )-], trimethylene group [-(CH ２ ) ３ -], isopropylidene group [-C(CH ３ ) ２ Among these, an ethylene group [-(CH ２ ) ２ -] or a propylene group [-CH(CH ３ ) CH ２ - or -CH ２ -CH(CH ３ )-] can be mentioned as a preferred example.

[0039] In the 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.

[0040] In the above general formula (1), n ​​is an integer of 2 to 6. When n is 2 or more, it is possible to ensure a sufficient boiling point of the specific solvent to provide stability to the ink composition on a printing machine, which is preferable, and when n is 6 or less, it is possible to achieve a viscosity that is preferable as a solvent for the ink composition.

[0041] Examples of the compound represented by the general formula (1) include diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monooctyl ether, diethylene glycol tridecyl ether, triethylene glycol monobutyl ether, triethylene glycol monodecyl ether, tetraethylene glycol monohexyl ether, pentaethylene glycol monobutyl ether, hexaethylene glycol monomethyl ether, 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, etc. Among these, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, etc. are preferred. These can be used alone or in combination of two or more.

[0042] The content of the specific solvent in the ink composition of the present invention is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, of the entire composition. A content of the specific solvent of 15% by mass or more of the entire composition is preferred because it can effectively suppress repelling and uneven application when the aqueous OP varnish is applied wet-on-wet.

[0043] In the ink composition of the present invention, it is preferable that the content of aromatic solvents such as linear alkylbenzenes, which have been used as solvents in ink compositions for metal printing, is less than 10% by mass. By keeping the content of aromatic compound-based solvents to less than 10% by mass, repelling and uneven application can be effectively suppressed when the aqueous OP varnish is applied wet-on-wet, which is preferable.

[0044] [Coloring Pigment] The coloring pigment is a component for imparting coloring power to the ink composition. Examples of the coloring pigment include, without particular limitation, organic and / or inorganic pigments that have conventionally been used in printing ink compositions.

[0045] Such color pigments include pigment yellow 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 15, 16, 17, 24, 32, 34, 35, 36, 37, 41, 42, 43, 49, 53, 55, 60, 61, 62, 63, 65, 73, 74, 75, 77, 81, 83, 87, 93, 94, 95, 97, 98, 99, 100, 101, 104, 105, 106, 108, 109, 110, 111, 113, 114, 116, 117, 119, 120, 123, 124, 126, 127, 128, 129, 130, 133, 138, 139, 150, 151, 152, 153, 154, 155, 165, 167, 168, 169, 170, 172, 173, 174, 175, 176, 179, 180, 181, 182, 183, 184, 185, 191, 193, 194, 199, 205, 206, 209, 212, 213, 214, 215, 219; Pigment Orange 1, 2, 3, 4, 5, 13, 15, 16, 17, 19, 20, 21, 24, 31, 34, 36, 38, 40, 43, 46, 48, 49, 51, 60, 61, 62, 64, 65, 66, 67, 68, 69, 71 , 72, 73, 74, 81; Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 21, 22, 23, 31, 32, 38, 41, 48, 48:1, 48:2, 48:3, 48:4, 48:5, 49, 52, 52:1, 52:2, 53:1, 54, 57:1, 58, 60:1, 63, 64:1, 68, 81:1, 83, 88, 89, 95, 101, 104, 105, 108, 112, 114, 119, 122, 123, 136, 144, 146, 147, 149, 150, 164, 166, 1 68, 169, 170, 171, 172, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 187, 188, 190, 193, 194, 200, 202, 206, 207, 208, 209, 210, 211, 213, 214, 216, 220, 220, 221, 224, 226, 237, 238, 239, 242, 245, 247, 248, 251, 253, 254, 255, 256, 257, 258, 260, 262, 263, 264, 266, 268, 269, 270, 271, 272, 279;Pigment Violet 1, 2, 3, 3:1, 3:3, 5:1, 13, 15, 16, 17, 19, 23, 25, 27, 29, 31, 32, 36, 37, 38, 42, 50; Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 15:6, 16, 17:1, 24, 24:1, 25, 26, 27, 28, 29, 36, 56, 60, 61, 62, 63, 75, 79, 80; Pigment Pigment Green 1, 4, 7, 8, 10, 15, 17, 26, 36, 50; Pigment Brown 5, 6, 23, 24, 25, 32, 41, 42; Pigment Black 1, 6, 7, 9, 10, 11, 20, 26, 28, 31, 32, 34; Pigment White 1, 2, 4, 5, 6, 7, 11, 12, 18, 19, 21, 22, 23, 26, 27, 28, etc., as well as glass flakes, pearl pigments, hollow particles, etc. Of the above, glass flakes, pearl pigments, and hollow particles may not generally be considered as color pigments, but in the present invention, such pigments that provide some kind of optical effect are also considered as color pigments. Among these, from the viewpoint of the color reproducibility, coating film strength and printability, Pigment Yellow 13, Pigment Yellow 17, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 139, Pigment Yellow 180, Pigment Yellow 185, Pigment Orange 13, Pigment Orange 16, Pigment Orange 43, Pigment Orange 64, Pigment Red 48:1, Pigment Red 48:2, Pigment Red Preferred examples of the pigments include Pigment Red 48:3, Pigment Red 48:4, Pigment Red 53:1, Pigment Red 122, Pigment Red 166, Pigment Red 185, Pigment Red 254, Pigment Red 264, Pigment Violet 23, Pigment Violet 32, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:6, Pigment Green 7, Pigment Black 7, and Pigment White 6. Metallic powder pigments for imparting metallic colors such as gold and silver to the ink composition are also considered to be colored pigments in the present invention. Examples of such metallic powder pigments include aluminum flakes, gold powder, bronze powder, and aluminum paste prepared by processing aluminum powder into a paste.

[0046] The amount of color pigment added is, for example, about 5 to 50 mass % of the total ink composition, but is not particularly limited. When preparing a yellow ink composition using a yellow pigment, a magenta ink composition using a magenta pigment, a cyan ink composition using a cyan pigment, or a black ink composition using a black pigment, it is also possible to use a pigment of another color in combination or add an ink composition of another color as a complementary color.

[0047] [Other Components] If necessary, the ink composition of the present invention may contain other components such as alkanolamines, known curing agents, pigment dispersants, solvents other than the above-mentioned specific solvents, waxes, silica particles, and stabilizers.

[0048] The use of an alkanolamine can reduce the occurrence of misting during printing. Examples of alkanolamines include triethanolamine, dibutylethanolamine, and methyldiethanolamine. When an alkanolamine is used, its content relative to the total ink composition is preferably 0.01 to 5 mass%, more preferably 0.05 to 3 mass%, and even more preferably 0.1 to 1.5 mass%.

[0049] As the curing agent, for example, an amino resin such as a melamine resin or a benzoguanamine resin can be used.

[0050] Examples of solvents other than the above-mentioned specific solvents include aliphatic or alicyclic hydrocarbons having a boiling point range of about 230 to 400° C., aromatic hydrocarbons such as alkylbenzenes, higher alcohols, etc. As already mentioned, when aromatic hydrocarbons are used as the solvent, it is preferable that their content in the ink composition is less than 10% by mass.

[0051] Silica particles are SiO ２These are commercially available as powders, and are readily available in the form of hydrophilic powders that have not been surface-treated or that have been hydrophilized, or hydrophobic powders that have been hydrophobized, etc. The content of silica particles in the ink composition is preferably 1 to 8 mass %, and more preferably 2 to 5 mass %.

[0052] The ink composition of the present invention can be prepared by mixing the components such as the color pigment, resin, and solvent including the specific solvent in a conventional manner using a roll mill, ball mill, bead mill, etc. The viscosity of the ink composition is, for example, 10 to 70 Pa s at 25°C as measured by a Raley viscometer, but is not particularly limited.

[0053] The metal for metal printing in the ink composition of the present invention is not particularly limited, but examples thereof include zinc-plated or tin-plated iron sheets, aluminum sheets, and metal cans made of these metal materials.

[0054] Furthermore, the aqueous OP varnish to be applied on the printed ink composition can be a commonly used one, and specific examples include those using an aqueous acrylic resin, aqueous polyester resin, aqueous alkyd resin, aqueous epoxy resin, or modified resins of two or more of these as a binder in combination with an amino resin as a curing agent. As already mentioned, by using the ink composition of the present invention, even when using an aqueous OP varnish containing less than 10% by mass of organic solvent, it is possible to suppress repelling and uneven application of the OP varnish during wet-on-wet application. In other words, the ink composition of the present invention can also be preferably used for undercoating printing for applying an aqueous OP varnish containing less than 10% by mass of organic solvent.

[0055] When printing on the surface of a metal material using the ink composition and aqueous OP varnish, first, printing is carried out using the ink composition of the present invention using a dry offset printing machine, an offset printing machine, or the like, and then, while the ink composition is still in a wet-on-wet state, the aqueous OP varnish is overcoated using a coater or the like, and then baking is carried out at 150 to 280°C for several seconds to several minutes.

[0056] <Set of Metallic Printing Ink Composition and Aqueous Overprint Varnish> The set of the above-mentioned metallic printing ink composition of the present invention and aqueous overprint varnish (aqueous OP varnish) also constitutes one aspect of the present invention. The aqueous OP varnish referred to here refers to a varnish containing a combination of a hydrophilic organic solvent and water as a solvent, with an organic solvent content of less than 10% by mass. The metallic printing ink composition included in this set has already been described, so further description here will be omitted.

[0057] As described above, the ink composition of the present invention suppresses cissing and uneven application of the aqueous OP varnish when it is applied wet-on-wet after printing with an aqueous OP varnish containing less than 10% by mass of organic solvent. For this reason, the ink composition of the present invention can be preferably used in combination with an aqueous OP varnish containing less than 10% by mass of organic solvent. The set of the present invention takes advantage of this point.

[0058] The aqueous OP varnish included in the set may be any one that contains less than 10% by mass of organic solvent and is used by coating the surface of the ink composition for metal printing after printing. Various types of such aqueous OP varnishes are commercially available, and such commercially available products can be obtained and used as a set with the ink composition of the present invention.

[0059] 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.

[0060] [Preparation of Alkyd Resin Varnish 1] 14.7 parts by mass of trimethylolpropane, 10 parts by mass of coconut oil fatty acid, and 15 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g, thereby carrying out the first-stage esterification. Then, 0.82 parts by mass of trimellitic anhydride was added, and the mixture was heated at 165°C under a nitrogen atmosphere for 30 minutes, thereby carrying out the second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain Alkyd Resin 1. 10 parts by mass of tripropylene glycol monobutyl ether was added to this Alkyd Resin 1 to obtain Alkyd Resin Varnish 1. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention. The fatty acid modification content of the synthesized Alkyd Resin 1 was 27.7% by mass.

[0061] [Preparation of Alkyd Resin Varnish 2] 14.7 parts by mass of trimethylolpropane, 15.5 parts by mass of coconut oil fatty acid, and 12.9 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g, thereby carrying out the first-stage esterification. Then, 0.91 parts by mass of trimellitic anhydride was added, and the mixture was heated at 165°C for 30 minutes under a nitrogen atmosphere, thereby carrying out the second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain alkyd resin 2. 10 parts by mass of tripropylene glycol monobutyl ether was added to this alkyd resin 2 to obtain alkyd resin varnish 2. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention. The fatty acid modification content of the synthesized alkyd resin 2 was 39.1% by mass.

[0062] [Preparation of Alkyd Resin Varnish 3] 14.7 parts by mass of trimethylolpropane, 18.5 parts by mass of coconut oil fatty acid, and 11.7 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g, thereby carrying out the first-stage esterification. Then, 0.95 parts by mass of trimellitic anhydride was added, and the mixture was heated at 165°C for 30 minutes under a nitrogen atmosphere, thereby carrying out the second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain Alkyd Resin 3. 10 parts by mass of tripropylene glycol monobutyl ether was added to this Alkyd Resin 3 to obtain Alkyd Resin Varnish 3. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention. The fatty acid modification content of the synthesized Alkyd Resin 3 was 44.6% by mass.

[0063] [Preparation of Alkyd Resin Varnish 4] 14.7 parts by mass of trimethylolpropane, 25 parts by mass of coconut oil fatty acid, and 9.3 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g, thereby carrying out the first-stage esterification. Then, 1.04 parts by mass of trimellitic anhydride was added, and the mixture was heated at 165°C for 30 minutes under a nitrogen atmosphere, thereby carrying out the second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain alkyd resin 4. To this alkyd resin 4, 10 parts by mass of tripropylene glycol monobutyl ether was added to obtain alkyd resin varnish 4. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention. The fatty acid modification content of the synthesized alkyd resin 4 was 54.7% by mass.

[0064] [Preparation of Alkyd Resin Varnish 5] 14.7 parts by mass of trimethylolpropane, 8.12 parts by mass of coconut oil fatty acid, and 15.69 parts by mass of isophthalic acid were reacted at 220°C under a nitrogen atmosphere until the acid value of the mixture reached 7 mgKOH / g, thereby carrying out the first-stage esterification. Then, 0.8 parts by mass of trimellitic anhydride was added, and the mixture was heated at 165°C for 30 minutes under a nitrogen atmosphere, thereby carrying out the second-stage esterification. These esterification reactions were carried out according to conventional methods to obtain Alkyd Resin 5. 10 parts by mass of tripropylene glycol monobutyl ether was added to this Alkyd Resin 5 to obtain Alkyd Resin Varnish 5. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention. The fatty acid modification content of the synthesized Alkyd Resin 5 was 23.0% by mass.

[0065] [Preparation of Alkyd Resin Varnish 6] 14.7 parts by weight of trimethylolpropane, 18.5 parts by weight of coconut oil fatty acid, and 11.7 parts by weight of isophthalic 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 esterification. Then, 0.95 parts by weight 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 conventional methods to obtain Alkyd Resin 6. To this Alkyd Resin 6, 10 parts by weight of commercially available linear alkylbenzene was added to obtain Alkyd Resin Varnish 6. Note that this linear alkylbenzene does not fall under the category of a specific solvent in the present invention and is an aromatic solvent. The fatty acid modification content of the synthesized Alkyd Resin 6 was 44.6% by weight.

[0066] [Preparation of Rosin-Modified Resin Varnish] 63.2 parts by mass of a rosin ester resin (hydroxyl value 20 to 30 mg KOH / g, acid value <10 mg KOH / 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, thereby obtaining a rosin-modified resin varnish. Note that this tripropylene glycol monobutyl ether corresponds to the specified solvent in the present invention.

[0067] [Test Water-Based OP Varnishes] Varnish A was a PPG iSENSE™ series water-based OP varnish (organic solvent content less than 10% by mass) manufactured by PPG, and Varnish C was a PPG iSENSE™ series water-based OP varnish (organic solvent content 15% by mass to 20% by mass) also manufactured by PPG. Furthermore, an aqueous OP varnish (organic solvent content less than 1.1% by mass) was prepared from a mixture of 47 parts by mass of Joncryl PDX7615 manufactured by BASF Japan Ltd., 47 parts by mass of Elitel KT-8803 manufactured by Unitika Ltd., and 6 parts by mass of Cymel 303LF manufactured by Allnex Corporation, and was designated Varnish B. Of these varnishes, Varnish A and Varnish B are water-based OP varnishes with an organic solvent content of less than 10% by mass, and Varnish C is an aqueous OP varnish with an organic solvent content of 10% by mass or more (15 to 20% by mass).

[0068] [Preparation of Ink Composition] Ink compositions of Examples and Comparative Examples were prepared according to the formulations shown in Tables 1 and 2. The numerical values ​​for each blend amount shown in Tables 1 and 2 are in parts by mass. When preparing the ink compositions, the components were mixed and then kneaded using a roll mill heated to 40°C. In Tables 1 and 2, "carbon black" refers to acidic carbon black having an average primary particle size of 24 nm and a DBP oil absorption of 66 mL / 100 g, "titanium oxide" refers to titanium oxide having an average primary particle size of 250 nm and a DBP oil absorption of 18 g / 100 g, "phthalocyanine blue" refers to commercially available phthalocyanine blue 15:3, "specific solvent 1" refers to tripropylene glycol monobutyl ether, "specific solvent 2" refers to triethylene glycol monobutyl ether, and "non-specific solvent" refers to linear alkylbenzene (aromatic solvent). In addition, in Tables 1 and 2, the percentage values ​​written in parentheses after the names of alkyd resin varnishes 1 to 6 are the fatty acid modified amounts (mass %) of the alkyd resin contained in each alkyd resin varnish.

[0069] [Transfer Evaluation] For each of the ink compositions of the Examples and Comparative Examples, 0.1 cc of the ink composition was applied to a 50 μm thick aluminum substrate using a high-speed color developer "PM-900PT" (manufactured by Mitsui Electric Seiki Co., Ltd.) at a printing pressure of 90 kgf and a color application speed of 9 m / s. The resulting applied products were evaluated according to the following criteria. The evaluation results are shown in the "Transfer" column of Tables 1 and 2. ○: No smearing was observed. △: Smearing was observed in less than 50% of the transferred area, but within the practical range. ×: Smearing was observed in 50% or more of the transferred area, poor.

[0070]

[0071]

[0072] [Evaluation of repelling of water-based OP varnish] Using the combinations of the ink compositions and water-based OP varnishes shown in Tables 3 and 4, the water-based OP varnish was applied in an amount of 25 mg / dm on a coating film of the ink composition applied to a metal piece. ２ The applied water-based OP varnish was applied wet-on-wet so that the applied amount was 25 mg / dm², and the presence or absence of cissing or penetration of the applied water-based OP varnish was visually inspected and evaluated. The evaluation criteria were as follows, and the results are shown in the "cissing evaluation" column in Tables 3 and 4. The applied amount of water-based OP varnish in this evaluation was 25 mg / dm². ２ is the amount of water-based OP varnish currently commonly used for two-piece cans (50-60 mg / dm ２ ), and can be said to be severe conditions that are likely to cause cissing and penetration of the aqueous OP varnish. Furthermore, in the "Ink Composition" column of Tables 3 and 4, notations such as "Ex. 1" represent "Example 1" and the like, notations such as "Comp. 1" represent "Comparative Example 1" and the like, and the numerical values ​​shown in the "Organic Solvent Amount" column represent the amount of organic solvent (mass %) contained in the aqueous OP varnish used. Furthermore, the "Reference" shown in the "Test Number" column of Tables 3 and 4 is a test using the currently widely used aqueous OP varnish C, which contains a large amount of organic solvent, and serves as a tentative performance target. ○: No cissing is observed and gloss is good △: Almost no cissing is observed, but gloss is slightly reduced ×: A tendency for cissing and penetration of the OP varnish is observed

[0073] [Pencil hardness] The metal pieces that had been coated with aqueous OP varnish in the above-mentioned evaluation of cissing were baked by heating in an electric oven at 200°C for 2 minutes. The metal pieces were then returned to room temperature, and the pencil hardness of the drawn surface was measured in accordance with JIS K5600-5-4. The results are shown in the "Pencil hardness" column in Tables 3 and 4.

[0074]

[0075]

[0076] As shown in Tables 3 and 4, the ink compositions of Examples 1 to 7 contained an aqueous OP varnish with an organic solvent content of less than 10% by mass at a coating amount of 25 mg / dm ２ Even when applied in such a small amount, none of the ink compositions exhibited cissing or penetration of the aqueous OP varnish, and the pencil hardness after baking was sufficient. Furthermore, as shown in Tables 1 and 2, the ink compositions of Examples 1 to 7 exhibited good transferability and sufficient performance in terms of printability. Among these, the ink composition of Example 7, which contained a rosin-modified resin, achieved the above-mentioned favorable results, demonstrating that the application of a rosin-modified resin to the ink composition of the present invention can increase the biomass content in the ink composition without causing a decline in various performance characteristics. On the other hand, the ink composition of Comparative Example 1, which contained an alkyd resin varnish with a fatty acid modification content exceeding 50% by mass, not only exhibited cissing upon application of the aqueous OP varnish, but also exhibited a significantly poor pencil hardness of B after baking. Furthermore, the ink composition of Comparative Example 2, which contained an alkyd resin with a fatty acid modification content of less than 25% by mass, exhibited good cissing upon application of the aqueous OP varnish and good pencil hardness after baking, but its poor transferability, as shown in Table 2, indicates that its basic printability is insufficient. Furthermore, it is clear that the ink composition of Comparative Example 3, which does not contain the specific solvent of the present invention, causes repelling when the water-based OP varnish is applied.

Claims

1. An ink composition for metal printing comprising a color pigment, an alkyd resin, and a solvent, wherein the solvent comprises at least one compound selected from the group consisting of compounds represented by the following general formula (1), and the alkyd resin is a fatty acid-modified alkyd resin, the amount of fatty acid modification being 25 to 50 mass%. (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. A in the general formula (1) is an ethylene group (-CH ２ CH ２ -) or propylene group (-CH(CH ３ ) CH ２ - or -CH ２ -CH(CH ３ 2. The ink composition for metal printing according to claim 1, wherein 3. A metal printing ink composition according to claim 1 or 2, characterized in that it is used for undercoating for applying an aqueous overprint varnish containing less than 10% by mass of organic solvent.

4. The ink composition for metal printing according to any one of claims 1 to 3, wherein the content of aromatic compounds in the solvent is less than 10% by mass.

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

6. A set comprising an ink composition for metal printing and an aqueous overprint varnish, wherein the ink composition for metal printing comprises a color pigment, an alkyd resin, and a solvent A, and the solvent A comprises at least one compound selected from the group consisting of compounds represented by the following general formula (1), the alkyd resin is a fatty acid-modified alkyd resin, and the amount of fatty acid modification is 25 to 50% by mass, and the content of organic solvents contained in the aqueous overprint varnish is less than 10% by mass of the entire aqueous overprint varnish. (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.) 7. In the general formula (1), A is an ethylene group (-CH ２ CH ２ -) or propylene group (-CH(CH ３ ) CH ２ - or -CH ２ -CH(CH ３ 7. The set according to claim 6, wherein 8. The set according to claim 6 or 7, wherein the content of aromatic compounds in said solvent A is less than 10% by mass.

9. The set according to any one of claims 6 to 8, characterized in that the ink composition for metal printing further contains a rosin-modified resin.

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