Primer composition for surface coating of flexible packaging, ink set, surface-coated printed matter, and inkjet printing method

Abstract

To provide a primer composition for surface printed flexible packaging, an ink set, a surface printed material, and an inkjet printing method which, in the case of an inkjet image formed after application of the primer composition, make it possible to give a coating layer with excellent solid uniformity, bleeding resistance, scratch resistance, alcohol resistance and heat resistance.SOLUTION: A primer composition for surface printed flexible packaging contains a polymer-emulsified acrylic resin emulsion, an N-oleoyl sarcosine, a hydrazine compound that has two or more hydrazine residues in the molecule, and a wax, wherein the content of the acrylic resin emulsion is 3-40 mass% in terms of solid content, and the glass transition temperature of the acrylic resin emulsion is between -40 and 30°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a primer composition for surface printing of flexible packaging, an ink set, a surface-printed product, and an inkjet printing method. More specifically, the present invention relates to a primer composition for surface printing of flexible packaging, an ink set, a surface-printed product, and an inkjet printing method that can impart excellent solid uniformity, anti-bleeding property, abrasion resistance, alcohol resistance, and heat resistance to a coating film when an inkjet image is provided after applying the primer composition.

Background Art

[0002] Conventionally, for foods, confectioneries, daily sundries, pet foods, etc., flexible packaging materials using various plastic films have been used from the viewpoints of designability, economy, content protectiveness, transportability, etc. Also, many flexible packaging materials are subjected to gravure printing or flexographic printing. The surface of the base film of the flexible packaging material is subjected to surface printing. A primer ink is applied to the film surface so that the ink is easily received by the base material and a clear design or the like is printed. Therefore, primer compositions used for surface printing of flexible packaging materials have been developed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The primer composition described in Patent Document 1 has room for improvement in the heat resistance of the resulting coating film when an inkjet image is provided after applying the primer composition. Also, the primer composition described in Patent Document 1 has room for improvement with respect to the water resistance and alcohol resistance of the coating film of the resulting inkjet image.

[0005] The present invention has been made in view of such conventional problems, and when an inkjet image is formed after applying a primer composition, it can impart excellent solid uniformity, anti-seepage property, anti-scrubbing property, alcohol resistance and heat resistance to a coating film. An object of the present invention is to provide a primer composition for surface printing of flexible packaging, an ink set, a surface printed product, and an inkjet printing method.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that by incorporating N-oleoylsarcosine, which has conventionally been used as a rust inhibitor, into the primer composition, the heat resistance of the coating film on which an inkjet image is formed is greatly improved. Furthermore, the present inventors have found that by incorporating a polymer-emulsified acrylic resin emulsion having a specific amount and a specific glass transition temperature, a hydrazine compound having a specific structure, and a wax, the above problems can be solved simultaneously, and the present invention has been completed. The present invention for solving the above problems mainly has the following configurations.

[0007] (1) A primer composition for surface printing of flexible packaging, comprising an acrylic resin emulsion emulsified with a polymer, N-oleoylsarcosine, a hydrazine compound having at least two or more hydrazine residues in the molecule, and a wax, wherein the content of the acrylic resin emulsion is 3 to 40% by mass in terms of solid content, and the glass transition temperature of the acrylic resin emulsion is -40 to 30°C.

[0008] According to such a configuration, when an inkjet image is formed after applying the primer composition for surface printing of flexible packaging, excellent solid uniformity, anti-seepage property, anti-scrubbing property, alcohol resistance and heat resistance can be imparted to the coating film.

[0009] (2) The primer composition for surface printing of flexible packaging according to (1), further comprising a white pigment.

[0010] According to such a configuration, a printed matter using a primer composition for surface printing of flexible packaging has even better design and visibility.

[0011] (3) The primer composition for surface printing of flexible packaging according to (1) or (2), further containing chlorinated polyolefin.

[0012] According to such a configuration, the primer composition for surface printing of flexible packaging has even better solid uniformity in a coating film on which an inkjet image is formed.

[0013] (4) An ink set including the primer composition for surface printing of flexible packaging according to any one of (1) to (3) and an ink composition for aqueous inkjet, wherein the ink composition for aqueous inkjet contains a pigment, a water-insoluble resin, and wax.

[0014] According to such a configuration, in a surface printed matter obtained using the ink set, the solid uniformity, bleed resistance, rub resistance, alcohol resistance, and heat resistance in a coating film on which an inkjet image is formed are excellent.

[0015] (5) A surface printed matter provided with the primer composition for surface printing of flexible packaging according to (4) and the ink composition for aqueous inkjet.

[0016] According to such a configuration, in the obtained surface printed matter, the solid uniformity, bleed resistance, rub resistance, alcohol resistance, and heat resistance in a coating film on which an inkjet image is formed are excellent.

[0017] (6) An inkjet printing method including a printing step of surface printing the primer composition for surface printing of flexible packaging according to (4) and the ink composition for aqueous inkjet on a substrate.

[0018] According to such a configuration, a surface printed matter excellent in solid uniformity, bleed resistance, rub resistance, alcohol resistance, and heat resistance in a coating film on which an inkjet image is formed can be obtained. [Effect of the Invention]

[0019] According to the present invention, when an inkjet image is formed after applying a primer composition, it is possible to provide a primer composition for surface printing of flexible packaging, an ink set, a surface-printed product, and an inkjet printing method that can impart excellent solid uniformity, bleed resistance, scratch resistance, alcohol resistance, and heat resistance to a coating film.

Mode for Carrying Out the Invention

[0020] <Primer Composition for Surface Printing of Flexible Packaging> The primer composition for surface printing of flexible packaging according to one embodiment of the present invention (hereinafter also referred to as a primer composition) contains an acrylic resin emulsion emulsified with a polymer, N-oleoylsarcosine, a hydrazine compound having at least two or more hydrazine residues in the molecule, and wax. The content of the acrylic resin emulsion is 3 to 40% by mass in terms of solid content. The glass transition temperature of the acrylic resin emulsion is -40 to 30°C. Hereinafter, each will be described.

[0021] (Acrylic Resin Emulsion Emulsified with a Polymer) The acrylic resin emulsion of the present embodiment is an acrylic resin emulsion emulsified with a polymer compound. Further, the glass transition temperature of the acrylic resin emulsion is -40 to 30°C. The acrylic resin emulsion emulsified with a polymer can adopt a core-shell structure composed of a shell that is a polymer functioning as a polymer emulsifier and a core composed of a resin having stronger hydrophobicity than the shell. Note that the acrylic resin emulsion emulsified with a polymer of the present embodiment is distinguished from, for example, an acrylic resin emulsion emulsified with an emulsifier such as a surfactant that is a low molecular compound.

[0022] The acrylic resin emulsion emulsified with a polymer is not particularly limited. For example, the acrylic resin emulsion emulsified with a polymer includes an acrylic resin emulsion, a styrene-acrylic resin emulsion, an acrylic-vinyl acetate resin emulsion, an acrylic-vinyl chloride resin emulsion, an acrylic-silicone resin emulsion, an acrylic-colloidal silica resin emulsion, and the like. Among these, the acrylic resin emulsion emulsified with a polymer is preferably an acrylic resin emulsion (that is, not a "mixed acrylic "system" resin emulsion", but an "acrylic resin emulsion") because of its excellent transparency and coating film resistance.

[0023] The glass transition temperature (Tg) of the acrylic resin emulsion emulsified with a polymer may be -40°C or higher, preferably -20°C or higher. Also, the glass transition temperature (Tg) of the acrylic resin emulsion emulsified with a polymer may be 30°C or lower, preferably 20°C or lower. When Tg is less than -40°C, the primer composition has a problem that the blocking resistance decreases. On the other hand, when Tg exceeds 30°C, the primer composition has a problem that the adhesion to the film becomes low and the coating film resistance decreases. In addition, the glass transition temperature of the resin in this embodiment is the theoretical glass transition temperature obtained by the following Wood's formula when the resin is an acrylic copolymer resin. Wood's formula: 1 / Tg = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 + ····· + Wx / Tgx [In the formula, Tg1 to Tgx are the glass transition temperatures of the respective homopolymers of monomers 1, 2, 3 ··· x constituting the resin, W1 to Wx are the polymerization fractions of monomers 1, 2, 3 ··· x, and Tg represents the theoretical glass transition temperature. However, the glass transition temperature in Wood's formula is the absolute temperature.]

[0024] The acid value of the acrylic resin emulsion emulsified with a polymer is preferably 10 mgKOH / g or more, more preferably 40 mgKOH / g or more. Also, the acid value is preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less. When the acid value is within the above range, the primer composition has the advantage that its solubility in water does not become too high, and the scratch resistance and alcohol resistance of the coating film are improved. In the present embodiment, the acid value is the theoretical acid value obtained arithmetically by calculating the number of milligrams of potassium hydroxide theoretically required to neutralize 1 g of the acrylic resin emulsion based on the composition of the monomers used to synthesize the acrylic resin emulsion.

[0025] The content of the acrylic resin emulsion emulsified with a polymer may be 3% by mass or more in terms of solid content in the primer composition, and preferably 10% by mass or more. Also, the content of the acrylic resin emulsion emulsified with a polymer may be 40% by mass or less in terms of solid content in the primer composition, and preferably 25% by mass or less. When the content of the acrylic resin emulsion emulsified with a polymer is less than 3% by mass, the alcohol resistance of the resulting coating film is poor when an inkjet image is formed after applying the primer composition. On the other hand, when the content of the acrylic resin emulsion emulsified with a polymer exceeds 40% by mass, the primer composition has a problem of decreased storage stability.

[0026] (N-oleoylsarcosine) N-oleoylsarcosine is blended to impart heat resistance to the primer composition. Thus, the primer composition of the present embodiment is characterized in that N-oleoylsarcosine, which has conventionally been used as a rust preventive agent, can impart heat resistance to the resulting coating film without deteriorating various properties when an inkjet image is formed after applying the primer composition in the application of the primer composition.

[0027] The content of N-oleoyl sarcosine is not particularly limited. For example, the content of N-oleoyl sarcosine is preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the primer composition. Also, the content of N-oleoyl sarcosine is preferably 6% by mass or less, more preferably 2% by mass or less in the primer composition. When the content of N-oleoyl sarcosine is within the above range, the primer composition has excellent heat resistance of the resulting coating film when an inkjet image is formed after applying the primer composition. Also, the primer composition has excellent storage stability.

[0028] (Hydrazine compound having at least two or more hydrazine residues in the molecule) The hydrazine compound having at least two or more hydrazine residues in the molecule is blended to impart alcohol resistance to the primer composition.

[0029] The hydrazine compound has two or more hydrazine residues and is preferably a water-soluble polyhydrazine or hydrazide compound. Also, the hydrazine compound is preferably hydrazine and an alkylene dihydrazine represented by the following general formula (1), or a dihydrazide compound of a saturated aliphatic dibasic acid or an unsaturated dibasic acid. H 2 N-NH-X-NH-NH 2 (1) (In the formula, X represents an alkylene group having 1 to 8 carbon atoms, or a residue of a saturated or unsaturated dibasic acid having 1 to 10 carbon atoms).

[0030] Alkylene dihydrazine includes methylene dihydrazine, ethylene dihydrazine, propylene dihydrazine, butylene dihydrazine and the like. Dihydrazide compounds of saturated aliphatic dibasic acids include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide and the like. Dihydrazide compounds of unsaturated dibasic acids include phthalic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide and the like.

[0031] The content of the hydrazine-based compound having at least two or more hydrazine residues in the molecule is not particularly limited. For example, the content of the hydrazine-based compound having at least two or more hydrazine residues in the molecule is preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the primer composition. Further, the hydrazine-based compound having at least two or more hydrazine residues in the molecule is preferably 6% by mass or less, more preferably 3% by mass or less in the primer composition. When the content of the hydrazine-based compound having at least two or more hydrazine residues in the molecule is within the above range, the primer composition has excellent alcohol resistance of the obtained coating film when an inkjet image is formed after applying the primer composition. Further, the primer composition has excellent storage stability.

[0032] (Wax) Wax is compounded to improve abrasion resistance. The wax is not particularly limited. For example, the wax may be a wax of animal or plant origin such as beeswax, lanolin wax, spermaceti wax, candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, etc., montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, petrolatum and other minerals, petroleum-based waxes, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax and other synthetic hydrocarbon-based waxes, fluororesin-based waxes such as polytetrafluoroethylene wax, a mixture of polytetrafluoroethylene wax and polyethylene wax, modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, hydrogenated waxes such as hydrogenated castor oil, hydrogenated castor oil derivatives, and polytetrafluoroethylene wax. Among these, the wax is preferably polyethylene wax, a mixture of polytetrafluoroethylene wax and polyethylene wax, fluororesin-based wax, Fischer-Tropsch wax, etc.

[0033] The average particle size of the wax is not particularly limited. For example, the average particle size of the wax is preferably 0.05 μm or more, more preferably 0.1 μm or more. Also, the average particle size of the wax is preferably 6 μm or less, more preferably 5 μm or less. By blending wax with a relatively large particle size in this way, the primer composition of the present embodiment can improve the blocking resistance of the resulting coating film when an inkjet image is formed after applying the primer composition. In the present embodiment, the average particle size of the wax can be measured with a nanotrack (UPA-EX150, manufactured by Nikkiso Co., Ltd.).

[0034] The wax content is not particularly limited. For example, the wax content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the primer composition in terms of solid content. Also, the wax content is preferably 12% by mass or less, more preferably 4% by mass or less in the primer composition in terms of solid content. When the wax content is within the above range, the primer composition has excellent blocking resistance of the resulting coating film when an inkjet image is formed after applying the primer composition.

[0035] (White pigment) The primer composition of this embodiment preferably contains a white pigment. By containing a white pigment, printed matter using the primer composition is further excellent in design and visibility.

[0036] The white pigment is not particularly limited. For example, the white pigment is various inorganic white pigments, organic white pigments, etc. Inorganic white pigments are titanium oxide, zinc oxide, cerium oxide, silica, alumina, magnesium oxide, zirconium dioxide, yttria-stabilized zirconium, indium oxide, antimony oxide, tin oxide, barium titanate, barium sulfate, calcium carbonate, fine silica, calcium silicate, talc, and clay, etc. Organic white pigments are organic compound salts shown in JP-A-11-129613, alkylene bismelamine derivatives shown in JP-A-11-140365, JP-A-2001-234093, etc. Among these, the white pigment is preferably various titanium oxides such as rutile type and anatase type from the viewpoint of excellent hiding power, and more preferably titanium oxide whose surface is coated with alumina, silica, an organic substance, etc.

[0037] The average particle diameter of the white pigment is not particularly limited. For example, the average particle diameter of the white pigment is preferably 100 nm or more, more preferably 150 nm or more. Also, the average particle diameter of the white pigment is preferably 500 nm or less, more preferably 400 nm or less. When the average particle diameter of the white pigment is within the above range, the primer composition has excellent hiding power of the resulting coating film when an inkjet image is formed after applying the primer composition. In the present embodiment, the average particle diameter is the volume average particle diameter measured by a laser diffraction particle size analyzer using Nano Track (UPA-EX150, manufactured by Nikkiso Co., Ltd.).

[0038] The content of the white pigment is not particularly limited. For example, the content of the white pigment is preferably 5% by mass or more, more preferably 10% by mass or more in the primer composition. Also, the content of the white pigment is preferably 20% by mass or less, more preferably 15% by mass or less in the primer composition. When the content of the white pigment is within the above range, the primer composition has excellent hiding power of the resulting coating film when an inkjet image is formed after applying the primer composition. Also, when the primer composition is applied to a flexible packaging material and a design such as a pattern is printed thereon, the design is easily visible.

[0039] (Chlorinated polyolefin) The primer composition of the present embodiment preferably further contains a chlorinated polyolefin. The chlorinated polyolefin is preferably used in the form of a chlorinated polyolefin emulsion. The chlorinated polyolefin emulsion is obtained by chlorinating a polyolefin resin and emulsifying it.

[0040] The chlorinated polyolefin is not particularly limited. For example, the chlorinated polyolefin includes chlorinated polypropylene resin, chlorinated polyethylene resin, etc. Further, the chlorinated polyolefin may be a modified product. The modified product is not particularly limited. For example, the modified product of the chlorinated polyolefin is a product obtained by graft-polymerizing a polymerizable acrylic compound (such as acrylic acid, methacrylic acid or their alkyl esters) or an unsaturated polycarboxylic acid (such as maleic acid, maleic anhydride, itaconic acid, itaconic anhydride) to the chlorinated polyolefin, or a product obtained by chlorinating a polyolefin graft-polymerized with the above unsaturated polycarboxylic acid, etc.

[0041] The chlorine content in the chlorinated polyolefin is not particularly limited. For example, the chlorine content is preferably 1% by mass or more, more preferably 10% by mass or more, based on the whole resin. Further, the chlorine content is preferably 40% by mass or less, more preferably 30% by mass or less, based on the whole resin. When the chlorine content is within the above range, the chlorinated polyolefin is easily soluble in a solvent and has excellent adhesion between the base material and the primer composition.

[0042] When the chlorinated polyolefin is included, the content of the chlorinated polyolefin is not particularly limited. For example, the content of the chlorinated polyolefin is preferably 0.5% by mass or more, more preferably 1% by mass or more, in terms of solid content in the primer composition. Further, the content of the chlorinated polyolefin is preferably 5% by mass or less, more preferably 2% by mass or less, in terms of solid content in the primer composition. When the content of the chlorinated polyolefin is within the above range, the primer composition has even better film gloss uniformity when an inkjet image is formed after applying the primer composition.

[0043] (Water-soluble organic solvent) The primer composition of this embodiment preferably further contains a water-soluble organic solvent. By including the water-soluble organic solvent, when an inkjet image is formed after applying the primer composition, the resulting coating film has even better gloss uniformity.

[0044] The water-soluble organic solvent is not particularly limited. For example, the water-soluble organic solvent is preferably an alcohol and a polyhydric alcohol-based solvent, and more preferably methanol, ethanol, propanol, butanol, hexanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dimethyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, dibutyl glycol, glycerin, etc.

[0045] When a water-soluble organic solvent is included, the content of the water-soluble organic solvent is not particularly limited. For example, the content of the water-soluble organic solvent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more in the primer composition. Also, the content of the water-soluble organic solvent is preferably 20% by mass or less, more preferably 10% by mass or less in the primer composition. When the content of the water-soluble organic solvent is within the above range, the primer composition has even better film gloss uniformity of the obtained coating film when an inkjet image is formed after applying the primer composition.

[0046] (Optional component) The primer composition of this embodiment may be appropriately blended with various additives such as tackifiers, crosslinking agents, lubricants, antiblocking agents, antistatic agents, surfactants, chelating agents, and hard resins.

[0047] (Method for producing primer composition) The method for producing the primer composition of this embodiment is not particularly limited. For example, the primer composition can be prepared by stirring and mixing a white pigment, an acrylic resin emulsion emulsified with a polymer, N-oleoylsarcosine, a hydrazine-based compound having at least two or more hydrazine residues in the molecule, wax, and various optional components, and then using various meat grinders such as bead mills, ball mills, sand mills, attritors, roll mills, pearl mills, etc. to grind the mixture.

[0048] The obtained primer composition preferably has a viscosity of 10 to 1000 mPa·s. Also, when the primer composition is used for gravure printing, it is preferably diluted with water or an organic solvent so that it has an appropriate viscosity according to the printing conditions at the ambient temperature during printing. Specifically, the efflux time of Zahn cup No. 3 is 12 to 23 seconds / 25°C, and about 14 to 16 seconds / 25°C for high-speed printing.

[0049] The obtained primer composition can be printed on an adherend such as a plastic film for various flexible packages as a primer composition for surface printing of flexible packages by, for example, a gravure printing method or the like. Examples of the plastic film include stretched and non-stretched polyolefins such as polyethylene and polypropylene, polyester, nylon, cellophane, vinylon, etc., in that printing integrated with the packaging material is possible. The obtained printed matter can be made into a bag and used as a packaging container for foods and the like.

[0050] As described above, according to the present embodiment, the primer composition has excellent storage stability and can impart excellent solid uniformity, bleeding resistance, scratch resistance, alcohol resistance, and heat resistance to the coating film when an inkjet image is formed after applying the primer composition.

[0051] <Ink set> An ink set according to an embodiment of the present invention includes the above-described primer composition for surface printing of flexible packages and an ink composition for aqueous inkjet. The ink composition for aqueous inkjet includes a pigment, a water-insoluble resin, and a wax. Each will be described below.

[0052] (Ink composition for aqueous inkjet) The ink composition for aqueous inkjet (hereinafter also referred to as the ink composition) includes a pigment, a water-insoluble resin, and a wax.

[0053] · Pigment The pigment is not particularly limited. For example, the pigment is various organic pigments and inorganic pigments. The organic pigments are dye lake pigments, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, perinone pigments, diketopyrrolopyrrole pigments, isoindolinone pigments, nitro pigments, nitroso pigments, flavanthrone pigments, quinophthalone pigments, pyranthrone pigments, indanthrone pigments, etc.

[0054] The inorganic pigments include carbon black, titanium oxide, zinc white, red iron oxide, graphite, iron black, chromium oxide green, aluminum hydroxide, etc.

[0055] The pigments may be those surface-treated with known surface treatment agents.

[0056] The yellow pigments include C.I.Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, 213, etc.

[0057] The magenta pigments include C.I.Pigment Red 5, 7, 12, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57, 57:1, 63:1, 101, 102, 112, 122, 123, 144, 146, 149, 168, 177, 178, 179, 180, 184, 185, 190, 202, 209, 224, 242, 254, 255, 270, C.I.Pigment Violet 19, etc.

[0058] The cyan pigments include C.I.Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc.

[0059] The black pigments include carbon black (C.I.Pigment Black 7), etc.

[0060] The white pigments include titanium oxide, aluminum oxide, etc. The white pigments may be surface-treated with various materials such as alumina and silica.

[0061] The content of the pigment is not particularly limited. For example, the content of the pigment is preferably 2% by mass or more, more preferably 4% by mass or more in the ink composition. Also, the content of the pigment is preferably 10% by mass or less, more preferably 8% by mass or less in the ink composition.

[0062] ·Water-insoluble resin The water-insoluble resin is not particularly limited. For example, the water-insoluble resin is an acrylic emulsion obtained by emulsion polymerization of a carboxyl group-containing monomer and other monomers by a known method.

[0063] The carboxyl group-containing monomers include maleic acid monoester compounds having an aliphatic hydrocarbon group with 8 to 13 carbon atoms such as acrylic acid, methacrylic acid, (anhydrous) maleic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, monolauryl maleate, maleic acid monomyristyl, maleic acid monocetyl, maleic acid monostearyl, maleic acid monooleyl, maleic acid monoicosyl, etc., maleic acid monoester compounds having an aliphatic hydrocarbon group with 14 to 20 carbon atoms, crotonic acid and its ester compounds, itaconic acid and its ester compounds, etc.

[0064] Other radically polymerizable unsaturated monomers include (meth)acrylic acid esters having aliphatic hydrocarbon groups such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, oleyl (meth)acrylate, and eicosyl (meth)acrylate; (meth)acrylic acid ester compounds having hydroxyalkyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate; (meth)acrylamide, acrylonitrile, olefinic compounds, etc.; styrene monomers such as styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and fluorostyrene; benzyl (meth)acrylate monomers such as benzyl methacrylate and benzyl acrylate; and phenyl (meth)acrylate monomers such as phenyl methacrylate and phenyl acrylate.

[0065] The glass transition temperature of the water-insoluble resin is not particularly limited. For example, the glass transition temperature is 50 to 120°C. When the glass transition temperature is within the above range, the resulting coating film has excellent resistance, and the storage stability and ejection stability of the ink composition are excellent.

[0066] The content of the water-insoluble resin is not particularly limited. For example, the content of the water-insoluble resin is preferably 150% by mass or more, more preferably 200% by mass or more, in terms of solid content based on 100% by mass of the pigment. Also, the content of the water-insoluble resin is preferably 400% by mass or less, more preferably 300% by mass or less, in terms of solid content based on 100% by mass of the pigment. When the content of the water-insoluble resin is within the above range, the ink composition has excellent storage stability and ejection stability.

[0067] · Wax The wax is the same as described above in relation to the primer composition.

[0068] (Optional component) The ink composition of this embodiment may be appropriately blended with various additives such as water-soluble resins, surfactants, water-soluble organic solvents, calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, talc and other extender pigments, inorganic fine particles and adhesive resins (acrylic resins, vinyl acetate resins) for imparting anti-slip properties, leveling agents for improving leveling properties, defoaming agents for imparting defoaming properties, basic compounds such as caustic soda for imparting redissolubility, film-forming emulsions, preservatives, rust preventives, crosslinking agents, etc.

[0069] ·Water-soluble resin The water-soluble resin is not particularly limited. For example, the water-soluble resin is various alkali-soluble resins and the like. The alkali-soluble resin is not particularly limited. For example, the alkali-soluble resin is a resin obtained by polymerizing a monomer having an unsaturated double bond, a resin obtained by the reaction of functional groups, and the like.

[0070] Specifically, the alkali-soluble resin is various binder resins such as acrylic resins copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene, etc. as main monomer components, styrene-acrylic resins, styrene-maleic acid resins, styrene-acrylic-maleic acid resins, polyurethane resins, polyester resins, and the like.

[0071] These alkali-soluble resins can be dissolved in water in the presence of a basic compound and used as a water-soluble resin varnish. The basic compound is not particularly limited. For example, the basic compound is ammonia, an organic amine, an alkali metal hydroxide, etc. The organic amine is an alkylamine such as diethylamine, triethylamine, ethylenediamine, etc., an alkanolamine such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, triethanolamine, etc. The alkali metal hydroxide is sodium hydroxide, potassium hydroxide, etc.

[0072] When the water-soluble resin is blended, the content of the water-soluble resin is not particularly limited. For example, the content of the water-soluble resin is preferably 1.0% by mass or more, more preferably 3.0% by mass or more in the ink composition. Also, the content of the water-soluble resin is preferably 10.0% by mass or less, more preferably 6.0% by mass or less in the ink composition.

[0073] ·Surfactant The surfactant is not particularly limited. For example, the surfactant is an acetylene-based surfactant, a silicone-based surfactant, etc.

[0074] Examples of the acetylene-based surfactant include commercially available products such as "Dynol 607", "Dynol 609", "Olfin E-1004", "Olfin E-1010", "Olfin E-1020", "Olfin PD-001", "Olfin PD-002W", "Olfin PD-004", "Olfin PD-005", "Olfin EXP.4001", "Olfin EXP.4200", "Olfin EXP.4123", "Olfin EXP.4300" (manufactured by Nissin Chemical Industry Co., Ltd.); "Surfynol 104E", "Surfynol 104H", "Surfynol 104A", "Surfynol 104BC", "Surfynol 104DPM", "Surfynol 104PA", "Surfynol 104PG-50", "Surfynol 420", "Surfynol 440", "Surfynol 465" (manufactured by EVONIK) etc.

[0075] Examples of silicone surfactants as commercially available products include "BYK-307", "BYK-333", "BYK-347", "BYK-348", "BYK-349", "BYK-345", "BYK-378", "BYK-3455" (manufactured by BYK Chemie Co., Ltd., etc.).

[0076] When a surfactant is blended, the content of the surfactant is not particularly limited. For example, the content of the surfactant is preferably 0.1% by mass or more, more preferably 0.3% by mass or more in the ink composition. Also, the content of the surfactant is preferably 10.0% by mass or less, more preferably 6.0% by mass or less in the ink composition.

[0077] ·Water-soluble organic solvent The water-soluble organic solvent is not particularly limited. For example, the water-soluble organic solvent may be methanol, ethanol, propanol, butanol, hexanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, dibutyl glycol, glycerin, etc.

[0078] When the water-soluble organic solvent is blended, the content of the water-soluble organic solvent is not particularly limited. For example, the content of the water-soluble organic solvent is preferably 5% by mass or more, more preferably 10% by mass or more in the ink composition. Also, the content of the surfactant is preferably 50% by mass or less, more preferably 40% by mass or less in the ink composition.

[0079] (Method for producing an ink composition) The manufacturing method of the ink composition of the present embodiment is not particularly limited. For example, the ink composition can be prepared by stirring and mixing a pigment, a water-insoluble resin, a wax, and various optional components, and then using various meat grinders, such as a bead mill, a ball mill, a sand mill, an attritor, a roll mill, a pearl mill, etc. to grind the mixture.

[0080] Returning to the description of the entire ink set, the ink set of the present embodiment includes the above-described primer composition and ink composition. Thereby, the surface printed matter obtained using the ink set is excellent in solidity uniformity, bleeding resistance, rubbing resistance, alcohol resistance, and heat resistance.

[0081] <Surface Printed Matter and Inkjet Printing Method> The surface printed matter according to an embodiment of the present invention is a surface printed matter to which the above-described primer composition for surface printing on flexible packaging and the above-described ink composition for aqueous inkjet are applied. Further, an inkjet printing method according to an embodiment of the present invention includes a printing step of surface printing the above-described primer composition for surface printing on flexible packaging and the above-described ink composition for aqueous inkjet on a substrate.

[0082] The substrate is not particularly limited. For example, the substrate is various plastic films for flexible packaging, etc. Plastic films are exemplified by stretched and non-stretched polyolefins such as polyethylene and polypropylene, polyester, nylon, cellophane, vinylon, etc. in that printing can be performed integrally with the packaging material.

[0083] From the viewpoint of imparting transparency, heat resistance, mechanical strength, etc., the plastic film is preferably subjected to uniaxial or biaxial stretching treatment. Further, it is preferable that the plastic film is subjected to plasma treatment, corona discharge treatment, etc. on the surface on the side where the primer composition is applied to enhance the adhesiveness and wettability with the above-described primer composition.

[0084] The printing step is a step of applying the above-described primer composition and ink composition to the substrate in order, for example, by a gravure printing method or the like.

[0085] Specifically, a primer composition is applied to a substrate to form a primer layer. By forming the primer layer, the printability of the ink composition can be improved, and the adhesion of the resulting printed layer can be improved.

[0086] Next, an ink composition is printed on the primer layer by an inkjet method. By printing the ink composition by the inkjet method, a printed layer is formed.

[0087] Note that, from the viewpoint that printing by the inkjet method enables printing at a higher speed, a single-pass printing method using a fixed-line head is preferable.

[0088] The coating amount of the ink composition is preferably 0.05 to 3.00 g / m in terms of solid content contained in the ink composition, from the viewpoint of the balance between the printing speed and the color density of the resulting printed matter. 2 It is more preferably 0.1 to 2.00 g / m. 2 This is even more preferable.

[0089] The obtained printed matter may be appropriately subjected to a drying process using various drying devices. Further, various laminating processes may be performed on the obtained printed matter.

[0090] As described above, the surface-printed matter obtained in this embodiment is excellent in solid uniformity, bleeding resistance, scratch resistance, alcohol resistance, and heat resistance.

Examples

[0091] Hereinafter, the present invention will be described more specifically by way of examples. The present invention is not limited to these examples in any way. Unless otherwise specified, “%” means “mass %” and “part” means “part by mass”.

[0092] The raw materials used and the preparation methods are shown below. <Aqueous resin varnish> 20 parts by mass of an acrylic acid / n-butyl acrylate / benzyl methacrylate / styrene copolymer having a glass transition temperature of 40 ° C, a weight average molecular weight of 30,000, and an acid value of 185 mgKOH / g was dissolved in a mixed solution of 2.5 parts by mass of potassium hydroxide and 77.5 parts by mass of water to obtain an aqueous resin varnish having a solid content of 20%. <Preparation of Aqueous Black Ink Base A> 60.3 parts by mass of water was added to and mixed with 23.7 parts by mass of the above aqueous resin varnish to prepare a resin varnish for pigment dispersion. To this varnish, 16 parts by mass of carbon black (Printex 90, manufactured by Orion Engineered Carbons) was further added, and after stirring and mixing, kneading was performed with a wet circulation mill to prepare an aqueous black ink base. <Preparation of Aqueous Black Ink Base B (Crosslinked Base)> 2.1 parts by mass of Epolite 1600 (a bifunctional epoxy compound, manufactured by Kyoeisha Chemical Co., Ltd.) and 22.9 parts by mass of water were added to 75 parts by mass of the above aqueous black ink base A, and the mixture was heated at 60 ° C for 24 hours to obtain an aqueous black ink base B. <Preparation of Aqueous Yellow Ink Base> 64.3 parts by mass of water was added to and mixed with 23.7 parts by mass of the above aqueous resin varnish to prepare a resin varnish for pigment dispersion. To this varnish, 12 parts by mass of a yellow pigment (Novaperm Yellow 4G01, manufactured by Clariant) was further added, and after stirring and mixing, kneading was performed with a wet circulation mill to prepare an aqueous yellow ink base. <Preparation of Aqueous Magenta Ink Base> 64.3 parts by mass of water was added to and mixed with 23.7 parts by mass of the above aqueous resin varnish to prepare a resin varnish for pigment dispersion. To this varnish, 12 parts by mass of a magenta pigment (Inkjet Magenta E5B02, manufactured by Clariant) was further added, and after stirring and mixing, kneading was performed with a wet circulation mill to prepare an aqueous magenta ink base. <Preparation of Aqueous Cyan Ink Base> 64.3 parts by mass of water was added to 23.7 parts by mass of the above aqueous resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish, 12 parts by mass of a cyan pigment (Helio Gen Blue L7101F, manufactured by BASF) was further added. After stirring and mixing, the mixture was kneaded with a wet circulation mill to prepare an aqueous cyan ink base. <Preparation of Aqueous White Pigment Base> 20.0 parts by mass of water was added to 40.0 parts by mass of the above aqueous resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish, 40 parts by mass of titanium oxide (R-960, manufactured by DuPont) was further added. After stirring and mixing, the mixture was kneaded with a wet circulation mill to prepare an aqueous white pigment base. <Surfactant> Orfin E1010 (solid content 100%, HLB 13 - 14, manufactured by Nissin Chemical Industry Co., Ltd.) Orfin E1004 (solid content 100%, HLB 7 - 9, manufactured by Nissin Chemical Industry Co., Ltd.) <Resin Emulsion> (Acrylic resin emulsion emulsified with a polymer) PE - 1126 (solid content 41.5%, polymer - emulsified acrylic resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: - 12°C) JE - 1113 (solid content 42.5%, polymer - emulsified acrylic resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: - 24°C) HE - 1335 (solid content 45.5%, polymer - emulsified acrylic - styrene resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: 15°C) QE - 1042 (solid content 40.5%, polymer - emulsified acrylic - styrene resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: 53°C) (Acrylic resin emulsion emulsified with an emulsifier) Movinyl 7320 (solid content 40.0%, emulsifier - emulsified acrylic resin emulsion, manufactured by Japan Coating Resin Co., Ltd., Tg: - 20°C) Movinyl 730L (solid content 46.0%, emulsifier - emulsified acrylic resin emulsion, manufactured by Japan Coating Resin Co., Ltd., Tg: - 13°C) Neo-Cryl A-1125 (solids content 19.5%, emulsifier-emulsified acrylic resin emulsion, manufactured by DSM Neoresins, Tg: 13°C) Neo-Cryl A-1093 (solids content 45.5%, emulsifier-emulsified acrylic-styrene resin emulsion, manufactured by DSM Neoresins, Tg: 17°C) <Polyvinyl resin> Neo-Cryl A-1094 (solids content 45.5%, acrylic-styrene resin emulsion, manufactured by DSM Neoresins) Neo-Cryl A-1125 (solids content 19.5%, acrylic resin emulsion, manufactured by DSM Neoresins) Vinibran 715S (solids content 23%, vinyl chloride resin emulsion, manufactured by Nissin Chemical Industry Co., Ltd.) Aurelen AE-301 (solids content 30%, polyolefin resin emulsion, manufactured by Nippon Paper Industries Co., Ltd.) Joncryl JDX-6639 (solids content 29%, acrylic-styrene resin aqueous solution, manufactured by BASF) 3401MA (solids content 40%, acrylic resin aqueous solution, manufactured by Daisheng Fine Chemical Co., Ltd.) <Polyurethane resin> Superflex 150HS (solids content 38%, polyurethane resin emulsion, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Hydran HW350 (solids content 30%, polyester polyurethane resin aqueous solution, manufactured by DIC Corporation) <Polyester resin> Eter KT-9204 (solids content 30%, polyester resin emulsion, manufactured by Unitika Ltd.) Plascoat Z-730 (solids content 25%, polyester resin aqueous solution, manufactured by Gohou Chemical Industry Co., Ltd.) <Wax emulsion> AQUACER531 (solids content 45%, polyethylene resin emulsion, average particle size 160 nm, manufactured by BYK) AQUACER539 (solids content 35%, polyethylene wax emulsion, average particle size 50 nm, manufactured by BYK) ChemPearl W-400 (solid content 40%, polyethylene resin emulsion, average particle size 4.0 μm, manufactured by Mitsui Chemicals, Inc.)

[0093] <Example 1> According to the mass ratios (mass %) shown in Table 1 below, each material was mixed and stirred to prepare a primer composition (P1). For the obtained primer composition, the storage stability was evaluated by the following evaluation method. The results are shown in Table 1. Also, according to the mass ratios (mass %) shown in Table 2 below, each material was kneaded with a paint conditioner to prepare an ink composition (K1). Using an ink set consisting of the primer composition (P1) and the ink composition (K1), gravure printing was performed under the following conditions to obtain a printed matter. For the obtained printed matter, the solid formation, bleeding of fine lines (bleeding resistance), scratch resistance, alcohol resistance, and heat resistance were evaluated according to the following evaluation methods. The results are shown in Tables 4 and 5.

[0094]

Table 1

[0095]

Table 2

[0096]

Table 3

[0097] <Examples 2 to 31, Comparative Examples 1 to 15> According to the descriptions in Tables 1 to 3, except for changing the types of the primer compositions used (P2 to P29), the types of the ink compositions (K1 to K15, Y1, M1, C1), and the formulations, printed matters were produced and evaluated in the same manner as in Example 1. The results are shown in Tables 4 and 5.

[0098] <Storage Stability of Primer Composition> The primer composition was placed in a glass bottle respectively, and the viscosity at 25°C was measured using a viscometer (RE100L type, manufactured by Toki Sangyo Co., Ltd.). Then, it was sealed and stored at 60°C for 1 month, and the viscosity (25°C) after storage was measured using a viscometer. The storage stability was evaluated by the viscosity change rate (100×(viscosity after 1 month at 60°C - viscosity before storage) / viscosity before storage). (Evaluation criteria) ○: The viscosity change rate was less than 5%. △: The viscosity change rate was 5% or more and less than 10%. ×: The viscosity change rate was 10% or more and less than 30%. (Primer layer formation conditions) The primer composition was printed and dried on the treated surface of the substrate using a gravure printing machine under the following printing conditions to form a primer layer. (Printing conditions) Substrate: Biaxially oriented polypropylene film treated by corona discharge, P-2111, manufactured by Toyobo Co., Ltd., thickness 20μm Printing equipment: Gravure printing machine Printing plate: Helio 175-line solid plate Printing speed: 15 m / min Drying conditions: 80°C (Solid formation) The ink composition in Table 3 was loaded onto an inkjet printer, and a solid image of 20 cm × 11.5 cm was printed on the surface of each primer layer prepared above. The obtained printed matter was visually observed and evaluated according to the following criteria. (Evaluation criteria) ○: The printed matter had no unevenness or streaks. △: Slight unevenness or streaks were observed in the printed matter. ×: Unevenness or streaks were visually found in the printed matter. (Bleeding of thin lines) The ink composition in Table 3 was loaded onto an inkjet printer, and thin lines of about 0.3 mm were printed on the surface of each primer layer prepared above. The thickening due to bleeding was visually observed and evaluated according to the following criteria. (Evaluation criteria) ○: There was no bleeding, and printing was possible with the original thickness. △: Slight thickening was observed, but thickening more than twice was not observed. ×: Overall, thickening more than twice was observed. <Scratch resistance> The printed matter of the solid image was cut into pieces of 2.5 cm × 20 cm to make test pieces. Using a Gakushin friction tester (manufactured by Dai-ichi Kogyo Seisakusho Co., Ltd.), a sunning cloth was placed on the printed surface, reciprocated 100 times under a load of 500 g, and the scratch resistance was evaluated according to the following evaluation criteria based on the degree of ink dropout. (Evaluation criteria) ○: The coating film with the solid image formed did not peel off at all. △: The coating film with the solid image formed peeled off slightly. ×: The coating film with the solid image formed peeled off almost completely. <Alcohol resistance> The printed matter of the solid image was cut into pieces of 2.5 cm × 20 cm to make test pieces. Using a Gakushin friction tester (manufactured by Dai-ichi Kogyo Seisakusho Co., Ltd.), a sunning cloth impregnated with 5 drops of 70% aqueous ethanol solution with an injection needle was placed on the printed surface, reciprocated 10 times under a load of 200 g, and the ethanol resistance was evaluated according to the following evaluation criteria based on the degree of ink dropout. (Evaluation criteria) ○: The coating film with the solid image formed did not peel off at all. △: The coating film with the solid image formed peeled off slightly. ×: The coating film with the solid image formed peeled off almost completely. <Heat resistance> Using a heat seal tester equipped with a hot plate having a heat gradient of 160 to 200 °C, the printed surface and the aluminum foil were pressed at a pressure of 2.0 kg / cm 2 for 1 second. The heat resistance was evaluated according to the following evaluation criteria based on the lowest temperature at which the ink on the printed surface transferred to the aluminum foil. (Evaluation criteria) ○: The lowest temperature at which the ink on the printed surface transferred to the aluminum foil was 200 °C or higher. △: The lowest temperature at which the ink on the printed surface transferred to the aluminum foil was 160 °C or higher and less than 200 °C. ×: The lowest temperature at which the ink on the printed surface transferred to the aluminum foil was less than 160 °C.

[0099]

Table 4

[0100]

Table 5

Claims

1. An acrylic resin emulsion emulsified with a polymer, N-oleoylsarcosine, a hydrazine compound having at least two or more hydrazine residues in the molecule, and a wax, wherein the content of the acrylic resin emulsion is 3 to 40% by mass in terms of solid content, and the glass transition temperature of the acrylic resin emulsion is -40 to 30°C, a primer composition for surface printing of flexible packaging.

2. The primer composition for surface printing of flexible packaging according to Claim 1, further comprising a white pigment.

3. The primer composition for surface printing of flexible packaging according to Claim 1 or 2, further comprising chlorinated polyolefin.

4. An ink set comprising the primer composition for surface printing of flexible packaging according to any one of Claims 1 to 3 and an ink composition for aqueous inkjet, wherein the ink composition for aqueous inkjet comprises a pigment, a water-insoluble resin, and a wax.

5. A surface-printed product having the primer composition for surface printing of flexible packaging according to Claim 4 and the ink composition for aqueous inkjet.

6. An inkjet printing method comprising a printing step of surface-printing the primer composition for surface printing of flexible packaging according to Claim 4 and the ink composition for aqueous inkjet on a substrate.

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