Underprint coating composition for soft packaging, ink set, underprint printed matter, and inkjet printing method

Abstract

The present invention provides a top print soft package primer composition, ink set, top print printed matter, and inkjet printing method, which are capable of imparting excellent solid printing uniformity, penetration resistance, scratch resistance, alcohol resistance, and heat resistance to a coating film when an inkjet image is formed after the primer composition is applied. The present invention provides a top print soft package primer composition, which comprises a high-molecular-emulsified acrylic resin emulsion, N-oleoyl sarcosine, a hydrazine-based compound having at least two or more hydrazine residues in the molecule, and a wax, the content of the acrylic resin emulsion being 3 to 40% by mass in terms of solid content, and the glass transition temperature of the acrylic resin emulsion being -40 to 30°C.

Description

Technical Field

[0001] This invention relates to a primer composition, ink group, surface-printed material, and inkjet printing method for surface-printed flexible packaging. More specifically, this invention relates to a primer composition, ink group, surface-printed material, and inkjet printing method for surface-printed flexible packaging that, when an inkjet image is applied after applying a primer composition, imparts excellent overall printing uniformity, bleed resistance, scratch resistance, alcohol resistance, and heat resistance to the coating film. Background Technology

[0002] Previously, flexible packaging materials, including those for food, snacks, household goods, and pet food, were used for design, economy, content protection, and transportability. These flexible packaging materials utilize various plastic films. Furthermore, gravure or flexographic printing was applied to many flexible packaging materials. Surface printing was then performed on the surface of the substrate film of the flexible packaging material. A primer ink was applied to the film surface to facilitate ink receptivity and allow for vivid printing designs. Therefore, a primer composition for surface printing of flexible packaging materials has been developed (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-24944 Summary of the Invention

[0006] The primer composition described in Patent Document 1 has potential for improvement in the heat resistance of the resulting coating film when an inkjet image is applied after applying the primer composition. Furthermore, the primer composition described in Patent Document 1 also has potential for improvement in the water resistance and alcohol resistance of the resulting inkjet image coating film.

[0007] The present invention was made in view of such existing problems, and its object is to provide a primer composition, ink composition, surface printed matter, and inkjet printing method for surface printed flexible packaging that can impart excellent overall printing uniformity, bleed resistance, scratch resistance, alcohol resistance, and heat resistance to the coating film when forming an inkjet image after applying a primer composition.

[0008] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by incorporating N-oleoylsarcosine, which has been used as a rust inhibitor, into the primer composition, the heat resistance of the coating film with inkjet images was significantly improved. Based on this, the inventors discovered that by incorporating specific amounts of a polymerically emulsified acrylic resin emulsion exhibiting a specific glass transition temperature, a hydrazine compound with a specific structure, and a wax, the above-mentioned problems could be solved simultaneously, thus completing the present invention.

[0009] One aspect of the present invention for solving the above-mentioned problems is a primer composition for surface printing flexible packaging, comprising an acrylic resin emulsion emulsified by a polymer, N-oleoylsarcosine, a hydrazine compound having at least two 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. Detailed Implementation

[0010] <Primer Composition for Surface Printing Flexible Packaging>

[0011] One embodiment of the primer composition for surface printing flexible packaging (hereinafter also referred to as primer composition) comprises an acrylic resin emulsion emulsified by a polymer, N-oleoylsarcosine, a hydrazine compound having at least two hydrazine residues in the molecule, and a wax. The content of the acrylic resin emulsion is 3 to 40% by mass, calculated on a solids basis. The glass transition temperature of the acrylic resin emulsion is -40 to 30°C. These will be described separately below.

[0012] (An acrylic resin emulsion emulsified with polymers)

[0013] The acrylic resin emulsion of this embodiment is an acrylic resin emulsion emulsified by a polymeric compound. Furthermore, the glass transition temperature of the acrylic resin emulsion is -40 to 30°C. The polymeric acrylic resin emulsion can employ a core-shell structure consisting of a polymer shell acting as a polymeric emulsifier and a core, wherein the core is composed of a resin with stronger hydrophobicity than the shell. It should be noted that the polymeric acrylic resin emulsion of this embodiment is, for example, distinct from acrylic resin emulsions emulsified by surfactants or other emulsifiers acting as low-molecular-weight compounds.

[0014] There is no particular limitation on the acrylic resin emulsion emulsified by polymers. For example, an acrylic resin emulsion emulsified by polymers could be 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, or an acrylic-colloidal silica resin emulsion. Among these, based on its excellent transparency and coating film resistance, an acrylic resin emulsion emulsified by polymers is preferred (i.e., not a "mixed acrylic" resin emulsion, but simply an "acrylic resin emulsion").

[0015] The glass transition temperature (Tg) of the polymer-emulsified acrylic resin emulsion only needs to be -40°C or higher, preferably -20°C or higher. Furthermore, the glass transition temperature (Tg) of the polymer-emulsified acrylic resin emulsion only needs to be 30°C or lower, preferably 20°C or lower. When the Tg is less than -40°C, the primer composition suffers from reduced anti-blocking properties. On the other hand, when the Tg exceeds 30°C, the primer composition suffers from reduced film adhesion and reduced coating durability. It should be noted that when the resin is an acrylic copolymer resin, the glass transition temperature of the resin in this embodiment is the theoretical glass transition temperature calculated using the following Wood formula.

[0016] Wood formula: 1 / Tg=W1 / Tg1+W2 / Tg2+W3 / Tg3+·····+Wx / Tgx

[0017] [In the formula, Tg1~Tgx represent the glass transition temperatures of the homopolymers of monomers 1, 2, 3...x constituting the resin, W1~Wx represent the polymerization fractions of monomers 1, 2, 3...x, and Tg represents the theoretical glass transition temperature. The glass transition temperature in Wood's formula is an absolute temperature.]

[0018] The acid value of the acrylic resin emulsion emulsified by the polymer is preferably 10 mg KOH / g or more, more preferably 40 mg KOH / g or more. Furthermore, the acid value is preferably 100 mg KOH / g or less, more preferably 80 mg KOH / g or less. With an acid value within the above range, the primer composition has the advantage of not becoming excessively soluble relative to water, and thus improving the scratch resistance and alcohol resistance of the coating film. It should be noted that, in this embodiment, the acid value of the acrylic resin emulsion is a theoretical acid value obtained by arithmetically calculating the number of mg 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.

[0019] The content of the polymer-emulsified acrylic resin emulsion in the primer composition, calculated as solids, should be 3% by mass or more, preferably 10% by mass or more. Furthermore, the content of the polymer-emulsified acrylic resin emulsion in the primer composition, calculated as solids, should be 40% by mass or less, preferably 25% by mass or less. When the content of the polymer-emulsified acrylic resin emulsion is less than 3% by mass, the resulting coating film, when formed into an inkjet image after being applied to the primer composition, exhibits poor alcohol resistance. On the other hand, when the content of the polymer-emulsified acrylic resin emulsion exceeds 40% by mass, the primer composition suffers from reduced storage stability.

[0020] (N-Oleoylsarcosine)

[0021] N-Oleylsarcosine is formulated to impart heat resistance to the primer composition. This results in the primer composition of this embodiment having the following characteristics: N-Oleylsarcosine, conventionally used as a rust inhibitor, can further impart heat resistance to the resulting coating film without reducing its various properties when the primer composition is applied to form an inkjet image.

[0022] The content of N-oleoylsarcosine is not particularly limited. As an example, the content of N-oleoylsarcosine in the primer composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. Furthermore, the content of N-oleoylsarcosine in the ink composition is preferably 6% by mass or less, more preferably 2% by mass or less. With the N-oleoylsarcosine content within the above range, the resulting coating film exhibits excellent heat resistance when an inkjet image is formed after applying the primer composition. Additionally, the primer composition demonstrates excellent storage stability.

[0023] (Hydrazine compounds having at least two hydrazine residues within the molecule)

[0024] Hydrazine compounds having at least two hydrazine residues in their molecules are formulated to impart alcohol resistance to primer compositions.

[0025] The hydrazine compound has two or more hydrazine residues, and is preferably a water-soluble polyhydrazine or acylhydrazine compound. In addition, the hydrazine compound is preferably hydrazine and alkylene dihydrazine represented by the following general formula (1), or a diacylhydrazine compound of a saturated aliphatic dicarboxylic acid or an unsaturated dicarboxylic acid.

[0026] H2N-NH-X-NH-NH2(1)

[0027] (In the formula, X represents an alkylene group having 1 to 8 carbon atoms, or a residue of a saturated or unsaturated dicarboxylic acid having 1 to 10 carbon atoms).

[0028] Alkyl dihydrazides include methylene dihydrazide, ethyl dihydrazide, propyl dihydrazide, and butyl dihydrazide. Diacyl hydrazides of saturated aliphatic dicarboxylic acids include oxalate dihydrazide, malonate dihydrazide, succinate dihydrazide, glutarate dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide. Diacyl hydrazides of unsaturated dicarboxylic acids include phthalate dihydrazide, fumarate dihydrazide, and itaconic acid dihydrazide.

[0029] The content of hydrazine compounds having at least two hydrazine residues within the molecule is not particularly limited. As an example, the content of hydrazine compounds having at least two hydrazine residues within the molecule in the primer composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. Furthermore, the content of hydrazine compounds having at least two hydrazine residues within the molecule in the primer composition is preferably 6% by mass or less, more preferably 3% by mass or less. By ensuring that the content of hydrazine compounds having at least two hydrazine residues within the molecule is within the above-mentioned range, the resulting coating film exhibits excellent alcohol resistance when an inkjet image is formed after the primer composition is applied. Additionally, the primer composition demonstrates excellent storage stability.

[0030] (wax)

[0031] Waxes are formulated to improve scratch resistance. There are no specific limitations on the type of wax. For example, waxes include beeswax, lanolin wax, whale wax, candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, and other plant and animal waxes; lignite wax, ceresin wax, pure ceresin wax, paraffin wax, microcrystalline wax, petrolatum, and other mineral and petroleum-based waxes; Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and other synthetic hydrocarbon waxes; polytetrafluoroethylene wax and other fluoropolymer waxes; mixtures of polytetrafluoroethylene wax and polyethylene wax; modified waxes such as lignite wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives; hydrogenated castor oil, hydrogenated castor oil derivatives, and other hydrogenated waxes; and polytetrafluoroethylene wax, etc. Among these, polyethylene wax, mixtures of polytetrafluoroethylene wax and polyethylene wax, fluoropolymer waxes, and Fischer-Tropsch wax are preferred.

[0032] 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. Furthermore, the average particle size of the wax is preferably 6 μm or less, more preferably 5 μm or less. By incorporating a wax with a relatively large particle size, the primer composition of this embodiment can improve the anti-blocking properties of the resulting coating film when forming an inkjet image after being applied to the primer composition. It should be noted that in this embodiment, the average particle size of the wax can be measured using a Nanotrac (UPA-EX150, manufactured by Nikkiso Co., Ltd.).

[0033] The wax content is not particularly limited. As an example, the wax content in the primer composition, calculated as solids, is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. Furthermore, the wax content in the primer composition, calculated as solids, is preferably 12% by mass or less, more preferably 4% by mass or less. With the wax content within the above range, when the primer composition is applied to form an inkjet image, the resulting coating exhibits excellent anti-blocking properties.

[0034] (White pigment)

[0035] The primer composition of this embodiment appropriately includes a white pigment. By including a white pigment, the design and visibility of prints using the primer composition are further improved.

[0036] There is no particular limitation on white pigments. For example, white pigments can be various inorganic white pigments, organic white pigments, etc. Inorganic white pigments include titanium dioxide, zinc oxide, cerium oxide, silicon dioxide, aluminum oxide, magnesium oxide, zirconium dioxide, yttrium-stabilized zirconium oxide, indium oxide, antimony oxide, tin oxide, barium titanate, barium sulfate, calcium carbonate, micronized silicate, calcium silicate, talc, and clay, etc. Organic white pigments include organic compound salts shown in Japanese Patent Application Publication No. 11-129613, alkylene dimelamine derivatives shown in Japanese Patent Application Publication No. 11-140365, and Japanese Patent Application Publication No. 2001-234093, etc. Among these, from the perspective of excellent concealment, various types of titanium dioxide such as rutile and anatase are preferred as white pigments, and titanium dioxide whose surface has been coated with aluminum oxide, silicon dioxide, organic matter, etc., is more preferred.

[0037] The average particle size of the white pigment is not particularly limited. For example, the average particle size of the white pigment is preferably 100 nm or more, more preferably 150 nm or more. Furthermore, the average particle size of the white pigment is preferably 500 nm or less, more preferably 400 nm or less. When the average particle size of the white pigment is within the above range, the resulting coating exhibits excellent concealment when the primer composition is applied to form an inkjet image. It should be noted that in this embodiment, the average particle size is the volume average particle size measured by laser diffraction particle size analysis using a Nanotrac (UPA-EX150, manufactured by Nikkiso Co., Ltd.).

[0038] The content of white pigment is not particularly limited. As an example, the content of white pigment in the primer composition is preferably 5% by mass or more, more preferably 10% by mass or more. Furthermore, the content of white pigment in the primer composition is preferably 20% by mass or less, more preferably 15% by mass or less. When the content of white pigment is within the above range, the resulting coating film exhibits excellent concealment when an inkjet image is formed after applying the primer composition. Additionally, when the primer composition is applied to flexible packaging materials, designs and other patterns are easily visible and legible when printed on them.

[0039] (Chlorinated polyolefins)

[0040] The primer composition of this embodiment preferably further comprises a chlorinated polyolefin. The chlorinated polyolefin is preferably used in the form of a chlorinated polyolefin emulsion. A chlorinated polyolefin emulsion is obtained by chlorinating and emulsifying a polyolefin resin.

[0041] Chlorinated polyolefins are not particularly limited. Examples of chlorinated polyolefins include chlorinated polypropylene resin and chlorinated polyethylene resin. Furthermore, chlorinated polyolefins can also be modified. Modifiers are not particularly limited. Examples of modified chlorinated polyolefins include substances obtained by graft polymerization of polymeric acrylic compounds (acrylic acid, methacrylic acid, or their alkyl esters, etc.) or unsaturated polycarboxylic acids (maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, etc.) with chlorinated polyolefins, or substances obtained by chlorinating polyolefins obtained by graft polymerization of the aforementioned unsaturated polycarboxylic acids.

[0042] The chlorine content in the chlorinated polyolefin is not particularly limited. As an example, the chlorine content is preferably 1% by mass or more relative to the total resin content, more preferably 10% by mass or more. Furthermore, the chlorine content is preferably 40% by mass or less relative to the total resin content, more preferably 30% by mass or less. When the chlorine content is within the above range, the chlorinated polyolefin is readily soluble in solvents, and the adhesion between the substrate and the primer composition is excellent.

[0043] When chlorinated polyolefins are included, the content of the chlorinated polyolefins is not particularly limited. As an example, the content of chlorinated polyolefins in the primer composition, calculated as solids, is preferably 0.5% by mass or more, more preferably 1% by mass or more. Furthermore, the content of chlorinated polyolefins in the primer composition, calculated as solids, is preferably 5% by mass or less, more preferably 2% by mass or less. With the content of chlorinated polyolefins within the above range, when the primer composition is applied to form an inkjet image, the overall printing uniformity of the resulting coating is further improved.

[0044] (Water-soluble organic solvent)

[0045] The primer composition of this embodiment preferably further comprises a water-soluble organic solvent. By including a water-soluble organic solvent, the overall printing uniformity of the resulting coating film is further improved when an inkjet image is formed after the primer composition is applied.

[0046] There are no particular limitations on the water-soluble organic solvent. However, to give an example, the preferred water-soluble organic solvent is an alcohol or polyol solvent, 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 monopropyl ether, triethylene glycol monopropyl ether, triethylene glycol monopropyl ether, triethylene glycol monopropyl ether, triethylene glycol monopropyl ether, triethylene glycol monoethyl ... Ethers, 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, ethylene glycol dibutyl ether, glycerol, etc.

[0047] When a water-soluble organic solvent is included, the content of the water-soluble organic solvent is not particularly limited. As an example, the content of the water-soluble organic solvent in the primer composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Furthermore, the content of the water-soluble organic solvent in the primer composition is preferably 20% by mass or less, more preferably 10% by mass or less. When the content of the water-soluble organic solvent is within the above range, the uniformity of the printed coating is further improved when an inkjet image is formed after the primer composition is applied.

[0048] (Any ingredients)

[0049] The ink composition of this embodiment may also be appropriately combined with various additives such as tackifiers, crosslinking agents, lubricants, antiblocking agents, antistatic agents, surfactants, chelating agents, and hard resins.

[0050] (Method for manufacturing primer composition)

[0051] The method for manufacturing the primer composition of this embodiment is not particularly limited. As an example, the primer composition can be prepared by mixing white pigment, acrylic resin emulsion emulsified by polymer, N-oleoylsarcosine, hydrazine compound having at least two hydrazine residues in the molecule, wax, and various other arbitrary components, and then mixing them using various mixing machines, such as bead mills, ball mills, sand mills, grinding mills, roller mills, pearl mills, etc.

[0052] The resulting primer composition preferably has a viscosity of 10 to 1000 mPa·s. Furthermore, when used in gravure printing, the primer composition is preferably diluted with water or an organic solvent to a flow rate of approximately 12 to 23 seconds / 25°C for a No. 3 Zein cup and approximately 14 to 16 seconds / 25°C for high-speed printing, so that the viscosity is appropriate according to the printing conditions and ambient temperature.

[0053] The resulting primer composition can be printed onto various flexible packaging plastic films and other substrates using methods such as gravure printing. Examples of plastic films suitable for integral printing with packaging materials include stretched and unstretched polyolefins such as polyethylene and polypropylene, polyester, nylon, celluloid, and vinylon. The resulting printed material can be used to make bags for use as packaging containers for food and other products.

[0054] According to this embodiment, the primer composition exhibits excellent storage stability, and when an inkjet image is formed after applying the primer composition, it can impart excellent overall printing uniformity, bleed resistance, scratch resistance, alcohol resistance, and heat resistance to the coating film.

[0055] <Ink Group>

[0056] One embodiment of the ink group of the present invention includes the above-described primer composition for surface printing flexible packaging and a water-based inkjet ink composition. The water-based inkjet ink composition includes pigments, water-insoluble resins, and waxes. These will be described separately below.

[0057] (Water-based inkjet ink composition)

[0058] Water-based inkjet ink compositions (hereinafter also referred to as ink compositions) contain pigments, water-insoluble resins, and waxes.

[0059] ·pigment

[0060] There are no specific limitations on pigments. If we were to give an example, pigments could refer to various organic and inorganic pigments. Organic pigments include dye lake pigments, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, violet ketone pigments, diketopyrrole pigments, isoindolinone pigments, nitro pigments, nitroso pigments, yellow anthrone pigments, quinophthalone pigments, pinantrone pigments, indigo anthraquinone pigments, etc.

[0061] Inorganic pigments include carbon black, titanium dioxide, zinc white, iron oxide red, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0062] Pigments can also be pigments that have undergone surface treatment using known surface treatment agents.

[0063] Yellow pigments include CI 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.

[0064] Magenta pigments include CI 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, and CI Pigment Violet 19, etc.

[0065] Cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc.

[0066] Black pigments include carbon black (CI Pigment Black 7), etc.

[0067] White pigments include titanium dioxide and aluminum oxide. White pigments can also be surface-treated using various materials such as aluminum oxide and silicon dioxide.

[0068] The pigment content is not particularly limited. As an example, the pigment content in the ink composition is preferably 2% by mass or more, more preferably 4% by mass or more. Furthermore, the pigment content in the ink composition is preferably 10% by mass or less, more preferably 8% by mass or less.

[0069] Water-insoluble resin

[0070] There is no particular limitation on water-insoluble resins. As an example, a water-insoluble resin may be an acrylic emulsion obtained by emulsion polymerization of a carboxyl-containing monomer with other monomers by a known method.

[0071] The compounds containing carboxyl monomers include acrylic acid, methacrylic acid, (anhydrous) maleic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, monolaurate maleate, etc., which are aliphatic hydrocarbons with 8 to 13 carbon atoms; monomyristyl maleate, monocetyl maleate, monostearin maleate, monooleate maleate, monoeicoyl maleate, etc., which are aliphatic hydrocarbons with 14 to 20 carbon atoms; crotonic acid and its ester compounds; itaconic acid and its ester compounds, etc.

[0072] Other free radical polymerizable unsaturated monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, myristyl methacrylate, cetyl methacrylate, stearyl methacrylate, oleyl methacrylate, eicosyl methacrylate, and other methacrylates with aliphatic hydrocarbon groups, such as 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate. (Meth)acrylate compounds with hydroxyalkyl groups, such as methyl propyl ester and 3-hydroxypropyl methacrylate; (meth)acrylamide; acrylonitrile; olefinic compounds; styrene monomers such as styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and fluorostyrene; benzyl methacrylate and benzyl acrylate monomers; phenyl methacrylate and phenyl acrylate monomers.

[0073] There is no particular limitation on the glass transition temperature of water-insoluble resins. For example, the glass transition temperature is 50–120°C. Coatings obtained with glass transition temperatures within this range exhibit excellent durability, and the ink compositions demonstrate excellent storage and discharge stability.

[0074] The content of water-insoluble resin is not particularly limited. As an example, the content of water-insoluble resin, relative to 100% by mass of the pigment, is preferably 150% by mass or more, more preferably 200% by mass or more, calculated as solids. Furthermore, the content of water-insoluble resin, relative to 100% by mass of the pigment, is preferably 400% by mass or less, more preferably 300% by mass or less, calculated as solids. With the water-insoluble resin content within the above range, the ink composition exhibits excellent storage stability and dispensing stability.

[0075] ·wax

[0076] The wax is associated with the primer composition, as described above.

[0077] (Any ingredients)

[0078] The ink composition of this embodiment may also be appropriately combined with water-soluble resins, surfactants, water-soluble organic solvents, calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, talc and other extender pigments, inorganic microparticles and adhesive resins (acrylic resin, vinyl acetate resin) for imparting anti-slip properties, leveling agents for improving leveling properties, defoamers for imparting defoaming properties, alkaline compounds such as caustic soda for imparting resolubility, film-forming emulsions, preservatives, rust inhibitors, crosslinking agents and other additives.

[0079] Water-soluble resins

[0080] Water-soluble resins are not particularly limited. For example, water-soluble resins include various alkali-soluble resins. Alkali-soluble resins are not particularly limited. For example, alkali-soluble resins include resins obtained by polymerizing monomers having unsaturated double bonds, resins obtained through the reaction of functional groups with each other, etc.

[0081] Specifically, alkali-soluble resins are various adhesive resins such as acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, styrene-acrylic acid-maleic acid resins, polyurethane resins, and polyester resins, which are copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene as the main monomer components.

[0082] These alkali-soluble resins can be dissolved in water in the presence of alkaline compounds and used as water-soluble resin varnishes. There are no particular limitations on the alkaline compounds. Examples include ammonia, organic amines, and alkali metal hydroxides. Organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, as well as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, triethanolamine, and other alkanolamines. Alkali metal hydroxides include sodium hydroxide and potassium hydroxide.

[0083] When a water-soluble resin is incorporated, the content of the water-soluble resin is not particularly limited. As an example, the content of the water-soluble resin in the ink composition is preferably 1.0% by mass or more, more preferably 3.0% by mass or more. Furthermore, the content of the water-soluble resin in the ink composition is preferably 10.0% by mass or less, more preferably 6.0% by mass or less.

[0084] Surfactants

[0085] There are no specific limitations on surfactants. If we were to give an example, surfactants could be acetylene-based surfactants, organosilicon-based surfactants, etc.

[0086] Commercially available acetylene surfactants include "Dinol 607", "Dinol 609", "Olfine E-1004", "Olfine E-1010", "Olfine E-1020", "Olfine PD-001", "Olfine PD-002W", "Olfine PD-004", "Olfine PD-005", "Olfine EXP.4001", "Olfine EXP.4200", "Olfine EXP.4123", and "Olfine EXP.4300" (all manufactured by Nissin Chemical Industry Co., Ltd.); "Surfynol 104E", "Surfynol 104H", "Surfynol 104A", "Surfynol 104BC", "Surfynol 104DPM", "Surfynol 104PA", "Surfynol 104PG-50", and "Surfynol..." "420", "Surfynol 440", "Surfynol 465" (the above are manufactured by EVONIK), etc.

[0087] Commercially available silicone surfactants include “BYK-307”, “BYK-333”, “BYK-347”, “BYK-348”, “BYK-349”, “BYK-345”, “BYK-378”, and “BYK-3455” (all manufactured by BYK Chemie).

[0088] When a surfactant is used, the content of the surfactant is not particularly limited. As an example, the surfactant content in the ink composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more. Furthermore, the surfactant content in the ink composition is preferably 10.0% by mass or less, more preferably 6.0% by mass or less.

[0089] Water-soluble organic solvents

[0090] There are no particular restrictions on water-soluble organic solvents. To give an example, water-soluble organic solvents include 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, ethylene glycol dibutyl ether, glycerin, etc.

[0091] When a water-soluble organic solvent is used, the content of the water-soluble organic solvent is not particularly limited. As an example, the content of the water-soluble organic solvent in the ink composition is preferably 5% by mass or more, more preferably 10% by mass or more. Furthermore, the content of the surfactant in the ink composition is preferably 50% by mass or less, more preferably 40% by mass or less.

[0092] (Method for manufacturing ink composition)

[0093] The method for manufacturing the ink composition of this embodiment is not particularly limited. As an example, the ink composition can be prepared by mixing pigments, water-insoluble resins, waxes, and various other arbitrary components, and then mixing them using various mixing machines, such as bead mills, ball mills, sand mills, grinding mills, roller mills, pearl mills, etc.

[0094] Returning to the overall description of the ink set, the ink set of this embodiment includes the primer composition and the ink composition described above. Therefore, surface-printed materials obtained using the ink set exhibit excellent uniformity of printing across the entire surface, resistance to smudging, scratch resistance, alcohol resistance, and heat resistance.

[0095] <Surface Printing and Inkjet Printing Methods>

[0096] One embodiment of the present invention provides a surface-printed product having the aforementioned surface-printed flexible packaging primer composition and the aforementioned water-based inkjet ink composition applied to it. Another embodiment of the present invention provides an inkjet printing method comprising a printing step of surface-printing the aforementioned surface-printed flexible packaging primer composition and the aforementioned water-based inkjet ink composition onto a substrate.

[0097] The substrate is not particularly limited. For example, various types of plastic films used for flexible packaging are suitable substrates. Examples of plastic films that can be printed integrally with the packaging material include stretched and unstretched polyolefins such as polyethylene and polypropylene, polyester, nylon, celluloid, and vinylon.

[0098] From the viewpoint of imparting transparency, heat resistance, and mechanical strength, the plastic film is preferably subjected to uniaxial or biaxial stretching treatment. Furthermore, to improve adhesion and wetting properties with the aforementioned primer composition, the surface of the plastic film coated with the primer composition is preferably subjected to plasma treatment, corona discharge treatment, or the like.

[0099] The printing process is a process in which the above-mentioned primer composition and ink composition are sequentially applied to a substrate by means of, for example, gravure printing.

[0100] Specifically, a primer composition is applied to a substrate to form a primer layer. By forming a primer layer, the printability of the ink composition is improved, thereby enhancing the adhesion of the resulting printed layer.

[0101] Next, the ink composition is printed onto the primer layer using an inkjet printing method. The ink composition is printed using an inkjet printing method to form a printed layer.

[0102] It should be noted that, from the perspective of being able to print at higher speeds, inkjet printing is preferably performed using a single-pass printing method with a fixed line printhead.

[0103] From the viewpoint of balancing printing speed and the color density of the resulting printed matter, the coating amount of the ink composition, calculated based on the solid content contained in the ink composition, is preferably 0.05 to 3.00 g / m³. 2 More preferably, it is 0.1–2.00 g / m 2 .

[0104] The resulting printed materials can also be dried using various drying devices. Furthermore, the resulting printed materials can be subjected to various lamination processes.

[0105] The surface-printed material obtained in this embodiment exhibits excellent uniformity of printing across the entire surface, resistance to smudges, scratch resistance, alcohol resistance, and heat resistance.

[0106] The above description describes one embodiment of the present invention. The present invention is not particularly limited to the above embodiment. It should be noted that the above embodiment mainly describes an invention having the following configuration.

[0107] (1) A primer composition for surface printing flexible packaging, comprising an acrylic resin emulsion emulsified by a polymer, N-oleoylsarcosine, a hydrazine compound having at least two 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.

[0108] Based on this composition, the primer composition for surface printing flexible packaging, when applied to form an inkjet image, can impart excellent overall printing uniformity, bleed resistance, scratch resistance, alcohol resistance, and heat resistance to the coating film.

[0109] (2) The primer composition for surface printing flexible packaging according to (1), wherein it further comprises a white pigment.

[0110] Based on this composition, the design and visibility of printed materials using the primer composition for surface printing flexible packaging are further improved.

[0111] (3) The primer composition for surface printing flexible packaging according to (1) or (2), wherein it further comprises chlorinated polyolefin.

[0112] Based on this configuration, the uniformity of printing inkjet images on the entire surface of the primer composition for surface printing flexible packaging is further improved.

[0113] (4) An ink group comprising a primer composition for surface printing flexible packaging as described in any one of (1) to (3) and an ink composition for water-based inkjet printing, wherein the ink composition for water-based inkjet printing comprises pigment, water-insoluble resin and wax.

[0114] Based on this configuration, the surface-printed material with inkjet images formed on the coating exhibits excellent uniformity of printing, resistance to bleed-through, scratch resistance, alcohol resistance, and heat resistance.

[0115] (5) A surface-printed material, provided with the surface-printed flexible packaging primer composition of (4) and the above-mentioned water-based inkjet composition.

[0116] Based on this configuration, the resulting surface-printed material exhibits excellent uniformity of printing, resistance to ink penetration, scratch resistance, alcohol resistance, and heat resistance.

[0117] (6) An inkjet printing method comprising a printing step of surface printing the primer composition for flexible packaging described in (4) and the water-based inkjet composition described above onto a substrate.

[0118] Based on this configuration, a surface-printed material with excellent uniformity of printing, resistance to bleed-through, scratch resistance, alcohol resistance, and heat resistance can be obtained, forming a coating with an inkjet image.

[0119] Example

[0120] The present invention will now be described in more detail with reference to the embodiments. The present invention is not limited to these embodiments in any way. It should be noted that, unless otherwise specified, "%" refers to "percentage by mass" and "parts" refers to "parts by mass".

[0121] The raw materials and preparation methods used are shown below.

[0122] <Water-based resin varnish>

[0123] 20 parts by mass of an acrylic acid / n-butyl acrylate / benzyl methacrylate / styrene copolymer with a glass transition temperature of 40℃, a weight-average molecular weight of 30000, and an acid value of 185 mgKOH / g were 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 with a solid content of 20%.

[0124] <Preparation of Water-based Black Ink Base A>

[0125] 60.3 parts by weight of water were added to 23.7 parts by weight of the above-mentioned water-based resin varnish and mixed to prepare a pigment dispersion resin varnish. 16 parts by weight of carbon black (Printex 90, manufactured by Orion Engineered Carbon) were further added to this varnish, and after stirring and mixing, it was kneaded using a wet circulating mill to prepare a water-based black ink base.

[0126] <Preparation of Water-Based Black Ink Base B (Crosslinking Base)>

[0127] Add 2.1 parts by weight of Epolight 1600 (a difunctional epoxy compound, manufactured by Kyoei Chemical Co., Ltd.) and 22.9 parts by weight of water to 75 parts by weight of the above-mentioned water-based black ink base material A, and heat at 60°C for 24 hours to obtain water-based black ink base material B.

[0128] <Preparation of Water-Based Yellow Ink Base>

[0129] 64.3 parts by weight of water were added to 23.7 parts by weight of the above-mentioned water-based resin varnish and mixed to prepare a pigment dispersion resin varnish. 12 parts by weight of yellow pigment (Novoperm Yellow 4G01, manufactured by Clariant) were further added to this varnish, and after stirring and mixing, it was kneaded using a wet circulating mill to prepare a water-based yellow ink base.

[0130] <Preparation of Water-Based Magenta Ink Base>

[0131] 64.3 parts by weight of water were added to 23.7 parts by weight of the above-mentioned water-based resin varnish and mixed to prepare a pigment dispersion resin varnish. 12 parts by weight of magenta pigment (Inkjet Magenta E5B02, manufactured by Clariant) were further added to this varnish, and after stirring and mixing, it was kneaded using a wet circulating mill to prepare a water-based magenta ink base.

[0132] <Preparation of Water-Based Cyan Ink Base>

[0133] 64.3 parts by weight of water were added to 23.7 parts by weight of the above-mentioned waterborne resin varnish and mixed to prepare a pigment dispersion resin varnish. 12 parts by weight of cyan pigment (Heliogen Blue L7101F, manufactured by BASF) were further added to this varnish, and after stirring and mixing, it was kneaded using a wet circulating mill to prepare a waterborne cyan base material.

[0134] <Preparation of Water-Based White Pigment Base>

[0135] 20.0 parts by weight of water were added to 40.0 parts by weight of the aforementioned waterborne resin varnish and mixed to prepare a pigment dispersion resin varnish. 40 parts by weight of titanium dioxide (R-960, manufactured by DuPont) were further added to this varnish, and after stirring and mixing, it was kneaded using a wet circulating mill to prepare a waterborne white pigment base.

[0136] <surfactants>

[0137] Olfine E1010 (100% solids, HLB 13-14, manufactured by Nissin Chemical Industry Co., Ltd.)

[0138] Olfine E1004 (100% solids, HLB 7-9, manufactured by Nissin Chemical Industry Co., Ltd.)

[0139] <Resin Emulsion>

[0140] (An acrylic resin emulsion emulsified with polymers)

[0141] PE-1126 (41.5% solids, high molecular weight emulsified acrylic resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: -12℃)

[0142] JE-1113 (42.5% solids, high molecular weight emulsion acrylic resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: -24℃)

[0143] HE-1335 (45.5% solids, high molecular weight emulsion acrylic-styrene resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: 15℃)

[0144] QE-1042 (40.5% solids, high molecular weight emulsion acrylic-styrene resin emulsion, manufactured by Starlight PMC Co., Ltd., Tg: 53℃)

[0145] (Acrylic resin emulsion emulsified by emulsifier)

[0146] Mowinyl 7320 (40.0% solids, emulsified acrylic resin emulsion, manufactured by Japan CoatingResin Co., Ltd., Tg: -20℃)

[0147] Mowinyl 730L (46.0% solids, emulsified acrylic resin emulsion, manufactured by Japan CoatingResin Co., Ltd., Tg: -13℃)

[0148] Neo-CrylA-1125 (19.5% solids, emulsified acrylic resin emulsion, manufactured by DSM Neoresins, Tg: 13℃)

[0149] Neo-CrylA-1093 (45.5% solids, emulsified acrylic-styrene resin emulsion, manufactured by DSM Neoresins, Tg: 17℃)

[0150] <Polyethylene-based resin>

[0151] Neo-Cryl A-1094 (45.5% solids, acrylic-styrene resin emulsion, manufactured by DSM Neoresins)

[0152] Neo-Cryl A-1125 (19.5% solids, acrylic resin emulsion, manufactured by DSM Neoresins)

[0153] Vinyblan 715S (23% solids, vinyl chloride resin emulsion, manufactured by Nisshin Chemical Industry Co., Ltd.)

[0154] Auroren AE-301 (30% solids, polyolefin resin emulsion, manufactured by Nippon Paper Co., Ltd.)

[0155] Joncryl JDX-6639 (29% solids, aqueous solution of acrylic-styrene resin, manufactured by BASF)

[0156] 3401MA (40% solids, aqueous solution of acrylic resin, manufactured by Taisei Fine Chemicals Co., Ltd.)

[0157] <Polyurethane Resins>

[0158] Superflex150HS (38% solids, polyurethane resin emulsion, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.)

[0159] Hyderun HW350 (30% solids, aqueous solution of polyester polyurethane resin, manufactured by DIC Corporation)

[0160] <Polyester Resins>

[0161] Elitel KT-9204 (30% solids, polyester resin emulsion, manufactured by Uniqlo Corporation)

[0162] Plascoat Z-730 (25% solids, aqueous solution of polyester resin, manufactured by Koyo Chemical Industry Co., Ltd.)

[0163] <Wax Emulsion>

[0164] AQUACER531 (45% solids, polyethylene resin emulsion, average particle size 160nm, manufactured by BYK)

[0165] AQUACER539 (35% solids, polyethylene wax emulsion, average particle size 50nm, manufactured by BYK)

[0166] Chemipearl W-400 (40% solids, polyethylene resin emulsion, average particle size 4.0 μm, manufactured by Mitsui Chemicals Co., Ltd.)

[0167] <Example 1>

[0168] According to the mass ratios (mass%) shown in Table 1 below, the materials were mixed and stirred to prepare a primer composition (P1). The storage stability of the obtained primer composition was evaluated using the following evaluation methods. The results are shown in Table 1. Additionally, according to the mass ratios (mass%) shown in Table 2 below, the materials were mixed using a paint mixer to prepare an ink composition (K1). Using the ink group consisting of the primer composition (P1) and the ink composition (K1), gravure printing was performed under the following conditions to obtain a printed object. The overall surface formation, fine line bleeding (bleed resistance), scratch resistance, alcohol resistance, and heat resistance of the obtained printed object were evaluated using the following evaluation methods. The results are shown in Tables 4 and 5.

[0169] [Table 1]

[0170]

[0171] [Table 2]

[0172]

[0173] [Table 3]

[0174]

[0175] <Examples 2-31, Comparative Examples 1-15>

[0176] The types of primer compositions (P2-P29), ink compositions (K1-K15, Y1, M1, C1), and formulations used were changed according to the records in Tables 1-3. Otherwise, printed materials were produced using the same method as in Example 1, and the results were evaluated. The results are shown in Tables 4 and 5.

[0177] <Storage stability of primer composition>

[0178] The primer compositions were taken separately from glass bottles, and their viscosity at 25°C was measured using a viscometer (RE100L type, manufactured by Toki Sangyo Co., Ltd.). The bottles were then sealed tightly and stored at 60°C for one month. The viscosity after storage (at 25°C) was measured using the viscometer. Storage stability was evaluated using the viscosity change rate (100 × (viscosity after 1 month at 60°C - viscosity before storage) / viscosity before storage).

[0179] (Evaluation Criteria)

[0180] ○: Viscosity change rate is less than 5%

[0181] △: Viscosity change rate is greater than 5% and less than 10%.

[0182] ×: Viscosity change rate is 10% or more but less than 30%.

[0183] <Conditions for preparing the primer layer>

[0184] The primer composition is printed onto the treated surface of the substrate using a gravure printing press under the following printing conditions, and then dried to form a primer layer.

[0185] (Printing conditions)

[0186] Substrate: Biaxially stretched polypropylene film, P-2111, manufactured by Toyobo Co., Ltd., with a thickness of 20 μm, treated with corona discharge.

[0187] Printing equipment: Gravure printing machine

[0188] Printing plate: 175-line engraving full-page plate

[0189] Printing speed: 15m / minute

[0190] Drying conditions: 80℃

[0191] <Full-face formation>

[0192] The ink compositions in Table 3 were mounted on an inkjet printer, and a full-page image of 20cm × 11.5cm was printed on the surface of each primer layer prepared above. The resulting prints were observed visually and evaluated using the following criteria.

[0193] (Evaluation Criteria)

[0194] ○: The printed material is free of unevenness and streaks.

[0195] △: Slight unevenness and streaks are visible in the printed material.

[0196] ×: Visually, the printed material is uneven and has streaks.

[0197] <The seepage of fine threads>

[0198] The ink composition in Table 3 was mounted on an inkjet printer, and fine lines of about 0.3 mm were printed on the surface of each primer layer prepared above. The thickening caused by seepage was observed by visual inspection, and the following criteria were used for evaluation.

[0199] (Evaluation Criteria)

[0200] ○: No bleeding, allowing printing to proceed at the original thickness.

[0201] △: Some areas show signs of thickening, but no thickening exceeding 2 times was observed.

[0202] ×: Overall, the thickness increased by more than 2 times.

[0203] <Abrasion Resistance>

[0204] The printed material with the full-page image was cut into 2.5cm×20cm pieces to make test pieces. Using a vibratory abrasion tester (manufactured by Daiei Scientific Instruments Co., Ltd.), bleached cloth was brought into contact with the printed surface and subjected to a 500g load for 100 cycles. The abrasion resistance was evaluated according to the following evaluation criteria based on the degree of ink fading.

[0205] (Evaluation Criteria)

[0206] ○: The coating with the full-face image formed did not peel off at all.

[0207] △: The coating with the full-face image is slightly peeled off.

[0208] ×: Most of the coating that forms a full-face image has peeled off.

[0209] <Alcohol Resistance>

[0210] The printed material with a full-page image was cut into 2.5cm × 20cm pieces to make test pieces. Using a vibratory friction tester (manufactured by Daiei Scientific Instruments Co., Ltd.), bleached cloth with 5 drops of 70% ethanol aqueous solution injected through an injection needle was brought into contact with the printed surface and subjected to a load of 200g for 10 cycles. The ethanol resistance was evaluated according to the following evaluation criteria based on the degree of ink fading.

[0211] (Evaluation Criteria)

[0212] ○: The coating with the full-face image formed did not peel off at all.

[0213] △: The coating with the full-face image is slightly peeled off.

[0214] ×: Most of the coating that forms a full-face image has peeled off.

[0215] <Heat resistance>

[0216] Using a heat-sealing tester equipped with a hot plate tilted at 160–200°C, the printed surface and aluminum foil were subjected to a heat seal test at 2.0 kg / cm². 2 Press the pressure for 1 second. Evaluate the heat resistance according to the following evaluation criteria based on the lowest temperature at which the ink on the printed surface transfers to the aluminum foil.

[0217] (Evaluation Criteria)

[0218] ○: The minimum temperature at which the ink on the printed surface is transferred to the aluminum foil is above 200°C.

[0219] △: The minimum temperature at which the ink on the printed surface is transferred to the aluminum foil is above 160℃ and below 200℃.

[0220] ×: The minimum temperature at which the ink on the printed surface transfers to the aluminum foil is less than 160°C.

[0221] [Table 4]

[0222]

[0223] [Table 5]

[0224]

Claims

1. A primer composition for surface printing on flexible packaging, comprising an acrylic resin emulsion emulsified by a polymer, N-oleoylsarcosine, a hydrazine compound having at least two hydrazine residues in its molecule, and a wax. The content of the acrylic resin emulsion, calculated based on solids content, is 3-40% by mass. The glass transition temperature of the acrylic resin emulsion is -40 to 30°C. in, The acid value of the polymer-emulsified acrylic resin emulsion is from 10 mg KOH / g to 100 mg KOH / g. The content of N-oleoylsarcosine in the primer composition is from 0.05% to 6% by mass. The hydrazine compounds are hydrazine and alkylene dihydrazides represented by the following general formula (1), or diacylhydrazine compounds of saturated aliphatic diacids or unsaturated diacids. H2N-NH-X-NH-NH2 (1) Wherein, X represents an alkylene group having 1 to 8 carbon atoms, or a residue of a saturated or unsaturated dicarboxylic acid having 1 to 10 carbon atoms. The content of the hydrazine compound having at least two hydrazine residues in the molecule is from 0.05% to 6% by mass in the primer composition. The wax particles have an average size of 0.05 μm to 6 μm, and The wax content, converted from solids, is 0.05% to 12% by mass in the primer composition.

2. The primer composition for surface printing flexible packaging according to claim 1, wherein, It also contains white pigment.

3. The primer composition for surface printing flexible packaging according to claim 1 or 2, wherein, It also contains chlorinated polyolefins.

4. An ink group comprising the primer composition for surface printing flexible packaging as described in any one of claims 1 to 3 and the water-based inkjet ink composition. The water-based inkjet ink composition comprises pigments, water-insoluble resins, and waxes.

5. A surface-printed material, provided with the surface-printed flexible packaging primer composition of claim 4 and the water-based inkjet ink composition.

6. An inkjet printing method, comprising a printing step of surface printing the primer composition for flexible packaging as described in claim 4 and the water-based inkjet ink composition onto a substrate.

Images