Printing ink composition for laminate and easy-tear laminate

Abstract

To provide a printing ink composition for laminate capable of exhibiting preferable color development and ease of tear, without using a large amount of a curing agent.SOLUTION: There is provided a printing ink composition for laminate including: a pigment; a binder resin; isophorone diisocyanate or an adduct thereof, the isophorone diisocyanate being a polyfunctional isocyanate compound and serving as a curing agent (except for a case in which, the polyfunctional isocyanate compound has an alkoxysilyl group); and an organic solvent. In the printing ink composition: the binder resin is a polyurethane resin which has a reaction group which may react with the isocyanate group in the polyfunctional isocyanate compound, in a high polymer diol being a raw material of the polyurethane resin, polyester diol is included by 70 mass% or more; a solid content inclusion ratio between the polyurethane resin and the curing agent is polyurethane resin:curing agent=1:0.25 to 0.90; the polyurethane resin is a following (1) or (2) or a mixture of the following (1) and (2), however, a case in which the printing ink composition for laminate includes vinyl chloride-vinyl acetate copolymerization resin is excepted. The following (1) is the polyurethane resin which has on a terminal, one or more kinds out of a primary amino group, secondary amine group and tertiary amino group, and has a hydroxy group, and the following (2) is the polyurethane resin which has on a terminal, one or more kinds out of, a primary amino group, a secondary amino group, and a tertiary amino group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a printing ink composition for lamination and an easily tearable laminate obtained by printing the printing ink for lamination on a substrate film, applying an adhesive thereto, and laminating a sealant film thereon. [Background technology]

[0002] Packaging materials made from various plastic films are used for food, confectionery, household goods, pet food, etc., taking into consideration functions such as design, economy, content protection, and transportability. Furthermore, many packaging materials are printed using gravure or flexographic printing with the intention of adding designs and messages that will appeal to consumers. To obtain the desired packaging material, front printing is performed on the surface of the base film of the packaging material, or reverse printing is performed by applying an adhesive or anchor agent to the printed surface of the base film of the packaging material as needed and laminating the film. In reverse printing, colored inks and white inks are printed sequentially onto various films such as polyester, nylon, and aluminum foil, and then a polyethylene film or polypropylene film is laminated onto the white ink printing layer for the purpose of heat sealing by dry lamination using an adhesive or extrusion lamination using an anchor coating agent (see, for example, Patent Document 1).

[0003] The laminate is then used as a laminated bag for foods such as sweets, soup, and miso soup. These laminated bags are opened by hand to remove the contents. If the tearability is poor, excessive force must be applied when opening the bag, and the bag may tear in an unintended direction, resulting in the contents spilling out. Therefore, good tearability is required. In particular, the areas where ink is printed tend to have poorer tearability because the bonding strength between the ink layer and the adhesive layer is weaker than in areas without ink. It is known that one way to improve tearability is to harden the laminate adhesive layer (see, for example, Patent Document 2). However, when there is a mixture of ink areas and blank areas where no ink is printed, if the adhesive layer is made hard enough to be torn at the ink areas, the blank areas will become too hard, and conversely, if it is made to match the blank areas, the tearability of the ink areas will be poor.

[0004] To solve this problem, it has been proposed to include in the ink layer a curing agent having two or more functional groups that can react with the same functional groups in the ink layer and the adhesive layer, and to form the ink layer from a composition consisting of a compound (a1) having only two or more hydroxyl groups as functional groups in the molecule, and a curing agent that reacts with the hydroxyl groups (see, for example, Patent Document 3). In the examples, the solid content ratio of the polyfunctional isocyanate curing agent to the polyurethane resin contained in the ink layer is very low at polyurethane resin:polyfunctional isocyanate curing agent = 1:0.25, so although the tearability is improved slightly, there are still problems such as resistance felt when tearing, which is not sufficient. Furthermore, the ink layer using such a compound does not have sufficiently good color development.

[0005] In Patent Document 4, a large amount of curing agent is used in a two-component ink to improve tearability, but the use of a large amount of curing agent has a large impact on costs, so there is room for improvement. In Patent Document 5, it is possible to reduce the amount of curing agent compared to Patent Document 4, but there is a demand for further reduction in the amount of curing agent while maintaining tearability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-97959 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-274061 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-125978 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-25143 [Patent Document 5] Patent No. 6545559 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to provide a printing ink composition for lamination that can exhibit good color development and easy tearability without using a large amount of curing agent, and an easy-tear laminate obtained by printing the printing ink for lamination on a base film, applying an adhesive thereto, and laminating a sealant film thereon. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have invented the following printing ink composition for laminate and laminate. The present invention provides [1] A printing ink composition for laminate containing a pigment, a binder resin, a polyfunctional isocyanate compound as a curing agent, and an organic solvent, wherein the binder resin is a polyurethane resin having a reactive group capable of reacting with an isocyanate group of the polyfunctional isocyanate compound, the polyurethane resin is made of a polymer diol that contains 70% by mass or more of polyester diol, and the solid content ratio of the polyurethane resin to the curing agent is polyurethane resin:curing agent=1:0.10 to 0.90. [2] The printing ink composition for laminate according to (1), wherein the polyurethane resin is the following (1) or (2), or a mixture of the following (1) and (2): (1) A polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at its terminal, and also having a hydroxyl group. (2) Polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at the terminal. [3] The printing ink composition for laminate according to the above [1] or [2], wherein the polyfunctional isocyanate compound is a tri- or higher functional isocyanate compound. [4] The printing ink composition for laminate according to any one of [1] to [3] above, characterized in that the pigment contains rutile-type titanium dioxide treated with silica and alumina and having an oil absorption of 20 to 35 g / 100 g. [5] The printing ink composition for laminate according to [4] above, characterized in that the pigment contains rutile-type titanium dioxide treated with silica and alumina and having an oil absorption of 25 to 35 g / 100 g. [6] The printing ink composition for laminate according to any one of the above [1] to [5], wherein the organic solvent is a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent. [7] An easily tearable laminate obtained by laminating a base film with a printed layer made of the printing ink for lamination according to any one of [1] to [6] above, an adhesive layer having a hydroxyl group, and a sealant film laminated in this order. [8] The easy-tear laminate according to [7] above, characterized in that it is obtained by printing the printing ink for lamination according to any one of [1] to [6] above onto the base film, applying an adhesive containing a resin having a hydroxyl group, and laminating a sealant film. [Effects of the Invention]

[0009] The printing ink composition for laminate of the present invention is a composition comprising the above-mentioned polyurethane resin as a binder resin and a polyfunctional isocyanate compound as a curing agent, with the solids content ratio of the polyurethane resin to the curing agent being polyurethane resin:curing agent = 1:0.10 to 0.90. The polyurethane resin has reactive groups that can react with the isocyanate groups of the polyfunctional isocyanate compound. Therefore, the curing agent in the printing ink composition for laminate reacts with the polyurethane resin in the ink composition and the hydroxyl groups in the adhesive layer, thereby increasing the bonding strength between the printing layer and the adhesive layer, and it is believed that this hardens the ink layer and improves tearability. In particular, when the polyurethane resin is (1) a polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at its terminal and also having a hydroxyl group, and / or (2) a polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at its terminal, and the curing agent is a polyfunctional isocyanate compound, polyurethane resin, and curing agent in a solids content ratio of polyurethane resin:curing agent = 1:0.10 to 0.90, the viscosity of the polyurethane resin can be adjusted to a viscosity range appropriate for printing ink, and pigment dispersibility is also good, making it possible to increase the resin content in the laminate printing ink composition. In addition, since the polyurethane resin contains hydroxyl groups, the curing agent in the laminate printing ink composition reacts with the hydroxyl groups in the adhesive layer, strengthening the bond between the printed layer and the adhesive layer, making the ink layer harder and improving tearability.In addition, the pigment dispersibility is improved, which is thought to result in good color development. DETAILED DESCRIPTION OF THE INVENTION

[0010] The printing ink composition for laminate and the easy-tearable laminate of the present invention will be described in more detail below. First, the printing ink composition for laminate of the present invention will be described. <Pigments> As the pigment that can be used in the present invention, various inorganic pigments and / or organic pigments that are generally used in printing inks can be used. The content of the pigment in the printing ink composition for laminate of the present invention is preferably in the range of 5 to 60% by mass in the ink composition. If the content of the pigment in the printing ink composition for laminate is less than the above range, the coloring power of the ink composition will decrease, and if it is more than the above range, the viscosity of the ink composition will increase, making the printed matter more susceptible to smearing. The pigment preferably contains rutile-type titanium dioxide treated with silica and alumina and having an oil absorption of 20 to 35 g / 100 g, and more preferably contains rutile-type titanium dioxide treated with silica and alumina and having an oil absorption of 25 to 35 g / 100 g. If the oil absorption is less than 20 g / 100 g, tearability may decrease, and if it exceeds 35 g / 100 g, pigment dispersibility may deteriorate.

[0011] <Binder resin> As the binder resin, a polyurethane resin having a reactive group capable of reacting with an isocyanate group of a polyfunctional isocyanate compound, which is a curing agent described below, can be used. As the polyurethane resin having a reactive group capable of reacting with the isocyanate group of the polyfunctional isocyanate compound, a polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group and / or a hydroxyl group at the terminal can be used. In particular, (1) a polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at the terminal and a hydroxyl group and / or (2) a polyurethane resin having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at the terminal is preferred. Such polyurethane resins can be obtained by synthesizing a urethane prepolymer by reacting a polyfunctional diisocyanate compound with a polymeric diol compound, and then reacting the resulting urethane prepolymer with (1) an amine compound containing a polyamine compound having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at both ends, and an amine compound having a hydroxyl group, or (2) an amine compound containing a polyamine compound having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at both ends. In this case, examples of the method for reacting the urethane prepolymer with (1) an amine compound containing a polyamine compound having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at both ends, and an amine compound having a hydroxyl group, and (2) an amine compound containing a polyamine compound having at least one of a primary amino group, a secondary amino group, and a tertiary amino group at both ends, include (A) a method in which the urethane prepolymer is chain-extended with a chain extender, and then the reaction is terminated with a reaction terminator, and (B) a method in which the urethane prepolymer is chain-extended with a chain extender and then the reaction is terminated with a reaction terminator simultaneously.

[0012] (Polyfunctional diisocyanate compounds) Polyfunctional diisocyanate compounds that can be used to obtain the binder resin include aromatic diisocyanate compounds such as tolylene diisocyanate, alicyclic diisocyanate compounds such as 1,4-cyclohexane diisocyanate and isophorone diisocyanate, aliphatic diisocyanate compounds such as hexamethylene diisocyanate, and aralkyl diisocyanate compounds such as α,α,α',α'-tetramethylxylylene diisocyanate. These compounds can be used singly or in combination. Among these, alicyclic diisocyanate compounds, aliphatic diisocyanate compounds, and aralkyl diisocyanate compounds are more preferred. Furthermore, trifunctional or higher functional isocyanate compounds can also be used. It is more preferred that the isocyanate component be a plant-derived bioisocyanate.

[0013] (polymeric diol compound) Examples of polymer diol compounds that can be used to obtain the binder resin include polyalkylene glycols such as polyethylene glycol and polypropylene glycol; polyether diol compounds such as alkylene oxide adducts of bisphenol A with ethylene oxide, propylene oxide, and the like; polyester diols obtained by the condensation reaction of one or more dibasic acids such as adipic acid, sebacic acid, and phthalic anhydride with one or more glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol; and polyester diol compounds such as polycaprolactone diols. These polymer diol compounds can be used singly or in combination. In the polymer diol, the polyester diol accounts for 70% by mass or more. A biopolyol component can be used as the polymer diol compound. Among these, a biopolyol obtained by reacting a short-chain diol component having 2 to 4 carbon atoms with a carboxylic acid component is preferred. It is more preferred that at least one of the short-chain diol component and the carboxylic acid component of the biopolyol component is plant-derived, and even more preferred that both are plant-derived. The plant-derived short-chain diol component having 2 to 4 carbon atoms is not particularly limited. For example, the short-chain diol component may be 1,3-propanediol, 1,4-butanediol, ethylene glycol, or the like, obtained from plant materials by the following methods. These may also be used in combination. 1,3-propanediol can be produced from glycerol via 3-hydroxypropylaldehyde (HPA) by a fermentation method in which glucose is obtained by decomposing plant resources (e.g., corn, etc.). 1,3-propanediol compounds produced by biomethods such as the above-mentioned fermentation method produce useful by-products such as lactic acid, which is safer than 1,3-propanediol compounds produced by the EO production method, and can also be produced at lower production costs. 1,4-butanediol can be produced by producing glycol from plant resources, fermenting the glycol, and then hydrogenating the resulting succinic acid. Ethylene glycol can also be produced from bioethanol obtained by a conventional method via ethylene.

[0014] The plant-derived carboxylic acid component is not particularly limited. Examples of the carboxylic acid component include sebacic acid, succinic acid, lactic acid, glutaric acid, azelaic acid, and dimer acid. These may be used in combination. Among these, it is preferable that the carboxylic acid component includes at least one selected from the group consisting of sebacic acid, succinic acid, and dimer acid.

[0015] Furthermore, in addition to the above-mentioned polymeric diol compounds, alkanediols such as 1,4-pentanediol, 2,5-hexanediol, and 3-methyl-1,5-pentanediol, and low molecular weight diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,3-butanediol can be used alone or in combination by mixing two or more kinds. In addition, in a mixture of an ester-based solvent and an alcohol-based solvent, using a polyether diol compound as the polymer diol compound tends to increase the solubility of the resulting polyurethane resin, making it preferable in that it allows for a wide range of ink designs to suit the required performance. The ratio of the organic diisocyanate compound to the polymeric diol compound used is such that the equivalent ratio of isocyanate groups to hydroxyl groups (isocyanate index) is usually in the range of 1.2:1 to 3.0:1, more preferably 1.3:1 to 2.0:1. If the isocyanate index is less than 1.2, the polyurethane resin tends to be flexible, and in cases where the ink has poor blocking resistance when printed, it may be preferable to use it in combination with another hard resin.

[0016] (Chain extender) Examples of chain extenders that can be used to obtain the binder resin include known chain extenders used in polyurethane resins as ink binders, such as aliphatic diamines such as ethylenediamine, propylenediamine, tetramethylenediamine, and hexamethylenediamine; alicyclic diamines such as isophoronediamine and 4,4'-dicyclohexylmethanediamine; polyamines such as diethylenetriamine and triethylenetetratriamine; aromatic diamines such as toluylenediamine; aromatic aliphatic diamines such as xylenediamine; diamines having a hydroxyl group such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine, and N,N'-di(2-hydroxyethyl)ethylenediamine; and diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, and triethylene glycol.

[0017] (reaction stopper) Examples of reaction terminators that can be used to obtain the binder resin include aliphatic diamines such as trimethylenediamine and hexamethylenediamine, alicyclic diamines such as isophoronediamine and 4,4'-dicyclohexylmethanediamine, polyamines such as diethylenetriamine and triethylenetetratriamine, aromatic diamines such as toluylenediamine, aromatic aliphatic diamines such as xylenediamine, polyamine compounds having primary amino groups at both ends, such as diamines having hydroxyl groups such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine and N,N'-di(2-hydroxyethyl)ethylenediamine, monoalkylamines such as n-propylamine and n-butylamine, dialkylamines such as di-n-butylamine, alkanolamines such as monoethanolamine and diethanolamine, and monoalcohols such as ethanol. To obtain a polyurethane resin having primary amino groups and / or secondary amino groups at both ends, a polyamine having primary amino groups and / or secondary amino groups at both ends is used as a reaction terminator. Examples of such polyamines having primary amino groups and / or secondary amino groups at both ends include aliphatic diamines such as ethylenediamine, propylenediamine, tetramethylenediamine, and hexamethylenediamine, alicyclic diamines such as isophoronediamine and 4,4'-dicyclohexylmethanediamine, polyamines such as diethylenetriamine and triethylenetetratriamine, aromatic diamines such as toluylenediamine, aromatic aliphatic diamines such as xylenediamine, and diamines having hydroxyl groups such as N-(2-hydroxyethyl)ethylenediamine and N-(2-hydroxyethyl)propylenediamine, among which polyamines having primary amino groups such as diethylenetriamine and triethylenetetratriamine are preferred. To obtain a polyurethane resin having hydroxyl groups, a compound having hydroxyl groups is used as a chain extender and / or a reaction terminator. Preferably, compounds having hydroxyl groups are used as both the chain extender and the reaction terminator. Examples of chain extenders include diamines having hydroxyl groups, such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine, and N,N'-di(2-hydroxyethyl)ethylenediamine. Examples of reaction terminators include diamines having a hydroxyl group, such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine, and N,N'-di(2-hydroxyethyl)ethylenediamine, and alkanolamines having a hydroxyl group, such as monoethanolamine and diethanolamine.

[0018] In the present invention, the polyurethane resin can be obtained using the above materials and a known polyurethane resin manufacturing method. Furthermore, since the hardness of the resulting polyurethane resin varies depending on the molecular weight, chemical structure, and equivalent ratio of each component, it is possible to adjust the printability and lamination suitability by appropriately selecting and combining these components. The content of the binder resin in the printing ink composition for laminate at the time of printing is preferably 5 to 15 mass % in terms of solid content. If the content of the binder resin is outside the above range, tearability tends to decrease. The polyurethane resin in the printing ink composition for laminate of the present invention preferably has a mass average molecular weight of 10,000 to 70,000, and more preferably 20,000 to 40,000. Furthermore, other binder resins such as cellulose resins, acrylic resins, vinyl chloride-vinyl acetate copolymers, polyamide resins, adhesive resins, etc. can be added as auxiliary binder resins. Among these, vinyl chloride-vinyl acetate copolymers are preferred, and from the viewpoint of reaction with the curing agent, vinyl chloride-vinyl acetate copolymers having hydroxyl groups are particularly preferred.

[0019] <Curing agent> The curing agent may be a polyfunctional polyisocyanate compound, such as biuret, isocyanurate, adduct, bifunctional polyfunctional isocyanate compound, or isophorone diisocyanate. Examples of the curing agent include 24A-100, 22A-75, TPA-100, TSA-100, TSS-100, TAE-100, TKA-100, P301-75E, E402-808, E405-70B, AE700-100, D101, D201, and A201H (manufactured by Asahi Kasei Corporation), Mytec Y260A (manufactured by Mitsubishi Chemical Corporation), Coronate CORONATE HX, Coronate CORONATE HL, and Coronate CORONATE L (manufactured by Tosoh Corporation), and Desmodur N75MPA / X (manufactured by Bayer). Among these, isophorone diisocyanate or an adduct thereof is preferred. Furthermore, tri- or higher functional isocyanate compounds can also be used. It is more preferable that the isocyanate component is a plant-derived bioisocyanate. The amount of this curing agent used is such that the mass ratio of the polyurethane resin to the curing agent is in the range of polyurethane resin:curing agent = 1:0.10 to 0.90 from the viewpoint of tearability, preferably polyurethane resin:curing agent = 1:0.13 to 0.40, and more preferably polyurethane resin:curing agent = 1:0.15 to 0.35.

[0020] <Organic solvents> Examples of organic solvents that can be used in the printing ink composition for laminate include toluene, ketone-based organic solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ester-based organic solvents (e.g., methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, etc.), alcohol-based organic solvents (e.g., methanol, ethanol, n-propanol, isopropanol, butanol, etc.), and hydrocarbon-based solvents (toluene, methylcyclohexane, etc.). In consideration of recent environmental concerns and the printability and drying properties of the ink, it is particularly preferred to use a mixed organic solvent of an ester-based organic solvent and an alcohol-based organic solvent as the organic solvent for the printing ink composition for lamination during printing, with the ester-based organic solvent / alcohol-based organic solvent ratio being in the range of 50 / 50 to 95 / 5, and preferably 60 / 40 to 85 / 15. Furthermore, from the viewpoint of printability of the ink, it is preferable that the printing ink composition for laminate contains 5% by mass or more, preferably 15% by mass or more, of propyl acetate during printing.

[0021] <Additives> The organic solvent-based gravure printing composition may further contain various additives such as a tackifier, a crosslinking agent, a lubricant, an anti-blocking agent, an antistatic agent, and a surfactant.

[0022] <Method for producing the printing ink composition for laminate of the present invention> The printing ink composition for laminate of the present invention is prepared by using any of the various conventionally used dispersion and kneading devices to prepare various materials other than the above-mentioned curing agent, and adjusting the content of each solid material and the combination of polyurethane resin and organic solvent to a viscosity of 10 to 1,000 mPa·s. From the viewpoint of stability over time, the curing agent is then added during printing, and the organic solvent is added and stirred at the ambient temperature during printing until the effluent time reaches an appropriate number of seconds depending on the printing conditions; specifically, until the effluent time reaches 12 to 23 seconds using a Zahn cup No. 3 test, preferably 14 to 16 seconds for high-speed printing.

[0023] <Easy-tear laminate> Next, we will explain an easy-tear laminate obtained by printing a laminating printing ink on a base film, applying an adhesive containing a polyester-based adhesive having a hydroxyl group and an isocyanate-based adhesive containing an isocyanate group, and laminating a sealant film.

[0024] (Base film) The base film of the easily tearable laminate of the present invention is not particularly limited, and various types of printing plastic films such as polyolefin films such as polyethylene and polypropylene, polyester films such as polyethylene terephthalate, polylactic acid and polycaprolactone, nylon and vinylon can be used. Furthermore, a biomass-based film made from a biomass-based resin can also be used.

[0025] (Laminate printing ink composition) As the printing ink composition for laminate, the above-mentioned printing ink composition for laminate can be used.

[0026] (glue) Adhesives containing resins having hydroxyl groups that have been conventionally used in extrusion lamination and dry lamination can be used, such as polyester adhesives containing hydroxyl groups and isocyanate adhesives containing isocyanate groups. Specifically, adhesives (anchor coating agents) used in extrusion lamination include A-3210 / A-3070, A-3210 / A3072, A-3210 / A-3075 (manufactured by Mitsui Chemicals, Inc.), Secadyne 2710A / Secadyne 2810C(T), Secadyne 2730A / Secadyne 2730B, Secadyne 2710A / Secadyne 2710C (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), LX-500, LX-901, LX747A, etc., and adhesives used in dry lamination include Dickdry LX-401A, 75A, 719, 703VL, 500, 510, etc. (manufactured by DIC Graphics, Dickdry is a registered trademark of DIC Graphics), Takelac / Takenate, etc. Examples include A-909 / A-5, A-977 / A-92, A-606 / A-50, A-515 / A-50, A-626 / A-50, A-525 / A-52, A-666 / A-65 (manufactured by Mitsui Chemicals, Inc.), RU-77, 771, 3600, 3900 (manufactured by Rock Paint Co., Ltd.), etc. Biomass-based adhesives made from biomass-based materials can also be used.

[0027] (sealant film) As the sealant film, resins that have been conventionally used as molten resins when laminating by dry lamination processing can be used, such as low-density polyethylene, LLDPE, ethylene-vinyl acetate copolymer, polypropylene, etc. Furthermore, as the plastic film used in the extrusion lamination process by laminating the formed film, conventionally used films such as unstretched plastic films (e.g., unstretched polyethylene film, unstretched polypropylene film, etc.) can be used.

[0028] <Easy-tearable laminate and easy-tearable laminate bag> The easy-tearable laminate and the easy-tearable laminate bag of the present invention will now be described. First, a desired pattern, letters, etc. are printed on the above-mentioned printing substrate using a general gravure printing method or flexographic printing method with the printing ink composition for laminate of the present invention. The resulting printed matter is then laminated with a heat-fusible polymer called a sealant. There are two main methods used for this lamination. The first is an extrusion lamination method in which printing is performed using a printing ink composition for lamination, and the printed portion is cured with a curing agent. After or before this, an adhesive (also known as an anchor coating agent) is applied to the surface of the resulting printed layer, and a heat-fusible polymer is then laminated as a molten resin. The extrusion lamination method involves applying an adhesive (e.g., an adhesive containing a polyester-based adhesive having hydroxyl groups and an isocyanate-based adhesive containing isocyanate groups) to the surface of the printed layer, and then laminating the molten resin using a known extrusion laminator. Furthermore, the molten resin can be used as an intermediate layer, and other materials can be laminated to form a sandwich-like laminate. Note that using an isocyanate-based anchor coating agent as the adhesive is preferable to using an imine-based anchor coating agent because of its superior adhesive strength. The second is dry lamination, in which printing is performed using a printing ink composition for lamination, and the printed portion is cured with a curing agent, and then, either before or after, an adhesive (for example, an adhesive containing a polyester-based adhesive having a hydroxyl group and an isocyanate-based adhesive containing an isocyanate group) is applied to the surface of the printed layer, followed by laminating a non-stretched plastic film. In particular, lamination can also be performed using a multilayer film in which a metal foil used in retort applications has been sandwiched in advance. The easily tearable laminate obtained by these methods is then finally heat-sealed with a heat sealer or the like so that the sealant surfaces of the laminate are heat-sealed together to form an easily tearable laminate bag. A common feature of these two methods is that when printing is performed using a printing ink composition for lamination, the printed area is cured with a curing agent, and then an adhesive is applied, the printing ink composition for lamination and the adhesive may be cured by different functional groups, i.e., by different curing mechanisms, or a curing agent that acts on the same functional group may be used. This makes it possible to select a more appropriate combination of the printing ink composition for lamination and the adhesive. On the other hand, when printing is performed using a printing ink composition for lamination and an adhesive is applied to the printed portion before curing with a curing agent, the printing ink composition for lamination and the adhesive may each use a curing agent having the same functional group acting thereon. [Example]

[0029] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0030] (Manufacturing polyurethane resin varnish) Polyurethane resin varnish A production example (100% by mass of polyester diol in polymer diol, with terminal primary amino groups and terminal hydroxyl groups) A four-neck flask equipped with a stirrer, condenser, and nitrogen gas inlet tube was charged with 400 parts by weight of 3-methyl-1,5-pentylene adipate diol with an average molecular weight of 2000, 33.3 parts by weight of isophorone diisocyanate, and 0.04 parts by weight of tetrabutyl titanate, and the mixture was allowed to react for 6 hours at 80-90°C while introducing nitrogen gas. After cooling to near room temperature, 824 parts by weight of propyl acetate and 206 parts by weight of isopropyl alcohol were added, followed by the addition of 7.6 parts by weight of isophorone diamine to extend the chain, and then 0.37 parts by weight of monoethanolamine was added to allow the reaction to proceed. The reaction was then terminated by the addition of 0.41 parts by weight of diethylenetriamine, yielding a polyurethane resin varnish A with a solids content of 30% by weight.

[0031] Polyurethane resin varnish B production example (100% by mass of polyester diol in polymer diol, with terminal primary amino groups, and hydroxyl groups within the molecule and at the terminals) A four-neck flask equipped with a stirrer, condenser, and nitrogen gas inlet tube was charged with 400 parts by weight of 3-methyl-1,5-pentylene adipate diol with an average molecular weight of 2000, 33.3 parts by weight of isophorone diisocyanate, and 0.04 parts by weight of tetrabutyl titanate, and the mixture was allowed to react for 6 hours at 80 to 90°C while introducing nitrogen gas. After cooling to near room temperature, 822 parts by weight of propyl acetate and 205 parts by weight of isopropyl alcohol were added, followed by the addition of a mixture of 3.8 parts by weight of isophorone diamine and 2.3 parts by weight of aminoethylethanolamine to extend the chain. 0.37 parts by weight of monoethanolamine was then added to allow the reaction to proceed. 0.41 parts by weight of diethylenetriamine was then added to terminate the reaction, yielding a polyurethane resin varnish B with a solids content of 30% by weight.

[0032] Polyurethane resin varnish C manufacturing example (polymer diol: polyester diol / polyether diol = 80 / 20 (mass ratio), terminal primary amino group, terminal hydroxyl group) In the production example of polyurethane resin varnish A, 400 parts by mass of 3-methyl-1,5-pentylene adipate diol having an average molecular weight of 2000 was changed to a mixture of 320 parts by mass of 3-methyl-1,5-pentylene adipate diol having an average molecular weight of 2000 and 80 parts by mass of polypropylene glycol having an average molecular weight of 2000, thereby obtaining polyurethane resin varnish C having a solid content of 30% by mass.

[0033] Polyurethane resin varnish D production example (100% polyester diol in polymer diol, primary amino group at terminal, no hydroxyl group) In the production example of polyurethane resin varnish A, monoethanolamine was changed to dibutylamine to obtain polyurethane resin varnish D having a solid content of 30 mass %.

[0034] Polyurethane resin varnish E manufacturing example (100% polyester diol in polymer diol, no primary amino groups at the ends, hydroxyl groups at both ends (i.e., two hydroxyl groups)) In the production example of polyurethane resin varnish A, diethylenetriamine was changed to monoethanolamine to obtain polyurethane resin varnish E having a solid content of 30 mass %.

[0035] Polyurethane resin varnish F production example (polymer diol: polyester diol / polyether diol = 50 / 50 (mass ratio), terminal primary amino group, terminal hydroxyl group) In the production example of polyurethane resin varnish A, 400 parts by mass of 3-methyl-1,5-pentylene adipate diol having an average molecular weight of 2000 was changed to a mixture of 200 parts by mass of 3-methyl-1,5-pentylene adipate diol having an average molecular weight of 2000 and 200 parts by mass of polypropylene glycol having an average molecular weight of 2000, thereby obtaining polyurethane resin varnish F having a solid content of 30% by mass.

[0036] Polyurethane Resin Varnish G Manufacturing Example (Polyurethane Resin Varnish A with reduced molecular weight: for Helio 200 wire) In the production example of polyurethane resin varnish A, the amount of isophoronediamine was changed to 6.8 parts by mass, the amount of monoethanolamine to 0.73 parts by mass, and the amount of diethylenetriamine to 0.82 parts by mass, thereby obtaining polyurethane resin varnish G with a solid content of 30% by mass.

[0037] (pigment) Titanium dioxide A (rutile-type titanium dioxide treated with silica and alumina, oil absorption 29g / 100g) Titanium dioxide B (rutile-type titanium dioxide treated with only alumina, oil absorption 29g / 100g)

[0038] (Chlorovinyl acetate resin varnish) 20 parts by mass of a vinyl chloride-vinyl acetate copolymer having hydroxyl groups (product name: Solvine TA3, manufactured by Nissin Chemical Industry Co., Ltd.) was dissolved in a mixed organic solvent consisting of 40 parts by mass of methyl ethyl ketone, 20 parts by mass of ethyl acetate, and 20 parts by mass of propyl acetate to obtain a vinyl chloride-vinyl acetate resin varnish A with a solids content of 20%.

[0039] (Production of printing ink composition for laminate) 35 parts by mass of pigments A to B, 30 parts by mass of polyurethane resin varnishes A to G, and 10 parts by mass of mixed solvent were kneaded using a paint conditioner, and the remainder of mixed solvent 1 was further added and mixed according to the formulation in Table 1. 100 parts by mass of each mixture was diluted with a curing agent (trade name "Mytec NY260A", manufactured by Mitsubishi Chemical Corporation) and mixed solvent 2 according to the formulation in Table 1 at the time of printing, and the viscosity was adjusted to 15 seconds using a Zahn cup #3 manufactured by Rigo Co., Ltd. to prepare the printing ink compositions for laminate of Examples 1 to 10 and Comparative Examples 1 to 4.

[0040] <Performance evaluation> For the printing ink compositions for laminate of Examples 1 to 8 and Comparative Examples 1 to 4, printing was carried out on the treated surface of ONY#15 (manufactured by Toyobo Co., Ltd., N-1102, thickness 15 μm, hereinafter referred to as the base film) at a printing speed of 100 m / min using a gravure printing machine (manufactured by Azumaya Manufacturing Co., Ltd.) equipped with an engraving plate (Helio 175 lines) for the printing ink compositions for laminate of Examples 9 and 10, and an engraving plate (Helio 200 lines).

[0041] (dry lamination) An adhesive containing a polyester adhesive having a hydroxyl group and an isocyanate adhesive containing an isocyanate group (A-515 / A-50 ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.) was applied to each of the printed materials of Examples 1 to 10 and Comparative Examples 1 to 4, and a sealant film LLDPE#50 (L-4104, manufactured by Toyobo Co., Ltd.) was laminated using a dry laminator to obtain a laminate.

[0042] (extrusion laminate) An adhesive (A-3210 / A-3070 (Mitsui Chemicals)) was applied to each of the printed materials of Examples 1 to 10 and Comparative Examples 1 to 4, and molten polyethylene was laminated on the printed materials using an extrusion laminator to obtain a laminate.

[0043] (Color development) The laminate printing ink compositions of Examples 1 to 10 and Comparative Examples 1 to 4 were printed on the above-mentioned base film using a gravure printing machine with a 175-line printing plate. The color development of each printed matter was visually observed and evaluated according to the following evaluation criteria, with the color development of the laminate printing ink composition of Comparative Example 3 as the standard. ○: The color development is clearly clearer than that of Comparative Example 3 ×: Color development not recognized as clear compared to Comparative Example 3

[0044] (Tearability) Each of the laminates obtained by dry lamination and extrusion lamination in Examples 1 to 10 and Comparative Examples 1 to 4 was left at 40°C for 3 days, and then cut with a cutter and torn by hand to evaluate ease of tearing. ○: Can be torn without resistance ○△: There is a slight resistance when tearing, but it can be torn without any problems △: Resistance is felt when tearing, or the sealant stretches slightly, but it can still be torn ×: Sealant stretches or does not tear at all

[0045] [Table 1]

[0046] Curing agent: Isophorone diisocyanate (IPDI adduct) (Mitsubishi Chemical Corporation, Mytec NY260A) Mixed solvents 1 and 2: ethyl acetate / propyl acetate / isopropyl alcohol = 50 / 25 / 25 (mass ratio)

[0047] The laminates of each example printed using the printing ink composition for laminate of the present invention exhibited good color development whether using a 175-line or 200-line printing plate, and also exhibited good tearability, meaning that they could be torn without resistance whether lamination was performed by dry lamination or extrusion lamination. In contrast, in Comparative Examples 1 and 2, in which the ratio of curing agent to polyurethane resin used was lower than the range specified in the present invention, color development was good but tearability was poor, and the sealant stretched slightly, but was only just able to be torn. In Comparative Example 3, in which a polyurethane resin having terminal hydroxyl groups but no amino groups was used, color development was poor and, in addition, resistance was felt when tearing. In Comparative Example 4, in which the polymer diol used as the raw material for the polyurethane resin contained 50% by mass of polyester diol, tearability was poor.

Claims

1. A printing ink composition for laminate containing a pigment containing rutile-type titanium dioxide treated with silica and alumina and having an oil absorption of 20 to 35 g / 100 g, a binder resin, a polyfunctional isocyanate compound, isophorone diisocyanate or an adduct thereof, as a curing agent (excluding cases where the polyfunctional isocyanate compound has an alkoxysilyl group), and an organic solvent, the binder resin is a polyurethane resin having a reactive group capable of reacting with an isocyanate group of the polyfunctional isocyanate compound, and a polyester diol accounts for 70 mass% or more of a polymer diol that is a raw material of the polyurethane resin; The solid content ratio of the polyurethane resin to the curing agent is polyurethane resin:curing agent=1:0.25 to 0.90, and A printing ink composition for laminate, wherein the polyurethane resin is the following (1) or (2), or a mixture of the following (1) and (2) (excluding cases where the printing ink composition for laminate contains a vinyl chloride-vinyl acetate copolymer resin): (1) At the terminal, one or more of a primary amino group, a secondary amino group, and a tertiary amino group are present. and a polyurethane resin having a hydroxyl group. (2) At the terminal, one or more of a primary amino group, a secondary amino group, and a tertiary amino group are present. Polyurethane resin having

2. 2. The printing ink composition for laminate according to claim 1, wherein the pigment comprises rutile titanium dioxide treated with silica and alumina and having an oil absorption of 25 to 35 g / 100 g.

3. 3. The printing ink composition for laminate according to claim 1, wherein the organic solvent is a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent.

4. An easily tearable laminate comprising a substrate film, a printed layer made of the printing ink for lamination according to any one of claims 1 to 3, an adhesive layer having a hydroxyl group, and a sealant film laminated in this order.

5. The easy-tear laminate according to claim 4, characterized in that it is obtained by printing the printing ink for lamination according to any one of claims 1 to 3 on the base film, applying an adhesive containing a resin having a hydroxyl group, and laminating a sealant film.

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