Laminating printing ink composition and easily tearable laminate

Abstract

To provide a printing ink composition for lamination that exhibits good color development and easy tearing properties without the need to use large amounts of hardening agent. [Solution] A laminating printing ink composition containing titanium dioxide pigment, a binder resin, isophorone diisocyanate or its adduct, which is a polyfunctional isocyanate compound, and an organic solvent as a curing agent: the content of the binder resin is 5 to 15% by mass in terms of solid content relative to the printing ink composition at the time of printing; the binder resin is a polyurethane resin having a reactive group that can react with the isocyanate group of the polyfunctional isocyanate compound, and in the polymer diol which is a raw material for the polyurethane resin A printing ink composition for lamination (excluding cases where the printing ink composition for lamination contains a vinyl chloride-vinyl acetate copolymer resin) wherein the polyester diol content is 70% by mass or more; the solid content ratio of the polyurethane resin to the curing agent is polyurethane resin:curing agent = 1:0.10~0.90; the content of the curing agent is 4 / 154 or less by mass relative to the printing ink composition at the time of printing; and the polyurethane resin is (1) or (2) below, or a mixture of (1) and (2) below): (1) At the end of the group, one or more of the following are present: primary amino group, secondary amino group, and tertiary amino group Polyurethane resin having and having hydroxyl groups (2) At the end of the group, one or more of the following are present: primary amino group, secondary amino group, and tertiary amino group Polyurethane resin containing [unclear].

Description

Technical Field

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

Background Art

[0002] For foods, confectioneries, daily sundries, pet foods, etc., packaging materials using various plastic films are used in consideration of functions such as design, economy, content protection, and transportability. In addition, gravure printing and flexographic printing are performed on many packaging materials to impart design and message appeal to consumers. And in order to obtain a packaging material for the intended use, surface printing printed on the surface of the base film of the packaging material, or an adhesive or an anchor agent is applied to the printed surface of the base film of the packaging material as needed, and reverse printing is performed by laminating the film. In reverse printing, after sequentially printing color ink and white ink on various films such as polyester, nylon, and aluminum foil, a polyethylene film, a polypropylene film, etc. are laminated for the purpose of heat sealing on the printed layer of the white ink by dry lamination using an adhesive or extrusion lamination using an anchor coat agent (for example, see Patent Document 1).

[0003] After that, the laminate is used as a laminated bag for foods such as confectioneries, soups, and miso soup. These laminated bags are opened by human hands in order to take out the contents. Here, if the tearability is poor, it is necessary to apply excessive force during opening, and furthermore, it may be cut in an unintended direction, resulting in a problem that the contents spill, so good tearability is required. In particular, in the portion where the ink is printed, the tearability tends to be inferior because the bonding strength between the ink layer and the adhesive layer is inferior to the non-printed portion. It is known that hardening the laminate adhesive layer improves tear resistance (see, for example, Patent Document 2). However, when inked areas and unprinted areas are mixed, if the adhesive layer is made hard enough to tear at the inked areas, the unprinted areas become too hard. Conversely, if it is made to match the unprinted areas, the inked areas suffer from poor tear resistance.

[0004] To solve this problem, it has been proposed that the ink layer contain 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 that the ink layer be formed from a composition consisting of a compound (a1) having only two or more hydroxyl groups as functional groups in its molecule, and a curing agent that reacts with those hydroxyl groups (see, for example, Patent Document 3). Furthermore, in the example, the solid content ratio of the polyfunctional isocyanate curing agent to the polyurethane resin in the ink layer is very low, at polyurethane resin:polyfunctional isocyanate curing agent = 1:0.25. As a result, although tear resistance is slightly improved, there are still problems that are not sufficient, such as resistance being felt when tearing. Furthermore, ink layers using such compounds do not exhibit sufficiently good color development.

[0005] Patent Document 4 describes how a large amount of curing agent is used in a two-component ink to improve tear resistance. However, the use of large amounts of curing agent has a significant 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 need for further reduction of the 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 Publication No. 2008-274061 [Patent Document 3] Japanese Patent Publication No. 2012-125978 [Patent Document 4] Japanese Patent Publication No. 2017-25143 [Patent Document 5] Patent No. 6545559 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0008] As a result of diligent research to solve the above problems, the present inventors have invented the following printing ink composition and laminate for lamination. The present invention [1] A printing ink composition for lamination 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 that can react with the isocyanate group of the polyfunctional isocyanate compound, the polymer diol used as a raw material for the polyurethane resin 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 = 1:0.10~0.90. [2] The laminating printing ink composition according to [1], characterized in that the polyurethane resin is (1) or (2) below, or a mixture of (1) and (2) below. (1) A polyurethane resin having one or more primary, secondary, and tertiary amino groups at its terminus, and also having a hydroxyl group. (2) A polyurethane resin having one or more of the primary amino group, secondary amino group, and tertiary amino group at its terminal end. [3] The laminating printing ink composition according to [1] or [2] above, characterized in that the polyfunctional isocyanate compound is a trifunctional or more isocyanate compound. [4] The laminating printing ink composition according to any one of [1] to [3] above, characterized in that the pigment contains rutile-type titanium dioxide treated with silica and alumina, having an oil absorption capacity of 20 to 35 g / 100 g. [5] The laminating printing ink composition according to [4] above, characterized in that the pigment contains rutile-type titanium dioxide treated with silica and alumina, having an oil absorption capacity of 25 to 35 g / 100 g. [6] The laminating printing ink composition according to any one of [1] to [5] above, characterized in that the organic solvent is a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent. [7] An easily tearable laminate comprising a base film, a printing layer made of a laminating printing ink as described in any of [1] to [6] above, an adhesive layer having hydroxyl groups, and a sealant film, laminated in that order. [8] The easily tearable laminate according to [7], characterized in that the base film is printed with a laminating printing ink according to any of [1] to [6] above, an adhesive containing a resin having a hydroxyl group is applied, and a sealant film is laminated. [Effects of the Invention]

[0009] The laminating printing ink composition of the present invention is a composition that uses the above-mentioned polyurethane resin as a binder resin and a polyfunctional isocyanate compound as a curing agent, in a range such that the solid content ratio of polyurethane resin to curing agent is 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, it is believed that the curing agent in the laminating printing ink composition reacts with the polyurethane resin in the ink composition and the hydroxyl groups of the adhesive layer, thereby increasing the bonding strength between the printing layer and the adhesive layer, making the ink layer harder and improving tear resistance. In particular, when using polyurethane resins such that (1) a polyurethane resin having one or more primary, secondary, and tertiary amino groups at its termini and having hydroxyl groups, and / or (2) a polyurethane resin having one or more primary, secondary, and tertiary amino groups at its termini, and a polyfunctional isocyanate compound as a curing agent, and the solid content ratio of the polyurethane resin and curing agent is in the range of polyurethane resin:curing agent = 1:0.10~0.90, the viscosity of the polyurethane resin can be adjusted to an appropriate viscosity range for printing inks, and pigment dispersibility is also good, so the resin content in the printing ink composition for lamination can be increased. Furthermore, since the polyurethane resin has hydroxyl groups, it reacts with the curing agent in the laminating ink composition and the hydroxyl groups in the adhesive layer, increasing the bonding strength between the printing layer and the adhesive layer. This is thought to result in a harder ink layer with good tear resistance. In addition, it is thought that the pigment dispersibility will be good, leading to good color development. [Modes for carrying out the invention]

[0010] The laminating printing ink composition and the easily tearable laminate of the present invention will be described in more detail below. First, the laminating printing ink composition of the present invention will be described. <Pigments> In this invention, various inorganic pigments and / or organic pigments commonly used in printing inks can be used as pigments. The pigment content in the laminating printing ink composition of the present invention is preferably in the range of 5 to 60% by mass in the ink composition. If the pigment content in the laminating ink composition falls below the above range, the coloring power of the ink composition decreases, and if it exceeds the above range, the viscosity of the ink composition increases, making the printed material more prone to smudging. The above pigment preferably contains rutile titanium oxide treated with silica and alumina and having an oil absorption of 20 to 35 g / 100 g, and more preferably contains rutile titanium oxide treated with silica and alumina and having an oil absorption of 25 to 35 g / 100 g. When the oil absorption is less than 20 g / 100 g, the tear resistance may decrease, and when it exceeds 35 g / 100 g, the pigment dispersibility may deteriorate.

[0011] <Binder resin> As the binder resin, a polyurethane resin having a reactive group capable of reacting with the isocyanate group of the 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 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 the terminal is preferable. Such a polyurethane resin is obtained by synthesizing a urethane prepolymer by reacting a polyfunctional diisocyanate compound with a high molecular weight diol compound, and reacting the obtained 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. At this time, methods 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 chain extension of the urethane prepolymer with a chain extender and the termination of the reaction with a reaction terminator are carried out simultaneously, etc.

[0012] (Polyfunctional diisocyanate compound) Examples of the polyfunctional diisocyanate compound 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 aromatic aliphatic diisocyanate compounds such as α,α,α’,α’-tetramethylxylylene diisocyanate. One kind or a mixture of two or more kinds thereof can be used. Among them, alicyclic diisocyanate compounds, aliphatic diisocyanate compounds, and aromatic aliphatic diisocyanate compounds are more preferable. Furthermore, polyisocyanate compounds having three or more functional groups can also be used. Also, it is more preferable that the isocyanate component is a bioisocyanate derived from plants.

[0013] (Polymeric diol compound) Polymeric diol compounds that can be used to obtain a binder resin include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, polyether diol compounds such as alkylene oxide adducts such as ethylene oxide and propylene oxide of bisphenol A, and polyester diol compounds such as polycaprolactone diols, which are obtained by condensation reactions 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. In the above polymer diol, polyester diol accounts for 70% by mass or more. Biopolyol components can be used as the polymeric diol compound. In particular, a biopolyester polyol obtained by reacting a short-chain diol component having 2 to 4 carbon atoms with a carboxylic acid component is preferred. It is more preferable 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 preferable that both are plant-derived. The plant-derived short-chain diol components with 2 to 4 carbon atoms are not particularly limited. For example, the short-chain diol components may be 1,3-propanediol, 1,4-butanediol, ethylene glycol, etc., obtained from plant raw materials by the following methods. These may be used in combination. 1,3-propanediol can be produced from glycerol via 3-hydroxypropylaldehyde (HPA) by a fermentation method that decomposes plant resources (e.g., corn) to obtain glucose. Compared to 1,3-propanediol compounds produced by bio-methods such as the above fermentation method, 1,3-propanediol compounds produced by EO production methods yield useful by-products such as lactic acid, which are safer, and also allow for lower production costs. 1,4-butanediol can be produced by obtaining succinic acid by producing glycol from plant resources and fermenting it, and then hydrogenating it. Furthermore, ethylene glycol can be produced from bioethanol obtained by conventional methods via ethylene.

[0014] The plant-derived carboxylic acid component is not particularly limited. For example, carboxylic acid components 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 polymer diol compounds, one or more alkanediols such as 1,4-pentanediol, 2,5-hexanediol, and 3-methyl-1,5-pentanediol, or low molecular weight diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,3-butanediol can be used in combination. Furthermore, in mixture systems of ester-based solvents and alcohol-based solvents, using a polyetherdiol compound as the polymer diol compound tends to result in higher solubility of the resulting polyurethane resin, which is preferable because it allows for a wide range of ink designs to suit the required performance. Furthermore, the ratio of the above-mentioned organic diisocyanate compound to the polymeric diol compound is such that the equivalent ratio of isocyanate group to hydroxyl group (isocyanate index) is typically in the range of 1.2:1 to 3.0:1, more preferably 1.3:1 to 2.0:1. When the above-mentioned isocyanate index is less than 1.2, the polyurethane resin tends to become more flexible, and in cases where the blocking resistance, etc., is low when ink is printed, it may be preferable to use it in combination with other rigid resins.

[0016] (Chain elongator) Chain extenders that can be used to obtain binder resins include known chain extenders used in polyurethane resins as ink binders, and examples 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; hydroxyl-containing diamines 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 inhibitor) Examples of reaction stoppers that can be used to obtain binder resins 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 with 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 and / or secondary amino groups at both ends, a polyamine having primary and / or secondary amino groups at both ends is used as a reaction stopper. Examples of such polyamines having primary 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 these, polyamines having primary amino groups such as diethylenetriamine and triethylenetetratriamine are preferred. To obtain a polyurethane resin having hydroxyl groups, compounds having hydroxyl groups are used as the chain extender and / or reaction stopper. Preferably, compounds having hydroxyl groups are used as both the chain extender and the reaction stopper. Examples of chain extenders include hydroxyl-containing diamines such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine, and N,N'-di(2-hydroxyethyl)ethylenediamine. Examples of reaction stoppers include diamines having hydroxyl groups such as N-(2-hydroxyethyl)ethylenediamine, N-(2-hydroxyethyl)propylenediamine, and N,N'-di(2-hydroxyethyl)ethylenediamine, and alkanolamines having hydroxyl groups such as monoethanolamine and diethanolamine.

[0018] In this invention, polyurethane resin can be obtained using the above materials and employing a known method for producing polyurethane resin. Furthermore, since the hardness of the resulting polyurethane resin differs 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 binder resin content is preferably 5 to 15% by mass in solid content in the printing ink composition for lamination during printing. If the binder resin content is outside this range, tear resistance tends to decrease. Furthermore, the polyurethane resin in the laminating printing ink composition 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 resin, acrylic resin, vinyl chloride vinyl acetate copolymer, polyamide resin, and adhesive resin can be added as auxiliary components. Among these, vinyl chloride vinyl acetate copolymer is preferred, and vinyl chloride vinyl acetate copolymer having hydroxyl groups is particularly preferred from the viewpoint of reaction with the curing agent.

[0019] <Hardening agent> Polyfunctional polyisocyanate compounds can be used as curing agents. Specifically, biuret, isocyanurate, adduct, bifunctional polyfunctional isocyanate compounds, and isophorone diisocyanate can be used, with examples including 24A-100, 22A-75, TPA-100, TSA-100, TSS-100, TAE-100, TKA-100, P301-75E, E402-808, E405-70B, AE700-100, D101, D201, A201H (manufactured by Asahi Kasei Corporation), Mytec Y260A (manufactured by Mitsubishi Chemical Corporation), Coronate HX, Coronate HL, Coronate L (manufactured by Tosoh Corporation), Desmodule N75MPA / X (manufactured by Bayer AG), etc. Among these, isophorone diisocyanates or their adducts are preferred. Furthermore, isocyanate compounds with three or more functionalities can also be used. Furthermore, it is preferable that the isocyanate component is a plant-derived bioisocyanate. stomach. The amount of curing agent used should be such that, from the viewpoint of tear resistance, the mass ratio of polyurethane resin to curing agent is in the range of polyurethane resin:curing agent = 1:0.10 to 0.90, but polyurethane resin:curing agent = 1:0.13 to 0.40 is preferred, and more preferably polyurethane resin:curing agent = 1:0.15 to 0.35.

[0020] <Organic solvents> Organic solvents that can be used in laminating printing ink compositions 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.). Furthermore, in response to recent environmental issues and considering the printability and drying properties of the ink, it is preferable to use a mixed organic solvent of an ester-based organic solvent and an alcohol-based organic solvent as the organic solvent in the printing ink composition for lamination during printing, such that the ratio of ester-based organic solvent to alcohol-based organic solvent is in the range of 50 / 50 to 95 / 5, preferably in the range of 60 / 40 to 85 / 15. Furthermore, from the viewpoint of ink printability, it is preferable to include 5% by mass or more, preferably 15% by mass or more, of propyl acetate in the printing ink composition for lamination during printing.

[0021] <Additives> The above organic solvent-based gravure printing composition may further contain various additives such as tackifiers, crosslinking agents, lubricants, antiblocking agents, antistatic agents, and surfactants.

[0022] <Method for producing the laminating printing ink composition of the present invention> The laminating printing ink composition of the present invention is manufactured using various conventional dispersion and mixing equipment to produce various materials other than the curing agent described above. The viscosity is then adjusted to 10 to 1000 mPa·s by adjusting the content of each solid material and the combination of polyurethane resin and organic solvent. For the sake of stability over time, the curing agent is added during printing. The composition is then obtained by adding and stirring the organic solvent until the flow time in Zaan Cup No. 3 is 12 to 23 seconds, preferably 14 to 16 seconds for high-speed printing, according to the printing conditions and ambient temperature during printing.

[0023] <Easily tearable laminate> Next, we will describe an easily tearable laminate obtained by printing a laminating ink onto a base film, then applying an adhesive containing a polyester adhesive having hydroxyl groups and an isocyanate adhesive containing isocyanate groups, 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 printing plastic films such as polyethylene, polypropylene, and other polyolefin films, polyester films such as polyethylene terephthalate, polylactic acid, and polycaprolactone, nylon, and vinylon can be used. Alternatively, a biomass-based film made from biomass-based resin can be used.

[0025] (Laminating ink composition) The above-described printing ink composition for lamination can be used as the printing ink composition for lamination.

[0026] (glue) Adhesives containing hydroxyl groups, which have been conventionally used in extrusion lamination and dry lamination processes, can be used. Examples include 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.), Secadine 2710A / Secadine 2810C(T), Secadine 2730A / Secadine 2730B, Secadine 2710A / Secadine 2710C (manufactured by Dainichi Seika Kogyo Co., Ltd.), LX-500, LX-901, LX747A, etc. Adhesives used in dry lamination include DIC Dry LX-401A, 75A, 719, 703VL, 500, 510, etc. (manufactured by DIC Graphics, DIC Dry is a registered trademark of DIC Graphics), Takelac / Takenate 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, etc. (manufactured by Mitsui Chemicals, Inc.), and RU-77, 771, 3600, 3900, etc. (manufactured by Rock Paint Co., Ltd.). Biomass-based adhesives made from biomass-based materials can also be used.

[0027] (Sealant film) As sealant films, conventionally used resins such as low-density polyethylene, LLDPE, ethylene-vinyl acetate copolymer, and polypropylene can be used as the molten resin when employing a lamination method by dry lamination. Furthermore, conventionally used films such as unoriented plastic films (e.g., unoriented polyethylene film, unoriented polypropylene film, etc.) can be used as the plastic film for extrusion lamination, which involves stacking molded films.

[0028] <Easy-tear laminates and easy-tear laminate bags> The present invention describes an easily tearable laminate and an easily tearable laminate bag. First, the desired pattern, characters, etc., are printed onto the above-mentioned printing substrate using a general gravure printing method or flexographic printing method, etc., with the laminating printing ink composition of the present invention. The resulting printed material is then laminated, a process that involves layering a heat-sealable polymer called a sealant. Two main methods are used for this lamination process. The first method is an extrusion lamination process in which printing is performed using a printing ink composition for lamination, and after curing the printed area with a curing agent, or before curing, an adhesive (also called an anchor coat agent) is applied to the surface of the resulting printed layer, and then a heat-fusible polymer is used as the molten resin to laminate it. The extrusion lamination process involves applying an adhesive (for example, a polyester adhesive having hydroxyl groups and an adhesive containing an isocyanate group) to the surface of the printed layer, and then laminating the molten resin using a known extrusion laminating machine. Furthermore, it is also possible to laminate in a sandwich-like manner by laminating other materials with the molten resin as an intermediate layer. It should be noted that using an isocyanate-based anchor coat agent is preferable to using an imine-based anchor coat agent because it provides superior adhesive strength. The second method is dry lamination, in which printing is performed using a laminating printing ink composition, and after curing the printed area with a curing agent, or before curing, an adhesive (for example, a polyester adhesive containing hydroxyl groups and an adhesive containing an isocyanate group) is applied to the surface of the printed layer, and then an unstretched plastic film is laminated. In particular, lamination can also be performed using a multi-layered film that has metal foil, used in retort applications, sandwiched in between beforehand. The easily tearable laminates obtained by these methods are then ultimately treated with a sealant. The material is sealed using a heat sealer or similar device to create an easily tearable laminated bag. A common feature of these two methods is that when printing is performed using a laminating ink composition, curing the printed area with a curing agent, and then applying an adhesive, the laminating ink composition and the adhesive may be cured by different functional groups, i.e., by different curing mechanisms, or a curing agent with the same functional groups can be used. As a result, it becomes possible to select a more appropriate combination of laminating ink composition and adhesive. On the other hand, when printing is performed using a laminating printing ink composition, and an adhesive is applied to the printed area before curing with a hardening agent, the laminating printing ink composition and the adhesive can use hardening agents that have the same functional groups acting on each other. [Examples]

[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 "mass%" and "parts" means "parts by mass".

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

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

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

[0033] Polyurethane resin varnish D manufacturing example (100% polyester diol in polymer diol, with primary amino groups at the ends, no hydroxyl groups) In the production example of polyurethane resin varnish A, a polyurethane resin varnish D with a solid content of 30% by mass was obtained by changing monoethanolamine to dibutylamine.

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

[0035] Polyurethane resin varnish F manufacturing example (Polyester diol / polyether diol in polymer diol = 50 / 50 (mass ratio), with primary amino group at the end, with hydroxyl group at the end) In the production example of polyurethane resin varnish A, 400 parts by mass of 3-methyl-1,5-pentylene adipate diol with an average molecular weight of 2000 was replaced with a mixture of 200 parts by mass of 3-methyl-1,5-pentylene adipate diol with an average molecular weight of 2000 and 200 parts by mass of polypropylene glycol with an average molecular weight of 2000 to obtain polyurethane resin varnish F with a solid content of 30% by mass.

[0036] Manufacturing example of polyurethane resin varnish G (lower molecular weight version of polyurethane resin varnish A: for Helio 200 wire) In the production example of polyurethane resin varnish A, a polyurethane resin varnish G with a solid content of 30% by mass was obtained by changing the amount of isophorone diamine 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.

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

[0038] (Vinyl chloride resin varnish) 20 parts by mass of vinyl chloride vinyl acetate copolymer having hydroxyl groups (product name: Solvine TA3, manufactured by Nisshin 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 vinyl chloride resin varnish A with a solid content of 20%.

[0039] (Manufacturing of printing ink compositions for lamination) 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 added and mixed according to the formulations in Table 1. 100 parts by mass of each mixture was then diluted with a curing agent (product name "Mytec NY260A", manufactured by Mitsubishi Chemical Corporation) and mixed solvent 2 according to the formulations in Table 1 during printing, and the viscosity was adjusted to 15 seconds using a Zahn cup #3 manufactured by Rigosha Co., Ltd. to prepare the laminating printing ink compositions of Examples 1 to 10 and Comparative Examples 1 to 4.

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

[0041] (Dry Laminate) Each printed material in Examples 1-10 and Comparative Examples 1-4 was coated with an adhesive containing a polyester adhesive having hydroxyl groups and an isocyanate adhesive containing isocyanate groups (A-515 / A-50 ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.), and a sealant film, LLDPE#50 (L-4104, manufactured by Toyobo Co., Ltd.), was laminated using a dry laminating machine to obtain a laminate.

[0042] (Extruded lamination) Adhesive (A-3210 / A-3070 (manufactured by Mitsui Chemicals, Inc.)) was applied to each of the printed materials in Examples 1 to 10 and Comparative Examples 1 to 4, and molten polyethylene was laminated using an extrusion laminating machine to obtain a laminate.

[0043] (Color development) The laminating 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 press with a 175-line printing plate. The color development of each printed material was visually observed, using the color development of the laminating ink composition of Comparative Example 3 as the standard, and evaluated according to the following evaluation criteria. ○: Clearly more vivid than the color development of Comparative Example 3. ×: Not considered to have the same vivid color development as Comparative Example 3.

[0044] (Tear-resistant) The laminates obtained by dry lamination and extrusion lamination in Examples 1-10 and Comparative Examples 1-4 were left at 40°C for 3 days, then cut with a cutter and evaluated by how easily they could be torn by hand. ○: Can be torn without resistance ○△: There is a slight resistance when tearing, but it can be torn without any problems. △: You will feel resistance when tearing, or the sealant will stretch slightly, but it will still be possible to tear it. ×: The sealant stretches or does not tear at all.

[0045] [Table 1]

[0046] Hardener: Isophorone diisocyanate (IPDI adduct) (manufactured by 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 embodiment, printed using the laminating ink composition of the present invention, exhibited good color development regardless of whether a 175-line or 200-line printing plate was used, and showed good tearability, being able to be torn without resistance regardless of whether the lamination was performed by dry lamination or extrusion lamination. In contrast, Comparative Examples 1 and 2, in which the ratio of curing agent to polyurethane resin used was less than the range specified in the present invention, exhibited good color development but poor tear resistance, resulting in only slight elongation of the sealant, and only just enough to be torn. Comparative Example 3, which used a polyurethane resin having hydroxyl groups at the ends but no amino groups, exhibited poor color development and, in addition, resistance was felt when tearing. Comparative Example 4, in which polyester diol accounted for 50% by mass of the polymer diol used as a raw material for the polyurethane resin, exhibited poor tear resistance.

Claims

1. A printing ink composition for lamination containing titanium dioxide pigment, a binder resin, a polyfunctional isocyanate compound such as isophorone diisocyanate or its adduct as a curing agent, and an organic solvent, The binder resin content is 5 to 15% by mass in terms of solid content relative to the printing ink composition at the time of printing. The binder resin is a polyurethane resin having reactive groups that can react with the isocyanate group of the polyfunctional isocyanate compound, and the polymer diol that is the raw material for the polyurethane resin contains 70% by mass or more polyester diol. The solid content ratio of the polyurethane resin to the curing agent is polyurethane resin:curing agent = 1:0.10 to 0.

90. The content of the curing agent is 4 / 154 or less by mass relative to the printing ink composition at the time of printing, and Laminating printing ink composition wherein the polyurethane resin is (1) or (2) below, or a mixture of (1) and (2) below (except when the laminating printing ink composition contains a vinyl chloride-vinyl acetate copolymer resin): (1) At the end of the molecule, one or more of the primary, secondary, and tertiary amino groups are present. Polyurethane resin having and having hydroxyl groups (2) At the end of the molecule, one or more of the primary, secondary, and tertiary amino groups are present. Polyurethane resin containing [unclear].

2. The laminating printing ink composition according to claim 1, characterized in that the titanium oxide pigment includes rutile-type titanium oxide treated with silica and alumina, having an oil absorption capacity of 20 to 35 g / 100 g.

3. The laminating printing ink composition according to claim 1, characterized in that the titanium oxide pigment includes rutile-type titanium oxide treated with silica and alumina, having an oil absorption capacity of 25 to 35 g / 100 g.

4. The laminating printing ink composition according to any one of claims 1 to 3, characterized in that the organic solvent is a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent.

5. An easily tearable laminate comprising a base film, a printing layer made of a laminating printing ink according to any one of claims 1 to 4, an adhesive layer having hydroxyl groups, and a sealant film, laminated in that order.

6. The easily tearable laminate according to claim 5, characterized in that, after printing a laminating printing ink according to any one of claims 1 to 4 onto the base film, an adhesive containing a resin having hydroxyl groups is applied, and a sealant film is laminated.

Images