packaging bags

Abstract

To provide a packaging bag which has a print-surface printed by a digital printer and suppresses peeling in an interface between an electrostatic ink layer and a primer layer, and in an interface between the electrostatic ink layer and an adhesive layer at the time of opening or tearing apart.SOLUTION: One aspect of the present disclosure is a packaging bag composed of a laminate having a base material, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order. The adhesive layer is composed of at least one of an adhesive composition containing a polyol, a polyisocyanate and an epoxy compound and a cured product thereof, the ink coverage of the electrostatic ink layer is 500% or less, and the laminate strength of the laminate is 2.0 N / 15 mm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to packaging pouches. [Background technology]

[0002] Packaging bags for sealing and preserving packaged items such as food are known. Packages made of thin films or sheets are used as packaging bags. Various information such as product, brand, and manufacturer is printed on such packaging bags. Digital printers using electrostatic ink compositions are known as a printing method for such packaging bags.

[0003] For example, Patent Document 1 proposes applying a primer resin to a first flexible substrate such as a PET film to obtain a coated surface, performing electrostatic printing on the coated surface using a digital printer (HP's Indigo 20000 label and packaging digital printer), and then applying a crosslinking composition. After performing the predetermined steps in this manner, the proposed technology involves laminating the first flexible substrate coated with the predetermined components and a second flexible substrate to obtain a packaging material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-530478 Summary of the Invention [Problem to be solved by the invention]

[0005] Digital printing using an electrostatic ink composition allows for small-lot production, and digitally printed laminates are used as materials for various packaging bags. However, the electrostatic ink layer formed by a digital printing machine may not have sufficient adhesive strength with the primer layer or adhesive layer, and peeling may occur between the electrostatic ink layer and the primer layer or adhesive layer when an external force is applied. For example, if peeling occurs between the electrostatic ink layer and the primer layer or adhesive layer when the package is torn open, the external force used to tear the packaging bag cannot be fully utilized to tear the substrate, and the bag may not be torn cleanly.

[0006] The present disclosure aims to provide a packaging bag that has a printed surface printed by a digital printing machine, but in which peeling is suppressed at the interface between the electrostatic ink layer and the primer layer, and at the interface between the electrostatic ink layer and the adhesive layer when the bag is opened or torn. [Means for solving the problem]

[0007] One aspect of the present disclosure provides a packaging bag composed of a laminate having a substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order, wherein the adhesive layer is composed of at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound, and a cured product thereof, the ink coverage of the electrostatic ink layer being 500% or less, and the laminate strength of the laminate being 2.0 N / 15 mm or more.

[0008] The laminate constituting the packaging bag has an adhesive layer composed of at least one of a specific adhesive composition and a cured product thereof, and the laminate strength of the laminate is equal to or greater than a predetermined value, so that even if the ink coverage of the electrostatic ink layer is relatively high, peeling at the interface between the electrostatic ink layer and the primer layer and at the interface between the electrostatic ink layer and the adhesive layer is suppressed when the packaging bag is opened or torn.When the packaging bag is opened or torn, the laminate near the torn portion can maintain its pre-tear state, so the visibility of information printed on the printed portion can be maintained.

[0009] One aspect of the present disclosure provides a packaging bag composed of a laminate having a substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order, wherein the adhesive layer is composed of at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound, and a cured product thereof, the ink coverage of the electrostatic ink layer is 100 to 400%, and where X is the laminate strength of the laminate and Y is the laminate strength of the laminate after retort heat treatment at 120°C for 30 minutes, the value of 100(YX) / X is greater than -30%.

[0010] The laminate constituting the above-mentioned package has an adhesive layer composed of at least one of a specific adhesive composition and its cured product, and the rate of change in laminate strength before and after a specified retort heat treatment (value of 100(YX) / X) is within a specified range. This prevents peeling at the interface between the electrostatic ink layer and the primer layer, and at the interface between the electrostatic ink layer and the adhesive layer, when the packaging bag is opened or torn, even if the ink coverage of the electrostatic ink layer is relatively high. The packaging bag can be opened or torn cleanly. Because the laminate strength of the above-mentioned packaging bag does not decrease significantly even after high-temperature hot water treatment at 120°C for 30 minutes, it is suitable for use as a packaging bag that is subject to sterilization treatment of packaged items by retort.

[0011] The polyol may include an aliphatic polyester polyol, and the epoxy compound may include one having epoxy groups at both ends. Such an adhesive layer has high adhesive strength, especially in high temperature environments.

[0012] The epoxy compound may include a bifunctional alicyclic epoxy compound. The bifunctionality of such an epoxy compound increases the number of crosslinking points with the electrostatic ink composition, thereby providing stronger adhesion to the printed surface (the main surface of the primer layer). Furthermore, the alicyclic nature of the epoxy compound can inhibit reaction with polyisocyanate due to steric hindrance. This allows for stable curing, resulting in excellent adhesion at the interface between the printed portion and the adhesive layer.

[0013] The polyisocyanate may contain a xylylene diisocyanate derivative. Such a polyisocyanate and a polyol have excellent reactivity. This improves the curability of the adhesive composition and further suppresses peeling at the interface between the electrostatic ink layer and the primer layer, and at the interface between the electrostatic ink layer and the adhesive layer.

[0014] The ink coating amount on the main surface of the primer layer on the sealant layer side is 0.5 g / m 2 It may be more than that.

[0015] The laminate may further include a barrier layer between the adhesive layer and the sealant layer. [Effects of the Invention]

[0016] According to the present disclosure, a packaging bag can be provided that has a printed surface printed by a digital printing machine, but that suppresses peeling at the interface between the electrostatic ink layer and the primer layer, and at the interface between the electrostatic ink layer and the adhesive layer, when opened or torn. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a plan view showing an example of a packaging bag. [Figure 2] FIG. 2 is a perspective view showing another example of a packaging bag. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a laminate. [Figure 4] FIG. 4 is a cross-sectional view showing another example of the laminate. [Figure 5] FIG. 5 is a diagram showing a part of the tear surface when the packaging bag is opened. [Figure 6] FIG. 6 is a diagram showing a part of the tear surface when a conventional packaging bag is opened. DETAILED DESCRIPTION OF THE INVENTION

[0018] Embodiments of the present disclosure will be described below with reference to the drawings where appropriate. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. In the description, the same elements or elements having the same functions will be designated by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0019] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0020] One embodiment of the packaging bag is composed of a laminate having a substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order. Fig. 1 is a plan view showing an example of the packaging bag.

[0021] The packaging bag 100 is formed by bonding the sealant layers of a pair of laminates 300 together. The packaging bag 100 includes a sealed portion 101 formed by bonding the peripheral edges of a pair of film-like, approximately rectangular laminates 300 together, and a storage portion 102 formed between the pair of laminates 300 by the sealed portion 101. That is, the side edges, bottom edge, and top edge of the packaging bag 100 are sealed by the sealed portion 101. The packaging bag 100 includes a storage portion 102 in which a packaged item (e.g., food or drink) is stored in a non-sealed portion (sheet portion) surrounded by the sealed portion 101. In this specification, a bag that stores and seals a packaged item is also particularly referred to as a package 200. Note that the sealed portion 101 at the bottom edge may be sealed after the packaged item is filled in the storage portion 102. The sealed portion 101 is formed by heat-sealing the sealant layers of the laminates 300 together.

[0022] It is not essential that the pair of laminates constituting the packaging bag 100 have the same layer structure, and for example, the pair of laminates may have different layer structures from each other.

[0023] The packaging bag 100 may be provided with opening means 120 for making it easier to open. The opening means has a pair of easy-open processed sections 124 consisting of V-shaped notches formed in the sealed section 101 at the side edge, and a half-cut line 121 between the pair of easy-open processed sections 124 that serves as a cutting path. The half-cut line 121 can be formed using a laser. The easy-open processed sections 124 are not limited to V-shaped notches, and may be U-shaped or I-shaped notches, or may be a group of scars.

[0024] The procedure for manufacturing the packaging bag 100 and the packaging body 200 using the laminate 300 is described below. A pair of laminates 300 formed into a predetermined shape is prepared. The sealant layers on one side of each laminate 300 are placed opposite each other and bonded together. This forms sealed portions 101 at the top and side edges, forming an unsealed portion surrounded by the sealed portions 101 in a U-shape. In this way, a packaging bag 110 is obtained in which only the top edge (or only the bottom edge) is unsealed, as shown in FIG. 2. In some other embodiments, the packaging bag may have some edges that are not sealed, as shown in FIG. 2.

[0025] Next, the contents to be packaged are filled from the unsealed upper end (or lower end). After that, the sealant layers of the laminate 300 are bonded together at the upper end (or lower end) to form a sealed portion 101 at the upper end (or lower end). In this way, a package 200 comprising a packaging bag 100 and the contents to be packaged contained therein can be manufactured.

[0026] The laminate constituting the packaging bag 100 will now be described. FIG. 3 is a cross-sectional view schematically showing an example of the laminate. FIG. 3 shows a cross-section along the lamination direction (thickness direction) of the laminate. The laminate 302 has a substrate 10, a primer layer 40, an adhesive layer 30, and a sealant layer 20, in this order. The substrate 10, the primer layer 40, the adhesive layer 30, and the sealant layer 20 may each be in the form of a film. An electrostatic ink layer 50 is provided on at least a portion of the main surface of the primer layer 40 on the sealant layer 20 side.

[0027] The thickness of the laminate 302 may be, for example, 15 to 200 μm, or 18 to 120 μm.

[0028] The substrate 10 and the sealant layer 20 may be flexible substrates, such as biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), oriented polyamide (OPA), solid polypropylene (CPP), linear low-density polyethylene (LLDPE), and low-density polyethylene (LDPE).

[0029] The substrate 10 may be, for example, a composite film in which a metal foil is laminated onto a flexible substrate, or a vapor-deposited film in which a metal is vapor-deposited onto a flexible substrate. The metal may be, for example, aluminum or aluminum oxide. From the viewpoint of improving gas barrier properties, the substrate 10 may be, for example, a vapor-deposited film (transparent vapor-deposited film) in which aluminum or aluminum oxide is vapor-deposited onto a PET film. The thickness of the substrate 10 may be, for example, 7 to 150 μm, 15 to 90 μm, or 20 to 80 μm.

[0030] Examples of the sealant layer 20 include a CPP film, an LLDPE film, and an OPP film. The thickness of the sealant layer 20 may be the same as or different from the thickness of the substrate 10, and may be, for example, 7 to 150 μm, 15 to 90 μm, or 20 to 80 μm.

[0031] The primer layer 40 may contain a resin. Examples of resins include polyvinyl alcohol resin, cellulose-based resin, polyester, polyamine, polyethyleneimine resin, polyamide resin, polyurethane, polyacrylic polymer, hydroxyl-containing resin, carboxyl-containing resin, and amine-based polymer. By providing the primer layer 40 on the substrate to be printed, printing of the electrostatic ink composition using a digital printer can be carried out smoothly. The amount of resin to be applied that constitutes the primer layer 40 is, for example, 0.01 to 1.5 g / m. 2 , or 0.05 to 1.0 g / m 2 It may be.

[0032] The laminate 302 has a printing surface 52 on the primer layer 40. An electrostatic ink layer 50 is provided on the printing surface 52. The electrostatic ink layer 50 is composed of an electrostatic ink composition and is provided by electrostatic printing using a digital printing machine. The multiple electrostatic ink layers 50 shown in FIG. 3 may have the same composition, or may have different compositions and therefore different colors. The electrostatic ink layers 50 may be provided so as to be dotted on the primer layer 40, or may be provided so as to cover the entire one side of the primer layer 40.

[0033] The electrostatic ink layer 50 on the printing surface 52 is composed of circular halftone dots of an electrostatic ink composition. In other words, even if it appears to be a single color and uniform, there are plain areas between the halftone dots. When printing a predetermined area to be printed in a single color, the electrostatic ink layer 50 is generally configured such that the circular halftone dots are spaced apart from one another. When printing in two or more colors, the electrostatic ink layer 50 is configured such that circular halftone dots of the electrostatic ink composition of the second or subsequent colors are arranged between the halftone dots printed in the first color or so as to overlap the halftone dots printed in the first color. The color density on the printing surface 52 can be adjusted by changing the size of the halftone dots, and the color tone on the printing surface 52 can also be adjusted by arranging halftone dots of different colors.

[0034] The ink coverage of the electrostatic ink layer 50 is 500% or less, but may be, for example, 450% or less, or 400% or less. By setting the ink coverage of the electrostatic ink layer 50 within the above range, the laminate has excellent lamination strength, and printing using multiple inks is possible, making it possible to accommodate a variety of printing methods. The ink coverage of the electrostatic ink layer 50 is not particularly limited, but may be, for example, 20% or more, 50% or more, 80% or more, or 100% or more. The ink coverage of the electrostatic ink layer 50 may be adjusted within the above range, and may be, for example, 20 to 500%, 50 to 400%, or 100 to 400%.

[0035] In this specification, ink coverage represents the ratio of halftone dot area per unit area. When a predetermined area to be printed is uniformly printed in a single color, the ink coverage is defined as 100%, and when an area without printing is defined as 0%. When printing with multiple colors of ink, the ink coverage is calculated for each color of ink, and the sum of these is defined as the ink coverage of the target electrostatic ink layer. The ink coverage is set on the digital printing press and can be adjusted by specifying the desired value in the ink coverage setting. Examples of digital printing presses that can be used include the HP Indigo 20000 label and packaging digital printing press (product name). The ink coverage of the electrostatic ink layer of the target laminate can also be confirmed by observing the printed surface of the packaging bag or laminate under an optical microscope.

[0036] Because the electrostatic ink layer 50 is composed of circular halftone dots of the electrostatic ink composition, even when the ink coverage is 100%, the main surface of the primer layer 40 can be confirmed by observing the surface of the electrostatic ink layer 50 facing the sealant layer 20 with an optical microscope or the like. That is, even when the ink coverage is 100%, the primer layer 40 and the adhesive layer 30 can be directly bonded. On the other hand, as the ink coverage increases, the proportion of the primer layer 40 present at the adhesive surface between the printed surface 52 and the adhesive layer 30 tends to decrease. When using conventional adhesives, as the ink coverage increases, the adhesive strength at the interface between the electrostatic ink layer and the primer layer or the interface between the electrostatic ink layer and the adhesive layer decreases, resulting in the laminate not achieving the expected laminate strength. In contrast, the laminate according to the present disclosure can achieve sufficient laminate strength even when the ink coverage is high by using the adhesive composition described below.

[0037] The amount of ink applied to the main surface of the primer layer 40 on the sealant layer 20 side is, for example, 0.5 g / m 2 More than 1.0g / m 2 More than 2.0g / m 2 or more, or 3.0 g / m 2By keeping the ink application amount within the above range, a variety of print expressions consisting of multiple colors can be obtained. The ink application amount on the main surface of the primer layer 40 on the sealant layer 20 side may be, for example, 8.0 g / m 2 or less, or 6.0 g / m 2 When the ink application amount is within the above range, it is possible to more sufficiently prevent a decrease in adhesive strength at the interface between the electrostatic ink layer 50 and the primer layer 40, or at the interface between the electrostatic ink layer 50 and the adhesive layer 30. In this specification, the ink application amount refers to the total amount (solid content amount) of the ink composition used for printing, and in the case of multi-color printing, refers to the total value.

[0038] The laminate strength of the laminate 302 is 2.0 N / 15 mm or greater, but by adjusting the ink coverage and the composition of the adhesive composition (described below), it can be increased to, for example, 2.2 N / 15 mm or greater, 2.5 N / 15 mm or greater, 2.7 N / 15 mm or greater, 2.9 N / 15 mm or greater, or 3.0 N / 15 mm or greater. Having a laminate strength within the above range means that the adhesive strength at the interface between the electrostatic ink layer and the primer layer and at the interface between the electrostatic ink layer and the adhesive layer is excellent, and the external force applied when tearing a packaging bag made of the laminate can be fully utilized to tear the substrate. This effect allows the packaging bag to be opened cleanly.

[0039] The term "laminate strength" as used herein means peel adhesive strength measured in accordance with the description of JIS K 6854-1:1999, and specifically, can be measured by the method described in the examples of this specification.

[0040] When the laminate strength of the laminate 302 is X and the laminate strength of the laminate after 30 minutes of retort heat treatment at 120°C is Y, the ratio (100(YX) / X [the rate of change in laminate strength]) is greater than -30%. The rate of change in laminate strength can be, for example, -25% or greater, -20% or greater, or -15% or greater. When the rate of change in laminate strength of the laminate 302 is within the above range, the laminate strength of the laminate is not significantly reduced even when subjected to high-temperature hot water treatment, such as sterilization of the packaged item by retort. This means that the adhesive strength at the interface between the electrostatic ink layer and the primer layer and at the interface between the electrostatic ink layer and the adhesive layer is excellent, and the external force when tearing a packaging bag made of the laminate can be fully utilized to tear the substrate. This effect allows the packaging bag to be opened cleanly even after high-temperature hot water treatment.

[0041] Fig. 4 is a cross-sectional view showing another example of a laminate. Laminate 304 in Fig. 4 differs from laminate 302 in Fig. 3 in that one surface of primer layer 40 is entirely covered with electrostatic ink layer 51. That is, in laminate 304, the coverage ratio of the main surface of primer layer 40 with electrostatic ink layer 50 is 100 area %. By using the adhesive composition described below, even in a configuration such as laminate 304 in which direct adhesion between primer layer 40 and adhesive layer 30 is difficult, sufficient adhesive strength is maintained and interlayer delamination in laminate 304 is suppressed.

[0042] The electrostatic ink compositions constituting the electrostatic ink layers 50, 51 in the laminates 302, 304 are ink compositions used in liquid electrophotographic printing, i.e., electrostatic printing, and are printed onto substrates such as paper and plastic, or onto a primer layer. The electrostatic ink composition may include colorants such as pigments and dyes, and resins. The electrostatic ink composition may also include a carrier fluid or carrier liquid. The electrostatic ink composition may include, for example, charge directors, charge adjuvants, surfactants, viscosity modifiers, emulsifiers, and other additives.

[0043] Examples of colorants include cyan pigments, magenta pigments, yellow pigments, and black pigments. To facilitate digital printing, resins with relatively low melting points (e.g., 100°C or less) can be used. Examples of resins include thermoplastic resins such as ethylene acrylic acid copolymers, propylene acrylic acid copolymers, ethylene methacrylic acid copolymers, propylene methacrylic acid copolymers, and ethylene vinyl acetate copolymers. The resin preferably contains at least one of ethylene acrylic acid copolymers and ethylene methacrylic acid copolymers.

[0044] Examples of carrier fluids and carrier liquids include hydrocarbons, silicone oils, and vegetable oils. Hydrocarbons include aliphatic hydrocarbons, branched-chain aliphatic hydrocarbons, and aromatic hydrocarbons. The electrostatic ink composition may be substantially free of carrier fluids and carrier liquids when printed on a substrate. The carrier fluids and carrier liquids may be removed, for example, by an electrophoretic process or evaporation during printing. This allows substantially only solids to be transferred onto the substrate or primer layer.

[0045] Charge directors function to maintain a sufficient electrostatic charge on particles contained in the electrostatic ink composition, and include, for example, ionic compounds such as metal salts of fatty acids, metal salts of sulfosuccinates, metal salts of oxyphosphates, metal salts of alkylbenzenesulfonic acids, metal salts of aromatic carboxylic acids, and metal salts of aromatic sulfonic acids, as well as zwitterionic and nonionic compounds such as polyoxyethylenated alkylamines, lecithin, polyvinylpyrrolidone, and organic acid esters of polyhydric alcohols.

[0046] Charge adjuvants have the effect of increasing or stabilizing the charge of particles contained in the electrostatic ink composition. Examples of charge adjuvants include barium petronate, calcium petronate, Co naphthenate, Ca naphthenate, Cu naphthenate, Mn naphthenate, Ni naphthenate, Zn naphthenate, Fe naphthenate, Ba stearate, Co stearate, Pb stearate, Zn stearate, Al stearate, Cu stearate, Fe stearate, and metal carboxylates.

[0047] The electrostatic ink composition may contain a crosslinked product crosslinked by components contained in the adhesive layer 30 and / or the primer layer 40. By containing a crosslinked product, the strength of the electrostatic ink layer 50 itself, the adhesive strength between the printing surface 52 and the electrostatic ink layer 50, and the adhesive strength between the electrostatic ink layer 50 and the primer layer 40 can be further improved.

[0048] The printed surface 52 of the electrostatic ink composition and the adhesive layer 30 are adhered to each other. That is, the printed surface 52 is the adhesive surface for the adhesive layer 30, and the electrostatic ink composition and the adhesive composition are in direct contact with each other.

[0049] The adhesive composition contains a polyol, a polyisocyanate, and an epoxy compound. These three components (polyol, polyisocyanate, and epoxy compound) may at least partially react with each other and harden to form a cured product. That is, the adhesive composition may be composed of at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound and a cured product thereof, and the adhesive layer 30 may be composed of the adhesive composition, the cured product thereof, or a mixture thereof. The polyol and polyisocyanate react as a base agent and a curing agent, respectively, to produce polyurethane (polyurethane adhesive).

[0050] The polyol has two or more hydroxyl groups in one molecule and may have, for example, a number average molecular weight of 400 or more. The number average molecular weight of the polyol may be, for example, 10,000 or less.

[0051] The polyol may contain, for example, at least one selected from the group consisting of polyester polyols and polyether polyols. Among these, the polyol may contain polyester polyol or aliphatic polyester polyol from the viewpoint of sufficiently increasing the adhesive strength of the adhesive layer 30 in a high-temperature environment.

[0052] The polyester polyol can be obtained, for example, by a condensation reaction or transesterification reaction between a polyhydric alcohol and a polybasic acid, an alkyl ester of a polybasic acid, an acid anhydride of a polybasic acid, or an acid halide of a polybasic acid.

[0053] Examples of polyhydric alcohols include low molecular weight diols, low molecular weight triols, and low molecular weight polyols having four or more hydroxyl groups.

[0054] Examples of low molecular weight diols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 3,3-dimethylolheptane, and 2-ethyl-2-butyl-1,3-propanediol.

[0055] Examples of low molecular weight triols include glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-(hydroxymethyl)pentane, and 2,2-bis(hydroxymethyl)-3-butanol.

[0056] Examples of low molecular weight polyols having four or more hydroxyl groups include tetramethylolmethane, pentaerythritol, dipentaerythritol, D-sorbitol, xylitol, D-mannitol, and D-mannite.

[0057] Examples of the alkyl ester of a polybasic acid include a methyl ester of a polybasic acid and an ethyl ester of a polybasic acid. Examples of the acid anhydrides of a polybasic acid include acid anhydrides derived from a polybasic acid. More specific examples of the acid anhydrides of a polybasic acid include oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, 2-alkyl (C12 to C18) succinic anhydride, tetrahydrophthalic anhydride, and trimellitic anhydride.

[0058] Examples of the acid halides of polybasic acids include those derived from the alkyl esters of the above-mentioned polybasic acids or the acid anhydrides of the above-mentioned polybasic acids. More specific examples of the acid halides of polybasic acids include oxalic acid dichloride, adipic acid dichloride, and sebacic acid dichloride.

[0059] Examples of polyether polyols include polyalkylene oxides. Polyether polyols may be obtained by, for example, adding alkylene oxides such as ethylene oxide and / or propylene oxide to a low-molecular-weight polyol as an initiator. More specific examples of polyether polyols include polyethylene glycol, polypropylene glycol, and polyethylene-polypropylene glycol (random or block copolymers). Other examples of polyether polyols include polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran.

[0060] The polyisocyanate has two or more isocyanate groups in one molecule. Examples of polyisocyanates include polyisocyanate monomers, polyisocyanate derivatives, and isocyanate-terminated prepolymers. The adhesive composition may contain multiple different polyisocyanates. The molar ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate to the hydroxyl groups of the polyol may be, for example, 0.5 to 10. Such an adhesive composition can form a cured product that has high adhesive strength and excellent flexibility.

[0061] Examples of the polyisocyanate monomer include aliphatic polyisocyanates, aromatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

[0062] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methylcaprate.

[0063] Examples of the aromatic aliphatic polyisocyanate include xylylene diisocyanate derivatives, such as xylylene diisocyanate (1,3-xylylene diisocyanate or 1,4-xylylene diisocyanate) (XDI), tetramethyl xylylene diisocyanate (1,3-tetramethyl xylylene diisocyanate or 1,4-tetramethyl xylylene diisocyanate) (TMXDI), ω,ω'-diisocyanato-1,4-diethylbenzene, and polyol-modified xylylene diisocyanate obtained by reacting xylylene diisocyanate with trimethylolpropane.

[0064] The content of the xylylene diisocyanate derivative relative to the entire polyisocyanate may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, from the viewpoint of improving the reactivity with the base agent (e.g., polyol). By making the content of the xylylene diisocyanate derivative relative to the entire polyisocyanate 30% by mass or more, the reactivity can be further increased.

[0065] Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorodiisocyanate) (IPDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), and norbornane diisocyanate (NBDI).

[0066] Examples of polyisocyanate derivatives include polymers of the above-mentioned polyisocyanate monomers, allophanate-modified products, polyol-modified products, polyol-modified products produced by the reaction of a monomer with an alcohol, biuret-modified products, urea-modified products, oxadiazinetrione-modified products, carbodiimide-modified products, uretdione-modified products, and uretonimine-modified products.

[0067] The isocyanate-terminated prepolymer is a urethane prepolymer having at least two isocyanate groups at the molecular terminal. It can be obtained by subjecting at least one member selected from the group consisting of a polyisocyanate monomer, a polyisocyanate derivative, and an isocyanate-terminated prepolymer to a urethane reaction with a polyol. The molar ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate to the hydroxyl groups of the polyol may be 0.5 or more, 0.6 or more, 0.8 or more, 1 or more, or 1.5 or more. The molar ratio (NCO / OH) may be 10 or less, 5 or less, 4 or less, or 3 or less. Examples of numerical ranges for the molar ratio (NCO / OH) include 0.5 to 10, 0.5 to 5, 0.8 to 4, and 0.6 to 3.

[0068] The epoxy compound may be a compound having one or more epoxy groups in one molecule. From the viewpoint of further increasing the adhesive strength of the adhesive layer 30 in a high-temperature environment, the epoxy compound may have epoxy groups at both ends. Examples of the epoxy compound include glycidyl ether type epoxy compounds, glycidyl amine type epoxy compounds, glycidyl ester type epoxy compounds, and alicyclic epoxy compounds (alicyclic epoxy compounds).

[0069] The molecular weight of the epoxy compound may be, for example, 500 or less, 450 or less, or 400 or less. When the molecular weight of the epoxy compound is within the above range, the epoxy compound can be sufficiently penetrated into the electrostatic ink composition that constitutes the electrostatic ink layer. The lower limit of the molecular weight of the epoxy compound may be, for example, 98 or more.

[0070] Examples of the alicyclic epoxy compounds include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis(epoxycyclohexyl)adipate.

[0071] Examples of monofunctional alicyclic epoxy compounds having one epoxy group per molecule include 3,4-epoxycyclohexylmethyl methacrylate and 1,2-epoxy-4-vinylcyclohexane. Examples of bifunctional epoxy compounds having two epoxy groups per molecule include 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, and 4-vinylcyclohexene dioxide. Furthermore, examples of epoxy compounds having one or more epoxy groups per molecule include the 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol represented by the following general formula (I):

[0072] [ka]

[0073] In the above general formula (I), n may be an integer of 1-4.

[0074] The epoxy compound preferably contains a bifunctional alicyclic epoxy compound. Being bifunctional increases the number of crosslinking points with the electrostatic ink composition and primer resin, accelerating the curing reaction of the adhesive and facilitating curing. Furthermore, being alicyclic suppresses reaction with polyisocyanate due to steric hindrance. This allows for stable curing and ensures excellent adhesion at the interface between the printing surface 52 and the adhesive layer 30.

[0075] In the adhesive composition, the content of the epoxy compound per 100 parts by mass of polyol may be 3 to 25 parts by mass, 6 to 25 parts by mass, or 8 to 20 parts by mass, from the viewpoint of achieving both high adhesive strength and excellent shear suppression. If the content of the epoxy compound is too high, the excellent shear suppression tends to be impaired. In other words, when the adhesive layer 30 is formed, the adhesive surface may shift or the adhesive composition may protrude. If the amount of the epoxy compound is too low, the adhesive strength under high-temperature hot water treatment conditions tends to decrease.

[0076] In the adhesive composition, the content of polyisocyanate per 100 parts by mass of polyol may be 10 to 50 parts by mass, 15 to 35 parts by mass, or 20 to 30 parts by mass, from the viewpoint of sufficiently increasing the seal strength and the adhesive strength under high-temperature hot water treatment conditions.

[0077] The molar ratio of the epoxy groups contained in the epoxy compound to the isocyanate groups contained in the polyisocyanate may be 0.5 to 10, 1.5 to 9, or 2.0 to 6.5, which allows a sufficiently high adhesive strength to be maintained under high-temperature hot water treatment conditions.

[0078] In addition to the components described above, the adhesive composition constituting the adhesive layer 30 may contain optional components such as additives. Examples of additives include antioxidants, UV absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coatability improvers, leveling agents, nucleating agents, lubricants, release agents, antifoaming agents, plasticizers, surfactants, pigments, dyes, organic fine particles, inorganic fine particles, antifungal agents, and flame retardants. The adhesive composition may contain a solvent such as an organic solvent.

[0079] The adhesive composition bonds the print surface 52, on which the electrostatic ink composition is printed, to the sealant layer 20. An optional layer may be provided between the adhesive layer 30 and the sealant layer 20. The laminates 302, 304 may further include, for example, a barrier layer or the like between the adhesive layer 30 and the sealant layer 20. In this case, the adhesive composition bonds the print surface 52 to the optional layer (e.g., a barrier layer, etc.). The adhesive composition forms a urethane bond by reaction with the polyol and polyisocyanate, thereby functioning as an adhesive. Even in the presence of an epoxy compound, the formation of the urethane bond proceeds smoothly, allowing the print surface 52 to be bonded to the sealant layer 20 or any optional layer with sufficiently high adhesive strength.

[0080] The adhesive composition may have the function of forming urethane bonds and cross-linking the electrostatic ink composition that forms the electrostatic ink layers 50 and 51. This can further improve the adhesive strength between the printing surface 52 and the sealant layer 20 or any other layer.

[0081] Generally, when the coverage rate of the electrostatic ink layer 50 relative to the main surface of the primer layer 40 increases, or when the ink coverage rate of the electrostatic ink layers 50 and 51 increases, the adhesive strength between the electrostatic ink layer 50 and the adhesive layer 30 tends to decrease. However, the adhesive composition described above can provide sufficient adhesive strength. Furthermore, when the coverage rate of the electrostatic ink layer 50 relative to the main surface of the primer layer 40 increases, or when the ink coverage rate of the electrostatic ink layers 50 and 51 increases, the epoxy compound content of the adhesive composition can be increased accordingly, thereby allowing the epoxy compound to sufficiently penetrate into the electrostatic ink layers 50 and 51 formed by the electrostatic ink composition, thereby further suppressing a decrease in adhesive strength. The penetrated epoxy compound crosslinks the electrostatic ink composition, thereby enhancing the strength of the electrostatic ink composition (electrostatic ink layers 50 and 51). Therefore, even when the ink coverage rate of the printing surface 52 increases, or when a heat treatment such as a retort heat treatment is performed, a decrease in adhesive strength can be sufficiently suppressed.

[0082] The adhesive composition maintains high adhesive strength even after heat treatment while also having an excellent pot life. This allows for excellent workability during coating and lamination processes, such as bonding a printed surface to a substrate. The adhesive composition may contain a urethane-forming polyol and polyisocyanate, and an epoxy compound, at least a portion of which may be cured to form the adhesive layer. This allows for a reduction in the number of layers constituting the laminate 300 compared to when an adhesive layer containing only polyurethane and an epoxy coating layer are separately provided. Therefore, when producing a laminate using a roll-to-roll process, for example, problems such as roll meandering after aging and wrinkling due to blocking do not occur. Furthermore, the aging process after coating can be eliminated, improving manufacturing efficiency.

[0083] In the laminates 302, 304 where the electrostatic ink layers 50, 51 and the adhesive layer 30 on the printing surface 52 are in direct contact, components such as epoxy compounds and / or polyisocyanates contained in the adhesive composition sufficiently penetrate into the electrostatic ink layers 50, 51. This crosslinks the electrostatic ink composition constituting the electrostatic ink layers 50, 51, improving the strength of the electrostatic ink composition (electrostatic ink layers 50, 51). It also improves the adhesive strength between the layers. Even if the printing surface 52 includes a plain area (transparent area) without the electrostatic ink layer 50, as shown in Figure 3, the epoxy compound contained in the adhesive layer eliminates stickiness. On the other hand, if an epoxy coating layer is provided separately from the adhesive layer 30, when the printing surface 52 includes a plain area, excess epoxy compound may be present near the plain area, making stickiness more likely. In this way, the laminate 300 can bond the printing surface 52, including the plain area without the electrostatic ink layer 50, with high adhesive strength while eliminating stickiness.

[0084] As described above, the laminates 302, 304 ensure sufficient adhesive strength between the electrostatic ink layers 50, 51 and the substrate 10, primer layer 40, and adhesive layer 30. This suppresses peeling between the electrostatic ink layers 50, 51 and the substrate 10, primer layer 40, and adhesive layer 30 near the tear surface, allowing for sufficient external force transmission to tear the substrate 10, resulting in a packaging bag with excellent tearability. When opening such a packaging bag, the bag can be opened along a predetermined tear line, preventing the packaged contents from scattering and leaving a clean opening surface. Information printed on the printed surface remains legible even after opening, making the bag useful as a packaging bag for food and beverages, sanitary products, and other items where appearance is important. However, applications are not limited to these. For example, because the bag maintains excellent adhesive and sealing strength even after high-temperature hot water treatment and retort heat treatment, it may also be used as a packaging material for retort pouches, microwave-safe packaging, and boiling packaging.

[0085] In the laminate according to the modified example, a primer layer 40 may be provided on each of the opposing surfaces of the substrate 10 and the sealant layer 20. Furthermore, from the viewpoint of improving the gas barrier property and water vapor barrier property of the laminates 302, 304, at least one of a metal layer such as an aluminum foil and a resin layer such as a nylon film may be provided between the substrate 10 and the sealant layer 20 and / or between the sealant layer 20 and the adhesive layer 30.

[0086] Specific examples of the layer structure of the laminate are shown below. In each example, the left end corresponds to the substrate 10 and the right end corresponds to the sealant layer 20, and the layers are laminated in order from left to right. The first adhesive layer is adhesive layer 30, and the second and third adhesive layers may be conventional adhesive layers.

[0087] (1) Transparent vapor-deposited PET film / primer layer / electrostatic ink layer / first adhesive layer / nylon layer / second adhesive layer / CPP film (non-oriented polypropylene film) (2) PET film / primer layer / electrostatic ink layer / first adhesive layer / aluminum layer / second adhesive layer / nylon layer / third adhesive layer / CPP film (non-oriented polypropylene film) (3) PET film / primer layer / electrostatic ink layer / first adhesive layer / nylon layer / second adhesive layer / CPP film (non-oriented polypropylene film) (4) PET film / primer layer / electrostatic ink layer / first adhesive layer / aluminum layer / second adhesive layer / polyethylene film

[0088] In each of the above specific examples, an optional layer may be provided at any position between the first adhesive layer and the sealant layer 20. (1) and (2) are suitable for use as laminates for retort pouches, (3) is suitable for use in microwave ovens, and (4) is suitable for use as a laminate containing supplements or face masks. However, the applications are not limited to those described above.

[0089] The above-described laminate can be prepared, for example, by the following method. One embodiment of a method for manufacturing a laminate is described below. In one example of the method for manufacturing a laminate, a laminate 302 shown in FIG. 3 is manufactured. The method includes the steps of first forming a primer layer 40 on one surface of a film-like substrate 10, printing an electrostatic ink composition on the primer layer 40 to form an electrostatic ink layer 50 and obtain a printed surface 52, and bonding the printed surface 52 and one surface of the sealant layer 20 together using the specific adhesive composition described above.

[0090] The primer layer 40 may be formed on one surface of the substrate 10 by flexographic printing, gravure printing, or the like. The primer layer 40 may be formed by crosslinking a resin raw material with a crosslinking agent. Crosslinking may be achieved by irradiation with ultraviolet light, heat, ionizing radiation such as an electron beam, or non-ionizing radiation such as microwave radiation.

[0091] The printing of the electrostatic ink composition can be carried out by electrostatic printing using a digital printing machine.

[0092] The adhesive composition can be used to bond the printing surface 52 and one side of the sealant layer 20 together by lamination. Lamination can be performed using any suitable device. The epoxy compound and / or polyisocyanate contained in the adhesive composition may penetrate into the electrostatic ink composition and primer layer 40 that make up the electrostatic ink layer 50 and crosslink with the components contained in the electrostatic ink composition and primer layer 40. This improves the strength of the electrostatic ink layer 50 and allows for the production of a laminate 300 in which the interfaces of the layers are sufficiently bonded. During lamination, at least a portion of the adhesive composition may be cured to form a cured product. In this manner, a laminate 302 can be produced, which includes the substrate 10, the primer layer 40, the electrostatic ink layer 50, the adhesive layer 30, and the sealant layer 20, in this order. The laminate 304 and the laminates according to the variations can also be produced in the same manner as the laminate 302.

[0093] The laminates 302 and 304 thus manufactured have the same configurations and properties as those described in the embodiments. The descriptions of the laminates 302 and 304 and their modifications also apply to the description of the above-described manufacturing method embodiments.

[0094] Although several embodiments have been described above, the descriptions of the common configurations can be applied to each other, and the present disclosure is not limited to the above-described embodiments. [Example]

[0095] The present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0096] Example 1 [Laminate fabrication] An alumina-deposited PET film (manufactured by Toppan Printing Co., Ltd., trade name: GLARH12, thickness: 12 μm) was prepared as a substrate. An aqueous primer resin (a resin containing polyethyleneimine, manufactured by Michelman, trade name: DP050) was applied to this alumina-deposited surface to form a primer layer. The amount of aqueous polyethyleneimine applied was 0.10 to 0.18 g / m 2 The coating was applied so that the

[0097] A predetermined printing was performed on the surface of the primer layer using a digital printer (HP Indigo 20000 label and packaging digital printer). The electrostatic ink composition used was an electrostatic ink composition (HP Indigo ElectroInk) containing a thermoplastic resin containing a copolymer of ethylene acrylic acid and ethylene methacrylic acid. As shown in Table 1, yellow (Y), magenta (M), and cyan (C) were used as the colors of the electrostatic ink composition. Several samples with different colors and ink coverages of the electrostatic ink composition were prepared. The ink coverages were as shown in Table 1. Each ink coverage was adjusted by the settings of the digital printer. As shown in Table 1, the total ink coverage was 200 to 400%.

[0098] An adhesive composition with a solids concentration of 36.5% by mass was prepared by blending an aliphatic polyester polyol (manufactured by Mitsui Chemicals, Inc., trade name: Takelac A626, hereinafter sometimes referred to as "(A)") as the base agent, a polyisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate A50, hereinafter sometimes referred to as "(B)") as the curing agent, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (hereinafter sometimes referred to as "C") as the epoxy compound, and ethyl acetate as the solvent. The structure of this epoxy compound is shown in formula (1) below. The blending ratio (by mass) of the components was (A):(B):(C) = 8:1:0.28.

[0099] The adhesive composition prepared as described above was applied to the surface printed with the electrostatic ink composition using a dry laminating device to form an adhesive layer. The amount of the adhesive composition applied was 4.0 g / m. 2 It was decided.

[0100] [ka]

[0101] A nylon film and a non-oriented polypropylene film were laminated together using a commercially available adhesive to produce a laminate. Using the dry laminating device, the nylon film and the adhesive layer were laminated together, with the adhesive layer on the substrate facing the nylon film of the laminated film. The aging time was 40°C for 2 days.

[0102] (Examples 2 and 3) A laminate was prepared in the same manner as in Example 1, except that the color of the electrostatic ink composition and the ink coverage were changed as shown in Table 1.

[0103] (Comparative Examples 1 to 3) A laminate was prepared in the same manner as in Examples 1 to 3, except that the epoxy compound (component (C)) was not added when preparing the adhesive composition.

[0104] <Evaluation of laminate strength of laminate> The laminate strength of each of the laminates prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was measured in accordance with the description of JIS K 6854-1:1999. Specifically, the prepared laminate was first cut into a 15 mm width to prepare a measurement sample. After peeling between the layers at the edge of the measurement sample, the peel strength between the layers of the laminate was measured using a tensile tester at an angle of 90°, a pulling rate of 300 mm / min, and room temperature. This peel strength was defined as the laminate strength at room temperature (20°C). The measurement results are shown in Table 1.

[0105] <Evaluation of tear resistance of laminate> For each of the laminates prepared in Examples 1 to 3 and Comparative Examples 1 to 3, the sealant layers were placed facing each other and heat-sealed to obtain a packaging bag with four sealed sides (as shown in FIG. 1). An I-shaped notch was made in one sealed side to prepare an evaluation sample. For each evaluation sample, the packaging bag was opened starting from the notch, and the appearance was visually inspected to evaluate the tearability. The tearability was evaluated based on the cleanliness of the opened cross section, according to the following evaluation criteria. A: No delamination was observed between the layers of the laminate, and there was little fluctuation in the tear surface. B: No delamination is observed between the layers of the laminate, but the tear plane is fluctuating. C: Delamination is observed between the layers of the laminate, and the tear plane is fluctuating.

[0106] The results are shown in Table 1. For reference, an example based on evaluation criterion A is shown in FIG. 5 , and an example based on evaluation criterion C is shown in FIG. 6 . In FIG. 5 , the tear location is indicated by A, the torn edge of the front laminate of the pair of laminates is indicated by A1, and the torn edge of the back laminate is indicated by A2. As shown in FIG. 5 , in the packaging bag of Example 1, A1 and A2 nearly coincided, confirming that the bag could be opened cleanly. In FIG. 6 , the tear location is indicated by B, the torn edge of the front laminate of the pair of laminates is indicated by B1, and the torn edge of the back laminate is indicated by B2. As shown in FIG. 6 , in the packaging bag of Comparative Example 1, it was confirmed that the positions of B1 and B2 were significantly misaligned. This misalignment is presumably due to peeling occurring on the printed surface of the laminate, as shown by C in FIG. 6 , and the external tearing force was not fully utilized to tear the substrate.

[0107] [Table 1]

[0108] Examples 4 to 6 Laminates were prepared in the same manner as in Examples 1 to 3, except that a laminate film prepared by laminating an aluminum thin film, a nylon film, and an unstretched polypropylene film in this order with a commercially available adhesive was used instead of the laminate film prepared by laminating a nylon film and an unstretched polypropylene film with a commercially available adhesive. The laminate strength and tear resistance of each obtained laminate were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0109] (Comparative Examples 4 to 6) Laminates were prepared in the same manner as in Comparative Examples 1 to 3, except that a laminate film prepared by laminating an aluminum thin film, a nylon film, and an unstretched polypropylene film in this order with a commercially available adhesive was used instead of the laminate film prepared by laminating a nylon film and an unstretched polypropylene film with a commercially available adhesive. The laminate strength and tear resistance of each obtained laminate were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0110] [Table 2]

[0111] Examples 7 to 9 A laminate was prepared in the same manner as in Examples 1 to 3.

[0112] (Comparative Examples 7 to 9) Laminates were prepared in the same manner as in Comparative Examples 1 to 3.

[0113] <Measurement of the rate of change in laminate strength before and after heat treatment of the laminate> Two measurement samples were prepared from each of the laminates prepared in Examples 7 to 9 and Comparative Examples 7 to 9, each cut to a width of 15 mm. The laminate strength value X of one sample was measured as is in the same manner as in Example 1. The other measurement sample was then subjected to a retort heat treatment at 120°C for 30 minutes. Specifically, the sealant layers of each of the laminates prepared in Examples 7 to 9 and Comparative Examples 7 to 9 were heat-sealed to form a packaging bag with three sides sealed. Next, 100 g of water was placed inside the package, and the remaining side was sealed to form a four-sided sealed bag (package). The resulting package was heat-sterilized using a retort sterilization tester at a temperature of 120°C for 30 minutes, after which the package was opened and cut to a width of 15 mm to obtain a measurement sample. The laminate strength of the measurement sample after the retort heat treatment was measured in the same manner as in Example 1. The value of 100(YX) / X was calculated from the measurement results to determine the rate of change in laminate strength. The results are shown in Table 3.

[0114] <Evaluation of tear resistance of laminate> The laminates prepared in Examples 7 to 9 and Comparative Examples 7 to 9 were evaluated for tearability in the same manner as in Example 1. The results are shown in Table 3.

[0115] [Table 3]

[0116] (Examples 10 to 11) Laminates were prepared in the same manner as in Examples 4 to 6. The rate of change in laminate strength of the obtained laminates was determined and the tear properties were evaluated in the same manner as in Example 7. The results are shown in Table 4.

[0117] (Comparative Examples 10 to 11) Laminates were prepared in the same manner as in Comparative Examples 4 to 6. The rate of change in laminate strength was determined and tear resistance was evaluated in the same manner as in Example 7. The results are shown in Table 4.

[0118] [Table 4]

[0119] The results of the above-described Examples and Comparative Examples confirmed that the use of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound can achieve improved laminate strength and tearability. The improved laminate strength and tearability are believed to be due to the improved strength of the electrostatic ink composition and the improved adhesive strength between the layers. For reference, examples of adhesive composition formulations are shown below.

[0120] (Reference example 1) [Create laminate] A laminate was produced in the same manner as in Example 1, except that the blending ratio by mass of the components in the adhesive composition (A):(B):(C) was changed as shown in Table 5. The laminate strength of the obtained laminate was measured in the same manner as in Example 1. The results are shown in Table 5.

[0121] (Reference example 2) A two-component adhesive was prepared in which a first component consisting of an aliphatic polyester polyol (A) (manufactured by Mitsui Chemicals, Inc., product name: Takelac A626) and a second component consisting of a polyisocyanate (B) (manufactured by Mitsui Chemicals, Inc., product name: Takenate A50) and an epoxy compound (C) were housed in separate containers. The first and second components were mixed to prepare an adhesive composition having the formulation shown in Table 5. A laminate was produced in the same manner as in Reference Example 1, except that this adhesive composition was used, and the adhesive strength was measured. The measurement results are shown in Table 5.

[0122] (Comparative Example 13) A laminate was produced in the same manner as in Reference Example 1, except that the epoxy compound (C) was not added when preparing the adhesive composition, and the adhesive strength was measured. The measurement results are shown in Table 5.

[0123] (Comparative Example 14) A laminate was prepared in the same manner as in Reference Example 1, except that an epoxy compound of formula (1) was applied to the printed surface of the electrostatic ink composition to form an epoxy coating layer, and the adhesive composition of Comparative Example 13 was applied to this epoxy coating layer, and the adhesive strength was measured. The amount of the epoxy coating layer applied was an amount equivalent to 0.53 parts by mass in the formulation shown in Table 5. The measurement results are shown in Table 5.

[0124] [Table 5]

[0125] The column [(B) / (A)] x 100 in Table 5 shows the amount (parts by mass) of polyisocyanate blended relative to 100 parts by mass of aliphatic polyester polyol. The column [(C) / (A)] x 100 in Table 5 shows the amount (parts by mass) of epoxy compound blended relative to 100 parts by mass of aliphatic polyester polyol. The column "Epoxy group / Isocyanate group" in Table 5 shows the molar ratio of epoxy groups contained in epoxy compound (C) to isocyanate groups contained in polyisocyanate (B).

[0126] As shown in Table 5, it was confirmed that the laminates of Reference Examples 1 and 2, in which an adhesive layer containing an epoxy compound was bonded to a printed surface, had higher adhesive strength than the laminate of Comparative Example 13, in which an adhesive layer not containing an epoxy compound was bonded to a printed surface. Comparative Example 14 achieved relatively high adhesive strength, but the number of steps increased because an epoxy coating layer was formed in addition to the adhesive layer. It took two days for the epoxy coating layer to harden (age), reducing productivity.

[0127] In the laminate of Comparative Example 13, peeling occurred near the interface between the electrostatic ink layer and the primer layer. In the laminate of Comparative Example 14, the electrostatic ink layer underwent cohesive failure. On the other hand, in the laminates of Reference Examples 1 and 2, peeling occurred at the interface between the electrostatic ink layer and the adhesive layer, and no cohesive failure of the electrostatic ink layer was observed. This suggests that the cohesive force of the electrostatic ink layer was improved. In Reference Examples 1 and 2, the molar ratio of isocyanate groups contained in the polyisocyanate (B) to hydroxyl groups of the aliphatic polyester polyol (A) was within the range of 0.5 to 10.

[0128] Next, in addition to the lamination strength, the hot water lamination strength and seal strength were measured for the laminates of Reference Example 1 and Comparative Example 14. For the measurements, samples with a total ink coverage of 500% and 200% were used. The details of the measurement procedure are as follows.

[0129] [Measurement of hot water laminate strength] The laminates of Reference Example 1 and Comparative Example 14 were each cut to a width of 15 mm to obtain a measurement sample. After peeling the layers at the edge of the measurement sample, the sample was immersed in hot water at 90°C and the peel strength was measured using a tensile tester. Specifically, the peel angle was free and the pulling rate was 300 mm / min. This peel strength is shown in Table 6 as the hot water laminate strength.

[0130] [Measurement of seal strength (before heat treatment)] Using a pair of laminates from Reference Example 1, the unstretched polypropylene films were overlapped and heat-sealed to form a sealed portion. This resulted in heat welding of the unstretched polypropylene films to each other, producing a 15 mm wide measurement sample. The seal strength of the sealed portion of the produced measurement sample was measured in accordance with JIS K 7127:1999. The measurement was performed using a tensile tester under the following conditions: a peel angle of 90°, a pulling rate of 300 mm / min, and room temperature (20°C), and the peel strength between the heat seals was measured. This peel strength was defined as the seal strength "before heat treatment." The measurement results are shown in Table 6. A similar measurement sample was produced using the laminate from Comparative Example 14, and the same measurements were performed. The measurement results are shown in Table 6.

[0131] [Seal strength measurement (after boiling)] The measurement samples prepared in the above "Measurement of seal strength (before heat treatment)" were heated in water at 100°C for 30 minutes. Thereafter, the seal strength was measured using the same procedure as in the above "Measurement of seal strength (before heat treatment)". The measurement results are shown in the "After boiling" column in Table 6.

[0132] [Measurement of seal strength after retort (120℃)] The measurement samples prepared in the "Measurement of seal strength (before heat treatment)" section above were subjected to retort heat treatment (120°C x 30 minutes). Peel strength was measured using a tensile tester in the same manner as in "Measurement of seal strength (before heat treatment)." The measurement results are shown in the "120°C x 30 minutes" section of Table 6.

[0133] [Measurement of seal strength after retort (130℃)] The measurement samples prepared in the "Measurement of seal strength (before heat treatment)" section above were subjected to retort heat treatment (130°C x 30 minutes). Peel strength was measured using a tensile tester in the same manner as in "Measurement of seal strength (without heat treatment)." The measurement results are shown in the "130°C x 30 minutes" section of Table 6.

[0134] [Table 6]

[0135] As shown in Table 6, the hot water lamination strength of Reference Example 1 was significantly higher than that of Comparative Example 14. It was also confirmed that Reference Example 1 had better seal strength than Comparative Example 14. In particular, the seal strength of Reference Example 1 was sufficiently high even after boiling, whereas the seal strength of Comparative Example 14 decreased significantly after boiling. It was confirmed that the laminate of Comparative Example 14 showed a significant decrease in lamination strength and seal strength when heated in the presence of moisture. [Industrial Applicability]

[0136] According to the present disclosure, a packaging bag can be provided that has a printed surface printed by a digital printing machine, but that suppresses peeling at the interface between the electrostatic ink layer and the primer layer, and at the interface between the electrostatic ink layer and the adhesive layer, when opened or torn. [Explanation of symbols]

[0137] 10...substrate, 20...sealant layer, 30...adhesive layer, 40...primer layer, 50, 51...electrostatic ink layer, 52...printed surface, 100, 110...packaging bag, 101...seal portion, 102...storage portion, 120...opening means, 121...half-cut line, 124...easy-open processing portion, 200...packaging body, 300, 302, 304...laminate

Claims

1. A packaging bag comprising a laminate having a substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order, the adhesive layer is composed of at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound and a cured product thereof; the epoxy compound is a difunctional alicyclic epoxy compound, and the molecular weight of the epoxy compound is 500 or less; a molar ratio of epoxy groups contained in the epoxy compound to isocyanate groups contained in the polyisocyanate is 0.5 to 10; the ink coverage of the electrostatic ink layer is 500% or less; A packaging bag, wherein the laminate strength of the laminate is 2.0 N / 15 mm or more.

2. A packaging bag comprising a laminate having a substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a sealant layer in this order, the adhesive layer is composed of at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound and a cured product thereof; the epoxy compound is a difunctional alicyclic epoxy compound, and the molecular weight of the epoxy compound is 500 or less; a molar ratio of epoxy groups contained in the epoxy compound to isocyanate groups contained in the polyisocyanate is 0.5 to 10; the ink coverage of the electrostatic ink layer is 100 to 400%; When the laminate strength of the laminate is X and the laminate strength of the laminate after retort heat treatment at 120°C for 30 minutes is Y, the value of 100(Y-X) / X is greater than -30%.

3. The packaging bag according to claim 1 or 2, wherein the polyol includes an aliphatic polyester polyol, and the epoxy compound includes one having epoxy groups at both ends.

4. The packaging bag according to any one of claims 1 to 3, wherein the polyisocyanate includes a xylylene diisocyanate derivative.

5. The ink application amount on the main surface of the primer layer on the sealant layer side is 0.5 g / m ２ The packaging bag according to any one of claims 1 to 4.

6. The packaging bag according to any one of claims 1 to 5, wherein the laminate further comprises a barrier layer between the adhesive layer and the sealant layer.

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