Laminate, manufacturing method thereof, and packaging bag

Abstract

To provide a laminate having sufficiently high adhesive strength between a first substrate and a second substrate and a method for producing the same, and a wrapping bag including the laminate.SOLUTION: A method for producing a laminate includes the step (A) for applying water-based ink onto the surface of a first substrate by printing to form an ink layer (A), the step (B) for coating the surface of the ink layer remote from the first substrate with a coating liquid, which is a mixture of at least a polyester polyol, a polyisocyanate (excluding a biuret of hexamethylene diisocyanate), and a biuret of hexamethylene diisocyanate, to form an adhesive layer (B), and the step (C) for depositing a second substrate on the surface of the adhesive layer remote from the ink layer. A constituent adhesive of the adhesive layer has a 100% modulus of 0.1-2.5 MPa at 25°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a laminate, a method for manufacturing the same, and a packaging bag. [Background technology]

[0002] Conventionally, as packaging materials used for packaging bags (for example, flexible packaging bags) that undergo heat treatment such as boiling or retort treatment or heat and pressure treatment, laminates having a laminated structure made of materials that have properties such as preservability of the contents, heat resistance, pressure resistance, durability (strength) against external stress, and printability, while taking cost-effectiveness into consideration, have been used.

[0003] In the field of packaging materials, efforts are being made to eliminate VOCs (volatile organic compounds) as an environmental response. That is, for forming ink layers such as letters, pictures, and patterns, there is a shift from oil-based inks containing solvents (toluene, methyl ethyl ketone, etc.) that are volatile organic compounds (VOCs) to solvent-free water-based inks. Because water-based inks do not contain organic solvents that are VOCs, they have the advantage of improving the environment at production sites and solving the problem of residual organic solvents in laminates. For example, Patent Document 1 discloses a heat-sterilizable packaging laminate that uses water-based ink. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-79986 Summary of the Invention [Problem to be solved by the invention]

[0005] In the production of conventional laminates used for flexible packaging bags that are subjected to heat treatment or heat-pressure treatment, when an ink layer is formed using a water-based ink, delamination is likely to occur between the ink layer and a layer in contact with it (for example, an adhesive layer). When delamination occurs, problems such as deterioration of the ink layer surface, reduced barrier properties, and an increased risk of bag breakage occur, making it difficult to sufficiently perform the heat treatment or heat-pressure treatment of the flexible packaging bag required for sterilization treatment.

[0006] In response to this, the provision of a specific laminating adhesive layer is proposed in Patent Document 1. However, the inventors' investigations have revealed that the method of Patent Document 1 does not provide sufficient adhesive strength between the ink layer and the laminating adhesive layer.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a laminate having sufficiently high adhesive strength between a first substrate and a second substrate, a method for manufacturing the same, and a packaging bag using the laminate. [Means for solving the problem]

[0008] Previous studies on improving the adhesive strength of an adhesive to an ink layer have focused on increasing the chemical affinity between the adhesive and the ink layer (for example, the chemical affinity between the material used in the ink layer and the material used in the adhesive layer). However, the present inventors conducted studies focusing on the physical properties of the adhesive. In the process, they discovered that the adhesive strength between the ink layer and the adhesive layer is improved when the 100% modulus at 25°C of the adhesive is 2.5 MPa or less, which led to the present disclosure.

[0009] The method for producing a laminate according to the present disclosure includes the steps of: (A) printing a water-based ink on the surface of a first substrate to form an ink layer; (B) applying a coating liquid comprising a mixture of at least polyester polyol, polyisocyanate (excluding a biuret of hexamethylene diisocyanate), and a biuret of hexamethylene diisocyanate to the surface of the ink layer opposite the first substrate to form an adhesive layer; and (C) laminating a second substrate onto the surface of the adhesive layer opposite the ink layer, wherein the 100% modulus at 25°C of the adhesive constituting the adhesive layer is 0.1 to 2.5 MPa.

[0010] According to the above-mentioned manufacturing method, a laminate having a sufficiently high adhesive strength (peel strength) between the first substrate and the second substrate can be obtained. The reason why such an effect is obtained is not clear, but the inventors speculate as follows.

[0011] Typically, the ink layer formed by printing with a water-based ink contains pores, which are interconnected gaps between pigments in a network-like pattern. Therefore, when the coating liquid is applied in step (B), the coating liquid penetrates into the ink layer, filling these pores and forming a network structure of adhesive within the ink layer. In conventional laminates, the adhesive lacks sufficient flexibility, making the adhesive network structure prone to breakage. It is believed that the adhesive that penetrates into the ink layer does not contribute significantly to improving the adhesion between the ink layer and the adhesive layer. In contrast, in the above-described manufacturing method, the 100% modulus of the adhesive at 25°C is 0.1 to 2.5 MPa, which is believed to prevent the network structure of the adhesive in the ink layer from breaking under stress and improve the stress compliance of the adhesive layer. Therefore, it is presumed that the adhesive strength between the ink layer and the adhesive layer is sufficiently high, resulting in a sufficiently high adhesive strength between the first substrate and the second substrate.

[0012] In the step (A), the aqueous ink may be printed by flexographic printing. When an ink layer is formed by flexographic printing using an aqueous ink for flexographic printing, the effect of improving the adhesive strength tends to be remarkable. The reason for this is presumed to be as follows.

[0013] Flexographic printing, which uses relief printing, is said to have inferior color development compared to gravure printing, which uses intaglio printing, because the amount of ink applied to the substrate is smaller. Therefore, the water-based inks used in flexographic printing tend to contain high concentrations of pigments to improve color development. When flexographic printing is performed using such water-based inks, voids are more likely to form between the pigments in the ink layer, resulting in a denser adhesive network structure within the ink layer. This is thought to significantly improve the adhesive strength between the ink layer and the adhesive layer through the above-mentioned mechanism.

[0014] The blending mass ratio of the polyester polyol to the polyisocyanate may be 2: 1 to 9: 1. In this case, the 100% modulus of the adhesive can be easily adjusted to the above range.

[0015] The amount of the biuret of hexamethylene diisocyanate blended may be 30 parts by mass or more per 100 parts by mass of the polyisocyanate blended, which makes it easy to bring the 100% modulus of the adhesive into the above range.

[0016] The laminate according to the present disclosure has a laminate structure in which a first substrate, an ink layer, an adhesive layer, and a second substrate are arranged in this order, and the adhesive layer is made of an adhesive containing a polyester polyol, a polyisocyanate (excluding a biuret of hexamethylene diisocyanate), and a urethane compound that is a reaction product of a biuret of hexamethylene diisocyanate, and the 100% modulus of the adhesive at 25°C is 0.1 to 2.5 MPa.

[0017] The laminate has a sufficiently high adhesive strength (peel strength) between the first substrate and the second substrate, for example, the peel strength between the first substrate and the second substrate at 25°C is 1.0 N / 15 mm or more.

[0018] The laminate may further include a sealant layer on the side of the second substrate opposite the adhesive layer side.

[0019] The first substrate and / or the second substrate may include a barrier layer.

[0020] The packaging bag according to the present disclosure is produced by manufacturing the above-described laminate.

[0021] The above-mentioned packaging bag can prevent problems such as deterioration of the ink layer surface, reduced barrier properties, and increased risk of bag breakage due to peeling between the ink layer and the adhesive layer, and also makes it easier to sufficiently perform the heating treatment or heating and pressurizing treatment of the flexible packaging bag required for sterilization treatment. [Effects of the Invention]

[0022] According to the present disclosure, an object is to provide a laminate having sufficiently high adhesive strength between a first substrate and a second substrate, a method for manufacturing the same, and a packaging bag using the laminate. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating one embodiment of a laminate according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view schematically showing one embodiment of a method for producing the laminate shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing another embodiment of the laminate according to the present disclosure. [Figure 4] FIG. 4 is a plan view schematically showing one embodiment of a packaging bag using the laminate according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0024] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limit values ​​described individually can be combined in any way.

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations will be omitted. The dimensional ratios of the drawings are not limited to those shown in the drawings.

[0026] <Laminate> FIG. 1 is a cross-sectional view schematically illustrating a laminate according to one embodiment. The laminate 10 shown in FIG. 1 is in the form of a sheet and includes a first substrate 1, an ink layer 2, an adhesive layer 3, and a second substrate 4A. The ink layer 2 contains a pigment 2a. The adhesive layer 3 is made of an adhesive containing a urethane compound that is a reaction product of a polyester polyol, a polyisocyanate (excluding a biuret of hexamethylene diisocyanate; hereinafter, also referred to as "polyisocyanate (A)"), and a biuret of hexamethylene diisocyanate (hereinafter, also referred to as "polyisocyanate (B)"). Here, the reaction product of a polyester polyol, a polyisocyanate (A), and a polyisocyanate (B) refers to a product obtained by reacting at least a polyester polyol, a polyisocyanate (A), and a polyisocyanate (B).

[0027] The 100% modulus of the adhesive at 25°C is 0.1 to 2.5 MPa. Here, the 100% modulus indicates the tensile stress when the test piece is elongated by 100%. The 100% modulus is a value measured in accordance with JIS K 7161 and is a physical property value specific to adhesives. Specifically, it can be measured by the method described in the Examples. An adhesive having a 100% modulus of 2.5 MPa or less can be said to be a flexible adhesive that easily expands and contracts when an external stress is applied. Furthermore, an adhesive having a 100% modulus of 0.1 MPa or more can be said to have sufficient hardness as an adhesive.

[0028] In the laminate 10 of this embodiment, the adhesive constituting the adhesive layer 3 has such physical properties, resulting in a sufficiently high adhesive strength (peel strength) between the ink layer 2 and the adhesive layer 3, and a sufficiently high adhesive strength (peel strength) between the first substrate 1 and the second substrate 4A. Specifically, for example, the peel strength between the first substrate 1 and the second substrate 4A at 25°C is 1.0 N / 15 mm or more. A laminate 10 having such peel strength is unlikely to experience interlayer delamination between the ink layer 2 and the adhesive layer 3, even when subjected to a heat treatment or a heat-and-pressure treatment. Therefore, the laminate 10 is suitable for use as a packaging material for packaging bags (e.g., flexible packaging bags) that undergo a heat treatment or a heat-and-pressure treatment, such as a boiling treatment or a retort treatment. The peel strength between the first substrate 1 and the second substrate 4A at 25°C is a value measured in accordance with JIS K 6854, and specifically, can be measured by the method described in the examples.

[0029] From the viewpoint of achieving superior adhesive strength, the 100% modulus of the adhesive at 25° C. may be 2.3 MPa or less, 2.1 MPa or less, or 1.9 MPa or less. The lower limit of the 100% modulus of the adhesive at 25° C. is sufficient if it is 0.1 MPa or more, but if higher hardness is required, it may be 1.0 MPa or more.

[0030] The 100% modulus of an adhesive can be adjusted, for example, by the types and amounts of components used in the adhesive (polyester polyol, polyisocyanate (A), polyisocyanate (B), etc.). For example, when the amount of polyester polyol is large, the molecular weight increases and the 100% modulus tends to be high, while when the amount of polyester polyol is small, the 100% modulus tends to be low. Furthermore, when the amount of polyisocyanate (B) is large, the 100% modulus tends to be low, while when the amount of polyisocyanate (B) is small, the 100% modulus tends to be high. Based on these trends, a person skilled in the art can easily prepare an adhesive having a 100% modulus of 0.1 to 2.5 MPa at 25°C.

[0031] Specifically, for example, when the blending mass ratio of polyester polyol to polyisocyanate (A) is 2:1 to 9:1, the 100% modulus of the adhesive tends to fall within the above range. From this perspective, the blending mass ratio of polyester polyol to polyisocyanate (A) is preferably 2:1 to 9:1, and may be 5:1 to 9:1, 7:1 to 9:1, 7.5:1 to 8.5:1, or 7.7:1 to 8.2:1. The blending mass ratio is the blending mass ratio of solid contents.

[0032] Furthermore, as will be described later, when the polyisocyanate (A) contains a modified hexamethylene diisocyanate, the 100% modulus of the adhesive tends to fall within the above range when the blending mass ratio of the polyester polyol to the polyisocyanate other than the modified hexamethylene diisocyanate is 2:1 to 9:1. From this perspective, the blending mass ratio of the polyester polyol to the polyisocyanate other than the modified hexamethylene diisocyanate is preferably 2:1 to 9:1, and may be 5:1 to 9:1, 7:1 to 9:1, 7.5:1 to 8.5:1, or 7.7:1 to 8.2:1. The blending mass ratios mentioned above are blending mass ratios of solid contents.

[0033] Furthermore, for example, when the blending amount of polyisocyanate (B) is 30 parts by mass or more per 100 parts by mass of polyisocyanate (A), the 100% modulus of the adhesive tends to fall within the above range. From this viewpoint, the blending amount of polyisocyanate (B) is preferably 30 parts by mass or more per 100 parts by mass of polyisocyanate (A), and may be 40 parts by mass or more or 50 parts by mass or more. From the viewpoint of cost and from the viewpoint of preventing deactivation due to reaction with moisture in the air, the blending amount of polyisocyanate (B) may be 200 parts by mass or less per 100 parts by mass of polyisocyanate (A). Note that the blending amount is the solid content.

[0034] Furthermore, as described below, when the polyisocyanate (A) contains a modified hexamethylene diisocyanate, the 100% modulus of the adhesive tends to fall within the above range when the blending amount of the modified hexamethylene diisocyanate (including polyisocyanate (B)) is 30 parts by mass or more per 100 parts by mass of the polyisocyanate other than the modified hexamethylene diisocyanate. From this perspective, the blending amount of the modified hexamethylene diisocyanate is preferably 30 parts by mass or more, and may be 40 parts by mass or more or 50 parts by mass or more per 100 parts by mass of the polyisocyanate other than the modified hexamethylene diisocyanate. From the perspectives of cost and preventing deactivation due to reaction with moisture in the air, the blending amount of the modified hexamethylene diisocyanate may be 200 parts by mass or less per 100 parts by mass of the polyisocyanate other than the modified hexamethylene diisocyanate. The content of the biuret form of hexamethylene diisocyanate in the modified product of hexamethylene diisocyanate may be 50% by mass or more. The above blending amounts are solid content amounts.

[0035] (First substrate) The first substrate 1 is, for example, a resin film. The first substrate 1 may be a resin film made of a resin such as a polyester resin, a polyamide resin, a polyaramid resin, a polypropylene resin, a polyvinyl chloride resin, a polystyrene resin, a polycarbonate resin, a polyacetal resin, or a fluorine-based resin. The first substrate 1 may be an unstretched resin film, or a uniaxially or biaxially stretched resin film. Specifically, the first substrate may be a polyethylene terephthalate (PET) resin film, a biaxially stretched polypropylene (OPP) resin film, or a biaxially stretched nylon (ONy polyamide resin) film.

[0036] The thickness of the first substrate 1 (e.g., a resin film) may be a thickness that satisfies the strength, rigidity, etc. required for heat and pressure treatment, and may be, for example, 10 μm to 100 μm or 12 μm to 50 μm. If the thickness of the first substrate 1 is 100 μm or less, the flexible packaging bag is easily torn by hand when opened, and production costs can be reduced. If the thickness of the first substrate 1 is 10 μm or more, sufficient strength, rigidity, etc. can be easily obtained.

[0037] (ink layer) The ink layer 2 is in contact with the first substrate 1 and the adhesive layer 3. The ink layer 2 is, for example, an aqueous ink layer formed by printing an aqueous ink containing a pigment 2a and a binder resin (also called a "vehicle") onto the first substrate.

[0038] The pigment 2a may be an inorganic pigment or an organic pigment. Examples of inorganic pigments include extender pigments such as titanium oxide (white pigment), carbon black (black pigment), barium sulfate, and calcium carbonate. Examples of organic pigments include azo pigments, phthalocyanine pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and dye lake pigments. The average primary particle diameter of the pigment 2a is, for example, 0.3 to 1.0 μm. Here, the average primary particle diameter of the pigment 2a is a value measured by laser diffraction.

[0039] The pigment 2a may be one type of pigment or multiple types of pigments. For example, the ink layer 2 may contain multiple pigments of different colors or multiple pigments of different particle sizes.

[0040] The content of pigment 2a may be 40 to 75% by mass based on the total mass of the ink layer 2. When the content of pigment 2a is 40% by mass or more, excellent color development is easily obtained, and the effect of improving adhesive strength tends to be significantly enhanced. When the content of pigment 2a is 75% by mass or less, delamination between the ink layer 2 and the adhesive layer 3 tends to be less likely to occur. From the viewpoint of achieving both excellent color development and suppressing delamination to an even higher degree, the content of pigment 2a may be, for example, 45 to 75% by mass or 50 to 70% by mass based on the total mass of the ink layer 2.

[0041] The binder resin contained in the ink layer 2 is, for example, an aqueous binder resin. Examples of aqueous binder resins include water-soluble binder resins, emulsion-type binder resins, and colloidal dispersion-type binder resins. Among these, the use of a water-soluble binder resin tends to improve the dispersion stability of the ink, the adhesion of the ink layer, and the strength of the ink layer. Examples of water-soluble binder resins include natural resin-based casein resins, shellac resins, synthetic resin-based rosin-modified maleic acid resins, styrene-maleic acid resins, styrene-acrylic acid resins, styrene-maleic acid-acrylic acid resins, acrylic acid-acrylic acid ester resins, acrylic resins, and polyester resins, as well as water-soluble polyamide resins and aqueous polyurethane resins. From the viewpoint of obtaining a more significant effect of improving adhesive strength, the aqueous binder resin may be a resin that does not have a urethane skeleton. The water-soluble binder resin may be a resin with no or a low acid value as the main component, and may be used in combination with a resin with a high acid value, from the viewpoint of improving the dispersion stability of the ink, the adhesion of the ink layer, and the strength of the ink layer. The content of the water-soluble binder resin may be, for example, 25 to 60 mass%, 25 to 55 mass%, or 30 to 50 mass%, based on the total mass of the ink layer 2.

[0042] The ink layer 2 may contain auxiliary agents such as dispersants, plasticizers, waxes, lubricants, and antifoaming agents. Examples of plasticizers include dioctyl terephthalate. Examples of waxes include polyethylene and polypropylene. Examples of lubricants include calcium carbonate, barium sulfate, and clay. Examples of antifoaming agents include silicone-based and hydrocarbon-based agents.

[0043] A portion of the ink solvent (e.g., water or a hydrophilic solvent contained in a water-based ink) may remain in the ink layer 2, but the content of the solvent (e.g., water or a hydrophilic solvent) is, for example, 1 mass % or less based on the total mass of the ink layer 2. Examples of hydrophilic solvents include alcohol-based solvents such as methanol, ethanol, propanol, and butanol.

[0044] Basic compounds such as ammonia, trimethylamine, sodium hydroxide, and potassium hydroxide may be added to aqueous inks in order to improve the solubility and dispersibility of the resin in the solvent, and the ink layer 2 may also contain these components.

[0045] The ink layer 2 has, for example, a network of continuous through-holes. The adhesive constituting the adhesive layer 3 may permeate the ink layer 2 from the ends of the through-holes present on the surface of the ink layer 2, thereby filling at least a portion of the through-holes with the adhesive. The through-holes in the ink layer 2 are formed, for example, by the pigments 2a contained in the ink layer 2 coming into contact with each other, forming continuous gaps between the pigments 2a. Therefore, by adjusting the content of the pigment 2a, it is possible to adjust the size of the through-holes, the volume ratio of the through-holes to the ink layer 2, and the like. The thickness of the ink layer 2 is, for example, 0.3 to 2.5 μm.

[0046] Although the ink layer 2 is shown as a single layer in Figure 1, the ink layer 2 may have a multi-layer structure of two or more layers. For example, the ink layer 2 may be a two-layer ink layer obtained by forming a first ink layer containing a pigment with a relatively small particle size on the surface of the first substrate 1, and then forming a second ink layer containing a pigment with a relatively large particle size (e.g., a white pigment) on the surface of this first ink layer. When the laminate includes a second ink layer containing a white pigment, the color development of the first ink layer tends to be further improved.

[0047] (adhesive layer) The adhesive layer 3 is interposed between the ink layer 2 and the second substrate 4A, and bonds these layers together. The adhesive constituting the adhesive layer 3 contains a urethane compound which is a reaction product of a polyester polyol, a polyisocyanate (A), and a polyisocyanate (B).

[0048] A polyester polyol is a compound having two or more hydroxyl groups and a polyester structure as its main skeleton. The polyester structure may be a polyester polyurethane structure. That is, the polyester polyol may be a polyester urethane polyol. The polyester polyol may further have a polyether structure in addition to the polyester structure and polyurethane structure. Specific examples of polyester polyols include polyadipate polyol and polycaprolactone diol. The polyester polyol may be a single polyester polyol or a combination of two or more polyester polyols.

[0049] Commercially available polyester polyols may be used, including Takelac A525 (trade name, "Takelac" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc. and DIC Dry LX-747 manufactured by DIC Corporation.

[0050] The polyisocyanate (A) is a compound having two or more isocyanate groups (excluding the biuret form of hexamethylene diisocyanate). The polyisocyanate (A) may be an aromatic compound or an aliphatic compound. The polyisocyanate (A) may be a low molecular weight compound or a high molecular weight compound. The polyisocyanate (A) may be a single polyisocyanate or a combination of two or more polyisocyanates.

[0051] Specific examples of the polyisocyanate (A) include phenyl isocyanate, isophorone diisocyanate, tetramethylene diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate (meta-xylylene diisocyanate and para-xylylene diisocyanate), hydrogenated xylylene diisocyanate, and modified products of these polyisocyanates (polymers, adducts thereof, etc.). Specific examples of modified polyisocyanates include isocyanurates, uretdione products, and adducts thereof (for example, polyhydric alcohol adducts such as TMP).

[0052] The polyisocyanate (A) may contain a modified product of hexamethylene diisocyanate (excluding biuret products), but in this case, it is preferable that the polyisocyanate (A) further contains a polyisocyanate other than the modified product of hexamethylene diisocyanate. Examples of polyisocyanates other than the modified products of hexamethylene diisocyanate include phenyl isocyanate, isophorone diisocyanate, tetramethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, and modified products of these polyisocyanates (polymers, adducts thereof, etc.). The amount of polyisocyanates other than modified hexamethylene diisocyanate contained in the polyisocyanate (A) may be 50% by mass or more, 70% by mass or more, or 90% by mass or more, based on the total mass of the polyisocyanate (A). The amount of polyisocyanates other than hexamethylene diisocyanate contained in the polyisocyanate (A) may be less than 100% by mass, or 95% by mass or less, or 90% by mass or less, based on the total mass of the polyisocyanate (A).

[0053] Commercially available products may be used as a supply material for the polyisocyanate (A), such as Takenate A52 (trade name, "Takenate" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc. and KX-75 manufactured by DIC Corporation.

[0054] The urethane compound (compound having a urethane bond) contained in the adhesive layer 3 may contain a polyol other than polyester polyol as a constituent component (a reaction component for obtaining a reaction product) as long as the effect of improving adhesive strength is not impaired. That is, the adhesive layer 3 may contain a urethane compound that is a reaction product of a polyester polyol, a polyol other than polyester polyol, a polyisocyanate (A), and a polyisocyanate (B). Examples of polyols other than polyester polyols include polyether polyols such as polyoxypropylene polyol, polyether polyol, and polyoxytetramethylene glycol, and hydrocarbon polyols such as polycarbonate polyol, polybutadiene polyol, and polyacrylate polyol.

[0055] The content of the urethane compound in the adhesive layer 3 may be, for example, 60% by mass or more, 75% by mass or more, or 90% by mass or more, based on the total mass of the adhesive layer 3. The adhesive layer 3 may consist essentially of the urethane compound. The content of the urethane compound in the adhesive layer 3 may be 100% by mass or less, 95% by mass or less, or 90% by mass or less, based on the total mass of the adhesive layer 3.

[0056] In addition to the urethane compound, the adhesive layer 3 may further contain additives such as a dispersant, an antifoaming agent, a leveling agent, a stabilizer, a filler, a lubricant, a slip agent, and wax. A portion of the solvent (diluent, etc.) contained in the coating liquid for forming the adhesive layer may remain in the adhesive layer 3, but the content of the solvent is, for example, 1 mass % or less based on the total mass of the adhesive layer 3. Examples of solvents include ethyl acetate and methyl ethyl ketone.

[0057] The thickness of the adhesive layer 3 is, for example, 0.5 to 5.0 μm. The thickness of the adhesive layer 3 means the shortest distance from the surface on the ink layer 2 side to the surface opposite the ink layer 2, and does not include the thickness of the region in the ink layer 2 where the adhesive has soaked in.

[0058] (Second substrate) The second base material 4A is, for example, a resin film. Examples of the resin film may be the resin films mentioned above as examples of the first base material 1.

[0059] The thickness of the second substrate 4A (e.g., a resin film) may be a thickness that satisfies the strength, rigidity, etc. required for heat and pressure treatment, and may be, for example, 10 μm to 100 μm or 12 μm to 50 μm. If the thickness of the second substrate is 100 μm or less, the flexible packaging bag is easily torn by hand when opened, and production costs can be reduced. If the thickness of the second substrate is 10 μm or more, sufficient strength, rigidity, etc. can be easily obtained.

[0060] The thickness (total thickness) of the laminate 10 may be, for example, 20 to 300 μm.

[0061] <Method of manufacturing laminate> Next, a method for manufacturing the laminate 10 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view that schematically shows one embodiment of a method for manufacturing the laminate 10. The method for manufacturing the laminate 10 includes the steps of: (A) printing a water-based ink on the surface of a first substrate 1 to form an ink layer 2 (see Fig. 2(a)); (B) applying a coating liquid for forming an adhesive layer to the surface of the ink layer 2 opposite the first substrate 1 to form an adhesive layer 3 (see Fig. 2(b)); and (C) laminating a second substrate 4A on the surface of the adhesive layer 3 opposite the ink layer 2 side (see Fig. 2(c)).

[0062] The aqueous ink contains, for example, the pigment 2a and a binder resin described above. The solvent (dispersion medium) of the aqueous ink is water or the hydrophilic solvent described above. The pigment is dispersed in the solvent, and the binder resin is dissolved or dispersed in the solvent. The content of the solvent in the aqueous ink is, for example, 40 to 80 mass % based on the total mass of the aqueous ink.

[0063] The water-based ink may further contain the auxiliary agents and basic compounds described above as components that can be contained in the ink layer 2.

[0064] The printing of the aqueous ink can be carried out by known methods such as gravure printing, flexographic printing, inkjet printing, etc. In step (A), an ink layer may be formed by solid printing, or an ink layer may be formed by pattern printing of letters, figures, symbols, pictures, or other desired patterns, or a first ink layer may be formed by solid printing, and then a desired pattern may be printed on the first ink layer to form a second ink layer.

[0065] The coating liquid for forming the adhesive layer is prepared by mixing at least the above-mentioned polyester polyol, polyisocyanate (A), and polyisocyanate (B). The coating liquid can be prepared, for example, by mixing the polyester polyol, polyisocyanate (A), and polyisocyanate (B) all at once.

[0066] The coating liquid can also be prepared by, for example, mixing a polyester polyol with a polyisocyanate other than a biuret of hexamethylene diisocyanate to obtain a liquid mixture, and then adding a biuret of hexamethylene diisocyanate (polyisocyanate (B)) to the liquid mixture and mixing. In this case, when adding polyisocyanate (B) to the liquid mixture, a polyisocyanate other than a biuret of hexamethylene diisocyanate may be added. For example, a mixture containing a biuret of hexamethylene diisocyanate as a main component (e.g., containing 50% by mass or more) may be added to the liquid mixture. The mixture may be, for example, a mixture (HDI mixture) containing a biuret of hexamethylene diisocyanate and at least one selected from the group consisting of an isocyanurate and a uretdione of hexamethylene diisocyanate, and adducts thereof. When an HDI mixture is used, the polyisocyanate other than the biuret of hexamethylene diisocyanate used to prepare the mixture may be a polyisocyanate other than a modified product of hexamethylene diisocyanate.

[0067] The coating liquid for forming the adhesive layer may be a solvent-free adhesive composition that does not contain a solvent, from the viewpoint of reducing VOCs, but it may also contain a solvent. For example, when the components used in preparing the coating liquid, such as polyester polyol, polyisocyanate (A), and polyisocyanate (B), are provided in a state diluted with a solvent (i.e., as a solution), the coating liquid contains a solvent for these solutions (diluted solution). The solvent may be the solvent described above as a component that can be contained in the adhesive layer 3.

[0068] The coating liquid for forming the adhesive layer contains, for example, polyester polyol, polyisocyanate (A) and polyisocyanate (B), and may also contain a reaction product (urethane compound) formed by partial reaction of these.

[0069] When preparing the coating liquid for forming the adhesive layer, components other than the polyester polyol, polyisocyanate (A) and polyisocyanate (B) (for example, the additives and solvents mentioned above as components that can be contained in the adhesive layer 3) may be blended.

[0070] As a method for applying the coating liquid, conventionally known methods such as commonly used casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metalling bar coating, chamber doctor combined coating, curtain coating, etc. can be used.

[0071] When the coating liquid contains a solvent, the coating may be dried by carrying out a drying treatment after coating in order to remove the solvent. The drying of the coating may be carried out at 25 to 120°C, for example.

[0072] Although the laminate and the manufacturing method thereof according to one embodiment have been described above, the laminate according to the present disclosure is not limited to the above embodiment.

[0073] 3 is a cross-sectional view schematically illustrating a laminate according to another embodiment. In a laminate 20 according to another embodiment, a second substrate 4B includes a substrate film 5 such as the resin film described above, and a barrier layer (gas barrier layer) 6 provided on the substrate film 5, and a sealant layer 7 on the surface of the second substrate 4B opposite to the adhesive layer 3. Except for these points, the configuration of the laminate 20 is the same as the configuration of the laminate 10.

[0074] In the laminate 20, the barrier layer 6 is in contact with the adhesive layer 3. The barrier layer 6 includes, for example, an inorganic thin film layer 6a and a gas barrier coating layer 6b provided on the surface of the inorganic thin film layer 6a facing the adhesive layer 3.

[0075] The inorganic thin-film layer 6a is formed by film formation (e.g., vacuum film formation) of, for example, a metal, or an oxide, nitride, or nitride oxide of silicon or the like. Specific examples of materials that can be used for the inorganic thin-film layer 6a include metals such as aluminum, titanium, copper, indium, and tin, or oxides thereof (e.g., alumina), silicon, silicon oxide, and even nitrides or nitride oxides of metals or silicon. The inorganic thin-film layer 6a may be a thin-film layer containing a plurality of these metals. In particular, inorganic thin-film layers containing oxides, nitrides, or nitride oxides of aluminum, titanium, copper, indium, or silicon tend to have both excellent transparency and barrier properties, and inorganic thin-film layers containing oxides or nitride oxides of silicon tend to have even better barrier properties.

[0076] The inorganic thin film layer 6a can be formed by vacuum deposition (resistance heating vacuum deposition, electron beam heating vacuum deposition, induction heating vacuum deposition), sputtering (reactive sputtering, dual magnetron sputtering), or PECVD (plasma generation methods include direct current (DC), radio frequency (RF), middle frequency (MF), DC pulse, RF pulse, and DC+RF superposition). The method for forming the inorganic thin film layer 6a can be selected appropriately depending on the purpose and application. For example, sputtering may be selected from the viewpoint of film uniformity, while vacuum deposition may be selected from the viewpoint of cost.

[0077] The thickness of the inorganic thin film layer 6a may be, for example, 5 nm or more, or 100 nm or less. When the thickness of the inorganic thin film layer 6a is 5 nm or more, good barrier properties are easily obtained, and when it is 100 nm or less, the occurrence of cracks is suppressed, the deterioration of the water vapor and oxygen barrier properties is small, and costs can be reduced due to a reduction in the amount of material used and a shortened formation time.

[0078] Metal foil such as aluminum foil may be used as inorganic thin film layer 6a, and in this case, the thickness of the metal foil may be 6 to 9 μm.

[0079] The gas barrier coating layer 6b can be formed by applying a coating liquid containing, for example, a polar compound such as polyvinyl alcohol, polyvinylpyrrolidone, or ethylene vinyl alcohol, a chlorine-containing compound such as polyvinylidene chloride, a compound containing a Si atom, a compound containing a Ti atom, a compound containing an Al atom, or a compound containing a Zr atom, onto the inorganic thin film layer, drying, and curing the liquid. By laminating the gas barrier coating layer 6b, various secondary damages in later processes can be prevented and high barrier properties can also be imparted.

[0080] The sealant layer 7 is made of, for example, a resin that can melt and fuse with heat. Examples of resins that make up the sealant layer include polyolefin resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, methylpentene polymer, polyethylene, and polypropylene, as well as acid-modified polyolefin resins obtained by modifying these with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid. The sealant layer may be made of one or more resins.

[0081] The thickness of the sealant layer 7 may be, for example, 5 to 300 μm, or may be 10 to 100 μm.

[0082] The sealant layer 7 can be formed by applying a coating liquid containing the above-mentioned resin using a conventionally known method such as dipping, roll coating, screen printing, spraying, etc. Alternatively, the sealant layer 7 can be formed by attaching a film or sheet made of the above-mentioned resin.

[0083] In the laminate 20, the second substrate 4B includes a substrate film 5 and a barrier layer 6, but the second substrate may not include a substrate film and may consist of only a barrier layer. Alternatively, the first substrate may include a barrier layer. In this case, the first substrate may or may not include a substrate film. The barrier layer may be included in either the first substrate or the second substrate, or may be included in both. Alternatively, a primer layer may be provided between the substrate film 5 and the barrier layer 6.

[0084] <Packaging bag> FIG. 4 is a plan view schematically showing one embodiment of a packaging bag using the laminate 10 (a packaging bag made from the laminate 10). The packaging bag 30 shown in FIG. 4 is processed into a bag shape by heat-sealing three sides L1, L2, and L3. After the contents are placed through the opening 30a, which is not heat-sealed, the opening 30a can also be heat-sealed to seal the packaging bag 30. However, the form of the packaging bag is not limited to this. Other examples of packaging bags include pillow packaging, three-side seal packaging, and gusset packaging. [Example]

[0085] The present disclosure will be described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0086] Example 1 (Manufacturing of laminates) [Process (A)] A 12 μm-thick barrier film (manufactured by Toppan Printing Co., Ltd., product name: GL-ARH) with a polyethylene terephthalate resin film as the base film was prepared as the first substrate, and a water-based ink for flexographic printing (manufactured by DIC Corporation, product name: XS-911) was printed on the surface of the first substrate by flexographic printing to form an ink layer with a thickness of 0.3 μm.

[0087] [Process (B)] A mixed solution was prepared by blending polyester polyol Takelac A525 manufactured by Mitsui Chemicals, Inc. and polyisocyanate Takenate A52 manufactured by Mitsui Chemicals, Inc. in a mass ratio (solids content ratio) of 7.9:1. The ratio (NCO / OH) of the total number of moles of hydroxyl groups in the polyester polyol (Takelac A525) to the total number of moles of isocyanate groups in the polyisocyanate (Takenate A52) was 1.3. Next, 40 parts by mass of a hexamethylene diisocyanate (HDI) mixture containing a biuret of HDI as the main component (biuret content: 50% by mass or more) per 100 parts by mass of polyisocyanate was added to the mixed solution obtained above and mixed to prepare a coating solution for forming an adhesive layer.

[0088] Next, the adhesive-forming coating liquid obtained above was applied to the surface of the ink layer formed in step (A) by roll coating and dried to form an adhesive layer with a thickness of 3.3 μm. The coating amount in the dry state was 3.0 g / m 2 It was.

[0089] [Process (C)] On the adhesive layer formed in step (B), a biaxially oriented nylon film (manufactured by Unitika Ltd., trade name: Emblem) having a thickness of 15 μm was laminated as a second substrate.

[0090] [Process (D)] A 60 μm thick non-axially oriented polypropylene film (manufactured by Toray Industries, Inc., product name: Pylen ZK207) was laminated as a sealant layer by dry lamination on the second substrate laminated in step (C). After lamination, the laminate was cured at 50° C. for 72 hours to obtain the laminate of Example 1.

[0091] (Packaging bag production) Two sheets measuring 140 mm long x 180 mm wide were cut out from the laminate, and these sheets were overlapped so that the sealant layers were in contact with each other, and the three edges were heat-sealed to produce a bag-shaped packaging container (packaging bag) as shown in Figure 4. The heat sealing was performed by heating the three edges at 160°C for 1 second with a 10 mm wide seal bar.

[0092] <Example 2, Comparative Examples 1 and 2> In step (B), when preparing the coating liquid for forming the adhesive layer, the amounts of polyester polyol (Takelac A525), polyisocyanate (Takenate A52), and HDI mixture were changed as shown in Table 1, except that the laminates and packaging bags of Example 2 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1.

[0093] <Evaluation of adhesive properties> The 100% modulus of the adhesives used to produce the laminates of Examples 1 and 2 and Comparative Examples 1 and 2 was measured in accordance with JIS K 7161. Specifically, a film was formed on release paper using a doctor blade using the adhesive-forming coating liquid prepared in step (B) above, and the film was dried at room temperature for 24 hours under a nitrogen atmosphere to remove the solvent. The film was then cured at 60°C for 6 days to form a cured film (film thickness 40 to 50 μm), from which a 5 mm wide strip-shaped test piece (sample) was prepared. The resulting test piece was used to measure the tensile stress in the longitudinal direction of the test piece at 24°C and a pulling rate of 300 mm / min, and the tensile stress (100% modulus) at which the test piece was elongated to 100% was determined.

[0094] <Adhesion strength and delamination evaluation> Test pieces with a width of 15 mm were cut out from the laminates of Examples 1 and 2 and Comparative Examples 1 and 2, and the initial adhesive strength (adhesive strength between the first substrate and the second substrate) of the laminates was measured at room temperature (20°C, 30% RH) using a tensile tester in accordance with JIS K 6854. The results are shown in Table 1.

[0095] Next, 100 ml of water was poured into the upper opening of the packaging bags of Examples 1 and 2 and Comparative Examples 1 and 2, and the opening (top) was then heat-sealed under the same conditions as when the packaging bags were made. The appearance of the sealed packaging bags was visually inspected to check for the presence or absence of delamination. Bags that did not have delamination were rated "○ (good)" and bags that had delamination were rated "× (bad)". The results are shown in Table 1.

[0096] Next, the sealed packaging bag was retorted in hot water at 121°C for 30 minutes. A 15mm wide test piece was cut out from the packaging bag after retort treatment, and the laminate strength after retort treatment was measured in the same manner as the initial laminate strength. In addition, the appearance of the packaging bag after retort treatment was visually inspected to check for the presence or absence of delamination. Bags without delamination were rated "○ (good)," and bags with delamination were rated "× (bad)." The results are shown in Table 1.

[0097] [Table 1]

[0098] 1...first substrate, 2...ink layer, 2a...pigment, 3...adhesive layer, 4A, 4B...second substrate, 5...substrate film, 6...barrier layer, 7...sealant layer, 10, 20...laminated body, 30...packaging bag.

Claims

1. A step (A) of printing an aqueous ink containing an organic pigment on a surface of a first substrate to form an ink layer; a step (B) of applying a coating liquid obtained by mixing at least polyester polyol, polyisocyanate (excluding a biuret of hexamethylene diisocyanate), and a biuret of hexamethylene diisocyanate to a surface of the ink layer opposite to the first substrate to form an adhesive layer; and (C) a step of laminating a second substrate on the surface of the adhesive layer opposite to the ink layer side, the blending mass ratio of the polyester polyol to the polyisocyanate is 2:1 to 9:1; the 100% modulus at 25°C of the adhesive constituting the adhesive layer is 0.1 to 2.5 MPa; A method for producing a laminate, wherein the content of the pigment in the ink layer is 40 to 75 mass % based on the total mass of the ink layer.

2. The method for producing a laminate according to claim 1 , wherein in the step (A), the aqueous ink is printed by flexographic printing.

3. The method for producing a laminate according to claim 1 or 2, wherein the amount of the biuret of the hexamethylene diisocyanate blended is 30 parts by mass or more per 100 parts by mass of the polyisocyanate blended.

4. a laminated structure in which a first substrate, an ink layer containing an organic pigment, an adhesive layer, and a second substrate are arranged in this order; the adhesive layer is made of an adhesive containing a polyester polyol, a polyisocyanate (excluding a biuret of hexamethylene diisocyanate), and a urethane compound that is a reaction product of a biuret of hexamethylene diisocyanate, the blending mass ratio of the polyester polyol to the polyisocyanate is 2:1 to 9:1; The adhesive has a 100% modulus at 25°C of 0.1 to 2.5 MPa, A laminate, wherein the content of the pigment in the ink layer is 40 to 75% by mass based on the total mass of the ink layer.

5. The laminate according to claim 4 , wherein the peel strength between the first substrate and the second substrate at 25° C. is 1.0 N / 15 mm or more.

6. The laminate according to claim 4 or 5, further comprising a sealant layer on the surface of the second substrate opposite the adhesive layer side.

7. The laminate according to any one of claims 4 to 6, wherein the first substrate and / or the second substrate comprises a barrier layer.

8. A packaging bag produced by producing the laminate according to any one of claims 4 to 7.

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