Packaging material and packaging bag

Abstract

Disclosed is a packaging material 10 which sequentially includes a first base material 1, an aqueous ink layer 2, an adhesive layer 3, and a second base material 4 in this order. The adhesive layer 3 is formed from a urethane-based adhesive that contains a polyisocyanate and a polyol. The polyisocyanate includes a chain isocyanate that has a symmetrical structure or an isocyanate polymer that is derived from the chain isocyanate. Some of the polyisocyanate penetrates to the vicinity of the interface between the aqueous ink layer 2 and the first base material 1 so as to satisfy formula (a).　Formula (a): (Ni - Nii) ≥ 0.5

Description

Packaging materials and bags

[0001] The present disclosure relates to packaging materials and packaging bags.

[0002] Conventionally, as packaging materials used for packaging bags (e.g., 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 provide the preservation properties of the contents, heat resistance, pressure resistance, durability (strength) against external stress, printability, etc., 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) in order to address environmental concerns. Specifically, for forming printed layers of letters, pictures, patterns, etc., oil-based inks containing solvents (toluene, methyl ethyl ketone, etc.), which are volatile organic compounds (VOCs), are being replaced with solvent-free water-based inks. Because water-based inks do not contain organic solvents, which are VOCs, they have the advantage of improving the production environment and eliminating the problem of residual organic solvents in packaging materials. For example, Patent Document 1 discloses a heat-sterilizable packaging laminate using water-based ink.

[0004] Japanese Patent Application Laid-Open No. 2001-79986

[0005] When a printed layer is formed using an aqueous ink, i.e., when a packaging material includes an aqueous ink layer as a printed layer, the adhesive strength between the aqueous ink layer and a layer in contact therewith (e.g., an adhesive layer) tends to decrease, resulting in a decrease in the seal strength of the packaging bag (pouch). This decrease in adhesive strength is particularly noticeable after retort treatment, and can cause interlayer delamination.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a packaging material that can be used to produce a packaging bag having sufficient seal strength, and a packaging bag using the packaging material.

[0007] Some aspects of the present disclosure provide the following [1] to

[11] .

[0008] [1] A packaging material comprising a first substrate, a water-based ink layer, an adhesive layer, and a second substrate in this order, wherein the adhesive layer is formed of a urethane-based adhesive containing a polyisocyanate and a polyol, the polyisocyanate contains a chain isocyanate having a symmetric structure or an isocyanate polymer derived from the chain isocyanate, and a portion of the polyisocyanate has penetrated to the vicinity of the interface between the water-based ink layer and the first substrate so as to satisfy the following formula (a): Formula (a): (N ｉ -N ｉｉ )≧0.5 [In formula (a), N ｉ represents the amount of nitrogen (unit: mass %) in the first substrate measured in a region (i) at a distance of 0.06 to 0.26 μm from the interface, and N ｉｉ represents the average value of the nitrogen amount (unit: mass %) in the first substrate measured in regions (ii), (iii), and (iv) each having a thickness of 1 μm, which include positions whose distances from the interface correspond to 30%, 60%, and 80% of the thickness of the first substrate.]

[0009] [2] The packaging material according to [1], wherein the polyisocyanate contains, as the isocyanate polymer, a biuret or isocyanurate of the chain isocyanate.

[0010] [3] The packaging material according to [1] or [2], wherein the chain isocyanate is hexamethylene diisocyanate.

[0011] [4] The packaging material according to any one of [1] to [3], wherein the aqueous ink layer is formed from an aqueous flexographic ink.

[0012] [5] The packaging material according to any one of [1] to [4], wherein the first substrate comprises at least one selected from the group consisting of a stretched polyethylene terephthalate film, a stretched polypropylene film, a stretched nylon film, and a stretched polyethylene film.

[0013] [6] The packaging material according to any one of [1] to [5], wherein the first substrate includes a water vapor barrier layer.

[0014] [7] The packaging material according to any one of [1] to [6], wherein the polyol comprises a polyester polyol.

[0015] [8] The packaging material according to any one of [1] to [7], wherein the urethane adhesive is a dry lamination adhesive.

[0016] [9] The (N ｉ -N ｉｉ ) is 1.2 or more.

[0017]

[10] The packaging material according to any one of [1] to [9], wherein the adhesive strength between the first substrate and the second substrate, as measured by the following procedures (1) to (5), is 1.5 N / 15 mm or more. (1): Two sheets measuring 140 mm wide and 100 mm long are cut out from the packaging material, and the two sheets are placed face-to-face with the second substrate side so that their four edges overlap. Three of the four edges are heat-sealed to produce a packaging bag with one opening. (2): 50 g of water is added to the packaging bag, and the opening edge of the packaging bag is heat-sealed to produce a test pouch. (3): The test pouch produced in (2) is subjected to a retort treatment at 121°C for 30 minutes. (4): After the retort treatment in (3), a test piece measuring 15 mm wide and 200 mm long is cut out from one of the two sheets constituting the test pouch. (5): A T-peel test is performed on the test piece at a peel rate of 300 mm / min and a width of 15 mm in accordance with JIS K 6854 under conditions of 20°C and 30% RH, and the adhesive strength between the first substrate and the second substrate is measured.

[0018]

[11] A packaging bag made from the packaging material according to any one of [1] to

[10] .

[0019] According to the present disclosure, it is possible to provide a packaging material that can be used to produce a packaging bag having sufficient seal strength, and a packaging bag using the packaging material.

[0020] Fig. 1 is a cross-sectional view schematically showing one embodiment of a packaging material according to the present disclosure. Fig. 2 is a cross-sectional view schematically showing another embodiment of a packaging material according to the present disclosure. Fig. 3 is a plan view schematically showing one embodiment of a packaging bag using the packaging material according to the present disclosure.

[0021] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. 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 ​​individually described can be combined arbitrarily. Furthermore, "A or B" may include either A or B, or may include both.

[0022] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings where necessary. Note that the present disclosure is not limited to the following embodiments. In the drawings, the same or equivalent parts are designated 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.

[0023] <Packaging Material> One embodiment of the present disclosure is a packaging material including a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate in this order, for example, a sheet-like laminate as shown in Fig. 1. The packaging material 10 in Fig. 1 comprises a first substrate 1, an aqueous ink layer 2, an adhesive layer 3, and a second substrate 4, and the adhesive layer 3 bonds the aqueous ink layer 2 and the second substrate 4. In Fig. 1, 2a denotes a pigment in the aqueous ink layer.

[0024] In the packaging material, the adhesive layer is formed of a urethane adhesive containing a polyisocyanate and a polyol, and the polyisocyanate contains a chain isocyanate having a symmetric structure or an isocyanate polymer derived from the chain isocyanate. Hereinafter, the chain isocyanate will be referred to as polyisocyanate (a1), and the isocyanate polymer will be referred to as polyisocyanate (a2), and these will be collectively referred to as polyisocyanate (A).

[0025] In the packaging material, a portion of the polyisocyanate penetrates to the vicinity of the interface between the aqueous ink layer and the first substrate so as to satisfy the following formula (a). Here, the interface between the aqueous ink layer and the first substrate refers to the outermost surface of the first substrate with which the aqueous ink layer is in direct contact. Furthermore, the vicinity of the interface between the aqueous ink layer and the first substrate refers to a range within a distance that will affect the semi-quantitative elemental values ​​when the interface is analyzed by SEM-EDX measurement, which will be described later (for example, a range within 0.4 μm of the distance from the interface). Formula (a): (N ｉ -N ｉｉ ) ≧0.5

[0026] In formula (a), N ｉ represents the amount of nitrogen (EDX elemental semi-quantitative value, unit: mass%) in the first substrate, measured in the region (i) at a distance of 0.06 to 0.26 μm from the interface (the interface between the first substrate and the water-based ink layer). ｉｉ The values ​​represent the average value of the nitrogen content (EDX elemental semi-quantitative value, unit: mass%) in the first substrate measured in 1 μm-thick regions (ii), (iii), and (iv), respectively, including positions where the distance from the interface corresponds to 30%, 60%, and 80% of the thickness of the first substrate. Note that regions (i), (ii), (iii), and (iv) do not overlap with each other. For example, when the thickness of the first substrate is 5 μm, region (ii) includes a position where the distance from the interface is 1.5 μm (a position corresponding to 30% of the thickness of the first substrate), but does not include a position where the distance from the interface is 3.0 μm (a position corresponding to 60% of the thickness of the first substrate).

[0027] The packaging material allows the production of packaging bags with sufficient sealing strength.

[0028] The seal strength of the packaging material is measured, for example, by the following steps (a1) to (a5). (a1) Two sheets measuring 90 mm wide and 140 mm long are cut out from the packaging material, and the two sheets are placed face to face with the second substrate side so that four sides overlap, and are bonded by heat sealing to prepare a laminated sample. (a2) A T-peel test is performed on the laminated sample at a width of 15 mm at a peel rate of 300 mm / min in accordance with JIS K 6854 under conditions of 20°C and 30% RH, and the seal strength of the laminated sample is measured. Note that the heat sealing in (a1) is performed by heating the two overlapping sheets at 150°C and 3 kg / cm. ２ This may be done by applying heat and pressure at 500 kJ / min for 0.5 seconds.

[0029] The seal strength measured by the above procedure is, for example, 45 N / 15 mm or more, and can also be 50 N / 15 mm or more, or 55 N / 15 mm or more. If the adhesion strength between the first substrate and the second substrate is insufficient, peeling occurs between these substrates, significantly reducing the seal strength. However, if the seal strength is 45 N / 15 mm or more, peeling between the substrates is suppressed, and it can be determined that the adhesion strength is sufficient. The upper limit of the seal strength measured by the above procedure is, for example, 70 N / 15 mm.

[0030] Furthermore, the packaging material provides sufficiently high interlayer (between the first substrate and the second substrate) adhesive strength even after retort treatment. Therefore, the packaging material is suitable for retort use, and this packaging material makes it possible to obtain a retort packaging bag that is less susceptible to delamination and is less susceptible to problems such as deterioration of the aqueous ink layer surface, reduced barrier properties, and increased risk of bag breakage due to delamination. Here, "for retort use" refers to a packaging bag that is to be retorted or is used to produce such a packaging bag. Retort treatment is, for example, a moist heat sterilization treatment defined by the Food Sanitation Act, and refers to moist heat sterilization treatment performed at a temperature of 100°C or higher. Retort treatment may also be performed under pressure (e.g., 0.2 Pa or higher).

[0031] The adhesive strength between the first substrate and the second substrate of the packaging material is measured, for example, by the following procedures (b1) to (b5). (b1): Two sheets measuring 140 mm wide and 100 mm long are cut out from the packaging material, and the second substrate sides of the two sheets are placed face to face so that the four sides overlap, and three of the four sides are heat-sealed to produce a packaging bag with one opening. (b2): 50 g of water is added to the packaging bag, and the opening side of the packaging bag is heat-sealed to produce a test pouch. (b3): ​​The test pouch produced in (b2) is subjected to a retort treatment at 121°C for 30 minutes. (b4): After the retort treatment in (b3), a test piece measuring 15 mm wide and 200 mm long is cut out from one of the two sheets constituting the test pouch. (b5): A T-peel test is performed on the test piece at a peel rate of 300 mm / min and a width of 15 mm in accordance with JIS K 6854 under conditions of 20°C and 30% RH to measure the adhesive strength between the first substrate and the second substrate. Note that the heat sealing of (b1) and (b2) is performed using a 15 mm wide seal bar at 150°C and 3 kg / cm on each side. ２ This may be done by applying heat and pressure at 500 kJ / min for 0.5 seconds.

[0032] The adhesive strength measured by the above procedure is, for example, 1.5 N / 15 mm or more, and can also be 2.5 N / 15 mm or more, or 3.5 N / 15 mm or more. The upper limit of the adhesive strength measured by the above procedure is, for example, 10 N / 15 mm.

[0033] Furthermore, although delamination in packaging bags made from packaging materials containing a water-based ink layer tends to occur particularly easily at low temperatures (for example, around 5°C), the packaging materials tend to exhibit sufficiently high interlayer adhesive strength even at low temperatures. Therefore, packaging bags made from the packaging materials are unlikely to experience problems such as contents spilling out due to delamination, even if the bag is dropped immediately after being taken out of a refrigerator.

[0034] The reason why the above-described effects are obtained is not clear, but the inventors of the present disclosure speculate as follows.

[0035] First, when a packaging material includes an aqueous ink layer as a printing layer, the adhesive strength between the aqueous ink layer and a layer in contact therewith is reduced because the binder resin used in the aqueous ink has low cohesive force. In contrast, in the above packaging material, a portion of the polyisocyanate penetrates to the vicinity of the interface between the aqueous ink layer and the first substrate so as to satisfy formula (a). N in formula (a) ｉ and N ｉｉ and correspond to the total amount of nitrogen (N) derived from the polyisocyanate that has penetrated to the vicinity of the interface and the nitrogen (N) derived from the nitrogen compound contained in the first base material itself, and the amount of nitrogen (N) derived from the nitrogen compound contained in the first base material itself, respectively. Therefore, the difference between these (N ｉ -N ｉｉ ) is considered to correspond to the amount of nitrogen (N) derived from the polyisocyanate that has penetrated to the vicinity of the interface between the aqueous ink layer and the first substrate. As such, in the above-mentioned packaging material, a certain amount or more of polyisocyanate has penetrated to the vicinity of the interface between the aqueous ink layer and the first substrate, and as a result, a network structure derived from the polyisocyanate is formed in the aqueous ink layer up to the vicinity of the interface between the aqueous ink layer and the first substrate, and this network structure compensates for the decrease in adhesive strength between the layers after retort treatment, so it is presumed that the above-mentioned effect is obtained. Note that, although it is not clear, when the polyisocyanate in the adhesive does not contain the above-mentioned polyisocyanate (A), (N ｉ -N ｉｉ ) is close to 0, it is presumed that the polyisocyanate (A) has the property of easily penetrating into the adhesive layer and contributes to the formation of a network structure in the vicinity of the interface. In other words, the polyisocyanate that has penetrated to the vicinity of the interface between the water-based ink layer and the first substrate may be the polyisocyanate (A).

[0036] (N ｉ -N ｉｉ ) is preferably 1.2 or more, more preferably 1.4 or more. ｉ -N ｉｉ The larger the N ), the higher the adhesive strength between the layers before and after retort treatment tends to be. ｉ -Nｉｉ The upper limit of (N) is, for example, 10.0, and may be 5.0 or 3.5. ｉ -N ｉｉ ) may be, for example, 0.5 to 10.0, 0.5 to 5.0, 0.5 to 3.5, 1.2 to 10.0, or 1.4 to 10.0. ｉ and N ｉｉ More specifically, the measurement of (N ｉ -N ｉｉ ) can be adjusted by changing the type and amount of polyisocyanate (A), as well as by changing the type and thickness of the aqueous ink layer, and by adjusting the drying and curing rates when forming the adhesive layer. For example, by lowering the heating temperature and lengthening the drying and curing times, the adhesive can be made to penetrate more easily to the vicinity of the interface, and (N ｉ -N ｉｉ ) can be increased.

[0037] (First substrate) The first substrate is a support for the aqueous ink layer, and can also be referred to as a printing substrate on which the aqueous ink is printed. The first substrate includes, for example, a resin film. Examples of resins constituting the resin film include polyester-based resins, polyamide-based resins, polyaramid-based resins, polypropylene-based resins, polyethylene-based resins, polyvinyl chloride-based resins, polystyrene-based resins, polycarbonate-based resins, polyacetal-based resins, and fluorine-based resins. The resin constituting the resin film may be one type or two or more types.

[0038] As the resin film, from the viewpoint that the adhesive strength between layers is likely to be higher before and after retort treatment, it is preferable to use a resin film containing at least one resin selected from the group consisting of polyester-based resins, polyamide-based resins, polyethylene-based resins, and polypropylene-based resins, and it is more preferable to use a resin film containing at least one resin selected from the group consisting of polyethylene terephthalate, polypropylene, and polyamide (nylon) polyethylene-based resins.

[0039] The resin film may be an unstretched resin film or a resin film stretched uniaxially or biaxially (stretched film). From the viewpoints of printability, dimensional stability, and puncture resistance, the resin film is preferably a biaxially stretched resin film (biaxially stretched resin film). From the viewpoint of increasing the interlayer adhesive strength before and after retort treatment, it is preferable to use at least one selected from the group consisting of stretched polyethylene terephthalate (PET) film, stretched polypropylene (OPP) film, stretched nylon (ONY) film, and stretched polyethylene film, and it is more preferable to use at least one selected from the group consisting of biaxially stretched polyethylene terephthalate film, doubly stretched polypropylene film, biaxially stretched nylon film, monostretched polyethylene film, and biaxially stretched polyethylene film.

[0040] The first substrate may include two or more types of resin films. That is, the first substrate may be a substrate (laminate) with a multilayer structure. When the first substrate has a multilayer structure, it is preferable that the resin film constitutes the outermost layer of the first substrate and is in contact with the aqueous ink layer, and it is more preferable that the resin film of the above-mentioned preferred embodiment constitutes the outermost layer of the first substrate and is in contact with the aqueous ink layer.

[0041] The thickness of the resin film may be a thickness that satisfies the strength, rigidity, etc. required for heat and pressure treatment, and may be, for example, 5 μm to 100 μm or 8 μm to 50 μm. If the thickness of the resin film 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 resin film is 8 μm or more, sufficient strength, rigidity, etc. can be easily obtained.

[0042] The first substrate may consist of only a resin film, or may include layers other than the resin film. For example, the first substrate may include a water vapor barrier layer in addition to the resin film. The water vapor barrier layer may be provided on the surface of the resin film facing the water-based ink layer, or on the surface of the resin film opposite the water-based ink layer. When the first substrate includes a water vapor barrier layer, the resin film may be in contact with the water-based ink layer, or the water vapor barrier layer may be in contact with the water-based ink layer.

[0043] The water vapor barrier layer may include an inorganic thin film layer and a water vapor barrier coating layer, as shown in Fig. 2. In the packaging material 20 shown in Fig. 2, the first substrate 1 is made of a resin film 1a and a water vapor barrier layer 1b, and the water vapor barrier layer 1b is made of an inorganic thin film layer 1c and a water vapor barrier coating layer 1d. As shown in Fig. 2, the inorganic thin film layer and the water vapor barrier coating layer may be provided in this order on the resin film.

[0044] The inorganic thin film layer 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 include metals such as aluminum, titanium, copper, indium, and tin, or oxides thereof (e.g., alumina), silicon, silicon oxide, and even nitrides and nitride oxides of metals or silicon. The inorganic thin film layer 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.

[0045] The inorganic thin film layer 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), and 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 can be appropriately selected depending on the purpose and application. For example, sputtering may be selected from the viewpoint of film uniformity, and vacuum deposition may be selected from the viewpoint of cost.

[0046] The thickness of the inorganic thin film layer may be, for example, 5 nm or more and 100 nm or less. When the thickness of the inorganic thin film layer 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, etc.

[0047] The inorganic thin film layer may be a metal foil such as an aluminum foil, and in this case, the thickness of the metal foil may be 6 to 9 μm.

[0048] The water vapor barrier coating layer 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, a compound containing a Zr atom, etc., onto the inorganic thin film layer, drying, and curing the liquid. By laminating the water vapor barrier coating layer, various secondary damages in later processes can be prevented and high barrier properties can also be imparted.

[0049] The thickness of the water vapor barrier coating layer may be, for example, 50 nm or more and 1000 nm or less. More preferably, it may be 200 nm or more and 500 nm or less. When the thickness of the water vapor barrier coating layer is 50 nm or more, good water vapor barrier properties are easily obtained, and when it is 1000 nm or less, defects in the water vapor barrier coating layer due to insufficient conformability can be suppressed.

[0050] The total thickness of the first substrate may be, for example, from 5 μm to 100 μm or from 8 μm to 50 μm.

[0051] (Aqueous Ink Layer) The aqueous ink layer is a layer formed with an aqueous ink. The aqueous ink layer is formed by printing an aqueous ink on the first substrate. The aqueous ink layer may be, for example, an aqueous colored ink layer formed with an aqueous colored ink, or an aqueous colorless ink layer formed with an aqueous colorless ink (medium).

[0052] The water-based colored ink contains, for example, a pigment, a binder resin (also called a "vehicle"), and a solvent (dispersion medium).

[0053] The pigment 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 ink 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.

[0054] The pigment may be one type of pigment or multiple types of pigments. For example, the aqueous ink layer may contain multiple pigments of different colors or multiple pigments of different particle sizes.

[0055] When the aqueous ink layer is an aqueous colored ink layer, the pigment content may be 30 to 90% by mass, based on the total mass of the aqueous ink layer. When the pigment content is 30% by mass or more, excellent color development is easily achieved, and the effect of improving adhesive strength tends to be significantly enhanced. Furthermore, when the pigment content is 90% by mass or less, delamination between the aqueous ink layer and the adhesive layer 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 pigment content may be, for example, 35 to 85% by mass, based on the total mass of the aqueous ink layer. When the aqueous ink layer is an aqueous colorless ink layer, such as a medium, it may contain a white pigment, but the pigment content is usually 0% by mass, based on the total mass of the aqueous ink layer. Such colorless inks are used as undercoats or for adjusting the color of colored inks.

[0056] When the aqueous ink contains a pigment, the pigments come into contact with each other inside the aqueous ink layer formed by printing the aqueous ink, forming gaps between the pigments, and these gaps form a network of continuous through holes from the surface of the aqueous ink layer. Therefore, when the aqueous ink contains a pigment, the adhesive (especially polyisocyanate) is more likely to penetrate into the aqueous ink layer when the adhesive layer is formed, and the above-mentioned (N ｉ -N ｉｉ ) tends to be large.

[0057] The binder resin is, for example, an aqueous binder resin, such as a water-soluble binder resin, an emulsion-type binder resin, or a colloidal dispersion-type binder resin.

[0058] Examples of aqueous 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, α-methylstyrene-acrylic acid resins, styrene-methacrylic acid resins, styrene-maleic acid-acrylic acid resins, acrylic acid-acrylic acid ester resins, acrylic acid-methacrylic acid ester resins, acrylic resins, urethane resins, acrylic-urethane resins, styrene 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. From the viewpoint of more easily improving the dispersion stability of the ink, the adhesion of the aqueous ink layer, and the strength of the aqueous ink layer, the water-soluble binder resin may be a resin that has no acid value or a low acid value as the main component, and the resin may be used in combination with a resin with a high acid value.

[0059] When the aqueous ink layer is an aqueous colored ink layer, the content of the aqueous binder resin may be, for example, 15 to 60 mass %, 25 to 55 mass %, or 30 to 50 mass % based on the total mass of the aqueous ink layer. When the aqueous ink layer is an aqueous colorless ink layer, the content of the aqueous binder resin may be, for example, 60 to 100 mass % or 80 to 100 mass % based on the total mass of the aqueous ink layer.

[0060] The solvent (dispersion medium) of the aqueous ink dissolves or disperses the binder resin in the aqueous ink. The solvent (dispersion medium) of the aqueous ink is, for example, water or a hydrophilic solvent. Examples of hydrophilic solvents include alcoholic solvents such as methanol, ethanol, propanol, and butanol. A portion of the solvent (dispersion medium) of the aqueous ink may remain in the aqueous ink layer, but the content of the solvent (dispersion medium) is, for example, 1 mass % or less based on the total mass of the aqueous ink layer.

[0061] Water-based inks may contain auxiliary agents such as dispersants, plasticizers, waxes, lubricants, and antifoaming agents. The water-based ink layer may contain these components. 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.

[0062] In order to improve the solubility or dispersibility of the resin in the solvent, a basic compound such as ammonia, trimethylamine, sodium hydroxide, or potassium hydroxide may be added to the aqueous ink. The aqueous ink layer may contain these components.

[0063] As the water-based ink, water-based flexographic ink used in water-based flexographic printing, water-based inkjet ink used in inkjet printing, etc. can be used. ｉ -N ｉｉ ) value tends to be large, and the adhesive strength between the layers tends to be high before and after retort treatment. Therefore, it is preferable that the aqueous ink layer is a layer formed with an aqueous flexographic ink. ｉ -N ｉｉ The reason why the value of ( ) tends to be large is not clear, but it is thought that this is because the water-based inks used in flexographic printing tend to contain high concentrations of pigments to improve color development, which results in voids being more likely to form between the pigments in the water-based ink layer.

[0064] The thickness of the aqueous ink layer is, for example, 0.2 to 5.0 mm as an average film thickness when measured at 10 points. The thickness of the aqueous ink layer may be 3 μm or less, or 1 μm or less. The smaller the thickness of the aqueous ink layer, the more the above (N ｉ -N ｉｉ ) tends to be large, and the adhesive strength between layers tends to be higher before and after retort treatment.

[0065] 1 and 2 show the aqueous ink layer as a single layer, the aqueous ink layer may have a multi-layer structure of two or more layers. For example, the aqueous ink layer may be formed by forming a first aqueous ink layer containing a pigment with a relatively small particle size on the surface of a first substrate, and then forming a second aqueous ink layer containing a pigment with a relatively large particle size (e.g., a white pigment) on the surface of the first aqueous ink layer, resulting in an aqueous ink layer with a two-layer or more structure. When the packaging material includes a second aqueous ink layer containing a white pigment, the color development of the first aqueous ink layer tends to be further improved.

[0066] (Adhesive Layer) The adhesive layer is formed of a urethane-based adhesive containing polyisocyanate and polyol. More specifically, the adhesive contains a base agent containing polyol and a curing agent containing polyisocyanate, and the adhesive hardens as the polyol and polyisocyanate react with each other to form the adhesive layer. Therefore, the adhesive layer contains polyurethane, which is a reaction product of polyol and polyisocyanate. The type of polyisocyanate that constitutes the polyurethane of the adhesive layer can be analyzed at the monomer level by pyrolysis GC / MS analysis.

[0067] [Polyol] Examples of polyols include polyether polyols such as polyoxypropylene polyol and polyoxytetramethylene glycol, hydrocarbon polyols such as polycarbonate polyol, polybutadiene polyol and polyacrylate polyol, and polyester polyols such as polyadipate polyol and polycaprolactone diol. Among these, polyester polyols are preferably used from the viewpoints of water resistance and heat resistance.

[0068] A polyester polyol is a compound having two or more polyol hydroxyl groups (hydroxyl groups) and a polyester structure as a 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. The polyester polyol may be a single polyester polyol or a combination of two or more polyester polyols.

[0069] The polyester polyol may be a commercially available product, such as Takelac A525 (trade name, "Takelac" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc., or DIC Dry LX-747 manufactured by DIC Corporation.

[0070] [Polyisocyanate] The polyisocyanate is a compound having two or more isocyanate groups. The polyisocyanate includes the polyisocyanate (A). The polyisocyanate may include either one of the polyisocyanate (a1) and the polyisocyanate (a2), or may include both of them.

[0071] The polyisocyanate (a1) is a chain isocyanate having a symmetrical structure. The polyisocyanate (a1) may be linear or branched. The polyisocyanate (a1) may be, for example, an aliphatic isocyanate. The aliphatic isocyanate may have, for example, 4 to 6 carbon atoms. Examples of the aliphatic isocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, and pentamethylene diisocyanate. One type of polyisocyanate (a1) may be used alone, or two or more types may be used in combination.

[0072] The polyisocyanate (a2) is an isocyanate polymer derived from a chain isocyanate having a symmetric structure. The polyisocyanate (a2) may be a polymer (multimer) obtained by reacting (polymerizing) chain isocyanates with each other, or may be a polymer obtained by further reacting (polymerizing) such polymers with each other. The polyisocyanate (a2) may also be a copolymer obtained by reacting (polymerizing) a chain isocyanate with a monomer capable of reacting with the isocyanate (for example, an active hydrogen-containing compound such as a polyol).

[0073] Examples of the polyisocyanate (a2) include an isocyanurate of the polyisocyanate (a1), a biuret of the polyisocyanate (a1), a polyhydric alcohol adduct of the polyisocyanate (a1) (e.g., a trimethylolpropane adduct), etc. One type of polyisocyanate (a2) may be used alone, or two or more types may be used in combination.

[0074] The polyisocyanate (A) is the same as that described above (N ｉ -N ｉｉ From the viewpoint of increasing the value of σ (σ) and increasing the interlayer adhesive strength before and after retort treatment, the polyisocyanate (A) preferably contains hexamethylene diisocyanate or an isocyanate polymer derived from the hexamethylene diisocyanate, more preferably contains an isocyanate polymer derived from hexamethylene diisocyanate, and even more preferably contains an isocyanurate of hexamethylene diisocyanate or a biuret of hexamethylene diisocyanate. From the viewpoint of water resistance, the polyisocyanate (A) particularly preferably contains an isocyanurate of hexamethylene diisocyanate.

[0075] The content of polyisocyanate (a1) is the same as that of the above (N ｉ -N ｉｉ) value is likely to be large, and the adhesive strength between layers before and after retort treatment is likely to be higher, the polyisocyanate (a1) content may be 3% by mass or more, 15% by mass or more, or 25% by mass or more, based on the total solid content of the adhesive, from the viewpoint of cost, the polyisocyanate (a1) content may be 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the polyisocyanate (a1) content may be 3 to 35% by mass or 3 to 15% by mass, based on the total solid content of the adhesive. In this specification, the total solid content of the adhesive means, when the adhesive contains a solvent, the amount obtained by excluding the amount of the solvent from the total amount of the adhesive, and when the adhesive does not contain a solvent, it means the total amount of the adhesive.

[0076] The content of polyisocyanate (a2) is the same as that of the above (N ｉ -N ｉｉ ) value is likely to be large and the adhesive strength between layers before and after retort treatment is likely to be higher, the content of polyisocyanate (a2) may be 3% by mass or more, 15% by mass or more, or 25% by mass or more, based on the total solid content of the adhesive. From the viewpoint of cost, the content of polyisocyanate (a2) may be 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (a2) may be 3 to 35% by mass or 3 to 15% by mass, based on the total solid content of the adhesive.

[0077] The content of polyisocyanate (A) is the same as that of the above (N ｉ -N ｉｉFrom the viewpoint that the value of (I) is likely to be large and the adhesive strength between layers before and after retort treatment is likely to be higher, the content of polyisocyanate (A) may be 3% by mass or more, 15% by mass or more, 25% by mass or more, or 50% by mass or more, based on the total solid content of the adhesive. From the viewpoint of cost, the content of polyisocyanate (A) may be 70% by mass or less, 50% by mass or less, 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (A) may be 3 to 70% by mass, 3 to 50% by mass, 3 to 35% by mass, or 3 to 15% by mass, or may be 15 to 70% by mass, 25 to 70% by mass, or 50 to 70% by mass, based on the total solid content of the adhesive.

[0078] The polyisocyanate may further contain a polyisocyanate other than the polyisocyanate (A) (hereinafter referred to as "polyisocyanate (B)").

[0079] Examples of the polyisocyanate (B) include aromatic polyisocyanates such as phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate (meta-xylylene diisocyanate and para-xylylene diisocyanate), alicyclic polyisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate, and isocyanate polymers derived from these polyisocyanates. Examples of the isocyanate polymers include isocyanurates of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates, biurets of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates, and polyhydric alcohol adducts of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates (e.g., trimethylolpropane adducts).

[0080] As the polyisocyanate (B), commercially available products may be used, 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.

[0081] The polyisocyanate (B) is the same as that described above (N ｉ -N ｉｉ ) value tends to be large, and the adhesive strength between layers before and after retort treatment tends to be higher, so it is preferable that the composition contains isophorone diisocyanate.

[0082] The content of the polyisocyanate (B) may be 8% by mass or more, or 14% by mass or more, based on the total solid content of the adhesive, from the viewpoint of the crosslinking density with the polyol and the film cohesive strength. ｉ -N ｉｉ From the viewpoint that the value of (a) is likely to be large and the adhesive strength between layers before and after retort treatment is likely to be higher, the content of polyisocyanate (B) may be 14 mass% or less based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (B) may be 8 to 14 mass% based on the total solid content of the adhesive.

[0083] The NCO value (unit: mol / g) of the polyisocyanate is set to 1.0×10 －３ or more, and may be 2.0 × 10 －３ or more or 5.0 x 10 －３ The NCO value may be measured in accordance with JIS K 6806 (potentiometric titration method).

[0084] The ratio (NCO / OH) of the number of moles of all isocyanate groups (NCO groups) in the isocyanate group-containing compound (such as a polyisocyanate) to the number of moles of all active hydrogen groups in the active hydrogen group-containing compound (such as a polyol) contained in the adhesive may be 2.0 or more, 11.5 or less, or 8.1 or less, or may be 2.0 to 11.5, or 2.0 to 8.1, from the viewpoint of the crosslink density of the adhesive layer.

[0085] In addition to the active hydrogen-containing compound and polyisocyanate, the adhesive may further contain additives such as a solvent, a dispersant, an antifoaming agent, a leveling agent, a stabilizer, a filler, a lubricant, a slip agent, and a wax. These components may be contained in the adhesive layer.

[0086] The adhesive may be a dry laminating adhesive or a non-solvent laminating adhesive.

[0087] The adhesive layer may contain a portion of the solvent (diluent, etc.) contained in the adhesive, but the content of the solvent is, for example, 1 mass % or less based on the total mass of the adhesive layer. Examples of the solvent include ethyl acetate and methyl ethyl ketone.

[0088] The thickness of the adhesive layer is, for example, 0.5 to 5.0 μm. The thickness of the adhesive layer means the shortest distance from the surface on the water-based ink layer side to the surface on the opposite side from the water-based ink layer, and does not include the thickness of the area in the water-based ink layer where the adhesive has soaked in.

[0089] (Second Base Material) The second base material 4 includes, for example, a sealant layer. The sealant layer is composed of, for example, a resin that can be melted and fused to each other by heat. The resin constituting the sealant layer may be, for example, a polyolefin resin 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, or polypropylene, or an acid-modified polyolefin resin obtained by modifying these with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride, or fumaric acid. The resin constituting the sealant layer may be one type or two or more types.

[0090] The thickness of the sealant layer may be, for example, 5 to 300 μm, or may be 10 to 100 μm.

[0091] The second substrate may consist of only the sealant layer, or may include layers other than the sealant layer. For example, the second substrate may include a water vapor barrier layer in addition to the sealant layer. The details of the water vapor barrier layer are the same as those of the water vapor barrier layer that may be included in the first substrate.

[0092] The total thickness of the second substrate may be, for example, 10 μm to 200 μm.

[0093] The thickness (total thickness) of the packaging material may be, for example, 20 to 300 μm. In particular, it is preferable that the thickness of the first substrate is 8 to 50 μm (e.g., 12 μm), the thickness of the aqueous ink layer is 0.2 to 5.0 μm (e.g., 3 μm), the thickness of the adhesive layer is 0.5 to 5.0 μm (e.g., 3 μm), and the thickness of the second substrate is 10 to 100 μm (e.g., 60 μm). When the packaging material is used as a packaging bag for packaging a liquid product, the thickness of the second substrate may be 100 to 200 μm (e.g., 120 μm).

[0094] <Method for manufacturing packaging material> Another embodiment of the present disclosure is a method for manufacturing a packaging material, including: step (A) of printing an aqueous ink on a surface of a first substrate to form an aqueous ink layer; step (B) of applying an adhesive to the surface of the aqueous ink layer opposite the first substrate to form an adhesive layer; and step (C) of laminating a second substrate on the surface of the adhesive layer opposite the aqueous ink layer side.

[0095] The aqueous ink may be the same as that used to form the aqueous ink layer (containing a pigment, a binder resin, and a solvent (dispersion medium)). The content of the solvent in the aqueous ink is, for example, 40 to 80% by mass based on the total mass of the aqueous ink.

[0096] 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), the aqueous ink layer may be formed by solid printing, or the aqueous ink layer may be formed by pattern printing of letters, figures, symbols, pictures, or other desired patterns, or a first aqueous ink layer may be formed by solid printing, and then a desired pattern may be printed on the first aqueous ink layer to form a second aqueous ink layer. As described above, it is preferable to use an aqueous flexographic ink as the aqueous ink, and it is preferable to print the aqueous ink by flexographic printing using the aqueous flexographic ink.

[0097] The adhesive may be the adhesive that forms the adhesive layer described above (an adhesive containing an active hydrogen-containing compound and a polyisocyanate). These components may be mixed immediately before coating. The adhesive may be applied by a conventionally known method such as a commonly used casting method, a dipping method, a roll coating method, a gravure coating method, a screen printing method, a reverse coating method, a spray coating method, a kit coating method, a die coating method, a metaling bar coating method, a chamber doctor combined coating method, or a curtain coating method.

[0098] When the adhesive 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, for example, 25 to 120°C.

[0099] The lamination of the second substrate (formation of the sealant layer) may be carried out by applying a coating liquid containing the above-mentioned resin that can be melted and fused to each other by heat using a conventionally known method such as dipping, roll coating, screen printing, spraying, etc. Alternatively, the sealant layer can be formed by attaching a film or sheet made of the above-mentioned resin.

[0100] In the manufacturing method of this embodiment, the amount of polyisocyanate that penetrates into the aqueous ink layer and the first substrate can be adjusted by, for example, adjusting the type and amount of polyisocyanate used in the adhesive, the type and thickness of the aqueous ink layer, etc., and thereby the packaging material of the above embodiment (i.e., a packaging material that satisfies formula (a)) can be obtained.

[0101] <Packaging Bag> Another embodiment of the present disclosure is a packaging bag made from the packaging material of the above embodiment. For example, as shown in FIG. 3 , the packaging bag is formed by heat-sealing three sides L1, L2, and L3 of two overlapping rectangular packaging materials. After contents are placed through the unheat-sealed opening 30a, the opening 30a can also be heat-sealed to seal the packaging bag 30. Note that the packaging bag configuration is not limited to this. Other examples of packaging bags include pillow packaging, three-sided seal packaging, and gusset packaging. Examples of contents include toiletries, liquid detergents, liquid seasonings, liquids such as soups, solids such as simmered dishes, and solid-liquid mixtures such as curry and oden. That is, the packaging bag may be a packaging bag for packaging liquids, solids, or solid-liquid mixtures.

[0102] The present disclosure will be described below based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0103] Example 1-1 (Manufacturing of packaging material) [Step (A)] A 15 μm thick biaxially oriented nylon film (manufactured by Unitika Ltd., product name: Emblem ONM (type: RT), "Emblem" is a registered trademark, and "ONY" in the table) was prepared as a first substrate, and a white water-based flexographic ink (XS-911 manufactured by DIC Corporation, "white ink" in the table) was printed on the surface of the first substrate by flexographic printing to form a 0.3 μm thick water-based ink layer. This gave a laminate 1 consisting of the first substrate and the water-based ink layer.

[0104] [Step (B) and Step (C)] Takelac A626 (polyester polyol, solid content: 60% by mass, OH value: 2.2 × 10) manufactured by Mitsui Chemicals, Inc. －４ mol / g, acid value: 3.0×10 －５ mol / g) and Takenate A52 (a polyisocyanate containing xylylene diisocyanate (XDI) and isophorone diisocyanate (IPDI), solid content: 75% by mass, NCO value: 2.5 × 10) manufactured by Mitsui Chemicals, Inc. －３mol / g) were blended in a mass ratio (solid content ratio) of 4.80:0.75 to prepare a mixed solution. Thereafter, a hexamethylene diisocyanate (HDI) biuret compound (manufactured by Asahi Kasei Corporation, trade name: 24A-100, NCO value: 5.9 × 10) was added as polyisocyanate (A) to the mixed solution obtained above. －３ The amount of polyisocyanate (A) added was such that the content of HDI biuret in the adhesive was 3.5 mass% based on the total solid content of the adhesive.

[0105] Next, using a dry laminator, an adhesive layer and a second substrate were laminated onto the aqueous ink layer of the laminate obtained in step (A). Specifically, first, in the coating section of the dry laminator, the adhesive (solid content concentration: 30% by mass) obtained above was applied to the surface of the aqueous ink layer and dried at 80°C for 1 minute to form an adhesive layer with a thickness of 3 μm. Next, a 60 μm-thick non-axially oriented polypropylene film (manufactured by Toray Industries, Inc., product name: Pylen ZK207) was prepared as a second substrate (sealant layer), and the second substrate was laminated onto the adhesive layer formed above in the laminating section of the dry laminator. After lamination, the packaging material of Example 1-1 was obtained by aging at 50°C for 72 hours.

[0106] Examples 1-2 to 1-4 Packaging materials of Examples 1-2 to 1-4 were produced in the same manner as in Example 1-1, except that the amount of polyisocyanate (A) added was adjusted so that the content of the HDI biuret form in the adhesive (based on the total solids content of the adhesive) would be the value shown in Table 1.

[0107] Examples 1-5 to 1-8 As the polyisocyanate (A), HDI nurate (manufactured by Asahi Kasei Corporation, trade name: TPA-100, NCO value: 5.9 × 10) was used instead of HDI biuret. －３ The packaging materials of Examples 1-5 to 1-8 were each produced in the same manner as in Example 1-1, except that a polyisocyanate (A) was used (mol / g) and the amount of polyisocyanate (A) added was adjusted so that the content of HDI nurate in the adhesive (based on the total solid content of the adhesive) would be the value shown in Table 1.

[0108] Examples 2-1 to 2-8 Laminate 2 was obtained in the same manner as in Example 1-1, except that a 12 μm thick biaxially oriented polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name: Toyobo Ester Film (Type: 5102), "Toyobo Ester" is a registered trademark, and "PET" in the table) was used as the first substrate instead of the biaxially oriented nylon film, and that a blue water-based flexographic ink (AQUALIONA manufactured by Toyo Ink Co., Ltd., "AQUALIONA" is a registered trademark (the same applies hereinafter), and "Blue Ink" in the table) was used instead of the white water-based flexographic ink. Next, packaging materials of Examples 2-1 to 2-8 were produced in the same manner as in Examples 1-1 to 1-8, except that laminate 2 was used instead of laminate 1.

[0109] Examples 3-1 to 3-3 Laminate 3 was obtained in the same manner as in Example 1-1, except that a 12 μm-thick barrier film (manufactured by Toppan Printing Co., Ltd., product name: GL-ARH, designated "GL" in the table) comprising a biaxially oriented polyethylene terephthalate film and a water vapor barrier layer (an Al-deposited layer and a water vapor barrier coating layer) was used as the first substrate instead of the biaxially oriented nylon film, and that a crimson water-based flexographic ink (Aquariona manufactured by Toyo Ink Co., Ltd., designated "Crimson ink" in the table) was used as the water-based ink instead of the white water-based flexographic ink. Next, packaging materials of Examples 3-1 to 3-3 were produced in the same manner as in Examples 1-2 to 1-4, respectively, except that laminate 3 was used instead of laminate 1.

[0110] Example 4 Laminate 4 was obtained in the same manner as in Example 1-1, except that a 32 μm thick unstretched polyethylene film (CNG, product name: GAP-222.20HB, "PE" in the table) was used as the first substrate instead of the biaxially oriented nylon film, and that a crimson water-based flexographic ink (Aquariona manufactured by Toyo Ink Co., Ltd., "Crimson ink" in the table) was used as the water-based ink instead of the white water-based flexographic ink. Next, a packaging material of Example 4 was produced in the same manner as in Example 1-4, except that laminate 4 was used instead of laminate 1.

[0111] Example 5 Laminate 5 was obtained in the same manner as in Example 1-1, except that a 20 μm thick biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, product name: U-1, indicated as "PP" in the table) was used as the first substrate instead of the biaxially oriented nylon film, and that a red water-based flexographic ink (Aquariona manufactured by Toyo Ink Co., Ltd., indicated as "Red Ink" in the table) was used as the water-based ink instead of the white water-based flexographic ink. Next, a packaging material of Example 5 was produced in the same manner as in Example 1-4, except that laminate 5 was used instead of laminate 1.

[0112] Comparative Examples 1 to 5 Packaging materials of Comparative Examples 1 to 5 were produced in the same manner as in Examples 1-1, 2-1, 3-1, 4 and 5, except that polyisocyanate (A) (HDI biuret form) was not used.

[0113] Example 6-1 Preparation of Solvent-Free Adhesive TSN4864A (polyester polyol, OH value: 1.8×10) manufactured by Toyo-Morton Co., Ltd. was used as the polyol base. －３ mol / g, acid value: 3.8×10 －３ mol / g), and a polyisocyanate (A), an HDI biuret compound (BASONATE HB-100 manufactured by BASF, NCO value: 5.3×10 －３ mol / g) and HDI nurate (Takenate D177N manufactured by Mitsui Chemicals, Inc., NCO value: 4.8 × 10 －３ The mixing ratio of the polyol base, HDI biuret, and HDI nurate was 100:20:80 by mass (solid content ratio). Thus, solventless adhesive 1 was prepared.

[0114] (Production of packaging material) After obtaining the laminate 1 by the method of Example 1-1, the solventless adhesive 1 was applied to the water-based ink layer using a nonsol laminator (SuperSimplex SL, manufactured by Nordmechanika) at a coating roll temperature of 70°C, a coating speed of 200 m / min, and a coating amount of 2.0 g / m ２The adhesive layer was coated with a 60 μm thick non-axially oriented polypropylene film (manufactured by Toray Industries, Inc., trade name: Pylen ZK207) as a second substrate (sealant layer), and the second substrate was laminated onto the adhesive layer formed above in the laminating section of a Nonsol laminator. After lamination, the product was aged at 40° C. for 72 hours to obtain the packaging material of Example 6-1.

[0115] Example 6-2 In addition to HDI biuret and HDI nurate, IPDI (VESTANAT T 1890 / 100 manufactured by Evonik, NCO value: 4.1 × 10) was used as an isocyanate to be mixed with the polyol base. －３ A solventless adhesive 2 was prepared in the same manner as in Example 6-1, except that a polyol base, HDI biuret, HDI nurate, and IPDI (mol / g) was used, and the mixing ratio by mass (solid content ratio) of the polyol base, HDI biuret, HDI nurate, and IPDI was 100:15:35:50. Next, a packaging material of Example 6-2 was produced in the same manner as in Example 6-1, except that the solventless adhesive 2 was used instead of the solventless adhesive 1.

[0116] Example 6-3 A solvent-free adhesive 3 was prepared in the same manner as in Example 6-2, except that the mixing ratio of the polyol base, HDI biuret, HDI nurate, and IPDI was changed to 100:35:15:50 by mass (solid content ratio). Next, a packaging material of Example 6-3 was produced in the same manner as in Example 6-2, except that the solvent-free adhesive 3 was used instead of the solvent-free adhesive 2.

[0117] Examples 7-1 to 7-3 The laminate 2 was obtained by the method of Examples 2-1 to 2-8. Next, laminates of Examples 7-1 to 7-3 were produced in the same manner as in Examples 6-1 to 6-3, except that laminate 2 was used instead of laminate 1.

[0118] Examples 8-1 to 8-3 The laminate 3 was obtained by the methods of Examples 3-1 to 3-3. Next, laminates of Examples 8-1 to 8-3 were produced in the same manner as in Examples 6-1 to 6-3, except that laminate 3 was used instead of laminate 1.

[0119] Examples 9-1 to 9-3 The laminate 4 was obtained by the method of Example 4. Next, laminates of Examples 9-1 to 9-3 were produced in the same manner as in Examples 6-1 to 6-3, except that laminate 4 was used instead of laminate 1.

[0120] Examples 10-1 to 10-3 The laminate 5 was obtained by the method of Example 5. Next, laminates of Examples 10-1 to 10-3 were produced in the same manner as in Examples 6-1 to 6-3, except that laminate 5 was used instead of laminate 1.

[0121] <Comparative Examples 6 to 10> Packaging materials of Comparative Examples 6 to 10 were produced in the same manner as in Examples 6-1, 7-1, 8-1, 9-1 and 10-1, except that polyisocyanate (A) (HDI biuret and HDI nurate) was not used.

[0122] <N ｉ -N ｉｉ Measurement of .gtoreq.(.gtoreq..times ...

[0123] The exposed cross section of the packaging material was subjected to SEM-EDX measurement of the following regions (i) to (iv) to determine the elemental semi-quantitative value of nitrogen (N) (unit: mass%). The SEM-EDX measurement was performed at an acceleration voltage of 3 kV and an SEM observation magnification of 50,000.

[0124] Region (i): A rectangular region in which the distance in the thickness direction of the first substrate from the interface between the first substrate and the aqueous ink layer is in the range of 0.06 to 0.26 μm, and the length in the surface direction of the first substrate (direction perpendicular to the thickness direction) is 2.5 μm. Region (ii): A rectangular region in which the distance in the thickness direction of the first substrate from the interface between the first substrate and the aqueous ink layer is equivalent to 30% of the thickness of the first substrate, the length in the thickness direction is 1 μm, and the length in the surface direction of the first substrate (direction perpendicular to the thickness direction) is 2.5 μm. Region (iii): A rectangular region in which the distance in the thickness direction of the first substrate from the interface between the first substrate and the aqueous ink layer is equivalent to 60% of the thickness of the first substrate, the length in the thickness direction is 1 μm, and the length in the surface direction of the first substrate (direction perpendicular to the thickness direction) is 2.5 μm. Region (iv): A rectangular region including a position where the distance in the thickness direction of the first substrate from the interface between the first substrate and the aqueous ink layer corresponds to 80% of the thickness of the first substrate, the length in the thickness direction being 1 μm, and the length in the surface direction of the first substrate (direction perpendicular to the thickness direction) being 2.5 μm.

[0125] The range of the distance from the interface between the first substrate and the water-based ink layer in the thickness direction of the first substrate in the regions (ii) to (iv) was as follows: In Examples 1-1 to 1-8, Examples 6-1 to 6-3, Comparative Example 1 and Comparative Example 6 (first substrate = 15 um thick ONY), the thickness was 4.0 to 5.0 μm (region (ii)), 8.5 to 9.5 μm (region (iii)), and 11.5 to 12.5 μm (region (iv)), respectively. In Examples 2-1 to 2-8, Examples 3-1 to 3-3, Examples 7-1 to 7-3, Examples 8-1 to 8-3, Comparative Examples 2 to 3, and Comparative Examples 7 to 8 (first substrate = 12 um thick PET or GL-ARH), the thickness was 3.0 to 4.0 μm (region (ii)), 6.5 to 7.5 μm (region (iii)), and 9.5 to 10.5 μm (region (iv)), respectively. In Example 4, Example 9, Comparative Example 4 and Comparative Example 9 (first substrate = PE having a thickness of 32 μm), the thicknesses were 9.0 to 10.0 μm (region (ii)), 18.5 to 19.5 μm (region (iii)) and 25.0 to 26.0 μm (region (iv)), respectively. In Example 5, Example 10, Comparative Example 5 and Comparative Example 10 (first substrate = PP having a thickness of 20 μm), the thicknesses were 5.5 to 6.5 μm (region (ii)), 11.5 to 12.5 μm (region (iii)) and 15.5 to 16.5 μm (region (iv)), respectively.

[0126] The semi-quantitative value of nitrogen in the above region (i) is N ｉ The average value of the semi-quantitative values ​​of nitrogen in the above regions (ii) to (iv) is N ｉｉ and the difference between these (N ｉ -N ｉｉ The results are shown in Table 1.

[0127] <Evaluation> (Measurement of seal strength) Two sheets each having a width of 90 mm and a length of 140 mm were cut out from the packaging material of each Example and Comparative Example, and the two sheets were placed so that the surfaces of the second substrate (sealant layer) of each sheet faced each other and the four sides of each sheet overlapped, and bonded by heat sealing to obtain a laminated sample of each Example and Comparative Example. The heat sealing was performed by bonding the two overlapping sheets at 150°C and 3 kg / cm ２The laminated sample was then subjected to a T-peel test at 20°C and 30% RH at a peel speed of 300 mm / min over a 15 mm width in accordance with JIS K 6854 to measure the seal strength of the laminated sample. The results are shown in Table 1. In this evaluation, a seal strength of 45 N / 15 mm or more was deemed to be sufficiently high.

[0128] (Adhesion Strength After Retort Treatment) The adhesive strength between the first substrate and the second substrate of each packaging material in each Example and Comparative Example after retort treatment was measured using the following procedures (1) to (5). The results are shown in Table 1. In this evaluation, adhesive strength of 1.5 N / 15 mm or more was determined to be sufficiently high. (1): Two sheets measuring 140 mm wide and 100 mm long were cut out from the packaging material. The second substrate-side surfaces of the two sheets were placed facing each other so that their four edges overlapped, and three of the four edges were heat-sealed to prepare a packaging bag with one opening. (2): 50 g of water was added to the packaging bag, and the opening edge of the packaging bag was heat-sealed to prepare a test pouch. (3): The test pouch prepared in (2) was subjected to retort treatment at 121°C for 30 minutes. (4): After the retort treatment in (3), a test piece measuring 15 mm in width and 200 mm in length was cut out from one of the two sheets constituting the test pouch. (5): A T-peel test was performed on the test piece at a width of 15 mm at a peel rate of 300 mm / min in accordance with JIS K 6854 under conditions of 20°C and 30% RH to measure the adhesive strength between the first substrate and the second substrate. Note that the heat sealing in (1) and (2) was performed using a 15 mm wide seal bar at 150°C and 3 kg / cm on each side. ２ The test was carried out by applying heat and pressure at 1000 kJ / min for 0.5 seconds.

[0129] (Production of packaging bags and evaluation of bag drop) Packaging bags were produced using the packaging materials of each Example and Comparative Example, and the packaging bags were evaluated for drop. Specifically, two sheets 130 mm wide and 250 mm long were first cut out from the packaging material, and the surfaces of the two sheets facing the second substrate (sealant layer) were placed together so that the four sides overlapped each other, and three of the four sides were heat-sealed to produce a bag-shaped packaging container (packaging bag) with one side open as shown in Figure 3. The heat sealing was performed using a 15 mm wide seal bar, with the three sides being heat-sealed at 150°C and 3 kg / cm. ２ The packaging bag was heated and pressurized at 500°C for 0.5 seconds. Next, 100 ml of water was poured into the upper opening of the packaging bag, and the opening (top) was heat-sealed under the same conditions as when the packaging bag was made. The sealed packaging bag was left to stand in a refrigerator at 5°C for 12 hours, and then, immediately after being removed from the refrigerator, it was dropped freely from a height of 1 m. The appearance of the packaging bag after the drop was visually confirmed to check for the presence or absence of delamination. Bags that did not undergo delamination were rated "○ (good)," and bags that did undergo delamination were rated "× (bad)." The results are shown in Table 1.

[0130]

[0131]

[0132] The "content" in Tables 1 and 2 refers to the content (total amount) of polyisocyanate (A) in the adhesive, based on the total amount of solids in the adhesive.

[0133] 1...first substrate, 2...water-based ink layer, 2a...pigment, 3...adhesive layer, 4...second substrate, 10, 20...packaging material, 30...packaging bag.

Claims

1. A packaging material comprising a first substrate, a water-based ink layer, an adhesive layer, and a second substrate in this order, wherein the adhesive layer is formed of a urethane-based adhesive containing a polyisocyanate and a polyol, the polyisocyanate contains a chain isocyanate having a symmetrical structure or an isocyanate polymer derived from the chain isocyanate, and a portion of the polyisocyanate penetrates to the vicinity of the interface between the water-based ink layer and the first substrate so as to satisfy the following formula (a): Formula (a): (N ｉ -N ｉｉ )≧0.5 [In formula (a), N ｉ represents the amount of nitrogen (unit: mass%) in the first substrate measured in an area (i) at a distance of 0.06 to 0.26 μm from the interface, ｉｉ represents the average value of the amount of nitrogen (unit: mass%) in the first substrate measured in regions (ii), (iii), and (iv) each having a thickness of 1 μm, the regions including positions whose distances from the interface correspond to 30%, 60%, and 80% of the thickness of the first substrate.] 2. The packaging material according to claim 1, wherein the polyisocyanate contains a biuret or isocyanurate of the chain isocyanate as the isocyanate polymer.

3. The packaging material according to claim 1, wherein the linear isocyanate is hexamethylene diisocyanate.

4. The packaging material according to claim 1, wherein the water-based ink layer is formed from a water-based flexographic ink.

5. The packaging material according to claim 1, wherein the first substrate comprises at least one material selected from the group consisting of oriented polyethylene terephthalate film, oriented polypropylene film, oriented nylon film, and oriented polyethylene film.

6. The packaging material of claim 1, wherein the first substrate comprises a water vapor barrier layer.

7. The packaging material of claim 1, wherein the polyol comprises a polyester polyol.

8. The packaging material according to claim 1, wherein the urethane adhesive is a dry lamination adhesive.

9. The above (N ｉ -N ｉｉ 2. The packaging material according to claim 1, wherein the coefficient of elasticity is 1.2 or more.

10. The packaging material according to claim 1, in which the adhesive strength between the first substrate and the second substrate measured by the following steps (1) to (5) is 1.5 N / 15 mm or more. (1): Two sheets measuring 140 mm wide and 100 mm long are cut out from the packaging material, and the second substrate sides of the two sheets are placed face to face so that the four sides overlap each other, and three of the four sides are heat-sealed to produce a packaging bag with one side open. (2): 50 g of water is added to the packaging bag, and the opening side of the packaging bag is heat-sealed to produce a test pouch. (3): The test pouch produced in (2) is subjected to a retort treatment at 121°C for 30 minutes. (4): After the retort treatment in (3), a test piece measuring 15 mm wide and 200 mm long is cut out from one of the two sheets constituting the test pouch. (5): A T-peel test is performed on the test piece at a peel speed of 300 mm / min and a width of 15 mm in accordance with JIS K 6854 under conditions of 20° C. and 30% RH to measure the adhesive strength between the first substrate and the second substrate.

11. A packaging bag made from the packaging material according to any one of claims 1 to 10.

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