Packaging materials, packaging bags and packaging bodies

Abstract

To provide a packaging material that is less prone to delamination at the interface between the adhesive layer and the water-based ink layer immediately after retort processing. [Solution] A packaging material 10 comprising a base layer 1, an aqueous ink layer 2, an adhesive layer 3, and a sealant layer 4 in this order, wherein the elastic modulus distribution of the adhesive layer 3 after retort treatment has a kurtosis of 16.0 or less and a strain of 2.9 or less in absolute value.

Description

[Technical Field]

[0001] This disclosure relates to packaging materials, packaging bags, and packaging bodies. [Background technology]

[0002] Conventionally, packaging materials used for packaging bags (e.g., flexible packaging bags) that undergo heat treatment such as boiling or retorting, or heat and pressure treatment, have been laminates having a layered structure made of materials that provide the preservation of contents, heat resistance, pressure resistance, durability against external stress (strength), and printability, while considering cost-effectiveness.

[0003] In the field of packaging materials, efforts are being made to eliminate VOCs (volatile organic compounds) as an environmental measure. Specifically, the formation of printed layers for letters, images, and patterns is being shifted from oil-based inks containing volatile organic compounds (VOCs) such as solvents (toluene, methyl ethyl ketone, etc.) to water-based inks. Using water-based inks has the advantage of improving the environment at the production site and resolving the problem of residual organic solvents in the packaging material. For example, Patent Document 1 discloses a laminated material for heat-sterilized packaging using water-based ink. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-79986 [Overview of the project] [Problems that the invention aims to solve]

[0005] When packaging materials contain a water-based ink layer, delamination (separation) is likely to occur at the interface between the adhesive layer and the water-based ink layer immediately after retort processing.

[0006] This disclosure is made in view of the above circumstances and aims to provide a packaging material that is less prone to delamination at the interface between the adhesive layer and the aqueous ink layer immediately after retort processing, as well as a packaging bag and packaging body using said packaging material. [Means for solving the problem]

[0007] Some aspects of this disclosure provide the following [1] to [8].

[0008] [1] A packaging material comprising a base layer, a water-based ink layer, an adhesive layer, and a sealant layer in this order, When retorting is performed according to the following procedures (A1) to (A3), and the elastic modulus is measured according to the following procedures (B1) to (B3), A packaging material wherein the elastic modulus distribution of the adhesive layer after the retort treatment has a kurtosis of 16.0 or less and a strain of 2.9 or less in absolute value. (A1): Two sheets measuring 140 mm in width and 100 mm in length are cut from the packaging material, and the sealant layer sides of the two sheets are placed facing each other so that their four sides overlap, and three of the four sides are heat-sealed to create a packaging bag with one side open. (A2): After adding 50g of water to the packaging bag, a test pouch is prepared by heat-sealing one side of the opening of the packaging bag. (A3): The test pouch prepared in (A2) above is subjected to retort treatment at 121°C for 80 minutes. (B1): The cross-section in the thickness direction of the packaging material 30 days after the retort processing is observed using the tapping mode of a scanning probe microscope, and the microscope is positioned so that the center of the field of view is at the center of the film thickness of the cross-section of the adhesive layer. (B2): Under a 25°C environment, force curve measurement is performed on the adhesive layer within the field of view using the contact mode of a scanning probe microscope. (B3): The elastic modulus of each measurement point is calculated by analyzing the force curve obtained in (B2) using the elastic contact model of the JKR theory. [2] The packaging material according to [1], wherein the elastic modulus distribution of the adhesive layer after the retort treatment has a kurtosis of 11.0 or less and a skewness of 2.2 or less in absolute value. [3] The packaging material according to [1] or [2], wherein the elastic modulus distribution of the adhesive layer before the retort treatment has a kurtosis of 19.0 or less and a skewness of 4.2 or less in absolute value. [4] The packaging material according to any one of [1] to [3], wherein the adhesive layer is formed of a urethane-based adhesive containing a polyisocyanate and a polyol. [5] The packaging material according to any one of [1] to [4], wherein the aqueous ink layer is formed of an aqueous flexographic ink. [6] The packaging material according to any one of [1] to [5], wherein the ratio of the thickness of the aqueous ink layer to the thickness of the adhesive layer is 0.5 to 3.5. [7] The packaging material according to any one of [1] to [6], wherein the base material layer contains 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. [8] A packaging bag formed by bagging the packaging material according to any one of [1] to [7]. [9] A package comprising the packaging bag according to [8] and the contents contained in the packaging bag. [Advantages of the Invention]

[0009] According to the present disclosure, it is possible to provide a packaging material that is difficult to cause peeling at the interface between the adhesive layer and the aqueous ink layer immediately after the retort treatment, and a packaging bag and a package using the packaging material. [Brief Description of the Drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an embodiment of the packaging material according to the present disclosure. [Figure 2]Figure 2 is a schematic cross-sectional view showing another embodiment of the packaging material according to this disclosure. [Figure 3] Figure 3 is a schematic plan view showing one embodiment of a packaging bag using the packaging material according to this disclosure. [Modes for carrying out the invention]

[0011] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Within the numerical ranges described in this specification, the upper or lower limits of the range may be replaced with the values ​​shown in the examples. Furthermore, the individually described upper and lower limits can be combined in any way. Also, "A or B" means that either A or B is included, or both are included.

[0012] The embodiments of this disclosure will be described in detail below, with reference to the drawings as appropriate. However, this disclosure is not limited to the embodiments described below. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. The dimensional ratios in the drawings are not limited to those shown.

[0013] <Packaging material> One embodiment of the present disclosure is a packaging material comprising a base layer, an aqueous ink layer, an adhesive layer, and a sealant layer in this order. The packaging material is, for example, a sheet-like laminate (packaging material 10) shown in Figure 1. The packaging material 10 in Figure 1 consists of a base layer 1, an aqueous ink layer 2, an adhesive layer 3, and a sealant layer 4, with the adhesive layer 3 bonding the aqueous ink layer 2 and the sealant layer 4. In Figure 1, 2a shows the pigment in the aqueous ink layer. The thickness (total thickness) of the packaging material is not particularly limited, but is, for example, 20 to 300 μm.

[0014] The above-mentioned packaging material is characterized in that the elastic modulus distribution of the adhesive layer after retort processing has a kurtosis of 16.0 or less and a skewness of 2.9 or less in absolute value. Here, the above-mentioned elastic modulus distribution refers to the elastic modulus distribution in a steady state after retort processing. The packaging material immediately after retort processing is in a non-steady state and the measured values ​​are not stable, so in this disclosure, the packaging material 30 days after retort processing is considered to be the packaging material in a steady state. Furthermore, the kurtosis of the elastic modulus distribution indicates the degree of peaking of the distribution, and the lower the kurtosis, the less the data is concentrated around the mean value and the flatter the distribution is. Furthermore, the skewness of the elastic modulus distribution indicates the shape and asymmetry of the distribution, and the closer the absolute value of the skewness is to 0, the more symmetrical the shape of the distribution is around the mean value. Hereinafter, the elastic modulus of the adhesive layer after retort treatment, as well as the kurtosis and strain of the elastic modulus distribution, will be referred to as "elastic modulus (Ea)", "kurtosis (Ka)", and "strain (Sa)", respectively. The elastic modulus of the adhesive layer before retort treatment, as well as the kurtosis and strain of the elastic modulus distribution, will be referred to as "elastic modulus (Eb)", "kurtosis (Kb)", and "strain (Sb)", respectively.

[0015] The above retort processing is carried out according to the following procedures (A1) to (A3). (A1): Cut out two sheets from the packaging material, each measuring 140 mm in width and 100 mm in length. Place the two sheets with their sealant-coated sides facing each other so that their four sides overlap, and heat-seal three of the four sides to create a packaging bag with one side open. (A2): After adding 50g of water to the packaging bag, a test pouch is prepared by heat-sealing one side of the opening of the packaging bag. (A3): The test pouch prepared in (A2) is subjected to retort treatment at 121°C for 80 minutes.

[0016] The packaging material described in (A1) above is the packaging material before retort processing. The heat seals in (A1) and (A2) are, for example, 15 mm wide sealing bars, with each side heated to 150°C and 3 kg / cm². 2 This can be done by heating and pressurizing for 0.5 seconds.

[0017] The measurement of the modulus of elasticity in this specification is performed according to the following procedure (B1) to (B3). (B1): Observe the cross-section of the packaging material in the thickness direction using a scanning probe microscope (hereinafter also referred to as "SPM") in tapping mode (AC mode), and position the microscope so that the center of the field of view is at the center of the film thickness of the cross-section of the adhesive layer. (B2): Under a 25°C environment, force curve (load-displacement curve) measurements are performed on the adhesive layer within the field of view using the contact mode of a scanning probe microscope. (B3): The elastic modulus of each measurement point is calculated by analyzing the force curve obtained in (B2) using the elastic contact model of the JKR (Johnson-Kendall-Roberts) theory.

[0018] The packaging material in (B1) above is the packaging material before or after retort processing, and cross-sectional samples of the packaging material are prepared, for example, by the following procedures (B0-1) to (B0-3). The packaging material after retort processing is the packaging material 30 days after retort processing, and one of the two sheets constituting the pouch is cut out from the test pouch 30 days after retort processing in (A3) above. The block pieces are prepared after being left to stand for 30 days after retort processing in an indoor environment (specifically, 30 days in an atmospheric environment at 25°C and 50% relative humidity). (B0-1) After corona treatment of both sides of the packaging material, the packaging material is cut into strips of 2 x 3 mm. (B0-2) The obtained strip-shaped packaging material is embedded in a photocurable resin, and the resin is cured by light irradiation to obtain a block piece consisting of the packaging material and the cured resin that embeds the packaging material. (B0-3) The obtained block pieces are fixed in an insert for the SPM sample holder, and at room temperature (25°C), the block pieces are trimmed and the cross section in the thickness direction of the packaging material (cross section perpendicular to the layer interface) is cut to obtain a cross-sectional sample. The cross section is cut until it becomes mirror-like.

[0019] The positioning described in (B1) above is performed, for example, under the conditions of a field of view of 0.2 μm vertically × 6.4 μm horizontally and a scanning speed of 2 Hz.

[0020] In the force curve measurement described in (B2) above, for example, within the field of view described in (B1) above (0.2 μm vertically × 6.4 μm horizontally), measurements are taken at 2 points at 200 nm intervals in the film thickness direction and at 50 points at 130 nm intervals in the direction parallel to the layer interface (a total of 100 points). The measurement conditions are a maximum load of 5 nN and a test speed of 500 nm / s, and force curves with displacements of 500 nm or more are obtained for both indentation and pull-out. The force curve measurement described in (B2) above is performed on at least 3 cross-sectional samples (i.e., force curves are obtained at a total of 300 points or more).

[0021] The analysis described in (B3) above can be performed, for example, by fitting analysis using SPM analysis software, with the elastic modulus, displacement origin, and maximum adhesion force of the sample as fitting parameters. In this case, the analysis range for each point of the force curve is defined as the range in which the load change during pull-out after reaching the maximum load is defined, starting from the load and displacement when the load first reaches "(maximum load + minimum load) × 0.5" and ending from the load and displacement when the minimum load is reached.

[0022] The elastic modulus distribution of the adhesive layer after the above retort treatment refers to the distribution of the elastic modulus of the 300 or more points obtained in (B3) above. The kurtosis and skewness of the elastic modulus distribution can be calculated using statistical functions for determining these (for example, the "KURT" and "SKEW" functions provided in Microsoft's spreadsheet software "Excel").

[0023] Packaging materials possessing the above characteristics are less prone to delamination at the interface between the adhesive layer and the water-based ink layer immediately after retort processing. The reason for this is not clear, but it is presumed to be as follows. First, from the distribution of the elastic modulus of the adhesive layer after retort processing, it can be said that the adhesive layer of the above packaging material has regions with an elastic modulus higher than average and regions with an elastic modulus lower than average after retort processing, and that these regions exist in a nearly equal proportion. It is presumed that the presence of multiple regions with different elastic moduli as described above creates multiple points of fracture when an external force is applied to the adhesive layer, thus distributing the stress and making it difficult for the adhesive layer to fracture (i.e., delamination at the interface). Furthermore, as a cause of delamination immediately after retort processing, it is thought that the physical properties of the adhesive layer change during the process of absorption and release of moisture in the adhesive layer due to changes in temperature and humidity caused by retort processing, resulting in the creation of areas with locally low cohesive force. On the other hand, since the kurtosis (Ka) and strain (Sa) of the adhesive of the above packaging material are within the above range, there are few regions with extremely high or extremely low elastic modulus, and it is presumed that it is less susceptible to changes in physical properties due to the absorption and release of moisture, and therefore less likely to delaminate at the interface immediately after retort processing.

[0024] According to the above packaging material, it is possible to obtain a retort packaging bag that is less prone to problems such as deterioration of the surface of the water-based ink layer, reduction of barrier properties, and increased risk of bag rupture due to delamination at the interface between the adhesive layer and the water-based ink layer. Here, "for retort" means that it is used for packaging bags that undergo retort processing. Furthermore, retort processing is a moist heat sterilization process defined by the Food Sanitation Law, and refers to moist heat sterilization performed at a temperature of 100°C or higher. Retort processing may also be performed under pressure (e.g., 0.2 Pa or higher).

[0025] The kurtosis (Ka) may be 15.0 or less, 11.0 or less, or 10.0 or less, from the viewpoint of making delamination between the water-based ink layer and the adhesive layer immediately after retort processing less likely to occur. The kurtosis (Ka) may be -2.0 or higher. That is, the kurtosis (Ka) may be between -2.0 and 16.0. When the kurtosis (Ka) is -2.0 or higher, the peel strength within the laminated structure of the packaging material in the steady state before and after retort processing is less likely to decrease.

[0026] The absolute value of the skewness (Sa) may be 2.5 or less, 2.2 or less, or 2.0 or less, from the viewpoint of making delamination between the water-based ink layer and the adhesive layer immediately after retort processing less likely to occur.

[0027] The skewness (Sa) can be positive or negative. That is, the elastic modulus distribution after retort processing can be either right-hand strain (positive strain) or left-hand strain (negative strain).

[0028] The above-mentioned kurtosis (Ka) and strain (Sa) tend to vary depending on the coefficient of variation of the kurtosis (Kb), strain (Sb), and elastic modulus (Eb) before retorting. Specifically, when (Kb) is large, the absolute values ​​of (Ka) and (Sa) tend to be large. Also, when the absolute value of (Sb) is large, the absolute values ​​of (Ka) and (Sa) tend to be large. Furthermore, when the coefficient of variation of (Eb) is large, the kurtosis and strain tend to change more easily due to retorting.

[0029] To keep the kurtosis (Ka) and strain (Sa) within the above-mentioned range, it is effective, for example, to suppress the kurtosis (Kb) and strain (Kb) before retort processing, and to control the composition and dimensions of the laminated structure to suppress changes in kurtosis and strain due to retort processing.

[0030] The arithmetic mean of the modulus of elasticity (Ea) may be, for example, 1 to 1000 MPa, or 10 to 800 MPa or 100 to 500 MPa.

[0031] The coefficient of variation of the elastic modulus (Ea) may be 1% or more, 3% or more, or 5% or more from the viewpoint of improving the adhesive strength after retort treatment, and may be 150% or less, 120% or less, or 25% or less from the viewpoint of suppressing changes in kurtosis and strain due to retort treatment. From the above viewpoint, the coefficient of variation of the elastic modulus (Ea) may be, for example, 1 to 150%, 3 to 120%, or 5 to 25%.

[0032] The kurtosis (Kb) may be 19.0 or less, 16.0 or less, 11.0 or less, or 8.0 or less, from the viewpoint of ensuring higher interlayer lamination strength (adhesion strength) immediately after retort processing. The kurtosis (Kb) may be -2.0 or greater. That is, the kurtosis (Kb) may be between -2.0 and 19.0. When the kurtosis (Kb) is 19.0 or less, the absolute values ​​of (Ka) and (Sa) tend to be smaller.

[0033] From the viewpoint of ensuring higher interlayer lamination strength (adhesion strength) immediately after retort processing, when the absolute value of strain (Sb) is 4.2 or less, 2.9 or less, or 2.2 or less, the absolute values ​​of (Ka) and (Sa) tend to decrease.

[0034] The skewness (Sb) can be positive or negative. That is, the elastic modulus distribution before retort processing can be either right-hand strain (positive strain) or left-hand strain (negative strain).

[0035] The arithmetic mean of the modulus of elasticity (Eb) may be, for example, 1 to 1000 MPa, or 10 to 800 MPa or 100 to 500 MPa.

[0036] The coefficient of variation of the elastic modulus (Eb) may be 1% or more, 4% or more, or 5% or more from the viewpoint of improving the cohesive force of the adhesive layer and affinity with the ink interface, and may be 199% or less, 170% or less, or 35% or less from the viewpoint of suppressing changes in kurtosis and strain due to retort treatment. From the above viewpoint, the coefficient of variation of the elastic modulus (Eb) may be, for example, 1 to 199%, 4 to 170%, or 5 to 35%.

[0037] The coefficients of variation of kurtosis (Kb), skewness (Sb), and elastic modulus (Eb) tend to vary depending on the type of adhesive forming the adhesive layer, the thickness of the adhesive layer, the thickness of the water-based ink layer, etc. Specifically, by using a urethane-based adhesive to form the adhesive layer and setting the NCO / OH (molar ratio) to a predetermined value, the coefficient of variation of the elastic modulus (Eb) tends to be within a desirable range. Furthermore, by setting the NCO value of the isocyanate constituting the urethane-based adhesive to a predetermined value, the kurtosis (Kb) and skewness (Sb) tend to be increased to a desirable range. In addition, by setting the thickness range of the adhesive layer and the water-based ink layer to a predetermined range, the absolute values ​​of kurtosis (Kb) and skewness (Sb) tend to be reduced to a desirable range.

[0038] In order to set the kurtosis (Kb) and strain (Sb) within the above-mentioned range, for example, the adhesive forming the adhesive layer should be a urethane-based adhesive, the NCO / OH (molar ratio) should be 2.0 to 11.5, and the NCO value of the isocyanate constituting the urethane-based adhesive should be 1.0 × 10⁻⁶. -3 ~3.0×10 -1 It is effective to use (mol / g) as the unit of measurement, and to set the thickness ratio of the adhesive layer to the water-based ink layer (thickness of the water-based ink layer / thickness of the adhesive layer) to a range of 0.5 to 3.5.

[0039] Next, the details of the base material layer, aqueous ink layer, adhesive layer, and sealant layer constituting the packaging material of the above embodiment will be described.

[0040] (base material layer) The substrate layer is a support for the aqueous ink layer and can also be described as the substrate on which the aqueous ink is printed. The substrate layer includes, for example, a resin film. Examples of resins that make up the resin film include polyester resins, polyamide resins, polyaramid resins, polypropylene resins, polyethylene resins, polyvinyl chloride resins, polystyrene resins, polycarbonate resins, polyacetal resins, and fluororesins. The resin film may consist of one type or two or more types of resins.

[0041] As for the resin film, it is preferable to use a resin film containing at least one resin selected from the group consisting of polyester resins, polyamide resins, polyethylene resins, and polypropylene resins, from the viewpoint of achieving higher interlayer lamination strength (adhesion strength) before and after retort processing, 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 resins.

[0042] The resin film may be an unstretched resin film, or it may be a resin film stretched uniaxially or biaxially (stretched film). From the viewpoint of printability, dimensional stability, and puncture resistance, the resin film is preferably a biaxially stretched resin film (biaxially oriented resin film). From the viewpoint of achieving higher interlayer lamination strength (adhesion strength) before and after retort processing, 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 oriented polyethylene terephthalate film, biaxially oriented polypropylene film, biaxially oriented nylon film, uniaxially oriented polyethylene film, and biaxially oriented polyethylene film.

[0043] The base layer may contain two or more resin films. That is, the base layer may consist of a multilayer laminate. When the base layer has a multilayer structure, it is preferable that the resin film constitutes the outermost layer of the base layer and is in contact with the aqueous ink layer, and it is more preferable that the resin film of the above preferred embodiment constitutes the outermost layer of the base layer and is in contact with the aqueous ink layer.

[0044] The thickness of the resin film may be such that it satisfies the strength, rigidity, etc., required for heat and pressure treatment, for example, 5 μm to 100 μm or 8 μm to 50 μm. If the resin film thickness is 100 μm or less, the flexible packaging bag will be easier to tear by hand when opened, and manufacturing costs can be reduced. If the resin film thickness is 8 μm or more, sufficient strength, rigidity, etc., can be easily obtained.

[0045] The base layer may consist solely of a resin film, or it may include other layers besides the resin film. For example, the base layer 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 to the water-based ink layer. When the base layer 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.

[0046] The water vapor barrier layer may include an inorganic thin film layer and a water vapor barrier coating layer, as shown in Figure 2. The packaging material 20 shown in Figure 2 has a base layer 1 consisting of a resin film 1a and a water vapor barrier layer 1b, and the water vapor barrier layer 1b consists of an inorganic thin film layer 1c and a water vapor barrier coating layer 1d. As shown in Figure 2, the inorganic thin film layer and the water vapor barrier coating layer may be provided on the resin film in this order.

[0047] Inorganic thin film layers are formed, for example, by depositing a metal, or an oxide, nitride, or oxide nitride of silicon (e.g., by vacuum deposition). Specifically, materials for inorganic thin film layers include metals such as aluminum, titanium, copper, indium, and tin, or their oxides (alumina, etc.), or silicon, silicon oxides, and even nitrides or oxide nitrides of metals or silicon. The inorganic thin film layer may also be a thin film layer containing multiple of these metals. In particular, inorganic thin film layers containing oxides, nitrides, or oxide nitrides of aluminum, titanium, copper, indium, or silicon tend to have excellent transparency and barrier properties, and among these, inorganic thin film layers containing oxides or oxide nitrides of silicon tend to have even higher barrier properties.

[0048] For forming inorganic thin film layers, vacuum deposition methods (resistance-heated vacuum deposition, electron beam-heated vacuum deposition, induction-heated vacuum deposition), sputtering methods (reactive sputtering, dual magnetron sputtering), and PECVD methods (with various plasma generation methods including DC (Direct Current), RF (Radio Frequency), MF (Middle Frequency), DC pulse, RF pulse, and DC+RF superposition) can be used. 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 homogeneity, while vacuum deposition may be selected from the viewpoint of cost.

[0049] The thickness of the inorganic thin film layer may be, for example, 5 nm or more, or 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, crack generation is suppressed, the decrease in water vapor and oxygen barrier properties is small, and costs can be reduced due to the reduction in material usage and shortening of formation time.

[0050] As the inorganic thin film layer, a metal foil such as aluminum foil may be used. In this case, the thickness of the metal foil may be 6 to 9 μm.

[0051] A water vapor barrier coating layer can be formed by applying a coating solution containing, for example, polar compounds such as polyvinyl alcohol, polyvinylpyrrolidone, and ethylene vinyl alcohol, chlorine-containing compounds such as polyvinylidene chloride, and compounds containing Si atoms, Ti atoms, Al atoms, and Zr atoms onto an inorganic thin film layer, drying it, and curing it. By laminating the water vapor barrier coating layer, it is possible to prevent various secondary damages in subsequent processes and to provide high barrier properties.

[0052] 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.

[0053] The total thickness of the substrate layer may be, for example, 5 μm to 100 μm or 8 μm to 50 μm.

[0054] (Water-based ink layer) The water-based ink layer is a layer formed of water-based ink. The water-based ink layer is formed by printing water-based ink onto a substrate layer. The water-based ink layer may be, for example, a water-based colored ink layer formed of water-based colored ink, or a water-based colorless ink layer formed of water-based colorless ink (medium).

[0055] Water-based colored inks, for example, contain a pigment, a binder resin (also called a "vehicle"), and a solvent (dispersion medium).

[0056] The pigment may be an inorganic or organic pigment. Examples of inorganic pigments include titanium dioxide (white pigment), carbon black (ink pigment), barium sulfate, calcium carbonate, and other extender pigments. Examples of organic pigments include azo pigments, phthalocyanine pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and underglaze lake pigments.

[0057] 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.

[0058] When the water-based ink layer is a water-based colored ink layer, the pigment content may be 30 to 90% by mass, based on the total mass of the water-based ink layer. A pigment content of 30% by mass or more tends to yield excellent color development and significantly improve laminate strength (adhesion strength). Furthermore, a pigment content of 90% by mass or less tends to reduce the likelihood of delamination between the water-based ink layer and the adhesive layer. From the viewpoint of achieving an even higher level of balance between excellent color development and suppression of delamination, the pigment content may be, for example, 35 to 85% by mass, based on the total mass of the water-based ink layer. Note that when the water-based ink layer is a water-based colorless ink layer, sometimes called a medium, the water-based ink layer may contain white pigment, but typically the pigment content is 0% by mass, based on the total mass of the water-based ink layer. Such colorless inks are used for base layers and color adjustment of colored inks.

[0059] When a water-based ink contains pigments, gaps are formed between the pigments as they come into contact with each other within the water-based ink layer formed by printing. These gaps form a continuous network of pores extending from the surface of the water-based ink layer. Therefore, when a water-based ink contains pigments, the adhesive (especially polyisocyanate) is more easily absorbed into the water-based ink layer during the formation of the adhesive layer. This creates a network structure derived from the adhesive within the water-based ink layer, and this network structure is expected to improve the laminate strength before and after retort processing.

[0060] The binder resin is, for example, a water-based binder resin. Examples of water-based binder resins include water-soluble binder resins, emulsion-type binder resins, and colloidal dispersion-type binder resins.

[0061] Examples of water-based binder resins include natural resins such as casein resin and shellac resin, and synthetic resins such as rosin-modified maleic acid resin, styrene-maleic acid resin, styrene-acrylic acid resin, α-methylstyrene-acrylic acid resin, styrene-methacrylic acid resin, styrene-maleic acid-acrylic acid resin, acrylic acid-acrylic acid ester resin, acrylic acid-methacrylic acid ester resin, acrylic resin, urethane resin, acrylic-urethane resin, styrene resin, polyester resin, as well as water-soluble polyamide resin and water-soluble polyurethane resin. From the viewpoint of obtaining a more significant improvement in laminate strength (adhesion strength), the water-based binder resin may be a resin that does not have a urethane skeleton. As for water-soluble binder resins, from the viewpoint of improving the dispersion stability of the ink, the adhesion of the water-soluble ink layer, and the strength of the water-soluble ink layer, a resin with no acid value or a low acid value may be used as the main component, and a resin with a high acid value may be used in combination with such a resin.

[0062] If the water-based ink layer is a water-based colored ink layer, the content of the water-based binder resin may be, for example, 15-60% by mass, 25-55% by mass, or 30-50% by mass, based on the total mass of the water-based ink layer. If the water-based ink layer is a water-based colorless ink layer, the content of the water-based binder resin may be, for example, 60-100% by mass or 80-100% by mass, based on the total mass of the water-based ink layer.

[0063] The solvent (dispersion medium) of the water-based ink dissolves or disperses the binder resin within the water-based ink. The solvent (dispersion medium) of the water-based ink is, for example, water or a hydrophilic solvent. Examples of hydrophilic solvents include alcohol-based solvents such as methanol, ethanol, propanol, and butanol. Some of the solvent (dispersion medium) of the water-based ink may remain in the water-based ink layer, but the solvent (dispersion medium) content is, for example, 1% by mass or less based on the total mass of the water-based ink layer.

[0064] Water-based inks may contain auxiliary agents such as dispersants, plasticizers, waxes, lubricants, and defoamers. These components may be present in the water-based ink layer. 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 defoamers include silicone-based and hydrocarbon-based defoamers.

[0065] Water-based inks may contain basic compounds such as ammonia, trimethylamine, sodium hydroxide, or potassium hydroxide to improve the solubility and dispersibility of the resin in the solvent. These components may be present in the water-based ink layer.

[0066] As for the water-based ink, water-based flexographic inks used in water-based flexographic printing and water-based inkjet inks used in inkjet printing can be used. Preferably, the water-based ink layer is a layer formed from water-based flexographic ink. When the water-based ink layer is a layer formed from water-based flexographic ink, the lamination strength (adhesion strength) between layers before and after retort processing tends to be higher. The reason for this is not clear, but it is presumed that because water-based inks used in flexographic printing tend to contain high concentrations of pigments to improve color development, voids between pigments are more easily formed within the water-based ink layer, and the adhesive penetrates into the water-based ink layer more easily, resulting in the above effect.

[0067] Within the water-based ink layer, the thickness and ink type distribution may vary depending on the printed image. The maximum thickness of the water-based ink layer may be 0.4 μm or more, and may be 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more. When the maximum thickness of the water-based ink layer is in the range of 0.4 μm or more, the printed color tends to be good. In other words, it is desirable that there be a region within the water-based ink layer with a thickness of 0.4 μm or more (preferably 0.5 μm or more), depending on the desired image expression. Furthermore, when the thickness of the water-based ink layer is 1.0 μm or more, the absolute values ​​of kurtosis (Ka) and strain (Sa) tend to be smaller, and the interlayer lamination strength (adhesion strength) before and after retort processing tends to be higher. The maximum thickness of the water-based ink layer may be 5.0 μm or less, and may be 4.0 μm or less, 3.0 μm or less, or 2.5 μm or less. When the thickness of the water-based ink layer is 5.0 μm or less, the lamination strength (adhesion strength) between layers before and after retort processing tends to be higher. From these viewpoints, the maximum thickness of the water-based ink layer may be, for example, 0.4 to 5.0 μm. The maximum thickness of the water-based ink layer is the thickness of the water-based ink layer in the thickest region within the plane of the water-based ink layer, and is determined by cross-sectional observation. The measurement of the maximum thickness of the water-based ink layer by cross-sectional observation is performed as follows.

[0068] First, three areas measuring 8 mm wide x 8 mm long are arbitrarily selected from within the surface of the packaging material containing the water-based ink layer, and these areas are cut out to collect three samples. Next, the three collected samples are embedded and fixed in a photocurable resin, and then cross-sections are made using an ultramicrotome. Subsequently, the obtained cross-sections are observed using an optical microscope or scanning electron microscope, and 30 cross-sectional images are acquired at approximately 0.2 mm intervals in the width direction at 1,000 to 5,000x magnification, and the maximum thickness of the water-based ink layer is measured for each image. Of the 90 measured values ​​(maximum thickness of the water-based ink layer) obtained from the above measurements for the three collected samples, the arithmetic mean of the top 15 values ​​is taken as the maximum thickness of the water-based ink layer.

[0069] Although the aqueous ink layer is shown as a single layer in Figures 1 and 2, the aqueous ink layer may have a multilayer structure of two or more layers. For example, the aqueous ink layer may be a multilayer structure of two or more layers obtained by forming a first aqueous ink layer containing a pigment with relatively small particle size on the surface of the substrate layer, and then forming a second aqueous ink layer containing a pigment with relatively large particle size (e.g., white pigment) on the surface of this first aqueous ink layer. 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.

[0070] (adhesive layer) The adhesive layer is formed, for example, by a urethane-based adhesive containing polyisocyanate and polyol. The urethane-based adhesive contains a main component containing polyol and a curing agent containing polyisocyanate. The adhesive hardens and forms the adhesive layer when the polyol and polyisocyanate react. Therefore, the adhesive layer formed by the urethane-based adhesive contains polyurethane, which is the reaction product of the polyol and polyisocyanate. The type of polyisocyanate constituting the polyurethane in the adhesive layer can be analyzed at the monomer level by pyrolysis GC / MS analysis.

[0071] [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 preferred from the viewpoint of water resistance and heat resistance.

[0072] A polyester polyol is a compound having two or more polyol hydroxyl groups and whose main skeleton has a polyester structure. The polyester structure may also be a polyester polyurethane structure. That is, a polyester polyol may also be a polyester urethane polyol. In addition to the polyester structure and polyurethane structure, a polyester polyol may further have a polyether structure. A polyester polyol may be a single polyester polyol or a combination of two or more polyester polyols.

[0073] Commercially available polyester polyols may be used. Examples of commercially available products include Takelac A525 (product name, "Takelac" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc., and DIC Dry LX-747 manufactured by DIC Corporation. That is the case.

[0074] [Polyisocyanate] Polyisocyanates consist of compounds having two or more isocyanate groups. From the viewpoint of generating highly regular hard segments and increasing the cohesive force of adhesives, polyisocyanates are preferably single in structure and have a highly regular structure. From a similar viewpoint, polyisocyanates may include chain-like isocyanates having a symmetric structure and / or isocyanate polymers derived from such chain-like isocyanates. Hereinafter, the chain-like isocyanates will be referred to as polyisocyanate (a1), the isocyanate polymers as polyisocyanate (a2), and these together will be referred to as polyisocyanate (A).

[0075] Polyisocyanate (a1) is a chain-like isocyanate having a symmetrical structure. Polyisocyanate (a1) may be linear or branched. Polyisocyanate (a1) may be, for example, an aliphatic isocyanate. The number of carbon atoms in the aliphatic isocyanate may be, for example, 4 to 6. Examples of aliphatic isocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, and pentamethylene diisocyanate. Polyisocyanate (a1) may be used alone or in combination of two or more types.

[0076] Polyisocyanate (a2) is an isocyanate polymer derived from a chain-like isocyanate having a symmetrical structure. Polyisocyanate (a2) may be a polymer (multimer) obtained by reacting (polymerizing) chain-like isocyanates with each other, or a polymer obtained by further reacting (polymerizing) such polymers with each other. Polyisocyanate (a2) may also be a copolymer obtained by reacting (polymerizing) a chain-like isocyanate with a monomer that can react with the isocyanate (for example, an active hydrogen-containing compound such as a polyol).

[0077] Examples of polyisocyanate (a2) include isocyanurate compounds of polyisocyanate (a1), uretdione compounds of polyisocyanate (a1), biuret compounds of polyisocyanate (a1), allophanate compounds of polyisocyanate (a1), adduct compounds of polyisocyanate (a1) (for example, polyhydric alcohol adduct compounds such as trimethylolpropane adduct compounds), and compounds having urethane bonds that are reaction products of polyisocyanate (a1) and polyhydric alcohols. Polyisocyanate (a2) may be used alone or in combination of two or more types. Polyisocyanate (a2) may also be an isocyanate polymer derived from multiple types of polyisocyanate (a1). Polyisocyanate (a2) may also be an isocyanate polymer derived from polyisocyanate (a1) through multiple reactions (polymerization).

[0078] From the viewpoint of increasing the interlayer lamination strength (adhesion strength) before and after retort treatment, polyisocyanate (A) preferably contains hexamethylene diisocyanate (HDI) or an isocyanate polymer derived from hexamethylene diisocyanate, more preferably contains an isocyanate polymer derived from hexamethylene diisocyanate, and even more preferably contains an isocyanurate of hexamethylene diisocyanate (HDI isocyanurate) or a biuret of hexamethylene diisocyanate (HDI biuret). From the viewpoint of water resistance, polyisocyanate (A) is particularly preferably containing an isocyanurate of hexamethylene diisocyanate.

[0079] From the viewpoint of achieving higher interlayer lamination strength (adhesive strength) before and after retort processing, 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 the amount obtained by subtracting the amount of solvent from the total amount of adhesive if the adhesive contains a solvent, and the total amount of adhesive if the adhesive does not contain a solvent.

[0080] From the viewpoint of achieving higher interlayer lamination strength (adhesive strength) before and after retort processing, the polyisocyanate (a2) 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 (a2) 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 (a2) content may be 3 to 35% by mass or 3 to 15% by mass, based on the total solid content of the adhesive.

[0081] The polyisocyanate (A) content may be 3-70% by mass, 3-50% by mass, 3-35% by mass, or 3-15% by mass, based on the total solid content of the adhesive, from the viewpoint of increasing the interlayer lamination strength (adhesive strength) before and after retort processing and decreasing the absolute values ​​of kurtosis (Ka) and strain (Sa). It may also be 15-70% by mass, 25-70% by mass, or 50-70% by mass.

[0082] When polyisocyanate (A) is used in combination with polyisocyanate (B) described later, 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 making the interlayer lamination strength (adhesive strength) before and after retort treatment easier to achieve and making the absolute values ​​of kurtosis (Ka) and strain (Sa) easier to achieve. In the above case, 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, 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.

[0083] When polyisocyanate (A) is used alone as the polyisocyanate, the content of polyisocyanate (A) may be 8% by mass or more, 11% by mass or more, 22% by mass or more, or 50% by mass or more, based on the total solid content of the adhesive, from the viewpoint of making the interlayer lamination strength (adhesion strength) before and after retort processing easier to achieve and making the absolute values ​​of kurtosis (Ka) and strain (Sa) easier to achieve. In the above case, from the viewpoint of cost, the content of polyisocyanate (A) may be 70% by mass or less, 50% by mass or less, or 41% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (A) may be 8-70% by mass, 8-50% by mass or 8-41% by mass, 11-70% by mass, 22-70% by mass or 50-70% by mass, based on the total solid content of the adhesive. That's fine.

[0084] Polyisocyanate may contain, in addition to or in place of polyisocyanate (A), a polyisocyanate other than polyisocyanate (A) (hereinafter referred to as "polyisocyanate (B)").

[0085] Examples of polyisocyanates (B) include aromatic polyisocyanates such as phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate (XDI), and alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate, as well as isocyanate polymers derived from these polyisocyanates. The xylylene diisocyanate may be either metaxylylene diisocyanate or paraxylylene diisocyanate. Examples of isocyanate polymers include isocyanurates of the above aromatic polyisocyanates or alicyclic polyisocyanates, biuret compounds of the above aromatic polyisocyanates or alicyclic polyisocyanates, and polyhydric alcohol adducts of the above aromatic polyisocyanates or alicyclic polyisocyanates (e.g., trimethylolpropane adducts).

[0086] Commercially available polyisocyanates (B) may be used. Examples of commercially available products include Takenate D-140N, Takenate D-110N, and Takenate A52 (product names, "Takenate" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc., and KX-75 manufactured by DIC Corporation.

[0087] The polyisocyanate (B) content may be 8 to 62% by mass, or 8 to 14% by mass or 18 to 62% by mass, based on the total solid content of the adhesive, from the viewpoint of crosslinking density with polyols, film cohesive force, and the tendency for the absolute values ​​of kurtosis (Ka) and strain (Sa) to be small.

[0088] When polyisocyanate (B) is used in combination with polyisocyanate (A), the content of 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 crosslinking density with polyol, film cohesive force, and the tendency for the absolute values ​​of kurtosis (Ka) and strain (Sa) to be smaller. In the above case, the content of polyisocyanate (B) may be 14% by mass or less, based on the total solid content of the adhesive, from the viewpoint of the tendency for the interlayer lamination strength (adhesion strength) to be higher before and after retort treatment. From these viewpoints, the content of polyisocyanate (B) may be 8 to 14% by mass, based on the total solid content of the adhesive.

[0089] When polyisocyanate (B) is used alone as the polyisocyanate, the content of polyisocyanate (B) may be 18% by mass or more, or 34% by mass or more, based on the total solid content of the adhesive, from the viewpoint of achieving higher interlayer lamination strength (adhesive strength) before and after retort processing and lowering the absolute values ​​of kurtosis (Ka) and strain (Sa). In the above case, from the viewpoint of cost, the content of polyisocyanate (B) may be 62% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (B) may be 18-62% by mass or 34-62% by mass, based on the total solid content of the adhesive.

[0090] The NCO value (unit: mol / g) of polyisocyanate is set to 1.0 × 10⁻⁶ from the perspective of increasing the cohesive strength of the adhesive layer before and after retort treatment. -3 The above is sufficient, and 2.0 × 10 -3 or more or 5.0 × 10 -3 The above is also acceptable. A higher NCO value of the polyisocyanate makes it easier to form an adhesive layer with high cohesive strength. For example, the NCO value (unit: mol / g) of the polyisocyanate is 1.0 × 10⁻⁶. -3 ~3.0×10 -1 This is acceptable. The above NCO value is measured according to JIS K 6806 (potentiometric titration method).

[0091] The ratio (NCO / OH) of the number of moles of isocyanate groups (NCO groups) in an isocyanate group-containing compound (polyisocyanate, etc.) to the number of moles of all active hydrogen groups in an active hydrogen group-containing compound (polyol, etc.) contained in the adhesive may be 2.0 or higher, 11.5 or lower, 8.1 or lower, or 2.0 to 11.5, from the viewpoint of crosslinking density of the adhesive layer and the ease with which an adhesive layer with high cohesive strength can be formed.

[0092] In addition to the active hydrogen-containing compound and polyisocyanate, the adhesive may further contain additives such as solvents, dispersants, defoamers, leveling agents, stabilizers, fillers, lubricants, and waxes. These components may be contained within the adhesive layer.

[0093] The adhesive may be a dry laminating adhesive or a non-solvent laminating adhesive.

[0094] The adhesive layer may contain some residual solvent (diluent, etc.) from the adhesive, but the solvent content should be, for example, 1% by mass or less based on the total mass of the adhesive layer. Examples of solvents include ethyl acetate and methyl ethyl ketone.

[0095] The thickness of the adhesive layer is, for example, 0.5 to 5.0 μm. Note that the thickness of the adhesive layer refers to the shortest distance from the surface on the water-based ink layer side to the surface on the opposite side, and does not include the thickness of the area in the water-based ink layer where the adhesive has permeated. The thickness of the adhesive layer can be measured using the top 15 cross-sectional images used to calculate the maximum thickness of the water-based ink layer as described above. Specifically, the thickness of the adhesive layer can be measured in the above 15 cross-sectional images and their arithmetic mean can be used as the thickness of the adhesive layer.

[0096] The ratio of the thickness of the water-based ink layer (maximum thickness) to the thickness of the adhesive layer (thickness of water-based ink layer / thickness of adhesive layer) may be 0.5 or more, and may be 1.0 or more, or 1.5 or more, from the viewpoint of suppressing the kurtosis and distortion of the adhesive layer after retort treatment. The ratio of the thickness of the water-based ink layer (maximum thickness) to the thickness of the adhesive layer (thickness of water-based ink layer / thickness of adhesive layer) may be 3.5 or less, and may be 3.0 or less, or 2.5 or less, from the viewpoint of improving the lamination strength (adhesive strength) between layers before and after retort treatment. From these viewpoints, the ratio of the thickness of the water-based ink layer (maximum thickness) to the thickness of the adhesive layer (thickness of water-based ink layer / thickness of adhesive layer) may be between 0.5 and 3.5.

[0097] (Sealant layer) The sealant layer is the outermost layer of the packaging material. The sealant layer is composed of a resin that can melt and fuse with each other when heated. The resins that make up the sealant layer may be 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, polypropylene, etc., or acid-modified polyolefin resins obtained by modifying these with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, etc. The resins that make up the sealant layer may be one type or two or more types.

[0098] The thickness of the sealant layer may be, for example, 5 to 300 μm, or 10 to 100 μm.

[0099] Although one embodiment of the packaging material has been described above, the packaging material of this disclosure is not limited to that described above.

[0100] The packaging material may consist only of a base layer, an aqueous ink layer, an adhesive layer, and a sealant layer, but may also include other layers. For example, the packaging material may further include other layers on at least one of the surfaces of the layer opposite the aqueous ink layer and on the surface of the sealant layer facing the aqueous ink layer. The other layer may be a water vapor barrier layer. The details of the water vapor barrier layer are the same as the details of the water vapor barrier layer that the base layer may include. The other layer may be a second base layer having the same configuration as the base layer. The second base layer may be the resin film described above, or a laminate of the resin film and an inorganic vapor deposition layer. The second base layer may be laminated via an adhesive layer. The details of the adhesive layer are the same as the details of the adhesive layer described above.

[0101] <Manufacturing method for packaging materials> Another embodiment of the present disclosure is a method for manufacturing a packaging material, comprising the steps of: (A) printing an aqueous ink onto the surface of a substrate layer to form an aqueous ink layer; (B) applying an adhesive to the surface of the aqueous ink layer opposite to the substrate layer to form an adhesive layer; and (C) laminating a sealant layer onto the surface of the adhesive layer opposite to the aqueous ink layer. In the following description, the contents common to the packaging material of the above embodiment will be omitted.

[0102] Water-based inks contain, for example, a pigment, a binder resin, and a solvent (dispersion medium). As the water-based ink, the water-based ink that forms the aforementioned water-based ink layer can be used. The solvent content in the water-based ink is, for example, 40 to 80% by mass based on the total mass of the water-based ink.

[0103] Water-based ink printing can be carried out by known methods such as gravure printing, flexographic printing, and inkjet printing. In step (A), a water-based ink layer may be formed by solid printing, or by pattern printing of characters, figures, symbols, pictures, or other desired patterns, or a second water-based ink layer may be formed by solid printing to form a first water-based ink layer, followed by pattern printing of a desired pattern on the first water-based ink layer. As described above, it is preferable to use water-based flexographic ink as the water-based ink, and it is preferable to print the water-based ink using a flexographic printing method with said water-based flexographic ink.

[0104] The adhesive contains, for example, an active hydrogen-containing compound and a polyisocyanate. As the adhesive, the adhesive that forms the adhesive layer described above can be used. The components of the adhesive (e.g., the active hydrogen-containing compound and the polyisocyanate) may be mixed and used immediately before coating. As for the coating method of the adhesive, conventionally known methods such as the commonly used casting method, dipping method, roll coating method, gravure coating method, screen printing method, reverse coating method, spray coating method, kit coating method, die coating method, metering bar coating method, chamber doctor combined coating method, and curtain coating method can be used.

[0105] If the adhesive contains a solvent (for example, if the adhesive is a dry laminating adhesive), a drying treatment may be performed after coating to remove the solvent and dry the coating film. The drying of the coating film may be performed at, for example, 25 to 120°C.

[0106] The lamination of sealant layers (for example, the formation of sealant layers) may be carried out by applying a coating liquid containing a resin that can be melted and fused together by heat, as described above, using conventionally known means such as dipping, roll coating, screen printing, or spraying. Alternatively, a sealant layer can be formed by attaching a film or sheet made of the above resin.

[0107] In the manufacturing method of this embodiment, the elastic modulus distribution of the adhesive layer before and after retort treatment can be adjusted, for example, by adjusting the type and amount of polyisocyanate used in the adhesive, the type and thickness of the aqueous ink layer, etc. In other words, in the manufacturing method of this embodiment, the packaging material of the above embodiment can be obtained, for example, by adjusting the type and amount of polyisocyanate used in the adhesive, the type and thickness of the aqueous ink layer, etc.

[0108] The manufacturing method of this embodiment may further include a step (C') of laminating a second base material layer on the surface of the adhesive layer (first adhesive layer) opposite to the water-based ink layer. In this case, the manufacturing method may further include a step (B') of applying a second adhesive to the surface of the second base material layer opposite to the water-based ink layer to form a second adhesive layer, and in step (C), a sealant layer may be laminated on the surface of the second adhesive layer opposite to the water-based ink layer. The manufacturing method of this embodiment may further include a step (B'') of applying a third adhesive to the surface of the base material layer (first base material layer) opposite to the water-based ink layer to form a third adhesive layer, in lieu of or in addition to step (B'), and may further include a step (C'') of laminating a third base material layer on the surface of the third adhesive layer opposite to the base material layer (first base material layer). Steps (B') and (B'') can be carried out in the same manner as step (B) described above. Steps (C') and (C'') can also be carried out in the same manner as step (C) described above. Furthermore, the second and third base material layers may be the same as the base material layer (first base material layer) described above, and the second and third adhesives may be the same as the adhesive (first adhesive) described above.

[0109] <Packaging bag> Another embodiment of the present disclosure is a packaging bag formed by bagging the packaging material of the above embodiment. As shown in FIG. 3, for example, the packaging bag is formed by heat-sealing three sides L1, L2, and L3 of two overlapping rectangular packaging materials to form a bag shape. After putting an object to be the content (such as food, pharmaceuticals, etc.) through the non-heat-sealed opening 30a, the opening 30a can also be heat-sealed to seal the packaging bag 30. Note that the form of the packaging bag is not limited to this. Other examples of the packaging bag include pillow packaging, three-side seal packaging, and gusset packaging.

[0110] <Package> Another embodiment of the present disclosure is a package including the packaging bag of the above embodiment and the content accommodated in the packaging bag.

[0111] The packaging bag of the above package may be retort-treated. That is, the package may be a retort-treated package.

[0112] The content of the package is not particularly limited, and may be, for example, food, pharmaceuticals, etc.

[0113] The above package can be obtained, for example, by accommodating an object (food, pharmaceuticals, etc.) to be the content into the package through the opening of the packaging bag of the above embodiment, closing the opening to make the inside of the package in a sealed state, and optionally performing retort treatment.

Example

[0114] Hereinafter, the present disclosure will be described based on examples and comparative examples. Note that the present disclosure is not limited to the following examples.

[0115] <Preparation Example 1> As the polyol main agent, TSN4864A manufactured by Toyo Morton Co., Ltd. (polyester polyol, OH value: 1.8×10 -3 mol / g, acid value: 3.8×10 -3A polyol-based compound (mol / g) was prepared. BASF's Basonate HB-100 (HDI biuret compound, NCO value: 5.3 × 10⁻¹⁰) was added to this polyol-based compound. -3 (mol / g) and Takenate D177N (HDI nurate, NCO value: 4.8 × 10) manufactured by Mitsui Chemicals, Inc. -3 (mol / g) and Evonik VESTANAT T 1890 / 100 (IPDI, NCO value: 4.1 × 10⁻¹⁰) -3 Adhesive 1 was prepared by blending the mol / g components in the mass ratio (solid content ratio) shown in Table 1.

[0116] <Preparation Examples 2-4> Adhesives 2-4 were prepared in the same manner as in Preparation Example 1, except that each component was blended in the mass ratio (solid content ratio) shown in Table 1.

[0117] [Table 1]

[0118] <Preparation Example 5> Takelac A626 (polyester polyol, solids 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 XDI and IPDI, manufactured by Mitsui Chemicals, Inc., with a solid content of 75% by mass and an NCO value of 2.5 × 10⁻¹⁶) -3 Adhesive 5 was prepared by mixing (mol / g) in the mass ratio (solid content ratio) shown in Table 2.

[0119] <Preparation Example 6> To the adhesive 5 obtained in Preparation Example 5, 24A-100 (HDI biuret compound, NCO value: 5.9 × 10) manufactured by Asahi Kasei Corporation was added as polyisocyanate (A). -3 Adhesive 6 was prepared by adding and mixing (mol / g). Each component was blended in the mass ratio (solid content ratio) shown in Table 2.

[0120] <Preparation Example 7> The adhesive 5 obtained in Preparation Example 5 contains, as polyisocyanate (A), Dulanate P301-75E (a polyisocyanate containing the trimethylolpropane adduct of HDI (HDI adduct), manufactured by Asahi Kasei Corporation, with an NCO value of 3.0 × 10⁻¹⁰) -3 Adhesive 7 was prepared by adding and mixing (mol / g). Each component was blended in the mass ratio (solid content ratio) shown in Table 2.

[0121] [Table 2]

[0122] <Example 1> (Manufacturing of packaging materials) [Process (A)] As the first substrate layer, a 20 μm thick biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, product name: U-1, "OPP1" in the table) was prepared, and a white aqueous flexographic ink (Aquariona TPN3 white, manufactured by Toyo Ink Co., Ltd.) was printed onto the surface of the first substrate layer by flexographic printing to form an aqueous ink layer ("ink" in the table) with a thickness of 3.5 μm. This obtained a laminate 1 consisting of the first substrate layer and the aqueous ink layer. Note that the thickness of the aqueous ink layer in this embodiment is the "maximum thickness" measured by the method described above.

[0123] [Step (B) and Step (C')] On the aqueous ink layer of the laminate 1 obtained above, the adhesive 1 was applied using a non-sol laminator (SuperSimplex SL, manufactured by Nordmechanica) at a coating roll temperature of 70°C, a coating speed of 200 m / min, and a coating amount of 1.6 g / m². 2 The material was applied under the specified conditions to form a 1.6 μm thick adhesive layer (non-solvent adhesive layer, labeled "NS" in the table). Next, a 20 μm thick biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, product name: U-1, labeled "OPP2" in the table) was prepared as a second substrate layer, and this second substrate layer was laminated onto the adhesive layer formed above in the laminating section of the non-solvent laminator. After lamination, the laminate 2 was obtained by curing at 40°C for 72 hours.

[0124] [Process (B') and Process (C)] The adhesive 1 was applied to the second base material layer of the laminate 2 obtained above under the same conditions as in step (B) above to form an adhesive layer (non-solvent adhesive layer, "NS" in the table) with a thickness of 1.6 μm. Next, a 60 μm thick unoriented polypropylene film (manufactured by Toray Industries, Inc., product name: Pyrene ZK207, "CPP" in the table) was prepared as a sealant layer, and the sealant layer was laminated onto the adhesive layer formed above in the laminating section of the non-solvent laminator. After lamination, the packaging material of Example 1 was obtained by curing at 40°C for 72 hours.

[0125] <Examples 2-4> Except for changing the type of adhesive as shown in Table 3 and changing the adhesive application conditions so that the thickness of the adhesive layer was as shown in Table 3, the packaging materials of Examples 2 to 4 were obtained in the same manner as in Example 1.

[0126] <Example 5> The packaging material of Example 5 was obtained in the same manner as in Example 4, except that the thickness of the aqueous ink layer of laminate 1 in step (A) was changed to 2.0 μm.

[0127] <Example 6> In steps (B) and (B'), a 3.0 μm thick adhesive layer (dry laminate adhesive layer, "DL" in the table) was formed by a dry laminate method using adhesive 5 instead of a non-solvent laminate method using adhesive 1, and a red aqueous flexographic ink (Aquariona TPN3 Red, manufactured by Toyo Ink Co., Ltd.) was used instead of a white aqueous flexographic ink. Except for these differences, the packaging material of Example 6 was obtained in the same manner as in Example 1. The adhesive layer was formed by applying the adhesive to the coated surface and drying it at 80°C for 1 minute. Dry lamination was performed using a dry laminator, and curing after lamination was carried out at 50°C for 72 hours.

[0128] <Example 7> Except for not performing steps (B') and (C'), the packaging materials of Examples 7 to 12 were obtained in the same manner as in Examples 1 to 6.

[0129] <Example 13> The packaging material for Example 13 was prepared in the same manner as in Example 12, except that a 15 μm thick biaxially oriented nylon film (manufactured by Unitika Ltd., product name: Emblem ONM (Type: RT), "Emblem" is a registered trademark, "ONY" in the table) was used as the first base layer instead of a biaxially oriented polypropylene film.

[0130] <Example 14> The packaging material for Example 14 was prepared in the same manner as in Example 13, except that adhesive 6 was used instead of adhesive 5.

[0131] <Comparative Example 1> The packaging material for Comparative Example 1 was obtained in the same manner as in Example 4, except that the thickness of the aqueous ink layer of laminate 1 was changed to 0.3 μm in step (A).

[0132] <Comparative Example 2> The packaging material for Comparative Example 2 was obtained in the same manner as in Example 6, except that the thickness of the aqueous ink layer of laminate 1 in step (A) was changed to 0.3 μm.

[0133] <Comparative Example 3> The packaging material for Comparative Example 3 was obtained in the same manner as in Example 6, except that the thickness of the aqueous ink layer of laminate 1 in step (A) was changed to 0.3 μm, and adhesive 7 was used instead of adhesive 5.

[0134] <Retort processing and measurement of elastic modulus distribution> The packaging materials prepared in the examples and comparative examples were subjected to retort processing using the following method, and the elastic modulus distribution of the adhesive layer (adhesive layer adjacent to the water-based ink layer) before and after retort processing was measured.

[0135] [Retort processing] First, two sheets measuring 140 mm in width and 100 mm in length were cut from the packaging material. The two sheets were placed facing each other with their sealant-layered sides overlapping on all four sides, and three of the four sides were heat-sealed to create a packaging bag with one side open. Next, 50 g of water was added to the resulting packaging bag, and the opening side of the packaging bag was heat-sealed to create a test pouch. The prepared test pouch was then retorted at 121°C for 30 minutes. The heat sealing was performed using a 15 mm wide sealing bar, at 150°C and 3 kg / cm² on each side. 2 The process was carried out by heating and pressurizing for 0.5 seconds. After retorting, the test pouch was removed from the water, and a 15 mm wide and 200 mm long piece of packaging material (test specimen) was cut from one of the two sheets constituting the test pouch and used to measure the elastic modulus distribution.

[0136] [Measurement of elastic modulus distribution] First, the front and back surfaces of the packaging material were corona-treated, and then the packaging material was cut into 2 x 3 mm strips. Next, the resulting strips of packaging material were embedded in a photocurable resin (Aronics LCRD-800, a visible light curable resin manufactured by Toagosei Co., Ltd.), and the resin was cured by light irradiation to obtain a block piece consisting of the packaging material and the cured resin that embedded the packaging material. The production of the block piece using the retort-treated packaging material was carried out after the retort-treated packaging material was left to stand for 30 days in an atmospheric environment at 25°C and 50% relative humidity.

[0137] Next, the obtained block pieces were fixed in an SPM sample holder insert (a Leica Microsystems AFM sample holder insert), and at room temperature (25°C), the block pieces were trimmed and the cross-section of the packaging material (a cross-section perpendicular to the layer interface) was cut with a glass knife. After that, the cross-section was cut with a diamond knife until the cross-section was mirror-finished. A Leica Microsystems ultramicrotome EM UC7 was used as the cross-section cutting device, with a cutting speed of 3 mm / s and a cutting film thickness of 500 nm. The cutting direction was horizontal to the layer interface.

[0138] Next, shape and elastic modulus measurements were performed on the cross-sectional samples using a scanning probe microscope (SPM). The SPM used was the JupiterXR (product name) manufactured by Oxford Instruments. For the SPM cantilever (measuring probe), the Biosphere B50-FM (product name) manufactured by Nanotools, with typical characteristic values ​​of a tip radius of 50 nm and a spring constant of 2.8 N / m, was used. In the measurement and calculation of elastic modulus, the tip radius of the cantilever was referenced from the individual characteristic values ​​of the product, while the spring constant and optical lever sensitivity of the cantilever were obtained using the GetReal method, the calibration function of the SPM.

[0139] First, using the SPM's AC mode (tapping mode), the field of view was set to 0.2 μm vertically x 6.4 μm horizontally, with a scanning speed of 2 Hz, so that the center of the field of view was aligned with the center of the adhesive layer's thickness in the cross-section. Next, using the SPM's contact mode, force curve measurements were performed to obtain the force curve (load-displacement curve) when the cantilever was pressed into the adhesive layer and then withdrawn. A total of 100 force curves were obtained within the positioning range determined by the shape measurement (2 points at 200 nm intervals in the film thickness direction, and 50 points at 130 nm intervals parallel to the layer interface). The force curve conditions were a maximum load of 5 nN and a test speed of 500 nm / s, and force curves with a displacement of 500 nm or more were obtained for both pressing and withdrawing. The above measurements were performed on three cross-sectional samples, and a total of 300 force curves were obtained.

[0140] The obtained force curves were analyzed using the JKR (Johnson-Kendall-Roberts) theory's elastic contact model to calculate the modulus of elasticity. The calculation of the modulus of elasticity using the JKR theory was performed by fitting analysis using SPM (JupiterXR) analysis software, with the sample's modulus of elasticity, displacement origin, and maximum adhesion force as fitting parameters. The analysis range for each point on the force curve was defined as the range from the load and displacement when the load first reached "(maximum load + minimum load) × 0.5" during pull-out after reaching the maximum load, to the load and displacement when the minimum load was reached. Furthermore, the modulus of elasticity of the cantilever was assumed to be 865 GPa, the Poisson's ratio 0.2, and the Poisson's ratio of the adhesive layer 0.33.

[0141] Following the above procedure, the elastic modulus of the 300 force curve points was determined, and the arithmetic mean of these elastic moduli was calculated. From the obtained elastic moduli of the 300 points, the strain, kurtosis, standard deviation, and coefficient of variation were calculated using Excel functions. The results are shown in Table 3.

[0142] <Evaluation: Adhesion strength evaluation test immediately after retort processing> In the same manner as described above, the packaging materials of each example and comparative example were subjected to retort treatment (hot water treatment). After that, the test pouches were removed from the water and left to stand for 40 minutes under conditions of 25°C and 55% RH. Then, the short side of the pouch was held with both hands and twisted forcefully 50 times. This operation was performed on 30 test pouches, and the presence or absence of delamination at the interface between the adhesive layer and the water-based ink layer was visually confirmed. The number of pouches in which delamination occurred at the interface between the adhesive layer and the water-based ink layer (delaminated pouches) was denoted as X, and the retort treatment resistance of the packaging material was evaluated according to the following criteria. The results are shown in Table 1. [standard] A:X=0 B:X=1~3 C:X≧4 If the rating is A or B, it is judged that the retort processing resistance is good.

[0143] [Table 3]

[0144] 1...Base layer, 2...Water-based ink layer, 2a...Pigment, 3...Adhesive layer, 3a...Sea area, 3b...Island area, 4...Sealant layer, 10, 20...Packaging material, 30...Packaging bag.

Claims

1. A packaging material comprising a base layer, a water-based ink layer, an adhesive layer, and a sealant layer in this order, When retorting is performed according to the following procedures (A1) to (A3), and the elastic modulus is measured according to the following procedures (B1) to (B3), A packaging material wherein the elastic modulus distribution of the adhesive layer after the retort treatment has a kurtosis of 16.0 or less and a strain of 2.9 or less in absolute value. (A1): Two sheets measuring 140 mm in width and 100 mm in length are cut from the packaging material, and the sealant layer sides of the two sheets are placed facing each other so that their four sides overlap, and three of the four sides are heat-sealed to produce a packaging bag with one side open. (A2): After adding 50 g of water to the packaging bag, a test pouch is prepared by heat-sealing one side of the opening of the packaging bag. (A3): The test pouch prepared in (A2) above is subjected to retort treatment at 121°C for 80 minutes. (B1): The cross-section in the thickness direction of the packaging material 30 days after the retort processing is observed using the tapping mode of a scanning probe microscope, and the microscope is positioned so that the center of the field of view is at the center of the thickness of the cross-section of the adhesive layer. (B2): Under a 25°C environment, force curve measurement is performed on the adhesive layer within the field of view using the contact mode of a scanning probe microscope. (B3): The elastic modulus of each measurement point is calculated by analyzing the force curve obtained in (B2) using the elastic contact model of the JKR theory.

2. The packaging material according to claim 1, wherein the elastic modulus distribution of the adhesive layer after the retort treatment has a kurtosis of 11.0 or less and a strain of 2.2 or less in absolute value.

3. The packaging material according to claim 1, wherein the elastic modulus distribution of the adhesive layer before retort treatment has a kurtosis of 19.0 or less and a strain of 4.2 or less in absolute value.

4. The packaging material according to claim 1, wherein the adhesive layer is formed of a urethane adhesive containing polyisocyanate and polyol.

5. The packaging material according to claim 1, wherein the aqueous ink layer is formed of aqueous flexographic ink.

6. The packaging material according to claim 1, wherein the ratio of the thickness of the aqueous ink layer to the thickness of the adhesive layer is 0.5 to 3.

5.

7. The packaging material according to claim 1, wherein the base layer includes at least one selected from the group consisting of stretched polyethylene terephthalate film, stretched polypropylene film, stretched nylon film, and stretched polyethylene film.

8. A packaging bag made by forming a bag from the packaging material described in any one of claims 1 to 7.

9. A packaging body comprising a packaging bag according to claim 8, and contents contained in the packaging bag.

Images