Multilayer body, packaging bag, and heat sterilization pouch

Abstract

Provided is a multilayer body which exhibits excellent impact resistance after retort processing in the case when used for a packaging bag such as a retort pouch. Provided is a multilayer body which sequentially comprises a second base material, a second adhesive layer, and a sealant layer in this order in the thickness direction. The multilayer body has only one base material, and the second base material has a multilayer structure that sequentially comprises a first surface resin layer, a polypropylene layer, and a second surface resin layer in this order in the thickness direction. The second surface resin layer is disposed so as to face the second adhesive layer side, and the second surface resin layer contains 50% by mass or more of a random copolymer of propylene and an α-olefin other than propylene with respect to the total amount of the second surface resin layer. The second adhesive layer has a thickness of 1 μm to 4.5 μm inclusive and an elastic modulus of 20 MPa to 50 MPa inclusive. The sealant layer is an unstretched polypropylene film, and has a composite elastic modulus of 900 MPa or less.

Description

Laminate, packaging bag and heat sterilization pouch CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese Patent Application No. 2023-166474 filed in Japan on September 27, 2023, and Japanese Patent Application No. 2023-167754 filed in Japan on September 28, 2023, the entire disclosures of which are incorporated herein by reference.

[0002] The present invention relates to a laminate, a packaging bag, and a heat sterilization pouch.

[0003] Conventionally, packaging bags have been constructed from laminates that use a base material such as a polyester film, which has excellent strength and heat resistance, or a nylon film, which has excellent impact resistance, and a sealant film such as a polyolefin film, which has excellent heat-sealing properties. However, with the growing demand for a recycling-oriented society in recent years, there has been a demand for packaging bags that are highly recyclable. However, with conventional packaging bags made from different resin materials, it has been difficult to separate the individual resin materials.

[0004] Therefore, from the viewpoint of using a single material (mono-material) that is easy to recycle, the use of a single material made of polypropylene has been studied (for example, Patent Document 1). Patent Document 1 discloses a laminate used as a packaging material for packaging bags, in which a stretched substrate containing polypropylene is used as the substrate instead of a polyester film or a nylon film, and is combined with a sealant film containing polypropylene. In this laminate, both the substrate and the sealant film are made of polypropylene, thereby improving recyclability.

[0005] Japanese Patent Application Laid-Open No. 2021-020391

[0006] Incidentally, when a laminate is used to make a packaging bag such as a retort pouch, the laminate used for the packaging bag is required to have drop impact resistance (impact resistance) that can withstand the impact of the pouch being dropped after heat sterilization treatment (retort treatment). However, the reality is that a laminate made of a single material such as polypropylene has not been sufficiently studied to satisfy these required properties.

[0007] One of the problems to be solved by the present disclosure is to provide a laminate that, when used in a packaging bag such as a retort pouch, has excellent impact resistance after retort treatment.

[0008] The laminate of the present disclosure is a laminate comprising a second substrate, a second adhesive layer, and a sealant layer, in this order in the thickness direction, wherein the laminate has only one substrate, the second substrate has a multilayer structure comprising a first surface resin layer, a polypropylene layer, and a second surface resin layer, in this order in the thickness direction, the second surface resin layer being disposed so as to face the second adhesive layer, the second surface resin layer containing 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene, relative to the total amount of the second surface resin layer, the second adhesive layer having a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer is an unstretched polypropylene film and has a composite elastic modulus of 900 MPa or less.

[0009] According to the present disclosure, it is possible to provide a laminate that, when used in a packaging bag such as a retort pouch, has excellent impact resistance after retort treatment.

[0010] FIG. 1 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 2 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 3 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 4 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 5 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 6 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 7 is a front view showing one embodiment of a packaging bag. FIG. 8 is a front view showing one embodiment of a packaging bag. FIG. 9 is a schematic view showing a method for measuring laminate strength. FIG. 10 is a view showing the measurement results of laminate strength.

[0011] In this specification, when multiple upper limit candidate values ​​and multiple lower limit candidate values ​​are listed for a certain parameter, the numerical range of the parameter may be formed by combining any one upper limit candidate value and any one lower limit candidate value. As an example, consider the following statement: "Parameter B is preferably A1 or more, more preferably A2 or more, even more preferably A3 or more, and preferably A4 or less, more preferably A5 or less, and even more preferably A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each layer more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each drawing, elements similar to those already described with reference to the previous drawings will be designated by the same reference numerals, and detailed description may be omitted as appropriate.

[0013] In this specification, the term "main component" in a layer or substrate refers to a component whose content in the layer or substrate is more than 50% by mass, preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0014] In the following description, each of the components (for example, polypropylene, α-olefin, resin material, additive, gas barrier resin, adhesive resin, inorganic oxide) may be used alone or in combination of two or more.

[0015] [Laminate] The laminate of the present disclosure includes a substrate (second substrate), an adhesive layer (second adhesive layer), and a sealant layer, in this order in the thickness direction (hereinafter simply referred to as "in this order"). The laminate includes only one substrate. The substrate is an oriented polypropylene substrate. Here, an "oriented polypropylene substrate" refers to a stretched substrate containing polypropylene as a primary component. The oriented polypropylene substrate has a multilayer structure including a first surface resin layer, a polypropylene layer, and a second surface resin layer, in this order in the thickness direction. The sealant layer is an unstretched polypropylene film. The unstretched polypropylene film contains polypropylene as a primary component. The laminate of the present disclosure may include at least one or more barrier layers. The barrier layer is a layer (such as a surface coating layer, inorganic oxide layer, coating layer, or surface resin layer, as described below) that exhibits gas barrier properties (e.g., oxygen barrier properties and water vapor barrier properties, particularly oxygen barrier properties). The laminate of the present disclosure may include a barrier substrate (also referred to as a "barrier film") that includes at least one or more barrier layers.

[0016] The laminate of the present disclosure may include only one substrate or two or more substrates. The laminate of the present disclosure may include only one adhesive layer or two or more adhesive layers. The laminate of the present disclosure preferably includes a first substrate, a first adhesive layer, a second substrate, a second adhesive layer, and a sealant layer, in this order.

[0017] The first substrate is an oriented polypropylene substrate containing polypropylene as a main component. The second substrate is an oriented polypropylene substrate containing polypropylene as a main component. The oriented polypropylene substrate of the second substrate has a multilayer structure including a first surface resin layer, a polypropylene layer, and a second surface resin layer in this order in the thickness direction. The oriented polypropylene substrate of the first substrate and the oriented polypropylene substrate of the second substrate may be the same or different. The laminate of the present disclosure may include one or more barrier layers. In the laminate of the present disclosure, the first substrate may be a barrier substrate including at least one or more barrier layers, or the second substrate may be a barrier substrate including at least one or more barrier layers.

[0018] In one embodiment of the laminate of the present disclosure, the first substrate is an oriented polypropylene substrate and the second substrate is a barrier substrate, that is, the laminate includes, in this order, the oriented polypropylene substrate, an optional printing layer, a first adhesive layer, a barrier substrate, a second adhesive layer, and a sealant layer.

[0019] In this embodiment, the barrier substrate is preferably arranged so that the barrier layer faces the first adhesive layer and the oriented polypropylene substrate faces the second adhesive layer. This arrangement firmly bonds the second surface resin layer and the second adhesive layer constituting the oriented polypropylene substrate of the second substrate (barrier substrate), thereby improving the adhesive strength between the barrier substrate and the sealant layer. In this embodiment, the laminate exhibits excellent interlayer adhesion. A packaging bag produced using the laminate of this embodiment exhibits excellent drop impact resistance (impact resistance) and hand tearability (openability) even after heat treatments such as retort treatment and boiling treatment.

[0020] 1 to 6 are schematic cross-sectional views showing one embodiment of a laminate according to the present disclosure. The laminate 1 shown in FIGS. 1 to 3 shows an example of a two-layer structure. The laminate 1 shown in FIG. 1 includes a barrier substrate 20 as a base material, an adhesive layer 40, and a sealant layer 30, in this order. The barrier substrate 20 includes an oriented polypropylene substrate 22 and an inorganic oxide layer 24 as a barrier layer. In this example, the barrier substrate 20 is disposed such that the oriented polypropylene substrate 22 faces the adhesive layer 40, and the inorganic oxide layer 24 forms the outermost layer of the laminate 1. The oriented polypropylene substrate 22 also has a multilayer structure including, in this order, a first surface layer 22b, a polypropylene layer 22a, and a second surface layer 22c. In this example, the oriented polypropylene substrate 22 is disposed such that the first surface layer 22b faces the inorganic oxide layer 24, and the second surface layer 22c faces the adhesive layer 40.

[0021] Figure 2 is the same as Figure 1 except that the barrier substrate 20 includes a surface coating layer 23 between an oriented polypropylene substrate 22 and an inorganic oxide layer 24. In this example, the oriented polypropylene substrate 22 is arranged so that the first surface layer 22b faces the surface coating layer 23 and the second surface layer 22c faces the adhesive layer 40. Figure 3 is the same as Figure 2 except that the barrier substrate 20 includes the oriented polypropylene substrate 22, the surface coating layer 23, the inorganic oxide layer 24, and the covering layer 25 in this order.

[0022] The laminate 1 shown in Figures 4 to 6 shows an example of a three-layer structure. The laminate 1 shown in Figure 4 includes, in this order, a oriented polypropylene substrate 10 as a first substrate, a first adhesive layer 40A, a barrier substrate 20 as a second substrate, a second adhesive layer 40B, and a sealant layer 30. The barrier substrate 20 includes a oriented polypropylene substrate 22 and an inorganic oxide layer 24. In this example, the barrier substrate 20 is arranged so that the oriented polypropylene substrate 22 faces the second adhesive layer 40B and the inorganic oxide layer 24 faces the first adhesive layer 40A. The oriented polypropylene substrate 22 has a multilayer structure including, in this order, a first surface layer 22b, a polypropylene layer 22a, and a second surface layer 22c. In this example, the oriented polypropylene substrate 22 is arranged so that the first surface layer 22b faces the inorganic oxide layer 24 and the second surface layer 22c faces the second adhesive layer 40B.

[0023] Figure 5 is the same as Figure 4 except that the barrier substrate 20 includes a surface coating layer 23 between an oriented polypropylene substrate 22 and an inorganic oxide layer 24. In this example, the oriented polypropylene substrate 22 is arranged so that the first surface layer 22b faces the surface coating layer 23 and the second surface layer 22c faces the second adhesive layer 40B. Figure 6 is the same as Figure 5 except that the barrier substrate 20 includes an oriented polypropylene substrate 22, a surface coating layer 23, an inorganic oxide layer 24, and a covering layer 25 in this order.

[0024] The polypropylene content (hereinafter also referred to as the "mono-material content rate") relative to the total amount of resin materials contained in the laminate of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 88% by mass or more, and particularly preferably 90% by mass or more. Packaging bags produced using such a laminate have excellent recyclability, for example. The upper limit of the polypropylene content relative to the total amount of resin materials contained in the laminate of the present disclosure is not particularly limited, and may be, for example, 99% by mass, 98% by mass, 97% by mass, 96% by mass, 95% by mass, or 94% by mass.

[0025] In this disclosure, the mono-material ratio refers to the ratio of the mass of a single polypropylene-based material to the total mass of resin materials contained in the laminate. However, if a layer contains polypropylene as the main component (i.e., more than 50% by mass), the mono-material ratio is calculated assuming that polypropylene constitutes 100% by mass of the layer.

[0026] <Barrier Substrate> The barrier substrate comprises a stretched polypropylene substrate and one or more barrier layers. Examples of barrier layers include a surface coating layer, an inorganic oxide layer, a covering layer, and a surface resin layer. The barrier substrate comprises, for example, a stretched polypropylene substrate and an inorganic oxide layer provided on one surface of the stretched substrate. The barrier substrate may comprise a surface coating layer between the stretched polypropylene substrate and the inorganic oxide layer. The barrier substrate may comprise a covering layer on the inorganic oxide layer. The barrier substrate may be transparent.

[0027] (Stretched polypropylene substrate) An example of the stretched polypropylene substrate included in the barrier substrate is a stretched polypropylene substrate having a multilayer structure including, in this order, a first surface resin layer, an optional adhesive resin layer, a polypropylene layer, an optional adhesive resin layer, and a second surface resin layer. In this embodiment, the barrier substrate includes a stretched polypropylene substrate and an inorganic oxide layer provided on the surface resin layer of the stretched polypropylene substrate. In this embodiment, the barrier substrate includes, in this order, the second surface resin layer, an optional adhesive resin layer, a polypropylene layer, an optional adhesive resin layer, the first surface resin layer, and an inorganic oxide layer.

[0028] "Polypropylene Layer" In the stretched polypropylene substrate, the polypropylene layer contains polypropylene as a main component. The polypropylene may be any of a homopolymer, a random copolymer, and a block copolymer, or a mixture of two or more selected from these. Biomass-derived polypropylene and / or recycled polypropylene may be used as the polypropylene. A propylene homopolymer is a polymer consisting of only propylene. A propylene random copolymer is a random copolymer of propylene and an α-olefin other than propylene. A propylene block copolymer is a copolymer having a polymer block consisting of propylene and a polymer block consisting of at least an α-olefin other than propylene. The polymer block consisting of at least an α-olefin other than propylene may be a polymer block consisting of propylene and an α-olefin other than propylene.

[0029] Examples of the α-olefin include α-olefins other than propylene having from 2 to 20 carbon atoms. Specific examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene.

[0030] Among polypropylenes, random copolymers are preferred from the viewpoint of transparency, homopolymers are preferred when emphasis is placed on the rigidity and heat resistance of the packaging bag, and block copolymers are preferred when emphasis is placed on the impact resistance of the packaging bag. In the present disclosure, among these polypropylenes, homopolymers and block copolymers are more preferred from the viewpoints of heat resistance, impact resistance, and ease of opening, and homopolymers (propylene homopolymers) are even more preferred.

[0031] From the viewpoint of film-forming property and processability, the melt flow rate (MFR) of the polypropylene is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, and is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less, for example, 0.1 g / 10 min or more and 50 g / 10 min or less. The MFR of the polypropylene is measured in accordance with JIS K7210-1:2014, Method A, under conditions of a temperature of 230°C and a load of 2.16 kg.

[0032] The polypropylene content in the polypropylene layer is preferably more than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 85% by mass or more, 90% by mass or more, or 95% by mass or more.

[0033] The polypropylene layer may contain a resin material other than polypropylene. Examples of the resin material include polyolefins other than polypropylene, acrylic resins, vinyl resins, cellulose resins, polyamides, polyesters, and ionomer resins. Examples of polyolefins other than polypropylene include polyethylene. The polypropylene layer may contain additives. Examples of the additives include crosslinkers, antioxidants, antiblocking agents, lubricants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0034] The polypropylene layer may have a single-layer structure or a multi-layer structure. The thickness of the polypropylene layer is preferably 10 μm or more, more preferably 15 μm or more, and also preferably 100 μm or less, more preferably 50 μm or less, for example, 10 μm or more and 100 μm or less. A laminate including a stretched substrate containing a polypropylene layer having a thickness equal to or greater than the lower limit has, for example, excellent strength and heat resistance. A laminate including a stretched substrate containing a polypropylene layer having a thickness equal to or less than the upper limit has, for example, excellent processability.

[0035] In this specification, the thickness of the substrate and each layer is measured as follows. A block is prepared by embedding the laminate in an embedding resin, and the block is cut using a commercially available rotary microtome at room temperature (25°C) to prepare a cross-section of the laminate. The cross-section is obtained by cutting the laminate in the thickness direction perpendicular to the main surface. Finishing is performed using a diamond knife. The thickness of the substrate and each layer is the arithmetic average of the thicknesses measured at five locations by observing the cross-section using a scanning electron microscope (SEM, Hitachi, Ltd., SU8000).

[0036] "Second Surface Resin Layer" The second surface resin layer is located between the adhesive layer or second adhesive layer on the sealant layer and the polypropylene layer. The second surface resin layer contains a random copolymer of propylene and an α-olefin other than propylene. By providing a second surface resin layer containing the random copolymer between the polypropylene layer and the adhesive layer or second adhesive layer, it is possible to improve the adhesive strength between the sealant layer and the oriented polypropylene substrate (i.e., barrier substrate) and also improve the impact resistance of the laminate.

[0037] Examples of the random copolymer include a propylene-ethylene random copolymer and a propylene-ethylene-butene random copolymer, and any one of these copolymers or a mixture of two or more of these copolymers can be used as the random copolymer.

[0038] In the propylene-ethylene random copolymer, the content of ethylene-derived structural units is preferably 2% by mass or more, more preferably 4% by mass or more. Furthermore, the content is preferably 50% by mass or less, more preferably 40% by mass or less. By having the content within the above preferred range, for example, drop impact resistance can be further improved. In the present disclosure, the content of structural units can be measured, for example, by thermal gradient interaction chromatography (TGIC).

[0039] In the propylene-ethylene-butene random copolymer, the content of ethylene-derived structural units and butene-derived structural units is preferably 2% by mass or more, more preferably 4% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less.

[0040] The content of the random copolymer in the second surface resin layer is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the second surface resin layer. By containing 50% by mass or more of the random copolymer, the second surface resin layer exhibits sufficient adhesive strength.

[0041] The second surface resin layer may contain the polypropylene other than the random copolymer or the resin material. The second surface resin layer may contain the additive. The second surface resin layer may be subjected to the surface treatment.

[0042] The ratio of the thickness of the second surface resin layer to the total thickness of the stretched polypropylene substrate is preferably 1% or more, more preferably 1.5% or more, and preferably 20% or less, more preferably 10% or less, for example, 1% or more and 20% or less. The thickness of the second surface resin layer is preferably 0.2 μm or more, more preferably 0.3 μm or more, and preferably 4 μm or less, more preferably 2 μm or less, for example, 0.2 μm or more and 4 μm or less. When the ratio or thickness is equal to or greater than the lower limit, for example, adhesion with the adhesive layer (second adhesive layer) can be improved, and the lamination strength of the laminate can be improved. When the ratio or thickness is equal to or less than the upper limit, for example, the film-forming and processability of the stretched polypropylene substrate and the recyclability of the laminate can be improved.

[0043] "First Surface Resin Layer" The first surface resin layer is located between the inorganic oxide layer and the polypropylene layer. In one embodiment, the first surface resin layer may have the same configuration as the second surface resin layer.

[0044] In one embodiment, the first surface resin layer contains a resin material having a melting point of 180°C or higher (hereinafter also referred to as a "high-melting-point resin material"). By providing a first surface resin layer containing a high-melting-point resin material between the polypropylene layer and the inorganic oxide layer, for example, it is possible to improve the adhesion of the inorganic oxide layer formed on the first surface resin layer and suppress a decrease in gas barrier properties. In one embodiment, the first surface resin layer may be provided on the polypropylene layer. That is, the first surface resin layer may be adjacent to the polypropylene layer. In one embodiment, when an adhesive resin layer is provided between the polypropylene layer and the first surface resin layer, the adhesive resin layer may be provided on the polypropylene layer, and the first surface resin layer may be provided on the adhesive resin layer. That is, the adhesive resin layer may be adjacent to the polypropylene layer, and the first surface resin layer may be adjacent to the adhesive resin layer.

[0045] The melting point of the high-melting-point resin material is preferably 185°C or higher, more preferably 190°C or higher, and even more preferably 205°C or higher. When the melting point is equal to or higher than the lower limit, for example, the adhesion of the inorganic oxide layer can be improved, the gas barrier property can be improved, and the laminate strength of the laminate can be improved. The melting point of the high-melting-point resin material is preferably 265°C or lower, more preferably 260°C or lower, and even more preferably 250°C or lower. This can improve, for example, the film-forming properties of the stretched polypropylene substrate.

[0046] In this specification, the melting point of a high-melting-point resin material or the like is measured in accordance with JIS K7121:2012 (Method for measuring transition temperature of plastics). Specifically, a differential scanning calorimetry (DSC) curve is measured at a temperature rise rate of 10°C / min using a DSC device, and the melting peak temperature is determined as the melting point.

[0047] The high-melting point resin material contained in the first surface resin layer has a melting point TA, and the polypropylene contained in the polypropylene layer has a melting point TB, and the difference between the melting points TA and TB is preferably 20°C or more. The difference between the melting points TA and TB is preferably 80°C or less, and more preferably 60°C or less. When the difference between the melting points TA and TB is equal to or greater than the lower limit, the adhesion between the first surface resin layer and the inorganic oxide layer can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaging bag can be further improved. In addition, when the difference between the melting points TA and TB is equal to or less than the upper limit, the film-forming properties of the stretched polypropylene substrate can be further improved.

[0048] The high-melting-point resin material preferably has a polar group. The polar group refers to a group containing one or more heteroatoms, and examples thereof include ester groups, epoxy groups, hydroxyl groups, amino groups, amide groups, urethane groups, carboxyl groups, carbonyl groups, carboxylic anhydride groups, sulfo groups, thiol groups, and halogen groups. Among these, hydroxyl groups, ester groups, amino groups, amide groups, carboxyl groups, and carbonyl groups are preferred, and amide groups are more preferred.

[0049] The high-melting-point resin material may have a melting point of 180°C or higher, and examples thereof include polyolefin, vinyl resin, acrylic resin, polyamide, polyimide, polyester, cellulose resin, and ionomer resin. For example, a resin material having a melting point of 180°C or higher and containing a polar group is preferred, and ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyester, and polyamides such as nylon 6, nylon 6,6, MXD nylon, and amorphous nylon are more preferred. The use of such a resin material can significantly improve the adhesion of the inorganic oxide layer formed on the first surface resin layer, and can effectively suppress a decrease in gas barrier properties.

[0050] In one embodiment, the high-melting-point resin material is preferably polyamide. By using polyamide as the high-melting-point resin material, it is possible to suppress the deterioration of gas barrier properties even after bending the laminate, and to improve the heat resistance of the laminate. In addition, it is possible to suppress the deterioration of gas barrier properties even after the laminate is subjected to a retort treatment and a boiling treatment, which will be described later. It is more preferable that the high-melting-point resin material be nylon 6.

[0051] The content of the high-melting-point resin material in the first surface resin layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0052] The first surface resin layer may contain the above-mentioned resin material other than the high-melting-point resin material. The first surface resin layer may contain the above-mentioned additive. The first surface resin layer may be subjected to the above-mentioned surface treatment.

[0053] The ratio of the thickness of the first surface resin layer to the total thickness of the oriented polypropylene substrate is preferably 1% or more, more preferably 1.5% or more, and preferably 10% or less, more preferably 5% or less, for example, 1% or more and 10% or less. The thickness of the first surface resin layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and preferably 5 μm or less, more preferably 4 μm or less, for example, 0.1 μm or more and 5 μm or less. When the ratio or thickness is equal to or greater than the lower limit, for example, the adhesion of the inorganic oxide layer can be improved, the gas barrier properties can be improved, and the lamination strength of the laminate can be improved. When the ratio or thickness is equal to or less than the upper limit, for example, the film-forming and processability of the oriented polypropylene substrate and the recyclability of the laminate can be improved.

[0054] "Adhesive Resin Layer" The stretched polypropylene substrate may have an adhesive resin layer between the polypropylene layer and either or both of the first and second surface resin layers. This improves adhesion between these layers. The thickness of the adhesive resin layer is, for example, 1 μm or more and 15 μm or less. By making the thickness of the adhesive resin layer equal to or greater than the lower limit, adhesion between the polypropylene layer and the first and second surface resin layers can be further improved. By making the thickness of the adhesive resin layer equal to or less than the upper limit, the processability of the barrier substrate can be improved. The adhesive resin layer can be formed, for example, from an adhesive resin. Examples of adhesive resins include polyether, polyester, polyurethane, silicone resin, epoxy resin, vinyl resin, phenolic resin, polyolefin, and acid-modified polyolefin. Among these, polyolefin and its acid-modified product are preferred from the viewpoint of recyclability of the laminate, and polypropylene and its acid-modified product are more preferred. Commercially available polypropylene can be used for the adhesive resin layer, for example, the Admer series manufactured by Mitsui Chemicals, Inc.

[0055] In one embodiment, the stretched polypropylene substrate is a coextruded stretched resin film. The coextruded stretched resin film can be produced, for example, by forming a laminated film using a T-die method, an inflation method, or the like, and then stretching the laminated film.

[0056] The stretching treatment of the oriented polypropylene substrate may be uniaxial stretching or biaxial stretching. When stretching in the MD direction, the stretching ratio is preferably 2 times or more, more preferably 5 times or more, and preferably 15 times or less, more preferably 13 times or less. When stretching in the TD direction, the stretching ratio is preferably 2 times or more, more preferably 5 times or more, and preferably 15 times or less, more preferably 13 times or less. By setting the stretching ratio to 2 times or more, the strength and heat resistance of the substrate can be improved. From the viewpoint of the breaking limit of the substrate, the stretching ratio is preferably 15 times or less. The oriented polypropylene substrate is, for example, a biaxially stretched substrate.

[0057] The thickness of the stretched polypropylene substrate is preferably 10 μm or more, more preferably 15 μm or more, and preferably 100 μm or less, more preferably 50 μm or less, for example, 10 μm or more and 100 μm or less. A laminate including a stretched substrate having a thickness equal to or greater than the lower limit has, for example, excellent strength and heat resistance. A laminate including a stretched substrate having a thickness equal to or less than the upper limit has, for example, excellent processability.

[0058] (Surface Coating Layer) The barrier substrate may have a surface coating layer containing a resin material having a polar group between the oriented polypropylene substrate (the first surface resin layer constituting the oriented polypropylene substrate) and the inorganic oxide layer. Such a barrier substrate has excellent adhesion to the inorganic oxide layer and also excellent gas barrier properties. Such a barrier substrate has, in this order, the oriented polypropylene substrate, the surface coating layer, and the inorganic oxide layer.

[0059] The polar group refers to a group containing one or more heteroatoms, and examples thereof include an ester group, an epoxy group, a hydroxyl group, an amino group, an amide group, a urethane group, a carboxyl group, a carbonyl group, a carboxylic anhydride group, a sulfo group, a thiol group, and a halogen group. Among these, the carboxyl group, the carbonyl group, the ester group, the hydroxyl group, the amino group, the amide group, and the urethane group are preferred, and the carboxyl group, the hydroxyl group, the amide group, and the urethane group are more preferred.

[0060] Examples of resin materials having a polar group include ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVA), polyester, polyethyleneimine, hydroxyl group-containing acrylic resin, polyamides such as nylon 6, nylon 6,6, aromatic-containing nylon, and amorphous nylon, and polyurethane. Among these, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, hydroxyl group-containing acrylic resin, polyamide, and polyurethane are more preferred.

[0061] The surface coating layer can be formed using, for example, an aqueous emulsion or a solvent-based emulsion. Examples of aqueous emulsions include polyamide-based emulsions, polyethylene-based emulsions, and polyurethane-based emulsions. Examples of solvent-based emulsions include acrylic resin-based emulsions and polyester-based emulsions.

[0062] The content of the resin material having a polar group in the surface coating layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The surface coating layer may contain the above-mentioned resin material other than the resin material having a polar group. The surface coating layer may also contain the above-mentioned additive.

[0063] The ratio of the thickness of the surface coating layer to the total thickness of the polypropylene oriented substrate and the surface coating layer is preferably 0.08% or more, more preferably 0.2% or more, even more preferably 1% or more, and preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and even more preferably 5% or less, for example, 0.08% or more and 20% or less. The thickness of the surface coating layer is preferably 0.02 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, even more preferably 0.2 μm or more, and preferably 10 μm or less, more preferably 5 μm or less, for example, 0.02 μm or more and 10 μm or less. When the ratio or thickness is equal to or greater than the lower limit, for example, the adhesion of the inorganic oxide layer can be improved, the gas barrier properties can be improved, and the laminate strength of the laminate can be improved. When the ratio or thickness is equal to or less than the upper limit, for example, the processability of the barrier substrate and the recyclability of the laminate can be improved.

[0064] For example, a polypropylene or a resin composition containing polypropylene is formed into a film using a T-die method, an inflation method, or the like to obtain a polypropylene substrate, and then the substrate is stretched. A coating liquid for forming a surface coating layer is applied to the obtained stretched substrate, followed by drying, thereby producing a resin substrate having a stretched polypropylene substrate and a surface coating layer.

[0065] (Inorganic oxide layer) The barrier substrate comprises an inorganic oxide layer. The inorganic oxide layer contains one or more inorganic oxides, for example, a vapor-deposited film of an inorganic oxide. A laminate comprising the barrier substrate has excellent gas barrier properties, specifically, oxygen barrier properties and water vapor barrier properties. A packaging bag produced using such a laminate can suppress oxidative deterioration of the contents filled in the packaging bag and suppress weight loss of the contents. The barrier substrate may, for example, comprise an inorganic oxide layer on the surface coating layer, or may comprise an inorganic oxide layer on the first surface resin layer.

[0066] Examples of inorganic oxides include aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). Among these, silica, silicon carbide oxide, and alumina are preferred.

[0067] In one embodiment, silica is more preferable as the inorganic oxide because it does not require aging treatment after forming the inorganic oxide layer. In one embodiment, carbon-containing silicon oxide is more preferable as the inorganic oxide because it can suppress deterioration of gas barrier properties even when the laminate is bent.

[0068] The thickness of the inorganic oxide layer is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 10 nm or more, and is preferably 150 nm or less, more preferably 60 nm or less, even more preferably 40 nm or less, for example, 1 nm or more and 150 nm or less. A laminate having an inorganic oxide layer whose thickness is equal to or greater than the lower limit has excellent oxygen barrier properties and water vapor barrier properties, for example. A laminate having an inorganic oxide layer whose thickness is equal to or less than the upper limit can suppress the occurrence of cracks in the inorganic oxide layer and has excellent recyclability, for example.

[0069] The surface of the inorganic oxide layer may be subjected to the above-mentioned surface treatment.

[0070] Examples of methods for forming an inorganic oxide layer, particularly an inorganic oxide vapor deposition film, include physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0071] The inorganic oxide layer may be a single layer formed by a single vapor deposition process, or may be a multilayer formed by multiple vapor deposition processes. When the inorganic oxide layer is a multilayer, each layer may be composed of the same inorganic oxide or different inorganic oxides. Each layer may be formed by the same method or different methods.

[0072] The inorganic oxide layer is preferably a vapor-deposited film formed by a CVD method, and more preferably a carbon-containing silicon oxide vapor-deposited film formed by a CVD method. A laminate including such an inorganic oxide layer has, for example, excellent flex resistance.

[0073] The carbon-containing silicon oxide vapor-deposited film contains silicon, oxygen, and carbon. In one embodiment of the carbon-containing silicon oxide vapor-deposited film, the carbon ratio C is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, and is preferably 50% or less, more preferably 40% or less, even more preferably 35% or less, relative to 100% of the total of the three elements silicon, oxygen, and carbon, for example, 3% or more and 50% or less. By setting the carbon ratio C within the above range, for example, deterioration of the gas barrier property can be suppressed even when the laminate is bent. In this specification, the ratio of each element is based on a molar basis.

[0074] In one embodiment of the carbon-containing silicon oxide vapor-deposited film, the silicon ratio Si is preferably 1% or more, more preferably 3% or more, even more preferably 8% or more, and is preferably 45% or less, more preferably 38% or less, even more preferably 33% or less, for example, 1% or more and 45% or less, relative to 100% of the total of the three elements silicon, oxygen, and carbon. The oxygen ratio O is preferably 10% or more, more preferably 20% or more, even more preferably 25% or more, and is preferably 70% or less, more preferably 65% ​​or less, even more preferably 60% or less, for example, 10% or more and 70% or less, relative to 100% of the total of the three elements silicon, oxygen, and carbon. By setting the silicon ratio Si and the oxygen ratio O within the above ranges, for example, deterioration of the gas barrier property can be further suppressed even when the laminate is bent.

[0075] In one embodiment of the carbon-containing silicon oxide vapor-deposited film, the oxygen ratio O is preferably higher than the carbon ratio C, and the silicon ratio Si is preferably lower than the carbon ratio C. The oxygen ratio O is preferably higher than the silicon ratio Si, that is, the ratios preferably decrease in the order of ratio O, ratio C, and ratio Si. This makes it possible to further suppress a decrease in gas barrier properties, for example, even when the laminate is bent.

[0076] The proportions C, Si, and O in the carbon-containing silicon oxide vapor-deposited film are measured by narrow scan analysis using X-ray photoelectron spectroscopy (XPS) under the following measurement conditions.

[0077] (Measurement conditions) Equipment used: "ESCA-3400" (Kratos) [1] Spectrum collection conditions Incident X-ray: MgKα (non-monochromated X-ray, hν=1253.6 eV) X-ray output: 150 W (10 kV, 15 mA) Measurement area: approx. 6 mmφ Photoelectron capture angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar+ Ar gas introduction pressure: 2.0 × 10 －２ Pa Acceleration voltage: 0.2 (kV) Emission current: 20 (mA) Ion sputtering time: 30 seconds, and the spectrum was collected.

[0078] (Coating Layer) The barrier substrate may further include a coating layer on the inorganic oxide layer. That is, the barrier substrate may further include a coating layer on the surface of the inorganic oxide layer opposite to the surface facing the stretched polypropylene substrate. A laminate including such a barrier substrate has, for example, excellent oxygen barrier properties and water vapor barrier properties.

[0079] In one embodiment, the coating layer contains a resin component. Examples of the resin component include polyolefins such as polyethylene, polypropylene, polybutene, and polymethylpentene, vinyl resins, acrylic resins, polyesters, urethane resins, melamine resins, and epoxy resins. The content of the resin component in the coating layer is preferably more than 50% by mass, more preferably 75% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, for example, more than 50% by mass and 95% by mass or less. The coating layer may contain the above-mentioned additives.

[0080] The thickness of the coating layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and is preferably 5 μm or less, more preferably 3 μm or less, even more preferably 1 μm or less, for example, 0.01 μm or more and 5 μm or less. Such a coating layer has, for example, excellent scratch resistance.

[0081] The coating layer can be formed, for example, by applying a coating liquid for the coating layer to the surface of the inorganic oxide layer and drying it. The coating liquid for the coating layer can be prepared, for example, by mixing the above-mentioned resin component with, if necessary, additives and a solvent. Details of these components are as described above. Known coating methods can be used to apply the coating liquid for the coating layer. Methods for drying the applied coating liquid for the coating layer include, for example, hot air drying, heat roll drying, and methods that apply heat, such as infrared irradiation. The drying temperature can be 50°C or higher and 150°C or lower.

[0082] In one embodiment, the coating layer may be a barrier coat layer containing a gas barrier resin. Examples of gas barrier resins include ethylene-vinyl alcohol copolymers, polyvinyl alcohol, polyacrylonitrile, polyester, polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide, polyurethanes, and acrylic resins. Among these, polyvinyl alcohol is preferred from the viewpoints of oxygen barrier properties and water vapor barrier properties. Furthermore, by including polyvinyl alcohol in the barrier coat layer, the occurrence of cracks in the inorganic oxide layer can be effectively prevented.

[0083] The content of the gas barrier resin in the barrier coat layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 75% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, for example, 50% by mass or more and 90% by mass or less. Such a barrier coat layer has, for example, excellent gas barrier properties. The barrier coat layer may contain the above-mentioned additives.

[0084] The thickness of the barrier coat layer containing the gas barrier resin is preferably 0.01 μm or more, more preferably 0.1 μm or more, and preferably 10 μm or less, more preferably 5 μm or less, for example, 0.01 μm or more and 10 μm or less. A barrier substrate having a barrier coat layer with a thickness equal to or greater than the lower limit exhibits, for example, excellent gas barrier properties. A barrier substrate having a barrier coat layer with a thickness equal to or less than the upper limit can improve, for example, the processability and recyclability of the laminate. Furthermore, as long as the thickness of the barrier coat layer is within the above range, recycling suitability is not impaired even if the gas barrier resin is a resin material other than polypropylene.

[0085] The barrier coat layer can be formed, for example, by dissolving or dispersing a material such as a gas barrier resin in water or an appropriate organic solvent, applying the resulting coating liquid to the surface of the inorganic oxide layer, and drying it. The barrier coat layer can also be formed, for example, by applying a commercially available barrier coating agent and drying it.

[0086] In one embodiment, the coating layer may be a gas barrier coating film formed by polycondensation treatment of a composition containing a metal alkoxide and a water-soluble polymer by a sol-gel method in the presence of a sol-gel catalyst, water, an organic solvent, etc. A barrier substrate having a gas barrier coating film on an inorganic oxide layer has, for example, excellent gas barrier properties. The gas barrier coating film contains a hydrolysis polycondensate obtained by hydrolyzing and polycondensing the metal alkoxide or the like by a sol-gel method. By providing such a gas barrier coating film on the inorganic oxide layer, for example, it is possible to effectively suppress the occurrence of cracks in the inorganic oxide layer.

[0087] The metal alkoxide is represented by, for example, formula (1): １ ｎ M (OR ２ ) ｍ (1) In formula (1), R １ and R ２ R each independently represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M. １ and R ２ Examples of the organic group in the formula (I) include alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-hexyl, and n-octyl. The metal atom M is, for example, silicon, zirconium, titanium, or aluminum. Examples of the metal alkoxide include alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

[0088] Examples of water-soluble polymers include hydroxyl group-containing polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Depending on the desired physical properties, such as oxygen barrier property, water vapor barrier property, water resistance, and weather resistance, either polyvinyl alcohol or ethylene-vinyl alcohol copolymer may be used, or both may be used in combination. Alternatively, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using an ethylene-vinyl alcohol copolymer may be laminated. The amount of water-soluble polymer used is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 500 parts by mass or less, per 100 parts by mass of the metal alkoxide. By ensuring that the content of the water-soluble polymer in the gas barrier coating film is equal to or greater than the lower limit, the oxygen barrier property and water vapor barrier property of the laminate can be further improved. Furthermore, by ensuring that the content of the water-soluble polymer in the gas barrier coating film is equal to or less than the upper limit, the film formability of the gas barrier coating film can be improved.

[0089] A silane coupling agent may be used together with the metal alkoxide. As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used, and an organoalkoxysilane having an epoxy group is preferred, such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The amount of the silane coupling agent used is preferably 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the metal alkoxide.

[0090] In the gas barrier coating film, the ratio of the metal alkoxide to the water-soluble polymer (metal alkoxide / water-soluble polymer) is, by mass, preferably 4.5 or less, more preferably 3.5 or less, and also preferably 1.0 or more, more preferably 1.7 or more, for example, 1.0 or more and 4.5 or less. By setting the ratio of the metal alkoxide to the water-soluble polymer to the upper limit or less, it is possible to suppress a decrease in gas barrier properties even after bending the laminate. By setting the ratio of the metal alkoxide to the water-soluble polymer to the lower limit or more, it is possible to improve the heat resistance of the laminate. Furthermore, it is possible to suppress a decrease in gas barrier properties even after the laminate is subjected to retort treatment and boiling treatment. Note that the above ratio is a solid content ratio.

[0091] The silicon atom to carbon atom ratio (Si / C) on the surface of the gas barrier coating film, as measured by X-ray photoelectron spectroscopy (XPS), is preferably 1.60 or less, more preferably 1.35 or less, and also preferably 0.50 or more, more preferably 0.90 or more. By setting the silicon atom to carbon atom ratio to the upper limit or less, it is possible to suppress a decrease in gas barrier properties even after bending the laminate. By setting the silicon atom to carbon atom ratio to the lower limit or more, it is possible to improve the heat resistance of the laminate. Furthermore, it is possible to suppress a decrease in gas barrier properties even after retort treatment and boiling treatment of the laminate. The above range of the silicon atom to carbon atom ratio can be achieved by appropriately adjusting the ratio of metal alkoxide to water-soluble polymer. Note that in this specification, the silicon atom to carbon atom ratio is based on molar basis.

[0092] The ratio of silicon atoms to carbon atoms by X-ray photoelectron spectroscopy (XPS) can be measured by narrow scan analysis under the following measurement conditions. (Measurement conditions) Instrument used: "ESCA-3400" (Kratos) [1] Spectrum collection conditions Incident X-ray: MgKα (monochromated X-ray, hν=1253.6 eV) X-ray output: 150 W (10 kV, 15 mA) X-ray scanning area (measurement area): approximately 6 mmφ Photoelectron acceptance angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar ＋Acceleration voltage: 0.2 (kV) Emission current: 20 (mA) Etch range: 10 mmφ Ion sputtering time: 30 seconds + 30 seconds + 60 seconds (total 120 seconds) and collect the spectrum

[0093] The gas barrier composition may contain water in an amount of preferably 0.1 mol or more, more preferably 0.5 mol or more, even more preferably 0.8 mol or more, and preferably 100 mol or less, more preferably 60 mol or less, even more preferably 2 mol or less, per mol of metal alkoxide. By setting the water content to the lower limit or more, for example, the oxygen barrier property and water vapor barrier property of the laminate can be improved. By setting the water content to the upper limit or less, for example, the hydrolysis reaction can be carried out quickly.

[0094] The gas barrier composition may contain an organic solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, or n-butyl alcohol.

[0095] The sol-gel catalyst is preferably an acid or an amine compound. Examples of acids include mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid; and organic acids such as acetic acid and tartaric acid. The amount of acid used is preferably 0.001 mol or more and 0.05 mol or less per mol of the total molar amount of the metal alkoxide and the alkoxide portion (e.g., silicate portion) of the silane coupling agent. By using an amount of acid equal to or greater than the lower limit, the catalytic effect can be improved. By using an amount of acid equal to or less than the upper limit, the thickness of the formed gas barrier coating film can be made uniform.

[0096] Suitable amine compounds are tertiary amines that are substantially insoluble in water and soluble in organic solvents, such as N,N-dimethylbenzylamine, tripropylamine, tributylamine, and tripentylamine. Among these, N,N-dimethylbenzylamine is preferred. The amount of the amine compound used is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and preferably 1.0 part by mass or less, more preferably 0.3 part by mass or less, per 100 parts by mass of the total amount of the metal alkoxide and the silane coupling agent. By using an amount of the amine compound that is equal to or greater than the lower limit, the catalytic effect can be improved. By using an amount of the amine compound that is equal to or less than the upper limit, the thickness of the gas barrier coating film formed can be made uniform.

[0097] Examples of methods for applying the gas barrier composition include roll coating using a gravure roll coater or the like, spray coating, spin coating, dipping, brush coating, bar coating, and applicator coating.

[0098] One embodiment of a method for forming a gas barrier coating film is described below. A gas barrier composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel catalyst, water, an organic solvent, and, if necessary, a silane coupling agent. A polycondensation reaction gradually progresses within the composition. The composition is applied to an inorganic oxide layer by a conventional method and dried. This drying further promotes polycondensation of the metal alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains one) to form a composite polymer layer. Multiple composite polymer layers may be laminated by repeating the above procedure. For example, the applied composition is heated at a temperature of preferably 20°C or higher, more preferably 50°C or higher, and even more preferably 70°C or higher, and preferably 250°C or lower, more preferably 220°C or lower, even more preferably 150°C or lower, even more preferably 120°C or lower, and particularly preferably 100°C or lower, for 1 second to 10 minutes. This allows the formation of a gas barrier coating film.

[0099] The thickness of the gas barrier coating film is preferably 0.01 μm or more, more preferably 0.1 μm or more, and is preferably 100 μm or less, more preferably 10 μm or less, even more preferably 2 μm or less, still more preferably 1 μm or less, and particularly preferably 0.5 μm or less, for example, from 0.01 μm to 100 μm. This can improve the gas barrier properties, suppress the occurrence of cracks in the inorganic oxide layer, and improve the recyclability of the packaging bag, for example.

[0100] <Stretched polypropylene substrate> The stretched polypropylene substrate as the first substrate may be the same as the stretched polypropylene substrate described in the <Barrier substrate> section. The stretched polypropylene substrate as the first substrate may also be a stretched substrate of another embodiment. The stretched polypropylene substrate as the first substrate and the stretched polypropylene substrate as the second substrate may be the same or different.

[0101] (Another embodiment of the stretched substrate) The stretched substrate of another embodiment contains polypropylene as a main component. Details of the polypropylene are as described above, and therefore further description will be omitted here.

[0102] In another embodiment, the polypropylene content in the stretched substrate is preferably more than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 85% by mass or more, 90% by mass or more, or 95% by mass or more.

[0103] The stretched substrate of another embodiment may contain the above-mentioned resin material other than polypropylene. The stretched substrate of another embodiment may contain the above-mentioned additive.

[0104] Another embodiment of the stretched substrate is a polypropylene substrate that has been subjected to a stretching treatment. A laminate including another embodiment of the stretched substrate has excellent heat resistance, impact resistance, water resistance, and dimensional stability, and is suitable as a packaging material for forming a packaging bag that is subjected to retort treatment or boiling treatment, for example. The stretching treatment may be uniaxial or biaxial. When stretching in the machine direction (the flow direction of the substrate, MD direction), the stretching ratio is preferably 2 times or more, more preferably 5 times or more, and preferably 15 times or less, more preferably 13 times or less. When stretching in the width direction (the direction perpendicular to the MD direction, TD direction), the stretching ratio is preferably 2 times or more, more preferably 5 times or more, and preferably 15 times or less, more preferably 13 times or less. By setting the stretching ratio to 2 times or more, the strength and heat resistance of the substrate can be improved, and the printability of the substrate can be improved. From the viewpoint of the breaking limit of the substrate, the stretching ratio is preferably 15 times or less. Another embodiment of the oriented substrate used as the first substrate is, for example, a biaxially oriented polypropylene substrate.

[0105] The stretched substrate of another embodiment may be subjected to a surface treatment. This can improve, for example, the adhesion between the stretched substrate of another embodiment and other layers. Examples of surface treatment methods include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and / or nitrogen gas, and glow discharge treatment; and chemical treatments such as oxidation treatment using chemicals. An easy-adhesion layer may be provided on the surface of the stretched substrate of another embodiment.

[0106] The stretched substrate of another embodiment may have a single-layer structure or a multi-layer structure. The thickness of the stretched substrate of another embodiment is preferably 10 μm or more, more preferably 15 μm or more, and also preferably 100 μm or less, more preferably 50 μm or less, for example, 10 μm or more and 100 μm or less. A laminate including a stretched substrate having a thickness equal to or greater than the lower limit has, for example, excellent strength and heat resistance. A laminate including a stretched substrate having a thickness equal to or less than the upper limit has, for example, excellent processability.

[0107] <Printed Layer> The laminate of the present disclosure may include a printed layer on the surface of a substrate such as a first substrate or a second substrate. The image formed on the printed layer is not particularly limited, and may include letters, patterns, symbols, and combinations thereof. The printed layer may also be formed using ink derived from biomass. This can further reduce the environmental impact.

[0108] Examples of methods for forming the printed layer include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing. Among these, flexographic printing is preferred from the viewpoint of reducing environmental impact. The thickness of the printed layer is, for example, 0.5 μm or more and 3 μm or less.

[0109] <Adhesive Layer> In one embodiment, the laminate of the present disclosure includes an adhesive layer (second adhesive layer) between the substrate (second substrate) and the sealant layer. In one embodiment, the laminate of the present disclosure includes a first adhesive layer between the first substrate and the second substrate. In one embodiment, the laminate of the present disclosure includes a second adhesive layer between the second substrate and the sealant layer. Such a laminate has excellent lamination strength, for example, between the substrate (second substrate) and the sealant layer, between the first substrate and the second substrate, and between the second substrate and the sealant layer.

[0110] (First adhesive layer) The elastic modulus of the cross section of the first adhesive layer measured using an atomic force microscope (AFM) is preferably 5 MPa or more, more preferably 10 MPa or more, even more preferably 12 MPa or more, and preferably 150 MPa or less, more preferably 100 MPa or less, even more preferably 80 MPa or less, for example, 5 MPa or more and 150 MPa or less. Packaging bags produced using a laminate including a first adhesive layer having an elastic modulus within the above range tend to have excellent gas barrier properties and appearance even after heat treatment such as retort treatment. Furthermore, when a printed layer is provided on the surface of the first substrate facing the first adhesive layer, a first adhesive layer having an elastic modulus below the upper limit tends to have excellent adhesion to the printed layer.

[0111] Here, the elastic modulus of the adhesive layer is measured on a cross section of the adhesive layer using an atomic force microscope (AFM). Details of the conditions for measuring the elastic modulus using an AFM are described in the Examples section.

[0112] The thickness of the first adhesive layer is 1.0 μm or more, preferably 1.5 μm or more, more preferably 2.0 μm or more, even more preferably 2.5 μm or more, and preferably 10.0 μm or less, more preferably 8.0 μm or less, even more preferably 6.0 μm or less, particularly preferably 5.0 μm or less, for example, 1.0 μm or more and 10.0 μm or less. When a printed layer is provided on the surface of the first substrate facing the first adhesive layer, a first adhesive layer having a thickness equal to or greater than the lower limit can effectively cover the steps caused by the printed layer, tending to produce a packaging bag with a good appearance. A laminate having a first adhesive layer having a thickness equal to or greater than the lower limit tends to have excellent laminate strength even after heat treatment.

[0113] (Second adhesive layer) The elastic modulus of the cross section of the second adhesive layer measured using an AFM is 20 MPa or more, preferably 25 MPa or more, and more preferably 30 MPa. Furthermore, the elastic modulus is 50 MPa or less, preferably 45 MPa or less, and more preferably 40 MPa or less. The elastic modulus of the second adhesive layer is, for example, 20 MPa or more and 50 MPa or less. A laminate including a second adhesive layer having an elastic modulus within the above range tends to have excellent lamination strength and excellent impact resistance. A second adhesive layer having such an elastic modulus can be formed, for example, by using a solvent-free adhesive described below and appropriately changing the type and molecular weight of the polymer component contained in the base agent, the type of curing agent, the molar ratio (NCO / OH), and the aging conditions described below.

[0114] The thickness of the second adhesive layer is 1.0 μm or more, preferably 1.2 μm or more, and more preferably 1.4 μm or more. The thickness of the second adhesive layer is 4.5 μm or less, preferably 4.0 μm or less, and more preferably 3.5 μm or less. The thickness of the second adhesive layer is 1.0 μm or more and 4.5 μm or less. A laminate having such a second adhesive layer can prevent blocking due to adhesive overflow or winding slippage during winding. Furthermore, packaging bags produced using such a laminate having a second adhesive layer tend to have excellent impact resistance, and therefore resistance to bag breakage due to dropping, as well as excellent tearability, and therefore excellent openability. Furthermore, the packaging bag has excellent recyclability, for example.

[0115] In one embodiment of the laminate of the present disclosure, the adhesive layer (e.g., an adhesive layer in a two-layer structure and a second adhesive layer in a three-layer structure) located between the sealant layer and the substrate adjacent to the sealant layer has a value obtained by multiplying the modulus of elasticity (MPa) and the thickness (μm) of the adhesive layer of preferably 35 or more, more preferably 40 or more, and even more preferably 50 or more. The value obtained by multiplying the modulus of elasticity and the thickness of the adhesive layer is preferably 95 or more, and preferably 80 or less, and more preferably 60 or less. The value obtained by multiplying the modulus of elasticity and the thickness of the adhesive layer is, for example, 35 or more and 95 or less.

[0116] In one embodiment of the laminate of the present disclosure, an adhesive layer having a value obtained by multiplying the modulus of elasticity (MPa) and the thickness (μm) of 35 to 95 is located between the sealant layer and the substrate adjacent to the sealant layer. Packaging bags produced using a laminate of this type tend to have better impact resistance (bag resistance to drop breakage) and hand tearability (ease of opening) after retort treatment.

[0117] (Adhesive) The adhesive layer, the first adhesive layer, and the second adhesive layer are each composed of an adhesive. The adhesive forming the first adhesive layer and the adhesive forming the second adhesive layer may be the same or different. The adhesive may be a one-component curing adhesive, a two-component curing adhesive, or a non-curing adhesive, and a two-component curing adhesive is preferred from the viewpoint of ease of adjusting the elastic modulus to the above-mentioned range.

[0118] A method for obtaining a laminate using an adhesive includes applying the adhesive to an object, then superimposing another object on the formed adhesive layer and allowing the adhesive layer sandwiched between them to harden. Examples of the object include a first substrate, a second substrate, and a sealant film. The process of allowing the adhesive layer to harden is hereinafter also referred to as the "aging process."

[0119] The aging conditions for the adhesive are described below. The aging temperature is preferably 25°C or higher, more preferably 30°C or higher, and even more preferably 35°C or higher, and is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. The aging time is preferably 5 hours or higher, more preferably 10 hours or higher, and even more preferably 20 hours or higher, and is preferably 150 hours or lower, more preferably 135 hours or lower, and even more preferably 120 hours or lower. By increasing the aging temperature, the elastic modulus of the adhesive layer tends to increase. By increasing the aging time, the elastic modulus of the adhesive layer tends to increase.

[0120] Examples of adhesives include polyurethane adhesives, polyester adhesives, polyether adhesives, rubber adhesives, vinyl adhesives, olefin adhesives, silicone adhesives, epoxy adhesives, and phenol adhesives. Among these, from the viewpoint of easily adjusting the elastic modulus within the above-mentioned range, polyurethane adhesives, polyester adhesives, and polyether adhesives are preferred, polyurethane adhesives and polyester adhesives are more preferred, polyurethane adhesives are even more preferred, and two-component curing polyurethane adhesives are particularly preferred.

[0121] The adhesive may be a solvent-based adhesive or a solventless adhesive. A solvent-based adhesive is an adhesive that is applied to an object, heated in an oven or the like to volatilize the solvent in the adhesive, and then bonded to another object. In the case of a two-component curing adhesive, either the base agent or the curing agent, or both, contain a solvent. Examples of the solvent include organic solvents, specifically hydrocarbon solvents such as toluene, xylene, n-hexane, and methylcyclohexane; ester solvents such as ethyl acetate, n-propyl acetate, n-butyl acetate, and isobutyl acetate; alcohol solvents such as methanol, ethanol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; and ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

[0122] A solvent-free adhesive is an adhesive that is applied to an object and then bonded to another object without necessarily undergoing a process of heating in an oven or the like to volatilize the solvent. In the case of a two-component curing adhesive, both the base agent and the curing agent are substantially free of solvent. "Substantially free" includes cases where the solvent used as a reaction medium during the production of the adhesive's components, or the base agent and / or curing agent in the case of a two-component curing adhesive, is not completely removed, leaving trace amounts of solvent remaining in the adhesive, or the base agent and / or curing agent in the case of a two-component curing adhesive.

[0123] The two-component curing polyurethane adhesive has a base agent and a curing agent. The two-component curing polyurethane adhesive may be a solvent-based or solventless type. The two-component curing polyurethane adhesive will be described below.

[0124] A polyurethane adhesive, for example, has a base agent containing a polyol compound and a curing agent containing a polyisocyanate compound. Examples of the cured product (reaction product) formed by mixing such a base agent and curing agent include polyurethane, specifically polyester polyurethane, polyether polyurethane, polycarbonate polyurethane, and acrylic polyurethane.

[0125] The polyol compound has two or more hydroxy groups in one molecule. Examples of the polyol compound include polyester polyurethane polyol, polyester polyol, polyether polyol, polycarbonate polyol, and acrylic polyol. Among these, polyester polyurethane polyol and polyester polyol are preferred from the viewpoint that an adhesive layer having an elastic modulus in the above-mentioned range can be easily obtained, and in the case of a solvent-based adhesive, polyester polyurethane polyol is more preferred, and in the case of a solventless adhesive, polyester polyol is more preferred.

[0126] Polyester polyurethane polyols are compounds having two or more hydroxy groups, two or more ester bonds, and two or more urethane bonds in one molecule, and have, for example, a polyester polyurethane structure as the main backbone. Polyester polyols are compounds having two or more hydroxy groups and two or more ester bonds in one molecule, and have, for example, a polyester structure as the main backbone. Polyether polyols are compounds having two or more hydroxy groups and two or more ether bonds in one molecule. Polycarbonate polyols are compounds having two or more hydroxy groups and two or more carbonate bonds in one molecule.

[0127] The weight average molecular weight (Mw) of the polymer component (e.g., polyol compound) contained in the base agent of the two-component curing solvent-based adhesive is preferably 11,000 or more, more preferably 13,000 or more, even more preferably 15,000 or more, even more preferably 18,000 or more, and particularly preferably 20,000 or more, from the viewpoint of coatability, and is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 40,000 or less. The smaller the Mw, the higher the elastic modulus of the adhesive layer tends to be, and the larger the Mw, the lower the elastic modulus of the adhesive layer tends to be. The polydispersity (Mw / Mn) of the polymer component (e.g., polyol compound) contained in the base agent is preferably 5.0 or less, more preferably 4.5 or less, even more preferably 4.0 or less, and preferably 1.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more. Here, Mn is the number average molecular weight of the polymer component (e.g., polyol compound) contained in the base agent. Each average molecular weight is measured by gel permeation chromatography (GPC) in accordance with JIS K7252-1:2016 and is a value converted into polystyrene.

[0128] The weight average molecular weight (Mw) of the polymer component (e.g., polyol compound) contained in the base agent of the two-component curing, solventless adhesive is preferably 800 or more, more preferably 1,200 or more, even more preferably 2,000 or more, from the viewpoint of coatability, and is preferably 10,000 or less, more preferably 8,000 or less, even more preferably 6,000 or less. The smaller the Mw, the higher the elastic modulus of the adhesive layer tends to be, and the larger the Mw, the lower the elastic modulus of the adhesive layer tends to be. The polydispersity (Mw / Mn) of the polymer component (e.g., polyol compound) contained in the base agent is preferably 2.8 or less, more preferably 2.7 or less, even more preferably 2.6 or less, particularly preferably 2.5 or less, and preferably 1.2 or more, more preferably 1.5 or more, even more preferably 2.0 or more. Here, Mn is the number average molecular weight of the polymer component (e.g., polyol compound) contained in the base agent.

[0129] The polyisocyanate compound has two or more isocyanate groups in one molecule. Examples of the polyisocyanate compound include aromatic isocyanates and aliphatic isocyanates. The polyisocyanate compound may be a blocked isocyanate compound obtained by addition reaction using a known isocyanate blocking agent by a known, conventional, appropriate method.

[0130] Examples of polyisocyanate compounds include aliphatic isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), norbornene diisocyanate, and isophorone diisocyanate (IPDI); aromatic isocyanate compounds such as diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate, tolylene diisocyanate (TDI), naphthalene diisocyanate, and α,α,α',α'-tetramethyl-m-xylylene diisocyanate; dimers and trimers (e.g., isocyanurates) derived from these compounds; and adducts, biuret compounds, and allophanate compounds obtained by reacting these compounds with low-molecular-weight active hydrogen compounds or alkylene oxide adducts thereof, or high-molecular-weight active hydrogen compounds.

[0131] Examples of low molecular weight active hydrogen compounds include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexamethylene glycol, 1,8-octamethylene glycol, 1,4-cyclohexanedimethanol, metaxylylene alcohol, 1,3-bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and metaxylylenediamine, with trimethylolpropane being preferred. Examples of high molecular weight active hydrogen compounds include polyesters, polyether polyols, and polyamides.

[0132] The base agent containing a polyol compound and the curing agent containing a polyisocyanate compound are preferably used in an amount ratio such that the molar ratio (NCO / OH) of all isocyanate groups in the polyisocyanate compound to all hydroxy groups in the polyol compound is as follows: That is, the molar ratio (NCO / OH) is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 1.5 or more, and preferably 8.0 or less, more preferably 6.0, even more preferably 5.0 or less, and in the case of a solventless adhesive, even more preferably 4.0 or less, particularly preferably 3.0 or less. The larger the molar ratio (NCO / OH), the higher the elastic modulus of the adhesive layer tends to be, and the smaller the molar ratio (NCO / OH), the lower the elastic modulus of the adhesive layer tends to be.

[0133] <Sealant Layer> The laminate of the present disclosure includes a sealant layer. The sealant layer is an unstretched polypropylene film containing polypropylene as a primary component. The sealant layer contains the same type of resin material as the stretched polypropylene substrate, i.e., polypropylene as a primary component. This allows the laminate to be made into a mono-material. In other words, after collecting used packaging bags, there is no need to separate the substrate and the sealant layer, improving the recyclability of the packaging bags. The sealant layer may have a single-layer structure or a multi-layer structure.

[0134] The polypropylene content in the sealant layer is preferably more than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 85% by mass or more, 90% by mass or more, or 95% by mass or more. A laminate including such a sealant layer has excellent recyclability, for example.

[0135] Examples of polypropylene include propylene homopolymers, propylene random copolymers such as propylene-α-olefin random copolymers, and propylene block copolymers such as propylene-α-olefin block copolymers. Details of α-olefins are as described above. From the viewpoint of heat sealability, the density of polypropylene is, for example, 0.88 g / cm. ３ 0.92g / cm or more ３ The density is measured in accordance with JIS K7112:1999, Method D (density gradient tube method, 23°C). From the viewpoint of reducing the environmental load, biomass-derived polypropylene and / or recycled polypropylene may be used. The sealant layer may contain the above-mentioned additives.

[0136] The thickness of the sealant layer is preferably 10 μm or more, more preferably 20 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, for example, 10 μm or more and 200 μm or less. A laminate having a sealant layer whose thickness is equal to or greater than the lower limit has, for example, excellent seal strength. A laminate having a sealant layer whose thickness is equal to or less than the upper limit has, for example, excellent processability. When a pouch (particularly a retort pouch) is produced from the laminate, the thickness of the sealant layer is preferably 30 μm or more and preferably 100 μm or less.

[0137] The sealant film can be produced by, for example, a conventionally known method. The sealant film can be obtained by mixing the above-mentioned materials by a conventional method and molding the resulting mixture into a film by a conventional method. The sealant film is preferably a film obtained by extrusion molding. The extrusion molding is preferably carried out by a T-die method or an inflation method. Specifically, the materials constituting the sealant film are dried as necessary, and then fed into a melt extruder heated to a temperature equal to or higher than the melting point of the material to melt the material, and extruded into a film form through a die such as a T-die, and the extruded film is rapidly cooled and solidified on a rotating cooling drum or the like, thereby forming a sealant film.

[0138] As the melt extruder, a single-screw extruder, a twin-screw extruder, a vent extruder, a tandem extruder, etc. can be used depending on the purpose. The temperature of the molten polymer when extruded from the melt extruder may be, for example, 200°C or higher and 300°C or lower, or 220°C or higher and 270°C or lower.

[0139] The composite elastic modulus of the sealant layer is preferably 900 MPa or less, more preferably 830 MPa or less, even more preferably 700 MPa or less, and is also preferably 300 MPa or more, more preferably 400 MPa or more, even more preferably 500 MPa or more, for example, 300 MPa or more and 900 MPa or less. Packaging bags produced using a laminate having a sealant layer with a composite elastic modulus within the above range tend to have excellent impact resistance, and therefore excellent resistance to bag breakage due to dropping.

[0140] The composite modulus of the sealant layer is measured by nanoindentation. Specifically, a nanoindenter is used to measure the composite modulus using the cross section of the sealant layer of the laminate as the measurement surface. The cross section is obtained by folding the laminate of the present disclosure into a V-shape with the sealant film side facing inward and heat-sealing it to a width of 130 mm and a height of 165 mm to produce a bag-like pouch. 100 mL of water is filled into the resulting pouch through the opening, and the opening is heat-sealed. The pouch is then cut in the thickness direction of the laminate after hot water retort sterilization at a retort temperature of 121°C for 30 minutes. The indenter is pressed into three positions in the thickness direction of the exposed cross section of the sealant layer: a position 2 μm inward from the interface with the adhesive layer, a position near the center, and a position 2 μm inward from the seal surface. For example, if the sealant layer has a three-layer structure, the position 2 μm inward from the sealing surface corresponds to the first layer (sealing layer), the position near the center corresponds to the second layer (core layer), and the position 2 μm inward from the interface with the adhesive layer corresponds to the third layer (surface layer). The measurement conditions are as follows: A Berkovich indenter (triangular pyramid indenter) is used as the indenter of the nanoindenter. The indenter is pressed into the sealant layer from the cross section of the sealant layer to a depth of 100 nm over 3 seconds, held in that state for 5 seconds, and then unloaded over 3 seconds, until the maximum load P ｍａｘ , contact projection area A at maximum depth ｐ A load-displacement curve is obtained. From the load-displacement curve obtained, the composite elastic modulus is calculated using the following formula (1).

[0141] In formula (1), A ｐ is the contact projection area, S is the contact stiffness, and E ｒ is the composite modulus of the sealant layer.

[0142] Measurements are performed at room temperature (23°C). Measurements are performed at five or more locations (five points) on the same cross section, and the composite modulus is reported as the arithmetic mean of the values ​​measured at five locations (five points) with good reproducibility. In the case where the sealant layer has a multilayer structure including two or more layers, the arithmetic mean calculated from the values ​​measured at a position near the center corresponding to the core layer is used as the composite modulus of the sealant layer. Details of the measurement conditions are described in the Examples section.

[0143] When the sealant layer contains a propylene block copolymer, the composite modulus of elasticity of the sealant layer can be adjusted by the content of ethylene-propylene rubber (EPR). Specifically, the higher the content of ethylene-propylene rubber (EPR), the lower the composite modulus of elasticity, while the lower the content, the higher the composite modulus of elasticity. Furthermore, when the sealant layer contains a propylene block copolymer, the composite modulus of elasticity of the sealant layer can be adjusted by the content of additives such as polyethylene and elastomer. Specifically, the higher the content of additives, the lower the composite modulus of elasticity, while the lower the content, the higher the composite modulus of elasticity.

[0144] From the viewpoint of heat sealing property, the sealant layer is preferably an unstretched polypropylene film, which can be produced by, for example, a casting method, a T-die method, an inflation method, etc. The sealant layer may be subjected to the above-mentioned surface treatment.

[0145] [Packaging Bag] The laminate of the present disclosure is suitable for use as a packaging material. The packaging material is used to produce a packaging bag. The packaging bag of the present disclosure includes the laminate. A packaging bag can be produced by using the laminate of the present disclosure as a packaging material. In one embodiment, a packaging bag can be produced by folding the laminate of the present disclosure in half and overlapping them so that the substrate or first substrate is on the outside and the sealant layer is on the inside, and then heat-sealing the edges, etc. In another embodiment, a packaging bag can be produced by overlapping multiple laminates of the present disclosure so that the sealant layers face each other, and heat-sealing the edges, etc. The entire packaging bag may be composed of the laminate, or only a portion of the packaging bag may be composed of the laminate.

[0146] Examples of packaging bags include various types of packaging bags such as standing pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, palm seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type. Examples of heat sealing methods include bar seal, rotary roll seal, belt seal, impulse seal, high frequency seal, and ultrasonic seal.

[0147] The packaging bag may have an easy-to-open portion. Examples of the easy-to-open portion include a notch portion that serves as a starting point for tearing the packaging bag, and a half-cut line formed by laser processing or a cutter as a path for tearing the packaging bag.

[0148] The packaging bag may be equipped with a steam release mechanism. The steam release mechanism is configured to connect the inside and outside of the packaging bag when the steam pressure inside the packaging bag reaches or exceeds a predetermined value, allowing steam to escape while preventing steam from escaping at locations other than the steam release mechanism. The steam release mechanism, for example, includes a steam release seal portion that protrudes from the side seal portion toward the inside of the packaging bag, and a non-sealed portion that is isolated from the content storage portion by the steam release seal portion. The non-sealed portion communicates with the outside of the packaging bag. The packaging bag, which has been filled with contents and has a heat-sealed opening, is heated using a microwave oven or the like. This increases the internal pressure and causes the steam release seal portion to peel. Steam passes through the peeled portion of the steam release seal portion and the non-sealed portion to escape to the outside of the packaging bag.

[0149] The contents contained in the packaging bag may be, for example, liquids, solids, powders, and gels. The contents may be food or beverages, or non-food or beverages such as chemicals, cosmetics, pharmaceuticals, metal parts, and electronic parts. After the contents are contained in the packaging bag, the opening of the packaging bag can be heat-sealed to seal the bag. The contents may also be heat-sterilized foods (heat-sterilized foods such as retort foods, boiled foods, and pasteurized beverages). The packaging bag of the present disclosure may be a pouch that contains heat-sterilized foods.

[0150] As specific examples of packaging bags, sachets and stand-up pouches will be described below. Sachets are small packaging bags used to hold contents of, for example, 1 g to 200 g. Examples of contents that can be held in sachets include sauces, soy sauce, dressings, ketchup, syrup, cooking alcohol, and other liquid or viscous seasonings; liquid soups, powdered soups, fruit juices; spices; pet food; liquid beverages, jelly-like beverages, instant foods, and other food and beverage products; and non-food products such as chemicals, cosmetics, pharmaceuticals, metal parts, and electronic parts.

[0151] Stand-up pouches are used to store contents of, for example, 50 g to 2000 g. Examples of contents that can be stored in stand-up pouches include shampoo, rinse, conditioner, hand soap, body soap, air freshener, deodorant, insect repellent, detergent; dressing, cooking oil, mayonnaise, other liquid or viscous seasonings; liquid beverages, jelly-like beverages, instant foods, other foods and beverages; pet food; cream; metal parts, and electronic parts.

[0152] In one embodiment, the contents of the packaging bag are pet food.

[0153] In one embodiment, the packaging bag of the present disclosure is suitable as a heat sterilization pouch or a microwave-safe packaging bag because it can suppress deterioration of gas barrier properties even when subjected to heat treatment. The packaging bag of the present disclosure is also suitable as a boil or retort pouch for microwave ovens. Here, a heat sterilization pouch refers to either a pouch that can be heat sterilized while containing contents, or a pouch that has been heat sterilized while containing contents. Furthermore, a microwave-safe packaging bag refers to a packaging bag that can be heated using a microwave oven.

[0154] Examples of heat sterilization pouches include pouches that have been subjected to pressure heat sterilization (hereinafter also referred to as "retort pouches"), pouches that have been subjected to boiling (hereinafter also referred to as "boil pouches"), and pouches that have been subjected to pasteurization (hereinafter "pasteurization pouches"). Retort pouches are packaging pouches that have been filled with contents such as food or drink and sealed, and then subjected to heat sterilization (pressure heat sterilization) using water or steam at a temperature exceeding 100°C under pressure. Boil pouches and pasteurization pouches are packaging pouches that have been filled with contents such as food or drink and sealed, and then subjected to boiling at a temperature of 100°C or less.

[0155] In one embodiment, the packaging bag of the present disclosure is a retort pouch. The conditions for the pressure and heat sterilization treatment can vary, but any pouch that has undergone a general pressure and heat sterilization treatment is included in the retort pouch. Among pressure and heat sterilization treatments, for example, a treatment temperature of 105°C or higher and 115°C or lower may be referred to as semi-retort treatment, a treatment temperature of higher than 115°C but lower than 130°C may be referred to as retort treatment, and a treatment temperature of higher than 135°C but lower than 140°C may be referred to as high-retort treatment. The retort treatment time is, for example, 5 minutes or longer and 60 minutes or shorter, preferably 15 minutes or longer and 40 minutes or shorter.

[0156] In one embodiment, the packaging bag of the present disclosure is a retort pouch. The oxygen permeability (unit: cc / m) of the retort pouch of the present disclosure is 2 ·day·atm) is measured in accordance with JIS K7126-2:2006 at a temperature of 23°C and a relative humidity of 90% RH. The oxygen transmission rate of the retort pouch is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.0 or less. If the oxygen transmission rate of the retort pouch after retort treatment is 3.0 or less, it can be suitably used as food packaging for long-term storage. The lower the lower limit of the oxygen transmission rate of the retort pouch, the better, but it may be, for example, 0.1.

[0157] 7 shows a packaging bag 50 obtained by bonding two laminates together. The hatched areas indicate the heat-sealed areas. The packaging bag 50 may have an easy-to-open portion 51. Examples of the easy-to-open portion 51 include a notch portion 52 that serves as a tearing starting point and a half-cut line 53 formed by laser processing or a cutter as a tearing path.

[0158] Figure 8 shows a simplified example of the configuration of a stand-up pouch. The shaded areas indicate the heat-sealed areas. In one embodiment, the stand-up pouch 60 comprises a body portion (side sheets) 61 and a bottom portion (bottom sheet) 62. The side sheets 61 and the bottom sheet 62 may be made of the same material, or may be made of different materials. The bottom sheet 62 maintains the shape of the side sheets 61, thereby imparting self-supporting properties to the pouch and enabling it to become a standing pouch. A storage space for storing contents is formed within the area surrounded by the side sheets 61 and the bottom sheet 62.

[0159] The standing pouch 60 may include a steam release mechanism 63. The steam release mechanism 63 includes a steam release seal portion 63a that protrudes from the side seal portion toward the inside of the packaging bag, and a non-sealed portion 63b that is isolated from the content-accommodating portion by the steam release seal portion 63a. The non-sealed portion 63b communicates with the outside of the packaging bag.

[0160] In a stand-up pouch, only the body portion may be made of the laminate of the present disclosure, only the bottom portion may be made of the laminate, or both the body portion and the bottom portion may be made of the laminate.

[0161] In one embodiment, the side sheet can be formed by forming a bag so that the sealant layer of the laminate of the present disclosure is the innermost layer. In one embodiment, the side sheet can be formed by preparing two laminates of the present disclosure, overlapping them so that the sealant layers face each other, and heat-sealing both side edges to form a bag.

[0162] In another embodiment, the side sheets can be formed by preparing two laminates of the present disclosure, overlapping them with the sealant layers facing each other, inserting two V-shaped laminates with the sealant layers facing outward between the laminates at both side edge portions of the overlapped laminates, and heat sealing them. This production method provides a stand-up pouch having a body portion with side gussets.

[0163] In one embodiment, the bottom sheet can be formed by inserting a laminate between the lower portions of the side sheets and heat sealing the laminate. More specifically, the bottom sheet can be formed by inserting a laminate folded into a V shape with the sealant layer facing outward between the lower portions of the side sheets and heat sealing the laminate.

[0164] In one embodiment, two laminates are prepared and stacked together with the sealant layers facing each other. Next, another laminate is folded in a V shape with the sealant layer facing outward, and this is sandwiched under the two laminates that have been stacked together and heat-sealed to form a bottom. Next, two sides adjacent to the bottom are heat-sealed to form a body. In this manner, a stand-up pouch according to one embodiment can be formed.

[0165] [Mechanism of Action] Laminates for packaging materials are used to produce packaging bags such as retort pouches. Packaging bags using the laminate are opened after undergoing retort treatment or the like with the contents inside. Here, gas barrier properties are required for the packaging bag after retort treatment, so a barrier substrate is used for the laminate. However, if the interlayer adhesion strength is weak in a laminate including a gas barrier substrate and a sealant layer, the packaging bag after retort treatment will lack drop impact resistance. Therefore, it is preferable that the interlayer adhesion be maintained even after retort treatment for a laminate used for a packaging bag.

[0166] If the adhesive layer provided between the layers is made thicker to improve the adhesion between the layers of the laminate, the adhesive may overflow when the laminate is wound up, causing blocking, or the lack of initial tack before curing may cause slippage during winding. Therefore, there is a limit to how much thickness can be adjusted using only the adhesive layer.

[0167] The laminate of the present disclosure comprises a barrier substrate and a sealant layer laminated together via an adhesive layer, with the elastic modulus and thickness of the adhesive layer and the elastic modulus of the sealant layer specified. The stretched polypropylene substrate constituting the barrier substrate is a stretched substrate having a multilayer structure including at least a first surface resin layer, a polypropylene layer, and a second surface resin layer, with the second surface resin layer containing a specific component facing the adhesive layer. This provides a strong bond between the second surface resin layer and the adhesive layer, resulting in excellent adhesion strength between the barrier substrate and the sealant layer in the laminate even after retort treatment. Therefore, when used in packaging bags such as retort pouches, the laminate of the present disclosure exhibits excellent drop impact resistance after retort treatment. Furthermore, the laminate of the present disclosure also exhibits excellent openability after retort treatment, since the elastic modulus and thickness of the adhesive layer and the elastic modulus of the sealant layer are specified.

[0168] The present disclosure relates to, for example, the following [1] to

[11] : [1] A laminate including a second substrate, a second adhesive layer, and a sealant layer in this order in the thickness direction, wherein the laminate includes only one substrate, the second substrate has a multilayer structure including a first surface resin layer, a polypropylene layer, and a second surface resin layer in this order in the thickness direction, and the second surface resin layer is disposed so as to face the second adhesive layer, the second surface resin layer contains 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene with respect to the total amount of the second surface resin layer, the second adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer is an unstretched polypropylene film and has a composite elastic modulus of 900 MPa or less. [2] A laminate comprising a first substrate, a first adhesive layer, a second substrate, a second adhesive layer, and a sealant layer, in this order in the thickness direction, wherein the first substrate is a stretched polypropylene substrate, the second substrate has a multilayer structure comprising a first surface resin layer, a polypropylene layer, and a second surface resin layer, in this order in the thickness direction, and is disposed so that the first surface resin layer faces the first adhesive layer and the second surface resin layer faces the second adhesive layer, the second surface resin layer contains 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene, relative to the total amount of the second surface resin layer, the second adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer is an unstretched polypropylene film and has a composite elastic modulus of 900 MPa or less. [3] The laminate according to [1] or [2], wherein the random copolymer comprises at least one of a propylene-ethylene random copolymer and a propylene-ethylene-butene random copolymer. [4] The laminate according to [1] or [2], wherein the polypropylene layer has a propylene homopolymer content of more than 50 mass%. [5] The laminate according to [1] or [2], wherein the first surface resin layer has the same structure as the second surface resin layer. [6] The laminate according to [1] or [2], wherein the laminate comprises one or more barrier layers.[7] The laminate according to [1] or [2], wherein the content of polypropylene relative to the total amount of resin materials contained in the laminate is 80% by mass or more. [8] The laminate according to any one of [1] to [7], which is a packaging material. [9] A packaging bag comprising the laminate according to [8].

[10] The packaging bag according to [9], which is a pouch for containing heat-sterilized food.

[11] A heat-sterilization pouch comprising the packaging bag of [9] or

[10] and heat-sterilized food contained in the packaging bag.

[0169] One embodiment of the present disclosure relates to, for example, the following [1A] to [13A]: [1A] A laminate including a substrate, an adhesive layer, and a sealant layer in this order in the thickness direction, wherein the substrate is a barrier substrate including, in this order in the thickness direction, a stretched substrate containing polypropylene as a main component and an inorganic oxide layer, the stretched substrate has a multilayer structure including, in this order in the thickness direction, a first surface resin layer, a polypropylene layer, and a second surface resin layer, and is disposed so that the first surface resin layer faces the inorganic oxide layer and the second surface resin layer faces the adhesive layer, the second surface resin layer contains 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene, relative to the total amount of the second surface resin layer, the adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer contains polypropylene as a main component and has a composite elastic modulus of 900 MPa or less. [2A] The laminate according to [1A], wherein the random copolymer comprises at least one of a propylene-ethylene random copolymer and a propylene-ethylene-butene random copolymer. [3A] The laminate according to [1A] or [2A], wherein the polypropylene layer contains a propylene homopolymer as a main component. [4A] The laminate according to any one of [1A] to [3A], wherein the first surface resin layer has the same structure as the second surface resin layer. [5A] The laminate according to any one of [1A] to [4A], wherein the adhesive layer has a value obtained by multiplying the elastic modulus (MPa) and the thickness (μm) of 35 or more and 95 or less. [6A] The laminate according to any one of [1A] to [5A], wherein the substrate further comprises a coating layer on a surface of the inorganic oxide layer opposite to the surface facing the stretched substrate. [7A] The laminate according to any one of [1A] to [6A], wherein the laminate comprises a first substrate, a second substrate, the adhesive layer, and the sealant layer in this order in the thickness direction, the second substrate is the barrier substrate, and the stretched substrate is disposed so that the first surface resin layer faces the inorganic oxide layer and the second surface resin layer faces the adhesive layer. [8A] The laminate according to [7A], wherein the first substrate is a stretched substrate containing polypropylene as a main component.[9A] The laminate according to [7A] or [8A], comprising: a first adhesive layer positioned between the first substrate and the second substrate; and a second adhesive layer positioned between the second substrate and the sealant layer, wherein the second adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the stretched substrate constituting the second substrate is disposed so that the first surface resin layer faces the inorganic oxide layer and the second surface resin layer faces the second adhesive layer. [10A] The laminate according to any one of [1A] to [9A], wherein a polypropylene content ratio relative to the total amount of resin materials contained in the laminate is 80 mass% or more. [11A] The laminate according to [10A], which is a packaging material. [12A] A packaging bag comprising the laminate according to [11A]. [13A] The packaging bag according to [12A], which is a pouch that has been retorted or boiled.

[0170] The laminate and packaging bag of the present disclosure will be specifically described below based on specific examples.

[0171] [Preparation of Transparent Barrier Substrate] Transparent Barrier Substrate 1 A hydroxyl-containing acrylic resin (number average molecular weight: 25,000, glass transition temperature: 99°C, hydroxyl value: 80 mgKOH / g) was diluted with a mixed solvent of methyl ethyl ketone and ethyl acetate (mixing ratio 1:1) to a solids concentration of 10 mass% to prepare a base material. An ethyl acetate solution containing tolylene diisocyanate (solids content 75 mass%) was added to the base material as a curing agent to obtain a solution for forming a surface coating layer. The amount of curing agent used was 10 mass parts per 100 mass parts of the base material.

[0172] A 20 μm-thick biaxially oriented polypropylene film was prepared, one side of which was corona-treated. The biaxially oriented polypropylene film was composed of three layers: a first surface resin layer (first skin layer) of 0.6 μm, a polypropylene layer (core layer) of 18.8 μm, and a second surface resin layer (second skin layer) of 0.6 μm. The resin content of the resin composition constituting the first and second surface resin layers was 100% by mass of propylene-ethylene-butene random copolymer. The resin content of the resin composition constituting the polypropylene layer (core layer) was 100% by mass of homopolypropylene. The surface coating layer-forming solution was applied to the corona-treated surface of the film (the surface of the first surface resin layer) and dried to form a surface coating layer with a thickness of 0.5 μm. In this manner, a resin substrate was obtained.

[0173] A carbon-containing silicon oxide (silica) vapor-deposited film having a thickness of 12 nm was formed on the surface coating layer of the resin substrate by a roll-to-roll method using a low-temperature plasma chemical vapor deposition apparatus while applying tension to the resin substrate (CVD method). The vapor-deposited film formation conditions were as follows:

[0174] (Forming conditions) Hexamethyldisiloxane: oxygen gas: helium = 1:10:10 (unit: slm) Power supplied to cooling / electrode drum: 22 kW Line speed: 100 m / min

[0175] The carbon percentage C, silicon percentage Si, and oxygen percentage O in the carbon-containing silicon oxide vapor-deposited film were measured. The carbon percentage C, silicon percentage Si, and oxygen percentage O were 32.7%, 29.8%, and 37.5%, respectively, based on a total of 100% for the three elements silicon, oxygen, and carbon. The percentages of each element were measured by narrow scan analysis using X-ray photoelectron spectroscopy (XPS) under the measurement conditions described above.

[0176] 385 g of water, 67 g of isopropyl alcohol, and 9.1 g of 0.5 N hydrochloric acid were mixed to obtain a solution with a pH of 2.2. This solution was mixed with 175 g of tetraethoxysilane as a metal alkoxide and 9.2 g of glycidoxypropyltrimethoxysilane as a silane coupling agent while cooling to 10°C to obtain solution A. 14.7 g of polyvinyl alcohol having a saponification degree of 99% or more and a polymerization degree of 2400 as a water-soluble polymer, 324 g of water, and 17 g of isopropyl alcohol were mixed to obtain solution B. Solution A and solution B were mixed at a mass ratio (solution A:solution B) of 6.5:3.5 to obtain a barrier coating agent. The barrier coating agent was coated on a vapor-deposited film formed on a resin substrate by spin coating, and the mixture was heated in an oven at 80°C for 60 seconds to form a barrier coating layer with a thickness of 300 nm.

[0177] In this way, a transparent barrier substrate (IBOPP) 1 was obtained which was provided, in this order, with a 20 μm-thick biaxially oriented polypropylene film, a 0.5 μm-thick surface coating layer, a 12 nm-thick carbon-containing silicon oxide (silica) vapor-deposited film, and a 300 nm-thick barrier coating layer.

[0178] Transparent barrier substrate 2 Transparent barrier substrate (IBOPP) 2 was obtained in the same manner as the transparent barrier substrate 1 described above, except that a biaxially oriented polypropylene film having a propylene-ethylene random copolymer content of 100 mass % was used for the second surface resin layer instead of the 20 μm-thick biaxially oriented polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello, Inc.).

[0179] Transparent barrier substrate 3 Transparent barrier substrate (IBOPP) 3 was obtained in the same manner as the above-mentioned transparent barrier substrate 1, except that the 20 μm-thick biaxially oriented polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello, Inc.) was replaced with a biaxially oriented polypropylene film having a propylene homopolymer content of 50 mass % and a propylene-ethylene-butene random copolymer content of 50 mass % for the second surface resin layer.

[0180] Transparent barrier substrate 4 Transparent barrier substrate (IBOPP) 4 was obtained in the same manner as the above-mentioned transparent barrier substrate 1, except that the 20 μm-thick biaxially oriented polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello, Inc.) was replaced with a biaxially oriented polypropylene film having a propylene homopolymer content of 70 mass % and a propylene-ethylene-butene random copolymer content of 30 mass % for the second surface resin layer.

[0181] Transparent barrier substrate 5 Transparent barrier substrate (IBOPP) 5 was obtained in the same manner as the transparent barrier substrate 1 described above, except that a biaxially oriented polypropylene film not having a second surface resin layer was used instead of the 20 μm-thick biaxially oriented polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello, Inc.).

[0182] [Adhesive] A two-component curing adhesive composed of the following base and curing agent was used. Adhesive A Base: Polyester polymer (Mw: 4,000) Curing agent: Mixture of HDI and XDI Molar ratio of base to curing agent (NCO / OH): 2 Adhesive A does not substantially contain solvent. Adhesive B Base: Polyester polyurethane polymer (Mw: 30,000) Curing agent: Mixture of isophorone diisocyanate (IPDI) trimer and xylylene diisocyanate (XDI) trimethylolpropane (TMP) adduct Molar ratio of base to curing agent (NCO / OH): 4 Adhesive B contains a solvent. Adhesive C Base: Polyester polymer (Mw: 30,000) Curing agent: Mixture of biuret form of hexamethylene diisocyanate (HDI) and nurate form of HDI Molar ratio of base to curing agent (NCO / OH): 2 Adhesive C does not substantially contain solvent. Adhesive D Base: Polyester polymer (Mw: 3,500) Curing agent: Mixture of IPDI and HDI (HDI content is higher than IPDI) Molar ratio of base to curing agent (NCO / OH): 2 Adhesive D does not substantially contain solvent.

[0183] [Unstretched Polypropylene Film] The following unstretched polypropylene substrates (hereinafter referred to as "CPP") were used: CPP film 1: A 60 μm thick unstretched polypropylene film (composite modulus: 691.1 MPa) with one surface corona-treated; CPP film 2: A 60 μm thick unstretched polypropylene film (composite modulus: 902.2 MPa) with one surface corona-treated.

[0184] [Example 1] A 20 μm-thick biaxially stretched polypropylene film (P2171, manufactured by Toyobo Co., Ltd., hereinafter also referred to as "OPP film") having one surface corona-treated was prepared as the first substrate. The transparent barrier substrate 1 described above was prepared as the second substrate. A CPP film 1 was prepared as the sealant layer.

[0185] A printed layer with a coating thickness of 1 μm (when dried) was formed on the corona-treated surface of an OPP film serving as the first substrate by gravure roll coating. Adhesive A was applied to the printed layer as a first adhesive layer by gravure roll coating, and the adhesive layer surface formed on the first substrate and the barrier coat layer surface of the transparent barrier substrate were bonded together, followed by aging at 40°C for 72 hours. Furthermore, the surface of the second surface resin layer of the transparent barrier substrate 1 was subjected to corona treatment, and Adhesive A was applied to a second adhesive layer by gravure roll coating, and the adhesive layer surface formed on the second surface resin layer of the transparent barrier substrate 1 and the corona-treated surface of the CPP film 1 were bonded together, followed by aging at 40°C for 72 hours. The thickness of each adhesive layer formed was 2.0 μm.

[0186] A laminate was obtained in this manner. The obtained laminate had a layer structure of OPP film (20 μm) / printed layer (1 μm) / adhesive layer (2.0 μm) / transparent barrier substrate 1 (21 μm) / adhesive layer (2.0 μm) / CPP film 1 (60 μm). The numbers in parentheses indicate the thickness of each layer. The second surface resin layer constituting the transparent barrier substrate had a propylene-ethylene-butene random copolymer content of 100% by mass.

[0187] [Examples 2 to 4] Laminates were produced in the same manner as in Example 1, except that the type of adhesive and / or the thickness of the second adhesive layer was changed as shown in Table 1. Here, the thickness of the first adhesive layer was also changed in the same way as the thickness of the second adhesive layer.

[0188] Examples 5 and 6 Laminates were prepared in the same manner as in Example 1, except that the type of the transparent barrier substrate used as the second substrate was changed as shown in Table 1.

[0189] Example 7 A laminate having a two-layer structure was produced in the same manner as in Example 1, except that the first substrate and the first adhesive resin layer were not used.

[0190] Comparative Example 1 A laminate was produced in the same manner as in Example 1, except that the type of the transparent barrier substrate used as the second substrate was changed as shown in Table 1.

[0191] [Comparative Examples 2 and 3] Laminates were produced in the same manner as in Example 1, except that the type of adhesive and / or the thickness of the second adhesive layer was changed as shown in Table 1. Here, the thickness of the first adhesive layer was also changed in the same way as the thickness of the second adhesive layer.

[0192] Comparative Examples 4 and 5 Laminates were prepared in the same manner as in Example 1, except that the type of adhesive was changed as shown in Table 1.

[0193] Comparative Example 6 A laminate was produced in the same manner as in Example 1, except that the unstretched polypropylene film as the sealant layer was changed to CPP film 2.

[0194] Comparative Example 7 A laminate was produced in the same manner as in Example 1, except that the type of the transparent barrier substrate used as the second substrate was changed as shown in Table 1.

[0195] [Measurement of Elastic Modulus] (Elastic Modulus of Adhesive Layer) The force curve of the laminate obtained in the above example was measured using an atomic force microscope (AFM), and the elastic modulus of the cross section of the adhesive layer was determined from the obtained force curve. The specific measurement procedure is as follows. The laminate obtained in the above example was embedded in an embedding resin to prepare a block, and the block was cut using a commercially available rotary microtome at room temperature (25°C) to prepare a cross section of the laminate. The cross section was obtained by cutting in the thickness direction perpendicular to the main surface of the laminate. Finishing was performed using a diamond knife. Using an atomic force microscope (AFM), mapping measurement was performed on the above cross section at a 2.5 μm square, including the cross section of the adhesive layer. 20 force curves that obtained appropriate force curve shapes were selected for the cross section of the adhesive layer. Each force curve was fitted using the Johnson-Kendall-Roberts (JKR) theory to calculate the elastic modulus, and the arithmetic mean value of the resulting 20 elastic moduli (hereinafter also referred to as the "first arithmetic mean value") was calculated. Here, the selected location of the force curve was near the center in the thickness direction of the adhesive layer, among the exposed cross-sections of the adhesive layer. Three elastic moduli close to the first arithmetic mean value were selected from the 20 elastic moduli, and the arithmetic mean value of the three elastic moduli (hereinafter also referred to as the "second arithmetic mean value") was calculated. The resulting second arithmetic mean value was used as the elastic modulus of the cross-section of the adhesive layer.

[0196] Details of the AFM measurement conditions are shown below. (AFM Elastic Modulus Measurement) - Device name: SPM-9700HT (Shimadzu Corporation) - Measurement atmosphere: Air, room temperature (25°C) - Measurement mode: Contact mode - Calibration method: Cantilever sensitivity measured using glass - Number of measurement points: 64 x 64 points (4096 points in total) - Field of view: 2.5 μm square - Cantilever type: CONTR (Nanoworld) - Cantilever tip radius: <8 nm - Cantilever spring constant: 0.2 N / m - Contact pressure: 0.5 V - Scan speed: 3 Hz - Elastic modulus calculation model: Johnson-Kendall-Roberts (JKR) theory - Poisson's ratio of sample: 0.4 - Analysis software: Nano 3D Mapping (Shimadzu Corporation)

[0197] (Composite Elastic Modulus of Sealant Layer) The composite elastic modulus of the sealant layer (E ｒ The elastic modulus E was measured using a nanoindenter (Bruker TI950 TriboIndenter) based on the nanoindentation method, with the cross section of the sealant layer as the measurement surface. A Berkovich indenter (triangular pyramid indenter; Berkovich_TI0039) was used as the indenter for the nanoindenter. Measurements were performed at five or more points on the same cross section, and the composite elastic modulus E ｒ The value is expressed as the arithmetic mean value of five points measured with good reproducibility. The number of data points measured was 200 points / sec.

[0198] The measurement conditions were a load control method (indentation load 30 μN, load 3 seconds / hold 5 seconds / unload 3 seconds), specifically as follows: the indenter was pressed into the sealant layer from the cross section of the sealant layer up to an indentation load of 30 μN over 3 seconds, and held in that state for 5 seconds. The load was then released over 3 seconds. This resulted in a maximum load P ｍａｘ , contact projection area A at maximum depth ｐ and load-displacement curves were obtained, and the value of the composite elastic modulus was calculated from the obtained load-displacement curves. Measurements were carried out in a room temperature (23°C) environment. The indenter was pressed into the vicinity of the center in the thickness direction of the sealant layer, among the portions where the cross section of the sealant layer was exposed. The above cross section was obtained by cutting the laminate in the thickness direction perpendicular to the main surface. The cross section was prepared by embedding the laminate in an embedding resin to prepare a block, and cutting the block using a commercially available rotary microtome in a room temperature (23°C) environment. Finishing was carried out using a diamond knife.

[0199] [Lamination strength] The laminate obtained in the above example was folded into a V shape with the sealant film side facing inward, and heat-sealed to a width of 130 mm and a height of 165 mm to produce a bag-like pouch. 100 mL of water was filled into the resulting pouch through the opening, and the opening was heat-sealed to seal. The sealed pouch was subjected to a hot water retort sterilization treatment at a retort temperature of 121°C for 30 minutes. Test pieces were obtained by cutting the laminate after retort sterilization into 15 mm wide strips extending in the MD direction of the film. The laminate strength (N / 15 mm) of the test specimen was measured in accordance with JIS Z1707:2019 using a tensile tester (Tensilon universal material testing machine, manufactured by Orientec Co., Ltd.) at a temperature of 20°C and a relative humidity of 65% using a 90° peel (T-peel method) at a peel rate of 50 mm / min. Specifically, the laminate was first cut out, and the sealant layer side B and the substrate side A were pre-peeled 15 mm in the long side direction to prepare a strip-shaped test specimen 100. Then, as shown in FIG. 9, the already-peeled portions of the sealant layer side B and the substrate side A were each gripped with the measuring instrument's gripper 110. The grippers 110 were pulled in opposite directions perpendicular to the plane of the portion where the sealant layer side B and the substrate side A were still laminated at a speed of 50 mm / min, and the average tensile stress F in the stable region (see FIG. 10 ) was measured. The spacing S2 between the grippers 110 at the start of pulling was 30 mm, and the spacing S2 between the grippers 110 at the end of pulling was 60 mm. FIG. 10 is a schematic diagram showing the change in tensile stress F with respect to the spacing S2 between the grippers 110. As shown in FIG. 10 , the change in tensile stress F with respect to the spacing S2 passes through a first region R1 and enters a second region R2, where the rate of change is smaller than that of the first region R1. The second region R2 is also referred to as the stable region. The average value of tensile stress F in the stable region R2 was measured for five test pieces 100, and this average value was used as the laminate strength.

[0200] [Evaluation of Seal Strength] The laminate obtained in the above example was folded into a V shape with the sealant film side facing inward, and heat-sealed to a width of 130 mm and a height of 165 mm to produce a bag-shaped pouch. 100 mL of water was filled into the resulting pouch through the opening, and the opening was heat-sealed to seal. The sealed pouch was subjected to a hot water retort sterilization treatment at a retort temperature of 121°C and a retort time of 30 minutes. A 15 mm wide test piece was cut out perpendicular to the seal of the laminate after retort sterilization treatment, and the test piece was attached to a tensile tester (Strograph VG1F, manufactured by Toyo Seiki Seisakusho Co., Ltd.) so that two ends were supported, and the seal strength of the laminate was measured. <Measurement Conditions> Tensile test speed: 300 mm / min Chuck distance: 25 mm

[0201] [Evaluation of Impact Resistance] The laminate obtained above was folded into a V shape with the sealant film side facing inward, and heat-sealed to a width of 130 mm and a height of 165 mm to produce 10 bag-shaped pouches. 150 mL of water was filled into the resulting pouch through the opening, and the opening was heat-sealed to seal. The sealed pouch was dropped 10 times horizontally from a height of 80 cm onto the floor (so that the body of the pouch hit the floor), and then dropped 10 times vertically from a height of 80 cm onto the floor (so that the bottom of the pouch hit the floor). The number of pouches that broke out of the 10 pouches was counted to evaluate impact resistance. The results are shown in Tables 1 and 2. <Evaluation Criteria> A: No breakage. B: No breakage, but retraction of the seal position was observed. C: One or more pouches were broken.

[0202]

[0203]

[0204] 1: Laminate, 10: Stretched polypropylene substrate, 20: Barrier substrate, 22: Stretched polypropylene substrate, 22a: Polypropylene layer, 22b: First surface resin layer, 22c: Second surface resin layer, 23: Surface coating layer, 24: Inorganic oxide layer, 25: Coating layer, 30: Sealant layer, 40, 40A, 40B: Adhesive layer, 50: Packaging bag, 51: Easy-open portion, 52: Notch portion, 53: Half-cut line, 60: Standing pouch, 61: Body portion (side sheet), 62: Bottom portion (bottom sheet), 63: Steam release mechanism, 63a: Steam release seal portion, 63b: Non-seal portion, 100: Test piece, 110: Grip

Claims

1. A laminate comprising a second substrate, a second adhesive layer and a sealant layer in this order in the thickness direction, wherein the laminate has only one substrate, the second substrate has a multilayer structure comprising a first surface resin layer, a polypropylene layer and a second surface resin layer in this order in the thickness direction, and is disposed so that the second surface resin layer faces the second adhesive layer, the second surface resin layer contains 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene relative to the total amount of the second surface resin layer, the second adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer is an unstretched polypropylene film and has a composite elastic modulus of 900 MPa or less.

2. A laminate comprising a first substrate, a first adhesive layer, a second substrate, a second adhesive layer, and a sealant layer in this order in the thickness direction, wherein the first substrate is a stretched polypropylene substrate, the second substrate has a multilayer structure comprising a first surface resin layer, a polypropylene layer, and a second surface resin layer in this order in the thickness direction, and is arranged so that the first surface resin layer faces the first adhesive layer and the second surface resin layer faces the second adhesive layer, the second surface resin layer contains 50 mass% or more of a random copolymer of propylene and an α-olefin other than propylene relative to the total amount of the second surface resin layer, the second adhesive layer has a thickness of 1 μm or more and 4.5 μm or less and an elastic modulus of 20 MPa or more and 50 MPa or less, and the sealant layer is an unstretched polypropylene film and has a composite elastic modulus of 900 MPa or less.

3. The laminate according to claim 1 or 2, wherein the random copolymer comprises at least one of a propylene-ethylene random copolymer and a propylene-ethylene-butene random copolymer.

4. The laminate according to claim 1 or 2, wherein the polypropylene layer has a propylene homopolymer content of more than 50 mass%.

5. A laminate according to claim 1 or 2, wherein the first surface resin layer has the same structure as the second surface resin layer.

6. The laminate of claim 1 or 2, wherein the laminate comprises one or more barrier layers.

7. The laminate according to claim 1 or 2, wherein the content of polypropylene in the total amount of resin materials contained in the laminate is 80 mass % or more.

8. The laminate according to claim 1 or 2, which is a packaging material.

9. A packaging bag comprising the laminate according to claim 8.

10. The packaging bag according to claim 9, which is a pouch for containing heat-sterilized food.

11. A heat sterilization pouch comprising the packaging bag of claim 10 and a heat sterilized food contained in the packaging bag.

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