JP2024112743A - Laminate and packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the resistance to bag breakage by dropping of a packaging bag prepared using a laminate comprising a barrier base material having a stretched base material containing propylene as a main component and an inorganic oxide layer and a sealant layer containing polypropylene as a main component.

SOLUTION: There is provided a laminate comprising a first base material, a first adhesive layer, a second base material, a second adhesive layer and a sealant layer in this order in the thickness direction, wherein the first base material has a polypropylene stretched base material, the second base material has a polypropylene stretched base material, at least one selected from the first base material and the second base material is a barrier base material which further has an inorganic oxide layer, the sealant layer contains polypropylene as a main component, the elastic modulus of the second adhesive layer, measured by AFM for a cross section of the second adhesive layer is 30.0 MPa or more and the second adhesive layer has a thickness of 0.5 μm or more and 3.0 μm or less.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

This disclosure relates to a laminate and a packaging bag.

Polyester films are excellent in mechanical properties, chemical stability, heat resistance, and transparency, and are inexpensive. For this reason, polyester films have traditionally been used as substrates for forming laminates used to produce packaging bags. Depending on the contents filled in the packaging bag, the packaging bag is required to have gas barrier properties such as oxygen barrier properties. To meet this requirement, an inorganic oxide layer containing alumina or silica is formed on the surface of the polyester film (see, for example, Patent Document 1). In recent years, substrates to replace polyester films have been sought.

JP 2005-053223 A

The present inventors have considered using a stretched substrate containing polypropylene as a main component, instead of a conventional polyester film, as the substrate constituting the laminate. Specifically, from the viewpoints of recyclability and gas barrier properties, the present inventors have considered using a laminate comprising a barrier substrate comprising the above stretched substrate and an inorganic oxide layer, and a sealant layer containing polypropylene as a main component. As a result of the consideration, the present inventors have found that packaging bags made using such a laminate are easily broken by impact when dropped, and may not have sufficient resistance to breakage due to dropping.

One of the problems to be solved by the present disclosure is to improve the drop-breakage resistance of a packaging bag produced using a laminate comprising a barrier substrate having an inorganic oxide layer and an oriented substrate containing polypropylene as a main component, and a sealant layer containing polypropylene as a main component.

The laminate of the present disclosure comprises 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, the first substrate comprises an oriented substrate containing polypropylene as a main component, the second substrate comprises an oriented substrate containing polypropylene as a main component, at least one selected from the first substrate and the second substrate is a barrier substrate further comprising an inorganic oxide layer, the sealant layer contains polypropylene as a main component, the elastic modulus measured on a cross section of the second adhesive layer using an atomic force microscope (AFM) is 30.0 MPa or more, and the thickness of the second adhesive layer is 0.5 μm or more and 3.0 μm or less.

According to the present disclosure, it is possible to improve the drop-breakage resistance of a packaging bag produced using a laminate comprising a barrier substrate having an inorganic oxide layer and an oriented substrate containing polypropylene as a main component, and a sealant layer containing polypropylene as a main component.

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 perspective view showing an embodiment of a packaging bag.

In this specification, when multiple upper limit candidates and multiple lower limit candidates are given for a certain parameter, the numerical range of the parameter may be formed by combining any one of the upper limit candidates and any one of the lower limit candidates. As an example, the description "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." will be explained. 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.

The following describes in detail the embodiments of the present disclosure. The present disclosure can be implemented in many different forms, and is not to be construed as being limited to the description of the embodiments exemplified below. In the drawings, the width, thickness, shape, etc. of each layer may be shown diagrammatically compared to the embodiments in order to clarify the explanation, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each figure, elements similar to those already explained with respect to the previous figures are given the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, the term "main component" in a layer or substrate refers to a component whose content in the layer or substrate is greater 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.

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

[Laminate]
The laminate of the present disclosure comprises 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 (hereinafter also referred to as "in this order").

The first substrate comprises a stretched substrate containing polypropylene as a main component. The second substrate comprises a stretched substrate containing polypropylene as a main component. The stretched substrate of the first substrate and the stretched substrate of the second substrate may be the same or different. At least one selected from the first substrate and the second substrate is a barrier substrate comprising the stretched substrate and an inorganic oxide layer. In the following description, the stretched substrate containing polypropylene as a main component is also referred to as a "polypropylene stretched substrate".
The sealant layer contains polypropylene as a main component.

In one embodiment of the laminate of the present disclosure, the first substrate is a stretched polypropylene substrate, and the second substrate is a barrier substrate. That is, the laminate includes, in this order, a stretched polypropylene substrate, and optionally a printing layer, a first adhesive layer, a barrier substrate, a second adhesive layer, and a sealant layer. In this embodiment, it is preferable that the barrier substrate is arranged so that the inorganic oxide layer faces the first adhesive layer, and the stretched polypropylene substrate faces the second adhesive layer. With such an arrangement, for example, deterioration of the inorganic oxide layer can be further suppressed.

In one embodiment of the laminate of the present disclosure, the first substrate is a barrier substrate, and the second substrate is an oriented polypropylene substrate. That is, the laminate includes a barrier substrate, an optional printing layer, a first adhesive layer, an oriented polypropylene substrate, a second adhesive layer, and a sealant layer, in this order. In this embodiment, the barrier substrate is preferably arranged so that the inorganic oxide layer faces the first adhesive layer and the oriented polypropylene substrate faces outward.

The laminate of the present disclosure exhibits excellent gas barrier properties (e.g., oxygen barrier properties and water vapor barrier properties, particularly oxygen barrier properties). A packaging bag made using the laminate of the present disclosure exhibits excellent gas barrier properties even after heat treatments such as retort treatment and boiling treatment. From the viewpoint of better protecting the inorganic oxide layer when subjected to heat treatment and exhibiting higher gas barrier properties, a laminate in which the first substrate is a stretched polypropylene substrate and the second substrate is a barrier substrate is preferred.

1 to 6 are schematic cross-sectional views showing one embodiment of a laminate according to the present disclosure.
1 includes, in this order, a stretched 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 stretched polypropylene substrate 22 and an inorganic oxide layer 24. In this example, the barrier substrate 20 is disposed such that the stretched polypropylene substrate 22 faces the second adhesive layer 40B, and the inorganic oxide layer 24 faces the first adhesive layer 40A.

Figure 2 is the same as Figure 1, except that the barrier substrate 20 has a surface coating layer 23 between the stretched polypropylene substrate 22 and the inorganic oxide layer 24. Figure 3 is the same as Figure 1, except that the barrier substrate 20 has a stretched polypropylene substrate 22, a surface coating layer 23, an inorganic oxide layer 24, and a coating layer 25, in this order.

The laminate 1 shown in FIG. 4 comprises, in this order, a barrier substrate 20 as a first substrate, a first adhesive layer 40A, a stretched polypropylene substrate 10 as a second substrate, a second adhesive layer 40B, and a sealant layer 30. The barrier substrate 20 comprises a stretched polypropylene substrate 22 and an inorganic oxide layer 24. In this example, the stretched polypropylene substrate 22 constitutes the outermost layer of the laminate 1, and the barrier substrate 20 is arranged so that the inorganic oxide layer 24 faces the first adhesive layer 40A.

Figure 5 is the same as Figure 4, except that the barrier substrate 20 has a surface coating layer 23 between the stretched polypropylene substrate 22 and the inorganic oxide layer 24. Figure 6 is the same as Figure 4, except that the barrier substrate 20 has a stretched polypropylene substrate 22, a surface coating layer 23, an inorganic oxide layer 24, and a coating layer 25, in this order.

The content ratio of polypropylene to the total amount of resin material 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, 92% by mass or more, 94% by mass or more, or 95% by mass or more. A packaging bag produced using such a laminate has, for example, excellent recyclability. The upper limit of the content ratio of polypropylene to the total amount of resin material contained in the laminate of the present disclosure is not particularly limited, but may be, for example, 99% by mass, 98% by mass, or 97% by mass.

<Polypropylene stretched substrate>
The oriented polypropylene substrate contains polypropylene as a major component.
The polypropylene may be any of a homopolymer, a random copolymer, and a block copolymer, and may be a mixture of two or more selected from these. As the polypropylene, biomass-derived polypropylene and/or recycled polypropylene may be used. A propylene homopolymer is a polymer 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 of propylene and a polymer block of at least an α-olefin other than propylene. The polymer block of at least an α-olefin other than propylene may be a polymer block of propylene and an α-olefin other than propylene.

Examples of α-olefins include α-olefins other than propylene that have 2 to 20 carbon atoms, specifically 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.

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.

From the viewpoint of film-forming and processability, the melt flow rate (MFR) of 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 polypropylene is measured in accordance with JIS K7210-1:2014, Method A, at a temperature of 230°C and a load of 2.16 kg.

The polypropylene content in the polypropylene oriented substrate is preferably greater than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more, 90% by mass or more, or 95% by mass or more.

The stretched polypropylene substrate may contain a resin material other than polypropylene, such as, for example, a polyolefin other than polypropylene, such as polyethylene, an acrylic resin, a vinyl resin, a cellulose resin, a polyamide, a polyester, or an ionomer resin.
The stretched polypropylene substrate may contain additives, such as crosslinkers, antioxidants, antiblocking agents, lubricants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

The stretched polypropylene substrate is a polypropylene substrate that has been subjected to a stretching treatment. A laminate including the stretched polypropylene substrate is excellent in, for example, heat resistance, impact resistance, water resistance, and dimensional stability, and is suitable as a packaging material for forming a packaging bag that is to be subjected to, for example, a retort treatment or a boiling treatment.
The stretching process may be uniaxial stretching or biaxial stretching.
The stretching ratio in the case of stretching in the machine direction (flow direction of the substrate, MD direction) is preferably 2 times or more, more preferably 5 times or more, and also preferably 15 times or less, more preferably 13 times or less. The stretching ratio in the case of stretching in the width direction (direction perpendicular to the MD direction, TD direction) is preferably 2 times or more, more preferably 5 times or more, and also preferably 15 times or less, more preferably 13 times or less. By setting the stretching ratio at 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.
The oriented polypropylene substrate is, for example, a biaxially oriented substrate.

The oriented polypropylene substrate may be surface-treated. This can improve the adhesion between the oriented polypropylene substrate and other layers, for example. 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 polypropylene substrate.

The oriented polypropylene substrate may have a single layer structure or a multi-layer structure.
The thickness of the polypropylene stretched substrate 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 having a stretched substrate with a thickness equal to or greater than the lower limit has, for example, excellent strength and heat resistance. A laminate having a stretched substrate with a thickness equal to or less than the upper limit has, for example, excellent processability.

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 at room temperature (25°C) using a commercially available rotary microtome 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 with a diamond knife. The thickness of the substrate and each layer is the arithmetic average value of the thicknesses measured at five points by observing the cross section using a scanning electron microscope (SEM, Hitachi, Ltd., SU8000).

<Barrier substrate>
The barrier substrate comprises a stretched polypropylene substrate and an inorganic oxide 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 coating layer on the inorganic oxide layer. The barrier substrate may have transparency.

(Polypropylene oriented substrate)
Examples of the oriented polypropylene substrate included in the barrier substrate include the oriented polypropylene substrates described in the section <oriented polypropylene substrate>. The oriented polypropylene substrate of the first substrate and the oriented polypropylene substrate of the second substrate may be the same or different.

The stretched polypropylene substrate provided in the barrier substrate may be, for example, a stretched substrate of another aspect that includes a polypropylene layer, an optional adhesive resin layer, and a surface resin layer described later, in this order. In this embodiment, the barrier substrate includes a stretched substrate of another aspect and an inorganic oxide layer provided on the surface resin layer of the stretched substrate. In this embodiment, the barrier substrate includes a polypropylene layer, an optional adhesive resin layer, a surface resin layer, and an inorganic oxide layer, in this order. In one embodiment, the stretched substrate of another aspect 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 or an inflation method, and then stretching the laminated film.

In other embodiments, the stretching treatment of the stretched substrate may be uniaxial stretching or biaxial stretching.
The stretching ratio in the MD direction is preferably 2 times or more, more preferably 5 times or more, and is preferably 15 times or less, more preferably 13 times or less. The stretching ratio in the TD direction is preferably 2 times or more, more preferably 5 times or more, and is preferably 15 times or less, more preferably 13 times or less.

(Surface Coating Layer)
The barrier substrate may include a surface coating layer containing a resin material having a polar group between the stretched polypropylene substrate and the inorganic oxide layer. Such a barrier substrate has excellent adhesion to the inorganic oxide layer and also has excellent gas barrier properties. Such a barrier substrate includes, in this order, a stretched polypropylene substrate, a surface coating layer, and an inorganic oxide layer.

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.

Examples of resin materials having polar groups include ethylene-vinyl alcohol copolymers (EVOH), polyvinyl alcohol (PVA), polyester, polyethyleneimine, hydroxyl-containing acrylic resins, polyamides such as nylon 6, nylon 6,6, MXD nylon and amorphous nylon, and polyurethane. Among these, ethylene-vinyl alcohol copolymers, polyvinyl alcohol, hydroxyl-containing acrylic resins, polyamides and polyurethanes are more preferred.

The surface coating layer can be formed, for example, using a water-based emulsion or a solvent-based emulsion. Examples of water-based 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.

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 materials other than the resin material having a polar group.
The surface coating layer may contain the above-mentioned additives.

The ratio of the thickness of the surface coat layer to the total thickness of the polypropylene stretched substrate and the surface coat layer is preferably 0.08% or more, more preferably 0.2% or more, even more preferably 1% or more, and also 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 coat 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 also 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 above 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 property can be improved, and the laminate strength of the laminate can be improved. When the above 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.

For example, a polypropylene or a resin composition containing polypropylene is formed into a film using a T-die method or an inflation method to obtain a polypropylene substrate, and then the substrate is stretched. A coating liquid for forming a surface coating layer is applied to the stretched substrate and dried to produce a resin substrate having a stretched polypropylene substrate and a surface coating layer.

(Polypropylene layer, surface resin layer and adhesive resin layer)
In another embodiment of the stretched substrate, the polypropylene layer contains polypropylene as a main component. The details of polypropylene are as described above, and will not be described in this section. The content of polypropylene 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, even 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.

The polypropylene layer may contain the above-mentioned resin materials other than polypropylene.
The polypropylene layer may contain the additives described above.

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 is preferably 100 μm or less, more preferably 50 μm or less, for example, 10 μm or more and 100 μm or less.

The 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 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 surface resin layer and also improve the gas barrier properties.

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. If 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 properties 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 substrate.

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) device is used to measure a DSC curve at a heating rate of 10°C/min, and the melting peak temperature is determined as the melting point.

The high melting point resin material preferably has a polar group. A 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 hydroxyl group, the ester group, the amino group, the amide group, the carboxyl group, and the carbonyl group are preferred, and the amide group is more preferred.

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 a polar group is preferred, and ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyester, and polyamides such as nylon 6 and nylon 6,6 are more preferred.

The content of the high melting point resin material in the 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.

The surface resin layer may contain the above-mentioned resin materials other than the high melting point resin material.
The surface resin layer may contain the above-mentioned additives.
The surface resin layer may be subjected to the above-mentioned surface treatment.

The ratio of the thickness of the surface resin layer to the total thickness of the stretched substrate of another embodiment having a polypropylene layer and a surface resin layer is preferably 1% or more, more preferably 1.5% or more, and also preferably 10% or less, more preferably 5% or less, for example 1% or more and 10% or less. The thickness of the surface resin layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and also 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 above 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 property can be improved, and the laminate strength of the laminate can be improved. When the above ratio or thickness is equal to or less than the upper limit, for example, the film formability and processability of the stretched substrate of another embodiment, and the recyclability of the laminate can be improved.

In another embodiment, the stretched substrate may have an adhesive resin layer between the polypropylene layer and the surface resin layer. This can improve the adhesion between these layers. The thickness of the adhesive resin layer is, for example, 1 μm or more and 15 μm or less. 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.

(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 oxidation deterioration of the contents filled in the packaging bag, and suppress the mass loss of the contents. The barrier substrate may, for example, comprise an inorganic oxide layer on a surface coat layer, or may comprise an inorganic oxide layer on a surface resin layer.

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.

In one embodiment, silica is more preferable as the inorganic oxide because no aging treatment is required after the formation of the inorganic oxide layer. In one embodiment, carbon-containing silicon oxide is more preferable as the inorganic oxide because it can suppress the deterioration of the gas barrier property even when the laminate is bent.

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, for example, excellent oxygen barrier properties and water vapor barrier properties. A laminate having an inorganic oxide layer whose thickness is equal to or less than the upper limit can, for example, suppress the occurrence of cracks in the inorganic oxide layer and has excellent recyclability.

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

Methods for forming inorganic oxide layers, particularly inorganic oxide vapor deposition films, include, for example, physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, as well as chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

The inorganic oxide layer may be a single layer formed by one deposition process, or may be a multilayer formed by multiple 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.

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

The carbon-containing silicon oxide vapor deposition 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, for example, 3% or more and 50% or less, relative to 100% in total of the three elements silicon, oxygen, and carbon. By setting the carbon ratio C in the above range, for example, even if the laminate is bent, the deterioration of the gas barrier property can be suppressed.
In this specification, the ratio of each element is on a molar basis.

In one embodiment of the carbon-containing silicon oxide vapor deposition film, the silicon ratio Si is preferably 1% or more, more preferably 3% or more, and even more preferably 8% or more, and is preferably 45% or less, more preferably 38% or less, and 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, and even more preferably 25% or more, and is preferably 70% or less, more preferably 65% or less, and 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 in the above ranges, for example, the deterioration of the gas barrier property can be further suppressed even when the laminate is bent.

In one embodiment of the carbon-containing silicon oxide vapor deposition 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 are preferably in the order of O, C, and Si. This makes it possible to further suppress the deterioration of the gas barrier properties, for example, even when the laminate is bent.

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

(Measurement conditions)
Equipment used: “ESCA-3400” (manufactured by Kratos)
[1] Spectrum collection conditions Incident X-ray: MgKα (monochromatic X-ray, hν = 1253.6 eV)
X-ray output: 150W (10kV/15mA)
X-ray scanning area (measurement area): Approximately 6 mm diameter
Photoelectron capture angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar ⁺
Acceleration voltage: 0.2 (kV)
Emission current: 20 (mA)
Etch range: 10mmφ
Ion sputtering time: 30 seconds, spectrum collected

(Covering 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.

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 is 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.

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.

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 and, if necessary, additives and a solvent. Details of these components are as described above. Methods for applying the coating liquid for the coating layer include known coating methods. Methods for drying the applied coating liquid for the coating layer include, for example, hot air drying, hot roll drying, and methods that apply heat such as infrared irradiation. The drying temperature may be 50°C or higher, or 150°C or lower.

In one embodiment, the coating layer may be a barrier coat layer containing a gas barrier resin. Examples of the gas barrier resin include ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyacrylonitrile, polyester, polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide, polyurethane, and acrylic resin. 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, and even more preferably 70% by mass or more. Such a barrier coat layer has, for example, excellent gas barrier properties.
The barrier coat layer may contain the above-mentioned additives.

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 also 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 whose thickness is equal to or greater than the lower limit has, for example, excellent gas barrier properties. A barrier substrate having a barrier coat layer whose thickness is equal to or less than the upper limit can improve, for example, the processability and recyclability of the laminate.

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.

In one embodiment, the coating layer may be a gas barrier coating film formed by polycondensing 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, and the like. 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 above-mentioned metal alkoxide, etc. by a sol-gel method. By providing such a gas barrier coating film on an inorganic oxide layer, for example, the occurrence of cracks in the inorganic oxide layer can be effectively suppressed.

The metal alkoxide is represented, for example, by the formula (1).
R ¹ _n M(OR ² ) _m (1)
In formula (1), R ¹ and R ² each independently represent 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 atomic valence of M. Examples of the organic group in R ¹ and R ² include alkyl groups having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-hexyl group, and an n-octyl group. 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.

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 properties, water vapor barrier properties, water resistance, and weather resistance, either polyvinyl alcohol or ethylene-vinyl alcohol copolymer may be used, or both may be used in combination. Also, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using 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 metal alkoxide.

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 organoalkoxysilanes having an epoxy group are 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.

The gas barrier composition may contain water in a ratio of preferably 0.1 mol or more, more preferably 0.5 mol or more, and preferably 100 mol or less, more preferably 60 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.

The gas barrier composition may contain an organic solvent. Examples of organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol.

The sol-gel process catalyst is preferably an acid or an amine compound.
Examples of the acid 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 the acid used is preferably 0.001 mol or more and 0.05 mol or less per 1 mol of the total molar amount of the metal alkoxide and the alkoxide portion (e.g., silicate portion) of the silane coupling agent.

As the amine compound, a tertiary amine that is substantially insoluble in water and soluble in an organic solvent is suitable, such as N,N-dimethylbenzylamine, tripropylamine, tributylamine, and tripentylamine. The amount of the amine compound used is preferably 0.01 part by mass or more, more preferably 0.03 part 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.

Methods for applying the gas barrier composition include, for example, application means such as roll coating using a gravure roll coater, spray coating, spin coating, dipping, brush coating, bar coating, and applicator.

Hereinafter, one embodiment of the method for forming a gas barrier coating film will be described.
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. In the composition, a polycondensation reaction gradually proceeds. The composition is applied on an inorganic oxide layer by a conventional method and dried. This drying causes the polycondensation of the metal alkoxide and the water-soluble polymer (and the silane coupling agent if the composition contains a silane coupling agent) to proceed further, forming a composite polymer layer. The above operation may be repeated to laminate a plurality of composite polymer layers. 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 also at a temperature of preferably 150° C. or lower, more preferably 120° C. or lower, and even more preferably 100° C. or lower for 1 second to 10 minutes. This allows the formation of a gas barrier coating film.

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 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less, for example, 0.01 μm or more and 2 μm or less. 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.

<Printed layer>
The laminate of the present disclosure may include a printed layer on the surface of a substrate such as a first substrate and a second substrate. The image formed on the printed layer is not particularly limited, and may be a character, a pattern, a symbol, or a combination thereof. The printed layer may be formed using an ink derived from biomass. This can further reduce the environmental load.

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 the environmental load.
The thickness of the printing layer is, for example, not less than 0.5 μm and not more than 3 μm.

<Sealant Layer>
The laminate of the present disclosure includes a sealant layer.
The sealant layer contains polypropylene as a main component. The sealant layer contains the same type of resin material as the oriented polypropylene substrate, i.e., polypropylene as a main 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 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, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more, 90% by mass or more, or 95% by mass or more. A laminate having such a sealant layer has, for example, excellent recyclability.

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 the α-olefins are as described above. From the viewpoint of heat sealability, the density of the polypropylene is, for example, 0.88 g/cm ³ or more and 0.92 g/cm ³ or less. The density is measured in accordance with JIS K7112:1999 D method (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.

The sealant layer may have a single-layer structure or a multi-layer structure.
The thickness of the sealant layer is preferably 10 μm or more, more preferably 20 μm or more, and also 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 also preferably 100 μm or less.

From the viewpoint of heat sealability, the sealant layer is preferably an unstretched polypropylene film, and the unstretched polypropylene film can be produced by utilizing, for example, a cast method, a T-die method, an inflation method, or the like.
The sealant layer may be subjected to the above-mentioned surface treatment.

<Adhesive Layer>
The laminate of the present disclosure includes a first adhesive layer between a first substrate and a second substrate. The laminate of the present disclosure includes a second adhesive layer between the second substrate and a sealant layer. Such a laminate has, for example, excellent lamination strength between the first substrate and the second substrate and between the second substrate and the sealant layer.

(Second Adhesive Layer)
The elastic modulus measured by atomic force microscope (AFM) for the cross section of the second adhesive layer is 30.0 MPa or more, preferably 33.0 MPa or more, more preferably 35.0 MPa or more. A packaging bag made using a laminate having a second adhesive layer with an elastic modulus of the lower limit or more and a thickness of 2.5 μm or less tends to have excellent impact resistance, and therefore excellent drop-break resistance, as well as excellent tearability, and therefore excellent openability. In addition, the packaging bag is, for example, excellent in recyclability.

The elastic modulus measured by AFM for the cross section of the second adhesive layer is preferably 120 MPa or less, more preferably 110 MPa or less, even more preferably 100 MPa or less, still more preferably 90.0 MPa or less, particularly preferably 80.0 MPa or less, 70.0 MPa or less, 60.0 MPa or less, or 50.0 MPa or less. A laminate having a second adhesive layer with an elastic modulus of less than the upper limit tends to have excellent laminate strength.
The elastic modulus of the second adhesive layer is, for example, not less than 30.0 MPa and not more than 120 MPa.
Details of the conditions for measuring the elastic modulus by AFM are described in the Examples section.

The second adhesive layer having the above elastic modulus can be formed, for example, by using a solvent-free adhesive as described below, and by 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, as described below.

The softening point of the cross section of the second adhesive layer measured by local thermal analysis using a thermal probe is preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, even more preferably 215°C or higher, and particularly preferably 220°C or higher or 225°C or higher. A packaging bag made using a laminate having a second adhesive layer with a softening point equal to or higher than the lower limit has excellent heat resistance, and tends to have excellent gas barrier properties, appearance, and laminate strength even after heat treatment such as retort treatment. Therefore, such a packaging bag can achieve both drop-breakage resistance and gas barrier properties after heat treatment.

The softening point of a cross section of the second adhesive layer measured by local thermal analysis using a thermal probe may be, for example, 330°C or less, 320°C or less, 310°C or less, 300°C or less, 290°C or less, 280°C or less, 270°C or less, or 260°C or less.
The softening point of the second adhesive layer is, for example, 200° C. or higher and 330° C. or lower.

The softening point of the adhesive layer is a value measured by local thermal analysis using a thermal probe. In local thermal analysis using a thermal probe, the thermal probe is placed in contact with the cross section of the adhesive layer, and the temperature is raised while measuring the normal displacement of the cross section of the adhesive layer from before heating the thermal probe to obtain a thermal expansion curve. The cross section is obtained by cutting the laminate in the thickness direction perpendicular to the main surface. The location where the thermal probe comes into contact is near the center of the adhesive layer in the thickness direction among the exposed parts of the cross section of the adhesive layer. Measurements are performed at five or more locations on the same cross section, and the softening point is recorded as the arithmetic average of the values measured at five locations with good reproducibility.

In local thermal analysis, the components in the adhesive layer expand when heated, pushing up the thermal probe. The slope of the thermal expansion curve (displacement/temperature) changes due to structural transitions in the components of the adhesive layer. When the structural transition of the components of the adhesive layer changes from expansion to softening, the tip of the thermal probe enters the component, causing the thermal probe to descend. The point where the displacement of the thermal probe changes from rising to falling corresponds to the peak of the thermal expansion curve, and is called the softening point. The softening point of the adhesive layer can be obtained by reading the temperature at the peak of the thermal expansion curve.
Details of the measurement conditions are described in the Examples section.

The thickness of the second adhesive layer is 3.0 μm or less, preferably 2.5 μm or less, more preferably 2.0 μm or less, even more preferably 1.5 μm or less, and also 0.5 μm or more, preferably 0.8 μm or more, more preferably 1.0 μm or more, for example, 0.5 μm or more and 3.0 μm or less. A packaging bag made using a laminate having a second adhesive layer with an elastic modulus of 30.0 MPa or more and a thickness of the upper limit or less tends to have excellent impact resistance, and therefore resistance to bag breakage due to dropping, and also tends to have excellent tearability, and therefore resistance to opening. A packaging bag made using a laminate having a second adhesive layer with an elastic modulus of 30.0 MPa or more and a thickness of the lower limit or more tends to have excellent impact resistance, and therefore resistance to bag breakage due to dropping. In addition, the packaging bag has excellent recyclability.

The thickness of the second adhesive layer relative to the total thickness of the laminate is preferably 0.5% or more, more preferably 0.8% or more, even more preferably 1.0% or more, and is preferably 3.0% or less, more preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.5% or less, for example, 0.5% or more and 3.0% or less.

(First Adhesive Layer)
The thickness of the first adhesive layer is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 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, 0.5 μm or more and 10.0 μm or less.

The softening point of the cross section of the first adhesive layer measured by local thermal analysis using a thermal probe is preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, even more preferably 215°C or higher, and particularly preferably 220°C or higher or 225°C or higher, and may be, for example, 330°C or lower, 320°C or lower, 310°C or lower, 300°C or lower, 290°C or lower, 280°C or lower, 270°C or lower, or 260°C or lower, for example, 200°C or higher and 330°C or lower. A packaging bag made using a laminate having a first adhesive layer with a softening point equal to or higher than the lower limit has excellent heat resistance, and tends to have excellent gas barrier properties, appearance, and laminate strength even after heat treatment such as retort treatment. Therefore, such a packaging bag can achieve both drop-breakage resistance and gas barrier properties after heat treatment.

In one embodiment (A), the elastic modulus measured by AFM on the cross section of the first adhesive layer is preferably 30.0 MPa or more, more preferably 33.0 MPa or more, even more preferably 35.0 MPa or more, and is preferably 120 MPa or less, more preferably 110 MPa or less, even more preferably 100 MPa or less, even more preferably 90.0 MPa or less, particularly preferably 80.0 MPa or less, 70.0 MPa or less, 60.0 MPa or less, or 50.0 MPa or less, for example, 30.0 MPa or more and 120 MPa or less. A laminate having a first adhesive layer with an elastic modulus of less than the upper limit tends to have excellent laminate strength. A first adhesive layer having such an elastic modulus can be formed, for example, by using a solvent-free adhesive described later, and by appropriately changing the type and molecular weight of the polymer component contained in the base agent, the type of the curing agent, the molar ratio (NCO/OH), and the aging conditions, each of which will be described later.

When the first adhesive layer has the modulus of elasticity of one embodiment (A), in one embodiment, the modulus of elasticity of the second adhesive layer is smaller than that of the first adhesive layer. A packaging bag made using a laminate of this type tends to have excellent impact resistance, and therefore resistance to bag breakage due to dropping, as well as excellent seal strength. This is presumably because the small modulus of elasticity of the second adhesive layer can prevent the surface layer of the second substrate from peeling off, thereby preventing a decrease in the laminate strength between the second substrate and the sealant layer.

When the first adhesive layer has the elastic modulus of one embodiment (A), the elastic modulus of the second adhesive layer is, in one embodiment, greater than the elastic modulus of the first adhesive layer. Packaging bags made using a laminate of this type tend to have superior tearability, and therefore superior openability.

When the first adhesive layer has the elastic modulus of one embodiment (A), the thickness of the first adhesive layer is, in one embodiment, preferably 3.0 μm or less, more preferably 2.5 μm or less, even more preferably 2.0 μm or less, even more preferably 1.5 μm or less, and also preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, for example 0.5 μm or more and 3.0 μm or less. In this embodiment, the thickness of the first adhesive layer relative to the thickness of the entire laminate is preferably 0.5% or more, more preferably 0.8% or more, even more preferably 1.0% or more, and also preferably 3.0% or less, more preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.5% or less, for example 0.5% or more and 3.0% or less. A packaging bag produced using a laminate having such a first adhesive layer tends to have excellent impact resistance, and therefore excellent drop-break resistance, as well as excellent tearability, and therefore excellent openability. In addition, the packaging bag has excellent recyclability, for example.

When the first adhesive layer has the elastic modulus of one embodiment (A), the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer in one embodiment. When a printed layer is provided on the surface of the first substrate facing the first adhesive layer, the first adhesive layer can effectively cover the step caused by the printed layer, and there is a tendency to obtain a packaging bag with a good appearance. The ratio of the thickness 1 of the first adhesive layer to the thickness 2 of the second adhesive layer (thickness 1/thickness 2) may be, for example, 0.16 or more, 0.5 or more, or 0.8 or more, and when the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer, it may be greater than 1.0, and may also be 6.0 or less, 3.0 or less, or 1.1 or less.

In one embodiment (B), the elastic modulus measured by AFM for the cross section of the first adhesive layer is preferably less than 30.0 MPa, more preferably 28.0 MPa or less, even more preferably 26.0 MPa or less, and also preferably 5.0 MPa or more, more preferably 10.0 MPa or more, even more preferably 15.0 MPa or more, even more preferably 16.0 MPa or more, particularly preferably 18.0 MPa or more, for example, 5.0 MPa or more and less than 30.0 MPa. A packaging bag made using a laminate having a first adhesive layer whose elastic modulus is equal to or less than the upper limit tends to have excellent gas barrier properties (e.g., oxygen barrier properties and water vapor barrier properties, especially oxygen barrier properties) and appearance even after heat treatment such as retort treatment. When a printing layer is provided on the surface of the first substrate facing the first adhesive layer, the first adhesive layer whose elastic modulus is equal to or less than the upper limit tends to have excellent adhesion to the printing layer. Packaging bags made using a laminate with a first adhesive layer having a modulus of elasticity equal to or greater than the lower limit tend to have excellent gas barrier properties and appearance even after heat treatment such as retort treatment. A second adhesive layer having such a modulus of elasticity can be formed, for example, by using a solvent-based adhesive as described below, and by 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, as described below.

When the first adhesive layer has the elastic modulus of one embodiment (B), the thickness of the first adhesive layer is, in one embodiment, preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 2.0 μm or more, particularly preferably 2.5 μm or more, and also 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. In this embodiment, the thickness of the first adhesive layer relative to the thickness of the entire laminate is preferably 1.0% or more, more preferably 1.5% or more, even more preferably 2.0% or more, particularly preferably 2.5% or more, and also preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, particularly preferably 5.0% or less, for example, 1.0% or more and 10.0% or less. In one embodiment, the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer. 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 step caused by the printed layer, and a packaging bag with a good appearance tends to be obtained. 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.

(glue)
The first adhesive layer and the second adhesive 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 any of a one-component curing adhesive, a two-component curing adhesive, and a non-curing adhesive, and a two-component curing adhesive is preferred from the viewpoint of easily adjusting the elastic modulus and softening point to the above-mentioned ranges.

One method for obtaining a laminate using an adhesive is to apply the adhesive to an object, then overlay another object on the formed adhesive layer and allow the adhesive layer sandwiched between the two to harden. Examples of objects 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."

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.

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, 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, from the viewpoint of ease of adjusting the elastic modulus and softening point to the above-mentioned ranges.

The adhesive may be a solvent-based adhesive or a solventless adhesive.
A solvent-based adhesive is an adhesive used in a method in which the adhesive is applied to an object, heated in an oven or the like to volatilize the solvent in the adhesive, and then the adhesive is bonded to another object. In the case of a two-liquid 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.

A solvent-free adhesive is an adhesive that is applied to an object and then bonded to another object without necessarily going through 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 contain substantially no solvent. "Substantially no solvent" includes cases where the solvent used as a reaction medium during the manufacture of the adhesive's components, or the base agent and/or curing agent in the case of a two-component curing adhesive, cannot be 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.

A two-component curing polyurethane adhesive has a base agent and a curing agent. A two-component curing polyurethane adhesive may be a solvent-based or solventless type. Two-component curing polyurethane adhesives are described below.

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 (reactant) formed by mixing such a base agent and a curing agent include polyurethane, specifically polyester polyurethane, polyether polyurethane, polycarbonate polyurethane, and acrylic polyurethane.

The polyol compound has two or more hydroxy groups in one molecule. Examples of polyol compounds 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 of easily obtaining an adhesive layer having an elastic modulus in the above-mentioned range, polyester polyurethane polyol is more preferred in the case of a solvent-based adhesive, and polyester polyol is more preferred in the case of a solventless adhesive.

Polyester polyurethane polyol is a compound that has two or more hydroxy groups, ester bonds, and urethane bonds in one molecule, and has, for example, a polyester polyurethane structure as the main backbone. Polyester polyol is a compound that has two or more hydroxy groups and ester bonds in one molecule, and has, for example, a polyester structure as the main backbone. Polyether polyol is a compound that has two or more hydroxy groups and ether bonds in one molecule. Polycarbonate polyol is a compound that has two or more hydroxy groups and carbonate bonds in one molecule.

From the viewpoint of coatability, the weight average molecular weight (Mw) of the polymer component (e.g., polyol compound) contained in the base agent of the two-component curing and solventless adhesive is preferably 800 or more, more preferably 1,200 or more, and even more preferably 2,000 or more, and is preferably 10,000 or less, more preferably 8,000 or less, and 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 is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or more, where Mn is the number average molecular weight of the polymer component (e.g., polyol compound) contained in the base agent.

The weight average molecular weight (Mw) of the polymer component (e.g., polyol compound) contained in the base of the two-component curing and solvent-based adhesive is, from the viewpoint of coatability, preferably 11,000 or more, more preferably 13,000 or more, even more preferably 15,000 or more, still more preferably 18,000 or more, particularly preferably 20,000 or more, 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, and even more preferably 4.0 or less, and is 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.

A polyisocyanate compound has two or more isocyanate groups in one molecule. Examples of polyisocyanate compounds 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.

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 allophanates obtained by reacting these compounds with low-molecular-weight active hydrogen compounds or their alkylene oxide adducts, or high-molecular-weight active hydrogen compounds.

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.

The base agent containing a polyol compound and the curing agent containing a polyisocyanate compound are preferably used in a quantity ratio such that the molar ratio (NCO/OH) of the total isocyanate groups of the polyisocyanate compound to the total hydroxyl groups of 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, and even more preferably 1.5 or more, and is preferably 8.0 or less, more preferably 6.0, and even more preferably 5.0 or less, and in the case of a solventless adhesive, is even more preferably 4.0 or less, and 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.

[Packaging bag]
The laminate of the present disclosure is preferably used as a packaging material. The packaging material is used to produce a packaging bag. The packaging bag of the present disclosure includes the laminate. By using the laminate of the present disclosure as a packaging material, a packaging bag can be produced. In one embodiment, the laminate of the present disclosure is folded in half and stacked so that the first substrate is located on the outside and the sealant layer is located on the inside, and the ends and the like are heat-sealed to produce a packaging bag. In another embodiment, a plurality of laminates of the present disclosure are stacked so that the sealant layers face each other, and the ends and the like are heat-sealed to produce a packaging bag. The entire packaging bag may be composed of the laminate, or a part of the packaging bag may be composed of the laminate.

Examples of packaging bags include packaging bags of various shapes, such as standing pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, grooving 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.

The packaging bag may have an easy-to-open portion. Examples of the easy-to-open portion include a notch portion that serves as the 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.

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

The contents to be placed in the packaging bag can be, for example, liquids, solids, powders, and gels. The contents can be food or beverages, or non-food or beverages such as chemicals, cosmetics, pharmaceuticals, metal parts, and electronic parts. After the contents are placed in the packaging bag, the opening of the packaging bag can be heat-sealed to seal the packaging bag.

As specific examples of packaging bags, a small bag and a standing pouch will be described below.
The sachet is a small packaging bag used to store contents of, for example, 1 g to 200 g. Examples of contents stored in the sachet include sauces, soy sauce, dressings, ketchup, syrups, 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 foods and beverages; and non-food items such as chemicals, cosmetics, medicines, metal parts, and electronic parts.

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

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

In one embodiment, the packaging bag of the present disclosure has excellent gas barrier properties even after heat treatment, and is therefore suitable as a retort-treated pouch (hereinafter also referred to as a "retort pouch") or a boiled pouch (hereinafter also referred to as a "boiled pouch"), or as a microwave-compatible packaging bag. The packaging bag of the present disclosure is also suitable as a boiled or retort pouch for use in a microwave oven. Here, a microwave-compatible packaging bag means a packaging bag that can be heated using a microwave oven.

A retort pouch is a packaging bag that is filled with food or beverages and other contents, sealed, and then heat-sterilized (retort processing) with water or steam at a temperature exceeding 100°C under pressure. A boil pouch is a packaging bag that is filled with food or beverages and other contents, sealed, and then boiled at a temperature of 100°C or less.

In one embodiment, the packaging bag of the present disclosure is a retort pouch. There are various conditions for the retort process, but any pouch that has undergone general retort processing is included in the above-mentioned retort pouch. Among retort processes, for example, when the processing temperature is 105°C or higher and 115°C or lower, it may be called semi-retort processing, when the processing temperature is higher than 115°C and 121°C or lower, it may be called retort processing, and when the processing temperature is higher than 121°C and 140°C or lower, it may be called high retort processing.

In one embodiment, the packaging bag of the present disclosure is a retort pouch.
In one embodiment, the oxygen permeability (unit: cc/ ^m2 ·day·atm) of the retort pouch of the present disclosure is preferably 2.0 or less, more preferably 1.5 or less, even more preferably 1.3 or less, and particularly preferably 1.0 or less. The oxygen permeability is measured in accordance with JIS K7126-2:2006 at a temperature of 23° C. and a relative humidity of 90% RH. The lower limit of the oxygen permeability is preferably as low as possible, but may be, for example, 0.1.

Figure 7 shows a packaging bag 50 obtained by bonding two laminates together. The shaded 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 the starting point for tearing, and a half-cut line 53 formed by laser processing or a cutter as a path for tearing.

Figure 8 shows a simplified example of the configuration of a standing pouch. The shaded areas indicate the heat-sealed areas. In one embodiment, the standing 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 retains the shape of the side sheets 61, which gives the pouch self-supporting properties and allows it to be 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.

The standing pouch 60 may be provided with 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-seal portion 63b that is isolated from the content storage portion by the steam release seal portion 63a. The non-seal portion 63b is in communication with the outside of the packaging bag.

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

In one embodiment, the side sheet can be formed by making 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, stacking them so that the sealant layers face each other, and heat-sealing the side edges on both sides to make a bag.

In another embodiment, the side sheet can be formed by preparing two laminates of the present disclosure, stacking them with the sealant layers facing each other, inserting two laminates folded in a V-shape with the sealant layers facing outward between the laminates at the side edges on both sides of the stacked laminates, and heat sealing them. This manufacturing method produces a standing pouch having a body with side gussets.

In one embodiment, the bottom sheet can be formed by inserting a laminate between the lower parts of the side sheets that have been made into a bag and heat sealing it. More specifically, the bottom sheet can be formed by inserting a laminate folded into a V shape with the sealant layer on the outside between the lower parts of the side sheets that have been made into a bag and heat sealing it.

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 between the lower part of the stacked laminates and heat sealed to form the bottom. Next, the two sides adjacent to the bottom are heat sealed to form the body. In this manner, the standing pouch of one embodiment can be formed.

The present disclosure relates to, for example, the following [1] to [16].
[1] 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 comprises an oriented substrate containing polypropylene as a main component, the second substrate comprises an oriented substrate containing polypropylene as a main component, at least one selected from the first substrate and the second substrate is a barrier substrate further comprising an inorganic oxide layer, the sealant layer contains polypropylene as a main component, the elastic modulus of the cross section of the second adhesive layer measured using an atomic force microscope (AFM) is 30.0 MPa or more, and the thickness of the second adhesive layer is 0.5 μm or more and 3.0 μm or less.
[2] The laminate described in [1], wherein the softening point measured by local thermal analysis using a thermal probe on a cross section of the second adhesive layer is 200°C or higher and 330°C or lower.
[3] The laminate described in [1] or [2], wherein the elastic modulus measured on a cross section of the first adhesive layer using an atomic force microscope (AFM) is 30.0 MPa or more, and the thickness of the first adhesive layer is 0.5 μm or more and 3.0 μm or less.
[4] The laminate described in [3], wherein the softening point measured by local thermal analysis using a thermal probe on a cross section of the first adhesive layer is 200°C or higher and 330°C or lower.
[5] The laminate described in [3] or [4], wherein the elastic modulus of the first adhesive layer is greater than the elastic modulus of the second adhesive layer.
[6] The laminate described in any one of [3] to [5], wherein the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer.
[7] The laminate described in [1] or [2], wherein the elastic modulus measured on a cross section of the first adhesive layer using an atomic force microscope (AFM) is less than 30.0 MPa, and the softening point measured on a cross section of the first adhesive layer by local thermal analysis using a thermal probe is 200°C or higher and 330°C or lower.
[8] The laminate described in [7], wherein the thickness of the first adhesive layer is 2.0 μm or more and 5.0 μm or less.
[9] The laminate described in [7] or [8], wherein the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer.
[10] The laminate according to any one of the above [1] to [9], wherein the barrier substrate further comprises a coating layer on a surface of the inorganic oxide layer opposite to a surface facing the stretched substrate.
[11] The laminate according to any one of the above [1] to [10], wherein the first substrate is the stretched substrate, the second substrate is the barrier substrate comprising the stretched substrate and the inorganic oxide layer, and the second substrate is disposed such that the inorganic oxide layer faces the first substrate side and the stretched substrate faces the sealant layer side.
[12] The laminate according to any one of [1] to [10], wherein the first substrate is a barrier substrate comprising the stretched substrate and the inorganic oxide layer, the first substrate is disposed such that the inorganic oxide layer faces the second substrate and the stretched substrate faces outward, and the second substrate is the stretched substrate.
[13] The laminate according to any one of [1] to [12], wherein the content of polypropylene in the total amount of resin material contained in the laminate is 80 mass% or more.
[14] The laminate according to any one of [1] to [13] above, which is a packaging material.
[15] A packaging bag comprising the laminate according to any one of [1] to [14] above.
[16] The packaging bag according to [15], which is a pouch that has been retorted or boiled.

The laminate and packaging bag of the present disclosure will be described in detail below using specific examples.

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

A 20 μm-thick biaxially stretched polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was prepared, with one side corona-treated. The above-mentioned surface coating layer-forming solution was applied to the corona-treated side of the film and dried to form a surface coating layer with a thickness of 0.5 μm. In this way, a resin substrate was obtained.

A carbon-containing silicon oxide (silica) vapor deposition film with a thickness of 12 nm was formed on the surface coating layer of the resin substrate using a low-temperature plasma chemical vapor deposition apparatus (CVD method) in a roll-to-roll manner while applying tension to the resin substrate. The conditions for forming the vapor deposition film were as follows:

(Formation Conditions)
Hexamethyldisiloxane: oxygen gas: helium = 1:10:10 (unit: slm)
・Cooling/electrode drum power supply: 22kW
Line speed: 100 m/min

The carbon percentage C, silicon percentage Si, and oxygen percentage O in the carbon-containing silicon oxide vapor deposition 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 the total of the three elements silicon, oxygen, and carbon being 100%. The percentages of each element were measured by narrow scan analysis using X-ray photoelectron spectroscopy (XPS) under the measurement conditions described above.

385g of water, 67g of isopropyl alcohol, and 9.1g of 0.5N hydrochloric acid were mixed to obtain a solution with a pH of 2.2. 175g of tetraethoxysilane as a metal alkoxide and 9.2g of glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed with this solution while cooling to 10°C to obtain solution A. 14.7g of polyvinyl alcohol with a saponification value of 99% or more and a polymerization degree of 2400 as a water-soluble polymer, 324g of water, and 17g 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 the deposition film formed on the resin substrate by spin coating, and the coating was heated in an oven at 80°C for 60 seconds to form a barrier coating layer with a thickness of 300 nm.

In this way, a transparent barrier substrate was obtained that had, in this order, 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 deposition film, and a 300 nm-thick barrier coating layer.

[glue]
A two-component curing adhesive composed of the following base agent and curing agent was used.
・Adhesive α
Base: Polyester polymer (Mw: 4,000)
Hardener: Hexamethylene diisocyanate (HDI)
Mixture of xylylene diisocyanate (XDI) Molar ratio of base agent to curing agent (NCO/OH): 2
The adhesive α does not substantially contain a solvent.
・Adhesive β
Base: Polyester polymer (Mw: 3,500)
Hardener: a mixture of isophorone diisocyanate (IPDI) and HDI
(HDI content is higher than IPDI)
Molar ratio of base agent to curing agent (NCO/OH): 2
The adhesive β does not substantially contain a solvent.
・Adhesive γ
Base: Polyester polymer (Mw: 3,500)
Curing agent: mixture of IPDI and HDI Molar ratio of base agent to curing agent (NCO/OH): 1
The adhesive γ is substantially free of solvent.
・Adhesive δ
Base: Polyester polymer (Mw: 20,000)
Hardener: A mixture of biuret HDI and nurate HDI. Molar ratio of base resin to hardener (NCO/OH): 1.5
The adhesive δ contains a solvent.

[Example 1]
As the first substrate, a biaxially stretched polypropylene film having a thickness of 20 μm (P2171, manufactured by Toyobo Co., Ltd., hereinafter also referred to as "OPP film") having one surface subjected to corona treatment was prepared. As the second substrate, the above-mentioned transparent barrier substrate was prepared. As the sealant layer, a non-stretched polypropylene film having a thickness of 60 μm (ET-20, manufactured by Okamoto Co., Ltd., hereinafter also referred to as "CPP film") having one surface subjected to corona treatment was prepared.

A printed layer with a coating thickness of 1 μm (when dry) was formed on the corona-treated surface of the OPP film as the first substrate by the gravure roll coating method. Adhesive α was applied onto the printed layer by the gravure roll coating method, and the adhesive layer surface of the first substrate and the barrier coat layer surface of the transparent barrier substrate were bonded together, and aged at 40°C for 72 hours. Furthermore, a corona treatment was performed on the non-barrier coat layer surface of the transparent barrier substrate, and adhesive α was applied by the gravure roll coating method, and the adhesive layer surface of the transparent barrier substrate and the corona-treated surface of the CPP film were bonded together, and aged at 40°C for 72 hours. The thickness of each adhesive layer formed was 0.45 μm.

In this way, a laminate was obtained. The resulting laminate has a layer structure of OPP film (20 μm)/printed layer (1 μm)/adhesive layer (0.45 μm)/transparent barrier substrate (21 μm)/adhesive layer (0.45 μm)/CPP film (60 μm). The numbers in parentheses indicate the thickness of each layer.

[Examples 2 to 7]
Laminates were prepared 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 described in Table 1. Here, the thickness of the first adhesive layer was also changed in the same manner as the thickness of the second adhesive layer.

[Example 8]
As the first substrate, a biaxially stretched polypropylene film (P2171, OPP film, manufactured by Toyobo Co., Ltd.) having a thickness of 20 μm and having one surface subjected to corona treatment was prepared. As the second substrate, the above-mentioned transparent barrier substrate was prepared. As the sealant layer, a non-stretched polypropylene film (ET-20, CPP film, manufactured by Okamoto Co., Ltd.) having a thickness of 60 μm and having one surface subjected to corona treatment was prepared.

A printed layer with a coating thickness of 1 μm (when dry) was formed on the corona-treated surface of the OPP film as the first substrate by the gravure roll coating method. Adhesive γ was applied onto the printed layer by the gravure roll coating method, and the adhesive layer surface of the first substrate and the barrier coat layer surface of the transparent barrier substrate were bonded together, and aged at 40°C for 72 hours. Furthermore, a corona treatment was performed on the non-barrier coat layer surface of the transparent barrier substrate, and adhesive γ was applied by the gravure roll coating method, and the adhesive layer surface of the transparent barrier substrate and the corona-treated surface of the CPP film were bonded together, and aged at 40°C for 72 hours. The thickness of each adhesive layer formed was 3.6 μm.

In this way, a laminate was obtained. The resulting laminate has a layer structure of OPP film (20 μm)/printed layer (1 μm)/adhesive layer (3.6 μm)/transparent barrier substrate (21 μm)/adhesive layer (3.6 μm)/CPP film (60 μm). The numbers in parentheses indicate the thickness of each layer.

[Softening point measurement]
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 the laminate in the thickness direction perpendicular to the main surface. Finishing was performed with a diamond knife. The thickness of the substrate and each layer can also be measured by observing the cross section using a scanning electron microscope (SEM, Hitachi, Ltd., SU8000).

The measurement device used was a nanoTA manufactured by ANASYS INSTRUMENTS, and the thermal probe used was a PR-EX-AN2-300-5 manufactured by ANASYS INSTRUMENTS.

Before the measurement, the following calibration was performed.
As the standard samples, nanoTA Calibration Samples manufactured by BRUKER were prepared. Polycaprolactone (softening point: 55°C), polyethylene (softening point: 116°C), and polyethylene terephthalate (softening point: 235°C), which have known softening points, were placed on the stand of the standard samples. Each standard sample was heated while being in contact with a thermal probe on its surface. During heating, the thermal expansion directly below the thermal probe was measured, and a graph showing the deflection against the voltage was obtained. The measurement conditions set in the device were as follows.
Measurement start temperature: 0.1V
Measurement end temperature: 10V
Temperature rise rate: 0.5 V/sec

Using the softening point of each standard sample, the graph showing the thermal probe displacement versus potential was converted into a graph showing displacement versus temperature. Calibration (n=10) was performed in this manner.

After calibration, the softening point of the adhesive layer was measured. The softening point was measured near the center of the adhesive layer in the thickness direction, among the exposed cross sections of the adhesive layer. Measurements were performed at five or more points on the same cross section, and the softening point was recorded as the arithmetic mean of the values measured at five points with good reproducibility. However, the measurement points were spaced at least 50 μm apart.

The measurement was performed by bringing a thermal probe into contact with the cross section of the adhesive layer, heating the adhesive layer under the conditions described below while the thermal probe was in contact, and obtaining a graph (thermal expansion curve) showing the displacement of the thermal probe versus temperature.
Measurement start temperature: 40℃
Measurement end temperature: 350°C
Heating rate: 28° C./sec

If a peak was obtained in the thermal expansion curve, the temperature of the peak was taken as the softening point. If multiple peaks were present in the obtained thermal expansion curve, the temperature of the peak that appeared on the lowest temperature side was taken as the softening point. A thermal expansion curve in which a continuous displacement drop of 0.2 V or more was measured from the maximum displacement was considered to have a peak.

[Measurement of Elastic Modulus]
For the laminate obtained in the above example, a force curve 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 at room temperature (25°C) using a commercially available rotary microtome to prepare a cross section of the laminate. The cross section was obtained by cutting the laminate in the thickness direction perpendicular to the main surface. Finishing was performed with a diamond knife.
Using an atomic force microscope (AFM), mapping measurements were performed on the above cross section at a 2.5 μm square including the cross section of the adhesive layer. For the cross section of the adhesive layer, 20 force curves that provided an appropriate force curve shape were selected. The elastic modulus was calculated by fitting each force curve according to the JKR (Johnson-Kendall-Roberts) theory, and the arithmetic mean value (hereinafter also referred to as the "first arithmetic mean value") of the obtained 20 elastic moduli was calculated. Here, the selected part of the force curve was the vicinity of the center in the thickness direction of the adhesive layer among the parts where the cross section of the adhesive layer was exposed. Three elastic moduli close to the first arithmetic mean value were selected from the above 20 elastic moduli, and the arithmetic mean value (hereinafter also referred to as the "second arithmetic mean value") of the three elastic moduli was calculated. The obtained second arithmetic mean value was taken as the elastic modulus of the cross section of the adhesive layer.

The details of the AFM measurement conditions are shown below.
(AFM Elastic Modulus Measurement)
・Device name: SPM-9700HT (Shimadzu Corporation)
Measurement atmosphere: Atmospheric air, room temperature (25°C)
Measurement mode: Contact mode Calibration method: Measure the cantilever sensitivity using glass Number of measurement points: 64 x 64 points (total 4096 points)
・Field of view: 2.5 μm square ・Cantilever type: CONTR (manufactured by Nano World)
Cantilever tip radius: <8 nm
Cantilever spring constant: 0.2 N/m
Contact pressure: 0.5V
Scan speed: 3Hz
Calculation model for elastic modulus: JKR (Johnson-Kendall-Roberts) theory Poisson's ratio of sample: 0.4
・Analysis software: Nano 3D Mapping (Shimadzu Corporation)

[Gas barrier property evaluation (after retort treatment)]
Two sheets of the laminate obtained in the above example were prepared, and these were stacked with the sealant layer (CPP film) facing each other, and three sides were heat-sealed under conditions of 180 ° C, 0.1 MPa, and 1 second to produce a flat pouch of B5 size (182 mm × 257 mm). 100 mL of water was filled into the obtained pouch from the opening, and the opening was heat-sealed under the above conditions to seal the pouch. Retort sterilization was performed on the obtained pouch under retort conditions of 121 ° C, 30 minutes, and 0.21 MPa. After retort sterilization, the laminate was cut out from the pouch to obtain a test piece. Using this test piece, the oxygen permeability (cc / m ² · day · atm) was measured by the following method.

Using an oxygen permeability measuring device (OX-TRAN2/20, manufactured by MOCON), the test piece was set so that the first substrate side was the oxygen supply side, and the oxygen permeability was measured in an environment of a temperature of 23°C and a relative humidity of 90% RH in accordance with JIS K7126-2:2006. The results are shown in Table 1.

[Tearability and drop-breakage of bags]
Two laminates obtained in the above example were prepared, and these were stacked with the sealant layer (CPP film) facing each other, and three sides were heat-sealed under conditions of 180 ° C, 0.1 MPa, and 1 second to produce a pouch with outer dimensions of 130 mm x 170 mm and inner dimensions of 110 mm x 150 mm. A notch portion having a length of 2 mm in the short direction was formed at a position 20 mm in the longitudinal direction from the top of the pouch. 180 mL of water was filled into the obtained pouch from the opening, and the opening was heat-sealed under the above conditions to seal the pouch. Retort sterilization was performed on the obtained pouch under retort conditions of 121 ° C, 30 minutes, and 0.21 MPa. The pouch after retort sterilization was left to stand in a 22 ° C environment for 1 day, and then tearability evaluation and drop bag breakage evaluation were performed.

(Tearability)
An evaluation was made as to whether the pouch could be opened by tearing it linearly along the cut direction of the notch.
AA: The pouch can be opened in a straight line.
The pouch could be opened without issue from the notch to the opposite end of the pouch.
BB: The pouch was torn in different directions on the front and back.
The pouch could be opened without issue from the notch to the opposite end of the pouch.
CC: The pouch is torn in different directions at the front and back.
The pouch could not be opened from the notch to the opposite end of the pouch.

(Bag falls and breaks)
Ten pouches of each type were prepared and dropped 10 times from a height of 120 cm in a direction such that the main surface of the pouch struck the floor, and further dropped 10 times in a direction such that the sealed portion at the bottom of the pouch (the side with an inner dimension of 110 mm) struck the floor, and the presence or absence of breakage of the pouch was visually confirmed.
AA: No breakage was observed, and no scratches or seal recession occurred.
BB: No breakage was observed, but scratches and seal recession occurred.
CC: One or more broken bags were confirmed.

[Polypropylene content]
The content of polypropylene relative to the total amount of resin materials contained in the laminates obtained in the above examples is shown in Table 1.

1: laminate, 10: oriented polypropylene substrate, 20: barrier substrate, 22: oriented polypropylene substrate, 23: surface coating layer, 24: inorganic oxide layer, 25: coating layer, 30: sealant layer, 40A, 40B: adhesive layers,
50: packaging bag, 51: easy-to-open portion, 52: notch portion, 53: half-cut line,
60: standing pouch, 61: body (side sheet), 62: bottom (bottom sheet), 63: steam release mechanism, 63a: steam release sealed portion, 63b: non-sealed portion

Claims (16)

A first substrate;
a first adhesive layer;
A second substrate;
a second adhesive layer; and
A sealant layer;
A laminate having the following in this order in the thickness direction:
the first substrate comprises a stretched substrate containing polypropylene as a main component, the second substrate comprises a stretched substrate containing polypropylene as a main component, and at least one selected from the first substrate and the second substrate is a barrier substrate further comprising an inorganic oxide layer;
The sealant layer contains polypropylene as a main component,
The elastic modulus measured on a cross section of the second adhesive layer using an atomic force microscope (AFM) is 30.0 MPa or more, and the thickness of the second adhesive layer is 0.5 μm or more and 3.0 μm or less.
Laminate. The laminate according to claim 1, wherein the softening point of the cross section of the second adhesive layer measured by local thermal analysis using a thermal probe is 200°C or higher and 330°C or lower. The laminate according to claim 1, wherein the elastic modulus measured on a cross section of the first adhesive layer using an atomic force microscope (AFM) is 30.0 MPa or more, and the thickness of the first adhesive layer is 0.5 μm or more and 3.0 μm or less. The laminate according to claim 3, wherein the softening point of the cross section of the first adhesive layer measured by local thermal analysis using a thermal probe is 200°C or higher and 330°C or lower. The laminate of claim 3, wherein the elastic modulus of the first adhesive layer is greater than the elastic modulus of the second adhesive layer. The laminate of claim 3, wherein the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer. The laminate according to claim 1, wherein the elastic modulus measured on a cross section of the first adhesive layer using an atomic force microscope (AFM) is less than 30.0 MPa, and the softening point measured on a cross section of the first adhesive layer by local thermal analysis using a thermal probe is 200°C or higher and 330°C or lower. The laminate according to claim 7, wherein the thickness of the first adhesive layer is 2.0 μm or more and 5.0 μm or less. The laminate of claim 7, wherein the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer. The laminate according to claim 1, wherein the barrier substrate further comprises a coating layer on the surface of the inorganic oxide layer opposite to the surface facing the stretched substrate. the first substrate is the stretched substrate,
the second substrate is the barrier substrate including the stretched substrate and the inorganic oxide layer, and the second substrate is disposed so that the inorganic oxide layer faces the first substrate side and the stretched substrate faces the sealant layer side;
The laminate according to claim 1 . the first substrate is a barrier substrate including the stretched substrate and the inorganic oxide layer, and the first substrate is disposed such that the inorganic oxide layer faces the second substrate and the stretched substrate faces outward;
The second substrate is the stretched substrate.
The laminate according to claim 1 . The laminate according to any one of claims 1 to 12, wherein the content of polypropylene in the total amount of resin material contained in the laminate is 80% by mass or more. The laminate according to any one of claims 1 to 12, which is a packaging material. A packaging bag comprising the laminate according to any one of claims 1 to 12. The packaging bag according to claim 15, which is a pouch that has been retorted or boiled.