JP7784059B2 - Laminate for packaging material, lid material and packaging container - Google Patents

Description

This disclosure relates to a laminate for packaging materials, a lid material, and a packaging container.

Resin films have traditionally been used as packaging materials. For example, resin films made from polyolefins are widely used as sealant films because they are flexible, transparent, and have excellent heat-sealing properties. Unstretched polyolefin resin films typically cannot be used as substrates due to their lack of strength and heat resistance, and are therefore laminated with polyester or nylon films. For this reason, typical packaging containers are made from laminated films in which the substrate and sealant film are made from different resin materials (see, for example, Patent Document 1).

In recent years, with growing calls for the creation of a recycling-oriented society, there has been a demand for packaging containers that are highly recyclable. However, conventional packaging containers are made up of different resin materials, and because it is difficult to separate the individual resin materials, they are not currently recycled.

Japanese Patent Application Laid-Open No. 2009-202519

The present inventors investigated the use of a single polypropylene material from the perspective of using a single material (mono-material) that is easy to recycle. Specifically, the present inventors investigated using a stretched substrate containing polypropylene instead of a polyester film or nylon film as the substrate, and combining it with a sealant film containing polypropylene. With this configuration, both the substrate and the sealant film are made of polypropylene, thereby improving the recyclability of the packaging container.

The substrate typically needs to be heat-resistant enough to withstand the heat applied during printing, heat sealing, and other processes. Therefore, it is desirable for the substrate to be heat-resistant even when made into a mono-material. However, compared to polyester film and nylon film, stretched substrates containing polypropylene tend to have insufficient heat resistance. Therefore, when using a laminate comprising a stretched substrate containing polypropylene and a sealant layer containing polypropylene, the temperature range in which heat sealing can be performed appropriately may be narrowed, such as by experiencing significant thermal shrinkage during heat sealing.

One of the problems to be solved by this disclosure is to provide a laminate for packaging materials that includes a stretched substrate containing polypropylene and a sealant layer containing polypropylene, and that has good heat-sealability over a wide temperature range.

The laminate for packaging materials disclosed herein comprises a first substrate and a sealant layer. The first substrate comprises an oriented resin layer containing polypropylene as a primary component, and the sealant layer is a resin layer containing polypropylene as a primary component. In one embodiment, the polypropylene contained in the oriented resin layer has an extrapolated melting initiation temperature (Tim) at the first temperature rise, as determined by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012, higher than the Tim at the first temperature rise, as determined by DSC, of the polypropylene contained in the sealant layer. In one embodiment, when the laminate is heat-sealed under heat-sealing conditions of a pressure of 0.1 MPa and a heat-sealing time of 1 second, the heat-sealing temperature range, 130°C to 190°C, at which the seal strength measured at a test speed of 300 mm/min and T-peel is 23 N/15 mm or greater and the shrinkage rate in the TD direction of the laminate is 0% to 1.0% is 5°C or greater.

According to the present disclosure, a laminate for packaging materials can be provided that includes a stretched substrate containing polypropylene and a sealant layer containing polypropylene, and that has good heat sealing properties over a wide temperature range. For example, it can provide a laminate that has excellent seal strength and suppresses thermal shrinkage during heat sealing.

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 the 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 schematic cross-sectional view showing one embodiment of a laminate. FIG. 8 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 9 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 10 is a front view showing one embodiment of a packaging container. FIG. 11 is a perspective view showing one embodiment of a packaging container.

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

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

[Laminate for packaging material]
The laminate of the present disclosure comprises a first substrate and a sealant layer.
The first substrate includes a stretched resin layer containing polypropylene as a main component. In the present disclosure, the term "stretched resin layer" refers to a resin layer that has been subjected to a stretching treatment.

In one embodiment, the first substrate is a polypropylene resin substrate composed of a stretched resin layer containing polypropylene as a main component, i.e., a polypropylene resin substrate that has been subjected to a stretching treatment.

In one embodiment, the first substrate is a barrier substrate comprising an oriented resin layer containing polypropylene as a main component and a vapor-deposited film composed of an inorganic oxide. The barrier substrate may further comprise the layers described below.

The sealant layer is a resin layer containing polypropylene as its main component.

In this disclosure, the extrapolated melting onset temperature (Tim) of polypropylene during the first heating cycle, obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012 (Method for measuring transition temperatures of plastics), is also referred to as "Tim1," and the extrapolated melting onset temperature (Tim) during the second heating cycle is also referred to as "Tim2."

In the present disclosure, in one embodiment, the Tim1 of the polypropylene contained in the stretched resin layer of the first substrate is higher than the Tim1 of the polypropylene contained in the sealant layer. The difference between the Tim1 of the polypropylene contained in the stretched resin layer of the first substrate and the Tim1 of the polypropylene contained in the sealant layer is preferably 2°C or more, more preferably 5°C or more, even more preferably 8°C or more, even more preferably 12°C or more, and particularly preferably 15°C or more, 18°C or more, or 20°C or more. A laminate that meets these requirements has excellent sealing properties, such as bag-making suitability and filling suitability, despite being a mono-material laminate. In other words, the laminate has a wide heat-sealable temperature range and excellent seal strength.

In the present disclosure, in one embodiment, the Tim2 of the polypropylene contained in the stretched resin layer of the first substrate is higher than the Tim2 of the polypropylene contained in the sealant layer. The difference between the Tim2 of the polypropylene contained in the stretched resin layer of the first substrate and the Tim2 of the polypropylene contained in the sealant layer is preferably 2°C or more, more preferably 5°C or more, even more preferably 8°C or more, and particularly preferably 10°C or more. A laminate that meets these requirements has excellent sealing properties, such as bag-making suitability and filling suitability, despite being a mono-material laminate. In other words, the laminate has a wide heat-sealable temperature range and excellent sealing strength.

The upper limit of the difference between Tim1 of the polypropylene contained in the stretched resin layer of the first substrate and Tim1 of the polypropylene contained in the sealant layer may be, for example, 40°C. The upper limit of the difference between Tim2 of the polypropylene contained in the stretched resin layer of the first substrate and Tim2 of the polypropylene contained in the sealant layer may be, for example, 30°C.

Tim is measured in accordance with JIS K7121:2012 (Method for Measuring Transition Temperature of Plastics) using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, product name: DSC7000X). The sample is held at 20°C for 1 minute, then heated from 20°C to 200°C at a heating rate of 10°C/min, held at 200°C for 5 minutes, then cooled from 200°C to 20°C at a cooling rate of 10°C/min, and held at 20°C for 5 minutes. The sample is then heated again from 20°C to 200°C at a heating rate of 10°C/min. The extrapolated melting onset temperature (Tim) is calculated as the temperature at the intersection of a straight line extending the low-temperature baseline toward the high-temperature side of the DSC curve during the first and second heating periods, and a tangent drawn to the curve at the maximum slope on the low-temperature side of the melting peak. If there are two or more timings, use the timing of the melting peak with the greatest peak intensity.

In one embodiment, the laminate of the present disclosure is characterized in that the heat sealing temperature range that satisfies the following requirements exists within a range of 130°C or higher and 190°C or lower by 5°C or more. That is, in one embodiment, when the laminate is heat-sealed under heat-sealing conditions of a temperature range of 130°C or higher and 190°C or lower, a pressure of 0.1 MPa, and a heat-sealing time of 1 second, the heat-sealing temperature range (temperature width) at which the seal strength is 23 N/15 mm or higher and the shrinkage rate in the TD direction of the laminate is 0% or higher and 1.0% or lower exists within a range of 130°C or higher and 190°C or lower by 5°C or more. Such a laminate has excellent heat resistance and, for example, can be used to produce packaging containers with good appearance when heat-sealed.

In one embodiment, the heat sealing temperature range (temperature width) that satisfies the above requirements may be 5°C or more in the range of 140°C to 185°C, 5°C or more in the range of 145°C to 180°C, 5°C or more in the range of 150°C to 180°C, or 5°C or more in the range of 160°C to 175°C. Furthermore, the heat sealing temperature range that satisfies the above requirements may be within the range of 5°C to 30°C, 5°C to 20°C, 5°C to 15°C, or 5°C to 10°C.

The above-mentioned seal strength is preferably 25 N/15 mm or more, more preferably 28 N/15 mm or more. By using such a laminate, for example, it is possible to produce packaging containers with good seal strength. Note that the seal strength required for the seal portion of packaging materials for retort-sterilized cooked foods is stipulated as 23 N/15 mm or more in the quality standards of the Food Sanitation Act.

The shrinkage and seal strength of laminates are measured as follows. First, two laminates are prepared and cut to a size of 100 mm x 100 mm. They are then overlapped with the sealant layer facing each other and heat-sealed in the transverse direction using a 10 mm-wide single-sided heated flat heat seal bar. Heat-sealing conditions are a temperature of 130°C to 190°C, a pressure of 0.1 MPa, and a time of 1 second. The transverse length of the heat-sealed portion of the sealed sample is measured using a 150 mm ruler, and the shrinkage (%) is calculated as follows: (length before sealing (100 mm) - length after sealing (mm)) / length before sealing (100 mm) x 100. The sealed sample is then cut to a width of 15 mm in the transverse direction to prepare a 15 mm wide, 100 mm long test specimen. Using this test specimen, seal strength is measured using a tensile tester at a test speed of 300 mm/min using a T-peel test.

For example, by using a polypropylene oriented resin layer with excellent heat resistance as the first substrate and an unoriented polypropylene resin layer with excellent low-temperature sealing properties as the sealant layer, it is possible to obtain a laminate that meets the requirements for Tim, shrinkage rate, and seal strength.

The laminate of the present disclosure is suitable for use as a packaging material.

In one embodiment, the laminate of the present disclosure further includes a second substrate (intermediate substrate) between the first substrate and the sealant layer, the second substrate including an oriented resin layer containing polypropylene as a primary component. That is, in one embodiment, the laminate of the present disclosure includes a first substrate, a second substrate, and a sealant layer in this order in the thickness direction.

In one embodiment, the second substrate is a barrier substrate comprising a stretched resin layer containing polypropylene as a primary component and a vapor-deposited film composed of an inorganic oxide. In one embodiment, the second substrate is a polypropylene resin substrate composed of a stretched resin layer containing polypropylene as a primary component, i.e., a polypropylene resin substrate that has been subjected to a stretching treatment.

The first substrate and the second substrate are each independently a barrier substrate or a polypropylene resin substrate. In one embodiment, one of the first substrate and the second substrate is a barrier substrate, and the other of the first substrate and the second substrate is a polypropylene resin substrate. In other embodiments, both the first substrate and the second substrate may be a barrier substrate, or both the first substrate and the second substrate may be a polypropylene resin substrate.

1 to 9 are schematic cross-sectional views showing an embodiment of a laminate.
1 includes a barrier substrate 20 as a first substrate, an adhesive layer 40, and a sealant layer 30, in this order in the thickness direction. The barrier substrate 20 includes a stretched resin layer 22 and a vapor-deposited film 24. In this example, the stretched resin layer 22 constitutes the outermost layer of the laminate 1, and the vapor-deposited film 24 is in contact with the adhesive layer 40.

Figure 2 is similar to Figure 1, except that the barrier substrate 20 has a surface coating layer or surface resin layer 23 between the stretched resin layer 22 and the vapor-deposited film 24.

Figure 3 is the same as Figure 1, except that the barrier substrate 20 comprises, in this order in the thickness direction, an oriented resin layer 22, a surface coating layer or surface resin layer 23, a vapor-deposited film 24, and a barrier coating layer 25. In this example, the barrier coating layer 25 contacts the adhesive layer 40.

The laminate 1 shown in Figure 4 comprises a polypropylene resin substrate 10 as a first substrate, an adhesive layer 40A, a barrier substrate 20 as a second substrate, an adhesive layer 40B, and a sealant layer 30, in that order in the thickness direction. The barrier substrate 20 comprises a stretched resin layer 22 and a vapor-deposited film 24. In this example, the stretched resin layer 22 is in contact with the adhesive layer 40B, and the vapor-deposited film 24 is in contact with the adhesive layer 40A.

Figure 5 is similar to Figure 4 except that the barrier substrate 20 has a surface coating layer or surface resin layer 23 between the stretched resin layer 22 and the vapor-deposited film 24.

Figure 6 is the same as Figure 4, except that the barrier substrate 20 comprises, in this order in the thickness direction, an oriented resin layer 22, a surface coating layer or surface resin layer 23, a vapor-deposited film 24, and a barrier coating layer 25. In this example, the barrier coating layer 25 contacts the adhesive layer 40A.

The laminate 1 shown in Figure 7 comprises a barrier substrate 20 as a first substrate, an adhesive layer 40A, a polypropylene resin substrate 10 as a second substrate, an adhesive layer 40B, and a sealant layer 30, in that order in the thickness direction. The barrier substrate 20 comprises a stretched resin layer 22 and a vapor-deposited film 24. In this example, the stretched resin layer 22 constitutes the outermost layer of the laminate 1, and the vapor-deposited film 24 is in contact with the adhesive layer 40A.

Figure 8 is similar to Figure 7 except that the barrier substrate 20 has a surface coating layer or surface resin layer 23 between the stretched resin layer 22 and the vapor-deposited film 24.

Figure 9 is the same as Figure 7, except that the barrier substrate 20 comprises, in this order in the thickness direction, an oriented resin layer 22, a surface coating layer or surface resin layer 23, a vapor-deposited film 24, and a barrier coating layer 25. In this example, the barrier coating layer 25 contacts the adhesive layer 40A.

Specific examples of the layer structure of the laminate of the present disclosure are shown below. "/" indicates the boundary between layers. "OPP film" refers to a polypropylene resin substrate that has been subjected to a stretching treatment.
(1) OPP film/printed layer/adhesive layer/sealant layer (2) Barrier substrate/printed layer/adhesive layer/sealant layer (3) OPP film/printed layer/adhesive layer/barrier substrate/adhesive layer/sealant layer (4) Barrier substrate/printed layer/adhesive layer/OPP film/adhesive layer/sealant layer (5) Barrier substrate/printed layer/adhesive layer/barrier substrate/adhesive layer/sealant layer (6) OPP film/printed layer/adhesive layer/OPP film/adhesive layer/sealant layer

In one embodiment, the laminate of the present disclosure comprises at least three elements: a polypropylene resin substrate, a barrier substrate, and a sealant layer. This allows for further improvement in gas barrier properties (particularly oxygen barrier properties and water vapor barrier properties).

When the first substrate is a barrier substrate, in one embodiment, the first substrate is positioned so that the vapor-deposited film faces the sealant layer and the stretched resin layer faces the side opposite the sealant layer.

When the second substrate is a barrier substrate, in one embodiment, the second substrate is arranged so that the vapor-deposited film faces the first substrate and the stretched resin layer faces the sealant layer, or the second substrate is arranged so that the vapor-deposited film faces the sealant layer and the stretched resin layer faces the first substrate. Among these, from the perspective of further suppressing deterioration of the vapor-deposited film, when the second substrate is a barrier substrate, it is preferable to arrange the second substrate so that the vapor-deposited film faces the first substrate and the stretched resin layer faces the sealant layer.

In one embodiment of the laminate of the present disclosure, the first substrate is a polypropylene resin substrate, and the second substrate is a barrier substrate (see Figures 4 to 6). In this embodiment, the laminate comprises a polypropylene resin substrate, a barrier substrate, and a sealant layer, in this order in the thickness direction. A laminate with this configuration adequately protects the vapor-deposited film when subjected to heat treatment or the like, and exhibits even higher gas barrier properties. Furthermore, the laminate of the above embodiment has a smaller heat shrinkage rate when subjected to heat treatment, and therefore has even better suitability for bag formation.

The proportion of polypropylene-based single material in the laminate of the present disclosure (hereinafter also referred to as the "mono-material ratio") 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. This makes it possible, for example, to produce mono-material packaging containers using the laminate, thereby improving the recyclability of the packaging containers. A higher mono-material ratio is preferable, but the upper limit may be, for example, 99% by mass or 98% by mass.

In this disclosure, the mono-material ratio refers to the proportion of a single polypropylene-based material relative to the total mass of the laminate. However, if a layer contains polypropylene as the primary component (i.e., more than 50% by mass), the mono-material ratio is calculated assuming that polypropylene constitutes 100% by mass of the layer. For example, in the case of a sealant layer composed of 80% by mass of polypropylene and 20% by mass of another resin material, the mono-material ratio is calculated assuming that the sealant layer is composed of 100% by mass of polypropylene.

<First substrate>
In one embodiment, the first substrate is a polypropylene resin substrate composed of a stretched resin layer. In one embodiment, the first substrate is a barrier substrate comprising a stretched resin layer and a vapor-deposited film composed of an inorganic oxide. Details of each layer that can be provided on the barrier substrate will be described later.

(Stretched resin layer)
The stretched resin layer of the first substrate contains polypropylene as a main component, i.e., more than 50% by mass of polypropylene. By providing the first substrate with the stretched resin layer, for example, it is possible to improve the oil resistance of a packaging container produced using the first substrate.

The polypropylene may be a propylene homopolymer, a propylene random copolymer, or a propylene block copolymer, or a mixture of two or more selected from these.

A propylene homopolymer is a polymer of propylene only. 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 also be a polymer block of propylene and an α-olefin other than propylene.

Examples of α-olefins include α-olefins having 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, it is preferable to use a random copolymer from the viewpoint of transparency. If the rigidity and heat resistance of the packaging container are important, it is preferable to use a homopolymer. If the drop impact resistance of the packaging container is important, it is preferable to use a block copolymer. In the stretched resin layer provided in the first substrate, a homopolymer is preferable from the viewpoint of heat resistance.

The Tim1 of the polypropylene that is the main component of the stretched resin layer in the first base material is preferably 146°C or higher, more preferably 146.5°C or higher, even more preferably 147°C or higher, and particularly preferably 147.5°C or higher. This allows, for example, the production of a packaging material with superior heat resistance, and can suppress thermal shrinkage during heat sealing, for example. The upper limit of Tim1 of the polypropylene that is the main component of the stretched resin layer is not particularly limited, but may be, for example, 170°C, 165°C, 160°C, or 155°C.

The Tim2 of the polypropylene that is the main component of the stretched resin layer in the first base material is preferably 150°C or higher, more preferably 150.5°C or higher, even more preferably 151°C or higher, and particularly preferably 151.5°C or higher. This allows, for example, the production of a packaging material with superior heat resistance, and can suppress thermal shrinkage during heat sealing, for example. The upper limit of Tim2 of the polypropylene that is the main component of the stretched resin layer is not particularly limited, but may be, for example, 170°C, 165°C, 160°C, or 155°C.

The Tim of polypropylene can be increased by, for example, reducing the amount of copolymerizable monomer-derived structural units in the polypropylene or setting it to 0% by mass, increasing the mesopentad fraction of the polypropylene, increasing the amount of low-molecular-weight components, or setting a high stretching temperature during substrate production. The amount of copolymerizable monomer-derived structural units in the polypropylene may be, for example, 0.1 mol% or less, 0.05 mol% or less, or 0.01 mol% or less.

The mesopentad fraction of the polypropylene contained in the stretched resin layer of the first substrate may be, for example, 96% or more, or 97% or more. A mesopentad fraction within this range improves crystallinity and reduces heat shrinkage at high temperatures. The mesopentad fraction may be, for example, 99.5% or less, or 99% or less.

The mesopentad fraction (isotactic mesopentad fraction) can be measured by ¹³ C-NMR. The mesopentad fraction is calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973)". ¹³ C-NMR measurement is performed using an "AVANCE 500" manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 (volume ratio) mixture of o-dichlorobenzene and deuterated benzene at 135°C and then at 110°C.

The weight-average molecular weight (Mw) of the polypropylene contained in the stretched resin layer of the first substrate may be, for example, 250,000 or more and 500,000 or less, or 260,000 or more and 450,000 or less. The polydispersity index of the polypropylene, weight-average molecular weight (Mw)/number-average molecular weight (Mn), may be, for example, 5.5 or more and 30 or less, or 6.5 or more and 25 or less.

When measuring the gel permeation chromatography (GPC) cumulative curve of the polypropylene contained in the stretched resin layer of the first substrate, the lower limit of the amount of components with a molecular weight of 10,000 or less may be, for example, 2% by mass or 3% by mass. The upper limit of the amount of components with a molecular weight of 10,000 or less in the GPC cumulative curve may be, for example, 20% by mass or 15% by mass.

When measuring the GPC cumulative curve of the polypropylene contained in the stretched resin layer of the first substrate, the lower limit of the amount of components with a molecular weight of 100,000 or less may be, for example, 35% by mass or 40% by mass. The upper limit of the amount of components with a molecular weight of 100,000 or less in the GPC cumulative curve may be, for example, 65% by mass or 60% by mass.

The molecular weight and polydispersity of each polypropylene are determined using GPC with monodisperse polystyrene as a standard. The measurement conditions, such as the column and solvent used in the GPC measurement, are as follows:
Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMH _HR -H(20)HT x 3
・Flow rate: 1.0ml/min
Detector: RI
・Measurement temperature: 140℃

Polypropylene is obtained by polymerizing the raw material propylene using, for example, a Ziegler-Natta catalyst or a metallocene catalyst. It is preferable to use a catalyst capable of highly regular polymerization, such as a Ziegler-Natta catalyst. Propylene can be produced by, for example, polymerizing propylene in an inert solvent such as hexane, heptane, toluene, or xylene; polymerizing in liquid propylene or ethylene; adding a catalyst to gaseous propylene or ethylene and polymerizing in the gas phase; or a combination of these methods.

For example, polypropylene can be obtained by producing high-molecular-weight and low-molecular-weight components separately and then mixing them, or by polymerizing them in multiple stages in a plant with a series of multiple reactors. In particular, a plant with multiple reactors can be used to first produce the high-molecular-weight component, and then produce the low-molecular-weight component in its presence. The molecular weight can be adjusted by the amount of hydrogen mixed into the system during polymerization.

In one embodiment, from the viewpoint of film-forming properties and processability, the melt flow rate (MFR) of the polypropylene may be 0.1 g/10 min or more and 50 g/10 min or less, or 0.3 g/10 min or more and 30 g/10 min or less. The MFR of the polypropylene is measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kg.

From the perspective of reducing the environmental impact, biomass-derived polypropylene or mechanically or chemically recycled polypropylene may be used as the polypropylene.

The polypropylene content in the stretched resin layer of the first substrate is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The stretched resin layer in the first substrate may contain a resin material other than polypropylene. Examples of resin materials include polyolefins such as polyethylene, (meth)acrylic resins, vinyl resins, cellulose resins, polyamides, polyesters, and ionomer resins.

The stretched resin layer in the first substrate may contain additives. Examples of additives include crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

The stretched resin layer in the first substrate is a layer that has been subjected to a stretching treatment. This can improve, for example, the heat resistance, drop impact resistance, water resistance, and dimensional stability of the laminate. A laminate including such a resin layer is suitable, for example, as a packaging material for constituting a packaging container that is subjected to a boiling treatment or a retort treatment.
The stretching treatment may be uniaxial stretching or biaxial stretching.

When stretching in the machine direction (machine direction, MD, the flow direction of the substrate), the stretching ratio is preferably 2 to 15, more preferably 5 to 13. When stretching in the transverse direction (direction perpendicular to the MD, TD, the stretching ratio is preferably 2 to 15, more preferably 5 to 13. By setting the stretching ratio to 2 or more, for example, the strength and heat resistance of the stretched resin layer can be further improved, and the printability of the stretched resin layer can be improved. From the perspective of the breaking limit of the stretched resin layer, a stretching ratio of 15 or less is preferred.

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

The stretched resin layer of the first substrate may have a single-layer structure or a multi-layer structure.
The thickness of the stretched resin layer in the first substrate is preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. When the thickness is equal to or more than the lower limit, for example, the strength and heat resistance of the laminate can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be further improved.

In one embodiment, the stretched resin layer of the first substrate is not particularly limited as long as it is a stretched polypropylene resin layer with excellent heat resistance, but for example, a commercially available stretched polypropylene film such as a biaxially stretched polypropylene film (P2171, manufactured by Toyobo Co., Ltd.) may be used.

(evaporated film)
In one embodiment, the first substrate is a barrier substrate including a stretched resin layer and a vapor-deposited film composed of an inorganic oxide. In one embodiment, the barrier substrate includes a stretched resin layer and a vapor-deposited film provided on one surface of the resin layer. This can improve the gas barrier properties of the laminate, specifically the oxygen barrier properties and water vapor barrier properties. A packaging container made using the laminate can suppress weight loss of the contents filled in the packaging container.

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). Of these, silica, silicon carbide oxide, and alumina are preferred.

In one embodiment, silica is more preferred as the inorganic oxide because it does not require aging treatment after forming the vapor-deposited film. In one embodiment, carbon-containing silicon oxide is more preferred as the inorganic oxide because it can suppress deterioration in gas barrier properties even when the laminate is bent.

The thickness of the vapor-deposited film is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less. When the thickness is equal to or greater than the lower limit, for example, the oxygen barrier property and water vapor barrier property of the laminate can be further improved. When the thickness is equal to or less than the upper limit, for example, the occurrence of cracks in the vapor-deposited film can be suppressed and the recyclability of the packaging container can be improved.

It is preferable that the surface of the vapor-deposited film is subjected to the above-mentioned surface treatment. This improves adhesion between the vapor-deposited film and adjacent layers.

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

The vapor-deposited film may be a single layer formed by a single vapor deposition process, or a multilayer formed by multiple vapor deposition processes. When the vapor-deposited film is 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 vapor-deposited film on the barrier substrate is preferably a vapor-deposited film formed by CVD, and more preferably a carbon-containing silicon oxide vapor-deposited film formed by CVD. This prevents a decrease in gas barrier properties even when the laminate is bent.

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

In one embodiment of the carbon-containing silicon oxide vapor-deposited film, the silicon percentage Si is preferably 1% to 45%, more preferably 3% to 38%, and even more preferably 8% to 33%, based on 100% of the total of the three elements silicon, oxygen, and carbon. The oxygen percentage O is preferably 10% to 70%, more preferably 20% to 65%, and even more preferably 25% to 60%, based on 100% of the total of the three elements silicon, oxygen, and carbon. By keeping the silicon percentage Si and the oxygen percentage O within the above ranges, it is possible to further suppress deterioration in gas barrier properties, for example, even when the laminate is bent.

In one embodiment of the carbon-containing silicon oxide vapor-deposited film, the oxygen percentage O is preferably higher than the carbon percentage C, and the silicon percentage Si is preferably lower than the carbon percentage C. The oxygen percentage O is preferably higher than the silicon percentage Si; that is, the percentages preferably decrease in the order of percentage O, percentage C, and percentage Si. This can further suppress a decrease in gas barrier properties, for example, even when the laminate is bent.

The C, Si, and O content in a carbon-containing silicon oxide vapor-deposited film can be 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): approx. 6 mmφ
Photoelectron capture angle: 90 degrees [2] Ion sputtering conditions Ion species: Ar ⁺
Acceleration voltage: 0.2 (kV)
Emission current: 20 (mA)
Etch range: 10 mm φ
Ion sputtering time: 30 seconds, spectrum collection

(Surface coating layer)
In one embodiment, the barrier substrate includes a surface coating layer containing a resin material having a polar group between the stretched resin layer and the vapor-deposited film. By providing the surface coating layer containing a resin material having a polar group, it is possible to improve the adhesion of the vapor-deposited film formed on the surface coating layer and also improve the gas barrier properties.

In this embodiment, the barrier substrate comprises a resin substrate having an oriented resin layer and a surface coating layer, and a vapor-deposited film provided on the surface coating layer. This barrier substrate comprises the oriented resin layer, the surface coating layer, and the vapor-deposited film in this order in the thickness direction.

A polar group refers to a group containing one or more heteroatoms, and examples include ester groups, epoxy groups, hydroxyl groups, amino groups, amide groups, urethane groups, carboxyl groups, carbonyl groups, carboxylic anhydride groups, sulfo groups, thiol groups, and halogen groups. Among these, from the perspective of the lamination properties of packaging containers, carboxyl groups, carbonyl groups, ester groups, hydroxyl groups, amino groups, amide groups, and urethane groups are preferred, with carboxyl groups, hydroxyl groups, amide groups, and urethane groups being more preferred.

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

The surface coating layer can be formed using, for example, 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 (meth)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 a resin material 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 coating layer to the total thickness of the resin substrate having the stretched resin layer and the surface coating layer is preferably 0.08% or more and 20% or less, more preferably 0.2% or more and 15% or less, even more preferably 1% or more and 10% or less, and even more preferably 1% or more and 5% or less. When this ratio is equal to or greater than the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further improved. When this ratio is equal to or less than the upper limit, for example, the processability of the resin substrate and the recyclability of the packaging container can be further improved.

The thickness of the surface coating layer is preferably 0.02 μm to 10 μm, more preferably 0.05 μm to 10 μm, even more preferably 0.1 μm to 10 μm, and even more preferably 0.2 μm to 5 μm. When the thickness is equal to or greater than the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the resin substrate and the recyclability of the packaging container can be further improved.

For example, a resin substrate having a stretched resin layer and a surface coating layer can be produced by forming a resin film from polypropylene or a resin composition containing polypropylene using a T-die method, inflation method, or the like, stretching the resin film, applying a coating liquid for forming a surface coating layer to the stretched resin film, and drying it.

(Surface resin layer)
In one embodiment, the barrier substrate includes a surface resin layer between the stretched resin layer and the vapor-deposited film, the surface resin layer containing 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, it is possible to improve the adhesion of the vapor-deposited film formed on the surface resin layer and also improve the gas barrier properties.

In this embodiment, the barrier substrate comprises a resin substrate having an oriented resin layer and a surface resin layer, and a vapor-deposited film provided on the surface resin layer. This barrier substrate comprises the oriented resin layer, the surface resin layer, and the vapor-deposited film in this order in the thickness direction.

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 above the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further 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 resin substrate.

The melting point of a high-melting-point resin material can be measured in accordance with JIS K7121:2012 (Method for measuring transition temperatures of plastics). Specifically, a DSC curve can be measured using differential scanning calorimetry (DSC) at a heating rate of 10°C/min, and the melting peak temperature can be determined as the melting point.

The difference between the melting point of the high-melting-point resin material contained in the surface resin layer and the melting point of the polypropylene contained in the stretched resin layer is preferably 20°C or higher and 80°C or lower, more preferably 20°C or higher and 60°C or lower. When this difference is at the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further improved. When this difference is at or below the upper limit, for example, the film-forming properties of the resin substrate can be further improved.

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 include ester groups, epoxy groups, hydroxyl groups, amino groups, amide groups, urethane groups, carboxy groups, carbonyl groups, carboxylic anhydride groups, sulfo groups, thiol groups, and halogen groups. Of these, from the perspective of the gas barrier properties and laminate strength of the packaging container, hydroxyl groups, ester groups, amino groups, amide groups, carboxy groups, and carbonyl groups are preferred, and amide groups are more preferred.

The high-melting-point resin material may have a melting point of 180°C or higher, and examples include polyolefins, vinyl resins, (meth)acrylic resins, polyamides, polyimides, polyesters, cellulose resins, and ionomer resins. For example, resin materials with a melting point of 180°C or higher and containing polar groups are preferred, with ethylene-vinyl alcohol copolymers, polyvinyl alcohol, polyesters, and polyamides such as nylon 6, nylon 6,6, and MXD nylon being 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 a resin material 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 resin substrate having the stretched resin layer and the surface resin layer is preferably 1% or more and 10% or less, more preferably 1% or more and 5% or less. When this ratio is equal to or greater than the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further improved. When this ratio is equal to or less than the upper limit, for example, the film-forming ability and processability of the resin substrate, as well as the recyclability of the packaging container, can be further improved.

The thickness of the surface resin layer is preferably 0.1 μm or more and 5 μm or less, more preferably 0.1 μm or more and 4 μm or less. When the thickness is equal to or greater than the lower limit, for example, the adhesion of the vapor-deposited film can be further improved, the gas barrier properties can be further improved, and the laminate strength of the packaging container can be further improved. When the thickness is equal to or less than the upper limit, for example, the film-forming ability and processability of the resin substrate, as well as the recyclability of the packaging container, can be further improved.

In one embodiment, the resin substrate can have an adhesive resin layer between the stretched resin layer and the surface resin layer. This can improve adhesion between these layers.

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, from the viewpoint of the recyclability of the packaging container, polyolefin and acid-modified polyolefin are preferred, and polypropylene and acid-modified polyolefin are more preferred.

The thickness of the adhesive resin layer is, for example, 1 μm or more and 15 μm or less. A thickness of 1 μm or more can, for example, further improve the adhesion between the stretched resin layer and the surface resin layer. A thickness of 15 μm or less can, for example, further improve the processability of the resin substrate.

In one embodiment, the resin substrate having a stretched resin layer and, optionally, an adhesive resin layer and a surface resin layer is a coextruded stretched resin film. A 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. By forming the film using the inflation method, the laminated film may be stretched simultaneously.

The stretching treatment may be uniaxial stretching or biaxial stretching.
The stretching ratio in the MD direction is preferably 2 to 15 times, more preferably 5 to 13 times. The stretching ratio in the TD direction is preferably 2 to 15 times, more preferably 5 to 13 times.

(Barrier coat layer)
In one embodiment, the barrier substrate may further include a barrier coating layer on the vapor-deposited film. That is, the barrier substrate may further include a barrier coating layer on the surface of the vapor-deposited film opposite to the surface on the stretched resin layer side. This can improve, for example, the oxygen barrier property and water vapor barrier property of the laminate.

In one embodiment, the barrier coat layer contains a gas barrier resin. Examples of gas barrier resins include ethylene-vinyl alcohol copolymers, polyvinyl alcohol, polyacrylonitrile, polyesters, polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide, polyurethanes, and (meth)acrylic resins.

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 configuration can improve, for example, the gas barrier properties of the barrier coat layer.
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 and 10 μm or less, more preferably 0.1 μm or more and 5 μm or less. By making the thickness of the barrier coat layer 0.01 μm or more, for example, gas barrier properties can be further improved. By making the thickness of the barrier coat layer 10 μm or less, for example, the processability of the laminate and the recyclability of the packaging container can be improved.

The barrier coat layer can be formed, for example, by applying and drying a coating liquid obtained by dissolving or dispersing a material such as a gas barrier resin in water or an appropriate organic solvent.

In another embodiment, the barrier coat layer is a gas barrier coating film formed by mixing a metal alkoxide, a water-soluble polymer, and, if necessary, a silane coupling agent, and optionally adding water, an organic solvent, and a sol-gel catalyst to obtain a gas barrier composition, which is then applied to a vapor-deposited film and dried. The gas barrier coating film contains a hydrolysis polycondensate obtained by hydrolyzing and polycondensing the metal alkoxide and the like by the sol-gel method. By providing such a barrier coat layer on a vapor-deposited film, the occurrence of cracks in the vapor-deposited film can be effectively suppressed.

The metal alkoxide is represented by, for example, formula (1).
R ¹ _n M (OR ² ) _m (1)
In formula (1), ^R1 and ^R2 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 ^R1 and ^R2 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 metal alkoxides 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 copolymers may be used, or both may be used in combination. Furthermore, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using ethylene-vinyl alcohol copolymer may be laminated together. The amount of water-soluble polymer used is preferably 3 to 500 parts by weight per 100 parts by weight of the metal alkoxide.

The silane coupling agent can be a known organoalkoxysilane containing an organic reactive group, with organoalkoxysilanes containing an epoxy group being preferred, such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The amount of 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 proportion of preferably 0.1 to 100 moles, more preferably 0.5 to 60 moles, per mole of metal alkoxide. By ensuring that the water content is equal to or greater than the lower limit, it is possible to improve the oxygen barrier property and water vapor barrier property of the laminate, for example. By ensuring that the water content is equal to or less than the upper limit, it is possible to rapidly carry out the hydrolysis reaction, for example.

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 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.

Amine compounds are preferably tertiary amines that are substantially insoluble in water and soluble in organic solvents, such as N,N-dimethylbenzylamine, tripropylamine, tributylamine, and tripentylamine. The amount of the amine compound used is preferably 0.01 to 1.0 parts by mass, more preferably 0.03 to 0.3 parts by mass, per 100 parts by mass of the total amount of the metal alkoxide and silane coupling agent.

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

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. A polycondensation reaction gradually progresses within the composition. The composition is then coated onto a vapor-deposited film by a conventional method and dried. This drying process further promotes polycondensation of the metal alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains one) to form a composite polymer layer. Multiple composite polymer layers may be laminated by repeating the above process. For example, the coated composition is heated at a temperature of preferably 20°C to 150°C, more preferably 50°C to 120°C, and even more preferably 70°C to 100°C, 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 and 100 μm or less, more preferably 0.1 μm or more and 50 μm or less, and even more preferably 0.1 μm or more and 5 μm or less. This can, for example, improve gas barrier properties, suppress the occurrence of cracks in the vapor-deposited film, and improve the recyclability of the packaging container.

<Second substrate>
The second substrate includes a stretched resin layer containing polypropylene as a main component.
The stretched resin layer of the second substrate contains polypropylene as a main component, i.e., more than 50% by mass of polypropylene. By providing the stretched resin layer on the second substrate, for example, it is possible to improve the oil resistance of a packaging container produced using the second substrate.

The polypropylene may be a propylene homopolymer, a propylene random copolymer, or a propylene block copolymer, or a mixture of two or more selected from these. Details of these are as described above, and a detailed explanation will be omitted here.

Among polypropylenes, it is preferable to use random copolymers from the viewpoint of transparency. If emphasis is placed on the rigidity and heat resistance of the packaging container, it is preferable to use homopolymers. If emphasis is placed on the drop impact resistance of the packaging container, it is preferable to use block copolymers.

In one embodiment, from the viewpoint of film-forming properties and processability, the melt flow rate (MFR) of the polypropylene may be 0.1 g/10 min or more and 50 g/10 min or less, or 0.3 g/10 min or more and 30 g/10 min or less. The MFR of the polypropylene is measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kg.

From the perspective of reducing the environmental impact, biomass-derived polypropylene or mechanically or chemically recycled polypropylene may be used as the polypropylene.

The polypropylene content in the stretched resin layer of the second substrate is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The stretched resin layer in the second substrate may contain a resin material other than polypropylene. Examples of resin materials include polyolefins such as polyethylene, (meth)acrylic resins, vinyl resins, cellulose resins, polyamides, polyesters, and ionomer resins.

The stretched resin layer in the second substrate may contain additives. Examples of additives include crosslinkers, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

The stretched resin layer in the second substrate is a layer that has been subjected to a stretching treatment. This can improve, for example, the heat resistance, drop impact resistance, water resistance, and dimensional stability of the laminate. A laminate including such a resin layer is suitable, for example, as a packaging material for constituting a packaging container that is subjected to a boiling treatment or a retort treatment.
The stretching treatment may be uniaxial stretching or biaxial stretching.
The details of the stretching process are as described above, and a detailed description thereof will be omitted here.

In one embodiment, the stretched resin layer of the second base material may be subjected to the above-mentioned surface treatment, which can improve the adhesion between the stretched resin layer and other layers, for example.
An easy-adhesion layer may be provided on the surface of the stretched resin layer of the second substrate.

The stretched resin layer of the second substrate may have a single-layer structure or a multi-layer structure.
The thickness of the stretched resin layer in the second substrate is preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. When the thickness is equal to or more than the lower limit, for example, the strength and heat resistance of the laminate can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be further improved.

In one embodiment, the second substrate is a barrier substrate comprising a stretched resin layer and a vapor-deposited film composed of an inorganic oxide. Details of the barrier substrate are as described above in the section on the first substrate, and a detailed description will be omitted here. In one embodiment, the second substrate is a polypropylene resin substrate composed of a stretched resin layer.

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

Methods for forming the printed layer include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing. Of these, flexographic printing is preferred from the perspective of reducing environmental impact.

The thickness of the printing layer is, for example, 0.5 μm or more and 3 μm or less.

<Sealant layer>
The laminate of the present disclosure includes a sealant layer.
The sealant layer contains polypropylene as a main component. That is, the sealant layer is composed of the same type of resin material as the stretched resin layer, i.e., polypropylene. This allows the packaging container to be made of a mono-material. After collecting used packaging containers, there is no need to separate the substrate and the sealant layer, improving the recyclability of the packaging container. By using polypropylene for the sealant layer, the oil resistance of the packaging container produced using the laminate can also be improved.

The polypropylene content in the sealant layer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. This can improve the recyclability of the packaging container, for example.

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, particularly Method D (density gradient tube method, 23°C). From the viewpoint of reducing the environmental load, biomass-derived polypropylene and/or recycled polypropylene may be used.
The sealant layer may contain the above-mentioned additives.

In the present disclosure, it is preferable to use polypropylene having Tim1 and/or Tim2, as described below, as the main component of the sealant layer. This allows, for example, the formation of a sealant layer with excellent low-temperature sealing properties.

The Tim1 of the polypropylene, which is the main component of the sealant layer, is preferably 145°C or less, more preferably 140°C or less, even more preferably 135°C or less, and particularly preferably 130°C or less. This allows, for example, the production of a packaging material with a wide heat-sealable temperature range and excellent seal strength. The lower limit of Tim1 of the polypropylene, which is the main component of the sealant layer, is not particularly limited, but may be, for example, 50°C, 60°C, 70°C, 80°C, or 90°C.

The Tim2 of the polypropylene, which is the main component of the sealant layer, is preferably 150°C or less, more preferably 148°C or less, even more preferably 145°C or less, and particularly preferably 143°C or less. This allows, for example, the production of a packaging material with a wide heat-sealable temperature range and excellent seal strength. The lower limit of the Tim2 of the polypropylene, which is the main component of the sealant layer, is not particularly limited, but may be, for example, 60°C, 70°C, 80°C, 90°C, or 100°C.

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 and 200 μm or less, more preferably 20 μm or more and 150 μm or less. When the thickness is equal to or more than the lower limit, for example, the laminate strength of a packaging container including the laminate can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be further improved. 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 100 μm or less, more preferably 40 μm or more and 100 μm or less, and even more preferably 60 μm or more and 100 μm or less.

Sealant films can be produced, for example, by conventional methods. The sealant film can be obtained by mixing the above-mentioned materials using a conventional method and molding the resulting mixture into a film using a conventional method. The sealant film is preferably a film obtained by extrusion molding. Extrusion molding is preferably carried out using a T-die method or an inflation method. Specifically, the materials that make up the sealant film are dried as needed, then fed into a melt extruder heated to a temperature above the melting point of the material to melt the material, and extruded into a film through a die such as a T-die. The extruded film is then rapidly cooled and solidified on a rotating cooling drum or the like, thereby forming a sealant film.

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

From the viewpoint of heat sealing properties, the sealant layer is preferably an unstretched resin film. The resin film can be produced by, for example, a casting method, a T-die method, or an inflation method.
The sealant layer may be subjected to the above-mentioned surface treatment.

In one embodiment, the sealant layer is not particularly limited as long as it is an unstretched polypropylene resin layer with excellent low-temperature sealing properties. For example, a commercially available unstretched polypropylene film such as unstretched polypropylene film (ET-20, manufactured by Okamoto Corporation) may be used.

For example, an unstretched resin film corresponding to the sealant layer may be laminated onto the first or second substrate via an adhesive layer as needed, or the sealant layer may be formed by melt-extruding polypropylene or a resin composition thereof onto the first or second substrate. Examples of adhesive layers include the following:

<Adhesive layer>
In one embodiment, the laminate includes an adhesive layer between the first substrate and the sealant layer. In one embodiment, the laminate includes a first adhesive layer between the first substrate and the second substrate. In one embodiment, the laminate includes a second adhesive layer between the second substrate and the sealant layer. This can improve the adhesion between the first substrate and the sealant layer, the adhesion between the first substrate and the second substrate, and the adhesion between the second substrate and the sealant layer.

The adhesive layer is composed of an adhesive. The adhesive may be a one-component curing adhesive, a two-component curing adhesive, or a non-curing adhesive. The adhesive may be a solventless adhesive or a solvent-based adhesive. In one embodiment, the laminate of the present disclosure comprises at least three elements: a polypropylene resin substrate, a barrier substrate, and a sealant layer. This allows the laminate to be manufactured using an adhesive without having to apply the adhesive directly onto the vapor-deposited film, thereby preventing deterioration of the vapor-deposited film.

Solvent-free adhesives, i.e., non-solvent laminate adhesives, include, for example, polyether-based adhesives, polyester-based adhesives, silicone-based adhesives, epoxy-based adhesives, and polyurethane-based adhesives. Of these, polyurethane-based adhesives are preferred, and two-component curing polyurethane-based adhesives are more preferred.

In one embodiment, the solventless adhesive is a two-component curing adhesive containing a base agent and a curing agent. From the standpoint of coatability, the weight-average molecular weight (Mw) of the polymer component contained in the base agent is preferably 800 to 10,000, more preferably 1,200 to 4,000. The polydispersity index (Mw/Mn) of the polymer component contained in the base agent is preferably 2.8 or less, more preferably 1.2 to 2.7, even more preferably 1.5 to 2.6, and particularly preferably 2.0 to 2.5. Here, Mn is the number-average molecular weight of the polymer component contained in the base agent. Each average molecular weight is measured by gel permeation chromatography (GPC) in accordance with JIS K7252-1 (2008) and is expressed in polystyrene equivalents.

Examples of solvent-based adhesives include rubber-based adhesives, vinyl-based adhesives, olefin-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and polyurethane-based adhesives. Of these, polyurethane-based adhesives are preferred, and two-component curing polyurethane-based adhesives are more preferred.

In one embodiment, forming an adhesive layer using a solvent-free adhesive can, for example, further reduce the amount of residual solvent in the laminate, specifically the amount of residual organic solvent. The laminate of the present disclosure includes an oriented resin layer containing polypropylene as a primary component. Therefore, when producing a laminate of the present disclosure using a solvent-based adhesive, the drying temperature must be lower than in polyester-based laminates to prevent deterioration and thermal shrinkage of the laminate. In this case, the solvent in the adhesive may not be sufficiently volatilized and remain in the laminate, leaving behind an odor due to the residual solvent. By using a solvent-free adhesive, the amount of residual solvent can be further reduced.

Examples of the organic solvent include 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.

In one embodiment, by using a solvent-free adhesive, for example, the adhesive layer can be made thinner than when a solvent-based adhesive is used. This allows the polypropylene content in the entire laminate to be further increased. Such a laminate is suitable for producing mono-material packaging containers.

The thickness of the adhesive layer is, for example, 0.1 μm or more and 10 μm or less, preferably 0.2 μm or more and 8 μm or less, and more preferably 0.5 μm or more and 6 μm or less. The thickness of the adhesive layer may be 2 μm or less.

The laminate of the present disclosure may be manufactured using any conventional method, such as dry lamination, melt extrusion lamination, or sand lamination. For example, in one embodiment, the laminate of the present disclosure may be manufactured by bonding a first substrate and a sealant film, or a first substrate, a second substrate, and a sealant film, using a non-solvent lamination method with a solvent-free adhesive, or by dry lamination with a solvent-based adhesive.

A two-component curing polyurethane adhesive will now be described. As this polyurethane adhesive, for example, an adhesive having a base agent containing a polyol compound such as polyester polyol and a curing agent containing an isocyanate compound is preferred.
Examples of the polyol compound include polyester polyol, polyether polyol, polycarbonate polyol, and (meth)acrylic polyol. Among these, polyester polyol is preferred.

Polyester polyols have two or more hydroxyl groups per molecule. They have, for example, a polyester structure or a polyester polyurethane structure as their main backbone. Polyester polyols can be obtained, for example, by a dehydration condensation reaction, transesterification, or ring-opening reaction between a polyhydric alcohol component and a polycarboxylic acid component.

Examples of polyhydric alcohol components include diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and cyclohexanedimethanol; and tri- or higher functional polyols such as glycerin, triethylolpropane, trimethylolpropane, pentaerythritol, and sorbitol.

Examples of polycarboxylic acid components include aliphatic polycarboxylic acids, alicyclic polycarboxylic acids, and aromatic polycarboxylic acids, as well as their ester derivatives and acid anhydrides. Examples of aliphatic polycarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, and dimer acid. Examples of alicyclic polycarboxylic acids include 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid.

If necessary, the polyester polyol can be pre-chain-lengthened with a polyisocyanate. Examples of polyisocyanates include diisocyanates such as 1,6-hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, m-xylylene diisocyanate, α,α,α'α'-tetramethyl-m-xylylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and diphenylmethane diisocyanate; as well as biuret, nurate, or trimethylolpropane adducts of diisocyanates.

From the viewpoint of coatability, the weight-average molecular weight (Mw) of polyol compounds such as polyester polyols is preferably 800 to 10,000, more preferably 1,200 to 4,000. The polydispersity (Mw/Mn) of polyol compounds such as polyester polyols is preferably 2.8 or less, more preferably 1.2 to 2.7, even more preferably 1.5 to 2.6, and particularly preferably 2.0 to 2.5. Here, Mn is the number-average molecular weight of the polyol compound. Each average molecular weight is measured by gel permeation chromatography (GPC) in accordance with JIS K7252-1 (2008) and is expressed in terms of polystyrene.

The isocyanate compound has two or more isocyanate groups in one molecule.
Examples of the isocyanate compound include aromatic isocyanates and aliphatic isocyanates. The isocyanate 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 isocyanate compounds include diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, m-xylylene diisocyanate, hydrogenated xylylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and α,α,α'α'-tetramethyl-m-xylylene diisocyanate; trimers of these diisocyanates; and adducts, biuret compounds, and allophanate compounds obtained by reacting these diisocyanate 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, meta-xylylene alcohol, 1,3-bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and meta-xylylenediamine. Examples of high-molecular-weight active hydrogen compounds include polyesters, polyether polyols, and polyamides.

[Packaging container]
The laminate of the present disclosure can be suitably used for packaging material applications.
The packaging material is used to produce a packaging container. The packaging material comprises the laminate of the present disclosure. The packaging container can be produced by using at least the packaging material comprising the laminate of the present disclosure.

The packaging container of the present disclosure includes the laminate of the present disclosure (hereinafter also simply referred to as the "laminate"). Examples of packaging containers include packaging bags, tube containers, and containers with lids. The container with lid includes a container body having a storage section and a lid material joined (heat sealed) to the container body so as to seal the storage section.

In one embodiment, the packaging container of the present disclosure maintains gas barrier properties even when subjected to high-temperature treatment and exhibits minimal deformation, making it suitable as a microwave oven container or a boiling or retort container. The packaging container of the present disclosure is also suitable as a microwave oven boiling or retort container. The packaging container of the present disclosure is particularly suitable as a boiling or retort pouch.

Heat sealing methods include, for example, bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

Packaging bags include various types, such as standing pouch, side seal, two-sided seal, three-sided seal, four-sided seal, envelope seal, palm seal (pillow seal), pleated seal, flat bottom seal, square bottom seal, and gusset seal.

The packaging container may be provided with an easy-to-open portion. Examples of easy-to-open portions include a notch portion that serves as the starting point for tearing the packaging container, and a half-cut line formed by laser processing or a cutter as a path for tearing the packaging container.

The packaging container may be equipped with a steam vent mechanism. The steam vent mechanism is configured to connect the inside and outside of the packaging container when the steam pressure inside the packaging container reaches or exceeds a predetermined value, allowing steam to escape while preventing steam from escaping from locations other than the steam vent mechanism.

The steam release mechanism, for example, comprises a steam release seal portion that protrudes from the side seal portion toward the inside of the packaging container, and an unsealed portion that is isolated from the content storage portion by the steam release seal portion. The unsealed portion is connected to the outside of the packaging container. The packaging container is filled with content and the opening is heat-sealed, and is then heated using a microwave oven or similar device. This increases the internal pressure, causing the steam release seal portion to peel. Steam escapes to the outside of the packaging container through the peeled steam release seal portion and the unsealed portion.

In one embodiment, a packaging bag can be produced by folding the laminate of the present disclosure in half and overlapping it so that the first substrate is on the outside and the sealant layer is on the inside, and then heat-sealing the edges, etc. In another embodiment, a packaging bag can be produced by overlapping multiple laminates of the present disclosure so that the sealant layers face each other, and then heat-sealing the edges, etc. The entire packaging bag may be composed of the above-mentioned laminate, or only a portion of the packaging bag may be composed of the above-mentioned laminate.

In one embodiment, the laminate of the present disclosure is used as a lid material for a lidded container. The lidded container comprises a container body having a storage section, and a lid material joined (heat sealed) to the container body so as to seal the storage section. Here, the lid material, i.e., the sealant layer of the laminate, and the container body are heat sealed. Examples of the shape of the container body include a cup shape and a cylindrical shape with a bottom. The container body is made of, for example, polystyrene, polypropylene, polyethylene, or paper.

Contents that can be placed in a packaging container include, for example, liquids, solids, powders, and gels. The contents can be food or beverages, or non-food or beverages such as chemicals, cosmetics, and pharmaceuticals. After the contents are placed in the packaging container, the opening of the packaging container can be heat-sealed to seal the packaging container.

As specific examples of packaging bags, small pouches and standing pouches will be described below.
The sachet is a small packaging bag used to store contents of, for example, 1 g to 200 g, such as sauces, soy sauce, dressings, ketchup, syrups, cooking alcohol, other liquid or viscous seasonings, liquid soups, powdered soups, fruit juices, spices, liquid beverages, jelly-like beverages, instant foods, and other foods and beverages.

Stand-up pouches are used to store contents, for example, between 50g and 2000g. Examples of contents that can be stored in stand-up pouches include shampoo, rinse, conditioner, hand soap, body soap, air fresheners, deodorants, insect repellents, detergents; dressings, cooking oils, mayonnaise, and other liquid or viscous condiments; liquid beverages, jelly-like beverages, instant foods, and other food and beverage products; and creams.

Figure 10 shows a packaging bag 50 obtained by bonding two laminates together. The shaded areas indicate the heat-sealed areas. The packaging bag 50 may also have an easy-to-open section 51. Examples of the easy-to-open section 51 include a notch 52 that serves as a tearing starting point, and a half-cut line 53 formed by laser processing or a cutter as a tearing path.

Figure 11 shows a simplified example of the structure of a stand-up pouch. The shaded areas indicate the heat-sealed areas. In one embodiment, the stand-up pouch 60 comprises a body portion (side sheets) 61 and a bottom portion (bottom sheet) 62. The side sheets 61 and the bottom sheet 62 may be made of the same material, or may be made of different materials. The bottom sheet 62 maintains the shape of the side sheets 61, giving the pouch the ability to stand on its own and allowing 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 equipped 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 container, and a non-sealed portion 63b that is isolated from the content storage portion by the steam release seal portion 63a. The non-sealed portion 63b is in communication with the outside of the packaging container.

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

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, overlapping them with their sealant layers facing each other, and heat-sealing the side edges on both sides to form a bag.

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

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

In one embodiment, two of the above laminates are prepared and stacked together with the sealant layers facing each other. Next, another of the above laminates is folded in a V shape with the sealant layer facing outward, and this is sandwiched between the lower part of the stacked bodies and heat-sealed to form the bottom. Next, 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 [18].
[1] A laminate for packaging materials comprising a first substrate and a sealant layer, wherein the first substrate comprises an oriented resin layer containing polypropylene as a primary component, and the sealant layer is a resin layer containing polypropylene as a primary component, and the polypropylene contained in the oriented resin layer has an extrapolated melting initiation temperature (Tim) at the first temperature rise, as measured by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012, that is higher than the Tim at the first temperature rise, as measured by DSC, of the polypropylene contained in the sealant layer, and the heat sealing temperature range in which the laminate achieves a seal strength of 23 N/15 mm or more at a test speed of 300 mm/min and a shrinkage rate of 0% or more and 1.0% or less in the transverse direction, exists at 5°C or higher in the range of 130°C to 190°C, when the laminate is heat-sealed under heat-sealing conditions of a pressure of 0.1 MPa and a heat-sealing time of 1 second, in a range of 130°C to 190°C.
[2] The laminate for packaging materials according to the above [1], wherein the difference between the Tim of the polypropylene contained in the stretched resin layer of the first base material at the first temperature rise, as measured by DSC, and the Tim of the polypropylene contained in the sealant layer at the first temperature rise, as measured by DSC, is 20°C or more.
[3] The laminate for packaging materials according to the above [1] or [2], wherein the difference between the Tim of the polypropylene contained in the stretched resin layer of the first base material at the second heating time, as measured by DSC, and the Tim of the polypropylene contained in the sealant layer at the second heating time, as measured by DSC, is 10°C or more.
[4] The laminate for packaging materials according to any one of the above [1] to [3], wherein the polypropylene contained in the sealant layer has a Tim of 145°C or less at the first temperature rise as measured by DSC.
[5] The laminate for packaging materials according to any one of the above [1] to [4], wherein the polypropylene contained in the sealant layer has a Tim at the second temperature rise obtained by DSC of 150°C or less.
[6] The laminate for packaging materials according to any one of the above [1] to [5], wherein the first substrate is a barrier substrate comprising a stretched resin layer and a vapor-deposited film composed of an inorganic oxide, or a polypropylene resin substrate composed of a stretched resin layer.
[7] The laminate for packaging materials according to any one of the above [1] to [6], further comprising a second substrate between the first substrate and the sealant layer, the second substrate comprising an oriented resin layer containing polypropylene as a main component, and the second substrate being a barrier substrate comprising an oriented resin layer and a vapor-deposited film composed of an inorganic oxide, or a polypropylene resin substrate composed of an oriented resin layer.
[8] The laminate for packaging materials according to the above [6] or [7], wherein the barrier substrate further comprises a surface coating layer between the stretched resin layer and the vapor-deposited film, and the surface coating layer contains a resin material having a polar group.
[9] The laminate for packaging materials according to the above [6] or [7], wherein the barrier substrate further comprises a surface resin layer between the stretched resin layer and the vapor-deposited film, and the surface resin layer contains a resin material having a melting point of 180°C or higher.
[10] The laminate for packaging materials according to the above [9], wherein the stretched resin layer and the surface resin layer in the barrier substrate constitute a co-extruded stretched resin film.
[11] The laminate for packaging materials according to any one of the above [6] to [10], further comprising a barrier coat layer on the vapor-deposited film.
[12] The laminate for packaging materials according to the above [7], wherein the first substrate is a polypropylene resin substrate composed of a stretched resin layer, and the second substrate is a barrier substrate.
[13] The laminate for packaging materials according to the above [7] or [12], which comprises a first adhesive layer between the first substrate and the second substrate, and a second adhesive layer between the second substrate and the sealant layer.
[14] The laminate for packaging materials according to any one of [1] to [13] above, wherein the proportion of a polypropylene-based single material is 80% by mass or more.
[15] A packaging container comprising the laminate for packaging materials according to any one of [1] to [14] above.
[16] The packaging container according to [15] above, which is a boilable or retort pouch.
[17] A lid material comprising the laminate for packaging materials according to any one of [1] to [14] above.
[18] A packaging container comprising a container body having a storage section and the lid material according to [17] above joined to the container body so as to seal the storage section.

The laminate of this disclosure will be specifically described below using examples.

[Example 1]
<Preparation of Transparent Barrier Substrate>
A hydroxyl group-containing (meth)acrylic resin (number average molecular weight: 25,000, glass transition temperature: 99°C, hydroxyl value: 80 mgKOH/g) was diluted with a mixed solvent of methyl ethyl ketone and ethyl acetate (mixing ratio 1:1) to a solids concentration of 10% by mass to prepare a base material. An ethyl acetate solution containing tolylene diisocyanate (solids 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 curing agent used was 10 parts by mass per 100 parts by mass of the base material.

A 20 μm-thick biaxially oriented polypropylene film (ME-1, manufactured by Mitsui Chemicals Tohcello, Inc.) with one side corona-treated was prepared. The above-described surface coating layer-forming solution was applied to the corona-treated surface of the film and dried to form a 0.5 μm-thick surface coating layer, yielding a resin substrate.

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

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

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 added to this solution while cooling to 10°C to obtain Solution A. 14.7g of polyvinyl alcohol with a saponification degree of 99% or more and a degree of polymerization of 2400 as a water-soluble polymer was mixed with 324g of water and 17g of isopropyl alcohol to obtain Solution B.

Solution A and solution B were mixed in a mass ratio (solution A:solution B) of 6.5:3.5 to obtain a barrier coating agent. The barrier coating agent was coated onto the vapor-deposited film formed on the resin substrate by spin coating, and then heat-treated in an oven at 80°C for 60 seconds to form a barrier coating layer with a thickness of 300 nm.
In this manner, a transparent barrier substrate was obtained.

<Preparation of Laminate>
A 20 μm-thick biaxially oriented polypropylene film (P2171, manufactured by Toyobo Co., Ltd.) with one surface corona-treated was prepared as the first substrate. A printed layer was formed on the corona-treated surface of the first substrate by gravure roll coating to a coating thickness of 1 μm (when dried). Next, a two-component curing polyurethane adhesive (RU-40/H-4, manufactured by Rock Paint Co., Ltd.) was coated on the printed layer by gravure roll coating to a coating thickness of 4 μm (when dried), and a transparent barrier substrate was dry-laminated as the second substrate (intermediate substrate) so that the barrier coat layer surface of the transparent barrier substrate contacted the adhesive layer surface.

The non-barrier coating surface of the transparent barrier substrate was subjected to corona treatment, and then a two-component curing polyurethane adhesive (RU-40/H-4, manufactured by Rock Paint Co., Ltd.) was applied using the gravure roll coating method to a thickness of 4 μm (when dry). A 60 μm thick unstretched polypropylene film (ET-20, manufactured by Okamoto Corporation) with one side corona-treated was dry-laminated to the adhesive layer surface as a sealant layer, with the corona-treated side of the film in contact.

In this way, a laminate approximately 109 μm thick was obtained. The laminate consisted of biaxially oriented polypropylene film (20 μm) / printed layer (1 μm) / solvent-based adhesive layer (4 μm) / transparent barrier substrate (approximately 20 μm) / solvent-based adhesive layer (4 μm) / unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 91% by mass.

[Example 2]
A laminate with a thickness of approximately 104 μm was obtained in the same manner as in Example 1, except that a non-solvent, two-component curing polyurethane adhesive (RN-920/HN-920, manufactured by Rock Paint Co., Ltd.) was applied as the adhesive layer using a roll coating method to a coating thickness of 1.5 μm (when dried). The laminate consisted of a biaxially oriented polypropylene film (20 μm)/printed layer (1 μm)/solvent-free adhesive layer (1.5 μm)/transparent barrier substrate (approximately 20 μm)/solvent-free adhesive layer (1.5 μm)/unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 96% by mass.

[Comparative Example 1]
A laminate with a thickness of approximately 109 μm was obtained in the same manner as in Example 1, except that a 60 μm thick unstretched polypropylene film (ZK500, manufactured by Toray Advanced Film Co., Ltd.) was used as the sealant layer. The laminate had a structure of biaxially oriented polypropylene film (20 μm)/printed layer (1 μm)/solvent-based adhesive layer (4 μm)/transparent barrier substrate (approximately 20 μm)/solvent-based adhesive layer (4 μm)/unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 91% by mass.

[Comparative Example 2]
A laminate with a thickness of approximately 109 μm was obtained in the same manner as in Example 1, except that a 20 μm thick biaxially oriented polypropylene film (P2161, manufactured by Toyobo Co., Ltd.) was used as the first substrate. The laminate had a structure of biaxially oriented polypropylene film (20 μm)/printed layer (1 μm)/solvent-based adhesive layer (4 μm)/transparent barrier substrate (approximately 20 μm)/solvent-based adhesive layer (4 μm)/unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 91% by mass.

[Comparative Example 3]
A laminate approximately 109 μm thick was obtained in the same manner as in Example 1, except that a 20 μm thick biaxially oriented polypropylene film (P2161, manufactured by Toyobo Co., Ltd.) was used as the first substrate and a 60 μm thick unstretched polypropylene film (ZK500, manufactured by Toray Advanced Film Co., Ltd.) was used as the sealant layer. The laminate had a configuration of biaxially oriented polypropylene film (20 μm)/printed layer (1 μm)/solvent-based adhesive layer (4 μm)/transparent barrier substrate (approximately 20 μm)/solvent-based adhesive layer (4 μm)/unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 91% by mass.

[Comparative Example 4]
A 96 μm thick laminate was obtained in the same manner as in Example 1, except that a 12 μm thick silica-vapor-deposited PET film (IB-PET-PIR2, manufactured by DNP Co., Ltd.) was used as the first substrate, a 15 μm thick biaxially oriented nylon film (Bonyl-W, manufactured by Kohjin Film & Chemicals Co., Ltd.) was used as the second substrate (intermediate substrate), and a 60 μm thick unstretched polypropylene film (ZK500, manufactured by Toray Advanced Film Co., Ltd.) was used as the sealant layer. The laminate had a structure of silica-vapor-deposited PET film (approximately 12 μm)/printed layer (1 μm)/solvent-based adhesive layer (4 μm)/biaxially oriented nylon film (15 μm)/solvent-based adhesive layer (4 μm)/unstretched polypropylene film (60 μm). The mono-material ratio of the laminate was approximately 62% by mass.

[evaluation]
<Differential Scanning Calorimetry (DSC)>
Measurements were carried out using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, product name: DSC7000X) in accordance with JIS K7121:2012 (Method for measuring transition temperatures of plastics). The measurement samples were a biaxially oriented polypropylene film of the first substrate and an unstretched polypropylene film of the sealant layer (referred to as OPP and CPP, respectively, in Table 1). At this time, the measurement sample was held at 20 ° C. for 1 minute, then heated from 20 ° C. to 200 ° C. at a heating rate of 10 ° C./min (1st), held at 200 ° C. for 5 minutes, then cooled from 200 ° C. to 20 ° C. at a cooling rate of 10 ° C./min, and held at 20 ° C. for 5 minutes. Then, the temperature was raised again from 20 ° C. to 200 ° C. at a heating rate of 10 ° C./min (2nd). This gave 1st and 2nd DSC curves. The extrapolated melting onset temperature (Tim) was measured as the temperature at the intersection of a straight line extending the low-temperature baseline toward the high-temperature side of the DSC curve and a tangent drawn at the point where the slope of the low-temperature side of the melting peak is maximum. When there were two or more Tims, the Tim of the melting peak with the greatest peak intensity was used. The nitrogen gas flow rate was 20 ml/min. The results are shown in Table 1.

<Retort test>
Two laminates obtained as described above were prepared and stacked with the sealant layer (unstretched polypropylene film) facing each other. The other laminate was then folded into a V shape with the sealant layer facing outward, and this was sandwiched between the lower part of the opposing laminate and heat-sealed to form a bottom. Two sides adjacent to the bottom were then heat-sealed to form a body. In this way, a standing pouch with a boat-shaped seal at the bottom, measuring 130 mm wide, 170 mm high, and 35 mm deep, was produced. The bottom seal width was 6 mm, and the side seal width was 6 mm. 210 g of water was poured into the resulting pouch through the opening, and the opening was heat-sealed to seal the pouch. The sealed pouch was then subjected to a hot water retort treatment at 121°C for 30 minutes.
In both Examples 1 and 2, no problems such as delamination or seal recession were observed.

<Sticker evaluation>
Two sheets of the laminate obtained above were prepared and each cut to a size of 100 mm x 100 mm. The unstretched polypropylene film sides were placed face-to-face and overlapped, and heat-sealed in the TD direction using a 10 mm-wide single-sided heated flat heat seal bar. Heat-sealing conditions were a temperature of 130-180°C, a pressure of 0.1 MPa, and a time of 1 second. The sealed sample was cut to a width of 15 mm in the MD direction to prepare a 15 mm wide, 100 mm long test piece. Using this test piece, the seal strength was measured using a tensile tester (STA-1150, manufactured by Orientec Co., Ltd.) at a test speed of 300 mm/min using a T-peel test. The results are shown in Table 2.

<Shrinkage rate>
Two sheets of the laminate obtained above were prepared and each cut to a size of 100 mm x 100 mm. The unstretched polypropylene film sides were placed face-to-face and overlapped, and heat-sealed in the TD direction using a 10 mm-wide single-sided heated flat heat seal bar. Heat-sealing conditions were a temperature of 130-190°C, a pressure of 0.1 MPa, and a time of 1 second. The TD length of the heat-sealed portion of the sealed sample was measured using a 150 mm ruler, and the shrinkage percentage (%) was calculated using the formula: (length before sealing (100 mm) - length after sealing (mm)) / length before sealing (100 mm) x 100. Samples that underwent significant thermal deformation due to heat sealing, making it impossible to calculate the shrinkage percentage, were rated "fail." The appearance of the sealed samples was visually evaluated, with samples with good appearance rated as AA, samples with fair appearance rated as BB, and samples with poor appearance rated as CC. The results are shown in Table 3.

1: Laminate, 10: Polypropylene resin substrate, 20: Barrier substrate, 22: Stretched resin layer, 23: Surface coating layer or surface resin layer, 24: Vapor deposition film, 25: Barrier 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 seal portion, 63b: Non-seal portion

Claims (18)

A laminate for packaging materials comprising a first substrate and a sealant layer,
the first base material includes a stretched resin layer containing polypropylene as a main component,
the sealant layer is a resin layer containing polypropylene as a main component,
the polypropylene contained in the stretched resin layer has an extrapolated melting initiation temperature (Tim) at the first temperature rise, as measured by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012, which is higher than the Tim at the first temperature rise, as measured by DSC, of the polypropylene contained in the sealant layer;
When the laminate is heat-sealed under heat-sealing conditions of a pressure of 0.1 MPa and a heat-sealing time of 1 second, the seal strength is 23 N/15 mm or more at a test speed of 300 mm/min in a T-peel test, and the shrinkage rate in the TD direction of the laminate is 0% or more and 1.0% or less, and the heat-sealing temperature range is 5°C or more in the range of 130°C or more and 190°C or less.
Laminate for packaging materials. The laminate for packaging materials according to claim 1, wherein the difference between the Tim of the polypropylene contained in the stretched resin layer of the first base material at the first temperature rise, as measured by DSC, and the Tim of the polypropylene contained in the sealant layer at the first temperature rise, as measured by DSC, is 20°C or more. The laminate for packaging materials according to claim 1 or 2, wherein the difference between the Tim of the polypropylene contained in the stretched resin layer of the first base material at the second heating time, as measured by DSC, and the Tim of the polypropylene contained in the sealant layer at the second heating time, as measured by DSC, is 10°C or more. The laminate for packaging materials according to any one of claims 1 to 3, wherein the Tim of the polypropylene contained in the sealant layer during the first heating cycle measured by DSC is 145°C or less. The laminate for packaging materials according to any one of claims 1 to 4, wherein the Tim of the polypropylene contained in the sealant layer during the second heating cycle, as measured by DSC, is 150°C or less. The laminate for packaging materials according to any one of claims 1 to 5, wherein the first substrate is a barrier substrate comprising the stretched resin layer and a vapor-deposited film composed of an inorganic oxide, or a polypropylene resin substrate composed of the stretched resin layer. the laminate further includes a second substrate between the first substrate and the sealant layer, the second substrate including a stretched resin layer containing polypropylene as a main component;
the second substrate is a barrier substrate comprising the stretched resin layer and a vapor-deposited film composed of an inorganic oxide, or a polypropylene resin substrate composed of the stretched resin layer;
The laminate for packaging materials according to any one of claims 1 to 6. The laminate for packaging materials according to claim 6 or 7, wherein the barrier substrate further comprises a surface coating layer between the stretched resin layer and the vapor-deposited film, and the surface coating layer contains a resin material having a polar group. The laminate for packaging materials according to claim 6 or 7, wherein the barrier substrate further comprises a surface resin layer between the stretched resin layer and the vapor-deposited film, and the surface resin layer contains a resin material having a melting point of 180°C or higher. The laminate for packaging materials according to claim 9, wherein the stretched resin layer and the surface resin layer of the barrier substrate constitute a co-extruded stretched resin film. The laminate for packaging materials according to any one of claims 6 to 10, further comprising a barrier coating layer on the vapor-deposited film. the first substrate is a polypropylene resin substrate constituted by the stretched resin layer,
the second substrate is the barrier substrate;
The laminate for packaging materials according to claim 7. a first adhesive layer between the first substrate and the second substrate;
a second adhesive layer between the second substrate and the sealant layer;
The laminate for packaging materials according to claim 7 or 12. The laminate for packaging materials according to any one of claims 1 to 13, wherein the proportion of polypropylene-based single material is 80% by mass or more. A packaging container comprising the packaging material laminate according to any one of claims 1 to 14. The packaging container according to claim 15, which is a boilable or retort pouch. A lid material comprising the packaging laminate according to any one of claims 1 to 14. a container body having a storage portion;
A packaging container comprising the lid according to claim 17 joined to the container body so as to seal the storage portion.