JP7785441B2 - Laminate - Google Patents

Description

The present invention relates to a laminate.

Bags made from flexible packaging materials are used to store fluid contents such as liquids and powders. The shape of the bag is determined by the seal formed by heat-sealing the flexible packaging material.

The packaging material that makes up the flexible packaging material consists of a laminate that includes a substrate and a sealant layer that is laminated on the substrate and melts by heat sealing. The layer structure of the laminate is determined, for example, from the perspective of mechanical strength. For example, in Patent Document 1, the substrate is made of nylon and the sealant layer is made of polyethylene. Nylon contributes to improving the mechanical strength of the laminate, such as puncture resistance.

Japanese Patent Application Publication No. 10-218204

Materials produced from petroleum, a fossil resource, have traditionally been used as materials for the substrate of laminates. In recent years, there has been a growing trend toward reducing the use of fossil fuels in various applications and reducing _CO2 emissions in consideration of the environment.

The present invention aims to provide a laminate that can effectively solve these problems.

The present invention relates to a laminate comprising at least a first stretched plastic film, a second stretched plastic film, and a sealant layer, in this order. The laminate further comprises a metal vapor-deposited layer provided on the second stretched plastic film, and at least one of the first stretched plastic film and the second stretched plastic film contains polyethylene terephthalate having ethylene glycol as the diol unit and terephthalic acid and isophthalic acid as the dicarboxylic acid unit.

In the laminate according to the present invention, the second stretched plastic film may contain polyethylene terephthalate having ethylene glycol as the diol unit and terephthalic acid and isophthalic acid as the dicarboxylic acid unit.

In the laminate according to the present invention, the first stretched plastic film may contain polyethylene terephthalate having ethylene glycol as the diol unit and terephthalic acid and isophthalic acid as the dicarboxylic acid unit.

In the laminate according to the present invention, the first stretched plastic film may contain polypropylene.

In the laminate according to the present invention, the first stretched plastic film includes a rigid film, which may include polyamide, polybutylene terephthalate, or polyester and have a loop stiffness of 0.0017 N or more in one direction.

In the laminate according to the present invention, the sealant layer may have a thickness of 18 μm or more and 120 μm or less.

In the laminate according to the present invention, the intrinsic viscosity of the polyethylene terephthalate may be 0.58 dl/g or more and 0.80 dl/g or less.

In the laminate according to the present invention, the Young's modulus of the laminate in one direction may be 3200 MPa or more.

According to the present invention, it is possible to provide a laminate that is excellent in CO ₂ reduction effect and also has designability.

1 is a schematic cross-sectional view showing an example of a packaging material according to the present embodiment. 1 is a schematic cross-sectional view showing an example of a packaging material according to the present embodiment. 1 is a schematic cross-sectional view showing an example of a packaging material according to the present embodiment. 1 is a schematic cross-sectional view showing an example of a packaging material according to the present embodiment. FIG. 1 is a schematic cross-sectional view showing an example of a recycled film. FIG. 1 is a plan view showing an example of a loop stiffness measuring device. FIG. 7 is a cross-sectional view of the loop stiffness measuring device of FIG. 6 taken along line VI-VI. FIG. 10 is a diagram illustrating a process of attaching a test piece to a loop stiffness measuring instrument. FIG. 10 is a diagram illustrating a step of forming a loop portion in a test piece. FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. FIG. 1 is a schematic front view showing an example of a packaging bag. FIG. 1 is a schematic front view showing an example of a packaging bag. FIG. 10 is a diagram showing an example of a method for measuring puncture strength.

<Laminate (packaging material)>
The laminate according to the present embodiment comprises at least a first stretched plastic film, a second stretched plastic film, and a sealant layer, in this order. The laminate may further comprise other layers, such as an adhesive layer, a printed layer, or a metal deposition layer. In this embodiment, an example will be described in which the laminate is used as a packaging material for forming a bag.

The packaging material according to this embodiment will be described with reference to the drawings. Examples of schematic cross-sectional views of the packaging material according to this embodiment are shown in Figures 1 to 4.

The packaging material 10 shown in FIG. 1 comprises, in this order, a first stretched plastic film 11, a printing layer 21, a first adhesive layer 16, a metal vapor deposition layer 22, a second stretched plastic film 12, a second adhesive layer 17, and a sealant layer 15. In a packaging bag comprising the packaging material 10 shown in FIG. 1 and FIGS. 2 to 4 described below, the sealant layer 15 forms the inner surface of the packaging bag. In the example shown in FIG. 1, the sealant layer 15 is formed by laminating a film constituting the sealant layer onto the second stretched plastic film 12. In the example shown in FIG. 1, the first adhesive layer 16 and the second adhesive layer 17 are adhesive layers described below. In the examples shown in FIG. 1 and FIGS. 2 to 4 described below, the metal vapor deposition layer 22 may be provided on the outer surface of the second stretched plastic film 12, or on the inner surface of the second stretched plastic film 12.

The packaging material 10 shown in Figure 2 comprises, in this order, a first stretched plastic film 11, a printing layer 21, a first anchor coat layer 18, a first adhesive layer 16, a metal vapor deposition layer 22, a second stretched plastic film 12, a second anchor coat layer 19, a second adhesive layer 17, and a sealant layer 15. In the example shown in Figure 1, the sealant layer 15 is formed by laminating a film constituting the sealant layer onto the second stretched plastic film 12. In the example shown in Figure 2, the first adhesive layer 16 and the second adhesive layer 17 are adhesive resin layers, which will be described later.

The packaging material 10 shown in Figure 3 comprises, in this order, a first stretched plastic film 11, a printing layer 21, a first adhesive layer 16, a metal vapor deposition layer 22, a second stretched plastic film 12, a second anchor coat layer 19, and a sealant layer 15. In the example shown in Figure 3, the sealant layer 15 is formed by molding a material constituting the sealant layer onto the second stretched plastic film 12. In the example shown in Figure 3, the first adhesive layer 16 is an adhesive layer, which will be described later.

The packaging material 10 shown in Figure 4 comprises, in this order, a first stretched plastic film 11, a printing layer 21, a first anchor coat layer 18, a first adhesive layer 16, a metal vapor deposition layer 22, a second stretched plastic film 12, a second anchor coat layer 19, and a sealant layer 15. In the example shown in Figure 4, the sealant layer 15 is formed by molding a material constituting the sealant layer onto the second stretched plastic film 12. In the example shown in Figure 4, the first adhesive layer 16 is an adhesive resin layer, which will be described later.

The films and layers that make up the packaging material 10 are described below.

[Stretched plastic film]
Both the first stretched plastic film 11 and the second stretched plastic film 12 are plastic films stretched in a predetermined direction. Each of the stretched plastic films 11, 12 may be a uniaxially stretched film stretched in one predetermined direction, or a biaxially stretched film stretched in two predetermined directions. The stretching direction of each of the stretched plastic films 11, 12 is not particularly limited. For example, the stretched plastic films 11, 12 may be stretched in the height direction of the packaging bag formed from the packaging material 10, or may be stretched in the width direction of the packaging bag. Furthermore, the stretching directions of each of the stretched plastic films 11, 12 may be the same or different. The stretching ratio of each of the stretched plastic films 11, 12 is, for example, 1.05 times or more.

At least one of the first stretched plastic film 11 and the second stretched plastic film 12 is a recycled film containing recycled PET. For example, the first stretched plastic film 11 may be a recycled film, and the second stretched plastic film 12 may be a recycled film. In this case, the non-recycled stretched plastic film of the first stretched plastic film 11 or the second stretched plastic film 12 is a virgin film containing PET derived from fossil fuels, a stretched polypropylene film containing polypropylene (hereinafter also referred to as OPP film), or a rigid film having rigidity.
Furthermore, both the first stretched plastic film 11 and the second stretched plastic film 12 may be recycled films.

Examples of combinations of the first stretched plastic film 11 and the second stretched plastic film 12 made of the above-mentioned recycled film, virgin film, OPP film, rigid film, etc. are shown in Table 1. In Examples 1 to 7, the metal vapor deposition layer 22 may be directed toward the outer surface of the second stretched plastic film 12, or may be provided on the inner surface of the second stretched plastic film 12.

The following explains recycled film, rigid film, virgin film, and OPP film.

(recycled film)
The recycled film includes polyethylene terephthalate (hereinafter, polyethylene terephthalate may be referred to as PET) recycled by mechanical recycling. Specifically, the recycled film includes PET obtained by mechanical recycling of PET bottles, in which the diol unit is ethylene glycol and the dicarboxylic acid unit is terephthalic acid and isophthalic acid. Mechanical recycling generally refers to a method in which collected polyethylene terephthalate resin products, such as PET bottles, are crushed and washed with alkali to remove surface contamination and foreign matter from the PET resin product, and then dried at high temperature and reduced pressure for a certain period of time to diffuse contaminants remaining inside the PET resin, thereby decontaminating the PET resin product and returning it to PET resin. Hereinafter, in this specification, polyethylene terephthalate recycled from PET bottles will be referred to as "recycled polyethylene terephthalate (hereinafter, also referred to as recycled PET)," and unrecycled polyethylene terephthalate will be referred to as "virgin polyethylene terephthalate (hereinafter, also referred to as virgin PET)."

The content of isophthalic acid in the PET contained in the recycled film is preferably 0.5 mol% to 5 mol% and more preferably 1.0 mol% to 2.5 mol% of the total dicarboxylic acid units constituting the PET. If the isophthalic acid content is less than 0.5 mol%, flexibility may not be improved, while if it exceeds 5 mol%, the melting point of the PET may decrease, resulting in insufficient heat resistance. In addition to conventional PET derived from fossil fuels, PET may also be biomass PET. "Biomass PET" contains biomass-derived ethylene glycol as the diol unit and fossil-fuel-derived dicarboxylic acid as the dicarboxylic acid unit. This biomass PET may be made solely from PET with biomass-derived ethylene glycol as the diol unit and fossil-fuel-derived dicarboxylic acid as the dicarboxylic acid unit, or it may be made from PET with biomass-derived ethylene glycol and fossil-fuel-derived diol as the diol unit and fossil-fuel-derived dicarboxylic acid as the dicarboxylic acid unit.

The PET used in PET bottles can be obtained by a conventionally known method of polycondensing the above-mentioned diol units and dicarboxylic acid units. Specifically, it can be produced by a common melt polymerization method in which an esterification reaction and/or transesterification reaction between the above-mentioned diol units and dicarboxylic acid units is carried out, followed by a polycondensation reaction under reduced pressure, or by a known solution heating dehydration condensation method using an organic solvent.

The amount of diol units used in producing the above-mentioned PET is essentially equimolar to 100 moles of dicarboxylic acid or its derivative, but generally, an excess of 0.1 mol % to 20 mol % is used due to distillation during the esterification and/or transesterification reaction and/or polycondensation reaction.

The polycondensation reaction is preferably carried out in the presence of a polymerization catalyst. The timing of adding the polymerization catalyst is not particularly limited, as long as it is added before the polycondensation reaction. It may be added when the raw materials are charged, or when pressure reduction begins.

After the PET recycled from PET bottles has been polymerized and solidified as described above, it may be subjected to solid-state polymerization as needed to further increase the degree of polymerization or to remove oligomers such as cyclic trimers. Specifically, solid-state polymerization is carried out by cutting the PET into chips and drying them, then heating them at a temperature of 100°C to 180°C for approximately 1 to 8 hours to pre-crystallize the PET, and then heating them at a temperature of 190°C to 230°C in an inert gas atmosphere or under reduced pressure for 1 to several tens of hours.

The intrinsic viscosity of the PET contained in the recycled film is preferably 0.58 dl/g or more and 0.80 dl/g or less. If the intrinsic viscosity is less than 0.58 dl/g, the mechanical properties required for the PET film as a substrate may be insufficient. On the other hand, if the intrinsic viscosity exceeds 0.80 dl/g, productivity in the film production process may be impaired. Note that the intrinsic viscosity is measured in an orthochlorophenol solution at 35°C.

The recycled film preferably contains recycled PET at a ratio of 50% to 95% by weight, and may contain virgin PET in addition to recycled PET. The PET content in the recycled film may be 80% by weight or more, 90% by weight or more, or even 95% by weight or more. Virgin PET may be PET in which the diol units are ethylene glycol and the dicarboxylic acid units contain terephthalic acid and isophthalic acid, as described above, or PET in which the dicarboxylic acid units do not contain isophthalic acid. The recycled film may also contain polyesters other than PET. For example, the dicarboxylic acid units may contain aliphatic dicarboxylic acids in addition to aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid.

Specific examples of aliphatic dicarboxylic acids include linear or alicyclic dicarboxylic acids typically having 2 to 40 carbon atoms, such as oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, and cyclohexanedicarboxylic acid. Derivatives of aliphatic dicarboxylic acids include lower alkyl esters of the above aliphatic dicarboxylic acids, such as methyl esters, ethyl esters, propyl esters, and butyl esters, and cyclic acid anhydrides of the above aliphatic dicarboxylic acids, such as succinic anhydride. Among these, preferred aliphatic dicarboxylic acids are adipic acid, succinic acid, dimer acid, or mixtures thereof, with those containing succinic acid as the main component being particularly preferred. More preferred derivatives of aliphatic dicarboxylic acids are methyl esters of adipic acid and succinic acid, or mixtures thereof.

Such recycled films made from PET may be single-layer or multi-layer. Figure 5 is a cross-sectional view showing an example of a recycled film 30. The recycled film 30 shown in Figure 5 has three layers: a first layer 31, a second layer 32, and a third layer 33. The third layer 33 is located on the sealant layer 15 side of the packaging material 10. In the example shown in Figure 5, it is preferable that the second layer 32 be a layer made solely of recycled PET or a mixed layer of recycled PET and virgin PET, and the first layer 31 and the third layer 33 be layers made solely of virgin PET. In this way, using only virgin PET for the first layer 31 and the third layer 33 prevents the recycled PET from appearing on the front or back surface of the recycled film 30. This ensures the hygienic properties of the packaging material 10. Alternatively, the recycled film 30 may have two layers: a second layer 32 and a third layer 33, without the first layer 31 shown in Figure 5. Furthermore, the recycled film 30 may have two layers, a first layer 31 and a second layer 32, without having the third layer 33 shown in Figure 5. Even in these cases, it is preferable that the second layer 32 be a layer made only of recycled PET or a mixed layer of recycled PET and virgin PET, and that the first layer 31 and the third layer 33 be layers made only of virgin PET.

When mixing recycled PET and virgin PET to form a single layer, there are several methods, including feeding them separately into the molding machine, or mixing them using a dry blend and then feeding them. Of these, mixing them using a dry blend is preferred from the perspective of ease of operation.

The PET that makes up the recycled film can contain various additives during or after its production process, provided that their properties are not impaired. Examples of additives include plasticizers, UV stabilizers, color inhibitors, matting agents, deodorizers, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, mold release agents, antioxidants, ion exchange agents, and color pigments. The additives are preferably added in an amount of 5% to 50% by weight, and more preferably 5% to 20% by weight, based on the total resin composition containing PET.

Recycled films can be formed by using the above-mentioned PET to form a film, for example, using the T-die method. Specifically, after drying the above-mentioned PET, it is fed into a melt extruder heated to a temperature above the melting point of PET (Tm) to Tm + 70°C, where the resin composition is melted and extruded into a sheet through a die such as a T-die. The extruded sheet is then rapidly cooled and solidified using a rotating cooling drum or the like to form a film. As the melt extruder, a single-screw extruder, twin-screw extruder, vent extruder, tandem extruder, etc. can be used depending on the purpose.

The film obtained as described above is preferably biaxially stretched. Biaxial stretching can be performed by conventional methods. For example, the film extruded onto the cooling drum as described above is subsequently heated by roll heating, infrared heating, or the like, and stretched in the machine direction to form a machine-stretched film. This stretching is preferably performed using the difference in peripheral speed between two or more rolls. Machine-stretching is usually performed at a temperature range of 50°C or higher and 100°C or lower. The machine-stretching ratio is preferably 2.5 times or higher and 4.2 times or lower, depending on the required properties of the film's application. If the stretching ratio is less than 2.5 times, the thickness of the PET film will become uneven, making it difficult to obtain a good film.

The longitudinally stretched film is then subjected to the subsequent processes of transverse stretching, heat setting, and heat relaxation to become a biaxially stretched film. Transverse stretching is typically carried out at a temperature between 50°C and 100°C. The transverse stretching ratio is preferably between 2.5 and 5.0 times, depending on the required properties of the application. If the ratio is less than 2.5 times, the film thickness will be uneven, making it difficult to obtain a good film, and if the ratio is more than 5.0 times, breakage will occur easily during film production.

After transverse stretching, heat setting is performed. The preferred heat setting temperature range is PET's Tg + 70 to Tm - 10°C. The heat setting time is preferably 1 to 60 seconds. Furthermore, for applications requiring reduced thermal shrinkage, heat relaxation may be performed as needed.

The thickness of the recycled film obtained as described above can be determined depending on its intended use, but is usually about 5 μm to 100 μm, preferably 5 μm to 25 μm. The breaking strength of the recycled film is 5 kg/ ^mm² to 40 kg/ ^mm² in the MD direction and 5 kg/mm² to ³⁵ kg/ ^mm² in the TD direction. The breaking elongation is 50% to 350% in the MD direction and 50% to 300% in the TD direction. The shrinkage when left in a 150°C environment for 30 minutes is 0.1% to 5%.

Virgin PET may be fossil fuel polyethylene terephthalate (hereinafter also referred to as fossil fuel PET) or biomass PET. Here, "fossil fuel PET" refers to PET in which the diol units are made from fossil fuel-derived diols and the dicarboxylic acids are made from fossil fuel-derived dicarboxylic acids. Recycled PET may be obtained by recycling PET resin products made from fossil fuel PET, or may be obtained by recycling PET resin products made from biomass PET.

(rigid film)
The rigid film is a film that provides strength such as puncture resistance to the packaging material 10. As the rigid film, any of the following stretched plastic films (1) to (3) can be used.
(1) Stretched plastic film containing polyamide as the main component (hereinafter also referred to as polyamide film)
(2) A stretched plastic film containing polybutylene terephthalate (hereinafter also referred to as PBT) as a main component (hereinafter also referred to as PBT film)
(3) A stretched plastic film having a loop stiffness of 0.0017 N or more in at least one direction and containing polyester as a main component (hereinafter also referred to as a high-stiffness film).
By using any of the stretched plastic films (1) to (3) to form a rigid film, the puncture strength of the rigid film can be increased, for example, to 10 N or more. This provides the rigidity required to prevent the bag from tearing even when a bag made of packaging material 10 containing the rigid film comes into contact with a sharp object having a pointed tip.

The stretched plastic films (1) to (3) are described below. First, polyamide film is described. Polyamide film contains 51% or more by mass of polyamide. The polyamide content in polyamide film may be 80% or more by mass, 90% or more by mass, or even 95% or more by mass. Examples of polyamide-based films include aliphatic polyamides and aromatic polyamides. Aliphatic polyamides include nylons such as nylon-6, nylon-6,6, and copolymers of nylon 6 and nylon 6,6, while aromatic polyamides include polymetaxylene adipamide (MXD6).

The thickness of the polyamide film is preferably 12 μm or more, and more preferably 15 μm or more. The thickness of the polyamide film is preferably 30 μm or less, and more preferably 25 μm or less.

A polyamide film may be composed of a single layer or multiple layers. When a polyamide film includes multiple layers, it is, for example, a co-extruded film produced by co-extrusion. A polyamide film produced by co-extrusion includes, for example, a first layer made of a polyester such as PET, a second layer made of a polyamide such as nylon, and a third layer made of a polyester such as PET, laminated in this order. Note that when the mass of the second layer made of a polyamide such as nylon is 51% or more of the total mass of the polyamide film, it can be said that the main component of the polyamide film produced by co-extrusion is polyamide.

Next, we will explain PBT film. PBT film contains 51% or more by mass of PBT. The PBT content in the PBT film may be 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, or even 95% or more by mass. The PBT film may have either the first or second structure described below.

The PBT film of the first configuration is produced by casting multiple layers of resins of the same composition, as disclosed, for example, in International Publication No. 2015/178390. In this case, the PBT film has a multilayer structure including at least 10 layers, preferably 60 layers or more, more preferably 250 layers or more, and even more preferably 1,000 layers or more. Each of the multiple layers preferably contains 51% by mass or more of PBT, more preferably 60% by mass or more of PBT. Among the multiple layers, the n+1th layer is laminated directly on the nth layer. In other words, no adhesive or bonding layer is interposed between the multiple layers. The thickness of each layer is preferably 3 nm or more, more preferably 10 nm or more. The thickness of each layer is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 75 nm or less.

The overall thickness of the PBT film is preferably 9 μm or more, more preferably 12 μm or more. Furthermore, the overall thickness of the PBT film of the first configuration is preferably 25 μm or less, more preferably 20 μm or less. By making the PBT film thicker than 9 μm, the PBT film has sufficient strength. Furthermore, by making the PBT film thicker than 25 μm, the PBT film exhibits excellent formability. Therefore, the process of manufacturing packaging bags by processing packaging material 10 containing PBT film can be carried out efficiently.

When the PBT film has a multilayer structure containing multiple layers as described above, some of the multiple layers may contain a polyester resin other than PBT as a primary component. For example, a PBT film having a first configuration may be composed of multiple layers containing PBT as a primary component and a layer containing, for example, PET as a primary component located between two PBT layers. In other words, a PBT film having a first configuration may be constructed by alternately laminating layers containing PBT as a primary component and layers containing, for example, PET as a primary component.

Preferably, the tensile strength of the PBT film of the first configuration divided by the tensile elongation in at least one direction is 2.0 MPa/% or more, for example, the tensile strength of the PBT film divided by the tensile elongation in the transverse direction (TD) is preferably 2.0 MPa/% or more, more preferably 2.2 MPa/% or more.
The tensile strength and tensile elongation can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a PBT film with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of the measurement is 100 mm, and the tensile speed is 300 mm/min. The length of the test piece can be adjusted as long as the test piece can be held by the pair of chucks. In this application, unless otherwise specified, the environmental temperature during the test is 25°C and the relative humidity is 50%.

The PBT film of the second configuration is a monolayer film containing a polyester whose main repeating unit is butylene terephthalate, as disclosed in JP 2014-133332 A, for example. For example, the PBT film contains a homo- or copolymer-type polyester obtained by condensing 1,4-butanediol or its ester-forming derivative as the glycol component and terephthalic acid or its ester-forming derivative as the dibasic acid component. The PBT content in the PBT film of the second configuration is preferably 51% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and most preferably 90% by mass or more. Furthermore, the PBT film of the second configuration is preferably composed only of polybutylene terephthalate and additives.

To impart mechanical strength to the PBT film of the second configuration, PBTs with a melting point of 200°C or higher and 250°C or lower and an IV value of 1.10 dl/g or higher and 1.35 dl/g or lower are preferred. Furthermore, PBTs with a melting point of 215°C or higher and 225°C or lower and an IV value of 1.15 dl/g or higher and 1.30 dl/g or lower are particularly preferred. These IV values may be satisfied by all of the materials constituting the PBT film. The IV value can be calculated based on JIS K 7367-5:2000.

The PBT film according to the second aspect may contain up to 30% by mass of a polyester resin other than PBT, such as PET. By incorporating PET in addition to PBT, PBT crystallization can be suppressed, improving the stretchability of the PBT film. The PET blended with the PBT in the PBT film can be a polyester whose main repeating unit is ethylene terephthalate. For example, a homotype primarily composed of ethylene glycol as the glycol component and terephthalic acid as the dibasic acid component is preferred. To impart good mechanical strength properties, PETs with a melting point of 240°C to 265°C and an IV value of 0.55 dl/g to 0.90 dl/g are preferred. Furthermore, PETs with a melting point of 245°C to 260°C and an IV value of 0.60 dl/g to 0.80 dl/g are particularly preferred.

Next, we will explain high-stiffness films. High-stiffness films contain polyester as a primary component and have a loop stiffness of 0.0017 N or greater in at least one direction.

Loop stiffness is a parameter that represents the stiffness of a film. Below, we will explain how to measure loop stiffness with reference to Figures 6 to 11. The measurement method described below can be used not only for single-layer films such as stretched plastic films, but also for films containing multiple layers, such as vapor-deposited films and laminated films. A vapor-deposited film is a film that contains a single-layer film, such as stretched plastic film, and a vapor-deposited layer formed on the single-layer film. A laminated film is a film that contains multiple laminated films, such as packaging material 10.

Figure 6 is a plan view showing the test specimen 60 and loop stiffness measuring device 65, and Figure 7 is a cross-sectional view of the test specimen 60 and loop stiffness measuring device 65 taken along line V-V in Figure 6. The test specimen 60 is a rectangular film having long and short sides. In this application, the length L1 of the long side of the test specimen 60 is 150 mm, and the length L2 of the short side is 15 mm. The loop stiffness measuring device 65 may be, for example, a No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Seisakusho. The length L1 of the long side of the test specimen 60 is adjustable as long as the test specimen 60 can be gripped by a pair of chucks 66, which will be described later.

The loop stiffness measuring device 65 has a pair of chuck portions 66 for gripping a pair of longitudinal ends of the test specimen 60, and a support member 67 for supporting the chuck portions 66. The chuck portions 66 include a first chuck 661 and a second chuck 662. In the state shown in Figures 6 and 7, the test specimen 60 is placed on the pair of first chucks 661, and the second chuck 662 has not yet gripped the test specimen 60 between itself and the first chuck 661. As described below, during measurement, the test specimen 60 is gripped between the first chuck 661 and the second chuck 662 of the chuck portions 66. The second chuck 662 may be connected to the first chuck 661 via a hinge mechanism.

If the film to be measured, such as a stretched plastic film, vapor-deposited film, or laminated film, is available in a state before it is processed into a packaging product, the test piece 60 may be prepared by cutting the film to be measured. Alternatively, the test piece 60 may be prepared by cutting a packaging product made from the packaging material 10, such as a packaging bag, and removing the film to be measured. For example, the test piece may be prepared by cutting the surface film 74 or the back film 75 of the packaging bag 70, as shown by the dotted lines labeled 60A and 60B in Figures 12 and 13 (described below). When measuring the loop stiffness of the packaging material 10 in the machine direction, the test piece is prepared by cutting the surface film 74 or the back film 75 of the packaging bag 70 so that the long side of the test piece aligns with the machine direction, as shown by the symbol 60A in Figures 12 and 13. When measuring the loop stiffness of the packaging material 10 in the vertical direction, a test specimen is prepared by cutting the front film 74 or back film 75 of the packaging bag 70 so that the long side direction of the test specimen coincides with the vertical direction, as shown by the reference symbol 60B in Figures 12 and 13. Although not shown, a test specimen may also be prepared by cutting the bottom film 76 so that the long side direction of the test specimen coincides with the machine direction or the vertical direction.

A method for measuring the loop stiffness of a test specimen 60 using a loop stiffness measuring device 65 will now be described. First, as shown in Figures 6 and 7, the test specimen 60 is placed on the first chuck 661 of a pair of chucks 66 spaced apart by a distance L3. In this application, the distance L3 is set so that the length of the loop portion 61 (described below, also referred to as the loop length) is 60 mm. The test specimen 60 includes an inner surface 60x located on the first chuck 661 side and an outer surface 60y located opposite the inner surface 60x. When the test specimen 60 is made of packaging material 10, the inner surface 60x and outer surface 60y of the test specimen 60 coincide with the inner surface and outer surface of the packaging material 10. When the loop portion 61 (described below) is formed on the test specimen 60, the inner surface 60x is located inside the loop portion 61, and the outer surface 60y is located outside the loop portion 61. Next, as shown in Figure 8, the second chuck 662 is placed on top of the test specimen 60 so that the end of the long side of the test specimen 60 is gripped between the second chuck 662 and the first chuck 661.

Next, as shown in FIG. 9, at least one of the pair of chuck portions 66 is slid on the support member 67 in a direction that reduces the distance between them. This allows a loop portion 61 to be formed on the test specimen 60. The test specimen 60 shown in FIG. 9 has a loop portion 61, a pair of intermediate portions 62, and a pair of fixing portions 63. The pair of fixing portions 63 are portions of the test specimen 60 that are gripped by the pair of chuck portions 66. The pair of intermediate portions 62 are portions of the test specimen 60 that are located between the loop portion 61 and the pair of intermediate portions 62. As shown in FIG. 9, the chuck portion 66 is slid on the support member 67 until the inner surfaces 60x of the pair of intermediate portions 62 come into contact with each other. This allows a loop portion 61 with a loop length of 60 mm to be formed. The loop length of the loop portion 61 is the length of the test piece 60 between position P1 where the surface of one second chuck 662 on the loop portion 61 side intersects with the test piece 60, and position P2 where the surface of the other second chuck 662 on the loop portion 61 side intersects with the test piece 60. If the thickness of the test piece 60 is ignored, the above-mentioned distance L3 is the value obtained by adding 2 x t to the length of the loop portion 61, where t is the thickness of the second chuck 662 of the chuck portion 66.

10, the posture of the chuck portion 66 is adjusted so that the protruding direction Y of the loop portion 61 relative to the chuck portion 66 is horizontal. For example, the posture of the chuck portion 66 supported by the support member 67 is adjusted by moving the support member 67 so that the normal direction of the support member 67 is horizontal. In the example shown in FIG. 10, the protruding direction Y of the loop portion 61 coincides with the thickness direction of the chuck portion. Furthermore, a load cell 68 is prepared at a position a distance Z1 away from the second chuck 662 in the protruding direction Y of the loop portion 61. In this application, the distance Z1 is set to 50 mm. Next, the load cell 68 is moved toward the loop portion 61 of the test specimen 60 at a speed V by a distance Z2 shown in FIG. 10. The distance Z2 is set so that the load cell 68 contacts the loop portion 61 and then pushes the loop portion 61 toward the chuck portion 66, as shown in FIGS. 10 and 11. In this application, distance Z2 is set to 40 mm. In this case, distance Z3 between the load cell 68 and the second chuck 662 of the chuck portion 66 when the load cell 68 is pressing the loop portion 61 toward the chuck portion 66 is 10 mm. The speed V at which the load cell 68 is moved is set to 3.3 mm/sec.

Next, as shown in Figure 11, the load cell 68 is moved a distance Z2 toward the chuck portion 66, and with the load cell 68 pressing into the loop portion 61 of the test piece 60, the load value applied to the load cell 68 from the loop portion 61 is recorded after it stabilizes. The load value obtained in this manner is used as the loop stiffness of the film that constitutes the test piece 60. Unless otherwise specified, in this application, the environment during loop stiffness measurement is a temperature of 23°C and a relative humidity of 50%.

By using a high-stiffness film having a loop stiffness of 0.0017 N or more in at least one direction as the first stretched plastic film 11 or the second stretched plastic film 12, the puncture strength of the first stretched plastic film 11 or the second stretched plastic film 12 can be increased. As a result, in a packaging material 10 including a high-stiffness film, the puncture strength of the packaging material 10 can be increased to, for example, 13 N or more, more preferably 14 N or more, and even more preferably 15 N or more or 16 N or more.

An example of a high-stiffness film is a high-stiffness PET film containing 51% or more by mass of PET. The PET content in the high-stiffness PET film may be 80% or more by mass, 90% or more by mass, or even 95% or more by mass. The thickness of the high-stiffness film is preferably 5 μm or more, and more preferably 7 μm or more. The thickness of the high-stiffness film may be 10 μm or more, or may be 14 μm or more. The thickness of the high-stiffness film is preferably 30 μm or less, and may be 25 μm or less, or may be 20 μm or less.

The preferred mechanical properties of the high stiffness film will now be further described.
The puncture strength of the high stiffness film is preferably 10 N or more, and more preferably 11 N or more.
The tensile strength of the high stiffness film in at least one direction is preferably 250 MPa or more, more preferably 280 MPa or more. For example, the tensile strength of the high stiffness film in the machine direction is preferably 250 MPa or more, more preferably 280 MPa or more. The tensile strength of the high stiffness film in the perpendicular direction is preferably 250 MPa or more, more preferably 280 MPa or more.
The tensile elongation of the high stiffness film in at least one direction is preferably 130% or less, more preferably 120% or less. For example, the tensile elongation of the high stiffness film in the machine direction is preferably 130% or less, more preferably 120% or less. The tensile elongation of the high stiffness film in the perpendicular direction is preferably 120% or less, more preferably 110% or less.
Preferably, the tensile strength of the high stiffness film divided by the tensile elongation in at least one direction is 2.0 [MPa/%] or more. For example, the tensile strength of the high stiffness film divided by the tensile elongation in the transverse direction (TD) is preferably 2.0 [MPa/%] or more, more preferably 2.2 [MPa/%] or more. The tensile strength of the high stiffness film divided by the tensile elongation in the machine direction (MD) is preferably 1.8 [MPa/%] or more, more preferably 2.0 [MPa/%] or more.

The heat shrinkage of the high stiffness film in at least one direction is preferably 0.7% or less, more preferably 0.5% or less. For example, the heat shrinkage of the high stiffness film in the machine direction is preferably 0.7% or less, more preferably 0.5% or less. The heat shrinkage of the high stiffness film in the perpendicular direction is preferably 0.7% or less, more preferably 0.5% or less. The heating temperature for measuring the heat shrinkage is 100°C, and the heating time is 40 minutes.
The Young's modulus of the high stiffness film in at least one direction is preferably 4.0 GPa or more, more preferably 4.5 GPa or more. For example, the Young's modulus of the high stiffness film in the machine direction is preferably 4.0 GPa or more, more preferably 4.5 GPa or more. The Young's modulus of the high stiffness film in the perpendicular direction is preferably 4.0 GPa or more, more preferably 4.5 GPa or more.

Like tensile strength and tensile elongation, Young's modulus can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a high-stiffness film with a width of 15 mm and a length of 150 mm can be used as a test specimen. The distance between the pair of chucks holding the test specimen at the start of measurement is 100 mm, and the tensile speed is 300 mm/min. The length of the test specimen can be adjusted as long as the test specimen can be held by the pair of chucks. Unless otherwise specified in this application, the environment during measurement of Young's modulus is a temperature of 25°C and a relative humidity of 50%.
The Young's modulus of the packaging material 10 is measured in the same manner as for the high-stiffness polyester film, except that the measuring instrument is an RTC-1310A tensile tester manufactured by Orientec Co., Ltd., and the distance between the pair of chucks holding the test specimen is 50 mm at the start of the measurement. When measuring the Young's modulus of the packaging material 10, a test specimen can be prepared by cutting the front film 74, back film 75, or bottom film 76 of the packaging bag 70 so that the long side direction of the test specimen coincides with the flow direction or the perpendicular direction, as in the case of measuring the loop stiffness.

In packaging material 10 including a high-stiffness film, the high-stiffness film may be provided with a metal vapor deposition layer 22 as described above. In this case, the high-stiffness film provided with the metal vapor deposition layer 22 may have mechanical properties equivalent to those of a high-stiffness film alone. For example, the high-stiffness film provided with the metal vapor deposition layer 22 may have a loop stiffness of 0.0017 N or more in at least one direction.

In the manufacturing process for high-stiffness films, for example, a plastic film obtained by melting and molding polyester is first stretched 3 to 4.5 times in both the machine direction and the perpendicular direction at 90 to 145°C in a first stretching step. This is followed by a second stretching step in which the plastic film is stretched 1.1 to 3.0 times in both the machine direction and the perpendicular direction at 100 to 145°C. This is then heat-set at a temperature of 190 to 220°C. This is followed by a relaxation treatment (treatment to reduce the film width) of approximately 0.2 to 2.5% in both the machine direction and the perpendicular direction at a temperature of 100 to 190°C. By adjusting the stretch ratio, stretching temperature, heat-setting temperature, and relaxation rate in these steps, a high-stiffness film with the mechanical properties described above can be obtained.

When packaging material 10 includes a rigid film such as a high-stiffness film, strength such as puncture resistance can be imparted to packaging material 10 and packaging products such as packaging bags 70 made from packaging material 10. This can prevent the packaging bag 70 from tearing when it comes into contact with a sharp object with a pointed tip. The puncture strength of packaging material 10 including a rigid film is, for example, 13.0 N or more, or alternatively, 14.0 N or more, 15.0 N or more, or 16.0 N or more.

Furthermore, when the packaging material 10 includes a rigid film such as a high-stiffness film, the Young's modulus of the packaging material 10 can be increased. The Young's modulus of the packaging material 10 in one direction is, for example, 3200 MPa or more, or may be 3300 MPa or more, 3400 MPa or more, 3500 MPa or more, 3600 MPa or more, or 3700 MPa or more. Furthermore, the Young's modulus of the packaging material 10 in a direction perpendicular to the above-mentioned one direction is, for example, 2700 MPa or more, or may be 2800 MPa or more, 2900 MPa or more, 3000 MPa or more, 3100 MPa or more, or 3200 MPa or more. For example, the Young's modulus of the packaging material 10 in the machine direction (MD) is, for example, 3200 MPa or more, or may be 3300 MPa or more, 3400 MPa or more, 3500 MPa or more, 3600 MPa or more, or 3700 MPa or more. When the packaging material 10 includes a PBT film or a high-stiffness film, the Young's modulus of the packaging material 10 in the machine direction (MD) can be 3500 MPa or more. Furthermore, the Young's modulus of the packaging material 10 in the transverse direction (TD), which is the direction perpendicular to the machine direction (MD), is, for example, 2700 MPa or more, or may be 2800 MPa or more, 2900 MPa or more, 3000 MPa or more, 3100 MPa or more, or 3200 MPa or more. A high Young's modulus of the packaging material 10 makes the packaging material 10 less likely to stretch. This increases the processing accuracy when processing the packaging material 10 during the manufacturing process of packaging products such as the packaging bag 70. Furthermore, when the packaging material 10 is used to produce a gusseted packaging bag 70 that is configured to be self-standing, as described below, the self-standing ability of the packaging bag 70 is improved.

(Virgin Films)
Virgin films are films made from non-recycled resins. Examples of virgin films include the above-mentioned fossil fuel PET and biomass PET. When a virgin film contains PET, such as fossil fuel PET or biomass PET, as a primary component, the PET content in the virgin film may be 80% by mass or more, 90% by mass or more, or even 95% by mass or more. The puncture strength of the virgin film is lower than that of the above-mentioned rigid film, for example, less than 10 N. The loop stiffness of the virgin film is lower than that of the above-mentioned high-stiffness film, for example, less than 0.0017 N in both the machine direction (MD) and the transverse direction (TD). The thickness of the virgin film varies depending on its application, but is typically between 5 μm and 100 μm, preferably between 5 μm and 25 μm.

(OPP film)
The OPP film contains polypropylene derived from fossil fuels. The puncture strength of the OPP film is lower than that of the aforementioned rigid film, for example, less than 10 N. The polypropylene content of the OPP film may be 80% by mass or more, 90% by mass or more, or even 95% by mass or more. The loop stiffness of the OPP film is lower than that of the aforementioned high-stiffness film, for example, less than 0.0017 N in both the machine direction (MD) and the transverse direction (TD). The thickness of the OPP film varies depending on its application, but is typically between 5 μm and 100 μm, preferably between 18 μm and 40 μm.

[Metal deposition layer]
Next, the metal vapor deposition layer 22 will be described. The metal vapor deposition layer 22 is a layer made of a metal vapor deposition film that can be formed by a conventionally known vapor deposition method. By providing the metal vapor deposition layer 22, it is possible to impart a metallic luster to the packaging bag, thereby improving the design. It is also possible to impart or improve light blocking properties that prevent the transmission of visible light, ultraviolet light, and the like. It can also contribute to gas barrier properties that prevent the transmission of oxygen gas, water vapor, and the like.

The material constituting the metal vapor deposition layer 22 can be, for example, one or more metal materials selected from the group consisting of aluminum (Al), magnesium (Mg), tin (Sn), sodium (Na), titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y), gold (Au), and chromium (Cr). For packaging bags in particular, it is preferable that the metal vapor deposition layer 22 comprise an aluminum vapor deposition layer.

The metal vapor deposition layer 22 may be composed of a single layer or multiple layers. Each of the single layer and multiple layers contains one or more metal materials selected from the group described above. When the metal vapor deposition layer 22 contains multiple layers, each layer may contain the same metal material or different metal materials.

The thickness of the metal vapor deposition layer 22 varies depending on the type of metal used, but can be selected from a range of, for example, 50 Å to 2000 Å, preferably 100 Å to 1000 Å. More specifically, in the case of an aluminum vapor deposition layer, the thickness should be 300 Å to 1000 Å, more preferably 350 Å to 900 Å.

Methods for forming the metal vapor deposition layer 22 include, for example, physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

The surface of the second stretched plastic film 12 on which the metal vapor deposition layer 22 is provided may be treated to improve adhesion of the metal vapor deposition layer 22 to the second stretched plastic film 12, or a layer may be formed to improve adhesion. For example, the surface of the second stretched plastic film 12 may be subjected to plasma treatment using plasma.

[Sealant layer]
The sealant layer 15 is disposed on the content side of the packaging bag when the packaging bag is manufactured using the packaging material 10, and functions to seal the packaging materials 10 together. The sealant layer is a layer formed of a thermoplastic resin that can be fused to each other by heat. The sealant layer 15 may contain a resin material derived from fossil fuels or a resin material derived from biomass.

The resin material forming the sealant layer 15 is not particularly limited as long as it is a resin that can be fused to each other by heat. Specific examples include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), ethylene-α-olefin copolymers polymerized using a metallocene catalyst, random or block copolymers of ethylene and polypropylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-methacrylic acid copolymer (EMA). A), ethylene-methyl methacrylate copolymer (EMMA), ionomer resin, heat-sealable ethylene-vinyl alcohol resin, or polyolefin resins such as methylpentene resin, ethylene-propylene copolymer, methylpentene polymer, polybutene polymer, polyethylene, polypropylene, or cyclic olefin copolymer, acid-modified polyolefin resins obtained by modifying polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, or itaconic acid, polyvinyl acetate resin, poly(meth)acrylic resin, polyvinyl chloride resin, and other resins. These may be used alone or as a mixture of two or more.

The sealant layer 15 may be formed by laminating a film or sheet of the above-mentioned resin to the second stretched plastic film 12 via the second adhesive layer 17. The sealant layer 15 of the packaging material 10 shown in Figures 1 and 2 above is an example of a sealant layer formed by laminating a film or sheet to the second stretched plastic film 12 via the second adhesive layer 17. The sealant layer 15 may also be formed by extruding the above-mentioned resin onto the second stretched plastic film 12. The sealant layer 15 of the packaging material 10 shown in Figures 3 and 4 above is an example of a sealant layer formed on the second stretched plastic film 12 by extrusion molding. When the sealant layer 15 is formed by extrusion molding, a second anchor coat layer 19 may be provided on the inner surface of the second stretched plastic film 12, as shown in Figures 3 and 4.

When polyethylene is used as the resin material forming the sealant layer 15, in addition to ethylene obtained from fossil fuels, polymerized ethylene derived from biomass may also be used as the raw material. Specific examples of biomass-derived ethylene include those described in JP 2012-251006 A. By using polyethylene obtained by polymerizing biomass-derived ethylene as the material constituting the sealant layer 15, a layer made of a carbon-neutral material can be formed, further reducing the amount of fossil fuel used and the environmental impact.

Commercially available biomass-derived ethylene may be used, such as Braskem's "C4LL-LL118 (d = 0.916, MFR = 1.0 g/10 min)" sugarcane-derived linear low-density polyethylene resin or "SBC118 (d = 0.918, MFR = 8.1 g/10 min)" sugarcane-derived low-density polyethylene resin.

In this embodiment, the sealant layer 15 is a single layer, but the sealant layer 15 may have two or more layers. When the sealant layer 15 has two or more layers, each layer may have the same composition or different compositions. For example, the sealant layer 15 may be composed of three layers, with a first layer, a second layer, and a third layer laminated in this order, and the first and third layers may be made of a resin material derived from fossil fuels, and the second layer may be made of a resin material containing a biomass-derived resin material. When the sealant layer 15 is composed of two or more layers, they can be laminated using a co-extrusion method.

The thickness of the sealant layer 15 is preferably 10 μm or more and 150 μm or less, and more preferably 18 μm or more and 120 μm or less.

[Adhesive layer]
The first adhesive layer 16 is a layer that bonds the film including the first stretched plastic film 11 to the film including the second stretched plastic film 12. The second adhesive layer 17 is a layer that bonds the film including the second stretched plastic film 12 to the film including the sealant layer 15. When the sealant layer 15 is formed on the second stretched plastic film 12 by extrusion molding, the packaging material 10 does not need to include the second adhesive layer 17, as shown in Figures 3 and 4 .

Adhesive layers such as the first adhesive layer 16 and the second adhesive layer 17 may be adhesive layers or adhesive resin layers. The adhesive layer and adhesive resin layer will be described below.

The adhesive layer can be formed by a conventional method, such as the dry lamination method. When bonding two layers using the dry lamination method, the adhesive layer is formed by applying an adhesive to the surface of the layer to be laminated and drying it. The adhesive to be applied can be, for example, a one-component or two-component curing or non-curing vinyl, (meth)acrylic, polyamide, polyester, polyether, polyurethane, epoxy, rubber, or other solvent-based, water-based, or emulsion adhesive. A two-component curing adhesive can be a cured product of a polyol and an isocyanate compound. The laminating adhesive can be applied by, for example, direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fountain coating, transfer roll coating, or other methods. The adhesive layer after drying has a thickness of, for example, 1 μm to 10 μm, preferably 2 μm to 5 μm.

The adhesive layer may contain a biomass-derived component. For example, if the adhesive layer contains a cured product of a polyol and an isocyanate compound, at least one of the polyol or the isocyanate compound may contain a biomass-derived component. This can further improve the biomass content of the packaging material 10.

The adhesive resin layer contains a thermoplastic resin. The adhesive resin layer can be formed by conventional methods, such as melt extrusion lamination or sand lamination. Thermoplastic resins that can be used for the adhesive resin layer include polyethylene resins, polypropylene resins, cyclic polyolefin resins, copolymer resins, modified resins, or mixtures (including alloys) that contain these resins as their main components. Examples of polyolefin resins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), ethylene-α-olefin copolymers polymerized using a metallocene catalyst, random or block copolymers of ethylene and polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-maleic acid copolymer, and ionomer resins. Acid-modified polyolefin resins obtained by modifying the above-mentioned polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid to improve interlayer adhesion can also be used. Furthermore, resins obtained by graft-polymerizing or copolymerizing unsaturated carboxylic acids, unsaturated carboxylic anhydrides, or ester monomers with polyolefin resins can also be used. These materials can be used alone or in combination of two or more. Examples of cyclic polyolefin resins that can be used include cyclic polyolefins such as ethylene-propylene copolymer, polymethylpentene, polybutene, and polynorbornene. These resins can be used alone or in combination. The adhesive resin layer has a thickness of, for example, 5 μm to 50 μm, preferably 10 μm to 30 μm.

The polyethylene-based resin may be one that uses biomass-derived ethylene as a monomer unit, as described for the sealant layer 15. This can further improve the biomass content of the packaging material 10.

[Anchor coat layer]
Anchor coat layers such as the first anchor coat layer 18 and the second anchor coat layer 19 are layers formed by applying an anchor coating agent onto a predetermined layer or film and drying it. The anchor coat layer can improve adhesion between the predetermined layer or film on which the anchor coat layer is provided and a layer formed by extrusion onto the predetermined layer or film. The anchor coat layer after drying has a thickness of, for example, 0.1 μm or more and 1 μm or less, preferably 0.3 μm or more and 0.5 μm or less.

When the first adhesive layer 16 is an adhesive resin layer, as shown in Figures 2 and 4, a first anchor coat layer 18 can be provided on the first stretched plastic film 11 or on a printed layer 21 provided on the first stretched plastic film 11. This can improve the adhesion of the first adhesive layer 16 to the first stretched plastic film 11 or the printed layer 21.
Furthermore, when the second adhesive layer 17 is an adhesive resin layer, a second anchor coat layer 19 can be provided on the second stretched plastic film 12, as shown in Figure 2. This can improve the adhesion of the second adhesive layer 17 to the second stretched plastic film 12.
When the sealant layer 15 is formed by extrusion molding, a second anchor coat layer 19 can be provided on the second stretched plastic film 12, as shown in Figures 3 and 4. This can improve the adhesion of the sealant layer 15 to the second stretched plastic film 12.

Anchor coating agents can be any resin with a heat resistance temperature of 135°C or higher, such as vinyl-modified resin, epoxy resin, urethane resin, polyester resin, or polyethyleneimine. However, anchor coating agents that are cured from a polyacrylic or polymethacrylic resin (polyol) with two or more hydroxyl groups in its structure and an isocyanate compound as a curing agent are particularly preferred. A silane coupling agent may also be used as an additive, and soluble nitrocellulose may also be used to enhance heat resistance.

The anchor coat layer may contain a biomass-derived component. For example, if the anchor coat layer contains a cured product of a polyol and an isocyanate compound, at least one of the polyol or the isocyanate compound may contain a biomass-derived component. This can further improve the biomass content of the packaging material 10.

[Printing layer]
The printing layer 21 is a layer on which any desired printed pattern such as letters, numbers, pictures, figures, symbols, designs, etc. is formed for the purpose of decoration, indication of contents, indication of expiration date, indication of manufacturer, seller, etc., or for imparting aesthetic appeal. The printing layer 21 can be provided as needed, and can be provided, for example, between the first stretched plastic film 11 and the first adhesive layer 16. The printing layer 21 may be provided on the entire surface of the first stretched plastic film 11, or on a part of it. The printing layer 21 can be formed using conventionally known pigments or dyes, and the method of forming it is not particularly limited.

The printing layer preferably has a thickness of 0.1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and even more preferably 1 μm or more and 3 μm or less.

The printed layer 21 may contain a biomass-derived component. For example, if the printed layer 21 contains a cured product of a polyol and an isocyanate compound, at least one of the polyol or the isocyanate compound may contain a biomass-derived component.

In this embodiment, as described above, the packaging material 10 includes a recycled film containing recycled PET in a proportion of, for example, 50% by weight to 95% by weight. Therefore, it is possible to provide a packaging material 10 that is more effective in reducing _CO2 emissions than packaging materials that do not contain recycled PET. Furthermore, by providing the packaging material 10 with the metal vapor deposition layer 22, it is possible to impart design features to the packaging material 10.

<Method of manufacturing packaging material>
Next, an example of a method for manufacturing the packaging material 10 will be described. First, an example of a method for manufacturing the packaging material 10 shown in FIG.

(Method for manufacturing the packaging material of FIG. 1)
First, prepare the above-described first stretched plastic film 11 and second stretched plastic film 12. The first stretched plastic film 11 may be provided with a printed layer 21 in advance. The second stretched plastic film 12 may be provided with a metal vapor deposition layer 22 in advance.

Next, the first stretched plastic film 11 and the second stretched plastic film 12 are laminated together using a dry lamination method, with the first adhesive layer 16 made of an adhesive layer interposed therebetween. Then, using a dry lamination method, the laminate including the first stretched plastic film 11 and the second stretched plastic film 12 is laminated together with the film that constitutes the sealant layer 15, with the second adhesive layer 17 made of an adhesive layer interposed therebetween. This allows for the production of a packaging material 10 that includes the first stretched plastic film 11, the second stretched plastic film 12, and the sealant layer 15.

Alternatively, the packaging material 10 may be produced by first laminating the second stretched plastic film 12 and the film constituting the sealant layer 15 by dry lamination via the second adhesive layer 17, which is an adhesive layer, and then laminating the first stretched plastic film 11 and the laminate including the second stretched plastic film 12 and the sealant layer 15 by dry lamination via the first adhesive layer 16, which is an adhesive layer.

In the dry lamination method, an adhesive composition is first applied to one of the two films to be laminated. The applied adhesive composition is then dried to volatilize the solvent. The two films are then laminated together via the dried adhesive composition. The two laminated films are then rolled up and aged, for example, in an environment of 20°C or higher for 24 hours or more.

Packaging material 10 can also be subjected to secondary processing to impart surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction/wear/lubrication functions, optical functions, thermal functions, and biocompatibility. Examples of secondary processing include embossing, painting, adhesives, printing, metallizing (plating, etc.), machining, and surface treatments (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.). Packaging material 10 can also be subjected to lamination (dry lamination or extrusion lamination), bag making, and other post-processing processes to produce molded products.

(Method for manufacturing the packaging material of FIG. 2)
Next, an example of a method for manufacturing the packaging material 10 shown in FIG. 2 will be described.

First, a first anchor coat layer 18 is provided on the printing layer 21 provided on the first stretched plastic film 11. Next, the first stretched plastic film 11 and the second stretched plastic film 12 are laminated together using a sand lamination method, with a first adhesive layer 16 made of an adhesive resin layer interposed therebetween. Next, a second anchor coat layer 19 is provided on the inner surface of the second stretched plastic film 12. After that, using a sand lamination method, a laminate including the first stretched plastic film 11 and the second stretched plastic film 12 is laminated with a film constituting the sealant layer 15 via a second adhesive layer 17 made of an adhesive resin layer. This allows for the production of a packaging material 10 comprising the first stretched plastic film 11, the second stretched plastic film 12, and the sealant layer 15.

Alternatively, the packaging material 10 may be produced by first laminating the second stretched plastic film 12 and the film constituting the sealant layer 15 by sandwich lamination via the second adhesive layer 17 made of an adhesive resin layer, and then sandwiching the first stretched plastic film 11 and the laminate including the second stretched plastic film 12 and the sealant layer 15 by sandwich lamination via the first adhesive layer 16 made of an adhesive resin layer.

In the sand lamination method, molten resin that will form the adhesive resin layer is first extruded onto one of the two films to be laminated. The other film is then laminated onto the resin extruded onto the other film.

(Method for manufacturing the packaging material of FIG. 3)
Next, an example of a method for manufacturing the packaging material 10 shown in FIG. 3 will be described.

First, as in the manufacturing method of the packaging material 10 in Figure 1, the first stretched plastic film 11 and the second stretched plastic film 12 are laminated together by dry lamination via the first adhesive layer 16, which is an adhesive layer. Next, a second anchor coat layer 19 is provided on the inner surface of the second stretched plastic film 12. Then, a sealant layer 15 is formed on the second anchor coat layer 19 provided on the second stretched plastic film 12 by melt extrusion lamination. This allows for the production of a packaging material 10 comprising the first stretched plastic film 11, the second stretched plastic film 12, and the sealant layer 15.

(Method for manufacturing the packaging material of FIG. 4)
Next, an example of a manufacturing method for the packaging material 10 of Fig. 4 will be described. First, as in the manufacturing method for the packaging material 10 of Fig. 2, a first stretched plastic film 11 and a second stretched plastic film 12 are laminated together by sand lamination via a first adhesive layer 16 made of an adhesive resin layer. Next, a second anchor coat layer 19 is provided on the inner surface of the second stretched plastic film 12. Thereafter, a sealant layer 15 is formed on the second anchor coat layer 19 provided on the second stretched plastic film 12 by melt extrusion lamination. This allows for the production of a packaging material 10 comprising the first stretched plastic film 11, the second stretched plastic film 12, and the sealant layer 15.

<Packaging bag>
The packaging material 10 is used as a material for forming packaging bags. For example, packaging bags of various shapes can be produced by folding the packaging material 10, or by preparing two sheets of the packaging material 10 and overlapping them with the sealant layer 15 of the front packaging material 10 facing the sealant layer 15 of the back packaging material 10, and then heat-sealing the peripheral edges using a heat seal method such as a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a flared seal type (pillow seal type), a flat bottom seal type, or a square bottom seal type. It is also possible to produce a gusset-type packaging bag by inserting the folded packaging material 10 between the front packaging material 10 and the back packaging material 10 and heat-sealing the materials. It is not necessary for all of the packaging materials constituting the packaging bag to be the packaging material 10 of the present invention. In other words, it is sufficient that at least a portion of the packaging material that makes up the packaging bag is packaging material 10 that includes a recycled film and a rigid film, and the other portion of the packaging material that makes up the packaging bag may be packaging material that does not include a recycled film or a rigid film.

Heat sealing can be performed using known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

Packaging bags formed using packaging material 10 can be suitably used to package a variety of food and beverage products, including food and beverages, fruit juices, juices, drinking water, alcohol, cooked foods, fish paste products, frozen foods, meat products, simmered dishes, rice cakes, liquid soups such as hot pot soup, seasonings, etc., as well as cosmetics such as liquid detergents, shampoos, rinses, and conditioners, hygiene products, daily necessities, and chemical products.

Figure 12 is a diagram showing an example of a packaging bag 70 comprising packaging material 10. The packaging bag 70 comprises a surface film 74 that forms the surface, a back film 75 that forms the back, and a lower film 76 that forms the lower part 72. The lower film 76 is folded back at fold-back portion 76f and is positioned between the surface film 74 and the back film 75. In this way, the packaging bag 70 shown in Figure 12 is a self-standing pouch with the lower part configured as a gusset portion.

The inner surfaces of the surface film 74, back film 75, and bottom film 76 are joined together by a seal. In front views of the packaging bag 70, such as Figure 12, the seal is hatched. As shown in Figure 12, the seal has an outer edge seal that extends along the outer edge of the packaging bag 70. The outer edge seal includes a lower seal 72a that extends to the bottom 72, and a pair of side seals 73a that extend along a pair of side portions 73. Note that, before the contents are filled into the packaging bag 70 (when no contents are filled), the top 71 of the packaging bag 70 forms an opening 71b, as shown in Figure 12. After the contents are placed in the packaging bag 70, the inner surfaces of the surface film 74 and the back film 75 are joined at the top 71 to form an upper seal, sealing the packaging bag 70.

The terms "surface film," "back film," and "bottom film" mentioned above merely distinguish between the films according to their positional relationships, and the method of providing packaging material 10 when manufacturing packaging bag 70 is not limited by the terms mentioned above. For example, packaging bag 70 may be manufactured using one sheet of packaging material 10 in which surface film 74, back film 75, and bottom film 76 are connected together; it may be manufactured using two sheets of packaging material 10, one sheet of packaging material 10 in which surface film 74 and bottom film 76 are connected together and one back film 75; or it may be manufactured using three sheets of packaging material 10, one sheet of surface film 74, one sheet of back film 75, and one bottom film 76.

As shown in FIG. 12, the packaging bag 70 may have a spout 85. The spout 85 is a portion through which the contents stored in the storage section 79 pass when being removed. In this case, the contents are a fluid liquid or the like. The width of the spout 85 is narrower than the width of the storage section 79. This allows the user to accurately determine the pouring direction of the contents as they are poured from the packaging bag 70 through the spout 85.

In the example shown in Figure 12, the spout section 85 is formed by a portion of the front film 74 and the back film 75. For example, the spout section 85 includes a spout seal section 86 that joins the front film 74 and the back film 75 to define the spout section 85, which has a width narrower than the storage section 79. A packaging bag 70 equipped with such a spout section 85 is suitable for use as a refill pouch for storing contents such as detergent, shampoo, and conditioner that can be refilled into a bottle.

At least one of the front film 74, back film 75, and bottom film 76 is made of packaging material 10 comprising recycled film and a metal vapor deposition layer 22. By using packaging material 10 comprising recycled film and a metal vapor deposition layer 22, it is possible to reduce the amount of fossil fuel used compared to conventional methods, thereby reducing the environmental impact. It also makes it possible to add design features to the packaging bag 70. Furthermore, when packaging material 10 comprises a rigid film, it is possible to prevent the packaging bag 70 from tearing even when a sharp object with a pointed tip comes into contact with the packaging bag 70.

Note that the configuration of the spout portion 85 is not limited to the configuration shown in FIG. 12, as long as the contents can be properly dispensed. For example, the spout portion 85 may be a separate member from the front film 74 and back film 75, such as a spout.

Figure 13 is a diagram showing another example of a packaging bag 70 including packaging material 10. The packaging bag 70 shown in Figure 13 is a pillow pouch formed by joining the inner surfaces of a film 77 folded into a cylindrical shape at an upper portion 71, a lower portion 72, and a seam portion 78. The upper portion 71 and the lower portion 72 include an upper seal portion 71a and a lower seal portion 72a. The seam portion 78 also includes a seam seal portion 78a that extends from the upper seal portion 71a to the lower seal portion 72a.

The packaging bag 70 shown in Figure 13 is suitable for use as a pouch or zipper bag for storing snacks, gummies, chocolate, and other confectionery, regular coffee bags, and small amounts of liquids (100 ml or less) such as miso, noodle soup, and sauces.

In the packaging bag 70 shown in Figure 13, the film 77 is also made of packaging material 10 including recycled film and a metal vapor deposition layer 22. This allows for a reduction in the amount of fossil fuel used compared to conventional methods, thereby reducing the environmental impact. It also allows for a more decorative design to be added to the packaging bag 70. Furthermore, if the packaging material 10 includes a rigid film, tearing of the packaging bag 70 can be prevented even if a sharp object with a pointed tip comes into contact with the packaging bag 70.

Although not shown, the packaging bag 70 may be a three-sided or four-sided sealed pouch formed by joining the front film 74 and the back film 75 on three or four sides along the outer edge.

In the above-described embodiment, an example has been shown in which the laminate of this embodiment is used as packaging material 10 for forming bags. However, the laminate of this embodiment may also be used for purposes other than packaging material. For example, the laminate of this embodiment may be used as a label that is affixed to an object by thermal welding.

Next, the present invention will be explained in more detail using examples, but the present invention is not limited to the description of the following examples as long as it does not depart from the gist of the invention.

[Example 1]
A biaxially stretched recycled PET film containing PET recycled by mechanical recycling was prepared as the first stretched plastic film 11. The recycled PET film contained 90% or more by mass of PET. The recycled PET film had a thickness of 12 μm. A printed layer 21 was also formed on the recycled PET film.

A biaxially stretched recycled PET film containing mechanically recycled PET was prepared as the second stretched plastic film 12. The recycled PET film contained 90% or more by mass of PET. The thickness of the recycled PET film can be selected within the range of 9 μm to 25 μm, but was set to 12 μm in this example. In addition, a metal vapor deposition layer 22 made of aluminum and having a thickness of 450 Å was formed on the recycled PET film.

Then, the adhesive was applied to the printed layer 21 on the recycled PET film of the first stretched plastic film 11 and dried to obtain the first adhesive layer 16. The recycled PET film of the first stretched plastic film 11 and the recycled PET film of the second stretched plastic film 12 were then bonded together via the first adhesive layer 16. The bonding was performed so that the metal vapor deposition layer 22 on the recycled PET film of the second stretched plastic film 12 faced the recycled PET film side of the first stretched plastic film 11.

A polyethylene film containing linear low-density polyethylene was prepared as the sealant layer 15. The thickness of the polyethylene film can be selected within the range of 20 μm to 100 μm, but in this case it was set to 30 μm.

Next, the laminate including the recycled PET film of the first stretched plastic film 11 and the recycled PET film of the second stretched plastic film 12 was bonded to a polyethylene film by dry lamination via a second adhesive layer 17 made of adhesive. In this way, the packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
Recycled PET12/Stamp/Adhesive/Vapor Deposition/Recycled PET12/Adhesive/PE(1)30
"Recycled PET" indicates recycled PET film. "Mark" indicates the printed layer. "Adhesive" indicates the adhesive layer. "Vapor deposition" indicates the metal vapor deposition layer. "PE(1)" means polyethylene film. The numbers indicate the layer thickness (unit: μm).

The packaging material 10 produced as described above was folded into a cylindrical shape, and the inner surfaces of the folded packaging material 10 were joined at the upper portion 71, lower portion 72, and gable portion 78 to produce the packaging bag 70 shown in Figure 13. The packaging bag 70 of this example can suitably store regular coffee.

[Example 2]
A biaxially stretched polypropylene film containing polypropylene was prepared as the first stretched plastic film 11. The stretched polypropylene film contained 90% or more by mass of polypropylene. The thickness of the stretched polypropylene film can be selected within a range of 20 μm to 40 μm, but was set to 20 μm in this example. A printed layer 21 was also formed on the stretched polypropylene film.

A biaxially stretched recycled PET film containing mechanically recycled PET was prepared as the second stretched plastic film 12. The recycled PET film contained at least 90% by mass of PET. The recycled PET film had a thickness of 12 μm. A metal vapor deposition layer 22 made of aluminum and having a thickness of 450 Å was also formed on the recycled PET film.

Next, as in Example 1, the stretched polypropylene film and the recycled PET film were bonded together by dry lamination via a first adhesive layer 16 made of adhesive.

A polyethylene film containing linear low-density polyethylene was prepared as the sealant layer 15. The thickness of the polyethylene film can be selected within the range of 20 μm to 80 μm, but here it was set to 30 μm.

Next, as in Example 1, the laminate containing the stretched polypropylene film and the recycled PET film was bonded to the polyethylene film by dry lamination via the second adhesive layer 17 made of adhesive. In this way, the packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
OPP20/Printing/Adhesive/Vapor deposition/Recycled PET12/Adhesive/PE(1)30
"OPP" stands for oriented polypropylene film.

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably store regular coffee.

[Example 3]
A biaxially stretched polypropylene film containing polypropylene was prepared as the first stretched plastic film 11. The stretched polypropylene film contained 90% or more by mass of polypropylene. The thickness of the stretched polypropylene film can be selected within a range of 18 μm to 40 μm, but was set to 20 μm in this example. A printed layer 21 was also formed on the stretched polypropylene film.

A biaxially stretched recycled PET film containing mechanically recycled PET was prepared as the second stretched plastic film 12. The recycled PET film contained at least 90% by mass of PET. The recycled PET film had a thickness of 12 μm. A metal vapor deposition layer 22 made of aluminum and having a thickness of 450 Å was also formed on the recycled PET film.

Next, a first anchor coat layer 18 was formed on the printed layer 21 on the stretched polypropylene film, and the stretched polypropylene film and recycled PET film were then bonded together using the sand lamination method via a first adhesive layer 16 made of adhesive resin. Low-density polyethylene was used as the adhesive resin. The thickness of the first adhesive layer 16 was 10 μm.

An unstretched polypropylene film was prepared as the sealant layer 15. The thickness of the unstretched polypropylene film can be selected within the range of 10 μm to 50 μm, but here it was set to 18 μm.

Next, a second anchor coat layer 19 was formed on the recycled PET film, and then the laminate including the stretched polypropylene film and the recycled PET film was bonded to the polyethylene film using the sand lamination method, with a second adhesive layer 17 made of an adhesive resin interposed between them. Low-density polyethylene was used as the adhesive resin. The thickness of the second adhesive layer 17 was 10 μm. In this way, the packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
OPP20/Stamp/AC/Adhesive Resin/Vapor Deposition/Recycled PET12/AC/Adhesive Resin/PP(1)18
"AC" represents an anchor coat layer. "Adhesive resin" represents an adhesive resin layer. "PP(1)" means a polypropylene film.

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably contain snack foods.

[Example 4]
A packaging material 10 was produced in the same manner as in Example 3, except that a biaxially stretched recycled PET film was used as the first stretched plastic film 11 instead of the stretched polypropylene film, and a polyethylene film containing linear low-density polyethylene was used as the sealant layer 15. The recycled PET film contained 90% or more by mass of PET. The thickness of the recycled PET film of the first stretched plastic film 11 was 12 μm. The thickness of the polyethylene film can be selected within a range of 10 μm to 50 μm, but was set to 30 μm here.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
Recycled PET12/Stamp/AC/Adhesive Resin/Vapor Deposition/Recycled PET12/AC/Adhesive Resin/PE(1)30

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably store regular coffee.

[Example 5]
In the same manner as in Example 3, a laminate was produced including a stretched polypropylene film as the first stretched plastic film 11 and a recycled PET film as the second stretched plastic film 12. Subsequently, a second anchor coat layer 19 was formed on the recycled PET film, and then molten low-density polyethylene was extruded onto the second anchor coat layer 19 to form a sealant layer 15 having a thickness of 30 μm. In this manner, a packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
OPP20/Stamp/AC/Adhesive resin/Vapor deposition/Recycled PET12/AC/PE(2)30
"PE(2)" represents a layer of polyethylene formed by melt extrusion lamination.

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably store regular coffee.

[Example 6]
A packaging material 10 was produced in the same manner as in Example 5, except that a biaxially stretched recycled PET film was used instead of the stretched polypropylene film as the first stretched plastic film 11. The recycled PET film contained 90% by mass or more of PET. The thickness of the recycled PET film of the first stretched plastic film 11 was 12 μm.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
Recycled PET12/Stamp/AC/Adhesive Resin/Vapor Deposition/Recycled PET12/AC/PE(2)30

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably store regular coffee.

[Example 7]
A laminate including a recycled PET film as the first stretched plastic film 11 and a recycled PET film as the second stretched plastic film 12 was produced in the same manner as in Example 1. Subsequently, a second anchor coat layer 19 was formed on the recycled PET film, and then molten low-density polyethylene was extruded onto the second anchor coat layer 19 to form a sealant layer 15 having a thickness of 30 μm. In this manner, a packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
Recycled PET12/Stamp/Adhesive/Vapor deposition/Recycled PET12/AC/PE(2)30

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, as in Example 1. The packaging bag 70 of this example can suitably store regular coffee.

[Example 8]
A packaging material 10 was produced in the same manner as in Example 7, except that a biaxially stretched nylon film was used instead of the stretched polypropylene film as the first stretched plastic film 11. The nylon film contained 90% by mass or more of polyamide. The thickness of the nylon film of the first stretched plastic film 11 was 15 μm.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
Nylon 15/printing/adhesive/metallization/recycled PET12/AC/PE(2)30
"Nylon" refers to nylon film.
As described in the above embodiment, a biaxially stretched PBT film or a biaxially stretched high-stiffness film may be used as the rigid film of the first stretched plastic film 11 instead of a nylon film.

Next, the packaging material 10 produced as described above was used to produce the packaging bag 70 shown in Figure 13, in the same manner as in Example 1. The packaging bag 70 of this example can suitably hold up to 100 ml of liquid, such as miso, noodle soup, or sauce.

[Example 9]
The laminate shown in Fig. 1 was produced in the same manner as in Example 2, except that a biaxially stretched polypropylene film was used instead of the polyethylene film as the sealant layer 15. The stretched polypropylene film contained 90% by mass or more of polypropylene. The thickness of the stretched polypropylene film of the sealant layer 15 can be selected within a range of 20 µm to 40 µm, but was set to 20 µm here.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
OPP20/Printing/Adhesive/Vapor Deposition/Recycled PET12/Adhesive/Heat Seal OPP20
"Heat-sealed OPP" refers to an oriented polypropylene film that has been given sealability by applying a heat-sealing agent.

Next, labels were made using the laminate prepared as described above.

The layer structures of the laminates in Examples 1 to 9 are summarized in Table 2 below.

[Example 10]
A biaxially stretched high-stiffness film (hereinafter also referred to as a high-stiffness PET film) having a loop stiffness of 0.0017 N or more and containing 90% by mass or more of PET was prepared as the first stretched plastic film 11. Specifically, XP-55 manufactured by Toray Industries, Inc. was used as the high-stiffness PET film. The high-stiffness film contained 90% by mass or more of PET. The thickness of the high-stiffness PET film was 16 μm. The measured loop stiffness of the high-stiffness PET film was 0.0021 N in both the machine direction and the perpendicular direction. The Young's modulus of the high-stiffness PET film in the machine direction was 4.8 GPa, and the Young's modulus of the high-stiffness PET film in the perpendicular direction was 4.7 GPa.
The tensile strength of the high-stiffness PET film in the machine direction was 292 MPa, and the tensile strength of the high-stiffness PET film in the perpendicular direction was 257 MPa. The tensile elongation of the high-stiffness PET film in the machine direction was 107%, and the tensile elongation of the high-stiffness PET film in the perpendicular direction was 102%. In this case, the tensile strength of the high-stiffness PET film in the machine direction divided by the tensile elongation was 2.73 [MPa/%], and the tensile strength of the high-stiffness PET film in the perpendicular direction divided by the tensile elongation was 2.52 [MPa/%].
The heat shrinkage of the high stiffness PET film in both the machine direction and the perpendicular direction was 0.4%.

As in Example 1, a biaxially stretched recycled PET film containing PET recycled by mechanical recycling was prepared as the second stretched plastic film 12. The recycled PET film contained at least 90% by mass of PET. The recycled PET film had a thickness of 12 μm. In addition, a metal vapor deposition layer 22 made of aluminum and having a thickness of 450 Å was formed on the recycled PET film.

Next, the high-stiffness PET film and the recycled PET film were bonded together using a dry lamination method via a first adhesive layer 16 made of adhesive.

A polyethylene film containing linear low-density polyethylene was prepared as the sealant layer 15. The thickness of the polyethylene film can be selected within the range of 10 μm to 150 μm, but in this case it was set to 120 μm.

Next, as in Example 1, the laminate including the high-stiffness PET film and the recycled PET film was bonded to the polyethylene film by dry lamination via the second adhesive layer 17 made of adhesive. In this way, the packaging material 10 was produced.

The layer structure of the packaging material 10 of this embodiment is expressed as follows.
High PET16/Printing/Adhesive/Vapor Deposition/Recycled PET12/Adhesive/PE(1)120
"High PET" means high stiffness PET film.

[Evaluation of puncture resistance]
Next, the puncture strength of the packaging material 10 was measured in accordance with JIS Z1707 7.4. An A&D Tensilon universal testing machine RTC-1310 was used as the measuring instrument. Specifically, as shown in FIG. 14 , a test piece of the fixed packaging material 10 was pierced from the outer surface 10y side with a semicircular needle 90 having a diameter of 1.0 mm and a tip radius of 0.5 mm at a speed of 50 mm/min (50 mm per minute), and the maximum stress until the needle 90 penetrated the packaging material 10 was measured. The maximum stress was measured for five or more test pieces, and the average value was taken as the puncture strength of the packaging material 10. The measurement was performed in an environment of 23°C temperature and 50% relative humidity. The resulting puncture strength was 16.3 N.

[Evaluation of tensile properties]
The tensile properties of the packaging material 10 were also evaluated in the machine direction and perpendicular directions. Specifically, the Young's modulus of the packaging material 10 was measured in the machine direction and perpendicular directions. The tensile properties of the packaging material 10 can be measured in accordance with JIS K7127. As a measuring instrument, a tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used. As a test piece, a rectangular film 15 mm wide and 150 mm long cut from the packaging material can be used. The distance between the pair of chucks holding the test piece at the start of the measurement was 50 mm, and the tensile speed was 300 mm/min. The measurement was performed in an environment with a temperature of 25°C and a relative humidity of 50%. As a result, the Young's modulus in the machine direction was 3736 MPa, and the Young's modulus in the perpendicular direction was 3112 MPa.

10 Packaging material 11 First stretched plastic film 12 Second stretched plastic film 15 Sealant layer 16 First adhesive layer 17 Second adhesive layer 18 First anchor coat layer 19 Second anchor coat layer 21 Printed layer 22 Metal vapor deposition layer 30 Recycled film 31 First layer 32 Second layer 33 Third layer

Claims (3)

A laminate comprising at least a first stretched plastic film, a second stretched plastic film, and a sealant layer in this order,
The laminate further includes a metal vapor-deposited layer provided on the second stretched plastic film,
The first stretched plastic film has a loop stiffness of 0.0017 N or more in at least one direction and contains polyester as a main component,
the second stretched plastic film is a recycled film containing recycled polyethylene terephthalate having ethylene glycol as a diol unit and terephthalic acid and isophthalic acid as dicarboxylic acid units, and the content of the isophthalic acid is 0.5 mol% or more and 5 mol% or less relative to all dicarboxylic acid units constituting the recycled polyethylene terephthalate,
the Young's modulus of the laminate in one direction, measured in accordance with JIS K7127 at a temperature of 25°C and a relative humidity of 50%, is 3200 MPa or more;
The Young's modulus is measured by pulling a rectangular test piece having a width of 15 mm and a length of 150 mm, which is cut out from the laminate, using a pair of chucks at a pulling rate of 300 mm/min.
The laminate, wherein the distance between the pair of chucks is 50 mm at the start of measuring the Young's modulus. The laminate according to claim 1 , wherein the sealant layer has a thickness of 18 μm or more and 120 μm or less. 3. The laminate according to claim 1 , wherein the recycled polyethylene terephthalate has an intrinsic viscosity of 0.58 dl/g or more and 0.80 dl/g or less.