Laminated film and packaging container

Abstract

To provide a multilayer film that is thin but still has a good heat-sealing property and a reduced environmental impact, and to also provide a packaging container.SOLUTION: There is provided a multilayer film 100 with a sealant layer 150 on one side of a base material layer 110, the film is configured in that: the sealant layer is formed of a thermoplastic polyester-based resin; the thermoplastic polyester-based resin contains a polyester-based copolymer that comprises a structural unit derived from a heat-sealing performance reinforcing component; and a content ratio of the structural unit derived from the heat-sealing performance reinforcing component in the polyester-based copolymer is 21 mass% or more. There is also provided a packaging container that is configured to use the multilayer film 100.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated film that is formed into a bag shape by thermally bonding, which is used for a packaging bag, or a lid material that is thermally bonded to a container body and used, and a packaging container.

Background Art

[0002] Currently, as packaging containers for packaging and storing contents such as liquid or solid foods, beverages, cosmetics, and pharmaceuticals, packaging bags (pouches) and cup containers with a lid material adhered thereto are used. For example, a packaging bag is used as a packaging container for storing contents such as shampoo, detergent, cooked or semi-cooked foods, etc. A laminated film with a sealant layer laminated on a base material layer is overlapped so that the sealant layers face each other, and the outer periphery is thermally bonded to form a bag shape, and the contents are stored in the inner storage part (see, for example, Patent Document 1). Further, as a cup container with a lid material adhered thereto, there is an example in which the sealant layer of a laminated film is thermally bonded and sealed to the edge flange of a cup-shaped container body for storing contents such as yogurt, jelly, and pudding (see, for example, Patent Document 2).

[0003] On the other hand, in packaging containers, in recent years, from the viewpoint of environmental load such as resource saving and environmental protection, reduction of plastic usage and recycling of plastics have been promoted. Regarding the reduction of plastic usage, it is conceivable to make the laminated film thinner. However, for example, if the sealant layer is made thinner, sufficient heat seal strength cannot be obtained, and thus there is a risk that the sealing performance will be low and leakage of the contents will occur. Conventionally, as materials for the sealant layer, olefin resins such as linear low-density polyethylene (LLDPE), high-pressure low-density polyethylene (LDPE), or unoriented polypropylene (CPP) have been widely used. However, depending on the type of material forming the base material layer, it may not be possible to obtain high-quality recycled pellets from the laminated film, and the recyclability may be extremely low.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-150807 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-46983 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] The present invention solves the above problems, and an object thereof is to provide a laminated film and a packaging container that have good heat sealability while being thin and have a reduced environmental load. [Means for Solving the Problems]

[0006] The laminated film of the present invention is a laminated film having a sealant layer provided on one side of a base material layer, The above-mentioned wherein the sealant layer is formed of a thermoplastic polyester resin, said thermoplastic polyester resin is one in which the content ratio of polytetramethylene ether glycol is 41% by mass or more and the content ratio of isophthalic acid is 8% by mass or less solves the above problems. The packaging container of the present invention is characterized by using the above laminated film. [Effects of the Invention]

[0007] According to the laminated film of the present invention, since the sealant layer is formed of a thermoplastic polyester resin, good heat sealability can be obtained while the layer is thin. As a result, a packaging container can be obtained in which the environmental load is reduced and the occurrence of leakage of the contents is prevented. In addition, since the sealant layer contains a thermoplastic polyester resin as the main material and the base material layer other than the sealant layer is formed of a polyester resin, the entire laminated film is composed mainly of a polyester resin. Therefore, it can be easily recycled into high-quality polyester materials and polyester products, resulting in high recyclability and further reducing the environmental load.

Brief Description of the Drawings

[0008]

Figure 1

Mode for Carrying Out the Invention

[0009] 〔Laminated Film〕 As shown in FIG. 1, the laminated film according to an embodiment of the present invention has a sealant layer 150 provided on one side (the upper side in FIG. 1) of a base material layer 110.

[0010] 〔Main Constituent Material of Sealant Layer〕 The sealant layer 150 is formed of a thermoplastic polyester resin. The thermoplastic polyester resin contains a heat-sealability enhancing component. Specifically, the thermoplastic polyester resin is a polyester copolymer containing a structural unit derived from a heat-sealability enhancing component (hereinafter, also referred to as "specific polyester copolymer"), a polyester polymer not containing a structural unit derived from a heat-sealability enhancing component (hereinafter, also referred to as "other polyester polymer"), a resin in which a heat-sealability enhancing component is dispersed and mixed (hereinafter, also referred to as "heat-sealability enhancing component mixed resin"), and mixtures thereof as the main materials.

[0011] Examples of specific polyester copolymers include those containing structural units derived from polyoxyalkylene glycol as heat-sealing property enhancing components among other polyester polymers described below. Examples of polyoxyalkylene glycol include polytetramethylene ether glycol (PTMG) and polyethylene glycol (PEG). As the specific polyester copolymer, it is preferable to use a polybutylene terephthalate copolymer containing structural units derived from PTMG (PTMG-containing PBT copolymer). These specific polyester copolymers can be used alone or in combination of two or more. Examples of other polyester polymers include polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene naphthalate, polyethylene furanoate, polyester thermoplastic elastomer (TPC), etc. In particular, from the viewpoints of mechanical properties, heat resistance, large throughput, low cost, and economic rationality, it is more preferable to use polyethylene terephthalate and polybutylene terephthalate. These resins may be copolymers containing copolymer components such as dicarboxylic acids like isophthalic acid, diols like 1,4-cyclohexanedimethanol and neopentyl glycol, and polyfunctional compounds like trimellitic acid and pentaerythritol. These other polyester polymers can be used alone or in combination of two or more. The heat-sealing property enhancing component mixed resin is based on the above-mentioned other polyester resin as the main material. When the thermoplastic polyester resin is based on a specific polyester copolymer as the main material, the above-mentioned other polyester polymer without the heat-sealing property enhancing component may be further mixed. In this case, the mixing ratio of the specific polyester copolymer in the thermoplastic polyester resin is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 100% by mass. When the mixing ratio of the specific polyester copolymer in the thermoplastic polyester resin is too small, the content of the specific polyester copolymer cannot be ensured sufficiently, and there is a risk that sufficient heat-sealing property cannot be obtained for the thinned sealant layer 150. Note that the sealant layer 150 may be formed of a mixed resin of the above-mentioned thermoplastic polyester resin and a thermoplastic resin other than polyester. However, from the viewpoint of recyclability, the mixing amount of the thermoplastic resin other than polyester needs to be suppressed to a trace amount at the additive level. Further, the above-mentioned thermoplastic polyester resin may be blended with various additives such as a lubricant (antiblocking agent), a light stabilizer, a compatibilizer, a plasticizer, an antistatic agent, a reaction catalyst, an anti-coloring agent, a radical inhibitor, an antistatic agent, a terminal blocking agent, an antioxidant, a heat stabilizer, a mold release agent, a flame retardant, an antibacterial agent, and an antifungal agent as required.

[0012] 〔Heat-sealing property enhancing component〕 The heat-sealing property enhancing component contained in the thermoplastic polyester resin refers to a component of a resin composition composed of a low melting point component that is highly dispersed in the thermoplastic polyester resin, is itself composed of an aliphatic compound, has high flexibility and a low melting point, and a crystallization inhibiting component that inhibits the crystallization of the thermoplastic polyester resin. From the viewpoint of obtaining high heat-sealing strength by short-time thermal adhesion, the low melting point component preferably has a melting point of 170°C or lower by itself. Polyethylene (LDPE: melting point 105 - 115°C, LLDPE: melting point 115 - 125°C) and polypropylene (melting point 160 - 170°C), which are commonly used as materials for the sealant layer, exhibit high heat-sealing strength in short-time thermal adhesion ranging from 0.1 second to several seconds. Further, it is necessary for the stable expression of physical properties that the low melting point component is highly dispersed in the thermoplastic polyester resin. The high dispersion of the low melting point component in the thermoplastic polyester resin can be achieved by a method of copolymerizing the low melting point component when polymerizing the thermoplastic polyester resin (a specific polyester copolymer), or a method of melt-kneading other polyester polymers and the low melting point component. From the above viewpoints of melting point and high dispersion, polyether polyols, polyacetal, polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, methoxy polyethylene glycol, etc., which can also be copolymerized as a specific polyester copolymer, are preferably used as the low melting point component. Among these, polytetramethylene ether glycol (PTMG) is more preferable because it can use tetrahydrofuran (THF), which is a by-product when producing polybutylene terephthalate, a kind of polyester, as a raw material, and thus using PTMG as the low melting point component has excellent economic rationality. The crystallization-inhibiting component is a component copolymerized when polymerizing a specific polyester copolymer, and examples thereof include isophthalic acid, adipic acid, sebacic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid, maleic acid, sodium 5-sulfoisophthalate, 5-hydroxyisophthalic acid, succinic acid, azelaic acid, dodecanedioic acid, phthalic acid, diphenic acid, itaconic acid, 1,4-cyclohexanedimethanol, neopentyl glycol, isosorbide, etc. From the viewpoint of being widely used as a material for PET bottle resins and being inexpensive and having economic rationality, it is particularly preferable to use isophthalic acid as the crystallization-inhibiting component.

[0013] The content ratio of the low melting point component in the thermoplastic polyester resin is preferably 5% by mass or more, more preferably 40 - 80% by mass, still more preferably 50 - 80% by mass, and particularly preferably 50 - 60% by mass. The content ratio of the low melting point component in the thermoplastic polyester resin means the total of the content ratio of the structural units derived from the low melting point component in a specific polyester copolymer in the thermoplastic polyester resin and the content ratio of the low melting point component in the heat sealability enhancing component mixed resin. When the content ratio of the low melting point component in the thermoplastic polyester resin is less than 5% by mass, the effect of softening of the sealant layer 150 becomes insufficient, and it may be difficult to use as a flexible packaging material such as a packaging bag or a lid material. The crystallization inhibitor component has the property that, when used together with the low melting point component, high heat seal strength can be obtained by short-time heat adhesion even if the content ratio of the low melting point component is suppressed. The content ratio of the crystallization inhibitor component in the thermoplastic polyester resin varies depending on its type and the content ratio of the low melting point component, but is generally preferably less than 30% by mass in order not to amorphize the thermoplastic polyester resin. Also, when the thermoplastic polyester resin sufficiently contains the low melting point component, the crystallization inhibitor component may not be contained. The content ratio of the heat sealability enhancing component in the thermoplastic polyester resin, that is, the total content ratio of the low melting point component and the crystallization inhibitor component in the thermoplastic polyester resin is preferably 21% by mass or more, more preferably 30 - 80% by mass, still more preferably 40 - 80% by mass, and particularly preferably 50 - 60% by mass. When the content ratio of the structural units derived from the heat sealability enhancing component in the thermoplastic polyester resin is within the above range, sufficient heat seal strength can be obtained for the sealant layer 150. This is presumably because the low melting point component which is itself of low melting point and the crystallization inhibitor component which inhibits crystallization are highly dispersed and present appropriately, thereby making the thermoplastic polyester resin easily meltable and softenable.

[0014] The PTMG-containing PBT copolymer will be described below. The PTMG-containing PBT copolymer is obtained by subjecting a dicarboxylic acid component mainly composed of terephthalic acid, a diol component containing 1,4-butanediol and PTMG, and other components used as needed to an esterification reaction and / or a transesterification reaction, and then performing a polycondensation reaction, and has structural units derived from the dicarboxylic acid component and structural units derived from the diol component.

[0015] The dicarboxylic acid component for forming the PTMG-containing PBT copolymer contains terephthalic acid as a main component, and the content of terephthalic acid in the total dicarboxylic acid component is preferably 70 mol% or more, more preferably 85 mol% or more, from the viewpoint of obtaining appropriate heat resistance and economic rationality. As other dicarboxylic acid components, it is preferable to contain isophthalic acid from the viewpoint of inexpensively suppressing the heat resistance of the sealant layer 150 to a low level.

[0016] Specific examples of dicarboxylic acid components other than terephthalic acid and isophthalic acid include aliphatic chain dicarboxylic acids such as oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, and their ester-forming derivatives; alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, and their ester-forming derivatives; aromatic dicarboxylic acids such as phthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and their ester-forming derivatives, 2,5-furandicarboxylic acid and its ester-forming derivatives, and the like. These dicarboxylic acid components are not limited to one type, and two or more types may be mixed and used. Among these dicarboxylic acid components, terephthalic acid and 2,5-furandicarboxylic acid can be synthesized from plant raw materials and are preferably used actively from the perspective of environmental consideration.

[0017] The diol components for forming the PTMG-containing PBT copolymer include 1,4-butanediol and PTMG. In the diol components, it is preferable that the structural units derived from 1,4-butanediol and the structural units derived from PTMG constitute the main components as a whole. Specifically, the total content of 1,4-butanediol and PTMG in all the diol components is preferably 70 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more. The molecular weight of PTMG in the diol components is, for example, 500 to 3,000. Usually, the molecular weight of the structural units derived from PTMG in the PTMG-containing PBT copolymer is maintained based on the molecular weight of the PTMG used as a raw material.

[0018] Specific examples of the diol components other than 1,4-butanediol and PTMG include linear aliphatic diols such as ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol; cyclic aliphatic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol; aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone; and diols derived from plant raw materials such as isosorbide, isomannide, isoidide, and erythritol. These diol components are not limited to one type, and two or more types may be mixed and used. Among these diol components, ethylene glycol, 1,3-propanediol, 1,4-butanediol, polyethylene glycol, polypropylene glycol, and PTMG can also be synthesized and polymerized from plant raw materials, and it is preferably used actively from the perspective of environmental consideration.

[0019] Other components that are further used as needed when forming the PTMG-containing PBT copolymer include hydroxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, and p-β-hydroxyethoxybenzoic acid, and trifunctional or higher polyfunctional carboxylic acids such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, and naphthalenetetracarboxylic acid; trifunctional or higher polyfunctional alcohols such as trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, and sugar esters. These other components are not limited to one type, and two or more types may be mixed and used.

[0020] The polyester-based copolymer may be maleic acid-modified. When the polyester-based copolymer is maleic acid-modified, the content ratio of the structural unit derived from maleic acid in the polyester-based copolymer is preferably 3.0% by mass or less.

[0021] 〔Layer structure of the sealant layer〕 The sealant layer 150 may be a single layer or a multilayer structure of two or more layers. However, when the sealant layer 150 has a multilayer structure, it is necessary that at least the outermost layer for heat sealing is made mainly of a thermoplastic polyester-based resin containing the heat-sealing property enhancing component detailed above.

[0022] 〔Thickness of the sealant layer〕 The thickness of the sealant layer 150 (the outermost layer in the case of a multilayer structure) is, for example, 40 μm or less, preferably 5 to 35 μm, more preferably 5 to 30 μm, and particularly preferably 5 to 25 μm. When the sealant layer 150 is excessively thick, a large amount of plastic is used, and the effect of sufficiently reducing the environmental load cannot be obtained. On the other hand, when the sealant layer 150 is excessively thin, there is a risk that the heat seal strength required for sealing the packaging container cannot be ensured.

[0023] 〔Other Layers〕 The base material layer 110 that constitutes the laminated film 100 together with the sealant layer 150 may be configured as a single-layer film or may be configured by a plurality of layers. In the laminated film 100 of the example of FIG. 1, it is composed of a surface layer 111 and an intermediate layer 112 interposed between this surface layer 111 and the sealant layer 150. When the base material layer 110 is configured as a single-layer film, for example, it can be composed of only the surface layer 111 described in detail below. At least the surface layer 111 among the layers constituting the base material layer 110 is preferably made of a material having a melting point of 200 °C or higher so as not to melt when heat-sealed. Also, each layer constituting the base material layer 110 is preferably made of a material mainly composed of a polyester-based resin. To be mainly composed of a polyester-based resin means that 80% by mass or more of all the materials forming the layer is a polyester-based resin, and it is preferable that all the materials (100% by mass) forming the layer are polyester-based resins. Since each layer constituting the base material layer 110 is made of a material mainly composed of a polyester-based resin, the entire laminated film 100 including the sealant layer 150 is configured mainly with a polyester-based resin. Therefore, high-quality recycled pellets can be obtained by the generation of compatibilizing components by transesterification during heating and kneading (re-pelletization) during recycling. Thus, high recyclability can be obtained, and the environmental load can be reduced.

[0024] Examples of the surface layer 111 include those made of polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate that does not contain structural units derived from PTMG, polyethylene naphthalate, polytrimethylene naphthalate, polybutylene naphthalate, polyethylene furanoate, and the like. The material forming the surface layer 111 is preferably a homopolymer that has been subjected to a stretching treatment (uniaxial stretching, biaxial stretching) from the viewpoints of mechanical properties and heat resistance, but may also be an unstretched product or a copolymer. Further, these can be used alone or in combination of two or more. The thickness of the surface layer 111 can be, for example, about 10 to 50 μm.

[0025] Examples of the intermediate layer 112 include a barrier layer provided with gas barrier properties and moisture barrier properties. Examples of the barrier layer include a vapor deposition film made of a metal oxide such as alumina or silicon oxide formed on the surface layer 111, and an MXD6 nylon layer having high barrier properties with similar molding processing conditions to polyester. The thickness of the intermediate layer 112 can be, for example, about 0.05 to 100 μm, depending on the intended use.

[0026] 〔Method for producing the laminated film〕 The laminated film 100 of the present invention can be manufactured by adopting known methods such as the dry lamination method, the extrusion lamination method, and the co-extrusion method according to its layer structure. For example, when laminating adjacent layers using the dry lamination method, adjacent layers can be laminated using an adhesive for dry lamination such as a urethane-based adhesive or an epoxy-based adhesive. For example, when laminating the sealant layer 150 on the intermediate layer 112 formed on the base material layer 110, the sealant layer 150 and the intermediate layer 112 can be adhered using an adhesive for dry lamination. In this case, an adhesive layer will be interposed between the sealant layer 150 and the intermediate layer 112. The thickness of the adhesive layer is 100 μm or less. Also, for example, when laminating adjacent layers using the extrusion lamination method, adjacent layers can be laminated through an anchor coat layer as necessary. The thickness of the anchor coat layer is thinner than that of the adhesive layer and is 10 μm or less. Also, for example, when the sealant layer 150 has a multilayer structure, the multilayer sealant layer 150 can be formed using the co-extrusion method.

[0027] The heat seal strength of the laminated film 100 of the present invention varies depending on the material, layer structure, thickness of the sealant layer 150, the material and thickness of the base material layer 110, etc. However, for example, it is preferably 40 N / 15 mm or more, and more preferably 60 N / 15 mm or more.

[0028] 〔Packaging Container〕 The packaging container of the present invention is a container having a sealing property using the above laminated film 100. Specifically, a packaging bag (pouch), a sealed container using the laminated film 100 as a lid material, etc. can be mentioned. The packaging bag (pouch) is configured such that a laminated film 100, in which sealant layers 150 are stacked so as to face each other, is heat-sealed (heat-sealed) around to form a bag shape. The packaging bag is not limited to, for example, a flat pouch having a rectangular outer shape in plan view and heat-sealed on all four sides, and can be applied to various types of pouches such as standing pouches, three-side seal types, pillow types, gusset types, etc. Further, the shape of the packaging bag may be any shape other than a rectangular shape in plan view, such as a trapezoid or an irregular shape with some unevenness. A sealed container using the laminated film 100 as a lid material is configured such that the laminated film 100 is disposed on the edge flange of a container body that houses the contents and heat-sealed in a state where the sealant layer 150 contacts this edge flange, so that the laminated film 100 is adhered and sealed. From the viewpoint of recyclability, the container body of such a sealed container is preferably made of, for example, polyethylene terephthalate (PET) or the like. Note that the container body of the sealed container may have any shape, such as a cup shape or a tray shape.

[0029] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims.

Example

[0030] Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[0031] 〔Example 1~ 5 , Comparative Examples 1 to 3, Reference Examples 1 to 4 〕 Laminated films A to L were prepared in which a sealant layer (innermost layer) shown in Table 1 was laminated on a biaxially stretched PET layer (outermost layer) with a thickness of 38 μm via an adhesive layer by a conventional dry lamination method. Each of the laminated films A to L has a different material and thickness for forming the sealant layer. As shown in Table 1, the sealant layer of each of the laminated films A to L is formed of a PTMG-containing PBT copolymer, linear low-density polyethylene with short-chain branches (metallocene-catalyzed LLDPE), high-pressure low-density polyethylene (LDPE), or unstretched polypropylene (CPP). The polyethylene and polypropylene used in the reference examples are common commercially available products used for standing pouches and retort pouches. Table 1 shows the resin composition of the PTMG-containing PBT copolymer. For each of the laminated films A to L, the content ratios of the structural units derived from isophthalic acid and PTMG in the sealant layer were calculated by analyzing the resin composition by proton NMR measurement using a nuclear magnetic resonance analyzer (manufactured by JEOL Ltd.). For the laminated films A to L, a heat seal strength test was conducted according to the following method, and the heat seal strength was evaluated. The results are shown in Table 1. In the present invention, a case where the heat seal strength is 40 (N / 15 mm) or more was evaluated as being practical.

[0032] <Heat Seal Strength Test> For the above laminated films A to L, each laminated film was overlapped so that the sealant layers faced each other, and a heat seal test apparatus (manufactured by Tester Sangyo Co., Ltd.) was used to perform heat sealing under the conditions of a seal width of 10 mm, a seal temperature of 210 °C (one side), a seal pressure of 0.3 MPa, and a seal time of 1.0 second to prepare test pieces A to L with a length of 80 mm (including a seal width of 10 mm) and a width of 15 mm. Then, for the test pieces A to L, a tensile test was carried out at 23 °C and 50% RH environment in accordance with JIS-Z1707 using a tensile universal testing machine (manufactured by A&D Company). In the tensile test, the test piece was opened 180° around the heat seal portion, both ends thereof were attached to the universal testing machine, and the maximum load (N) pulled at a speed of 300 mm / min was determined. The maximum load with respect to the width of the test piece was measured as the heat seal strength (N / 15 mm).

[0033]

Table 1

[0034] From the results in Table 1, it was confirmed that in the laminated films A to F according to Examples 1 to 6, high heat seal strength can be ensured even with a relatively thin sealant layer.

Explanation of Reference Numerals

[0035] 100 ··· Laminated film 110 ··· Base material layer 111 ··· Surface layer 112 ··· Intermediate layer 150 ··· Sealant layer

Claims

Claim 1 A laminated film having a sealant layer provided on one side of a base material layer, wherein the sealant layer is formed of a thermoplastic polyester resin, and the thermoplastic polyester resin has a content ratio of polytetramethylene ether glycol of 41% by mass or more and a content ratio of isophthalic acid of 8% by mass or less. The laminated film is characterized by this. Claim 2 The laminated film according to claim 1, characterized in that the heat seal strength of the laminated film is 40 N / 15 mm or more. Claim 3 The laminated film according to claim 1 or claim 2, characterized in that the thickness of the base material layer is 10 to 50 μm. Claim 4 The laminated film according to any one of claims 1 to 3, characterized in that the base material layer is made of a material mainly composed of a polyester resin. Claim 5 The laminated film according to any one of claims 1 to 4, characterized in that the thickness of the sealant layer is 40 μm or less. Claim 6 A packaging container characterized by using the laminated film according to any one of claims 1 to 5. Claim 7 The packaging container according to claim 6, characterized in that the packaging container is a sealed container using a packaging bag or a lid material made of the laminated film.

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