JP2023061529A - Laminate film and packaging container - Google Patents

Abstract

To provide a laminate film with good heat sealability and reduced environmental impact despite its thinness, and a packaging container.SOLUTION: A laminate film 100 according to the present invention having a sealant layer 150 disposed on one side of a base layer is characterized that the sealant layer is formed from thermoplastic polyester-based resin, the thermoplastic polyester-based resin contains a heat-sealable reinforcing component, and the content of the heat-sealable reinforcing component in the thermoplastic polyester-based resin is 21 mass% or more, and its piercing strength is 4 N or more. A packaging container according to the present invention is characterized by using the laminate film.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a laminated film for a packaging bag that is formed into a bag shape by thermally bonding laminated films, a laminated film for a lid material that is thermally bonded to a container body, and a packaging container.

Currently, packaging bags (pouches) and cup containers with lids adhered are used as packaging containers for packaging and containing contents such as liquid and solid foods, beverages, cosmetics, and pharmaceuticals. . For example, a packaging bag is used as a packaging container for containing contents such as shampoo, detergent, and cooked or semi-cooked foods. are superimposed so as to face each other, the outer periphery is heat-bonded to form a bag-like shape, and the content is stored in the inner storage portion (see, for example, Patent Document 1). Further, the cup container to which the lid material is adhered includes those in which the sealant layer of the laminated film is heat-bonded and sealed to the edge flange of the cup-shaped container main body for storing contents such as yogurt, jelly, and pudding. (See Patent Document 2, for example).

On the other hand, with regard to packaging containers, in recent years, from the viewpoint of environmental load such as resource saving and environmental protection, the reduction of the amount of plastic used and the recycling of plastic have been promoted.
In order to reduce the amount of plastic used, it is conceivable to reduce the thickness of the laminated film. Leakage or the like may occur.
Conventionally, olefinic resins such as linear short-chain branched polyethylene (LLDPE), high-pressure low-density polyethylene (LDPE), or unstretched polypropylene (CPP) have been widely used as materials for sealant layers. Depending on the type of material forming the base material layer, there is a possibility that high-quality recycled pellets cannot be obtained from the laminated film, resulting in extremely low recyclability.
Laminated films for forming packaging bags are also required to have puncture resistance. A point of external contact where the packaging bag does not tear when a sharp member with a sharp tip touches the packaging bag, and a packaging bag does not tear when filled with not only liquids but also solids with corners. In terms of internal contact, high puncture resistance is required. In addition to bag breakage, film with low puncture strength is fragile, so it requires a high degree of care during film production and processing. It is not preferable because it can be

JP 2015-150807 A JP 2014-46983 A

The present invention is intended to solve the above-mentioned problems, obtains good heat-sealability even though it is a thin layer, reduces environmental load, and obtains high puncture strength both before and after retort treatment. An object of the present invention is to provide a laminated film and a packaging container.

The laminated film of the present invention is a laminated film in which a sealant layer is provided on one side of a substrate layer,
The sealant layer is formed of a thermoplastic polyester resin,
The thermoplastic polyester resin contains a heat-sealing reinforcing component,
The content of the heat-sealing reinforcing component in the thermoplastic polyester resin is 21% by mass or more,
The above problem is solved by having a puncture strength of 4N or more.
A packaging container of the present invention is characterized by using the laminated film described above.

According to the laminated film of the present invention, since the sealant layer is made of a thermoplastic polyester-based resin, good heat-sealability can be obtained while being a thin layer, and as a result, the environmental load can be reduced. However, it is possible to obtain a packaging container in which leakage of contents is prevented. Furthermore, when the base material layer is formed of a material containing polybutylene terephthalate-based resin as a main component, when this laminated film is used as a material for a packaging bag for retort applications, it can be used before and after retort treatment. High puncture strength is also obtained.
Further, the sealant layer contains a thermoplastic polyester-based resin as a main material, and the base layer other than the sealant layer is formed of a polyester-based resin, so that the entire laminated film is composed of a polyester-based resin as a main material. Therefore, it can be easily recycled into high-quality polyester-based materials and polyester-based products, achieving high recyclability and further reducing the environmental load.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the outline of the laminated|multilayer film which concerns on one Embodiment of this invention.

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

[Main constituent material of sealant layer]
The sealant layer 150 is made of thermoplastic polyester resin.
The thermoplastic polyester resin contains a heat-sealing reinforcing component. Specifically, the thermoplastic polyester resin is a polyester copolymer containing a structural unit derived from a heat-sealing reinforcing component (hereinafter also referred to as a "specific polyester copolymer"), or a heat-sealing A resin obtained by dispersing and mixing a heat-sealing reinforcing component in a polyester polymer that does not contain a structural unit derived from a heat-sealing component (hereinafter also referred to as "other polyester polymer") (hereinafter referred to as "heat-sealing Also referred to as "reinforcement component mixed resin"), and mixtures thereof as main materials. Since the sealant layer 150 is made of a thermoplastic polyester resin containing a heat-sealing reinforcing component, even when the sealant layer 150 has a thin thickness of, for example, 25 μm or less, the heat seal strength of the laminated film 100 can be improved. can be 30 N/15 mm or more.

Specific polyester-based copolymers include other polyester-based polymers described later that contain a structural unit derived from polyoxyalkylene glycol as a heat-sealing reinforcing component. Examples of polyoxyalkylene glycols include polytetramethylene ether glycol (PTMG) and polyethylene glycol (PEG). As the specific polyester-based copolymer, it is preferable to use a polybutylene terephthalate copolymer containing structural units derived from PTMG (PTMG-containing PBT copolymer). These specific polyester-based copolymers can be used singly or in combination of two or more.
Examples of other polyester polymers include polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene naphthalate, polyethylene furanoate, and polyester thermoplastic elastomer (TPC). , mechanical properties, heat resistance, high distribution volume, low cost, and economic rationality, it is more preferable to use polyethylene terephthalate and polybutylene terephthalate. These resins are copolymers containing copolymer components such as dicarboxylic acids such as isophthalic acid, diols such as 1,4-cyclohexanedimethanol and neopentyl glycol, and polyfunctional compounds such as trimellitic acid and pentaerythritol. There may be. These other polyester polymers can be used singly or in combination of two or more.
The heat-sealing reinforcing component mixed resin is mainly composed of the other polyester-based resins described above.
When the thermoplastic polyester-based resin is mainly composed of a specific polyester-based copolymer, it may be further mixed with the above-described other polyester-based polymer that is not mixed with the heat-sealing reinforcing component. 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-based copolymer in the thermoplastic polyester-based resin is too small, the content of the specific polyester-based copolymer is not sufficiently ensured, and the thinned sealant layer 150 Sufficient heat sealability may not be obtained.
In addition, the sealant layer 150 may be formed from a mixed resin of the above thermoplastic polyester resin and a thermoplastic resin other than the polyester resin. However, from the viewpoint of recyclability, it is necessary to limit the amount of the thermoplastic resin other than the polyester to a very small amount, such as that of the additive. Furthermore, the above thermoplastic polyester resin may optionally contain a lubricant (antiblocking agent), a light stabilizer, a compatibilizer, a plasticizer, an antistatic agent, a reaction catalyst, an anti-coloring agent, a radical inhibitor, Various additives such as antistatic agents, terminal blocking agents, antioxidants, heat stabilizers, release agents, flame retardants, antibacterial agents, and antifungal agents may be added.

[Heat-sealing reinforcing component]
The heat-sealing reinforcing component contained in the thermoplastic polyester-based resin is highly dispersed in the thermoplastic polyester-based resin, and is itself made of an aliphatic compound and has a high flexibility and a low melting point. A component of a resin composition comprising a crystallization-inhibiting component that inhibits crystallization of the system resin.
The low-melting-point component preferably has a melting point of 170° C. or lower from the viewpoint of obtaining a high heat-sealing strength in a short-time thermal adhesion. 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, can be used for a short time of 0.1 seconds to several seconds. Exhibits high heat seal strength in thermal adhesion at In addition, the low-melting-point component is required to be highly dispersed in the thermoplastic polyester-based resin in order to exhibit stable physical properties. The high dispersion of the low-melting point component in the thermoplastic polyester resin is achieved by copolymerizing the low-melting point component when polymerizing the thermoplastic polyester resin (specific polyester copolymer), or by using other polyester polymers. It can be realized by a method of melt-kneading the combination and the low-melting-point component, or the like. From the viewpoint of the above melting point and high dispersion, the low melting point component is a polyether polyol that can be copolymerized as a specific polyester copolymer, such as polyacetal, polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, poly Tetramethylene ether glycol, methoxypolyethylene glycol and the like are preferred. Among these, polytetramethylene ether glycol (PTMG) can be used as a raw material from tetrahydrofuran (THF), which is produced as a by-product in the production of polybutylene terephthalate, which is a type of polyester. is excellent in economic rationality and is more preferable.
The crystallization-inhibiting component is a component that is copolymerized when polymerizing a specific polyester copolymer, and includes isophthalic acid, adipic acid, sebacic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid, and maleic acid. , 5-sodium sulfoisophthalate, 5-hydroxyisophthalic acid, succinic acid, azelaic acid, dodecanedioic acid, orthophthalic acid, diphenic acid, itaconic acid, 1,4-cyclohexanedimethanol, neopentyl glycol, isosorbide and the like. . As the crystallization-inhibiting component, it is particularly preferable to use isophthalic acid, which is widely used as a material for resins for PET bottles, is inexpensive, and is economically rational.

The content of the low melting point component in the thermoplastic polyester resin is preferably 5% by mass or more, more preferably 40 to 80% by mass, still more preferably 50 to 80% by mass, and particularly preferably 50 to 60% by mass. be. The content ratio of the low melting point component in the thermoplastic polyester resin is the content ratio of the structural unit derived from the low melting point component in the specific polyester copolymer in the thermoplastic polyester resin, and the heat sealability reinforcing component It means the sum of the content ratio of the low-melting-point component in the mixed resin.
If the content of the low melting point component in the thermoplastic polyester resin is less than 5% by mass, the effect of softening the sealant layer 150 is insufficient, making it difficult to use as a flexible packaging material such as a packaging bag or a lid material. There is a risk.
The crystallization-inhibiting component has the property that, when used together with the low-melting component, high heat-sealing strength can be obtained by thermal bonding in a short time even if the content of the low-melting component is suppressed. The content of the crystallization-inhibiting component in the thermoplastic polyester resin varies depending on the type and the content of the low-melting-point component. Preferably. In addition, when the thermoplastic polyester resin contains a sufficient amount of the low-melting-point component, the crystallization-inhibiting component may not be contained.
The content ratio of the heat-sealing reinforcing component in the thermoplastic polyester resin, that is, the total content ratio of the low melting point component and the crystallization inhibiting component in the thermoplastic polyester resin is preferably 21% by mass or more, more preferably. 30 to 80% by mass, more preferably 40 to 80% by mass, particularly preferably 50 to 60% by mass.
When the content of structural units derived from the heat-sealing reinforcing component in the thermoplastic polyester resin is within the above range, the sealant layer 150 can have sufficient heat-sealing strength. This is due to the fact that the thermoplastic polyester-based resin is easily melted and softened by the presence of a highly dispersed and moderate amount of a low-melting component that itself has a low melting point and a crystallization-inhibiting component that inhibits crystallization. It is assumed that

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 optionally other components to an esterification reaction and/or Alternatively, it is obtained by transesterification followed by polycondensation, and has a structural unit derived from a dicarboxylic acid component and a structural unit derived from a diol component.

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 adjusted from the viewpoint of obtaining appropriate heat resistance and economic rationality. , preferably 70 mol % or more, more preferably 85 mol % or more.
As another dicarboxylic acid component, it is preferable to contain isophthalic acid from the viewpoint of suppressing the heat resistance of the sealant layer 150 at low cost.

Specific examples of dicarboxylic acid components other than terephthalic acid and isophthalic acid include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, and dodecanedicarboxylic acid. and ester-forming derivatives thereof; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid and ester-forming derivatives thereof; phthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenyl dioxydicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenyl Aromatic dicarboxylic acids such as sulfonedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, ester-forming derivatives thereof, 2,5-furandicarboxylic acid and ester-forming derivatives thereof, 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 positively from the viewpoint of environmental consideration.

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

Specific diol components other than 1,4-butanediol and PTMG include 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 and other linear aliphatic diols; 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1- Cycloaliphatic diols such as cyclohexanedimethylol and 1,4-cyclohexanedimethylol; xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl) ) Aromatic diols such as sulfone; diols derived from plant materials such as isosorbide, isomannide, isoidet, erythritan, and the like. 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 are actively used from the viewpoint of environmental consideration. is preferably used for

Other components used as necessary when forming the PTMG-containing PBT copolymer include hydroxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid, and tricarbaryl. tri- or higher polyfunctional carboxylic acids such as acid, trimellitic acid, trimesic acid, pyromellitic acid, and naphthalenetetracarboxylic acid; A functional alcohol etc. are mentioned. These other components are not limited to one type, and two or more types may be mixed and used.

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

[Layer structure of sealant layer]
The sealant layer 150 may be a single layer or may have a multi-layer structure of two or more layers. However, when the sealant layer 150 has a multi-layer structure, at least the outermost layer to be heat-sealed should be mainly made of the thermoplastic polyester resin containing the heat-sealing reinforcing component described in detail above. is required.

[Thickness of 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, particularly preferably 5 to 25 μm. .
If the sealant layer 150 is too thick, the amount of plastic used is large and the effect of reducing the environmental load is not sufficiently obtained. On the other hand, if the sealant layer 150 is too thin, the heat seal strength required for sealing the packaging container may not be ensured.

[Other layers]
The base layer 110, which constitutes the laminate film 100 together with the sealant layer 150, may be configured as a single-layer film, or may be configured with multiple layers. The laminate film 100 in the example of FIG. When the substrate layer 110 is configured as a single-layer film, it may consist of only the surface layer 111 described in detail below, for example.
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, for example, 200° C. or higher so as not to melt when heat-sealed.
Moreover, each layer constituting the base material layer 110 is preferably made of a material containing a polyester-based resin as a main component. Having a polyester resin as a main component means that 80% by mass or more of all materials forming the layer are polyester resins, and all materials (100% by mass) forming the layer are polyester resins. Preferably. Since each layer constituting the base material layer 110 is made of a material containing a polyester resin as a main component, the entire laminated film 100 including the sealant layer 150 is mainly made of a polyester resin. High-quality recycled pellets can be obtained by the generation of compatibilizing components by transesterification during heating and kneading (re-pelletization), and therefore, high recyclability can be obtained and the environmental load can be reduced.

As the surface layer 111, for example, polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate not containing a structural unit derived from PTMG, polyethylene naphthalate, polytrimethylene naphthalate, polybutylene naphthalate, polyethylene furanoate, or the like. In particular, from the viewpoint of improving mechanical strength such as puncture resistance of the laminated film 100, polybutylene terephthalate not containing a structural unit derived from PTMG, particularly homopolymer polybutylene terephthalate It is preferably made of polybutylene terephthalate resin. Since the surface layer 111 (or the base layer 110) is made of a material containing a polybutylene terephthalate resin as a main component, high puncture strength can be obtained both before and after retort treatment. From the viewpoint of mechanical properties and heat resistance, the material forming the surface layer 111 is preferably a homopolymer that has been stretched (uniaxially stretched, biaxially stretched). good too. Moreover, these can also be used individually by 1 type or in combination of 2 or more types. In particular, the surface layer 111 is made of a material containing a polybutylene terephthalate-based resin as a main component, so that the laminate film 100 has a puncture strength of 4N or more before and after retort treatment. can be done.
The thickness of the surface layer 111 can be, for example, approximately 10 to 50 μm, preferably 25 to 50 μm, particularly preferably 40 to 50 μm. By having the surface layer 111 having such a thickness, the laminated film 100 can be reliably imparted with the above puncture strength.

As the intermediate layer 112, for example, a barrier layer imparted with gas barrier properties or moisture barrier properties can be used. As the barrier layer, a deposited film of metal oxide such as alumina or silicon oxide formed on the surface layer 111, or an MXD6 nylon layer having a high barrier property because molding conditions are close to those of polyester can be used. Further, the intermediate layer 112 can be provided at various positions as long as it is in contact with the surface layer 111 . For example, it can be provided on one side or both sides of the surface layer 111 or between a plurality of surface layers 111 .
The thickness of the intermediate layer 112 may be, for example, about 0.05 to 100 μm, depending on the intended use.

In the laminated film 100, an anti-blocking layer (anti-blocking layer) for preventing blocking between films may be further provided on the surface of the sealant layer 150 opposite to the base layer 110 (inner surface side).

The laminated film 100 has a puncture strength of 4N or more, preferably 5N or more, and more preferably 6N or more before retorting.
Further, the puncture strength of the laminated film 100 after retorting is preferably 4N or more, more preferably 5N or more, and still more preferably 6N or more.
Laminated film 100 preferably has a puncture strength of 5 N or more both before and after retort treatment. For example, unstretched polypropylene (CPP) is used as a material for forming a sealant layer that can also be applied to general retort applications, but a laminated film having a sealant layer using CPP has a puncture resistance of 5N or more. However, if strength is to be obtained, the sealant layer alone must have a thickness of, for example, 70 μm or more, or it will not be applicable to a wide range of uses. If the thickness of the sealant layer by CPP is, for example, 50 μm, the laminated film having this can be applied to retort applications, but it is necessary to deal with the amount of contents, the size of the packaging bag, and putting it in a separate box. As a result, its application is limited. As described above, from the viewpoint of applying to a wide range of applications, it is preferable to have a puncture strength equal to or higher than that of a laminated film having a sealant layer made of CPP with a thickness of 70 μm, that is, a puncture strength of 5 N or more before and after retort treatment. It is preferable to have sufficient strength. The laminated film 100 of the present invention can be widely used as a substitute for a sealant layer using CPP. In addition, when the laminated film 100 has a puncture strength of 6 N or more before and after the retort treatment, when this laminated film 100 is used as a substitute for the sealant layer of CPP, the packaging bag having a more excellent puncture strength can be obtained. can be obtained.

Also, the rate of change in puncture strength of this laminated film 100 before and after retort treatment is preferably within ±20%, more preferably within ±17%, and even more preferably within ±11%. Since the rate of change in puncture strength before and after the retort treatment is within the above range, a high puncture strength can be obtained while the substrate layer 110 is thin, and as a result, the environmental load can be reduced. The rate of change in puncture strength becomes a negative value when the puncture strength after retort treatment is lower than the puncture strength before retort treatment.
Retort processing is often performed in the temperature range of 120-135°C. The treatment time is often 20 to 30 minutes at 120°C and 5 to 10 minutes at 135°C. In the present invention, heating at 127° C. for 30 minutes is the condition for retort treatment.
The piercing strength of the laminated film 100 was determined by stretching the film on a ring with a diameter of 40 mm without slack, using a needle with a tip angle of 60 degrees and a tip radius of 0.5 mm, and piercing the center of the circle at a speed of 50 mm / min. It is a value measured as a load (N) when a needle penetrates (in accordance with JIS-Z1707:2019).

[Method for producing laminated film]
The laminated film 100 of the present invention can be produced by adopting a known method such as a dry lamination method, an extrusion lamination method, or a coextrusion method, depending on its layer structure.
For example, when adjacent layers are laminated using a coextrusion method, a coextruded film portion can be obtained by laminating the materials of each layer by coextrusion. When the base layer 110 of the laminated film 100 is configured as a single layer film (surface layer 111), the laminated film 100 in which the coextruded film portion consists of only the sealant layer 150 and the base layer 110 can be obtained in one step. can be done. An appropriate layer may be further laminated on the coextruded film portion obtained by coextrusion using, for example, an adhesive for dry lamination.
Further, for example, when adjacent layers are laminated using a dry lamination method, the adjacent layers can be laminated using a dry lamination adhesive such as a urethane-based adhesive or an epoxy-based adhesive. For example, when the sealant layer 150 is laminated on the intermediate layer 112 formed on the base material layer 110, the sealant layer 150 and the intermediate layer 112 can be bonded using a dry lamination adhesive. In this case, an adhesive layer is interposed between the sealant layer 150 and the intermediate layer 112 . The thickness of the adhesive layer is 100 μm or less.
Further, for example, when adjacent layers are laminated using an extrusion lamination method, the adjacent layers can be laminated via an anchor coat layer as necessary. The thickness of the anchor coat layer is thinner than the adhesive layer and is 10 μm or less. Further, for example, when the sealant layer 150 has a multilayer structure, the sealant layer 150 having a multilayer structure can be formed using a co-extrusion method.
Among the above-mentioned methods, the co-extrusion method, which does not require a solvent or an adhesive and does not require a step of bonding films, is particularly preferable from the viewpoint of low environmental load and high production efficiency. Furthermore, when using a co-extrusion method, if a material containing polybutylene terephthalate-based resin as a main component is used as the material for forming the base material layer, a thermoplastic resin containing a heat-sealing reinforcing component for forming the sealant layer can be used. After coextrusion with the polyester-based resin, the substrate layer is crystallized by cooling and winding as it is, and a film having excellent heat resistance and mechanical strength is obtained, which is more preferable.

The heat seal strength of the laminated film 100 of the present invention varies depending on the material, layer structure, and thickness of the sealant layer 150, the material and thickness of the base layer 110, and the like. is 60 N/15 mm or more. In particular, when the thickness of the sealant layer 150 of the laminate film 100 is 25 μm or less, the heat seal strength of the laminate film 100 is preferably 30 N/15 mm or more.

[Packaging container]
The packaging container of the present invention is a sealed container using the laminated film 100 described above. Specific examples include a packaging bag (pouch), a sealed container using the laminated film 100 as a lid material, and the like.
The packaging bag (pouch) is formed by thermally adhering (heat-sealing) the periphery of the laminated films 100 stacked so that the sealant layers 150 face each other so as to form a bag shape. The packaging bag, for example, has a rectangular outer shape in plan view, is not limited to a flat pouch heat-sealed on all sides, and can be of various types such as a standing pouch, a three-sided seal type, a pillow type, and a gusset type. can be applied. Moreover, the shape of the packaging bag may be any shape other than a rectangular shape in a plan view, such as a trapezoidal shape, a partially irregular shape, or the like.
A sealed container using the laminated film 100 as a lid material is produced by placing the laminated film 100 on the edge flange of the container body containing the contents in such a manner that the sealant layer 150 is in contact with the edge flange and thermally bonding the laminated film 100 to the edge flange. , laminated film 100 is adhered and hermetically sealed. From the viewpoint of recyclability, the container body of such a sealed container is preferably made of, for example, polyethylene terephthalate (PET). Note that the container body of the sealed container may be of any shape such as a cup shape or a tray shape.

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

Specific examples of the present invention will be described below, but the present invention is not limited to these.

[Examples 1 to 5, Comparative Example 1]
PTMG-containing PBT copolymer 1 (or PTMG-containing PBT copolymer 2) and a resin composition obtained by mixing 5% by mass of hydrophilic silica with PBT (indicated as “MB” in the table). %, supplied from the hopper of twin-screw extruder A, and melted at 240-245°C. Furthermore, polybutylene terephthalate (PBT) containing no PTMG-derived structural unit was supplied from the hopper of twin-screw extruder B and melt-kneaded at 260 to 270°C. The resin extruded from these twin-screw extruders A and B is supplied to a multi-manifold T die, extruded into a film and cooled and solidified with a cast roll (50 ° C.) to obtain a laminated film having a thickness shown in Table 2. A to E were produced. Table 1 shows the resin composition of the PTMG-containing PBT copolymer used (indicated simply as "copolymer" in the table). Table 2 shows the thickness of the layer (sealant layer) of the PTMG-containing PBT copolymer and MB and the thickness of the PBT layer (base layer) of the laminated films A to E.
Also, the PTMG-containing PBT copolymer 3 was fed from the hopper of the twin-screw extruder A and melted at 240-245°C. Furthermore, polybutylene terephthalate (PBT) containing no PTMG-derived structural unit was supplied from the hopper of twin-screw extruder B and melt-kneaded at 260 to 270°C. The resin extruded from these twin-screw extruders A and B is supplied to a multi-manifold T die, extruded into a film and cooled and solidified with a cast roll (50 ° C.) to obtain a laminated film having a thickness shown in Table 2. made F. Table 1 shows the resin composition of the PTMG-containing PBT copolymer 3 used. Table 2 shows the thickness of the layer (sealant layer) of the PTMG-containing PBT copolymer and the thickness of the PBT layer (base material layer) of the laminated film F.

The puncture strength of these laminated films A to F was measured as follows. That is, the film is stretched on a ring with a diameter of 40 mm without slack, a needle with a tip angle of 60 degrees and a tip radius of 0.5 mm is used to pierce the center of the circle at a speed of 50 mm / min, and the load when the needle penetrates (N) was defined as puncture strength (according to JIS-Z1707:2019). The puncture strength was measured from the substrate layer side and the sealant layer side. Each type of laminated film was measured 5 times, and the average value of the measured values for 3 times excluding the minimum and maximum values was taken as the puncture strength. The puncture strength was measured for each of the laminated films before and after the retort treatment. Table 2 shows the results.
In addition, in order to evaluate the heat seal strength of the laminated films A to F, the laminated films A' to F' for evaluation were prepared separately, and a heat seal strength test was performed according to the following method using these films. The strength was evaluated. Laminated films A' to F' for evaluation are films in which sealant layers related to laminated films A to F are formed as single layers on a biaxially stretched PET layer (base material layer) having a thickness of 12 μm via an adhesive layer. It is laminated by a conventional dry lamination method. Table 2 shows the results.
In the present invention, a heat seal strength of 30 (N/15 mm) or more was evaluated as practically acceptable.

<Heat seal strength test>
Regarding the above laminated films A' to F', each laminated film is stacked so that the sealant layers face each other, and a heat seal test device (manufactured by Tester Sangyo Co., Ltd.) is used to seal the seal width 10 mm and seal temperature 210 ° C. (single side). , a sealing pressure of 0.3 MPa, and a sealing time of 1.0 second to prepare test pieces A to F each having a length of 80 mm (including a sealing width of 10 mm) and a width of 15 mm. Then, the test pieces A to F were subjected to a tensile test under an environment of 23° C. and 50% RH according to JIS-Z1707 using a Tensilon universal testing machine (manufactured by A&D Co., Ltd.). In the tensile test, the test piece was opened 180° around the heat-sealed portion, both ends of the test piece were attached to a universal testing machine, and the maximum load (N) was determined by pulling at a speed of 300 mm/min. The maximum load against the width of the test piece is measured as the heat seal strength (N/15mm).
One type of laminate film was measured five times, and the average value of the three measurements excluding the minimum and maximum values was taken as the heat seal strength of the laminate film.

From the results in Table 2, in the laminated films A to E according to Examples 1 to 5, high heat seal strength was obtained and high puncture strength was obtained both before and after retort treatment. It was confirmed that the rate of change in puncture strength between the front and back was small. In particular, in Examples 1 to 4 in which the thickness of the substrate layer was 30 μm or more, a puncture strength of 5 N or more was obtained both before and after the retort treatment, and the thickness of the substrate layer was 40 μm. In Examples 1, 3, and 4 described above, it was confirmed that a high puncture strength of 6 N or more was obtained both before and after retort treatment.
On the other hand, in the laminated film F according to Comparative Example 1, although high puncture strength was obtained, it was confirmed that a thin sealant layer could not provide sufficient heat seal strength.

[Reference Examples 1 to 6, Comparative Reference Examples 1 to 3]
Laminated films G to O were prepared by laminating a sealant layer (innermost layer) shown in Table 3 on a 38 μm-thick biaxially stretched PET layer (outermost layer) via an adhesive layer by a conventional dry lamination method. Each laminated film G to O differs in the material forming the sealant layer and its thickness. As shown in Table 3, the sealant layer of each laminate film G to O is formed from a PTMG-containing PBT copolymer. Table 3 shows the resin composition of the PTMG-containing PBT copolymer.
The content ratio of structural units derived from isophthalic acid and PTMG in the sealant layer in each laminated film G to O is calculated by analyzing the resin composition by proton NMR measurement using a nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd.). bottom.
The laminate films G to O were subjected to a heat seal strength test in the same manner as in Example 1 to measure the heat seal strength. Table 3 shows the results.

From the results in Table 3, it can be seen that in the laminated films G to L according to Reference Examples 1 to 6, in which the content ratio of the heat-sealing reinforcing component in the PTMG-containing PBT copolymer constituting the sealant layer is 21% by mass or more, relative It was confirmed that even a thin sealant layer can ensure high heat seal strength.

[Reference Example 7, Comparative Reference Examples 4 to 9]
Base layers having the materials and thicknesses shown in Table 4 were produced as single-layer films, and the puncture strength before and after retort treatment was measured for each in the same manner as described above. The retort processing of the monolayer film is as follows. A piece of monolayer film was fixed on a glass plate, placed in a retort bottle, filled with water and sealed. The retort bottle was heated in an autoclave at 127° C. for 30 minutes. Table 4 shows the results.
In Table 4, "IA-modified PET" is polyethylene terephthalate copolymerized with isophthalic acid, "block PP" is block polypropylene, and "PE composition" is linear short-chain branched polyethylene (methaselon catalyst LLDPE) and high-pressure low-density polyethylene (LDPE), and "MODIC" is a polyester resin: trade name "MODIC QC430" (manufactured by Mitsubishi Chemical Corporation).

As shown in Table 4, when the base material layer was PBT, the puncture strength before and after retort treatment was both high, and it was confirmed that the rate of change in puncture strength before and after retort treatment was small. .

DESCRIPTION OF SYMBOLS 100... Laminated film 110... Base material layer 111... Surface layer 112... Intermediate layer 150... Sealant layer

Claims (10)

A laminated film having a sealant layer on one side of a base layer,
The sealant layer is formed of a thermoplastic polyester resin,
The thermoplastic polyester resin contains a heat-sealing reinforcing component,
The content of the heat-sealing reinforcing component in the thermoplastic polyester resin is 21% by mass or more,
A laminated film having a puncture strength of 4N or more. 2. The laminated film according to claim 1, wherein the laminated film includes a coextruded film portion obtained by laminating the sealant layer on one side of the substrate layer by a coextrusion method. 3. The laminate film according to claim 1, wherein the sealant layer has a thickness of 25 [mu]m or less, and the laminate film has a heat seal strength of 30 N/15 mm or more. 4. The laminated film according to claim 3, wherein a rate of change in puncture strength of said laminated film before and after retort treatment is within ±20%. 5. The laminated film according to any one of claims 1 to 4, wherein the base layer of the laminated film is made of a material containing a polybutylene terephthalate resin as a main component. At least one of the heat-sealing reinforcing components is polyoxyalkylene glycol, and the content of the polyoxyalkylene glycol in the thermoplastic polyester resin is 5% by mass or more. Item 6. The laminated film according to any one of Item 5. 7. The laminated film according to any one of claims 1 to 6, wherein the base layer has a thickness of 10 to 50 µm. 8. The laminated film according to any one of claims 1 to 7, wherein an anti-blocking layer is provided on the surface of the sealant layer opposite to the base layer. A packaging container using the laminated film according to any one of claims 1 to 8. 10. The packaging container according to claim 9, wherein the packaging container is a packaging bag or a sealed container using a lid made of the laminated film.

Images