Multilayer film, deep drawing molding, method for manufacturing deep drawing molding and deep drawing package

Abstract

To provide a multilayer film which enables molding of a package having both heat sealability to seal contents, and heat resistance to enable high temperature cooking by an oven or the like.SOLUTION: A multilayer film 10 includes a heat resistant layer (A) 11 and a sealant layer (B) 12, wherein the heat resistant layer (A) 11 contains a first resin having a melting point of 170°C or higher, and the sealant layer (B) 12 contains a second resin which is crosslinked with an electron beam and having a melting point of 140°C or lower. A deep drawing molding is formed by deep drawing molding of the multilayer film 10 at a molding temperature of 95°C or higher and 200°C or lower. A deep drawing package includes a deep drawing molding and a lid material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multilayer film, a deep-drawn molded product, a method for producing a deep-drawn molded product, and a deep-drawn package. [Background technology]

[0002] Deep-draw packaging bodies in which the packaged item is sandwiched between a lid material and a base material having a recess and heat-sealed in a tightly contacted state are widely used. An example of such a packaging body is disclosed in, for example, JP 2016-222259 A (Patent Document 1). This packaging body is less likely to wrinkle and has a good appearance, so it is preferably used to package ham, raw meat, cooked foods, and the like as the packaged item. At this time, the base material and the lid material are tightly sealed to reliably seal the packaged item.

[0003] As such heat-sealed packages, packages that can be cooked in a microwave oven, etc. are known. For example, JP 2021-17262 A (Patent Document 2) discloses a skin pack package that can be heated in a microwave oven as is. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-222259 A [Patent Document 2] Patent Publication No. 2021-17262 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, cooked foods such as gratin and doria that are prepared through a baking process can be thought of as being able to have a texture and flavor similar to that of freshly baked foods if they can be heated in a high-temperature oven when eaten. However, a package made of a heat-sealable multilayer film usually does not have heat resistance sufficient to withstand high-temperature oven heating, and if a cooked food is heated in an oven while contained in the package, thermal shrinkage or the like occurs. Thus, there is a demand for a package that combines heat sealability that allows the contents to be sealed and heat resistance that allows high-temperature heating in an oven or the like, and a multilayer film that can be molded into the package. [Means for solving the problem]

[0006] The present invention has been made in consideration of the above-mentioned problems, and the multilayer film according to the present disclosure is a multilayer film comprising a heat-resistant layer (A) and a sealant layer (B), wherein the heat-resistant layer (A) contains a first resin having a melting point of 170°C or more, and the sealant layer (B) contains an electron beam crosslinked second resin having a melting point of 140°C or less.

[0007] According to this configuration, the multilayer film contains at least the heat-resistant layer (A) containing a first resin having a melting point of 170° C. or more and the sealant layer (B) containing a second resin crosslinked by electron beams having a melting point of 140° C. or less, so that the multilayer film can have both heat sealability and heat resistance. That is, since the heat-resistant layer (A) contains the first resin having a melting point of 170° C. or more, it has high rigidity when heated, and the heat shrinkage during high-temperature heating in an oven or the like is reduced, so that the multilayer film can function as a support for the sealant layer (B). Furthermore, since the sealant layer (B) contains the second resin crosslinked by electron beams having a melting point of 140° C. or less, it has heat resistance while enabling heat sealing. Therefore, the multilayer film of the present invention can be formed into a package that has both heat sealability that allows the contents to be sealed and heat resistance that allows high-temperature cooking in an oven or the like.

[0008] In addition, the deep drawn molded product according to the present disclosure is a multilayer film comprising a heat-resistant layer (A) and a sealant layer (B), the heat-resistant layer (A) containing a first resin having a melting point of 170°C or more, and the sealant layer (B) containing an electron beam crosslinked second resin having a melting point of 140°C or less, the multilayer film being molded using a hot plate at 95°C or more and 200°C or less.

[0009] In addition to the effect of the multilayer film, the deep-drawn molded article of the present configuration is molded using a hot plate at 95° C. or higher and 200° C. or lower, so that heat shrinkage is unlikely to occur during heat sealing.

[0010] In addition, the deep drawn packaging body according to the present disclosure includes the deep drawn body and a lid material.

[0011] In addition, the manufacturing method of the deep drawn molded body according to the present disclosure includes a laminated film preparation step of producing a laminated film by co-extrusion molding a layer of a first resin having a melting point of 170°C or more that forms the heat-resistant layer (A) and a layer of a second resin having a melting point of 140°C or less that forms the sealant layer (B), an electron beam irradiation step of irradiating the laminated film with an electron beam, and a molding step of deep drawing the laminated film after electron beam irradiation at a molding temperature of 95°C or more and 200°C or less.

[0012] According to this configuration, since electron beam irradiation is performed before the molding process involving heating, the heat-resistant layer (A) and the sealant layer (B) have heat resistance during molding, and it is possible to prevent the resin of the multilayer film from adhering to the hot plate during molding, thereby preventing damage to the appearance (hot plate failure, etc.) and molding defects.

[0013] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited to the preferred embodiments described below.

[0014] As one embodiment, it is preferable that in the multilayer film of the present invention, the proportion of the second resin in the total resin components of the sealant layer (B) is 70% by mass or more and 100% by mass or less.

[0015] In one embodiment, the multilayer film of the present invention is preferably such that the second resin is a polyethylene-based resin.

[0016] In one embodiment, the multilayer film of the present invention is preferably such that the first resin is crosslinked by electron beam.

[0017] In one embodiment, the multilayer film of the present invention is preferably such that the first resin is a polyamide-based resin or a polyester-based resin.

[0018] In one embodiment, the multilayer film of the present invention preferably comprises an adhesive layer (C) between the heat-resistant layer (A) and the sealant layer (B) and in contact with the sealant layer (B).

[0019] As one embodiment, it is preferable that in the multilayer film of the present invention, the adhesive layer (C) contains a modified polyolefin resin having an unsaturated carboxylic acid modifying group.

[0020] In one embodiment, the multilayer film of the present invention preferably has an overall thickness of 50 μm or more and 400 μm or less.

[0021] In one embodiment, the multilayer film of the present invention preferably has a storage modulus of 300 MPa or less at a measurement temperature of 95° C. in dynamic viscoelasticity measurement in a tensile mode in the MD direction.

[0022] In one embodiment, the multilayer film of the present invention preferably has a storage modulus of 10 MPa or more at a measurement temperature of 200° C. in dynamic viscoelasticity measurement in a tensile mode in the MD direction.

[0023] In one embodiment, the deep drawn package of the present invention preferably has heat resistance at 200° C. for 20 minutes or more.

[0024] In one embodiment, the deep drawn package of the present invention is preferably a food container.

[0025] As one embodiment, in the method for producing a deep drawn body of the present invention, it is preferable that the absorbed dose of the electron beam in the electron beam irradiation step is 30 kGy or more and 250 kGy or less.

[0026] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments, which are given with reference to the drawings. [Brief description of the drawings]

[0027] [Figure 1] 1 is a schematic cross-sectional view showing a layer structure of a multilayer film according to an embodiment of the present invention; [Diagram 2] Schematic cross-sectional view showing the layer structure of a deep-drawn body according to an embodiment. [Diagram 3] Schematic cross-sectional view showing the layer structure of a deep-drawn package according to an embodiment. [Figure 4] FIG. 3 is a diagram showing a method for manufacturing the deep-drawn body of FIG. 2; [Diagram 5] FIG. 2 is a schematic cross-sectional view showing a layer structure of a multilayer film according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, the multilayer film 10, the deep drawn molded product 30, and the deep drawn package 100 according to the embodiment will be described with reference to the drawings.

[0029] [Multi-layer film composition] The multilayer film 10 includes a heat-resistant layer (A) 11 and a sealant layer (B) 12, and in this embodiment, as shown in Fig. 1, an adhesive layer (C) 13 is provided between the heat-resistant layer (A) 11 and the sealant layer (B) 12. The multilayer film 10 includes the sealant layer (B) 12 as the outermost layer.

[0030] In this embodiment, the heat-resistant layer (A) 11 contains a first resin having a melting point of 170° C. or higher. When the first resin constituting the heat-resistant layer (A) 11 has a melting point of 170° C. or higher, it is possible to impart high heat resistance to the multilayer film 10, and shrinkage during heating can be suppressed. The heat-resistant layer (A) 11 not only imparts high heat resistance but also functions as a support for the sealant layer (B) 12, and the presence of both the heat-resistant layer (A) 11 and the sealant layer (B) 12 allows the multilayer film 10 to have both heat resistance and heat sealability.

[0031] In this embodiment, the first resin is crosslinked by electron beam. Since the first resin, which has a melting point of 170°C or more, is further crosslinked by electron beam, it is possible to impart high heat resistance to the multilayer film 10, and shrinkage during heating can be further suppressed. Since electron beam crosslinking does not require heating, the crystallinity and crystallinity of the polymer crystals do not change significantly before and after crosslinking, and the glass transition temperature and melting temperature of the first resin are hardly changed before and after crosslinking. It is believed that the non-crystalline region of the polymer chain of the first resin is crosslinked by the electron beam, suppressing the flow of the polymer chain, thereby improving the heat resistance in practical use.

[0032] The ratio of the first resin to the total resin components of the heat-resistant layer (A) 11 is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 100% by mass. The ratio of the first resin to the total resin components of the heat-resistant layer (A) 11 is a value calculated by dividing the mass of the first resin of the heat-resistant layer (A) by the total mass of the resin components (polymeric materials) of the heat-resistant layer (A) 11. Here, the resin components do not include additives such as plasticizers and lubricants. It is not prohibited for the heat-resistant layer (A) 11 to contain a resin other than the first resin, as long as the purpose and function of the heat-resistant layer (A) 11 are not impaired. In addition, it is also a preferred embodiment that the heat-resistant layer (A) contains a lubricant as an additive other than the resin components.

[0033] In this embodiment, the first resin is a polyamide-based resin or a polyester-based resin. Polyamide-based resins and polyester-based resins can be used as resins constituting the heat-resistant layer (A) 11 in a high-temperature environment (for example, 170 to 200°C) such as an oven in combination with a sealant layer (B) 12 described later. The first resin is preferably a polyamide-based resin in that it is easily crosslinked by electron beams and is not easily thermally shrunk. The first resin is not limited to a polyamide-based resin or a polyester-based resin. Any resin that is electron beam crosslinked and has a melting point of 170°C or higher can be used in the same manner.

[0034] Here, the "polyamide resin" refers to a polymer in which the repeating unit of an amide bond constitutes the main chain. Examples of the polyamide resin include at least one selected from the group consisting of nylon 4, nylon 6, nylon 6T, nylon 9T, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610, nylon 6 / 66 copolymer, nylon 6 / 12 copolymer, nylon 6 / 66 / 12 copolymer, and nylon MXD6 (a polycondensate of metaxylylenediamine and adipic acid). Among the polyamide resins, at least one selected from the group consisting of nylon 6, nylon 66, and nylon 11 is preferable from the viewpoints of heat resistance and moldability.

[0035] Moreover, the term "polyester resin" refers to a polymeric compound obtained by condensation polymerization of a polyvalent carboxylic acid and a polyhydric alcohol. Examples of polyester resins include at least one selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate, polybutylene naphthalate, and glycol-modified polyethylene terephthalate (PETG). The polyester resin preferably contains at least one of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and glycol-modified polyethylene terephthalate (PETG), and preferably contains polyethylene terephthalate (PET) because of its high heat resistance (melting point).

[0036] The sealant layer (B) 12 is a layer that melts in a relatively low temperature range of, for example, 100°C to 150°C, and is integrated with the sealant layer of another film and heat-sealed. In this embodiment, the sealant layer (B) 12 contains a second resin that has a melting point of 140°C or less and is crosslinked by electron beam. The second resin constituting the sealant layer (B) 12 has a melting point of 140°C or less and is crosslinked by electron beam, so that the heat-sealing property of the sealant layer (B) 12 is maintained while improving the heat resistance. Since the electron beam crosslinking does not require heating, the crystallinity and crystallinity of the polymer crystals do not change significantly before and after crosslinking, and the glass transition temperature and melting temperature of the second resin do not change much before and after crosslinking. It is considered that the non-crystalline region of the polymer chain of the second resin is crosslinked by the electron beam, and the flow of the polymer chain is suppressed, thereby improving the heat resistance in practical use. Since the thermal behavior of the crystalline region of the second resin does not change before and after crosslinking, the heat-sealing property is maintained. If heat molding is performed using a hot plate at a high temperature (e.g., 150°C or higher) without electron beam crosslinking, the resin of the sealant layer (B) 12 in particular may adhere to the hot plate, which may result in peeling of the sealant layer (B) 12 from the multilayer film 10 or poor appearance.

[0037] In this embodiment, the ratio of the second resin to the total resin components of the sealant layer (B) 12 is 70 mass% or more and 100 mass% or less. The ratio of the second resin is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass%. The ratio of the second resin to the total resin components of the sealant layer (B) 12 is a value calculated by dividing the mass of the second resin of the sealant layer (B) 12 by the total mass of the resin components (polymer materials) contained in the sealant layer (B) 12.

[0038] In this embodiment, the second resin is a polyethylene-based resin. A "polyethylene-based resin" is a polymer consisting of a homopolymer and copolymer of ethylene. An ethylene homopolymer resin is a polyethylene consisting essentially of ethylene monomers. From the viewpoint of transparency, the density of an ethylene homopolymer resin is 910 kg / m 3 More than 930kg / m 3It is preferable that the branched polyethylene is less than 100%. A preferable example of such a branched polyethylene is low-density polyethylene (LDPE). The ethylene copolymer resin is a resin composed of an ethylene monomer and other comonomers. It is preferable that the ethylene copolymer resin is a linear ethylene copolymer resin having a linear polyethylene main chain and a side chain derived from a comonomer. The ethylene copolymer resin may be used in a mixed form of a plurality of types. The first resin is not limited to a polyethylene resin. The first resin is an electron beam crosslinked resin having a melting point of 140°C or less, and any resin having heat sealability can be used in the same manner.

[0039] Examples of polyethylene resins (PE) include those mentioned above, high density polyethylene resins (HDPE), medium density polyethylene resins (MDPE), low density polyethylene resins (LDPE), linear low density polyethylene resins (LLDPE), etc.

[0040] The sealant layer (B) 12 may contain a polypropylene-based resin as a resin other than the second resin. When the polypropylene-based resin is contained, the ratio of the polypropylene-based resin to the total resin components of the sealant layer (B) 12 is 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less. There is no lower limit, but when contained, it is usually 1% by mass or more. Some polypropylene-based resins have a structure that disintegrates when irradiated with an electron beam, but as long as it is 30% by mass or less, the effect of the second resin is not hindered.

[0041] In addition, the presence or absence of crosslinking of the first resin in the heat-resistant layer (A) 11 and the second resin in the sealant layer (B) 12 can be confirmed by, for example, performing the following measurement after separating each layer. (1) Dynamic shear viscoelasticity measurement: Measures temperature dependence in viscoelasticity measurement using a rotational rheometer. The viscosity of uncrosslinked resin decreases when it exceeds the melting point, but crosslinked resin maintains a constant viscosity even when it exceeds the melting point. This method is applicable to all resins. (2) Measurement of gel fraction (degree of cross-linking) according to JIS K 6796: If the second resin, a polyethylene resin, is cross-linked, a gel fraction that is insoluble in xylene solvent remains, and the resin has a certain gel fraction. (3) Heat resistance test: When the sealant layer (B) 12 is placed against a high-temperature hot plate, it is visually determined whether the surface of the sealant layer (B) 12 flows. If the surface does not flow, it is crosslinked.

[0042] In this embodiment, the adhesive layer (C) 13 is configured to be in contact with the sealant layer (B) 12. This configuration allows the heat-resistant layer (A) 11 and other layers that are not directly bonded to the sealant layer (B) 12 to be bonded.

[0043] In this embodiment, the adhesive layer (C) contains a modified polyolefin resin having an unsaturated carboxylic acid modified group. The modified polyolefin resin having an unsaturated carboxylic acid modified group is provided with adhesiveness by introducing the unsaturated carboxylic acid modified group into the polyolefin resin. Examples of the polyolefin resin forming the modified polyolefin resin include polyethylene resins and polypropylene resins. Examples of the unsaturated carboxylic acid that becomes the unsaturated carboxylic acid modified group include maleic acid, fumaric acid, and its acid anhydride. Among them, the unsaturated carboxylic acid modified group is preferably a maleic acid modified group or a maleic anhydride modified group.

[0044] Examples of modified polyethylene resins having unsaturated carboxylic acid modifying groups include ethylene-unsaturated carboxylic acid copolymers and ethylene-vinyl acetate-unsaturated carboxylic acids, specifically maleic anhydride modified polyethylene.Specific examples of modified polypropylene resins having unsaturated carboxylic acid modifying groups include modified polymers obtained by graft copolymerizing unsaturated carboxylic acids or their acid anhydrides, such as maleic acid and fumaric acid, with polypropylene resins such as polypropylene, propylene-α-olefin copolymers, and ternary copolymers of propylene, ethylene, and α-olefin.

[0045] The adhesive layer (C) may be composed of, in addition to a modified polyolefin resin having an unsaturated carboxylic acid modifying group, an ethylene-vinyl acetate resin (EVA) (e.g., ethylene-vinyl acetate copolymer, etc.), an ethylene-vinyl alcohol resin (EVOH) (e.g., ethylene-vinyl alcohol copolymer, etc.), an ethylene-methyl acrylate resin (e.g., ethylene-methyl acrylate copolymer (EMA), etc.), an ethylene-methacrylic acid resin (e.g., ethylene-methacrylic acid copolymer (EMAA)), an ethylene-aliphatic unsaturated carboxylic acid resin, an ethylene-aliphatic unsaturated carboxylic acid ester resin, an ionomer resin, etc.

[0046] In addition to the above, known additives may be added to the resin components (polymeric materials) used in each layer constituting the multilayer film 10 in this embodiment. Examples of additives include plasticizers, antioxidants, flame retardants, stabilizers, UV absorbers, antistatic agents, lubricants, water repellents, and oil repellents.

[0047] In this embodiment, the thickness of the entire multilayer film 10 is 50 μm or more and 400 μm or less. If the thickness is in this range, the formability during deep drawing is excellent. The thickness of the entire multilayer film 10 is preferably 55 μm or more, more preferably 60 μm or more. If the thickness of the multilayer film 10 is less than 50 μm, the thickness of the deep-drawn molded body 30 may be too thin. The thickness of the entire multilayer film 10 is preferably 350 μm or less, more preferably 300 μm or less. There is no problem in terms of performance even if the thickness of the multilayer film 10 exceeds 400 μm, but from the viewpoint of not increasing the amount of plastic used and the amount of waste, 400 μm or less is preferable.

[0048] In this embodiment, the multilayer film 10 has a storage modulus of 300 MPa or less at a measurement temperature of 95°C in dynamic viscoelasticity measurement in a tensile mode in the MD (machine direction). The storage modulus is preferably 250 MPa or less, and more preferably 200 MPa or less. In this way, the multilayer film 10 can be provided with thermoformability (following ability) required for deep drawing. There is no lower limit to the storage modulus at a measurement temperature of 95°C, but it is preferably 15 MPa or more, and more preferably 20 MPa or more.

[0049] In this embodiment, the multilayer film 10 has a storage modulus of 10 MPa or more at a measurement temperature of 200°C in dynamic viscoelasticity measurement in a tensile mode in the MD direction. The storage modulus is preferably 15 MPa or more, and more preferably 20 MPa or more. There is no upper limit to the storage modulus at a measurement temperature of 200°C, but it is preferably 250 MPa or less, and more preferably 200 MPa or less. In this way, appearance defects such as wrinkles are less likely to occur when the multilayer film 10 is deep-draw molded.

[0050] The storage modulus at the measurement temperatures of 95° C. and 200° C. can be measured by dynamic mechanical analysis (DMA) as described in the Examples below.

[0051] [Method of manufacturing multilayer film 10] Next, a description will be given of a method for producing the multilayer film 10. As shown in Fig. 4, the multilayer film 10 is produced by a laminate film production step (S11) in which a first resin having a melting point of 170°C or higher forming the heat-resistant layer (A) 11 and a second resin having a melting point of 140°C or lower forming the sealant layer (B) 12 are co-extruded to produce a laminate film, and an electron beam irradiation step (S12) in which the obtained laminate film is irradiated with an electron beam.

[0052] An example of the co-extrusion method is a method in which the heat-resistant layer (A) 11, the adhesive layer (C) 13, and the sealant layer (B) 12 are extruded from a mold such as a T-die at an extrusion temperature (e.g., 240 to 260°C) so that the thicknesses of the layers are in a predetermined ratio, and then cooled with a cooling roll or the like and wound up on a roll. The electron beam irradiation step (S12) may be performed before winding up on a roll in the series of steps from the co-extrusion method, or may be performed as a separate step after winding up on a roll.

[0053] In this embodiment, the absorbed dose of the electron beam in the electron beam irradiation step is 30 kGy or more and 250 kGy or less. The absorbed dose of the electron beam is preferably 60 kGy or more, more preferably 90 kGy or more. The absorbed dose of the electron beam is preferably 220 kGy or less, more preferably 190 kGy or less. In the present invention, the absorbed dose of the electron beam in the electron beam irradiation step is not limited, and it is sufficient that at least the second resin of the sealant layer (B) 12 is electron beam crosslinked, and the first resin of the heat-resistant layer (A) 11 and other resins are not necessarily electron beam crosslinked. When the absorbed dose of the electron beam irradiation is within this range, not only the second resin of the sealant layer (B) 12 of the multilayer film 10 but also the first resin of the heat-resistant layer (A) 11 is easily electron beam crosslinked, and shrinkage during heating can be suppressed.

[0054] The reason why the resin of the multilayer film 10 is crosslinked by electron beam irradiation is not clear, but taking the second resin of the sealant layer (B) as an example, it is considered as follows. That is, when the multilayer film 10 is irradiated with an electron beam, the carbon-hydrogen bonds of the polymer chains in the non-crystalline region of the polyethylene resin contained in the sealant layer (B) 12 are broken, and radicals are generated at the ends of the broken bonds. It is considered that the generated radicals come into contact with other polyethylene molecular chains due to the molecular motion of the molecular chains, extract hydrogen atoms, and bond with carbon atoms in the polyethylene molecular chains, resulting in the formation of a crosslinked structure. It is presumed that the same phenomenon occurs in the heat-resistant layer (A) 11, and the same is true for the adhesive layer (C) 13 and other layers. However, the above-mentioned mechanism is merely presumed, and the scope of the present invention is not affected by its truth or falsity.

[0055] In this embodiment, electron beam irradiation is performed from the sealant layer (B) 12 side of the laminated film. In this way, it is possible to effectively improve the heat resistance of the sealant layer (B) 12 side, which is the side that comes into contact with the contents such as food. As long as the second resin of the sealant layer (B) 12 is electron beam crosslinked, the irradiation surface of the electron beam is not limited, and it may be performed from either side.

[0056] Through the above steps, a multilayer film 10 can be obtained. The multilayer film 10 is used as a deep-drawn molded body 30 for use as a base material for a deep-drawn packaging body 100 described below, but may also be used to form a lid material 40. When used as a lid material 40, the thickness of each layer and the overall thickness of the multilayer film 10 may be about 40 to 60% of that when used as a deep-drawn molded body 30.

[0057] [Structure of deep-drawn molded body] The deep-drawn body 30 is obtained by deep-drawing the multilayer film 10 with a hot plate of 95° C. or more and 200° C. or less. That is, the deep-drawn body 30 is obtained by forming the multilayer film 10, which includes a heat-resistant layer (A) 11 and a sealant layer (B) 12, the heat-resistant layer (A) 11 containing a first resin cross-linked by electron beam and having a melting point of 170° C. or more and the sealant layer (B) 12 containing a second resin cross-linked by electron beam and having a melting point of 140° C. or less, with a hot plate of 95° C. or more and 200° C. or less.

[0058] As described above, the deep drawn body 30 of this embodiment forms a base material having a recess in the deep drawn package 100 as a sealed container. In this embodiment, a sheet-like film is deep drawn into a base material having a recess capable of accommodating the contents, using a mold having a specific shape according to the contents. The shape of the recess in the deep drawn body 30, the seal width between the lid material 40 and the base material described later, and the like can be appropriately selected depending on the shape and form of the contents to be packaged.

[0059] [Method of manufacturing deep drawn body 30] Next, a method for producing the deep-drawn molded body 30 will be described as a series of steps from the multilayer film 10. As shown in FIG. 4, the method for producing the deep-drawn molded body 30 in this embodiment includes a laminated film production step (S11) in which a layer of a first resin having a melting point of 170° C. or more that forms the heat-resistant layer (A) 11 and a layer of a second resin having a melting point of 140° C. or less that forms the sealant layer (B) 12 are co-extruded to produce a laminated film, an electron beam irradiation step (S12) in which the laminated film is irradiated with an electron beam, and a molding step (S13) in which the laminated film after electron beam irradiation is deep-draw molded at a molding temperature of 95° C. or more and 200° C. or less. The laminated film production step (S11) and the electron beam irradiation step (S12) are the same as the above-mentioned steps.

[0060] In this embodiment, the molding temperature in the molding step (S13) is 95°C or higher and 200°C or lower. The molding temperature is preferably 105°C or higher, and more preferably 115°C or higher. The molding temperature is preferably 195°C or lower, and more preferably 185°C or lower. By setting the molding temperature within the above range, it is possible to suppress appearance defects such as wrinkles and patterns on the deep-drawn molded body 30, and also to reduce thermal shrinkage. In this manner, the deep-drawn molded body 30 is obtained.

[0061] [Configuration of deep drawn packaging body 100] In this embodiment, the above-mentioned deep-drawn molded body 30 is used as a base material, and a lid material 40 is heat-sealed to this to form a deep-drawn package 100.

[0062] [Method of manufacturing deep drawn package 100] In this embodiment, a multilayer film for a base material and a multilayer film for a lid material are supplied to a deep draw packaging machine, and the deep draw forming step (S13) of the multilayer film for the base material and the heat sealing step of the deep draw formed body 30 and the lid material 40 are carried out continuously, to obtain a deep draw packaged body 100 as shown in Fig. 3. The deep draw formed body 30 is the product after the deep draw forming step (S13) and before heat sealing.

[0063] The method for heat-sealing the deep-drawn body 30 and the lid material 40 is not particularly limited, and any known method can be selected as appropriate, and examples thereof include a method in which the deep-drawn body 30 is filled with a content in a recess, and then the lid material 40 is placed over the deep-drawn body 30, and the internal space is evacuated to a vacuum or replaced with an inert gas or the like, and the contact portion between the deep-drawn body 30 and the lid material 40 is heat-sealed. The conditions for the heat-sealing step are not particularly limited, and examples thereof include a heating temperature of 100° C. to 150° C. and a heating time of 0.5 seconds to 5.0 seconds.

[0064] The deep drawn molded body 30 and the deep drawn packaged body 100 of the present embodiment described above have heat resistance for 20 minutes or more at 200° C. The heat resistance is evaluated by the method of the examples described later.

[0065] The deep-drawn molded body 30 thus obtained and the deep-drawn packaged body 100 including the deep-drawn molded body 30 and the lid material 40 are used as food containers. Examples of the contents of the food containers include foods produced through a baking process, such as gratin and doria. The deep-drawn molded body 30 has heat resistance and oil resistance because the sealant layer (B) 12 is a polyethylene-based resin blend layer crosslinked by electron beams, and is therefore less likely to deform. In addition, the heat-resistant layer (A) 11, which has high heat resistance, serves as a support material for the sealant layer (B) 12, and therefore suppresses the thermal shrinkage of the entire multilayer film 10 when the multilayer film 10 is heated. Therefore, before eating the food, which is the content, the food can be heated in a high-temperature oven, such as 170°C to 200°C, in a state packaged in the deep-drawn packaged body 100 (or in a state where the lid material 40 is peeled off after packaging).

[0066] Next, a multilayer film 50 according to another embodiment will be described. 5, the multilayer film 50 of the other embodiment differs from the previous embodiment in that the heat-resistant layer (A) is composed of two layers, a first heat-resistant layer 11A and a second heat-resistant layer 11B, and further layers, an intermediate layer 14 and a second adhesive layer 15, are provided between the first heat-resistant layer 11A and the second heat-resistant layer 11B. In detail, four layers, the first heat-resistant layer 11A, the intermediate layer 14, the second adhesive layer 15, and the second heat-resistant layer 11B, are laminated in this order on the surface of the adhesive layer (hereinafter referred to as the first adhesive layer) 13 opposite to the sealant layer (B) 12.

[0067] In another embodiment of the multi-layer film 50, the first heat-resistant layer 11A contains a polyamide-based resin as the first resin, and the second heat-resistant layer 11B contains a polyester-based resin as the first resin. In this way, the heat-resistant layer (A) may contain both a polyamide-based resin layer and a polyester-based resin layer. In this case, as in the multi-layer film 50, if the outermost layer is a layer of a polyester-based resin such as polyethylene terephthalate (PET) and the inner layer is a layer of a polyamide-based resin (for example, nylon 6), the polyamide-based resin having excellent heat resistance as the heat-resistant layer (A) can be disposed in the vicinity of the sealant layer (B) 12, and the heat resistance can be improved. The intermediate layer 14 is made of an ethylene-vinyl alcohol-based resin (EVOH), and the second adhesive layer 15 that bonds the intermediate layer 14 and the second heat-resistant layer 11B is made of an unsaturated carboxylic acid-modified polyolefin resin. In this way, other layers (adhesive layers and intermediate layers) may be provided between the polyamide-based resin and the polyester-based resin.

[0068] The multilayer film 50 is produced by irradiating the entire film with an electron beam, as in the previous embodiment, and the first resin contained in the heat-resistant layer (A) (first heat-resistant layer 11A, second heat-resistant layer 11B) and the second resin contained in the sealant layer (B) 12 are both crosslinked by electron beams. The adhesive layer (C) and other layers may also be crosslinked by electron beams.

[0069] As in this configuration, the heat resistance can be further improved by providing a plurality of electron beam crosslinked heat-resistant layers (A). The function of the intermediate layer 14 is not particularly limited, but preferably imparts gas barrier properties to the multilayer film 50. "Gas barrier properties" refers to the resistance to gas permeation. The intermediate layer 14 imparts gas barrier properties against, for example, carbon dioxide gas (CO2), nitrogen gas (N2), and oxygen gas (O2) to the multilayer film 50. In this embodiment, the intermediate layer 14 is an ethylene-vinyl alcohol copolymer blended layer. Here, the ethylene-vinyl alcohol copolymer blended layer is a layer in which an ethylene-vinyl alcohol copolymer (EVOH) is blended. The ethylene-vinyl alcohol copolymer blended layer in the intermediate layer 14 is an oxygen barrier layer in which an ethylene-vinyl alcohol copolymer is blended at a concentration of preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0070] [Other embodiments] In the above embodiment, the multilayer film 10 is described as having an adhesive layer (C) 13. However, the present invention is not limited to such an example, and the multilayer film 10 may not have the adhesive layer (C) 13. In addition to the heat-resistant layer (A) and the sealant layer (B) 12, other layers may be provided, such as the other embodiments described above. For example, a moldable layer may be provided on the inner layer side (heat-resistant layer (A) side) of the sealant layer (B) 12. In that case, various resins can be blended in the other layers as long as there is no contradiction with the present invention. It is not desirable to blend resins that cause molding defects or resins that are unstable against electron beam irradiation. The moldable layer is composed of, for example, ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylic acid copolymer (EMAA), ionomer (ION), ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), and other polymeric materials having moldability.

[0071] The heat-resistant layer (A) may be a single layer (single layer) like the multilayer film 10, or may have two or more layers like the multilayer film 50. When the heat-resistant layer (A) has multiple layers, it is not limited to the example of the multilayer film 50, and the multiple layers may be the same or different from each other, and may not be adjacent to each other. The combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention. The heat-resistant layer (A) may be located in the outermost layer as in the above embodiment, but it does not necessarily have to be located in the outermost layer.

[0072] The sealant layer (B) 12 may be composed of one layer (single layer) located at the outermost layer, as in the multilayer films 10 and 50, or may be composed of multiple layers. When the sealant layer (B) 12 is composed of multiple layers, these multiple layers are provided adjacent to each other. As long as it functions as the sealant layer (B) 12, the components may be the same or different, but it is preferable that they contain the same second resin. For example, the sealant layer (B) 12 may be composed so that only the outermost layer contains a lubricant, and the inner layers are composed of the same resin but do not contain a lubricant.

[0073] The manufacturing method of the multilayer films 10, 50 is not particularly limited, and in addition to the coextrusion method described above, the multilayer films 10, 50 may be manufactured by laminating the films using an adhesive using any of a dry lamination method, a hot melt lamination method, and a wet lamination method.

[0074] In the above embodiment, the method for producing the deep drawn molded body 30 including the laminated film molding step S11, the electron beam irradiation step S12, and the molding step S13 has been described as an example. However, the present invention is not limited to such an example, and other steps may be included. For example, a lid material molding step, a gravure printing step, etc. may be further provided.

[0075] The method for producing the deep-drawn body 30 is not limited to the above-mentioned deep-draw forming method, and is not particularly limited, and any known method can be appropriately selected depending on the purpose.

[0076] In addition, the configurations disclosed in the above-mentioned embodiments can be applied in combination with configurations disclosed in other embodiments as long as no contradiction occurs. Regarding other configurations, the embodiments disclosed in this specification are merely examples in all respects. Therefore, various modifications can be made as appropriate within the scope of the present disclosure. EXAMPLES

[0077] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples.

[0078] Multilayer films 10 (or films) for base materials were produced in the following Examples 1 to 4 and Comparative Examples 1 to 3. The same multilayer film for cover materials as in Example 1 was used in all Examples and Comparative Examples.

[0079] Example 1 [Preparation of laminated film for base material] The following resins were used for each layer. First resin of heat-resistant layer (A): Nylon 6 (UBE Nylon (registered trademark) 1030B2 manufactured by UBE Corporation) (melting point 220°C) Adhesive layer (C): Maleic anhydride modified polyethylene resin ("Admer (registered trademark) NF536" manufactured by Mitsui Chemicals, Inc.) Second resin of sealant layer (B): Linear low-density polyethylene (LLDPE) ("Yumerit (registered trademark) 1520F" manufactured by Ube Maruzen Polyethylene Co., Ltd.)

[0080] The laminated film for the base material was produced by co-extrusion molding at an extrusion temperature of 260°C for the heat-resistant layer (A), 240°C for the sealant layer (B) and 240°C for the sealant layer (B), taking into consideration the thickness ratio of each layer so that the total thickness of the laminated film was 200 μm, with the heat-resistant layer (A) being 60 μm thick, the adhesive layer (C) being 40 μm thick, and the sealant layer (B) being 100 μm thick.

[0081] [Preparation of laminated film for covering] The laminated film was produced using the same materials and methods as the multi-layer film for the base material, taking into consideration the thickness ratio of each layer so that the heat-resistant layer (A) was 30 μm thick, the adhesive layer (C) was 20 μm thick, and the sealant layer (B) was 50 μm thick, for a total thickness of 100 μm.

[0082] [Electron beam irradiation process] The resulting laminated film for base material and laminated film for cover material were each irradiated with electron beams from the sealant layer side at an absorbed dose of 150 kGy to prepare a multilayer film for base material and a multilayer film for cover material.

[0083] Example 2 A multilayer film 10 was produced using the same materials and methods as in Example 1, except that low-density polyethylene (LDPE) (UBE Polyethylene (registered trademark) F222NH manufactured by Ube Maruzen Polyethylene Co., Ltd.) (melting point 110°C) and polypropylene resin (homopolymer) (Sumitomo Noblen (registered trademark) FS2011DG2 manufactured by Sumitomo Chemical Co., Ltd.) were used as the resins forming the sealant layer (B), the ratio of polyethylene resin:polypropylene resin was 75:25 by mass, and the thickness of the sealant layer (B) was 100 μm.

[0084] Example 3 The multilayer film 50 was configured as shown in Fig. 5. The specific components of each layer were as follows. First resin of the first heat-resistant layer 11A: Nylon 6 (UBE Nylon (registered trademark) 1030B2 manufactured by UBE Corporation) (melting point 220°C) First resin of second heat-resistant layer 11B: polyethylene terephthalate (PET) (SK Chemicals' "SKYPET (registered trademark) BR8040") (melting point 236°C) Adhesive layer (C) 13: Maleic anhydride modified polyethylene resin ("Admer (registered trademark) NF536" manufactured by Mitsui Chemicals, Inc.) Second resin of sealant layer (B): Linear low-density polyethylene (LLDPE) ("Yumerit (registered trademark) 1520F" manufactured by Ube Maruzen Polyethylene Co., Ltd.) Intermediate layer 14: Ethylene-vinyl alcohol resin (EVOH) ("EVAL (registered trademark) J171B" manufactured by Kuraray Co., Ltd.) Second adhesive layer 15: Maleic anhydride modified polyolefin ("Admer (registered trademark) SF728" manufactured by Mitsui Chemicals, Inc.)

[0085] In the laminated film, the first heat-resistant layer 11A had a thickness of 40 μm, the second heat-resistant layer 11B had a thickness of 50 μm, the adhesive layer (C) 13 had a thickness of 10 μm, the sealant layer (B) 12 had a thickness of 80 μm, the intermediate layer 14 had a thickness of 10 mm, and the second adhesive layer 15 had a thickness of 10 mm, and the total thickness was 200 μm. The thickness ratio of each layer was taken into consideration, and a laminated film for a base material was produced by co-extrusion molding. The first heat-resistant layer 11A and the second heat-resistant layer 11B were extruded at a temperature of 260° C., and the other layers, including the layer (C), were extruded at a temperature of 240° C. The multilayer film 50 for a base material was otherwise produced in the same manner as in Example 1.

[0086] Comparative Example 1 A 200 μm film was produced without including the heat-resistant layer (A) 11 or the adhesive layer (C) 13, and only the sealant layer (B) 12. The other steps were carried out using the same materials and methods as in Example 1.

[0087] Comparative Example 2 A 200 μm film was produced without the sealant layer (B) 12 or the adhesive layer (C) 13, and only the heat-resistant layer (A) 11. The other steps were carried out using the same materials and methods as in Example 1.

[0088] Comparative Example 3 A multilayer film was produced using the same materials, thickness and method as in Example 1, except that a polypropylene resin (Sumitomo Noblen (FS2011DG2) manufactured by Sumitomo Chemical Co., Ltd.) (melting point 158°C) was used as the resin forming the sealant layer (B) 12, and a maleic acid-modified polypropylene (Admer (QF551) manufactured by Mitsui Chemicals, Inc.) was used as the resin forming the adhesive layer (C).

[0089] Comparative Example 4 A multilayer film (laminated film) was produced using the same materials and methods as in Example 1, except that the electron beam irradiation step was not performed.

[0090] The storage modulus at 95°C and 200°C of the obtained films of the examples and comparative examples was measured.

[0091] "Dynamic Mechanical Analysis (DMA)" The storage modulus was measured by dynamic mechanical analysis (DMA) under the following conditions.

[0092] (Measurement conditions) - Multi-layer film shape: length 20mm, width 4mm, thickness 200μm Test equipment model: DMA7100 (Hitachi High-Tech Fielding Corporation) Measurement temperature: 95℃ or 200℃ Measurement mode: Tensile Frequency: 10Hz ·Minimum tension: 50mN Tension Gain: 1.2 Initial force amplitude: 50mN

[0093] Next, the films for the base material and the film for the lid material of Examples 1 to 3 and Comparative Examples 1 to 4 were fed to a deep drawing packaging machine "R535" manufactured by Multivac Japan Co., Ltd. so that the sealant layers of each film faced each other (Comparative Example 2, which did not have the sealant layer 13, was used as it was in one layer), and a deep drawing package was produced in which the base material (deep drawing molded body 30) and the lid material 40 were sealed by heat sealing without being filled with contents. The deep drawing packaged body 100 after molding was a rectangle with a length of 160 mm and a width of 130 mm in a plan view, and the base material had a recess with a depth of 50 mm. The molding temperature in the deep drawing mold for the base material was 200°C, and the molding time was 2.5 seconds. The heat sealing conditions for the deep drawing molded body 30 and the lid material 40 were a sealing temperature of 140°C, a sealing time of 1.5 seconds, and a heat seal width of 7 mm in both the film width direction and the film length direction.

[0094] The moldability and heat sealability during the production of the deep-drawn package were evaluated by the following methods.

[0095] "Moldability" The moldability was evaluated based on two items: the heat plate damage of the molding die during molding, and the appearance of the container after molding.

[0096] <Evaluation of hot plate trauma> After molding, the condition of heat plate damage was visually checked from the molding die for the base material and the package, and evaluated based on the following items. A: The packaging body is not deformed by the hot plate of the molding die, and no resin adheres to the hot plate. B: The packaging body is deformed by the hot plate of the molding die, but there is no resin adhesion to the hot plate. C: The packaging was deformed by the hot plate of the molding die, and there was also resin adhering to the hot plate. <Appearance evaluation after molding> The base material of the molded container was visually inspected to see if it could be used as a container, and whether there were any defects in appearance such as whitening, wrinkles, patterns, etc., and was evaluated based on the following items. In the judgment between A and B, if even the slightest defects in appearance were found, it was judged as B. A: A molded product usable as a container is obtained, and there are no defects in appearance such as whitening, wrinkles, patterns, etc. B: A molded product usable as a container is obtained, but has poor appearance such as whitening, wrinkles, patterns, etc. C: The base material is torn or loses its shape, and a molded article usable as a container cannot be obtained.

[0097] "Heat sealability" Heat sealability was measured by measuring the peel strength of the sealed width (15 mm) of the deep drawn package after molding. The sealed portions were cut into strips of 15 mm width and subjected to a tensile test at 23°C, where they were pulled at a tensile speed of 200 mm / min to measure the stress (peel strength) and were evaluated as follows: A: The base film and the cover film are thermally bonded together, with a peel strength of 0.5N / 15mm width or more. B: The base film and the cover film are thermally bonded together, and the peel strength is less than 0.5N / 15mm width. C: The base film and the cover film are not thermally bonded and heat sealed.

[0098] "Heat resistance (no contents)" The evaluation sample for heat resistance without contents was produced by producing an empty gas pack container from a package obtained from the multilayer film for base material and the multilayer film for lid material of the Examples and Comparative Examples. The empty containers of the Examples and Comparative Examples were left in an oven (DN63 manufactured by Yamato Scientific Co., Ltd.) at 200°C for 20 minutes, and the evaluation was carried out based on the volume reduction rate of the space formed by the base material and the lid material. Note that when left in the oven, a part of the gas pack lid material was opened before the test. A: Volume reduction rate of the space is less than 20% (substantially no reduction) B: Volume reduction rate of the space is 20% or more but less than 40% C: Volume reduction rate of the space is 40% or more (dents are visible on the surface)

[0099] "Heat resistance (with contents)" The evaluation sample for heat resistance with contents was produced by forming a package obtained from the multilayer film for the base material and the multilayer film for the lid material of the Examples and Comparative Examples into a shape with a recess of 30 mm in depth, and filling the recess with a cooked food (gratin) in a vacuum pack form. After leaving it to stand in an oven at 200°C for 20 minutes, the appearance of the package was checked for the presence or absence of abnormalities such as melting or seal loss (broken bag), and it was evaluated according to the following items. A: No abnormalities B: There is slight abnormality such as melting or missing seal.

[0100] The results of each test are shown in Table 1. The abbreviations for the resin names in Table 1 are as follows. PE: Polyethylene EVOH: Ethylene-vinyl alcohol copolymer PET: Polyethylene terephthalate PP: Polypropylene NY: Nylon

[0101] [Table 1]

[0102] As shown in Table 1, the containers molded using the multilayer films of Examples 1 to 3 obtained good results in all of moldability, heat sealability, and heat resistance. In contrast, Comparative Example 1, which had only the sealant layer (B) without the heat-resistant layer (A), showed a volume reduction rate of 75% in the heat resistance evaluation without contents, and was indented and unable to maintain its shape, so that it lacked heat resistance. Comparative Example 2, which did not have the sealant layer (B), showed that the lid material was not thermally bonded and had no heat sealability. In Comparative Example 2, the lid material could not be heat-sealed, so that the heat resistance was evaluated only for the base material. In Comparative Example 3, in which the sealant layer (B) was made of a resin with a melting point exceeding 140°C, hot plate traction occurred and normal deep drawing could not be performed at 200°C, so that heat sealability and heat resistance could not be evaluated. In Comparative Example 3, the storage modulus at 200°C could not be measured because the film broke before it reached 200°C. In Comparative Example 4, in which the electron beam crosslinking step was not performed, similarly to Comparative Example 3, hot plate failure occurred during molding, and normal deep drawing molding at 200°C was not possible, and the heat sealability and heat resistance could not be evaluated. [Explanation of symbols]

[0103] 10: Multilayer film 11: Heat resistant layer 11A: First heat-resistant layer 11B: Second heat-resistant layer 12: Sealant layer 13: Adhesive layer (first adhesive layer) 14: Middle class 15:Second adhesive layer 21: Heat resistant layer 22: Sealant layer 23: Adhesive layer 30: Deep-drawn molded body (base material) 40: Lid material 50: Multilayer film 100: Deep-drawn packaging S1: Laminated film production process S2: Electron beam irradiation process S3: Molding process

Claims

1. A multilayer film comprising a heat-resistant layer (A) and a sealant layer (B), The heat-resistant layer (A) contains a first resin having a melting point of 170° C. or higher, The sealant layer (B) comprises a second resin that has been crosslinked by electron beam and has a melting point of 140° C. or less.

2. The multilayer film according to claim 1 , wherein the ratio of the second resin to the total resin components of the sealant layer (B) is 70% by mass or more and 100% by mass or less.

3. The multilayer film according to claim 1 , wherein the second resin is a polyethylene-based resin.

4. The multilayer film of claim 1 , wherein the first resin is electron beam crosslinked.

5. The multilayer film according to any one of claims 1 to 4, wherein the first resin is a polyamide-based resin or a polyester-based resin.

6. The multilayer film according to claim 1 , further comprising an adhesive layer (C) between the heat-resistant layer (A) and the sealant layer (B) and in contact with the sealant layer (B).

7. The multilayer film according to claim 6 , wherein the adhesive layer (C) comprises a modified polyolefin resin having an unsaturated carboxylic acid modifying group.

8. 2. The multilayer film according to claim 1, having a total thickness of 50 μm or more and 400 μm or less.

9. 2. The multilayer film according to claim 1, which has a storage modulus of 300 MPa or less at a measurement temperature of 95°C in dynamic viscoelasticity measurement in a tensile mode in the MD direction.

10. 2. The multilayer film according to claim 1, which has a storage modulus of 10 MPa or more at a measurement temperature of 200°C in dynamic viscoelasticity measurement in a tensile mode in the MD direction.

11. A deep-draw molded product is obtained by molding a multilayer film, which has a heat-resistant layer (A) and a sealant layer (B), in which the heat-resistant layer (A) contains a first resin having a melting point of 170°C or more, and the sealant layer (B) contains an electron beam crosslinked second resin having a melting point of 140°C or less, using a hot plate at 95°C or more and 200°C or less.

12. A deep-drawn packaging body comprising the deep-drawn molded body according to claim 11 and a lid material.

13. The deep-draw packaging body according to claim 12, having a heat resistance of 200°C for 20 minutes or more.

14. 14. The deep-draw packaging of claim 12 or 13, which is a food container.

15. a laminated film preparation step of forming a laminated film by co-extrusion molding a layer of a first resin having a melting point of 170° C. or more that forms a heat-resistant layer (A) and a layer of a second resin having a melting point of 140° C. or less that forms a sealant layer (B); an electron beam irradiation step of irradiating the laminated film with an electron beam; A molding step of deep drawing the laminated film after electron beam irradiation at a molding temperature of 95 ° C. or more and 200 ° C. or less; A method for producing a deep-drawn body, comprising:

16. The method for producing a deep drawn body according to claim 15, wherein an absorbed dose of the electron beam in the electron beam irradiation step is 30 kGy or more and 250 kGy or less.

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