Multilayer films and packaging

Abstract

To provide a multilayer film having excellent followability to an object to be stored and thermal time melt strength and to provide a package using the same (for example, a skin pack packaging body).SOLUTION: There is provided a multilayer film formed by laminating a sealant layer, a following layer and a gas barrier layer in this order in the thickness direction, wherein the following layer contains an ionomer, the melt strength of the ionomer at a temperature of 180°C is 60 to 540 mN, the ratio of a thickness of the gas barrier layer to a thickness of the multilayer film is 2 to 25%, the dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is 1×104 Pa or more and 1×107 Pa or less and the oxygen permeation amount of the multilayer film 1 under conditions at a temperature of 23°C and a relative humidity of 60% is 100 cc / (m2 day atm)) or less, as measured according to JIS K 7126-2:2006.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to multilayer films and packaging materials. [Background technology]

[0002] A packaging method in which the contents (packaged items) are placed on a rigid tray and sealed with a film by vacuum sealing is called a skin pack. In a skin pack, the film, i.e., the skin pack film, is transparent, allowing the contents to be easily seen through it. Furthermore, the skin pack film is flexible, and by vacuum sealing the storage area inside the skin pack, it can be made to adhere tightly to the contents without causing wrinkles (see, for example, Patent Document 1). In addition, because the skin pack is equipped with a rigid tray (bottom material), it can be displayed upright without causing the contents to shift position. In light of these characteristics, skin packs are mainly used as packaging for food products. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-222259 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the case of skin packs for food, pharmaceuticals, and cosmetics, in order to prevent oxidative deterioration of food, pharmaceuticals, and cosmetics, the multilayer film constituting the skin pack needs to be provided with a gas barrier layer. However, there has been a problem that the followability of the skin pack to food, pharmaceuticals, and cosmetics (the ability to adhere without causing wrinkles) decreases due to the presence of the gas barrier layer. In recent years, there has been a trend towards shifting from conventional chamber-type skin pack machines (indirect heating method) with a low number of shots to continuous skin pack packaging machines (direct heating method) with a high number of shots, and a melt strength that can withstand the method of directly heating the film to a high temperature on a heated hot plate is required.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a multilayer film excellent in followability to the contained material and melt strength during heating, and a package (for example, a skin pack package) using the same.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention adopts the following configuration. [1]. A multilayer film, wherein the multilayer film is composed of a sealant layer, a follow layer, and a gas barrier layer laminated in this order in the thickness direction thereof, the follow layer contains an ionomer, the melt strength of the ionomer at a temperature of 180 ° C is 60 to 540 mN, the ratio of the thickness of the gas barrier layer to the thickness of the multilayer film is 2 to 25%, and the dynamic elastic modulus E' of the multilayer film at a temperature of 140 ° C is 1 × 10

[0006] , , 2 , 4 , 7 , , , Pa or more and 1 × 10 7 Pa or less, and the oxygen permeability of the multilayer film under the conditions of a temperature of 23 ° C and a relative humidity of 60% measured in accordance with JIS K 7126-2:2006 is 100 cc / (m 2 ·day·atm) or less, a multilayer film. [2]. The multilayer film according to [1], wherein the temperature at which a displacement of 2000 μm is exhibited during thermomechanical analysis of the multilayer film is 120 ° C or higher. [3]. The multilayer film according to [1] or [2], wherein the gel fraction of the multilayer film is 30% or more. [4]. The multilayer film according to [2], wherein the displacement at a temperature of 100 °C during the thermomechanical analysis of the multilayer film is 500 μm or less. [5]. The multilayer film according to any one of [1] to [4], wherein the multilayer film is irradiated with an electron beam under the conditions of an absorbed dose of 13 to 300 kGy. [6]. The multilayer film according to any one of [1] to [5], wherein the gas barrier layer contains an ethylene-vinyl alcohol copolymer. [7]. The multilayer film according to any one of [1] to [6], wherein the ratio of the thickness of the follow layer to the thickness of the multilayer film is 10% or more. [8]. The multilayer film according to any one of [1] to [7], wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more. [9]. A package comprising the multilayer film according to any one of [1] to [8].

[10] . The package according to [9], wherein the package is a skin pack package.

Advantages of the Invention

[0007] The multilayer film of the present invention is composed of a sealant layer, a follow layer, and a gas barrier layer laminated in this order in their thickness directions. The follow layer contains an ionomer, and the melt strength of the ionomer at a temperature of 180 °C is 60 to 540 mN. The ratio of the thickness of the gas barrier layer to the thickness of the multilayer film is 2 to 25%. The dynamic elastic modulus E' of the multilayer film at a temperature of 140 °C is 1 × 10 4 Pa or more and 1 × 10 7 Pa or less. The oxygen transmission rate of the multilayer film under the conditions of a temperature of 23 °C and a relative humidity of 60%, measured in accordance with JIS K 7126-2:2006, is 100 cc / (m 2 ·day·atm) or less. Therefore, it is excellent in followability to the contents and melt strength during heating.

[0008] In addition, since the package of the present invention includes the above multi-layer film, it is excellent in followability to the contained material and melt strength during heating.

Brief Description of the Drawings

[0009] [Figure 1] It is a cross-sectional view schematically showing an example of a multi-layer film according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of a package according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0010] <<Multi-layer film (lid material)>> The multi-layer film (lid material) according to an embodiment of the present invention is configured by laminating a sealant layer, a follow layer, and a gas barrier layer in this order in their thickness directions, and the follow layer contains an ionomer. The multi-layer film (lid material) is not particularly limited as long as it satisfies the conditions of the melt strength of the ionomer, the ratio of the thickness of the gas barrier layer, the dynamic elastic modulus E', and the oxygen transmission rate, which will be described later.

[0011] The oxygen transmission rate of the multi-layer film (lid material) under the conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m 2 ·day·atm) or less. By the oxygen transmission rate being 100 cc / (m 2 ·day·atm) or less, deterioration of the packaged contained material can be suppressed and it can be stored for a long time.

[0012] The oxygen transmission rate of the multi-layer film (lid material) under the conditions of a temperature of 23°C and a relative humidity of 60% is preferably 95 cc / (m 2 ·day·atm) or less, more preferably 90 cc / (m 2 ·day·atm) or less, still more preferably 85 cc / (m 2 ·day·atm) or less, particularly preferably 80 cc / (m <​​It may be less than or equal to (day·atm). By keeping the oxygen permeability below the upper limit, the effect of suppressing the deterioration of the packaged contents and enabling long-term storage can be further improved.

[0013] On the other hand, the oxygen permeation rate is 0 cc / (m³). 2 (day·atm) or more, and 0.1cc / (m 2 It is preferable that the value be 0.2cc / (m³) or higher, and 0.2cc / (m³) 2 It is more preferable that it be 0.3cc / (m³) or more, and 0.3cc / (m³) 2 It is even more preferable that it be 0.4cc / (m³) or more, and 0.4cc / (m³) 2 It is particularly preferable that the concentration be 0.5 cc / (m³) or higher, for example, 0.5 cc / (m³). 2 It may be greater than or equal to (day·atm). By ensuring that the oxygen permeability is greater than or equal to the lower limit, the thickness of the gas barrier layer will be within an appropriate range, and adverse effects on conformability can be suppressed.

[0014] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) can be measured in accordance with JIS K 7126-2:2006.

[0015] The oxygen permeability of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the type and content of the components in the gas barrier layer, the thickness and proportion of the gas barrier layer, etc., as described later.

[0016] The temperature at which a displacement of 2000 μm occurs during thermomechanical analysis (TMA) of the multilayer film (lid material) is preferably 120°C or higher, more preferably 120 to 200°C, even more preferably 123 to 190°C, and may be, for example, 130 to 190°C. A temperature above the lower limit further improves the heat resistance of the multilayer film. A temperature below the upper limit further suppresses excessive heat resistance of the multilayer film.

[0017] During thermomechanical analysis of the multilayer film, the displacement at a temperature of 100°C is preferably 500 μm or less, more preferably 40 to 500 μm, and even more preferably 45 to 400 μm, for example, 50 to 350 μm, 55 to 340 μm, and 55 to 250 μm. When the displacement is below the upper limit, the melt tension of the multilayer film is further improved, and as a result, the conformability of the multilayer film to its contents is further improved. When the displacement is above the lower limit, excessive melt tension of the multilayer film is further suppressed.

[0018] The thermomechanical analysis of the aforementioned multilayer film can be performed in accordance with JIS K 7196 by measuring the thermal expansion of the sample from the difference in thermal expansion when a standard sample and the sample to be analyzed are heated at a constant rate. Thermomechanical analysis of multilayer films can be performed, for example, by using a sample with a width of 40 mm, a length of 150 mm, and a thickness of 120 μm, and measuring the displacement (amount of thermal expansion) of this sample in the film flow direction (MD).

[0019] During thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs and the displacement at a temperature of 100°C can be adjusted, for example, by irradiating the multilayer film with an electron beam and adjusting the conditions of the electron beam irradiation. For example, the temperature and displacement can be more easily adjusted by adjusting the conditions of electron beam irradiation to the outer layer or follow-up layer in the multilayer film.

[0020] The multilayer film is preferably irradiated with an electron beam at an absorbed dose of 13 to 300 kGy, more preferably at an absorbed dose of 15 to 250 kGy, and may also be irradiated with an electron beam at any of the following conditions: absorbed dose of 20 to 250 kGy, 45 to 250 kGy, or 70 to 250 kGy. By having the absorbed dose within this range, it is easier to obtain a multilayer film in which, during thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs and the displacement at a temperature of 100°C are both within the above numerical ranges. On the other hand, by having the absorbed dose above the lower limit, the crosslinking density of the multilayer film (especially the outer layer and follow-up layer in this multilayer film) is further improved, resulting in improved heat resistance and melt tension, and improved conformability to the contents of the multilayer film as a whole. By having the absorbed dose below the upper limit, the excessive strength of the multilayer film is further suppressed.

[0021] The reason why electron beam irradiation improves the crosslinking density of the multilayer film (particularly the outer layer and follow-up layer within the multilayer film) is not clear, but it is presumed that the following occurs: When the multilayer film is irradiated with an electron beam, carbon-hydrogen bonds in the resin (e.g., polyethylene, ionomer) are broken, and radicals are generated at the broken bond ends. The generated radicals, through the molecular motion of their molecular chains, come into contact with molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), extract hydrogen atoms, and bond with carbon atoms in the molecular chains of the other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), resulting in the formation of a crosslinked structure.

[0022] The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV, more preferably 120 to 280 kV, and even more preferably 140 to 260 kV. By having the acceleration voltage during electron beam irradiation within this range, it becomes easier to obtain a multilayer film in which, during thermomechanical analysis of the multilayer film, the temperature at which a displacement of 2000 μm occurs and the displacement at 100°C are both within the above numerical ranges. On the other hand, by having the acceleration voltage during electron beam irradiation above the lower limit, the crosslinking density of the multilayer film (especially the outer layer and follow-up layer within the multilayer film) is further improved, resulting in improved heat resistance and melt tension, and improved conformability to the contents of the multilayer film as a whole. By having the acceleration voltage during electron beam irradiation below the upper limit, excessive strength of the multilayer film is further suppressed.

[0023] The gel fraction of the multilayer film is preferably 30% or more, more preferably 30-90%, and even more preferably 32-85%, and may be, for example, 40-82%, 48-82%, and 55-82%. When the gel fraction of the multilayer film is above the lower limit, the heat resistance and melt tension of the multilayer film are further improved, and as a result, the conformability to the contents is further improved. When the gel fraction of the multilayer film is below the upper limit, the excessive strength of the multilayer film is further suppressed.

[0024] The gel fraction of the multilayer film can be measured in accordance with JIS K 6769 by utilizing the fact that the crosslinked portion of the film does not dissolve in the solvent. That is, the multilayer film is immersed in an organic solvent such as xylene, the insoluble film remaining without dissolving is dried, and then the mass of the resulting dried product is measured. The gel fraction can then be calculated from the mass of the multilayer film before dissolution and the mass of the dried insoluble film. More specifically, for example, a multilayer film (mass Xg) is wrapped in a stainless steel mesh (mass Yg), immersed in a heated solvent, and then the multilayer film wrapped in the stainless steel mesh (in other words, the insoluble film) is removed. Next, it is vacuum-dried, and the mass (Zg) of the multilayer film wrapped in the stainless steel mesh (in other words, the insoluble film) after drying is measured. Then, the following formula (1): Gel fraction (mass%) of multilayer film = (ZY) / X × 100 (1) The gel fraction of the multilayer film is calculated using this method.

[0025] The gel fraction of the multilayer film can be adjusted, for example, by irradiating the multilayer film (particularly the outer layer or follow-up layer within the multilayer film) with an electron beam and adjusting the conditions of the electron beam irradiation. In this case, the conditions for electron beam irradiation can be the same as those used to adjust the temperature at which a displacement of 2000 μm occurs and the displacement at a temperature of 100°C during the thermomechanical analysis of the multilayer film described above, including the absorbed dose and the acceleration voltage of the electron beam irradiation.

[0026] Preferably, the multilayer film satisfies either one of the above-mentioned conditions: a temperature at which a displacement of 2000 μm is observed during thermomechanical analysis, and a gel fraction, or both conditions. That is, examples of the multilayer film include: one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is 120°C or higher and the gel fraction is less than 30%; one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is less than 120°C and the gel fraction is 30% or higher; and one at which the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis is 120°C or higher and the gel fraction is 30% or higher. However, generally, the multilayer film is more preferably one that satisfies both of the above conditions, namely, one at which the temperature at which it exhibits a displacement of 2000 μm during thermomechanical analysis is 120°C or higher, and one with a gel fraction of 30% or higher.

[0027] At a temperature of 140°C, the dynamic modulus E' of the multilayer film (lid material) is 1 × 10⁻⁶ 4 Pa or more 1×10 7 It is less than or equal to Pa. Since the dynamic modulus E' is greater than or equal to the lower limit, the conformability of the lid material to the contents can be improved. As a result, dripping during storage is suppressed, preventing the leakage of flavor components and allowing for long-term storage without a decline in taste. Since the dynamic modulus E' is less than or equal to the upper limit, the contents can be packaged without compressing their shape, and deformation of the bottom container can be suppressed when it comes into close contact with the food.

[0028] At a temperature of 140°C, the dynamic modulus E' of the multilayer film (lid material) is 1.1 × 10⁻⁶. 4 Pa or more 9.9×10 6 It is preferable that it is less than or equal to Pa, and 1.2 × 10 4 Pa or more 9.8×10 6 It is more preferable that it be less than or equal to Pa, 1.3 × 10 4 Pa or more 9.7×10 6 It is even more preferable that it be less than or equal to Pa, for example, 1.4 × 10⁻⁶ 4 Pa or more 9.6×10 6 It may be less than or equal to Pa. If the dynamic modulus E' is greater than or equal to the lower limit, the conformability of the lid material to the contents can be further improved. If the dynamic modulus E' is less than or equal to the upper limit, the contents can be packaged without compressing their shape, and deformation of the bottom container can be further suppressed when it is in close contact with food.

[0029] The dynamic modulus E' of the multilayer film (lid material) at a temperature of 140°C can be measured in accordance with JIS K7244-4. Specifically, it can be measured using, for example, a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation's "DMA 7100"). The measurement conditions can be, for example, using a sample with a width of 4 mm, in tensile mode over a temperature range of 25°C to 160°C, with a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 3°C / min.

[0030] When the crosslinking density of the multilayer film (lid material) is improved, the heat resistance and melt tension of the multilayer film (lid material) are improved, as is the dynamic modulus E'. Therefore, the dynamic modulus E' of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the absorbed dose of electron beam irradiation.

[0031] Generally, the resin contained in the gas barrier layer (for example, the gas barrier-impregnating resin described later) has a higher dynamic modulus E' than ordinary resins. Therefore, the dynamic modulus E' of the multilayer film (lid material) can be more easily adjusted by adjusting the type and amount of resin contained in the gas barrier layer, the thickness and proportion of the gas barrier layer, etc.

[0032] The thickness of the multilayer film (lid material) is preferably 60 μm or more, more preferably 70 to 400 μm, even more preferably 80 to 300 μm, and may be, for example, 100 to 200 μm. When the thickness of the multilayer film is above the lower limit, the strength of the multilayer film is further improved. When the thickness of the multilayer film is below the upper limit, the excessive thickness of the multilayer film is further suppressed.

[0033] The aforementioned multilayer film (lid material) is constructed by laminating, for example, a sealant layer, a follow-up layer, and a gas barrier layer in this order in the thickness direction.

[0034] In the aforementioned multilayer film (lid material), regardless of its type, all layers are transparent, and it is preferable that the multilayer film is transparent, that is, that the multilayer film is a transparent multilayer film. In a package made using such a multilayer film, the contents can be easily seen through the multilayer film (lid material).

[0035] The more detailed composition of the aforementioned multilayer film (lid material) and its manufacturing method will be described separately.

[0036] The present invention will be described in more detail below with reference to the drawings. Note that, for convenience in making the features of the present invention easier to understand, the drawings may show enlarged versions of key parts, and the dimensional ratios of each component may not be the same as in reality.

[0037] <<Multilayer film (lid material)>> Figure 1 is a schematic cross-sectional view showing an example of the multilayer film (laminated film) among the multilayer film (lid material) in this embodiment. The multilayer film 1 shown here is constructed by laminating a sealant layer 11, a follower layer 13 (more specifically, a first follower layer 131), and a gas barrier layer 14 in this order in the thickness direction.

[0038] Furthermore, the multilayer film 1 includes an outer layer 12 positioned on the surface of the gas barrier layer 14 opposite to the sealant layer 11 side. Furthermore, the multilayer film 1 includes a follow-up layer 13 (more specifically, a second follow-up layer 132) positioned between the gas barrier layer 14 and the outer layer 12. Furthermore, the multilayer film 1 includes an adhesive layer 15 (more specifically, a first adhesive layer 151) disposed between the first follow-up layer 131 and the gas barrier layer 14, and an adhesive layer 15 (more specifically, a second adhesive layer 152) disposed between the gas barrier layer 14 and the second follow-up layer 132. In other words, the multilayer film 1 is constructed by laminating the sealant layer 11, the first follow-up layer 131, the first adhesive layer 151, the gas barrier layer 14, the second adhesive layer 152, the second follow-up layer 132, and the outer layer 12 in this order in the thickness direction. In the multilayer film 1, the outer layer 12 is one outermost layer, and the sealant layer 11 is the other outermost layer.

[0039] <Sealant layer> The sealant layer 11 may contain polyethylene-based resins such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, or polyethylene copolymer (referred to as "polyethylene-based resin in the sealant layer" in this specification). The inclusion of a polyethylene-based resin in the sealant layer 11 improves the easy-peel properties of the multilayer film 1 by creating pseudo-adhesion to the adherend.

[0040] In this specification, "polyethylene resin" means a resin having at least structural units derived from ethylene, which may have only structural units derived from ethylene, or may have structural units derived from ethylene and other structural units.

[0041] The sealant layer 11 may contain only polyethylene resin in the sealant layer (i.e., it may consist only of polyethylene resin in the sealant layer), or it may contain polyethylene resin in the sealant layer and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of polyethylene resin in the sealant layer and the other components).

[0042] The other components included in the sealant layer 11 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other resin component is a resin that does not fall under the category of polyethylene-based resin in the sealant layer. The other component, which is a resin component, may be a homopolymer, which is a polymer of one monomer, or a copolymer, which is a polymer of two or more monomers.

[0043] Other non-resin components include, for example, additives known in the art. Examples of the aforementioned additives include antioxidants, antistatic agents, nucleating agents, inorganic particles, viscosity reducers, viscosity thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

[0044] The other components contained in the sealant layer 11 may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0045] In the sealant layer 11, the ratio of the polyethylene resin content in the sealant layer to the total mass of the sealant layer 11 is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 75 to 100% by mass, and may be, for example, 85 to 100% by mass. When the ratio is above the lower limit, the easy-peel properties due to the development of pseudo-adhesion with the adherend are further improved. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of polyethylene resin in the sealant layer to the total content (parts by mass) of components that do not vaporize at room temperature in the sealant layer forming composition described later.

[0046] In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0047] The sealant layer 11 may consist of one layer (single layer) or of two or more layers. If the sealant layer 11 consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0048] In this specification, not only in the case of the sealant layer 11, "multiple layers may be identical or different from one another" means "all layers may be identical, all layers may be different, or only some layers may be identical," and further, "multiple layers are different from one another" means "at least one of the constituent materials and thickness of each layer is different from the other."

[0049] The thickness of the sealant layer 11 is not particularly limited, but is preferably 4 to 96 μm, more preferably 7 to 93 μm, and even more preferably 10 to 90 μm. For example, it may be any of 10 to 70 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the sealant layer 11 is greater than or equal to the lower limit, the strength of the sealant layer 11 is increased. When the thickness of the sealant layer 11 is less than or equal to the upper limit, the thickness of the sealant layer 11 is suppressed, and the seal strength is increased when the multilayer film 1 is sealed by heating. Here, "thickness of sealant layer 11" refers to the total thickness of the sealant layer 11. For example, the thickness of a sealant layer 11 consisting of multiple layers refers to the total thickness of all the layers that make up the sealant layer 11.

[0050] The ratio of the thickness of the sealant layer 11 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 5% or more, more preferably 6-80%, and even more preferably 7-75%. When the ratio is above the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side is enhanced. When the ratio is below the upper limit, the excessive thickness of the sealant layer 11 is further suppressed, and the seal strength is enhanced when the multilayer film 1 is sealed by heating.

[0051] The exposed surface 11a of the sealant layer 11 opposite to the outer layer 12 (sometimes referred to as the "first surface" in this specification) is the sealing surface.

[0052] <Outer layer> The outer layer 12 may contain a polyolefin resin such as polyethylene (PE), or a polyester resin such as polyethylene terephthalate resin (PET, PETG) (in this specification, the polyolefin resin and the polyester resin may be referred to as "outer layer resin"). By containing the outer layer resin in the outer layer 12, the crosslinking density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with an electron beam. As a result, the conformability of the multilayer film 1 to its contents is further improved.

[0053] The outer layer 12 may contain only the outer layer resin (i.e., it may consist solely of the outer layer resin), or it may contain the outer layer resin and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of the outer layer resin and the other components).

[0054] The resin contained in the outer layer 12 has a density of 0.945 g / cm³. 3 The following low-density polyethylene is preferred, with a density of 0.943 g / cm³. 3 It is more preferable that the low-density polyethylene has a density of 0.941 g / cm³. 3 It is even more preferable that the polyethylene is low-density polyethylene. By including such low-density polyethylene (LDPE), the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12.

[0055] The resin contained in the outer layer 12 may be of only one type, or it may be of two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0056] The other components included in the outer layer 12 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other components, which are resin components, are resins other than the resin in the outer layer.

[0057] The other components contained in the outer layer 12 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0058] The ratio of the resin content in the outer layer 12 to the total mass of the outer layer 12 is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass. For example, it may be any of 70 to 100% by mass and 85 to 100% by mass. By having the ratio be equal to or greater than the lower limit, the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12 side. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of the resin in the outer layer to the total content (parts by mass) of components that do not vaporize at room temperature in the outer layer forming composition described later.

[0059] The outer layer 12 may consist of one layer (single layer) or of two or more layers. If the outer layer 12 consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0060] The thickness of the outer layer 12 is not particularly limited, but is preferably 4 to 146 μm, more preferably 7 to 143 μm, and even more preferably 10 to 140 μm. For example, it may be any of 10 to 110 μm, 10 to 100 μm, 10 to 90 μm, 10 to 80 μm, and 10 to 70 μm. If the thickness of the outer layer 12 is greater than or equal to the lower limit, the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12 side. If the thickness of the outer layer 12 is less than or equal to the upper limit, the thickness of the outer layer 12 is prevented from becoming excessive. Here, "thickness of outer layer 12" refers to the total thickness of the outer layer 12. For example, the thickness of an outer layer 12 consisting of multiple layers refers to the total thickness of all the layers that make up the outer layer 12.

[0061] The ratio of the thickness of the outer layer 12 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 12-88%, and even more preferably 14-86%. When the ratio is above the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam from the outside of the outer layer 12 is enhanced. When the ratio is below the upper limit, the thickness of the outer layer 12 is prevented from becoming excessive.

[0062] <Follower layer> The follow-up layer 13 contains an ionomer. The ionomer refers to a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid, which is formed into an ionic bridged structure by salt formation between the acid portion and metal ions.

[0063] Examples of the aforementioned metal ions include sodium ions and zinc ions. In this specification, ionomers in which the metal ion is a sodium ion are sometimes referred to as sodium-based ionomers, and ionomers in which the metal ion is a zinc ion are sometimes referred to as zinc-based ionomers.

[0064] The melt strength of the ionomer at a temperature of 180°C is 60 to 540 mN. A melt strength above the lower limit suppresses clouding of the multilayer film 1 when it adheres to the heating plate. A melt strength below the upper limit suppresses deformation of the bottom container when the multilayer film 1 adheres to its contents.

[0065] The melt strength of the ionomer at a temperature of 180°C is preferably 62 to 538 mN, more preferably 64 to 536 mN, and even more preferably 66 to 534 mN. A melt strength above the lower limit allows for greater suppression of clouding of the multilayer film 1 when it adheres to the heating plate. A melt strength below the upper limit allows for greater suppression of deformation of the bottom container when the multilayer film 1 adheres to its contents.

[0066] The melt strength of the ionomer at a temperature of 180°C can be measured in accordance with JIS K7199.

[0067] The melt strength of the ionomer at 180°C can be more easily controlled, for example, by adjusting the type of ionomer.

[0068] The conforming layer 13 may contain polyethylene-based resins other than ionomer, such as ethylene-vinyl acetate copolymer (EVA), polyethylene, or polyethylene copolymer (in this specification, the ionomer and the polyethylene-based resin may be referred to as "polyethylene-based resin in the conforming layer"). By containing polyethylene-based resin in the conforming layer 13, the crosslinking density of the conforming layer 13 can be improved when the multilayer film 1 is irradiated with an electron beam. As a result, the conformability of the packaging made using the multilayer film 1 to its contents is further improved.

[0069] The follow-up layer 13 may consist of one layer (single layer) or of two or more layers. If the follow-up layer 13 consists of multiple layers, these layers may be the same or different from each other, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0070] In this embodiment, follow-up layers 13 are provided at different positions on the multilayer film 1. In this embodiment, in order to distinguish these follow-up layers 13 from one another, the follow-up layer 13 located between the sealant layer 11 and the first adhesive layer 151 may be referred to as the first follow-up layer 131, and the follow-up layer 13 located between the second adhesive layer 152 and the outer layer 12 may be referred to as the second follow-up layer 132, if necessary. These tracking layers 13 (the first tracking layer 131 and the second tracking layer 132) may be the same as or different from each other.

[0071] The follow-up layer 13 may contain only an ionomer (i.e., it may consist of an ionomer), or it may contain an ionomer and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of an ionomer and the other components).

[0072] The ionomer contained in the follow-up layer 13 may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0073] The other components included in the follow-up layer 13 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other components, which are resin components, are resins other than ionomers.

[0074] The other components contained in the follow-up layer 13 may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0075] The ratio of ionomer content in the follow-up layer 13 to the total mass of the follow-up layer 13 is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, for example, it may be any of 70 to 100% by mass and 85 to 100% by mass. By having the ratio be equal to or greater than the lower limit, the crosslinking density of the follow-up layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. The aforementioned ratio is typically the same as the ratio of the ionomer content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the follow-up layer forming composition described later.

[0076] The thickness of the follow-up layer 13 (the thickness of the first follow-up layer 131 and the second follow-up layer 132, respectively) is preferably 4 to 146 μm, more preferably 7 to 143 μm, and even more preferably 10 to 140 μm. For example, it may be any of 10 to 110 μm, 10 to 80 μm, 10 to 50 μm, and 10 to 30 μm. If the thickness of the follow-up layer 13 is greater than or equal to the lower limit, the crosslinking density of the follow-up layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. If the thickness of the follow-up layer 13 is less than or equal to the upper limit, the thickness of the follow-up layer 13 is prevented from becoming excessive. Here, "thickness of the follow-up layer 13" refers to the total thickness of the follow-up layer 13 (for example, the total thickness of the follow-up layer 13 located between the sealant layer 11 and the first adhesive layer 151, or the total thickness of the follow-up layer 13 located between the second adhesive layer 152 and the outer layer 12). For example, the thickness of a follow-up layer 13 consisting of multiple layers refers to the total thickness of all the layers that make up the follow-up layer 13.

[0077] The ratio of the thickness of the follow-up layer 13 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11-89%, and even more preferably 12-88%. When the ratio is above the lower limit, the effect obtained by irradiating the multilayer film 1 with an electron beam is enhanced. When the ratio is below the upper limit, the thickness of the follow-up layer 13 is prevented from becoming excessive.

[0078] <Gas barrier layer> The gas barrier layer 14 imparts strong gas barrier properties (in other words, properties that suppress the permeation of oxygen gas) to the multilayer film 1.

[0079] The gas barrier layer 14 preferably contains an ethylene-vinyl alcohol copolymer (EVOH, also known as ethylene-vinyl acetate copolymer saponified). The inclusion of EVOH in the gas barrier layer 14 can further improve the gas barrier properties of the multilayer film 1.

[0080] The gas barrier layer 14 may contain polyvinylidene chloride (PVDC) in addition to EVOH (in this specification, EVOH and PVDC may be referred to as "gas barrier-imparting resins"). By including a gas barrier-imparting resin in the gas barrier layer 14, the gas barrier properties of the multilayer film 1 can be further improved.

[0081] The gas barrier layer 14 may contain only a gas barrier resin (i.e., it may consist solely of a gas barrier resin), or it may contain a gas barrier resin and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of a gas barrier resin and the other components).

[0082] The other components included in the gas barrier layer 14 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other component, which is a resin component, is a resin other than a gas barrier-impregnating resin. Other non-resin components include, for example, the same additives mentioned earlier as other components of the sealant layer 11.

[0083] The other components contained in the gas barrier layer 14 may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0084] The ratio of the content of the gas barrier resin to the total mass of the gas barrier layer 14 is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, even more preferably 70 to 100% by mass, and may be, for example, 85 to 100% by mass. When the ratio is above the lower limit, the gas barrier properties of the multilayer film 1 are further enhanced. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of the gas barrier-imparting resin to the total content (parts by mass) of components that do not vaporize at room temperature in the gas barrier layer-forming composition described later.

[0085] The gas barrier layer 14 may consist of one layer (single layer) or of two or more layers. If the gas barrier layer 14 consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0086] The thickness of the gas barrier layer 14 is preferably 1 to 100 μm, more preferably 1.5 to 90 μm, and even more preferably 2 to 80 μm, and may be, for example, 4 to 60 μm, 4 to 40 μm, and 4 to 20 μm. When the thickness of the gas barrier layer 14 is greater than or equal to the lower limit, the gas barrier properties of the multilayer film 1 are further enhanced. When the thickness of the gas barrier layer 14 is less than or equal to the upper limit, the excessive thickness of the gas barrier layer 14 is suppressed. Here, "thickness of the gas barrier layer 14" refers to the total thickness of the gas barrier layer 14. For example, the thickness of a gas barrier layer 14 consisting of multiple layers refers to the total thickness of all the layers that make up the gas barrier layer 14.

[0087] The ratio of the thickness of the gas barrier layer 14 to the thickness of the multilayer film 1 is 2 to 25%. By keeping this ratio above the lower limit, the breakdown of the gas barrier layer is suppressed, and the gas barrier properties of the multilayer film 1 can be improved. In this specification, "breakdown of the gas barrier layer" means that a portion of the gas barrier layer is not formed in the multilayer film, which occurs, for example, when the thickness of the gas barrier layer is too thin. By keeping this ratio below the upper limit, the dynamic modulus E' of the multilayer film 1 at a temperature of 140°C is reduced to 1 × 10⁻⁶. 7 It can be set to Pa or less, and the shape of the packaged contents can be maintained.

[0088] The ratio of the thickness of the gas barrier layer 14 to the thickness of the multilayer film 1 is more preferably 2.2 to 24.8%, and even more preferably 2.4 to 24.6%. When the ratio is above the lower limit, layer breakage of the gas barrier layer is suppressed, and the gas barrier properties of the multilayer film 1 can be further improved. When the ratio is below the upper limit, the dynamic modulus E' of the multilayer film 1 at a temperature of 140°C is 1 × 10⁻⁶. 7 The Pa level can be reduced to less than Pa, allowing the shape of the packaged contents to be better preserved.

[0089] In the case of food packaging, a gas barrier layer is required in the multilayer film that makes up the packaging in order to suppress oxidative deterioration of the food. However, the presence of the gas barrier layer has the problem of reducing the packaging's conformability to food (the property of adhering to food without causing wrinkles). In contrast, the packaging made using the multilayer film 1 of this embodiment, which has an outer layer 12 and a conforming layer 13, has this problem improved. This is because the presence of the outer layer 12 and the conforming layer 13 improves the heat resistance, melt tension, and dynamic modulus E' of the multilayer film 1, and as a result the multilayer film 1 has excellent conformability to its contents.

[0090] Furthermore, recently, there has been a shift from conventional chamber-type skin pack machines (indirect heating method) with a low number of shots to continuous-type skin pack packaging machines (direct heating method) with a high number of shots, and there is a need for melt strength that can withstand the method in which the film is directly heated at high temperatures on a heated hot plate. If the melt strength of the packaging is low, there is a problem in that the film becomes cloudy when it adheres to the hot plate. In contrast, this problem is improved in packaging made using the multilayer film 1 of this embodiment which is equipped with a follow-up layer 13. This is because the presence of ionomer contained in the follow-up layer 13 gives the multilayer film 1 excellent melt strength when heated.

[0091] <Adhesive layer> The adhesive layer 15 contains an adhesive. The adhesive layer 15 adheres two adjacent layers to both sides of itself. In the multilayer film 1, the adhesive layer 15 located between the pinhole-resistant layer 16 and the gas barrier layer 14 adheres the pinhole-resistant layer 16 and the gas barrier layer 14, and the adhesive layer 15 located between the gas barrier layer 14 and the follow-up layer 13 adheres the gas barrier layer 14 and the follow-up layer 13. In this specification, in order to distinguish these two adhesive layers 15 from each other, the adhesive layer 15 located between the pinhole-resistant layer 16 and the gas barrier layer 14 may be referred to as the first adhesive layer 151, and the adhesive layer 15 located between the gas barrier layer 14 and the follow-up layer 13 may be referred to as the second adhesive layer 152, as necessary. These two adhesive layers 15 (the first adhesive layer 151 and the second adhesive layer 152) may be identical or different.

[0092] The adhesive contained in the adhesive layer 15 is not particularly limited, as long as it can bond the two layers to be bonded with sufficient strength. Examples of adhesives include adhesive resins such as olefin resins (i.e., polymers of olefins that are one or more monomers).

[0093] More specifically, examples of the olefin resin contained in the adhesive layer 15 include ethylene copolymers, propylene copolymers, butene copolymers, and the like. The aforementioned ethylene copolymer is a copolymer of ethylene and a monomer other than ethylene. The aforementioned propylene copolymer is a copolymer of propylene and a monomer other than propylene. The aforementioned butene copolymer is a copolymer of butene and a monomer other than butene.

[0094] Examples of the ethylene-based copolymer contained in the adhesive layer 15 include copolymers of ethylene and vinyl group-containing monomers. Examples of copolymers of ethylene and vinyl group-containing monomers include maleic anhydride graft-modified linear low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ionomers (ION), and ethylene-based thermoplastic elastomers. Examples of the ionomer mentioned above include the same ionomer previously listed as being included in the follower layer 13.

[0095] Examples of the propylene copolymer contained in the adhesive layer 15 include a copolymer of propylene and a vinyl group-containing monomer. Examples of copolymers of propylene and vinyl group-containing monomers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers.

[0096] Examples of the butene-based copolymer contained in the adhesive layer 15 include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products (modified copolymers) of these copolymers.

[0097] The adhesive layer 15 may contain only an adhesive (i.e., it may consist of an adhesive), or it may contain an adhesive and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of an adhesive and the other components).

[0098] The adhesive layer 15 may contain only one type of adhesive, or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0099] The other components included in the adhesive layer 15 are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components.

[0100] The other components contained in the adhesive layer 15 may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0101] The ratio of the adhesive content in the adhesive layer 15 to the total mass of the adhesive layer 15 may be, for example, 50 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the adhesive layer-forming composition described later.

[0102] The adhesive layer 15 may consist of one layer (single layer) or of two or more layers. If the adhesive layer 15 consists of multiple layers, these layers may be the same or different from each other, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0103] The thickness of the adhesive layer 15 (the thickness of the first adhesive layer 151 and the second adhesive layer 152, respectively) is preferably 4 to 96 μm, more preferably 7 to 93 μm, and may be, for example, 7 to 80 μm, 7 to 60 μm, 7 to 40 μm, and 7 to 20 μm. When the thickness of the adhesive layer 15 is greater than or equal to the lower limit, the adhesive strength of the two layers to be bonded is increased. When the thickness of the adhesive layer 15 is less than or equal to the upper limit, the thickness of the adhesive layer 15 is prevented from becoming excessive. Here, "thickness of adhesive layer 15" refers to the total thickness of the adhesive layer 15 (for example, the total thickness of the adhesive layer 15 placed between the pinhole-resistant layer 16 and the gas barrier layer 14, or the total thickness of the adhesive layer 15 placed between the gas barrier layer 14 and the follow-up layer 13). For example, the thickness of an adhesive layer 15 consisting of multiple layers refers to the total thickness of all the layers that make up the adhesive layer 15.

[0104] <Other layers> The multilayer film 1 may also include other layers that do not fall under any of the sealant layer 11, outer layer 12, follow-up layer 13, gas barrier layer 14, or adhesive layer 15, as long as the effects of the present invention are not impaired.

[0105] The types and placement positions of the other layers are not particularly limited and can be arbitrarily selected according to the purpose.

[0106] The other layers provided in the multilayer film 1 may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0107] Each of the aforementioned other layers may consist of one layer (single layer) or two or more layers. If the aforementioned other layers consist of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0108] The thickness of the other layers can be set arbitrarily depending on their type and is not particularly limited.

[0109] If the multilayer film 1 includes the other layers, it may further include an adhesive layer (for example, an adhesive layer 15, etc.) for bonding the other layers to the other layers.

[0110] The thickness of the multilayer film 1 is the same as the thickness of the multilayer film (lid material) described earlier.

[0111] The multilayer film in this embodiment is not limited to those described above, and some components may be modified, deleted, or added without departing from the spirit of the present invention. For example, the multilayer film may not include one or two of the outer layer and the adhesive layer. However, it is preferable that the multilayer film comprises a sealant layer, a follow-up layer, an adhesive layer, a gas barrier layer, an adhesive layer, a follow-up layer, and an outer layer in this order, as shown in Figure 1.

[0112] <<Manufacturing method for multilayer film (lid material)>> The aforementioned multilayer film (lid material) can be manufactured by known methods depending on its type. For example, laminated films such as the multilayer film can be manufactured by a feed block method in which resins or resin compositions that form each layer are melt-extruded using several extruders, a co-extrusion T-die method such as a multi-manifold method, or an air-cooled or water-cooled co-extrusion inflation method.

[0113] Furthermore, the laminated film can also be manufactured by coating the surface of another layer that constitutes the laminated film with a resin or resin composition that will be the forming material for any of the layers therein, drying it as necessary to form the laminated structure within the laminated film, and further laminating other layers as necessary to achieve the desired arrangement.

[0114] Furthermore, the laminated film can also be manufactured by separately preparing two or more films in advance to form any two or more of the layers, laminating these films together using an adhesive by one of the following methods: dry lamination, extrusion lamination, hot melt lamination, or wet lamination, and further laminating other layers as needed to achieve the desired arrangement. In this case, an adhesive capable of forming the adhesive layer may be used.

[0115] Furthermore, the laminated film can also be manufactured by laminating two or more films that have been prepared separately in advance, without using adhesive, using a thermal lamination method or the like, and then further laminating other layers as needed to achieve the desired arrangement.

[0116] When manufacturing the aforementioned laminated film, two or more of the methods for forming any of the layers (films) in the laminated film, as described above, may be combined.

[0117] Regardless of the manufacturing method, the resin composition that forms any of the layers in the laminated film can be manufactured by adjusting the types and amounts of the constituent components so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. For example, the ratio of the amounts of components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the amounts of those components in the layer formed from this resin composition.

[0118] Examples of resin compositions for forming a sealant layer (sealant layer 11 in the multilayer film 1 shown in Figure 1) include those comprising a polyethylene resin in the sealant layer and, if necessary, the other components.

[0119] Examples of resin compositions for forming the outer layer (outer layer 12 in the multilayer film 1 shown in Figure 1) (sometimes referred to as "outer layer forming composition" in this specification) include the resin in the outer layer and, if necessary, the other components.

[0120] Examples of resin compositions for forming a follow-up layer (in the multilayer film 1 shown in Figure 1, the follow-up layer 13) include those comprising a polyethylene-based resin in the follow-up layer and, if necessary, the other components.

[0121] Examples of resin compositions for forming a gas barrier layer (gas barrier layer 14 in the multilayer film 1 shown in Figure 1) (sometimes referred to as "gas barrier layer forming composition" in this specification) include the gas barrier-impregnating resin and, if necessary, the other components.

[0122] Examples of resin compositions for forming an adhesive layer (adhesive layer 15 in the multilayer film 1 shown in Figure 1) (sometimes referred to as "adhesive layer forming composition" in this specification) include the adhesive and, if necessary, the other components.

[0123] The multilayer film 1 can be used as a lid material. The packaging of this embodiment can be manufactured by heat-sealing this lid material and the bottom material.

[0124] <<Bottom material>> The aforementioned bottom material has an oxygen permeability of 300 cc / (m³). 2It is not particularly limited as long as it is less than or equal to (day·atm) and can be used as a base material for packaging. The aforementioned base material may be one of known types.

[0125] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the base material is 300 cc / (m³). 2 (day·atm) or less, 260cc / (m 2 It is preferable that it be less than or equal to (day·atm), for example, 200cc / (m 2 ·day · atm) or less, 150cc / (m 2 ·day · atm) or less, 100cc / (m 2 ·day · atm) or less, and 50cc / (m 2 (・day・atm) Any of the following may be acceptable. On the other hand, the oxygen permeation rate is 0 cc / (m³). 2 (This is the total value for days and hours.)

[0126] Under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the bottom material can be measured in accordance with JIS K 7126-2:2006.

[0127] The oxygen permeability of the substrate can be more easily adjusted by, for example, adjusting the type and amount of components contained in the substrate, the thickness of the substrate, etc.

[0128] The thickness of the base material is preferably 100 μm or more, more preferably 110 μm or more, and even more preferably 120 μm or more. The strength of the base material is further improved when the thickness of the base material is greater than or equal to the lower limit. The thickness of the base material is preferably 6000 μm or less. By keeping the thickness of the base material below the above upper limit, the thickness of the base material is prevented from becoming excessive. The thickness of the base material can be adjusted as appropriate within a range set by any combination of the lower and upper limits mentioned above.

[0129] In the case of the base material, regardless of its type, all layers may be transparent, and the base material may be transparent, or all or some layers may not be transparent, and the base material may not be transparent. In a package made with a transparent base material, the contents can be easily seen through the base material.

[0130] The detailed composition of the base material and its manufacturing method will be explained separately.

[0131] <<One embodiment of the base material>> The base material is preferably a laminated body composed of multiple layers stacked together. A preferred laminated base material is, for example, a resin laminate comprising a foamed resin layer and a non-foamed resin layer provided on the foamed resin layer.

[0132] The foamed resin layer may be of known origin. Examples of the foamed resin layer include a resin layer containing a foamed polystyrene resin (PSP).

[0133] The density of the foamed resin layer is not particularly limited, but is generally 0.05 to 0.5 g / cm³. 3 It is preferable that this be the case. The foaming ratio of the foamed resin layer is not particularly limited, but is preferably 2 to 20 times. The thickness of the foamed resin layer is not particularly limited, but is preferably 500 to 6000 μm.

[0134] Examples of the non-foamed resin layers include a multilayer film for base materials, in which an easy-peel layer, a gas barrier layer, a pinhole-resistant layer, and an adhesive layer are laminated in this order in the thickness direction. In the multilayer film for base materials, the easy-peel layer is the outermost layer on one side, and the adhesive layer is the outermost layer on the other side.

[0135] The multilayer film for the base material may, for example, include an intermediate adhesive layer between the easy-peel layer and the gas barrier layer for bonding these two layers together. Furthermore, the multilayer film for the base material may include, for example, an intermediate adhesive layer between the gas barrier layer and the pinhole-resistant layer for bonding these two layers together. In other words, the multilayer film for the base material may be constructed by laminating an easy-peel layer, an intermediate adhesive layer, a gas barrier layer, an intermediate adhesive layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction.

[0136] In this specification, in order to distinguish between these two intermediate adhesive layers, the intermediate adhesive layer located between the easy-peel layer and the gas barrier layer may be referred to as the first intermediate adhesive layer, and the intermediate adhesive layer located between the gas barrier layer and the pinhole-resistant layer may be referred to as the second intermediate adhesive layer, as necessary. These two intermediate adhesive layers (first intermediate adhesive layer, second intermediate adhesive layer) may be the same as or different from each other.

[0137] <Easy Peel Layer> Examples of the easy-peel layer in the multilayer film for base materials include those that exhibit peelability due to cohesive failure. An example of an easy-peel layer that exhibits peelability due to cohesive failure is one that contains two types of incompatible polyolefins.

[0138] Examples of two incompatible polyolefins included in the easy-peel layer of a multilayer film for base materials include an ethylene-based polymer having at least one structural unit derived from ethylene and a propylene-based polymer having at least one structural unit derived from propylene. In other words, the easy-peel layer includes, for example, an ethylene-based polymer having at least structural units derived from ethylene, and a propylene-based polymer having at least structural units derived from propylene.

[0139] Examples of ethylene-based polymers included in the easy-peel layer of a multilayer film for base materials include ethylene homopolymers and ethylene-based copolymers.

[0140] Examples of the ethylene homopolymers include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (mLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0141] The ethylene copolymer comprises structural units derived from ethylene and structural units derived from monomers other than ethylene. Examples of the ethylene-based copolymers include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), and ionomers (ION). Examples of the ionomer mentioned above include the same ionomer previously listed as being included in the follow-up layer 13 of the multilayer film 1 described earlier.

[0142] In multilayer films for base materials, the easy-peel layer preferably contains low-density polyethylene as the ethylene-based polymer. The easy-peel properties of such an easy-peel layer are better.

[0143] The propylene-based polymer contained in the easy-peel layer of the multilayer film for base materials includes propylene homopolymers (i.e., polypropylene or homopolypropylene, hPP) and propylene copolymers.

[0144] The propylene copolymer comprises structural units derived from propylene and structural units derived from monomers other than propylene. Examples of the propylene copolymer include propylene-ethylene random copolymer (also known as polypropylene random copolymer, rPP) and propylene-ethylene block copolymer (also known as polypropylene block copolymer, bPP).

[0145] In multilayer films for base materials, the easy-peel layer preferably contains polypropylene as the propylene-based polymer. The easy-peel properties of such an easy-peel layer are better.

[0146] The easy-peel layer in a multilayer film for base materials may contain only one type of component that exhibits easy-peel properties, or it may contain two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose. For example, if the components that exhibit easy-peel properties are the two incompatible polyolefins mentioned above, the easy-peel layer may contain only one type of these polyolefins, or it may contain two or more types.

[0147] In the easy-peel layer of the multilayer film for the base material, the ratio of the content (parts by mass) of the ethylene polymer to the total content (parts by mass) of the ethylene polymer and the propylene polymer is preferably 10 to 90% by mass, and may be, for example, 30 to 90% by mass, 45 to 90% by mass, or 60 to 90% by mass. When the ratio is above the lower limit, the easy-peel properties of the easy-peel layer are improved. When the ratio is below the upper limit, the peel strength is more stable. The aforementioned ratio is typically the same as the ratio of the ethylene polymer content (parts by mass) to the total content (parts by mass) of the ethylene polymer and propylene polymer in the easy-peel layer forming composition for base materials described later.

[0148] The easy-peel layer in a multilayer film for base materials may contain other components besides the components that exhibit easy-peel properties (for example, the two incompatible polyolefins mentioned above), as long as the easy-peel properties are not impaired. The other components contained in the Easy Peel layer may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0149] In the easy-peel layer of the multilayer film for base material, the ratio of the content of the component that exhibits easy-peel properties (for example, the ratio of the total content of the two types of incompatible polyolefins mentioned above) to the total mass of the easy-peel layer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and may be any of 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 97 to 100% by mass, and 99 to 100% by mass. The easier-peel properties of the easy-peel layer are improved when the ratio is above the lower limit. The aforementioned ratio is typically the same as the ratio of the content (parts by mass) of the component that exhibits easy-peel properties to the total content (parts by mass) of the component that does not vaporize at room temperature in the easy-peel layer forming composition for base materials described later.

[0150] Other components included in the Easy Peel layer of the multilayer film for base materials include, for example, anti-fogging agents and anti-blocking agents.

[0151] The easy-peel layer in the multilayer film for base material may consist of one layer (single layer) or of two or more layers. When the easy-peel layer consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0152] The thickness of the easy-peel layer in the multilayer film for the base material is preferably 2 to 50 μm. When the thickness of the easy-peel layer is above the lower limit, the seal strength of the easy-peel layer is moderately high. When the thickness of the easy-peel layer is below the upper limit, the easy-peel properties are further enhanced. Here, "Easy Peel layer thickness" refers to the total thickness of the Easy Peel layer. For example, the thickness of an Easy Peel layer consisting of multiple layers refers to the total thickness of all the layers that make up the Easy Peel layer.

[0153] The ratio of the thickness of the easy-peel layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the seal strength of the easy-peel layer is moderately high. When the ratio is below the upper limit, the easy-peel properties are further enhanced.

[0154] <Gas barrier layer> The aforementioned gas barrier layer imparts gas barrier properties (in other words, properties that suppress the permeation of oxygen gas) to the multilayer film for the base material.

[0155] In the multilayer film for the base material, the gas barrier layer preferably contains ethylene-vinyl alcohol copolymer (EVOH, also known as ethylene-vinyl acetate copolymer saponified) or polyamide.

[0156] Examples of the polyamides include 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-nylon, 612-nylon, 6T-nylon, 6I-nylon, copolymer of 6-nylon and 66-nylon (nylon 6 / 66), copolymer of 6-nylon and 610-nylon, copolymer of 6-nylon and 611-nylon, copolymer of 6-nylon and 12-nylon (nylon 6 / 12), copolymer of 6-nylon and 612-nylon, 6- Examples include copolymers of nylon and 6T-nylon, copolymers of 6-nylon and 6I-nylon, copolymers of 6-nylon, 66-nylon and 610-nylon, copolymers of 6-nylon, 66-nylon and 12-nylon (nylon 6 / 66 / 12), copolymers of 6-nylon, 66-nylon and 612-nylon, copolymers of 66-nylon and 6T-nylon, copolymers of 66-nylon and 6I-nylon, copolymers of 6T-nylon and 6I-nylon, and copolymers of 66-nylon, 6T-nylon and 6I-nylon.

[0157] The polyamide is preferably 6-nylon (sometimes abbreviated as "Ny6" in this specification), 12-nylon, 66-nylon, nylon 6 / 66, nylon 6 / 12, or nylon 6 / 66 / 12, in terms of heat resistance, mechanical strength, and availability.

[0158] The polyamide contained in the gas barrier layer of the multilayer film for base materials may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0159] The gas barrier layer in a multilayer film for base materials may contain only one or both of ethylene-vinyl alcohol copolymer and polyamide (i.e., it may consist of either one or both of ethylene-vinyl alcohol copolymer and polyamide), or it may contain either one or both of ethylene-vinyl alcohol copolymer and polyamide, and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of either one or both of ethylene-vinyl alcohol copolymer and polyamide, and the other components).

[0160] The other components included in the gas barrier layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other component that is a resin component is a resin that does not fall under either ethylene-vinyl alcohol copolymer or polyamide. Other non-resin components include, for example, the same additives mentioned earlier as other components included in the sealant layer 11 of the multilayer film 1 described above.

[0161] The other components included in the gas barrier layer of the multilayer film for base materials may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0162] In the gas barrier layer of the multilayer film for the base material, the ratio of the total content of ethylene-vinyl alcohol copolymer and polyamide to the total mass of the gas barrier layer is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and may be, for example, 70 to 100% by mass and 85 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the total content (parts by mass) of ethylene-vinyl alcohol copolymer and polyamide to the total content (parts by mass) of components that do not vaporize at room temperature in the gas barrier layer forming composition for the base material described later.

[0163] The gas barrier layer in the multilayer film for the base material may consist of one layer (single layer) or of two or more layers. When the gas barrier layer consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0164] The thickness of the gas barrier layer in the multilayer film for the base material is preferably 2 to 20 μm. A thickness of the gas barrier layer greater than or equal to the lower limit enhances its gas barrier properties. A thickness of the gas barrier layer less than or equal to the upper limit prevents the gas barrier layer from becoming excessively thick. Here, "gas barrier layer thickness" refers to the total thickness of the gas barrier layer. For example, the thickness of a gas barrier layer consisting of multiple layers refers to the total thickness of all the layers that make up the gas barrier layer.

[0165] The ratio of the thickness of the gas barrier layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 15%. When the ratio is above the lower limit, the gas barrier properties of the multilayer film for the base material are further enhanced. When the ratio is below the upper limit, the thickness of the gas barrier layer is prevented from becoming excessive.

[0166] <Pinhole-resistant layer> The aforementioned pinhole-resistant layer is a layer that protects the structure of the multilayer film used for bottoming materials, such as by suppressing the occurrence of pinholes in the multilayer film used for bottoming materials.

[0167] In the multilayer film for the base material, the pinhole-resistant layer preferably contains polyolefin. Examples of the polyolefins include polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (mLLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE); and polypropylene.

[0168] The pinhole-resistant layer in the multilayer film for base material may contain only polyolefin (i.e., it may consist solely of polyolefin), or it may contain polyolefin and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of polyolefin and the other components).

[0169] The other components included in the pinhole-resistant layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components. The other component, which is a resin component, is a resin other than polyolefin. Other non-resin components include, for example, the same additives mentioned earlier as other components included in the sealant layer 11 of the multilayer film 1 described above.

[0170] The other components included in the pinhole-resistant layer of the multilayer film for base materials may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0171] In the pinhole-resistant layer of the multilayer film for the base material, the ratio of the polyolefin content to the total mass of the pinhole-resistant layer is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and may be, for example, 70 to 100% by mass and 85 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the polyolefin content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the pinhole-resistant layer-forming composition for base materials described later.

[0172] The pinhole-resistant layer in the multilayer film for the base material may consist of one layer (single layer) or of two or more layers. When the pinhole-resistant layer consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0173] The thickness of the pinhole-resistant layer in the multilayer film for the base material is preferably 2 to 50 μm. A thickness of the pinhole-resistant layer greater than or equal to the lower limit enhances its protective ability. A thickness of the pinhole-resistant layer less than or equal to the upper limit prevents the pinhole-resistant layer from becoming excessively thick. Here, "thickness of the pinhole-resistant layer" refers to the total thickness of the pinhole-resistant layer. For example, the thickness of a pinhole-resistant layer consisting of multiple layers refers to the total thickness of all the layers that make up the pinhole-resistant layer.

[0174] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the pinhole resistance of the multilayer film for the base material is further enhanced. When the ratio is below the upper limit, the thickness of the pinhole-resistant layer is prevented from becoming excessive.

[0175] <Adhesive layer> The adhesive layer is a layer for bonding a multilayer film for the base material to the foamed resin layer, and contains an adhesive.

[0176] The adhesive is preferably an adhesive resin, and more preferably an ethylene-vinyl acetate copolymer resin. The ethylene-vinyl acetate copolymer resin has constituent units derived from ethylene and constituent units derived from vinyl acetate, and may or may not have other constituent units. Examples of preferred ethylene-vinyl acetate copolymer resins include partially saponified ethylene-vinyl acetate copolymers.

[0177] The adhesive layer in the multilayer film for base material may contain only an adhesive (i.e., consist of an adhesive), or it may contain an adhesive and other components (which may be referred to as "other components" in this specification) (i.e., it may consist of an adhesive and the other components).

[0178] The adhesive layer in the multilayer film for base materials may contain only one type of adhesive, or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0179] The other components included in the adhesive layer of the multilayer film for base material are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components.

[0180] The other components in the adhesive layer of the multilayer film for base materials may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0181] The ratio of the adhesive content in the adhesive layer of the multilayer film for the base material to the total mass of the adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the adhesive layer forming composition for base materials described later.

[0182] The adhesive layer in the multilayer film for the base material may consist of one layer (single layer) or of two or more layers. When the adhesive layer consists of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0183] The thickness of the adhesive layer in the multilayer film for the base material is preferably 2 to 40 μm. A thickness of the adhesive layer greater than or equal to the lower limit increases the adhesive strength between the two layers to be bonded. A thickness of the adhesive layer less than or equal to the upper limit prevents the adhesive layer from becoming excessively thick. Here, "thickness of the adhesive layer" refers to the total thickness of the adhesive layer. For example, the thickness of an adhesive layer consisting of multiple layers refers to the sum of the thicknesses of all the layers that make up the adhesive layer.

[0184] The ratio of the thickness of the adhesive layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 5 to 40%. When the ratio is above the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is below the upper limit, the thickness of the adhesive layer is prevented from becoming excessive.

[0185] <First intermediate adhesive layer, second intermediate adhesive layer> The first and second intermediate adhesive layers each contain an adhesive. The adhesive is preferably an adhesive resin. Examples of the adhesive resin include polyolefin resins. The aforementioned polyolefin resin is a resin having structural units derived from olefins, and may be a modified polyolefin such as an acid-modified polyolefin having an acidic group (for example, acid-modified polyethylene, acid-modified polypropylene). Examples of polyolefin resins include ethylene copolymers, propylene copolymers, butene copolymers, and modified products of these copolymers (in other words, modified copolymers). For polyolefin resins, random copolymers, graft copolymers, or block copolymers are preferable in terms of improved adhesion.

[0186] Examples of the ethylene copolymer include the ethylene copolymer described earlier as being included in the easy-peel layer, and its modified product (modified copolymer). Examples of the propylene copolymer include copolymers of propylene and vinyl group-containing monomers, and modified products thereof (modified copolymers). More specifically, examples of such propylene copolymers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers. Examples of the butene-based copolymers include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products (modified copolymers) of these copolymers.

[0187] The first and second intermediate adhesive layers may consist solely of an adhesive (i.e., they may consist of an adhesive), or they may consist of an adhesive and other components (which may be referred to as "other components" in this specification) (i.e., they may consist of an adhesive and the other components).

[0188] The adhesives contained in the first and second intermediate adhesive layers may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0189] The other components included in the first and second intermediate adhesive layers are not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, resin components and non-resin components.

[0190] The other components contained in the first and second intermediate adhesive layers may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0191] The ratio of the adhesive content in the first intermediate adhesive layer in the multilayer film for the base material to the total mass of the first intermediate adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the first intermediate adhesive layer forming composition for the base material, which will be described later. The ratio of the adhesive content in the second intermediate adhesive layer in the multilayer film for the base material to the total mass of the second intermediate adhesive layer may be, for example, 50 to 100% by mass. The aforementioned ratio is typically the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the second intermediate adhesive layer forming composition for the base material, which will be described later.

[0192] The first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for base material may each consist of one layer (single layer) or two or more layers. When the first intermediate adhesive layer or the second intermediate adhesive layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0193] In the multilayer film for the base material, the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer are preferably 2 to 15 μm independently. When the thickness of the first and second intermediate adhesive layers is greater than or equal to the lower limit, the adhesive strength of the two layers to be bonded is increased. When the thickness of the first and second intermediate adhesive layers is less than or equal to the upper limit, it is prevented from becoming excessively thick. Here, "thickness of the first intermediate adhesive layer" refers to the total thickness of the first intermediate adhesive layer. For example, if the first intermediate adhesive layer consists of multiple layers, the thickness refers to the total thickness of all the layers that make up the first intermediate adhesive layer. The same applies to the second intermediate adhesive layer.

[0194] The ratio of the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer to the thickness of the multilayer film for the base material is not particularly limited, but is preferably 3 to 20%. When the ratio is above the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is below the upper limit, the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer is prevented from becoming excessive.

[0195] <Other layers> The multilayer film for the base material may include other layers that do not fall under any of the following categories, as long as they do not impair the effects of the present invention: the easy-peel layer, the first intermediate adhesive layer, the gas barrier layer, the second intermediate adhesive layer, the pinhole-resistant layer, and the adhesive layer.

[0196] The types and positions of the other layers in the multilayer film for the base material are not particularly limited and can be arbitrarily selected according to the purpose.

[0197] The other layers in the multilayer film for the base material may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0198] In the multilayer film for the base material, the other layers may consist of one layer (single layer) or two or more layers. When the other layers consist of multiple layers, these layers may be identical or different, and the combination of these layers is not particularly limited as long as it does not impair the effects of the present invention.

[0199] The thickness of the other layers in the multilayer film for the base material can be set arbitrarily according to their type and is not particularly limited.

[0200] If the multilayer film for the base material includes the aforementioned other layers, it may further include an intermediate adhesive layer for bonding the aforementioned other layers to the other layers. Examples of such intermediate adhesive layers include those similar to the first or second intermediate adhesive layer described above.

[0201] The thickness of the non-foamed resin layer, such as a multilayer film for the base material, is not particularly limited, but is preferably 40 to 120 μm.

[0202] <<Manufacturing method for base material>> The aforementioned base material can be manufactured by known methods, depending on its type. For example, if the base material is a resin laminate comprising the foamed resin layer and the non-foamed resin layer described above, the base material can be manufactured by bonding one surface of the foamed resin layer to one surface of the non-foamed resin layer (or the adhesive layer within it if the non-foamed resin layer is the multilayer film for the base material) by heat lamination. This heat lamination may be carried out by, for example, a melt-pressure lamination method as described later in the examples, or by an extrusion lamination method. Among the non-foamed resin layers, the multilayer film for the base material can be manufactured in the same manner as the multilayer film (lid material) described above, except that the type of resin or resin composition used to form each layer is different.

[0203] Regardless of the manufacturing method, the resin composition that forms any of the layers in the multilayer film for the base material can be manufactured by adjusting the types and amounts of the constituent components so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. For example, the ratio of the amounts of components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the amounts of those components in the layer formed from this resin composition.

[0204] Examples of resin compositions for forming an easy-peel layer in a multilayer film for base materials (which may be referred to herein as "composition for forming an easy-peel layer for base materials") include the polyolefin and, if necessary, the other components.

[0205] Examples of resin compositions for forming a gas barrier layer in a multilayer film for base materials (which may be referred to herein as "composition for forming a gas barrier layer for base materials") include those comprising either or both of an ethylene-vinyl alcohol copolymer and a polyamide, and optionally the aforementioned other components.

[0206] Examples of resin compositions for forming a pinhole-resistant layer in a multilayer film for base materials (which may be referred to herein as "composition for forming a pinhole-resistant layer for base materials") include the polyolefin and, if necessary, the other components.

[0207] Examples of resin compositions for forming an adhesive layer in a multilayer film for base materials (sometimes referred to herein as "composition for forming an adhesive layer for base materials"), a resin composition for forming a first intermediate adhesive layer (sometimes referred to herein as "composition for forming a first intermediate adhesive layer for base materials"), and a resin composition for forming a second intermediate adhesive layer (sometimes referred to herein as "composition for forming a second intermediate adhesive layer for base materials") include, for example, the adhesive and, if necessary, the other components.

[0208] <<Packaging>> Figure 2 is a schematic cross-sectional view showing an example of the packaging according to this embodiment. In Figure 2, components that are the same as those shown in previously explained figures are denoted by the same reference numerals as in those previously explained figures, and their detailed explanations are omitted. Note that in Figure 2, the distinction between each layer in the multilayer film 1 is omitted.

[0209] The packaging 10 shown here is composed of a multilayer film (lid material) 1 and a bottom material 8, as shown in Figure 1.

[0210] The packaging 10 is preferably a skin pack packaging. In this specification, "skin pack" refers to packaging in which the contents are placed on cardboard, corrugated cardboard, a bottom film, a tray, etc., a heated film is placed over it, and a vacuum is created in a chamber so that the film adheres tightly to the contents. The name "skin pack" comes from the characteristic that the film adheres to the product body as if it were skin, conforming to the shape of the product.

[0211] In the packaging 10, the multilayer film (lid material) 1 is constructed by laminating a sealant layer 11, a follow-up layer 13, and a gas barrier layer 14 in this order in the thickness direction, with the follow-up layer 13 containing an ionomer, and the melt strength of the ionomer at a temperature of 180°C being 60 to 540 mN. In the packaging 10, the ratio of the thickness of the gas barrier layer 14 to the thickness of the multilayer film (lid material) 1 is 2 to 25%. In the packaging 10, the dynamic modulus E' of the multilayer film (lid material) 1 at a temperature of 140°C is 1 × 10⁻⁶. 4 Pa or more 1×10 7 It is below Pa. In the packaging 10, under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the multilayer film (lid material) 1 is 100 cc / (m²). 2 (•day•atm) is less than or equal to the following: In the packaging 10, it is preferable that the temperature at which a displacement of 2000 μm is observed during thermomechanical analysis of the multilayer film (lid material) 1 is 120°C or higher. In the packaging 10, it is preferable that the gel fraction of the multilayer film (lid material) 1 is 30% or more. In the packaging 10, it is preferable that the displacement of the multilayer film (lid material) 1 at a temperature of 100°C is 500 μm or less during the thermomechanical analysis. In the packaging 10, it is preferable that the multilayer film (lid material) 1 is irradiated with an electron beam under conditions of an absorbed dose of 13 to 300 kGy. In the packaging 10, it is preferable that the gas barrier layer 14 contains an ethylene-vinyl alcohol copolymer. In the packaging 10, it is preferable that the ratio of the thickness of the follow-up layer 13 to the thickness of the multilayer film (lid material) 1 is 10% or more. In the packaging 10, it is preferable that the ratio of the thickness of the sealant layer 11 to the thickness of the multilayer film (lid material) 1 is 5% or more.

[0212] In the packaging 10, under conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen permeability of the bottom material 8 is 300 cc / (m³). 2 It is preferable that it be less than or equal to (day·atm).

[0213] The packaging body 10 uses a multilayer film 1 as the lid material, which provides excellent conformability to the contents 9 and superior heat melt strength. Furthermore, because the packaging 10 uses a multilayer film (lid material) 1 and a bottom material 8, it has high oxygen barrier properties for the contents 9, and the shelf life of the contents 9 is longer than that of conventional packaging.

[0214] One surface of the base material 8 (sometimes referred to as the "first surface" in this specification) 8a is a sealing surface, and a portion of the first surface 8a is in close contact with a portion of the first surface 11a of the sealant layer 11 in the multilayer film 1 by a seal. In Figure 2, the portion where the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11 in the multilayer film 1 are in direct contact is the sealing portion. As a result, a storage portion 10a is formed between the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11. The contents 9 are sealed within this storage portion 10a.

[0215] If the base material 8 is the multilayer film for base material, the first surface 8a of the base material 8 is the surface of the easy-peel layer opposite to the gas barrier layer side.

[0216] In Figure 2, some gaps can be seen between the contents 9 and the multilayer film 1, and between the contents 9 and the bottom material 8 within the storage section 10a of the packaging body 10. However, these gaps may not exist in the packaging body 10 when the contents 9 are stored inside.

[0217] The packaging of this embodiment is not limited to those described above, and some components may be modified, deleted, or added without departing from the spirit of the present invention. In Figure 2, a packaging body 10 is shown that is constructed using the multilayer film 1 shown in Figure 1 as the lid material. However, the packaging body of this embodiment may be constructed using other multilayer films (lid materials).

[0218] <<Manufacturing method for packaging>> The packaging of this embodiment is one in which the contents are vacuum-packed by the bottom material and the lid material of the packaging of this embodiment.

[0219] The packaging of this embodiment can be manufactured, for example, by placing the contents on the side of the base material that seals with the lid material, covering the surface of the base material and the contents with the lid material from above, and vacuuming the area between the base material and the lid material where the contents are placed, thereby tightly fixing the lid material to the contents, while heat sealing the base material and the lid material in the area where the contents are not placed. The test packaging described later can also be manufactured using the same method.

[0220] The sealing temperature during heat sealing is not particularly limited, but is preferably between 100 and 170°C. A sealing temperature above the lower limit results in higher seal strength while maintaining easy-peel properties. A sealing temperature below the upper limit makes opening the package easier.

[0221] The sealing time during heat sealing can be adjusted as appropriate depending on the sealing temperature, but is usually preferably 10 to 30 seconds. When the sealing time is above the lower limit, the seal strength is increased while maintaining easy peelability. When the sealing time is below the upper limit, the package can be opened more easily.

[0222] The pressure in the area where the contents are placed, due to vacuuming during heat sealing, is 5000 Pa (50 mbar) or less, preferably 300 Pa to 5000 Pa, more preferably 400 Pa to 4900 Pa, even more preferably 500 Pa to 4800 Pa, and particularly preferably 600 Pa to 4700 Pa. By keeping the pressure below the upper limit, a package is obtained in which the lid material conforms to (seals) the contents more effectively, resulting in a package with superior preservation suitability. [Examples]

[0223] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below.

[0224] [Example 1] <<Manufacturing of multilayer film (lid material)>> A multilayer film with the configuration shown in Figure 1 was manufactured using the following procedure. Specifically, ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Mitsui Dow Polychemicals) was prepared as the resin constituting the sealant layer. The resin that makes up the outer layer is low-density polyethylene (LDPE, density 0.922 g / cm³). 3 We prepared "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd. Ionomer (ION, "1601" manufactured by Mitsui Dow Polychemicals) was prepared as the resin constituting the follow-up layers (first follow-up layer and second follow-up layer). As the resin constituting the gas barrier layer, we prepared ethylene-vinyl alcohol copolymer (EVOH, "GH3804B" manufactured by Nippon Synthetic Co., Ltd.). As the adhesive (adhesive resin) constituting the adhesive layers (first adhesive layer and second adhesive layer), maleic anhydride-modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

[0225] The temperature of the die was set at 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (120 μm thick) in which a sealant layer (24 μm thick), a follow layer (first follow layer, 29 μm thick), an adhesive layer (first adhesive layer, 8 μm thick), a gas barrier layer (10 μm thick), an adhesive layer (second adhesive layer, 8 μm thick), a follow layer (second follow layer, 17 μm thick), and an outer layer (24 μm thick) were laminated in this order in their thickness directions.

[0226] Next, the multilayer film obtained above was irradiated with an electron beam from the outside on the outer layer side under the conditions of an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. Thus, the target multilayer film irradiated with an electron beam (hereinafter sometimes referred to as "lid material (I)") was obtained.

[0227] <<Evaluation of Multilayer Film (Lid Material)>> <Measurement of Dynamic Elastic Modulus at 140°C> Regarding the multilayer film (lid material (I)) irradiated with an electron beam obtained above, using a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Technologies Corporation), in accordance with JIS K7244-4, using a sample with a width of 4 mm, in a tensile mode in the temperature range from 25°C to 160°C, the dynamic elastic modulus (E') was measured under the conditions of a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 升温速度3℃ / min. The results are shown in Table 1.

[0228] <Ionomer Melt Strength at 180°C> Regarding the multilayer film (lid material (I)) irradiated with an electron beam obtained above, using a melt strength measuring device ("Capillograph" manufactured by Toyo Seiki Seisakusho), in accordance with JIS K7199, under the condition of a winding speed of 15 m / min, the melt strength of the ionomer contained in the first follow layer was measured. The results are shown in Table 1.

[0229] <Temperature Indicating a Displacement of 2000 μm, Identification of Displacement at a Temperature of 100°C> The electron beam-irradiated multilayer film (lid material (I)) obtained above was subjected to thermomechanical analysis in accordance with JIS K 7196 using a thermal analyzer (SII Corporation's "EXSTAR6000"). From the resulting thermomechanical analysis curve, the temperature (°C) at which a displacement of 2000 μm occurred and the displacement (μm) at a temperature of 100°C were determined. The results are shown in Table 1.

[0230] <Measurement of gel fraction> The gel fraction of the electron beam-irradiated multilayer film (lid material (I)) obtained above was measured in accordance with JIS K 6769. Specifically, a test piece measuring 3 cm x 3 cm (approximately 0.09 g) was cut from the multilayer film, wrapped in a 400-mesh stainless steel wire mesh (100 g), and immersed in xylene (18 mL) at 110 °C for 24 hours. Next, the test specimen, along with the wire mesh, was removed from the xylene solution and vacuum-dried at 110°C for 24 hours under a pressure of 1.7 kPa to obtain a dried sample of the immersed test specimen. The mass of the obtained dried sample was measured, and the gel fraction (%) of the electron-irradiated multilayer film was determined. The results are shown in Table 1.

[0231] <Measurement of oxygen permeability> The electron beam-irradiated multilayer film (lid material (I)) obtained above was subjected to oxygen permeability testing (cc / (m³)) in accordance with JIS K 7126-2:2006 under conditions of 23°C and 60% relative humidity. 2 We measured (day and atm). The results are shown in Table 1.

[0232] <Evaluation of gas barrier layer breakage> The multilayer film (lid material (I)) obtained above, after electron beam irradiation, was visually inspected for gas barrier layer defects, and the presence or absence of breaks in the gas barrier layer was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: No breaks have occurred in the gas barrier layer. B: Some layer breaks have occurred in the gas barrier layer. C: A gap has occurred in the gas barrier layer.

[0233] <<Manufacturing of base material>> <Manufacturing of multilayer films for base materials> The multilayer film for the base material was manufactured using the following procedure. Specifically, low-density polyethylene (LDPE, "L211" manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (PP, "FS2011DG2" manufactured by Sumitomo Chemical Co., Ltd.) were prepared as resins to constitute the easy-peel layer. The resin used to constitute the pinhole-resistant layer is metallocene-catalyzed linear low-density polyethylene (mLLDPE) (manufactured by Ube Maruzen Polyethylene Co., Ltd., "Yumerit® 1520F", density 0.913 g / cm³). 3 I prepared ). The resin used to constitute the gas barrier layer is ethylene-vinyl alcohol copolymer (EVOH, Kuraray Co., Ltd. "J171B", density: 1180 kg / m³). 3 I prepared a dose with an MFR of 4.2g / 10min. Acid-modified polypropylene (acid-modified PP, adhesive resin, "Admer QF551" manufactured by Mitsui Chemicals) was prepared as the resin constituting the first intermediate adhesive layer. Acid-modified polyethylene (acid-modified PE, adhesive resin, "Admer NF536" manufactured by Mitsui Chemicals) was prepared as the resin for the second intermediate adhesive layer. As the resin constituting the adhesive layer, we prepared an ethylene-vinyl acetate copolymer resin (EVA-based resin, adhesive resin, "Mersen® MX02D" manufactured by Tosoh Corporation).

[0234] A composition for forming an easy-peel layer for bottom materials was produced by mixing the aforementioned LDPE (70 parts by mass) and the aforementioned PP (30 parts by mass) at room temperature.

[0235] By setting the die temperature to 250°C and co-extruding the easy-peel layer forming composition for the base material, the acid-modified PP, the EVOH, the acid-modified PE, the mLLDPE, and the EVA-based resin in this order (co-extrusion T-die method), a multilayer film for base material (thickness 70 μm) was produced, consisting of an easy-peel layer (thickness 25.9 μm), a first intermediate adhesive layer (thickness 5.6 μm), a gas barrier layer (thickness 8.4 μm), a second intermediate adhesive layer (thickness 5.6 μm), a pinhole-resistant layer (thickness 10.5 μm), and an adhesive layer (thickness 14 μm) laminated in this order in the thickness direction.

[0236] <Manufacturing of base materials> A foamed resin sheet containing polystyrene resin (PSP) foam (manufactured by Chuo Kagaku Co., Ltd., 3000 μm thick) was used, and the exposed adhesive layer of the multilayer film for the base material obtained above was bonded to one side of the foamed resin sheet by heat lamination to obtain a base material (hereinafter sometimes referred to as "base material (α)"). The heat lamination of the foamed resin sheet and the multilayer film for the base material was performed by heat lamination using a roll device equipped with a melt-pressure roll. The melt-pressure roll was composed of a heating roll and a counter roll provided opposite to the heating roll, and the foamed resin sheet and the multilayer film for the base material were bonded together by melt-pressure bonding at 180°C between the heating roll and the counter roll.

[0237] <<Evaluation of the base material>> <Measurement of oxygen permeability> The oxygen permeability (cc / (m³)) of the bottom material obtained above was measured under conditions of 23°C and 60% relative humidity in accordance with JIS K 7126-2:2006 for the bottom material (bottom material (α)). 2 We measured the day and atm. The results are shown in Table 4.

[0238] <<Manufacturing of packaging (test packaging)>> 400 g of beef thigh meat was cut out and used as test meat. Then, with a continuous skin packager (Multivac's "T300"), the sealant layer in the lid material (I) obtained above and the easy peel layer in the bottom material (α) were opposed to each other, and the test meat was placed between these lid material (I) and bottom material (α). While evacuating the location where the test meat was placed, the peripheral portions of the lid material (I) and the bottom material (α) were heat-sealed under the conditions of a hot plate temperature (sealing temperature) of 140 °C and a sealing time of 10 seconds, thereby producing a test package which is a package (skin pack package). During evacuation, the pressure in the area where the test meat was placed was set to 1000 Pa (10 mbar). As the bottom material (α), one with a size of 20 cm × 20 cm was used. By the same procedure, a plurality of the test packages were produced. These test packages were frozen and stored at -30 °C in an air atmosphere.

[0239] <<Evaluation of Package (Test Package)>> <State of Film> When the test package was adhered to the hot plate, visual observation was performed, and the presence or absence of film clouding was evaluated according to the following criteria. The results are shown in Table 5. [Evaluation Criteria] A: The film is not clouded. B: The film is slightly clouded. C: The film is clouded.

[0240] <Bottom Material Container Deformation> When the test package was adhered to the test meat, visual observation was performed, and the presence or absence of deformation of the bottom material container was evaluated according to the following criteria. The results are shown in Table 5. [Evaluation Criteria] A: The bottom material container is not deformed. B: The bottom material container is slightly deformed. C: The bottom material container is deformed.

[0241] <Shape of Contents> Fourteen days after the start of storage, the samples were thawed from a frozen state of -30°C to 4°C over a period of 16 hours. Immediately after thawing, the unopened test packages were visually inspected from the lid side, and the shape of the test meat was evaluated according to the following criteria. The results are shown in Table 5. [Evaluation Criteria] A: The shape of the test meat is being maintained. B: The shape of the test meat is slightly crushed. C: The shape of the test meat is crushed.

[0242] <Discoloration of contents> Fourteen days after the start of storage, the samples were thawed from a frozen state of -30°C to 4°C over a period of 16 hours. Immediately after thawing, the unopened test packages were visually inspected from the lid side, and the presence or absence of discoloration (surface oxidation discoloration) of the test meat was evaluated according to the following criteria. The results are shown in Table 5. [Evaluation Criteria] A: No discoloration has occurred in the test meat. B: The test meat has slightly discolored. C: Discoloration has occurred in the test meat.

[0243] <Drip> Fourteen days after the start of storage, the samples were thawed from -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was removed from the unopened test packaging and visually observed after 5 minutes. The amount of drip was evaluated according to the following criteria. The results are shown in Table 5. [Evaluation Criteria] A: No dripping has occurred. B: There is some dripping. C: Drip is occurring.

[0244] [Example 2] Except for changing the absorbed dose from 175 kGy to 120 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (II)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (II)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 4, and 5.

[0245] [Example 3] Except for changing the absorbed dose from 175 kGy to 90 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (III)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (III)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 4, and 5.

[0246] [Example 4] Except for changing the absorbed dose from 175 kGy to 15 kGy during electron beam irradiation of the multilayer film, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (IV)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (IV)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 1, 4, and 5.

[0247] [Comparative Example 1] Except for not irradiating the multilayer film with an electron beam, a lid material (multilayer film without electron beam irradiation, hereinafter sometimes referred to as "lid material (V)") was manufactured and evaluated using the same method as in Example 1. Except for using a non-electron beam irradiated multilayer film (lid material (V)), the packaging (test packaging) was manufactured and evaluated using the same method as in Example 1. The results are shown in Tables 1, 4, and 6.

[0248] [Example 5] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VI)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 20 μm), a follow-up layer (first follow-up layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 18 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 17 μm), and an outer layer (thickness 20 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (VI)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 5.

[0249] [Example 6] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VII)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 16 μm), a follow-up layer (first follow-up layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 26 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 17 μm), and an outer layer (thickness 16 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (VII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 5.

[0250] [Comparative Example 2] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (VIII)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 12 μm), a follow-up layer (first follow-up layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 34 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 17 μm), and an outer layer (thickness 12 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (VIII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 6.

[0251] [Example 7] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (IX)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 27 μm), a follow-up layer (first follow-up layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 4 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 17 μm), and an outer layer (thickness 27 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (IX)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 5.

[0252] [Comparative Example 3] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (X)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 28 μm), a follow-up layer (first follow-up layer, thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 1 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 17 μm), and an outer layer (thickness 29 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (X)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 6.

[0253] [Example 8] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XI)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 32 μm), a follow-up layer (first follow-up layer, thickness 21 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 9 μm), and an outer layer (thickness 32 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (XI)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 2, 4, and 5.

[0254] [Example 9] A lid material (electron beam irradiated multilayer film, hereinafter sometimes referred to as "lid material (XII)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 40 μm), a follow-up layer (first follow-up layer, thickness 7 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 7 μm), and an outer layer (thickness 40 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (XII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 4, and 5.

[0255] [Example 10] A lid material (electron beam irradiated multilayer film, sometimes referred to as "lid material (XIII)") was manufactured and evaluated in the same manner as in Example 1, except that the die temperature was set to 250°C, and the EVA, ION, modified PE, EVOH, modified PE, ION, and LDPE were co-extruded in this order (co-extrusion T-die method), resulting in a multilayer film (thickness 120 μm) composed of a sealant layer (thickness 41 μm), a follow-up layer (first follow-up layer, thickness 6 μm), an adhesive layer (first adhesive layer, thickness 8 μm), a gas barrier layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a follow-up layer (second follow-up layer, thickness 5 μm), and an outer layer (thickness 42 μm) laminated in this order in the thickness direction. Except for using the electron beam-irradiated multilayer film (lid material (XIII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 4, and 5.

[0256] [Comparative Example 4] Except for using 6-nylon (Ny, Ube Industries, Ltd. "1030B2") as the resin constituting the gas barrier layer instead of the aforementioned EVOH (Nippon Gosei Co., Ltd. "GH3804B"), a lid material (a multilayer film irradiated with electron beams, hereinafter sometimes referred to as "lid material (XIV)") was manufactured and evaluated using the same method as in Example 1. Except for using the electron beam-irradiated multilayer film (lid material (XIV)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 4, and 6.

[0257] [Example 11] A lid material (a multilayer film irradiated with an electron beam, hereinafter sometimes referred to as "lid material (XV)") was manufactured and evaluated in the same manner as in Example 1, except that an ionomer (ION, manufactured by Mitsui Dow Polychemicals, "1855") was used instead of the aforementioned ION (manufactured by Mitsui Dow Polychemicals, "1601") as the resin constituting the follow-up layers (first follow-up layer and second follow-up layer). Except for using the electron beam-irradiated multilayer film (lid material (XV)), the packaging (test packaging) was manufactured and evaluated using the same method as in Example 1. The results are shown in Tables 3, 4, and 5.

[0258] [Comparative Example 5] A lid material (a multilayer film irradiated with electron beams, hereinafter sometimes referred to as "lid material (XVI)") was manufactured and evaluated in the same manner as in Example 1, except that an ionomer (ION, manufactured by Mitsui Dow Polychemicals, "1652") was used instead of the ION (manufactured by Mitsui Dow Polychemicals, "1601") as the resin constituting the follow-up layers (first follow-up layer and second follow-up layer). Except for using the electron beam-irradiated multilayer film (lid material (XVI)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 4, and 6.

[0259] [Comparative Example 6] A lid material (a multilayer film irradiated with electron beams, hereinafter sometimes referred to as "lid material (XVII)") was manufactured and evaluated in the same manner as in Example 1, except that an ionomer (ION, manufactured by Mitsui Dow Polychemicals, "1554W") was used instead of the aforementioned ION (manufactured by Mitsui Dow Polychemicals, "1601") as the resin constituting the follow-up layers (first follow-up layer and second follow-up layer). Except for using the electron beam-irradiated multilayer film (lid material (XVII)), the packaging (test packaging) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 3, 4, and 6.

[0260] [Table 1]

[0261] [Table 2]

[0262] [Table 3]

[0263] [Table 4]

[0264] [Table 5]

[0265] [Table 6]

[0266] In Examples 1 to 11, the lid material of the test packaging had a ratio of the gas barrier layer thickness to the thickness of the multilayer film of 2% or more, and therefore, no tearing of the gas barrier layer occurred in any of them. The test packaging materials of Examples 1 to 11 had a dynamic modulus of elasticity of 1 × 10 at 140°C. 4 Furthermore, since the ionomer melt strength at 180°C was 60 mN or more, the film did not become cloudy when in contact with the hot plate in any of the cases. In addition, in the test packaging of Examples 1 to 11, the proportion of the gas barrier layer thickness was 25% or less, resulting in a dynamic modulus of elasticity E' of 1 × 10 at 140°C. 7 Since the elastic modulus was less than or equal to Pa, and the ionomer melt strength at 180°C was 540 mN or less, the bottom container did not deform when in contact with the test meat in any case. Furthermore, the dynamic modulus of elasticity at 140°C for the test packaging of Examples 1 to 11 was 1 × 10⁻⁶ 7 Since the pressure was below Pa, all of them were able to maintain the shape of the packaged test meat. In addition, the test packaging of Examples 1 to 11 had a gas barrier layer thickness of 2% or more, and the oxygen permeability was 100 cc / (m³). 2 Since the temperature was below (day·atm), no discoloration occurred in the packaged test meat in any of the cases. Furthermore, the dynamic modulus of elasticity at 140°C for the test packages of Examples 1 to 11 was 1 × 10⁻⁶. 4 Therefore, although some drip occurred in the test meat removed from the test packaging in Example 10, no drip occurred in the test packaging in Examples 1-9 and 11. Thus, the test packaging materials of Examples 1 to 11 exhibited excellent conformability to the contents and superior thermal melt strength.

[0267] In contrast, the test packaging of Comparative Example 1 did not exhibit improved heat resistance because the multilayer film was not irradiated with an electron beam, and the film became cloudy when in contact with the hot plate. Furthermore, because the multilayer film was not irradiated with an electron beam, the dynamic modulus E' at 140°C was 1 × 10⁻⁶. 4 Because the pressure dropped below Pa, the lid material's ability to conform to the test meat decreased, and when the test meat was removed from the hot plate, it began to drip. In Comparative Example 2, the test packaging had a gas barrier layer thickness ratio of over 25% to the multilayer film thickness, resulting in a dynamic modulus of elasticity E' of 1 × 10⁻⁶ at 140°C.7 Because the Pa level exceeded the limit, the bottom container deformed when it came into contact with the test meat. Additionally, the packaged test meat was crushed. In Comparative Example 3, the test packaging had a gas barrier layer thickness ratio of less than 2% to the thickness of the multilayer film, which resulted in the gas barrier layer tearing and discoloration of the packaged test meat. In Comparative Example 4, the test packaging used Ny as the resin constituting the gas barrier layer, resulting in an oxygen permeability of 100 cc / (m²) of the multilayer film. 2 Because the temperature exceeded (day·atm), discoloration occurred in the packaged test meat. In Comparative Example 5, the test packaging material had a melt strength of less than 60 mN for the ionomer contained in the first follow-up layer, resulting in the film becoming cloudy when in contact with the hot plate. In Comparative Example 6, the ionomer contained in the first follow-up layer of the test packaging had a melt strength exceeding 540 mN, causing the bottom container to deform when it came into contact with the test meat. [Industrial applicability]

[0268] The present invention provides a multilayer film with excellent conformability to contents and thermal melt strength, and a packaging body (e.g., a skin pack packaging body) using the same. [Explanation of symbols]

[0269] 1. Multilayer film (lid material) 11. Sealant layer 12...outer layer 13. Follower layer 131...First Follower Layer 132...Second Follower Layer 14. Gas barrier layer 15...adhesive layer 151...1st adhesive layer 152...Second adhesive layer 10. Packaging (test packaging) 8...Bottom material 9. Contents (test meat)

Claims

1. It is a multilayer film, The aforementioned multilayer film is constructed by laminating a sealant layer, a follow-up layer, a gas barrier layer, and an outer layer in this order in the thickness direction. The aforementioned follow-up layer contains an ionomer, Using a melt strength measuring device, the molten ionomer was extruded from the die in accordance with JIS K7199, and then the extruded ionomer was wound up at a temperature of 180°C and a winding speed of 15 m / min. The melt strength of the ionomer measured was 60 to 540 mN. The ratio of the thickness of the gas barrier layer to the thickness of the multilayer film is 2 to 25%. The dynamic modulus E' of the multilayer film, measured under conditions of a temperature of 140°C and a vibration frequency of 1 Hz, is 1 × 10⁻⁶. ４ Pa or more 1×10 ７ It is less than or equal to Pa, The oxygen permeability of the multilayer film, measured in accordance with JIS K 7126-2:2006 under conditions of 23°C and 60% relative humidity, was 100 cc / (m²). ２ (day ATM) is less than or equal to, The outer layer comprises a polyolefin resin or a polyester resin, A multilayer film having a thickness of 60 μm or more.

2. The multilayer film according to claim 1, wherein the temperature at which a displacement of 2,000 μm is observed during thermomechanical analysis of the multilayer film is 120°C or higher.

3. The multilayer film according to claim 1 or 2, wherein the gel fraction of the multilayer film is 30% or more.

4. The multilayer film according to claim 2, wherein, during the thermomechanical analysis of the multilayer film, the displacement at a temperature of 100°C is 500 μm or less.

5. The multilayer film according to any one of claims 1 to 4, wherein the multilayer film is irradiated with an electron beam under conditions of an absorbed dose of 13 to 300 kGy.

6. The multilayer film according to any one of claims 1 to 5, wherein the gas barrier layer comprises an ethylene-vinyl alcohol copolymer.

7. The multilayer film according to any one of claims 1 to 6, wherein the ratio of the thickness of the follow-up layer to the thickness of the multilayer film is 10% or more.

8. The multilayer film according to any one of claims 1 to 7, wherein the ratio of the thickness of the sealant layer to the thickness of the multilayer film is 5% or more.

9. A packaging body comprising a multilayer film according to any one of claims 1 to 8.

10. The packaging body according to claim 9, wherein the packaging body is a skin pack packaging body.

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