Manufacturing method of frozen raw meat vacuum package

Abstract

To provide a manufacturing method of frozen raw meat vacuum package which has better appearance than conventional ones by storing frozen-packaged raw meat for a long time and preventing post-frozen raw meat color from deteriorating.SOLUTION: A manufacturing method of frozen raw meat vacuum package in which raw meat is packaged with a lid material and a base material includes: a process for placing raw meat on the base material; a process for placing the lid material in an area on the base material that covers the raw meat and its surroundings; a process for heating the lid material to 90-250°C and bringing it into contact with the raw meat, forming a shape along the raw meat, and bonding a portion of the lid material that is in contact with the base material to the base material, thereby packaging the raw meat with the lid material and base material; and a process for rapidly freezing the raw meat to a central temperature of -20°C or less within 6 hours immediately after packaging. Under conditions of a temperature of 23°C and a relative humidity of 60%, the lid material has an oxygen permeability of 100 cc / (m2 / day / atm) or less, and the base material has an oxygen permeability of 300 cc / (m2 / day / atm) or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a vacuum package for frozen raw meat.

Background Art

[0002] Edible raw meat is, for example, packaged together with a resin tray using a transparent resin film with low oxygen barrier properties while placed on the resin tray, or packaged in a bag-shaped package and retailed (see Patent Document 1). However, in the form placed on the resin tray, the edible period is about 3 days at 10°C, about 6 days at 4°C, and about 7 days at 0°C. In order to extend the edible period further, barrier vacuum packaging is common, and if stored in a frozen state, the edible period can be extended by more than two months (Test Method Guidelines for Meat Expiration Labeling). Furthermore, by performing vacuum packaging using a barrier skin pack, frozen packaged raw meat can be stored for a long time, drip generated during thawing can be suppressed, and by preventing the outflow of umami components, it has been found that a package that can be stored for a long time without degrading the taste can be provided.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, when slow freezing, which is a common freezing method for barrier vacuum-packaged raw meat, is performed, reduction of meat tissue progresses due to the action of myoglobin enzyme in the raw meat, and color development generally decreases. Conventional barrier vacuum packages for raw meat have room for improvement in this regard.

[0005] The present invention aims to provide a method for manufacturing a vacuum package for frozen raw meat that can be stored for a long time with better appearance than before by storing frozen-packaged raw meat for a long time and preventing the color of the raw meat from deteriorating after freezing.

Means for Solving the Problems

[0006] To solve the above problems, the present invention adopts the following configuration. [1]. A method for manufacturing a vacuum package for frozen raw meat in which raw meat is packaged with a lid material and a bottom material, comprising a step of arranging the raw meat on the bottom material, a step of arranging the lid material in a region covering the raw meat and its periphery among the regions on the bottom material, a step of contacting the lid material with the raw meat while heating the lid material to 90 to 250°C, shaping it along the raw meat, and adhering the portion of the lid material in contact with the bottom material to the bottom material to package the raw meat with the lid material and the bottom material, and a step of rapidly freezing the central temperature of the raw meat to -20°C or lower within 6 hours immediately after packaging. The lid material is composed of a multilayer film, and the multilayer film has an oxygen transmission rate of 100 cc / (m 2 ·day·atm) or less under the conditions of a temperature of 23°C and a relative humidity of 60%, and the oxygen transmission rate of the bottom material is 300 cc / (m 2 ·day·atm) or less. A method for manufacturing a vacuum package for frozen raw meat. [2]. The method for manufacturing a vacuum package for frozen raw meat according to [1], wherein the dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is 10 4 or more and 10 7 Pa or less. [3]. The method for manufacturing a vacuum package for frozen raw meat according to [1] or [2], wherein the temperature at which the multilayer film shows a displacement of 2000 μm during thermomechanical analysis is 120°C or higher. [4]. The method for manufacturing a vacuum package for frozen raw meat according to any one of [1] to [3], wherein the gel fraction of the multilayer film is 30% or more. [5]. The method for manufacturing a vacuum package for frozen raw meat according to any one of [1] to [4], wherein the multilayer film is irradiated with an electron beam under the condition of an absorbed dose of 13 to 300 kGy. [6]. The manufacturing method of the vacuum packaging body for frozen fresh meat according to any one of [1] to [5], wherein, during the thermomechanical analysis of the multilayer film, the displacement at a temperature of 100 °C is 500 μm or less. [7]. The manufacturing method of the vacuum packaging body for frozen fresh meat according to any one of [1] to [6], wherein the multilayer film includes an outer layer containing polyethylene, a functional layer containing an ionomer and adjacent to the outer layer, an oxygen barrier layer, and a sealant layer containing ethylene-vinyl acetate resin. [8]. The manufacturing method of the vacuum packaging body for frozen fresh meat according to any one of [1] to [7], wherein the vacuum packaging body for frozen fresh meat is a skin pack packaging body for frozen fresh meat. [9]. The manufacturing method of the vacuum packaging body for frozen fresh meat according to any one of [1] to [8], wherein the vacuum packaging body for frozen fresh meat is a vacuum packaging body for frozen fresh meat stored at -40 °C or higher and lower than 0 °C. [Advantages of the Invention]

[0007] According to the present invention, there is provided a packaging body that can store the packaged fresh meat in a good-looking state with the color maintained for a long time under frozen conditions, and further suppress the generation of drip after thawing, so that the deliciousness can be maintained. [Brief Description of the Drawings]

[0008]

Figure 1

Figure 2

[0009] [[Multilayer Film (Lid Material)]] The multilayer film according to an embodiment of the present invention is a multilayer film for the lid material of a vacuum packaging body for frozen fresh meat including a lid material and a bottom material. The multilayer film (lid material) is not particularly limited as long as it satisfies the conditions of the oxygen transmission rate described below and can be used to produce the lid material of the vacuum packaging body for frozen fresh meat.

[0010] In this specification, "freezing" means artificially freezing raw meat at a temperature below 0°C using equipment (a freezer or a refrigerator) or liquid nitrogen, etc. for maintaining the quality of raw meat, or freezing raw meat at a temperature below 0°C under a natural environment. The temperature is preferably, for example, -84°C or higher and -20°C or lower, more preferably -83°C or higher and -20°C or lower, still more preferably -82°C or higher and -20°C or lower, and particularly preferably -81°C or higher and -20°C or lower.

[0011] In this specification, "vacuum packaging" means evacuating the area where raw meat is placed so that the pressure becomes 5000 Pa (50 mbar) or less. The pressure is preferably, for example, 300 Pa or higher and 5000 Pa or lower, more preferably 400 Pa or higher and 4900 Pa or lower, still more preferably 500 Pa or higher and 4800 Pa or lower, and particularly preferably 600 Pa or higher and 4700 Pa or lower.

[0012] The vacuum package for frozen raw meat is preferably a skin pack package for frozen raw meat. In this specification, "skin pack" means a package in which the contents are placed on cardboard, corrugated cardboard, a bottom film, a tray, etc., covered with a heated film thereon, and evacuated in a chamber so that the film adheres and fixes to the contents. The feature that the film adheres closely to the product body like skin along the shape of the product is the origin of the name "skin pack".

[0013] The oxygen transmission rate of the multilayer 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. When the oxygen transmission rate of the multilayer 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, the deterioration of the frozen-packaged raw meat can be suppressed and it can be stored for a long time.

[0014] Under the conditions of a temperature of 23°C and a relative humidity of 60%, the oxygen transmission rate of the multilayer film (lid material) is preferably 95 cc / (m 2 ·day·atm) or less, more preferably 90 cc / (m 2 ·day·atm) or less, even more preferably 85 cc / (m 2 ·day·atm) or less, particularly preferably 80 cc / (m 2 ·day·atm) or less, and for example, it may be 75 cc / (m 2 ·day·atm) or less. By the oxygen transmission rate of the multilayer film (lid material) being below the above upper limit under the conditions of a temperature of 23°C and a relative humidity of 60%, the deterioration of the frozen-packaged raw meat can be suppressed and the effect of long-term storage can be further improved. On the other hand, the oxygen transmission rate is 0 cc / (m 2 ·day·atm) or more.

[0015] The oxygen transmission rate of the multilayer film (lid material) under the conditions of a temperature of 23°C and a relative humidity of 60% can be measured in accordance with JIS K 7126-2:2006.

[0016] The oxygen transmission rate of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the types and contents of the components contained in the multilayer film, the thickness of the multilayer film, etc.

[0017] The dynamic elastic modulus E' of the multilayer film (lid material) at a temperature of 140°C is preferably 10 4 or more and 10 7 Pa or less. By the dynamic elastic modulus E' of the multilayer film (lid material) at a temperature of 140°C being 10 4 or more and 10 7 Pa or less, the followability of the lid material to the packaged object (contents) can be improved. As a result, the drip generated during thawing can be suppressed, the outflow of umami components can be prevented, and long-term storage can be achieved without reducing the taste more than before.

[0018] The dynamic elastic modulus E' of the multilayer film (lid material) at a temperature of 140°C is 1.0×104 Above 1.0×10 7 Pa, preferably below 1.1×10 4 Pa, more preferably above 9.9×10 6 Pa and below 9.8×10 4 Pa, even more preferably above 1.2×10 6 Pa and below 9.7×10 4 Pa, particularly preferably above 1.3×10 6 Pa and below 9.6×10 4 Pa. For example, it may be above 1.4×10 6 Pa and below 9.6×10. When the dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is equal to or higher than the lower limit value, the followability of the lid material to the packaged product (contained product) can be further improved. When the dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is equal to or lower than the upper limit value, the shape of the packaged product (contained product) can be packaged without being more compressed.

[0019] The dynamic elastic modulus E' of the multilayer film (lid material) at a temperature of 140°C can be measured in accordance with JIS K7244-4. Specifically, for example, it can be measured by a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Tech Sciences Corporation). Further, the measurement conditions can be, for example, using a sample with a width of 4 mm, in a tensile mode in the temperature range from 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.

[0020] The dynamic elastic modulus E' of the multilayer film (lid material) can be more easily adjusted, for example, by adjusting the type and content of the components contained in the multilayer film, the thickness of the multilayer film, etc.

[0021] It is preferable that the temperature indicating a displacement of 2000 μm during the thermomechanical analysis (TMA) of the multilayer film is 120°C or higher, or the gel fraction is 30% or higher. Thereby, the heat resistance of the multilayer film is improved, and as a result, the followability of the multilayer film to the contained product is improved.

[0022] When performing thermomechanical analysis on the multi-layer film (lid material), the temperature at which a displacement of 2000 μm is exhibited 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. When the temperature is at or above the lower limit value, the heat resistance of the multi-layer film is further improved, and as a result, the followability of the multi-layer film to the contained material is further improved. When the temperature is at or below the upper limit value, it is possible to suppress the heat resistance of the multi-layer film from becoming excessive.

[0023] When performing thermomechanical analysis on the multi-layer film, the displacement at a temperature of 100°C is preferably 500 μm or less, more preferably 40 to 500 μm, even more preferably 45 to 400 μm, and may be any one of, for example, 50 to 350 μm, 55 to 340 μm, and 55 to 250 μm. When the displacement is at or below the upper limit value, the melt tension of the multi-layer film is improved, and as a result, the followability of the multi-layer film to the contained material is further improved. When the displacement is at or above the lower limit value, it is possible to suppress the melt tension of the multi-layer film from becoming excessive.

[0024] The thermomechanical analysis of the multi-layer film can be performed by measuring the thermal expansion amount of the sample from the difference in the thermal expansion amount when the standard sample and the sample to be analyzed are heated at a constant rate in accordance with JIS K 7196.

[0025] When performing thermomechanical analysis on the multi-layer film, the temperature at which a displacement of 2000 μm is exhibited and the displacement at a temperature of 100°C can be adjusted, for example, by irradiating the multi-layer film with electron beams and adjusting the conditions of the electron beam irradiation at this time. For example, when the multi-layer film is the multi-layer film described later, the temperature and the displacement can be adjusted more easily by adjusting the conditions of the electron beam irradiation to the outer layer or the functional layer in the multi-layer film.

[0026] The multilayer film is preferably irradiated with an electron beam under the condition of an absorbed dose of 13 to 300 kGy, more preferably irradiated with an electron beam under the condition of an absorbed dose of 15 to 250 kGy. For example, it may be irradiated with an electron beam under any one of the conditions of an absorbed dose of 20 to 250 kGy, 45 to 250 kGy, and 70 to 250 kGy. When the absorbed dose is within such a range, a multilayer film in which both the temperature showing a displacement of 2000 μm and the displacement at a temperature of 100 °C are within the above numerical ranges during the thermomechanical analysis of the multilayer film can be more easily obtained. On the other hand, when the absorbed dose is equal to or higher than the lower limit value, the crosslinking density of the multilayer film (particularly, when the multilayer film is the multilayer film described later, the outer layer and the functional layer in this multilayer film) is further improved. As a result, the heat resistance and the melt tension of the entire multilayer film are further improved. When the absorbed dose is equal to or lower than the upper limit value, it is possible to suppress the strength of the multilayer film from becoming excessive.

[0027] The reason why the crosslinking density of the multilayer film (particularly, when the multilayer film is the multilayer film described later, the outer layer and the functional layer in this multilayer film) is improved by electron beam irradiation is not clear, but it is presumed as follows. That is, when the multilayer film is irradiated with an electron beam, the carbon-hydrogen bonds in the resin (for example, polyethylene, ionomer) are broken, and radicals are generated at the broken bond ends. The generated radicals come into contact with the molecular chains of other resins (for example, other polyethylene molecular chains, other ionomer molecular chains) by the molecular motion of the molecular chains, pull out hydrogen atoms, and bond to carbon atoms in the molecular chains of other resins (for example, other polyethylene molecular chains, other ionomer molecular chains). As a result, it is presumed that a crosslinked structure is formed.

[0028] 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. When the acceleration voltage during electron beam irradiation is within such a range, it is easier to obtain the multilayer film in which both the temperature showing a displacement of 2000 μm and the displacement at a temperature of 100°C are within the above-mentioned numerical ranges during the thermomechanical analysis of the multilayer film. On the other hand, when the acceleration voltage during electron beam irradiation is equal to or higher than the lower limit value, the crosslinking density of the multilayer film (particularly, when the multilayer film is the multilayer film described later, the outer layer and the functional layer in the multilayer film) is further improved. As a result, the heat resistance and the melt tension of the entire multilayer film are further improved. When the acceleration voltage during electron beam irradiation is equal to or lower than the upper limit value, it is possible to suppress the strength of the multilayer film from becoming excessive.

[0029] The gel fraction of the multilayer film is preferably 30% or more, more preferably 30 to 90%, even more preferably 32 to 85%, and may be any of, for example, 40 to 82%, 48 to 82%, and 55 to 82%. When the gel fraction of the multilayer film is equal to or higher than the lower limit value, the heat resistance and the melt tension of the multilayer film are improved. As a result, the followability to the contained material is improved. When the gel fraction of the multilayer film is equal to or lower than the upper limit value, it is possible to suppress the strength of the multilayer film from becoming excessive.

[0030] 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 that remains undissolved is dried, and then the mass of the obtained dried product is measured, and the gel fraction can be calculated from the mass of the multilayer film before dissolution and the mass of the dried product of the insoluble film. More specifically, for example, a multilayer film (mass X g) is wrapped with a stainless steel wire mesh (mass Y g) and immersed in a heated solvent, and then the multilayer film wrapped with the stainless steel wire mesh (in other words, the insoluble film) is taken out. Next, this is vacuum dried, and the mass (Z g) of the multilayer film wrapped with the stainless steel wire mesh after drying (in other words, the insoluble film) is measured. And the following formula (1): Gel fraction (mass %) of multilayer film = (Z - Y) / X × 100 (1) is used to calculate the gel fraction of the multilayer film.

[0031] The gel fraction of the multilayer film can be adjusted, for example, by irradiating the multilayer film (particularly, when the multilayer film is the multilayer film described later, the outer layer or the functional layer in this multilayer film) with electron beams and adjusting the conditions of the electron beam irradiation at this time. As the conditions at the time of electron beam irradiation in this case, the absorbed dose and the acceleration voltage of the electron beam irradiation, which are the same as those when adjusting the temperature showing a displacement of 2000 μm and the displacement at a temperature of 100°C during the thermomechanical analysis of the multilayer film described above, can be adopted.

[0032] It is preferable that the multilayer film satisfies either one or both of the conditions of the temperature showing a displacement of 2000 μm and the gel fraction during the above-described thermomechanical analysis. That is, examples of the multilayer film include those in which the temperature showing a displacement of 2000 μm during its thermomechanical analysis is 120°C or higher and the gel fraction is less than 30%; those in which the temperature showing a displacement of 2000 μm during its thermomechanical analysis is less than 120°C and the gel fraction is 30% or higher; and those in which the temperature showing a displacement of 2000 μm during its thermomechanical analysis is 120°C or higher and the gel fraction is 30% or higher. However, usually, the multilayer film preferably satisfies both of the above conditions, that is, the temperature at which the displacement of 2000 μm is shown during its thermomechanical analysis is 120°C or higher, and the gel fraction is 30% or higher.

[0033] The thickness of the multilayer film (lid material) is preferably 60 μm or more, more preferably 70 to 400 μm, still more preferably 80 to 300 μm, and may be, for example, 100 to 200 μm. When the thickness of the multilayer film is at least the lower limit value, the strength of the multilayer film is further improved. When the thickness of the multilayer film is at most the upper limit value, it is possible to suppress the thickness of the multilayer film from becoming excessive.

[0034] The multilayer film is preferably a laminated film formed by laminating a plurality of layers. Examples of the preferable multilayer film which is a laminated film include a multilayer film including an outer layer, a functional layer adjacent to the outer layer, an oxygen barrier layer, and a sealant layer.

[0035] In the multilayer film (lid material), regardless of its type, all layers have transparency, and it is preferable that the multilayer film has transparency, that is, the multilayer film is a transparent resin film. In a vacuum package for frozen raw meat configured using such a multilayer film, the raw meat as the contained material can be easily visually recognized through the multilayer film (lid material).

[0036] The more detailed configuration of the multilayer film (lid material) and its manufacturing method will be described in detail separately.

[0037] Hereinafter, the present invention will be described in more detail with reference to the drawings. Note that the drawings used in the following description may show an enlarged view of the main part for the sake of easy understanding of the features of the present invention, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0038] <<One Embodiment of Multilayer Film (Lid Material)>> FIG. 1 is a cross-sectional view schematically showing an example of the multilayer film (laminated film) among the multilayer films (lid materials) in the present embodiment. The multilayer film 1 shown here includes an outer layer 12, a functional layer 13 adjacent to the outer layer 12, an oxygen barrier layer 14, and a sealant layer 11. In the multilayer film 1, the outer layer 12 is one outermost layer, and the sealant layer 11 is the other outermost layer.

[0039] Furthermore, the multilayer film 1 includes a pinhole-resistant layer 16 disposed on the sealant layer 11, an adhesive layer 15 disposed between the pinhole-resistant layer 16 and the oxygen barrier layer 14, and an adhesive layer 15 disposed between the oxygen barrier layer 14 and the functional layer 13, from the sealant layer 11 side toward the outer layer 12 side. That is, the multilayer film 1 is configured by laminating the sealant layer 11, the pinhole-resistant layer 16, the adhesive layer 15, the oxygen barrier layer 14, the adhesive layer 15, the functional layer 13, and the outer layer 12 in this order in their thickness directions.

[0040] <Sealant Layer> The sealant layer 11 may contain a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, polyethylene-based copolymer (which may be referred to as "polyethylene-based resin in the sealant layer" in this specification). When the sealant layer 11 contains the polyethylene-based resin in the sealant layer, the easy peelability due to the pseudo-adhesiveness of the multilayer film 1 to the adherend is improved. The sealant layer 11 preferably contains an ethylene-vinyl acetate resin.

[0041] In this specification, the "polyethylene-based resin" is a resin having at least a structural unit derived from ethylene, which may have only a structural unit derived from ethylene, or may have a structural unit derived from ethylene and other structural units.

[0042] The sealant layer 11 may contain only a polyethylene-based resin in the sealant layer (that is, it may be composed of only a polyethylene-based resin in the sealant layer), or may contain a polyethylene-based resin in the sealant layer and other components (which may be referred to as "other components" in this specification).

[0043] The other components contained in the sealant layer 11 are not particularly limited and can be arbitrarily selected according to the purpose. For example, they can be either resin components or non-resin components. The other components that are resin components are resins that do not correspond to the polyethylene-based resin in the sealant layer. The other components that are resin components may be homopolymers that are polymers of one type of monomer, or may be copolymers that are polymers of two or more types of monomers.

[0044] Examples of the other components that are non-resin components include additives known in the art. Examples of the additives include antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, and the like.

[0045] The other components contained in the sealant layer 11 may be only one type, or may be two or more types. In the case of two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0046] The ratio of the content of the polyethylene-based resin in the sealant layer to the total mass of the sealant layer 11 in the sealant layer 11 is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 75 to 100% by mass, and may be, for example, 85 to 100% by mass. When the ratio is equal to or higher than the lower limit value, the easy peelability due to the pseudo-adhesion with the adherend is further improved. The ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene-based resin in the sealant layer to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the sealant layer described below.

[0047] In this specification, "room temperature" means a temperature at which it is not particularly cooled or heated, that is, the normal temperature. For example, a temperature of 15 to 25°C can be mentioned.

[0048] The sealant layer 11 may be composed of one layer (single layer) or may be composed of two or more layers. When the sealant layer 11 is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0049] In this specification, not limited to the case of the sealant layer 11, "the plurality of layers may be the same as or different from each other" means that "all the layers may be the same, all the layers may be different, or only some of the layers may be the same", and further, "the plurality of layers are different from each other" means that "at least one of the constituent materials and thicknesses of each layer is different from each other".

[0050] The thickness of the sealant layer 11 is not particularly limited, but is preferably 4 to 96 μm, more preferably 7 to 93 μm, still more preferably 10 to 90 μm, and may be any of, for example, 10 to 70 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the sealant layer 11 is equal to or greater than the lower limit value, the strength of the sealant layer 11 becomes higher. When the thickness of the sealant layer 11 is equal to or less than the upper limit value, it is possible to suppress the thickness of the sealant layer 11 from becoming excessive, and the seal strength becomes higher when the multilayer film 1 is heat-sealed. Here, the "thickness of the sealant layer 11" means the thickness of the entire sealant layer 11. For example, the thickness of the sealant layer 11 composed of a plurality of layers means the total thickness of all the layers constituting the sealant layer 11.

[0051] The exposed surface (which may be referred to as the "first surface" in this specification) 11a of the sealant layer 11 on the side opposite to the outer layer 12 side is a 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 collectively referred to as the "resin in the outer layer"). By the outer layer 12 containing the resin in the outer layer, the crosslinking density of the outer layer 12 can be improved by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side. As a result, the followability to the contents of the vacuum package for frozen raw meat constituted by using the multilayer film 1 is improved. It is preferable that the outer layer 12 contains polyethylene.

[0053] The outer layer 12 may contain only the resin in the outer layer (that is, it may be composed of the resin in the outer layer), or may contain the resin in the outer layer and other components (which may be referred to as "other components" in this specification) (that is, it may be composed of the resin in the outer layer and the said other components).

[0054] The resin in the outer layer contained in the outer layer 12 preferably has a density of 0.945 g / cm 3 or less of the following low-density polyethylene, more preferably has a density of 0.943 g / cm 3 or less of the following low-density polyethylene, and even more preferably has a density of 0.941 g / cm 3 or less of the following low-density polyethylene. By containing such low-density polyethylene (LDPE), the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side.

[0055] The resin in the outer layer 12 may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios 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 according to the purpose. For example, they can be either resin components or non-resin components. The other components that are resin components are resins other than the resin in the outer layer.

[0057] The other components included in the outer layer 12 may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0058] The ratio of the content of the resin in the outer layer to the total mass of the outer layer 12 in the outer layer 12 is preferably 50% by mass or more, more preferably 55 - 100% by mass, and even more preferably 60 - 100% by mass. For example, it may be either 70 - 100% by mass or 85 - 100% by mass. When the ratio is at least the lower limit value, the crosslinking density of the outer layer 12 can be further improved by irradiating the outer layer 12 with electron beams from the outside on the outer layer 12 side with respect to the multilayer film 1. The ratio is usually 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 the components that do not vaporize at room temperature in the outer layer-forming composition described later.

[0059] The outer layer 12 may be composed of one layer (single layer) or may be composed of two or more layers. When the outer layer 12 is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[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, still more preferably 10 to 140 μm, and may be any of, for example, 10 to 110 μm, 10 to 100 μm, 10 to 90 μm, 10 to 80 μm, and 10 to 70 μm. When the thickness of the outer layer 12 is equal to or greater than the lower limit value, the crosslinking density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side. When the thickness of the outer layer 12 is equal to or less than the upper limit value, it is possible to suppress the thickness of the outer layer 12 from becoming excessive. Here, the "thickness of the outer layer 12" means the total thickness of the entire outer layer 12. For example, the thickness of the outer layer 12 composed of multiple layers means the total thickness of all the layers constituting 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 to 88%, and still more preferably 14 to 86%. When the ratio is equal to or greater than the lower limit value, the effect obtained by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side becomes higher. When the ratio is equal to or less than the upper limit value, it is possible to suppress the thickness of the outer layer 12 from becoming excessive.

[0062] <Functional layer> The functional layer 13 contains a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, and polyethylene-based copolymer (which may be referred to as "polyethylene-based resin in the functional layer" in this specification), and may be adjacent to the outer layer 12. Since the functional layer 13 contains a polyethylene-based resin in the functional layer, when the multilayer film 1 is irradiated with electron beams from the outside on the outer layer 12 side, the crosslinking density of the functional layer 13 can be improved. As a result, the followability of the vacuum package for frozen raw meat constituted by using the multilayer film 1 to the contents is further improved. The functional layer 13 preferably contains an ionomer.

[0063] The functional layer 13 may contain only a polyethylene-based resin in the functional layer (i.e., it may be composed of a polyethylene-based resin in the functional layer), or may contain a polyethylene-based resin in the functional layer and other components (which may be referred to as "other components" in this specification).

[0064] Examples of the polyethylene-based resin in the functional layer contained in the functional layer 13 include resins having an ion cross-linked structure formed by salt formation between the acid portion therein and metal ions, such as copolymers of ethylene and a small amount of acrylic acid or methacrylic acid.

[0065] Examples of the metal ions include sodium ions, zinc ions, etc. In this specification, an ionomer when the metal ion is a sodium ion may be referred to as a sodium-based ionomer, and an ionomer when the metal ion is a zinc ion may be referred to as a zinc-based ionomer.

[0066] The polyethylene-based resin in the functional layer contained in the functional layer 13 may be only one type, or may be two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0067] The other components contained in the functional layer 13 are not particularly limited and can be arbitrarily selected according to the purpose. For example, they can be either resin components or non-resin components. The other component that is a resin component is a resin other than the polyethylene-based resin in the functional layer.

[0068] The other components contained in the functional layer 13 may be only one type, or may be two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0069] In the functional layer 13, the ratio of the content of the polyethylene-based resin in the functional layer to the total mass of the functional layer 13 is preferably 50% by mass or more, more preferably 55 to 100% by mass, even more preferably 60 to 100% by mass, and may be, for example, either 70 to 100% by mass or 85 to 100% by mass. When the ratio is at least the lower limit value, the crosslinking density of the functional layer 13 can be further improved by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side. The ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene-based resin in the functional layer to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the functional layer described below.

[0070] The functional layer 13 may be composed of one layer (single layer) or may be composed of two or more layers. When the functional layer 13 is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0071] The thickness of the functional layer 13 is preferably 4 to 146 μm, more preferably 7 to 143 μm, even more preferably 10 to 140 μm, and may be, for example, any one of 10 to 110 μm, 10 to 80 μm, 10 to 50 μm, and 10 to 30 μm. When the thickness of the functional layer 13 is at least the lower limit value, the crosslinking density of the functional layer 13 can be further improved by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side. When the thickness of the functional layer 13 is at most the upper limit value, it is possible to suppress the thickness of the functional layer 13 from becoming excessive. Here, the "thickness of the functional layer 13" means the total thickness of the functional layer 13. For example, the thickness of the functional layer 13 composed of a plurality of layers means the total thickness of all the layers constituting the functional layer 13.

[0072] The ratio of the thickness of the functional layer 13 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11 to 89%, and even more preferably 12 to 88%. When the ratio is at least the lower limit value, the effect obtained by irradiating the multilayer film 1 with electron beams from the outside on the outer layer 12 side becomes higher. When the ratio is at most the upper limit value, it is possible to suppress the thickness of the functional layer 13 from becoming excessive.

[0073] <Oxygen barrier layer> The oxygen barrier layer 14 imparts strong oxygen barrier properties (in other words, the property of suppressing the permeation of oxygen gas) to the multilayer film 1.

[0074] The oxygen barrier layer 14 preferably contains an ethylene-vinyl alcohol copolymer (EVOH, also known as: saponified ethylene-vinyl acetate copolymer) or polyvinylidene chloride (PVDC) (in this specification, EVOH and PVDC may be collectively referred to as "oxygen barrier property-imparting resin"). The oxygen barrier property of the multilayer film 1 provided with such an oxygen barrier layer 14 becomes higher.

[0075] The oxygen barrier layer 14 may contain only the oxygen barrier property-imparting resin (that is, it may be composed of the oxygen barrier property-imparting resin), or may contain the oxygen barrier property-imparting resin and other components (in this specification, may be referred to as "other components") (that is, it may be composed of the oxygen barrier property-imparting resin and the other components).

[0076] The other components contained in the oxygen barrier layer 14 are not particularly limited and can be arbitrarily selected according to the purpose. For example, they may be either a resin component or a non-resin component. The other component that is a resin component is a resin other than the oxygen barrier property-imparting resin. Examples of the other component that is a non-resin component include the same additives as those previously listed as the other components contained in the sealant layer 11.

[0077] The other components included in the oxygen barrier layer 14 may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0078] In the oxygen barrier layer 14, the proportion of the content of the oxygen barrier property-imparting resin with respect to the total mass of the oxygen barrier layer 14 is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, still more preferably 70 to 100% by mass. For example, it may be 85 to 100% by mass. When the proportion is at least the lower limit value, the oxygen barrier property of the multilayer film 1 becomes higher. The proportion is usually the same as the proportion of the content (parts by mass) of the oxygen barrier property-imparting resin with respect to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the oxygen barrier layer described later.

[0079] The oxygen barrier layer 14 may be composed of one layer (single layer) or may be composed of two or more layers. When the oxygen barrier layer 14 is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0080] The thickness of the oxygen barrier layer 14 is preferably 1 to 100 μm, more preferably 1.5 to 90 μm, still more preferably 2 to 80 μm. For example, it may be any one of 4 to 60 μm, 4 to 40 μm, and 4 to 20 μm. When the thickness of the oxygen barrier layer 14 is at least the lower limit value, the oxygen barrier property of the multilayer film 1 becomes higher. When the thickness of the oxygen barrier layer 14 is at most the upper limit value, it is possible to suppress the thickness of the oxygen barrier layer 14 from becoming excessive. Here, the "thickness of the oxygen barrier layer 14" means the total thickness of the entire oxygen barrier layer 14. For example, the thickness of the oxygen barrier layer 14 composed of a plurality of layers means the total thickness of all the layers constituting the oxygen barrier layer 14.

[0081] The ratio of the thickness of the oxygen barrier layer 14 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 1% or more, more preferably 2 to 30%, and even more preferably 3 to 25%. When the ratio is at least the lower limit value, the oxygen barrier property of the multilayer film 1 becomes higher. When the ratio is at most the upper limit value, it is possible to suppress the thickness of the oxygen barrier layer 14 from becoming excessive.

[0082] In the case of a skin pack package for food, in order to suppress oxidative deterioration of the food, it is required that the multilayer film constituting the skin pack package is provided with an oxygen barrier layer. However, there has been a problem that the followability of the skin pack package to the food (the property of closely adhering to the food without causing wrinkles) decreases due to the presence of the oxygen barrier layer. On the other hand, in the skin pack package constituted by using the multilayer film 1 of the present embodiment including the outer layer 12 and the functional layer 13, such a problem is improved. The reason is that due to the presence of the outer layer 12 and the functional layer 13, the heat resistance and melt tension of the multilayer film 1 are improved, and as a result, the multilayer film 1 is excellent in followability to the contents.

[0083] <Adhesive layer> The adhesive layer 15 contains an adhesive. The adhesive layer 15 adheres the two layers adjacent to both sides thereof. In the multilayer film 1, the adhesive layer 15 disposed between the pinhole resistant layer 16 and the oxygen barrier layer 14 adheres the pinhole resistant layer 16 and the oxygen barrier layer 14, and the adhesive layer 15 disposed between the oxygen barrier layer 14 and the functional layer 13 adheres the oxygen barrier layer 14 and the functional layer 13. In this specification, in order to distinguish these two adhesive layers 15 from each other, if necessary, the adhesive layer 15 disposed between the pinhole resistant layer 16 and the oxygen barrier layer 14 may be referred to as the first adhesive layer 151, and the adhesive layer 15 disposed between the oxygen barrier layer 14 and the functional layer 13 may be referred to as the second adhesive layer 152. These two adhesive layers 15 (the first adhesive layer 151 and the second adhesive layer 152) may be the same as or different from each other.

[0084] The adhesive included in the adhesive layer 15 is not particularly limited as long as it can bond two layers to be bonded with sufficient strength. Examples of the adhesive include adhesive resins such as olefin resins (i.e., polymers of olefins that are one or more monomers).

[0085] More specifically, examples of the olefin resin included in the adhesive layer 15 include ethylene copolymers, propylene copolymers, butene copolymers, and the like. The ethylene copolymer is a copolymer of ethylene and a monomer other than ethylene. The propylene copolymer is a copolymer of propylene and a monomer other than propylene. The butene copolymer is a copolymer of butene and a monomer other than butene.

[0086] Examples of the ethylene copolymer included in the adhesive layer 15 include copolymers of ethylene and vinyl group-containing monomers. Examples of the copolymer of ethylene and a vinyl group-containing monomer 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), ionomer (ION), ethylene-based thermoplastic elastomer, and the like. Examples of the ionomer include the same ionomers as those previously mentioned as included in the functional layer 13.

[0087] Examples of the propylene copolymer included in the adhesive layer 15 include copolymers of propylene and vinyl group-containing monomers. Examples of the copolymer of propylene and a vinyl group-containing monomer include maleic anhydride graft-modified linear low-density polypropylene, propylene-based thermoplastic elastomer, and the like.

[0088] Examples of the butene-based copolymer contained in the adhesive layer 15 include a copolymer of 1-butene and a vinyl group-containing monomer, a copolymer of 2-butene and a vinyl group-containing monomer, and modified products (modified copolymers) of these copolymers.

[0089] The adhesive layer 15 may contain only an adhesive (i.e., it may be composed of an adhesive), or may contain an adhesive and other components (which may be referred to as "other components" in this specification).

[0090] The adhesive contained in the adhesive layer 15 may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0091] The other components contained in the adhesive layer 15 are not particularly limited and can be arbitrarily selected according to the purpose. For example, they may be either a resin component or a non-resin component.

[0092] The other components contained in the adhesive layer 15 may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0093] The ratio of the content of the adhesive to the total mass of the adhesive layer 15 in the adhesive layer 15 may be, for example, 50 to 100% by mass. Usually, the ratio is the same as the ratio of the content (parts by mass) of the adhesive to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the adhesive layer described below.

[0094] The adhesive layer 15 may consist of one layer (single layer) or may consist of a plurality of two or more layers. When the adhesive layer 15 consists of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0095] The thickness of the adhesive layer 15 is preferably 4 to 96 μm, more preferably 7 to 93 μm, and may be, for example, any of 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 equal to or greater than the lower limit value, the adhesive strength between the two layers to be adhered becomes higher. When the thickness of the adhesive layer 15 is equal to or less than the upper limit value, it is possible to suppress the thickness of the adhesive layer 15 from becoming excessive. Here, the "thickness of the adhesive layer 15" means the thickness of the entire adhesive layer 15 (for example, the thickness of the entire adhesive layer 15 disposed between the pinhole-resistant layer 16 and the oxygen barrier layer 14, the thickness of the entire adhesive layer 15 disposed between the oxygen barrier layer 14 and the functional layer 13), and for example, the thickness of the adhesive layer 15 composed of a plurality of layers means the total thickness of all the layers constituting the adhesive layer 15.

[0096] <Pinhole-resistant layer> The multilayer film 1 may not include the pinhole-resistant layer 16, but by including the pinhole-resistant layer 16, its pinhole resistance becomes higher. And in the package formed using this multilayer film 1, it is possible to suppress a decrease in strength during the heat treatment.

[0097] The pinhole-resistant layer 16 preferably contains a polyethylene-based resin such as an ionomer, ethylene-vinyl acetate copolymer (EVA), polyethylene, or a polyethylene-based copolymer (which may be referred to as "the polyethylene-based resin in the pinhole-resistant layer" in this specification). When the pinhole-resistant layer 16 contains the polyethylene-based resin in the pinhole-resistant layer, the pinhole resistance of the multilayer film 1 becomes higher, and when the multilayer film 1 is irradiated with an electron beam from the outside on the outer layer 12 side, the crosslink density of the pinhole-resistant layer 16 can be improved. As a result, the followability of the vacuum package for frozen fresh meat constituted by using the multilayer film 1 to the contents is further improved.

[0098] The pinhole-resistant layer 16 may contain only the polyethylene-based resin in the pinhole-resistant layer (that is, it may be composed of the polyethylene-based resin in the pinhole-resistant layer), or may contain the polyethylene-based resin in the pinhole-resistant layer and other components (which may be referred to as "other components" in this specification) (that is, it may be composed of the polyethylene-based resin in the pinhole-resistant layer and the said other components).

[0099] The polyethylene-based resin in the pinhole-resistant layer contained in the pinhole-resistant layer 16 may be only one kind, or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0100] The said other components contained in the pinhole-resistant layer 16 are not particularly limited and can be arbitrarily selected according to the purpose. For example, they may be either a resin component or a non-resin component. The said other components that are resin components are resins other than the polyethylene-based resin in the pinhole-resistant layer.

[0101] The said other components contained in the pinhole-resistant layer 16 may be only one kind, or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0102] In the pinhole-resistant layer 16, the ratio of the content of the polyethylene-based resin in the pinhole-resistant layer to the total mass of the pinhole-resistant layer 16 is preferably 50% by mass or more, more preferably 55 to 100% by mass, still more preferably 60 to 100% by mass, and may be, for example, either 70 to 100% by mass or 85 to 100% by mass. When the ratio is at least the lower limit value, the effect obtained by the multilayer film 1 containing the polyethylene-based resin in the pinhole-resistant layer becomes higher. Usually, the ratio is the same as the ratio of the content (parts by mass) of the polyethylene-based resin in the pinhole-resistant layer to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the pinhole-resistant layer described later.

[0103] The pinhole-resistant layer 16 may be composed of one layer (single layer) or may be composed of two or more layers. When the pinhole-resistant layer 16 is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0104] The thickness of the pinhole-resistant layer 16 is preferably 4 to 146 μm, more preferably 7 to 143 μm, still more preferably 10 to 140 μm, and may be, for example, any one of 10 to 110 μm, 10 to 80 μm, and 10 to 50 μm. When the thickness of the pinhole-resistant layer 16 is at least the lower limit value, the pinhole resistance of the multilayer film 1 becomes higher. When the thickness of the pinhole-resistant layer 16 is at most the upper limit value, it is possible to suppress the thickness of the pinhole-resistant layer 16 from becoming excessive. Here, the "thickness of the pinhole-resistant layer 16" means the total thickness of the entire pinhole-resistant layer 16. For example, the thickness of the pinhole-resistant layer 16 composed of a plurality of layers means the total thickness of all the layers constituting the pinhole-resistant layer 16.

[0105] The ratio of the thickness of the pinhole-resistant layer 16 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11 to 89%, and even more preferably 12 to 88%. When the ratio is at least the lower limit value, the pinhole resistance of the multilayer film 1 becomes higher. When the ratio is at most the upper limit value, it is possible to suppress the thickness of the pinhole-resistant layer 16 from becoming excessive.

[0106] <Other layer> The multilayer film 1 may include another layer that does not correspond to any of the sealant layer 11, the outer layer 12, the functional layer 13, the oxygen barrier layer 14, the adhesive layer 15, and the pinhole-resistant layer 16 within a range that does not impair the effects of the present invention.

[0107] The type and arrangement position of the other layer are not particularly limited and can be arbitrarily selected according to the purpose.

[0108] The multilayer film 1 may include only one type of the other layer or two or more types of the other layer. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0109] Each of the other layers may be composed of one layer (single layer) or two or more layers. When the other layer is composed of a plurality of layers, these layers may be the same as or different from each other, and the combinations of these layers are not particularly limited as long as the effects of the present invention are not impaired.

[0110] The thickness of the other layer can be arbitrarily set according to its type and is not particularly limited.

[0111] When the multilayer film 1 includes the other layer, it may further include an adhesive layer (for example, the adhesive layer 15, etc.) for adhering the other layer to the other layers.

[0112] The thickness of the multilayer film 1 is the same as the thickness of the multilayer film (lid material) described above.

[0113] The multilayer film in this embodiment is not limited to the above, and within the scope not departing from the gist of the present invention, some configurations may be changed, deleted, or added. For example, the multilayer film may not include any one or two or more of a pinhole resistant layer, an adhesive layer, and a functional layer. However, as shown in FIG. 1, it is preferable that the multilayer film includes a sealant layer, a pinhole resistant layer, an adhesive layer, an oxygen barrier layer, an adhesive layer, a functional layer, and an outer layer in this order.

[0114] <<Method for manufacturing multilayer film (lid material)>> The multilayer film (lid material) can be manufactured by a known method according to its type. For example, laminated films such as the multilayer film can be manufactured by a feed block method in which resins, resin compositions, etc. that are forming materials for each layer are melt-extruded using several extruders, a coextrusion T-die method such as a multi-manifold method, an air-cooled or water-cooled coextrusion inflation method, or the like.

[0115] In addition, the laminated film can be manufactured by coating a resin, a resin composition, etc. that is a forming material for any one of the layers on the surface of another layer constituting the laminated film, drying it as necessary to form a laminated structure in the laminated film, and further laminating these other layers as necessary so as to have a desired arrangement form.

[0116] In addition, the laminated film can be manufactured by separately preparing two or more films for constituting any two or more of them in advance, and laminating these films by any one of a dry lamination method, an extrusion lamination method, a hot melt lamination method, and a wet lamination method using an adhesive, and further laminating these other layers as necessary so as to have a desired arrangement form. At this time, an adhesive capable of forming the adhesive layer may be used as the adhesive.

[0117] Further, as described above, the laminated film can be manufactured by laminating two or more films prepared separately in advance without using an adhesive by a thermal (heat) lamination method or the like, and further laminating other layers as needed so as to have a desired arrangement form.

[0118] When manufacturing the laminated film, two or more of the formation methods of any layer (film) in the laminated film listed so far may be combined.

[0119] Regardless of the manufacturing method, the resin composition that is the formation material of any layer in the laminated film may be manufactured by adjusting the types and contents of the contained components so that the layer to be formed contains the target components (constituent materials) in the target contents. For example, the ratio of the contents of the components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the contents of the components in the layer formed from this resin composition.

[0120] Examples of the resin composition for forming the sealant layer (sealant layer 11 in the multilayer film 1 shown in FIG. 1, which may be referred to as "sealant layer forming composition" in this specification) include those containing a polyethylene-based resin in the sealant layer and, if necessary, the other components.

[0121] Examples of the resin composition for forming the outer layer (outer layer 12 in the multilayer film 1 shown in FIG. 1, which may be referred to as "outer layer forming composition" in this specification) include those containing a resin in the outer layer and, if necessary, the other components.

[0122] Examples of the resin composition for forming the functional layer (functional layer 13 in the multilayer film 1 shown in FIG. 1, which may be referred to as "functional layer forming composition" in this specification) include those containing a polyethylene-based resin in the functional layer and, if necessary, the other components.

[0123] As the resin composition for forming an oxygen barrier layer (in the multilayer film 1 shown in FIG. 1, the oxygen barrier layer 14) (which may be referred to as the "composition for forming an oxygen barrier layer" in this specification), for example, those containing the oxygen barrier property-imparting resin and, if necessary, the other components may be mentioned.

[0124] As the resin composition for forming a pinhole-resistant layer (in the multilayer film 1 shown in FIG. 1, the pinhole-resistant layer 16) (which may be referred to as the "composition for forming a pinhole-resistant layer" in this specification), for example, those containing the polyethylene-based resin in the pinhole-resistant layer and, if necessary, the other components may be mentioned.

[0125] As the resin composition for forming an adhesive layer (in the multilayer film 1 shown in FIG. 1, the adhesive layer 15) (which may be referred to as the "composition for forming an adhesive layer" in this specification), for example, those containing the adhesive and, if necessary, the other components may be mentioned.

[0126] <<Substrate>> The substrate is not particularly limited as long as its oxygen transmission rate is 300 cc / (m 2 ·day·atm) or less and it can be used as a substrate for a vacuum package for frozen raw meat. The substrate may be a known one.

[0127] The oxygen transmission rate of the substrate under the conditions of a temperature of 23°C and a relative humidity of 60% is 300 cc / (m 2 ·day·atm) or less, preferably 260 cc / (m 2 ·day·atm) or less, for example, it may be any of 200 cc / (m 2 ·day·atm) or less, 150 cc / (m 2 ·day·atm) or less, 100 cc / (m 2 ·day·atm) or less, and 50 cc / (m 2 ·day·atm) or less. On the other hand, the oxygen transmission rate is 0 cc / (m 2 ·day·atm) or more.

[0128] The oxygen transmission rate of the base material under the conditions of a temperature of 23°C and a relative humidity of 60% can be measured in accordance with JIS K 7126-2:2006.

[0129] The oxygen transmission rate of the base material can be more easily adjusted, for example, by adjusting the type and content of the components contained in the base material, the thickness of the base material, etc.

[0130] 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. When the thickness of the base material is at or above the lower limit value, the strength of the base material is further improved. The thickness of the base material is preferably 6000 μm or less. When the thickness of the base material is at or below the upper limit value, it is possible to suppress the thickness of the base material from becoming excessive. The thickness of the base material can be appropriately adjusted within a range set by arbitrarily combining any of the above lower limit values and the upper limit value.

[0131] In the base material, regardless of its type, all layers may have transparency, and the base material may have transparency, or all layers or some layers may not have transparency, and the base material may not have transparency. In a vacuum package for frozen raw meat composed of a transparent base material, the raw meat as the contained material can be easily visually recognized through the base material.

[0132] The more detailed configuration of the base material and its manufacturing method will be described in detail separately.

[0133] <<An Embodiment of the Base Material>> The base material is preferably a laminate formed by laminating a plurality of layers. Preferred examples of the base material that is a laminate include, for example, a resin laminate including a foamed resin layer and a non-foamed resin layer provided on the foamed resin layer.

[0134] The foamed resin layer may be a known one. Examples of the foamed resin layer include a resin layer containing a foam of a polystyrene-based resin (PSP).

[0135] The density of the foamed resin layer is not particularly limited, but is preferably 0.05 to 0.5 g / cm 3 . 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.

[0136] Examples of the non-foamed resin layer include a multilayer film for a substrate in which an easy-peel layer, an oxygen barrier layer, a pinhole-resistant layer, and an adhesive layer are laminated in this order in the thickness direction thereof. In the multilayer film for a substrate, the easy-peel layer is one outermost layer, and the adhesive layer is the other outermost layer.

[0137] The multilayer film for a substrate may include, for example, an intermediate adhesive layer for bonding these two layers between the easy-peel layer and the oxygen barrier layer. Further, the multilayer film for a substrate may include, for example, an intermediate adhesive layer for bonding these two layers between the oxygen barrier layer and the pinhole-resistant layer. That is, the multilayer film for a substrate may be laminated and configured in the thickness direction in this order with an easy-peel layer, an intermediate adhesive layer, an oxygen barrier layer, an intermediate adhesive layer, a pinhole-resistant layer, and an adhesive layer.

[0138] In this specification, in order to distinguish between these two intermediate adhesive layers, if necessary, the intermediate adhesive layer disposed between the easy-peel layer and the oxygen barrier layer is referred to as a first intermediate adhesive layer, and the intermediate adhesive layer disposed between the oxygen barrier layer and the pinhole-resistant layer may be referred to as a second intermediate adhesive layer. These two intermediate adhesive layers (the first intermediate adhesive layer and the second intermediate adhesive layer) may be the same as or different from each other.

[0139] <Easy peel layer> Examples of the easy peel layer in the multilayer film for a substrate include those showing peelability due to cohesive failure. Examples of the easy peel layer showing peelability due to cohesive failure include those containing two incompatible polyolefins.

[0140] Examples of the two incompatible polyolefins contained in the easy peel layer in the multilayer film for a substrate include an ethylene-based polymer having at least a structural unit derived from ethylene and a propylene-based polymer having at least a structural unit derived from propylene. That is, examples of the easy peel layer include those containing an ethylene-based polymer having at least a structural unit derived from ethylene and a propylene-based polymer having at least a structural unit derived from propylene.

[0141] Examples of the ethylene-based polymer contained in the easy peel layer in the multilayer film for a substrate include a homopolymer of ethylene and an ethylene-based copolymer.

[0142] Examples of the homopolymer of ethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene-catalyzed linear low density polyethylene (mLLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), etc.

[0143] The ethylene-based copolymer has a structural unit derived from ethylene and a structural unit derived from a monomer other than ethylene. Examples of the ethylene-based copolymer 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), ionomer (ION), and the like. Examples of the ionomer include the same ionomers as those previously mentioned as being included in the functional layer 13 in the multilayer film 1 described above.

[0144] The easy-peel layer in the multilayer film for the substrate preferably contains low-density polyethylene as the ethylene-based polymer. The easy-peel property of such an easy-peel layer is better.

[0145] Examples of the propylene-based polymer included in the easy-peel layer in the multilayer film for the substrate include a homopolymer of propylene (i.e., polypropylene or homopolypropylene, hPP) and a propylene-based copolymer.

[0146] The propylene-based copolymer has a structural unit derived from propylene and a structural unit derived from a monomer other than propylene. Examples of the propylene-based copolymer include a propylene-ethylene random copolymer (also known as polypropylene random copolymer, rPP), a propylene-ethylene block copolymer (also known as polypropylene block copolymer, bPP), and the like.

[0147] The easy-peel layer in the multilayer film for the substrate preferably contains polypropylene as the propylene-based polymer. The easy-peel property of such an easy-peel layer is better.

[0148] The component(s) that exhibit easy peelability and are included in the easy peel layer in the multilayer film for a substrate may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose. For example, when the components that exhibit easy peelability are the above-mentioned two incompatible polyolefins, each of these polyolefins included in the easy peel layer may be only one kind or two or more kinds.

[0149] In the easy peel layer in the multilayer film for a substrate, the ratio of the content (parts by mass) of the ethylene-based polymer to the total content (parts by mass) of the ethylene-based polymer and the propylene-based polymer is preferably 10 to 90% by mass, and may be any of, for example, 30 to 90% by mass, 45 to 90% by mass, and 60 to 90% by mass. When the ratio is at least the lower limit value, the easy peelability of the easy peel layer becomes better. When the ratio is at most the upper limit value, the peel strength becomes more stable. Usually, the ratio is the same as the ratio of the content (parts by mass) of the ethylene-based polymer to the total content (parts by mass) of the ethylene-based polymer and the propylene-based polymer in the composition for forming the easy peel layer for a substrate described below.

[0150] The easy peel layer in the multilayer film for a substrate may contain other components in a range that does not impair the easy peelability, in addition to the component(s) that exhibit easy peelability (for example, the above-mentioned two incompatible polyolefins). The other components included in the easy peel layer may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0151] In the easy peel layer of the multilayer film for a substrate, the ratio of the content of the component that exhibits easy peelability to the total mass of the easy peel layer (for example, the ratio of the total content of the above-mentioned two incompatible polyolefins) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and may be any of, for example, 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. When the ratio is equal to or higher than the lower limit value, the easy peelability of the easy peel layer becomes better. Usually, the ratio is the same as the ratio of the content (parts by mass) of the component that exhibits easy peelability to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the easy peel layer for a substrate described below.

[0152] Examples of the other components included in the easy peel layer in the multilayer film for a substrate include an anti-fogging agent, an anti-blocking agent, and the like.

[0153] The easy peel layer in the multilayer film for a substrate may be composed of one layer (single layer) or may be composed of two or more layers. When the easy peel layer is composed of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0154] The thickness of the easy peel layer in the multilayer film for a substrate is preferably 2 to 50 μm. When the thickness of the easy peel layer is equal to or higher than the lower limit value, the seal strength of the easy peel layer becomes moderately high. When the thickness of the easy peel layer is equal to or lower than the upper limit value, the easy peelability becomes higher. Here, the "thickness of the easy peel layer" means the thickness of the entire easy peel layer. For example, the thickness of the easy peel layer composed of a plurality of layers means the total thickness of all the layers constituting the easy peel layer.

[0155] The ratio of the thickness of the easy-peel layer to the thickness of the multilayer film for the substrate is not particularly limited, but is preferably 5 to 40%. When the ratio is at least the lower limit value, the seal strength of the easy-peel layer becomes moderately high. When the ratio is at most the upper limit value, the easy-peel property becomes higher.

[0156] <Oxygen barrier layer> The oxygen barrier layer imparts oxygen barrier properties (in other words, the property of suppressing the permeation of oxygen gas) to the multilayer film for the substrate.

[0157] The oxygen barrier layer in the multilayer film for the substrate preferably contains an ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer) or polyamide.

[0158] Examples of the polyamide 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, a copolymer of 6-nylon and 66-nylon (nylon 6 / 66), a copolymer of 6-nylon and 610-nylon, a copolymer of 6-nylon and 611-nylon, a copolymer of 6-nylon and 12-nylon (nylon 6 / 12), a copolymer of 6-nylon and 612-nylon, a copolymer of 6-nylon and 6T-nylon, a copolymer of 6-nylon and 6I-nylon, a copolymer of 6-nylon, 66-nylon and 610-nylon, a copolymer of 6-nylon, 66-nylon and 12-nylon (nylon 6 / 66 / 12), a copolymer of 6-nylon, 66-nylon and 612-nylon, a copolymer of 66-nylon and 6T-nylon, a copolymer of 66-nylon and 6I-nylon, a copolymer of 6T-nylon and 6I-nylon, a copolymer of 66-nylon, 6T-nylon and 6I-nylon, etc.

[0159] In terms of heat resistance, mechanical strength, ease of availability, etc., the polyamide is preferably 6-nylon (which may be abbreviated as "Ny6" in this specification), 12-nylon, 66-nylon, nylon 6 / 66, nylon 6 / 12 or nylon 6 / 66 / 12.

[0160] The polyamide contained in the oxygen barrier layer in the multilayer film for the substrate may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0161] The oxygen barrier layer in the multilayer film for the substrate may contain only one or both of the ethylene-vinyl alcohol copolymer and the polyamide (that is, it may be composed of only one or both of the ethylene-vinyl alcohol copolymer and the polyamide), or may contain one or both of the ethylene-vinyl alcohol copolymer and the polyamide and other components (which may be referred to as "other components" in this specification) (that is, it may be composed of one or both of the ethylene-vinyl alcohol copolymer and the polyamide and the said other components).

[0162] The said other components contained in the oxygen barrier layer in the multilayer film for the substrate are not particularly limited and can be arbitrarily selected according to the purpose. For example, they may be either resin components or non-resin components. The said other components that are resin components are resins that do not correspond to either the ethylene-vinyl alcohol copolymer or the polyamide. Examples of the said other components that are non-resin components include the same additives as those listed above as the other components contained in the sealant layer 11 in the multilayer film 1 described above.

[0163] The other components contained in the oxygen barrier layer in the multilayer film for the substrate may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0164] In the oxygen barrier layer in the multilayer film for a substrate, the ratio of the total content of the ethylene-vinyl alcohol copolymer and the polyamide to the total mass of the oxygen barrier layer is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and may be, for example, either 70 to 100% by mass or 85 to 100% by mass. Usually, the above ratio is the same as the ratio of the total content (parts by mass) of the ethylene-vinyl alcohol copolymer and the polyamide to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the oxygen barrier layer for a substrate, which will be described later.

[0165] The oxygen barrier layer in the multilayer film for a substrate may consist of one layer (single layer) or may consist of two or more layers. When the oxygen barrier layer consists of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0166] The thickness of the oxygen barrier layer in the multilayer film for a substrate is preferably 2 to 20 μm. When the thickness of the oxygen barrier layer is at least the above lower limit value, the oxygen barrier property of the oxygen barrier layer becomes higher. When the thickness of the oxygen barrier layer is at most the above upper limit value, it is possible to suppress the thickness of the oxygen barrier layer from becoming excessive. Here, the "thickness of the oxygen barrier layer" means the thickness of the entire oxygen barrier layer. For example, the thickness of the oxygen barrier layer composed of a plurality of layers means the total thickness of all the layers constituting the oxygen barrier layer.

[0167] The ratio of the thickness of the oxygen barrier layer to the thickness of the multilayer film for a substrate is not particularly limited, but is preferably 5 to 15%. When the ratio is at least the above lower limit value, the oxygen barrier property of the multilayer film for a substrate becomes higher. When the ratio is at most the above upper limit value, it is possible to suppress the thickness of the oxygen barrier layer from becoming excessive.

[0168] <Pinhole-resistant layer> The pinhole-resistant layer is a layer for protecting the structure of the multilayer film for substrate, such as suppressing the generation of pinholes in the multilayer film for substrate.

[0169] The pinhole-resistant layer in the multilayer film for substrate preferably contains a polyolefin. Examples of the polyolefin 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.

[0170] The pinhole-resistant layer in the multilayer film for substrate may contain only a polyolefin (i.e., may be composed of a polyolefin), or may contain a polyolefin and other components (which may be referred to as "other components" in this specification).

[0171] The other components contained in the pinhole-resistant layer in the multilayer film for substrate are not particularly limited and can be arbitrarily selected according to the purpose. For example, they may be either resin components or non-resin components. The other components that are resin components are resins other than polyolefins. Examples of the other components that are non-resin components include the same additives as those previously listed as the other components contained in the sealant layer 11 in the multilayer film 1 described above.

[0172] The other components contained in the pinhole-resistant layer in the multilayer film for substrate may be only one type, or may be two or more types. In the case of two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0173] In the pinhole-resistant layer in the multilayer film for a substrate, the ratio of the content of the polyolefin 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, either 70 to 100% by mass or 85 to 100% by mass. Usually, the ratio is the same as the ratio of the content (parts by mass) of the polyolefin to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the pinhole-resistant layer for a substrate, which will be described later.

[0174] The pinhole-resistant layer in the multilayer film for a substrate may consist of one layer (single layer) or may consist of two or more layers. When the pinhole-resistant layer consists of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0175] The thickness of the pinhole-resistant layer in the multilayer film for a substrate is preferably 2 to 50 μm. When the thickness of the pinhole-resistant layer is equal to or greater than the lower limit value, the protective ability of the pinhole-resistant layer becomes higher. When the thickness of the pinhole-resistant layer is equal to or less than the upper limit value, it is possible to suppress the thickness of the pinhole-resistant layer from becoming excessive. Here, the "thickness of the pinhole-resistant layer" means the total thickness of the pinhole-resistant layer. For example, the thickness of a pinhole-resistant layer composed of a plurality of layers means the total thickness of all the layers constituting the pinhole-resistant layer.

[0176] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multilayer film for a substrate is not particularly limited, but is preferably 5 to 40%. When the ratio is equal to or greater than the lower limit value, the pinhole resistance of the multilayer film for a substrate becomes higher. When the ratio is equal to or less than the upper limit value, it is possible to suppress the thickness of the pinhole-resistant layer from becoming excessive.

[0177] <Adhesive layer> The adhesive layer is a layer for adhering the multilayer film for a substrate to the foamed resin layer and contains an adhesive.

[0178] The adhesive is preferably an adhesive resin, more preferably an ethylene-vinyl acetate copolymer resin system. The ethylene-vinyl acetate copolymer resin system has a structural unit derived from ethylene and a structural unit derived from vinyl acetate, and may or may not have other structural units other than these. Preferred examples of the ethylene-vinyl acetate copolymer resin system include partially saponified ethylene-vinyl acetate copolymers.

[0179] The adhesive layer in the multilayer film for the substrate may contain only the adhesive (i.e., it may be composed of only the adhesive), or may contain the adhesive and other components (which may be referred to as "other components" in this specification).

[0180] The adhesive contained in the adhesive layer in the multilayer film for the substrate may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0181] The other components contained in the adhesive layer in the multilayer film for the substrate are not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, either a resin component or a non-resin component.

[0182] The other components contained in the adhesive layer in the multilayer film for the substrate may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0183] The ratio of the content of the adhesive to the total mass of the adhesive layer in the adhesive layer in the multilayer film for the substrate may be, for example, 50 to 100% by mass. The ratio is usually the same as the ratio of the content (parts by mass) of the adhesive to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the adhesive layer for the base material, which will be described later.

[0184] The adhesive layer in the multilayer film for the base material may consist of one layer (single layer) or may consist of two or more layers. When the adhesive layer consists of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0185] The thickness of the adhesive layer in the multilayer film for the base material is preferably 2 to 40 μm. When the thickness of the adhesive layer is at least the lower limit value, the adhesive strength between the two layers to be adhered becomes higher. When the thickness of the adhesive layer is at most the upper limit value, it is possible to suppress the thickness of the adhesive layer from becoming excessive. Here, the "thickness of the adhesive layer" means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer composed of a plurality of layers means the total thickness of all the layers constituting the adhesive layer.

[0186] 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 at least the lower limit value, the adhesive strength between the two layers to be adhered becomes higher. When the ratio is at most the upper limit value, it is possible to suppress the thickness of the adhesive layer from becoming excessive.

[0187] <The first intermediate adhesive layer, the second intermediate adhesive layer> The first intermediate adhesive layer and the second intermediate adhesive layer contain an adhesive. The adhesive is preferably an adhesive resin. Examples of the adhesive resin include polyolefin resins and the like. The polyolefin resin is a resin having a structural unit derived from an olefin, 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 the polyolefin resin include ethylene copolymers, propylene copolymers, butene copolymers, modified products of these copolymers (in other words, modified copolymers), and the like. The polyolefin resin is preferably a random copolymer, a graft copolymer or a block copolymer in terms of further improving the adhesiveness.

[0188] Examples of the ethylene copolymer include the ethylene copolymer described above as included in the easy peel layer, modified products thereof (modified copolymers), and the like. Examples of the propylene copolymer include copolymers of propylene and vinyl group-containing monomers, modified products thereof (modified copolymers), and the like. More specifically, examples of such propylene copolymers include maleic anhydride graft-modified linear low-density polypropylene, propylene-based thermoplastic elastomers, and the like. Examples of the butene copolymer include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, modified products of these copolymers (modified copolymers), and the like.

[0189] The first intermediate adhesive layer and the second intermediate adhesive layer may contain only an adhesive (that is, may be composed of an adhesive), or may contain an adhesive and other components (which may be referred to as "other components" in this specification) (that is, may be composed of an adhesive and the other components).

[0190] The adhesive contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be only one type, or may be two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0191] The other components contained in the first intermediate adhesive layer and the second intermediate adhesive layer are not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, either a resin component or a non-resin component.

[0192] The other components included in the first intermediate adhesive layer and the second intermediate adhesive layer may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0193] In the first intermediate adhesive layer in the multilayer film for a substrate, the ratio of the content of the adhesive to the total mass of the first intermediate adhesive layer may be, for example, 50 to 100% by mass. Usually, the ratio is the same as the ratio of the content (parts by mass) of the adhesive to the total content (parts by mass) of the components that do not vaporize at normal temperature in the composition for forming the first intermediate adhesive layer for a substrate described later. In the second intermediate adhesive layer in the multilayer film for a substrate, the ratio of the content of the adhesive to the total mass of the second intermediate adhesive layer may be, for example, 50 to 100% by mass. Usually, the ratio is the same as the ratio of the content (parts by mass) of the adhesive to the total content (parts by mass) of the components that do not vaporize at normal temperature in the composition for forming the second intermediate adhesive layer for a substrate described later.

[0194] Both the first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for a substrate may each consist of one layer (single layer) or may consist of two or more layers. When the first intermediate adhesive layer or the second intermediate adhesive layer consists of a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of these plurality of layers is not particularly limited as long as the effects of the present invention are not impaired.

[0195] The thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for a substrate are preferably 2 to 15 μm independently of each other. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or greater than the lower limit value, the adhesive strength between the two layers to be adhered becomes higher. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or less than the upper limit value, it is possible to suppress the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer from becoming excessive. Here, the "thickness of the first intermediate adhesive layer" means the thickness of the entire first intermediate adhesive layer. For example, the thickness of the first intermediate adhesive layer composed of multiple layers means the total thickness of all the layers constituting the first intermediate adhesive layer. The same applies to the second intermediate adhesive layer.

[0196] The ratios of the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer to the thickness of the multilayer film for a substrate are not particularly limited, but are preferably 3 to 20% respectively. When the ratio is at least the lower limit value, the adhesive strength between the two layers to be adhered becomes higher. When the ratio is at most the upper limit value, it is possible to suppress the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer from becoming excessive.

[0197] <Other layers> The multilayer film for a substrate may include other layers that do not correspond to any of the easy peel layer, the first intermediate adhesive layer, the oxygen barrier layer, the second intermediate adhesive layer, the pinhole resistant layer, and the adhesive layer, as long as the effects of the present invention are not impaired.

[0198] The types and arrangement positions of the other layers in the multilayer film for a substrate are not particularly limited and can be arbitrarily selected according to the purpose.

[0199] The other layers included in the multilayer film for a substrate may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected according to the purpose.

[0200] Each of the other layers in the multilayer film for a substrate may be composed of one layer (single layer) or two or more layers. When the other layers are composed of multiple layers, these multiple layers may be the same as or different from each other, and the combinations of these multiple layers are not particularly limited as long as the effects of the present invention are not impaired.

[0201] The thickness of the other layers in the multilayer film for a substrate can be arbitrarily set according to their types and is not particularly limited.

[0202] When the multilayer film for the substrate includes the other layer, it may further include an intermediate adhesive layer for adhering the other layer to other layers. In this case, examples of the intermediate adhesive layer include those similar to the above-described first intermediate adhesive layer or second intermediate adhesive layer.

[0203] The thickness of the non-foamed resin layer such as the multilayer film for the substrate is not particularly limited, but is preferably 40 to 120 μm.

[0204] [[Manufacturing Method of Substrate]] The substrate can be manufactured by a known method according to its type. For example, when the substrate is a resin laminate including the above-described foamed resin layer and non-foamed resin layer, the substrate can be manufactured by heat-laminating one surface of the foamed resin layer and one surface of the non-foamed resin layer (when the non-foamed resin layer is the multilayer film for the substrate, the adhesive layer therein). The heat lamination at this time may be performed, for example, by the melt pressure bonding lamination method or the extrusion lamination method as described later in the examples. Among the non-foamed resin layers, the multilayer film for the substrate can be manufactured in the same manner as in the case of the above-described multilayer film (lid material), except that the types of resins or resin compositions serving as the forming materials for each layer are different.

[0205] Regardless of the manufacturing method, the resin composition serving as the forming material for any layer in the multilayer film for the substrate may be manufactured by adjusting the types and contents of the contained components so that the layer to be formed contains the target components (constituent materials) in the target contents. For example, the ratio of the contents of the components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the contents of the components in the layer formed from this resin composition.

[0206] As a resin composition for forming an easy peel layer in a multilayer film for a substrate (which may be referred to as "resin composition for forming an easy peel layer for a substrate" in this specification), for example, those containing the polyolefin and, if necessary, the other components are mentioned.

[0207] As a resin composition for forming an oxygen barrier layer in a multilayer film for a substrate (which may be referred to as "resin composition for forming an oxygen barrier layer for a substrate" in this specification), for example, those containing either one or both of an ethylene-vinyl alcohol copolymer and a polyamide and, if necessary, the other components are mentioned.

[0208] As a resin composition for forming a pinhole resistant layer in a multilayer film for a substrate (which may be referred to as "resin composition for forming a pinhole resistant layer for a substrate" in this specification), for example, those containing the polyolefin and, if necessary, the other components are mentioned.

[0209] As a resin composition for forming an adhesive layer in a multilayer film for a substrate (which may be referred to as "resin composition for forming an adhesive layer for a substrate" in this specification), a resin composition for forming a first intermediate adhesive layer (which may be referred to as "resin composition for forming a first intermediate adhesive layer for a substrate" in this specification), and a resin composition for forming a second intermediate adhesive layer (which may be referred to as "resin composition for forming a second intermediate adhesive layer for a substrate" in this specification), all of them, for example, those containing the adhesive and, if necessary, the other components are mentioned.

[0210] <<An embodiment of a vacuum package for frozen raw meat>> FIG. 2 is a cross-sectional view schematically showing an example of the vacuum package for frozen raw meat of this embodiment. In the figures after FIG. 2, the same components as those shown in the already explained figures are given the same reference numerals as in the case of the already explained figures, and the detailed description thereof is omitted.

[0211] The vacuum package 10 for frozen fresh meat shown here is composed of a multilayer film (lid material) 1 shown in FIG. 1 and a bottom material 8. In FIG. 2, the distinction between the layers in the multilayer film 1 is omitted.

[0212] In the vacuum package 10 for frozen fresh meat, the oxygen transmission rate under the conditions of a temperature of 23°C and a relative humidity of 60% is preferably 100 cc / (m 2 ·day·atm) or less. In the vacuum package 10 for frozen fresh meat, the dynamic elastic modulus E' of the multilayer film (lid material) 1 at a temperature of 140°C is preferably 10 4 or more and 10 7 Pa or less. In the vacuum package 10 for frozen fresh meat, during the thermomechanical analysis of the multilayer film (lid material) 1, the temperature at which a displacement of 2000 μm is shown is preferably 120°C or more, or the gel fraction of the multilayer film (lid material) 1 is preferably 30% or more. In the vacuum package 10 for frozen fresh meat, the oxygen transmission rate of the multilayer film (lid material) 1 under the conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m 2 ·day·atm) or less. In the vacuum package 10 for frozen fresh meat, during the thermomechanical analysis of the multilayer film (lid material) 1, the displacement at a temperature of 100°C is preferably 500 μm or less. In the vacuum package 10 for frozen fresh meat, it is preferable that the multilayer film (lid material) 1 is irradiated with an electron beam under the conditions of an absorbed dose of 13 to 300 kGy.

[0213] In the vacuum package 10 for frozen fresh meat, the oxygen transmission rate of the bottom material 8 under the conditions of a temperature of 23°C and a relative humidity of 60% is 300 cc / (m 2 ·day·atm) or less.

[0214] The vacuum package 10 for frozen fresh meat uses the multilayer film 1 and thus has excellent followability to the fresh meat 9 as the contained material. In addition, the vacuum package 10 for frozen raw meat uses the multilayer film (lid material) 1 and the bottom material 8, so that the oxygen barrier property against the raw meat 9 is high, and the storage period of the raw meat 9 is longer than that of the conventional package.

[0215] One surface of the bottom material 8 (which may be referred to as the "first surface" in this specification) 8a is a sealing surface, and a part of the first surface 8a and a part of the first surface 11a of the sealant layer 11 in the multilayer film 1 are in close contact by sealing. In FIG. 2, the part where the first surface 8a of the bottom material 8 and the first surface 11a of the sealant layer 11 in the multilayer film 1 are in direct contact is the seal part. As a result, a storage part 10a is formed between the first surface 8a of the bottom material 8 and the first surface 11a of the sealant layer 11. And the raw meat 9 is sealed in this storage part 10a.

[0216] When the bottom material 8 is the multilayer film for the bottom material, the first surface 8a of the bottom material 8 is the surface on the side opposite to the oxygen barrier layer of the easy peel layer.

[0217] In FIG. 2, in the storage part 10a of the vacuum package 10 for frozen raw meat, there are some gaps between the raw meat 9 and the multilayer film 1, and between the raw meat 9 and the bottom material 8, but these gaps may not exist in the vacuum package 10 for frozen raw meat in the state where the raw meat 9 is stored.

[0218] The vacuum package for frozen raw meat of this embodiment is not limited to the above, and within the scope not departing from the gist of the present invention, some configurations may be changed, deleted or added. For example, in FIG. 2, the vacuum package 10 for frozen raw meat configured using the multilayer film 1 shown in FIG. 1 is shown as the lid material, but the package of this embodiment may be configured using other lid materials.

[0219] <<Method for manufacturing a vacuum package for frozen raw meat>> The method for manufacturing the vacuum package for frozen raw meat of this embodiment includes the following steps (1) to (4). (1) Step of arranging raw meat on the bottom material. (2) A step of disposing a lid material on a region of the base material that covers the raw meat and its periphery. (3) A step of bringing the lid material into contact with the raw meat while heating the lid material to 90 to 250 °C, shaping it along the raw meat, and adhering the portion of the lid material in contact with the base material to the base material, thereby packaging the raw meat with the lid material and the base material. (4) A step of rapidly freezing the central temperature of the raw meat to -20 °C or lower within 6 hours immediately after packaging.

[0220] In the step (3), the temperature for heating the lid material is 90 to 250 °C. When the temperature is at or above the lower limit value, the shaping of the lid material becomes easy. When the temperature is at or below the upper limit value, the heating of the raw meat can be suppressed. The heating time of the lid material can be appropriately adjusted according to the heating temperature of the lid material. In the step (2), when disposing the lid material on the region covering the raw meat and its periphery, the pre-heated lid material may be disposed on the raw meat. In this case, the temperature of the lid material in the step (2) may be set so that the lid material can be brought into contact with the raw meat while maintaining the state where the lid material is heated to 90 to 250 °C in the step (3). Also, as a method of adhering the portion of the lid material in contact with the base material to the base material, it is not particularly limited, but it is preferable to hermetically and liquid-tightly seal the raw meat in the vacuum package for frozen raw meat by heat sealing.

[0221] In the step (4), the central temperature of the raw meat within 6 hours immediately after packaging is -20 °C or lower. When the central temperature is at or below the upper limit value, the color fading of the frozen raw meat is prevented, and a vacuum package for frozen raw meat that looks better than before and can be stored for a long time can be provided. In the step (4), from the viewpoint of further preventing the color fading of the frozen raw meat, the time for the central temperature of the raw meat to reach -20 °C or lower within 6 hours immediately after packaging is more preferably within 3 hours, even more preferably within 1 hour, and even more preferably within 30 minutes.

[0222] As a method for measuring the central temperature of the raw meat, it is not particularly limited. The temperature may be measured non - contact from the outside of the vacuum package for frozen raw meat, or a thermometer may be installed in the raw meat inside the vacuum package for frozen raw meat. After the freezing conditions under which the central temperature is equal to or lower than the upper limit value are established, the step of measuring the central temperature of the raw meat may be omitted. By rapidly freezing the raw meat under the same conditions in the step (4) carried out while measuring the central temperature of the raw meat in the test process and the step (4) carried out without measuring the central temperature of the raw meat in the manufacturing process, reproducibility and productivity can be achieved simultaneously and improved.

[0223] The raw meat is not particularly limited, and examples include meats such as beef, pork, horse meat, mutton, and goat meat, and poultry meats such as chicken and duck meat. The raw meat may be general - use or commercial - use meat. The content volume of the raw meat contained in the vacuum package for frozen raw meat is not particularly limited, and examples include 0.1 - 10 kg, 0.2 - 5.0 kg, 0.3 - 3.0 kg, etc.

[0224] <<Raw meat package and its manufacturing method>> The raw meat package of this embodiment is one in which the raw meat is vacuum - packaged by the bottom material and the lid material in the vacuum package for frozen raw meat of this embodiment. When manufacturing a vacuum package for frozen raw meat using the manufacturing method of the vacuum package for frozen raw meat of this embodiment, a raw meat package in which frozen raw meat is packaged in the vacuum package for frozen raw meat is manufactured at the same time.

[0225] In the step (1), the raw meat may be placed on the surface of the bottom material on the side to be sealed with the lid material. In the step (2), the lid material may be covered over the surface of the bottom material and the raw meat from above them. In the step (3), by evacuating the region where the raw meat is arranged between the bottom material and the lid material, while closely fixing the lid material to the raw meat, the bottom material and the lid material may be heat - sealed in the region where the raw meat is not arranged. The step (4) may be to freeze the raw meat so that the central temperature of the raw meat becomes - 20°C or lower within 6 hours immediately after the completion of the step (3). The test package described below can also be manufactured by the same method.

[0226] The sealing temperature during heat sealing is not particularly limited, but is preferably 100 to 170°C. When the sealing temperature is at least the lower limit value, the sealing strength becomes higher while having easy peelability. When the sealing temperature is at most the upper limit value, the opening of the package becomes easier.

[0227] The sealing time during heat sealing can be appropriately adjusted according to the sealing temperature, but is usually preferably 10 to 30 seconds. When the sealing time is at least the lower limit value, the sealing strength becomes higher while having easy peelability. When the sealing time is at most the upper limit value, the opening of the package becomes easier.

[0228] The pressure in the region where the raw meat is placed by evacuation during heat sealing is 5000 Pa (50 mbar) or less, preferably 300 Pa or more and 5000 Pa or less, more preferably 400 Pa or more and 4900 Pa or less, still more preferably 500 Pa or more and 4800 Pa or less, and particularly preferably 600 Pa or more and 4700 Pa or less. When the pressure is at most the upper limit value, a raw meat package with higher followability (adhesion) of the lid material to the raw meat and more excellent storage suitability can be obtained.

[0229] <<Method for storing raw meat>> The method for storing raw meat according to this embodiment is a method of storing the raw meat package at a temperature below 0°C, and the vacuum package for frozen raw meat is preferably a vacuum package for frozen raw meat stored at -40°C or more and less than 0°C. The temperature is preferably, for example, -40°C or more and less than 0°C, more preferably -40°C or more and -1°C or less, still more preferably -40°C or more and -2°C or less, and particularly preferably -40°C or more and -3°C or less.

Examples

[0230] Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

[0231] [Example 1] [Manufacture of Multilayer Film (Lid Material)] A multilayer film having the configuration shown in FIG. 1 was manufactured according to the procedure shown below. That is, as the resin constituting the sealant layer, ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Mitsui Dow Polychemical Co., Ltd.) was prepared. As the resin constituting the outer layer, low-density polyethylene (LDPE, density 0.922 g / cm 3 , "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared. As the resin constituting the functional layer and the pinhole-resistant layer, sodium-based ionomer (ION, "1601" manufactured by Mitsui DuPont Polychemical Co., Ltd.) was prepared. As the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (EVOH, "GH3804B" manufactured by Nippon Gosei Co., Ltd.) was prepared. As the adhesive (adhesive resin) constituting the adhesive layer (first adhesive layer and second adhesive layer), maleic anhydride-modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

[0232] The temperature of the die was set at 250 ° C, and the EVA, the ION, the modified PE, the EVOH, the modified PE, the ION, and the LDPE were co-extruded in this order (co-extrusion T-die method) to form a sealant layer (thickness 24 μm), a pinhole-resistant layer (thickness 29 μm), an adhesive layer (first adhesive layer, thickness 8 μm), an oxygen barrier layer (thickness 10 μm), an adhesive layer (second adhesive layer, thickness 8 μm), a functional layer (thickness 17 μm), and an outer layer (thickness 24 μm) were laminated in this order in the thickness direction to manufacture a multilayer film (thickness 120 μm).

[0233] 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. As described above, the intended multilayer film irradiated with electron beams (hereinafter sometimes referred to as "lid material (I)") was obtained.

[0234] <<Evaluation of Multilayer Film (Lid Material)>> <Measurement of Dynamic Elastic Modulus at 140°C> Regarding the electron beam-irradiated multilayer film (lid material (I)) obtained above, using a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Technologies Corporation), in accordance with JIS K7244-4, a sample with a width of 4 mm was used, and in the 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 3°C / min. The results are shown in Table 1.

[0235] <Temperature Indicating a Displacement of 2000 μm and Identification of Displacement at a Temperature of 100°C> Regarding the electron beam-irradiated multilayer film (lid material (I)) obtained above, using a thermal analyzer ("EXSTAR6000" manufactured by SII), in accordance with JIS K 7196, thermomechanical analysis was performed. Then, from the obtained thermomechanical analysis curve, the temperature (°C) indicating a displacement of 2000 μm and the displacement (μm) at a temperature of 100°C were determined. The results are shown in Table 1.

[0236] <Measurement of Gel Fraction> Regarding the electron beam-irradiated multilayer film (lid material (I)) obtained above, the gel fraction was measured in accordance with JIS K 6769. That is, a test piece with a size of 3 cm × 3 cm (about 0.09 g) was cut out from the multilayer film, this test piece was wrapped with a 400-mesh stainless steel wire mesh (100 g), and immersed in xylene (18 mL) at 110°C for 24 hours. Next, the test piece was taken out from the xylene together with the wire mesh and vacuum-dried at 110°C for 24 hours under a pressure of 1.7 kPa to obtain a dried product of the test piece after immersion. The mass of the obtained dried product was measured, and the gel fraction (%) of the electron beam-irradiated multilayer film was determined. The results are shown in Table 1.

[0237] <Measurement of Oxygen Permeation Rate> For the electron beam irradiated multilayer film (lid material (I)) obtained above, the oxygen permeation rate (cc / (m 2 ·day·atm)) was measured in accordance with JIS K 7126-2:2006 under the conditions of a temperature of 23°C and a relative humidity of 60%. The results are shown in Table 1.

[0238] <<Manufacture of Substrate>> <Manufacture of Multilayer Film for Substrate> A multilayer film for the substrate was manufactured according to the procedure shown below. That is, as the resins constituting the easy peel layer, low density polyethylene (LDPE, "L211" manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (PP, "FS2011DG2" manufactured by Sumitomo Chemical Co., Ltd.) were prepared. As the resin constituting the pinhole resistant layer, metallocene catalyzed linear low density polyethylene (mLLDPE) ("Yumelite (registered trademark) 1520F" manufactured by Ube Maruzen Polyethylene Co., Ltd., density 0.913 g / cm 3 ) was prepared. As the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (EVOH, "J171B" manufactured by Kuraray Co., Ltd., density: 1180 kg / m 3 , MFR: 4.2 g / 10 min) was prepared. As the resin constituting the first intermediate adhesive layer, acid modified polypropylene (acid modified PP, adhesive resin, "Admer QF551" manufactured by Mitsui Chemicals, Inc.) was prepared. As the resin constituting the second intermediate adhesive layer, acid modified polyethylene (acid modified PE, adhesive resin, "Admer NF536" manufactured by Mitsui Chemicals, Inc.) was prepared. As the resin constituting the adhesive layer, ethylene-vinyl acetate copolymer resin (EVA-based resin, adhesive resin, "Melsen (registered trademark) MX02D" manufactured by Tosoh Corporation) was prepared.

[0239] By mixing the above LDPE (70 parts by mass) and the above PP (30 parts by mass) at room temperature, a composition for forming an easy peel layer for the substrate was manufactured.

[0240] The temperature of the die was set at 250°C, and the composition for forming the easy-peel layer for the substrate, the acid-modified PP, the EVOH, the acid-modified PE, the mLLDPE, and the EVA-based resin were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film for substrate (thickness: 70 μm) in which an easy-peel layer (thickness: 25.9 μm), a first intermediate adhesive layer (thickness: 5.6 μm), an oxygen 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) were laminated in this order in the thickness direction thereof.

[0241] <Manufacture of Substrate> Using a foamed resin sheet (manufactured by Central Chemical Co., Ltd., thickness: 3000 μm) containing a foam of a polystyrene-based resin (PSP), the exposed surface of the adhesive layer of the multilayer film for substrate obtained above was bonded to one surface thereof by heat lamination to obtain a substrate (hereinafter sometimes referred to as "substrate (α)"). The heat lamination of the foamed resin sheet and the multilayer film for substrate was performed by melt pressure bonding lamination using a roll device equipped with a melt pressure bonding roll. The melt pressure bonding roll is 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 substrate were melt pressure bonded at 180°C between the heating roll and the counter roll to bond them together.

[0242] <<Evaluation of Substrate>> <Measurement of Oxygen Permeation Rate> Regarding the substrate (substrate (α)) obtained above, the oxygen permeation rate (cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 23°C and a relative humidity of 60% in accordance with JIS K 7126-2:2006. The results are shown in Table 3.

[0243] <<Manufacture of Vacuum Package for Frozen Fresh Meat (Test Package)>> The side meat was obtained from a slaughtered Japanese black beef and stored once at 4°C for 2 days in an air atmosphere. Next, sub-meat was obtained from the forequarter after the first storage, and this sub-meat (25 kg) was vacuum-packed with an oxygen barrier film and stored for 5 days at 4°C in an air atmosphere. The oxygen barrier film was composed of a polyethylene layer, an ethylene-vinyl acetate copolymer layer, a polyvinylidene chloride layer, an ethylene-vinyl acetate copolymer layer, and a very low density polyethylene layer laminated in this order in the thickness direction thereof (thickness 50 μm, size 30 cm × 50 cm), and its oxygen transmission rate measured in accordance with JIS K 7126-2:2006 was 10 cc / (m 2 ·day·atm) or less. The vacuum packaging was performed by setting the seal temperature at 120°C and the seal time at 3 seconds during heat sealing, and setting the pressure in the region where the sub-meat was placed at 30 mbar (3000 Pa).

[0244] Next, from the sub-meat in the vacuum package after the second storage, test meat of the sirloin part with a mass of 0.3 kg was cut out. Then, 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 the lid material (I) and the bottom material (α). While evacuating the location where the test meat was placed, after the lid material and the bottom material were sealed at the heated temperature, a test package which was a vacuum package for frozen raw meat (skin pack package for frozen raw meat) was produced by rapid freezing. During evacuation, the pressure at the location where the test meat was placed was set at 30 mbar (3000 Pa). 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 at -30°C in an air atmosphere and stored for the third time. Furthermore, in the same manner as above, test meat was prepared for the peach part and the arm part, and the production and storage of packages were similarly performed.

[0245] <<Evaluation of Vacuum Package for Frozen Raw Meat (Test Package)>> <Evaluation of Meat Discoloration> Sixty days after the start of the third storage, thawing was carried out from a frozen state at -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was taken out from the unopened test package and visually observed to evaluate the presence or absence of discoloration of the test meat. The results are shown in Table 4.

[0246] <Evaluation of followability> The test package immediately after packing was visually observed, and the followability of the lid material to the test meat was evaluated according to the following criteria. The results are shown in Table 4. [Evaluation criteria] A: There is no or very little lifting of the lid material from the test meat, and the followability is high. B: Inferior to A, but there is little lifting of the lid material from the test meat, and the followability is good. C: There is a lot of lifting of the lid material from the test meat, and the followability is low. D: The lid material does not follow the test meat.

[0247] <Evaluation of drip> Sixty days after the start of the third storage, thawing was carried out from a frozen state at -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was taken out from the unopened test package and left for 5 minutes, and the amount of drip generated and the turbidity of the drip were visually observed according to the following criteria. The results are shown in Table 4. [Evaluation criteria] A: There is no or very little drip generated. B: Inferior to A, but the amount of drip generated is small and the turbidity of the drip is also small. C: The amount of drip generated is large and the turbidity of the drip is also large.

[0248] <Evaluation of juiciness> Sixty days after the start of the third storage, thawing was carried out from the frozen state at -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was taken out from the unopened test package, prepared to a thickness of 1 cm × 3.5 cm × 4.5 cm, and the surface of the test meat was heated for 60 seconds and the back surface was heated for 90 seconds on a hot plate heated to 220°C. Then, the test meat slices cut into three equal parts were taken as one piece, and a taste sample was prepared with one piece per test meat per person. Seven panelists (sensory examiners) evaluated the taste and evaluated the juiciness and flavor when chewing according to the following criteria. The results are shown in Table 4. [Evaluation Criteria (Juiciness)] A: The juiciness is good. B: Inferior to A, but there is juiciness. C: There is almost no juiciness and it is dry and tough. [Evaluation Criteria (Flavor)] A: The flavor as meat is good. B: Inferior to A, but there is a flavor as meat. C: The flavor as meat is almost gone.

[0249] [Example 2] When irradiating the multilayer film with electron beams, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (II)") was manufactured and evaluated in the same manner as in Example 1, except that the absorbed dose was changed to 120 kGy instead of 175 kGy. A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1, except that this electron beam-irradiated multilayer film (lid material (II)) was used. The results are shown in Tables 1, 3 and 4.

[0250] [Example 3] When irradiating the multilayer film with electron beams, an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (III)") was manufactured and evaluated in the same manner as in Example 1, except that the absorbed dose was changed to 90 kGy instead of 175 kGy. A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1, except that the multilayer film irradiated with electron beams (lid material (III)) was used. The results are shown in Tables 1, 3, and 4.

[0251] [Example 4] An electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (IV)") was manufactured and evaluated in the same manner as in Example 1, except that the absorbed dose was changed to 15 kGy instead of 175 kGy during the irradiation of the electron beam to the multilayer film. A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1, except that the electron beam-irradiated multilayer film (lid material (IV)) was used. The results are shown in Tables 1, 3, and 4.

[0252] [Example 5] [Manufacture and Evaluation of Substrate] A multilayer film for substrate was manufactured in the same manner as in Example 1, except that 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd., melting point 225°C) was used instead of the EVOH ("J171B" manufactured by Kuraray Co., Ltd.) as the resin constituting the oxygen barrier layer. The multilayer film for substrate manufactured in this example is a multilayer film for substrate (thickness 70 μm) in which an easy peel layer (thickness 25.9 μm), a first intermediate adhesive layer (thickness 5.6 μm), an oxygen 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) are laminated in this order in the thickness direction thereof. Then, a substrate (hereinafter sometimes referred to as "substrate (β)") was manufactured and evaluated in the same manner as in Example 1, except that the multilayer film for substrate was used. The results are shown in Table 3.

[0253] [Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat] A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1, except that the substrate (β) obtained above was used. The results are shown in Table 4.

[0254] [Comparative Example 1] A lid material (a multilayer film not irradiated with electron beams, hereinafter sometimes referred to as "lid material (V)") was produced and evaluated in the same manner as in Example 1, except that the multilayer film was not irradiated with electron beams. A vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1, except that the multilayer film not irradiated with electron beams (lid material (V)) was used. The results are shown in Tables 1, 3, and 5.

[0255] [Comparative Example 2] [Manufacture and Evaluation of Substrate] A multilayer film for substrate was produced in the same manner as in Example 1, except that metallocene-catalyzed linear low-density polyethylene (mLLDPE, "4040FC" manufactured by Ube Maruzen Polyethylene Co., Ltd., melting point 126°C) was used instead of the EVOH ("J171B" manufactured by Kuraray Co., Ltd.) as the resin constituting the oxygen barrier layer. The multilayer film for substrate produced in this comparative example is a multilayer film for substrate (thickness 70 μm) in which an easy peel layer (thickness 25.9 μm), a first intermediate adhesive layer (thickness 5.6 μm), an oxygen 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) are laminated in this order in the thickness direction thereof. Then, a substrate (hereinafter sometimes referred to as "substrate (γ)") was produced and evaluated in the same manner as in Example 1, except that the multilayer film for substrate was used. The results are shown in Table 3.

[0256] [Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat] A vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1, except that the substrate (γ) obtained above was used. The results are shown in Table 5.

[0257] [Comparative Example 3] [Manufacture and Evaluation of Multilayer Film (Lid Material)] As the resin constituting the oxygen barrier layer, except that 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd., melting point 225°C) was used instead of the above-mentioned EVOH ("GH3804B" manufactured by Nippon Gohsei), an electron beam irradiated multilayer film (hereinafter sometimes referred to as "lid material (VI)") was produced in the same manner as in Example 1. The electron beam irradiated multilayer film (lid material (VI)) produced in this Comparative Example is a multilayer film (thickness 120μm) in which a sealant layer (thickness 24μm), a pinhole resistant layer (thickness 29μm), an adhesive layer (first adhesive layer, thickness 8μm), an oxygen barrier layer (thickness 10μm), an adhesive layer (second adhesive layer, thickness 8μm), a functional layer (thickness 17μm), and an outer layer (thickness 24μm) are laminated in this order in the thickness direction thereof, and is obtained by irradiating 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. Then, the electron beam irradiated multilayer film (lid material (VI)) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0258] <<Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat>> A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1, except that the lid material (VI) obtained above was used. The results are shown in Table 5.

[0259] [Comparative Example 4] <<Manufacture and Evaluation of Multilayer Film (Lid Material)>> A multilayer film was manufactured according to the procedure shown below. That is, low density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared as the resin constituting the sealant layer. Amorphous polyethylene terephthalate (PETG, "S2008" manufactured by SK Chemicals Co., Ltd.) was prepared as the resin constituting the outer layer. 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd.) was prepared as the resin constituting the pinhole resistant layer. As the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (EVOH, "J171B" manufactured by Kuraray Co., Ltd.) was prepared. As the resin constituting the cushion layer, low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared. As the adhesive (adhesive resin) constituting the adhesive layer (first adhesive layer), maleic anhydride-modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared. As the adhesive (adhesive resin) constituting the adhesive layer (second adhesive layer), maleic anhydride-modified polyethylene (modified PE, "F515A" manufactured by Mitsubishi Chemical Corporation) was prepared.

[0260] The temperature of the die was set at 250 °C, and the above LDPE, the above LDPE, the above modified PE, the above NY, the above EVOH, the above modified PE, and the above PETG were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) in which a sealant layer (thickness 12 μm), a cushion layer (thickness 17 μm), an adhesive layer (first adhesive layer, thickness 6 μm), a pinhole-resistant layer (thickness 20 μm), an oxygen barrier layer (thickness 12 μm), an adhesive layer (second adhesive layer, thickness 8 μm), and an outer layer (thickness 45 μm) were laminated in this order in the thickness direction of these layers.

[0261] 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 (VII)") was obtained. Then, this multilayer film irradiated with an electron beam (lid material (VII)) was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0262] <<Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat>> A vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1 except that the lid material (VII) obtained above was used. The results are shown in Table 5.

[0263] [Comparative Example 5] [Manufacture and Evaluation of Multilayer Film (Lid Material)] As the resin constituting the sealant layer, instead of low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.), an ionomer (ION, "1855" manufactured by Mitsui Dow Polychemical Co., Ltd.) was used. As the resin constituting the outer layer, instead of amorphous polyethylene terephthalate (PETG, "S2008" manufactured by SK Chemicals Co., Ltd.), 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd.) was used. As the resin constituting the cushion layer, instead of low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.), an ethylene-methacrylic acid copolymer (EMAA, "N0903HC" manufactured by Mitsui Dow Polychemical Co., Ltd.) was used. Except for this point, a multilayer film irradiated with electron beams (hereinafter sometimes referred to as "lid material (VIII)") was manufactured in the same manner as in Comparative Example 4. The electron beam-irradiated multilayer film (lid material (VIII)) manufactured in this comparative example is a multilayer film (with a thickness of 120 μm) in which a sealant layer (thickness: 24 μm), a cushion layer (thickness: 40 μm), an adhesive layer (first adhesive layer, thickness: 8 μm), a pinhole-resistant layer (thickness: 24 μm), an oxygen barrier layer (thickness: 6 μm), an adhesive layer (second adhesive layer, thickness: 10 μm), and an outer layer (thickness: 8 μm) are laminated in this order in the thickness direction. It was obtained by irradiating electrons 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. Then, this electron beam-irradiated multilayer film (lid material (VIII)) was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0264] [Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat] Except for using the lid material (VIII) obtained above, a vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0265] [Comparative Example 6] [Manufacture and Evaluation of Multilayer Film (Lid Material)] As the resin constituting the sealant layer, except that low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was used instead of ionomer (ION, "1855" manufactured by Mitsui Dow Chemical Co., Ltd.), an electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (IX)") was produced in the same manner as in Comparative Example 5. The electron beam-irradiated multilayer film (lid material (IX)) produced in this comparative example is a multilayer film (with a thickness of 120 μm) in which a sealant layer (8 μm thick), a cushion layer (46 μm thick), an adhesive layer (first adhesive layer, 8 μm thick), a pinhole-resistant layer (30 μm thick), an oxygen barrier layer (6 μm thick), an adhesive layer (second adhesive layer, 10 μm thick), and an outer layer (12 μm thick) are laminated in this order in the thickness direction. It was obtained by irradiating 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. Then, this electron beam-irradiated multilayer film (lid material (IX)) was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0266] [Manufacture and Evaluation of Vacuum Package for Frozen Raw Meat] Except for using the lid material (IX) obtained above, a vacuum package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0267] [Comparative Example 7] [Manufacture and Evaluation of Degassed Seal Package for Frozen Raw Meat] Except that the sealant layer in the lid material (I) obtained above and the sealant layer in the lid material (I) were opposed to each other, the test meat was placed between these lid materials (I) and (I), and while degassing the location where the test meat was placed, the peripheral portions of the lid materials (I) and (I) were heat-sealed under the conditions of a seal temperature of 140°C and a seal time of 2 seconds to produce a test package which is a degassed seal package for frozen raw meat. A degassed seal package for frozen raw meat (test package) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0268] [Example 6] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -40°C. The results are shown in Table 4.

[0269] [Example 7] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -50°C. The results are shown in Table 4.

[0270] [Example 8] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -60°C. The results are shown in Table 4.

[0271] [Comparative Example 8] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -20°C. The results are shown in Table 5.

[0272] [Comparative Example 9] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -15°C. The results are shown in Table 5.

[0273] [Comparative Example 10] A vacuum package for frozen raw meat was produced and evaluated in the same manner as in Example 1, except that the rapid freezing condition was changed to a method of storing at -40°C. The results are shown in Table 5.

[0274]

Table 1

[0275]

Table 2

[0276]

Table 3

[0277]

Table 4

[0278]

Table 5

[0279] As is clear from the above results, in Examples 1 to 8, in any of the test meats of the sirloin part, the peach part, and the arm part, discoloration of the packaged test meat did not occur. Thus, the vacuum packages for frozen raw meat of Examples 1 to 8 were able to suppress the deterioration of the frozen packaged raw meat and store it for a long time in any of the test meats of the sirloin part, the peach part, and the arm part. In the vacuum packages for frozen raw meat of Examples 1 to 8, the oxygen transmission rate of the lid material was 6 cc / (m 2 ·day·atm), and the oxygen transmission rate of the bottom material was 250 cc / (m 2 ·day·atm) or less (2 to 250 cc / (m 2 ·day·atm)).

[0280] In the vacuum packages for frozen raw meat of Examples 1 to 8, in any of the test meats of the sirloin part, the peach part, and the arm part, the followability of the lid material to the raw meat was good, and it had favorable characteristics as a vacuum package for frozen raw meat. Among them, in the vacuum packages for frozen raw meat of Examples 1 to 3 and 5 to 8, the followability of the lid material to the raw meat was particularly excellent. In the lid materials of Examples 1 to 8, the dynamic elastic modulus at 140 °C was 10 4 or more and 10 6 Pa or less (5.5×10 4 ~5.2×10 6and the absorbed dose is 15 kGy or more (15 to 175 kGy), the temperature at which a displacement of 2000 μm occurs during the thermomechanical analysis is 125°C or more (125 to 185°C), the displacement at a temperature of 100°C during the thermomechanical analysis is 320 μm or less (62 to 320 μm), and the gel fraction is 35% or more (35 to 78%). Among them, in the lid materials of Examples 1 to 3 and 5 to 8, the absorbed dose is 90 kGy or more (90 to 175 kGy), the temperature at which a displacement of 2000 μm occurs during the thermomechanical analysis is 135°C or more (135 to 185°C), the displacement at a temperature of 100°C during the thermomechanical analysis is 120 μm or less (62 to 120 μm), and the gel fraction is 60% or more (60 to 78%).

[0281] In addition, in Examples 1 to 8, the amount of drip generation was well suppressed, and the juiciness was also good. Among them, the vacuum packages for frozen fresh meat of Examples 1 to 3 and 5 to 8 were particularly excellent. Thus, the vacuum packages for frozen fresh meat of Examples 1 to 8 did not become brittle even under freezing, suppressed the drip generated during thawing, prevented the outflow of umami components, and could be stored for a long time without degrading the taste compared to the conventional ones.

[0282] On the other hand, in the vacuum package for frozen fresh meat of Comparative Example 1, in any of the test meats of the sirloin part, the pork loin part, and the arm part, the followability of the lid material to the fresh meat was low, and it did not have preferable characteristics as a vacuum package for frozen fresh meat. Also, drip oozed out into the empty space of the package during storage, and the meat color deteriorated. Furthermore, since the umami components leaked out, the taste of the heated meat became dry and tough. Note that if the amount of drip generation is large, bacteria are likely to grow in the free drip rich in nutrients, and as a result, it is considered that the meat color deteriorates. The lid material (multilayer film) of Comparative Example 1 was not irradiated with electron beams. As a result, the dynamic elastic modulus at 140°C was low, the temperature at which a displacement of 2000 μm occurred during the thermomechanical analysis was low, the displacement at a temperature of 100°C during the thermomechanical analysis was large, and the gel fraction was low.

[0283] In Comparative Example 2, discoloration occurred on the bottom material side of the test meat for any of the packaged sirloin part, thigh part, and arm part. Thus, the vacuum package for frozen raw meat of Comparative Example 2 could not suppress the deterioration of the frozen packaged raw meat and could not be stored for a long time. In the vacuum package for frozen raw meat of Comparative Example 2, the oxygen transmission rate of the bottom material was 500 cc / (m 2 ·day·atm), which was a large amount.

[0284] In Comparative Example 3, discoloration occurred on the lid material side of the packaged test meat for any of the sirloin part, thigh part, and arm part. Thus, the vacuum package for frozen raw meat of Comparative Example 3 also could not suppress the deterioration of the frozen packaged raw meat and could not be stored for a long time. In the vacuum package for frozen raw meat of Comparative Example 3, the oxygen transmission rate of the lid material was 120 cc / (m 2 ·day·atm), which was a large amount.

[0285] In Comparative Examples 4 to 6, for any of the sirloin part, thigh part, and arm part of the test meat, the lid material compressed the shape of the raw meat and did not have favorable characteristics as a vacuum package for frozen raw meat. Also, at the time of packing, for any of the sirloin part, thigh part, and arm part of the test meat, the raw meat was packed in a state where the cytoplasm of the raw meat was destroyed, so drip flowed out at the time of opening, and turbidity was also seen in the color of the drip. Furthermore, since the umami components flowed out, the taste of the heated meat became dry. Thus, the vacuum packages for frozen raw meat of Comparative Examples 4 to 6 could not suppress the drip generated during thawing and prevent the outflow of umami components, so the taste deteriorated more than before when stored for a long time. In the vacuum packages for frozen raw meat of Comparative Examples 4 to 6, the dynamic elastic modulus at 140 °C was high and the gel fraction was low.

[0286] Note that since the degassing seal package for frozen fresh meat in Comparative Example 7 only degassed and sealed the lid material, the lid material did not follow the fresh meat in any of the test meats at the sirloin part, thigh part, or arm part, and excessive wrinkles occurred. Also, drips oozed out into the empty space of the package during storage, and the color of the drips was also cloudy. Furthermore, since the umami components leaked out, the texture of the heated meat became dry and the flavor of the meat was also lost. Thus, since the degassing seal package for frozen fresh meat in Comparative Example 7 could not suppress the drips generated during thawing and prevent the outflow of umami components, the taste deteriorated more than before after long-term storage.

[0287] In Comparative Examples 8 to 10, since the central temperature of the fresh meat 30 minutes after packaging was higher than -20°C, the reduction of the meat tissue progressed due to the action of the myoglobin enzyme in the fresh meat, and the frozen fresh meat became purplish-brown, resulting in a decrease in color development. Thus, the vacuum packages for frozen fresh meat in Comparative Examples 8 to 10 could not suppress the deterioration of the frozen-packaged fresh meat and could not be stored for a long time.

Industrial Applicability

[0288] The present invention can provide a method for manufacturing a vacuum package for frozen fresh meat that can be stored for a long time with a better appearance than before by storing the frozen-packaged fresh meat for a long time and preventing a decrease in color development of the fresh meat after freezing.

Explanation of Signs

[0289] 1 ··· Multilayer film (lid material) 11 ··· Sealant layer 12 ··· Outer layer 13 ··· Functional layer 14 ··· Oxygen barrier layer 15 ··· Adhesive layer 151 ··· First adhesive layer 152 ··· Second adhesive layer 16 ··· Pinhole-resistant layer 10 ··· Vacuum package for frozen fresh meat (test package) 8 ··· Bottom material 9···Raw meat (test meat)

Claims

1. A method for manufacturing a vacuum package for frozen raw meat in which raw meat is packaged with a lid material and a bottom material, comprising: a step of disposing the raw meat on the bottom material; a step of disposing the lid material in a region covering the raw meat and its periphery among the regions on the bottom material; a step of bringing the lid material into contact with the raw meat while heating the lid material to 90 to 250 °C, shaping it along the raw meat, and adhering the portion of the lid material in contact with the bottom material to the bottom material, thereby packaging the raw meat with the lid material and the bottom material; a step of rapidly freezing the central temperature of the raw meat to -20 °C or lower within 6 hours immediately after packaging; The lid material is composed of a multilayer film, and the multilayer film has an oxygen transmission rate of 100 cc / (m ２ ·day·atm) or less under the conditions of a temperature of 23°C and a relative humidity of 60%. The oxygen transmission rate of the base material is 300 cc / (m ２ ·day·atm) or less, a method for producing a vacuum package for frozen raw meat.

2. The dynamic elastic modulus E' of the multilayer film at a temperature of 140°C is 10 ４ or more and 10 ７ Pa or less. The method for producing a vacuum packaging body for frozen fresh meat according to claim 1.

3. The method for manufacturing a vacuum package for frozen raw meat according to claim 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.

4. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, wherein the gel fraction of the multilayer film is 30% or higher.

5. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, wherein the multilayer film is irradiated with an electron beam under the condition of an absorption dose of 13 to 300 kGy.

6. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, wherein the displacement at a temperature of 100 °C during thermomechanical analysis of the multilayer film is 500 μm or less.

7. The multilayer film is an outer layer containing polyethylene, a functional layer containing an ionomer and adjacent to the outer layer, an oxygen barrier layer, and a sealant layer containing ethylene-vinyl acetate resin. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, which is a multilayer film provided with these.

8. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, wherein the vacuum package for frozen raw meat is a skin pack package for frozen raw meat.

9. The method for manufacturing a vacuum package for frozen raw meat according to claim 1, wherein the vacuum package for frozen raw meat is a vacuum package for frozen raw meat stored at -40 °C or higher and lower than 0 °C.

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