Vacuum packaging for frozen raw meat, raw meat packaging, and method for preserving raw meat

Abstract

To provide a package which avoids embrittlement of a film under freezing, suppresses deterioration in frozen and packaged fresh meat and enables long-term storage, suppresses drip generated in thawing and prevents overflow of a delicious taste component, and enables the long-term storage without deteriorating in taste than a conventional package.SOLUTION: A resin film for a lid material of a vacuum package for frozen fresh meat having a lid material and a bottom material has an oxygen permeation amount under conditions of a temperature of 23°C and relative humidity of 60% of 100 cc / (m2 day atm) or less, and dynamic elastic modulus E' at a temperature of 140°C of 104 or more and 107 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a resin film, a package, a package for raw meat, and a method for preserving raw meat. [Background technology]

[0002] For example, raw meat for consumption is placed on a plastic tray and packaged in a transparent plastic film with low oxygen barrier properties, or packaged in a bag-like package before being sold at retail (see Patent Document 1). However, when placed on a plastic tray, the edible period is approximately three days at 10°C, approximately six days at 4°C, and approximately seven days at 0°C. To extend the edible period beyond this, barrier vacuum packaging is commonly used, and if stored in a frozen state, the edible period can be extended by two months or more (Guidelines for Testing Methods for Labeling Expiration Dates on Meat). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6370290 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, when vacuum-packed raw meat is frozen, drips leak out when thawed after storage, causing the meat to lose its flavor. Conventional vacuum packages for raw meat have room for improvement in this regard. Another issue is that the packaging material of conventional trays and vacuum packages becomes brittle under frozen conditions, making them unsuitable for storage.

[0005] To provide a package in which the film does not become brittle even under freezing conditions, the frozen-packaged raw meat can be stored for a long period while suppressing deterioration, and further the dripping occurring during thawing is suppressed to prevent the outflow of umami components, thereby enabling long-term storage without deteriorating the taste as compared with conventional packages. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following configuration. [1] A resin film for a lid material of a vacuum package for frozen raw meat, which has a lid material and a base material, and has an oxygen permeability of 100 cc / (m under conditions of a temperature of 23°C and a relative humidity of 60%. 2 ·day·atm) or less, and the dynamic modulus of elasticity E' at a temperature of 140°C is 10 4 Over 10 7 Resin film with a temperature of 0.1 Pa or less. [2] The resin film according to [1], wherein the temperature at which the resin film shows a displacement of 2000 μm during thermomechanical analysis is 120° C. or higher. [3] The resin film according to [1], wherein the resin film has a gel fraction of 30% or more. [4] The resin film according to any one of [1] to [3], wherein the resin film is irradiated with an electron beam at an absorbed dose of 13 to 300 kGy. [5] The resin film according to [2], wherein the displacement at a temperature of 100°C during the thermomechanical analysis of the resin film is 500 μm or less. [6] The resin film according to any one of [1] to [5], wherein the resin film is a multilayer film having an outer layer, a functional layer adjacent to the outer layer, an oxygen barrier layer, and a sealant layer. [7] The resin film according to [6], wherein the outer layer contains polyethylene. [8] The resin film according to [6] or [7], wherein the functional layer contains an ionomer. [9] The resin film according to any one of [6] to [8], wherein the sealant layer contains a polyethylene resin.

[10] The resin film according to any one of [1] to [9], wherein the vacuum package for frozen raw meat is a skin pack package for frozen raw meat.

[11] . A vacuum package for frozen raw meat having a lid and a base, the lid being made of the resin film according to any one of [1] to

[10] .

[12] The oxygen permeability of the base material is 300cc / (m2

[11] The package according to

[11] , wherein the temperature is 100°C (-day-atm) or less.

[13] . A raw meat package in which raw meat is vacuum-packaged using the base material and lid material of the package described in

[11] or

[12] .

[14] . A method for storing raw meat, comprising storing the raw meat package described in

[13] at a temperature of -84°C or higher and lower than 0°C. [Effects of the Invention]

[0007] According to the present invention, a package is provided in which the film does not become brittle even under freezing conditions, the deterioration of frozen-packaged raw meat is suppressed and it can be stored for a long period of time, and further the dripping that occurs during thawing is suppressed to prevent the outflow of umami components, and it can be stored for a long period of time without deteriorating in taste as compared to conventional packages. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a resin film according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically showing an example of a vacuum package for frozen raw meat according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] <<Resin film (lid material)>> A resin film according to one embodiment of the present invention is a resin film for use as a lid material for a vacuum package for frozen raw meat, which includes a lid material and a base material. The resin film (lid material) is not particularly limited as long as it satisfies the conditions of oxygen permeability and dynamic modulus of elasticity E' described below and can be used to produce a lid material for a vacuum package for frozen raw meat.

[0010] As used herein, "freezing" means artificially freezing raw meat at a temperature below 0°C using equipment (a freezer or refrigerator) or liquid nitrogen or the like in order to preserve the quality of the raw meat, or freezing raw meat at a temperature below 0°C in a natural environment. The temperature is, for example, preferably −84°C or higher and lower than 0°C, more preferably −83°C or higher and −1°C or lower, even more preferably −82°C or higher and −2°C or lower, and particularly preferably −81°C or higher and −3°C or lower.

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

[0012] The vacuum package for frozen raw meat is preferably a skin pack package for frozen raw meat. In this specification, "skin pack" refers to a package in which the contents are placed on cardboard, corrugated board, a bottom film, a tray, etc., and then a heated film is placed over the contents, and a vacuum is drawn in a chamber so that the film adheres tightly to the contents. The name "skin pack" comes from the feature that the film adheres tightly to the product body, conforming to the shape of the product, just like skin.

[0013] The oxygen permeability of the resin 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 oxygen permeability of the resin film (lid material) under the conditions of a temperature of 23°C and a relative humidity of 60% is 100cc / (m 2 By keeping the freezing temperature below 100°C (days atm), deterioration of frozen-packaged raw meat can be suppressed and it can be stored for a long period of time.

[0014] The oxygen permeability of the resin film (lid material) under the conditions of a temperature of 23°C and a relative humidity of 60% is 95 cc / (m2 ·day·atm) or less, and 90cc / (m 2 ·day·atm) or less is more preferable, and 85cc / (m 2 ·day·atm) or less is more preferable, and 80cc / (m 2 ·day·atm) or less, for example, 75cc / (m 2 When the oxygen transmission rate of the resin film (lid material) under conditions of a temperature of 23°C and a relative humidity of 60% is equal to or less than the upper limit, 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 permeation rate is 0 cc / (m 2 ·day·atm) or more.

[0015] The oxygen permeation amount of the resin film (lid material) under 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 permeability of the resin film (lid material) can be more easily adjusted by, for example, adjusting the type and content of the components contained in the resin film, the thickness of the resin film, and the like.

[0017] The dynamic elastic modulus E' of the resin film (lid material) at a temperature of 140°C is 10 4 Over 10 7 The dynamic elastic modulus E' of the resin film (lid material) at a temperature of 140°C is 10 4 Over 10 7 By keeping the pressure at or below 100 Pa, the lid material can conform to the contents (packaged items) better. As a result, dripping that occurs during thawing is suppressed, preventing the loss of umami components, and allowing for long-term storage without any deterioration in flavor.

[0018] The dynamic elastic modulus E' of the resin film (lid material) at a temperature of 140°C is 1.0 × 10 4 Pa or more 1.0×10 7 Pa or less, and4 Pa or more 9.9×10 6 Pa or less is more preferable, and 1.2 × 10 4 Pa or more 9.8×10 6 Pa or less, more preferably 1.3 × 10 4 Pa or more 9.7×10 6 It is particularly preferable that the pressure is 1.4×10 Pa or less, for example. 4 Pa or more 9.6×10 6 The dynamic elastic modulus E' of the resin film at a temperature of 140°C may be equal to or greater than the lower limit, thereby further improving the ability of the lid material to conform to the packaged item (content). The dynamic elastic modulus E' of the resin film at a temperature of 140°C is equal to or less than the upper limit, thereby enabling packaging to be performed without compressing the shape of the packaged item (content).

[0019] The dynamic modulus of elasticity E' of the resin film (lid material) at a temperature of 140°C can be measured in accordance with JIS K7244-4. Specifically, it can be measured, for example, using a dynamic viscoelasticity measuring device ("DMA 7100" manufactured by Hitachi High-Tech Science Corporation). The measurement conditions are, for example, using a 4 mm wide sample in a tensile mode in the temperature range of 25°C to 160°C, a displacement of 10 μm, a vibration frequency of 1 Hz, and a temperature rise rate of 3°C / min.

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

[0021] It is preferable that the temperature at which the resin film shows a displacement of 2000 μm during thermomechanical analysis (TMA) is 120° C. or higher, or that the gel fraction is 30% or higher, thereby improving the heat resistance of the resin film and, as a result, improving the ability of the resin film to conform to the contents contained therein.

[0022] In thermomechanical analysis of the resin film (lid material), the temperature at which it shows a displacement of 2000 μm is preferably 120°C or higher, more preferably 120 to 200°C, and even more preferably 123 to 190°C, and may be, for example, 130 to 190°C. When the temperature is equal to or higher than the lower limit, the heat resistance of the resin film is further improved, and as a result, the ability of the resin film to conform to the contents is further improved. When the temperature is equal to or lower than the upper limit, the heat resistance of the resin film is prevented from becoming excessive.

[0023] During thermomechanical analysis of the resin film, the displacement at a temperature of 100°C is preferably 500 μm or less, more preferably 40 to 500 μm, and even more preferably 45 to 400 μm, and may be, for example, any one of 50 to 350 μm, 55 to 340 μm, and 55 to 250 μm. When the displacement is equal to or less than the upper limit, the melt tension of the resin film is improved, and as a result, the ability of the resin film to conform to the contents is further improved. When the displacement is equal to or more than the lower limit, the melt tension of the resin film is prevented from becoming excessive.

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

[0025] In thermomechanical analysis of the resin film, the temperature at which a displacement of 2000 μm occurs and the displacement at a temperature of 100° C. can be adjusted, for example, by irradiating the resin film with an electron beam and adjusting the conditions of the electron beam irradiation. For example, when the resin film is a multilayer film described below, the temperature and displacement can be more easily adjusted by adjusting the conditions of electron beam irradiation on an outer layer or a functional layer in the multilayer film.

[0026] The resin film is preferably irradiated with an electron beam at an absorbed dose of 13 to 300 kGy, more preferably 15 to 250 kGy. For example, the resin film may be irradiated with an electron beam at an absorbed dose of 20 to 250 kGy, 45 to 250 kGy, or 70 to 250 kGy. By ensuring that the absorbed dose is within this range, it is possible to more easily obtain a resin film in which, during thermomechanical analysis, the temperature at which the resin film exhibits a displacement of 2000 μm and the displacement at a temperature of 100°C are both within the above-mentioned numerical ranges. On the other hand, by ensuring that the absorbed dose is equal to or greater than the lower limit, the crosslink density of the resin film (particularly, when the resin film is a multilayer film, as described below, of the outer layer and functional layer in the multilayer film) is further improved, resulting in improved heat resistance and melt tension for the entire resin film. By ensuring that the absorbed dose is equal to or less than the upper limit, excessive strength of the resin film is prevented.

[0027] The reason why electron beam irradiation improves the crosslink density of the resin film (particularly, when the resin film is a multilayer film described below, the outer layer and functional layer in this multilayer film) is not clear, but is presumed to be as follows. That is, when the resin film is irradiated with an electron beam, carbon-hydrogen bonds in the resin (e.g., polyethylene, ionomer) are broken, and radicals are generated at the ends of the broken bonds. It is presumed that the generated radicals come into contact with molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains) due to molecular chain motion, abstract hydrogen atoms, and bond to carbon atoms in the molecular chains of other resins (e.g., other polyethylene molecular chains, other ionomer molecular chains), resulting in the formation of a crosslinked structure.

[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. By using such an acceleration voltage during electron beam irradiation, it is possible to more easily obtain a resin film in which, during thermomechanical analysis, the temperature at which the resin film shows a displacement of 2000 μm and the displacement at a temperature of 100°C are both within the above-mentioned numerical ranges. On the other hand, by using an acceleration voltage during electron beam irradiation that is equal to or greater than the lower limit, the crosslink density of the resin film (particularly, when the resin film is a multilayer film, as described below, of the outer layer and functional layer in the multilayer film) is further improved, resulting in improved heat resistance and melt tension for the entire resin film. By using an acceleration voltage during electron beam irradiation that is equal to or less than the upper limit, excessive strength of the resin film is prevented.

[0029] The gel fraction of the resin film is preferably 30% or more, more preferably 30 to 90%, and even more preferably 32 to 85%, and may be, for example, any one of 40 to 82%, 48 to 82%, and 55 to 82%. When the gel fraction of the resin film is equal to or greater than the lower limit, the heat resistance and melt tension of the resin film are improved, and as a result, the ability to conform to the contents is improved. When the gel fraction of the resin film is equal to or less than the upper limit, excessive strength of the resin film is prevented.

[0030] The gel fraction of the resin film can be measured in accordance with JIS K 6769, taking advantage of the fact that the crosslinked portion of the film is insoluble in the solvent. Specifically, the resin film is immersed in an organic solvent such as xylene, and the remaining insoluble film is dried. The mass of the resulting dried product is then measured, and the gel fraction can be calculated from the mass of the resin film before dissolution and the mass of the dried insoluble film. More specifically, for example, the resin film (mass Xg) is wrapped in a stainless steel mesh (mass Yg) and immersed in a heated solvent. The resin film wrapped in the stainless steel mesh (in other words, the insoluble film) is then removed. This is then vacuum-dried, and the mass (Zg) of the dried resin film wrapped in the stainless steel mesh (in other words, the insoluble film) is measured. The following formula (1) is then used: Gel fraction of resin film (mass%) = (ZY) / X × 100 (1) The gel fraction of the resin film is calculated by the above formula.

[0031] The gel fraction of the resin film can be adjusted, for example, by irradiating the resin film (particularly, when the resin film is a multilayer film described below, the outer layer or functional layer in the multilayer film) with an electron beam and adjusting the conditions for the electron beam irradiation. In this case, the conditions for the electron beam irradiation can be the same as those for adjusting the temperature at which a displacement of 2000 μm occurs and the displacement at a temperature of 100° C. in the thermomechanical analysis of the resin film described above.

[0032] The resin film preferably satisfies either one or both of the conditions of the temperature at which it shows a displacement of 2000 μm during thermomechanical analysis and the gel fraction. That is, examples of the resin film include those having a temperature of 120° C. or higher at which it shows a displacement of 2000 μm during thermomechanical analysis and a gel fraction of less than 30%; those having a temperature of less than 120° C. at which it shows a displacement of 2000 μm during thermomechanical analysis and a gel fraction of 30% or higher; and those having a temperature of 120° C. or higher at which it shows a displacement of 2000 μm during thermomechanical analysis and a gel fraction of 30% or higher. However, it is usually more preferable that the resin film satisfy both of the above conditions, i.e., that the temperature at which it shows a displacement of 2000 μm during thermomechanical analysis is 120°C or higher and that it has a gel fraction of 30% or higher.

[0033] The thickness of the resin film (lid material) is preferably 60 μm or more, more preferably 70 to 400 μm, and even more preferably 80 to 300 μm, and may be, for example, 100 to 200 μm. When the thickness of the resin film is equal to or greater than the lower limit, the strength of the resin film is further improved. When the thickness of the resin film is equal to or less than the upper limit, the resin film is prevented from becoming excessively thick.

[0034] The resin film is preferably a laminated film formed by laminating a plurality of layers. A preferred example of the resin film that is a laminated film is a multilayer film that includes an outer layer, a functional layer adjacent to the outer layer, an oxygen barrier layer, and a sealant layer.

[0035] It is preferable that all layers of the resin film (lid material) have transparency regardless of the type, that is, that the resin film is transparent. In a vacuum package for frozen raw meat made using such a resin film, the raw meat contained therein can be easily seen through the resin film (lid material).

[0036] The detailed structure of the resin film (lid material) and the method for producing the same will be described separately.

[0037] The present invention will be described in more detail below with reference to the drawings. Note that the drawings used in the following description may show essential parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional proportions of the components may not necessarily be the same as in reality.

[0038] <<One embodiment of resin film (lid material)>> FIG. 1 is a cross-sectional view that schematically shows an example of the multilayer film (laminate film) among the resin films (covering materials) in this embodiment. The multilayer film 1 shown here comprises 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 of the outermost layers, and the sealant layer 11 is the other outermost layer.

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

[0040] <Sealant layer> The sealant layer 11 may contain a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, or polyethylene-based copolymer (sometimes referred to herein as a "polyethylene-based resin in the sealant layer"). When the sealant layer 11 contains a polyethylene-based resin in the sealant layer, the multilayer film 1 exhibits pseudo-adhesion to the adherend, improving the easy-peelability.

[0041] In this specification, the term "polyethylene resin" refers to a resin having at least structural units derived from ethylene, and may have only structural units derived from ethylene, or may have structural units derived from ethylene and other structural units.

[0042] The sealant layer 11 may contain only a polyethylene-based resin in the sealant layer (i.e., the sealant layer may consist of a polyethylene-based resin), or may contain a polyethylene-based resin and other components (sometimes referred to as "other components" in this specification) in the sealant layer (i.e., the sealant layer may consist of a polyethylene-based resin and the other components).

[0043] The other components contained in the sealant layer 11 are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other resin component is a resin that does not fall under the category of polyethylene resin in the sealant layer. The other component, which is a resin component, may be a homopolymer, which is a polymer of one type of monomer, or a copolymer, which is a polymer of two or more types of monomers.

[0044] Examples of the other 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, and ultraviolet absorbers.

[0045] The other components contained in the sealant layer 11 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

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

[0047] In this specification, "room temperature" means a temperature that is neither particularly cold nor hot, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0048] The sealant layer 11 may consist of one layer (single layer) or two or more layers. When the sealant layer 11 consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0049] In this specification, not only in the case of the sealant layer 11, "multiple layers may be the same or different" means "all layers may be the same, all layers may be different, or only some layers may be the same," and further, "multiple layers are different" means "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, and even more preferably 10 to 90 μm, and may be, for example, any one of 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, the strength of the sealant layer 11 is increased. When the thickness of the sealant layer 11 is equal to or less than the upper limit, the sealant layer 11 is prevented from becoming excessively thick, and the seal strength is increased when the multilayer film 1 is sealed by heating. Here, "the thickness of the sealant layer 11" means the thickness of the entire sealant layer 11, and for example, the thickness of the sealant layer 11 consisting of multiple layers means the total thickness of all layers that make up the sealant layer 11.

[0051] An exposed surface 11a of the sealant layer 11 opposite to the outer layer 12 side (sometimes referred to as the "first surface" in this specification) 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, polyolefin resins and polyester resins may be collectively referred to as "outer layer resin"). When the outer layer 12 contains a resin, the crosslink density of the outer layer 12 can be improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. As a result, the conformability of a vacuum package for frozen raw meat made using the multilayer film 1 to the contents is improved.

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

[0054] The resin contained in the outer layer 12 has a density of 0.945 g / cm 3 Preferably, the polyethylene is a low density polyethylene having a density of 0.943 g / cm or less. 3 More preferably, the polyethylene is a low density polyethylene having a density of 0.941 g / cm or less. 3 The following low-density polyethylene is more preferable: By including such a low-density polyethylene (LDPE), the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side.

[0055] The resin contained in the outer layer 12 may be one kind or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0056] The other components contained in the outer layer 12 are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other resin component is a resin other than the resin in the outer layer.

[0057] The outer layer 12 may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0058] The proportion of the resin content in the outer layer 12 relative to the total mass of the outer layer 12 is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, and may be, for example, any of 70 to 100% by mass and 85 to 100% by mass. When the proportion is equal to or greater than the lower limit, the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam 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 resin in the outer layer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the outer layer, which will be described later.

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

[0060] The thickness of the outer layer 12 is not particularly limited, but is preferably 4 to 146 μm, more preferably 7 to 143 μm, and even more preferably 10 to 140 μm, and may be, for example, any one of 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, the crosslink density of the outer layer 12 can be further improved by irradiating the multilayer film 1 with an electron beam 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, the outer layer 12 is prevented from becoming excessively thick. Here, "thickness of outer layer 12" means the thickness of the entire outer layer 12; for example, the thickness of an outer layer 12 consisting of multiple layers means the total thickness of all layers that make up the outer layer 12.

[0061] The ratio of the thickness of the outer layer 12 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 12 to 88%, and even more preferably 14 to 86%. When this ratio is equal to or greater than the lower limit, the effect obtained by externally irradiating the multilayer film 1 with an electron beam from the outer layer 12 side is enhanced. When this ratio is equal to or less than the upper limit, the outer layer 12 is prevented from becoming excessively thick.

[0062] <Functional layer> The functional layer 13 contains a polyethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene, ionomer, or polyethylene-based copolymer (sometimes referred to herein as a "polyethylene-based resin in the functional layer"), and may be adjacent to the outer layer 12. When the functional layer 13 contains a polyethylene-based resin in the functional layer, the crosslink density of the functional layer 13 can be improved when the multilayer film 1 is irradiated with an electron beam from the outside on the outer layer 12 side. As a result, the conformability of a vacuum package for frozen raw meat made using the multilayer film 1 to the contents inside is further improved.

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

[0064] The polyethylene-based resin contained in the functional layer 13 may be, for example, a resin in which a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid has an ionic cross-linked structure due to salt formation between the acid portion and metal ions.

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

[0066] The polyethylene resin contained in the functional layer 13 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0067] The other components contained in the functional layer 13 are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than the polyethylene-based resin in the functional layer.

[0068] The functional layer 13 may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0069] The proportion of the polyethylene resin in the functional layer 13 relative to the total mass of the functional layer 13 is preferably 50 mass% or more, more preferably 55 to 100 mass%, and even more preferably 60 to 100 mass%, and may be, for example, 70 to 100 mass% or 85 to 100 mass%. When the proportion is equal to or greater than the lower limit, the crosslink density of the functional layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. This ratio is usually the same as the ratio of the content (parts by mass) of the polyethylene resin in the functional layer to the total content (parts by mass) of 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 two or more layers. When the functional layer 13 is composed of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0071] The thickness of the functional layer 13 is preferably 4 to 146 μm, more preferably 7 to 143 μm, and 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 equal to or greater than the lower limit, the crosslink density of the functional layer 13 can be further improved by irradiating the multilayer film 1 with an electron beam from the outside on the outer layer 12 side. When the thickness of the functional layer 13 is equal to or less than the upper limit, the functional layer 13 is prevented from becoming excessively thick. Here, "thickness of functional layer 13" means the thickness of the entire functional layer 13; for example, the thickness of functional layer 13 consisting of multiple layers means the total thickness of all layers that make up 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 equal to or greater than the lower limit, the effect obtained by externally irradiating the multilayer film 1 with an electron beam from the outer layer 12 side is enhanced. When the ratio is equal to or less than the upper limit, the functional layer 13 is prevented from becoming excessively thick.

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

[0074] The oxygen barrier layer 14 preferably contains ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer) or polyvinylidene chloride (PVDC) (EVOH and PVDC may be collectively referred to as "oxygen barrier resins" in this specification.) The oxygen barrier properties of the multilayer film 1 including such an oxygen barrier layer 14 are further improved.

[0075] The oxygen barrier layer 14 may contain only the oxygen barrier property-imparting resin (i.e., it may consist of the oxygen barrier property-imparting resin), or it may contain the oxygen barrier property-imparting resin and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist 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 selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than the oxygen barrier property-imparting resin. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer 11.

[0077] The oxygen barrier layer 14 may contain only one other component, or two or more components. When there are two or more components, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0078] The content of the oxygen barrier property-imparting resin in the oxygen barrier layer 14 relative to the total mass of the oxygen barrier layer 14 is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and even more preferably 70 to 100 mass%, and may be, for example, 85 to 100 mass%. When this proportion is equal to or greater than the lower limit, the oxygen barrier property of the multilayer film 1 is further improved. This ratio is usually the same as the ratio of the content (parts by mass) of the oxygen barrier property-imparting resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an oxygen barrier layer, which will be described later.

[0079] The oxygen barrier layer 14 may consist of one layer (single layer) or two or more layers. When the oxygen barrier layer 14 consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0080] The thickness of the oxygen barrier layer 14 is preferably 1 to 100 μm, more preferably 1.5 to 90 μm, and even more preferably 2 to 80 μm, and may be, for example, 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 equal to or greater than the above lower limit, the oxygen barrier property of the multilayer film 1 is improved. When the thickness of the oxygen barrier layer 14 is equal to or less than the above upper limit, the oxygen barrier layer 14 is prevented from becoming excessively thick. Here, the "thickness of the oxygen barrier layer 14" means the thickness of the entire oxygen barrier layer 14; for example, the thickness of the oxygen barrier layer 14 consisting of multiple layers means the total thickness of all layers that make up 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 this ratio is equal to or greater than the lower limit, the oxygen barrier properties of the multilayer film 1 are improved. When this ratio is equal to or less than the upper limit, the oxygen barrier layer 14 is prevented from becoming excessively thick.

[0082] In the case of skin pack packaging for food, the multilayer film constituting the skin pack packaging is required to have an oxygen barrier layer to prevent oxidative deterioration of the food. However, the presence of an oxygen barrier layer has the problem of reducing the skin pack packaging's ability to conform to food (its ability to adhere to food without wrinkling). In contrast, this problem is resolved by the skin pack packaging constructed using the multilayer film 1 of the present embodiment, which has an outer layer 12 and a functional layer 13. This is because the presence of the outer layer 12 and the functional layer 13 improves the heat resistance and melt tension of the multilayer film 1, resulting in the multilayer film 1 having excellent conformability to the contents.

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

[0084] The adhesive contained in adhesive layer 15 is not particularly limited as long as it can bond two layers to be bonded together with sufficient strength. The adhesive may be, for example, an adhesive resin such as an olefin-based resin (that is, a polymer of one or more olefin monomers).

[0085] More specific examples of the olefin-based resin contained in the adhesive layer 15 include ethylene-based copolymers, propylene-based copolymers, and butene-based copolymers. 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] The ethylene copolymer contained in the adhesive layer 15 may be, for example, a copolymer of ethylene and a vinyl group-containing monomer. Examples of copolymers of ethylene and vinyl group-containing monomers include maleic anhydride-grafted 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), and ethylene-based thermoplastic elastomer. Examples of the ionomer include the same ionomers as those listed above as those contained in the functional layer 13.

[0087] The propylene copolymer contained in the adhesive layer 15 may be, for example, a copolymer of propylene and a vinyl group-containing monomer. Examples of copolymers of propylene and vinyl group-containing monomers include maleic anhydride graft-modified linear low-density polypropylene and propylene-based thermoplastic elastomers.

[0088] Examples of the butene 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 of these copolymers (modified copolymers).

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

[0090] The adhesive layer 15 may contain only one type of adhesive, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

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

[0092] The other components contained in adhesive layer 15 may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0093] The content of the adhesive in the adhesive layer 15 relative to the total mass of the adhesive layer 15 may be, for example, 50 to 100 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 components that do not vaporize at room temperature in the adhesive layer-forming composition described below.

[0094] The adhesive layer 15 may consist of one layer (single layer) or two or more layers. When the adhesive layer 15 consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[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 one 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, the adhesive strength between the two layers to be bonded is increased. When the thickness of the adhesive layer 15 is equal to or less than the upper limit, the adhesive layer 15 is prevented from becoming excessively thick. Here, "thickness of adhesive layer 15" means the total thickness of adhesive layer 15 (for example, the total thickness of adhesive layer 15 arranged between pinhole-resistant layer 16 and oxygen barrier layer 14, or the total thickness of adhesive layer 15 arranged between oxygen barrier layer 14 and functional layer 13), and for example, the thickness of adhesive layer 15 consisting of multiple layers means the total thickness of all layers that make up adhesive layer 15.

[0096] <Pinhole-resistant layer> Although the multilayer film 1 does not necessarily have to include the pinhole-resistant layer 16, the pinhole resistance is enhanced by including the pinhole-resistant layer 16. Furthermore, in a package constructed using this multilayer film 1, the decrease in strength during heat treatment can be suppressed.

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

[0098] The pinhole-resistant layer 16 may contain only polyethylene-based resin in the pinhole-resistant layer (i.e., the pinhole-resistant layer may consist of polyethylene-based resin), or it may contain polyethylene-based resin and other components (sometimes referred to as "other components" in this specification) in the pinhole-resistant layer (i.e., the pinhole-resistant layer may consist of polyethylene-based resin and the other components).

[0099] The polyethylene resin contained in the pinhole-resistant layer 16 may be one type or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0100] The other components contained in the pinhole-resistant layer 16 are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than the polyethylene resin in the pinhole resistant layer.

[0101] The other components contained in the pinhole resistant layer 16 may be one type only, or two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0102] The proportion of the polyethylene resin in pinhole-resistant layer 16 relative to the total mass of pinhole-resistant layer 16 is preferably 50% by mass or more, more preferably 55 to 100% by mass, and even more preferably 60 to 100% by mass, and may be, for example, 70 to 100% by mass or 85 to 100% by mass. When the proportion is equal to or greater than the lower limit, the effect obtained by including a polyethylene resin in the pinhole-resistant layer of multilayer film 1 is further enhanced. This ratio is usually the same as the ratio of the content (parts by mass) of polyethylene resin in the pinhole-resistant layer to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the pinhole-resistant layer described below.

[0103] The pinhole-resistant layer 16 may consist of one layer (single layer) or two or more layers. When the pinhole-resistant layer 16 consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0104] The thickness of the pinhole-resistant layer 16 is preferably 4 to 146 μm, more preferably 7 to 143 μm, and even 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 above-mentioned lower limit, the pinhole resistance of the multilayer film 1 is further improved. When the thickness of the pinhole-resistant layer 16 is at most the above-mentioned upper limit, the pinhole-resistant layer 16 is prevented from becoming excessively thick. Here, "the thickness of the pinhole-resistant layer 16" means the thickness of the entire pinhole-resistant layer 16; for example, the thickness of the pinhole-resistant layer 16 consisting of multiple layers means the total thickness of all the layers that make up 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 this ratio is equal to or greater than the lower limit, the pinhole resistance of the multilayer film 1 is improved. When this ratio is equal to or less than the upper limit, the pinhole-resistant layer 16 is prevented from becoming excessively thick.

[0106] <Other layers> The multilayer film 1 may also have other layers that do not fall under any of the sealant layer 11, outer layer 12, functional layer 13, oxygen barrier layer 14, adhesive layer 15, and pinhole-resistant layer 16, as long as the effects of the present invention are not impaired.

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

[0108] The multilayer film 1 may have only one type of other layer, or two or more types. When there are two or more types, the combination and ratio of the layers can be selected arbitrarily depending on the purpose.

[0109] The other layers may each consist of one layer (single layer) or two or more layers. When the other layers consist of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0110] The thickness of the other layer can be set arbitrarily depending on the type of the other layer, and is not particularly limited.

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

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

[0113] The multilayer film of this embodiment is not limited to the one described above, and some of the configuration may be changed, deleted, or added within the scope of the spirit of the present invention. For example, the multilayer film does not necessarily have to include one or more of the pinhole-resistant layer, adhesive layer, and functional layer, but preferably 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, as shown in Figure 1.

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

[0115] The laminated film can also be produced by coating a resin or resin composition, etc., that will be used to form one of the layers, on the surface of another layer that will form the laminated film, and drying it as needed to form a laminated structure in the laminated film, and then, as needed, further laminating other layers so as to form the desired arrangement.

[0116] Alternatively, the laminated film can be produced by separately preparing two or more films for constituting any two or more of the layers, laminating these films together using an adhesive by any of dry lamination, extrusion lamination, hot melt lamination, and wet lamination, and then laminating other layers as needed to form the desired arrangement. In this case, the adhesive used may be one capable of forming the adhesive layer.

[0117] The laminated film can also be produced by laminating two or more films that have been prepared separately in advance, as described above, by a thermal lamination method or the like without using an adhesive, and, if necessary, further laminating other layers so as to achieve the desired arrangement.

[0118] When producing the laminated film, two or more of the methods for forming any of the layers (films) in the laminated film mentioned above may be combined.

[0119] Regardless of the manufacturing method, the resin composition that forms one of the layers in the laminated film may be manufactured by adjusting the types and contents of the components contained therein so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. 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 resin compositions (sometimes referred to herein as "sealant layer-forming compositions") for forming a sealant layer (sealant layer 11 in the multilayer film 1 shown in Figure 1) include those containing the polyethylene resin in the sealant layer and, if necessary, the other components described above.

[0121] Examples of resin compositions (sometimes referred to herein as "compositions for forming outer layers") for forming outer layers (outer layer 12 in the multilayer film 1 shown in Figure 1) include those containing the resins in the outer layer and, if necessary, the other components.

[0122] Examples of resin compositions (sometimes referred to in this specification as "compositions for forming functional layers") for forming functional layers (functional layer 13 in the multilayer film 1 shown in Figure 1) include those containing a polyethylene-based resin in the functional layer and, if necessary, the other components described above.

[0123] Examples of resin compositions (sometimes referred to herein as "oxygen barrier layer-forming compositions") for forming an oxygen barrier layer (oxygen barrier layer 14 in the multilayer film 1 shown in FIG. 1) include those containing the oxygen barrier property-imparting resin and, if necessary, the other components described above.

[0124] Examples of resin compositions (sometimes referred to in this specification as "compositions for forming pinhole-resistant layers") for forming a pinhole-resistant layer (pinhole-resistant layer 16 in the multilayer film 1 shown in Figure 1) include those containing the polyethylene resin in the pinhole-resistant layer and, if necessary, the other components described above.

[0125] Examples of resin compositions (sometimes referred to in this specification as "adhesive layer-forming compositions") for forming an adhesive layer (adhesive layer 15 in the multilayer film 1 shown in Figure 1) include those containing the adhesive and, if necessary, the other components described above.

[0126] <<Bottom material>> The base material has an oxygen permeability of 300cc / (m 2 There are no particular limitations as long as the material is usable as a base material for vacuum-packaged frozen raw meat and has a viscosity of not more than 1000 kJ / day atm. The base material may be a known material.

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

[0128] The oxygen permeability of the base material under 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 permeability of the sole material can be more easily adjusted by adjusting, for example, the type and amount of components contained in the sole material, the thickness of the sole 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 equal to or greater than the lower limit, the strength of the base material is further improved. The thickness of the base material is preferably 6000 μm or less. By keeping the thickness of the base material at or below the upper limit value, the base material is prevented from becoming excessively thick. The thickness of the base material can be adjusted appropriately within a range set by any combination of any of the above-mentioned lower limit values ​​and upper limit values.

[0131] Regardless of the type of base material, all layers may be transparent and the base material may be transparent, or all or some of the layers may not be transparent and the base material may not be transparent. In a vacuum package for frozen raw meat constructed using a transparent base material, the raw meat contained therein can be easily seen through the base material.

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

[0133] <<One embodiment of the base material>> The base material is preferably a laminated body formed by laminating a plurality of layers. A preferred example of a base material that is a laminate is a resin laminate that includes 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. The foamed resin layer may be, for example, a resin layer containing a foamed polystyrene 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 It is preferable that: The expansion ratio of the foamed resin layer is not particularly limited, but is preferably 2 to 20. The thickness of the foamed resin layer is not particularly limited, but is preferably 500 to 6000 μm.

[0136] The non-foamed resin layer may be, for example, a multi-layer film for base materials, which is constructed by laminating an easy-peel layer, an oxygen barrier layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction, where the easy-peel layer is one of the outermost layers and the adhesive layer is the other outermost layer.

[0137] The multi-layer film for a base material may include, for example, an intermediate adhesive layer between the easy-peel layer and the oxygen barrier layer for bonding these two layers together. The multi-layer film for base materials may also include, for example, an intermediate adhesive layer between the oxygen barrier layer and the pinhole resistant layer for bonding these two layers together. That is, the multilayer film for base materials may be constructed by laminating an easy-peel layer, an intermediate adhesive layer, an oxygen barrier layer, an intermediate adhesive layer, a pinhole-resistant layer, and an adhesive layer in this order in the thickness direction.

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

[0139] <Easy-peel layer> The easy peel layer in the multi-layer film for base materials may be one that exhibits peelability by cohesive failure. An example of an easy-peel layer that exhibits peelability by cohesive failure is one that contains two incompatible polyolefins.

[0140] Examples of the two incompatible polyolefins contained in the easy-peel layer of the multilayer film for base materials 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, the easy-peel layer may include, for example, 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] The ethylene polymer contained in the easy-peel layer of the multi-layer film for base materials includes an ethylene homopolymer and an ethylene copolymer.

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

[0143] The ethylene copolymer has structural units derived from ethylene and structural units derived from a monomer other than ethylene. Examples of the ethylene 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), and ionomer (ION). Examples of the ionomer include the same ionomers as those listed above as those contained in the functional layer 13 in the multilayer film 1 described above.

[0144] The easy-peel layer in the multi-layer film for base materials preferably contains low-density polyethylene as the ethylene polymer, which provides better easy-peel properties.

[0145] Examples of the propylene-based polymer contained in the easy-peel layer of the multi-layer film for base materials include a homopolymer of propylene (that is, polypropylene or homopolypropylene, hPP) and a propylene-based copolymer.

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

[0147] The easy-peel layer in the multi-layer film for base materials preferably contains polypropylene as the propylene-based polymer, which provides better easy-peel properties.

[0148] The component that exhibits easy peelability contained in the easy peel layer of the multilayer film for base materials may be only one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily depending on the purpose. For example, when the component that exhibits easy peelability is the above-mentioned two incompatible polyolefins, the easy peel layer may contain only one type or two or more types of these polyolefins.

[0149] In the easy-peel layer of the multilayer film for base materials, the ratio of the content (parts by mass) of the ethylene polymer to the total content (parts by mass) of the ethylene polymer and the propylene polymer is preferably 10 to 90% by mass, and may be, for example, 30 to 90% by mass, 45 to 90% by mass, or 60 to 90% by mass. When this ratio is equal to or greater than the lower limit, the easy-peel property of the easy-peel layer becomes better. When this ratio is equal to or less than the upper limit, the peel strength becomes more stable. The ratio is usually 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 an easy-peel layer for a base material, which will be described later.

[0150] The easy-peel layer in the multilayer film for base materials may contain other components in addition to the components that exhibit easy-peel properties (for example, the two incompatible polyolefins described above) as long as the easy-peel properties are not impaired. The other components contained in the easy-peel layer may be one kind or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0151] In the easy-peel layer of the multilayer film for base materials, the ratio of the content of the component that exhibits easy-peel properties to the total mass of the easy-peel layer (for example, the ratio of the combined content of the two incompatible polyolefins described above) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and may be, for example, any of 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 97 to 100% by mass, and 99 to 100% by mass. When this ratio is equal to or greater than the lower limit, the easy-peel property of the easy-peel layer becomes better. The above ratio is usually the same as the ratio of the content (parts by mass) of components that exhibit easy peel properties to the total content (parts by mass) of components that do not evaporate at room temperature in the composition for forming an easy peel layer for base materials described below.

[0152] Examples of the other components contained in the easy-peel layer in the multi-layer film for base materials include an anti-fogging agent and an anti-blocking agent.

[0153] The easy-peel layer in the multi-layer film for base materials may consist of one layer (single layer) or two or more layers. When the easy-peel layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0154] The thickness of the easy-peel layer in the multilayer film for base materials is preferably 2 to 50 μm. When the thickness of the easy-peel layer is equal to or greater than the lower limit, the seal strength of the easy-peel layer is appropriately increased. When the thickness of the easy-peel layer is equal to or less than the upper limit, the easy-peel property is further increased. Here, "thickness of the easy peel layer" means the thickness of the entire easy peel layer, for example, the thickness of an easy peel layer consisting of multiple layers means the total thickness of all layers that make up the easy peel layer.

[0155] The ratio of the thickness of the easy-peel layer to the thickness of the multilayer film for base material is not particularly limited, but is preferably 5 to 40%. When the ratio is equal to or greater than the lower limit, the seal strength of the easy-peel layer is appropriately increased. When the ratio is equal to or less than the upper limit, the easy-peel property is further increased.

[0156] <Oxygen barrier layer> The oxygen barrier layer imparts oxygen barrier properties (in other words, the property of inhibiting the permeation of oxygen gas) to the multi-layer film for base materials.

[0157] The oxygen barrier layer in the multilayer film for base materials preferably contains 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, and 6- Examples include copolymers of nylon and 6T-nylon, copolymers of 6-nylon and 6I-nylon, copolymers of 6-nylon, 66-nylon and 610-nylon, copolymers of 6-nylon, 66-nylon and 12-nylon (nylon 6 / 66 / 12), copolymers of 6-nylon, 66-nylon and 612-nylon, copolymers of 66-nylon and 6T-nylon, copolymers of 66-nylon and 6I-nylon, copolymers of 6T-nylon and 6I-nylon, and copolymers of 66-nylon, 6T-nylon and 6I-nylon.

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

[0160] The oxygen barrier layer in the multilayer film for base materials may contain only one type of polyamide, or two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0161] The oxygen barrier layer in the multilayer film for base materials may contain only one or both of an ethylene-vinyl alcohol copolymer and a polyamide (i.e., it may consist of one or both of an ethylene-vinyl alcohol copolymer and a polyamide), or it may contain one or both of an ethylene-vinyl alcohol copolymer and a polyamide and components other than these (sometimes referred to as "other components" in this specification) (i.e., it may consist of one or both of an ethylene-vinyl alcohol copolymer and a polyamide and the other components).

[0162] The other component contained in the oxygen barrier layer in the multilayer film for base materials is not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component that is a resin component is a resin that does not fall into either an ethylene-vinyl alcohol copolymer or a polyamide. Examples of the other components that are non-resin components include the same additives as those listed above as other components contained in the sealant layer 11 in the multilayer film 1 described above.

[0163] The oxygen barrier layer in the multilayer film for base materials may contain only one type of other component, or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0164] In the oxygen barrier layer in the multilayer film for base material, the proportion of the total content of the ethylene-vinyl alcohol copolymer and polyamide relative to the total mass of the oxygen barrier layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, either 70 to 100 mass% or 85 to 100 mass%. This ratio is usually the same as the ratio of the total content (parts by mass) of ethylene-vinyl alcohol copolymer and polyamide to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an oxygen barrier layer for base materials described below.

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

[0166] The thickness of the oxygen barrier layer in the multilayer film for base materials is preferably 2 to 20 μm. When the thickness of the oxygen barrier layer is equal to or greater than the lower limit, the oxygen barrier properties of the oxygen barrier layer are improved. When the thickness of the oxygen barrier layer is equal to or less than the upper limit, the oxygen barrier layer is prevented from becoming excessively thick. Here, the "thickness of the oxygen barrier layer" means the thickness of the entire oxygen barrier layer, and for example, the thickness of an oxygen barrier layer consisting of multiple layers means the total thickness of all layers that make up the oxygen barrier layer.

[0167] The ratio of the thickness of the oxygen barrier layer to the thickness of the multi-layer film for base materials is not particularly limited, but is preferably 5 to 15%. When the ratio is equal to or greater than the lower limit, the oxygen barrier properties of the multi-layer film for base materials are improved. When the ratio is equal to or less than the upper limit, the oxygen barrier layer is prevented from becoming excessively thick.

[0168] <Pinhole-resistant layer> The pinhole-resistant layer is a layer for protecting the structure of the multi-layer film for base material, for example, by suppressing the occurrence of pinholes in the multi-layer film for base material.

[0169] The pinhole-resistant layer in the multi-layer film for base materials preferably contains polyolefin. Examples of the polyolefin include polyethylenes 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 base materials may contain only polyolefin (i.e., it may consist of polyolefin), or it may contain polyolefin and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of polyolefin and the other components).

[0171] The other components contained in the pinhole-resistant layer in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component. The other component, which is a resin component, is a resin other than polyolefin. Examples of the other components that are non-resin components include the same additives as those listed above as 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 base materials may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0173] The proportion of the polyolefin content in the pinhole-resistant layer in the multilayer film for base materials relative to the total mass of the pinhole-resistant layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and may be, for example, either 70 to 100 mass% or 85 to 100 mass%. The ratio is usually the same as the ratio of the polyolefin content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a pinhole-resistant layer for base materials described below.

[0174] The pinhole-resistant layer in the multilayer film for base materials may consist of one layer (single layer) or two or more layers. When the pinhole-resistant layer consists of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0175] The thickness of the pinhole-resistant layer in the multilayer film for base materials is preferably 2 to 50 μm. When the thickness of the pinhole-resistant layer is equal to or greater than the lower limit, the protective ability of the pinhole-resistant layer is enhanced. When the thickness of the pinhole-resistant layer is equal to or less than the upper limit, the pinhole-resistant layer is prevented from becoming excessively thick. Here, "thickness of the pinhole-resistant layer" means the thickness of the entire pinhole-resistant layer; for example, the thickness of a pinhole-resistant layer consisting of multiple layers means the total thickness of all layers that make up the pinhole-resistant layer.

[0176] The ratio of the thickness of the pinhole-resistant layer to the thickness of the multi-layer film for base materials is not particularly limited, but is preferably 5 to 40%. When this ratio is equal to or greater than the lower limit, the pinhole resistance of the multi-layer film for base materials is improved. When this ratio is equal to or less than the upper limit, the pinhole-resistant layer is prevented from becoming excessively thick.

[0177] <Adhesive layer> The adhesive layer is a layer for adhering the base multi-layer film 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. The ethylene-vinyl acetate copolymer resin has a structural unit derived from ethylene and a structural unit derived from vinyl acetate, and may or may not have other structural units. A preferred example of the ethylene-vinyl acetate copolymer resin is a partially saponified ethylene-vinyl acetate copolymer.

[0179] The adhesive layer in the multilayer film for base materials may contain only an adhesive (i.e., it may consist of an adhesive), or it may contain an adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., it may consist of an adhesive and the other components).

[0180] The adhesive layer in the multi-layer film for base materials may contain only one type of adhesive, or two or more types. When two or more types are used, the combination and ratio of the adhesives can be selected as desired depending on the purpose.

[0181] The other components contained in the adhesive layer in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on 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 multi-layer film for base materials may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0183] The content of the adhesive in the adhesive layer in the multi-layer film for a base material may be, for example, 50 to 100% by mass relative to the total mass of the adhesive layer. 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 components that do not vaporize at room temperature in the composition for forming an adhesive layer for a base material, which will be described later.

[0184] The adhesive layer in the multi-layer film for base materials may consist of one layer (single layer) or two or more layers. When the adhesive layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0185] The thickness of the adhesive layer in the multi-layer film for base materials is preferably 2 to 40 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded is increased. When the thickness of the adhesive layer is equal to or less than the upper limit, the adhesive layer is prevented from becoming excessively thick. Here, "thickness of adhesive layer" means the thickness of the entire adhesive layer; for example, the thickness of an adhesive layer consisting of multiple layers means the total thickness of all layers that make up the adhesive layer.

[0186] The ratio of the thickness of the adhesive layer to the thickness of the multi-layer film for base materials is not particularly limited, but is preferably 5 to 40%. When the ratio is equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded is increased. When the ratio is equal to or less than the upper limit, the adhesive layer is prevented from becoming excessively thick.

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

[0188] Examples of the ethylene copolymer include the ethylene copolymers described above as being contained in the easy-peel layer, and modified products thereof (modified copolymers). Examples of the propylene copolymer include a copolymer of propylene and a vinyl group-containing monomer, a modified product thereof (modified copolymer), etc. More specific examples of such a propylene copolymer include maleic anhydride-grafted modified linear low-density polypropylene, a propylene-based thermoplastic elastomer, etc. Examples of the butene copolymer 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 of these copolymers (modified copolymers).

[0189] The first intermediate adhesive layer and the second intermediate adhesive layer may contain only adhesive (i.e., may consist of adhesive), or may contain adhesive and other components (sometimes referred to as "other components" in this specification) (i.e., may consist of adhesive and the other components).

[0190] The adhesive contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be one type only or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on 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 selected arbitrarily depending on the purpose, and may be, for example, either a resin component or a non-resin component.

[0192] The other components contained in the first intermediate adhesive layer and the second intermediate adhesive layer may be one type only or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0193] The content of the adhesive in the first intermediate adhesive layer in the multi-layer film for a base material may be, for example, 50 to 100% by mass relative to the total mass of the first intermediate adhesive layer. This ratio is usually the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not evaporate at room temperature in the composition for forming the first intermediate adhesive layer for the base material described below. The content of the adhesive in the second intermediate adhesive layer in the multi-layer film for a base material may be, for example, 50 to 100% by mass relative to the total mass of the second intermediate adhesive layer. This ratio is usually the same as the ratio of the adhesive content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming the second intermediate adhesive layer for the base material described below.

[0194] The first and second intermediate adhesive layers in the multilayer film for base materials may each consist of one layer (single layer) or two or more layers. When the first or second intermediate adhesive layer consists of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0195] The thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer in the multilayer film for base materials are preferably each independently 2 to 15 μm. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or greater than the lower limit, the adhesive strength between the two layers to be bonded is increased. When the thicknesses of the first intermediate adhesive layer and the second intermediate adhesive layer are equal to or less than the upper limit, the first intermediate adhesive layer and the second intermediate adhesive layer are prevented from becoming excessively thick. Here, the "thickness of the first intermediate adhesive layer" refers to the overall thickness of the first intermediate adhesive layer, for example, the thickness of a first intermediate adhesive layer consisting of multiple layers refers to the total thickness of all layers that make up the first intermediate adhesive layer. This also applies to the second intermediate adhesive layer.

[0196] The ratio of the thickness of the first intermediate adhesive layer and the second intermediate adhesive layer to the thickness of the multilayer film for base material is not particularly limited, but is preferably 3 to 20%. When the ratio is equal to or greater than the lower limit, the adhesive strength of the two layers to be bonded is increased. When the ratio is equal to or less than the upper limit, the first intermediate adhesive layer and the second intermediate adhesive layer are prevented from becoming excessively thick.

[0197] <Other layers> The multilayer film for base materials may also have other layers that do not fall under 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 positions of the other layers in the multi-layer film for base materials are not particularly limited and can be selected arbitrarily depending on the purpose.

[0199] The other layer provided in the multilayer film for base materials may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0200] The other layers in the multi-layer film for base materials may each consist of one layer (single layer) or two or more layers. When the other layers consist of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

[0201] The thickness of the other layers in the multi-layer film for base material can be set arbitrarily depending on the type of the other layers, and is not particularly limited.

[0202] When the multilayer film for base materials has the other layer, it may further have an intermediate adhesive layer for adhering the other layer to other layers, and in this case, the intermediate adhesive layer may be, for example, the same as the first intermediate adhesive layer or the second intermediate adhesive layer described above.

[0203] The thickness of the non-foamed resin layer of the multi-layer film for base material is not particularly limited, but is preferably 40 to 120 μm.

[0204] <<Sole manufacturing method>> The base material can be produced by a known method depending on the type. For example, when the base material is a resin laminate comprising the above-mentioned foamed resin layer and non-foamed resin layer, the base material can be produced by bonding one side of the foamed resin layer to one side of the non-foamed resin layer (or the adhesive layer therein, when the non-foamed resin layer is the multilayer film for base material) by heat lamination. The heat lamination in this case may be carried out by, for example, a melt-press lamination method as described later in the Examples, or by an extrusion lamination method. Of the non-foamed resin layers, the multi-layer film for base material can be produced in the same manner as the resin film (lid material) described above, except that the types of resins or resin compositions used to form each layer are different.

[0205] Regardless of the manufacturing method, the resin composition that forms one of the layers in the multi-layer film for base material may be manufactured by adjusting the types and contents of the components contained therein so that the layer to be formed contains the desired components (constituent materials) in the desired amounts. 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] Examples of resin compositions for forming an easy-peel layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming an easy-peel layer for base materials") include those containing the above-mentioned polyolefins and, if necessary, the above-mentioned other components.

[0207] Examples of resin compositions for forming an oxygen barrier layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming an oxygen barrier layer for base materials") include those containing either or both of an ethylene-vinyl alcohol copolymer and a polyamide, and, if necessary, the other components described above.

[0208] Examples of resin compositions for forming a pinhole-resistant layer in a multilayer film for base materials (sometimes referred to in this specification as "compositions for forming pinhole-resistant layers for base materials") include those containing the polyolefins described above and, if necessary, the other components described above.

[0209] The resin composition for forming the adhesive layer in the multilayer film for base material (sometimes referred to in this specification as the "composition for forming an adhesive layer for base material"), the resin composition for forming the first intermediate adhesive layer (sometimes referred to in this specification as the "composition for forming a first intermediate adhesive layer for base material"), and the resin composition for forming the second intermediate adhesive layer (sometimes referred to in this specification as the "composition for forming a second intermediate adhesive layer for base material") can all contain, for example, the adhesive and, if necessary, the other components described above.

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

[0211] The vacuum package 10 for frozen raw meat shown here is configured to include a multilayer film (lid material) 1 shown in FIG. In FIG. 2, the distinction between the layers in the multilayer film 1 is omitted.

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

[0213] In the vacuum package 10 for frozen raw meat, the oxygen permeability of the base 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 is preferable.

[0214] The vacuum package 10 for frozen raw meat uses the multilayer film 1, and therefore has excellent conformability to the raw meat 9 contained therein. In addition, the vacuum packaging 10 for frozen raw meat uses a multilayer film (lid material) 1 and a base material 8, which provides high oxygen barrier properties to the raw meat 9, and the storage period of the raw meat 9 is longer than in the case of conventional packaging.

[0215] One surface 8a of the base material 8 (sometimes referred to herein as the "first surface") is a sealing surface, and a portion of the first surface 8a is in close contact with a portion of the first surface 11a of the sealant layer 11 in the multilayer film 1 by sealing. In FIG. 2, the area where the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11 in the multilayer film 1 are in direct contact is the sealed portion. As a result, a storage portion 10a is formed between the first surface 8a of the base material 8 and the first surface 11a of the sealant layer 11. The raw meat 9 is sealed in this storage portion 10a.

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

[0217] In Figure 2, some gaps can be seen between the raw meat 9 and the multilayer film 1, and between the raw meat 9 and the base material 8 within the storage section 10a of the vacuum package 10 for frozen raw meat, but these gaps may not be present in the vacuum package 10 for frozen raw meat when the raw meat 9 is stored therein.

[0218] The vacuum packaging for frozen raw meat of this embodiment is not limited to the one described above, and some of the configuration may be changed, deleted, or added within the scope that does not deviate from the spirit of the present invention. For example, Figure 2 shows a vacuum package 10 for frozen raw meat that is constructed using the multilayer film 1 shown in Figure 1 as the lid material, but the package of this embodiment may also be constructed using other lid materials.

[0219] <<Fresh meat packaging and its manufacturing method>> The raw meat package of this embodiment is obtained by vacuum-packaging raw meat using the base material and the lid material of the vacuum package for frozen raw meat of this embodiment.

[0220] The raw meat packaging of this embodiment can be manufactured, for example, by placing raw meat on the surface of the base material that will seal with the lid material, covering the surface of the base material and the raw meat with the lid material from above, and vacuuming the area between the base material and the lid material where the raw meat is located, thereby tightly fixing the lid material to the raw meat, while heat-sealing the base material and the lid material in the area where the raw meat is not located. The test package described below can also be produced in the same manner.

[0221] The sealing temperature during heat sealing is not particularly limited, but is preferably 100 to 170° C. When the sealing temperature is equal to or higher than the lower limit, the seal strength is increased while maintaining easy peelability. When the sealing temperature is equal to or lower than the upper limit, the package is easier to open.

[0222] The heat-sealing time can be adjusted as appropriate depending on the sealing temperature, but is usually preferably 10 to 30 seconds. When the sealing time is equal to or greater than the lower limit, the seal strength is increased while maintaining easy peelability. When the sealing time is equal to or less than the upper limit, the package is easier to open.

[0223] The pressure in the region where the raw meat is placed due to evacuation during heat sealing is 5000 Pa (50 mbar) or less, preferably 300 Pa to 5000 Pa, more preferably 400 Pa to 4900 Pa, even more preferably 500 Pa to 4800 Pa, and particularly preferably 600 Pa to 4700 Pa. By keeping the pressure at or below the upper limit, the lid material has better conformability (adhesion) to the raw meat, and a raw meat package with better storage suitability can be obtained.

[0224] <<How to store raw meat>> The method for preserving raw meat in this embodiment is a method for preserving the raw meat package at a temperature below 0°C, and the temperature is, for example, preferably -84°C or higher and lower than 0°C, more preferably -83°C or higher and -1°C or lower, even more preferably -82°C or higher and -2°C or lower, and particularly preferably -81°C or higher and -3°C or lower. [Example]

[0225] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the examples shown below.

[0226] [Example 1] <<Manufacturing of multilayer film (lid material)>> A multilayer film having the structure shown in FIG. 1 was produced according to the following procedure. That is, an ethylene-vinyl acetate copolymer (EVA, "V5714C" manufactured by Mitsui Dow Polychemicals) was prepared as the resin constituting the sealant layer. The resin that makes up the outer layer is low-density polyethylene (LDPE, density 0.922 g / cm 3 and "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) were prepared. A sodium-based ionomer (ION, "1601" manufactured by DuPont-Mitsui Polychemicals Co., Ltd.) was prepared as the resin for forming the functional layer and the pinhole-resistant layer. An ethylene-vinyl alcohol copolymer (EVOH, "GH3804B" manufactured by Nippon Synthetic Co., Ltd.) was prepared as the resin for forming the oxygen barrier layer. As the adhesive (adhesive resin) constituting the adhesive layers (first adhesive layer and second adhesive layer), maleic anhydride modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

[0227] The die temperature was set to 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 produce a multilayer film (120 μm thick) composed of a sealant layer (24 μm thick), a pinhole-resistant layer (29 μm thick), an adhesive layer (first adhesive layer, 8 μm thick), an oxygen barrier layer (10 μm thick), an adhesive layer (second adhesive layer, 8 μm thick), a functional layer (17 μm thick), and an outer layer (24 μm thick) laminated in this order in the thickness direction.

[0228] Next, the multilayer film obtained above was irradiated with an electron beam from the outside of the outer layer side under conditions of an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. In this way, the desired electron beam irradiated multilayer film (hereinafter, sometimes referred to as "lid material (I)") was obtained.

[0229] <<Evaluation of multilayer film (lid material)>> <Measurement of dynamic elastic modulus at 140℃> The dynamic modulus of elasticity (E') of the electron beam-irradiated multilayer film (covering material (I)) obtained above was measured using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation, "DMA 7100") in accordance with JIS K7244-4 in a tensile mode using a 4 mm wide sample in the temperature range of 25°C to 160°C, with a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 3°C / min. The results are shown in Table 1.

[0230] <Temperature showing a displacement of 2000 μm, determination of displacement at a temperature of 100°C> The electron beam irradiated multilayer film (covering material (I)) obtained above was subjected to thermomechanical analysis in accordance with JIS K 7196 using a thermal analyzer ("EXSTAR6000" manufactured by SII Corporation). From the obtained thermomechanical analysis curve, the temperature (°C) showing a displacement of 2000 μm and the displacement (μm) at a temperature of 100°C were determined. The results are shown in Table 1.

[0231] <Gel fraction measurement> The gel fraction of the electron beam irradiated multilayer film (lid material (I)) obtained above was measured in accordance with JIS K 6769. That is, a test piece measuring 3 cm x 3 cm (approximately 0.09 g) was cut out from the multilayer film, wrapped in a 400-mesh stainless steel wire mesh (100 g), and immersed in xylene (18 mL) at 110°C for 24 hours. The test piece together with the wire mesh was then removed from the xylene 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 calculated. The results are shown in Table 1.

[0232] <Oxygen transmission rate measurement> The electron beam irradiated multilayer film (covering material (I)) obtained above was measured for oxygen permeability (cc / (m)) in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 60%. 2 The results are shown in Table 1.

[0233] <Flexibility test> The electron beam-irradiated multilayer film (lid material (I)) obtained above was subjected to a Gelbo Flex test under frozen conditions in accordance with ASTM F392 after moist heat sterilization. The sample was cut to 200 mm × 280 mm and rolled into a cylindrical shape with the 200 mm side circumferential and the 280 mm side axial. The cylindrical sample was placed in a Gelbo Flex tester. The Gelbo Flex tester used was a BE-1005 manufactured by Tester Sangyo Co., Ltd. With this tester, the sample was held at both ends and repeatedly crushed in the axial direction while twisting a certain angle and then returning to its original position. The axial crush stroke was 174 mm. The twist angle was 440°. The repetition rate was 45 cpm. The number of repetitions was 500. The test environment temperature was −20°C.

[0234] <Flexibility evaluation> The number of pinholes in the test sample was counted as follows: The test sample was opened, flattened, and placed on a piece of filter paper. Red ink was applied to the top surface of the test sample. The test sample was then removed, and the number of red ink spots on the filter paper was counted. The results are shown in Table 1.

[0235] <<Manufacture of soles>> <Manufacturing multi-layer film for base materials> A multi-layer film for a base material was produced according to the following procedure. That is, low-density polyethylene (LDPE, "L211" manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (PP, "FS2011DG2" manufactured by Sumitomo Chemical Co., Ltd.) were prepared as resins for forming the easy-peel layer. The resin constituting the pinhole-resistant layer was metallocene-catalyzed linear low-density polyethylene (mLLDPE) (Ube Maruzen Polyethylene Co., Ltd., "Yumerit (registered trademark) 1520F", density 0.913 g / cm 3 ) was prepared. The resin constituting the oxygen barrier layer was an ethylene-vinyl alcohol copolymer (EVOH, "J171B" manufactured by Kuraray Co., Ltd., density: 1180 kg / m 3 , MFR: 4.2g / 10min) 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) 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, an ethylene-vinyl acetate copolymer resin (EVA resin, adhesive resin, "MELTHEN (registered trademark) MX02D" manufactured by Tosoh Corporation was prepared.

[0236] The LDPE (70 parts by mass) and the PP (30 parts by mass) were mixed at room temperature to prepare a composition for forming an easy peel layer for a base material.

[0237] The die temperature was set to 250°C, and the composition for forming the easy-peel layer for base materials, 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 base materials (70 μm thick) composed of an easy-peel layer (25.9 μm thick), a first intermediate adhesive layer (5.6 μm thick), an oxygen barrier layer (8.4 μm thick), a second intermediate adhesive layer (5.6 μm thick), a pinhole-resistant layer (10.5 μm thick), and an adhesive layer (14 μm thick) laminated in this order in the thickness direction.

[0238] <Manufacture of soles> A foamed resin sheet (manufactured by Chuo Chemical Co., Ltd., thickness 3000 μm) containing a foamed polystyrene resin (PSP) was used, and the exposed surface of the adhesive layer of the multi-layer film for base material obtained above was bonded to one side of the sheet by heat lamination to obtain a base material (hereinafter sometimes referred to as "base material (α)"). The foamed resin sheet and the multi-layer film for base material were heat-laminated by melt-press lamination using a roll device equipped with a melt-press roll. The melt-press roll was composed of a heated roll and an opposing roll arranged opposite the heated roll, and the foamed resin sheet and the multi-layer film for base material were bonded together by melt-press lamination at 180°C between the heated roll and the opposing roll.

[0239] <<Evaluation of base material>> <Oxygen transmission rate measurement> The obtained base material (base material (α)) was measured for oxygen permeability (cc / (m)) in accordance with JIS K 7126-2:2006 under the conditions of a temperature of 23°C and a relative humidity of 60%. 2 The results are shown in Table 3.

[0240] <<Manufacturing of vacuum-packaged frozen raw meat (test packaging)>> Carcasses were obtained from slaughtered Wagyu cattle and stored in an air atmosphere at 4°C for two days. Next, a cull of meat was obtained from the carcass after this primary storage, and this cull of meat (25 kg) was vacuum-packed in an oxygen barrier film and stored for 5 days at 4°C in an air atmosphere. The oxygen barrier film was constructed by laminating a polyethylene layer, an ethylene-vinyl acetate copolymer layer, a polyvinylidene chloride layer, an ethylene-vinyl acetate copolymer layer, and an ultra-low density polyethylene layer in this order in the thickness direction (thickness 50 μm, size 30 cm × 50 cm), and its oxygen permeability measured in accordance with JIS K 7126-2:2006 was 10 cc / (m 2 The vacuum packaging was performed by setting the heat sealing temperature at 120°C, the sealing time at 3 seconds, and the pressure in the area where the meat portion was placed at 30 mbar (3000 Pa).

[0241] Next, a test piece of sirloin meat weighing 0.3 kg was cut from the cut meat in the vacuum package after the secondary storage. The sealant layer in the lid material (I) and the easy-peel layer in the base material (α) were then placed opposite each other, and the test meat was placed between the lid material (I) and the base material (α). While evacuating the area where the test meat was placed, the periphery of the lid material (I) and the base material (α) were heat-sealed at a sealing temperature of 150°C for a sealing time of 10 seconds, thereby producing a test package, which was a vacuum package for frozen raw meat (a skin-pack package for frozen raw meat). During evacuation, a pressure of 30 mbar (3000 Pa) was applied to the area where the test meat was placed. The base material (α) measured 20 cm x 20 cm. A plurality of test packages were prepared using the same procedure. These test packages were frozen at -30°C in an air atmosphere and stored for tertiary storage. Furthermore, test meat was prepared from the thigh and arm parts in the same manner as above, and packaging and storage were carried out in the same manner.

[0242] <<Evaluation of vacuum packaging for frozen raw meat (test packaging)>> <Evaluation of meat discoloration> Sixty days after the start of the tertiary storage, the meat was thawed from a frozen state of -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was removed 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.

[0243] <Evaluation of tracking ability> Sixty days after the start of the tertiary storage, the frozen test packages were thawed from -30°C to 4°C over 16 hours. Immediately after thawing, the unopened test packages were visually inspected and the ability of the lid material to conform 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 piece, and it has high conformability. B: Although inferior to A, there is little lift of the lid material from the test piece and the conformability is good. C: The lid material floats significantly from the test piece, and conformability is poor. D: The lid material does not conform to the test meat.

[0244] <Drip evaluation> Sixty days after the start of the tertiary storage, the meat was thawed from a frozen state of -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was removed from the unopened test package and left for 5 minutes, after which the amount of dripping and the cloudiness of the dripping were visually observed according to the following criteria. The results are shown in Table 4. [Evaluation criteria] A: There is no or very little dripping. B: Inferior to A, but less dripping occurs and the dripping is less cloudy. C: A large amount of dripping occurs and the dripping is often cloudy.

[0245] <Evaluation of juiciness and flavor> Sixty days after the start of the tertiary storage, the meat was thawed from a frozen state at -30°C to 4°C over 16 hours. Immediately after thawing, the test meat was removed from the unopened test package and cut into a 1cm x 3.5cm x 4.5cm thick piece. The test meat was heated on a hot plate heated to 220°C for 60 seconds on the front side and 90 seconds on the back side. The test meat was then cut into three equal pieces, each serving per test meat. Taste samples were prepared, with one piece per person. Seven panelists (sensory testers) tasted the meat and evaluated its juiciness and flavor when chewed according to the following criteria. The results are shown in Table 4. [Evaluation criteria (succulent)] A: Good juiciness. B: Less juicy than A, but still succulent. C: It has almost no juice and is dry. [Evaluation criteria (flavor)] A: The meat has a good flavor. B: Inferior to A, but still has a meaty flavor. C: The meat has almost lost its flavor.

[0246] [Example 2] An electron beam-irradiated multilayer film (hereinafter sometimes referred to as "lid material (II)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was changed from 175 kGy to 120 kGy. A vacuum package for frozen raw meat (test package) was produced 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.

[0247] [Example 3] An electron beam-irradiated multilayer film (hereinafter sometimes referred to as "covering material (III)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was 90 kGy instead of 175 kGy. A vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (lid material (III)) was used. The results are shown in Tables 1, 3 and 4.

[0248] [Example 4] An electron beam-irradiated multilayer film (hereinafter sometimes referred to as "covering material (IV)") was produced and evaluated in the same manner as in Example 1, except that the absorbed dose when irradiating the multilayer film with electron beams was 15 kGy instead of 175 kGy. A vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1, except that this electron beam irradiated multilayer film (lid material (IV)) was used. The results are shown in Tables 1, 3 and 4.

[0249] [Example 5] <<Production and evaluation of base materials>> A multilayer film for base material was produced 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 as the resin constituting the oxygen barrier layer instead of the EVOH ("J171B" manufactured by Kuraray Co., Ltd.). The multilayer film for base materials produced in this example is a multilayer film for base materials (thickness 70 μm) composed of 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) laminated in the thickness direction in this order. Then, except for using this multi-layer film for a base material, a base material (hereinafter sometimes referred to as "base material (β)") was produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0250] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the base material (β) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0251] [Comparative Example 1] A lid material (a multilayer film not irradiated with electron beams, hereinafter sometimes referred to as "lid material (V)") was manufactured 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 this multilayer film (lid material (V)) that had not been irradiated with electron beams was used. The results are shown in Tables 1, 3 and 5.

[0252] Comparative Example 2 <<Production and evaluation of base materials>> A multilayer film for base material was produced in the same manner as in Example 1, except that metallocene-catalyzed linear low-density polyethylene (mLLDPE, Ube Maruzen Polyethylene's "4040FC", melting point 126°C) was used as the resin constituting the oxygen barrier layer instead of the EVOH (Kuraray's "J171B"). The multilayer film for base materials produced in this comparative example is a multilayer film for base materials (thickness 70 μm) constructed by laminating 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) in this order in the thickness direction. Then, except for using this multi-layer film for a base material, a base material (hereinafter sometimes referred to as "base material (γ)") was produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0253] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the base material (γ) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0254] Comparative Example 3 <<Production and evaluation of multilayer film (lid material)>> An electron beam irradiated multilayer film (hereinafter sometimes referred to as "lid material (VI)") was produced 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 as the resin constituting the oxygen barrier layer instead of the EVOH ("GH3804B" manufactured by Nippon Synthetic Co., Ltd.). The electron beam irradiated multilayer film (covering material (VI)) produced in this comparative example was obtained by irradiating an electron beam from the outside of the outer layer side of a multilayer film (120 μm thick) composed of a sealant layer (24 μm thick), a pinhole-resistant layer (29 μm thick), an adhesive layer (first adhesive layer, 8 μm thick), an oxygen barrier layer (10 μm thick), an adhesive layer (second adhesive layer, 8 μm thick), a functional layer (17 μm thick), and an outer layer (24 μm thick) laminated in this order in the thickness direction, at an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. This electron beam irradiated multilayer film (covering material (VI)) was then evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0255] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the lid material (VI) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0256] Comparative Example 4 <<Production and evaluation of multilayer film (lid material)>> The multilayer film was produced according to the following procedure. 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) was prepared as the resin for forming the outer layer. As the resin for forming the pinhole-resistant layer, 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd.) was prepared. As the resin for forming the oxygen barrier layer, an ethylene-vinyl alcohol copolymer (EVOH, "J171B" manufactured by Kuraray Co., Ltd.) was prepared. Low-density polyethylene (LDPE, "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared as the resin for forming the cushion layer. 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.

[0257] The die temperature was set to 250°C, and the LDPE, the LDPE, the modified PE, the NY, the EVOH, the modified PE, and the PETG were co-extruded in this order (co-extrusion T-die method) to produce a multilayer film (thickness 120 μm) composed of 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) laminated in this order in the thickness direction.

[0258] Next, the multilayer film obtained above was irradiated with an electron beam from the outside of the outer layer side under conditions of an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. In this way, the desired electron beam irradiated multilayer film (hereinafter, sometimes referred to as "covering material (VII)") was obtained. This electron beam irradiated multilayer film (covering material (VII)) was then evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0259] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the lid material (VII) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0260] Comparative Example 5 <<Production and evaluation of multilayer film (lid material)>> An electron beam irradiated multilayer film (hereinafter sometimes referred to as "lid material (VIII)") was produced in the same manner as in Comparative Example 4, except that an ionomer (ION, Mitsui Dow Polychemicals "1855") was used instead of low-density polyethylene (LDPE, Ube Maruzen Polyethylene "F222NH") ​​as the resin constituting the sealant layer, 6-nylon (Ny6, Ube Industries "1030B2") was used instead of amorphous polyethylene terephthalate (PETG, SK Chemicals "S2008") as the resin constituting the outer layer, and ethylene-methacrylic acid copolymer (EMAA, Mitsui Dow Polychemicals "N0903HC") was used instead of low-density polyethylene (LDPE, Ube Maruzen Polyethylene "F222NH") ​​as the resin constituting the cushion layer. The electron beam irradiated multilayer film (covering material (VIII)) produced in this comparative example was obtained by irradiating an electron beam from the outside of the outer layer side of a multilayer film (120 μm thick) composed of a sealant layer (24 μm thick), cushion layer (40 μm thick), adhesive layer (first adhesive layer, 8 μm thick), pinhole-resistant layer (24 μm thick), oxygen barrier layer (6 μm thick), adhesive layer (second adhesive layer, 10 μm thick) and outer layer (8 μm thick) laminated in this order in the thickness direction, at an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. This electron beam irradiated multilayer film (covering material (VIII)) was then evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0261] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the lid material (VIII) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0262] Comparative Example 6 <<Production and evaluation of multilayer film (lid material)>> 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, 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 Polychemicals Co., Ltd.) as the resin constituting the sealant layer. The electron beam irradiated multilayer film (covering material (IX)) produced in this comparative example was obtained by irradiating an electron beam from the outside of the outer layer side of a multilayer film (120 μm thick) composed of a sealant layer (8 μm thick), cushion layer (46 μm thick), adhesive layer (first adhesive layer, 8 μm thick), pinhole-resistant layer (30 μm thick), oxygen barrier layer (6 μm thick), adhesive layer (second adhesive layer, 10 μm thick) and outer layer (12 μm thick) laminated in this order in the thickness direction, at an absorbed dose of 175 kGy and an acceleration voltage of 160 kV. This electron beam irradiated multilayer film (lid material (IX)) was then evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0263] <<Production and evaluation of vacuum packaging for frozen raw meat>> Except for using the lid material (IX) obtained above, a vacuum package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0264] Comparative Example 7 <<Production and Evaluation of Vacuum-Sealed Packages for Frozen Raw Meat>> The sealant layer in the lid material (I) obtained above was placed opposite the sealant layer in the lid material (I), the test meat was placed between these lid materials (I), and while degassing the area where the test meat was placed, the lid material (I) and the periphery of the lid material (I) were heat-sealed at a sealing temperature of 140°C for a sealing time of 2 seconds to produce a test package that was a vacuum-sealed package for frozen raw meat. A vacuum-sealed package for frozen raw meat (test package) was produced and evaluated in the same manner as in Example 1, except that the test package was produced by heat-sealing the periphery of the lid material (I) and the lid material (I) at a sealing temperature of 140°C for a sealing time of 2 seconds while degassing the area where the test meat was placed. The results are shown in Table 5.

[0265] [Table 1]

[0266] [Table 2]

[0267] [Table 3]

[0268] [Table 4]

[0269] [Table 5]

[0270] As is clear from the above results, in Examples 1 to 5, no discoloration occurred in the packaged test meat, whether it was the sirloin, thigh or arm portion. As described above, the vacuum packaging for frozen raw meat of Examples 1 to 5 was able to suppress deterioration of the frozen-packaged raw meat and store it for a long period of time, regardless of whether the test meat was sirloin, thigh, or arm. In the vacuum packages for frozen raw meat of Examples 1 to 5, the oxygen permeability of the lid material was 6 cc / (m 2 ·day·atm), and the oxygen permeability of the base material is 250cc / (m 2 ·day · atm) or less (2~250cc / (m 2 The number of Gelboflex pinholes was 8 or less.

[0271] In the vacuum packages for frozen raw meat of Examples 1 to 5, the lid material had good conformability to the raw meat for all test meats, including sirloin, thigh, and arm, and had preferable properties as a vacuum package for frozen raw meat. In particular, the vacuum packages for frozen raw meat of Examples 1 to 3 and 5 had particularly excellent conformability to the raw meat. In the lid materials of Examples 1 to 5, the dynamic modulus of elasticity at 140°C was 10 4 Over 10 6 Pa or less (5.5×10 4 ~5.2×10 6 ), the absorbed dose was 15 kGy or more (15 to 175 kGy), the temperature at which a displacement of 2000 μm was observed during the thermomechanical analysis was 125°C or more (125 to 185°C), the displacement at a temperature of 100°C during the thermomechanical analysis was 320 μm or less (62 to 320 μm), and the gel fraction was 35% or more (35 to 78%). Among these, the covering materials of Examples 1 to 3 and 5 had an absorbed dose of 90 kGy or more (90 to 175 kGy), the temperature at which a displacement of 2000 μm was observed during the thermomechanical analysis was 135°C or more (135 to 185°C), the displacement at a temperature of 100°C during the thermomechanical analysis was 120 μm or less (62 to 120 μm), and the gel fraction was 60% or more (60 to 78%).

[0272] Furthermore, the amount of dripping was well suppressed and the juiciness was also good in Examples 1 to 5. Among these, the vacuum packages for frozen raw meat in Examples 1 to 3 and 5 were particularly excellent. As described above, the vacuum packaging for frozen raw meat of Examples 1 to 5 did not cause the film to become brittle even when frozen, suppressed dripping that occurred when thawing, and prevented the leakage of umami components, making it possible to store the product for a long period of time without any deterioration in taste compared to conventional packaging.

[0273] In contrast, in the vacuum package for frozen raw meat of Comparative Example 1, the lid material had poor conformability to the raw meat for all test meats (sirloin, thigh, and arm), and did not have desirable characteristics as a vacuum package for frozen raw meat. Furthermore, drips leaked into the open space of the package during storage, causing the meat color to deteriorate. Furthermore, umami components leaked out, resulting in the cooked meat having a dry taste. Furthermore, it is thought that when a large amount of drip is produced, bacteria are more likely to grow in the released nutrient-rich drip, resulting in a poor meat color. The lid material (multilayer film) of Comparative Example 1 was not irradiated with electron beams, and as a result, it had a low dynamic modulus at 140°C, a low temperature at which it showed a displacement of 2000 μm during the thermomechanical analysis, a large displacement at a temperature of 100°C during the thermomechanical analysis, and a low gel fraction. Furthermore, the number of Gelboflex pinholes was 12, which was a large number.

[0274] In Comparative Example 2, discoloration occurred on the base material side of the packaged test meat, which was the sirloin, thigh, or arm portion. As described above, the vacuum package for frozen raw meat of Comparative Example 2 was unable to prevent deterioration of the frozen-packaged raw meat and enable long-term storage. In the vacuum package for frozen raw meat of Comparative Example 2, the oxygen permeability of the base material was 500 cc / (m 2 ·day·atm), which was a lot.

[0275] In Comparative Example 3, discoloration occurred on the lid side of the packaged test meat in all test meats, including the sirloin, thigh and arm parts. Thus, the vacuum package for frozen raw meat of Comparative Example 3 was also unable to prevent deterioration of the frozen-packaged raw meat and enable long-term storage. In the vacuum package for frozen raw meat of Comparative Example 3, the oxygen permeability of the lid material was 120 cc / (m 2 The number of Gelboflex pinholes was 15, which was also a large number.

[0276] In Comparative Examples 4 to 6, the lid material compressed the shape of the raw meat in all test meats (sirloin, thigh, and arm), and did not have desirable properties as a vacuum package for frozen raw meat. Furthermore, in all test meats (sirloin, thigh, and arm), the cytoplasm of the raw meat was destroyed during packaging, causing drips to leak out when opened, and the drips became cloudy in color. Furthermore, because umami components leaked out, the cooked meat tasted dry. As described above, the vacuum packages for frozen raw meat of Comparative Examples 4 to 6 were unable to suppress dripping that occurs during thawing and prevent the outflow of umami components, and therefore tasted worse than before when stored for a long period of time. The vacuum packages for frozen raw meat of Comparative Examples 4 to 6 had a high dynamic modulus of elasticity and a low gel fraction at 140° C. The number of Gelboflex pinholes was also high, at 40 or more (40 to 72).

[0277] In addition, the vacuum-sealed package for frozen raw meat in Comparative Example 7 only had a vacuum-sealed lid, so the lid did not conform to the shape of the raw meat, regardless of whether it was sirloin, thigh, or arm, resulting in excessive wrinkles. Furthermore, drips leaked into the open space in the package during storage, and the color of the drips became cloudy. Furthermore, because umami components leaked out, the cooked meat became dry and the flavor of the meat was lost. As described above, the vacuum sealed package for frozen raw meat of Comparative Example 7 was unable to suppress dripping that occurs during thawing and prevent the leakage of umami components, and therefore the taste deteriorated compared to conventional packages when stored for a long period of time. [Industrial Applicability]

[0278] To provide a package in which the film does not become brittle even under freezing conditions, the deterioration of frozen-packaged raw meat is suppressed and it can be stored for a long period of time, and further the dripping that occurs during thawing is suppressed to prevent the outflow of umami components, and it can be stored for a long period of time without deteriorating the taste as compared with conventional packages. [Explanation of symbols]

[0279] 1. Multilayer film (lid material) 11. Sealant layer 12...outer layer 13. Functional Layer 14. Oxygen barrier layer 15...Adhesive layer 151...1st adhesive layer 152...Second adhesive layer 16. Pinhole-resistant layer 10. Vacuum packaging for frozen raw meat (test packaging) 8...Bottom material 9. Raw meat (test meat)

Claims

1. A vacuum package for frozen raw meat having a lid material and a bottom material, The oxygen permeability under the conditions of a temperature of 23°C and a relative humidity of 60% is 100 cc / (m ２ ·day·atm) or less, and the dynamic modulus of elasticity E' at a temperature of 140°C is 10 ４ Pa or more 10 ７ The lid material is a resin film for lid material having a viscosity of 100 Pa or less, The resin film for lid material is An outer layer; a functional layer adjacent to the outer layer; an oxygen barrier layer; a sealant layer; a pinhole resistant layer adjacent to the sealant layer; a first adhesive layer that bonds the pinhole resistant layer and the oxygen barrier layer; a second adhesive layer that bonds the oxygen barrier layer and the functional layer; A multilayer film comprising: the outer layer comprises polyethylene; the functional layer contains a sodium-based ionomer, the oxygen barrier layer comprises an ethylene-vinyl alcohol copolymer; the sealant layer comprises an ethylene-vinyl acetate copolymer; the pinhole-resistant layer contains a sodium-based ionomer, the first adhesive layer comprises maleic anhydride-modified polyethylene; the second adhesive layer comprises maleic anhydride-modified polyethylene; A vacuum package for frozen raw meat, wherein the oxygen permeability of the base material is 300 cc / (m 2 ·day·atm) or less.

2. 2. The vacuum packaging for frozen raw meat according to claim 1, wherein the temperature at which the resin film for lid material shows a displacement of 2000 μm during thermomechanical analysis is 120° C. or higher.

3. 2. The vacuum package for frozen raw meat according to claim 1, wherein the resin film for lid material has a gel fraction of 30% or more.

4. The vacuum packaging body for frozen raw meat according to any one of claims 1 to 3, wherein the resin film for lid material is irradiated with electron beams under conditions of an absorbed dose of 13 to 300 kGy.

5. 3. The vacuum packaging for frozen raw meat according to claim 2, wherein the displacement of the resin film for lid material at a temperature of 100°C during the thermomechanical analysis is 500 μm or less.

6. The vacuum package for frozen raw meat according to any one of claims 1 to 5, wherein the vacuum package for frozen raw meat is a skin pack package for frozen raw meat.

7. A raw meat package in which raw meat is vacuum-packaged using the base material and the lid material in a vacuum package for frozen raw meat described in any one of claims 1 to 6.

8. A method for storing raw meat, comprising storing the raw meat package according to claim 7 at a temperature of -84°C or higher and lower than 0°C.

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