JP7547838B2 - Laminated film and packaging material - Google Patents

Description

The present invention relates to a laminated film and a packaging body.

Various foods, including processed meat products such as ham, sausages, and bacon, are distributed in vacuum-packed packages.
In vacuum packaging, for example, a base material and a lid material made of a resin film are used, the packaged item (food) is sandwiched between the lid material and the base material, the portion that will become the storage section is vacuumed, and the lid material and the base material are heat-sealed to package the packaged item. The base material may have a recess formed therein to form a storage section for the packaged item. In this case, the packaged item is placed in the recess in the base material, the packaged item is sandwiched between the lid material and the base material, the inside of the storage section formed by the lid material and the base material is vacuumed in the recess, and the periphery of the lid material and the base material are heat-sealed into a frame shape to package the packaged item. A resin film suitable for forming a package for such purposes has been disclosed (see Patent Document 1).

JP 2016-222259 A

In order to maintain the quality of the packaged food for a long period of time, the package produced by vacuum packaging of food may be subjected to high-pressure sterilization before shipping. High-pressure sterilization of the package is carried out by holding the package in high-pressure water for a specific period of time.
However, when packaging made from conventional resin films is subjected to high-pressure sterilization, some foods may discolor during long-term storage. Even if the discoloration is slight and does not affect the quality for consumption, the change in appearance reduces the commercial value of the food.

The objective of the present invention is to provide a resin film suitable for vacuum packaging food, which enables high-pressure sterilization of the package obtained by vacuum packaging food, and which can suppress discoloration of the food during long-term storage of the package after high-pressure sterilization, and a package using the resin film.

In order to solve the above problems, the present invention employs the following configuration.
[1] A laminate film, wherein when the laminate film is subjected to a Gelbo flex test in accordance with ASTM F392 at a temperature of 23°C and 500 flexes, the number of pinholes observed in the laminate film after the Gelbo flex test is 100 or less, and the oxygen transmission rate of the laminate film measured in accordance with JIS K 7126-2:2006 at a temperature of 23°C and a relative humidity of 50% is 1.0 ml/( ^m2 ·24h·atm) or less.
[2]. A test package is prepared by using a test lid material made of a resin film having a sealant layer containing linear low-density polyethylene, and a test base material made of the laminated film having a recess formed therein for forming a storage section for the packaged item, placing the packaged item in the recess, sandwiching the packaged item between the test lid material and the test base material, evacuating the inside of the storage section formed by the test lid material and the test base material in the recess at a temperature of 140°C and a vacuuming time of 2 seconds, and then sealing the peripheral parts of the test lid material and the test base material into a frame shape at a sealing temperature of 140°C and a sealing time of 2 seconds to form a frame seal section, thereby providing the frame seal section, and further providing a surface seal section formed by the test lid material and the test base material on the storage section side of the frame seal section, and the test package is prepared according to JIS Z 0238:1998, the peel strength of the frame seal portion and the peel strength of the face seal portion of the test package are measured, the peel strength of the frame seal portion is greater than the peel strength of the face seal portion, the peel strength of the frame seal portion is 1.0 to 8.0 N/15 mm, and the peel strength of the face seal portion is 0.5 to 6.0 N/15 mm.

[3] The laminate film according to [1] or [2], wherein the laminate film has an oxygen barrier layer, the oxygen barrier layer contains an ethylene-vinyl alcohol copolymer, and the ethylene-vinyl alcohol copolymer has a ratio of a content of structural units derived from ethylene to a total content of structural units of 25 to 30 mol %.
[4] The laminate film according to any one of [1] to [3], wherein the laminate film comprises an easy peel layer, and the easy peel layer contains low-density polyethylene.
[5] The laminate film according to any one of [1] to [4], wherein when the laminate film is subjected to high-pressure sterilization in water under conditions of a water temperature of 10°C, a pressure of 600 MPa, and a time of 3 minutes, the ratio of the oxygen permeation amount of the laminate film 24 hours after the end of the high-pressure sterilization to the oxygen permeation amount of the laminate film before the high-pressure sterilization is 150% or less.
[6] A packaging body comprising the laminate film according to any one of [1] to [5].
[7] The packaging body according to [6], wherein the packaging body includes a lid material and a base material, the packaging body is formed by sealing the lid material and the base material, and the base material is made of the laminate film.

The present invention provides a resin film suitable for vacuum packaging food, which enables high-pressure sterilization of the package obtained by vacuum packaging food, and which can suppress discoloration of the food during long-term storage of the package after high-pressure sterilization, and a package using the resin film.

FIG. 1 is a cross-sectional view illustrating an example of a laminated film according to an embodiment of the present invention. FIG. 2 is a front view showing a schematic diagram of an example of a package produced by vacuum packaging using a lid material and a base material. 3 is a cross-sectional view of the package taken along line II in FIG. 2. FIG. 2 is a cross-sectional view illustrating a schematic view of another example of a laminate film according to one embodiment of the present invention.

<<Laminated film>>
A laminate film according to one embodiment of the present invention is a laminate film in which, when a Gelbo flex test is performed on the laminate film at a temperature of 23°C and 500 flexes in accordance with ASTM F392, the number of pinholes observed in the laminate film after the Gelbo flex test is 100 or less, and the oxygen transmission amount of the laminate film, measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 50%, is 1.0 ml/( ^m2 ·24 h·atm) or less.

When the laminated film of this embodiment satisfies the evaluation results of the Gelbo Flex test described above, the package obtained by vacuum packaging the packaged object using the laminated film can be sterilized at high pressure. In other words, when the package is sterilized at high pressure, damage such as holes or tears in the package is suppressed, and high pressure sterilization can be performed normally.

Furthermore, the laminated film of this embodiment satisfies the above-mentioned oxygen transmission measurement results, and therefore has excellent oxygen barrier properties. When a package obtained by vacuum packaging food (packaged object) using the laminated film is stored for a long period of time after high-pressure sterilization, discoloration of the food in the package is suppressed.
The present inventors have investigated the cause of discoloration of food during long-term storage in a package produced by vacuum packaging food using a conventional resin film. As a result, they have found that the main cause of discoloration is the permeation of oxygen gas from the outside to the inside of the package through the resin film. Based on this knowledge, the laminated film of the present embodiment has a configuration with high oxygen barrier properties.

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

FIG. 1 is a cross-sectional view illustrating an example of the laminated film of the present embodiment.
The laminated film 1 shown here comprises an easy peel layer 11, and a flexible layer 12, a pinhole resistant layer 14, an oxygen barrier layer 15 and an outer layer 17 are laminated in this order in the thickness direction on the easy peel layer 11. The laminated film 1 further comprises a first adhesive layer 13 between the flexible layer 12 and the pinhole resistant layer 14, and a second adhesive layer 16 between the oxygen barrier layer 15 and the outer layer 17.
That is, the laminated film 1 is constructed by stacking an easy peel layer 11, a flexible layer 12, a first adhesive layer 13, a pinhole-resistant layer 14, an oxygen barrier layer 15, a second adhesive layer 16 and an outer layer 17 in this order in the thickness direction.

<Easy peel layer>
The easy peel layer 11 is one of the outermost layers of the laminated film 1 and is disposed on one of the outermost sides in the lamination direction of the layers constituting the laminated film 1 .
The side 11b of the easy peel layer 11 opposite the flexible layer 12 (sometimes referred to as the "second side" in this specification) is one of the outermost surfaces (sometimes referred to as the "second side" in this specification) 1b of the laminated film 1 and is the exposed surface.

The easy peel layer 11 is an easy peel type sealant layer.
A package can be constructed by heat sealing the laminated films 1 together at the easy-peel layers 11 therein, or by heat sealing the laminated film 1 to another film or sheet at the easy-peel layer 11 therein.
The second surface 11b of the easy peel layer 11 serves as a sealing surface between the easy peel layers 11 or with another film or sheet.
The easy peel layer 11 preferably has transparency.

The constituent material of the easy peel layer 11 may be a known material.
Preferred easy peel layers 11 include those that exhibit peelability by cohesive failure.
An example of an easy-peel layer 11 that exhibits peelability by cohesive failure is one that contains two incompatible polyolefins.

Examples of the two incompatible polyolefins contained in the easy peel layer 11 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 11 may, for example, contain 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.

The ethylene-based polymer contained in the easy-peel layer 11 includes an ethylene homopolymer and an ethylene-based copolymer.

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).

The ethylene-based copolymer has structural units derived from ethylene and structural units derived from a monomer other than ethylene.
Examples of the ethylene-based copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), and ionomer resin (ION resin).
The ionomer resin 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 crosslinking structure due to the formation of a salt between the acid portion in the copolymer and a metal ion.

It is preferable that the easy peel layer 11 contains low density polyethylene as the ethylene polymer. The easy peel properties of such an easy peel layer 11 are better.

The propylene-based polymer contained in the easy peel layer 11 includes a propylene homopolymer (i.e., polypropylene or homopolypropylene, hPP) and a propylene-based copolymer.

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

It is preferable that the easy peel layer 11 contains polypropylene as the propylene-based polymer. Such an easy peel layer 11 has better easy peel properties.

The component that exhibits easy peel properties contained in the easy peel layer 11 may be only one type or may be two or more types, and when there are two or more types, the combination and ratio of the components can be selected arbitrarily according to the purpose. For example, when the component that exhibits easy peel properties is the above-mentioned two incompatible polyolefins, the easy peel layer 11 may contain only one type or two or more types of these polyolefins.

In the easy peel layer 11, the ratio of the content (parts by mass) of the ethylene-based polymer to the total content (parts by mass) of the ethylene-based polymer and the propylene-based polymer is preferably 10 to 90% by mass, and may be, for example, any one of 30 to 90% by mass, 50 to 90% by mass, and 70 to 90% by mass. When the ratio is equal to or more than the lower limit, the easy peel property of the easy peel layer 11 becomes better. When the 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 described below.

The easy peel layer 11 may contain components other than the components that exhibit easy peel properties (for example, the above-mentioned two incompatible polyolefins) as long as the easy peel properties are not impaired.
The other components contained in the easy peel layer 11 may be one type or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

In the easy peel layer 11, the ratio of the content of the component that exhibits easy peel property to the total mass of the easy peel layer 11 (for example, the ratio of the total content of the above-mentioned two incompatible polyolefins) is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, and may be, for example, any one of 80 to 100 mass%, 90 to 100 mass%, 95 to 100 mass%, 97 to 100 mass%, and 99 to 100 mass%. When the ratio is equal to or more than the lower limit, the easy peel property of the easy peel layer 11 becomes better.
This ratio is usually the same as the ratio of the content (parts by mass) of the component that exhibits easy peel properties to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming the easy peel layer described below.

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

Examples of other components contained in the easy peel layer 11 include anti-fogging agents, anti-blocking agents, etc.

The anti-fogging agent contained in the easy peel layer 11 is a component for suppressing fogging of the laminate film 1 , particularly fogging on the exposed surface of the easy peel layer 11 .
The anti-fogging agent contained in the easy peel layer 11 may be a known one. Examples of the anti-fogging agent include polyglycerin fatty acid ester and diglycerin fatty acid ester.

The anti-blocking agent is a component that prevents the laminated films 1 from sticking to each other or to an adjacent film or sheet (blocking) when the laminated films 1 are stacked on top of each other or when the laminated film 1 is stacked on top of another film or sheet. The embodiment of "stacking laminated films 1" also includes the embodiment of "wrapping one laminated film 1 into a roll."

The antiblocking agent contained in the easy peel layer 11 may be a known agent. Examples of antiblocking agents include silica, such as natural silica and synthetic silica.

The easy peel layer 11 may consist of one layer (single layer) or may consist of two or more layers. When the easy peel layer 11 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.

In this specification, not only in the case of the easy peel layer 11, "multiple layers may be the same or different from each other" 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 from each other" means "at least one of the constituent materials and thickness of each layer is different from each other".

The thickness of the easy peel layer 11 is preferably 3 to 40 μm, more preferably 4 to 30 μm, and even more preferably 5 to 20 μm. When the thickness of the easy peel layer 11 is equal to or greater than the lower limit, the seal strength of the easy peel layer 11 is appropriately high. When the thickness of the easy peel layer 11 is equal to or less than the upper limit, the easy peelability is further improved.
Here, "the thickness of easy peel layer 11" means the entire thickness of easy peel layer 11, and for example, the thickness of easy peel layer 11 consisting of multiple layers means the total thickness of all layers that make up easy peel layer 11.

<Flexible layer>
The flexible layer 12 is a layer for improving the flexibility of the laminated film 1 .
The flexible layer 12 is preferably transparent.

The flexible layer 12 is preferably a resin layer containing resin.

Examples of the resin contained in the flexible layer 12 include polyolefins.

The polyolefin is not particularly limited as long as it is a resin having structural units derived from an olefin. For example, it may be a homopolymer having only one type of structural unit, or a copolymer having two or more types of structural units. The copolymer may be, for example, either a block copolymer or a random copolymer.

Examples of the polyolefin include polyethylene (PE), polypropylene (PP), ethylene copolymers, ionomer resins (ION resins), etc.

Examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and metallocene-catalyzed linear low density polyethylene (mLLDPE).
Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH).
The ionomer resin may be the same as those described above.

The flexible layer 12 may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The flexible layer 12 preferably contains polyolefin, more preferably contains polyethylene, and even more preferably contains low-density polyethylene. Such a flexible layer 12 has a higher flexibility.

The flexible layer 12 may contain only the resin, or may contain the resin and other non-resin components.

Examples of the non-resin components include additives known in the art.
Examples of the additives include antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

The non-resin components contained in the flexible layer 12 may be one type or two or more types. If there are two or more types, the combination and ratio of these can be selected as desired depending on the purpose.

In the flexible layer 12, the content ratio of the resin to the total mass of the flexible layer 12 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the effect obtained by using the resin in the flexible layer 12 is enhanced.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer described below.

When the flexible layer 12 contains the polyolefin, the ratio of the content of the polyolefin to the total content of the resin in the flexible layer 12 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the effect obtained by the flexible layer 12 containing the polyolefin is enhanced.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the polyolefin to the total content (parts by mass) of the resin in the composition for forming a flexible layer described below.

The flexible layer 12 may be made up of one layer (single layer) or two or more layers. When the flexible layer 12 is made up 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.

The thickness of the flexible layer 12 is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 95 μm, and even more preferably 15 to 90 μm. When the thickness of the flexible layer 12 is equal to or greater than the lower limit, the flexibility of the laminated film 1 is further improved. When the thickness of the flexible layer 12 is equal to or less than the upper limit, the flexible layer 12 is prevented from becoming excessively thick, and for example, the laminated film 1 can be made thinner.
Here, "the thickness of flexible layer 12" means the thickness of the entire flexible layer 12; for example, the thickness of flexible layer 12 consisting of multiple layers means the total thickness of all layers that make up flexible layer 12.

<Pinhole-resistant layer>
The pinhole resistant layer 14 is a layer for protecting the structure of the laminated film 1, for example by suppressing the occurrence of pinholes in the laminated film 1.
The pinhole resistant layer 14 is preferably transparent.

The pinhole-resistant layer 14 is preferably a resin layer containing resin.

Examples of the resin contained in the pinhole-resistant layer 14 include polyamide, polyester, polyolefin, polyvinyl resin, polycarbonate, etc.

For example, a pinhole-resistant layer 14 containing polyamide has higher strength, and damage to the pinhole-resistant layer 14 is significantly suppressed. Furthermore, by providing such a pinhole-resistant layer 14, the protective effect on the layers in the laminate film 1 that are closer to the easy-peel layer 11 than the pinhole-resistant layer 14, and the protective effect on the packaged items in the package described below, are significantly increased. In this way, the pinhole-resistant layer 14, which is a resin layer containing polyamide, is preferable in that it has higher strength.

Examples of the polyamide contained in the pinhole resistant layer 14 include polyamides obtained by polymerizing or copolymerizing nylon salts obtained by reacting cyclic lactams (lactams having 3 or more ring members), amino acids, or diamines with dicarboxylic acids.

Examples of the cyclic lactam include ε-caprolactam, ω-enantholactam, ω-laurolactam, α-pyrrolidone, and α-piperidone.

Examples of the amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

Examples of the diamine that forms the nylon salt include aliphatic amines such as tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine;
Alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, isophoronediamine, piperazine, bis(4-aminocyclohexyl)methane, and 2,2-bis-(4-aminocyclohexyl)propane;
Examples of the diamine include aromatic diamines such as metaxylylenediamine and paraxylylenediamine.

Examples of the dicarboxylic acid that forms the nylon salt include aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatic acid, undecanedioic acid, and dodecanedioic acid;
Alicyclic carboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid;
Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

More specifically, the polyamide may be, for example, 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-nylon, 612-nylon, 6T-nylon, 6I nylon, copolymer of 6-nylon and 66-nylon (nylon 6/66), copolymer of 6-nylon and 610-nylon, copolymer of 6-nylon and 611-nylon, copolymer of 6-nylon and 12-nylon (nylon 6/12), copolymer of 6-nylon and 612 nylon. , copolymers of 6-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, copolymers of 66-nylon, 6T-nylon and 6I-nylon, and copolymers of 66-nylon, 6T-nylon and 6I-nylon.

In terms of heat resistance, mechanical strength, and availability, 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.

Examples of the polyester contained in the pinhole-resistant layer 14 include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.

Examples of the polyolefin contained in the pinhole resistant layer 14 include polyethylene and polypropylene.

The polyvinyl resin contained in the pinhole-resistant layer 14 is a resin having structural units derived from a monomer having a vinyl group (ethenyl group). Examples of the polyvinyl resin include polyvinyl chloride (PVC) and ethylene-vinyl alcohol copolymer (EVOH).

The pinhole-resistant layer 14 may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The pinhole-resistant layer 14 preferably contains one or more selected from the group consisting of polyamide, polyester, polyolefin, polyvinyl resin, and polycarbonate, and more preferably contains polyamide. Such a laminate film 1 has higher pinhole resistance during its heat molding.

The pinhole resistant layer 14 may contain only the resin, or may contain the resin and other non-resin components.
The non-resin components include, for example, additives known in the art.
The additives may include the same additives as those previously described for flexible layer 12 .

The non-resin components contained in the pinhole resistant layer 14 may be one type or two or more types. When there are two or more types, the combination and ratio of the non-resin components can be selected as desired depending on the purpose.

In the pinhole resistant layer 14, the proportion of the resin content relative to the total mass of the pinhole resistant layer 14 is preferably 80 mass % or more, more preferably 90 mass % or more, and may be, for example, any one of 95 mass % or more, 97 mass % or more, and 99 mass % or more. When the proportion is equal to or more than the lower limit, the effect obtained by using the resin in the pinhole resistant layer 14 is enhanced.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the pinhole-resistant layer-forming composition described below.

When the pinhole-resistant layer 14 contains the polyamide, the ratio of the content of the polyamide to the total content of the resin in the pinhole-resistant layer 14 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the protective ability of the laminated film 1 by the pinhole-resistant layer 14 is improved. In addition, the high-pressure sterilization suitability (the property of being able to stably maintain the packaged state during high-pressure sterilization) of the package obtained using the laminated film 1 is improved.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the polyamide to the total content (parts by mass) of the resin in the pinhole-resistant layer-forming composition described below.

The pinhole-resistant layer 14 may be made of one layer (single layer) or may be made of two or more layers. When the pinhole-resistant layer 14 is made 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.

The thickness of the pinhole-resistant layer 14 is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 95 μm, and even more preferably 15 to 90 μm. When the thickness of the pinhole-resistant layer 14 is equal to or greater than the lower limit, the protective ability of the pinhole-resistant layer 14 is enhanced. In addition, the high-pressure sterilization suitability (the property of being able to stably maintain the packaged state during high-pressure sterilization) of the package obtained using the laminated film 1 is enhanced. When the thickness of the pinhole-resistant layer 14 is equal to or less than the upper limit, the pinhole-resistant layer 14 is prevented from becoming excessively thick, and for example, the laminated film 1 can be made thinner.
Here, "the thickness of pinhole-resistant layer 14" means the thickness of the entire pinhole-resistant layer 14; for example, the thickness of pinhole-resistant layer 14 consisting of multiple layers means the total thickness of all layers that make up pinhole-resistant layer 14.

<Oxygen Barrier Layer>
The oxygen barrier layer 15 is a layer for suppressing the transmission of oxygen gas through the laminate film 1. By providing the oxygen barrier layer 15, the laminate film 1 has high oxygen barrier properties.
The oxygen barrier layer 15 is preferably transparent.

The oxygen barrier layer 15 is preferably a resin layer containing a resin.

Examples of the resin contained in the oxygen barrier layer 15 include ethylene-vinyl alcohol copolymer (EVOH, also known as saponified ethylene-vinyl acetate copolymer), polyvinylidene chloride (PVDC), polyamide, polyvinyl alcohol, polyacrylonitrile, etc.

The ratio of the amount of structural units derived from ethylene to the total amount of structural units in the ethylene-vinyl alcohol copolymer (sometimes abbreviated as "copolymerization ratio of ethylene" in this specification) is preferably 25 to 30 mol%, more preferably 26.5 to 29.5 mol%, and even more preferably 27 to 29 mol%. When the ratio is equal to or greater than the lower limit, the laminated film 1 can be more easily molded (the laminated film 1 has higher moldability), and a package having a desired shape can be more precisely manufactured using the laminated film 1. When the ratio is equal to or less than the upper limit, the adhesiveness of the package manufactured using the laminated film 1 to the packaged item is higher. Furthermore, the package obtained using the laminated film 1 has higher storage stability of the packaged item (for example, the effect of suppressing discoloration of food).

The polyamide contained in the oxygen barrier layer 15 may be, for example, the same polyamide as that described above as contained in the pinhole resistant layer 14.

The oxygen barrier layer 15 may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

In order to improve the oxygen barrier properties of the oxygen barrier layer 15 and the laminated film 1, it is preferable that the oxygen barrier layer 15 contains an ethylene-vinyl alcohol copolymer.

The oxygen barrier layer 15 may contain only the resin, or may contain the resin and other non-resin components.
The non-resin components include, for example, additives known in the art.
The additives may include the same additives as those previously described for flexible layer 12 .

The oxygen barrier layer 15 may contain only one type of non-resin component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

In the oxygen barrier layer 15, the content of the resin relative to the total mass of the oxygen barrier layer 15 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the content is equal to or more than the lower limit, the effect obtained by using the resin in the oxygen barrier layer 15 (for example, the oxygen barrier property of the oxygen barrier layer 15 and the laminate film 1) becomes higher.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the 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 described below.

When the oxygen barrier layer 15 contains one or more oxygen barrier resins selected from the group consisting of ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamide, polyvinyl alcohol, and polyacrylonitrile, the ratio of the total content of the oxygen barrier resins to the total content of the resins in the oxygen barrier layer 15 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the oxygen barrier property of the oxygen barrier layer 15 and the laminated film 1 is improved. Then, in a package obtained using the laminated film 1, the storage stability of the packaged item (for example, the effect of suppressing discoloration of food) is improved.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the total content (parts by mass) of the oxygen barrier resins to the total content (parts by mass) of the resins in the composition for forming an oxygen barrier layer, which will be described later.

The oxygen barrier layer 15 preferably contains an ethylene-vinyl alcohol copolymer, and in this case, the ratio of the content of the ethylene-vinyl alcohol copolymer to the total content of the resin in the oxygen barrier layer 15 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the oxygen barrier property of the oxygen barrier layer 15 and the laminated film 1 is further improved. Then, in a package obtained using the laminated film 1, the storage stability of the packaged item (for example, the effect of suppressing discoloration of food) is further improved.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the ethylene-vinyl alcohol copolymer to the total content (parts by mass) of the resin in the composition for forming an oxygen barrier layer described below.

A more preferred example of the oxygen barrier layer 15 is one that contains an ethylene-vinyl alcohol copolymer, in which the ratio of the amount of structural units derived from ethylene to the total amount of structural units is 25 to 30 mol %.
A more preferable example of the oxygen barrier layer 15 is one which contains an ethylene-vinyl alcohol copolymer, in which the ratio of the amount of structural units derived from ethylene to the total amount of structural units in the ethylene-vinyl alcohol copolymer is 25 to 30 mol %, and in which the content of the ethylene-vinyl alcohol copolymer to the total content of the resin in the oxygen barrier layer 15 is 80 mass % or more.

The oxygen barrier layer 15 may consist of one layer (single layer) or may consist of two or more layers. When the oxygen barrier layer 15 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.

The thickness of the oxygen barrier layer 15 is not particularly limited, but is preferably 2 μm or more, more preferably 4 μm or more, and may be, for example, any of 7.5 μm or more, 12.5 μm or more, 17.5 μm or more, and 22.5 μm or more. When the thickness of the oxygen barrier layer 15 is equal to or more than the lower limit, the oxygen barrier properties of the oxygen barrier layer 15 and the laminated film 1 are improved. In addition, in a package obtained using the laminated film 1, the storage stability of the packaged item (for example, the effect of suppressing discoloration of food) is improved.
Here, the "thickness of the oxygen barrier layer 15" means the thickness of the entire oxygen barrier layer 15. For example, the thickness of the oxygen barrier layer 15 consisting of multiple layers means the total thickness of all layers constituting the oxygen barrier layer 15.

The upper limit of the thickness of the oxygen barrier layer 15 is not particularly limited. In order to improve the formability of the laminated film 1 and to prevent the oxygen barrier layer 15 from becoming excessively thick, for example, to make the laminated film 1 thinner, it is preferable that the thickness of the oxygen barrier layer 15 is 32 μm or less.

The thickness of the oxygen barrier layer 15 can be appropriately adjusted within a range set by any combination of any of the above-mentioned lower limit values and upper limit values.
For example, in one embodiment, the oxygen barrier layer 15 may have a thickness of any of the following: 2 to 32 μm, 4 to 32 μm, 7.5 to 32 μm, 12.5 to 32 μm, 17.5 to 32 μm, and 22.5 to 32 μm.

When the oxygen barrier layer 15 contains the ethylene-vinyl alcohol copolymer, the thickness of the oxygen barrier layer 15 may be adjusted according to the copolymerization ratio of ethylene in the ethylene-vinyl alcohol copolymer.
For example, when the copolymerization ratio of ethylene is preferably less than 28 mol%, more preferably 25 mol% or more and less than 28 mol%, the thickness of the oxygen barrier layer 15 is 28 μm or less, and when the copolymerization ratio of ethylene is preferably 28 mol% or more, more preferably 28 to 30 mol%, the thickness of the oxygen barrier layer 15 may be 32 μm or less. By using such a laminate film 1, a package having higher strength and higher suitability for high-pressure sterilization can be manufactured.

<Outer layer>
The outer layer 17 is a layer for protecting the other layers that make up the laminate film 1, and by appropriately selecting its constituent materials, it is possible to make it a layer that imparts new properties to the laminate film 1.
The outer layer 17 is preferably transparent.

The outer layer 17 is the other outermost layer of the laminate film 1, and the surface of the outer layer 17 opposite the oxygen barrier layer 13 (sometimes referred to as the "first surface" in this specification) 17a is the other outermost surface of the laminate film 1 (sometimes referred to as the "first surface" in this specification) 1a, which is the exposed surface.

The outer layer 17 is preferably a resin layer containing resin.

Examples of the resin that is the constituent material of the outer layer 17 include polyamide, polyolefin, etc.

The polyamide contained in the outer layer 17 may be, for example, the same polyamide as that described above as contained in the pinhole resistant layer 14.

The polyolefin contained in the outer layer 17 may be, for example, polypropylene.

The resin contained in the outer layer 17 may be one type or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

It is preferable that the outer layer 17 contains one or more selected from the group consisting of polyamides and polyolefins. In such a case, the outer layer 17 has a higher ability to protect the laminated film 1.

The outer layer 17 may contain only the resin, or may contain the resin and other non-resin components.
The non-resin components include, for example, additives known in the art.
The additives may include the same additives as those previously described for flexible layer 12 .

The non-resin components contained in the outer layer 17 may be one type or two or more types. When there are two or more types, the combination and ratio of the non-resin components can be selected as desired depending on the purpose.

In the outer layer 17, the proportion of the content of the resin relative to the total mass of the outer layer 17 is preferably 80 mass% or more, more preferably 90 mass% or more, and may be, for example, any one of 95 mass% or more, 97 mass% or more, and 99 mass% or more. When the proportion is equal to or more than the lower limit, the effect obtained by using the resin in the outer layer 17 is enhanced.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the resin 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.

When the outer layer 17 contains one or more selected from the group consisting of polyamides and polyolefins, the ratio of the total content of the polyamides and polyolefins to the total content of the resins in the outer layer 17 is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the protective ability of the outer layer 17 for the laminated film 1 is further increased.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
The ratio is usually the same as the ratio of the total content (parts by mass) of the polyamide and polyolefin to the total content (parts by mass) of the resin in the composition for forming an outer layer, which will be described later.

The outer layer 17 may be made of one layer (single layer) or may be made of two or more layers. When the outer layer 17 is made 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.

The thickness of the outer layer 17 is not particularly limited, but is preferably 5 to 45 μm, more preferably 10 to 40 μm, and even more preferably 15 to 35 μm. When the thickness of the outer layer 17 is equal to or greater than the lower limit, the outer layer 17 is able to better protect the laminated film 1. When the thickness of the outer layer 17 is equal to or less than the upper limit, the outer layer 17 is prevented from becoming excessively thick, and for example, the laminated film 1 can be made thinner.
Here, the "thickness of outer layer 17" means the thickness of the entire outer layer 17, and for example, the thickness of outer layer 17 consisting of multiple layers means the total thickness of all layers that make up outer layer 17.

<First adhesive layer>
The first adhesive layer 13 is a layer for adhering two adjacent layers (here, the flexible layer 12 and the pinhole resistant layer 14) in the laminate film 1, and contains a component that exhibits adhesive properties.
The first adhesive layer 13 preferably has transparency.
The first adhesive layer 13 has an optional configuration, and the laminated film 1 does not necessarily have to have the first adhesive layer 13, but by having the first adhesive layer 13, the structure becomes more stable.

The first adhesive layer 13 is preferably a resin layer containing an adhesive resin.

The adhesive resin may be, for example, a polyolefin resin.
The polyolefin resin is a resin having structural units derived from an olefin, and may be, for example, a modified polyolefin such as an acid-modified polyolefin having an acidic group.
Examples of polyolefin resins include ethylene copolymers, propylene copolymers, butene copolymers, modified products of these copolymers (in other words, modified copolymers), acid-modified polyethylene, acid-modified polypropylene, and the like.
The polyolefin resin may be a random copolymer, a graft copolymer or a block copolymer, in terms of further improving adhesiveness.

Examples of the ethylene-based copolymer contained in the first adhesive layer 13 include the ethylene-based copolymers described above as being contained in the easy-peel layer 11, modified products thereof (modified copolymers), and the like.
Examples of the propylene-based copolymer contained in the first adhesive layer 13 include a copolymer of propylene and a vinyl group-containing monomer, a modified product thereof (modified copolymer), etc. More specifically, examples of such a propylene-based copolymer include maleic anhydride-grafted modified linear low-density polypropylene, a propylene-based thermoplastic elastomer, etc.
Examples of the butene-based copolymer contained in the first adhesive layer 13 include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products of these copolymers (modified copolymers).

The component that exhibits adhesiveness (e.g., the adhesive resin) contained in the first adhesive layer 13 may be of only one type or of two or more types. When there are two or more types, the combination and ratio of the components can be selected arbitrarily according to the purpose.

The first adhesive layer 13 may contain components other than the component that exhibits adhesiveness (for example, the adhesive resin) as long as the adhesiveness is not impaired.
Examples of the other components contained in the first adhesive layer 13 include an antioxidant.

The other components contained in the first adhesive layer 13 may be one type only, or two or more types. If there are two or more types, the combination and ratio of these components can be selected arbitrarily according to the purpose.

In the first adhesive layer 13, the ratio of the content of the component that exhibits adhesiveness (for example, the content of the adhesive resin) to the total mass of the first adhesive layer 13 is preferably 80 mass% or more, and more preferably 90 mass% or more. When the ratio is equal to or more than the lower limit, the adhesiveness of the first adhesive layer 13 becomes higher.
The upper limit of the ratio is not particularly limited as long as the ratio is 100% by mass or less.
This ratio is usually the same as the ratio of the content (parts by mass) of the component that exhibits adhesiveness to the total content (parts by mass) of the components that do not vaporize at room temperature in the composition for forming an adhesive layer described below.

The first adhesive layer 13 may consist of one layer (single layer) or may consist of two or more layers. When the first adhesive layer 13 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.

The thickness of the first adhesive layer 13 is not particularly limited, but is preferably 0.1 to 25 μm, more preferably 0.5 to 20 μm, and even more preferably 1 to 20 μm. When the thickness of the first adhesive layer 13 is equal to or greater than the lower limit, the first adhesive layer 13 has better adhesiveness. When the thickness of the first adhesive layer 13 is equal to or less than the upper limit, the first adhesive layer 13 is prevented from becoming excessively thick.
Here, "the thickness of the first adhesive layer 13" means the thickness of the entire first adhesive layer 13, and for example, the thickness of the first adhesive layer 13 consisting of multiple layers means the total thickness of all layers that make up the first adhesive layer 13.

<Second adhesive layer>
The second adhesive layer 16 is a layer for adhering two adjacent layers (here, the oxygen barrier layer 15 and the outer layer 17) in the laminate film 1, and contains a component that exhibits adhesiveness.
The second adhesive layer 16 preferably has transparency.
The second adhesive layer 16 has an optional configuration, and the laminated film 1 does not necessarily have to have the second adhesive layer 16, but by having the second adhesive layer 16, the structure becomes more stable.

The second adhesive layer 16 is similar to the first adhesive layer 13, except for its position in the laminated film 1, and a detailed description of it will be omitted.

In the laminated film 1, the first adhesive layer 13 and the second adhesive layer 16 may be the same as or different from each other. Here, the first adhesive layer 13 and the second adhesive layer 16 being different from each other means that at least one of the constituent material and the thickness is different between the first adhesive layer 13 and the second adhesive layer 16.

The thickness of the laminate film 1 is not particularly limited, but is preferably 100 to 250 μm, and may be, for example, any of 100 to 210 μm, 100 to 170 μm, 140 to 250 μm, 180 to 250 μm, 110 to 220 μm, and 120 to 190 μm. When the thickness of the laminate film 1 is equal to or greater than the lower limit, the storage stability of the packaged item (e.g., the effect of suppressing discoloration of food) is improved in the package obtained using the laminate film 1, and the suitability of the package for high-pressure sterilization (the property of being able to stably maintain the packaged state during high-pressure sterilization) is improved. When the thickness of the laminate film 1 is equal to or less than the upper limit, the moldability of the laminate film 1 is improved.

It is preferable that all layers of the laminate film 1 have transparency, that is, that the laminate film 1 is transparent, i.e., the laminate film 1 is a transparent laminate film. In a package obtained using such a laminate film 1, the packaged item can be easily seen through the laminate film 1.

<Characteristics of laminated film>
[Resistance to Gelboflex test]
When the Gelbo flex test is performed on the laminate film 1 in accordance with ASTM F392 under conditions of a temperature of 23° C. and 500 flex cycles, the number of pinholes found in the laminate film 1 after the Gelbo flex test is 100 or less. The laminate film 1 to be subjected to the Gelbo flex test is the one before the test in which no pinholes are found (the number of pinholes is 0). A package obtained by vacuum packaging an object to be packaged using the laminate film 1 satisfying such conditions is suppressed from being damaged, such as by holes or tears, when the package is sterilized at high pressure, as explained above.

In the laminate film 1, the number of pinholes observed after the Gelbo Flex test is preferably 90 or less, and may be, for example, any one of 75 or less, 55 or less, and 35 or less. The fewer the number of pinholes, the higher the suitability of the package including the laminate film 1 for high-pressure sterilization.
On the other hand, the number of the pinholes is 0 or more.

It is envisaged that the package obtained using the laminated film 1 will be subjected to high-pressure sterilization by holding the package in high-pressure water for a specific period of time.
In such high pressure sterilization, the water temperature is preferably 5 to 15° C., the pressure is preferably 300 to 900 MPa, and the high pressure sterilization time is preferably 1 to 10 minutes.

The number of pinholes in the laminate film 1 can be adjusted, for example, by adjusting the types of components contained in each layer constituting the laminate film 1, the thickness of each layer, etc. In particular, the number of pinholes in the laminate film 1 can be more easily adjusted by adjusting the types of components contained in the pinhole-resistant layer 14 and the outer layer 17, the thicknesses of the pinhole-resistant layer 14 and the outer layer 17, etc.

[Oxygen permeability]
(Oxygen permeability before high-pressure sterilization)
The oxygen transmission rate of the laminated film 1 measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity (RH) of 50% is 1.0 ml/( ^m2 ·24 h·atm) or less. When a package obtained by vacuum packaging a food (packaged object) using the laminated film 1 satisfying such conditions is stored for a long period of time after high-pressure sterilization, discoloration of the food in the package is suppressed, as explained above.

The oxygen permeability of the laminated film 1 is preferably 0.85 ml/( ^m2 ·24h·atm) or less, more preferably 0.7 ml/( ^m2 ·24h·atm) or less, and may be, for example, 0.55 ml/( ^m2 ·24h·atm) or less, 0.4 ml/( ^m2 ·24h·atm) or less, or 0.2 ml/( ^m2 ·24h·atm) or less. When the oxygen permeability of the laminated film 1 is equal to or less than the upper limit, the effect of suppressing discoloration of the food in the package is further increased.

There is no particular limitation on the lower limit of the oxygen transmission rate of the laminate film 1. For example, the oxygen transmission rate of the laminate film 1 may be 0.05 ml/( ^m2 ·24 h·atm) or more, in terms of ease of production of such a laminate film 1.

(Oxygen transmission rate after high-pressure sterilization)
The laminated film 1 before high-pressure sterilization is immersed in water and high-pressure sterilized in water under conditions of a water temperature of 10°C, a pressure of 600 MPa, and a time of 3 minutes, and then 24 hours after the end of high-pressure sterilization, the oxygen transmission amount of the laminated film 1 after high-pressure sterilization is preferably 1.02 ml/( ^m2 ·24h·atm) or less, measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 50%. When a package obtained by vacuum packaging a food (packaged object) using a laminated film 1 satisfying such conditions is stored for a long period after high-pressure sterilization, discoloration of the food in the package is further suppressed.

There is no particular limitation on the lower limit of the oxygen transmission rate of the laminated film 1 after the high-pressure sterilization. For example, the oxygen transmission rate of the laminated film 1 after the high-pressure sterilization may be 0.05 ml/( ^m2 ·24 h·atm) or more, in terms of ease of manufacturing such a laminated film 1.

In this specification, unless otherwise specified, the mere mention of "oxygen permeability" of a laminated film means "the oxygen permeability of the laminated film before high-pressure sterilization."

(Oxygen permeability change rate)
The ratio of the oxygen transmission amount of the laminate film 1 24 hours after the end of the high-pressure sterilization (the oxygen transmission amount of the laminate film 1 after the high-pressure sterilization) to the oxygen transmission amount of the laminate film 1 before the high-pressure sterilization ([the oxygen transmission amount of the laminate film 1 after the high-pressure sterilization]/[the oxygen transmission amount of the laminate film 1 before the high-pressure sterilization]×100, which may be referred to as the "oxygen transmission amount change rate" in this specification) is preferably 150% or less, more preferably 145% or less, and even more preferably 140% or less, and may be, for example, any of 125% or less, 110% or less, and 95% or less. When a package obtained by vacuum packaging a food (packaged object) using a laminate film 1 having the oxygen transmission amount change rate of the upper limit or less is stored for a long period of time after high-pressure sterilization, discoloration of the food in the package is further suppressed.

The lower limit of the rate of change in oxygen transmission rate is not particularly limited. For example, the rate of change in oxygen transmission rate may be 50% or more, which is easier to manufacture such a laminated film 1.

The oxygen permeability of the laminated film 1 can be adjusted, for example, by adjusting the type of components contained in the oxygen barrier layer 15, the thickness of the oxygen barrier layer 15, etc.

[Peel strength of seal part]
The suitability of a package obtained by vacuum packaging food (packaged object) using laminated film 1 for high-pressure sterilization can be determined by the peel strength of the frame seal portion and the peel strength of the face seal portion of a test package shown below.

That is, using a test lid material made of a resin film equipped with a sealant layer containing linear low density polyethylene (LLDPE) and a test base material made of laminated film 1 having a recess formed therein for forming a storage area for the packaged item, the packaged item is placed in the recess, the packaged item is sandwiched between the test lid material and the test base material, and the inside of the storage area formed by the test lid material and the test base material in the recess is evacuated under conditions of a temperature of 140°C and a vacuum time of 2 seconds.
Next, the peripheral edges of the test lid material and the test base material are sealed into a frame shape at a sealing temperature of 140°C and a sealing time of 2 seconds to form a frame seal portion, thereby producing a test package having the frame seal portion and, further, a surface seal portion formed by the test lid material and the test base material on the storage portion side of the frame seal portion.

In the sealant layer, the proportion of the LLDPE content relative to the total mass of the sealant layer is preferably 95 mass % or more.
The thickness of the sealant layer is preferably 30 μm.

The width of the frame seal portion is preferably, for example, 1 cm.
The area of the face seal portion is preferably, for example, ¹⁵⁰ cm2.

Here, the test package and other packages produced by vacuum packaging using a lid material and a base material will be described with reference to Figures 2 and 3. Figure 2 is a front view showing a schematic diagram of one example of the package, and Figure 3 is a cross-sectional view of the package taken along line I-I in Figure 2.

The packaging body 101 shown here is configured with a cover material 8 and a base material 7 .
The lid material 8 is in a sheet form, and is usually preferably transparent.
The base material 7 has a recess 70 formed therein. The base material 7 is obtained by deep drawing a film, and is usually preferably transparent.
Since either or both of the lid material 8 and the base material 7 are transparent, the packaged item 9 packaged in the package 101 can be easily viewed from the outside of the package 101.

In the packaging body 101, one side 7b of the area of the base material 7 excluding the recess 70 (sometimes referred to as the "second side" in this specification) and one side 8b of the lid material 8 (sometimes referred to as the "second side" in this specification) are both sealing surfaces and face each other. The second side 7b of the base material 7 is the side from which the packaged item 9 is exposed when the packaged item 9 is stored in the recess 70 without constituting the packaging body 101.

Furthermore, the package 101 is formed by sealing the lid material 8 and the base material 7. More specifically, the second surface 7b of the base material 7 except for the recess 70 and the second surface 8b of the lid material 8 are overlapped and sealed to each other at their peripheries. As a result, a storage section 101a is formed between the second surface 7b of the base material 7 and the second surface 8b of the lid material 8 in the region of the recess 70 of the base material 7. The packaged item 9 is stored in this storage section 101a. The packaged item 9 is preferably a food item.

The peripheral edge of the packaging body 101 forms a sealed portion (frame sealed portion) 1011. The region of the packaging body 101 that is closer to the storage section 101a than the frame sealed portion 1011 and that is not included in the storage section 101a forms a surface sealed portion 1012. In the surface sealed portion 1012, the base material 7 and the lid material 8 are in a lightly sealed state, and are in a tightly contacted state due to the effect of reduced pressure caused by drawing a vacuum inside the storage section 101a during packaging.
2, when the packaging body 101 is viewed from above the lid member 8 side in a plan view, in the packaging body 101, the face seal portion 1012 exists so as to surround the storage portion 101a, and the frame seal portion 1011 exists so as to surround the face seal portion 1012. In addition, the frame seal portion 1011 is formed along the outer periphery of the packaging body 101.

In the package 101, typically, the lid material 8 and the packaged item 9 are in direct contact. The area of the recess 70 of the base material 7, particularly the area of the bottom of the recess 70 (e.g., the area of the recess 70 facing the lid material 8), is in direct contact with the packaged item 9. In FIG. 3, the side portion of the area of the recess 70 of the base material 7 is not in direct contact with the packaged item 9, and a gap is visible, but there may be direct contact.

When the packaging body 101 is the test packaging body, the lid material 8 is the test lid material, the base material 7 is the test base material, the recess 70 is a recess in the test packaging body, the frame seal portion 1011 is a frame seal portion in the test packaging body, and the face seal portion 1012 is a face seal portion in the test packaging body.
The base material 7 (test base material) is made of the laminate film 1. The second surface 7b of the base material 7 corresponds to the second surface 11b of the easy-peel layer 11 in the laminate film 1, and the surface 7a opposite to the second surface 7b of the base material 7 (sometimes referred to as the "first surface" in this specification) corresponds to the first surface 17a of the outer layer 17 in the laminate film 1.
The second surface 8b of the lid material 8 (test lid material) is one surface (sealing surface) of the sealant layer containing LDPE.
In addition, in Figs. 2 and 3, the distinction between the layers in the base material 7 (laminated film 1) is omitted.

In this embodiment, it is preferable that the peel strength of the frame seal portion and the peel strength of the face seal portion of the test package are greater than the peel strength of the face seal portion when the peel strengths of the frame seal portion and the face seal portion of the test package are measured in accordance with JIS Z 0238: 1998. A test package that satisfies such conditions (a package obtained by vacuum packaging a food using the laminate film 1) can maintain a more stable packaged state during high-pressure sterilization.
In this specification, unless otherwise specified, "peel strength of frame seal" refers to the peel strength between the cover material (test cover material) and the base material (test base material) at the frame seal. Similarly, "peel strength of face seal" refers to the peel strength between the cover material (test cover material) and the base material (test base material) at the face seal, unless otherwise specified.

In this embodiment, the peel strength of the frame seal portion of the test package, measured in accordance with JIS Z 0238:1998, is preferably 1.0 to 8.0 N/15 mm. When the peel strength of the frame seal portion is equal to or greater than the lower limit, the effect of suppressing unintended peeling of the frame seal portion during handling of the test package (a package obtained by vacuum packaging a food using the laminate film 1) is enhanced. When the peel strength of the frame seal portion is equal to or less than the upper limit, the test package (a package obtained by vacuum packaging a food using the laminate film 1) can be opened more easily.
In this specification, unless otherwise specified, "opening a package (test package)" means opening a package by peeling off the lid material (test lid material) and the base material (test base material).

In this embodiment, the peel strength of the face seal portion of the test package measured in accordance with JIS Z 0238:1998 is preferably 0.5 to 6.0 N/15 mm. When the peel strength of the face seal portion is equal to or greater than the lower limit, peeling of the face seal portion is further suppressed. For example, in a package having a plurality of recesses in which packaged items are stored (a package obtained by vacuum packaging food using laminate film 1), the movement of ingredients in the recesses between the recesses is significantly suppressed. When the peel strength of the face seal portion is equal to or less than the upper limit, the test package (a package obtained by vacuum packaging food using laminate film 1) is easier to open.

In this embodiment, it is particularly preferable that all of the above-mentioned three conditions relating to the peel strength of the frame seal portion and the peel strength of the face seal portion are satisfied.
That is, in this embodiment, when the peel strengths of the frame seal portion and the face seal portion of the test package are measured in accordance with JIS Z 0238: 1998, it is particularly preferable that the peel strength of the frame seal portion is greater than that of the face seal portion, that the peel strength of the frame seal portion is 1.0 to 8.0 N/15 mm, and that the peel strength of the face seal portion is 0.5 to 6.0 N/15 mm. A package obtained by vacuum packaging an object to be packaged using such a laminate film 1 has particularly excellent properties for use in high-pressure sterilization.

FIG. 4 is a cross-sectional view that illustrates a schematic diagram of another example of the laminated film of the present embodiment.
In FIG. 4, the same components as those shown in the drawings already described are given the same reference numerals as in the drawings already described, and detailed description thereof will be omitted.

The laminate film 2 shown here is the same as the laminate film 1 shown in FIG.
That is, the laminated film 2 is constructed by laminating an easy peel layer 11, a flexible layer 12, a first adhesive layer 13, an oxygen barrier layer 15, a second adhesive layer 16 and an outer layer 17 in this order in the thickness direction.
The second surface 11b of the easy peel layer 11 is the second surface 2b of the laminate film 2 and is the exposed surface.
The first surface 17a of the outer layer 17 is the first surface 2a of the laminated film 2 and is the exposed surface.

Laminated film 2 does not have the pinhole-resistant layer 14 of laminated film 1, but since outer layer 17 also functions as a pinhole-resistant layer, laminated film 2 has pinhole resistance.

Laminated film 2 has the same properties as laminated film 1 (resistance to the Gelbo Flex test, oxygen permeability, peel strength of the frame seal, and peel strength of the face seal).

Laminated film 2 has the same effect as laminated film 1.

The laminate film of this embodiment is not limited to laminate films 1 and 2, and some of the configurations of laminate films 1 and 2 may be changed, deleted, or added within the scope of the present invention.
For example, the layers that laminate film 1 or laminate film 2 has include an easy peel layer, a flexible layer, a first adhesive layer, a pinhole resistant layer, an oxygen barrier layer, a second adhesive layer, and an outer layer, but the laminate film of this embodiment may have layers other than these.

<Other layers>
The type, number and arrangement of the other layers can be arbitrarily selected depending on the purpose.
Examples of the other layer include a layer that does not correspond to either the first adhesive layer or the second adhesive layer as an adhesive layer for adhering two adjacent layers; a layer that is disposed between the easy peel layer and the outer layer in the thickness direction of the laminated film and that imparts other properties to the laminated film that do not correspond to any of flexibility, oxygen barrier properties, pinhole resistance, and adhesion.

The laminated film of this embodiment needs to have at least an outer layer and an easy-peel layer, and the other layers may be of any configuration, and layers other than the outer layer and the easy-peel layer may be selected as desired depending on the purpose.

The laminated film of the present embodiment is suitable for forming various packages, and is particularly suitable as a base material or a lid material in packages for vacuum packaging. In this case, the packaged object may be, for example, food.
That is, the laminated film of the present embodiment is more suitable for vacuum packaging of food, and is particularly suitable for vacuum packaging of food that requires high-pressure sterilization.

<<Laminated film manufacturing method>>
The laminated film of this embodiment can be produced, for example, 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 co-extrusion T-die method such as a multi-manifold method, or an air-cooled or water-cooled co-extrusion inflation method.

The laminated film of this embodiment can also be produced by coating the surface of another layer that constitutes the laminated film with a resin or resin composition that will form one of the layers, and drying it as necessary to form a laminated structure in the laminated film, and then further laminating other layers as necessary to obtain the desired arrangement.

The laminated film of this embodiment can also 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 the dry lamination method, extrusion lamination method, hot melt lamination method, and wet lamination method, and further laminating other layers as necessary to achieve the desired arrangement. In this case, the adhesive used may be one capable of forming the adhesive layers (first adhesive layer, second adhesive layer).

The laminated film of this embodiment can also be produced by laminating two or more films, which have been prepared separately in advance, 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.

When manufacturing the laminated film of this embodiment, two or more of the methods for forming any of the layers (films) in the laminated film described above may be combined.

Regardless of the manufacturing method, the resin composition that is the material for forming any of the layers in the laminated film may be manufactured by adjusting the type and content of the components so that the layer to be formed contains the desired components (constituent materials) in the desired content. For example, the content ratio of the components that do not vaporize at room temperature in the resin composition is usually the same as the content ratio of the components in the layer formed from this resin composition.

Examples of resin compositions (sometimes referred to herein as "compositions for forming easy peel layers") for forming easy peel layers (easy peel layer 11 in laminate film 1 shown in FIG. 1 and laminate film 2 shown in FIG. 4) include those that contain a component that exhibits the easy peel properties and, if necessary, the other components.

The resin composition (sometimes referred to herein as "flexible layer forming composition") for forming the flexible layer (flexible layer 12 in laminate film 1 shown in FIG. 1 and laminate film 2 shown in FIG. 4) may, for example, be one that contains the polyolefin and, if necessary, the non-resin component.

The resin composition (sometimes referred to herein as the "composition for forming a pinhole-resistant layer") for forming the pinhole-resistant layer (pinhole-resistant layer 14 in the laminate film 1 shown in FIG. 1) may, for example, contain one or more selected from the group consisting of polyamide, polyester, polyolefin, polyvinyl resin, and polycarbonate, and, if necessary, the non-resin component.

The resin composition (sometimes referred to herein as "oxygen barrier layer forming composition") for forming the oxygen barrier layer (oxygen barrier layer 15 in laminate film 1 shown in FIG. 1 and laminate film 2 shown in FIG. 4) may, for example, contain the oxygen barrier resin and, if necessary, the non-resin component.

The resin composition (sometimes referred to herein as "composition for forming outer layer") for forming the outer layer (outer layer 17 in laminate film 1 shown in FIG. 1 and laminate film 2 shown in FIG. 4) may, for example, contain one or more selected from the group consisting of polyamides and polyolefins, and, if necessary, the non-resin component.

Examples of resin compositions (sometimes referred to herein as "adhesive layer-forming compositions") for forming the first adhesive layer or the second adhesive layer (first adhesive layer 13 and second adhesive layer 16 in laminate film 1 shown in FIG. 1 and laminate film 2 shown in FIG. 4) include those that contain a component that exhibits the adhesive properties and, if necessary, the other components.

<<Packaging>>
A packaging body according to one embodiment of the present invention includes the laminate film according to one embodiment of the present invention described above.
Since the packaging body of the present embodiment is constructed using the laminated film, it is possible to subject the packaged items, such as food, to high-pressure sterilization while they are vacuum-packaged, and discoloration of the packaged food items can be suppressed during long-term storage after high-pressure sterilization.

The food to be packaged in the packaging body of this embodiment is not particularly limited. Examples of the food include fresh foods such as raw meat, raw fish, and raw vegetables; various processed foods including processed meat products such as ham, sausages, and bacon; and other well-known foods.

A preferred example of the packaging body is a packaging body that has a lid material and a base material, and is formed by sealing the lid material and the base material, and one or both of the lid material and the base material are made of the laminate film.
In particular, since the advantageous effects of using the laminated film are particularly prominent, it is preferable that the package is a package that includes a lid material and a base material, is formed by sealing the lid material and the base material, and the base material is made of the laminated film. In such a package, the lid material may be made of the laminated film. The laminated film can make molding easier (the moldability of the laminated film can be increased), and by using such a laminated film, a package of the desired shape can be manufactured more precisely.

When the packaging body 101 shown in Figures 2 and 3 is a packaging body of this embodiment, it is preferable that either one or both of the lid material 8 and the base material 7 are made of the laminate film, and that at least the base material 7 is made of the laminate film.
For example, when the base material 7 consists of the laminate film 1 shown in Figure 1 or the laminate film 2 shown in Figure 4, the second surface 7b of the base material 7 corresponds to the second surface 11b of the easy peel layer 11 in the laminate film 1 or the laminate film 2, and the first surface 7a of the base material 7 corresponds to the first surface 17a of the outer layer 17 in the laminate film 1 or the laminate film 2.
When the lid material 8 is made of the laminate film 1 shown in Figure 1 or the laminate film 2 shown in Figure 4, the second surface 8b of the lid material 8 corresponds to the second surface 11b of the easy peel layer 11 in the laminate film 1 or the laminate film 2, and the first surface 8a of the lid material 8 corresponds to the first surface 17a of the outer layer 17 in the laminate film 1 or the laminate film 2.
In addition, in Figs. 2 and 3, when either or both of the cover material 8 and the base material 7 are made of the laminated film, the distinction between the layers in the laminated film is omitted.

In the case where the lid material 8 of the package 101 is not made of the laminated film according to one embodiment of the present invention, the lid material 8 may be any material that can be used in ordinary deep-draw packages. Examples of such lid materials 8 include those made of single-layer or multi-layer resin films.
In the case where the base material 7 of the package 101 is not made of the laminated film according to one embodiment of the present invention, the base material 7 may be any material that can be used in ordinary deep-draw packages. Examples of such base materials 7 include those made by deep-drawing a single-layer or multi-layer resin film.

In the packaging body 101, when the lid material 8 or the base material 7 is made of a laminate film according to one embodiment of the present invention described above, the thickness of the lid material 8 or the base material 7 is the same as the thickness of the laminate film described above.
When the cover material 8 or the base material 7 is made of a film other than the laminated film, the thickness of the cover material 8 or the base material 7 may be the same as the thickness of the laminated film.

The packaging of this embodiment is not limited to the above, and some of the configuration may be changed, deleted, or added without departing from the spirit of the present invention.

<<Manufacturing method of packaging body>>
The packaging body of this embodiment can be manufactured in the same manner as the conventional packaging body, except that the laminated film is used instead of the conventional film.
For example, a package having a lid material and a base material, which is constituted by sealing the lid material and the base material, and one or both of the lid material and the base material are made of the laminated film, can be manufactured by overlapping the lid material and the base material to form the storage section, and heat sealing (forming a seal portion by heating). At this time, the frame seal portion and the face seal portion may be formed as the seal portion.
In manufacturing a package including the lid material and the base material, an object to be packaged is placed in the storage section before heat sealing the lid material and the base material. Then, the lid material and the base material may be heat sealed in a state in which the inside of the storage section is evacuated.

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

[Example 1]
<<Manufacturing of Laminated Film>>
A laminated film having the structure shown in FIG. 1 was produced by the following procedure.
That is, as the resin constituting the easy peel layer, a low density polyethylene (1) (LDPE (1), "L211" manufactured by Sumitomo Chemical Co., Ltd.) and a polypropylene (1) (PP (1), "FS2011DG2" manufactured by Sumitomo Chemical Co., Ltd.) were prepared.
As a resin constituting the flexible layer, low-density polyethylene (2) (LDPE (2), "F222NH" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was prepared.
As the resin for forming the pinhole resistant layer and the outer layer, 6-nylon (Ny6, "1030B2" manufactured by Ube Industries, Ltd.) was prepared.
As a resin constituting the oxygen barrier layer, an ethylene-vinyl alcohol copolymer (1) (EVOH (1), "L171B" manufactured by Kuraray Co., Ltd., copolymerization ratio of the ethylene was 27 mol %) was prepared.
As the adhesive resin constituting the first adhesive layer and the second adhesive layer, maleic anhydride modified polyethylene (modified PE, "NF536" manufactured by Mitsui Chemicals, Inc.) was prepared.

The LDPE (1) (75 parts by mass) and the PP (1) (25 parts by mass) were mixed at room temperature to produce a composition for forming an easy peel layer.

The die temperature was set to 250°C, and the easy peel layer forming composition, the LDPE (2), the modified PE, the Ny6, the EVOH (1), the modified PE, and the Ny6 were co-extruded in this order (co-extrusion T-die method) to obtain a laminated film (thickness 150 μm) composed of an easy peel layer (thickness 10 μm), a soft layer (thickness 42 μm), a first adhesive layer (thickness 12 μm), a pinhole resistant layer (thickness 37 μm), an oxygen barrier layer (thickness 15 μm), a second adhesive layer (thickness 12 μm), and an outer layer (thickness 22 μm) stacked in this order in the thickness direction.

<<Evaluation of laminated film>>
<Measurement of oxygen transmission rate>
The amount of oxygen transmitted to the laminated film obtained above before high-pressure sterilization was measured under conditions of a temperature of 23° C. and a relative humidity of 50% in accordance with JIS K 7126-2: 2006. The results are shown in Table 1.

<Measurement of oxygen transmission rate after high-pressure sterilization and calculation of change rate of oxygen transmission rate>
The laminated film after measuring the oxygen transmission amount before high-pressure sterilization was immersed in water, and the laminated film was sterilized under high-pressure conditions of a water temperature of 10°C, a pressure of 600 MPa, and a time of 3 minutes. The laminated film was then removed from the water, and 24 hours after the end of high-pressure sterilization, the oxygen transmission amount of the laminated film after high-pressure sterilization was measured under conditions of a temperature of 23°C and a relative humidity of 50% in accordance with JIS K 7126-2:2006. Furthermore, the change rate of the oxygen transmission amount of the laminated film was calculated from this measurement value and the measurement value of the oxygen transmission amount before high-pressure sterilization previously measured. The results are shown in Table 1.

<Gelboflex test>
The laminated film obtained above was subjected to a Gelbo flex test in accordance with ASTM F392 under the conditions of a temperature of 23° C. and 500 bending cycles. After the test, the laminated film was visually observed to confirm the number of pinholes found in the laminated film. The results are shown in Table 1.

<Evaluation of suitability for high-pressure sterilization (checking the number of breakages during high-pressure sterilization)>
(Manufacturing of packaging bodies)
A resin film having a width of 420 mm and a sealant layer containing linear low density polyethylene (LLDPE) was prepared as a lid material for the packaging body. In the sealant layer of this resin film for lid material, the content of LLDPE relative to the total mass of the sealant layer was 99 mass%, and the thickness of the sealant layer was 30 μm.

Using a deep drawing machine (Mulchvac's "R-535"), the laminated film obtained above, measuring 422 mm in width, was deep drawn under conditions of a heating temperature of 95°C, a heating time of 2.0 seconds, and a forming time of 2.5 seconds to form a recess, thereby producing the base material for the packaging body.

A processed meat product (100g of loin ham) was placed in the recess of the base material, the sealant layer of the lid material and the easy peel layer of the base material (laminated film) were placed opposite each other, and the processed meat product was sandwiched between the lid material and the base material, and the inside of the storage section formed by the lid material and the base material in the recess was evacuated at a temperature of 140°C and a vacuuming time of 2 seconds. Next, the periphery of the lid material and the base material were sealed in a frame shape at a sealing temperature of 140°C and a sealing time of 2 seconds to form a frame seal section with a width of 1 cm, thereby producing a package (vacuum package) having the frame seal section and further having a surface seal section formed by the lid material and the base material between the processed meat product and the frame seal section on the storage section side of the frame seal section.
Ten of the above packages were produced using the same procedure.

(High pressure sterilization of packaging)
The package obtained above was immersed in water and subjected to high-pressure sterilization in water under conditions of a water temperature of 10° C., a pressure of 600 MPa, and a time of 3 minutes.

(Evaluation of suitability for high-pressure sterilization)
After the high-pressure sterilization, each of the 10 packages was visually observed to check for damage such as holes, tears, etc. The number of packages that were found to be damaged (number of breaks) is shown in Table 1.

<Evaluation of storage stability of packaged items>
Packages that were not found to be damaged during the above-mentioned evaluation of suitability for high-pressure sterilization were stored in the atmosphere at a temperature of 10° C. for 70 days.
Next, the meat products vacuum-packed in the packages were visually observed, and if no packages were found to have discolored meat products, they were rated as "A", and if one or more were found, they were rated as "B". The results are shown in Table 1.

<Measurement of peel strength of sealed portion>
(Manufacturing of packaging bodies)
The packages were manufactured in the same manner as in the evaluation of high pressure sterilization suitability described above.

(Peel strength of seal part)
The peel strength of the frame seal portion and the face seal portion of the package obtained above were measured in accordance with JIS Z 0238: 1998. The results are shown in Table 1.

<<Production and Evaluation of Laminated Film>>
[Example 2]
A laminated film was produced and evaluated in the same manner as in Example 1, except that the thickness of the flexible layer was changed from 42 μm to 47 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 10 μm by changing the amount of ethylene-vinyl alcohol copolymer (1) used. The results are shown in Table 1.

[Example 3]
A laminated film was produced and evaluated in the same manner as in Example 1, except that the thickness of the flexible layer was changed from 42 μm to 37 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 20 μm by changing the amount of ethylene-vinyl alcohol copolymer (1) used. The results are shown in Table 1.

[Example 4]
A laminated film was produced and evaluated in the same manner as in Example 1, except that an ethylene-vinyl alcohol copolymer (2) (EVOH (2), "DT2904RB" manufactured by Mitsubishi Chemical Corporation, copolymerization ratio of ethylene: 29 mol%) was used instead of the ethylene-vinyl alcohol copolymer (1) (EVOH (1), "L171B" manufactured by Kuraray Co., Ltd., copolymerization ratio of the ethylene: 27 mol%) as the resin constituting the oxygen barrier layer. The results are shown in Table 1.

[Example 5]
A laminated film was produced and evaluated in the same manner as in Example 4, except that the thickness of the flexible layer was changed from 42 μm to 47 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 10 μm by changing the amount of ethylene-vinyl alcohol copolymer (2) used. The results are shown in Table 1.

[Example 6]
A laminated film was produced and evaluated in the same manner as in Example 4, except that the thickness of the flexible layer was changed from 42 μm to 37 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 20 μm by changing the amount of ethylene-vinyl alcohol copolymer (2) used. The results are shown in Table 2.

[Example 7]
A laminated film was produced and evaluated in the same manner as in Example 4, except that the thickness of the flexible layer was changed from 42 μm to 27 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 30 μm by changing the amount of ethylene-vinyl alcohol copolymer (2) used. The results are shown in Table 2.

[Example 8]
A laminated film was produced and evaluated in the same manner as in Example 4, except that the thickness of the flexible layer was changed from 42 μm to 52 μm by changing the amount of low-density polyethylene (2) used, and the thickness of the oxygen barrier layer was changed from 15 μm to 5 μm by changing the amount of ethylene-vinyl alcohol copolymer (2) used. The results are shown in Table 2.

[Example 9]
A laminated film was produced and evaluated in the same manner as in Example 4, except that high density polyethylene (HDPE, Prime Polymer's "3300F") was used instead of low density polyethylene (2) (LDPE (2), Ube Maruzen Polyethylene's "F222NH") as the resin constituting the flexible layer. The results are shown in Table 2.

[Example 10]
<<Manufacturing of Laminated Film>>
A laminated film having the structure shown in FIG. 4 was produced by the following procedure.
That is, the resins constituting the easy peel layer, the resin constituting the flexible layer, the resin constituting the oxygen barrier layer, the resin constituting the outer layer, and the adhesive resins constituting the first adhesive layer and the second adhesive layer were each the same as in Example 4 (LDPE (1), PP (1), LDPE (2), EVOH (2), Ny6, modified PE).

The composition for forming the easy peel layer was the same as that in Example 4.

The die temperature was set to 250°C, and the easy peel layer forming composition, the LDPE (2), the modified PE, the EVOH (2), the modified PE, and the Ny6 were co-extruded in this order (co-extrusion T-die method) to obtain a laminated film (thickness 150 μm) composed of an easy peel layer (thickness 10 μm), a soft layer (thickness 79 μm), a first adhesive layer (thickness 12 μm), an oxygen barrier layer (thickness 15 μm), a second adhesive layer (thickness 12 μm), and an outer layer (thickness 22 μm) stacked in this order in the thickness direction.

<<Evaluation of laminated film>>
The laminated film obtained above was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 11]
<<Manufacturing of Laminated Film>>
A laminated film having the structure shown in FIG. 1 was produced by the following procedure.
That is, the resin constituting the easy peel layer, the resin constituting the flexible layer, the resin constituting the oxygen barrier layer, the resin constituting the pinhole resistant layer, and the adhesive resin constituting the first adhesive layer were each the same as in Example 4 (LDPE (1), PP (1), LDPE (2), EVOH (2), Ny6, modified PE).
As a resin constituting the outer layer, polypropylene (2) (PP (2), "FL8115A" manufactured by Sumitomo Chemical Co., Ltd.) was prepared.
As the adhesive resin constituting the second adhesive layer, an unsaturated carboxylic acid modified polypropylene (modified PP, "QF551" manufactured by Mitsui Chemicals, Inc.) was prepared.

The composition for forming the easy peel layer was the same as that in Example 4.

The die temperature was set to 250°C, and the easy peel layer forming composition, the LDPE (2), the modified PE, the Ny6, the EVOH (2), the modified PP, and the PP (2) were co-extruded in this order (co-extrusion T-die method) to obtain a laminated film (thickness 150 μm) composed of an easy peel layer (thickness 10 μm), a soft layer (thickness 42 μm), a first adhesive layer (thickness 12 μm), a pinhole resistant layer (thickness 37 μm), an oxygen barrier layer (thickness 15 μm), a second adhesive layer (thickness 12 μm), and an outer layer (thickness 22 μm) stacked in this order in the thickness direction.

<<Evaluation of laminated film>>
The laminated film obtained above was evaluated in the same manner as in Example 1. The results are shown in Table 3.

<<Production and Evaluation of Laminated Film>>
[Comparative Example 1]
A laminated film was produced and evaluated in the same manner as in Example 7, except that, as the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (1) (EVOH (1), Kuraray Co., Ltd. "L171B", copolymerization ratio of the ethylene: 27 mol%) was used in place of ethylene-vinyl alcohol copolymer (2) (EVOH (2), Mitsubishi Chemical Co., Ltd. "DT2904RB", copolymerization ratio of the ethylene: 29 mol%). The results are shown in Table 3.

[Comparative Example 2]
A laminated film was produced and evaluated in the same manner as in Example 1, except that, as the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (3) (EVOH (3), Kuraray Co., Ltd. "J171B", copolymerization ratio of the ethylene: 32 mol%) was used in place of ethylene-vinyl alcohol copolymer (1) (EVOH (1), Kuraray Co., Ltd. "L171B", copolymerization ratio of the ethylene: 27 mol%). The results are shown in Table 3.

[Comparative Example 3]
A laminate film was produced and evaluated in the same manner as in Example 1, except that, as the resin constituting the oxygen barrier layer, ethylene-vinyl alcohol copolymer (3) (EVOH (3), Kuraray Co., Ltd. "J171B", copolymerization ratio of the ethylene: 32 mol%) was used instead of ethylene-vinyl alcohol copolymer (1) (EVOH (1), Kuraray Co., Ltd. "L171B", copolymerization ratio of the ethylene: 27 mol%), the amount of ethylene-vinyl alcohol copolymer (3) used was changed to change the thickness of the oxygen barrier layer from 15 μm to 25 μm, and the amount of low-density polyethylene (2) used was changed to change the thickness of the flexible layer from 42 μm to 32 μm. The results are shown in Table 3.

As is clear from the above results, in the laminated films of Examples 1 to 11, the number of pinholes observed in the Gelbo Flex test was kept at a low level of 80 or less (20 to 80), and no damage was observed during high-pressure sterilization in the packages produced using these laminated films. Thus, the packages obtained by vacuum packaging processed meat products using the laminated films of Examples 1 to 11 were capable of high-pressure sterilization.
In the packages manufactured using the laminated films of Examples 1 to 11, the peel strength of the frame seal was 3.8 to 5.1 N/15 mm, and the peel strength of the face seal was 1.7 to 2.4 N/15 mm, and further, in each Example, the peel strength of the frame seal was greater than the peel strength of the face seal.

In the packages manufactured using the laminated films of Examples 1 to 11, no discoloration of the processed meat products was observed after storage for 70 days, and discoloration of the processed meat products during long-term storage after high-pressure sterilization was suppressed.
The oxygen transmission rate (oxygen transmission rate before high-pressure sterilization) of the laminated films of Examples 1 to 11 was 0.6 ml/( ^m2 ·24h·atm) or less (0.1 to 0.6 ml/( ^m2 ·24h·atm)). The oxygen transmission rate after high-pressure sterilization of the laminated films of Examples 1 to 11 was 0.65 ml/( ^m2 ·24h·atm) or less (0.12 to 0.65 ml/( ^m2 ·24h·atm)). The change rate of oxygen transmission rate of the laminated films was 89.3 to 120.0%.

In contrast, the laminated film of Comparative Example 1 had a high number of pinholes (110) in the Gelboflex test, and packages manufactured using this laminated film were found to be damaged during high-pressure sterilization. Thus, the packages obtained by vacuum packaging processed meat products using the laminated film of Comparative Example 1 were not suitable for high-pressure sterilization.

In the packages manufactured using the laminated films of Comparative Examples 2 and 3, discoloration of the processed meat products was observed after storage for 70 days, and discoloration of the processed meat products during long-term storage after high-pressure sterilization was not suppressed.
The oxygen transmission rate (oxygen transmission rate before high-pressure sterilization) of the laminated films of Comparative Examples 2 and 3 was 1.1 ml/( ^m2 ·24h·atm) or more (1.1 to 1.8 ml/( ^m2 ·24h·atm)). The oxygen transmission rate after high-pressure sterilization of the laminated films of Comparative Examples 2 and 3 was 1.05 ml/( ^m2 ·24h·atm) or more (1.05 to 1.8 ml/( ^m2 ·24h·atm)). The change rate of oxygen transmission rate of the laminated films was 99.5 to 100.0%.

The present invention can be used for packaging that vacuum packages food.

1, 2: Laminated film 11: Easy peel layer 15: Oxygen barrier layer
7...Bottom material (test bottom material)
70: Recess of base material 8: Lid material (test lid material)
9...Packaged object 101...Package (test package)
101a: Storage of package 1011: Frame seal portion of package 1012: Face seal portion of package

Claims (6)

A laminated film,
The laminated film is configured by laminating an easy peel layer, a flexible layer, a first adhesive layer, an oxygen barrier layer, a second adhesive layer, and an outer layer in this order in a thickness direction,
the easy peel layer comprises low density polyethylene and homopolypropylene;
In the easy peel layer, a ratio of a content of the low-density polyethylene to a total content of the low-density polyethylene and the homopolypropylene is 50 to 90 mass%;
The easy peel layer has a thickness of 5 to 20 μm,
the flexible layer comprises polyethylene;
the oxygen barrier layer comprises an ethylene-vinyl alcohol copolymer;
In the ethylene-vinyl alcohol copolymer, the ratio of the amount of structural units derived from ethylene to the total amount of structural units is 25 to 30 mol%, and when the ratio is 25 mol% or more and less than 28 mol%, the thickness of the oxygen barrier layer is 28 μm or less, and when the ratio is 28 to 30 mol%, the thickness of the oxygen barrier layer is 32 μm or less,
The outer layer comprises one or more selected from the group consisting of polyamides and polyolefins,
The first adhesive layer and the second adhesive layer contain a polyolefin resin as an adhesive resin,
when the laminated film is subjected to a Gelbo flex test in accordance with ASTM F392 at a temperature of 23° C. and 500 flex cycles, the number of pinholes observed in the laminated film after the Gelbo flex test is 100 or less;
The oxygen transmission rate of the laminate film, measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23°C and a relative humidity of 50%, is 1.0 ml/( ^m2 ·24 h·atm) or less. The laminate film according to claim 1 , further comprising a pinhole resistant layer between the first adhesive layer and the oxygen barrier layer, the pinhole resistant layer comprising polyamide. a test package comprising a test lid material made of a resin film provided with a sealant layer containing linear low density polyethylene, and a test base material made of the laminate film, the test lid material being provided with a recess for forming a storage section for the packaged item, the packaged item being placed in the recess, the packaged item being sandwiched between the test lid material and the test base material, the inside of the storage section formed by the test lid material and the test base material in the recess being evacuated at a temperature of 140°C and a vacuuming time of 2 seconds, and then the peripheral portions of the test lid material and the test base material being sealed into a frame shape at a sealing temperature of 140°C and a sealing time of 2 seconds to form a frame seal portion, and further comprising a surface seal portion formed by the test lid material and the test base material on the storage section side of the frame seal portion;
3. The laminate film according to claim 1, wherein, when the peel strength of the frame seal portion and the peel strength of the face seal portion of the test package are measured in accordance with JIS Z 0238:1998, the peel strength of the frame seal portion is greater than the peel strength of the face seal portion, the peel strength of the frame seal portion is 1.0 to 8.0 N/15 mm, and the peel strength of the face seal portion is 0.5 to 6.0 N/15 mm. 4. The laminate film according to claim 1, wherein when the laminate film is subjected to high-pressure sterilization in water under conditions of a water temperature of 10°C, a pressure of 600 MPa, and a time of 3 minutes, the ratio of the oxygen permeation amount of the laminate film 24 hours after the end of the high-pressure sterilization to the oxygen permeation amount of the laminate film before the high-pressure sterilization is 150 % or less. A packaging body comprising the laminate film according to any one of claims 1 to 4 . The packaging body comprises a lid material and a base material,
The packaging body is formed by sealing the lid material and the base material,
The packaging body according to claim 5 , wherein the base material is made of the laminated film.

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