JP6741121B2 - Multi-layer film and packaging - Google Patents

Description

The present invention relates to a multilayer film and a package.

A package in which the contents are placed on a hard tray and the contents are sealed with a film is called a skin pack. In the skin pack, the film, that is, the film for skin pack, is transparent so that the contents can be easily visually confirmed. In addition, the film for skin pack is soft, and it is possible to bring the film into close contact with an item to be stored without causing wrinkles by evacuation of the storage section in the skin pack (for example, see Patent Document 1). Further, since the skin pack is provided with the hard tray, it can be displayed in a standing position without causing the displacement of the contents. In view of such characteristics, the skin pack is mainly used as a food packaging body.

JP, 2016-222259, A

In the case of a skin pack for food, it is necessary that the multilayer film constituting the skin pack is provided with an oxygen barrier layer in order to prevent oxidative deterioration of the food. However, there is a problem in that the presence of the oxygen barrier layer deteriorates the ability of the skin pack to follow food (that is, the skin pack can be adhered without causing wrinkles).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multilayer film excellent in conformability to a stored item and a package (for example, a skin pack package) using the multilayer film.

In order to solve the above problems, the present invention employs the following configurations.
[1]. An outer layer containing polyethylene, a functional layer containing an ionomer and adjacent to the outer layer, an oxygen barrier layer, and a sealant layer containing an ethylene vinyl acetate copolymer, and a temperature exhibiting a displacement of 2000 μm in thermomechanical analysis. Is 120° C. or higher, a multilayer film.
[2]. The multilayer film according to [1], wherein the multilayer film is irradiated with an electron beam under the condition of absorbed dose of 20 to 300 kGy.
[3]. The multilayer film according to [1] or [2], which has a displacement of 500 μm or less at a temperature of 100° C. in thermomechanical analysis.
[4]. The multilayer film according to any one of [1] to [3], wherein the thickness of the multilayer film is 60 μm or more.

[5]. The multilayer film according to any one of [1] to [4], wherein the polyethylene is low-density polyethylene having a density of 0.945 g/cm ³ or less.
[6]. The multilayer film according to any one of [1] to [5], wherein the oxygen barrier layer contains an ethylene-vinyl alcohol copolymer (EVOH).
[7]. The multilayer film according to any one of [1] to [6], wherein the oxygen barrier layer contains EVOH in an amount of 3% by mass or more and 25% by mass or less of the total mass of the oxygen barrier layer.
[8]. A package comprising the multilayer film according to any one of [1] to [7].
[9]. The package according to [8], wherein the package is a skin pack package.

The multilayer film of the present invention comprises an outer layer containing polyethylene, a functional layer adjacent to the outer layer containing an ionomer, an oxygen barrier layer, and a sealant layer containing an ethylene vinyl acetate copolymer, and in thermomechanical analysis. Since the temperature showing a displacement of 2000 μm is 120° C. or higher, it is excellent in the conformability to the contained object.

It is sectional drawing which shows the multilayer film which concerns on one Embodiment of this invention typically. It is sectional drawing which shows the multilayer film which concerns on one Embodiment of this invention typically. It is sectional drawing which shows typically the package which concerns on one Embodiment of this invention.

<<Multi-layer film>>
A multilayer film according to an embodiment of the present invention comprises an outer layer containing polyethylene, an ionomer, a functional layer adjacent to the outer layer, an oxygen barrier layer, and a sealant layer containing an ethylene vinyl acetate copolymer. In thermomechanical analysis, the temperature at which a displacement of 2000 μm is shown is 120° C. or higher.
The multilayer film of this embodiment can form a package (for example, a skin pack package) together with a hard tray. In the present specification, the term "skin pack" means that the contents are placed on a cardboard, a cardboard, a bottom film, a tray, etc., a heated film is placed on the contents, and a vacuum is drawn in the chamber. A package in which the film is intimately fixed to the contents. The name comes from the feature that the film adheres to the product body almost like a skin along the shape of the product.

Hereinafter, the present invention will be described in detail with reference to the drawings. Note that, in the drawings used in the following description, in order to facilitate understanding of the features of the present invention, for the sake of convenience, there may be a case where an essential part is enlarged and the dimensional ratios of the respective components are the same as the actual ones. Not necessarily.

FIG. 1 is a sectional view schematically showing a multilayer film according to an embodiment of the present invention.
The multilayer film 1 shown here includes an outer layer 12 and a sealant layer 11. In the multilayer film 1, the outer layer 12 is one outermost layer and the sealant layer 11 is the other outermost layer.
Furthermore, the multilayer film 1 includes the adhesive layer 15, the oxygen barrier layer 14 disposed on the adhesive layer 15, and the adhesive layer 15 disposed on the oxygen barrier layer 14 from the sealant layer 11 side toward the outer layer 12 side. And a functional layer 13 disposed on the adhesive layer 15, and is composed of a plurality of layers.

<Sealant layer>
The sealant layer 11 contains an ethylene vinyl acetate copolymer. When the sealant layer 11 contains the ethylene-vinyl acetate copolymer, the easy peeling property is improved due to the pseudo adhesiveness with the adherend.
The sealant layer 11 may include only the ethylene-vinyl acetate copolymer (that is, may be composed of the ethylene-vinyl acetate copolymer), the ethylene-vinyl acetate copolymer, and the other components. (In the present specification, it may be referred to as “other component”) (that is, it may be composed of an ethylene-vinyl acetate copolymer and the other component). ..

The other component contained in the sealant layer 11 is not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, either a resin component or a non-resin component.
The other component which is the resin component is a resin other than the ethylene-vinyl acetate copolymer.
The other component which is the resin component may be a homopolymer which is a polymer of one kind of monomer, or a copolymer which is a polymer of two or more kinds of monomers.
More specifically, examples of the other component that is a resin component include ethylene methacrylic acid copolymers, ionomers, polyolefins such as polypropylene, and olefin copolymers such as ethylene propylene copolymers. The sealant layer 11 containing these other components (resin components) further improves the easy peeling property due to the expression of pseudo-adhesiveness with the adherend.

Examples of the other component that is a non-resin component include additives known in the art.
Examples of the additives include antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, thickeners, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

The other component contained in the sealant layer 11 may be only one type, or may be two or more types, and in the case of two or more types, their combination and ratio may be arbitrarily determined depending on the purpose. You can choose.

In the sealant layer 11, the ratio of the content of the ethylene vinyl acetate copolymer to the total mass of the sealant layer 11 is preferably 4% by mass or more, and more preferably 7% by mass or more and 100% by mass or less. More preferably, it is 10% by mass or more and 100% by mass or less. When the ratio is equal to or more than the lower limit value, the easy peeling property due to the expression of pseudo-adhesiveness with the adherend is further improved.

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

In addition, in the present specification, not only the case of the sealant layer 11, but “a plurality of layers may be the same or different from each other” means that “all layers may be the same or all layers may be the same”. "May be different, only some of the layers may be the same", and "a plurality of layers are different from each other" means that "at least one of the constituent material and the thickness of each layer is different from each other". Means that.

As a case where the sealant layer 11 is composed of a plurality of layers, for example, as shown in FIG. 1, a case where the sealant layer is composed of two layers of a first sealant layer 111 and a second sealant layer 112 can be mentioned. In this case, the ethylene-vinyl acetate copolymer contained in the first sealant layer 111 preferably has a copolymerization ratio of ethylene and vinyl acetate of 96/4 to 60/40, and 93/7 to 63/37. It is more preferable that it is, and it is further preferable that it is 90/10 to 66/34. Further, the copolymerization ratio of ethylene and vinyl acetate of the ethylene-vinyl acetate copolymer contained in the second sealant layer 112 is preferably 93/7 to 50/50, and 90/10 to 53/47. More preferably, it is more preferably 87/13 to 56/44. When the copolymerization ratio is within the above range, the easy peeling property due to the expression of pseudo-adhesiveness with the adherend is further improved.

The thickness of the sealant layer 11 is preferably 4 μm or more and 96 μm or less, more preferably 7 μm or more and 93 μm or less, and further preferably 10 μm or more and 90 μm or less. When the thickness of the sealant layer 11 is equal to or more than the lower limit value, the strength of the sealant layer 11 becomes higher. When the thickness of the sealant layer 11 is equal to or less than the upper limit value, it is possible to prevent the sealant layer 11 from having an excessive thickness, and also to increase the sealing strength when the multilayer film 1 is sealed by heating.
Here, the “thickness of the sealant layer 11” means the total thickness of the sealant layer 11, and for example, the thickness of the sealant layer 11 composed of a plurality of layers is the total of all layers constituting the sealant layer 11. Means the thickness of.

An exposed surface (sometimes referred to as “first surface” in the present specification) 11a of the sealant layer 11 on the side opposite to the functional layer 13 side is a sealing surface.

<Outer layer>
The outer layer 12 includes polyethylene. When the outer layer 12 contains polyethylene, the crosslink density of the outer layer 12 can be improved when the multilayer film 1 is irradiated with an electron beam from the outer layer 12 side.
The outer layer 12 may include only polyethylene (that is, may be made of polyethylene), or may include polyethylene and other components (which may be referred to as “other components” in the present specification). A) may be contained (that is, it may consist of polyethylene and the above-mentioned other components).

The polyethylene contained in the outer layer 12 is preferably a low density polyethylene having a density of 0.945 g/cm ³ or less, more preferably a low density polyethylene having a density of 0.943 g/cm ³ or less, and a density of 0.941 g/cm 3. More preferably, it is a low density polyethylene of ³ or less. By including such a low-density polyethylene, the crosslink density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with an electron beam from the outer layer 12 side.

The polyethylene contained in the outer layer 12 may be only one kind, or two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof can be arbitrarily selected according to the purpose.

The other component contained in the outer layer 12 is not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, a resin component or a non-resin component.
The other component which is a resin component is a resin other than polyethylene.
Examples of the other component that is a non-resin component include the same additives as the other components included in the sealant layer 11 described above.

The other component contained in the outer layer 12 may be only one type, or may be two or more types, and in the case of two or more types, their combination and ratio are arbitrarily selected according to the purpose. it can.

In the outer layer 12, the ratio of the content of polyethylene with respect to the total mass of the outer layer 12 is preferably 50% by mass or more, more preferably 55% by mass or more and 100% by mass or less, and 60% by mass or more and 100% by mass. % Or less is more preferable. When the ratio is equal to or more than the lower limit value, the crosslink density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with the electron beam from the outer layer 12 side.

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

The thickness of the outer layer 12 is preferably 4 μm or more and 146 μm or less, more preferably 7 μm or more and 143 μm or less, and further preferably 10 μm or more and 140 μm or less. When the thickness of the outer layer 12 is equal to or more than the lower limit value, the crosslink density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with the electron beam from the outer layer 12 side. When the thickness of the outer layer 12 is equal to or less than the upper limit value, the outer layer 12 is prevented from having an excessive thickness.
Here, the “thickness of the outer layer 12” means the total thickness of the outer layer 12, and for example, the thickness of the outer layer 12 composed of a plurality of layers means the total thickness of all the layers constituting the outer layer 12. means.

The ratio of the thickness of the outer layer 12 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 12% or more and 88% or less, and 14% or more and 86% or less. Is more preferable. When the ratio is equal to or more than the lower limit value, the crosslink density of the outer layer 12 can be further improved when the multilayer film 1 is irradiated with the electron beam from the outer layer 12 side. On the other hand, when the ratio is less than or equal to the upper limit value, the outer layer 12 is prevented from having an excessive thickness.

In the case of a skin pack for food, it is necessary that the multilayer film constituting the skin pack is provided with an oxygen barrier layer in order to prevent oxidative deterioration of the food. However, there is a problem in that the presence of the oxygen barrier layer deteriorates the ability of the skin pack to follow food (that is, the skin pack can be adhered without causing wrinkles). On the other hand, the multilayer film 1 of the present embodiment is provided with the outer layer 12 and the functional layer 13 to solve this problem. That is, due to the presence of the outer layer 12 and the functional layer 13, the heat resistance and melt tension of the multilayer film 1 are improved, and as a result, the multilayer film 1 excellent in conformability to a stored item can be obtained.

<Functional layer>
The functional layer 13 includes an ionomer and is adjacent to the outer layer 12. When the functional layer 13 contains an ionomer, the crosslink density of the functional layer 13 can be improved when the multilayer film 1 is irradiated with an electron beam from the outer layer 12 side. As a result, it is possible to further improve the followability during skin pack.
The functional layer 13 may contain only an ionomer (that is, may be composed of an ionomer), or an ionomer and other components (in the present specification, referred to as “other components”). )) (that is, it may consist of an ionomer and the other component).

Examples of the ionomer contained in the functional layer 13 include ethylene ionomers having a copolymer structure of ethylene and a monomer other than ethylene.

The ionomer contained in the functional layer 13 may be only one kind, or two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof can be arbitrarily selected according to the purpose.

The other component contained in the functional layer 13 is not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, either a resin component or a non-resin component.
The other component which is the resin component is a resin other than the ionomer.
Examples of the other component that is a non-resin component include the same additives as the other components included in the sealant layer 11 described above.

The other component contained in the functional layer 13 may be only one kind, or may be two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof may be arbitrarily selected depending on the purpose. You can choose.

In the functional layer 13, the ratio of the ionomer content to the total mass of the functional layer 13 is preferably 50% by mass or more, more preferably 55% by mass or more and 100% by mass or less, and 60% by mass or more. It is more preferably 100% by mass or less. When the ratio is equal to or more than the lower limit value, the crosslinking density of the functional layer 13 can be further improved when the multilayer film 1 is irradiated with the electron beam from the outer layer 12 side.

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

The thickness of the functional layer 13 is preferably 4 μm or more and 146 μm or less, more preferably 7 μm or more and 143 μm or less, and further preferably 10 μm or more and 140 μm or less. When the thickness of the functional layer 13 is equal to or more than the lower limit value, the crosslink density of the functional layer 13 can be further improved when the multilayer film 1 is irradiated with an electron beam from the outer layer 12 side. When the thickness of the functional layer 13 is equal to or less than the upper limit value, it is possible to prevent the functional layer 13 from having an excessive thickness.
Here, the “thickness of the functional layer 13” means the total thickness of the functional layer 13, and for example, the thickness of the functional layer 13 composed of a plurality of layers means the total of all layers constituting the functional layer 13. Means the thickness of.

The ratio of the thickness of the functional layer 13 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11% or more and 89% or less, and 12% or more and 88%. The following is more preferable. When the ratio is equal to or more than the lower limit value, the crosslinking density of the functional layer 13 can be further improved when the multilayer film 1 is irradiated with the electron beam from the outer layer 12 side. On the other hand, when the ratio is equal to or less than the upper limit value, the functional layer 13 is prevented from having an excessive thickness.

<Oxygen barrier layer>
The multilayer film 1 includes an oxygen barrier layer 14. By including the oxygen barrier layer 14 in the multilayer film 1, a strong oxygen barrier property (in other words, a property of suppressing permeation of oxygen gas) can be imparted to the multilayer film 1.

The oxygen barrier layer 14 preferably contains an ethylene-vinyl alcohol copolymer (also known as a saponified product of an ethylene-vinyl acetate copolymer, which may be abbreviated as “EVOH” in this specification).

The oxygen barrier layer 14 may contain only EVOH (that is, may be made of EVOH), or may contain EVOH and other components (herein, referred to as “other components”). In some cases) (that is, it may consist of EVOH and the above-mentioned other components).

The other component contained in the oxygen barrier layer 14 is not particularly limited and can be arbitrarily selected according to the purpose. For example, it may be either a resin component or a non-resin component.
The other component which is a resin component is a resin other than EVOH.
Examples of the other component that is a non-resin component include the same additives as the other components included in the sealant layer 11 described above.

The other components contained in the oxygen barrier layer 14 may be only one kind, or may be two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof may be arbitrarily selected depending on the purpose. You can choose.

The proportion of the EVOH content in the oxygen barrier layer 14 with respect to the total mass of the oxygen barrier layer 14 is preferably 3% by mass or more and 25% by mass or less, and more preferably 4% by mass or more and 24% by mass or less. It is preferably 5% by mass or more and 23% by mass or less. When the ratio is equal to or more than the lower limit value, the multilayer film 1 can be provided with a stronger oxygen barrier property. When the ratio is less than or equal to the upper limit value, it is possible to suppress deterioration of the followability during skin pack.

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

The thickness of the oxygen barrier layer 14 is preferably 2 μm or more and 100 μm or less, more preferably 3 μm or more and 90 μm or less, and further preferably 4 μm or more and 80 μm or less. When the thickness of the oxygen barrier layer 14 is equal to or more than the lower limit value, the multilayer film 1 can be provided with a stronger oxygen barrier property. When the thickness of the oxygen barrier layer 14 is equal to or less than the upper limit value, the oxygen barrier layer 14 is prevented from having an excessive thickness.
Here, the “thickness of the oxygen barrier layer 14 ”means the total thickness of the oxygen barrier layer 14, and for example, the thickness of the oxygen barrier layer 14 composed of a plurality of layers means all the constituents of the oxygen barrier layer 14. Means the total thickness of the layers.

<Adhesive layer>
The adhesive layer 15 contains an adhesive.
The adhesive layer 15 adheres two layers adjacent to both surfaces thereof. In the multilayer film 1, the adhesive layer 15 arranged between the sealant layer 11 and the oxygen barrier layer 14 adheres the sealant layer 11 and the oxygen barrier layer 14, and between the oxygen barrier layer 14 and the functional layer 13. The adhesive layer 15 disposed in the above section bonds the oxygen barrier layer 14 and the functional layer 13 together.
These two adhesive layers 15 may be the same or different from each other.

The adhesive contained in the adhesive layer 15 is not particularly limited as long as it can bond two layers to be bonded with sufficient strength.
Examples of the adhesive include an adhesive resin such as an olefin resin (that is, a polymer of olefin which is one kind or two or more kinds of monomers).

More specifically, examples of the olefin-based resin include ethylene-based copolymers, propylene-based copolymers, butene-based copolymers, and the like.
The ethylene-based copolymer is a copolymer of ethylene and a monomer other than ethylene.
The propylene-based copolymer is a copolymer of propylene and a monomer other than propylene.
The butene-based copolymer is a copolymer of butene and a monomer other than butene.

Examples of the ethylene-based copolymer include a copolymer of ethylene and a vinyl group-containing monomer.
Examples of the copolymer of ethylene and a vinyl group-containing monomer include maleic anhydride graft-modified linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer. Polymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ionomer, ethylene-based thermoplastic elastomer and the like. .. The ionomer means a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid, which has an ionic bridge structure by salt formation between an acid moiety and a metal ion.

The adhesive layer 15 may include only an adhesive (that is, may be composed of an adhesive), or the adhesive and other components (in the present specification, “other components”). May be referred to as) (that is, it may consist of an adhesive and the other component).

The adhesive contained in the adhesive layer 15 may be only one kind, or two or more kinds, and in the case of two or more kinds, their combination and ratio can be arbitrarily selected according to the purpose. ..

The other component contained in the adhesive layer 15 is not particularly limited and may be arbitrarily selected according to the purpose, and may be, for example, a resin component or a non-resin component.

The other component contained in the adhesive layer 15 may be only one kind, or may be two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof may be arbitrarily selected depending on the purpose. You can choose.

The ratio of the content of the adhesive in the adhesive layer 15 to the total mass of the adhesive layer 15 may be, for example, 50% by mass or more and 100% by mass or less.

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

The thickness of the adhesive layer 15 is preferably 4 μm or more and 96 μm or less, more preferably 7 μm or more and 93 μm or less, and further preferably 10 μm or more and 90 μm or less. When the thickness of the adhesive layer 15 is equal to or more than the lower limit value, the adhesive strength of the two layers to be adhered becomes higher. When the thickness of the adhesive layer 15 is equal to or less than the upper limit value, the adhesive layer 15 is prevented from having an excessive thickness.
Here, the "thickness of the adhesive layer 15" means the total thickness of the adhesive layer 15 (for example, the total thickness of the adhesive layer 15 disposed between the sealant layer 11 and the oxygen barrier layer 14, the oxygen barrier). The total thickness of the adhesive layer 15 disposed between the layer 14 and the functional layer 13) means, for example, the thickness of the adhesive layer 15 composed of a plurality of layers means that all the layers constituting the adhesive layer 15 have the same thickness. Means total thickness.

<Pinhole resistant layer>
In the multilayer film 1, as shown in FIG. 2, the second sealant layer 112 may be changed to the pinhole resistant layer 16. The pinhole resistance layer 16 can improve the pinhole resistance of the multilayer film 1. Moreover, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs when heat treatment is performed.

The pinhole-resistant layer 16 may include an ionomer (that is, may be made of an ionomer), or an ionomer and other components (referred to as “other components” in the present specification). In some cases) (that is, it may consist of an ionomer and the other component).

Examples of the ionomer contained in the pinhole resistant layer 16 include ethylene ionomers having a copolymer structure of ethylene and a monomer other than ethylene.

The ionomer contained in the pinhole-resistant layer 16 may be only one kind, or two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof are arbitrarily selected according to the purpose. it can.

The other component contained in the pinhole resistant layer 16 is not particularly limited and can be arbitrarily selected according to the purpose, and may be, for example, a resin component or a non-resin component.
The other component which is the resin component is a resin other than the ionomer.
Examples of the other component that is a non-resin component include the same additives as the other components included in the sealant layer 11 described above.

The other components contained in the pinhole-resistant layer 16 may be only one kind, or may be two or more kinds, and in the case of two or more kinds, the combination and the ratio thereof may be depending on the purpose. It can be arbitrarily selected.

In the pinhole-resistant layer 16, the ratio of the ionomer content to the total mass of the pinhole-resistant layer 16 is preferably 50% by mass or more, more preferably 55% by mass or more and 100% by mass or less, More preferably, it is 60% by mass or more and 100% by mass or less. When the ratio is not less than the lower limit value, the pinhole resistance of the multilayer film 1 can be improved.

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

The thickness of the anti-pinhole layer 16 is preferably 4 μm or more and 146 μm or less, more preferably 7 μm or more and 143 μm or less, and further preferably 10 μm or more and 140 μm or less. When the thickness of the pinhole resistant layer 16 is equal to or more than the lower limit value, the pinhole resistant property of the multilayer film 1 can be improved. When the thickness of the pinhole resistant layer 16 is equal to or less than the upper limit value, the pinhole resistant layer 16 is prevented from having an excessive thickness.
Here, the “thickness of the pinhole-resistant layer 16” means the total thickness of the pinhole-resistant layer 16, and for example, the thickness of the pinhole-resistant layer 16 made up of a plurality of layers means the pinhole-resistant layer 16. It means the total thickness of all the layers constituting the.

The ratio of the thickness of the pinhole resistant layer 16 to the thickness of the multilayer film 1 is not particularly limited, but is preferably 10% or more, more preferably 11% or more and 89% or less, and 12% or more. It is more preferably 88% or less. When the ratio is not less than the lower limit value, the pinhole resistance of the multilayer film 1 can be improved. On the other hand, when the ratio is less than or equal to the upper limit value, the pinhole resistant layer 16 is prevented from having an excessive thickness.

The temperature at which the multilayer film 1 exhibits a displacement of 2000 μm in the thermomechanical analysis is 120° C. or higher. The temperature at which the multilayer film 1 exhibits a displacement of 2000 μm in thermomechanical analysis is preferably 125° C. or higher and 200° C. or lower, and more preferably 130° C. or higher and 195° C. or lower. In the multi-layer film 1, when the temperature exhibiting a displacement of 2000 μm in the thermomechanical analysis is equal to or higher than the lower limit value, the heat resistance of the multi-layer film 1 is improved, and as a result, the conformability to the stored item is improved. When the temperature at which the multilayer film 1 exhibits a displacement of 2000 μm in the thermomechanical analysis is equal to or lower than the upper limit value, the heat resistance of the multilayer film 1 is suppressed from becoming excessive.

In the thermomechanical analysis, the multilayer film 1 preferably has a displacement of 500 μm or less at a temperature of 100° C. In the thermomechanical analysis, the multilayer film 1 preferably has a displacement of 50 μm or more and 490 μm or less at a temperature of 100° C., and more preferably 100 μm or more and 480 μm or less. In the multilayer film 1, in the thermomechanical analysis, the displacement at a temperature of 100° C. is equal to or more than the lower limit value, whereby the melt tension of the multilayer film 1 is suppressed from becoming excessive. In the thermo-mechanical analysis of the multilayer film 1, the displacement at a temperature of 100° C. is equal to or less than the upper limit value, whereby the melt tension of the multilayer film 1 is improved, and as a result, the conformability to the contained object is improved.

The thermomechanical analysis of the multilayer film 1 can be performed by the following method. That is, based on JISK7196, the measurement is performed by the method of measuring the thermal expansion amount of the sample from the difference in the thermal expansion amount when the temperature of the standard sample and the measurement sample is raised at a constant rate.

The displacement in the thermomechanical analysis of the multilayer film 1 can be adjusted by, for example, the condition of electron beam irradiation on the outer layer 12 and the functional layer 13.

It is preferable that the multilayer film 1 be irradiated with an electron beam under the condition of the absorbed dose of 20 kGy or more and 300 kGy or less. By irradiating the multilayer film 1 with an electron beam at 20 kGy or more and 300 kGy or less, the crosslinking density of the multilayer film 1 (in particular, the outer layer 12 and the functional layer 13) can be improved. As a result, the heat resistance and the melt tension of the multilayer film 1 as a whole can be improved.

The reason why the cross-linking density of the multilayer film 1 is improved by electron beam irradiation is not clear, but it is considered as follows. That is, when the multilayer film 1 is irradiated with an electron beam, the carbon-hydrogen bond in the polyethylene of the outer layer 12 of the multilayer film 1 is broken, and a radical is generated at the cut bond end. The generated radicals are thought to come into contact with other polyethylene molecular chains due to molecular motion of the molecular chains, withdraw hydrogen atoms and bond with carbon atoms in the polyethylene molecular chain, resulting in the formation of a crosslinked structure. .. It is presumed that the same phenomenon occurs in the functional layer 13.

The absorbed dose of electron beam irradiation is more preferably 20 kGy or more and 300 kGy or less, and further preferably 25 kGy or more and 250 kGy or less. When the absorbed dose of electron beam irradiation is not less than the lower limit value, the crosslink density of the multilayer film 1 can be further improved. When the absorbed dose of electron beam irradiation is not more than the upper limit value, the multilayer film 1 is prevented from having excessive strength.

The acceleration voltage for electron beam irradiation is preferably 100 kV or more and 300 kV or less, more preferably 120 kV or more and 280 kV or less, and further preferably 140 kV or more and 260 kV or less. When the acceleration voltage of electron beam irradiation is not less than the lower limit value, the crosslink density of the multilayer film 1 can be further improved. When the acceleration voltage of electron beam irradiation is not more than the upper limit value, the multilayer film 1 is prevented from having excessive strength.

The thickness of the multilayer film 1 is preferably 60 μm or more, more preferably 70 μm or more and 400 μm or less, and further preferably 80 μm or more and 300 μm or less. When the thickness of the multilayer film 1 is at least the above lower limit value, the strength of the multilayer film 1 can be improved. When the thickness of the multilayer film 1 is less than or equal to the upper limit value, the multilayer film 1 is prevented from having an excessive thickness.

<Other layers>
The multilayer film 1 includes any one of the sealant layer 11, the outer layer 12, the functional layer 13, the oxygen barrier layer 14, the adhesive layer 15, and the pinhole resistant layer 16 within a range that does not impair the effects of the present invention. Other layers that do not correspond to the above may be provided.
The other layer is not particularly limited and can be arbitrarily selected according to the purpose.
When the multilayer film 1 includes the other layer, the multilayer film 1 may further include an adhesive layer (for example, the adhesive layer 15 or the like) for adhering the other layer to the other layer.

The multilayer film of the present embodiment is not limited to the above-mentioned one, and may have a part of the configuration changed, deleted or added without departing from the spirit of the present invention.

<<Manufacturing method of multilayer film>>
The multi-layer film of the present embodiment uses, for example, a co-extrusion T-die method such as a feed block method of melt-extruding a resin or a resin composition, which is a material for forming each layer, or a multi-manifold method, using several extruders. It can be produced by an air-cooled or water-cooled coextrusion inflation method or the like.

In addition, the multilayer film of the present embodiment, if necessary by coating the surface of another layer constituting the multilayer film with a resin or a resin composition that is a forming material of any of the layers, if necessary. It can also be produced by forming a laminated structure in the multilayer film by drying by drying and then further laminating layers other than these so as to have a desired arrangement form.

In the multilayer film of the present embodiment, two or more films for constituting any two or more of them are separately prepared in advance, and these films are dry-laminated by an adhesive method or extruded. It can also be manufactured by laminating by laminating any of a laminating method, a hot-melt laminating method and a wet laminating method, and further laminating other layers as necessary so as to have a desired arrangement form. At this time, an adhesive that can form the adhesive layer may be used.

In addition, the multilayer film of the present embodiment is obtained by laminating two or more films, which are separately prepared in advance as described above, by a thermal laminating method or the like without using an adhesive. If necessary, the layer can be manufactured by further stacking layers other than these so as to have a desired arrangement form.

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

<<<Package>>>
A package according to one embodiment of the present invention includes the above-described multilayer film according to one embodiment of the present invention. Such a package is excellent in conformability to the contained items.
The package of the present embodiment is suitable as a skin pack package. Further, the skin pack package of the present embodiment is suitable as, for example, a packaging bag or a packaging container for packaging foods and the like.

FIG. 3 is a cross-sectional view schematically showing a package according to one embodiment of the present invention.
In FIG. 3, the same components as those shown in FIG. 1 or 2 are designated by the same reference numerals as those in FIG. 1 or 2, and detailed description thereof will be omitted.

The package 10 shown here is configured to include the multilayer film 1 shown in FIG. 1 or 2 and a hard tray 2.
By using the multilayer film 1, the package 10 is excellent in conformability to the contained items 3.
In FIG. 3, the distinction of each layer in the multilayer film 1 is omitted.

The hard tray 2 is obtained by molding a film, and is usually made of an opaque multilayer resin film.
As shown in FIG. 3, a part of one surface (sometimes referred to as “first surface” in this specification) 2 a of the hard tray 2 and a part of the first surface 11 a of the multilayer film 1 Is adhered by a seal. As a result, the storage portion 10a is formed between the first surface 2a of the hard tray 2 and the first surface 11a of the multilayer film 1. Then, the contents 3 are hermetically sealed in the storage portion 10a.
In addition, in FIG. 3, in the storage portion 10a of the package 10, some gaps can be seen between the stored item 3 and the multilayer film 1 and between the stored item 3 and the hard tray 2. The existence of these gaps is not indispensable in the package 10 in the state in which the container 3 is stored.

The thickness of the hard tray 2 is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 300 μm or more. When the thickness of the hard tray 2 is equal to or more than the lower limit value, the strength of the hard tray 2 can be increased.
On the other hand, the upper limit of the thickness of the hard tray 2 is not particularly limited.

The contents 3 can be arbitrarily selected according to the purpose and are not particularly limited, but are preferably foods.

The package according to the present embodiment is not limited to the above-mentioned one, and may have a part of the configuration changed, deleted or added within the scope of the present invention.

<<Method of manufacturing package>>
The package of the present embodiment can be manufactured by stacking and heat-sealing the multilayer film and the hard tray so as to form the storage portion.
At the time of manufacturing the package, the contents are stored in the storage section before heat-sealing the multilayer film and the hard tray.

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

<<Manufacture of multilayer film and package>>
[Example 1]
The multilayer film having the structure shown in FIG. 1 and the package having the structure shown in FIG. 3 were manufactured by the following procedure.

<Manufacture of multilayer film>
As a resin constituting the first sealant layer, an ethylene vinyl acetate copolymer (copolymerization ratio of ethylene:vinyl acetate=84:16, manufactured by Mitsui DuPont Polychemical Co., Ltd., V5714RC) was prepared.
As a resin forming the second sealant layer, an ethylene vinyl acetate copolymer (copolymerization ratio of ethylene:vinyl acetate=81:19, manufactured by Mitsui DuPont Polychemical Co., Ltd., V430RC) was prepared.
As the polyethylene constituting the outer layer, low-density polyethylene (density 0.922 g/cm ³ , Ube Maruzen Polyethylene Co., F222NH) was prepared.
An ionomer (1601 manufactured by Mitsui DuPont Polychemical Co., Ltd.) was prepared as a substance constituting the functional layer.
EVOH (Nippon Gosei Co., Ltd. GH3804B) was prepared as a resin which comprises an oxygen barrier layer.
A modified polyolefin resin (NF536 manufactured by Mitsui Chemicals, Inc.) was prepared as a resin forming the adhesive layer.
Then, the first sealant layer, the second sealant layer, the adhesive layer, the oxygen barrier layer, the adhesive layer, the functional layer, and the outer layer were coextruded in this order to produce a multilayer film.
The obtained multilayer film has a first sealant layer (thickness=20 μm), a second sealant layer (thickness=24 μm), an adhesive layer (thickness=7 μm), an oxygen barrier layer (thickness=8 μm), an adhesive layer. (Thickness=7 μm), a functional layer (thickness=14 μm), and an outer layer (thickness=20 μm) are laminated in this order in the thickness direction, and have a thickness of 100 μm.

Next, electron beam irradiation was performed from the outer layer side of the multilayer film (absorbed dose 50 kGy, acceleration voltage 150 kV).
Then, based on JISK7196, thermomechanical analysis of the multilayer film was performed by using EXSTAR6000 manufactured by SII. From the obtained thermomechanical analysis curve, “temperature (° C.) showing displacement of 2000 μm” and “displacement (μm) at temperature of 100° C.” were obtained. The measurement results are shown in Table 2 below.

<Manufacture of hard tray>
Polypropylene (Sumitomo Chemical Co., Ltd., FH1016) was prepared as a resin constituting the outer layer.
EVOH (BF3203B manufactured by Nippon Gosei Co., Ltd.) was prepared as a resin forming the oxygen barrier layer.
As a resin forming the adhesive layer, a polyolefin-based adhesive resin (ER313-E1 manufactured by Mitsubishi Chemical Corporation) was prepared.
Then, the outer layer, the adhesive layer, the oxygen barrier layer, the adhesive layer, and the outer layer were coextruded in this order to produce a multilayer film.
The obtained multilayer film had an outer layer (thickness=364 μm), an adhesive layer (thickness=20 μm), an oxygen barrier layer (thickness=32 μm), an adhesive layer (thickness=20 μm), and an outer layer (thickness=364 μm). 2) is laminated in this order in the thickness direction, and has a thickness of 800 μm.

<Manufacture of packaging>
The ready meal was placed on the hard tray obtained above. The multilayer film (heated to 130° C.) obtained above is covered on the ready meal, and the storage portion of the ready meal is evacuated in the chamber to firmly fix the multilayer film to the ready meal. While performing the heat treatment, the multilayer film and the hard tray were heat-sealed. As the ready meal, two types of smoked cheese (spherical, 5 g) and fried chicken (amorphous, 30 to 40 g) were used.
As described above, a package having the ready meal stored in the storage section was manufactured.

[Example 2]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 1 except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 3]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 1 except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy and the acceleration voltage was changed from 150 kV to 175 kV.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 4]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed in the same manner as in Example 1 except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy and the acceleration voltage was changed from 150 kV to 200 kV.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Comparative Example 1]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 1 except that the electron beam irradiation was not performed.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 5]
<Manufacture of multilayer film>
A multilayer film was produced in the same manner as in Example 1 except that the amount of resin used to form each layer was changed.
The obtained multilayer film has a first sealant layer (thickness=28 μm), a second sealant layer (thickness=34 μm), an adhesive layer (thickness=9.5 μm), an oxygen barrier layer (thickness=11 μm), The adhesive layer (thickness=10 μm), the functional layer (thickness=20 μm), and the outer layer (thickness=28 μm) are laminated in this order in the thickness direction and have a thickness of 140 μm. is there.
Thermomechanical analysis of the multilayer film was performed in the same manner as in Example 1.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 6]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 5, except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 7]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed in the same manner as in Example 5, except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy and the acceleration voltage was changed from 150 kV to 175 kV.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 8]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 5, except that the absorbed dose of electron beam irradiation was changed from 50 kGy to 30 kGy and the acceleration voltage was changed from 150 kV to 200 kV.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Comparative Example 2]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 5 except that the electron beam irradiation was not performed.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 9]
<Manufacture of multilayer film>
The same method as in Example 1 except that the second sealant layer was changed to a pinhole-resistant layer and an ionomer (made by Mitsui DuPont Polychemical Co., Ltd., 1652) was prepared as a resin forming the pinhole-resistant layer. A multilayer film was manufactured and a thermomechanical analysis was performed.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 10]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 75 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 11]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 100 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 12]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 125 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 13]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 150 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 14]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 175 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 15]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 200 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

[Example 16]
<Manufacture of multilayer film>
A multilayer film was produced and thermomechanical analysis was performed by the same method as in Example 7, except that the absorbed dose of electron beam irradiation was changed from 30 kGy to 225 kGy.

<Manufacture of packaging>
A package was manufactured in the same manner as in Example 1 except that the multilayer film obtained above was used.

実施例１〜１６並びに比較例１〜２の包装体について、収容物への追従性を評価した結果を以下の表２に示す。 <<Evaluation of followability>>
The ability of the package to follow the contents of the package was visually evaluated. The evaluation criteria are as shown in Table 1 below. In addition, the following "float" means a gap between the package and the contained item.

Table 2 below shows the results of evaluation of the conformability to the contained items with respect to the packages of Examples 1 to 16 and Comparative Examples 1 and 2.

As is clear from the above results, in Examples 1 to 9, the temperature (° C.) showing a displacement of 2000 μm is 125° C. or higher and 130° C. or lower, so that the heat resistance is improved, and the temperature at 100° C. Since the displacement was 105 μm or more and 334 μm or less, the melt tension was improved. As a result, excellent followability with spherical smoked cheese was obtained.

Further, in Examples 10 to 16, the temperature (° C.) showing a displacement of 2000 μm is 145° C. or higher and 205° C. or lower, so that the heat resistance is further improved, and the displacement at a temperature of 100° C. is 55 μm or higher and 83 μm. Since it was below, the melt tension was further improved. As a result, excellent followability was obtained not only for spherical smoked cheese but also for fried chicken of irregular shape.

On the other hand, in Comparative Examples 1 and 2, the temperature (° C.) showing a displacement of 2000 μm is less than 120° C., so that the heat resistance is lowered, and the displacement at a temperature of 100° C. is more than 500 μm. Therefore, the melt tension was lowered. As a result, the followability was inferior to Examples 1 to 16.

INDUSTRIAL APPLICABILITY The present invention can be applied to a skin pack package used when storing food.

1... Multilayer film 2... Hard tray 2a... One surface of hard tray (first surface)
3... Package 10... Package 10a... Storage 11... Sealant layer 111... First sealant layer 112... Second sealant layer 11a... One surface of multilayer film (First side)
12... Outer layer 13... Functional layer 14... Oxygen barrier layer 15... Adhesive layer 16... Pinhole resistant layer

Claims (13)

An outer layer containing polyethylene,
A functional layer including an ionomer and adjacent to the outer layer,
An oxygen barrier layer,
A sealant layer containing an ethylene vinyl acetate copolymer,
A multilayer film, which has a temperature of 155 ° C. or more, which exhibits a displacement of 2000 μm in thermomechanical analysis. The multilayer film according to claim 1, wherein the multilayer film is irradiated with an electron beam under a condition of absorbed dose of 20 to 300 kGy. The multilayer film according to claim 1 or 2, which has a displacement of 500 µm or less at a temperature of 100°C in thermomechanical analysis. The multilayer film according to claim 3, wherein a displacement at a temperature of 100° C. is 75 μm or less in a thermomechanical analysis. The thickness is 60μm or more of the multilayer film, the multilayer film according to any one of claims 1-4. The polyethylene, the density 0.945 g / cm ³ or less of low density polyethylene, multilayer film according to any one of claims 1-5. The oxygen barrier layer is an ethylene - vinyl alcohol copolymer containing (EVOH), a multilayer film according to any one of claims 1-6. The oxygen barrier layer is a EVOH, the oxygen barrier layer the total mass of 3 mass% or more, including more than 25 wt%, the multilayer film according to any one of claims 1-7. The outer layer is one outermost layer of the multilayer film,
The sealant layer is the other outermost layer of the multilayer film,
From the sealant layer side to the outer layer side,
A first adhesive layer is disposed,
The oxygen barrier layer is disposed on the first adhesive layer,
A second adhesive layer is disposed on the oxygen barrier layer,
The multilayer film according to claim 1, wherein the functional layer is disposed on the second adhesive layer. The sealant layer includes a first sealant layer and a second sealant layer,
The constituent materials of the first sealant layer and the second sealant layer are different from each other,
The ethylene-vinyl acetate copolymer contained in the first sealant layer has a copolymerization ratio of ethylene and vinyl acetate of 90/10 to 66/34,
The multilayer film according to claim 1, wherein the ethylene-vinyl acetate copolymer contained in the second sealant layer has a copolymerization ratio of ethylene and vinyl acetate of 87/13 to 56/44. .. The sealant layer includes a first sealant layer and a pinhole resistant layer,
The first sealant layer includes an ethylene vinyl acetate copolymer having a copolymerization ratio of ethylene and vinyl acetate of 96/4 to 60/40,
The multilayer film according to any one of claims 1 to 9, wherein the pinhole-resistant layer contains an ionomer. With a multi-layer film according to any one of claims 1 to 11 package. The package according to claim 12 , wherein the package is a skin pack package.

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