JP2009096198A - Coextrusion multilayer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coextrusion multilayer film which forms a lid member for an inert gas flushed package and a vacuum package, is improved in unsealing property, sealing property and transparency, and further has capability to make the package difficult in being tampered or tricked. <P>SOLUTION: The coextrusion multilayer film is composed of at least two layers which are a sealant layer (A) which is formed of a blend of a propylene based resin having a melting point of 155°C or higher and a polyethylene based resin, and a polyethylene based resin support layer (B) adjoining the sealant layer (A). Preferably, the propylene based resin in the sealant layer (A) is a propylene resin having a melting point of 155°C or higher, especially homopolymer of propylene. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to various packaging films, and particularly to a coextruded multilayer film suitably used as a cover material or a bottom material for replacement packaging with inert gas or vacuum packaging for food packaging.

  Conventionally, in order to improve the preservability of food, a gas replacement package in which a package containing food is filled with an inert gas or a vacuum package in which the gas remaining in the package is vacuum deaerated has been used. ing. For example, a package is known in which a bottom material molded by a deep drawing machine is filled with food and filled with an inert gas or evacuated to seal the lid. As the film for the bottom material or the lid material, a composite multilayer film having both sealing properties and easy opening properties is generally used. Known techniques for simultaneously providing such sealability and easy-openability include, for example, an ethylene-propylene random copolymer obtained by copolymerizing an ethylene component with a polypropylene resin and two incompatible types such as a polyethylene resin. A so-called cohesive failure mechanism is generally known in which the above resins are blended and used in a sealant layer, and the layer is peeled off by cohesive failure when opened.

  Some composite films that are opened by such a cohesive failure mechanism have good sealing properties and easy opening properties, but two or more types of resins that are inherently incompatible are mixed. Therefore, the haze on the film surface and the internal haze due to rough skin on the surface of the sealant layer are large, and the transparency tends to be inferior. When such a composite film is used as a base material or a cover material for an inert gas replacement package or a vacuum package, the transparency of the package is not sufficient and often causes an appearance problem.

  As a composite film using a cohesive failure mechanism, there is a proposal of a composite film including a sealant layer using a polyolefin-based resin and a layer having cohesive failure properties adjacent thereto. For example, there is one that tried to improve the transparency due to surface haze by disposing a polyolefin resin layer on the cohesive failure layer, but when such a composite film is used, the polyolefin layer of the surface layer is used for opening A force for both the breaking strength of the resin layer and the breaking strength of the cohesive failure layer is required, which is not preferable from the viewpoint of easy opening (for example, Patent Document 1).

  In another proposal, in a composite film in which the total haze of the film is 6% or less, the interlayer adhesive strength between the sealant layer and the adjacent base material layer is determined from the sealing strength, that is, the adhesive strength at the heat-sealed sealant layer interface. A so-called delamination type layer structure has also been proposed.

  According to this proposal, the sealing performance is maintained during distribution, and when the contents are taken out, peeling occurs between the sealant layer and the base material layer adjacent to the sealant layer. However, the sealant layer formed by such delamination tends to have low peel strength at high temperatures, and there is a problem in that the sealant layer heated during heat sealing causes delamination with the base material layer. In addition, when a defect such as a seal failure due to poor contact with the hot plate occurs during heat sealing, there is no means to confirm this, and there is a risk that the contents will be damaged quickly if distributed with a seal failure (for example, Patent Document 2).

JP 2001-253028 A JP-A-2002-241716

  The object of the present invention is to have excellent transparency, openability and sealability, and easy opening properties suitable as a cover material and bottom material for gas replacement packaging and vacuum packaging using inert gas. It is to provide a coextruded multilayer film having. More specifically, the object of the present invention is to provide highly transparent and highly visible contents in airtight packaging bodies such as inert gas replacement packaging bodies and vacuum packaging bodies mainly used for food packaging. Providing a coextruded multilayer film with easy-openability that can easily check for opening and disguise and prevent mischief and mischief because the haze of the film in the heat-sealed portion changes greatly when opened while holding There is to do. Furthermore, the present invention provides a package having excellent sealing properties while keeping the force required when opening the hermetic package low.

The inventor has intensively studied to solve the above problems. As a result, in a coextruded multilayer film composed of at least two layers of a sealant layer and a support layer made of a polyethylene resin adjacent thereto, the propylene film having a melting point of 155 ° C. or higher with respect to the polyethylene resin as the sealant layer The knowledge that the above-mentioned problems can be solved by blending a resin has been obtained, and the present invention has been completed.
The present invention provides a sealant layer (A) obtained by mixing a propylene resin having a melting point of 155 ° C. or higher and a polyethylene resin, and a support layer (B) comprising a polyethylene resin adjacent to the sealant layer (A). A coextruded multilayer film composed of at least two layers and a package using the same are provided.

  In the multilayer film of the present invention, the propylene-based resin used for the sealant layer (A) is preferably a polypropylene resin having a melting point of 155 ° C. or higher, particularly a propylene homopolymer. The polyethylene resin preferably has a melting point lower by 25 ° C. or more. The polyethylene resin of the support layer is preferably a polyethylene resin having a melting point lower by 25 ° C. or more than the propylene resin used as in the case of the sealant layer. The blending amount of the propylene-based resin is preferably 5 to 40% by weight. The thickness of the sealant layer is preferably 1 to 15 μm, and the total thickness of the multilayer film composed of at least two layers of the sealant layer and the support layer is preferably 30 to 300 μm. In the airtight package using the multilayer film of the present invention, it is peeled off near the layer interface between the sealant layer (A) and the support layer (B) at the time of opening, or the sealant layer (A) or the support layer (B ) Occurs due to one cohesive failure. At this time, the haze of the multilayer film when the sealant layer (A) and the support layer (B) adjacent thereto are peeled increases by 10% or more as compared with before peeling according to the measurement method defined in JIS K7105. Is preferred.

Conventionally, as a propylene-based resin used for a sealant layer, unlike the present invention, a random copolymer resin copolymerized with an ethylene component, so-called ethylene-propylene random copolymer resin (hereinafter abbreviated as R-PP) is used. It has been. Although such a multi-layer film using R-PP alone has good low-temperature sealing properties and the like, good transparency cannot be obtained even when mixed with a polyethylene resin, and the adjacent layer is made of a polyethylene resin. In this case, since the ethylene resin is copolymerized, it is very difficult to peel off between the layers.
In addition, the sealant layer is often set as thin as several microns to several tens of microns, and when an incompatible resin having a large melting point difference is used as described in this specification, unmelted material is generated. This is usually a factor, and an adequate melting temperature cannot be obtained, and sufficient sealing performance cannot be obtained.
On the other hand, the coextruded multilayer film of the present invention has compatibility with the resin of the sealant layer (A) by using a propylene-based resin having a melting point of 155 ° C. or higher, which has not been blended in the past. The above-mentioned problem was solved by newly obtaining knowledge that no defect occurred. In particular, it was found that the use of a polyethylene resin having a melting point lower than that of the propylene resin by 25 ° C. or more as the main material of the sealant layer (A) provides an appropriate melting temperature and does not cause a problem in compatibility.

  As a method for using the coextruded multilayer film of the present invention, as a so-called bottom material, which is generally preheated in a replacement package or a vacuum package with an inert gas, and then appropriately shaped into an arbitrary shape. You can use it. Further, it may be used as a sealant layer for a bag-shaped package that is not subjected to a molding process such as a pillow package.

  According to the coextruded multilayer film of the present invention, peeling occurs between the sealant layer (A) and the support layer (B) due to interlayer or cohesive failure in the vicinity of the interlayer interface. Although the sealant layer (A) and the support layer (B) are both made of polyethylene resin as a main material, a predetermined amount of propylene resin, particularly a propylene homopolymer having a melting point of 155 ° C. or higher is used for the sealant layer (A). By blending, a coextruded multilayer film having a good peeling feeling without generation of fluff at the time of opening can be obtained. According to the present invention, an easy-open coextruded multilayer film for gas replacement packaging and vacuum packaging that is hygienic and highly transparent and has excellent gloss, sealing properties, heat resistance, and easy-opening properties can be obtained. . In the vicinity of the interlayer interface between the sealant layer (A) and the support layer (B), peeling occurs due to cohesive failure in the interlayer or in the layer, and the transparency of the peeled portion of the heat seal part changes before and after opening, Haze increases by 10% or more (measured by the method defined in JISK7105). Thereby, the presence or absence of opening of a package can be confirmed more clearly.

One specific example of the coextruded multilayer film form of the present invention will be described in more detail.
That is, this coextruded multilayer film is a coextruded multilayer film composed of at least two layers of a sealant layer (A) and a support layer (B) adjacent thereto.

(A) Sealant layer A mixture of polyethylene resin and propylene resin is used for the sealant layer (A). Any polyethylene resin may be used as long as it has a melting point lower by 25 ° C. or more than the propylene resin. Moreover, you may mix | blend resin other than the above with a sealant layer suitably in the range which does not impair the objective of this invention.

(Polyethylene resin)
Examples of the polyethylene resin used in the sealant layer (A) include a high-density polyethylene resin (HDPE) having a density d of 0.940 or more as a linear polyethylene resin, and a copolymer polymer with an α-olefin. A linear low density polyethylene resin (LLDPE), a very low density polyethylene resin (VLDPE) having a density d of 0.910 or less, a low density polyethylene resin (LDPE) as a branched polyethylene resin, and a copolymer with a polar monomer. For example, ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate resin (EEA), ethylene-methyl acrylate resin (EMA), ethylene-methacrylic acid resin (EMAA) Ionomer resin intermolecularly bonded with ions of metals such as zinc ( ON), ethylene-acrylic acid copolymer resin (EAA), and ethylene-propylene rubber (EPR), ethylene-propylene diene terpolymer (EPDM), chlorinated polyethylene, etc. alone or as a mixture. May be used.

(Polypropylene resin)
As the polypropylene resin blended in the sealant layer, a polypropylene resin having a melting point measured by a differential scanning calorimetry (DSC) test method defined in JIS K7121 is 155 ° C. or higher, preferably 160 ° C. or higher. Such a resin is preferably a homopolymer of propylene, so-called homopolypropylene resin. When the melting point is lower than the above range, the heat resistance may be insufficient. In addition, the adhesion to the polyethylene resin and the inhibitory effect on the fusing property are not sufficient, and an appropriate peel strength cannot be obtained between the adjacent support layers (B).
In the sealant layer, the amount of the propylene-based resin is 5 to 40% by weight, preferably 10 to 30% by weight. If the blending amount of the propylene resin is less than this, an appropriate seal strength cannot be obtained and becomes stiff, and if it exceeds this range, the seal strength becomes too light to obtain an appropriate sealing strength, and the transparency is also haze. Tends to get bigger and worse. In addition, as long as melting | fusing point is said range, 2 or more types may be used together for propylene-type resin, and also when R-PP is used, if the propylene-type resin prescribed | regulated to this invention is prescribed | regulated, the effect of this invention When using in combination, it is important to use a propylene homopolymer having a melting point of 155 ° C. or higher.
In the multilayer film of the present invention, the thickness of the sealant layer (A) is 1 to 15 μm, and preferably 2 to 10 μm. If the thickness of the sealant layer (A) is thinner than this, the required sealing performance may not be obtained. On the other hand, if it is thicker than the above range, it may cause fluff at the time of opening and impair the appearance, or the strength at the time of opening becomes too strong, and a preferable opening property cannot be obtained.

(B) Support Layer As the polyethylene resin used in the support layer (B), any of the polyethylene resins described for the sealant layer can be adopted, and copolymer resins of various polyethylene resins may be used as appropriate. Further, the polyethylene resin used for the support layer may be the same as or different from the resin used for the sealant layer. Moreover, resin used may be individual and may mix and use 2 or more types.
In addition, a 10-20 μm biaxially stretched polyethylene terephthalate film may be provided on the support layer (B) side of the coextruded multilayer film, and when used as a bottom material, a polyethylene terephthalate resin system, a polyethylene resin A film, a sheet such as a polypropylene resin system, and a polystyrene resin system may be similarly provided on the support layer (B) side by a known dry laminating method or the like. These may be stretched or unstretched.

The thickness of the multilayer film including the sealant layer (A) and the support layer (B) is 30 to 300 μm, preferably 40 to 200 μm. If the total thickness is thinner than this, the strength is not sufficient, and if it is thick, the transparency may not be excellent. Moreover, although the thickness of a support layer (B) may be suitably prepared within the range of the thickness of the whole multilayer film, Preferably it is 20-100 micrometers. If the thickness of the support layer (B) is thinner than this, it is difficult to stabilize the thickness during film formation. On the other hand, if the thickness is larger than the above range, it is not preferable because it does not meet the market demand for thin film and low cost, and excellent transparency cannot be obtained.
The multilayer film of the present invention is a film composed of at least two layers of a sealant layer (A) and a support layer (B) when the sealant layer (A) and the support layer (B) adjacent thereto are peeled off. When the haze after peeling is measured by the method defined in JIS K7105 as compared with before peeling, the haze increases by 10% or more. For this reason, the presence or absence of opening of a package can be confirmed more clearly by this.

In the multilayer film of the present invention, various resin layers laminated on the easy-open multilayer film other than the sealant layer and the support layer may be used. For example, the following resin layers may be employed depending on the purpose. .
(1) A biaxially stretched polyethylene terephthalate film having a thickness of 10 to 20 μm is disposed to impart rigidity to the printing substrate or packaging material, and bonded to the following coextruded multilayer film by a known laminating method. Hereinafter, the coextruded multilayer film is provided with a copolymer polyester resin layer for the purpose of imparting transparency and rigidity, and with an ethylene-vinyl alcohol copolymer resin layer for the purpose of imparting an oxygen gas barrier property. A polyamide resin layer is provided to give toughness and pinhole resistance to the resin, and a support layer (B) made of a low-density polyethylene resin is provided. The polyethylene resin and propylene specified in this specification are provided. Co-extrusion in which the blending ratio of the propylene resin is 5 to 40% by weight and the sealant layer (A) in which the polyethylene resin is a low density polyethylene resin is sequentially laminated in this order. It is a multilayer film.
(2) 10-20 μm biaxially stretched polyethylene terephthalate film / ethylene-vinyl alcohol copolymer resin layer / polyamide resin layer / support layer (B) / polyethylene resin comprising low-density polyethylene as in (1) above A co-extruded multilayer film or the like in which the sealant layer (A) is composed of a propylene resin, the polyethylene resin is an ethylene-methacrylic acid resin, and the blending ratio of the propylene resin is less than 40% is sequentially laminated. It is done.
(3) An unstretched polyethylene terephthalate film having a thickness of 200 to 300 μm is disposed in order to impart rigidity, shape retention and the like to the packaging material, and bonded to the following coextruded multilayer film by a known laminating method. Hereinafter, the coextruded multilayer film is provided with an ethylene-vinyl alcohol copolymer resin layer for the purpose of imparting oxygen gas barrier properties, and with a polyamide resin layer for imparting toughness and pinhole resistance to the film. And / or a support layer (B) made of a low density polyethylene resin, and a layer made of a polyethylene resin and a propylene resin as defined in this specification, wherein the blending ratio of the propylene resin is 5 A co-extruded multilayer film in which the sealant layer (A), which is ˜40% by weight and the polyethylene resin is a low density polyethylene resin, is sequentially laminated in this order.
(4) If a coextruded multilayer film is used in the present invention, an ethylene-vinyl alcohol copolymer resin layer is provided for the purpose of imparting oxygen gas barrier properties, and toughness and pinhole resistance are imparted to the film. A polyamide resin layer, a support layer (B) made of a low density polyethylene resin, and a layer made of a polyethylene resin and a propylene resin as defined in this specification, This is a co-extruded multilayer film in which the blending ratio of the propylene-based resin is 5 to 40% by weight and the sealant layer (A) in which the polyethylene-based resin is a low-density polyethylene resin is sequentially laminated in this order.
The layer configuration of the coextruded multilayer film is not limited to these as long as it satisfies the requirements described in the claims of the present invention. Specifically, the multilayer film described in the present invention is adjacent to the sealant layer (A) formed by mixing a propylene-based resin and a polyethylene-based resin having a melting point of 155 ° C. or more, and the sealant layer (A). In order to form a multilayer film in which at least two layers of the support layer (B) made of polyethylene resin are formed by a co-extrusion method and more resin layers are laminated, a layer to be newly added is It may be co-extruded and laminated simultaneously with the co-extruded multilayer film having the structure of two or more layers described in the present invention, or a single layer or a multilayer formed separately using a known laminating method. There is no problem even if it is laminated with a film.
Further, in order to increase the interlayer strength of each resin layer, a known adhesive resin layer may be disposed in addition to the interlayer between the sealant layer (A) and the support layer (B).

(Adhesive resin layer)
Examples of the adhesive resin used for the adhesive resin layer include EVA, ethylene-maleic anhydride copolymer, EAA, EEA, ethylene-methacrylate-glycidyl acrylate terpolymer, or various polyolefins, acrylic acid , Monobasic unsaturated fatty acids such as methacrylic acid, dibasic unsaturated fatty acids such as maleic acid, fumaric acid, itaconic acid or the like grafted with these, eg maleic acid grafted EVA, maleic acid grafted Well-known things, such as an ethylene-alpha-olefin copolymer, can be used suitably.

(Additive)
In addition, the sealant layer (A) of the coextruded multilayer film of the present invention and the support layer (B) adjacent thereto are appropriately prevented for the purpose of preventing slipperiness and blocking and imparting antifogging properties, if necessary. Known lubricants and additives may be added. In that case, the present invention is not limited to these, but as preferable examples, in terms of slipperiness and blocking prevention, organic lubricants such as oleic acid amide and erucic acid amide, inorganic lubricants such as silica, zeolite, and calcium carbonate Can be mentioned. The addition amount is preferably 0.1 to 5% by weight and is usually added in the form of a masterbatch. In addition, in order to impart antifogging properties, known surfactants and the like can be appropriately added and used.

(Film forming method and package manufacturing method)
The film forming method of the co-multilayer film of the present invention shall be a multi-layer or composite film by a known co-extrusion method.

The co-extruded multilayer film of the present invention is used as a packaging film for gas-displacement packaging bodies using inert gas and air-tight packaging bodies such as vacuum packaging bodies, and has a desired shape by applying a known deep drawing technique. In order to accommodate the lid material or the contents, it is molded appropriately to form a bottom material, and the contents are accommodated in this to be heat-sealed to produce a product. The temperature of the heat seal is not particularly limited, but is usually preferably 100 to 150 ° C. In deep drawing, contact heating with a hot plate is performed from one side of the film, and when the entire film is softened with a sufficient amount of heat, a molded product according to the mold is obtained by compressed air or vacuum forming. Then, after replacing with inert gas or removing air from the package by vacuum degassing, fresh food such as raw meat, processed foods such as ham, sausage, wiener and hamburger, other side dishes, marine products, etc. The contents are sealed in the bottom material and heat sealed with the lid.
As described above, the heat seal temperature in this field is usually 100 to 150 ° C. However, a propylene-based resin having a melting point of 155 ° C. or higher is used for the sealant layer of the multilayer film of the present invention, and such a component structure has not conventionally been easily conceivable from a thermal aspect.

Next, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited thereto. The raw resin used for the production of the multilayer film is as follows.
(Resin material)
(1) OPET film:
Biaxially stretched polyethylene terephthalate film; manufactured by Teijin DuPont Films Ltd.),
Tetron film GE
(2) PETG: copolymerized polyethylene terephthalate;
Eastman Chemical Japan Co., Ltd., GN071
(3) EVOH: Kuraray Co., Ltd., Eval JU102B
Density 1.17g / cm ³ , melt index 2.0g / 10min (measured at 190 ° C)
Melting point 183 ° C, ethylene content 32 mol%
(4) NY: manufactured by Ube Industries, Ltd., Ube nylon 1013B, density 1.14
(5) Support layer (B):
Low density polyethylene resin, Sumitomo Chemical Co., Ltd., Sumikasen L211
Density 0.924kg / m ³ , MFR 2.0g / 10min (measured at 190 ° C), melting point 113 ° C
(6) Sealant layer (A)
(i) Low density polyethylene resin, manufactured by Sumitomo Chemical Co., Ltd., Sumikasen L211
Density 0.924kg / m ³ , MFR 2.0g / 10min (measured at 190 ° C), melting point 113 ° C
(ii) Polyethylene resin, manufactured by Nippon Polyethylene Co., Ltd., Hi-Zex 530M
Density 0.956kg / m ³ , MFR 0.38g / 10min (measured at 190 ° C), melting point 136 ° C
(iii) Homopolypropylene resin: manufactured by Sumitomo Chemical Co., Ltd., Nobrene FS2111DG3
Density 0.910kg / m ³ , MFR 2.5g / 10min (measured at 230 ° C), melting point 158 ° C
(iv) Polypropylene resin: Noblen FH3315, manufactured by Sumitomo Chemical Co., Ltd.
Density 0.910kg / m ³ , MFR 3.0g / min (measured at 230 ° C), melting point 144 ° C
(7) APET sheet Polyethylene terephthalate unstretched single layer sheet; manufactured by Toyobo Co., Ltd.
PETMAX A750FEIR
(8) Aluminum-deposited OPET (VM-PET) film:
Biaxially stretched aluminum-deposited polyethylene terephthalate film;
Toray Film Processing Co., Ltd., 1510 (# 12)
(9) OPP film:
Biaxially stretched polypropylene film; manufactured by Toyobo Co., Ltd.
Pyrene film-OT P2002 (30μ)
(10) LLDPE film Linear low density polyethylene unstretched film; manufactured by Toyobo Co., Ltd.
LIX-NP L4103 (30μ)

Example 1
A multilayer film having a 6-layer structure was prepared using the resin composition and the layer structure shown in Table 1 below. Lamination was carried out by extrusion processing in the order of PETG / EVOH / NY / support layer (B) / sealant layer (A), and OPET was laminated on the PETG side of the multilayer film by a dry lamination method. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 102 μm.
(Example 2)
A multilayer film was produced in the same manner as in Example 1 except that the resin composition and thickness of the sealant layer were changed as shown in Table 1. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 98 μm.

(Example 3)
A multilayer film having a three-layer structure was formed using the resin composition and the layer structure shown in Table 1 below. The layers were laminated by extrusion processing in the order of NY / support layer (B) / sealant layer (A), and OPET was further laminated on the NY layer side of the multilayer film by a dry laminating method. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 52 μm.

Example 4
A multilayer film was produced in the same manner as in Example 1 except that the resin composition of the sealant layer was changed as shown in Table 1. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 102 μm.
(Example 5)
A multilayer film was produced in the same manner as in Example 1 except that the resin composition and thickness of the sealant layer were changed as shown in Table 1. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 112 μm.

Example 6
A multilayer film having a five-layer structure was prepared using the resin composition and the layer structure shown in Table 1 below. Lamination was performed by extrusion processing in the order of EVOH / NY / support layer (B) / sealant layer (A), and APET was laminated on the EVOH side of the multilayer film by a dry laminating method. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 250 μm.

(Example 7)
A multilayer film having a four-layer structure was prepared using the resin composition and the layer structure shown in Table 1 below. The layers were extruded and laminated in the order of EVOH / NY / support layer (B) / sealant layer (A). Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 150 μm.

(Comparative Example 1)
In Example 1, the polypropylene resin used for the sealant layer (A) was an ethylene-polypropylene random copolymer resin (manufactured by Sumitomo Chemical Co., Ltd., Nobrene FH3315), and the ratio was changed in the same manner as in Example 1. A multilayer film was produced. Each layer thickness (μm) of the obtained film was as shown in Table 1, and the total thickness was 102 μm. As a result, the interlayer strength between the sealant layer (A) and the support layer (B) was high, and an appropriate sealing strength could not be obtained.

(Comparative Example 2)
In Example 1, the propylene-based resin used for the sealant layer (A) was an ethylene-polypropylene random copolymer resin (manufactured by Sumitomo Chemical Co., Ltd., Nobrene FH3315), and the ratio was changed in the same manner as in Example 5. A multilayer film was produced. As a result, the interlayer strength between the sealant layer (A) and the support layer (B) was high, and an appropriate sealing strength could not be obtained. In addition, the change in haze before and after opening was small, and an effective tampering prevention effect could not be obtained.

(Evaluation methods)
About the multilayer film obtained in Examples 1-5 and the comparative example, the characteristic evaluation was performed using the vacuum made from a mulch bag, and a gas substitution packaging machine (R530 series). A container having a size of length 200 mm × width 90 mm × depth 25 mm is formed, and the layer structure is amorphous polyethylene terephthalate resin / adhesive / EVOH / adhesive / polyethylene resin (each layer thickness is 250/5/30/5 / 80 g of sliced ham was filled as a content into a rectangular tray formed and processed having a total thickness of 10 μm and a total thickness of 300 μm. The container was heat sealed (135 ° C. × 1.5 seconds, sealing pressure 0.5 MPa) using the multilayer film as a lid material to obtain a package. The state when the package was opened was evaluated according to the following criteria. The results are summarized in Table 1.
Further, the characteristics of the multilayer film obtained in Example 7 were evaluated using the same vacuum produced by Mulch Bag Co., Ltd. and a gas replacement packaging machine (R530 series). A bottom material container having a size of length 200 mm × width 90 mm × depth 25 mm was formed. Also, a multilayer film comprising a biaxially stretched polypropylene film / biaxially stretched aluminum vapor-deposited polyethylene terephthalate film / linear low density polyethylene film (each layer thickness is 30/12/30 μm, total thickness is 72 μm) is dry laminated. The lid was laminated to form a lid, and the bottom container was filled with 80 g of sliced ham as the contents and heat sealed (135 ° C. × 1.5 seconds, seal pressure 0.5 MPa) to obtain a package. The state when the package was opened was evaluated according to the following criteria. The results are also summarized in Table 1.
Further, the characteristics of the multilayer film obtained in Example 8 were evaluated using the same vacuum produced by Mulch Bag Co., Ltd. and a gas replacement packaging machine (R530 series). A cylindrical bottom material container having a diameter of 80 mm and a depth of 15 mm was formed. In addition, a multilayer film consisting of a biaxially stretched polypropylene film / biaxially stretched polyethylene terephthalate film / linear low density polyethylene film (each layer thickness is 20/12/30 μm, total thickness is 62 μm) is used in the dry laminating method. After laminating it as a cover material, this bottom material container was filled with 50 g of sliced ham as a content, degassed, and then heat sealed (135 ° C. × 1.5 seconds, seal pressure 0.5 MPa). Obtained. The state when the package was opened was evaluated according to the following criteria. The results are also summarized in Table 1.

(1) Good fuzz: No fibrous film pieces were confirmed, and good openability could be confirmed.
Occurrence: Many fibrous film pieces are generated and are conspicuous.
(2) No delamination: There is no film peeling or tearing between the layers of the multilayer film.
Partial generation: Partial film peeling occurred between the layers of the multilayer film.
(3) Hardness Appropriate: In an opening test with 10 monitors, 6 or more people judged that the hardness was moderate.
Hard: In an opening test with 10 monitors, 6 or more people were judged heavy and hard.
Light: In an opening test with 10 monitors, it was determined that 6 or more people were too light.

  The package using the co-extruded multilayer film of the present invention has good easy-openability, sealing properties, and transparency, and is an excellent inert gas replacement package or vacuum that can effectively prevent tampering and mischief by opening the package. A package is obtained.

  The inert gas replacement packaging body and the vacuum packaging body formed from the coextruded multilayer film of the present invention have high sealing properties and can be easily opened and have good transparency. Furthermore, once the package is opened, an opening mark remains clearly, which is effective in preventing tampering and mischief due to, for example, opening on a display shelf of a store.

Claims (6)

At least two layers of a sealant layer (A) obtained by mixing a propylene resin having a melting point of 155 ° C. or higher and a polyethylene resin, and a support layer (B) made of a polyethylene resin adjacent to the sealant layer (A). A co-extruded multilayer film comprising: The coextruded multilayer film according to claim 1, wherein the propylene-based resin is a homopolymer of propylene. The coextruded multilayer film according to claim 1 or 2, wherein the amount of the propylene-based resin is 5 to 40% by weight. The thickness of the sealant layer (A) is 1 to 15 µm, and the total thickness of the multilayer film composed of at least two layers of the sealant layer (A) and the support layer (B) is 30 to 300 µm. The coextruded multilayer film according to any one of the above. The haze of the multilayer film when peeling the sealant layer (A) and the supporting layer (B) adjacent thereto causes an increase of 10% or more compared to before peeling according to the measurement method defined in JIS K7105. The coextrusion multilayer film in any one of 1-4. It is a package which consists of a cover material (H) and a bottom material (S), Comprising: Either the said cover material (H) or a bottom material (S) is a coextrusion of any one of Claims 1-5 Packaging that is a multilayer film.