JP6728683B2 - Multilayer film - Google Patents

Description

The present invention relates to multilayer films.

Conventionally, in order to improve the storability of food, a gas replacement package filled with an inert gas in a package containing food or a vacuum package obtained by vacuum degassing the gas remaining in the package is used. ing. For example, there is known a package in which a bottom material formed by a deep drawing machine is filled with food and filled with an inert gas or vacuumed to seal a lid material. As the film for the bottom material or the lid material, it is common to use a composite multilayer film having both sealing properties and easy opening properties.

Here, Patent Document 1 and Patent Document 2 disclose known techniques for simultaneously providing such a sealing property and an easy-open property. Specifically, in Patent Document 1 and Patent Document 2, an ethylene vinyl acetate copolymer saponified resin layer, a polyamide resin layer, an adhesive resin layer and a polypropylene resin layer (base material layer) are sequentially laminated, and the polypropylene On the resin layer (base material layer) side, a sealant layer was prepared by blending two or more incompatible resins such as an ethylene-propylene random copolymer obtained by copolymerizing a polypropylene resin with an ethylene component and a polyethylene resin. , An easy-open composite film (multilayer film) is disclosed.

According to the easily openable composite film disclosed in Patent Document 1 and Patent Document 2, when used as a film for a lid material, for example, the sealant layer undergoes cohesive failure at the time of opening, and thus can be easily peeled off. It is said that. As described above, the sealant layer is a layer that ensures the easy-open property, and thus is also called an easy peel layer.

Japanese Patent No. 3642925 JP 2005-288793 A

However, when the above-mentioned conventionally known easily-openable composite film is used as a bottom material or a lid material for an inert gas displacement package or a vacuum package, the seal strength is locally increased and a stable easy is obtained. There was a problem that the peel could not be realized.

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 that is excellent in sealing property and easy-opening property and suppresses the occurrence of delamination, and is also excellent in visibility. ..

In order to solve the above problems, the inventors of the present invention have diligently studied and found that the cause of locally increasing the seal strength is that the starting point of peeling is not inside the easy peel layer but at the intersection of the base material layer and the easy peel layer. I found out that. Further, in order to realize stable easy-opening property, it is essential that the starting point of peeling is inside the easy peel layer and that the base material layer has heat resistance so as not to flow during sealing. I found out. Therefore, in place of the polypropylene resin as the base material layer, a polyethylene resin having high heat resistance and a nucleating agent for improving transparency, which deteriorates when a polyethylene resin having high heat resistance is used, are blended to solve the above problems. The present invention has been completed based on the finding that it can be solved.

That is, the present invention has the following configurations.
The invention according to claim 1 includes a sealant layer, and a base material layer provided adjacent to the sealant layer and containing a polyethylene resin having a melting point of 120 to 140°C and a nucleating agent, wherein the sealant layer is propylene. includes a system resin and polyethylene resin comprises the propylene-based resin, melting point Ri homopolypropylene resin der is 155 ° C. or higher, the base layer, the melting point of 120 to 140 ° C. polyethylene resin least 50 wt% the sealant layer, the amount of the propylene resin is Ru 5-40% by mass, the multilayer film.

The invention according to claim 2 is the multilayer film according to claim 1, wherein the density of the polyethylene resin having the melting point of 120 to 140°C is in the range of 0.925 to 0.970 (g/cm ³ ). is there.

The invention according to claim 3 is the multilayer film according to claim 1 or 2 , wherein the base material layer has a thickness of 5 to 75 µm.

The invention according to claim 4, the ratio of the thickness of said sealant layer of the base layer, 80: 20 to 20: 80 in the range of, in any one of claims 1 to 3 It is the described multilayer film.

The invention according to claim 5 is the multilayer film according to any one of claims 1 to 4 , wherein the haze value of the entire multilayer film is 10% or less.

In the multilayer film of the present invention, the base material layer adjacent to the sealant layer is composed of a polyethylene resin having a melting point of 120 to 140° C. and a nucleating agent and is excellent in transparency, and thus excellent in sealing property and easy opening property, Excellent visibility while suppressing the occurrence of delamination.

It is a cross-sectional schematic diagram which shows an example of a structure of the multilayer film which is one embodiment to which this invention is applied.

Hereinafter, the structure of the multilayer film, which is an embodiment to which the present invention is applied, will be described in detail. Note that, in the drawings used in the following description, in order to make the features easy to understand, there may be a case where the featured portions are enlarged for convenience, and the dimensional ratios of the respective constituent elements are not necessarily the same as the actual ones. Absent.

First, an example of the configuration of a multilayer film that is an embodiment to which the present invention is applied will be described.
FIG. 1 is a schematic sectional view of a multilayer film 1 which is an embodiment to which the present invention is applied. As shown in FIG. 1, the multilayer film 1 of the present embodiment is roughly configured to include a sealant layer 2 and a base material layer 3 provided adjacent to the sealant layer 2. More specifically, the multilayer film 1 includes a coextruded multilayer film 7 in which a sealant layer 2, a base material layer 3, an adhesive layer 4, a tear resistant layer 5 and a gas barrier layer 6 are laminated in this order by a coextrusion method, and a support. The layer 9 and the layer 9 are laminated by the adhesive layer 8. This multi-layer film 1 should be applied to applications of airtight packages (hereinafter sometimes simply referred to as “packages” etc.) such as inert gas replacement packages and vacuum packages mainly used for food packaging. You can

The sealant layer 2 is provided on one of the outermost layers of the multilayer film 1. The sealant layer 2 enables the sealant layers 2 to be bonded to each other or to other members. The bonding method is not particularly limited, but specific examples include heat sealing, ultrasonic sealing, high frequency sealing, impulse sealing and the like. In this way, the multi-layer film 1 including the sealant layer 2 is adhered to each other to form a package.

The material of the sealant layer 2 is not particularly limited, but as long as it has an adhesive function and does not adversely affect the contents (non-adsorption, etc.) of the package when used as a package, it has been conventionally used as a sealing material. A general resin material used can be appropriately selected and used. Specific examples of such a material include polyethylene resin and polypropylene resin. The sealant layer 2 preferably contains a polypropylene resin, and more preferably a mixture of a polyethylene resin and a propylene resin.

As the polypropylene resin blended in the sealant layer 2, a polypropylene resin having a melting point of 155° C. or higher, preferably 160° C. or higher measured by a differential scanning calorimetry (DSC) test method defined in JIS K7121 is preferable. As such a resin, a homopolymer of propylene, a so-called homopolypropylene resin is preferable. When the melting point is within the above range, heat resistance will not be insufficient. Further, the effect of inhibiting the adhesion to the polyethylene resin and the fusion property becomes sufficient, and an appropriate peel strength between the adjacent base material layer 3 can be obtained.

The polyethylene resin blended in the sealant layer 2 preferably has a melting point lower than that of the propylene resin by 25° C. or more. Specifically, for example, as a linear polyethylene resin, a high density polyethylene resin (HDPE) having a density d of 0.940 or more, a medium density polyethylene resin (MDPE) of 0.925 or more, and a copolymerization with α-olefin. A linear low-density polyethylene resin (LLDPE) which is a polymer, an ultra-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 polar monomer Copolymers, for example, ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate resin (EEA), ethylene-methyl acrylate resin (EMA), ethylene-methacrylic acid resin (EMAA) or intermolecular between these. An ionomer resin (ION) having an intermolecular bond with a metal ion such as sodium or zinc, an ethylene-acrylic acid copolymer resin (EAA), and an ethylene-propylene rubber (EPR) as an elastomer, an ethylene-propylenediene ternary resin. Examples thereof include a copolymer (EPDM) and chlorinated polyethylene. These may be used alone or in combination.

The compounding amount of the propylene-based resin in the sealant layer 2 is preferably in the range of 5 to 40% by mass, more preferably 10 to 30% by mass. When the blending amount of the propylene-based resin is within the above range, proper sealing strength and sealing strength are obtained, and transparency is secured. Two or more propylene-based resins may be used in combination as long as the melting point is within the above range. In addition, the sealant layer 2 may be appropriately blended with a resin other than the above resins within a range that does not impair the object of the present invention.

The sealant layer 2 may contain other components such as an antifogging agent (for example, PE antifogging masterbatch) in addition to the polypropylene resin and the polyethylene resin described above.

The thickness of the sealant layer 2 is not particularly limited, but is preferably in the range of 1 to 15 μm, more preferably 2 to 10 μm. When the thickness of the sealant layer 2 is within the above range, preferable sealability and openability are obtained.

The base material layer 3 is a resin layer provided adjacent to the sealant layer 2. More specifically, the base material layer 3 is laminated so as to be between the sealant layer 2 and the adhesive layer 4. The base material layer 3 imparts excellent flexibility to the multilayer film 1.

The base material layer 3 is a resin layer containing a polyethylene resin having a melting point of 120 to 140° C. measured by a differential scanning calorimetry (DSC) test method defined in JIS K7121 and a nucleating agent. Here, when the melting point of the resin forming the base material layer 3 is lower than 120° C., when the multilayer film 1 is used for a package or the like, the resin forming the base material layer 3 flows out when sealing. Therefore, delamination may occur, which is not preferable.

The polyethylene resin having a melting point of 120 to 140° C. that constitutes the base material layer 3 is not particularly limited, but the density is in the range of 0.925 to 0.970 (generally, medium density to high). A polyethylene resin having a density) is preferable, and a polyethylene resin having a range of 0.941 to 0.970 (generally, a high density) is more preferable.

Further, as the polyethylene resin constituting the base material layer 3, if the melting point of the base material layer itself (whole) measured by the above-mentioned DSC is in the range of 120 to 140° C., the polyethylene resin having the density within the above range is used. It may be composed of one polyethylene resin, or may contain a plurality of polyethylene resins having different densities.

Further, the base material layer 3 preferably contains 50% by mass or more of a polyethylene resin having a density within the above-mentioned range, the melting point of which is in the range of 120 to 140°C.

As the nucleating agent blended in the base material layer 3, a polyethylene-based crystallization nucleating agent having a density range of 0.925 to 0.970 (g/cm ³ ) is preferable. Further, the content of the nucleating agent in the base material layer 3 is preferably in the range of 1.5 to 3.5 parts by mass with respect to 100 parts by mass of the polyethylene resin.

The base material layer 3 may contain other components such as an antifogging agent (for example, PE-based antifogging masterbatch) in addition to the above-mentioned polyethylene resin and nucleating agent.

By the way, in the conventional easy-opening composite film (multilayer film), the polypropylene resin having a high melting point is used as the base material layer, so that the resin forming the base material layer does not flow out at the time of sealing, and the delamination occurs. There was an advantage that it can suppress.

However, when a general polypropylene-based resin is used for the base material layer, the seal strength locally increases, it is difficult to peel off, and stable easy peeling does not occur.

On the other hand, when a polyethylene-based resin is used as the base material layer, the haze value can be easily improved by including the nucleating agent, so that the visibility of the content can be secured. However, when a polyethylene resin having a melting point of less than 120° C., such as a low density polyethylene resin (LDPE), is used as the base material layer, the resin forming the base material layer flows out when sealing, and thus the delamination There is a problem that it is difficult to suppress the occurrence of

On the other hand, according to the multilayer film 1 of the present embodiment, the base material layer 3 is a resin layer containing a polyethylene resin having a melting point of 120 to 140° C. (density range: 0.925 to 0.970 g/cm ³ ). Since it is configured, the resin forming the base material layer does not flow out at the time of sealing, and the occurrence of delamination can be suppressed. Furthermore, the haze value of the polyethylene resin is improved by the base material layer 3 containing the nucleating agent. Therefore, the visibility of the contents can be ensured.

The thickness of the base material layer 3 is not particularly limited, but specifically, for example, a range of 5 to 50 μm is preferable, and a range of 5 to 45 μm is more preferable. When the thickness of the base material layer 3 is within the above range, excellent transparency can be imparted to the multilayer film 1, which is preferable.

Regarding the transparency of the base material layer 3, the haze value at a thickness of 0.15 mm is preferably 40% or less, and more preferably 35% or less. Here, when the haze value at a thickness of 0.15 mm is 40% or less, for example, when the haze value is 5 μm or more and 50 μm or less as a base material layer of a package for food, the transparency is sufficient to allow the contents to be visually recognized. It is preferable because the property is obtained. The haze of the polyethylene resin layer can be measured, for example, by a method based on JIS K7136.

In the multilayer film 1 of this embodiment, the ratio of the thickness of the sealant layer 2 to the thickness of the base material layer 3 is preferably in the range of 80:20 to 20:80. When the ratio of the thickness of the sealant layer 2 to the thickness of the base material layer 3 is within the above range, flow disturbance of the sealant layer and the base material layer does not occur, and a stable appearance is obtained, which is preferable.

The adhesive layer 4 is provided between the base material layer 3 and the tear resistant layer 5 in order to bond the base material layer 3 and the tear resistant layer 5 together. Thereby, the adhesive force between the base material layer 3 and the tear resistant layer 5 is increased, and in the multilayer film 1, peeling at the interface between them can be prevented.

The material of the adhesive layer 4 is not particularly limited, and specifically, for example, an adhesive polypropylene resin, an adhesive polyethylene resin, or the like can be used. An anchor coating agent or the like may be used depending on the purpose.

The tear resistance layer 5 is an arbitrary resin layer provided for imparting the tear resistance of the multilayer film 1. In this embodiment, the tear resistant layer 5 is provided between the adhesive layer 4 and the gas barrier layer 6, and is laminated and provided so as to be adjacent to the adhesive layer 4 and the gas barrier layer 6.

The resin component of the tear resistant layer 5 is not particularly limited, but specific examples thereof include nylon resins.

As for the tear resistance of the tear resistant layer 5, the tear strength is preferably 150 (N/mm) or more, and more preferably 200 (N/mm) or more. As a result, it is possible to prevent holes called pinholes and damage due to cracks.

The thickness of the tear resistant layer 5 is not particularly limited, but specifically, for example, 5 μm or more is preferable, and 10 μm or more is more preferable. It is preferable that the thickness of the tear resistant layer 5 is within the above range, because sufficient tear resistance can be exhibited.

The tear resistant layer 5 can be manufactured by melt-kneading a nylon resin and laminating the molten resin by several different extruders to produce a film containing the nylon resin.

The gas barrier layer 6 is a resin layer provided mainly for suppressing the permeation of oxygen. Further, the gas barrier layer 6 is provided so as to be laminated on the support layer 9 side in the coextruded multilayer film 7 that constitutes the multilayer film 1 of the present embodiment. By providing the gas barrier layer 6 on the support layer 9 side, when a packaging body or the like is formed using the multilayer film 1, oxygen is prevented from entering the packaging body or the like from the support layer 9 side. be able to.

The material of the gas barrier layer 6 (that is, the barrier material) is not particularly limited as long as it does not impair the transparency of the multilayer film 1. Specifically, for example, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer (EVOH), polyester such as polyethylene terephthalate (PET), and aromatic polyamide such as polymetaxylylene adipamide (МXD6) It is preferable to use an oxygen barrier resin. Among these, it is more preferable to use the ethylene-vinyl alcohol copolymer (EVOH).

The thickness of the gas barrier layer 6 is not particularly limited, but specifically, for example, preferably 5 μm or more, more preferably 7 μm or more. When the thickness of the gas barrier layer 6 is within the above range, the gas barrier property is exerted depending on the contents, the contents are protected from external oxygen, and the internal flavor is prevented from leaking to the outside. It is preferable because it can.

In the multilayer film 1 of the present embodiment, the sealant layer 2, the base material layer 3, the adhesive layer 4, the tear resistant layer 5, and the gas barrier layer 6 described above are laminated in this order to form the coextruded multilayer film 7. The coextrusion multilayer film 7 can be formed by the coextrusion method. In the coextruded multilayer film 7, one of the surface layers is the sealant layer 2 and the other of the surface layers is the gas barrier layer 6.

The thickness of the coextruded multilayer film 7 is not particularly limited, but specifically, for example, 30 μm or more and 100 μm or less is preferable, and 40 μm or more and 90 μm or less is more preferable. It is preferable for the thickness of the coextruded multilayer film 7 to be in the above range because it has excellent transparency.

The adhesive layer 8 is provided between the coextruded multilayer film 7 and the support layer 9 in order to bond the coextruded multilayer film 7 and the support layer 9. By providing this adhesive layer 8, the adhesive force between the layers of the coextruded multilayer film 7 and the support layer 9 is increased, and peeling at the interface between them can be prevented. The material of the adhesive layer 8 is not particularly limited, but specifically, for example, the same material as the adhesive layer 4 can be used. Further, the adhesive layer 8 may use a material different from that of the adhesive layer 4.

The support layer 9 is a transparent resin layer provided for imparting shape retention (rigidity), heat resistance and transparency to the multilayer film 1 of this embodiment. The support layer 9 is laminated on the coextruded multilayer film 7 via the adhesive layer 8 and is provided so as to be the other surface of the multilayer film 1 (that is, the surface opposite to the sealant layer 2). There is.

The material of the support layer 9 is not particularly limited, but preferable materials include, for example, polyolefins such as low-density polyethylene, high-density polyethylene and polypropylene; polyamides of nylon (registered trademark); polyesters such as polyethylene terephthalate (PET); vinyl-based materials. Resins: Resins such as cellulose (cellophane and paper are also included in the cellulose) and the like.
Among these, the material of the support layer 9 is more preferably uniaxially or biaxially stretched polyolefin, nylon (registered trademark), or polyester.

The thickness of the support layer 9 is not particularly limited, but for example, preferably 5 to 300 μm, more preferably 10 to 250 μm. When the thickness of the support layer 9 is within the above range, the appearance when used in a gas pack is good, which is preferable.

The total thickness of the multilayer film 1 of the present embodiment is not particularly limited, but is, for example, preferably 35 to 400 μm, and more preferably 50 to 340 μm. It is preferable that the total thickness of the multilayer film 1 is within the above range, since it looks good when used in a gas pack.

Further, the haze value of the entire multilayer film 1 of the present embodiment is preferably 10% or less, and more preferably 9% or less. Here, when the haze value is 10% or less, for example, when the total thickness of the multilayer film 1 as a package for food or the like is set to 35 μm or more and 400 μm or less, sufficient transparency that allows the contents to be visually recognized. Is preferred. The haze value of the multilayer film 1 can be measured, for example, by a method based on JIS K7136.

Next, an example of a method for manufacturing the above-described multilayer film 1 of the present embodiment will be described.
The method for producing the multilayer film 1 is not particularly limited, but for example, a feed block method of melt-extruding a resin as a raw material by a plurality of extruders, a co-extrusion T-die method such as a multi-manifold method, an air-cooled method. Alternatively, a water-cooled coextrusion inflation method and a method of laminating a film extruded in a single layer may be mentioned. Among them, a method of forming a film by a coextrusion T-die method is particularly preferable in terms of excellent control of the thickness of each layer.

Specifically, for example, first, the raw material resins up to the sealant layer 2, the base material layer 3, the adhesive layer 4, the tear resistant layer 5 and the gas barrier layer 6 are coextruded to form a coextruded multilayer film 7. Next, the coextruded multilayer film 7 formed via the adhesive layer 8 and the support layer 9 are laminated to manufacture the multilayer film 1 of the present embodiment.

The method for producing a package using the multilayer film 1 of the present embodiment is not particularly limited, but, for example, first, using a commonly used deep-drawing machine, vacuum forming, The accommodating portion is formed in the molding package (laminated film) by pressure molding, plug molding, or the like.

Next, after the contents (for example, food) are filled in the storage part of the above-mentioned molding package, the multilayer film 1 of the present embodiment is overlapped as a cover film to form the molding package and the cover film (multilayer film 1). ) And are adhered together, it is possible to manufacture a package.

As described above, according to the multilayer film 1 of the present embodiment, the base material layer 3 adjacent to the sealant layer 2 is configured to include a polyethylene resin having a melting point of 120 to 140° C. and a nucleating agent and is also transparent. Since it is excellent, it is excellent in sealing property and easy opening property, and is excellent in visibility while suppressing the occurrence of delamination.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. The use of the multilayer film 1 of this embodiment is not particularly limited. Specifically, it may be, for example, a foodstuff such as meat, processed meat and fruits and vegetables, or a packaging bag for accommodating medical instruments such as an injection needle, a syringe, a test kit and a catheter.

The effects of the present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited thereto.

<Resin material>
In order to verify the effect of the multilayer film of the present invention, a multilayer film having the structure shown in FIG. 1 was produced. Here, the raw material resins of the respective layers used in the production of the multilayer film are as follows.

"Sealant layer"
(A) Low-density polyethylene resin Ube Polyethylene F324C manufactured by Ube Maruzen Polyethylene Co., Ltd.
・Density: 0.924 g/cm ³
・Melting point: 112°C
(B) Homo polypropylene resin Prime Polymer Co., Ltd., Prime Polypro Y400GP
・Density: 0.905 g/cm ³
・Melting point: 158°C
(C) Polyethylene anti-fog MB
Takemoto Yushi Co., Ltd., Elecut Master L117A
・Density of base PE: 0.923 g/cm ³
-Base PE melting point: 111°C

"Base material layer"
(A) High-density polyethylene resin Hi-Zex 3300F, made by Prime Polymer Co., Ltd.
・Density: 0.950 g/cm ³
・Melting point: 132°C
(B) High-density polyethylene-based nucleating agent MB
Riken Vitamin Co., Ltd., Rikemaster CN002
(C) Polyethylene anti-fog MB
Takemoto Yushi Co., Ltd., Elecut Master L117A
(D) Low-density polyethylene resin Sumitomo Chemical Co., Ltd., Sumikasen L211
・Density: 0.924 g/cm ³
・Melting point: 113°C
(E) Polypropylene resin Sumitomo Chemical Co., Ltd., Noblen FH3315
・Density: 0.910 g/cm ³
・Melting point: 144°C

"Adhesive layer"
Polyethylene adhesive resin: Mitsui Chemicals, Inc., Admer NF536
・Density: 0.905 g/cm ³
・Melting point 120℃
"Tear resistant layer"
NY: Ube Nylon 1030B2 manufactured by Ube Industries, Ltd.
・Density: 1.14 g/cm ³
・Melting point: 225°C
"Gas barrier layer"
EVOH: Eval E173B manufactured by Kuraray Co., Ltd.
・Density: 1.17 g/cm ³
・Melting point: 165°C
・Ethylene content: 44 mol%
"adhesive"
Takelac A manufactured by Mitsui Chemicals, Inc.

"Support layer"
(A) OPET film Biaxially stretched polyethylene terephthalate film: Tetron film GE, manufactured by Teijin DuPont Films Ltd.
(B) APET sheet Polyethylene terephthalate unstretched single layer sheet: manufactured by Toyobo Co., Ltd., PETMAX A750FEIR

<Production of multilayer film>
A multilayer film having the structure shown in FIG. 1 was produced. Specifically, the raw material resins up to the sealant layer, the base material layer, the adhesive layer, the tear resistant layer and the gas barrier layer are co-extruded to form a co-extruded multilayer film, and then a support layer is provided via an adhesive (adhesive layer). Were laminated to produce multilayer films of Examples 1 to 4 and Comparative Examples 1 to 3. Table 1 below shows specific configurations (type of resin, layer thickness, compounding ratio, etc.) of each layer (particularly, the base material layer and the sealant layer).

The melting point of the base material layer was evaluated by DSC (differential scanning calorimetry). Furthermore, the transparency of the base material layer was evaluated by a method based on JIS K7136. The respective results are shown in Table 1 below.

(Example 1)
First, the resins were mixed at the compounding ratio shown in Table 1 to prepare a raw material resin for the sealant layer. Further, the high-density polyethylene resin (A), the nucleating agent (B), and the antifogging agent (C) were mixed at a compounding ratio shown in Table 1 to prepare a raw material resin for the base material layer.
Next, the raw material resins up to the sealant layer, the base material layer, the adhesive layer, the tear resistant layer and the gas barrier layer were coextruded to form a coextruded multilayer film. Then, a biaxially stretched polyethylene terephthalate film (A) was laminated as a supporting layer using an adhesive to produce a multilayer film having the layer constitution shown in Table 1 (multilayer film of Example 1).

The melting point (that is, the melting point of the raw material resin, hereinafter the same) in a single layer of the base material layer (high-density polyethylene resin (A)+nucleating agent (B)+antifog agent (C)) constituting Example 1 is , 126°C. The haze value at a thickness of the base material layer of 0.15 mm was 25%. Furthermore, the total thickness of the multilayer film of Example 1 was 72 μm, and the haze value of the entire multilayer film was 4%.

(Example 2)
Example 2 Example 2 was repeated in the same manner as in Example 1 except that the constitution of the base material layer was changed to only the high-density polyethylene resin (A) and the nucleating agent (B) (without the antifogging agent (C)). Was produced.

The melting point of the single layer of the base material layer (high-density polyethylene resin (A)+nucleating agent (B)) constituting Example 2 was 132°C. The haze value at a thickness of the base material layer of 0.15 mm was 30%. Furthermore, the total thickness of the multilayer film of Example 2 was 72 μm, and the haze value of the entire multilayer film was 5%.

(Example 3)
A multilayer film of Example 3 was produced in the same manner as in Example 1 except that the constitution of the support layer was changed to the polyethylene terephthalate unstretched single layer sheet (B).
The thickness of the entire multilayer film of Example 3 was 260 μm, and the haze value of the entire multilayer film was 6%.

(Example 4)
The coextruded multilayer film formed in Example 1 was used as the multilayer film of Example 4. The thickness of the entire multilayer film of Example 4 was 60 μm, and the haze value of the entire multilayer film was 3%.

(Comparative Example 1)
A comparative example was carried out in the same manner as in Example 1 except that the high density polyethylene resin (A) was replaced with a polypropylene resin (E) and the nucleating agent (B) was not included in the constitution of the base material layer. A multilayer film of 1 was produced.

The melting point of the single layer of the base material layer (polypropylene resin (E)+antifog agent (C)) constituting Comparative Example 1 was 138°C. The haze value at a thickness of the base material layer of 0.15 mm was 15%. Furthermore, the thickness of the entire multilayer film of Comparative Example 1 was 72 μm, and the haze value of the entire multilayer film was 6%.

(Comparative example 2)
In the constitution of the base material layer, a comparison was made in the same manner as in Example 1 except that the high density polyethylene resin (A) was replaced with the low density polyethylene resin (D) and the nucleating agent (B) was not included. The multilayer film of Example 2 was produced.

The melting point of the single layer of the base material layer (low density polyethylene resin (D) + antifogging agent (C)) constituting Comparative Example 2 was 112°C. The haze value at a thickness of the base material layer of 0.15 mm was 8%. Furthermore, the thickness of the entire multilayer film of Comparative Example 2 was 72 μm, and the haze value of the entire multilayer film was 3%.

(Comparative example 3)
Comparative Example 3 was carried out in the same manner as in Example 1 except that the structure of the base material layer was changed to only the high-density polyethylene resin (A) and the antifogging agent (C) (without the nucleating agent (B)). Was produced.

The melting point of the single layer of the base material layer (high-density polyethylene resin (A)+antifog agent (C)) constituting Comparative Example 3 was 126°C. The haze value at the thickness of the base material layer of 0.15 mm was 45%. Furthermore, the thickness of the entire multilayer film of Comparative Example 3 was 72 μm, and the haze value of the entire multilayer film was 11%.

<Evaluation of multilayer film>
With respect to the produced multilayer films of Examples 1 to 4 and Comparative Examples 1 to 3, delamination resistance, seal strength and visibility were evaluated.

(Evaluation of delamination resistance)
The characteristics of the multilayer films produced in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated using a vacuum manufactured by Multivac Co., Ltd. and a gas displacement packaging machine (R535 series).
Specifically, first, a container having a size of 200 mm in length×90 mm in width×25 mm in depth is formed, and the layer structure is amorphous polyethylene terephthalate resin/adhesive resin/EVOH/NY/adhesive resin/polyethylene resin ( 80 g of sliced ham was filled as a content in a formed rectangular tray having a layer thickness of 140/10/8/8/12/12 μm and a total thickness of 190 μm). This container was heat-sealed (145° C.×1.5 s, sealing pressure 6 kgf/cm ² ) using the multilayer films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 as a lid material to form an evaluation container.

Next, the presence or absence of delamination (delamination resistance) was evaluated based on the following criteria for the state of the obtained evaluation container when it was opened. The results are also shown in Table 1 below.
・No delamination: No peeling or tearing of the film between the layers of the multilayer film ・Partial occurrence: Partial peeling of the film between the layers of the multilayer film

(Evaluation of seal strength)
Similarly, an evaluation container was formed using the multilayer films produced in Examples 1 to 4 and Comparative Examples 1 to 3.
Next, the peeling feeling (firmness) when peeling off the lid material of the evaluation containers of Examples 1 to 4 and Comparative Examples 1 to 3 was monitored according to the following criteria. The results are also shown in Table 1 below.
・Appropriate: 6 people or more are judged to be moderately hard in the opening test by 10 monitors. ・Hard: 6 people or more are heavy or hard in the opening test by 10 monitors.

(Evaluation of visibility)
Similarly, an evaluation container was formed using the multilayer films produced in Examples 1 to 4 and Comparative Examples 1 to 3.
Next, in order to confirm the visibility of the contents in the obtained evaluation container, monitoring was performed according to the following criteria, and a practical evaluation of transparency (visibility) was performed. The results are shown in Table 1 below.
・Good: Visual confirmation from the lid material side by 10 monitors determines that 6 or more people have good visibility. ・Poor: Visual confirmation from the lid material side by 10 people, 6 people or more determine that the visibility is poor.

As shown in Table 1, the multilayer sheet of Comparative Example 1 uses a polypropylene-based resin as a resin forming the base material layer, and therefore is excellent both in the base material layer alone and in the whole multilayer sheet without using a nucleating agent. Although it has transparency (visibility), delamination resistance and seal strength are uneven, so that stable easy peel cannot be realized when used as a lid material.

In addition, since the multilayer sheet of Comparative Example 2 uses a low-density polyethylene resin as a resin that constitutes the base material layer, excellent transparency (both as a base material layer alone and as a whole multi-layered sheet) without using a nucleating agent ( Although it has visibility, the delamination resistance was not sufficient when used as a lid material.

In addition, since the multilayer sheet of Comparative Example 3 uses a high-density polyethylene resin that does not contain a nucleating agent as the resin that constitutes the base material layer, the transparency (visibility) of the base material layer alone and the multilayered sheet as a whole is high. Was not enough.

On the other hand, the multilayer sheets of Examples 1 to 4 have a structure in which the base material layer contains a polyethylene resin having a temperature of 120 to 140° C. and a nucleating agent. It was confirmed that it is excellent in visibility and excellent in visibility while suppressing the occurrence of delamination.

INDUSTRIAL APPLICABILITY The multilayer film of the present invention is applicable to packaging bags, packaging containers, etc. for packaging foods, pharmaceuticals, medical instruments, and the like.

DESCRIPTION OF SYMBOLS 1... Multilayer film, 2... Sealant layer, 3... Substrate layer, 4... Adhesive layer, 5... Tear resistant layer, 6... Gas barrier layer, 7... Coextrusion multilayer film, 8... Adhesive layer, 9... Support layer

Claims (5)

A sealant layer; and a base material layer provided adjacent to the sealant layer and containing a polyethylene resin having a melting point of 120 to 140° C. and a nucleating agent,
The sealant layer contains a propylene resin and a polyethylene resin ,
The propylene-based resin, Ri homopolypropylene resin der is a melting point of 155 ° C. or higher,
The base layer contains 50% by mass or more of the polyethylene resin having the melting point of 120 to 140° C.,
The sealant layer, the amount of the propylene resin is Ru 5-40% by mass, the multilayer film. The multilayer film according to claim 1, wherein the polyethylene resin having a melting point of 120 to 140° C. has a density in the range of 0.925 to 0.970 (g/cm ³ ). The multilayer film according to claim 1, wherein the base material layer has a thickness of 5 to 75 μm. The multilayer film according to any one of claims 1 to 3, wherein the ratio of the thickness of the base material layer to the thickness of the sealant layer is in the range of 80:20 to 20:80. The multilayer film according to any one of claims 1 to 4, wherein a haze value of the entire multilayer film is 10% or less.

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