JP7399006B2 - Coextruded films and packaging - Google Patents

Description

The present invention relates to a coextruded film having a sealing layer containing an antifogging agent and a base layer containing a cyclic polyolefin resin, and a package using the coextruded film.

Polyolefin resin films having heat-sealability are widely used as sealant films for packaging, and are frequently used as packaging materials for bags and as lid materials for bottom materials of trays and cups.
In addition, when the contents of the package contain moisture, such as foods, during distribution, storage, and display under refrigeration, water droplets may adhere to the surface of the sealant film on the side of the contents and become cloudy, making it difficult to visually inspect the contents. This made it difficult to confirm. In order to deal with this phenomenon, a film was considered in which a solution containing an antifogging agent was applied to the surface of the sealant film and dried to form an antifogging layer, but this film did not maintain its antifogging properties for a long time. First, it impeded sealing performance.

Under such circumstances, sealant films in which antifogging agents are kneaded into resin have been considered.
For example, in Patent Document 1, the content of a cyclic polyolefin resin (b1) is 10 to 40% by mass on one side of a sealing layer (A) containing a polyolefin resin (a1) and an antifogging agent, A sealant film having a resin layer (B) containing 60 to 90% by mass of a polyolefin resin (b2) other than a cyclic polyolefin resin is disclosed.
Further, Patent Document 2 discloses that a resin layer (B) containing 50% by mass or more of a cyclic polyolefin resin (b1) is formed on one side of a sealing layer (A) containing a polyolefin resin (a1) and an antifogging agent. A sealant film having the following is disclosed.

International Publication No. 2016/148129 International Publication No. 2016/148130

Patent Document 1 and Patent Document 2 both have a technical idea of suppressing the interlayer migration of the antifogging agent in the sealing layer (A) by using the cyclic polyolefin resin (b1) of the resin layer (B) and maintaining the antifogging effect. It is based on However, the inventors investigated and found that with the technology of Patent Document 1, there was a decrease in anti-fog properties during long-term storage and a decrease in laminate adhesive strength, which is presumed to be caused by interlayer migration of the anti-fog agent. .
In addition, in the technology of Patent Document 2, the highly rigid cyclic polyolefin resin greatly affects the properties of the sealant film, and folding wrinkles occur in the inflation film forming method, making it impossible to form a stable film for a long time. Ta.

The present invention was developed in view of the above circumstances, and has a long-lasting antifogging property and sufficient lamination adhesive strength when used as a sealant film, and also stabilizes the film formed by the inflation method for a long time. An object of the present invention is to provide a coextruded film that can be produced by

As a result of intensive research by the present inventors, a coextruded film having at least a sealing layer and a base layer, the sealing layer containing an acyclic polyolefin resin and an antifogging agent,
The base layer contains an acyclic polyolefin resin from more than 50% by mass to less than 60% by mass and a cyclic polyolefin resin from more than 40% by mass to less than 50% by mass, and the thickness ratio of the base layer to the total thickness of the film is less than 30%. The inventors have discovered that the problem can be solved by a certain coextruded film, and have completed the following invention.

A first aspect of the present invention is a coextrusion film having at least a sealing layer and a base layer, wherein the sealing layer contains an acyclic polyolefin resin and an antifogging agent, and the base layer contains an acyclic polyolefin resin 50 and an antifogging agent. A coextruded film comprising more than 40% by mass to less than 50% by mass of a cyclic polyolefin resin, and a thickness ratio of the base layer to the total thickness of the film is less than 30%. be.

In the first aspect of the present invention, the sealing layer contains as a main component at least one kind selected from the group consisting of polyethylene resin and polypropylene resin as the acyclic polyolefin resin, and the coextruded film and the homopolypropylene sheet It is preferable that the peel strength when heat sealing and peeling is 5 to 20 N/15 mm width.

In the first aspect of the present invention, an intermediate layer is provided between the seal layer and the base layer, the intermediate layer contains an acyclic polyolefin resin and an antifogging agent, and the content of the antifogging agent in the intermediate layer is is preferably equal to or lower than the content of the antifogging agent in the seal layer.

In the first invention, it is preferable that the tensile modulus of the film in the machine direction is 250 to 400 MPa.

The second invention is a laminated film comprising a thermoplastic resin film on the base layer side of the coextruded film of the first invention.

The third invention is a package using the coextruded film of the first invention or the laminated film of the second invention.

The coextruded film of the present invention has long-term antifogging properties and sufficient lamination adhesive strength, so it is possible to visually check the contents for a long period of time when packaging contents that are stored under refrigeration and contain moisture, such as foods. In addition, the laminate packaging material (laminated film) produced using coextruded film does not peel between layers (no delamination occurs), making it possible to create highly practical packaging materials. It can be made. Furthermore, since film production can be carried out stably for a long period of time, it is effective in improving production efficiency.

Embodiments of the present invention will be described below. Note that the following embodiments are illustrative for explaining the present invention, and the present invention is not limited only to the embodiments.
In this application, easy openability is synonymous with easy peelability and easy peelability. Further, the sealant film is sometimes referred to as a heat seal film or a heat sealable film.
Peel strength, which is used as an index of ease of opening, is synonymous with sealing strength, and is a measure of opening and sealing properties, and is sometimes referred to as tearing strength.
Moreover, "containing as a main component" means 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more. When the numerical range is indicated as "○○~△△", it means ○○ or more and △△ or less.

<Coextrusion film>
(Seal layer)
The coextruded film of the present invention (hereinafter sometimes referred to as the present film) has at least a sealing layer and a base layer, and the sealing layer contains an acyclic polyolefin resin and an antifogging agent.

・Acyclic polyolefin resin The acyclic polyolefin resin constituting the seal layer of this film is not particularly limited, but examples include polyethylene resins (ultra-low density polyethylene, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene). , high-density polyethylene, etc.), polyethylene elastomers, copolymers of ethylene and α-olefins having 3 to 18 carbon atoms, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, ethylene- Ionomers of (meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, polybutenes, ethylene-conjugated diene copolymers such as ethylene-butadiene copolymers, ethylene-isoprene copolymers, ethylene- Examples include non-conjugated diene copolymers, polypropylene resins (polypropylene, propylene copolymers, etc.), and the like.
Among these, low-density polyethylene, linear low-density polyethylene, polypropylene, polybutene, and polyethylene-based elastomers are preferred in terms of heat-sealability and ease of developing antifogging properties. Furthermore, polypropylene polymerized with a metallocene catalyst is preferable because it has excellent low-temperature sealing properties, transparency, and the like.

Further, in order to heat seal with a polypropylene adherend and exhibit easy peelability, it is preferable that the sealing layer has a polyethylene resin or a polypropylene resin as a main component as the acyclic polyolefin resin. For example, when the total amount of resin constituting the seal layer is 100% by mass, the sum of 50 to 90% by mass of polyethylene resin and 50 to 10% by mass of polypropylene resin, or polypropylene resin and other acyclic polyolefin resin. %, or 50 to 90% by mass of polypropylene resin and 50 to 10% by mass of polyethylene resin or the sum of polyethylene resin and other acyclic polyolefin resin.
Among them, the seal layer is made of polypropylene polymerized with low-density polyethylene and a metallocene catalyst because it contains an antifogging agent, has good heat sealability with polypropylene adherends, and provides easy peelability after sealing. Blending with a system resin is preferred, and the blending mass % is preferably 50-90:50-10, more preferably 60-80:40-20, even more preferably 70-80:30-20.

In addition, from the viewpoint of producing this film by the inflation film forming method, the acyclic polyolefin resin constituting the seal layer preferably has a melt flow rate of 0.2 to 15 g/10 minutes, and 0.5 to 10 g/10 minutes. More preferred. The melting point is preferably 100 to 130°C.

- Anti-fogging agent The anti-fogging agent contained in the seal layer of the present film is not particularly limited, and examples thereof include cationic surfactants, anionic surfactants, and nonionic surfactants. Among these, nonionic surfactants are preferred because they have good mixing affinity with polyolefin resins and bleed out appropriately.

Examples of antifogging agents include glycerin fatty esters such as glycerin monopalmitate, glycerin monostearate, glycerin monooleate, and glycerin monouralate, and sorbitan fatty esters such as sorbitan uralate, sorbitan palmitate, and sorbitan stearate. , and polyglycerin fatty acid esters such as diglycerin laurate, diglycerin stearate, diglycerin caprylate, diglycerin monolaurate, diglycerin monostearate, diglycerin monooleate, diglycerin laurate, etc., and ethylene oxide addition. Examples include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene glycerin monostearate, and the like. The antifogging agent may be used alone or in combination of two or more types.

The antifogging agent may be added to the seal layer by adding it to the extruder during film formation, or it may be added to the extruder during film formation, or it may be added to the acyclic polyolefin resin or compatible with the acyclic polyolefin resin constituting the seal layer before film formation. Alternatively, a masterbatch may be prepared using a resin and the masterbatch is added to an extruder. Although the concentration of the antifogging agent in the masterbatch is not particularly limited, it is preferable that the content of the antifogging agent component after film formation is the concentration described below.

The sealing layer of the present film preferably has an antifogging agent content of 0.5 to 3.0% by mass when the total content of the sealing layer is 100% by mass. The lower limit is more preferably 1.0% by mass or more, and the upper limit is more preferably 2.5% by mass or less. When the content is 0.5% by mass or more, it is easy to obtain long-lasting antifogging properties in the structure of the present film. When the amount is 3.0% by mass or less, contamination of the film manufacturing machine due to excessive bleed-out can be prevented.

(base layer)
The base layer contains an acyclic polyolefin resin of more than 50% by mass to less than 60% by mass and a cyclic polyolefin resin of more than 40% by mass to less than 50% by mass.

- Acyclic polyolefin resin The acyclic polyolefin resin constituting the base layer of this film can be selected from one or more types of acyclic polyolefin resins that can be used for the seal layer. Among them, low-density polyethylene and linear low-density polyethylene are preferred from the viewpoint of film-forming properties and compatibility with cyclic polyolefin resins.

In addition, from the viewpoint of producing this film by an inflation film forming method, the melt flow rate of the acyclic polyolefin resin constituting the base layer is preferably 0.2 to 10 g/10 minutes, and 0.5 to 5.0 g/10 minutes. is more preferable. The melting point is preferably 100 to 140°C.

- Cyclic polyolefin resin The cyclic polyolefin resin constituting the base layer of the present film is not particularly limited, and examples thereof include norbornene polymers, vinyl alicyclic hydrocarbon polymers, and cyclic conjugated diene polymers. Among these, norbornene polymers are preferred. In addition, norbornene-based polymers include ring-opening polymers of norbornene-based monomers (hereinafter also referred to as "COP"), norbornene-based monomers (cyclic monomers) and α-olefins such as ethylene (linear Examples include norbornene copolymers (hereinafter also referred to as "COC"), which are copolymerized with monomers). Further, hydrogenated products of COP and COC, and mixtures of COP and COC can also be used. From the viewpoint of dispersibility with the acyclic polyolefin resin, COC is preferred.

COCs include linear monomers such as α-olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, and octene-1, and cyclic monomers such as tetracyclododecene and norbornene. Examples include cyclic polyolefin copolymers obtained from The linear monomer and the cyclic monomer can be used alone or in combination of two or more types. Moreover, such cyclic polyolefin copolymers can be used alone or in combination.
The COC is preferably an ethylene-cyclic polyolefin copolymer in which the linear monomer is ethylene. Furthermore, the cyclic monomer is preferably norbornene.

Further, in the present invention, the ethylene/cyclic polyolefin copolymer preferably has an ethylene/cyclic polyolefin content ratio of 15 to 40/85 to 60 by weight. More preferably it is 30-40/70-60. If the ethylene content is less than 15% by weight, the rigidity becomes too high and the inflation moldability and bag-making suitability are deteriorated, which is not preferable. On the other hand, if the ethylene content exceeds 40% by weight, sufficient tearability, rigidity, and barrier properties cannot be obtained, which is not preferable. If the content ratio is within this range, it is preferable because the rigidity, tearability, processing stability, and impact strength of the film are improved.

The glass transition temperature of cyclic polyolefin resin varies depending on the type of cyclic polyolefin skeleton and copolymerization ratio, and is generally about 50 to 180°C. From the viewpoint of suppressing the occurrence of wrinkles during aging, the glass transition temperature of the cyclic polyolefin resin is preferably 60 to 120°C, more preferably 70 to 90°C. If the glass transition point is less than 60° C., for example, there is a risk that the suppression of interlayer migration of the antifogging agent will be reduced, sufficient rigidity will not be obtained, and suitability for high-speed packaging machines will be poor. On the other hand, if the glass transition point exceeds 120° C., it is not preferable because the melt moldability of the copolymer and the adhesiveness with the olefin resin may deteriorate.
Glass transition temperature can be measured according to JIS K 7121.

The melt flow rate (MFR) of the cyclic polyolefin resin is preferably 0.5 to 12 g/10 minutes, more preferably 1.0 to 10 g/10 minutes, from the viewpoint of melt extrusion after mixing with the acyclic polyolefin resin. MFR can be measured at 260° C. and 2.16 kg according to ISO 1133.

The composition ratio (mass %) of acyclic polyolefin resin and cyclic polyolefin resin in the base layer of this film is (more than 50 to less than 60): (less than 50 to 40), with the total content of the base layer being 100 mass %. (super) is preferable, and (52 or more and 58 or less): (48 or less and 42 or more) is more preferable.
When the cyclic polyolefin resin is less than 50% by mass, flexibility can be imparted to the film, and folds and wrinkles are less likely to occur when film is formed by the inflation method, making it possible to form a film stably for a long time. It has excellent production efficiency and economic efficiency.
When the cyclic polyolefin resin is more than 40% by mass, migration of the antifogging agent in the seal layer to the base layer side can be suppressed, which is effective for long-term antifogging properties.

(middle class)
It is preferable that the film is an intermediate layer between the seal layer and the base layer, and contains an acyclic polyolefin resin and an antifogging agent.

- Acyclic polyolefin resin The acyclic polyolefin resin constituting the intermediate layer of this film can be selected from one or more types of acyclic polyolefin resins that can be used for the seal layer. Among these, low density polyethylene and linear low density polyethylene with a melt flow rate of 0.5 to 6.0 g/10 min are preferred from the viewpoint of stable film formation.

・Anti-fog agent The anti-fog agent constituting the intermediate layer of this film can be selected from the types of anti-fog agents constituting the sealing layer, and one type may be selected and used, or multiple types may be selected. It may also be used as

The content of the antifogging agent in the intermediate layer is preferably equal to or lower than the content of the antifogging agent in the sealing layer. Further, it is more preferable that the content of the antifogging agent in the intermediate layer is lower than the content of the antifogging agent in the sealing layer.
By including the antifogging agent in the intermediate layer, the concentration of the antifogging agent in the entire film can be increased, and the concentration gradient of the antifogging agent in the thickness direction of the film becomes gentle, thereby increasing the antifogging agent concentration in the sealing layer. The migration of the agent to the base layer side can be suppressed, and the antifogging effect of the seal layer can be easily exerted.
Specifically, the antifogging agent content in the intermediate layer is preferably 0.5 to 3.0% by mass, when the total content of the intermediate layer is 100% by mass. The lower limit is more preferably 0.8% by mass or more. The upper limit is more preferably 2.5% by mass or less, even more preferably 2.3% by mass or less, and particularly preferably 2.0% by mass or less. When the antifogging agent content of the intermediate layer is lower than the antifogging agent content of the seal layer, the content difference between the two is not particularly limited, but is preferably within 1.0% by mass, and 0.8% by mass. It is more preferable that it is within the range.

(Other ingredients)
Each layer of the present film can contain other resins and additives within a range that does not impair the properties of the present film.
Examples of other resins include polystyrene resins, polyvinyl chloride resins, polyester resins, polycarbonate resins, polyamide resins, polyacetal resins, polyethylene oxide resins, polyurethane resins, and silicone resins. .
Examples of additives include colorants, inorganic fillers, organic fillers, ultraviolet absorbers, light stabilizers, heat stabilizers, antioxidants, lubricants, anti-blocking agents, hydrolysis inhibitors, plasticizers, and flame retardants. etc. can be mentioned.

(Layer structure)
The present film may be a coextruded film having at least a sealing layer and a base layer, and may have an intermediate layer or other resin layer. Other resin layers include, for example, a layer made of adhesive resin to improve interlayer adhesion between the seal layer, intermediate layer, and base layer, and another resin layer outside the base layer to increase film strength. may also be provided.
For example, seal layer/base layer, seal layer/intermediate layer/base layer, seal layer/other resin layer/base layer, seal layer/other resin layer/intermediate layer/base layer, seal layer/other resin layer/intermediate layer/etc. Examples include resin layer/base layer, seal layer/base layer/other resin layer, seal layer/intermediate layer/base layer/other resin layer, and the like.

The thickness of the seal layer is preferably 5 to 50 μm, and more preferably the upper limit is 30 μm or less, from the viewpoint of sufficient seal adhesion to the adherend.
The thickness of the base layer is preferably 3 to 20 μm, and more preferably the upper limit is 10 μm or less, from the viewpoint of suppressing the antifogging agent in the seal layer. The base layer contains a cyclic polyolefin resin, and the cyclic polyolefin resin has a characteristic of high rigidity, so the ratio of the base layer thickness to the total thickness of the film is preferably less than 30%, and 25% or less. It is more preferably 20% or less. The lower limit of the thickness ratio is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. When the thickness ratio is less than 30%, the thickness of the resin film tends to be even and uniform during bubble expansion in blown film formation, so the film is less likely to be folded and creased, resulting in high production stability. When the thickness ratio is 5% or more, the antifogging agent in the seal layer does not migrate to the base layer side, and sustainable antifogging properties on the seal layer surface and good laminate adhesion on the base layer surface can be achieved.
The thickness of the intermediate layer is preferably 10 to 50 μm, and more preferably the upper limit is 30 μm or less, from the viewpoint of film formation stability.
The total thickness of the film is preferably 20 to 120 μm from the viewpoint of sealability and processing suitability, and the upper limit is more preferably 100 μm or less, and even more preferably 70 μm or less.

(Film characteristics)
- Tensile modulus The film preferably has a tensile modulus in the machine direction (MD) of 250 to 400 MPa, more preferably 300 to 400 MPa. By having such physical properties, even if the present film is produced by an inflation method, a film with few folding wrinkles can be obtained.

- Heat-sealing property, easy peelability The present film preferably has excellent heat-sealing adhesion to an adherend made of polyolefin resin, particularly polypropylene resin. For example, when a homopolypropylene sheet with a thickness of 300 μm is used as the adherend and heat-sealed facing the sealing layer surface of this film under the conditions of a sealing temperature of 160°C, a sealing pressure of 0.2 MPa, and a sealing time of 1 second, Seal peel strength is preferably 5 N/15 mm width or more and 20 N/15 mm width or less, the lower limit is more preferably 8 N/15 mm width or more, and the upper limit is more preferably 15 N/15 mm width or less. When the width is 5N/15mm or more, sufficient adhesion can be obtained, contents contained in the package are less likely to leak out, and the sealing property against foreign substances is also excellent. A width of 20N/15mm or less is preferable because it can be easily peeled off by hand.
Heat-seal peel strength is based on JIS Z0238:1998, and a tensile test is performed with the heat-sealed part in the center, a peel angle of 180 degrees, and a tensile speed of 300 mm/min, and the peel strength (unit: N/15 mm width) is measured. do.

- Anti-fogging property This film has excellent anti-fogging properties and exhibits long-term anti-fogging properties even when used for packaging items containing moisture. Moreover, even if this film is stored in roll form at room temperature, the antifogging properties are unlikely to deteriorate. Furthermore, it is preferable that the antifogging property is unlikely to deteriorate even when stored at high temperatures for a long period of time.
The antifogging property is evaluated by heat-sealing the film with the sealing layer side facing the edge of a polypropylene container filled with water, and observing the progress in a refrigerated environment.

・Transparency The transparency of this film is preferably 15% or less haze, more preferably 12% or less, and the lower limit is not particularly limited, from the viewpoints of visibility of stored items, aesthetics of the package, design, etc. The smaller the value, the better the transparency, which is preferable.
Haze is measured by a method based on JIS K7136:2000, with a cellophane tape or the like attached to the base layer side to make the surface flat.

<Coextrusion film manufacturing method>
The method for producing this film is not particularly limited, and can be produced by a known T-die method, inflation method, or the like. The main component of each layer of this film is an acyclic polyolefin resin, and by making the ratio of the thickness of the base layer containing a rigid cyclic polyolefin resin less than 30% of the total film thickness, Preferably, by controlling the tensile modulus in the machine direction (MD) of the film to 250 to 400 MPa, even if the film is formed by an air-cooled inflation method, folding wrinkles are unlikely to occur, and production can be performed efficiently and stably. . Furthermore, compared to the T-die method, the inflation method increases the crystallinity of the resin, increases the film's elastic modulus, and improves suitability for lamination.
The method for producing the coextrusion film is not particularly limited, but a known feed block method, multi-manifold method, or a combination thereof can be used.
This film may be unstretched, or may be subjected to uniaxial stretching, simultaneous biaxial stretching, or sequential biaxial stretching. Moreover, this film can also be subjected to surface treatments and surface treatments such as corona treatment, printing, coating, and vapor deposition, if necessary.

<Laminated film, packaging (applications of coextruded film)>
This film may be used as a single film, or may be used as a laminate by providing a layer of other materials such as a film made of thermoplastic resin or paper on the base layer side. A known method can be used for the lamination method, and examples thereof include a thermal lamination method, an extrusion lamination method, and a dry lamination method.
From the viewpoint of the strength of the laminated film, the film made of thermoplastic resin to be dry laminated is preferably a stretched film, and when dry laminating, the MD direction of the film and the MD direction of the film made of thermoplastic resin are aligned. From the viewpoint of production efficiency, it is preferable to laminate the material. For example, there may be mentioned a laminated film in which the base layer side of this film and a film made of a thermoplastic resin such as biaxially oriented polyethylene terephthalate are dry laminated using a two-component curing adhesive.

There are no particular restrictions on the use or shape of this film or packaging bodies using the above-mentioned laminated film, but since this film has good heat-sealing properties, it can be used as a base material for bags, cups, trays, etc. It can be used as a lid material to form a package. In addition, since it has long-term antifogging properties, it is useful for packaging objects containing moisture.

The present invention will be explained in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited by the Examples and the like.
Films were produced using the following raw materials and methods, and were tested and evaluated, and the results are summarized in Table 1.
The melt flow rate (MFR) of the resin used was measured in accordance with JIS K7210:2014 at a test temperature of 190° C. and a test load of 2.16 kg. The density was measured in accordance with JIS K7112:1999. The melting point and glass transition temperature were measured in accordance with JIS K7121:2012.

(Acyclic polyolefin resin)
PO1: Polypropylene produced with metallocene catalyst (MFR9.5g/10min)
PO2: Low density polyethylene (MFR2.0g/10min, melting point 112°C)
PO3: Low density polyethylene (MFR2.8g/10min, melting point 113°C)
PO4: Linear low-density polyethylene produced with metallocene catalyst (MFR 1.9 g/10 min, melting point 122°C)
PO5; low density polyethylene (MFR2.2g/10min, melting point 111°C)
PO6: Linear low-density polyethylene produced with metallocene catalyst (MFR 0.8 g/10 min, melting point 124°C)

(Cyclic polyolefin resin)
COC1: norbornene copolymer copolymerized with ethylene (MFR5.5g/10min, glass transition temperature 78°C)

(Anti-fog agent masterbatch)
AF1; Elecut Master LE870 manufactured by Takemoto Yushi Co., Ltd. (linear low-density polyethylene resin masterbatch with antifogging agent content of 15% by mass)

<Examples 1 to 5, Comparative Examples 1 to 4>
Using the above raw materials, the formulations shown in Table 1 were supplied to each extruder for each layer, and a film was formed by an air-cooled inflation coextrusion method at an extrusion temperature of 180°C.
In Examples 1 to 5 and Comparative Examples 1 to 3, coextruded films having a layer structure of 15 μm thick seal layer/10 μm thick intermediate layer/5 μm thick base layer were obtained.
In Comparative Example 4, a coextruded film having a layer structure of seal layer 15 μm thick/base layer 10 μm thick/other resin layer 5 μm thick was obtained.
Next, the surface of the base layer of the coextruded film was subjected to corona discharge treatment, and a 12 μm thick biaxially stretched polyethylene terephthalate film was dry laminated using a two-component curing type ether-based polyurethane adhesive, and aged at 37°C for 48 hours. A "laminated film A" was obtained. Note that dry lamination was performed by aligning the machine direction (MD) of the coextruded film with the machine direction (MD) of the biaxially stretched polyethylene terephthalate film.
In addition, as an aging acceleration test, the coextruded films obtained in Examples and Comparative Examples were stored in roll form at a temperature of 45°C for 3 months, and then dry laminated and aged using the same materials and methods as above. "Laminated film B" was obtained.
The following evaluations were performed and the results are summarized in Table 1.

<Evaluation method>
(1) Film Formability For the coextruded films of Examples and Comparative Examples that were formed by air-cooled inflation coextrusion method, the number of folds and creases per 4000 m in length was measured and evaluated based on the following criteria.
○: Less than once ×: More than once

(2) Tensile modulus The tensile modulus in the machine direction (MD) was measured using a tensile tester manufactured by Orientec Co., Ltd. according to the method described in JIS K7161:2014 for the coextruded films obtained in Examples and Comparative Examples. (Young's modulus) was measured and evaluated based on the following criteria.
〇：250～400MPa
×: over 400MPa

(3) Transparency The haze of the coextruded films obtained in Examples and Comparative Examples was measured using a measurement method based on JIS K7136:2000, with the surface flattened by attaching cellophane tape or the like to the base layer side. It was measured and evaluated based on the following criteria.
○: Less than 15% ×: 15% or more

(4) Anti-fogging property 10 mL of water was placed in a cylindrical polypropylene container with a diameter of 7.1 mm and a height of 5.3 mm, and laminated film A and laminated film B obtained in Examples and Comparative Examples were used as lid materials. The sealing layer side was heat-sealed toward the mouth of the container, and the container was stored in a refrigerator at a set temperature of 5° C. or lower for 3 days, and the degree of cloudiness of the laminated film was observed.
Laminated film A was evaluated as "short-term antifogging property", and laminated film B, which was subjected to an aging acceleration test, was evaluated as "long-term antifogging property".
◎: A water film is formed on the film surface, and visibility is good. ○: There are large water droplets on the film surface, but visibility is good. △: There are small water droplets on a part of the film surface, but visibility is good. ×: Film The entire surface is covered with water droplets and visibility is poor.

(5) Heat-sealability, easy peelability The sealing layer surface of the laminated film A obtained in Examples and Comparative Examples was stacked facing the 300 μm thick homopolypropylene sheet of the adherend, and one end of the layer was placed in a heat-sealing machine. Heat-sealing was carried out under the conditions of a seal width of 5 mm, a seal temperature of 160° C., a seal pressure of 0.2 MPa, and a seal time of 1 second.
Thereafter, the laminated film was cut into strips with a length of 50 mm in the machine direction (MD) and a width of 15 mm in the horizontal direction (TD), and the laminated film was assembled with the heat-sealed part in the center in accordance with JIS Z0238:1998. Each end of the adherend was attached to the grip of a tensile tester, and peeled in the longitudinal direction of the strip, that is, in the machine direction (MD) of the coextruded film, at a peeling angle of 180 degrees and a peeling speed of 300 mm/min. Or, it was pulled until it broke, and the measured maximum stress was measured as peel strength (unit: N/15 mm width), and the heat sealability and easy peelability were evaluated based on the following criteria.
○: 5-20N/15mm
×: Less than 5N/15mm

(6) Lamination adhesion Regarding the laminated films A obtained in Examples and Comparative Examples, the peeling accuracy was 180 degrees and the peeling speed was 300 mm/min between the coextruded film and the biaxially oriented polyethylene terephthalate film that constituted the laminated film. The condition of the peel test under the following conditions was evaluated based on the following criteria.
○: Strongly adhered and the film breaks ×: Easily peeled off

In Examples 1 to 5, the effect of the antifogging agent blended in the sealing layer is sustained and the long-term antifogging properties are good (△ to ◎), and the laminate adhesion is also good, and the base layer containing an appropriate amount of cyclic polyolefin resin This is thought to be due to the effect of suppressing the migration of the antifogging agent to the surface of the base layer. Furthermore, film formation by the inflation method was also performed stably.
Among them, Examples 1 and 2, in which the antifogging agent content in the seal layer was higher than the antifogging agent content in the intermediate layer, had better long-term antifogging properties (◎).
Further, in Examples 1 to 4, where the ratio of the polyethylene resin and polypropylene resin constituting the seal layer is in the range of 70 to 80:30 to 20, the total of the polyethylene resin and polypropylene resin constituting the seal layer is in the range of 70 to 80:30 to 20. It was possible to achieve a good combination of heat sealability and easy peelability after sealing.

Comparative Examples 1 and 2 had insufficient antifogging properties and lamination adhesion, and because the base layer did not contain a cyclic polyolefin resin or had a low content of cyclic polyolefin resin, the antifogging agent was a coextruded film. It is thought that it migrated outside (to the surface of the base layer).
In Comparative Example 3, the content of the cyclic polyolefin resin in the base layer was high, the tensile modulus of the film increased, and wrinkles appeared during the blown film formation.
In Comparative Example 4, since the thickness of the base layer containing the cyclic polyolefin resin was 30% or more of the total film thickness, uneven thickness of bubbles occurred during blown film production, making stable film production difficult. This resulted in folding wrinkles.

The film of the present invention has long-lasting antifogging properties and sufficient lamination adhesive strength, so it is highly usable as a sealant film for packaging bodies containing moisture-containing contents such as foods. The visibility of the contents is good due to the cloudiness, so it is effective for storage management of the contents. Furthermore, since film formation using the inflation method can be carried out stably for a long period of time, it is also beneficial in terms of production efficiency and economic efficiency.

Claims (5)

A coextruded film having at least a sealing layer and a base layer,
When the total amount of resin constituting the seal layer is 100% by mass, the sealing layer contains 50 to 90% by mass of polyethylene resin, the sum of polypropylene resin polymerized with a metallocene catalyst and other acyclic polyolefin resins of 10% by mass. Contains ~50% by mass and an antifogging agent,
The base layer contains an acyclic polyolefin resin of more than 50% by mass to less than 60% by mass and a cyclic polyolefin resin of more than 40% by mass to less than 50% by mass,
The thickness ratio of the base layer to the total film thickness is less than 30%,
an intermediate layer is provided between the seal layer and the base layer, the intermediate layer contains an acyclic polyolefin resin and an antifogging agent, and the content of the antifogging agent in the intermediate layer is the same as that of the antifogging agent in the sealing layer. A coextruded film with a content equal to or lower than that of the agent . The sealing layer contains as a main component at least one type selected from the group consisting of polyethylene resins and polypropylene resins as an acyclic polyolefin resin, and the coextruded film and the homopolypropylene sheet are heat-sealed and peeled off. The coextruded film according to claim 1, which has a peel strength of 5 to 20 N/15 mm width. The coextruded film according to claim 1 or 2 , wherein the tensile modulus in the machine direction of the film is 250 to 400 MPa. A laminated film comprising a thermoplastic resin film on the base layer side of the coextruded film according to any one of claims 1 to 3 . A package using the coextruded film according to any one of claims 1 to 3 or the laminated film according to claim 4 .