JP2022053375A - Film, co-extruded film, package, and bag - Google Patents

Abstract

To provide a film capable of forming a package that has such characteristics that steam naturally escapes from the package when heated in a microwave oven (natural unsealing/opening property at high temperature), and that good sealing property and easy peeling property are combined at room temperature, by selecting the films with some specific characteristics and without making the package into a special shape or applying a special processing to it.SOLUTION: In the film that includes at least a sealing layer, composition of the sealing layer consists of, in a case where the entire sealing layer is 100 mass%, (a) 30 to 90 mass% of polyethylene resins having a density of 900 to 950 kg/m3 of that are selected from low density polyethylene, linear low density polyethylene, ultra-low density polyethylene, ethylene-(meth)acrylic acid ester copolymer, and ethylene-vinyl acetate copolymer, (b) 5 to 40 mass% of polybutene resins, and (c) 5 to 30 mass% of ethylene-α-olefin copolymer having a density of less than 900 kg/m3.SELECTED DRAWING: None

Description

The present invention relates to films, coextruded films, packages, and bags.

With the progress of simplification of cooking, shortening of time, and individualization, the number of cooking by heating in a microwave oven while containing raw materials and cooked foods in a package is increasing. If the contents such as food are heated in a microwave oven while being contained in the package, the package swells and bursts due to the steam of the moisture of the contents.

The following are examples of conventional methods for preventing the package from bursting when the contents such as food are housed in the package and heated in a microwave oven.
(1) Give caution instructions to the user to make a notch in the package or make a small hole in advance before putting it in the microwave.
(2) As described in Patent Documents 1 to 3, the package is provided with a vent hole and a seal portion through which steam can escape.
(3) As described in Patent Document 4, polyethylene, polystyrene, polypropylene, etc. are used for the sealing layer as a packaging film that can be heated in a microwave oven while being sealed without performing processing such as drilling. Using the blended inflation film, the difference in peel strength in the flow direction and the vertical direction of the film is utilized.

International Publication No. 06/1007048 Japanese Unexamined Patent Publication No. 10-211972 Japanese Unexamined Patent Publication No. 2010-11440 Japanese Patent Application Laid-Open No. 2002-321326 Japanese Unexamined Patent Publication No. 2002-146343

The above method (1) has a problem that it takes time and effort to make a notch and the like, and there is a risk that the package may burst and be burned if it is placed in a microwave oven without these treatments.
The method (2) above requires a manufacturing cost, such as requiring a dedicated manufacturing part or a manufacturing process for manufacturing the package.
The method (3) above is expected to have the effect of giving selectivity in the opening direction, but does not have the effect of promoting natural opening at high temperatures.
Further, in Patent Document 5, which is a general sealant film having an easy peeling property, polyethylene and polybutene are mixed to form a sealant layer as a film having both heat sealing property and an easy peeling property. Natural opening does not occur under microwave heating.

In view of the above circumstances, the present invention does not provide a special shape or processing to the package, and due to the characteristics of the film, steam naturally escapes from the package when heated in a microwave oven (natural opening / opening at high temperature). Properties) It is an object of the present invention to provide a film capable of forming a package having both sealing properties and easy peeling properties at room temperature.
In addition, "easy peeling property" is synonymous with easy opening property and easy peeling property, and means that the package can be opened neatly by hand without using tools such as scissors.
In addition, "natural opening / opening" means that the package opens naturally (inflated by internal pressure) even if it is not opened by a person.

As a result of diligent studies, the present inventors have found that the above problems can be solved by forming the seal layer of the film constituting the package with predetermined three components, and have completed the following invention.

In the first invention, at least in a film having a seal layer, when the composition of the seal layer is 100% by mass of the entire seal layer, (a) low density polyethylene, linear low density polyethylene, ultra-low. 30-90% by mass of polyethylene resin selected from density polyethylene, ethylene- (meth) acrylic acid ester copolymer, and ethylene-vinyl acetate copolymer and having a density of 900 to 950 kg / m ³ (b). It is a film containing 5 to 40% by mass of a polyethylene-based resin and (c) 5 to 30% by mass of an ethylene-α-olefin copolymer having a density of less than 900 kg / m ³ .

In the first film of the present invention, the peel strength under 25 ° C. conditions is 5.0 to 25.0 N / 15 mm width, and the peel strength under 80 ° C. conditions is 0.4 to 2.0 N / 15 mm width. Is preferable.

In the first film of the present invention, it is preferable that the (c) ethylene-α-olefin copolymer is an ethylene-butene copolymer.

In the first film of the present invention, the melt flow rate (MFR) of the polyethylene resin (a) is 0.5 to 20 g / 10 minutes, and the melt flow rate (MFR) of the polybutene resin (b) is 0.5 to 20 g / 10 minutes. It is preferably 0.5 to 10 g / 10 minutes, and the melt flow rate (MFR) of the (c) ethylene-α-olefin copolymer is preferably 0.1 to 25 g / 10 minutes.

The second invention is a coextruded film having a polyolefin resin layer adjacent to the seal layer of the film of the first invention.

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

A fourth aspect of the present invention is a bag body in which the seal layers of the film of the first invention or the coextruded film of the second invention are heat-sealed so as to face each other.

By using the film of the present invention, no special shape or processing is provided on the package, and due to the characteristics of the film, steam naturally escapes from the package when heated in a microwave oven (natural opening / opening at high temperature). Properties), it is possible to form a package having both sealing properties and easy peeling properties at room temperature.

Hereinafter, the film of the present invention as an example of the embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below.

<Film>
The film of the present invention is a film having at least a seal layer, and the seal layer is (a) polyethylene-based resin 30 to 90% by mass, (b) polybutene-based resin 5 when the entire seal layer is 100% by mass. It contains from 40% by mass and (c) 5 to 30% by mass of the ethylene-α-olefin copolymer.

((A) Polyethylene resin)
The (a) polyethylene-based resin constituting the seal layer of this film includes low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), and ethylene- (meth) acrylic acid ester. One or more selected from polymers (EMA, EMMA, etc.) and ethylene-vinyl acetate copolymers (EVA) can be used, among which low density polyethylene (LDPE) and linear low density polyethylene (Linear low density polyethylene) can be used. LLDPE) is preferable because it has less fisheye during molding.

・ MFR
(A) The melt flow rate (MFR) of the polyethylene resin is preferably 0.5 to 20 g / 10 minutes, more preferably 2.0 to 15 g / 10 minutes, and particularly preferably 4.0 to 10 g / 10 minutes. Within this range, the molding processability is good, and it is easy to manufacture films, sheets and the like.

-Melting point (a) The melting point of the polyethylene resin is preferably 90 to 140 ° C, more preferably 100 to 130 ° C. If the melting point exceeds 140 ° C., satisfactory film-forming properties and secondary molding cannot be obtained. On the other hand, from the viewpoint of heat resistance, the melting point is preferably 90 ° C. or higher.

-Density (a) The density of the polyethylene-based resin is 900 to 950 kg / m ³ , preferably 900 to 940 kg / m ³ . When the density exceeds 950 kg / m ³ , the dispersed structure with other components is not satisfactorily formed, and sufficient easy peeling property is not exhibited. On the other hand, from the viewpoint of versatility, the density is preferably 900 kg / m ³ or more. By setting the temperature to 900 kg / m ³ or more, heat sealing at a low temperature can be performed.

In the film of the present invention, the methods for measuring various properties are as follows.
The MFR is measured based on the JIS K7210-1: 2014 method under the conditions of a test temperature of 190 ° C. and a load of 2.16 kg.
The melting point is measured based on the JIS K7121: 2012 method.
Density is measured according to JIS K7112: 1999 method.

((B) Polybutene resin)
The (b) polybutene-based resin is selected from a homopolymer of 1-butene and a copolymer of 1-butene and another α-olefin. The α-olefin is preferably an α-olefin having 2, 3 or 5 to 10 carbon atoms, and is, for example, ethylene, propylene, 1-pentene, 1-hexene, 1-heptene, 1-octene. Examples thereof include 1-decene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene and 4,4-dimethyl-1-hexene propylene. , Preferably ethylene, propylene, 1-hexene, 4-methyl-1-pentene, 1-octene, and more preferably ethylene and propylene.

(B) Specifically, the polybutene-based resin is preferably a 1-butene homopolymer, an ethylene / 1-butene copolymer, a propylene / 1-butene copolymer or an ethylene / propylene / 1-butene copolymer. .. As the above-mentioned copolymer, a random copolymer is preferable. (B) If necessary, the polybutene-based resin may be copolymerized with other comonomer in a small amount as long as the effect of the present invention is not impaired.

(B) The 1-butene content of the polybutene-based resin is usually 90 to 100 mol%, preferably 95 to 100 mol%, more preferably 98 to 100 mol%, and the α-olefin content is 0 to 10 mol%. , Preferably 0-5 mol%, more preferably 0-2 mol%.

-Density (b) The density of the polybutene-based resin is preferably 900 to 930 kg / m ³ , and more preferably 910 to 920 kg / m ³ . If the density of the polybutene resin is too low, film blocking is likely to occur. If the density is too high, the film will curl and the handleability will deteriorate.

-Melting point (b) The melting point of the polybutene-based resin is preferably 50 to 135 ° C, more preferably 70 to 125 ° C. If the melting point is less than 50 ° C., the appearance of the peeled surface at the time of opening is inferior. If the melting point exceeds 135 ° C., the opening strength may become excessively high. Further, if (b) the melting point of the polybutene-based resin is too low, film blocking may easily occur. On the other hand, if (b) the melting point of the polybutene resin is too high, the heat seal start temperature becomes high.

・ MFR
(B) The MFR (190 ° C.) of the polybutene resin is preferably 0.5 to 10 g / 10 minutes, more preferably 1.0 to 5.0 g / 10 minutes, in consideration of film forming property. preferable. When this MFR is less than 0.5 g / 10 minutes, the peel strength of the package becomes excessively high. On the other hand, when the MFR exceeds 10 g / 10 minutes, the appearance of the peeled surface at the time of opening is inferior. Further, (b) when the MFR of the polybutene-based resin is too low, the viscosity at the time of melting is high, so that the resin pressure in the extruder increases in the production of the film and the productivity is significantly deteriorated, while (b) If the MFR of the polybutene resin is too high, film blocking is likely to occur.

((C) Ethylene-α-olefin copolymer)
(C) The ethylene-α-olefin copolymer is preferably a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, and 1-decene. , 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eikosen and the like. Among these, propylene, 1-butene, 1-hexene and 1-octene are preferable, and 1-butene is particularly preferable.
(C) The ethylene-α-olefin copolymer is preferably a random copolymer, and the proportion of the constituent units derived from ethylene in the copolymer is preferably 50% by mass or more.

(C) The ethylene-α-olefin copolymer is produced by copolymerizing each monomer in the presence of a catalyst. Specifically, (c) the ethylene-α-olefin copolymer uses a catalyst such as a Cheegler catalyst, a phillips catalyst, or a metallocene catalyst as an olefin polymerization catalyst, and uses a vapor phase method, a solution method, and a high pressure method. It can be produced by copolymerizing ethylene with α-olefins such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene by a process such as a slurry method.

・ MFR
(C) The MFR (190 ° C.) of the ethylene-α-olefin copolymer is preferably 0.1 to 25 g / 10 minutes, and the lower limit is more preferably 1.0 g / 10 minutes or more. The upper limit is more preferably 10 g / 10 minutes or less, further preferably less than 4.0 g / 10 minutes, and particularly preferably less than 2.0 g / 10 minutes. When this MFR is less than 0.1 g / 10 minutes, it affects the dispersion of (a) polyethylene resin and (b) polybutene resin, for example, dispersed particles in the film flow direction (MD) and width direction (TD). The shape is remarkably different, and the difference in peel strength (heat seal strength) in both directions tends to be large. On the other hand, when the MFR exceeds 25 g / 10 minutes, the fluidity of the melted portion increases too much at the time of heat sealing, and there is a concern that the natural opening / opening property at high temperature is deteriorated.

-Density and melting point The low-density (c) ethylene-α-olefin copolymer has a low melting point, and the addition of the component (c) lowers the heat resistance of the seal layer and lowers the layer cohesive force at high temperatures. Then a natural opening occurs.
The density is less than 900 kg / m ³ and preferably less than 890 kg / m ³ . The melting point is preferably 50 to 80 ° C, more preferably 60 to 70 ° C. If the melting point is too low, it will be difficult to handle during extrusion molding, and if it is too high, there is a concern that the natural opening and opening properties at high temperatures will deteriorate.

(Contents of each component in the seal layer)
The composition ratio of (a) polyethylene-based resin, (b) polybutene-based resin, and (c) ethylene-α-olefin copolymer is (30 to 90) :( 5) when the entire seal layer is 100% by mass. ~ 40): The range of (5 to 30) is preferable, and the range of (35 to 80) :( 10 to 40) :: (10 to 25) is more preferable. (B) If the ratio of the polybutene resin is out of the range, there is a concern that the heat seal strength may be extremely strong or, conversely, too weak. Further, (c) if the ratio of the ethylene-α-olefin copolymer is out of the range, there is a concern that the natural opening / opening effect may be insufficient or the heat sealability may be impaired.

<Coextruded film>
The film of the present invention described above can be a coextruded film having a polyolefin-based resin layer adjacent to the seal layer. Hereinafter, the polyolefin-based resin layer is referred to as an "adjacent layer".

(Adjacent layer)
The polyolefin-based resin used for the adjacent layer is not particularly limited, but when (a) polyethylene-based resin or (b) polybutene-based resin constituting the above-mentioned seal layer is used, the interlayer adhesion between the seal layer and the adjacent layer is enhanced. Can be preferred. Among them, low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) composed of a copolymer of ethylene and α-olefin are preferable from the viewpoint of film-forming property of coextruded film. For example, when a coextruded film is formed by an inflation method, the bubbles are stable and it is easy to perform arbitrary blow-up.

Further, a modified adhesive resin can be used as the polyolefin-based resin of the adjacent layer. For example, a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof is preferably used. As the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like can be used. Further, as the derivative of the unsaturated carboxylic acid, the above-mentioned ester of the unsaturated carboxylic acid, an anhydride or the like can be used, and for example, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate and the like can be used. , Butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate and the like. In addition, vinyl acetate and the like can also be used. When the adjacent layer is made of an adhesive resin, the adhesion between the layers of the film can be improved when another layer is provided on the side opposite to the seal layer side of the adjacent layer.

(Other layers)
The coextruded film of the present invention may have at least a seal layer and the above-mentioned adjacent layer adjacent to the seal layer, but further has another layer on the side opposite to the seal layer side of the adjacent layer. You may be doing it.
Examples of the resin constituting the other layer include a polyolefin resin such as polyethylene and polypropylene, a gas barrier resin represented by an ethylene-vinyl acetate copolymer satanized product and an aromatic polyamide, a polyamide 6, a polyamide 66, and a polyamide 6. , 66 Polyamide resins such as copolymers, polyethylene terephthalates, polyethylene naphthalates, polyester resins such as polybutylene terephthalates, adhesive resins and the like can be used according to the film requirements. Further, a plurality of other layers may be provided.

(Other ingredients)
Each layer of the film and the coextruded film of the present invention can appropriately contain additives as long as the characteristics are not impaired. For example, colorants, inorganic fillers, organic fillers, UV absorbers, light stabilizers, heat stabilizers, antioxidants, lubricants, blocking agents, hydrolysis inhibitors, plasticizers, flame retardants, antistatic agents, Antifogging agents and the like can be mentioned. The amount of these additives added is not particularly limited, and can be appropriately determined within a range that does not impair the desired physical properties of the present invention.

<Manufacturing method of film and coextruded film>
The method for producing the film and the coextruded film of the present invention is not particularly limited, and can be produced by a known T-die method, inflation method, or the like. Further, in the method for producing a coextruded film of the present invention, a known feed block method, multi-manifold method, or a combination thereof can be used. Further, the other layers can also be formed by a thermal laminating method or an extrusion laminating method.
The film or coextruded film of the present invention may be unstretched, uniaxially stretched, simultaneous biaxially stretched, or sequentially biaxially stretched.
Further, the film or coextruded film of the present invention can be subjected to surface treatment such as corona treatment, printing, coating, vapor deposition and the like, if necessary.

The thickness of the film (single-layer film) of the present invention is preferably 5 to 30 μm.
In the case of the coextruded film of the present invention, the thickness of the seal layer is 1 to 10 μm in terms of both heat-sealing property, good cohesive peeling property (easy peeling property) without stringing and film pulling, and transparency. Is preferable, 2 to 8 μm is more preferable, and 3 to 5 μm is even more preferable. The total thickness of the coextruded film including the adjacent layer and other layers is preferably 2 to 50 μm, more preferably 3 μm or more, still more preferably 5 μm or more, from the viewpoint of film strength, handleability, and secondary processability. .. The upper limit is more preferably 40 μm or less, further preferably 30 μm or less.
The thickness of the film, the total thickness of the coextruded film, and the thickness of each layer can be measured from a stylus type thickness gauge and a cross-sectional observation of the film.

<Characteristics of film and coextruded film>
The film or coextruded film of the present invention (hereinafter, these may be collectively referred to as "the present film") preferably has the following characteristics.

(Heat seal sealability, easy opening property)
This film was heat-sealed at room temperature, preferably at a set temperature of 120 to 200 ° C., more preferably at a set temperature of 140 to 180 ° C., with the seal layers of the film facing each other (hereinafter referred to as "face-to-face seal"). In some cases, it is preferable to have sufficient heat-seal sealing property and coagulation-breaking type easy-opening property.
As an evaluation method, for example, the sealing surfaces of this film are face-to-face with each other, and heat-sealed under the conditions of a sealing temperature of 140 to 180 ° C., a sealing width of 5 mm, a sealing pressure of 0.2 MPa, and a sealing time of 1 second to prepare a sample for evaluation. To make.
To measure the heat-seal adhesion and easy-opening property, cut the heat-sealed sample into strips with a width of 15 mm to prepare test pieces, and based on JIS Z0238: 1998, heat-seal the heat-seal part at room temperature (25 ° C). A tensile test is performed under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm / min at the center, and the peeling strength (unit: N / 15 mm width, also referred to as “heat seal strength”) is measured.

The lower limit of the peel strength is preferably 5.0 N / 15 mm width or more, more preferably 7.0 N / 15 mm width or more, and further preferably 10.0 N / 15 mm width or more. The upper limit is preferably 25.0 N / 15 mm width or less, more preferably 20.0 N / 15 mm width or less, and even more preferably 18.0 N / 15 mm width or less. As long as it has a peeling strength in the above range, it adheres with sufficient strength and can be easily peeled and opened by hand. In addition, this film can be peeled and opened by coagulating and breaking the inside of the seal layer, and it can be easily peeled without stringing or film pulling. It is more preferable to obtain a beautiful peeled appearance without causing.

(Natural opening / opening under high temperature)
When a package made using this film is heat-treated with a microwave oven or the like while the contents containing water are still packaged, the internal pressure of the package increases due to steam, and the heat seal of this film is achieved. It is preferable that the seal layer is coagulated and broken in the portion and the package is opened naturally to release the steam.
As the index, the peel strength measured in a temperature atmosphere of 80 ° C. is used. The measurement conditions of the evaluation sample, the test piece, etc. other than the atmospheric temperature are the same as the above-mentioned conditions for heat seal sealing property and easy opening property.
The upper limit of the peel strength measured in the surface seal of this film under a temperature atmosphere of 80 ° C. is preferably 2.0 N / 15 mm width or less, and more preferably 1.8 N / 15 mm width or less. If the width exceeds 2.0 N / 15 mm, there is a risk of a plosive sound at the time of opening, and in some cases, the contents may pop out. The lower limit is not particularly limited, but is preferably 0.4 N / 15 mm width or more, and more preferably 0.5 N / 15 mm width or more.

(transparency)
The transparency of this film is preferably 25% or less, more preferably 20% or less, still more preferably 15% or less, from the viewpoint of visibility, aesthetics, design and the like of the contents. The lower limit is not particularly limited, and a smaller value is preferable because transparency is good.
Haze is measured according to JIS K7136: 2000.

<Packaging body, bag body>
Since the film and the coextruded film of the present invention have good heat-sealing properties and easy peeling properties (easy peeling properties), they can be heat-sealed in a shape suitable for the contents to form a package. In particular, since this film is suitable for cooking and heating in a microwave oven and naturally opening, it is suitable for packaging such as bags and pouches that are center-sealed in the shape of a gassho.
It can also be used in a package in which a lid material made of the film and coextruded film of the present invention and a bottom material made of polypropylene-based resin are heat-sealed. When a coextruded film is used, the seal layer side is set to the adherend (for example, bottom material) side, and the package is heat-sealed with the bottom material to produce a package.
Further, the film and coextruded film of the present invention can be laminated with other plastic films and sheets, metal foils, papers, etc. by a known method such as dry laminating, and can be used as a packaging material. Packaging and bag bodies can be manufactured.

<Use of packaging and bag>
In the package and bag of the present invention, when the contents containing water are packaged, the internal pressure of the package or bag is increased by steam when heat treatment is performed by a microwave oven or the like, and the film of the present invention is used. In the heat-sealed portion, coagulation breakage in the seal layer occurs and the package is naturally opened / opened, and steam is released. That is, the package and bag of the present invention are suitable for applications in which food or the like is housed in the package and heat-treated by a microwave oven or the like.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited by the following examples and the like.

<Examples 1 to 5, Comparative Example 1>
A low-density polyethylene with a density of 925 kg / m ³ is used for the adjacent layer, and the resin composition shown in Table 1 is used for the seal layer. 30 μm) was produced using an air-cooled inflation coextrusion film film forming machine at an extrusion temperature of 175 ° C. The peel strength and haze of the seals were measured according to the following evaluation methods and summarized in Table 1.

<Components and physical characteristics of the seal layer>
The abbreviations of the seal layer components are as follows.
(A) -1; Low density polyethylene MFR 9.0 g / 10 minutes (190 ° C) Density 904 kg / m ³
(A) -2; Low-density polyethylene MFR 4.0 g / 10 minutes (190 ° C) Density 918 kg / m ³
(B) -1; Homopolybutene MFR 2.0 g / 10 minutes (190 ° C) Density 915 kg / m ³
(C) -1; Ethylene-butene copolymer MFR 3.6 g / 10 minutes (190 ° C) Density 885 kg / m ³
(C) -2; Ethylene-butene copolymer MFR 1.2 g / 10 minutes (190 ° C) Density 885 kg / m ³

<Evaluation method>
(Peeling strength of various seals)
The seal layer surfaces of the prepared coextruded film were put together facing each other, and heat-sealed under the conditions of a sealing temperature of 140 to 180 ° C., a sealing width of 5 mm, a sealing pressure of 0.2 MPa, and a sealing time of 1 second to prepare a sample for evaluation. Heat sealing was performed at three types of sealing temperatures of 140 ° C., 160 ° C., and 180 ° C., and the following peel strength was measured for each.
・ Peeling strength of surface seals at 25 ° C (N / 15 mm width)
The sample heat-sealed above was cut into strips with a width of 15 mm to prepare test pieces. Based on JIS Z0238: 1998, the heat-sealed part was centered at room temperature (25 ° C), the peeling angle was 180 degrees, and the tensile speed. A tensile test was performed under the condition of 300 mm / min, and the peel strength (unit: N / 15 mm width, also referred to as "heat seal strength") was measured.
・ Peeling strength of face-to-face seals at 80 ° C (N / 15 mm width)
The peel strength was measured by the same method except that the above tensile test was carried out at 80 ° C.

(Haze)
Haze was measured according to JIS K7136: 2000.

Examples 1 to 5 showed good heat seal sealing property, easy opening property, and natural opening property at high temperature. Furthermore, the haze was low and visibility was obtained.
In Comparative Example 1, the heat seal sealing property and the easy opening property were good, but the natural opening property under high temperature was insufficient, and there was a risk of bag breakage due to the heating of the microwave oven.

The film and the co-extruded film of the present invention can be suitably used for producing a package or a bag for heating in a microwave oven while containing a content containing water.

Claims (7)

In a film having at least a sealing layer, when the composition of the sealing layer is 100% by mass of the entire sealing layer, (a) low density polyethylene, linear low density polyethylene, ultralow density polyethylene, ethylene- (meth). ) Polyethylene resin 30-90% by mass, selected from acrylic acid ester copolymer and ethylene-vinyl acetate copolymer and density 900-950 kg / m ³ , (b) Polybutene resin 5-40 mass. %, And (c) a film containing 5 to 30% by mass of an ethylene-α-olefin copolymer having a density of less than 900 kg / m ³ . The film according to claim 1, wherein the peel strength under 25 ° C. conditions is 5.0 to 25.0 N / 15 mm width, and the peel strength under 80 ° C. conditions is 0.4 to 2.0 N / 15 mm width. The film according to claim 1 or 2, wherein the (c) ethylene-α-olefin copolymer is an ethylene-butene copolymer. The melt flow rate (MFR) of the polyethylene resin (a) is 0.5 to 20 g / 10 minutes, and the melt flow rate (MFR) of the polybutene resin (b) is 0.5 to 10 g / 10 minutes. The film according to any one of claims 1 to 3, wherein the melt flow rate (MFR) of the (c) ethylene-α-olefin copolymer is 0.1 to 25 g / 10 minutes. A coextruded film having a polyolefin-based resin layer adjacent to the seal layer of the film according to any one of claims 1 to 3. A package using the film according to any one of claims 1 to 5. A bag body in which the seal layers of the film according to any one of claims 1 to 5 are heat-sealed so as to face each other.