JP2023010777A - Food product packaging film and food product packaging body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a food product packaging film having sufficient steam barrier property and transparency, and capable of achieving a food product packaging body excellent in balance of heat seal property and antistatic property.

SOLUTION: A food product packaging film 100 of the invention is a film for packaging a food product and comprises: a biaxial oriented film layer 101 including a propylene polymer; and a heat seal layer 103 provided on one face of the biaxial oriented film layer 101, in which, a total value (T₁+T₂) of a tension elastic modulus T₁ in a MD direction and a tension elastic modulus T₂ in a TD direction of the food product packaging film 100 which is measured in a condition of measurement temperature of 23±2°C, 50±5%RH and tension speed of 300 mm/min according to JIS K7127 (1999), using a tension test machine, is 3000 MPa or more and 6000 MPa or less.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to food packaging films and food packages.

Biaxially oriented polypropylene film (hereinafter also referred to as OPP film) has an excellent balance of performance such as workability, water vapor barrier property, transparency, mechanical strength and rigidity, and is used as a packaging film for packaging food. It is

Technologies related to food packaging films using such OPP films include, for example, those described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-73926) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-82499). be done.

Patent Document 1 describes a biaxially stretched film made of a propylene polymer composition containing 75 to 90% by weight of a propylene homopolymer (A) and 25 to 10% by weight of a tackifier (D). A layer comprising a propylene/α-olefin random copolymer (C) having a melting point in the range of 125 to 145° C. is interposed between the layers comprising the above propylene-based polymer (B), and in addition to the above biaxially stretched film describes a biaxially oriented multilayer polypropylene film characterized by having a layer comprising a propylene-based polymer (E) on one side.
Patent Literature 1 describes that the biaxially oriented multilayer polypropylene film having the structure described above can suppress exudation of petroleum resin or the like onto the film surface, and is excellent in lamination strength and moisture resistance.

In Patent Document 2, an adhesive layer is applied to at least one surface of a biaxially oriented polypropylene resin layer containing 10 to 40% by weight of a highly crystalline resin and 6 to 15% by weight of a petroleum resin. , a multilayer resin film further having a polyvinyl alcohol-based resin layer, wherein the oxygen permeability at a relative humidity of 85% RH and a temperature of 23 ° C. is 600 mL / m ² day MPa or less, and the relative humidity is 90% A multilayer resin film characterized by having a water vapor transmission rate of 3.5 g/m ² ·day·20 µm or less at RH and a temperature of 40°C is described.
Patent Document 2 describes that the multilayer resin film having the structure described above has excellent oxygen gas barrier properties and moisture resistance.

JP-A-2008-73926 JP-A-2004-82499

Although the OPP film has sufficient water vapor barrier properties and transparency, it has high surface resistivity and poor antistatic properties. Therefore, when the OPP film is used for a food package such as a food packaging bag, it is necessary to increase the amount of the antistatic agent added. By increasing the amount of the antistatic agent added to the OPP film, the surface specific resistance of the resulting food package can be lowered and the antistatic properties can be improved.
However, when the amount of the antistatic agent added to the OPP film is increased, the antistatic agent may bleed out to the film surface, resulting in deterioration of heat sealability and transparency. Therefore, there is room for improvement in terms of improving the antistatic property while suppressing the amount of the antistatic agent added to the OPP film used for the food package.

The present invention has been made in view of the above circumstances, and a food packaging film capable of realizing a food packaging body having sufficient water vapor barrier properties and transparency, as well as an excellent balance between heat-sealing properties and antistatic properties. It provides

The present inventors have made intensive studies to solve the above problems. As a result, by controlling the tensile modulus of the film within a specific range, the surface resistivity of the film can be effectively reduced without increasing the amount of the antistatic agent added, and as a result, the heat-sealability can be improved. The present inventors have found that a food package having an excellent balance of antistatic properties can be obtained, and have completed the present invention.

That is, according to the present invention, the following food packaging film and food package are provided.

[1]
A film for packaging food,
a biaxially stretched film layer comprising a propylene polymer;
a heat seal layer provided on one side of the biaxially stretched film layer;
with
According to JIS K7127 (1999), measured using a tensile tester under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min, the MD direction tensile of the food packaging film A food packaging film having a total value (T ₁ +T ₂ ) of an elastic modulus T ₁ and a tensile elastic modulus T ₂ in the TD direction of 3000 MPa or more and 6000 MPa or less.
[2]
In the food packaging film described in [1] above,
A food packaging film, wherein the difference (T ₂ −T ₁ ) between the tensile elastic modulus T ₂ in the TD direction and the tensile elastic modulus T ₁ in the MD direction of the food packaging film is 2250 MPa or less.
[3]
In the food packaging film according to [1] or [2] above,
A food packaging film having _a tensile elastic modulus T1 in the MD direction of 1000 MPa or more and 2500 MPa or less.
[4]
In the food packaging film according to any one of [1] to [3] above,
A food packaging film having a thermal shrinkage of 4.5% or less in the TD direction when heat-treated at 120°C for 15 minutes.
[5]
In the food packaging film according to any one of [1] to [4] above,
When the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the food packaging film after heat treatment at 120 ° C. for 15 minutes are respectively X _TD [%] and X _MD [%],
A food packaging film having an X _TD -X _MD of -5.0% or more and 5.0% or less.
[6]
In the food packaging film according to any one of [1] to [5] above,
A food packaging film further comprising a surface layer on the surface of the biaxially stretched film layer opposite to the surface provided with the heat seal layer.
[7]
In the food packaging film according to [6] above,
The food packaging film, wherein the surface layer comprises one or more selected from homopolypropylene and random copolymers of propylene and α-olefins having 2 to 10 carbon atoms.
[8]
In the food packaging film according to any one of [1] to [7] above,
The food packaging film, wherein the heat seal layer is provided so as to be in direct contact with the one surface of the biaxially stretched film layer.
[9]
In the food packaging film according to any one of [1] to [8] above,
Food packaging film used for outer packaging bags.
[10]
In the food packaging film according to any one of [1] to [9] above,
A food packaging film in which the heat seal layer contains one or more selected from homopolypropylene and random copolymers of propylene and α-olefins having 2 to 10 carbon atoms.
[11]
A food package using the food packaging film according to any one of [1] to [10] above.

According to the present invention, it is possible to provide a food packaging film that has sufficient water vapor barrier properties and transparency, and that can realize food packaging bodies that are excellent in balance between heat-sealing properties and antistatic properties.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically an example of the structure of the food packaging film of embodiment which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically an example of the structure of the food packaging film of embodiment which concerns on this invention.

An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings are schematic diagrams and do not correspond to actual dimensional ratios. In addition, unless otherwise specified, "~" between numbers in the text represents the following from the above.

<Food packaging film>
1 and 2 are cross-sectional views schematically showing an example of the structure of a food packaging film 100 according to an embodiment of the present invention.
The food packaging film 100 according to the present embodiment is a film for packaging food, and includes a biaxially stretched film layer 101 containing a propylene polymer and a A heat seal layer 103, and is measured using a tensile tester in accordance with JIS K7127 (1999) under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. The total value (T ₁ +T ₂ ) of the tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction of the packaging film 100 is 3000 MPa or more and 6000 MPa or less.

As described above, the OPP film has sufficient water vapor barrier properties and transparency, but has high surface resistivity and poor antistatic properties. Therefore, when the OPP film is used for a food package such as a food packaging bag, it is necessary to increase the amount of the antistatic agent added. By increasing the amount of the antistatic agent added to the OPP film, the surface specific resistance of the resulting food package can be lowered and the antistatic properties can be improved.
However, when the amount of the antistatic agent added to the OPP film is increased, the antistatic agent may bleed out to the film surface, resulting in deterioration of heat sealability and transparency. Therefore, there is room for improvement in terms of improving the antistatic property while suppressing the amount of the antistatic agent added to the OPP film used for the food package.

The present inventors have made intensive studies to solve the above problems. As a result, by controlling the tensile modulus of the food packaging film 100 provided with the biaxially stretched film layer 101 containing the propylene polymer within the above range, the surface specific resistance of the film can be reduced without increasing the amount of the antistatic agent added. can be effectively reduced, and as a result, a food package having an excellent balance between heat-sealing properties and antistatic properties can be obtained.
Here, the reason why the surface specific resistance of the film can be effectively reduced without increasing the amount of the antistatic agent by controlling the tensile modulus of the food packaging film 100 within the above range is not necessarily clear. No, but it is presumed that this is because the food packaging film 100 has appropriate elasticity and the charge on the surface of the film can easily move.
That is, the food packaging film 100 according to the present embodiment has a biaxially stretched film layer containing a propylene polymer and has a specific tensile elastic modulus, thereby providing sufficient water vapor barrier properties and transparency. It is possible to realize a food package that has a good balance between heat-sealing properties and antistatic properties. In addition, the food packaging film 100 according to this embodiment has excellent surface antistatic properties. Therefore, the printability of the surface of the food package can be improved, and adhesion of foreign matter such as dust to the surface of the food package can be suppressed.
As described above, according to the present embodiment, it is possible to realize a food package having sufficient water vapor barrier properties and transparency, and a food package having an excellent balance between heat-sealing properties and antistatic properties. A packaging film 100 can be provided for.

Here, the food package produced using the food packaging film 100 according to the present embodiment exhibits sufficient performance in terms of water vapor barrier properties. Therefore, it can be particularly suitably used as a film constituting a food package for packaging foods (for example, dry foods) that require water vapor barrier properties but do not require much oxygen barrier properties.

The food packaging film 100 according to the present embodiment conforms to JIS K7127 (1999) and is measured using a tensile tester under conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. The lower limit of the total value (T ₁ + T ₂ ) of the tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction is 3000 MPa or more, preferably 3500 MPa or more, and 4000 MPa or more is more preferred.
When the total value (T ₁ +T ₂ ) of the tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction is equal to or greater than the above lower limit, the heat sealability of the food packaging film 100 according to the present embodiment , a good balance between water vapor barrier properties and transparency can be obtained. Furthermore, the food packaging film 100 according to the present embodiment can be made to have good stiffness, and as a result, it is possible to suppress positional deviation of the film during heat sealing, and it is possible to suppress the occurrence of sealing defects. .
That is, when the total value (T ₁ +T ₂ ) of the tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction is equal to or greater than the above lower limit, the heat of the food packaging film 100 according to the present embodiment A good balance of sealability, water vapor barrier properties, transparency and packaging suitability can be achieved.

In addition, in the food packaging film 100 according to the present embodiment, in accordance with JIS K7127 (1999), a tensile tester is used at a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. The upper limit of the total value (T ₁ + T ₂ ) of the measured tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction is 6000 MPa or less, more preferably 5800 MPa or less, and 5700 MPa or less. is more preferable.
When the total value (T ₁ + T ₂ ) of the tensile elastic modulus T ₁ in the MD direction and the tensile elastic modulus T ₂ in the TD direction is equal to or less than the above upper limit value, the antistatic agent of the present embodiment can be obtained without increasing the amount of antistatic agent added. The surface specific resistance of the food packaging film 100 can be effectively reduced, and as a result, the antistatic property can be improved while maintaining the good heat-sealing property of the food packaging film 100.

In addition, in the food packaging film 100 according to the present embodiment, the difference (T ₂ −T ₁ ) between the tensile elastic modulus T ₂ in the TD direction and the tensile elastic modulus T ₁ in the MD direction is preferably 2250 MPa or less, It is more preferably 2200 MPa or less.
When the difference (T ₂ −T ₁ ) between the tensile elastic modulus T ₂ in the TD direction and the tensile elastic modulus T ₁ in the MD direction is equal to or less than the above upper limit, the antistatic property of the food packaging film 100 can be improved while heat is applied. Shrinkage can be suppressed, and as a result, misalignment of the sealing portion in the food package, wrinkles in the food package, breakage of the food package itself, and the like can be more effectively suppressed.
In the food packaging film 100 according to the present embodiment, the lower limit of the difference (T ₂ −T ₁ ) between the tensile elastic modulus T ₂ in the TD direction and the tensile elastic modulus T ₁ in the MD direction is not particularly limited. 1200 MPa or more.

In addition, in the food packaging film ₁₀₀ according to the present embodiment, the lower limit of the tensile elastic modulus T1 in the MD direction is preferably 1000 MPa or more, more preferably 1100 MPa or more, and further preferably 1200 MPa or more. preferable.
When the tensile elastic modulus T1 in the MD direction is at _least the above lower limit, the food packaging film 100 according to the present embodiment can have a better balance of heat sealability, water vapor barrier properties, and transparency. Furthermore, the food packaging film 100 according to the present embodiment can have a better stiffness, and as a result, it is possible to suppress the positional deviation of the film during heat sealing, and to prevent the occurrence of sealing defects. can be further suppressed.
That is, when the tensile elastic modulus T1 in the MD direction is equal to or higher _than the above lower limit, the food packaging film 100 according to the present embodiment has a better balance among heat sealability, water vapor barrier property, transparency and packaging suitability. can do.
In addition, in the food packaging film 100 according to the present embodiment, the _upper limit of the tensile elastic modulus T1 in the MD direction is preferably 2500 MPa or less, more preferably 1800 MPa or less, and further preferably 1750 MPa or less. preferable.
When the tensile elastic modulus T1 in the MD direction is equal to or _less than the upper limit, the surface specific resistance of the food packaging film 100 according to the present embodiment is more effectively reduced without increasing the amount of the antistatic agent added. As a result, the antistatic property of the food packaging film 100 can be further improved.

The tensile modulus of the food packaging film 100 according to the present embodiment can be adjusted, for example, by adjusting the type and content of the propylene polymer contained in the biaxially stretched film layer 101 and various conditions during the stretching treatment. This can be achieved by adjusting the material, thickness, etc. of the sealing layer 103 and the surface layer 105 .
More specifically, the presence or absence and ratio of functional groups copolymerized with the propylene polymer contained in the biaxially stretched film layer 101, the stretch ratio during stretching, the temperature during stretching, the temperature and time of heat treatment, and the like are determined. The tensile modulus of the food packaging film 100 can also be adjusted by appropriately adjusting the modulus of elasticity.

In the food packaging film 100 according to the present embodiment, the heat shrinkage in the TD direction when heat-treated at 120 ° C. for 15 minutes is preferably 4.5% or less, more preferably 4.2% or less. preferable.
As a result, misalignment of the sealing portion in the food package, occurrence of wrinkles in the food package, breakage of the food package itself, and the like can be more effectively suppressed.
Such a heat shrinkage rate is, for example, the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the tensile modulus of the food packaging film 100, the constituent materials of the heat seal layer 103 and the surface layer 105, It can be achieved by adjusting the thickness and the like.

In the food packaging film 100 according to the present embodiment, the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction when heat-treated at 120 ° C. for 15 minutes were defined as X _TD [%] and X _MD [%]. When X _TD -X _MD is preferably -5.0% or more and 5.0% or less, more preferably -4.0% or more and 3.0% or less, -3.5% or more 2 It is more preferably 0.0% or less, and particularly preferably -3.0% or more and 1.0% or less.
When X _TD -X _MD is within the above range, it is possible to more effectively suppress misalignment of the sealing portion in the food package, occurrence of wrinkles in the food package, and breakage of the food package itself. can.
Such X _TD -X _MD is, for example, the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the tensile elastic modulus of the food packaging film 100, the configuration of the heat seal layer 103 and the surface layer 105 It can be achieved by adjusting the material, thickness, and the like.
Moreover, X _TD [%] and X _MD [%] of the food packaging film 100 according to the present embodiment are calculated by the following method.
First, a test piece of 10 cm×10 cm is cut out from the food packaging film 100, and this test piece is heat-treated at 120° C. for 15 minutes. Next, when the length of the test piece in the TD direction after heat treatment is TD ₁ [cm] and the length of the test piece in the MD direction after heat treatment is MD ₁ [cm], X _TD [%] is It is calculated by 100×(10−TD ₁ )/10, and X _MD [%] is calculated by 100×(10−MD ₁ )/10.

A food package produced using the food packaging film 100 according to this embodiment has sufficient water vapor barrier properties. In the food packaging film 100, the water vapor transmission rate measured by the following method is 8.0 g/(m ² ·24 h) or less from the viewpoint of stably obtaining a food package having excellent water vapor barrier properties. is preferably 7.0 g/(m ² ·24 h) or less, and particularly preferably 6.5 g/(m ² ·24 h) or less.
(Measuring method)
The food packaging film 100 is folded so that the heat-seal layer 103 faces inside, and the two sides are heat-sealed to form a bag. After that, calcium chloride is added as the content. The other side is then heat-sealed to form a bag with a surface area of 0.01 m ² . The resulting bag is then stored for 72 hours under conditions of 40° C. and 90% RH. The weight of calcium chloride before and after storage is measured, and the water vapor permeability (g/(m ² ·24h)) is calculated from the difference.
Such water vapor permeability is, for example, the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the tensile modulus of the food packaging film 100, the constituent materials of the heat seal layer 103 and the surface layer 105, and the It can be achieved by adjusting the thickness and the like.

The food packaging film 100 according to this embodiment has excellent heat sealability. In the food package produced using the food packaging film 100, from the viewpoint of further improving the sealing strength, the heat seal layers 103 of the food packaging film 100 were heated to 115°C, a pressure of 1.0 kgf, and a sealing time of 0.5. The heat seal strength of the portion heat-sealed under the condition of seconds is preferably 2.5 N/15 mm or more, more preferably 3.0 N/15 mm or more, and particularly preferably 3.5 N/15 mm or more.
Here, the heat seal strength can be measured by the following method. First, the heat seal layers 103 of two food packaging films 100 are heat-sealed under conditions of 115° C., pressure of 1.0 kgf, and sealing time of 0.5 seconds to obtain a laminated film. Next, the two food packaging films 100 are peeled off under the conditions of 15 mm width, 90 degree peeling, and peeling speed of 300 mm/min, and the peel strength at that time is defined as the heat seal strength.
Such heat-sealing strength can be achieved by adjusting the tensile modulus of elasticity of the food packaging film 100, and the constituent materials and thickness of the heat-sealing layer 103 and the surface layer 105, for example.

In the food packaging film 100 according to the present embodiment, from the viewpoint of improving transparency, the haze measured using a haze meter in accordance with JIS K7105 is preferably less than 2.5%. It is more preferably less than 0.0%.
Such a haze can be achieved, for example, by adjusting the type and content of the propylene polymer contained in the biaxially stretched film layer 101, the constituent materials and thickness of the heat seal layer 103 and the surface layer 105, and the like.

In addition, on both sides of the food packaging film 100 according to the present embodiment, in accordance with JIS C2139, from the viewpoint of improving the antistatic property, using a digital ultra-high resistance microammeter, 20 ± 2 ° C., 50 5. The surface resistivity of the sample after storage for 24 hours or more under the conditions of ±5% RH is preferably 1.0×10 ¹⁴ Ω or less, more preferably 5.0×10 ¹³ Ω or less. 0×10 ¹² Ω or less is particularly preferable.
Such a surface specific resistance can be achieved, for example, by adjusting the tensile elastic modulus of the food packaging film 100, the constituent materials and thickness of the heat seal layer 103 and the surface layer 105, and the like.

Although the thickness of the food packaging film 100 according to the present embodiment is not particularly limited, it can be arbitrarily set according to desired purposes such as water vapor barrier properties, cost, mechanical strength, transparency, etc., and is not particularly limited. , usually 5 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less, more preferably 15 μm or more and 40 μm or less.
When the thickness of the food packaging film 100 is within the above range, the bag-making properties, mechanical properties, handleability, appearance, transparency, moldability, lightness, etc. are well balanced.

Each layer constituting the food packaging film 100 will be described below.

[Biaxially stretched film layer]
The biaxially stretched film layer 101 according to this embodiment is formed by, for example, biaxially stretching a film composed of a resin composition (P) containing a propylene polymer.

The biaxially stretched film layer 101 according to the present embodiment may be a single layer, or may be a structure in which a plurality of layers composed of the resin composition (P) are laminated, but it may be biaxially stretched. is necessary.

In addition, in the food packaging film 100, the ratio of the thickness of the biaxially stretched film layer 101 to the overall thickness of the food packaging film 100 is preferably 0.50 or more and 0.998 or less, more preferably 0.60. 0.99 or less, more preferably 0.70 or more and 0.97 or less, and particularly preferably 0.75 or more and 0.95 or less.

(Propylene polymer)
The resin composition (P) according to this embodiment, that is, the biaxially stretched film layer 101 contains a propylene polymer. This makes it possible to obtain the biaxially stretched film layer 101 having an excellent balance of properties such as heat resistance, water vapor barrier properties, transparency, mechanical properties and rigidity.
Examples of the propylene polymer according to the present embodiment include homopolypropylene, copolymers of propylene and ethylene or α-olefins having 4 to 20 carbon atoms, and the like. Examples of the α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like. Among these, ethylene or an α-olefin having 4 to 10 carbon atoms is preferred, and ethylene is more preferred. These α-olefins may form random copolymers or block copolymers with propylene. The content of structural units derived from ethylene or an α-olefin having 4 to 20 carbon atoms is preferably 5 mol% or less, preferably 2 mol% or less, based on 100 mol% of the entire propylene polymer. It is more preferable to have The propylene polymer in the biaxially stretched film layer 101 may be used singly or in combination of two or more.
Among these, homopolypropylene is preferable as the propylene polymer from the viewpoint of obtaining a biaxially stretched film layer 101 having a better balance of performance such as heat resistance, water vapor barrier properties, mechanical properties and rigidity. Polypropylene has a content of structural units derived from propylene of 99.0 mol% or more, preferably 99.5 mol% or more, when the total content of structural units constituting homopolypropylene is 100 mol%. It is preferably 99.9 mol % or more, particularly preferably 100.0 mol %.

The propylene polymer according to this embodiment can be produced by various methods. For example, it can be produced using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts.

The melting point of the propylene polymer according to the present embodiment is preferably 150° C. or higher and 170° C. or lower, from the viewpoint of further improving the balance among heat resistance, transparency, mechanical properties, rigidity, fluidity and moldability. It is more preferably in the range of 155°C or higher and 168°C or lower.

The melt flow rate (MFR) of the propylene polymer according to the present embodiment measured under conditions of 230° C. and a load of 2.16 kg according to ASTM D1238 is preferably 0.5 g from the viewpoint of fluidity and moldability. /10 min or more, more preferably 1 g/10 min or more, still more preferably 2 g/10 min or more, and from the viewpoint of further stabilizing moldability, preferably 20 g/10 min or less, more preferably 10 g/10 min. 7 g/10 minutes or less, more preferably 7 g/10 minutes or less.

(polyolefin)
The resin composition (P) according to this embodiment may further contain a polyolefin other than the propylene polymer. The tensile modulus of the food packaging film 100 according to this embodiment can be adjusted by adding a polyolefin having a modulus different from that of the propylene polymer to the resin composition (P).
Examples of the polyolefin according to the present embodiment include polyethylene such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene. Among these, low-density polyethylene and linear low-density polyethylene are preferred, and linear low-density polyethylene is more preferred. One type of polyethylene may be used, or two or more types may be used in combination.

The melting point of the polyethylene according to the present embodiment is preferably 95° C. or more and 135° C. or less, more preferably 95° C. or more and 135° C. or less, from the viewpoint of further improving the balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, and moldability. is in the range of 100°C to 130°C

The density of the polyethylene according to the present embodiment is 900 kg/m ³ or more and 965 kg/m ³ or less from the viewpoint of further improving the balance of heat resistance, transparency, mechanical properties, rigidity, fluidity and moldability. It is preferably 900 kg/m ³ or more and 940 kg/m ³ or less. Here, the density of the polyethylene according to this embodiment can be measured according to JIS K7112 (1999).

The melt flow rate (MFR) of the polyethylene according to the present embodiment measured under conditions of 190° C. and a load of 2.16 kg according to ASTM D1238 is preferably 0.5 g/10 from the viewpoint of fluidity and moldability. minutes or more, more preferably 1 g/10 minutes or more, still more preferably 2 g/10 minutes or more, and from the viewpoint of further stabilizing moldability, preferably 30 g/10 minutes or less, more preferably 20 g/10 minutes or less, More preferably, it is 10 g/10 minutes or less.

The method for producing polyethylene according to the present embodiment is not particularly limited, and it can be produced by a known method. In addition, commercially available polyethylene may be used.

The resin composition (P) according to the present embodiment, that is, the lower limit of the content of polyethylene contained in the biaxially stretched film layer 101, further improves the balance between the heat-sealing property and the antistatic property of the food packaging film 100. From the viewpoint, when the total amount of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101 is 100% by mass, it is preferably 0.5% by mass or more, more preferably 1.0% by mass or more. , more preferably 2.0% by mass or more, and particularly preferably 3.0% by mass or more.
In addition, the upper limit of the content of polyethylene contained in the resin composition (P) according to the present embodiment, that is, the biaxially stretched film layer 101, suppresses a decrease in the bending elasticity of the food packaging film 100, heat sealability From the viewpoint of further improving water vapor barrier properties, transparency, etc., when the total amount of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101 is 100% by mass, it is preferably 25% by mass or less. , more preferably 20% by mass or less, still more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

The total content of the propylene polymer and polyethylene contained in the resin composition (P) according to the present embodiment, that is, the biaxially stretched film layer 101, is preferably 100% by mass of the entire resin composition (P). is 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, still more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 95% by mass or more and 100% by mass or less. This makes it possible to improve the balance among water vapor barrier properties, mechanical properties, handleability, appearance, transparency, moldability, heat-sealing properties, antistatic properties, and the like.

(other ingredients)
The resin composition (P) according to the present embodiment may optionally contain a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, and an antiblocking agent. , antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, and the like may be added within a range that does not impair the purpose of the present embodiment.

(Method for preparing resin composition (P))
For the resin composition (P) according to the present embodiment, for example, each component is mixed or melted by dry blending, a tumbler mixer, a Banbury mixer, a single screw extruder, a twin screw extruder, a high speed twin screw extruder, a hot roll, or the like. • Can be prepared by kneading.

[Heat seal layer]
The food packaging film 100 according to this embodiment has a heat seal layer 103 on at least one surface of the biaxially stretched film layer 101 in order to impart heat sealability. The heat seal layer 103 may be provided on both sides of the biaxially stretched film layer 101 .
Moreover, the heat seal layer 103 is preferably provided as the outermost layer of the food packaging film 100 according to the present embodiment from the viewpoint of improving the heat sealability of the food packaging film 100 .

Moreover, the heat seal layer 103 is preferably provided on the surface of the biaxially stretched film layer 101 so as to be in direct contact therewith. Thereby, the manufacturing process of the food packaging film 100 can be simplified.

In the food packaging film 100, the thickness of the heat seal layer 103 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 9 μm or less, still more preferably 0.5 μm or more and 8 μm or less, and particularly preferably 1 μm or more and 8 μm. It is below. Here, the thickness of the heat seal layer 103 refers to the thickness of the heat seal layer 103 provided on one side of the biaxially stretched film layer 101 .
When the thickness of the heat seal layer 103 is equal to or greater than the above lower limit, the heat sealability of the food packaging film 100 can be further improved.
Further, since the thickness of the heat seal layer 103 is equal to or less than the above upper limit, the adhesiveness with the biaxially stretched film layer 101 is improved, and the heat seal layer 103 can be formed on the biaxially stretched film layer 101 without using an adhesive. can be easily stacked.
That is, since it becomes easy to provide the heat seal layer 103 so as to be in direct contact with the surface of the biaxially stretched film layer 101, the manufacturing process of the food packaging film 100 can be simplified.
Here, in the present embodiment, when the heat seal layer 103 is provided on both sides of the biaxially stretched film layer 101, the thickness of the heat seal layer 103 is equal to the thickness of the heat seal layer 103 provided on one side of the biaxially stretched film layer 101. thickness.

In the food packaging film 100, the heat seal layer 103 provided on one side is preferably a single layer. Thereby, the manufacturing process of the food packaging film 100 can be further simplified.

Moreover, the heat seal layer 103 is preferably formed by biaxially stretching simultaneously with the film of the biaxially stretched film layer 101 before biaxial stretching. As a result, the food packaging film 100 can be produced using a molding method such as a co-extrusion molding method, that is, the laminated film produced by one-time molding, thereby further simplifying the manufacturing process of the food packaging film 100. can do. Therefore, the heat seal layer 103 is preferably biaxially stretched.

(polyolefin)
The heat seal layer 103 according to this embodiment is composed of, for example, a polyolefin-based resin composition (A) containing polyolefin. Examples of the polyolefin constituting the heat seal layer 103 include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1; High pressure low density polyethylene; linear low density polyethylene (LLDPE); high density polyethylene; polypropylene; random copolymer of propylene and α-olefin having 2 to 10 carbon atoms; ethylene/vinyl acetate copolymer (EVA ); and ionomer resins.
Among these, as the polyolefin constituting the heat seal layer 103, the number of carbon atoms is 2 or more and 10 or less with homopolypropylene and propylene from the viewpoint of excellent balance of adhesiveness with the biaxially stretched film layer 101 and heat sealability. is preferably at least one selected from random copolymers with α-olefins.

The propylene/α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and α-olefin (where α-olefin excludes propylene). , 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or in combination of two or more.
Among the propylene/α-olefin random copolymers, propylene/ethylene random copolymers, propylene/ethylene/1-butene random copolymers, and propylene/1-butene random copolymers are preferred.

The melting point of the polyolefin constituting the heat seal layer 103 according to the present embodiment is preferably in the range of 60°C to 175°C, more preferably 65°C to 170°C, even more preferably 70°C to 167°C. When the melting point of the polyolefin is at least the above lower limit, stickiness of the surface of the heat seal layer 103 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved.
Further, when the melting point of the polyolefin is equal to or lower than the above upper limit, the heat sealability of the food packaging film 100 can be improved.

The melt flow rate (MFR) of the polyolefin constituting the heat seal layer 103 according to the present embodiment, which is measured under the conditions of 230° C. and a load of 2.16 kg according to ASTM D1238, is, from the viewpoint of fluidity and moldability, It is preferably 0.5 g/10 min or more, more preferably 1 g/10 min or more, still more preferably 2 g/10 min or more, and from the viewpoint of further stabilizing moldability, preferably 20 g/10 min or less, more preferably is 10 g/10 minutes or less, more preferably 7 g/10 minutes or less.

The content of polyolefin in the polyolefin resin composition (A) according to the present embodiment, that is, the heat seal layer 103, is preferably 50% by mass or more when the entire polyolefin resin composition (A) is taken as 100% by mass. It is 100 mass % or less, more preferably 70 mass % or more and 100 mass % or less, still more preferably 90 mass % or more and 100 mass % or less, and particularly preferably 95 mass % or more and 100 mass % or less. As a result, the adhesiveness to the biaxially stretched film layer 101 and the heat-sealing property can be well balanced.

(other ingredients)
The polyolefin resin composition (A) constituting the heat seal layer 103 according to the present embodiment may optionally contain a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, Various additives such as slip agents, nucleating agents, anti-blocking agents, antistatic agents, anti-fogging agents, pigments, dyes, inorganic or organic fillers may be added as long as they do not impair the purpose of the present embodiment.

(Method for preparing polyolefin resin composition (A))
The polyolefin-based resin composition (A) according to the present embodiment is prepared by, for example, dry blending each component, tumbler mixer, Banbury mixer, single-screw extruder, twin-screw extruder, high-speed twin-screw extruder, hot roll, etc. Alternatively, it can be prepared by melting and kneading.

[Surface layer]
In order to improve the printability of the surface of the food packaging film 100 according to this embodiment, as shown in FIG. It is preferable to further include a surface layer 105 on the surface.
Moreover, from the viewpoint of improving the printability of the food packaging film 100, the surface layer 105 is preferably provided as the outermost layer of the food packaging film 100 according to the present embodiment.

Moreover, the surface layer 105 is preferably provided so as to be in direct contact with the surface of the biaxially stretched film layer 101 . Thereby, the manufacturing process of the food packaging film 100 can be simplified.

In the food packaging film 100, the thickness of the surface layer 105 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 9 μm or less, still more preferably 0.5 μm or more and 8 μm or less, and particularly preferably 1 μm or more and 8 μm or less. is. Here, the thickness of the surface layer 105 refers to the thickness of the surface layer 105 provided on one side of the biaxially stretched film layer 101 .
When the thickness of the surface layer 105 is at least the above lower limit, the printability of the food packaging film 100 can be further improved.
Further, since the thickness of the surface layer 105 is equal to or less than the above upper limit, the adhesion with the biaxially stretched film layer 101 is improved, and the surface layer 105 is laminated on the biaxially stretched film layer 101 without using an adhesive. It becomes easier to let
That is, since it becomes easy to provide the surface layer 105 so as to be in direct contact with the surface of the biaxially stretched film layer 101, the manufacturing process of the food packaging film 100 can be simplified.

In the food packaging film 100, the surface layer 105 is preferably a single layer. Thereby, the manufacturing process of the food packaging film 100 can be further simplified.

Moreover, the surface layer 105 is preferably formed by biaxially stretching simultaneously with the film of the biaxially stretched film layer 101 before biaxial stretching. As a result, the food packaging film 100 can be produced using a molding method such as a co-extrusion molding method, that is, the laminated film produced by one-time molding, thereby further simplifying the manufacturing process of the food packaging film 100. can do. Therefore, the surface layer 105 is preferably biaxially stretched.

Moreover, the surface layer 105 may be surface-treated from the viewpoint of improving the printability of the food packaging film 100 . Specifically, surface activation treatment such as corona treatment, flame treatment, plasma treatment, primer coating treatment, and ozone treatment may be performed.

(polyolefin)
The surface layer 105 according to this embodiment is composed of, for example, a polyolefin-based resin composition (B) containing polyolefin. Examples of the polyolefin constituting the surface layer 105 include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1; Law low density polyethylene; linear low density polyethylene (LLDPE); high density polyethylene; polypropylene; random copolymer of propylene and α-olefin having 2 to 10 carbon atoms; ethylene/vinyl acetate copolymer (EVA) ; and ionomer resins.
Among these, as the polyolefin constituting the surface layer 105, homopolypropylene and propylene and alpha having 2 or more and 10 or less carbon atoms are used because they have an excellent balance of adhesiveness with the biaxially stretched film layer 101 and printability. - At least one selected from random copolymers with olefins is preferred.

The propylene/α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and α-olefin (where α-olefin excludes propylene). , 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or in combination of two or more.
Among the propylene/α-olefin random copolymers, propylene/ethylene random copolymers, propylene/ethylene/1-butene random copolymers, and propylene/1-butene random copolymers are preferred.

The melting point of the polyolefin forming the surface layer 105 according to the present embodiment is preferably in the range of 90°C to 175°C, more preferably 95°C to 170°C, even more preferably 100°C to 167°C. When the melting point of the polyolefin is equal to or higher than the above lower limit, stickiness of the surface of the surface layer 105 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved.

The melt flow rate (MFR) of the polyolefin constituting the surface layer 105 according to the present embodiment, which is measured under the conditions of 230° C. and a load of 2.16 kg in accordance with ASTM D1238, is preferable from the viewpoint of fluidity and moldability. is 0.5 g/10 min or more, more preferably 1 g/10 min or more, still more preferably 2 g/10 min or more, and from the viewpoint of further stabilizing moldability, preferably 20 g/10 min or less, more preferably It is 10 g/10 minutes or less, more preferably 7 g/10 minutes or less.

The content of polyolefin in the polyolefin resin composition according to the present embodiment, that is, the surface layer 105, is preferably 50% by mass or more and 100% by mass or less when the entire polyolefin resin composition (B) is taken as 100% by mass. , more preferably 70% by mass or more and 100% by mass or less, still more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 95% by mass or more and 100% by mass or less. This makes it possible to improve the balance between adhesion to the biaxially stretched film layer 101 and printability.

(other ingredients)
The polyolefin resin composition (B) constituting the surface layer 105 according to the present embodiment may optionally contain a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, and a slip. Various additives such as agents, nucleating agents, anti-blocking agents, antistatic agents, anti-fogging agents, pigments, dyes, inorganic or organic fillers may be added to the extent that the purpose of the present embodiment is not impaired.

(Method for preparing polyolefin resin composition (B))
The polyolefin-based resin composition (B) according to the present embodiment is prepared by, for example, dry blending each component using a tumbler mixer, a Banbury mixer, a single screw extruder, a twin screw extruder, a high speed twin screw extruder, a hot roll, or the like. Alternatively, it can be prepared by melting and kneading.

<Method for producing food packaging film>
The food packaging film 100 according to the present embodiment includes, for example, a resin composition (P) for forming the biaxially stretched film layer 101 and a polyolefin resin composition (A) for forming the heat seal layer 103. and, if necessary, the polyolefin resin composition (B) for forming the surface layer 105, and a laminated film obtained by co-extrusion molding into a film is subjected to a known simultaneous biaxial stretching method or successive biaxial stretching. It can be obtained by biaxially stretching using a biaxially stretched film manufacturing method such as a stretching method.
The molding apparatus and molding conditions are not particularly limited, and conventionally known molding apparatuses and molding conditions can be employed. A multi-layer T-die extruder, a multi-layer inflation molding machine, or the like can be used as a molding device. For the biaxial stretching conditions, for example, known OPP film production conditions can be adopted. More specifically, in the sequential biaxial stretching method, for example, the longitudinal stretching temperature is 100° C. to 145° C., the longitudinal stretching ratio is 4.5 to 6 times, the lateral stretching temperature is 130° C. to 190° C., and the lateral stretching is Magnification may be in the range of 9 to 11 times.
In addition, the food packaging film 100 according to the present embodiment is obtained by separately forming the biaxially stretched film layer 101, the heat seal layer 103, and the surface layer 105 as necessary, laminating them, and thermoforming. can also be obtained by

<Uses of food packaging films>
The food packaging film 100 according to this embodiment can also be suitably used as a film constituting a food package. The food package according to the present embodiment is, for example, a packaging bag itself used for containing food or a food contained in the bag. In addition, the food packaging film 100 may be used for a part of the food package according to the present embodiment, or the food packaging film 100 may be used for the entire food package. .

The food packaging film 100 according to the present embodiment is preferably used for exterior packaging bags that particularly require water vapor barrier properties, transparency and antistatic properties.
Further, when the food packaging film 100 according to the present embodiment is used for an integrated package composed of a food, an individual packaging bag for individually packaging the food, and an exterior packaging bag for packaging a plurality of individual packaging bags, the food is The packaging film 100 for packaging is preferably used for exterior packaging bags for which moisture barrier properties, transparency and antistatic properties are particularly required in integrated packages. This makes it possible to obtain an integrated package having sufficient water vapor barrier properties, transparency and antistatic properties.

Although the embodiments of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than those described above can also be adopted.

Hereinafter, the present embodiment will be described in detail with reference to examples and comparative examples. It should be noted that the present embodiment is not limited to the description of these examples.

1. Raw Materials Raw materials used in Examples and Comparative Examples are shown below.
(1) Polypropylene PP1: homopolypropylene (MFR: 3 g/10 minutes, melting point: 157°C, manufactured by Prime Polymer Co., Ltd.)
PP2: propylene/α-olefin random copolymer (MFR: 7 g/10 min, melting point: 137°C, manufactured by Prime Polymer Co., Ltd.)
PP3: propylene/α-olefin random copolymer (MFR: 7 g/10 min, melting point: 74°C, manufactured by Mitsui Chemicals, Inc.)
PP4: homopolypropylene (MFR: 3.5 g/10 minutes, melting point: 159°C, manufactured by Prime Polymer Co., Ltd.)
(2) Polyethylene PE1: polyethylene (MFR: 2.3 g/10 min, density: 916 kg/m ³ , melting point: 126°C, manufactured by Braskem)
(3) Additive A1: antiblocking agent

2. Measurement and evaluation method (1) MFR of polypropylene
It was measured under conditions of 230° C. and a load of 2.16 kg according to ASTM D1238.

(2) MFR of polyethylene
It was measured under conditions of 190° C. and a load of 2.16 kg according to ASTM D1238.

(3) Melting Points of Polypropylene and Polyethylene The maximum melting peak temperature of the DSC curves of polypropylene and polyethylene obtained using a DSC (differential scanning calorimeter) was taken as the melting point.

(4) Tensile modulus A test piece of 15 mm x 15 cm was cut out from the food packaging films obtained in Examples and Comparative Examples. Next, using a tensile tester manufactured by Orientec Co., Ltd., in accordance with JIS K7127 (1999), the MD direction of the test piece under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. _The tensile modulus T1 and the tensile modulus T2 in the TD direction were measured _respectively .

(5) Thermal Shrinkage A test piece of 10 cm×10 cm was cut out from the food packaging films obtained in Examples and Comparative Examples. Then, the test piece was heat-treated at 120° C. for 15 minutes. Next, when the length of the test piece in the TD direction after heat treatment is TD ₁ [cm] and the length of the test piece in the MD direction after heat treatment is MD ₁ [cm], X _TD [%] is It was calculated by 100×(10−TD ₁ )/10, and X _MD [%] was calculated by 100×(10−MD ₁ )/10.

(6) Transparency The haze of the food packaging films obtained in Examples and Comparative Examples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH300A) in accordance with JIS K7105.
Then, the transparency of the food packaging film was evaluated according to the following criteria.
◎◎: Haze is less than 2.0% ◎: Haze is 2.0% or more and less than 2.5% ○: Haze is 2.5% or more and less than 3.0% ×: Haze is 3.0% or more

(7) Antistatic property According to JIS C2139, using a digital ultra-high resistance microammeter (manufactured by Advantest, trade name: 8340A), the heat seal layer of the food packaging film obtained in Examples and Comparative Examples The surface resistivity of the side was measured. The measurement conditions are as follows.
Measurement conditions: After storage for 24 hours or more at 20 ± 2 ° C. and 50 ± 5% RH, measure under conditions of 20 ± 2 ° C. and 50 ± 5% RH Next, charge the food packaging film according to the following criteria. Preventive properties were evaluated.
◎◎: Surface specific resistance of 5.0×10 ¹² Ω or less ◎: Surface specific resistance of more than 5.0×10 ¹² Ω and 5.0×10 ¹³ Ω or less ○: Surface specific resistance of 5.0×10 ¹³ Ω Exceeds 1.0 × 10 ¹⁴ Ω or less ×: Surface specific resistance exceeds 1.0 × 10 ¹⁴ Ω

(8) Water vapor barrier property The food packaging films obtained in Examples and Comparative Examples were folded so that the heat-seal layer was on the inner surface, and the two sides were heat-sealed to form a bag. After that, calcium chloride was added as the content. Then, the other side was heat-sealed to prepare a bag having a surface area of 0.01 m ² . The resulting bag was then stored for 72 hours under conditions of 40° C. and 90% RH. The weight of calcium chloride before and after storage was measured, and the water vapor permeability (g/(m ² ·24h)) was calculated from the difference.
Next, the water vapor barrier property of the food packaging film was evaluated according to the following criteria.
◎◎: Water vapor transmission rate is 6.5 g / (m ² · 24 h) or less ◎: Water vapor transmission rate exceeds 6.5 g / (m ² · 24 h) 8.0 g / (m ² · 24 h) or less ○: Water vapor transmission 8.0 g / (m ² · 24 h) more than 10.0 g / (m ² · 24 h) or less ×: Water vapor permeability exceeds 10.0 g / (m ² · 24 h)

(9) Heat-sealability The heat-sealed layers of two food packaging films cut to a width of 15 mm were heat-sealed to each other under the conditions of 115°C, pressure of 1.0 kgf, and sealing time of 0.5 seconds to form a laminated film. Obtained. Then, the two food packaging films were peeled under the conditions of 15 mm width, 90 degree peeling, and peeling speed of 300 mm/min, and the peel strength at that time was taken as the heat seal strength.
Then, the heat sealability of the food packaging film was evaluated according to the following criteria.
◎◎: Heat seal strength is 3.5 N/15 mm or more ◎: Heat seal strength is 2.5 N/15 mm or more and less than 3.5 N/15 mm ○: Heat seal strength is 1.0 N/15 mm or more and less than 2.5 N/15 mm × : Heat seal strength is less than 1.0 N/15 mm

[Examples 1 to 5 and Comparative Example 1]
Each layer was co-extruded with the layer structure shown in Table 1, and then biaxially stretched to prepare a food packaging film, and each evaluation was performed. Co-extrusion molding conditions and biaxial stretching conditions are as follows.
Multi-layer extruder: 60 mmφ multi-layer T-die extruder (L/D = 27, manufactured by Screw Seiki Co., Ltd.)
Extrusion setting temperature: 200-250°C, processing speed: 13.5m/min
Longitudinal stretching temperature: 110-120°C
Longitudinal draw ratio: 5.0 times Lateral draw temperature: 140-170°C
Lateral draw ratio: 10.0 times

When the food packaging film of the example was used, it was possible to obtain a food package having sufficient water vapor barrier properties and transparency, as well as having an excellent balance between heat-sealing properties and antistatic properties.

100 food packaging film 101 biaxially stretched film layer 103 heat seal layer 105 surface layer

Claims (11)

A film for packaging food,
a biaxially stretched film layer comprising a propylene polymer;
a heat seal layer provided on one side of the biaxially stretched film layer;
with
According to JIS K7127 (1999), measured using a tensile tester under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min, the MD direction tensile of the food packaging film A food packaging film having a total value (T ₁ +T ₂ ) of an elastic modulus T ₁ and a tensile elastic modulus T ₂ in the TD direction of 3000 MPa or more and 6000 MPa or less. In the food packaging film according to claim 1,
A food packaging film, wherein the difference (T ₂ −T ₁ ) between the tensile elastic modulus T ₂ in the TD direction and the tensile elastic modulus T ₁ in the MD direction of the food packaging film is 2250 MPa or less. In the food packaging film according to claim 1 or 2,
A food packaging film having _a tensile elastic modulus T1 in the MD direction of 1000 MPa or more and 2500 MPa or less. In the food packaging film according to any one of claims 1 to 3,
A food packaging film having a thermal shrinkage of 4.5% or less in the TD direction when heat-treated at 120° C. for 15 minutes. In the food packaging film according to any one of claims 1 to 4,
When the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction of the food packaging film after heat treatment at 120 ° C. for 15 minutes are respectively X _TD [%] and X _MD [%],
A food packaging film having an X _TD -X _MD of -5.0% or more and 5.0% or less. In the food packaging film according to any one of claims 1 to 5,
A food packaging film further comprising a surface layer on the surface of the biaxially stretched film layer opposite to the surface provided with the heat seal layer. In the food packaging film according to claim 6,
The food packaging film, wherein the surface layer comprises one or more selected from homopolypropylene and random copolymers of propylene and α-olefins having 2 to 10 carbon atoms. In the food packaging film according to any one of claims 1 to 7,
The food packaging film, wherein the heat seal layer is provided so as to be in direct contact with the one surface of the biaxially stretched film layer. In the food packaging film according to any one of claims 1 to 8,
Food packaging film used for outer packaging bags. In the food packaging film according to any one of claims 1 to 9,
A food packaging film in which the heat seal layer contains one or more selected from homopolypropylene and random copolymers of propylene and α-olefins having 2 to 10 carbon atoms. A food package using the food packaging film according to any one of claims 1 to 10.

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