Food packaging film and food packaging body

Abstract

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 (T+T) of a tension elastic modulus Tin a MD direction and a tension elastic modulus Tin 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

Description

[Technical Field]

[0001] The present invention relates to a food packaging film and a food package. [Background technology]

[0002] Biaxially oriented polypropylene film (hereinafter referred to as OPP film) has an excellent balance of performance such as processability, water vapor barrier properties, transparency, mechanical strength, and rigidity, and is used as a packaging film for packaging food.

[0003] Examples of technologies relating to food packaging films using such OPP films include those described in Patent Document 1 (JP-A No. 2008-73926) and Patent Document 2 (JP-A No. 2004-82499).

[0004] Patent Document 1 describes a biaxially oriented multilayer polypropylene film characterized by having a layer of a propylene-α-olefin random copolymer (C) having a melting point in the range of 125 to 145°C on one side of a biaxially oriented 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), with a layer of a propylene-based polymer (B) having a melting point of 155°C or higher sandwiched therebetween, and a layer of a propylene-based polymer (E) on the other side of the biaxially oriented film. Patent Document 1 describes that a biaxially oriented multilayer polypropylene film having the above-described structure can inhibit the seepage of petroleum resins and the like onto the film surface, and has excellent lamination strength and moisture resistance.

[0005] Patent Document 2 describes a multilayer resin film that further comprises a polyvinyl alcohol resin layer via an adhesive layer on 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, and that has an oxygen permeability of 600 mL / m at a relative humidity of 85% RH and a temperature of 23°C. 2·day·MPa or less, and the water vapor permeability at a relative humidity of 90%RH and a temperature of 40°C is 3.5g / m 2 The multilayer resin film is characterized by a thickness of 20 μm or less. Patent Document 2 describes that a multilayer resin film having the above-described structure has excellent oxygen gas barrier properties and moisture resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-73926 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-82499 Summary of the Invention [Problem to be solved by the invention]

[0007] Although OPP film has sufficient water vapor barrier properties and transparency, it has high surface resistivity and poor antistatic properties. Therefore, when using OPP film for food packaging such as food packaging bags, it has been necessary to add an increased amount of antistatic agent. By adding an increased amount of antistatic agent to the OPP film, the surface resistivity of the resulting food packaging can be reduced, improving its antistatic properties. However, if the amount of antistatic agent added to OPP film is increased, the antistatic agent may bleed out onto the film surface, resulting in poor heat-sealing properties and a decrease in transparency. Therefore, there is room for improvement in OPP films used in food packaging in terms of improving antistatic properties while limiting the amount of antistatic agent added.

[0008] The present invention has been made in consideration of the above circumstances, and provides a food packaging film that can realize food packaging that has sufficient water vapor barrier properties and transparency, as well as an excellent balance of heat sealability and antistatic properties. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that by controlling the tensile modulus of a film within a specific range, it is possible to effectively reduce the surface resistivity of the film without increasing the amount of antistatic agent added, thereby obtaining a food package that has an excellent balance between heat-sealing properties and antistatic properties, thereby completing the present invention.

[0010] That is, according to the present invention, there are provided the food packaging film and food package shown below.

[0011] [1] A film for packaging food, comprising: a biaxially oriented film layer containing homopolypropylene; a heat seal layer provided on one surface of the biaxially stretched film layer; Equipped with a surface layer is further provided on the surface of the biaxially stretched film layer opposite to the surface on which the heat seal layer is provided, the surface layer comprises one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms, A food packaging film in which the sum of the tensile modulus of elasticity in the MD direction (T1) and the tensile modulus of elasticity in the TD direction (T2), measured in accordance with JIS K7127 (1999) using a tensile testing machine at a temperature of 23±2°C, 50±5% RH, and a pulling speed of 300 mm / min (T1+T2), is 3500 MPa or more and 5700 MPa or less. [2] In the food packaging film described in [1] above, The food packaging film has a difference (T2-T1) between the tensile modulus of elasticity T2 in the TD direction and the tensile modulus of elasticity T1 in the MD direction of the food packaging film of 2250 MPa or less. [3] In the food packaging film according to the above [1] or [2], The food packaging film has a tensile modulus of elasticity 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 rate in the TD direction of 4.5% or less when heated at 120°C for 15 minutes. [5] In the food packaging film according to any one of [1] to [4] above, The heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the above food packaging film when heated at 120°C for 15 minutes are respectively X and TD [%] and X MD When set to [%], X TD -X MD Food packaging film with a modulus of elasticity of -5.0% or more and 5.0% or less. [6 ] above Notes [1] to [ 5

[0023] In the food packaging film according to any one of

[0024] 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 oriented film layer. [7] Above [1] to [ 6

[0023] In the food packaging film according to any one of

[0024] Food packaging film used for outer packaging bags. [8] Above [1] to [ 7

[0023] In the food packaging film according to any one of

[0024] The food packaging film wherein the heat seal layer comprises one or more materials selected from the group consisting of homopolypropylene and random copolymers of propylene and an α-olefin having 2 to 10 carbon atoms. [ 9 ] Above [1] to [ 8 10. A food packaging product using the food packaging film according to any one of the preceding claims. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a food packaging film that can realize a food package having sufficient water vapor barrier properties and transparency, as well as an excellent balance of heat sealability and antistatic properties. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of the structure of a food packaging film according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of the structure of a food packaging film according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic diagrams and do not correspond to the actual dimensional ratios. Note that "~" between numbers in the text indicates "above" to "below" unless otherwise specified.

[0015] <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 of this embodiment is a film for packaging food, and comprises a biaxially oriented film layer 101 containing a propylene polymer and a heat seal layer 103 provided on one side of the biaxially oriented film layer 101. The total value (T1+T2) of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 of the food packaging film 100 is 3000 MPa or more and 6000 MPa or less, as measured using a tensile tester in accordance with JIS K7127 (1999) at a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 300 mm / min.

[0016] As mentioned above, although OPP film has sufficient water vapor barrier properties and transparency, it has high surface resistivity and poor antistatic properties. Therefore, when using OPP film for food packaging such as food packaging bags, it has been necessary to increase the amount of antistatic agent added. By increasing the amount of antistatic agent added to the OPP film, the surface resistivity of the resulting food packaging can be reduced, improving its antistatic properties. However, if the amount of antistatic agent added to OPP film is increased, the antistatic agent may bleed out onto the film surface, resulting in poor heat-sealing properties and a decrease in transparency. Therefore, there is room for improvement in OPP films used in food packaging in terms of improving antistatic properties while limiting the amount of antistatic agent added.

[0017] The present inventors have conducted extensive research to solve the above problems, and as a result, have found that by controlling the tensile modulus of food packaging film 100 including biaxially oriented film layer 101 containing a propylene polymer within the above range, the surface resistivity of the film can be effectively reduced without increasing the amount of antistatic agent added, and as a result, a food package having an excellent balance of heat sealability and antistatic properties can be obtained. Here, it is not entirely clear why controlling the tensile modulus of the food packaging film 100 within the above range can effectively reduce the surface resistivity of the film without increasing the amount of antistatic agent added, but it is presumed that this is because the food packaging film 100 has moderate elasticity, making it easier for charges on the film surface to move. That is, the food packaging film 100 according to this embodiment includes a biaxially oriented film layer containing a propylene polymer and has a specific tensile modulus, thereby realizing a food package that has sufficient water vapor barrier properties and transparency, as well as an excellent balance of heat sealability and antistatic properties. Furthermore, the food packaging film 100 according to this embodiment has excellent surface antistatic properties. This improves the printability of the surface of the food package and also prevents dust and other foreign matter from adhering to the surface of the food package. As described above, according to this embodiment, a food packaging film 100 can be provided that can realize food packaging that has sufficient water vapor barrier properties and transparency, and also has an excellent balance of heat sealing properties and antistatic properties.

[0018] Here, food packages produced using the food packaging film 100 according to this embodiment exhibit sufficient water vapor barrier properties, and are therefore particularly suitable for use as films constituting food packages for packaging foods (e.g., dried foods) that require water vapor barrier properties but do not necessarily require oxygen barrier properties.

[0019] In the food packaging film 100 according to this embodiment, the lower limit of the sum (T1+T2) of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 measured using a tensile tester in accordance with JIS K7127 (1999) at a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 300 mm / min is 3000 MPa or more, preferably 3500 MPa or more, and more preferably 4000 MPa or more. When the sum of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 (T1 + T2) is equal to or greater than the lower limit, the food packaging film 100 according to this embodiment can achieve a good balance between heat sealability, water vapor barrier property, and transparency. Furthermore, the food packaging film 100 according to this embodiment can have good stiffness, which can prevent film misalignment during heat sealing and prevent sealing defects. In other words, when the sum of the tensile modulus of elasticity T1 in the MD direction and the tensile modulus of elasticity T2 in the TD direction (T1 + T2) is equal to or greater than the above-mentioned lower limit, the food packaging film 100 of this embodiment can achieve a good balance between heat sealability, water vapor barrier properties, transparency, and packaging suitability.

[0020] Furthermore, in the food packaging film 100 according to this embodiment, the upper limit of the sum (T1+T2) of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 measured in accordance with JIS K7127 (1999) 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 is 6000 MPa or less, more preferably 5800 MPa or less, and even more preferably 5700 MPa or less. When the sum of the tensile modulus of elasticity T1 in the MD direction and the tensile modulus of elasticity T2 in the TD direction (T1 + T2) is below the above upper limit value, the surface resistivity of the food packaging film 100 of this embodiment can be effectively reduced without increasing the amount of antistatic agent added, and as a result, the antistatic properties of the food packaging film 100 can be improved while maintaining good heat sealing properties.

[0021] In the food packaging film 100 according to this embodiment, the difference (T2-T1) between the tensile modulus of elasticity T2 in the TD direction and the tensile modulus of elasticity T1 in the MD direction is preferably 2250 MPa or less, more preferably 2200 MPa or less. When the difference (T2-T1) between the tensile modulus T2 in the TD direction and the tensile modulus T1 in the MD direction is less than the above upper limit, the antistatic properties of the food packaging film 100 can be improved while suppressing thermal shrinkage, and as a result, misalignment of the seal within the food packaging, the occurrence of wrinkles within the food packaging, and damage to the food packaging itself can be more effectively suppressed. In the food packaging film 100 according to this embodiment, the lower limit of the difference (T2-T1) between the tensile modulus of elasticity in the TD direction T2 and the tensile modulus of elasticity in the MD direction T1 is not particularly limited, but is, for example, 1200 MPa or more.

[0022] In the food packaging film 100 according to this embodiment, the lower limit of the tensile modulus T1 in the MD direction is preferably 1000 MPa or more, more preferably 1100 MPa or more, and even more preferably 1200 MPa or more. When the tensile modulus T1 in the MD direction is equal to or greater than the lower limit, the food packaging film 100 according to this embodiment can have a better balance of heat sealability, water vapor barrier property, and transparency. Furthermore, the stiffness of the food packaging film 100 according to this embodiment can be improved, which in turn can prevent the film from shifting position during heat sealing, thereby further preventing the occurrence of sealing defects. In other words, when the tensile modulus T1 in the MD direction is equal to or greater than the above lower limit, the food packaging film 100 according to this embodiment can achieve an even better balance of heat sealability, water vapor barrier properties, transparency, and packaging suitability. In the food packaging film 100 according to this embodiment, the upper limit of the tensile modulus T1 in the MD direction is preferably 2500 MPa or less, more preferably 1800 MPa or less, and even more preferably 1750 MPa or less. When the tensile modulus T1 in the MD direction is below the above upper limit, the surface resistivity of the food packaging film 100 according to this embodiment can be reduced more effectively without increasing the amount of antistatic agent added, thereby further improving the antistatic properties of the food packaging film 100.

[0023] The tensile modulus of the food packaging film 100 according to this embodiment can be achieved, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101 and the conditions during the stretching process, as well as by adjusting the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105. More specifically, the elastic modulus can be adjusted by appropriately adjusting the presence or absence and ratio of functional groups copolymerized in the propylene polymer contained in the biaxially stretched film layer 101, the stretching ratio during stretching treatment, the temperature during stretching, the temperature and time of heat treatment, etc., thereby adjusting the elastic modulus and thereby adjusting the tensile elastic modulus of the food packaging film 100.

[0024] In the food packaging film 100 according to this embodiment, the thermal shrinkage rate in the TD direction when heated at 120° C. for 15 minutes is preferably 4.5% or less, and more preferably 4.2% or less. This makes it possible to more effectively prevent the seals in the food packaging from shifting out of position, the occurrence of wrinkles in the food packaging, and damage to the food packaging itself. Such a heat shrinkage rate can be achieved, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101, the tensile modulus of the food packaging film 100, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, etc.

[0025] In the food packaging film 100 according to this embodiment, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction when heat-treated at 120°C for 15 minutes are respectively X TD [%] and X MD When set to [%], 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, even more preferably −3.5% or more and 2.0% or less, and particularly preferably −3.0% or more and 1.0% or less. X TD -X MD When the thickness is within the above range, it is possible to more effectively prevent displacement of the seal portion within the food package, the occurrence of wrinkles within the food package, and damage to the food package itself. Such an X TD -X MD This can be achieved, for example, by adjusting the type and content of the propylene polymer contained in the biaxially stretched film layer 101, the tensile modulus of the food packaging film 100, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, etc. In addition, X of the food packaging film 100 according to this embodiment TD [%] and X MD [%] is calculated using the following method. First, a 10 cm x 10 cm test piece 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 in the TD direction of the test piece after heat treatment is TD1 [cm] and the length in the MD direction of the test piece after heat treatment is MD1 [cm], X TD [%] is calculated by 100×(10-TD1) / 10, where X MD [%] is calculated by 100×(10-MD1) / 10.

[0026] Food packages produced using the food packaging film 100 according to this embodiment have sufficient water vapor barrier properties. From the viewpoint of stably obtaining food packages with excellent water vapor barrier properties, the food packaging film 100 is required to have a water vapor permeability of 8.0 g / (m 2 ) or more as measured by the following method. 2 24h) or less, and 7.0g / (m 2 24h) or less is more preferable, and 6.5g / (m 2 It is particularly preferable that the time is 24 hours or less. (Measurement method) The food packaging film 100 is folded back so that the heat seal layer 103 faces inward, and the two sides are heat sealed to form a bag. Calcium chloride is then placed inside as the contents. 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 at 40°C and 90% RH for 72 hours. The weight of the calcium chloride is measured before and after storage, and the difference is used to determine the water vapor permeability (g / (m 2 Calculate the time (24h). Such a water vapor permeability can be achieved, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101, the tensile modulus of the food packaging film 100, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, etc.

[0027] The food packaging film 100 according to this embodiment has excellent heat sealability. To further improve the seal strength of a food package produced using the food packaging film 100, the heat seal strength of the portion where the heat seal layers 103 of the food packaging film 100 are heat-sealed together under conditions of 115°C, a pressure of 1.0 kgf, and a sealing time of 0.5 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. 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 together at 115°C, a pressure of 1.0 kgf, and a sealing time of 0.5 seconds to obtain a laminated film. Next, the two food packaging films 100 are peeled together at a width of 15 mm, a 90-degree peel angle, and a peel speed of 300 mm / min, and the peel strength at this point is taken as the heat seal strength. Such heat seal strength can be achieved by adjusting, for example, the tensile modulus of the food packaging film 100, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

[0028] In the food packaging film 100 according to this 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%, and more preferably less than 2.0%. Such haze can be achieved by adjusting, for example, the type and content of the propylene polymer contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

[0029] Furthermore, in order to improve the antistatic properties of both surfaces of the food packaging film 100 according to this embodiment, a sample was stored at 20±2°C and 50±5% RH for 24 hours or more using a digital ultra-high resistance microcurrent meter in accordance with JIS C2139, and the surface resistivity of the sample was measured to be 1.0×10 14 Ω or less is preferable, and 5.0×10 13 Ω or less is more preferable, and 5.0×1012 It is particularly preferable that it is Ω or less. Such a surface resistivity can be achieved by adjusting, for example, the tensile modulus of the food packaging film 100, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

[0030] The thickness of the food packaging film 100 according to this embodiment is not particularly limited, but can be set arbitrarily depending on the desired objectives such as water vapor barrier properties, cost, mechanical strength, transparency, etc., and is not particularly limited, but is usually 5 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less, and 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 balance of bag-making properties, mechanical properties, handling properties, appearance, transparency, moldability, light weight, and the like is better.

[0031] Each layer that constitutes the food packaging film 100 will be described below.

[0032] [Biaxially stretched film layer] The biaxially stretched film layer 101 according to this embodiment is formed, for example, by biaxially stretching a film made of a resin composition (P) containing a propylene polymer.

[0033] The biaxially stretched film layer 101 according to this embodiment may be a single layer, or may be a laminate of multiple layers made of the resin composition (P), but it is necessary that it is biaxially stretched.

[0034] In addition, in the food packaging film 100, the ratio of the thickness of the biaxially oriented film layer 101 to the total thickness of the food packaging film 100 is preferably 0.50 or more and 0.998 or less, more preferably 0.60 or more and 0.99 or less, even more preferably 0.70 or more and 0.97 or less, and particularly preferably 0.75 or more and 0.95 or less.

[0035] (propylene polymer) The resin composition (P) according to this embodiment, i.e., the biaxially stretched film layer 101, contains a propylene polymer, which makes it possible to obtain a biaxially stretched film layer 101 that has 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 this embodiment include homopolypropylene and copolymers of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms. Examples of the α-olefin 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, and 1-eicosene. 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, and more preferably 2 mol % or less, when the entire propylene polymer is taken as 100 mol %. 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 preferred as the propylene polymer from the viewpoint of obtaining a biaxially stretched film layer 101 with a better balance of properties such as heat resistance, water vapor barrier properties, mechanical properties, and rigidity. In the homopolypropylene of this embodiment, when the total content of the structural units constituting the homopolypropylene is taken as 100 mol %, the content of structural units derived from propylene is 99.0 mol % or more, preferably 99.5 mol % or more, more preferably 99.9 mol % or more, and particularly preferably 100.0 mol %.

[0036] The propylene polymer according to the present embodiment can be produced by various methods, for example, by using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0037] The melting point of the propylene polymer according to this embodiment is preferably in the range of 150°C or higher and 170°C or lower, more preferably 155°C or higher and 168°C or lower, from the viewpoint of achieving a better balance between heat resistance, transparency, mechanical properties, rigidity, flowability, moldability, and the like.

[0038] The melt flow rate (MFR) of the propylene polymer according to the present embodiment, measured in accordance with ASTM D1238 under conditions of 230°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 20 g / 10 min or less, more preferably 10 g / 10 min or less, and even more preferably 7 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0039] (Polyolefin) The resin composition (P) according to this embodiment may further contain a polyolefin other than the propylene polymer. By adding a polyolefin having a different modulus of elasticity from the propylene polymer to the resin composition (P), the tensile modulus of elasticity of the food packaging film 100 according to this embodiment can be adjusted. Examples of polyolefins according to the present embodiment include polyethylenes 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.

[0040] The melting point of the polyethylene according to this embodiment is preferably in the range of 95°C or higher and 135°C or lower, more preferably 100°C or higher and 130°C or lower, from the viewpoint of achieving a better balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, etc.

[0041] The density of the polyethylene according to this embodiment is 900 kg / m from the viewpoint of achieving a better balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, and the like. 3 More than 965kg / m 3 Preferably less than 900 kg / m 3 More than 940kg / m 3 The following is more preferable: Here, the density of the polyethylene according to this embodiment can be measured in accordance with JIS K7112 (1999).

[0042] The melt flow rate (MFR) of the polyethylene according to the present embodiment, measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0043] The method for producing the polyethylene according to the present embodiment is not particularly limited, and the polyethylene can be produced by a known method. In addition, commercially available polyethylene may be used.

[0044] In order to further improve the balance between the heat sealability and antistatic properties of the food packaging film 100, the lower limit of the content of polyethylene contained in the resin composition (P) of this embodiment, i.e., the biaxially oriented film layer 101, is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, and particularly preferably 3.0% by mass or more, when the total amount of the propylene polymer and polyethylene contained in the biaxially oriented film layer 101 is taken as 100% by mass. Furthermore, the upper limit of the polyethylene content in the resin composition (P) according to this embodiment, i.e., the biaxially oriented film layer 101, is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less, when the total amount of the propylene polymer and polyethylene contained in the biaxially oriented film layer 101 is taken as 100% by mass, from the viewpoint of suppressing a decrease in the bending elasticity of the food packaging film 100 and further improving the heat sealability, water vapor barrier properties, transparency, etc.

[0045] The total content of the propylene polymer and polyethylene contained in the resin composition (P) according to this embodiment, i.e., the biaxially stretched film layer 101, is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, even 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, when the entire resin composition (P) is taken as 100% by mass. This makes it possible to achieve a better balance of water vapor barrier properties, mechanical properties, handleability, appearance, transparency, moldability, heat sealability, antistatic properties, etc.

[0046] (Other ingredients) If necessary, various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slipping agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers may be added to the resin composition (P) according to this embodiment, provided that the object of this embodiment is not impaired.

[0047] (Method for preparing resin composition (P)) The resin composition (P) according to this embodiment can be prepared, for example, by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heated roll, or the like.

[0048] [Heat seal layer] The food packaging film 100 according to this embodiment has a heat seal layer 103 on at least one side of the biaxially oriented film layer 101 to provide heat sealability. The heat seal layer 103 may be provided on both sides of the biaxially oriented film layer 101. In addition, from the viewpoint of improving the heat sealability of the food packaging film 100, the heat seal layer 103 is preferably provided as the outermost layer of the food packaging film 100 according to this embodiment.

[0049] Moreover, the heat seal layer 103 is preferably provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. This allows the manufacturing process of the food packaging film 100 to be simplified.

[0050] In the food packaging film 100, the thickness of the heat seal layer 103 is preferably 0.1 μm to 10 μm, more preferably 0.2 μm to 9 μm, even more preferably 0.5 μm to 8 μm, and particularly preferably 1 μm to 8 μm. 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. Furthermore, by having the thickness of the heat seal layer 103 be equal to or less than the above upper limit, the adhesion to the biaxially oriented film layer 101 is improved, making it easier to laminate the heat seal layer 103 onto the biaxially oriented film layer 101 without using an adhesive. That is, since it is easy to provide the heat seal layer 103 so that it is 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 this embodiment, when the heat seal layer 103 is provided on both sides of the biaxially stretched film layer 101, the above thickness of the heat seal layer 103 indicates the thickness of the heat seal layer 103 provided on one side of the biaxially stretched film layer 101.

[0051] In the food packaging film 100, the heat seal layer 103 provided on one side is preferably a single layer, which can further simplify the manufacturing process of the food packaging film 100.

[0052] Furthermore, the heat seal layer 103 is preferably formed by biaxially stretching simultaneously with the biaxially stretched film layer 101 in a state before biaxial stretching. This allows the food packaging film 100 to be produced using a molding method such as co-extrusion, i.e., a laminated film produced in a single molding operation, thereby further simplifying the manufacturing process for the food packaging film 100. Therefore, the heat seal layer 103 is preferably biaxially stretched.

[0053] (Polyolefin) The heat seal layer 103 according to this embodiment is made of, for example, a polyolefin-based resin composition (A) containing a 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 copolymers of propylene and α-olefins having from 2 to 10 carbon atoms; ethylene-vinyl acetate copolymer (EVA); and ionomer resins. Among these, the polyolefin constituting the heat seal layer 103 is preferably at least one selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms, as this has an excellent balance of adhesion to the biaxially oriented film layer 101, heat sealability, etc.

[0054] The propylene-α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and an α-olefin (however, the α-olefin does not include propylene), and examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. 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.

[0055] The melting point of the polyolefin constituting the heat seal layer 103 according to this embodiment is preferably in the range of 60° C. to 175° C., more preferably 65° C. to 170° C., and even more preferably 70° C. to 167° C. When the melting point of the polyolefin is equal to or higher than the lower limit, stickiness on the surface of the heat seal layer 103 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved. Furthermore, when the melting point of the polyolefin is equal to or lower than the upper limit, the heat sealability of the food packaging film 100 can be improved.

[0056] The melt flow rate (MFR) of the polyolefin constituting the heat seal layer 103 according to this embodiment, measured in accordance with ASTM D1238 at 230°C under a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 20 g / 10 min or less, more preferably 10 g / 10 min or less, and even more preferably 7 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0057] The content of polyolefin in the polyolefin resin composition (A) according to this embodiment, i.e., the heat seal layer 103, is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, even 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, when the entire polyolefin resin composition (A) is taken as 100% by mass. This allows for a better balance between adhesion to the biaxially stretched film layer 101, heat sealability, etc.

[0058] (Other ingredients) If necessary, various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, etc. may be added to the polyolefin resin composition (A) constituting the heat seal layer 103 according to this embodiment, within a range that does not impair the object of this embodiment.

[0059] (Method for preparing polyolefin resin composition (A)) The polyolefin resin composition (A) according to the present embodiment can be prepared, for example, by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heated roll, or the like.

[0060] [Surface layer] In order to improve the printability of the surface, the food packaging film 100 of this embodiment preferably further comprises a surface layer 105 on the side of the biaxially oriented film layer 101 opposite to the side on which the heat seal layer 103 is provided, as shown in Figure 2. 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 this embodiment.

[0061] Moreover, it is preferable that the surface layer 105 is provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. This simplifies the manufacturing process of the food packaging film 100.

[0062] In the food packaging film 100, the thickness of the surface layer 105 is preferably 0.1 μm to 10 μm, more preferably 0.2 μm to 9 μm, even more preferably 0.5 μm to 8 μm, and particularly preferably 1 μm to 8 μm. 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 equal to or greater than the above lower limit, the printability of the food packaging film 100 can be further improved. Furthermore, by having the thickness of the surface layer 105 be equal to or less than the above upper limit, the adhesion to the biaxially stretched film layer 101 is improved, making it easier to laminate the surface layer 105 onto the biaxially stretched film layer 101 without using an adhesive. That is, since it is easy to provide the surface layer 105 so that it is 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.

[0063] In the food packaging film 100, the surface layer 105 is preferably a single layer, which can further simplify the manufacturing process of the food packaging film 100.

[0064] Furthermore, it is preferable that the surface layer 105 is formed by biaxial stretching simultaneously with the biaxially stretched film layer 101 in a state before biaxial stretching. This allows the food packaging film 100 to be produced by a molding method such as co-extrusion, i.e., using a laminated film produced in a single molding operation, thereby further simplifying the manufacturing process for the food packaging film 100. Therefore, it is preferable that the surface layer 105 is biaxially stretched.

[0065] The surface layer 105 may be subjected to a surface treatment in order to improve the printability of the food packaging film 100. Specifically, the surface layer 105 may be subjected to a surface activation treatment such as a corona treatment, a flame treatment, a plasma treatment, a primer coating treatment, or an ozone treatment.

[0066] (Polyolefin) The surface layer 105 according to this embodiment is made of, for example, a polyolefin-based resin composition (B) containing a 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; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; polypropylene; random copolymers of propylene and α-olefins having from 2 to 10 carbon atoms; ethylene-vinyl acetate copolymer (EVA); and ionomer resins. Among these, the polyolefin constituting the surface layer 105 is preferably at least one selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms, as this has an excellent balance of adhesion to the biaxially oriented film layer 101, printability, etc.

[0067] The propylene-α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and an α-olefin (however, the α-olefin does not include propylene), and examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. 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.

[0068] The melting point of the polyolefin constituting the surface layer 105 according to this embodiment is preferably in the range of 90° C. to 175° C., more preferably 95° C. to 170° C., and even more preferably 100° C. to 167° C. When the melting point of the polyolefin is equal to or higher than the 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.

[0069] The melt flow rate (MFR) of the polyolefin constituting the surface layer 105 according to this embodiment, measured in accordance with ASTM D1238 at 230°C under a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 20 g / 10 min or less, more preferably 10 g / 10 min or less, and even more preferably 7 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0070] The content of polyolefin in the polyolefin resin composition according to this embodiment, i.e., the surface layer 105, is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, even 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, when the entire polyolefin resin composition (B) is taken as 100% by mass. This allows for a better balance of adhesion to the biaxially stretched film layer 101, printability, etc.

[0071] (Other ingredients) If necessary, various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, etc. may be added to the polyolefin resin composition (B) constituting the surface layer 105 of this embodiment, within a range that does not impair the object of this embodiment.

[0072] (Method for preparing polyolefin resin composition (B)) The polyolefin resin composition (B) according to the present embodiment can be prepared, for example, by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0073] <Method of manufacturing food packaging film> The food packaging film 100 of this embodiment can be obtained, for example, by co-extrusion molding a resin composition (P) for forming the biaxially stretched film layer 101, a polyolefin-based resin composition (A) for forming the heat seal layer 103, and, if necessary, a polyolefin-based resin composition (B) for forming the surface layer 105 into a film-like laminated film, and then biaxially stretching the laminated film using a known biaxially stretched film manufacturing method such as a simultaneous biaxial stretching method or a sequential biaxial stretching method. The molding apparatus and molding conditions are not particularly limited, and conventionally known molding apparatus and molding conditions can be used. Examples of molding apparatus that can be used include a multilayer T-die extruder and a multilayer inflation molding machine. For biaxial stretching conditions, for example, known OPP film production conditions can be used. More specifically, in the sequential biaxial stretching method, the longitudinal stretching temperature may be 100°C to 145°C, the longitudinal stretching ratio may be 4.5 to 6 times, the transverse stretching temperature may be 130°C to 190°C, and the transverse stretching ratio may be 9 to 11 times. In addition, the food packaging film 100 of this embodiment can also be obtained by separately molding the biaxially oriented film layer 101, the heat seal layer 103, and optionally the surface layer 105, and then laminating and heat molding these.

[0074] <Applications of food packaging film> 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 this embodiment is, for example, a packaging bag used for containing food, or a bag containing food. Furthermore, the food package according to this embodiment may use the food packaging film 100 in part, or the food packaging film 100 may be used for the entire food package, depending on the application.

[0075] The food packaging film 100 according to this embodiment is preferably used for outer packaging bags, which particularly require water vapor barrier properties, transparency, and antistatic properties. Furthermore, when the food packaging film 100 according to this embodiment is used in an integrated package consisting of food, individual packaging bags for individually packaging the food, and an outer packaging bag for packaging a plurality of the individual packaging bags, the food packaging film 100 is preferably used in the outer packaging bag, which is particularly required to have water vapor barrier properties, transparency, and antistatic properties in the integrated package, thereby making it possible to obtain an integrated package with sufficient water vapor barrier properties, transparency, and antistatic properties.

[0076] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted. The following is a reference form. [1] A film for packaging food, comprising: a biaxially oriented film layer comprising a propylene polymer; a heat seal layer provided on one surface of the biaxially stretched film layer; Equipped with The tensile modulus T of the food packaging film in the MD direction is measured using a tensile tester in accordance with JIS K7127 (1999) at a temperature of 23±2°C, 50±5% RH, and a tension speed of 300 mm / min. 1 and tensile modulus in the TD direction T 2 The sum of (T 1 +T 2 ) is 3000MPa or more and 6000MPa or less. [2] In the food packaging film described in [1] above, The tensile modulus T of the food packaging film in the TD direction 2 and tensile modulus in MD direction T 1 The difference between (T 2 -T 1 ) is 2250MPa or less. [3] In the food packaging film according to the above [1] or [2], The tensile modulus T of the food packaging film in the MD direction 1 Food packaging film having a compressive strength 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 rate in the TD direction of 4.5% or less when heated at 120°C for 15 minutes. [5] In the food packaging film according to any one of [1] to [4] above, The heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the above food packaging film when heated at 120°C for 15 minutes are respectively X and TD [%] and X MD When set to [%], X TD -X MD Food packaging film with a modulus of elasticity 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, The food packaging film further comprises a surface layer on the side of the biaxially oriented film layer opposite to the side on which the heat seal layer is provided. [7] In the food packaging film described in [6] above, The surface layer is a food packaging film containing one or more materials selected from the group consisting of homopolypropylene and random copolymers of propylene and an α-olefin 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 oriented 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, The food packaging film wherein the heat seal layer comprises one or more materials selected from the group consisting of homopolypropylene and random copolymers of propylene and an α-olefin having 2 to 10 carbon atoms.

[11] A food packaging product using the food packaging film according to any one of [1] to

[10] above. [Example]

[0077] The present embodiment will be described in detail below with reference to examples and comparative examples, but the present embodiment is not limited to the descriptions of these examples.

[0078] 1.Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Polypropylene PP1: Homopolypropylene (MFR: 3 g / 10 min, 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) PP4: Homopolypropylene (MFR: 3.5 g / 10 min, 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) Additives A1: Anti-blocking agent

[0079] 2. Measurement and evaluation methods (1) MFR of polypropylene Measured in accordance with ASTM D1238 at 230°C under a load of 2.16 kg.

[0080] (2) MFR of polyethylene Measured in accordance with ASTM D1238 at 190°C under a load of 2.16 kg.

[0081] (3) Melting points of polypropylene and polyethylene The temperatures of the maximum melting peaks in the DSC curves of polypropylene and polyethylene obtained using a DSC (differential scanning calorimeter) were taken as the melting points.

[0082] (4) Tensile modulus Test pieces measuring 15 mm x 15 cm were cut out from the food packaging films obtained in the Examples and Comparative Examples. The MD and TD tensile moduli T1 and T2 of the test pieces were measured in accordance with JIS K7127 (1999) using a tensile tester manufactured by Orientec Co., Ltd., at a temperature of 23±2°C, 50±5% RH, and a pulling rate of 300 mm / min.

[0083] (5) Heat shrinkage rate Test pieces measuring 10 cm x 10 cm were cut out from the food packaging films obtained in the Examples and Comparative Examples. Then, the test pieces were heat-treated at 120°C for 15 minutes. Next, when the length in the TD direction of the test piece after the heat treatment is TD1 [cm] and the length in the MD direction of the test piece after the heat treatment is MD1 [cm], X TD [%] is calculated by 100 × (10-TD1) / 10, and X MD [%] was calculated by 100 × (10-MD1) / 10.

[0084] (6) Transparency The haze of the food packaging films obtained in the 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. Next, the transparency of the food packaging film was evaluated according to the following criteria. ◎◎: Haze less than 2.0% ◎: Haze is 2.0% or more and less than 2.5% Good: Haze is 2.5% or more and less than 3.0% ×: Haze is 3.0% or more

[0085] (7) Antistatic The surface resistivity of the heat seal layer side of the food packaging films obtained in the Examples and Comparative Examples was measured using a digital ultra-high resistance microcurrent meter (manufactured by Advantest Corporation, product name: 8340A) in accordance with JIS C2139. The measurement conditions were as follows: Measurement conditions: After storing for 24 hours or more at 20±2°C and 50±5% RH, measure under the conditions of 20±2°C and 50±5% RH Next, the antistatic properties of the food packaging films were evaluated according to the following criteria. ◎◎: Surface resistivity is 5.0×10 12 Ω or less ◎: Surface resistivity is 5.0×10 12 Ω exceeded 5.0×10 13 Ω or less 〇: Surface resistivity is 5.0×10 13 Ω exceeded 1.0×10 14 Ω or less ×: Surface resistivity is 1.0×10 14 Exceeding Ω

[0086] (8) Water vapor barrier properties The food packaging films obtained in the Examples and Comparative Examples were folded over so that the heat-sealable layer was on the inside, and the two sides were heat-sealed to form a bag. Calcium chloride was then placed inside as the contents. The other side was then heat-sealed to form a bag with a surface area of 0.01 m. 2 The bags were then stored at 40°C and 90% RH for 72 hours. The weight of the calcium chloride was measured before and after storage, and the difference in weight was used to determine the water vapor permeability (g / (m 2 ·24h)) were calculated respectively. Next, the water vapor barrier properties of the food packaging films were evaluated according to the following criteria. ◎◎: Water vapor permeability is 6.5g / (m 2 ·24h) or less ◎: Water vapor permeability is 6.5g / (m 2 ·24h) Excess 8.0g / (m 2 ·24h) or less 〇: Water vapor permeability is 8.0g / (m 2 ·24h) Excess 10.0g / (m 2 ·24h) or less ×: Water vapor permeability is 10.0 g / (m 2 ·24h) exceeded

[0087] (9) Heat sealability The heat-sealed layers of two 15mm-wide pieces of food packaging film were heat-sealed together at 115°C, a pressure of 1.0 kgf, and a sealing time of 0.5 seconds to obtain a laminated film. The two food packaging films were then peeled together at a 90-degree angle with a 15mm width and a peel speed of 300 mm / min, and the peel strength measured at this point was recorded as the heat-seal strength. Next, the heat sealability of the food packaging film was evaluated according to the following criteria. ◎◎: Heat seal strength is 3.5N / 15mm or more ◎: Heat seal strength is 2.5N / 15mm or more and less than 3.5N / 15mm Good: Heat seal strength is 1.0N / 15mm or more and less than 2.5N / 15mm ×: Heat seal strength is less than 1.0N / 15mm

[0088] [Examples 1 to 5 and Comparative Example 1] Each layer was co-extruded and then biaxially stretched to produce food packaging films, each with the layer structure shown in Table 1, and each evaluation was performed. The co-extrusion conditions and biaxial stretching conditions were as follows: Multi-layer extrusion molding machine: 60 mmφ multi-layer T-die extrusion molding machine (L / D=27, manufactured by Screw Seiki Co., Ltd.) Extrusion temperature setting: 200-250℃, processing speed: 13.5m / min Longitudinal stretching temperature: 110-120℃ Longitudinal stretching ratio: 5.0 times Lateral stretching temperature: 140~170℃ Lateral stretching ratio: 10.0 times

[0089] [Table 1]

[0090] When the food packaging films of the Examples were used, food packages were obtained that had sufficient water vapor barrier properties and transparency, as well as an excellent balance of heat sealability and antistatic properties. [Explanation of symbols]

[0091] 100 Food packaging film 101 Biaxially oriented film layer 103 Heat seal layer 105 Surface layer

Claims

1. A food packaging film for packaging food, a biaxially oriented film layer containing homopolypropylene and a polyolefin different from the homopolypropylene; a heat seal layer provided on one surface of the biaxially stretched film layer; Equipped with a surface layer is further provided on the surface of the biaxially stretched film layer opposite to the surface on which the heat seal layer is provided, the surface layer comprises one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having from 2 to 10 carbon atoms, The tensile modulus T of the food packaging film in the MD direction 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. １ and the tensile modulus in the TD direction T ２ The sum of (T １ +T ２ ) is 3500 MPa or more and 5700 MPa or less, The heat shrinkage rate of the food packaging film in the TD direction when heated at 120°C for 15 minutes is 4.5% or less, A food packaging film, wherein the ratio of the thickness of the biaxially stretched film layer to the total thickness of the food packaging film is 0.50 or more and 0.998 or less.

2. A food packaging film for packaging food, a biaxially oriented film layer containing homopolypropylene and a polyolefin different from the homopolypropylene; a heat seal layer provided on one surface of the biaxially stretched film layer; Equipped with a surface layer is further provided on the surface of the biaxially stretched film layer opposite to the surface on which the heat seal layer is provided, the surface layer comprises one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having from 2 to 10 carbon atoms, The tensile modulus T of the food packaging film in the MD direction 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. １ and the tensile modulus in the TD direction T ２ The sum of (T １ +T ２ ) is 3500 MPa or more and 5700 MPa or less, The heat shrinkage rate of the food packaging film in the TD direction and the MD direction when heated at 120°C for 15 minutes was determined as X ＴＤ [%] and X ＭＤ When set to [%], X ＴＤ -X ＭＤ is -5.0% or more and 5.0% or less, A food packaging film, wherein the ratio of the thickness of the biaxially stretched film layer to the total thickness of the food packaging film is 0.50 or more and 0.998 or less.

3. The food packaging film according to claim 1 or 2, The tensile modulus T of the food packaging film in the TD direction ２ and tensile modulus in the MD direction T １ The difference between (T ２ -T １ ) is 2250 MPa or less.

4. The food packaging film according to any one of claims 1 to 3, The tensile modulus T of the food packaging film in the MD direction １ A food packaging film having a compressive strength of 1000 MPa or more and 2500 MPa or less.

5. The food packaging film according to any one of claims 1 to 4, The heat seal layer is provided so as to be in direct contact with the one surface of the biaxially oriented film layer.

6. The food packaging film according to any one of claims 1 to 5, Food packaging film used for outer packaging bags.

7. The food packaging film according to any one of claims 1 to 6, The heat seal layer of the food packaging film comprises one or more materials selected from the group consisting of homopolypropylene and random copolymers of propylene and an α-olefin having from 2 to 10 carbon atoms.

8. A food packaging product using the food packaging film according to any one of claims 1 to 7.

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