Food packaging film and food packaging bag

Abstract

Provided are a food packaging film and a food packaging bag excellent in heat sealability. The packaging film according to the present invention comprises a first resin layer (11) and a second resin layer (12) positioned on one surface (11a) of the first resin layer (11). The first resin layer (11) is the outermost layer. The first resin layer (11) contains an ethylene-propylene-butene copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide (11p). The second resin layer (12) contains a polyolefin-based homopolymer.

Description

Food packaging films and food packaging bags

[0001] This application claims priority to Japanese Patent Application No. 2024-013290, filed on January 31, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, a laminated film having a laminated structure in which calcium hydroxide is blended in the outermost layer on the side that becomes the innermost layer when formed into a bag has been known as a food packaging film for producing food packaging bags that maintain the freshness of fresh foods such as vegetables contained therein. Food packaging bags made using such laminated films can, due to the action of calcium hydroxide, prevent fresh foods contained in the food packaging bag from fermenting or spoiling due to bacteria.

[0003] Generally, food packaging bags are made by sealing predetermined locations of a food packaging film while it is being transported to form a bag. However, calcium hydroxide can fall off from the food packaging film due to external forces applied to the food packaging film during transport or sealing. When calcium hydroxide falls off, the food packaging bag is less likely to exhibit sufficient freshness-retaining properties. Furthermore, after fresh food is placed through the opening of the food packaging bag, external forces applied to the bag can also cause calcium hydroxide to fall off from the inner surface of the bag when the opening is sealed, and the fallen calcium hydroxide can become mixed into the fresh food as foreign matter.

[0004] Therefore, as a film that prevents calcium hydroxide from falling off, Patent Document 1 discloses a food packaging film in which an ethylene-propylene-butene copolymer is blended in the outermost layer containing calcium hydroxide.

[0005] Japanese Patent No. 7320234

[0006] However, the heat sealability of the food packaging film described in Patent Document 1 is not necessarily satisfactory. An object of the present invention is to provide a food packaging film and a food packaging bag that have excellent heat sealability.

[0007] The present invention has the following aspects. [1] A food packaging film comprising a first resin layer and a second resin layer located on one surface of the first resin layer, the first resin layer being an outermost layer, the first resin layer comprising an ethylene-propylene-butene copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide, and the second resin layer comprising a polyolefin-based homopolymer. [2] The food packaging film of [1], wherein the first resin layer comprises 9% by mass to 20% by mass of the polyolefin having a melting point of 120°C or less, relative to the total mass of the first resin layer. [3] The food packaging film of [1] or [2], further comprising a third resin layer located on the surface of the second resin layer opposite to the first resin layer, the third resin layer having a thickness of 0.01 μm to 10 μm. [4] The food packaging film of [3], wherein the third resin layer comprises a crystalline polyolefin-based resin having a melting point of 140°C or more. [5] The food packaging film according to any one of [1] to [4], wherein the first resin layer contains 0.1 mass % or more and 12 mass % or less of the calcium hydroxide relative to the total mass of the first resin layer. [6] A food packaging bag made of the food packaging film according to any one of [1] to [5], wherein the first resin layer is the innermost layer of the food packaging bag.

[0008] According to the present invention, a food packaging film and a food packaging bag having excellent heat-sealing properties can be provided.

[0009] 1 is a cross-sectional view schematically showing an example of a food packaging film of the present invention. FIG. 2 is a perspective view schematically showing an example of a food packaging bag of the present invention. FIG. 3 is a side view of the food packaging bag shown in FIG. 2, seen from the opening side.

[0010] An embodiment of a food packaging film and a food packaging bag according to the present invention will be described below in detail with appropriate reference to Figures 1 to 3. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional proportions of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the food packaging film and food packaging bag according to the present invention are not limited thereto and can be appropriately modified and implemented without departing from the spirit and scope of the present invention.

[0011] [Food packaging film] Figure 1 shows an example of a food packaging film of the present invention. Food packaging film 10 of this embodiment comprises a first resin layer 11, a second resin layer 12 located on one surface 11a of first resin layer 11, and a third resin layer 13 located on a surface 12a of second resin layer 12 opposite to first resin layer 11. That is, food packaging film 10 of this embodiment has a laminated structure in which second resin layer 12 is a central layer and first resin layer 11 and third resin layer 13 are located on opposing surfaces of second resin layer 12.

[0012] <First Resin Layer> The first resin layer 11 is located as the outermost layer of the food packaging film 10. The first resin layer 11 contains an ethylene-propylene-butene copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide 11p. In addition to the ethylene-propylene-butene copolymer, the polyolefin having a melting point of 120°C or less, and calcium hydroxide, the first resin layer 11 preferably further contains one or more resins selected from the group consisting of ethylene-propylene-butene copolymers, polyolefins having a melting point of 120°C or less (hereinafter also referred to as "other resins (I)"), erucic acid amide, and calcium stearate. The first resin layer 11 may further contain, as necessary, components other than the ethylene-propylene-butene copolymer, the polyolefin having a melting point of 120°C or less, calcium hydroxide, the other resins (I), erucic acid amide, and calcium stearate (hereinafter also referred to as "optional components (I)"), as long as the effects of the present invention are not impaired.

[0013] (Ethylene-Propylene-Butene Copolymer) Ethylene-propylene-butene copolymer (hereinafter also referred to as "EPB copolymer") is a copolymer whose main components are structural units derived from propylene, ethylene, and 1-butene, respectively, and is a resin typically obtained by a multistage copolymerization method. When the first resin layer 11 contains an EPB copolymer, it is possible to suppress the detachment of calcium hydroxide 11p contained in the first resin layer 11. The EPB copolymer may be composed solely of structural units derived from propylene (hereinafter also referred to as "propylene units"), structural units derived from ethylene (hereinafter also referred to as "ethylene units"), and structural units derived from 1-butene (hereinafter also referred to as "1-butene units"), or it may further contain structural units derived from monomers other than propylene, ethylene, and 1-butene (hereinafter also referred to as "other monomer units") (hereinafter also referred to as "other monomer units"). One type of EPB copolymer may be used alone, or two or more types may be used in combination.

[0014] The composition of the EPB copolymer is preferably such that, relative to the total mass of all structural units constituting the EPB copolymer, the propylene unit content is 50% by mass or more and the sum of the ethylene unit content and the 1-butene unit content is 50% by mass or less, since this allows for better suppression of calcium hydroxide 11p detachment and maintains good heat-sealability even when heat-sealed at a relatively low temperature (e.g., about 140°C). The composition of the EPB copolymer is preferably such that, relative to the total mass of all structural units constituting the EPB copolymer, the propylene unit content is 99% by mass or less and the sum of the ethylene unit content and the 1-butene unit content is 1% by mass or more, more preferably such that the propylene unit content is 97% by mass or less and the sum of the ethylene unit content and the 1-butene unit content is 3% by mass or more, and even more preferably such that the propylene unit content is 95% by mass or less and the sum of the ethylene unit content and the 1-butene unit content is 5% by mass or more. In particular, when the total content of ethylene units and 1-butene units is 3% by mass or more, the contents of ethylene units and 1-butene units are each preferably 1% by mass or more relative to the total mass of all structural units constituting the EPB copolymer. The contents of propylene units, ethylene units, 1-butene units, and other monomer units generally correspond to the amounts of propylene, ethylene, 1-butene, and other monomers charged when producing the EPB copolymer, respectively.

[0015] The melting point of the EPB copolymer is preferably 125°C or higher, more preferably 130°C or higher, and preferably 135°C or lower, more preferably 132°C or lower. The above upper and lower limits can be combined arbitrarily. For example, the melting point of the EPB copolymer is preferably 125°C or higher and 135°C or lower, more preferably 130°C or higher and 132°C or lower.

[0016] The melting point of the EPB copolymer is a value measured using a power compensation DSC apparatus according to the following procedure. An example of a power compensation DSC apparatus is a "Diamond DSC" manufactured by PerkinElmer. (i) 5 mg of the EPB copolymer is weighed, placed in an aluminum sample holder, and set in the power compensation DSC apparatus. (ii) Under a nitrogen stream, the temperature is increased from -40°C to 300°C at a rate of 20°C / min, and held at 300°C for 5 minutes. Thereafter, the temperature is reduced at a rate of 20°C / min and held at -40°C for 5 minutes. (iii) The temperature is again increased to 300°C at a rate of 20°C / min, and the melting point is determined from the DSC curve obtained at this time. The melting point is the peak temperature of the melting peak (the largest melting peak if multiple peaks exist in the DSC curve) as defined in JIS K 7121:2012, 9.1(1). The corresponding international standard to JIS K 7121:2012 is ISO 11357-2:2020.

[0017] The melt mass flow rate (MFR) of the EPB copolymer is preferably 0.5 g / 10 min or more, more preferably 3 g / 10 min or more, even more preferably 4 g / 10 min or more, and preferably 10 g / 10 min or less, more preferably 8 g / 10 min or less, and even more preferably 7 g / 10 min or less. The above upper and lower limits can be arbitrarily combined. For example, the MFR of the EPB copolymer is preferably 0.5 g / 10 min or more and 10 g / 10 min or less, more preferably 3 g / 10 min or more and 8 g / 10 min or less, and even more preferably 4 g / 10 min or more and 7 g / 10 min or less. If the MFR of the EPB copolymer is within the above range, the first resin composition (I) described below for constituting the first resin layer 11 will have appropriate fluidity, as will be described in detail later, and a food packaging film 10 of the desired thickness can be accurately produced.

[0018] The MFR of the EPB copolymer is a value measured using a melt flow rate tester (melt indexer) in accordance with JIS K 7210-1: 2014 at a measurement temperature of 230°C and a load of 2.16 kg. The corresponding international standard for JIS K 7210-1: 2014 is ISO 1133-1: 2011.

[0019] The content of the EPB copolymer in the first resin layer 11 is preferably 50% by mass or more, and more preferably 60% by mass or more, relative to the total mass of the first resin layer 11. When the content of the EPB copolymer is equal to or more than the above-mentioned lower limit, falling off of calcium hydroxide 11p can be further suppressed.

[0020] (Polyolefin with a melting point of 120°C or less) When the first resin layer 11 contains a polyolefin with a melting point of 120°C or less, the heat sealability of the first resin layer 11 is improved. The melting point of the polyolefin is preferably 60°C or more, more preferably 70°C or more, and also 120°C or less, preferably 110°C or less. The above upper and lower limits can be combined arbitrarily. For example, the melting point of the polyolefin is 120°C or less, preferably 60°C or more and 120°C or less, more preferably 70°C or more and 110°C or less. When the melting point of the polyolefin is above the above lower limit, the strength of the sealed portion after heat sealing is less likely to decrease, and bag breakage at the sealed portion is less likely to occur. When the melting point of the polyolefin is below the above upper limit, the heat sealability of the first resin layer 11 is improved. In addition, the adhesion and compatibility with the second resin layer are improved. The melting point of the polyolefin is measured in the same manner as the melting point of the EPB copolymer.

[0021] The melting point of the polyolefin, which will be described in detail later, is preferably lower than the melting point of the polyolefin homopolymer contained in the second resin layer. Specifically, when the melting point of the polyolefin is "M1" and the melting point of the polyolefin homopolymer contained in the second resin layer is "M2," the difference in melting point (M2-M1) is preferably 40°C or higher, more preferably 50°C or higher, and preferably 100°C or lower, more preferably 90°C or lower. The above upper and lower limits can be combined arbitrarily. For example, the difference in melting point (M2-M1) is preferably 40°C or higher and 100°C or lower, more preferably 50°C or higher and 90°C or lower.

[0022] The polyolefin may be a homopolymer of an olefin (a polyolefin homopolymer) or a copolymer of an olefin. When the polyolefin is a copolymer, it may be a random copolymer or a block copolymer.

[0023] Examples of olefins include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Among these, ethylene, propylene, and 1-butene are preferred. The olefins may be used alone or in combination of two or more.

[0024] Specific examples of polyolefins include random copolymers or block copolymers of propylene and 1-butene (hereinafter, these are also collectively referred to as "propylene-butene copolymers" or "PB copolymers"); random copolymers or block copolymers of ethylene and 1-butene (hereinafter, these are also collectively referred to as "ethylene-butene copolymers" or "EB copolymers"); and ethylene homopolymers (ethylene homopolymers) such as low-density polyethylene and linear low-density polyethylene. Among these, PB copolymers are preferred, and random copolymers of propylene and 1-butene are more preferred. Polyolefins having a melting point of 120°C or less may be used alone or in combination of two or more types.

[0025] The content of polyolefins having a melting point of 120°C or less in the first resin layer 11 is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 9% by mass or more, particularly preferably 10% by mass or more, and preferably 30% by mass or less, more preferably 23% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less, relative to the total mass of the first resin layer 11. The above upper and lower limits can be arbitrarily combined. For example, the content of polyolefins having a melting point of 120°C or less is preferably 3% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 23% by mass or less, even more preferably 9% by mass or more and 20% by mass or less, and particularly preferably 10% by mass or more and 15% by mass or less, relative to the total mass of the first resin layer 11. If the content of polyolefins having a melting point of 120°C or less is equal to or greater than the above lower limit, the heat sealability of the first resin layer 11 is further improved. If the content of the polyolefin having a melting point of 120°C or less is equal to or less than the above upper limit, contamination of the parts of the equipment used to manufacture the food packaging film 10 that come into contact with the first resin layer 11, such as stretching rolls, can be suppressed, and the food packaging film 10 can be manufactured with good productivity. In addition, the manufacturing cost of the food packaging film 10 can be reduced.

[0026] (Calcium hydroxide) When the first resin layer 11 contains calcium hydroxide 11p, the freshness of the food contained therein can be well maintained when the food packaging film 10 is used as a food packaging bag. The calcium hydroxide 11p may be used alone or in combination of two or more types with different purities.

[0027] The purity of calcium hydroxide 11p is preferably 90% or more, more preferably 95% or more, even more preferably 97% or more, and particularly preferably 100%. When calcium hydroxide 11p contains calcium oxide, the content of calcium oxide in calcium hydroxide 11p is preferably 1% by mass or less relative to the total mass of calcium hydroxide 11p. Calcium hydroxide 11p does not necessarily need to contain calcium oxide.

[0028] The calcium hydroxide 11p is preferably in particulate form. The average particle diameter of the calcium hydroxide 11p is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. The above upper and lower limits can be arbitrarily combined. For example, the average particle diameter of the calcium hydroxide 11p is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less. If the average particle diameter of the calcium hydroxide 11p is equal to or greater than the above lower limit, the freshness of the food contained inside can be improved when the food packaging film 10 is used as a food packaging bag. If the average particle diameter of the calcium hydroxide 11p is equal to or less than the above upper limit, the falling off of the calcium hydroxide 11p can be suppressed.

[0029] The average particle size of calcium hydroxide 11p refers to the particle size at cumulative 50% (D50: median diameter) in the volume-based particle size distribution measured before blending using a laser diffraction particle size analyzer in accordance with JIS Z 8825:2022. Specifically, calcium hydroxide is dispersed in a water tank, and the laser diffraction particle size analyzer is used to measure and analyze the light diffraction and scattering intensity distribution, thereby calculating the particle size and volume-based particle size distribution. An example of a laser diffraction particle size analyzer is the "SALD-2300" manufactured by Shimadzu Corporation. The measurement method, measurement range, and light source are as follows: Measurement method: laser diffraction and scattering. Measurement range: 0.017 to 2500 μm. Light source: semiconductor laser (wavelength 680 nm, output 3 mW). The corresponding international standard to JIS Z 8825:2022 is ISO 13320:2020.

[0030] The content of calcium hydroxide 11p in the first resin layer 11 is preferably 0.1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 12% by mass or less, more preferably 10% by mass or less, and even more preferably 9% by mass or less, relative to the total mass of the first resin layer 11. The above upper and lower limits can be arbitrarily combined. For example, the content of calcium hydroxide 11p is preferably 0.1% by mass or more and 12% by mass or less, more preferably 3% by mass or more and 10% by mass or less, and even more preferably 5% by mass or more and 9% by mass or less, relative to the total mass of the first resin layer 11. When the content of calcium hydroxide 11p is equal to or greater than the above lower limit, the freshness of the food contained inside can be better maintained when the food packaging film 10 is used as a food packaging bag. When the food contained inside is a banana, the occurrence of spots on the banana peel, known as sugar spots, can be suppressed. If the content of calcium hydroxide is equal to or less than the upper limit, calcium hydroxide 11p is not added in excess, and production costs can be reduced.

[0031] (Other Resins (I)) Examples of the other resins (I) include crystalline polyolefin-based resins having a melting point of more than 120°C. Examples of the crystalline polyolefin-based resins include homopolymers or copolymers containing olefins such as ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene as monomers. The crystalline polyolefin-based resins may be used alone or in combination of two or more. Specific examples of the crystalline polyolefin-based resins include propylene-ethylene copolymers (hereinafter also referred to as "PE copolymers") and polyolefin-based homopolymers.

[0032] When the first resin layer 11 contains another resin (I), the content of the other resin (I) in the first resin layer 11 is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, relative to the total mass of the first resin layer 11. The first resin layer 11 does not necessarily contain the other resin (I).

[0033] (Erucamide) If the first resin layer 11 contains erucamide, the calcium hydroxide 11p can be further prevented from falling off. As a result, when the food packaging film 10 is used as a food packaging bag, the appearance of the food contained therein can be further prevented from changing over time, and the growth of bacteria such as E. coli over time can be suppressed.

[0034] When erucic acid amide is contained in the first resin layer 11, the content of erucic acid amide in the first resin layer 11 is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, relative to the total mass of the first resin layer 11. It is also preferably 1% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.07% by mass or less. The above upper and lower limits can be arbitrarily combined. For example, the content of erucic acid amide is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.2% by mass or less, more preferably 0.03% by mass or more and 0.1% by mass or less, and particularly preferably 0.03% by mass or more and 0.07% by mass or less, relative to the total mass of the first resin layer 11.

[0035] (Calcium stearate) If the first resin layer 11 contains calcium stearate, the falling off of calcium hydroxide 11p can be further suppressed. In addition, when the food packaging film 10 is used as a food packaging bag, the openability is improved. In particular, it is more preferable that the first resin layer 11 contains both erucic acid amide and calcium stearate. If the first resin layer 11 contains both erucic acid amide and calcium stearate, the effect of suppressing the falling off of calcium hydroxide 11p is further enhanced.

[0036] When calcium stearate is contained in the first resin layer 11, the content of calcium stearate in the first resin layer 11 is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and preferably 1% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.07% by mass or less, relative to the total mass of the first resin layer 11. The above upper and lower limits can be arbitrarily combined. For example, the content of calcium stearate is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.2% by mass or less, more preferably 0.02% by mass or more and 0.1% by mass or less, and particularly preferably 0.02% by mass or more and 0.07% by mass or less, relative to the total mass of the first resin layer 11.

[0037] (Optional Component (I)) Examples of the optional component (I) include additives such as antistatic agents, antioxidants, antiblocking agents, etc. The optional component (I) may be used alone or in combination of two or more.

[0038] When the first resin layer 11 contains the optional component (I), the content of the optional component (I) in the first resin layer 11 (when two or more optional components (I) are contained, the content of each of the optional components (I)) is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and is preferably 1% by mass or less, more preferably 0.5% by mass or less, relative to the total mass of the first resin layer 11. The above upper and lower limits can be arbitrarily combined. For example, the content of the optional component (I) is preferably 0.05% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass of the first resin layer 11.

[0039] (Thickness of First Resin Layer) The thickness of the first resin layer 11 is preferably 0.01 μm or more, more preferably 1 μm or more, even more preferably 1.5 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. The above upper and lower limits can be combined arbitrarily. For example, the thickness of the first resin layer 11 is preferably 0.01 μm or more and 10 μm or less, more preferably 1 μm or more and 8 μm or less, and even more preferably 1.5 μm or more and 5 μm or less. If the thickness of the first resin layer 11 is within the above range, the food packaging film 10 can be produced at low cost. In addition, the haze of the food packaging film 10 tends to be low, and when used as a food packaging bag, the visibility of the food contained therein is improved and the freshness of the food can be sufficiently maintained.

[0040] The thickness of the first resin layer 11 can be measured using an electron microscope. Specifically, the cross section of the food packaging film 10 is observed at a magnification of 500 times, the thickness of 10 randomly selected points on the first resin layer 11 is measured, and the thickness can be determined by arithmetically averaging these measured values.

[0041] <Second Resin Layer> The second resin layer 12 is located on one surface 11a of the first resin layer 11. The second resin layer 12 contains a polyolefin homopolymer. In addition to the polyolefin homopolymer, the second resin layer 12 may further contain a resin other than the polyolefin homopolymer (hereinafter also referred to as "other resin (II)"). The second resin layer 12 may further contain a component other than the polyolefin homopolymer and the other resin (II) (hereinafter also referred to as "optional component (II)"), as necessary, within a range that does not impair the effects of the present invention.

[0042] (Polyolefin homopolymer) A polyolefin homopolymer is a homopolymer of an olefin. Examples of the olefin include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Among these, ethylene and propylene are preferred, and propylene is more preferred.

[0043] Specific examples of polyolefin homopolymers include homopolymers of low-density polyethylene (LDPE), homopolymers of medium-density polyethylene (MDPE), homopolymers of high-density polyethylene (HDPE), homopolymers of biaxially oriented polypropylene (OPP), homopolymers of non-oriented polypropylene (CPP), etc. The low-density polyethylene homopolymer may be a homopolymer of linear low-density polyethylene (LLDPE), a homopolymer of metallocene linear low-density polyethylene, a homopolymer of metallocene low-density polyethylene, or a homopolymer of very low-density polyethylene. Low-density polyethylene refers to polyethylene having a density of 0.93 g / cm. ３ Medium density polyethylene is polyethylene with a density of 0.93 g / cm ３ 0.94g / cm or more ３ High density polyethylene is polyethylene with a density of 0.94 g / cm ３ The above polyethylene.

[0044] The content of the polyolefin homopolymer in the second resin layer 12 is preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total mass of the second resin layer 12 .

[0045] (Other Resins (II)) Examples of the other resins (II) include crystalline polyolefin-based resins. Examples of the crystalline polyolefin-based resins include homopolymers or copolymers containing olefins as monomers, such as ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. The crystalline polyolefin-based resins may be used alone or in combination of two or more.

[0046] (Optional Component (II)) Examples of the optional component (II) include additives such as antistatic agents, antioxidants, antiblocking agents, etc. The optional component (II) may be used alone or in combination of two or more.

[0047] When the second resin layer 12 contains the optional component (II), the content of the optional component (II) in the second resin layer 12 (when two or more optional components (II) are contained, the content of each of the optional components (II)) is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and is preferably 1% by mass or less, more preferably 0.6% by mass or less, relative to the total mass of the first resin layer 11. The above upper and lower limits can be arbitrarily combined. For example, the content of the optional component (II) is preferably 0.05% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.6% by mass or less, relative to the total mass of the second resin layer 12.

[0048] (Thickness of Second Resin Layer) The thickness of the second resin layer 12 is preferably greater than 10 μm, more preferably greater than 12 μm, even more preferably greater than 15 μm, particularly preferably greater than 20 μm, and preferably less than 60 μm, more preferably less than 40 μm, and even more preferably less than 30 μm. The above upper and lower limits can be arbitrarily combined. For example, the thickness of the second resin layer 12 is preferably greater than 10 μm and less than 60 μm, more preferably greater than 12 μm and less than 60 μm, more preferably greater than 15 μm and less than 40 μm, and particularly preferably greater than 20 μm and less than 30 μm. Furthermore, the thickness of the second resin layer 12 is preferably at least one-third of the total thickness of the food packaging film 10. If the thickness of the second resin layer 12 is within the above range, the stiffness (suppleness) of the food packaging film 10 can be maintained well. The thickness of the second resin layer 12 can be measured using the same method as for the thickness of the first resin layer 11.

[0049] <Third Resin Layer> The third resin layer 13 is located on the surface 12a of the second resin layer 12 opposite the first resin layer 11. In the case of the food packaging film 10 of FIG. 1 , the third resin layer 13 is located on the outermost layer of the food packaging film 10 opposite the first resin layer 11. The third resin layer 13 preferably contains a crystalline polyolefin resin having a melting point of 140°C or higher. The third resin layer 13 may further contain, in addition to the crystalline polyolefin resin having a melting point of 140°C or higher, one or more selected from erucic acid amide and calcium stearate. The third resin layer 13 may further contain a component (hereinafter also referred to as "optional component (III)") other than the crystalline polyolefin resin having a melting point of 140°C or higher, erucic acid amide, and calcium stearate, as necessary, within a range that does not impair the effects of the present invention.

[0050] (Crystalline Polyolefin Resin with a Melting Point of 140°C or More) When the third resin layer 13 contains a crystalline polyolefin resin with a melting point of 140°C or more, contamination of the heat seal bar can be suppressed when producing a food packaging bag. Examples of the crystalline polyolefin resin with a melting point of 140°C or more include those with a melting point of 140°C or more among the crystalline polyolefin resins with a melting point of over 120°C exemplified above in the description of the first resin layer 11. Specific examples include propylene-ethylene copolymers (hereinafter also referred to as "PE copolymers") and polyolefin homopolymers. The crystalline polyolefin resin with a melting point of 140°C or more may be used alone or in combination of two or more.

[0051] The content of the crystalline polyolefin resin having a melting point of 140°C or higher in the third resin layer 13 is preferably 90% by mass or more, more preferably 95% by mass or more, based on the total mass of the third resin layer 13. When the food packaging film 10 is formed into a bag, one sheet of the food packaging film 10 is folded and heat-sealed so that the first resin layer 11 is on the inside, or two sheets of the food packaging film 10 are overlapped and heat-sealed so that the first resin layers 11 are in contact with each other. Therefore, the third resin layer 13 comes into contact with the heat seal bar (heat seal hot plate) provided in the heat sealing machine. If the content of the crystalline polyolefin resin having a melting point of 140°C or higher is equal to or greater than the above-mentioned lower limit, adhesion of the third resin layer 13 to the heat seal bar can be suppressed when the food packaging film 10 is heat-sealed, the heat seal bar is less likely to be contaminated, and food packaging bags can be produced with high productivity.

[0052] (Erucic acid amide) When erucic acid amide is contained in the third resin layer 13, the content of erucic acid amide in the third resin layer 13 is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, relative to the total mass of the third resin layer 13. It is also preferably 1% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.07% by mass or less. The above upper and lower limits can be arbitrarily combined. For example, the content of erucic acid amide is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.2% by mass or less, more preferably 0.03% by mass or more and 0.1% by mass or less, and particularly preferably 0.03% by mass or more and 0.07% by mass or less, relative to the total mass of the third resin layer 13.

[0053] (Calcium Stearate) When calcium stearate is contained in the third resin layer 13, the content of calcium stearate in the third resin layer 13 is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and preferably 1% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.07% by mass or less, relative to the total mass of the third resin layer 13. The above upper and lower limits can be arbitrarily combined. For example, the content of calcium stearate is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.2% by mass or less, more preferably 0.02% by mass or more and 0.1% by mass or less, and particularly preferably 0.02% by mass or more and 0.07% by mass or less, relative to the total mass of the third resin layer 13.

[0054] (Optional Component (III)) Examples of the optional component (III) include additives such as antistatic agents, antioxidants, antiblocking agents, etc. The optional component (III) may be used alone or in combination of two or more.

[0055] When the optional component (III) is contained in the third resin layer 13, the content of the optional component (III) in the third resin layer 13 (the content of each of the optional components (III) when two or more types of optional components (III) are contained) is preferably 0.05% by mass or more, more preferably 0.5% by mass or more, and is preferably 1% by mass or less, more preferably 0.1% by mass or less, relative to the total mass of the third resin layer 13. The above upper and lower limits can be arbitrarily combined. For example, the content of the optional component (III) is preferably 0.05% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass of the third resin layer 13.

[0056] (Thickness of Third Resin Layer) The thickness of the third resin layer 13 is preferably 0.01 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. The above upper and lower limits can be combined arbitrarily. For example, the thickness of the third resin layer 13 is preferably 0.01 μm or more and 10 μm or less, more preferably 0.1 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 3 μm or less. The thickness of the third resin layer 13 can be measured using the same method as for the thickness of the first resin layer 11.

[0057] <Thickness of Food Packaging Film> The thickness of the food packaging film 10 is preferably greater than 10 μm, more preferably greater than 16 μm, even more preferably greater than 23 μm, and preferably equal to or less than 80 μm, more preferably equal to or less than 46 μm, and even more preferably equal to or less than 33 μm. The above upper and lower limits can be combined arbitrarily. For example, the thickness of the food packaging film 10 is preferably greater than 10 μm and equal to or less than 80 μm, more preferably equal to or greater than 16 μm and equal to or less than 46 μm, and even more preferably equal to or greater than 23 μm and equal to or less than 33 μm. The thickness of the food packaging film 10 can be measured using the same method as for the thickness of the first resin layer 11.

[0058] <Production of food packaging film> The food packaging film 10 can be produced, for example, by co-extrusion molding a first resin composition (I) constituting the first resin layer 11, a second resin composition (II) constituting the second resin layer 12, and a third resin composition (III) constituting the third resin layer 13.

[0059] The first resin composition (I) contains an EPB copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide. The first resin composition (I) preferably further contains, in addition to the EPB copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide, one or more selected from another resin (I), erucic acid amide, and calcium stearate. The first resin composition (I) may further contain an optional component (I) within a range that does not impair the effects of the present invention. The first resin composition (I) can be obtained, for example, by melt-kneading resin pellets obtained by molding a resin containing an EPB copolymer into pellets, resin pellets obtained by molding a resin (e.g., a propylene-ethylene copolymer) containing a predetermined amount of calcium hydroxide into pellets, and resin pellets obtained by molding a resin containing a polyolefin having a melting point of 120°C or less into pellets, and, if necessary, resin pellets obtained by molding another resin (I) into pellets. The melt-kneading temperature is preferably 200°C or higher and 300°C or lower. As the resin pellets obtained by molding a resin containing an EPB copolymer into pellets, commercially available products can be used, such as "FL6741G" manufactured by Sumitomo Chemical Co., Ltd. and "5C37F" manufactured by Basel Chemical Industries, Ltd. One or more of the resin pellets described above may contain one or more of erucic acid amide, calcium stearate, and optional component (I).

[0060] The second resin composition (II) contains a polyolefin homopolymer. The second resin composition (II) may further contain another resin (II) in addition to the polyolefin homopolymer. The second resin composition (II) may further contain an optional component (II) as long as the effects of the present invention are not impaired. The second resin composition (II) can be obtained, for example, by melt-kneading resin pellets obtained by molding a resin containing a polyolefin homopolymer into pellets and, if necessary, resin pellets obtained by molding another resin (II) into pellets. The melt-kneading temperature is preferably 200°C or higher and 300°C or lower. Commercially available resin pellets obtained by molding a resin containing a polyolefin homopolymer into pellets can be used, such as those available from Prime Polymer Co., Ltd. under the trade names "F-300SP" and "E-200GP." The resin pellets described above may also contain the optional component (II).

[0061] The third resin composition (III) preferably contains a crystalline polyolefin resin having a melting point of 140°C or higher. The third resin composition (III) may further contain one or more selected from erucic acid amide and calcium stearate in addition to the crystalline polyolefin resin having a melting point of 140°C or higher. The third resin composition (III) may further contain an optional component (III) within a range that does not impair the effects of the present invention. The third resin composition (III) can be obtained, for example, by melt-kneading resin pellets obtained by molding a resin containing a crystalline polyolefin resin having a melting point of 140°C or higher into pellets. The melt-kneading temperature is preferably 200°C or higher and 300°C or lower. Commercially available resin pellets obtained by molding a resin containing a crystalline polyolefin resin having a melting point of 140°C or higher into pellets can be used, such as commercially available products such as "PC412A" manufactured by SunAllomer Co., Ltd., or those exemplified in the description of the second resin composition (II). The resin pellets may contain one or more of erucamide, calcium stearate, and optional component (III).

[0062] Examples of coextrusion molding include a coextrusion multilayer T-die method. Examples of coextrusion multilayer T-die methods include a feedblock method and a multi-manifold method. The coextrusion multilayer T-die method can be performed using various known coextrusion multilayer molding devices. The food packaging film 10 may be coextruded and then stretched. The stretching is preferably biaxial stretching. When stretching is performed by biaxial stretching, stretching in the MD direction (the direction in which the molten resin flows) is preferably performed at a temperature of 100°C or higher and 140°C or lower, and at a stretching ratio of 3 to 6 times. Stretching in the TD direction (the direction perpendicular to the MD direction) is preferably performed at a temperature of 130°C or higher and 160°C or lower, and at a stretching ratio of 8 to 12 times. The food packaging film 10 may be non-stretched or stretched, but is preferably stretched, and more preferably biaxially stretched.

[0063] <Effects> The food packaging film 10 of the present embodiment described above has excellent heat-sealing properties because the first resin layer 11, which is the outermost layer and contains the EPB copolymer and calcium hydroxide 11p, further contains a polyolefin with a melting point of 120°C or less. Furthermore, because the first resin layer 11 contains calcium hydroxide 11p, the freshness of the food contained inside can be well maintained when the food packaging film 10 is used as a food packaging bag. Moreover, as will be described in detail later, the action of the EPB copolymer contained in the first resin layer 11 can prevent the calcium hydroxide 11p from falling off.

[0064] In other words, the food packaging film 10 of this embodiment is a film with excellent heat sealing properties and, moreover, is capable of preventing the calcium hydroxide 11p from falling off, and is therefore also a film with excellent effectiveness in preserving the freshness of food (a freshness-preserving film). The food packaging film 10 is suitable as a film for bags for packaging food, particularly fresh foods such as fruits and vegetables, fresh fish, and meat.

[0065] [Food packaging bag] Figures 2 and 3 show an example of the food packaging bag of the present invention. Note that Figure 3 is a side view of the food packaging bag 100 shown in Figure 2 as seen from the opening side (side A in Figure 2). The food packaging bag 100 of this embodiment is a bag body made from the food packaging film 10 of the present invention described above. In the food packaging bag 100, the innermost layer of the bag is the first resin layer of the food packaging film 10.

[0066] The food packaging bag 100 is constructed by sealing edge portions 112, 113 extending perpendicular to a fold line 111 formed when the food packaging film 10 is folded in half with the first resin layer on the inside, as shown in Figures 2 and 3.

[0067] When the food to be stored inside is fresh produce that respires a lot, it is preferable that the food packaging film 10 constituting the food packaging bag 100 has through holes. When the food packaging film 10 constituting the food packaging bag 100 has through holes, the diameter of the through holes is preferably 0.2 mm or more and 5.0 mm or less, more preferably 0.5 mm or more and 3.5 mm or less, even more preferably 1.0 mm or more and 2.0 mm or less, and most preferably 1.0 mm or more and 1.5 mm or less. If the diameter of the through holes is within the above range, the bag can be prevented from expanding due to gas or water vapor generated by the respiration of fresh produce, while maintaining its freshness-preserving effect. When the food packaging film 10 constituting the food packaging bag 100 has through holes, the number of through holes is 25 or more and 500 or less per m ２ is preferably 25 or more and 300 or less per m ２ More preferably, 30 or more and 200 or less per m ２ More preferably, 40 or more and 100 or less / m ２ When the number of through-holes is within the above range, the bag can be prevented from expanding due to gas or water vapor generated by respiration of fruits and vegetables while maintaining the freshness-preserving effect.

[0068] By setting the diameter of the through-holes to the above upper limit or less, or by setting the number of through-holes to the above upper limit or less, the atmosphere inside the bag can be easily maintained alkaline, and a good freshness-preserving effect can be easily maintained.By setting the diameter of the through-holes to the above lower limit or more, or by setting the number of through-holes to the above lower limit or more, gas generated inside can be released to the outside of the packaging bag, thereby preventing the bag from expanding and increasing in volume, which would reduce transportation efficiency.

[0069] The food packaging bag 100 is manufactured, for example, as follows. First, the food packaging film 10 is folded in half with the first resin layer facing inward. Next, the edge portions 112, 113 extending in a direction perpendicular to the fold line 111 formed by folding the food packaging film 10 in half are sealed. The edge portions 112, 113 can be sealed by heat sealing. Because the first resin layer of the food packaging film 10 has excellent heat sealing properties, the first resin layers adhere sufficiently to each other, resulting in high heat seal strength.

[0070] The food packaging bag 100 of the present embodiment described above is made of the food packaging film 10 of the present invention, and therefore calcium hydroxide is less likely to fall off and is excellent at preserving the freshness of food, making it suitable as a packaging bag for food, particularly fresh food. The reason why calcium hydroxide is less likely to fall off in the food packaging bag 100 of the present embodiment is not clear, but the following is thought to be the reason.

[0071] Generally, a bag made of a resin film is produced by folding the resin film in half and heat-sealing the edge portion extending in a direction perpendicular to the fold line. Since the resin film is usually stretch-molded, if the outermost layer of the resin film contains calcium hydroxide, it is believed that voids are formed between the resin constituting the outermost layer and the calcium hydroxide during stretch-molding of the resin film, and that these voids remain in the molded resin film. Furthermore, when a resin film containing an EPB copolymer and a resin film containing a random copolymer are stretch-molded at the same temperature, the melting point of the EPB copolymer generally tends to be lower than the melting point of the random copolymer, which is thought to increase interfacial adhesion with the calcium hydroxide and make it less likely for voids to form during stretch-molding. Thus, since fewer voids are formed during stretch molding of the resin film, the food packaging bag according to this embodiment is thought to be less susceptible to the effect of calcium hydroxide falling off due to external forces applied when manufacturing food packaging bags from the food packaging film (for example, external forces applied to the food packaging film during transport of the food packaging film or during sealing of the food packaging film). As a result, it is presumed that calcium hydroxide particles are less likely to fall off from the first resin layer in the food packaging bag according to this embodiment.

[0072] The food packaging bag of the present invention is not limited to the above-described one. For example, the food packaging bag may be obtained by stacking two of the above-described substantially rectangular food packaging films of the present invention so that the first resin layers are in contact with each other to form a laminate, and then heat-sealing three of the four sides of the laminate to form a bag.

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The embodiments of the present invention can be modified in various ways as long as the gist of the present invention is not changed.

[0074] [Measurement and Evaluation] <Evaluation of Heat Sealability> Two rectangular samples (films) measuring 230 mm in the MD direction and 50 mm in the TD direction were cut out from the food packaging film, and the first resin layers of the two cut-out films were stacked so that they were in contact with each other to prepare a test piece. A total of 10 test pieces were prepared. A predetermined location of the obtained test piece was heat-sealed using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "HG-100-2") under conditions of a heat seal temperature of 135°C, a seal pressure of 0.2 MPa, a seal time of 2 seconds, and a seal area of ​​10 mm x 25 mm. Next, using a tensile tester (manufactured by MinebeaMitsumi Inc., product name "TGI-1kN"), the two films constituting the heat-sealed test piece were T-peeled at a tensile speed of 300 mm / min, and the recorded maximum load was taken as the heat seal peel strength. The same tensile test was carried out on 10 test pieces, and the minimum value of the heat seal peel strength of the 10 test pieces was scored according to the following criteria to evaluate the heat sealability. (Criteria) 4 points: Minimum value is 4.0 N / 25 mm or more. 3 points: Minimum value is 3.0 N / 25 mm or more and less than 4.0 N / 25 mm. 2 points: Minimum value is 2.0 N / 25 mm or more and less than 3.0 N / 25 mm. 1 point: Minimum value is less than 2.0 N / 25 mm.

[0075] <Evaluation of Contamination Resistance of Seal Bar> Two A4-sized samples (films) measuring 297 mm in the MD direction and 210 mm in the TD direction were cut out from a food packaging film, and the first resin layers of the two cut-out films were stacked so that they were in contact with each other to prepare a test piece. A predetermined location of the obtained test piece was heat-sealed using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., product name "TP-701-B") under the following conditions: heat seal temperature 135 ° C, seal pressure 2.0 MPa, seal time 1.0 second, seal width 10 mm. When the test piece was heat-sealed, the adhesion state of the film to the seal bar (heat seal hot plate) of the heat seal tester was visually confirmed and scored according to the following criteria to evaluate the contamination resistance of the seal bar. (Criteria) 3 points: The film did not adhere to the seal bar during heat sealing. 2 points: The film adhered to the seal bar for a moment during heat sealing, but immediately peeled off from the seal bar. 1 point: The film remains attached to the seal bar during heat sealing.

[0076] <Evaluation of film productivity> During the production of the food packaging film, the condition (fouling) of the roll stretched in the MD direction was visually checked and scored according to the following criteria to evaluate the film productivity. (Criteria) 3 points: Only a small amount of material adheres to the roll in contact with the first resin layer, allowing for continuous operation for one day or more. 2 points: Material adheres to the roll in contact with the first resin layer, but continuous operation for half a day or more but less than one day is possible. 1 point: A large amount of material adheres to the roll in contact with the first resin layer, preventing continuous operation for half a day or more.

[0077] <Overall Evaluation> The scores for the heat sealability, the stain resistance of the seal bar, and the film productivity were totaled to give an overall evaluation. A total score of 7 points or more was considered to be pass, and a total score of 6 points or less was considered to be fail.

[0078] [Example 1] As the ethylene-propylene-butene copolymer, resin pellets 5C37F (MFR = 5.5 g / 10 min, melting point = 132 ° C.) manufactured by Basel and resin pellets FL6741G (MFR = 6.0 g / 10 min, melting point = 130 ° C.) manufactured by Sumitomo Chemical Co., Ltd. were used in a mass ratio of 5C37F:FL6741G = 60:40. As the propylene-ethylene copolymer, resin pellets WFX4M (melting point = 127 ° C.) manufactured by Japan Polypropylene Corporation or resin pellets PC412A (melting point = 159 ° C.) manufactured by SunAllomer Co., Ltd. were used. As the propylene-butene copolymer, resin pellets XM7070 (melting point = 77 ° C.) manufactured by Mitsui Chemicals, Inc. were used. As the homopolypropylene (polypropylene homopolymer), resin pellets F-300SP (melting point = 164°C) manufactured by Prime Polymer Co., Ltd. and resin pellets E-200GP (melting point = 164°C) manufactured by Prime Polymer Co., Ltd. were used in a mass ratio of F-300SP:E-200GP = 70:30. As the calcium hydroxide, calcium hydroxide particles (calcium hydroxide particles derived from scallop shells, purity = 95% or more, average particle size = 2.7 μm) obtained by calcining scallop shells at 1100°C or higher and then slaked were used. Other additives used included an antioxidant and an antiblocking agent.

[0079] A calcium hydroxide-containing masterbatch was prepared by mixing calcium hydroxide with resin pellets WFX4M so as to obtain the composition shown in Table 1. Note that calcium stearate, erucic acid amide, and other additives are contained in at least one of the resin pellets 5C37F, FL6741G, WFX4M, XM7070, F-300SP, and E-200GP.

[0080] Resin pellets 5C37F and FL6741G, resin pellets XM7070, resin pellets F-300SP and E-200GP, and a calcium hydroxide-containing masterbatch were melt-kneaded at 250 ° C. to obtain the formulation shown in Table 1, to prepare a first resin composition (I). Resin pellets F-300SP and E-200GP were melt-kneaded with an antistatic agent at 250 ° C. to obtain the formulation shown in Table 1, to prepare a second resin composition (II). Resin pellets PC412A were melt-kneaded at 250 ° C. to obtain the formulation shown in Table 1, to prepare a third resin composition (III).

[0081] The first resin composition (I), the second resin composition (II), and the third resin composition (III) were coextruded using a multilayer T-die coextrusion method, followed by biaxial stretching to produce a food packaging film with a total thickness of 30.6 μm, in which a first resin layer (thickness = 2.0 μm), a second resin layer (thickness = 26.0 μm), and a third resin layer (thickness = 2.6 μm) were laminated in this order. The multilayer T-die coextrusion method was performed using a multilayer coextrusion device equipped with three single-screw extruders. The extrusion rates of the first resin composition (I), the second resin composition (II), and the third resin composition (III) were in a mass ratio of first resin composition (I):second resin composition (II):third resin composition (III) = 0.7:8.5:0.8. The biaxial stretching was performed by stretching the film 4.6 times in the MD direction at 123°C, and by stretching the film 10 times in the TD direction at 151°C. The heat sealability, stain resistance of the seal bar, and film productivity of the resulting food packaging film were evaluated. The results are shown in Table 1.

[0082] [Examples 2, 3, 5, 6] Resin pellets 5C37F and FL6741G, resin pellets XM7070, resin pellets F-300SP and E-200GP, and a calcium hydroxide-containing masterbatch were melt-kneaded at 250°C to prepare a first resin composition (I) so as to obtain the formulation shown in Tables 1 and 2. A food packaging film was produced and evaluated in the same manner as in Example 1, except that the obtained first resin composition (I) was used. The results are shown in Tables 1 and 2.

[0083] [Example 4] A third resin composition (III) was prepared by melt-kneading resin pellets F-300SP and resin pellets E-200GP at 250°C to obtain the composition shown in Table 1. A food packaging film was produced and evaluated in the same manner as in Example 1, except that the obtained third resin composition (III) was used. The results are shown in Table 1.

[0084] [Example 7] Resin pellets 5C37F, resin pellets FL6741G, and resin pellets PC412A were melt-kneaded at 250°C to prepare a third resin composition (III) so as to obtain the composition shown in Table 2. A food packaging film was produced and evaluated in the same manner as in Example 1, except that the obtained third resin composition (III) was used. The results are shown in Table 2.

[0085] Comparative Example 1 A first resin composition (I) was prepared by melt-kneading resin pellets 5C37F and FL6741G, resin pellets F-300SP and E-200GP, and a calcium hydroxide-containing masterbatch at 250°C to obtain the formulation shown in Table 2. A third resin composition (III) was prepared by melt-kneading resin pellets 5C37F and FL6741G and resin pellets PC412A at 250°C to obtain the formulation shown in Table 2. A food packaging film was produced and evaluated in the same manner as in Example 1, except that the obtained first resin composition (I) and third resin composition (III) were used. The results are shown in Table 2.

[0086]

[0087]

[0088] The abbreviations in Tables 1 and 2 are as follows: EPB copolymer: ethylene-propylene-butene copolymer. PE copolymer: propylene-ethylene copolymer. PB copolymer: propylene-butene copolymer. AB agent: antiblocking agent.

[0089] As is clear from the results in Tables 1 and 2, the food packaging films obtained in each Example had excellent heat sealability. In particular, the food packaging films obtained in Examples 1 to 5 and 7 also had good film productivity. The food packaging films obtained in Examples 1 to 6 also had excellent resistance to seal bar contamination. On the other hand, the food packaging film obtained in Comparative Example 1 had inferior heat sealability compared to the food packaging films obtained in each Example. It also easily contaminated the seal bar.

[0090] <Evaluation of freshness retention (appearance) of food packaging bags> The color change of the edamame beans after storage at 10°C after filling the food packaging bag and sealing the opening was visually confirmed, relative to the color of the raw edamame beans before filling into a food packaging bag made of food packaging film, and freshness retention was evaluated by scoring according to the following criteria: (Criteria) 3 points: The area of ​​discolored parts after 2 weeks is less than 1% of the total. 2 points: The area of ​​discolored parts after 2 weeks is 1% or more but less than 10% of the total. 1 point: The area of ​​discolored parts after 2 weeks is 10% or more of the total.

[0091] <Evaluation of the swelling of food packaging bags> Fresh edamame beans were filled into food packaging bags made of food packaging film, the openings were sealed, and the food packaging bags were stored at 10°C. The degree of swelling of the food packaging bags was then visually inspected and scored according to the following criteria to evaluate the swelling. (Criteria) 3 points: The food packaging bag has not swelled at all after 2 weeks. 2 points: The food packaging bag has swelled more than zero after 2 weeks. 1 point: The food packaging bag has swelled after 2 weeks.

[0092] <Overall evaluation> The scores for the evaluation of freshness retention and swelling were totaled to give an overall evaluation. The higher the total score, the higher the product value.

[0093] Reference Example 1 The food packaging film obtained in Example 1 was punched to form through-holes with a diameter of 1.0 mm in a checkerboard pattern, with the holes spaced equally apart. The resulting food packaging film with through-holes was used to produce a food packaging bag as shown in food packaging bag 100 in Figure 2. The portions corresponding to the edge portions 112 and 113 were heat-sealed using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., product name "TP-701-B") at a heat seal temperature of 135°C, a sealing pressure of 2.0 MPa, a sealing time of 1.0 second, and a sealing width of 10 mm. The resulting food packaging bag measured 210 mm in length and 170 mm in width, excluding the edge portions, and had two through-holes (through-hole density of 50 / m) in each of two sheets of food packaging film facing each other. ２ )

[0094] The resulting food packaging pouch with through holes was filled with 200 g of freshly purchased raw edamame beans, and the opening was heat-sealed under the same conditions as above, in the same manner as in the locations corresponding to edge portions 112 and 113. The resulting food packaging pouch with through holes containing edamame beans was stored at 10°C, and its freshness retention and expansion were evaluated. The results are shown in Table 3.

[0095] [Reference Examples 2 to 7] Food packaging bags were produced and evaluated in the same manner as in Reference Example 1, except that the food packaging film was punched so that the through holes had the diameters and numbers shown in Table 3. The results are shown in Table 3.

[0096] Reference Example 8 Food packaging bags were produced and evaluated in the same manner as in Reference Example 1, except that no through holes were formed in the food packaging film as shown in Table 3. The results are shown in Table 3.

[0097] Reference Example 9 Resin pellets 5C37F, FL6741G, XM7070, F-300SP, and E-200GP were melt-kneaded at 250°C to prepare a first resin composition (I) so as to obtain the composition shown in Table 3. Food packaging was produced and evaluated in the same manner as in Reference Example 1, except that the obtained first resin composition (I) was used. The results are shown in Table 3.

[0098]

[0099] As is clear from the results in Table 3, the food packaging bags obtained in Reference Examples 1 to 3 and 5 to 8 were particularly excellent in freshness retention. In particular, the food packaging bags obtained in Reference Examples 1 to 6 were excellent in bulging prevention. Furthermore, the food packaging bag obtained in Reference Example 9, which did not contain calcium hydroxide, was inferior in freshness retention.

[0100] According to the present invention, it is possible to provide a food packaging film having excellent heat-sealing properties, and a food packaging bag using this food packaging film.

[0101] REFERENCE SIGNS LIST 10 Food packaging film 11 First resin layer 11a One surface 11p Calcium hydroxide 12 Second resin layer 12a Surface opposite to first resin layer 13 Third resin layer 100 Food packaging bag 111 Folding line 112 Edge portion 113 Edge portion

Claims

1. A food packaging film comprising a first resin layer and a second resin layer located on one surface of the first resin layer, the first resin layer being the outermost layer, the first resin layer containing an ethylene-propylene-butene copolymer, a polyolefin having a melting point of 120°C or less, and calcium hydroxide, and the second resin layer containing a polyolefin homopolymer.

2. A food packaging film as described in claim 1, wherein the first resin layer contains 9% by mass or more and 20% by mass or less of polyolefin having a melting point of 120°C or less relative to the total mass of the first resin layer.

3. The food packaging film according to claim 1, further comprising a third resin layer located on the surface of the second resin layer opposite to the first resin layer, and the thickness of the third resin layer is 0.01 μm or more and 10 μm or less.

4. The food packaging film according to claim 3, wherein the third resin layer contains a crystalline polyolefin resin having a melting point of 140°C or higher.

5. A food packaging film as described in claim 1, wherein the first resin layer contains calcium hydroxide in an amount of 0.1 mass % or more and 12 mass % or less relative to the total mass of the first resin layer.

6. A food packaging bag made from the food packaging film according to any one of claims 1 to 5, wherein the innermost layer of the food packaging bag is the first resin layer.

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