Food packaging and method for manufacturing food packaging

Abstract

To provide a food packaging material that has sufficient water vapor barrier properties and is also excellent in cost and productivity. [Solution] The food packaging of the present invention is used to package food and is made of food packaging film, and when a coloring liquid is sprayed onto the heat-sealed portion of the food packaging from inside the food packaging, pores are present through which the coloring liquid penetrates by capillary action.

Description

[Technical Field]

[0001] The present invention relates to food packages and methods of using food packages. [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 2 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 water vapor barrier properties, it has poor heat-sealing properties. Therefore, when using OPP film in food packaging such as food packaging bags, it has been necessary to laminate a film with excellent heat-sealing properties, such as a non-oriented polypropylene film (hereinafter also referred to as CPP film), to the OPP film. By further laminating a CPP film to the OPP film, the heat-sealing strength of the resulting food packaging is increased, the penetration of moisture and oxygen at the seal area is suppressed, and the water vapor barrier properties and oxygen barrier properties of the food packaging can be improved. However, because OPP film and CPP film have poor adhesion, the CPP film had to be laminated to the OPP film using an adhesive. As a result, food packaging films using OPP film used in food packages require a step of further laminating the CPP film using an adhesive, which requires many manufacturing steps, leaving room for improvement in terms of simplifying the manufacturing process and reducing costs.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a food packaging material that has sufficient water vapor barrier properties and is also excellent in terms of cost and productivity. [Means for solving the problem]

[0009] The present inventors conducted extensive research to solve the above problems, and as a result, they discovered that even food packaging with poor heat-sealing properties, such as the presence of pores in the heat-sealed portion through which a coloring liquid penetrates by capillary action, has sufficient water vapor barrier properties and can be satisfactorily used as a food packaging, leading to the present invention.

[0010] That is, according to the present invention, there are provided the following food packaging and method of using the food packaging.

[0011] [1] A food packaging body used for packaging food and made of a food packaging film, The food packaging has pores through which the coloring liquid penetrates by capillary action when the coloring liquid is sprayed onto the heat-sealed portion of the food packaging from inside the food packaging. [2] In the food packaging described in [1] above, A food packaging material in which the length of the coloring liquid that has permeated the pores is 0.1 mm or more and 50 mm or less. [3] In the food packaging according to [1] or [2] above, The food packaging material has a pore diameter of 0.05 mm or more and 5.0 mm or less. [4] In the food packaging according to any one of [1] to [3] above, The food packaging film comprises a biaxially stretched film layer made of a propylene polymer composition containing a propylene polymer, and a heat seal layer provided so as to be in direct contact with at least one surface of the biaxially stretched film layer, The food packaging body wherein the heat seal layer is the outermost layer and has a thickness of 0.1 μm or more and 10 μm or less. [5] In the food packaging described in [4] above, The food packaging material has a single heat seal layer. [6] In the food packaging according to [4] or [5] above, The food packaging material wherein the heat seal layer is biaxially stretched. [7] In the food packaging according to any one of [4] to [6] above, The food packaging material, wherein the heat seal layer comprises at least one selected from a propylene-α-olefin random copolymer and a propylene homopolymer. [8] In the food packaging according to any one of [4] to [7] above, A food package in which 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. [9] In the food packaging according to any one of [1] to [8] above, The food package wherein the food comprises a dried food.

[10] In the food packaging according to [9] above, A food packaging material in which the water activity of the dried food is 0.05 or more and 0.3 or less.

[11] In the food packaging according to any one of [1] to

[10] above, Food packaging used as an outer packaging bag.

[12] A method for using the food packaging according to any one of [1] to [8] above as a packaging material for dried food.

[13] In the method of using the food packaging material described in

[12] above, A method for using the food packaging material, in which the water activity of the dried food is 0.05 or more and 0.3 or less.

[14] In the method of using the food packaging material according to

[12] or

[13] above, The food packaging material is used as an outer packaging bag. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a food packaging material that has sufficient water vapor barrier properties and is also excellent in cost and productivity. [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 for forming a food package 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> The food package according to this embodiment is a food package used to package food and made of a food packaging film. When a coloring liquid is sprayed onto the heat-sealed portion of the food package from the inside of the food package, pores exist through which the coloring liquid penetrates by capillary action. The food package according to this embodiment is, for example, a packaging bag used for containing food, or a bag containing food. Examples of packaging forms for the food package according to this embodiment include three-sided bags, four-sided bags, pillow bags, gable bags, stick bags, gusset bags, and stand-up pouches, all or part of which have a heat-sealed portion formed by heat sealing along the periphery. In addition to food, oxygen absorbers and the like may also be placed inside the food package. Here, Ageless Seal Check Spray (red penetrating liquid, manufactured by Mitsubishi Gas Chemical Co., Inc.) can be used as the coloring liquid. When Ageless Seal Check Spray is sprayed onto the heat-sealed portion from the inside of the food packaging, the red liquid seeps out from the pores, making it possible to identify the pores into which the coloring liquid has penetrated.

[0016] Here, conventionally, food packaging with poor heat sealing properties, such as the presence of pores in the heat-sealed portion through which a coloring liquid penetrates due to capillary action, has been considered to have poor water vapor barrier properties due to poor sealing properties, and has not been adopted as a product, being discarded as a defective product during the manufacturing process. However, through investigations by the present inventors, it has been found that even such food packaging surprisingly has sufficient water vapor barrier properties and can be used satisfactorily as a food packaging. Although the food packaging according to this embodiment has poorer oxygen barrier properties than packaging with excellent sealing properties, it exhibits sufficient water vapor barrier properties, making it particularly suitable for use as a food packaging for packaging foods (e.g., dried foods) that require water vapor barrier properties but not so much oxygen barrier properties. Furthermore, the food packaging according to this embodiment can be produced by, for example, omitting the step of laminating a CPP film with excellent heat-sealing properties using an adhesive, and by controlling the sealing temperature and pressure over a wide range of heat-sealing conditions, resulting in excellent cost and productivity. As described above, according to this embodiment, it is possible to provide a food packaging body that has sufficient water vapor barrier properties and is also excellent in cost and productivity.

[0017] In the food packaging of this embodiment, the length of the coloring liquid that has penetrated into the pores is preferably 0.1 mm or more, more preferably 1 mm or more, and even more preferably 3 mm or more, from the viewpoint of productivity of the food packaging, and is preferably 50 mm or less, more preferably 30 mm or less, even more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 10 mm or less, from the viewpoint of water vapor barrier properties.

[0018] In the food packaging of this embodiment, the pore size is preferably 0.001 mm or more, more preferably 0.01 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.1 mm or more, from the viewpoint of productivity of the food packaging, and is preferably 5.0 mm or less, more preferably 4.0 mm or less, even more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.0 mm or less, from the viewpoint of water vapor barrier properties.

[0019] The food packaging body according to this embodiment can exhibit sufficient water vapor barrier properties even for dried foods, which require particularly high water vapor barrier properties, and is therefore particularly suitable for use as a packaging body for packaging foods, including dried foods. Here, the term "dried food" in this embodiment refers to food in a dry or semi-dried state (including pet food). Here, "dried food" refers to food with a moisture content of 15% by mass or less, and "semi-dried food" refers to food with a moisture content of more than 15% by mass and less than 50% by mass. Examples of dried foods include nuts, snack foods, cereals, luxury foods, dried noodles and pasta, grains and flours, dried vegetables, confectioneries, rice crackers, dairy products, and seasonings. Among these, from the viewpoint of more effectively obtaining the effects of this embodiment, it is preferable that the dried food include rice crackers, and it is more preferable that the dried food include dried rice crackers and dried beans coated with soy sauce, or rice crackers that are not coated with soy sauce on the surface. Furthermore, from the viewpoint of more effectively obtaining the effects of this embodiment, the water activity of the dried food is preferably 0.05 or more and 0.3 or less.

[0020] The food packaging body according to this embodiment is preferably used as an outer packaging bag that requires water vapor barrier properties. Furthermore, when the food packaging according to the present embodiment is used in an integrated package that is made up of food, individual packaging bags for individually packaging the food, and an outer packaging bag for packaging the plurality of individual packaging bags, the food packaging according to the present embodiment is preferably used in the outer packaging bag that is required to have water vapor barrier properties in the integrated package, thereby making it possible to obtain an integrated package that has sufficient water vapor barrier properties.

[0021] <Food packaging film> FIG. 1 is a cross-sectional view showing a schematic example of the structure of a food packaging film 100 for forming a food package according to an embodiment of the present invention. The food packaging film 100 according to this embodiment may be, for example, a film comprising a biaxially stretched film layer 101 made of a propylene polymer composition containing a propylene polymer, and a heat seal layer 103 provided so as to be in direct contact with at least one surface of the biaxially stretched film layer 101. Here, the heat seal layer 103 is the outermost layer, and the thickness of the heat seal layer 103 is preferably 0.1 μm or more and 10 μm or less. 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.

[0022] As mentioned above, OPP film has water vapor barrier properties but poor heat sealing properties. Therefore, when using OPP film for food packaging such as food packaging bags, it is necessary to laminate a CPP film or other film with excellent heat sealing properties to the OPP film. By further laminating a CPP film on the OPP film, the heat sealing strength of the resulting food package is increased, the intrusion of moisture and oxygen at the seal area is suppressed, and the water vapor barrier properties and oxygen barrier properties of the food package can be improved. However, because OPP film and CPP film have poor adhesion, the CPP film had to be laminated to the OPP film using an adhesive. As a result, food packaging films using OPP film used in food packages require a step of further laminating the CPP film using an adhesive, which requires many manufacturing steps, leaving room for improvement in terms of simplifying the manufacturing process and reducing costs.

[0023] On the other hand, in the food packaging film 100 according to this embodiment, the heat seal layer 103 can be formed directly on the biaxially oriented film layer 101, so there is no need to further laminate the CPP film using an adhesive as in the case of a laminated film of an OPP film and a CPP film, which simplifies the manufacturing process and improves productivity. Furthermore, because there is no need to use a CPP film, costs can be reduced.

[0024] Here, food packages made using the food packaging film 100 according to this embodiment have lower heat seal strength and poorer airtightness than food packages made using a laminated film of an OPP film and a CPP film, and therefore have inferior oxygen barrier properties, but surprisingly, despite the poor airtightness, they exhibit sufficient water vapor barrier properties. Therefore, they are particularly suitable for use as films constituting food packages for packaging foods that require water vapor barrier properties but not so much oxygen barrier properties (e.g., dried foods).

[0025] 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 mechanical properties, handling properties, appearance, formability, light weight, and the like is better.

[0026] Each layer that constitutes the food packaging film 100 will be described below.

[0027] [Biaxially stretched film layer] The biaxially stretched film layer 101 (also referred to as a biaxially stretched polypropylene-based film layer) in this embodiment is formed, for example, by biaxially stretching a film made of a propylene polymer composition containing a propylene polymer.

[0028] The thickness of the biaxially stretched film layer 101 in this embodiment is not particularly limited and can be set arbitrarily depending on the desired objectives such as water vapor barrier properties, cost, mechanical strength, transparency, etc., but is usually 10 μm or more and 100 μm or less, preferably 15 μm or more and 75 μm or less, and more preferably 20 μm or more and 50 μm or less. When the thickness of the biaxially stretched film layer 101 is within the above range, the balance of mechanical properties, handling properties, appearance, formability, lightweight properties, and the like is better.

[0029] 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 a propylene polymer composition, but it is necessary that it is biaxially stretched.

[0030] 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, more preferably 0.70 or more and 0.97 or less, and even more preferably 0.75 or more and 0.95 or less.

[0031] (Propylene polymer composition) The propylene polymer composition according to this embodiment contains a propylene polymer. The content of the propylene polymer in the propylene polymer composition 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 propylene polymer composition is taken as 100% by mass. This makes it possible to achieve a better balance between water vapor barrier properties, mechanical properties, handleability, appearance, moldability, etc.

[0032] (propylene polymer) Examples of the propylene polymer according to this embodiment include propylene homopolymers 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 alone or in combination of two or more. Among these, propylene homopolymer is preferred as the propylene polymer from the viewpoint of obtaining a biaxially stretched film layer 101 having a better balance of properties such as heat resistance, water vapor barrier properties, mechanical properties, and rigidity.

[0033] 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.

[0034] The melt flow rate (MFR) of the propylene polymer 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 viewpoints 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.

[0035] (Other ingredients) If necessary, various additives such as a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slipping agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added to the propylene polymer composition according to the present embodiment, within a range that does not impair the object of the present embodiment.

[0036] (Method for preparing propylene polymer composition) The propylene polymer composition according to the present embodiment can be prepared 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.

[0037] [Heat seal layer] In order to provide heat sealing properties, the food packaging film 100 according to this embodiment has a heat seal layer 103 as the outermost layer on at least one side of the biaxially oriented film layer 101. The heat seal layer 103 may be provided on both sides of the biaxially oriented film layer 101.

[0038] 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 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, and it becomes possible to laminate the heat seal layer 103 on the biaxially oriented film layer 101 without using an adhesive. In other words, it becomes possible to provide the heat seal layer 103 so that it is in direct contact with the surface of the biaxially oriented film layer 101, which simplifies the manufacturing process of the food packaging film 100, i.e., the manufacturing process of the food package according to this embodiment.

[0039] The heat seal layer 103 provided on one side of the food packaging film 100 is preferably a single layer, which can further simplify the manufacturing process of the food packaging film 100, i.e., the manufacturing process of the food package according to this embodiment.

[0040] Furthermore, the heat seal layer 103 is preferably formed by biaxially stretching simultaneously with the biaxially stretched film layer 101 in its pre-biaxially stretched state. 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, i.e., the manufacturing process for the food package according to this embodiment. Therefore, the heat seal layer 103 is preferably biaxially stretched.

[0041] (Polyolefin) The heat seal layer 103 according to this embodiment is made of, for example, a polyolefin-based resin composition containing polyolefin. Examples of the polyolefin constituting the heat seal layer 103 include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; polypropylene; propylene-α-olefin random copolymers; ethylene-vinyl acetate copolymers (EVA); and ionomer resins. Among these, at least one polyolefin selected from propylene-α-olefin random copolymers and propylene homopolymers is preferred as the polyolefin constituting the heat seal layer 103, as it has an excellent balance of adhesion to the biaxially oriented film layer 101, heat sealability, etc.

[0042] 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.

[0043] The melting point of the polyolefin constituting the heat seal layer 103 according to this embodiment is preferably in the range of 90° C. or higher and 170° C. or lower, more preferably 95° C. or higher and 165° C. or lower, and even more preferably 100° C. or higher and 163° 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 properties 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.

[0044] 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.

[0045] The content of polyolefin in the polyolefin resin composition 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 is taken as 100% by mass. This allows for a better balance between adhesion to the biaxially stretched film layer 101, heat sealability, etc.

[0046] (Other ingredients) If necessary, various additives such as 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 polyolefin resin composition constituting the heat seal layer 103 according to this embodiment, within a range that does not impair the object of this embodiment.

[0047] Furthermore, from the viewpoint of improving the heat sealability of the heat seal layer 103, it is preferable that the heat seal layer 103 does not substantially contain a tackifier. More specifically, the content of the tackifier in the heat seal layer 103 is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, even more preferably 0.01% by mass or less, and particularly preferably 0% by mass. Here, the tackifier is a resinous substance that has the property of imparting adhesiveness and is generally manufactured and sold as a tackifier. Examples of such tackifiers include chroman-based resins such as chroman-indene resins; phenol-based resins such as phenol-formaldehyde resins and xylene-formaldehyde resins; terpene-based resins such as terpene-phenolic resins, terpene resins (α,β-pinene resins), aromatic-modified terpene resins, and hydrogenated terpene resins; petroleum-based hydrocarbon resins such as synthetic polyterpene resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, aliphatic-cyclic hydrocarbon resins, aliphatic-alicyclic petroleum resins, aliphatic-aromatic petroleum resins, unsaturated hydrocarbon polymers, and hydrocarbon-based tackifying resins; hydrogenated products of the above petroleum-based hydrocarbon resins (also called hydrogenated petroleum hydrocarbon resins); and rosin-based resins such as pentaerythritol esters of rosin, glycerin esters of rosin, hydrogenated rosin, hydrogenated rosin esters, special rosin esters, and rosin-based tackifiers.

[0048] (Method for preparing polyolefin resin composition) The propylene polymer composition according to the present embodiment can be prepared 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.

[0049] <Method of manufacturing food packaging film> The food packaging film 100 according to this embodiment can be obtained, for example, by co-extrusion molding the above-mentioned propylene polymer composition for forming the biaxially stretched film layer 101 and the above-mentioned polyolefin resin composition for forming the heat seal layer 103 into a film, and then biaxially stretching the resulting laminated film using a known biaxially stretched film manufacturing method such as simultaneous biaxial stretching or sequential biaxial stretching. 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. The food packaging film 100 according to this embodiment can also be obtained by separately molding the biaxially stretched film layer 101 and the heat seal layer 103, laminating them together, and then heat molding them.

[0050] 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. [Example]

[0051] 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.

[0052] 1.Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Propylene polymer PP1: Propylene homopolymer (MFR: 3 g / 10 min, melting point: 157°C, manufactured by Prime Polymer Co., Ltd.) PP2: Propylene-ethylene random copolymer (MFR: 6 g / 10 min, melting point: 109°C, manufactured by Prime Polymer Co., Ltd.)

[0053] 2. Measurement and evaluation methods (1) MFR of propylene polymer Measured in accordance with ASTM D1238 at 230°C under a load of 2.16 kg.

[0054] (2) Melting point of propylene polymer The temperature of the maximum melting peak in the DSC curve of the propylene polymer obtained using a DSC (differential scanning calorimeter) was taken as the melting point.

[0055] (3) Water vapor barrier properties The food packaging bags prepared in the Examples and Comparative Examples were stored for 72 hours at 40°C and 90% RH. The weight of the calcium chloride was measured before and after storage, and the difference was used to calculate the water vapor permeability (g / (m 2 ·24h)) were calculated respectively.

[0056] (4) Pore evaluation, Approximately 5 mL of Ageless Seal Check Spray (red penetrant, manufactured by Mitsubishi Gas Chemical Company, Inc.) was sprayed onto the heat-sealed portion from the inside of the food packaging bags prepared in the Examples and Comparative Examples. The bag was then hung vertically with the heat-sealed portion sprayed with Ageless Seal Check Spray facing downwards and left for 0.5 hours. After that, the heat-sealed portion was observed and evaluated for the presence or absence of pores through which the coloring liquid penetrated by capillary action, the pore diameter, the length of the coloring liquid that penetrated the pores, and the number of pores.

[0057] (5) Productivity The productivity of food packaging bags was evaluated according to the following criteria. ○: The range of heat sealing conditions can be widened (there is no need to increase the heat sealing temperature or pressure to block the pores through which the coloring liquid penetrates due to capillary action) ×: The range of heat sealing conditions cannot be widened (it is necessary to increase the heat sealing temperature and pressure to block the pores through which the coloring liquid penetrates due to capillary action).

[0058] [Examples 1 to 12 and Comparative Example 1] PP1 for forming the biaxially stretched film layer (thickness: 27 μm) and PP2 for forming the heat seal layer (thickness: 3 μm) were coextruded and then biaxially stretched to produce a food packaging film. The coextrusion 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 Next, the food packaging film was folded back so that the heat-sealed layer was on the inside, and the two sides were heat-sealed to form a bag. A PET film (12 μm thick) with a width of 0.3 mm to 5 mm was sandwiched between one of the heat-sealed parts, and heat-sealing was performed on each side. After removing the PET film, calcium chloride was 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 Food packaging bags were produced so that the pore diameter was 0.3 mm or more and 5.0 mm or less. As a result, food packaging bags of Examples 1 to 12 were obtained, each having a pore diameter of 0.3 mm or more and 5.0 mm or less. Note that the food packaging bag of Comparative Example 1 was obtained in the same manner as in Examples 1 to 12, except that no PET film was sandwiched. The pore size was adjusted by adjusting the width of the PET film sandwiched between the heat-sealed portions, and the number of pores was adjusted by adjusting the number of PET films sandwiched between the heat-sealed portions. The heat sealing conditions are as follows: Heat sealing temperature: 120℃ Heat sealing time: 0.5 seconds Heat sealing pressure: 1.0kgf

[0059] [Table 1]

[0060] [Table 2]

[0061] [Table 3]

[0062] The food packages of the examples, which had pores in the heat-sealed portions through which the coloring liquid penetrated, had water vapor barrier properties equivalent to those of the comparative food packages, which did not have such pores. This demonstrates that the food packages of this embodiment have sufficient water vapor barrier properties. [Explanation of symbols]

[0063] 100 Food packaging film 101 Biaxially oriented film layer 103 Heat seal layer

Claims

1. A food package containing dried food inside and made of food packaging film, When a coloring liquid is sprayed onto the heat-sealed portion of the food packaging from inside the food packaging, the coloring liquid penetrates into the pores by capillary action (excluding those in which the coloring liquid penetrates partway through the sealed portion). ) exists, The water activity of the dried food is 0.05 or more and 0.3 or less, The pore diameter is 0.05 mm or more and 5.0 mm or less, The food packaging film comprises a biaxially oriented film layer made of a propylene polymer composition containing a propylene polymer, and a heat seal layer provided on at least one surface of the biaxially oriented film layer.

2. The food packaging according to claim 1, The food packaging material has a length of the coloring liquid that has permeated the pores that is 0.1 mm or more and 50 mm or less.

3. The food packaging according to claim 1 or 2, the heat seal layer is provided so as to be in direct contact with at least one surface of the biaxially stretched film layer, The food packaging body, wherein the heat seal layer is the outermost layer and has a thickness of 0.1 μm or more and 10 μm or less.

4. The food packaging according to claim 3, The food packaging material wherein the heat seal layer is a single layer.

5. The food packaging according to claim 3 or 4, The food packaging material wherein the heat seal layer is biaxially stretched.

6. The food packaging according to any one of claims 3 to 5, The heat seal layer comprises at least one selected from a propylene-α-olefin random copolymer and a propylene homopolymer.

7. The food packaging according to any one of claims 3 to 6, A food package, wherein the ratio of the thickness of the biaxially oriented film layer to the total thickness of the food packaging film is 0.50 or more and 0.998 or less.

8. The food packaging according to any one of claims 1 to 7, Food packaging used as an outer packaging bag.

9. A method for manufacturing a food package that contains dried food inside and is made of a food packaging film, wherein when a coloring liquid is sprayed from inside the food package, the coloring liquid penetrates into pores by capillary action (excluding those in which the coloring liquid penetrates halfway through the sealed portion). forming a heat-sealed portion so that The water activity of the dried food is 0.05 or more and 0.3 or less, The pore diameter is 0.05 mm or more and 5.0 mm or less, A method for producing a food packaging body, wherein the food packaging film comprises a biaxially oriented film layer made of a propylene polymer composition containing a propylene polymer, and a heat seal layer provided on at least one surface of the biaxially oriented film layer.

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