Food packaging containers

Abstract

To provide a food packaging container that exhibits high strength and has excellent sealing and cutting properties. [Solution] A food packaging container formed into a bag shape via a sealant layer, wherein a laminated sheet comprising a sealant layer, a base layer, an adhesive layer, a printed layer, and a cover layer in this order is formed via a sealant layer, the sealant layer contains linear low-density polyethylene resin, the base layer contains polyethylene resin and heavy calcium carbonate powder, the adhesive layer contains a urethane adhesive, the printed layer has a urethane ink, the cover layer is made of a biaxially oriented film of nylon 6, the content of heavy calcium carbonate powder in the base layer is 35% by mass or more and 45% by mass or less of the total mass, the ratio of the thickness of the sealant layer to the base layer is 1:3 to 1:4, the thickness of the adhesive layer is 1 to 10 μm, and the thickness of the cover layer is 10 to 25 μm.

Description

[Technical Field]

[0001] This invention relates to a food packaging container. More specifically, this invention relates to a food packaging container based on a laminated sheet molded into a bag shape, which has high strength and excellent sealing and cutting properties. [Background technology]

[0002] Conventionally, laminated sheets, including composite multilayer films made by lamination, have been known as food packaging containers such as retort pouches for enclosing pre-cooked retort foods. Such packaging bags and other packages, for example, packages based on laminated sheets using polyolefin resin compositions containing inorganic fillers, are indispensable for food packaging because they possess high strength, light-blocking properties, good printability and aesthetic appeal, and characteristics such as long-term storage due to oxygen barrier properties. For this reason, various types of food packaging containers based on laminated sheets have been developed to date.

[0003] For example, Patent Document 1 discloses a packaging container in which a barrier resin layer made of nylon is laminated with a layer made of a resin composition containing titanium as a white pigment, and a layer made of a resin composition containing carbon black as a black pigment. Patent Document 2 discloses a sealant film for packaging materials that includes a layer in which an inorganic filler such as talc surface-treated with a silane coupling agent is dispersed in a polyolefin-containing matrix. Patent Document 3 discloses a sealant film having multiple layers containing zeolite and talc together with a specific linear low-density polyethylene.

[0004] Here, by including linear low-density polyethylene in one or more layers constituting the laminated sheet, as described in Patent Document 3, the heat-sealability and cutability of the sealant film can be improved. Patent Document 4 also discloses a sealant film using similar polyethylene. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-80506 [Patent Document 2] Japanese Patent Publication No. 2019-85127 [Patent Document 3] Japanese Patent Publication No. 2023-63172 [Patent Document 4] Japanese Patent Publication No. 2023-64752 [Overview of the project] [Problems that the invention aims to solve]

[0006] Although food packaging containers based on laminated sheets possess the excellent properties described above, there is often a trade-off between mechanical properties such as strength, rigidity, and impact resistance, and ease of cutting when opening the package manually, light shielding, and heat sealability. For example, in packaging containers based on resin compositions containing inorganic fillers, as described in Patent Documents 1-3, cutability and light shielding are good, but heat sealability and laminate strength may be insufficient. In packaging containers using low-density polyethylene, as described in Patent Documents 3-4, heat sealability is good, but mechanical strength such as rigidity tends to be insufficient. Insufficient strength in either the heat-sealed portion or the main body poses a risk of damage, particularly during sterilization or when strong external force is applied, preventing the food from being completely sealed. Thus, conventional packaging containers have had issues such as room for improvement in the sealing of contents and poor cutability.

[0007] This invention has been made in view of the above circumstances, and aims to provide a food packaging container that exhibits high strength and excellent sealing and cutting properties. [Means for solving the problem]

[0008] To solve the above problems, the inventors diligently studied the layer structure of the laminated sheet constituting the food packaging container. As a result, they found that by adjusting the type and blending ratio of resins and inorganic fillers contained in each layer of the laminated sheet, as well as the thickness and thickness ratio of each layer, a food packaging container with high strength and excellent sealing and cutting properties can be obtained.

[0009] In other words, the present invention, which solves the above problems, is a food packaging container formed in a bag shape via the sealant layer, in which a laminated sheet is formed in which a sealant layer, a base layer, an adhesive layer, a printed layer, and a cover layer are laminated in this order, The sealant layer contains a linear low-density polyethylene resin, The base layer comprises polyethylene resin and heavy calcium carbonate powder. The adhesive layer contains a urethane-based adhesive. The aforementioned printing layer has a urethane-based ink, The aforementioned cover layer is made of a biaxially oriented film of nylon 6. The content of the heavy calcium carbonate powder in the base layer is 35% by mass or more and 45% by mass or less, relative to the total mass of the base layer. The food packaging container has a thickness ratio of 1:3 to 1:4 between the sealant layer and the base material layer, a thickness of 1 μm or more and 10 μm or less between the adhesive layer and the thickness of 10 μm or more and 25 μm or less between the cover layer.

[0010] In one embodiment of the food packaging container of the present invention, the food packaging container is described in which the polyethylene resin in the base layer includes a linear low-density polyethylene resin.

[0011] In one embodiment of the food packaging container of the present invention, the average particle size of the heavy calcium carbonate powder measured by the air permeability method according to JIS M-8511 is 0.7 μm or more and 6.0 μm or less.

[0012] In one aspect of the food packaging container of the present invention, the heavy calcium carbonate powder is a heavy calcium carbonate powder that has not been surface-treated, and the above food packaging container is shown.

[0013] In one aspect of the food packaging container of the present invention, the arithmetic mean height (Ra) of the surface of the base material layer conforming to JIS B0601:2013 is 0.4 μm or more and 1.0 μm or less, and the above food packaging container is shown.

Effects of the Invention

[0014] According to the present invention, a food packaging container is provided that exhibits high strength and is excellent in sealing properties and cutting properties.

Modes for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described in detail based on embodiments

[0016] ≪Food Packaging Container≫ A food packaging container according to an embodiment of the present invention is a food packaging container formed into a bag shape through a sealant layer from a laminated sheet in which a sealant layer, a base material layer, an adhesive layer, a printing layer, and a cover layer are laminated in this order, the sealant layer contains linear low-density polyethylene resin, the base material layer contains polyethylene resin and heavy calcium carbonate powder, the adhesive layer contains a urethane-based adhesive, the printing layer has urethane-based ink, the cover layer is made of a biaxially stretched film of 6 nylon, the content of the heavy calcium carbonate powder in the base material layer is 35% by mass or more and 45% by mass or less with respect to the total mass of the base material layer, the ratio of the thickness of the sealant layer to the base material layer is 1:3 to 1:4, the thickness of the adhesive layer is defined to be 1 μm or more and 10 μm or less, and the thickness of the cover layer is defined to be 10 μm or more and 25 μm or less.

[0017] In the food packaging container of this embodiment, the laminated sheet includes the five layers described above, and the composition of each layer, such as the type and mixing ratio of resins and inorganic fillers contained in each layer, as well as the physical composition, such as the thickness and thickness ratio of each layer, are defined as described above. As a result of the combination of these definitions, high strength, excellent sealing properties, and cutability are achieved. Below, each of these components will be described in order, focusing on the structure of each layer.

[0018] <(1) Sealant layer> In the food packaging container of this embodiment, the sealant layer contains linear low-density polyethylene resin. The inclusion of linear low-density polyethylene provides good heat-sealability and cutability for the food packaging container. The sealant layer is the innermost layer of the food packaging container of this embodiment and functions as a sealant when the laminated sheet is formed into a bag shape.

[0019] (Linear low-density polyethylene resin) Here, linear low-density polyethylene resin itself is well known. Its density is 0.940 g / cm³. 3 It is a linear polyethylene of a certain magnitude, and is also abbreviated as LLDPE. It is usually produced by copolymerization of ethylene with a small amount of α-olefin, such as 1-butene, 1-hexene, 4-methylpentene-1, and / or 1-octene. Any general-purpose LLDPE can be used in this invention, and there are no particular restrictions on its density, copolymer composition, molecular weight, melt viscosity, etc.

[0020] However, in this embodiment, the sealant layer uses a relatively low-density LLDPE, specifically one with a density of 0.925 g / cm³. 3 For example, anything below a certain level, such as 0.910-0.925 g / cm³. 3 The degree, especially 0.910-0.920 g / cm³ 3 It is preferable to use something of a certain quality.

[0021] (Composition of the sealant layer) The sealant layer in this embodiment may also contain various additives in addition to LLDPE, for example, in an amount of about 0.01 to 10% by mass, particularly in an amount of about 0.1 to 5% by mass. Examples of additives include, but are not limited to, inorganic fillers such as silica, zeolite, talc, and calcium carbonate; slip agents such as amides and polyesters; softeners such as oils; and anti-aging agents.

[0022] (Thickness of the sealant layer, etc.) In this embodiment, there are no particular restrictions on the thickness of the sealant layer itself; it is sufficient as long as the thickness ratio with the base layer, as described later, falls within the range of 1:3 to 1:4. Preferably, the thickness of the sealant layer is 1 to 50 μm, particularly 5 to 20 μm. With such a sealant layer thickness, a better balance can be achieved between the sealing properties and cutability of the contents.

[0023] <(2) Base material layer> In the food packaging container of this embodiment, the base layer contains polyethylene resin and heavy calcium carbonate powder. Here, the content of heavy calcium carbonate powder relative to the total mass of the base layer is 35% by mass or more and 45% by mass or less, preferably about 37-42% by mass. By including an amount of heavy calcium carbonate powder in this range, the base layer becomes a high-strength, rigid layer with good light-shielding properties. Because the food packaging container of this embodiment is equipped with such a base layer, it has a well-balanced and excellent combination of properties such as strength, sealing ability of contents, cutability, and light-shielding properties, and also has a good appearance.

[0024] (Polyethylene resin) As polyethylene resins, for example, the following are known, but any of these known polyethylenes can be used in the base layer of this embodiment. It may also be a resin copolymerized with components other than ethylene. • High-density polyethylene (HDPE): 0.942 g / cm³ 3 Polyethylene having the above density • Medium-density polyethylene: 0.930 g / cm³ 3 More than 0.942g / cm 3Polyethylene with a density less than · Low-density polyethylene (LDPE): 0.910 g / cm 3 Greater than or equal to 0.930 g / cm 3 Polyethylene with a density less than · Linear low-density polyethylene (LLDPE): 0.940 g / cm 3 Linear polyethylene with a density less than. When the density is less than 0.910 g / cm 3 It may also be distinguished as "ultra-low density polyethylene (ULDPE)".

[0025] From the perspective of the characteristic balance of food packaging containers, it is preferable that the polyethylene resin in the base material layer contains linear low-density polyethylene resin (LLDPE). More preferably, the polyethylene resin in the base material layer consists solely of LLDPE.

[0026] (Heavy calcium carbonate powder) Heavy calcium carbonate is obtained by mechanically pulverizing natural calcium carbonate, etc., and is clearly distinguished from synthetic calcium carbonate (light calcium carbonate) produced by chemical precipitation reactions, etc. In the base material layer of this embodiment, any heavy calcium carbonate powder may be used. For example, heavy calcium carbonate obtained by pulverizing and classifying natural calcium carbonate such as calcite (limestone, chalk, marble, etc.), shells, and coral can be used. Also, the form of heavy calcium carbonate is not particularly limited, but from the perspective of good dispersibility in the resin in the base material layer, it is preferably in particulate form.

[0027] When heavy calcium carbonate is in particulate form, its average particle size is preferably 0.7 μm to 6.0 μm, more preferably 1.0 μm to 5.0 μm, and even more preferably 1.5 μm to 3.0 μm. Here, the average particle size can be measured, for example, by the air permeability method according to JIS M-8511. If the average particle size of heavy calcium carbonate is within the above range, it will have good dispersibility in polyethylene resin, and problems such as heavy calcium carbonate particles protruding and falling off from the surface of the laminated sheet, or impairing mechanical strength, will be further suppressed.

[0028] The heavy calcium carbonate powder preferably has a roundness of 0.50 to 0.95, and particularly 0.60 to 0.90. Here, roundness represents the degree of spherical shape, and can be determined, for example, by analyzing the projection image of the particles obtained with a scanning microscope or stereomicroscope using commercially available image analysis software. A lower roundness indicates a higher degree of irregularity.

[0029] The heavy calcium carbonate powder may be surface-treated with, for example, a coupling agent, surfactant, or fatty acid. However, in the base layer of this embodiment, it is preferable to use heavy calcium carbonate powder that has not been surface-treated. Using untreated heavy calcium carbonate powder has the advantages of being economical and being preferable for food packaging container applications.

[0030] (Composition of the base layer) In this embodiment, the substrate layer contains 35-45% by mass of heavy calcium carbonate as described above, but other additives may also be included. There are no particular restrictions on the additives, and various known ones can be used. Examples include lubricants such as zinc stearate and magnesium stearate, dispersants such as sodium polyacrylate, polyglycerin fatty acid esters and sorbitan fatty acid esters, plasticizers such as acetyl tributyl citrate, triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, o-benzoyl benzoate, diacetin and epoxidized soybean oil, waxes such as polyethylene and polyester, polyolefin-based, polyester-based and fatty acid-based oils, and even flame retardants and antioxidants, but are not limited to these.

[0031] When using these additives, it is preferable that the amount of each additive be, for example, 0.1 to 3% by mass, particularly 0.2 to 2% by mass, relative to the total mass of the base layer. Furthermore, it is preferable that the total weight of the additives be 10% by mass or less, particularly 0.1 to 5% by mass, relative to the total mass of the base layer. It is also possible to use polymers other than polyethylene and inorganic fillers other than heavy calcium carbonate as additives, but since these may affect the balance of the properties of the food packaging container, it is preferable to use them in amounts of about 0.1 to 5% by mass, and even more preferable not to use them at all.

[0032] (Thickness of the base layer, etc.) In the food packaging container of this embodiment, the ratio of the sealant layer to the base layer thickness is 1:3 to 1:4, as described above. There are no particular restrictions on the thickness of the base layer itself, but it is preferably, for example, 10 to 200 μm, more preferably 15 to 100 μm, and especially preferably 20 to 50 μm. With such a base layer thickness, the food packaging container of this embodiment can have an even better balance of various properties such as strength, sealing ability, and cutability. The base layer may be a single layer, or it may consist of multiple layers of the same or different compositions.

[0033] Furthermore, the surface of the substrate layer, particularly the surface on the adhesive layer side, preferably has an arithmetic mean height (Ra) of 0.4 μm to 1.0 μm, and more preferably 0.5 to 0.9 μm, in accordance with JIS B0601:2013. Having a substrate layer with such roughness increases adhesive strength and ensures better sealing performance.

[0034] <(3) Adhesive layer> In the food packaging container of this embodiment, the adhesive layer is a layer containing a urethane-based adhesive and having a thickness of 1 μm to 10 μm. When such an adhesive layer is combined with the base material layer described above, good laminate strength can be achieved.

[0035] (Urethane-based adhesive) There are no particular restrictions on the urethane adhesive, and various known urethane adhesives can be used in the adhesive layer of this embodiment. Examples include, but are not limited to, adhesives based on polyester urethane, polyether urethane, polycarbonate urethane, etc. Other components besides polyurethane may be included, such as plasticizers, oils, tackifiers, antioxidants, fillers, etc. Commercially available one-component or two-component products, as well as other types, can be used. For example, it is possible to mix urethane raw materials such as isocyanate and polyester polyol and react them when laminating with a base layer, etc., to form a urethane adhesive-containing layer.

[0036] (Thickness of the adhesive layer) In this embodiment, the thickness of the adhesive layer is 1 to 10 μm as described above, but it is preferable to have a thickness of about 2 to 5 μm. If the adhesive layer is of this thickness, the food packaging container can have better properties such as adhesive strength.

[0037] <(4) Printing layer> In the food packaging container of this embodiment, the printed layer has a urethane-based ink. Examples of urethane-based inks include, but are not limited to, those based on polyester-based urethane, polyether-based urethane, polycarbonate-based urethane, etc., and containing pigments such as dyes. They may also contain oils such as epoxidized soybean oil, dispersants, antioxidants, and other general-purpose additives. Any commercially available urethane-based ink can also be used.

[0038] There are no particular restrictions on the thickness of the printed layer in this embodiment, and it can be set to any desired thickness depending on the design of the food packaging container, the type of ink, etc. From the viewpoint of the layer balance of the laminated sheet, it is preferable that the thickness of the printed layer be, for example, 0.1 to 5.0 μm, and particularly 0.5 to 2.0 μm.

[0039] <(5) Cover layer> In the food packaging container of this embodiment, the cover layer is made of a biaxially oriented film of nylon 6, with a thickness of 10 μm to 25 μm. Nylon 6 has the advantages of excellent strength and heat resistance, as well as low oxygen permeability and moisture absorption. Therefore, the food packaging container of this embodiment, which has a cover layer made of a biaxially oriented film of nylon 6, can be made of high strength, as well as excellent heat resistance and food preservation properties.

[0040] (Biaxially oriented film) Biaxially oriented nylon 6 film itself is well known, and any commercially available biaxially oriented nylon 6 film can be used in the food packaging container of this embodiment. Extruded film may also be used. Of course, it is also possible to prepare an unoriented nylon 6 film by biaxial stretching. The nylon 6 film may also contain resins and additives other than nylon 6 in amounts of, for example, about 0.01 to 10% by mass, particularly about 0.1 to 5% by mass. As additives, those similar to those contained in the sealant layer and base layer can be used. Examples include, but are not limited to, crosslinking agents, antioxidants, antiblocking agents, lubricants, ultraviolet absorbers, light stabilizers, reinforcing agents, antistatic agents, and pigments. Fillers such as talc, silica, and calcium carbonate may also be contained.

[0041] There are no particular restrictions on the stretching ratio of biaxially oriented films. For example, the stretching ratio in the machine direction (the direction of substrate flow, MD direction: longitudinal stretching) may be 2 to 15 times, particularly 5 to 10 times, and the stretching ratio in the width direction (the direction perpendicular to the MD direction, TD direction: transverse stretching) may be 2 to 15 times, particularly 5 to 10 times. By setting the stretching ratio to 2 times or more, good strength and heat resistance are more easily achieved. Also, by setting the stretching ratio to 15 times or less, defects such as breakage during stretching are suppressed.

[0042] Here, longitudinal stretching can be performed, for example, during film forming, by applying a difference in peripheral speed to the roll group of the manufacturing equipment at a temperature about 10°C or more higher than the glass transition temperature of nylon 6. Transverse stretching can be performed, for example, by placing the formed sheet on a tenter.

[0043] The cover layer may also be surface-treated. This can improve adhesion with other layers. Surface treatment methods include, but are not limited to, physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen plasma, glow discharge treatment, and chemical treatments such as oxidation treatment with chemicals.

[0044] (Thickness of the cover layer) In this embodiment, the thickness of the cover layer is 10 to 25 μm as described above, but it is preferable to have a thickness of about 12 to 20 μm. If the cover layer is of this thickness, the food packaging container can have superior properties such as strength, heat resistance, and food preservation.

[0045] <(6) Structure of the laminated sheet> In the food packaging container of this embodiment, the laminated sheet comprises a sealant layer, a base layer, an adhesive layer, a printed layer, and a cover layer as described above, but it may also include other layers such as an easy-adhesion layer. The base layer may also have a two-layer structure. As for the thickness of the laminated sheet, there are no particular restrictions as long as the ratio of the thickness of the sealant layer to the thickness of the base layer is 1:3 to 1:4, the thickness of the adhesive layer is 1 to 10 μm, and the thickness of the cover layer is 10 to 25 μm.

[0046] (7) Characteristics of food packaging containers The food packaging container of this embodiment is formed from a laminated sheet having the five layers described above, and therefore exhibits excellent balance in strength, impact resistance, sealing properties of contents, cutability, and adhesion between layers, such as heat sealability. For example, it is resistant to damage during sterilization or when strong external forces are applied, and can stably seal food. Furthermore, since the amount of heavy calcium carbonate powder in the base material is specified as 35-45% by mass, and the inner layer has a sealant layer containing linear low-density polyethylene resin, it has good cutability, is easy to process, has a clean surface, and the risk of inorganic filler contact with packaged food is low. On the other hand, since more than one-third of the base material layer is calcium carbonate, the amount of resin used can be reduced, which can contribute to environmental protection. It also has good light-shielding properties, heat resistance, printability, and aesthetic appeal, and can also possess characteristics such as long-term storage due to oxygen barrier properties.

[0047] ≪Method of manufacturing food packaging containers≫ A food packaging container according to one embodiment of the present invention can be obtained by folding a laminated sheet having the above-described configuration with the sealant layer facing inward and sealing the edges to form a bag shape. Alternatively, two laminated sheets may be prepared and the sealant layers of each sheet may be placed facing each other to form a bag shape in the same manner.

[0048] <Method for manufacturing laminated sheets> There are no particular restrictions on the manufacturing method of the laminated sheet, and various conventional methods can be employed. For example, the five layers may be co-extruded, or each layer may be formed into a sheet and then laminated using a press or calender roll. From the viewpoint of ease of manufacturing, it is preferable to co-extrude the sealant layer and the base material layer to form a sheet, and then laminate the adhesive layer, the printed layer, and the cover layer. For example, a urethane-based adhesive or urethane-based emulsion dissolved in a solvent is applied to the base material side surface of the laminate of the co-extruded sealant layer and base material layer, and dried to form an adhesive layer. At the same time, a printed layer of the desired design is formed on a separately prepared cover layer using a conventional printing method. Next, the laminate with the adhesive layer and the cover layer with the printed layer are joined using a calender roll or press or other method. The laminated sheet in this embodiment may be formed by such a method.

[0049] <Method for molding food packaging containers> The laminated sheets manufactured as described above can be stacked with the sealant layer facing inward and the edges sealed to form a bag-shaped food packaging container. There are no particular restrictions on the sealing method, and various methods such as heat sealing and bonding with adhesives can be used. Heat sealing of the edges is particularly preferred. The melting point of the linear low-density polyethylene resin in the sealant is lower than that of the nylon 6 in the cover layer and is among the lowest of polyethylene resins, so the edges of the food packaging container can be easily sealed without damaging the shape or properties of the cover layer or base layer. [Examples]

[0050] The present invention will be described more specifically below based on examples. These examples are provided solely for the purpose of illustrating specific aspects and embodiments to facilitate understanding of the concepts and scope of the present invention disclosed herein and described in the appended claims, and the present invention is not limited in any way to these examples.

[0051] [Example 1] [Fabrication of laminated sheets] LLDPE (density 0.915g / cm 3 Raw material pellets were prepared by mixing and kneading 16 parts by mass of MFR (190℃, 2.16kg) 1.0g / 10min, 80 parts by mass of heavy calcium carbonate (average particle size: 2.2μm, no surface treatment), and 4 parts by mass of processing aid (paraffin + fatty acid (salt)) using an HTM50 type twin-screw extruder with opposite rotation (manufactured by CTC Co., Ltd.).

[0052] The obtained raw material pellets and LLDPE (density 0.915 g / cm³) 3 Mix MFR (190℃, 2.16kg) 1.0g / 10min) in a mass ratio of 50:50 (calcium carbonate content 40% by mass) and LLDPE (density 0.915g / cm³). 3 The material was co-extruded with MFR (190°C, 2.16 kg) 1.0 g / 10 min. A screw extruder and a feed block type T-die were used for co-extrusion, and a two-layer sheet consisting of a substrate layer and a sealant layer made of LLDPE was extruded and rapidly cooled on a cooling roll. The thickness of each layer in the resulting two-layer sheet was 35 μm for the substrate layer and 10 μm for the sealant layer. Next, the surface of the substrate layer was subjected to corona treatment. The arithmetic mean height (Ra) of the substrate layer side surface of the treated two-layer sheet was 0.57 μm.

[0053] A 15μm thick biaxially oriented nylon 6 film, with one side corona-treated, was subjected to gravure printing with urethane-based ink on the corona-treated side. A urethane-based adhesive dissolved in a solvent was then applied (3μm thick) on top of the printed surface. After drying, the two layers were pressed together with a heated roll to perform dry lamination, forming a laminated film.

[0054] [Preparation of test specimens] The laminate film obtained above was cut to A5 size, and two of these pieces were stacked with the sealant layer facing inward. The three sides were then heat-sealed to form a bag. 185g of water was placed in the resulting bag, and the remaining open side was heat-sealed under the same conditions to create a test specimen of a food packaging container with water sealed inside. Two pentagonal cuts, 1.5mm wide and 2mm long from end to tip, were made at the ends of the test specimen.

[0055] [Characteristic evaluation] The strength, sealability, and cutability of the test specimens prepared as described above were evaluated based on the following test methods. The evaluation results, along with the evaluation results regarding processability during the preparation of laminated sheets (see below), are shown in Table 1 below. • Drop test: Ten of the above test specimens were placed in a single case and dropped onto a concrete surface from a height of 120 cm. This operation was repeated 50 times, and if no specimens were damaged, it was evaluated as "○" (good), and if even one specimen was damaged, it was evaluated as "×" (bad). • Hand tearing test: The test specimens were torn 10 cm by hand from the cut point. If all 10 specimens could be cut without any resistance, it was rated as "○" (good). If even one specimen showed any resistance, it was rated as "×" (bad). • Processability: Products where the resin composition was easy to knead during the preparation of the base layer and the thickness variation of the two-layer extruded sheet was good (less than 10% of the total thickness) were rated as "○", while products with poor kneadability and thickness variation were rated as "×".

[0056] [Examples 2-5, Comparative Examples 1-9] The same procedure as in Example 1 was followed, except that the composition of the base layer, the material of the cover layer, and the thickness of each layer were changed as shown in Table 1. The characteristics evaluation results, along with the characteristics of each test specimen, are shown in Table 1.

[0057] [Table 1]

[0058] From the above, it has become clear that when the sealant layer contains LLDPE, the base layer contains polyethylene resin and heavy calcium carbonate powder, the cover layer is made of a biaxially oriented nylon 6 film, the heavy calcium carbonate powder content in the base layer is 35-45% by mass, and each layer has a specific thickness and thickness ratio, a food packaging container can be obtained that exhibits high strength, has excellent sealing and cutting properties, and is easy to mold.

Claims

1. A food packaging container is formed in a bag shape via the sealant layer, in which a laminated sheet is formed in the order of a sealant layer, a base layer, an adhesive layer, a printed layer, and a cover layer. The sealant layer contains a linear low-density polyethylene resin, The base layer comprises polyethylene resin and heavy calcium carbonate powder. The adhesive layer contains a urethane-based adhesive. The aforementioned printing layer has a urethane-based ink, The aforementioned cover layer is made of a biaxially oriented film of nylon 6. The content of the heavy calcium carbonate powder in the base layer is 35% by mass or more and 45% by mass or less, relative to the total mass of the base layer. A food packaging container in which the ratio of the thickness of the sealant layer to the thickness of the base material layer is 1:3 to 1:4, the thickness of the adhesive layer is 1 μm or more and 10 μm or less, and the thickness of the cover layer is 10 μm or more and 25 μm or less.

2. The food packaging container according to claim 1, wherein the polyethylene resin in the base layer includes a linear low-density polyethylene resin.

3. The food packaging container according to claim 1, wherein the average particle size of the heavy calcium carbonate powder, as determined by the air permeation method according to JIS M-8511, is 0.7 μm or more and 6.0 μm or less.

4. The food packaging container according to claim 3, wherein the heavy calcium carbonate powder is heavy calcium carbonate powder that has not undergone surface treatment.

5. The food packaging container according to claim 1, wherein the arithmetic mean height (Ra) of the surface of the base layer, in accordance with JIS B0601:2013, is 0.4 μm or more and 1.0 μm or less.

Images