Laminated sheet and container

Abstract

To provide an inorganic substance powder-containing laminated sheet and a container that are excellent in cold resistance and heat resistance.SOLUTION: The present invention provides, e.g., a laminated sheet having three or more layers. The laminated sheet includes at least an inner layer, and a first outer layer and a second outer layer laminated on a surface of the inner layer. The laminated sheet includes a thermoplastic resin that satisfies predetermined requirements.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated sheet and a container. [Background technology]

[0002] In recent years, from the viewpoint of environmental protection, attempts have been made to reduce the resin component content in various resin molded products. One such attempt is to blend inorganic powder such as calcium carbonate in a resin molded product (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6857428 [Patent Document 2] Patent No. 7113579 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, although resin molded products containing inorganic powders have a low environmental impact, there are still issues to be addressed in adjusting the strength and other properties of the resin molded products according to their intended use. In particular, there is a need for a resin molded product that is both cold-resistant and heat-resistant.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inorganic substance powder-containing laminated sheet and a container that are excellent in cold resistance and heat resistance. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by using a thermoplastic resin that satisfies certain requirements as a material, and have completed the present invention. More specifically, the present invention provides the following.

[0007] (1) A laminated sheet of three or more layers, the laminated sheet comprises at least an inner layer, and a first outer layer and a second outer layer laminated on a surface of the inner layer; the laminate sheet contains a thermoplastic resin, the inner layer contains an inorganic powder, the ratio of the thickness of the first outer layer and the thickness of the second outer layer to the total thickness of the laminated sheet is 2.0% or more and 20.0% or less, the inorganic substance powder includes calcium carbonate, the thermoplastic resin includes a polyethylene-based resin, The thermoplastic resin has a weight average molecular weight of 230,000 or more and 330,000 or less as measured by gel permeation chromatography (GPC), an area of ​​a molecular weight region corresponding to 1 / 5 or less of the peak top molecular weight (Mp) determined from a GPC elution curve of the thermoplastic resin is 20% or more and 33% or less of the total area of ​​the GPC elution curve; Laminated sheet.

[0008] (2) The laminate sheet according to (1), wherein the content of the inorganic substance powder is 30.0% by mass or more and 80.0% by mass or less with respect to the laminate sheet.

[0009] (3) The laminated sheet according to (1), wherein the calcium carbonate has a maximum particle size of 30 μm or less.

[0010] (4) The laminate sheet according to (1), wherein the thermoplastic resin includes high-density polyethylene.

[0011] (5) The laminate sheet according to (1), wherein the thermoplastic resin consists solely of a polyethylene-based resin.

[0012] (6) The laminate sheet according to (1), wherein the thermoplastic resin of the first outer layer and the second outer layer comprises a high-density polyethylene resin.

[0013] (7) The laminate sheet according to (1), wherein the calcium carbonate has an average particle size of 0.7 μm or more and 6.0 μm or less, as measured by an air permeability method in accordance with JIS M-8511:2014.

[0014] (8) A laminate sheet according to any one of (1) to (7) above, which is used for a vacuum-formed product.

[0015] (9) A laminated sheet according to any one of (1) to (7) above, which is used for a food packaging container.

[0016] (10) A container comprising: The container is made of a laminated sheet of three or more layers, the laminated sheet comprises at least an inner layer, and a first outer layer and a second outer layer laminated on a surface of the inner layer; the laminate sheet contains a thermoplastic resin, the inner layer contains an inorganic powder, the ratio of the thickness of the first outer layer and the thickness of the second outer layer to the total thickness of the laminated sheet is 2.0% or more and 20.0% or less, the inorganic substance powder includes calcium carbonate, the thermoplastic resin includes a polyethylene-based resin, The thermoplastic resin has a weight average molecular weight of 230,000 or more and 330,000 or less as measured by gel permeation chromatography (GPC), an area of ​​a molecular weight region corresponding to 1 / 5 or less of the peak top molecular weight (Mp) determined from a GPC elution curve of the thermoplastic resin is 20% or more and 33% or less of the total area of ​​the GPC elution curve; container.

[0017] (11) The container has a recessed storage portion capable of storing an article, The storage portion has a bottom portion and a side portion formed along the outer periphery of the bottom portion, the storage section has a plurality of support sections that are spaced apart from each other and that are capable of supporting the article on the inner surfaces of the bottom and side sections, The plurality of support portions are provided at intervals in the circumferential direction of the bottom portion, and protrude inward from the outer circumferential side of the bottom portion to the bottom side of the side portion, A plurality of grooves are formed on the inner surface of the side portion at intervals in the circumferential direction and extending in the depth direction of the storage portion. (10) A container as described in (10).

[0018] (12) The container has a connecting portion that integrally connects the plurality of storage portions so that the storage portions can be separated by applying a predetermined stress. (11) A container as described in (11).

[0019] (13) The side portion is provided at a distance from the support portion and has a step portion formed by projecting outward from the bottom portion side toward the outer periphery. (11) A container as described in (11).

[0020] (14) The bottom portion has convex portions formed thereon at intervals with respect to the plurality of support portions and protruding inward. (11) A container as described in (11).

[0021] (15) The container according to any one of (10) to (14), wherein the container is a vacuum-formed product.

[0022] (16) A container according to any one of (10) to (14), which is for packaging food.

[0023] (17) A container according to any one of (10) to (14), which is for packaging frozen food. [Effects of the Invention]

[0024] According to the present invention, an inorganic substance powder-containing laminated sheet and a container are provided which are excellent in cold resistance and heat resistance. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a plan view of a container according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to this.

[0027] <Laminated sheet> A laminate sheet according to one embodiment of the present invention is a laminate sheet having a structure of three or more layers (i.e., an inner layer and a first outer layer and a second outer layer laminated on the surface of the inner layer), and satisfies all of the following requirements: The laminate sheet contains a thermoplastic resin. The inner layer contains inorganic powder. The ratio of the thickness of the first outer layer and the second outer layer to the total thickness of the laminate sheet is 2.0% or more and 20.0% or less. The inorganic powder contains calcium carbonate. The thermoplastic resin includes a polyethylene resin. The weight average molecular weight of the thermoplastic resin measured by gel permeation chromatography (GPC) is 230,000 or more and 330,000 or less. The area of ​​the molecular weight region that is 1 / 5 or less of the peak top molecular weight (Mp) determined from the GPC elution curve of the thermoplastic resin is 20% or more and 33% or less of the total area of ​​the GPC elution curve.

[0028] A laminated sheet containing a high content of inorganic powder has the advantage of being environmentally friendly, but it may be subject to deformation due to cooling or heating due to uneven distribution of the inorganic powder. Under the above circumstances, the inventors conducted research and unexpectedly found that the molecular weight characteristics of the thermoplastic resin to be blended affect the cold resistance and heat resistance of the resulting laminated sheet or container.

[0029] In the present invention, "cold resistance" includes the laminated sheet or container being less likely to crack even under refrigerated conditions (for example, 4°C or lower) or frozen conditions (for example, -4°C or lower). The cold resistance can be evaluated by the method shown in the examples.

[0030] In the present invention, "heat resistance" includes the property that deformation or the like does not easily occur in the laminated sheet or container even when heated. Examples of heat treatment include microwave heating. In the present invention, "microwave heating" includes heating treatment using microwaves, for example, heating at 500 to 1500 W. In one embodiment of the present invention, "microwave oven" includes those that meet the definition set forth by the Consumer Affairs Agency of Japan. The heating time in a microwave oven is adjusted appropriately depending on the wattage, the type and size of the food, etc., and can be, for example, from a few seconds to 20 minutes. The heat resistance can be evaluated by the method shown in the examples.

[0031] In the present invention, the phrase "consisting of component A" means that the composition does not substantially contain any components other than component A.

[0032] In the present invention, "substantially free of component B" includes an embodiment in which the content of component B is less than 0.1% by mass, more preferably 0.01% by mass or less, and even more preferably no component B is contained, relative to the entire blended object (for example, a laminate sheet).

[0033] The configuration of the laminate sheet of the present invention will be described in detail below.

[0034] (1) Inorganic powder contained in the laminated sheet The inorganic substance powder is not particularly limited except that it contains calcium carbonate.

[0035] (1-1) Calcium carbonate Calcium carbonate includes both heavy calcium carbonate and light calcium carbonate. "Heavy calcium carbonate" is calcium carbonate obtained by mechanically crushing (dry method, wet method, etc.) natural raw materials (limestone, etc.) whose main component is CaCO3. "Precipitated calcium carbonate" is calcium carbonate prepared by a synthetic method (such as chemical precipitation reaction). Therefore, heavy calcium carbonate and light calcium carbonate are clearly distinguished from each other.

[0036] The content of calcium carbonate is preferably 70% by mass or more, more preferably 80% by mass or more, and most preferably 100% by mass, based on the total amount of the inorganic substance powder.

[0037] Whether or not calcium carbonate is contained in the inorganic powder in the laminated sheet and its content can be determined by firing the laminated sheet and analyzing its ash content (JIS K 7250-1:2006).

[0038] The difference between heavy calcium carbonate and light calcium carbonate can be identified, for example, from the circularity calculated based on the analysis of SEM images. The roundness of the heavy calcium carbonate powder is, for example, in the range of 0.50 to 0.95, and the roundness of the precipitated calcium carbonate powder is, for example, approximately 1.00.

[0039] In the present invention, "circularity" is a value expressed by the following formula, and is an index of the degree of irregular shape of particles. The closer the circularity is to "1" (maximum value), the closer it is to a perfect circle, and the lower the value, the higher the degree of irregular shape. "Circularity" = (projected area of ​​particle) / (area of ​​a circle with the same perimeter as the projected perimeter of the particle)

[0040] The average particle size of calcium carbonate such as heavy calcium carbonate used as a material (i.e., inorganic substance powder that has not been processed into a laminated sheet or a container) as determined by an air permeability method in accordance with JIS M-8511:2014 is preferably 0.7 μm or more and 6.0 μm or less, and more preferably 1.0 μm or more and 5.5 μm or less, from the viewpoint of easily realizing the desired maximum particle size.

[0041] In one embodiment of the present invention, the maximum particle size of calcium carbonate such as ground calcium carbonate is preferably 30 μm or less, more preferably 20 μm or less. When calcium carbonate such as heavy calcium carbonate having a maximum particle size of 30 μm or less is used, it is easily dispersed uniformly in the resin, shear heat generated by kneading occurs locally, and it becomes easier to satisfy the molecular weight characteristics specified in the present invention. When calcium carbonate such as heavy calcium carbonate having a maximum particle size of 20 μm or less is used, deformation of the laminated sheet and the container, particularly during heating, is easily suppressed. Furthermore, when calcium carbonate such as heavy calcium carbonate having a smaller maximum particle size is used, in addition to the above-mentioned effect, separation of the containers can be facilitated. This effect can be stably achieved when the maximum particle size of the calcium carbonate such as heavy calcium carbonate is 20 μm or less. Therefore, in one embodiment of the present invention, the maximum particle size of calcium carbonate, such as ground calcium carbonate, is 30 μm or less, preferably 20 μm or less.

[0042] In the present invention, the "maximum particle size" does not mean the particle size of the inorganic substance powder as a material, but the maximum particle size of the inorganic substance powder contained in the final product (laminated sheet or container), and is determined by the following method. First, using an electron microscope, the particle size (major axis) of the inorganic powder is measured at 5 locations, preferably 20 locations (field of view: 100 μm×100 μm) randomly selected from the cross section of the inner layer of the final product. Next, the maximum particle size of the inorganic substance powder measured within each field of view is taken as the maximum particle size of the inorganic substance powder.

[0043] (1-2) Types of inorganic powder in the laminated sheet The laminated sheet may or may not contain inorganic powder other than calcium carbonate. The inorganic substance powder other than calcium carbonate is not particularly limited, and may be one contained in ordinary resin products, etc. The inorganic substance powder may be one type of substance used alone, or two or more types of substances used in combination.

[0044] The inorganic powders contained in the layers of the laminated sheet may all be the same material or may be different materials. However, from the viewpoint of easily achieving the effects of the present invention, it is preferable that the inorganic substance powder contained in each layer of the laminate sheet is the same substance. From the viewpoint of easily achieving the effects of the present invention in particular, it is preferable that the inorganic substance powder is contained only in the inner layer.

[0045] Examples of inorganic substance powders other than calcium carbonate include the following: carbonates, sulfates, silicates, phosphates, or borates of metals (magnesium, aluminum, titanium, iron, zinc, etc.); oxides of metals (calcium, magnesium, aluminum, titanium, iron, zinc, etc.); Hydrates of the above salts or oxides, etc.

[0046] Examples of inorganic substance powders include magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, and graphite.

[0047] The inorganic powder may be synthetic or derived from natural minerals.

[0048] In order to enhance the dispersibility and reactivity of the inorganic substance powder, the surface of the inorganic substance powder may or may not be previously modified in accordance with a conventional method. Examples of surface modification methods include physical treatment methods (plasma treatment, etc.) and chemical treatment methods (methods using coupling agents or surfactants).

[0049] The shape of the inorganic substance powder is not particularly limited, and may be any of particles (spherical, irregular, etc.), flakes, granules, fibers, and the like.

[0050] (1-3) Amount of inorganic powder in the laminated sheet The content of the inorganic substance powder is preferably 30.0 mass% or more, more preferably 35.0 mass% or more, and even more preferably 40.0 mass% or more, relative to the laminate sheet, from the viewpoints that deformation, etc. is unlikely to occur even under large temperature changes, shear heat due to kneading occurs locally, and it becomes easier to satisfy the molecular weight characteristics specified in the present invention.

[0051] The content of the inorganic substance powder is preferably 80% by mass or less, more preferably 70.0% by mass or less, even more preferably 65.0% by mass or less, and even more preferably 60.0% by mass or less, relative to the laminate sheet, from the viewpoint of blending in an amount of thermoplastic resin sufficient to impart sufficient surface smoothness, etc.

[0052] (2)Thermoplastic resin The thermoplastic resin includes a polyethylene-based resin and satisfies predetermined molecular weight characteristics. In one embodiment of the present invention, the resin component of the laminate sheet comprises a thermoplastic resin.

[0053] The thermoplastic resin used in the present invention preferably has a glass transition point (Tg) in the range of -130°C or more and 5°C or less throughout, from the viewpoint that the molecular weight characteristics specified in the present invention can be easily satisfied. The glass transition temperature is specified based on JIS K7121:2012.

[0054] (2-1) Polyethylene resin The polyethylene resin may be a resin containing ethylene units as a main component, and may be used alone or in combination of two or more. The polyethylene resin in the present invention includes a resin in which ethylene component units are preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and most preferably 80% by mass or more.

[0055] Examples of polyethylene resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), ultra-low-density polyethylene (ULDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-butene 1 copolymer, ethylene-butene 1 copolymer, ethylene-hexene 1 copolymer, ethylene-4-methylpentene 1 copolymer, and ethylene-octene 1 copolymer.

[0056] "High density polyethylene (HDPE)" is 0.942 g / cm 3 It is polyethylene having a density of 100% or more. "Medium density polyethylene (MDPE)" is 0.930 g / cm 3 More than 0.942g / cm 3 It is polyethylene having a density less than 1000 .mu.m. "Low density polyethylene (LDPE)" is 0.910 g / cm 3 More than 0.930g / cm 3 It is polyethylene having a density less than 1000 .mu.m. "Ultra-low density polyethylene (ULDPE)" is 0.910 g / cm 3 It is polyethylene having a density less than 1000 .mu.m. "Linear low-density polyethylene (LLDPE)" is 0.911 g / cm 3 More than 0.940g / cm 3 Density less than (preferably 0.912 g / cm 3 More than 0.928g / cm 3 It is polyethylene with a density less than 1000 kJ / cm2.

[0057] As the polyethylene-based resin, from the viewpoint of easily achieving the effects of the present invention, a resin containing high-density polyethylene and linear low-density polyethylene is preferred, and a resin consisting of high-density polyethylene alone is more preferred.

[0058] (2-2) Resins other than polyethylene resins The thermoplastic resin may or may not contain a resin other than a polyethylene-based resin.

[0059] In a preferred embodiment of the present invention, the thermoplastic resin consists solely of a polyethylene-based resin, from the viewpoint of excellent cold resistance.

[0060] In one embodiment of the present invention, the thermoplastic resin contains a polyethylene-based resin and a polypropylene-based resin, and in this case, the mass ratio of the polyethylene-based resin to the polypropylene-based resin is preferably 99:1 to 50:50, and more preferably 99:1 to 70:30.

[0061] Resins other than polyethylene-based resins include polypropylene-based resins, such as polypropylene homopolymers (propylene homopolymers), block polypropylene copolymers, and copolymers of propylene and other α-olefins (copolymerizable with propylene).

[0062] In one embodiment of the present invention, when the thermoplastic resin contains a resin other than a polyethylene-based resin, the content of the polyethylene-based resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to the thermoplastic resin.

[0063] (2-3) Molecular weight characteristics In one embodiment of the present invention, the thermoplastic resin must satisfy the following molecular weight characteristics:

[0064] (2-3-1) Weight average molecular weight The thermoplastic resin has a weight average molecular weight (Mw) of 230,000 or more and 330,000 or less as measured by gel permeation chromatography (GPC). In the present invention, the "weight average molecular weight (Mw) measured by gel permeation chromatography (GPC)" is Mw calculated in terms of polystyrene. When the Mw of the thermoplastic resin is within this range, the impact resistance of the resulting resin product is easily improved.

[0065] Gel permeation chromatography (GPC), also known as size exclusion chromatography or gel filtration chromatography, is a technique that separates molecules according to their size (volume). In this method, a calibration curve is first created from the elution time and weight-average molecular weight using a standard substance (polystyrene) with a known weight-average molecular weight and an analytical gel column that elutes high molecular weight components first. Next, the weight average molecular weight (Mw) of the resin to be measured is determined based on the obtained calibration curve. The curve obtained during this calculation is called the "GPC elution curve."

[0066] (2-3-2) Area of ​​molecular weights less than 1 / 5 of the peak top molecular weight (Mp) The ratio of the area of ​​the region of molecular weight equal to or less than 1 / 5 of the peak top molecular weight (Mp) determined from the GPC elution curve of the thermoplastic resin (hereinafter also referred to as the "20% area") to the total area of ​​the GPC elution curve is 20% or more and 33% or less, preferably 24% or more and 30% or less.

[0067] On the premise that the Mw of the thermoplastic resin is 230,000 or more and 330,000 or less, by satisfying the above requirements, both the cold resistance and the heat resistance are surprisingly good. In the thermoplastic resin, if the proportion of the 20% area is less than 20%, the cold resistance may be poor, whereas if the proportion of the 20% area is more than 33%, the heat resistance may be poor.

[0068] In the present invention, the "peak top molecular weight (Mp)" means the weight molecular weight showing a peak in a GPC elution curve. When the GPC elution curve has multiple peaks, the molecular weight at the peak showing the most abundant weight molecular weight is set as the peak top molecular weight (Mp).

[0069] In the present invention, the "area of ​​the area (20% area) of a molecular weight equal to or less than 1 / 5 of the peak top molecular weight (Mp) identified from the GPC elution curve of a thermoplastic resin" means the area of ​​the area corresponding to components having a molecular weight equal to or less than 1 / 5 (20%) of "Mp" when the total area of ​​the GPC elution curve is taken as 100%. Therefore, the 20% area corresponds to the proportion (%) of components having a molecular weight of 1 / 5 or less of "Mp" in the thermoplastic resin.

[0070] The method for preparing a thermoplastic resin having the desired 20% area ratio is not particularly limited, but examples include a method of blending multiple thermoplastic resins (such as high-density polyethylene resin) with different weight-average molecular weights and molecular weight distributions together with the inorganic substance powder described above.

[0071] (3) Inner layer In the present invention, at least the inner layer contains inorganic powder.

[0072] (3-1) Inorganic powder blended in the inner layer The inorganic powder to be blended in the inner layer is not particularly limited as long as it satisfies the above-mentioned requirements for the inorganic powder contained in the laminate sheet.

[0073] (3-2) Thermoplastic resin blended in the inner layer In one embodiment of the present invention, the inner layer may contain a thermoplastic resin, which may be any of the thermoplastic resins described above.

[0074] The thermoplastic resin contained in the inner layer preferably contains a polyethylene-based resin. In addition to the polyethylene-based resin, a polypropylene-based resin may or may not be blended.

[0075] (3-3) Other ingredients blended into the inner layer The inner layer may or may not contain any other components other than the inorganic substance powder and the thermoplastic resin, as long as the effects of the present invention are not impaired.

[0076] As the other components, any components that can be usually blended in a resin sheet can be used. Such components include lubricants, dispersants, antistatic agents, antioxidants, heat stabilizers, and ultraviolet absorbers. The types and amounts of these components can be appropriately determined depending on the desired effect.

[0077] A preferred embodiment of the present invention includes a laminated sheet in which the inner layer consists solely of ground calcium carbonate particles, a thermoplastic resin, a lubricant, and an antioxidant.

[0078] (3-4) Ratio of ingredients in the inner layer The content of the components blended in the inner layer is not particularly limited.

[0079] From the viewpoint of easily achieving the effects of the present invention, it is preferable that the inner layer contains a sufficient amount of inorganic substance powder, and therefore the lower limit of the content of inorganic substance powder relative to the inner layer is preferably 40.0 mass% or more, more preferably 45.0 mass% or more, and even more preferably 50.0 mass% or more.

[0080] In order to provide the laminate sheet with sufficient moldability, the upper limit of the content of the inorganic substance powder relative to the inner layer is preferably 80.0% by mass or less, more preferably 75.0% by mass or less, and even more preferably 70.0% by mass or less.

[0081] The content of the inorganic substance powder in the inner layer may be a number determined by the following method. The number determined by the following method may overlap with the examples of the content of the inorganic substance powder in the inner layer given above. (1) Process 1 First, SEM images of the cross section of the laminate sheet are obtained at any five points on the laminate sheet. The total mass of the laminated sheet is also recorded. Based on the obtained SEM images of the five locations, the area occupied by the inorganic substance powder relative to the entire cross section of the laminated sheet (area 1) and the area occupied by the inorganic substance powder relative to the inner layer of the cross section of the laminated sheet (area 2) are determined. (2) Process 2 The laminated sheet is then fired to obtain ash (dry powder). Based on the obtained ash content, the type and mass of the inorganic powder are identified. (3) Process 3 The content (mass %) of the inorganic substance powder in the inner layer is determined based on the following formula. Inorganic powder content of inner layer (mass%) = "Mass of inorganic powder" x "Area 2 / Area 1" ÷ "Total mass of laminated sheet"

[0082] In step 1, the lower limit of "area 2 / area 1" is preferably 0.7 or more, and more preferably 1.0.

[0083] The content of the thermoplastic resin can be adjusted depending on the content of the inorganic substance powder. The lower limit of the content of the inorganic substance powder relative to the inner layer is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, and even more preferably 30.0% by mass or more. The upper limit of the content of the thermoplastic resin relative to the inner layer is preferably 60.0% by mass or less, more preferably 55.0% by mass or less, and even more preferably 50.0% by mass or less.

[0084] (4) Outer layer The outer layers are a pair of layers laminated on two surfaces of the inner layer (that is, in the laminate sheet of the present invention, two outer layers are formed so as to sandwich the inner layer). In the present invention, the pair of layers is referred to as a first outer layer and a second outer layer.

[0085] The first outer layer and the second outer layer may have the same or different configurations, provided that the first outer layer and the second outer layer each contain a thermoplastic resin.

[0086] A preferred embodiment of the present invention includes an embodiment in which the first outer layer and the second outer layer have the same configuration (composition, thickness, shape, etc.).

[0087] (4-1) Thermoplastic resin blended in the outer layer The thermoplastic resin blended into the outer layer may include a polyethylene-based resin (preferably a high-density polyethylene resin). The polyethylene-based resin may be used alone or in combination of two or more materials.

[0088] In the laminate sheet, the thermoplastic resin blended in the outer layer and the thermoplastic resin blended in the inner layer may be the same or different.

[0089] Preferred embodiments of the present invention include all of the following embodiments. (Embodiment 1) An embodiment in which the thermoplastic resin blended in the outer layer and the thermoplastic resin blended in the inner layer are all the same (Aspect 2) Aspect in which the thermoplastic resin blended in the first outer layer, the thermoplastic resin blended in the second outer layer, and the thermoplastic resin blended in the inner layer are all different (Embodiment 3) An embodiment in which only two of the thermoplastic resins blended in the first outer layer, the second outer layer, and the inner layer are the same.

[0090] (4-2) Other ingredients blended into the outer layer The outer layer may or may not contain components other than the thermoplastic resin, as long as the effects of the present invention are not impaired.

[0091] As the other components, any components that can be usually blended in a resin sheet can be used. Such components include the above-mentioned inorganic substance powders, lubricants, dispersants, antistatic agents, antioxidants, heat stabilizers, ultraviolet absorbers, and the like. The types and amounts of these components can be appropriately determined depending on the desired effect.

[0092] (4-3) Ratio of ingredients in the outer layer The content of the thermoplastic resin or the like blended in the outer layer is not particularly limited.

[0093] The proportion of the thermoplastic resin to be blended in the outer layer is not particularly limited as long as it is within a range that allows the resin sheet to be molded.

[0094] The lower limit of the content of the thermoplastic resin relative to the outer layer is preferably 80.0% by mass or more, more preferably 90.0% by mass or more, and even more preferably 99.0% by mass or more.

[0095] The upper limit of the content of the thermoplastic resin is preferably 100.0% by mass with respect to the outer layer.

[0096] In a preferred embodiment of the present invention, when inorganic material powder is blended into the outer layer, the proportion of inorganic material powder in the inner layer (i.e., the proportion of inorganic material powder in the entire inner layer) is greater than the proportion of the total amount of inorganic material powder in the first outer layer and the second outer layer (i.e., the proportion of inorganic material powder in the entire first outer layer and the second outer layer). By adjusting in this way, it becomes easier to obtain a laminated sheet that is less likely to deform even when in contact with food that is exposed to large temperature changes (such as food that is heated in a microwave oven).

[0097] Whether the proportion of the inorganic powder in the inner layer is greater than the total proportion of the inorganic powder in the first outer layer and the second outer layer can be determined based on an analysis of an SEM image of a cross section of the laminated sheet. Specifically, if in a cross-sectional image of the laminated sheet the area proportion occupied by the inorganic substance powder in the inner layer is greater than the sum of the area proportions of the inorganic substance powder in the first outer layer and the second outer layer, it can be determined that the proportion of the inorganic substance powder in the inner layer is greater than the proportion of the total amount of inorganic substance powder in the first outer layer and the second outer layer.

[0098] The ratio of the total amount of inorganic substance powder content in the first outer layer and the second outer layer to the amount of inorganic substance powder content in the inner layer (total amount of inorganic substance powder content in the first outer layer and the second outer layer / inorganic substance powder content in the inner layer) may be less than 1.0, but the smaller this ratio, the easier it is to obtain the effects of the present invention. In a most preferred embodiment, the first outer layer and the second outer layer do not contain inorganic powder.

[0099] A preferred embodiment of the present invention includes a laminated sheet in which each outer layer is made solely of a thermoplastic resin.

[0100] (5) Thickness of each layer of the laminated sheet In the laminate sheet of the present invention, the ratio of the thickness of the first outer layer and the second outer layer to the total thickness of the laminate sheet is 2.0% to 20.0%, respectively. In other words, in the laminate sheet of the present invention, the total thickness of the outer layers (the sum of the thicknesses of the first outer layer and the second outer layer) is 4.0% to 40.0% of the total thickness of the laminate sheet. By making the thickness of the outer layer thinner than the thickness of the inner layer, the laminated sheet of the present invention can not only suppress deformation during heating in a microwave oven, but also improve moldability and other properties.

[0101] The lower limit of the thickness ratio of the first outer layer and the second outer layer is 2.0% or more, preferably 2.5% or more, and more preferably 3.0% or more, respectively, relative to the total thickness of the laminated sheet, from the viewpoint of easily achieving a good appearance.

[0102] In order to more easily achieve the effects of the present invention, the upper limit of the thickness ratio of the first outer layer and the second outer layer is 20.0% or less, preferably 18.0% or less, more preferably 16.0% or less, and most preferably 10.0% or less, respectively, relative to the total thickness of the laminated sheet.

[0103] In the laminate sheet of the present invention, the ratio of the thickness of the inner layer is adjusted depending on the thickness of the outer layer, and is 60.0% or more and 96.0% or less of the total thickness of the laminate sheet.

[0104] The lower limit of the thickness of each of the first outer layer and the second outer layer is preferably 5.0 μm or more, and more preferably 10.0 μm or more, from the viewpoint of easily obtaining a good appearance.

[0105] The upper limit of the thickness of each of the first outer layer and the second outer layer is preferably 50.0 μm or less, and more preferably 45.0 μm or less, from the viewpoint of easily realizing good moldability and the like.

[0106] The lower limit of the thickness of the inner layer is preferably 50.0 μm or more, more preferably 100.0 μm or more, from the viewpoint of easily obtaining good mechanical properties.

[0107] The upper limit of the thickness of the inner layer is preferably 950.0 μm or less, more preferably 900.0 μm or less, from the viewpoint of good moldability and the like.

[0108] The lower limit of the total thickness of the laminate sheet is adjusted depending on the thickness of the outer layer and the inner layer, and is preferably 100.0 μm or more, more preferably 150.0 μm or more.

[0109] The upper limit of the total thickness of the laminate sheet is adjusted depending on the thickness of the outer layer and the inner layer, and is preferably 990.0 μm or less, more preferably 700.0 μm or less.

[0110] The density of the laminated sheet is not particularly limited.

[0111] The laminated sheet may be a three-layer sheet consisting of an inner layer, a first outer layer, and a second outer layer, or may be a four-layer or more sheet with other layers provided outside the outer layer (outermost layer). As the other layer, any layer (printed layer, etc.) can be selected as long as it does not impair the effects of the present invention. However, one embodiment of the present invention includes an embodiment in which the laminate sheet is a three-layer sheet consisting of an inner layer, a first outer layer, and a second outer layer.

[0112] (6) Manufacturing method of laminated sheet The method for producing the laminated sheet of the present invention is not particularly limited, and any conventional method for producing a multilayer sheet or laminate can be employed.

[0113] Examples of methods for producing a laminate sheet include the following methods. A method of laminating inner and outer layers formed into sheets using a calendar roll. Co-extrusion of inner and outer layers A method of melt-mixing the raw materials for the inner layer and co-extrusion molding of the inner and outer layers in the same process using a multi-layer T-die type twin-screw extruder. - Extrusion inflation method using multiple annular dies

[0114] The laminated sheet may be stretched as necessary.

[0115] The conditions for producing the laminate sheet are not particularly limited. The kneading temperature may be equal to or higher than the melting temperature of the thermoplastic resin, for example, in the range of 160 to 200°C.

[0116] (7) Uses of laminated sheets The laminated sheet of the present invention can be used as a material for any container. The container can be stored in a freezer or refrigerator, or can be subjected to a heat treatment (heating in a microwave oven, etc.).

[0117] The container may have any conventionally known configuration. Preferred configurations include those listed in the section "(8) Container."

[0118] The laminate sheet of the present invention can be subjected to any molding method to obtain a container (for example, a food packaging container). Such a molding method is not particularly limited, and examples thereof include vacuum molding, pressure molding, and matched mold molding. Of these, vacuum forming is preferred from the viewpoint of ease of forming, and therefore the laminate sheet of the present invention includes an embodiment that is a laminate sheet for vacuum forming.

[0119] (8) Container One aspect of the present invention also includes a container made of the laminated sheet of the present invention, having the following structure:

[0120] The container has a recessed storage section capable of storing an item. The storage section has a bottom and a side section formed along the outer periphery of the bottom. The storage section has a plurality of support sections spaced apart from the inner surfaces of the bottom and side sections, capable of supporting an item. The support sections are spaced apart from each other in the circumferential direction of the bottom and protrude inward from the outer periphery of the bottom to the bottom sides of the side sections. A plurality of grooves are formed on the inner surface of the side sections, spaced apart from each other in the circumferential direction, and extending in the depth direction of the storage section.

[0121] The container may have a connecting portion that connects the plurality of storage portions together so that the storage portions can be separated by applying a predetermined stress.

[0122] The side of the container may have a step portion that is spaced apart from the support portion and that protrudes outward from the bottom side toward the outer periphery.

[0123] The bottom of the container may be provided with a plurality of support parts spaced apart from each other and may have projections that protrude inward.

[0124] The container shown in FIGS. 1 and 2 is a preferred example of a container made from the laminated sheet of the present invention.

[0125] The arrangement of items in the container is not particularly limited, but it is preferable to store one item (e.g., frozen food) in one storage section with a gap between it and the inner surfaces of the bottom and side, thereby preventing contact between the item and the liquid generated by heating the item, and allowing steam generated by heating the item to pass between the inner surfaces of the side and the item.

[0126] The method for forming the container of the present invention is not particularly limited, and examples thereof include vacuum forming, pressure forming, matched mold forming, and the like. Of these, vacuum forming is preferred from the viewpoint of ease of forming, and therefore the container of the present invention includes an embodiment that is a vacuum formed product. [Example]

[0127] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0128] <Test 1: Preparation and evaluation of laminated sheets and containers-1> A laminate sheet and a container were produced by the following method and evaluated.

[0129] (1) Preparation of materials The materials for each layer were prepared as follows:

[0130] (1-1) Inorganic substance powder As the inorganic substance powder, heavy calcium carbonate particles (Ca-1) with an average particle size of 4.9 μm were used, except for Example 7, where heavy calcium carbonate particles (Ca-2) with an average particle size of 9.8 μm were used.

[0131] (1-1-1) Average particle size The average particle size of the inorganic powder was determined based on the air permeability method in accordance with JIS M-8511: 2014. The average particle size was measured for the inorganic powder used as the material (i.e., the inorganic powder in a state that was not processed into a laminated sheet or a container).

[0132] (1-1-2) Maximum particle size measurement method The maximum particle size of the inorganic powder in the laminated sheet or container was determined by the following procedure. First, using an electron microscope, the particle size (major axis) of calcium carbonate particles was measured at five randomly selected points (field of view: 100 μm×100 μm) from the cross section of the inner layer. Next, the maximum particle size of the calcium carbonate particles measured within each field of view was determined as the maximum particle size of the calcium carbonate particles. As a result, in all examples using Ca-1, the maximum particle size was 21.4 to 26.7 μm, and in Example 7 using Ca-2, the maximum particle size was 36.2 μm.

[0133] (1-2)Thermoplastic resin A plurality of high-density polyethylene resins (PE) with different weight-average molecular weights and a block polypropylene copolymer (PP) were prepared. A mixture of these resins in a mass ratio of high density polyethylene resin:block polypropylene copolymer=85:15 was also prepared. As described below, after preparing a laminate sheet, the molecular weight characteristics of each thermoplastic resin were evaluated, and the results are shown in Table 1.

[0134] (1-2-1) Weight average molecular weight The weight average molecular weight (Mw, polystyrene equivalent) of the thermoplastic resin contained in the laminate sheet was measured by gel permeation chromatography (GPC). Furthermore, the ratio of the number average molecular weight (Mn) to the weight average molecular weight (Mw) (polydispersity (Mw / Mn)) was calculated.

[0135] (1-2-2) Molecular weight distribution The molecular weight distribution of the thermoplastic resin contained in the laminate sheet was measured using GPC. As a result, a GPC elution curve was obtained, with the vertical axis showing the "differential distribution value" and the horizontal axis showing the "logarithm of molecular weight (Log M)." The GPC elution curves showed a single peak for all resins.

[0136] Based on the GPC elution curves, the following were identified: Mp: Peak top molecular weight of the GPC elution curve 20% area: The ratio of the area of ​​the molecular weight of 1 / 5 or less of "Mp" (20% area) to the total area of ​​the GPC elution curve

[0137] (2) Preparation of laminated sheets Using the materials shown in Table 2, a three-layer laminate sheet was produced by the multi-layer T-die method at 180°C. The total thickness of the laminated sheet was set to 400 μm. The thickness of the inner layer was set to 360 μm (90% of the total thickness of the laminated sheet). Outer layers (first outer layer and second outer layer) were provided on both sides of the inner layer, and the thickness of each outer layer was set to 20 μm (5% of the total thickness of the laminated sheet).

[0138] (3) Preparation of the container Each of the laminated sheets obtained above was preheated with a far-infrared heater and then molded into a container with a vacuum forming machine. The outline of the container shape is shown in Figures 1 and 2.

[0139] This container 1 has a plurality of storage sections 10 formed in a concave shape and capable of containing food. The container 1 has a connecting section 2 that connects the plurality of storage sections 10 together so that the storage sections 10 can be separated by applying a predetermined stress. Each of the storage sections 10 that make up the container 1 contains one approximately spherical food item. The container 1 shown in the figure has two storage sections 10. In a plan view, the container 1 has a longitudinal dimension of 200 mm, a lateral dimension of 100 mm, and a height dimension of 50 mm. Furthermore, the storage sections 10 have a radial dimension of 80 mm and a depth dimension of 50 mm.

[0140] The storage section 10 has a bottom 11, a side 12 formed along the outer periphery of the bottom 11, and a plurality of support sections 13 spaced apart from the inner surfaces of the bottom 11 and the side 12 to support food.

[0141] The bottom 11 is formed in a disk shape with an outer diameter of 75 mm. A convex portion 11a is formed on the radial center side of the bottom 11, spaced 10 mm apart from the plurality of support portions 13, and protrudes inward. The convex portion 11a is formed in a truncated quadrangular pyramid shape with a base side of 15 mm, a tip side of 9.5 mm, and a height of 6.5 mm, and contacts the food contained in the storage portion 10 from the bottom 11 side. This forms a gap between the food contained in the storage portion 10 and the inner surface of the bottom 11. When liquid (water, oil, etc.) is generated on the outside of the food contained in the storage portion 10 due to evaporation or the like caused by heating, the liquid collects between the convex portion 11a on the inner surface of the bottom 11 and the support portion 13, preventing contact between the food and the liquid during or after heating.

[0142] The side portion 12 is cylindrical. Grooves 12a are formed on the inner circumferential surface of the side portion 12, spaced apart circumferentially and extending in the depth direction of the storage portion 10. The grooves 12a are 3 mm wide and 1.5 mm deep, and have a semicircular cross section. When food is heated in the storage portion 10, steam from water, oil, or the like circulates along the grooves 12a in the thickness direction of the storage portion 10. The side portion 12 also has stepped portions 12b, which are spaced apart from the multiple support portions 13 in the depth direction of the storage portion 10 and extend radially outward from the bottom portion 11. The stepped portions 12b are formed by extending the side portion 12 radially outward by 4 mm relative to the bottom portion 11. The food stored in the storage portion 10 is stably supported by the multiple support portions 13 and the corners of the stepped portions 12b.

[0143] The multiple support portions 13 are spaced 10 mm apart around the periphery of the bottom portion 11 and protrude inward from the outer periphery of the bottom portion 11 to the bottom 11 side of the side portions 12. Each of the multiple support portions 13 has a length of 19 mm on the bottom 11 side, a length of 30 mm on the side portions 12 side, and a height of 6.5 mm in the circumferential direction of the bottom portion 11. The storage portion 10 of the container 1 shown in the figures has four support portions 13. Each of the multiple support portions 13 has a groove 13a extending in the depth direction of the storage portion 10 and allowing the passage of steam generated by heating food. The groove 13a has a semicircular cross section with a width of 3 mm and a depth of 1.5 mm.

[0144] (4) Evaluation of the container The cold resistance and heat resistance of the containers were evaluated by the following methods, and the results are shown in Tables 2 and 3.

[0145] (4-1) Cold resistance Each container was placed in a freezer (-18°C) and left to stand for 100 hours, after which it was dropped from a height of 3 m to the ground. Next, the container was visually inspected for the presence or absence of cracks and the extent of the cracks, and evaluated according to the following criteria.

[0146] [Cold resistance evaluation criteria] A: No cracks were found in the container. B: A small amount of cracking was observed in the container. C: Cracks in the container were clearly observed.

[0147] (4-2) Heat resistance An equal amount of salad oil was placed in each container and heated in a microwave oven (600W, 80 seconds). Next, the presence or absence and degree of deformation of the container was visually observed and evaluated according to the following criteria.

[0148] [Heat resistance evaluation criteria] A: No deformation of the container was observed. B: Slight deformation of the container was observed. C: Deformation of the container was clearly observed.

[0149] [Table 1]

[0150] [Table 2]

[0151] [Table 3]

[0152] As shown in the table, by using a thermoplastic resin that satisfies the requirements of the present invention, both cold resistance and heat resistance were good.

[0153] On the other hand, it was a very surprising finding that even if the thermoplastic resin is of the same type, if it does not satisfy the molecular weight characteristics of the present invention, either the cold resistance or the heat resistance will be inferior.

[0154] In this example, a polypropylene resin (such as a block polypropylene copolymer) was used in addition to a polyethylene resin as the thermoplastic resin, but the same tendency as above was observed when only a polyethylene resin was used.

[0155] In the table, "Example 6" and "Reference Example" are examples in which the same materials as "Example 5" were used, but the proportion of calcium carbonate in the inner layer was changed. From these results, it was found that when the content of the inorganic substance powder is 30.0 mass or more relative to the laminate sheet, good cold resistance and heat resistance are easily achieved.

[0156] In the table, "Example 7" is an example in which the same thermoplastic resin and component ratio as those in "Example 5" are used, but calcium carbonate with a different maximum particle size is used. These results show that when the maximum particle size of calcium carbonate is 30 μm or less, good cold resistance and heat resistance can be easily achieved.

[0157] <Test 2: Preparation and evaluation of laminated sheets and containers-2> As shown in the above Test 1, it was found that by using a thermoplastic resin that satisfies the requirements of the present invention, both cold resistance and heat resistance become good. Therefore, in this example, the constitution of the thermoplastic resin was changed and a test similar to Test 1 was carried out to confirm whether the same effect as Test 1 could be obtained. Hereinafter, various analyses and the production of laminated sheets and containers were carried out under the same conditions as in Test 1 unless otherwise specified.

[0158] In this example, a plurality of high-density polyethylene resins (PE) with different weight-average molecular weights were prepared as the thermoplastic resin, and these were mixed appropriately for use (other types of thermoplastic resins were not included). After preparing a laminated sheet in the same manner as in Test 1, the molecular weight characteristics of each thermoplastic resin were evaluated, and the results are shown in Table 4. In addition, in all examples, only PE was used as the thermoplastic resin. Hereinafter, the names of the tests in these examples correspond to Test 1. For example, for "Example-1PE" in Test 2, samples were prepared and evaluated under the same conditions as "Test-1" in Test 1, except that the thermoplastic resin was changed to PE.

[0159] The evaluation results of the cold resistance and heat resistance of the containers are shown in Tables 5 and 6.

[0160] [Table 4]

[0161] [Table 5]

[0162] [Table 6]

[0163] As shown in Tables 4 to 6, it was confirmed that the same tendency as in Test 1 was observed even when the composition of the thermoplastic resin was changed.

[0164] In addition, in this example, only a polyethylene-based resin was used as the thermoplastic resin, and this embodiment tended to be superior to the example of Test 1 in terms of cold resistance.

[0165] In the table, "Example 6PE" and "Reference Example PE" are examples in which the same materials as "Example 5PE" were used, but the proportion of calcium carbonate in the inner layer was changed. From these results, it was found that when the content of the inorganic substance powder is 30.0 mass or more relative to the laminate sheet, good cold resistance and heat resistance are easily achieved.

[0166] In the table, "Example 7PE" is an example in which the same thermoplastic resin and component ratio as "Example 5PE" were used, but calcium carbonate with a different maximum particle size was used. These results show that when the maximum particle size of calcium carbonate is 30 μm or less, good cold resistance and heat resistance can be easily achieved.

Claims

1. A laminated sheet of three or more layers, the laminated sheet includes at least an inner layer, and a first outer layer and a second outer layer laminated on a surface of the inner layer; the laminate sheet contains a thermoplastic resin, the inner layer contains an inorganic powder, the ratio of the thickness of the first outer layer and the thickness of the second outer layer to the total thickness of the laminated sheet is 2.0% or more and 20.0% or less, the inorganic substance powder includes calcium carbonate, the thermoplastic resin includes a polyethylene-based resin, The thermoplastic resin has a weight average molecular weight of 230,000 or more and 330,000 or less as measured by gel permeation chromatography (GPC), an area of ​​a molecular weight region corresponding to 1 / 5 or less of a peak top molecular weight (Mp) determined from a GPC elution curve of the thermoplastic resin is 20% or more and 33% or less of the total area of ​​the GPC elution curve; Laminated sheet.

2. The laminate sheet according to claim 1 , wherein the content of the inorganic substance powder is 30.0 mass % or more and 80.0 mass % or less with respect to the laminate sheet.

3. 2. The laminated sheet according to claim 1, wherein the calcium carbonate has a maximum particle size of 30 μm or less.

4. The laminate sheet of claim 1 , wherein the thermoplastic resin comprises high density polyethylene.

5. 2. The laminate sheet according to claim 1, wherein the thermoplastic resin consists solely of a polyethylene-based resin.

6. 10. The laminate sheet of claim 1, wherein the thermoplastic resin of the first outer layer and the second outer layer comprises a high density polyethylene resin.

7. The laminate sheet according to claim 1, wherein the calcium carbonate has an average particle size of 0.7 μm or more and 6.0 μm or less, as measured by an air permeation method in accordance with JIS M-8511:2014.

8. The laminate sheet according to any one of claims 1 to 7, which is used for a vacuum formed product.

9. The laminate sheet according to any one of claims 1 to 7, which is used for a food packaging container.

10. A container, The container is made of a laminated sheet of three or more layers, the laminated sheet includes at least an inner layer, and a first outer layer and a second outer layer laminated on a surface of the inner layer; the laminate sheet contains a thermoplastic resin, the inner layer contains an inorganic powder, the ratio of the thickness of the first outer layer and the thickness of the second outer layer to the total thickness of the laminated sheet is 2.0% or more and 20.0% or less, the inorganic substance powder includes calcium carbonate, the thermoplastic resin includes a polyethylene-based resin, The thermoplastic resin has a weight average molecular weight of 230,000 or more and 330,000 or less as measured by gel permeation chromatography (GPC), an area of ​​a molecular weight region corresponding to 1 / 5 or less of a peak top molecular weight (Mp) determined from a GPC elution curve of the thermoplastic resin is 20% or more and 33% or less of the total area of ​​the GPC elution curve; container.

11. The container has a storage portion formed in a concave shape and capable of storing an item, The storage portion has a bottom portion and a side portion formed along the outer periphery of the bottom portion, the storage section has a plurality of support sections that are spaced apart from each other and that are capable of supporting the article on the inner surfaces of the bottom and side sections, The plurality of support portions are provided at intervals in the circumferential direction of the bottom portion, and protrude inward from the outer circumferential side of the bottom portion to the bottom side of the side portion, A plurality of grooves are formed on the inner surface of the side portion at intervals in the circumferential direction and extending in the depth direction of the storage portion.

11. The container of claim 10.

12. The container has a connecting portion that connects the plurality of storage portions together so that the storage portions can be separated by applying a predetermined stress.

12. The container of claim 11.

13. The side portion is provided at a distance from the support portion and has a step portion formed by projecting outward from the bottom portion side toward the outer periphery.

12. The container of claim 11.

14. The bottom portion has convex portions formed thereon, the convex portions being spaced apart from the plurality of support portions and protruding inward.

12. The container of claim 11.

15. 15. The container according to any one of claims 10 to 14, wherein the container is a vacuum-formed product.

16. 15. The container according to any one of claims 10 to 14, wherein the container is for packaging food.

17. 15. The container according to any one of claims 10 to 14, wherein the container is for packaging frozen food.

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