Sheet and food packaging container

Abstract

To provide a sheet which enables formation of a container that suppresses occurrence of damage when receiving an impact under low temperature environment.SOLUTION: A sheet contains an inorganic filler and a thermoplastic resin, and has a tensile breaking elongation at -25°C of 4% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sheet and a food packaging container. [Background technology]

[0002] Sheets containing inorganic fillers and thermoplastic resins have been developed as sheets for forming food packaging containers. For example, Patent Document 1 discloses a laminated sheet having an inner layer and a pair of outer layers laminated on both sides of the inner layer, the inner layer containing an inorganic filler and a thermoplastic resin, and the outer layer containing a thermoplastic resin, and describes that it has been discovered that when a specific surface treatment is performed on an inorganic filler containing calcium carbonate particles, the dispersibility and reactivity of the inorganic filler containing calcium carbonate particles are increased and the porosity of the inner layer becomes appropriate, thereby improving the moldability, mechanical properties, and appearance of the laminated sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-2690 Summary of the Invention [Problem to be solved by the invention]

[0004] As demand for frozen foods and other foods increases, there is a need for food packaging containers that can withstand low-temperature environments. Because frozen foods are stored and transported in a frozen state, food packaging containers that are resistant to damage even when subjected to impacts in low-temperature environments are required.

[0005] An object of the present disclosure is to provide a sheet that can be used to form a container that is less likely to break when subjected to impact in a low-temperature environment. [Means for solving the problem]

[0006] In order to provide a sheet capable of forming a container that is resistant to breakage even when subjected to impact in a low-temperature environment, the present inventors attempted to adjust various mechanical properties of the sheet in a low-temperature environment. As a result, it was surprisingly found that breakage when subjected to impact in a low-temperature environment could be suppressed not by increasing the impact strength of the sheet in a low-temperature environment, but by increasing the tensile elongation at break in a low-temperature environment.

[0007] In some aspects, the present disclosure provides the following [1] to [9]. [1] A sheet containing an inorganic filler and a thermoplastic resin, having a tensile elongation at break of 4% or more at -25°C. [2] The sheet according to [1], having a tensile modulus at 100°C of 330 MPa or more. [3] The sheet according to [1] or [2], wherein the thermoplastic resin comprises a polyolefin. [4] The sheet according to any one of [1] to [3], wherein the polyolefin comprises high-density polyethylene, low-density polyethylene, and block polypropylene. [5] The sheet according to any one of [1] to [4], wherein the content of the inorganic filler is 35 mass % or more based on the total mass of the sheet. [6] The sheet according to any one of [1] to [5], wherein the inorganic filler contains at least one of calcium carbonate and talc. [7] The sheet according to any one of [1] to [6], which is used for forming a food packaging container. [8] The sheet according to any one of [1] to [7], which is used for vacuum forming. [9] A food packaging container formed from the sheet according to any one of [1] to [8]. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, there is provided a sheet that can be used to form a container that is less likely to break when subjected to an impact in a low-temperature environment. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a sheet. [Figure 2] FIG. 10 is a schematic cross-sectional view showing another embodiment of the sheet. [Figure 3] FIG. 10 is a schematic cross-sectional view showing another embodiment of the sheet. [Figure 4] FIG. 1 is a schematic perspective view of a lunch container molded for evaluating distortion after heating. [Figure 5] FIG. 10 is a schematic cross-sectional view for explaining a method for evaluating deflection after heating. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0011] The sheet according to one embodiment includes an inorganic filler. Examples of materials constituting the inorganic filler include metal salts, oxides, hydroxides, and hydrates thereof, as well as elemental metals. The metals may be calcium, magnesium, sodium, barium, aluminum, titanium, iron, zinc, molybdenum, etc.

[0012] Examples of metal salts include metal carbonates, sulfates, sulfites, silicates, phosphates, borates, and titanates. Examples of metal carbonates include calcium carbonate and magnesium carbonate. Metal carbonates may be contained in the inorganic filler as carbonate minerals such as dolomite and hydrotalcite.

[0013] Examples of metal sulfates include calcium sulfate, magnesium sulfate, sodium sulfate, barium sulfate, and aluminum sulfate. Examples of metal sulfites include calcium sulfite. Examples of metal silicates include calcium silicate, magnesium silicate, and aluminum silicate. Metal silicates may be included in inorganic fillers as silicate-containing clays, silicate minerals, etc. Examples of silicate-containing clays include bentonite and kaolin. Examples of silicate minerals include talc, zeolite, sericite, and mica.

[0014] Examples of metal phosphates include calcium phosphate, magnesium phosphate, and aluminum phosphate. Examples of titanates include potassium titanate and calcium titanate.

[0015] Examples of metal oxides include magnesium oxide, alumina, titanium oxide, and zinc oxide. Examples of metal hydroxides include magnesium hydroxide and aluminum hydroxide.

[0016] The above-mentioned components may be contained in the inorganic filler as a bio-based material containing the above-mentioned components. An example of the bio-based material is eggshell. Eggshell contains, for example, calcium carbonate.

[0017] Other examples of constituent materials of the inorganic filler include silica (quartz sand), diatomaceous earth, pumice, shirasu, glass beads, glass flakes, glass fiber, boron fiber, carbon fiber, carbon black, and graphite.

[0018] The inorganic filler may contain only one of the above-mentioned constituent materials of the inorganic filler, or may contain two or more of them. The inorganic filler may contain at least one of calcium carbonate and talc.

[0019] The inorganic filler may be, for example, particulate. The average particle size of the particulate inorganic filler may be 0.5 μm or more, 1 μm or more, or 3 μm or more, and may be 30 μm or less, 25 μm or less, or 20 μm or less. In this specification, the average particle size refers to the median size measured by laser diffraction.

[0020] The content of the inorganic filler may be 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, based on the total mass of the sheet, in order to further suppress deformation of the sheet when heated, and may be 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0021] The sheet according to one embodiment contains a thermoplastic resin. Examples of thermoplastic resins include polyolefin, polyester, polystyrene, polyamide, and acrylonitrile-butadiene-styrene copolymer (ABS resin). The thermoplastic resin may contain only one of these, or two or more of them. In this specification, the thermoplastic resin (such as polyolefin) may be a petroleum-derived thermoplastic resin or a bio-derived thermoplastic resin. The bio-derived thermoplastic resin is a thermoplastic resin produced using raw materials including bio-derived raw materials, and contains bio-derived carbon. The thermoplastic resin may also contain a thermoplastic resin derived from recycled materials (such as scraps and recycled materials).

[0022] Examples of polyolefins include polyethylene and polypropylene. The thermoplastic resin preferably includes polyethylene and polypropylene.

[0023] Polyethylene is a polymer containing primarily ethylene as a monomer unit. The melting point of polyethylene may be less than 150°C, and more preferably 140°C or less. Examples of polyethylene include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE).

[0024] HDPE is 0.942g / cm 3 MDPE is polyethylene with a density of 0.930 g / cm or more. 3 More than 0.942g / cm 3 LDPE is polyethylene with a density less than 0.910 g / cm 3 More than 0.930g / cm 3 LLDPE is a polyethylene with a long chain branching structure and a density of less than 0.911 g / cm. 3 More than 0.940g / cm 3 It is a polyethylene having a density of less than 1000 kJ / cm2 and having no long chain branching structure. The density of polyethylene is determined by the specific gravity measured under standard conditions in accordance with JIS K7112:1999 Method A.

[0025] The melting point of LDPE may be 95°C or higher and 115°C or lower. The melting point of LLDPE may be 115°C or higher and 125°C or lower. LDPE may have a side chain with 6 or more carbon atoms, while LLDPE may not have a side chain with 6 or more carbon atoms. The presence or absence of a side chain with 6 or more carbon atoms is 13 This can be confirmed by C-NMR measurement.

[0026] The melt mass-flow rate (MFR) of the HDPE may be 0.1 g / 10 min or more, 0.2 g / 10 min or more, or 0.3 g / 10 min or more, and may be 1.5 g / 10 min or less, 1.0 g / 10 min or less, 0.8 g / 10 min or less, 0.6 g / 10 min or less, or 0.4 g / 10 min or less. In this specification, MFR means the value measured in accordance with JIS K7210-1:2014 Method A at a test temperature of 230°C and a nominal load of 2.16 kg.

[0027] The MFR of the LDPE may be 0.1 g / 10 min or more, 0.2 g / 10 min or more, or 0.3 g / 10 min or more, and may be 1.5 g / 10 min or less, 1.0 g / 10 min or less, 0.8 g / 10 min or less, 0.6 g / 10 min or less, or 0.4 g / 10 min or less.

[0028] Polyethylene (such as HDPE or LDPE) may be a homopolymer of ethylene, or a copolymer of ethylene and another monomer copolymerizable with ethylene (polyethylene copolymer).

[0029] Examples of other monomers copolymerizable with ethylene include α-olefins other than ethylene and vinyl acetate. The α-olefin may be, for example, an α-olefin having 3 to 10 carbon atoms. Examples of α-olefins having 3 to 10 carbon atoms include propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, 1-nonene, and 1-decene.

[0030] Examples of polyethylene copolymers include ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-1-butene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-4 methyl-1-pentene copolymer, and ethylene-1-octene copolymer.

[0031] The thermoplastic resin may contain one or more of the polyethylenes described above. When the thermoplastic resin contains polyethylene, the polyethylene may contain at least one of HDPE and LDPE.

[0032] The content of HDPE may be 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, 18 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, and may be 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 35 parts by mass or less, relative to 100 parts by mass of the total thermoplastic resins contained in the sheet.

[0033] The LDPE content may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more, and may be 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 17 parts by mass or less, or 12 parts by mass or less, relative to 100 parts by mass of the total thermoplastic resins contained in the sheet.

[0034] The mass ratio of the HDPE content to the LDPE content (HDPE / LDPE) may be 0.8 / 1 or more, 1.1 / 1 or more, 1.3 / 1 or more, 1.5 / 1 or more, 1.7 / 1 or more, 1.9 / 1 or more, or 2.0 / 1 or more, and may be 8.0 / 1 or less, 7.0 / 1 or less, 5.0 / 1 or less, 4.0 / 1 or less, 3.5 / 1 or less, 3.0 / 1 or less, 2.7 / 1 or less, or 2.5 / 1 or less. In layer (A) 11, the mass ratio of the HDPE content to the LDPE content may be, for example, 1.1 / 1 to 3.0 / 1. When the thermoplastic resin contains HDPE and LDPE, the tensile elongation at break at -25°C and the tensile modulus at 100°C of the sheet can be adjusted by adjusting the HDPE / LDPE mass ratio.

[0035] The MDPE content may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, based on 100 parts by mass of the total thermoplastic resin contained in the sheet. The thermoplastic resin in the sheet may be substantially free of MDPE. In this specification, "substantially free of a certain component" means that the component is not contained at all, or that the component is contained only as an unavoidable impurity.

[0036] From the viewpoint of further suppressing deformation of the sheet when heated, the content of LLDPE may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less per 100 parts by mass of the total thermoplastic resins contained in the sheet. The thermoplastic resin in the sheet may be substantially free of LLDPE.

[0037] The polyethylene content (when the sheet contains multiple types of polyethylene, the total content of those polyethylenes) may be 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40 parts by mass or more, relative to 100 parts by mass of the total thermoplastic resins contained in the sheet, or may be 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

[0038] Polypropylene is a polymer containing mainly propylene as a monomer unit. The melting point of polypropylene may be 150°C or higher, and more preferably 160°C or higher. Examples of polypropylene include homopolypropylene (a homopolymer of propylene) and block polypropylene.

[0039] The block polypropylene refers to a mixture in which a rubber component is dispersed in a continuous phase containing homopolypropylene or random polypropylene. The block polypropylene may be an impact-resistant polypropylene polymer (PP-B) according to JIS K6921-1.

[0040] The random polypropylene that can be contained in the continuous phase of the block polypropylene may be, for example, a random copolymer of propylene and another monomer copolymerizable with propylene. Examples of the other monomer copolymerizable with propylene include α-olefins other than propylene. The α-olefins other than propylene may be, for example, an α-olefin having 2 carbon atoms (ethylene) or an α-olefin having 4 to 10 carbon atoms.

[0041] The rubber component in the block polypropylene may include, for example, an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer, an ethylene-octene copolymer, a propylene-butene copolymer, a propylene-hexene copolymer, a propylene-octene copolymer, and the like.

[0042] Block polypropylene is produced, for example, by forming homopolypropylene or random polypropylene that forms a continuous phase in a first polymerization stage, and then forming a rubber component in the presence of the homopolypropylene or random polypropylene in a second polymerization stage. Specifically, the block polypropylene may have a sea-island structure in which rubber components (islands) made of polyethylene are dispersed in a continuous phase (sea) made of polypropylene, or a sea-island structure in which rubber components (islands) made of polyethylene covered with an ethylene-propylene copolymer (ethylene-propylene rubber) are dispersed in a continuous phase (sea) made of homopolypropylene.

[0043] The density of block polypropylene is 0.8 g / cm 3 More than 0.85g / cm 3 or more, or 0.88 g / cm 3 may be 0.95 g / cm or more, 3 or less, or 0.93 g / cm 3 It may be the following:

[0044] The MFR of the block polypropylene may be 0.5 g / 10 min or more, 0.8 g / min or more, 1.0 g / 10 min or more, or 1.2 g / 10 min or more, and may be 3.0 g / 10 min or less, 2.5 g / 10 min or less, 2.0 g / 10 min or less, or 1.5 g / 10 min or less.

[0045] The polypropylene content (when the sheet contains multiple types of polypropylene, the total content of those polypropylenes) may be 10 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, or 55 parts by mass or more, relative to 100 parts by mass of the total thermoplastic resins contained in the sheet, or may be 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 75 parts by mass or less, 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less.

[0046] The content of the thermoplastic resin may be 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 45% by mass or more, based on the total mass of the sheet, and may be 80% by mass or less, 70% by mass or less, 60% by mass or less, or 55% by mass or less.

[0047] The sheet may further contain other components in addition to the inorganic filler and the thermoplastic resin, such as a colorant, a lubricant, a dispersant, an antistatic agent, an antioxidant, a heat stabilizer, and an ultraviolet absorber.

[0048] In the sheet, the content of other components may be, for example, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total mass of the sheet.

[0049] The thickness of the sheet may be 200 μm or more, 300 μm or more, or 350 μm or more, and may be 500 μm or less, or 450 μm or less. In this specification, the thickness of the entire sheet and the thickness of the layers constituting the sheet refer to values ​​measured using a micrometer in accordance with JIS K7130:1999.

[0050] The density of the sheet is 1g / cm 3 More than 1.2g / cm 3 or more, or 1.3 g / cm 3 may be equal to or greater than 2 g / cm 3 Below, 1.8 / cm 3 or less, or 1.6 g / cm 3 It may be the following:

[0051] The sheet according to one embodiment has a tensile elongation at break of 4% or more at -25°C. Because the sheet according to one embodiment has a tensile elongation at break of 4% or more at -25°C, the occurrence of breakage at low temperatures is suppressed. The tensile elongation at break of the sheet at -25°C may be 5% or more, 6% or more, 8% or more, or 10% or more, and may be 30% or less, 20% or less, or 15% or less. In order to set the tensile elongation at break of the sheet at -25°C within the above numerical range, for example, it may be considered to adjust the content of a resin having a glass transition temperature of 0°C or less.

[0052] In this specification, the tensile elongation at break, maximum tensile strength, and tensile modulus of a sheet refer to those measured according to ASTM D638 using a measurement sample prepared with any direction of the sheet as the longitudinal direction. The tensile elongation at break, maximum tensile strength, and tensile modulus at a certain temperature refer to the tensile elongation at break, maximum tensile strength, and tensile modulus measured under the environment of that temperature, respectively. Furthermore, the tensile elongation at break, maximum tensile strength, and tensile modulus in the MD of the sheet, and the tensile elongation at break, maximum tensile strength, and tensile modulus in the TD of the sheet refer to the tensile elongation at break, maximum tensile strength, and tensile modulus of the sheet measured with the MD (machine direction; sheet flow direction) and TD (transverse direction; direction perpendicular to the sheet flow direction) of the sheet as the longitudinal direction, respectively.

[0053] The tensile break elongation of a sheet at -25°C being within a specific range means that at least both the MD and TD tensile break elongation of the sheet at -25°C are within the specific range. The MD tensile break elongation of the sheet at -25°C may be 5% or more, 6% or more, 8% or more, or 10% or more, and may be 30% or less, 20% or less, or 15% or less. Furthermore, the TD tensile break elongation of the sheet at -25°C may be 4.5% or more, 5% or more, 6% or more, or 7.5% or more, and may be 30% or less, 20% or less, or 15% or less.

[0054] The maximum tensile strength of the sheet at -25°C may be 15 MPa or more, 20 MPa or more, or 25 MPa or more, and may be 50 MPa or less, 45 MPa or less, or 40 MPa or less. The maximum tensile strength in MD and the maximum tensile strength in TD of the sheet at -25°C may each independently be within the numerical ranges described above for the maximum tensile strength of the sheet at -25°C.

[0055] The impact strength of the sheet at −25° C. may be 1.5 J / mm or more, or 2 J / mm or more, and may be 4 J / mm or less, or 3.5 J / mm or less. In this specification, the impact strength of the sheet at −25° C. means the value determined in accordance with ASTM D3420 using a film impact tester (for example, No. 181-L manufactured by Yasuda Seiki Seisakusho Co., Ltd.).

[0056] From the viewpoint of easily suppressing deformation of the sheet when heated, the tensile modulus of the sheet at 100°C may be 150 MPa or more, 200 MPa or more, 300 MPa or more, 330 MPa or more, 350 MPa or more, 380 MPa or more, 400 MPa or more, 410 MPa or more, or 420 MPa or more. The tensile modulus of the sheet at 100°C may be, for example, 600 MPa or less, 500 MPa or less, or 480 MPa or less.

[0057] The tensile modulus of the sheet at 100° C. being within a specific range means that at least both the MD tensile modulus and the TD tensile modulus of the sheet are within the specific range. From the viewpoint of easily suppressing deformation of the sheet when heated, the MD tensile modulus of the sheet at 100° C. may be 150 MPa or more, 200 MPa or more, 300 MPa or more, 330 MPa or more, 350 MPa or more, 380 MPa or more, 400 MPa or more, 410 MPa or more, or 420 MPa or more, for example, 600 MPa or less, 500 MPa or less, or 480 MPa or less. The TD tensile modulus of the sheet at 100°C may be 150 MPa or more, 200 MPa or more, 300 MPa or more, 330 MPa or more, 350 MPa or more, 380 MPa or more, 400 MPa or more, 410 MPa or more, or 420 MPa or more, for example, 600 MPa or less, 500 MPa or less, or 480 MPa or less.

[0058] The sheet described above may be a sheet consisting of a single layer, or may be a laminated sheet having multiple layers. Fig. 1 is a schematic cross-sectional view showing one embodiment of a laminated sheet. The sheet (laminated sheet) 1 shown in Fig. 1 has a layer (A) 11 and a layer (B) 12 provided on one side of the layer (A) 11. In the sheet 1, the layer (B) 12 forms one surface of the sheet 1.

[0059] Layer (A) 11 contains, for example, at least a portion of the inorganic filler and at least a portion of the thermoplastic resin. The inorganic filler in layer (A) 11 (at least a portion of the inorganic filler in sheet 1) may contain at least one of calcium carbonate and talc.

[0060] The thermoplastic resin in layer (A) 11 preferably contains polyethylene and polypropylene. The polyethylene may contain at least one of HDPE and LDPE. The MFR of the HDPE may be within the range of values ​​described above for the MFR of the HDPE that may be contained in the sheet. The melting point and MFR of the LDPE may be within the range of values ​​described above for the melting point and MFR of the LDPE that may be contained in the sheet. The LDPE may have a side chain with 6 or more carbon atoms.

[0061] The thermoplastic resin in layer (A) 11 may contain polyethylene other than HDPE and LDPE. Examples of polyethylene other than HDPE and LDPE include MDPE and LLDPE. The LLDPE does not need to have a side chain with 6 or more carbon atoms.

[0062] In layer (A) 11, the polyethylene (such as HDPE or LDPE) may be an ethylene homopolymer or a polyethylene copolymer. Details of the polyethylene copolymer may be as described above for the polyethylene that may be contained in the sheet.

[0063] In the layer (A) 11, the polypropylene may include, for example, block polypropylene. The thermoplastic resin in the layer (A) 11 may include polyethylene other than block polypropylene.

[0064] The layer (A) 11 may further contain components other than the inorganic filler and the thermoplastic resin, such as a colorant, a lubricant, a dispersant, an antistatic agent, an antioxidant, a heat stabilizer, and an ultraviolet absorber.

[0065] The thickness of layer (A) 11 may be 100 μm or more, 150 μm or more, 200 μm or more, 230 μm or more, or 250 μm or more, and may be 500 μm or less, 450 μm or less, 400 μm or less, 350 μm or less, or 300 μm or less.

[0066] The layer (B) 12 contains, for example, a polyolefin. The polyolefin in the layer (B) 12 may include one or more selected from the group consisting of HDPE, LDPE, and block polypropylene.

[0067] The MFR of the HDPE in layer (B) 12 may be within the ranges described above for the MFR of the HDPE that can be contained in the sheet. The melting point and MFR of the LDPE may be within the ranges described above for the melting point and MFR of the LDPE that can be contained in the sheet. The LDPE may have a side chain with 6 or more carbon atoms.

[0068] The polyolefin in layer (B) 12 may include polyethylene other than HDPE and LDPE. Examples of polyethylene other than HDPE and LDPE include MDPE and LLDPE. The LLDPE does not need to have a side chain with 6 or more carbon atoms.

[0069] In layer (B) 12, the polyethylene (such as HDPE or LDPE) may be an ethylene homopolymer or a polyethylene copolymer. Details of the polyethylene copolymer may be as described above for the polyethylene that may be contained in layer (A) 11.

[0070] The density and MFR of the block polypropylene in layer (B) may be within the above-mentioned ranges for the density and MFR of the block polypropylene that may be contained in the sheet. The polyolefin in layer (B) 12 may contain polypropylene other than block polypropylene.

[0071] The layer (B) 12 may further contain a thermoplastic resin other than polyolefin. Examples of the thermoplastic resin other than polyolefin include polyester, polystyrene, polyamide, and acrylonitrile-butadiene-styrene copolymer (ABS resin).

[0072] Layer (B) 12 may further contain at least a portion of the inorganic filler. Layer (B) 12 may contain other components in addition to the polyolefin and inorganic filler. Examples of other components include colorants, lubricants, dispersants, antistatic agents, antioxidants, heat stabilizers, and UV absorbers.

[0073] The thickness of layer (B) 12 may be 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more, and may be 100 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less.

[0074] 1 is composed of two layers, a layer (A) and a layer (B) provided on one side of the layer (A), but the configuration of the laminated sheet is not limited to this. The laminated sheet may also be composed of three or more layers.

[0075] Fig. 2 is a schematic cross-sectional view showing another embodiment of a sheet. The sheet (laminated sheet) 2 shown in Fig. 2 includes a layer (A) 11, a layer (B) 12 provided on one side of the layer (A) 11, and a layer (C) 13 provided on the other side of the layer (A) 11. In the sheet 2, the layer (B) 12 forms one surface of the sheet 2, and the layer (C) 13 forms the other surface of the sheet 2.

[0076] There are no particular limitations on the composition and thickness of layer (C) 13. Layer (C) 13 may be, for example, a layer containing a polyolefin. As the polyolefin, the polyolefins described above for layer (B) 12 can be used without particular limitations.

[0077] When layer (C) 13 is a layer containing a polyolefin, the polyolefin may include, for example, HDPE, LDPE, and block polypropylene. The polyolefin may also include polyethylene other than HDPE and LDPE (e.g., MDPE and LLDPE), or polypropylene other than block polypropylene (e.g., homopolypropylene and random polypropylene).

[0078] Details of the various polyethylenes (HDPE, LDPE, etc.) and various polypropylenes (block polypropylene, etc.) in layer (C) 13 may be the same as those described above for the various polyethylenes (HDPE, LDPE, etc.) and various polypropylenes (block polypropylene, etc.) in layer (B) 12.

[0079] Layer (C) 13 may or may not contain at least a portion of the inorganic filler. Layer (C) 13 may contain other components in addition to the polyolefin and the inorganic filler. Details of the other components may be the same as those described above for the other components in layer (B) 12. Layer (C) 13 may have the same composition (types of components contained) as layer (B) 12.

[0080] Layer (C) 13 may also be a layer containing at least a portion of the inorganic filler and a thermoplastic resin. Details of the thermoplastic resin may be the same as those described above for the thermoplastic resin contained in layer (A) 11. The thermoplastic resin in layer (C) 13 may contain, for example, at least one of polypropylene and polyethylene. In these cases, layer (C) 13 may have a different composition (type of thermoplastic resin and inorganic filler) from layer (A) 11.

[0081] The thickness of the layer (C) 13 may be within the range of values ​​described above for the thickness of the layer (B) 12. The layer (C) 13 may have the same thickness as the layer (B) 12.

[0082] The three-layer laminate sheet is not limited to the sheet 2 shown in FIG. 2. For example, in a three-layer laminate sheet, layer (B) may constitute one surface of the laminate sheet, and layer (A) may constitute the other surface of the laminate sheet. In this case, the laminate sheet includes an intermediate layer, layer (B) provided on one surface of the intermediate layer, and layer (A) provided on the other surface of the intermediate layer. The intermediate layer may be, for example, a layer made of polypropylene, or a layer containing polyethylene, polypropylene, and at least a portion of the inorganic filler. When the intermediate layer is a layer containing polyethylene, polypropylene, and at least a portion of the inorganic filler, the intermediate layer may have a different composition (type of polyethylene, polypropylene, and inorganic filler) from layer (A) 11. The details of the polyethylene and polypropylene may be the same as those described above for the polyethylene and polypropylene contained in layer (A) 11.

[0083] In another embodiment, the laminate sheet may be composed of four or more layers. In this case, the laminate sheet includes a plurality of other layers in addition to the layer (A) and the layer (B).

[0084] Fig. 3 is a schematic cross-sectional view showing another embodiment of a laminate sheet. The sheet (laminated sheet) 3 shown in Fig. 3 includes a layer (A) 11, a layer (B) 12 provided on one side of the layer (A) 11, a layer (C) 13 provided on the other side of the layer (A) 11, and a layer (D) 14 provided on the surface of the layer (B) 12 opposite to the layer (A) 11 side. In the sheet 3, the layer (D) 14 forms one surface of the sheet 3, and the layer (C) 13 forms the other surface of the sheet 3.

[0085] Layer (D) 14 may be a layer containing, for example, a thermoplastic resin. Details of the thermoplastic resin may be the same as those described above for the thermoplastic resin contained in layer (A) 11. The thermoplastic resin in layer (D) 14 may contain a polyolefin. The polyolefin may contain at least one of polyethylene and polypropylene, and may particularly contain block polypropylene.

[0086] In the laminate sheet of each of the above embodiments, the thickness of Layer (A) 11 may be 50% or more, 60% or more, 65% or more, or 70% or more, and 99% or less, 95% or less, 90% or less, 80% or less, or 75% or less, based on the total thickness of the laminate sheet (100%). Furthermore, the thicknesses of Layer (B) 12 and Layer (C) 13 may each independently be 1% or more, 2% or more, 3% or more, 5% or more, 10% or more, or 13% or more, and 50% or less, 40% or less, 30% or less, or 20% or less, based on the total thickness of the laminate sheet (100%). The thickness of Layer (D) 14 may be 1% or more, 2% or more, or 3% or more, and 10% or less, or 5% or less, based on the total thickness of the laminate sheet (100%).

[0087] The sheet described above can be produced, for example, by a multilayer T-die method. Specifically, it can be produced by a method including the steps of preparing the material for layer (A), the material for layer (B), and, if necessary, the materials for other layers such as layer (C) and layer (D), and the steps of melting the materials for each layer and co-extruding them to obtain a sheet (laminated sheet).

[0088] The sheet according to one embodiment has a tensile elongation at break of 4% or more at -25°C, and therefore food packaging containers formed using the sheet are less likely to break at low temperatures. Therefore, the sheet according to one embodiment is particularly suitable as a food packaging material for food packaging containers (e.g., frozen food packaging containers). The sheet may be used to form food packaging containers.

[0089] Another embodiment of the present invention is a food packaging container formed by molding a sheet. A known method can be used to manufacture the food packaging container from the sheet, and for example, a thermoforming method such as vacuum forming or pressure forming can be used. The sheet may be one that is suitable for vacuum forming. [Example]

[0090] The present disclosure will be described in more detail below based on examples, but the present invention is not limited to these examples in any way.

[0091] [Sheet manufacturing] <Material> In the examples and comparative examples, the following materials were used. HDPE: High-density polyethylene (Prime Polymer Co., Ltd. "5202B", density: 0.960 g / cm 3 , MFR:0.33g / 10min) LDPE: Low-density polyethylene (Braskem "SBF0323HC", density: 0.923 g / cm 3 , MFR: 0.32g / 10min, LDPE produced using raw materials including bio-based raw materials) LLDPE: Linear low-density polyethylene (Braskem "SLH118", density: 0.916 g / cm 3 , MFR: 1.0g / 10min, LLDPE produced using raw materials including bio-based raw materials)

[0092] Block PP: Block polypropylene (SunAllomer Co., Ltd. "VB370A", density: 0.9 g / cm 3 , MFR: 1.3g / 10min, rubber component made of polyethylene dispersed in a continuous phase made of polypropylene) Homo PP: Homo polypropylene (SunAllomer Co., Ltd. "PL400A", density: 0.9 g / cm 3 , MFR: 2.0g / 10min)

[0093] Composite pellet a: Composite pellet containing calcium carbonate particles and polypropylene ("LIMEX PP75" manufactured by TBM Co., Ltd., calcium carbonate particle content based on the total mass of the pellet: 75 mass%, average particle diameter of calcium carbonate particles: 1.2 μm, polypropylene content: 25 mass%) Composite pellet b: Composite pellet containing talc particles and polypropylene ("SG-137U" manufactured by Asada Flour Milling Co., Ltd., talc particle content based on the total mass of the pellet: 80 mass%, average particle diameter of talc particles: 17 μm, polypropylene content: 20 mass%) Colorant: Black colorant (Sankyo Chemical Industry Co., Ltd. "10H316")

[0094] <Examples 1 to 8, 10 and Comparative Examples 1 to 2> The materials for layers (A), (B), and (C) were hand-blended with the types and amounts shown in Tables 1 and 2. Block PP was also prepared for layer (D). The molten materials for each layer were laminated using a 115 mmφ single-screw extruder for layer (A), a 75 mmφ single-screw extruder for layers (B) and (C), a 50 mmφ single-screw extruder for layer (D), and a four-type, four-layer feedblock. Four-layer coextrusion molding was performed using a coat hanger die to produce a sheet consisting of layers (D), (B), (A), and (C) laminated in this order. The thickness ratio of each layer was adjusted by adjusting the screw rotation speed of the extruder used to produce each layer. The thickness of the resulting sheet was as shown in Tables 1 and 2. The thickness of layer (D) was 8 μm (2% of the total thickness of the sheet), and the thickness ratio of layers (A), (B), and (C) (layer (B) / layer (A) / layer (C)) was as shown in Tables 1 and 2.

[0095] Example 9 The material for layer (A) was prepared by hand-blending the materials of the types and amounts shown in Table 2. Block PP was also prepared as the material for layer (B). Using a 115 mmφ single-screw extruder for producing layer (A), a 50 mmφ single-screw extruder for producing layer (B), and a two-type, two-layer feed block, the molten materials for each layer were laminated, and two-layer coextrusion molding was performed using a coat hanger die to produce a sheet in which layer (B) and layer (A) were laminated in this order. The thickness of the obtained sheet was as shown in Table 2. The thickness of layer (B) was 8 μm (2% of the total sheet thickness).

[0096] <Density measurement> The density of the sheets of each example and comparative example was measured according to JIS K7112:1999 Method A under the standard conditions specified in JIS K 7100:1999. The results are shown in Table 3.

[0097] <Impact strength measurement> The sheets of each example and comparative example were cut into 70 mm x 70 mm pieces to prepare measurement samples. The impact strength (pendulum impact hole opening strength) of each measurement sample was measured in accordance with ASTM D3420 using a film impact tester (Yasuda Seiki Seisakusho Co., Ltd., No. 181-L). Each measurement sample was measured in an environment of 23°C and in an environment of -25°C in a thermostatic chamber. The results are shown in Table 3.

[0098] <Measurement of tensile modulus, maximum tensile strength and tensile elongation at break> Measurement samples were prepared by cutting the sheets of each Example and Comparative Example into the shape of a No. 1 dumbbell so that the longitudinal direction was the machine direction or transverse direction of the sheet. The tensile modulus, maximum tensile strength, and tensile elongation at break of each measurement sample were measured using an autograph (Shimadzu Corporation, AGS-X) according to ASTM D638. The measurement results, measured at 23°C, -25°C in a thermostatic chamber, and 100°C, are shown in Table 3.

[0099] <Evaluation of damage in low temperature environments> Using a vacuum and pressure forming machine (Wakisaka Engineering, FVS-500), the sheets of each example and comparative example were molded into bowls (bowl-shaped (frustum-shaped) containers with an opening diameter of 15 cm, a bottom diameter of 10 cm, and a height of 10 cm). The resulting bowls were stored in a -30°C environment for one day. After storage, a 400g weight was placed in the bowl, and the bowl containing the weight was dropped from a height of 1m. The weight was a resin pellet contained in a bag with a zipper. The weight was placed in the bowl so that it roughly conformed to the internal shape of the bowl. The bowls were inspected for cracks after the drop, and were rated A if no cracks were found and B if cracks were found. The results are shown in Table 3.

[0100] <Evaluation of deflection after heating> The sheets of each example and comparative example were molded into a rectangular lunch container with a partition (long side 28 cm, short side 20 cm) using a vacuum / compressed air molding machine (Wakisaka Engineering, FVS-500). The MD of the sheet was aligned with the long side of the lunch container. A schematic perspective view of the molded lunch container is shown in Figure 4. Note that Figure 4 is merely a schematic representation, and the scale of each component shown in Figure 4 does not necessarily correspond to the scale of the actual components. The lunch container 4 has a partition 5 located approximately in the center of the long side, and a first storage section 6A and a second storage section 6B separated by the partition 5. The top end of the partition 5 and the top end of the periphery of the lunch container 4 are located at approximately the same height, higher than the bottom of each storage section 6A, 6B. After placing polished rice (200 g) in the first storage section 6A of such a lunch box container 4 and fried chicken (approximately 200 g) in the second storage section 6B, the lunch box container 4 was heated for 65 seconds in a 1500 W microwave oven. Immediately after heating, one of the short sides of the lunch box container 4 (the side facing the first storage section 6A) was grasped and lifted. Whether or not the lunch box warped as a result of this operation was checked, and cases where no warping occurred were evaluated as A, and cases where warping occurred were evaluated as B. Figure 5 is a schematic cross-sectional view showing an example of a lunch box container 4 after the above operation. The cross section in Figure 5 corresponds to the cross section taken along line II-II in Figure 4. In the lunch box container 4 in Figure 5, polished rice 7A is placed in the first storage section 6A, and fried chicken 7B is placed in the second storage section 6B. When the above operation is performed, the weight of the contents of the lunch container 4 (rice 7A and fried chicken 7B) can cause the storage section 6B to tilt downward, as shown in Figure 5. In Figure 5, surface 8 represents a surface that is approximately flush with the upper end surface of the edge of the lunch container 4 on the first storage section 6A side, and surface 9 represents a surface that is approximately flush with the upper end surface of the edge of the lunch container 4 on the second storage section 6B side. The angle (acute angle) θ between surfaces 8 and 9 was evaluated as A if there was no visual change before and after the above operation, and as B if a visual change was observed. When θ before the above operation was θ0 and θ after the above operation was θ1, a B was given for cases where θ1 - θ0 > 10°. The results are shown in Table 3.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3] [Explanation of symbols]

[0104] 1,2,3...sheets, 11...layer (A), 12...layer (B), 13...layer (C), 14...layer (D).

Claims

1. Contains an inorganic filler and a thermoplastic resin, A sheet having a tensile elongation at break of 4% or more at -25°C.

2. The sheet according to claim 1, having a tensile modulus at 100°C of 330 MPa or more.

3. The sheet of claim 1 , wherein the thermoplastic resin comprises a polyolefin.

4. 4. The sheet of claim 3, wherein the polyolefin comprises high density polyethylene, low density polyethylene, and block polypropylene.

5. The sheet according to claim 1 , wherein the content of the inorganic filler is 35% by mass or more based on the total mass of the sheet.

6. The sheet according to claim 1 , wherein the inorganic filler comprises at least one of calcium carbonate and talc.

7. The sheet according to any one of claims 1 to 6, which is used for forming a food packaging container.

8. The sheet according to any one of claims 1 to 6, which is used for vacuum forming.

9. A food packaging container formed from the sheet according to any one of claims 1 to 6.

Images