Food Containers

Abstract

To provide a laminated sheet having a heat resistance and an excellent impact resistance in a frozen environment.SOLUTION: There is provided a laminated sheet 1, comprising: a heat-resistant base material layer 2 composed of a mixture containing block polypropylene in a range of 50 to 80 wt.% and polyethylene in a range of 8 to 32 wt.%; a first surface layer 3 that is formed of a polypropylene-based resin and that is laminated and fixed to one surface of the heat-resistant base material layer 2; and a second surface layer 4 that is formed of a polypropylene-based resin and that is laminated and fixed to other surface of the heat-resistant base material layer 2, and the sheet is used as a material for thermoforming a food container used in a frozen environment, for example.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate sheet having excellent heat resistance and cold resistance, and a food container formed from the laminate sheet. [Background technology]

[0002] Conventionally, a laminate sheet has been used as a material for thermoforming food containers that can be used in a microwave oven, as disclosed in Patent Document 1. This laminate sheet is formed by laminating outer layers made of polyolefin resin on both sides of a base layer made of a composition containing a filler and a polypropylene resin, and this laminate sheet is thermoformed to form a food container having heat resistance and oil resistance.

[0003] Furthermore, Patent Document 2 also discloses a similar laminate sheet having heat resistance. The laminate sheet of Patent Document 2 is a two-kind, three-layer laminate sheet consisting of a base layer made of 92-82% by weight of polyolefin resin, in which the weight ratio of polypropylene resin to high-density polyethylene is 80:20-30:70, 8-18% by weight of talc, and surface layers on both sides made of polyolefin resin mainly composed of polypropylene resin. For example, Example 12 in Table 2 of Patent Document 2 discloses a laminate sheet in which the base layer contains 15% by weight of talc, and the remaining 85% by weight of the polyolefin resin is 27.2% by weight of homopolypropylene, 30.6% by weight of block polypropylene, and 27.2% by weight of high-density polyethylene. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-207843 A [Patent Document 2] Patent No. 4565939 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, food containers having heat resistance that can be used in a microwave oven, for example, are often transported in a frozen environment with food contained therein, stored in a freezer, and transported from the freezer when necessary. When such storage, preservation, or transportation is performed in a frozen environment, for example, polyolefin-based sheets become brittle in the frozen environment, so unless food containers made of materials with excellent impact resistance in a frozen environment are used, there is a high risk that the food containers will be damaged by shocks such as vibrations during transportation, drops, and collisions during transportation in a frozen environment. Therefore, there is a strong demand for materials that can ensure heat resistance and at the same time have excellent impact resistance in a frozen environment.

[0006] The present invention has been proposed in consideration of the above-mentioned problems, and aims to provide a laminated sheet that is heat resistant and at the same time has excellent impact resistance in a freezing environment, and a food container formed from such a laminated sheet. [Means for solving the problem]

[0007] The laminate sheet of the present invention is characterized by comprising a heat-resistant base layer composed of a mixture containing 50 to 80% by weight of block polypropylene and 8 to 32% by weight of polyethylene, a first surface layer formed of a polypropylene-based resin and laminated and fixed to one side of the heat-resistant base layer, and a second surface layer formed of a polypropylene-based resin and laminated and fixed to the other side of the heat-resistant base layer. According to this, the heat-resistant base layer containing 8 to 32% by weight of polyethylene can reduce drawdown during the production of food containers, i.e., when the laminated sheet is molded into a desired shape, and can ensure the required heat resistance of the laminated sheet. In addition, the rubber phase of the block polypropylene contained in the heat-resistant base layer at a high weight ratio of 50 to 80% by weight can increase the impact resistance of the laminated sheet in a freezing environment.

[0008] The laminate sheet of the present invention is characterized in that the heat-resistant substrate layer contains an inorganic filler in the range of 8 to 21% by weight. According to this, by making the heat-resistant base layer contain 8% by weight or more of inorganic filler, it is possible to reliably and stably improve the heat resistance, rigidity, and strength of the heat-resistant base layer and the laminate sheet. In addition, by keeping the content of inorganic filler to 21% by weight or less and increasing the content of block polypropylene and polyethylene in the heat-resistant base layer, it is possible to more reliably improve the impact resistance in a freezing environment.

[0009] The laminate sheet of the present invention is characterized in that the heat-resistant base layer contains 58 to 76% by weight of block polypropylene, 8 to 26% by weight of polyethylene, and 11 to 21% by weight of an inorganic filler. According to this, the heat-resistant base layer, in which the polyethylene content is suppressed to 26 weight % or less, can more reliably ensure the required heat resistance of the laminate sheet, while the rubber phase of the block polypropylene contained in the heat-resistant base layer at a high weight ratio of 58 to 76 weight % can reliably increase the impact resistance of the laminate sheet in a freezing environment.

[0010] The laminate sheet of the present invention is characterized in that the heat-resistant substrate layer contains polyethylene in the range of 8 to 16% by weight. The laminated sheet of the present invention comprises a heat-resistant base layer composed of a mixture containing 50 to 80% by weight of block polypropylene and 8 to 16% by weight of polyethylene, a first surface layer formed of a polypropylene-based resin and laminated and fixed to one side of the heat-resistant base layer, and a second surface layer formed of a polypropylene-based resin and laminated and fixed to the other side of the heat-resistant base layer, the heat-resistant base layer containing an inorganic filler in the range of 8% by weight to less than 20% by weight, more preferably, the heat-resistant base layer contains 58 to 76% by weight of block polypropylene, 8 to 16% by weight of polyethylene, and 8 to 20% by weight of inorganic filler. More preferably, the heat-resistant base layer contains 58 to 76% by weight of block polypropylene, 8 to 15% by weight of polyethylene, and 8 to 20% by weight of inorganic filler. According to this, by suppressing the blending ratio of polyethylene, the heat resistance of the heat-resistant base layer and the laminate sheet can be more reliably improved.

[0011] The laminate sheet of the present invention is characterized in that the polyethylene constituting the heat-resistant substrate layer is biomass-derived polyethylene. According to this, by using biomass-derived polyethylene as the polyethylene, it is possible to reduce the amount of fossil fuel used and reduce the environmental burden.

[0012] The food container of the present invention is characterized in that it is formed by thermoforming the laminate sheet of the present invention. A preferred food container of the present invention is characterized in that it comprises a heat-resistant base layer composed of a mixture containing 50 to 80% by weight of block polypropylene and 8 to 16% by weight of polyethylene, a first surface layer formed of a polypropylene-based resin and laminated and fixed to one side of the heat-resistant base layer, and a second surface layer formed of a polypropylene-based resin and laminated and fixed to the other side of the heat-resistant base layer, and the heat-resistant base layer is formed by thermoforming a laminate sheet containing an inorganic filler in the range of 8% by weight or more and less than 20% by weight. Further, a preferred food container of the present invention is characterized in that the heat-resistant base layer of the laminate sheet contains 58 to 76% by weight of block polypropylene and 8% by weight or more and less than 15% by weight of polyethylene. Further, a preferred food container of the present invention is characterized in that the polyethylene constituting the heat-resistant base layer of the laminate sheet is polyethylene derived from biomass. This makes it possible to obtain a food container that has sufficient rigidity and strength as a food container and has the effects of the laminated sheet of the present invention. Furthermore, since the risk of the food container being damaged is extremely low even when used in a freezing environment, it is possible to more reliably prevent consumers from ingesting pieces of the food container. Effect of the Invention

[0013] According to the present invention, it is possible to obtain a laminated sheet or a food container that can ensure heat resistance and at the same time has excellent impact resistance in a freezing environment. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a partial vertical cross-sectional view showing a laminate sheet according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a longitudinal sectional view of a food container formed from the laminate sheet of the embodiment. [Diagram 3] 1 is a graph showing the results of an impact resistance test for Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Laminated sheet and food container according to the embodiment] A laminate sheet 1 according to an embodiment of the present invention is a synthetic resin laminate sheet 1 shown in Fig. 1, and includes a heat-resistant base layer 2 composed of a mixture containing block polypropylene and polyethylene, a first surface layer 3 formed of a polypropylene-based resin and laminated and fixed to one surface of the heat-resistant base layer 2, and a second surface layer 4 formed of a polypropylene-based resin and laminated and fixed to the other surface of the heat-resistant base layer 2. The laminate sheet 1 is preferably used as a material for food containers for frozen foods and the like, and a food container 10 as shown in Fig. 2 is formed by thermoforming the laminate sheet 1 using a mold of a predetermined shape.

[0016] The heat-resistant base layer 2 is composed of a mixture containing 50 to 80% by weight of block polypropylene and 8 to 32% by weight of polyethylene, and the heat-resistant base layer 2 of this embodiment is composed of a mixture containing block polypropylene, high-density polyethylene, and an inorganic filler. The content of block polypropylene is more preferably 58 to 76% by weight, the content of polyethylene is more preferably 8 to 26% by weight, and even more preferably 8 to 16% by weight. The content of inorganic filler is preferably 8 to 21% by weight, and more preferably 11 to 21% by weight.

[0017] The polypropylene resin of the first surface layer 3 and the polypropylene resin of the second surface layer 4 are preferably homopolypropylene resins having excellent heat resistance, but as long as the required heat resistance can be ensured, polypropylene polymers, propylene-ethylene block copolymers, block polypropylenes, propylene-ethylene random copolymers, etc. can also be used as appropriate. From the viewpoint of improving production efficiency, it is preferable to use the same type of polypropylene resin for the first surface layer 3 and the polypropylene resin for the second surface layer 4 to make the laminate sheet 1 a two-type three-layer laminate sheet, but it is also possible to use different types of polypropylene resins for the first surface layer 3 and the polypropylene resin for the second surface layer 4.

[0018] The polyethylene constituting the heat-resistant substrate layer 2 is not particularly limited, but for example, low-density polyethylene, high-density polyethylene, linear low-density polyethylene, etc. are preferable, and high-density polyethylene with high versatility is particularly preferable. In addition, if biomass-derived polyethylene is used as the polyethylene, the amount of fossil fuel used can be reduced, and the environmental load can be reduced. Biomass-derived polyethylene is polyethylene made from renewable organic resources derived from living organisms, excluding fossil resources, such as polyethylene made from sugarcane.

[0019] The inorganic filler constituting the heat-resistant base layer 2 is not particularly limited, but for example, silica, alumina, calcium carbonate, talc, clay, mica, glass balloons, glass beads, calcium silicate, glass fiber, carbon fiber, etc. are preferable, and among them, flake-shaped and spherical talc are particularly preferable. These fillers can be used alone or in combination of two or more. In addition, when talc is used as the inorganic filler, the particle size of the talc is suitable to be relatively large, with an average particle size of 5 μm or more, since rigidity is easily obtained, but if it is too large, the unevenness of the layer increases, so the average particle size is preferably 1 to 20 μm.

[0020] The thickness of the heat-resistant base layer 2 of the laminated sheet 1 suitable as a food container material is preferably 300 to 1000 μm, more preferably 300 to 750 μm, and even more preferably 400 to 650 μm, and the thickness of the first surface layer 3 and the second surface layer 4 are each preferably 0.6 to 150 μm, more preferably 0.8 to 100 μm, and even more preferably 1 to 18 μm. Similarly, the total thickness of the laminated sheet 1 is preferably 300 to 1000 μm, and more preferably 300 to 800 μm. The volume ratio of the heat-resistant base layer 2 to the first surface layer 3 and the second surface layer 4 of the laminated sheet 1 suitable as a food container material is preferably 70:15:15 to 99.6:0.2:0.2, and more preferably 80:10:10 to 99:0.5:0.5.

[0021] The tensile modulus (MPa) of the laminated sheet 1 suitable as a food container material is preferably 1200 MPa or more, more preferably 1400 MPa or more, and even more preferably 1500 MPa or more. Similarly, the DuPont impact strength (E50(J)) of the laminated sheet 1 at a drop load of 0.3 kg and a measurement temperature of -20°C is preferably 1.5 J or more, more preferably 1.7 J or more, and even more preferably 1.9 J or more. Similarly, the density of the laminated sheet 1 is 0.8 to 1.4 g / cm 3 is preferable, and 1.0 to 1.2 g / cm 3 is more preferred.

[0022] Moreover, the heat resistance temperature of the food container 10 formed from the laminate sheet 1 is preferably 140° C. or higher, more preferably 145° C. or higher, and even more preferably 150° C. or higher.

[0023] The laminate sheet 1 can be manufactured by any suitable manufacturing method within the applicable range, and for example, it is suitable to manufacture it by a co-extrusion method using a T-die or a feed block. The food container 10 formed from the laminate sheet 1 can also be manufactured by any suitable manufacturing method within the applicable range, and for example, it can be manufactured by a process using vacuum molding or compressed air molding, or by a method using indirect heating or direct heating.

[0024] According to this embodiment, the heat-resistant base layer 2 having a polyethylene content of 8 to 32% by weight can reduce drawdown during food container production, i.e., when the laminate sheet is molded into a desired shape, and can ensure the required heat resistance of the laminate sheet 1. In addition, the rubber phase of the block polypropylene contained in the heat-resistant base layer 2 at a high weight ratio of 50 to 80% by weight can increase the impact resistance of the laminate sheet 1 in a freezing environment.

[0025] Furthermore, by incorporating 8% by weight or more of an inorganic filler in the heat-resistant base material layer 2, it is possible to reliably and stably increase the heat resistance, rigidity, and strength of the heat-resistant base material layer 2 and the laminate sheet 1. Furthermore, by limiting the content of the inorganic filler to 21% by weight or less and increasing the content of block polypropylene and polyethylene in the heat-resistant base material layer 2, it is possible to more reliably improve the impact resistance in a freezing environment.

[0026] Furthermore, when the heat-resistant base layer 2 contains 58 to 76% by weight of block polypropylene, 8 to 26% by weight of polyethylene, and 11 to 21% by weight of inorganic filler, the heat-resistant base layer 2 containing the polyethylene content at 26% or less can more reliably ensure the required heat resistance of the laminate sheet 1, and the rubber phase of the block polypropylene contained in the heat-resistant base layer 2 at a high weight ratio of 58 to 76% by weight can reliably improve the impact resistance of the laminate sheet 1 in a freezing environment. Furthermore, when the polyethylene content of the heat-resistant base layer 2 is set in the range of 8 to 16% by weight and the blending ratio of polyethylene is suppressed, the heat resistance of the heat-resistant base layer 2 and the laminate sheet 1 can be more reliably improved.

[0027] Furthermore, food container 10 formed by thermoforming laminate sheet 1 has sufficient rigidity and strength as a food container, and can exhibit the effects corresponding to laminate sheet 1. Furthermore, since there is an extremely low risk of food container 10 being damaged even when used in a freezing environment, it is possible to more reliably prevent consumers from ingesting pieces of food container 10.

[0028] [Scope of the invention disclosed herein] The inventions disclosed in this specification include, in addition to the inventions and embodiments listed as inventions, those specified by changing partial contents of these to other contents disclosed in this specification, those specified by adding other contents disclosed in this specification to these contents, or those specified by deleting partial contents of these to the extent that partial effects can be obtained, and specifying them as a higher-level concept. The inventions disclosed in this specification also include the following modified examples and added contents.

[0029] For example, the laminate sheet 1 includes a laminate sheet consisting of a heat-resistant base layer 2, a first surface layer 3, and a second surface layer 4, as well as a laminate sheet in which a laminate film having a pattern or the like is laminated and bonded to the outside of the first surface layer 3, the outside of the second surface layer 4, or both the outside of the first surface layer 3 and the outside of the second surface layer 4. In addition, additives such as pigments and lubricants can be added to the heat-resistant base layer 2 of the laminate sheet 1 as required depending on the application. In addition, the heat-resistant base layer of the laminate sheet of the present invention also includes a base layer that is made heat-resistant by containing a raw material other than talc as an inorganic filler.

[0030] [Evaluation of Examples and Comparative Examples] Next, laminate sheets of examples according to the present invention and laminate sheets of comparative examples, as well as the evaluation results thereof, will be described.

[0031] Laminated sheets of Examples 1 to 4 and Comparative Examples 1 and 2 having a three-layer structure similar to that of the laminated sheet 1 of the embodiment were formed (see Table 1). The laminated sheets of Examples 1 to 4 have a three-layer structure in which a surface layer having a composition of 100% homopolypropylene (H-PP) is laminated on one side and the other side of a base layer which is a heat-resistant base layer, the layer thickness of the base layer is 596 μm and is non-foamed, and the layer thickness of the surface layer on one side and the surface layer on the other side are each 2 μm. The laminated sheets of Comparative Examples 1 and 2 have a three-layer structure in which a surface layer having a composition of 100% homopolypropylene (H-PP) is laminated on one side and the other side of a base layer, the layer thickness of the base layer is 596 μm and is non-foamed, and the layer thickness of the surface layer on one side and the surface layer on the other side are each 2 μm. The contents of block polypropylene (B-PP), high density polyethylene (HDPE), and talc as an inorganic filler in the base layer in the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2 are as shown in Table 1.

[0032] [Table 1]

[0033] Then, for the laminate sheets of Examples 1 to 4 and the laminate sheets of Comparative Examples 1 and 2, the sheet physical properties and the physical properties of the molded products molded from the laminate sheets were evaluated.

[0034] Regarding the DuPont impact strength, which is one of the sheet properties, test pieces measuring 100 mm long x 50 mm wide were prepared from each of the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2, and the 50% fracture energy E50 (J) of the test pieces was measured using a DuPont impact tester in accordance with JIS K7211-1. The drop load was 0.3 kg and the measurement temperature was -20°C.

[0035] As for the tensile modulus (MPa) of the sheet physical properties, test pieces of 140 mm length × 15 mm width were prepared from each of the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2, and the tensile modulus (MPa) of these test pieces was measured using a tensile tester in accordance with JIS K7161 at a measurement temperature of 23°C, a chuck distance of 100 mm, and a tensile speed of 1 mm / min.

[0036] In the heat resistance test of the physical properties of the molded products, each of the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2 was thermoformed to form food containers, and a heat resistance test was performed on these food containers in accordance with the heat resistance test of the Household Products Quality Labeling Act. Specifically, the molded containers (samples) were placed in a thermo-hygrostat chamber whose temperature was adjusted every 10°C for 60 minutes, and deformation thereafter was visually confirmed, and the value obtained by subtracting 10°C from the temperature of the thermo-hygrostat chamber at which deformation occurred was determined as the heat resistance temperature.

[0037] In the heat load resistance test for the physical properties of molded products, each of the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2 was thermoformed to form food containers, and the heat load resistance test was performed on these food containers. Specifically, the molded containers were placed with the opening side facing down in a thermo-hygrostat chamber whose temperature was adjusted to 130°C, and immediately after that, a 150g iron plate was placed on the container and heated for 30 minutes, and then the degree of deformation was measured with a straight ruler.

[0038] The overall evaluation in Table 1 is a practical evaluation result as a laminate sheet based on a comprehensive comparison and weighing of the laminate sheets of Examples 1 to 4 and Comparative Examples 1 and 2 in four items: DuPont impact strength, tensile strength, heat resistance test, and heat load resistance test. The evaluation was made on a four-level scale: ◎: very excellent, ○: good, △: usable but with limitations, ×: difficult to use.

[0039] As can be seen from Table 1 and FIG. 3, the laminate sheets of Comparative Examples 1 and 2 have low DuPont impact strength in a freezing environment of -20°C and are easily damaged in a freezing environment when molded into food containers, whereas the laminate sheets of Examples 1 to 4 have high DuPont impact strength of more than 1.6 J in a freezing environment of -20°C and are therefore extremely unlikely to be damaged in a freezing environment when molded into food containers.

[0040] Moreover, it is clear that the food containers thermoformed from the laminate sheets of Examples 1 to 4 all have a heat resistance of 150°C or higher, and thus have high heat resistance sufficient for practical use. Moreover, the deformation amounts of the food containers thermoformed from the laminate sheets of Examples 1 to 4 in the heat load test are all within a range that does not cause problems for practical use as food containers.

[0041] Next, in order to compare the case where fossil fuel-derived polyethylene is used for the base layer and the case where biomass-derived polyethylene is used, laminate sheets of Examples 5 and 6 and laminate sheets of Comparative Examples 3 and 4 having a three-layer structure similar to that of the laminate sheet 1 of the embodiment were formed (see Table 2). The laminate sheets of Examples 5 and 6 also have a three-layer structure in which a surface layer having a composition of 100% homopolypropylene (H-PP) is laminated on one side and the other side of the base layer, which is a heat-resistant base layer, and the layer thickness of the base layer is 396 μm and is non-foamed, and the layer thickness of the surface layer on one side and the surface layer on the other side are each 2 μm. The laminate sheets of Comparative Examples 3 and 4 also have a three-layer structure in which a surface layer having a composition of 100% homopolypropylene (H-PP) is laminated on one side and the other side of the base layer, and the layer thickness of the base layer is 396 μm and is non-foamed, and the layer thickness of the surface layer on one side and the surface layer on the other side are each 2 μm.

[0042] The content ratios of block polypropylene (B-PP), high density polyethylene (HDPE), and talc as an inorganic filler in the base layer in the laminate sheets of Examples 5 and 6 and Comparative Examples 3 and 4 are as shown in Table 2. Example 5 and Comparative Example 3 contain polyethylene derived from fossil fuels (density 0.96 g / cm 3 , MFR 0.1 g / 10 min (JIS K7120)) was used, and biomass-derived polyethylene (density 0.96 g / cm 3 , MFR 0.3g / 10min (190℃ / load 2.16kg) (ASTM D1238) was used. In Table 2, HDPE1 is polyethylene derived from fossil fuels, and HDPE2 is polyethylene derived from biomass.

[0043] [Table 2]

[0044] Regarding the DuPont impact strength, which is one of the sheet properties, test pieces measuring 100 mm long x 50 mm wide were prepared from each of the laminate sheets of Examples 5 and 6 and Comparative Examples 3 and 4, and the 50% fracture energy E50(J) of the test pieces was measured using a DuPont impact tester in accordance with JIS K7211-1. The drop load was 0.3 kg and the measurement temperature was -20°C.

[0045] As for the tensile modulus (MPa) of the sheet physical properties, test pieces of 140 mm length × 15 mm width were prepared from each of the laminate sheets of Examples 5 and 6 and each of the laminate sheets of Comparative Examples 3 and 4, and the tensile modulus (MPa) of these test pieces was measured using a tensile tester in accordance with JIS K7161 at a measurement temperature of 23°C, a chuck distance of 100 mm, and a tensile speed of 1 mm / min.

[0046] In the heat resistance test of the physical properties of molded products, each of the laminate sheets of Examples 5 and 6 and each of the laminate sheets of Comparative Examples 3 and 4 was thermoformed to form food containers, and a heat resistance test was performed on these food containers in accordance with the heat resistance test of the Household Products Quality Labeling Act. Specifically, the molded containers (samples) were placed in a thermo-hygrostat chamber whose temperature was adjusted every 10°C for 60 minutes, and deformation thereafter was visually confirmed, and the value obtained by subtracting 10°C from the temperature of the thermo-hygrostat chamber at which deformation occurred was determined as the heat resistance temperature.

[0047] The overall evaluation in Table 2 is a practical evaluation result as a laminate sheet based on a comprehensive comparison and weighing of the DuPont impact strength, tensile strength, and heat resistance tests for the laminate sheets of Examples 5 and 6 and the laminate sheets of Comparative Examples 3 and 4, and was evaluated on a four-level scale: ◎: very excellent, ○: good, △: usable but with limitations, ×: difficult to use.

[0048] From the overall evaluation of Examples 5 and 6, it is found that a laminated sheet excellent in heat resistance and impact resistance in a freezing environment can be obtained by setting the block polypropylene (B-PP), polyethylene, and inorganic filler within a specified range, whether fossil fuel-derived polyethylene or biomass-derived polyethylene is used. In addition, it is found that the food containers thermoformed from the laminated sheets of Examples 5 and 6 both have a heat resistance of 150°C or more, and are sufficiently high in heat resistance for practical use.

[0049] In contrast, the laminated sheets of Comparative Examples 3 and 4, in which the blending ratio of block polypropylene is outside the range of 50-80% by weight and the blending ratio of the inorganic filler talc is outside the range of 8-21% by weight, have excellent tensile strength and heat resistance, but have low DuPont impact strength in a frozen environment of -20°C. Therefore, when molded into food containers, they are easily damaged in a frozen environment and are difficult to use. The same results are obtained for Comparative Example 3, which uses polyethylene derived from fossil fuels, and Comparative Example 4, which uses polyethylene derived from biomass. [Industrial Applicability]

[0050] The present invention can be used, for example, in forming a food container for containing food. [Explanation of symbols]

[0051] REFERENCE SIGNS LIST 1...Laminated sheet 2...Heat-resistant base layer 3...First surface layer 4...Second surface layer 10...Food container

Claims

1. A food container comprising a heat-resistant base layer composed of a mixture containing 50 to 80% by weight of block polypropylene and 8 to 16% by weight of polyethylene, a first surface layer formed of a polypropylene-based resin and laminated and fixed to one surface of the heat-resistant base layer, and a second surface layer formed of a polypropylene-based resin and laminated and fixed to the other surface of the heat-resistant base layer, the heat-resistant base layer being formed by thermoforming a laminate sheet containing 8% by weight or more and less than 20% by weight of an inorganic filler.

2. A food container as described in claim 1, characterized in that the heat-resistant base layer of the laminated sheet contains 58 to 76 weight % block polypropylene and 8 weight % or more but less than 15 weight % polyethylene.

3. A food container as described in claim 1 or 2, characterized in that the polyethylene constituting the heat-resistant base layer of the laminated sheet is polyethylene derived from biomass.

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