Molded containers

Abstract

The present invention provides a packaging container that minimizes the occurrence of holes and other damage when used in a microwave oven, and also offers cold-impact resistance, preventing film tearing due to food punctures when the container is stored or transported in a refrigerated or frozen environment. [Solution] The heat-resistant polystyrene resin laminated foam sheet 10 consists of a polyolefin resin film layer 1, a dry laminate adhesive layer 2, a heat-resistant polystyrene resin film layer 3, and a heat-resistant polystyrene resin foam sheet layer 4, with the polyolefin resin film layer 1 being the inner surface of the container, and the heat-resistant polystyrene resin film layer 3 containing 70-100% by mass of syndiotactic polystyrene.

Description

[Technical Field]

[0001] This invention relates to a polystyrene foam container with excellent heat resistance and cold shock resistance. The polystyrene foam container of this invention can be used as a food packaging container for microwave heating due to its excellent heat resistance, and can also be suitably used as a packaging container for chilled and frozen foods. [Background technology]

[0002] Polystyrene foam containers, made by thermoforming polystyrene foam sheets, are used as food packaging containers. Among these, foam containers made with heat-resistant polystyrene resin are used as food packaging containers for microwave heating.

[0003] For example, Patent Document 1 below describes a polystyrene resin laminated foam sheet including a laminated structure of a heat-resistant polystyrene resin foam sheet and an impact-resistant polystyrene resin film, and a container molded therefrom.

[0004] However, it was found that while using impact-resistant polystyrene resin film can improve cold impact resistance, it tends to result in insufficient oil and acid resistance, and in addition, problems such as holes forming in the film can occur when used in a microwave oven. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-55588 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a packaging container with cold resistance impact resistance that suppresses the occurrence of perforations even when used in a microwave oven and also has a low probability of film breakage due to piercing of food ingredients when a packaging container containing food ingredients is stored and transported in a refrigerated or frozen environment.

Means for Solving the Problems

[0007] The formed container according to the present invention is composed of a heat-resistant polystyrene-based resin laminated foam sheet in which a polyolefin-based resin film layer, a dry laminate adhesive layer, a heat-resistant polystyrene-based resin film layer, and a heat-resistant polystyrene-based resin foamed sheet layer are laminated in this order. The polyolefin-based resin film layer is the inner surface of the container, and the heat-resistant polystyrene-based resin film layer contains 70 to 100% by mass of syndiotactic polystyrene.

Effects of the Invention

[0008] With the above configuration, a packaging container with cold resistance impact resistance that suppresses the occurrence of perforations even when used in a microwave oven and also has a low probability of film breakage due to piercing of food ingredients when a packaging container containing food ingredients is stored and transported in a refrigerated or frozen environment can be obtained.

Brief Description of the Drawings

[0009] [Figure 1] Cross-sectional view of the formed container according to an embodiment of the present invention. [Figure 2] Enlarged view of part A in FIG. 1.

Mode for Carrying Out the Invention

[0010] A molded container according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of the cross-sectional shape of the molded container 20 in this embodiment. Further, FIG. 2 shows the layer structure of the molded container 20. The molded container 20 is made of a heat-resistant polystyrene-based resin laminated foam sheet 10, and the laminated foam sheet 10 is formed by thermoforming such as vacuum forming. Incidentally, a top seal lid may be attached to the molded container 20 as described later, or it may be pillow-packed.

[0011] The heat-resistant polystyrene-based resin laminated foam sheet 10 includes a polyolefin-based resin film layer 1, a dry laminate adhesive layer 2, a heat-resistant polystyrene-based resin film layer 3, and a heat-resistant polystyrene-based resin foam sheet layer 4. Each layer is laminated in the order of the polyolefin-based resin film layer 1, the dry laminate adhesive layer 2, the heat-resistant polystyrene-based resin film layer 3, and the heat-resistant polystyrene-based resin foam sheet layer 4. And the polyolefin-based resin film layer 1 constitutes the inner surface of the molded container 20.

[0012] <Polyolefin-based resin film layer 1> The films constituting the polyolefin-based resin film layer 1 are roughly classified into polypropylene-based resin films and polyethylene-based resin films. Examples of the polypropylene-based resin film include an unstretched polypropylene film (CPP film), a biaxially stretched polypropylene film (OPP film), etc. Examples of the polyethylene-based resin film include a high-density polyethylene film (HDPE film), a low-density polyethylene film (LDPE film), a linear low-density polyethylene film (LLDPE film), etc. Among these, as the polypropylene-based resin film, a CPP film is preferable from the viewpoint of moldability, etc., and as the polyethylene-based resin film, an LLDPE film is preferable from the viewpoint of cold impact resistance, etc. The thickness of the film is 10 to 100 μm, preferably 15 to 60 μm, and most preferably 25 to 40 μm.

[0013] <Heat-resistant polystyrene-based resin film layer 3> The heat-resistant polystyrene resin film layer 3 contains syndiotactic polystyrene (SPS). Syndiotactic polystyrene (SPS) is a styrene-based polymer that mainly has a syndiotactic structure. A syndiotactic structure is a stereochemical structure in which the phenyl groups, which are the side chains, are alternately positioned in opposite directions relative to the main chain formed from carbon-carbon bonds. Examples include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and copolymers containing these structural units. Particularly preferred styrene-based polymers include styrene-p-methylstyrene copolymers containing 3 to 20 mol% of p-methylstyrene repeating units.

[0014] For SPS, a crystallization peak temperature (the peak temperature when the sample resin is heated to 300°C to melt it and then cooled at a rate of 20°C / min) measured with a differential scanning calorimeter "DSC60A Plus" (manufactured by Shimadzu Corporation) is preferably less than 236°C, more preferably less than 230°C, and a MFR (measurement conditions: 300°C, 2.16 kg) of preferably 0.5 to 20 g / 10 min, more preferably 1 to 15 g / 10 min is preferred as it provides a good balance from the viewpoint of heat resistance and processability.

[0015] The heat-resistant polystyrene resin film layer 3 may contain thermoplastic resins other than syndiotactic polystyrene (SPS). Preferred thermoplastic resins other than syndiotactic polystyrene (SPS) include polystyrene-based resins other than syndiotactic polystyrene (SPS), such as styrene homopolymers and copolymers composed of styrene and monomers other than styrene. More specifically, examples include general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS), styrene-acrylonitrile copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, and styrene-based thermoplastic elastomers (SBS, SEBS, SIS, SEPS).

[0016] The heat-resistant polystyrene resin film layer 3 preferably contains 70% by mass or more of syndiotactic polystyrene (SPS), and more preferably 80% by mass or more. The higher the amount of syndiotactic polystyrene (SPS) blended, the better the microwave heating puncture resistance. Preferably, the heat-resistant polystyrene resin film layer 3 contains 10 to 30% by mass, more preferably 10 to 20% by mass, of rubber components other than syndiotactic polystyrene (SPS), such as high-impact polystyrene (HIPS) or styrene-based thermoplastic elastomers (SBS, SEBS, SIS, SEPS). When using styrene-based thermoplastic elastomers (SBS, SEBS, SIS, SEPS) as the rubber component, the upper limit of the amount added is preferably 20% by mass, as a high blending amount can easily cause the film to lose its stiffness. When using styrene-based elastomers, hydrogenated SEBS or SEPS is more preferably used.

[0017] <Heat-resistant polystyrene foam sheet layer 4> The heat-resistant polystyrene foam sheet that forms the heat-resistant polystyrene foam sheet layer 4 is formed by foaming polystyrene resin alone, or a resin mixture consisting of polystyrene resin as the main component and a thermoplastic resin other than polystyrene resin. Here, "primarily composed of polystyrene resin" means that the proportion of polystyrene resin in the entire resin mixture is 50% by mass or more (similarly, "main component" in a resin mixture means a component that accounts for 50% by mass or more of the resin mixture). Various additives such as foaming agents and, if necessary, foam regulators are added to these polystyrene resins alone or resin mixtures with polystyrene resin as the main component, and the mixture is heated, melted, and kneaded in an extruder. After cooling to a predetermined temperature, it is extruded from a die into a sheet shape and foamed, and then immediately cooled to form the sheet.

[0018] Polystyrene resins that can be used include styrene homopolymers and copolymers consisting of styrene and monomers other than styrene. Specifically, examples include general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS), styrene-acrylonitrile copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, and styrene-based thermoplastic elastomers (SBS, SEBS, SIS, SEPS).

[0019] Examples of thermoplastic resins other than polystyrene resins include polyphenylene ethers, and examples of polyphenylene ethers include poly(2,6-dimethylphenylene-1,4-ether) and poly(2,6-diethylphenylene-1,4-ether), with poly(2,6-dimethylphenylene-1,4-ether) being preferred.

[0020] In particular, PPE-based heat-resistant polystyrene resin foam sheets, which consist of a resin mixture of general-purpose polystyrene (GPPS) and polyphenylene ether (PPE), or "MAA-based heat-resistant polystyrene resin foam sheets," which mainly consist of a styrene-methacrylic acid copolymer, a copolymer of styrene (St) and methacrylic acid (MAA), are preferably used (hereinafter, the styrene-methacrylic acid copolymer may be referred to as "St / MAA").

[0021] In PPE-based heat-resistant polystyrene foam sheets, the ratio of general-purpose polystyrene (GPPS) to polyphenylene ether (PPE) is preferably such that the resin mixture consisting of polystyrene resin and polyphenylene ether contains polyphenylene ether in the range of 10 to 50% by mass. Polyphenylene ether contributes to improving the heat resistance of the foam sheet. If the amount of polyphenylene ether is less than 10% by mass, the heat resistance of the foam sheet may not be sufficient. On the other hand, if the amount of polyphenylene ether exceeds 50% by mass, the effect of adding polyphenylene ether is less likely to be exhibited further. Furthermore, since polyphenylene ether is generally more expensive than polystyrene resin, incorporating polyphenylene ether beyond the above range is not desirable from the standpoint of material cost.

[0022] The styrene-methacrylic acid copolymer used to form the MAA-based heat-resistant polystyrene foam sheet is preferably composed of 85-95% by mass of styrene monomer and 5-15% by mass of methacrylic acid monomer. It is preferable that 80-100% by mass of this styrene-methacrylic acid copolymer with such monomer composition is present in the thermoplastic resin component of the foam sheet. With such a composition, the MAA-based heat-resistant polystyrene foam sheet has sufficient heat resistance. In addition, thermoplastic resins other than styrene-methacrylic acid copolymer may be included. For example, thermoplastic resins such as styrene-based thermoplastic elastomers (SBS, SEBS, SIS, SEBS) or polyphenylene ether may be included individually or in combination.

[0023] The basis weight of the heat-resistant polystyrene-based resin foamed sheet is preferably 90 g / m 2 ~500 g / m 2 and more preferably 100 g / m 2 ~400 g / m 2 and most preferably 100 g / m 2 ~350 g / m 2 is.

[0024] The thickness of the heat-resistant polystyrene-based resin foamed sheet is 0.5 mm to 5.0 mm, preferably 0.5 mm to 4.0 mm, and most preferably 1.0 mm to 3.0 mm.

[0025] Also, the apparent density of the heat-resistant polystyrene-based resin foamed sheet is preferably 0.05 to 0.20 g / cm 3 and more preferably 0.06 to 0.15 g / cm 3 from the viewpoints of strength and heat insulation.

Example

[0026] <Evaluation Method for Microwave Heating Resistance to Holes> In the prepared container, 30 g of commercially available spaghetti carbonara was placed close to the corner at the bottom of the container, and heating was carried out at 1900 W for 20 seconds in an open state without using a lid or a wrap film. After heating, the spaghetti was removed from the container, and the area and number of holes in the film on the bottom surface of the container were measured and evaluated according to the following evaluation criteria. ○: Within 1 hole and within 1 mm 2 in size ×: 2 or more holes or a hole area exceeding 1 mm 2 in size

[0027] <Evaluation Method for Cold Resistance Impact (Common for Chilled and Frozen)> 500g of ice was placed in the prepared container and sealed with a top seal film. The top seal film used consisted of three layers: a PET film layer, an adhesive layer, and a sealant layer. For the sealant layer, Mitsui Chemicals Tohcello's "CMPS017C" (30μm thick) was used. A 12μm thick PET film was laminated using adhesive, and after positioning the "CMPS017C" so that it was in contact with the molded container, the container was top-sealed at 120°C. The container was left to stand for 24 hours or more under freezing conditions of -20°C or chilling conditions of 0°C, and then a drop test was performed under the same conditions. The container after the drop was evaluated according to the following evaluation criteria. Three samples were prepared and evaluated for each sample. ○: When dropped once from a height of 100 cm (drop surface: bottom of container), there was no tearing of the inner film on the container in any of the three samples. ×: When the container was dropped once from a height of 100 cm (drop surface: bottom of the container), one or more samples showed tearing of the film on the inside of the container.

[0028] <List of materials for polyolefin resin film layer 1> • CPP film: Unstretched polypropylene film (KL12, manufactured by Sun-Tox Co., Ltd., 25μm, 100μm) • OPP film: Biaxially oriented polypropylene film (Futamura Chemical Co., Ltd. "FOR#25", 25μm) • LLDPE film: Metallocene linear low-density polyethylene film (Osakafil Co., Ltd. "SP8N-XB", 25μm, 100μm) • LDPE film: Low-density polyethylene film (Okura Industries Co., Ltd.'s "LDPE Film #25", 25μm) • HDPE film: High-density polyethylene film (Skyfilm Co., Ltd.'s "HDPE Natural Trimming Film", 25μm)

[0029] <List of materials for dry laminate adhesive layer 2> Main ingredient: "AD-393" manufactured by Toyo Morton Co., Ltd. Hardener: "CAT-EP1" manufactured by Toyo Morton Co., Ltd.

[0030] <List of Materials for the Heat-Resistant Polystyrene-Based Resin Film Layer 3> · Syndiotactic polystyrene (SPS): "142ZE" manufactured by Idemitsu Kosan Co., Ltd. (MFR: 14 g / 10 min·300 °C, melting point peak temperature: 250 °C) · High-impact polystyrene (HIPS): "GH-8300-5" manufactured by DIC Corporation (MFR: 2.4 g / 10 min·190 °C) · General-purpose polystyrene (GPPS): "HP-100F-2" manufactured by DIC Corporation (MFR: 1.5 g / 10 min·190 °C) · Styrenic thermoplastic elastomer 1 (SEBS): "G1657" manufactured by Kuraray Co., Ltd. · Styrenic thermoplastic elastomer 2 (SBS): "TR2003" manufactured by ENEOS Materials Co., Ltd. · Styrenic thermoplastic elastomer 3 (SEPS): "Hybrar 7125F" manufactured by Kuraray Co., Ltd. · Styrenic thermoplastic elastomer 4 (SIS): "SIS5403P" manufactured by ENEOS Materials Co., Ltd.

[0031] <List of Materials for the Heat-Resistant Polystyrene-Based Resin Foamed Sheet Layer 4> <PPE-based Heat-Resistant Polystyrene-Based Resin Foamed Sheet> · "HFS-4000A-200 (PPE concentration 21 mass%)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200 g / m 2 , thickness 2.1 mm, apparent density 0.10 g / cm 3 ) · "HFS-2200A-300 (PPE concentration 21 mass%)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 110 g / m 2 , thickness 1.7 mm, apparent density 0.06 g / cm 3 ) · "HFS-PD-70A (PPE concentration 21 mass%)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 350 g / m 2 , thickness 3.0 mm, apparent density 0.12 g / cm 3 ) · "HFS-4000A-200 (PPE concentration 14 mass%; prototype grade for evaluation)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200 g / m2 , thickness 2.1 mm, apparent density 0.10 g / cm 3 ) · "HFS-4000A-200 (PPE concentration 30 mass%; prototype grade for evaluation)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200 g / m 2 , thickness 2.1 mm, apparent density 0.10 g / cm 3 ) <MAA-based heat-resistant polystyrene resin foam sheet> · "CHS-Y4000-200B (St / MAA (92 mass% / 8 mass%) concentration 95 mass%)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200 g / m 2 , thickness 1.9 mm, apparent density 0.11 g / cm 3 )

[0032] [Examples 1 to 19] <Film formation of the film of the heat-resistant polystyrene resin film layer 3> According to the formulation described in the table, syndiotactic polystyrene (SPS) and other resin components were supplied to a single-screw extruder (diameter φ30 mm) and melt-kneaded, extruded from an inflation die with a diameter of φ50 mm connected to the tip of the single-screw extruder, and a film with a thickness of 25 μm was produced by adjusting the speed of the take-up roll while cooling.

[0033] <Method for producing a laminated film> As the polyolefin resin film layer 1, a CPP film ("KL12" manufactured by Sun Tox Co., Ltd., thickness 25 μm) was used. A urethane-based adhesive (main agent "AD-393", curing agent "CAT-EP1" manufactured by Toyo Morton Co., Ltd.) was applied to this CPP film with a gravure roll to form a dry lamination adhesive layer 2 on one side of the CPP film, and the film of the heat-resistant polystyrene resin film layer 3 was laminated thereto to produce a laminated film.

[0034] <Method for producing a laminated sheet> A heat-resistant polystyrene resin foam sheet of the polyphenylene ether (PPE) type ("HFS-4000A-200" manufactured by Sekisui Chemical Co., Ltd. (PPE concentration 21 mass%, basis weight 200 g / m2 Thickness 2.1 mm, apparent density 0.10 g / cm³ 3 A heat-resistant polystyrene resin laminated foam sheet 10 was prepared by laminating the above-mentioned laminated film using a heat lamination method, with the heat-resistant polystyrene resin film layer 3 side of the laminated film being used as the heat-sealing surface. The heat lamination conditions were set to a heating roll temperature of 220°C and a roll speed of 5 to 14 m / min according to the thickness of the laminated film.

[0035] <Method for manufacturing thermoformed containers> The heat-resistant polystyrene resin laminated foam sheet 10 described above was thermoformed using a vacuum pressure forming machine with the polyolefin resin film layer 1 facing the inner surface of the container to produce a rectangular container with a long side of 174 mm, a short side of 139 mm, and a depth of 50 mm. The production of the foam container will be described in more detail. Using a prototype single-stage press molding machine (KFM-060P-D manufactured by Kinki Machinery Industry Co., Ltd.) having a cavity (concave) corresponding to the outer shape of the foam container and a plug (convex) corresponding to the inside of the container, the heat-resistant polystyrene resin laminated foam sheet 10 was heated and then the foam container was produced by vacuum pressure forming. The molding conditions were an upper heater set temperature of 300°C, a lower heater set temperature of 290°C, and a sheet heating time of 6.0 seconds.

[0036] [Examples 20-23] A thermoformed container for evaluation was prepared and evaluated in the same manner as in Examples 1 to 19, except that the thickness of the heat-resistant polystyrene resin film layer 3 was set to 15 μm.

[0037] [Examples 24-27] The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the thickness of the heat-resistant polystyrene resin film layer 3 was set to 50 μm, and a CPP film (KL12 manufactured by Sun-Tox Co., Ltd., 100 μm thick) was used as the polyolefin resin film layer 1.

[0038] [Examples 28-31] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-2200A-300 (PPE concentration 21% by mass)" (basis weight 110g / m²) is used. 2 Thickness 1.7 mm, apparent density 0.06 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the following was used.

[0039] [Examples 32-35] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-PD-70A (PPE concentration 21% by mass)" (basis weight 350 g / m²) is used. 2 Thickness 3.0 mm, apparent density 0.12 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the following was used.

[0040] [Examples 36-39] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-4000A-200 (PPE concentration 14% by mass; prototype grade for evaluation)" (basis weight 200g / m²) is used. 2 Thickness 2.1 mm, apparent density 0.10 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the following was used.

[0041] [Examples 40-43] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-4000A-200 (PPE concentration 30% by mass; prototype grade for evaluation)" (basis weight 200g / m²) is used. 2 Thickness 2.1 mm, apparent density 0.10 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the following was used.

[0042] [Examples 44-47] As the heat-resistant polystyrene foam sheet layer 4, the MAA-based heat-resistant polystyrene foam sheet is "CHS-Y4000-200B (St / MAA (92% by mass / 8% by mass) concentration 95% by mass)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200g / m²) 2Thickness 1.9 mm, apparent density 0.11 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the following was used.

[0043] [Examples 48-51] The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that an OPP film (Futamura Chemical Co., Ltd.'s "FOR#25", 25 μm) was used as the polyolefin resin film layer 1.

[0044] [Comparative Examples 1-6] For the heat-resistant polystyrene resin film layer 3, syndiotactic polystyrene (SPS) was added at 60% by mass, and the other components were added according to the formulations listed in the table. The evaluation was carried out in the same manner as in Examples 1 to 19 above.

[0045] [Comparative Example 7] For the heat-resistant polystyrene resin film layer 3, 75% by mass of high-impact polystyrene (HIPS): "GH-8300-5" manufactured by DIC Corporation (MFR: 2.4g / 10min·190℃) and 25% by mass of general-purpose polystyrene (GPPS): "HP-100F-2" manufactured by DIC Corporation (MFR: 1.5g / 10min·190℃) were used as the film material, and the evaluation was carried out in the same manner as in Examples 1 to 19 above.

[0046] [Examples 52-70] The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that an LLDPE film: metallocene linear low-density polyethylene film (Osakafil Co., Ltd. "SP8N-XB", 25 μm) was used as the polyolefin resin film layer 1.

[0047] [Examples 71-74] The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the thickness of the heat-resistant polystyrene resin film layer 3 was set to 15 μm.

[0048] [Examples 75-78] The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that an LLDPE film: metallocene linear low-density polyethylene film (Osakafil Co., Ltd. "SP8N-XB", 100 μm) was used as the polyolefin resin film layer 1, and the thickness of the heat-resistant polystyrene resin film layer 3 was set to 50 μm.

[0049] [Examples 79-82] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-2200A-300 (PPE concentration 21% by mass)" (basis weight 110g / m²) is used. 2 Thickness 1.7 mm, apparent density 0.06 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the following was used.

[0050] [Examples 83-86] As the heat-resistant polystyrene foam sheet layer 4, Sekisui Chemical Co., Ltd.'s "HFS-PD-70A (PPE concentration 21% by mass)" (basis weight 350 g / m²) is used. 2 Thickness 3.0 mm, apparent density 0.12 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the following was used.

[0051] [Examples 87-90] As the heat-resistant polystyrene foam sheet layer 4, the MAA-based heat-resistant polystyrene foam sheet is "CHS-Y4000-200B (St / MAA (92% by mass / 8% by mass) concentration 95% by mass)" manufactured by Sekisui Chemical Co., Ltd. (basis weight 200g / m²) 2 Thickness 1.9 mm, apparent density 0.11 g / cm³ 3 The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the following was used.

[0052] [Examples 91-94] The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the polyolefin resin film layer 1 used an LDPE film: low-density polyethylene film (LDPE film #25, 25 μm, manufactured by Okura Industries Co., Ltd.).

[0053] [Examples 95-98] The evaluation was carried out in the same manner as in Examples 52 to 70 above, except that the polyolefin resin film layer 1 used was an HDPE film: high-density polyethylene film (Skyfilm Co., Ltd.'s "HDPE Natural Trimming Film", 25 μm).

[0054] [Comparative Examples 8-13] For the heat-resistant polystyrene resin film layer 3, syndiotactic polystyrene (SPS) was blended at 60% by mass, and the other components were blended as shown in the table. Otherwise, the evaluation was carried out in the same manner as in Examples 52 to 70 above.

[0055] [Comparative Example 14] For the heat-resistant polystyrene resin film layer 3, a film was prepared by using 75% by mass of high-impact polystyrene (HIPS): "GH-8300-5" manufactured by DIC Corporation (MFR: 2.4g / 10min·190℃) and 25% by mass of general-purpose polystyrene (GPPS): "HP-100F-2" manufactured by DIC Corporation (MFR: 1.5g / 10min·190℃). Otherwise, the evaluation was carried out in the same manner as in Examples 52 to 70 above.

[0056] [Comparative Examples 15-18] The evaluation was carried out in the same manner as in Examples 1 to 19 above, except that the polyolefin resin film layer 1 was omitted.

[0057] <Evaluation Results> The evaluation results are shown in Tables 1 to 3. Note that in each table, the unit for thickness is μm, and the unit for basis weight is g / m². 2 That is the case.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] [Examples 1-98] In all examples, good results were obtained in the evaluation of microwave heating perforation resistance and cold shock resistance (chilled and frozen).

[0062] [Comparative Examples 1-18] On the other hand, Comparative Examples 1 to 14 failed to meet the criteria in the evaluation of microwave heating perforation resistance. Furthermore, Comparative Examples 15 to 18 failed to meet the criteria in the evaluation of cold shock resistance (chilled and frozen). [Explanation of Symbols]

[0063] 1. Polyolefin resin film layer 2. Dry laminate adhesive layer 3. Heat-resistant polystyrene resin film layer 4. Heat-resistant polystyrene foam sheet layer 10 Heat-resistant polystyrene resin laminated foam sheet 20 Molded containers

Claims

[Claim 1] It consists of a heat-resistant polystyrene resin laminated foam sheet, which is laminated in the following order: a polyolefin resin film layer, a dry laminate adhesive layer, a heat-resistant polystyrene resin film layer, and a heat-resistant polystyrene resin foam sheet layer. The polyolefin resin film layer forms the inner surface of the container. The heat-resistant polystyrene resin film layer is a molded container containing 70 to 100% by mass of syndiotactic polystyrene.

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