Synthetic resin sheet and method for producing the same, laminated sheet, and food container

Abstract

To provide a synthetic resin sheet that is formed of a recycling raw material containing a methacrylic acid which secures desired specification in a form of a molded article such as a food container, hardly expresses a foreign matter according to a mixing degree of a methacrylic acid and a styrene component, and is easy to be effectively utilized as a recycling raw material again.SOLUTION: A synthetic resin sheet 1 is composed of a mixture containing less than 40 wt.% of a recycling raw material derived from a polystyrene-based resin sheet containing a methacrylic acid, wherein the mixture contains styrene as a main component, a methacrylic acid and a rubber component, and specific gravity of the mixture is within the range of 0.95 to 1.10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a synthetic resin sheet containing recycled raw materials including methacrylic acid, a method for producing the same, a laminated sheet including the synthetic resin sheet, and a food container. [Background technology]

[0002] Conventionally, resin compositions containing rubber have had the problem that the rubber remains in the extruder during sheet molding, causing thermal degradation, resulting in the inclusion of black burnt foreign matter in the sheet and the resulting defective product. For example, when a sheet that has been extruded once is molded into a container and punched out, and the remaining portion (offcuts) is re-extruded into a sheet for reuse, the occurrence of this burnt foreign matter has been significant. The offcuts may be edges cut off to make the sheet width uniform in the extrusion process, or sheets (skeleton) remaining after punching out containers in the cutting process.

[0003] For example, Patent Document 1 provides a polystyrene resin sheet containing, as a main component, a polystyrene resin composition that is resistant to resin burns while maintaining impact resistance and rigidity, and the polystyrene resin composition contains, as essential components, 20 to 76 mass % of a polystyrene resin, 20 to 50 mass % of a high-impact polystyrene resin, 1 to 5 mass % of a styrene-conjugated diolefin thermoplastic elastomer, and 3 to 25 mass % of a styrene-butadiene-butylene-styrene thermoplastic elastomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4987429 Summary of the Invention [Problem to be solved by the invention]

[0005] However, depending on the proportion of styrene components such as polystyrene (PS) contained in the scrap material reused as a recycled raw material and the proportion of methacrylic acid contained in the heat-resistant polystyrene-based copolymer obtained by copolymerizing methacrylic acid as the polystyrene-based resin composition, the styrene component and the methacrylic acid may not mix well when molding a polystyrene-based resin sheet containing the polystyrene-based resin composition as a main component, and foreign matter may appear in the polystyrene-based resin sheet.

[0006] Polystyrene paper (PSP), which is primarily composed of styrene, is given heat resistance by adding methacrylic acid. When scraps of the heat-resistant polystyrene paper (heat-resistant PSP) obtained in this way are used as recycled raw materials to produce new synthetic resin sheets, the inventors have discovered that the above-mentioned foreign matter is less likely to appear depending on the correlation between the proportion of the recycled raw materials contained in the mixture and the proportions of methacrylic acid and other components contained in the mixture.

[0007] Therefore, an object of the present invention is to provide a synthetic resin sheet formed from recycled raw materials containing methacrylic acid that ensures desired specifications when molded into molded products such as food containers, is less likely to produce foreign matter depending on the degree of mixing of the methacrylic acid and styrene components, and can be easily reused as a recycled raw material; a method for manufacturing the same; and a laminate sheet and food container that include the synthetic resin sheet. [Means for solving the problem]

[0008] That is, the synthetic resin sheet of the present invention is composed of a mixture containing less than 40% by weight of recycled raw materials derived from polystyrene-based resin sheets containing methacrylic acid, the mixture being mainly composed of styrene and containing methacrylic acid and a rubber component, and the specific gravity of the mixture being in the range of 0.95 to 1.10.

[0009] According to this configuration, by using a synthetic resin sheet containing styrene as the main component and methacrylic acid and a rubber component, it is possible to obtain a synthetic resin sheet that satisfies one or more of the desired specifications of rigidity, strength, impact resistance, and tensile modulus when molded into a molded product such as a food container. Therefore, molded products such as food containers formed from the synthetic resin sheet can be prevented from becoming brittle and prone to cracking. Furthermore, because methacrylic acid and the styrene component are easily mixed and foreign matter is less likely to appear in the synthetic resin sheet, scraps generated when molding a molded product from the synthetic resin sheet can be effectively used as recycled raw materials.

[0010] The mixture preferably contains 80 to 95% by weight of styrene, 5 to 10% by weight of rubber, and 0.1 to 2% by weight of methacrylic acid, and more preferably contains 86 to 90% by weight of styrene, 5 to 8.5% by weight of rubber, and 0.1 to 1% by weight of methacrylic acid.

[0011] According to these configurations, it is possible to more reliably obtain a synthetic resin sheet that meets the above specifications, and also to more reliably utilize the synthetic resin sheet as the above-mentioned recycled raw material.

[0012] The method for producing a synthetic resin sheet of the present invention includes blending styrene and rubber with the recycled raw material without blending propylene, heating and kneading the blended raw material to form a molten resin, and forming a synthetic resin sheet.

[0013] According to this method, the stability and uniformity of the physical properties of the synthetic resin sheet containing the recycled raw material can be further improved, and the amount of methacrylic acid contained in the recycled raw material can be reduced, thereby further suppressing the emergence of foreign matter from the synthetic resin sheet. Furthermore, since propylene, which has poor compatibility with polystyrene, is not blended during production, the synthetic resin sheet can be easily recycled and reclaimed after use as a molded product such as a food container.

[0014] The laminate sheet of the present invention is characterized in that it has the synthetic resin sheet of the present invention as a base layer, and a surface layer of a non-expanded polystyrene resin laminated and fixed to at least one surface of the base layer.

[0015] According to this configuration, the surface layer laminated and fixed to the base layer can improve the hygiene of the synthetic resin sheet and further suppress the emergence of foreign matter from the synthetic resin sheet containing recycled raw materials derived from a polystyrene-based resin sheet containing methacrylic acid. Furthermore, by using a non-expanded polystyrene-based resin for the surface layer instead of a material that has poor compatibility with polystyrene, such as polypropylene, the molded product, such as a food container, made of the synthetic resin sheet can be easily recycled and reclaimed after use.

[0016] The food container of the present invention is characterized in that it is formed by thermoforming at least the synthetic resin sheet of the present invention.

[0017] According to this configuration, a food container having the effects of the synthetic resin sheet of the present invention can be obtained. [Effects of the Invention]

[0018] According to the present invention, it is possible to ensure the desired specifications when molded into a food container or other molded product, and it is also expected that foreign matter depending on the degree of mixing of the methacrylic acid and styrene components is less likely to appear, making it easier to effectively reuse the product as a recycled raw material. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a partial vertical cross-sectional view showing a synthetic resin sheet according to an embodiment of the present invention. [Figure 2] 1 is a partial longitudinal cross-sectional view showing a laminate sheet having a synthetic resin sheet as a base layer according to an embodiment; [Figure 3] FIG. 3 is a longitudinal cross-sectional view of a food container formed from the laminated sheet of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a laminate sheet according to one embodiment of the present invention, a method for producing the same, and a food container will be described with reference to FIGS.

[0021] A synthetic resin sheet 1 of an embodiment is shown in Figure 1. The synthetic resin sheet of the embodiment is made of a mixture containing less than 40% by weight of recycled material derived from a polystyrene-based resin sheet containing methacrylic acid, and the mixture contains styrene as a main component and methacrylic acid and a rubber component. The polystyrene-based resin sheet containing methacrylic acid as a recycled material may be a non-foamed polystyrene-based resin sheet or a foamed polystyrene-based resin sheet.

[0022] The polystyrene resin sheet containing methacrylic acid may be composed of a styrene-methacrylic acid copolymer, which is a copolymer of a styrene monomer and methacrylic acid. Examples of styrene monomers include styrene, methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, paramethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, and vinylxylene. A portion of the styrene monomer may be replaced with a small amount of another monomer copolymerizable with the two components. Examples of other copolymerizable monomers include acrylonitrile, methacrylonitrile, methyl methacrylate, and maleic anhydride. The styrene-methacrylic acid copolymer preferably contains 94 to 98% by weight of styrene and 2 to 6% by weight of methacrylic acid.

[0023] The mixture constituting the synthetic resin sheet 1 preferably contains 80 to 95% by weight, more preferably 83 to 92% by weight, and even more preferably 86 to 90% by weight of styrene, preferably 5 to 10% by weight, more preferably 6 to 9% by weight, and even more preferably 7 to 8.5% by weight of rubber, and preferably 0.1 to 2.0% by weight, and more preferably 0.1 to 1.0% by weight of methacrylic acid.

[0024] The specific gravity of the mixture constituting the synthetic resin sheet 1 is preferably in the range of 0.95 to 1.10, more preferably 1.00 to 1.05, and even more preferably 1.037 to 1.039. A value less than 0.95 will result in a relatively reduced polystyrene content and a relatively increased rubber content, making it difficult to achieve the expected effects. A value greater than 1.10 will result in a relatively increased polystyrene content and a relatively decreased rubber content, making it difficult to achieve the expected effects. Here, the specific gravity may be measured using Method A (underwater displacement method) specified in JIS K7112:1999 "Method for measuring density and specific gravity of plastics - non-foamed plastics."

[0025] The mixture constituting the synthetic resin sheet 1 is preferably not foamed, and for example, the foaming ratio may be 0.95 to 1.05. This is because if it is a foam, the stacking height may increase when it is made into a container.

[0026] The mixture constituting the synthetic resin sheet 1 may further contain less than 10% by weight of propylene, more preferably 0.5 to 7% by weight, and even more preferably 1 to 5% by weight of propylene. Such propylene may be derived from a laminate film laminated on a polystyrene resin sheet containing methacrylic acid as a recycled raw material.

[0027] It is preferable that the mixture constituting the synthetic resin sheet 1 contains as few components as possible other than styrene, rubber, methacrylic acid, and propylene. Specifically, the content may be 1% by weight or less, 0.5% by weight or less, or 0.001 to 0.5% by weight.

[0028] The rubber or rubber component contained in the mixture constituting the synthetic resin sheet 1 refers to the soft segment (flexible component) contained in the thermoplastic elastomer, such as butadiene rubber (BR), isoprene rubber (IR), hydrogenated high vinyl (BR), or hydrogenated (IR). As a compound containing such rubber, for example, a styrene-based thermoplastic elastomer is preferred, and an SBR-based thermoplastic elastomer such as styrene-butadiene-based thermoplastic elastomer (SBS), styrene-butadiene-butylene-based thermoplastic elastomer (SBBS), or styrene-ethylene-butylene-based thermoplastic elastomer (SEBS) is more preferred, and among SBR-based thermoplastic elastomers, styrene-butadiene-based thermoplastic elastomer (SBS) is even more preferred.

[0029] When manufacturing the synthetic resin sheet 1, it is preferable to blend styrene and rubber without blending propylene with less than 40% by weight of recycled raw material derived from a polystyrene-based resin sheet containing methacrylic acid, heat and knead it to form a molten resin, and the recycled raw material is preferably 35% by weight or less, more preferably 10 to 30% by weight, and even more preferably 10 to 25% by weight. The recycled raw material preferably contains 2 to 6% by weight of methacrylic acid, and may also contain propylene, and even recycled raw materials containing propylene can be recycled as the synthetic resin sheet 1.

[0030] The recycled raw material is obtained by heating and kneading scraps generated during the thermoforming of a heat-resistant polystyrene-based resin sheet containing methacrylic acid to form a molten resin, which is then extruded and cut into pellets. In addition to using the same type of recycled raw material, multiple different types can also be used. Here, the amount of methacrylic acid contained in the recycled raw material is preferably less than 5% by weight, more preferably less than 3% by weight, and even more preferably less than 2% by weight.

[0031] The styrene blended separately from the recycled raw materials during production can be any suitable styrene within the applicable range, such as general-purpose polystyrene (GPPS) or high-impact polystyrene (HIPS). Alternatively, recycled raw materials derived from expanded polystyrene sheets (PSP) may also be used. Recycled raw materials derived from polystyrene-based resin sheets containing methacrylic acid can contain various additives, such as pigments, colorants such as dyes, adhesives, and cell regulators.

[0032] As shown in Figure 2, a laminate sheet 2 is preferably formed using a synthetic resin sheet 1 as a base layer, with a first surface layer 3 laminated and fixed to one side of the base layer and a second surface layer 4 laminated and fixed to the other side of the base layer. The first surface layer 3 and the second surface layer 4 can be formed as non-foamed layers made of a material that improves hygiene, such as polystyrene resin or polypropylene resin. However, from the perspective of improving recyclability, it is more preferable to form both the first surface layer 3 and the second surface layer 4 from a non-foamed polystyrene resin. Examples of non-foamed polystyrene resins include general-purpose polystyrene (GPPS) and high-impact polystyrene (HIPS). The first surface layer 3 and the second surface layer 4 can also be made of different materials.

[0033] When manufacturing the laminate sheet 2, it is possible to appropriately use a method in which the first surface layer 3 and the second surface layer 4 are laminated on both sides of the synthetic resin sheet 1 by co-extrusion, a method in which the first surface layer 3 and the second surface layer 4 are laminated on both sides of the synthetic resin sheet 1 by thermocompression bonding, or a method in which the first surface layer 3 and the second surface layer 4 are laminated on both sides of the synthetic resin sheet 1 by bonding with an adhesive, etc. When the first surface layer 3 and the second surface layer 4 are laminated on both sides of the synthetic resin sheet 1 by co-extrusion, the heating temperature when the blended raw materials are made into a molten resin is preferably 180 to 240°C. Furthermore, when the synthetic resin sheet 1 is formed alone by thermocompression bonding or bonding the first surface layer 3 and the second surface layer 4 in a subsequent process, the heating temperature when the blended raw materials are made into a molten resin is preferably 180 to 240°C.

[0034] The synthetic resin sheet 1 of this embodiment or the laminate sheet 2 using the synthetic resin sheet 1 as a base layer is preferably used as a material for food containers, and a food container 10 as shown in Fig. 3 is formed by thermoforming the laminate sheet 1 using a mold of a predetermined shape. A laminate film or the like having a pattern or the like may be laminated and adhered to the outside of the first surface layer 3 and / or the outside of the second surface layer 4 of the laminate sheet 2 of the food container 10, as needed.

[0035] The synthetic resin sheet 1 constituting the base layer of the laminate sheet 2 has a thickness of 150 to 2000 μm, more preferably 150 to 1500 μm, even more preferably 200 to 1200 μm, and may be 250 to 500 μm or 300 to 380 μm. The first surface layer 3 and the second surface layer 4 each have a thickness of 0.5 to 400 μm, more preferably 0.5 to 375 μm, and even more preferably 1 to 150 μm. By increasing the thickness of the surface layers, a concealing effect can be expected, making any foreign matter that may be present less noticeable. The overall thickness of the laminate sheet 2 is 150 to 2000 μm, more preferably 150 to 1500 μm, and may be 250 to 500 μm or 300 to 380 μm. The layer ratio (thickness ratio) of the synthetic resin sheet 1, the first surface layer 3 and the second surface layer 4 constituting the base layer of the laminated sheet 2 is preferably 40:30:30 to 80:10:10, and more preferably 50:25:25 to 70:15:15.

[0036] The DuPont impact strength (E50(J)) of the laminate sheet 2 at a drop load of 0.3 kg and a measurement temperature of 23°C is preferably 0.3 J or more, more preferably 0.4 J or more, and even more preferably 0.5 J or more, with an upper limit of 3.0 J. The tensile modulus (MPa) of the laminate sheet 2 is preferably 2000 MPa or more, more preferably 2050 MPa or more, and even more preferably 2100 MPa or more, with an upper limit of 4000 MPa. The glossiness (outside the container) of the laminate sheet 2 is preferably 10 or more, more preferably 25 or more, and more preferably 40 or more.

[0037] According to this embodiment, by using a synthetic resin sheet 1 containing styrene as the main component and also methacrylic acid and a rubber component, it is possible to obtain a synthetic resin sheet 1 that satisfies the desired specifications of one or more of rigidity, strength, impact resistance, and tensile modulus when molded into a molded product such as a food container 10. This prevents molded products such as food containers 10 formed from the synthetic resin sheet 1 from becoming brittle and prone to cracking. Furthermore, because methacrylic acid and the styrene component are easily mixed and foreign matter is less likely to appear in the synthetic resin sheet 1, scraps generated when moldings are made from the synthetic resin sheet can be effectively used as recycled raw materials.

[0038] Furthermore, the mixture constituting the synthetic resin sheet 1 may contain 80 to 95% by weight of styrene, 5 to 10% by weight of rubber, and 0.1 to 2% by weight of methacrylic acid, respectively. However, if the mixture contains 86 to 90% by weight of styrene, 5 to 8.5% by weight of rubber, and 0.1 to 1% by weight of methacrylic acid, respectively, a synthetic resin sheet 1 that more reliably meets the above specifications can be obtained, and it can also more reliably be effectively utilized as the recycled raw material.

[0039] Furthermore, when the mixture constituting the synthetic resin sheet 1 contains less than 10% by weight of propylene, scraps generated when forming a molded product from, for example, a polystyrene-based resin sheet containing methacrylic acid to which a laminate film made of propylene is attached can be effectively utilized as recycled raw material.

[0040] Furthermore, when the amount of recycled raw material derived from a polystyrene-based resin sheet containing methacrylic acid is kept to 10 to 30% by weight, it is possible to further improve the stability and uniformity of the physical properties of the synthetic resin sheet 1 containing the recycled raw material, and reduce the amount of methacrylic acid used in the recycled raw material, thereby further suppressing the emergence of foreign matter from the synthetic resin sheet 1. Furthermore, by manufacturing the synthetic resin sheet 1 without blending polypropylene, which has poor compatibility with polystyrene, the molded product, such as food container 10, can be easily recycled and reclaimed after use.

[0041] Furthermore, the surface layers 3 and 4 laminated and fixed to the base layer of the synthetic resin sheet 1 in the laminate sheet 2 can improve the hygiene of the synthetic resin sheet 1 and further prevent foreign matter from appearing in the synthetic resin sheet 1, which contains recycled raw materials derived from a polystyrene-based resin sheet containing methacrylic acid. Furthermore, by using a non-expanded polystyrene-based resin for the surface layers instead of a material that has poor compatibility with polystyrene, such as polypropylene, the molded product, such as a food container 10, made of the synthetic resin sheet 1 can be easily recycled and reclaimed after use.

[0042] <Scope of the invention disclosed in this specification> The inventions disclosed in this specification include, in addition to the individual inventions and embodiments listed as inventions, those specified by modifying partial contents of these with 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 creating a generic concept. The inventions disclosed in this specification also include the following modifications and additions.

[0043] The synthetic resin sheet of the present invention is composed of a mixture containing less than 40% by weight of recycled raw materials derived from polystyrene-based resin sheets containing methacrylic acid, and includes those in which the mixture is mainly composed of styrene and contains methacrylic acid and a rubber component, and also includes, for example, synthetic resin sheets that do not contain propylene.

[0044] The laminate sheet of the present invention also includes a laminate sheet having a base layer made of the synthetic resin sheet of the present invention and a surface layer made of a non-expanded polystyrene resin laminated and fixed to at least one side of the base layer, and also includes a laminate sheet having a surface layer made of a non-expanded polystyrene resin laminated and fixed to only one side of the base layer. The laminate sheet of the present invention also includes a laminate sheet having a base layer made of the synthetic resin sheet of the present invention and a surface layer having a configuration similar to the first surface layer 3 or second surface layer 4 in the above-mentioned embodiment, laminated and fixed so that another layer is interposed between the base layer and the surface layer, and a laminate sheet having a base layer made of the synthetic resin sheet of the present invention and an outermost layer such as a laminate film, e.g., a polystyrene film, laminated and fixed to the outside of the surface layer having a configuration similar to the first surface layer 3 or second surface layer 4 in the above-mentioned embodiment. [Example]

[0045] <Evaluation of Examples and Comparative Examples> Next, we will explain an example laminate sheet corresponding to the laminate sheet 2 in which the first surface layer 3 and the second surface layer 4 are laminated and fixed to both sides of the synthetic resin sheet 1 of the above embodiment, and a comparative example laminate sheet, as well as their evaluation results.

[0046] <Materials used in Examples and Comparative Examples> The materials used in the examples and comparative examples are as follows. GPPS: 100% by weight of styrene Styrene-butadiene rubber (SBS): 40% styrene by weight, 60% rubber by weight Recycled material 1: 83% by weight of styrene, 14% by weight of polypropylene, 1.5% by weight of rubber, 1.5% by weight of methacrylic acid Recycled material 2: 79% styrene, 14% polypropylene, 2.0% rubber, 5.0% methacrylic acid Recycled material derived from high impact polystyrene (HIPS) (R-HI): 93% styrene by weight, 7.0% rubber by weight The usable ranges of each material in Examples 1 and 2 are 50% by weight or less for GPPS, 5 to 10% by weight for styrene-butadiene rubber (SBS), 55% by weight or less for recycled material 1, 60% by weight or less for R-HI, and 2% by weight or less for pigment.

[0047] The laminated sheets of Examples 1 and 2 have a base layer corresponding to the synthetic resin sheet 1, and have a two-kind three-layer structure in which surface layers are laminated on one side and the other side of the base layer. The base layer in Examples 1 and 2 has a layer thickness of 150 μm, and the layer thickness of the surface layer on one side and the surface layer on the other side is 75 μm, respectively, for a total thickness of 300 μm. The base layer is composed of styrene, propylene, rubber, and methacrylic acid, and the surface layer is composed of styrene, propylene, and rubber. composition The weight ratio of each component is shown in Table 1.

[0048] The base layer in Example 1 is formed by blending styrene-rubber (styrene-butadiene thermoplastic elastomer (SBS)), recycled material 1, which is a recycled raw material derived from a polystyrene resin sheet containing methacrylic acid, recycled material (R-HI) derived from impact-resistant polystyrene, and a pigment, and the blending ratios of each compound are as shown in Table 1.

[0049] The base layer in Example 2 is formed by blending general-purpose polystyrene (GPPS), styrene-rubber (styrene-butadiene thermoplastic elastomer (SBS)), recycled material 1, which is a recycled raw material derived from a polystyrene-based resin sheet containing methacrylic acid, recycled material (R-HI) derived from impact-resistant polystyrene, and a pigment, and the blending ratios of each compound are as shown in Table 1.

[0050] The laminate sheet of Comparative Example 1 has a base layer and a two-type three-layer structure in which surface layers are laminated on one side and the other side of the base layer. The base layer in Comparative Example 1 has a layer thickness of 150 μm, and the surface layer on one side and the surface layer on the other side are each 75 μm thick. The base layer is composed of styrene, propylene, rubber, and methacrylic acid, and the weight ratio of the composition is as shown in Table 1.

[0051] The base layer in Comparative Example 1 is formed by blending styrene-rubber (styrene-butadiene thermoplastic elastomer (SBS)), recycled material 2, which is a recycled raw material derived from a polystyrene resin sheet containing methacrylic acid, recycled material (R-HI) derived from impact-resistant polystyrene, and a pigment, and the blending ratios of each compound are as shown in Table 1.

[0052] The surface layers in Examples 1 and 2 and the Comparative Example were formed by blending general-purpose polystyrene (GPPS), styrene-rubber (styrene-butadiene thermoplastic elastomer (SBS)), pigment, and high impact polystyrene (HIPS), and the blending ratios of each compound were as shown in Table 1.

[0053] The physical properties and overall comparative weights of the laminate sheets of the example and comparative example were evaluated as shown in Table 1. The specific gravity of both the example and comparative example laminate sheets was 1.038.

[0054] The DuPont impact strength was measured by preparing test pieces measuring 100 mm long x 50 mm wide from each of the laminate sheets of the examples and the comparative examples, and measuring the 50% fracture energy E50(J) of these test pieces using a DuPont impact tester in accordance with JIS K7211-1. The drop load was 0.3 kg and the measurement temperature was 23°C.

[0055] The tensile modulus (MPa) was measured by preparing test pieces measuring 140 mm in length and 15 mm in width from each of the laminate sheets of the examples and the comparative examples, and measuring the tensile modulus (MPa) of these test pieces using a tensile tester in accordance with JIS K7161 at a measurement temperature of 23°C, a chuck distance of 100 mm, and a pulling speed of 1 mm / min.

[0056] The gloss was measured by preparing test pieces measuring 140 mm long x 15 mm wide from each of the laminate sheets of the example and the comparative example in accordance with Method 3 (60-degree specular gloss) of JIS Z8741.

[0057] The sheet surface condition was a practical evaluation result for the laminate sheet, which was obtained by comprehensively comparing and weighing the DuPont impact strength, tensile modulus, and glossiness of the laminate sheets of the examples and comparative examples, and was evaluated on a two-level scale: ○: good, ×: unusable.

[0058] The sheet evaluation was a comprehensive comparative weighing of the laminated sheets of the examples and the comparative examples based on three items: DuPont impact strength, tensile modulus, and glossiness, and was rated on a two-point scale: ○: usable without any practical problems; ×: problems may occur in practical use.

[0059] The laminate sheets of Examples 1 and 2 were either usable for practical use or had no problems in terms of DuPont impact strength, tensile modulus, and gloss, whereas the laminate sheet of Comparative Example 1 had foreign matter on the sheet surface, making it impossible to measure DuPont impact strength, tensile modulus, or gloss, and thus causing practical problems and making it unusable.

[0060] [Table 1]

[0061] The food container shown in Figure 3 is used to package foods such as prepared dishes, bento lunches, sushi, sashimi, and salads sold in supermarkets and other retail stores, and may include a container body that contains the food and a lid that is attached to the container body. This packaging container may be rectangular, such as a square or rectangular, or circular or elliptical in plan view, and may be of any size that can be placed on a display shelf in a retail store, with no restrictions on dimensions such as length, width, and height. [Explanation of symbols]

[0062] 1 Synthetic resin sheet 2. Laminated sheet 3. The First Surface 4 The Second Surface 10 Food containers

Claims

1. It is composed of a mixture containing less than 40% by weight of recycled raw materials derived from polystyrene-based resin sheets containing methacrylic acid, The mixture contains styrene as a main component and also contains methacrylic acid and a rubber component, The specific gravity of the mixture is in the range of 0.95 to 1.

10. A synthetic resin sheet characterized by:

2. The mixture contains 80 to 95% by weight of styrene, 5 to 10% by weight of rubber, and 0.1 to 2% by weight of methacrylic acid.

2. The synthetic resin sheet according to claim 1.

3. The mixture contains 86 to 90% by weight of styrene, 5 to 8.5% by weight of rubber, and 0.1 to 1% by weight of methacrylic acid.

2. The synthetic resin sheet according to claim 1.

4. A method for producing a synthetic resin sheet according to any one of claims 1 to 3, The recycled raw material is mixed with styrene and rubber without mixing propylene, and then heated and kneaded to form a molten resin, which is then used to form a synthetic resin sheet. A method for manufacturing a synthetic resin sheet, comprising:

5. A synthetic resin sheet according to any one of claims 1 to 3 is used as a substrate layer, A surface layer of non-expanded polystyrene resin is laminated and fixed to at least one surface of the base layer. A laminated sheet characterized by:

6. The synthetic resin sheet according to any one of claims 1 to 3 is thermoformed. A food container characterized by:

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