Polystyrene-based resin foam sheet, polystyrene-based resin laminated foam sheet, and polystyrene-based resin foam container

Abstract

To provide a polystyrene-based resin foam sheet, a polystyrene-based resin laminate foam sheet, and a polystyrene-based resin foam container which achieve both high strength and bubble suppression.SOLUTION: A polystyrene-based resin foam sheet has a foam layer as an inner layer and a skin layer as a surface layer where a product D1×F of average thickness D1 μm of thicknesses at nine places of the skin layer and an expansion ratio F times of the whole polystyrene-based resin foam sheet is 100 μm times to 1,000 μm times.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polystyrene-based resin foam sheet, a laminated polystyrene-based resin foam sheet, and a polystyrene-based resin foam container. [Background technology]

[0002] Containers obtained by thermoforming a polystyrene-based resin foam sheet and containers obtained by thermoforming a laminated polystyrene-based resin foam sheet in which a non-foamed resin film is laminated on a polystyrene-based resin foam sheet are widely used in convenience stores and the like as various containers such as trays, lunch boxes, rice bowls, and cups.

[0003] The recent COVID-19 pandemic has led to an increase in stay-at-home demand and a rise in demand for home-cooked meals. This has led to increased demand for tray containers for fresh food and instant noodle containers, and the quality requirements for these containers are rising. For example, tray containers require high strength to prevent buckling when used in pillow packaging.

[0004] Several polystyrene-based resin foam sheets and polystyrene-based resin laminated foam sheets that have been developed with the aim of improving strength have been reported (for example, Patent Documents 1 and 2).

[0005] However, increasing the strength of a polystyrene-based resin foam sheet or a polystyrene-based resin laminated foam sheet poses a problem that bubbles (floats) are more likely to occur on the surface of the container, particularly when a foamed container is made by thermoforming a foamed sheet laminated with a non-foamed layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-111339 [Patent Document 2] Japanese Patent Application Publication No. 2014-080562 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above-mentioned problems of the prior art, and a main object of the present invention is to provide a polystyrene-based resin foam sheet, a laminated polystyrene-based resin foam sheet, and a polystyrene-based resin foam container that combine high strength with bubble suppression. [Means for solving the problem]

[0008] The polystyrene-based resin foam sheet according to an embodiment of the present invention comprises: A polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer, The product D1×F of the average thickness D1 μm of the nine portions of the skin layer and the expansion ratio F times of the entire polystyrene resin foam sheet is 100 μm· times to 1000 μm· times.

[0009] In one embodiment, the maximum value D1 among the thicknesses at the nine locations is max μm and minimum value D1 min Difference D1 from μm max -D1 min When Rμm is used, R / D1 is 0.1 or more.

[0010] In one embodiment, the polystyrene-based resin foam sheet according to the embodiment of the present invention has a shrinkage rate of 50% or less when sliced ​​20 mm in the MD direction and 20 mm in the TD direction to a thickness of 200 μm from the surface and heated at 100°C for 90 seconds.

[0011] In one embodiment, the polystyrene-based resin foam sheet according to the embodiment of the present invention has a shrinkage rate of 40% or less after a slice sliced ​​to a size of 20 mm in the MD direction and 20 mm in the TD direction is heated at 125°C for 150 seconds.

[0012] The laminated polystyrene resin foam sheet according to an embodiment of the present invention is obtained by laminating a non-foamed resin film on the polystyrene resin foam sheet according to an embodiment of the present invention.

[0013] The polystyrene-based resin foam container according to an embodiment of the present invention is obtained by thermoforming the polystyrene-based resin foam sheet according to an embodiment of the present invention or the laminated polystyrene-based resin foam sheet according to an embodiment of the present invention.

[0014] A polystyrene-based resin foam container according to another embodiment of the present invention comprises: A polystyrene-based resin foam container obtained by thermoforming a polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer, or a polystyrene-based resin laminated foam sheet obtained by laminating a non-foamed resin film on the polystyrene-based resin foam sheet, The shrinkage rate of a slice of the inner side wall of the polystyrene-based resin foam container, sliced ​​30 mm in the MD direction, 10 mm in the TD direction, and 200 μm thick from the surface, after heating at 100°C for 90 seconds is 40% or less. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a polystyrene-based resin foam sheet, a laminated polystyrene-based resin foam sheet, and a polystyrene-based resin foam container that combine high strength with bubble suppression. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a polystyrene-based resin foam sheet according to an embodiment of the present invention. [Figure 2] FIG. 2 is a typical scanning electron microscope (SEM) image of the vicinity of the surface of a polystyrene-based resin foam sheet according to an embodiment of the present invention. [Figure 3] FIG. 2 is a typical scanning electron microscope (SEM) image of the vicinity of the surface of the laminated polystyrene resin foam sheet according to an embodiment of the present invention. [Figure 4]1 is a schematic perspective view of a polystyrene-based resin foam container according to an embodiment of the present invention. [Figure 5] FIG. 2 is one of explanatory views for explaining a method for measuring an average thickness D1 of nine points of the skin layer, and is a plan view of the polystyrene-based resin foam sheet to be measured, as viewed from the planar direction. [Figure 6] This is one of the explanatory diagrams for explaining the method for measuring the average thickness D1 of the skin layer at nine locations, and is an explanatory diagram for explaining the method for measuring the thickness of the skin layer by photographing a cross section of the measurement sample from the MD direction using a scanning electron microscope (SEM). DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0018] In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0019] <<A. Polystyrene resin foam sheet>> The polystyrene-based resin foam sheet according to the embodiment of the present invention has a foam layer as an inner layer and skin layers as surface layers. Typically, the polystyrene-based resin foam sheet according to the embodiment of the present invention has skin layers on both sides of the foam layer.

[0020] The foam layer is a foam layer formed by foaming a resin composition.

[0021] The skin layer is a thin layer formed on the surface layer portion during the production of a polystyrene-based resin foam sheet. Unlike the foam layer, the skin layer is a surface layer whose thickness extends from the surface (one or the other surface) of the polystyrene-based resin foam sheet to the end face of the bubble with a diameter of 70 μm or more located closest to the surface. Therefore, the skin layer and the foam layer can be distinguished by any appropriate means, and for example, the skin layer and the foam layer can be clearly distinguished by a scanning electron microscope (SEM).

[0022] Fig. 1 is a schematic cross-sectional view of a polystyrene-based resin foam sheet according to an embodiment of the present invention. As shown in Fig. 1, a polystyrene-based resin foam sheet 100 according to an embodiment of the present invention has a foam layer 10 as an inner layer and a skin layer 20 as a surface layer.

[0023] Fig. 2 is a typical scanning electron microscope (SEM) image of the surface vicinity of the polystyrene-based resin foam sheet according to the embodiment of the present invention. When the surface vicinity of the polystyrene-based resin foam sheet 100 according to the embodiment of the present invention is imaged by a scanning electron microscope (SEM), a foam layer 10 as an inner layer and a skin layer 20 as a surface layer are observed, as shown in Fig. 2.

[0024] In the polystyrene-based resin foam sheet according to the embodiment of the present invention, the product D1×F of the average thickness D1 μm of nine locations on the skin layer and the expansion ratio F of the entire polystyrene-based resin foam sheet is preferably 100 μm·times to 1000 μm·times, more preferably 100 μm·times to 900 μm·times, even more preferably 100 μm·times to 850 μm·times, and particularly preferably 100 μm·times to 800 μm·times. When D1×F is within the above range, the polystyrene-based resin foam sheet according to the embodiment of the present invention can achieve both high strength and bubble suppression. If D1×F is too small outside the above range, high strength may not be achieved. If D1×F is too large outside the above range, bubbles may be generated.

[0025] The method for measuring the average thickness D1 (unit: μm) of the skin layer at nine locations will be described later.

[0026] The average thickness D1 of the skin layer at nine points is preferably 1.0 μm to 75 μm, more preferably 2.0 μm to 70 μm, even more preferably 5.0 μm to 65 μm, and particularly preferably 8.0 μm to 60 μm, in order to better demonstrate the effects of the present invention.

[0027] In the polystyrene-based resin foam sheet according to the embodiment of the present invention, the maximum value D1 among the thicknesses of the nine points of the skin layer is max μm and minimum value D1 min Difference D1 from μm max -D1 min When R / D1 is R μm, R / D1 is preferably 0.1 or more, more preferably 0.5 to 10, further preferably 0.8 to 10, and particularly preferably 1.0 to 10. When R / D1 is within the above range, the skin layer has a moderately thick portion and a moderately thin portion, and the polystyrene resin foam sheet according to the embodiment of the present invention can further achieve both high strength and bubble suppression.

[0028] The polystyrene-based resin foam sheet according to the embodiment of the present invention has a shrinkage rate of preferably 50% or less, more preferably 43% or less, even more preferably 41% or less, and particularly preferably 39% or less, after being heated at 100°C for 90 seconds in a slice sliced ​​20 mm in the MD and 20 mm in the TD from the surface to a thickness of 200 µm. This shrinkage rate is an index of the shrinkage rate in the vicinity of the surface of the polystyrene-based resin foam sheet (the range from the surface to a thickness of 200 µm). If this shrinkage rate is within the above range, stretching during molding tends to be alleviated, and embrittlement of the resulting foamed container can be suppressed, thereby improving the strength.

[0029] The polystyrene-based resin foam sheet according to the embodiment of the present invention has a shrinkage percentage of preferably 40% or less, more preferably 34% or less, even more preferably 31% or less, and particularly preferably 29% or less, after being sliced ​​20 mm in the MD and 20 mm in the TD and heated at 125° C. for 150 seconds. This shrinkage percentage is an index of the shrinkage percentage of the entire polystyrene-based resin foam sheet, and if this shrinkage percentage is within the above range, stretching during molding tends to be alleviated, and embrittlement of the resulting foamed container can be suppressed, thereby improving the strength.

[0030] The polystyrene-based resin foam sheet according to the embodiment of the present invention may have any appropriate thickness as long as the effects of the present invention are not impaired. In terms of further exhibiting the effects of the present invention, the thickness of the polystyrene-based resin foam sheet according to the embodiment of the present invention is preferably 0.5 mm to 4.0 mm, more preferably 0.8 mm to 3.5 mm, even more preferably 1.0 mm to 3.0 mm, and particularly preferably 1.1 mm to 2.5 mm.

[0031] The polystyrene-based resin foam sheet according to the embodiment of the present invention may have any appropriate basis weight as long as the effects of the present invention are not impaired. In order to further exhibit the effects of the present invention, the polystyrene-based resin foam sheet according to the embodiment of the present invention preferably has a basis weight of 60 g / m 2 ~500g / m 2 and more preferably 70 g / m 2 ~400g / m 2 and more preferably 80 g / m 2 ~300g / m 2 and more preferably 90 g / m 2 ~300g / m 2 and more preferably 100 g / m 2 ~250g / m 2 and particularly preferably 100 g / m 2 More than 250g / m 2 and most preferably less than 100 g / m 2 ~200g / m 2 is.

[0032] The basis weight of the polystyrene-based resin foam sheet can be measured, for example, by the following method. That is, excluding 20 mm from both ends in the width direction of the polystyrene-based resin foam sheet, ten pieces of 10 cm x 10 cm are cut out at equal intervals in the width direction, and the mass (g) of each piece is measured to the nearest 0.001 g. The average mass (g) of each piece is calculated as 1 m 2 The value converted to the mass per unit area is used as the basis weight (g / m) of the polystyrene resin foam sheet. 2 )

[0033] The apparent density of the polystyrene-based resin foam sheet according to the embodiment of the present invention may be any appropriate apparent density within a range that does not impair the effects of the present invention. In terms of being able to further exhibit the effects of the present invention, the apparent density of the polystyrene-based resin foam sheet according to the embodiment of the present invention is preferably 0.021 g / cm. 3 ~0.50g / cm 3 and more preferably 0.030 g / cm 3 ~0.40g / cm 3 and more preferably 0.040 g / cm 3 ~0.30g / cm 3 and particularly preferably 0.050 g / cm 3 ~0.20g / cm 3 is.

[0034] The apparent density of the polystyrene-based resin foam sheet can be determined, for example, by measurement in accordance with JIS K 7222:2005 "Foam plastics and rubber - Determination of apparent density." Specifically, the mass and apparent volume of a test piece of the polystyrene-based resin foam sheet cut without changing the original cell structure are measured, and the apparent density is calculated using the following formula. Apparent density (g / cm) of polystyrene resin foam sheet 3 ) = mass of test piece (g) / apparent volume of test piece (cm 3 )

[0035] The overall expansion ratio of the polystyrene-based resin foamed sheet according to the embodiment of the present invention may be any appropriate expansion ratio within a range that does not impair the effects of the present invention. In order to further exhibit the effects of the present invention, the overall expansion ratio of the polystyrene-based resin foamed sheet according to the embodiment of the present invention is preferably 2 to 20 times, more preferably 3 to 18 times, even more preferably 4 to 17 times, and particularly preferably 5 to 16 times.

[0036] The polystyrene-based resin foam sheet according to the embodiment of the present invention may have any suitable average cell diameter as long as the effects of the present invention are not impaired. In order to further exhibit the effects of the present invention, the average cell diameter of the polystyrene-based resin foam sheet according to the embodiment of the present invention is preferably 100 μm to 3000 μm, more preferably 150 μm to 2500 μm, even more preferably 200 μm to 2000 μm, and particularly preferably 250 μm to 1500 μm.

[0037] The average cell diameter of the polystyrene-based resin foam sheet can be measured in accordance with the method described in ASTM2842-69.

[0038] The polystyrene-based resin foam sheet according to the embodiment of the present invention is typically formed by foaming a resin composition containing a polystyrene-based resin, preferably formed by extrusion-foaming a resin composition containing a polystyrene-based resin and a foaming agent, and more preferably formed by heating, melting, and kneading a resin composition containing a polystyrene-based resin, a foaming agent, and various additives such as a cell regulator added as needed, in an extruder, cooling to a predetermined temperature, extruding the resulting composition through a die into a sheet shape and foaming it, and immediately cooling the resulting composition to form a sheet.

[0039] Examples of polystyrene-based resins include homopolymers of styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, bromostyrene, and chlorostyrene; copolymers of the above styrene-based monomers; copolymers of the above styrene-based monomers and carboxylic acid esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cetyl (meth)acrylate, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, and ethyl fumarate); copolymers of the above styrene-based monomers and bifunctional monomers (e.g., divinylbenzene and alkylene glycol dimethacrylate); and high-impact polystyrenes (HIPS) such as block copolymers having a rubber component block such as butadiene or isoprene and a styrene block, and graft copolymers in which the rubber component block is grafted onto a molecular chain composed of styrene. The polystyrene-based resin (I) may be a polystyrene-based resin made from recycled materials. The styrene-based monomer preferably contains at least styrene. The content of styrene relative to the total amount of styrene-based monomers is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0040] The polystyrene resin may be one type of polystyrene resin or a mixture of two or more types of polystyrene resins.

[0041] The polystyrene-based resin may be a non-recycled polystyrene-based resin, such as general-purpose polystyrene resin (GPPS), commercially available polystyrene-based resin, or polystyrene-based resin newly prepared by methods such as suspension polymerization. It may also be a recycled polystyrene-based resin. The recycled material is a used foamed polystyrene-based resin. Examples of recycled materials include food packaging trays, fish boxes, and cushioning materials for home appliances, which are recovered and regenerated using a limonene dissolution method or a thermal volume reduction method. Another usable recycled material may be non-foamed polystyrene-based resin molded bodies separated and recovered from home appliances (e.g., televisions, refrigerators, washing machines, air conditioners, etc.) or office equipment (e.g., copiers, facsimiles, printers, etc.), which are crushed, melt-kneaded, and re-pelletized.

[0042] The polystyrene resin may be a commercially available product mixed with other resins, and the other resins may be one type only or two or more types.

[0043] The polystyrene resin may be used in combination with other resins, and the other resins may be one type only or two or more types.

[0044] In order to further exert the effects of the present invention, the content of the polystyrene resin in the resin composition is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass.

[0045] Examples of other resins include polyolefin resins, (meth)acrylic resins, polyphenylene ether resins such as poly(2,6-dimethylphenylene-1,4-ether), poly(2,6-diethylphenylene-1,4-ether), and poly(2,6-dichlorophenylene-1,4-ether), styrene-butadiene-styrene copolymer rubber (SBS), styrene-isoprene-styrene block copolymer rubber (SIPS), styrene-butadiene-butylene-styrene copolymer rubber (SBBS), styrene-ethylene-butylene-styrene block copolymer rubber (SEBS), styrene-ethylene-propylene-styrene block copolymer rubber (SEPS), acrylonitrile-butadiene-styrene copolymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, and poly-paramethylstyrene resin.

[0046] Examples of polyolefin resins include polyethylene resins such as branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and crosslinked polymers of these polymers; and polypropylene resins such as propylene homopolymer, propylene-vinyl acetate copolymer, ethylene-propylene random copolymer, propylene-1-butene copolymer, and ethylene-propylene-butene random copolymer. The low density is preferably 0.91 g / cm. 3 ~0.94g / cm 3 and more preferably 0.91 g / cm 3 ~0.93g / cm 3 The high density is preferably 0.95 g / cm 3 ~0.97g / cm 3 and more preferably 0.95 g / cm 3 ~0.96g / cm 3 Medium density is a density between low and high density.

[0047] Any suitable blowing agent may be used as long as it does not impair the effects of the present invention. Examples of such blowing agents include at least one selected from propane, i-butane, n-butane, i-pentane, n-pentane, N2, CO2, N2 / CO2, dimethyl ether, water, a mixture of water and a compound having a group such as -OH, -COOH, -CN, -NH3, -OSO3H, -NH, CO, NH2, -CONH2, -COOR, -CHSO3H, -SO3H, or -COONH4, and mixtures thereof. In terms of further enhancing the effects of the present invention, the blowing agent is preferably at least one selected from i-butane and n-butane.

[0048] The content of the foaming agent relative to 100 parts by mass of the polystyrene-based resin is preferably 0.5 parts by mass to 10 parts by mass, more preferably 1.0 parts by mass to 8.0 parts by mass, even more preferably 1.5 parts by mass to 7.0 parts by mass, and particularly preferably 1.5 parts by mass to 6.0 parts by mass, in order to better exhibit the effects of the present invention.

[0049] The resin composition containing a polystyrene resin and a foaming agent may contain additives such as a cell regulator, a stabilizer, an ultraviolet absorber, an antioxidant, a colorant (including a pigment), a deodorizer, a foam nucleating agent, a nucleating agent, a lubricant, a flame retardant, an antistatic agent, etc. The additives may be of one kind or two or more kinds.

[0050] Examples of the foam regulator include inorganic powders such as talc and silica; acid salts of polycarboxylic acids; and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate.

[0051] Examples of the stabilizer include calcium zinc-based heat stabilizers, tin-based heat stabilizers, and lead-based heat stabilizers.

[0052] Examples of the ultraviolet absorber include cesium oxide-based ultraviolet absorbers and titanium oxide-based ultraviolet absorbers.

[0053] Examples of antioxidants include cerium oxide, cerium oxide / zirconia solid solution, cerium hydroxide, carbon, carbon nanotubes, titanium oxide, and fullerene.

[0054] Examples of colorants include titanium oxide, carbon black, titanium yellow, iron oxide, ultramarine, cobalt blue, calcined pigments, metallic pigments, mica, pearl pigments, zinc oxide, precipitated silica, and cadmium red.

[0055] Examples of deodorizing agents include silica, zeolite, zirconium phosphate, and calcined hydrotalcite.

[0056] <<B. Method for forming polystyrene resin foam sheet>> The polystyrene-based resin foam sheet according to the embodiment of the present invention may be formed by any appropriate method as long as the method forms the foam layer and the skin layer described in the section <<A. Polystyrene-based resin foam sheet>> within a range that does not impair the effects of the present invention.

[0057] The polystyrene-based resin foam sheet according to the embodiment of the present invention can be formed, in order to more effectively exhibit the effects of the present invention, by heating, melting, and kneading a resin composition containing a polystyrene-based resin, a foaming agent, and various additives such as a cell regulator, which are added as needed, in an extruder, and extruding the resin composition through a die while foaming, followed by immediately cooling the extrusion foaming. The formed polystyrene-based resin foam sheet is preferably left to stand for a while to replace the remaining foaming gas with air.

[0058] In extrusion foaming, the foam layer and skin layer described in the section <<A. Polystyrene-based Resin Foam Sheet>> can be effectively formed, and typically, the foam is extruded from the outlet of a die (e.g., a circular die) attached to the tip of an extruder and extruded to foam into a foamed sheet, and cooling air is blown onto the foamed sheet at a predetermined position from the outlet, followed by further cooling with a cooling mandrel.

[0059] The flow rate of the cooling air is preferably 0.1 Nm3 in order to more effectively demonstrate the effects of the present invention. 3 / min~10.0Nm 3 / min, more preferably 0.2 Nm 3 / min~9.0Nm 3 / min, and more preferably 1.0 Nm 3 / min~8.0Nm 3 / min, and particularly preferably 1.5 Nm 3 / min~7.0Nm 3 / min, and most preferably 2.0 Nm 3 / min~6.0Nm 3 / min.

[0060] The position where the cooling air hits is as follows. The distance between the position on the foamed sheet where the cooling air hits and the discharge port of the circular mold is used as an index indicating the position where the cooling air hits. It is assumed that the cooling air is discharged in a straight line from the discharge port. In order to further exhibit the effects of the present invention, the index indicating the position where the cooling air hits is preferably 0.05 mm to 40 mm, more preferably 0.10 mm to 30 mm, even more preferably 0.10 mm to 25 mm, particularly preferably 0.15 mm to 20 mm, and most preferably 0.20 mm to 15 mm.

[0061] The surface temperature of the polystyrene resin foam sheet after cooling with the cooling mandrel (measured at the tail end of the cooling mandrel) is preferably 10°C to 70°C, more preferably 20°C to 65°C, even more preferably 20°C to 60°C, particularly preferably 20°C to 55°C, and most preferably 20°C to 50°C, in order to better exhibit the effects of the present invention.

[0062] <<C. Polystyrene-based resin laminated foam sheet>> The laminated polystyrene resin foam sheet according to an embodiment of the present invention is obtained by laminating a non-foamed resin film on the polystyrene resin foam sheet according to an embodiment of the present invention.

[0063] Examples of non-foamed resin films include non-foamed impact-resistant polystyrene-based resin films and non-foamed films containing thermoplastic resins.

[0064] The polystyrene-based resin laminate foam sheet according to an embodiment of the present invention comprises, as a constituent element, a polystyrene-based resin laminate foam sheet according to an embodiment of the present invention having a foam layer and a skin layer, and further laminated with a non-foamed resin film as a non-foamed layer. Thus, the polystyrene-based resin laminate foam sheet according to an embodiment of the present invention preferably has a foam layer as an inner layer and a skin layer as a surface layer (at least one selected from a skin layer derived from the polystyrene-based resin laminate foam sheet according to an embodiment of the present invention, a skin layer derived from a non-foamed resin film, and a skin layer formed by laminating a skin layer derived from the polystyrene-based resin laminate foam sheet according to an embodiment of the present invention and a skin layer derived from a non-foamed resin film).

[0065] 3 is a typical scanning electron microscope (SEM) image of the surface of the polystyrene-based resin laminate foam sheet according to the embodiment of the present invention. When the surface of the polystyrene-based resin laminate foam sheet 500 according to the embodiment of the present invention is imaged by a scanning electron microscope (SEM), a foam layer 10 as an inner layer and a skin layer 20 as a surface layer are observed, as shown in FIG.

[0066] The average thickness D2 of the skin layer at nine points of the laminated polystyrene resin foam sheet according to the embodiment of the present invention is preferably 1.0 μm to 100 μm, more preferably 2.0 μm to 90 μm, even more preferably 5.0 μm to 80 μm, and particularly preferably 7.0 μm to 70 μm, in order to further exhibit the effects of the present invention. The method for measuring the average thickness D2 (unit: μm) of the skin layer at nine points will be described later.

[0067] The polystyrene-based resin laminate foam sheet according to the embodiment of the present invention has a shrinkage rate of preferably 50% or less, more preferably 43% or less, even more preferably 41% or less, and particularly preferably 39% or less, after being heated at 100°C for 90 seconds in a slice obtained by slicing the polystyrene-based resin laminate foam sheet 20 mm in the MD and 20 mm in the TD from the surface to a thickness of 200 µm. This shrinkage rate is an index of the shrinkage rate in the vicinity of the surface of the polystyrene-based resin laminate foam sheet (the range from the surface to a thickness of 200 µm). If this shrinkage rate is within the above range, stretching during molding tends to be alleviated, and embrittlement of the resulting foamed container can be suppressed, thereby improving the strength.

[0068] The polystyrene-based resin laminate foam sheet according to the embodiment of the present invention has a shrinkage percentage of preferably 40% or less, more preferably 35% or less, even more preferably 31% or less, and particularly preferably 29% or less, after being sliced ​​20 mm in the MD and 20 mm in the TD and heated at 125°C for 150 seconds. This shrinkage percentage is an index of the shrinkage percentage of the entire polystyrene-based resin laminate foam sheet, and if this shrinkage percentage is within the above range, stretching during molding tends to be alleviated, and embrittlement of the resulting foamed container can be suppressed, resulting in improved strength.

[0069] The polystyrene-based resin laminate foam sheet according to an embodiment of the present invention can be produced by any appropriate method as long as the effects of the present invention are not impaired. A typical example of such a production method is laminating a non-foamed resin film onto the polystyrene-based resin foam sheet according to an embodiment of the present invention. For example, the raw materials constituting the non-foamed resin film are fed into an extruder together with various additives, if necessary, and then heated, melted, kneaded, cooled to a predetermined temperature, extruded through a die into a film, and laminated onto the surface of the polystyrene-based resin foam sheet according to an embodiment of the present invention before it is completely cooled, and then heat-treated during lamination. For example, another method for laminating a non-foamed resin film onto the polystyrene-based resin foam sheet according to an embodiment of the present invention is to thermally laminate a separately prepared non-foamed resin film onto the surface of the polystyrene-based resin foam sheet according to an embodiment of the present invention by pressing the non-foamed resin film onto the surface of the polystyrene-based resin foam sheet according to an embodiment of the present invention with a heated roll. As yet another means for laminating a non-foamed resin film onto the polystyrene-based resin foamed sheet according to the embodiment of the present invention, for example, lamination is performed using a binder, an adhesive, etc. In this way, the non-foamed resin film is laminated onto the polystyrene-based resin foamed sheet according to the embodiment of the present invention.

[0070] Examples of various additives that may be added as needed to the raw materials constituting the non-foamed resin film include stabilizers, ultraviolet absorbers, antioxidants, colorants (including pigments), deodorizers, lubricants, flame retardants, and antistatic agents. The additives may be one type or two or more types. The explanations for these additives that may be added in the production of the heat-resistant polystyrene-based resin foam layer (A1) and the polystyrene-based resin foam layer (A2) can be cited.

[0071] <C-1. Non-foamed impact-resistant polystyrene resin film> The thickness of the non-foamed impact-resistant polystyrene resin film can be any appropriate thickness depending on the purpose, as long as the effects of the present invention are not impaired. In consideration of various purposes, the thickness of the impact-resistant polystyrene resin film is preferably 80 μm to 180 μm, more preferably 80 μm to 170 μm, even more preferably 80 μm to 150 μm, and particularly preferably 100 μm to 145 μm. The thickness of the non-foamed impact-resistant polystyrene resin film is preferably smaller than the thickness of the laminated polystyrene resin foam sheet according to an embodiment of the present invention.

[0072] The non-foamed impact-resistant polystyrene resin film is typically formed from a resin composition containing a polystyrene resin and a rubber-modified polystyrene resin.

[0073] The polystyrene-based resin may be any polystyrene-based resin that can be used to form the polystyrene-based resin foam sheet according to the embodiment of the present invention.

[0074] The polystyrene resin may be of only one type, or of two or more types.

[0075] The rubber-modified polystyrene resin may be one in which the molecules themselves are modified, or one in which the resin is modified in a bulk state. Examples of such rubber-modified polystyrene resins include copolymers of one or more styrene monomers and one or more rubber component monomers, and blends of one or more polystyrene resins and one or more rubbers.

[0076] Specific examples of rubber-modified polystyrene resins include so-called high impact polystyrene resin (HIPS) and mixed resins of high impact polystyrene resin (HIPS: high impact polystyrene) and styrene homopolymers called general-purpose polystyrene resin (GPPS).

[0077] When a mixed resin of high impact polystyrene resin (HIPS) and general-purpose polystyrene resin (GPPS) is used as the rubber-modified polystyrene resin, it is preferable to contain 40 mass% or more of high impact polystyrene resin (HIPS) in the mixed resin from the viewpoint of imparting impact resistance, etc.

[0078] Any suitable high impact polystyrene resin (HIPS) can be used as long as it does not impair the effects of the present invention. Examples of such high impact polystyrene resin (HIPS) include those in which a styrene-butadiene copolymer is dispersed in a salami structure and the particle size is 0.3 μm to 10 μm. Furthermore, examples of the polystyrene resin (II) forming the polystyrene resin layer include linear low-density polyethylene, high-density polyethylene, low-density polyethylene, propylene homopolymer, ethylene-propylene random polymer, ethylene-propylene block polymer, ethylene-propylene-butene terpolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymer (e.g., ethylene-methyl methacrylate copolymer), ethylene-unsaturated carboxylic acid metal salt copolymer (e.g., ethylene-magnesium (or zinc) acrylate copolymer), propylene-vinyl chloride copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer), unsaturated carboxylic acid (e.g., maleic anhydride) modified polyethylene or polypropylene, ethylene-propylene rubber, atactic polypropylene, polyethylene terephthalate, polybutylene terephthalate, and mixtures thereof.

[0079] <C-2. Non-foamed film containing thermoplastic resin> By laminating a non-foamed film containing a thermoplastic resin, the surface of the polystyrene-based resin laminate foamed sheet according to the embodiment of the present invention becomes more beautiful, the rigidity becomes higher, and the heat resistance and oil resistance become more improved.

[0080] Examples of thermoplastic resins that form non-foamed films containing a thermoplastic resin include polystyrene resins, impact-resistant polystyrene resins, polyethylene resins, polypropylene resins, polyethylene terephthalate resins, polyphenylene ether resins, polyvinylidene chloride resins, ethylene-vinyl alcohol copolymer resins, etc. These may be used alone or in combination of two or more.

[0081] The non-foamed film containing a thermoplastic resin may be one layer or two or more layers. When it is two or more layers, the layers may be laminated by, for example, dry lamination.

[0082] A coloring agent (pigment, dye, etc.) may be added to a non-foamed film containing a thermoplastic resin. By adding a coloring agent (pigment, dye, etc.), it can be colored in various colors, and various patterns and designs can be displayed by printing on the surface.

[0083] The thickness of the non-foamed film containing a thermoplastic resin may be any appropriate thickness within a range that does not impair the effects of the present invention. Such a thickness is preferably 10 μm to 150 μm, more preferably 10 μm to 100 μm, in order to further exhibit the effects of the present invention. If the thickness of the non-foamed film containing a thermoplastic resin is too thin and outside the above range, the film may be difficult to stretch during thermoforming, and may be prone to damage. If the thickness of the non-foamed film containing a thermoplastic resin is too thick and outside the above range, costs may increase, and the film may not be able to be laminated at low temperatures, resulting in a loss of gloss.

[0084] <<D. Polystyrene resin foam container>> A polystyrene-based resin foam container according to one embodiment of the present invention (referred to as a first polystyrene-based resin foam container) is obtained by thermoforming a polystyrene-based resin foam sheet according to an embodiment of the present invention or a laminated polystyrene-based resin foam sheet according to an embodiment of the present invention.

[0085] Another embodiment of the polystyrene-based resin foam container of the present invention (referred to as a second polystyrene-based resin foam container) is a polystyrene-based resin foam container obtained by thermoforming a polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer, or a polystyrene-based resin laminated foam sheet obtained by laminating a non-foamed resin film to the polystyrene-based resin foam sheet, and the shrinkage rate of a slice sliced ​​30 mm in the MD direction, 10 mm in the TD direction, and 200 μm thick from the surface of the inner side wall of the polystyrene-based resin foam container after heating at 100°C for 90 seconds is 40% or less.

[0086] A polystyrene-based resin foam container according to an embodiment of the present invention (first polystyrene-based resin foam container or second polystyrene-based resin foam container) is typically formed by molding a laminated polystyrene-based resin foam sheet into a container shape with the polystyrene-based resin foam sheet on the inside and the non-foamed polystyrene-based resin film on the outside, as shown in Fig. 4. In Fig. 4, the inside of the container of polystyrene-based resin foam container 1000 is 200 and the outside of the container is 300.

[0087] <D-1. First polystyrene resin foam container> The first polystyrene-based resin foam container is obtained by thermoforming a polystyrene-based resin foam sheet according to an embodiment of the present invention or a laminated polystyrene-based resin foam sheet according to an embodiment of the present invention, and therefore can be a foam container that combines high strength with bubble suppression.

[0088] The first polystyrene-based resin foam container is typically produced by heating a rolled polystyrene-based resin foam sheet according to an embodiment of the present invention or a laminated polystyrene-based resin foam sheet according to an embodiment of the present invention to a constant temperature in a heating zone of a molding machine, and then molding the sheet into a desired container shape in a molding zone. The container shape can be, for example, a bowl shape, a cup shape, a box shape, a tray shape, or any of a variety of other shapes.

[0089] <D-2. Secondary polystyrene resin foam container> The second polystyrene-based resin foam container is a polystyrene-based resin foam container obtained by thermoforming a polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer, or a polystyrene-based resin laminated foam sheet obtained by laminating a non-foamed resin film to the polystyrene-based resin foam sheet, and the shrinkage rate of a slice sliced ​​30 mm in the MD direction, 10 mm in the TD direction, and 200 μm thick from the surface of the inner side wall of the polystyrene-based resin foam container after heating at 100°C for 90 seconds is 40% or less.

[0090] The second polystyrene-based resin foam container has a shrinkage rate of 40% or less, preferably 38% or less, more preferably 35% or less, even more preferably 33% or less, and particularly preferably 30% or less, after heating at 100°C for 90 seconds in a section sliced ​​30 mm in the MD direction and 10 mm in the TD direction from the surface to a thickness of 200 μm on the inner sidewall of the polystyrene-based resin foam container. This shrinkage rate is an index of the shrinkage rate near the surface of the inner sidewall of the second polystyrene-based resin foam container (in the range from the surface to a thickness of 200 μm). If this shrinkage rate is within the above range, embrittlement of the foam container can be suppressed and its strength can be improved. Here, the sidewall refers to the area 200 in FIG. 4.

[0091] A polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer typically has skin layers on both sides of the foam layer. The foam layer is a foam layer formed by foaming a resin composition. The skin layer is a thin layer formed on the surface layer portion during production of the polystyrene-based resin foam sheet. The difference between the foam layer and the skin layer can be understood from the explanation in the section <<A. Polystyrene-based resin foam sheet>>.

[0092] The skin layer has an average thickness D1 of 9 positions, which is preferably 1.0 μm to 75 μm, more preferably 2.0 μm to 70 μm, even more preferably 5.0 μm to 65 μm, and particularly preferably 8.0 μm to 60 μm, in order to further exhibit the effects of the present invention. Here, the method for measuring the average thickness D1 of 9 positions on the skin layer can be found in the explanation in the section <<A. Polystyrene-based resin foam sheet>>.

[0093] The product D1×F of the average thickness D1 μm of nine points on the skin layer and the expansion ratio F times of the entire polystyrene-based resin foam sheet is preferably 100 μm· times to 1000 μm· times, more preferably 100 μm· times to 900 μm· times, even more preferably 100 μm· times to 850 μm· times, and particularly preferably 100 μm· times to 800 μm· times, in order to further exhibit the effects of the present invention.

[0094] The maximum value D1 among the nine thicknesses of the skin layer max μm and minimum value D1 min Difference D1 from μm max -D1 min When R / D1 is R μm, R / D1 is preferably 0.1 or more, more preferably 0.5 to 10, even more preferably 0.8 to 10, and particularly preferably 1.0 to 10, in order to further exhibit the effects of the present invention.

[0095] The polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming has a shrinkage rate of preferably 50% or less, more preferably 43% or less, even more preferably 41% or less, and particularly preferably 39% or less, of a slice sliced ​​20 mm in the MD and 20 mm in the TD from the surface to a thickness of 200 μm, after heating at 100° C. for 90 seconds, in order to further exhibit the effects of the present invention. Here, the explanation in the section “A. Polystyrene-based resin foam sheet” may be cited for the shrinkage rate.

[0096] The polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming has a shrinkage rate of preferably 40% or less, more preferably 34% or less, even more preferably 31% or less, and particularly preferably 29% or less, after a slice sliced ​​20 mm in the MD and 20 mm in the TD is heated at 125°C for 150 seconds, in order to further exhibit the effects of the present invention. Here, the explanation in the section <<A. Polystyrene-based resin foam sheet>>> may be cited for the above shrinkage rate.

[0097] The thickness of the polystyrene-based resin foam sheet that can be thermoformed to provide the second polystyrene-based resin foam container is preferably 0.5 mm to 4.0 mm, more preferably 0.8 mm to 3.5 mm, even more preferably 1.0 mm to 3.0 mm, and particularly preferably 1.1 mm to 2.5 mm, in order to better exhibit the effects of the present invention.

[0098] The basis weight of the polystyrene foamed resin sheet capable of providing the second polystyrene foamed resin container by thermoforming is preferably 60 g / m2 in order to further exhibit the effects of the present invention. 2 ~500g / m 2 and more preferably 70 g / m 2 ~400g / m 2 and more preferably 80 g / m 2 ~300g / m 2 and more preferably 90 g / m 2 ~300g / m 2 and more preferably 100 g / m 2 ~250g / m 2 and particularly preferably 100 g / m 2 More than 250g / m 2 and most preferably less than 100 g / m 2 ~200g / m 2 Here, the method for measuring the basis weight can be found in the explanation given in the section <<A. Polystyrene-based resin foam sheet>>.

[0099] The apparent density of the polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming is preferably 0.02 g / cm3 in order to more effectively exhibit the effects of the present invention. 3 ~0.50g / cm 3 and more preferably 0.03 g / cm 3 ~0.40g / cm 3 and more preferably 0.04 g / cm 3 ~0.30g / cm 3 and particularly preferably 0.05 g / cm 3 ~0.20g / cm 3 Here, the method for measuring the apparent density can be found in the description in the section <<A. Polystyrene-based resin foam sheet>>.

[0100] The average cell diameter of the polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming is preferably 100 μm to 3000 μm, more preferably 150 μm to 2500 μm, still more preferably 200 μm to 2000 μm, and particularly preferably 250 μm to 1500 μm, in order to further exhibit the effects of the present invention. Here, the explanation in the section <<A. Polystyrene-based resin foam sheet>>> can be cited for the method for measuring the average cell diameter.

[0101] The polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming is typically formed by foaming a resin composition containing a polystyrene-based resin, preferably formed by extrusion-foaming a resin composition containing a polystyrene-based resin and a foaming agent, and more preferably formed by heating and melting a resin composition containing a polystyrene-based resin, a foaming agent, and various additives such as a cell regulator added as needed, in an extruder, kneading the resulting mixture, cooling it to a predetermined temperature, extruding it from a die into a sheet shape and foaming it, and immediately cooling it to form a sheet.

[0102] For the polystyrene resin, other resins that can be used in combination with the polystyrene resin, foaming agents, and additives, the explanations in the section <<A. Polystyrene Resin Foam Sheet>> can be cited.

[0103] The polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming can be formed by any appropriate method as long as the method forms the foam layer and skin layer as described above within a range that does not impair the effects of the present invention. As a method for forming a polystyrene-based resin foam sheet capable of providing the second polystyrene-based resin foam container by thermoforming, the explanation in the section <<B. Method for forming polystyrene-based resin foam sheet>> can be preferably used, in that the effects of the present invention can be more effectively exhibited.

[0104] With regard to the polystyrene-based resin laminate foam sheet that can provide the second polystyrene-based resin foam container by thermoforming, i.e., the polystyrene-based resin laminate foam sheet obtained by laminating a non-foamed resin film on the above-mentioned polystyrene-based resin foam sheet, the explanation in the section <<C. Polystyrene-based resin laminate foam sheet>> can be cited. [Example]

[0105] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating each property are as follows.

[0106] <Thickness of foam sheet> For the foam sheet to be measured, 13 measurement points were determined evenly in the TD (transverse) direction, and the thickness was measured at each of the 13 points using a thickness gauge (manufactured by Tuftec Corp.) The average value of the thicknesses measured at the 13 points was taken as the thickness of the foam sheet.

[0107] <Basis weight of foam sheet> The foam sheet to be measured was cut into 10 pieces of 10cm x 10cm evenly spaced in the TD direction (width direction), the mass of each of the 10 pieces was measured, and the average of the masses of the 10 pieces was multiplied by 100 to obtain the basis weight (unit: g / m 2 ) was calculated.

[0108] <Expansion ratio of foam sheet> The expansion ratio was calculated using the thickness and basis weight of the foamed sheet according to the following formula. Expansion ratio (times) = (polystyrene resin density x 1000 x foam sheet thickness (mm)) ÷ foam sheet basis weight (g / m 2 ) However, the resin density of polystyrene was set to 1.05.

[0109] <Average thickness D1 of nine points on the skin layer of the foam sheet> FIG. 5 is one of explanatory diagrams for explaining a method for measuring the average thickness D1 of nine locations on the skin layer, and is a plan view of the polystyrene-based resin foam sheet 100 to be measured. As shown in FIG. 5, three straight lines L1 were drawn in the MD direction on the polystyrene-based resin foam sheet 100 to be measured, dividing the sheet into four equal parts in the TD direction. Next, as shown in FIG. 5, the sheet was cut into 1 cm x 1 cm pieces so that each line L1 passed through the center of the sample to obtain three measurement samples S1, S2, and S3. The centers of the three measurement samples S1, S2, and S3 were positioned on the same line L2 in the TD direction. Next, a cross section of each of the three obtained measurement samples from the MD direction was photographed using a scanning electron microscope (SEM).

[0110] 6 is one of the explanatory diagrams for explaining the method for measuring the average thickness D1 of the skin layer at nine locations, and explains the method for measuring the thickness of the skin layer by photographing a cross section in the MD direction of measurement sample S1, one of the three measurement samples obtained, with a scanning electron microscope (SEM). As shown in Fig. 6, for cross section A in the MD direction of measurement sample S1, a line passing through the midpoint in the TD direction was aligned so as to pass through the center of the image in the lateral direction (TD direction), and the vicinity of the surface of measurement sample S1 was photographed with a scanning electron microscope (SEM) at 300x magnification, obtaining images P1 on the surface 1 side and P2 on the surface 2 side.

[0111] Next, for the obtained image P1, as shown in FIG. 6, three straight lines L3 were drawn in the thickness direction, dividing the image into four equal parts in the TD direction. The distance from the surface to the edge of the bubble directly below each line was measured on each line, and thicknesses D111, D112, and D113 were obtained at three locations on the surface 1 side. The same procedure was repeated for the obtained image P2, as shown in FIG. 6, to obtain thicknesses D121, D122, and D123 at three locations on the surface 2 side. The same procedure was repeated for measurement sample S2, to obtain thicknesses D211, D212, and D213 at three locations on the surface 1 side and thicknesses D221, D222, and D223 at three locations on the surface 2 side. The same procedure was repeated for measurement sample S3, to obtain thicknesses D311, D312, and D313 at three locations on the surface 1 side and thicknesses D321, D322, and D323 at three locations on the surface 2 side. Surface 1 of measurement sample S1, surface 1 of measurement sample S2, and surface 1 of measurement sample S3 were surfaces located on the same one surface of the polystyrene-based resin foam sheet 100 being measured, and surface 2 of measurement sample S1, surface 2 of measurement sample S2, and surface 2 of measurement sample S3 were surfaces located on the same other surface of the polystyrene-based resin foam sheet 100 being measured.

[0112] The average thickness values ​​of the nine locations on the surface 1 side of the three measurement samples S1, S2, and S3 were compared with the average thickness values ​​of the nine locations on the surface 2 side, and the thickness of the nine locations on the side giving the larger average value was used as the thickness of the nine locations on the skin layer, and this average value was used as the average thickness D1 (unit: μm) of the nine locations on the skin layer.

[0113] <Average thickness D2 of nine points on the skin layer of the laminated foam sheet> The measurement object was a polystyrene-based resin laminated foam sheet instead of a polystyrene-based resin foam sheet, and the interface between the non-foamed layer and the foamed layer was observed with a microscope. The distance from the interface to the end face of the bubble directly below was measured in the same manner as the average thickness D1 of the nine thicknesses of the skin layer, and this was defined as the average thickness D2 (unit: μm) of the nine thicknesses of the skin layer.

[0114] <Shrinkage rate of the 200 μm thick surface layer of the foam sheet> The surface of the polystyrene foam sheet was sliced ​​20 mm in the MD and 20 mm in the TD, with a slicer or razor, to a thickness of 200 μm from the surface, so that the center of each slice was the intersection (three points) of three lines dividing the TD into four equal parts and one arbitrary TD line. The resulting three slices were placed in a heating furnace and heated at 100°C for 90 seconds. The MD dimensions after heating were measured, and the average of the three measurements was calculated as the post-heating dimension. The shrinkage of the 200 μm-thick surface layer of the polystyrene foam sheet (shrinkage of the foam sheet surface layer at 200 μm) was calculated using the following formula:

[0115] Shrinkage rate of foam sheet surface 200 μm (%) = (dimension before heating - dimension after heating) ÷ dimension before heating × 100

[0116] <Shrinkage rate of the 200 μm thick surface layer of laminated foam sheet> The surface of the polystyrene-based resin laminated foam sheet, laminated with the non-foamed resin film, was sliced ​​20 mm in the MD and 20 mm in the TD, with a slicer or razor, to a thickness of 200 μm from the surface, so that the centers of the slices were the intersections (three locations) of three lines dividing the TD into four equal parts and one arbitrary TD line. The resulting three slices were placed in a heating furnace and heated at 100°C for 90 seconds. The MD dimensions after heating were measured, and the average of the three measurements was calculated as the post-heating dimension. The shrinkage of the 200 μm thick surface layer of the polystyrene-based resin laminated foam sheet (shrinkage of the 200 μm surface layer of the laminated foam sheet) was measured using the following formula:

[0117] Laminated foam sheet surface 200μm shrinkage rate (%) = (dimension before heating - dimension after heating) ÷ dimension before heating × 100

[0118] <Shrinkage rate of the 200 μm thick surface layer of the inner side wall of the foam container> Measurements were performed on the inner sidewall of a polystyrene foam container (200 mm x 200 mm tray type). The surface of the inner sidewall of the container was sliced ​​using a slicer or razor, measuring 30 mm in the MD and 10 mm in the TD, to a thickness of 200 μm from the surface. The two slices were placed in a heating furnace and heated at 100°C for 90 seconds. The dimensions in the MD after heating were measured, and the average of the two measurements was calculated as the post-heating dimension. The shrinkage rate of the 200 μm thick surface layer of the polystyrene foam container (shrinkage rate of the foam container surface layer at 200 μm) was measured using the following formula.

[0119] Shrinkage rate of foam container surface 200 μm (%) = (dimension before heating - dimension after heating) ÷ dimension before heating × 100

[0120] <Shrinkage rate of foam sheet or laminated foam sheet> The polystyrene-based resin foam sheet or polystyrene-based resin laminated foam sheet was sliced ​​into 10 cm sections in the MD and 10 cm sections in the TD using a slicer or razor so that the centers of the slices would be the intersections (five locations) of five lines dividing the TD into six equal parts and one arbitrary TD line. The five slices obtained were placed in a heating furnace and heated at 125°C for 150 seconds. The dimensions of the front and back sides in the MD and TD after heating were measured, and the shrinkage rate was calculated using the following formula for the shortest dimension among these dimensions.

[0121] Shrinkage rate (%) = (dimension before heating - dimension after heating) ÷ dimension before heating × 100

[0122] <bubble> Evaluation was carried out using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.). The temperature of the heating furnace was set to 400°C, and the polystyrene-based resin laminated foam sheet was set so that the surface laminated with the non-foamed resin film was facing up, and heated. The heating time was increased in 0.5-second increments until the surface was burned. Evaluation was based on the following criteria. 〇: Only the surface (top) is cooked and no bubbles (floating) occur. △: Bubbles (floats) appear as soon as the surface (top) bakes. ×: Bubbles (floating) occur before the surface (top) is cooked.

[0123] <Container strength evaluation> The flange portion of the polystyrene-based resin foam container was held with both hands and evaluated according to the following criteria. ×: When the flange of the container is held with both hands and compressed, it immediately breaks. △: When the container flange is held with both hands and compressed, it is rigid but breaks easily. Good: When the container flange is held with both hands and compressed, it is rigid and does not break easily.

[0124] [Example 1] <Polystyrene resin foam sheet> 100 parts by mass of polystyrene resin (DIC Corporation, XC-515) was blended with 0.7 parts by mass of talc as a cell control agent, and the blend was placed in a φ115 single-screw extruder, melt-kneaded, and then butane gas was injected. The blend was then cooled in a φ180 single-screw extruder and extruded at a rate of 350 kg / h from a circular die outlet with a diameter of φ175 mm and an opening width of 0.36 mm. At this time, the index indicating the position where the cooling air hits was set at 13 mm, and the air volume was 3.2 Nm. 3 The sheet was then cooled on a cooling mandrel and taken up in a roll. The surface temperature of the polystyrene resin foam sheet after cooling on the cooling mandrel (measured at the tail of the cooling mandrel) was 45°C. The obtained polystyrene resin foam sheet (1A) had a thickness of 2.0 mm and a basis weight of 150 g / m 2 The width was 1050 mm and the expansion ratio was 14 times. The results are shown in Table 1.

[0125] <Polystyrene-based resin laminated foam sheet> The obtained polystyrene-based resin foam sheet (1A) was cured at room temperature for 2 weeks, and then a polystyrene film having a thickness of 15 μm was laminated thereon by heat lamination at a pressure of 0.4 MPa using a heated roll at 140°C and a take-up speed of 4 m / min to obtain a laminated polystyrene-based resin foam sheet (1B). The results are shown in Table 1.

[0126] <Polystyrene-based resin foam container> The obtained polystyrene-based resin laminate foam sheet (1B) was molded into a 200 mm x 200 mm tray container using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.) to produce a polystyrene-based resin foam container (1C). In molding, the temperature of the heater tank was set to 430°C, and the heating time was set so that the thickness after heating would be 3.7 mm. A resin mold was used as the mold for the tray container, and matched mold molding was performed. In addition, when molding the polystyrene-based resin foam container, the polystyrene-based resin laminate foam sheet was set so that the inner surface of the foam container would be a non-foamed layer. The results are shown in Table 1.

[0127] [Example 2] <Polystyrene resin foam sheet> 100 parts by mass of polystyrene resin (DIC Corporation, XC-515) was blended with 0.7 parts by mass of talc as a cell control agent, and the blend was placed in a φ115 single-screw extruder, melt-kneaded, and then butane gas was injected. The blend was then cooled in a φ180 single-screw extruder and extruded at a rate of 350 kg / h from a circular die with a diameter of φ175 mm and an opening width of 0.36 mm. At this time, the index indicating the position where the cooling air hits was set at 1.0 mm, and the air volume was 3.2 Nm. 3 The sheet was then cooled on a cooling mandrel and taken up in a roll. The surface temperature of the polystyrene resin foam sheet after cooling on the cooling mandrel (measured at the tail of the cooling mandrel) was 45°C. The obtained polystyrene resin foam sheet (2A) had a thickness of 2.0 mm and a basis weight of 150 g / m 2The width was 1050 mm and the expansion ratio was 14 times. The results are shown in Table 1.

[0128] <Polystyrene-based resin laminated foam sheet> The obtained polystyrene-based resin foam sheet (2A) was cured at room temperature for 2 weeks, and then a polystyrene film having a thickness of 15 μm was laminated thereon. The lamination was performed by pressing at a pressure of 0.4 MPa using a heated roll at 140°C and a take-up speed of 4 m / min, to obtain a polystyrene-based resin laminated foam sheet (2B). The results are shown in Table 1.

[0129] <Polystyrene-based resin foam container> The obtained polystyrene-based resin laminated foam sheet (2B) was molded into a 200 mm x 200 mm tray container using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.) to produce a polystyrene-based resin foam container (2C). In molding, the temperature of the heater tank was set to 430°C, and the heating time was set so that the thickness after heating would be 3.7 mm. A resin mold was used as the mold for the tray container, and matched molding was performed. The results are shown in Table 1.

[0130] [Example 3] <Polystyrene resin foam sheet> 100 parts by mass of polystyrene resin (DIC Corporation, XC-515) was blended with 0.7 parts by mass of talc as a cell control agent, and the blend was placed in a φ115 single-screw extruder, melt-kneaded, and then butane gas was injected. The blend was then cooled in a φ180 single-screw extruder and extruded at a rate of 350 kg / h from a circular die with a diameter of φ175 mm and an opening width of 0.36 mm. At this time, the index indicating the position where the cooling air hits was set at 0.22 mm, and the air volume was 5.0 Nm. 3 / m of cooling air was applied to the sheet. Thereafter, the sheet was cooled on a cooling mandrel and taken up in a roll. The surface temperature of the polystyrene resin foam sheet after cooling on the cooling mandrel (measured at the tail of the cooling mandrel) was 40°C. The obtained polystyrene-based resin foam sheet (3A) had a thickness of 2.0 mm and a basis weight of 150 g / m 2 The width was 1050 mm and the expansion ratio was 14 times. The results are shown in Table 1.

[0131] <Polystyrene-based resin laminated foam sheet> The obtained polystyrene resin foam sheet (3A) was cured at room temperature for 2 weeks, and then a polystyrene film having a thickness of 15 μm was laminated thereon by heat lamination at a pressure of 0.4 MPa using a heated roll at 140°C and a take-up speed of 4 m / min to obtain a laminated polystyrene resin foam sheet (3B). The results are shown in Table 1.

[0132] <Polystyrene-based resin foam container> The obtained polystyrene-based resin laminated foam sheet (3B) was molded into a 200 mm x 200 mm tray container using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.) to produce a polystyrene-based resin foam container (3C). In molding, the temperature of the heater tank was set to 430°C, and the heating time was set so that the thickness after heating would be 3.7 mm. A resin mold was used as the mold for the tray container, and matched molding was performed. The results are shown in Table 1.

[0133] [Comparative Example 1] <Polystyrene resin foam sheet> 100 parts by mass of polystyrene resin (DIC Corporation, XC-515) was blended with 0.7 parts by mass of talc as a cell control agent, and the blend was placed in a φ115 single-screw extruder, melt-kneaded, and then butane gas was injected. The blend was then cooled in a φ180 single-screw extruder and extruded at a rate of 350 kg / h from a circular die outlet with a diameter of φ175 mm and an opening width of 0.36 mm. At this time, the index indicating the position where the cooling air hits was set at 35 mm, and the air volume was 1.0 Nm. 3 / m of cooling air was applied to the sheet. Thereafter, the sheet was cooled on a cooling mandrel and taken up in a roll. The surface temperature of the polystyrene resin foam sheet after cooling on the cooling mandrel (measured at the tail of the cooling mandrel) was 65°C. The obtained polystyrene-based resin foam sheet (C1A) had a thickness of 2.0 mm and a basis weight of 150 g / m 2 The width was 1050 mm and the expansion ratio was 14 times. The results are shown in Table 1.

[0134] <Polystyrene-based resin laminated foam sheet> The obtained polystyrene resin foam sheet (C1A) was cured at room temperature for 2 weeks, and then a polystyrene film having a thickness of 15 μm was laminated thereon. The lamination was performed by pressing with a heated roll at 140°C under a pressure of 0.4 MPa and at a take-up speed of 4 m / min, to obtain a laminated polystyrene resin foam sheet (C1B). The results are shown in Table 1.

[0135] <Polystyrene-based resin foam container> The obtained polystyrene-based resin laminated foam sheet (C1B) was molded into a 200 mm x 200 mm tray container using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.) to produce a polystyrene-based resin foam container (C1C). During molding, the temperature of the heater tank was set to 430°C, and the heating time was set so that the thickness after heating would be 3.7 mm. A resin mold was used as the mold for the tray container, and matched molding was performed. The results are shown in Table 1.

[0136] Comparative Example 2 <Polystyrene resin foam sheet> 100 parts by mass of polystyrene resin (DIC Corporation, XC-515) was blended with 0.7 parts by mass of talc as a cell control agent, and the blend was placed in a φ115 single-screw extruder, melt-kneaded, and then butane gas was injected. The blend was then cooled in a φ180 single-screw extruder and extruded at a rate of 350 kg / h from a circular die with a diameter of φ175 mm and an opening width of 0.36 mm. At this time, the index indicating the position where the cooling air hits was set at 0.1 mm, and the air volume was 7.2 Nm. 3 / m of cooling air was applied to the sheet. Thereafter, the sheet was cooled on a cooling mandrel and taken up in a roll. The surface temperature of the polystyrene resin foam sheet after cooling on the cooling mandrel (measured at the tail of the cooling mandrel) was 30°C. The obtained polystyrene-based resin foam sheet (C2A) had a thickness of 2.0 mm and a basis weight of 150 g / m 2 The width was 1050 mm and the expansion ratio was 14 times. The results are shown in Table 1.

[0137] <Polystyrene-based resin laminated foam sheet> The obtained polystyrene-based resin foam sheet (C2A) was cured at room temperature for 2 weeks, and then a 15 μm-thick polystyrene film was laminated on the sheet. The lamination was performed by pressing the sheet with a heated roll at 140°C under a pressure of 0.4 MPa and at a take-up speed of 4 m / min, to obtain a laminated polystyrene-based resin foam sheet (C2B). The results are shown in Table 1.

[0138] <Polystyrene-based resin foam container> The obtained polystyrene-based resin laminated foam sheet (C2B) was molded into a 200 mm x 200 mm tray container using a molding machine (product name: FVS-500, manufactured by Wakisaka Engineering Co., Ltd.) to produce a polystyrene-based resin foam container (C2C). During molding, the temperature of the heater tank was set to 430°C, and the heating time was set so that the thickness after heating would be 3.7 mm. A resin mold was used as the mold for the tray container, and match molding was performed. The results are shown in Table 1.

[0139] [Table 1] [Industrial Applicability]

[0140] The polystyrene resin foam sheet according to the embodiment of the present invention or a container obtained by thermoforming the laminated polystyrene resin foam sheet according to the embodiment of the present invention can be widely used as various containers such as trays, lunch boxes, rice bowls, and cups in convenience stores and the like. [Explanation of symbols]

[0141] 100 Polystyrene resin foam sheet 500 Polystyrene resin laminated foam sheet 10 Foam layer 20 Skin Layer 1000 Polystyrene resin foam container 200 Inside the container 300 Outside the container

Claims

1. A polystyrene-based resin foam sheet having a foam layer as an inner layer and a skin layer as a surface layer, The skin layer is a thin layer formed on the surface layer portion during production of the polystyrene-based resin foam sheet, the product D1×F of the average thickness D1 μm of the nine thicknesses of the skin layer and the expansion ratio F times of the entire polystyrene-based resin foamed sheet is 100 μm times to 1000 μm times, The maximum value D1 among the thicknesses at the nine points max μm and minimum value D1 min Difference D1 from μm max -D1 min is R μm, R / D1 is 0.1 or more, The basis weight is 90 g / m 2 to 200 g / m 2 , Polystyrene resin foam sheet.

2. 2. The polystyrene-based resin foam sheet according to claim 1, wherein a slice obtained by slicing the sheet 20 mm in the MD direction and 20 mm in the TD direction from the surface to a thickness of 200 μm has a shrinkage rate of 50% or less after heating at 100° C. for 90 seconds.

3. 3. The polystyrene-based resin foam sheet according to claim 1, wherein a slice sliced ​​to a size of 20 mm in the machine direction and 20 mm in the transverse direction has a shrinkage rate of 40% or less after heating at 125°C for 150 seconds.

4. A laminated polystyrene resin foam sheet, comprising the polystyrene resin foam sheet according to any one of claims 1 to 3 and a non-foamed resin film laminated thereon.

5. A polystyrene resin foam container obtained by thermoforming the polystyrene resin foam sheet according to any one of claims 1 to 3 or the laminated polystyrene resin foam sheet according to claim 4.

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