Polystyrene foam sheet and method for manufacturing a polystyrene foam sheet

Abstract

Simply using polystyrene foam sheets containing polyolefin resin as recycled raw materials can lead to a decrease in the physical properties of the resulting polystyrene foam sheets because polyolefin resin and polystyrene resin are incompatible. In light of these circumstances, the aim is to improve the moldability of polystyrene foam sheets even when using recycled raw materials. [Solution] The device has a foamed layer, the foamed layer contains a thermoplastic resin including a polystyrene resin, the thermoplastic resin contains recycled materials, and the recycled materials consist of a polystyrene resin, a polyolefin resin, and a styrene thermoplastic resin elastomer.

Description

[Technical Field]

[0001] This invention relates to a polystyrene-based resin foam sheet and a method for producing a polystyrene-based resin foam sheet. [Background technology]

[0002] Some food containers are made by thermoforming polystyrene foam sheets, which are the raw material. With the growing concern for environmental issues in recent years, there is a demand in the market for food containers that have a low environmental impact. One way to reduce the environmental impact is to recycle the raw materials used in the manufacture of the raw material, that is, to use recycled polystyrene resin (hereinafter sometimes simply referred to as "recycled material") as the raw resin.

[0003] Polystyrene foam sheets, molded as microwaveable food containers, have a polypropylene resin film laminated onto the food contact surface for oil resistance. Furthermore, from the perspective of reducing environmental impact, polystyrene foam sheets may contain plant-derived polyethylene resin (for example, Patent Document 1). If polystyrene foam sheets containing polyolefin resins such as polyethylene resins are simply used as recycled raw materials, the resulting polystyrene foam sheets may suffer from a decrease in physical properties because polyolefin resins and polystyrene resins are incompatible. When molded products such as containers are formed using polystyrene foam sheets with reduced physical properties, the polystyrene foam sheets become less stretchable, resulting in uneven thickness or a damaged appearance of the molded product (poor moldability).

[0004] To address these problems, a polystyrene foam sheet containing recycled materials including polystyrene resin and polyolefin resin, along with a specific compatibilizer, has been proposed (Patent Document 2). According to the invention of Patent Document 2, it is possible to achieve good moldability into foam molded products (e.g., containers) while utilizing recycled materials. Furthermore, a polystyrene foam sheet has been proposed that contains a polystyrene resin containing polyphenylene ether, a recycled material containing a polyolefin resin, a specific compatibilizer, and virgin material in specific proportions (Patent Document 3). According to the invention of Patent Document 3, it is possible to achieve good moldability into foam molded products while utilizing recycled materials. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-039375 [Patent Document 2] Japanese Patent Publication No. 2012-040868 [Patent Document 3] Japanese Patent Publication No. 2013-028711 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, there is a need for further improvements in the moldability of polystyrene foam sheets, including those made from recycled materials. Therefore, the present invention aims to provide a polystyrene-based resin foam sheet with good moldability even when using recycled materials. [Means for solving the problem]

[0007] Conventional technology improves the moldability of the resulting polystyrene foam sheet by dispersing polyolefin resin in polystyrene resin using the effect of a compatibilizer. As a result of diligent research by the inventors, we discovered that by employing a specific method for dispersing polyolefin resin in polystyrene resin, the moldability of polystyrene resin foam sheets containing recycled materials can be improved, leading to the completion of the present invention.

[0008] The present invention includes the following embodiments. <1> Having a foamed layer, Said foam layer contains a thermoplastic resin including a polystyrene-based resin, Said thermoplastic resin includes a recycled raw material, Said recycled raw material is a polystyrene-based resin foam sheet comprising a polystyrene-based resin, a polyolefin-based resin, and a styrene-based thermoplastic resin elastomer. <2> Said recycled raw material is derived from a laminate having a foam and a non-foam body disposed on at least one surface of said foam, Said foam includes a polystyrene-based resin, Said non-foam body includes a polyolefin-based resin, the polystyrene-based resin foam sheet according to <1>. <3> Said non-foam body includes a styrene-based thermoplastic resin elastomer, the polystyrene-based resin foam sheet according to <2>. <4> The polystyrene-based resin foam sheet according to any one of <1> to <3>, which has a non-foam layer containing a thermoplastic resin on one or both surfaces of said foam layer. <5> A method for producing a polystyrene-based resin foam sheet having a foam layer containing a thermoplastic resin, a recycled raw material production step of melt-kneading a recycled product containing a polystyrene-based resin and a polyolefin-based resin in the presence of a styrene-based thermoplastic resin elastomer to obtain a recycled raw material, and a foam layer production step of extruding a foamable resin composition containing said recycled raw material, a foaming agent, and optionally an additional new thermoplastic resin into a sheet form, and foaming the resulting sheet to obtain said foam layer, the method for producing a polystyrene-based resin foam sheet. <6> Said recycled product includes a laminate, Said laminate has a foam and a non-foam body disposed on at least one surface of said foam, Said foam includes a polystyrene-based resin, Said non-foam body includes a polyolefin-based resin, the method for producing a polystyrene-based resin foam sheet according to <5>. <7> The non-foamed material comprises a styrene-based thermoplastic resin elastomer. <6> A method for producing a polystyrene-based resin foam sheet as described above. <8> The recycled material manufacturing process obtains the recycled material in pellet form. <5> ~ <7> A method for producing a polystyrene-based resin foam sheet as described in any of the following. <9> The lamination process includes providing a non-foamed layer containing a thermoplastic resin on one or both sides of the foamed layer. <5> ~ <8> A method for producing a polystyrene-based resin foam sheet as described in any of the following. [Effects of the Invention]

[0009] According to the polystyrene-based resin foam sheet of the present invention, good moldability is achieved even when using recycled raw materials. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing one embodiment of the polystyrene-based resin foam sheet of the present invention. [Figure 2] This is a flow chart showing an example of a method for manufacturing polystyrene foam sheets. [Figure 3] This is a schematic diagram showing an example of a foam layer manufacturing apparatus. [Figure 4] This is a schematic diagram showing an example of a repelletization system used in the production of recycled pellets. [Modes for carrying out the invention]

[0011] In this specification, "~" represents a range that includes the values ​​at both ends as the lower and upper limits.

[0012] The following describes preferred embodiments of the present invention using a polystyrene resin foam sheet having a foamed layer and a non-foamed layer provided on one side of the foamed layer (a polystyrene resin foam sheet having a foamed layer and a non-foamed layer (foam sheet) is sometimes specifically referred to as a "laminated foam sheet") as an example. In a laminated foam sheet, the non-foamed layer may be provided on one side of the foamed layer, or the non-foamed layer may be provided on both sides of the foamed layer. The resin foam sheet may consist of a single foamed layer, or it may have two or more foamed layers. The non-foamed layer may consist of a single non-foamed layer, or it may have two or more non-foamed layers.

[0013] (Polystyrene foam sheet) One embodiment of the polystyrene-based resin foam sheet of the present invention will be described using a laminated foam sheet as an example. The laminated foam sheet of this embodiment comprises a foamed layer and a non-foamed layer laminated on one or both sides of the foamed layer. One embodiment of a laminated foam sheet will be described with reference to the drawings.

[0014] Figure 1 is a cross-sectional view of the laminated foam sheet 1 of this embodiment. The laminated foam sheet 1 has a sheet-like foam layer 10 and a non-foamed layer 20 laminated on one side of the foam layer 10.

[0015] The thickness T1 of the laminated foam sheet 1 can be determined considering the application. For example, the thickness T1 is preferably 0.5 to 7.5 mm, more preferably 0.7 to 5.0 mm, and even more preferably 1.0 to 4.0 mm. If the thickness T1 is above the lower limit, the strength and impact resistance of the container formed from the laminated foam sheet 1 can be increased. If the thickness T1 is below the upper limit, the moldability of the laminated foam sheet 1 can be further increased. The thickness T1 can be measured, for example, using a dial thickness gauge.

[0016] The basis weight of laminated foam sheet 1 is, for example, 70-850 g / m². 2 Preferably, 120-700 g / m² 2 More preferably, 170-550 g / m 2is even more preferred. When the basis weight of the laminated foam sheet 1 is at or above the above lower limit, the impact resistance of the container can be further enhanced. When the basis weight of the laminated foam sheet 1 is at or below the above upper limit, the moldability of the laminated foam sheet 1 can be further enhanced. The basis weight of the laminated foam sheet 1 can be measured by the following method. Excluding 20 mm from both ends in the width direction (TD direction) of the laminated foam sheet 1, 10 pieces of 10 cm × 10 cm sections are cut out at equal intervals in the width direction, and the mass (g) of each section is measured to the unit of 0.001 g. The average value of the mass (g) of each section is converted to the mass per 1 m 2 to obtain the value as the basis weight (g / m 2 ) of the laminated foam sheet 1.

[0017] The apparent density of the laminated foam sheet 1 is, for example, preferably 0.060 to 0.716 g / cm 3 , more preferably 0.086 to 0.540 g / cm 3 , even more preferably 0.130 to 0.363 g / cm 3 . When the apparent density of the laminated foam sheet 1 is at or above the above lower limit, the impact resistance of the molded article can be further enhanced. When the apparent density of the laminated foam sheet 1 is at or below the above upper limit, the molded article can be made lighter, and the heat insulation property can be further enhanced.

[0018] The apparent density of the laminated foam sheet 1 can be determined by measuring in accordance with JIS K7222:2005 "Foamed plastics and rubbers - Determination of apparent density". Specifically, for a test piece of the laminated foam sheet 1 cut so as not to change the original cell structure, the mass and the apparent volume thereof are measured, and the value is calculated by the following formula (1). Apparent density of laminated foam sheet 1 (g / cm 3 ) = Mass of test piece (g) / Apparent volume of test piece (cm 3 )···(1)

[0019] <Foam layer> The foamed layer 10 is a layer formed by foaming a foamable resin composition containing a polystyrene resin, and air bubbles are formed within the resin. The resin contained in the foamed resin composition (i.e., the resin constituting the foamed layer 10) is a thermoplastic resin.

[0020] Thermoplastic resins may be made from recycled materials, virgin materials, or a combination of both. Virgin materials are those that have not undergone the manufacturing process of extrusion molding and molded product molding. Virgin resin materials are sometimes specifically called virgin resins.

[0021] Examples of polystyrene resins include homopolymers or copolymers thereof of styrene monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene; copolymers mainly composed of styrene monomers, with styrene monomers and vinyl monomers polymerizable thereto; and so-called high-impact polystyrenes, which are copolymers of styrene monomers and rubber components such as butadiene, homopolymers or copolymers thereof, or mixtures or polymers of copolymers of styrene monomers and vinyl monomers and diene-based rubbery polymers.

[0022] Examples of vinyl monomers polymerizable with styrene monomers include alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, and cetyl(meth)acrylate, as well as difunctional monomers such as (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, divinylbenzene, and alkylene glycol dimethacrylate. These vinyl monomers may be used individually or in combination of two or more. Here, "(meth)acrylate" refers to either or both "acrylate" and "methacrylate," and "(meth)acrylonitrile" refers to either or both "acrylonitrile" and "methacrylonitrile."

[0023] Examples of diene-based rubbery polymers include polybutadiene, styrene-butadiene copolymers, and ethylene-propylene-non-conjugated diene three-dimensional copolymers. These polystyrene resins may be used individually or in combination of two or more types. As for the polystyrene-based resin, a polystyrene-based resin containing 50 mole% or more of units derived from styrene monomer is preferred, and among these, polystyrene is more preferred.

[0024] The polystyrene resin may be general-purpose polystyrene resin (GPPS), commercially available polystyrene resin, or polystyrene resin newly prepared by methods such as suspension polymerization. It may also be a non-recycled polystyrene resin (virgin PS resin) or a recycled polystyrene resin. In the present invention, the foamed layer 10 contains a polystyrene resin made from recycled raw materials.

[0025] Examples of recycled materials include used polystyrene foam molded products, such as fish boxes, home appliance cushioning materials, and food packaging trays, which are collected and recycled using methods such as limonene dissolution or heat volume reduction (these are PS-based recycled materials). In addition to materials obtained by recycling molded products such as used foam containers, usable recycled materials include non-foamed polystyrene resins collected separately from home appliances (e.g., televisions, refrigerators, washing machines, air conditioners, etc.) and office equipment (e.g., photocopiers, fax machines, printers, etc.).

[0026] In the present invention, the recycled material includes, in addition to polystyrene resin, polyolefin resin and styrene-based thermoplastic resin elastomer. Examples of such recycled material include recycled material (recycled pellets) obtained by melt-kneading a recycled laminate having a foam containing polystyrene resin and a non-foamed surface containing polyolefin resin provided on at least one surface of the foam in the presence of a ethylene-based thermoplastic resin elastomer and then forming it into pellets. By pre-melting and kneading polystyrene resin and polyolefin resin in the presence of a ethylene-based thermoplastic resin elastomer, which acts as a compatibilizer, the polyolefin resin is considered to be more finely and uniformly dispersed within the polystyrene resin, thus becoming a recycled raw material. Using such a recycled raw material, the resulting foamed sheet containing the foamed layer 10 exhibits excellent moldability.

[0027] Examples of styrene-based thermoplastic resin elastomers include copolymers of styrene, butadiene, and styrene (SBS polymer), copolymers of styrene, isoprene, and styrene (SIS polymer), and hydrogenated styrene-based thermoplastic elastomers obtained by hydrogenating these. Examples of hydrogenated styrene-based thermoplastic elastomers include copolymers of styrene, ethylene, butylene, and styrene (SEBS polymer), copolymers of styrene, butadiene, butylene, and styrene (SBBS polymer), and copolymers of styrene, ethylene, propylene, and styrene (SEPS polymer). Among these, SEBS polymer is preferred as the styrene-based thermoplastic resin elastomer because it offers even greater compatibility. Furthermore, whether or not styrene-based thermoplastic resin elastomer is present in the recycled raw material can be confirmed by analyzing the ratio of styrene, olefin, and butadiene derived from the styrene-based thermoplastic resin elastomer.

[0028] The mass-average molecular weight Mw of the polystyrene resin contained in the foam layer 10 is preferably 120,000 to 450,000, and more preferably 150,000 to 400,000. The mass-average molecular weight Mw is a value obtained by converting the value measured by gel permeation chromatography (GPC) based on a calibration curve using standard polystyrene.

[0029] The melt flow rate (MFR) of the polystyrene resin contained in the foamed layer 10 is preferably 0.5 to 6.0 g / 10 min, and more preferably 0.7 to 3.0 g / 10 min. If the MFR of the polystyrene resin is above the lower limit, the strength of the container can be further increased. If the MFR of the polystyrene resin is below the upper limit, the moldability of the foamed layer 10 can be further increased. The MFR of the polystyrene resin contained in the foam layer 10 refers to the value measured in accordance with Method B described in JIS K7210:1999 "Plastics - Test methods for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics," under the conditions of a test temperature of 200°C, a test load of 49.03N, and a preheating time of 5 minutes.

[0030] The content of polystyrene resin relative to 100 parts by mass of thermoplastic resin constituting the foamed layer 10 is preferably 50 parts by mass or more, more preferably 75 parts by mass or more, even more preferably 90 parts by mass or more, and particularly preferably 95 parts by mass or more. When the polystyrene resin content is above the lower limit of the above value, the moldability of the foamed layer 10 can be further improved and the rigidity of the molded article can be increased. The upper limit of the polystyrene resin content is not particularly limited, and may be 100 parts by mass per 100 parts by mass of thermoplastic resin constituting the foamed layer 10.

[0031] The content of recycled raw materials relative to 100 parts by mass of thermoplastic resin constituting the foamed layer 10 is preferably 5 to 70 parts by mass, more preferably 10 to 65 parts by mass, and even more preferably 15 to 60 parts by mass. If the content of recycled raw materials is above the lower limit, the environmental burden can be further reduced. If the content of recycled raw materials is below the upper limit, the moldability of the foamed layer 10 can be further improved, and the rigidity of the molded article can be increased.

[0032] The foamed resin composition may contain polystyrene resins and thermoplastic resins other than recycled materials (optional resin for the foamed layer). Examples of optional resins for the foamed layer include virgin polyethylene, polyolefin resins such as polypropylene, and 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).

[0033] The foamed resin composition may also contain a heat-resistant resin. Examples of heat-resistant resins include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and polyphenylene ether resins.

[0034] The foamed resin composition contains a foaming agent. Examples of foaming agents include hydrocarbons such as propane, butane, and pentane; halogenated hydrocarbons such as tetrafluoroethane, chlorodifluoroethane, and difluoroethane; and among these, hydrocarbons are preferred, and butane is preferred. As for butane, n-butane or isobutane may be used individually, or n-butane and isobutane may be used in any proportion. These foaming agents may be used individually or in combination of two or more.

[0035] The amount of foaming agent in the foamed resin composition is preferably, for example, 0.1 to 10 parts by mass, more preferably 1 to 7 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of thermoplastic resin.

[0036] The foamed resin composition may contain other components besides the thermoplastic resin and foaming agent (hereinafter also referred to as "optional foaming layer components"). Examples of optional foaming layer components include foam regulators, stabilizers, UV absorbers, antioxidants, colorants, deodorants, lubricants, flame retardants, and antistatic agents. The type of optional component in the foam layer is determined by considering the physical properties required for the foam layer 10. The optional components of the foam layer may be a single component or a combination of two or more components.

[0037] Examples of foam modifiers include mixtures of inorganic powders such as talc and silica. These foam modifiers increase the percentage of closed cells in the foamed layer 10, making it easier to form the foamed layer. Examples of stabilizers include calcium-zinc-based heat stabilizers, tin-based heat stabilizers, and lead-based heat stabilizers. Examples of UV absorbers include cesium oxide-based UV absorbers and titanium dioxide-based UV absorbers. Examples of antioxidants include cerium oxide, cerium oxide / zirconia solid solution, cerium hydroxide, carbon, carbon nanotubes, titanium dioxide, and fullerenes. Examples of colorants include titanium dioxide, carbon black, titanium yellow, iron oxide, ultramarine, cobalt blue, calcined pigments, metallic pigments, mica, pearl pigments, zinc oxide, precipitated silica, and cadmium red. Examples of deodorizers include silica, zeolite, zirconium phosphate, and hydrotalcite calcined products.

[0038] The content of the optional foaming layer component in the foamed resin composition is preferably, for example, 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5.0 parts by mass, per 100 parts by mass of thermoplastic resin. When the content of the optional foaming layer component is above the lower limit, the effects derived from the optional foaming layer component can be exhibited. When the content of the optional foaming layer component is below the upper limit, clogging of dies and the like can be prevented more effectively, and the appearance of the foaming layer 10 can be improved.

[0039] The thickness T10 of the foam layer 10 is preferably 0.3 to 5.0 mm, more preferably 0.4 to 3.0 mm, and even more preferably 0.5 to 2.5 mm. If the thickness T10 of the foam layer 10 is above the lower limit, the impact resistance of the foam container can be further improved. If the thickness T10 of the foam layer 10 is below the upper limit, the foam container can be made lighter and its moldability can be further improved. The thickness T10 of the foam layer 10 is determined in the same way as the thickness T1 of the laminated foam sheet 1.

[0040] The basis weight of foam layer 10 is, for example, 50-600 g / m². 2 Preferably, 90-500 g / m² 2 More preferably, 150-400 g / m 2This is even more preferable. If the basis weight of the foam layer 10 is above the lower limit, the impact resistance of the foam container can be further improved. If the basis weight of the foam layer 10 is below the upper limit, the molded body can be made lighter and moldability can be further improved. In addition, if the basis weight of the foam layer 10 is below the upper limit, the heating time during heat molding will not be too long, and the productivity of the molded body can be further improved. The basis weight of the foamed layer 10 is determined in the same way as the basis weight of the laminated foamed sheet 1.

[0041] The apparent density of the foam layer 10 is, for example, 0.050 to 0.666 g / cm³. 3 Preferably, 0.066 to 0.500 g / cm³ 3 More preferably, 0.100~0.333 g / cm³ 3 This is even more preferable. If the apparent density of the foam layer 10 is above the lower limit, the impact resistance of the molded body can be further improved. If the apparent density of the foam layer 10 is below the upper limit, the molded body can be made lighter and its thermal insulation properties can be further improved. The apparent density of the foam layer 10 is determined in the same way as the apparent density of the laminated foam sheet 1.

[0042] The foaming ratio of the foamed layer 10 is preferably 1.5 to 20 times, more preferably 2 to 15 times, and even more preferably 3 to 10 times. If the foaming ratio of the foamed layer 10 is above the lower limit, the impact resistance of the molded article can be further improved. If the foaming ratio of the foamed layer 10 is below the upper limit, the moldability of the foamed layer 10 can be further improved. The foaming ratio of foam layer 10 is 1, which is the apparent density of foam layer 10 (g / cm³). 3 This is the value obtained by dividing by ")".

[0043] The average bubble diameter of the foamed layer 10 is preferably 80 to 450 μm, more preferably 150 to 400 μm, and even more preferably 200 to 350 μm. If the average bubble diameter of the foamed layer 10 is above the lower limit, the impact resistance of the molded article can be further improved. If the average bubble diameter of the foamed layer 10 is below the upper limit, the surface smoothness of the molded article can be further improved. The average bubble diameter of the foam layer 10 can be measured in accordance with the method described in ASTM D2842-69.

[0044] The closed-cell ratio of the foam layer 10 is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and may be 100%. The closed-cell ratio of the foam layer 10 can be measured in accordance with the method described in JIS K7138:2006 "Rigid foamed plastics - Method for determining open-cell ratio and closed-cell ratio".

[0045] <Non-foaming layer> The non-foamed layer 20 contains a polyolefin resin and is a layer in which substantially no air bubbles are formed. In addition, the non-foamed layer 20 is a layer that substantially does not contain a blowing agent. Although the non-foamed layer 20 is a layer in which substantially no air bubbles are formed, it may contain a small amount of blowing agent when the non-foamed layer 20 is formed by a co-extrusion method, etc.

[0046] The non-foamed layer 20 is a layer containing a layer of polyolefin resin. The non-foamed layer 20 may be a single layer or a multilayer structure of two or more layers. The non-foamed layer 20 may be formed by curing a non-foamed resin composition containing a polyolefin resin, or a non-foamed sheet formed from a non-foamed resin composition containing a polyolefin resin may be laminated to the foamed layer 10, or a laminate thereof may also be used. Examples of polyolefin resins include polyethylene resins and polypropylene resins. Among polyolefin resins, polyethylene resins are preferred because they exhibit good moldability when mixed with polystyrene resins. Examples of polyethylene resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). Among polyethylene resins, HDPE is preferred because it can provide higher container strength. Examples of non-foamed sheets include unoriented polypropylene (CPP) film, unoriented polystyrene (CPS) film, and laminated (CPPS) films thereof, with CPPS film being preferred among them.

[0047] In this specification, high-density polyethylene refers to a resin density of 0.940 g / cm³. 3 More than 0.970g / cm 3 The following polyethylene resins are referred to. Medium-density polyethylene refers to a resin density of 0.930 g / cm³. 3 Super 0.940g / cm 3 This refers to polyethylene resins with a density of less than 0.910 g / cm³. Low-density polyethylene is defined as a resin with a density of 0.910 g / cm³. 3 More than 0.930g / cm 3 The following polyethylene-based resins are referred to. Linear low-density polyethylene refers to low-density polyethylene in a linear configuration. The resin density of polyethylene-based resins can be measured in accordance with the method described in JIS K7112:1999 "Plastics - Method for determining the density and specific gravity of non-foamed plastics," Method B (pycnometer method).

[0048] Polyolefin resins are preferably made of high-density polyethylene and low-density polyethylene, as this enhances their lamination properties. When the polyolefin resin contains high-density polyethylene and low-density polyethylene, the mass ratio of high-density polyethylene to low-density polyethylene (high-density polyethylene:low-density polyethylene) is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. When the mass ratio of high-density polyethylene to low-density polyethylene is 10:90 or higher, drawdown during molding of the foam layer 10 can be further suppressed. When the mass ratio of high-density polyethylene to low-density polyethylene is 90:10 or lower, the melt elongation of the mixed resin can be further increased, and the take-up stability can be further improved. Here, "lamination processability" is one of the indicators used to evaluate the moldability of the non-foamed layer 20 when extruding the mixed resin, and can be evaluated from neck-in and take-up stability. In this specification, "neck-in" refers to the neck-in phenomenon, which is the phenomenon in which the thickness of both ends of the non-foamed layer 20 in the width direction (TD direction) increases. "Take-up stability" refers to suppressing fluctuations in the thickness of the non-foamed layer 20 when the take-up speed is increased when taking up the non-foamed layer 20. By improving the lamination properties, the moldability of the non-foamed layer 20 can be further enhanced, and the productivity of the laminated foamed sheet 1 can be further increased.

[0049] The polyolefin resin contained in the non-foaming layer 20 is preferably a plant-derived resin because it can reduce the environmental impact. Examples of plant-derived resins include polymers derived from plant materials such as sugarcane and corn. "Derived from plant materials" refers to polymers synthesized or extracted from plant materials. For example, "derived from plant materials" refers to polymers in which monomers synthesized or extracted from plant materials are polymerized. "Monomers synthesized or extracted from plant materials" includes monomers synthesized using compounds synthesized or extracted from plant materials as raw materials. Plant-derived resins include those in which a portion of the monomers are "derived from plant materials". Examples of plant-derived resins include so-called bio-PE, bio-PP, plant-derived polyethylene resins, and plant-derived polypropylene resins.

[0050] When the polyolefin resin is a polyethylene resin, the MFR of the polyethylene resin is preferably 0.1 to 15.0 g / 10 min, and more preferably 0.2 to 8.0 g / 10 min. If the MFR of the polyethylene resin is above the lower limit, the fluidity during melting is good, and productivity can be further increased. If the MFR of the polyethylene resin is below the upper limit, the elongation during molding is good, and moldability can be further increased. In this specification, the MFR of polyethylene resin refers to the value measured in accordance with Method B described in JIS K7210:1999 "Plastics - Test methods for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics," under the conditions of a test temperature of 190°C, a test load of 21.18 N, and a preheating time of 5 minutes.

[0051] When the polyolefin resin is a polypropylene resin, the MFR of the polypropylene resin is preferably 2.0 to 20.0 g / 10 min, and more preferably 4.0 to 14.0 g / 10 min. If the MFR of the polypropylene resin is above the lower limit, the fluidity during melting is good, and productivity can be further increased. If the MFR of the polypropylene resin is below the upper limit, the elongation during molding is good, and moldability can be further increased. In this specification, the MFR of polypropylene resin refers to the value measured in accordance with Method B described in JIS K7210:1999 "Plastics - Test methods for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics," under the conditions of a test temperature of 230°C, a test load of 21.18 N, and a preheating time of 5 minutes.

[0052] The content of polyolefin resin relative to 100 parts by mass of thermoplastic resin constituting the non-foamed layer 20 is preferably 2 to 50 parts by mass, and more preferably 3 to 40 parts by mass. If the polyolefin resin content is above the lower limit, drawdown during molding can be further suppressed. If the polyolefin resin content is below the upper limit, the container strength and peel strength can be further increased.

[0053] The non-foaming resin composition may also contain resins other than polyolefin resins (any resin for the non-foaming layer). Examples of optional resins for the non-foamed layer include polystyrene resins. The polystyrene resin of the optional non-foamed layer is the same as the polystyrene resin of the foamed layer 10, and the polystyrene resin of the optional non-foamed layer may be the same as or different from the polystyrene resin of the foamed layer 10. In particular, it is preferable that the optional non-foamed layer contains a high-impact polystyrene resin. By including a high-impact polystyrene resin in the optional non-foamed layer, the impact resistance of the molded article can be further enhanced.

[0054] The non-foaming resin composition may contain a compatibilizer. By including a compatibilizer in the non-foaming resin composition, the compatibility between the polyolefin resin and the non-foaming layer's arbitrary resin (e.g., polystyrene resin) can be improved, thereby further enhancing the physical properties of the laminated foam sheet 1.

[0055] The compatibilizer can be determined by considering the combination of resins contained in the non-foaming resin composition, for example, a styrene-based thermoplastic elastomer. The styrene-based thermoplastic elastomer contained in the non-foaming resin composition is the same as the styrene-based thermoplastic elastomer contained in the recycled raw materials blended into the foaming resin composition. The styrene-based thermoplastic elastomer contained in the non-foaming resin composition may be the same as or different from the styrene-based thermoplastic elastomer contained in the recycled raw materials.

[0056] When a non-foaming resin composition contains a compatibilizer, the compatibilizer content is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, based on 100 parts by mass of the total amount of thermoplastic resin constituting the non-foaming resin composition. Compatibility can be enhanced when the compatibilizer content is within the above numerical range.

[0057] The thickness T20 of the non-foamed layer 20 is preferably 15 to 400 μm, more preferably 30 to 300 μm, even more preferably 50 to 200 μm, and particularly preferably 90 to 160 μm. If the thickness T20 of the non-foamed layer 20 is greater than or equal to the lower limit value mentioned above, the strength of the molded body can be further increased. If the thickness T20 of the non-foamed layer 20 is below the above upper limit, the moldability can be further improved. The thickness T20 of the non-foamed layer 20 is the average value of the thicknesses of 10 arbitrary points observed with a microscope or the like when the laminated foam sheet 1 is cut in the thickness direction.

[0058] The non-foaming resin composition may contain other components besides thermoplastic resins (hereinafter also referred to as "optional non-foaming layer components"). Examples of optional non-foaming layer components include the same components as those described above for the optional foaming layer components. When a non-foaming resin composition contains an optional non-foaming layer component, the content of the optional non-foaming layer component is preferably, for example, 0.05 to 10 parts by mass, more preferably 0.1 to 5.0 parts by mass, and even more preferably 0.3 to 3.0 parts by mass, based on 100 parts by mass of the total amount of thermoplastic resin constituting the non-foaming resin composition. If the content of the optional non-foaming layer component is above the lower limit, the effects derived from the optional non-foaming layer component can be exhibited. If the content of the optional non-foaming layer component is below the upper limit, the fluidity during melting is good, and productivity can be further increased.

[0059] (Manufacturing method) The method for manufacturing a laminated foam sheet comprises a recycled raw material manufacturing process and a foam layer manufacturing process. The recycled raw material manufacturing process involves melting and kneading recycled materials containing polystyrene resin and polyolefin resin in the presence of a styrene-based thermoplastic elastomer to obtain recycled raw materials. The foamed layer manufacturing process involves extruding a foamed resin composition containing recycled raw materials obtained in the recycled raw material manufacturing process, a foaming agent, and optionally a new thermoplastic resin into a sheet, and then foaming it to obtain a foamed layer.

[0060] An example of a method for manufacturing the laminated foam sheet of the present invention will be described. As shown in Figure 2, the manufacturing method of this embodiment includes a recycled raw material manufacturing step S10, a foamed layer manufacturing step S20, and a lamination step S30.

[0061] The recycled raw material manufacturing process S10 of this embodiment includes a first melting and kneading operation S12 and a pelletizing operation S14. First, a styrene-based thermoplastic elastomer is added to the recycled material that will become the raw material for the recycled material, and these are melt-kneaded to form a recycled compound (first melt-kneading operation S12). That is, in the first melt-kneading step S12, the recycled material is melt-kneaded in the presence of the styrene-based thermoplastic elastomer. By going through the first melt-kneading step S12, the polystyrene-based resin and polyolefin-based resin contained in the recycled material become more compatible, resulting in a recycled material in which the polyolefin-based resin is dispersed more finely and uniformly within the polystyrene-based resin. By using such a recycled material, the moldability of the resulting foamed sheet can be improved. However, if the recycled material contains a sufficient amount of styrene-based thermoplastic elastomer, it is not necessary to add new styrene-based thermoplastic elastomer in the first melt-kneading step S12.

[0062] Examples of equipment used in the first melting and mixing operation S12 include extruders, short-screw extruders, twin-screw extruders, and the like.

[0063] Examples of recycled materials include scraps generated when the laminated foam sheet 1 of the above embodiment is molded into containers, etc., and used materials that have been collected. Scraps are the remaining material after the laminated foam sheet 1 is punched out into a predetermined shape when it is molded into containers, etc.

[0064] The polyolefin resin content in recycled products is preferably 4 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 6 to 14 parts by mass, per 100 parts by mass of polystyrene resin. If the polyolefin resin content is above the lower limit, the degree of variation in the quality of the foamed sheet can be suppressed. If the polyolefin resin content is below the upper limit, compatibility can be further improved, and moldability can be further enhanced.

[0065] In the first melt-kneading operation S12, the content of styrene-based thermoplastic elastomer (including styrene-based thermoplastic elastomer derived from recycled material) per 100 parts by mass of recycled material is preferably 0.5 to 20 parts by mass, and more preferably 1.5 to 15 parts by mass. If the content of styrene-based thermoplastic elastomer is above the lower limit, the polyolefin resin can be dispersed more finely and uniformly in the polystyrene resin. If the content of styrene-based thermoplastic elastomer is below the upper limit, the foam layer will not become soft, and the strength of the molded article can be further increased.

[0066] The melting temperature in the first melt mixing step S12 is preferably, for example, 210 to 270°C. If the melting temperature is above the lower limit, the polyolefin resin can be dispersed more finely and uniformly in the polystyrene resin. If the melting temperature is below the upper limit, the generation of volatile components due to thermal degradation can be further suppressed.

[0067] Next, the recycled mixture obtained in the first melt-kneading step S12 is extruded from the die to obtain recycled pellets (recycled pellets), which are recycled raw materials (pelletization operation S14). Through the pelletization operation S14, the recycled raw materials are obtained in the form of pellets, which are easy to handle.

[0068] The size of the recycled pellets is not particularly limited and can be determined as appropriate, taking into consideration the size of the virgin pellets, as described later.

[0069] The foamed layer manufacturing process S20 of this embodiment includes a second melting and kneading operation S22, an extrusion foaming operation S24, and a cooling operation S26.

[0070] An example of a manufacturing apparatus used in the foam layer manufacturing process S20 will be described. The foam sheet manufacturing apparatus 100 shown in Figure 3 is a device for obtaining foam sheets by extrusion molding. The manufacturing apparatus 100 comprises an extruder 110, a foaming agent supply source 118, a circular die 120, a mandrel 130, and two winding machines 140. The extruder 110 is a so-called single-type extruder. The extruder 110 is equipped with a hopper 114. A foaming agent supply source 118 is connected to the extruder 110. A circular die 120 is connected to the extruder 110. Downstream of the circular die 120 is a mandrel 130 equipped with a cutter 132. A cooling fan (not shown) is provided between the circular die 120 and the mandrel 130. Furthermore, the extruder 110 of the manufacturing apparatus 100 may be an extruder other than a single-type extruder, or it may be a so-called tandem-type extruder. Furthermore, the extruder 110 of the manufacturing apparatus 100 may be a single-screw extruder or a multi-screw extruder such as a twin-screw extruder.

[0071] The raw materials that make up the foam layer (recycled materials, virgin resin, and optional components for the foam layer) are fed from the hopper 114 into the extruder 110. In the extruder 110, the raw materials are heated to a desired temperature and mixed to form a resin molten product (second melt-kneading operation S22). A blowing agent is supplied from the blowing agent supply source 118 to the extruder 110, and the blowing agent is mixed with the resin molten product to form a foamable resin composition. The heating temperature is determined appropriately, taking into account the type of resin, etc., within a range where the resin melts but no arbitrary components are altered.

[0072] The foamed resin composition is further mixed in the extruder 110. After being heated to a desired temperature, the foamed resin composition is guided into the resin channel in the circular die 120. The foamed resin composition guided into the resin channel is discharged from the outlet of the circular die 120, and the foaming agent foams up to form a cylindrical foamed layer 10a (extrusion foaming operation S24). This foamed layer 10a is formed solely of foam. The cylindrical foam layer 10a is guided onto the mandrel 130 while cooling air blown from a cooling fan is applied to it. The cylindrical foam layer 10a passes over the outer surface of the mandrel 130, cools to a desired temperature and hardens into a foamed material (cooling operation S26), and is then cut into two pieces by the cutter 132 to become foam layers 10 (cutting operation). The foam layers 10 are then wrapped around guide rolls 142 and 144, respectively, and wound onto the winding machine 140 to become foam sheet rolls 4.

[0073] The shear rate for the foamed resin composition at the discharge port of the circular die 120 is, for example, 1000 to 10000 s. -1 It is preferable.

[0074] Lamination step S30 is a step of providing a non-foamed layer 20 on one or both sides of the obtained foamed layer 10. In this embodiment, the lamination step S30 involves extruding the molten non-foaming resin composition onto the surface of the foamed layer 10, and then curing the extruded non-foaming resin composition to form a non-foaming layer 20. Alternatively, in the lamination step S30, a pre-prepared non-foaming sheet may be placed on one or both sides of the foamed layer 10 and bonded together by heat fusion or the like.

[0075] (Molded body) The molded article of the present invention is obtained by molding the foamed sheet of the present invention described above. Examples of molded products include trays with a plan view shape such as a perfect circle, ellipse, semicircle, polygon, or fan shape; bowl-shaped containers; cylindrical or rectangular containers with bottoms; containers with lids such as those for natto; and lids that are attached to the container body.

[0076] As described above, the foamed sheet of the present invention has a foamed layer made from recycled raw materials that have been melt-kneaded with styrene-based thermoplastic elastomer in advance, and therefore exhibits excellent moldability.

[0077] (Other embodiments) In the embodiments described above, the foam layer is a single layer, but the present invention is not limited thereto, and the foam layer may have a multilayer structure of two or more layers. When the foam layer has a multilayer structure, the composition of each layer may be the same or different. An example of a multilayer foamed layer is a two-layer structure consisting of a heat-resistant foamed layer containing a heat-resistant resin such as styrene-methacrylic acid copolymer, and a non-heat-resistant foamed layer that does not contain a heat-resistant resin.

[0078] In the embodiments described above, a non-foamed layer is present, but the present invention is not limited thereto, and the foamed sheet of the present invention may consist only of a foamed layer. [Examples]

[0079] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0080] (Manufacturing Example 1) Method for manufacturing recycled raw materials (MMA-based - R1~R3, R5) <Manufacturing of recycled products> A laminated foam sheet made from recycled materials was obtained using the following procedure, according to the configuration shown in Table 1. As the base polymer for the heat-resistant foam layer, 80 parts by mass of styrene-methacrylic acid copolymer (product name "G9001", manufactured by PS Japan Co., Ltd.) and 20 parts by mass of high-impact polystyrene resin (product name "H8117", manufactured by PS Japan Co., Ltd.) were mixed, and 1.0 part by mass of talc masterbatch (product name "DSM1401A", manufactured by Toyo Styrene Co., Ltd.) was added as a foam regulator to a tandem extruder, where the mixture was mixed, melted, and kneaded. 3 parts by mass of butane gas (isobutane) was injected under pressure into the molten material at a predetermined position, kneaded, and then supplied to a merger mold. In a separate tandem extruder, the material for forming the non-heat-resistant foam layer was melted and kneaded, and then supplied to the aforementioned confluence mold. As the material for forming the non-heat-resistant foam layer, 95 parts by mass of polystyrene resin (product name "HRM12", manufactured by Toyo Styrene Co., Ltd.) and 5 parts by mass of high-impact polystyrene resin (product name "E641N", manufactured by Toyo Styrene Co., Ltd.) were mixed as the base polymer, and 1.0 part by mass of talc masterbatch (product name "DSM1401A", manufactured by Toyo Styrene Co., Ltd.) was added as a foam regulator to a tandem extruder, where the mixture was mixed, melted, and kneaded. 3 parts by mass of butane gas (isobutane) was injected under pressure into the molten material at a predetermined position, kneaded, and then supplied to a merger mold. At this time, the amount (mass) of the heat-resistant foam layer and the non-heat-resistant foam layer supplied to the merging mold was adjusted to be equal. After the two types of molten mixtures supplied to the merging mold were merged and laminated within the merging mold, the cylindrical foam was extruded from the circular die, cooled on a predetermined mandrel, cut and formed into a sheet, and a foamed sheet (raw material sheet) having a laminated structure of a heat-resistant foam layer and a non-heat-resistant foam layer was obtained and wound up. The obtained raw material sheet had a thickness of 1.75 mm and a basis weight of 180 g / m². 2 The apparent density is 0.103 g / cm³. 3 That was the case.

[0081] According to the specifications for the first non-foaming layer in Table 1, a polyolefin resin, a polystyrene resin (high-impact polystyrene resin, general-purpose polystyrene resin), and a compatibilizer (SEBS polymer) were blended and mixed in a mixing drum to obtain the first non-foaming resin composition. In the composition of the first layer, those indicated with "-" in the blending amount indicate that they were not blended. On one side of the raw material sheet (foamed layer) (the surface of the heat-resistant foamed layer), the first layer of non-foamed resin composition is extruded using an extruder (T-die) with a basis weight of 120 g / m². 2 The material was adjusted and extruded, then laminated using the T-die method at a take-up speed of 13 m / min to create the first non-foamed layer and obtain a laminated foamed sheet. Next, a non-foamed sheet (a 50 μm thick CPPS dry laminate film: a dry laminate film made by laminating a 30 μm thick unoriented polypropylene film and a 20 μm thick unoriented polystyrene film with an adhesive layer in between) was laminated to the surface of the first layer by a heat-pressing method, such that the unoriented polystyrene film side was adhered to the surface of the first layer. In this way, a laminated foamed sheet was obtained having the first and second non-foamed layers in this order on one side of the foamed layer. The resulting laminated foam sheet had a thickness of 1.87 mm (the second layer (CPPS dry laminate film) was 50 μm thick, the first layer was 120 μm thick, and the foam layer was 1.70 mm thick), and a basis weight of 348 g / m². 2 The apparent density is 0.186 g / cm³. 3 That was the case.

[0082] <Manufacturing of recycled materials> A repellet system was used to produce recycled pellets, which are recycled raw materials. The repellet system used in the manufacturing process is shown in Figure 4. The pellet repellet system 300 in Figure 4 includes a twin-screw extruder 310, a cutting chamber 320, a dewatering dryer 322, a pump 324, a water tank 326, a heated vibrating screen 328, and a storage container 330. The cutting chamber 320 is located at the tip of the twin-screw extruder 310. The cutting chamber 320 is connected to the dewatering dryer 322 via piping 321. The cutting chamber 320 is connected to the dewatering dryer 322 via piping 323. The pump 324 and the water tank 326 are connected to piping 323. The dewatering dryer 322 is connected to the heated vibrating screen 328 via piping 327. The heated vibrating screen 328 is connected to the storage container 330 via piping 329. The twin-screw extruder 310 has a hopper 312 and a vent hole 314.

[0083] Next, we will explain the manufacturing method for recycled pellets. The recycled material obtained in the "manufacturing of recycled materials" described above (a laminated foam sheet having a foamed layer and a non-foamed layer in that order as the first and second layers) was crushed in a crusher to obtain resin chips. Pump 324 was started, and the cooling liquid (70°C) in the water tank 326 was circulated through piping 323, the cutting chamber 320, and piping 321 in that order. Exhaust was performed through the vent hole 314 to reduce the pressure inside the twin-screw extruder 310. Resin chips were placed in hopper 312, melted and kneaded in twin-screw extruder 310 (φ75mm), and the molten material was extruded from the tip (φ1.2mm) into the cooling liquid in cutting chamber 320, where it was cut with a cutter to form pellets. The pellets, along with the cooling liquid, were transferred to dewatering dryer 322 via piping 321. The transferred pellets were dried in dewatering dryer 322 and then transferred to heated vibrating sieve machine 328 via piping 327. The pellets were crystallized and classified in heated vibrating sieve machine 328, which was heated to 160°C, to obtain recycled raw materials (MMA-based - R1~R3, R5) for each example of pellets with the desired particle size.

[0084] (Manufacturing Example 2) Method for manufacturing recycled raw materials (MMA-based R4) <Manufacturing of recycled products> A recycled pellet raw material (MMA-based-R4) was obtained in the same manner as in Manufacturing Example 1, except that the first layer was not provided in the laminated foam sheet of the recycled product.

[0085] (Manufacturing Example 3) Manufacturing method for recycled PPE (PPE-R1~R3) A laminated foam sheet made from recycled materials was obtained using the following procedure, according to the configuration shown in Table 3. 30 parts by mass of polyphenylene ether (PPE) resin (product name "Noryl EFN4230", manufactured by Sabic Co., Ltd.) and 70 parts by mass of polystyrene resin (product name "XC515", manufactured by DIC Corporation) were mixed, and 1.0 part by mass of talc masterbatch (product name "DSM1401A", manufactured by Toyo Styrene Co., Ltd.) was added as a foam regulator to a tandem extruder, where the mixture was mixed, melted, and kneaded. 4 parts by mass of butane gas (isobutane) was injected under pressure into the molten material at a predetermined position and kneaded. The cylindrical foam was then extruded from a circular die, cooled on a predetermined mandrel, cut, and formed into a sheet to obtain a raw material sheet (foamed sheet) with a single-layer structure of heat-resistant foam, which was then wound up. The obtained raw material sheet had a thickness of 1.65 mm and a basis weight of 140 g / m². 2 The apparent density is 0.085 g / cm³. 3 That was the case. Next, in the same manner as in Manufacturing Example 1, a first layer and a second layer were provided to obtain a laminated foam sheet (recycled PPE: PPE-R1~R3) having the first and second non-foamed layers in that order on one side of the foamed layer. The resulting laminated foam sheet had a thickness of 1.77 mm (the second layer (CPPS dry laminate film) was 50 μm thick, the first layer was 120 μm thick, and the foam layer was 1.60 mm thick), and a basis weight of 308 g / m². 2 The apparent density is 0.174 g / cm³. 3 That was the case.

[0086] <Manufacturing of recycled materials> The process was the same as in Manufacturing Example 1, except that the recycled material was the laminated foam sheet obtained in Manufacturing Example 3. Recycled pellet raw material (PPE-based - R1~R3)

[0087] (Manufacturing Example 4) Method for manufacturing recycled raw materials (PPE-based - R4~R5) Recycled pellet raw materials (PPE-based - R4~R5) were obtained in the same manner as in Manufacturing Example 3, except that the first layer was not provided in the laminated foam sheet of the recycled product.

[0088] (Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-2) Following the configuration shown in Table 2, a foamed sheet (raw material sheet) with a two-layer structure consisting of a heat-resistant foamed layer and a non-heat-resistant foamed layer was obtained in the same manner as in Manufacturing Example 1. A non-foamed sheet (a 50 μm thick CPPS dry laminate film: a dry laminate film made by laminating a 30 μm thick unoriented polypropylene film and a 20 μm thick unoriented polystyrene film with an adhesive layer in between) was laminated to the surface of the heat-resistant foamed layer of the obtained raw material sheet using a heat-pressing method, such that the unoriented polystyrene film side was adhered to the surface of the foamed layer. In this way, a laminated foamed sheet having a non-foamed layer on one side of the foamed layer was obtained. The obtained laminated foam sheets were evaluated for their appearance during molding and their elongation during molding, and the results are shown in the table.

[0089] (Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-2) According to the configuration in Table 4, a foamed sheet (raw material sheet) was obtained in the same manner as in Manufacturing Example 3. A non-foamed sheet (a 50 μm thick CPPS dry laminate film: a dry laminate film made by laminating a 30 μm thick unoriented polypropylene film and a 20 μm thick unoriented polystyrene film with an adhesive layer in between) was laminated to the surface of the heat-resistant foamed layer of the obtained raw material sheet using a heat-pressing method, such that the unoriented polystyrene film side was adhered to the surface of the foamed layer. In this way, a laminated foamed sheet having a non-foamed layer on one side of the foamed layer was obtained. The obtained laminated foam sheets were evaluated for their appearance during molding and their elongation during molding, and the results are shown in the table.

[0090] (Evaluation method) <Manufacturing of foamed containers> After leaving the laminated foam sheets from each example at 27±3℃ and 60±5% relative humidity for 24 hours, a flat rectangular test piece measuring 700mm in length and 1040mm in width was cut from the laminated foam sheet. Next, a single-shot molding machine (manufactured by Tosei Sangyo Co., Ltd., product name "FM-3A") was used. The average temperature of the upper heater of this single-shot molding machine was set to 270°C, the average temperature of the lower heater to 220°C, and the ambient temperature to 155°C. Next, the above test specimens were introduced into a single-shot molding machine and heated for 15 seconds. Then, 18 foamed containers with an opening at the top were produced for each example by thermoforming. The container shape was a circular foamed container in plan view (opening diameter 190 mm, bottom diameter 170 mm, height 50 mm) with a thermoplastic resin layer on the inner surface of the container.

[0091] ≪Appearance during molding≫ The foamed containers obtained in each example were visually observed, and their appearance during molding was evaluated based on the following evaluation criteria.

[0092] Evaluation Criteria Excellent: All 18 pieces were perfectly molded. Good: Some of the 18 containers showed variations in color intensity on the surface of the foam layer. Unacceptable: Burning was observed in some of the 18 containers.

[0093] <<Elongation during molding>> The foamed containers obtained in each example were held by hand, and their strength was evaluated based on the evaluation criteria below.

[0094] Evaluation Criteria Excellent: All 18 pieces exhibit uniform strength when the sides of the container are pressed from the outside. Good: Some of the 18 containers have weak points on the sides when pressed from the outside. Acceptable: All 18 containers have weak points on their sides when pressed from the outside. Unacceptable: Some of the 18 containers showed signs of cracking or wrinkling.

[0095] [Table 1]

[0096] [Table 2]

[0097] [Table 3]

[0098] [Table 4]

[0099] As shown in Tables 2 and 4, in all of Examples 1-1 to 1-5 and 2-1 to 2-5 to which the present invention was applied, the sheet appearance and sheet elongation during molding were "good" or "excellent". Comparative Examples 1-1 and 2-1, which used recycled materials that did not contain SEBS polymer, showed "acceptable" sheet elongation during molding. Comparative Examples 1-2, which used recycled raw materials that did not contain SEBS polymer and incorporated 9 parts by mass of SEBS polymer during the production of the foamed sheet, showed "acceptable" sheet elongation during molding. Comparative Example 2-2, which used recycled raw materials that did not contain SEBS polymer and incorporated 15 parts by mass of SEBS polymer during the production of the foamed sheet, showed that the sheet appearance and sheet elongation during molding were "unacceptable". These results confirm that the moldability can be improved by applying the present invention. [Explanation of Symbols]

[0100] 1. Polystyrene foam sheet 10 Foam layer 20 Non-foaming layer S10 Recycled Material Manufacturing Process S20 Foam layer manufacturing process S30 Lamination process

Claims

1. Having a foamed layer, The foamed layer contains a thermoplastic resin including a polystyrene resin, The aforementioned thermoplastic resin contains recycled materials, The recycled material is a polystyrene foam sheet containing polystyrene resin, polyolefin resin, and styrene thermoplastic resin elastomer.

2. The recycled material is derived from a laminate having a foam and a non-foamed material provided on at least one surface of the foam. The foam contains a polystyrene resin, The non-foamed material comprises a polyolefin resin, as described in claim 1, for a polystyrene resin foam sheet.

3. The non-foamed material comprises a styrene-based thermoplastic resin elastomer, as described in claim 2, for the polystyrene-based resin foam sheet.

4. The polystyrene-based resin foam sheet according to claim 1 or 2, wherein one or both sides of the foam layer have a non-foamed layer containing a thermoplastic resin.

5. A method for producing a polystyrene resin foam sheet having a foamed layer containing a thermoplastic resin, A recycled material manufacturing process involves melt-kneading recycled materials containing polystyrene resin and polyolefin resin in the presence of a styrene-based thermoplastic resin elastomer to obtain recycled raw materials. A method for producing a polystyrene resin foam sheet, comprising a foaming resin composition containing the recycled raw material, a foaming agent, and optionally a new thermoplastic resin, which is extruded into a sheet and foamed to obtain the foamed layer.

6. The aforementioned recycled product includes a laminate, The laminate comprises a foam and a non-foamed material provided on at least one surface of the foam. The foam contains a polystyrene resin, The method for producing a polystyrene resin foam sheet according to claim 5, wherein the non-foamed material comprises a polyolefin resin.

7. The method for producing a polystyrene-based resin foam sheet according to claim 6, wherein the non-foamed material comprises a styrene-based thermoplastic resin elastomer.

8. The method for producing a polystyrene-based resin foam sheet according to claim 5 or 6, wherein the recycled material production step is to obtain the recycled material in pellet form.

9. A method for producing a polystyrene-based resin foam sheet according to claim 5 or 6, comprising a lamination step of providing a non-foamed layer containing a thermoplastic resin on one or both sides of the foamed layer.

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