Method for producing recycled foamable styrene resin particles, method for producing recycled pre-foamed styrene resin particles, and method for producing recycled styrene resin foam molded articles

Abstract

This invention provides a method for producing recycled foamed styrene resin particles that have a high environmental impact, suppress odors characteristic of recycled materials, exhibit good spheroidization, and have excellent moldability. It also provides recycled foamed styrene resin particles obtained by such a production method, which suppress odors characteristic of recycled materials, exhibit good spheroidization, and have excellent moldability. Furthermore, it provides recycled pre-foamed styrene resin particles obtained from such recycled foamed styrene resin particles. Finally, it provides a recycled styrene resin foam molded article formed from such recycled pre-foamed styrene resin particles. [Solution] The method for producing foamed styrene-based resin particles according to an embodiment of the present invention is a method for producing recycled foamed styrene-based resin particles by injecting a foaming agent under pressure into a suspension containing recycled styrene-based resin raw material (A) and a dispersant, wherein when the glass transition temperature of the recycled styrene-based resin raw material (A) is Tg, the temperature at which the foaming agent is injected under pressure is T1, and the temperature at which the foaming agent is impregnated is T2, T1 is in the range of (Tg-50℃) or more and (Tg+40℃) or less, and T2 is in the range of (Tg-50℃) or more and (Tg+40℃) or less.

Description

Technical Field

[0001] The present invention relates to a method for producing recycled expandable styrene resin particles, a method for producing recycled pre-expanded styrene resin particles, and a method for producing a recycled styrene resin foam molded body.

Background Art

[0002] Foam molded bodies are used as heat insulating materials for housing and automobiles, heat insulating materials for building materials, embankment materials for foam styrene civil engineering methods, transportation packaging materials such as fish boxes and food containers, and cushioning materials because they are lightweight, have excellent heat insulation and mechanical strength. Among them, in-mold foam molded bodies produced from expandable particles (typically expandable polystyrene resin particles or pre-expanded styrene resin particles obtained by pre-expanding them) are widely used because they have advantages such as being easy to obtain a desired shape. Such a foam molded body is composed of a plurality of expandable particles fused to each other.

[0003] On the other hand, the amount of plastic waste is increasing year by year. Most of the plastic waste is disposed of by incineration or landfill, but this has become a major social problem such as environmental pollution, global warming, and a shortage of landfill disposal sites. Therefore, the recycling of plastic waste is strongly demanded socially, and various studies have been conducted on the recycling of plastic waste, such as in response to the implementation of the Home Appliance Recycling Law. Among the various recycling methods proposed, material recycling that reuses plastic waste as a plastic member of a product again has attracted attention from the viewpoints of resource circulation and reduction of environmental load, and such material recycling has also been studied for styrene resin foam molded bodies.

[0004] As a material recycling method for styrene resin foam molded bodies, conventionally, several methods have been proposed in which recovered raw materials are melted and extruded to obtain recovered pellets, and a foaming agent is impregnated into these to obtain recycled expandable styrene resin particles.

[0005] A method for obtaining recycled foamable styrene-based resin particles has been reported by impregnating recycled resin pellets, molded from recovered styrene-based resin foam molded products, with a foaming agent at a temperature of 100°C to 140°C (Patent Documents 1 and 2). Furthermore, a method for obtaining recycled foamable styrene-based resin particles has been reported by impregnating recycled resin pellets, molded from recovered styrene-based resin foam molded products, with a foaming agent at a temperature of 90°C to 130°C (Patent Document 3).

[0006] A method has been reported for obtaining recycled foamable styrene-based resin particles by injecting a foaming agent into recycled resin pellets molded from recovered styrene-based resin foam molded products at a temperature of 95°C to 130°C, then impregnating them (in the example, the injection temperature was 100°C and the impregnation temperature was 118°C), and then shaping the particles into spheres at 110°C to 130°C (Patent Document 4).

[0007] A method has been reported for obtaining recycled foamable styrene-based resin particles (recycled resin pellet content of 70% by mass or less) by adding styrene monomer to recycled resin pellets molded from recovered styrene-based resin foam molded products, polymerizing at 60°C to 105°C, then injecting a foaming agent by injection (in the example, the injection temperature was 100°C), and then impregnating with the foaming agent at an impregnation temperature of 100°C or higher (Patent Document 5). Another method has been reported for obtaining recycled foamable styrene-based resin particles (recycled resin pellet content of 20% to 70% by mass) by adding styrene monomer to recycled resin pellets molded from recovered styrene-based resin foam molded products, polymerizing at 60°C to 105°C, then injecting a foaming agent by injection (in the example, the injection temperature was 100°C), and then impregnating with the foaming agent at an impregnation temperature of 100°C to 140°C (Patent Document 6). Furthermore, a method has been reported for obtaining recycled foamable styrene-based resin particles (with a recycled resin pellet content of 30% to 70% by mass) by adding styrene monomer to recycled resin pellets molded from recovered styrene-based resin foam molded products, polymerizing at 60°C to 105°C, then injecting a blowing agent (injection temperature of 100°C in the example), and then impregnating with the blowing agent (impregnation temperature of 115°C in the example). It has also been reported that a flame retardant may be impregnated when impregnating with the blowing agent (Patent Document 7). In addition, a method has been reported for obtaining recycled foamable styrene-based resin particles (with a recycled resin pellet content of 20% to 70% by mass) by adding styrene monomer to recycled resin pellets molded from recovered styrene-based resin foam molded products, polymerizing at 60°C to 105°C, then injecting a blowing agent (injection temperature of 100°C in the example), and then impregnating with the blowing agent at an impregnation temperature of 90°C or higher (Patent Document 8).

[0008] However, conventional recycled foamed styrene resin particles have a problem in that they have an odor characteristic of recycled materials, especially compared to foamed styrene resin particles that do not use recovered raw materials. Furthermore, the recycled preliminary foamed styrene resin particles and recycled styrene resin foam molded articles obtained from them also have a problem in that they emit an odor characteristic of recycled materials to a noticeable degree.

[0009] Furthermore, recycled foamed styrene resin particles obtained by conventional methods have problems such as deviating from a spherical shape, poor filling properties into molding dies, poor surface elongation of molded articles, and low fusion rates between foamed particles in molded articles. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 3044942 [Patent Document 2] Patent No. 4234832 [Patent Document 3] Patent No. 4261676 [Patent Document 4] Patent No. 6788428 [Patent Document 5] Patent No. 4052193 [Patent Document 6] Japanese Patent Publication No. 2006-160905 [Patent Document 7] Patent No. 4912567 [Patent Document 8] Patent No. 5128246 [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide a method for producing recycled foamed styrene resin particles that have a high contribution to the environment, suppress odors characteristic of recycled materials, exhibit good spheroidization, and have excellent moldability. Furthermore, it is also to provide recycled foamed styrene resin particles obtained by such a production method that suppress odors characteristic of recycled materials, exhibit good spheroidization, and have excellent moldability. Furthermore, it is also to provide recycled pre-foamed styrene resin particles obtained from such recycled foamed styrene resin particles. Furthermore, it is also to provide a recycled styrene resin foam molded article formed from such recycled pre-foamed styrene resin particles. [Means for solving the problem]

[0012] [1] A method for producing recycled foamable styrene-based resin particles according to an embodiment of the present invention is a method for producing recycled foamable styrene-based resin particles by injecting a foaming agent under pressure into a suspension containing a recycled styrene-based resin raw material (A) and a dispersant, wherein when the glass transition temperature of the recycled styrene-based resin raw material (A) is Tg, the temperature at which the foaming agent is injected under pressure is T1, and the temperature at which the foaming agent is impregnated is T2, T1 is in the range of (Tg-50°C) or more and (Tg+40°C) or less, and T2 is in the range of (Tg-50°C) or more and (Tg+40°C) or less. [2] In the method for producing recycled foamable styrene-based resin particles described in [1] above, T1 may be in the range of (Tg-50°C) or higher and (Tg+40°C) or lower, and T2 may be in the range of (Tg-50°C) or higher and less than (Tg+10°C). [3] In the method for producing recycled foamable styrene resin particles described in [2] above, the dispersant may be at least one selected from the group consisting of organic dispersants and poorly soluble inorganic salts. [4] In the method for producing recycled foamable styrene-based resin particles described in [1] above, T1 may be in the range of (Tg+10°C) or higher and (Tg+30°C) or lower, and T2 may be in the range of (Tg+10°C) or higher and (Tg+30°C) or lower. [5] In the method for producing recycled foamed styrene-based resin particles described in [4] above, the dispersant may be magnesium pyrophosphate. [6] In the method for producing recycled foamable styrene-based resin particles described in any of [1] to [5] above, the blending ratio of the dispersant to 100 parts by mass of the recycled styrene-based resin raw material (A) may be 0.1 parts by mass to 2 parts by mass. [7] In the method for producing regenerated foamable styrene-based resin particles according to any of [1] to [6] above, the suspension may contain a surfactant. [8] In the method for producing recycled foamable styrene-based resin particles described in [7] above, the blending ratio of the surfactant to 100 parts by mass of the recycled styrene-based resin raw material (A) may be 0.005 parts by mass to 0.1 parts by mass. [9] In the method for producing recycled foamable styrene-based resin particles described in any of [1] to [8] above, polymer particles obtained by adding a styrene monomer to a suspension containing recycled styrene-based resin raw material particles (a) and polymerizing it may be used as the recycled styrene-based resin raw material (A).

[10] In the method for producing recycled foamable styrene-based resin particles described in any of [1] to [8] above, recycled styrene-based resin raw material particles (a) may be used as recycled styrene-based resin raw material (A).

[11] In the method for producing recycled foamable styrene resin particles described in [9] or

[10] above, the recycled styrene resin raw material particles (a) may be at least one selected from extruded strand pellets obtained by extruding spent styrene resin with an extruder and performing strand cutting, underwater cut pellets obtained by an underwater cut method in which spent styrene resin is extruded with an extruder and cut in water at the same time, and hot cut pellets obtained by a hot cut method in which spent styrene resin is cut and cooled immediately after coming out of the die of an extruder.

[12] Recycled foamable styrene resin particles according to embodiments of the present invention can be obtained by the method for producing recycled foamable styrene resin particles described in any of [1] to

[11] above.

[13] The recycled pre-expanded styrene resin particles according to an embodiment of the present invention are recycled pre-expanded styrene resin particles obtained by pre-expanding the recycled expandable styrene resin particles described in

[12] above, and the bulk expansion ratio of the pre-expansion is 2 to 150 times.

[14] The recycled styrene resin foam molded body according to an embodiment of the present invention is molded from the recycled pre-expanded styrene resin particles described in

[13] above.

[15] In the recycled styrene resin foam molded body described in

[14] above, it may be at least one selected from a molded body for a heat insulating material, a molded body for a heat retaining material, a molded body for an embankment material, a molded body for a food container, a molded body for an industrial product container, a molded body for a cushioning material, and a molded body for a packaging material.

[16] The recycled pre-expanded styrene resin particles described in

[13] above may be at least one selected from a core material and an aggregate of a cushion. [Effect of the Invention]

[0013] According to the present invention, it is possible to provide a method for producing recycled expandable styrene resin particles that have a high environmental contribution, suppress the odor peculiar to recycled materials, exhibit good spheroidization, and are excellent in moldability. Further, it is possible to provide recycled expandable styrene resin particles obtained by such a production method, which suppress the odor peculiar to recycled materials, exhibit good spheroidization, and are excellent in moldability. Further, it is possible to provide recycled pre-expanded styrene resin particles obtained from such recycled expandable styrene resin particles. Further, it is possible to provide a recycled styrene resin foam molded body molded from such recycled pre-expanded styrene resin particles. [Embodiments for Carrying Out the Invention]

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0015] In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0016] A. Method for producing recycled foamed styrene-based resin particles The method for producing recycled foamable styrene-based resin particles according to an embodiment of the present invention involves impregnating a suspension containing recycled styrene-based resin raw material (A) and a dispersant by injecting a foaming agent under pressure.

[0017] ≪A-1. Recycled styrene-based resin raw material (A)≫ Examples of recycled styrene resin raw materials (A) used in the method for producing recycled foamable styrene resin particles according to embodiments of the present invention include recycled styrene resin raw material particles, recycled foamable styrene resin particles, recycled pre-foamed styrene resin particles, and recycled styrene resin foam molded products.

[0018] Recycled styrene resin raw material particles are used styrene resin, and may be in the form of pellets, shrunk material, or molten material. Recycled foamable styrene resin particles are particles in which a foaming agent is injected or impregnated into the recycled styrene resin raw material particles. Recycled pre-foamed styrene resin particles are particles obtained by pre-foaming recycled foamable styrene resin particles. Recycled styrene resin foam molded articles are recycled styrene resin foam molded articles formed from recycled pre-foamed styrene resin particles.

[0019] A preferred embodiment of the recycled styrene resin raw material (A) used in the method for producing recycled foamed styrene resin particles according to an embodiment of the present invention is: (Embodiment 1 of recycled styrene resin raw material (A)) In this embodiment, polymer particles obtained by adding a styrene monomer to a suspension containing recycled styrene resin raw material particles (a) and polymerizing them are used as the recycled styrene resin raw material (A). (Embodiment 2 of recycled styrene resin raw material (A)) Two embodiments can be cited as recycled styrene resin raw material (A), in which recycled styrene resin raw material particles (a) are used as is.

[0020] The recycled styrene-based resin raw material particles (a) may be of one type only, or of two or more types.

[0021] As the material for the recycled styrene resin raw material particles (a), any suitable recycled styrene resin can be used, as long as it does not impair the effects of the present invention. Examples of such recycled styrene resins include expanded polystyrene (molded products, block molded products, etc.), foamed sheets (tray containers, sheet waste, etc.), and recycled plastic materials used in home appliances, packaging containers, cushion beads, etc.

[0022] The recycled styrene-based resin raw material particles (a) may contain other recycled resins other than any suitable recycled styrene-based resin, as long as the effects of the present invention are not impaired. Examples of such other recycled resins include recycled resins of AS resin, ABS resin, HIPS (high-impact polystyrene); polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polycarbonate (PC); polyamide resins such as nylon (PA); and polyolefin resins such as polyethylene (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and EVA (ethylene-vinyl acetate copolymer)). There may be only one type of other resin, or two or more types. In this specification, recycled resins consisting only of AS resin, recycled resins consisting only of ABS resin, and recycled resins consisting only of HIPS (high-impact polystyrene) are not included in the category of recycled styrene-based resins described above.

[0023] As recycled styrene-based resin raw material particles (a), molded products made from the product name "Epslem" manufactured by Sekisui Chemical Co., Ltd. may be used.

[0024] As recycled styrene resin raw material particles (a), a pulverized product obtained by heating and / or reducing the volume of used styrene resin may be used. The recycled styrene resin raw material particles may be pellets formed by extruding this pulverized product, or these pellets may be further pulverized. Alternatively, it may be recovered by reducing the volume using a solvent such as limonene.

[0025] The recycled styrene-based resin raw material particles (a) are preferably pellets obtained by a melt extrusion method. A typical melt extrusion method involves supplying crushed used styrene-based resin, ingots, or foamed particles to a resin supply device, melting them in the resin supply device, extruding them through small holes in a die attached to the tip of the resin supply device, and then cooling them to obtain pellets.

[0026] The pellets obtained by the melt extrusion method described above are preferably at least one selected from extruded strand pellets obtained by extruding spent styrene resin with an extruder and performing strand cutting, underwater cut pellets obtained by an underwater cut method in which spent styrene resin is extruded with an extruder and cut in water at the same time, and hot cut pellets obtained by a hot cut method in which spent styrene resin is cut and cooled immediately after coming out of the die of the extruder.

[0027] As recycled styrene-based resin raw material particles (a), pellets obtained by the above-described melt extrusion method may be used as is, or they may be made into so-called "mini-pellets" by melt extrusion or other methods to obtain smaller pellets.

[0028] The recycled styrene-based resin raw material particles (a) may be shrunk or molten styrene-based resin obtained by coarsely crushing used styrene-based resin to an appropriate size as needed, and then performing processes such as thermal shrinkage, compression-induced bubble bursting shrinkage, frictional heat shrinkage, and melting. Examples of used styrene-based resin include molded products made by mold molding of foamed styrene-based resin, and products obtained by heating and foaming such products.

[0029] The recycled styrene-based resin raw material particles (a) may contain finely powdered inorganic and / or organic lubricants. These can typically function as foam regulators.

[0030] Examples of finely powdered inorganic materials include talc, calcium carbonate, and silica. Here, talc typically refers to a mixture mainly composed of silicon dioxide and magnesium oxide, with trace amounts of aluminum oxide, iron oxide, etc.

[0031] The average particle size of the finely powdered inorganic material is preferably 100 μm or less, and more preferably 30 μm or less. If the average particle size of the finely powdered inorganic material exceeds 100 μm, the effect of reducing the bubble size of the recycled pre-expanded styrene resin particles may decrease.

[0032] The content of finely powdered inorganic matter is preferably 0.1% to 5% by mass, and more preferably 0.5% to 2% by mass, relative to the recycled styrene-based resin raw material particles (a). If the content of finely powdered inorganic matter relative to the recycled styrene-based resin raw material particles (a) is less than 0.1% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene-based resin particles may decrease. If the content of finely powdered inorganic matter relative to the recycled styrene-based resin raw material particles (a) exceeds 5% by mass, the bubble size of the recycled pre-expanded styrene-based resin particles becomes extremely small, and the recycled pre-expanded styrene-based resin particles may melt during molding, potentially degrading the appearance of the molded product.

[0033] Examples of organic lubricants include liquid paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisatomids such as methylenebisstearylamide, ethylenebisstearylamide, and ethylenebisoleamide; and metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

[0034] The content of the organic lubricant is preferably 0.01% to 2.0% by mass, more preferably 0.02% to 1.8% by mass, and in some cases even more preferably 0.02% to 0.2% by mass, and particularly preferably 0.02% to 0.1% by mass, relative to the recycled styrene resin raw material particles (a). If the content of the organic lubricant relative to the recycled styrene resin raw material particles (a) is less than 0.01% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene resin particles may decrease. If the content of the organic lubricant relative to the recycled styrene resin raw material particles (a) exceeds 2.0% by mass, the bubble size of the recycled pre-expanded styrene resin particles becomes extremely small, the recycled pre-expanded styrene resin particles may melt during molding, and the appearance of the molded product tends to be poor.

[0035] A specific method for incorporating finely powdered inorganic and / or organic lubricants into recycled styrene-based resin raw material particles (a) is, for example, a method of kneading the finely powdered inorganic and / or organic lubricants during extrusion molding. In this case, preferably, the pulverized material and the foam regulator are mixed beforehand before extrusion molding. The method of mixing the pulverized material and the foam regulator can be any suitable method as long as it does not impair the effects of the present invention. Examples of such methods include mixing using mixers such as tumblers, ribbon blenders, V-blenders, Henschel mixers, and Readygay mixers.

[0036] The recycled styrene-based resin raw material particles (a) are preferably thermally melted for the purpose of adjusting their specific gravity. In this step, the specific gravity of the recycled styrene-based resin raw material particles (a) is preferably adjusted to 0.6 or higher, and more preferably to 0.9 or higher. If the specific gravity of the recycled styrene-based resin raw material particles (a) is less than 0.6, the dispersion of the recycled styrene-based resin raw material particles (a) is unstable, which may lead to the generation of excessive particles during the subsequent polymerization step and a decrease in yield. The thermal melting of the recycled styrene-based resin raw material particles (a) can be carried out by any suitable method that does not impair the effects of the present invention. Examples of such methods include using an extruder or a hot roll. It is preferable that the thermal melting is followed by cooling and solidification in a state where no strain remains in the obtained resin, or where the strain is small. If strain remains in the resin particles, the strain will be relieved in the subsequent step, causing shrinkage in the stretching direction, and the resulting recycled foamable styrene-based resin particles may not be spherical but flattened. Therefore, it is preferable to perform thermal melting without stretching using an extruder. If thermal melting is performed in a stretched state, there is a risk that strain will remain in the stretched resin obtained after cooling and solidification. However, even if strain remains in the resin due to thermal melting, the strain can be alleviated by curing it at a temperature above the resin's softening point for a certain period of time.

[0037] When obtaining recycled styrene-based resin raw material particles (a), any type of pulverizer can be used for grinding, as long as it does not impair the effects of the present invention. For example, a pulverizer for plastics can be used, and a pulverizer for polystyrene is preferred.

[0038] The recycled styrene-based resin raw material particles (a) can be sieved as needed and then subjected to melting again using an extruder or the like.

[0039] The average particle diameter of the recycled styrene-based resin raw material particles (a) is preferably 0.2 mm to 3.0 mm, more preferably 0.3 mm to 2.5 mm, even more preferably 0.4 mm to 2.0 mm, and particularly preferably 0.5 mm to 1.7 mm. If the average particle diameter of the recycled styrene-based resin raw material particles (a) exceeds 3 mm, the resulting recycled foamed styrene-based resin particles may not be spherical. If the average particle diameter of the recycled styrene-based resin raw material particles (a) is less than 0.2 mm, the resulting recycled foamed styrene-based resin particles may have an average particle diameter that is too small.

[0040] The L (long side) / D (short side) ratio of the recycled styrene-based resin raw material particles (a) is preferably 1.0 to 6.0, more preferably 1.0 to 5.0, even more preferably 1.0 to 4.0, particularly preferably 1.0 to 3.0, and most preferably 1.0 to 2.5. If the L (long side) / D (short side) ratio of the recycled styrene-based resin raw material particles (a) falls outside the above range, the resulting recycled foamable styrene-based resin particles may not be spherical.

[0041] It is preferable that the recycled styrene-based resin raw material particles (a) contain less than 1% by mass of particles with an average particle diameter of 200 μm or less. If the recycled styrene-based resin raw material particles (a) contain 1% or more by mass of particles with an average particle diameter of 200 μm or less, the appearance of the recycled foamed styrene-based resin particles obtained using them may deteriorate.

[0042] The weight-average molecular weight of the recycled styrene-based resin raw material particles (a) is preferably 100,000 to 510,000, and more preferably 150,000 to 490,000. If the weight-average molecular weight of the recycled styrene-based resin raw material particles (a) is less than 100,000, sufficient strength may not be obtained. If the weight-average molecular weight of the recycled styrene-based resin raw material particles (a) exceeds 510,000, the recycled styrene-based resin raw material particles may not form spherical shapes easily, and the foaming properties may decrease, resulting in a poor appearance of the molded product.

[0043] The styrene monomer used in Embodiment 1 of the recycled styrene resin raw material (A) may be one type or two or more types.

[0044] The styrene monomer includes styrene or a styrene derivative. Examples of styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. The styrene monomer may be one type or two or more types. The styrene monomer preferably contains at least styrene. The styrene content relative to the total amount of the styrene monomer 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.

[0045] The styrene monomer may contain any suitable vinyl monomer other than the styrene monomer, as long as it does not impair the effects of the present invention. Examples include polyfunctional monomers, (meth)acrylic acid monomers, maleic acid monomers, and fumaric acid monomers. Such vinyl monomers may be one type or two or more types.

[0046] Specific examples of polyfunctional monomers include, for example, divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene; and alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate. Specific examples of (meth)acrylic acid ester monomers include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and hexyl (meth)acrylate. An example of a maleic acid ester monomer is dimethyl maleate. An example of a fumarate ester monomer is dimethyl fumarate, diethyl fumarate, and ethyl fumarate.

[0047] In Embodiment 1 of the recycled styrene-based resin raw material (A), the content ratio of the recycled styrene-based resin raw material particles (a) to the total amount of recycled styrene-based resin raw material particles (a) and styrene monomers is preferably 5% to 90% by mass, more preferably 10% to 85% by mass, even more preferably 15% to 80% by mass, particularly preferably 20% to 75% by mass, and most preferably 20% to 70% by mass. If the above content ratio is too low and outside the above range, the environmental contribution may be reduced. Also, if the above content ratio is too low or too high and outside the above range, good spheroidization may not occur in the recycled foamable styrene-based resin particles according to the embodiment of the present invention, and moldability may be reduced.

[0048] The recycled styrene resin raw material (A) is obtained by adding a styrene monomer to a suspension containing recycled styrene resin raw material particles (a) and polymerizing it. Any suitable polymerization method can be used as long as it does not impair the effects of the present invention. One preferred embodiment of such polymerization is a method in which a suspension is obtained by dispersing recycled styrene resin raw material particles (a) in water with the recycled styrene resin raw material particles (a) as nuclei, to which an emulsion containing a polymerization initiator and a styrene monomer is added to impregnate the recycled styrene resin raw material particles (a), and then the styrene monomer is added and polymerization is carried out.

[0049] In Embodiment 1 of the recycled styrene-based resin raw material (A), when obtaining the recycled styrene-based resin raw material (A), the addition temperature when adding the styrene monomer to the recycled styrene-based resin raw material particles (a) is preferably 40°C to 119°C, preferably 40°C to 118°C, more preferably 40°C to 117°C, even more preferably 50°C to 117°C, and particularly preferably 60°C to 115°C, in order to better express the effects of the present invention. By adjusting the addition temperature when adding the styrene monomer to the recycled styrene-based resin raw material particles (a) within the above range, the styrene monomer can be incorporated while maintaining the recycled styrene-based resin raw material particles (a) at an appropriate hardness, so that good spheroidization of the recycled styrene-based resin raw material (A) can be achieved, and the recycled foamable styrene-based resin particles obtained can exhibit good spheroidization and excellent moldability. If the addition temperature when adding styrene monomers to recycled styrene resin raw material particles (a) is too low and outside the above range, the recycled styrene resin raw material particles (a) will become too hard. When styrene monomers are incorporated in this state, the recycled styrene resin raw material (A) will have difficulty forming into spheres, and the resulting recycled foamed styrene resin particles may have difficulty forming into spheres or may have poor moldability. If the addition temperature when adding styrene monomers to recycled styrene resin raw material particles (a) is too high and outside the above range, the recycled styrene resin raw material particles (a) will become too soft. When styrene monomers are incorporated in this state, the recycled styrene resin raw material (A) will have difficulty forming into spheres, and the resulting recycled foamed styrene resin particles may have difficulty forming into spheres or may have poor moldability. Furthermore, the "addition temperature when adding styrene monomers to recycled styrene resin raw material particles (a)" as used herein refers to the addition temperature during the addition of the emulsion containing the polymerization initiator and styrene monomers, and the subsequent addition of styrene monomers.

[0050] When obtaining a suspension by dispersing recycled styrene-based resin raw material particles (a) in an aqueous medium with the particles acting as nuclei, any suitable method can be used for dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium, as long as it does not impair the effects of the present invention. Preferably, such a dispersion method involves using a device equipped with a stirring blade. A method for even finer dispersion can be achieved by using a homomixer.

[0051] When obtaining a suspension by dispersing recycled styrene resin raw material particles (a) in an aqueous medium with the recycled styrene resin raw material particles (a) as nuclei, it is preferable to use a dispersant in the dispersion of the recycled styrene resin raw material particles (a) in the aqueous medium. Any suitable dispersant can be used as long as it can be used in suspension polymerization and does not impair the effects of the present invention. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose; and sparingly soluble inorganic salts such as magnesium phosphate, magnesium pyrophosphate, and tricalcium phosphate. Among these, magnesium pyrophosphate is preferred as a dispersant because it can better express the effects of the present invention.

[0052] The blending ratio of the dispersant to 100 parts by mass of recycled styrene resin raw material (A) is preferably 0.1 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, and even more preferably 0.1 to 1.0 part by mass.

[0053] When obtaining a suspension by dispersing recycled styrene resin raw material particles (a) in an aqueous medium with the particles as nuclei, it is preferable to use a surfactant in the dispersion of the recycled styrene resin raw material particles (a) in the aqueous medium. Any suitable surfactant can be used as long as it can be used in suspension polymerization and does not impair the effects of the present invention. Examples of such surfactants include sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylsulfonate, sodium alkyldiphenyl ether disulfonate, and sodium α-olefin sulfonate. Among these, sodium dodecylbenzenesulfonate is preferred as the surfactant because it can better express the effects of the present invention.

[0054] The blending ratio of surfactant to 100 parts by mass of recycled styrene-based resin raw material (A) is preferably 0.005 parts by mass to 0.1 parts by mass, more preferably 0.005 parts by mass to 0.08 parts by mass, and even more preferably 0.005 parts by mass to 0.06 parts by mass.

[0055] As for the method of emulsion when obtaining an emulsion containing a polymerization initiator and styrene monomers, any suitable method can be used as long as it does not impair the effects of the present invention. Preferably, such a dispersion method is dispersion using an apparatus equipped with a stirring blade. As a method for finer dispersion, a homomixer can be used. In this case, it is preferable to disperse until the oil droplet diameter of the dispersion containing the styrene monomers is less than or equal to the particle diameter of the nucleus. This is because if the oil droplet diameter is larger than the particle diameter of the nucleus when added to an aqueous medium, multiple recycled styrene resin raw material particles (a) will be incorporated into the oil droplets of the dispersion containing the styrene monomers, causing adhesion, plasticization, and coalescence of the recycled styrene resin raw material particles (a), which can easily lead to the generation of excessively large particles.

[0056] When obtaining an emulsion containing a polymerization initiator and a styrene monomer, any suitable polymerization initiator can be used as the polymerization initiator, as long as it is used in suspension polymerization and does not impair the effects of the present invention. Examples of such polymerization initiators include organic peroxides such as benzoyl peroxide, t-butyl peroxy-2-ethylhexyl carbonate, and t-butyl perbenzoate; and azo compounds such as azobisisobutyronitrile. There may be only one polymerization initiator or two or more.

[0057] The amount of polymerization initiator used is preferably 0.1% to 1.0% by mass, and more preferably 0.1% to 0.8% by mass, relative to the styrene monomer.

[0058] The polymerization initiator is preferably added dissolved in a styrene monomer or a solvent. Examples of solvents include aromatic hydrocarbons such as ethylbenzene and toluene; and aliphatic hydrocarbons such as heptane and octane. When a solvent is used, it is usually used in an amount of 10% by mass or less relative to the styrene monomer.

[0059] As for the method of adding styrene monomers after impregnating a suspension containing recycled styrene resin raw material particles (a) with an emulsion containing styrene monomers, any suitable method can be used as long as it does not impair the effects of the present invention. Examples of such methods include partial addition and continuous addition. The addition rate is appropriately selected according to the capacity and shape of the polymerization apparatus, polymerization temperature, etc.

[0060] After impregnating a suspension containing recycled styrene resin raw material particles (a) with an emulsion containing styrene monomers, the polymerization reaction may be continued at any appropriate temperature and time as needed.

[0061] A suspension containing recycled styrene resin raw material particles (a) or an emulsion containing styrene monomers may contain a foam regulator. Examples of such foam regulators include fatty acid monoamides such as oleamide, stearamide, and hydroxystearamide; and fatty acid bisamides such as methylenebisstearamide and ethylenebisstearamide.

[0062] ≪A-2. Injection and Impregnation of Foaming Agent≫ Typical methods for injecting and impregnating with a foaming agent include placing recycled styrene-based resin raw material (A) and a dispersant into a reactor such as an autoclave, and then injecting the foaming agent under pressure to impregnate the material.

[0063] The blending ratio of the dispersant to 100 parts by mass of recycled styrene resin raw material (A) is preferably 0.1 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, and even more preferably 0.1 to 1.0 part by mass.

[0064] The foaming agent may be one type or two or more types.

[0065] As a blowing agent, any suitable blowing agent can be used as long as it does not impair the effects of the present invention. Preferably, a volatile blowing agent is used. Preferably, a volatile blowing agent is an organic compound that has a boiling point below the softening point of the styrene resin and is gaseous or liquid at atmospheric pressure. Specific examples include, for example, aliphatic hydrocarbons such as propane, n-butane, isobutane, pentane (n-pentane, isopentane, neopentane), and n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, and isopropyl alcohol; low-boiling point ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane; and others. Inorganic gases such as carbon dioxide, nitrogen, and ammonia may also be used as volatile blowing agents. Among these, the volatile foaming agent is preferably at least one selected from n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, and cyclopentadiene, and more preferably at least one selected from n-butane, isobutane, n-pentane, and isopentane, in terms of being able to better express the effects of the present invention.

[0066] The amount of foaming agent can be appropriately set depending on the purpose, as long as it is in an amount sufficient to form recycled pre-foamed styrene resin particles and recycled styrene resin foam molded articles. The amount of foaming agent is preferably 2 to 15 parts by mass when the amount of recycled styrene resin raw material (A) is 100 parts by mass.

[0067] As a dispersant, any suitable dispersant can be used as long as it does not impair the effects of the present invention. There may be only one type of dispersant or two or more types. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose; and sparingly soluble inorganic salts such as metal phosphate salts. Among these, sparingly soluble inorganic salts are preferred as dispersants in that they can better express the effects of the present invention. Examples of sparingly soluble inorganic salts include monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, monomagnesium phosphate, dicalnesium phosphate, trimagnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate.

[0068] The blending ratio of the dispersant to 100 parts by mass of recycled styrene resin raw material (A) is preferably 0.1 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, and even more preferably 0.1 to 1.0 part by mass.

[0069] As the surfactant, any suitable surfactant can be used as long as it does not impair the effects of the present invention. There may be only one type or two or more types. Examples of such surfactants include sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylsulfonate, sodium alkyldiphenyl ether disulfonate, and sodium α-olefin sulfonate. Among these, sodium dodecylbenzenesulfonate is preferred as the surfactant because it can better express the effects of the present invention.

[0070] The blending ratio of surfactant to 100 parts by mass of recycled styrene-based resin raw material (A) is preferably 0.005 parts by mass to 0.1 parts by mass, more preferably 0.005 parts by mass to 0.08 parts by mass, and even more preferably 0.005 parts by mass to 0.06 parts by mass.

[0071] In the method for producing recycled foamable styrene resin particles according to an embodiment of the present invention, when the glass transition temperature of the recycled styrene resin raw material (A) is Tg, the temperature at which the foaming agent is injected is T1, and the temperature at which the foaming agent is impregnated is T2, T1 is within the range of (Tg-50°C) or higher and (Tg+40°C) or lower, and T2 is within the range of (Tg-50°C) or higher and (Tg+40°C) or lower. By having T1 and T2 within the above ranges, the odor characteristic of recycled materials is suppressed, good spheroidization can be achieved, and recycled foamable styrene resin particles with excellent moldability can be produced. Typically, the present invention has been found to be able to produce recycled foamable styrene resin particles with excellent moldability by adjusting the temperature at which the foaming agent is injected and the temperature at which the foaming agent is impregnated to a specific range based on the glass transition temperature of the recycled styrene resin raw material (A), thereby suppressing the odor characteristic of recycled materials, achieving good spheroidization, and producing recycled foamable styrene resin particles with excellent moldability.

[0072] The glass transition temperature Tg of the recycled styrene-based resin raw material (A) is preferably 85°C to 115°C, more preferably 88°C to 111°C, even more preferably 91°C to 109°C, particularly preferably 93°C to 107°C, and most preferably 95°C to 105°C, in order to better exhibit the effects of the present invention.

[0073] As mentioned above, the lower limit of T1 is (Tg-50°C) or higher, and more preferably (Tg-40°C) or higher, more preferably (Tg-30°C) or higher, even more preferably (Tg-20°C) or higher, even more preferably (Tg-10°C) or higher, even more preferably (Tg-7°C) or higher, particularly preferably (Tg-5°C) or higher, and most preferably (Tg-3°C) or higher, in order to better exhibit the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T1 is 50°C or higher, preferably 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, even more preferably 90°C or higher, particularly preferably 93°C or higher, and most preferably 95°C or higher.

[0074] As mentioned above, the lower limit of T2 is (Tg-50°C) or higher, and more preferably (Tg-40°C) or higher, more preferably (Tg-30°C) or higher, even more preferably (Tg-20°C) or higher, even more preferably (Tg-10°C) or higher, even more preferably (Tg-7°C) or higher, particularly preferably (Tg-5°C) or higher, and most preferably (Tg-3°C) or higher, in order to better exhibit the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T2 is 50°C or higher, preferably 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, even more preferably 90°C or higher, particularly preferably 93°C or higher, and most preferably 95°C or higher.

[0075] As mentioned above, the upper limit of T1 is (Tg + 40°C) or less, and is preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 25°C) or less, and particularly preferably (Tg + 20°C) or less, in order to better exhibit the effects of the present invention and to reduce manufacturing costs. As a typical example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T1 is 140°C or less, preferably 135°C or less, more preferably 130°C or less, even more preferably 125°C or less, and particularly preferably 120°C or less.

[0076] As mentioned above, the upper limit of T2 is (Tg + 40°C) or less, and more preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 25°C) or less, and particularly preferably (Tg + 20°C) or less, in order to better demonstrate the effects of the present invention and reduce manufacturing costs. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T2 is 140°C or less, more preferably 135°C or less, more preferably 130°C or less, even more preferably 125°C or less, and particularly preferably 120°C or less.

[0077] One preferred embodiment (sometimes referred to as "Embodiment 1") is such that T1 is in the range of (Tg-50°C) or higher and (Tg+40°C) or lower, and T2 is in the range of (Tg-50°C) or higher and less than (Tg+10°C). As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, then in Embodiment 1, T1 is in the range of 50°C or higher and 140°C or lower, and T2 is in the range of 50°C or higher and less than 110°C.

[0078] Another preferred embodiment (sometimes referred to as "Embodiment 2") is in which T1 is in the range of (Tg + 10°C) or higher and (Tg + 30°C) or lower, and T2 is in the range of (Tg + 10°C) or higher and (Tg + 30°C) or lower. As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, in Embodiment 2, T1 is in the range of 110°C or higher and 130°C or lower, and T2 is in the range of 110°C or higher and 130°C or lower.

[0079] If Embodiment 1 is selected, any suitable dispersant can be used as the dispersant, as long as it does not impair the effects of the present invention. As such a dispersant, it is preferable to use at least one selected from the group consisting of organic dispersants and sparingly soluble inorganic salts, in that it can better express the effects of the present invention. Examples of organic dispersants, as mentioned above, include polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. Examples of sparingly soluble inorganic salts, as mentioned above, include monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, monomagnesium phosphate, dicalnesium phosphate, trimagnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate.

[0080] Therefore, one preferred embodiment of the method for producing recycled foamable styrene-based resin particles of the present invention is when Embodiment 1 is selected, and is a method for producing recycled foamable styrene-based resin particles in which a foaming agent is injected under pressure into a suspension containing a recycled styrene-based resin raw material (A) and a dispersant, wherein when the glass transition temperature of the recycled styrene-based resin raw material (A) is Tg, the temperature at which the foaming agent is injected under pressure is T1, and the temperature at which the foaming agent is impregnated is T2, T1 is in the range of (Tg-50°C) or higher and (Tg+40°C) or lower, T2 is in the range of (Tg-50°C) or higher and (Tg+10°C) or lower, and the dispersant is at least one selected from the group consisting of organic dispersants and sparingly soluble inorganic salts.

[0081] When Embodiment 2 is selected, it is preferable to use a sparingly soluble inorganic salt as the dispersant in such a way that the effects of the present invention can be better expressed. Examples of sparingly soluble inorganic salts, as mentioned above, include monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, monomagnesium phosphate, dicalnesium phosphate, trimagnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate, with magnesium pyrophosphate being particularly preferred.

[0082] Therefore, another preferred embodiment of the method for producing recycled foamable styrene-based resin particles of the present invention is when Embodiment 2 is selected, wherein a foaming agent is injected under pressure into a suspension containing a recycled styrene-based resin raw material (A) and a dispersant to impregnate the suspension, and the glass transition temperature of the recycled styrene-based resin raw material (A) is Tg, the temperature at which the foaming agent is injected under pressure is T1, and the temperature at which the foaming agent is impregnated is T2, wherein T1 is in the range of (Tg + 10°C) or more and (Tg + 30°C) or less, and the dispersant is a sparingly soluble inorganic salt, particularly preferably magnesium pyrophosphate.

[0083] In Embodiment 1, the lower limit of T1 is, as described above, (Tg-50°C) or higher, and more preferably (Tg-40°C) or higher, more preferably (Tg-30°C) or higher, even more preferably (Tg-20°C) or higher, even more preferably (Tg-10°C) or higher, even more preferably (Tg-7°C) or higher, particularly preferably (Tg-5°C) or higher, and most preferably (Tg-3°C) or higher, in order to better exhibit the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T1 in Embodiment 1 is 50°C or higher, preferably 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, even more preferably 90°C or higher, particularly preferably 93°C or higher, and most preferably 95°C or higher.

[0084] In Embodiment 1, the lower limit of T2 is, as described above, (Tg-50°C) or higher, and more preferably (Tg-40°C) or higher, more preferably (Tg-30°C) or higher, even more preferably (Tg-20°C) or higher, even more preferably (Tg-10°C) or higher, even more preferably (Tg-7°C) or higher, particularly preferably (Tg-5°C) or higher, and most preferably (Tg-3°C) or higher, in order to better express the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T2 in Embodiment 1 is 50°C or higher, preferably 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, even more preferably 90°C or higher, particularly preferably 93°C or higher, and most preferably 95°C or higher.

[0085] In Embodiment 1, the upper limit of T1 is, as described above, (Tg + 40°C) or less, and more preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 27°C) or less, particularly preferably (Tg + 25°C) or less, and most preferably (Tg + 23°C) or less, in order to better exhibit the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T1 in Embodiment 1 is 140°C or less, preferably 135°C or less, more preferably 130°C or less, even more preferably 127°C or less, particularly preferably 125°C or less, and most preferably 123°C or less.

[0086] In Embodiment 1, the upper limit of T2 is, as described above, less than (Tg + 10°C), and is preferably (Tg + 9°C) or less, more preferably (Tg + 8°C) or less, even more preferably (Tg + 7°C) or less, particularly preferably (Tg + 6°C) or less, and most preferably (Tg + 5°C) or less, in order to better exhibit the effects of the present invention. As a representative example, when the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T2 in Embodiment 1 is less than 110°C, preferably 109°C or less, more preferably 108°C or less, even more preferably 107°C or less, particularly preferably 106°C or less, and most preferably 105°C or less.

[0087] In Embodiment 2, the lower limit of T1 is (Tg + 10°C) or higher, as described above. As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T1 in Embodiment 2 is 110°C or higher.

[0088] In Embodiment 2, the lower limit of T2 is (Tg + 10°C) or higher, as described above. As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the lower limit of T2 in Embodiment 2 is 110°C or higher.

[0089] In Embodiment 2, the upper limit of T1 is (Tg + 30°C) or less, as described above. As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T1 in Embodiment 2 is 130°C or less.

[0090] In Embodiment 2, the upper limit of T2 is (Tg + 30°C) or less, as described above. As a typical example, if the glass transition temperature Tg of the recycled styrene resin raw material (A) is 100°C, the upper limit of T2 in Embodiment 2 is 130°C or less.

[0091] The impregnation time of the foaming agent into the recycled styrene-based resin raw material (A) can be any appropriate time, as long as it does not impair the effects of the present invention. Preferably, such an impregnation time is 1 to 10 hours.

[0092] In the method for producing recycled foamed styrene resin particles according to embodiments of the present invention, a flame retardant may be added at any appropriate timing to enhance the flame retardancy of the resulting recycled foamed styrene resin particles. In order to better exhibit the effects of the present invention, it is preferable that the flame retardant be added before the foaming agent is injected into the recycled styrene resin raw material (A). By adding the flame retardant before the foaming agent is injected, the flame retardant can be added at a temperature as low as that at which the foaming agent is injected, thereby enabling good spheroidization and excellent moldability of the resulting recycled foamed styrene resin particles.

[0093] The flame retardant may be of one type only, or of two or more types.

[0094] As a flame retardant, any suitable flame retardant can be used as long as it does not impair the effects of the present invention. Preferred flame retardants include bromine compounds that are compatible with polystyrene, such as tetrabromoethane, tetrabromocyclooctane, hexabromocyclododecane, hexabromocyclohexane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol F, tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-diglycidyl ether, 2,2-bis[4'(2'',3''-dibromoalkoxy)-3',5'-dibromophenyl]-propane, tris(tribromophenoxy)triazine, 2,2-bis(4-alyroxy-3,5-dibromo)propane, and hexabromobenzene.

[0095] When using flame retardants, flame retardant additives may be used in combination. Examples of flame retardant additives include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenylhexane.

[0096] The total amount of flame retardant and flame retardant aid used can be any appropriate amount, as long as it does not impair the effects of the present invention. Such an amount is preferably 0.5% to 5.0% by mass relative to the recycled styrene-based resin raw material (A).

[0097] The temperature at which the flame retardant is added is preferably 5°C to 89°C, more preferably 5°C to 87°C, even more preferably 5°C to 85°C, particularly preferably 5°C to 83°C, and most preferably 5°C to 80°C, in order to better exhibit the effects of the present invention.

[0098] In the method for producing regenerative foamable styrene-based resin particles according to embodiments of the present invention, a foam regulator may be used. The foam regulator may be one type or two or more types. Examples of foam regulators include higher fatty acid amides, partial esters of higher fatty acids and alcohols, talc, calcium carbonate, mica, citric acid, and sodium bicarbonate. Examples of higher fatty acid amides include fatty acid monoamides such as oleamide, stearamide, and hydroxystearamide; and fatty acid bisamides such as methylenebisstearamide and ethylenebisstearamide. Examples of higher fatty acids in partial esters of higher fatty acids and alcohols include fatty acids with 15 or more carbon atoms such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid. Examples of partial esters of higher fatty acids and alcohols include monoglyceride stearate and diglyceride stearate.

[0099] The amount of foam regulator used is preferably 0 to 3.0 parts by mass, and more preferably 0.03 to 1.0 parts by mass, per 100 parts by mass of recycled styrene-based resin raw material (A). Methods for adding the foam regulator include, for example, adding it together with the foaming agent, or employing commonly used methods such as the dry blending method, masterbatch method, or melt injection method.

[0100] In the method for producing regenerated foamable styrene-based resin particles according to embodiments of the present invention, foaming aids may be used. There may be only one type of foaming aid, or there may be two or more types. Examples of foaming aids include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil.

[0101] In the method for producing recycled foamed styrene-based resin particles according to embodiments of the present invention, other additives may be used. These other additives may be one type or two or more types. Examples of other additives include pigments, radiant heat transfer inhibitors, crosslinking agents, plasticizers, stabilizers, fillers, lubricants, colorants, antistatic agents, spreading agents, weathering agents, anti-aging agents, anti-fogging agents, and fragrances.

[0102] <<B. Recycled foamed styrene resin particles>> The recycled foamed styrene resin particles according to the embodiments of the present invention are typically obtained by the method for producing recycled foamed styrene resin particles according to the embodiments of the present invention.

[0103] The recycled foamed styrene resin particles according to the embodiments of the present invention have a particle shape as a whole. The average particle diameter of the recycled foamed styrene resin particles is preferably 0.40 mm to 2.0 mm, and more preferably 0.6 mm to 1.8 mm. The average particle diameter can be measured in accordance with JIS Z 8815. Specifically, the average particle diameter is the value measured as the particle size of 50% of the cumulative value from the particle size distribution obtained by the sieving test of JIS Z 8815.

[0104] The shape of the recycled foamed styrene resin particles according to the embodiments of the present invention can be any appropriate shape, as long as it does not impair the effects of the present invention. Specific examples of such shapes include, for example, spherical, substantially spherical, and ellipsoidal (egg-shaped). In terms of exhibiting the effects of the present invention, the shape of the recycled foamed styrene resin particles according to the embodiments of the present invention is preferably spherical, substantially spherical, and more preferably spherical. However, in practice, it is difficult to distinguish between spherical and substantially spherical shapes; therefore, in this specification, both are collectively referred to as spherical.

[0105] The weight-average molecular weight of the regenerated foamable styrene-based resin particles according to the embodiments of the present invention can be any appropriate weight-average molecular weight, as long as it does not impair the effects of the present invention. Such a weight-average molecular weight is preferably 100,000 to 510,000, more preferably 110,000 to 490,000, even more preferably 120,000 to 470,000, and particularly preferably 130,000 to 460,000.

[0106] ≪B-1. Surface Treatment≫ The recycled foamable styrene resin particles according to embodiments of the present invention may be surface-treated. Such surface treatment is preferably performed using at least one selected from silicone oil, an antistatic agent, a fatty acid metal salt, and a fusion accelerator.

[0107] When surface treatment with silicone oil is performed on recycled foamed styrene resin particles, the amount of silicone oil used per 100 parts by mass of recycled foamed styrene resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.003 to 0.28 parts by mass, even more preferably 0.005 to 0.25 parts by mass, particularly preferably 0.008 to 0.23 parts by mass, and most preferably 0.01 to 0.23 parts by mass. If the amount of silicone oil used is too little and falls outside the above range, for example, when an antistatic agent is used, the affinity with the antistatic agent during pre-foaming may not be sufficient, and static electricity may easily be generated. If the amount of silicone oil used is too much and falls outside the above range, the surface may be lost due to the surface melting during molding, etc.

[0108] The silicone oil may be of one type or two or more types.

[0109] Any suitable silicone oil can be used as the silicone oil, as long as it does not impair the effects of the present invention. In terms of being able to better express the effects of the present invention, examples of straight silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane are used, and dimethylpolysiloxane is preferred.

[0110] When recycled foamed styrene resin particles are surface-treated with an antistatic agent, the amount of antistatic agent used per 100 parts by mass of recycled foamed styrene resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of antistatic agent is too small and outside the above range, static electricity may easily be generated during pre-foaming. If the amount of antistatic agent is too large and outside the above range, the surface of the recycled pre-foamed styrene resin particles or the recycled styrene resin foam molded product may become sticky.

[0111] The antistatic agent may be one type or two or more types.

[0112] As an antistatic agent, any suitable antistatic agent can be used as long as it does not impair the effects of the present invention. In terms of being able to better exhibit the effects of the present invention, at least one selected from nonionic surfactants and fatty acid glycerides can be used as an antistatic agent, and preferably a combination of a nonionic surfactant and a fatty acid glyceride.

[0113] The nonionic surfactant may be one type or two or more types.

[0114] As the nonionic surfactant, any suitable nonionic surfactant can be used as long as it does not impair the effects of the present invention. Examples of nonionic surfactants that can better express the effects of the present invention include polyethylene glycol, glycerin, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyhydric alcohols, and 1-amino-2-hydroxy compounds. Specific examples of polyoxyethylene alkyl ethers include polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. Specific examples of polyoxyethylene alkyl esters include polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, and polyoxyethylene oleate. Specific examples of polyhydric alcohols include glycerin and propylene glycol. Examples of 1-amino-2-hydroxy compounds include, for example, N-hydroxyethyl-N-(2-hydroxyalkyl)amine, N,N-bis(hydroxyethyl)dodecylamine, N,N-bis(hydroxyethyl)tetradecylamine, N,N-bis(hydroxyethyl)hexadecylamine, N,N-bis(hydroxyethyl)octadecylamine, N-hydroxyethyl-N-(2-hydroxytetradecyl)amine, N-hydroxyethyl-N-(2-hydroxyhexadecyl)amine, N-hydroxyethyl-N-(2-hydroxyoctadecyl)amine, and N-hydroxypropyl-N Examples include -(2-hydroxytetradecyl)amine, N-hydroxybutyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2-hydroxyhexadecyl)amine, N-hydroxypentyl-N-(2-hydroxyoctadecyl)amine, N,N-bis(2-hydroxyethyl)dodecylamine, N,N-bis(2-hydroxyethyl)tetradecylamine, N,N-bis(2-hydroxyethyl)hexadecylamine, N,N-bis(2-hydroxyethyl)octadecylamine, and their salts.Polyethylene glycol is preferred as the nonionic surfactant in terms of being able to better exhibit the effects of the present invention.

[0115] When a nonionic surfactant is used as at least a part of the antistatic agent, the amount of the nonionic surfactant used per 100 parts by mass of regenerated foamable styrene-based resin particles before surface treatment is preferably 0.001 to 2.0 parts by mass, more preferably 0.001 to 1.5 parts by mass, even more preferably 0.001 to 1.0 parts by mass, even more preferably 0.001 to 0.5 parts by mass, even more preferably 0.001 to 0.3 parts by mass, even more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of nonionic surfactant is too small and falls outside the above range, static electricity may easily be generated during pre-foaming. If the amount of nonionic surfactant exceeds the above range, the surface of the recycled pre-expanded styrene resin particles or the recycled styrene resin foam molded product may become sticky.

[0116] The fatty acid glycerides may be one type or two or more types.

[0117] Any suitable fatty acid glyceride can be used as the fatty acid glyceride, as long as it does not impair the effects of the present invention. Specifically, examples of fatty acid glycerides that can better express the effects of the present invention include monoglyceride stearate and monoglyceride linoleate. Monoglyceride stearate is preferred as the fatty acid glyceride in terms of better expressing the effects of the present invention.

[0118] When fatty acid glycerides are used as at least a part of the antistatic agent, the amount of fatty acid glycerides per 100 parts by mass of recycled foamable styrene resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of fatty acid glycerides is too small and outside the above range, static electricity may be easily generated during pre-foaming. If the amount of fatty acid glycerides is too large and outside the above range, the surface of the recycled pre-foamed styrene resin particles or the recycled styrene resin foam molded product may become sticky.

[0119] When surface treatment with a fatty acid metal salt is performed on recycled foamable styrene resin particles, the amount of fatty acid metal salt used per 100 parts by mass of recycled foamable styrene resin particles before surface treatment is preferably 0.005 to 0.5 parts by mass, more preferably 0.007 to 0.45 parts by mass, even more preferably 0.01 to 0.4 parts by mass, particularly preferably 0.015 to 0.35 parts by mass, and most preferably 0.02 to 0.3 parts by mass. If the amount of fatty acid metal salt is too small and outside the above range, a lot of blocking may occur during pre-foaming, and it may not be possible to obtain a good styrene resin foam molded article. If the amount of fatty acid metal salt is too large and outside the above range, a lot of metal salt will be present during pre-foaming, making it easy to become charged and generating static electricity, which may lead to poor fusion of the molded article.

[0120] The fatty acid metal salt may be one type or two or more types.

[0121] As the fatty acid metal salt, any suitable fatty acid metal salt can be used as long as it does not impair the effects of the present invention. Examples of fatty acid metal salts that can better express the effects of the present invention include stearate metal salts and laurate metal salts. Specific examples of stearate metal salts include magnesium stearate, calcium stearate, zinc stearate, barium stearate, aluminum stearate, and lithium stearate. Specific examples of laurate metal salts include zinc laurate and barium laurate. Magnesium stearate and zinc stearate are preferred as fatty acid metal salts that can better express the effects of the present invention.

[0122] When recycled foamed styrene resin particles are surface-treated with a fusion accelerator, the amount of fusion accelerator used per 100 parts by mass of recycled foamed styrene resin particles before surface treatment is preferably 0.01 to 0.8 parts by mass, more preferably 0.01 to 0.7 parts by mass, even more preferably 0.01 to 0.6 parts by mass, particularly preferably 0.01 to 0.55 parts by mass, and most preferably 0.013 to 0.5 parts by mass. If the amount of fusion accelerator is too small and outside the above range, the fusion properties will decrease during molding, and it may not be possible to obtain a good recycled styrene resin foam molded article. If the amount of fusion accelerator is too large and outside the above range, blocking may occur during pre-foaming.

[0123] The fusion accelerator may be one type or two or more types.

[0124] As a fusion accelerator, any suitable fusion accelerator can be used as long as it does not impair the effects of the present invention. Examples of fusion accelerators that can better express the effects of the present invention include fatty acid triglycerides, fatty acid diglycerides, fatty acid monoglycerides, and vegetable oils. Specific examples of fatty acid triglycerides include lauric acid triglyceride, stearate triglyceride, linoleic acid triglyceride, and hydroxystearate triglyceride. Specific examples of fatty acid diglycerides include lauric acid diglyceride, stearate diglyceride, and linoleic acid diglyceride. Specific examples of fatty acid monoglycerides include lauric acid monoglyceride. Specific examples of vegetable oils include hydrogenated castor oil. Stearic acid triglyceride and hydroxystearate triglyceride are preferred as fusion accelerators that can better express the effects of the present invention.

[0125] <<<C. Recycled Pre-Expanded Styrene Resin Particles>>> The recycled pre-foamed styrene resin particles according to the embodiment of the present invention are obtained by pre-foaming the recycled foamable styrene resin particles according to the embodiment of the present invention.

[0126] The recycled pre-expanded styrene resin particles preferably have an average bubble diameter of 0.01 mm to 0.80 mm, more preferably 0.01 mm to 0.70 mm, even more preferably 0.01 mm to 0.60 mm, particularly preferably 0.01 mm to 0.50 mm, and most preferably 0.01 mm to 0.40 mm. If the average bubble diameter of the recycled pre-expanded styrene resin particles is within the above range, blocking during foaming and molding can be better prevented, and furthermore, while suppressing electrostatic charge during foaming and molding, better fusion properties and surface properties can be exhibited, making it possible to mold recycled styrene resin foam molded articles with less static electricity. If the average bubble diameter of the recycled pre-expanded styrene resin particles is smaller than 0.01 mm, there is a risk that the surface will melt and shrink during molding.

[0127] Pre-foaming involves foaming recycled foamable styrene-based resin particles to a desired bulk expansion ratio (bulk density) using water vapor or the like. The bulk expansion ratio of the recycled pre-foamed styrene-based resin particles is preferably 2 to 150 times, more preferably 2 times or more and less than 100 times, more preferably 5 to 90 times, even more preferably 10 to 85 times, and particularly preferably 15 to 83 times. The bulk density is the reciprocal of the bulk expansion ratio. By having the bulk expansion ratio of the recycled pre-foamed styrene-based resin particles within the above range, blocking during foaming and molding can be further prevented, and furthermore, recycled pre-foamed styrene-based resin particles can be provided that exhibit better fusion properties and surface properties while further suppressing electrostatic charge during foaming and molding, and that recycled styrene-based resin foam molded articles with less static electricity can be molded.

[0128] In one representative embodiment, recycled pre-expanded styrene resin particles can be used in the molding of recycled styrene resin foam molded articles. In another embodiment, recycled pre-expanded styrene resin particles can be used as is as a cushioning material, heat insulating material, concrete aggregate, etc. When recycled pre-expanded styrene resin particles are used as is, they can preferably be used as a filler in which a large number of recycled pre-expanded styrene resin particles are filled into a bag. Such recycled pre-expanded styrene resin particles are suitable for, for example, at least one selected from cushion core material (foamed granules filled inside a cushion) and aggregate.

[0129] <<<D. Recycled styrene-based resin foam molded product>>> A recycled styrene-based resin foam molded article according to one embodiment of the present invention is a recycled styrene-based resin foam molded article formed from recycled foamable styrene-based resin particles according to an embodiment of the present invention. A recycled styrene-based resin foam molded article according to another embodiment of the present invention is a recycled styrene-based resin foam molded article formed from recycled pre-foamed styrene-based resin particles according to an embodiment of the present invention.

[0130] Recycled styrene-based foam molded articles typically contain recycled expanded styrene-based resin particles (hereinafter sometimes simply referred to as "foamed particles") obtained by further foaming recycled pre-expanded styrene-based resin particles.

[0131] Recycled styrene-based foamed molded articles are typically composed of multiple foamed particles that are fused together.

[0132] A recycled styrene foam molded article can typically be produced by placing recycled pre-expanded styrene resin particles into a mold having a predetermined shape according to the purpose, and performing in-mold foam molding. More specifically, in-mold foam molding includes (i) filling a closed mold having a large number of small holes with recycled pre-expanded styrene resin particles, (ii) heating and foaming the recycled pre-expanded styrene resin particles with a heat transfer medium (e.g., pressurized steam) to obtain foamed particles, and (iii) filling the gaps between the foamed particles and fusing the foamed particles together to form a single integrated product through this heating and foaming. The density of the recycled styrene foam molded article can be appropriately set according to the purpose. The density of the recycled styrene foam molded article can be adjusted, for example, by pre-adjusting the bulk expansion ratio of the pre-expanded styrene resin particles to be filled into the mold, or by adjusting the amount of recycled pre-expanded styrene resin particles to be filled into the mold.

[0133] The heating foaming temperature (essentially the temperature of the heat transfer medium) is preferably 90°C to 150°C, and more preferably 110°C to 130°C. The heating foaming time is preferably 5 seconds to 50 seconds, and more preferably 10 seconds to 50 seconds. The molding vapor pressure (gauge pressure of the heat transfer medium) during heating foaming is preferably 0.04 MPa to 0.1 MPa, and more preferably 0.04 MPa to 0.08 MPa. Under these conditions, the foamed particles can be well fused together.

[0134] If necessary, the recycled pre-expanded styrene resin particles may be aged before forming the recycled styrene resin foam molded body. The aging temperature of the recycled pre-expanded styrene resin particles is preferably 20°C to 60°C. If the aging temperature is too low, an excessively long aging time may be required. If the aging temperature is too high, the blowing agent in the recycled pre-expanded styrene resin particles may dissipate and the moldability may decrease.

[0135] The expansion ratio of the expanded particles in the recycled styrene resin foam molded body is preferably 2 times or more and less than 110 times, more preferably 5 times to 90 times, still more preferably 10 times to 85 times, and particularly preferably 15 times to 80 times.

[0136] ≪≪E. Use of Recycled Styrene Resin Foam Molded Body≫≫ The recycled styrene resin foam molded body according to the embodiment of the present invention is lightweight, excellent in heat insulation and mechanical strength, and thus can be preferably used for at least one selected from a molded body for a heat insulating material, a molded body for a heat retaining material, a molded body for an embankment material, a molded body for a food container, a molded body for an industrial product container, a molded body for a cushioning material, and a molded body for a packaging material. Examples of the molded body for a heat insulating material include a heat insulating material for walls, a heat insulating material for floors, a heat insulating material for roofs, and a heat insulating material for automobiles. Examples of the molded body for a heat retaining material include a heat retaining material for a hot water tank, a heat retaining material for piping, a heat retaining material for a solar system, and a heat retaining material for a water heater. Examples of the molded body for a food container include a food container such as a fish box. Examples of the molded body for an industrial product container include a tote box. Examples of the molded body for a cushioning material include a cushioning material, a float, and a block. Examples of the molded body for a packaging material include a packaging material for fish and agricultural products. It can also be used as a core material for tatami mats.

Examples

[0137] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods for each property are as follows. <Measurement Method of Tg> The glass transition temperature (Tg) was measured using the methods described in JIS K7121:1987 and JIS K7121:2012. However, the sampling method and temperature conditions were as follows: 5.5 ± 0.5 mg of the recycled styrene resin raw material was packed into the bottom of an aluminum measuring container without any gaps, and then an aluminum lid was placed over it. Differential scanning calorimetry was then performed using a Hitachi High-Tech Science Corporation "DSC7000X, AS-3" differential scanning calorimetry instrument. Under a nitrogen gas flow rate of 20 mL / min, the sample was heated and cooled in the following steps to obtain the DSC curve. (Step 1) Increase the temperature from 30°C to 200°C at a rate of 20°C / min and hold for 10 minutes. (Step 2) Quickly remove the sample and allow it to cool in an environment of 25±10℃. (Step 3) Heat from 30°C to 200°C at a rate of 20°C / min. From the obtained DSC curve, the intermediate glass transition temperature observed during the second heating process (step 3) was calculated using the analysis software provided with the instrument. Alumina was used as the reference material in this calculation. This intermediate glass transition temperature was determined from JIS K7121:1987 (section 9.3).

[0138] <Odor Evaluation> The odors of expanded styrene resin particles or styrene resin particles, pre-expanded styrene resin particles, and molded articles obtained therefrom were evaluated using olfactory sensory evaluation tests as follows. ×: Strong odor △: Easily detectable odors ○: Weak odor ◎: A smell that can finally be detected

[0139] <Moldability> The molded body was comprehensively evaluated based on the elongation of the surface and the fusion rate when the molded body was fractured. The elongation of the surface of the molded body was evaluated by visually inspecting the appearance of the obtained foamed molded body. Specifically, the condition of the boundary areas where the foam particles bonded on the surface of the foamed molded body was visually evaluated. Furthermore, to evaluate the fusion rate between foam particles when the molded body was fractured, the obtained plate-shaped foamed molded body was fractured by impact, and the total number of foam particles (A) and the number of particles fractured within the particle (B) were counted at the fracture surface, and the fusion rate (%) was calculated using the following formula. Fusion rate (%) = {(B) / (A)} × 100 The following criteria were used for evaluation. ◎: The surface is smooth and the fusion rate is 80% or higher. ○: The surface is smooth and the fusion rate is 70% or higher. △: The surface is mostly smooth, but there are some irregularities at the boundaries, and the fusion rate is between 60% and 70%. ×: The surface has unevenness at the boundaries, resulting in poor smoothness and a fusion rate of less than 60%.

[0140] <Shape of resin particles> Ten arbitrary styrene-based resin particles were selected, and the ratio (L / D) was calculated by dividing the long side (L) by the short side (D). An L / D of 1.0 indicates that the particle is considered perfectly spherical, and the closer the L / D is to 1.0, the closer it is to a perfect sphere.

[0141] <Measurement of bulk density and expansion ratio of pre-expanded styrene resin particles> The bulk density and expansion ratio of the pre-expanded styrene resin particles were measured as follows. (Method for measuring bulk density) Pre-expanded styrene resin particles were allowed to fall naturally into a graduated cylinder as a sample. The bottom of the graduated cylinder was then tapped to stabilize the sample volume, and its volume and mass were measured and calculated using the following formula. Bulk density (g / mL) = Sample mass (g) / Sample volume in graduated cylinder (mL) (Method for measuring the expansion ratio) Pre-expanded styrene resin particles were allowed to fall naturally into a graduated cylinder as a sample. The bottom of the graduated cylinder was then tapped to stabilize the sample volume, and its volume and mass were measured and calculated using the following formula. The specific gravity of the resin was assumed to be 1.0 for styrene resins. Expanding ratio (times) = Sample volume in graduated cylinder (mL) / Sample mass (g) × Resin specific gravity The bulk expansion ratio may also be calculated as the reciprocal of the bulk density.

[0142] <Measurement of density and foaming ratio of styrene-based resin foam molded products> (Method for measuring density) The density of the styrene foam molded article was calculated using the following formula, after measuring the dimensions and mass of the test specimen to at least three significant figures. Density (g / cm 3 ) = Mass of test specimen (g) / Volume of test specimen (cm³) 3 ) (Method for measuring foaming ratio) The foaming ratio of the styrene-based resin foam molded article was calculated using the following formula, after measuring the dimensions and mass of the test specimen to at least three significant figures. The resin specific gravity was assumed to be 1.0 for styrene-based resins. Expansion ratio (times) = Test specimen volume (cm³) 3 ) / Test specimen mass (g) × Resin specific gravity

[0143] [Manufacturing Example 1] <Manufacturing of recycled styrene-based resin raw material particles (a)> Used styrene resin (recycled styrene resin made from expanded polystyrene) was supplied to a single-screw extruder, heated and melted at 200°C, and then cut from the mold underwater to obtain recycled styrene resin raw material particles (a) with an average particle diameter of 0.75 mm (approximately spherical).

[0144] [Example 1] <Preparation of recycled foamed styrene-based resin particles> In a 100-liter reactor with a stirrer, 36 kg of pure water, 3 g of sodium dodecylbenzenesulfonate, and 150 g of tricalcium phosphate were added. Then, 12.6 kg of recycled styrene resin raw material particles (a) were added, and the mixture was stirred at 140 rpm to suspend it, preparing suspension (1). Separately, 1.9 kg of styrene monomer, in which 125 g of benzoyl peroxide (75% purity) and 21 g of t-butyl peroxy-2-ethylhexyl monocarbonate were dissolved, was added to a dispersion of 2.5 kg of pure water and 0.8 g of sodium dodecylbenzenesulfonate as polymerization initiators. The mixture was stirred with a homomixer to create an emulsion, and emulsion (1) was prepared. The above suspension (1) in a 100-liter reactor with a stirrer was maintained at 75°C, and the above emulsion (1) was added. Subsequently, the recycled styrene resin raw material particles (a) were held at 75°C for 30 minutes to ensure good absorption of the styrene monomer and polymerization initiator. Immediately after this period, 27.5 kg of styrene monomer was added dropwise over 130 minutes. The addition temperature was gradually increased from 75°C to 105°C. Subsequently, the temperature was raised to 125°C over 30 minutes, held at 125°C for 1 hour, and then cooled to 60°C over 1 hour. This prepared recycled styrene-based resin particles (1) in the reactor. The Tg of the recycled styrene-based resin particles (1) was 100°C. Separately, 50 g of ethylenebis-stearamide and 150 g of dicumyl peroxide were added to a dispersion of 3.2 kg of pure water, 1.7 g of sodium dodecylbenzenesulfonate as a surfactant, and 20 g of tricalcium phosphate as a dispersant. The mixture was stirred in a homomixer to prepare emulsion (2), and this emulsion (2) was added to the reactor cooled to 60°C. Ten minutes after this addition, 660 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes. Next, 3410g of pentane (isopentane / n-pentane = 20% by mass / 80% by mass) was injected as a blowing agent at an injection temperature of Tg -50°C for the recycled styrene resin particles (1), and held in that state for 5 hours to slowly impregnate the particles with the blowing agent. That is, the injection temperature of the blowing agent was Tg -50°C for the recycled styrene resin particles (1), and the impregnation temperature of the blowing agent was Tg -50°C for the recycled styrene resin particles (1). After that, the temperature inside the reactor was cooled to 30°C. Subsequently, the contents were removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene-based resin particles (1). <Surface treatment of recycled foamed styrene-based resin particles> 40 kg of the obtained recycled foamed styrene resin particles (1), along with 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglycerides, and 16 g of fatty acid monoglycerides, were placed in a tumbler mixer and stirred for 30 minutes to perform surface treatment, thereby obtaining surface-treated recycled foamed styrene resin particles (1'). <Preparation of recycled polystyrene-based resin particles> The obtained recycled foamed styrene resin particles (1') were stored in a refrigerated storage facility at 15°C for 15 days, then placed into a cylindrical batch-type foaming machine with a volume of 25 liters, and heated with steam for 2 minutes to obtain recycled pre-foamed styrene resin particles (1). The bulk density of the recycled pre-foamed styrene resin particles (1) was 0.02 g / cm³. 3 The expansion ratio was 50 times. <Fabrication of Recycled Styrene Resin Foam Moldings> The obtained recycled pre-expanded styrene resin particles (1) were left in a room temperature atmosphere for 24 hours. Then, using a molding machine with a mold having a cavity size of 300 mm in width, 400 mm in length, and 30 mm in thickness, the recycled pre-expanded styrene resin particles (1) were filled into the cavity of the mold, heated at a vapor pressure of 0.08 MPa (gauge pressure) for 30 seconds, and then cooled until the internal pressure of the mold reached 0.03 MPa. After that, the material was released from the mold to obtain a plate-shaped recycled styrene resin foam molded body (1) corresponding to the mold. The density of the recycled styrene resin foam molded body (1) was 0.02 g / cm³. 3The foaming ratio was 50 times. Subsequently, the recycled styrene-based resin foam molded product (1) was stored in a drying chamber at 50°C for one day. The results of various evaluations are shown in Table 1. Furthermore, the foamed styrene resin particles, foamed styrene resin particles, pre-foamed styrene resin particles, and styrene resin foam molded articles described in Examples 2 to 58 and Comparative Examples 1 to 8 are similarly recycled foamed styrene resin particles, recycled foamed styrene resin particles, recycled pre-foamed styrene resin particles, and recycled styrene resin foam molded articles, respectively.

[0145] [Example 2] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 1, and recycled foamable styrene resin particles (2), surface-treated recycled foamable styrene resin particles (2'), recycled pre-foamed styrene resin particles (2), and recycled styrene resin foam molded articles (2) were obtained. The results of various evaluations are shown in Table 1.

[0146] [Example 3] Except for changing the injection temperature and impregnation temperature of the foaming agent to Tg -25°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (3), surface-treated recycled foamable styrene resin particles (3'), recycled pre-foamed styrene resin particles (3), and recycled styrene resin foam molded article (3). The results of various evaluations are shown in Table 1.

[0147] [Example 4] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 3 to obtain recycled foamable styrene resin particles (4), surface-treated recycled foamable styrene resin particles (4'), recycled pre-foamed styrene resin particles (4), and recycled styrene resin foam molded articles (4). The results of various evaluations are shown in Table 1.

[0148] [Example 5] Except for changing the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (5), surface-treated recycled foamable styrene resin particles (5'), recycled pre-foamed styrene resin particles (5), and recycled styrene resin foam molded article (5). The results of various evaluations are shown in Table 1.

[0149] [Example 6] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 5, and recycled foamable styrene resin particles (6), surface-treated recycled foamable styrene resin particles (6'), recycled pre-foamed styrene resin particles (6), and recycled styrene resin foam molded articles (6) were obtained. The results of various evaluations are shown in Table 1.

[0150] [Example 7] Except for changing the injection temperature of the foaming agent to -30°C of the Tg of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1, and recycled foamable styrene resin particles (7), surface-treated recycled foamable styrene resin particles (7'), recycled pre-foamed styrene resin particles (7), and recycled styrene resin foam molded article (7) were obtained. The results of various evaluations are shown in Table 1.

[0151] [Example 8] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 7, and recycled foamable styrene resin particles (8), surface-treated recycled foamable styrene resin particles (8'), recycled pre-foamed styrene resin particles (8), and recycled styrene resin foam molded articles (8) were obtained. The results of various evaluations are shown in Table 1.

[0152] [Example 9] Except for changing the injection temperature of the foaming agent to -10°C of the Tg of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1, and recycled foamable styrene resin particles (9), surface-treated recycled foamable styrene resin particles (9'), recycled pre-foamed styrene resin particles (9), and recycled styrene resin foam molded article (9) were obtained. The results of various evaluations are shown in Table 1.

[0153] [Example 10] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 9 to obtain recycled foamable styrene resin particles (10), surface-treated recycled foamable styrene resin particles (10'), recycled pre-foamed styrene resin particles (10), and recycled styrene resin foam molded articles (10). The results of various evaluations are shown in Table 1.

[0154] [Example 11] Except for changing the injection temperature of the foaming agent to -5°C of the Tg of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (11), surface-treated recycled foamable styrene resin particles (11'), recycled pre-foamed styrene resin particles (11), and recycled styrene resin foam molded article (11). The results of various evaluations are shown in Table 1.

[0155] [Example 12] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 11 to obtain recycled foamable styrene resin particles (12), surface-treated recycled foamable styrene resin particles (12'), recycled pre-foamed styrene resin particles (12), and recycled styrene resin foam molded articles (12). The results of various evaluations are shown in Table 1.

[0156] [Example 13] Except for changing the injection temperature of the foaming agent to the Tg of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1, and recycled foamable styrene resin particles (13), surface-treated recycled foamable styrene resin particles (13'), recycled pre-foamed styrene resin particles (13), and recycled styrene resin foam molded article (13) were obtained. The results of various evaluations are shown in Table 1.

[0157] [Example 14] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (14), surface-treated recycled foamable styrene resin particles (14'), recycled pre-foamed styrene resin particles (14), and recycled styrene resin foam molded articles (14). The results of various evaluations are shown in Table 1.

[0158] [Example 15] Except for changing the impregnation temperature of the foaming agent to Tg + 10°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (15), surface-treated recycled foamable styrene resin particles (15'), recycled pre-foamed styrene resin particles (15), and recycled styrene resin foam molded article (15). The results of various evaluations are shown in Table 1.

[0159] [Example 16] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 15 to obtain recycled foamable styrene resin particles (16), surface-treated recycled foamable styrene resin particles (16'), recycled pre-foamed styrene resin particles (16), and recycled styrene resin foam molded articles (16). The results of various evaluations are shown in Table 1.

[0160] [Example 17] Except for changing the injection temperature of the foaming agent to Tg + 5°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (17), surface-treated recycled foamable styrene resin particles (17'), recycled pre-foamed styrene resin particles (17), and recycled styrene resin foam molded article (17). The results of various evaluations are shown in Table 1.

[0161] [Example 18] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 17 to obtain recycled foamable styrene resin particles (18), surface-treated recycled foamable styrene resin particles (18'), recycled pre-foamed styrene resin particles (18), and recycled styrene resin foam molded articles (18). The results of various evaluations are shown in Table 1.

[0162] [Example 19] Except for changing the injection temperature of the foaming agent to Tg + 10°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 15 to obtain recycled foamable styrene resin particles (19), surface-treated recycled foamable styrene resin particles (19'), recycled pre-foamed styrene resin particles (19), and recycled styrene resin foam molded article (19). The results of various evaluations are shown in Table 1.

[0163] [Example 20] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 19 to obtain recycled foamable styrene resin particles (20), surface-treated recycled foamable styrene resin particles (20'), recycled pre-foamed styrene resin particles (20), and recycled styrene resin foam molded articles (20). The results of various evaluations are shown in Table 1.

[0164] [Example 21] Except for changing the injection temperature of the foaming agent to Tg + 15°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 15°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (21), surface-treated recycled foamable styrene resin particles (21'), recycled pre-foamed styrene resin particles (21), and recycled styrene resin foam molded article (21). The results of various evaluations are shown in Table 1.

[0165] [Example 22] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 21 to obtain recycled foamable styrene resin particles (22), surface-treated recycled foamable styrene resin particles (22'), recycled pre-foamed styrene resin particles (22), and recycled styrene resin foam molded articles (22). The results of various evaluations are shown in Table 1.

[0166] [Example 23] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (23), surface-treated recycled foamable styrene resin particles (23'), recycled pre-foamed styrene resin particles (23), and recycled styrene resin foam molded article (23). The results of various evaluations are shown in Table 1.

[0167] [Example 24] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 23 to obtain recycled foamable styrene resin particles (24), surface-treated recycled foamable styrene resin particles (24'), recycled pre-foamed styrene resin particles (24), and recycled styrene resin foam molded articles (24). The results of various evaluations are shown in Table 1.

[0168] [Example 25] Except for changing the injection temperature of the foaming agent to Tg + 25°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 25°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (25), surface-treated recycled foamable styrene resin particles (25'), recycled pre-foamed styrene resin particles (25), and recycled styrene resin foam molded article (25). The results of various evaluations are shown in Table 1.

[0169] [Example 26] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 25 to obtain recycled foamable styrene resin particles (26), surface-treated recycled foamable styrene resin particles (26'), recycled pre-foamed styrene resin particles (26), and recycled styrene resin foam molded articles (26). The results of various evaluations are shown in Table 1.

[0170] [Example 27] Except for changing the injection temperature of the foaming agent to Tg + 30°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 30°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 14, and recycled foamable styrene resin particles (27), surface-treated recycled foamable styrene resin particles (27'), recycled pre-foamed styrene resin particles (27), and recycled styrene resin foam molded article (27) were obtained. The results of various evaluations are shown in Table 1.

[0171] [Example 28] Except for changing the injection temperature of the foaming agent to Tg + 40°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 40°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 14, and recycled foamable styrene resin particles (28), surface-treated recycled foamable styrene resin particles (28'), recycled pre-foamed styrene resin particles (28), and recycled styrene resin foam molded article (28) were obtained. The results of various evaluations are shown in Table 1.

[0172] [Example 29] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to Tg + 8°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (29), surface-treated recycled foamable styrene resin particles (29'), recycled pre-foamed styrene resin particles (29), and recycled styrene resin foam molded article (29). The results of various evaluations are shown in Table 1.

[0173] [Example 30] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 29 to obtain recycled foamable styrene resin particles (30), surface-treated recycled foamable styrene resin particles (30'), recycled pre-foamed styrene resin particles (30), and recycled styrene resin foam molded articles (30). The results of various evaluations are shown in Table 1.

[0174] [Example 31] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to Tg + 10°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (31), surface-treated recycled foamable styrene resin particles (31'), recycled pre-foamed styrene resin particles (31), and recycled styrene resin foam molded article (31). The results of various evaluations are shown in Table 1.

[0175] [Example 32] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 31 to obtain recycled foamable styrene resin particles (32), surface-treated recycled foamable styrene resin particles (32'), recycled pre-foamed styrene resin particles (32), and recycled styrene resin foam molded articles (32). The results of various evaluations are shown in Table 1.

[0176] [Example 33] Except for changing the impregnation temperature of the foaming agent to Tg + 18°C ​​of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (33), surface-treated recycled foamable styrene resin particles (33'), recycled pre-foamed styrene resin particles (33), and recycled styrene resin foam molded article (33). The results of various evaluations are shown in Table 1.

[0177] [Example 34] Except for using 150 g and 20 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 33 to obtain recycled foamable styrene resin particles (34), surface-treated recycled foamable styrene resin particles (34'), recycled pre-foamed styrene resin particles (34), and recycled styrene resin foam molded articles (34). The results of various evaluations are shown in Table 1.

[0178] [Example 35] Except for using 37 g and 5 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 14 to obtain recycled foamable styrene resin particles (35), surface-treated recycled foamable styrene resin particles (35'), recycled pre-foamed styrene resin particles (35), and recycled styrene resin foam molded articles (35). The results of various evaluations are shown in Table 1.

[0179] [Example 36] Except for using 757 g and 103 g of magnesium pyrophosphate as dispersants instead of 150 g and 20 g of tricalcium phosphate in the preparation of the suspension (1) and emulsion (2), the procedure was carried out in the same manner as in Example 14 to obtain recycled foamable styrene resin particles (36), surface-treated recycled foamable styrene resin particles (36'), recycled pre-foamed styrene resin particles (36), and recycled styrene resin foam molded articles (36). The results of various evaluations are shown in Table 1.

[0180] [Example 37] Except for changing the amount of sodium dodecylbenzenesulfonate used as the surfactant in the preparation of suspension (1), emulsion (1), and (2) from 3 g, 0.8 g, and 1.7 g to 1.2 g, 0.3 g, and 0.6 g, the procedure was carried out in the same manner as in Example 14, and recycled foamable styrene resin particles (37), surface-treated recycled foamable styrene resin particles (37'), recycled pre-foamed styrene resin particles (37), and recycled styrene resin foam molded articles (37) were obtained. The results of various evaluations are shown in Table 1.

[0181] [Example 38] Except for changing the amount of sodium dodecylbenzenesulfonate used as the surfactant in the preparation of suspension (1), emulsion (1), and (2) from 3 g, 0.8 g, and 1.7 g to 22.9 g, 6.1 g, and 13 g, the procedure was carried out in the same manner as in Example 14, and recycled foamable styrene resin particles (38), surface-treated recycled foamable styrene resin particles (38'), recycled pre-foamed styrene resin particles (38), and recycled styrene resin foam molded article (38) were obtained. The results of various evaluations are shown in Table 1.

[0182] [Example 39] <Preparation of recycled foamed styrene-based resin particles> In a 100-liter reactor with a stirrer, 42 kg of pure water, 5.5 g of sodium dodecylbenzenesulfonate, and 170 g of tricalcium phosphate were added. 42 kg of recycled styrene resin raw material particles (a) were then added, followed by 34 g of ethylenebis-stearamide. The mixture was stirred at 145 rpm to suspend the mixture and prepare suspension (2). This yielded recycled styrene resin particles (39) in the reactor. The Tg of the recycled styrene resin particles (39) was 100°C. The above suspension (2) in a 100-liter reactor with a stirrer was maintained at 60°C, and 150 g of dicumyl peroxide was added. Ten minutes after this addition, 650 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes. Subsequently, the temperature was raised to 100°C over 30 minutes. Then, 3360g of pentane (isopentane / n-pentane = 20% by mass / 80% by mass) was injected as a blowing agent at the injection temperature of the Tg of the recycled styrene resin particles (39), and the mixture was held in that state for 5 hours to slowly impregnate the particles with the blowing agent. That is, the injection temperature of the blowing agent was equal to the Tg of the recycled styrene resin particles (39), and the impregnation temperature of the blowing agent was equal to the Tg of the recycled styrene resin particles (39). After that, the temperature inside the reactor was cooled to 30°C. Subsequently, the contents were removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene-based resin particles (39). <Surface treatment of recycled foamed styrene-based resin particles> 40 kg of the obtained recycled foamed styrene resin particles (39), along with 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglycerides, and 16 g of fatty acid monoglycerides, were placed in a tumbler mixer and stirred for 30 minutes to perform surface treatment, thereby obtaining surface-treated recycled foamed styrene resin particles (39'). <Preparation of recycled polystyrene-based resin particles> The obtained recycled foamed styrene resin particles (39') were stored in a refrigerated storage facility at 15°C for 15 days. They were then placed in a cylindrical batch-type foaming machine with a volume of 25 liters and heated with steam for 2 minutes to obtain recycled pre-foamed styrene resin particles (39). The bulk density of the recycled pre-foamed styrene resin particles (39) was 0.02 g / cm³. 3 The expansion ratio was 50 times. <Fabrication of styrene-based foamed molded products> The obtained recycled pre-expanded styrene resin particles (39') were left at room temperature for 24 hours. Then, using a molding machine with a mold having a cavity size of 300 mm in width, 400 mm in length, and 30 mm in thickness, the pre-expanded styrene resin particles (39') were filled into the cavity of the mold, heated at a vapor pressure of 0.08 MPa (gauge pressure) for 40 seconds, and then cooled until the internal pressure of the mold reached 0.03 MPa. After demolding, a block-shaped recycled styrene resin foam molded body (39) corresponding to the mold was obtained. The density of the recycled styrene resin foam molded body (39) was 0.02 g / cm³. 3 The foaming ratio was 50 times. Subsequently, the recycled styrene-based resin foam molded product (39) was stored in a drying chamber at 50°C for one day. The results of various evaluations are shown in Table 1.

[0183] [Example 40] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (40), surface-treated recycled foamable styrene resin particles (40'), recycled pre-foamed styrene resin particles (40), and recycled styrene resin foam molded articles (40). The results of various evaluations are shown in Table 1.

[0184] [Example 41] Except for changing the impregnation temperature of the foaming agent to Tg + 10°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (41), surface-treated recycled foamable styrene resin particles (41'), recycled pre-foamed styrene resin particles (41), and recycled styrene resin foam molded article (41). The results of various evaluations are shown in Table 1.

[0185] [Example 42] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 41 to obtain recycled foamable styrene resin particles (42), surface-treated recycled foamable styrene resin particles (42'), recycled pre-foamed styrene resin particles (42), and recycled styrene resin foam molded articles (42). The results of various evaluations are shown in Table 1.

[0186] [Example 43] Except for changing the impregnation temperature of the foaming agent to Tg + 18°C ​​of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (43), surface-treated recycled foamable styrene resin particles (43'), recycled pre-foamed styrene resin particles (43), and recycled styrene resin foam molded article (43). The results of various evaluations are shown in Table 1.

[0187] [Example 44] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 43 to obtain recycled foamable styrene resin particles (44), surface-treated recycled foamable styrene resin particles (44'), recycled pre-foamed styrene resin particles (44), and recycled styrene resin foam molded articles (44). The results of various evaluations are shown in Table 1.

[0188] [Example 45] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (39) and the impregnation temperature of the foaming agent to Tg + 8°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (45), surface-treated recycled foamable styrene resin particles (45'), recycled pre-foamed styrene resin particles (45), and recycled styrene resin foam molded article (45). The results of various evaluations are shown in Table 1.

[0189] [Example 46] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 45 to obtain recycled foamable styrene resin particles (46), surface-treated recycled foamable styrene resin particles (46'), recycled pre-foamed styrene resin particles (46), and recycled styrene resin foam molded article (46). The results of various evaluations are shown in Table 1.

[0190] [Example 47] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (39) and changing the impregnation temperature of the foaming agent to Tg + 10°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (47), surface-treated recycled foamable styrene resin particles (47'), recycled pre-foamed styrene resin particles (47), and recycled styrene resin foam molded article (47). The results of various evaluations are shown in Table 1.

[0191] [Example 48] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 47 to obtain recycled foamable styrene resin particles (48), surface-treated recycled foamable styrene resin particles (48'), recycled pre-foamed styrene resin particles (48), and recycled styrene resin foam molded article (48). The results of various evaluations are shown in Table 1.

[0192] [Example 49] Except for changing the injection temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (39) and the impregnation temperature of the foaming agent to Tg + 20°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (49), surface-treated recycled foamable styrene resin particles (49'), recycled pre-foamed styrene resin particles (49), and recycled styrene resin foam molded article (49). The results of various evaluations are shown in Table 1.

[0193] [Example 50] Except for using 170 g of magnesium pyrophosphate instead of 170 g of tricalcium phosphate as a dispersant in the preparation of suspension (2), the procedure was carried out in the same manner as in Example 49 to obtain recycled foamable styrene resin particles (50), surface-treated recycled foamable styrene resin particles (50'), recycled pre-foamed styrene resin particles (50), and recycled styrene resin foam molded articles (50). The results of various evaluations are shown in Table 1.

[0194] [Example 51] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 13 to obtain recycled foamable styrene resin particles (51), surface-treated recycled foamable styrene resin particles (51'), recycled pre-foamed styrene resin particles (51), and recycled styrene resin foam molded articles (51). The results of various evaluations are shown in Table 1.

[0195] [Example 52] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 14 to obtain recycled foamable styrene resin particles (52), surface-treated recycled foamable styrene resin particles (52'), recycled pre-foamed styrene resin particles (52), and recycled styrene resin foam molded articles (52). The results of various evaluations are shown in Table 1.

[0196] [Example 53] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 29 to obtain recycled foamed styrene resin particles (53), surface-treated recycled foamed styrene resin particles (53'), recycled pre-foamed styrene resin particles (53), and recycled styrene resin foam molded articles (53). The results of various evaluations are shown in Table 1.

[0197] [Example 54] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 30 to obtain recycled foamable styrene resin particles (54), surface-treated recycled foamable styrene resin particles (54'), recycled pre-foamed styrene resin particles (54), and recycled styrene resin foam molded articles (54). The results of various evaluations are shown in Table 1.

[0198] [Example 55] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamed styrene resin particles (55), surface-treated recycled foamed styrene resin particles (55'), recycled pre-foamed styrene resin particles (55), and recycled styrene resin foam molded articles (55). The results of various evaluations are shown in Table 1.

[0199] [Example 56] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 40 to obtain recycled foamed styrene resin particles (56), surface-treated recycled foamed styrene resin particles (56'), recycled pre-foamed styrene resin particles (56), and recycled styrene resin foam molded articles (56). The results of various evaluations are shown in Table 1.

[0200] [Example 57] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 45 to obtain recycled foamed styrene resin particles (57), surface-treated recycled foamed styrene resin particles (57'), recycled pre-foamed styrene resin particles (57), and recycled styrene resin foam molded articles (57). The results of various evaluations are shown in Table 1.

[0201] [Example 58] Except for not using a flame retardant (tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)) and a flame retardant additive (dicumyl peroxide), the procedure was carried out in the same manner as in Example 46 to obtain recycled foamed styrene resin particles (58), surface-treated recycled foamed styrene resin particles (58'), recycled pre-foamed styrene resin particles (58), and recycled styrene resin foam molded articles (58). The results of various evaluations are shown in Table 1.

[0202] [Comparative Example 1] Except for changing the injection temperature of the foaming agent to Tg-60°C of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to Tg-30°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (C1), surface-treated recycled foamable styrene resin particles (C1'), recycled pre-foamed styrene resin particles (C1), and recycled styrene resin foam molded article (C1). The results of various evaluations are shown in Table 1.

[0203] [Comparative Example 2] Except for changing the injection temperature of the foaming agent to -60°C of the Tg of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to the Tg of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (C2), surface-treated recycled foamable styrene resin particles (C2'), recycled pre-foamed styrene resin particles (C2), and recycled styrene resin foam molded articles (C2). The results of various evaluations are shown in Table 1.

[0204] [Comparative Example 3] Except for changing the injection temperature of the foaming agent to the Tg of the recycled styrene resin particles (1) and changing the impregnation temperature of the foaming agent to Tg -60°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1 to obtain recycled foamable styrene resin particles (C3), surface-treated recycled foamable styrene resin particles (C3'), recycled pre-foamed styrene resin particles (C3), and recycled styrene resin foam molded article (C3). The results of various evaluations are shown in Table 1.

[0205] [Comparative Example 4] Except for changing the injection temperature of the foaming agent to Tg + 50°C of the recycled styrene resin particles (1) and the impregnation temperature of the foaming agent to Tg + 50°C of the recycled styrene resin particles (1), the procedure was carried out in the same manner as in Example 1, and recycled foamable styrene resin particles (C4), surface-treated recycled foamable styrene resin particles (C4'), recycled pre-foamed styrene resin particles (C4), and recycled styrene resin foam molded article (C4) were obtained. The results of various evaluations are shown in Table 1.

[0206] [Comparative Example 5] Except for changing the injection temperature of the foaming agent to Tg-60°C of the recycled styrene resin particles (39) and changing the impregnation temperature of the foaming agent to Tg-30°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (C5), surface-treated recycled foamable styrene resin particles (C5'), recycled pre-foamed styrene resin particles (C5), and recycled styrene resin foam molded articles (C5). The results of various evaluations are shown in Table 1.

[0207] [Comparative Example 6] Except for changing the injection temperature of the foaming agent to Tg-60°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (C6), surface-treated recycled foamable styrene resin particles (C6'), recycled pre-foamed styrene resin particles (C6), and recycled styrene resin foam molded article (C6). The results of various evaluations are shown in Table 1.

[0208] [Comparative Example 7] Except for changing the injection temperature of the foaming agent to the impregnation temperature Tg -60°C of the foaming agent for recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (C7), surface-treated recycled foamable styrene resin particles (C7'), recycled pre-foamed styrene resin particles (C7), and recycled styrene resin foam molded articles (C7). The results of various evaluations are shown in Table 1.

[0209] [Comparative Example 8] Except for changing the injection temperature of the foaming agent to Tg + 50°C of the recycled styrene resin particles (39) and the impregnation temperature of the foaming agent to Tg + 50°C of the recycled styrene resin particles (39), the procedure was carried out in the same manner as in Example 39 to obtain recycled foamable styrene resin particles (C8), surface-treated recycled foamable styrene resin particles (C8'), recycled pre-foamed styrene resin particles (C8), and recycled styrene resin foam molded articles (C8). The results of various evaluations are shown in Table 1.

[0210] [Table 1] [Industrial applicability]

[0211] The recycled foamable styrene-based resin particles, recycled pre-foamed styrene-based resin particles, and recycled styrene-based resin foam molded articles according to embodiments of the present invention are suitably used as insulation materials for houses and automobiles, heat-insulating materials for building materials, transport packaging materials for fish boxes and food containers, cushioning materials, etc. More specifically, the recycled foamable styrene-based resin particles, recycled pre-foamed styrene-based resin particles, and recycled styrene-based resin foam molded articles according to embodiments of the present invention are suitably used as insulation materials for walls, floors, roofs, automobiles, hot water tanks, pipes, solar systems, water heaters, containers for food and industrial products (e.g., food containers such as fish boxes, returnable containers), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, embankment materials (embankment blocks, etc.), tatami mat core materials, cushion core materials, concrete aggregates, etc.

Claims

1. A method for producing recycled foamable styrene resin particles, comprising impregnating a suspension containing recycled styrene resin raw material (A) and a dispersant with a foaming agent by pressurizing it, When the glass transition temperature of the recycled styrene-based resin raw material (A) is Tg, the temperature at which the foaming agent is injected is T1, and the temperature at which the foaming agent is impregnated is T2, T1 is within the range of (Tg - 50°C) or (Tg + 40°C), and T2 is within the range of (Tg - 50°C) or (Tg + 40°C), As the recycled styrene-based resin raw material (A), recycled styrene-based resin raw material particles (a) are used as is. The recycled styrene resin raw material particles (a) are either water-cut pellets obtained by an underwater cutting method in which used styrene resin is extruded by an extruder and simultaneously cut underwater, or mini-pellets obtained by repeatedly using a melt extrusion method in which used styrene resin is extruded by an extruder, resulting in pellets smaller in size than the initially obtained pellets. A method for producing recycled foamed styrene-based resin particles.

2. A method for producing recycled foamable styrene-based resin particles according to claim 1, wherein T1 is in the range of (Tg - 50°C) or more and (Tg + 40°C) or less, and T2 is in the range of (Tg - 50°C) or more and less than (Tg + 10°C).

3. The method for producing recycled foamable styrene-based resin particles according to claim 2, wherein the dispersant is at least one selected from the group consisting of organic dispersants and sparingly soluble inorganic salts.

4. A method for producing recycled foamable styrene-based resin particles according to claim 1, wherein T1 is in the range of (Tg + 10°C) or more and (Tg + 30°C) or less, and T2 is in the range of (Tg + 10°C) or more and (Tg + 30°C) or less.

5. The method for producing regenerative foamable styrene-based resin particles according to claim 4, wherein the dispersant is magnesium pyrophosphate.

6. A method for producing recycled foamable styrene-based resin particles according to claim 1, wherein the blending ratio of the dispersant to 100 parts by mass of the recycled styrene-based resin raw material (A) is 0.1 parts by mass to 2 parts by mass.

7. A method for producing regenerative foamable styrene-based resin particles according to claim 1, wherein the suspension contains a surfactant.

8. A method for producing recycled foamable styrene-based resin particles according to claim 7, wherein the blending ratio of the surfactant to 100 parts by mass of the recycled styrene-based resin raw material (A) is 0.005 parts by mass to 0.1 parts by mass.

9. Recycled foamable styrene resin particles produced by the manufacturing method described in any one of claims 1 to 8 are pre-foamed at a bulk expansion ratio of 2 to 150 times to form recycled pre-foamed styrene resin particles. A method for producing recycled pre-expanded styrene resin particles.

10. A method for producing a recycled styrene-based resin foam molded article, comprising molding a recycled styrene-based resin foam molded article using recycled pre-expanded styrene-based resin particles produced by the manufacturing method described in claim 9.

11. The method for producing a recycled styrene-based foam molded article according to claim 10, wherein the recycled styrene-based resin foam molded article is at least one selected from a molded article for thermal insulation, a molded article for heat retention, a molded article for embankment material, a molded article for food containers, a molded article for industrial product containers, a molded article for cushioning material, and a molded article for packaging material.

12. The method for producing recycled pre-expanded styrene resin particles according to claim 9, wherein the recycled pre-expanded styrene resin particles are at least one selected from the core material and the aggregate material of a cushion.

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