Recycled foamed styrene resin particles

Abstract

To provide recycled foamed styrene resin particles that have a high environmental impact and improved moldability. [Solution] The recycled foamable styrene resin particles according to the embodiment of the present invention are recycled foamable styrene resin particles obtained by injecting and impregnating recycled styrene resin particles (A) with a foaming agent, and have a weight-average molecular weight of 300,000 to 1,000,000, and contain 50.0% or more by mass fraction of polymer components whose molecular weight M obtained by GPC measurement is greater than 200,000.

Description

Technical Field

[0001] The present invention relates to recycled expandable styrene-based resin particles.

Background Art

[0002] Foamed molded articles are lightweight, excellent in heat insulation and mechanical strength, and are therefore widely used as heat insulating materials for housing and automobiles, heat insulating materials for building materials, embankment materials for foamed styrene civil engineering methods, transport packaging materials such as fish boxes and food containers, and cushioning materials. Among them, in-mold foamed molded articles produced from expandable particles (typically expandable polystyrene-based resin particles or pre-expanded styrene-based resin particles obtained by pre-expanding them) are widely used because of advantages such as being easy to obtain a desired shape. Such a foamed molded article 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, etc., which has become a major social problem such as environmental pollution, global warming, and a shortage of landfill disposal sites. For this reason, 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, from the viewpoints of resource circulation and reduction of environmental load, material recycling that reuses plastic waste as a plastic member of a product again has attracted attention, and such material recycling has also been studied for styrene-based resin foamed molded articles.

[0004] As material recycling of styrene-based resin foamed molded articles, conventionally, several types of recycled expandable styrene-based resin particles have been proposed, which are obtained by melting and extruding recovered raw materials to obtain recovered pellets and impregnating them with a foaming agent.

[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, either by impregnation or by injection followed by impregnation (Patent Documents 1-4). Furthermore, a method for obtaining recycled foamable styrene-based resin particles has been reported by adding styrene monomers to recycled resin pellets, molded from recovered styrene-based resin foam molded products, performing nuclear polymerization, and then impregnating or by injection followed by impregnation with a foaming agent (Patent Documents 5-9).

[0006] However, conventional recycled foamed styrene resin particles have a problem in that, due to foreign matter in the recovered raw materials, the bubbles in the foamed particles become very fine, resulting in a thin bubble film. This thin bubble film is prone to rupture during molding, leading to molding defects. [Prior art documents] [Patent Documents]

[0007] [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 [Patent Document 9] Japanese Patent Publication No. 2022-153315 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide recycled foamed styrene resin particles that have a high contribution to the environment and improved moldability. [Means for solving the problem]

[0009] [1] Recycled foamed styrene resin particles according to embodiments of the present invention are Recycled foamable styrene resin particles obtained by injecting and impregnating recycled styrene resin particles (A) with a foaming agent, The weight-average molecular weight is between 300,000 and 1,000,000. It contains 50.0% or more by mass fraction of polymer components with a molecular weight M greater than 200,000, as determined by GPC measurement. [2] In the recycled foamable styrene resin particles described in [1] above, the recycled styrene resin particles (A) may be obtained by nucleation polymerization of styrene monomers with recycled styrene resin raw material particles (a) as a nucleus in the presence of a polymerization initiator. [3] In the recycled foamable styrene resin particles described in [2] above, the polymerization initiator may include a peroxyester polymerization initiator. [4] In the recycled foamable styrene resin particles described in [2] or [3] above, the polymerization initiator in the nuclear polymerization may be 0.05% to 1.00% by mass relative to the styrene monomer. [5] In the recycled foamable styrene resin particles described in any one of [2] to [4] above, the weight-average molecular weight of the recycled styrene resin raw material particles (a) may be 100,000 to 450,000. [6] The recycled foamable styrene resin particles described in any one of [1] to [5] above may contain 8.0% or more by mass fraction of a polymer component having a molecular weight M greater than 1 million. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide recycled foamed styrene-based resin particles that have a high environmental impact and improved moldability.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0012] In this specification, when "(meth)acryl" is mentioned, it means acrylic and / or methacrylic, and when "(meth)acrylate" is mentioned, it means acrylate and / or methacrylate.

[0013] ≪≪1. Recyclable Foamable Styrene Resin Particles≫≫ The recyclable foamable styrene resin particles according to the embodiment of the present invention have a particle shape as a whole. The average particle diameter of the recyclable foamable styrene resin particles is preferably 0.40 mm to 2.0 mm, 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 taken as the particle diameter at the 50% integrated value from the particle size distribution by the sieving test of JIS Z 8815.

[0014] As the shape of the recyclable foamable styrene resin particles according to the embodiment of the present invention, any appropriate shape can be adopted as long as the effects of the present invention are not impaired. Specific examples of such shapes include, for example, spherical, substantially spherical, elliptical spherical (oval), and the like. As the shape of the recyclable foamable styrene resin particles according to the embodiment of the present invention, from the viewpoint of expressing the effects of the present invention, it is preferably spherical or substantially spherical, and more preferably spherical. However, in reality, it is difficult to distinguish between spherical and substantially spherical, so in this specification, both are combined and regarded as spherical.

[0015] The weight average molecular weight Mw of the recycled foaming styrenic resin particles according to the embodiments of the present invention is from 300,000 to 1,000,000, preferably from 400,000 to 1,000,000, more preferably from 400,000 to 920,000, still more preferably from 420,000 to 780,000, still more preferably from 430,000 to 760,000, further preferably from 440,000 to 740,000, particularly preferably from 440,000 to 720,000, and most preferably from 480,000 to 720,000. Alternatively, the weight average molecular weight Mw of the recycled foaming styrenic resin particles is more preferably from 450,000 to 1,000,000, and further preferably from 480,000 to 950,000.

[0016] The recycled foaming styrenic resin particles according to the embodiments of the present invention contain, by mass fraction, 50.0% or more of a polymer component having a molecular weight M of more than 200,000 obtained by gel permeation chromatography (GPC) measurement. In the recycled foaming styrenic resin particles according to the embodiments of the present invention, the mass fraction of the polymer component having a molecular weight M of more than 200,000 is preferably 50.5% or more, more preferably 51.0% or more, still more preferably 55.0% or more, and particularly preferably 59.0% or more. The upper limit value of the mass fraction of the polymer component having a molecular weight M of more than 200,000 is, for example, 100.0%, and preferably 90.0% or less.

[0017] With the above configuration, the recycled foaming styrenic resin particles according to the embodiments of the present invention can exhibit improved moldability.

[0018] In this specification, "containing, by mass fraction, 50% or more of a polymer component having a molecular weight M of more than 200,000 obtained by GPC measurement" means that in the integral molecular weight distribution curve obtained for the molecular weight M obtained by GPC measurement, the component having a molecular weight M of 200,000 or less is less than 50% of the whole, that is, in the integral molecular weight distribution curve, the component having a molecular weight M of more than 200,000 is 50% or more of the whole.

[0019] The recycled foaming styrenic resin particles according to the embodiments of the present invention preferably contain, by mass fraction, 8.0% or more of a polymer component having a molecular weight M of more than 1,000,000 obtained by GPC measurement.

[0020] From another aspect, the present invention provides recycled foamable styrene resin particles obtained by injecting and impregnating recycled styrene resin particles (A) with a foaming agent, wherein the weight-average molecular weight is 400,000 to 800,000, and the polymer component has a molecular weight M greater than 1,000,000 as determined by GPC measurement, and contains 8.0% or more by mass fraction of this polymer component.

[0021] In the recycled foamed styrene resin particles, the mass fraction of polymer components with a molecular weight M greater than 1 million is preferably 10.0% or more, more preferably 11.0% or more, even more preferably 11.5% or more, even more preferably 12.0% or more, and particularly preferably 13.0% or more. The upper limit of the mass fraction of polymer components with a molecular weight M greater than 1 million is, for example, 70.0% or less, and preferably 50.0% or less.

[0022] The average Z molecular weight Mz of the recycled foamable styrene-based resin particles according to the embodiments of the present invention can be any suitable average Z molecular weight Mz within a range that does not impair the effects of the present invention. Such an average Z molecular weight Mz is preferably 580,000 to 5,000,000, more preferably 600,000 to 4,500,000, more preferably 750,000 to 4,000,000, more preferably 900,000 to 4,000,000, more preferably 1,000,000 to 4,000,000, even more preferably 1,100,000 to 4,000,000, particularly preferably 1,200,000 to 4,000,000, and most preferably 1,350,000 to 4,000,000. In some cases, the average Z molecular weight Mz of the recycled foamable styrene-based resin particles may be 3,500,000 or less, or 3,000,000 or less.

[0023] As the Z+1 average molecular weight Mz+1 of the recycled foamable styrene-based resin particles according to the embodiments of the present invention, any suitable Z+1 average molecular weight Mz+1 can be adopted within a range that does not impair the effects of the present invention. Such a Z+1 average molecular weight Mz+1 is preferably 1.1 million to 15 million, more preferably 1.2 million to 12 million, more preferably 1.5 million to 11 million, more preferably 2 million to 10 million, more preferably 2.3 million to 10 million, even more preferably 2.4 million to 10 million, particularly preferably 2.5 million to 10 million, and most preferably 2.7 million to 10 million. In some cases, the Z+1 average molecular weight Mz+1 of the recycled foamable styrene-based resin particles may be 7 million or less, or 6 million or less.

[0024] <1-1. Recycled styrene resin particles (A)> The recycled foamable styrene-based resin particles according to the embodiment of the present invention are obtained by pressurizing and impregnating recycled styrene-based resin particles (A) with a foaming agent.

[0025] The weight-average molecular weight of the recycled styrene-based resin particles (A) can be any appropriate weight-average molecular weight within a range that does not impair the effects of the present invention. For example, such a weight-average molecular weight is 300,000 to 1,000,000, preferably 400,000 to 1,000,000, more preferably 400,000 to 920,000, more preferably 420,000 to 850,000, more preferably 430,000 to 800,000, even more preferably 440,000 to 750,000, and particularly preferably 450,000 to 720,000. Alternatively, the weight-average molecular weight of the recycled styrene-based resin particles (A) is more preferably 450,000 to 1,000,000, and even more preferably 480,000 to 950,000.

[0026] Recycled styrene resin particles (A) are typically obtained by nuclear polymerization of styrene monomers using recycled styrene resin raw material particles (a) as a nucleus in the presence of a polymerization initiator.

[0027] The recycled styrene-based resin raw material particles (a) may consist of only one type or two or more types.

[0028] 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 such as fish boxes and agricultural product boxes, cushioning materials, block molded products, etc.), expanded polystyrene sheets (tray containers, sheet scraps, etc.), recycled plastic materials used in home appliances, packaging containers, cushion beads, and OPS (biaxially oriented polystyrene sheets). The recycled styrene resin raw material particles (a) may contain one type of recycled styrene resin from the above materials, or may contain two or more types of recycled styrene resins.

[0029] The recycled styrene-based resin raw material particles (a) may contain any other suitable recycled resins other than recycled styrene-based resins, 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), and 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 of AS resin, recycled resins of ABS resin, and recycled resins of HIPS (high-impact polystyrene) are not included in the category of recycled styrene-based resins.

[0030] As recycled styrene-based resin raw material particles (a), molded products made from the product names "Epsurem" or "Esrenbeads RNW" manufactured by Sekisui Chemical Co., Ltd. may be used.

[0031] As recycled styrene resin raw material particles (a), a pulverized product obtained by heating and / or reducing the volume of used foamed 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.

[0032] 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.

[0033] The pellets obtained by the melt extrusion method described above are preferably at least one selected from: extruded strand pellets obtained by extruding spent expanded styrene resin with an extruder and performing strand cutting; underwater cut pellets obtained by an underwater cut method in which spent expanded styrene resin is extruded with an extruder and simultaneously cut underwater; and hot cut pellets obtained by a hot cut method in which spent expanded styrene resin particles are cut and cooled immediately after coming out of the die of the extruder.

[0034] 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.

[0035] The recycled styrene resin raw material particles (a) may be a shrunk or molten product of expanded styrene resin obtained by coarsely crushing used expanded styrene resin to an appropriate size as needed, and then performing processes such as thermal shrinkage, shrinkage due to bubble bursting by compression, shrinkage due to frictional heat, or melting.

[0036] Examples of used expanded polystyrene resins include molded products made by molding expanded polystyrene resin using a mold, and products made by heat-foaming these products.

[0037] 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.

[0038] 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.

[0039] The average particle size of the finely powdered inorganic material is preferably 100 μm or less, and more preferably 30 μm or less.

[0040] 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 function as a bubble regulator may not be exhibited. 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 moldability and the appearance of the molded product.

[0041] Examples of organic lubricants include liquid paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisatomids such as methylenebisstearamide, ethylenebisstearamide, and ethylenebisoleamide; and metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

[0042] 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) exceeds 2.0% by mass, the bubble size of the recycled pre-expanded styrene resin particles becomes extremely small, which may cause the recycled pre-expanded styrene resin particles to melt during molding, potentially worsening the moldability of the molded product, including its appearance.

[0043] 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 a mixer such as a tumbler, ribbon blender, V-blender, Henschel mixer, or Readygay mixer.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The weight-average molecular weight of the recycled styrene-based resin raw material particles (a) is preferably 100,000 to 450,000, more preferably 100,000 to 300,000, even more preferably 100,000 to 250,000, particularly preferably 120,000 to 230,000, and most preferably 150,000 to 220,000. By satisfying the above numerical range for the weight-average molecular weight of the recycled styrene-based resin raw material particles (a), the moldability of the resulting recycled foamable styrene-based resin particles during foaming and molding can be further improved. In some cases, the weight-average molecular weight of the recycled styrene-based resin raw material particles (a) may be 170,000 or less, and may be 100,000 to 170,000, or even 100,000 to 150,000. In some cases, it may be 200,000 or more, and may be 200,000 to 250,000, or even 220,000 to 250,000.

[0051] In embodiments of the present invention, recycled styrene resin particles (A) are typically obtained by nucleation polymerization of styrene monomers using recycled styrene resin raw material particles (a) as a nucleus. Any suitable method can be used as such a nucleation polymerization method, as long as it does not impair the effects of the present invention.

[0052] One preferred embodiment of such a nucleation polymerization method is a method in which recycled styrene resin raw material particles (a) are dispersed in an aqueous medium with the particles as nuclei, and an emulsion containing a polymerization initiator and styrene monomers is added to the suspension to impregnate the recycled styrene resin raw material particles (a), and then styrene monomers are added to carry out polymerization.

[0053] Another preferred embodiment of the nucleation polymerization method is a method in which a polymerization initiator, a styrene monomer, and a polyfunctional monomer are added to a suspension obtained by dispersing recycled styrene resin raw material particles (a) in an aqueous medium around a nucleus, and polymerization is carried out. In this case, an emulsion containing the polymerization initiator and the styrene monomer may be added to the suspension to impregnate the recycled styrene resin raw material particles (a), and then the styrene monomer and polyfunctional monomer may be added. The polyfunctional monomer may be added separately from the styrene monomer, or it may be added together with the styrene monomer. When the polyfunctional monomer is added to the suspension together with the styrene monomer, typically the polyfunctional monomer is dissolved in the styrene monomer before being added.

[0054] The styrene monomer may be one type or two or more types.

[0055] 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.

[0056] 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. Polyfunctional monomers may also be polyfunctional vinyl aromatic compounds. Polyfunctional vinyl aromatic compounds are aromatic compounds having two or more vinyl groups.

[0057] When using polyfunctional monomers, there may be only one type of polyfunctional monomer, or there may be two or more types.

[0058] The ratio of polyfunctional monomers to styrene monomers used in nuclear polymerization is, for example, 0 ppm to 1000 ppm by mass fraction, preferably 5 ppm to 1000 ppm, more preferably 10 ppm to 900 ppm, even more preferably 20 ppm to 950 ppm, and particularly preferably 50 ppm to 800 ppm.

[0059] The styrene monomer may include any suitable styrene monomer and vinyl monomers other than polyfunctional monomers, as long as the effects of the present invention are not impaired. Such vinyl monomers may be one type or two or more types. Examples of such vinyl monomers include (meth)acrylic acid monomers, maleic acid monomers, and fumaric acid monomers.

[0060] In embodiments of the present invention, the content ratio of recycled styrene-based resin raw material particles (a) to the total amount of recycled styrene-based resin raw material particles (a) and styrene-based monomers is preferable from the viewpoint of environmental contribution, as high as possible. However, from the viewpoint of producing recycled styrene-based resin particles (A) by nuclear polymerization, the content ratio of recycled styrene-based resin raw material particles (a) to the total amount of recycled styrene-based resin raw material particles (a) and styrene-based monomers is preferably 5% to 90% by mass, more preferably 10% to 85% by mass, even more preferably 15% to 80% by mass, even more preferably 20% to 75% by mass, and particularly preferably 25% to 70% by mass.

[0061] When obtaining recycled styrene-based resin particles (A), the addition temperature when adding styrene monomers to recycled styrene-based resin raw material particles (a) is preferably 40°C to 119°C, more preferably 40°C to 118°C, even more preferably 40°C to 117°C, particularly preferably 50°C to 117°C, and most preferably 60°C to 115°C, in order to better exhibit the effects of the present invention. By adjusting the addition temperature when adding styrene monomers to recycled styrene-based resin raw material particles (a) within the above range, the styrene monomers can be incorporated while maintaining the recycled styrene-based resin raw material particles (a) at an appropriate hardness, thereby enabling good spheroidization of recycled styrene-based resin particles (A), and ultimately resulting in recycled foamable styrene-based resin particles with 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 particles (A) will have difficulty becoming spherical, and the resulting recycled foamed styrene resin particles may have difficulty becoming spherical or 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 particles (A) will have difficulty becoming spherical, and the resulting recycled foamed styrene resin particles may have difficulty becoming spherical or have poor moldability.

[0062] 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.

[0063] When obtaining a suspension by dispersing recycled styrene-based resin raw material particles (a) in an aqueous medium with the particles as a nucleus, it is preferable to use a dispersant in the dispersion of the recycled styrene-based 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 pyrophosphate and tricalcium phosphate. Among these, magnesium pyrophosphate is preferred as a dispersant because it can better express the effects of the present invention.

[0064] The blending ratio of the dispersant to 100 parts by mass of recycled styrene resin particles (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.

[0065] 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.

[0066] The blending ratio of surfactant to 100 parts by mass of recycled styrene resin particles (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.

[0067] 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.

[0068] The method of adding a polymerization initiator to a suspension obtained by dispersing recycled styrene resin raw material particles (a) in an aqueous medium around a core is not limited to the emulsion method described above. For example, the polymerization initiator may be added directly to the suspension, or it may be added to the suspension mixed with a styrene monomer. However, it is preferable to add the polymerization initiator to the suspension in the form of an emulsion containing the polymerization initiator and the styrene monomer, as described above.

[0069] The polymerization initiator is preferably a peroxyester-based polymerization initiator. Peroxyester-based polymerization initiators include, for example, peroxyalkyl ester peroxides. Examples of such polymerization initiators include t-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane. There may be only one polymerization initiator or two or more.

[0070] By including a peroxyester-based polymerization initiator, the occurrence of bubble film rupture, surface melting, and shrinkage during molding is further reduced. Therefore, the moldability of recycled foamed styrene-based resin particles can be further improved.

[0071] The amount of polymerization initiator used is preferably 0.1% to 1.0% by mass relative to the styrene monomer, more preferably 0.1% to 0.8% by mass, and even more preferably 0.1% to 0.5% by mass.

[0072] 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.

[0073] As a method for impregnating a suspension containing recycled styrene-based resin raw material particles (a) with an emulsion containing styrene-based monomers, and then adding styrene-based monomers or styrene-based monomers and polyfunctional monomers, any suitable method can be adopted 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.

[0074] After impregnating a suspension containing recycled styrene resin raw material particles (a) with an emulsion containing styrene monomers, styrene monomers or styrene monomers and polyfunctional monomers may be added, and the polymerization reaction may be continued at any appropriate temperature and time as needed.

[0075] 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.

[0076] The recycled foamable styrene resin particles of the present invention are obtained by injecting and impregnating recycled styrene resin particles (A) with a foaming agent.

[0077] Typical methods for injecting and impregnating with a foaming agent include placing recycled styrene resin particles (A) in a reactor such as an autoclave and injecting and impregnating them with a foaming agent.

[0078] The foaming agent may be one type or two or more types.

[0079] Any suitable blowing agent can be used as the blowing agent, as long as it does not impair the effects of the present invention. The blowing agent referred to herein is preferably a volatile blowing agent. Preferably, the 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 the blowing agent. Among these, the foaming agent is preferably at least one selected from propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, and cyclopentadiene, in terms of being able to better express the effects of the present invention; more preferably at least one selected from propane, n-butane, isobutane, n-pentane, and isopentane; and even more preferably at least one selected from n-butane and isobutane.

[0080] The amount of foaming agent can be appropriately set according to 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 total amount of recycled styrene resin raw material particles (a) and styrene monomers is 100 parts by mass.

[0081] The injection temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 40°C to 140°C, even more preferably 40°C to 130°C, even more preferably 40°C to 123°C, particularly preferably 40°C to 110°C, and most preferably 40°C to 105°C. The injection temperature of the foaming agent into the recycled styrene resin particles (A) may be varied within the above range. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is within the above range, the foaming agent can be injected at a lower temperature. By injecting the foaming agent at such a low temperature and then raising the temperature, the rapid impregnation of the foaming agent into the recycled styrene resin particles (A) is suppressed, enabling uniform impregnation. For example, areas that shrink and melt when molded into a recycled styrene resin foam molded article can be reduced. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too low and outside the above range, the foaming agent will not easily impregnate the recycled styrene resin particles (A) during injection. When the temperature rises, the foaming agent will be impregnated rapidly, resulting in uneven impregnation of the recycled styrene resin particles (A), which can easily lead to variations in bubbles and surface shrinkage during molding. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too high and outside the above range, the foaming agent will be impregnated rapidly into the recycled styrene resin particles (A) during injection. This can result in uneven impregnation of the recycled styrene resin particles (A), which can easily lead to variations in bubbles and surface shrinkage during molding.

[0082] One embodiment of the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 40°C to 140°C, even more preferably 40°C to 130°C, even more preferably 40°C to 123°C, even more preferably 40°C or more and less than 110°C, particularly preferably 40°C to 105°C, and most preferably 40°C to 102°C.

[0083] Another embodiment of the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is preferably a temperature above the injection temperature of the foaming agent into the recycled styrene resin particles (A) (which may be the same as the injection temperature of the foaming agent into the recycled styrene resin particles (A)), preferably 93°C to 130°C, more preferably 94°C to 129°C, even more preferably 95°C to 128°C, particularly preferably 96°C to 127°C, and most preferably 97°C to 126°C.

[0084] The impregnation temperature of the foaming agent into the recycled styrene resin particles (A) may be varied within the above range. If the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is within the above range, in conjunction with the adjustment of the injection temperature, the rapid impregnation of the foaming agent into the recycled styrene resin particles (A) is suppressed, enabling uniform impregnation. For example, areas that shrink and melt when molded into a foamed recycled styrene resin molded product can be reduced. If the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is too low and outside the above range, the foaming agent may not be impregnated to the center of the recycled styrene resin particles (A), leaving non-foamed areas, which may prevent the acquisition of a good molded product. If the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is too high and outside the above range, the foaming agent may be too deeply impregnated into the recycled styrene resin particles (A), potentially causing them to melt during molding.

[0085] A particularly representative embodiment of the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 50°C to 130°C, even more preferably 60°C to 120°C, even more preferably 70°C or more and less than 110°C, even more preferably 80°C or more and less than 110°C, especially preferably 90°C or more and less than 110°C, and most preferably 95°C to 105°C.

[0086] The impregnation time of the foaming agent into the recycled styrene resin particles (A) can be any appropriate time, as long as it does not impair the effects of the present invention. Such an impregnation time is preferably 1 to 10 hours.

[0087] The recycled foamed styrene resin particles of the present invention may contain any other suitable components, as long as they do not impair the effects of the present invention. Such other components may be one or two or more.

[0088] The recycled foamed styrene resin particles of the present invention may contain a flame retardant to enhance flame retardancy. The flame retardant may be one type or two or more types.

[0089] 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.

[0090] 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.

[0091] 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 0.1% to 15% by mass, more preferably 0.2% to 10% by mass, even more preferably 0.2% to 5% by mass, and particularly preferably 0.2% to 3% by mass, relative to the recycled styrene-based resin raw material particles (a).

[0092] The flame retardant can be added at any appropriate time, as long as it does not impair the effects of the present invention. Preferably, the flame retardant is added before the foaming agent is injected. 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 foamable styrene resin particles.

[0093] The temperature at which the flame retardant is added is preferably 5°C to 120°C, more preferably 5°C to 118°C, even more preferably 5°C to 115°C, even more preferably 5°C to 113°C, even more preferably 5°C to 110°C, even more preferably 40°C to 89°C, even more preferably 40°C to 87°C, even more preferably 40°C to 85°C, particularly preferably 40°C to 83°C, and most preferably 40°C to 80°C.

[0094] In producing recycled foamable styrene resin particles, a partial ester of a higher fatty acid and an alcohol may be used as a foam regulator. That is, the recycled foamable styrene resin particles may contain a partial ester of a higher fatty acid and an alcohol. There may be only one type of partial ester of a higher fatty acid and an alcohol, or there may be two or more types. Examples of higher fatty acids include fatty acids with 15 or more carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid, and their monoglycerides and diglycerides can be used. Preferably, the partial ester of a higher fatty acid and an alcohol is monoglyceride stearate or diglyceride stearate. The content ratio of the partial ester of a higher fatty acid and an alcohol is preferably 0 to 3.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of recycled styrene resin particles (A). As for the method of adding the partial ester of a higher fatty acid and an alcohol, for example, it may be added together with a foaming agent, or a commonly used method such as the dry blending method, masterbatch method, or melt injection method may be employed.

[0095] When manufacturing recycled foamable styrene resin particles, foaming aids may be used. That is, recycled foamable styrene resin particles may contain foaming aids. 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.

[0096] In manufacturing recycled foamed styrene resin particles, a foam regulator may be used. That is, recycled foamed styrene resin particles may contain a foam regulator. There may be only one type of foam regulator, or there may be two or more types. Examples of foam regulators include fatty acid monoamides such as oleamide, stearamide, and hydroxystearamide; and fatty acid bisamides such as methylenebisstearamide and ethylenebisstearamide.

[0097] The amount of foam regulator 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 to 5.0 parts by mass, more preferably 0.02 to 3.0 parts by mass, even more preferably 0.02 to 2.0 parts by mass, and particularly preferably 0.02 to 1.0 parts by mass, per 100 parts by mass of recycled styrene resin particles (A).

[0098] The recycled foamed styrene resin particles may contain foam regulators such as talc, calcium carbonate, mica, citric acid, and sodium bicarbonate. The foam regulator may be one type or two or more types.

[0099] Other additives include, for example, 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.

[0100] The recycled foamed styrene resin particles may be surface-treated. Such surface treatment is preferably performed using at least one selected from silicone oil, antistatic agents, fatty acid metal salts, and fusion accelerators.

[0101] 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.

[0102] The silicone oil may be of one type or two or more types.

[0103] 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 methylphenylpolysiloxane is preferred.

[0104] 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.

[0105] The antistatic agent may be one type or two or more types.

[0106] 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.

[0107] The nonionic surfactant may be one type or two or more types.

[0108] 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.

[0109] 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.

[0110] The fatty acid glycerides may be one type or two or more types.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] The fatty acid metal salt may be one type or two or more types.

[0115] 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.

[0116] 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.

[0117] The fusion accelerator may be one type or two or more types.

[0118] 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.

[0119] ≪≪2. 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.

[0120] The recycled pre-expanded styrene resin particles preferably have an average bubble diameter of 0.01 mm to 1.10 mm, more preferably 0.01 mm to 1.00 mm, even more preferably 0.01 mm to 0.90 mm, particularly preferably 0.01 mm to 0.80 mm, and most preferably 0.01 mm to 0.70 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.

[0121] Pre-foaming involves foaming recycled foamable styrene 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 resin particles is preferably 2 to 150 times, more preferably 2 to 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 resin particles within the above range, blocking during foaming and molding can be further prevented, and furthermore, while suppressing electrostatic charge during foaming and molding, better fusion properties and surface properties can be exhibited, and recycled styrene resin foam molded articles with less static electricity can be molded.

[0122] 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 example, as a core material for cushions (foamed granules filled inside cushions).

[0123] ≪≪3. 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.

[0124] 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.

[0125] Recycled styrene-based foamed molded articles are typically composed of multiple foamed particles that are fused together.

[0126] 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.

[0127] The temperature for heat foaming (essentially the temperature of the heat transfer medium) is preferably 90°C to 150°C, and more preferably 110°C to 130°C. The heat 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) for heat foaming is preferably 0.04 MPa to 0.1 MPa, and more preferably 0.06 MPa to 0.08 MPa. Under these conditions, the foamed particles can be well fused together.

[0128] 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 formability may decrease.

[0129] The expansion ratio of the expanded particles in the recycled styrene resin foam molded body is preferably 2 to 110 times, more preferably 5 to 90 times, still more preferably 10 to 85 times, and particularly preferably 15 to 80 times.

[0130] 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 is suitable for wall heat insulation materials, floor heat insulation materials, roof heat insulation materials, automobile heat insulation materials, hot water tank heat insulation materials, pipe heat insulation materials, solar system heat insulation materials, water heater heat insulation materials, containers for food and industrial products (e.g., food containers such as fish boxes, tote boxes), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, embankment molded bodies, tatami core materials, cushion core materials, concrete aggregates, etc.

Examples

[0131] 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.

[0132] <GPC measurement> The molecular weight M, weight average molecular weight Mw, Z average molecular weight Mz, and Z+1 average molecular weight Mz+1 are relative molecular weights in terms of polystyrene (PS) measured using gel permeation chromatography (GPC). Specifically, they were measured according to the following procedure. 3 mg of the sample was left standing at room temperature in 10 mL of tetrahydrofuran (THF) for 72 hours to be completely dissolved, and then filtered through a non-aqueous 0.45 μm chromatographic disk. The filtrate was measured using a chromatograph under the following measurement conditions. (Measurement conditions) Equipment: High-speed GPC equipment Product Name: Tosoh HLC-8320GPC EcoSEC System (with built-in RI detector) Analysis conditions: Guard column: TSKguardcolumn SuperHZ-H (4.6mm ID x 2cm L) x 1 Column: TSKgel SuperHZM-H (4.6mm I.D × 15cm L) × 2 tubes Column temperature: 40℃ Temperature: 40°C Mobile phase: THF Mobile phase flow rate: Sample-side pump = 0.175 mL / min Reference pump = 0.175 mL / min Detector: RI detector Sample concentration: 0.3g / L Injection volume: 50μL Measurement time: 0 min ~ 25 min Runtime: 25 min Sampling pitch: 200 msec Using a calibration curve prepared in advance for standard polystyrene, the molecular weight M, weight-average molecular weight Mw, Z-average molecular weight Mz, and Z+1-average molecular weight Mz+1 were determined. From the percentage p1[%] of components with a molecular weight M of 200,000 or less and the percentage p2[%] of components with a molecular weight M of 1,000,000 or less in the integrated molecular weight distribution curve obtained by GPC measurement, the percentage of polymer components with a molecular weight M greater than 200,000 and the percentage of polymer components with a molecular weight M greater than 1,000,000 were calculated as follows. Percentage of polymer components with molecular weight M greater than 200,000 [%] = 100 - p1 The percentage of polymer components with a molecular weight M greater than 1 million [%] = 100 - p² (Creating a calibration curve) For the calibration curve, standard polystyrene samples were used, manufactured by Tosoh Corporation and marketed as "TSK standard POLYSTYRENE," with weight-average molecular weights of 5,480,000, 3,480,000, 1,090,000, 377,000, 110,000, 37,900, 9,100, 2,630, and 589. The standard polystyrene samples for the calibration curve described above were divided into three groups: Group A (weight-average molecular weight of 1,090,000), Group B (weight-average molecular weights of 3,480,000, 110,000, 9,100, and 589), and Group C (weight-average molecular weights of 5,480,000, 377,000, 37,900, and 2,630). 5 mg of the standard polystyrene sample belonging to Group A with a weight-average molecular weight of 1,090,000 was weighed and dissolved in 20 mL of THF, and 50 μL of the resulting solution was injected into the sample column. 5 mg, 5 mg, 5 mg, and 10 mg of the standard polystyrene samples belonging to Group B with weight-average molecular weights of 3,480,000, 110,000, 9,100, and 589 were weighed in the order described above, dissolved in 50 mL of THF, and 50 μL of the resulting solution was injected into the sample column. Standard polystyrene samples belonging to Group C, with weight-average molecular weights of 5,480,000, 377,000, 37,900, and 2,630, were weighed in the order listed above (1 mg, 5 mg, 5 mg, and 5 mg respectively). These samples were then dissolved in 40 mL of THF, and 50 μL of the resulting solution was injected into the sample column. Calibration curves (cubic equations) were created from the retention times of these standard polystyrene samples using the HLC-8320GPC dedicated data analysis program GPC Workstation (EcoSEC-WS), and these were used as the calibration curve.

[0133] <Evaluation of moldability> Moldability was evaluated based on the fusion rate between foam particles in the resulting foamed molded article and the appearance of the foamed molded article.

[0134] (Fusion rate) The fusion rate between foam particles in a foamed molded body was evaluated by fracturing the foamed molded body with impact and observing the fracture surface. More specifically, a thin cut was made in a plate-shaped foamed molded body with a cutter, and then the foamed molded body was struck forcefully to fracture it. The cut was made on the main surface of the plate-shaped foamed molded body along a center line that bisects the long side. The total number of foam particles (A) and the number of particles that were fractured within the particle (B) were counted in the fracture surface, and the fusion rate was calculated using the following formula. Fusion rate [%] = {(B) / (A)} × 100 The evaluation criteria were as follows: ○: The fusion rate is 70% or higher. △: The fusion rate is 60% or more but less than 70%. ×: The fusion rate is less than 60%.

[0135] (exterior) The appearance of the foamed molded body was evaluated by visually observing its surface. Specifically, it was evaluated by counting the number of gaps observed between foamed particles (at the boundaries where foamed particles are joined) on the surface of the foamed molded body (a 100 mm x 100 mm area). The evaluation criteria were as follows: ◎: Less than 10 items ○: 10 or more but less than 30 △: 30 or more but less than 100 ×: 100 or more pieces

[0136] [Manufacturing Example 1] Used polystyrene foam pellets were mixed so that the weight-average molecular weight of the recycled styrene resin raw material particles (a) to be manufactured would be 220,000 and 150,000, respectively. The mixture was then supplied to a single-screw extruder, heated and melted at 200°C, extruded from a mold, and cut underwater to an average particle size of 0.75 mm (approximately spherical) to produce recycled styrene resin raw material particles (a) having a predetermined weight-average molecular weight. The recycled styrene-based resin raw material particles (a) manufactured were of the following two types. Recycled styrene-based resin raw material particles (a22): weight-average molecular weight 220,000 Recycled styrene-based resin raw material particles (a15): weight-average molecular weight 150,000

[0137] [Example 1] <Preparation of recycled foamed styrene-based resin particles (1)> In a 100-liter reactor with a stirrer, 36 kg of water, 3.5 g of sodium dodecylbenzenesulfonate, and 150 g of magnesium pyrophosphate were added. Then, 12.6 kg of recycled styrene resin raw material particles (a22) obtained in Production Example 1 were added, and the mixture was stirred at 150 rpm to suspend it and prepare suspension (1). Separately, 2.3 kg of styrene monomer, in which 90 g of t-butyl peroxy-2-ethylhexanoate and 20 g of t-butyl peroxy-2-ethylhexyl monocarbonate were dissolved, was added to a dispersion of 2.5 kg of water and 0.8 g of sodium dodecylbenzenesulfonate. The mixture was then stirred with a homomixer to create an emulsion (1). The above suspension (1) in a 100-liter reactor with a stirrer was maintained at 75°C, and the above emulsion (1) was added. Then, the reactor was maintained at 75°C for 30 minutes so that the styrene monomer and polymerization initiator would be well absorbed into the recycled styrene resin raw material particles (a22). Immediately after this, 27.1 kg of styrene monomer was added dropwise over 120 minutes. The addition temperature was gradually increased from 75°C to 105°C. Then, the temperature was increased to 125°C over 30 minutes, maintained at 125°C for 30 minutes, and then cooled to 100°C over 30 minutes to produce recycled styrene resin particles (A1) in the reactor. Next, 450 g of cyclohexane, 1.3 g of sodium dodecylbenzenesulfonate, 18 g of magnesium pyrophosphate, 295 g of diisobutyl adipate, 84 g of styrene monomer, 21 g of hydroxystearate, and 21 g of ethylenebisstearate were added to 3.3 liters of water and stirred with a homomixer to prepare emulsion (2). This emulsion (2) was added to the reactor cooled to 100°C. Subsequently, 9.0% by mass of butane (isobutane / n-butane = 20% by mass / 80% by mass) as a blowing agent was injected into the reactor under pressure, and the mixture was held in this state for 5 hours to slowly impregnate the particles with the blowing agent. After that, the temperature inside the reactor was cooled to 25°C. Subsequently, the contents were removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene-based resin particles (1).

[0138] <Surface treatment of recycled foamed styrene resin particles (1)> Recycled foamed styrene resin particles (1) were stored at 15°C and aged. To the aged recycled foamed styrene resin particles (1), 0.02% by mass of polyethylene glycol, 0.1% by mass of zinc stearate, 0.03% by mass of fatty acid triglycerides, and 0.04% by mass of fatty acid monoglycerides were added to a tumbler mixer and stirred for 30 minutes to perform surface treatment, thereby obtaining surface-treated recycled foamed styrene resin particles (1').

[0139] <Preparation of recycled pre-expanded styrene resin particles (pf1)> The surface-treated recycled foamable styrene resin particles (1') obtained were placed in a cylindrical batch-type pressurized foaming machine with a volume of 25 liters and heated with steam for 2 minutes to obtain recycled pre-foamed styrene resin particles (pf1). The bulk density of the recycled pre-foamed styrene resin particles (pf1) was 0.017 g / cm³. 3 The expansion ratio was 60 times.

[0140] <Preparation of recycled styrene-based foamed molded product (f1)> A molding machine with a cavity mold measuring 300mm (length) x 400mm (width) x 30mm (thickness) was used. Recycled pre-expanded styrene resin particles (pf1) were left at room temperature for 24 hours, then filled into the cavity of the mold of the molding machine, 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 demolding, a plate-shaped recycled styrene resin foam molded body (f1) corresponding to the mold was obtained. The density of the recycled styrene resin foam molded body (f1) was 0.017 g / cm³. 3 The foaming ratio was 60 times. Subsequently, this recycled styrene-based resin foam molded product (f1) was stored at room temperature for one day. The moldability of the obtained recycled styrene-based resin foam molded article (f1) was evaluated. The results are shown in Table 1.

[0141] [Example 2] In the preparation of emulsion (1), the procedure was carried out in the same manner as in Example 1, except that the amount of t-butyl peroxy-2-ethylhexanoate used was 80 g. Recycled styrene resin particles (A2), recycled foamable styrene resin particles (2), recycled pre-foamed styrene resin particles (pf2), and recycled styrene resin foam molded article (f2) were obtained. The results are shown in Table 1.

[0142] [Example 3] In the preparation of emulsion (1), the procedure was the same as in Example 1, except that the amount of t-butyl peroxy-2-ethylhexanoate used was 70 g. Recycled styrene resin particles (A3), recycled foamable styrene resin particles (3), recycled pre-foamed styrene resin particles (pf3), and recycled styrene resin foam molded article (f3) were obtained. The results are shown in Table 1.

[0143] [Example 4] Except for the use of 70g of benzoyl peroxide (75% purity) instead of 90g of t-butyl peroxy-2-ethylhexanoate in the preparation of emulsion (1), the procedure was carried out in the same manner as in Example 1, yielding recycled styrene resin particles (A4), recycled foamable styrene resin particles (4), recycled pre-foamed styrene resin particles (pf4), and recycled styrene resin foam molded article (f4). The results are shown in Table 1.

[0144] [Example 5] Recycled styrene resin particles (A5) were prepared in the reactor in the same manner as the recycled styrene resin particles (A1) in Example 1. Next, 450 g of cyclohexane, 5.0 g of sodium dodecylbenzenesulfonate, 18 g of magnesium pyrophosphate, 295 g of diisobutyl adipate, 84 g of styrene monomer, 21 g of hydroxystearate, 21 g of ethylenebisstearate, and 185 g of dicumyl peroxide were added to 3.3 liters of water and stirred with a homomixer to prepare emulsion (2). This emulsion (2) was added to the reactor cooled to 60°C. Ten minutes after this addition, 756 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. Stirring was continued for 30 minutes after the addition. Next, 9.0% by mass of butane (isobutane / n-butane = 20% by mass / 80% by mass) was injected under pressure into the reactor to form the regenerated foamable styrene resin particles, and the mixture was held in this state for 5 hours to allow the foaming agent to slowly impregnate the particles. After that, the temperature inside the reactor was cooled to 25°C. Subsequently, the contents were removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene-based resin particles (5). The above-mentioned recycled foamable styrene resin particles (5) were subjected to surface treatment, pre-foaming, and molding in the same manner as in Example 1 to obtain recycled pre-foamed styrene resin particles (pf5) and recycled styrene resin foam molded articles (f5). The results are shown in Table 1.

[0145] [Example 6] Recycled styrene resin particles (A6) were prepared in the reactor in the same manner as the recycled styrene resin particles (A1) in Example 1. Next, 1.3 g of sodium dodecylbenzenesulfonate, 18 g of magnesium pyrophosphate, 21 g of hydroxystearate, and 21 g of ethylenebisstearate were added to 3.3 liters of water and stirred with a homomixer to emulsify and prepare emulsion (2). This emulsion (2) was added to the reactor cooled to 100°C. Subsequently, 9.0% by mass of pentane (isopentane / n-pentane = 20% by mass / 80% by mass) and 1.0% by mass of propane were injected into the reactor as a blowing agent, and the mixture was held in this state for 5 hours to slowly impregnate the resulting regenerated foamable styrene resin particles with the blowing agent. After that, the temperature inside the reactor was cooled to 25°C. Subsequently, the contents were removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene-based resin particles (6). The above-mentioned recycled foamable styrene resin particles (6) were subjected to surface treatment, pre-foaming, and molding in the same manner as in Example 1 to obtain recycled pre-foamed styrene resin particles (pf6) and recycled styrene resin foam molded articles (f6). The results are shown in Table 1.

[0146] [Example 7] The preparation of suspension (1) was carried out in the same manner as in Example 1, except that recycled styrene resin particles (a15) were used instead of recycled styrene resin particles (a22). Recycled styrene resin particles (A7), recycled foamable styrene resin particles (7), recycled pre-foamed styrene resin particles (pf7), and recycled styrene resin foam molded article (f7) were obtained. The results are shown in Table 1.

[0147] [Example 8] Suspension (1) was prepared in the same manner as in Example 1, except that recycled styrene resin particles (a15) were used instead of recycled styrene resin particles (a22). Emulsion (1) was prepared in the same manner as in Example 1. The above suspension (1) in a 100-liter reactor with a stirrer was maintained at 75°C, and the above emulsion (1) was added. Then, the mixture was maintained at 75°C for 30 minutes so that the styrene monomer and polymerization initiator would be well absorbed into the recycled styrene resin raw material particles (a15). Immediately after this, a mixture of 27.1 kg of styrene monomer and 7 g of divinylbenzene was continuously added dropwise over 120 minutes. The addition temperature was gradually increased from 75°C to 105°C. Then, the temperature was increased to 125°C over 30 minutes, maintained at 125°C for 30 minutes, and then cooled to 25°C over 1 hour and 30 minutes to produce recycled styrene resin particles (A8) in the reactor. The procedure was carried out in the same manner as in Example 1, except that the recycled styrene resin particles (A8) described above were used, to obtain recycled foamable styrene resin particles (8), recycled pre-foamed styrene resin particles (pf8), and recycled styrene resin foam molded article (f8). The results are shown in Table 1.

[0148] [Example 9] In the preparation of emulsion (1), 125 g of benzoyl peroxide (75% purity) was used instead of 90 g of t-butyl peroxy-2-ethylhexanoate, and the amount of divinylbenzene used was changed to 15 g. The procedure was carried out in the same manner as in Example 8, and recycled styrene resin particles (A9), recycled foamable styrene resin particles (9), recycled pre-foamed styrene resin particles (pf9), and recycled styrene resin foam molded article (f9) were obtained. The results are shown in Table 1.

[0149] [Example 10] In the preparation of emulsion (1), the procedure was carried out in the same manner as in Example 8, except that the amount of t-butyl peroxy-2-ethylhexanoate used was changed to 110 g. Recycled styrene resin particles (A10), recycled foamable styrene resin particles (10), recycled pre-foamed styrene resin particles (pf10), and recycled styrene resin foam molded article (f10) were obtained. The results are shown in Table 1.

[0150] [Comparative Example 1] The preparation of emulsion (1) was carried out in the same manner as in Example 1, except that 125 g of benzoyl peroxide (75% purity) was used instead of 90 g of t-butyl peroxy-2-ethylhexanoate. Recycled styrene resin particles (CA1), recycled foamable styrene resin particles (C1), recycled pre-foamed styrene resin particles (Cpf1), and recycled styrene resin foam molded article (Cf1) were obtained. The results are shown in Table 1.

[0151] [Table 1]

[0152] 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. Recycled foamable styrene resin particles obtained by pressurizing and impregnating recycled styrene resin particles (A) with a foaming agent, The weight-average molecular weight is between 300,000 and 1,000,000. It contains 50.0% or more by mass fraction of polymer components with a molecular weight M greater than 200,000, as determined by GPC measurement. Recycled foamed styrene resin particles.

2. The recycled styrene resin particles (A) are obtained by nuclear polymerization of styrene monomers using recycled styrene resin raw material particles (a) as a nucleus in the presence of a polymerization initiator, as described in claim 1.

3. The recycled foamable styrene-based resin particles according to claim 2, wherein the polymerization initiator comprises a peroxyester-based polymerization initiator.

4. The recycled foamable styrene-based resin particles according to claim 2, wherein the polymerization initiator in the nuclear polymerization is 0.05% by mass to 1.00% by mass relative to the styrene-based monomer.

5. The recycled foamable styrene-based resin particles according to claim 2, wherein the weight-average molecular weight of the recycled styrene-based resin raw material particles (a) is 100,000 to 450,000.

6. The recycled foamable styrene-based resin particles according to claim 1, comprising 8.0% or more by mass fraction of a polymer component having a molecular weight M greater than 1 million.

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