Expandable particles of regenerated styrene-based resin, pre-expanded particles of regenerated styrene-based resin, and molded foam of regenerated styrene-based resin

Abstract

Expandable particles of a regenerated styrene-based resin according to an embodiment of the present invention are obtained by forcing / infiltrating a blowing agent into particles (A) of the regenerated styrene-based resin, wherein the particles (A) of the regenerated styrene-based resin, in a measurement of uniaxial elongational viscosity under the conditions of 160°C and a constant strain rate of 0.1 s-1, have a maximum value of uniaxial elongational viscosity of 5.0×104 Pa·s to 1.0×1010 Pa·s and the particles (A) of the regenerated styrene-based resin have a weight-average molecular weight of 150,000-1,000,000.

Description

Recycled foamable styrene resin particles, recycled pre-foamed styrene resin particles, and recycled styrene resin foam molded articles

[0001] The present invention relates to recycled foamable styrene resin particles, recycled pre-foamed styrene resin particles, and recycled styrene resin foam molded articles.

[0002] Because foamed molded products are lightweight and have excellent thermal insulation and mechanical strength, they are widely used as insulation materials in houses and automobiles, heat-insulating materials in building materials, embankment materials in expanded polystyrene civil engineering methods, transport packaging materials such as fish boxes and food containers, and cushioning materials. Among these, in-mold foamed molded products manufactured using foamed particles (typically foamed polystyrene resin particles or pre-foamed polystyrene resin particles obtained by pre-foaming them) are widely used due to advantages such as the ease with which desired shapes can be obtained. Such foamed molded products are composed of multiple foamed particles that are fused together.

[0003] On the other hand, the amount of plastic waste is increasing year by year. The majority of plastic waste is disposed of by incineration or landfill, but this has become a major social problem, leading to environmental pollution, global warming, and a shortage of landfill sites. For this reason, there is a strong social demand for the reuse of plastic waste, and various studies on plastic waste recycling are being considered, such as the enforcement of the Home Appliance Recycling Law. Among the various recycling methods that have been proposed, material recycling, which reuses plastic waste as plastic components in products, is attracting attention from the perspective of resource circulation and reduction of environmental impact, and such material recycling is also being considered for styrene foam molded products.

[0004] As a material recycling method for styrene foam molded products, several recycled foamable styrene resin particles have been proposed, which are obtained by melting and extruding recovered raw materials to produce recovered pellets, and then impregnating these pellets 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, undergoing 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, kegging (a state in which the foamed particles melt, collapse, or shrink) is likely to occur on the surface of the foamed molded product during molding. In addition, conventional recycled foamed styrene resin particles have a problem in that they are particularly susceptible to heat generated during foaming and molding, and tend to shrink, compared to foamed styrene resin particles that do not use recovered raw materials.

[0007] Japanese Patent Publication No. 3044942 Japanese Patent Publication No. 4234832 Japanese Patent Publication No. 4261676 Japanese Patent Publication No. 6788428 Japanese Patent Publication No. 4052193 Japanese Unexamined Patent Publication No. 2006-160905 Japanese Patent Publication No. 4912567 Japanese Patent Publication No. 5128246 Japanese Unexamined Patent Publication No. 2022-153315

[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. Furthermore, it is also to provide recycled pre-foamed styrene resin particles obtained from such recycled foamed styrene resin particles. Moreover, it is also to provide a recycled styrene resin foam molded article formed from such recycled pre-foamed styrene resin particles.

[0009] [1] The recycled foamable styrene resin particles according to the embodiment of the present invention are recycled foamable styrene resin particles obtained by pressurizing and impregnating recycled styrene resin particles (A) with a foaming agent, wherein the recycled styrene resin particles (A) are subjected to a constant strain rate of 0.1 s at 160°C. -1 Under these conditions, in uniaxial extensional viscosity measurements, the maximum value of the uniaxial extensional viscosity was 5.0 × 10⁻⁶. 4Pa・s~1.0×10 10 [1] The molecular weight is Pa·s, and the weight-average molecular weight of the recycled styrene resin particles (A) is 150,000 to 1,000,000. [2] 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 described in [1] above. [3] The recycled styrene resin foam molded article according to the embodiment of the present invention is molded from the recycled pre-foamed styrene resin particles described in [2] above.

[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.

[0011] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

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

[0013] <<A. Recycled Expandable Styrene Resin Particles>> The recycled expandable styrene resin particles according to the embodiment of the present invention have a particle shape as a whole. The average particle diameter of the recycled expandable styrene resin particles is preferably 0.40 mm to 2.0 mm, and more preferably 0.60 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.

[0014] 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, so in this specification, both are collectively referred to as spherical.

[0015] The recycled expandable styrene resin particles according to an embodiment of the present invention are recycled expandable styrene resin particles obtained by press-fitting and impregnating a foaming agent into recycled styrene resin particles (A). In the uniaxial extensional viscosity measurement of the recycled styrene resin particles (A) under the conditions of 160°C and a constant strain rate of 0.1 s -1 , the maximum value of the uniaxial extensional viscosity is 5.0 × 10 4 Pa·s to 1.0 × 10 10 Pa·s, and the weight average molecular weight of the recycled styrene resin particles (A) is 150,000 to 1,000,000.

[0016] The weight average molecular weight of the recycled styrene resin particles (A) is 150,000 to 1,000,000, preferably 160,000 to 980,000, more preferably 170,000 to 950,000, and still more preferably 200,000 to 900,000. The weight average molecular weight of the recycled styrene resin particles (A) can be measured by gel permeation chromatography (GPC). Incidentally, even when the recycled expandable styrene resin particles are subjected to GPC, the weight average molecular weight of the recycled styrene resin particles (A) can be measured.

[0017] In the uniaxial extensional viscosity measurement of the recycled styrene resin particles (A) under the conditions of 160°C and a constant strain rate of 0.1 s -1 , the maximum value of the uniaxial extensional viscosity is 5.0 × 10 4 Pa·s to 1.0 × 10 10 Pa·s. The maximum value of the uniaxial extensional viscosity of the recycled styrene resin particles (A) in the above uniaxial extensional viscosity measurement is preferably 8.0 × 10 4 Pa·s to 9.0 × 10 9 Pa·s, more preferably 9.0 × 10 4 Pa·s to 8.0 × 10 9 Pa·s, and still more preferably 1.0 × 10 5 Pa·s to 5.0 × 10 9 Pa·s.

[0018] 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 150,000 to 1,000,000, more preferably 160,000 to 980,000, even more preferably 170,000 to 950,000, and particularly preferably 200,000 to 900,000.

[0019] Two preferred embodiments of the regenerated foamable styrene resin particles of the present invention are as follows: Embodiment (1): Regenerated foamable styrene resin particles obtained by injecting and impregnating a foaming agent into regenerated styrene resin particles (A), wherein the regenerated styrene resin particles (A) are obtained by nuclear polymerization of styrene monomers with regenerated styrene resin raw material particles (a) as the core. Embodiment (2): Regenerated foamable styrene resin particles obtained by injecting and impregnating a foaming agent into regenerated styrene resin particles (A), wherein the regenerated styrene resin particles (A) are regenerated styrene resin raw material particles (a) having a weight-average molecular weight of 150,000 to 1,000,000.

[0020] The recycled foamed styrene resin particles according to the embodiments of the present invention have a high environmental contribution. The recycled foamed styrene resin particles in embodiment (1) have a recycling rate of preferably 10% or more, more preferably 20% or more, and even more preferably 25% or more. The recycled foamed styrene resin particles in embodiment (2) have a recycling rate of typically 100%. The recycling rate is the proportion of recovered styrene resin in the styrene resin contained in the recycled foamed styrene resin particles.

[0021] Below, we will first describe the above embodiments (1) and (2).

[0022] ≪A-1. Preferred Embodiment (1) of Recycled Foamable Styrene Resin Particles≫ One preferred embodiment (1) of the recycled foamable styrene resin particles of the present invention is a recycled foamable styrene resin particle obtained by pressurizing and impregnating a foaming agent into a recycled styrene resin particle (A), wherein the recycled styrene resin particle (A) is obtained by nuclear polymerization of styrene monomers with a recycled styrene resin raw material particle (a) as a nucleus, and has a weight-average molecular weight of 150,000 to 1,000,000.

[0023] <A-1-1. Recycled styrene resin particles (A) in Embodiment (1)> The recycled styrene resin particles (A) in Embodiment (1) are obtained by nuclear polymerization of styrene monomers using recycled styrene resin raw material particles (a) as a nucleus. Preferably, the recycled styrene resin particles (A) are obtained by nuclear polymerization of a monomer composition (C) containing a polyfunctional vinyl aromatic compound and a styrene monomer using recycled styrene resin raw material particles (a) as a nucleus.

[0024] The recycled styrene-based resin raw material particles (a) may consist of only one type or two or more types.

[0025] 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.

[0026] The recycled styrene-based resin raw material particles (a) may contain any suitable recycled resin other than recycled styrene-based resin, as long as it does not impair the effects of the present invention. 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, the recycled resins of AS resin, ABS resin, and HIPS (high-impact polystyrene) mentioned above are not included in the category of recycled styrene-based resins.

[0027] 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.

[0028] 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.

[0029] 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 or ingot-like or foamed particles of used styrene-based resin 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.

[0030] As the pellets obtained by the above melt extrusion method, preferably, at least one selected from extrusion strand pellets obtained by extruding used foamed styrene resin with an extruder and performing strand cutting, underwater cut pellets obtained by an underwater cutting method in which the used foamed styrene resin is extruded with an extruder and cut underwater at the same time, and hot cut pellets obtained by a hot cutting method in which the used foamed styrene resin particles are cut immediately after exiting from the die of the extruder and cooled.

[0031] As the recycled styrene resin raw material particles (a), the pellets obtained by the above melt extrusion method may be used as they are, or in order to obtain pellets of a smaller size, they may be made into so-called "mini pellets" again by a melt extrusion method or the like.

[0032] As the recycled styrene resin raw material particles (a), a shrinkage product or melt of a foamed styrene resin obtained by coarsely pulverizing used foamed styrene resin to an appropriate size as necessary and then performing heat shrinkage, bubble destruction shrinkage by compression, shrinkage by frictional heat, melting, etc. may be used.

[0033] Examples of the used foamed styrene resin include molded products obtained by molding a foaming styrene resin and those obtained by heating and foaming the same.

[0034] The recycled styrene resin raw material particles (a) can contain fine powder inorganic substances and / or organic lubricants. These can typically function as bubble regulators.

[0035] Examples of the fine powder inorganic substances include talc, calcium carbonate, and silica. Here, talc typically refers to a mixture mainly composed of silicon oxide and magnesium oxide and containing trace amounts of aluminum oxide, iron oxide, etc.

[0036] The average particle diameter of the fine powder inorganic substances is preferably 100 μm or less, more preferably 30 μm or less.

[0037] The content ratio of the fine powder inorganic substance is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 2% by mass, with respect to the recycled styrene resin raw material particles (a). If the content ratio of the fine powder inorganic substance with respect to the recycled styrene 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 ratio of the fine powder inorganic substance with respect to the recycled styrene resin raw material particles (a) exceeds 5% by mass, the bubble size of the recycled pre-expanded styrene resin particles becomes extremely small, and the recycled pre-expanded styrene resin particles may melt during molding, which may deteriorate the moldability and the appearance of the molded product.

[0038] Examples of the organic lubricant include liquid paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisamides such as methylene bisstearic acid amide, ethylene bisstearic acid amide, and ethylene bisoleic acid amide; metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

[0039] The content ratio of the organic lubricant is preferably 0.01% by mass to 2.0% by mass, more preferably 0.02% by mass to 1.8% by mass, and in some cases, even more preferably 0.02% by mass to 0.2% by mass, and particularly preferably 0.02% by mass to 0.1% by mass, with respect to the recycled styrene resin raw material particles (a). If the content ratio of the organic lubricant with respect 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, and the recycled pre-expanded styrene resin particles may melt during molding, which may deteriorate the moldability and the appearance of the molded product.

[0040] 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.

[0041] 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.

[0042] 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 plastics pulverizer can be used, and a polystyrene pulverizer is preferred.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In embodiment (1), when obtaining recycled styrene resin particles (A) having a weight-average molecular weight of 150,000 to 1,000,000, the weight-average molecular weight of the recycled styrene resin raw material particles (a) is preferably 100,000 to 450,000. By satisfying the above numerical range for the weight-average molecular weight of the recycled styrene resin raw material particles (a), the moldability of the obtained recycled foamable styrene resin particles during foaming and molding can be further improved. The weight-average molecular weight of the recycled styrene resin raw material particles (a) can be adjusted, for example, by appropriately mixing multiple recycled styrene resins.

[0048] The monomer composition (C) used in nuclear polymerization typically includes polyfunctional vinyl aromatic compounds and styrene monomers.

[0049] The styrene monomer may be one type or two or more types.

[0050] The styrene monomer contains 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.

[0051] The content of styrene monomers in monomer composition (C) is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, and particularly preferably 65% ​​to 85% by mass.

[0052] A polyfunctional vinyl aromatic compound is an aromatic compound having two or more vinyl groups. Furthermore, the vinyl group may have a structure in which the hydrogen atom bonded to the carbon atom constituting it is substituted by another group (e.g., a methyl group). When the hydrogen atom of the carbon atom where the vinyl group's bond is located is substituted by another group, the vinyl group is also called a vinylidene group. The vinyl groups in a polyfunctional vinyl aromatic compound may be contained within the (meth)acryloyl group located at the molecular terminal.

[0053] The inclusion of a polyfunctional vinyl aromatic compound in monomer composition (C) further reduces surface melting and shrinkage during molding. Therefore, the moldability of recycled foamed styrene resin particles can be further improved.

[0054] Polyfunctional vinyl aromatic compounds are preferably difunctional vinyl aromatic compounds. Difunctional vinyl aromatic compounds are aromatic compounds having two vinyl groups. Specific examples of polyfunctional vinyl aromatic compounds include, for example, divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene; diisopropenylbenzenes such as 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene, and 1,4-diisopropenylbenzene; 1,3-divinylnaphthalene, 1,8-divinylnaphthalene, 1,4-divinylnaphthalene, 1,5-divinylnaphthalene, 2,3-divinylnaphthalene, 2,7-divinylnaphthalene, and 2,6 Examples include divinylnaphthalenes such as -divinylnaphthalene; divinylbiphenyls such as 4,4'-divinylbiphenyl, 4,3'-divinylbiphenyl, 4,2'-divinylbiphenyl, 3,2'-divinylbiphenyl, 3,3'-divinylbiphenyl, 2,2'-divinylbiphenyl, and 2,4-divinylbiphenyl; 1,2-divinyl-3,4-dimethylbenzene; 1,3-divinyl-4,5,8-tributylnaphthalene; and 2,2'-divinyl-4-ethyl-4'-propylbiphenyl. The polyfunctional vinyl aromatic compound may be one type or two or more types. The polyfunctional vinyl aromatic compound preferably contains divinylbenzene. The content of divinylbenzene relative to the total amount of the polyfunctional vinyl aromatic compound 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.

[0055] The content of the polyfunctional vinyl aromatic compound in monomer composition (C) is preferably 5 ppm to 1000 ppm by mass relative to the styrene monomer, more preferably 10 ppm to 900 ppm, even more preferably 20 ppm to 950 ppm, and particularly preferably 50 ppm to 800 ppm.

[0056] The monomer composition (C) may contain any suitable vinyl monomer other than styrene monomers and polyfunctional vinyl aromatic compounds, as long as the effects of the present invention are not impaired. Examples of such vinyl monomers include polyfunctional monomers without aromatic rings, (meth)acrylic acid monomers, maleic acid monomers, and fumaric acid monomers. There may be only one or more such vinyl monomers.

[0057] Specific examples of polyfunctional monomers that do not have aromatic rings include 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.

[0058] In Embodiment (1), the ratio of recycled styrene-based resin raw material particles (a) to the total amount of recycled styrene-based resin raw material particles (a) and monomer composition (C) 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 ratio of recycled styrene-based resin raw material particles (a) to the total amount of recycled styrene-based resin raw material particles (a) and monomer composition (C) 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.

[0059] In Embodiment (1), recycled styrene resin particles (A) are obtained by nuclear polymerization of a monomer composition (C) with recycled styrene resin raw material particles (a) as the nucleus. Any suitable method can be used as such a nuclear polymerization method, as long as it does not impair the effects of the present invention. One preferred embodiment of such a nuclear polymerization method is a method in which a suspension is obtained by dispersing recycled styrene resin raw material particles (a) in an aqueous medium with the nucleus, 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 monomer composition (C) is added to carry out polymerization.

[0060] When obtaining recycled styrene-based resin particles (A), the addition temperature when adding the monomer composition (C) to the 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 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, thereby enabling good spheroidization of the 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 the monomer composition (C) to the 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 the styrene monomers to the 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 monomer composition (C) is 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.

[0061] 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 achieving a finer dispersion can be achieved by using a homomixer.

[0062] 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 pyrophosphate and tricalcium phosphate. Among these, magnesium pyrophosphate is preferred as a dispersant because it can better express the effects of the present invention.

[0063] 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.

[0064] When obtaining a suspension by dispersing recycled styrene-based 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-based 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.

[0065] 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.

[0066] 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 dispersion is carried out 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.

[0067] 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, t-butyl peroxy-2-ethylhexanoate, and t-butyl perbenzoate; and azo compounds such as azobisisobutyronitrile. There may be only one polymerization initiator or two or more.

[0068] The amount of polymerization initiator used is preferably 0.1% to 1.0% by mass, more preferably 0.1% to 0.8% by mass, and even more preferably 0.1% to 0.5% by mass, relative to the monomer composition (C).

[0069] The polymerization initiator is preferably added dissolved in a styrene monomer or 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 20% by mass or less relative to the styrene monomer or solvent.

[0070] As for the method of adding monomer composition (C) after impregnating a suspension containing recycled styrene-based resin raw material particles (a) with an emulsion containing styrene-based 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, shape, polymerization temperature, etc., of the polymerization apparatus.

[0071] After impregnating a suspension containing recycled styrene resin raw material particles (a) with an emulsion containing styrene monomers, monomer composition (C) may be added, and the polymerization reaction may be continued at any appropriate temperature and time as needed.

[0072] 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.

[0073] <A-1-2. Pressurization and impregnation of foaming agent in Embodiment (1)> The recycled foamable styrene resin particles in Embodiment (1) are obtained by pressurizing and impregnating recycled styrene resin particles (A) with a foaming agent.

[0074] A typical method for injecting and impregnating the foaming agent in Embodiment (1) is to place recycled styrene resin particles (A) in a reactor such as an autoclave and inject and impregnate them with the foaming agent.

[0075] The foaming agent may be one type or two or more types.

[0076] 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 so on. 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 order to better exhibit the effects of the present invention, and more preferably at least one selected from propane, n-butane, isobutane, n-pentane, and isopentane.

[0077] 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 monomer composition (C) is 100 parts by mass.

[0078] 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) when injected. 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) when injected. 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.

[0079] One embodiment of the impregnation temperature of the foaming agent into 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.

[0080] 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.

[0081] In embodiment (1), 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, uniform impregnation becomes possible, and for example, areas that shrink and melt when molded into a recycled styrene resin foam molded article 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, and it may not be possible to obtain a good molded article. 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), and may melt during molding.

[0082] In Embodiment (1), 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, particularly preferably 90°C or more and less than 110°C, and most preferably 95°C to 105°C.

[0083] In embodiment (1), 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.

[0084] <A-1-3. Other Components in Embodiment (1)> The recycled foamable styrene resin particles in Embodiment (1) 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 type or two or more types.

[0085] The recycled foamed styrene resin particles in Embodiment (1) may contain a flame retardant to enhance flame retardancy. The flame retardant may be one type or two or more types.

[0086] 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-alyloxy-3,5-dibromo)propane, and hexabromobenzene.

[0087] When using flame retardants, flame retardant additives may also be used. 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.

[0088] 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).

[0089] 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.

[0090] 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.

[0091] In producing the regenerated foamable styrene resin particles in Embodiment (1), a partial ester of a higher fatty acid and an alcohol may be used as a foam regulator. That is, the regenerated foamable styrene resin particles in Embodiment (1) 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 monoglycerides and diglycerides of these 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 the regenerated styrene resin particles (A). Methods for adding partial esters of higher fatty acids and alcohols include, for example, adding them together with a foaming agent, or employing commonly used methods such as dry blending, masterbatch, or melt injection.

[0092] In producing the recycled foamable styrene resin particles in Embodiment (1), a foaming aid may be used. That is, the recycled foamable styrene resin particles in Embodiment (1) may contain a foaming aid. 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.

[0093] In producing the recycled foamable styrene resin particles in Embodiment (1), a foam regulator may be used. That is, the recycled foamable styrene resin particles in Embodiment (1) 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 methylenebisstearate and ethylenebisstearate.

[0094] 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).

[0095] The recycled foamable styrene resin particles in Embodiment (1) may contain foam regulators such as talc, calcium carbonate, mica, citric acid, and sodium bicarbonate. There may be only one foam regulator or two or more.

[0096] 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.

[0097] <A-1-4. Surface Treatment> The recycled foamable styrene resin particles in Embodiment (1) may be surface treated. Preferably, such surface treatment is performed using at least one selected from silicone oil, antistatic agents, fatty acid metal salts, and fusion accelerators.

[0098] In the embodiment (1), when surface treatment with silicone oil is performed on the recycled foamable styrene resin particles, the amount of silicone oil used per 100 parts by mass of recycled foamable styrene resin particles before surface treatment is preferably 0.001 parts by mass to 0.3 parts by mass, more preferably 0.003 parts by mass to 0.28 parts by mass, even more preferably 0.005 parts by mass to 0.25 parts by mass, particularly preferably 0.008 parts by mass to 0.23 parts by mass, and most preferably 0.01 parts by mass to 0.23 parts by mass. If the amount of silicone oil used is too little and outside the above range, for example, when an antistatic agent is used, the affinity with the antistatic agent may not be sufficient during pre-foaming, and static electricity may be easily generated. If the amount of silicone oil used is too much and outside the above range, the surface may be lost due to the surface melting during molding, etc.

[0099] The silicone oil may be of one type or two or more types.

[0100] 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.

[0101] In the embodiment (1), when the recycled foamable styrene resin particles are surface-treated with an antistatic agent, the amount of antistatic agent used 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 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 article may become sticky.

[0102] The antistatic agent may be one type or two or more types.

[0103] 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.

[0104] The nonionic surfactant may be one type or two or more types.

[0105] 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, specifically, 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.

[0106] 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 regenerative 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.

[0107] The fatty acid glycerides may be of one type or two or more types.

[0108] 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.

[0109] 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.

[0110] In the embodiment (1), when surface treatment with a fatty acid metal salt is performed on the recycled foamable styrene-based resin particles, the amount of fatty acid metal salt used per 100 parts by mass of recycled foamable styrene-based resin particles before surface treatment is preferably 0.005 parts by mass to 0.5 parts by mass, more preferably 0.007 parts by mass to 0.45 parts by mass, even more preferably 0.01 parts by mass to 0.4 parts by mass, particularly preferably 0.015 parts by mass to 0.35 parts by mass, and most preferably 0.02 parts by mass 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-based 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, which may lead to the generation of static electricity and poor fusion of the molded article.

[0111] The fatty acid metal salt may be one type or two or more types.

[0112] 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.

[0113] In the embodiment (1), when surface treatment with a fusion accelerator is performed on the recycled foamable styrene resin particles, the amount of fusion accelerator used per 100 parts by mass of recycled foamable 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.

[0114] The fusion accelerator may be one type or two or more types.

[0115] 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.

[0116] ≪A-2. Preferred Embodiment (2) of Recycled Expandable Styrene Resin Particles≫ One preferred embodiment (2) of the recycled expandable styrene resin particles of the present invention is a recycled expandable styrene resin particle obtained by pressurizing and impregnating recycled styrene resin particles (A) with a foaming agent, wherein the recycled styrene resin particle (A) is a recycled styrene resin raw material particle (a) having a weight-average molecular weight of 150,000 to 1,000,000.

[0117] <A-2-1. Recycled styrene resin particles (A) in Embodiment (1)> In Embodiment (2), the recycled styrene resin particles (A) are typically recycled styrene resin raw material particles (a). That is, in Embodiment (2), recycled styrene resin raw material particles (a) are used as recycled styrene resin particles (A). For recycled styrene resin raw material particles (a) that can be adopted as recycled styrene resin particles (A) in Embodiment (2), the description of recycled styrene resin raw material particles (a) in the above section <A-1-1. Recycled styrene resin particles (A) in Embodiment (1)> may be used by reference. However, the weight-average molecular weight of recycled styrene resin raw material particles (a), which are recycled styrene resin particles (A) in Embodiment (2), is as follows.

[0118] The weight-average molecular weight of the recycled styrene-based resin raw material particles (a) in embodiment (2) is 150,000 to 1,000,000, preferably 160,000 to 980,000, more preferably 170,000 to 950,000, and even more preferably 200,000 to 900,000. The recycled foamable styrene-based resin particles according to embodiment (2), in which the recycled styrene-based resin raw material particles (a) satisfy the above, have reduced collapse and shrinkage due to melting of the foamed particles during foaming, and improved moldability. The weight-average molecular weight of the recycled styrene-based resin raw material particles (a) can be adjusted, for example, by appropriately mixing multiple recycled styrene-based resins.

[0119] <A-2-2. Pressurization and Impregnation of Foaming Agent in Embodiment (2)> The recycled foamable styrene resin particles in Embodiment (2) are obtained by pressurizing and impregnating recycled styrene resin particles (A), which utilize recycled styrene resin raw material particles (a) as they are, with a foaming agent.

[0120] Typical methods for injecting and impregnating the foaming agent in Embodiment (2) include: Injection and impregnation method (1): A suspension containing recycled styrene resin particles (A) (using recycled styrene resin raw material particles (a) as is) is placed in a reactor such as an autoclave, and the foaming agent is injected and impregnated into it; Injection and impregnation method (2): Recycled styrene resin particles (A) (using recycled styrene resin raw material particles (a) as is) are placed in an extruder, the foaming agent is injected and impregnated into the extruder midway through the process, and the extruder is cut underwater at the same time as it is extruded.

[0121] Regarding the injection and impregnation method (1), the explanation in the section <A-1-2. Injection and impregnation of the foaming agent in embodiment (1)> above can be used as a reference. However, the injection temperature and impregnation temperature of the foaming agent into the recycled styrene resin particles (A) are as follows.

[0122] Regarding the injection / impregnation method (1) in Embodiment (2), the injection temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 145°C, even more preferably 80°C to 140°C, particularly preferably 100°C to 135°C, and most preferably 110°C to 130°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, for example, even if the recycled styrene resin particles (A) are irregularly shaped particles, it becomes easier to spheroidize them, reducing adhesion between particles, and also making it easier to remove odors characteristic of recycled raw materials. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too low and outside the above range, it may become difficult to spheroidize them. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too high and outside the above range, it may cause the particles to flatten or increase the number of particles that adhere to each other.

[0123] Regarding the press-fitting and impregnation method (1) in Embodiment (2), the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 130°C, even more preferably 80°C to 120°C, even more preferably 90°C or more and less than 110°C, particularly preferably 95°C or more and less than 110°C, and most preferably 100°C or more and less than 110°C. 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, for example, the foaming agent can be efficiently impregnated into the recycled styrene resin particles (A), and the foaming agent can be absorbed uniformly, making it easier to control subsequent foaming and molding, and also making it easier to remove odors characteristic of recycled raw materials. If the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is too low and outside the above range, there is a risk that the foaming agent will not be absorbed to the center of the recycled styrene resin particles (A), or that only a portion of the injected foaming agent will be absorbed by the recycled styrene resin particles (A). If the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is too high and outside the above range, there is a risk that the particles may become flattened or that the number of bonded particles may increase.

[0124] The press-fitting and impregnation method (2) in embodiment (2) involves placing recycled styrene resin particles (A) (using recycled styrene resin raw material particles (a) as they are) into an extruder, press-fitting and impregnating a foaming agent into the extruder midway through the process, and simultaneously extruding the particles from the extruder and cutting them underwater.

[0125] In more detail, the press-fitting and impregnation method (2) in embodiment (2) involves supplying recycled styrene-based resin particles (A) (using recycled styrene-based resin raw material particles (a) as they are) to an extruder, heating and melting them, injecting a foaming agent using a high-pressure pump from the middle of the extruder, extruding the resulting resin composition from a porous die into water, cutting it in water simultaneously with the extrusion, and then dewatering and drying it to obtain recycled foamable styrene-based resin particles.

[0126] For information on foaming agents, refer to the explanation of foaming agents in the section <A-1-2. Pressurization and Impregnation of Foaming Agents> mentioned above.

[0127] As the extruder, any known extruder used in the extrusion molding of resin compositions can be used. Examples of such extruders include single-screw extruders, twin-screw extruders, and tandem extruders.

[0128] <A-2-3. Other Components in Embodiment (2)> The recycled foamable styrene resin particles in Embodiment (2) 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 type or two or more types.

[0129] For other components, refer to the explanation in the section <A-1-3. Other components in Embodiment (1)> mentioned above.

[0130] <A-2-4. Surface Treatment> The recycled foamable styrene resin particles in Embodiment (2) may be subjected to surface treatment. The explanation in the section <A-1-4. Surface Treatment> above can be used as a reference for such surface treatment.

[0131] <<B. Recycled Pre-Expanded Styrene Resin Particles>> Recycled pre-expanded styrene resin particles according to the embodiment of the present invention are obtained by pre-expanding recycled expandable styrene resin particles according to the embodiment of the present invention.

[0132] 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, and recycled styrene resin foam molded articles with less static electricity can be molded. 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.

[0133] 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. Furthermore, when the bulk expansion ratio of recycled pre-expanded styrene resin particles is in the medium to high expansion range (for example, in the bulk expansion range of 60 times or more), surface melting is particularly likely to occur when molding the recycled styrene resin foamed molded product. However, with the recycled pre-expanded styrene resin particles according to the embodiment of the present invention, surface melting during molding can be reduced, and the moldability of the recycled expandable styrene resin particles can be improved.

[0134] 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).

[0135] <<C. Recycled Styrene Resin Foam Molded Articles>> A recycled styrene resin foam molded article according to one embodiment of the present invention is a recycled styrene resin foam molded article formed from recycled foamable styrene resin particles according to an embodiment of the present invention. A recycled styrene resin foam molded article according to another embodiment of the present invention is a recycled styrene resin foam molded article formed from recycled pre-foamed styrene resin particles according to an embodiment of the present invention.

[0136] Recycled styrene-based foam molded articles typically include recycled expanded styrene-based resin particles (hereinafter sometimes simply referred to as "foamed particles") which are obtained by further foaming recycled pre-expanded styrene-based resin particles.

[0137] Recycled styrene-based foamed molded articles are typically composed of multiple foamed particles that are fused together.

[0138] 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. 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.

[0139] The temperature for heat foaming (essentially the temperature of the heat transfer medium) is preferably 90°C to 150°C, more preferably 110°C to 130°C. The heat foaming time is preferably 5 seconds to 50 seconds, 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, more preferably 0.06 MPa to 0.08 MPa. Under these conditions, the foamed particles can be well fused together.

[0140] If necessary, the recycled pre-expanded styrene resin particles may be aged before molding the recycled styrene resin foam molded product. The preferred aging temperature for the recycled pre-expanded styrene resin particles is 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 foaming agent in the recycled pre-expanded styrene resin particles may dissipate, reducing moldability.

[0141] The foaming ratio of the foamed particles in the recycled styrene-based resin foam molded article is 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.

[0142] The recycled styrene-based resin foam molded articles according to embodiments of the present invention are lightweight and have excellent heat insulation and mechanical strength, making them suitable for use as wall insulation, floor insulation, roof insulation, automobile insulation, hot water tank insulation, pipe insulation, solar system insulation, water heater insulation, containers for food and industrial products (e.g., food containers such as fish boxes, reusable containers), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, molded articles for embankments, core materials for tatami mats, core materials for cushions, aggregates for concrete, and the like.

[0143] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement and evaluation methods for each characteristic are as follows.

[0144] <Measurement of Weight-Average Molecular Weight> The weight-average molecular weight (Mw) was measured using GPC (gel permeation chromatography). Here, weight-average molecular weight refers to the weight-average molecular weight on a polystyrene basis. Specifically, the measurement was performed using the following procedure: 3 mg of the sample was dissolved completely in 10 mL of tetrahydrofuran (THF) at room temperature for 72 hours, and then filtered through a non-aqueous 0.45 μm chromatographic disk. The filtrate was measured using a chromatograph under the following measurement conditions. The weight-average molecular weight was determined from a calibration curve of standard polystyrene that had been prepared in advance. (Measurement conditions) Equipment: High-speed GPC instrument Product name: Tosoh HLC-8320GPC EcoSEC system (built-in RI detector) Analysis conditions: Guard column: TSKguardcolumn SuperHZ-H (4.6 mm ID × 2 cmL) × 1 Column: TSKgel SuperHZM-H (4.6 mm I.D × 15 cmL) × 2 Column temperature: 40°C System temperature: 40°C Mobile phase: THF Mobile phase flow rate: Sample side pump = 0.175 mL / min Reference side pump = 0.175 mL / min Detector: RI detector Sample concentration: 0.3 g / L Injection volume: 50 μL Measurement time: 0 min to 25 min Runtime: 25 min Sampling pitch: 200 msec (Calibration curve creation) For the calibration curve, standard polystyrene samples were used, specifically "TSK standard POLYSTYRENE" manufactured by Tosoh Corporation, 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. These calibration curve standard polystyrene samples were grouped 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). A standard polystyrene sample belonging to Group A, with a weight-average molecular weight of 1,090,000, was weighed out at a dose of 5 mg, dissolved in 20 mL of THF, and 50 μL of the resulting solution was injected into the sample column.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 as 5 mg, 5 mg, 5 mg, and 10 mg, respectively. These were then 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 described above as 1 mg, 5 mg, 5 mg, and 5 mg, respectively. These 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-8320 GPC dedicated data analysis program GPC workstation (EcoSEC-WS), and these were used as calibration curves for measuring polystyrene-equivalent weight-average molecular weight.

[0145] <Measurement of Uniaxial Extensional Viscosity> Uniaxial extensional viscosity was measured using a viscoelasticity measuring device ("PHYSICA MCR301", manufactured by Anton Paar) and a temperature control system CTD450. First, resin particles were hot-pressed in a hot press at a temperature of 190°C for 5 minutes to create strip-shaped samples with a width of 10 mm and a thickness of approximately 1.2 mm. Next, these strip-shaped samples were cut to a length of 20-25 mm and set in the uniaxial extensional viscosity measurement jig (SER2) of the viscoelasticity measuring device, which was heated to a measurement temperature of 160°C. After waiting for 10 seconds under a nitrogen atmosphere at a temperature of 160°C ± 0.5°C, the strain rate was 0.1 s. -1 Uniaxial extensional viscosity was measured. For the measurement, the measurement point interval was set to "acquire measurement point interval logarithmically," and with the start of measurement set to 0 seconds, the start of measurement point acquisition was set to 0.01 seconds and the end of acquisition to 26 seconds. The maximum number of measurement points was set to 200. The actual measurement time with the above settings was 34 seconds. However, if the measurement limit of the measuring device was reached before the end of the measurement, the acquisition of measurement points was stopped at the point where the measurement limit was reached. Here, the point at which the measurement limit was reached also includes the point at which the sample broke. From the uniaxial extensional viscosity measured in the above manner, the maximum value was determined.

[0146] <Evaluation of Moldability> Moldability was evaluated by visually inspecting the appearance of the obtained foam molded product. Specifically, it was evaluated by the number of depressions (depressions) that occurred on a 300 mm x 400 mm surface of the molded plate (number of depressed foam particles). The evaluation criteria were as follows: ○: 1 or fewer depressed particles △: 2 to 5 depressed particles ×: 6 or more depressed particles

[0147] [Manufacturing Example 1]: Manufacturing of recycled styrene resin raw material particles (a) Recycled 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 100,000, 150,000, and 200,000, respectively. The mixture was supplied to a single-screw extruder, heated and melted at 200°C, extruded from a mold, and cut underwater to an average particle diameter of 0.75 mm (approximately spherical), thereby manufacturing recycled styrene resin raw material particles (a) having a predetermined weight-average molecular weight. The manufactured recycled styrene resin raw material particles (a) were of the following three types: Recycled styrene resin raw material particle (a10): Weight-average molecular weight 100,000 Recycled styrene resin raw material particle (a15): Weight-average molecular weight 150,000 Recycled styrene resin raw material particle (a20): Weight-average molecular weight 200,000

[0148] [Example 1] <Preparation of recycled foamable styrene resin particles (1)> 36 kg of water, 3.5 g of sodium dodecylbenzenesulfonate, and 170 g of magnesium pyrophosphate were added to a 100-liter reactor with a stirrer. Then, 12.6 kg of recycled styrene resin raw material particles (a) obtained in Production Example 1 were added and stirred at 150 rpm to suspend the mixture and prepare suspension (1). Separately, 2.3 kg of styrene monomer, in which 125 g of benzoyl peroxide (75% purity) (BPO) and 20 g of t-butyl peroxy-2-ethylhexyl monocarbonate (TBEC) were dissolved as polymerization initiators, was added to a dispersion of 2.5 kg of water and 0.8 g of sodium dodecylbenzenesulfonate, and stirred with a homomixer to emulsify the mixture and prepare emulsion (1). The above suspension (1) in the 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 kept at 75°C for 30 minutes to ensure good absorption of the styrene monomer and polymerization initiator. Immediately after this period, 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, held at 125°C for 30 minutes, and then cooled to 60°C over 1 hour to produce recycled styrene resin particles (A1) in the reactor. The uniaxial extension viscosity of these recycled styrene resin particles (A1) was measured using the method described above. Next, separately, 189 g of dicumyl peroxide and 35 g of ethylenebis-stearate amide, which are flame retardant aids, were added to a dispersion of 3.5 kg of water, 1.5 g of sodium dodecylbenzenesulfonate, and 20 g of magnesium pyrophosphate, and the mixture was stirred with a homomixer to emulsify and prepare emulsion (2). This emulsion (2) was added to the reactor cooled to 60°C as described above. Ten minutes after this addition, 756 g of the flame retardant tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes.Next, the temperature was raised to 100°C, and 7.5% by mass of pentane (isopentane / n-pentane = 20% by mass / 80% by mass) and 1.0% by mass of propane were injected under pressure as a blowing agent into the recycled styrene resin particles (A1). The mixture was then held in this state for 5.5 hours to slowly impregnate the particles with the blowing agent. After that, the temperature inside the reactor was cooled to 25°C. The contents were then removed from the reactor, dehydrated, dried, and classified to obtain recycled blowable styrene resin particles (1).

[0149] <Surface treatment of 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 recycled foamed styrene resin particles (1) in a tumbler mixer and stirred for 30 minutes to perform surface treatment, thereby obtaining surface-treated recycled foamed styrene resin particles (1').

[0150] <Preparation of Recycled Pre-Expanded Styrene Resin Particles (pf1)> The obtained surface-treated recycled expandable styrene resin particles (1') were placed in a cylindrical batch-type pressurized foaming machine with a volume of 25 liters and heated with steam for 3 minutes to obtain recycled pre-expanded styrene resin particles (pf1). The bulk density of the recycled pre-expanded styrene resin particles (pf1) was 0.017 g / cm³. 3 The expansion ratio was 60 times.

[0151] <Preparation of Recycled Styrene Resin Foam Molded Body (f1)> A molding machine with a mold having a cavity measuring 300 mm in length, 400 mm in width, and 30 mm in thickness was used. Recycled pre-foamed styrene resin particles (pf1) were left at room temperature for 24 hours, then filled into the mold cavity 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. 3The foaming ratio was 60 times. The recycled styrene-based resin foam molded article (f1) was then 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.

[0152] [Example 2] A suspension (1) and emulsion (1) were prepared in the same manner as in Example 1. The suspension (1) in a 100-liter reactor with a stirrer was maintained at 75°C, and the 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 (a). Immediately after this, a mixture of 27.1 kg of styrene monomer and divinylbenzene was continuously added dropwise over 120 minutes. Here, the amount of divinylbenzene added to the reactor was set to 100 ppm relative to the total amount of styrene monomer (27.1 kg + 2.3 kg = 29.4 kg). The addition temperature was gradually raised from 75°C to 105°C. Then, the temperature was raised to 125°C over 30 minutes, maintained at 125°C for 30 minutes, and then cooled to 60°C over 1 hour to produce recycled styrene resin particles (A2) in the reaction vessel. The procedure was carried out in the same manner as in Example 1, except that the recycled styrene resin particles (A2) described above were used, to obtain recycled foamable styrene resin particles (2), recycled pre-foamed styrene resin particles (pf2), and recycled styrene resin foam molded article (f2). The results are shown in Table 1.

[0153] [Examples 3-6] The process was carried out in the same manner as in Example 2, except that the amount of divinylbenzene was changed as shown in Table 1 in the preparation of recycled styrene resin particles (A), and recycled styrene resin particles (A3)-(A6), recycled foamable styrene resin particles (3)-(6), recycled pre-foamed styrene resin particles (pf3)-(pf6), and recycled styrene resin foam molded articles (f3)-(f6) were obtained. The results are shown in Table 1.

[0154] [Example 7] The procedure was carried out in the same manner as in Example 1, except that recycled styrene resin raw material particles (a15) were used as recycled styrene resin raw material particles (a), to obtain 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). The results are shown in Table 2.

[0155] [Examples 8-12] The procedure was the same as in Example 2, except that recycled styrene resin raw material particle (a15) was used as recycled styrene resin raw material particle (a), and the amount of divinylbenzene was as shown in Table 2. Recycled styrene resin particles (A8) to (A12), recycled foamable styrene resin particles (8) to (12), recycled pre-foamed styrene resin particles (pf8) to (pf12), and recycled styrene resin foam molded articles (f8) to (f12) were obtained. The results are shown in Table 2.

[0156] [Example 13] The procedure was carried out in the same manner as in Example 7, except that in the preparation of emulsion (1), 125 g of benzoyl peroxide (75% purity) (BPO) was replaced with 103 g of t-butyl peroxy-2-ethylhexanoate (TBEH), and recycled styrene resin particles (A13), recycled foamable styrene resin particles (13), recycled pre-foamed styrene resin particles (pf13), and recycled styrene resin foam molded article (f13) were obtained. The results are shown in Table 2.

[0157] [Example 14] The same procedure as in Example 13 was followed, except that the amount of divinylbenzene was changed as shown in Table 2 in the preparation of recycled styrene resin particles (A), and recycled styrene resin particles (A14), recycled foamable styrene resin particles (14), recycled pre-foamed styrene resin particles (pf14), and recycled styrene resin foam molded article (f14) were obtained. The results are shown in Table 2.

[0158] [Example 15] The procedure was carried out in the same manner as in Example 9, except that dicumyl peroxide, a flame retardant aid, and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), a flame retardant, were not used in the preparation of emulsion (2). Recycled styrene resin particles (A15), recycled foamable styrene resin particles (15), recycled pre-foamed styrene resin particles (pf15), and recycled styrene resin foam molded article (f15) were obtained. The results are shown in Table 2.

[0159] [Examples 16-21] The procedure was the same as in Example 2, except that recycled styrene resin raw material particle (a20) was used as recycled styrene resin raw material particle (a), and the amount of divinylbenzene was as shown in Table 3. Recycled styrene resin particles (A16) to (A21), recycled foamable styrene resin particles (16) to (21), recycled pre-foamed styrene resin particles (pf16) to (pf21), and recycled styrene resin foam molded articles (f16) to (f21) were obtained. The results are shown in Table 3.

[0160] [Example 22] The procedure was carried out in the same manner as in Example 16, except that in the preparation of emulsion (1), 125 g of benzoyl peroxide (75% purity) (BPO) was replaced with 103 g of t-butyl peroxy-2-ethylhexanoate (TBEH), and in the preparation of recycled styrene resin particles (A), the amount of divinylbenzene was changed as shown in Table 3. Recycled styrene resin particles (A22), recycled foamable styrene resin particles (22), recycled pre-foamed styrene resin particles (pf22), and recycled styrene resin foam molded article (f22) were obtained. The results are shown in Table 3.

[0161] [Example 23] The procedure was the same as in Example 18, except that the preparation of emulsion (2) was carried out in the same manner as in Example 18, except that dicumyl peroxide, a flame retardant aid, and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), a flame retardant, were not used. Recycled styrene resin particles (A23), recycled foamable styrene resin particles (23), recycled pre-foamed styrene resin particles (pf23), and recycled styrene resin foam molded article (f23) were obtained. The results are shown in Table 3.

[0162] [Comparative Examples 1-3] The process was carried out in the same manner as in Example 2, except that the recycled styrene resin raw material particles (a) shown in Tables 1-3 were used in the preparation of recycled styrene resin particles (A), and the amount of divinylbenzene was changed as shown in Tables 1-3. Recycled styrene resin particles (AC1)-(AC3), recycled foamable styrene resin particles (C1)-(C3), recycled pre-foamed styrene resin particles (pfC1)-(pfC3), and recycled styrene resin foam molded articles (fC1)-(fC3) were obtained. The results are shown in Tables 1-3.

[0163] [Example 24] <Preparation of recycled foamable styrene resin particles (24)> 48 kg of water, 5.7 g of sodium dodecylbenzenesulfonate, and 280 g of magnesium pyrophosphate were added to a 100-liter reactor with a stirrer. 40 kg of recycled styrene resin raw material particles (a15) were then added and the mixture was stirred at 150 rpm to suspend it, preparing suspension (2). The suspension (2) in the 100-liter reactor with a stirrer was maintained at 60°C, and 180 g of dicumyl peroxide was added. Ten minutes after this addition, 720 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 120°C over 60 minutes, and then 7.5 parts by mass of pentane (isopentane / n-pentane = 20% by mass / 80% by mass) as a blowing agent was injected into the recycled styrene resin raw material particles (a15) under pressure. The temperature was raised to 108°C over 10 minutes, and then held at that temperature for 5.5 hours to slowly impregnate the particles with the blowing agent. After that, the temperature inside the reactor was cooled to 25°C. The contents were then removed from the reactor, dehydrated, dried, and classified to obtain recycled foamable styrene resin particles (24).

[0164] <Surface treatment of recycled foamed styrene resin particles (24)> Surface treatment was performed in the same manner as in Example 1 to obtain surface-treated recycled foamed styrene resin particles (24').

[0165] <Preparation of recycled pre-expanded styrene resin particles (pf24)> From the obtained recycled expandable styrene resin particles (24'), recycled pre-expanded styrene resin particles (pf24) were obtained in the same manner as in Example 1.

[0166] <Preparation of Recycled Styrene Resin Foam Molded Article (f24)> From the obtained recycled pre-foamed styrene resin particles (pf24), a recycled styrene resin foam molded article (f24) was obtained in the same manner as in Example 1. The results are shown in Table 4.

[0167] [Example 25] The procedure was carried out in the same manner as in Example 24, except that recycled styrene resin raw material particles (a20) were used as recycled styrene resin raw material particles (a), and recycled styrene resin particles (A25), recycled foamable styrene resin particles (25), recycled pre-foamed styrene resin particles (pf25), and recycled styrene resin foam molded article (f25) were obtained. The results are shown in Table 4.

[0168] [Comparative Example 4] The procedure was carried out in the same manner as in Example 24, except that recycled styrene resin raw material particles (a10) were used as recycled styrene resin raw material particles (a), to obtain recycled styrene resin particles (AC4), recycled foamable styrene resin particles (C4), recycled pre-foamed styrene resin particles (pfC4), and recycled styrene resin foam molded article (fC4). The results are shown in Table 4.

[0169]

[0170]

[0171]

[0172]

[0173] The abbreviations in Table 1-3 are as follows: BPO: Benzoyl peroxide TBEC: t-Butyl peroxy-2-ethylhexyl monocarbonate TBEH: t-Butyl peroxy-2-ethylhexanoate

[0174] 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-based resin particles obtained by pressurizing and impregnating recycled styrene-based resin particles (A) with a foaming agent, wherein the recycled styrene-based resin particles (A) are subjected to a constant strain rate of 0.1 s at 160°C. -1 Under these conditions, in uniaxial extensional viscosity measurements, the maximum value of the uniaxial extensional viscosity was 5.0 × 10⁻⁶. 4 Pa・s~1.0×10 10 Recycled foamable styrene resin particles having a Pa·s molecular weight of 150,000 to 1,000,000.

2. Recycled pre-foamed styrene resin particles obtained by pre-foaming the recycled foamable styrene resin particles described in claim 1.

3. A recycled styrene-based resin foam molded article formed from recycled pre-expanded styrene-based resin particles as described in claim 2.

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