JP2024092402A - Recycled expandable styrene resin particles, recycled pre-expanded styrene resin particles, and recycled styrene resin foam molded body - Google Patents

Abstract

To provide recycled foamable styrenic resin particles having high environmental contribution which can exhibit excellent moldability, and can impart high strength to an obtained molding, recycled pre-foamed styrenic resin particles obtained from the recycled foamable styrenic resin particles, and a recycled styrenic resin foam molding which is obtained by molding the recycled pre-foamed styrenic resin particles and can exhibit high strength.SOLUTION: Recycled foamable styrenic resin particles are recycled foamable styrenic resin particles which become recycled pre-foamed styrenic resin particles by pre-foaming, wherein the average foam diameter of the recycled pre-foamed styrenic resin particles is more than 5 μm and less than 520 μm, secondary foamability of the recycled pre-foamed styrenic resin particles is more than 1.00 time, and a bulk foaming ratio of the recycled pre-foamed styrenic resin particles is 5 times to 120 times.SELECTED DRAWING: None

Description

The present invention relates to recycled expandable styrene-based resin particles, recycled pre-expanded styrene-based resin particles, and recycled styrene-based resin foam molded articles.

Since foamed molded articles are lightweight and have excellent insulating properties and mechanical strength, they are widely used as insulating materials for houses and automobiles, heat retaining materials for building materials, embankment materials for polystyrene foam civil engineering, transport packaging materials for fish boxes and food containers, and cushioning materials. Among them, in-mold foamed molded articles manufactured using expandable particles (typically expandable polystyrene-based resin particles or pre-expanded styrene-based resin particles obtained by pre-expanding them) as a raw material are widely used because of the advantage that the desired shape can be easily obtained. Such foamed molded articles are composed of multiple expandable particles fused together.

On the other hand, the amount of plastic waste is increasing year by year. Most plastic waste is disposed of by incineration or landfilling, but it has become a major social issue due to environmental pollution, global warming, and a lack of landfill sites. For this reason, there is a strong social demand for the reuse of plastic waste, and various methods for recycling plastic waste are being considered, such as with the enforcement of the Home Appliance Recycling Law. Among the various recycling methods proposed, material recycling, in which plastic waste is reused as plastic components for products, has attracted attention from the perspective of resource circulation and reducing environmental load, and such material recycling is also being considered for styrene resin foam moldings.

Several methods have been proposed for recycling styrene-based resin foamed moldings, in which the recovered raw material is melted and extruded to produce recovered pellets, which are then impregnated with a foaming agent to obtain recycled expandable styrene-based resin particles.

A method has been reported for obtaining recycled expandable styrene resin particles by impregnating or pressurizing and then impregnating with a blowing agent into recycled resin pellets molded from recovered styrene resin foam moldings (Patent Documents 1 to 4). A method has been reported for obtaining recycled expandable styrene resin particles by adding styrene monomer to recycled resin pellets molded from recovered styrene resin foam moldings, polymerizing the pellets, and then impregnating or pressurizing and then impregnating with a blowing agent (Patent Documents 5 to 8).

However, conventional recycled expandable styrene resin particles have problems in that moldability is reduced, such as poor elongation of the surface of the molded body and a low fusion rate between the foam particles of the molded body, compared to expandable styrene resin particles that do not use recycled raw materials. In addition, conventional recycled expandable styrene resin particles have problems in that the strength of the molded body is reduced, compared to expandable styrene resin particles that do not use recycled raw materials.

In addition, recycled raw materials often contain impurities, and conventional recycled expandable styrene-based resin particles made from recycled raw materials containing such impurities have problems such as reduced moldability and being easily flammable.

Patent No. 3044942 Patent No. 4234832 Japanese Patent No. 4261676 Patent No. 6788428 Patent No. 4052193 JP 2006-160905 A Patent No. 4912567 Patent No. 5128246

The present invention has been made to solve the above-mentioned problems of the prior art, and its main objective is to provide recycled expandable styrene-based resin particles that are highly environmentally friendly, can exhibit excellent moldability, and can impart high strength to the resulting molded article. It also aims to provide recycled pre-expanded styrene-based resin particles obtained from such recycled expandable styrene-based resin particles. It also aims to provide recycled styrene-based resin foam molded articles that are produced by molding such recycled pre-expanded styrene-based resin particles and can exhibit high strength.

[1] The recycled expandable styrene-based resin particles according to an embodiment of the present invention are recycled expandable styrene-based resin particles which become recycled pre-expanded styrene-based resin particles by pre-expanding, the average bubble diameter of the recycled pre-expanded styrene-based resin particles being more than 5 μm and less than 520 μm, the secondary expandability of the recycled pre-expanded styrene-based resin particles being more than 1.00 times, and the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles being 5 times to 120 times.
[2] In the recycled expandable styrene-based resin particles described in [1] above, the recycled expandable styrene-based resin particles may be obtained by pressurizing a blowing agent into a suspension containing the recycled styrene-based resin raw material (A) and a dispersant to impregnate the particles.
[3] In the recycled expandable styrene-based resin particles described in [2] above, the recycled styrene-based resin raw material (A) may be polymer particles obtained by adding a styrene-based monomer to a suspension containing recycled styrene-based resin raw material particles (a) and polymerizing the mixture.
[4] In the recycled expandable styrene-based resin particles described in [3] above, the recycled styrene-based resin raw material particles (a) may be at least one selected from extruded strand pellets obtained by extruding a used styrene-based resin with an extruder and strand-cutting it, underwater-cut pellets obtained by an underwater cutting method in which a used styrene-based resin is extruded with an extruder and simultaneously cut in water, and hot-cut pellets obtained by a hot-cut method in which a used styrene-based resin is cut and cooled immediately after it comes out of a die of an extruder.
[5] In the recycled expandable styrene-based resin particles described in the above [2], the recycled styrene-based resin raw material particles (a) may be used as they are as the recycled styrene-based resin raw material (A).
[6] In the recycled expandable styrene-based resin particles described in [5] above, the recycled styrene-based resin raw material particles (a) may be at least one selected from extruded strand pellets obtained by extruding a used styrene-based resin with an extruder and strand-cutting it, underwater-cut pellets obtained by an underwater cutting method in which a used styrene-based resin is extruded with an extruder and simultaneously cut in water, and hot-cut pellets obtained by a hot-cut method in which a used styrene-based resin is cut and cooled immediately after it comes out of a die of an extruder.
[7] The recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention are obtained by pre-expanding the recycled expandable styrene-based resin particles according to any one of [1] to [6] above.
[8] The recycled styrene-based resin foamed molded article according to an embodiment of the present invention is obtained by molding the recycled pre-expanded styrene-based resin particles described in [7] above.
[9] In the recycled styrene-based resin foam molded article according to the above [8], the 10% compressive strength measured in accordance with JIS A 9521 may be 0.03 MPa to 0.90 MPa.

According to the present invention, it is possible to provide recycled expandable styrene-based resin particles that are highly environmentally friendly, can exhibit excellent moldability, and can impart high strength to the resulting molded article. It is also possible to provide recycled pre-expanded styrene-based resin particles obtained from such recycled expandable styrene-based resin particles. It is also possible to provide a recycled styrene-based resin foam molded article that exhibits high strength and is formed by molding such recycled pre-expanded styrene-based resin particles.

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

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

<<A. Recycled expandable styrene-based resin particles>>
The recycled expandable styrene-based resin particles according to the embodiment of the present invention become recycled pre-expanded styrene-based resin particles by pre-expanding.

The recycled expandable styrene resin particles according to an 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 3.0 mm, and more preferably 0.6 mm to 2.5 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 diameter at 50% of the cumulative value from the particle size distribution by the sieving test of JIS Z 8815.

The shape of the recycled expandable styrene resin particles according to the embodiment of the present invention may 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, a spherical shape, a nearly spherical shape, and an elliptical spherical shape (egg-shaped shape). In terms of achieving the effects of the present invention, the shape of the recycled expandable styrene resin particles according to the embodiment of the present invention is preferably a spherical shape or a nearly spherical shape, and more preferably a spherical shape. However, in reality, it is difficult to distinguish between a spherical shape and a nearly spherical shape, so in this specification, both are collectively referred to as a spherical shape.

The weight average molecular weight of the recycled expandable styrene-based resin particles according to an embodiment of the present invention can be any appropriate weight average molecular weight within a range that does not impair the effects of the present invention. Such a weight average molecular weight is preferably 100,000 to 510,000, more preferably 110,000 to 490,000, even more preferably 120,000 to 470,000, and particularly preferably 130,000 to 460,000.

The recycled expandable styrene resin particles according to an embodiment of the present invention are pre-expanded to produce recycled pre-expanded styrene resin particles, and the average bubble diameter of the recycled pre-expanded styrene resin particles is preferably more than 5 μm and less than 520 μm, more preferably 5 μm to 500 μm, even more preferably 5 μm to 450 μm, particularly preferably 5 μm to 400 μm, and most preferably 5 μm to 380 μm. By adjusting the average bubble diameter of the recycled pre-expanded styrene resin particles to within the above range, the effects of the present invention can be achieved, and the recycled expandable styrene resin particles according to an embodiment of the present invention can exhibit excellent moldability and impart high strength to the resulting molded article. If the average bubble diameter of the recycled pre-expanded styrene resin particles is outside the above range, there is a risk that excellent moldability cannot be exhibited or high strength cannot be imparted to the resulting molded article.

The recycled expandable styrene-based resin particles according to an embodiment of the present invention have a secondary expandability of preferably more than 1.00 times, more preferably 1.05 times or more, even more preferably 1.10 times or more, particularly preferably 1.15 times or more, and most preferably 1.20 times or more. The upper limit of the secondary expandability is preferably 6.0 times or less, more preferably 5.0 times or less, even more preferably 4.0 times or less, and particularly preferably 3.5 times or less, from the viewpoint of increasing the surface pressure during molding, lengthening the cooling time and lengthening the molding cycle, and from the viewpoint of increasing the environmental load and increasing costs due to leaving residual gas more than necessary for molding. By adjusting the secondary expandability of the recycled pre-expanded styrene-based resin particles within the above range, the effects of the present invention can be expressed, and the recycled expandable styrene-based resin particles according to an embodiment of the present invention can express excellent moldability and impart high strength to the obtained molded body. If the secondary expandability of the recycled pre-expanded styrene-based resin particles falls outside the above range, there is a risk that excellent moldability will not be achieved, or that the resulting molded article will not have high strength.

The recycled expandable styrene-based resin particles according to an embodiment of the present invention are pre-expanded to produce recycled pre-expanded styrene-based resin particles with a bulk expansion ratio of preferably 5 to 120 times, more preferably 2 to less than 100 times, more preferably 5 to 90 times, even more preferably 10 to 85 times, and particularly preferably 15 to 83 times. By adjusting the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles to within the above range, the effects of the present invention can be achieved, and the recycled expandable styrene-based resin particles according to an embodiment of the present invention can exhibit excellent moldability and impart high strength to the resulting molded article. If the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles is outside the above range, there is a risk that excellent moldability cannot be exhibited or high strength cannot be imparted to the resulting molded article.

The recycled expandable styrene resin particles according to an embodiment of the present invention can be produced by any appropriate means as long as the effects of the present invention are not impaired. In terms of being able to further express the effects of the present invention, the recycled expandable styrene resin particles according to an embodiment of the present invention are typically obtained by pressurizing a blowing agent into a suspension containing a recycled styrene resin raw material (A) and a dispersant to impregnate the suspension.

<A-1. Description of recycled styrene-based resin raw material (A)>
Examples of the recycled styrene-based resin raw material (A) include recycled styrene-based resin raw material particles, recycled expandable styrene-based resin particles, recycled pre-expanded styrene-based resin particles, and recycled styrene-based resin foam moldings.

The recycled styrene resin raw material particles are used styrene resin, and may be pellets, shrinkage, or melt. The recycled expandable styrene resin particles are particles in which a blowing agent is pressed into or impregnated into recycled styrene resin raw material particles. The recycled pre-expanded styrene resin particles are particles formed by pre-expanding recycled expandable styrene resin particles. The recycled styrene resin foam molded product is a recycled styrene resin foam molded product molded from the recycled pre-expanded styrene resin particles.

Preferred embodiments of the recycled styrene-based resin raw material (A) include:
(Embodiment 1 of Recycled Styrenic Resin Raw Material (A)) An embodiment in which, as the recycled styrenic resin raw material (A), polymer particles obtained by adding a styrenic monomer to a suspension containing recycled styrenic resin raw material particles (a) and polymerizing the mixture are used;
(Embodiment 2 of Recycled Styrenic Resin Raw Material (A)) An embodiment in which recycled styrene-based resin raw material particles (a) are used as is as the recycled styrene-based resin raw material (A);
There are two embodiments:

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

As the material for the recycled styrene-based resin raw material particles (a), any appropriate recycled styrene-based resin may be used as long as it does not impair the effects of the present invention. Examples of such recycled styrene-based resins include recycled products of plastic materials used in polystyrene foam (molded products, block molded products, etc.), foam sheets (tray containers, broken sheets, etc.), home appliances, packaging containers, cushion beads, etc.

The recycled styrene-based resin raw material particles (a) may contain any suitable recycled resin other than the recycled styrene-based resin, as long as the effect of the present invention is not impaired. Examples of such other recycled resins include 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). The other resins may be one type or two or more types. In this specification, recycled resins consisting only of AS resin, recycled resins consisting only of ABS resin, and recycled resins consisting only of HIPS (high impact polystyrene) are not included in the category of the above recycled styrene-based resins.

As the recycled styrene-based resin raw material particles (a), a molded product made from "EPSREM" manufactured by Sekisui Plastics Co., Ltd. may be used.

As the recycled styrene-based resin raw material particles (a), crushed material obtained by crushing recycled resin obtained by heating and/or reducing the volume of used styrene-based resin may be used. The recycled styrene-based resin raw material particles may be pellets obtained by extruding the crushed material into pellets, or may be pellets obtained by further crushing the pellets. Alternatively, the recycled styrene-based resin raw material particles may be particles obtained by reducing the volume and recovering the resin using a solvent such as limonene.

The recycled styrene resin raw material particles (a) are preferably pellets obtained by melt extrusion. The melt extrusion method is a method in which crushed styrene resin, ingots, foamed particles, etc., used are fed to a resin feeder, melted in the resin feeder, extruded through small holes in a die attached to the tip of the resin feeder, and then cooled to obtain pellets.

The pellets obtained by the melt extrusion method are preferably at least one selected from extruded strand pellets obtained by extruding used styrene resin with an extruder and strand cutting it, underwater cut pellets obtained by an underwater cutting method in which used styrene resin is extruded with an extruder and simultaneously cut in water, and hot cut pellets obtained by a hot cutting method in which used styrene resin is cut and cooled immediately after it comes out of the die of the extruder.

As the recycled styrene-based resin raw material particles (a), the pellets obtained by the above-mentioned melt extrusion method may be used as they are, or they may be made into so-called "mini-pellets" by melt extrusion again to obtain smaller pellets.

The recycled styrene resin raw material particles (a) may be a styrene resin shrinkage or melt obtained by coarsely crushing used styrene resin to an appropriate size as necessary, and then subjecting it to thermal shrinkage, bubble destruction shrinkage due to compression, shrinkage due to frictional heat, melting, or the like. Examples of used styrene resin include molded products obtained by molding expandable styrene resin in a mold, and products obtained by heating and foaming this.

The recycled styrene-based resin raw material particles (a) may contain fine powdered inorganic matter and/or organic lubricants. These may typically function as bubble regulators.

Examples of finely powdered inorganic substances include talc, calcium carbonate, and silica. Here, talc typically refers to a mixture whose main components are silicon oxide and magnesium oxide, and which also contains trace amounts of aluminum oxide, iron oxide, etc.

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

The content of the fine powdered inorganic matter relative to the recycled styrene-based resin raw material particles (a) is preferably 0.01% to 5% by mass, and more preferably 0.05% to 2% by mass. If the content of the fine powdered inorganic matter relative to the recycled styrene-based resin raw material particles (a) is less than 0.1% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene-based resin particles may be reduced. If the content of the fine powdered inorganic matter relative to the recycled styrene-based resin raw material particles (a) exceeds 5% by mass, the bubble size of the recycled pre-expanded styrene-based resin particles becomes extremely small, and the recycled pre-expanded styrene-based resin particles may melt during molding, resulting in a deterioration in the appearance of the molded product.

Examples of organic lubricants include liquid paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisatomids such as methylene bisstearylamide, ethylene bisstearylamide, and ethylene bisoleic acid amide; and metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

The content of the organic lubricant is preferably 0.01% to 2.0% by mass, more preferably 0.02% to 1.8% by mass, and in some cases, even more preferably 0.02% to 1.5% by mass, and particularly preferably 0.02% to 1.0% by mass, relative to the recycled styrene-based resin raw material particles (a). If the content of the organic lubricant relative to the recycled styrene-based resin raw material particles (a) is less than 0.01% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene-based resin particles may decrease. If the content of the organic lubricant relative to the recycled styrene-based resin raw material particles (a) exceeds 2.0% by mass, the bubble size of the recycled pre-expanded styrene-based resin particles becomes extremely small, and the recycled pre-expanded styrene-based resin particles melt during molding, which tends to result in poor appearance of the molded product.

Specific methods for incorporating fine powder inorganic substances and/or organic lubricants into the recycled styrene-based resin raw material particles (a) include, for example, a method of kneading fine powder inorganic substances and/or organic lubricants during extrusion molding. In this case, it is preferable to mix the pulverized material with a bubble regulator in advance and then extrude the mixture. The pulverized material and the bubble regulator can be mixed by any appropriate method as long as it does not impair the effects of the present invention. Examples of such methods include mixing methods using mixers such as a tumbler, ribbon blender, V blender, Henschel mixer, and Redigay mixer.

The recycled styrene resin raw material particles (a) are preferably heat-melted for the purpose of adjusting the specific gravity. In this process, the specific gravity of the recycled styrene resin raw material particles (a) is preferably adjusted to 0.6 or more, more preferably 0.9 or more. If the specific gravity of the recycled styrene resin raw material particles (a) is less than 0.6, the dispersion of the recycled styrene resin raw material particles (a) is unstable, so that excessively large particles may be generated during the subsequent polymerization process, resulting in a decrease in yield. The heat melting of the recycled styrene resin raw material particles (a) can be performed by any appropriate method within a range that does not impair the effects of the present invention. Examples of such methods include a method using an extruder or a heat roll. It is preferable that the heat melting is performed by cooling and solidifying the resin obtained in a state where no distortion remains in the resin obtained or where the distortion is small. If distortion remains in the resin particles, the distortion is relaxed in the subsequent process, the resin particles shrink in the stretching direction, and the resulting recycled expandable styrene resin particles may become flat rather than spherical. Therefore, it is preferable to use an extruder for the thermal melting without stretching. If the thermal melting is performed in a stretched state, there is a risk that distortion will remain in the stretched resin obtained by cooling and solidifying. Even if distortion remains in the resin due to thermal melting, it is possible to alleviate the distortion by curing the resin for a certain period of time at a temperature above the softening point of the resin.

When obtaining the recycled styrene-based resin raw material particles (a), any pulverizer may be used as long as it does not impair the effects of the present invention. As such a pulverizer, for example, a pulverizer for plastics may be used, and a pulverizer for polystyrene is preferred.

The recycled styrene-based resin raw material particles (a) can be sieved as necessary and subjected to melting again using an extruder, etc.

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 shape of the resulting recycled expandable styrene-based resin particles may be difficult to obtain. If the average particle diameter of the recycled styrene-based resin raw material particles (a) is less than 0.2 mm, the average particle diameter of the resulting recycled expandable styrene-based resin particles may be too small.

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 shape of the resulting recycled expandable styrene-based resin particles may be difficult to obtain.

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 size of 200 μm or less. Recycled styrene-based resin raw material particles (a) containing 1% by mass or more of particles with an average particle size of 200 μm or less may deteriorate the appearance of the recycled expandable styrene-based resin particles obtained using the recycled styrene-based resin raw material particles (a).

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

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

The styrene monomer includes styrene or a styrene derivative. Examples of the styrene derivative 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 content of styrene 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.

The styrene monomer may contain any suitable vinyl monomer other than the styrene monomer, as long as the effect of the present invention is not impaired. For example, a multifunctional monomer, a (meth)acrylic acid ester monomer, a maleic acid ester monomer, or a fumaric acid ester monomer may be included. Such vinyl monomers may be one type only, or two or more types.

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

In the first embodiment of the recycled styrene resin raw material (A), the content ratio of the recycled styrene resin raw material particles (a) to the total amount of the recycled styrene resin raw material particles (a) and the styrene monomer is preferably 5% to 90% by mass, more preferably 10% to 85% by mass, even more preferably 15% to 80% by mass, particularly preferably 20% to 75% by mass, and most preferably 20% to 70% by mass. If the content ratio is too low outside the above range, the environmental contribution may be reduced. In addition, if the content ratio is too low or too high outside the above range, the recycled expandable styrene resin particles according to the embodiment of the present invention may not be able to exhibit good spheroidization, and moldability may be reduced.

The recycled styrene-based resin raw material (A) is obtained by adding a styrene-based monomer to a suspension containing recycled styrene-based resin raw material particles (a) and polymerizing the mixture. Any suitable method can be used as the polymerization method as long as it does not impair the effects of the present invention. One preferred embodiment of such a polymerization method is to add an emulsion containing a polymerization initiator and a styrene-based monomer to a suspension obtained by dispersing recycled styrene-based resin raw material particles (a) as nuclei in water, thereby impregnating the recycled styrene-based resin raw material particles (a), and then adding a styrene-based monomer to carry out polymerization.

In the first embodiment of the recycled styrene-based resin raw material (A), the addition temperature when adding the styrene monomer to the recycled styrene-based resin raw material particles (a) when obtaining the recycled styrene-based resin raw material (A) is preferably 40°C to 119°C, preferably 40°C to 118°C, more preferably 40°C to 117°C, even more preferably 50°C to 117°C, and particularly preferably 60°C to 117°C, in order to further express the effects of the present invention. If the addition temperature when adding the styrene monomer to the recycled styrene-based resin raw material particles (a) is adjusted within the above range, the styrene monomer can be incorporated while maintaining the recycled styrene-based resin raw material particles (a) at a moderate hardness, so that good spheroidization of the recycled styrene-based resin raw material (A) can be expressed, and the finally obtained recycled expandable styrene-based resin particles can be expressed in good spheroidization and excellent moldability. If the temperature at which the styrene monomer is added to the recycled styrene resin raw material particles (a) is too low outside the above range, the recycled styrene resin raw material particles (a) become too hard, and when the styrene monomer is incorporated in this state, the recycled styrene resin raw material (A) becomes difficult to spheroidize, and the finally obtained recycled expandable styrene resin particles may be difficult to spheroidize or have poor moldability. If the temperature at which the styrene monomer is added to the recycled styrene resin raw material particles (a) is too high outside the above range, the recycled styrene resin raw material particles (a) become too soft, and when the styrene monomer is incorporated in this state, the recycled styrene resin raw material (A) becomes difficult to spheroidize, and the finally obtained recycled expandable styrene resin particles may be difficult to spheroidize or have poor moldability. In addition, the "addition temperature when adding styrene monomer to recycled styrene resin raw material particles (a)" refers to the addition temperature during the addition of the emulsion containing the polymerization initiator and styrene monomer, and the subsequent addition of the styrene monomer.

When dispersing the recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium to obtain a suspension, any appropriate method may be adopted as a method for dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium, as long as the effects of the present invention are not impaired. As a preferred dispersion method, dispersion is performed using an apparatus equipped with stirring blades. A method for more fine dispersion is, for example, a method using a homomixer.

When dispersing the recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium to obtain a suspension, it is preferable to use a dispersant in dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium. Any appropriate dispersant that can be used in suspension polymerization can be used as long as it does not impair the effects of the present invention. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose; and poorly soluble inorganic salts such as magnesium phosphate, magnesium pyrophosphate, and calcium triphosphate. Among these, magnesium pyrophosphate is preferred as a dispersant in that it can better express the effects of the present invention.

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

When dispersing the recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium to obtain a suspension, it is preferable to use a surfactant in dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium. Any appropriate surfactant that can be used in suspension polymerization can be used as long as it does not impair the effects of the present invention. Examples of such surfactants include sodium dodecylbenzenesulfonate, sodium alkane sulfonate, sodium alkylsulfonate, sodium alkyldiphenyletherdisulfonate, and sodium α-olefinsulfonate. Among these, sodium dodecylbenzenesulfonate is preferred as the surfactant in that it can more effectively express the effects of the present invention.

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

As an emulsification method for obtaining an emulsion containing a polymerization initiator and a styrene-based monomer, any appropriate method can be adopted as long as it does not impair the effects of the present invention. As a method for such dispersion, a device equipped with an agitator is preferably used. As a method for more fine dispersion, a method using a homomixer is exemplified. In this case, it is preferable to disperse until the oil droplet diameter of the dispersion in which the styrene-based monomer is dispersed becomes equal to or smaller than the particle diameter of the nucleus. If the oil droplet diameter is larger than the particle diameter of the nucleus when added to an aqueous medium, multiple recycled styrene-based resin raw material particles (a) are taken into the oil droplets of the dispersion in which the styrene-based monomer is dispersed, and adhesion, plasticization, and coalescence of the recycled styrene-based resin raw material particles (a) occur, which makes it easy for excessively large particles to be generated.

As the polymerization initiator used to obtain an emulsion containing a polymerization initiator and a styrene-based monomer, any suitable polymerization initiator may be used as long as it is used in a suspension polymerization method and does not impair the effects of the present invention. Examples of such polymerization initiators include organic peroxides such as benzoyl peroxide, t-butylperoxy-2-ethylhexyl carbonate, and t-butyl perbenzoate; and azo compounds such as azobisisobutyronitrile. The polymerization initiator may be of only one type, or of two or more types.

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

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

As a method for adding the styrene monomer after adding an emulsion containing the styrene monomer to the suspension containing the recycled styrene resin raw material particles (a) and impregnating the suspension, any appropriate method can be adopted as long as it does not impair the effects of the present invention. Such methods include, for example, divided addition and continuous addition. The addition rate is appropriately selected depending on the capacity, shape, polymerization temperature, etc. of the polymerization apparatus.

After adding an emulsion containing a styrene monomer to the suspension containing the recycled styrene resin raw material particles (a) to impregnate it, the styrene monomer is added, and the polymerization reaction may be continued at any appropriate temperature and time, as necessary.

The suspension containing the recycled styrene-based resin raw material particles (a) and the emulsion containing the styrene-based monomer may contain a bubble regulator. Examples of such bubble regulators include fatty acid monoamides such as oleic acid amide, stearic acid amide, and hydroxystearic acid amide; and fatty acid bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide.

<A-2. Detailed description of recycled expandable styrene resin particles>
In order to more effectively exert the effects of the present invention, the recycled expandable styrene-based resin particles according to an embodiment of the present invention are typically obtained by pressurizing a blowing agent into a suspension containing a recycled styrene-based resin raw material (A) and a dispersant to impregnate the same.

A typical method for injecting and impregnating the foaming agent is to place the recycled styrene-based resin raw material (A) and a dispersant in a reactor such as an autoclave, and then inject the foaming agent to impregnate the mixture.

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

As the foaming agent, any suitable foaming agent can be used as long as it does not impair the effects of the present invention. As the foaming agent, preferably, a volatile foaming agent is used. As the volatile foaming agent, preferably, the boiling point is equal to or lower than the softening point of the styrene-based resin, and the organic compound is in a gaseous or liquid state at normal pressure. Specific examples include, for example, aliphatic hydrocarbons such as propane, normal butane, isobutane, pentane (normal pentane, isopentane, neopentane), normal hexane, etc.; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene, etc.; ketones such as acetone and methyl ethyl ketone, etc.; alcohols such as methanol, ethanol, and isopropyl alcohol, etc.; low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether, etc.; halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane, etc.; and the like. As the volatile foaming agent, inorganic gases such as carbon dioxide, nitrogen, and ammonia may be used. Among these, in terms of further exerting the effects of the present invention, the volatile blowing agent is preferably at least one selected from normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, and cyclopentadiene, and more preferably at least one selected from normal butane, isobutane, normal pentane, and isopentane. Preferred embodiments of the blowing agent include, for example, a mixed gas (A) of normal pentane and isopentane (normal pentane/isopentane is preferably 99% by mass/1% by mass to 50% by mass/50% by mass, more preferably 95% by mass/5% by mass to 55% by mass/45% by mass, even more preferably 90% by mass/10% by mass to 60% by mass/40% by mass, and particularly preferably 85% by mass/15% by mass to 65% by mass/35% by mass), a mixed gas (B) of normal butane and isobutane (normal butane/isobutane is preferably 99% by mass/1% by mass to 50% by mass/50% by mass, more preferably 95% by mass/5% by mass to 55% by mass/45% by mass, and even more preferably 90% by mass/10% by mass to 60% by mass/40% by mass, particularly preferably 85% by mass/15% by mass to 65% by mass/35% by mass), and a combination of these two mixed gases (A) and (B) (mixed gas (A) of normal pentane and isopentane/mixed gas (B) of normal butane and isobutane is preferably 99% by mass/1% by mass to 1% by mass/99% by mass, more preferably 90% by mass/10% by mass to 10% by mass/90% by mass, even more preferably 80% by mass/20% by mass to 20% by mass/80% by mass, particularly preferably 70% by mass/30% by mass to 30% by mass/70% by mass, and most preferably 60% by mass/40% by mass to 40% by mass/60% by mass). In addition to the combined use of a mixed gas (A) of normal pentane and isopentane and a mixed gas (B) of normal butane and isobutane, a combined use by mixing normal pentane, isopentane, and normal butane and isobutane, respectively, can also be mentioned. In this case, normal pentane/isopentane is preferably 99% by mass/1% by mass to 50% by mass/50% by mass, more preferably 95% by mass/5% by mass to 55% by mass/45% by mass, even more preferably 90% by mass/10% by mass to 60% by mass/40% by mass, and particularly preferably 85% by mass/15% by mass to 65% by mass/35% by mass, and normal butane/isobutane is preferably 99% by mass/1% by mass to 50% by mass/50% by mass. %, more preferably 95% by mass/5% by mass to 55% by mass/45% by mass, even more preferably 90% by mass/10% by mass to 60% by mass/40% by mass, and particularly preferably 85% by mass/15% by mass to 65% by mass/35% by mass. The total amount of normal pentane and isopentane/total amount of normal butane and isobutane is preferably 99% by mass/1% by mass to 1% by mass/99% by mass, more preferably 90% by mass/10% by mass to 10% by mass/90% by mass, even more preferably 80% by mass/20% by mass to 20% by mass/80% by mass, particularly preferably 70% by mass/30% by mass to 30% by mass/70% by mass, and most preferably 60% by mass/40% by mass to 40% by mass/60% by mass.

The content of the blowing agent can be appropriately set according to the purpose (adjustment of bulk expansion ratio, secondary expandability, expansion ratio, average cell diameter, etc.) so long as it is sufficient to form recycled pre-expanded styrene-based resin particles and recycled styrene-based resin foamed molded bodies. In terms of being able to further demonstrate the effects of the present invention, the content of the blowing agent is preferably 2.0 parts by mass to 15.0 parts by mass, more preferably 2.5 parts by mass to 14.5 parts by mass, even more preferably 3.0 parts by mass to 14.0 parts by mass, particularly preferably 3.5 parts by mass to 13.5 parts by mass, and most preferably 4.0 parts by mass to 13.0 parts by mass, when the amount of the recycled styrene-based resin raw material (A) is taken as 100 parts by mass.

As the dispersant, any suitable dispersant may be used as long as it does not impair the effects of the present invention. The dispersant may be one type or two or more types. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and methyl cellulose; and poorly soluble inorganic salts such as metal phosphates. Among these, poorly soluble inorganic salts are preferred as dispersants in that they can further exert the effects of the present invention. Examples of poorly soluble inorganic salts include dibasic calcium phosphate, tribasic calcium phosphate, dibasic magnesium phosphate, tribasic magnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate.

The amount of dispersant used can be appropriately set depending on the purpose. In order to further exert the effects of the present invention, the amount of dispersant used 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 parts by mass, when the amount of recycled styrene-based resin raw material (A) is taken as 100 parts by mass.

When the recycled styrene-based resin raw material (A) and the dispersant are placed in a reactor such as an autoclave, a surfactant may be added. Any appropriate surfactant may be used as the surfactant as long as it does not impair the effects of the present invention. Only one type of surfactant may be used, or two or more types may be used. Examples of such surfactants include sodium dodecylbenzenesulfonate, sodium alkane sulfonate, sodium alkylsulfonate, sodium alkyldiphenyletherdisulfonate, and sodium α-olefinsulfonate. Among these, sodium dodecylbenzenesulfonate is preferred as the surfactant in that it can more effectively bring out the effects of the present invention.

The amount of surfactant used can be appropriately set depending on the purpose. In order to further exert the effects of the present invention, the amount of surfactant used 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, when the amount of recycled styrene-based resin raw material (A) is taken as 100 parts by mass.

The temperature at which the blowing agent is injected into the recycled styrene-based resin raw material (A) is T1, where Tg is the glass transition temperature of the recycled styrene-based resin raw material (A), T1 is the temperature at which the blowing agent is injected, and T2 is the temperature at which the blowing agent is impregnated. T1 and T2 are in the range of (Tg-50°C) or more and (Tg+40°C) or less. By having T1 and T2 in the above ranges, it is possible to provide recycled expandable styrene-based resin particles that can exhibit excellent moldability and impart high strength to the resulting molded article.

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

As described above, the lower limit of T1 is (Tg-50°C) or more, and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg-40°C) or more, more preferably (Tg-30°C) or more, even more preferably (Tg-20°C) or more, even more preferably (Tg-10°C) or more, even more preferably (Tg-7°C) or more, particularly preferably (Tg-5°C) or more, and most preferably (Tg-3°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T1 is 50°C or more, preferably 60°C or more, more preferably 70°C or more, even more preferably 75°C or more, even more preferably 80°C or more, even more preferably 85°C or more, even more preferably 90°C or more, particularly preferably 93°C or more, and most preferably 95°C or more.

As described above, the lower limit of T2 is (Tg-50°C) or more, and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg-40°C) or more, more preferably (Tg-30°C) or more, even more preferably (Tg-20°C) or more, even more preferably (Tg-10°C) or more, even more preferably (Tg-7°C) or more, particularly preferably (Tg-5°C) or more, and most preferably (Tg-3°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T2 is 50°C or more, preferably 60°C or more, more preferably 70°C or more, even more preferably 75°C or more, even more preferably 80°C or more, even more preferably 85°C or more, even more preferably 90°C or more, particularly preferably 93°C or more, and most preferably 95°C or more.

As described above, the upper limit of T1 is (Tg + 40°C) or less, and in terms of being able to more effectively express the effects of the present invention and reducing manufacturing costs, it is preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 25°C) or less, and particularly preferably (Tg + 20°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T1 is 140°C or less, preferably 135°C or less, more preferably 130°C or less, even more preferably 125°C or less, and particularly preferably 120°C or less.

As described above, the upper limit of T2 is (Tg + 40°C) or less, and from the viewpoint of being able to more effectively express the effects of the present invention and reducing manufacturing costs, it is preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 25°C) or less, and particularly preferably (Tg + 20°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T2 is 140°C or less, preferably 135°C or less, more preferably 130°C or less, even more preferably 125°C or less, and particularly preferably 120°C or less.

In one preferred embodiment (sometimes referred to as "embodiment 1"), T1 is in the range of (Tg-50°C) or more and (Tg+40°C) or less, and T2 is in the range of (Tg-50°C) or more and less than (Tg+10°C). As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, in embodiment 1, T1 is in the range of 50°C or more and 140°C or less, and T2 is in the range of 50°C or more and less than 110°C.

In another preferred embodiment (sometimes referred to as "embodiment 2"), T1 is in the range of (Tg + 10°C) or more and (Tg + 30°C) or less, and T2 is in the range of (Tg + 10°C) or more and (Tg + 30°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, in embodiment 2, T1 is in the range of 110°C or more and 130°C or less, and T2 is in the range of 110°C or more and 130°C or less.

When embodiment 1 is selected, any suitable dispersant may be used as the dispersant as long as it does not impair the effects of the present invention. As such a dispersant, it is preferable to use at least one selected from the group consisting of organic dispersants and poorly soluble inorganic salts, in that the effects of the present invention can be more effectively expressed. As described above, examples of organic dispersants include polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. As described above, examples of poorly soluble inorganic salts include dibasic calcium phosphate, tribasic calcium phosphate, dibasic magnesium phosphate, tribasic magnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate.

Therefore, one preferred embodiment of the method for producing recycled expandable styrene-based resin particles of the present invention is the case where embodiment 1 is selected, and is a method for producing recycled expandable styrene-based resin particles in which a blowing agent is injected into a suspension containing recycled styrene-based resin raw material (A) and a dispersant to impregnate the suspension, in which Tg is the glass transition temperature of the recycled styrene-based resin raw material (A), T1 is the temperature at which the blowing agent is injected, and T2 is the temperature at which the blowing agent is impregnated. T1 is within the range of (Tg-50°C) or more and (Tg+40°C) or less, T2 is within the range of (Tg-50°C) or more and less than (Tg+10°C), and the dispersant is at least one selected from the group consisting of organic dispersants and sparingly soluble inorganic salts.

When embodiment 2 is selected, it is preferable to use a poorly soluble inorganic salt as the dispersant, since this can further exert the effects of the present invention. As described above, examples of poorly soluble inorganic salts include monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, monomagnesium phosphate, dimagnesium phosphate, trimagnesium phosphate, magnesium pyrophosphate, and magnesium metaphosphate, and magnesium pyrophosphate is particularly preferred.

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

In the first embodiment, the lower limit of T1 is (Tg-50°C) or more as described above, and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg-40°C) or more, more preferably (Tg-30°C) or more, even more preferably (Tg-20°C) or more, even more preferably (Tg-10°C) or more, even more preferably (Tg-7°C) or more, particularly preferably (Tg-5°C) or more, and most preferably (Tg-3°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T1 in the first embodiment is 50°C or more, preferably 60°C or more, more preferably 70°C or more, even more preferably 75°C or more, even more preferably 80°C or more, even more preferably 85°C or more, even more preferably 90°C or more, particularly preferably 93°C or more, and most preferably 95°C or more.

As described above, the lower limit of T2 in embodiment 1 is (Tg-50°C) or more, and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg-40°C) or more, more preferably (Tg-30°C) or more, even more preferably (Tg-20°C) or more, even more preferably (Tg-10°C) or more, even more preferably (Tg-7°C) or more, particularly preferably (Tg-5°C) or more, and most preferably (Tg-3°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T2 in embodiment 1 is 50°C or more, preferably 60°C or more, more preferably 70°C or more, even more preferably 75°C or more, even more preferably 80°C or more, even more preferably 85°C or more, even more preferably 90°C or more, particularly preferably 93°C or more, and most preferably 95°C or more.

As described above, the upper limit of T1 in embodiment 1 is (Tg + 40°C) or less, and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg + 35°C) or less, more preferably (Tg + 30°C) or less, even more preferably (Tg + 27°C) or less, particularly preferably (Tg + 25°C) or less, and most preferably (Tg + 23°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T1 in embodiment 1 is 140°C or less, preferably 135°C or less, more preferably 130°C or less, even more preferably 127°C or less, particularly preferably 125°C or less, and most preferably 123°C or less.

As described above, the upper limit of T2 in embodiment 1 is less than (Tg + 10°C), and in terms of being able to more effectively express the effects of the present invention, it is preferably (Tg + 9°C) or less, more preferably (Tg + 8°C) or less, even more preferably (Tg + 7°C) or less, particularly preferably (Tg + 6°C) or less, and most preferably (Tg + 5°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T2 in embodiment 1 is less than 110°C, preferably 109°C or less, more preferably 108°C or less, even more preferably 107°C or less, particularly preferably 106°C or less, and most preferably 105°C or less.

As described above, the lower limit of T1 in embodiment 2 is (Tg + 10°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T1 in embodiment 2 is 110°C or more.

As described above, the lower limit of T2 in embodiment 2 is (Tg + 10°C) or more. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the lower limit of T2 in embodiment 2 is 110°C or more.

As described above, the upper limit of T1 in embodiment 2 is (Tg + 30°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T1 in embodiment 2 is 130°C or less.

As described above, the upper limit of T2 in embodiment 2 is (Tg + 30°C) or less. As a representative example, when the glass transition temperature Tg of the recycled styrene-based resin raw material (A) is 100°C, the upper limit of T2 in embodiment 2 is 130°C or less.

The time for impregnating the recycled styrene-based resin particles (A) with the blowing agent may be any appropriate time within a range that does not impair the effects of the present invention. Such an impregnation time is preferably 1 to 10 hours, and more preferably 1 to 8 hours.

The recycled expandable styrene-based resin particles according to an embodiment of the present invention may contain a flame retardant. The flame retardant may be one type or two or more types.

When the recycled expandable styrene-based resin particles according to an embodiment of the present invention contain a flame retardant, any appropriate content of the flame retardant may be adopted as long as the effects of the present invention are not impaired. In terms of being able to further manifest the effects of the present invention, the content of the flame retardant is preferably 0.01 parts by mass to 10.0 parts by mass, more preferably 0.05 parts by mass to 8.0 parts by mass, even more preferably 0.08 parts by mass to 6.0 parts by mass, particularly preferably 0.1 parts by mass to 4.0 parts by mass, and most preferably 0.1 parts by mass to 3.0 parts by mass, when the amount of the recycled styrene-based resin raw material (A) is taken as 100 parts by mass.

As the flame retardant, any suitable flame retardant may be used as long as it does not impair the effects of the present invention. As such a flame retardant, a bromine compound compatible with polystyrene is preferable, and examples thereof include tetrabromoethane, tetrabromocyclooctane, hexabromocyclododecane, hexabromocyclohexane, trisdibromopropylphosphate, 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-allyloxy-3,5-dibromo)propane, and hexabromobenzene.

The flame retardant may be added at any appropriate timing. In order to further exert the effects of the present invention, it is preferable that the flame retardant is added before the blowing agent is pressed into the recycled styrene-based resin raw material (A). By adding the flame retardant before the blowing agent is pressed, the flame retardant can be added at a temperature equal to or lower than the temperature at which the blowing agent is pressed, and the resulting recycled expandable styrene-based resin particles can be made to have good spheroidization and excellent moldability.

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

The recycled expandable styrene-based resin particles according to an embodiment of the present invention may contain a flame retardant assistant. The flame retardant assistant may be of only one type or of two or more types.

When the recycled expandable styrene-based resin particles according to an embodiment of the present invention contain a flame retardant auxiliary, any appropriate content of the flame retardant auxiliary may be adopted as long as the effects of the present invention are not impaired. In terms of being able to further manifest the effects of the present invention, the content of the flame retardant auxiliary is preferably 0.005 parts by mass to 3.0 parts by mass, more preferably 0.006 parts by mass to 2.5 parts by mass, even more preferably 0.007 parts by mass to 2.0 parts by mass, particularly preferably 0.008 parts by mass to 1.5 parts by mass, and most preferably 0.01 parts by mass to 1.0 parts by mass, when the amount of the recycled styrene-based resin raw material (A) is taken as 100 parts by mass.

Any suitable flame retardant auxiliary may be used as long as it does not impair the effects of the present invention. Examples of such flame retardants include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenylhexane.

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

When producing the recycled expandable styrene-based resin particles according to an embodiment of the present invention, a bubble regulator may be used. The bubble regulator may be one type only, or two or more types may be used. Examples of the bubble regulator include higher fatty acid amides, partial esters of higher fatty acids and alcohols, talc, calcium carbonate, mica, citric acid, and sodium bicarbonate. Examples of higher fatty acid amides include fatty acid monoamides such as oleic acid amide, stearic acid amide, and hydroxystearic acid amide; and fatty acid bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide. Examples of higher fatty acids in the partial esters of higher fatty acids and alcohols include fatty acids with 15 or more carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid. Examples of partial esters of higher fatty acids and alcohols include stearic acid monoglyceride and stearic acid diglyceride.

The amount of the cell regulator used is preferably 0 to 3.0 parts by mass, and more preferably 0.03 to 1.0 parts by mass, per 100 parts by mass of the recycled styrene-based resin raw material (A). The cell regulator can be added, for example, before the blowing agent is injected, or together with the blowing agent, or by a commonly used method such as a dry blend method, a master batch method, or a melt injection method.

When producing the recycled expandable styrene-based resin particles according to an embodiment of the present invention, a foaming aid may be used. The foaming aid may be one type only, or two or more types may be used. Examples of the foaming aid include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil.

When producing recycled expandable styrene-based resin particles according to an embodiment of the present invention, other additives may be used. The other additives may be one type only, or two or more types. Examples of the other additives include pigments, radiant heat transfer suppressing components, crosslinking agents, plasticizers, stabilizers, fillers, lubricants, colorants, antistatic agents, spreading agents, weather resistance agents, antiaging agents, antifogging agents, and fragrances.

In the production of the recycled expandable styrene resin particles according to the embodiment of the present invention, the temperature at which the recycled expandable styrene resin particles are impregnated with a blowing agent and removed from the reactor can be appropriately set according to the purpose (such as adjusting the average bubble diameter) as long as it is sufficient to form recycled pre-expanded styrene resin particles and recycled styrene resin foamed molded bodies. In order to further demonstrate the effects of the present invention, the upper limit of the temperature at which the recycled expandable styrene resin particles are removed from the reactor is preferably 50°C or lower, more preferably 48°C or lower. In order to further demonstrate the effects of the present invention, the lower limit of the temperature at which the recycled expandable styrene resin particles are removed from the reactor is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and particularly preferably 18°C or higher.

<A-3. Surface treatment>
The recycled expandable styrene-based resin particles according to the embodiment of the present invention may be subjected to a surface treatment, preferably a surface treatment with at least one selected from silicone oil, an antistatic agent, a fatty acid metal salt, and a fusion accelerator.

When the recycled expandable styrene resin particles are surface-treated with silicone oil, the amount of silicone oil used per 100 parts by mass of the recycled expandable styrene resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.003 to 0.28 parts by mass, even more preferably 0.005 to 0.25 parts by mass, particularly preferably 0.008 to 0.23 parts by mass, and most preferably 0.01 to 0.23 parts by mass. If the amount of silicone oil used is too small outside the above range, for example, when an antistatic agent is used, the affinity with the antistatic agent during pre-foaming may be insufficient, and static electricity may be easily generated. If the amount of silicone oil used is too large outside the above range, the surface may melt during molding, resulting in a loss of surface properties.

There may be only one type of silicone oil, or two or more types.

As the silicone oil, any appropriate silicone oil may be used as long as it does not impair the effects of the present invention. In terms of being able to further exhibit the effects of the present invention, examples of silicone oils that can be used include straight silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane, and dimethylpolysiloxane is preferred.

When the recycled expandable styrene resin particles are surface-treated with an antistatic agent, the amount of the antistatic agent used per 100 parts by mass of the recycled expandable 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 the antistatic agent is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of the antistatic agent is too large outside the above range, the surface of the recycled pre-expanded styrene resin particles or the recycled styrene resin foam molded body may become sticky.

The antistatic agent may be of one type or of two or more types.

As the antistatic agent, any suitable antistatic agent may be used as long as it does not impair the effects of the present invention. In order to further exert the effects of the present invention, the antistatic agent may be at least one selected from a nonionic surfactant and a fatty acid glyceride, and preferably a combination of a nonionic surfactant and a fatty acid glyceride.

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

As the nonionic surfactant, any suitable nonionic surfactant may be used as long as it does not impair the effects of the present invention. In terms of being able to further express the effects of the present invention, examples of nonionic surfactants 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. Specific examples of the 1-amino-2-hydroxy compound include 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, N-hydroxypropyl-N -(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 salts thereof. Polyethylene glycol is preferred as the nonionic surfactant in that it can more effectively exert the effects of the present invention.

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 recycled expandable styrene-based resin particles before surface treatment is preferably 0.001 parts by mass to 2.0 parts by mass, more preferably 0.001 parts by mass to 1.5 parts by mass, even more preferably 0.001 parts by mass to 1.0 parts by mass, even more preferably 0.001 parts by mass to 0.5 parts by mass, even more preferably 0.001 parts by mass to 0.3 parts by mass, even more preferably 0.005 parts by mass to 0.28 parts by mass, even more preferably 0.01 parts by mass to 0.27 parts by mass, particularly preferably 0.015 parts by mass to 0.26 parts by mass, and most preferably 0.02 parts by mass to 0.25 parts by mass. If the amount of the nonionic surfactant is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of nonionic surfactant is too high and falls outside the above range, the surfaces of the recycled pre-expanded styrene resin particles and the recycled styrene resin foamed moldings may become sticky.

The fatty acid glyceride may be one type or two or more types.

As the fatty acid glyceride, any appropriate fatty acid glyceride may be used as long as it does not impair the effects of the present invention. Specific examples of the fatty acid glyceride that can further exert the effects of the present invention include stearic acid monoglyceride and linoleic acid monoglyceride. As the fatty acid glyceride, stearic acid monoglyceride is preferred in that it can further exert the effects of the present invention.

When fatty acid glyceride is used as at least a part of the antistatic agent, the amount of the fatty acid glyceride relative to 100 parts by mass of recycled expandable styrene-based 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 glyceride is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of fatty acid glyceride is too large outside the above range, the surface of the recycled pre-expanded styrene-based resin particles or the recycled styrene-based resin foam molded body may become sticky.

When the recycled expandable styrene resin particles are surface-treated with a fatty acid metal salt, the amount of fatty acid metal salt used per 100 parts by mass of recycled expandable styrene 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 outside the above range, blocking may occur frequently during pre-expansion, and a good styrene resin foam molded product may not be obtained. If the amount of fatty acid metal salt is too large outside the above range, a large amount of metal salt is present during pre-expansion, which may cause charging and static electricity to be easily generated, resulting in poor fusion of the molded product.

The fatty acid metal salt may be of one type or of two or more types.

As the fatty acid metal salt, any appropriate fatty acid metal salt may be used as long as it does not impair the effects of the present invention. In terms of being able to further exert the effects of the present invention, examples of the fatty acid metal salt include metal stearates and metal laurates. Specific examples of the metal stearates include magnesium stearate, calcium stearate, zinc stearate, barium stearate, aluminum stearate, and lithium stearate. Specific examples of the metal laurate include zinc laurate and barium laurate. In terms of being able to further exert the effects of the present invention, magnesium stearate and zinc stearate are preferred as fatty acid metal salts.

When the recycled expandable styrene resin particles are surface-treated with a fusion promoter, the amount of the fusion promoter used per 100 parts by mass of the recycled expandable 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 the fusion promoter is too small outside the above range, the fusion property may decrease during molding, and it may not be possible to obtain a good recycled styrene resin foam molded product. If the amount of the fusion promoter is too large outside the above range, blocking may occur during pre-expansion.

The adhesion promoter may be of one type or of two or more types.

As the fusion promoter, any suitable fusion promoter may be used as long as it does not impair the effects of the present invention. In terms of being able to further express the effects of the present invention, examples of the fusion promoter include fatty acid triglycerides, fatty acid diglycerides, fatty acid monoglycerides, and vegetable oils. Specific examples of fatty acid triglycerides include lauric acid triglyceride, stearic acid triglyceride, linoleic acid triglyceride, and hydroxystearic acid triglyceride. Specific examples of fatty acid diglycerides include lauric acid diglyceride, stearic acid diglyceride, and linoleic acid diglyceride. Specific examples of fatty acid monoglycerides include lauric acid monoglyceride. Specific examples of vegetable oils include hydrogenated castor oil. In terms of being able to further express the effects of the present invention, stearic acid triglyceride and hydroxystearic acid triglyceride are preferred as fusion promoters.

<<B. Recycled pre-expanded styrene-based resin particles>>
The recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention are obtained by pre-expanding the recycled expandable styrene-based resin particles according to an embodiment of the present invention.

The recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention have an average bubble diameter, as described above, preferably greater than 5 μm and less than 520 μm, more preferably 5 μm to 500 μm, even more preferably 5 μm to 450 μm, particularly preferably 5 μm to 400 μm, and most preferably 5 μm to 380 μm. By adjusting the average bubble diameter of the recycled pre-expanded styrene-based resin particles within the above range, the effects of the present invention can be realized, and the recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention can exhibit excellent moldability and impart high strength to the resulting molded article. If the average bubble diameter of the recycled pre-expanded styrene-based resin particles is outside the above range, there is a risk that excellent moldability cannot be exhibited or high strength cannot be imparted to the resulting molded article.

As described above, the recycled pre-expanded styrene-based resin particles according to the embodiment of the present invention have a secondary expandability of preferably more than 1.00 times, more preferably 1.05 times or more, even more preferably 1.10 times or more, particularly preferably 1.15 times or more, and most preferably 1.20 times or more. The upper limit of the secondary expandability is preferably 6.0 times or less, more preferably 5.0 times or less, even more preferably 4.0 times or less, and particularly preferably 3.5 times or less, from the viewpoint of increasing the surface pressure during molding, lengthening the cooling time and lengthening the molding cycle, and from the viewpoint of leaving more residual gas than necessary for molding, which increases the environmental load and increases costs. By adjusting the secondary expandability of the recycled pre-expanded styrene-based resin particles within the above range, the effects of the present invention can be expressed, and the recycled pre-expanded styrene-based resin particles according to the embodiment of the present invention can express excellent moldability and impart high strength to the obtained molded body. If the secondary expandability of the recycled pre-expanded styrene-based resin particles is outside the above range, there is a risk that excellent moldability cannot be expressed or that high strength cannot be imparted to the obtained molded body.

The bulk expansion ratio of the recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention is, as described above, preferably 5 to 120 times, more preferably 2 to less than 100 times, more preferably 5 to 90 times, even more preferably 10 to 85 times, and particularly preferably 15 to 83 times. By adjusting the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles within the above range, the effects of the present invention can be realized, and the recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention can exhibit excellent moldability and can impart high strength to the resulting molded article. If the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles is outside the above range, there is a risk that excellent moldability cannot be exhibited or high strength cannot be imparted to the resulting molded article.

In one representative embodiment, the recycled pre-expanded styrene-based resin particles according to the present invention can be used to mold recycled styrene-based resin foamed articles.

In another representative embodiment, the recycled pre-expanded styrene-based resin particles according to the embodiment of the present invention can be used as they are as a cushioning material, a heat insulating material, an aggregate for concrete, etc. When the recycled pre-expanded styrene-based resin particles according to the embodiment of the present invention are used as they are, the recycled pre-expanded styrene-based resin particles can preferably be used as a filler in which a large number of recycled pre-expanded styrene-based resin particles are filled in a bag. Such recycled pre-expanded styrene-based resin particles are suitable for at least one type selected from, for example, the core material of a cushion (the foamed particles filled inside the cushion) and aggregate.

<<C. Recycled styrene-based resin foam molded body>>
The recycled styrene-based resin foam molded article according to the embodiment of the present invention is obtained by molding the recycled pre-expanded styrene-based resin particles according to the embodiment of the present invention. Note that the recycled expandable styrene-based resin particles according to the embodiment of the present invention can also be molded into the recycled styrene-based resin foam molded article according to the embodiment of the present invention.

The recycled styrene-based resin foamed molded article according to an embodiment of the present invention is formed by molding recycled expandable styrene-based resin particles according to an embodiment of the present invention, or by molding recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention which are obtained by pre-expanding recycled expandable styrene-based resin particles according to an embodiment of the present invention, and therefore has a 10% compressive strength measured in accordance with JIS A 9521 of preferably 0.03 MPa to 0.90 MPa, more preferably 0.03 MPa to 0.80 MPa, even more preferably 0.03 MPa to 0.70 MPa, even more preferably 0.03 MPa to 0.60 MPa, even more preferably 0.03 MPa to 0.50 MPa, even more preferably 0.03 MPa to 0.40 MPa, particularly preferably 0.03 MPa to 0.30 MPa, and most preferably 0.03 MPa to 0.20 MPa. If the 10% compression strength of the recycled styrene-based resin foam molded article according to the embodiment of the present invention is within the above range, the molded article can have high strength.

The recycled styrene resin foamed molding according to the embodiment of the present invention is formed by molding recycled expandable styrene resin particles according to the embodiment of the present invention, or by molding recycled pre-expanded styrene resin particles according to the embodiment of the present invention, which are obtained by pre-expanding recycled expandable styrene resin particles according to the embodiment of the present invention. Therefore, in a combustion test conducted in accordance with JIS A 9521 (Method A), the flame is preferably extinguished within 3 seconds, there is no residual fuel, and the product does not burn beyond the flammability limit indicator line.

Recycled styrene-based resin foamed moldings typically contain recycled expanded styrene-based resin particles (hereinafter sometimes simply referred to as "expanded particles") that are produced by further expanding recycled pre-expanded styrene-based resin particles.

Recycled styrene-based resin foam molded products are typically made up of multiple foam particles fused together.

The recycled styrene resin foam molding can be typically produced by loading 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 recycled pre-expanded styrene resin particles into a closed mold having a large number of small holes, (ii) heating and foaming the recycled pre-expanded styrene resin particles with a heat medium (e.g., pressurized steam, etc.) to obtain foam particles, and (iii) filling the voids between the foam particles by the heating and foaming, and fusing the foam particles to each other to integrate them. The density of the recycled styrene resin foam molding can be appropriately set according to the purpose. The density of the recycled styrene resin foam molding can be adjusted, for example, by adjusting the bulk expansion ratio of the pre-expanded styrene resin particles to be filled in the mold in advance, or by adjusting the amount of recycled pre-expanded styrene resin particles filled in the mold.

The heat foaming temperature (effectively, 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 of the heat foaming (gauge pressure of the heat transfer medium blown in) is preferably 0.04 MPa to 0.1 MPa, more preferably 0.04 MPa to 0.09 MPa. If the heat foaming is performed under these conditions, the foam particles can be well fused to each other.

If necessary, the recycled pre-expanded styrene-based resin particles may be aged before molding into a recycled styrene-based resin foamed article. The aging temperature of the recycled pre-expanded styrene-based resin particles is preferably 20°C to 60°C. If the aging temperature is too low, an excessively long aging time may be required. If the aging temperature is too high, the blowing agent in the recycled pre-expanded styrene-based resin particles may dissipate, resulting in reduced moldability.

The expansion ratio of the foamed particles in the recycled styrene-based resin foamed molding is preferably 2 times or more and less than 110 times, more preferably 5 times to 90 times, even more preferably 10 times to 85 times, and particularly preferably 15 times to 80 times.

D. Uses of recycled styrene-based resin foam moldings
The recycled styrene-based resin foam molded article according to the embodiment of the present invention is lightweight and has excellent flame retardancy and mechanical strength, and therefore can be preferably used for at least one selected from heat insulating material molded articles, heat retaining material molded articles, embankment material molded articles, food container molded articles, industrial product container molded articles, cushioning material molded articles, and packaging material molded articles. Examples of heat insulating material molded articles include wall insulation materials, floor insulation materials, roof insulation materials, and automobile insulation materials. Examples of heat retaining material molded articles include insulation materials for hot water tanks, insulation materials for piping, insulation materials for solar systems, and insulation materials for water heaters. Examples of food container molded articles include food containers such as fish boxes. Examples of industrial product container molded articles include returnable boxes. Examples of cushioning material molded articles include cushioning materials, floats, and blocks. Examples of packaging material molded articles include packaging materials for fish and agricultural products. They can also be used as core materials for tatami mats.

The present invention will be described in detail 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.

<Measurement of the average cell diameter of recycled pre-expanded styrene-based resin particles>
The cross section of the recycled pre-expanded styrene resin particles was measured using a scanning electron microscope "SU3800" manufactured by Hitachi High-Technologies Corp. Specifically, the cross section of the recycled pre-expanded styrene resin particles was enlarged in the range of 18 to 1000 times according to the bubble diameter at an acceleration voltage of 5 kV and a spot intensity of 30, and 20 particles were selected in order of proximity to the center (center of gravity) of the image (measured in a straight line passing through the center of the bubble), and the average of the 18 points other than the maximum and minimum values was calculated to calculate the average bubble diameter.

<Measurement of bulk density and bulk expansion ratio of recycled pre-expanded styrene-based resin particles>
The bulk density and bulk expansion ratio of the recycled pre-expanded styrene-based resin particles were measured as follows.
(Method of measuring bulk density)
The recycled pre-expanded styrene resin particles were allowed to fall naturally into a measuring cylinder as a sample, and the bottom of the measuring cylinder was struck to make the sample volume constant. The volume and mass were then measured and calculated according to the following formula.
Bulk density (g/mL) = sample mass (g) / sample volume in measuring cylinder (mL)
(Method of measuring bulk expansion ratio)
The recycled pre-expanded styrene resin particles were allowed to fall naturally into a measuring cylinder as a sample, and the bottom of the measuring cylinder was struck to make the sample volume constant. The volume and mass were measured and calculated using the following formula. The resin specific gravity was set to 1.0 for styrene resin.
Bulk expansion ratio (times)=volume of sample in measuring cylinder (mL)/mass of sample (g)×specific gravity of resin The bulk expansion ratio may be calculated as the reciprocal of the bulk density.

<Measurement of secondary expansion property of recycled pre-expanded styrene-based resin particles>
The recycled pre-expanded styrene-based resin particles were left to stand at room temperature (approximately -10°C to 35°C), and after 24 hours, 2 g of the particles were placed in a steamer and heated for 30 seconds to 10 minutes in a box-type expansion machine heated to 100°C with steam (blowing steam pressure 0.07 MPa) to obtain secondary expanded particles. The secondary expansion ratio at each time was calculated using the following formula, and the maximum secondary expansion ratio was listed in Table 1 as the secondary expandability. Each expansion ratio was evaluated as the bulk expansion ratio using a 500 mL measuring cylinder.
Expansion ratio (times) of secondary expanded particles = volume (mL) of secondary expanded particles / mass (g) of sample x specific gravity of resin Secondary expandability (times) = (expansion ratio of secondary expanded particles) / (expansion ratio of recycled pre-expanded styrene-based resin particles)

<Measurement of expansion ratio of recycled styrene-based resin foam molded product>
The expansion ratio of the recycled styrene-based resin foam molded product was calculated by measuring the dimensions and mass of the test piece to three or more significant figures and using the following formula: The resin specific gravity was set to 1.0 in the case of styrene-based resin.
Expansion ratio (times)=volume of test piece (cm ³ )/mass of test piece (g)×specific gravity of resin

<Moldability>
The elongation of the molded body surface and the fusion rate when the molded body was broken were used to comprehensively evaluate the elongation of the molded body surface. The appearance of the obtained foamed molded body was visually evaluated. Specifically, the state of the boundary part where the foamed particles on the surface of the foamed molded body were bonded was visually evaluated. The fusion rate between the foamed particles when the molded body was broken was evaluated by breaking the obtained plate-shaped foamed molded body by impact, counting the total number of foamed particles (A) on the fracture surface and the number of particles broken within the particles (B), and calculating the fusion rate (%) according to the following formula.
Fusion rate (%) = {(B)/(A)} x 100
The evaluation was based on the following criteria.
⊚: The appearance is smooth and the fusion rate is 80% or more.
A: The appearance is smooth and the fusion rate is 70% or more.
Δ: Most of the appearance is smooth, but there are some unevenness at the boundaries, and the fusion rate is 60% or more and less than 70%.
x: The boundary portion of the appearance is uneven, the smoothness is poor, and the fusion rate is less than 60%.

<Measurement of 10% Compressive Strength of Recycled Styrene-Based Resin Foam Molded Product>
The 10% compression strength of the recycled styrene-based resin foam molded article was measured in accordance with JIS A 9521. Specifically, a molded article of 50 mm x 50 mm x 30 mm thickness was compressed at a speed of 10 mm per minute. The stress when the molded article was compressed by 10% was taken as the 10% compression strength.

<Combustion test of recycled styrene-based resin foam molded body>
A combustion test of the recycled styrene-based resin foam molded product was carried out in accordance with JIS A 9521 (Method A). In this combustion test, it was confirmed whether the flame was extinguished within 3 seconds, there was no residual fuel, and the product did not burn beyond the flammability limit indicator line.
○: The flame goes out within 3 seconds, there is no residual fuel, and the fire does not burn beyond the flammability limit indicator line.
×: Flame does not go out within 3 seconds, residual flame remains, or burning exceeds the flammability limit indicator line.

[Production Example 1]
<Production of Recycled Styrene-Based Resin Raw Material Particles (a)>
Used styrene-based resin (recycled styrene-based resin made of expanded polystyrene) was fed into a single-screw extruder, heated and melted at 200°C, and then cut underwater from a die to give recycled styrene-based resin raw material particles (a) having an average particle diameter of 0.75 mm (approximately spherical).

[Example 1]
<Preparation of recycled expandable styrene-based resin particles>
In a 100-liter reactor equipped with a stirrer, 36 kg of pure water, 3.7 g of sodium dodecylbenzenesulfonate, and 146 g of magnesium pyrophosphate were placed, and 12.6 kg of recycled styrene-based resin raw material particles (a) were added and suspended by stirring at 145 rpm to prepare suspension (1).
Separately, 2.3 kg of styrene monomer in which 123 g of benzoyl peroxide (purity 75%) as a polymerization initiator and 20 g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved was added to a dispersion of 2.5 kg of pure water and 0.8 g of sodium dodecylbenzenesulfonate, and the mixture was emulsified by stirring with a homomixer to prepare an emulsion (1A).
The above suspension (1) in a 100 liter stirred reactor was kept at 75° C., and the above emulsion (1A) was added.
Then, the mixture was kept at 75°C for 30 minutes so that the styrene monomer and the polymerization initiator were well absorbed in the recycled styrene-based resin raw material particles (a), and immediately after that, 27.1 kg of styrene monomer was continuously added dropwise over 130 minutes. The addition temperature was gradually increased from 75°C to 105°C.
The temperature was then raised to 125° C. over 30 minutes, held at 125° C. for 30 minutes, and then cooled to 60° C. over 1 hour. This produced recycled styrene-based resin particles (1) in the reactor. The Tg of the recycled styrene-based resin particles (1) was 100° C.
Separately, 126 g of ethylenebisstearic acid amide and 150 g of dicumyl peroxide were added as a cell regulator to a dispersion of 3.3 kg of pure water, 1.2 g of sodium dodecylbenzenesulfonate as a surfactant, and 18 g of magnesium pyrophosphate as a dispersant, and the mixture was emulsified by stirring with a homomixer to prepare emulsion (1), which was then added to the reactor cooled to 60° C. Ten minutes after this addition, 695 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60° C. for 30 minutes.
Next, 3360 g of butane (normal butane/isobutane=70% by mass/30% by mass) was injected as a blowing agent at the injection temperature of the Tg of the recycled styrene-based resin particles (1) and held in that state for 5 hours to slowly impregnate the blowing agent. That is, the injection temperature of the blowing agent=the Tg of the recycled styrene-based resin particles (1), and the impregnation temperature of the blowing agent=the Tg of the recycled styrene-based resin particles (1). Then, the temperature in the reactor was cooled to 30°C.
Thereafter, the contents were removed from the reactor at 30° C., and were dehydrated, dried and classified to obtain regenerated expandable styrene-based resin particles (1).
<Surface treatment of recycled expandable styrene resin particles>
40 kg of the obtained recycled expandable styrene-based resin particles (1), 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglyceride, and 16 g of fatty acid monoglyceride were placed in a tumbler mixer and stirred for 30 minutes to perform a surface treatment, thereby obtaining surface-treated recycled expandable styrene-based resin particles (1').
<Preparation of Recycled Pre-Expanded Styrene-Based Resin Particles>
The obtained recycled expandable styrene-based resin particles (1') were stored in a refrigerator at 15°C for 15 days, and then placed in a cylindrical batch-type pressure expansion machine with a volume of 340 liters and heated with steam for 2 minutes to obtain recycled pre-expanded styrene-based resin particles (1). The recycled pre-expanded styrene-based resin particles (1) had a bulk density of 0.02 g/ ^cm3 and a bulk expansion ratio of 50 times.
<Preparation of recycled styrene-based resin foam molded body>
The obtained recycled pre-expanded styrene resin particles (1) were left for 24 hours under room temperature atmosphere, and then the recycled pre-expanded styrene resin particles (1) were filled into the cavity of the mold using a molding machine having a mold with a cavity size of 400 mm in height, 500 mm in width, and 300 mm in depth, and heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds, and then cooled until the pressure inside the mold became -0.02 MPa, and then released from the mold to obtain a block-shaped recycled styrene resin foam molded product (1) corresponding to the mold. The density of the recycled styrene resin foam molded product (1) was 0.02 g/cm ³ , and the expansion ratio was 50 times. The recycled styrene resin foam molded product (1) was then stored in a drying room at 50°C for 1 day.
The results of various evaluations are shown in Table 1.

[Example 2]
In producing the recycled expandable styrene-based resin particles, the same procedure as in Example 1 was carried out except that the amount of ethylene bisstearic acid amide as the cell regulator was 84 g, and 1,680 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 1,680 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the foaming agents, to obtain recycled expandable styrene-based resin particles (2), surface-treated recycled expandable styrene-based resin particles (2'), recycled pre-expanded styrene-based resin particles (2), and recycled styrene-based resin foamed molded products (2).
The results of various evaluations are shown in Table 1.

[Example 3]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 1, except that 3,150 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the foaming agent, to obtain recycled expandable styrene-based resin particles (3), surface-treated recycled expandable styrene-based resin particles (3'), recycled pre-expanded styrene-based resin particles (3), and recycled styrene-based resin foamed molded products (3).
The results of various evaluations are shown in Table 1.

[Example 4]
In producing the recycled expandable styrene-based resin particles, the same procedure as in Example 1 was carried out except that the amount of ethylene bisstearic acid amide as the cell regulator was 34 g and 3,360 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (4), surface-treated recycled expandable styrene-based resin particles (4'), recycled pre-expanded styrene-based resin particles (4), and recycled styrene-based resin foamed molded products (4).
The results of various evaluations are shown in Table 1.

[Example 5]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 1, except that the amount of ethylene bisstearic acid amide used as the cell regulator was 21 g and 3,360 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (5), surface-treated recycled expandable styrene-based resin particles (5'), recycled pre-expanded styrene-based resin particles (5), and recycled styrene-based resin foamed molded products (5).
The results of various evaluations are shown in Table 1.

[Example 6]
In producing the recycled expandable styrene-based resin particles, the same procedure as in Example 1 was carried out except that the amount of ethylene bisstearic acid amide as the cell regulator was 12.6 g, and 420 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 2,940 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the foaming agents, to obtain recycled expandable styrene-based resin particles (6), surface-treated recycled expandable styrene-based resin particles (6'), recycled pre-expanded styrene-based resin particles (6), and recycled styrene-based resin foamed molded products (6).
The results of various evaluations are shown in Table 1.

[Example 7]
In producing the recycled expandable styrene-based resin particles, the same procedure as in Example 1 was carried out except that the amount of ethylene bisstearic acid amide as a cell regulator was 8.4 g, 420 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 2,940 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the foaming agents, and the temperature inside the reactor was cooled to 37° C., to obtain recycled expandable styrene-based resin particles (7), surface-treated recycled expandable styrene-based resin particles (7′), recycled pre-expanded styrene-based resin particles (7), and recycled styrene-based resin foamed molded products (7).
The results of various evaluations are shown in Table 1.

[Example 8]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 1, except that ethylenebisstearic acid amide was not used as the cell regulator, 3,360 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, and the temperature inside the reactor was cooled to 37° C., to obtain recycled expandable styrene-based resin particles (8), surface-treated recycled expandable styrene-based resin particles (8′), recycled pre-expanded styrene-based resin particles (8), and recycled styrene-based resin foamed molded products (8).
The results of various evaluations are shown in Table 1.

[Example 9]
<Preparation of recycled expandable styrene-based resin particles>
In a 100-liter reaction vessel equipped with a stirrer, 42 kg of pure water, 5.5 g of sodium dodecylbenzenesulfonate, and 170 g of magnesium pyrophosphate were added, and 42 kg of recycled styrene-based resin raw material particles (a) were added, and 84 g of ethylenebisstearic acid amide was added as a cell regulator, and the mixture was stirred at 145 rpm to suspend the mixture, thereby preparing a suspension (9). As a result, recycled styrene-based resin particles (9) were obtained in the reaction vessel. The Tg of the recycled styrene-based resin particles (9) was 100°C.
The above suspension (9) in a 100-liter reactor equipped with a stirrer was kept at 60° C., and 150 g of dicumyl peroxide was added. After 10 minutes from the addition, 650 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60° C. for 30 minutes.
Then, the temperature was raised to 120°C over 60 minutes, and then 1680 g of butane (normal butane/isobutane = 70 mass%/30 mass%) and 1680 g of pentane (normal pentane/isopentane = 80 mass%/20 mass%) were injected as a blowing agent at 120°C, cooled to 108°C, and held in that state for 5 hours to slowly impregnate the blowing agent. Then, the temperature inside the reaction vessel was cooled to 30°C.
Thereafter, the contents were removed from the reactor, dehydrated, dried and classified to obtain regenerated expandable styrene-based resin particles (9).
<Surface treatment of recycled expandable styrene resin particles>
The obtained recycled expandable styrene-based resin particles (9) (40 kg), 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglyceride, and 16 g of fatty acid monoglyceride were charged into a tumbler mixer, stirred for 30 minutes, and surface-treated to obtain surface-treated recycled expandable styrene-based resin particles (9').
<Preparation of Recycled Pre-Expanded Styrene-Based Resin Particles>
The obtained recycled expandable styrene-based resin particles (9') were stored in a refrigerator at 15°C for 15 days, and then placed in a cylindrical batch-type pressure expansion machine with a volume of 340 liters and heated with steam for 2 minutes to obtain recycled pre-expanded styrene-based resin particles (9). The recycled pre-expanded styrene-based resin particles (9) had a bulk density of 0.02 g/ ^cm3 and a bulk expansion ratio of 50 times.
<Preparation of recycled styrene-based resin foam molded body>
The obtained recycled pre-expanded styrene resin particles (9) were left for 24 hours under room temperature atmosphere, and then the recycled pre-expanded styrene resin particles (9) were filled into the cavity of the mold using a molding machine having a mold with a cavity size of 400 mm in height, 500 mm in width, and 300 mm in depth, and heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds, and then cooled until the pressure inside the mold was -0.02 MPa, and then released from the mold to obtain a block-shaped recycled styrene resin foam molded product (9) corresponding to the mold. The density of the recycled styrene resin foam molded product (9) was 0.02 g/cm ³ , and the expansion ratio was 50 times. The recycled styrene resin foam molded product (9) was then stored in a drying room at 50°C for 1 day.
The results of various evaluations are shown in Table 1.

[Example 10]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 9, except that the amount of ethylene bisstearic acid amide used as the cell regulator was 42 g and 3,360 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (10), surface-treated recycled expandable styrene-based resin particles (10'), recycled pre-expanded styrene-based resin particles (10), and recycled styrene-based resin foamed molded products (10).
The results of various evaluations are shown in Table 1.

[Example 11]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 9, except that the amount of ethylene bisstearic acid amide used as the cell regulator was 21 g and 3,360 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (11), surface-treated recycled expandable styrene-based resin particles (11'), recycled pre-expanded styrene-based resin particles (11), and recycled styrene-based resin foamed molded products (11).
The results of various evaluations are shown in Table 1.

[Comparative Example 1]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 1, except that the amount of ethylene bisstearic acid amide used as the cell regulator was 462 g and 3,360 g of butane (normal butane/isobutane=70% by mass/30% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (C1), surface-treated recycled expandable styrene-based resin particles (C1'), recycled pre-expanded styrene-based resin particles (C1), and recycled styrene-based resin foamed molded products (C1).
The results of various evaluations are shown in Table 1.

[Comparative Example 2]
The same procedures as in Example 1 were carried out to produce recycled expandable styrene-based resin particles, except that no amount of ethylene bisstearic acid amide was used as the cell regulator, 2,520 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, and the temperature inside the reactor was cooled to 42° C., to obtain recycled expandable styrene-based resin particles (C2), surface-treated recycled expandable styrene-based resin particles (C2'), recycled pre-expanded styrene-based resin particles (C2), and recycled styrene-based resin foamed molded products (C2).
The results of various evaluations are shown in Table 1.

[Comparative Example 3]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 9, except that the amount of ethylene bisstearic acid amide used as the cell regulator was 462 g and 3,360 g of butane (normal butane/isobutane=70% by mass/30% by mass) was used as the blowing agent, to obtain recycled expandable styrene-based resin particles (C3), surface-treated recycled expandable styrene-based resin particles (C3'), recycled pre-expanded styrene-based resin particles (C3), and recycled styrene-based resin foamed molded products (C3).
The results of various evaluations are shown in Table 1.

[Comparative Example 4]
The same procedure as in Example 9 was repeated to produce recycled expandable styrene-based resin particles, except that no amount of ethylene bisstearic acid amide was used as the cell regulator, 2,520 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent, and the temperature inside the reactor was cooled to 42° C., to obtain recycled expandable styrene-based resin particles (C4), surface-treated recycled expandable styrene-based resin particles (C4'), recycled pre-expanded styrene-based resin particles (C4), and recycled styrene-based resin foamed molded products (C4).
The results of various evaluations are shown in Table 1.

[Example 12]
<Preparation of recycled expandable styrene-based resin particles>
In a 100-liter reactor equipped with a stirrer, 36 kg of pure water, 3.7 g of sodium dodecylbenzenesulfonate, and 146 g of magnesium pyrophosphate were placed, and 12.6 kg of recycled styrene-based resin raw material particles (a) were added and suspended by stirring at 145 rpm to prepare suspension (12).
Separately, 2.3 kg of styrene monomer in which 123 g of benzoyl peroxide (purity 75%) as a polymerization initiator and 20 g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved was added to a dispersion of 2.5 kg of pure water and 0.8 g of sodium dodecylbenzenesulfonate, and the mixture was emulsified by stirring with a homomixer to prepare an emulsion (12A).
The above suspension (12) in a 100 liter stirred reactor was maintained at 75° C. and the above emulsion (12A) was added.
Then, the mixture was kept at 75°C for 30 minutes so that the styrene monomer and the polymerization initiator were well absorbed in the recycled styrene-based resin raw material particles (a), and immediately after that, 27.1 kg of styrene monomer was continuously added dropwise over 130 minutes. The addition temperature was gradually increased from 75°C to 105°C.
Thereafter, the temperature was raised to 125° C. over 30 minutes, and the temperature was maintained at 125° C. for 30 minutes, and then the temperature was cooled to 60° C. over 1 hour. In this manner, recycled styrene-based resin particles (12) were prepared in the reactor. The Tg of the recycled styrene-based resin particles (12) was 100° C.
Separately, 34 g of ethylene bisstearic acid amide and 150 g of dicumyl peroxide were added to a dispersion of 3.3 kg of pure water, 1.2 g of sodium dodecylbenzenesulfonate as a surfactant, and 18 g of magnesium pyrophosphate as a dispersant, and the mixture was emulsified by stirring with a homomixer to prepare emulsion (12B), which was then added to the above-mentioned reactor cooled to 60° C. Ten minutes after this addition, 695 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60° C. for 30 minutes.
Next, 1680 g of pentane (normal pentane/isopentane = 80% by mass/20% by mass) was injected as a blowing agent at the injection temperature of the Tg of the recycled styrene-based resin particles (11) and held in that state for 5 hours to slowly impregnate the blowing agent. That is, the injection temperature of the blowing agent = the Tg of the recycled styrene-based resin particles (12), and the impregnation temperature of the blowing agent = the Tg of the recycled styrene-based resin particles (12). Then, the temperature in the reactor was cooled to 30 ° C.
Thereafter, the contents were removed from the reactor at 30° C., dehydrated, dried and classified to obtain regenerated expandable styrene-based resin particles (12).
<Surface treatment of recycled expandable styrene resin particles>
The obtained recycled expandable styrene-based resin particles (12) (40 kg), 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglyceride, and 16 g of fatty acid monoglyceride were charged into a tumbler mixer and stirred for 30 minutes to perform a surface treatment, thereby obtaining surface-treated recycled expandable styrene-based resin particles (12').
<Preparation of Recycled Pre-Expanded Styrene-Based Resin Particles>
The obtained recycled expandable styrene-based resin particles (12') were stored in a refrigerator at 15°C for 15 days, and then placed in a cylindrical batch-type pressure expansion machine with a volume of 340 liters and heated with steam for 2 minutes to obtain recycled pre-expanded styrene-based resin particles (12). The recycled pre-expanded styrene-based resin particles (12) had a bulk density of 0.02 g/ ^cm3 and a bulk expansion ratio of 50 times.
<Preparation of recycled styrene-based resin foam molded body>
The obtained recycled pre-expanded styrene resin particles (12) were left for 24 hours under room temperature atmosphere, and then the recycled pre-expanded styrene resin particles (12) were filled into the cavity of the mold using a molding machine having a mold with a cavity size of 400 mm in height, 500 mm in width, and 300 mm in depth, and heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds, and then cooled until the pressure inside the mold was -0.02 MPa, and then released from the mold to obtain a block-shaped recycled styrene resin foam molded product (12) corresponding to the mold. The density of the recycled styrene resin foam molded product (12) was 0.02 g/cm ³ , and the expansion ratio was 50 times. The recycled styrene resin foam molded product (12) was then stored in a drying room at 50°C for 1 day.
The results of various evaluations are shown in Table 2.

[Example 13]
The same procedure as in Example 12 was carried out except that 2,520 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent in the preparation of the recycled expandable styrene-based resin particles, to obtain recycled expandable styrene-based resin particles (13), surface-treated recycled expandable styrene-based resin particles (13′), recycled pre-expanded styrene-based resin particles (13), and recycled styrene-based resin foamed molded products (13).
The results of various evaluations are shown in Table 2.

[Example 14]
The same procedure as in Example 12 was carried out except that 3,570 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent in the preparation of the recycled expandable styrene-based resin particles, to obtain recycled expandable styrene-based resin particles (14), surface-treated recycled expandable styrene-based resin particles (14'), recycled pre-expanded styrene-based resin particles (14), and recycled styrene-based resin foamed molded products (14).
The results of various evaluations are shown in Table 2.

[Example 15]
The same procedure as in Example 12 was carried out except that 3,780 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent in the preparation of the recycled expandable styrene-based resin particles, to obtain recycled expandable styrene-based resin particles (15), surface-treated recycled expandable styrene-based resin particles (15'), recycled pre-expanded styrene-based resin particles (15), and recycled styrene-based resin foamed molded products (15).
The results of various evaluations are shown in Table 2.

[Example 16]
In producing the recycled expandable styrene-based resin particles, the same procedure as in Example 12 was carried out except that 420 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 4,200 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the blowing agents, to obtain recycled expandable styrene-based resin particles (16), surface-treated recycled expandable styrene-based resin particles (16'), recycled pre-expanded styrene-based resin particles (16), and recycled styrene-based resin foamed molded products (16).
The results of various evaluations are shown in Table 2.

[Example 17]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 12, except that 840 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 5,040 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the blowing agents, to obtain recycled expandable styrene-based resin particles (17), surface-treated recycled expandable styrene-based resin particles (17'), recycled pre-expanded styrene-based resin particles (17), and recycled styrene-based resin foamed molded products (17).
The results of various evaluations are shown in Table 2.

[Example 18]
<Preparation of recycled expandable styrene-based resin particles>
In a 100-liter reactor equipped with a stirrer, 42 kg of pure water, 5.5 g of sodium dodecylbenzenesulfonate, and 170 g of magnesium pyrophosphate were added, and 42 kg of recycled styrene-based resin raw material particles (a) were added, and 34 g of ethylenebisstearic acid amide was added as a bubble adjuster, and the mixture was stirred at 145 rpm to suspend the mixture, thereby preparing a suspension (18). As a result, recycled styrene-based resin particles (18) were obtained in the reaction vessel. The Tg of the recycled styrene-based resin particles (18) was 100°C.
The above suspension (18) in a 100-liter stirred reactor was kept at 60° C., and 150 g of dicumyl peroxide was added. 10 minutes after the addition, 650 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60° C. for 30 minutes.
Then, the temperature was raised to 120° C. over 60 minutes, and then 2310 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was injected as a blowing agent at 120° C., cooled to 108° C., and held in that state for 5 hours to slowly impregnate the blowing agent. Then, the temperature inside the reaction vessel was cooled to 30° C.
Thereafter, the contents were removed from the reactor, dehydrated, dried and classified to obtain recycled expandable styrene-based resin particles (18).
<Surface treatment of recycled expandable styrene resin particles>
The obtained recycled expandable styrene-based resin particles (18) (40 kg), 8 g of polyethylene glycol, 44 g of zinc stearate, 12 g of fatty acid triglyceride, and 16 g of fatty acid monoglyceride were charged into a tumbler mixer, stirred for 30 minutes, and surface-treated to obtain surface-treated recycled expandable styrene-based resin particles (18').
<Preparation of Recycled Pre-Expanded Styrene-Based Resin Particles>
The obtained recycled expandable styrene-based resin particles (18') were stored in a refrigerator at 15°C for 15 days, and then placed in a cylindrical batch-type pressure expansion machine with a volume of 340 liters and heated with steam for 2 minutes to obtain recycled pre-expanded styrene-based resin particles (18). The recycled pre-expanded styrene-based resin particles (18) had a bulk density of 0.02 g/ ^cm3 and a bulk expansion ratio of 50 times.
<Preparation of recycled styrene-based resin foam molded body>
The obtained recycled pre-expanded styrene resin particles (18) were left for 24 hours under room temperature atmosphere, and then the recycled pre-expanded styrene resin particles (18) were filled into the cavity of the mold using a molding machine having a mold with a cavity size of 400 mm in height, 500 mm in width, and 300 mm in depth, and heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds, and then cooled until the pressure inside the mold was -0.02 MPa, and then released from the mold to obtain a block-shaped recycled styrene resin foam molded product (18) corresponding to the mold. The density of the recycled styrene resin foam molded product (18) was 0.02 g/cm ³ , and the expansion ratio was 50 times. The recycled styrene resin foam molded product (18) was then stored in a drying room at 50°C for 1 day.
The results of various evaluations are shown in Table 2.

[Example 19]
The same procedure as in Example 18 was carried out except that 3,570 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent in the preparation of recycled expandable styrene-based resin particles, to obtain recycled expandable styrene-based resin particles (19), surface-treated recycled expandable styrene-based resin particles (19′), recycled pre-expanded styrene-based resin particles (19), and recycled styrene-based resin foamed molded products (19).
The results of various evaluations are shown in Table 2.

[Example 20]
The same procedure as in Example 18 was carried out except that 3,654 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) was used as the blowing agent in the preparation of the recycled expandable styrene-based resin particles, to obtain recycled expandable styrene-based resin particles (20), surface-treated recycled expandable styrene-based resin particles (20′), recycled pre-expanded styrene-based resin particles (20), and recycled styrene-based resin foamed molded products (20).
The results of various evaluations are shown in Table 2.

[Comparative Example 5]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 12, except that 21 g of ethylene bisstearic acid amide was used as the cell regulator, and 210 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 420 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the foaming agents, to obtain recycled expandable styrene-based resin particles (C5), surface-treated recycled expandable styrene-based resin particles (C5'), recycled pre-expanded styrene-based resin particles (C5), and recycled styrene-based resin foamed molded products (C5).
The results of various evaluations are shown in Table 2.

[Comparative Example 6]
The recycled expandable styrene-based resin particles were produced in the same manner as in Example 18, except that 21 g of ethylene bisstearic acid amide was used as the cell regulator, and 210 g of butane (normal butane/isobutane=70% by mass/30% by mass) and 420 g of pentane (normal pentane/isopentane=80% by mass/20% by mass) were used as the foaming agents, to obtain recycled expandable styrene-based resin particles (C6), surface-treated recycled expandable styrene-based resin particles (C6'), recycled pre-expanded styrene-based resin particles (C6), and recycled styrene-based resin foamed molded products (C6).
The results of various evaluations are shown in Table 2.

The recycled expandable styrene resin particles, recycled pre-expanded styrene resin particles, and recycled styrene resin foam molded bodies according to the embodiment of the present invention are preferably used as insulation materials for houses and automobiles, heat-retaining materials for building materials, transport packaging materials such as fish boxes and food containers, cushioning materials, etc. More specifically, the recycled expandable styrene resin particles, recycled pre-expanded styrene resin particles, and recycled styrene resin foam molded bodies according to the embodiment of the present invention are preferably used as wall insulation materials, floor insulation materials, roof insulation materials, automobile insulation materials, hot water tank insulation materials, piping insulation materials, solar system insulation materials, water heater insulation materials, containers for food and industrial products (e.g., food containers such as fish boxes, commuting boxes), 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 (9)

Recycled expandable styrene-based resin particles that become recycled pre-expanded styrene-based resin particles by pre-expanding,
The average bubble diameter of the recycled pre-expanded styrene-based resin particles is more than 5 μm and less than 520 μm,
The secondary expandability of the recycled pre-expanded styrene-based resin particles is more than 1.00 times,
The bulk expansion ratio of the recycled pre-expanded styrene-based resin particles is 5 to 120 times.
Recycled expandable styrene resin particles. The recycled expandable styrene-based resin particles according to claim 1, obtained by pressurizing a blowing agent into a suspension containing a recycled styrene-based resin raw material (A) and a dispersant to impregnate the suspension. The recycled expandable styrene-based resin particles according to claim 2, in which the recycled styrene-based resin raw material (A) is a polymer particle obtained by adding a styrene-based monomer to a suspension containing recycled styrene-based resin raw material particles (a) and polymerizing the mixture. The recycled expandable styrene-based resin particles according to claim 3, wherein the recycled styrene-based resin raw material particles (a) are at least one selected from extruded strand pellets obtained by extruding used styrene-based resin with an extruder and strand cutting it, underwater cut pellets obtained by an underwater cutting method in which used styrene-based resin is extruded with an extruder and simultaneously cut in water, and hot cut pellets obtained by a hot cutting method in which used styrene-based resin is cut and cooled immediately after it comes out of the die of an extruder. The recycled expandable styrene-based resin particles according to claim 2, in which the recycled styrene-based resin raw material particles (a) are used as is as the recycled styrene-based resin raw material (A). The recycled expandable styrene-based resin particles according to claim 5, wherein the recycled styrene-based resin raw material particles (a) are at least one selected from extruded strand pellets obtained by extruding used styrene-based resin with an extruder and strand cutting it, underwater cut pellets obtained by an underwater cutting method in which used styrene-based resin is extruded with an extruder and simultaneously cut in water, and hot cut pellets obtained by a hot cutting method in which used styrene-based resin is cut and cooled immediately after it comes out of the die of the extruder. Recycled pre-expanded styrene-based resin particles obtained by pre-expanding the recycled expandable styrene-based resin particles according to any one of claims 1 to 6. A recycled styrene-based resin foam molded product obtained by molding the recycled pre-expanded styrene-based resin particles according to claim 7. The recycled styrene-based resin foam molded article according to claim 8, having a 10% compressive strength measured in accordance with JIS A 9521 of 0.03 MPa to 0.90 MPa.