Regenerated expandable styrene-based resin particles, regenerated pre-expanded styrene-based resin particles, and regenerated styrene-based resin foam molded body

Abstract

The present invention provides regenerated expandable styrene-based resin particles which have a high degree of contribution to the environment and exhibit beautiful white tone with suppressed yellowness. The present invention also provides regenerated pre-expanded styrene-based resin particles which are obtained from such regenerated expandable styrene-based resin particles. The present invention additionally provides a regenerated styrene-based resin foam molded body which is molded from such regenerated pre-expanded styrene-based resin particles.　Regenerated expandable styrene-based resin particles according to one embodiment of the present invention are obtained by press-fitting and impregnating a foaming agent into regenerated styrene-based resin particles (A). In the L*a*b* color system, the color tone value calculated by L* + |a*| + (|b*|)3 is 20 or more.

Description

Recycled expandable styrene resin particles, recycled pre-expanded styrene resin particles, and recycled styrene resin foam molded article

[0001] 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.

[0002] Because foamed molded articles are lightweight and have excellent thermal insulation and mechanical strength, they are widely used as insulation materials for homes and automobiles, thermal insulation materials for building materials, embankment materials used in polystyrene foam civil engineering, transport packaging materials for fish boxes and food containers, cushioning materials, etc. Among these, in-mold foamed molded articles produced from expandable particles (typically expandable polystyrene-based resin particles or pre-expanded styrene-based resin particles obtained by pre-expanding them) are widely used because of advantages such as the ease of obtaining the desired shape. Such foamed molded articles are composed of a plurality of expandable particles fused to each other.

[0003] On the other hand, the amount of plastic waste is increasing year by year. Most plastic waste is disposed of by incineration or landfilling, but this has become a major social problem, causing environmental pollution, global warming, and a shortage of landfill sites. For this reason, there is a strong social demand for the reuse of plastic waste, and various methods for recycling plastic waste are being considered, including 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 perspectives of resource circulation and reducing environmental impact, and such material recycling is also being considered for styrene resin foam molded products.

[0004] As a material recycling method for styrene-based resin foam moldings, several methods have been proposed for producing recycled expandable styrene-based resin particles, which are obtained by melting and extruding recovered raw materials to form recovered pellets, and then impregnating these with a blowing agent.

[0005] Methods for obtaining recycled expandable styrene resin particles by impregnating or pressurizing and then impregnating recycled resin pellets molded from recovered styrene resin foam molded articles with a blowing agent have been reported (Patent Documents 1 to 4). Also reported are methods for obtaining recycled expandable styrene resin particles by adding styrene monomer to recycled resin pellets molded from recovered styrene resin foam molded articles, causing nuclear polymerization, and then impregnating or pressurizing and then impregnating with a blowing agent (Patent Documents 5 to 9).

[0006] However, conventional recycled expandable styrene resin particles have a problem in that they have a noticeable yellowish tinge and poor color tone.

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

[0008] The present invention has been made to solve the above-mentioned problems of the related art, and its main object is to provide recycled expandable styrene-based resin particles that are highly environmentally friendly and exhibit a beautiful white tone with reduced yellowness. It is also an object of the present invention to provide recycled pre-expanded styrene-based resin particles obtained from such recycled expandable styrene-based resin particles. It is also an object of the present invention to provide recycled styrene-based resin foam molded articles molded from such recycled pre-expanded styrene-based resin particles.

[0009] [1] The recycled expandable styrene-based resin particles according to an embodiment of the present invention are recycled expandable styrene-based resin particles obtained by injecting and impregnating a blowing agent into recycled styrene-based resin particles (A), and are L * a * b * In the color system, L * + | a * |+(|b * |) 3The color value calculated by the formula (2) is 20 to 800. [2] The recycled expandable styrene-based resin particles described in [1] above may be obtained by nuclear polymerization of a styrene monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc as a nucleus. [3] The recycled expandable styrene-based resin particles described in [1] above may be obtained by nuclear polymerization of a styrene monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc as a nucleus. [4] Recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention are recycled pre-expanded styrene-based resin particles obtained by pre-expanding the recycled expandable styrene-based resin particles described in any one of [1] to [3] above, and the bulk expansion ratio of the pre-expanded particles is 2 to 150 times. [5] The recycled styrene-based resin foam molded article according to an embodiment of the present invention is molded from the recycled pre-expanded styrene-based resin particles described in [4] above.

[0010] According to the present invention, it is possible to provide recycled expandable styrene-based resin particles that are highly environmentally friendly and exhibit a beautiful white color with reduced yellowness. It is also possible to provide recycled pre-expanded styrene-based resin particles obtained from such recycled expandable styrene-based resin particles. Furthermore, it is also possible to provide a recycled styrene-based resin foam molded article molded from such recycled pre-expanded styrene-based resin particles.

[0011] FIG. 1 is a schematic cross-sectional view showing an example of an apparatus suitable for producing recycled expandable styrene-based resin particles according to an embodiment of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0013] In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0014] <<A. Recycled Expandable Styrenic Resin Particles>> The recycled expandable styrenic 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 styrenic resin particles is preferably 0.40 mm to 2.0 mm, and more preferably 0.60 mm to 1.8 mm. The average particle diameter can be measured in accordance with JIS Z 8815. Specifically, the average particle diameter can be the value measured as the particle diameter at 50% of the cumulative value from the particle size distribution obtained by the sieving test of JIS Z 8815.

[0015] The shape of the recycled expandable styrene-based resin particles according to an embodiment of the present invention can be any appropriate shape as long as it does not impair the effects of the present invention. Specific examples of such shapes include spherical, approximately spherical, and oval spherical (egg-shaped). In terms of achieving the effects of the present invention, the shape of the recycled expandable styrene-based resin particles according to an embodiment of the present invention is preferably spherical or approximately spherical, and more preferably spherical. However, in reality, it is difficult to distinguish between spherical and approximately spherical, so in this specification, both shapes are collectively referred to as spherical.

[0016] 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 450,000.

[0017] The recycled expandable styrene resin particles according to an embodiment of the present invention are L * a * b * In the color system, L * + | a * |+(|b * |) 3 The color value calculated by is 20 to 800, preferably 25 to 800, more preferably 30 to 750, even more preferably 35 to 750, particularly preferably 40 to 700, and most preferably 45 to 700. * + | a * |+(|b *|) 3 If the color value calculated by the above formula is within the above range, the recycled expandable styrene resin particles according to an embodiment of the present invention can exhibit a beautiful white color tone with reduced yellowness. * + | a * |+(|b * |) 3 The color value calculated by L * a * b * b in the color system * It is an index weighted by b. * is a color dimension that reflects yellowness, and L * + | a * |+(|b * |) 3 By adjusting the color tone value calculated by the above formula to fall within the above range, a beautiful white tone with reduced yellowness can be achieved. * + | a * |+(|b * |) 3 If the color value calculated by is too small and outside the above range, the molded article may appear dull. * + | a * |+(|b * |) 3 If the color value calculated by |a is too large and deviates from the above range, the molded article may take on a yellowish tinge, and may appear to have yellowed and deteriorated. * | is a * means the absolute value of |b * | is b * means the absolute value of

[0018] Preferred embodiments of the recycled expandable styrene-based resin particles of the present invention include the following two embodiments. Embodiment (1): Recycled expandable styrene-based resin particles obtained by injecting and impregnating recycled styrene-based resin particles (A) with a blowing agent, wherein the recycled styrene-based resin particles (A) are obtained by nuclear polymerization of a styrene monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc as nuclei. Embodiment (2): Recycled expandable styrene-based resin particles obtained by injecting and impregnating recycled styrene-based resin particles (A) with a blowing agent, wherein the recycled styrene-based resin particles (A) contain 10 mg / kg to 800 mg / kg of metallic zinc.

[0019] The recycled expandable styrene-based resin particles according to the embodiment of the present invention have a high environmental contribution. The recycled expandable styrene-based resin particles in the above embodiment (1) have a recycling rate of preferably 10% or more, more preferably 20% or more, and even more preferably 25% or more. The recycled expandable styrene-based resin particles in the above embodiment (2) have a recycling rate of preferably 50% or more, more preferably 70% or more, even more preferably 90% or more, particularly preferably 95% or more, and most preferably 100%. The recycling rate is the proportion of recovered styrene-based resin in the styrene-based resin contained in the recycled expandable styrene-based resin particles.

[0020] First, the above-mentioned embodiment (1) and embodiment (2) will be described below.

[0021] <A-1. Preferred embodiment (1) of recycled expandable styrene-based resin particles> One preferred embodiment (1) of the recycled expandable styrene-based resin particles of the present invention is recycled expandable styrene-based resin particles obtained by pressurizing and impregnating recycled styrene-based resin particles (A) with a blowing agent, and the recycled styrene-based resin particles (A) are recycled expandable styrene-based resin particles obtained by nuclear polymerization of a styrene-based monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc element as nuclei.

[0022] <A-1-1. Recycled styrene-based resin particles (A) in embodiment (1)> The recycled styrene-based resin particles (A) in embodiment (1) are obtained by nuclear polymerization of a styrene-based monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc as cores.

[0023] The recycled styrene-based resin raw material particles (a) may be of one type only or of two or more types.

[0024] Any suitable recycled styrene resin can be used as the material for the recycled styrene resin raw material particles (a) as long as the effects of the present invention are not impaired. Examples of such recycled styrene resins include recycled products of plastic materials used in polystyrene foam (molded products such as fish boxes and agricultural product boxes, cushioning materials, block molded products, etc.), foam sheets (tray containers, sheet waste, etc.), home appliances, packaging containers, cushion beads, etc.

[0025] 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 effects of the present invention are not impaired. Examples of such other recycled resins include recycled resins of AS resin, ABS resin, HIPS (high-impact polystyrene); polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polycarbonate (PC); polyamide resins such as nylon (PA); and polyolefin resins such as polyethylene (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and EVA (ethylene-vinyl acetate copolymer). The other resins may be one type or two or more types. In this specification, the recycled AS resin, recycled ABS resin, and recycled HIPS (high-impact polystyrene) resin are not included in the category of recycled styrene-based resins.

[0026] As the recycled styrene-based resin raw material particles (a), molded products made from "EPSULEM" or "ESLEM BEAD RNW" manufactured by Sekisui Plastics Co., Ltd. may be used.

[0027] The recycled styrene-based resin raw material particles (a) may be pulverized material obtained by pulverizing recycled resin obtained by heating and / or reducing the volume of used expanded styrene-based resin. The recycled styrene-based resin raw material particles may be pelletized material obtained by extruding the pulverized material and then pulverizing the pellets. Alternatively, the recycled styrene-based resin raw material particles may be pelletized material obtained by reducing the volume using a solvent such as limonene.

[0028] The recycled styrene resin raw material particles (a) are preferably pellets obtained by melt extrusion, which is a method in which crushed styrene resin, ingots, foamed styrene resin particles, etc., are fed into 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.

[0029] The pellets obtained by the melt extrusion method are preferably at least one type selected from extruded strand pellets obtained by extruding used styrene foam resin using an extruder and strand cutting the extruded pellets; underwater cut pellets obtained by an underwater cutting method in which used styrene foam resin is extruded using an extruder and simultaneously cut in water; and hot cut pellets obtained by a hot cutting method in which used styrene foam resin particles are cut and cooled immediately after emerging from the die of the extruder.

[0030] 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 or the like again to obtain smaller pellets.

[0031] The recycled styrene-based resin raw material particles (a) may be a shrinkage or melting product of a styrene-based resin, which is obtained by coarsely crushing used styrene-based resin to an appropriate size as needed, and then subjecting the resin to heat shrinkage, bubble destruction shrinkage due to compression, shrinkage due to frictional heat, melting, or the like.

[0032] Examples of used foamed styrene resins include molded articles obtained by molding foamable styrene resins into molds, and those obtained by heating and foaming these.

[0033] The recycled styrene resin raw material particles (a) may contain finely powdered inorganic and / or organic lubricants, which typically function as cell regulators.

[0034] Examples of finely powdered inorganic substances include talc, calcium carbonate, and silica. Here, talc typically refers to a mixture containing silicon oxide and magnesium oxide as main components, with trace amounts of aluminum oxide, iron oxide, etc.

[0035] The average particle size of the finely powdered inorganic material is preferably 100 μm or less, 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.

[0036] The content of the finely powdered inorganic material relative to the recycled styrene-based resin raw material particles (a) is preferably 0.1% to 5% by mass, more preferably 0.5% to 2% by mass. If the content of the finely powdered inorganic material 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 finely powdered inorganic material 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 may become extremely small, causing the recycled pre-expanded styrene-based resin particles to melt during molding, which may deteriorate the appearance of the molded product.

[0037] Examples of organic lubricants include liquid paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisatomids such as methylene bisstearic acid amide, ethylene bisstearic acid amide, and ethylene bisoleic acid amide; and metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

[0038] The content of the organic lubricant relative to the recycled styrene-based resin raw material particles (a) is preferably 0.01% to 2.0% by mass, more preferably 0.02% to 1.8% by mass, and in some cases even more preferably 0.02% to 0.2% by mass, and particularly preferably 0.02% to 0.1% by mass. 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 cell size of the recycled pre-expanded styrene-based resin particles may be reduced. If the content of the organic lubricant relative to the recycled styrene-based resin raw material particles (a) exceeds 2.0% by mass, the cell size of the recycled pre-expanded styrene-based resin particles becomes extremely small, which tends to cause the recycled pre-expanded styrene-based resin particles to melt during molding, resulting in poor appearance of the molded product.

[0039] A specific method for incorporating a fine powder inorganic material and / or an organic lubricant into the recycled styrene-based resin raw material particles (a) is, for example, a method of kneading a fine powder inorganic material and / or an organic lubricant during extrusion molding. In this case, preferably, the pulverized material and the cell control agent are mixed in advance, and then extrusion molding is performed. The pulverized material and the cell control agent can be mixed by any appropriate method as long as the effects of the present invention are not impaired. Examples of such methods include mixing using a mixer such as a tumbler, ribbon blender, V blender, Henschel mixer, or Redige mixer.

[0040] The recycled styrene-based resin raw material particles (a) are preferably heat-melted to adjust their specific gravity. In this process, the specific gravity of the recycled styrene-based 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-based resin raw material particles (a) is less than 0.6, the dispersion of the recycled styrene-based resin raw material particles (a) will be unstable, which may result in excessively large particles during the subsequent polymerization process, resulting in reduced yield. The recycled styrene-based resin raw material particles (a) can be heat-melted by any appropriate method as long as the effects of the present invention are not impaired. Examples of such methods include methods using an extruder or a heated roll. The heat-melting is preferably performed by cooling and solidifying the resulting resin with no or minimal residual strain. If residual strain remains in the resin particles, the strain may be relieved in the subsequent process, causing shrinkage in the stretching direction, resulting in the resulting recycled expandable styrene-based resin particles being 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, distortion may remain in the stretched resin obtained by cooling and solidifying. Even if distortion remains in the resin due to the thermal melting, the distortion can be alleviated by curing the resin for a certain period of time at a temperature above the softening point of the resin.

[0041] For the pulverization to obtain the recycled styrene-based resin raw material particles (a), any pulverizer can 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 can be used, and a pulverizer for polystyrene is preferred.

[0042] The recycled styrene resin raw material particles (a) can be sieved as necessary and subjected to melting again in an extruder or the like.

[0043] 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 achieve. 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.

[0044] 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) is outside the above range, the shape of the resulting recycled expandable styrene-based resin particles may be difficult to achieve.

[0045] The recycled styrene-based resin raw material particles (a) preferably contain less than 1% by mass of particles having 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 having 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).

[0046] The weight-average molecular weight of the recycled styrene-based resin raw material particles (a) is preferably 100,000 to 510,000, 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) is more than 510,000, the recycled styrene-based resin raw material particles may not be easily spherical, or the foaming properties may be reduced, resulting in poor appearance of the molded product.

[0047] In embodiment (1), the recycled styrene-based resin raw material particles (a) contain 10 mg / kg to 800 mg / kg of metallic zinc. That is, in embodiment (1), the content of metallic zinc in the recycled styrene-based resin raw material particles (a) is 10 mg / kg to 800 mg / kg, preferably 15 mg / kg to 700 mg / kg, more preferably 20 mg / kg to 600 mg / kg, even more preferably 25 mg / kg to 500 mg / kg, and particularly preferably 30 mg / kg to 450 mg / kg. In embodiment (1), if the content of metallic zinc in the recycled styrene-based resin raw material particles (a) is within the above range, the effects of the present invention can be more effectively exhibited, and the recycled expandable styrene-based resin particles according to the present invention can exhibit a more beautiful white tone with less yellowness. In embodiment (1), if the content of metallic zinc in the recycled styrene-based resin raw material particles (a) is too low outside the above range, the molded product may appear dull. In embodiment (1), if the content of metallic zinc element in the recycled styrene-based resin raw material particles (a) is too high and outside the above range, the molded product may become yellowish, appearing to have yellowed and deteriorated, or the fusion rate between the expanded particles during molding may deteriorate, resulting in reduced moldability.

[0048] In embodiment (1), the method for adjusting the content of metallic zinc element in the recycled styrene-based resin raw material particles (a) to 10 mg / kg to 800 mg / kg can be any suitable method as long as it does not impair the effects of the present invention. For example, when producing recycled styrene-based resin raw material particles (a), if necessary, (i) recycled styrene-based resins having a high content of metallic zinc element (e.g., greater than 800 mg / kg) and (ii) recycled styrene-based resins having a low content of metallic zinc element (e.g., less than 10 mg / kg) are used to adjust the content of metallic zinc element in the resulting recycled styrene-based resin raw material particles (a) to 10 mg / kg to 800 mg / kg.

[0049] The styrene-based monomer used in the nuclear polymerization may be one kind or two or more kinds.

[0050] The styrene-based monomer includes styrene or a styrene derivative. Examples of styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. The styrene-based monomer may be one type or two or more types. The styrene-based monomer preferably contains at least styrene. The content of styrene relative to the total amount of the styrene-based monomer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0051] The styrene monomer may contain any suitable vinyl monomer other than the styrene monomer, as long as the effects of the present invention are not impaired. Examples include polyfunctional monomers, (meth)acrylic acid ester monomers, maleic acid ester monomers, and fumaric acid ester monomers. Such vinyl monomers may be used alone or in combination of two or more types.

[0052] 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. Specific examples of maleic acid ester monomers include dimethyl maleate. Specific examples of fumaric acid ester monomers include dimethyl fumarate, diethyl fumarate, and ethyl fumarate.

[0053] In embodiment (1), the content ratio of the recycled styrene-based resin raw material particles (a) to the total amount of the recycled styrene-based resin raw material particles (a) and the styrene-based monomer is preferably as high as possible from the viewpoint of environmental contribution. However, from the viewpoint of producing the recycled styrene-based resin particles (A) by nuclear polymerization, the content ratio of the recycled styrene-based resin raw material particles (a) to the total amount of the recycled styrene-based resin raw material particles (a) and the styrene-based monomer is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 85% by mass, even more preferably 15% by mass to 80% by mass, particularly preferably 20% by mass to 75% by mass, and most preferably 25% by mass to 70% by mass.

[0054] In embodiment (1), the recycled styrene-based resin particles (A) are obtained by nuclear polymerization of a styrene-based monomer using recycled styrene-based resin raw material particles (a) as nuclei. Any appropriate method can be used as this nuclear polymerization method as long as it does not impair the effects of the present invention. One preferred embodiment of this nuclear polymerization method is a method in which an emulsion containing a polymerization initiator and a styrene-based monomer is added to a suspension obtained by dispersing recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium, thereby impregnating the recycled styrene-based resin raw material particles (a), and then a styrene-based monomer is added and polymerization is carried out.

[0055] When obtaining recycled styrene-based resin particles (A), the addition temperature when adding the styrene monomer to the recycled styrene-based resin raw material particles (a) is preferably 40°C to 119°C, more preferably 40°C to 118°C, even more preferably 40°C to 117°C, particularly preferably 50°C to 117°C, and most preferably 60°C to 115°C, in order to further demonstrate 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 an appropriate hardness, thereby achieving good spheroidization of the recycled styrene-based resin particles (A), and the final recycled expandable styrene-based resin particles can exhibit good spheroidization and excellent moldability. If the addition temperature when adding the styrene monomer to the recycled styrene resin raw material particles (a) is too low outside the above range, the recycled styrene resin raw material particles (a) will become too hard, and when the styrene monomer is incorporated in this state, the recycled styrene resin particles (A) will be difficult to spheroidize, and the finally obtained recycled expandable styrene resin particles may be difficult to spheroidize and may have poor moldability. If the addition temperature when adding the styrene monomer to the recycled styrene resin raw material particles (a) is too high outside the above range, the recycled styrene resin raw material particles (a) will become too soft, and when the styrene monomer is incorporated in this state, the recycled styrene resin particles (A) will be difficult to spheroidize, and the finally obtained recycled expandable styrene resin particles may be difficult to spheroidize and may have poor moldability. The "addition temperature when adding a styrene-based monomer to the recycled styrene-based resin raw material particles (a)" means the addition temperature during the addition of the emulsion containing the polymerization initiator and the styrene-based monomer, and the subsequent addition of the styrene-based monomer.

[0056] When dispersing the recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium to obtain a suspension, any suitable method can be adopted as a method for dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium as long as it does not impair the effects of the present invention. As a dispersion method, a dispersion using an apparatus equipped with a stirring blade is preferred. A method for more fine dispersion can be mentioned, for example, a method using a homomixer.

[0057] When dispersing 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 to disperse the recycled styrene-based resin raw material particles (a) in the aqueous medium. Any suitable dispersant can be used as long as it can be used in suspension polymerization and does not impair the effects of the present invention. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose; and sparingly soluble inorganic salts such as magnesium pyrophosphate and calcium triphosphate. Among these, magnesium pyrophosphate is preferred as the dispersant because it can better demonstrate the effects of the present invention.

[0058] The blending ratio of the dispersant per 100 parts by mass of the recycled styrene-based resin particles (A) is preferably 0.1 to 2.0 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.

[0059] When dispersing 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 when dispersing the recycled styrene-based resin raw material particles (a) in the aqueous medium. Any suitable 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 alkanesulfonate, sodium alkylsulfonate, sodium alkyldiphenyletherdisulfonate, and sodium α-olefinsulfonate. Among these, sodium dodecylbenzenesulfonate is preferred as the surfactant, as it can more effectively demonstrate the effects of the present invention.

[0060] The blending ratio of the surfactant per 100 parts by mass of the recycled styrene-based resin particles (A) is preferably 0.005 parts by mass to 0.10 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.

[0061] Any suitable emulsification method can be used to obtain an emulsion containing a polymerization initiator and a styrene-based monomer, as long as it does not impair the effects of the present invention. A preferred dispersion method is dispersion using an apparatus equipped with a stirring blade. A method using a homomixer is an example of a method for more fine dispersion. In this case, it is preferable to disperse the styrene-based monomer until the oil droplet diameter of the dispersion becomes equal to or smaller than the particle diameter of the nuclei. If the oil droplet diameter is larger than the particle diameter of the nuclei when the dispersion is added to an aqueous medium, multiple recycled styrene-based resin raw material particles (a) will be incorporated into the oil droplets of the dispersion, causing adhesion, plasticization, and coalescence of the recycled styrene-based resin raw material particles (a), which is likely to result in the generation of excessively large particles.

[0062] As the polymerization initiator used to obtain an emulsion containing a polymerization initiator and a styrene-based monomer, any appropriate polymerization initiator can be used as long as it is one that is used in suspension polymerization, as long as it 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 one type or two or more types.

[0063] The amount of the polymerization initiator used is preferably 0.1% by mass to 1.0% by mass, more preferably 0.1% by mass to 0.8% by mass, and even more preferably 0.1% by mass to 0.5% by mass, based on the styrene-based monomer.

[0064] The polymerization initiator is preferably added after being dissolved in the styrene-based 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 based on the styrene-based monomer.

[0065] After adding an emulsion containing a styrene monomer to a suspension containing recycled styrene resin raw material particles (a) to impregnate the particles, any suitable method can be used to add the styrene monomer as long as it does not impair the effects of the present invention. Examples of such methods include divided addition and continuous addition. The addition rate is appropriately selected depending on the capacity, shape, polymerization temperature, etc. of the polymerization apparatus.

[0066] After adding an emulsion containing a styrene monomer to a suspension containing recycled styrene resin raw material particles (a) to impregnate the particles, the styrene monomer may be added, and then the polymerization reaction may be continued at any appropriate temperature and for any appropriate time, as necessary.

[0067] The suspension containing the recycled styrene-based resin raw material particles (a) and the emulsion containing the styrene-based monomer may contain a cell regulator, such as 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.

[0068] <A-1-2. Pressurized injection and impregnation of blowing agent in embodiment (1)> The recycled expandable styrene-based resin particles in embodiment (1) are obtained by pressurizing and impregnating a blowing agent into the recycled styrene-based resin particles (A).

[0069] A representative method for injecting and impregnating the blowing agent in embodiment (1) is to place the recycled styrene-based resin particles (A) in a reactor such as an autoclave, and then inject and impregnate the blowing agent.

[0070] The foaming agent may be one kind or two or more kinds.

[0071] Any appropriate blowing agent can be used as long as it does not impair the effects of the present invention. The blowing agent referred to here is preferably a volatile blowing agent. The blowing agent is preferably an organic compound whose boiling point is equal to or lower than the softening point of the styrene-based resin and which is gaseous or liquid at normal pressure. Specific examples include aliphatic hydrocarbons such as propane, n-butane, isobutane, pentane (n-pentane, isopentane, neopentane), and n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, and isopropyl alcohol; low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; and halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane. Inorganic gases such as carbon dioxide, nitrogen, and ammonia may also be used as the blowing agent. Among these, the blowing agent is preferably at least one selected from n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, and cyclopentadiene, and more preferably at least one selected from n-butane, isobutane, n-pentane, and isopentane, in terms of being able to further exhibit the effects of the present invention.

[0072] The content of the blowing agent can be appropriately set depending on the purpose as long as it is an amount sufficient to form recycled pre-expanded styrenic resin particles and recycled styrenic resin foam molded articles. The content of the blowing agent is preferably 2 to 15 parts by mass when the total amount of the recycled styrenic resin raw material particles (a) and the styrenic monomer is 100 parts by mass.

[0073] In embodiment (1), the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 50°C to 140°C, even more preferably 60°C to 130°C, even more preferably 70°C to 123°C, even more preferably 80°C to 115°C, particularly preferably 90°C to 110°C, and most preferably 95°C to 105°C. The temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) may be varied within the above range. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is within the above range, the blowing agent is prevented from being rapidly impregnated into the recycled styrene-based resin particles (A), allowing for uniform impregnation. For example, this can reduce areas that shrink and melt when molded into a recycled styrene-based resin foam, and can also make it easier to remove odors unique to recycled raw materials. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is too low and outside the above range, the blowing agent will not be easily impregnated into the recycled styrene-based resin particles (A) when the blowing agent is injected; for example, the blowing agent will be rapidly impregnated when the temperature is raised, and the recycled styrene-based resin particles (A) will not be uniformly impregnated with the blowing agent, which will likely cause variations in the bubbles and lead to surface shrinkage during molding. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is too high and outside the above range, the blowing agent will be rapidly impregnated into the recycled styrene-based resin particles (A) when the blowing agent is injected, and the recycled styrene-based resin particles (A) will not be uniformly impregnated with the blowing agent, which will likely cause variations in the bubbles and lead to surface shrinkage during molding.

[0074] In embodiment (1), one embodiment of the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is preferably 40°C to 150°C, more preferably 40°C to 140°C, even more preferably 40°C to 130°C, even more preferably 40°C to 123°C, still more preferably 40°C or higher but lower than 110°C, particularly preferably 40°C to 105°C, and most preferably 40°C to 102°C.

[0075] In embodiment (1), another embodiment of the impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) is preferably a temperature equal to or higher than the injection temperature of the blowing agent into the recycled styrene-based resin particles (A) (which may be the same as the injection temperature of the blowing agent into the recycled styrene-based resin particles (A)), preferably 93°C to 130°C, more preferably 94°C to 129°C, even more preferably 95°C to 128°C, particularly preferably 96°C to 127°C, and most preferably 97°C to 126°C.

[0076] The impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) may be varied within the above range. When the impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) is within the above range, in combination with the adjustment of the pressure-injection temperature, the blowing agent is prevented from being rapidly impregnated into the recycled styrene-based resin particles (A), enabling uniform impregnation. For example, areas that shrink and melt when molded into a recycled styrene-based resin foamed molded article can be reduced. If the impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) is too low outside the above range, the blowing agent may not be impregnated to the center of the recycled styrene-based resin particles (A), leaving unfoamed areas, which may result in an unsatisfactory molded article. If the impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) is too high outside the above range, the blowing agent may be impregnated too far into the recycled styrene-based resin particles (A), causing the blowing agent to melt during molding.

[0077] In embodiment (1), a particularly representative embodiment of the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is preferably 40°C to 150°C, more preferably 50°C to 130°C, even more preferably 60°C to 120°C, even more preferably 70°C or higher but lower than 110°C, even more preferably 80°C or higher but lower than 110°C, particularly preferably 90°C or higher but lower than 110°C, and most preferably 95°C to 105°C.

[0078] The time for impregnating the recycled styrene-based resin particles (A) with the blowing agent can be any appropriate time within the range that does not impair the effects of the present invention, and is preferably 1 to 10 hours.

[0079] <A-1-3. Other Components in Embodiment (1)> The recycled expandable styrene-based resin particles in embodiment (1) may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be one type only, or two or more types.

[0080] The recycled expandable styrene-based resin particles in embodiment (1) may contain a flame retardant to enhance flame retardancy. The flame retardant may be one type or two or more types.

[0081] As the flame retardant, any appropriate flame retardant can 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 preferred, 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.

[0082] When a flame retardant is used, a flame retardant aid may be used in combination. Examples of the flame retardant aid include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenylhexane.

[0083] The total amount of the flame retardant and the flame retardant aid may be any appropriate amount within the range that does not impair the effects of the present invention. Such an amount is preferably 0.1% to 15% by mass, more preferably 0.2% to 10% by mass, even more preferably 0.2% to 5% by mass, and particularly preferably 0.2% to 3% by mass, based on the recycled styrene-based resin raw material particles (a).

[0084] The flame retardant may be added at any appropriate timing as long as the effects of the present invention are not impaired. To further enhance the effects of the present invention, the flame retardant is preferably added before the blowing agent is injected. Adding the flame retardant before the blowing agent can allow the flame retardant to be added at a low temperature equivalent to the temperature at which the blowing agent is injected, thereby enabling the resulting recycled expandable styrene-based resin particles to be well spherical and have excellent moldability.

[0085] The addition temperature when adding the flame retardant is preferably 5°C to 120°C, more preferably 5°C to 118°C, even more preferably 5°C to 115°C, even more preferably 5°C to 113°C, even more preferably 5°C to 110°C, even more preferably 40°C to 89°C, even more preferably 40°C to 87°C, even more preferably 40°C to 85°C, particularly preferably 40°C to 83°C, and most preferably 40°C to 80°C, from the viewpoint of being able to further exhibit the effects of the present invention.

[0086] In producing the recycled expandable styrene-based resin particles of embodiment (1), a partial ester of a higher fatty acid and an alcohol may be used as the cell control agent. That is, the recycled expandable styrene-based resin particles of embodiment (1) may contain a partial ester of a higher fatty acid and an alcohol. The partial ester of a higher fatty acid and an alcohol may be one type or two or more types. Examples of higher fatty acids include fatty acids having 15 or more carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid, and monoglycerides and diglycerides thereof can be used. Examples of the partial ester of a higher fatty acid and an alcohol include preferred stearic acid monoglyceride and stearic acid diglyceride. The content of the partial ester of a higher fatty acid and an alcohol is preferably 0 to 3.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the recycled styrene-based resin particles (A). The partial ester of higher fatty acid and alcohol can be added by adding it together with a blowing agent, or by any commonly used method such as dry blending, master batching, or melt injection.

[0087] In producing the recycled expandable styrene-based resin particles in embodiment (1), a foaming aid may be used. That is, the recycled expandable styrene-based resin particles in embodiment (1) may contain a foaming aid. The foaming aid may be one type or two or more types. Examples of the foaming aid include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil.

[0088] In producing the recycled expandable styrene-based resin particles in embodiment (1), a cell regulator may be used. That is, the recycled expandable styrene-based resin particles in embodiment (1) may contain a cell regulator. The cell regulator may be one type or two or more types. Examples of the cell regulator 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.

[0089] The amount of the cell control agent used may be any appropriate amount within the range that does not impair the effects of the present invention. Such an amount is preferably 0 to 5.0 parts by mass, more preferably 0.02 to 3.0 parts by mass, even more preferably 0.02 to 2.0 parts by mass, and particularly preferably 0.02 to 1.0 part by mass, relative to 100 parts by mass of the recycled styrene-based resin particles (A).

[0090] The recycled expandable styrene-based resin particles in embodiment (1) may contain a cell regulator such as talc, calcium carbonate, mica, citric acid, sodium bicarbonate, etc. The cell regulator may be one type or two or more types.

[0091] In addition to the above, other additives include, for example, pigments, radiant heat transfer suppressing components, crosslinking agents, plasticizers, stabilizers, fillers, lubricants, colorants, antistatic agents, spreading agents, weather resistance agents, antioxidants, anti-fogging agents, and fragrances.

[0092] <A-1-4. Surface Treatment> The recycled expandable styrene-based resin particles in embodiment (1) may be surface-treated. Such surface treatment is preferably performed with at least one selected from silicone oil, antistatic agents, fatty acid metal salts, and fusion accelerators.

[0093] When the recycled expandable styrene-based resin particles in embodiment (1) are surface-treated with silicone oil, the amount of silicone oil used per 100 parts by weight of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.30 parts by weight, more preferably 0.003 to 0.28 parts by weight, even more preferably 0.005 to 0.25 parts by weight, particularly preferably 0.008 to 0.23 parts by weight, and most preferably 0.01 to 0.23 parts by weight. 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, making static electricity more likely to be 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.

[0094] The silicone oil may be used alone or in combination of two or more kinds.

[0095] As the silicone oil, any suitable silicone oil can be adopted 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, as the silicone oil, for example, straight silicone oil such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, etc. can be mentioned, and preferably methylphenylpolysiloxane.

[0096] When the recycled expandable styrene-based resin particles in embodiment (1) are surface-treated with an antistatic agent, the amount of antistatic agent used per 100 parts by weight of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.3 parts by weight, more preferably 0.005 to 0.28 parts by weight, even more preferably 0.01 to 0.27 parts by weight, particularly preferably 0.015 to 0.26 parts by weight, and most preferably 0.02 to 0.25 parts by weight. If the amount of antistatic agent is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of antistatic agent is too large outside the above range, the surfaces of the recycled pre-expanded styrene-based resin particles and recycled styrene-based resin foam molded articles may become sticky.

[0097] The antistatic agent may be used alone or in combination of two or more kinds.

[0098] As the antistatic agent, any appropriate antistatic agent can 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, 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.

[0099] The nonionic surfactant may be used alone or in combination of two or more kinds.

[0100] As the nonionic surfactant, any appropriate nonionic surfactant can be used as long as it does not impair the effects of the present invention. Examples of nonionic surfactants that can further exhibit the effects of the present invention include polyethylene glycol, glycerin, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyhydric alcohols, and 1-amino-2-hydroxy compounds. Specific examples of polyoxyethylene alkyl ethers include polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. Specific examples of polyoxyethylene alkyl esters include polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, and polyoxyethylene oleate. Specific examples of polyhydric alcohols include glycerin and propylene glycol. 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 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.As the nonionic surfactant, polyethylene glycol is preferred in that it can more effectively exhibit the effects of the present invention.

[0101] 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 weight of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.001 to 2.0 parts by weight, more preferably 0.001 to 1.5 parts by weight, even more preferably 0.001 to 1.0 parts by weight, even more preferably 0.001 to 0.5 parts by weight, even more preferably 0.001 to 0.3 parts by weight, even more preferably 0.005 to 0.28 parts by weight, even more preferably 0.01 to 0.27 parts by weight, particularly preferably 0.015 to 0.26 parts by weight, and most preferably 0.02 to 0.25 parts by weight. If the amount of 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 large and outside the above range, the surfaces of the recycled pre-expanded styrene resin particles and the recycled styrene resin foam molded article may become sticky.

[0102] The fatty acid glyceride may be one kind or two or more kinds.

[0103] As the fatty acid glyceride, any appropriate fatty acid glyceride can 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 demonstrate 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 terms of further demonstrating the effects of the present invention.

[0104] When a fatty acid glyceride is used as at least a part of the antistatic agent, the amount of the fatty acid glyceride per 100 parts by weight of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.30 parts by weight, more preferably 0.005 to 0.28 parts by weight, even more preferably 0.010 to 0.27 parts by weight, particularly preferably 0.015 to 0.26 parts by weight, and most preferably 0.020 to 0.25 parts by weight. If the amount of fatty acid glyceride is too low outside the above range, static electricity may be easily generated during pre-expansion. If the amount of fatty acid glyceride is too high outside the above range, the surfaces of the recycled pre-expanded styrene-based resin particles and the recycled styrene-based resin foam molded articles may become sticky.

[0105] When the recycled expandable styrene-based resin particles in embodiment (1) are surface-treated with a fatty acid metal salt, the amount of fatty acid metal salt used per 100 parts by weight of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.005 to 0.50 parts by weight, more preferably 0.007 to 0.45 parts by weight, even more preferably 0.01 to 0.40 parts by weight, particularly preferably 0.015 to 0.35 parts by weight, and most preferably 0.02 to 0.30 parts by weight. If the amount of fatty acid metal salt is too low outside the above range, blocking may occur frequently during pre-expansion, making it difficult to obtain a good styrene-based resin foam molded article. If the amount of fatty acid metal salt is too high outside the above range, too much metal salt may be present during pre-expansion, making the particles more likely to become charged, generating static electricity, and potentially resulting in poor fusion of the molded article.

[0106] The fatty acid metal salt may be of one kind or of two or more kinds.

[0107] As the fatty acid metal salt, any appropriate fatty acid metal salt can be used as long as it does not impair the effects of the present invention. Examples of fatty acid metal salts that can further demonstrate the effects of the present invention include metal stearates and metal laurates. Specific examples of metal stearates include magnesium stearate, calcium stearate, zinc stearate, barium stearate, aluminum stearate, and lithium stearate. Specific examples of metal laurates include zinc laurate and barium laurate. As fatty acid metal salts, magnesium stearate and zinc stearate are preferred in terms of further demonstrating the effects of the present invention.

[0108] When the recycled expandable styrene-based resin particles in embodiment (1) are surface-treated with a fusion accelerator, the amount of fusion accelerator used per 100 parts by mass of the recycled expandable styrene-based resin particles before surface treatment is preferably 0.01 to 0.80 parts by mass, more preferably 0.01 to 0.70 parts by mass, even more preferably 0.01 to 0.60 parts by mass, particularly preferably 0.01 to 0.55 parts by mass, and most preferably 0.013 to 0.50 parts by mass. If the amount of fusion accelerator is too small outside the above range, the fusion properties during molding may be reduced, and it may be impossible to obtain a good recycled styrene-based resin foam molded article. If the amount of fusion accelerator is too large outside the above range, blocking may occur during pre-expansion.

[0109] The fusion promoter may be of one kind or of two or more kinds.

[0110] Any appropriate fusion promoter may be used as the fusion promoter as long as it does not impair the effects of the present invention. Examples of fusion promoters that can further demonstrate the effects of the present invention include fatty acid triglycerides, fatty acid diglycerides, fatty acid monoglycerides, and vegetable oils. Specific examples of fatty acid triglycerides include lauric acid triglyceride, 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. Specific examples of stearic acid triglyceride and hydroxystearic acid triglyceride are preferred as fusion promoters in that they can further demonstrate the effects of the present invention.

[0111] <A-2. Preferred embodiment (2) of recycled expandable styrene-based resin particles> One preferred embodiment (2) of the recycled expandable styrene-based resin particles of the present invention is recycled expandable styrene-based resin particles obtained by pressurizing and impregnating recycled styrene-based resin particles (A) with a blowing agent, wherein the recycled styrene-based resin particles (A) contain 10 mg / kg to 800 mg / kg of metallic zinc element.

[0112] <A-2-1. Recycled styrene-based resin particles (A) in embodiment (2)> The recycled styrene-based resin particles (A) in embodiment (2) are typically recycled styrene-based resin raw material particles (a). That is, in embodiment (2), recycled styrene-based resin raw material particles (a) are used as the recycled styrene-based resin particles (A). In embodiment (2), the description of the recycled styrene-based resin raw material particles (a) in the above section <A-1-1. Recycled styrene-based resin particles (A) in embodiment (1)> can be used for the recycled styrene-based resin raw material particles (a) that can be used as the recycled styrene-based resin particles (A).

[0113] In embodiment (2), the recycled styrene-based resin particles (A) contain 10 mg / kg to 800 mg / kg of metallic zinc. That is, in embodiment (2), the content of metallic zinc in the recycled styrene-based resin particles (A) is 10 mg / kg to 800 mg / kg, preferably 15 mg / kg to 700 mg / kg, more preferably 20 mg / kg to 600 mg / kg, even more preferably 25 mg / kg to 500 mg / kg, and particularly preferably 30 mg / kg to 450 mg / kg. In embodiment (2), if the content of metallic zinc in the recycled styrene-based resin particles (A) is within the above range, the effects of the present invention can be more effectively exhibited, and the recycled expandable styrene-based resin particles according to the present invention can exhibit a more beautiful white tone with less yellowing. In embodiment (2), if the content of metallic zinc in the recycled styrene-based resin particles (A) is too low outside the above range, the molded product may appear dull. In embodiment (2), if the content of metallic zinc element in the recycled styrene-based resin particles (A) is too high and outside the above range, the molded product may become yellowish, appearing to have yellowed and deteriorated, or the fusion rate between the foamed particles during molding may deteriorate, resulting in reduced moldability.

[0114] In embodiment (2), the method for adjusting the metallic zinc element content in the recycled styrene-based resin particles (A) to 10 mg / kg to 800 mg / kg can be any appropriate method as long as it does not impair the effects of the present invention. For example, when preparing the recycled styrene-based resin particles (A), if necessary, at least one selected from the group consisting of (i) a recycled styrene-based resin having a high metallic zinc element content (e.g., greater than 800 mg / kg) and (ii) a recycled styrene-based resin having a low metallic zinc element content (e.g., less than 10 mg / kg) is used to adjust the metallic zinc element content in the resulting recycled styrene-based resin particles (A) to 10 mg / kg to 800 mg / kg.

[0115] <A-2-2. Injection and Impregnation of Blowing Agent in Embodiment (2)> The recycled expandable styrene-based resin particles in embodiment (2) are obtained by injecting and impregnating a blowing agent into recycled styrene-based resin particles (A) which are made directly from recycled styrene-based resin raw material particles (a).

[0116] Representative methods for injecting and impregnating the blowing agent in embodiment (2) include: Injection and impregnation method (1): a method in which a suspension containing recycled styrene-based resin particles (A) (recycled styrene-based resin raw material particles (a) are used as they are) is placed in a reactor such as an autoclave, and the blowing agent is injected and impregnated; and Injection and impregnation method (2): a method in which recycled styrene-based resin particles (A) (recycled styrene-based resin raw material particles (a) are used as they are) are placed in an extruder, and the blowing agent is injected and impregnated midway through the extruder, and the particles are extruded from the extruder and simultaneously cut underwater.

[0117] For the injection / impregnation method (1), the explanation in the above section <A-1-2. Injection / impregnation of blowing agent in embodiment (1)> can be used. However, the injection temperature and impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) are as follows.

[0118] Regarding the injection / impregnation method (1) in embodiment (2), the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 145°C, even more preferably 80°C to 140°C, particularly preferably 100°C to 135°C, and most preferably 110°C to 130°C. The temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) may be varied within the above range. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is within the above range, for example, the recycled styrene-based resin particles (A) can be easily spheroidized even if they are irregularly shaped particles, particle adhesion can be reduced, and odors specific to recycled raw materials can be easily removed. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is too low outside the above range, spheroidization may be difficult. If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is too high and outside the above range, the particles may become flattened or the number of coalesced particles may increase.

[0119] Regarding the pressure-injection / impregnation method (1) in embodiment (2), the temperature at which the blowing agent is impregnated into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 130°C, even more preferably 80°C to 120°C, even more preferably 90°C or higher but less than 110°C, particularly preferably 95°C or higher but less than 110°C, and most preferably 100°C or higher but less than 110°C. The temperature at which the blowing agent is impregnated into the recycled styrene-based resin particles (A) may be varied within the above range. If the impregnation temperature of the blowing agent into the recycled styrene-based resin particles (A) is within the above range, for example, the blowing agent is more efficiently impregnated into the recycled styrene-based resin particles (A), and the blowing agent is uniformly absorbed, making it easier to control subsequent foaming and molding, and also making it easier to remove odors specific to recycled raw materials. If the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is too low and outside the above range, the blowing agent may not be absorbed into the center of the recycled styrene-based resin particles (A), or only a portion of the blowing agent injected may be absorbed into the recycled styrene-based resin particles (A).If the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is too high and outside the above range, the particles may become flattened or the number of coalesced particles may increase.

[0120] The injection / impregnation method (2) in embodiment (2) is a method in which recycled styrene-based resin particles (A) (recycled styrene-based resin raw material particles (a) are used as they are) are placed in an extruder, a blowing agent is injected and impregnated into the extruder midway, and the particles are extruded from the extruder and simultaneously underwater cut (underwater cutting method).

[0121] In more detail, in the injection / impregnation method (2) in embodiment (2), recycled styrene-based resin particles (A) (recycled styrene-based resin raw material particles (a) are used as they are) are fed into an extruder, heated and melted, a blowing agent is injected midway through the extruder, the resulting resin composition is extruded through a multi-hole die into water, and simultaneously with extrusion, the resin composition is cut in water to form resin particles.

[0122] Regarding the foaming agent, the explanation of the foaming agent in the above section <A-1-2. Injection and impregnation of foaming agent> can be used.

[0123] Regarding the injection / impregnation method (2) in embodiment (2), the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 130°C, even more preferably 80°C to 120°C, particularly preferably 90°C to 115°C, and most preferably 95°C to 110°C. The temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) may be varied within the above range. If the injection temperature of the blowing agent into the recycled styrene-based resin particles (A) is within the above range, for example, the blowing agent is more easily impregnated into the recycled styrene-based resin particles (A) and is more uniformly absorbed, making it easier to control subsequent foaming and molding, and also to remove odors specific to recycled raw materials. If the injection temperature of the blowing agent into the recycled styrene-based resin particles (A) is too low outside the above range, there is a risk that the blowing agent will not be absorbed to the center of the recycled styrene-based resin particles (A). If the temperature at which the blowing agent is injected into the recycled styrene-based resin particles (A) is too high and outside the above range, there is a risk that the particles will become more likely to coalesce.

[0124] Regarding the pressure-injection / impregnation method (2) in embodiment (2), the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is preferably 40°C to 150°C, more preferably 40°C to 140°C, even more preferably 40°C to 130°C, even more preferably 40°C to 123°C, particularly preferably 40°C or higher but less than 110°C, and most preferably 40°C to 105°C. The temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent may be varied within the above range. If the impregnation temperature for the blowing agent for the recycled styrene-based resin particles (A) is within the above range, the blowing agent is more efficiently impregnated into the recycled styrene-based resin particles (A) and is uniformly absorbed, making it easier to control subsequent foaming and molding, and also to remove odors specific to recycled raw materials. If the impregnation temperature for the blowing agent for the recycled styrene-based resin particles (A) is too low outside the above range, there is a risk that only a portion of the injected blowing agent will be absorbed into the recycled styrene-based resin particles (A). If the temperature for impregnating the recycled styrene-based resin particles (A) with the blowing agent is too high and outside the above range, the particles may become flattened or the number of coalesced particles may increase.

[0125] When cutting in water simultaneously with extrusion, the water temperature is preferably 15°C to 60°C, more preferably 20°C to 50°C. If the water temperature is lower than 15°C, the die surface will be cooled too much, the die holes will be easily clogged, and the pressure inside the die will increase, which may make extrusion difficult. If the water temperature is higher than 60°C, it may be difficult to suppress foaming, and if the water temperature exceeds 80°C, the resin particles obtained by cutting may be prone to coalescence.

[0126] The temperature of the water is preferably 100° C. to 200° C. lower than the temperature of the resin composition when it flows into the die. If the temperature difference between the water temperature and the resin composition temperature is less than 100° C., the resulting resin particles may not be sufficiently cooled, making it difficult to suppress foaming, and if the temperature difference between the water temperature and the resin composition temperature exceeds 200° C., the resulting resin particles may be deformed due to the temperature difference between the surface and interior of the resin particles, and may not become perfectly spherical.

[0127] In the underwater cutting method, a mold with 50 to 500 discharge holes in the multi-hole die is used, and the water pressure is preferably adjusted to 0 MPa to 2.00 MPa and the discharge rate to 50 kg / hour to 300 kg / hour. In the underwater cutting method, the water pressure corresponds to the resistance force when the resin is extruded from the die into the water, and the discharge rate corresponds to the force in the extrusion direction when the resin composition is extruded from the die into the water. Therefore, in the underwater cutting method, expandable styrene-based resin particles can be successfully produced by appropriately adjusting the water pressure and discharge rate. In particular, when recycled styrene-based resin is used as the resin component, the molecular weight tends to decrease and the fluidity tends to increase due to the thermal history of the recycled styrene-based resin during recycling. In addition, the fluidity and viscoelasticity change due to the inclusion of an arbitrary amount of additives derived from recycled raw materials, requiring strict adjustment of the water pressure and discharge rate in the underwater cutting method.

[0128] The water pressure in the underwater cutting method is preferably 0.12 MPa to 1.90 MPa, more preferably 0.13 MPa to 1.85 MPa, even more preferably 0.15 MPa to 1.80 MPa, and particularly preferably 0.20 MPa to 1.60 MPa.

[0129] The discharge rate in the underwater cutting method is preferably 60 kg / hour to 280 kg / hour, more preferably 80 kg / hour to 270 kg / hour, even more preferably 100 kg / hour to 260 kg / hour, and particularly preferably 120 kg / hour to 250 kg / hour.

[0130] An example of an apparatus suitable for producing recycled expandable styrenic resin particles in embodiment (2) by the underwater cutting method of pressure-injection / impregnation method (2) is shown in Figure 1. This production apparatus includes an extruder 1 equipped with a raw material supply hopper 11 for introducing resin component (B) upstream in the resin flow direction (from left to right in Figure 1), a blowing agent supply port 12 with a high-pressure pump 13 downstream of the extruder 1 in the resin flow direction, and a multi-hole die 2 at the end of the resin flow direction, a cutting chamber 3 arranged to cover the outlet of the multi-hole die 2 and having a rotatable cutter 31 disposed therein and configured to circulate water therein, a water tank 6 and a water pump 4 for supplying water to the cutting chamber 3, a dehydrator 5 for introducing the recycled expandable styrenic resin particles cut in the cutting chamber 3 together with water and separating the water from the recycled expandable styrenic resin particles, and a container 7 for storing the recycled expandable styrenic resin particles separated in the dehydrator 5.

[0131] The extruder 1 can be a known extruder used in extrusion molding of resin compositions. Examples of such extruders include a single-screw extruder, a twin-screw extruder, and a tandem extruder. The extruder 1 receives the resin component (B) from a raw material supply hopper 11, heats and kneads the mixture, and transports the resulting molten mixture downstream in the resin flow direction. When the molten mixture reaches the blowing agent supply port 12, a blowing agent pumped by a high-pressure pump 13 is mixed into the molten mixture. The resulting resin composition is then extruded through the multi-hole die 2 into the cutting chamber 3, where it comes into contact with water and is cut underwater by a cutter 31. The cut resin composition becomes spherical particles of approximately uniform particle size and is transported from the cutting chamber 3 to the dehydrator 5 by the circulating water flow. The recycled expandable styrene-based resin particles obtained after separation and drying in the dehydrator 5 are stored in a container 7, while the water is sent to a water tank 6.

[0132] <A-2-3. Other Components in Embodiment (2)> The recycled expandable styrene-based resin particles in embodiment (2) may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be one type only, or two or more types.

[0133] As for the other components, the explanation in the above section <A-1-3. Other components in embodiment (1)> can be cited.

[0134] <A-2-4. Surface Treatment> The recycled expandable styrene-based resin particles in embodiment (2) may be subjected to a surface treatment. The explanation in the above section <A-1-4. Surface Treatment> can be used for such surface treatment.

[0135] B. Recycled Pre-Expanded Styrenic Resin Particles The recycled pre-expanded styrenic resin particles according to an embodiment of the present invention are obtained by pre-expanding the recycled expandable styrenic resin particles according to an embodiment of the present invention.

[0136] The recycled pre-expanded styrene-based resin particles preferably have an average cell diameter of 0.01 mm to 1.10 mm, more preferably 0.01 mm to 1.00 mm, even more preferably 0.01 to 0.90 mm, particularly preferably 0.01 mm to 0.80 mm, and most preferably 0.01 mm to 0.70 mm. When the average cell diameter of the recycled pre-expanded styrene-based resin particles is within the above range, blocking during expansion and molding can be more effectively prevented. Furthermore, the recycled pre-expanded styrene-based resin particles can exhibit better fusion properties and surface properties while further suppressing electrostatic charge during expansion and molding, thereby enabling the formation of recycled styrene-based resin foam molded articles with less static electricity. If the average cell diameter of the recycled pre-expanded styrene-based resin particles is less than 0.01 mm, there is a risk of the surface melting and shrinking during molding.

[0137] Pre-expansion involves expanding recycled expandable styrene-based resin particles to a desired bulk expansion ratio (bulk density) using steam or the like. The bulk expansion ratio of the recycled pre-expanded styrene-based resin particles is preferably 2 to 150, more preferably 2 to less than 100, even more preferably 5 to 90, particularly preferably 10 to 85, and most preferably 15 to 83. The bulk density is the reciprocal of the bulk expansion ratio. When the bulk expansion ratio of the recycled pre-expanded styrene-based resin particles is within the above range, blocking during expansion and molding can be further prevented, and further, electrostatic charge during expansion and molding can be further suppressed while exhibiting better fusion properties and surface properties, making it possible to provide recycled pre-expanded styrene-based resin particles that can mold recycled styrene-based resin foam molded articles with less static electricity.

[0138] In one exemplary embodiment, the recycled pre-expanded styrene-based resin particles can be used to form recycled styrene-based resin foamed molded articles. In another embodiment, the recycled pre-expanded styrene-based resin particles can be used as they are as cushioning material, heat insulating material, concrete aggregate, etc. When the recycled pre-expanded styrene-based resin particles are used as they are, they can preferably be used as a filler in which a large number of recycled pre-expanded styrene-based resin particles are filled into a bag. Such recycled pre-expanded styrene-based resin particles are suitable, for example, for the core material of a cushion (the foam particles filled inside the cushion).

[0139] C. Recycled styrene-based resin foam molded product A recycled styrene-based resin foam molded product according to one embodiment of the present invention is a recycled styrene-based resin foam molded product molded from recycled expandable styrene-based resin particles according to an embodiment of the present invention. A recycled styrene-based resin foam molded product according to another embodiment of the present invention is a recycled styrene-based resin foam molded product molded from recycled pre-expanded styrene-based resin particles according to an embodiment of the present invention.

[0140] The recycled styrene-based resin foam molded article typically contains recycled expandable styrene-based resin particles (hereinafter sometimes simply referred to as "expanded particles") obtained by further expanding recycled pre-expanded styrene-based resin particles.

[0141] A recycled styrene-based resin foam molded article is typically composed of a plurality of foam particles fused together.

[0142] Recycled styrene-based resin foam molded articles can typically be produced by loading recycled pre-expanded styrene-based 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 the recycled pre-expanded styrene-based resin particles into a closed mold having a large number of small holes, (ii) heating and expanding the recycled pre-expanded styrene-based resin particles with a heat medium (e.g., pressurized steam, etc.) to obtain expanded particles, and (iii) filling the voids between the expanded particles and fusing the expanded particles together to form a single integrated product by the heat expansion. The density of the recycled styrene-based resin foam molded article can be appropriately set depending on the purpose. The density of the recycled styrene-based resin foam molded article can be adjusted, for example, by adjusting the bulk expansion ratio of the pre-expanded styrene-based resin particles filled into the mold in advance or by adjusting the amount of recycled pre-expanded styrene-based resin particles filled into the mold.

[0143] The heat-foaming temperature (substantially the temperature of the heat transfer medium) is preferably 90°C to 150°C, more preferably 110°C to 130°C. The heat-foaming time is preferably 5 seconds to 50 seconds, more preferably 10 seconds to 50 seconds. The molding vapor pressure (gauge pressure of the heat transfer medium blowing in) of the heat-foaming is preferably 0.04 MPa to 0.1 MPa, more preferably 0.06 MPa to 0.08 MPa. Heat-foaming under these conditions allows the expanded particles to be well fused to each other.

[0144] If necessary, the recycled pre-expanded styrene-based resin particles may be aged before molding into a recycled styrene-based resin foamed molded 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 a decrease in moldability.

[0145] The expansion ratio of the expanded beads in the recycled styrene-based resin foamed molded article 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.

[0146] The recycled styrene-based resin foam molded article according to an embodiment of the present invention is lightweight and has excellent heat insulation properties and mechanical strength, and is therefore suitable for use as wall insulation, floor insulation, roof insulation, automobile insulation, hot water tank insulation, piping insulation, solar system insulation, water heater insulation, containers for food and industrial products (e.g., food containers such as fish boxes, returnable boxes), cushioning material, floats, blocks, packaging material for fish and agricultural products, etc., earth filling moldings, core material for tatami mats, core material for cushions, concrete aggregate, etc.

[0147] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating each property are as follows.

[0148] <L * + | a * |+(|b * |) 3 A color difference meter manufactured by Konica Minolta Sensing Co., Ltd. (product name "CR-400") and a standard white calibration plate (Y: 84.6, x: 0.318, y: 0.3224) were used for standardization, and the color value calculated by the following formula was obtained. * Value (lightness: white > black), a * value (hue: red > green), b * Specifically, approximately 2 g of particles to be measured was filled (to the brim) in a measurement container (powder cell manufactured by Konica Minolta Sensing Co., Ltd., product name "CR-A50"), and the filled part was measured with a measurement diameter of φ8 mm, and the L * Value, a * value, b * From the obtained values, L * + | a * |+(|b * |) 3 The color value was calculated by the following formula.

[0149] <Analysis of Metallic Zinc Element Amount> The amount of metallic zinc element contained in the recycled styrene-based resin raw material particles or recycled styrene-based resin particles was measured as follows. Approximately 0.5 g of a precisely weighed measurement sample was heated at 475°C for 3 hours and incinerated. The resulting ash was mixed with 2 mL of concentrated hydrochloric acid (Ultrapur-100, ultra-high purity reagent, manufactured by Kanto Chemical Co., Ltd.). The insoluble matter in the mixture was filtered using ADAVANTEC No. 7 filter paper, and the filtrate was diluted to 50 mL with pure water to prepare a test solution. The metallic zinc element concentration of the test solution was measured under the following conditions. The metallic zinc element concentration was determined from a calibration curve. The amount of metallic zinc element in the sample was calculated using the following formula. The lower limit of measurement was 1 mg / kg. Amount of metallic zinc element (mg / kg) = Concentration of metallic zinc element (μg / mL) × 50 (mL) ÷ Mass of measured sample (g) (ICP measurement conditions) Measurement device = Shimadzu Corporation's "ICPE-9000" multi-type ICP optical emission spectrometer Measurement element = Zn (202.548 nm) Observation direction = Axial direction High frequency output = 1.20 kW Carrier flow rate = 0.7 L / min Plasma flow rate = 10.0 L / min Auxiliary flow rate = 0.6 L / min Exposure time = 30 seconds Standard solutions for calibration curve = SPEX, USA's "XSTC-13" general-purpose mixed standard solution 31 elements mixed (base 5% HNO3): approximately 10 mg / L each, SPEX, USA's "XSTC-8" general-purpose mixed standard solution 13 elements mixed (base H2O / trace HF): approximately 10 mg / L each The standard solution for the calibration curve was diluted with pure water to prepare standard solutions of 5 ppm, 2.5 ppm, 1 ppm, and 0.25 ppm for measurement. (Ashing conditions) Measurement equipment: "Muffle furnace FP-410" manufactured by Yamato Scientific Co., Ltd. Ashing conditions: 475°C x 3 hours (sample amount: approximately 0.5 g)

[0150] <Evaluation of aesthetics> Evaluation of aesthetics was carried out by a sensory test conducted by five people. ◯: Three or more people felt it was a warm color. △: Three or more people felt it was dull. ×: Three or more people felt it was yellowed.

[0151] [Production Example 1]: Production of recycled styrene-based resin raw material particles (a) Recovered pellets from used fish boxes and, if necessary, zinc stearate were fed into a single-screw extruder, heated and melted at 200 ° C, extruded through a mold, and cut underwater to produce particles with an average particle diameter of 0.75 mm (approximately spherical). Various recycled styrene-based resin raw material particles (a) containing a predetermined amount of metallic zinc element were produced. The recycled styrene-based resin raw material particles (a) produced were the following 12 types. Recycled styrene-based resin raw material particles (a10): Metallic zinc element content = 10 mg / kg Recycled styrene-based resin raw material particles (a25): Metallic zinc element content = 25 mg / kg Recycled styrene-based resin raw material particles (a60): Metallic zinc element content = 60 mg / kg Recycled styrene-based resin raw material particles (a85): Metallic zinc element content = 85 mg / kg Recycled styrene-based resin raw material particles (a120): Metallic zinc element content = 120 mg / kg Recycled styrene-based resin raw material particles (a140): Metallic zinc element content = 140 mg / kg Recycled styrene-based resin raw material particles (a200): Metallic zinc element content = 200 mg / kg Recycled styrene-based resin raw material particles (a450): Metallic zinc element content = 450 mg / kg Recycled styrene-based resin raw material particles (a650): Metallic zinc element content = 650 mg / kg Recycled styrene-based resin raw material particles (a750): Metallic zinc element content = 750 mg / kg Recycled styrene-based resin raw material particles (a5): Metallic zinc element content = 5 mg / kg Recycled styrene-based resin raw material particles (a805): Metallic zinc element content = 805 mg / kg

[0152] Example 1 Preparation of Recycled Expandable Styrenic Resin Particles (1) A 100-liter reactor equipped with a stirrer was charged with 36 kg of water, 3.5 g of sodium dodecylbenzenesulfonate, and 150 g of magnesium pyrophosphate. 12.6 kg of recycled styrene-based resin raw material particles (a10) obtained in Production Example 1 (recycled styrene-based resin raw material particles (a)) was added and suspended by stirring at 150 rpm to prepare suspension (1). Separately, a dispersion of 2.5 kg of water and 0.8 g of sodium dodecylbenzenesulfonate was added with 125 g of benzoyl peroxide (75% purity) as a polymerization initiator and 2.3 kg of styrene monomer dissolved with 20 g of t-butylperoxy-2-ethylhexyl monocarbonate, and the mixture was emulsified by stirring with a homomixer to prepare emulsion (1). The suspension (1) in the 100-liter reactor equipped with a stirrer was maintained at 75°C, and the emulsion (1) was added. The mixture was then held at 75°C for 30 minutes to ensure that the styrene monomer and polymerization initiator were fully absorbed into the recycled styrene-based resin raw material particles (a). Immediately after this, 27.1 kg of styrene monomer was added dropwise over 120 minutes. The addition temperature was gradually increased from 75°C to 105°C. The mixture was then heated 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 (A1) in a reaction vessel. Next, 189 g of dicumyl peroxide and 35 g of ethylenebisstearamide were added to a dispersion of 3.5 kg of water, 1.5 g of sodium dodecylbenzenesulfonate, and 20 g of magnesium pyrophosphate, and the mixture was emulsified by stirring with a homomixer to prepare emulsion (2). This emulsion (2) was then added to the reactor cooled to 60°C. Ten minutes after this addition, 756 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes. Subsequently, the temperature was raised to 100°C, and 3,200 g of pentane (isopentane / normal pentane=20% by mass / 80% by mass) was injected as a blowing agent. This state was maintained for 5.5 hours to slowly impregnate the blowing agent. Thereafter, the temperature inside the reactor was cooled to 30°C.Thereafter, the contents were removed from the reactor, dehydrated, dried and classified to obtain recycled expandable styrene resin particles (1).

[0153] <Surface treatment of recycled expandable styrene-based resin particles (1)> 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 surface treatment, thereby obtaining surface-treated recycled expandable styrene-based resin particles (1′).

[0154] <Preparation of Recycled Pre-Expanded Styrenic Resin Particles (1)> The obtained surface-treated recycled expandable styrene-based resin particles (1') were stored in a refrigerator at 15°C for 20 days, and then placed in a cylindrical batch-type pressure foaming 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 bulk density of the recycled pre-expanded styrene-based resin particles (1) was 0.02 g / cm. 3 The bulk expansion ratio was 50 times.

[0155] <Preparation of Recycled Styrenic Resin Foam Molded Article (1)> A molding machine having a mold with a cavity of 400 mm high x 500 mm wide x 300 mm deep was used. After leaving the recycled pre-expanded styrene-based resin particles (1) in a room temperature atmosphere for 24 hours, they were filled into the cavity of the mold of the molding machine and heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds. Then, they were cooled until the pressure inside the mold became -0.002 MPa, and then released from the mold to obtain a plate-shaped recycled styrene-based resin foam molded article (1) corresponding to the mold. The density of the recycled styrene-based resin foam molded article (1) was 0.02 g / cm 3 The expansion ratio was 50. Thereafter, this recycled styrene-based resin foam molded article (1) was stored in a drying room at 50° C. for 1 day. The results are shown in Table 1.

[0156] Examples 2 to 10 Recycled styrene-based resin particles (A2) to (A10), recycled expandable styrene-based resin particles (2) to (10), recycled pre-expanded styrene-based resin particles (2) to (10), and recycled styrene-based resin foam molded articles (2) to (10) were obtained in the same manner as in Example 1, except that the recycled styrene-based resin raw material particles (a) were replaced with the recycled styrene-based resin raw material particles shown in Table 1. The results are shown in Table 1.

[0157] Comparative Examples 1 and 2 Recycled styrene-based resin particles (AC1) to (AC2), recycled expandable styrene-based resin particles (C1) to (C2), recycled pre-expanded styrene-based resin particles (C1) to (C2), and recycled styrene-based resin foam molded articles (C1) to (C2) were obtained in the same manner as in Example 1, except that the recycled styrene-based resin raw material particles (a) were replaced with the recycled styrene-based resin raw material particles shown in Table 1. The results are shown in Table 1.

[0158] Example 11 Preparation of Recycled Expandable Styrenic Resin Particles (11) A 100-liter reactor equipped with a stirrer was charged with 42 kg of water, 5.7 g of sodium dodecylbenzenesulfonate, and 295 g of magnesium pyrophosphate. 42 kg of recycled styrene-based resin raw material particles (a10) obtained in Production Example 1 as recycled styrene-based resin particles (A) was then added and suspended at 150 rpm to prepare suspension (3). The suspension (3) in the 100-liter reactor equipped with a stirrer was maintained at 60°C, and 189 g of dicumyl peroxide and 34 g of ethylenebisstearamide were added. Ten minutes after this addition, 756 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. The temperature was then raised to 120°C over 60 minutes, and 4,200 g of pentane (isopentane / normal pentane = 20% by mass / 80% by mass) was then pressure-injected as a blowing agent. The temperature was raised to 108°C over 10 minutes, and the temperature was maintained at 108°C for 5 hours, allowing the blowing agent to be slowly impregnated. The temperature inside the reactor was then cooled to 30°C. The contents were then removed from the reactor, dehydrated, dried, and classified to obtain recycled expandable styrene-based resin particles (11).

[0159] <Surface treatment of recycled expandable styrene-based resin particles (11)> 40 kg of the obtained recycled expandable styrene-based resin particles (11), 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 surface treatment, thereby obtaining surface-treated recycled expandable styrene-based resin particles (11′).

[0160] <Preparation of Recycled Pre-Expanded Styrenic Resin Particles (11)> The obtained surface-treated recycled expandable styrene-based resin particles (11') were stored in a refrigerator at 15°C for 20 days, and then placed in a cylindrical batch-type pressure foaming machine with a volume of 340 liters and heated with steam for 2 minutes to obtain recycled pre-expanded styrene-based resin particles (11). The bulk density of the recycled pre-expanded styrene-based resin particles (11) was 0.02 g / cm. 3 The bulk expansion ratio was 50 times.

[0161] <Preparation of Recycled Styrenic Resin Foam Molded Article (11)> A molding machine having a mold with a cavity of 400 mm high x 500 mm wide x 300 mm deep was used. The recycled pre-expanded styrene-based resin particles (11) were left in a room temperature atmosphere for 24 hours, then filled into the cavity of the mold of the molding machine, heated at a vapor pressure of 0.04 MPa (gauge pressure) for 40 seconds, and then cooled until the pressure inside the mold was -0.002 MPa. After that, the mold was released, and a plate-shaped recycled styrene-based resin foam molded article (11) corresponding to the mold was obtained. The density of the recycled styrene-based resin foam molded article (11) was 0.02 g / cm 3 The expansion ratio was 50. Thereafter, this recycled styrene-based resin foam molded article (11) was stored in a drying room at 50° C. for 1 day. The results are shown in Table 2.

[0162] [Examples 12 to 20] Recycled expandable styrene-based resin particles (12) to (20), recycled pre-expanded styrene-based resin particles (12) to (20), and recycled styrene-based resin foam molded articles (12) to (20) were obtained in the same manner as in Example 11, except that the recycled styrene-based resin raw material particles shown in Table 2 were used as the recycled styrene-based resin particles (A). The results are shown in Table 2.

[0163] Comparative Examples 3 to 4 Recycled expandable styrene-based resin particles (C3) to (C4), recycled pre-expanded styrene-based resin particles (C3) to (C4), and recycled styrene-based resin foam molded articles (C3) to (C4) were produced in the same manner as in Example 11, except that the recycled styrene-based resin raw material particles shown in Table 2 were used as the recycled styrene-based resin particles (A). The results are shown in Table 2.

[0164]

[0165]

[0166] The recycled expandable styrene-based resin particles, recycled pre-expanded styrene-based resin particles, and recycled styrene-based resin foam molded articles according to embodiments of the present invention are suitable for use as insulation materials for homes and automobiles, thermal insulation materials for building materials, transport packaging materials for fish boxes and food containers, cushioning materials, etc. More specifically, the recycled expandable styrene-based resin particles, recycled pre-expanded styrene-based resin particles, and recycled styrene-based resin foam molded articles according to embodiments of the present invention are suitable for use as wall insulation materials, floor insulation materials, roof insulation materials, automotive 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, returnable containers), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, embankment materials (e.g., embankment blocks), tatami mat core materials, cushion core materials, concrete aggregates, etc.

Claims

1. Regenerated expandable styrene-based resin particles obtained by injecting and impregnating a blowing agent into recycled styrene-based resin particles (A), * a * b * In the color system, L * + | a * |+(|b * |) 3 The recycled expandable styrene-based resin particles have a color value of 20 to 800 as calculated by the above formula (1).

2. The recycled expandable styrene-based resin particles according to claim 1, wherein the recycled styrene-based resin particles (A) are obtained by nuclear polymerization of a styrene-based monomer using recycled styrene-based resin raw material particles (a) containing 10 mg / kg to 800 mg / kg of metallic zinc element as a nucleus.

3. The recycled expandable styrene-based resin particles according to claim 1, wherein the recycled styrene-based resin particles (A) contain 10 mg / kg to 800 mg / kg of metallic zinc element.

4. 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 3, wherein the pre-expanded bulk expansion ratio is 2 to 150 times.

5. A recycled styrene-based resin foamed molding produced from the recycled pre-expanded styrene-based resin particles according to claim 4.

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