Expandable styrene resin particles, pre-expanded styrene resin particles, and styrene resin foam molded article

Abstract

Provided are foamable styrene-based resin particles and a method for manufacturing the same. The foamable styrene-based resin particles have a high environmental contribution and excellent mechanical strength as a molded product and include a resin component containing a styrene-based resin and a resin other than the styrene-based resin. Also provided are pre-foamed styrene-based resin particles obtained from such foamable styrene-based resin particles. Additionally provided is a styrene-based resin foam molded article molded from such foamable styrene-based resin particles or pre-foamed styrene-based resin particles.　Foamable styrene-based resin particles according to an embodiment of the present invention include: a resin component containing 70-99 mass% of a styrene-based resin (A), 1-30 mass% of a resin (B) other than the styrene-based resin (A); and a volatile foaming agent. At least 50 mass% of the styrene-based resin (A) is a recycled styrene-based resin, the resin (B) contains an AS resin, and the proportion of the AS resin is 0.001-20 mass% relative to the styrene-based resin (A).

Description

[Technical Field]

[0001] The present invention relates to expandable styrene-based resin particles, pre-expanded styrene-based resin particles, and foamed styrene-based resin molded articles. [Background technology]

[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, heat-retaining materials for building materials, transport packaging materials for fish boxes and food containers, cushioning materials, etc. Among these, in-mold foamed molded articles produced using expandable particles (typically expandable polystyrene-based resin particles or pre-expanded styrene-based resin particles obtained by pre-expanding them) as a raw material are widely used because of advantages such as the ease of obtaining the desired shape. Such foamed molded articles are composed of a plurality of expandable particles fused together.

[0003] Styrenic resin foam molded products, which are typical foam molded products, have drawbacks due to the characteristics of styrene resins, such as being brittle to impacts and being vulnerable to oils and solvents. To overcome these drawbacks, foamed products made from olefin resins such as ethylene resins and propylene resins, and foamed products made from ethylene-styrene polymers, have been proposed (see, for example, Patent Document 1). However, these foamed products require rapid pre-expansion after production of the foamed olefin resin particles or expandable ethylene-styrene polymer particles, due to the tendency of the volatile blowing agent impregnated into these raw material particles to escape, and the produced particles must be stored in a pressurized container, resulting in complex manufacturing and storage issues.

[0004] In addition, a foam molded article has been proposed in which a styrene-based resin and a resin other than a styrene-based resin are melt-blended in advance in a kneader such as an extruder, and then the mixture is impregnated with a volatile blowing agent and foamed. Specifically, a technology has been proposed for producing a foam in which pellets of a vinyl aromatic polymer raw material containing a resin other than a styrene-based resin are heat-melted and then impregnated with a blowing agent and foamed (e.g., Patent Document 2). However, this technology involves mixing a resin other than a styrene-based resin to adjust the cell diameter of the foam, and the content of the resin other than a styrene-based resin in the resin components is small, so blending a resin other than a styrene-based resin does not lead to an improvement in the mechanical properties of a styrene-based resin foam molded article.

[0005] Meanwhile, with growing calls for the creation of a recycling-oriented society, there is a desire to move away from fossil fuels in the materials field, just as there is in energy, and the use of bioplastics as an alternative to fossil fuel-derived plastics has attracted attention. Representative examples of bioplastics include biomass plastics made from biomass as a raw material and biodegradable plastics that are not made from biomass as a raw material. Biomass is an organic compound photosynthesized from carbon dioxide and water, and by utilizing it, it can be converted back into carbon dioxide and water, making it a so-called carbon-neutral renewable energy source. Recently, the practical application of biomass plastics made from biomass has been progressing rapidly, and attempts have been made to produce various resins from biomass raw materials (e.g., Patent Document 3).

[0006] Furthermore, 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 issue, causing environmental pollution, global warming, and a lack of landfill sites. For this reason, there is a strong social demand for the reuse of plastic waste, and various methods for recycling plastic waste are being considered, 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, is attracting attention from the perspective of resource circulation and reducing environmental impact. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 48-101457 [Patent Document 2] Special Publication No. 47-26097 [Patent Document 3] Japanese Patent Application Publication No. 2019-182528 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above-mentioned problems of the related art, and its main object is to provide expandable styrene-based resin particles that are environmentally friendly and contain a resin component that includes a styrene-based resin and a resin other than a styrene-based resin, and that result in molded articles with excellent mechanical strength, and a method for producing the same. Another object is to provide pre-expanded styrene-based resin particles obtained from such expandable styrene-based resin particles. Another object is to provide a styrene-based resin foam molded article molded from such expandable styrene-based resin particles or pre-expanded styrene-based resin particles. [Means for solving the problem]

[0009] The expandable styrene-based resin particles according to an embodiment of the present invention are Expandable styrene-based resin particles containing a resin component containing 70% by mass to 99% by mass of a styrene-based resin (A) and 1% by mass to 30% by mass of a resin (B) other than the styrene-based resin (A), and a volatile blowing agent, 50% by mass or more of the styrene-based resin (A) is recycled styrene-based resin, the resin (B) comprises an AS resin, The content of the AS resin is 0.001% by mass to 20% by mass relative to the styrene-based resin (A).

[0010] In one embodiment, the styrene-based resin (A) is polystyrene.

[0011] In one embodiment, the resin (B) includes an ABS resin.

[0012] In one embodiment, the content of the ABS resin is 0.001% by mass to 5% by mass relative to the styrene-based resin (A).

[0013] In one embodiment, the resin (B) comprises a PC resin.

[0014] In one embodiment, the content of the PC resin is 0.001% by mass to 5% by mass relative to the styrene-based resin (A).

[0015] The pre-expanded styrene-based resin particles according to an embodiment of the present invention are Pre-expanded styrene-based resin particles obtained by pre-expanding the expandable styrene-based resin particles, The bulk expansion ratio of the pre-expanded foam is 1.6 times or more and less than 80 times.

[0016] The styrene-based resin foam molded article according to the embodiment of the present invention is molded from the expandable styrene-based resin particles.

[0017] The styrene-based resin foamed molded article according to the embodiment of the present invention is molded from the pre-expanded styrene-based resin particles. [Effects of the Invention]

[0018] According to the present invention, there are provided expandable styrene-based resin particles that are highly environmentally friendly and contain a resin component that includes a styrene-based resin and a resin other than a styrene-based resin, and that result in molded articles with excellent mechanical strength, as well as a method for producing the same. Furthermore, there are also provided pre-expanded styrene-based resin particles obtained from the expandable styrene-based resin particles. Furthermore, there are also provided styrene-based resin foam molded articles molded from the expandable styrene-based resin particles or pre-expanded styrene-based resin particles. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an apparatus suitable for producing expandable styrene-based resin particles according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0021] In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0022] <<A. Expandable styrene resin particles>> The expandable styrene-based resin particles according to an embodiment of the present invention have a particle shape as a whole.

[0023] The average particle diameter of the expandable styrene-based resin particles according to an embodiment of the present invention is preferably 0.3 mm to 3.0 mm, and more preferably 0.3 mm to 2.0 mm. The average particle diameter can be measured in accordance with JIS Z 8815. Specifically, the average particle diameter is the value measured as the particle diameter at 50% of the cumulative value from the particle size distribution in the sieving test of JIS Z 8815. The shape of the expandable styrene-based resin particles 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, oval spherical (egg-shaped), cylindrical, and approximately cylindrical shapes.

[0024] The MFR of the expandable styrene-based resin particles according to an embodiment of the present invention is preferably 2 g / 10 min to 20 g / 10 min, more preferably 3 g / 10 min to 18 g / 10 min, even more preferably 4 g / 10 min to 16 g / 10 min, and particularly preferably 5 g / 10 min to 14 g / 10 min, in order to further exhibit the effects of the present invention. The MER of the expandable styrene-based resin particles according to an embodiment of the present invention is a value measured under conditions of 200°C and a load of 5 kg.

[0025] The weight average molecular weight of the expandable styrene-based resin particles according to an embodiment of the present invention is preferably 150,000 to 300,000, more preferably 160,000 to 290,000, even more preferably 170,000 to 280,000, and particularly preferably 180,000 to 270,000, in order to further exhibit the effects of the present invention.

[0026] The expandable styrene-based resin particles according to an embodiment of the present invention are expandable styrene-based resin particles containing a resin component containing 70% by mass to 99% by mass of a styrene-based resin and 1% by mass to 30% by mass of a resin other than a styrene-based resin, and a volatile blowing agent, wherein 50% by mass or more of the styrene-based resin is recycled styrene-based resin.

[0027] <A-1. Resin components> The resin component contains 70% to 99% by mass of a styrene-based resin (A) and 1% to 30% by mass of a resin (B) other than the styrene-based resin (A). The resin (B) may be any resin other than the styrene-based resin (A), and may be, for example, a styrene-based resin other than the styrene-based resin (A) (such as an AS resin or an ABS resin).

[0028] The content ratio of each resin in the resin components can be analyzed by infrared spectroscopy (single reflection ATR method). The presence or absence and content ratio of the resin can be confirmed based on the component peaks of the resin obtained by infrared spectroscopy (single reflection ATR method). For example, the presence and content ratio of polystyrene can be confirmed by -1 Based on the peak observed at 2240 cm, the presence and content of AS resin were confirmed. -1 Based on the peak observed at 965 cm, the presence and content of ABS resin was confirmed. -1 Based on the peak observed at 1770 cm, the presence and content of PC resin were confirmed. -1 This can be confirmed based on the peaks observed at

[0029] Infrared spectroscopy (single reflection ATR method) can be measured, for example, using the following equipment and conditions. Measurement equipment: Fourier transform infrared spectrophotometer "Nicolet iS10" (manufactured by Thermo Scientific) ·Single-reflection horizontal ATR: Smart-iTR (manufactured by Thermo SCIENTIFIC) ATR crystal: Diamond with ZnSe lens, angle = 42° ·Measurement method: -ATR method ·Measurement wavenumber range: 4000cm -1 ~650cm -1 Wavenumber dependence of measurement depth: Uncorrected Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter ·Resolution: 4cm -1 Number of measurements: 16 (same as for background measurement)

[0030] <A-1-1. Styrenic resin (A)> The styrenic resin (A) may be only one kind or two or more kinds.

[0031] Typically, the content ratio of the styrenic resin (A) in the resin component is 70% to 99% by mass, preferably 72% to 98.5% by mass, more preferably 75% to 98% by mass, particularly preferably 77% to 98% by mass, and most preferably 80% to 98% by mass. If the content ratio of the styrenic resin (A) in the resin component is within the above range, the effects of the present invention can be more effectively expressed. If the content ratio of the styrenic resin (A) in the resin component is too low outside the above range, there is a risk that the characteristics of the styrenic resin (A) cannot be fully expressed. If the content ratio of the styrenic resin (A) in the resin component is too high outside the above range, the mechanical properties of the molded product may be inferior.

[0032] The styrenic resin (A) includes a styrenic polymer containing a styrenic monomer as a monomer component. The content ratio of the styrenic polymer in the styrenic resin (A) can adopt any appropriate content ratio within the range that does not impair the effects of the present invention. Such a content ratio is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more. The upper limit of the above content ratio is preferably 100% by mass or less.

[0033] [ The styrene-based monomer includes styrene or a styrene derivative. Examples of the styrene derivative include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. The styrene-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.

[0034] The styrene polymer containing a styrene monomer as a monomer component is preferably a styrene polymer containing a styrene monomer as the main monomer component. Examples of such styrene polymers include copolymers of a styrene monomer and a copolymerization component. A typical example of the copolymerization component is a vinyl monomer. In this specification, the term "main component" refers to a component whose content in all components 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.

[0035] Examples of the vinyl monomer include polyfunctional monomers, (meth)acrylic acid ester monomers, maleic acid ester monomers, fumaric acid ester monomers, etc. Only one type of vinyl monomer may be used, or two or more types may be used.

[0036] 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. The use of polyfunctional monomers can impart a branched structure to the polystyrene resin. The content of the polyfunctional monomer in the total monomer components constituting the styrene resin is preferably 0% by mass to 0.1% by mass, and more preferably 0.005% by mass to 0.05% by mass.

[0037] 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. Among these (meth)acrylic acid ester monomers, butyl acrylate, 2-ethylhexyl acrylate, and ethyl acrylate are preferred, with butyl acrylate being more preferred. Use of a (meth)acrylic acid ester monomer can lower the glass transition temperature (Tg) of the styrene-based resin. The content of the acrylic acid ester monomer in the total monomer components constituting the styrene-based resin is preferably 0% by mass to 4.0% by mass, and more preferably 0.1% by mass to 3.0% by mass.

[0038] An example of the maleate monomer is dimethyl maleate.

[0039] Examples of the fumarate monomer include dimethyl fumarate, diethyl fumarate, and ethyl fumarate.

[0040] The styrene-based resin (A) is preferably polystyrene, since it can more effectively exhibit the effects of the present invention.

[0041] The styrene resin (A) typically contains 50% by mass or more of recycled styrene resin. The content ratio of the recycled styrene resin in the styrene resin is preferably 60% to 100% by mass, more preferably 70% to 100% by mass, still more preferably 80% to 100% by mass, particularly preferably 90% to 100% by mass, and most preferably substantially 100% by mass. If the content ratio of the recycled styrene resin in the styrene resin (A) is within the above range, expandable styrene resin particles with a high environmental contribution can be provided.

[0042] The recycled styrene resin may be only one kind or two or more kinds.

[0043] As the recycled styrene resin, any appropriate recycled styrene resin can be adopted as long as the effects of the present invention are not impaired. Examples of such recycled styrene resins include recycled products of foamed styrene (molded products, block molded products, etc.), foamed sheets (tray containers, sheet waste materials, etc.), and plastic materials used in household electrical appliances. As the recycled styrene resin, commercially available products such as the product named "Epsrem" manufactured by Sekisui Chemical Co., Ltd. may be adopted.

[0044] If the amount of the recycled styrene resin used as the styrene resin (A) is small, there is a risk that the environmental contribution will be low.

[0045] <A-1-2. Resin (B)> The resin (B) is a resin other than the styrene resin (A). That is, the resin (B) may be a styrene resin other than the styrene resin (A), such as an AS resin or an ABS resin, or a resin other than the styrene resin other than the styrene resin (A), such as a PC resin. The resin (B) may be only one kind or two or more kinds.

[0046] The content of resin (B) in the resin component is typically 1% by mass to 30% by mass, preferably 1.5% by mass to 28% by mass, more preferably 2% by mass to 25% by mass, particularly preferably 2% by mass to 23% by mass, and most preferably 2% by mass to 20% by mass. When the content of resin (B) in the resin component is within the above range, the effects of the present invention can be more effectively achieved. If the content of resin (B) in the resin component is too low outside the above range, the mechanical properties of the molded product may be poor. If the content of resin (B) in the resin component is too high outside the above range, the MFR decreases, resulting in poor flowability and increased clogging of the die discharge holes. In addition, shear heat generation during discharge from the multi-hole die increases, and cooling after underwater cutting is difficult, which may cause particle contact and coalescence, resulting in an increase in interlocked particles.

[0047] In an embodiment of the present invention, resin (B) typically comprises an AS resin.

[0048] The content of the AS resin relative to the styrene-based resin (A) is typically 0.001% to 20% by mass, preferably 0.01% to 18% by mass, more preferably 0.1% to 15% by mass, even more preferably 1% to 12% by mass, particularly preferably 2% to 10% by mass, and most preferably 3% to 8% by mass. When the AS resin content is within the above range, the effects of the present invention can be more effectively exhibited, and in particular, the mechanical strength of the molded article can be further improved. Furthermore, when the AS resin content is within the above range, the viscosity of the resin component is more likely to increase, which reduces the likelihood of coalescence of resin particles immediately after cutting during the production of expandable styrene-based resin particles according to an embodiment of the present invention, thereby reducing the number of coalesced particles and the occurrence of cutting defects. Furthermore, when the AS resin content is within the above range, the heat resistance of the molded article can be improved. Furthermore, when the AS resin content is within the above range, the oil resistance of the molded article can be improved.

[0049] In an embodiment of the present invention, the resin (B) may include an ABS resin.

[0050] The content of the ABS resin relative to the styrene-based resin (A) is preferably 5% by mass or less, more preferably 0.001% to 5% by mass, even more preferably 0.01% to 4% by mass, particularly preferably 0.1% to 3% by mass, and most preferably 0.5% to 3% by mass. When the content of the ABS resin is within the above range, the elastic modulus of the molded article can be further improved. Furthermore, when the content of the ABS resin is within the above range, the bending stress of the molded article can be improved, and bending fatigue resistance can be improved.

[0051] In an embodiment of the present invention, the resin (B) may include a PC resin (polycarbonate resin).

[0052] The content of the PC resin relative to the styrene-based resin (A) is preferably 5% by mass or less, more preferably 0.001% by mass to 5% by mass, even more preferably 0.01% by mass to 4% by mass, particularly preferably 0.1% by mass to 3% by mass, and most preferably 0.5% by mass to 3% by mass. If the content of the PC resin is within the above range, the impact resistance of the molded article can be further improved.

[0053] Resin (B) may contain any other appropriate resin, such as an olefin resin or polyester, as long as the effect of the present invention is not impaired.

[0054] <A-2. Volatile foaming agent> The volatile foaming agent may be of one type only, or may be of two or more types.

[0055] In an embodiment of the present invention, the volatile blowing agent preferably contains isopentane. When the volatile blowing agent contains isopentane, the appearance of the molded article can be excellent. This is presumably due to the plasticizing effect of isopentane, which improves the elongation of the resin component.

[0056] The content of isopentane in the volatile blowing agent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, even more preferably 80% by mass to 100% by mass, still more preferably 90% by mass to 100% by mass, particularly preferably 95% by mass to 100% by mass, and most preferably substantially 100% by mass.

[0057] In an embodiment of the present invention, any suitable volatile blowing agent other than isopentane may be used as long as it does not impair the effects of the present invention. Such a volatile 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, n-pentane, 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 volatile blowing agent.

[0058] The content of the volatile blowing agent can be appropriately set depending on the purpose, as long as it is an amount sufficient to form pre-expanded styrene-based resin particles and a styrene-based resin foam molded article. The content of the volatile blowing agent is preferably 1.0 to 10 parts by mass, more preferably 2.0 to 9.0 parts by mass, even more preferably 3.0 to 8.0 parts by mass, and particularly preferably 4.0 to 7.0 parts by mass, per 100 parts by mass of the resin component, in order to further exhibit the effects of the present invention.

[0059] <A-3. Other ingredients> The expandable styrene-based resin particles according to an embodiment of the present invention may contain a partial ester of a higher fatty acid and an alcohol to prevent the escape of a volatile blowing agent. 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 monoglycerides and stearic acid diglycerides. The content of the partial ester of a higher fatty acid and an alcohol is preferably 0 to 3 parts by mass, more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the resin component. The partial ester of a higher fatty acid and an alcohol can be added to the resin component by commonly used methods, such as a dry blending method, a masterbatch method, or a melt injection method.

[0060] The expandable styrene-based resin particles according to an embodiment of the present invention 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.

[0061] The expandable styrene-based resin particles according to an embodiment of the present invention may contain a flame retardant or a flame retardant aid. The flame retardant or flame retardant aid may be a single type or two or more types. Examples of flame retardants include tetrabromocyclooctane, hexabromocyclododecane, hexabromocyclohexane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol F, tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-diglycidyl ether, 2,2-bis[4'(2'',3''-dibromoalkoxy)-3',5'-dibromophenyl]-propane, and tris(tribromophenoxy)triazine. 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.

[0062] The expandable styrene-based resin particles according to an embodiment of the present invention 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.

[0063] The expandable styrene-based resin particles according to an embodiment of the present invention may contain other additives. Examples of such other additives include pigments, radiant heat transfer suppressing components, crosslinkers, plasticizers, stabilizers, fillers, lubricants, colorants, antistatic agents, spreading agents, weathering agents, antioxidants, antifogging agents, and fragrances. The other additives may be one type only or two or more types.

[0064] <A-4. Surface treatment> The expandable styrene-based resin particles according to an embodiment of the present invention may be surface-treated, preferably with at least one selected from silicone oil, antistatic agents, fatty acid metal salts, and fusion accelerators.

[0065] When the expandable styrene-based resin particles according to an embodiment of the present invention are surface-treated with silicone oil, the amount of silicone oil used per 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.003 to 0.28 parts by mass, even more preferably 0.005 to 0.25 parts by mass, particularly preferably 0.008 to 0.23 parts by mass, and most preferably 0.01 to 0.23 parts by mass. If the amount of silicone oil used is too small outside the above range, for example, when an antistatic agent is used, the affinity with the antistatic agent during pre-expansion 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.

[0066] The silicone oil may be of one type only, or of two or more types.

[0067] 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.

[0068] When the expandable styrene-based resin particles according to an embodiment of the present invention are surface-treated with an antistatic agent, the amount of the antistatic agent used per 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of the antistatic agent is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of the antistatic agent is too large outside the above range, the surface of the pre-expanded styrene-based resin particles or the styrene-based resin foam molded article may become sticky.

[0069] The antistatic agent may be of one type only, or may be of two or more types.

[0070] Any appropriate antistatic agent may be used as long as it does not impair the effects of the present invention. In order to further enhance 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.

[0071] The nonionic surfactant may be one type only, or two or more types may be used.

[0072] As the nonionic surfactant, any appropriate nonionic surfactant may be used as long as it does not impair the effects of the present invention. Examples of nonionic surfactants that can further enhance 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,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.

[0073] When a nonionic surfactant is used as at least a part of the antistatic agent, the amount of the nonionic surfactant used per 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of 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 outside the above range, the surface of the pre-expanded styrene-based resin particles or the styrene-based resin foam molded article may become sticky.

[0074] The fatty acid glyceride may be one kind or two or more kinds.

[0075] 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.

[0076] When a fatty acid glyceride is used as at least a part of the antistatic agent, the amount of the fatty acid glyceride relative to 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.005 to 0.28 parts by mass, even more preferably 0.01 to 0.27 parts by mass, particularly preferably 0.015 to 0.26 parts by mass, and most preferably 0.02 to 0.25 parts by mass. If the amount of fatty acid glyceride is too small outside the above range, static electricity may be easily generated during pre-expansion. If the amount of fatty acid glyceride is too large outside the above range, the surface of the pre-expanded styrene-based resin particles or the styrene-based resin foam molded article may become sticky.

[0077] When the expandable styrene-based resin particles according to an embodiment of the present invention are surface-treated with a fatty acid metal salt, the amount of fatty acid metal salt used per 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.005 to 0.5 parts by mass, more preferably 0.007 to 0.45 parts by mass, even more preferably 0.01 to 0.4 parts by mass, particularly preferably 0.015 to 0.35 parts by mass, and most preferably 0.02 to 0.3 parts by mass. If the amount of fatty acid metal salt is too small 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 large outside the above range, too much metal salt may be present during pre-expansion, making the particles more likely to be charged, generating static electricity, and potentially resulting in poor fusion of the molded article.

[0078] The fatty acid metal salt may be of one kind or of two or more kinds.

[0079] 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.

[0080] When the expandable styrene-based resin particles according to an embodiment of the present invention are surface-treated with a fusion accelerator, the amount of the fusion accelerator used per 100 parts by mass of the expandable styrene-based resin particles before surface treatment is preferably 0.01 to 0.8 parts by mass, more preferably 0.01 to 0.7 parts by mass, even more preferably 0.01 to 0.6 parts by mass, particularly preferably 0.01 to 0.55 parts by mass, and most preferably 0.013 to 0.5 parts by mass. If the amount of the fusion accelerator is too small outside the above range, the fusion properties may decrease during molding, making it impossible to obtain a good styrene-based resin foam molded article. If the amount of the fusion accelerator is too large outside the above range, blocking may occur during pre-expansion.

[0081] The fusion promoter may be of one kind or two or more kinds.

[0082] 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 hydroxystearic acid triglyceride are preferred as the fusion promoter in that they can further demonstrate the effects of the present invention.

[0083] <A-5. Method for producing expandable styrene resin particles> The expandable styrene-based resin particles according to an embodiment of the present invention can be produced by any appropriate method as long as the effects of the present invention are not impaired. In terms of being able to further demonstrate the effects of the present invention, the expandable styrene-based resin particles are preferably obtained by an underwater cutting method in which a resin composition containing a resin component and a volatile blowing agent is extruded from an extruder and simultaneously cut in water.

[0084] More specifically, the method for producing expandable styrene-based resin particles according to an embodiment of the present invention by the underwater cutting method involves feeding a resin component containing 70% by mass to 99% by mass of a styrene-based resin and 1% by mass to 30% by mass of a resin other than a styrene-based resin into an extruder, heating and melting the resin, injecting a volatile blowing agent under pressure midway through the extruder, and extruding the resulting resin composition into water through a multi-hole die, and simultaneously cutting the resin composition in water to form resin particles.

[0085] 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 may be cooled too much, the die holes may be easily clogged, the pressure inside the die may increase, and extrusion may become 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.

[0086] 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.

[0087] In the underwater cutting method, a mold having 50 to 500 discharge holes in a multi-hole die is used, and the water pressure is preferably adjusted to 0.10 MPa to 2.00 MPa, and the discharge rate is preferably adjusted to 50 kg / h to 300 kg / h. 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 tend to change due to the inclusion of additives derived from recycled raw materials in arbitrary amounts, requiring strict adjustment of the water pressure and discharge rate in the underwater cutting method.

[0088] 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, still more preferably 0.15 MPa to 1.80 MPa, and particularly preferably 0.20 MPa to 1.60 MPa.

[0089] 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.

[0090] An example of an apparatus suitable for producing expandable styrene-based resin particles according to an embodiment of the present invention by the underwater cutting method is shown in Fig. 1. This production apparatus comprises an extruder 1 having a raw material supply hopper 11 for charging resin components upstream in the resin flow direction (from left to right in Fig. 1), a volatile blowing agent supply port 12 having a high-pressure pump 13 downstream of the raw material supply hopper 11 in the resin flow direction, and a multi-hole die 2 at the end in the resin flow direction; a cutting chamber 3 arranged to cover the outlet of the multi-hole die 2, having a cutter 31 rotatably 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 into which the expandable styrene-based resin particles cut in the cutting chamber 3 are introduced together with water and which separates the water from the expandable styrene-based resin particles; and a container 7 for storing the expandable styrene-based resin particles separated in the dehydrator 5.

[0091] The extruder 1 can be a known extruder used in extrusion molding of resin compositions. Examples of such extruders include single-screw extruders, twin-screw extruders, and tandem extruders. The extruder 1 receives resin components from a raw material supply hopper 11, heats and kneads them within the extruder 1, and transports the molten mixture downstream in the resin flow direction. When the molten mixture reaches a volatile blowing agent supply port 12, a volatile blowing agent pumped by a high-pressure pump 13 is mixed into the molten mixture. The resulting resin composition is then extruded through a multi-hole die 2 into a cutting chamber 3, where it comes into contact with water and is cut by a cutter 31 underwater. The cut resin composition becomes spherical particles of approximately uniform particle size and is transported from the cutting chamber 3 to a dehydrator 5 by a circulating water flow. The 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.

[0092] <<B. Pre-expanded styrene resin particles>> The pre-expanded styrene-based resin particles are obtained by pre-expanding expandable styrene-based resin particles.

[0093] The pre-expanded styrene-based resin particles preferably have an average cell diameter of 0.04 mm to 1.10 mm, more preferably 0.04 mm to 1.00 mm, even more preferably 0.04 mm to 0.90 mm, particularly preferably 0.04 mm to 0.80 mm, and most preferably 0.04 mm to 0.70 mm. When the average cell diameter of the pre-expanded styrene-based resin particles is within the above range, it is possible to provide pre-expanded styrene-based resin particles that can better prevent blocking during expansion and molding, and that can exhibit better fusion properties and surface properties while further suppressing electrostatic charge during expansion and molding, thereby enabling the molding of styrene-based resin foam molded articles with less static electricity.

[0094] That is, the pre-expanded styrene-based resin particles according to an embodiment of the present invention are obtained by pre-expanding the expandable styrene-based resin particles described in Section A above. Pre-expanding involves expanding the expandable styrene-based resin particles to a desired bulk expansion ratio (bulk density) using steam or the like. The bulk expansion ratio of the pre-expanded styrene-based resin particles is preferably 1.6 times or more and less than 80 times, more preferably 2 times to 78 times, even more preferably 10 times to 75 times, and particularly preferably 15 times to 72 times. The bulk density is the reciprocal of the bulk expansion ratio. The bulk expansion ratio and bulk density can be determined, for example, as follows. When the bulk expansion ratio of the 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 pre-expanded styrene-based resin particles that can mold styrene-based resin foam molded articles with less static electricity.

[0095] A measurement sample of W (g) of expandable styrene resin particles is collected. This measurement sample is allowed to fall naturally into a measuring cylinder, and the volume of the measurement sample dropped into the measuring cylinder is V (cm 3 ) is measured using an apparent density measuring instrument conforming to JIS K 6911. From the mass and volume of the measurement sample, the bulk expansion ratio and bulk density can be calculated according to the following formulas. Bulk foaming ratio (times = cm 3 / g) = Volume of measurement sample (V) / Mass of measurement sample (W) Bulk density (g / cm 3 ) = mass of measurement sample (W) / volume of measurement sample (V)

[0096] In one representative embodiment, the pre-expanded styrene-based resin particles can be used to form a styrene-based resin foamed molded article. In another embodiment, the pre-expanded styrene-based resin particles can be used as they are as a buffer material, a heat insulating material, etc. When the pre-expanded styrene-based resin particles are used as they are, the pre-expanded styrene-based resin particles can preferably be used as a packed body in which a large number of the pre-expanded styrene-based resin particles are filled into a bag.

[0097] <<C. Styrene-based resin foam molded body>> A styrene-based resin foam molded article according to one embodiment of the present invention is a styrene-based resin foam molded article molded from expandable styrene-based resin particles. Another styrene-based resin foam molded article according to another embodiment of the present invention is a styrene-based resin foam molded article molded from pre-expanded styrene-based resin particles obtained by pre-expanding expandable styrene-based resin particles.

[0098] The styrene-based resin foam molded article typically contains expanded styrene-based resin particles (hereinafter sometimes simply referred to as "expanded particles") obtained by further expanding pre-expanded styrene-based resin particles.

[0099] A styrene-based resin foam molded article is typically composed of a plurality of foam particles fused together.

[0100] Styrenic resin foam molded articles can typically be produced by placing pre-expanded styrene-based resin particles in a mold having a predetermined shape depending on the purpose and performing in-mold foam molding. More specifically, in-mold foam molding includes (i) filling pre-expanded styrene-based resin particles into a closed mold having a large number of small holes, (ii) heating and expanding the 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 integrate them by the heat expansion. The density of the styrene-based resin foam molded article can be appropriately set depending on the purpose. The density of the styrene-based resin foam molded article can be adjusted, for example, by previously adjusting the bulk expansion ratio of the pre-expanded styrene-based resin particles to be filled in the mold or by adjusting the amount of pre-expanded styrene-based resin particles filled in the mold.

[0101] 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 120 seconds, more preferably 10 seconds to 80 seconds. The molding vapor pressure of the heat-foaming (gauge pressure of the heat transfer medium blown in) is preferably 0.04 MPa to 0.1 MPa, more preferably 0.06 MPa to 0.09 MPa. Heat-foaming under these conditions allows the expanded particles to be well fused to each other.

[0102] If necessary, the pre-expanded styrene-based resin particles may be aged before molding into a styrene-based resin expansion molded article. The aging temperature of the 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 pre-expanded styrene-based resin particles may dissipate, resulting in a decrease in moldability.

[0103] The bulk expansion ratio of the expanded beads in the styrene resin expansion molded article is preferably 1.6 times or more and less than 80 times, more preferably 2 times to 78 times, still more preferably 10 times to 75 times, and particularly preferably 15 times to 72 times.

[0104] The styrene-based resin expansion molded article according to one embodiment of the present invention has excellent mechanical strength, and the 10% compressive stress of a 60-fold expansion molded article is preferably 0.06 MPa or more, more preferably 0.07 MPa to 0.26 MPa, even more preferably 0.08 MPa to 0.25 MPa, and particularly preferably 0.09 MPa to 0.24 MPa.

[0105] The styrene resin expansion molded article according to one embodiment of the present invention has excellent mechanical strength, and the maximum bending stress of a 60-fold expansion molded article is preferably 0.11 MPa or more, more preferably 0.12 MPa to 0.35 MPa, even more preferably 0.13 MPa to 0.34 MPa, and particularly preferably 0.14 MPa to 0.33 MPa.

[0106] ≪≪D.Applications≫≫ The expandable styrene-based resin particles according to an embodiment of the present invention, the pre-expanded styrene-based resin particles according to an embodiment of the present invention, and the styrene-based resin foam molded article according to an embodiment of the present invention can be used in any suitable application, such as packaging cushioning material, iceboxes, and cushion filler, from the viewpoint of making the most of the effects of the present invention. [Example]

[0107] 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.

[0108] <Evaluation of coalesced grain ratio> The expandable polystyrene resin particles that had been separated from the water and dried in a dehydrator were placed in a sieve equipped with a sieve mesh with 1.44 mm openings, and the weight of the particles that did not pass through was measured.

[0109] <Measurement of maximum bending stress> Measurements were performed in accordance with JIS-A-9511. A molded piece measuring 400mm x 300mm x 27mm was prepared and dried in a drying room at 40°C for 24 hours. Three test pieces measuring 75mm x 300mm x 27mm were cut from the molded piece and cured for 24 hours at 23°C and 50% RH. A bending test jig was attached to a universal testing machine (Tensilon UCT-5T), the support span was set to 200mm, and the test piece was placed with the 75mm x 300mm face up and down. A load was applied at a rate of 10mm / min, and the maximum point stress (MPa) was calculated. Three tests were performed.

[0110] <Measurement of 10% compressive stress> Measurements were performed in accordance with JIS-A-9511. A molded piece measuring 400 mm x 300 mm x 27 mm was prepared and dried in a drying room at 40°C for 24 hours. Five test pieces measuring 50 mm x 50 mm x 27 mm were cut from the molded piece and cured for 24 hours at a temperature of 23°C and a humidity of 50% RH. A compression test jig was attached to a universal testing machine (Tensilon UCT-5T), and the test piece was placed with the 50 mm x 50 mm side facing up and down. A load was applied at a rate of 10 mm / min, and the stress (MPa) at 10% compression was calculated. Five tests were performed.

[0111] <Evaluation of fusion of molded products> A 400mm x 300mm x 27mm molded product was prepared and dried in a drying room at 40°C for 24 hours. After drying, a 2mm deep cut was made on the 400mm x 300mm surface of the molded product, and the molded product was broken. The foam particles on the fracture cross section were visually inspected, and the number of broken foam particles and those that had peeled off between particles and were not broken was counted. The evaluation criteria were as follows: ⊚: 90% or more of the foamed grains were broken. ◯: 70% or more but less than 90% of the foamed grains were broken.

[0112] <Productivity evaluation> We determined the impact on continuous production of the increase in extruder pressure caused by the resin's lower MFR (thicker viscosity). The evaluation criteria were as follows: 〇: Pressure is 12 MPa or less. It was determined that production was possible without any problems. △: Pressure 12-20 MPa or less. It was determined that strict adjustment of conditions such as temperature was necessary during production. ×: Pressure 20 MPa or less. It was determined that extrusion was not possible.

[0113] Example 1 The recycled styrene resin (polystyrene resin recovered from waste home appliances, manufactured by Sekisui Plastics Kanto Co., Ltd., IFS-K, MFR (200°C, 5kgf) = 3.5g / 10min): 94% by mass, AS resin (manufactured by Denka Polymer, GR-AT-R, acrylonitrile-styrene copolymer) (MFR (220°C, 98N) = 13g / 10min, MFR (200°C, 49N) = 1g / 10min): 4.0% by mass, and ABS resin (manufactured by Denka Polymer, GR-2000, acrylonitrile-butadiene-styrene copolymer) (MFR (220°C, 98N) = 13g / 10min, MFR (200°C, 49N) = 1g / 10min): 4.0% by mass. A mixed resin (100% by mass) of 1.0% by mass of propylene copolymer (MFR (220°C, 98N) = 13 g / 10 min), 1.0% by mass of PC resin (Teijin, K-1300Y, polycarbonate resin) (MFR (300°C, 1.2 kg) = 2.8 g / 10 min), and 0.7 parts by mass of talc were fed into a φ100 mm single-screw extruder and melted by heating. Then, 5.5 parts by mass of isopentane (100%) as a volatile blowing agent was injected per 100 parts by mass of the mixed resin, and melt-mixed. The resin composition molten in the extruder was then kneaded and cooled, and extruded at a resin composition temperature of 181°C through a multi-hole die with 312 extrusion holes φ0.5 mm into a cutting chamber filled with water at 70°C. The resin composition was immediately cut in water and dehydrated through a stretching dehydrator to obtain a bulk density of 0.6 g / cm. 3 As a result, expandable styrene resin particles (1) with an average particle size of about 1.2 mm were obtained. The extrusion conditions were as follows: Discharge amount=146kg / hour Screw rotation speed = 70 rpm Extruder pressure = 11.6 MPa Gas flow rate = 7.4 kg / hour Cutter rotation speed = 3000 rpm Water pressure = 0.50 MPa 100 parts by mass of the obtained expandable styrene-based resin particles (1) were charged into a tumbler mixer with 0.10 parts by mass of zinc stearate, 0.20 parts by mass of stearic acid triglyceride, 0.06 parts by mass of stearic acid monoglyceride, and 0.03 parts by mass of polyethylene glycol, and the mixture was stirred for 15 minutes to surface-treat the expandable styrene-based resin particles (1). The surface-treated expandable styrene-based resin particles (1) were stored in a refrigerator at 15°C for one day, then placed in a 25-liter cylindrical batch-type expansion machine and heated with steam at a gauge pressure of 0.08 MPa for 300 seconds to obtain pre-expanded styrene-based resin particles (1). The expansion ratio of the pre-expanded styrene-based resin particles (1) was 70 times. The pre-expanded styrene resin particles (1) were left in a room temperature atmosphere for 24 hours, and then the pre-expanded styrene resin particles (1) were filled into the cavity of a molding machine having a mold cavity with dimensions of 300 mm in height, 400 mm in width, and 27 mm in depth. The pre-expanded styrene resin particles (1) were heated with steam at a gauge pressure of 0.08 MPa for 60 seconds, and then cooled until the internal pressure of the mold reached 0.01 MPa. The mold was then released from the mold, yielding a plate-shaped styrene resin foam molded product (1) corresponding to the mold. The expansion ratio of the styrene resin foam molded product (1) was 60 times. The styrene resin foam molded product (1) was then dried in a drying chamber at 30°C. The obtained styrene resin foam molded article (1) was evaluated. The results are shown in Table 1.

[0114] Examples 2 to 4 Expandable styrene-based resin particles (2) to (4) and pre-expanded styrene-based resin particles (2) to (4) were obtained in the same manner as in Example 1, except that the resin ratios and various conditions were changed as shown in Table 1. The expansion ratios of the pre-expanded styrene-based resin particles (2) to (4) were each 70 times. After leaving the pre-expanded styrene resin particles (2) to (4) at room temperature for 24 hours, a molding machine with a mold cavity measuring 300 mm in height, 400 mm in width, and 27 mm in depth was used to fill the mold cavity with the pre-expanded styrene resin particles (2) to (4). The mold cavity was heated with steam at a gauge pressure of 0.08 MPa for 60 seconds, and then cooled until the internal pressure of the mold reached 0.01 MPa. The mold was then released from the mold, yielding plate-shaped styrene resin foam molded articles (2) to (4) corresponding to the mold. The expansion ratio of the styrene resin foam molded articles (2) to (4) was 60 times, respectively. The styrene resin foam molded articles (2) to (4) were then dried in a drying chamber at 30°C. The obtained styrene resin foam molded articles (2) to (4) were evaluated. The results are shown in Table 1.

[0115] Comparative Example 1 Expandable styrene-based resin particles (C1) and pre-expanded styrene-based resin particles (C1) were obtained in the same manner as in Example 1, except that the resin ratios and various conditions were changed as shown in Table 1. The expansion ratio of the pre-expanded styrene-based resin particles (C1) was 70 times. The pre-expanded styrene resin particles (C1) were left at room temperature for 24 hours, and then filled into the cavity of a molding machine with a mold cavity measuring 300 mm in height, 400 mm in width, and 27 mm in depth. The pre-expanded styrene resin particles (C1) were heated for 60 seconds with steam at a gauge pressure of 0.08 MPa, and then cooled until the internal pressure of the mold reached 0.01 MPa. The mold was then released from the mold, yielding a plate-shaped styrene resin foam molded product (C1) corresponding to the mold. The expansion ratio of the styrene resin foam molded product (C1) was 60 times. The styrene resin foam molded product (C1) was then dried in a drying chamber at 30°C. The obtained styrene resin expansion molded article (C1) was evaluated. The results are shown in Table 1.

[0116] Comparative Example 2 Expandable styrene-based resin particles (C2) and pre-expanded styrene-based resin particles (C2) were obtained in the same manner as in Example 1, except that the resin ratios and various conditions were changed as shown in Table 1. The expansion ratio of the pre-expanded styrene-based resin particles (C2) was 70 times. After leaving the pre-expanded styrene resin particles (C2) in a room temperature atmosphere for 24 hours, a molding machine having a mold cavity with dimensions of 300 mm in height, 400 mm in width, and 27 mm in depth was used to fill the cavity of the mold with the pre-expanded styrene resin particles (C2), which were then heated for 60 seconds with steam at a gauge pressure of 0.08 MPa. The mold was then cooled until the pressure inside the mold reached 0.01 MPa, after which the particles were released from the mold. An attempt was made to produce a plate-shaped styrene resin foam molded product corresponding to the mold, but the particle diameter was too large, resulting in a poor appearance and failure to produce the product.

[0117] Comparative Example 3 An attempt was made to produce expandable styrene-based resin particles in the same manner as in Example 1, except that the resin ratio and various conditions were changed as shown in Table 1, but the extruder interlock stopped and production was not possible.

[0118] Comparative Example 4 Except for changing the volatile blowing agent to normal pentane, the same procedure as in Comparative Example 1 was carried out to obtain expandable styrene-based resin particles (C4) and pre-expanded styrene-based resin particles (C4). The expansion ratio of the pre-expanded styrene-based resin particles (C4) was 50 times. The pre-expanded styrene resin particles (C4) were left at room temperature for 24 hours, and then filled into the cavity of a molding machine with a mold cavity measuring 300 mm in height, 400 mm in width, and 27 mm in depth. The pre-expanded styrene resin particles (C4) were heated for 60 seconds with steam at a gauge pressure of 0.08 MPa, and then cooled until the internal pressure of the mold reached 0.01 MPa. The mold was then released from the mold, yielding a plate-shaped styrene resin foam molded product (C4) corresponding to the mold. The expansion ratio of the styrene resin foam molded product (C4) was 40 times. The styrene resin foam molded product (C4) was then dried in a drying chamber at 30°C. The obtained styrene resin foam molded article (C4) was evaluated. The results are shown in Table 1.

[0119] [Table 1]

[0120] Example 5 The expandable styrene resin particles (1) obtained in Example 1 were analyzed by infrared spectroscopy (single reflection ATR method) using the following equipment to determine the content ratio of each resin in the resin components contained therein. Based on the component peaks of the resins observed by this analysis, the presence or absence of mixtures and their content ratios were confirmed. The presence and content ratio of polystyrene was confirmed at 700 cm -1 Based on the peak observed at 2240 cm, the presence and content of AS resin were confirmed.-1 Based on the peak observed at 965 cm, the presence and content of ABS resin was confirmed. -1 Based on the peak observed at 1770 cm, the presence and content of PC resin were confirmed. -1 This was confirmed based on the peak observed at Measurement equipment: Fourier transform infrared spectrophotometer "Nicolet iS10" (manufactured by Thermo Scientific) ·Single-reflection horizontal ATR: Smart-iTR (manufactured by Thermo SCIENTIFIC) ATR crystal: Diamond with ZnSe lens, angle = 42° ·Measurement method: -ATR method ·Measurement wavenumber range: 4000cm -1 ~650cm -1 Wavenumber dependence of measurement depth: Uncorrected Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter ·Resolution: 4cm -1 Number of measurements: 16 (same as for background measurement) The measurement results showed that the resin components contained 94.0 mass% polystyrene, 4.0 mass% AS resin, 1.0 mass% ABS resin, and 1.0 mass% PC resin.

[0121] Example 6 The expandable styrene resin particles (2) obtained in Example 2 were examined in the same manner as in Example 5 to determine the content of each resin in the resin components contained therein. The measurement results showed that the resin components contained 85.0 mass% polystyrene, 10.0 mass% AS resin, 2.5 mass% ABS resin, and 2.5 mass% PC resin.

[0122] Example 7 The expandable styrene resin particles (3) obtained in Example 3 were examined in the same manner as in Example 5 to determine the content of each resin in the resin components contained therein. The measurement results showed that the resin components contained 70.0 mass% polystyrene, 20.0 mass% AS resin, 5.0 mass% ABS resin, and 5.0 mass% PC resin.

[0123] Example 8 The content of each resin in the resin components contained in the expandable styrene resin particles (4) obtained in Example 4 was confirmed in the same manner as in Example 5. The measurement results showed that the resin component contained 98.0 mass% polystyrene and 2.0 mass% AS resin. [Industrial Applicability]

[0124] The expandable styrene-based resin particles, pre-expanded styrene-based resin particles, and styrene-based resin foam molded articles according to embodiments of the present invention are suitable for use as heat insulating materials for homes and automobiles, etc., heat insulating materials for building materials, etc., transport packaging materials for fish boxes and food containers, packaging cushioning materials, ice boxes, cushion filling materials, etc. More specifically, the expandable styrene-based resin particles, pre-expanded styrene-based resin particles, and styrene-based resin foam molded articles are suitable for use as wall insulating materials, floor insulating materials, roof insulating materials, automobile insulating materials, hot water tank insulating materials, piping insulating materials, solar system insulating materials, water heater insulating materials, containers for food and industrial products, etc., packaging materials for fish and agricultural products, etc., embankment materials, tatami mat core materials, packaging cushioning materials, ice boxes, cushion filling materials, etc. [Explanation of symbols]

[0125] 1. Extruder 2 multi-hole die 3 Cutting Room 4. Water pump 5 Dehydration dryer 6. Aquarium 7 containers 11 Raw material supply hopper 12 Volatile foaming agent supply port 13 High-pressure pump 31 Cutter

Claims

1. A method for producing expandable styrene-based resin particles, comprising a resin component containing 70% by mass to 99% by mass of a styrene-based resin (A) and 1% by mass to 30% by mass of a resin (B) other than the styrene-based resin (A), and a volatile blowing agent, 50% by mass or more of the styrene-based resin (A) is recycled styrene-based resin, The resin (B) contains an AS resin, the content of the AS resin is 0.001% by mass to 20% by mass relative to the styrene-based resin (A); a resin composition containing the resin component and the volatile foaming agent is extruded from an extruder and simultaneously cut in water to form resin particles; A method for producing expandable styrene-based resin particles.

2. 2. The method for producing expandable styrene-based resin particles according to claim 1, wherein the styrene-based resin (A) is polystyrene.

3. The method for producing expandable styrene-based resin particles according to claim 1 , wherein the resin (B) comprises an ABS resin.

4. 4. The method for producing expandable styrene-based resin particles according to claim 3, wherein the content of the ABS resin is 0.001% by mass to 5% by mass relative to the styrene-based resin (A).

5. The method for producing expandable styrene-based resin particles according to claim 1 , wherein the resin (B) comprises a PC resin.

6. 6. The method for producing expandable styrene-based resin particles according to claim 5, wherein the content of the PC resin is 0.001% by mass to 5% by mass relative to the styrene-based resin (A).

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