Foamable styrenic resin particle, styrenic resin foam molding, and method for producing foamable styrenic resin particle

Abstract

To provide foamable styrenic resin particles which enable simple formation of a styrenic resin foam molding excellent in heat insulation property and heat resistance without requiring a special technique, and are excellent in moldability of a foam molding, and its related technique.SOLUTION: Foamable styrenic resin particles contain a styrenic base material resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a foaming agent, wherein the base material resin contains at least a first styrenic resin having 3 to 20% of a constitutional unit derived from a (meth)acrylic acid, a content ratio of the first styrenic resin to the whole base material resin is 70 wt.% or more and 90 wt.% or less, and laser scattering intensity per radiation heat transfer inhibitor unit solution concentration in the foamable styrenic resin particles is 5.0 {% / (mg / ml)} / wt.% or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to expandable styrene-based resin particles, a styrene-based resin foamed molded product, and a method for producing the expandable styrene-based resin particles. [Background technology]

[0002] Since foam molded products using polystyrene as a base resin have excellent light weight and heat insulating properties, they are widely used as heat insulating materials for housing, etc. As one measure for imparting heat insulating properties to the foam molded products, a radiation heat transfer inhibitor such as graphite is contained in the foam molded products (e.g., Patent Documents 1 and 2).

[0003] On the other hand, from the viewpoint of heat resistance, polystyrene foam molded products have a large dimensional change rate when heated, so they may be difficult to use in contact with high-temperature parts (for example, the surface of a hot water tank, etc.) As one measure to address this problem, a copolymer of styrene and other monomers is used as the base resin to reduce the dimensional change rate of the foam molded product and provide heat resistance.

[0004] In addition, it is known that expandable styrene resin particles can be molded into foams of unspecified shapes according to the mold used, and therefore have a wide range of applications.In order to utilize this advantage, it is preferable that the expandable styrene resin particles have excellent moldability.For example, it is desired that the expandable styrene resin particles can always obtain high-quality foamed molded products without being significantly affected by the conditions during pre-expansion or molding.

[0005] Patent Document 3 describes matters related to expandable styrene-based resin particles containing a styrene-(meth)acrylic acid copolymer, polystyrene, graphite, and a foaming agent. The expandable styrene-based resin particles are obtained by impregnating and polymerizing styrene into styrene-based polymer seed particles containing a styrene-(meth)acrylic acid copolymer and graphite, and styrene is unevenly distributed on the resin particle surface. It is said that this allows for the production of a styrene-based resin expanded bead molding with few gaps between particles and a good shape. On the other hand, when styrene is not impregnated and polymerized into styrene-based polymer seed particles containing a styrene-(meth)acrylic acid copolymer and graphite, it is not possible to mold an expanded molded product, or only an expanded molded product with large gaps between the expanded particles is obtained, and the moldability is significantly inferior (Comparative Example 1-3).

[0006] Patent Document 4 describes expandable thermoplastic resin particles based on a mixed resin of a heat-resistant resin and a polystyrene resin. However, the expandable thermoplastic resin particles do not contain a radiation heat transfer inhibitor such as graphite, and are not intended to provide high thermal insulation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2019 / 198790 [Patent Document 2] JP 2020-033481 A [Patent Document 3] JP 2014-148558 A [Patent Document 4] JP 2010-229205 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present disclosure is to provide expandable styrene-based resin particles and a production method thereof that can easily provide styrene-based resin foamed molded articles having excellent insulation properties and heat resistance without requiring special techniques such as unevenly distributing styrene on the surface of resin particles, and that have excellent moldability for foamed molded articles, as well as styrene-based resin foamed molded articles. [Means for solving the problem]

[0009] One aspect of the present disclosure is an expandable styrene-based resin particle comprising a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent, wherein the base resin comprises at least a first styrene-based resin having 3 to 20% of structural units derived from (meth)acrylic acid, the content of the first styrene-based resin relative to the entire base resin is 70% by weight or more and 90% by weight or less, and the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particle is 5.0{% / (mg / ml)} / weight% or more.

[0010] Preferably, the radiation heat transfer inhibitor includes a carbon-based radiation heat transfer inhibitor.

[0011] Preferably, the radiation heat transfer inhibitor is contained in an amount of 2 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the base resin.

[0012] Preferably, the brominated flame retardant has a 1% weight loss temperature in thermogravimetric analysis of 210° C. or higher and 280° C. or lower, and a bromine content of 60% by weight or higher and lower than 70% by weight.

[0013] Preferably, the base resin further contains a second styrene-based resin different from the first styrene-based resin, and the second styrene-based resin has a glass transition temperature of 95° C. or higher and 110° C. or lower.

[0014] Preferably, the blowing agent comprises an aliphatic hydrocarbon having 4 carbon atoms and / or an aliphatic hydrocarbon having 5 carbon atoms.

[0015] Preferably, the foaming agent contains at least an aliphatic hydrocarbon having 5 carbon atoms, and the content of the aliphatic hydrocarbon having 5 carbon atoms in the entire foaming agent is 70% by weight or more.

[0016] Preferably, the expandable styrene-based resin particles have a bulk density of 20 kg / m 3 The thermal conductivity of the styrene-based resin foamed molded product obtained by foaming and molding the material after curing at 60°C for 48 hours is less than 31 mW / mK.

[0017] Preferably, the expandable styrene-based resin particles have a bulk density of 20 kg / m 3 The dimensional change of the styrene-based resin foam molded product obtained by foaming and molding the product at 90°C for 168 hours is within ±1%.

[0018] One aspect of the present disclosure is a styrene-based resin foamed molded article obtained by pre-expanding the above-mentioned expandable styrene-based resin particles and foaming the pre-expanded particles.

[0019] One aspect of the present disclosure is a method for producing expandable styrene-based resin particles, the method comprising the steps of melt-kneading a styrene-based base resin, a radiation heat transfer inhibitor, and a bromine-based flame retardant in an extruder and extruding the melt-kneaded resin through small holes, cutting the extruded resin to obtain resin particles, and suspending the resin particles in water and incorporating a blowing agent to obtain expandable styrene-based resin particles, wherein the base resin comprises at least a first styrene-based resin having 3 to 20% of a constituent unit derived from (meth)acrylic acid, the content of the first styrene-based resin relative to the entire base resin is 70% by weight or more and 90% by weight or less, and the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0{% / (mg / ml)} / weight% or more.

[0020] One aspect of the present disclosure is a method for producing expandable styrene-based resin particles, the method comprising the steps of preparing a resin melt containing a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent, and extruding the resin melt through a die having a plurality of small holes into pressurized circulating water and cutting the resin melt with a rotary cutter to form particles, wherein the base resin contains at least a first styrene-based resin having 3 to 20% of a structural unit derived from (meth)acrylic acid, the content of the first styrene-based resin relative to the entire base resin is 70% by weight or more and 90% by weight or less, and the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0{% / (mg / ml)} / weight% or more. Effect of the Invention

[0021] According to the present disclosure, a styrene-based resin foam molded article having excellent heat insulation and heat resistance can be easily provided without requiring special techniques for unevenly distributing styrene on the surface of resin particles, and expandable styrene-based resin particles having excellent moldability for foam molded articles and a production method thereof, as well as a styrene-based resin foam molded article are provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <Expandable styrene resin particles> The expandable styrene-based resin particles according to one embodiment of the present disclosure contain a styrene-based base resin, a radiant heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent, and have a variety of properties.

[0023] <Base resin> The styrene-based base resin in the present disclosure contains at least a first styrene-based resin having 3 to 20% of structural units derived from (meth)acrylic acid. The first styrene-based resin is, in other words, a styrene-(meth)acrylic acid copolymer having 3 to 20% of structural units derived from (meth)acrylic acid. The structural units derived from (meth)acrylic acid in the first styrene-based resin are usually 3 to 20%, preferably 4 to 15%, and more preferably 4 to 12%.

[0024] The content of the first styrene resin relative to the entire base resin is usually 70% by weight or more and 90% by weight or less, preferably 70% by weight or more and 85% by weight or less, more preferably 70% by weight or more and 80% by weight or less. If the content of the first styrene resin is 70% by weight or more, a foamed molded product having excellent heat resistance can be obtained. If the content of the first styrene resin is 90% or less, a good foamed molded product can be obtained with a general EPS molding machine.

[0025] The Vicat softening temperature of the first styrene resin is not particularly limited, but is preferably from 110° C. to 130° C., and more preferably from 110° C. to 125° C. If the Vicat softening temperature of the first styrene resin is 110° C. or higher, a foam molded product having excellent heat resistance can be obtained, and if it is 130° C. or lower, a good foam molded product can be obtained with a general EPS molding machine.

[0026] The base resin has the first styrene-based resin as an essential component, but may further contain a resin other than the first styrene-based resin. The resin other than the first styrene-based resin may be only one type, or may be two or more types. The resin is preferably a styrene-based resin of a type different from the first styrene-based resin. In particular, it is preferable that the resin is at least one type selected from the group consisting of styrene homopolymer, styrene-acrylonitrile copolymer, styrene-methyl (meth)acrylate copolymer, and styrene-butyl (meth)acrylate copolymer, because it is relatively inexpensive among styrene-based resins, can be foamed with low-pressure steam without using a special method, and has an excellent balance of heat insulation, flame retardancy, and cushioning properties.

[0027] In one preferred embodiment, the base resin further contains a second styrene-based resin having a glass transition temperature of 95° C. or more and 110° C. or less, different from the first styrene-based resin. Examples of the second styrene-based resin include the above-mentioned styrene homopolymer, styrene-acrylonitrile copolymer, styrene-methyl (meth)acrylate copolymer, and styrene-butyl (meth)acrylate copolymer. The glass transition temperature of the second styrene-based resin is preferably 95° C. or more and 110° C. or less, and more preferably 100° C. or more and 110° C. or less. If the glass transition temperature of the second styrene-based resin is 95° C. or more, heat resistance is not impaired, and if it is 110° C. or less, moldability is not impaired.

[0028] In one preferred embodiment, the second styrene-based resin contains a styrene homopolymer. Also, in one preferred embodiment, the base resin is composed of the first styrene-based resin and the second styrene-based resin.

[0029] <Radiation heat transfer inhibitor> The expandable styrene-based resin particles according to one embodiment of the present disclosure contain a radiation heat transfer inhibitor. This makes it possible to obtain a foamed molded article having high thermal insulation properties. Here, the "radiation heat transfer inhibitor" refers to a substance that has the property of reflecting, scattering, or absorbing light in the infrared region (for example, a wavelength region of about 0.8 μm to 100 μm).

[0030] The radiation heat transfer inhibitor is not particularly limited, but from the viewpoints of dispersibility in polystyrene resins and cost, a carbon-based radiation heat transfer inhibitor is preferred. Examples of carbon-based radiation heat transfer inhibitors include graphite, carbon black, activated carbon, graphene, carbon nanotubes, etc., and graphite is more preferably used. That is, it is particularly preferred that the radiation heat transfer inhibitor contains graphite as a main component. Here, "contains as a main component" refers to a content ratio of more than 50% by weight. In a preferred embodiment, the content ratio of graphite in the entire radiation heat transfer inhibitor is more than 50% by weight, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 100% by weight (total amount).

[0031] Examples of the graphite include flake graphite, earthen graphite, spherical graphite, and artificial graphite. In the present disclosure, the term "flake" also includes scaly, flaky, or plate-like graphite. These graphites can be used alone or in combination of two or more. Among these, a graphite mixture mainly composed of flake graphite is preferred, and flake graphite is more preferred, in terms of its high radiation heat transfer suppression effect.

[0032] Examples of radiation heat transfer inhibitors other than carbon-based radiation heat transfer inhibitors include aluminum-based compounds, zinc-based compounds, magnesium-based compounds, titanium-based compounds, heat ray reflectors, metal sulfates, antimony-based compounds, metal oxides, heat ray absorbers, metal particles, etc. Specific examples include titanium oxide, aluminum, copper, etc.

[0033] The above-mentioned radiation heat transfer inhibitors may be used alone or in combination of two or more.

[0034] The average particle size of the radiation heat transfer inhibitor in the present disclosure is not particularly limited, but is preferably 12 μm or less and 2 μm or more, more preferably 10 μm or less and 2 μm or more, and even more preferably 7 μm or less and 2 μm or more. By setting the average particle size to 12 μm or less, the moldability during foam molding of the resin particles becomes good, and by setting it to 2 μm or more, it can be handled without impairing the handleability. The average particle size of the radiation heat transfer inhibitor referred to here refers to the particle size D50 (i.e., 50% volume cumulative particle size) when the cumulative volume of the total particles is 50% when the particle size distribution is measured and analyzed by a laser diffraction scattering method based on the Mie theory in accordance with ISO13320:2009 and JIS Z8825-1.

[0035] The content of the radiation heat transfer inhibitor is not particularly limited, but for example, the radiation heat transfer inhibitor can be included in an amount of 2 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the base resin. The radiation heat transfer inhibitor may be included in an amount of 3 parts by weight or more and 15 parts by weight or less, 3 parts by weight or more and 10 parts by weight or less, 4 parts by weight or more and 10 parts by weight or less, per 100 parts by weight of the base resin. In addition, the content ratio of the radiation heat transfer inhibitor to the entire expandable styrene-based resin particles can be 2.0% by weight or more and 10.0% by weight or less, 3.0% by weight or more and 8.0% by weight or less, etc. If the content of the radiation heat transfer inhibitor is 20 parts by weight or less, it becomes easier to control the expansion ratio when producing a foamed molded product, and a high expansion ratio is easily obtained. If the content of the radiation heat transfer inhibitor is 2 parts by weight or more, the desired heat insulation can be achieved.

[0036] <Laser scattering intensity> In the expandable styrene-based resin particles according to one embodiment of the present disclosure, the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0{% / (mg / ml)} / wt% or more. In this embodiment, the laser scattering intensity is a predetermined value or more, so that the dispersion of the radiation heat transfer inhibitor in the resin particles is good. As a result, the thermal conductivity of the foamed molded article is reduced, and the heat insulation is improved. A specific method for measuring the laser scattering intensity will be described in the Examples below.

[0037] <Brominated flame retardants> The bromine-based flame retardant contained in the expandable styrene-based resin particles according to one embodiment of the present disclosure is not particularly limited, and various bromine-based flame retardants can be used. In one preferred embodiment, a bromine-based flame retardant having a 1% weight loss temperature of 210°C or more and 280°C or less in thermogravimetric analysis and a bromine content of 60% by weight or more and less than 70% by weight is used.

[0038] Examples of brominated flame retardants include brominated bisphenol compounds, brominated styrene-butadiene copolymers, and brominated isocyanurate compounds. Specific examples of brominated bisphenol compounds include 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)), 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromopropyl ether)), and the like. Brominated styrene-butadiene copolymers include brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers. Examples of brominated isocyanurate compounds include tris(2,3-dibromopropyl)isocyanurate, etc. Other compounds include tetrabromocyclooctane, etc. These brominated flame retardants may be used alone or in combination of two or more.

[0039] The content of the bromine-based flame retardant is not particularly limited, but for example, the content ratio of the bromine-based flame retardant to the entire expandable styrene resin particles can be 0.8% by weight or more and 5.0% by weight or less. If the content ratio of the bromine-based flame retardant is 0.8% by weight or more, the desired flame retardant performance can be achieved. If the content ratio of the bromine-based flame retardant is 5.0% by weight or less, the adverse effect on the foam moldability can be suppressed.

[0040] The foaming agent contained in the expandable styrene-based resin particles according to one embodiment of the present disclosure is not particularly limited, but from the viewpoint of a good balance between expandability and product life and easy high expansion ratio in actual use, a volatile foaming agent is preferable, a saturated hydrocarbon is more preferable, and an aliphatic hydrocarbon having 4 or 5 carbon atoms is even more preferable. Examples of the hydrocarbon include normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, etc. These foaming agents may be used alone or in combination of two or more. In one preferred embodiment, the foaming agent contains an aliphatic hydrocarbon having 4 carbon atoms and / or an aliphatic hydrocarbon having 5 carbon atoms. In one preferred embodiment, the foaming agent contains at least an aliphatic hydrocarbon having 5 carbon atoms, and the content ratio of the aliphatic hydrocarbon having 5 carbon atoms to the entire foaming agent is 70% by weight or more, more preferably 85% by weight or more.

[0041] The content of the foaming agent is not particularly limited, but for example, assuming a mixture consisting of all components excluding the foaming agent among the components constituting the expandable styrene-based resin particles, the foaming agent is 4.0 parts by weight or more and 10.0 parts by weight or less per 100 parts by weight of the mixture, preferably 4.5 parts by weight or more and 9.5 parts by weight or less, more preferably 5.0 parts by weight or more and 9.0 parts by weight or less per 100 parts by weight of the mixture.

[0042] <Heat stabilizer> The expandable styrene-based resin particles according to one embodiment of the present disclosure may contain other components, for example, a heat stabilizer, within a range that does not impair the performance. By further containing a heat stabilizer, it is possible to suppress the deterioration of flame retardancy due to the decomposition of the bromine-based flame retardant in the manufacturing process and the deterioration of the expandable styrene-based resin particles. There is no particular limitation on the heat stabilizer, and it is appropriately selected depending on the type of base resin, the type and content of the foaming agent, the type and content of the radiation heat transfer inhibitor, the type and content of the bromine-based flame retardant, and the like. Examples of heat stabilizers include hindered amine compounds, phosphorus-based compounds, epoxy compounds, and the like, with hindered amine compounds and phosphorus-based compounds being particularly preferred. These heat stabilizers may be used alone or in combination of two or more.

[0043] <Other ingredients> The expandable styrene-based resin particles according to one embodiment of the present disclosure may further contain other components within a range that does not impair the performance thereof. Examples of the other components include a radical generator, a processing aid, a light resistance stabilizer, a nucleating agent, a foaming aid, an antistatic agent, a colorant such as a pigment, and the like.

[0044] <Method of producing expandable styrene-based resin particles> The method for producing the expandable styrene-based resin particles according to one embodiment of the present disclosure is not particularly limited, but it is preferable to produce the particles by a melt-kneading method in which a base resin and various components are melt-kneaded using an extruder, and then cut into particles. By using the melt-kneading method, the uniformity of the (meth)acrylic acid component units in the resin particles is increased. Furthermore, the radiation heat transfer inhibitor is more uniformly dispersed throughout the resin particles. Examples of the melt-kneading method include the following first melt-kneading method and second melt-kneading method.

[0045] In the first melt-kneading method, first, the base resin, the radiation heat transfer inhibitor, the bromine-based flame retardant, and other components as necessary are melt-kneaded in an extruder. Next, the foaming agent is dissolved and dispersed in the melt-kneaded product by the extruder or a mixing device installed after the extruder. Next, the melt-kneaded product containing the foaming agent is extruded into a cutter chamber filled with pressurized circulating water through a die having many small holes installed after the extruder or the mixing device, and the melt-kneaded product is cut by a rotating cutter immediately after extrusion and cooled and solidified by the pressurized circulating water. This allows the desired expandable styrene-based resin particles to be obtained. At this time, the melt-kneading by the extruder can be appropriately selected from a single extruder, a plurality of extruders connected together, and a second kneading device such as an extruder, a static mixer, and a stirrer without a screw.

[0046] In the second melt-kneading method, the base resin, the radiation heat transfer inhibitor, the bromine-based flame retardant, and other components as necessary are melt-kneaded in an extruder. Next, the melt-kneaded product is extruded through a die having many small holes, and then cut with a cutter to obtain resin particles (cold cut method or hot cut method). Then, the resin particles are suspended in water and a foaming agent is added to the resin particles. This results in the desired expandable styrene-based resin particles. The average particle diameter of the expandable styrene-based resin particles is preferably 2 mm or less, more preferably 1.5 mm or less. If the average particle diameter is 2 mm or less, the expandable resin particles after pre-expansion can have sufficient mold filling properties.

[0047] <Method of manufacturing styrene resin foam molded product> A known method can be used to manufacture a foamed molded article using the expandable styrene-based resin particles according to one embodiment of the present disclosure. For example, the expandable styrene-based resin particles are pre-expanded to prepare pre-expanded resin particles. Then, the pre-expanded resin particles are molded using a molding machine to manufacture a styrene-based resin foamed molded article.

[0048] <Pre-expanded particles> The pre-expanded resin particles can be produced, for example, by expanding expandable styrene-based resin particles 10 to 110 times with heated steam. The pre-expanded resin particles are used for molding after being cured for a certain period of time as necessary. The obtained pre-expanded resin particles are molded (for example, molded in a mold) with steam using a known molding machine to produce a foamed molded product. Depending on the shape of the mold used, a molded product with a complex shape and a block-shaped molded product can be obtained.

[0049] <Characteristics of styrene resin foam molded products> In one embodiment of the present disclosure, the expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m 3The thermal conductivity of the styrene-based resin foamed molded product obtained by foaming and molding after curing at 60° C. for 48 hours is preferably less than 31 mW / mK, more preferably less than 30.5 mW / mK, and even more preferably less than 30 mW / mK. The thermal conductivity can be the thermal conductivity at an average temperature of 23° C. and a temperature difference of 20° C. measured by a heat flow meter method in accordance with JIS A1412-2:1999.

[0050] In one embodiment of the present disclosure, the expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m 3 It is preferable that the dimensional change rate of the styrene-based resin foamed molded article obtained by foaming and molding the resin is within ±1% after heating at 90° C. for 168 hours.

[0051] In one embodiment of the present disclosure, the expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m 3 The styrene-based resin foamed molded article obtained by foaming and molding preferably has an oxygen index of 26 or more.

[0052] The styrene-based resin foam molded article having the above-mentioned properties is suitably used as a heat insulating material for houses, warehouses, hot water tanks, etc., but is not limited to this use.

[0053] The present disclosure includes the following items (1) to (20).

[0054] (1) Expandable styrene-based resin particles comprising a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent, The base resin contains at least a first styrene-based resin having 3 to 20% of structural units derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, The expandable styrene-based resin particles have a laser scattering intensity per unit solution concentration of a radiation heat transfer inhibitor in the expandable styrene-based resin particles of 5.0{% / (mg / ml)} / wt % or more.

[0055] (2) The expandable styrene-based resin particles according to (1), wherein the radiation heat transfer inhibitor includes a carbon-based radiation heat transfer inhibitor.

[0056] (3) The expandable styrene-based resin particles according to (2), wherein the carbon-based radiation heat transfer inhibitor is graphite, carbon black, activated carbon, graphene, or carbon nanotubes.

[0057] (4) The expandable styrene-based resin particles according to (1), wherein the radiation heat transfer inhibitor contains graphite as a main component.

[0058] (5) The expandable styrene-based resin particles according to any one of (1) to (4), wherein the radiation heat transfer inhibitor has an average particle size of 12 μm or less.

[0059] (6) The expandable styrene-based resin particles according to any one of (1) to (5), wherein the radiation heat transfer inhibitor is contained in an amount of 2 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the base resin.

[0060] (7) The expandable styrene-based resin particles according to any one of (1) to (6), wherein the base resin further contains a second styrene-based resin different from the first styrene-based resin, and the second styrene-based resin has a glass transition temperature of 95°C or higher and 110°C or lower.

[0061] (8) The expandable styrene-based resin particles according to any one of (1) to (7), wherein the bromine-based flame retardant has a 1% weight loss temperature in thermogravimetric analysis of 210°C or higher and 280°C or lower and a bromine content of 60% by weight or higher and less than 70% by weight.

[0062] (9) The expandable styrene-based resin particles according to any one of (1) to (8), wherein the brominated flame retardant is at least one selected from the group consisting of a brominated bisphenol-based compound, a brominated styrene-butadiene copolymer, and a brominated isocyanurate-based compound.

[0063] (10) The expandable styrene-based resin particles according to any one of (1) to (8), wherein the brominated flame retardant is at least one selected from the group consisting of brominated styrene-butadiene copolymer, 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane, and 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane.

[0064] (11) The expandable styrene-based resin particles according to any one of (1) to (10), wherein the foaming agent contains an aliphatic hydrocarbon having 4 carbon atoms and / or an aliphatic hydrocarbon having 5 carbon atoms.

[0065] (12) The foaming agent contains at least an aliphatic hydrocarbon having 5 carbon atoms, The expandable styrene-based resin particles according to (11), wherein the content of the aliphatic hydrocarbon having 5 carbon atoms in the entire blowing agent is 70% by weight or more.

[0066] (13) The expandable styrene resin particles are mixed with a bulk density of 20 kg / m 3 The expandable styrene-based resin particles according to any one of (1) to (12), wherein the expandable styrene-based resin particles are expanded and molded into a styrene-based resin foam having a thermal conductivity of less than 31 mW / mK after curing at 60°C for 48 hours.

[0067] (14) The expandable styrene resin particles are mixed with a bulk density of 20 kg / m 3 The expandable styrene-based resin particles according to any one of (1) to (13), wherein the dimensional change rate of the styrene-based resin expansion molded product obtained by foaming and molding the particles is within ±1% after heating at 90°C for 168 hours.

[0068] (15) The expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m 3 The expandable styrene-based resin particles according to any one of (1) to (14), wherein the expandable styrene-based resin particles are expanded and molded to give a styrene-based resin expansion molded article having an oxygen index of 26 or more.

[0069] (16) A styrene-based resin foamed molded article obtained by expanding the pre-expanded particles obtained by pre-expanding the expandable styrene-based resin particles according to any one of (1) to (15) above, and foam-molding the pre-expanded particles.

[0070] (17) A method for producing expandable styrene-based resin particles, comprising the steps of: A step of melt-kneading a styrene-based base resin, a radiation heat transfer inhibitor, and a bromine-based flame retardant in an extruder, and extruding the melt-kneaded resin through small holes; A step of cutting the extruded resin to obtain resin particles; and A step of suspending the resin particles in water and adding a blowing agent to obtain expandable styrene-based resin particles, The base resin contains at least a first styrene-based resin having 3 to 20% of structural units derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, A method for producing expandable styrene-based resin particles, wherein the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0{% / (mg / ml)} / weight % or more.

[0071] (18) A method for producing expandable styrene-based resin particles, comprising the steps of: A step of preparing a resin melt containing a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent; The resin melt is extruded through a die having a plurality of small holes into pressurized circulating water, and cut into particles by a rotary cutter; The base resin contains at least a first styrene-based resin having 3 to 20% of structural units derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, A method for producing expandable styrene-based resin particles, wherein the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0{% / (mg / ml)} / weight % or more.

[0072] (19) A method for producing expandable styrene-based resin particles according to any one of (1) to (15), comprising the steps of: A step of melt-kneading a styrene-based base resin, a radiation heat transfer inhibitor, and a bromine-based flame retardant in an extruder, and extruding the melt-kneaded resin through small holes; A step of cutting the extruded resin to obtain resin particles; and A step of suspending the resin particles in water and adding a blowing agent to obtain expandable styrene-based resin particles; A method for producing expandable styrene-based resin particles, comprising:

[0073] (20) A method for producing expandable styrene-based resin particles according to any one of (1) to (15), comprising the steps of: A step of preparing a resin melt containing a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent; a step of extruding the molten resin through a die having a plurality of small holes into pressurized circulating water and cutting the resin into particles with a rotary cutter; A method for producing expandable styrene-based resin particles, comprising: EXAMPLES

[0074] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0075] First, the raw materials used in each experimental example are listed below. <Styrene-based resin> (A1) Styrene-methacrylic acid copolymer [PS Japan Co., Ltd., G9001, glass transition temperature 123°C, methacrylic acid 8% by mass] (A2) Styrene homopolymer [PS Japan Co., Ltd., 680, glass transition temperature 103°C] Incidentally, (A1) corresponds to the first styrene-based resin, and (A2) corresponds to the second styrene-based resin.

[0076] <Radiation heat transfer inhibitor> (B) Graphite [Marutoyo Foundry Manufacturing Co., Ltd., flake graphite SGP-40B, average particle size D50 = 5.8 μm]

[0077] <Brominated flame retardants> (C) 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., SR-130, bromine content = 66% by weight]

[0078] <Heat stabilizer> (D1) Tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane [ADEKA Corporation, LA-57] (D2) Bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite [ADEKA Corporation, PEP-36]

[0079] <Mixture of brominated flame retardants and heat stabilizers> (E) Brominated flame retardant (C), heat stabilizers (D1) and (D2) were mixed in a mixer to obtain a mixture (E) of brominated flame retardant and heat stabilizer (hereinafter sometimes abbreviated as mixture (E)). The weight ratio (weight %) of each material was (C):(D1):(D2) = 95:2:3 ((C) + (D1) + (D2) = 100% by weight). For example, 2.5 g of mixture (E) contains 2.375 g of brominated flame retardant (C).

[0080] <Foaming agent> (F1) Normal pentane [SK Sangyo Co., Ltd.] (F2) Isopentane [SK Sangyo Co., Ltd.]

[0081] (Experimental Example 1) 1. Preparation of expandable styrene resin particles The styrene resin (A1), the styrene resin (A2), the radiation heat transfer inhibitor (B), and the mixture (E) were fed by feeders to a tandem-type two-stage extruder in which a 40 mm diameter twin-screw extruder (first extruder) and a 90 mm diameter single-screw extruder (second extruder) were connected in series, and melt-kneaded at a set temperature of 190°C and a rotation speed of 167 rpm for the first extruder. The weight ratio of each material was (A1):(A2):(B):(E)=74.4:18.6:4.5:2.5, and the total feed rate was 55.6 kg / h.

[0082] 80 parts by weight of normal pentane (F1) and 20 parts by weight of isopentane (F2) were mixed to prepare a mixed pentane. The mixed pentane was injected at a ratio of 8.0 parts by weight per 100 parts by weight of the melt of the resin mixture from the middle of the first extruder. Then, the mixed pentane was fed to the second extruder through a continuation pipe set at 210°C.

[0083] The temperature of the molten resin was cooled to 160°C in the second extruder, and then the molten resin was extruded into pressurized circulating water at a temperature of 84°C and a pressure of 1.1 MPa from a die having 60 small holes with a diameter of 0.65 mm and a land length of 5.0 mm attached to the tip of the second extruder set at 255°C. The extruded molten resin was cut and pelletized using a rotary cutter with six blades that came into contact with the die, and transferred to a centrifugal dehydrator to obtain expandable styrene-based resin particles.

[0084] 2. Preparation of Pre-expanded Particles The obtained expandable styrene resin particles were stored at 15°C for more than one week. 0.04 parts by weight of zinc stearate and 0.1 parts by weight of hydroxystearic acid triglyceride were added as external additives to 100 parts by weight of the expandable styrene resin particles, and dry blended. 330 g of the expandable styrene resin particles containing the external additives were put into a pre-expander [batch-type pre-expander manufactured by Daikai Kogyo Co., Ltd.], and 0.1 MPa of steam was introduced into the pre-expander to expand the particles, resulting in pre-expanded particles with a bulk ratio of 58 times.

[0085] 3. Preparation of styrene-based resin foam molded body The obtained pre-expanded particles were cured at 30°C for 24 hours, then filled into a mold for in-mold molding (length 400mm x width 400mm x thickness 50mm) attached to a polystyrene foam molding machine [KR-57, manufactured by Daisen Kogyo Co., Ltd.], and 0.09MPa steam was introduced to cause in-mold foaming, followed by spraying water on the mold to cool it. The foam molded body was held in the mold until the pressure of the foam molded body pressing the mold reached 0.01MPa (gauge pressure), and then the foam molded body was removed to obtain a styrene-based resin foam molded body. The expansion ratio of the obtained styrene-based resin foam molded body was 57 times. Hereinafter, the styrene-based resin foam molded product may be abbreviated to "foam molded product".

[0086] (Experimental Example 2) The same operations as in Experimental Example 1 were carried out, except that the target expansion ratio of the foamed molded article was set to 50 times.

[0087] (Experimental Example 3) The same procedure as in Experimental Example 1 was carried out, except that the target expansion ratio of the foamed molded article was set to 40 times.

[0088] (Experimental Example 4) The same operations as in Experimental Example 1 were carried out, except that the weight ratio of each material was (A1):(A2):(B):(E) = 65.1:27.9:4.5:2.0 and the target expansion ratio of the foamed molded product was set to 50 times.

[0089] (Experimental Example 5) The same procedure as in Experimental Example 1 was carried out, except that only (A1) was used as the styrene-based resin and the weight ratio of each material was (A1):(B):(E)=93.0:4.5:2.0.

[0090] (Experimental Example 6) The same operations as in Experimental Example 1 were carried out, except that the weight ratio of each material was (A1):(A2):(B):(E)=55.8:37.2:4.5:2.0.

[0091] (Experimental Example 7) The same procedure as in Experimental Example 1 was carried out, except that only (A2) was used as the styrene-based resin, the weight ratio of each material was (A2):(B):(E) = 93.0:4.5:2.0, and the target expansion ratio of the foamed molded body was set to 50 times.

[0092] That is, in Experimental Examples 1 to 3, the base resin is composed of the styrene-based resin (A1) and the styrene-based resin (A2), and the content ratio of the first styrene-based resin (styrene-based resin (A1)) to the entire base resin is 80% by weight. In Experimental Example 4, the base resin is composed of the styrene-based resin (A1) and the styrene-based resin (A2), and the content ratio of the first styrene-based resin to the entire base resin is 70% by weight. In Experimental Example 5, the base resin is composed only of the styrene-based resin (A1), and the content ratio of the first styrene-based resin to the entire base resin is 100% by weight. In Experimental Example 6, the base resin is composed of the styrene-based resin (A1) and the styrene-based resin (A2), and the content ratio of the first styrene-based resin to the entire base resin is 60% by weight. In Experimental Example 7, the base resin is composed only of the styrene-based resin (A2), and the content ratio of the first styrene-based resin to the entire base resin is 0% by weight.

[0093] In the expandable styrene resin particles of Experimental Examples 1 to 7, 4.5 parts by weight of the radiation heat transfer inhibitor (B) is contained per 93 parts by weight of the base resin, so 4.8 parts by weight of the radiation heat transfer inhibitor (B) is contained per 100 parts by weight of the base resin. Also, in Experimental Examples 1 to 7, 4.5 g of the radiation heat transfer inhibitor (B) is contained in 108 g of the expandable styrene resin particles, so the content of the radiation heat transfer inhibitor (B) relative to the entire expandable styrene resin particles is 4.2 wt%.

[0094] In Experimental Examples 1 to 7, 2.375 g of the brominated flame retardant (C) was contained in 108 g of the expandable styrene resin particles, and the content of the brominated flame retardant (C) in the entire expandable styrene resin particles was 2.2% by weight.

[0095] In Experimental Examples 1 to 7, 8.0 parts by weight of mixed pentane as a foaming agent was contained per 100 parts by weight of the total of the styrene-based resin (A1), the styrene-based resin (A2), the radiation heat transfer inhibitor (B), and the mixture (E).

[0096] The various properties of the expandable styrene resin particles and the styrene resin foamed molded articles produced in each of the experimental examples were measured by the following methods.

[0097] <Measurement of average particle size D50 and laser scattering intensity (%) of graphite> (1) Preparation of sample solution 500 mg of expandable styrene resin particles were dissolved and dispersed in 20 mL of 0.1% (w / w) Span 80 toluene solution to prepare a sample solution. The above-mentioned dissolution / dispersion refers to a state in which the resin is dissolved and the graphite is dispersed. A 0.1% (w / w) Span 80 toluene solution refers to toluene to which 0.1% (w / w) of the surfactant Span 80 has been added.

[0098] Next, the sample solution was irradiated with ultrasonic waves in an ultrasonic cleaner to relax the aggregation of graphite.

[0099] (2) Ultrasonic irradiation conditions Equipment used: Ultrasonic cleaner manufactured by AS ONE Corporation, model number USM Oscillation frequency: 42kHz Irradiation time: 10 minutes Temperature: room temperature

[0100] (3) Particle size measurement conditions Measurement equipment: Malvern Laser Diffraction Particle Size Distribution Analyzer Mastersizer 3000 Light source: 632.8nm red He-Ne laser and 470nm blue LED Dispersion unit: Wet dispersion unit Hydro MV

[0101] The analysis was carried out with the following settings, and the volume distribution was obtained and the D50 particle size of carbon in the sample was calculated by measurement and analysis using a laser diffraction and scattering method based on the Mie theory in accordance with ISO13320:2009 and JIS Z8825-1. Particle type: non-spherical Graphite refractive index: 2.42 Graphite Absorption Rate: 1.0 Dispersion medium: 0.1% (w / w) Span 80 in toluene Refractive index of dispersion medium: 1.49 Agitation speed in dispersion unit: 2500 rpm Analysis model: General purpose, single mode preserving Measurement temperature: room temperature

[0102] (4) Measurement procedure 120 mL of 0.1% (w / w) Span 80 toluene solution was poured into the dispersion unit, stirred at 2500 rpm, and stabilized. The light intensity measured by the central detector when 632.8 nm red He-Ne laser light was irradiated in the measurement cell without the sample solution sample and only the dispersion medium was used as the transmitted light intensity Lb. Next, 2 mL of the ultrasonically treated sample solution was taken and added to the dispersion unit. The light intensity measured by the central detector when 632.8 nm red He-Ne laser light was irradiated 1 minute after the addition of the sample solution was used as the transmitted light intensity Ls. At the same time, the particle size (D50) was measured. From the obtained Ls and Lb, the laser scattering intensity Ob of the sample solution was calculated using the following formula. Ob = (1-Ls / Lb) x 100 (%)

[0103] The central detector is a detector located in front of the output of the laser light, and the light detected here is a measure of the transmitted light that was not used for scattering. The laser scattering intensity is a measure of the amount of laser light lost when the sample is scattered by the laser of the analytical device.

[0104] (5) Calculation of laser scattering intensity per unit solution concentration of expandable styrene resin particles The laser scattering intensity X (% / (mg / ml)) per unit solution concentration of the expandable styrene resin particles was calculated using the following formula. X(% / (mg / ml))=laser scattering intensity (Ob) / {sample weight (500mg) / toluene amount (20mL) x sample injection amount (2mL) / total amount of toluene in dispersion unit (120mL+2mL)}

[0105] Here, the laser scattering intensity per unit solution concentration is the measured laser scattering intensity divided by the sample concentration in toluene. Since the measurement device used here is an apparatus that requires measurement in solution, the sample concentration in the toluene solution is kept constant, and the measured value is obtained for a constant sample amount.

[0106] (6) Calculation of laser scattering intensity per unit solution concentration of radiation heat transfer inhibitor for expandable styrene resin particles The laser scattering intensity Y{% / (mg / ml)} / wt% per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene-based resin particles (hereinafter referred to as "measurement subject") was calculated using the following formula. Y{% / (mg / ml)} / weight% = laser scattering intensity per unit solution concentration of the target (% / (mg / ml)) / graphite content of the target (weight%)

[0107] <Expansion ratio of styrene resin in-mold foamed products> A sample measuring 300 mm in length, 300 mm in width, and 25 mm in thickness was cut out from the styrene-based resin in-mold foamed product. The weight (g) of the sample was measured, and the length, width, and thickness were measured using a caliper. The volume (cm 3 ) was calculated, and the expansion ratio was calculated according to the following formula. Expansion ratio (times) = sample volume (cm 3 ) / sample weight (g) The expansion ratio of styrene resin molded foam is conventionally expressed as "cm 3 It is also expressed as " / g".

[0108] <Measurement of thermal conductivity of styrene-based resin foam molded body> A sample measuring 300 mm in length × 300 mm in width × 25 mm in thickness was cut out from the styrene-based resin foam molded article. The sample was left to stand at 60°C for 48 hours and then at 23°C for 24 hours, after which the thermal conductivity was measured at an average temperature of 23°C and a temperature difference of 20°C by the heat flow meter method using a thermal conductivity measuring device (HC-074, manufactured by Eiko Seiki Co., Ltd.) in accordance with JIS A1412-2:1999.

[0109] <Measurement of dimensional change rate of styrene resin foam molded body> A sample measuring 150 mm long x 150 mm wide x 25 mm thick was cut out from the styrene-based resin foam molded body. The sample was left to stand at 23°C for 168 hours, and then three parallel lines were drawn in the vertical and horizontal directions at 50 mm intervals in the center of the test piece. The test piece was placed in a hot air circulation dryer at 90°C for 168 hours, then removed and left in a place under standard conditions (temperature 23±2°C, humidity 50±5%) for 1 hour. The dimensions of the vertical and horizontal lines were measured, and the thermal dimensional change rate S (%) was calculated using the following formula. S = (L1-L0) / L0 x 100 In the formula, S represents the rate of dimensional change due to heating (%), L0 represents the initial dimension (mm), and L1 represents the dimension after heating (mm).

[0110] <Flame retardancy evaluation - burning time> The produced foam molded body was left to stand at 60°C for 48 hours, and then left to stand at 23°C for 24 hours, after which five test pieces measuring 200 mm in length, 25 mm in width, and 10 mm in thickness were cut out from one styrene-based resin in-mold foam molded body. A flame retardancy test was then conducted in accordance with JIS A 9521:2017 (Foamed Plastic Thermal Insulation Material) Flammability Measurement Method A, and the average flame extinction time of the five test pieces was calculated.

[0111] <Flame retardancy evaluation - oxygen index> The foamed molded article thus produced was allowed to stand at 70° C. for 168 hours and then at 23° C. for 24 hours, after which the oxygen index was measured in accordance with JIS K7201.

[0112] Table 1 shows the blending amounts of expandable styrene-based resin particles in each experimental example and the measurement results of each evaluation item.

[0113] [Table 1]

[0114] The expansion ratio of the foamed molded articles obtained in each experiment is shown in Table 1.

[0115] Experimental Examples 1 to 3, in which the content of the styrene-based resin (A1) relative to the entire base resin was 80% by weight, and Experimental Example 4, in which the content was 70% by weight, were excellent in all aspects, including the laser scattering intensity (corresponding to the dispersibility of graphite) per unit solution concentration of the radiation heat transfer inhibitor of the expandable styrene-based resin particles, as well as the thermal conductivity (corresponding to the thermal insulation property), dimensional change rate, flame retardancy (burning time), and flame retardancy (oxygen index) of the styrene-based resin foamed moldings.

[0116] On the other hand, in Experimental Example 5, in which the base resin was composed only of the styrene-based resin (A1), the moldability was low and it was not possible to mold a foamed molded product. In Experimental Example 6, in which the content ratio was 60% by weight, the continuous production stability was low and it was not possible to produce resin particles themselves. In Experimental Example 7, in which the base resin was composed only of the styrene-based resin (A2), the thermal dimensional change rate S of the foamed molded product was -20%, and only a foamed molded product that significantly shrunk when heated was obtained.

Claims

1. Expandable styrene-based resin particles comprising a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent, the base resin contains at least a first styrene-based resin having 3 to 20% of a structural unit derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, The expandable styrene-based resin particles have a laser scattering intensity per unit solution concentration of a radiation heat transfer inhibitor in the expandable styrene-based resin particles of 5.0 {% / (mg / ml)} / wt % or more.

2. The expandable styrene-based resin particles according to claim 1 , wherein the radiation heat transfer inhibitor comprises a carbon-based radiation heat transfer inhibitor.

3. The expandable styrene-based resin particles according to claim 1 , wherein the radiation heat transfer inhibitor is contained in an amount of 2 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the base resin.

4. 2. The expandable styrene-based resin particles according to claim 1, wherein the bromine-based flame retardant has a 1% weight loss temperature in thermogravimetric analysis of 210° C. or higher and 280° C. or lower and a bromine content of 60% by weight or higher but lower than 70% by weight.

5. The expandable styrene-based resin particles according to claim 1, wherein the base resin further comprises a second styrene-based resin different from the first styrene-based resin, and the second styrene-based resin has a glass transition temperature of 95°C or higher and 110°C or lower.

6. 2. The expandable styrene-based resin particles according to claim 1, wherein the foaming agent contains an aliphatic hydrocarbon having 4 carbon atoms and / or an aliphatic hydrocarbon having 5 carbon atoms.

7. The foaming agent contains at least an aliphatic hydrocarbon having 5 carbon atoms, 2. The expandable styrene-based resin particles according to claim 1, wherein the content of said aliphatic hydrocarbon having 5 carbon atoms in said foaming agent is 70% by weight or more.

8. The expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m ３ 2. The expandable styrene-based resin particles according to claim 1, wherein the expandable styrene-based resin particles are expanded and molded to produce a styrene-based resin foamed molded article, which has a thermal conductivity of less than 31 mW / mK after curing at 60° C. for 48 hours.

9. The expandable styrene-based resin particles are mixed with a bulk density of 20 kg / m ３ 2. The expandable styrene-based resin particles according to claim 1, which is capable of producing a styrene-based resin foamed molded article having a dimensional change rate of within ±1% after heating at 90° C. for 168 hours by foaming and molding the foamed molded article.

10. A styrene-based resin foamed molded article obtained by foaming the pre-expanded particles obtained by pre-expanding the expandable styrene-based resin particles according to any one of claims 1 to 9.

11. A method for producing expandable styrene-based resin particles, comprising the steps of: A step of melt-kneading a styrene-based base resin, a radiation heat transfer inhibitor, and a bromine-based flame retardant in an extruder, and extruding the melt-kneaded resin through small holes; A step of cutting the extruded resin to obtain resin particles; and A step of suspending the resin particles in water and adding a blowing agent to obtain expandable styrene-based resin particles, the base resin contains at least a first styrene-based resin having 3 to 20% of a structural unit derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0 {% / (mg / ml)} / wt % or more; A method for producing expandable styrene-based resin particles.

12. A method for producing expandable styrene-based resin particles, comprising the steps of: A step of preparing a resin melt containing a styrene-based base resin, a radiation heat transfer inhibitor, a bromine-based flame retardant, and a blowing agent; The resin melt is extruded through a die having a plurality of small holes into pressurized circulating water, and cut into particles by a rotary cutter; the base resin contains at least a first styrene-based resin having 3 to 20% of a structural unit derived from (meth)acrylic acid, The content ratio of the first styrene-based resin to the entire base resin is 70% by weight or more and 90% by weight or less, A method for producing expandable styrene-based resin particles, wherein the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor in the expandable styrene-based resin particles is 5.0 {% / (mg / ml)} / wt % or more.

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