JP2024140138A - Expandable styrene resin particles - Google Patents

Abstract

[Problem] To provide expandable styrene-based resin particles that are excellent in heat resistance and capable of producing styrene-based resin foamed molded articles with a high expansion ratio. [Solution] The expandable styrene-based resin particles according to the present disclosure are expandable styrene-based resin particles that contain a styrene-based resin composition containing a styrene-based resin and a carbon-based radiation heat transfer inhibitor, and a blowing agent, wherein the styrene-based resin has a melt flow rate of 7.5 to 15.5 g/10 min at 200°C under a load of 5.0 kg, and the blowing agent contains isobutane. [Selected Figures] None

Description

The present invention relates to expandable styrene-based resin particles.

Styrene-based resin foam is a well-balanced foam that has light weight, insulating properties, and cushioning properties, and has been widely used in food containers, cooler boxes, cushioning materials, and insulating materials for housing, etc.

In particular, in recent years, in relation to various issues such as global warming, there has been a trend toward energy conservation through improved insulation of buildings such as homes, and it is expected that the demand for styrene resin foamed molded products obtained using expandable styrene resin particles will increase. For this reason, various studies are being conducted on reducing the weight and improving the insulation properties of the styrene resin foamed products by increasing the expansion ratio.

For example, Patent Document 1 discloses expandable styrene resin particles used for forming bead foams, which contain a styrene resin and a foaming agent, with pentane as the foaming agent, and further contain butane as the foaming agent, the foaming agent being contained in a ratio of 2 parts by mass to 10 parts by mass to 100 parts by mass of the styrene resin, the pentane and butane being contained in a mass ratio of 20:80 to 80:20, and multiple bubbles being formed inside so that the expansion ratio is 1.05 times to 1.25 times.

JP 2013-136688 A

The expandable styrene resin particles disclosed in Patent Document 1 were not blended with a carbon-based radiation heat transfer inhibitor. Furthermore, according to the inventors' studies, it has been confirmed that while the incorporation of a carbon-based radiation heat transfer inhibitor improves the insulation properties, it also reduces the foaming performance. It was therefore thought that it would be difficult to obtain a foamed molded article with a high expansion ratio if a carbon-based radiation heat transfer inhibitor was applied to expandable styrene resin particles that did not contain the carbon-based radiation heat transfer inhibitor.

The present inventors aim to provide expandable styrene-based resin particles that have excellent heat resistance and can produce styrene-based resin foamed molded articles with a high expansion ratio.

An example of this embodiment is described as follows:

[1] Expandable styrene-based resin particles comprising a styrene-based resin composition containing a styrene-based resin and a carbon-based radiation heat transfer inhibitor, and a blowing agent,
The expandable styrene-based resin particles have a melt flow rate of 7.5 to 15.5 g/10 min at 200° C. under a load of 5.0 kg, and the foaming agent contains isobutane.
[2] The expandable styrene-based resin particles according to [1], wherein the expandable styrene-based resin particles have an apparent density of more than 950 kg/ ^m3 and not more than 1200 kg/ ^m3.
[3] The expandable styrene-based resin particles according to [1] or [2], wherein the styrene-based resin composition contains a flame retardant, and the flame retardant is more than 1.0% by weight and not more than 6.0% by weight in 100% by weight of the styrene-based resin composition.
[4] The expandable styrene-based resin particles according to any one of [1] to [3], wherein the carbon-based radiation heat transfer inhibitor is more than 2% by weight and not more than 20% by weight, based on 100% by weight of the styrene-based resin composition.
[5] The expandable styrene-based resin particles according to any one of [1] to [4], wherein the carbon-based radiation heat transfer inhibitor is at least one carbon-based radiation heat transfer inhibitor selected from graphite, carbon black, carbon nanotubes, graphene, and activated carbon.
[6] The amount of the foaming agent in the foamable styrene-based resin particles is more than 1.0 parts by weight and not more than 8.0 parts by weight per 100 parts by weight of the styrene-based resin composition. [1] to [5].
[7] The expandable styrene-based resin particles according to any one of [1] to [6], wherein the amount of isobutane is 15 to 90% by weight based on 100% by weight of the blowing agent.
[8] The expandable styrene-based resin particles according to any one of [1] to [7], wherein the blowing agent contains a saturated hydrocarbon having 5 to 6 carbon atoms. [9] The expandable styrene-based resin particles according to any one of [1] to [8], wherein the blowing agent contains pentane.
[10] Pre-expanded styrene-based resin particles obtained by expanding the expandable styrene-based resin particles according to any one of [1] to [9].
[11] A foamed molded product of a styrene-based resin obtained by molding the pre-expanded particles of the styrene-based resin according to [10].

The expandable styrene-based resin particles disclosed herein have excellent heat resistance and can produce styrene-based resin foams with a high expansion ratio.

The present invention will be described in detail below. The expandable styrene-based resin particles according to this embodiment are expandable styrene-based resin particles containing a styrene-based resin composition containing a styrene-based resin and a carbon-based radiation heat transfer inhibitor, and a foaming agent, and the styrene-based resin has a melt flow rate of 7.5 to 15.5 g/10 min at 200° C. and a load of 5.0 kg, and the foaming agent contains isobutane. The expandable styrene-based resin particles of the present disclosure control the melt flow rate (MFR) of the styrene-based resin within the above-mentioned range, and contain isobutane as a foaming agent, thereby making it possible to obtain a styrene-based resin foamed molded product with excellent heat resistance and high expansion ratio. In addition, the obtained styrene-based resin foamed molded product has excellent moldability. In one aspect of the expandable styrene-based resin particles according to this embodiment, a styrene-based resin foamed molded product with a high expansion ratio can be obtained even when the amount of foaming agent is relatively less than that of the conventional product. Reducing the amount of foaming agent brings about an effect of reducing environmental load such as reducing VOCs (volatile organic compounds) and a cost reduction effect.

(styrene resin)
The styrene-based resin may be a styrene homopolymer or a styrene copolymer. As the styrene copolymer, a styrene copolymer obtained by copolymerizing styrene with another monomer or a derivative thereof that is copolymerizable with styrene can be used. The repeating unit derived from styrene contained in the styrene-based copolymer is preferably 60% by weight or more, more preferably 80% by weight or more, based on 100% by weight of the styrene-based copolymer. As the styrene-based resin, one type may be used alone, or two or more types may be used. However, in this embodiment, the styrene-based resin usually excludes the brominated styrene-butadiene copolymer described later.

Examples of other monomers or derivatives thereof that can be copolymerized with styrene (hereinafter sometimes referred to as "other monomers or derivatives thereof") include styrene derivatives such as methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and trichlorostyrene; polyfunctional vinyl compounds such as divinylbenzene; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, and butyl acrylate. and (meth)acrylic acid ester compounds such as butyl methacrylate; vinyl cyanide compounds such as (meth)acrylonitrile; diene compounds or derivatives thereof such as butadiene; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; and N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(2-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, and N-(1-naphthyl)maleimide. The other monomers or derivatives thereof may be used alone or in combination of two or more.

The styrene-based resin may be blended with homopolymers or copolymers of other monomers or their derivatives, as long as the effect of the present invention is not impaired.

From the viewpoint of impact resistance, heat resistance, etc., the styrene resin may be blended with, for example, diene rubber-reinforced polystyrene, acrylic rubber-reinforced polystyrene, and/or polyphenylene ether resin.

The styrene-based resin is preferably at least one selected from styrene homopolymer, styrene-acrylonitrile copolymer, and styrene-butyl acrylate copolymer, and more preferably contains styrene homopolymer, because it is relatively inexpensive, can be foamed using low-pressure steam without using special methods, and has an excellent balance of heat insulation, flame retardancy, and cushioning properties.

The styrene resin has a melt flow rate of 7.5 to 15.5 g/10 min at 200° C. and a load of 5.0 kg, preferably 8.0 to 15.0 g/10 min, and more preferably 8.5 to 14.5 g/10 min. The melt flow rate is also referred to as MFR. When the melt flow rate is within the above range, it is possible to obtain expandable resin particles having excellent moldability, and it is possible to obtain a styrene resin foamed molded product having excellent heat resistance and a high expansion ratio. In this disclosure, when the styrene resin is two or more types of resin (polymer), the MFR of the styrene resin does not mean the MFR of each resin, but the MFR of the entire styrene resin. In other words, when two or more types of resin are used, the resins contained in the styrene resin composition are melt-kneaded in the ratio contained in the styrene resin composition to prepare pellets, and the MFR of the pellets is measured to know the MFR of the styrene resin contained in the styrene resin composition. In the present invention, the MFR is a value measured in accordance with JIS K7210. The MFR can be measured by the method described in the examples below.

As the styrene resin, it is one of the preferred embodiments to use two types of styrene resins. In one embodiment, two types of styrene resins are used as the styrene resin, and the MFR of at least one of the styrene resins is outside the range of 7.5 to 15.5 g/10 min. In one preferred embodiment, two types of styrene resins are used as the styrene resin, and the MFR of one of the styrene resins is less than 7.5 g/10 min, and the MFR of the other styrene resin is more than 15.5 g/10 min. When two types of styrene resins are used as the styrene resin, it is preferable that one styrene resin and the other styrene resin are contained in a ratio of 99:1 to 1:99 (weight ratio).

In a preferred embodiment, the styrene resin is a styrene resin having an MFR of less than 7.5 g/10 min, preferably 1.0 to 7.4 g/10 min, more preferably 2.0 to 7.3 g/10 min, even more preferably 3.0 to 7.2 g/10 min, and particularly preferably 5.5 to 7.1 g/10 min, and a styrene resin having an MFR of more than 15.5 g/10 min, preferably 15.6 to 25 g/10 min, and more preferably 16 to 22 g/10 min. In this case, it is preferable that the styrene resin having an MFR of less than 7.5 g/10 min: the styrene resin having an MFR of more than 15.5 g/10 min is 20:80 to 90:10 (weight ratio). By using two types of styrene resin, it is easy to adjust the MFR and it is possible to easily obtain expandable resin particles having excellent moldability.

In the present invention, the content of the styrene-based resin is not particularly limited, but is preferably 75 to 99.9% by weight, and more preferably 80 to 95% by weight, based on 100% by weight of the styrene-based resin composition.

In addition, other resins may be used in combination with the styrene-based resin as the main component, so long as the effects of the present invention are not impaired. Examples of other resins include homopolymers of the above-mentioned other monomers or their derivatives, or copolymers thereof, polyolefin-based resins, polyester-based resins, polycarbonate-based resins, acrylic-based resins, and the like. The content of the other resins is not particularly limited, but is preferably 20% by weight or less, and more preferably 10% by weight or less, based on 100% by weight of the styrene-based resin composition.

(Carbon-based radiation heat transfer inhibitor)
The expandable styrene resin particles are obtained by forming a styrene resin foamed molded article having high thermal insulation properties because the styrene resin composition contains a carbon-based radiation heat transfer inhibitor. Here, the carbon-based radiation heat transfer inhibitor refers to a carbon material having the property of reflecting, scattering, or absorbing light in the near infrared or infrared region (for example, a wavelength region of about 800 to 3000 nm). Examples of the carbon-based radiation heat transfer inhibitor include graphite, graphene, carbon black, expanded graphite, activated carbon, carbon nanotubes, and carbon nanofibers. The carbon-based radiation heat transfer inhibitor can be used alone or in combination of two or more. The carbon-based radiation heat transfer inhibitor is preferably at least one carbon-based radiation heat transfer inhibitor selected from graphite, carbon black, carbon nanotubes, graphene, and activated carbon, from the viewpoints of dispersibility in the styrene resin and cost, and more preferably graphite.

Examples of graphite include flake graphite, earthy graphite, spherical graphite, and artificial graphite. In this specification, the term "flake" also includes scaly, flaky, or plate-like. The graphite may be used alone or in combination of two or more. Among these, flake graphite or 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.

The average particle size of the carbon-based radiation heat transfer inhibitor is preferably 1 to 9 μm, more preferably 1.5 to 8 μm, and even more preferably 2 to 7 μm. The smaller the average particle size of the carbon-based radiation heat transfer inhibitor, the higher the manufacturing cost. Carbon-based radiation heat transfer inhibitors with an average particle size of less than 1 μm are very expensive due to the high manufacturing cost, including the cost of crushing, and the cost of the expandable styrene-based resin particles tends to be high. On the other hand, if the average particle size exceeds 9 μm, the cell membrane tends to break easily when producing pre-expanded particles and styrene-based resin foamed molded bodies from the expandable styrene-based resin particles, making it difficult to achieve a high expansion ratio, reducing ease of molding, and tending to reduce the compressive strength of the styrene-based resin foamed molded body. In this disclosure, the average particle size of the carbon-based radiation heat transfer inhibitor means the particle size (D50) (volume average particle size measured by the laser diffraction scattering method) when the particle size distribution is measured and analyzed by the laser diffraction scattering method based on the Mie theory in accordance with JIS Z8825-1 and the cumulative volume of the total volume of the particles is 50%.

In addition, if the average particle size of the carbon-based radiation heat transfer inhibitor is 6.0 μm or less, the molded body will have excellent surface beauty and a lower thermal conductivity, i.e., higher insulation.

The content of the carbon-based radiation heat transfer inhibitor is not particularly limited, but is preferably more than 2% by weight and not more than 20% by weight, more preferably 3 to 18% by weight, even more preferably 4 to 16% by weight, and particularly preferably 4.5 to 14% by weight, based on 100% by weight of the styrene-based resin composition. This range is preferable because it is easy to control the expansion ratio to the desired level and tends to have a good balance of thermal conductivity reduction effects, etc.

In addition to the carbon-based radiation heat transfer inhibitor, other radiation heat transfer inhibitors may be used as long as they do not impair the effects of the present invention. The other radiation heat transfer inhibitors are not particularly limited as long as they are non-carbon-based radiation heat transfer inhibitors, but examples 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.

(Foaming Agent)
The expandable styrene-based resin particles of the present disclosure contain a foaming agent. The foaming agent also contains isobutane. By using the specific styrene-based resin described above and containing isobutane as at least a part of the foaming agent, it is possible to obtain a styrene-based resin foamed molded product having excellent heat resistance and a high expansion ratio.

The blowing agent may contain a blowing agent other than isobutane. The blowing agent other than isobutane is not particularly limited, but from the viewpoint of a good balance between foaming property and product life and easy high expansion when actually used, a hydrocarbon having 3 to 6 carbon atoms (excluding isobutane) is preferable, a hydrocarbon having 4 to 6 carbon atoms (excluding isobutane) is more preferable, and a hydrocarbon having 5 to 6 carbon atoms is even more preferable. If the number of carbon atoms of the blowing agent is 3 or more, the volatility is low and the blowing agent is less likely to dissipate when made into expandable styrene-based resin particles, so that when actually used, the blowing agent remains sufficiently in the expansion process, making it possible to obtain sufficient foaming power, and it is easy to increase the expansion ratio, which is preferable. In addition, if the number of carbon atoms is 6 or less, the boiling point of the blowing agent is not too high, so it is easy to obtain sufficient foaming power by heating during pre-expansion, and there is a tendency for it to be easy to increase the foaming ratio. In addition, it is preferable for the hydrocarbon to be a saturated hydrocarbon from the viewpoint of foaming power. As the blowing agent, saturated hydrocarbons having 3 to 6 carbon atoms (excluding isobutane) are preferred, saturated hydrocarbons having 4 to 6 carbon atoms (excluding isobutane) are more preferred, and saturated hydrocarbons having 5 to 6 carbon atoms are even more preferred. Examples of the hydrocarbons having 3 to 6 carbon atoms (excluding isobutane) include hydrocarbons such as propane, normal butane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, and cyclohexane. These may be used alone or in combination of two or more. From the perspective of the balance between the ease of achieving a high blowing ratio and the product life, it is preferred to use isobutane and a blowing agent other than isobutane as the blowing agent. It is preferred that the blowing agent contains pentane. It is also preferred that the blowing agent contains isobutane and at least one blowing agent selected from the group consisting of normal butane, isopentane, and normal pentane. It is particularly preferable that the blowing agent contains isobutane and at least one blowing agent selected from the group consisting of normal pentane and isopentane, and it is even more preferable that the blowing agent contains isobutane, normal pentane, and isopentane.

The amount of isobutane in the blowing agent is usually 15 to 90% by weight, preferably 20 to 80% by weight, and more preferably 25 to 70% by weight, based on 100% by weight of the blowing agent. In a preferred embodiment, isobutane, normal pentane, and isopentane are used as the blowing agent, and in this embodiment, the weight ratio of isobutane to pentane (normal pentane and isopentane) (isobutane/pentane) is usually 20/80 to 90/10, preferably 40/60 to 70/30, and more preferably 50/50 to 60/40. In addition, the weight ratio of normal pentane to isopentane (normal pentane/isopentane) is, for example, 30/70 to 90/10, and preferably 50/50 to 85/15. Within the above range, the expandable styrene-based resin particles tend to have excellent high expandability.

The amount of the blowing agent added is preferably more than 1.0 part by weight and not more than 8.0 parts by weight, more preferably 2.0 to 7.0 parts by weight, even more preferably 3.0 to 6.0 parts by weight, and particularly preferably 3.5 to 5.5 parts by weight, relative to 100 parts by weight of the styrene-based resin composition. The expandable styrene-based resin particles of the present disclosure control the MFR of the styrene-based resin within the above-mentioned range and contain isobutane as a blowing agent, so that a styrene-based resin foamed molded product with a high expansion ratio can be obtained even with a relatively small amount of blowing agent compared to conventional products. This has the effect of reducing the environmental load, such as reducing VOCs, and the effect of reducing costs. In addition, the obtained styrene-based resin foamed molded product has excellent moldability and also excellent heat resistance.

(Flame retardant)
The flame retardant is not particularly limited, and any flame retardant conventionally used in styrene resin foam moldings can be used. Among them, bromine-based flame retardants, which have a high flame retardancy-imparting effect, are preferred.

Examples of the brominated flame retardant include brominated bisphenol compounds such as 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)) or 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromopropyl ether)), brominated styrene-butadiene copolymers such as brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers. Examples of the brominated flame retardant include the heat-stable brominated copolymers disclosed in JP-T-2009-516019. Brominated flame retardants may be used alone or in combination of two or more.

The flame retardant is preferably more than 1.0% by weight and not more than 6.0% by weight, more preferably 1 to 4% by weight, of 100% by weight of the styrene-based resin composition, because it is easy to control the expansion ratio to the desired value, and in terms of the balance of flame retardancy when carbon is added, etc. If the content is more than 1% by weight, the flame retardant effect is not reduced, and if it is 6.0% by weight or less, the strength of the resulting styrene-based resin foam molding is less likely to decrease.

(Heat stabilizer)
The expandable styrene resin particles may further contain a heat stabilizer. The heat stabilizer is preferably contained in the styrene resin composition. By using the heat stabilizer, it is possible to suppress deterioration of the flame retardancy and deterioration of the expandable styrene resin particles due to decomposition of the flame retardant during the production process.

Thermal stabilizers can be used in appropriate combinations depending on the type of styrene-based resin used, the type and content of the carbon-based radiation heat transfer inhibitor, the type and content of the flame retardant, the type and content of the foaming agent, etc.

As the heat stabilizer used in the present invention, a hindered amine compound, a phosphorus-based compound, or an epoxy compound is preferable because it allows the 1% weight loss temperature of the styrene-based resin composition to be arbitrarily controlled in thermogravimetric analysis. The heat stabilizers can be used alone or in combination of two or more. An example of the hindered amine compound is tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane, and an example of the phosphorus-based compound is bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite.

The heat stabilizer is preferably 0.05 to 3 wt %, more preferably 0.1 to 2.8 wt %, and even more preferably 0.11 to 2.5 wt % per 100 wt % styrene resin composition, because it is easy to control the expansion ratio to the desired value, and because it balances flame retardancy when a carbon-based radiation heat transfer inhibitor is added. If it is 0.05 wt % or more, the flame retardant is less likely to decompose, and the flame retardant effect is not reduced, and if it is 3 wt % or less, the strength of the resulting styrene resin foam molding is less likely to decrease.

(Other additives)
The expandable styrene-based resin particles and the styrene-based resin composition may contain, as necessary, other additives, for example, one or more other additives selected from the group consisting of radical generators, processing aids, light resistance stabilizers, nucleating agents, foaming aids, antistatic agents, and colorants such as pigments, within the scope not impairing the effects of the present invention.

Examples of radical generators include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and poly-1,4-isopropylbenzene.

Processing aids include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin, etc.

Examples of light resistance stabilizers include phenol-based antioxidants, nitrogen-based stabilizers, sulfur-based stabilizers, and benzotriazoles. Note that light resistance stabilizers also include those that act as heat stabilizers, such as hindered amine compounds, phosphorus-based compounds, phenol-based stabilizers, and epoxy compounds, but in this disclosure, those that belong to both light resistance stabilizers and heat stabilizers are considered to be heat stabilizers.

Examples of nucleating agents include inorganic compounds such as silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, or talc; polymeric compounds such as methyl methacrylate copolymers or ethylene-vinyl acetate copolymer resins; olefin waxes such as polyethylene wax; and fatty acid bisamides such as methylene bisstearamide, ethylene bisstearamide, hexamethylene bispalmitamide, or ethylene bisoleamide.

As the foaming aid, a solvent with a boiling point of 200°C or less at atmospheric pressure can be preferably used, for example, aromatic hydrocarbons such as styrene, toluene, ethylbenzene, and xylene, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, and acetates such as ethyl acetate and butyl acetate.

As antistatic agents and colorants, those used in various resin compositions can be used without any particular limitations.

These other additives can be used alone or in combination of two or more.

The expandable styrene-based resin particles of the present invention preferably have an apparent density of more than 950 kg/m ³ and not more than 1200 kg/m ^3. From the viewpoint of expandability, it is preferably more than 950 kg/m ³ , and more preferably 1000 kg/m ³ or more. On the other hand, from the viewpoint of heat insulating performance, it is preferably 1170 kg/m ³ or less, more preferably 1150 kg/m ³ or less, and particularly preferably 1140 kg/m ³ or less. When the apparent density of the expandable styrene-based resin particles is within the above range, it is considered that the expansion of the styrene-based resin melt containing the styrene-based resin composition and the foaming agent during extrusion is suppressed. By obtaining expandable styrene-based resin particles in which expansion during extrusion is suppressed, the closed cell rate in the pre-expanded particles is increased, and the strength of the cell structure is increased, which is preferable because it is possible to suppress shrinkage immediately after pre-expansion.

In addition, if the apparent density of the expandable styrene resin particles is low, the pre-expanded particles are prone to shrinkage, and if the shrinkage immediately after pre-expansion is large, the cells of the pre-expanded particles will buckle and the expansion rate will not recover even if cured at high temperatures. However, since the expandable styrene resin particles of the present invention are inhibited from shrinking, there is no need to cure the pre-expanded particles at high temperatures, and it is easy to manage the expansion rate after curing. Furthermore, by increasing the apparent density of the expandable styrene resin particles, the bulk density of the expandable styrene resin particles does not decrease, making them easier to pack and reducing the space required for storage.

In the expandable styrene-based resin particles of the present invention, the bulk ratio of the pre-expanded particles obtained by pre-expanding the expandable styrene-based resin particles is preferably 70 times or more, and more preferably 80 times or more. When the pre-expanded particles have a bulk ratio of 70 times or more, the density of the styrene-based resin foam molded product obtained by molding the pre-expanded particles is reduced, making it possible to produce a lighter styrene-based resin foam molded product. In addition, increasing the bulk ratio allows the amount of resin used to be reduced, which also leads to cost reduction.

(Method for producing expandable styrene-based resin particles)
The expandable styrene-based resin particles can be obtained by a known melt-kneading method. Specifically, the particles can be produced by melt-kneading a styrene-based resin, a carbon-based radiation heat transfer inhibitor, and a foaming agent in an extruder (melt-kneading step), extruding the molten mixture through a die having small holes attached to the tip of the extruder into a chamber filled with pressurized circulating water (extrusion step), cutting the molten mixture immediately after extrusion with a rotating cutter, and cooling and solidifying it with pressurized circulating water (cooling step).

One example of a method for producing expandable styrene-based resin particles is a method for producing expandable styrene-based resin particles, which comprises preparing a styrene-based resin composition containing a styrene-based resin and a carbon-based radiation heat transfer inhibitor by melt kneading, adding a blowing agent to the molten styrene-based resin composition, further kneading, extruding the molten material containing the styrene-based resin composition and the blowing agent through a die having multiple small holes into pressurized circulating water, and cutting the material into particles with a rotary cutter. The type and amount of the styrene-based resin, the type and amount of the carbon-based radiation heat transfer inhibitor, the type and amount of the blowing agent, and other additives can be appropriately set based on the above description.

In the above-mentioned manufacturing method, from the viewpoint of dispersibility between the styrene resin and the various components, a preferred embodiment is to first use a kneading device equipped with a twin-shaft agitator (such as a Banbury mixer) to knead a portion of the styrene resin with the various components under load to produce a kneaded product such as a master batch, and then feed the resulting kneaded product together with new styrene resin and other components into an extruder to melt-knead and then cut into particles.

In one preferred embodiment of the above manufacturing method, a styrene-based resin and a carbon-based radiation heat transfer inhibitor are kneaded in a kneading device equipped with a two-shaft agitator such as a Banbury mixer to prepare a master batch, and the master batch thus prepared is melt-kneaded with new styrene-based resin and, if necessary, other components such as a flame retardant in an extruder, and then a foaming agent is added. The resulting molten resin is extruded through a die with small holes attached to the tip of the extruder into a cutter chamber filled with pressurized circulating water, and immediately after extrusion, it is cut with a rotating cutter and cooled and solidified by the pressurized circulating water.

In another preferred embodiment of the above manufacturing method, a styrene-based resin and a carbon-based radiation heat transfer inhibitor are mixed in a mixer equipped with a twin-shaft agitator such as a Banbury mixer to prepare a master batch, and a styrene-based resin, a flame retardant, and a heat stabilizer are mixed in a mixer equipped with a twin-shaft agitator such as a Banbury mixer to prepare another master batch. The two master batches prepared are melt-mixed in an extruder with a new styrene-based resin and, if necessary, other components. A foaming agent is then added, and the resulting resin melt is extruded through a die with small holes attached to the tip of the extruder into a cutter chamber filled with pressurized circulating water, and immediately after extrusion, it is cut with a rotating cutter and cooled and solidified by the pressurized circulating water.

In the above manufacturing method, the melt kneading in the extruder may be performed using a single extruder, multiple extruders may be connected, or an extruder may be used in combination with a second kneading device such as a static mixer or a stirrer without a screw, and can be selected as appropriate.

When two or more types of blowing agents are used in combination, the method of addition is not particularly limited as long as each blowing agent is added, and the agents may be added simultaneously or in two or more portions.

(Pre-expanded particles and styrene-based resin foamed molded products)
A styrene-based resin foamed molded article can be obtained by using the expandable styrene-based resin particles. In order to obtain a styrene-based resin foamed molded article, the expandable styrene-based resin particles may be pre-expanded and then foamed in a mold. The pre-expanded particles are also referred to as pre-expanded particles. That is, the present disclosure includes pre-expanded particles of a styrene-based resin obtained by expanding the expandable styrene-based resin particles described above, and a foamed molded article of a styrene-based resin obtained by molding the pre-expanded particles of a styrene-based resin.

The expandable styrene resin particles can be expanded 10 to 110 times using a conventional pre-expanding process, for example, with heated steam to form pre-expanded particles, which can then be used for molding after being cured for a certain period of time as necessary. The expansion ratio is preferably 50 times or more, and more preferably 70 times or more. The obtained pre-expanded particles can be molded (for example, molded in a mold) with steam using a conventional molding machine to produce a styrene resin foam molded article. Depending on the shape of the mold used, it is possible to obtain molded articles with complex shapes or block-shaped molded articles.

The expandable styrene resin particles can be molded into a styrene resin foamed molded article with a high expansion ratio. The expansion ratio of the foamed molded article is preferably 40 times or more, more preferably 60 times or more, even more preferably 70 times or more, and particularly preferably 80 times or more. The expandable styrene resin particles make it possible to achieve high expansion of the foamed molded article even when the amount of blowing agent is less than that of the conventional method.

For insulation materials, since they are used for a long period of time, maintaining the insulation performance after a long period of time is an important issue. For the styrene-based resin foam molded body molded with the styrene-based resin composition and expandable styrene-based resin particles according to the present invention, a sample for measuring thermal conductivity is cut out from the styrene-based resin foam molded body, the sample is annealed at 70°C for 35 days, and even after being left to stand for 24 hours at 23°C, a low thermal conductivity can be achieved. By annealing at 70°C for 35 days, the content of hydrocarbon-based blowing agents such as butane and pentane contained in the styrene-based resin foam molded body is 1.0% or less, and the effect of the blowing agent on the thermal conductivity is negligible, and the thermal conductivity of the styrene-based resin foam molded body when used for a long period of time at room temperature can be evaluated.

When the expandable styrene resin particles are used to produce an expanded molded product with an expansion ratio of 80 times, the 80-fold expanded molded product is allowed to stand at 70°C for 35 days, and then allowed to stand at 23°C for 24 hours. The thermal conductivity at 23°C measured according to JIS A9511:2006R is preferably 0.034 W/mK or less. In other words, if the thermal conductivity is 0.034 W/mK or less, it can be said that a very low thermal conductivity and therefore high thermal insulation can be maintained for a long period of time. It is more preferably 0.033 W/mK or less, and even more preferably 0.032 W/mK or less.

In this specification, the expansion ratio is expressed in units of "times" or "cm ³ /g", but these have the same meaning.

The pre-expanded particles and the resulting styrene-based resin foamed molded product preferably have an average cell diameter of 70 to 300 μm, more preferably 90 to 250 μm, and even more preferably 100 to 200 μm. By having an average cell diameter within the aforementioned range, a styrene-based resin foamed molded product with higher thermal insulation properties is obtained. If the average cell diameter is 70 μm or more, it tends to be easier to increase the expansion ratio, and if it is 300 μm or less, an increase in thermal conductivity, i.e., a deterioration in thermal insulation performance, can be avoided.

(Applications of foamed molded products)
The foamed molded article made by using the expandable styrene-based resin particles has excellent surface beauty, a high expansion ratio, a high closed cell ratio, low thermal conductivity, a significant suppression of the increase in thermal conductivity over time, and high long-term heat insulation, and is therefore suitable for various applications such as building insulation materials, food container boxes, cold storage boxes, cushioning materials, agricultural and fishery boxes, bathroom insulation materials, and hot water tank insulation materials.

The manufacturing conditions for the expandable styrene-based resin particles disclosed herein and the method for measuring the physical properties of the resulting product can be carried out by appropriately referring to JP 2019-65073 A in addition to those disclosed in this specification.

The present embodiment will be described below with reference to examples, but the present disclosure is not limited to these examples.

The methods for measuring and evaluating the various physical properties in the following examples and comparative examples are as follows:

(Method of measuring melt flow rate (MFR) of styrene-based resin)
The melt flow rate of the styrene resin was measured in accordance with the method described in JIS K7210 "Plastics - Determination of melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics" Method B. More specifically, the melt flow rate of the styrene resin (styrene resin pellets) was measured using a "semi-automatic melt flow index tester" manufactured by Yasuda Seiki Seisakusho under the measurement conditions of a test temperature of 200°C and a load of 5.0 kg.

(Method for measuring apparent density of expandable styrene-based resin particles)
The expandable styrene-based resin particles were collected as a measurement sample of W (kg), and the measurement sample was allowed to fall naturally into a measuring cylinder containing ethanol. The mass (kg) and volume (m ³ ) of the measurement sample were measured, and the apparent density was calculated based on the following formula:
Apparent density (kg/m ³ )=weight of measurement sample (W)/volume of measurement sample (V)

(Method for measuring bulk magnification of pre-expanded particles)
A measurement sample of W (g) was taken from the pre-expanded particles, and this measurement sample was allowed to fall naturally into a measuring cylinder, and the measuring cylinder was then tapped to keep the apparent volume V ( ^cm3 ) of the sample constant. The mass (g) and volume ( ^cm3 ) of the sample were then measured, and the bulk ratio was calculated based on the following formula:
Bulk ratio (cm ³ /g)=volume of measurement sample (V)/weight of measurement sample (W)

(Expansion ratio of styrene-based resin foamed molding)
The styrene-based resin foam molded article was removed from the mold and dried at 30° C. for 24 hours, after which the weight (g) of the foam molded article was measured, and the length, width, and thickness were measured using a vernier caliper. The volume (cm ³ ) of the styrene-based resin foam molded article was calculated from each of the measured dimensions, and the expansion ratio was calculated according to the following formula.
Expansion ratio (cm ³ /g)=test piece volume (cm ³ )/test piece weight (g)
The expansion ratio "times" of the styrene-based resin foamed molded article is customarily expressed in "cm ³ /g".

(Method of measuring thermal conductivity of styrene-based resin foam molded products)
It is generally known that the higher the average temperature at which thermal conductivity is measured, the higher the thermal conductivity value, and it is necessary to determine the average temperature at which thermal conductivity is measured in order to compare thermal insulation. In this specification, the standard temperature of 23°C, which is set by JIS A9511:2006R, which is a standard for foamed plastic insulation materials, is adopted. The thermal conductivity was measured after leaving the styrene-based resin foamed molded body at 70°C for 35 days, cutting out a sample for measuring thermal conductivity, and leaving it at 23°C for 24 hours.

More specifically, the styrene-based resin foam molded body was left to stand at 70°C for 35 days, and then a sample of 300 mm length x 300 mm width x 25 mm was cut out. The sample was then left to stand at 23°C for 24 hours, and the thermal conductivity was measured using a thermal conductivity measuring device (HC-074, manufactured by Eiko Seiki Co., Ltd.) at an average temperature of 23°C and a temperature difference of 20°C by the heat flow meter method in accordance with JIS A1412-2:1999.

(Evaluation of surface properties of styrene-based resin foam molded articles)
The surface properties of the obtained styrene-based resin foam molded articles were visually observed in a field of 300 mm×300 mm and evaluated according to the following criteria.
AA: The number of foamed beads with depressions on the surface of the molded article is 100 or less.
BB: More than 100 foamed beads have depressions on the surface of the molded article.

(Evaluation of dimensional change rate of styrene-based resin foam molded body at high temperatures)
The dimensional change rate at high temperature in this specification is a value measured in accordance with the B method of dimensional stability at high temperature specified in JIS K6767. More specifically, a sample of 150 mm length x 150 mm width x 25 mm length was cut out, and the sample was left at 23°C for 24 hours, and then three straight lines were drawn on the sample in parallel in the vertical and horizontal directions at 50 mm intervals. The lengths of the three lines were measured in the vertical and horizontal directions, and the average value was taken as the initial dimension (L1). The sample was heated at 80°C for 22 hours, removed, and left at 23°C for 1 hour, and then the lengths of the three lines were measured in the vertical and horizontal directions, and the average value was taken as the dimension after heating (L2). The dimensional change rate was calculated according to the following calculation formula.
Dimensional change rate (%) = (L2 (mm) - L1 (mm)) / (L1 (mm)) x 100

(Evaluation of heat resistance of styrene-based resin foam molded bodies)
From the above-mentioned evaluation of the dimensional change rate at high temperatures, the heat resistance performance of the styrene-based resin foam molded article was evaluated based on the following criteria.
AA: Dimensional change rate is more than -3.0% and less than +3.0% BB: Dimensional change rate is less than -3.0% or more than +3.0%

The raw materials used in the examples and comparative examples are listed below.

(styrene resin)
(A1) Styrene homopolymer [manufactured by PS Japan Co., Ltd., 680] (MFR: 7.0 g/10 min)
(A2) Styrene homopolymer [manufactured by PS Japan Co., Ltd., 679] (MFR: 18.0 g/10 min)
(Carbon-based radiation heat transfer inhibitor)
(B) Graphite [flake graphite SGP-40B, manufactured by Marutoyo Foundry Co., Ltd.]

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

(Foaming Agent)
(E1) Normal pentane [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent product]
(E2) Isopentane [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent product]
(E3) Isobutane [manufactured by Mitsui Chemicals, Inc.]
(Other additives)
(F) Ethylene bis stearic acid amide [NOF Corporation, Alflow H-50S]

(Production Example 1) (Graphite Masterbatch (G))
The raw materials were charged into a Banbury mixer so that the total weight (A1+B+F) of 49% by weight of styrene resin (A1), 50% by weight of graphite (B), and 1% by weight of ethylene bisstearic acid amide (F) was 100% by weight, and kneaded for 20 minutes without heating or cooling under a load of 5 kgf/ ^cm2 . At this time, the resin temperature was measured to be 180°C. The strand-shaped resin was fed to a ruder and extruded at 250 kg/hr through a die with small holes attached to the tip, cooled and solidified in a water tank at 30°C, and then cut to obtain a master batch (G). The graphite content in the master batch (G) was 50% by weight.

(Production Example 2) (Masterbatch (H) of a mixture of a brominated flame retardant and a heat stabilizer)
A styrene-based resin (A1) was fed into a twin-screw extruder and melt-kneaded, and then a mixture of a brominated flame retardant (C), a heat stabilizer (D1) and (D2) was fed from the middle of the extruder and further melt-kneaded. However, the weight ratio of each material was (A1): (C): (D1): (D2) = 70: 28.5: 0.6: 0.9, (A1) + (C) + (D1) + (D2) = 100 wt%. A strand-shaped resin extruded at 300 kg/hr through a die with small holes attached to the tip of the extruder was cooled and solidified in a water tank at 20 ° C., and then cut to obtain a master batch (H) of a mixture of a brominated flame retardant and a heat stabilizer. The extruder was set at a temperature of 170 ° C.

Example 1
[Preparation of styrene-based resin pellets]
The styrene resin (A1) and the styrene resin (A2) were uniformly blended in a mixer, melt-kneaded in a 26 mm diameter unidirectional twin-screw extruder, and then extruded into strands through a die attached to the extruder tip, cooled and solidified in a water tank, and then cut with a strand cutter to obtain styrene resin pellets. The weight ratio of (A1):(A2) was 80:20, and the total supply amount was 5 kg/h. The MFR of the obtained styrene resin pellets was 9.2 (g/10 min).

[Preparation of expandable styrene-based resin particles]
A mixture of styrene-based resin (A1) and styrene-based resin (A2) uniformly blended with a mixer, a graphite masterbatch (G), and a masterbatch (H) of a mixture of a bromine-based flame retardant and a heat stabilizer were fed 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 40 mm diameter extruder. The weight ratio of (A1):(A2):(G):(H)=54.2:17.5:20:8.3, and the total feed amount was 55.7 kg/h. From the middle of the 40 mm diameter extruder (first extruder), mixed pentane [a mixture of 80% by weight of normal pentane (E1) and 20% by weight of isopentane (E2)] was injected at a ratio of 1.8 parts by weight per 100 parts by weight of the melt of the resin mixture (resin composition), and 2.4 parts by weight of isobutane (E3) was injected per 100 parts by weight of the resin composition, adding a total of 4.2 parts by weight of a foaming agent. Then, the mixture was supplied to a 90 mm diameter extruder (second extruder) through a continuation pipe set at 200°C.

The molten resin was cooled to a resin temperature of 170°C using a 90 mm diameter extruder (second extruder), and then extruded from a die with 40 small holes, each with a diameter of 0.75 mm and a land length of 5.0 mm, attached to the tip of the second extruder set at 260°C into pressurized circulating water at a temperature of 70°C and a pressure of 1.3 MPa. The extruded molten resin was cut and granulated using a rotating cutter with six blades that contacted the die, and transferred to a centrifugal dehydrator to obtain expandable styrene-based resin particles. At this time, the residence time in the first extruder was 2 minutes, and the residence time in the second extruder was 5 minutes.

The weight ratio of (A1):(A2) in the resin composition is 54.2 + 20 x 0.49 + 8.3 x 0.7:17.5 ≒ 80:20, taking into account the styrene-based resin (A1) contained in masterbatches (G) and (H). Therefore, the MFR of the styrene-based resin pellets can be considered to be the same as the MFR of the styrene-based resin in the resin composition. Similarly, the MFR of the styrene-based resin pellets in the other examples and comparative examples can be considered to be the same as the MFR of the styrene-based resin in each resin composition.

[Preparation of pre-expanded particles]
The obtained expandable styrene resin particles were stored at 15°C for one week or more, and then 0.04 parts by weight of zinc stearate and 0.1 parts by weight of hydroxystearic acid triglyceride, which are external additives, were dry-blended with the expandable styrene resin particles. 270 g of the expandable styrene resin particles containing the external additives were placed in a pre-expander [batch-type pre-expander manufactured by Daikai Kogyo Co., Ltd.], the pressure inside the can was set to 0.015 MPa to 0.025 MPa, and 0.12 MPa of steam was introduced into the pre-expander to expand the particles to a bulk ratio of 80 times, thereby obtaining pre-expanded particles. The expansion ratio of the obtained pre-expanded particles was 82 times.

[Preparation of styrene-based resin foam molded body]
The obtained pre-expanded particles were cured at 30°C for 24 hours, and then filled into a mold for in-mold molding (length 400 mm x width 400 mm x thickness 25 mm) attached to a polystyrene foam molding machine [KR-57, manufactured by Daisen Kogyo Co., Ltd.], and 0.05 MPa of water vapor was introduced to cause in-mold foaming, and then water was sprayed onto the mold to cool it. The styrene-based resin foam molded body was held in the mold until the pressure of the styrene-based resin foam molded body pressing the mold reached 0.01 MPa (gauge pressure), and then the styrene-based resin 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 82 times, and the thermal conductivity of the styrene-based resin foam molded body was measured by the above-mentioned measurement method, and was 0.02980 W/mK.

The various properties of the resulting expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded articles were measured and evaluated using the measurement and evaluation methods described above.

Example 2
In the preparation of styrene-based resin pellets, except that the weight ratio of (A1):(A2) was changed from 80:20 to 60:40, styrene-based resin pellets were prepared in the same manner as in Example 1. The MFR of the obtained styrene-based resin pellets was 11.4 (g/10 min).

In [Preparation of expandable styrene-based resin particles], expandable styrene-based resin particles were prepared by the same process as in Example 1, except that the weight ratio of (A1):(A2):(G):(H) was changed from 54.2:17.5:20:8.3 to 36.7:35:20:8.3. Using the prepared expandable styrene-based resin particles, pre-expanded particles and styrene-based resin foamed molded products were obtained by the same method as in Example 1.

The various properties of the resulting expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded articles were measured and evaluated using the measurement and evaluation methods described above.

Example 3
In the preparation of styrene-based resin pellets, except that the weight ratio of (A1):(A2) was changed from 80:20 to 40:60, styrene-based resin pellets were prepared in the same manner as in Example 1. The MFR of the obtained styrene-based resin pellets was 13.6 (g/10 min).

In [Preparation of expandable styrene-based resin particles], expandable styrene-based resin particles were prepared by the same process as in Example 1, except that the weight ratio of (A1):(A2):(G):(H) was changed from 54.2:17.5:20:8.3 to 19.2:52.5:20:8.3.

[Preparation of pre-expanded particles] Pre-expanded particles were prepared in the same manner as in Example 1, except that the pressure setting in the can was changed from 0.015 MPa to 0.025 MPa to 0.005 MPa to 0.015 MPa. Using the prepared pre-expanded particles, a styrene-based resin foam molded article was obtained in the same manner as in Example 1.

The various properties of the resulting expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded articles were measured and evaluated using the measurement and evaluation methods described above.

(Comparative Example 1)
In the preparation of styrene-based resin pellets, except that the weight ratio of (A1):(A2) was changed from 80:20 to 100:0, styrene-based resin pellets were prepared in the same manner as in Example 1. The MFR of the obtained styrene-based resin pellets was 7.0 (g/10 min).

In [Preparation of expandable styrene-based resin particles], expandable styrene-based resin particles were prepared by the same process as in Example 1, except that the weight ratio of (A1):(A2):(G):(H) was changed from 54.2:17.5:20:8.3 to 71.7:0:20:8.3. Using the prepared expandable styrene-based resin particles, pre-expanded particles and styrene-based resin foamed molded products were obtained by the same method as in Example 1.

The obtained styrene resin foam molded body had scattered sunken foam particles on the surface of the molded body, making it impossible to measure its dimensions, so it was impossible to measure the molded body's magnification and evaluate its dimensional change rate at high temperatures. With regard to the molded body's magnification, dimensional change rate at high temperatures, and heat resistance, various properties were measured and evaluated for the obtained expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded body using the measurement and evaluation methods described above.

(Comparative Example 2)
In the preparation of styrene-based resin pellets, except that the weight ratio of (A1):(A2) was changed from 80:20 to 100:0, styrene-based resin pellets were prepared in the same manner as in Example 1. The MFR of the obtained styrene-based resin pellets was 7.0 (g/10 min).

In [Preparation of expandable styrene-based resin particles], expandable styrene-based resin particles were prepared by the same process as in Example 1, except that the weight ratio of (A1):(A2):(G):(H) was changed from 54.2:17.5:20:8.3 to 71.7:0:20:8.3, the mixed pentane was changed from 1.8 parts by weight to 4.2 parts by weight, and the isobutane (E3) was changed from 2.4 parts by weight to 0 parts by weight.

[Preparation of pre-expanded particles] In the preparation of pre-expanded particles, the same process as in Example 1 was carried out, but the expansion ratio of the resulting expanded particles was 60 times, and it was not possible to expand the particles to 80 times. Using the prepared pre-expanded particles, a styrene-based resin foam molded product was obtained by the same method as in Example 1.

The various properties of the resulting expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded articles were measured and evaluated using the measurement and evaluation methods described above.

(Comparative Example 3)
In the preparation of styrene-based resin pellets, except that the weight ratio of (A1):(A2) was changed from 80:20 to 18:82, styrene-based resin pellets were prepared in the same manner as in Example 1. The MFR of the obtained styrene-based resin pellets was 16.0 (g/10 min).

In the [Preparation of expandable styrene-based resin particles], expandable styrene-based resin particles were prepared by the same process as in Example 1, except that the weight ratio of (A1):(A2):(G):(H) was changed from 54.2:17.5:20:8.3 to 0:71.7:20:8.3.

[Preparation of pre-expanded particles] Pre-expanded particles were prepared in the same manner as in Example 1, except that the pressure setting in the can was changed from 0.015 MPa to 0.025 MPa to 0.005 MPa to 0.015 MPa. Using the prepared pre-expanded particles, a styrene-based resin foam molded article was obtained in the same manner as in Example 1.

The various properties of the resulting expandable styrene resin particles, pre-expanded particles, and styrene resin foam molded articles were measured and evaluated using the measurement and evaluation methods described above.

For each example and comparative example, the composition of the styrene resin pellets, MFR, the amount of each component in the styrene resin composition, the amount of each blowing agent, the apparent density of the expandable styrene resin particles, the bulk magnification of the pre-expanded particles, the expansion magnification (molded product magnification) of the styrene resin foamed molded product, the surface properties of the molded product, the dimensional change rate at high temperatures, and the heat resistance performance are shown in Table 1.

As can be seen from Table 1, by using the expandable styrene-based resin particles of the present disclosure, it is possible to obtain a styrene-based resin foamed molded product with excellent heat resistance and a high expansion ratio.

The upper and/or lower limit values of the numerical ranges described in this specification can be arbitrarily combined to define a preferred range. For example, the upper and lower limit values of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limit values of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limit values of the numerical ranges can be arbitrarily combined to define a preferred range. In this application, a numerical range expressed using the symbol "~" includes the numerical values written before and after the symbol "~" as the lower and upper limits, respectively.

Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope that does not deviate from the gist of this disclosure, they are included in this disclosure.

Claims (11)

A styrene-based resin composition containing a styrene-based resin and a carbon-based radiation heat transfer inhibitor, and an expandable styrene-based resin particle containing a blowing agent,
The expandable styrene-based resin particles have a melt flow rate of 7.5 to 15.5 g/10 min at 200° C. under a load of 5.0 kg, and the foaming agent contains isobutane. The expandable styrene-based resin particles according to claim 1, wherein the expandable styrene-based resin particles have an apparent density of more than 950 kg/ ^m3 and not more than 1,200 kg/ ^m3 . The expandable styrene-based resin particles according to claim 1, wherein the styrene-based resin composition contains a flame retardant, and the flame retardant is more than 1.0% by weight and not more than 6.0% by weight in 100% by weight of the styrene-based resin composition. The expandable styrene-based resin particles according to claim 1, in which the carbon-based radiation heat transfer inhibitor is more than 2% by weight and not more than 20% by weight in 100% by weight of the styrene-based resin composition. The expandable styrene-based resin particles according to claim 1, wherein the carbon-based radiation heat transfer inhibitor is at least one carbon-based radiation heat transfer inhibitor selected from graphite, carbon black, carbon nanotubes, graphene, and activated carbon. The expandable styrene-based resin particles according to claim 1, wherein the amount of the blowing agent in the expandable styrene-based resin particles is more than 1.0 parts by weight and not more than 8.0 parts by weight per 100 parts by weight of the styrene-based resin composition. The expandable styrene-based resin particles according to claim 1, in which isobutane is 15 to 90% by weight out of 100% by weight of the blowing agent. The expandable styrene-based resin particles according to claim 1, wherein the blowing agent contains a saturated hydrocarbon having 5 to 6 carbon atoms. The expandable styrene-based resin particles according to claim 1, wherein the blowing agent comprises pentane. Pre-expanded styrene resin particles obtained by expanding the expandable styrene resin particles according to claim 1. A foamed molded article of a styrene-based resin obtained by molding the pre-expanded particles of the styrene-based resin according to claim 10.