JP2024142436A - Method for producing styrene-based resin composition and method for producing expandable styrene-based resin particles - Google Patents

Abstract

To provide a method for producing a styrenic resin composition which enables production of a styrenic resin foam molding with excellent heat insulation performance and can improve costs than conventional methods.SOLUTION: A method for producing a styrenic resin composition includes a step A of supplying a styrenic resin, carbon, a bromine-based flame retardant and a stabilizer to a multiaxial extruder, and melting and kneading the materials, wherein the carbon, the bromine-based flame retardant and the stabilizer are supplied to the multiaxial extruder in powder states, and a ratio of carbon/(bromine-based flame retardant+stabilizer) which is a weight ratio of the carbon to the total amount of the bromine-based flame retardant and the stabilizer is 1.4 or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a styrene-based resin composition and a method for producing 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-based resin particles made of a styrene-based resin composition containing graphite and a foaming agent, the graphite content being 2 to 10% by weight based on 100% by weight of the styrene-based resin composition, and the number of bubbles present within a radius of 300 μm from the center point of the perpendicular bisecting plane relative to the major axis diameter in the expandable styrene-based resin particles being 550 or less per square millimeter.

JP 2018-090707 A

It is disclosed in Patent Document 1 that the expandable styrene resin particles disclosed can suppress shrinkage immediately after pre-expansion in the resulting pre-expanded particles even during high expansion ratios, and that it is possible to obtain a styrene resin foamed molded article that has both a high expansion ratio and high thermal insulation properties. Patent Document 1 also discloses a manufacturing method for expandable polystyrene resin particles, which includes a step of preparing a master batch containing a styrene resin and graphite.

The inventors of the present invention conducted extensive research into a method that can produce a styrene resin foam molded article with excellent heat insulating properties and that can reduce costs compared to conventional methods. As a result, they discovered a method for producing a styrene resin composition in which specific materials are supplied to a multi-screw extruder in specific conditions and in specific amounts, and completed the present invention.

An example of this embodiment is described as follows:

[1] A process A includes supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture;
The carbon, the brominated flame retardant, and the stabilizer are fed in powder form to a multi-screw extruder;
A method for producing a styrene-based resin composition, wherein a weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer, carbon/(brominated flame retardant+stabilizer), is 1.4 or less.
[2] The multi-screw extruder is a twin-screw extruder,
The method for producing a styrene-based resin composition according to [1], wherein the Q/N of the twin-screw extruder is within the range of the following formula.
Q/N ≦ 8.0×10 ^-6 ×D ³
(In the above formula, Q represents the twin-screw extruder extrusion rate (kg/hr), N represents the screw rotation speed (rpm), and D represents the twin-screw extruder barrel inner diameter (mm).)
[3] The method for producing a styrene-based resin composition according to [1] or [2], wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite.
[4] A process A includes supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture;
The carbon, the brominated flame retardant, and the stabilizer are fed in powder form to a multi-screw extruder;
A method for producing expandable styrene-based resin particles, wherein a weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer, carbon/(brominated flame retardant+stabilizer), is 1.4 or less.
[5] The multi-screw extruder is a twin-screw extruder,
The method for producing expandable styrene-based resin particles according to [4], wherein the Q/N of the twin-screw extruder is within the range of the following formula:
Q/N ≦ 8.0×10 ^-6 ×D ³
(In the above formula, Q represents the twin-screw extruder extrusion rate (kg/hr), N represents the screw rotation speed (rpm), and D represents the twin-screw extruder barrel inner diameter (mm).)
[6] The method for producing expandable styrene-based resin particles according to [4] or [5], wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite.
[7] A method for producing expandable styrene-based resin particles according to any one of [4] to [6], comprising: a step B of further adding a blowing agent to the styrene-based resin composition obtained in the step A to obtain an expandable styrene-based resin composition; and a step C of granulating the expandable styrene-based resin composition to obtain expandable styrene-based resin particles.
[8] A method for producing expandable styrene-based resin particles according to any one of [4] to [6], comprising: a step D of granulating the styrene-based resin composition obtained in the step A to obtain styrene-based resin particles; and a step E of impregnating the styrene-based resin particles with a blowing agent to obtain expandable styrene-based resin particles.
[9] A method for producing pre-expanded styrene-based resin particles, comprising expanding the expandable styrene-based resin particles obtained by the method for producing expandable styrene-based resin particles according to any one of [4] to [8].
[10] A method for producing a styrene-based resin foamed molded article, comprising molding the styrene-based resin pre-expanded particles obtained by the method for producing the styrene-based resin pre-expanded particles according to [9].

In the manufacturing method of the present disclosure, carbon can be well dispersed in the styrene-based resin composition without including an additional step such as preparing a masterbatch. By using the styrene-based resin composition, expandable styrene-based resin composition, or expandable styrene-based resin particles obtained by the manufacturing method of the present disclosure, it is possible to obtain a styrene-based resin foamed molded article with excellent heat insulating performance. In addition, there is no need to prepare a masterbatch, and manufacturing costs are improved.

The present invention will be described in detail below. The method for producing a styrene-based resin composition according to this embodiment includes a step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture, and the carbon, the bromine-based flame retardant, and the stabilizer are supplied to the multi-screw extruder in powder form, and the weight ratio of the carbon to the total amount of the bromine-based flame retardant and the stabilizer, carbon/(bromine-based flame retardant+stabilizer), is 1.4 or less. The method for producing expandable styrene-based resin particles according to this embodiment includes a step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture, and the carbon, the bromine-based flame retardant, and the stabilizer are supplied to the multi-screw extruder in powder form, and the weight ratio of the carbon to the total amount of the bromine-based flame retardant and the stabilizer, carbon/(bromine-based flame retardant+stabilizer), is 1.4 or less.

(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 copolymerizable with styrene or a derivative thereof can be used. As the styrene-based resin, one type may be used alone, or two or more types may be used. However, in the present embodiment, the styrene-based resin generally excludes a 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 melt flow rate (hereinafter referred to as "MFR") of the styrene resin is preferably 1 to 15 g/10 min. When the MFR is in this range, it is easy to obtain expandable styrene resin particles, pre-expanded styrene resin particles, and styrene resin foam molded articles that are excellent in expandability (high expansion ratio, high air ratio) and surface beauty. The obtained styrene resin foam molded articles have a good balance of mechanical strength such as compressive strength, bending strength, or bending deflection, and properties such as toughness. A more preferable range for the MFR is 2 to 10 g/10 min. The MFR in the present invention is a value measured in accordance with JIS K7210.

In addition, as long as the effects of the present invention are not impaired, other resins may be used in combination with the styrene-based resin as the main component. 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, etc.

(carbon)
The carbon acts as a radiation heat transfer inhibitor in this embodiment. By using carbon together with a styrene resin, a styrene resin foam molded article having high thermal insulation properties can be obtained. In this disclosure, the radiation heat transfer inhibitor refers to a substance having the property of reflecting, scattering, or absorbing light in the near infrared or infrared region.

The carbon is preferably at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. The carbon may be used alone or in combination of two or more. Among carbons, graphite is preferred because of its high radiation heat transfer suppression effect relative to cost. Examples of graphite include flake graphite, earthy graphite, spherical graphite, and artificial graphite, and of these, flake graphite is preferred because it exhibits a high radiation heat transfer suppression effect. In this disclosure, the term "flake" also includes scaly, thin, or plate-like graphite. The graphite may be used alone or in combination of two or more.

The graphite preferably has an average particle size of 0.5 to 9.0 μm, more preferably 2.5 to 9.0 μm, and even more preferably 2.5 to 6.0 μm. In this disclosure, the average particle size of the graphite refers to the particle size (D50) (volume average particle size measured by the laser diffraction scattering method) at which the cumulative volume of the total particle volume 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.

The larger the average particle size of graphite, the lower the manufacturing cost. In particular, graphite with an average particle size of 2.5 μm or more is very inexpensive and can reduce costs due to its low manufacturing cost, including the cost of crushing. If the average particle size is 9.0 μm or less, the cell membrane is less likely to break when producing pre-expanded particles and styrene-based resin foamed molded products from expandable styrene-based resin particles, which tends to make it easier to achieve high expansion, increase ease of molding, and increase the compressive strength of styrene-based resin foamed molded products.

Furthermore, if the average particle size of the graphite is 6.0 μm or less, the surface of the molded body will be excellent in appearance and will have a lower thermal conductivity, i.e., higher thermal insulation.

In the present invention, the carbon content is not particularly limited, but is preferably 0.1 to 20% by weight, and more preferably 2 to 10% by weight, based on 100% by weight of the styrene-based resin composition.

The use of graphite as carbon is preferable from the viewpoint of the balance between the thermal conductivity reduction effect and the dispersibility of graphite in the styrene resin composition. As for the amount of graphite, the graphite content is preferably 2% by weight or more and 10% by weight or less in 100% by weight of the styrene resin composition. When the graphite content is 2% by weight or more, the thermal conductivity reduction effect tends to be sufficient, and when the graphite content is 10% by weight or less, when the cell membrane is not easily broken when producing pre-expanded particles and styrene resin foamed molded bodies from graphite and styrene resin, it is easy to achieve high expansion and easy to control the expansion ratio. Furthermore, the graphite content is more preferably 3% by weight or more and 8% by weight or less. When the graphite content is 3% by weight or more, the thermal conductivity becomes lower, that is, higher insulation can be obtained. In addition, when the graphite content is 8% by weight or less, the expandability and the surface beauty of the molded body become good.

The expandable styrene-based resin particles of the present disclosure preferably have a carbon content of 2 to 10% by weight based on 100% by weight of the expandable styrene-based resin particles. Even when graphite is contained as an embodiment of the expandable styrene-based resin particles of the present disclosure, the graphite content is preferably 2% by weight or more and 10% by weight or less in the resin composition of the expandable styrene-based resin particles, and the above more preferred ranges are similarly applicable.

(Brominated flame retardants)
The bromine-based flame retardant is not particularly limited, and any flame retardant containing bromine as a constituent atom that has been conventionally used for styrene-based resin foam molded articles can be used. 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)), tetrabromocyclooctane, tris(2,3-dibromopropyl)isocyanurate, brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers. As the brominated flame retardant, for example, the thermally stable brominated copolymer disclosed in JP-A-2009-516019 may be used. The brominated flame retardant may be used alone or in combination of two or more kinds.

The amount of bromine-based flame retardant used can be determined based on the amount of bromine (bromine content) constituting the bromine-based flame retardant. For example, the amount of bromine-based flame retardant contained in a styrene-based resin composition can be determined by the product of the amount of bromine-based flame retardant (wt%) contained in the composition and the bromine content (wt%) of the bromine-based flame retardant. The bromine-based flame retardant is preferably 0.8 wt% or more and 8.0 wt% or less in 100 wt% of the styrene-based resin composition, because it is easy to control the expansion ratio to the desired value, and from the viewpoint of the balance of flame retardancy when carbon is added, etc. If the bromine content is 0.8 wt% or more, the effect of imparting flame retardancy tends to be large, and if it is 8.0 wt% or less, the strength of the resulting styrene-based resin foam molding is likely to increase. The bromine content in the styrene-based resin composition or the expandable styrene-based resin particles is more preferably 1.0 to 7.0 wt%.

(Stabilizer)
The stabilizer is not particularly limited, but it is preferable to use a heat stabilizer that can suppress the deterioration of flame retardancy due to the decomposition of the bromine-based flame retardant and the deterioration of the styrene-based resin. The stabilizers can be used in appropriate combinations depending on the type of styrene-based resin used, the type and content of carbon, the type and content of the bromine-based flame retardant, the type and content of the foaming agent described below, and the like.

As the heat stabilizer, a hindered amine compound, a phosphorus-based compound, a phenol-based stabilizer, or an epoxy compound is preferable because it allows the weight loss temperature of a mixture containing a bromine-based flame retardant 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.

In the present invention, the content of the stabilizer is not particularly limited, but is preferably 0.01 to 5% by weight, and more preferably 0.03 to 3% by weight, based on 100% by weight of the styrene-based resin composition. In addition, in the present invention, the content of the stabilizer is not particularly limited, but the weight ratio of bromine to stabilizer in the bromine-based flame retardant is preferably 99:1 to 80:20, and more preferably 95:5 to 90:10.

(Foaming Agent)
In the present disclosure, a foaming agent may be further added to the styrene resin composition to form an expandable styrene resin composition. The expandable styrene resin composition can be molded into expandable styrene resin particles or in-mold foamed molded bodies described below, or extruded foamed bodies. The foaming agent is not particularly limited, but from the viewpoint of a good balance between expandability and product life and easy high expansion ratio when actually used, a hydrocarbon having 3 to 6 carbon atoms is preferable, and a hydrocarbon having 4 to 5 carbon atoms is more preferable. When the carbon number of the foaming agent is 3 or more, the volatility is low and the foaming agent is less likely to dissipate when the foaming agent is made into expandable styrene resin particles, so that the foaming agent remains sufficiently in the foaming process when actually used, making it possible to obtain sufficient foaming power, and it is easy to increase the expansion ratio, which is preferable. In addition, when the carbon number is 6 or less, the boiling point of the foaming agent is not too high, so that sufficient foaming power is easily obtained by heating during pre-foaming, and there is a tendency for high foaming to be easy. Examples of the hydrocarbon having 3 to 6 carbon atoms include hydrocarbons such as propane, normal butane, isobutane, 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 high expansion ratio and the product life, it is particularly preferable that the blowing agent contains at least one selected from the group consisting of isobutane, normal butane, isopentane, and normal pentane. It is particularly preferable that the blowing agent contains at least one selected from the group consisting of normal pentane, isopentane, and isobutane, and it is even more preferable that the blowing agent contains normal pentane, isopentane, and isobutane.

The amount of the foaming agent added is preferably 2 to 10 parts by weight, more preferably 4 to 10 parts by weight, relative to 100 parts by weight of the styrene resin composition. In the above range, when expandable styrene resin particles are obtained, the balance between the expansion speed and the expansion power is better, and it is easier to achieve a high expansion ratio more stably. When the amount of the foaming agent added is 4 parts by weight or more, the expansion power required for expansion is sufficient, making it easier to achieve high expansion and tends to make it easier to produce a styrene resin foam molded product with a high expansion ratio of 50 times or more. In addition, when the amount of the foaming agent is 10 parts by weight or less, the flame retardant performance is good and the production time (molding cycle) when producing a styrene resin foam molded product is shortened, so the production cost tends to be lower. In addition, the amount of the foaming agent added is more preferably 4.5 to 9 parts by weight, more preferably 5 to 8.5 parts by weight, relative to 100 parts by weight of the styrene resin composition.

(Other additives)
The styrene-based resin composition and the expandable styrene-based resin composition according to the present invention may contain, as necessary, other additives, for example, one or more other additives selected from the group consisting of a radical generator, a processing aid, a light resistance stabilizer, a nucleating agent, a foaming aid, an antistatic agent, and a colorant such as a pigment, within a range that does not impair the effects of the present invention.

When a radical generator is included, high flame retardant performance can be achieved by using it in combination with a brominated flame retardant.

The radical generators can be used in appropriate combinations depending on the type of styrene resin used, the type and content of carbon, the type and content of bromine-based flame retardant, the type and content of foaming agent, etc.

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

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.

(Method for producing styrene-based resin composition)
The method for producing a styrene-based resin composition according to the present embodiment includes a step A in which a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer are supplied to a multi-screw extruder and melt-kneaded. A styrene-based resin composition is obtained by the step A. The method for producing expandable styrene-based resin particles according to the present embodiment includes the step A, in other words, the method for producing a styrene-based resin composition, as a part thereof.

In step A, the carbon, the brominated flame retardant, and the stabilizer are supplied to the multi-screw extruder in powder form. As the powder, each of the carbon powder, the brominated flame retardant powder, and the stabilizer powder may be supplied to the multi-screw extruder, or the carbon powder and the powder of a mixture of the brominated flame retardant and the stabilizer may be supplied to the multi-screw extruder. That is, in step A, a master batch such as a master batch prepared by pre-kneading carbon and a styrene-based resin, a master batch prepared by pre-kneading a brominated flame retardant and a styrene-based resin, a master batch prepared by pre-kneading a stabilizer and a styrene-based resin, and a master batch prepared by pre-kneading a brominated flame retardant, a stabilizer, and a styrene-based resin is not supplied to the multi-screw extruder. Therefore, the manufacturing method of this embodiment can obtain a styrene-based resin composition that can provide a styrene-based resin foam molded product with excellent manufacturing cost and heat insulation performance.

In step A, the weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer, carbon/(brominated flame retardant + stabilizer), is 1.4 or less. In general, in order to fully exert the radiation heat transfer suppression effect of graphite, it is necessary to disperse the graphite well in the resin composition. As a method for dispersing the graphite well, a styrene resin and graphite have been mixed in advance under load using a kneading device equipped with an agitator such as a Banbury mixer, and used in the form of a master batch. Although a styrene resin foam molded product with excellent heat insulation performance can be obtained by the conventional method, a process for producing a master batch containing a styrene resin and graphite is required in the process for producing a styrene resin foam molded product. According to the study by the present inventors, by supplying the carbon, the brominated flame retardant, and the stabilizer in powder form to a multi-screw extruder and setting the weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer within the above range, a styrene-based resin composition can be obtained that can produce a styrene-based resin foam molded article with excellent heat insulation performance without using a master batch. The weight ratio is preferably 1.2 or less, more preferably 1.0 or less, and particularly preferably 0.9 or less. There is no particular limit to the lower limit of the weight ratio, but it is, for example, 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, and particularly preferably 0.4 or more.

In step A, when the multi-screw extruder is a twin-screw extruder, it is preferable that Q/N in the twin-screw extruder is in the range of the following formula.
Q/N ≦ 8.0×10 ^-6 ×D ³
(In the above formula, Q represents the twin-screw extruder extrusion rate (kg/hr), N represents the screw rotation speed (rpm), and D represents the twin-screw extruder barrel inner diameter (mm).)

By ensuring that the Q/N ratio in the twin-screw extruder is within the above-mentioned specific range, the dispersion state of the carbon in the styrene-based resin becomes good, which in turn tends to make it possible to obtain a highly expandable styrene-based resin foamed molded article with high thermal insulation performance at low cost, which is preferable.

The multi-screw extruder used in the present invention can be a known multi-screw extruder. Examples of multi-screw extruders include twin-screw extruders and four-screw extruders. From the viewpoints of kneading properties and productivity, twin-screw extruders are preferred, and co-rotating intermeshing twin-screw extruders are more preferred. Among kneading equipment that can continuously obtain a styrene-based resin composition, single-screw extruders tend to have poor carbon dispersibility compared to multi-screw extruders. Also, kneaders such as batch-type mixers and kneaders tend to have excellent carbon dispersibility compared to continuous extruders, but tend to have poor productivity. For the above reasons, a multi-screw extruder is used as the method for producing a styrene-based resin composition in this embodiment, preferably a twin-screw extruder, and more preferably a continuous twin-screw extruder.

(Conditions in the melt-kneading process)
Regarding the conditions of the melt-kneading step of the styrene resin and carbon in a multi-screw extruder in the production process of the styrene resin composition, a description will be given of the case where the multi-screw extruder is a twin-screw extruder.

(Q/N)
The Q/N in the twin-screw extruder is preferably 8.0×10 ⁻⁶ ×D ³ or less in both step A and step B described below. The lower the Q/N, the better the dispersion state of carbon tends to be, and as a result, a styrene-based resin composition or an expandable styrene-based resin composition that can provide a styrene-based resin foamed molded article having high thermal insulation performance can be obtained. If it exceeds 8.0×10 ⁻⁶ ×D ³ , the dispersion of carbon in the styrene-based resin becomes insufficient, and the thermal insulation performance tends to deteriorate. In order to ensure high thermal insulation performance, the preferred range is 6.5×10 ⁻⁶ ×D ³ or less.

Q/N indicates the extrusion rate per unit time (kg/hr) of the twin-screw extruder divided by the screw rotation speed (rpm) of the twin-screw extruder, and D indicates the barrel inner diameter (mm) of the twin-screw extruder. In general, the extrusion rate is roughly determined by the barrel inner diameter of the twin-screw extruder, and the larger D, the greater the extrusion rate that can be processed. As a result of intensive research by the inventors, in the present invention, it was found that by controlling Q/N within a certain range, regardless of the value of D, i.e., regardless of the extruder size and production scale, a highly dispersed state of carbon can be achieved in the present invention, and as a result, a styrene-based resin composition that can give a styrene-based resin foam with high thermal insulation performance can be easily obtained.

(Method for producing expandable styrene-based resin composition)
The method for producing an expandable styrene-based resin composition according to this embodiment includes step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading them, and step B of obtaining an expandable styrene-based resin composition by further adding a blowing agent to the styrene-based resin composition obtained in step A. The expandable styrene-based resin composition is obtained by steps A and B. In one aspect, the method for producing expandable styrene-based resin particles according to this embodiment includes steps A and B, in other words, a method for producing an expandable styrene-based resin composition, as a part thereof.

Step A can be carried out by the method described in the section on the method for producing a styrene-based resin composition above. Step B is a step carried out following step A. Step B is, for example, a step in which a foaming agent is dissolved and dispersed in a styrene-based resin by the multi-screw extruder or a dispersing facility following the multi-screw extruder, and the method is not particularly limited. In step B, for example, a foamable styrene-based resin composition can be obtained by further supplying a foaming agent to the styrene-based resin composition midway through a multi-screw extruder similar to step A, in other words, downstream of the point where the raw materials used in step A are supplied.

(Method for producing expandable styrene-based resin particles)
The method for producing expandable styrene-based resin particles according to the present embodiment includes step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture. Step A can be carried out by the method described in the above section on the method for producing a styrene-based resin composition.

The method for producing expandable styrene-based resin particles according to this embodiment can be roughly divided into the following aspects 1 and 2. The method for producing expandable styrene-based resin particles of aspect 1 includes, in addition to the step A, a step B of further adding a blowing agent to the styrene-based resin composition obtained in step A to obtain an expandable styrene-based resin composition, and a step C of granulating the expandable styrene-based resin composition to obtain expandable styrene-based resin particles. The method for producing expandable styrene-based resin particles of aspect 2 includes, in addition to the step A, a step D of granulating the styrene-based resin composition obtained in step A to obtain styrene-based resin particles, and a step E of impregnating the styrene-based resin particles with a blowing agent to obtain expandable styrene-based resin particles.

In the step C, the expandable styrene resin composition obtained in the step B can be processed into particles, and there is no particular limitation on the method. An example of the step C is a step of supplying the expandable styrene resin composition to a die having a plurality of small holes attached after the multi-screw extruder, extruding the molten expandable styrene resin composition into a cutter chamber filled with pressurized circulating water, cutting the molten expandable styrene resin composition with a rotating cutter that comes into contact with the die immediately after extrusion, and cooling and solidifying it.

In the step D, the styrene-based resin composition obtained in the step A can be processed into particles, and there are no particular limitations on the method used. Step D can be carried out in the same manner as the above-mentioned step C, except that the expandable styrene-based resin composition is replaced with a styrene-based resin composition.

In step E, the styrene-based resin particles obtained in step D may be impregnated with a blowing agent, and there are no particular limitations on the method used. For example, step E may be a method in which the styrene-based resin particles are suspended in water, and a blowing agent is supplied to impregnate the particles.

From the viewpoint of simplicity of equipment, mode 1 is preferred as a method for producing expandable styrene-based resin particles.

(Pre-expanded particles and styrene-based resin foamed molded products)
The styrene-based resin composition and the expandable styrene-based resin composition obtained by the above-mentioned manufacturing method can be used as raw materials for expandable styrene-based resin particles. 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 subjected to in-mold foaming. The pre-expanded particles are also referred to as pre-expanded particles or styrene-based resin pre-expanded particles. That is, the present disclosure includes a method for producing a styrene-based resin pre-expanded particle, which expands the expandable styrene-based resin particles obtained by the above-mentioned manufacturing method for expandable styrene-based resin particles, and a method for producing a styrene-based resin foamed molded article, which molds the styrene-based resin pre-expanded particles obtained by the manufacturing method for the styrene-based resin pre-expanded particles.

The expandable styrene resin particles can be made into pre-expanded particles by a conventional pre-expanding process, for example, by expanding them 10 to 110 times with heated steam, and then cured for a certain period of time as necessary before being used for molding. 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 foamed 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, and particularly preferably 80 times or more. The styrene resin composition, expandable styrene resin composition, and expandable styrene resin particles obtained by the above manufacturing method can achieve low thermal conductivity even when a styrene resin foamed molded article with an expansion ratio of 80 times or more is formed, and the above manufacturing method is also excellent in terms of manufacturing costs because it does not require the preparation of a master batch.

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, the styrene-based resin foamed molded product will have higher thermal insulation properties. 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 styrene resin composition obtained by the above-mentioned production method, the expandable styrene resin composition, and the foamed molded article molded using the expandable styrene resin particles have excellent surface beauty, high expansion ratio and high closed cell ratio, low thermal conductivity, the increase in thermal conductivity over time is significantly suppressed, and the heat insulation property is high for a long time. Therefore, they are 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 of the styrene-based resin composition, expandable styrene-based resin composition, and expandable styrene-based resin particles manufacturing method of the present disclosure, and the method for measuring the physical properties of the obtained products can be carried out by appropriately referring to JP 2019-172828 A in addition to the disclosures 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:

(Measurement of average particle size D50 (μm) and laser scattering intensity (%) of carbon)
(1) Conditions for preparing sample solution (a) When the measurement target is expandable styrene resin particles, 500 mg of expandable styrene resin particles (sample) was dissolved and dispersed in 20 mL of 0.1% (w/w) toluene solution of Span 80. Span 80 is a nonionic surfactant, to prepare a sample solution.

(b) When the measurement target is carbon before kneading, i.e., the raw material carbon itself, a sample solution was prepared by dissolving and dispersing 20 mg of carbon and 480 mg of the styrene-based resin (A) in 20 mL of a 0.1% (w/w) Span 80 toluene solution.

Note that the above dissolution and dispersion refers to a state in which the resin is dissolved and the carbon is dispersed.

(2) Ultrasonic Irradiation Next, the sample solution was irradiated with ultrasonic waves under the following conditions in an ultrasonic cleaner to relax the aggregation of carbon.
Equipment used: Ultrasonic cleaner, model USM, manufactured by AS ONE Corporation
Oscillation frequency: 42kHz
Irradiation time: 10 minutes Temperature: Room temperature

(3) Particle size measurement conditions Measuring device: Malvern Laser Diffraction Particle Size Distribution Measuring Device, Mastersizer 3000
Light source: 632.8 nm red He-Ne laser and 470 nm blue LED
Dispersion unit: Wet dispersion unit, Hydro MV
The analysis was performed with the following settings, and the volume distribution was determined 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, and the D50 particle size of carbon in the sample was calculated.
Particle type: Aspherical carbon Refractive index: 2.42
Carbon absorption rate: 1.0
Dispersion medium: 0.1% (w/w) Span 80 in toluene Refractive index of dispersion medium: 1.49
Agitation speed in the dispersion unit: 2500 rpm
Analysis model: General purpose, maintains single mode Measurement temperature: Room temperature

(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 irradiating 632.8 nm red He-Ne laser light in the state where there was no sample solution sample in the measurement cell and only the dispersion medium was used as the transmitted light intensity Lb. Next, 2 mL of the ultrasonically treated sample solution was collected and added to the dispersion unit. The light intensity measured by the central detector when irradiating 632.8 nm red He-Ne laser light 1 minute after adding 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)×100(%)

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

(5) Calculation of Laser Scattering Intensity per Unit Solution Concentration of Expandable Styrenic Resin Particles The laser scattering intensity per unit solution concentration of expandable styrene-based resin particles was calculated using the following formula.

Laser scattering intensity per unit solution concentration of expandable styrene-based resin particles (sample) (%/(mg/ml))=laser scattering intensity (O b )/{sample weight (500 mg)/toluene amount (20 mL)×sample injection amount (2 mL)/total toluene amount in dispersion unit (120 mL+2 mL)}
The laser scattering intensity per unit solution concentration is the measured laser scattering intensity divided by the sample concentration in toluene. Because this measurement device requires measurement in solution, the sample concentration in the toluene solution is kept constant, and measurements are obtained for a constant sample amount.

(6) Calculation of laser scattering intensity per unit weight of carbon in expandable styrene-based resin particles The laser scattering intensity per unit weight of carbon contained in the expandable styrene-based resin particles (hereinafter abbreviated as "measurement subject") was calculated using the following formula.

Laser scattering intensity per unit weight of carbon in the measurement target {%/(mg/ml)}/weight% = Laser scattering intensity per unit solution concentration of the measurement target (%/(mg/ml))/carbon content of the measurement target (weight%)

The state of carbon dispersion can be evaluated by using the laser scattering intensity per unit solution concentration of carbon.

The graphite dispersion state in the expandable styrene resin particles is determined by the graphite dispersion state in the styrene resin composition, so the laser scattering intensity per carbon unit solution concentration of the expandable styrene resin particles is substantially the same as the laser scattering intensity per carbon unit solution concentration of the styrene resin composition (expandable styrene resin composition).

The higher the laser scattering intensity per unit carbon solution concentration of the expandable styrene-based resin composition, the higher the thermal insulation performance of the resulting styrene-based resin foamed molding.

(Method of measuring the expansion ratio 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 struck to keep the apparent volume V ( ^cm3 ) of the sample constant. The weight (g) and volume ( ^cm3 ) of the sample were then measured, and the expansion ratio was calculated based on the following formula:
Expansion ratio (cm ³ /g)=volume (V) of measurement sample/weight (W) of measurement sample

(Calculation of foaming ratio)
A sample of 300 mm length x 300 mm width x 25 mm thickness was cut out from the styrene-based resin foam molded body in the same manner as in the case of measuring thermal conductivity described later. The weight (g) of the sample was measured, and the length, width and thickness were measured using a caliper. The volume (cm ³ ) of the sample was calculated from each measured dimension, and the expansion ratio was calculated according to the following formula.

Expansion ratio (cm ³ /g)=sample volume (cm ³ )/sample weight (g)
Conventionally, the term "times" in the expansion ratio of a styrene-based resin foam molded product is synonymous with "cm ³ /g."

(Measurement of thermal conductivity of styrene-based resin foam molded body)
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, 23°C, which is the standard for foamed plastic insulation materials, is used as the standard. A sample for measuring thermal conductivity was cut out from a styrene-based resin foam molded body, and the sample was left at 70°C for 4 days, and then left at 23°C for 24 hours, after which the thermal conductivity was measured.

More specifically, a sample measuring 300 mm in length, 300 mm in width, and 25 mm in thickness was cut out from the styrene-based resin foam molded body. The sample was left to stand at 70°C for 4 days, and then at 23°C for 24 hours. After that, the thermal conductivity was measured at an average temperature of 23°C and a temperature difference of 20°C using a thermal conductivity measuring device (HC-074, manufactured by Eiko Seiki Co., Ltd.) by the heat flow meter method in accordance with JIS A1412-2:1999.

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

(styrene resin)
(A) Styrene homopolymer [manufactured by PS Japan Co., Ltd., 680]
(carbon)
(B) Graphite [flake graphite SGP-40B, manufactured by Marutoyo Foundry Co., Ltd.] (powder)
Average particle size D50 = 5.8 μm
Laser scattering intensity per unit solution concentration of carbon (graphite) = 3.7%

(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]
(Mixture of brominated flame retardants and stabilizers)
(E) The brominated flame retardant (C), the stabilizers (D1) and (D2) were mixed in a mixer to obtain a powder mixture (E) of the brominated flame retardant and the stabilizers, with the weight ratio (wt%) of each material being (C):(D1):(D2) = 95:2:3 ((C) + (D1) + (D2) = 100 wt%).

(Foaming Agent)
(F1) Normal pentane [SK Sangyo Co., Ltd.]
(F2) Isopentane (SK Sangyo Co., Ltd.)
(F3) Isobutane [Mitsui Chemicals, Inc.]
(Additives)
(G) Ethylene bis stearic acid amide

(Production Example 1) (Graphite Masterbatch (H))
The raw materials were charged into a Banbury mixer so that the total weight (A+B+G) of 49% by weight of styrene resin (A), 50% by weight of graphite (B), and 1% by weight of ethylene bisstearic acid amide (G) 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 (H). The graphite content in the master batch (H) was 50% by weight.

Example 1
[Preparation of expandable styrene-based resin particles]
The styrene resin (A), graphite (B), and the mixture (E) of the bromine-based flame retardant and the heat stabilizer 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 40 mm diameter extruder. The ratio and amount of the raw materials used were (A):(B):(E)=89.5:4.5:6.0 by weight, and the total feed amount was 55.7 kg/h. From the middle of the 40 mm diameter extruder (first extruder), mixed pentane [mixture of 80% by weight of normal pentane (F1) and 20% by weight of isopentane (F2)] was injected at a ratio of 4.7 parts by weight per 100 parts by weight of the melt of the resin mixture (styrene-based resin composition), and 2.3 parts by weight of isobutane (F3) was injected per 100 parts by weight of the styrene-based resin composition, and a total of 7.0 parts by weight of foaming agent was added, and the total supply amount of the resin mixture and the foaming agent was 60 kg/h. Then, it was supplied to a 90 mm diameter extruder (second extruder) through a continuation pipe set at 200 ° C.

In the first extruder for preparing the expandable styrene-based resin composition, the total supply amount of the resin mixture and the blowing agent, 60 kg/h, corresponds to the twin-screw extruder extrusion amount (kg/h), so Q/N was approximately 0.359 (60/167), and 8.0× ¹⁰⁻⁶ × ^D3 was 0.512, satisfying Q/N≦8.0× ¹⁰⁻⁶ × ^D3 .

The molten resin was cooled to a resin temperature of 160°C using a 90 mm diameter extruder (second extruder), and then extruded from a die with 60 small holes, each 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 250°C into pressurized circulating water at a temperature of 62°C and a pressure of 1.1 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.

[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. 250 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 0.05 kg/cm ² to 0.15 kg/cm ² , and 0.10 MPa of water vapor was introduced into the pre-expander to expand to an expansion ratio of 80 times, thereby obtaining pre-expanded particles.

[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 400mm x width 400mm x thickness 50mm) attached to a polystyrene foam molding machine [KR-57, manufactured by Daisen Kogyo Co., Ltd.], and 0.06MPa 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 0.01MPa (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 80 times, and the thermal conductivity after standing at 70°C for 4 days was 29.9mW/mK.

The various properties of the produced 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
The procedure was the same as in Example 1, except that the weight ratio of the raw materials was changed from (A):(B):(E) = 89.5:4.5:6.0 to (A):(B):(E) = 86.5:4.5:9.0, and expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles were obtained.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the weight ratio of the raw materials was changed from (A):(B):(E)=89.5:4.5:6.0 to (A):(B):(E)=93.0:4.5:2.5, and expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles were obtained.

(Comparative Example 2)
The procedure was the same as in Example 1, except that the weight ratio of the raw materials was changed from (A):(B):(E) = 89.5:4.5:6.0 to (A):(B):(E) = 93.5:4.5:2.0, and expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles were obtained.

(Comparative Example 3)
The procedure was repeated in the same manner as in Example 1, except that the weight ratio of the raw materials was changed from (A):(B):(E)=89.5:4.5:6.0 to (A):(B):(E)=94.0:4.5:1.5, and expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles were obtained.

(Comparative Example 4)
The same procedure as in Example 1 was carried out except that the weight ratio of the raw materials was changed from (A):(B):(E)=89.5:4.5:6.0 to (A):(B):(E)=94.5:4.5:1.0, and expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles were obtained.

(Reference Example 1)
The styrene resin (A), the graphite master batch (H), and the mixture of the bromine-based flame retardant and the heat stabilizer (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 40 mm diameter extruder. The ratio and amount of the raw materials used were (A):(H):(E)=88.5:9.0:2.5 by weight, and the total feed amount was 55.7 kg/h. From the middle of the 40 mm diameter extruder (first extruder), mixed pentane [mixture of 80% by weight of normal pentane (F1) and 20% by weight of isopentane (F2)] was injected at a ratio of 4.7 parts by weight per 100 parts by weight of the melt of the resin mixture (styrene-based resin composition), and 2.3 parts by weight of isobutane (F3) was injected per 100 parts by weight of the styrene-based resin composition, and a total of 7.0 parts by weight of a foaming agent was added. Then, the mixture was supplied to a 90 mm diameter extruder (second extruder) through a continuation pipe set at 200°C.

The subsequent operations were carried out in the same manner as in Example 1 to obtain expandable styrene-based resin particles, pre-expanded particles, and a styrene-based resin foamed molded product.

(Reference Example 2)
The same procedure as in Reference Example 1 was repeated, except that the weight ratio of the raw materials was changed from (A):(H):(E) = 88.5:9.0:2.5 to (A):(H):(E) = 85.5:12.0:2.5, to obtain expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles.

(Reference Example 3)
The same procedure as in Reference Example 1 was repeated, except that the weight ratio of the raw materials was changed from (A):(H):(E) = 88.5:9.0:2.5 to (A):(H):(E) = 81.5:16.0:2.5, to obtain expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles.

(Reference Example 4)
The same procedure as in Reference Example 1 was repeated, except that the weight ratio of the raw materials was changed from (A):(H):(E) = 88.5:9.0:2.5 to (A):(H):(E) = 77.5:20.0:2.5, to obtain expandable styrene-based resin particles, pre-expanded particles, and styrene-based resin foamed molded articles.

For each Example, Comparative Example, and Reference Example, the amount of graphite (B) used, the amount of the mixture (E) of the bromine-based flame retardant and stabilizer, the weight ratio thereof, the amount of graphite master batch (H), the laser scattering intensity per unit weight of carbon in the expandable styrene-based resin particles, and the expansion ratio and thermal conductivity of the styrene-based resin foamed molded body are shown in Table 1. Note that in Table 1, for the Reference Examples that used the graphite master batch (H), the amount of graphite (B) used as the master batch (H) is also shown in parentheses. In addition, in Table 1, "laser scattering intensity per unit weight of carbon in the expandable styrene-based resin particles" is simply referred to as "laser scattering intensity per unit weight of carbon."

From Table 1, it is suggested that the method described in the Examples has a laser scattering intensity per unit weight of carbon in the expandable styrene-based resin particles that is equal to or greater than that of Reference Examples 1 to 4, which use masterbatches, even though the method does not use a masterbatch, and that the carbon is sufficiently dispersed. In other words, it is suggested that the manufacturing method disclosed herein is a method that can obtain styrene-based resin compositions, expandable styrene-based resin particles, etc., of equal or greater quality than conventional methods at a low cost.

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 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 (10)

The process includes a step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture,
The carbon, the brominated flame retardant, and the stabilizer are fed in powder form to a multi-screw extruder;
A method for producing a styrene-based resin composition, wherein a weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer, carbon/(brominated flame retardant+stabilizer), is 1.4 or less. The multi-screw extruder is a twin-screw extruder,
The method for producing a styrene-based resin composition according to claim 1, wherein the Q/N of the twin-screw extruder is within the range of the following formula:
Q/N ≦ 8.0×10 ^-6 ×D ³
(In the above formula, Q represents the twin-screw extruder extrusion rate (kg/hr), N represents the screw rotation speed (rpm), and D represents the twin-screw extruder barrel inner diameter (mm).) The method for producing a styrene-based resin composition according to claim 1, wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. The process includes a step A of supplying a styrene-based resin, carbon, a bromine-based flame retardant, and a stabilizer to a multi-screw extruder and melt-kneading the mixture,
The carbon, the brominated flame retardant, and the stabilizer are fed in powder form to a multi-screw extruder;
A method for producing expandable styrene-based resin particles, wherein a weight ratio of the carbon to the total amount of the brominated flame retardant and the stabilizer, carbon/(brominated flame retardant+stabilizer), is 1.4 or less. The multi-screw extruder is a twin-screw extruder,
The method for producing expandable styrene-based resin particles according to claim 4, wherein the Q/N of the twin-screw extruder is within the range of the following formula:
Q/N ≦ 8.0×10 ^-6 ×D ³
(In the above formula, Q represents the twin-screw extruder extrusion rate (kg/hr), N represents the screw rotation speed (rpm), and D represents the twin-screw extruder barrel inner diameter (mm).) The method for producing expandable styrene-based resin particles according to claim 4, wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. The method for producing expandable styrene-based resin particles according to claim 4, comprising step B of adding a blowing agent to the styrene-based resin composition obtained in step A to obtain an expandable styrene-based resin composition, and step C of granulating the expandable styrene-based resin composition to obtain expandable styrene-based resin particles. The method for producing expandable styrene-based resin particles according to claim 4, comprising step D of granulating the styrene-based resin composition obtained in step A to obtain styrene-based resin particles, and step E of impregnating the styrene-based resin particles with a blowing agent to obtain expandable styrene-based resin particles. A method for producing pre-expanded styrene resin particles, which comprises expanding the expandable styrene resin particles obtained by the method for producing expandable styrene resin particles described in claim 4. A method for producing a styrene-based resin foamed molded article, which comprises molding the styrene-based resin pre-expanded particles obtained by the method for producing the styrene-based resin pre-expanded particles described in claim 9.