Styrene-based resin extruded foam and method for producing the same

Abstract

To provide a styrene-based resin extruded foam that exhibits excellent thermal insulation, flame retardancy, and thermal resistance.SOLUTION: The styrene-based resin extruded foam comprises a polystyrene-based resin, a bromine-containing polymer as a flame retardant, and an epoxy compound as a stabilizer. The polystyrene-based resin includes a styrene-(meth)acrylic acid copolymer, and the amount of (meth)acrylic acid is 1.4 to 4.0 pts.wt. per 100 pts.wt. of the total monomer components constituting the polystyrene-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an extruded styrene resin foam and a method for producing the same. [Background technology]

[0002] Because of their high thermal insulation properties, extruded styrene resin foams are used as thermal insulation materials for houses and buildings, refrigerators, etc. Extruded styrene resin foams are produced by melt-kneading a composition containing a polystyrene resin and a blowing agent in an extruder, and then extruding the mixture through a die slit or the like into a low-pressure region.

[0003] When extruded styrene resin foams are used as thermal insulation materials for construction, the surface of the foams is heated by sunlight or the like at the construction site, causing swelling, dimensional changes, and deformation, which can lead to poor installation. Therefore, extruded styrene resin foams are required to be resistant to volume changes due to heating and to have excellent heat resistance. A method for improving the heat resistance of extruded styrene resin foams is known in which polystyrene and a styrene-(meth)acrylic acid copolymer are used in combination (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-62653 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the inclusion of a styrene-(meth)acrylic acid copolymer in an extruded styrene-based resin foam tends to improve heat resistance, the use of a bromine-containing polymer such as a brominated styrene-butadiene block copolymer as a flame retardant results in low thermal stability, and there is a problem that the flame retardancy and thermal insulation properties of the foam tend to deteriorate when the resin is recycled. Although the use of a bromine-containing polymer in combination with an epoxy compound as a thermal stabilizer tends to improve thermal stability, the use of an epoxy compound in combination tends to lower the closed cell ratio of the foam and reduce thermal insulation properties.

[0006] In view of the above, an object of the present invention is to provide an extruded styrene resin foam that has high heat insulating properties and excellent flame retardancy and heat resistance even when a bromine-containing polymer is used as a flame retardant. [Means for solving the problem]

[0007] The extruded styrene resin foam contains a polystyrene resin, and further contains at least one bromine-containing polymer as a flame retardant and at least one epoxy compound as a stabilizer. The polystyrene resin contains a styrene-(meth)acrylic acid copolymer, and the amount of (meth)acrylic acid is 1.4 to 4.0 parts by weight per 100 parts by weight of the total of the monomer components constituting the polystyrene resin.

[0008] Examples of epoxy compounds used as stabilizers include bisphenol A diglycidyl ether epoxy resins, cresol novolac epoxy resins, and phenol novolac epoxy resins. The content of the epoxy compound may be 0.3 to 1.0 parts by weight per 100 parts by weight of the polystyrene resin. The content of the epoxy compound may be 10 to 20 parts by weight per 100 parts by weight of the bromine-containing polymer used as a flame retardant.

[0009] An extruded styrene resin foam is produced by melt-kneading a composition containing a polystyrene resin, a blowing agent, a flame retardant, and a stabilizer, and extruding the mixture into a low-pressure region for foaming. When an alkyl chloride is used as the blowing agent, the amount of alkyl chloride is preferably 2 to 6 parts by weight per 100 parts by weight of the polystyrene resin. The extruded styrene resin foam may contain 0.10 to 1.0 mol / kg of alkyl chloride. The thickness of the extruded styrene resin foam may be 10 to 150 mm. [Effects of the Invention]

[0010] The foam of the present invention has excellent heat insulating properties, flame retardancy and heat resistance, and can be suitably used as a heat insulating material for houses, buildings, refrigerators and the like. DETAILED DESCRIPTION OF THE INVENTION

[0011] Extruded styrene resin foams are produced by extruding a foamable molten composition into a low pressure region, which is prepared by blending a blowing agent with a resin composition containing a polystyrene resin and melt-kneading the resulting composition, to foam-mold the composition.

[0012] [Composition] The foamable melt composition contains a flame retardant and a stabilizer in addition to a polystyrene resin and a blowing agent, and further contains additives such as a flame retardant aid, a radiation suppressant, a lubricant, a water absorbent, and a moldability improver, as needed. Below, each component contained in the foamable melt composition (sometimes simply referred to as the "composition") will be described in detail. Unless otherwise specified, each component described below may be used alone or in combination of two or more.

[0013] <Polystyrene resin> The polystyrene resin includes a styrene polymer. Examples of the styrene polymer include a homopolymer of a styrene monomer (polystyrene); a copolymer of two or more types of styrene monomers; and a copolymer of a styrene monomer and another monomer. When the styrene polymer is a copolymer, the amount of the styrene monomer in the total monomers is preferably 60% by weight or more, more preferably 70% by weight or more. The polymer sequence of the copolymer is not particularly limited, and may be either a random copolymer or a block copolymer. The copolymer may be a graft copolymer. The styrene polymer may be a polymer having a branched structure.

[0014] Examples of styrene-based monomers include styrene, methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, trichlorostyrene, vinyltoluene, vinylxylene, etc. Examples of other monomers include polyfunctional vinyl compounds such as divinylbenzene, acrylic acid, methacrylic acid, (meth)acrylic acid ester compounds such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate, cyanide vinyl compounds such as (meth)acrylonitrile, diene compounds 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)-chlorophenylmaleimide, N-(4)-bromophenylmaleimide, and N-(1)-naphthylmaleimide.

[0015] In the present invention, at least one styrene-(meth)acrylic acid copolymer, which is a copolymer of styrene and acrylic acid or methacrylic acid, is used as the polystyrene-based resin. When the polystyrene-based resin contains a styrene-(meth)acrylic acid copolymer, the heat resistance of the foam tends to be improved and dimensional change due to heating tends to be suppressed. In this specification, "(meth)acrylic" means "methacrylic and / or acrylic."

[0016] The styrene-(meth)acrylic acid copolymer may contain a monomer other than a styrene-based monomer and (meth)acrylic acid, but the total amount of the styrene-based monomer and (meth)acrylic acid is 80 parts by weight or more relative to 100 parts by weight of the total constituent monomers. The total amount of the styrene-based monomer and (meth)acrylic acid relative to 100 parts by weight of the total constituent monomers of the styrene-(meth)acrylic acid copolymer is preferably 90 parts by weight or more, more preferably 95 parts by weight or more, and may be 99 parts by weight or more or 100 parts by weight.

[0017] The amount of (meth)acrylic acid relative to 100 parts by weight of the total of the constituent monomers of the styrene-(meth)acrylic acid copolymer is preferably 3 to 20 parts by weight, more preferably 4 to 17 parts by weight, and even more preferably 5 to 15 parts by weight. If the amount of (meth)acrylic acid is too small, the heat resistance of the foam tends to be poor, while if the amount of (meth)acrylic acid is too large, the foamability is low and the closed cell ratio of the foam is low, so the heat insulation tends to be poor.

[0018] The amount of (meth)acrylic acid per 100 parts by weight of the total of the constituent monomer components of the polystyrene resin is preferably 1.4 to 4.0 parts by weight, and may be 1.5 to 3.7 parts by weight, 1.6 to 3.5 parts by weight, or 1.7 to 3.3 parts by weight. When the amount of (meth)acrylic acid is within this range, even when the composition contains a bromine-containing polymer as a flame retardant and an epoxy compound as a stabilizer, the composition has good foaming moldability, and therefore a foam with a high closed cell content can be obtained.

[0019] When only a styrene-(meth)acrylic acid copolymer is used as the polystyrene-based resin, the amount of (meth)acrylic acid in the styrene-(meth)acrylic acid copolymer may be adjusted to fall within the above range. When the polystyrene-based resin is a blend resin containing a styrene-(meth)acrylic acid copolymer and another styrene-based polymer, the ratio of the styrene-(meth)acrylic acid copolymer may be adjusted to fall within the above range in terms of the amount of (meth)acrylic acid relative to the total amount of monomer components constituting the blend resin.

[0020] The polystyrene resin is preferably a blend resin containing a styrene-(meth)acrylic acid copolymer and other styrene-based polymers, and the amount of the styrene-(meth)acrylic acid copolymer relative to a total of 100 parts by weight of the polystyrene-based resins is preferably 20 to 50 parts by weight, and may be 25 to 45 parts by weight.

[0021] The polystyrene-based resin may contain a polymer other than a styrene-based polymer, such as a polyolefin, an acrylic polymer, a polyester, or a polyphenylene ether, as long as the effects of the present invention are not adversely affected. When the polystyrene-based resin contains a polymer other than a styrene-based polymer, the content thereof is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less, and may be 3 parts by weight or less, or 1 part by weight or less, relative to 100 parts by weight of the styrene-based polymer.

[0022] The polystyrene resin may be a commercially available polystyrene resin (so-called virgin resin), or may be a recycled polystyrene resin (for example, a recycled polystyrene resin recycled using a recycling extruder or the like after being used in the production of foam, or a recycled polystyrene resin recycled from food trays or fish boxes collected on the market). Virgin resin and recycled polystyrene resin may be mixed.

[0023] The melt flow rate (MFR) of the polystyrene resin measured according to JIS K7210 is preferably 50 g / 10 min or less. If the MFR is 50 g / 10 min or less, the blowing agent is easily dispersed uniformly in the polystyrene resin during melt kneading, and stable extrusion and foam molding can be performed, improving production stability. The MFR of the polystyrene resin may be 0.5 to 40 g / 10 min, or 1 to 30 g / 10 min.

[0024] <Brominated flame retardants> The composition contains a brominated flame retardant, which provides flame retardancy to the foam. Brominated flame retardants include polymers and low molecular weight compounds, but the present invention uses a bromine-containing polymer.

[0025] Examples of bromine-containing polymers used as flame retardants include copolymers of brominated styrene with aliphatic monomers such as butadiene, such as brominated styrene-butadiene block copolymer, brominated-epoxidized styrene-butadiene block copolymer, brominated styrene-butadiene random copolymer, and brominated styrene-butadiene graft copolymer; brominated polyolefins such as brominated polybutadiene; and brominated polyolefin copolymers such as brominated butadiene-styrene block copolymer and brominated butadiene-styrene random copolymer.

[0026] The amount of bromine-based flame retardant (bromine-containing polymer) in the composition is not particularly limited, but from the viewpoint of achieving both flame retardancy and moldability during foaming, it is preferably 1 to 8 parts by weight, or may be 2 to 7 parts by weight, or 3 to 6 parts by weight, per 100 parts by weight of the polystyrene-based resin. In addition to the bromine-containing monomer, a bromine-containing low-molecular-weight compound or a non-bromine-based flame retardant may also be used in combination as the flame retardant.

[0027] <Flame retardant synergist> The composition may contain a flame retardant synergist in addition to the bromine-based flame retardant to improve flame retardancy. Examples of the flame retardant synergist include radical generators such as 2,3-dimethyl-2,3-diphenylbutane and poly-1,4-diisopropylbenzene; and phosphorus-based flame retardants such as phosphate esters and phosphine oxides. When the composition contains a radical generator and a phosphorus-based flame retardant, the amount of the radical generator is, for example, about 0.05 to 0.8 parts by weight per 100 parts by weight of the polystyrene-based resin, and the amount of the phosphorus-based flame retardant is, for example, about 0.1 to 2 parts by weight per 100 parts by weight of the polystyrene-based resin.

[0028] <Stabilizer> The composition contains a stabilizer intended to improve the thermal stability of the foam. Bromine-containing polymers used as flame retardants often have low thermal stability, but the use of an epoxy compound as a stabilizer improves the thermal stability of the flame retardant. Examples of epoxy stabilizers include bisphenol A diglycidyl ether epoxy resins, cresol novolac epoxy resins, and phenol novolac epoxy resins.

[0029] The amount of the epoxy compound as a stabilizer is preferably 0.3 to 1 part by weight, and may be 0.4 to 0.9 parts by weight or 0.5 to 0.8 parts by weight, per 100 parts by weight of the polystyrene resin. The amount of the epoxy compound as a stabilizer is preferably 5 to 25 parts by weight, and may be 7 to 20 parts by weight or 8 to 15 parts by weight, per 100 parts by weight of the bromine-containing polymer as a flame retardant. If the amount of the epoxy compound is too small, the thermal stability tends to decrease, and particularly when the resin is recycled, the flame retardancy and heat resistance of the foam tend to decrease. If the amount of the epoxy compound is too large, the stabilizing effect becomes excessive, and the flame retardant does not decompose effectively when the foam is burned, which tends to decrease the flame retardancy.

[0030] In the case of an extruded styrene resin foam containing a styrene-(meth)acrylic acid copolymer as a polystyrene resin, if a bromine-containing polymer is used as a flame retardant and an epoxy compound is blended to improve thermal stabilization, the foam may have a low closed cell content and poor thermal insulation. In the present invention, by adjusting the ratio of (meth)acrylic acid contained in the polystyrene resin within a predetermined range as described above, a foam having a high closed cell content and excellent thermal insulation properties can be obtained while ensuring heat resistance and flame retardancy.

[0031] The composition may contain, as a stabilizer, a compound other than an epoxy compound (a non-epoxy stabilizer) in addition to the epoxy compound. Examples of the non-epoxy stabilizer include polyhydric alcohol esters, which are reaction products of polyhydric alcohols such as pentaerythritol, dipentaerythritol, and tripentaerythritol with carboxylic acids such as acetic acid, propionic acid, adipic acid, and glutamic acid; triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate], and octadecyl 3-(3,5-di-tert-butyl)propionate. phenol-based stabilizers such as 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite.

[0032] <Heat radiation suppressant> A heat radiation inhibitor may be added to the composition to improve the heat insulating properties of the foam. A heat radiation inhibitor is a substance that has the properties of reflecting, scattering, and absorbing electromagnetic waves in the near-infrared or infrared region. The inclusion of a heat radiation inhibitor tends to further improve the heat insulating properties of the foam.

[0033] Examples of the heat radiation inhibitor include white particles such as graphite, titanium oxide, barium sulfate, zinc oxide, aluminum oxide, and antimony oxide. Among these, graphite is particularly preferred because of its high heat radiation suppression effect. Among the white particles, titanium oxide is particularly preferred.

[0034] Specific examples of graphite include scaly (flake) graphite, amorphous graphite, spherical graphite, and artificial graphite. Among these, graphite containing scaly (flake) graphite as the main component is preferred because of its high heat radiation suppression effect. The fixed carbon content of the graphite is preferably 80% or more, and more preferably 85% or more.

[0035] The average particle size of the graphite is preferably 15 μm or less, and more preferably 10 μm or less. The smaller the average particle size, the larger the specific surface area, which increases the probability of collision with thermal radiation, resulting in a greater effect in suppressing thermal radiation. The average particle size of the graphite is determined by measuring and analyzing the particle size distribution using a laser diffraction scattering method based on Mie theory in accordance with ISO13320:2009 and JIS Z8825:2013, and is the particle size (volume average particle size) when the cumulative volume of the total particle volume is 50%.

[0036] When a heat radiation inhibitor such as graphite is used, the amount of the heat radiation inhibitor in the composition is preferably 0.1 to 6 parts by weight, more preferably 0.5 to 5 parts by weight, and may be 0.8 to 4 parts by weight or 1 to 3.5 parts by weight, per 100 parts by weight of the polystyrene-based resin. If the amount of the heat radiation inhibitor is small, a sufficient heat radiation suppression effect cannot be obtained. On the other hand, if the amount of the heat radiation inhibitor is excessively large, the dispersibility in the composition is poor, making it difficult to obtain a heat radiation suppression effect commensurate with the content. Furthermore, if the content of a solid additive such as a heat radiation inhibitor increases, the number of nucleation points increases, which tends to reduce the size of the foam cells, making it difficult to impart a beautiful surface to the foam or to obtain a foam with a large thickness. Solid additives such as heat radiation inhibitors may be added to the composition as a masterbatch in which they are dispersed in advance in the polystyrene-based resin.

[0037] <Water absorbent> When water is used as the blowing agent, the composition preferably contains a water-absorbing agent. Water has low solubility in polystyrene resins, and the presence of undissolved water in the composition tends to cause the formation of large bubbles, which can lead to bubble bursting. By including a water-absorbing agent in the composition, the solubility of water in the composition is increased and the water is uniformly dispersed, thereby suppressing molding defects such as the generation of large bubbles and bubble bursting, and enabling stable extrusion foam molding.

[0038] Examples of water-absorbing agents include water-absorbing minerals (such as smectite and zeolite), silica, and hydrophilic organic substances. Examples of smectite include natural bentonite, purified bentonite, organically modified bentonite, and hectorite. Examples of zeolites include natural zeolites, artificial zeolites, and synthetic zeolites. Examples of silica include anhydrous silica, modified silica with hydroxyl groups on its surface, and porous silica. Examples of hydrophilic organic substances include polyacrylate polymers, starch-acrylic acid graft copolymers, polyvinyl alcohol polymers, vinyl alcohol-acrylate copolymers, ethylene-vinyl alcohol copolymers, polyacrylonitrile-methyl methacrylate-butadiene copolymers, polyethylene oxide copolymers, and derivatives thereof, polyvinylpyrrolidone, sodium carboxymethylcellulose, hydroxyethylcellulose, polyhydric alcohols, and melamine.

[0039] The amount of the water absorbing agent used may be adjusted appropriately depending on the amount of water used, etc. The amount of the water absorbing agent in the composition is about 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.2 to 2.5 parts by weight, and may be 0.3 to 2 parts by weight, or 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the polystyrene resin. The ratio (weight ratio) of the water absorbing agent to the water in the composition is about 0.05 to 5, preferably 0.1 to 4.5, and may be 0.2 to 4 or 0.3 to 3.

[0040] <Other additives> In addition to the above, the composition may contain additives such as flame retardant adjusters (iron oxide, iron complexes, diphenylalkanes, diketones, etc.), lubricants (sodium stearate, calcium stearate, etc.), cell size adjusters (talc, etc.), processing aids (fatty acid metal salts, fatty acid amides, fatty acid esters, liquid paraffin, olefin waxes, etc.), antistatic agents, surfactants, colorants (pigments, dyes, etc.), neutralizing agents, ultraviolet absorbers, fluorescent brighteners, plasticizers, fillers, etc.

[0041] <Foaming agent> The blowing agent is not particularly limited, and suitable examples include hydro(chloro)fluoroolefin, alkyl chloride, water, saturated hydrocarbons having 3 to 5 carbon atoms, ethers, ketones, saturated alcohols having 1 to 4 carbon atoms, carboxylic acid esters, and carbon dioxide. From the viewpoint of improving the heat insulating properties of the foam, it is preferable to use at least hydro(chloro)fluoroolefin and alkyl chloride as the blowing agent. Note that "hydro(chloro)fluoroolefin" means "hydrofluoroolefin and / or hydrochlorofluoroolefin."

[0042] As the hydrofluoroolefin, tetrafluoropropene is preferred because it has a low thermal conductivity as a gas and is highly safe. Specific examples of tetrafluoropropene include 1,3,3,3-tetrafluoropropene (HFO-1234ze) and 2,3,3,3-tetrafluoropropene (HFO-1234yf). As the hydrochlorofluoroolefin, hydrochlorotrifluoropropene is preferred because it has a low thermal conductivity as a gas and is highly safe. Specific examples of hydrochlorotrifluoropropene include 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd).

[0043] From the viewpoint of improving the heat insulating properties of the foam, the amount of hydro(chloro)fluoroolefin used is preferably 0.1 to 10 parts by weight, and may be 0.5 to 7 parts by weight, or 1 to 5 parts by weight, per 100 parts by weight of the polystyrene-based resin. The greater the amount of hydro(chloro)fluoroolefin used, the more the heat insulating properties of the foam tend to improve. On the other hand, even if the amount of hydro(chloro)fluoroolefin used is excessively large, a significant improvement in heat insulating properties cannot be expected. Furthermore, if the amount of hydro(chloro)fluoroolefin used is excessively large, the blowing agent may separate from the resin melt, causing spot pores on the surface of the foam, or the closed cell ratio may decrease, impairing the heat insulating properties.

[0044] As the alkyl chloride, methyl chloride or ethyl chloride is preferred because it has a low thermal conductivity in a gaseous state and contributes greatly to improving heat insulation. The amount of alkyl chloride used is preferably 2 to 6 parts by weight, more preferably 2.5 to 5 parts by weight, per 100 parts by weight of polystyrene-based resin. The amount of alkyl chloride in the foam is preferably 0.1 to 1 mol, and may be 0.2 to 8 mol or 0.25 to 7 mol, per 1 kg of foam. If the amount of alkyl chloride is too small, the effect of improving heat insulation by the alkyl chloride may not be fully exerted. On the other hand, if the amount of alkyl chloride is too large, the plasticizing effect on the polystyrene-based resin is strong, which may cause a decrease in the heat resistance and strength of the foam.

[0045] The use of water as a blowing agent increases surface tension, facilitating the formation of bubbles with relatively large diameters, thereby enabling the formation of thick foams. The amount of water used is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2 parts by weight, and even more preferably 0.4 to 1.5 parts by weight, per 100 parts by weight of the polystyrene-based resin. If the amount of water is too small, it may be difficult to obtain thick foams. On the other hand, if the amount of water is too large, coarse bubbles are likely to form, and pores may be generated, which may result in poor appearance of the foam and reduced thermal insulation properties.

[0046] When alkyl chloride and water are used as the blowing agent, the alkyl chloride and water come into contact with each other and mix inside the extruder during or after the blowing agent is injected, generating acidic gases such as hydrogen chloride, which can corrode metals in the extruder, piping, etc. Adding an acid neutralizer to the composition has the effect of neutralizing the acidic gas, thereby suppressing corrosion of equipment. The acid neutralizer may be dissolved in water as a blowing agent and added to the composition.

[0047] The acid neutralizing agent may be either organic or inorganic, as long as it is a compound capable of neutralizing acid, and examples of organic substances include amines. Examples of inorganic substances include oxides, hydroxides, carbonates, bicarbonates, silicates, etc. of alkali metals or alkaline earth metals. Inorganic substances are preferred because they have little effect on foaming properties and the physical properties of the foam, and among these, carbonates or bicarbonates are preferred. Examples of alkali metal carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of alkali metal bicarbonates include lithium bicarbonate, sodium bicarbonate, and potassium bicarbonate. Among these, alkali metal carbonates such as sodium carbonate and potassium carbonate are particularly preferred because they are easy to handle and have a strong acid neutralizing effect.

[0048] The amount of the acid neutralizer is preferably 0.003 to 0.7 times, more preferably 0.005 to 0.5 times, and may be 0.008 to 0.1 times or 0.01 to 0.05 times, in molar ratio, relative to the alkyl chloride used as the blowing agent.

[0049] When a saturated hydrocarbon having 3 to 5 carbon atoms is used as a blowing agent, the plasticizing effect of the polystyrene resin increases the fluidity of the molten composition, which can contribute to reducing the load on the extruder. From the viewpoint of foamability, propane, normal butane, and isobutane are preferred among the saturated hydrocarbons having 3 to 5 carbon atoms, and from the viewpoint of the heat insulating properties of the foam, normal butane and isobutane are particularly preferred.

[0050] When a saturated hydrocarbon having 3 to 5 carbon atoms is used as a blowing agent, from the viewpoint of improving the heat insulating properties of the foam, the amount of the saturated hydrocarbon having 3 to 5 carbon atoms used is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 0.7 parts by weight or more, and may be 0.9 parts by weight or more or 1 part by weight or more, relative to 100 parts by weight of the polystyrene-based resin. On the other hand, from the viewpoint of suppressing molding defects such as cell bursting, the amount of the saturated hydrocarbon having 3 to 5 carbon atoms used is preferably 5 parts by weight or less, more preferably 4.5 parts by weight or less, and may be 4 parts by weight or less or 3.5 parts by weight or less, relative to 100 parts by weight of the polystyrene-based resin.

[0051] Examples of blowing agents other than those mentioned above include saturated hydrocarbons having 3 to 5 carbon atoms, such as propane, normal butane, isobutane, normal pentane, isopentane, and di-pentane; alcohols having 1 to 4 carbon atoms, such as ethanol, methanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, and t-butyl alcohol; dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether, furan, furfural, 2-methylfuran, tetrahydrofuran, and tetrahydropyrrolidine; ethers such as lan; ketones such as dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl-i-butyl ketone, methyl-n-amyl ketone, methyl-n-hexyl ketone, ethyl-n-propyl ketone, and ethyl-n-butyl ketone; organic blowing agents typified by carboxylic acid esters such as methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl propionate, and ethyl propionate; inorganic blowing agents such as carbon dioxide, and chemical blowing agents such as azo compounds and tetrazole.

[0052] The amount of the blowing agent used (total amount of all blowing agents) is preferably 2 to 20 parts by weight, more preferably 3 to 15 parts by weight, even more preferably 4 to 12 parts by weight, and may be 5 to 10 parts by weight, per 100 parts by weight of the polystyrene resin. When the amount of the blowing agent used is within the above range, the foaming power of the composition is ensured, and an extruded styrene resin foam having a desired thickness is likely to be stably obtained.

[0053] [Method of manufacturing foam] To produce extruded styrene-based resin foam, an extrusion foaming apparatus is used, in which a melt-kneading section and a foam-molding section having a die are arranged in this order from upstream to downstream in the extrusion direction of the composition. The melt-kneading section and the foam-molding section are connected. A cooling section for lowering the temperature of the composition may be disposed between the melt-kneading section and the foam-molding section. Extruded styrene-based resin foam is produced by melt-kneading a resin composition containing a polystyrene-based resin and a foaming agent (melt-kneading step), and then extruding the foamable molten composition into a low-pressure region and foam-molding it (foaming step).

[0054] In the melt-kneading step, a resin composition containing a polystyrene-based resin and additives is supplied to a melt-kneading section and kneaded. Methods for blending various additives into a polystyrene-based resin include, for example, a method of adding various additives to a polystyrene-based resin and mixing them by dry blending; a method of adding various additives to a molten polystyrene-based resin from a supply section provided in the melt-kneading section; and a method of preparing a masterbatch in advance by using an extruder, kneader, Banbury mixer, roll, etc. to incorporate various additives into a polystyrene-based resin at a high concentration, and then mixing the masterbatch with a polystyrene-based resin by dry blending.

[0055] The melt-kneading section may be, for example, an extruder using a screw. As the extruder using a screw, a single-screw extruder or a twin-screw extruder can be used. The screw rotation direction of the twin-screw extruder may be the same or different. The heating temperature in the melt-kneading section may be equal to or higher than the temperature at which the polystyrene-based resin melts, and is preferably about 150°C to 260°C from the viewpoint of suppressing deterioration of the resin. The melt-kneading time may be appropriately set depending on the type of polystyrene-based resin and the extrusion amount per unit time.

[0056] In the melt-kneading step, a foamable molten composition is prepared by blending (injecting) a foaming agent into the resin composition under high pressure conditions. The timing of blending the foaming agent is not particularly limited, and the foaming agent may be blended at any stage of the melt-kneading step, such as before, during, or after the resin composition is heated and melted. The pressure when the foaming agent is injected may be higher than the internal pressure of the melt-kneading section.

[0057] In the melt-kneading step, after melt-kneading the resin composition and the foaming agent, the foamable molten composition to be supplied to the foaming step may be cooled within a temperature range in which the composition does not solidify. For example, the composition may be cooled in a cooling section disposed between the melt-kneading section and the foam-molding section. When the composition is cooled, the temperature of the composition at the outlet of the cooling section is preferably 105°C to 140°C, and may be 110°C to 130°C.

[0058] In the foaming step, the foamable molten composition is extruded from the die of the foam molding section into a low-pressure region (for example, an atmospheric pressure region), causing the volume of the foaming agent to increase rapidly, forming an extruded styrene resin foam.

[0059] The foam-molding section may include a molding plate connected downstream of the die to foam-mold the foamable molten composition extruded from the die immediately after pressure is released. The molding plate is composed of two plates, one above the other, and the composition extruded into a low-pressure region through a die slit, which is a linear opening in the die, foams in the space between the two molding plates, resulting in a foamed plate with a certain thickness. The two plates may be arranged parallel to the extrusion direction, or may be arranged so that the gap between them gradually increases from the inlet (upstream side) to the outlet (downstream side).

[0060] The foaming pressure of extrusion foaming (the pressure applied to the foamable melt immediately before being extruded through the die slit) is, for example, about 2.5 to 15 MPa, and may be 3 to 10 MPa, or 3.5 to 8 MPa. If the foaming pressure is 2.5 MPa or higher, the foaming agent can be sufficiently dissolved in the composition, thereby preventing problems such as the foaming agent being ejected as a gas from the die slit. If the foaming pressure is 15 MPa or lower, the extrusion rate of the composition can be increased, ensuring productivity. The foaming pressure can be adjusted to a desired range by adjusting the feed rate of the composition (extrusion rate per unit time), the opening of the die slit, the temperature of the die slit, etc.

[0061] [Physical properties of foam] The foam is formed, for example, into a plate shape. The thickness of the plate-shaped foam is not particularly limited and can be appropriately selected depending on the application. For example, the foam obtained by the above method can be used as an insulating material for houses, buildings, refrigerators, etc. Foams used as these insulating materials preferably have a thickness of 10 mm or more to impart high insulating properties and high compressive strength. The thickness of the foam may be 20 mm or more, 30 mm or more, 40 mm or more, 50 mm or more, or 60 mm or more. The thickness of the foam may be 150 mm or less, 130 mm or less, or 120 mm or less.

[0062] In the case of extruded styrene resin foams, after giving them a shape through extrusion foam molding, the surface layer (skin layer) that was in contact with the mold may be removed by about 5 mm in the thickness direction to produce the final product, but the thickness mentioned above is the thickness of the foam before the skin layer is removed.

[0063] When alkyl chloride is used as the blowing agent, the extruded styrene resin foam preferably contains 0.10 to 1.0 mol of alkyl chloride per 1 kg. The inclusion of alkyl chloride in the foam tends to enhance the heat insulating properties. On the other hand, if the alkyl chloride content is too high, the foam may have a reduced heat resistance due to excessive plasticization. The alkyl chloride content of the foam may be 0.15 to 0.8 mol / kg, or 0.2 to 0.7 mol / kg.

[0064] Considering applications as a thermal insulation material for buildings and refrigerators, the thermal conductivity of the foam is preferably 0.0244 W / mK or less, more preferably 0.0230 W / mK or less, and even more preferably 0.0220 W / mK or less. The lower the thermal conductivity, the better, but the thermal conductivity of extruded styrene resin foam is generally 0.018 W / mK or more, and may be 0.019 W / mK or more.

[0065] From the viewpoint of achieving both lightness and strength, the apparent density of the foam is 20 to 60 kg / m 3 is preferable, and 25 to 40 kg / m 3 The apparent density of the foam is calculated from the volume and mass of a rectangular parallelepiped cut out of the foam.

[0066] The closed cell ratio of the foam is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more. The higher the closed cell ratio, the better the thermal insulation tends to be. The closed cell diameter of the foam is determined by the true volume V1 of the foam (the apparent volume minus the volume of the non-closed cell portion), the apparent volume V2 of the foam, the mass W of the foam, and the true density ρ (approximately 1.05 g / cm for polystyrene resins). 3 ) is calculated based on the following formula: Closed cell ratio (%)=100×(V1-W / ρ) / (V2-W / ρ)

[0067] The average cell diameter of the foam is preferably 0.05 to 0.3 mm, more preferably 0.07 to 0.24 mm, and may be 0.1 to 0.22 mm. If the average cell diameter is too small, the distance between the cell walls of the foam will be small, narrowing the range of cell movement during foam molding and making deformation difficult, which tends to make it difficult to impart a beautiful surface to the extruded foam or increase the foam thickness. On the other hand, if the average cell diameter is large, the heat insulating properties tend to decrease.

[0068] When the expansion ratio is large (for example, 20 times or more) and the closed cell ratio is high as described above, the thickness of the cell walls is so small that it can be ignored compared to the cell diameter, and the average cell diameter can be roughly calculated from the number of cells per unit length. The average cell diameter of a foam is calculated using the following formula: draw three 2 mm long straight lines in the thickness direction at any point on an enlarged cross-sectional image of the foam, and use the number a of cells that intersect or touch the lines. Average bubble diameter = 2 x 3 / a

[0069] The foam preferably has excellent thermal stability and exhibits little volume change (expansion) upon heating. The volume change rate of the foam after heating at 90°C for 24 hours is preferably 10% or less, more preferably less than 5%.

[0070] The foam of the present invention has high heat insulating properties, excellent flame retardancy and heat resistance, and can be suitably used as a heat insulating material for houses, buildings, refrigerators, etc. [Example]

[0071] The following examples will explain the present invention in more detail, but the present invention is not limited to the examples below.

[0072] [Preparation of graphite masterbatch] 48 parts by weight of polystyrene resin A (PS Japan "PSJ-Polystyrene GPPS 680"; MFR: 7.0 g / 10 min), 50 parts by weight of graphite (Marutoyo Foundry Manufacturing Co., Ltd. "M-885"; flake graphite, average particle size 5.5 μm, fixed carbon content 89%), and 2 parts by weight of stearic acid monoglyceride (Rikemal S-100P, Riken Vitamin Co., Ltd.) were placed in a Banbury mixer and melt-mixed for 20 minutes under a pressure of 0.49 MPa without heating or cooling. The resin temperature during mixing was 190°C. The mixture was fed into a ruder and extruded through a die attached to the tip of the ruder at a rate of 250 kg / hr. The resin strands were cooled and solidified in a water bath at 30°C and then cut to obtain graphite masterbatches.

[0073] [Preparation of resin mixture] Resin mixtures 1 to 9 (hereafter referred to as "GP1" to "GP9") were prepared by dry-blending polystyrene resin, the graphite masterbatch, flame retardant, flame retardant aid, epoxy and non-epoxy compounds as stabilizers, radiation suppressant, cell size regulator, lubricant, water absorbent, and moldability improver according to the formulations shown in Table 1. The amount of graphite masterbatch was 5 parts by weight relative to a total of 97.6 parts by weight of polystyrene resin B (PS Japan "PSJ-Polystyrene GPPS G9401", MFR: 2.1 g / 10 min) and styrene-methacrylic acid copolymer (PS Japan "PSJ-Polystyrene G9001", methacrylic acid content: 7 wt%, MFR: 1.5 g / 10 min).

[0074] Polystyrene resin A, graphite, and stearic acid monoglyceride in Table 1 are components derived from the graphite masterbatch. The amount of each component in Table 1 is the blending amount (parts by weight) relative to a total of 100 parts by weight of the polystyrene resin.

[0075] [Table 1]

[0076] [Example 1] <Preparation of extruded foam> Extrusion foam molding was carried out using a manufacturing apparatus equipped with an extruder in which a first extruder (single-screw extruder, 150 mm diameter), a second extruder (single-screw extruder, 200 mm diameter), a cooler, and a slit die (5 mm nozzle gap) were connected in series in this order, two upper and lower molding plates connected downstream of the slit die of the extruder, and a molding roll located downstream of the molding plates.

[0077] GP1 was fed into the first extruder from the raw material feeder at 800 kg / hr, melt-kneaded in the first extruder at 250 °C, and the amount of foaming agent shown in Table 2 was injected near the downstream end of the first extruder. The composition was then cooled while being kneaded in the second extruder connected to the first extruder, and further cooled to 123 °C (foaming temperature) in a cooler connected to the second extruder. The cooled composition was then passed through a die slit and extruded into the atmosphere at a foaming pressure of 4 MPa. The extruded foam was then passed through a molding plate and a molding roll to obtain a plate-shaped extruded foam with a cross-section of 60 mm thick and 1000 mm wide. This extruded foam was cut with a cutter to a thickness of 50 mm, width of 910 mm, and length of 1820 mm (this foam is designated as the "zeroth recycled" foam).

[0078] <Production of extruded foam using recycled resin> The foam from the zeroth recycling run, crushed in a crusher, and the cutting waste generated during foam molding were fed into a 120 mm diameter single-screw extruder, heated to approximately 230°C to melt, plasticize, and knead the mixture. After removing the remaining blowing agent from the foam under open-vent conditions, the mixture was extruded through a die and pelletized by strand cutting to obtain recycled pellets. The "first recycled" foam was obtained in the same manner as in <Preparation of Extruded Foam> above, except that a 50:50 mixture of GP1 and recycled pellets was used as the resin composition.

[0079] The foam from the first recycling was crushed in a crusher, and scraps generated during foam molding were used to make recycled pellets, which were then mixed with GP1 in a 50:50 weight ratio to produce the "second recycling" foam. The production of recycled pellets and extruded foam was then repeated, resulting in the "fifth recycling" foam.

[0080] [Example 2, Comparative Examples 1 to 3, Reference Examples 1 and 2] GP2 to GP7 were used as the resin mixture instead of GP1, and the foaming temperature was changed as shown in Table 2. Except for this, extrusion foam molding was carried out in the same manner as in Example 1, to obtain foams with recycling counts of 0 to 5 times.

[0081] [Examples 3 to 5] GP1 was used as the resin mixture, and the composition of the blowing agent and the foaming conditions were changed as shown in Table 2. Except for this, extrusion foam molding was carried out in the same manner as in Example 1, to obtain foams with a recycling count of 0 to 5 times.

[0082] [Example 6, Comparative Example 4] As the resin mixture, GP6 and GP7 were used instead of GP1, and the foaming agent composition and foaming conditions were changed as shown in Table 2. Except for these, extrusion foam molding was performed in the same manner as in Example 1, and foams with recycling counts of 0 to 5 were obtained.

[0083] The details of the foaming agents shown in Table 2 are as follows: To prevent corrosion by ethyl chloride, an aqueous solution of sodium bicarbonate in which 10 wt % of sodium carbonate was dissolved in water was used as the foaming agent. Water: pure water HCFO-1233zd: 1-chloro-3,3,3-trifluoropropene, manufactured by Honeywell Japan HFO-1234ze: 1,3,3,3-tetrafluoropropene, manufactured by Honeywell Japan Isobutane: Mitsui Chemicals Ethyl chloride: Nippon Specialty Chemical Industry Co., Ltd.

[0084] [Evaluation of foam] <Apparent density> A rectangular specimen measuring approximately 200 mm in length (extrusion direction) and 900 mm in width was cut from the center of the width direction of the foam. The apparent density (mass / volume) was calculated from the apparent volume calculated from the outer dimensions of the specimen measured using a vernier caliper (Mitutoyo, M-type standard vernier caliper N30) and the mass of the specimen.

[0085] <Closed bubble diameter> Test pieces measuring 40 mm thick, 25 mm long, and 25 mm wide were cut out from three locations on the foam: the widthwise center A, and points B and C, 150 mm from each end in the widthwise direction. The closed cell ratio of each sample was determined, and the average closed cell ratio of the three test pieces was calculated. The closed cell ratio was calculated according to procedure C of ASTM-D2856-70, using an air-comparison hydrometer (Tokyo Science Model 1000) to measure the true volume V1 (the apparent volume minus the volume of the non-closed cell portion), the apparent volume V2 calculated from the outer dimensions of the test piece measured using a vernier caliper, the mass W of the test piece, and the true density ρ of the test piece (the density of polystyrene resin, 1.05 g / cm). 3 The calculation was based on the following formula: Closed cell ratio (%)=100×(V1-W / ρ) / (V2-W / ρ)

[0086] <Average bubble diameter> As with the evaluation of closed cell diameter described above, test specimens were cut from three locations A, B, and C in the width direction, and 100x magnified photographs of the width and length cross sections of each test specimen were taken using a microscope (Keyence Digital Microscope VHX-900). Three 2-mm-long lines were drawn in the thickness direction at random locations on each enlarged photograph, and the total number of bubbles intersecting or touching the three lines, a, was calculated to determine the average thickness-wise bubble diameter (= 2 × 3 / a) for that cross section. The average thickness-wise bubble diameter calculated from each of the six enlarged cross-sectional photographs (two enlarged cross-sectional photographs were taken for each of the three test specimens) was used as the average bubble diameter of the foam.

[0087] <Thermal conductivity> In accordance with JIS A 9521:2017, a test piece with a thickness length (extrusion direction) of 300 mm × width of 300 mm was cut out from the central part in the width direction of the foam immediately after production, and it was left standing in the standard atmosphere class 3 of JIS K 7100:1999 for one week for conditioning. In an environment with an average temperature of 23°C, the thermal conductivity of the conditioned test piece was measured using a thermal conductivity measuring device ("HC-074" manufactured by Eihiro Seiki Co., Ltd.).

[0088] <JIS Flammability> In accordance with JIS A 9521:2017, a test piece with a thickness of 10 mm × length (extrusion direction) of 200 mm × width of 25 mm was cut out from the central part in the width direction of the foam immediately after production, and after leaving it standing in the standard atmosphere class 3 of JIS K 7100:1999 for one week for conditioning, its flame retardancy was evaluated. Those that met the criterion of "the flame goes out within 3 seconds, there is no remaining char, and it does not burn beyond the combustion limit indicator line" were marked as ○, and those that did not meet the criterion were marked as ×.

[0089] <Heat Resistance> Similar to the evaluation of the above-mentioned independent cell diameter, test pieces with a length (extrusion direction) of 300 mm × width of 300 mm were cut out from three locations A, B, and C in the width direction, and after leaving them standing in the standard atmosphere class 3 of JIS K 7100:1999 for one week for conditioning, they were heated in an oven maintained at 85°C for 24 hours. The thickness, length, and width of the test pieces before and after heating were measured using a vernier caliper to calculate the volume. From the volume V0 before heating and the volume V1 after heating, the volume change rate = 100×(V1 - V0) / V0 was calculated, and the heat resistance was evaluated based on the following criteria from the average value of the volume change rates of the three test pieces. 〇: Volume change rate is less than 5% △: Volume change rate is 5 - 10% ×: Volume change rate exceeds 10%

[0090] <Mw Retention Rate> By gel permeation chromatography (GPC), under the following conditions, the weight average molecular weight Mw of the foam with 0 recycling times and the foam with 5 recycling times was determined. Equipment used: e2695 manufactured by Waters Columns used: Shodex GPC-K-806M, two columns connected directly Sample concentration: 2.5 mg / mL Solvent: Chloroform Temperature; 40℃ Sample injection volume: 50 μL Flow rate: 1.0mL / min Detection method: UV (254 nm) Standard polystyrene: Shodex STANDARD SM-105 manufactured by Resonac

[0091] The ratio of Mw of a foam recycled 5 times to Mw of a foam recycled 0 times was taken as Mw retention, and Mw retention of 0.90 or more was evaluated as ◯, and Mw retention of less than 0.90 was evaluated as ×.

[0092] Table 2 shows the type and composition of the resin mixture used in each example, comparative example, and reference example (ratio of MMA to the total polystyrene resin, type of brominated flame retardant and amount blended per 100 parts by weight of polystyrene resin, amount of epoxy stabilizer blended per 100 parts by weight of polystyrene resin and 100 parts by weight of brominated polymer), amount of blowing agent injected (weight per 100 parts by weight of polystyrene resin), foaming conditions, and evaluation results of foams recycled five times. For Example 1 and Comparative Example 3, evaluation results of foams recycled zero times are also shown.

[0093] [Table 2]

[0094] In Reference Examples 1 and 2, which used GP8 and GP9 containing bromine-containing low-molecular-weight compounds as flame retardants, the foams recycled five times had excellent insulation, flame retardancy, and heat resistance. In Comparative Example 3, which used a bromine-containing polymer as a flame retardant, the foam recycled zero times had good flame retardancy, but the foam recycled five times had reduced flame retardancy and also reduced insulation and heat resistance compared to the foam recycled zero times.

[0095] In Comparative Example 3, the weight-average molecular weight Mw of the foam recycled five times was reduced, which is thought to be due to resin degradation caused by the thermal history during extrusion foaming. Comparing the compositions of GP5 with GP8 and GP9, in Comparative Example 3 using GP5, the bromine-containing polymer used as a flame retardant had low heat resistance, and this thermal degradation is thought to be the main cause of the specific deterioration in flame retardancy, etc.

[0096] Example 1, which used GP1, which contained a higher amount of epoxy stabilizer than GP5, had a high Mw retention rate, and both the foam recycled 0 times and the foam recycled 5 times had excellent insulation, flame retardancy, and heat resistance, similar to Reference Examples 1 and 2. The same was true for Examples 3 to 5, which used different types and amounts of blowing agents.

[0097] Example 2, which used GP2, which had a lower ratio of styrene-methacrylic acid copolymer than GP1, had excellent heat insulation, flame retardancy, and heat resistance, similar to Example 1. Comparative Example 2, which used GP4, which did not contain styrene-methacrylic acid copolymer, showed a large change in volume upon heating of the foam and poor heat resistance.

[0098] On the other hand, in Comparative Example 1, which used GP3 with a high ratio of styrene-methacrylic acid copolymer, the closed cell ratio of the foam was small, resulting in high thermal conductivity and insufficient heat insulation. A comparison between Example 6, which used GP6 as the resin mixture, and Comparative Example 4, which used GP7 with a high ratio of styrene-methacrylic acid copolymer, also shows that when the ratio of styrene-methacrylic acid copolymer (the ratio of methacrylic acid in the polystyrene resin) is excessively high, the closed cell ratio is small and the thermal conductivity is high.

[0099] These results show that foams containing styrene-(meth)acrylic acid copolymer as a polystyrene-based resin have excellent heat resistance, and that even when a bromine-containing polymer is used as a flame retardant, excellent insulation, thermal stability, and flame retardancy can be maintained by adjusting the ratio of (meth)acrylic acid.

Claims

1. An extruded styrene-based resin foam comprising a polystyrene-based resin, a flame retardant, and a stabilizer, the polystyrene-based resin contains a styrene-(meth)acrylic acid copolymer, and the amount of (meth)acrylic acid is 1.4 to 4.0 parts by weight per 100 parts by weight of the total of monomer components constituting the polystyrene-based resin; the flame retardant comprises at least one bromine-containing polymer; The stabilizer comprises at least one epoxy compound. Extruded styrene resin foam.

2. 2. The extruded styrene-based resin foam according to claim 1, wherein the epoxy compound comprises at least one selected from the group consisting of bisphenol A diglycidyl ether epoxy resins, cresol novolac epoxy resins, and phenol novolac epoxy resins.

3. 2. The extruded styrene resin foam according to claim 1, wherein the content of the epoxy compound is 0.3 to 1.0 parts by weight per 100 parts by weight of the polystyrene resin.

4. 2. The extruded styrene resin foam according to claim 1, wherein the content of the epoxy compound is 10 to 20 parts by weight per 100 parts by weight of the bromine-containing polymer.

5. The extruded styrene resin foam according to claim 1, comprising 0.10 to 1.0 mol / kg of alkyl chloride.

6. The extruded styrene resin foam according to claim 1, having a thickness of 10 mm or more and 150 mm or less.

7. A method for producing the extruded styrene resin foam according to any one of claims 1 to 6, A method for producing an extruded styrene-based resin foam, comprising melt-kneading a composition containing a polystyrene-based resin, a blowing agent, a flame retardant, and a stabilizer, and extruding the mixture into a low-pressure region to form an extrusion foam.

8. the blowing agent comprises an alkyl chloride; The method for producing an extruded styrene resin foam according to claim 7, wherein the amount of the alkyl chloride is 2 to 6 parts by weight per 100 parts by weight of the polystyrene resin.

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