Foamable polystyrene resin particle, method for producing the same, pre-foamed polystyrene resin particle and foamed molding

Abstract

To provide foamable polystyrene resin particles that can form a polystyrene resin foamed molding with an optimal balance between flame resistance and compressive strength, a method for producing the foamable polystyrene resin particles, pre-foamed polystyrene resin particles comprising the foamable polystyrene resin particles, and a foamed molding comprising the pre-foamed polystyrene resin particles.SOLUTION: Foamable polystyrene resin particles comprise a polystyrene resin (A), a brominated flame retardant (B), and a foamer (E), where the polystyrene resin (A) comprises regenerated polystyrene resin (A1) and the foamer (E) comprises pentane and butane, with their weight ratio being expressed by pentane:butane=45:55-99:1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to expandable polystyrene-based resin particles, a method for producing the same, pre-expanded polystyrene-based resin particles using the expandable polystyrene-based resin particles, and a foamed molded article. [Background technology]

[0002] Foamed molded articles obtained by expanding expandable polystyrene-based resin particles are lightweight and have excellent shock-absorbing and heat-insulating properties, and therefore are widely used as packaging materials (trays) for food containers and the like, various packaging materials, construction and civil engineering components, automobile components, and the like. In recent years, the use of recycled materials has become more common in order to reduce the burden on the environment. In particular, there is an increasing demand for foam-molded products made from post-consumer materials, which are made by recovering and recycling raw materials from waste from used products.

[0003] Expandable polystyrene-based resin particles used for such applications include, for example, recycled flame-retardant expandable styrene-based resin particles obtained by impregnating recycled styrene-based resin particles with a styrene-based monomer, polymerizing the resulting particles, and then impregnating the particles with a flame retardant and a blowing agent. The recycled styrene-based resin used as the raw material is melted without stretching to adjust the ratio of the weight average molecular weight of the recycled styrene-based resin particles to the weight average molecular weight of the recycled flame-retardant expandable styrene-based resin particles to be within a specific range (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-064211 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 is limited to a manufacturing method in which a styrene monomer is impregnated into specific gravity-adjusted recycled styrene resin particles, polymerized, and then impregnated with a flame retardant and a foaming agent. In addition, there is no consideration of making the compressive strength of the obtained recycled polystyrene resin foam molded product closer to the compressive strength of a foam molded product using a virgin polystyrene resin.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide expandable polystyrene-based resin particles capable of forming a polystyrene-based resin expansion molded article having a good balance between flame retardancy and compressive strength, a method for producing the expandable polystyrene-based resin particles, pre-expanded polystyrene-based resin particles using the expandable polystyrene-based resin particles, and an expansion molded article using the pre-expanded polystyrene-based resin particles. [Means for solving the problem]

[0007] The present inventors have discovered that the above problems can be solved by using pentane and butane in combination in a specific ratio as a blowing agent in expandable polystyrene-based resin particles containing a polystyrene-based resin including recycled polystyrene-based resin, a bromine-based flame retardant, and a blowing agent, and have completed the present invention.

[0008] Aspects of the present disclosure relate to the following expandable polystyrene-based resin particles, a method for producing the expandable polystyrene-based resin particles, pre-expanded polystyrene-based resin particles using the expandable polystyrene-based resin particles, and a foamed molded article using the pre-expanded polystyrene-based resin particles.

[0009] [1] Expandable polystyrene-based resin particles comprising a polystyrene-based resin (A), a brominated flame retardant (B), and a blowing agent (E), The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The expandable polystyrene resin particles, wherein the blowing agent (E) contains pentane and butane, and the weight ratio thereof is pentane:butane=45:55 to 99:1. [2] The expandable polystyrene-based resin particles according to [1], wherein the content of the recycled polystyrene-based resin (A1) is 20% by weight or more based on the total amount of the polystyrene-based resin (A). [3] The butane includes isobutane, The expandable polystyrene-based resin particles according to [1] or [2], wherein the content of the isobutane is 50% by weight or more and 100% by weight or less with respect to the total amount of the butane. [4] Pre-expanded polystyrene-based resin particles obtained by pre-expanding the expandable polystyrene-based resin particles according to [1] or [2]. [5] A foam obtained by molding the pre-expanded polystyrene-based resin particles described in [4]. [6] The foam described in [5], which is for use in embankments. [7] A method for producing expandable polystyrene-based resin particles, comprising extruding a polystyrene-based resin melt containing a polystyrene-based resin (A), a brominated flame retardant (B), and a blowing agent (E) through a die having a plurality of small holes into pressurized circulating water, and cutting the melt into particles with a rotating cutter, comprising the steps of: The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The method for producing expandable polystyrene-based resin particles, wherein the foaming agent (E) contains pentane and butane, and the weight ratio thereof is pentane:butane=45:55 to 99:1. Effect of the Invention

[0010] According to the present invention, there can be provided expandable polystyrene-based resin particles capable of forming an expanded molded article having a good balance between flame retardancy and compressive strength, a method for producing the expandable polystyrene-based resin particles, pre-expanded polystyrene-based resin particles using the expandable polystyrene-based resin particles, and an expanded molded article using the pre-expanded polystyrene-based resin particles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Expandable polystyrene resin particles> The expandable polystyrene-based resin particles of the present embodiment contain a polystyrene-based resin (A), a bromine-based flame retardant (B), and a blowing agent (E). The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The blowing agent (C) contains pentane and butane, and the weight ratio thereof is pentane:butane=45:55 to 99:1.

[0012] According to the expandable polystyrene-based resin particles of this embodiment, since pentane and butane are used in combination in a specific ratio as the blowing agent (E), it is possible to form a polystyrene-based resin foamed molding having a good balance between flame retardancy and compressive strength.

[0013] Hereinafter, essential and optional components contained in the expandable polystyrene-based resin particles will be described.

[0014] <Polystyrene resin (A)> In one embodiment of the present invention, the polystyrene resin (A) contains a recycled polystyrene resin (A1).

[0015] (Recycled polystyrene resin (A1)) The recycled polystyrene resin (A1) means a polystyrene resin derived from a recycled product. Examples of the polystyrene resin derived from a recycled product include recycled raw materials obtained by recovering used polystyrene resin foam molded bodies such as fish boxes, household appliance cushioning materials, or food packaging trays, and regenerating them by a limonene dissolution method or a heat volume reduction method; recycled raw materials obtained by crushing non-foamed polystyrene molded bodies separated and recovered from household appliances, melt-kneading them, and repelletizing them; recycled raw materials obtained by crushing scraps generated after punching food packaging trays, etc. from a polystyrene resin foam sheet, melt-kneading them, and repelletizing them. Examples of the polystyrene resin here include the same examples of polystyrene resins described below, and may include only one type or two or more types.

[0016] The content of the recycled polystyrene resin (A1) is preferably 20% by weight or more, more preferably 25% by weight or more, and even more preferably 30% by weight or more, based on the total amount of the polystyrene resin (A), from the viewpoint of forming a polystyrene resin foam molded article having a good balance between flame retardancy and compressive strength. The upper limit is preferably 80% by weight or less, and more preferably 100% by weight or less, based on the total amount of the polystyrene resin (A), from the viewpoint of reducing the environmental load.

[0017] (Virgin polystyrene resin (A2)) In one embodiment of the present invention, the polystyrene resin (A) may be used in combination with a virgin polystyrene resin (A2). The virgin polystyrene resin (A2) is a so-called virgin polystyrene resin, and refers to a new polystyrene resin excluding recycled polystyrene resins. The virgin polystyrene resin (A2) preferably contains a styrene homopolymer (polystyrene homopolymer) because it has excellent compatibility with the recycled polystyrene resin (A1). By using the polystyrene homopolymer, expandable particles and blocks with excellent expandability and moldability can be obtained.

[0018] The virgin polystyrene resin (A2) may be a copolymer of styrene and another monomer copolymerizable with styrene or a derivative thereof, provided that the effect of the present invention is not impaired. These may be used alone or in combination of two or more.

[0019] Examples of other monomers copolymerizable with styrene 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; unsaturated carboxylic acids such as acrylic acid and 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 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)-chlorophenylmaleimide, N-(4)-bromophenylmaleimide, and N-(1)-naphthylmaleimide. These may be used alone or in combination of two or more.

[0020] <Brominated flame retardants (B)> Examples of the brominated flame retardant (B) 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)) and 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromopropyl ether)), brominated butadiene-vinyl aromatic hydrocarbon copolymers such as brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers (for example, those disclosed in JP-T-2009-516019 A), and tetrabromocyclooctane. These brominated flame retardants (B) may be used alone or in combination of two or more.

[0021] The bromine-based flame retardant (B) is easy to control to the desired expansion ratio, and from the viewpoint of the balance of flame retardancy, etc., the bromine content is preferably 0.8% by weight or more, more preferably 5.0% by weight or less, based on the total amount (100% by weight) of the expandable polystyrene resin particles. If the bromine content is 0.8% by weight or more, the effect of imparting flame retardancy tends to be large, and if it is 5.0% by weight or less, the strength of the pre-expanded particles and the foamed molded article provided by the obtained expandable polystyrene resin particles tends to increase. The bromine-based flame retardant (B) is blended with the expandable polystyrene resin particles so that the bromine content based on the total amount of the expandable polystyrene resin particles is preferably 0.8% by weight to 5.0% by weight, more preferably 1.0% by weight to 3.5% by weight.

[0022] <Foaming agent (E)> The blowing agent (E) includes butane and pentane. Examples of butane include normal butane and isobutane. Examples of pentane include normal pentane, isopentane, neopentane, and cyclopentane.

[0023] The weight ratio of pentane to butane is pentane:butane=45:55 to 99:1, and from the viewpoint of cell miniaturization, it is preferably 50:50 to 80:20, and more preferably 55:45 to 70:30.

[0024] The butane preferably contains isobutane. From the viewpoint of mechanical strength, the content of isobutane is preferably 50% by weight or more and 100% by weight or less, more preferably 70% by weight or more and 100% by weight or less, and even more preferably 85% by weight or more and 100% by weight or less, based on the total amount of butane.

[0025] The blowing agent may be a hydrocarbon blowing agent other than butane and pentane, as long as the effect of the present invention is not impaired. For example, a hydrocarbon having 3 carbon atoms (propane) or a hydrocarbon having 6 carbon atoms (normal hexane, cyclohexane) may be used.

[0026] The content of the foaming agent (E) is not particularly limited, and is preferably 3 parts by weight or more and 10 parts by weight or less, and more preferably 3.5 parts by weight or more and 8 parts by weight or less, relative to 100 parts by weight of the polystyrene resin (A). When the content of the foaming agent (E) is 3 parts by weight or more, the foaming power is sufficient, and it is easy to achieve a high expansion ratio, and it is easy to produce a polystyrene resin foam molded article with a high expansion ratio. In addition, when the content of the foaming agent (E) is 10 parts by weight or less, the flame retardant performance is unlikely to deteriorate, and the production time (molding cycle) when producing a polystyrene resin foam molded article is shortened, so that the production cost can be reduced.

[0027] (Other ingredients) The expandable polystyrene resin particles may contain components other than the polystyrene resin (A), the bromine-based flame retardant (B), and the blowing agent (E) (hereinafter also referred to as "other components") as long as the effects of the present invention are not impaired. Examples of the other components include heat stabilizers, flame retardant assistants, nucleating agents, radical generators, fiber reinforcements, processing assistants, blowing assistants, antistatic agents, colorants such as pigments, anti-light stabilizers, radiation heat transfer inhibitors, surfactants, etc. These other components may be used alone or in combination of two or more.

[0028] (Heat stabilizer) In one embodiment of the present invention, the use of a heat stabilizer in combination can suppress deterioration of the flame retardancy and degradation of the polystyrene resin (A) due to decomposition of the brominated flame retardant (B) during the production process. The heat stabilizers in the present invention can be used in appropriate combinations depending on the type of polystyrene resin (A) used, the type and content of the foaming agent (E), the type and content of the brominated flame retardant (B), etc. The heat stabilizer used in the present invention is preferably a hindered amine compound, a phosphorus compound, a phenolic stabilizer, or an epoxy compound, because it can arbitrarily control the weight loss temperature in the thermogravimetric analysis of the mixture containing a bromine-based flame retardant. The heat stabilizer can be used alone or in combination of two or more. These heat stabilizers can also be used as light resistance stabilizers.

[0029] The content of the heat stabilizer is not particularly limited, and is preferably from 1 to 25 parts by weight, more preferably from 2 to 20 parts by weight, and even more preferably from 3 to 18 parts by weight, relative to 100 parts by weight of the brominated flame retardant (B).

[0030] (Flame retardant assistant) As the flame retardant auxiliary, it is preferable to use a compound having cumene as a basic structural unit. As the flame retardant auxiliary, it is preferable to use a compound having a 10% thermal decomposition temperature of 150°C or more and 250°C or less. The 10% decomposition temperature means a temperature at which the weight loss rate exceeds 10% when a sample is heated from 35°C at a temperature increase rate of 10°C / min in an atmosphere with nitrogen flowing in at 100mL / min. Such a compound is also called a CC initiator. Examples of the flame retardant auxiliary include 1,1'-(1,1,2,2-tetramethyl)dibenzene, poly-1,4-diisopropylbenzene, 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, 3,4-diethyl-3,4-diphenylhexane, 2,7-dimethyl-4,5-diethyl-4,5-diphenyloctane, 3,4-dibenzyl-3,4-ditolylhexane, 1,1,2,2-tetraphenyl-1,2-ethanediol, etc. The flame retardant auxiliary may be used alone or in combination of two or more.

[0031] The content of the flame retardant auxiliary is not particularly limited, and is preferably from 0.1 to 2.0 parts by weight, more preferably from 0.3 to 1.0 part by weight, per 100 parts by weight of the polystyrene resin (A).

[0032] (Nucleating agent) Examples of the nucleating agent include a mixture of sodium bicarbonate and citric acid, monosodium citrate, talc, calcium carbonate, etc. The nucleating agent may be used alone or in combination of two or more.

[0033] The content of the nucleating agent is not particularly limited, and is preferably from 0.5 to 5.0 parts by weight, and more preferably from 1.0 to 3.0 parts by weight, per 100 parts by weight of the polystyrene resin (A). (Radical generator) In the present invention, by further containing a radical generator, high flame retardant performance can be achieved by using it in combination with a brominated flame retardant. The radical generator in the present invention can be used in appropriate combination depending on the type of polystyrene resin (A) used, the type and content of the blowing agent (E), and the type and content of the brominated flame retardant (B). Examples of the radical generator used in the present invention include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, etc. The radical generators may be used alone or in combination of two or more.

[0034] From the viewpoint of compressive strength, the expandable polystyrene resin particles of this embodiment preferably have a closed cell ratio of 93% or more when expanded to a bulk ratio of 50 times, more preferably 94% or more, even more preferably 95% or more, and particularly preferably 96% or more.

[0035] The expandable polystyrene resin particles of the present embodiment have an average cell diameter of preferably 100 μm or more, more preferably 120 μm or more, and even more preferably 130 μm or more when expanded to a bulk ratio of 50. On the other hand, the average cell diameter is preferably 280 μm or less, more preferably 270 μm or less, and even more preferably 250 μm.

[0036] <Method for producing expandable polystyrene resin particles> As one embodiment of the present invention, a method for producing expandable polystyrene-based resin particles includes extruding a polystyrene-based resin melt containing a polystyrene-based resin (A), a brominated flame retardant (B), and a blowing agent (E) through a die having a plurality of small holes into pressurized circulating water, and cutting the melt into particles with a rotary cutter, comprising the steps of: The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The foaming agent (E) contains pentane and butane, and the weight ratio of these is pentane:butane=45:55 to 99:1.

[0037] According to the method for producing expandable polystyrene-based resin particles of the present embodiment, the expandable resin particles can be produced in the same facility, so that the running costs can be reduced.

[0038] Each component used in this manufacturing method is the above-mentioned "expandable polystyrene resin particles" This is the same as the embodiment described in the section.

[0039] In a preferred embodiment of the present method, polystyrene resin (A), bromine-based flame retardant (B), foaming agent (C), and other components such as heat stabilizer, flame retardant assistant, nucleating agent, etc. are melt-kneaded in an extruder, and the resulting polystyrene resin melt is extruded into a cutter chamber filled with pressurized circulating water through a die having small holes attached to the tip of the extruder, cut by a rotating cutter immediately after extrusion, and cooled and solidified by pressurized circulating water. At this time, the melt-kneading in the extruder may be performed using a single extruder, a plurality of extruders may be connected, or an extruder may be used in combination with a second kneading device such as a static mixer or a stirrer without a screw, and may be appropriately selected.

[0040] The set temperature of the melt-kneading section of the extruder is preferably 100°C to 250°C. In addition, the residence time in the extruder from the supply of the polystyrene resin (A) and various components to the extruder until the end of melt-kneading is preferably 10 minutes or less. If the set temperature in the melt-kneading section of the extruder is 250°C or less and / or the residence time in the extruder until the end of melt-kneading is 10 minutes or less, the decomposition of the brominated flame retardant (B) does not occur when the brominated flame retardant (B) is added, and the desired flame retardancy can be obtained, and there is no need to add an excessive amount of the brominated flame retardant (B) to impart the desired flame retardancy. On the other hand, if the set temperature in the melt-kneading section of the extruder is 100°C or more, the load on the extruder is not large, extrusion is stable, and the dispersibility of the added components is improved.

[0041] Here, the melt-kneading section of the extruder means the section from the feed section to the tip of the final downstream extruder when the extruder is an extruder having a single or twin screw, or the section from the feed section of the first extruder to the tip of the second kneading device when the first extruder is used in combination with a second kneading device such as a static mixer or a stirrer without a screw.

[0042] The water pressure of the pressurized circulating water is preferably 0.9 MPa or more and 1.5 MPa or less, more preferably 0.95 MPa or more and 1.4 MPa or less. If the water pressure is 0.9 MPa or more, foaming can be suppressed, the bulk density of the expandable polystyrene resin particles increases, and the decrease in the expansion ratio and the decrease in the transport efficiency are unlikely to occur. On the other hand, if the water pressure is 1.5 MPa or less, the rotary cutter is not pushed back by the water pressure, and the extruded molten resin does not wrap around the rotary cutter, so that the expandable polystyrene resin particles can be stably produced. In addition, the strain applied to the molten resin is not large, the shape of the expandable polystyrene resin particles becomes good, and the expandability and moldability are excellent. The temperature of the pressurized circulating water is preferably 50° C. or higher and 80° C. or lower, and more preferably 55° C. or higher and 670° C. or lower. By setting the temperature at 55° C. or higher, blockage of the die hole is less likely to occur. In addition, by setting the temperature at 70° C. or lower, micro-expansion of the expandable particles can be suppressed.

[0043] The above-mentioned die is not particularly limited, but examples thereof include those having small holes with a diameter of 0.3 mm to 2.0 mm, preferably 0.4 mm to 1.0 mm.

[0044] The cutting device for cutting the molten resin extruded into the pressurized circulating water is not particularly limited, but examples thereof include a device in which the molten resin is cut into small pellets by a rotating cutter that comes into contact with a die lip, and then transported to a centrifugal dehydrator for dehydration and aggregation.

[0045] <Polystyrene resin foam molded body and its manufacturing method> The polystyrene resin foamed molded article can be produced, for example, by a pre-expanding method in which molding is carried out using pre-expanded polystyrene resin particles obtained by expanding the above-mentioned expandable polystyrene resin particles to a predetermined expansion ratio.

[0046] The expandable polystyrene resin particles are expanded 10 to 100 times by a known pre-expanding process, for example, by steam to form pre-expanded particles (pre-expanding process), and after curing for a certain period of time as necessary, the pre-expanded particles are molded by steam using a known molding machine to produce a polystyrene resin foamed molded article. Depending on the shape of the mold used, a molded article with a complex shape or a block-shaped molded article can be obtained.

[0047] (Pre-foaming process) The pre-expansion step can be carried out using a pre-expansion machine in the same manner as in the pre-expansion of conventional expandable polystyrene-based resin particles.

[0048] As the pre-expanding machine, a known machine can be used, for example, a pre-expanding machine equipped with a stirrer, a can in which expandable polystyrene-based resin particles are accommodated, a steam chamber disposed below the can for supplying water vapor to the can, and a pre-expanded particle outlet is used.

[0049] The internal pressure (cage pressure) when steam is introduced is not particularly limited, but is preferably 0.001 to 0.15 MPa, more preferably 0.01 to 0.10 MPa, and even more preferably 0.03 to 0.08 MPa. When the internal pressure is 0.01 MPa or more, the time for introducing steam in pre-expansion can be set to 500 seconds or less when obtaining 40 to 50 times expanded particles. When the internal pressure is 0.15 MPa or less, it is not necessary to increase the pressure of steam, the occurrence of blocking phenomenon decreases, and the pre-expansion yield increases.

[0050] The pre-expansion step can be carried out either continuously or batchwise.

[0051] The continuous method is a method in which expandable polystyrene resin particles are continuously fed into a can and pre-expanded particles are continuously discharged from a discharge port provided at the top of the can. The expansion ratio of the pre-expanded particles can be adjusted, for example, by appropriately selecting the amount (weight) of expandable polystyrene resin particles fed into the can per unit time. In the case of the continuous method, the residence time in the pre-expanding machine can from the time the expandable polystyrene resin particles are fed into the can to the time the pre-expanded particles are discharged is defined as the steam feeding time.

[0052] The batch method is a method in which a predetermined amount of expandable polystyrene resin particles is put into a can, and after pre-expanding the particles to a predetermined expansion ratio, the supply of steam is stopped, and then air is blown into the can as necessary to cool and dry the pre-expanded particles, which are then taken out of the can. The expansion ratio of the pre-expanded particles can be adjusted by appropriately selecting the amount (weight) of expandable polystyrene resin particles put into the can per batch. Since the batch method is a method in which the put-in expandable polystyrene resin particles are pre-expanded to a predetermined volume, the smaller the amount put in per batch, the higher the expansion ratio of the pre-expanded particles obtained.

[0053] The polystyrene-based resin foam molded article is suitable for use in, for example, embankments. The polystyrene-based resin foam molded article can also be used in various applications, such as building insulation materials used for floors, walls, roofs, etc., agricultural and marine boxes, such as boxes for transporting marine products such as fish and boxes for transporting agricultural products such as vegetables, bathroom insulation materials, and hot water tank insulation materials. EXAMPLES

[0054] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0055] <Ingredients> In the examples and comparative examples, the following A1-1 was used as the recycled polystyrene resin (A1). A1-1: Fish boxes were collected as used polystyrene-based resin foam moldings, and the collected fish boxes were recycled by a heating and dissolving method, and the resulting recycled polystyrene raw material was used. In the examples and comparative examples, the following A2-1 was used as the virgin polystyrene-based resin (A2). A2-1: Styrene homopolymer (PS Japan "680")

[0056] In the examples and comparative examples, the following B1 to B2 were used as the brominated flame retardant (B). B1: 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromo] Bromophenyl]propane (Daiichi Kogyo Seiyaku Co., Ltd. "SR-130", bromine content = 66% by weight) B2: Brominated styrene-butadiene block copolymer (LANXESS "EMERALD INNOVATION 3000", bromine content: 65% by weight)

[0057] In the examples and comparative examples, the following C1 to C5 were used as the heat stabilizer (C). C1: Tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane (ADEKA "LA-57") C2: Bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite (ADEKA "PEP-36") C3: 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (ADDIVANT "Ultranox626") C4: Pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate] ("ANOX20" manufactured by ADDIVANT) C5: Cresol novolac type epoxy resin (Huntsman Japan "ECN-1280", epoxy equivalent 212-233g / eq.)

[0058] In the examples and comparative examples, the flame retardant (B) and the heat stabilizer (C) were mixed in a mixer to obtain a mixture (D) of the flame retardant (B) and the heat stabilizer (C). As the mixture (D), the following D1 to D2 were used. The weight ratios of each component of D1 to D2 are shown below. D1:(B1):(C1):(C2)=100:2.1:3.2 D2:(B2):(C3):(C4):(C5)=100:0.5:10:5

[0059] In the examples and comparative examples, the following E1 to E3 were used as the foaming agent (E). E1: Normal pentane (Wako Pure Chemical Industries, Ltd., reagent) E2: Isopentane (Wako Pure Chemical Industries, Ltd., reagent) E3: Isobutane (Mitsui Chemicals, reagent)

[0060] In the examples and comparative examples, the following F1 to F2 were used as the flame retardant auxiliary (F). F1: 1,1'-(1,1,2,2-tetramethyl)dibenzene ("CUROX CC-DC" manufactured by United Initiators) F2: Poly-1,4-diisopropylbenzene ("CUROX CC-PIB" manufactured by United Initiators)

[0061] In the examples and comparative examples, the following G1 was used as the nucleating agent (G). G1: Talc (Tamura Talc Industrial Co., Ltd. "Fine Talc TP-20")

[0062] <Preparation of expandable polystyrene resin particles> Example 1 Virgin polystyrene resin (A2), recycled polystyrene resin (A1), and a mixture (D2) of brominated flame retardant (B) and heat stabilizer (C) were each placed in a blender and blended for 10 minutes to obtain a resin mixture. Also, the nucleating agent (G), which is a powder, and the flame retardant auxiliary (F) were dry-blended to obtain a powder mixture. The obtained resin mixture and powder mixture were fed to a tandem type two-stage extruder in which a 40 mm diameter twin screw extruder (first extruder) and a 90 mm diameter single screw extruder (second extruder) were connected in series, and melt-kneaded in the first extruder at a set temperature of 190°C and a rotation speed of 167 rpm. From the middle of the first extruder, 2.8 parts by weight of mixed pentane [E1 / E2=4 / 1 (weight ratio) mixture] was injected per 100 parts by weight of the above resin mixture, and 1.7 parts by weight of isobutane (E3) was injected per 100 parts by weight of the above resin mixture, and a total of 4.5 parts by weight of foaming agent (E) was added. Then, the mixture was fed to the second extruder through a continuation pipe set at 200°C.

[0063] The obtained polystyrene resin melt was cooled to 160°C in the second extruder, and then extruded from a die attached to the tip of the second extruder, which had 60 small holes with a diameter of 0.65 mm and a land length of 3.0 mm and was set at 250°C, at a discharge rate of 58.2 kg / hour into pressurized circulating water at a temperature of 62°C and 1.05 MPa. The extruded resin melt was cut and granulated using a rotary cutter with eight blades that contacted the die, and transferred to a centrifugal dehydrator to obtain expandable polystyrene resin particles. At this time, the residence time in the first extruder was 2 minutes, and the residence time in the second extruder was 5 minutes.

[0064] (Examples 2 to 6, Comparative Examples 1 to 2) The expandable polystyrene resin particles of Examples 2 to 6 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the above components were melt-kneaded according to the formulations shown in Table 1.

[0065] <Preparation of pre-expanded particles> (Examples 1A to 6A, Comparative Examples 1A to 2A) The expandable polystyrene resin particles of Examples 1 to 6 and Comparative Examples 1 and 2 were stored at 15° C. for one week or more, and then 0.04 parts by weight of zinc stearate was dry-blended as an additive with respect to 100 parts by weight of each expandable polystyrene resin particle. 410 g of each expandable polystyrene resin particle containing the additive was placed in a pre-expander (manufactured by Daikai Kogyo Co., Ltd., 0.5 MPa pressurized pre-expander), and the pressure inside the can was set to 0.05 kg / cm. 2 ~0.15kg / cm 2 Then, water vapor of 0.10 MPa was introduced into the pre-expander to expand the mixture to a bulk ratio of 50 times, thereby obtaining pre-expanded particles of Examples 1A to 6A and Comparative Examples 1A to 2A.

[0066] <Preparation of foamed molded body> (Examples 1B to 6B, Comparative Examples 1B to 2B) The pre-expanded particles of Examples 1A to 6A and Comparative Examples 1A to 2A were cured at 30°C for 24 hours, and then the pre-expanded particles were filled into an in-mold molding die (length 400 mm x width 400 mm x thickness 80 mm) attached to a polystyrene foam molding machine (KR-57, manufactured by Daisen Kogyo Co., Ltd.), and 0.06 MPa of water vapor was introduced to cause in-mold foaming, followed by spraying water on the die to cool. The foam molded body was held in the die until the pressure of the foam molded body pressing the die reached 0.01 MPa (gauge pressure), and then the foam molded body was removed to obtain the foam molded bodies of Examples 1B to 6B and Comparative Examples 1B to 2B.

[0067] <Evaluation> The cell size, closed cell ratio, expansion ratio, 10% compressive strength, and LOI of the obtained foamed molded article were measured according to the following methods. The results are shown in Table 1.

[0068] (cell diameter) The center of the polystyrene resin foam molded article was cut with a razor, and the cross section was observed with an optical microscope. The number of cells present within a 1000 μm × 1000 μm square area of ​​the cross section was counted, and the value measured using the following formula (area average diameter) was taken as the average cell diameter. The average cell diameter of five samples was measured, and the average was taken as the average cell diameter for each level. Average cell diameter (μm) = 2 × [1000 μm × 1000 μm / (number of cells × π)] 1 / 2

[0069] (Closed bubble rate) The volume Vc (cm) of the foamed molded specimen was measured using an air pycnometer (Tokyo Science Co., Ltd., air comparison specific gravity meter Model 1000) in accordance with the method described in ASTM D2856. 3 Next, the same test piece after the measurement was submerged in a measuring cylinder containing ethanol, and the volume Va (cm 3 ) was obtained and the closed cell ratio (%) was calculated according to the following formula. Closed cell rate (%) = (Vc / Va) x 100

[0070] (Expansion Ratio) The weight (g) of the foamed molded sample was measured, and the length, width, and thickness were measured using a caliper. The volume (cm 3 ) was calculated, and the expansion ratio was calculated according to the following formula. Expansion ratio (cm 3 / g) = sample volume (cm 3 ) / sample weight (g) The expansion ratio of foamed molded products is conventionally expressed as "cm 3 / g".

[0071] (10% compressive strength) The foamed molded product was left to stand at 23°C for 48 hours, and then cut into a test piece of 50mm x 50mm x 50mm size. The 10% deformation compressive stress was then measured according to JIS-K7220:2006, and the compressive strength was evaluated according to the following criteria. 〇:12N / cm 2 End △: 10N / cm 2 More than 12N / cm 2 less than ×:10N / cm 2 less than

[0072] (LOI) The foamed molded product was cut into test pieces measuring 10 mm x 10 mm x 150 mm, and allowed to stand at 60°C for 168 hours, and then allowed to stand at 23°C for 24 hours. The minimum oxygen index was then measured in accordance with JIS K7201.

[0073] [Table 1]

[0074] From Table 1, in Comparative Example 1, in which only butane was used as the blowing agent (E), the 10% compressive strength of the foamed molded article was poor. On the other hand, when butane and pentane were used in combination as the blowing agent (E), the 10% compressive strength was significantly improved as shown in Example 1. Moreover, the results of Example 3 compared to Comparative Example 2 showed similar results.

Claims

1. Expandable polystyrene-based resin particles comprising a polystyrene-based resin (A), a brominated flame retardant (B), and a blowing agent (E), The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The expandable polystyrene-based resin particles, wherein the foaming agent (E) contains pentane and butane, and the weight ratio thereof is pentane:butane=45:55 to 99:

1.

2. The expandable polystyrene-based resin particles according to claim 1, wherein the content of the recycled polystyrene-based resin (A1) is 20% by weight or more based on the total amount of the polystyrene-based resin (A).

3. The butane comprises isobutane, 3. The expandable polystyrene-based resin particles according to claim 1, wherein the content of said isobutane is 50% by weight or more and 100% by weight or less based on the total amount of said butanes.

4. 3. Pre-expanded polystyrene-based resin particles obtained by pre-expanding the expandable polystyrene-based resin particles according to claim 1 or 2.

5. A foam obtained by molding the pre-expanded polystyrene-based resin particles according to claim 4.

6. The foam according to claim 5, which is for use in soil filling.

7. A method for producing expandable polystyrene-based resin particles, comprising extruding a polystyrene-based resin melt containing a polystyrene-based resin (A), a brominated flame retardant (B), and a blowing agent (E) through a die having a plurality of small holes into pressurized circulating water, and cutting the melt into particles with a rotary cutter, comprising the steps of: The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The method for producing expandable polystyrene-based resin particles, wherein the foaming agent (E) contains pentane and butane, and the weight ratio thereof is pentane:butane=45:55 to 99:1.

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