Foamable polystyrene-based resin particle, method for producing the same, prefoamed polystyrene-based resin particle and foamed molded article

Abstract

To provide foamable polystyrene-based resin particles capable of forming a polystyrene-based resin foamed molded article having compressive strength and bending strength close to those of a foamed molded article using a virgin polystyrene-based resin while suppressing the decrease in compressive strength and bending strength; a method for producing the foamable polystyrene-based resin particles; prefoamed polystyrene-based resin particles using the foamable polystyrene-based resin particles; and a foamed molded article made of the prefoamed polystyrene-based resin particles.SOLUTION: There are provided foamable polystyrene-based resin particles comprising a polystyrene-based resin (A) and a foaming agent (B), wherein the polystyrene-based resin (A) comprises a recycled polystyrene-based resin (A1), the foaming agent (B) comprises butane and pentane, the butane comprises isobutane, the content of the isobutane to the total amount of the butane is more than 80 wt.%, and the content of the isobutane to the total amount of the foaming agent (B) is 25 wt.% or more and 95 wt.% or less.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] 2. Description of the Related Art Conventionally, used polystyrene-based resin foam molded articles have been actively used as recycled raw materials.

[0003] For example, Patent Document 1 discloses a technology for reusing recycled styrene-based resin recovered from used styrene-based resin moldings into flame-retardant expandable styrene-based resin, in which recycled styrene-based resin particles are impregnated with a styrene-based monomer, polymerized, and then impregnated with a blowing agent to obtain recycled expandable styrene-based resin particles, in which the ratio of the weight average molecular weight of the recycled styrene-based resin particles to the weight average molecular weight of the recycled styrene-based resin particles is within a specific range. [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, although Patent Document 1 shows that the obtained polystyrene-based resin foam molded article has excellent bending strength, the compressive strength and bending strength are lower than those of foam molded articles using virgin polystyrene-based resins, and as a result, the molded article is prone to cracking and chipping, which is problematic in practical use.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide expandable polystyrene-based resin particles that can form polystyrene-based resin foamed molded articles having compressive strength and flexural strength that are suppressed from decreasing and that are close to those of foamed molded articles made from virgin polystyrene-based resin, 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. [Means for solving the problem]

[0007] The present inventors have discovered that the above problems can be solved by including a specific content of isobutane as butane relative to the total amount of the blowing agent in expandable polystyrene-based resin particles that contain a polystyrene-based resin including recycled polystyrene-based resin and a blowing agent that contains butane and pentane, 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) and a blowing agent (B), The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The blowing agent (B) comprises butane and pentane; The butane comprises isobutane, The content of the isobutane relative to the total amount of the butane is greater than 80% by weight; The expandable polystyrene-based resin particles have a content of the isobutane of 25% by weight or more and 95% by weight or less based on the total amount of the blowing agent (B). [2] The expandable polystyrene-based resin particles according to [1], wherein the content of the blowing agent (B) is 3.0 parts by weight or more and 10.0 parts by weight or less per 100 parts by weight of the polystyrene-based resin (A). [3] The expandable polystyrene-based resin particles according to [1] or [2], wherein the polystyrene-based resin (A) is 100% by weight and the recycled polystyrene-based resin (A1) is contained in an amount of 50% by weight or more. [4] Further comprising a nucleating agent (C), The average particle size of the nucleating agent (C) is 0.5 μm or more and 20 μm or less, The expandable polystyrene-based resin particles according to any one of [1] to [3], wherein the content of the nucleating agent (C) is 1.1 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the polystyrene-based resin (A). [5] Apparent density 1010kg / m 3 More than 1040kg / m 3 The expandable polystyrene-based resin particles according to any one of [1] to [4] below: [6] Pre-expanded polystyrene-based resin particles obtained by pre-expanding the expandable polystyrene-based resin particles according to any one of [1] to [5]. [7] A foam obtained by molding the pre-expanded polystyrene-based resin particles described in [6]. [8] A method for producing expandable polystyrene-based resin particles, comprising extruding a polystyrene-based resin melt containing a polystyrene-based resin (A) and a blowing agent (B) 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 blowing agent (B) comprises butane and pentane; The butane comprises isobutane, The content of the isobutane relative to the total amount of the butane is greater than 80% by weight; The content of the isobutane relative to the total amount of the blowing agent (B) is 25% by weight or more and 95% by weight or less. A method for producing expandable polystyrene-based resin particles. Effect of the Invention

[0010] According to the present invention, there can be provided expandable polystyrene-based resin particles capable of forming a polystyrene-based resin foamed molded article having compressive strength and flexural strength similar to those of a foamed molded article made from a virgin polystyrene-based resin, a method for producing the expandable polystyrene-based resin particles, pre-expanded polystyrene-based resin particles made from the expandable polystyrene-based resin particles, and a foamed molded article made from 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) and a blowing agent (B). The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The blowing agent (B) contains butane and pentane, The butane includes isobutane. The content of the isobutane relative to the total amount of the butanes is greater than 80% by weight; The content of the isobutane relative to the total amount of the blowing agent (B) is 25% by weight or more and 95% by weight or less.

[0012] According to the expandable polystyrene-based resin particles of this embodiment, since the butane-based isobutane content is specific relative to the total amount of the blowing agent (B), it is possible to form a polystyrene-based resin foamed molded product having compressive strength and flexural strength close to those of a foamed molded product using a virgin polystyrene-based resin.

[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.

[0016] (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-based resin (A2) preferably contains a styrene homopolymer (polystyrene homopolymer) because it has excellent compatibility with the recycled polystyrene-based resin (A1). By using the polystyrene homopolymer, expandable particles and blocks with excellent expandability and moldability can be obtained.

[0017] 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.

[0018] 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.

[0019] As the virgin polystyrene-based resin (A2), it is preferable that it contains a styrene homopolymer, since it is relatively inexpensive, can be foam-molded with low-pressure steam or the like without using a special method, and has an excellent balance of heat insulation and cushioning properties. The content of the styrene homopolymer is preferably 80% by weight or more, and more preferably 90% by weight or more, based on 100% by weight of the virgin polystyrene-based resin (A2).

[0020] The polystyrene resin (A) contains a recycled polystyrene resin (A1) as an essential component. In a polystyrene resin (A) of 100% by weight, from the viewpoint of environmental consideration, the recycled polystyrene resin (A1) is preferably 25% by weight or more, more preferably 50% by weight or more, even more preferably 65% ​​by weight or more, even more preferably 70% by weight or more, and particularly preferably 75% by weight or more. In response to a demand for a high recycling rate, the recycled polystyrene resin (A1) may be contained at 100% by weight. In addition, since the raw material is easily available, the polystyrene resin (A) may contain a virgin polystyrene resin (A2). In a polystyrene resin (A) of 100% by weight, the virgin polystyrene resin (A2) is preferably 75% by weight or less, more preferably 50% by weight or less, even more preferably 35% by weight or less, even more preferably 30% by weight or less, and particularly preferably 25% by weight or less.

[0021] <Foaming agent (B)> The blowing agent (B) includes butane and pentane. Examples of butane include isobutane and normal butane. Examples of pentane include normal pentane, isopentane, neopentane, and cyclopentane. Butane and pentane may be used alone or in combination of two or more kinds.

[0022] The weight ratio of butane and pentane is not particularly limited, but from the viewpoint of foaming property and product life and being able to form a polystyrene-based resin foamed molded product, butane:pentane=95:5 to 20:80 is preferable, 90:10 to 20:80 is more preferable, 80:20 to 30:70 is even more preferable, and 50:50 to 30:70 is still more preferable.

[0023] The content of isobutane relative to the total amount of butane is more than 80% by weight, preferably from 85% by weight to 100% by weight, and more preferably from 90% by weight to 100% by weight, from the viewpoint of forming a polystyrene-based resin foamed molded product having excellent compressive strength and flexural strength.

[0024] The content of isobutane relative to the total amount of the foaming agent (B) is 25% by weight or more and 95% by weight or less from the viewpoint of forming a polystyrene-based resin foam molded article having excellent compressive strength and bending strength. The lower limit is preferably 26% by weight, more preferably 30% by weight, even more preferably 32% by weight, even more preferably 33% by weight, and particularly preferably 35% by weight or more. On the other hand, the upper limit is preferably 90% by weight, more preferably 85% by weight, even more preferably 80% by weight, even more preferably 75% by weight, even more preferably 70% by weight, and particularly preferably 65% ​​by weight or less. The content of isobutane is not particularly limited, and is preferably 0.75 parts by weight or more and 8 parts by weight or less, and more preferably 1 part by weight or more and 5.6 parts by weight or less, relative to 100 parts by weight of the polystyrene resin (A). When the content of isobutane is 0.75 parts by weight or more, it is preferable from the viewpoint of improving physical properties, and when it is 8 parts by weight or less, it is preferable since extrusion stability is not reduced. The content of pentane is not particularly limited, and is preferably 0.04 parts by weight or more and 7.5 parts by weight or less, and more preferably 0.05 parts by weight or more and 5.25 parts by weight or less, relative to 100 parts by weight of the polystyrene resin (A). When the content of pentane is 0.05 parts by weight or more, it is preferable from the viewpoint of a balance between the strength of the molded body and the moldability, and when it is 5.25 parts by weight or less, it is preferable from the viewpoint of physical properties. The blowing agent (B) may be used in combination with a hydrocarbon blowing agent other than butane and pentane, as long as the effects of the present invention are not impaired. Examples of the blowing agent include a hydrocarbon having 3 carbon atoms (propane) and a hydrocarbon having 6 carbon atoms (normal hexane, cyclohexane).

[0025] The content of the foaming agent (B) is not particularly limited, and is preferably 3.0 parts by weight or more and 10.0 parts by weight or less with respect to 100 parts by weight of the polystyrene resin (A). The lower limit is more preferably 3.5 parts by weight or more, more preferably 4.0 parts by weight or more, and even more preferably 4.5 parts by weight or more. The upper limit is more preferably 9.0 parts by weight or less, more preferably 8.0 parts by weight or less, and even more preferably 7.0 parts by weight or less. When the content of the foaming agent (B) is 3.0 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 (B) is 10.0 parts by weight or less, the flame retardant performance is less likely 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.

[0026] (Other ingredients) The expandable polystyrene resin particles may contain components other than the polystyrene resin (A) and the blowing agent (B) (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 nucleating agents, bromine-based flame retardants, flame retardant assistants, light stabilizers, heat stabilizers, radical generators, blowing assistants, colorants such as pigments, antistatic agents, and radiation heat transfer inhibitors. These other components may be used alone or in combination of two or more.

[0027] (Nucleating agent (C)) Examples of the nucleating agent (C) include a mixture of sodium bicarbonate and citric acid, monosodium citrate, talc, calcium carbonate, etc. The nucleating agent (C) may be used alone or in combination of two or more kinds.

[0028] The average particle size of the nucleating agent (C) is preferably 0.5 μm or more and 20 μm or less.

[0029] The content of the nucleating agent (C) is preferably 1.1 parts by weight or more and 5 parts by weight or less, more preferably 1.2 parts by weight or more and 4.5 parts by weight or less, and even more preferably 1.4 parts by weight or more and 4.5 parts by weight or less, per 100 parts by weight of the polystyrene-based resin (A).

[0030] (Apparent density) The apparent density of the expandable polystyrene resin particles is 1010 kg / m to prevent deterioration of the physical properties of the molded product. 3 More than 1040kg / m 3 It is preferable that the saturation temperature is 1015 kg / m or less. 3 More than 1040m 3 It is more preferable that:

[0031] <Method for producing expandable polystyrene resin particles> The method for producing expandable polystyrene-based resin particles of the present embodiment includes extruding a polystyrene-based resin melt containing a polystyrene-based resin (A) and a blowing agent (B) through a die having a plurality of small holes into pressurized circulating water, and cutting the melt into particles with a rotary cutter, The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The blowing agent (B) contains butane and pentane, The butane comprises isobutane, The content of the isobutane relative to the total amount of the butanes is greater than 80% by weight; The content of the isobutane relative to the total amount of the foaming agent (B) is 25% by weight or more and 95% by weight or less.

[0032] 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.

[0033] 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.

[0034] In a preferred embodiment of the present method, polystyrene resin (A), foaming agent (B), and optionally nucleating agent (C) and other components are melt-kneaded in an extruder, and the resulting polystyrene resin melt is extruded through a die having small holes attached to the tip of the extruder into a cutter chamber filled with pressurized circulating water, cut by a rotating cutter immediately after extrusion, and cooled and solidified by pressurized circulating water. In this case, 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.

[0035] The temperature setting in the melt-kneading section of the extruder is preferably 100° C. to 250° C. The residence time in the extruder from when the polystyrene resin (A) and various components are fed to the extruder until the end of melt-kneading is preferably 10 minutes or less.

[0036] 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.

[0037] 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 apparent density of the expandable polystyrene resin particles is increased, 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, and 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 is good, and the expandability and moldability are excellent.

[0038] 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.

[0039] 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.

[0040] <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.

[0041] The expandable polystyrene resin particles are expanded by a known pre-expansion process, for example, by 10 to 110 times with steam to form pre-expanded particles (pre-expansion 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.

[0042] (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.

[0043] 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.

[0044] 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 a high expansion ratio is to be obtained. 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.

[0045] The pre-expansion step can be carried out either continuously or batchwise.

[0046] 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.

[0047] 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.

[0048] Polystyrene-based resin foam molded products can be used for 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; returnable boxes (shippers) used by consumer cooperatives; bathroom insulation materials; and hot water tank insulation materials. EXAMPLES

[0049] 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.

[0050] <Ingredients> In the examples and comparative examples, the following A1-1 was used as the recycled polystyrene resin (A1). A1-1: The ingot was made by reducing the volume of used polystyrene-based resin foam moldings, and was then crushed, melt-extruded, and pelletized.

[0051] 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")

[0052] In the examples and comparative examples, the following B1 to B4 were used as the foaming agent (B). B1: Isobutane (Mitsui Chemicals, reagent) B2: Normal butane (Mitsui Chemicals, reagent product) B3: Normal pentane (Wako Pure Chemical Industries, Ltd., reagent product) B4: Isopentane (Wako Pure Chemical Industries, Ltd., reagent)

[0053] In the examples and comparative examples, the following C1 and C2 were used as the nucleating agent (C). C1: Talc (Tamura Talc Industrial Co., Ltd. "Fine Talc TP-20", average particle size 12.1 μm) C2: Talc (Hayashi Kasei Co., Ltd. "KHP-125B", average particle size 6.9 μm)

[0054] <Preparation of expandable polystyrene resin particles> Example 1 The virgin polystyrene resin (A2) and the recycled polystyrene resin (A1) were charged into a blender in a weight ratio of 75:25, respectively, and blended for 10 minutes to obtain a resin mixture. The obtained resin mixture and nucleating agent (C1) 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, 2.5 parts by weight of foaming agent (B1) were injected per 100 parts by weight of the above resin mixture, and 4.0 parts by weight of mixed pentane [mixture of B3 / B4 = 4 / 1 (weight ratio)] was injected per 100 parts by weight of the above resin mixture, and a total of 6.5 parts by weight of foaming agent (B) was added. Then, it was fed to the second extruder through a continuation pipe set at 200°C.

[0055] 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 64°C and 1.1 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.

[0056] (Examples 2 to 13, Comparative Examples 1 to 4) The expandable polystyrene resin particles of Examples 2 to 13 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the above components were melt-kneaded according to the formulations shown in Tables 1 and 2.

[0057] (Apparent density of expandable polystyrene resin particles) A measurement sample of W (kg) of expandable polystyrene resin particles was taken, and this measurement sample was allowed to fall naturally into a measuring cylinder containing ethanol, and its mass (kg) and volume (m3 ) was measured, and the apparent density was calculated based on the following formula. The results are shown in Tables 1 and 2. Apparent density (kg / m 3 ) = weight of measured sample (W) / volume of measured sample (V).

[0058] <Preparation of pre-expanded particles> (Examples 1A to 13A, Comparative Examples 1A to 4A) The expandable polystyrene resin particles of Examples 1 to 13 and Comparative Examples 1 to 4 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. 512 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 40 times, thereby obtaining pre-expanded particles of Examples 1A to 13A and Comparative Examples 1A to 4A.

[0059] <Preparation of polystyrene resin foam molded body> (Examples 1B to 13B, Comparative Examples 1B to 4B) After pre-expanded particles of Examples 1A to 13A and Comparative Examples 1A to 4A were cured at 30°C for 24 hours, the pre-expanded particles were filled into a mold for in-mold molding (length 400 mm x width 400 mm x thickness 25 mm) attached to a polystyrene foam molding machine (KR-57, manufactured by Daisen Kogyo Co., Ltd.), and 0.06 MPa water vapor was introduced to cause in-mold foaming, followed by spraying water on the mold to cool it. The polystyrene-based resin foam molded body was held in the mold until the pressure of the polystyrene-based resin foam molded body pressing the mold reached 0.01 MPa (gauge pressure), and then the polystyrene-based resin foam molded body was taken out to obtain polystyrene-based resin foam molded bodies of Examples 1B to 13B and Comparative Examples 1B to 4B.

[0060] (Examples 1C to 13C, Comparative Examples 1C to 4C) Except for using a molding die having a length of 400 mm, a width of 400 mm, and a thickness of 50 mm, the polystyrene-based resin foam molded articles of Examples 1C to 13C and Comparative Examples 1C to 4C were obtained in the same manner as in Examples 1B to 13B and Comparative Examples 1B to 4B.

[0061] <Evaluation> The resulting polystyrene resin foam molded articles were evaluated for expansion ratio, bending strength, 5% compressive strength, and surface elongation according to the following methods. The results are shown in Tables 1 and 2.

[0062] (Expansion Ratio) The weight (g) of the polystyrene resin foam 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 polystyrene resin foam moldings is conventionally expressed as "cm 3 / g".

[0063] (Bending strength) The polystyrene resin foam molded bodies of Examples 1B to 13B and Comparative Examples 1B to 4B were left to stand at 23°C for 48 hours, and then cut into three test pieces measuring 300 mm long x 100 mm wide x 25 mm thick. For each test piece, the maximum stress was measured when the test piece was deformed at a speed of 20 mm / min in accordance with JIS K 7221:2006, and the average value of the maximum stresses of the three test pieces was calculated, and the bending strength was evaluated according to the following evaluation criteria. Particularly good: bending strength of 0.41 MPa or more Good: Bending strength is 0.38 MPa or more and less than 0.41 MPa Poor: Bending strength is less than 0.38 MPa

[0064] (5% compressive strength) The polystyrene resin foam molded bodies of Examples 1C to 13C and Comparative Examples 1C to 4C were left to stand at 23°C for 48 hours, and then cut into three test pieces measuring 50 mm long x 50 mm wide x 25 mm thick. For each test piece, the zero deformation point and deformation were calculated from the elastic deformation linear portion of the force-deformation curve when compressed at a speed of 2.5 mm / min in accordance with JIS K7220:2006 to determine the 5% deformation compressive stress. The average value of the 5% deformation compressive stress of the three test pieces was calculated.

[0065] (Surface stretch) The surface condition of four sections of the polystyrene resin foam molded product was visually observed and rated on the following five-point scale. The average value of the four sections was taken as the surface elongation score. The higher the score, the fewer the gaps between the foam particles and the smoother and cleaner the surface. A score of "4" or higher indicates a satisfactory appearance that does not impair merchantability. 5: I can't find any gaps 4: There are some gaps, but they are barely noticeable. 3: There are some gaps here and there, but overall it is acceptable 2: Gaps are noticeable 1: Many gaps

[0066] (comprehensive evaluation) The polystyrene resin foam molded articles were comprehensively evaluated according to the following evaluation criteria. Particularly good (◎): Bending strength is 0.41 MPa or more, compressive strength is 0.18 MPa, and surface elongation is "4" or more Good (○): Bending strength is 0.38 MPa or more and less than 0.41 MPa, and compressive strength is 0.18 MPa, and surface elongation is "4" or more. Poor (×): Bending strength is 0.37 or less and compressive strength is 0.17 MPa or less No evaluation (-): There are no problems with the physical properties of the molded product, but since it is a foam that does not contain recycled polystyrene resin (A1), it cannot be evaluated as a molded product containing recycled polystyrene.

[0067] [Table 1]

[0068] [Table 2]

[0069] From Tables 1 and 2, it can be seen that when the content of isobutane is 25% by weight or more relative to the total amount of foaming agent (B), a foamed molded product having compressive strength and flexural strength close to those of the foamed molded product of Comparative Example 1 using a virgin polystyrene-based resin can be formed.

Claims

1. Expandable polystyrene-based resin particles comprising a polystyrene-based resin (A) and a blowing agent (B), The polystyrene-based resin (A) contains a recycled polystyrene-based resin (A1), The blowing agent (B) comprises butane and pentane; The butane comprises isobutane, The content of the isobutane relative to the total amount of the butane is more than 80% by weight; The expandable polystyrene-based resin particles have a content of the isobutane of 25% by weight or more and 95% by weight or less based on the total amount of the blowing agent (B).

2. 2. The expandable polystyrene-based resin particles according to claim 1, wherein the content of the foaming agent (B) is 3.0 parts by weight or more and 10.0 parts by weight or less based on 100 parts by weight of the polystyrene-based resin (A).

3. 3. The expandable polystyrene-based resin particles according to claim 1, wherein the polystyrene-based resin (A) contains 50% by weight or more of the recycled polystyrene-based resin (A1) in 100% by weight of the polystyrene-based resin (A).

4. Further, it contains a nucleating agent (C), The average particle size of the nucleating agent (C) is 0.5 μm or more and 20 μm or less, 3. The expandable polystyrene-based resin particles according to claim 1, wherein the content of the nucleating agent (C) is 1.1 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the polystyrene-based resin (A).

5. Apparent density is 1010 kg / m ３ More than 1040kg / m ３ The expandable polystyrene-based resin particles according to claim 1 or 2, which is:

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

7. A foam obtained by molding the pre-expanded polystyrene-based resin particles according to claim 6.

8. A method for producing expandable polystyrene-based resin particles, comprising extruding a polystyrene-based resin melt containing a polystyrene-based resin (A) and a blowing agent (B) 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 blowing agent (B) comprises butane and pentane; The butane comprises isobutane, The content of the isobutane relative to the total amount of the butane is more than 80% by weight; The content of the isobutane relative to the total amount of the blowing agent (B) is 25% by weight or more and 95% by weight or less. A method for producing expandable polystyrene-based resin particles.

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