JP2013071998A - Foamable polystyrene-based resin particle, method for producing the same, polystyrene-based resin pre-foamed particle and polystyrene-based resin foamed compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: foamable polystyrene-based resin particles that produce a foamed compact having excellent mechanical strength and a high expansion ratio; a method for producing the same; polystyrene-based resin pre-foamed particles; and a polystyrene-based resin foamed compact.SOLUTION: The foamable polystyrene-based resin particles are obtained by forming a foaming agent-containing polystyrene-based resin into a particle shape. The foamable polystyrene-based resin particles have a plasticizer having a boiling point of ≥50°C uniformly contained in the inside of the particles.

Description

  TECHNICAL FIELD The present invention relates to an expandable polystyrene resin particle comprising a polystyrene resin particle containing a foaming agent and a method for producing the same, and an expandable polystyrene resin particle capable of being easily expanded at a high magnification by adding a plasticizer and the method for producing the same. Further, the present invention relates to a polystyrene resin pre-expanded particle and a polystyrene resin foam molded article.

As one of the methods for producing expandable polystyrene resin particles, a polystyrene resin particle is obtained by polymerizing a styrene monomer in an aqueous medium by suspension polymerization or seed polymerization, and further, the polystyrene series in an autoclave. There is known an impregnation method in which resin particles are impregnated with a foaming agent to obtain expandable polystyrene resin particles.
In addition, in a conventional impregnation method, a technique has been proposed in which polystyrene resin particles contain a plasticizer such as cyclohexane or diisobutyl adipate (for example, see Patent Document 1).

  In Patent Document 1, an aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon having a boiling point lower than the softening point of the resin is contained in a resin particle made of polystyrene, a styrene copolymer or a styrene graft polymer. Expandable thermoplastic resin particles characterized by containing 1 to 15% by weight of the resin and 0.2 to 3.0% by mass of diisobutyl adipate are disclosed.

Japanese Patent No. 3292634

  When the plasticizer is included in the conventional impregnation method, since the impregnation is performed from the surface of the polystyrene resin particles, the obtained expandable polystyrene resin particles have a plasticizer concentration that increases from the center toward the surface layer. Therefore, the plasticizer cannot be uniformly present in the resin particles. In this way, the expandable polystyrene resin particles having a concentration distribution such that the concentration of the plasticizer increases from the central portion toward the surface layer is expanded by heating the resin particles to form pre-expanded particles. There is a problem that the foaming performance is deteriorated and it is difficult to obtain pre-expanded particles having a high expansion ratio.

  The present invention has been made in view of the above circumstances, and it is an object to provide expandable polystyrene-based resin particles that can obtain pre-expanded particles having a high expansion ratio and that can produce a foamed molded article that is lightweight and has sufficient mechanical strength. Yes.

  In order to achieve the above object, the present invention is an expandable polystyrene resin particle in which a polystyrene resin containing a foaming agent is in the form of particles, and a plasticizer having a boiling point of 50 ° C. or higher is uniformly contained inside the particle. Expandable polystyrene resin particles are provided.

  The expandable polystyrene resin particles of the present invention are obtained by press-fitting and kneading a foaming agent into a polystyrene resin melted in a resin supply device, and a small hole in a die provided with a foaming agent-containing molten resin at the tip of the resin supply device. It is obtained by a melt extrusion method that extrudes directly into a cooling liquid and simultaneously cuts the extrudate with a high-speed rotary blade and cools and solidifies the extrudate by contact with the liquid to obtain expandable polystyrene resin particles. It is preferable that

  In the expandable polystyrene resin particles of the present invention, the plasticizer preferably contains a high boiling point plasticizer having a boiling point of 150 ° C. or higher.

  In the expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably an ester plasticizer.

  In the expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably an adipate ester plasticizer.

  In the expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably diisobutyl adipate.

  In the expandable polystyrene resin particles of the present invention, the content of the high-boiling plasticizer is preferably in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.

  In the expandable polystyrene resin particles of the present invention, the content of the high boiling point plasticizer is preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.

  In the expandable polystyrene resin particles of the present invention, the plasticizer preferably contains a hydrocarbon having a boiling point of 50 ° C. or higher.

  In the expandable polystyrene resin particles of the present invention, the hydrocarbon content is preferably in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.

  In the expandable polystyrene resin particles of the present invention, the hydrocarbon content is preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.

  The expandable polystyrene resin particles of the present invention preferably contain butane as the foaming agent.

  In addition, the present invention is a method in which a foaming agent is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and the foaming agent-containing molten resin is directly contained in a cooling liquid from a small hole of a die attached to the tip of the resin supply device The extrudate is cut with a high-speed rotary blade at the same time as extrusion and the extrudate is cooled and solidified by contact with a liquid to obtain expandable polystyrene resin particles. Production of expandable polystyrene resin particles by melt extrusion A method for producing expandable polystyrene resin particles, wherein a plasticizer having a boiling point of 50 ° C. or higher is added to a polystyrene resin to obtain expandable polystyrene resin particles in which the plasticizer is uniformly contained inside the particles. provide.

  In the method for producing expandable polystyrene resin particles of the present invention, the plasticizer preferably contains a high boiling point plasticizer having a boiling point of 150 ° C. or higher.

  In the method for producing expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably an ester plasticizer.

  In the method for producing expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably an adipate ester plasticizer.

  In the method for producing expandable polystyrene resin particles of the present invention, the high boiling point plasticizer is preferably diisobutyl adipate.

  In the method for producing expandable polystyrene resin particles of the present invention, the content of the high-boiling plasticizer is preferably in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, the content of the high-boiling plasticizer is preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, the plasticizer preferably contains a hydrocarbon having a boiling point of 50 ° C. or higher.

  In the method for producing expandable polystyrene resin particles of the present invention, the hydrocarbon content is preferably in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, the hydrocarbon content is preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, it is preferable that butane is included as the foaming agent.

  The present invention also provides polystyrene resin pre-expanded particles obtained by heating and foaming the expandable polystyrene resin particles.

  In the polystyrene-based resin pre-expanded particles of the present invention, it is preferable that the average cell diameter in the state of being pre-expanded to a bulk expansion ratio of 50 times is in the range of 50 to 300 μm.

  The present invention also provides a polystyrene resin foam molded article obtained by filling the polystyrene resin pre-expanded particles into a cavity of a molding die and heating and molding in-mold foam molding.

  Further, in the present invention, it is preferable that the average cell diameter in a state where the foaming ratio is 50 times is within a range of 50 to 300 μm.

  The expandable polystyrene resin particles of the present invention are made of polystyrene resin containing a foaming agent in the form of particles, and a plasticizer having a boiling point of 50 ° C. or higher is uniformly contained inside the particles. Particles can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

  In the method for producing expandable polystyrene resin particles of the present invention, when producing expandable polystyrene resin particles by a melt extrusion method, a plasticizer having a boiling point of 50 ° C. or more is added to the polystyrene resin, and the plasticizer Expanded polystyrene resin particles that are uniformly contained in the inside of the particles so that pre-expanded particles with a high expansion ratio can be obtained, and foamed molded articles that are lightweight and have sufficient mechanical strength can be produced. It is possible to efficiently produce expandable polystyrene resin particles.

It is a block diagram which shows an example of the manufacturing apparatus of the expandable polystyrene-type resin particle by a melt extrusion method. It is the schematic which shows the measurement result of the light absorbency ratio (D1730 / D1600) of the cross section of the expandable polystyrene-type resin particle manufactured in Example 1. FIG. It is the schematic which shows the measurement result of the light absorbency ratio (D1730 / D1600) of the cross section of the expandable polystyrene-type resin particle manufactured by the comparative example 3. FIG.

(Expandable polystyrene resin particles)
The expandable polystyrene resin particles of the present invention are characterized in that a polystyrene resin containing a foaming agent is in the form of particles, and a plasticizer having a boiling point of 50 ° C. or higher is uniformly contained inside the particles.
In the present invention, the “boiling point” of a plasticizer refers to the boiling point under 1 atm.

  The polystyrene resin used for the expandable polystyrene resin particles of the present invention is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromo Examples thereof include homopolymers of styrene monomers such as styrene or copolymers thereof, and polystyrene resins containing 50% by mass or more of styrene are preferable, and polystyrene is more preferable.

  Further, the polystyrene resin may be a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the main component of which is the styrene monomer. As, for example, alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl In addition to fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

  If a polystyrene resin is the main component, other resins may be added. Examples of the resin to be added include polybutadiene, styrene-butadiene copolymer to improve the impact resistance of the foam molded article. Examples thereof include rubber-modified polystyrene resins to which a diene rubbery polymer such as a polymer, ethylene-propylene-nonconjugated diene three-dimensional copolymer is added, so-called high impact polystyrene. Alternatively, a polyethylene resin, a polypropylene resin, an acrylic resin, an acrylonitrile-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer, and the like can be given.

The polystyrene resin used as a raw material is a non-recycled polystyrene resin (virgin polystyrene) such as a commercially available ordinary polystyrene resin or a polystyrene resin newly produced by a method such as suspension polymerization. In addition, a regenerated polystyrene resin obtained by regenerating a used polystyrene resin foam molded article can be used.
As this recycled polystyrene-based resin, used polystyrene-based resin foam molded products, for example, fish boxes, household appliance cushioning materials, food packaging trays, etc. are recovered and recycled by the limonene dissolution method or heating volume reduction method. Can be used. In addition, recycled polystyrene resins that can be used are not only those obtained by reprocessing used polystyrene resin foam moldings, but also household electrical appliances (for example, televisions, refrigerators, washing machines, air conditioners, etc.) In addition, a recycled polystyrene resin obtained by pulverizing, melt-kneading, and re-pelletizing a non-foamed polystyrene resin molded product separated and collected from office equipment (for example, a copying machine, a facsimile machine, a printer, etc.) can be used.

  Examples of the foaming agent contained in the expandable polystyrene resin particles of the present invention include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane, 1,1-dichloro-1-fluoroethane ( HCFC-141b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), chlorodifluoromethane (HCFC-22), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) and other chlorofluorocarbons, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC- 134a), fluorocarbons such as difluoromethane (HFC-32), various alcohols, carbon dioxide, water And physical blowing agents can be mentioned such as nitrogen, can be used in combination one or more of these. Among these, preferable blowing agents include n-butane, isobutane, n-pentane, isopentane, and a blowing agent obtained by mixing two or more of these, and particularly preferable blowing agents include n-butane, isobutane, and these. The foaming agent which mixed these. The addition amount of a foaming agent shall be the range of 1-15 mass parts with respect to 100 mass parts of polystyrene-type resins, More preferably, it shall be the range of 3-12 mass parts.

  The plasticizer contained in the expandable polystyrene resin particles of the present invention may be any plasticizer that has a boiling point of 50 ° C. or higher and can exert an effect as a plasticizer when added to the polystyrene resin. It can be used by appropriately selecting from the agents, and examples thereof include ester plasticizers, aromatic hydrocarbons, alicyclic hydrocarbons, and terpene hydrocarbons.

Examples of the ester plasticizer include adipic acid esters such as diisobutyl adipate, isononyl adipate and dioctyl adipate, sebacic acid esters such as dibutyl sebacate and dioctyl sebacate, phosphate esters such as tricresyl phosphate, and glycerin. Examples include fatty acid glycerides such as diacetomonolaurate.
Examples of the aromatic hydrocarbon include toluene, xylene, and styrene.
Examples of the alicyclic hydrocarbon include cyclohexane and cyclopentane.
Examples of the terpene hydrocarbon include limonene and pinene.

In preferable embodiment of this invention, it is preferable that the said plasticizer contains the high boiling point plasticizer whose boiling point is 150 degreeC or more.
The high-boiling plasticizer is preferably an ester plasticizer, and among them, adipic acid esters such as diisobutyl adipate, isononyl adipate and dioctyl adipate are more preferred, and diisobutyl adipate (DIBA) is particularly preferred. . The high boiling point plasticizer may be used alone or in combination of two or more.

  The content of the high boiling point plasticizer is preferably in the range of 0.2 to 7 parts by mass, more preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin. When the content of the high-boiling plasticizer is less than the above range, the plasticizing effect by the plasticizer cannot be sufficiently obtained, it is difficult to obtain pre-foamed particles having a high expansion ratio, and the foam has light weight and sufficient mechanical strength. It becomes difficult to manufacture a molded body. If the content of the high-boiling plasticizer is larger than the above range, the mechanical strength of the obtained foamed molded product may be lowered, and the appearance of the foamed molded product may be deteriorated.

In a preferred embodiment of the present invention, the plasticizer preferably contains a hydrocarbon having a boiling point of 50 ° C. or higher.
Examples of the hydrocarbon include alicyclic hydrocarbons and aromatic hydrocarbons. Among them, cyclohexane and styrene are preferable.

The hydrocarbon content is preferably in the range of 0.2 to 7 parts by mass, more preferably in the range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.
When the hydrocarbon content is less than the above range, the plasticizing effect by the plasticizer cannot be sufficiently obtained, it is difficult to obtain pre-expanded particles having a high expansion ratio, and the foam molding has a light weight and sufficient mechanical strength. It becomes difficult to manufacture the body. When the content of the hydrocarbon is larger than the above range, the mechanical strength of the obtained foamed molded product may be lowered, and the appearance of the foamed molded product may be deteriorated.

In addition to the foaming agent and the plasticizer, the foamable polystyrene resin particles of the present invention preferably contain an inorganic foam nucleating agent uniformly. Examples of the inorganic foam nucleating agent include talc, silica, and other inorganic powders. Among these, talc is preferable.
The amount of the inorganic foam nucleating agent is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.1 to 2 parts by mass with respect to 100 parts by mass of the polystyrene resin.
The average particle diameter of the inorganic foam nucleating agent to be used is preferably in the range of 0.1 to 30 μm, and more preferably in the range of 0.5 to 10 μm.
By incorporating an expandable polystyrene resin particle with an inorganic foam nucleating agent such as talc together with a plasticizer, the effect of increasing the bulk expansion ratio of the pre-expanded particles and the effect of improving the mechanical strength of the foamed molded product can be enhanced.
The inorganic foam nucleating agent needs to be uniformly contained throughout the expandable polystyrene resin particles. If the inorganic foam nucleating agent is unevenly distributed in a local part of the resin particle, for example, a surface layer part of the resin particle, the mechanical strength of the obtained foamed molded product may be lowered.

  In the foamable polystyrene resin particles of the present invention, additives such as a crosslinking agent, a plasticizer, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant may be added within a range that does not impair the physical properties. Well, if powder metal soaps such as zinc stearate are applied on the surface of the expandable styrene resin particles, the polystyrene resin pre-expanded particles are bonded together in the pre-expanding step of the expandable polystyrene resin particles. Is preferable.

  The particle size of the expandable polystyrene resin particles of the present invention is not particularly limited, but is usually preferably in the range of 0.5 to 3.0 mm, more preferably in the range of 0.7 to 2.0 mm. The shape of the particles is not particularly limited, but is preferably spherical or substantially spherical.

  The expandable polystyrene resin particles of the present invention are those in which a polystyrene resin containing a foaming agent is formed into particles in the entire expandable polystyrene resin particles, and a plasticizer having a boiling point of 50 ° C. or more is uniformly contained inside the particles. Therefore, pre-expanded particles having a high expansion ratio can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

(Method for producing expandable polystyrene resin particles)
The method for producing expandable polystyrene resin particles according to the present invention includes a die in which a foaming agent is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and a foamed agent-containing molten resin is attached to the tip of the resin supply device. Extrusion into the cooling liquid directly from the small holes of the glass, and simultaneously extruding, the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid to obtain expandable polystyrene resin particles. In the method for producing expandable polystyrene resin particles according to the method, a plasticizer having a boiling point of 50 ° C. or higher is added to the polystyrene resin to obtain expandable polystyrene resin particles in which the plasticizer is uniformly contained inside the particles. It is characterized by.

  FIG. 1 is a configuration diagram showing an example of a production apparatus used in the method for producing expandable polystyrene resin particles of the present invention. The production apparatus of this example includes an extruder 1 as a resin supply apparatus, and an extruder 1. A die 2 having a large number of small holes attached to the tip of the resin, a raw material supply hopper 3 for introducing a resin raw material or the like into the extruder 1, and a foaming agent through the foaming agent supply port 5 to the molten resin in the extruder 1. A high pressure pump 4 to be press-fitted, a cutting chamber 7 provided so that cooling water is brought into contact with a resin discharge surface in which a small hole of the die 2 is formed, and cooling water is circulated and supplied into the chamber, and a small hole of the die 2 The cutter 6 is rotatably provided in the cutting chamber 7 so as to cut the resin extruded from the resin, and the expandable polystyrene resin particles carried along with the flow of cooling water from the cutting chamber 7 are separated from the cooling water. And dehydration Dehydration dryer 10 with a solid-liquid separation function to obtain expandable polystyrene resin particles by drying, a water tank 8 for storing cooling water separated by the dehydration dryer 10 with a solid-liquid separation function, and cooling in the water tank 8 A high-pressure pump 9 for sending water to the cutting chamber 7 and a storage container 11 for storing expandable polystyrene resin particles dehydrated and dried by a dehydration dryer 10 with a solid-liquid separation function are configured.

  As the extruder 1, either an extruder using a screw or an extruder not using a screw can be used. Examples of the extruder using a screw include a single-screw extruder, a multi-screw extruder, a vent-type extruder, and a tandem extruder. Examples of the extruder that does not use a screw include a plunger type extruder and a gear pump type extruder. Moreover, any extruder can use a static mixer. Among these extruders, an extruder using a screw is preferable from the viewpoint of productivity. Moreover, the conventionally well-known thing used in the granulation method by melt extrusion of resin can also be used for the cutting chamber 7 which accommodated the cutter 6. FIG.

  In order to produce expandable polystyrene resin particles using the production apparatus shown in FIG. 1, first, the raw material polystyrene resin, plasticizer, inorganic foam nucleating agent, foam nucleating agent added as necessary, etc. The desired additive is weighed and charged into the extruder 1 from the raw material supply hopper 3. The raw polystyrene resin may be pelletized or granulated and mixed well in advance and then fed from one raw material supply hopper. For example, when multiple lots are used, the supply amount for each lot may be reduced. A plurality of adjusted raw material supply hoppers may be charged and mixed in an extruder. Also, when using a combination of recycled materials from multiple lots, mix the raw materials from multiple lots in advance and remove foreign matter using appropriate sorting methods such as magnetic sorting, sieving, specific gravity sorting, and air blowing sorting. It is preferable to keep it. In addition, it is preferable to add additive components such as a plasticizer and an inorganic foam nucleating agent in advance by preparing a master batch in which the additive component is added in high concentration to a thermoplastic resin such as a polystyrene resin.

  After supplying polystyrene-based resin, plasticizer, inorganic foam nucleating agent and other additives into the extruder 1, the resin is heated and melted, and the molten resin is transferred to the die 2 side. A foaming agent is injected by a pump 4 to mix the foaming agent with the molten resin, and is passed through a screen for removing foreign substances provided in the extruder 1 as necessary. The melt added with the agent is extruded from a small hole in the die 2 attached to the tip of the extruder 1. Further, the plasticizer and the inorganic foam nucleating agent may be added by press-fitting from a supply port beside the extruder.

  The resin discharge surface in which the small holes of the die 2 are drilled is disposed in the cutting chamber 7 in which cooling water is circulated and supplied into the chamber, and the resin extruded from the small holes of the die 2 is placed in the cutting chamber 7. A cutter 6 is provided so as to be rotatable. Extruding the melt with the blowing agent added through a small hole in the die 2 attached to the tip of the extruder 1 causes the melt to be cut into granules, and at the same time, brought into contact with cooling water and rapidly cooled to solidify while suppressing foaming. Thus, expandable polystyrene resin particles are obtained.

  The formed expandable polystyrene resin particles are transferred from the cutting chamber 7 to the dewatering dryer 10 with a solid-liquid separation function along with the flow of the cooling water, where the expandable polystyrene resin particles are separated from the cooling water. And dehydrated and dried. The dried expandable polystyrene resin particles are stored in the storage container 11.

  The method for producing a polystyrene resin foam molded article of the present invention comprises adding a plasticizer having a boiling point of 50 ° C. or higher to a polystyrene resin when producing expandable polystyrene resin particles by a melt extrusion method. As a result, it is possible to obtain pre-expanded particles having a high expansion ratio compared to the conventional technique in which a resin particle is impregnated with a plasticizer. It is possible to efficiently produce expandable polystyrene resin particles capable of producing a foamed molded article having sufficient mechanical strength.

(Polystyrene resin pre-expanded particles and polystyrene resin foam molding)
The expandable polystyrene resin particles of the present invention are pre-expanded by heating with water vapor heating or the like using a well-known apparatus and method in the field of manufacturing foamed resin molded articles, and then polystyrene-based resin pre-expanded particles (hereinafter referred to as pre-expanded particles). ). The pre-expanded particles are pre-expanded so as to have a bulk density equivalent to the density of the foamed molded product to be manufactured. In the present invention, its bulk density is not limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the bulk density of the pre-expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”.
<Bulk density of pre-expanded particles>
First, Wg was sampled from pre-expanded particles as a measurement sample, this measurement sample was naturally dropped into a graduated cylinder, and the volume Vcm ³ of the measurement sample dropped into the graduated cylinder was measured using an apparent density measuring instrument based on JIS K6911. The bulk density of the pre-expanded particles is measured based on the following formula.
Bulk density (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Bulk expansion ratio of pre-expanded particles>
Moreover, the bulk expansion ratio of the pre-expanded particles is a numerical value calculated by the following equation.
Bulk foaming factor = 1 / bulk density (g / cm ³ )

The pre-expanded particles are filled in a cavity of a mold using a well-known apparatus and method in the field of manufacturing a foamed resin molded article, heated by steam heating or the like, and subjected to in-mold foam molding. -Based resin foam molded body (hereinafter referred to as foam molded body) is produced.
Although the density of the foamed molded article of the present invention is not particularly limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the density of the foamed molded product refers to the density of the foamed molded product measured by the method described in JIS K7122: 1999 “Measurement of foamed plastic and rubber-apparent density”.
<Density of foam molding>
A test piece of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) was cut so as not to change the original cell structure of the material, its mass was measured, and calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test specimen condition adjustment and measurement specimens were cut from a sample that had passed 72 hours or more after molding, and were subjected to atmospheric conditions of 23 ° C ± 2 ° C x 50% ± 5% or 27 ° C ± 2 ° C x 65% ± 5%. It has been left for more than an hour.

<Folding multiple of foamed molded product>
Further, the expansion factor of the foamed molded product is a numerical value calculated by the following equation.
Foaming factor = 1 / density (g / cm ³ )

  The foamed molded product of the present invention is obtained by heating and foaming the expandable polystyrene resin particles according to the present invention, and the resulting pre-foamed particles are obtained by in-mold foam molding. You can get a body. In addition, a foamed molded article that is lightweight and excellent in mechanical strength such as bending strength can be obtained.

[Example 1]
(Manufacture of master batch)
Polystyrene resin (trade name “G9305” manufactured by PS Japan Co., Ltd.) is used as the base resin, and diisobutyl adipate (boiling point: 293 ° C., product name “DI4A” manufactured by Taoka Chemical Industries, Ltd.) is 10% by mass as the plasticizer. A master batch was prepared.

(Manufacture of expandable polystyrene resin particles)
What mixed previously the masterbatch with respect to polystyrene resin 100 mass part with respect to polystyrene resin (PS Japan company make, G9305) as base resin so that it may become 2.1 mass parts of diisobutyl adipate with respect to 100 mass parts of polystyrene resin. After feeding into a single screw extruder with a diameter of 90 mm at a rate of 160 kg / hr per hour and heating and melting the resin, 6 parts by weight of butane (isobutane: normal butane = 30: 70 (mass ratio)) was pressed from the middle of the extruder. Then, while kneading the resin and the foaming agent in the extruder, while cooling so that the resin temperature at the tip of the extruder is 170 ° C., the diameter is 0.6 mm, connected to the extruder and held at 290 ° C. by the heater. Then, through a granulation die having 200 nozzles with a land length of 3.0 mm, it was extruded into an underwater cutting chamber in which cooling water with a temperature of 50 ° C. and a water pressure of 1.5 MPa circulated, and at the same time, 10 blades in the circumferential direction A high-speed rotating cutter having the above structure was brought into close contact with a die, cut at 3000 rpm, dehydrated and dried to obtain spherical expandable polystyrene resin particles. The obtained expandable polystyrene resin particles had an average particle size of 1.1 mm without the occurrence of deformation or beard.
Next, 2000 g of the above expandable polystyrene resin particles, 2500 g of distilled water, 4 g of magnesium pyrophosphate, and 0.2 g of sodium dodecylbenzenesulfonate were placed in an autoclave with a stirrer having an internal volume of 5.7 liters, and suspended by stirring. After pressurizing the inside of the autoclave to 2 MPa with nitrogen, the temperature was raised to 100 ° C. and held for 5 minutes, then cooled to 20 ° C., taken out, washed, dehydrated and dried.

(Surface coating of expandable polystyrene resin particles)
Polyethylene glycol 0.03 parts by mass, zinc stearate 0.05 parts by mass, stearic acid monoglyceride 0.05 parts by mass, hydroxystearic acid triglyceride 0 with respect to 100 parts by mass of the expandable polystyrene resin particles obtained as described above. 0.05 part by mass was uniformly coated on the entire surface of the expandable polystyrene resin particles.

(Manufacture of foam moldings)
Subsequently, the expandable polystyrene resin particles were supplied to a cylindrical batch type pre-foaming machine and heated with steam having a blowing pressure of 0.05 MPa to obtain pre-foamed particles. The obtained pre-expanded particles had a bulk density of 0.020 g / cm ³ (bulk expansion ratio: 50 times).
Subsequently, the pre-expanded particles obtained were allowed to stand at room temperature for 24 hours, and then the pre-expanded particles were filled into a mold having a rectangular cavity of length 400 mm × width 300 mm × height 25 mm. , Molding steam pressure 0.08 MPa (gauge pressure), mold heating 3 seconds, one heating 10 seconds, reverse one heating 3 seconds, double side heating 10 seconds, water cooling 5 seconds, set extraction surface pressure 0.02 MPa went. The obtained foamable form had a density of 0.020 g / cm ³ (foaming factor: 50 times).
The following measurements / evaluations were performed on the expandable polystyrene resin particles, the pre-expanded particles, and the foamed molded product thus produced. The results are shown in Table 1.

<Measurement of foamability>
In order to examine the foamability of the obtained expandable polystyrene-based resin particles, foaming was performed in a foaming tank with steam having a foaming steam pressure of 0.01 MPa (gauge pressure). The heating time at that time was changed to 2 minutes, 5 minutes, and 10 minutes to foam, and 2 g of this foamed particle was placed in a graduated cylinder, the volume was measured, and the apparent foaming factor (cm ³ / g) was divided by 2 g of mass. Asked.
The maximum value of the apparent expansion ratio of foaming by changing the heating time to 2 minutes, 5 minutes and 10 minutes is as follows:
Especially good when the maximum expansion ratio is 55 times or more (◎)
Excellent foaming ratio of 45 times to less than 55 times is good (○)
If the maximum foaming factor is less than 45 times, it is defective (×)
Based on the evaluation.

<Strength evaluation>
About the foaming molding obtained in the Example (and comparative example), bending strength was measured according to the method of JISA9511: 2006 "foaming plastic heat insulating material". That is, using a Tensilon universal testing machine UCT-10T (manufactured by Orientec Co., Ltd.), the specimen size is 75 mm × 300 mm × 50 mm, the compression speed is 10 mm / min, the tip jig is a pressure wedge 10R, and a support base 10R. Measurement was performed under the condition of a distance between fulcrums of 200 mm, and the bending strength was calculated by the following formula. The number of test pieces was three, and the average value was obtained.
Bending strength (MPa) = 3FL / 2bh ² (where F represents the bending maximum load (N), L represents the distance between supporting points (mm), b represents the width (mm) of the test piece, h represents Represents the thickness (mm) of the test piece.)
In this way, the average value of the bending strength is obtained, and the following evaluation criteria:
Particularly good when bending strength is 0.31 MPa or more (◎),
The bending strength is good (O) when the bending strength is 0.28 MPa or more and less than 0.31 MPa,
Bending strength of less than 0.28 MPa is poor (x),
Based on this, the strength was evaluated.

<Appearance evaluation of foam molding>
The appearance of the foamed molded product was visually evaluated. The following evaluation criteria:
Especially good when the boundary part where the foam particles on the surface of the molded product are joined is very smooth (◎)
Good when the smoothness of the boundary part where the foam particles on the surface of the molded product are joined is slightly inferior (○)
If the boundary of the foam particles on the surface of the molded product has irregularities and the smoothness is inferior (×)
Based on this, the appearance was evaluated.

<Evaluation of fusion rate>
The obtained box-shaped foamed molded article was ruptured by impact, and the total number of particles (A) and the number of particles broken in the particles (in an arbitrary range including 100 to 150 expanded particles on the fracture surface ( B) was counted, and the fusion rate (%) was calculated by the following formula.
Fusing rate = (B) × 100 / (A)
The following evaluation criteria:
80% or more and less than 100% are particularly good (◎)
60% or more and less than 80% are good (○)
Less than 60% is defective (×)
Based on this, the appearance was evaluated.

<Comprehensive evaluation>
The overall evaluation is based on the following four evaluation criteria: foamability, appearance, fusion and strength.
There is no x and ◎ is particularly good when 3 or more (◎)
Good with no cross (○)
Defects with at least one × (×)
Based on the evaluation.

[Example 2]
Except having used the masterbatch described in Example 1 to be 0.1 parts by mass of diisobutyl adipate with respect to 100 parts by mass of the resin, a foam molded article was produced in the same manner as in Example 1, and the same Measurement and evaluation were performed. The results are shown in Table 1.

[Example 3]
Except that the master batch described in Example 1 was used in an amount of 0.23 parts by mass of diisobutyl adipate with respect to 100 parts by mass of the resin, a foam molded article was produced in the same manner as in Example 1, and the same Measurement and evaluation were performed. The results are shown in Table 1.

[Example 4]
A foam molded article was produced in the same manner as in Example 1 except that the master batch described in Example 1 was used in an amount of 5.1 parts by mass of diisobutyl adipate with respect to 100 parts by mass of the resin. Measurement and evaluation were performed. The results are shown in Table 1.

[Example 5]
A foam molded article was produced in the same manner as in Example 1 except that the master batch described in Example 1 was used so as to be 7.4 parts by mass of diisobutyl adipate with respect to 100 parts by mass of the resin. Measurement and evaluation were performed. The results are shown in Table 1.

[Example 6]
In the production of the master batch of Example 1, glycerin diacetomonolaurate (boiling point: 401.6 ° C., manufactured by Riken Vitamin Co., Ltd., trade name “Riquemar PL-102”) was used instead of diisobutyl adipate, and an expandable polystyrene type Except that the master batch was used so that the glycerin diacetomonolaurate was 2.1 parts by mass with respect to 100 parts by mass of the resin during the production of the resin particles, a foam molded article was produced in the same manner as in Example 1, Similar measurements were made. The results are shown in Table 1.

[Example 7]
Dioctyl adipate (boiling point: 335 ° C., Taoka Chemical Industries, trade name “DOA”) was used in place of diisobutyl adipate during the production of the master batch of Example 1, and the master was produced during the production of expandable polystyrene resin particles. Except that the batch was used so that dioctyl adipate was 2.1 parts by mass with respect to 100 parts by mass of the resin, a foamed molded article was produced in the same manner as in Example 1, and the same measurement and evaluation were performed. The results are shown in Table 1.

[Example 8]
In the production of the master batch of Example 1, tricresyl phosphate (boiling point: 410 ° C., trade name “Durad TCP”) was used instead of diisobutyl adipate, and the master was produced during the production of expandable polystyrene resin particles. Except that the batch was used so that tricresyl phosphate was 2.1 parts by mass with respect to 100 parts by mass of the resin, a foamed molded article was produced in the same manner as in Example 1, and the same measurement and evaluation were performed. The results are shown in Table 1.

[Example 9]
In the production of the master batch of diisobutyl adipate of Example 1, a master batch was prepared by further adding cyclohexane (boiling point: 80.7 ° C., Japan Energy, trade name “Cactus Solvent CHX”) to 10% by mass. The same as in Example 1 except that the masterbatch was used so that diisobutyl adipate was 2.1 parts by mass and cyclohexane was 1.1 parts by mass with respect to 100 parts by mass of the resin during the production of expandable polystyrene resin particles. A foamed molded article was produced by the method described above, and the same measurement and evaluation were performed. The results are shown in Table 1.

[Example 10]
Cyclohexane is used in place of diisobutyl adipate in the production of the master batch of Example 1, and the mass of the master batch is 2.1 parts by mass with respect to 100 parts by mass of the resin in the production of expandable polystyrene resin particles. A foamed molded article was produced in the same manner as in Example 1 except that it was used, and the same measurement and evaluation were performed. The results are shown in Table 1.

[Example 11]
A foamed molded article was produced in the same manner as in Example 1 except that isobutane was used instead of butane as the foaming agent during the production of the expandable polystyrene resin particles of Example 1, and the same measurement / evaluation was performed. Went. The results are shown in Table 1.

[Comparative Example 1]
A foamed molded article was produced in the same manner as in Example 1 except that the masterbatch of diisobutyl adipate was not used at the production of the expandable polystyrene resin particles of Example 1 (no plasticizer added). Was measured and evaluated. The results are shown in Table 1.

[Comparative Example 2]
Example 1 except that no diisobutyl adipate masterbatch was used in the production of the expandable polystyrene resin particles of Example 1 (no plasticizer added), and isopentane was used instead of butane as the foaming agent. A foamed molded product was produced in the same manner as described above, and the same measurement and evaluation were performed. The results are shown in Table 1.

[Comparative Example 3]
(Preparation of styrene polymer seed particles)
An autoclave with a stirrer having an internal volume of 100 liters (hereinafter also referred to as a reactor) 120 g of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 4 g of sodium dodecylbenzenesulfonate, 140 g of benzoyl peroxide (purity 75%), t-butyl per After charging 30 g of oxy-2-ethylhexyl monocarbonate, 40 kg of ion exchange water and 40 kg of styrene monomer, the mixture was dissolved and dispersed under stirring at 100 rpm to form a suspension.
Subsequently, the temperature in the autoclave was raised to 90 ° C. while stirring the stirring blade at 100 rpm, and then held at 90 ° C. for 6 hours.
After that, the temperature inside the autoclave is further raised to 120 ° C. and held at 120 ° C. for 2 hours, then the temperature inside the autoclave is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified. Styrenic polymer seed particles having a diameter of 0.5 to 0.7 mm and a weight average molecular weight of 300,000 were obtained.

(Production of expandable styrene resin particles)
Next, 5.2 kg of the above styrene polymer seed particles, 19.5 kg of distilled water, 161 g of magnesium pyrophosphate, and 1.8 g of sodium dodecylbenzenesulfonate are placed in an autoclave equipped with a stirrer with an internal volume of 50 liters, stirred and suspended. It was.
Next, 2000 g of distilled water prepared in advance, 36 g of magnesium pyrophosphate, 0.9 g of sodium dodecylbenzenesulfonate and 1350 g of styrene were stirred with a homomixer to prepare a suspension, and the reactor was maintained at 72 ° C. The polystyrene particles were allowed to absorb styrene for 15 minutes.
Subsequently, 61 g of benzoyl peroxide (purity 75%) as a polymerization initiator and 26.5 g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved in 1000 g of styrene, 0.4 g of sodium dodecylbenzenesulfonate, and 2000 g of distilled water. A suspension prepared by stirring with a homomixer was added to a reactor maintained at 72 ° C.
The reactor internal temperature is maintained at 72 ° C. for 60 minutes from the start of adding the suspension containing the polymerization initiator to the reactor, and the styrene resin seed particles absorb styrene and the polymerization initiator. While continuously supplying into the reactor in 3 hours, the temperature in the reactor was continuously increased so as to reach 109 ° C. at the end of the styrene supply.
Subsequently, the temperature was raised to 120 ° C. and held for 60 minutes, and then added with 700 g of distilled water 22 g of magnesium pyrophosphate and 2 g of sodium dodecylbezene sulfonate 64 g of diisobutyl adipate as an ester plasticizer was added as a foaming aid. A suspension was prepared by stirring and the suspension was pressed into the reactor. Then, after cooling to 100 ° C., 2250 g of butane (isobutane: normal butane = 30: 70 (mass ratio)) as a blowing agent was injected and held at 100 ° C. for 2 hours, then cooled to 20 ° C. and taken out, Washed, dehydrated and dried. When the expandable polystyrene particles were washed, the coalesced particles that did not pass through the JIS 1000 μm sieve and the fine powdery polymer that passed through the JIS 500 μm sieve were removed, and their weights were measured. Further, the foamed styrene polymer particles having a median diameter of 0.85 mm were obtained by aging at 15 ° C. for 5 days until the bubble diameter after foaming was completely stabilized.
After the production of the expandable styrene resin particles, a foamed molded product was produced in the same manner as in Example 1, and the same measurement was performed. The results are shown in Table 1.

  From the results of Table 1, the expandable polystyrene resin particles obtained in Examples 1 to 11 according to the present invention have good expandability, and can obtain pre-expanded resin particles and expanded molded articles having a high expansion ratio. did it. Moreover, the foaming molding obtained in Examples 1-11 was excellent in the external appearance, the melt | fusion of foaming particle | grains was favorable, and was excellent also in intensity | strength.

On the other hand, the expandable polystyrene resin particles obtained in Comparative Examples 1 and 2 to which no plasticizer was added had poor foaming performance, and any of the appearance, the degree of fusion, and the strength of the foamed molded product was inferior.
Furthermore, the expandable polystyrene resin particles obtained in Comparative Example 3 to which a plasticizer was added by an impregnation method had poor foaming performance, and it was difficult to obtain pre-foamed resin particles and foamed molded articles having a high expansion ratio.

<Measurement of absorbance ratio>
The cross-sections of the expandable polystyrene resin particles produced in Example 1 and Comparative Example 3 were subjected to particle surface analysis by ATR infrared spectroscopy to determine the absorbance ratio (D1730 / D1600), and the plasticizer (adipic acid The distribution state of (diisobutyl) was examined.
The absorbance ratio (D1730 / D1600) is measured as follows.
That is, the ATR method red is used for the surface of each of 10 resin particles selected at random (reference A in FIG. 2) and the central portion of the cross section cut through the center (reference B in FIG. 2). An infrared absorption spectrum is obtained by particle surface analysis by external spectroscopic analysis.
The absorbance ratio (D1730 / D1600) was calculated from each infrared absorption spectrum, the arithmetic average of the absorbance ratio calculated for surface A was defined as the absorbance ratio (A), and the arithmetic average of the absorbance ratio calculated for center B was the absorbance. The ratio (B).
The absorbances D1730 and D1600 are measured using a measuring device sold by, for example, Nicolet Corporation under the trade name “Fourier Transform Infrared Spectrometer MAGMA 560”.
The absorbance D1600 at 1600 cm ⁻¹ obtained from the infrared absorption spectrum refers to the height of a peak appearing in the vicinity of 1600 cm ⁻¹ derived from the in-plane vibration of the benzene ring contained in the polystyrene resin.
Further, the absorbance D 1730 at 1730 cm ⁻¹ obtained from the infrared absorption spectrum refers to the height of a peak appearing in the vicinity of 1730 cm ⁻¹ derived from stretching vibration between C = 0 of the ester group contained in the acrylate ester.

FIG. 2 is a schematic view showing the measurement result of the absorbance ratio (D1730 / D1600) of the cross section of the expandable polystyrene resin particles produced in Example 1. FIG. The expandable polystyrene resin particles 20 of Example 1 had a uniform absorbance ratio (D1730 / D1600) over the entire resin particles, and contained a plasticizer at a uniform concentration throughout the resin particles.
FIG. 3 is a schematic diagram showing the measurement result of the absorbance ratio (D1730 / D1600) of the cross section of the expandable polystyrene resin particles produced in Comparative Example 3. In the expandable polystyrene resin particles 30 of Comparative Example 3 in which the resin particles are impregnated with the plasticizer by the impregnation method, the plasticizer is localized in the surface layer portion 31 and the central portion 32 contains almost no plasticizer.

  The present invention relates to a method for producing expandable polystyrene resin particles by melt extrusion, and relates to a foamable polystyrene resin particle capable of obtaining a foamed molded article having a high expansion ratio and excellent mechanical strength, a method for producing the same, and a polystyrene type The present invention relates to resin pre-expanded particles and polystyrene-based resin foam moldings.

  DESCRIPTION OF SYMBOLS 1 ... Extruder (resin supply apparatus), 2 ... Die, 3 ... Raw material supply hopper, 4 ... High pressure pump, 5 ... Foam supply port, 6 ... Cutter, 7 ... Cutting chamber, 8 ... Water tank, 9 ... High pressure pump, DESCRIPTION OF SYMBOLS 10 ... Dehydration dryer with a solid-liquid separation function, 11 ... Storage container, 20 ... Expandable polystyrene resin particle, 30 ... Expandable polystyrene resin particle, 31 ... Surface layer part, 32 ... Center part.

Claims (27)

Expandable polystyrene resin particles having a polystyrene resin containing a foaming agent in the form of particles,
Expandable polystyrene resin particles in which a plasticizer having a boiling point of 50 ° C. or higher is uniformly contained inside the particles.   When a foaming agent is press-fitted and kneaded into the polystyrene resin melted in the resin supply device, the molten resin containing the foaming agent is extruded directly into the cooling liquid through a small hole in the die attached to the tip of the resin supply device. The expandable polystyrene system according to claim 1, obtained by a melt extrusion method, wherein the extrudate is simultaneously cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with a liquid to obtain expandable polystyrene resin particles. Resin particles.   The expandable polystyrene resin particles according to claim 1 or 2, wherein the plasticizer contains a high-boiling plasticizer having a boiling point of 150 ° C or higher.   The expandable polystyrene resin particles according to claim 3, wherein the high boiling point plasticizer is an ester plasticizer.   The expandable polystyrene resin particles according to claim 4, wherein the high-boiling plasticizer is an adipate ester plasticizer.   The expandable polystyrene resin particles according to claim 5, wherein the high-boiling plasticizer is diisobutyl adipate.   Content of the said high boiling point plasticizer is the range of 0.2-7 mass parts with respect to 100 mass parts of resin, The expandable polystyrene resin particle of any one of Claims 3-6.   Content of the said high boiling point plasticizer is the range of 0.2-5 mass parts with respect to 100 mass parts of resin, The expandable polystyrene resin particle of any one of Claims 3-7.   The expandable polystyrene resin particle according to any one of claims 1 to 8, wherein the plasticizer contains a hydrocarbon having a boiling point of 50 ° C or higher.   The expandable polystyrene resin particles according to claim 9, wherein the hydrocarbon content is in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.   The expandable polystyrene resin particles according to claim 9 or 10, wherein a content of the hydrocarbon is in a range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.   The expandable polystyrene resin particle according to any one of claims 1 to 11, comprising butane as the foaming agent. When a foaming agent is press-fitted and kneaded into the polystyrene resin melted in the resin supply device, the molten resin containing the foaming agent is extruded directly into the cooling liquid through a small hole in the die attached to the tip of the resin supply device. At the same time, the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with a liquid to obtain expandable polystyrene resin particles. In the method for producing expandable polystyrene resin particles by melt extrusion,
A method for producing expandable polystyrene resin particles, wherein a plasticizer having a boiling point of 50 ° C. or more is added to a polystyrene resin to obtain expandable polystyrene resin particles in which the plasticizer is uniformly contained inside the particles.   The method for producing expandable polystyrene resin particles according to claim 13, wherein the plasticizer contains a high-boiling plasticizer having a boiling point of 150 ° C or higher.   The method for producing expandable polystyrene resin particles according to claim 14, wherein the high boiling point plasticizer is an ester plasticizer.   The method for producing expandable polystyrene resin particles according to claim 15, wherein the high boiling point plasticizer is an adipate ester plasticizer.   The method for producing expandable polystyrene resin particles according to claim 16, wherein the high-boiling plasticizer is diisobutyl adipate.   The method for producing expandable polystyrene resin particles according to any one of claims 14 to 17, wherein a content of the high-boiling plasticizer is in a range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 14 to 18, wherein a content of the high-boiling plasticizer is in a range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 13 to 19, wherein the plasticizer contains a hydrocarbon having a boiling point of 50 ° C or higher.   The method for producing expandable polystyrene resin particles according to claim 20, wherein the hydrocarbon content is in the range of 0.2 to 7 parts by mass with respect to 100 parts by mass of the resin.   The method for producing expandable polystyrene resin particles according to claim 20 or 21, wherein a content of the hydrocarbon is in a range of 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 13 to 22, comprising butane as the foaming agent.   Polystyrene resin pre-expanded particles obtained by heating and foaming the expandable polystyrene resin particles according to any one of claims 1 to 12.   The polystyrene-based resin pre-expanded particles according to claim 24, wherein an average cell diameter in a state of being pre-expanded to a bulk expansion ratio of 50 times is in a range of 50 to 300 µm.   A polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 24 or 25 in a cavity of a molding die and heating and molding the resin in-mold.   27. The polystyrene-based resin foam molded article according to claim 26, wherein an average cell diameter in a state where the foaming ratio is 50 times is within a range of 50 to 300 [mu] m.

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