JP2019151781A - Foamable polystyrene resin particle, polystyrene foam particle and polystyrene foam molding - Google Patents

Abstract

To provide a foamable polystyrene resin particle that stably maintains its cell diameter without enlargement, even when stored at high temperature, and also prevents the occurrence of cell roughness.SOLUTION: The present invention provides: a foamable polystyrene resin particle containing ethyl benzene of 10-50 ppm, and carbon-based radiation heat transfer inhibitor; a polystyrene foam particle obtained by foaming the foamable polystyrene resin particle; and a polystyrene foam molding obtained by in-mold molding of the polystyrene foam particle.SELECTED DRAWING: None

Description

  The present invention relates to expandable polystyrene resin particles, polystyrene foam particles, and polystyrene foam moldings.

  Polystyrene-based foamed moldings are materials with excellent lightness, heat insulation, and buffering properties, and are also commonly called polystyrene foams. Traditionally, they are used as cold storage boxes such as fish boxes and as cushioning materials for home appliances, as well as housing. It is also widely used as a heat insulating material.

  The polystyrene-based foamed molded article contains a styrene-based monomer that is a residue that has not been consumed when a polystyrene resin is produced by polymerization from a styrene-based monomer. The aromatic organic compound may be added as a plasticizer in a necessary amount, contained as an impurity such as a styrene monomer, or contained as a decomposition product of a polymerization initiator.

  In recent years, to suppress volatilization of aromatic organic compounds such as styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene contained in the polystyrene foam molded product when using the polystyrene foam molded product, In particular, polystyrene-based foam molded articles used in residential heat insulating materials, automotive applications, food containers and the like are required to reduce the content of volatile organic compounds such as aromatic organic compounds.

  Therefore, for example, as disclosed in Patent Documents 1 to 9, the aromatic organic compound contained in the expandable polystyrene resin particles is adjusted. .

  In addition, polystyrene-based expanded particles have a large number of independent spaces called cells. Since the cell diameter, which is the size of the cell, affects the performance of the polystyrene-based foamed molded article, the cell diameter is adjusted to a desired cell diameter. Since the cell diameter tends to decrease as the number of cells inside the polystyrene foam particles increases, the cell diameter adjustment is specifically the adjustment of the number of cells. When pre-foaming the expandable polystyrene resin particles with water vapor, Need to control the number of cells generated.

  Conventionally, cells of polystyrene-based expanded particles can be stored by refrigerated storage after production of expandable polystyrene-based resin particles (Patent Document 10) or by controlling the content of a cell forming agent called a nucleating agent (Patent Document 11). The diameter has been adjusted.

JP-A-2005-270414 JP 2002-356575 A JP 2008-075051 JP 2006-213850 A JP 2003-327739 A JP 2006-152029 A JP 2010-1000086 JP 2005-126537 A JP2011-093953A JP 06-049262 A JP 09-071679 A

  In the method of refrigerated storage after production of expandable polystyrene resin particles, if the storage time is short, it may not be possible to adjust to the desired cell diameter, so it is necessary to set a long inventory period and the productivity is poor.

  On the other hand, the cell diameter adjustment by the nucleating agent is considered that the starting point of foaming is controlled by creating an interface with a foreign substance inside the expandable polystyrene resin particles. In this method, the cell diameter can be controlled by the addition amount of the nucleating agent, but the number of generated cells may suddenly decrease and the cell diameter may enlarge (cell roughness). The cause of the phenomenon called cell roughening has not been clarified, but cell roughing often occurs in the summer when the outside air temperature is high, and since it is not known until preliminary foaming, there is a problem that many losses occur. .

  Then, an object of this invention is to provide an expandable polystyrene-type resin particle which is hard to generate | occur | produce cell roughening.

  As a result of repeated studies by the present inventor, the mechanism of the phenomenon that the cell diameter changes depending on the storage temperature is not clear, but it exists as an impurity in the styrene monomer and is contained in the usual expandable polystyrene resin particles by about 100 to 200 ppm. It was found that when a certain amount of ethylbenzene contained was contained, the cell diameter was stably maintained without being enlarged even when stored at a high temperature, and the present invention was completed.

  That is, the present invention is an expandable polystyrene resin particle containing 10 to 50 ppm of ethylbenzene (hereinafter sometimes referred to as “expandable polystyrene resin particle of the present invention”).

  The expandable polystyrene resin particles of the present invention preferably contain a carbon-based radiant heat transfer inhibitor.

  The polystyrene foam particles of the present invention are obtained by foaming the expandable polystyrene resin particles of the present invention.

  The polystyrene foam molded article of the present invention is obtained by molding the polystyrene foam particles of the present invention in a mold.

  According to the expandable polystyrene resin particles of the present invention, the occurrence of cell roughness is suppressed and the cell diameter adjustment stability is increased. Therefore, it is not necessary to lengthen the refrigerator storage period after producing the expandable polystyrene resin particles, and the probability of cell roughening in the summer can be greatly reduced.

[Expandable polystyrene resin particles]
(Polystyrene resin)
The expandable polystyrene resin particles of the present invention are those in which a foaming agent is contained in a polystyrene resin composition. The polystyrene resin composition used for the expandable polystyrene resin particles of the present invention contains a polystyrene resin as a base resin. The polystyrene resin may be not only a styrene homopolymer (styrene homopolymer), but also a copolymer of styrene with another monomer copolymerizable with styrene or a derivative thereof. These may be used alone or in combination of two or more.

  Examples of other monomers copolymerizable with styrene or derivatives thereof include, for example, methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, Styrene derivatives such as trichlorostyrene; polyfunctional vinyl compounds such as divinylbenzene; (meth) acrylic acid ester compounds such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate; Vinyl cyanide compounds such as (meth) acrylonitrile; diene compounds such as butadiene or derivatives thereof; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; N-methylmaleimide and N-butylmaleimide N- cyclohexyl maleimide, N- phenylmaleimide, N- (2) - chlorophenyl maleimide, N- (4) - bromo-phenyl maleimide, N- (1) - N- alkyl-substituted maleimide compounds such as naphthyl maleimide, and the like. These may be used alone or in combination of two or more.

  In the present invention, from the viewpoint of impact resistance and heat resistance, for example, diene rubber reinforced polystyrene, acrylic rubber reinforced polystyrene, polyphenylene ether resin, and the like can be blended.

  The polystyrene resin used in the present invention is relatively inexpensive, can be foam-molded with low-pressure steam or the like without using a special method, and has excellent balance of heat insulation, flame retardancy, and buffering properties. Preferably it includes a homopolymer.

  In the present invention, as long as the effects of the present invention are not impaired, other resins may be used in combination with a polystyrene resin as a main component. Other resins include polyolefin resins, polyester resins, polycarbonate resins, acrylic resins, homopolymers of other monomers or derivatives thereof copolymerizable with the above-mentioned styrene, and copolymers thereof. Is mentioned.

(Foaming agent)
In the expandable polystyrene resin particles of the present invention, a hydrocarbon having 3 to 6 carbon atoms is preferable as the foaming agent. Examples thereof include propane, normal butane, isobutane, normal pentane, isopentane, cyclopentane, neopentane, normal hexane, cyclohexane and the like. These foaming agents can be used alone or in admixture of two or more. Among these foaming agents, hydrocarbons having 4 carbon atoms and / or 5 hydrocarbons are preferable from the viewpoint of easy control of the target expansion ratio, and normal butane, isobutane, It is particularly preferable to use at least one selected from the group consisting of normal pentane and isopentane.

  It is preferable that the addition amount of a foaming agent is 4-10 weight part with respect to 100 weight part of polystyrene-type resin compositions. When the addition amount of the foaming agent is 4 parts by weight or more, the foaming force is sufficient and the foaming is easy to achieve high foaming, and it becomes easy to produce a polystyrene-based resin foam molded article having a high foaming ratio. Moreover, since the manufacturing time (molding cycle) at the time of manufacturing a polystyrene-type foaming molding will become short if the quantity of a foaming agent is 10 weight part or less, manufacturing cost can be held down. In addition, it is more preferable that it is 4.5-9 weight part with respect to 100 weight part of polystyrene-type resin compositions, and, as for the addition amount of a foaming agent, it is still more preferable that it is 5-8 weight part.

(Additive)
The expandable polystyrene resin particles of the present invention are at least selected from the group consisting of a carbon-based radiation heat transfer inhibitor, a flame retardant, a heat stabilizer, a radical generator, a nucleating agent, and other additives as necessary. One optional component may be contained.

  A preferred embodiment of the expandable polystyrene resin particles of the present invention contains a polystyrene resin, a carbon-based radiation heat transfer inhibitor, a foaming agent and a flame retardant, and optionally includes a heat stabilizer, a radical generator, and a nucleating agent. You may contain at least 1 sort (s) of the group which consists of an agent and another additive. As a more preferred form, it contains a polystyrene-based resin, a carbon-based radiant heat transfer inhibitor, a foaming agent, a flame retardant, and a heat stabilizer, and includes a radical generator, a nucleating agent, and other additives as optional components. You may contain at least 1 sort (s) of these. As a more preferable form, it contains a polystyrene-based resin, a carbon-based radiation heat transfer inhibitor, a foaming agent, a flame retardant, a heat stabilizer and a nucleating agent, and includes a radical generator and other additives as optional components. You may contain at least 1 sort (s) of a group.

(Flame retardants)
The flame retardant that can be used in the present invention is not particularly limited, and any known flame retardant conventionally used for polystyrene resin foam molded articles can be used, and among them, bromine having a high flame retardant effect. Series flame retardants are preferred.

  The flame retardant is not particularly limited, and any flame retardant conventionally used for a styrene resin foam molded article can be used. Among them, a brominated flame retardant having a high flame retardant imparting effect is desirable. Examples of the brominated flame retardant used in one embodiment of the present invention include 2,2-bis [4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl] propane (also known as: Tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether)), or 2,2-bis [4- (2,3-dibromopropoxy) -3,5-dibromophenyl] propane (also known as: Brominated bisphenol compounds such as tetrabromobisphenol A-bis (2,3-dibromopropyl ether)), brominated styrene / butadiene block copolymer, brominated random styrene / butadiene copolymer, or brominated styrene / butadiene Brominated butadiene / vinyl aromatic hydrocarbon copolymers such as graft copolymers (for example, JP2009-516) Disclosed in 19 JP by that), and the like. These brominated flame retardants may be used alone or in combination of two or more.

  The flame retardant is easily controlled to the target expansion ratio, and the flame retardant is 0.5% in 100% by weight of the polystyrene resin composition from the viewpoint of balance such as flame retardancy when the carbon-based radiation heat transfer inhibitor is added. It is preferably ˜6% by weight, more preferably 1 to 4% by weight. When the content is 0.5% by weight or more, the effect of imparting flame retardancy is not reduced, and when it is 6% by weight or less, the strength of the resulting polystyrene-based resin foam molded article is hardly lowered.

(Heat stabilizer)
In the expandable polystyrene resin particles of the present invention, by further using a heat stabilizer, it is possible to suppress the deterioration of flame retardancy due to the decomposition of the flame retardant in the production process and the deterioration of the expandable polystyrene resin particles. it can.

  The heat stabilizer in the present invention is appropriately selected according to the type of polystyrene resin used, the type and content of the foaming agent, the type and content of the carbon-based radiation heat transfer inhibitor, the type and content of the flame retardant, and the like. They can be used in combination.

  As the heat stabilizer used in the present invention, a hindered amine compound, a phosphorus compound, and an epoxy compound are desirable because the 1% weight loss temperature in the thermogravimetric analysis of the flame retardant-containing mixture can be arbitrarily controlled. A heat stabilizer can be used individually by 1 type or in combination of 2 or more types. These heat stabilizers can also be used as light-resistant stabilizers as described later.

  The heat stabilizer is easy to control to the target expansion ratio, and the heat stabilizer is 0 in 100% by weight of the polystyrene resin composition from the viewpoint of the balance of flame retardancy when the carbon-based radiation heat transfer inhibitor is added. It is preferably 5 to 3% by weight. When the amount is 0.5% by weight or more, the flame retardant is hardly decomposed, and the effect of imparting flame retardancy is not reduced.

(Carbon-based radiation heat transfer inhibitor)
In the present invention, by adding a carbon-based radiation heat transfer inhibitor, a styrene-based resin foam molded body having high heat insulation can be obtained. The term “radiation heat transfer inhibitor” as used herein refers to a substance having the property of reflecting, scattering, or absorbing near-infrared or infrared light.

  Examples of the carbon-based radiation heat transfer inhibitor used in the present invention include graphite, graphene, carbon black, carbon nanotube, and activated carbon expanded graphite. These carbons can be used alone or in combination of two or more. Among these, graphite is preferable because of its high carbon-based radiation heat transfer suppressing effect on cost. Examples of graphite include flaky graphite, earthy graphite, spherical graphite, and artificial graphite. Among these, flaky graphite is preferable because it exhibits a high radiation suppressing effect. In the present specification, the term “scale-like” also includes a scale-like, flaky or plate-like one.

  The content of the carbon-based radiation heat transfer inhibitor in the expandable polystyrene resin particles of the present invention is preferably 2 to 10% by weight in 100% by weight of the polystyrene resin composition. It is more preferably 3 to 7% by weight, and further preferably 3 to 6% by weight, from the viewpoint of easy control of the target foaming ratio and balance such as a thermal conductivity reduction effect. If the content of the carbon-based radiation heat transfer inhibitor is 2% by weight or more, the effect of reducing the thermal conductivity is sufficient. On the other hand, if it is 10% by weight or less, the expanded polystyrene resin particles to the pre-expanded particles and polystyrene Since the cell membrane is less likely to be broken when producing a resin-based resin foam molded article, it becomes easy to achieve high foaming and control of the expansion ratio is facilitated.

  In the present invention, other radiation heat transfer inhibitors may be added in addition to the carbon-based radiation heat transfer inhibitor as long as the effects of the present invention are not impaired. Although it will not specifically limit if it is a well-known radiation heat transfer inhibitor, For example, an aluminum compound, a zinc compound, a magnesium compound, a titanium compound, a heat ray reflective agent, a metal sulfate, an antimony compound, a metal oxide, a heat ray Examples include absorbents and metal particles.

(Other additives)
The polystyrene-based resin composition of the expandable polystyrene-based resin particles of the present invention is a radical generator, a processing aid, a light-resistant stabilizer, a nucleating agent, a foam as necessary, as long as the effects of the present invention are not impaired. It may contain one or more other additives selected from the group consisting of colorants such as auxiliaries, antistatic agents and pigments. Examples of the radical generator include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, or poly-1,4-isopropylbenzene. It is done. Examples of the processing aid include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin, and the like. Examples of the light-resistant stabilizer include hindered amines, phosphorus-based stabilizers, and epoxy compounds described above, phenol-based antioxidants, nitrogen-based stabilizers, sulfur-based stabilizers, and benzotriazoles. Examples of nucleating agents include silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, talc and other inorganic compounds, methyl methacrylate copolymers, ethylene-vinyl acetate. Examples thereof include polymer compounds such as copolymer resins, olefinic waxes such as polyethylene wax, and fatty acid bisamides such as methylene bisstearyl amide, ethylene bisstearyl amide, hexamethylene bispalmitic acid amide, and ethylene bisoleic acid amide. As the foaming aid, a solvent having a boiling point of 200 ° C. or lower under atmospheric pressure can be desirably used. For example, aromatic hydrocarbons such as styrene, toluene, or xylene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane An acetic acid ester such as ethyl acetate or butyl acetate; In addition, as an antistatic agent and a coloring agent, what is used for various resin compositions can be used without limitation. These other additives can be used alone or in combination of two or more.

(Average cell diameter)
The average cell diameter of the polystyrene foam particles and polystyrene foam molded article of the present invention is preferably adjusted to 50 μm or more and 300 μm or less, more preferably 70 μm or more and 250 μm or less, and further preferably 90 μm or more and 200 μm or less. . When the average cell diameter is in the above range, mechanical properties such as compressive strength can be increased.

(Rough cell)
A state in which the average cell diameter exceeds 300 μm is called cell roughening. When cell roughening occurs, it becomes difficult to foam to a desired foaming ratio, and mechanical properties such as compressive strength tend to decrease. .

[Method for producing expandable polystyrene resin particles]
The expandable polystyrene resin particles of the present invention can be produced by a known suspension polymerization method or melt kneading method.

  The melt kneading method is more preferable because the amount of ethylbenzene is easy to control. The melt kneading methods include the following first melt kneading method and second melt kneading method, which can be appropriately selected.

  As the first melt-kneading method, the resin component and the foaming agent are melt-kneaded by an extruder and extruded into a cutter chamber filled with pressurized circulating water through a die having a small hole attached to the tip of the extruder, There is a method of cutting with a rotary cutter immediately after extrusion and cooling and solidifying with pressurized circulating water. In this case, the melt kneading by the extruder uses a second kneader such as a single extruder, a case where a plurality of extruders are connected, and an extruder and a stirrer having no static mixer or screw. In some cases, it can be selected as appropriate.

  As the second melt-kneading method, the resin component is melt-kneaded with an extruder, resin pellets are obtained using a cold cut method or a hot cut method, the resin pellets are suspended in water, and the resin pellets There is a method in which a foaming agent is contained.

  In the first and second melt-kneading methods, if necessary, other additives may be melt-kneaded with an extruder.

(Ethylbenzene content adjustment method)
In recent years, from the viewpoint of environmental hygiene, it has been desired that the content of ethylbenzene be reduced. On the other hand, from the viewpoint of weight reduction and raw material cost reduction, market demands for high foaming of expandable polystyrene resin particles are increasing. Since ethylbenzene acts as a foaming aid, if the content of ethylbenzene is excessively reduced, there is a concern that the foamability of the expandable polystyrene resin particles may be affected. However, the expandable polystyrene resin particles of the present invention are characterized in that the content of ethylbenzene is controlled to 10 to 50 ppm. By satisfying the range of ethylbenzene, polystyrene-based expanded particles obtained by expanding expandable polystyrene-based resin particles have a cell diameter adjusted as desired, and the cells are rough even if stored under high temperature conditions. Is suppressed. Since the stability of the cell diameter adjustment is excellent, the foamability of the expandable polystyrene resin particles is also stable.

  In the present invention, it is preferable to use a styrene monomer or a polystyrene resin in which the ethylbenzene content is adjusted in terms of easy adjustment of the ethylbenzene content.

  The method for adjusting the ethylbenzene content when using a styrene monomer or polystyrene resin with an ethylbenzene content less than the required amount is a method of dissolving ethylbenzene in a predetermined amount in the foaming agent to be used, or adding liquid when melt kneading. A method is mentioned.

  In order to improve quantitativeness, a method of dissolving a predetermined amount in a foaming agent in advance is preferable.

  Examples of the method for adjusting the ethylbenzene content in the melt-kneading method using a polystyrene resin having an ethylbenzene content higher than the required amount include a method in which the amount of ethylbenzene is reduced during extrusion by a melt vent method.

[Polystyrene resin foam molding]
The expandable polystyrene resin particles of the present invention are not particularly limited, but the foamable polystyrene resin particles are pre-expanded to a predetermined expansion ratio to form polystyrene-based expanded particles, and molding is performed using the polystyrene-based expanded particles. Thereby, a polystyrene-type foaming molding can be manufactured. That is, the polystyrene-based expanded particles of the present invention are the expanded polystyrene-based resin particles of the present invention expanded (pre-expanded) at a predetermined expansion ratio. Moreover, the polystyrene-type foam molded article of the present invention is molded using the polystyrene-based foam particles of the present invention. Note that the polystyrene-based expanded particles may further expand during molding.

  The expandable polystyrene resin particles of the present invention are foamed 10 to 110 times with a known pre-foaming step, for example, with water vapor to form polystyrene-based foam particles (pre-foaming step), and after curing for a certain time if necessary. Using a known molding machine, the polystyrene foam particles are molded with water vapor to produce a polystyrene foam molding. Depending on the shape of the mold used, it is possible to obtain a molded article having a complicated shape or a block-like molded article.

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

  As the pre-foaming machine, a known one can be used. For example, a can equipped with a stirring device and containing expandable polystyrene resin particles, a steam chamber installed under the can and supplying water vapor to the can, A pre-foaming machine having a polystyrene-based foamed particle outlet is used.

  The polystyrene-based foam molded article of the present invention is, for example, a building insulation material used for floors, walls, roofs, etc., a box for transporting marine products such as fish and a box for transporting agricultural products such as vegetables, and a bathroom It can be used for various applications such as thermal insulation for hot water tanks and hot water storage tanks.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to these.

  In addition, the measuring methods and evaluation methods in the following examples and comparative examples are as follows.

(Ethylbenzene content measurement method)
Dissolve expandable polystyrene resin particles in methylene chloride (internal standard cyclopentanol) and use gas chromatography (GC) to determine the amount of ethylbenzene (ppm) contained in expandable polystyrene resin particles under the following conditions. did.
Measuring apparatus: Gas chromatography GC-2014 manufactured by Shimadzu Corporation
Column: Capillary column (GL Science Rtx-1)
Column temperature conditions: 50 → 80 ° C. temperature rise (3 ° C./min), then 80 → 180 ° C. temperature rise (10 ° C./min)
Carrier gas: helium.

(Foaming method)
The expandable polystyrene resin particles were stored at 15 ° C. for 1 week, and then left to stand in a dryer at a temperature of 40 ° C. for 3 hours. Next, 1200 g of the expandable polystyrene resin particles was put into a pre-foaming machine [BHP-300, manufactured by Daikai Kogyo Co., Ltd.], and the internal pressure of the can was set to 0.05 kg / cm2 to 0.15 kg / cm2, and 0.10 MPa. Of water vapor was introduced into a pre-foaming machine and foamed 60 times (pre-foaming). In the case where foaming did not occur up to 60 times, foaming was terminated after a water vapor charging time of 300 seconds.
Below, implementation of this foaming method may be called "foaming process." The foaming treatment was carried out separately for the expandable polystyrene resin particles (hereinafter sometimes referred to as each level) produced in each example and each comparative example.

(Average cell diameter measurement method)
(1) Observation condition apparatus: DIGITAL MICROSCOPE VHX-900 manufactured by Keyence Corporation
Observation magnification: 100 times (2) Measurement conditions The polystyrene foam particles produced by the above-described foaming method are cut with a razor on a perpendicular bisector with respect to the major axis diameter, and the cross section is used by DIGITAL MICROSCOPE manufactured by Keyence Corporation. Then, take a picture at an observation magnification of 100 times. The number of cells existing within a 1000 μm × 1000 μm square within a radius of 1000 μm from the center point of the cross section is counted. Using the number of cells, the cell diameter was calculated based on the following formula.

Cell diameter (μm)
= 2 × [1000 μm × 1000 μm / (number of cells × circumference)] 0.5
Ten polystyrene foam particles are randomly selected from the polystyrene foam particles produced by one foaming treatment, the cell diameter is calculated from the 10 polystyrene foam particles, and the average cell diameter is calculated. Calculated as

(Cell roughness evaluation method)
The foaming process was performed 10 times for each level. The average cell diameter of the polystyrene-based expanded particles obtained by each foaming treatment was calculated by the above average cell diameter measuring method, and the presence or absence of cell roughness was determined for each calculated average cell diameter.
Cell roughness was determined as cell roughness when the calculated average cell diameter was 300 μm or more. Then, the number of times of cell roughness determined during 10 foaming treatments at each level was evaluated as the “cell roughness frequency” at each level.

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

(Polystyrene resin)
(A) Styrene homopolymer [Suspension polymerization was carried out using a styrene monomer not containing ethylbenzene to produce a resin having a weight average molecular weight (Mw) of 200,000. ]
(Carbon-based radiation heat transfer inhibitor)
(B) Graphite [manufactured by Maruho Castings Co., Ltd., scaly graphite SGP-40B]
(Brominated flame retardant)
(C) 2,2-bis [4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl] propane [Daiichi Kogyo Seiyaku Co., Ltd., SR-130, bromine content = 66% by weight].

(Foaming agent)
(E1) Normal pentane [Wako Pure Chemical Industries, Ltd., reagent product]
(E2) Isopentane [Wako Pure Chemical Industries, Ltd., reagent product]
(F) Ethylbenzene [Wako Pure Chemical Industries, Ltd., reagent product]

Example 1
[Production of expandable polystyrene resin particles]
0.034 parts by weight of ethylbenzene (F) was mixed with 100 parts by weight of mixed pentane mixed at a ratio of 80% by weight of normal pentane (E1) and 20% by weight of isopentane (E2).

  In a tandem type two-stage extruder in which a 40-mm unidirectional twin-screw extruder (first extruder) and a 90-mm uniaxial extruder (second extruder) are connected in series, a polystyrene resin (A), graphite (B), the brominated flame retardant (C) is supplied to the first extruder at a weight ratio (A) :( B) :( C): = 93.5: 4.0: 2.5, Melting and kneading were performed at a preset temperature of 190 ° C. and a rotation speed of 150 rpm in a 40 mm extruder. From the middle of the 40 mm-diameter extruder (first extruder), the mixed pentane mixed with ethylbenzene at a ratio of 6.5 parts by weight with respect to 100 parts by weight of the mixture (A) + (B) + (C). Press-fitted. Then, it supplied to the 90 mm caliber extruder (2nd extruder) through the continuation pipe | tube set to 200 degreeC.

  After cooling the molten resin to 160 ° C. with a 90 mm diameter extruder (second extruder), the diameter was 0.65 mm attached to the tip of the second extruder set at 250 ° C., and the land length was 3.0 mm. A die having 36 small holes was extruded at a discharge rate of 50 kg / hour into pressurized circulating water at a temperature of 65 ° C. and 1.3 MPa. The extruded molten resin was cut and granulated using a rotary cutter having six blades in contact with a die, and transferred to a centrifugal dehydrator to obtain expandable polystyrene resin particles.

  The above-described measurements and determinations were performed on the obtained expandable polystyrene resin. The measurement and determination results are shown in Table 1.

(Examples 2 to 4 and Comparative Examples 1 to 5)
The same procedure as in Example 1 was carried out except that the amount of ethylbenzene mixed in the mixed pentane was adjusted so that the ethylbenzene content contained in the expandable polystyrene resin particles became the content shown in Table 1.

  Each measurement / evaluation was performed on the obtained expandable polystyrene resin particles in the same manner as in Example 1. The measurement and determination results are shown in Table 1.

  Note that “average cell diameter (excluding cell roughness)” in Table 1 means the total number of average cell diameters that were not determined as cell roughness at each level (ie, “10 -The value divided by the number of cell roughening times)).

Claims (4)

  Expandable polystyrene resin particles containing 10-50 ppm of ethylbenzene.   Expandable polystyrene resin particles containing a carbon-based radiation heat transfer inhibitor.   A polystyrene-based expanded particle obtained by expanding the expandable polystyrene-based resin particle according to claim 1 or 2. A polystyrene-based foam-molded product obtained by molding the polystyrene-based foamed particles according to claim 3 in a mold.