JP2020033481A - Foamable polystyrene resin particle, polystyrene resin pre-foamed particle, and polystyrene resin foam molding - Google Patents

Abstract

To provide a foamable polystyrene resin particle that can give a polystyrene resin foam molding having both of a high expansion ratio and high heat insulation performance.SOLUTION: A foamable polystyrene resin particle has a polystyrene resin composition containing a carbon-based radiation heat transfer inhibitor and a foaming agent, the foamable polystyrene resin particles having an aspect ratio of 0.95 or less and a sphericity of 0.970 or more.SELECTED DRAWING: None

Description

  The present invention relates to expandable polystyrene resin particles, pre-expanded particles thereof, and a foam molded article using the same.

  Polystyrene resin foam is a foam having excellent balance, such as light weight, heat insulation, and cushioning properties, and has been widely used as a heat insulation material for food container boxes, cool boxes, cushioning materials, and houses. ing.

  Above all, in recent years, in connection with various problems such as global warming, energy saving by improving the heat insulating property of buildings such as houses has been pursued, and a polystyrene resin foam molded article obtained using expandable polystyrene resin particles has been developed. Demand expansion is expected. Therefore, various studies have been made on the improvement of the foaming property and heat insulating property of the polystyrene resin foam.

  For example, according to the invention of Patent Document 1, in an expandable polystyrene resin particle to which a radiation heat transfer inhibitor is added, a bromine atom is a ratio of a bromine atom content derived from a bromine-based flame retardant to a radiation inhibitor content. By setting the content / radiation heat transfer inhibitor content in a specific range, both heat insulation and flame retardancy can be achieved.

  According to the invention of Patent Literature 2, the content ratio of the hydrocarbon having 4 carbon atoms and the hydrocarbon having 5 carbon atoms in the expandable polystyrene resin particles is 2/98 to 20/80, so that the flame-retardant resin is used. Uses a flame retardant that has not been reduced and has excellent environmental compatibility, and also contains a radiant heat transfer inhibitor, so it has low thermal conductivity, high flame retardancy and heat insulation It is possible to provide expandable polystyrene-based resin particles which do not require an aging period.

Patent Document 3 describes a method for producing thermoplastic resin expandable particles, in which the shearing rate of the blowing agent-containing molten resin when passing through the small-hole land portion of the die is 12000 to 35000 sec ⁻¹ , and the resin is apparent. Disclosed is a method for producing thermoplastic resin expandable particles capable of producing an expanded molded article having a perfect spherical shape and excellent mechanical strength by extruding a melt viscosity of 100 to 700 poise. .

JP 2014-080514 A JP 2014-118474 A International Publication No. WO2005 / 028173

  An object of the present invention is to provide a polystyrene resin foam molded article having both high expansion ratio and high heat insulation.

  The higher the expansion ratio, the lower the amount of expandable polystyrene-based resin particles used in the raw material of the polystyrene-based resin foam. Therefore, the foam of the polystyrene-based resin must be highly foamed while maintaining the heat insulating properties of the polystyrene-based resin foam. Is desired. However, Patent Documents 1 and 2 are inventions for obtaining a polystyrene-based resin foam molded article having both flame retardancy and high heat insulation, but the foaming property at the time of high magnification foaming is not studied. Therefore, there is still room for improvement in foamability.

  Patent Document 3 discloses a method for producing a thermoplastic resin expandable particle capable of producing an expanded molded article having a resin particle having a true spherical shape and excellent mechanical strength. However, no study has been made on the foaming property at the time of high foaming when a radiation heat transfer inhibitor such as graphite is blended.

  The method for producing expandable polystyrene resin particles containing a radiation heat transfer inhibitor is roughly classified into a method of including a radiation heat transfer inhibitor in a polymerization step of a styrene monomer (hereinafter, referred to as a “polymerization method”). ) And a method of melt-kneading a styrene-based resin and a radiation heat transfer inhibitor that have been polymerized in advance using a kneading facility such as an extruder (hereinafter, referred to as “melt kneading method”).

  Further, the melt-kneading method is roughly classified into two production methods.

  In the first melt-kneading method, a polystyrene resin, a radiant heat transfer inhibitor, and other additives are supplied to an extruder, melt-kneaded, and the foaming agent is dissolved in the resin by the extruder or a dispersing device after the extruder, Disperse and extrude the blowing agent-containing molten resin into a cutter chamber filled with pressurized circulating water through a die having many small holes. Immediately after the extrusion, the molten resin is cut by a rotary cutter in contact with the dies and pressurized and circulated. This is a method of obtaining expandable styrene resin particles by cooling and solidifying with water.

  The second melt-kneading method involves melting and kneading a polystyrene-based resin, a radiation heat transfer inhibitor, and other additives with an extruder, extruding the resin melt through a die having small holes, and cutting the resin with a cutter. After obtaining the particles, the polystyrene resin particles are suspended in water, a blowing agent is supplied, and the blowing agent is contained in the polystyrene resin particles to obtain expandable styrene resin particles. .

  Among these production methods, the melt-kneading method using the extrusion kneading equipment is superior to the polymerization method in terms of initial investment and simplicity of production. Further, from the viewpoint of productivity, the first melt-kneading method is superior to the second melt-kneading method.

  On the other hand, the expandable polystyrene resin particles obtained by the polymerization method or the second melt kneading method achieve an aspect ratio extremely close to 1, whereas the expandable polystyrene resin particles obtained by the first melt kneading method. Resin particles have an aspect ratio out of 1 and tend to be distorted. As a result of the study by the present inventors, the expandable polystyrene resin particles having an aspect ratio obtained by the first melt-kneading method deviating from 1 are obtained by the polymerization method or the second melt-kneading method. It was found that the pre-expanded particles tended to shrink more easily than the polystyrene resin particles.

  For the above reasons, further improvement is desired for the expandability of the expandable polystyrene resin particles obtained by the first melt-kneading method which is excellent in production cost.

  The present inventors have studied to solve the above-mentioned problem, and surprisingly, it is surprising that the foaming property is generally considered to be better as the aspect ratio is closer to 1, but the aspect ratio slightly deviates from 1. Even for expandable polystyrene resin particles, by controlling the sphericity of the expandable polystyrene resin particles, the shrinkage of the polystyrene resin pre-expanded particles immediately after foaming can be suppressed, and the high expansion ratio polystyrene resin It has been found that foamed particles, and thus a polystyrene resin foam molded article, can be obtained, and the present invention has been completed.

  That is, the present invention relates to expandable polystyrene-based resin particles containing a carbon-based radiant heat transfer inhibitor, and has an aspect ratio of 0.95 or less and a sphericity of 0.970 or more. Particles (hereinafter sometimes referred to as “expandable polystyrene resin particles of the present invention”). Here, the aspect ratio is the ratio of the minor axis to the major axis of the projected view of the expandable polystyrene resin particles. The sphericity is a value determined from the ratio of the peripheral length to the area of the projected view of the expandable polystyrene resin particles. Compared to the aspect ratio, the sphericity can also consider the influence of the unevenness of the surface of the expandable polystyrene resin particles. The detailed method of measuring the aspect ratio and sphericity will be described later.

  In the expandable polystyrene resin particles of the present invention, the sphericity is preferably 0.980 or more.

  In the expandable polystyrene resin particles of the present invention, the carbon-based radiation heat transfer inhibitor is preferably 2 to 10% by weight based on 100% by weight of the polystyrene-based resin composition.

  In the expandable polystyrene resin particles of the present invention, the carbon-based radiation heat transfer inhibitor is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. preferable.

  In the expandable polystyrene resin particles of the present invention, the blowing agent preferably contains pentane and / or butane.

  In the expandable polystyrene resin particles of the present invention, the blowing agent preferably contains isobutane.

  In the expandable polystyrene resin particles of the present invention, it is preferable that the blowing agent contains more than 20% by weight and 50% by weight or less of isobutane based on 100% by weight of the total amount of pentane and butane.

  In the expandable polystyrene resin particles of the present invention, the pentane preferably has a weight ratio of normal pentane and isopentane of 100/0 to 60/40.

In the expandable polystyrene resin particles of the present invention, it is preferable that the true density of the expandable polystyrene resin particles is 950 to 1060 kg / m ³ .

In the expandable polystyrene resin particles of the present invention, the heat of the expanded molded article when the expandable polystyrene resin particles are pre-expanded and the pre-expanded particles having a bulk magnification of 75 cm ³ / g or more and 85 cm ³ / g or less are foam-formed. Preferably, the conductivity is 0.0330 W / m · K or less.

  The pre-expanded particles of the present invention are pre-expanded particles of the expandable polystyrene resin particles of the present invention.

The pre-expanded particles of the present invention are pre-expanded particles of the expandable polystyrene resin particles of the present invention, and preferably have a bulk magnification of 75 cm ³ / g or more.

  The expanded molded article of the present invention is an expanded polystyrene resin molded article obtained by molding the expandable polystyrene resin particles of the present invention or the pre-expanded particles of the present invention.

  According to the expandable polystyrene resin particles of the present invention, it is possible to obtain a foamed molded article having both high expansion ratio and high heat insulation.

[Expandable polystyrene resin particles]
The expandable polystyrene-based resin particles of the present invention are expandable polystyrene-based resin particles containing a carbon-based radiation heat transfer inhibitor, and the carbon-based radiation heat transfer inhibitor and the foaming agent are contained in the polystyrene-based resin particles. Things.

  The expandable polystyrene resin particles of the present invention have a sphericity of 0.970 or more and an aspect ratio of 0.95 or less. In general, when the aspect ratio is in the above range, shrinkage after foaming is likely to occur, but when the sphericity satisfies the above range, the preliminary ratio obtained even when the expandable polystyrene resin particles are foamed at a high magnification. In the expanded particles, the shrinkage immediately after the pre-expansion is suppressed, and the cured particles can recover to a desired expansion ratio after curing. In addition, since the expandable polystyrene resin particles of the present invention are suppressed from shrinking, it is not necessary to cure the pre-expanded particles at a high temperature, and it becomes easier to control the magnification after curing.

The aspect ratio in the present invention is calculated by the following formula from the minor axis and major axis of the projected view of the expandable polystyrene resin particles.
Aspect ratio = (minor axis) / (major axis)
From the characteristics of the first melt-kneading method, the aspect ratio is 0.95 or less. On the other hand, in order to satisfy the sphericity of 0.970 or more, the aspect ratio is preferably 0.75 or more.

The sphericity in the present invention is calculated from the perimeter and the area of the projected view of the expandable polystyrene resin particles by the following formula.
Sphericity = 4 x π x (area) / (perimeter) ²
From the viewpoint of suppressing shrinkage, the sphericity is preferably 0.970 or more, and more preferably 0.980 or more. When the sphericity is 0.980 or more, it is possible to recover to a high magnification even in a state where the volatile component has been reduced after a lapse of time since the production of the expandable polystyrene resin particles. The detailed method of measuring the aspect ratio and sphericity of the expandable polystyrene resin particles will be described later.

(Polystyrene resin)
As the polystyrene-based resin, not only a styrene homopolymer (polystyrene homopolymer) but also a copolymer of styrene with another monomer copolymerizable with styrene or a derivative thereof, as long as the effects of the present invention are not impaired. It may be. These may be used alone or in combination of two or more. However, a brominated polystyrene / butadiene copolymer described below is excluded.

  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) acrylate 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 anhydrides such as maleic anhydride and itaconic anhydride; N-methylmaleimide, 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.

  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 a good balance of heat insulation, flame retardancy, and buffering properties. Preferably, it contains a homopolymer.

  In the present invention, a polystyrene-based resin may be used as a main component, and another resin may be used in combination as long as the effects of the present invention are not impaired. As other resins, such as polyolefin resins, polyester resins, polycarbonate resins, acrylic resins, homopolymers of the above-mentioned other monomers copolymerizable with styrene or derivatives thereof, and copolymers thereof Is mentioned. From the viewpoint of shock absorption and heat resistance, for example, a diene rubber reinforced polystyrene, an acrylic rubber reinforced polystyrene, a polyphenylene ether resin, or the like can be blended.

(Carbon-based radiation heat transfer inhibitor)
In the present invention, a foamed polystyrene resin article having high heat insulating properties can be obtained by incorporating the carbon-based radiation heat transfer inhibitor into the foamable polystyrene resin particles. Here, the carbon-based radiation heat transfer inhibitor refers to a carbon material having a property of reflecting, scattering, or absorbing light in a near-infrared region or an infrared region (for example, a wavelength region of about 800 to 3000 nm).

  Examples of the carbon-based radiant heat transfer inhibitor include graphite (graphite), graphene, carbon black, expanded graphite, activated carbon, carbon nanotube, and carbon nanofiber. Among them, dispersibility in polystyrene resin and cost In view of this, graphite is preferred.

Examples of graphite include flaky graphite, earthy graphite, spherical graphite, artificial graphite, and the like. In this specification, the term “scale” includes scale, flake or plate. These graphites can be used alone or in combination of two or more. Among these, a graphite mixture containing flaky graphite as a main component is preferable, and flaky graphite is more preferable, from the viewpoint of high radiation heat transfer suppressing effect. From the viewpoints of high foaming, heat insulation, and moldability, the average particle size of graphite is preferably 1 to 9 μm, and more preferably 2 to 6 μm. As the average particle size of graphite decreases, the production cost increases. Since graphite having an average particle size of less than 1 μm has a high production cost including the cost of pulverization, it is very expensive and the cost of expandable polystyrene resin particles tends to be high. On the other hand, when the average particle size exceeds 9 μm, the cell membrane is easily broken when the pre-expanded particles and the polystyrene resin foam molded article are produced from the expandable polystyrene resin particles, so that high foaming becomes difficult or the molding becomes difficult. There is a tendency that easiness is reduced or the compressive strength of the polystyrene resin foam molded article is reduced. Here, the average particle size of the graphite refers to _{D 50} particle diameter calculated by a laser diffraction scattering method based on Mie theory conforming to JIS Z8825-1.

  The content of the carbon-based radiation heat transfer inhibitor in the expandable polystyrene-based resin particles of the present invention is preferably 2 to 10% by weight based on 100% by weight of the polystyrene-based resin composition. It is more preferably 3 to 7% by weight, and still more preferably 3 to 6% by weight, from the viewpoint of easy control of the desired expansion ratio and the balance of the effect of reducing the thermal conductivity. When the content of the carbon-based radiant heat transfer inhibitor is 2% by weight or more, the effect of reducing the thermal conductivity is sufficient. On the other hand, when the content is 10% by weight or less, the expandable polystyrene-based resin particles are converted into pre-expanded particles and polystyrene. Since the cell membrane is less likely to be broken during the production of the resin-based foamed molded article, foaming is easily performed, and the control of the expansion ratio is facilitated.

  In the present invention, other radiation heat transfer suppressors may be added in addition to the carbon-based radiation heat transfer suppressor as long as the effects of the present invention are not impaired. Although it is not particularly limited as long as it is a known radiation heat transfer inhibitor, for example, aluminum compounds, zinc compounds, magnesium compounds, titanium compounds, heat ray reflectors, metal sulfates, antimony compounds, metal oxides, heat rays Absorbents, metal particles and the like can be mentioned.

(Foaming agent)
The foaming agent used in the present invention is not particularly limited, but is preferably a hydrocarbon having 3 to 6 carbon atoms, and more preferably, from the viewpoint that the foaming property and the product life are well-balanced, and the magnification is easily increased when actually used. Is a hydrocarbon having 4 to 5 carbon atoms. When the carbon number of the foaming agent is 3 or more, the volatility becomes low, and when the foaming polystyrene resin particles are used, the foaming agent does not easily dissipate. This is preferable because sufficient foaming power can be obtained and high magnification can be easily achieved. If the number of carbon atoms is 6 or less, the boiling point of the foaming agent is not too high, so that sufficient foaming power is easily obtained by heating at the time of preliminary foaming, and the foaming tends to be easily performed. Examples of the hydrocarbon having 3 to 6 carbon atoms include hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, and cyclohexane. These may be used alone or in combination of two or more.

  Further, foaming agents other than hydrocarbons may be used. For example, ethers such as dimethyl ether and diethyl ether, alcohols such as methanol and ethanol, carbon dioxide, nitrogen, and water can be used. These foaming agents may be used alone or in a combination of two or more. Moreover, you may use together with the said hydrocarbon.

  It is more preferable to use butane and pentane in combination from the viewpoint of easily increasing the magnification.

  As butane, it is preferable to use isobutane from the viewpoint of foaming more easily. Further, it is preferable that isobutane is contained in an amount of more than 20% by weight and 50% by weight or less in the total amount of pentane and butane of 100% by weight. From the viewpoint of increasing the magnification by suppressing shrinkage immediately after prefoaming and increasing production stability, isobutane is more preferably 25% by weight to 45% by weight, still more preferably 25% by weight to 40% by weight, and more preferably 25% by weight to 30% by weight. Particularly preferred. When the isobutane content is more than 20% by weight, it is easy to increase the magnification. On the other hand, when the isobutane content is 50% by weight or less, foaming during the production of expandable polystyrene resin particles can be suppressed in the case of production by a melt-kneading method. As a result, the collection of expandable polystyrene resin particles is stabilized.

  As pentane, it is preferable to use normal pentane and / or isopentane in terms of cost. In consideration of the balance between the suppression of shrinkage after prefoaming and the flame retardancy of the foamed molded article, the weight ratio of normal pentane and isopentane (normal pentane / isopentane) is preferably 100/0 to 60/40, 98/2 to 60/40 are more preferred, and 98/2 to 70/30 are even more preferred.

  The addition amount of the blowing agent in the present invention is preferably 4 to 10 parts by weight, more preferably 4.5 to 9 parts by weight, and more preferably 5 to 8 parts by weight, based on 100 parts by weight of the polystyrene resin composition. More preferably, it is part by weight. When the amount of the foaming agent is 4 parts by weight or more, the foaming power is sufficient, the foaming is easily performed, and a polystyrene resin foam molded article having a high magnification is easily manufactured. Further, when the amount of the foaming agent is 10 parts by weight or less, the flame-retardant performance does not easily deteriorate, and the production time (molding cycle) for producing the polystyrene resin foam molded article is shortened, so that the production cost is suppressed. be able to.

  The expandable polystyrene-based resin particles of the present invention contain a polystyrene-based resin, a carbon-based radiant heat transfer inhibitor and a foaming agent, and, if necessary, a flame retardant, a heat stabilizer, a radical generator, a nucleating agent, and others. At least one optional component selected from the group consisting of the additives described above.

(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-based resin foam molded articles can be used. Among them, bromine having a high flame retardancy-imparting effect is particularly preferred. Flame retardants are preferred. As the brominated flame retardant that can be used in the present invention, for example, 2,2-bis [4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl] propane (alias: tetrabromo Bisphenol A-bis (2,3-dibromo-2-methylpropyl ether)), 2,2-bis [4- (2,3-dibromopropoxy) -3,5-dibromophenyl] propane (alias: tetrabromobisphenol Brominated bisphenol compounds such as A-bis (2,3-dibromopropyl ether)), brominated styrene / butadiene block copolymer, brominated random styrene / butadiene copolymer, brominated styrene / butadiene graft copolymer Butadiene / vinyl aromatic hydrocarbon copolymers (for example, JP-T-2009-516019) Disclosed), tetrabromobisphenol cyclooctane and the like. One of these brominated flame retardants may be used alone, or two or more thereof may be used in combination.

  The flame retardant is easy to control to the desired expansion ratio, and from the viewpoint of the balance of the flame retardancy when the carbon-based radiation heat transfer inhibitor is added, the flame retardant is 0.5% in 100% by weight of the polystyrene resin composition. The content is preferably in the range of 6 to 6% by weight, and more preferably 1 to 4% by weight. When the content of the flame retardant is 0.5% by weight or more, the effect of imparting flame retardancy does not decrease, and when the content is 6% by weight or less, the strength of the obtained polystyrene-based resin foam molded article does not easily decrease.

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

  The heat stabilizer in the present invention, depending on the type of polystyrene resin used, the type and content of the blowing agent, the type and content of the carbon-based radiant heat transfer inhibitor, the type and content of the flame retardant, etc. 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 preferable because the weight loss temperature in the thermogravimetric analysis of the mixture containing a flame retardant can be arbitrarily controlled. The heat stabilizers can be used alone or in combination of two or more. In addition, these heat stabilizers can also be used as a light resistance stabilizer as described later.

  The heat stabilizer is easily controlled to the desired expansion ratio, and from the viewpoint of the balance of flame retardancy when the carbon-based radiation heat transfer inhibitor is added, the heat stabilizer is 0% in 100% by weight of the polystyrene resin composition. It is preferably from 0.5 to 3% by weight. When the content is 0.5% by weight or more, the flame retardant is hardly decomposed, the effect of imparting flame retardancy is not reduced, and when the content is 3% by weight or less, the strength of the obtained polystyrene resin foam molded article is hard to decrease.

(Other additives)
In addition to the above-mentioned additives, the expandable polystyrene-based resin particles of the present invention may further include a radical generator, a processing aid, a light-fast stabilizer, and a nucleating agent, 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 a coloring agent such as an agent, a foaming aid, an antistatic agent, and a pigment. Examples of the radical generator include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and poly-1,4-isopropylbenzene. Can be Examples of the processing aid include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, and liquid paraffin. Examples of the light fastness stabilizer include the above-mentioned hindered amines, phosphorus stabilizers, epoxy compounds, phenolic antioxidants, nitrogen stabilizers, sulfur stabilizers, benzotriazoles and the like. As a nucleating agent, silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, inorganic compounds such as talc, methyl methacrylate copolymer, ethylene-vinyl acetate Examples thereof include polymer compounds such as copolymer resins, olefin-based waxes such as polyethylene wax, fatty acid bisamides such as methylene bisstearyl amide, ethylene bisstearyl amide, hexamethylene bispalmitic amide, and ethylene bis oleic amide. As the foaming aid, a solvent having a boiling point of 200 ° C. or less at atmospheric pressure can be desirably used. For example, aromatic hydrocarbons such as styrene, toluene, ethylbenzene, and xylene; and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. Examples include hydrogen, ethyl acetate, and acetic acid esters such as butyl acetate. In addition, as an antistatic agent and a coloring agent, those used for various resin compositions can be used without particular limitation. These other additives can be used alone or in combination of two or more.

  The average cell diameter of the polystyrene resin pre-expanded particles of the present invention is preferably 350 μm or less, more preferably 80 μm to 350 μm, further preferably 100 μm to 300 μm, and particularly preferably 130 μm to 280 μm. By setting the average cell diameter to 350 μm or less, the number of cells existing in the pre-expanded particles increases, radiant heat decreases, and thermal conductivity improves.

The expandable polystyrene resin particles of the present invention preferably have a true density of 950 to 1060 kg / m ³ , more preferably 1000 to 1055 kg / m ³ , and more preferably 1010 to 1055 kg / m ³ , from the viewpoint of transportation efficiency and storage space. 1050 kg / m ³ is more preferable, and 1010 to 1040 kg / m ³ is particularly preferable.

  The expandable polystyrene resin particles of the present invention may have a volatile content of 4.5% to 5.8% when the expandable polystyrene resin particles are prefoamed and cured at 10 ° C. for 24 hours. Preferably, it is 4.5% to 5.4%, more preferably 4.6% to 5.2%. Here, the volatile content of the pre-expanded particles refers to a ratio obtained by dividing the mass change before and after heating the pre-expanded particles at 150 ° C. for 30 minutes by the mass of the pre-expanded particles before the heating. This means that the internal pressure of the expanded particles is reduced, and shrinkage is likely to occur.

  When the volatile content of the pre-expanded particles satisfies the range of 4.5% to 5.8%, the internal pressure of the pre-expanded particles increases, and the pre-expanded particles shrink even when the bulk ratio is increased to 75 times or more. Can be suppressed, and the surface beauty of the polystyrene-based resin foam molded article is improved.

  The expandable polystyrene-based resin particles of the present invention are obtained by pre-expanding expandable polystyrene-based resin particles, and heat-curing the foamed pre-expanded particles having a bulk ratio of 75 times or more into a polystyrene-based resin foam molded article. λ is preferably 0.0330 W / m · K or less. When the thermal conductivity λ of the polystyrene resin foam molded article is 0.0330 W / m · K or less, the thickness of the foam molded article can be reduced when used as a heat insulating material for walls and roofs, and other heat insulating materials such as glass wool can be used. The cost can be reduced as much as the material.

[Method for producing expandable polystyrene resin particles]
The expandable polystyrene-based resin particles of the present invention can be obtained by a known melt-kneading method. Specifically, a polystyrene-based resin, a carbon-based radiation heat transfer inhibitor, and a foaming agent are melt-kneaded with an extruder ( Melt kneading process), extruding the melt-kneaded material through a die with small holes attached to the extruder tip into a chamber filled with pressurized circulating water (extrusion process), and cutting the melt-kneaded material immediately after extrusion with a rotary cutter In addition, it can be manufactured by cooling and solidifying (cooling step) with pressurized circulating water (hereinafter, may be referred to as “the manufacturing method of the present invention”).
In the production method of the present invention, from the viewpoint of the dispersibility of the polystyrene resin and the various components, the polystyrene resin and the various components are loaded in advance using a kneading apparatus equipped with a biaxial stirrer (for example, a Banbury mixer). It is preferable that the mixture is kneaded to prepare a kneaded product, the obtained kneaded product and a polystyrene resin are put into an extruder, melt-kneaded, and then cut into particles.

  As a preferred embodiment of the manufacturing method of the present invention, a polystyrene-based resin and a carbon-based radiant heat transfer inhibitor are kneaded by a kneading apparatus equipped with a biaxial stirrer such as a Banbury mixer to prepare a masterbatch, and The masterbatch, a new polystyrene resin, a foaming agent, and other components such as a flame retardant, if necessary, are melt-kneaded with an extruder, and the resulting resin melt is injected into a small hole attached to the tip of the extruder. Is extruded into a cutter chamber filled with pressurized circulating water through a die having the above, cut immediately after extrusion by a rotary cutter, and cooled and solidified by pressurized circulating water. In this case, the melt-kneading in the extruder, when using a single extruder, when connecting a plurality of extruders, when using a second kneading device such as an extruder and a stirrer without a static mixer or a screw may be used in combination. Yes, and can be selected appropriately.

  Kneading the polystyrene-based resin and the carbon-based radiant heat transfer suppressor with a kneading device equipped with a biaxial stirrer, such as an intensive mixer, an internal mixer, or a Banbury mixer capable of kneading the resin under a load. To prepare a master batch. In this case, the concentration of the masterbatch is not particularly limited, but it is preferable to prepare the masterbatch at a concentration of the carbon-based radiation heat transfer inhibitor of 20% by weight to 80% by weight in view of the balance between kneading properties and cost. The prepared masterbatch, polystyrene resin, foaming agent, and if necessary, a flame retardant, a heat stabilizer, and other additives are added to the first extruder and, if necessary, the second kneading device attached to the extruder. After melt-kneading and cooling the obtained resin melt to a predetermined temperature, it is extruded through a die having small holes into a cutter chamber filled with pressurized circulating water. Immediately after the extrusion, pellets are formed by cutting with a rotary cutter, and the obtained pellets (resin particles) are cooled and solidified by pressurized circulating water to obtain expandable polystyrene resin particles. In addition, regarding other additives such as a flame retardant and a heat stabilizer, similarly, a master batch of a polystyrene-based resin and other additives may be prepared in advance and charged into an extruder or the like. Absent.

  The set temperature of the melt-kneading section of the extruder is preferably from 100C to 250C. Further, it is preferable that the residence time in the extruder from the supply of the polystyrene resin and various components to the end of the melt kneading is 10 minutes or less. If the set temperature in the melt kneading section of the extruder is 250 ° C. or less, and / or the residence time in the extruder until the end of the melt kneading is 10 minutes or less, the flame retardant is not decomposed when the flame retardant is added. The desired flame retardancy can be obtained, and there is no need to add an excessive amount of a flame retardant to impart the desired flame retardancy. On the other hand, when the set temperature in the melt-kneading section of the extruder is 100 ° C. or higher, the load on the extruder is not increased, the extrusion is stabilized, and the dispersibility of the added component is improved.

  The resin temperature of the melt-kneaded product immediately before being introduced into the die is preferably Tg + 50 ° C. or higher and lower than Tg + 90 ° C. with respect to the glass transition point (hereinafter, Tg) of the base resin. When the base resin is a styrene homopolymer, the temperature is preferably higher than 150 ° C. and lower than 190 ° C. When the base resin is a styrene homopolymer, if the resin temperature of the melt-kneaded material immediately before being introduced into the die is 190 ° C. or higher, the resin temperature at the time of cutting the resin in the die increases, and the foamable styrene-based The distortion of the shape of the resin particles may increase, and if the temperature exceeds 210 ° C., the resin may be easily wound around the cutter during cutting with the cutter, and the cutting may be extremely difficult. On the other hand, when the resin temperature of the melt-kneaded product immediately before being introduced into the die is 150 ° C. or lower, the viscosity of the extruded molten resin increases, small pore clogging is likely to occur, and a substantial decrease in the small pore opening ratio is caused. There is a risk of getting up.

  The pressure of the pressurized circulating water is preferably 0.7 MPa to 1.5 MPa, more preferably 0.75 to 1.4 MPa. When the water pressure is 0.7 MPa or more, foaming can be suppressed, the true density of the expandable polystyrene-based resin particles increases, and a decrease in the expansion ratio and a decrease in transport efficiency hardly occur. On the other hand, when the water pressure is 1.5 MPa or less, the rotary cutter is not pushed back by the water pressure, and the extruded molten resin does not wind around the rotary cutter, thereby enabling stable production.

  The die used in the present invention is not particularly limited, and examples thereof include a die having a small hole having a diameter of 0.3 mm to 2.0 mm, preferably 0.4 mm to 1.0 mm.

  The cutting device for cutting the molten resin extruded into the pressurized circulating water is not particularly limited. For example, the cutting device is cut by a rotary cutter in contact with a die lip, pulverized, transferred to a centrifugal dehydrator, and dewatered / aggregated. And the like.

  In the production method of the present invention, the aspect ratio and sphericity of the obtained expandable polystyrene resin particles can be controlled by appropriately controlling the temperature of the molten resin, the temperature and pressure of the cooling water, the shear rate, and the like.

[Polystyrene resin foam molding]
The expandable polystyrene-based resin particles of the present invention are not particularly limited, but are formed by expanding the expandable polystyrene-based resin particles to a predetermined expansion ratio to form pre-expanded particles, and performing a molding using the pre-expanded particles by a pre-expansion method. Thus, a polystyrene-based resin foam molded article can be manufactured.

  According to the present invention, a polystyrene-based resin foam molded article has a higher expansion ratio, and the amount of expandable polystyrene-based resin particles used as a raw material is smaller. Can be manufactured. It should be noted that high-expansion foaming was difficult in conventional expandable polystyrene resin particles containing graphite. However, the expandable polystyrene-based resin particles of the present invention and the expandable polystyrene-based resin particles obtained by the production method of the present invention have high shrinkage without significant shrinkage by controlling the sphericity of the expandable polystyrene-based resin particles. Foaming can be performed at a high magnification, and a light-weight, easy-to-handle and cheaper heat insulating material can be supplied.

  The expandable polystyrene-based resin particles of the present invention are formed in a known pre-expansion step, for example, by foaming 10 to 110 times with steam to obtain pre-expansion particles (pre-expansion step), and after curing for a certain period of time, if necessary, Using a known molding machine, the pre-expanded particles are molded with water vapor to produce a polystyrene resin foam molded article. Depending on the shape of the mold used, a molded article having a complicated shape or a block-shaped molded article can be obtained.

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

  As the pre-foaming machine, known ones can be used.For example, a can provided with a stirrer and containing expandable polystyrene resin particles, and a steam chamber installed below the can and supplying steam to the can And a pre-expanding machine provided with a pre-expanded particle discharge port.

  The pressure in the can (cage pressure) at the time of introducing steam is not particularly limited, but is preferably 0.001 to 0.15 MPa, more preferably 0.01 to 0.10 MPa, and still more preferably 0.03 to 0.08 MPa. . When the pressure in the can is 0.001 MPa or more, the steam injection time in the pre-foaming can be made 500 seconds or less when a high foaming ratio is obtained. When the pressure in the can is 0.15 MPa or less, it is not necessary to increase the pressure of water vapor, the number of occurrences of the blocking phenomenon is reduced, and the prefoaming yield is increased.

  Further, the pre-foaming step can be performed by any of a continuous method and a batch method.

  The continuous method is a method of continuously supplying the expandable polystyrene resin particles into the can and discharging the pre-expanded particles from a discharge port provided at the top of the can. The expansion ratio of the pre-expanded particles can be adjusted, for example, by appropriately selecting the amount (weight) of the expandable polystyrene resin particles charged into the can per hour. In the case of the continuous method, the residence time in the prefoaming machine can from the supply of the expandable polystyrene resin particles into the can to the discharge of the prefoamed particles is defined as the steam injection time.

  In the batch method, a predetermined amount of expandable polystyrene resin particles are put in a can, and after pre-foaming the particles to a predetermined expansion ratio, the supply of water vapor is stopped, and then air is introduced into the can as necessary. This is a method in which the pre-expanded particles are blown, cooled and dried, and taken out of the can. The expansion ratio of the pre-expanded particles can be adjusted by appropriately selecting the amount (weight) of the expandable polystyrene resin particles charged into the can per batch. Since the batch method is a method of pre-expanding the charged expandable polystyrene resin particles to a predetermined volume, the expansion ratio of the obtained pre-expanded particles increases as the input amount per batch decreases.

  It is better to cure the pre-expanded particles immediately after the pre-expansion. At the time of prefoaming, steam is present in the foamed particles. However, in the cooling step after foaming, the steam is condensed into water, so that the inside of the prefoamed particles immediately after the prefoaming is in a reduced pressure state. Under reduced pressure, the strength of the pre-expanded particles is low and shrinkage may easily occur. Therefore, a curing step in which the inside of the pre-expanded particles is replaced with air and the pressure is returned to atmospheric pressure is effective.

  The temperature at the time of curing is not particularly limited, but is preferably 5 to 80 ° C, more preferably 10 to 70 ° C, and further preferably 23 to 60 ° C. When the curing temperature is 5 ° C. or higher, air is easily introduced into the pre-expanded particles that have been in a reduced pressure state, and the inside of the expanded particles is easily returned to the atmospheric pressure. When the curing temperature is 80 ° C. or lower, the foaming agent present in the pre-expanded particles does not easily escape, the foaming power does not decrease, and the surface beauty of the molded body does not decrease.

  When the expandable polystyrene resin particles of the present invention are pre-expanded to obtain pre-expanded particles, the pre-expanded particles preferably have a bulk magnification of 75 times or more, more preferably 80 times or more. When the bulk expansion ratio of the pre-expanded particles is 75 times or more, the density of the polystyrene-based resin foam molded product obtained by molding the pre-expanded particles is reduced, and a lighter weight polystyrene-based resin foam molded product is produced. Becomes possible. In addition, increasing the bulk magnification can reduce the amount of resin used, leading to cost reduction.

  Polystyrene resin foam molded article of the present invention, for example, floors, walls, building insulation used for roofs, etc., agricultural and fishery boxes such as boxes for transporting marine products such as fish and boxes for transporting agricultural products such as vegetables, It can be used for various applications such as bathroom insulation and hot water storage tank insulation.

  Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the measuring method and evaluation method of each physical property and characteristic in the following Examples and Comparative Examples are as follows.

(Sphericity and aspect ratio of expandable polystyrene resin particles)
· measuring device;
CAMSIZER P4 manufactured by Retsch Technology
(2) setting conditions;
The feeder and funnel parameters were set to the following conditions.
・ Control level when moving forward at high speed: 55
・ Maximum time when moving forward at high speed [sec]: 60
・ Level at the start of measurement: 50
・ Maximum control level: 75
・ Target coverage area [%]: 0.5
-Feeder width [mm]: 60
・ Guidance sheet was used Under the following conditions, it was adopted as measurement data.
-Basic camera cover area [%] <3
・ Zoom camera cover area [%] <5
However, particles satisfying the following conditions from the photographed projection view were excluded from the measurement data.
・ Convexity ≧ 0.99
When the particles overlap each other and fall to the measurement point of the projection view, the shape of each particle cannot be accurately evaluated. Therefore, the feeder and funnel parameters were set to the above conditions. In addition, if a large amount of particles drop at the same time, it may not be possible to accurately evaluate the shape of each particle. For this reason, when particles larger than the set cover area fell, the projections and data were excluded.
Further, in order to exclude the influence of minute foreign substances such as dust, the analysis was performed by excluding data having a convexity (surface unevenness) of 0.99 or more.

(3) measurement method;
A projection view of about 50 g of expandable polystyrene resin particles was taken by CAMSIZER P4 set as described above, and the perimeter, area, major axis, and minor axis of each of the obtained expandable polystyrene resin particles were measured. did. The average value of the sphericity was calculated from the perimeter and the area of the projection of the obtained expandable polystyrene resin particles based on the following formula.

Here, S _i is the area of the i-th particle (mm ² ), and R _i is the circumference of the i-th particle (mm).

  Further, the average value of the aspect ratio was calculated from the major axis and the minor axis of the projection view of each of the obtained expandable polystyrene resin particles based on the following equation.

Here, S _i is the minor axis (mm) of the i-th particle, and l _i is the major axis (mm) of the i-th particle.

(Grain weight of expandable polystyrene resin particles)
The weight of 100 expandable polystyrene resin particles was measured, and the particle weight was calculated based on the following equation.

  Particle weight (mg / particle) = weight of 100 expandable polystyrene resin particles (mg) / 100

(True density of expandable polystyrene resin particles)
The expandable polystyrene resin particles were collected as W (kg) as a measurement sample, the measurement sample was naturally dropped into a graduated cylinder containing ethanol, and its mass (kg) and volume (m ³ ) were measured. The true density was measured based on the equation.

True density (kg / m ³ ) = weight of measurement sample (W) / volume of measurement sample (V).

(Volatile content of expandable polystyrene resin particles)
The volatile content of the expandable polystyrene resin particles was measured on the expandable polystyrene resin particles 7 days after the production and 15 days after the production.

  Expandable polystyrene resin particles were collected as W (g) as a measurement sample, and the measurement sample was put into an aluminum container, heated in a thermostat at 150 ° C. for 30 minutes, and the volatile content was calculated from the change in mass before and after heating.

Volatile content (%) = {(W1-W2) / W1} × 100
Here, W1 is the mass (g) of the expandable polystyrene resin particles before heating, and W2 is the mass (g) of the expandable polystyrene resin particles after heating.

(Measurement of pre-expanded particles)
The pre-expanded particles shown below are pre-expanded particles obtained by pre-expanding expandable polystyrene-based resin particles 7 days after production and pre-expanded by expanding foamable polystyrene-based resin particles 15 days after production. The measurement was performed on the expanded particles.

(Bulk magnification of pre-expanded particles)
Each of the pre-expanded particles was sampled as W (g) as a measurement sample, and the measurement sample was naturally dropped into a graduated cylinder. After the graduated cylinder was knocked, the apparent volume V (cm ³ ) of the sample was fixed, and its mass (g) was measured. And the volume (cm ³ ) were measured, and the bulk magnification was measured based on the following equation.

Bulk magnification (cm ³ / g) = volume of measurement sample (V) / weight of measurement sample (W)

In the pre-expanded particles, the bulk magnification measured within 5 to 10 minutes after the pre-expanded particles are discharged from the pre-expanding machine is defined as the bulk magnification immediately after foaming.
Furthermore, after measuring the bulk magnification immediately after foaming, the bulk magnification of the pre-expanded particles after curing at 10 ° C. for 24 hours is defined as the bulk magnification after curing.
Incidentally, the bulk magnification “times” of the polystyrene-based resin pre-expanded particles is conventionally also expressed in “cm ³ / g”.

(Volatile content of pre-expanded particles after curing)
The measurement was performed on the pre-expanded particles after curing at 10 ° C. for 24 hours. The pre-expanded particles after curing at 10 ° C. for 24 hours were sampled as W (g) as a measurement sample, and the measurement sample was put into an aluminum container, heated in a thermostat at 150 ° C. for 30 minutes, and the change in mass before and after heating was measured. The volatile content was calculated.
Volatile content (%) = {(W3-W4) / W3} × 100
Here, W3 is the mass (g) of the pre-expanded particles before heating, and W4 is the mass (g) of the pre-expanded particles after heating.

(Measurement of polystyrene resin foam molding)
In the following measurement, the molded article obtained by foaming the pre-expanded particles obtained by pre-expanding the expandable polystyrene resin particles 7 days after production and the expandable polystyrene resin particles 15 days after production were pre-expanded. And a molded article obtained by subjecting the pre-expanded particles obtained in this manner to foam molding.

(Expansion ratio of foamed polystyrene resin)
After drying the polystyrene-based resin foam molded product taken out of the molding die at 30 ° C. for 24 hours, the weight (g) of the foam molded product is measured, and the vertical dimension, the horizontal dimension, and the thickness dimension are measured using calipers. Was measured. The volume (cm ³ ) of the polystyrene resin foam molded article was calculated from the measured dimensions, and the expansion ratio was calculated according to the following formula.

Foaming ratio (cm ³ / g) = volume of test piece (cm ³ ) / weight of test piece (g)
In addition, the expansion ratio “times” of the polystyrene-based resin foam molded body is conventionally also expressed as “cm ³ / g”.

(Thermal conductivity of foamed polystyrene resin)
It is generally known that the larger the measured average temperature of the thermal conductivity is, the larger the value of the thermal conductivity is. It is necessary to determine the measured average temperature in order to compare the heat insulation properties. In this specification, 23 ° C. defined in JIS A9511: 2006R, which is a standard for foamed plastic heat insulating materials, is adopted as a reference.

  From the middle layer of the polystyrene resin foam molded article, a test piece without skin having a length of 300 mm × a width of 300 mm × 25 mm was cut out. The test piece was allowed to stand at 60 ° C. for 48 hours, and further allowed to stand at 23 ° C. for 24 hours. Then, using a thermal conductivity measuring device (manufactured by Eiko Seiki Co., Ltd., HC-074), JIS A1412- 2: The heat conductivity was measured at an average temperature of 23 ° C. and a temperature difference of 20 ° C. by a heat flow meter method according to 1999.

(Average cell diameter of foamed polystyrene resin)
(1) Observation condition device: DIGITAL MICROSCOPE VHX-900 manufactured by KEYENCE CORPORATION
(2) Measurement conditions A polystyrene-based resin foam molded article was cut with a razor, and a cross section was photographed at 100 × magnification using DIGITAL MICROSCOPE manufactured by KEYENCE CORPORATION. The number of cells existing within a 1000 μm × 1000 μm square area of the cross section was counted. Using the number of cells, an average cell diameter was calculated based on the following equation.
Average cell diameter (μm) = 2 × {1000 μm × 1000 μm / (number of cells × pi)} ^0.5
Hereinafter, raw materials used in Examples and Comparative Examples are shown.

(Styrene resin)
(A) Styrene homopolymer [680 g, manufactured by PS Japan Ltd.]
(Graphite)
(B) Graphite [Scaly graphite SGP-40B manufactured by Maruho Casting Co., Ltd.]
(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]

(Heat stabilizer)
(D1) Tetrakis (2,2,6,6-tetramethylpiperidyloxycarbonyl) butane [LA-57 manufactured by ADEKA Corporation]
(D2) Bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite [PEP-36 manufactured by ADEKA Corporation]

(Foaming agent)
(E1) Normal pentane [Wako Pure Chemical Industries, Ltd., reagent product]
(E2) Isopentane [Wako Pure Chemical Industries, Ltd., reagent product]
(E3) Isobutane [manufactured by Mitsui Chemicals, Inc.]

(Other additives)
(F) Ethylene bisstearic acid amide [NOF Corporation, Alflow H-50S]

(Production Example 1) (Graphite Masterbatch (G))
Into a Banbury mixer, 49 parts by weight of a polystyrene resin (A), 50 parts by weight of graphite (B), and 1 part by weight of ethylene bisstearic acid amide (F) were added, and a load of 5 kgf / cm ² was applied. Melt kneading was performed for 20 minutes without performing cooling. At this time, the resin temperature was measured to be 180 ° C. A strand-like resin extruded at a discharge of 250 kg / hr through a die having a small hole attached to the tip by being supplied to a ruder is cooled and solidified in a water bath at 30 ° C., and then cut to obtain a master batch (G). . The graphite content in the masterbatch (G) was 50% by weight.

(Production Example 2) (Master batch (H) of a mixture of a brominated flame retardant and a heat stabilizer)
After the polystyrene resin (A) is supplied to the twin screw extruder and melt-kneaded, a mixture of the bromine flame retardant (C), the stabilizer (D1) and the (D2) is supplied from the middle of the extruder. It was melt-kneaded. However, the weight ratio of each material is (A) :( C) :( D1) :( D2) = 70: 28.5: 0.6: 0.9, (A) + (C) + (D1) + (D2) = 100% by weight. A strand-like melt extruded at a discharge of 300 kg / hr is cooled and solidified in a water bath at 20 ° C. through a die having a small hole attached to the tip of the extruder, and then cut to obtain a brominated flame retardant and a heat stabilizer. To obtain a master batch (H). At this time, the set temperature of the extruder was 170 ° C.

(Reference Example 1)
[Preparation of polystyrene resin particles]
The polystyrene-based resin (A), the masterbatch (H), and the graphite masterbatch (G) were each charged into a blender and blended for 10 minutes to obtain a resin mixture. The weight ratio of each material was (A) :( H) :( G) = 83.65: 8.35: 8.00, (A) + (H) + (G) = 100% by weight. The obtained resin mixture is supplied to a coaxial twin-screw extruder having a diameter of 40 mm, melt-kneaded at a set temperature of 190 ° C. and a screw rotation speed of 230 rpm, and 30 small holes having a diameter of 1.4 mm attached to the extruder tip are provided. The strand resin extruded at a discharge rate of 70 kg / hour through the die thus obtained was cooled and solidified in a water bath at 20 ° C., and then cut with a strand cutter to obtain styrene resin particles. At this time, the resin temperature at the extruder tip was 220 ° C.

[Preparation of expandable polystyrene resin particles]
Next, 200 parts by weight of deionized water, 1 part by weight of tricalcium phosphate, and 0.03 parts by weight of sodium dodecylbenzenesulfonate were added to an autoclave with a stirrer having a volume of 6 L based on 100 parts by weight of the obtained styrene resin particles. And 1 part by weight of sodium chloride, and the pressure vessel was sealed. Thereafter, the mixture was heated to 105 ° C. in 1 hour, and 7 parts by weight of mixed pentane (a mixture of 80% normal pentane and 20% isopentane) and 1.5 parts by weight of isobutane were added as a blowing agent to the pressure vessel over 30 minutes. The temperature was raised to 115 ° C. over 10 minutes, and the temperature was maintained for 4 hours. After holding, the mixture is cooled to room temperature, the resin particles impregnated with the foaming agent are taken out of the autoclave, pickled with hydrochloric acid, washed with water, dehydrated with a centrifugal separator, and then dried with a flash dryer to remove moisture adhering to the resin particle surfaces. Let dry. The particle weight of the obtained expandable polystyrene resin particles was 1.5 mg / particle, the aspect ratio was 0.985, and the sphericity was 0.988. After dry blending 0.08 parts by weight of zinc stearate with respect to 100 parts by weight of the obtained expandable polystyrene resin particles, the mixture was stored at 10 ° C.

[Preparation of pre-expanded particles]
Expandable polystyrene resin particles were prepared, and stored at 10 ° C., and 15 days later, 250 g of expandable polystyrene resin particles were charged into a batch type pre-expansion machine manufactured by Daikai Kogyo Co., Ltd. It was introduced into a foaming machine and foamed. The bulk magnification immediately after prefoaming was 80 cm ³ / g. Thereafter, the bulk ratio of the pre-expanded particles after curing at 10 ° C. for 24 hours was 81 cm ³ / g.

[Preparation of foamed polystyrene resin]
The pre-expanded particles after curing are filled in an in-mold molding die (length 400 mm × width 400 mm × thickness 50 mm) attached to a styrofoam molding machine [KR-57 manufactured by Daisen Industries Co., Ltd.] After introducing water vapor of 0.06 MPa to cause foaming in the mold, water was sprayed on a mold and cooled. After holding the polystyrene resin foam molded article in the mold until the pressure at which the polystyrene resin foam molded article presses the mold becomes 0.01 MPa (gauge pressure), take out the polystyrene resin foam molded article and remove it at 30 ° C. After drying for an hour, a polystyrene-based resin foam molded article was obtained. The expansion ratio of the obtained polystyrene resin foam was 81 cm ³ / g.

  Various characteristics of the produced expandable polystyrene-based resin particles, pre-expanded particles, and foamed polystyrene-based resin were measured and evaluated by the above-described measurement methods and evaluation methods. Table 1 shows the measurement results and the evaluation results.

(Example 1)
[Production of expandable polystyrene resin particles]
The polystyrene-based resin (A), the masterbatch (H), and the graphite masterbatch (G) were each charged into a blender and blended for 10 minutes to obtain a resin mixture. The weight ratio of each material was (A) :( H) :( G) = 83.65: 8.35: 8.00 ((A) + (H) + (G) = 100% by weight). .

    The obtained resin mixture is supplied to a tandem-type two-stage extruder in which a coaxial twin-screw extruder (first extruder) having a diameter of 40 mm and a single-screw extruder (second extruder) having a diameter of 90 mm are connected in series, The mixture was melt-kneaded at a set temperature of 190 ° C. and a rotation number of 230 rpm in a 40 mm extruder. In the middle of a 40 mm-diameter extruder (first extruder), mixed pentane (a mixture of 80% by weight of normal pentane (E1) and 20% by weight of isopentane (E2)) was added to 100 parts by weight of the above resin mixture. Parts by weight and 2.5 parts by weight of isobutane (E3) were introduced, and a total of 7.7 parts by weight of a blowing agent was added. Then, it supplied to the 90-mm diameter extruder (2nd extruder) through the continuous pipe | tube set to 200 degreeC.

  After cooling the molten resin to a resin temperature of 159 ° C. with a 90 mm diameter extruder (second extruder), a diameter of 0.65 mm and a land length of 5.0 mm were attached to the tip of the second extruder set at 250 ° C. Was extruded from a die having 78 small holes into pressurized circulating water at a temperature of 65 ° C. and 1.4 MPa at a discharge rate of 76 kg / hour. The extruded molten resin is cut and reduced in size at 2100 rpm using a rotary cutter having six blades that come into contact with a die, and transferred to a centrifugal dehydrator to obtain expandable polystyrene resin particles. Was. The particle weight of the obtained expandable polystyrene resin particles was 1.6 mg / particle, the aspect ratio was 0.918, and the sphericity was 0.988. After dry blending 0.08 parts by weight of zinc stearate with respect to 100 parts by weight of the obtained expandable polystyrene resin particles, the mixture was stored at 30 ° C.

[Preparation of pre-expanded particles]
Seven days after producing expandable polystyrene resin particles and storing at 30 ° C., 250 g of expandable polystyrene resin particles were put into a batch type prefoaming machine manufactured by Daikai Kogyo Co., Ltd. 0.1 MPa of steam was introduced into a prefoaming machine to foam. The bulk magnification immediately after prefoaming was 77 cm ³ / g. Thereafter, the bulk magnification of the pre-expanded particles after curing at 10 ° C. for 24 hours was 83 cm ³ / g.

Further, in order to confirm the bead life of the expandable polystyrene resin particles, expandable polystyrene resin particles were prepared and stored at 30 ° C., and after 15 days, 250 g of expandable polystyrene resin particles were manufactured by Daikai Kogyo Co., Ltd. It was charged into a batch type prefoaming machine, and steam of 0.1 MPa was introduced into the prefoaming machine to foam. The bulk magnification immediately after prefoaming was 75 cm ³ / g. Thereafter, the bulk expansion ratio of the pre-expanded particles after curing at 10 ° C. for 24 hours was 80 cm ³ / g.

[Production of foamed polystyrene resin]
The same processing as in Reference Example 1 was performed to produce a polystyrene resin foam molded article. Evaluation was performed in the same manner as in Reference Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 2)
Except that the temperature of the molten resin was cooled to 168 ° C. by a 90 mm diameter extruder (second extruder) in [Production of polystyrene resin particles], a foamed polystyrene resin article was obtained by the same treatment as in Example 1. Produced. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 3)
In [Production of polystyrene-based resin particles], a polystyrene-based resin foam was formed by the same treatment as in Example 1 except that the temperature of the molten resin was cooled to 177 ° C. with a 90 mm-diameter extruder (second extruder). Produced. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 4)
In [Production of polystyrene-based resin particles], a foamed polystyrene-based resin article was produced in the same manner as in Example 1 except that the temperature of the molten resin was cooled to 182 ° C. using a 90 mm-diameter extruder (second extruder). Produced. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 5)
In [Production of polystyrene-based resin particles], a polystyrene-based resin foam was formed by the same treatment as in Example 1 except that the temperature of the molten resin was cooled to 186 ° C. by a 90 mm-diameter extruder (second extruder). Produced. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Comparative Example 1)
In [Production of polystyrene-based resin particles], a polystyrene-based resin foam molded article was processed in the same manner as in Example 1 except that the temperature of the molten resin was cooled to 190 ° C. with a 90 mm-diameter extruder (second extruder). Produced. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

From the results of the examples shown in Table 1, the expandable polystyrene resin particles obtained in Examples 1 to 5 have a sphericity of 0.970 or more, and the expandable polystyrene resin obtained 7 days after production. The bulk ratio of the pre-expanded particles obtained by pre-expanding the particles after curing is as high as 80 times or more. In Examples 1 and 2 in which the sphericity is 0.980 or more, the bulk magnification after curing of the pre-expanded particles obtained by pre-expanding the expandable polystyrene resin particles 15 days after production is also 80 times or more. Has achieved a high magnification. On the other hand, in Comparative Example 1 in which the sphericity is less than 0.970, the shrinkage of the pre-expanded particles is remarkable, and the bulk magnification after curing is less than 80 times, which is clearly inferior in foamability. .
Although the expandable polystyrene resin particles obtained in Examples 1 to 5 are smaller than the aspect ratio of the expandable polystyrene resin particles of Reference Example 1, the shrinkage of the pre-expanded particles is suppressed, and the same expandability is obtained. It is clear that In other words, even if the aspect ratio of the expandable polystyrene resin particles is 0.95 or less, by controlling the sphericity of the expandable polystyrene resin particles to satisfy the requirements of the present invention, a high expansion ratio, It can be seen that polystyrene expandable styrene resin particles capable of providing a polystyrene resin foam molded article having both low thermal conductivity, that is, high heat insulation performance, can be provided.

Claims (13)

Expandable polystyrene resin particles comprising a polystyrene resin composition containing a carbon-based radiation heat transfer inhibitor and a foaming agent,
Expandable polystyrene resin particles, wherein the expandable polystyrene resin particles have an aspect ratio of 0.95 or less and a sphericity of 0.970 or more.   The expandable polystyrene resin particles according to claim 1, having a sphericity of 0.980 or more.   The expandable polystyrene resin particles according to claim 1 or 2, wherein the carbon-based radiation heat transfer inhibitor is 2 to 10% by weight based on 100% by weight of the polystyrene-based resin composition.   The carbon-based radiation heat transfer inhibitor is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite, according to any one of claims 1 to 3. Expandable polystyrene resin particles.   The expandable polystyrene resin particles according to any one of claims 1 to 4, wherein the blowing agent includes pentane and / or butane.   The expandable polystyrene resin particles according to claim 5, wherein the blowing agent includes butane, and the butane includes isobutane.   The expandable polystyrene resin particles according to claim 6, wherein the blowing agent includes pentane, and the isobutane includes more than 20% by weight and 50% by weight or less based on 100% by weight of the total amount of the pentane and the butane.   The expandable polystyrene resin particles according to any one of claims 5 to 7, wherein the blowing agent includes pentane, and the pentane has a weight ratio of normal pentane and isopentane of 100/0 to 60/40. The true density of the expandable polystyrene resin particles are 950~1060kg / ^{m 3,} expandable polystyrene resin particles according to any one of claims 1-8. When the foamed polystyrene resin particles are pre-foamed, the thermal conductivity of the foamed molded article when the foamed molded article having a bulk magnification of 75 cm ³ / g or more and 85 cm ³ / g or less is foamed is 0.0330 W / m · K or less. The expandable polystyrene resin particles according to any one of claims 1 to 9, wherein   Pre-expanded particles of the expandable polystyrene resin particles according to any one of claims 1 to 10. The pre-expanded particles according to claim 11, wherein the bulk expansion ratio is 75 cm ³ / g or more. An expanded polystyrene resin molded article obtained by molding the expandable polystyrene resin particles according to any one of claims 1 to 10, or the pre-expanded particles according to claim 11 or 12.