JP2014148661A - Foamable styrene resin particle, its manufacturing method and styrene resin foamed particle molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamable styrene resin particle excellent in foamability and capable of providing a foamed particle molded article excellent in adiabaticity, its manufacturing method and a styrene resin foamed particle molded article.SOLUTION: There are provided a foamable styrene resin particle containing graphite and a foaming agent, its manufacturing method and a styrene resin foamed particle molded article obtained by fusing pre-foamed particles, which are obtained by heat foaming the foamable styrene resin particle, each other in a mold. A base material resin of the foamable styrene resin particle is obtained by impregnating and polymerizing styrene in a styrene polymer seed particle containing a polystyrene resin. The content of graphite is 0.1 to 6 pts.mass based on 100 pts.mass of the base material resin.

Description

  The present invention relates to an expandable styrene resin particle using a styrene resin as a base resin and an aliphatic hydrocarbon as a foaming agent, a method for producing the same, and a styrene resin foam obtained using the expandable styrene resin particles. The present invention relates to a particle compact.

When a plastic foam such as a polystyrene foam has a low density of, for example, 25 kg / m ³ or less, the thermal conductivity rapidly increases and the heat insulation performance decreases. This is because as the density is reduced, the thickness of the foam film of the foam decreases, and the influence of radiant heat transfer increases.
Therefore, in order to prevent the heat insulation performance from being lowered due to the reduction in density, a polystyrene foam containing a filler such as graphite or metal powder having infrared shielding ability has been developed (see Patent Documents 1 and 2). However, such polystyrene foam has a low heat resistant temperature of, for example, 70 to 80 ° C., and its application range is limited from the viewpoint of heat resistance.

  On the other hand, in order to improve the heat resistance of the foamed particle molded body, a foamed particle molded body produced by melt-kneading a styrene- (meth) acrylic acid copolymer and polystyrene with an extruder has been developed (Patent Document). 3).

JP-T-2001-522383 JP 2005-008822 A JP 2010-229205 A

  However, when a filler such as graphite is mixed with a molten mixture of styrene- (meth) acrylic acid copolymer and polystyrene, there is a problem that foamability is remarkably deteriorated. Therefore, it was difficult to obtain a foamed particle molded body having a good shape.

  The present invention has been made in view of such a background, and while being able to obtain a foamed particle molded article excellent in heat insulating properties, expandable styrene resin particles excellent in foam moldability, a method for producing the same, and An object of the present invention is to provide a styrene resin expanded resin molded article obtained by using the expandable styrene resin particles.

One aspect of the present invention is an expandable styrenic resin particle containing graphite and an aliphatic hydrocarbon having 3 to 6 carbon atoms as a foaming agent,
The base resin of the expandable styrenic resin particles is formed by impregnating and polymerizing styrene polymer seed particles containing polystyrene resin,
The expandable styrenic resin particles are characterized in that the graphite content is 0.1 to 6 parts by mass with respect to 100 parts by mass of the base resin.

  Another aspect of the present invention is a styrenic resin expanded particle molded article obtained by fusing pre-expanded particles obtained by heating and foaming the expandable styrene resin particles to each other in a mold. It is in.

Still another embodiment of the present invention is a method for producing the expandable styrenic resin particles.
A suspending step of suspending the styrenic polymer seed particles containing a polystyrene resin and containing graphite in an aqueous medium to obtain a suspension;
An impregnation polymerization step of adding the styrene to the suspension and impregnating and polymerizing the styrene polymer seed particles with the styrene to obtain styrene resin particles;
A foaming styrene comprising a foaming agent impregnation step of impregnating a resin particle with a foaming agent comprising an aliphatic hydrocarbon having 3 to 6 carbon atoms during and / or after the polymerization of styrene in the impregnation polymerization step A method for producing resin particles.

The expandable styrene resin particles (hereinafter referred to as “expandable resin particles” as appropriate) contain the predetermined amount of graphite. Therefore, the expandable resin particles can prevent a decrease in heat insulation performance due to a reduction in density during foaming. That is, even if the expandable resin particles are expanded to a low density of, for example, about 20 kg / m ³ , a styrene resin expanded resin molded article exhibiting excellent heat insulation can be obtained.

  In the foamable resin particles, the base resin is formed by impregnating and polymerizing styrene polymer seed particles including a polystyrene resin. Therefore, even if the expandable resin particles contain graphite as described above, the bubble film is not easily destroyed by the graphite at the time of preliminary foaming or secondary foaming at the time of in-mold molding, and excellent foam moldability is achieved. Can show. Therefore, when the expandable resin particles are used, there can be obtained a styrenic resin expanded particle molded body having a good shape with few gaps between the particles.

Next, the styrene-based resin expanded particle molded body (hereinafter, appropriately referred to as “expanded particle molded body”) is obtained by fusing together pre-expanded particles obtained by heating and foaming the expandable resin particles in a mold. Obtained.
Therefore, the foamed particle molded body can exhibit excellent heat insulating properties by taking advantage of the above-described excellent characteristics of the expandable resin particles. Moreover, the said foaming particle molded object can make the shape favorable.

Next, the expandable resin particles can be produced by performing a suspension process, an impregnation polymerization process, and a foaming agent impregnation process.
In the suspending step, the styrene polymer seed particles containing a polystyrene resin and containing graphite are suspended in an aqueous medium. This gives a suspension.
In the impregnation polymerization step, styrene is added to the suspension, and the styrene polymer seed particles are impregnated and polymerized. Thereby, styrene resin particles can be obtained.
In the foaming agent impregnation step, the resin particles are impregnated with a foaming agent composed of an aliphatic hydrocarbon having 3 to 6 carbon atoms during and / or after the polymerization of styrene in the impregnation polymerization step. Thereby, the said expandable resin particle can be obtained.

  In the said manufacturing method, by performing the said impregnation polymerization process, even if it contains graphite, the expandable styrene-type resin particle which is excellent in expandability and a melt | fusion property can be obtained easily.

The photograph substitute figure which shows the TEM photograph of the expandable styrene-type resin particle in Example 2. FIG. FIG. 5 is a photograph substitute diagram showing a digital photograph of the appearance of a styrene-based resin expanded particle molded body in Example 2. The photograph substitute figure which shows the TEM photograph of the expandable styrene-type resin particle in the comparative example 1. FIG. The photograph substitute figure which shows the digital photograph of the external appearance of the styrene resin expanded resin molded object in the comparative example 1. FIG.

Next, a preferred embodiment of the expandable resin particle will be described.
The expandable resin particles are obtained by impregnating and polymerizing styrene polymer seed particles containing a polystyrene resin, and include graphite and an aliphatic hydrocarbon having 3 to 6 carbon atoms as a foaming agent. As the styrene polymer of the seed particles, for example, a styrene- (meth) acrylic acid copolymer can be used. In this case, the expandable resin particle uses a composite resin of a styrene- (meth) acrylic acid copolymer and a polystyrene resin as a base resin. Hereinafter, the case where a styrene- (meth) acrylic acid copolymer is used as the styrene polymer will be described, but the same applies to the case where another styrene polymer such as a polystyrene resin is used.
When the content of the styrene- (meth) acrylic acid copolymer in the base resin is too small and the content of the polystyrene resin is too large, there is a possibility that a foamed particle molded article having excellent heat resistance cannot be obtained. On the other hand, when the content of the styrene- (meth) acrylic acid copolymer in the base resin is too large and the content of the polystyrene resin is too small, the foamability of the foamable resin particles is lowered and the foamability is reduced. There is a possibility that it is difficult to foam the resin particles to a target expansion ratio. From this viewpoint, the mass ratio of the styrene- (meth) acrylic acid copolymer to the polystyrene resin in the base resin (however, the styrene- (meth) acrylic acid copolymer: polystyrene resin) is 20:80 to 80: 20, preferably 30:70 to 70:30, and more preferably 40:60 to 65:35.

  When the internal cross section of the expandable resin particle was observed with a transmission electron microscope, the cross section was a styrene- (meth) acrylic acid copolymer as a continuous phase (sea phase) and a polystyrene resin as a dispersed phase (island). It is preferable to have a sea-island structure. In the case of a phase structure having a polystyrene resin as a continuous phase, foam moldability is deteriorated, and it may be difficult to obtain a good foamed particle molded body.

The average dispersed phase diameter of the dispersed phase made of polystyrene resin is preferably 10 μm or less, and more preferably 0.3 to 3 μm.
The average dispersed phase diameter is the dispersion of all (preferably 100 or more) on the photograph from a transmission electron micrograph of the center of the expandable resin particles (the center of the cross section that bisects the expandable resin particles). About a phase, each dispersed phase diameter (longest diameter) is measured, and these can be calculated by weighted averaging. A specific method for calculating the average dispersed phase diameter will be described in detail in Examples described later.

  The weight average molecular weight of the base resin is preferably 150,000 to 600,000, and more preferably 180,000 to 450,000. When the weight average molecular weight of the base resin is within the above range, the balance between the foamability of the foamable resin particles and the strength of the foamed particle molded body obtained using the foamable resin particles is particularly excellent. It will be. The weight average molecular weight of the base resin is a standard polystyrene equivalent value measured by the GPC method.

Moreover, the said expandable resin particle contains a C3-C6 aliphatic hydrocarbon as a foaming agent. Considering the retention property and foamability of the foaming agent, an aliphatic hydrocarbon having 4 to 5 carbon atoms is more preferable as the foaming agent.
Examples of the aliphatic hydrocarbon having 3 to 6 carbon atoms include propane, normal butane, isobutane, cyclobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, cyclohexane, 2-methylpentane, 3-methylpentane, 2 One or two or more selected from 1,3-dimethylbutane and the like can be used.

Further, the content of the foaming agent in the expandable resin particles can be appropriately adjusted depending on the desired apparent density. However, when the content of the foaming agent is too small, for example, a low density of 20 kg / m ³ or less. There is a possibility that it becomes difficult to foam the expandable resin particles. On the other hand, when there is too much content of a foaming agent, the bubble diameter of the foaming particle obtained after foaming will become coarse, and there exists a possibility that the intensity | strength of a molded object may fall. In this case, there is a possibility that the heat insulating property may be adversely affected. Therefore, the expandable resin particles preferably contain 2 to 15% by mass of the aliphatic hydrocarbon. More preferably, the content of the aliphatic hydrocarbon is 3 to 10% by mass.
The content of the aliphatic hydrocarbon can be determined by gas chromatography by dissolving foamable resin particles in a solvent such as dimethylformamide (DMF).

The expandable resin particles contain graphite.
When the graphite content is too high, the foamability is adversely affected by the formation of the bubble film, or the foamability and surface appearance of the particles in the foamed particle molded body obtained using the foamable resin particles are reduced. There is a risk of getting worse. On the other hand, when the graphite content is too small, there is a possibility that the effect of improving the heat insulating property cannot be obtained sufficiently. Therefore, the graphite content in the expandable resin particles is preferably 0.1 to 6 parts by mass with respect to 100 parts by mass of the base resin. The graphite content is more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 4 parts by mass.

As graphite, powders of various shapes such as plate, scale, flake, sphere, granule, indefinite shape, and needle shape can be used. A flaky shape and a scaly shape are preferable.
Moreover, from the viewpoint that a high heat insulation improvement effect is obtained, the average particle diameter of the graphite is preferably 0.1 to 50 μm, and more preferably 1 to 20 μm. The average particle diameter of the graphite powder can be measured by dispersing the graphite powder in water and using a laser diffraction scattering method or the like. Specifically, the average particle size can be determined by the particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction scattering method.

Further, in the pre-expanded particles obtained by pre-expanding the expandable resin particles, the content (% by mass) of the (meth) acrylic acid component unit in the particle surface portion is the content of the (meth) acrylic acid component unit in the entire particle. It is preferably lower than the rate (mass%).
In this case, it is possible to maintain the inherent fusing property of the polystyrene-based resin expanded particles, and to easily fuse the pre-expanded particles to each other at the time of molding, and to obtain a foamed particle molded body particularly excellent in strength. Moreover, the foamed particle molded body excellent in surface appearance can be obtained.

Moreover, in the said foamable resin particle, it is preferable that the glass transition temperature of the styrene- (meth) acrylic acid copolymer in base-material resin is 110-130 degreeC, and it is more preferable that it is 110-120 degreeC. . When the glass transition temperature of the styrene- (meth) acrylic acid copolymer is within the above range, the balance between the foamability of the foamable resin particles and the heat resistance of the resulting foamed molded article is excellent.
The glass transition temperature of the styrene- (meth) acrylic acid copolymer is from a foamable resin particle, its foamed particle, or its foamed particle molded body to a styrene resin using a press machine heated to a temperature of 180 ° C. This film is obtained by performing differential scanning calorimetry (DSC) on this film. In the above-mentioned expandable resin particles, a baseline shift is usually observed at two locations in a DSC curve obtained by differential scanning calorimetry. These are derived from the glass transition temperature derived from the polystyrene resin observed on the low temperature side (for example, around 100 ° C.) and the styrene- (meth) acrylic acid copolymer observed on the high temperature side (for example, around 120 ° C.), respectively. The glass transition temperature to be shown. And let the glass transition temperature observed on the high temperature side be a glass transition temperature of a styrene- (meth) acrylic acid copolymer.

The expandable resin particles preferably contain 0.5 to 10 parts by mass of a brominated flame retardant with respect to 100 parts by mass of the base resin.
In this case, flame retardancy can be imparted to the expandable resin particles. When the amount of the brominated flame retardant is too small, there is a possibility that sufficient flame retardancy cannot be obtained. On the other hand, as the blending amount increases, the moldability of the pre-expanded particles obtained by foaming the expandable resin particles tends to decrease, and the mechanical properties of the obtained expanded particle molded body tend to decrease. From this viewpoint, in the expandable resin particles, the amount of the brominated flame retardant is preferably 0.5 to 10 parts by mass as described above with respect to 100 parts by mass of the base resin. More preferably, it is mass%.

  Examples of brominated flame retardants include 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5′-dibromophenyl] propane, 2,2-bis [4. '-(2 ", 3" -dibromopropoxy) -3', 5'-dibromophenyl] propane, 2,2-bis [4 '-(2 ", 3" -dibromo-2-methylpropoxy) -3' , 5′-dibromophenyl] sulfone, 2,2-bis [4 ′-(2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] sulfone, 1,3,5-tris (2 ′ , 3′-Dibromo-2′-methylpropyl) isocyanurate, 1,3,5-tris (2 ′, 3′-dibromopropyl) isocyanurate, 2,4,6-tribromophenol-2 ′, 3 ′ -Dibromo-2'-methylpropyl ether 2,4,6-tribromophenol-2 ′, 3′-dibromopropyl ether, 1,2,5,6,9,10-hexabromocyclododecane, 1,2,5,6-tetrabromocyclooctane, etc. A brominated polymer such as brominated styrene-butadiene copolymer, brominated polystyrene, brominated epoxy resin, or the like can also be used. Alternatively, it is possible to use two or more kinds, preferably 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5 ′ as the brominated flame retardant. -Dibromophenyl] propane and 2,2-bis [4 '-(2 ", 3" -dibromopropoxy) -3', 5'-dibromophenyl] propane are preferably used in combination.

The expandable resin particles are obtained by impregnating and polymerizing seed particles mainly composed of the styrene- (meth) acrylic acid copolymer and impregnating the foaming agent.
In this case, a sea-island structure having a styrene- (meth) acrylic acid copolymer as a continuous phase and a polystyrene resin as a dispersed phase over a wide blending ratio of styrene- (meth) acrylic acid copolymer and polystyrene resin is shown. Expandable resin particles can be obtained. Such expandable resin particles have excellent foamability as described above. Furthermore, in this case, expandable resin particles in which the content of the (meth) acrylic acid component unit in the particle surface portion is lower than the content of the (meth) acrylic acid component unit in the entire particle can be easily obtained. Since such expandable resin particles are particularly excellent in fusibility as described above, by using the expandable resin particles, it is possible to obtain a expanded particle molded body excellent in strength and surface appearance.

Next, a preferred embodiment of the method for producing the expandable resin particles will be described.
The said expandable resin particle can be manufactured by performing a suspension process, an impregnation polymerization process, and a foaming agent impregnation process.
In the suspending step, first, seed particles containing a styrene- (meth) acrylic acid copolymer as a main component and containing graphite are prepared.
As the styrene- (meth) acrylic acid copolymer used for the seed particles, a styrene- (meth) acrylic acid copolymer obtained by a known polymerization method can be used. The styrene- (meth) acrylic acid copolymer is a copolymer of (meth) acrylic acid and styrene, but contains (meth) acrylic acid or another vinyl compound that can be copolymerized with styrene in the molecule. You may do. Examples of such vinyl compounds include aromatic vinyl compounds such as α-methylstyrene, p-methylstyrene, t-butylstyrene, and divinylbenzene. Moreover, there are (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. As the vinyl compound, one or two or more selected from these aromatic vinyl compounds, (meth) acrylic acid alkyl esters and the like can be used. In order to make the glass transition temperature derived from the styrene- (meth) acrylic acid copolymer of the base resin into the above range, the glass transition temperature is 110 to 135 ° C as the styrene- (meth) acrylic acid copolymer. It is preferable to use a thing, and the thing of 115-130 degreeC is more preferable.

The seed particles contain a polystyrene resin in advance. In this case, the impregnation property of styrene can be improved. As a result, it is possible to easily obtain expandable resin particles having excellent foamability and fusion property. In this case, the yield of the expandable resin particles can be increased.
Therefore, when a styrene- (meth) acrylic acid copolymer is used as the styrenic polymer, the seed particles are obtained by melt-kneading a styrene- (meth) acrylic acid copolymer and a polystyrene resin. The mass ratio of the styrene- (meth) acrylic acid copolymer and the polystyrene resin in the seed particles is 99: 1 to 70:30 (provided that the styrene- (meth) acrylic acid copolymer: polystyrene resin). Preferably). The mass ratio of the styrene- (meth) acrylic acid copolymer and the polystyrene resin in the seed particles is more preferably 95: 5 to 75:25. Furthermore, as described above, when using seed particles obtained by melt-kneading a styrene- (meth) acrylic acid copolymer and a small amount of polystyrene resin, the content (parts by mass) of the polystyrene resin in the seed particles is used. The ratio of the amount of styrene added to the suspension (parts by mass) is preferably 2 or more, and more preferably 3 or more. That is, when the mass of the polystyrene resin in the seed particles is M _A (parts by mass) and the amount of styrene added to the suspension is M _B (parts by mass), M _B / M _A ≧ 2 is preferable. _B / M _A ≧ 3 is more preferable.

  The seed particles can be produced by blending the styrene- (meth) acrylic acid copolymer, graphite powder, and polystyrene resin, and melt-kneading and then finely granulating the seed particles. The graphite powder can be blended with the seed particles in the form of a powder or a master batch. Melt kneading can be performed by an extruder. The graphite content in the seed particles may be appropriately adjusted so that the graphite content in the expandable resin particles is 0.1 to 6 parts by mass with respect to 100 parts by mass of the base resin. It is preferable that 0.12 to 30% by mass of graphite is blended in.

Moreover, when producing the expandable resin particle containing a flame retardant as described above, it is preferable to add a flame retardant to the seed particles. The flame retardant is preferably blended into the styrene- (meth) acrylic acid copolymer and graphite as a powder or as a master batch.
The seed particles can contain additives such as a bubble regulator, a pigment, a slip agent, an antistatic agent, and a plasticizer as long as the effects of the present invention are not impaired.

Examples of the air conditioner include aliphatic monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bis stearic acid, methyl methacrylate copolymer, and silicone.
As the plasticizer, fatty acid esters such as glycerin tristearate, glycerin trioctoate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, butyl stearate, glycerin diacetomonolaurate can be used. Moreover, organic compounds, such as a cyclohexane and a liquid paraffin, can also be used.
Commercially available products and known products can be used as the pigment, slip agent, and antistatic agent.

Moreover, in order to obtain the expandable resin particles capable of obtaining a foamed particle molded body having excellent heat insulation properties, the graphite powder is uniformly distributed in the styrene- (meth) acrylic acid copolymer of the seed particles. It is preferable to disperse. Therefore, for example, melt kneading is preferably performed using a single-screw extruder or a twin-screw extruder of a high kneading type screw such as a dalmage type, a Maddock type, or a unimelt type.
The seed particles can be refined by melt-kneading with an extruder, and then by a strand cut method, a hot cut method, an underwater cut method, or the like. Any other method can be used as long as the desired particle size can be obtained.

  If the weight of the seed particles is too small, the productivity of the seed particles may be significantly reduced. On the other hand, when the weight of the seed particles is too large, the particle diameter of the expandable resin particles increases, and the particle diameter of the pre-expanded particles obtained accordingly increases. As a result, the filling property of the pre-expanded particles into the mold may be deteriorated during the molding in the mold. From this viewpoint, the particle weight of the seed particles is preferably 0.1 to 3 mg, more preferably 0.3 to 1.5 mg. In addition, when using an extruder, adjustment of particle weight can be performed by extruding resin from the hole which has a diameter of about 0.5-2 mm, for example, and changing cut speed.

Next, in the suspension step, the seed particles are suspended in an aqueous medium to obtain a suspension. Dispersion in the aqueous medium can be performed using, for example, a closed container equipped with a stirrer. Examples of the aqueous medium include deionized water.
The seed particles are preferably dispersed in an aqueous medium together with a suspending agent. As the suspending agent, for example, hydrophilic polymers such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone and the like can be used. In addition, a poorly water-soluble inorganic salt such as tricalcium phosphate or magnesium pyrophosphate can also be used as a suspending agent. Furthermore, you may use surfactant together as needed. When using a poorly water-soluble inorganic salt, it is preferable to use an anionic surfactant such as sodium alkyl sulfonate, sodium dodecylbenzene sulfonate, disodium dodecyl diphenyl ether sulfonate, sodium α-olefin sulfonate. .

  As for the usage-amount of a suspension agent, 0.01-5 mass parts is preferable with respect to 100 mass parts of seed particles. As described above, when the poorly water-soluble inorganic salt and the anionic surfactant are used in combination, 0.05 to 3 parts by weight of the poorly water-soluble inorganic salt and the anionic surfactant are used with respect to 100 parts by weight of the seed particles. Is preferably used in an amount of 0.0001 to 0.5 parts by mass. The above-mentioned surfactants can be used alone or in combination. Preferably, an anionic surfactant is used. More preferably, it is an alkylsulfonic acid alkali metal salt (preferably a sodium salt) having 8 to 20 carbon atoms. Thereby, the suspension can be sufficiently stabilized.

  In addition, an electrolyte such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate, sodium acetate, or sodium succinate may be added to the above suspension as necessary. Can do.

Next, in the impregnation polymerization step, styrene is added to the suspension, and the seed particles are impregnated and polymerized with styrene, and styrene using a styrene- (meth) acrylic acid copolymer and a polystyrene resin as a base resin. System resin particles are obtained.
When impregnating the seed particles with styrene, not only styrene but also α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-ethylstyrene, 2,4-dimethyl Styrene, p-methoxystyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, pn-butylstyrene, pt-butylstyrene, p- Aromatic vinyl compounds such as n-hexyl styrene, p-octyl styrene, divinylbenzene, styrene sulfonic acid, sodium styrene sulfonate and the like can be impregnated with styrene. One or more aromatic vinyl compounds can be used. If necessary, vinyl compounds such as (meth) acrylic acid alkyl esters such as methyl (meth) acrylate and ethyl (meth) acrylate (butyl) can be copolymerized with aromatic vinyl compounds. You can also
In addition, when the said monomer other than styrene is added with styrene and it is made to copolymerize with styrene in a seed particle, the copolymer is made into a polystyrene resin. In this case, the glass transition temperature of the polystyrene resin in the base resin is preferably less than 110 ° C, more preferably 105 ° C or less, further preferably 102 ° C or less, and even more preferably 100 ° C or less. The blending ratio of monomers other than styrene can be appropriately set within a range that satisfies the glass transition temperature of the polystyrene resin. The mixing ratio of monomers other than styrene is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 0% by mass, that is, only styrene is used. Is good.

The amount of styrene added may be adjusted so that the mass ratio of the styrene- (meth) acrylic acid copolymer in the base resin of the expandable resin particles is 20 to 80% by mass, but the styrene in the seed particles -It is preferable that it is 25-400 mass parts with respect to 100 mass parts of methacrylic acid copolymers. More preferably, it is 40-150 mass parts, More preferably, it is 50-120 mass parts.
In addition, the mass ratio of the polystyrene resin in the base resin is such that the content of the polystyrene resin present in the seed particles in advance, the blending amount of styrene, and the blending amount of the other monomers added as necessary. It can be obtained from

  In order to uniformly polymerize styrene in the seed particles, it is preferable to perform polymerization by impregnating the seed particles with styrene and a polymerization initiator. Further, when the seed particles are impregnated with styrene for polymerization, the addition of styrene may be performed all at once or divided into a plurality of times. Moreover, a polymerization initiator may be dissolved in styrene and added, or a polymerization initiator may be added alone.

Examples of the polymerization initiator include organic peroxides and azo compounds that are soluble in styrene and have a 10-hour half-life temperature of 50 to 120 ° C. Organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl peroxybenzoate, benzoyl peroxide, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl mono Carbonate, t-amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, lauroyl peroxide, dicumyl peroxide, 2,5-t-butyl perbenzoate, 1,1-bis-t-butyl Peroxycyclohexane, cumene hydroxy peroxide, dicumyl peroxide and the like can be used. As the azo compound, azobisisobutyronitrile and the like can be used. These polymerization initiators can be used alone or in combination of two or more. As for the usage-amount of a polymerization initiator, 0.01-3 mass parts is preferable with respect to 100 mass parts of styrene.
Although superposition | polymerization temperature changes with kinds of polymerization initiator to be used, it is preferable to set it as 60-120 degreeC.

Next, in the foaming agent impregnation step, the foaming agent is impregnated in the resin particles.
Impregnation with the blowing agent can be performed during or after the polymerization of styrene.
Specifically, a foaming agent is press-fitted into a container containing the resin particles during or after polymerization, and the resin particles are impregnated with the foaming agent.

Further, after impregnation with the foaming agent, the foamable resin particles can be dehydrated and dried, and the surface coating agent can be coated on the surface of the foamable resin particles as necessary.
Examples of the surface coating agent include zinc stearate, stearic acid triglyceride, stearic acid monoglyceride, castor oil, and antistatic agent. The amount of the surface coating agent added is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the expandable resin particles.

The expandable resin particles can be used for heating and pre-expanding the expandable resin particles and fusing the obtained pre-expanded particles together in a mold to obtain a expanded particle molded body.
As a method of heating and foaming the expandable resin particles, specifically, there is a method of supplying a heating medium such as steam to the expandable resin particles. Thereby, expandable resin particles can be expanded to obtain pre-expanded particles. In addition, it is preferable that the bulk density of the pre-expanded particles obtained is 10 to 100 kg / m ³ , and more preferably 12 to ³⁰ kg / m ³ .

In the expanded particles, the ratio of the content of (meth) acrylic acid monomer units in the vicinity of the surface of the expanded particles to the content of (meth) acrylic acid monomer units in the entire expanded particles is 90% by mass or less. It is preferably 60 to 85% by mass. In this case, it becomes easy to obtain a foamed particle molded body having a high degree of fusion inside the molded body.
A foamed particle molded body can be obtained by molding the foamed particles in a mold by a known molding means. Incidentally, it is preferable that the density of the obtained foamed bead molded article is 10 to 100 kg / m ^3, more preferably 12~30kg / m ^3.

Example 1
(1) Preparation of seed particles Using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 87 parts by mass of a styrene-methacrylic acid copolymer (PS Japan, G9001: glass transition temperature 121 ° C.), graphite 13 parts by mass of a master batch (average particle diameter of graphite powder: about 15 μm, graphite concentration: 40% by mass, base resin (polystyrene): remainder) was melt-kneaded. The molten resin was extruded in a strand form from a die having a hole diameter of 1.4 mm. The extrudate was immediately introduced into a water bath, cooled, and then cut to produce about 0.8 mg / piece of cylindrical pellets (seed particles). Thus, seed particles were obtained.

(2) Production of expandable resin particles 788 g of deionized water, 4.6 g of sodium pyrophosphate, and 11.4 g of magnesium nitrate were put into an autoclave with a stirrer and a volume of 3 L, and suspended in the autoclave by salt exchange. Magnesium pyrophosphate as a suspending agent was synthesized. Next, 0.2 g of sodium alkyl sulfonate as a surfactant, 6 g of sodium chloride and 3 g of sodium nitrate as an electrolyte, and 414 g of seed particles were added to this suspension. In this way, the seed particles were suspended in an aqueous medium to obtain a suspension.

  Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 72 ° C. while stirring the suspension at 350 rpm. In addition, 146 g of deionized water, 0.12 g of sodium alkyl sulfonate, 87 g of styrene, 2.1 g of benzoyl peroxide (manufactured by NOF Corporation, Nyper BW), t-butylperoxy-2-ethylhexyl monocarbonate (Kayaku Akzo) Manufactured by Trigonox 117), 2.4 g of dicumyl peroxide (manufactured by NOF Corporation, Park Mill D) 3.0 g was adjusted to an emulsion using a homogenizer. Then, after the temperature in the autoclave reached the above-mentioned 72 ° C., the emulsion was put into the autoclave. Subsequently, after keeping the inside of the autoclave at a temperature of 72 ° C. for 1 hour, the temperature was raised to 93 ° C. over 4 hours. After reaching the temperature of 93 ° C., the temperature was maintained at 93 ° C. for 3 hours, and the temperature was further increased to 120 ° C. over 3 hours. Next, this temperature was maintained at 120 ° C. for 2 hours, and then cooled to room temperature. During the temperature increase from 72 ° C. to 93 ° C., 190 g of styrene was continuously added into the autoclave over 4 hours. Moreover, 83 hours of pentane (80% of n-pentane, 20% of i-pentane) as a blowing agent was added to the autoclave over 30 minutes after the temperature reached 93 ° C., and the resin particles were impregnated with the blowing agent. It was.

After the inside of the autoclave was cooled to room temperature, expandable resin particles containing a foaming agent were taken out from the autoclave. The foamable resin particles were washed with dilute nitric acid to dissolve and remove the suspending agent attached to the resin particle surfaces. Subsequently, it was washed with water and dehydrated with a centrifuge. Next, after coating 0.01 parts by mass of an alkyldiethanolamine as an antistatic agent with respect to 100 parts by mass of the expandable resin particles, moisture on the surface of the resin particles was removed by fluid drying (room temperature air, 10 minutes). . 100 parts by mass of the obtained expandable resin particles were coated with 0.1 part by mass of zinc stearate as an antiblocking agent and 0.05 part by mass of glycerin monostearate as an antistatic agent.
In this way, expandable resin particles were obtained.

(3) Production of foamed particle molded body 500 g of the foamable resin particles obtained as described above was charged into a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine to obtain foaming resin particles. Was heated and foamed to obtain pre-expanded particles having a bulk density of about 20 kg / m ³ . The obtained pre-expanded particles were aged at room temperature for 1 day, and then filled in a mold of a mold molding machine (DSM-0705VS manufactured by DABO). Then, the pre-expanded particles filled in the mold with steam of 0.09 MPa (gauge pressure) were heated for 15 seconds. As a result, the pre-expanded particles were fused to each other in the mold. Next, after cooling the inside of the mold for a predetermined time, a foamed particle molded body obtained by fusing the pre-foamed particles with each other was taken out from the mold.
In this way, a foamed particle molded body was obtained.
In the production method of this example, the amount of graphite (mass%) and the amount of PS (mass%) in the seed particles, the amount of styrene added, the composition of the base resin (resin composition; parts by mass), the blending ratio of various additives, etc. The manufacturing conditions are shown in Table 1 described later. Tables 1 and 3 show similar production conditions for Examples 2 to 11 and Comparative Examples 1 to 5 described later.

(Example 2)
This example is an example in which the compounding of seed particles and styrene is changed from Example 1, and a flame retardant is further added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 78 parts by mass of a styrene-methacrylic acid copolymer, 13 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 9 A mass part was melt-kneaded. As the styrene-methacrylic acid copolymer and the graphite masterbatch, the same ones as in Example 1 were used, and the brominated flame retardant masterbatch had a composition of 2,2-bis [4 ′-(2 ″, 3 "-dibromo-2" -methylpropoxy) -3 ', 5'-dibromophenyl] propane: 23% by mass, 2,2-bis [4'-(2 ", 3" -dibromopropoxy) -3 ', 5′-dibromophenyl] propane: 15% by mass, base resin (polystyrene): the remainder was used Next, the molten resin was extruded in a strand shape in the same manner as in Example 1, cooled, and then cut. Cylindrical seed particles were prepared.

Next, expandable resin particles were produced using the seed particles. In the foamable resin particles of this example, Example 1 was used except that the amount of seed particles added was changed to 449 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 155 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 3)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 74 parts by mass of a styrene-methacrylic acid copolymer, 15 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 11 A mass part was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In preparing the expandable resin particles of this example, first, a suspension of magnesium pyrophosphate was synthesized in an autoclave in the same manner as in Example 1 except that the amount of deionized water was changed to 642 g. did.
Next, 0.2 g of sodium alkyl sulfonate as a surfactant, 6 g of sodium chloride, 3 g of sodium nitrate as an electrolyte, and 345 g of seed particles were charged into the autoclave in which the suspension was synthesized. In this way, the seed particles were suspended in an aqueous medium to obtain a suspension.

  Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 72 ° C. while stirring the suspension at 350 rpm. In addition, 146 g of deionized water, 0.12 g of sodium alkyl sulfonate, 87 g of styrene, 2.4 g of t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by Kayaku Akzo, Trigonox 117), dicumyl peroxide (NOF) A mixture of 3.0 g (Park Mill D) was adjusted to an emulsion with a homogenizer. This is hereinafter referred to as Emulsion A. And after the temperature in an autoclave reached the above-mentioned 72 ° C, emulsified liquid A was supplied into an autoclave. Further, a mixture of 146 g of deionized water, 0.12 g of sodium alkyl sulfonate, 70 g of styrene, and 2.1 g of benzoyl peroxide (manufactured by NOF Corporation, Nyper BW) was adjusted to an emulsion using a homogenizer. This is hereinafter referred to as emulsion B. And 1 hour after the temperature in the autoclave reached the above-mentioned 72 ° C., the emulsion B was charged into the autoclave.

And after hold | maintaining the inside of an autoclave for 2 hours at the temperature of 72 degreeC, while heating on the conditions similar to Example 1, styrene and pentane were added. In this way, expandable resin particles were produced.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 4)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 78 parts by mass of a styrene-methacrylic acid copolymer, 13 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 9 A mass part was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In the foamable resin particles of this example, Example 1 was used except that the amount of seed particles charged was changed to 483 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 121 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 5)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 61 parts by mass of a styrene-methacrylic acid copolymer, 21 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 18 A mass part was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. The expandable resin particles of this example were produced in the same manner as in Example 1 except that the seed particles produced in this example were used.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 6)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 87.5 parts by mass of a styrene-methacrylic acid copolymer, 7.5 parts by mass of a graphite masterbatch, 5 parts by mass of a fuel master batch was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. The expandable resin particles of this example were the same as in Example 1 except that the amount of seed particles was changed to 431 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 173 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 7)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 69 parts by mass of a styrene-methacrylic acid copolymer, 18 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 13 A mass part was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In producing the expandable resin particles of this example, first, a suspension of magnesium pyrophosphate was synthesized in an autoclave in the same manner as in Example 1.
Next, 0.2 g of sodium alkyl sulfonate as a surfactant, 6 g of sodium chloride and 3 g of sodium nitrate as an electrolyte, and 311 g of seed particles were charged into the autoclave in which the suspension was synthesized. In this way, the seed particles were suspended in an aqueous medium to obtain a suspension.

  Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 72 ° C. while stirring the suspension at 350 rpm. Moreover, the emulsion A similar to Example 3 was produced, and after the temperature in the autoclave reached the above-mentioned 72 ° C., the emulsion A was charged into the autoclave. Further, an emulsion B similar to that of Example 3 was prepared, and this emulsion B was charged into the autoclave 1 hour after the temperature in the autoclave reached 72 ° C. described above.

The autoclave was held at a temperature of 72 ° C. for 2 hours, and then foamed in the same manner as in Example 1 except that the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 224 g. Resin particles were prepared.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 8)
This example is an example in which the blending of seed particles and styrene is further changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 83.5 parts by mass of a styrene-methacrylic acid copolymer, 10 parts by mass of a graphite master batch, and a brominated flame retardant master. 6.5 parts by mass of the batch was melt-kneaded. The same styrene-methacrylic acid copolymer and graphite masterbatch as those used in Example 1 were used, and the same bromine-based flame retardant masterbatch as used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. The expandable resin particles of this example are the same as in Example 1 except that the amount of seed particles added was changed to 552 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 52 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

Example 9
This example is an example in which the blending of seed particles and styrene and the average particle diameter of graphite are changed from Example 1, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 78 parts by mass of a styrene-methacrylic acid copolymer, 13 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 9 A mass part was melt-kneaded. In this example, as the graphite masterbatch, a graphite powder having an average particle size of about 5 μm, a graphite concentration of 40% by mass, and a base resin (polystyrene): the balance was used. Further, the same styrene-methacrylic acid copolymer as in Example 1 was used, and the same brominated flame retardant masterbatch as in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. The expandable resin particles of this example were the same as in Example 1 except that the amount of seed particles was changed to 431 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 173 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 10)
This example is different from Example 1 in that the type of styrene-methacrylic acid copolymer, the blend of seed particles and styrene are changed, and a flame retardant is added to produce expandable resin particles, pre-expanded particles, and expanded particle molded bodies. This is an example.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 78 parts by mass of a styrene-methacrylic acid copolymer, 13 parts by mass of a graphite masterbatch, and a brominated flame retardant masterbatch 9 A mass part was melt-kneaded. In this example, as the styrene-methacrylic acid copolymer, Lurex A-14 (glass transition temperature 129 ° C.) manufactured by DIC was used. In addition, the same graphite masterbatch as in Example 1 was used, and the same bromine-based flame retardant masterbatch as in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In the foamable resin particles of this example, Example 1 was used except that the amount of seed particles added was changed to 449 g and the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 155 g. It produced similarly.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Example 11)
This example is different from Example 1 in that the composition of seed particles and styrene, the average particle diameter of graphite, and the composition of the foaming agent are changed, and further, a flame retardant is added to obtain expandable resin particles, pre-expanded particles, and expanded particle molded bodies. It is an example which produces.
Specifically, first, using a φ30 mm single screw extruder, at a temperature of 210 to 230 ° C., 48.4 parts by mass of a styrene-methacrylic acid copolymer, 4.6 parts by mass of a polystyrene resin, and 8 parts by mass of a graphite master batch. And 9 parts by mass of a brominated flame retardant master batch were melt-kneaded. As the styrene-methacrylic acid copolymer, the same one as in Example 1 was used, and as the polystyrene resin, “679” (weight average molecular weight 180,000) manufactured by PS Japan Ltd. was used. In this example, as the graphite masterbatch, a graphite powder having an average particle size of about 5 μm, a graphite concentration of 40% by mass, and a base resin (polystyrene): the balance was used. Further, the same brominated flame retardant master batch as that used in Example 2 was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In the foamable resin particles of this example, the amount of seed particles added was changed to 431 g, the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 173 g, and pentane (n-pentane as a blowing agent) was changed. 80%, i-pentane 20%) 72 g and butane (n-butane 65%, i-butane 35%) 22 g were used in the same manner as in Example 1 except that 22 g was used in combination.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

  In Examples 1 to 11 described above, styrene- (meth) acrylic acid copolymer and polystyrene were obtained by impregnating and polymerizing seed particles containing styrene- (meth) acrylic acid copolymer (seed polymerization). Expandable resin particles having a base resin as a composite resin with a resin were prepared. On the other hand, the following Comparative Examples 1 to 3 are obtained by melting and kneading a styrene- (meth) acrylic acid copolymer and a polystyrene resin without impregnating seed particles with styrene and polymerizing them. It is an example which produces the expandable resin particle which uses mixed resin as base resin.

(Comparative Example 1)
Specifically, first, using a φ26 mm same-direction twin screw extruder, at a temperature of 200 ° C., 52 parts by mass of a styrene-methacrylic acid copolymer, 35 parts by mass of a polystyrene resin, 7.5 parts by mass of a graphite master batch, bromine 5.5 parts by mass of the flame retardant master batch of the system flame was kneaded. In this example, polystyrene “680” (weight average molecular weight 180,000) manufactured by PS Japan Co., Ltd. was used as the polystyrene resin. Moreover, as a styrene-methacrylic acid copolymer and a graphite masterbatch, the thing similar to Example 1 was used, and the thing similar to Example 2 was used as a brominated flame retardant masterbatch.
Next, the molten resin was extruded in a strand shape from a small hole having a hole diameter of 1.5 mm, immediately introduced into a water bath, cooled, and then cut to obtain 4 mg / piece of cylindrical mixed resin particles on average.

  Next, 900 g of deionized water, 4.6 g of sodium pyrophosphate, and 11.4 g of magnesium nitrate are added to an autoclave with a 3 L internal volume equipped with a stirrer, and pyrophosphoric acid as a suspending agent in the autoclave by salt exchange. Magnesium was synthesized. Next, 0.3 g of sodium alkyl sulfonate as a surfactant, 6 g of sodium chloride and 3 g of sodium nitrate as an electrolyte, 600 g of the mixed resin particles, dicumyl peroxide (manufactured by NOF Corporation, Park Mill D) ) 3.0 g was charged. In this way, the mixed resin particles were suspended in an aqueous medium to obtain a suspension.

Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 120 ° C. while stirring the suspension at 350 rpm. Then, after reaching the temperature of 120 ° C., 72 g of pentane (n-pentane 80%, i-pentane 20%) as a blowing agent was added to the autoclave over 30 minutes to impregnate the mixed resin particles with the blowing agent. After the inside of the autoclave was cooled to room temperature, the expandable resin particles were taken out from the autoclave. Next, in the same manner as in Example 1, foaming resin particles were obtained by performing washing, dehydration, coating with an antistatic agent and an antiblocking agent.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Comparative Example 2)
In this example, a polystyrene resin having a molecular weight different from that of Comparative Example 1 is used, and a mixed resin showing a sea-island structure in which a styrene- (meth) acrylic acid copolymer is a continuous phase and a polystyrene resin is a dispersed phase is used as a base resin. This is an example of producing expandable resin particles using as a base resin a mixed resin in which the sea-island structure of the expandable resin particles of Comparative Example 1 is reversed.
Specifically, polystyrene “GX-154” (weight average molecular weight 270,000) manufactured by PS Japan Co., Ltd. is used as the polystyrene resin, and melt kneaded and melted at a temperature of 200 ° C. with a φ30 mm same-direction twin screw extruder. Comparative Example 1 except that the resin was extruded in a strand shape from a small hole having a hole diameter of 1.0 mm, immediately introduced into a water tank, cooled, and then cut to produce 1.5 mg / piece of cylindrical mixed resin particles on average. In the same manner, mixed resin particles were obtained.

  Next, 900 g of deionized water, 4.6 g of sodium pyrophosphate, and 11.4 g of magnesium nitrate are added to an autoclave with a 3 L internal volume equipped with a stirrer, and pyrophosphoric acid as a suspending agent in the autoclave by salt exchange. Magnesium was synthesized. Next, 0.3 g of sodium alkyl sulfonate as a surfactant, 9 g of sodium chloride and 4.5 g of sodium nitrate as an electrolyte, 600 g of the mixed resin particles, dicumyl peroxide (manufactured by NOF Corporation, Park Mill D) 2.6 g was charged. In this way, the mixed resin particles were suspended in an aqueous medium to obtain a suspension.

Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 120 ° C. while stirring the suspension at 350 rpm. Then, after reaching the temperature of 120 ° C., 78 g of pentane (n-pentane 80%, i-pentane 20%) as a foaming agent was added to the autoclave over 30 minutes to impregnate the mixed resin particles with the foaming agent. After the inside of the autoclave was cooled to room temperature, the expandable resin particles were taken out from the autoclave. Next, in the same manner as in Example 1, foaming resin particles were obtained by performing washing, dehydration, coating with an antistatic agent and an antiblocking agent.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Comparative Example 3)
This example is an example in which expandable resin particles using a mixed resin of a styrene-methacrylic acid copolymer and a polystyrene resin having a higher mass ratio of styrene-methacrylic acid copolymer than Comparative Example 2 as a base resin were prepared. It is.

Specifically, first, by a same-direction twin screw extruder of φ30 mm, at a temperature of 200 ° C., 66 parts by weight of a styrene-methacrylic acid copolymer, 21 parts by weight of a polystyrene resin, 7.5 parts by weight of a graphite master batch, bromine-based 5.5 parts by weight of a flame retardant master batch was melt-kneaded. In this example, the same styrene-methacrylic acid copolymer and graphite masterbatch as in Example 1 were used, the same polystyrene resin as in Comparative Example 1 was used, and the brominated flame retardant masterbatch was carried out. The same as in Example 2 was used.
Next, the molten resin was extruded in a strand shape from a small hole having a hole diameter of 1.0 mm, immediately introduced into a water tank, cooled, and then cut to produce 1.5 mg / piece of cylindrical mixed resin particles on average. And except for the point which used this mixed resin particle, it carried out similarly to the comparative example 2, and obtained the expandable resin particle, the pre-expanded particle, and the expanded particle molded object.

(Example 12)
In this example, expandable resin particles are produced by increasing the mass ratio of polystyrene in the composite resin particles very high.

  Specifically, first, 70 parts by mass of a styrene-methacrylic acid copolymer and 30 parts by mass of a graphite master batch were melt-kneaded at a temperature of 210 to 230 ° C. using a φ30 mm single screw extruder. The same styrene-methacrylic acid copolymer and graphite master batch as those used in Example 1 were used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. In producing the expandable resin particles of this example, first, a suspension of magnesium pyrophosphate was synthesized in an autoclave in the same manner as in Example 1 except that the amount of deionized water was changed to 552 g. did.
Next, 0.2 g of sodium alkyl sulfonate as a surfactant, 6 g of sodium chloride and 3 g of sodium nitrate as an electrolyte, and 173 g of seed particles were charged into the autoclave in which the suspension was synthesized. In this way, the seed particles were suspended in an aqueous medium to obtain a suspension.

  Next, after the inside of the autoclave was purged with nitrogen, the autoclave was sealed, and the temperature inside the autoclave was raised to 72 ° C. while stirring the suspension at 350 rpm. In addition, a mixture of 146 g of deionized water, 0.12 g of sodium alkyl sulfonate, 34.8 g of styrene, t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by Kayaku Akzo, Trigonox 117) was emulsified with a homogenizer. Adjusted to liquid. This is hereinafter referred to as Emulsion C. And after the temperature in an autoclave reached the above-mentioned 72 ° C, emulsion C was thrown into the autoclave. A mixture of 146 g of deionized water, 0.12 g of sodium alkyl sulfonate, 24.4 g of styrene, and 2.1 g of benzoyl peroxide (manufactured by NOF Corporation, Nyper BW) was prepared into an emulsion using a homogenizer. This is hereinafter referred to as emulsion D. And 1 hour after the temperature in the autoclave reached the above-mentioned 72 ° C., the emulsion D was charged into the autoclave.

The autoclave was held at a temperature of 72 ° C. for 2 hours, and then foamed in the same manner as in Example 1 except that the amount of styrene added during the temperature increase from 72 ° C. to 93 ° C. was changed to 459 g. Resin particles were prepared.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

(Comparative Example 4)
In Examples 1 to 11, expandable resin particles obtained by impregnating and polymerizing styrene polymer seed particles containing polystyrene resin with styrene- (meth) acrylic acid copolymer and polystyrene resin as a base resin. Was made. On the other hand, in this example, styrene polymer seed particles not containing polystyrene resin are impregnated and polymerized with styrene to produce expandable resin particles using acrylonitrile-styrene copolymer and polystyrene resin as base resins. It is an example.

  Specifically, first, 80 parts by mass of acrylonitrile-styrene copolymer and 20 parts by mass of graphite masterbatch were melt-kneaded at a temperature of 220 to 240 ° C. using a φ30 mm single screw extruder. In this example, as the acrylonitrile-styrene copolymer, “AG-XGS” manufactured by Denki Kagaku Kogyo Co., Ltd. was used, and as the graphite master batch, the average particle diameter of the graphite powder: about 15 μm, the graphite concentration: 25% by mass, Base resin (acrylonitrile-styrene copolymer): the balance was used. Next, in the same manner as in Example 1, the molten resin was extruded into a strand shape, cooled, and then cut to produce cylindrical seed particles.

Next, expandable resin particles were produced using the seed particles. The expandable resin particles of this example were produced in the same manner as in Example 1 except that the seed particles produced in this example were used.
Further, using the expandable resin particles, pre-expanded particles were produced in the same manner as in Example 1, and further, using these pre-expanded particles, a foamed particle molded body was produced in the same manner as in Example 1.

About each expandable resin particle produced in the above Examples 1-12 and Comparative Examples 1-4, the content of the foaming agent, the glass transition temperature, the average molecular weight, the morphology observation of the expandable resin particle cross section, the average dispersed phase diameter Evaluation was performed as follows. Moreover, about each pre-expanded particle, content of the (meth) acrylic acid component unit in the skin and the whole, an average cell diameter, and a moldability were evaluated as follows. In addition, since the comparative example 5 did not contain a styrene- (meth) acrylic acid copolymer, the evaluation of the content, the form observation of the cross section of the expandable resin particles, and the evaluation of the average dispersed phase diameter were omitted. These results are shown in Tables 1 to 3.
Moreover, about each foamed particle molded object, the molded article density, the heating dimensional change rate, the combustibility, the oxygen index, and the thermal conductivity were evaluated as follows. However, these evaluations were omitted for Comparative Examples 1 to 3 and Comparative Example 5 in which good foamed particle molded bodies could not be produced. Moreover, about Example 1 and Comparative Examples 1-5 which do not contain a flame retardant, evaluation of combustibility and an oxygen index was abbreviate | omitted. The results are shown in Tables 2 and 3. Moreover, about the expanded particle molded object of Example 2 and the comparative example 1, the external appearance was taken in as image data with the scanner, and the result (digital photograph) is shown in FIG.2 and FIG.4, respectively.

(A) Foaming agent content Foamable resin particles were dissolved in dimethylformamide (DMF), the content of the added blowing agent was measured by gas chromatography, and the content of each component was totaled. Specifically, the quantitative determination of the blowing agent by gas chromatography was performed according to the following procedure.
First, about 5 g of cyclopentanol was precisely weighed to the third decimal place in a 100 mL volumetric flask (the weight at this time was set to Wi), and DMF was added to make a total of 100 mL. This DMF solution was further diluted 100 times with DMF to obtain an internal standard solution. Next, about 1 g of the expandable resin particles to be measured was precisely weighed to the third decimal place, and the weight at this time was defined as Ws (g). A precisely weighed sample of expandable resin particles was dissolved in about 18 mL of DMF, and 2 mL of the internal standard solution was accurately added to the lysate using a whole pipette. 1 μL of this solution was collected with a microsyringe and introduced into gas chromatography to obtain a chromatogram. The peak area of each foaming agent component and internal standard was determined from the obtained chromatogram, and the concentration of each component was determined by the following equation (1).
Concentration of each component (mass%) = [(Wi / 10000) × 2] × [An / Ai] × Fn ÷ Ws × 100 (1)
here,
Wi: Weight of cyclopentanol when the internal standard solution was prepared (g)
Ws: weight of sample dissolved in DMF (g)
An: Peak area of each foaming agent component at the time of gas chromatographic measurement Ai: Peak area of the internal standard substance at the time of gas chromatographic measurement Fn: Correction coefficient of each foaming agent component obtained from a calibration curve prepared in advance The above gas chromatographic analysis The conditions were as follows.
Equipment used: Gas chromatograph GC-6AM manufactured by Shimadzu Corporation
Detector: FID (hydrogen flame ionization detector)
Column material: Glass column with an inner diameter of 3 mm and a length of 5000 mm Column filler: [Liquid phase name] FFAP (free fatty acid), [Liquid phase impregnation rate] 10 mass%, [Carrier name] Diatomaceous earth Comasorb W for gas chromatography, [Carrier Particle size] 60/80 mesh, [carrier treatment method] AW-DMCS (washing, baking, acid treatment, silane treatment), [filling amount] 90 mL
Inlet temperature: 250 ° C
Column temperature: 120 ° C
Detector temperature: 250 ° C
Carrier gas: N ₂ , flow rate 40 ml / min

(B) Measurement of glass transition temperature (Tg) First, using a press machine heated to a temperature of 180 ° C., a styrenic resin film was prepared from the expandable resin particles, the pre-expanded particles, or the expanded particle molded body. A 2 to 4 mg test piece was cut out from this film, and a differential scanning calorimetry (DSC) analysis was performed on the test piece. The DSC measurement was performed according to JIS K 7121 (1987) using a DSC measuring apparatus “Q1000 DSC” manufactured by TI Instruments. And the midpoint glass transition temperature of the DSC curve obtained on temperature rising rate 10 degree-C / min conditions was calculated | required. The glass transition temperature derived from the polystyrene resin observed on the low temperature side was Tg1, and the glass transition temperature derived from the styrene- (meth) acrylic acid copolymer observed on the high temperature side was Tg2.

(C) Measurement of average molecular weight The average molecular weight (number average molecular weight, weight average molecular weight, Z average molecular weight) of the base resin of the expandable resin particles is measured by a gel permeation chromatography (GPC) method using polystyrene as a standard substance. be able to.
Specifically, using HLC-8320GPC EcoSEC manufactured by Tosoh Corporation, measurement was performed under the measurement conditions of eluent: tetrahydrofuran (THF), THF flow rate: 0.6 ml / min, and sample concentration: 0.1 wt%. As the column, a column in which TSK guard column Super H-H × 1 and TSK-GEL Super HM-H × 2 were connected in series was used. That is, the expandable resin particles or the expanded particles thereof or the molded particles thereof were dissolved in tetrahydrofuran (THF), and the molecular weight was measured by gel permeation chromatography (GPC). And the measured value was calibrated with standard polystyrene and the number average molecular weight, the weight average molecular weight, and the Z average molecular weight were calculated | required, respectively.

(D) Morphological observation of cross section of expandable resin particle The vicinity of the center of the expandable resin particle was cut out and embedded in an epoxy resin. After staining with ruthenium tetroxide, ultrathin sections were prepared with an ultramicrotome. This ultrathin slice was placed on a grid, and the cross section of the expandable resin particles was observed with a transmission electron microscope (JEM1010, manufactured by JEOL Ltd.). Transmission electron microscope (TEM) observation was performed under the conditions of an acceleration voltage of 100 kV and an observation magnification of 10,000 times. Then, the morphology of the base resin constituting the expandable resin particles was examined. The TEM photograph in the cross section of the expandable resin particle of Example 2 and Comparative Example 1 is shown in FIGS. 1 and 3, respectively.
Further, the average dispersed phase diameter was calculated from the TEM photograph. Specifically, for a TEM photograph, the diameter of 100 randomly selected dispersed phases (the longest diameter of each dispersed phase) was measured, and the average dispersed phase diameter (μm) was calculated by weighted averaging of the measured values. Asked. When the shape of the dispersed phase is, for example, a perfect circle, the diameter is the longest diameter of the dispersed phase. When the shape of the dispersed phase is, for example, an ellipse, the long diameter is the longest diameter of the dispersed phase.

(E) Measurement of content of (meth) acrylic acid component unit The content of the (meth) acrylic acid component unit was measured using a total reflection absorption measuring apparatus. As the total reflection absorption measurement, an infrared spectrophotometer “FT / IR-460plus” manufactured by JASCO Corporation and a total reflection absorption measurement apparatus “ATR PRO 450-S type” manufactured by the same company were used. The measurement conditions on the total reflection absorption measuring apparatus side were prism: ZnSe and incident angle: 45 °.
Specifically, first, the pre-expanded particles were pressed against the prism of the total reflection absorption measuring apparatus, and the infrared absorption spectrum of the surface of the pre-expanded particles was measured. Next, the pre-expanded particles were hot-pressed at a temperature of 180 ° C. to produce a film, and the infrared absorption spectrum of the film was measured using a total reflection absorption measuring apparatus. This measured the infrared absorption spectrum of the whole pre-expanded particle. Next, after ATR correction was performed on the obtained infrared absorption spectrum, an absorbance I _{698 of 698} cm ⁻¹ derived from the styrene component unit and an absorbance I ₁₇₀₀ of ₁₇₀₀ cm ⁻¹ derived from the (meth) acrylic acid component unit were measured. The absorbance ratio (I ₁₇₀₀ / I ₆₉₈ ) was determined. And the content (mass%) of the (meth) acrylic acid component unit in the pre-expanded particle surface and the whole was calculated | required using the analytical curve created beforehand. For the 10 pre-expanded particles, the content of (meth) acrylic acid component units was measured in the same manner, and arithmetically averaged to obtain the content of (meth) acrylic acid component units on the surface and the whole of the pre-expanded particles (mass%). ) In addition, the ratio of the content of the (meth) acrylic acid component unit on the surface of the prefoamed particle to the content of the (meth) acrylic acid component unit in the entire prefoamed particle (skin / whole; percentage) was calculated.

The calibration curve was created as follows.
That is, first, using an extruder, a styrene-methacrylic acid copolymer (“G9001” manufactured by PS Japan) and a polystyrene resin (“680” manufactured by PS Japan) were converted into 100/0, 75/25, Pellets were prepared by melt-kneading at a weight ratio of 50/50, 25/75, and 0/100 (styrene-methacrylic acid copolymer / polystyrene resin). Next, the pellets were formed into a film by a press machine heated to a temperature of 180 ° C. The infrared absorption spectrum of the obtained film was measured using the above-mentioned total reflection absorption measuring apparatus. After ATR correction of this infrared absorption spectrum, the absorbances I ₆₉₈ and I ₁₇₀₀ were measured in the same manner as described above, and the absorbance ratio (I ₁₇₀₀ / I ₆₉₈ ) was determined. The content of the methacrylic acid component unit of the styrene-methacrylic acid copolymer (“G9001” manufactured by PS Japan) is set to 8.2% by elemental analysis, and the content of the (meth) acrylic acid component unit and the absorbance ratio A calibration curve was created.

(F) Measurement of average bubble diameter Using a razor blade, pre-expanded particles were cut into two so as to pass through the center thereof, and after vapor deposition (Au-Pd target), a scanning electron microscope (manufactured by Keyence Corporation, VE7800) Thus, a cross-section of the pre-expanded particles was photographed (observation magnification 30 times). In the obtained electron micrograph, draw a straight line so as to pass through the center of the pre-expanded particles, measure the actual length of the straight line, and the number of bubbles existing on the straight line, and calculate the diameter of the pre-expanded particles by the number of bubbles. To obtain a bubble diameter (μm). The cell diameter was measured in the same manner for 10 pre-expanded particles, and the average cell diameter was determined by arithmetic average.

(G) Evaluation of moldability The appearance of the expanded foam molded body prepared from the pre-expanded particles was visually observed and judged according to the following criteria.
A: When the surface of the molded body is smooth with few voids (gap between foamed particles).
○: When some voids are seen on the surface of the molded body, but the level is satisfactory as a product.
X: When it cannot shape | mold or when only a molded object with a big gap | interval between expanded particles from the molded object surface to the inside is obtained.

(H) Molded Product Density The volume was determined from the outer dimensions of the foamed particle molded body, then the mass of the foamed particle molded body was measured, and the mass was divided by the volume to calculate the molded product density.

(I) Measurement of heating dimensional change rate A plate-like test piece of 50 mm × 50 mm × 25 mm was cut out from the foamed particle molded body, and the test piece was left at a temperature of 23 ° C. for 1 day or more. Then, using a caliper, the vertical and horizontal dimensions of the test piece were measured to the second decimal place. Subsequently, the test piece after the dimension measurement was held for 22 hours (about 1 day) in a forced circulation oven set at a temperature of 80 ° C., 90 ° C., or 100 ° C. Thereafter, the test piece was taken out of the oven and allowed to stand at a temperature of 23 ° C. for 1 day. Subsequently, the dimension of the same place as before heating was measured, the heating dimensional change rate of each length and width was calculated from the following formula (2), and the arithmetic average value was defined as the heating dimensional change rate.
Heating dimensional change rate (%) = (dimension before heating−dimension after heating) × 100 / dimension before heating (2)

(J) Evaluation of flammability The evaluation of flammability was performed in accordance with the combustion test (Method A) of JIS A 9511 (2006). Specifically, the foamed particle molded body was first cured at a temperature of 40 ° C. for 3 days and at room temperature for 1 day. Thereafter, five test pieces having a rectangular parallelepiped shape of 200 mm × 25 mm × 10 mm were cut out from the foamed particle molded body. Next, using a candle, the test piece was ignited to the ignition limit indicator line and the combustion limit indicator line, and then the candle was quickly retracted from the test piece. And the time (flame extinction time) until the flame of a test piece disappeared from the moment which retracted the candle was measured.

(K) Measurement of oxygen index The oxygen index was measured in accordance with the test method of JIS K7201-2 (2007). In the measurement, the foamed particle molded body was allowed to stand at a temperature of 40 ° C. for 3 days, further cured at room temperature for 1 day, and then 15 specimens having dimensions of 150 mm × 10 mm × 10 mm cut out from the foamed particle molded body were produced. The oxygen index was measured for these specimens.

(L) Measurement of thermal conductivity Measured according to the heat flow meter method (HFM method) defined in JIS A 1412-2 (1999). In the measurement, the foamed particle molded body was allowed to stand at a temperature of 60 ° C. for 7 days, further cured at room temperature for 1 day, and then a test piece having a size of 200 mm × 200 mm × 25 mm cut out from the foamed particle molded body was produced. Then, the test piece is sandwiched between the heating plate and the cooling hot plate of the measuring device, and the thermal conductivity (W / m · K) is measured under the conditions of a test piece temperature difference of 20 ° C. and a test side average temperature of 23 ° C. went.

As shown in Tables 1 and 2, expandable resin particles according to examples using a composite resin obtained by impregnating and polymerizing styrene into seed particles mainly composed of a styrene- (meth) acrylic acid copolymer. Shows a low thermal conductivity of 0.034 W / m · K or less even when foamed to a low density of about 20 kg / m ³ , and is excellent in heat insulation. Moreover, when the expandable resin particle concerning an Example is used, it turns out that the expanded particle molded object which has the outstanding heat resistance that the heating dimensional change rate in the temperature of 80 degreeC and 90 degreeC is less than +/- 2% is obtained.

Moreover, as shown in Table 1 and Table 2, even if the expandable resin particle concerning an Example contains graphite, it becomes difficult to destroy a bubble film | membrane by graphite at the time of foaming, and shows the outstanding foam moldability. As a result, when these expandable resin particles were used, there were few gaps between the particles, and a foamed particle molded body having a good shape could be obtained (see FIG. 2).
Moreover, as known from Tables 1 and 2, flame retardancy could be imparted to the foamed particle molded body by adding a brominated flame retardant to the foamable resin particles according to the examples.

  On the other hand, the foamed resin particles of Comparative Examples 1 to 3 are obtained by adding a foaming agent to the mixed resin particles having a base resin as a mixed resin obtained by melt-kneading a polystyrene resin and a styrene- (meth) acrylic acid copolymer. It was produced by impregnation. In this case, as is known from Table 3, even if the base resin has a sea-island structure in which the polystyrene resin is a continuous phase and the styrene- (meth) acrylic acid copolymer is a dispersed phase, the styrene- Even when it has a sea-island structure with a (meth) acrylic acid copolymer as a continuous phase and a polystyrene resin as a dispersed phase, the foam moldability is insufficient and a good foamed particle molded body can be obtained. None (see FIG. 4). In addition, since the favorable expanded particle molded object was not obtained, evaluation of the expanded particle molded object was abbreviate | omitted about Comparative Examples 1-3 (refer Table 3).

Moreover, as shown in Table 3, in Example 12 where the ratio of the styrene- (meth) acrylic acid copolymer in the base resin is as low as 18 parts by mass, the dimensional change rate at a temperature of 90 ° C. is 3%, The heat resistance was poor.
Moreover, as shown in Table 3, in Comparative Example 4 using acrylonitrile-styrene copolymer and polystyrene resin as the base resin, the foam moldability is insufficient, and a good foamed particle molded body cannot be obtained. It was. In addition, since the favorable expanded particle molded object was not obtained, the evaluation of the expanded particle molded object was abbreviate | omitted about the comparative example 4 (refer Table 3).

Claims (7)

Expandable styrene resin particles containing graphite and an aliphatic hydrocarbon having 3 to 6 carbon atoms as a foaming agent,
The base resin of the expandable styrenic resin particles is formed by impregnating and polymerizing styrene polymer seed particles containing polystyrene resin,
Expandable styrenic resin particles, wherein the graphite content is 0.1 to 6 parts by mass with respect to 100 parts by mass of the base resin.   The expandable styrene resin particle according to claim 1, wherein the expandable styrene resin particle contains 0.5 to 10 parts by mass of a brominated flame retardant with respect to 100 parts by mass of the base resin. Characteristic foamable styrene resin particles.   The expandable styrenic resin particle according to claim 1 or 2, wherein the expandable styrene resin particle contains 1.2 to 5 parts by mass of a brominated flame retardant with respect to 100 parts by mass of the base resin. Expandable styrenic resin particles.   The expandable styrene resin particle according to claim 2 or 3, wherein the brominated flame retardant is 2,2-bis [4 '-(2 ", 3" -dibromo-2 "-methylpropoxy) -3'. , 5′-dibromophenyl] propane, 2,2-bis [4 ′-(2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] propane, 2,2-bis [4 ′-( 2 ", 3" -dibromo-2-methylpropoxy) -3 ', 5'-dibromophenyl] sulfone, 2,2-bis [4'-(2 ", 3" -dibromopropoxy) -3 ', 5' -Dibromophenyl] sulfone, 1,3,5-tris (2 ', 3'-dibromo-2'-methylpropyl) isocyanurate, 1,3,5-tris (2', 3'-dibromopropyl) isocyanurate 2,4,6-tribromopheno -2 ', 3'-dibromo-2'-methylpropyl ether, 2,4,6-tribromophenol-2', 3'-dibromopropyl ether, 1,2,5,6,9,10-hexabromo It is characterized in that it is one or more selected from cyclododecane, 1,2,5,6-tetrabromocyclooctane, brominated styrene-butadiene copolymer, brominated polystyrene, and brominated epoxy resin. Expandable styrenic resin particles.   The expandable styrene resin particle according to any one of claims 1 to 4, wherein the expandable styrene resin particle contains 2 to 15% by mass of the aliphatic hydrocarbon. Styrenic resin particles.   A styrene resin obtained by fusing pre-expanded particles obtained by heating and foaming the expandable styrene resin particles according to any one of claims 1 to 5 in a mold. Expanded particle molded body. In the method for producing expandable styrenic resin particles according to any one of claims 1 to 5,
A suspending step of suspending the styrenic polymer seed particles containing a polystyrene resin and containing graphite in an aqueous medium to obtain a suspension;
An impregnation polymerization step of adding the styrene to the suspension and impregnating and polymerizing the styrene polymer seed particles with the styrene to obtain styrene resin particles;
A foaming styrene comprising a foaming agent impregnation step of impregnating a resin particle with a foaming agent comprising an aliphatic hydrocarbon having 3 to 6 carbon atoms during and / or after the polymerization of styrene in the impregnation polymerization step For producing resin-based resin particles.