JP2012067215A - Styrene-based resin foam and method for producing foamable styrene-based resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam having satisfactory thermal insulation performance.SOLUTION: A styrene-based resin foam contains air bubbles enclosed with an air bubble film and having an average air bubble diameter of 100-300 μm, and slices (excluding a surface layer) of the styrene-based resin foam sliced in a thickness of 1 mm have an average infrared radiation transmittance of ≤20% in a wavenumber range of 400-1,000 cm.

Description

  The present invention relates to a styrene resin foam and a method for producing expandable styrene resin particles. More specifically, the present invention relates to a styrene resin foam excellent in heat insulation performance due to its low infrared transmittance and a method for producing expandable styrene resin particles that can be used in the production of the foam.

Styrenic resin foams are generally foamed by heating and foaming expandable styrene resin particles with steam or the like to form pre-expanded particles, which are filled into a closed mold having a large number of small holes, and heated again with pressurized steam or the like. It is manufactured by foaming, filling gaps between the foamed particles, and fusing the foamed particles together, then cooling and taking out from the mold.
The expandable styrene resin particles are usually produced by suspending and polymerizing a styrene monomer in water and impregnating with a foaming agent, or as disclosed in Japanese Patent Publication No. 49-2994 (Patent Document 1). The styrene resin particles are produced by a method of suspending styrene resin particles in water, supplying a styrene monomer continuously or intermittently thereto for polymerization, and impregnating with a foaming agent (seed polymerization method). Furthermore, it is manufactured by melting a styrene resin in an extruder, kneading a foaming agent, and then extruding it into a heated heating medium from a mold having small holes and cutting it into particles.

Styrenic resin foam is used, for example, as a wall material of a building by being sandwiched between panels as a heat insulating material. In such a use, since high heat insulation performance is requested | required of a styrene resin foam, it is desired to make heat conductivity as low as possible. Conventionally, a foam having an expansion ratio of about 30 to 40 times is frequently used for a styrene resin foam as a heat insulating material.
On the other hand, in the styrene resin foam, in order to reduce the manufacturing cost, it is necessary to reduce the amount of the styrene monomer used as a raw material or to reduce the thickness of the foam. Moreover, when the thickness of the foam is reduced, there is also an advantage that the living space can be widened. Therefore, there is a demand for a styrene resin foam capable of achieving higher foaming without reducing the heat insulating performance.

Japanese Patent Publication No. 57-34296 (Patent Document 2) discloses a method of obtaining a styrene resin foam in which a large number of fine bubbles are formed by containing a specific thiourea compound in a styrene resin particle together with a foaming agent. Are listed. Japanese Patent Publication No. 55-49631 (Patent Document 3) contains a specific thiodipropionic acid ester or thiodibutyric acid ester together with a predetermined foaming agent in a styrene-based resin particle, A method for obtaining a styrene resin foam in which a large number of air bubbles are formed is described.
However, the styrene resin foam has a property that the thermal conductivity increases as the expansion ratio increases.

  For example, “6-2 polystyrene particles described in page 89 (Non-patent Document 1) of the well-known and commonly used technology collection 57 (1982) -133 [3347] published on August 3, 1982 In the “1. Thermal conductivity” column of “Physical properties of foam (general)”, a graph showing the relationship between the specific gravity and the thermal conductivity is described.In this graph, the expansion ratio is 33 times (specific gravity). The thermal conductivity is about 0.030 Kcal / m · h · ° C. at 30 g / l), whereas the thermal conductivity is about 0.034 to 0.035 Kcal / m · at 50 times (specific gravity 20 g / l). It has been shown to increase to h · ° C.

The same is described in Japanese Patent Laid-Open No. 56-50935 (Patent Document 4). That is, according to the publication, in a foamed resin such as polystyrene, the thermal conductivity is the lowest when the expansion ratio is 20 to 30 times, and the thermal conductivity increases as the expansion ratio increases.
Japanese Patent Application Laid-Open No. 56-50935 (Patent Document 5) describes the knowledge that such an increase in thermal conductivity at a high expansion ratio can be eliminated by reducing the influence of radiant thermal conductivity. Yes. In this publication, based on this knowledge, an additive having a chemical structure that absorbs a specific infrared wavelength and a specific absorption rate for blackbody radiation at 300 ° K. It is disclosed that it is contained in a resin foam.

Japanese Patent Publication No.49-2994 Japanese Patent Publication No.57-34296 Japanese Patent Publication No. 55-49631 JP 56-50935 A JP 56-50935 A

89 pages of 57 (1982) -133 [3347], a collection of well-known and commonly used techniques published on August 3, 1982

  However, none of the above documents has been able to provide a foam having sufficient heat insulation performance.

Thus, according to the present invention, in a sliced product (but not including the surface layer) having a mean bubble diameter of 100 to 300 μm surrounded by a bubble film and sliced at a thickness of 1 mm, the wave number 400 is 20% or less. There is provided a styrenic resin foam characterized by having an average transmittance of infrared rays of ˜1000 cm ⁻¹ .
Moreover, according to the present invention, there is provided a method for producing expandable styrene resin particles used for producing the styrene resin foam,
Styrene resin seed particles dispersed in an aqueous medium in a reaction vessel are impregnated with a styrene monomer and then polymerized or polymerized while impregnated to obtain styrene resin particles, and the styrene resin Impregnating the resin particles with a foaming agent or impregnating the foaming agent during the polymerization of the styrenic monomer,
The impregnation and polymerization of the styrenic monomer are performed in a reaction vessel maintained at an oxygen concentration of 15% by volume or more,
The styrenic monomer is supplied into the aqueous medium so that the amount of the styrenic monomer in the styrenic growing resin particles from the beginning of impregnation of the styrenic monomer to the end of polymerization is 60% by mass or less. A method for producing expandable styrene resin particles is provided.

ADVANTAGE OF THE INVENTION According to this invention, the styrene resin foam excellent in the heat insulation performance by an infrared transmittance | permeability being low can be provided. In addition, it is possible to provide a method for producing expandable styrene resin particles suitable for the production of the foam.
Moreover, when it has a density of 10 to ³⁰ kg / m ³ and an average cell thickness of 0.5 to 2.0 μm, it is possible to provide a styrenic resin foam having more excellent heat insulation performance.
Furthermore, when containing 1.0-20 mass% of scaly silicates having an average particle diameter of 10-200 μm, it is possible to provide a styrenic resin foam having more excellent heat insulation performance.
Moreover, when the scaly silicate is mica or sericite, it is possible to provide a styrenic resin foam having more excellent heat insulation performance.

In order to improve the heat insulation performance of the styrene resin foam (hereinafter also referred to as a foam), the inventor of the present invention reviewed the configuration of the foam from the viewpoint of a heat conduction mechanism as shown below.
That is, in general, the thermal conductivity of a foam is determined from its conduction mechanism: (a) conduction of a solid phase (resin), (b) conduction of a gas phase, (c) radiation between bubble membranes, and (d) gas in a bubble. Divided into convection. In the case of a high foam (a foam with a high expansion ratio), since the volume occupied by the resin is very small, the proportion of the solid phase conduction in (a) in the thermal conductivity is small. The gas phase conduction (b) is advantageous in reducing the thermal conductivity if a fluorocarbon gas having a high molecular weight is used as the foaming agent, and immediately after removal from the mold. However, since the gas gradually dissipates from the foam and is replaced with air, the influence of the fluorocarbon gas on the thermal conductivity decreases with time. The convection of the gas in the bubble in (d) is observed when the bubble diameter is 4 mm or more, and the normal foam can be ignored because the bubble diameter is considerably smaller than 4 mm. Therefore, the highest degree of influence on the thermal conductivity is radiation between the bubble films in (c).

In general, the effect of attenuating radiant heat transfer is large due to the solid (resin) surface forming the bubbles. Therefore, the bubble diameter of the foam is closely related to the blocking of radiant heat. The smaller the bubble diameter, the greater the number of heat flow interruptions per unit thickness (that is, the number of bubble films that attenuate radiant heat transfer). The conductivity is thought to be small.
Furthermore, according to the result of the study by the present inventors, the thermal conductivity, which is an index of the heat insulation performance in the styrene resin foam, is not limited to the above indices (a) to (d). It has also been found that there is a close relationship with the amount of transmitted infrared rays having a wave number of 1000 cm ⁻¹ or less, particularly in relation to the amount.

(Foam)
From the viewpoint of the above index (c) and infrared transmittance, the foam of the present invention comprises 100-300 μm air bubbles with an average cell diameter surrounded by a cell membrane, and is sliced with a thickness of 1 mm (however, In this case, the average transmittance of infrared rays having a wave number of 400 to 1000 cm ⁻¹ is 20% or less.
When the average bubble diameter is less than 100 μm and greater than 300 μm, the average transmittance of infrared rays having a wave number of 400 to 1000 cm ⁻¹ cannot be reduced to 20% or less, so that the foam has poor heat insulating performance. The average cell diameter is preferably in the range of 150 to 250 μm.
The inventor has found that infrared rays having a wave number of 400 to 1000 cm ⁻¹ have a greater influence on the heat insulating performance of the foam than infrared rays having wave numbers outside this range. The average infrared transmittance is preferably as small as possible. In the present invention, a foam of 15% or less, 10% or less, or 6% or less can be realized.

The foam preferably has a density of 10-30 kg / m ³ and / or an average cell thickness of 0.5-2.0 μm. By having the density in this specific range, it is possible to provide a foam having higher heat insulation performance. A more preferable density is 12.5 to 20.0 kg / m ³ . Moreover, the foam with higher heat insulation performance can be provided by having the average bubble film thickness of the said specific range. A more preferable average bubble film thickness is 0.7 to 1.5 μm.
The foam can be used for applications such as cushioning materials (cushion materials) such as home appliances, electronic parts, various industrial materials, food containers and the like. Moreover, it can also be suitably used as an impact energy absorbing material such as a vehicle bumper core or a door interior cushioning material.

(1) Styrenic resin The foam is made of a styrene resin. The styrene resin is not particularly limited, and for example, a styrene monomer such as styrene, α-methyl styrene, paramethyl styrene, vinyl toluene, chlorostyrene, ethyl styrene, i-propyl styrene, dimethyl styrene, bromo styrene, or the like. Examples thereof include a polymer or a copolymer thereof. The styrene resin preferably contains 50% by mass or more of a component derived from styrene, and more preferably consists of polystyrene.

  The styrene resin may be a copolymer of a styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. In the case of a copolymer, it is preferable that a component derived from a styrene monomer occupies a main component (50% by mass or more, preferably 80% by mass or more, more preferably 99.8 to 99.9% by mass). Examples of such vinyl monomers include alkyl (meth) acrylates having 1 to 8 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate, (meth) In addition to acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate, maleic anhydride, N-vinylcarbazole and the like can be mentioned.

(2) Scale-like silicate Furthermore, heat insulation performance can further be improved because a foam contains 1.0-20 mass% of scale-like silicate of an average particle diameter of 10-200 micrometers. When the average particle diameter is less than 10 μm and more than 200 μm, the effect of improving the heat insulation performance from the uncontaining foam may be small. A more preferable average particle diameter is 15 to 150 μm. When content is less than 1.0 mass% and more than 20 mass%, the improvement effect of the heat insulation performance from a non-containing foam may be small. A more preferable content is 3 to 15% by mass.
Examples of scaly silicate include natural mica, synthetic mica, and sericite. Unlike natural mica, synthetic mica is an artificially produced mica having a composition in which all —OH groups in the crystal structure of natural mica are substituted with —F groups, and KMg ₃ AlSi ₃ O ₁₀ F ₂ is the ideal composition.

The surface of the scaly silicate may be coated with a metal oxide. Examples of such metal oxides include titanium oxide and iron oxide. Specific examples of the scaly silicate having a surface coated include natural mica or synthetic mica whose surface is coated with titanium oxide, and natural mica or synthetic mica whose surface is coated with iron oxide.
The content of the metal oxide is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and particularly preferably 30 to 60% by mass in the scale-like silicate whose surface is coated with the metal oxide.

  The scaly silicate preferably has such a size that it cannot pass through a sieve having an opening of 3 μm and can pass through a sieve having an opening of 200 μm or less. When the scale-like silicate is too small, the heat insulating performance of the foam may be deteriorated. On the other hand, if it is large, the foam film of the foam is easily broken, and it may be difficult to obtain a foam having a high expansion ratio. A more preferable size is a size that cannot pass through a sieve having an opening of 5 μm and an opening of 150 μm or less, and a particularly preferable size is that it cannot pass through a sieve having a size of 5 μm. Is a size that can pass through a sieve of 100 μm or less.

Moreover, it is preferable that an average particle diameter is 10-300 micrometers from the reason similar to the above. A more preferable average particle diameter is 15 to 250 μm.
Furthermore, if the thickness of the scaly silicate is thin, it may be crushed by the time of production of the foam and may not exhibit the desired heat insulating performance. On the other hand, when it is thick, the foam film of the foam is easily broken, and it may be difficult to obtain a foam with a high expansion ratio. Therefore, the thickness of the scaly silicate is preferably 0.01 to 5 μm, more preferably 0.01 to 3 μm, and particularly preferably 0.01 to 1 μm.

(3) Method for producing foam The foam is obtained by impregnating a styrene resin particle with a foaming agent to obtain a foamable styrene resin particle, and then prefoaming the foamable styrene resin particle to obtain a prefoamed particle. Then, it can be manufactured by filling this into a mold and heating and foaming.
As expandable styrene resin particles, (i) styrene resin seed particles (hereinafter referred to as seed particles) are dispersed in an aqueous medium, and a styrene monomer is continuously or intermittently supplied to this to present the presence of a polymerization initiator. The presence of a polymerization initiator by suspension-polymerization under the impregnation with a foaming agent, particles obtained by so-called seed polymerization, or (ii) supplying a styrenic monomer continuously or intermittently into an aqueous medium Particles obtained by suspension polymerization under the above and impregnating with a foaming agent, so-called suspension polymerization can be used. In particular, the seed polymerization method is preferable for obtaining a foam having an average cell diameter in a specific range according to the present invention because the cell diameter is easier to prepare than that obtained by the suspension polymerization method.

  As will be described below, the average cell diameter is adjusted to 100 to 300 μm by a method of selecting the type of surfactant, an additive having a cell preparation effect (for example, stearate, sulfur compound, low molecular weight polyethylenes). ), A method for adjusting the polymerization temperature, a method for selecting the type of the polymerization initiator, a method for selecting the type of the foaming agent, a method for preparing the impregnation amount of the foaming agent, and a monomer for the seed polymerization method In general, it can be carried out by a method generally used for preparing bubbles of styrenic resin foam, such as a method for adjusting the supply rate of styrene.

(A) Seed particles As the monomer for obtaining seed particles, any of the styrenic monomers and vinyl monomers mentioned in the section of the foam can be used. When the styrene-based weight average molecular weight of the styrene resin constituting the seed particles is small, the mechanical strength of the foam obtained by foaming the expandable styrene resin particles may be lowered. On the other hand, if it is large, the foamability of the expandable styrene resin particles may be lowered. A preferable average molecular weight is 120,000 to 600,000.

  If the particle diameter of the seed particles is within a narrow range, the particle diameter of the expandable styrene resin particles can be well aligned. In view of this, it is possible to use, as seed particles, particles prepared by once sieving the particles obtained by the suspension polymerization method so that the particle diameter is in the range of ± 20% of the average particle diameter. When seed particles are obtained by the bulk polymerization method, pellets having a desired particle size can be used. Therefore, according to the seed polymerization method, expandable styrene resin particles having a desired particle size range according to the application can be produced with a yield of almost 100%. For example, particles classified as 0.3 to 0.5 mm, 0.5 to 0.7 mm, 0.7 to 1.2 mm, 1.2 to 1.5 mm, 1.5 to 2.5 mm are desired. It can be selected according to the average particle diameter of the expandable styrene resin particles.

The seed particles preferably contain a styrene resin and a scaly silicate.
It is preferable that the scaly silicate is previously charged in seed particles in an amount to be contained in the foam. Therefore, it is preferable to use seed particles containing 1.2 to 40% by mass of flaky silicate. When the scale-like silicate in the seed particles is less than 1.2% by mass, the heat insulation performance of the foam obtained from the expandable styrene resin particles may be deteriorated. Moreover, when it exceeds 40 mass%, it may become difficult to manufacture seed particles. As for content of the scale-like silicate in a seed particle, it is more preferable that it is 3-30 mass%.

(B) Aqueous medium Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol).
(C) Styrenic monomer As the styrenic monomer, the styrenic monomer mentioned in the column of the foam can be used. Moreover, you may add the vinyl monomer quoted in the column of the said foam to the styrene-type monomer.

(D) Polymerization initiator As the polymerization initiator, any radical-generating polymerization initiator used in usual suspension polymerization of styrene can be used. For example, benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-t-butyl peroxybutane, organic peroxides such as t-butylperoxy 3, 3, 5 trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. It is done. These polymerization initiators may be used alone or in combination of two or more. In order to adjust the molecular weight and reduce the residual monomer, the polymerization temperature is in the range of 50-80 ° C to obtain a half-life of 10 hours, and the decomposition temperature is in the range of 80-120 ° C It is desirable to use a polymerization initiator in combination.

(E) Use amount of seed particles The use amount of seed particles is preferably 10 to 90 mass%, more preferably 15 to 50 mass%, based on the total amount of resin particles at the end of polymerization. When the amount of seed particles used is less than 10% by mass, it is difficult to control the polymerization rate of the particles to an appropriate range when supplying the styrene monomer, and the resulting particles have a high molecular weight or a large amount of fine powder is generated. Doing so is disadvantageous industrially, such as a reduction in production efficiency. On the other hand, if it exceeds 90% by mass, it is difficult to obtain excellent foam moldability.

(F) Other components A suspension stabilizer may be used to stabilize the dispersibility of the styrene monomer droplets and seed particles.
Examples of the suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. Here, when a poorly soluble inorganic compound is used, an anionic surfactant is usually used in combination.
The anionic surfactant functions as an auxiliary stabilizer for stabilizing the dispersion by the suspension stabilizer, and is obtained by being partially dissolved or entrained in the styrene polymer particles. This may affect the size of the bubble diameter in the foam. Therefore, what is necessary is just to select the kind of anionic surfactant so that an average bubble diameter may enter into the range of 100-300 micrometers.

  Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzenesulfonates such as calcium dodecylbenzenesulfonate and sodium dodecylbenzenesulfonate, alkyls Sulfonates such as naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, higher alcohol sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, polyoxy Examples thereof include sulfuric acid ester salts such as ethylene alkylphenyl ether sulfate, and phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

  Furthermore, in order to adjust the average cell diameter of the foam obtained by foaming the expandable styrene resin particles, 5-10 minutes before the end of the seed polymerization, immediately after the end of the seed polymerization, or on the styrene resin particles After impregnating the foaming agent, the cell preparation agent may be added to the styrene resin particles so as to be 0.01 to 0.8% by mass. Examples of such foam preparation agents include stearates such as ethylene bis stearic acid amide, triglycerin fatty acid esters, and the like.

(G) Polymerization conditions The polymerization is usually carried out by maintaining heating at 60 to 150 ° C for 1 to 10 hours, although it varies depending on the monomer species, polymerization initiator species, polymerization atmosphere species, and the like.
Examples of the polymerization atmosphere include an atmosphere in which the oxygen concentration in the reaction vessel during the polymerization reaction is maintained at 15% by volume or more. This particular oxygen concentration is useful when the foam contains scaly acid salts. That is, when the oxygen concentration is less than 15% by volume, a large amount of scaly silicate tends to be contained on the surface of the expandable styrene resin particles. Therefore, when pre-expanded particles obtained by pre-expanding expandable styrenic resin particles are secondarily expanded, bubbles on the surface of the pre-expanded particles may be broken by scaly silicate. As a result, high foaming magnification of the foam may be hindered. In addition, it is impossible to obtain a foaming pressure for sufficiently preliminarily fusing the pre-expanded particles by fusing, resulting in inadequate heat fusing integration between the expanded particles. The mechanical strength of the resulting foam may be reduced. A more preferable oxygen concentration is in the range of 15 to 21% by volume.

And the usage-amount of a styrene resin seed particle and dispersion liquid so that the scale-like silicate contained in a seed particle may become the range of 3-10 mass parts with respect to 100 mass parts of styrene resin particles obtained. It is preferable to prepare the total amount of styrenic monomer supplied to.
When the content of the scaly silicate in the styrene resin particles is small, the heat insulation performance of the foam obtained using the expandable styrene resin particles may be lowered. Moreover, when there is much content, when foaming an expandable styrene-type resin particle, a flaky silicate may cause a tear to a bubble film | membrane. As a result, it may be difficult to obtain a foam with a high expansion ratio.

(F) Styrenic resin particles The particle diameter of the styrene resin particles is preferably 0.3 to 2.0 mm from the viewpoint of filling into the mold of pre-expanded particles described later, More preferably, it is 1.4 mm.
Furthermore, if the styrene-based weight average molecular weight (Mw) of the styrene resin constituting the styrene resin particles is small, the mechanical strength of the foam obtained by foaming the expandable styrene resin particles may decrease. . On the other hand, if it is large, the foamability of the expandable styrenic resin particles is lowered, and a foam having a high expansion ratio may not be obtained. A preferable weight average molecular weight is 100,000 to 700,000 suitable for ordinary foam molding, and more preferably 150,000 to 400,000. Moreover, it is preferable to prepare the weight average molecular weight of the seed particles in a range suitable for the above foam molding.

In order to adjust the weight average molecular weight to a range suitable for ordinary foam molding, it is important to make the polymerization initiator work efficiently. To prevent unnecessary decomposition and generate radicals throughout the polymerization process, In the distribution, polymerization temperature program, and seed polymerization method, it is preferable to further adjust and control the monomer supply rate, the polymerization rate during polymerization, and the like.
The styrene resin constituting the styrene resin particles preferably has a melt tension in the range of 5 to 40 gf.

  The melt tension is related to the uniformity of the thickness of the bubble film. In the case of a styrene resin having a melt tension of less than 5 gf, the thickness of the bubble film obtained by foaming becomes uneven, and a very thin portion of the bubble film is formed. Therefore, it becomes difficult to sufficiently block the radiant heat, and as a result, the thermal conductivity may be increased. On the other hand, when the melt tension is 5 gf or more, the thickness of the bubble film becomes almost uniform and there is no very thin portion of the bubble film, so that it is possible to prevent a decrease in the ability to block radiant heat. Furthermore, when the melt tension exceeds 40 gf, it is difficult to increase the expansion ratio. In order to set the melt tension within the above range, for example, the type and amount of the polymerization initiator, the polymerization temperature, the polymerization time, etc. may be appropriately adjusted.

(G) Impregnation step The impregnation with the foaming agent may be performed on the particles after the polymerization of the styrene monomer, or the growing particles may be impregnated with the foaming agent. Impregnation during the polymerization can be performed by a method of impregnation in an aqueous medium (wet impregnation method). The impregnation after polymerization can be carried out by a wet impregnation method or a method of impregnation in the absence of a medium (dry impregnation method). Moreover, it is preferable to perform the impregnation in the middle of polymerization normally in the latter stage of polymerization.

Examples of the blowing agent include readily volatile compounds having a boiling point equal to or lower than the softening point of the polymer, such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, and petroleum ether. Hydrocarbons such as acetone, methyl ethyl ketone, alcohols such as methanol, ethanol, isopropyl alcohol, low boiling point ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, HCFC-141b, HCFC- 142b, HCFC-124, HFC-134a, HFC-152a and other halogen-containing hydrocarbons, carbon dioxide, nitrogen, ammonia and other inorganic gases. These foaming agents may be used alone or in combination of two or more. Among these, it is preferable to use hydrocarbons from the viewpoint of preventing the destruction of the ozone layer, and from the viewpoint of quickly replacing with the air and suppressing the change with time of the foam. Of the carbon hydrogen, it is more preferable to use butane.
The amount of the foaming agent used is preferably 1 to 10% by mass and more preferably 2 to 7% by mass with respect to 100 parts by mass of the expandable styrene resin particles.

(H) Others A solvent or a plasticizer may be added to the expandable styrene resin particles.
Examples of the solvent include aromatic organic compounds such as styrene, toluene, ethylbenzene, and xylene, cyclic aliphatic hydrocarbons such as cyclohexane and methylcyclohexane, ethyl acetate, and butyl acetate.
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate, and diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.

When the content of the solvent and the plasticizer in the expandable styrene resin particles is small, the effect of adding the solvent and the plasticizer may not be exhibited. On the other hand, when the content is large, the foam obtained using the expandable styrene-based resin particles may be contracted or melted to deteriorate the appearance. The preferable content is 0.1 to 1.5% by mass, and more preferably 0.2 to 1.0% by mass, based on the total amount of the expandable styrene resin particles.
The impregnation with the solvent and the plasticizer can be performed on the particles after the polymerization of the styrenic monomer or the growing particles. Further, a solvent or a plasticizer may be added to the seed particles in advance.
When the impregnation temperature of the solvent and the plasticizer into the styrene resin particles, seed particles or growing particles is low, the impregnation takes time, and the production efficiency of the expandable styrene resin particles may be lowered. On the other hand, when it is high, coalescence of the expandable styrene resin particles may occur in a large amount. The impregnation temperature is preferably 60 to 120 ° C, more preferably 70 to 100 ° C.

Furthermore, the expandable styrenic resin particles of the present invention contain other additives such as a foam cell nucleating agent, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant within a range that does not impair the physical properties. You may go out. Other additives can be included in the expandable styrene resin particles in the same manner as the solvent and plasticizer.
Examples of the flame retardant include tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, and the like. And when there is little content of the flame retardant in an expandable styrene resin particle, the flame retardance of the foam obtained using an expandable styrene resin particle may become inadequate. On the other hand, in many cases, the moldability of the expandable styrene resin particles may decrease. The content of the flame retardant is preferably 0.5 to 1.5% by mass.

  Moreover, as a flame retardant adjuvant, the organic peroxide like a dicumyl peroxide is mentioned, for example. And when there is little content of a flame retardant adjuvant in an expandable styrene-type resin particle, the effect which added the flame retardant adjuvant may not express. On the other hand, in many cases, the foam moldability of the expandable styrene resin particles may be lowered. The content of the flame retardant aid is preferably 0.05 to 0.5% by mass.

(I) Pre-expanded particles The expandable styrenic resin particles are pre-expanded particles having a large number of small holes by being pre-expanded using water vapor or the like in a pre-foaming machine. The bulk magnification of the pre-expanded particles is in the range of 30 to 100 times. When the bulk expansion ratio of the pre-expanded particles is larger than 100 times, the resulting foam may shrink and the appearance may be deteriorated. In addition, the thermal insulation performance and mechanical strength of the foam may decrease. On the other hand, when the bulk density is less than 30 times, not only the lightness of the foam is lowered, but also the effect of adding scaly silicate may be reduced.

(J) Molding of foam The pre-foamed particles are filled in a closed mold having a large number of small holes, and again heated and foamed with pressurized steam or the like to fill the gaps between the pre-foamed particles and A foam can be manufactured by fusing. At that time, it is preferable that the density (bulk density) ρ of the foam is in the range of 10 to ³⁰ g / cm ³ by adjusting the filling amount of the pre-expanded particles in the mold. A more preferable density is 12.5 to 20.0 g / cm ³ .

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples. Various measurement methods in the examples are described below.
<Average particle size of scaly silicate>
Examples of methods for measuring the average particle size of the flaky silicate include a method for obtaining an average particle size by a microtrack laser diffraction method or a micro sieve mesh sieve method, a method for obtaining by observation with an electron microscope, and the like. Although there is a difference in the particle diameter depending on the measurement method, the micro sieve mesh sieve method and the electron microscope are close to the actual particle diameter, and the micro track laser diffraction method is slightly larger than the actual particle diameter. The average particle diameter in the present specification is measured by a microtrack laser diffraction method from the viewpoint of ease of measurement and high reproducibility.

<Styrene monomer amount>
The method for measuring the amount of styrene monomer in styrene resin growing particles (hereinafter referred to as growing particles) refers to those measured in the following manner.
That is, the growing particles are taken out from the dispersion, and the water adhering to the surface is wiped off using gauze. 0.08 g of the growing particles are collected, and the collected growing particles are dissolved in 24 ml of toluene to prepare a toluene solution. Next, 10 ml of the Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to the toluene solution. The result obtained by titrating the obtained solution with an N / 40 sodium thiosulfate solution is defined as a titration constant (milliliter) of the sample. The Wis reagent is obtained by dissolving 8.7 g of iodine and 7.9 g of iodine trichloride in 2 liters of glacial acetic acid.

On the other hand, without dissolving the growing particles, 10 ml of Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to 24 ml of toluene. The resulting solution was titrated with a N / 40 sodium thiosulfate solution to give a blank titration (in milliliters).
From the obtained droplet constant, the amount of styrene monomer in the growing particles is calculated based on the following formula.
Amount of styrenic monomer in the growing particles (% by mass)
= 0.1322 × (blank drop constant−sample drop constant) / sample drop constant

<Weight average molecular weight>
A weight average molecular weight means the styrene conversion weight average molecular weight measured in the following ways.
That is, 30 mg of styrene resin is dissolved in 10 ml of chloroform. The resulting solution is filtered through a non-aqueous 0.45 μm chromatographic disk, and the average molecular weight is measured under the following conditions using a chromatograph.
Gas chromatograph: Product name “Detector 484, Pump 510” manufactured by Water
Column: Showa Denko Corporation trade name “Shodex GPC K-806L (φ8.0 × 300 mm)” Column temperature: 40 ° C.
Carrier gas: Chloroform Carrier gas flow rate: 1.2 ml / min injection / pump temperature: room temperature detection: UV254 nm
Injection amount: Standard polystyrene for 50 microliter calibration curve: Trade name “shodex” manufactured by Showa Denko KK Weight average molecular weight: 1030000 Polystyrene

<Melting tension>
The melt tension is the tension when the molten styrene resin is pulled under the following conditions.
Measuring device: Capillograph (Toyo Seiki Seisakusho)
Test temperature: 200 ° C
Capillary properties: Diameter 2.05 mm, length 8.0 mm, inflow angle 45 °
Preheating time: 5 minutes Extrusion speed: 20 mm / min Winding speed: 8 m / min

<Scaly silicate content>
The foamable styrene resin particles are treated at 150 ° C. for 3 hours to dissipate the foaming agent. Place 1.0 g (mass of sample before ashing) of the residue after dissipation into a magnetic crucible with a capacity of 30 mL. The residue is incinerated by heating at 550 ° C. for 5 hours in an electric furnace (muffle furnace STR-15K (made by Isuzu)). The magnetic crucible is allowed to cool to room temperature (25 ° C.) in a desiccator. The mass of the sample after ashing in the magnetic crucible after standing to cool is measured. By substituting the mass of the sample before and after ashing into the following equation, the scaly silicate content (parts by mass) relative to 100 parts by mass of the styrene resin is calculated.
Scale-like silicate content (parts by mass) = Sample mass after ashing / Sample mass before ashing

<Bulk multiple>
The bulk magnification of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)
The bulk multiple is the reciprocal of the bulk density.

<Foam density>
The mass (a) and the volume (b) of a test piece (example 75 × 300 × 35 mm) cut out from a foam (after molding and dried at 40 ° C. for 20 hours or more) are 3 significant digits or more, respectively. And the density of the foam (kg / m ³ ) is determined by the formula (a) / (b).

<Thermal conductivity>
A rectangular parallelepiped test piece having a length of 200 mm, a width of 200 mm, and a thickness of 30 mm is cut out from the foam. Then, the thermal conductivity of this test piece is measured at a measurement temperature of 23 ° C. by a flat plate heat flow meter method in accordance with JIS A1412-2 (1999 “foamed plastic insulation material”). The case where the obtained thermal conductivity is less than 0.0350 W / mk is evaluated as ◯ (good heat insulation), and the case where it is 0.0350 W / mk or more is evaluated as x evaluation (insufficient heat insulation).

<Average bubble diameter>
In accordance with ASTM-D-2842-69, the average chord length (t) is measured from the number of bubbles applied on a straight line (60 mm) of the cut surface from a scanning electron micrograph of the cut surface of the foam. Is calculated by the following equation.
Average chord length t = 60 / number of bubbles Average bubble diameter d = t / 0.616

<Average infrared transmittance>
A sliced product (but not including the surface layer) obtained by slicing the molded product with a thickness of 1 mm is obtained, and transmission infrared absorption measurement is performed. In the resulting absorption curve, for between 400～1000Cm ^-1, it calculates the transmittance of each 50 cm ^-1, an average value. The average value is the average transmittance of infrared rays.

<Thermal conductivity>
In accordance with JIS-A-1412-2, the thermal conductivity at 23 ° C. is measured using a thermal conductivity meter (AUTO-AHC-072) manufactured by Eiko Seiki Co., Ltd. The measured value is evaluated according to the following criteria.
(Evaluation)
Thermal conductivity 0.035w / mk or less ・ ・ ・ ◎
0.037w / mk or less ・ ・ ・ ○
Greater than 0.037 w / mk ... ×

<Moldability>
The case where the adhesive strength between the pre-expanded particles is weak and the shape cannot be maintained as a foam is indicated as x, and the case where the shape can be maintained is indicated as ◯.

Example 1
In a polymerization vessel equipped with a stirrer having an internal volume of 100 liters, 40.0 liters of water, 100 g of tribasic calcium phosphate and 2.0 g of calcium dodecylbenzenesulfonate were added, followed by stirring with 40.0 kg of styrene, 96.0 g of benzoyl peroxide, 28.0 g of t-butyl peroxybenzoate was added, and the temperature was raised to 90 ° C. to obtain a polymerization temperature.
And it hold | maintained at the temperature for 6 hours, and also after heating up to 125 degreeC, after 2 hours, it cooled and obtained the polystyrene particle (A). It was 17.4 gf when the melt tension of this polystyrene particle | grain (A) was measured on the above-mentioned conditions.
The polystyrene particles (A) were sieved to obtain seed particles for seed polymerization having a particle diameter of 0.9 to 0.6 mm.

In a polymerization vessel equipped with a stirrer having an internal volume of 5 liters, 2000 g of water, 500 g of seed particles, 6.0 g of magnesium pyrophosphate, and 0.3 g of calcium dodecylbenzenesulfonate as a surfactant used for suspension polymerization of the seed particles were added. The mixture was heated to 70 ° C. with stirring.
Next, 4.5 g of benzoyl peroxide and 1.1 g of t-butyl peroxybenzoate were dissolved in 200 g of styrene and placed in a polymerization vessel. 30 minutes later, the temperature was raised to 90 ° C., and 1300 g of styrene was fed into the polymerization vessel by a constant amount (650 g / hour) over 150 minutes (seed polymerization).

Thereafter, the temperature was raised to 125 ° C., and after 2 hours, it was cooled to take out polystyrene particles. This was dried to obtain polystyrene particles (B). It was 12.2 gf when the melt tension of this polystyrene particle (B) was measured on the above-mentioned conditions. The maximum value of the styrene monomer amount during the polymerization was 30% by mass. The weight average molecular weight of the polystyrene particles (B) was 311,000.
In an autoclave with a stirrer having an internal volume of 5 liters, 2200 g of water, 1800 g of the polystyrene particles (B), 6.0 g of magnesium pyrophosphate and 0.4 g of sodium dodecylbenzenesulfonate were heated to 70 ° C. while stirring.

Next, 23.4 g of tetrabromocyclooctane and 5.4 g of dicumyl peroxide were put in an autoclave, sealed, heated to 90 ° C., and then 162 g of butane was injected and held for 4 hours. Then, it cooled to 30 degreeC and taken out the expandable polystyrene particle. The particles taken out were dried, stored in a constant temperature room at 15 ° C. for 4 days, and then pre-foamed with a steam foaming machine. The pre-expanded particles thus obtained were aged in a room at 20 ° C. for 24 hours, and then molded with a molding machine for expanded polystyrene (ACE-11QS manufactured by Sekisui Koki Co., Ltd.), and a plate-like foam having dimensions of 25 mm × 200 mm × 200 mm. Got. This plate-like foam was cured for 7 days in a drying room at 50 ° C., and then the density was measured and found to be 16 kg / m ³ .

(Example 2)
In the seed polymerization of Example 1, a plate-like foam was obtained in the same manner as in Example 1 except that 1300 g of styrene was supplied to the polymerization vessel by a fixed amount (650 g / hour) with a pump over 120 minutes. The maximum value of the amount of styrene monomer during polymerization was 35.3% by mass. The polystyrene particles (B) had a melt tension of 11.3 gf and a weight average molecular weight of 294,000.
(Example 3)
In the seed polymerization of Example 1, a plate-like foam was obtained in the same manner as in Example 1 except that 1300 g of styrene was supplied to the polymerization vessel by a fixed amount (650 g / hour) by a pump over 240 minutes. The maximum value of the amount of styrene monomer during polymerization was 30.2% by mass. The polystyrene particles (B) had a melt tension of 17.8 gf and a weight average molecular weight of 34,000.

Example 4
8000 parts by mass of a styrene resin (A) having a weight average molecular weight of 250,000 in terms of styrene (MS-100 manufactured by Sekisui Plastics Co., Ltd.) and a sieve that does not pass through a sieve with an opening of 30 μm and an opening of 50 μm 2,000 parts by mass of natural mica (A-61 manufactured by Yamaguchi Mica Industry Co., Ltd.) passing through is supplied to a twin-screw extruder, melted and kneaded at 230 ° C., and extruded from the extruder into strands. The cylindrical styrene resin seed particles (diameter: 1.0 mm, length: 1.5 mm) containing 20% by mass of flaky silicate were prepared.
Next, 2,000 parts by weight of water, 500 parts by weight of seed particles, 6 parts by weight of magnesium pyrophosphate, and 0.3 parts by weight of calcium dodecylbenzenesulfonate are supplied to a polymerization vessel equipped with a stirrer and heated to 70 ° C. while stirring. A dispersion was prepared.
Subsequently, 4.5 parts by mass of benzoyl peroxide and 1.1 parts by mass of t-butylperoxybenzoate were dissolved in 200 parts by mass of styrene monomer, and all the styrene monomer was supplied to the dispersion while stirring.

  Then, 30 minutes after supplying the styrene monomer into the dispersion, the dispersion is heated to 90 ° C., and 1300 parts by mass of styrene monomer is further supplied into the dispersion at a constant supply rate over 3 hours. Then, seed polymerization was performed, and after supplying all the styrene monomers, the mixture was heated to 125 ° C. and allowed to stand for 2 hours, and then cooled to obtain styrene resin particles (B). When the amount of styrene monomer in the growing styrene-based resin growing particles was measured every 10 minutes from the start of supplying the styrene monomer into the dispersion, the maximum value was 28.6% by mass. The melt tension of the styrenic resin particles (B) was 24.5 gf, and the weight average molecular weight was 333,000.

  Next, after the dispersion liquid in which the styrene resin particles (B) are dispersed is heated to 70 ° C., 23.4 parts by mass of tetrabromocyclooctane as a flame retardant and 5.4 parts by mass of dicumyl peroxide as a flame retardant aid. Was supplied to the dispersion, and the polymerization vessel was sealed and heated to 90 ° C. Subsequently, 162 parts by mass of butane was pressed into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles (B), the polymerization vessel was cooled to 30 ° C. and foamed. Styrenic resin particles were obtained. The obtained expandable styrene resin particles had a natural mica content of 4.7% by mass.

After applying polyethylene glycol as an antistatic agent to the surface of the expandable styrene resin particles, zinc stearate and hydroxystearic acid triglyceride were applied to the surface of the expandable styrene resin particles. In addition, each of zinc stearate and hydroxystearic acid triglyceride was prepared to be 0.05% by mass in the expandable styrene resin particles.
Thereafter, the expandable styrenic resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. Then, the expandable styrene resin particles were heated and pre-expanded to a bulk density of 0.0160 g / cm ³ to obtain pre-expanded particles. The pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the pre-expanded particles were filled in a mold and heated and foamed to obtain a plate-like foam having a length of 400 mm × width of 300 mm × thickness of 30 mm.

(Example 5)
Expandable styrenic resin in the same manner as in Example 4 except that cylindrical styrene resin seed particles (diameter: 1.0 mm, length: 1.5 mm) containing 7% by weight of flaky silicate were used. Particles were obtained. The expandable styrenic resin particles had a natural mica content of 1.5% by mass. The maximum value of the amount of styrene monomer during the polymerization was 29.0% by mass. The melt tension of the styrene resin particles (B) was 25.5 gf, and the weight average molecular weight was 331,000.

(Example 6)
6600 parts by mass of a styrene resin (A) having a weight average molecular weight of 250,000 in terms of styrene (MS-100, manufactured by Sekisui Plastics Kogyo Co., Ltd.) and a sieve having an opening of 50 μm that does not pass through a sieve having an opening of 30 μm 3400 parts by mass of natural mica passing through (A-61 manufactured by Yamaguchi Mica Industry Co., Ltd.) is supplied to a twin-screw extruder, melted and kneaded at 230 ° C., and extruded into a strand from the extruder. The columnar styrene resin seed particles (diameter: 1.0 mm, length: 1.5 mm) containing 34% by mass of flaky silicate were prepared.
Next, in a polymerization vessel equipped with a stirrer, water is supplied at a mass of 70 parts by mass while supplying 1000 parts by mass of styrene resin seed particles, 6 parts by mass of magnesium pyrophosphate and 0.3 parts by mass of calcium dodecylbenzenesulfonate. A dispersion was prepared by heating.

Subsequently, 3.0 parts by mass of benzoyl peroxide and 0.7 parts by mass of t-butylperoxybenzoate were dissolved in 200 parts by mass of styrene monomer, and all of the styrene monomer was supplied to the dispersion while stirring.
Then, 30 minutes after supplying the styrene monomer into the dispersion, the dispersion is heated to 90 ° C., and further 800 parts by mass of the styrene monomer is supplied into the dispersion at a constant supply rate over 3 hours. Then, seed polymerization was performed, and after supplying all the styrene monomers, the mixture was heated to 125 ° C. and allowed to stand for 2 hours, and then cooled to obtain styrene resin particles (B). The maximum value of the amount of styrene monomer during polymerization was 19.5% by mass. The melt tension of the styrene resin particles (B) was 8.9 gf, and the weight average molecular weight was 285,000.

  Next, after the dispersion liquid in which the styrene resin particles (B) are dispersed is heated to 70 ° C., 23.4 parts by mass of tetrabromocyclooctane as a flame retardant and 5.4 parts by mass of dicumyl peroxide as a flame retardant aid. Was supplied to the dispersion, and the polymerization vessel was sealed and heated to 90 ° C. Subsequently, 162 parts by mass of butane was pressed into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles (B), the polymerization vessel was cooled to 30 ° C. and foamed. Styrenic resin particles were obtained. The foamable styrene resin particles obtained had a natural mica content of 16.0% by mass. And the plate-like foam was obtained like Example 1 using the foamable styrene-type resin particle obtained as mentioned above.

(Comparative Example 1)
In the seed polymerization of Example 1, 1300 g of styrene in which 2 parts of polyethylene wax was dissolved was supplied in a fixed amount (650 g / hour) to the polymerization vessel by a pump over 120 minutes, and the plate-like foaming was performed in the same manner as in Example 1. Got the body. The maximum value of the amount of styrene monomer during polymerization was 34.9% by mass. The polystyrene particles (B) had a melt tension of 23.7 gf and a weight average molecular weight of 315,000.
(Comparative Example 2)
In the seed polymerization of Example 1, 1300 g of styrene was supplied to a polymerization vessel by a fixed amount (650 g / hour) by a pump over 240 minutes, and N-pentane was used instead of butane as a blowing agent. In the same manner as in Example 1, a plate-like foam was obtained. The maximum value of the amount of styrene monomer during polymerization was 29.9% by mass. The polystyrene particles (B) had a melt tension of 9.9 gf and a weight average molecular weight of 307,000.

(Example 7)
A plate was obtained in the same manner as in Example 4 except that cylindrical styrene resin seed particles (diameter: 1.0 mm, length: 1.5 mm) containing 2% by mass of flaky silicate were used. A foam was obtained. The expandable styrenic resin particles had a natural mica content of 0.5% by mass. The maximum value of the amount of styrene monomer during polymerization was 30.0% by mass. The melt tension of the styrene resin particles (B) was 10.4 gf, and the weight average molecular weight was 313,000.

(Comparative Example 3)
In Example 6, foaming properties were obtained in the same manner as in Example 4 except that cylindrical styrene resin seed particles (diameter: 1.0 mm, length: 1.5 mm) containing 46% by mass of natural mica were used. Styrene resin particles were obtained. The expandable styrenic resin particles had a natural mica content of 23.0% by mass. The maximum amount of styrene monomer during polymerization was 22.1% by mass. The melt tension of the styrene-based resin particles (B) was 7.6 gf, and the weight average molecular weight was 287,000.
The foaming styrenic resin particles obtained by this method have not only very low foaming performance, but also have poor adhesive strength between the pre-foamed particles, and a good foam cannot be obtained.
Table 1 summarizes the foam density, the content of scaly silicate, the average cell diameter, the average cell thickness, the average infrared transmittance, the thermal conductivity, the evaluation and the moldability.

  From Table 1, it can be seen that a foam having an average cell diameter of 100 to 300 μm and an average transmittance of infrared rays having a specific fraction of 20% or less has low thermal conductivity and good moldability. In particular, it can be seen that a foam containing 1.0 to 20% by mass of flaky silicate has a lower thermal conductivity.

Claims (6)

In a sliced product (but not including the surface layer) sliced with a thickness of 1 mm comprising bubbles with an average bubble diameter of 100 to 300 μm surrounded by a bubble film, infrared rays with a wave number of 400 to 1000 cm ⁻¹ of 20% or less A styrene resin foam characterized by having an average transmittance. The styrenic resin foam according to claim 1, having a density of 10 to ³⁰ kg / m ³ and an average cell thickness of 0.5 to 2.0 μm.   Furthermore, the styrene resin foam of Claim 1 or 2 containing 1.0-20 mass% of scaly silicates with an average particle diameter of 10-200 μm.   The styrenic resin foam according to claim 3, wherein the scaly silicate is natural mica, synthetic mica or sericite. It is the manufacturing method of the expandable styrene resin particle used for manufacture of the styrene resin foam as described in any one of Claims 1-4,
Styrene resin seed particles dispersed in an aqueous medium in a reaction vessel are impregnated with a styrene monomer and then polymerized or polymerized while impregnated to obtain styrene resin particles, and the styrene resin Impregnating the resin particles with a foaming agent or impregnating the foaming agent during the polymerization of the styrenic monomer,
The impregnation and polymerization of the styrenic monomer are performed in a reaction vessel maintained at an oxygen concentration of 15% by volume or more,
The styrenic monomer is supplied into the aqueous medium so that the amount of the styrenic monomer in the styrenic growing resin particles from the beginning of impregnation of the styrenic monomer to the end of polymerization is 60% by mass or less. A process for producing expandable styrenic resin particles.   The method for producing expandable styrene resin particles according to claim 5, wherein the styrene resin seed particles contain scaly silicate having an average particle diameter of 10 to 200 μm.