JP2005248098A - Method for manufacturing expandable styrene resin particle, expandable styrene resin particle, pre-expanded styrene resin particle and expanded styrene resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an expandable styrene resin particle, by which the expandable styrene resin particle remaining only a small amount of residual styrene monomers and having excellent mechanical strengths and heat insulating properties can be produced. <P>SOLUTION: The method for manufacturing the expandable styrene resin particle comprises supplying a styrene monomer to a dispersion liquid obtained by dispersing expandable styrene resin seed particles containing a scale-like silicate into water, impregnating and polymerizing the styrene monomer with the styrene resin seed particles, and impregnating the resultant styrene resin particles with a foaming agent after growing the styrene resin seed particles to produce the styrene resin particles, or in the middle of growth of the styrene resin seed particles. The styrene monomer is supplied in the dispersion liquid in such a way that an amount of the styrene monomer in the styrene resin grown particles in which the styrene resin seed particles are in a process of being grown as seed particles, is ≤60 wt.%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an expandable styrene resin particle capable of producing a styrene resin foam molded article having a small amount of residual styrene monomer and excellent in mechanical strength and heat insulation, a method for producing the same, and the foamability thereof. The present invention relates to styrene resin pre-expanded particles using styrene resin particles and a styrene resin foam molded article.

  Conventionally, since a styrene resin foam molded article is excellent in heat insulation, it is widely used as a heat insulating material for building materials and a heat insulation container. In particular, in building material applications, in addition to increasing the foaming ratio, improvement in heat insulation is required from the viewpoint of cost.

  Therefore, in Patent Document 1, a styrene monomer is polymerized in a suspension aqueous solution in the presence of graphite particles together with a comonomer of 20% by weight of the styrene monomer if necessary, and a blowing agent is added before the polymerization. A method for producing an expandable styrene polymer, which is characterized by adding during or after polymerization, has been proposed.

  However, the addition of graphite particles improves the heat insulation of the foamed styrene resin foam obtained by foaming the expandable styrene polymer, but inhibits the polymerization of styrene, so that residual styrene in the expandable styrene polymer. As a result, the amount of the monomer is large, and as a result, the amount of the volatile organic compound in the styrene resin foamed molded article is increased, which is not preferable for environmental hygiene.

JP-T-2001-522383

  The present invention relates to an expandable styrene resin particle capable of producing a styrene resin foam having a small amount of residual styrene monomer and excellent mechanical strength and heat insulation, a method for producing the same, and the expandable styrene. A styrene resin pre-expanded particle and a styrene resin foam molded article using the resin resin particle are provided.

  The method for producing expandable styrene resin particles of the present invention comprises supplying a styrene monomer into a dispersion obtained by dispersing styrene resin seed particles containing scaly silicate in water, and converting the styrene monomer to styrene. Expandable styrenic resin particles impregnated with a foaming agent after the styrene resin seed particles are produced by impregnating the polymer resin seed particles and polymerized to grow the styrene resin seed particles or during the growth of the styrene resin seed particles The styrenic resin in the dispersion is such that the amount of the styrenic monomer in the growing styrenic resin growing particles is 60% by weight or less. A monomer is supplied.

  In the method for producing expandable styrene resin particles of the present invention, first, a dispersion is prepared by dispersing styrene resin seed particles containing scaly silicate in water. In this way, the styrene resin particles produced are obtained by preliminarily containing the scaly silicate in the styrene resin seed particles and performing seed polymerization using the styrene resin seed particles as a core. On the other hand, a large amount of scaly silicate is contained in the surface, whereas only a small amount of scaly silicate is contained or not contained in the vicinity of the surface.

  The styrene resin constituting the styrene resin seed particles is not particularly limited, and examples thereof include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. Examples include homopolymers of styrene monomers or copolymers thereof, and styrene resins containing 50% by weight or more of styrene are preferable, and polystyrene is more preferable.

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

Examples of the scaly silicate contained in the styrene resin seed particles include kaolin, talc, 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 scale-like silicate may have its surface coated with a metal oxide, and examples of such a metal oxide include titanium oxide and iron oxide. Examples thereof include natural mica or synthetic mica whose surface is coated, and natural mica or synthetic mica whose surface is coated with iron oxide.

  Further, when the surface of the scaly silicate is coated with a metal oxide, the content of the metal oxide in the scaly silicate whose surface is coated with the metal oxide is preferably 10 to 70% by weight. 60 weight% is more preferable and 30 to 60 weight% is especially preferable.

  And as a magnitude | size of the said scale-like silicate, the magnitude | size which can not pass a sieve with an opening of 3 micrometers, and the opening of an opening is 200 micrometers or less is preferable, and an opening is 5 micrometers. More preferably, the size cannot pass through the sieve and the sieve can pass through a sieve having a mesh size of 150 μm or less, and the sieve cannot pass through a sieve having a mesh size of 100 μm or less. A size capable of forming is particularly preferred.

  This is because if the scaly silicate is small, the heat insulation property of the styrene resin foam molded article obtained by foaming the expandable styrene resin particles may decrease, whereas if the scale silicate is large, the expandable styrene resin particles may be reduced. This is because, when foamed, the bubble film is easily broken, and the styrene-based resin foam molded article may not be able to achieve a high expansion ratio.

  Furthermore, when the thickness of the scaly silicate is thin, it is easily crushed during the production of the styrene resin seed particles or when the expandable styrene resin particles are foamed, whereas when the thickness is large, the expandable styrene resin particles are foamed. In some cases, the bubble film is easily broken, and it may not be possible to achieve a high expansion ratio of the styrene resin foam molded article. Therefore, 0.01 to 5 μm is preferable, 0.01 to 3 μm is more preferable, and 0.01 to 1 μm is particularly preferable.

  And as content of the scale-like silicate in a styrene-type resin seed particle, when it is small, while heat insulation of the styrene-type resin foam molding obtained by foaming an expandable styrene-type resin particle falls, when it is many When foaming styrenic resin particles are foamed, the cell membrane may be easily broken, and it may not be possible to increase the expansion ratio of the styrene resin foam molded article. 3 to 30% by weight is more preferable.

  In addition, content of the scale-like silicate in a styrene resin seed particle means what was measured in the following way. That is, styrene resin seed particles are collected as a measurement sample, and the weight of the measurement sample (the weight of the measurement sample before ashing) is measured. Then, the measurement sample is placed on a 30 milliliter magnetic crucible and heated to 550 ° C. for 5 hours to incinerate the measurement sample, and then left in a desiccator to cool. Thereafter, the weight of the measurement sample after ashing on the magnetic crucible (measurement sample after ashing) is measured, and the content of scaly silicate in the styrene resin seed particles is calculated based on the following formula.

Scale-like silicate in styrene resin seed particles (wt%)
= 100 × weight of measurement sample after ashing / weight of measurement sample before ashing

  As a method for producing the styrenic resin seed particles containing the flaky silicate, a general-purpose method is used. For example, after dispersing the flaky silicate in the styrenic monomer, the styrenic monomer is added in water. A method of producing styrene resin seed particles by suspension polymerization, supplying a styrene resin and scaly silicate to an extruder, melt-kneading, extruding into a strand from the extruder, and cutting at predetermined lengths Examples thereof include a method for producing styrene resin seed particles.

  And when the styrene conversion weight average molecular weight of the styrene resin constituting the styrene resin seed particles is small, the mechanical strength of the styrene resin foam molded article obtained by foaming the expandable styrene resin particles is low. On the other hand, if it is large, the foamability of the expandable styrene-based resin particles may be lowered, so 120,000 to 600,000 is preferable.

  In addition, in this invention, the styrene conversion weight average molecular weight of styrene resin means what was measured in the following way. That is, 30 mg of a styrene resin was dissolved in 10 ml of chloroform, filtered through a non-aqueous 0.45 μm chromatographic disk, and then measured using a chromatograph.

Specifically, it can be measured under the following conditions using the following chromatograph. Gas chromatograph: Product name “Detector 484, Pump 510” manufactured by Water
Column: Showa Denko
Product name "Shodex GPC K-806L (φ8.0 x 300mm)" 2 Column temperature: 40 ℃
Carrier gas: Chloroform Carrier gas flow rate: 1.2 ml / min Injection / pump temperature: Room temperature Detection: UV254 nm
Injection volume: 50 microliters Standard polystyrene for calibration curve: Product name “shodex” manufactured by Showa Denko KK
Weight average molecular weight: 1030000
Made by Tosoh Corporation
Weight average molecular weight: 540000,3840000,355000
102000,37900,9100,2630,495

  Next, a styrene monomer is supplied into a dispersion obtained by dispersing the styrenic resin seed particles containing the flaky silicate in water, and the styrene resin seed particles are impregnated into the styrene resin seed particles for polymerization. Seed polymerization is carried out in the presence of an initiator, and styrene resin seed particles are grown as seed particles to produce styrene resin particles.

  As the styrenic monomer to be supplied to the dispersion, the styrenic monomer used in the above-mentioned styrenic resin seed particles can be used, and the above-mentioned vinyl monomer copolymerizable with this styrenic monomer can be used in combination. Good. As this vinyl monomer, divinylbenzene and alkylene glycol dimethacrylate are preferred. In addition, as the usage-amount of a vinyl monomer, 0.01-0.02 mol% is preferable with respect to the total amount of a styrene-type monomer and a vinyl monomer.

  In the method for producing expandable styrene resin particles of the present invention, the amount of styrene monomer in the styrene resin growing particles, which are in the process of growth using styrene resin seed particles as seed particles, is 60% by weight or less. Preferably, the styrenic monomer needs to be supplied into the dispersion so as to be 40% by weight or less, more preferably 30% by weight or less.

  This is because when the amount of styrene monomer in the styrene resin growing particles is large, the styrene monomer is polymerized near the center of the styrene resin growing particles, and as a result, the surface of the resulting expandable styrene resin particles Contains a large amount of scaly silicate.

  Thus, if the surface of the expandable styrene resin particles contains a large amount of scaly silicate, the styrene resin pre-expanded particles obtained by pre-expanding the expandable styrene-based resin particles are secondarily expanded. In this case, the surface portion of the styrene resin pre-expanded particles breaks down due to the scaly silicate, and the high expansion ratio of the styrene resin foam molded article cannot be achieved. By foaming, it is not possible to obtain a foaming pressure for sufficiently heat-sealing and integrating the styrene resin pre-foamed particles, and as a result, the heat-sealing integration between the foamed particles becomes insufficient and obtained. This is because the mechanical strength of the styrenic resin foam molded article is lowered.

  In addition, the measuring method of the amount of styrene-type monomers in a styrene-type resin growth particle says what was measured in the following way. That is, the styrene-based resin growth particles are taken out from the dispersion, and the moisture adhering to the surface of the styrene-based resin growth particles is wiped off with gauze.

  Then, 0.08 g of styrene resin growth particles are collected, and the collected styrene resin growth particles are dissolved in 24 ml of toluene to prepare a toluene solution. Next, 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 supplied into this toluene solution, and titrated with an N / 40 sodium thiosulfate solution. Set the drop constant (milliliter). 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 styrene-based resin growth particles, 10 ml of Wis reagent, 30 ml of 5 wt% potassium iodide aqueous solution and 30 ml of 1 wt% starch aqueous solution were supplied in 24 ml of toluene, and N / 40 Titrate with sodium thiosulfate solution to blank titration (in milliliters).

And the amount of styrene-type monomers in a styrene-type resin growth particle is computable based on a following formula.
Amount of styrene monomer in styrene resin growth particles (wt%)
= 0.1322 × (blank drop constant−sample drop constant) / sample drop constant

  The total amount of the styrene monomer finally supplied to the dispersion is preferably 10 to 90% by weight, more preferably 15 to 15% by weight, of the styrene resin seed particles in the styrene resin particles obtained. It is adjusted to 80% by weight, particularly preferably 15 to 70% by weight.

  This is because when the content ratio of the styrene resin seed particles in the obtained styrene resin particles is small, it becomes difficult to control the amount of the styrene monomer in the styrene resin growth particles within a predetermined range, or While the styrene resin constituting the resin particles may have a high molecular weight or a large amount of fine powder particles may be generated, the production efficiency may be reduced. On the other hand, if large, the flaky silicic acid contained in the styrene resin seed particles This is because the salt may be uniformly contained in the expandable styrenic resin particles and the moldability may deteriorate.

  And styrene is used so that the content of scaly silicate is preferably 1 to 20% by weight, more preferably 2 to 20% by weight, and particularly preferably 3 to 20% by weight in the expandable styrene resin particles. It is preferable to adjust the usage amount of the resin-based resin seed particles and the total supply amount of the styrene-based monomer into the dispersion. The method for measuring the content of flaky silicate in expandable styrene resin particles is the same as the method for measuring the content of flaky silicate in styrene resin seed particles. Since it is the same except that the conductive styrene resin particles are used, the description thereof is omitted.

  This is because when the content of the scaly silicate in the expandable styrene resin particles is small, the heat insulation property of the styrene resin foam molded article obtained using the expandable styrene resin particles may decrease, When the foamed styrene resin particles are foamed, the foam film may be broken due to the flaky silicate, making it difficult to obtain a styrene resin foam molded article having a high expansion ratio. Because there is.

  Further, the polymerization initiator used when the styrene monomer is impregnated in the styrene resin seed particles and seed polymerization is not particularly limited, and examples thereof include benzoyl peroxide, lauryl peroxide, t-butyl peroxide. Benzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-t-butyl peroxybutane, t-butyl peroxy-3, Examples include organic peroxides such as 3,5 trimethylhexanoate and di-t-butylperoxyhexahydroterephthalate, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. Can also be used together, but a half-life of 10 hours It is preferable that the decomposition temperature for obtaining the combination of a plurality of types of the polymerization initiator in the 80 to 120 ° C..

  And when performing the seed polymerization, a suspension stabilizer may be used to stabilize the dispersibility of the styrene monomer droplets and the styrene resin seed particles, and as such a suspension stabilizer, Examples 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. An active agent is usually used in combination.

  Examples of such anionic surfactants include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, and dialkyl sulfosuccinates. Sulfonates such as alkyl sulfoacetates, α-olefin sulfonates, higher alcohol sulfates, secondary higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, etc. Examples thereof include phosphoric acid ester salts such as salts, alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

  Furthermore, in order to adjust the average cell diameter of the styrene resin foam molded article obtained by foaming the expandable styrene resin particles, 5 to 10 minutes before the end of the seed polymerization, immediately after the end of the seed polymerization, or styrene After impregnating the resin-based resin particles with a foaming agent, a cell regulator may be added to the styrene-based resin particles so as to be 0.01 to 0.8% by weight. Examples of such air conditioners include stearates such as ethylene bis stearic acid amide and triglycerin fatty acid esters.

  Further, the particle diameter of the styrene resin particles is preferably 0.3 to 2.0 mm, and more preferably 0.3 to 1.4 mm, from the viewpoint of filling the styrene resin pre-expanded particles described later into the mold. . Furthermore, when the styrene-based weight average molecular weight (Mw) of the styrene resin constituting the styrene resin particles is small, the mechanical strength of the styrene resin foam molded article obtained by foaming the expandable styrene resin particles decreases. On the other hand, if it is large, the foamability of the expandable styrene resin particles is lowered, and there is a possibility that a styrene resin foam molded article having a high expansion ratio cannot be obtained, so 120,000 to 600,000 is preferable. .

  Next, the styrene resin particles obtained by the seed polymerization are impregnated with a foaming agent, or the styrene resin growth particles are impregnated with the foaming agent during the seed polymerization to produce expandable styrene resin particles. To do.

  As the blowing agent, general-purpose ones are used. For example, aliphatic hydrocarbons such as propane, butane, pentane; 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1 -Difluoroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1- Examples thereof include CFC-based blowing agents such as difluoroethane (HFC-152a), and aliphatic hydrocarbons are preferable. In addition, a foaming agent may be used independently or may be used together.

  If the content of the foaming agent in the expandable styrene resin particles is small, it may be difficult to increase the expansion ratio of the styrene resin foam molded article obtained using the expandable styrene resin particles. The foamed styrenic resin particles obtained by foaming may be insufficiently heat-sealed between the foamed particles, and the appearance of the styrenic resin foamed molded product may be deteriorated. When foam molding is performed using resin particles, shrinkage occurs in the resulting styrene resin foam molded article, or adjustment of foam gas in styrene resin pre-foamed particles obtained by pre-foaming foamable styrene resin particles, Since time is required for foam molding and the production efficiency may be lowered, 2.0 to 9.0% by weight is preferable, and 3.0 to 7.0% by weight is more preferable. The content of the foaming agent in the expandable styrene resin particles was measured after being left in a thermostatic chamber at 13 ° C. for 5 days immediately after production.

  Furthermore, the amount of residual styrene monomer contained in the expandable styrene resin particles is preferably 500 ppm or less, more preferably 300 ppm or less, and particularly preferably 200 ppm or less with respect to the total amount of the expandable styrene resin particles. This is because the residual styrene monomer contained in the expandable styrene resin particles also remains in the styrene resin foam molded product obtained by using the expandable styrene resin particles, and is in the air during use. This is because the manufacturing efficiency of the foamed molded product may be reduced, for example, because it takes a long time to dry the styrene resin foamed molded product.

  Here, the amount of residual styrene monomer contained in the expandable styrene resin particles refers to that measured in the following manner. That is, 1 g of expandable styrene resin particles was collected as a measurement sample, and a dimethylformamide solution of 0.1% by volume of cyclopentanol was added to the measurement sample, and further dimethylformamide was added to prepare 20 mL of the measurement solution. To do. Then, the amount of residual styrene monomer in the measurement solution can be measured by an internal standard method using a gas chromatograph, and the amount of residual styrene monomer contained in the expandable styrene resin particles can be calculated. In addition, it can measure on the following conditions using the following gas chromatograph, for example.

Gas chromatograph: Shimadzu Corporation product name "GC-14A"
Detector: FID
Column: GL Sciences
Product name "PEG-20MPT (25%) Uniport B (60/80) 2m"
Column temperature: 105 ° C
Detector temperature: 220 ° C
Inlet temperature: 220 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 50 ml / min Measurement solution injection volume: 3 ml

  Further, a solvent or a plasticizer may be added to the expandable styrene resin particles. Examples of such a 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 phthalic acid esters, glycerin diacetomonolaurate, glycerin tristearate, glycerin fatty acid esters such as diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.

  When the contents of the solvent and the plasticizer in the expandable styrene resin particles are small, the effect of adding the solvent and the plasticizer may not be manifested. On the other hand, when the contents are large, the expandable styrene resin particles are used. The resulting styrene-based resin foamed molded article may shrink or melt, resulting in a decrease in appearance and the like. Therefore, 0.1 to 1.5% by weight is preferable, and 0.2 to 1.0% by weight Is more preferable.

  The solvent and the plasticizer may be impregnated into the styrene resin particles after the styrene resin seed particles are grown by the seed polymerization to produce the styrene resin particles, or the styrene resin seed particles are grown by seed polymerization. On the way, that is, impregnated with styrene resin growing particles. A solvent or a plasticizer may be added to the styrene resin seed particles in advance.

  When the temperature for impregnating the styrene resin particles, the styrene resin seed particles or the styrene resin growth particles with the solvent and the plasticizer is low, the impregnation takes time, and the production efficiency of the expandable styrene resin particles is increased. On the other hand, if it is high, a large amount of coalescence between the expandable styrene resin particles may occur, so 60 to 120 ° C is preferable, and 70 to 100 ° C is more preferable.

  Further, in the expandable styrene resin particles of the present invention, the foamed cell nucleating agent, the filler, the flame retardant, the flame retardant aid, the lubricant, the colorant and the like are added to the above-mentioned solvents and plasticizers as long as the physical properties are not impaired. May be added as appropriate in the same manner as described above.

  Examples of the flame retardant include tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, and the like. When the content of the flame retardant in the expandable styrene resin particles is small, the flame retardancy of the styrene resin foam molded article obtained using the expandable styrene resin particles may be insufficient. If it is too much, the moldability of the expandable styrene resin particles may be lowered, so 0.5 to 1.5% by weight is preferable.

  Examples of the flame retardant aid include organic peroxides such as dicumyl peroxide. If the content of the flame retardant aid in the expandable styrene resin particles is small, the effect of adding the flame retardant aid may not be manifested. Since the property may be lowered, 0.05 to 0.5% by weight is preferable.

The expandable styrene resin particles obtained in this way are pre-expanded by a pre-foaming machine to be styrene resin pre-expanded particles. Here, if the bulk density of the styrene resin pre-expanded particles is low, the resulting styrene resin foam molded product may shrink and the appearance may deteriorate, or the heat insulation and mechanical properties of the styrene resin foam molded product may decrease. while the strength is lowered, the large, the weight of the resulting styrene resin foam molded article may be decreased, preferably 0.01~0.03g / cm ^3, 0.01~0. 25 g / cm ³ is more preferable.

In addition, the bulk density of the styrene resin pre-expanded particles refers to that measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. First, Wg was collected using styrene resin pre-expanded particles as a measurement sample, this measurement sample was naturally dropped into a graduated cylinder, and the volume Vcm ³ of the measurement sample dropped into the graduated cylinder was measured as an apparent density in accordance with JIS K6911. The bulk density of the styrene resin pre-expanded particles was measured based on the following formula.

Bulk density (g / cm ³ ) of styrene resin pre-expanded particles
= Weight of measurement sample (W) / Volume of measurement sample (V)

  The resulting styrene resin pre-expanded particles are aged at normal pressure, filled in a mold of a foam molding machine, and then secondarily expanded by a heating medium such as heating steam. A styrenic resin foam molded body having a desired shape is formed by heat fusion and integration with each other.

  If the aging temperature of the styrene resin pre-foamed particles is low, the aging time of the styrene resin pre-foamed particles may be long. On the other hand, if it is high, the foaming agent in the styrene resin pre-foamed particles is dissipated. Since a moldability falls, 20-60 degreeC is preferable.

  On the other hand, if the average cell diameter of the styrene resin foam molded article is small, the heat insulation property of the styrene resin foam molded article may be lowered, whereas if it is large, the mechanical strength of the styrene resin foam molded article is lowered. Therefore, 50 to 500 μm is preferable, 80 to 400 μm is more preferable, and 100 to 350 μm is particularly preferable.

  In addition, the average cell diameter of a styrene-type resin foaming molding means what was calculated based on the average chord length measured based on the test method of ASTM D2842-69. Specifically, the styrenic resin foam molding is cut in any direction, and the central part of each cut surface is enlarged by 17 to 20 times (in some cases 200 times) using a scanning electron microscope. To do.

Next, the average chord length (t) of each bubble is calculated based on the following formula 1 from the number of bubbles on a straight line of a length of 60 mm in each photograph taken.
Average chord length (t) = 60 / (number of bubbles × photo magnification) Formula 1

And the bubble diameter D in each photograph is computed by following formula 2, and let the arithmetic mean of the bubble diameter of each photograph be an average bubble diameter of a styrene resin foaming molding.
Bubble diameter D = t / 0.616

  In the method for producing expandable styrene resin particles of the present invention, styrene resin seed particles containing scaly silicate are dispersed in water in advance, seed polymerization is performed using the styrene resin seed particles as seed particles, and dispersed. Since the styrene monomer is supplied to the liquid so that the amount of the styrene monomer in the styrene resin growing particles is not more than a predetermined amount, the resulting styrene resin particles have scaly silicic acid at the center. While the salt is abundantly contained, it is not contained in the surface portion or is contained only in a small amount even if it is contained.

  Accordingly, when a styrene resin pre-foamed particle is produced by secondary foaming of a styrene resin pre-foamed particle obtained by pre-foaming expandable styrene resin particles, a scaly shape is formed on the surface portion of the styrene resin pre-foamed particle. It is possible to prevent foam breakage caused by silicate and to ensure a foaming pressure necessary for heat-sealing styrene resin pre-foamed particles.

  Therefore, there is no decrease in the heat-fusibility at the surface portion of the styrene resin pre-expanded particles or it can be minimized. When the styrene resin pre-expanded particles are filled in a mold and foamed, styrene The foamed particles obtained by foaming the base resin pre-expanded particles are strongly heat-bonded and integrated with each other, and the resulting styrene-based resin foam molded article has excellent mechanical strength and appearance. And since the bubble-breaking in the surface part of a styrene resin pre-expanded particle is prevented effectively as mentioned above, the high expansion ratio of the obtained styrene resin foam molding can also be achieved reliably.

  Furthermore, the scaly silicate that is abundantly contained in the center of the expandable styrene resin particles may impair the expandability of the styrene resin pre-expanded particles as the expandable styrene resin particles expand. It diffuses substantially uniformly throughout the foamed particles without impairing the heat-fusibility between the foamed particles, and is almost uniformly contained throughout the resulting styrenic resin foamed molded product. The body has excellent heat insulation.

  In addition, in the production of styrene resin particles, scaly silicate is preliminarily contained in seed particles as seed particles, and only styrene monomer is dispersed without supplying scaly silicate in the subsequent seed polymerization. Since the amount of styrene monomer in the styrene resin growing particles is supplied within the predetermined range, the polymerization of the styrene monomer in the styrene resin growing particles can be carried out smoothly and obtained. The amount of residual styrene monomer in the styrene resin particles obtained can be reduced.

  Therefore, the styrene resin foam molded article obtained by using the expandable styrene resin particles obtained by the production method of the present invention has a small amount of residual styrene monomer and is excellent in environmental hygiene.

(Example 1)
In a twin screw extruder, 8000 parts by weight of a polystyrene-based resin having a styrene-converted weight average molecular weight of 200,000 and 2000 parts by weight of natural mica that does not pass through a sieve with an opening of 30 μm and passes through a sieve with an opening of 50 μm. Supply and melt knead at 230 ° C., extrude into a strand form from an extruder, cut this strand for each predetermined length, cylindrical styrene resin seed particles (diameter 20% by weight of flaky silicate) : 1.0 mm, length: 1.5 mm).

  Next, in a polymerization vessel with a stirrer, 2,000 parts by weight of water, 500 parts by weight of styrene resin seed particles, 6 parts by weight of magnesium pyrophosphate and 0.3 parts by weight of calcium dodecylbenzenesulfonate were supplied and stirred at 70 ° C. A dispersion was prepared by heating.

  Subsequently, 4.5 parts by weight of benzoyl peroxide and 1.1 parts by weight of t-butylperoxybenzoate were dissolved in 200 parts by weight 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 1300 parts by weight of the styrene monomer is further supplied into the dispersion at a constant supply rate over 3 hours. Then, seed polymerization is performed using styrene resin seed particles as seed particles to grow styrene resin seed particles, and after supplying all the styrene monomers, the mixture is heated to 125 ° C. and allowed to stand for 2 hours and then cooled. Thus, styrene resin particles were obtained. 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 weight.

  Next, after the dispersion liquid in which the styrene resin particles are dispersed is heated to 70 ° C., 23.4 parts by weight of tetrabromocyclooctane as a flame retardant and 5.4 parts by weight of dicumyl peroxide as a flame retardant aid are dispersed. Then, the polymerization vessel was sealed and heated to 90 ° C.

  Subsequently, 162 parts by weight of butane was injected into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles, the inside of the polymerization vessel was cooled to 30 ° C. Resin particles were obtained. The expandable styrene resin particles obtained had a natural mica content of 5.0% by weight and a residual styrene monomer content of 180 ppm relative to the total amount of expandable styrene resin particles.

  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 adjusted to be 0.05% by weight in the expandable styrenic resin particles.

  Thereafter, the expandable styrenic resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. The butane content in the expandable styrene resin particles after standing was measured using a gas chromatograph and found to be 5.1% by weight.

Then, the expandable styrene resin particles were heated and pre-expanded to a bulk density of 0.0167 g / cm ³ to obtain styrene resin pre-expanded particles. The styrene resin pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the styrene resin pre-expanded particles were filled in a mold and heated and foamed to obtain a styrene resin foamed plate having a length of 400 mm × width of 300 mm × thickness of 30 mm.

This styrene resin foam plate was aged in a drying room at 50 ° C. for 6 hours, and then the density of the styrene resin foam plate was measured to be 0.0167 g / cm ³ . This styrene resin foam board was excellent in appearance without shrinkage.

(Example 2)
In the production of styrene resin seed particles, styrene was used in the same manner as in Example 1 except that natural mica that did not pass through a sieve with an opening of 3 μm and passed through a sieve with an opening of 5 μm was used as natural mica. A resin-based resin foam plate was obtained. The content of natural mica in the styrene resin seed particles was 19.7% by weight. Further, 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 weight.

  Further, the expandable styrene resin particles had a natural mica content of 4.9% by weight and a residual styrene monomer content of 190 ppm based on the total amount of the expandable styrene resin particles.

(Example 3)
In the production of styrene-based resin seed particles, styrene was used in the same manner as in Example 1 except that natural mica that did not pass through a sieve with an opening of 100 μm and passed through a sieve with an opening of 200 μm was used as natural mica. A resin-based resin foam plate was obtained. The content of natural mica in the styrene resin seed particles was 20% by weight. Further, 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 weight.

  Further, the expandable styrene resin particles had a natural mica content of 5.0% by weight and a residual styrene monomer content of 200 ppm with respect to the total amount of the expandable styrene resin particles.

Example 4
In production of styrene-based resin seed particles, 9520 parts by weight of polystyrene-based resin having a styrene-converted weight average molecular weight of 200,000 is used in place of 8000 parts by weight, and 480 parts by weight of natural mica is used in place of 2000 parts by weight. Obtained a styrene resin foam board in the same manner as in Example 1. The content of natural mica in the styrene resin seed particles was 4.8% by weight. Further, 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 weight.

  Further, the expandable styrene resin particles had a natural mica content of 1.2% by weight and a residual styrene monomer content of 180 ppm based on the total amount of the expandable styrene resin particles.

(Example 5)
6600 parts by weight of polystyrene-based resin having a weight average molecular weight of 200,000 in terms of styrene and 3400 parts by weight of natural mica that does not pass through a sieve having an opening of 30 μm and passes through a sieve having an opening of 50 μm are used in a twin screw extruder. Supply and melt knead at 230 ° C., extrude into a strand form from an extruder, cut this strand every predetermined length, cylindrical styrene resin seed particles (diameter 34% by weight of flaky silicate) : 1.0 mm, length: 1.5 mm).

  Next, in a polymerization vessel equipped with a stirrer, 2000 parts by weight of water, 1000 parts by weight of styrene resin seed particles, 6 parts by weight of magnesium pyrophosphate and 0.3 parts by weight of calcium dodecylbenzenesulfonate were supplied and stirred at 70 ° C. A dispersion was prepared by heating.

  Subsequently, 3.0 parts by weight of benzoyl peroxide and 0.7 parts by weight of t-butylperoxybenzoate were dissolved in 200 parts by weight 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 weight of the styrene monomer is supplied to the dispersion at a constant supply rate over 3 hours. Then, seed polymerization is performed using styrene resin seed particles as seed particles to grow styrene resin seed particles, and after supplying all the styrene monomers, the mixture is heated to 125 ° C. and allowed to stand for 2 hours and then cooled. Thus, styrene resin particles were obtained. 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 16.7% by weight.

  Next, after the dispersion liquid in which the styrene resin particles are dispersed is heated to 70 ° C., 23.4 parts by weight of tetrabromocyclooctane as a flame retardant and 5.4 parts by weight of dicumyl peroxide as a flame retardant aid are dispersed. Then, the polymerization vessel was sealed and heated to 90 ° C.

  Subsequently, 162 parts by weight of butane was injected into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles, the inside of the polymerization vessel was cooled to 30 ° C. Resin particles were obtained. The expandable styrene resin particles obtained had a natural mica content of 17.0% by weight and a residual styrene monomer content of 185 ppm relative to the total amount of expandable styrene resin particles. And the styrene resin foamed board was obtained like Example 1 using the foamable styrene resin particle obtained as mentioned above.

(Example 6)
In the production of styrenic resin seed particles, instead of natural mica, synthetic mica (titanium oxide coating) whose surface does not pass through a 30 μm sieve and through which a 50 μm sieve passes is coated with titanium oxide A styrene-based resin foam plate was obtained in the same manner as in Example 1 except that synthetic mica) was used. The titanium oxide content in the titanium oxide-coated synthetic mica was 30% by weight. The content of titanium oxide-coated synthetic mica in the styrene resin seed particles was 20% by weight. Further, 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 28.7% by weight.

  Further, the expandable styrene resin particles had a titanium oxide-coated synthetic mica content of 5.0% by weight and a residual styrene monomer content of 190 ppm based on the total amount of the expandable styrene resin particles.

(Example 7)
In the production of styrene-based resin seed particles, the same procedure as in Example 1 was used, except that sericite that did not pass through a 30 μm sieve and passed through a 50 μm sieve was used instead of natural mica. A styrene resin foamed plate was obtained. The sericite content in the styrene resin seed particles was 19.6% by weight. Further, 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 28.7% by weight.

  Further, the expandable styrene resin particles had a sericite content of 4.9% by weight and a residual styrene monomer content of 178 ppm relative to the total amount of expandable styrene resin particles.

(Example 8)
In seed polymerization, a styrenic resin was prepared in the same manner as in Example 1 except that 1.5 hours was used instead of 3 hours for supplying the styrene monomer to the dispersion after heating the dispersion to 90 ° C. A foam plate was obtained. The content of natural mica in the styrene resin seed particles was 20% by weight. Further, 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 55.0% by weight.

  Further, the expandable styrene resin particles had a natural mica content of 5.0% by weight and a residual styrene monomer content of 170 ppm based on the total amount of the expandable styrene resin particles.

Example 9
In seed polymerization, the styrene-based resin foamed plate was treated in the same manner as in Example 1 except that the dispersion was heated to 90 ° C. and then the styrene monomer was supplied to the dispersion for 4 hours instead of 3 hours. Got. The content of natural mica in the styrene resin seed particles was 20% by weight. Further, 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 28.7% by weight.

  Further, the expandable styrene resin particles had a natural mica content of 5.0% by weight and a residual styrene monomer content of 174 ppm based on the total amount of the expandable styrene resin particles.

(Comparative Example 1)
In the production of styrene resin seed particles, a polystyrene resin foam plate was obtained in the same manner as in Example 1 except that the polystyrene resin was changed to 10000 parts by weight instead of 8000 parts by weight, and natural mica was not used. 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 28.7% by weight. The expandable styrene resin particles had a residual styrene monomer content of 190 ppm with respect to the total amount of expandable styrene resin particles.

(Comparative Example 2)
In a twin screw extruder, 7000 parts by weight of a polystyrene-based resin having a weight-average molecular weight in terms of styrene of 200,000 and 3000 parts by weight of natural mica that does not pass through a sieve with an opening of 30 μm and passes through a sieve with an opening of 50 μm. Supply and melt knead at 230 ° C., extrude into a strand form from an extruder, cut this strand every predetermined length, columnar styrene resin seed particles (diameter 30% containing scaly silicate) : 1.0 mm, length: 1.5 mm).

  Next, 5000 parts by weight of water, 1500 parts by weight of styrenic resin seed particles, 12 parts by weight of magnesium pyrophosphate and 0.5 parts by weight of calcium dodecylbenzenesulfonate are supplied to a polymerization vessel equipped with a stirrer while stirring at 70 ° C. A dispersion was prepared by heating.

  Subsequently, 7 parts by weight of benzoyl peroxide and 1 part by weight of t-butylperoxybenzoate were dissolved in 200 parts by weight of styrene monomer, and all of the styrene monomer was supplied to the dispersion while stirring.

  Then, after 30 minutes have passed since the styrene monomer was supplied to the dispersion, the dispersion was heated to 90 ° C., and 1300 parts by weight of styrene monomer was further added to the dispersion at a constant supply rate over 1.5 hours. The styrene resin seed particles are used as seed particles for seed polymerization to grow styrene resin seed particles, and after all the styrene monomers have been supplied, they are heated to 125 ° C. and left for 2 hours. After cooling, styrene resin particles were obtained. 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 65.0% by weight.

  Next, after the dispersion liquid in which the styrene resin particles were dispersed was heated to 70 ° C., 36 parts by weight of tetrabromocyclooctane as a flame retardant and 9 parts by weight of dicumyl peroxide as a flame retardant aid were supplied into the dispersion. The polymerization vessel was sealed above and heated to 90 ° C.

  Subsequently, 180 parts by weight of butane was injected into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles, the inside of the polymerization vessel was cooled to 30 ° C. Resin particles were obtained. The expandable styrene resin particles obtained had a natural mica content of 15.0% by weight and a residual styrene monomer content of 198 ppm with respect to the total amount of expandable styrene resin particles.

  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 adjusted to be 0.05% by weight in the expandable styrenic resin particles.

  Thereafter, the expandable styrenic resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. The butane content in the expandable styrene resin particles after standing was measured using a gas chromatograph and found to be 5.4% by weight.

Then, the expandable styrene resin particles were heated and pre-expanded to a bulk density of 0.0169 g / cm ³ to obtain styrene resin pre-expanded particles. The styrene resin pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the styrene resin pre-expanded particles were filled in a mold, heated and foamed to obtain a styrene resin foamed plate having a length of 400 mm × width of 300 mm × thickness of 30 mm. This styrene resin foam plate was aged in a drying room at 50 ° C. for 6 hours, and then the density of the styrene resin foam plate was measured to be 0.0169 g / cm ³ .

(Comparative Example 3)
In a polymerization vessel equipped with a stirrer, 5000 parts by weight of water, 9 parts by weight of benzoyl peroxide, and 2000 parts by weight of styrene monomer in which 1.5 parts by weight of t-butylperoxybenzoate were dissolved, did not pass through a sieve having an opening of 30 μm and Supply 100 parts by weight of graphite particles passing through a sieve with an opening of 50 μm, 12 parts by weight of magnesium pyrophosphate, and 0.5 parts by weight of calcium dodecylbenzenesulfonate, and heat to 90 ° C. with stirring for 7 hours. Suspension polymerization was continued, followed by heating to 125 ° C. and further suspension polymerization for 2 hours, followed by cooling to obtain styrene resin particles.

  After the styrene resin particle suspension was heated to 70 ° C., 36 parts by weight of tetrabromocyclooctane as a flame retardant and 9 parts by weight of dicumyl peroxide as a flame retardant aid were supplied into the suspension. The vessel was sealed and heated to 90 ° C.

  Subsequently, 180 parts by weight of butane was injected into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles, the inside of the polymerization vessel was cooled to 30 ° C. Resin particles were obtained. The obtained expandable styrene resin particles had a graphite particle content of 5% by weight and a residual styrene monomer content of 980 ppm relative to the total amount of expandable styrene resin particles.

  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 adjusted to be 0.05% by weight in the expandable styrenic resin particles.

  Thereafter, the expandable styrenic resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. The butane content in the expandable styrene resin particles after standing was measured using a gas chromatograph and found to be 5.9% by weight.

Then, the expandable styrene resin particles were heated and pre-expanded to a bulk density of 0.0169 g / cm ³ to obtain styrene resin pre-expanded particles. The styrene resin pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the styrene resin pre-expanded particles were filled in a mold, heated and foamed to obtain a styrene resin foamed plate having a length of 400 mm × width of 300 mm × thickness of 30 mm. This styrene resin foam plate was aged in a drying room at 50 ° C. for 6 hours, and then the density of the styrene resin foam plate was measured to be 0.0169 g / cm ³ .

(Comparative Example 4)
In a twin screw extruder, 9000 parts by weight of a polystyrene resin having a weight average molecular weight of 200,000 in terms of styrene and 1000 parts by weight of natural mica that does not pass through a sieve with an opening of 30 μm and passes through a sieve with an opening of 50 μm. Supply and melt knead at 230 ° C., extrude into a strand form from an extruder, cut this strand every predetermined length, cylindrical styrene resin seed particles containing 10.0% by weight of flaky silicate (Diameter: 1.0 mm, length: 1.5 mm) was produced.

  Next, in a polymerization vessel with a stirrer, 2,000 parts by weight of water, 2000 parts by weight of styrene resin seed particles, 6 parts by weight of magnesium pyrophosphate and 0.3 parts by weight of calcium dodecylbenzenesulfonate were supplied and stirred at 70 ° C. A dispersion was prepared by heating.

  Thereafter, in a state where the dispersion liquid in which the styrenic resin seed particles are dispersed is maintained at 70 ° C., 26 parts by weight of tetrabromocyclooctane as a flame retardant and 6 parts by weight of dicumyl peroxide as a flame retardant aid are contained in the dispersion. After feeding, the polymerization vessel was sealed and heated to 90 ° C.

  Subsequently, 180 parts by weight of butane was injected into the polymerization vessel and held for 6 hours. After impregnating butane into the styrene resin particles, the inside of the polymerization vessel was cooled to 30 ° C. Resin particles were obtained. The expandable styrene resin particles obtained had a natural mica content of 10.0% by weight.

  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 adjusted to be 0.05% by weight in the expandable styrenic resin particles.

  Thereafter, the expandable styrenic resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. The butane content in the expandable styrenic resin particles after standing was measured using a gas chromatograph and found to be 5.7% by weight.

Then, the expandable styrene resin particles were heated and pre-expanded to a bulk density of 0.0167 g / cm ³ to obtain styrene resin pre-expanded particles. The styrene resin pre-expanded particles were aged at 20 ° C. for 24 hours. Next, the styrene resin pre-expanded particles were filled in a mold, heated and foamed to obtain a styrene resin foamed plate having a length of 400 mm × width of 300 mm × thickness of 30 mm. This styrene resin foam plate was aged in a drying room at 50 ° C. for 6 hours, and then the density of the styrene resin foam plate was measured to be 0.0167 g / cm ³ .

  The heat insulation property, internal fusion rate, and maximum bending strength of the obtained styrene-based resin foam plate were measured as shown below, and the results are shown in Table 1. In Table 1, the maximum value of the amount of styrene monomer in the growing styrene-based resin growing particles is defined as “maximum styrene monomer amount”, and the content of scaly silicate in the expandable styrene-based resin particles is expressed as “silicic acid”. It was described as “salt content”.

(Thermal insulation properties)
A rectangular parallelepiped test piece having a length of 200 mm, a width of 200 mm, and a thickness of 30 mm was cut out from the styrene resin foam plate. And the heat conductivity of this test piece was measured at the measurement temperature of 20 degreeC by the flat plate heat flow meter method based on JISA1412.

(Internal fusion rate)
A cutting line having a depth of about 5 mm in the longitudinal direction is formed in the center portion in the horizontal direction of the styrene resin foam board using a cutter knife, and the styrene resin foam board is formed along the cut line. Divided by hand in the horizontal direction.

Then, an arbitrary area of 60 cm ^{2 in} the fracture surface of the styrene resin foam plate is visually observed, and the number of foam particles (a) broken in the foam particles and the heat fusion interface between the foam particles. The number of foam particles broken (b) was counted, and the internal fusion rate was calculated based on the following formula. Note that the higher the internal fusion rate, the stronger the foamed particles are integrated by heat fusion.
Internal fusion rate (%) = 100 × (a) / [(a) + (b)]

(Maximum bending strength)
The maximum bending strength of the styrene resin foam plate was measured in accordance with the method described in JIS K9511: 1999 “Foamed plastic heat insulating material”. Specifically, a rectangular parallelepiped test piece having a length of 75 mm, a width of 300 mm, and a thickness of 15 mm was cut out from the styrene resin foam plate. Thereafter, the maximum bending strength of this test piece was measured using a bending strength measuring device (trade name “UCT-10T” manufactured by Orientec Co., Ltd.), a compression speed of 10 mm / min, a distance between fulcrums of 200 mm, a pressure wedge 10R, and a support. It measured on the conditions of the base 10R. Three test pieces were prepared, the maximum bending strength was measured for each test piece as described above, and the arithmetic average was taken as the maximum bending strength.

Claims (6)

A styrene monomer is supplied into a dispersion obtained by dispersing styrene resin seed particles containing scaly silicate in water, and the styrene resin seed particles are impregnated into the styrene resin to polymerize the styrene resin. A method for producing expandable styrene resin particles in which a foaming agent is impregnated after growing seed particles to produce styrene resin particles or during the growth of styrene resin seed particles, A foamable styrene resin, characterized in that the styrene monomer is supplied into the dispersion so that the amount of the styrene monomer in the growing styrene resin growing particles as seed particles is 60% by weight or less. Particle manufacturing method. A foamable styrene resin particle produced by the method for producing an expandable styrene resin particle according to claim 1, wherein the content of scaly silicate is 1 to 20% by weight. Styrenic resin particles. The expandable styrenic resin particles according to claim 2, wherein the scaly silicate is mica. The expandable styrene resin particles according to claim 2 or 3, wherein the content of the residual styrene monomer is 500 ppm or less with respect to the total weight of the styrene resin particles. Styrenic resin pre-expanded particles obtained by pre-expanding the expandable styrene resin particles according to any one of claims 2 to 4 to a bulk density of 0.01 to 0.03 g / cm ³ . A styrene resin foamed molded article obtained by filling the foamed styrene resin pre-expanded particles according to claim 5 in a mold.