JP5403803B2 - Expandable styrenic resin particles and foamed moldings thereof - Google Patents

Description

  The present invention relates to expandable styrene resin particles. Specifically, the present invention relates to expandable styrene resin particles obtained by classifying polystyrene resin particles obtained by suspension polymerization and impregnating with a foaming agent. More specifically, the present invention relates to expandable styrene resin particles, expanded particles, and expanded molded articles suitable for an expansion ratio of 5 to 40 times, which have a low styrene monomer content, good fusion properties, and good appearance. .

In general, a foam-molded product obtained from expandable styrene-based resin particles is excellent in lightness, heat insulation, strength, and hygiene, and is widely used for food containers, cushioning materials, heat insulation materials and the like. The expandable styrene resin particles of the present invention are suitable for an expansion ratio of 5 to 40 times.
In the field of residential building materials in recent years, the problem of sick house syndrome, which is generally said to be caused by volatile organic compounds (VOC) contained in building materials, has been greatly taken up, and there is a strong demand for low VOC raw materials.
On the other hand, when foamable styrene resin particles are used as a floor heating panel, the particle size is 200 to 600 μm, the content of residual styrene monomer is 1000 ppm or less, and 2 to 6% by weight of butane is used as a foaming agent. The foamable styrene resin particles contained are proposed in Patent Document 1. When this expandable styrenic resin particle is used for building materials such as a floor heating panel, the preliminary foaming capacity is small and the appearance is poor, the particles are not fused well, and the dimensional change of the foamed molded product over time The rate was great.
On the other hand, Patent Document 2 proposes to use hydrocarbons having a boiling point of 50 ° C. or higher as foaming aids as expandable styrene-based resin particles that can be foamed at low and medium magnifications. However, hydrocarbons having a large molecular weight are not preferred because they are listed as substances that generate VOCs.

JP 2004-155870 A JP-A-11-286571

  The present invention is a foam that has a low residual styrene monomer and can be reduced in VOC, is suitable for building materials that are compatible with sick house syndrome, has good fusion properties, has a good appearance, and has a small rate of dimensional change over time. An object is to obtain expandable styrene resin particles suitable for a magnification of 5 to 40 times.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor obtained by impregnating polystyrene resin particles obtained by suspension polymerization with a foaming agent, having a particle diameter of 300 to 800 μm and containing a residual styrene monomer. A plasticizer having an expandable resin particle amount of 500 ppm or less, containing 3 to 7% by weight of butane as a foaming agent, and having a solubility parameter value (SP value) of 8.3 or more and 9.4 or less. By using expandable styrenic resin particles containing 0.2 to 2.0% by weight, a foamed molded article having an expansion ratio of 5 to 40 times has a small dimensional change rate with time and excellent dimensional stability. The present invention was completed by finding that the fusion of the resin was good, excellent in appearance, and sufficient in strength.

  In particular, the present invention relates to expandable styrene resin particles obtained by classifying polystyrene resin particles obtained by a suspension polymerization method with a sieve of 300 to 800 μm and impregnating at a temperature equal to or higher than the boiling point of the foaming agent. When the particle size distribution by the JIS standard sieve is 80% or more in the range of 0.425 to 0.71 mm and the average particle size is 0.45 to 0.65 mm, the dimensional change rate of the molded product is small. Good filling properties for molds with thin wall thickness for building materials.

  The present invention is an expandable resin particle obtained by impregnating a polystyrene resin particle obtained by a suspension polymerization method with a foaming agent and having a particle size of 300 to 800 μm and a residual styrene monomer content of 500 ppm or less. Further, it contains 3 to 7% by weight of butane as a foaming agent and 0.2 to 2.0% by weight of a plasticizer having a solubility parameter value (SP value) of 8.3 or more and 9.4 or less. The foamed molded product obtained by pre-foaming the foamable styrene resin particles at a foaming ratio of 5 to 40 times and molding has a small dimensional change rate over time, excellent dimensional stability, and good fusion between the particles, A foamed molded article having excellent appearance and sufficient strength can be provided.

  As the styrenic resin particles used in the present invention, those produced by a usual suspension polymerization method are used. It is a monomer polymer or copolymer containing styrene as a main component and containing 50% or more of styrene. Monomers copolymerizable with styrene include styrene derivatives such as α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, acrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate, and methacrylic acid. Or a copolymer with various monomers such as acrylonitrile, dimethyl fumarate and ethyl fumarate. Moreover, you may use together bifunctional monomers, such as divinylbenzene and alkylene glycol dimethacrylate.

  In the present invention, as a suspension stabilizer used for suspending a monomer in an aqueous medium, conventionally known polyvinyl alcohol, methyl cellulose, polyacrylamide, polyvinyl pyrrolidone generally used in suspension polymerization are used. And water-soluble polymers such as tricalcium phosphate and poorly water-soluble inorganic compounds such as magnesium pyrophosphate. When using a poorly water-soluble inorganic compound, an anionic surfactant such as sodium dodecylbenzenesulfonate is usually used in combination.

  In the present invention, in order to obtain polystyrene resin particles having a uniform particle diameter, for example, polystyrene resin particles obtained by suspension polymerization on a 0.475 to 0.63 mm sieve are classified and used. The foamable polystyrene resin particles of interest are obtained by impregnating the sieved polystyrene resin particles with a foaming agent.

  The particle diameter of the expandable styrene resin particles in the present invention is 300 to 800 μm. When the particle diameter is less than 300 μm, the coalescence during impregnation increases, which is not preferable. When the particle diameter exceeds 800 μm, the filling property into a thin mold having a thin wall thickness for building materials and the like tends to be deteriorated.

  Moreover, 0.425-0.71mm is 80% or more of the particle size distribution by the standard sieve of JIS. Preferably it is 95% or more, More preferably, it is 100%. When the particle size distribution by the JIS standard sieve is less than 80%, the particle size distribution of the expandable styrenic resin particles becomes wide. The average particle diameter of the expandable styrene resin particles is 0.45 to 0.65 mm. When the average particle diameter is smaller than 0.45 mm, the amount of foaming agent used is increased, and the dimensional change rate of the molded product is increased. If the average particle diameter is larger than 0.65 mm, the filling property into a mold having a thin wall thickness for building materials and the like tends to deteriorate, which is not preferable.

  The weight-average molecular weight of the polystyrene resin particles is usually in the range of 200000-350,000, preferably 220,000-320,000.

  As the polymerization initiator in the present invention, a radical generating polymerization initiator generally used in suspension polymerization of styrene can be used. For example, benzoyl peroxide, lauryl peroxide, t-butylperoxy-2-ethylhexa Noate, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, 2,2-t-butyl peroxybutane, Examples thereof include organic peroxides such as t-butylperoxy-3,3,5-trimethylhexanoate and di-t-butylperoxyhexayl hydroterephthalate, and azo compounds such as azobisdimethylvaleronitrile. These polymerization initiators can be used alone or in combination of two or more. Usually, in order to adjust the molecular weight and reduce the amount of residual monomer, a polymerization initiator having a decomposition temperature in the range of 50 to 80 ° C. for obtaining a half-life of 10 hours, and a decomposition temperature of 80 to 120 ° C. Different polymerization initiators in the range are used in combination.

  The amount of residual styrene contained in the expandable styrene resin particles in the present invention is 500 ppm or less. Preferably the amount of residual styrene is 200 ppm or less, optimally 160 ppm or less. If the amount of residual styrene exceeds 500 ppm, the amount of styrene diffused indoors in the molded article for building material obtained by prefoaming and molding is not preferable. As a method for lowering the amount of residual styrene contained in the expandable styrene resin particles to 500 ppm or less, a polymerization initiator is used at a decomposition temperature of 80 to 120 ° C. in a range of 0.03 parts by weight or more, and a temperature of 110 ° C. or more. Can be achieved by securing a process for reducing the residual styrene for 1 hour or longer.

  As the blowing agent in the present invention, butane is used, but hydrocarbons such as propane and pentane having a volatility whose boiling point is lower than the softening point of the polymer may be used together. The butane content in the expandable styrene resin particles in the present invention is 3 to 7% by weight, preferably 3.5 to 6% by weight. If the amount is less than 3% by weight, the pre-foaming time becomes longer and the fusion at the time of molding becomes worse. If it exceeds 7% by weight, the variation in foaming between the particles at the time of foaming increases and the cooling time at the time of molding increases and the productivity is increased. Is unfavorable because it is damaged. Moreover, about the composition of butane, the ratio of isobutane is 10 to 45 weight% by weight ratio. If the weight ratio of isobutane is less than 10% by weight, there are many particle gaps in the molded body and the fusion during molding becomes worse, and if it exceeds 45% by weight, the dimensional shrinkage ratio over time of the molded product increases.

  In the present invention, a heat-resistant and pressure-resistant autoclave with a stirrer is used as a reactor. As a method for adding the blowing agent to the autoclave, butane which is a gas at normal temperature and normal pressure is added in a liquid state at a temperature of 20 to 130 ° C. in the system. If it is added as a gas, the pressure rise in the autoclave system is so large that it is difficult to add the foaming agent into the autoclave.

  In the present invention, the expanded particles obtained by pre-expanding the expandable styrene resin particles 5 to 45 times contain 1 to 6% by weight of butane as a foaming agent in the expanded particles after 24 hours at 20 ° C. . When the content of butane in the expanded particles is less than 1% by weight, there are many particle gaps in the molded body and the fusion during molding becomes worse, and when it exceeds 6% by weight, the dimensional shrinkage ratio of the molded product with time increases and molding takes place. This is not preferable because the cooling time and the productivity are impaired. The particle diameter of the expanded particles is 500 to 3000 μm. If the particle diameter of the expanded particles is less than 500 μm, the fusion during molding is poor, and if it exceeds 3000 μm, the filling property of the expanded particles into a thin mold for building materials is not preferable.

The plasticizer in the present invention contains 0.2 to 2.0% by weight of a plasticizer having a solubility parameter value (SP value) of 8.3 or more and 9.4 or less. As for the plasticizer, for example, diisobutyl adipate, diisononyl adipate for adipic acid esters, dioctyl phthalate, dibutyl phthalate for phthalic acid esters, dibutyl sebacate for sebacic acid esters, etc. In particular, diisobutyl adipate is preferred.
Examples of the plasticizer include organic substances having an SP value (Solubility parameter) of 8.3 or more and 9.4 or less, preferably adipic acid esters having an SP value of 8.5 or more and 9.2 or less. Diisobutyl adipate (DIBA) (SP value = 8.9) and isononyl adipate (DINA) are preferred. The SP value of the present invention is calculated by substituting evaporation energy ΔE and molar volume V per unit volume of one molecule into the following equation.
(SP) ² = ΔE / V

About a plasticizer, it contains 0.2 to 2.0 weight%. Preferably, it is 0.5 to 1.5% by weight. If it is less than 0.2% by weight, there will be many particle gaps in the molded product and the fusion during molding will be poor, and if it exceeds 2.0% by weight, there will be more coalescence of the expanded particles during pre-foaming and molding. This is not preferable because the cooling time and the productivity are impaired.
For the plasticizer, a boiling point of 1 atm is 150 ° C. or higher. Preferably, the boiling point at 1 atm is 200 ° C. or higher. If the boiling point at 1 atm is less than 150 ° C., the plastic component is dissipated from the molded article after foam molding, and therefore it is not preferable because it is regarded as a VOC substance.

  In the present invention, in addition to the foaming agent and the plasticizer, it is used for producing foamable styrene resin particles such as a foamed cell nucleating agent, a filler, a flame retardant, a flame retardant aid, a lubricant, a colorant, and a crosslinking agent. You may add an additive suitably as needed.

  The expandable styrene resin particles in the present invention may be surface-coated within a range that does not impair the physical properties. The coating agent can be mixed and adhered by a mixer or the like as necessary when producing expandable styrene resin particles. Examples of the coating agent include powdered metal soaps such as zinc stearate, stearic acid triglyceride, stearic acid monoglyceride, castor oil, amide compounds, silicones, and polyethylene glycol.

  Hereinafter, although an example is given and explained further, the present invention is not limited by these examples. Various measurement methods and production conditions described in the examples will be described below.

Example 1
(Preparation of polystyrene resin particles)
Add 120 g of tricalcium phosphate (manufactured by Taihei Chemical Co., Ltd.), 0.2 g of sodium bisulfite and 0.2 g of potassium persulfate to an autoclave with a stirrer (hereinafter also referred to as “reactor”) having an internal volume of 100 liters. After adding 136 g of benzoyl (purity 75%), 30 g of t-butylperoxy-2-ethylhexyl monocarbonate, 40 kg of ion exchange water and 40 kg of styrene, the mixture was dissolved and dispersed under stirring to form a suspension.
Next, styrene was subjected to a polymerization reaction at 90 ° C. for 6 hours and further at 125 ° C. for 2 hours under stirring at 200 rpm. After completion of the reaction, it is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated and dried, and then classified at 0.475 to 0.63 mm, and the particle size is 0.355 to 0.71 mm and weight. Styrene polymer seed particles having an average molecular weight of 300,000 were obtained.

(Creation of expandable styrene resin particles)
Next, 42 kg of the above styrene resin particles, 36 kg of distilled water, 168 g of magnesium pyrophosphate, and 8 g of sodium dodecylbenzenesulfonate are placed in an autoclave equipped with a stirrer with an internal volume of 100 liters, stirred and suspended at 140 rpm, and then up to 100 ° C. The temperature rose.
Thereafter, 20 g of magnesium pyrophosphate was added to 2000 g of distilled water, and 420 g of diisobutyl adipate (DIBA) as a plasticizer was added to 2 g of sodium dodecylbenzenesulfonate, and the suspension was press-fitted into the reactor by stirring with a homomixer. . Thereafter, 3108 g of butane (35% by weight of isobutane) as a blowing agent was injected into the reactor in a liquid state. Thereafter, the inside of the reactor was kept at 100 ° C. for 2 hours, cooled to 20 ° C., particles were taken out, washed, dehydrated and dried. The obtained expandable styrene resin particles had a particle size distribution of 0.355 to 0.71 mm. Furthermore, the foamed particles after the pre-expansion were aged at 15 ° C. for 3 days until the cell diameters were completely stabilized to obtain expandable styrene resin particles. The foaming agent content of the expandable styrene resin particles was measured after aging at 15 ° C. for 3 days after production of the expandable styrene resin particles.

(Coating of expandable particles)
5 kg of the expandable styrene resin particles were put into a radige mixer M20 type (with an internal volume of 20 liters) manufactured by Matsuzaka Trading Co., Ltd. Subsequently, 4 g of magnesium stearate, 18 g of 12-hydroxystearic acid triglyceride, 4 g of calcium carbonate, and 2 g of stearic acid monoglyceride were sequentially added, followed by stirring at 230 rpm for 3 minutes. Next, 1.5 g of polyethylene glycol having a weight average molecular weight of 300 and 2 g of dimethylpolysiloxane having a weight of 100 cs were added and stirred at 230 rpm for 5 minutes to coat the surface of the expandable styrene resin particles.

(Foam molding)
The coated expandable styrenic resin particles were pre-expanded to 20 times the bulk by heating with atmospheric steam at a gauge pressure of 0.05 MPa using a small batch type pre-foaming machine with a capacity of 40 liters.
The obtained pre-expanded particles were left at 20 ° C. for 24 hours, dried and aged. Then, after measuring the amount of the foaming agent, it was filled in the mold of a foam molding machine (trade name “ACE-3SP” manufactured by Sekisui Koki Co., Ltd.) and subjected to secondary foaming using water vapor, thereby A plate-like foamed molded product of 300 mm × width 400 mm × height 10 mm was obtained.

(Measurement of the bulk multiple of expanded particles)
A 1 liter graduated cylinder was prepared, the expanded particles were filled to the 1 liter mark of the graduated cylinder, and the weight (g) of the filled expanded particles was weighed to the order of 0.1 g. From the obtained weight of the expanded particles per liter, the bulk multiple (liter / g) of the expanded particles was determined.

(Measurement of foaming agent content)
Samples of expandable styrene resin particles and pre-expanded particles (stored for 24 hours at 20 ° C. after manufacture) 10-20 mg are precisely weighed and sealed in a 20 ml glass vial and set in a Perkins Elmer headspace sampler TurboMatrixHS40 Then, after heating at 160 ° C. for 30 minutes, quantification was performed using a gas chromatograph Clarus500GC (detector: FID) manufactured by Perkins Elmer. The measurement conditions in the headspace sampler are a needle temperature of 160 ° C., a sample introduction time of 0.08 minutes, a transfer line temperature of 160 ° C., and the measurement conditions in the gas chromatograph are DB-1 (0.25 mmφ × 60 m, membrane manufactured by J & W) Thickness 1 μm, column temperature: 50 ° C. for 10 minutes, heating up to 270 ° C. at 20 ° C./minute, 270 ° C. for 1 minute), carrier gas helium (introduction conditions: 18 psi for 10 minutes, 0.5 psi / minute at 24 psi) And the inlet temperature (200 ° C.). The measured value was converted into a value for 100 parts by mass of the resin.

(Measurement of residual styrene monomer)
1 g of the obtained expandable styrene resin particles were precisely weighed, and 1 ml of a dimethylformamide solution containing 0.1% by volume of cyclopentanol was added as an internal standard solution to 1 g of the expandable styrene resin particles. Thereafter, dimethylformamide was further added to prepare a 25 ml measurement solution. And 1.8 microliters of this measurement solution was supplied to a gas chromatograph (trade name “GC-14A” manufactured by Shimadzu Corporation) and measured under the following measurement conditions to obtain a chart of the compounds in the measurement solution. And based on the calibration curve of the styrene monomer measured in advance, the amount of the styrene monomer in the measurement solution is calculated, whereby the residual styrene monomer with respect to the total weight of the expandable styrene resin particles (Ppm) was calculated and the results are shown in Table 1.

Detector: FID
Column: GL Sciences Inc. (inner diameter 3mm x 2.5m)
Liquid phase (PEG-20M PT 25%)
Carrier (Chromosorb W AW-DWCS)
Mesh: 60/80
Column temperature: 100 ° C
DET temperature: 230 ° C
Detector temperature: 230 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 40ml / min

(Measurement of amount of adipic acid ester)
2 mg of the obtained expandable styrene resin particles are precisely weighed and dissolved in 1 ml of toluene to prepare a toluene solution. Furthermore, 1 microliter of methanol solution containing 1000 μg / ml of pyrene is added to the toluene solution to prepare a test solution. On the other hand, a plurality of types of standard solutions containing adipic acid ester and pyrene and having different adipic acid ester concentrations are prepared, and these standard solutions are supplied to a gas chromatograph to prepare a calibration curve of adipic acid ester.
And the said test liquid is supplied to a gas chromatograph, the chart of adipic acid ester is obtained, and the total amount of adipic acid ester is computed based on the said analytical curve from this chart. From the total amount of adipic acid ester, the amount of adipic acid ester contained per 1 g of expandable styrene resin particles can be calculated.
The amount of adipic acid ester on the surface portion of the pre-expanded particles can be specifically measured under the following conditions using a gas chromatograph commercially available from Shimadzu Corporation under the trade name “GCMS QP5000”. it can. The column oven is heated from 70 ° C. at a rate of 15 ° C./min, heated from 260 ° C. at a rate of 10 ° C./min, and held at 300 ° C. for 3 minutes.
Separation column: Product name “DB-1” (1 μm × 0.25 mmφ × 60 m) manufactured by J & W
Carrier gas: Helium He flow rate: 1 ml / min Inlet temperature: 240 ° C
Interface temperature: 260 ° C
Split ratio: 10

(Measurement of average particle diameter of expandable styrene resin particles)
The obtained expandable styrene resin particles were sieved to each particle size based on a JIS standard sieve. In Table 1, the average particle diameter is a particle diameter at a point corresponding to 50% in cumulative weight percent. The weight% of 0.425 to 0.71 mm is a total value of the weight percentages of 0.425 to 0.500 mm, 0.500 to 0.600 mm, and 0.600 to 0.710 mm.

(Evaluation of fusion rate of foamed molded product)
The obtained plate-like foamed molded article was broken by impact, and the total number of particles (A) and the number of particles broken within the particles (B) in an arbitrary range including 100 to 150 expanded particles of the fractured surface (B ) And the fusion rate (%) is calculated by the following formula.
Fusing rate = (B) × 100 / (A)
In the evaluation of the fusion rate, 70% or more is good and less than 70% by weight is bad.

(Evaluation of expansion of foamed molded product)
The appearance of the obtained plate-like foamed molded product is visually evaluated. Specifically, the case where the boundary portion where the foamed particles on the surface of the molded body are joined is smooth, and the case where the boundary portion is uneven and the smoothness is inferior are regarded as bad.

(Comprehensive evaluation of foamed molded products)
In the evaluation of the fusion rate and the spread, a case where it is 70% or more and good is evaluated as ◯, and other cases are evaluated as ×.

(Measurement of dimensional change rate of foamed molded product)
This foam-molded plate-shaped foamed molded product having a length of 300 mm × width of 400 mm × height of 10 mm was left to stand at 23 ° C. for 2 days, and a rectangular parallelepiped test piece having a length of 120 mm × width of 120 mm × height of 10 mm was cut out. Was measured in accordance with JIS K6767: 1999 after standing at 23 ° C. for 672 hours. The case where the dimensional change rate was within ± 0.5% was indicated as “◯”, and the case where the dimensional change rate was below −0.5% or exceeded 0.5% was indicated as “X”.

  Various measurement results are shown in Tables 1 and 2.

(Example 2)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 2016 g of butane (35% by weight of isobutane) as a blowing agent was used. The evaluation results are shown in Tables 1 and 2.
(Example 3)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 4116 g of butane (35% by weight of isobutane) as a blowing agent was used. The evaluation results are shown in Tables 1 and 2.
Example 4
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 210 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Example 5)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 630 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.

(Example 6)
A plate-like foamed molded article was obtained in the same manner as in Example 1 except that the bulk expansion ratio of the pre-expanded particles was 10 times.
(Example 7)
A plate-like foamed molded article was obtained in the same manner as in Example 1 except that the bulk expansion ratio of the pre-expanded particles was 35 times.

(Comparative Example 1)
Expandable styrenic resin particles, expanded particles, and a plate-like foamed molded article were obtained in the same manner as in Example 1 except that 1200 g of butane (35% by weight of isobutane) as a foaming agent was used. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 2)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 4510 g of butane (35% by weight of isobutane) as a blowing agent was used. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 3)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 3108 g of butane (50% by weight of isobutane) as a blowing agent was used. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 4)
Expandable styrene resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 3108 g of normal butane (weight ratio of isobutane of 0%) as a blowing agent was used. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 5)
The foaming property is the same as in Example 1 except that the mesh size for sieving the polystyrene resin particles obtained by suspension polymerization is changed to 0.355 to 0.475 mm and the average particle size is changed to 0.40 mm. Styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 6)
The foaming property is the same as in Example 1 except that the mesh size for screening the polystyrene resin particles obtained by suspension polymerization is changed to 0.63 to 0.85 mm and the average particle size is changed to 0.68 mm. Styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 7)
Expandable styrene resin particles, expanded particles, and a plate-like foamed molded article were obtained in the same manner as in Example 1 except that 1050 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 8)
Expandable styrenic resin particles, expanded particles, and a plate-like expanded molded article were obtained in the same manner as in Example 1 except that 67 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 9)
Expandable styrenic resin particles, expanded particles, and plate-like foamed molded articles were obtained in the same manner as in Example 1 except that the plasticizer was dimethyl phthalate (SP value = 10.7) instead of diisobutyl adipate. It was. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 10)
Expandable styrenic resin particles, expanded particles, and plate-like expanded molded articles were obtained in the same manner as in Example 1 except that the plasticizer was liquid paraffin (SP value = 7.5) instead of diisobutyl adipate. . The evaluation results are shown in Tables 1 and 2.
(Comparative Example 11)
Expandable styrene resin particles, expanded particles, and a plate-like foamed molded article were obtained in the same manner as in Example 1 except that the residual styrene treating agent was changed to 4 g of t-butylperoxy-2-ethylhexyl monocarbonate. It was. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 12)
A plate-like foamed molded article was obtained in exactly the same manner as in Example 1 except that the bulk magnification of the pre-expanded particles was 45 times.

  The present invention is widely used in the field of residential building materials such as floor heating panels, and particularly in food containers, cushioning materials, heat insulating materials and the like suitable for a foaming ratio of 5 to 40 times.

Claims (4)

Obtained by impregnating polystyrene resin particles obtained by suspension polymerization with a foaming agent,
A particle size of 355 to 710 μm and an average particle size of 0.45 to 0.65 mm,
Expandable resin particles having a residual styrene monomer content of 160 ppm or less,
3 to 7% by weight of butane as a blowing agent , and butane as a blowing agent is 10 to 45% by weight of isobutane by weight ratio,
0.2 to 2.0% by weight of a plasticizer having a solubility parameter value (SP value) of 8.3 or more and 9.4 or less, and
An expandable styrene resin particle, wherein the expansion ratio of the expanded molded article obtained by pre-expanding and molding the expandable styrene resin particle is 5 to 40 times. The expandable styrene resin particles according to claim 1, wherein the particle size distribution by a JIS standard sieve is 80% or more in a range of 0.425 to 0.71 mm . A foamed particle obtained by pre-expanding the expandable styrenic resin particles according to claim 1 5 to 45 times, and containing 1 to 6% by weight of butane as a foaming agent in the expanded particles after 24 hours at 20 ° C. And the expanded particle whose particle diameter is 500-3000 micrometers. A foam-molded product obtained by pre-foaming and molding the expandable styrenic resin particles according to claim 1.