JP5403802B2 - 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 seed polymerization using polystyrene resin particles obtained by suspension polymerization as seed particles. 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.

JP 2004-155870 A

  The present invention has a low residual styrene monomer and can be made into a low VOC, is a building material application that is compatible with sick house syndrome, has good fusion properties, has a good appearance, and has a small dimensional change rate with time. The object is to obtain expandable styrene resin particles suitable for up to 40 times.

  As a result of diligent studies to solve the above problems, the present inventor obtained by seed polymerization using polystyrene resin particles obtained by suspension polymerization as seed particles, and having a particle size of 300 to 800 μm and a residual styrene monomer. Of expandable resin particles having a content of 800 ppm or less, 3 to 7% by weight of butane as a foaming agent, and 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 of the agent, the expanded molded article having an expansion ratio of 5 to 40 times has a small rate of dimensional change over time and excellent dimensional stability. The present inventors have found that the fusion between the particles is good, the appearance is excellent, and the particles have sufficient strength.

  Also, polystyrene resin particles obtained by the suspension polymerization method are suspended as seed particles in an aqueous medium, a styrene monomer is added to the aqueous suspension, and seed polymerization is performed in the presence of a polymerization initiator. In the method for producing expandable styrene resin particles by impregnating with a foaming agent, all or substantially all of the polymerization initiator required for the polymerization of the styrene monomer is added at the initial stage of the reaction, and The monomer is added as an aqueous suspension, polymerization is started in the presence of a styrene monomer, the reaction temperature at the start of polymerization is A ° C., and the reaction temperature after the supply of the remaining styrene monomer is completed. Expandable styrene resin particles, characterized in that when B ° C., styrene monomer is continuously or intermittently supplied and polymerized while raising the temperature so that B ° C. ≧ A ° C. + 20 ° C. It is a manufacturing method.

The present invention is an expandable resin particle obtained by seed polymerization using polystyrene resin particles obtained by suspension polymerization as seed particles, and having a particle size of 300 to 800 μm and a content of residual styrene monomer of 800 ppm or less. In addition, 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 to be expanded to 5 to 40 times and molding has a small dimensional change rate with time and excellent dimensional stability and good fusion between the particles. Thus, it is possible to provide a foamed molded article having excellent appearance and sufficient strength.

  As the styrene resin particles as seed particles used in the present invention, those produced by an ordinary 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.

  The styrene resin particles in the present invention can be obtained by a seed polymerization method in which a styrene monomer is added continuously or intermittently to styrene resin seed particles dispersed in an aqueous suspension for polymerization.

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

  In the seed polymerization method of the present invention, if the particle diameter of the seed particles is within a narrow range, the particle diameters of the styrene resin particles obtained are well aligned. That is, by carrying out a seed polymerization method using seed particles having a uniform particle diameter in advance, a styrene resin particle having a desired uniform particle diameter, for example, 0.3-0.5 mm seed particles are all styrene-based. When 50% by weight of the resin particles are used, styrene resin particles having a particle diameter of 0.35 to 0.65 mm can be obtained. Therefore, as the seed particles, polymer particles obtained by classifying the polymer particles obtained by the suspension polymerization method once with a sieve can be used.

  The particle diameter of the expandable resin particles in the present invention is 300 to 800 μm. When the particle diameter is less than 300 μm, the coalescence of particles increases at the time of seed polymerization, which is not preferable. When the particle diameter exceeds 800 μm, the filling property into a mold having a thin wall thickness tends to deteriorate. . The method of obtaining particles of 300 to 800 μm is obtained by a seed polymerization method in which the particle size range of the seed particles and the amount of the monomer to be added and polymerized are appropriately selected. The weight average molecular weight of polystyrene polymer particles obtained by seed polymerization with seed particles is usually in the range of 200,000 to 350,000, preferably 220,000 to 320,000. Usually, it is desirable that the weight average molecular weights of the seed particles and the seed polymer particles are approximately equal.

  In the seed polymerization of the present invention, when the seed particle diameter increases, the absorption efficiency and internal diffusion of the polymerization initiator decrease, and the molecular weight tends to increase. If the ratio is too small, it is difficult to control the polymerization rate of the styrene monomer supply, the reaction time is prolonged, and the molecular weight adjustment of the polymer particles becomes difficult. In order to adjust the weight average molecular weight of the polymer particles to a range suitable for foam molding, it is necessary to work the polymerization initiator efficiently, and a polymerization initiator that generates radicals by the polymerization initiator throughout the seed polymerization. It is necessary to control the distribution of the polymer, the polymerization temperature program, the monomer supply rate, the adjustment of the polymerization rate during seed polymerization, and the like. In addition, since the polymerization initiator needs to diffuse not only to the surface layer portion of the polymer particles but also to the inside during seed polymerization, the polymer particles have a styrene monomer ratio of 35 wt. The monomer may be supplied so that the reaction does not exceed%. When the ratio of the monomer is 5% by weight or less, the polymerization initiator is wasted and the resulting polymer has a high molecular weight, which is not preferable.

  In the present invention, when the reaction temperature at the start of seed polymerization is A ° C. and the reaction temperature at the end of the supply of the remaining styrene monomer is B ° C., B ° C ≧ A ° C. + 20 ° C. While increasing the temperature, a styrene monomer is added continuously or intermittently for polymerization. In this way, the foamable styrenic resin particles obtained have the weight average molecular weight of the inner layer occupying the majority within the normal range described above, and the molecular weight of the surface layer portion is at least equivalent, usually It becomes high molecular weight and has excellent foam moldability. When the reaction temperature B ° C. at the end of the monomer supply is less than A ° C. + 20 ° C., the obtained expandable styrenic resin particles cannot obtain an effect that fills the gaps between the expanded particles at the time of molding. . That is, a product having a good appearance at the time of foam molding cannot be obtained.

  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 polymerization initiator is preferably added as a liquid since it is necessary to uniformly absorb the seed particles. When the polymerization initiator is added directly to the aqueous suspension, it becomes difficult to be uniformly absorbed by the seed particles. Therefore, the polymerization initiator is added in a state suspended or emulsified in an aqueous medium, or a small amount of styrene-based monomer is added. It is desirable to dissolve in a monomer, add an inorganic suspension stabilizer and / or an anionic surfactant and add as an aqueous suspension.

  In the present invention, at the end of the supply of the styrenic monomer, the decomposition temperature for obtaining a 10-hour half-life is set so that there is almost no polymerization initiator having a temperature of 50 to 80 ° C. The weight average molecular weight of the surface layer is increased. The polymerization initiator is added at the initial stage of the reaction to add the total amount required for the polymerization of the styrenic monomer, the polymerization is performed, and the initial polymerization temperature is set at a relatively low temperature so that the decomposition of the polymerization initiator works effectively. It is effective to increase the temperature by applying a temperature gradient so that polymerization initiators are gradually generated appropriately at the time of supplying the body.

  The amount of residual styrene contained in the expandable styrene resin particles in the present invention is 800 ppm or less. Preferably, the amount of residual styrene is 300 ppm or less. If the amount of residual styrene exceeds 800 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 reducing the amount of residual styrene contained in the expandable styrene-based resin particles to 800 ppm or less, a polymerization initiator is used in an amount of 0.03 parts by weight or more in the range of 80 to 120 ° C., 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 foaming agent in the present invention, butane is used, but hydrocarbons such as propane, pentane and cyclohexane having a volatility whose boiling point is lower than the softening point of the polymer may be used in combination. 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.

  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 to this. Various measurement methods and production conditions described in the examples will be described below.

Example 1
(Creation of seed particles)
160 g of tricalcium phosphate (manufactured by Taihei Chemical Co., Ltd.), 0.2 g of sodium hydrogen sulfite and 0.2 g of potassium persulfate are added to an autoclave with a stirrer (hereinafter also referred to as a reactor) having an internal volume of 100 liters, and further peroxide 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 polymerized at 90 ° C. for 6 hours under stirring at 200 rpm, and further at 120 ° C. for 2 hours. After completion of the reaction, the mixture is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified to obtain styrene polymer seed particles having a particle diameter of 0.212 to 0.355 mm and a weight average molecular weight of 300,000. Obtained.

(Creation of expandable styrene resin particles)
Next, 11.1 kg of the above styrene polymer seed particles, 32 kg of distilled water, 220 g of magnesium pyrophosphate, and 10 g of sodium dodecylbenzenesulfonate were placed in an autoclave with a stirrer having an internal volume of 100 liters, and suspended by stirring at 140 rpm. .
Subsequently, 3000 g of distilled water prepared in advance, 20 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate and 2662 g of styrene were stirred to prepare a suspension. This suspension was added to a reactor maintained at 72 ° C. (temperature at the start of polymerization: A), and styrene was absorbed by the seed particles for 15 minutes.
Subsequently, 118 g of benzoyl peroxide having a purity of 75% as a polymerization initiator and 12 g of t-butylperoxy-2-ethylhexyl monocarbonate as a residual styrene treating agent were dissolved in 2028 g of styrene. The obtained solution was stirred with a homomixer together with 2000 g of distilled water and added to a reactor maintained at 72 ° C.
The reactor was kept at 72 ° C. for 60 minutes from the start of adding the suspension containing the polymerization initiator to the reactor, and the polymerization was started by absorbing the styrene and the polymerization initiator in the seed particles. Thereafter, 28710 g of styrene was continuously added to the reactor at a rate of 9570 g / hr in 3 hours. At the end of styrene addition, the temperature in the reactor was continuously raised to 105 ° C. (reaction temperature after completion of the supply of styrene monomer: B).
Subsequently, the temperature was raised to 120 ° C. and held for 90 minutes. Thereafter, 20 g of magnesium pyrophosphate was added to 2000 g of distilled water, 445 g of diisobutyl adipate (DIBA) as a plasticizer was added to 3 g of sodium dodecylbenzenesulfonate, and the suspension was press-fitted into the reactor by stirring with a homomixer. . Then, it cooled to 100 degreeC and 3293g of butane (35% of isobutane weight ratio) which is a foaming agent was press-fit in the reactor in the 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 0.3 to 0.7 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

(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 2136 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 4361 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 222 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Example 5)
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 668 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Example 6)
Expandable styrene in the same manner as in Example 1, except that the temperature (A) at the start of polymerization was 80 ° C. and the reaction temperature (B) after the end of the supply of the styrene monomer was changed to 100 ° C. Resin particles, expanded particles, and plate-like expanded molded article were obtained. The evaluation results are shown in Tables 1 and 2.

(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 10 times.
(Example 8)
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 expanded molded article were obtained in the same manner as in Example 1 except that 1271 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 2)
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 4778 g of butane (weight ratio of isobutane of 35%) was used as a foaming agent. 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 3293 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-based resin particles, expanded particles, and plate-like foamed molded articles were obtained in the same manner as in Example 1 except that 3293 g of normal butane (weight ratio of isobutane 0%) as a foaming agent was used. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 5)
Expandable styrene resin particles, expanded particles, and plate-like foamed molded articles were obtained in the same manner as in Example 1 except that the particle diameter of the polystyrene resin seed particles was changed to 0.50 to 0.65 mm. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 6)
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 1113 g of diisobutyl adipate (DIBA) as a plasticizer was added. The evaluation results are shown in Tables 1 and 2.
(Comparative Example 7)
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 71 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 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 9)
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 10)
Expandable styrene in the same manner as in Example 1, except that the temperature (A) at the start of polymerization was 72 ° C. and the reaction temperature (B) after the end of the supply of the styrene monomer was changed to 90 ° C. Resin particles, expanded particles, and plate-like expanded molded article were obtained. 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 (5)

The polystyrene resin particles obtained by the suspension polymerization method are suspended in an aqueous medium as seed particles, a styrene monomer is added to the aqueous suspension, and seed polymerization is performed in the presence of a polymerization initiator. In the method for producing expandable styrene resin particles by impregnating a foaming agent after the polymerization step is completed,
  While adding the total amount of polymerization initiator required for the polymerization of the styrenic monomer at the beginning of the reaction, adding the styrenic monomer as an aqueous suspension, starting the polymerization in the presence of the styrenic monomer, When the reaction temperature at the start of polymerization is A ° C and the reaction temperature after the supply of the remaining styrenic monomer is B ° C,
A method for producing expandable styrene resin particles, characterized in that a styrene monomer is continuously or intermittently supplied and polymerized while raising the temperature so that B ° C. ≧ A ° C. + 20 ° C. The method for producing expandable styrene resin particles according to claim 1, wherein the expandable styrene resin particles are expandable styrene resin particles for building materials. A heat-resistant and pressure-resistant jacketed autoclave with a stirrer is used as a reactor, and butane, which is a blowing agent that is a gas at normal temperature and normal pressure, is added as a liquid at a temperature of 20 to 130 ° C. Item 3. A method for producing expandable styrene resin particles according to Item 1 or 2. It is a manufacturing method of the foaming particle which pre-expanded the expandable styrene resin particle obtained by the manufacturing method as described in any one of Claims 1-3 5-45 times, Comprising: 24 hours passed at 20 degreeC. The manufacturing method of the expanded particle which contains 1-6 weight% butane as a foaming agent in an expanded particle, and the particle diameter of an expanded particle is 500-3000 micrometers. The manufacturing method of the foaming molding obtained by pre-foaming and shape | molding the expandable styrene-type resin particle obtained by the manufacturing method as described in any one of Claims 1-3 .