JP2001302838A - Method for manufacturing foaming styrene resin particle, foaming styrene resin particle and foamed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide foaming styrene particles able to give a molding excellent in water-leak preventing property, a method for manufacturing the same, and a foamed molding. SOLUTION: The method for manufacturing foaming styrene resin particles comprises a process in which a styrene monomer is subjected to suspension polymerization or seed polymerization in the presence of a suspension stabilizer and radical polymerization initiators to impregnate the resin particles with a foaming agent. The polymerization is carried out with a low temperature-type polymerization initiator having a decomposition temperature of 50-80 deg.C at which the half time is 10 hr and subsequently with a high temperature-type polymerization initiator consisting of n-butyl-4,4-bis(t-butylperoxy)valerate and/or t- hexylperoxyisopropyl monocarbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing expandable styrene resin particles for obtaining a foam molded article having excellent water leakage prevention properties, expandable styrene resin particles obtained by the method, and an expanded molded article. More specifically, at the time of polymerization, by using a specific polymerization initiator, a method for producing expandable styrene-based resin particles capable of obtaining a foamed molded article excellent in water leakage prevention properties, and a method for producing expandable styrene-based resin particles obtained by the method. Foamable styrenic resin particles and foamed molded articles.

[0002]

2. Description of the Related Art Expandable styrene resin particles are produced by impregnating styrene resin particles with a foaming agent, and are used as raw materials for producing foamed molded articles having various shapes. Further, the foamed molded article is usually obtained by in-mold molding of foamed particles obtained by prefoaming foamable styrene resin particles. Therefore, the quality of the expandable styrene-based resin particles is determined by the ease of the foam molding operation and the quality of the finally obtained foam molded article.

[0003]

When the foamed molded article is used, for example, as a fish box, the fresh fish is transported together with ice, so that the fusion ratio between the foamed particles in the foamed molded article and the strength of the molded article are sufficient. However, even if the gap between the particles on the surface and inside of the molded body is sufficiently small and small, it is a problem that water leaks from the fish box due to the influence of body fluids and fats and oils of fresh fish. Was. As a technique for preventing leakage of contents such as water from the foamed molded article, for example, a foamed molded article obtained by foaming foamable styrene resin particles coated with a sucrose ester or a derivative thereof is disclosed ( JP-B-56-34172) and a foamed molded product obtained by foam-forming foamable styrene-based resin particles coated with a copolymer containing a fluorine-containing vinyl-based monomer are disclosed (JP-A-Hei. 2-88652).

However, these methods require a step of coating the expandable styrene resin particles with a specific substance in advance, and have a problem that the production process is complicated and the production cost is increased. An object of the present invention is to obtain expandable styrene-based resin particles for obtaining a foamed molded product that does not easily leak water without adding or coating a specific substance.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that a specific radical polymerization initiator is used in suspension polymerization or seed polymerization of a styrene monomer. Molded product obtained by foaming the expandable styrene resin particles obtained by the above method, the fusion between the foamed particles, the gap between the particles on the surface and inside of the molded product, etc. are equivalent to those of the conventional foamed molded product. Nevertheless, the inventor has found that water leakage is unlikely, and has completed the present invention.

Thus, according to the present invention, in the presence of a suspension stabilizer and a radical polymerization initiator, a styrene monomer is subjected to suspension polymerization in an aqueous medium, and a volatile organic blowing agent is subjected to suspension polymerization. A method for producing expandable styrene-based resin particles by adding during or after completion of suspension polymerization, wherein the decomposition temperature of suspension polymerization is 50 hours to obtain a half-life of 10 hours as the radical polymerization initiator. A low-temperature polymerization initiator having a temperature of 〜80 ° C., and then a high-temperature polymerization initiator comprising n-butyl-4,4-bis (t-butylperoxy) valerate and / or t-hexylperoxyisopropyl monocarbonate And a method for producing expandable styrene resin particles, wherein the method is performed using

Further, according to the present invention, a styrene monomer is continuously or intermittently added to styrene resin particles suspended in an aqueous medium in the presence of a suspension stabilizer and a radical polymerization initiator. A method for producing expandable styrene-based resin particles by adding seed polymerization and adding a volatile organic blowing agent during seed polymerization or after completion of seed polymerization,
In the seed polymerization, a low-temperature polymerization initiator having a decomposition temperature of 50 to 80 ° C. for obtaining a half-life of 10 hours is used as the radical polymerization initiator, and then n-butyl-4,4-
A method for producing expandable styrene-based resin particles, characterized by being carried out using a high-temperature polymerization initiator comprising bis (t-butylperoxy) valerate and / or t-hexylperoxyisopropyl monocarbonate. You. Further, according to the present invention, there are provided expandable styrene-based resin particles obtained by the above method, and a foamed molded article obtained by subjecting the resin particles to foam molding.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Styrene monomers used in suspension polymerization and seed polymerization for obtaining expandable styrene resin particles of the present invention include, in addition to styrene, for example, α
-Styrene derivatives such as methylstyrene, vinyltoluene and chlorostyrene. As the styrene-based monomer, other monomers copolymerizable with the styrene-based monomer can be used as long as the effects of the present invention are not impaired. Such other monomers include, for example, alkyl (meth) acrylates such as methyl methacrylate and n-butyl acrylate, acrylonitrile, dimethyl maleate, diethyl fumarate, divinyl benzene and the like.

The suspension stabilizer used in the present invention includes:
For example, a water-soluble polymer compound such as polyvinyl alcohol and polyvinylpyrrolidone, and a hardly water-soluble inorganic salt such as a hardly water-soluble phosphate are exemplified, and among them, a hardly water-soluble phosphate is preferable. Examples of the poorly water-soluble phosphate include tricalcium phosphate, magnesium phosphate, magnesium pyrophosphate and the like. The amount of the suspension stabilizer used is 0.1% by weight or more based on the total amount of the styrene monomer used for the suspension polymerization or the total amount of the styrene monomer and the styrene resin particles used for the seed polymerization. It is preferred that Even when the suspension stabilizer is used in an amount exceeding 1% by weight, the effect corresponding to the increase is not improved, so that the amount is usually preferably 1% by weight or less.

In the method of the present invention, a surfactant may be used as a stabilizing aid together with the suspension stabilizer. In particular, when a sparingly water-soluble phosphate is used as the suspension stabilizer, an anionic surfactant is preferably used. Examples of the anionic surfactant include an alkyl sulfate such as sodium lauryl sulfate, an alkylbenzene sulfonate such as sodium dodecylbenzenesulfonate, a higher fatty acid salt such as sodium oleate, β-
And tetrahydroxynaphthalenesulfonate. The suspension polymerization and the seed polymerization in the present invention are performed at a relatively low temperature (80 to 100 ° C), and then at a relatively high temperature (105 to 140 ° C).

The polymerization at a relatively low temperature can be carried out at a constant temperature within the above-mentioned temperature range or while increasing or decreasing the temperature. For polymerization at a relatively low temperature, a low-temperature polymerization initiator having a decomposition temperature (hereinafter referred to as “decomposition temperature”) of 50 to 80 ° C. for obtaining a half-life of 10 hours is used as a radical polymerization initiator. Specifically, for example, benzoyl peroxide (decomposition temperature: 74 ° C.), t-butylperoxy 2-ethylhexanoate (decomposition temperature: 7
2 ° C.), t-butyl peroxyisobutyrate (decomposition temperature: 77 ° C.), lauroyl peroxide (decomposition temperature:
62 ° C), stearoyl peroxide (decomposition temperature: 6
(2 ° C.) and azo compounds such as azobisisobutyronitrile (decomposition temperature: 63 ° C.).
The amount of the low-temperature polymerization initiator to be added is appropriately determined according to the molecular weight of the target expandable styrene-based resin particles, and is not particularly limited. About 0.4% by weight is preferable.

The polymerization at a relatively high temperature can be carried out at a constant temperature within the above-mentioned temperature range or while increasing or decreasing the temperature. For polymerization at a relatively high temperature, n-butyl-4,4-bis (t-
A high-temperature polymerization initiator consisting of (butylperoxy) valerate and / or t-hexylperoxyisopropyl monocarbonate is used. The amount of the high-temperature polymerization initiator added is 0.01 to 0.5% by weight based on the total amount of the monomers.
Degree is preferable, and about 0.05 to 0.2% by weight is more preferable. 0.01% by weight of high-temperature polymerization initiator
If the amount is less than the above range, the resulting foamed molded article is not preferable because the water leakage preventing property is not sufficiently exhibited. When the amount of addition is 0.5
When the amount is more than 10% by weight, the effect of preventing water leakage is sufficiently exhibited, but not only the improvement of the effect of preventing water leakage is not observed with an increase in the amount added, but also the cost is increased, and the obtained expandable styrene is obtained. It is not preferable because physical properties such as strength are decreased due to a decrease in the molecular weight of the resin particles.

The polymerization at a relatively low temperature and the polymerization at a relatively high temperature may be performed continuously. As the styrene-based resin particles used in the seed polymerization of the present invention, it is preferable to use resin particles obtained by polymerizing the styrene-based monomer as described above, and suspending the styrene-based monomer as described above. It is more preferable to use resin particles obtained by polymerization. In the seed polymerization of the present invention, in order to make the particle diameters of the obtained styrene resin particles uniform, it is desirable that the particle diameters of the styrene resin particles serving as seeds are previously made uniform. The weight average molecular weight (Mw) of the styrene-based resin particles obtained by the method of the present invention is from 200,000 to 3 as measured by gel permeation chromatography.
Preferably, it is adjusted to 50,000. Mw 20000
If it is less than 0, physical properties such as mechanical strength of the obtained foamed molded article are reduced, and problems such as melting of the surface of the molded article during molding are likely to occur.

On the other hand, if Mw exceeds 350,000, the degree of fusion of the resin particles in the foamed molded article decreases, and in order to maintain this, the steam heating at the time of molding must be increased more than usual. It is not preferable because it causes a problem such as up. In the method of the present invention, expandable styrene resin particles are obtained by impregnating the styrene resin particles with a volatile organic blowing agent. The impregnation of the volatile organic foaming agent is usually carried out by press-fitting the volatile organic foaming agent during the suspension polymerization or the seed polymerization performed in the pressure vessel or after the polymerization, and heating. It is. It is also possible to separate the styrene-based resin particles obtained after the polymerization from the aqueous medium and impregnate them again.

The volatile organic blowing agent used in the present invention is not particularly limited, but may be an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon having a boiling point of 100 ° C. or lower, or a halide thereof. Is preferred. Examples of the aliphatic hydrocarbon include propane, butane, pentane, hexane, petroleum ether and the like. Examples of the cycloaliphatic hydrocarbon include cyclopentane, cyclohexane and the like. Examples of the hydrocarbon halides include, for example, methyl chloride and dichlorodifluoromethane. In the method of the present invention, a foaming aid may be used in order to supplement the foam moldability of the foaming agent.

Examples of the foaming aid include aromatic hydrocarbons such as toluene and xylene, and plasticizers such as phthalic acid ester and adipic acid ester. The obtained expandable styrene resin particles are separated from the aqueous medium, washed, and then dried. In addition, the expandable styrene resin particles of the present invention can be sieved to a desired particle size according to the application. The expandable styrene-based resin particles of the present invention are formed into expanded particles by preliminary expansion, and the obtained expanded particles are formed into a molded article. Prior to the pre-expansion, the expandable styrene resin particles of the present invention may be coated with a conventionally used coating agent.

Examples of the coating agent include, but are not particularly limited to, metal soaps such as zinc stearate for preventing agglomeration of foamed particles in prefoaming, fatty acid amides, and polyethylene glycol for preventing static electricity of foamed particles. And partial esters of polyhydric alcohols such as stearic acid monoglyceride. As a method of coating the coating agent on the foamed particles, for example, the method is performed by using a mixer such as a tumbler mixer, a ribbon blender, a Loedige mixer, and a super mixer.
The pre-expansion is performed by heating the expandable styrene resin particles with steam, hot air, or the like. For example, the expandable styrene resin particles are heated by steam using a foaming machine having a stirrer to form foamed particles having a predetermined density. The obtained expanded particles are allowed to stand until they are in a state suitable for molding, then filled in a mold, heated again, and further expanded. As a result, the particles are fused to each other to form a foamed molded article faithful to the bulk shape of the mold. After heating, the molded article is cooled and taken out to a state where it does not expand or deform.

[0018]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 2 kg of ion-exchanged water was charged into a 5-liter internal stainless steel autoclave having a stirring device, and sodium dodecylbenzenesulfonate 1 was added under stirring.
g of tricalcium phosphate [manufactured by Taihei Chemical Co., Ltd.] was added and dispersed to obtain an aqueous suspension medium. Next, 5 g of benzoyl peroxide (decomposition temperature: 74 ° C.) and n-butyl-4,4 were added to 2 kg of styrene.
A styrene monomer mixture in which 2 g of -bis (t-butylperoxy) valerate was dissolved was poured into the aqueous medium, and dispersed under stirring to form a suspension. This suspension is
The mixture was heated under stirring at 00 rpm, heated to 90 ° C. over 30 minutes, and kept at 90 ° C. for 5 hours to perform the first stage polymerization. Then, 2 g of tricalcium phosphate was additionally charged, and 30 g of cyclohexane and 180 g of n-butane were further injected by using nitrogen pressure, the temperature was raised to 120 ° C. over 30 minutes, and the temperature was maintained at 120 ° C. for 3 hours. The second stage of polymerization and impregnation of the blowing agent was performed. Subsequently, the suspension was taken out by cooling, and the resin particles were separated, washed and dried to obtain expandable styrene resin particles. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Example 2 n-butyl 4,4-bis (t
Expandable styrene resin particles were obtained in the same manner as in Example 1 except that 2 g of t-hexylperoxyisopropyl monocarbonate was used instead of 2 g of -butylperoxy) valerate. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results. Example 3 Instead of 2 g of n-butyl 4,4-bis (t-butylperoxy) valerate, n-butyl 4,4-
1 g of bis (t-butylperoxy) valerate and t
-Hexyl peroxyisopropyl monocarbonate 1
Except for using g, expandable styrene resin particles were obtained in the same manner as in Example 1. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Example 4 n-butyl 4,4-bis (t
Expandable styrene resin particles were obtained in the same manner as in Example 1 except that the amount of (-butylperoxy) valerate was changed to 6 g. The fusion rate of the foam molded article obtained by foam molding the obtained expandable styrene resin particles, the surface particle gap,
Water leakage prevention was evaluated. Table 1 shows the results. Example 5 Expandable styrene resin particles were obtained in the same manner as in Example 1 except that the amount of n-butyl 4,4-bis (t-butylperoxy) valerate was changed to 1 g.
The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Example 6 n-butyl 4,4-bis (t
-Butylperoxy) valerate was added in an amount of 0.06 g.
Was obtained in the same manner as in Example 1 except that the styrene resin particles were expanded. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results. [Example 7] Expandable styrene resin particles were obtained in the same manner as in Example 1 except that the addition amount of n-butyl 4,4-bis (t-butylperoxy) valerate was changed to 0.02 g. . The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Example 8 n-butyl 4,4-bis (t
-Butylperoxy) valerate was added at 0.016
Except that g was changed, foamable styrene resin particles were obtained in the same manner as in Example 1. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results. [Comparative Example 1] An expandable styrene resin in the same manner as in Example 1 except that 2 g of t-butyl peroxybenzoate was used instead of 2 g of n-butyl 4,4-bis (t-butylperoxy) valerate. Particles were obtained. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Comparative Example 2 n-butyl 4,4-bis (t
-Butylperoxy) valerate instead of 2 g, 1,1-
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that 2 g of bis- (t-butylperoxy) -3,3,5-trimethylcyclohexane was used. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results. [Comparative Example 3] Expandable styrene in the same manner as in Example 1 except that 2 g of t-butyl peroxyisopropyl carbonate was used instead of 2 g of n-butyl 4,4-bis (t-butylperoxy) valerate. Based resin particles were obtained. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.

Reference Example 1 The expandable styrene resin particles obtained in Comparative Example 1 were mixed with sucrose ester (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: DK Ester F-50) at 0.05% by weight. Covered. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 1 shows the results.
Shown in Example 9 A stainless steel autoclave having an internal volume of 5 liters and having a stirrer was placed in a stainless steel autoclave having a particle size of 0.47 to 0.58.
500 g of styrene resin particles of 2 mm, ion exchange water 2k
Then, 1 g of sodium dodecylbenzenesulfonate was added and dissolved with stirring, and 6 g of tricalcium phosphate [manufactured by Taihei Chemical Co., Ltd.] was added and dispersed to obtain an aqueous suspension medium. This was heated to 85 ° C. over 30 minutes while stirring at 200 rpm. After the temperature was raised, the temperature was maintained at 85 ° C., and styrene alone obtained by dissolving 6 g of benzoyl peroxide (decomposition temperature: 74 ° C.) and 2 g of n-butyl-4,4bis (t-butylperoxy) valerate in 100 g of styrene. The body mixture was added dropwise over 10 minutes. After 10 minutes have passed since the end of the dripping and feeding,
1.4 kg of styrene was continuously dropped and charged at a constant rate over 4 hours to carry out the first stage polymerization. After 30 minutes from the end of the dropping and charging of styrene, 2 g of tricalcium phosphate was further charged, and cyclohexane 30 g was further added.
g and 180 g of n-butane were injected using nitrogen pressure, the temperature was raised to 120 ° C. over 30 minutes, and the temperature was maintained at 120 ° C. for 3 hours to perform the second stage polymerization and impregnation with a blowing agent. . Subsequently, the suspension was taken out by cooling, and the resin particles were separated, washed and dried to obtain expandable styrene resin particles.

The fusion ratio, surface particle gap, and the like of the foamed molded article obtained by foaming and molding the obtained expandable styrene resin particles are described below.
Water leakage prevention was evaluated. Table 2 shows the results. The obtained expandable styrene resin particles had a uniform particle diameter of 0.7 to 1 mm. Almost all of the dropped and charged styrene monomer was absorbed by the styrene resin particles and polymerized.

Comparative Example 4 n-butyl 4,4-bis (t
Expandable styrene resin particles were obtained in the same manner as in Example 9 except that 2 g of t-butyl peroxybenzoate was used instead of 2 g of (-butylperoxy) valerate. The fusion ratio, surface particle gap, and water leakage prevention of the foamed molded product obtained by subjecting the obtained expandable styrene resin particles to foam molding were evaluated. Table 2 shows the results. As shown in Tables 1 and 2, the foamed molded article obtained by foaming the expandable styrene resin particles obtained by the method of the present invention has a fusion ratio and a surface gap state of Comparative Examples. Although it is equivalent to that of Comparative Example 1, it is superior to that of Comparative Example in water leak prevention property and is equivalent to that of Reference Example 1. Therefore, it is possible to obtain a foamed molded article excellent in water leakage prevention without adding or coating a specific substance to the expandable styrene resin particles obtained by the method of the present invention.

[Production of Expanded Molded Article] The expandable styrene resin particles obtained in Examples 1 to 8, Comparative Examples 1 to 3 and Reference Example 1 were previously sieved to a particle diameter of 0.7 to 1.0 mm. In other words, Example 9 and Comparative Example 4 were used as they were without adjusting the particle diameter. The expandable styrene resin particles obtained in each of the Examples, Comparative Examples and Reference Examples were mixed with 0.1% by weight of zinc stearate and 0.08% by weight of stearic acid monoglyceride based on the expandable resin particles. After coating, the bulk density was 60 cm ³ / g with steam at a pressure of 0.05 MPa using a foaming machine having an internal volume of 25 liters equipped with a stirrer.
Was prefoamed. The pre-expanded particles obtained were left at 23 ° C. under atmospheric pressure for 24 hours and then molded. The shape of the obtained foamed molded product has a bottom surface and a side wall rising from the outer periphery of the bottom surface, a flat box having an open top surface is a rectangular box-shaped container, the bottom surface is 300 mm × 400 mm, and the side wall height is 1 mm.
00mm, molded body thickness of bottom and side wall 20mm
Met. The molding conditions were ACE-3SP type molding machine [manufactured by Sekisui Koki Seisakusho Co., Ltd.] and the steam pressure was 0.08MP.
After heating for 30 seconds at a, the molded body was cooled until it was not deformed even after being removed from the mold.

[Evaluation method] [Evaluation of fusion rate] In the fracture surface when the foamed molded article is torn, the fractured surface of the foamed particles is not separated at the fusion surface between the foamed particles, but is the whole of the one torn inside the foamed particles. The percentage is expressed as a percentage. [Surface Particle Gap] The number of particle gaps within a rectangular area of 50 × 70 mm in the same portion of each foam molded product surface was visually counted. [Evaluation of Water Leak Prevention Property] A coloring agent [Kanto Chemical Co., Ltd.] was added to 100 parts by weight of a 0.1% by weight aqueous solution of a nonionic surfactant [trade name: Emulgen 810] in the recesses of the obtained foamed molded product. Ltd., trade name: Eriochrome Black T]
It was left at 3 ° C. under atmospheric pressure for 1 hour, and the state of leakage to the outer surface of the molded body was visually evaluated as the degree of coloring according to the following criteria. ：: No coloration on outer surface, no leakage observed: Particle boundary surface on outer surface is slightly colored, but surface wetting is not substantially observed. Δ: Wetting on outer surface is observed. X: Remarkable wetting on outer surface. , Liquid leaks to the outer peripheral surface

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The expandable styrenic resin particles obtained by the method of the present invention can provide a foam molded article excellent in water leakage prevention without adding or covering a specific substance. In addition, according to the method of the present invention, a step of adding a specific substance or coating can be omitted, so that the production process is complicated and the cost is not increased, and the obtained foam molded article is excellent. Has water leakage prevention properties.

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Claims (4)

[Claims] 1. A styrenic monomer is subjected to suspension polymerization in an aqueous medium in the presence of a suspension stabilizer and a radical polymerization initiator, and a volatile organic foaming agent is added during or during suspension polymerization. A method for producing expandable styrenic resin particles by adding after completion, wherein the suspension polymerization has a decomposition temperature of 50 to 50 hours to obtain a half-life of 10 hours as the radical polymerization initiator.
A low-temperature polymerization initiator at 80 ° C. is used, and then a high-temperature polymerization initiator of n-butyl-4,4-bis (t-butylperoxy) valerate and / or t-hexylperoxyisopropyl monocarbonate is used. A method for producing expandable styrene resin particles. 2. A styrene-based monomer is added to styrene-based resin particles suspended in an aqueous medium in the presence of a suspension stabilizer and a radical polymerization initiator, and seed polymerization is performed on the styrene-based resin particles. A method for producing expandable styrenic resin particles by adding an agent during seed polymerization or after completion of seed polymerization, wherein seed polymerization is performed as the radical polymerization initiator,
Decomposition temperature for obtaining half-life of 10 hours is 50-80 ° C
And then n-butyl-
A process for producing expandable styrene resin particles, wherein the process is carried out using a high-temperature polymerization initiator of 4,4-bis (t-butylperoxy) valerate and / or t-hexylperoxyisopropyl monocarbonate. . 3. Expandable styrene resin particles obtained by the method according to claim 1. 4. A foam molded article obtained by foam molding the expandable styrene resin particles according to claim 3.