JP6645227B2 - Expanded particle molded article and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a foamed molded article containing a brominated styrene-butadiene copolymer as a flame retardant and having a low content of unreacted styrene-based monomer, and a method for producing the same.

  BACKGROUND ART A foamed styrene-based resin particle obtained from expandable styrene-based resin particles has excellent heat-insulating performance, and is therefore used for a heat-insulating material for a house, a cool box, and the like. In addition, since the styrene-based resin foamed particle molded article is excellent in lightness and cushioning performance, a styrene-based resin foamed particle molded article containing a flame retardant is used as an interior material such as an automobile cushioning material and a floor-raising material. Have been. Since automobiles have a narrow interior space, molded articles that emit less organic solvent than residential heat insulating materials are required. Since the unreacted styrene-based monomer is contained in the styrene-based resin foam molded article, it is desired to reduce the amount of the unreacted styrene-based monomer.

  For example, Patent Documents 1 to 3 disclose expandable styrene resin particles containing a flame retardant and having a low content of unreacted styrene monomer.

JP 2007-9018 A JP 2015-117282 A JP 2010-195936 A

  However, the content of the styrene-based monomer in Patent Documents 1 and 2 is several hundred ppm, which is insufficient for applications such as automotive interior materials. On the other hand, in Patent Document 3, a styrene resin particle containing no flame retardant and a foaming agent is once synthesized, and then the foaming agent and the flame retardant are impregnated into the styrene resin particles in a separate step from this synthesis. It left a challenge in terms of efficiency.

  The present invention has been made in view of the above problems, and has an object to provide a foamed particle molded article having excellent flame retardancy and capable of preventing emission of a styrene monomer, and a method for producing the same. is there.

One embodiment of the present invention uses a styrene-based resin obtained by suspension polymerization of a styrene-based monomer in the presence of a flame retardant as a base resin, and the styrene-based resin expanded particles containing the flame retardant are fused to each other. A molded body,
The flame retardant contains a bromide of a styrene-butadiene copolymer,
The weight average molecular weight of the styrene resin is 150,000 or more,
The content of the styrene monomer in the shaped body is Ri der 10 mass ppm or less,
Emission amount of the styrenic monomer of the molded body is Ru der 100 [mu] g / m ³ or less, in the foamed bead molded article.

Another embodiment of the present invention is a polymerization step of obtaining a styrene resin particle by suspension polymerization of a styrene monomer in the presence of a flame retardant containing bromide of a styrene-butadiene copolymer,
An impregnation step of impregnating the styrenic resin particles with an organic physical blowing agent to obtain expandable styrenic resin particles,
A foaming step of foaming the expandable styrene-based resin particles by heating with steam to obtain expanded styrene-based resin particles,
A molding step of fusing the expanded styrene resin particles to each other in a molding die to obtain a foamed particle molded body,
When the expandable styrene resin particles are blown into the expandable styrene resin particles by blowing steam having a gauge pressure of 0.03 MPa in a box-type batch type pre-expander, the steam blow time is in the range of 200 to 400 seconds. Having a foaming property such that the minimum bulk density A of the test foamed particles obtained in the above becomes 15 to 125 kg / m ³ ,
In the expanding step, the bulk density B of the expanded styrene-based resin particles obtained after the expanding step and the minimum bulk density A satisfy the relationship of 0.6 ≦ B / A ≦ 0.9. The present invention relates to a method for producing a foamed particle molded article, which foams expandable styrene resin particles.

  The foamed particle molded article (hereinafter, appropriately referred to as “molded article”) contains a flame retardant composed of a brominated styrene-butadiene copolymer, and contains a styrene resin having a predetermined weight average molecular weight. And, the content of the styrene monomer in the molded article is 10 ppm by mass or less. Such a molded article can prevent emission of the styrene monomer while exhibiting excellent flame retardancy. Further, the molded body has excellent bending strength. Therefore, it is suitable for use in automobile interior materials and the like that are used in a narrow space and require excellent flame retardancy and the like.

  The molded article can be produced, for example, by performing the polymerization step, the impregnation step, the foaming step, and the molding step as described above. In the polymerization step, the styrene monomer is subjected to suspension polymerization in the presence of a flame retardant containing bromide of a styrene-butadiene copolymer. Thereby, styrene-based resin particles containing a flame retardant (hereinafter, appropriately referred to as “resin particles”) can be obtained. By performing the suspension polymerization of the styrene monomer in the presence of the flame retardant as in this polymerization step, it is not necessary to separately provide a step of adding the flame retardant. Therefore, resin particles containing a flame retardant can be obtained with high productivity. Further, in the polymerization step, since a brominated product of a styrene-butadiene-based copolymer, which hardly inhibits polymerization of a styrene-based monomer as compared with other brominated flame-retardants, is used as the flame retardant, a styrene-based monomer is used. Resin particles having a low body content can be obtained.

  In the impregnation step, the styrene-based resin particles are impregnated with an organic physical blowing agent to obtain expandable styrene-based resin particles (hereinafter referred to as “expandable particles” as appropriate). The particles are expanded to obtain expanded styrene-based resin particles (hereinafter referred to as “expanded particles” as appropriate). In the expansion step, the minimum bulk density of the test expanded particles obtained by expanding the expandable particles under the above-described predetermined conditions In the foaming step, the bulk density B of the foamed particles obtained after the foaming step and the above-mentioned minimum bulk density A satisfy the above-mentioned predetermined relationship. The foaming particles satisfying the predetermined relationship are appropriately referred to as “severe foaming.” Styrene-based particles that may remain in the foamed particles due to the severe foaming Further reduction of the body is possible, and the content of the styrene monomer in the molded body obtained after the above-mentioned molding step can be reduced to, for example, 10 mass ppm or less. Using a bromide of a styrene-butadiene copolymer, a molded product obtained by performing the above-mentioned polymerization step, impregnation step, foaming step, and molding step satisfies, for example, the combustion standard of FMVSS No. 302. This makes it possible to exhibit excellent flame retardancy and excellent bending strength.

A preferred embodiment of the method for manufacturing the above-mentioned molded body will be described.
In the polymerization step, styrene-based monomers are subjected to suspension polymerization in the presence of a flame retardant to obtain styrene-based resin particles. The flame retardant contains a bromide of a styrene-butadiene copolymer. As the brominated styrene-butadiene copolymer, for example, a brominated styrene-butadiene block copolymer can be used.

  As the flame retardant, a bromine-based flame retardant other than a bromide of a styrene-butadiene-based copolymer can be used in combination as long as the intended object of the present invention is achieved.

  The suspension polymerization of the styrene monomer in the polymerization step can be performed in an aqueous medium containing, for example, a suspending agent. The flame retardant can be supplied to the aqueous medium in a state of being dissolved in the styrene-based monomer in advance. Further, the flame retardant can be dispersed in an aqueous medium together with, for example, a suspending agent without being dissolved in the styrene-based monomer. The blending amount of the flame retardant is preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the styrene-based resin obtained by polymerization of the styrene-based monomer. In this case, the flame retardancy can be further improved, and the increase in the production cost due to the increase in the amount of the flame retardant can be prevented. Furthermore, polymerization inhibition of the styrene-based monomer can be further prevented, and the content of the styrene-based monomer in the molded article can be further reduced. From the viewpoint of further reducing the content of the styrene-based monomer, the blending amount of the flame retardant with respect to 100 parts by mass of the styrene-based resin is more preferably less than 1 part by mass, and less than 0.5 part by mass. More preferably, it is particularly preferably 0.1 parts by mass or less. The amount of the above-mentioned flame retardant usually becomes equal to the content of the flame retardant in the molded article.

  Styrene can be used as the styrene monomer. In addition to styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-methoxystyrene, pn-butyl Styrene compounds such as styrene, pt-butylstyrene, divinylbenzene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, styrenesulfonic acid and sodium styrenesulfonate Can be used. The styrene monomers may be used alone or as a mixture of two or more. The main component of the styrene-based monomer is preferably styrene from the viewpoint of the production cost and the ease of molding the molded body.

  Further, a vinyl monomer copolymerizable with a styrene monomer may be used in combination. Such vinyl monomers include (meth) acrylic acid, (meth) acrylic acid ester, vinyl monomer containing a nitrile group, organic acid vinyl compound, olefin compound, diene compound, vinyl halide compound, vinylidene halide compound, And maleimide compounds. In addition, "(meth) acrylic acid" is a concept including "acrylic acid" and "methacrylic acid", and means one or both of these.

  Examples of (meth) acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and methacrylic acid. Examples thereof include 2-ethylhexyl, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Examples of the vinyl monomer containing a nitrile group include acrylonitrile and methacrylonitrile. Examples of the organic acid vinyl compound include vinyl acetate and vinyl propionate. Examples of the olefin compound include ethylene, propylene, 1-butene, 2-butene and the like. Examples of the diene compound include butadiene, isoprene, chloroprene, and the like. Examples of the vinyl halide compound include vinyl chloride and vinyl bromide. Examples of the vinylidene halide compound include vinylidene chloride. Examples of the maleimide compound include N-phenylmaleimide and N-methylmaleimide.

  In the polymerization step, for example, a styrene-based monomer, a flame retardant, an organic peroxide (specifically, a polymerization initiator) and a suitable suspending agent are placed in a closed container equipped with a stirrer. The polymerization reaction can be initiated by dispersing in an aqueous medium.

  Examples of the organic peroxide include benzoyl peroxide, stearoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, and t-hexylperoxy-2-ethylhexanoate. , T-amylperoxy-2-ethylhexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexa Noate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, t-butylperoxybenzoate , T-amyl peroxyisopropyl carbonate, t-amido Peroxy-2-ethylhexyl carbonate, t-hexylperoxyisopropyl carbonate, t-butylperoxy-3,5,5-trimethylhexanoate, 1,1-bis (t-butylperoxy) -3,3,5 -Trimethylcyclohexane, 1,1-bis (t-butylperoxy) -2-methylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane And 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane. The organic peroxides may be used alone or as a mixture of two or more. The organic peroxide is preferably used in combination with an organic peroxide having a one-hour half-life temperature of 80 to 100 ° C and an organic peroxide having a one-hour half-life temperature of 100 to 130 ° C. In this case, polymerization inhibition of the styrene monomer can be more efficiently prevented, and the amount of the styrene monomer in the molded article can be further reduced.

  The amount of the organic peroxide to be added is preferably 0.01 to 2 parts by mass based on 100 parts by mass of the styrene monomer. If the addition amount is smaller than this range, the polymerization rate is slowed, and the productivity is reduced. If the addition amount is larger than this range, the production cost may be increased. The addition amount of the organic peroxide is more preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the styrene monomer.

  As described above, in the polymerization step in which the styrene monomer is subjected to suspension polymerization in the presence of a flame retardant, a bromide of a styrene-butadiene copolymer (hereinafter, appropriately referred to as “Br-SBC”) is used as the flame retardant. And the polymerization step is carried out at a relatively low temperature in a pre-stage polymerization step in which most of the styrene-based monomer is polymerized, and in a post-stage polymerization in which the remaining styrene-based monomer is polymerized at a higher temperature than in the pre-stage polymerization step. It is preferable to divide into multiple steps including the steps. Specifically, while using Br-SBC as a flame retardant, the polymerization step is a pre-stage polymerization step of polymerizing a styrene monomer at a temperature of 110 ° C. or less until the polymerization conversion rate becomes 90% by mass or more; It is preferable to further include a post-polymerization step of further polymerizing the styrene monomer in a temperature range of more than 115 ° C. and 135 ° C. or less. In this case, the amount of unreacted styrene-based monomer in the resin particles obtained in the polymerization step can be further reduced, and the amount of styrene-based monomer in the molded article can be further reduced. Br-SBC is less likely to inhibit the polymerization of styrene monomers as compared to conventional bromine-based flame retardants, and enables the reduction of unreacted styrene monomers by increasing the polymerization temperature in the subsequent stage, and Even if the polymerization temperature in the latter stage is increased, the molecular weight of the styrene resin is not significantly reduced. Therefore, by performing the multi-stage polymerization step as described above, it is possible to obtain resin particles having a lower content of unreacted styrene monomer and a higher molecular weight while containing a flame retardant. Hereinafter, the polymerization temperature in the latter polymerization step is appropriately referred to as “final polymerization temperature”.

  From the viewpoint of suppressing the decrease in the weight average molecular weight of the styrene-based resin and improving the mechanical strength of the molded article, the polymerization temperature in the first polymerization step is preferably 110 ° C or lower as described above, and is preferably 105 ° C or lower. More preferably, there is. On the other hand, the lower limit is about 70 ° C. from the viewpoint of polymerization efficiency. Further, from the viewpoint of more sufficiently reducing the amount of unreacted styrene monomer in the post-polymerization step performed after the pre-polymerization step, the polymerization conversion of the styrene monomer in the pre-polymerization step is as described above. The polymerization is preferably performed until the content becomes 90% by mass or more, more preferably the polymerization is performed until the content becomes 95% by mass or more, and even more preferably the polymerization is performed until the content becomes 98% by mass or more.

  From the viewpoint that the unreacted styrene monomer can be efficiently reduced and the decrease in the weight average molecular weight of the styrene-based resin is more prevented, the final polymerization temperature in the subsequent polymerization step is as described above. The temperature is preferably higher than 115 ° C and 135 ° C or lower, more preferably 118 to 130 ° C. Under these production conditions, the content of the styrene monomer can be further reduced while further suppressing the decrease in the weight average molecular weight of the styrene resin. The amount of unreacted styrene monomer in the latter polymerization step can be controlled by the holding time at the final polymerization temperature.

  In the polymerization step, a flame retardant auxiliary may be used as necessary. As the flame retardant aid, a radical generator having a one-hour half-life temperature exceeding 130 ° C. can be used. The mass ratio of the flame retardant to the flame retardant auxiliary is preferably from 1: 0.1 to 1: 5 (however, the flame retardant: the flame retardant auxiliary). In this case, the flame retardancy of the molded body can be further improved. Examples of the flame retardant aid include dicumyl peroxide, di-t-butyl peroxide, cumyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenyl. Hexane, poly (1,4-diisopropylbenzene) and the like can be used.

  In suspension polymerization of the styrene monomer, a suspending agent can be used. That is, the styrene monomer can be polymerized in a dispersion medium such as water to which a suspending agent has been added. As the suspending agent, for example, hydrophilic polymers such as polyvinyl alcohol, methyl cellulose, and polyvinylpyrrolidone can be used. As the suspending agent, poorly water-soluble inorganic salts such as tribasic calcium phosphate, magnesium pyrophosphate, hydroxyapatite, aluminum oxide, talc, kaolin and bentonite can also be used. Further, a surfactant can be used together with the suspending agent, if necessary. When a poorly water-soluble inorganic salt is used as the suspending agent, it is preferable to use an anionic surfactant such as sodium alkylsulfonate or sodium dodecylbenzenesulfonate in combination.

  The use amount of the suspending agent is preferably 0.01 to 5 parts by mass based on 100 parts by mass of the styrene monomer. When a suspending agent comprising a poorly water-soluble inorganic salt and an anionic surfactant are used in combination as described above, 0.05 to 3 parts by mass of the suspending agent is added to 100 parts by mass of the styrene-based monomer. It is preferable to use 0.0001 to 0.5 parts by mass of a surfactant.

As long as the effects of the present invention are not impaired, the styrene-based monomer may include a bubble nucleating agent (bubble regulator), a plasticizer, a chain transfer agent, a phosphorus-based flame retardant, an inorganic flame retardant, an antistatic agent, and an oxidizing agent. Additives such as an inhibitor, an ultraviolet absorber, a light stabilizer, a conductive filler, an organic antibacterial agent, and an inorganic antibacterial agent can be added.
As the cell nucleating agent, for example, polyethylene wax, talc, silica, ethylenebisstearylamide, methyl methacrylate-based copolymer, silicone and the like can be used.
As the plasticizer, for example, liquid paraffin, glycerin diacetomonolaurate, glycerin tristearate, di-2-ethylhexyl phthalate, di-2-ethylhexyl adipate and the like can be used.
As the chain transfer agent, for example, octyl mercaptan, dodecyl mercaptan, α-methylstyrene dimer and the like can be used.

As the phosphorus-based flame retardant, for example, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate and the like can be used.
As the inorganic flame retardant, aluminum hydroxide, magnesium hydroxide, calcium carbonate, calcium aluminate, antimony trioxide, expandable graphite, red phosphorus and the like can be used.

As the antistatic agent, alkyl diethanolamine, glycerin fatty acid ester, sodium alkyl sulfonate and the like can be used.
As the antioxidant, phenol-based, phosphorus-based, sulfur-based or other antioxidants can be used.
As the ultraviolet absorber, a benzotriazole-based or benzophenone-based ultraviolet absorber can be used.
As the light stabilizer, a hindered amine-based light stabilizer or the like can be used.
As the conductive filler, conductive carbon black, graphite powder, copper zinc alloy powder, copper powder, silver powder, gold powder and the like can be used.
As the organic antibacterial agent, 3-iodo-2-propynylbutylcarbamate (IPBC), thiabendazole (TBZ), carbendazim (BCM), chlorothalonil (TPN) and the like can be used.
As the inorganic antibacterial agents, for example, antibacterial agents such as silver-based, copper-based, zinc-based, and titanium oxide-based can be used.
Further, rubber components such as butadiene rubber, styrene-butadiene rubber, isoprene rubber, and ethylene-propylene rubber may be added to the styrene monomer as long as the effects of the present invention are not impaired.

  Next, in the impregnation step, the styrene resin particles are impregnated with an organic physical blowing agent to obtain expandable styrene resin particles. The impregnation of the blowing agent in the impregnation step may be performed on the resin particles in the course of polymerization, on the resin particles after polymerization, or on both of them. That is, the “resin particles” in the impregnation step is a concept including at least one of the resin particles during polymerization and the resin particles after polymerization. It is preferable to add a foaming agent when the polymerization conversion of the styrene monomer is 80% by mass or more. In this case, the content of the unreacted styrene monomer can be further reduced. From the same viewpoint, it is more preferable that the blowing agent is added at a timing when the polymerization conversion of the styrene monomer is 88% by mass or more.

  As the organic physical foaming agent, a hydrocarbon having 3 to 6 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, n-hexane, and cyclohexane can be used. These foaming agents can be used alone or in combination of two or more. The content of the blowing agent in the expandable styrene resin particles is preferably 2 to 10% by mass. An amount such that the content of the foaming agent in the foamable particles becomes 1 to 20% by mass is supplied into the closed container. The foaming agent can be obtained, for example, by adding the foaming agent in a closed container to obtain foamable particles.

When the expandable particles are expanded by blowing steam having a gauge pressure of 0.03 MPa into the expandable particles in a box-type batch type pre-expander, the minimum of the test expanded particles obtained in the range of 200 to 400 seconds of steam blowing time is obtained. It is preferable to have a foaming property such that the bulk density A is 15 to 125 kg / m ³ . The test foamed particles are particles used for measuring the minimum bulk density A and are foamed under the above-mentioned predetermined conditions, and are different from foamed particles obtained by an actual foaming process. The minimum bulk density A of the expandable particles is, for example, the above range by adjusting the type and content of the organic physical blowing agent in the expandable particles, the type and content of the plasticizer, the molecular weight of the styrene resin, and the like. Can be adjusted within.

  As a box-type batch type prefoaming machine, a well-known and commonly used technical book published on August 3, 1982 by the Japan Patent Office. The same type as described in 38 can be used. A box-type batch type prefoaming machine generally has a box having a steam room whose front surface can be opened and closed by a door.A large number of steam holes are opened in the inner wall of the box, and steam is introduced into the steam chamber from a steam pipe leading to the box. It has a configuration to be supplied. In the measurement of the minimum bulk density A, for example, a foaming box (with a wire mesh stretched on the bottom of the stove) in which a foaming particle is sprayed is put in a steam chamber, the door is closed, and the blowing steam pressure is 0.03 MPa (G: gauge pressure). Send steam. The door does not need to be airtight and there is little pressure in the box. The steam blowing time is determined in the range of 200 to 400 seconds so that the bulk density of the test expanded particles obtained by expanding the expandable particles is minimized. The minimum value of the bulk density of the test expanded particles is defined as the minimum bulk density A. Since almost no pressure is applied inside the box-type batch type foaming machine, the minimum bulk density A indicates the minimum bulk density obtained by foaming under atmospheric pressure.

  The content of the styrene monomer in the expandable particles obtained after the impregnation step is preferably 50 mass ppm or less. In this case, the content of the styrene monomer in the molded article obtained through the foaming step and the molding step is easily reduced to, for example, 10 mass ppm or less. From the viewpoint that the content of the styrene-based monomer in the molded article is more reliably reduced to 10 mass ppm or less and the amount of styrene-based monomer emitted from the molded article is further reduced, the styrene in the expandable particles is The content of the system monomer is more preferably 30 ppm by mass or less, further preferably 20 ppm by mass or less. Further, by performing severe foaming, even when the content of the styrene-based monomer in the expandable particles exceeds 10 mass ppm or more, the content of the styrene monomer in the molded body can be effectively reduced. It can be reduced to 10 mass ppm or less. The styrene-based monomer in the expandable particles can be measured using a head space gas chromatograph mass spectrometer. As the measurement sample, a dissolved substance obtained by dissolving the expandable particles in dimethylformamide can be used.

  The water content in the expandable particles is preferably 1.5% by mass or less. In this case, it is easier to suppress the coarsening of the bubbles of the foamed particles obtained by using the foamable particles, and the aging period until the size of the bubbles becomes uniform can be further shortened. Then, even if the aging period of the expandable particles is shortened, it is possible to further suppress a decrease in mechanical strength of the foamed molded article and to further improve the appearance of the foamed molded article. The aging period is a period in which the expandable styrene resin particles are stored in a closed container under a low-temperature environment of, for example, 10 ° C. or lower. The water content of the expandable particles is more preferably 1% by mass or less. The water content in the expandable styrene resin particles can be determined by a Karl Fischer moisture meter equipped with a heating and vaporizing device.

  Next, in the foaming step, the foamable particles are foamed by heating with steam to obtain foamed particles. The expanded particles are generally called pre-expanded particles. The foaming step can be performed, for example, by supplying steam to the foamable particles introduced into a batch type prefoaming machine equipped with a stirring device.

  Normally, the expandability of the expandable particles is adjusted so that the relationship between the bulk density B of the expandable particles and the above-described minimum bulk density A satisfies B / A ≧ 1. That is, the expandable particles are expanded within a range not exceeding the maximum expandability at normal pressure. On the other hand, in the expanding step, the bulk density B of the expanded particles and the minimum bulk density A satisfy the relationship of 0.6 ≦ B / A ≦ 0.9, that is, at normal pressure. Foamable particles exceeding the maximum foaming capacity of When B / A exceeds this range, the content of the styrene monomer contained in the molded product obtained after the molding step may not be sufficiently reduced. From the viewpoint of further reducing the content of the styrene monomer, B / A ≦ 0.85 is preferable. On the other hand, when B / A is lower than the above range, there is a possibility that the foamed particles mutually adhere during the foaming step. In order to further avoid this, it is preferable that B / A ≧ 0.7.

The bulk density B of the expanded particles can be controlled by adjusting the expansion conditions of the expandable particles. The foaming conditions include, for example, steam pressure (specifically, gauge pressure), heating time by steam, and the like. If the bulk density B of the foamed particles is low, the strength of the molded body is insufficient, and if the bulk density B is high, the cost may increase. Therefore, the bulk density B of the foamed particles may be 12 to 100 kg / m ^3. preferable.

  Next, in the molding step, the foamed particles are fused with each other in a molding die to obtain a foamed particle molded body. The molding step can be performed by an in-mold molding method. Specifically, for example, a molded product can be obtained by supplying steam to the foamed particles filled in a molding die and performing heating.

  Next, a preferred embodiment of the molded article will be described. As described above, the molded article has a styrene-based resin obtained by suspension polymerization of a styrene-based monomer in the presence of a flame retardant as a base resin. In the molded article, a large number of expanded particles containing a flame retardant are fused to each other. The flame retardant contained in the molded article is as described above, and contains at least a bromide of a styrene-butadiene copolymer.

  Expanded particles using a styrene-based resin as a base resin obtained by suspension-polymerizing a styrene-based monomer in the presence of a flame retardant have a uniform distribution of the flame retardant in the expanded particles. Therefore, a molded article in which the flame retardant is uniformly distributed in the molded article can be obtained by molding the expanded particles in a mold. That is, the flame retardant concentration on a mass basis becomes uniform between the surface layer portion and the inside of the molded body. When the flame retardant is uniformly distributed in the molded product, the molded product more stably exhibits the flame retardancy.

  The weight average molecular weight of the styrenic resin in the molded product is preferably 150,000 or more. If it is less than 150,000, the strength of the molded article may be reduced. In light of further improving the strength of the molded body, the weight average molecular weight is more preferably equal to or greater than 180,000, and still more preferably equal to or greater than 200,000. In addition, from the viewpoint that the expandability of the expandable particles can be improved, the weight average molecular weight is preferably 350,000 or less, more preferably 300,000 or less. The weight average molecular weight is a standard polystyrene equivalent value measured by a gel permeation chromatography method (that is, GPC method).

  It is preferable that the content of the styrene-based monomer in the molded article is 10 ppm by mass or less. In this case, it is possible to sufficiently reduce the amount of the styrene monomer emitted from the molded body. Therefore, the molded body is more suitable for use in a narrow space such as an interior material of an automobile. From the same viewpoint, the content of the styrene monomer in the molded article is more preferably 5 ppm by mass or less. The content of the styrene-based monomer in the molded article can be measured using a head space gas chromatograph mass spectrometer, as in the case of the expandable particles described above. As a measurement sample, a lysate obtained by dissolving a test piece collected from a molded body in dimethylformamide can be used.

The apparent density of the molded body is preferably 12~100kg / m ^3. In this case, the molded body can achieve both physical properties such as strength and flammability and lightness.

  Hereinafter, examples and comparative examples of the foamed particle molded body will be described.

(Example 1)
The method for producing the molded article of this example will be described below. First, 16 kg of deionized water, 14.4 g of tribasic calcium phosphate (suspension agent), 0.6 g of sodium α-olefin sulfonate (surfactant), and alkyl biphenyl were placed in an autoclave having a stirrer and having a 50 L internal volume. 0.2 g of disodium disulfonate (surfactant) and 24.4 g of sodium acetate (electrolyte) were charged. Then, 43.2 g of benzoyl peroxide ("Nipper BW" manufactured by NOF Corp., water-diluted powder, polymerization initiator) which is an organic peroxide having a one-hour half-life temperature of 92 ° C was reduced by one hour and a half. -Butylperoxy-2-ethylhexyl monocarbonate ("Perbutyl E" manufactured by NOF CORPORATION, polymerization initiator) which is an organic peroxide having an initial temperature of 119 ° C, 25.6 g of brominated styrene-butadiene block 12.8 g of a copolymer ("Emerald Innovation 3000" manufactured by Chemtura Japan Co., Ltd., flame retardant), manufactured by Dicumyl Peroxide Nippon Oil Co., Ltd., which is an organic oxide having a one-hour half-life temperature of 136 ° C. "Park Mill D", a flame retardant aid) 51.2 g, liquid paraffin ("MORESCO WHITE P-60" manufactured by MORESCO, plasticizer) 128 g, and polyethylene wax powder Zehnder (TOYO ADL Co. Ltd. "Polywax 1000", nucleating agent) 3.2g were mixed in styrene 16 kg, were put into the autoclave with stirring the mixture at a rotational speed 210 rpm. The flame retardant used in this example is hereinafter referred to as "flame retardant A" as appropriate. The bromine content and the 5% weight loss temperature of the flame retardant A are shown in Table 1 below.

  Next, after the air in the autoclave is replaced with nitrogen, the temperature is raised to 90 ° C. in one and a half hours, and after reaching the temperature of 90 ° C., the temperature in the autoclave is further raised to 100 ° C. in 6 hours and 30 minutes. Let warm. Thereafter, the inside of the autoclave was further heated to a temperature of 120 ° C. over 2 hours, and the inside of the autoclave was maintained at the temperature of 120 ° C. for 5 hours. Then, it cooled to temperature 30 degreeC over about 6 hours. In the course of raising the temperature from 90 ° C. to 100 ° C. and when 5 hours and 30 minutes have elapsed after reaching 90 ° C., pentane (a mixture of 80% n-pentane and 20% isopentane) is used as a blowing agent. 320 g and 880 g of butane (a mixture of 70% n-butane and 30% isobutane) were pressed into the autoclave over 30 minutes. At the start of the addition of the blowing agent, that is, when 5 hours and 30 minutes had elapsed after the temperature reached 90 ° C., the polymerization conversion of styrene was 89% by mass. At the end of the first polymerization step, that is, when the temperature reached 100 ° C., the polymerization conversion of styrene was 99% by mass. The method of measuring each polymerization conversion is as described below.

  After cooling, take out the contents (expandable particles) from the autoclave, add nitric acid to the expandable particles to remove tribasic calcium phosphate attached to the surface of the expandable particles, dehydrate with a centrifuge, and fluidize and dry Moisture adhering to the surface was removed with an apparatus. Thus, expandable particles having an average particle size of about 1.0 mm were obtained.

  Next, the expandable particles were sieved to select and take out particles of 0.5 to 1.4 mm. Thereafter, 0.005 parts by mass of N, N-bis (2-hydroxyethyl) alkylamine (antistatic agent) is added to 100 parts by mass of the expandable particles to coat the expandable particles with the antistatic agent. did. Furthermore, 0.1 parts by mass of zinc stearate, 0.05 parts by mass of glycerin tristearate, and 0.05 parts by mass of glycerin monostearate are added to 100 parts by mass of the expandable particles, and a mixture thereof is added. Covered the expandable particles. Thereafter, aging was performed by placing the expandable particles in a closed container and storing them in a cold storage at 6 ° C.

  For the expandable particles, the amount of the blowing agent, the amount of the styrene-based monomer, the amount of water, and the expandability (specifically, the minimum bulk density A of the test expandable particles) were measured. Table 2 shows the results. The method for measuring the polymerization conversion is shown below.

`` Polymerization conversion rate at the end of the first polymerization step ''
The pre-polymerization step was separately performed under the same conditions as the pre-polymerization step performed during the preparation of the expandable particles. At the same time as the completion of the first-stage polymerization step, the temperature of the contents of the autoclave was rapidly cooled to 30 ° C. or less within 10 minutes to stop the polymerization reaction. After cooling, the styrene-based resin particles in the course of polymerization were removed from the autoclave, dehydrated by a centrifuge, and water adhering to the surface was removed by a fluidized drier. Thus, styrene resin particles at the end of the first-stage polymerization step were obtained. The content of unreacted styrene monomer in the obtained styrene-based resin particles was determined by gas chromatography. The measuring method will be described later. Then, the polymerization conversion was determined from the following equation (1). This operation was performed three times, and the arithmetic average value of each polymerization conversion was determined.
Polymerization conversion (% by mass) = 100-content of styrene monomer (% by mass) (1)

`` Polymerization conversion rate when impregnating blowing agent ''
Under the same conditions as in the production of the expandable particles, polymerization was separately performed, and immediately before the addition of the blowing agent was started, the temperature of the contents of the autoclave was rapidly cooled to 30 ° C. or less within 10 minutes to stop the polymerization reaction. . Then, the same operation as in the measurement of the polymerization conversion rate at the end of the above-mentioned first-stage polymerization step was performed to determine the polymerization conversion rate at the time of impregnation with the blowing agent. This operation was performed three times, and the arithmetic average value of each polymerization conversion was determined.

"Content of foaming agent"
The content of the foaming agent was measured by performing gas chromatography on a solution obtained by dissolving the foamable particles in dimethylformamide (DMF). Specifically, first, about 5 g of cyclopentanol was precisely weighed to the third decimal place in a 100 mL measuring flask. This weight is hereinafter referred to as Wi (unit: g). Further, DMF was added into the volumetric flask to make the total volume 100 mL. This DMF solution was further diluted 100 times with DMF. This was used as an internal standard solution. Next, about 1 g of the expandable particles to be measured were precisely weighed to three decimal places. This weight is hereinafter referred to as Ws (unit: g). A precisely weighed sample of the expandable particles was dissolved in about 18 mL of DMF, and 2 mL of the internal standard solution was accurately added using a whole pipette. 1 μL of the solution thus obtained was collected with a microsyringe and introduced into gas chromatography to obtain a chromatogram. The peak area of the foaming agent component and the internal standard was determined from the obtained chromatogram, and the concentration of each component was determined from the following equation (1).
Component concentration (unit: mass%) = (Wi / 10000) ² × (An / Ai) × Fn ÷ Ws × 100 (1)
Here, Wi: weight (g) of cyclopentanol when an internal standard solution was prepared, Ws: weight of a sample dissolved in DMF (unit: g), An: peak area of each component at the time of gas chromatography measurement, Ai : Peak area of the internal standard substance at the time of gas chromatographic measurement, Fn: correction coefficient of each component obtained from a calibration curve prepared in advance. The conditions of gas chromatographic analysis were as follows. Equipment used: Gas chromatograph GC-6AM manufactured by Shimadzu Corporation, Detector: FID (hydrogen flame ionization detector), Column material: Glass column with inner diameter 3 mm, length 5000 mm, Column filler: [Liquid phase name] FFAP (Free fatty acid), [Liquid phase impregnation rate] 10% by mass, [Carrier name] Diatomaceous earth Chromasorb W for gas chromatography, [Carrier particle size] 60/80 mesh, [Carrier treatment method] AW-DMCS (Washing / Baking / Acid Treatment / silane treatment), [filling amount] 90 mL, inlet temperature: 100 ° C, column temperature: 40 ° C, detector temperature: 100 ° C, carrier gas: N ₂ , flow rate 40 ml / min

"Styrene monomer content"
The content of unreacted styrene in the expandable particles was measured by a head space gas chromatograph mass spectrometer. As a sample, a lysate obtained by dissolving the expandable particles in dimethylformamide (ie, DMF) was used. Specifically, first, a standard solution is prepared such that the styrene concentration in DMF becomes 5 mass ppm, 50 mass ppm, and 500 mass ppm. Next, 0.2 g of the standard solution was precisely weighed in a vial having a capacity of 20 ml, and 1 ml of DMF was put therein and sealed. The temperature was maintained by a headspace sampler, the gas phase was measured by a gas chromatograph mass spectrometer, and a calibration curve was created from the obtained chromatogram. Next, 0.2 g of the sample was precisely weighed in a 20 ml vial, 1 ml of DMF was sealed, and the solution was kept at room temperature for 1 day to completely dissolve. The temperature was maintained by a headspace sampler, the gas phase was measured by a gas chromatograph mass spectrometer, and the content of the unreacted styrene monomer was determined from the obtained chromatogram and a calibration curve prepared in advance.
The conditions for gas chromatography mass spectrometry were as follows.
Gas chromatograph mass spectrometer: GCMS-QP2020 manufactured by Shimadzu Corporation
Headspace sampler: HS-20 manufactured by Shimadzu Corporation
Capillary column: GL Sciences Corporation Stabilwax, inner diameter 0.32 mm, length 30 m
Headspace sampler heat retention condition: 90 ° C, 1 hour Column temperature: 50 ° C × 2 minutes → (10 ° C / min) → 90 ° C → (5 ° C / min) → 120 ° C → (20 ° C / min) → 230 ° C × 2 minutes Ion source temperature: 200 ° C
Carrier gas: helium, column flow rate 2 ml / min Split ratio: 1/10

"amount of water"
The water content of the expandable particles was measured using a Karl Fischer moisture meter. Specifically, about 0.28 g of a sample of the expandable particles was precisely weighed. Next, the sample was heated at a temperature of 160 ° C. to vaporize the water by a water vaporizer CHK-501 manufactured by Kyoto Electronics Industry Co., Ltd., and the water content was measured using a Karl Fischer moisture meter (coulometric Titration method) It measured using MKC-610.

"Minimum bulk density A of test expanded particles"
In a box-type batch type prefoaming machine, steam having a gauge pressure of 0.03 MPa was blown into the aged expandable particles to expand them, thereby producing test expanded particles. Then, the minimum value (minimum bulk density A) of the bulk density of the test foamed particles obtained in the range of 200 to 400 seconds of the steam blowing time was determined. The measurement of the bulk density was performed on the foamed particles air-dried all day and night. After air-drying, the foamed particles were filled up to the mark position of 1 L in a 1 L measuring cylinder and weighed, and the mass W _P (unit: g) of the foamed particles having a bulk volume of 1 L was weighed to the first decimal place. Then, the bulk density (unit: kg / m ³ ) was determined by performing unit conversion.

  Next, 3.6 kg of the aged expandable styrene resin particles are charged into a pressurized batch foaming machine (DYHL-500U manufactured by Daisen Industries Co., Ltd.), and the pressure in the foaming machine (however, gauge pressure) is reduced to 0.023 MPa. Steam having a gauge pressure of 0.15 MPa was supplied and heated for 130 seconds to obtain expanded particles having an expansion ratio of about 50 times. The bulk density B of the obtained expanded particles was measured in the same manner as in the test expanded particles described above. Further, the ratio (B / A) of the bulk density B of the foamed particles to the minimum bulk density A of the test foamed particles was calculated. Table 2 shows the results.

  Next, after the foamed particles were aged at room temperature for one day, they were filled in a mold of a DABO Co., Ltd. mold molding machine and heated at a steam pressure of 0.08 MPa (gauge pressure) for 15 seconds. Next, after cooling for a predetermined time, it was taken out of the mold to obtain a plate-shaped molded body of 300 mm × 300 mm × 25 mm in which a large number of expanded particles were fused to each other. Next, the molded article was measured for the molecular weight of the styrene-based resin, the content of the unreacted styrene monomer, the amount of the styrene-based monomer emitted, and the bending strength, and evaluated for a combustion test. Table 2 shows the results.

"Molecular weight"
The molecular weight (number average molecular weight, weight average molecular weight, Z average molecular weight) of the styrene resin in the molded article was measured by gel permeation chromatography using polystyrene as a standard substance. Specifically, the measurement was performed using HLC-8320GPC EcoSEC manufactured by Tosoh Corporation under the measurement conditions of eluent: tetrahydrofuran (THF), THF flow rate: 0.6 ml / min, and sample concentration: 0.1 wt%. As a column, a column in which one TSKguardcolumn SuperH-H and two TSK-GEL SuperHM-H were connected in series was used. That is, a test piece collected from a molded article was dissolved in tetrahydrofuran, and the molecular weight was measured by gel permeation chromatography. Then, the measured values were calibrated with standard polystyrene, and the number average molecular weight, weight average molecular weight, and Z average molecular weight were determined.

"Styrene monomer content"
As a sample, measurement was carried out in the same manner as the above-mentioned expandable particles, except that a melt obtained by dissolving a part of the molded body in dimethylformamide (ie, DMF) was used.

"Emission amount of styrene monomer"
A foam molded article was obtained under the same molding conditions as above, except that a molding die for molding a plate-like molded article having a size of 100 mm × 80 mm × 15 mm was used. The molded body was dried at 40 ° C. for one day, and further left for one day or more at a temperature of 23 ° C. and a humidity of 50% to adjust the state of the molded body. Thereafter, the molded body was placed in a 10 L Tedlar bag and heat sealed. Next, after purging the inside of the Tedlar bag three times with nitrogen, 4 L of nitrogen was injected into the bag and kept at a temperature of 40 ° C. for 2 hours. 1.0 L of a styrene-based monomer generated from the molded product was collected in a Tenax-TA collecting tube at a flow rate of 0.1 ml / min. Then, thermal desorption - to quantify the styrene monomer of the collecting vessel by a gas chromatograph mass spectrometer, styrene monomer per gas 1 m ³ (Unit: μg / m ³⁾ was determined.

"Flammability test"
The flammability was evaluated in accordance with FMVSS No. 302. Specifically, the molded body was left at a temperature of 40 ° C. for 3 days, and further left at room temperature for 1 day to cure. Next, a plate-shaped test piece of 355 mm × 100 mm × 12.7 mm was cut out from the molded body. Two lines are drawn at 38 mm (combustion time measurement start line) and 292 mm (combustion time measurement end line) from one end of the test piece. Dimensions: 381 mm × 203 mm × 356 mm FMVSS No 302 A test piece was fixed to a metal U-shaped frame in a dedicated chamber and held horizontally. The flame height of a Bunsen burner having an inner diameter of 9 mm using natural gas was adjusted to 38 mm. The air intake of the burner was fully closed, and the height of the flame was adjusted according to the amount of gas. Both were arranged so that the distance between the tip of the burner and the lower end of the test piece was 19 mm. After 15 seconds of indirect flame at the open end of the test piece, the flame was moved away, and timing was started when the flame reached the combustion time measurement start line. The time taken to pass between the combustion time measurement start line and the combustion time measurement end line (that is, the combustion time, unit: second) was measured. If the fire was extinguished on the way, the time until the fire was extinguished was measured. The distance between the combustion time measurement start line and the combustion time measurement end line is defined as the combustion distance (unit: mm). When the fire was extinguished on the way, the distance from the combustion time measurement start line to the point where the fire was extinguished was measured, and the burning speed was determined from the burning distance and the burning time based on the following equation (2).
Burning speed (unit: mm / min) = burning distance (unit: mm) / burning time (unit: second) x 60 ... (2)
If the burning rate is 102 mm / min or less, or the fire is extinguished within a burning distance of 51 mm and within 60 seconds from the burning time measurement start line, it shall conform to FMVSS No 302.

"Bending strength"
The molded body is cut to prepare a test piece having a length of 300 mm, a width of 75 mm and a thickness of 25 mm, and a distance between fulcrums of 200 mm, a pressure wedge 10R and a support base 10R according to JIS K 7221-2: 2006. A three-point bending test was performed under the condition that the pressure wedge descends at a rate of 10 mm / min, and the bending strength was measured.

(Example 2)
Example 1 was repeated except that the amount of the foaming agent was 320 g of pentane (a mixture of 80% n-pentane and 20% isopentane) and 928 g of butane (a mixture of 70% n-butane and 30% isobutane).

(Example 3)
Example 1 was repeated except that the amount of the foaming agent added was 320 g of pentane (a mixture of 80% n-pentane and 20% isopentane) and 976 g of butane (a mixture of 70% n-butane and 30% isobutane).

(Example 4)
After replacing the air in the autoclave with nitrogen, the temperature is raised to 90 ° C. in one and a half hours, and after the polymerization temperature reaches 90 ° C., the operation is performed until the temperature in the autoclave is raised to 100 ° C. in 6 hours and 30 minutes. Was performed in the same manner as in Example 1. Next, the temperature was further increased to 115 ° C. over 2 hours, and the temperature was maintained at 115 ° C. for 5 hours. Then, it cooled to 30 degreeC over about 6 hours. The operation after cooling was performed in the same manner as in Example 1.

(Comparative Example 1)
Example 1 was repeated except that the amount of the foaming agent added was 400 g of pentane (a mixture of 80% n-pentane and 20% isopentane) and 1200 g of butane (a mixture of 70% n-butane and 30% isobutane). .

(Comparative Example 2)
As in Example 1, except that 160 g of 2,2-bis (4 '-(2 ", 3" -dibromo-2 "-methylpropoxy-3', 5'-dibromophenyl) propane was used as the flame retardant. The flame retardant used in this example is hereinafter referred to as “flame retardant B.” The bromine content of the flame retardant B and the 5% weight loss temperature are shown in Table 1 below.

As shown in Table 2, it can be seen that the molded articles of Examples 1 to 4 had a low styrene monomer content, and thus the styrene monomer emission was as low as 100 μg / m ³ or less. In addition, since the weight average molecular weight of the styrene resin is maintained at 150,000 or more, it has excellent flexural strength, contains brominated styrene-butadiene copolymer as a flame retardant, and complies with the flammability test of FMVSS No 302. are doing. In Example 4, since the final polymerization temperature was lowered to 115 ° C., the molecular weight of the obtained polymer was increased, and the bending strength of the molded body was improved. On the other hand, the content of the styrene monomer in the molded product is slightly increased. Further, as can be seen from Table 2, the molded articles of Examples have at least a bromide of a styrene-butadiene copolymer as a flame retardant and a foaming property having a foaming property in which the minimum bulk density A falls within a predetermined range. It can be produced by using the particles and performing at least the above-mentioned severe foaming in which the B / A falls within a predetermined range.

On the other hand, Comparative Example 1 is an example in which the amounts of butane and pentane, which are blowing agents, were increased as compared with Example 1. As a result, the ratio B / A of the bulk density B to the minimum bulk density A increased to 1.28, and the reduction of the styrene monomer during the foaming step was insufficient. The content is as high as 11.4 mass ppm. This shows that the amount of styrene monomer emitted from the molded article is as large as 127 μg / m ³ .

  Comparative Example 2 did not use a brominated styrene-butadiene copolymer as a flame retardant, but instead used flame retardant B shown in Table 1, namely, 2,2-bis (4 ′-(2 ″, 3 ″ -dibromo). In this case, the polymerization of the styrene monomer in the polymerization step is liable to be hindered, and the styrene-based monomer in the expandable particles is difficult to disperse. 13. The content of the styrene-based monomer was increased, and the content of the styrene-based monomer in the molded article obtained after the foaming step and the molding step was also increased. Since it was as low as 50,000, only a molded article having inferior bending strength was obtained.

Claims (8)

A molded article in which styrene-based resin obtained by suspension polymerization of styrene-based monomer in the presence of a flame retardant is used as a base resin, and styrene-based resin expanded particles containing the flame retardant are fused to each other,
The flame retardant contains a bromide of a styrene-butadiene copolymer,
The weight average molecular weight of the styrene resin is 150,000 or more,
The content of the styrene monomer in the shaped body is Ri der 10 mass ppm or less,
Emission amount of the styrenic monomer of the molded body is Ru der 100 [mu] g / m ³ or less, the foamed bead molded article. Apparent density of the shaped body is 12~100kg / m ^3, the foamed bead molded article of claim 1. The foamed particle molded product according to claim 1 or 2, wherein a blending amount of the flame retardant with respect to 100 parts by mass of the styrene resin is 0.05 parts by mass or more and less than 0.5 parts by mass . Used as automobile interior materials, expanded beads molded article according to any one of claims 1 to 3. A suspension polymerization of styrene monomer in the presence of a flame retardant comprising a brominated butadiene copolymer obtain styrene resin particles polymerization process, - scan styrene
An impregnation step of impregnating the styrenic resin particles with an organic physical blowing agent to obtain expandable styrenic resin particles,
A foaming step of foaming the expandable styrene-based resin particles by heating with steam to obtain expanded styrene-based resin particles,
A molding step of fusing the expanded styrene resin particles to each other in a molding die to obtain a foamed particle molded body,
When the expandable styrene resin particles are foamed by blowing steam having a gauge pressure of 0.03 MPa into the expandable styrene resin particles in a box-type batch type prefoaming machine, the steam blow time is in the range of 200 to 400 seconds. Having a foaming property such that the minimum bulk density A of the test foamed particles obtained in the above becomes 15 to 125 kg / m ³ ,
In the expanding step, the bulk density B and the minimum bulk density A of the expanded styrene-based resin particles obtained after the expanding step satisfy the relationship of 0.6 ≦ B / A ≦ 0.9. A method for producing a foamed particle molded article, comprising foaming expandable styrene resin particles. The bulk density B of the foamed styrene resin particles are 12~100kg / m ^3, foam method for producing particles molded article according to claim 5. The method for producing a foamed particle molded product according to claim 5 or 6 , wherein the content of the styrene-based monomer in the foamed particle molded product is 10 mass ppm or less . The content of styrene monomer of expandable styrene resin particles is not more than 50 mass ppm, the production method of the expanded beads molded article according to any one of claims 5-7.