JP6263987B2 - Method for producing expandable polystyrene resin particles - Google Patents

Description

  The present invention relates to a method for producing expandable polystyrene resin particles containing graphite and a brominated flame retardant.

  Polystyrene resin foam moldings are used for heat insulating materials for buildings, cold storage boxes, and the like due to their excellent heat insulation performance. The polystyrene-based resin foam molding is produced using, for example, expandable polystyrene-based resin particles. Specifically, first, foamed polystyrene-based resin particles are obtained by foaming expandable polystyrene-based resin particles. Next, a polystyrene resin foam molded article is obtained by fusing a large number of polystyrene resin foam particles to each other in a mold.

In order to reduce the weight, when the expansion ratio of the polystyrene-based resin foam molded article is increased to lower the density, the heat insulation performance of the polystyrene-based resin foam molded article tends to decrease from a density of about 25 kg / m ³ . Therefore, in order to further improve the heat insulation performance of the low-density polystyrene resin foam molded article, a technique for blending graphite into the polystyrene resin foam molded article is known.

  On the other hand, the polystyrene-based resin foam molded article containing graphite has a problem that it easily burns. Then, the technique which mix | blends a flame retardant further with a foaming molding is known. In general, it is known that expandable polystyrene resin particles containing graphite or a flame retardant are produced by suspension polymerization using a styrene monomer, a flame retardant, and graphite (see Patent Document 1). However, the expandable polystyrene resin particles obtained by this method have a problem that the amount of residual monomer increases and a problem that the variation in particle size distribution increases. In order to solve such problems, there is a method (seed polymerization method) for producing expandable polystyrene resin particles by impregnating and polymerizing a polystyrene resin seed particle containing graphite with a styrene monomer in which a flame retardant is dissolved. It has been developed (see Patent Documents 2 and 3).

JP 2001-522383 A JP-T 2009-536687 JP 2013-209608 A

  However, the expandable polystyrene resin particles obtained by the conventional seed polymerization method described above have the problem that the amount of flame retardant added to obtain the desired flame retardancy increases, and foam moldability. There is a problem of getting worse. As a result, there arises a problem that the fusion rate of the polystyrene-based resin foam molded article is lowered. Moreover, the surface of a foaming molding becomes a patchy pattern, or when many voids generate | occur | produce between the foaming particles which comprise a foaming molding, the problem that the external appearance of a foaming molding worsens arises.

  The present invention has been made in view of such a background, and is capable of obtaining a polystyrene-based resin foam molded article having excellent flame retardancy and heat insulation, high fusion rate, and excellent appearance, and the amount of residual monomers. Therefore, an object of the present invention is to provide a method for producing expandable polystyrene-based resin particles with a small variation in particle size distribution.

One aspect of the present invention is a method for producing expandable polystyrene resin particles containing graphite and a brominated flame retardant,
A dispersion step of dispersing polystyrene resin seed particles obtained by kneading a polystyrene resin, graphite, and a brominated flame retardant in an aqueous medium;
A polymerization step of supplying a styrene monomer into the aqueous medium, impregnating and polymerizing the polystyrene resin seed particles with the styrene monomer; and
The physical blowing agent during or after polymerization in the polymerization step impregnated into the resin particles have a a foaming agent impregnating step of obtaining the expandable polystyrene resin particles,
The brominated flame retardant is in the method for producing expandable polystyrene resin particles, wherein the brominated butadiene polymer der Rukoto.

  As described above, the production method includes a dispersion step, a polymerization step, and a blowing agent impregnation step. That is, in the above production method, polystyrene resin seed particles are obtained by kneading polystyrene resin (hereinafter referred to as “PS resin” as appropriate), graphite, and bromine flame retardant (hereinafter referred to as “flame retardant” as appropriate). (Hereinafter referred to as “seed particles” as appropriate), and the seed particles are impregnated and polymerized with a styrene monomer, and further impregnated with a physical foaming agent. In the said manufacturing method, since the graphite is kneaded into the said seed particle, the expandable resin particle containing a graphite is manufactured. Then, by using the expandable resin particles, a polystyrene-based resin foam molded article containing graphite (hereinafter referred to as “foam molded article” as appropriate) is obtained. Since the foamed molded article contains graphite, it can exhibit excellent heat insulation even at a low density. Further, in the above production method, a flame retardant is kneaded into the seed particles. Therefore, by using the expandable resin particles obtained by the above production method, a polystyrene-based resin foam molded article that can exhibit excellent flame retardancy can be obtained even if the amount of flame retardant added is reduced.

  Moreover, since the flame retardant is kneaded in the seed particles as described above, expandable resin particles having excellent foamability can be obtained. Generally, when the amount of the flame retardant is increased, the foamability tends to be reduced. However, the foamable resin particles obtained by the above production method can exhibit excellent foamability even if the amount of the flame retardant is increased. .

  Moreover, since the flame retardant is kneaded in the seed particles as described above, it is possible to prevent the fusion rate of the foamed molded body obtained using the foamable resin particles from being lowered. That is, a foamed molded product having a high fusion rate can be obtained. Moreover, it can prevent that a foaming molding becomes a patch pattern, or many voids generate | occur | produce between the foaming particles which comprise a foaming molding. That is, it is possible to prevent the appearance of the foamed molded product from being deteriorated. Moreover, melting of the surface of the foamed molded product can also be prevented.

  Moreover, in the said manufacturing method, the said styrene-type monomer is impregnated and polymerized by performing the said superposition | polymerization process. Therefore, variation in the particle size distribution of the expandable resin particles can be reduced, and the amount of residual monomer can be reduced.

The photograph substitute figure which shows the electron micrograph of the expandable resin particle in Example 1. FIG. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in Example 2. FIG. FIG. 3 is a photograph substitute diagram showing an electron micrograph of expandable resin particles in Example 3. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in Example 4. FIG. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in the comparative example 1. FIG. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in the comparative example 2. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in the comparative example 3. FIG. The photograph substitute figure which shows the electron micrograph of the expandable resin particle in the comparative example 4.

Next, a preferred embodiment in the method for producing the expandable resin particles will be described.
The foamable resin particles are foamed to produce polystyrene-based resin foamed particles (hereinafter referred to as “foamed particles” as appropriate), and the foamed particles are molded in-mold to form the foamed molded product. It is used for manufacturing. As described above, the expandable resin particles are produced by performing a dispersion step, a polymerization step, and a blowing agent impregnation step.

  In the dispersion step, seed particles obtained by kneading a PS resin, graphite, and a flame retardant are used. The seed particles can be produced by blending a PS resin, graphite, and a flame retardant, melting and kneading these, and then refining. Graphite and flame retardant can be blended directly in powder form, but a master batch of graphite and / or flame retardant using PS resin as a base resin is prepared, and the master batch is blended with PS resin. You can also. The above melt-kneading can be performed by an extruder.

  The PS resin refers to a resin having a styrene monomer component unit of 50% by mass or more. That is, PS resin can be copolymerized with not only a homopolymer of styrene monomer but also a copolymer of two or more styrene monomers as well as one or more styrene monomers. It is a concept including a copolymer with a vinyl monomer. The styrene monomer component unit in the PS resin is preferably 80% by mass or more, and more preferably 90% by mass or more.

  Examples of the styrene monomer include styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, p-methoxy styrene, p- n-butylstyrene, pt-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, divinylbenzene, styrenesulfonic acid, sodium styrenesulfonate, etc. Can be mentioned. These may be used alone or in combination of two or more.

Other vinyl monomers that can be copolymerized with styrene monomers include acrylic acid esters, methacrylic acid esters, vinyl compounds containing hydroxyl groups, vinyl compounds containing nitrile groups, vinyl acid organic compounds, and olefins. Examples thereof include compounds, diene compounds, vinyl halide compounds, vinylidene halide compounds, maleimide compounds and the like.
Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.
Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate.
Examples of the vinyl compound containing a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.
Examples of the vinyl compound 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, and 2-butene.
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 maleimide compounds include N-phenylmaleimide and N-methylmaleimide.
These vinyl monomers may be used alone or in combination of two or more.

  The seed particles are composed of PS resin. As the PS-based resin for seed particles, polystyrene is particularly preferable from the viewpoint of enhancing foamability. The seed particles may contain other thermoplastic resins other than polystyrene resins such as polyethylene resins, polypropylene resins and polyester resins, and thermoplastic elastomers such as styrene elastomers and olefin elastomers. it can. When these thermoplastic resins and thermoplastic elastomers are blended, the blending amount is preferably 20 parts by mass or less, preferably 10 parts by mass or less, with respect to 100 parts by mass of the PS resin of the seed particles. Is more preferable, and it is still more preferable to set it as 5 mass parts or less.

  The glass transition temperature (Tg) of the seed particles is preferably 90 ° C. or higher and lower than 110 ° C. In this case, the foamability of the foamable resin particles can be improved, and shrinkage during foaming can be prevented. Furthermore, at the time of in-mold molding of the foamed particles obtained after foaming, the fusion property between the foamed particles can be improved, and the dimensional stability of the foamed molded product can be improved. The Tg of the seed particles is more preferably 95 to 105 ° C, and further preferably 95 to 100 ° C.

  As the graphite, powders having various shapes such as a plate shape, a scale shape, a flake shape, a spherical shape, a granular shape, an indefinite shape, and a needle shape can be used. A flaky shape and a scaly shape are preferable. From the viewpoint of obtaining a high heat insulating effect, the average particle diameter of graphite is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm. The average particle diameter of graphite can be measured by dispersing a graphite powder in water and using a laser diffraction scattering method or the like. Specifically, the average particle size can be determined by the particle size at a volume integrated value of 50% in the particle size distribution obtained by the laser diffraction scattering method.

Further, from the viewpoint of surely improving the heat insulating property of the foam molded article, the content of graphite in the foamable resin particles is 0.1 parts by mass or more with respect to 100 parts by mass of the PS resin of the foamable resin particles. It is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more. In addition, from the viewpoint of further improving the foamability of the foamable resin particles or further improving the surface appearance of the foamed molded article, the graphite content in the foamable resin particles is based on 100 parts by mass of the PS resin. It is preferably 6 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 3 parts by mass or less.
In addition, what is necessary is just to adjust suitably content of the graphite in a seed particle so that content of the graphite in an expandable resin particle may become the above-mentioned range as mentioned above.

  The blending amount of the flame retardant in the expandable resin particles can be appropriately adjusted according to the desired flame retardancy. For example, from the viewpoint of imparting high flame retardancy that satisfies the flammability standard of 5.13.1 of JIS A9511 (2006R) to the foamed resin molded product, 100 mass of PS resin of the foamable resin particles It is preferable to blend the flame retardant with the seed particles so that the blending ratio of the flame retardant to the part is 0.5 parts by mass or more. On the other hand, from the viewpoint of obtaining desired in-mold moldability and mechanical properties, it is difficult for the seed particles so that the blending ratio of the flame retardant with respect to 100 parts by mass of the PS resin of the expandable resin particles is 4 parts by mass or less. It is preferable to add a flame retardant. From the same viewpoint, the blending amount of the flame retardant is more preferably 0.7 to 3 parts by mass with respect to 100 parts by mass of the PS resin of the expandable resin particles.

  From the viewpoint that it is possible to reliably impart excellent flame retardancy to the foamed molded article obtained using the expandable resin particles, the blending amount of the flame retardant in the seed particles is preferably 1% by mass or more. . In addition, from the viewpoint of further improving the foamability of the foamable resin particles or making the appearance of the foamed molded article better, the blending amount of the flame retardant in the seed particles may be 10% by mass or less. Preferably, it is 5 mass% or less.

From the viewpoint of imparting higher flame retardancy, the bromine content in the flame retardant is preferably 60% by mass or more, and more preferably 63% by mass or more. The bromine content can be determined based on JIS K7392 (2009).
Further, from the viewpoint of suppressing decomposition of the flame retardant during the production of seed particles, the 5% weight reduction temperature of the flame retardant is preferably 250 to 280 ° C, and more preferably 255 to 270 ° C. The 5% reduction temperature of the flame retardant can be determined by a thermogravimetric method (TG method).

  Examples of the flame retardant include 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5′-dibromophenyl] propane, 2,2-bis [4′- (2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] propane, 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2-methylpropoxy) -3 ′, 5 '-Dibromophenyl] sulfone, 2,2-bis [4'-(2 ", 3" -dibromopropoxy) -3 ', 5'-dibromophenyl] sulfone, 1,3,5-tris (2', 3 '-Dibromo-2'-methylpropyl) isocyanurate, 1,3,5-tris (2', 3'-dibromopropyl) isocyanurate, 2,4,6-tribromophenol-2 ', 3'-dibromo -2'-methylpropyl ether, 2, Bromination of 1,6-tribromophenol-2 ′, 3′-dibromopropyl ether, 1,2,5,6,9,10-hexabromocyclododecane, 1,2,5,6-tetrabromocyclooctane, etc. Organic compounds can be used, and brominated polymers such as brominated butadiene polymers, brominated polystyrenes, brominated epoxy resins, etc. Flame retardants can be used alone or in combination. Can do.

Preferably, it is a flame retardant of the following (1) and / or (2). In this case, it is possible to obtain expandable resin particles that are superior in flame retardancy with a small addition amount.
(1) Brominated butadiene-based polymer (2) 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5′-dibromophenyl] propane 25-75 % Of a composite flame retardant of 2% by mass and 2,2-bis [4 ′-(2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] propane Is 100% by mass)

  Particularly preferred is a brominated butadiene polymer. In this case, expandable resin particles with a small amount of water can be obtained. Further, in the process of obtaining the foamed molded product from the foamable resin particles, a period for storing the foamable resin particles before foaming is usually provided in a low temperature environment of, for example, 10 ° C. or less. This period is called the aging period. When a brominated butadiene polymer is used as a flame retardant, this aging period can be shortened.

  In consideration of compatibility with the seed particles, the brominated butadiene-based polymer is preferably a block copolymer, a random copolymer, or a graft copolymer containing a component unit of a styrene monomer. (They are also referred to as “brominated butadiene-styrene copolymer”), and a block copolymer of a polystyrene polymer block and a brominated polybutadiene block is more preferable. Examples of the styrene monomer in the brominated butadiene polymer include styrene, brominated styrene, chlorinated styrene, 2-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, α-methylstyrene, and the like. . Among these, styrene, 4-methylstyrene, α-methylstyrene, or a mixture thereof is preferable, and styrene is more preferable.

  A brominated butadiene-styrene block copolymer, which is a typical brominated butadiene polymer, can be represented by the following general formula (1). In the general formula (1), X, Y, and Z are positive integers. The block copolymer in the general formula (1) is a triblock copolymer, but may be a diblock copolymer.

The brominated butadiene-styrene block copolymer is produced, for example, by brominating a styrene-butadiene block copolymer. Preferable examples of the brominated butadiene-styrene block copolymer include commercially available products such as “Emerald 3000” manufactured by Chemtura and “FR122P” manufactured by ICL-IP.
The average molecular weight in terms of polystyrene of the brominated butadiene-based polymer is preferably 1,000 or more and 300,000 or less, more preferably 10,000 or more and 200,000 or less, and further preferably 100,000 or more and 150,000 or less.

  Moreover, in order to improve the thermal stability of the flame retardant during the production of seed particles, a stabilizer such as an epoxy compound or an antioxidant can be used in combination with the flame retardant.

  The epoxy compound has a property of capturing HBr derived from bromine released from the flame retardant when the seed particles are extruded. Utilizing this property, the epoxy compound can suppress the decomposition of the PS resin by HBr. Examples of the epoxy compound include a bisphenol type epoxy compound and a novolac type epoxy compound. More specifically, for example, commercially available products such as “F2200HM” manufactured by ICL-IP, “EPICLON series” manufactured by DIC, and “Araldite ECN1280” manufactured by HUNTUMAN can be exemplified. As these epoxy compounds, 1 type (s) or 2 or more types can be used together. It is preferable that the usage-amount of an epoxy compound is 1-30 mass parts with respect to 100 mass parts of flame retardants, and it is more preferable that it is 5-20 mass parts.

  Examples of the antioxidant include a phenolic antioxidant, a hindered amine antioxidant, and a phosphite antioxidant. These antioxidants can be used alone or in combination of two or more. Antioxidants have the property of capturing halogen radicals and halogen ions generated by decomposition of the brominated butadiene-based polymer during the extrusion process of seed particles. Utilizing this property, the antioxidant can suppress a decrease in molecular weight and coloring of the PS resin. From such a viewpoint, it is preferable to use a phenol-based antioxidant and a phosphite-based antioxidant in combination as the antioxidant. It is preferable that the usage-amount of antioxidant is 0.2-20 mass parts with respect to 100 mass parts of flame retardants, and it is more preferable that it is 1-15 mass parts.

  In addition to the above-described epoxy compound and antioxidant, other stabilizers can be used in combination. Examples of such stabilizers include metal soaps, organotin compounds, lead compounds, hydrotalcite, polyhydric alcohols, β-ketones, sulfur compounds, and the like.

  As long as the effects of the present invention are not impaired, additives such as a known air conditioner, pigment, slip agent, antistatic agent, plasticizer and the like can be further added to the seed particles.

  Examples of the foam regulator include ethylene bis fatty acid amide, fatty acid mono amide, fatty acid bis amide, talc, silica, polyethylene wax, methylene bis stearic acid, methyl methacrylate copolymer, silicone, and the like, preferably ethylene. Bis fatty acid amide is preferably used. As a method for adding the bubble regulator, the seed particles may be kneaded into the seed particles, or may be impregnated into the seed particles together with styrene by adding to the aqueous medium. As for the addition amount of a bubble regulator, 0.01-1 weight part is preferable with respect to 100 weight part of expandable styrene-type resin particles. This makes it possible to sufficiently stabilize the bubble diameter.

  Further, in order to obtain a foamed molded article having better heat insulation properties, it is preferable to disperse graphite uniformly in the PS-based resin of seed particles. Therefore, it is preferable to perform melt-kneading using a single-screw extruder or a twin-screw extruder having a high kneading type screw such as a dalmage type, a Maddock type, or a unimelt type. The seed particles can be refined by melt-kneading with an extruder and then by a strand cut method, a hot cut method, an underwater cut method, or the like. The seed particles can be made finer by other methods as long as a desired particle diameter can be obtained.

  From the viewpoint of the productivity of seed particles and the filling properties of the foamed particles obtained from the seed particles into the mold, the particle weight of the seed particles is preferably 0.1 to 3 mg, more preferably 0.3 to 1.5 mg. . From the same viewpoint, the particle diameter of the seed particles is preferably 0.1 to 3.0 mm. In addition, when using an extruder, the weight and particle diameter of a seed particle can be adjusted by extruding resin from the hole which has a diameter of about 0.5-2 mm, for example, and changing cut speed. The particle diameter of the seed particles can be measured, for example, as follows. That is, first, seed particles are observed with a micrograph, and the maximum diameter of each kind of 200 or more seed particles is measured. Then, the arithmetic average value of the measured maximum diameter is taken as the particle diameter of the seed particles.

  In the dispersion step, seed particles are dispersed in an aqueous medium. Dispersion in the aqueous medium can be performed using, for example, a closed container equipped with a stirrer. Examples of the aqueous medium include deionized water. In the dispersing step, it is preferable to disperse seed particles in an aqueous medium containing a suspending agent. As the suspending agent, for example, hydrophilic polymers such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone and the like can be used. In addition, a poorly water-soluble inorganic salt such as tricalcium phosphate or magnesium pyrophosphate can also be used as a suspending agent. Furthermore, you may use surfactant together as needed. When using a poorly water-soluble inorganic salt, it is preferable to use an anionic surfactant such as sodium alkyl sulfonate, sodium dodecylbenzene sulfonate, disodium dodecyl diphenyl ether sulfonate, sodium α-olefin sulfonate. .

  As for the usage-amount of a suspension agent, 0.01-5 mass parts is preferable with respect to 100 mass parts of seed particles. As described above, when the poorly water-soluble inorganic salt and the anionic surfactant are used in combination, 0.05 to 3 parts by weight of the poorly water-soluble inorganic salt and the anionic surfactant are used with respect to 100 parts by weight of the seed particles. Is preferably used in an amount of 0.0001 to 0.5 parts by mass. The above-mentioned surfactants can be used alone or in combination. Preferably, an anionic surfactant is used. More preferably, it is an alkylsulfonic acid alkali metal salt (preferably a sodium salt) having 8 to 20 carbon atoms. Thereby, the suspension can be sufficiently stabilized.

  Moreover, electrolytes, such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate, sodium acetate, sodium succinate, can be added to the aqueous medium as necessary. .

Next, in the polymerization step, a styrene monomer is supplied into an aqueous medium in which seed particles are dispersed. Then, styrene monomer is impregnated into the seed particles and polymerized.
As the styrene monomer used in the polymerization step, the above-mentioned styrene monomer can be used. Particularly preferred is styrene. In this case, the foamability of the expandable resin particles can be enhanced. A vinyl monomer other than the styrene monomer can be added together with the styrene monomer and copolymerized with the styrene monomer in the seed particles. In this case, the glass transition temperature of the PS resin is preferably less than 110 ° C, more preferably 105 ° C or less, further preferably 102 ° C or less, and even more preferably 100 ° C or less. The compounding ratio of the vinyl monomer can be appropriately set within a range satisfying the glass transition temperature of the above-mentioned PS resin. The blending ratio of monomers other than styrene is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0 in all monomers to be added.

  The addition amount of the styrene monomer in the polymerization step is preferably 15 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the seed particles. In this case, the seed particles are easily impregnated with the styrene monomer. Furthermore, in this case, the molecular weight of the PS-based resin on the surface side can be made higher than that on the inner side of the expandable resin particles. As a result, the foam moldability of the expandable resin particles can be further improved. The addition amount of the styrenic monomer is more preferably 20 parts by mass or more and more preferably 50 parts by mass or more with respect to 100 parts by mass of the seed particles. Moreover, the addition amount of the styrene monomer is more preferably 200 parts by mass or less, and further preferably 120 parts by mass or less. The addition amount of a styrene-type monomer can be determined from all the combinations of the preferable range of the above-mentioned upper limit and lower limit, a more preferable range, and a further preferable range.

  When the seed particles are impregnated with a styrene monomer and polymerized, the entire amount of the styrene monomer used can be added at once. It is also possible to divide into a plurality of monomers such as a monomer, a second monomer, and a third monomer, and add these monomers at different timings. As in the latter case, by adding the styrene monomer divided into a plurality of times, it becomes possible to sufficiently suppress the condensation of the resin particles during the polymerization.

  Specifically, in the dispersion step, first, a first monomer (a part of the total amount of styrene monomers to be blended) and a polymerization initiator are added to the aqueous medium in which the seed particles are dispersed. The first monomer can be dispersed in the aqueous medium. Next, the aqueous medium is heated, and the second monomer (the remainder of the total amount of styrene monomers to be blended) can be added to the aqueous medium over a predetermined addition time at a predetermined temperature. Thereby, seed particles can be polymerized by impregnating these styrene monomers.

In addition, the seed ratio of the first monomer (the blending ratio of the first monomer to the seed particles (mass ratio: mass of the first monomer / mass of the seed particles)) is preferably 0.1 or more. In this case, the foamable resin particles can be prevented from being flattened, and the filling property at the time of molding can be improved. From the same viewpoint, the seed ratio of the first monomer is more preferably 0.2 or more.
The seed ratio of the first monomer is preferably 1 or less. In this case, it is possible to suppress the polymerization before the styrenic monomer is sufficiently impregnated into the seed particles. In this case, the styrenic monomer can be stabilized, and the generation of resin lumps can be suppressed. From the same viewpoint, the seed ratio of the first monomer is more preferably 0.5 or less. The range of the seed ratio of the first monomer can be determined from all the combinations of the preferable range and the more preferable range regarding the upper limit and the lower limit described above.

The polymerization initiator is preferably soluble in a styrene monomer and has a 10-hour half-life temperature of 50 to 120 ° C.
Specifically, examples of the polymerization initiator include cumene hydroxy peroxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxybenzoate, benzoyl peroxide, t-butyl peroxide. Organic peroxides such as oxyisopropyl carbonate, t-amyl peroxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, lauroyl peroxide can be used. . As the polymerization initiator, an azo compound such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more. Further, from the viewpoint of easily reducing the amount of residual styrene monomer, it is preferable to use at least t-butylperoxy-2-ethylhexyl monocarbonate as the polymerization initiator. Although superposition | polymerization temperature changes with kinds of polymerization initiator to be used, it is preferable that it is 60-120 degreeC.

  Moreover, a well-known plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a flame retardant adjuvant, dye, a bubble regulator etc. can be added to a styrene-type monomer as needed.

  Next, in the foaming agent impregnation step, the resin particles are impregnated with a physical foaming agent (hereinafter also simply referred to as “foaming agent”) during and / or after the polymerization of the styrene monomer in the seed particles. Thereby, expandable resin particles are obtained. Specifically, a foaming agent is press-fitted into a container containing the resin particles during or after polymerization, and impregnated in the resin particles. In addition, the above-mentioned resin particle is the concept containing the particle | grains in the middle of the impregnation polymerization of the styrene-type monomer in a seed particle, and the particle | grains after an impregnation polymerization.

  As the blowing agent, for example, a saturated hydrocarbon compound having 3 to 6 carbon atoms, a lower alcohol having 5 or less carbon atoms, an ether compound, or the like can be used. Specifically, as the saturated hydrocarbon compound, for example, propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, cyclohexane and the like can be used. As the lower alcohol, methanol, ethanol or the like can be used. Moreover, as an ether compound, dimethyl ether, diethyl ether, etc. can be used. These foaming agents can be used alone or in a mixture of two or more. In addition, as an ether compound, a C6 or less thing can be used, for example. Preferably, as a foaming agent, it is good to use 1 type, or 2 or more types chosen from a C3-C6 saturated hydrocarbon compound.

  Moreover, it is preferable that content of the foaming agent in an expandable resin particle is 3-10 mass%. In this case, the foamability of the foamable resin particles can be further improved, and shrinkage during foaming can be prevented. Furthermore, at the time of in-mold molding of the foamed particles obtained after foaming, the fusion property between the foamed particles can be further improved, and the dimensional stability of the foamed molded product can be improved.

  In addition, after the foaming agent impregnation step, the foamable resin particles can be dehydrated and dried, and if necessary, the surface coating agent can be coated on the foamable resin particles. As the surface coating agent, for example, a metal soap such as zinc stearate can be used. In addition, as the surface coating agent, stearic acid triglyceride, stearic acid monoglyceride, castor oil or the like can be used. Moreover, a well-known antiblocking agent, an antistatic agent, etc. can also be used as a functional surface coating agent. The amount of the surface coating agent added is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the expandable resin particles.

  The foamable resin particles obtained by the above production method can be used for foam-molding them to obtain the foam-molded product. The foamed molded product can be used as a heat insulating material for houses, hot water tanks, pipes, automobiles and the like.

Example 1
Next, the manufacturing method of the expandable polystyrene resin particle concerning an Example is demonstrated. In this example, expandable polystyrene resin particles having graphite and a flame retardant are prepared by performing a dispersion step, a polymerization step, and a foaming agent impregnation step. This will be specifically described below.

(1) Preparation of seed particles First, using a φ30 mm single-screw extruder, 86 parts by mass of a polystyrene resin (“680” manufactured by PS Japan), 4 parts by mass of a flame retardant composition, and a graphite masterbatch (hereinafter, 10 parts by mass (referred to as “graphite MB” as appropriate) were melt-kneaded at a temperature of 210 to 230 ° C. Next, the melt-kneaded product was extruded in a strand form from a die having a hole diameter of 1.4 mm of an extruder. The extrudate was immediately introduced into a water bath and cooled, and then cut by strand cutting. Thereby, 0.9 mg / piece pellet was produced. This pellet is the seed particle of this example (hereinafter, the seed particle of this example is referred to as “seed particle A”). About seed particle A, the compounding composition, the kind of flame retardant used, the compounding quantity of a flame retardant, and the compounding quantity of graphite are shown in Table 1 mentioned later. In addition, the flame retardant composition in this example (hereinafter referred to as “flame retardant composition A” as appropriate) is a brominated butadiene-styrene block copolymer (“Emerald 3000” manufactured by Chemtura, Inc., polystyrene equivalent weight) as a flame retardant. 80 parts by mass of average molecular weight: 130,000, bromine content: 64% by mass, 5% weight reduction temperature: 262 ° C.) and novolac type epoxy resin (“EPICLON N680” manufactured by DIC) as a stabilizer (epoxy compound) 10 parts by mass and pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (“Irganox 1010” manufactured by BASF) as a stabilizer (phenolic antioxidant) 5 Parts by weight and bis (2,6-di-t-butyl-4-methyl) as a stabilizer (phosphite antioxidant) Ruphenyl) pentaerythritol diphosphite (“PEP36” manufactured by ADEKA) and 5 parts by mass are melt-kneaded. The flame retardant used in this example (“Emerald 3000” manufactured by Chemtura) is hereinafter referred to as “flame retardant a” as appropriate. Graphite MB contains 40 parts by mass of graphite having an average particle diameter (d50) of about 5 μm (flaky graphite “J-CPB” manufactured by Nippon Graphite Co., Ltd.), and the balance is made of polystyrene resin (however, graphite and The total with the polystyrene resin is 100 mass).

(2) Preparation of expandable resin particles 783 g of deionized water, 4.6 g of sodium pyrophosphate, and 11.4 g of magnesium nitrate are put into an autoclave with a stirring volume of 3 L, and salt exchange is performed. As a result, magnesium pyrophosphate as a suspending agent was synthesized in an autoclave. Next, in the autoclave, 0.09 g of sodium alkyl sulfonate as a surfactant, 0.7 g of ethylenebisstearic acid amide (“Kao wax EB-FF” manufactured by Kao Corporation) as a foam regulator, seed particles 345 g was charged. In this way, the seed particles were dispersed in the aqueous medium.

  Next, 146 g of deionized water, 0.12 g of sodium alkyl sulfonate as a surfactant, 104 g of styrene (first monomer) as a styrenic monomer, and t-butylperoxy- as a polymerization initiator 2.6 g of 2-ethylhexyl monocarbonate (“Trigonox 117” manufactured by Kayaku Akzo, 10 hour half-life temperature: 98 ° C.), and dicumyl peroxide (“PARK Mill D” manufactured by NOF Corporation) as a flame retardant aid The emulsion A was obtained by mixing 3.5 g of a 10 hour half-life temperature: 116 ° C.) using a homogenizer.

Next, after the air in the autoclave was replaced with nitrogen, the autoclave was sealed.
Next, the temperature of the dispersion in the autoclave was increased to 80 ° C. while stirring at 350 rpm. After reaching this temperature of 80 ° C., the above emulsion A was charged into the autoclave. Subsequently, after keeping the inside of the autoclave at a temperature of 80 ° C. for 1 hour, the temperature was raised to 100 ° C. over 4 hours. During the temperature increase from 80 ° C. to 100 ° C., 242 g of styrene (second monomer) as a styrene monomer was continuously added into the autoclave over 4 hours. After reaching the temperature of 100 ° C., the temperature was maintained at 100 ° C. for 3 hours, and further the temperature was raised to 112 ° C. over 2 hours. Next, this temperature was maintained at 112 ° C. for 3 hours, and then cooled to room temperature. When the temperature reaches 100 ° C., 46 g of pentane (n-pentane 80%, i-pentane 20%) as a blowing agent is added to the autoclave over 30 minutes, and butane (n-butane as a blowing agent). The resin particles were impregnated with a foaming agent by adding 10 g of 60%, i-butane 40%) over 10 minutes.

After the inside of the autoclave was cooled to room temperature, the expandable resin particles were taken out from the autoclave. By washing the expandable resin particles with dilute nitric acid, the suspension agent adhering to the surface was dissolved and removed. Next, the foamable resin particles were washed with water, and the foamable resin particles were dehydrated using a centrifuge.
Next, 0.01 parts by mass of alkyldiethanolamine as an antistatic agent was added to 100 parts by mass of the expandable resin particles, and the surface of the expandable resin particles was coated with the antistatic agent. Then, the water | moisture content on the surface of the expandable resin particle was removed by making room temperature air flow for 10 minutes. To 100 parts by mass of the obtained expandable resin particles, 0.1 part by mass of zinc stearate as an antiblocking agent and 0.05 parts by mass of glycerin monostearate as an antistatic agent are added, and the expandable resin particles The surface of was coated with these antiblocking agents and antistatic agents. Thus, the expandable resin particle (expandable polystyrene resin particle) of this example was obtained.

(3) Production of expanded molded body The expandable resin particles obtained as described above were aged at a temperature of 6 ° C for 1 week. Thereafter, 500 g of expandable resin particles were put into an atmospheric pressure batch foaming machine having a volume of 30 L, steam was supplied into the foaming machine, and the expandable resin particles were heated to obtain expanded particles having a bulk density of 16 kg / m ³ . . The obtained expanded particles were aged at room temperature for 1 day, and then filled in a mold attached to a mold molding machine (“DSM-0705VS” manufactured by DABO). Then, the foamed particles filled in the mold with steam having a gauge pressure of 0.07 MPa were heated for 10 seconds. Subsequently, after cooling, a foamed molded product (polystyrene resin foamed molded product) in which the foamed particles were fused to each other was taken out from the mold. In this way, a foamed molded product was obtained.

(Example 2)
This example is an example of producing expandable resin particles and a foam molded article using seed particles having a composition different from that of Example 1. In this specification, Example 2, Example 3, Example 6, and Example 7 are reference examples in the present invention.
Specifically, first, 86.5 parts by mass of a polystyrene resin (“680” manufactured by PS Japan) and a flame retardant containing a stabilizer (hereinafter referred to as “flame retardant composition B” as appropriate) 3.5 parts by mass. And 10 parts by mass of graphite MB were melt-kneaded in the same manner as in Example 1. The flame retardant composition B in this example is composed of 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5′-dibromophenyl] propane (a flame retardant). “SR130” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 60 parts by mass of bromine content: 65.8 mass%, 5% weight reduction temperature: 260 ° C.) and 2,2-bis [4′- as a flame retardant (2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] propane (“SR720” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., bromine content: 67.8 mass%, 5% weight loss temperature : 296 ° C.) 40 parts by mass and bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as a stabilizer (hindered amine antioxidant) (“TINUVIN 770DF” manufactured by Ciba Japan) It is a mixture with 2 parts by mass. Among the flame retardants used in this example, 2,2-bis [4 ′-(2 ″, 3 ″ -dibromo-2 ″ -methylpropoxy) -3 ′, 5′-dibromophenyl] propane (Daiichi Kogyo Seiyaku) “SR130” manufactured by Co., Ltd.) is hereinafter referred to as “flame retardant b” as appropriate. 2,2-bis [4 ′-(2 ″, 3 ″ -dibromopropoxy) -3 ′, 5′-dibromophenyl] Propane (“SR720” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is hereinafter referred to as “flame retardant c” as appropriate. Graphite MB is the same as in Example 1.

And the pellet was produced like Example 1 from the melt-kneaded material. This pellet is the seed particle of this example (hereinafter referred to as “seed particle B”). About seed particle B, the compounding composition, the kind of flame retardant used, the compounding quantity of a flame retardant, and the compounding quantity of graphite are shown in Table 1 mentioned later. Subsequently, expandable resin particles were produced in the same manner as in Example 1 except that the seed particles B were used. And the foaming molding was produced like Example 1 using this expandable resin particle. In the production of the foamed molded product in this example, foamed particles having a bulk density of 18 kg / m ³ were used.

(Example 3)
In this example, the seed particle B described above (see Example 2) is used as the seed particle, the seed particle input amount is changed to 207 g, the styrene addition amount as the first monomer is changed to 62 g, Expandable resin particles were produced in the same manner as in Example 1 except that the amount of styrene added as the monomer was changed to 421 g. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 21 kg / m ³ were used.

Example 4
In this example, first, except that the addition amount of the polystyrene resin at the time of preparation of the seed particles was changed to 87.9 parts by mass, and the addition amount of the flame retardant containing the stabilizer was changed to 2.1 parts by mass. Produced seed particles in the same manner as in Example 1. Hereinafter, the seed particles of this example are referred to as “seed particles C”. About seed particle C, the compounding composition, the kind of flame retardant used, the compounding quantity of a flame retardant, and the compounding quantity of graphite are shown in Table 1 mentioned later. Next, using this seed particle C, the input amount of seed particles was changed to 276 g, the addition amount of ethylenebisstearic acid amide as a bubble regulator was changed to 0.35 g, and the addition amount of styrene as the first monomer Was changed to 83 g, and expandable resin particles were produced in the same manner as in Example 1 except that the amount of styrene added as the second monomer was changed to 331 g. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 17 kg / m ³ were used.

(Example 5)
In this example, the seed particle C described above (see Example 4) was used as the seed particle, the amount of seed particle charged was changed to 552 g, and the amount of ethylene bis-stearic acid amide added as a bubble regulator was 6.9 g. In the same manner as in Example 1, except that the addition amount of styrene as the first monomer was changed to 110 g and the addition amount of styrene as the second monomer was changed to 28 g. Particles were made. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 18 kg / m ³ were used.

(Example 6)
In this example, the seed particles B described above (see Example 2) are used as seed particles, the input amount of seed particles is changed to 621 g, the addition amount of styrene as the first monomer is changed to 69 g, Expandable resin particles were produced in the same manner as in Example 1 except that no monomer was added. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 20 kg / m ³ were used.

(Example 7)
In this example, a suspending agent was synthesized in the same manner as in Example 1 except that the input amount of deionized water was changed to 651 g. Next, seed particles were dispersed in an aqueous medium in the same manner as in Example 1 except that the seed particles B (see Example 2) were used as seed particles. Next, after the air in the autoclave was replaced with nitrogen, the autoclave was sealed. Next, the dispersion in the autoclave was heated to 72 ° C. while being stirred at 350 rpm, and then the autoclave was maintained at this temperature of 72 ° C. for 1 hour.

  When the temperature reached 72 ° C., the following emulsion B was charged into the autoclave, and after 1 hour after reaching 72 ° C., the following emulsion C was charged. Emulsion B consists of 145 g of deionized water, 0.12 g of sodium alkyl sulfonate as a surfactant, 35 g of styrene (first monomer) as a styrenic monomer, and t-butyl persulfate as a polymerization initiator. 2.6 g of oxy-2-ethyl monocarbonate (“Trigonox 117” manufactured by Kayaku Akzo, 10-hour half-life temperature: 98 ° C.) and dicumyl peroxide (manufactured by NOF Corporation) Park Mill D ”, 10 hours half-life temperature: 116 ° C.) and 3.5 g were mixed using a homogenizer. Emulsion C is composed of 145 g of deionized water, 0.12 g of sodium alkyl sulfonate as a surfactant, 35 g of styrene (second monomer) as a styrene monomer, and benzoyl peroxide as a polymerization initiator. ("NIPER BW" manufactured by NOF Corporation, 10 hours half-life temperature: 74 ° C) was mixed with 1.7 g using a homogenizer.

Next, the temperature inside the autoclave was raised from a temperature of 72 ° C. to a temperature of 93 ° C. over 4 hours. During the temperature increase from 72 ° C. to 93 ° C., 276 g of styrene (third monomer) as a styrene monomer was continuously added into the autoclave over 4 hours. After reaching the temperature of 93 ° C., the inside of the autoclave was maintained at this temperature of 93 ° C. for 3 hours, and further heated to 112 ° C. over 2 hours. Next, the inside of the autoclave was kept at this temperature of 112 ° C. for 3 hours, and then cooled to room temperature. When reaching a temperature of 93 ° C., 46 g of pentane (n-pentane 80%, i-pentane 20%) as a blowing agent was added to the autoclave over 30 minutes, and butane (n-butane 60%) as a blowing agent. , I-butane 40%) was added over 10 minutes to impregnate the resin particles with the blowing agent. Thereafter, the same operation as in Example 1 was performed to obtain expandable resin particles. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 15 kg / m ³ were used.

(Comparative Example 1)
This example uses seed particles that do not contain a flame retardant, and impregnates the seed particles with a styrene monomer in which the flame retardant is dissolved and polymerizes them to produce expandable resin particles that contain the flame retardant. It is an example. Hereinafter, this example will be described in detail.
(1) Preparation of seed particles First, 90 parts by mass of polystyrene resin (“680” manufactured by PS Japan) and 10 parts by mass of graphite MB were melt-kneaded at a temperature of 210 to 230 ° C. using a φ30 mm single screw extruder. did. The same graphite MB as in Example 1 was used. Next, pellets were produced from the melt-kneaded material in the same manner as in Example 1. This pellet is the seed particle of this example (hereinafter referred to as “seed particle D”). About seed particle D, the compounding composition and the compounding quantity of graphite are shown in below-mentioned Table 1.

(2) Production of expandable resin particles First, in the same manner as in Example 1, magnesium pyrophosphate as a suspending agent was synthesized in an autoclave with an internal volume of 3 L equipped with a stirrer. Next, 0.09 g of sodium alkyl sulfonate as a surfactant and 345 g of seed particles (seed particles D) were charged into the autoclave. In this way, the seed particles were dispersed in the aqueous medium.

  In addition, 146 g of deionized water, 11.7 g of a brominated butadiene-styrene block copolymer ("Emerald 3000" manufactured by Chemtura, flame retardant a) as a flame retardant, and sodium alkyl sulfonate 0 as a surfactant .12 g, 2.6 g of t-butylperoxy-2-ethylhexyl monocarbonate (“Trigonox 117” manufactured by Kayaku Akzo) as a polymerization initiator, and dicumyl peroxide (NOF Corporation) as a flame retardant aid Emulsified liquid D was obtained by mixing 3.5 g of manufactured “Park Mill D”) and 104 g of styrene (first monomer) as a styrene monomer using a homogenizer.

Next, after the air in the autoclave was replaced with nitrogen, the autoclave was sealed. Next, the temperature of the dispersion in the autoclave was increased to 80 ° C. while stirring at 350 rpm. And after reaching | attaining temperature 80 degreeC, the above-mentioned emulsion D was thrown in in an autoclave. Subsequently, after keeping the inside of the autoclave at a temperature of 80 ° C. for 1 hour, the temperature was raised to 100 ° C. over 4 hours. During the temperature increase from 80 ° C. to 100 ° C., 242 g of styrene (second monomer) as a styrene monomer was continuously added into the autoclave over 4 hours. Then, after reaching the temperature of 100 ° C., the temperature was held at 100 ° C. for 3 hours, and the temperature was further increased to 112 ° C. over 2 hours. Next, this temperature was maintained at 112 ° C. for 3 hours, and then cooled to room temperature. When the temperature reaches 100 ° C., 46 g of pentane (n-pentane 80%, i-pentane 20%) as a blowing agent is added to the autoclave over 30 minutes, and butane (n-butane as a blowing agent). The resin particles were impregnated with a foaming agent by adding 10 g of 60%, i-butane 40%) over 10 minutes. Thereafter, the same operation as in Example 1 was performed to obtain expandable resin particles. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 22 kg / m ³ were used.

(Comparative Example 2)
In this example, a foamable resin was prepared in the same manner as in Comparative Example 1 except that an emulsion was prepared using flame retardant b (“SR130” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as the flame retardant. Particles were made. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 24 kg / m ³ were used.

(Comparative Example 3)
In this example, except that the flame retardant b (“SR130” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the flame retardant, and the blending amount of the flame retardant b into the emulsion was changed to 6.9 g. Produced foamable resin particles in the same manner as in Comparative Example 1. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 18 kg / m ³ were used.

(Comparative Example 4)
In this example, the foamable resin particles were prepared in the same manner as in Comparative Example 1 except that the blending amount of the flame retardant a (“Emerald 3000” manufactured by Chemtura) into the emulsion was changed to 6.9 g. Produced. Further, a foamed molded product was produced in the same manner as in Example 1 using the foamable resin particles. In the production of the foamed molded product in this example, foamed particles having a bulk density of 22 kg / m ³ were used.

(Comparative Example 5)
In this example, expandable resin particles are produced by impregnating a polystyrene resin particle kneaded with a flame retardant with a foaming agent without performing impregnation polymerization of the styrene monomer into the seed particles as described above. This is an example. Hereinafter, this example will be described in detail.
(1) Production of polystyrene-based resin particles Using a φ30 mm single screw extruder, 94 parts by mass of polystyrene resin (“680” manufactured by PS Japan), 1 part by mass of a flame retardant composition, and 5 parts by mass of graphite MB Melt kneading was performed at a temperature of 210 to 230 ° C. The same flame retardant composition and graphite MB as those used in Example 1 were used. Next, pellets were produced from the melt-kneaded material in the same manner as in Example 1. This pellet is the styrene resin particle of this example. In this example, seed polymerization is not performed as described later. Therefore, although the styrene resin particles of this example are not strictly seed particles, the styrene resin particles are appropriately referred to as “seed particles E” for convenience of explanation. The compounding composition of seed particles E, the type of flame retardant used, the compounding amount of the flame retardant, and the compounding amount of graphite are shown in Table 1 below.

(2) Production of expandable resin particles In an autoclave with an internal volume of 3 L equipped with a stirrer, 900 g of deionized water, 0.9 g of sodium alkyl sulfonate, dicumyl peroxide (“PARK Mill” manufactured by NOF Corporation) D ") 2.6 g, sodium chloride 6.4 g, sodium nitrate 2.6 g, and seed particles E 600 g were added. Next, after the air in the autoclave was replaced with nitrogen, the autoclave was sealed. Subsequently, the temperature of the dispersion in the autoclave was increased to 120 ° C. while stirring at 350 rpm. Then, after reaching this temperature of 120 ° C., 48 g of pentane (n-pentane 80%, i-pentane 20%) was added to the autoclave over 60 minutes, and the foaming agent was impregnated into the resin particles. Thereafter, the same operation as in Example 1 was performed to obtain expandable resin particles. Using the foamable resin particles, a foam molded article was produced in the same manner as in Example 1, but the surface of the foam molded article was melted. In order to prevent this melting, in this example, the foamed molded body was produced by heating the foamed particles filled in the mold with steam having a gauge pressure of 0.05 MPa for 10 seconds. In the production of the foamed molded product in this example, foamed particles having a bulk density of 14 kg / m ³ were used.

(Comparative Example 6)
In this example, expandable resin particles are produced by suspension polymerization of a styrene monomer in which a flame retardant is dissolved. Hereinafter, this example will be described in detail.
First, 761 g of deionized water, 2.7 g of sodium pyrophosphate, and 5 g of magnesium nitrate were put into an autoclave with an internal volume of 3 L equipped with a stirrer, and salt exchange was performed. Magnesium pyrophosphate was synthesized in an autoclave. In addition, 5 g of flame retardant b (“SR130” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 2.3 g of dicumyl peroxide (“Park Mill D” manufactured by NOF Corporation), and benzoyl peroxide (manufactured by NOF Corporation) "Nyper BW") 0.8 g, polystyrene resin (PS Japan "680") 99 g, and an average particle diameter (d50) of graphite powder (SEC carbon company scaly graphite "SNO-5" ]) 15.2 g was dispersed in 661 g of styrene to obtain a mixture of styrene and graphite. Next, the above-mentioned mixture of styrene and graphite was charged into the autoclave while stirring the aqueous medium containing the suspending agent in the autoclave at 350 rpm.

Next, after the air in the autoclave was replaced with nitrogen, the autoclave was sealed. Next, while stirring the dispersion in the autoclave at 350 rpm, the temperature was raised to 80 ° C. over 1 hour and 40 minutes. Then, after reaching this temperature of 80 ° C., 0.14 g of sodium alkyl sulfonate was added into the autoclave. Next, the temperature of the dispersion in the autoclave was raised to 90 ° C. over 20 minutes, and further raised to 134 ° C. over 4 hours. Next, the temperature in the autoclave was maintained at 134 ° C. for 4 hours, and then cooled to room temperature. In addition, 65 hours of i-butane was added into the autoclave 2 hours after the temperature of the dispersion reached 90 ° C., and the resin particles were impregnated with the foaming agent. Thereafter, the same operation as in Example 1 was performed to obtain expandable resin particles. Using this foamable resin particle, a foamed molded product was produced in the same manner as in Example 1. In the production of the foamed molded product in this example, foamed particles having a bulk density of 14 kg / m ³ were used.

(Experimental example)
Next, the following evaluation was performed on the expandable resin particles and the foamed molded body produced in the above-described Examples and Comparative Examples. The results are shown in Tables 2 and 3. In these tables, for the expandable resin particles of each example and comparative example, the polymerization conditions at the time of manufacture, the type of the flame retardant used, the blending amount of the flame retardant with respect to 100 parts by mass of the PS resin (parts by mass) ) And the compounding amount (parts by mass) of graphite. Moreover, about the expandable resin particle obtained in Examples 1-4 and Comparative Examples 1-4, these electron micrographs were image | photographed. The results are shown in FIGS.

`` Particle size distribution ''
The particle size distribution of the expandable resin particles obtained in each of Examples and Comparative Examples was examined using a particle size distribution measuring apparatus “Millitrack JPA” manufactured by Nikkiso Co., Ltd. Specifically, first, 40 g of the expandable resin particles were freely dropped from the sample supply feeder of the measuring apparatus, and a projected image was taken with a CCD camera. Next, calculation / combination processing was sequentially performed on the captured image information, and measurement was performed under conditions of an image analysis method for outputting a particle size distribution / shape index result. Thereby, the particle size (d90) at the volume integrated value 90%, the particle size (d50) at the volume integrated value 50%, the particle size (d10) at the volume integrated value 10%, and the particle size less than 0.21 mm in the particle size distribution. The ratio (mass%) of the fine particles was determined. Further, the particle size ratio ((d90-d10) / d50) was calculated.

"Content of foaming agent"
First, the expandable resin particles obtained in each Example and Comparative Example were dissolved in dimethylformamide (DMF). The content of each added blowing agent component was measured by performing gas chromatography on the obtained dissolved matter. The content of the foaming agent was determined by summing the content of each foaming agent component. Specifically, the gas chromatograph was quantified by the following procedure.

First, about 5 g of cyclopentanol was accurately weighed to the third decimal place in a 100 mL volumetric flask. This weight is Wi. Next, DMF was added to cyclopentanol in the volumetric flask to adjust the total volume to 100 mL. This DMF solution was further diluted 100 times with DMF to prepare an internal standard solution. Next, about 1 g of the expandable resin particles to be measured was accurately weighed to the third decimal place. This weight is Ws (g). The weighed expandable resin particles were dissolved in about 18 mL of DMF. To the obtained lysate, 2 mL of an internal standard solution was added using a whole pipette. 1 μL of this solution was collected with a microsyringe and introduced into a gas chromatography apparatus to obtain a chromatogram. From the obtained chromatogram, the peak area of each foaming agent component and internal standard was determined, and the concentration of each component was determined by the following equation.
Concentration of each component (mass%) = [(Wi / 10000) × 2] × [An / Ai] × Fn ÷ Ws × 100
Wi: Weight of cyclopentanol used for preparation of internal standard solution (g)
Ws: Weight of expandable resin particles dissolved in DMF (g)
An: Peak area of each foaming agent component at the time of gas chromatographic measurement Ai: Peak area of the internal standard substance at the time of gas chromatographic measurement Fn: Correction coefficient of each foaming agent component obtained from a calibration curve prepared in advance

The conditions for the gas chromatograph 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 an inner diameter of 3 mm and a length of 5000 mm Column filler: [Liquid phase name] FFAP (free fatty acid), [Liquid phase impregnation rate] 10 mass%, [Carrier name] Diatomaceous earth Comasorb 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: 250 ° C
Column temperature: 120 ° C
Detector temperature: 250 ° C
Carrier gas: N ₂ , flow rate 40 ml / min

`` Residual monomer amount ''
Similarly to the measurement of the content of the foaming agent described above, the content of the styrene monomer in the expandable resin particles obtained in each Example and Comparative Example was measured by performing gas chromatography. And it quantified by calibrating a measured value with a calibration curve. The conditions for gas chromatography are as described above.

"amount of water"
Using a Karl Fischer moisture meter, the moisture content of the expandable resin particles immediately after production in each Example and Comparative Example was determined.

"Average molecular weight"
The average molecular weight (number average molecular weight, weight average molecular weight, Z average molecular weight) of the expandable resin particles was measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. Specifically, using HLC-8320GPC EcoSEC manufactured by Tosoh Corporation, measurement was performed under the measurement conditions of eluent: tetrahydrofuran (THF), THF flow rate: 0.6 ml / min, and sample concentration: 0.1 wt%. As the column, a column in which TSK guard column Super H-H × 1 and TSK-GEL Super HM-H × 2 were connected in series was used. That is, expandable resin particles were dissolved in tetrahydrofuran (THF), and the molecular weight was measured by gel permeation chromatography (GPC). And the number average molecular weight, the weight average molecular weight, and the Z average molecular weight were calculated | required by calibrating a measured value with standard polystyrene, respectively.

"Evaluation of foamability"
Evaluation of foamability was performed by measuring the bulk density of foamed particles obtained by foaming foamable resin particles with a shelf-type foaming machine. Specifically, first, the expandable resin particles obtained in each Example and Comparative Example were air-dried at room temperature. Next, the expandable resin particles were expanded in a shelf type foaming machine to obtain expanded particles. Foaming was performed by supplying steam with a gauge pressure of 3 kPa into the foaming machine for 270 seconds and heating the foamable resin particles. The obtained expanded particles were cured at room temperature for 1 day. Thereafter, a 1 L graduated cylinder was prepared, and the expanded particles were filled up to the 1 L marked line in this graduated cylinder. And (g) was measured for the mass of the expanded particles per 1 L of this volume. Subsequently, the bulk density (kg / m ³ ) was calculated by converting the mass per 1 L of volume into a unit.

"Required aging days"
The expandable resin particles immediately after production in each Example and Comparative Example were placed in a sealed container and stored at a temperature of 6 ° C. The foamable resin particles are taken out from the sealed container at the start of storage and every 24 hours after the start of storage, and the foamed resin particles are expanded by a shelf-type foaming machine in the same manner as the evaluation of foamability described above. Obtained. The obtained expanded particles were cured at room temperature for 1 day, and then the average cell diameter of the expanded particles was measured. When the average bubble diameter was 0.3 mm or less, it was determined that aging was completed, and the time (days) required to complete aging was measured. The average cell diameter of the expanded particles was measured as follows.
Specifically, first, the foamed particles were cut into two so as to pass through the center using a razor blade, and after vapor deposition (Au—Pd target), a scanning electron microscope (manufactured by Keyence Corporation “ VE7800 "), a cross section of the expanded particles was photographed (observation magnification 20 times). In the obtained electron micrograph, draw a straight line so that it passes through the center of the foamed particles, measure the actual length of the straight line, and the number of bubbles on the straight line, and divide the diameter of the foamed particles by the number of bubbles. The bubble diameter (mm) was obtained. The cell diameter was measured in the same manner for the 10 expanded particles, and the average cell diameter was determined by arithmetic average.

"Bulk density of expanded particles"
A 1 L graduated cylinder was prepared, and the expanded particles obtained in each of the examples and comparative examples were filled up to the 1 L mark in this graduated cylinder. And the mass (g) of the expanded particle per 1 L of this volume was measured. Subsequently, the bulk density (kg / m ³ ) was calculated by converting the mass per 1 L of volume into a unit.

"Average bubble diameter of expanded particles"
The average cell diameter was measured for the expanded particles obtained in each Example and Comparative Example. The method for measuring the average bubble diameter is as described above.

"Fusion rate"
First, a test piece of 150 mm (length) × 75 mm (width) × 25 mm (thickness) was cut out from the foamed molding obtained in each of the examples and comparative examples. A notch having a depth of 2 mm was made on one surface (one surface of a surface having a length of 150 mm and a width of 25 mm) at the center in the length direction of the test piece so as to cross the entire width. Next, the test piece was bent in the direction in which the cut of the test piece was expanded until the test piece was broken or until both ends of the test piece were in contact. Next, the fracture surface of the test piece was observed, and the number of foam particles peeled at the interface and the foam particles fractured internally were measured. Next, the ratio of the foam particles broken inside to the total number of the foam particles broken inside and the foam particles peeled off at the interface was calculated, and this was expressed as a percentage to obtain a fusion rate (%). In addition, the said test was done with respect to five different test pieces, and the arithmetic average value of the fusion rate obtained about each test piece was shown in the table | surface.

"color"
The appearance of the foamed molded product obtained in each example and comparative example was visually observed. And the color of the foaming molding was evaluated based on the following criteria.
○: When the color of the surface of the foamed molded product is uniform ×: When the color of the surface of the foamed molded product is uneven

"Surface void"
The appearance of the foamed molded product obtained in each example and comparative example was visually observed. And based on the following criteria, the space | gap (void) between the foaming particles in the surface of a foaming molding was evaluated.
○: When the surface between the foamed particles on the surface of the foamed molded product is small and the surface is smooth. ×: When the surface of the foamed molded product has many spaces between the foamed particles and the surface is not smooth.

"Apparent density"
Volume was calculated | required from the external dimension of the foaming molding obtained in each Example and the comparative example, and the mass of the foaming molding was then measured. And the apparent density (kg / m < ³ >) of the foaming molding was computed by remove | dividing mass by volume.

"Thermal insulation properties"
Evaluation of heat insulation was performed by measuring the thermal conductivity of the foam molded body obtained in each of Examples and Comparative Examples.
First, a plate-shaped test piece of 200 mm × 200 mm × 25 mm was cut out from the foamed molded body. The test piece was allowed to stand for 1 week or more in an atmosphere at a temperature of 60 ° C., and further allowed to stand for 1 day or more at a temperature of 23 ° C. And about this test piece, the heat conductivity was measured based on JISA1412-2 (1999). The measurement was performed under the condition that a test piece was sandwiched between a heating plate and a cooling hot plate having a temperature difference of 20 ° C., and the average temperature of the test piece was 23 ° C.

"Flame retardance"
First, a plate-shaped test piece of 200 mm × 25 mm × 10 mm was cut out from the foamed molded body in each Example and Comparative Example. The test piece was allowed to stand at a temperature of 40 ° C. for 3 days, and further allowed to stand at a temperature of 23 ° C. for 1 day. About this test piece, the combustion test was performed based on the combustion test (Method A) of JIS A 9511 (2006), and the time until extinguishing was measured. The measurement was performed up to 3 seconds, and when it took 3 seconds or more to extinguish the fire, the result was “3 seconds or more”.

  As is known from Tables 1 and 2, by using polystyrene resin seed particles obtained by kneading polystyrene resin, graphite, and bromine flame retardant, this seed particle is impregnated with styrene monomer and polymerized. It is possible to produce expandable polystyrene resin particles that are excellent in foamability, have a small amount of residual monomer, and have a small variation in particle size distribution (see Examples 1 to 7). In the appearance of the expandable polystyrene resin particles, there are no spots or the like due to the flame retardant (see FIGS. 1 to 4). Moreover, by using the expandable polystyrene resin particles thus obtained, a polystyrene resin foam molded article having excellent flame retardancy and heat insulation, high fusion rate, and excellent appearance can be obtained. (See Examples 1-7).

  On the other hand, as is known from Table 1 and Table 3, in the expandable resin particles prepared by impregnating and polymerizing seed particles with a styrene monomer in which a flame retardant is dissolved, the expandable resin of the above-mentioned Examples The foam moldability was worse than the particles. As a result, the fusion rate in the foamed molded product was reduced, and many voids were generated between the foamed particles (see Comparative Examples 1 and 2). As for the appearance of the expandable resin particles, a coating in which the flame retardant is aggregated is formed on the surface of the black expandable resin particles (see FIG. 5), or the surface of the black expandable resin particles is caused by the flame retardant. A white spot pattern was formed (see FIG. 6). Further, the foamed molded article obtained using such expandable resin particles has a problem in appearance as described above (see Comparative Examples 1 and 2).

  In addition, in the foamable resin particles produced by impregnating and polymerizing seed particles with a styrene monomer in which a flame retardant is dissolved, reducing the amount of the flame retardant suppresses the formation of the above-mentioned coatings and spots. Although it was possible (see FIGS. 7 and 8), only a foamed molded article with insufficient flame retardancy was obtained (see Comparative Examples 3 and 4). Moreover, the foam moldability was not greatly improved, and the fusion rate of the foam molded product was a low value.

In addition, foamable resin particles obtained by impregnating a polystyrene resin particle kneaded with a flame retardant without impregnating polymerization of a styrene monomer with a foaming agent have a problem in foam moldability. It was. As a result, melting was observed on the surface of the foamed molded product under the same heating condition of steam pressure as in the examples (see Comparative Example 5). Thus, in-mold molding was performed with the steam pressure lowered, but the fusion rate in the foamed molded product was reduced, and many voids were generated between the foamed particles (see Comparative Example 5).
Further, in the foamable resin particles obtained by suspension polymerization of a styrene polymer in which a flame retardant was dissolved, the amount of residual monomer was large and the dispersion of particle size distribution was large (see Comparative Example 6). In the foamed particles obtained using such foamable resin particles, the average cell diameter is large, and in the foamed molded product, the fusion rate is lowered.

  In addition, as is known from Table 2, by using brominated butadiene polymer as a flame retardant, it is possible to reduce the moisture content of the expandable resin particles and shorten the aging period when obtaining the foamed molded product. become.

Claims (3)

A method for producing expandable polystyrene resin particles containing graphite and a brominated flame retardant,
A dispersion step of dispersing polystyrene resin seed particles obtained by kneading a polystyrene resin, graphite, and a brominated flame retardant in an aqueous medium;
A polymerization step of supplying a styrene monomer into the aqueous medium, impregnating and polymerizing the polystyrene resin seed particles with the styrene monomer; and
The physical blowing agent during or after polymerization in the polymerization step impregnated into the resin particles have a a foaming agent impregnating step of obtaining the expandable polystyrene resin particles,
The brominated flame retardant, a manufacturing method of the expandable polystyrene resin particles, wherein the brominated butadiene polymer der Rukoto.   2. The method for producing expandable polystyrene resin particles according to claim 1, wherein a blending amount of the brominated flame retardant in the polystyrene resin seed particles is 1 to 10% by mass. The amount of the styrene monomer added is 15 to 300 parts by mass with respect to 100 parts by mass of the polystyrene resin seed particles. The expandable polystyrene resin particles according to claim 1 or 2, Manufacturing method .