JP5044375B2 - Method for producing flame retardant expandable polystyrene resin particles - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing flame retardant expandable polystyrene resin particles capable of producing a flame retardant polystyrene resin foam molded article suitably used in the field of building materials requiring flame retardancy.

  In general, as a method for producing a polystyrene resin foam molded article having a desired shape such as a rectangular parallelepiped shape, the expandable polystyrene resin particles are heated and pre-foamed, and the obtained pre-foamed particles are filled into a mold cavity. In other words, so-called in-mold foam molding is employed in which the pre-foamed particles are secondarily foamed and the pre-foamed particles are thermally fused and integrated to form a polystyrene resin foam molded article.

  In addition, when a polystyrene resin foam molding is used for building materials, the polystyrene resin foam molding must be cut using a nichrome wire that is energized and heated in order to match the intended dimensions and shape. There is.

  In recent years, the use of polystyrene-based resin foam molded bodies cut with nichrome wires as described above (hereinafter referred to as “nichrome cuts”) for building material panels has increased, and accordingly, nichrome. The required quality for cut surfaces is increasing.

  On the other hand, polystyrene-based resin foam moldings used for building materials are required to have a certain standard of flame retardancy, and in order to clear this standard, a flame retardant is contained as expandable polystyrene-based resin particles. Is used.

  As a method of adding a flame retardant to the expandable polystyrene resin particles, there is a method of directly adding a powdered flame retardant to a reaction kettle (autoclave). In this method, the powdered flame retardant is suspended in a suspension. Due to secondary aggregation, the dispersion of the flame retardant in the suspension becomes non-uniform, resulting in non-uniform absorption of the powdered flame retardant into the resin particles, making some resin particles difficult. The problem of absorbing much of the flame retardant occurred.

  Expandable polystyrene resin particles containing a large amount of such flame retardants are inferior in heat resistance, so they cannot withstand the heating during foam molding and break up and shrink to form hardened granules. When Nichrome is cut, the Nichrome wire bounces off at the hardened grains, resulting in uneven streaks on the Nichrome cut surface of the polystyrene-based resin foam molding, significantly reducing the value of the product, and sufficient for the panel. There was a problem that a sufficient adhesive strength could not be obtained.

  In order to solve such problems, Patent Document 1 includes (a) 100 parts by weight of vinyl aromatic polymer particles, about 50 to 500 parts by weight of water, an effective amount of suspending agent, and an average particle size. Forming an aqueous suspension of about 0.1 to 2.5 parts by weight of hexabromocyclododecane of 100 microns or less, about 3 to 20 parts by weight of a C4 to C6 aliphatic hydrocarbon blowing agent; (b) The suspension is heated at a temperature of about 40-140 ° C. for about 0.5-15 hours to incorporate hexabromocyclododecane and blowing agent into the polymer particles to form refractory, expandable thermoplastic beads. (C) A method for producing a fire-resistant and expandable thermoplastic bead comprising separating the bead from water is disclosed.

  However, in the above thermoplastic bead manufacturing method, the flame retardant charging mode is not clearly described, and it is considered that the flame retardant is charged as powder from the description, and thus the flame retardant is charged as powder. Then, the absorption to the beads becomes non-uniform, and by making the flame retardant finer, the flame retardant becomes easy to secondary agglomerate in the liquid, in addition to the vicinity of the surface of the obtained thermoplastic beads. Many flame retardants tend to be present, and the secondary foam particles are fused and bonded to each other at the time of pre-foaming by this flame retardant, so-called blocking is likely to occur.

  Patent Document 2 discloses tetrafluorobisphenol A diallyl ether having an average particle size of 120 μm or less in a foamable styrene resin particle containing a foaming agent in a styrene resin particle body, and a styrene resin particle body. There is disclosed an expandable styrene resin particle having flame retardancy, which is impregnated within a range of 1.0 to 5.0% by weight with respect to the total amount of tetrabromobisphenol A diallyl ether.

  However, the flame retardant can be dispersed in water with stirring in the presence of a surfactant. However, when the dispersion liquid in which the flame retardant is dispersed is sent from the tank to the reaction kettle (autoclave), the dispersion liquid is stirred. As a result, in addition to the problem that the flame retardant settles in the lower part of the tank and the piping line and there is a risk that the piping line may be blocked, there are many difficulties near the surface of the resulting expandable styrene resin particles. A flame retardant tends to exist, and this flame retardant has a problem that secondary foam particles are fused and bonded during pre-foaming, so-called blocking is likely to occur.

  Furthermore, in Patent Document 3, flame retardant is supplied into the autoclave in paragraph [0062], but the supply point of the flame retardant is not clearly described as in Patent Document 1, and it is difficult from the description. It is considered that the flame retardant is charged as powder. When the flame retardant is charged as powder in this way, the absorption to the expandable styrenic resin particles becomes non-uniform as in Patent Document 1, or the flame retardant is added. Problems such as secondary agglomeration or occurrence of blocking were likely to occur.

JP-A-4-132746 JP 11-255946 A JP 2006-213850 A

  The present invention is capable of uniformly impregnating resin particles with a powdered flame retardant, and in-mold foam molding of a flame retardant polystyrene resin foam molded article that provides a good cut surface when Nichrome is cut. The manufacturing method of the flame-retardant foaming polystyrene-type resin particle which can be obtained by this is provided.

  The method for producing flame retardant expandable polystyrene resin particles of the present invention is as follows. Before or during impregnation of the polystyrene resin particles dispersed in an aqueous suspension with a foaming agent, 100 parts by weight of a plasticizer is powdered. 14 to 200 parts by weight of the above flame retardant is heated and dissolved, and then cooled to precipitate a flame retardant, and the flame retardant dispersion is supplied into the aqueous suspension. It is characterized by impregnating with a flame retardant.

  As the polystyrene resin particles, those produced by a known method can be used. For example, (1) an aqueous medium, a styrene monomer and a polymerization initiator are supplied into an autoclave and heated in the autoclave. Suspension polymerization method for producing polystyrene resin particles by suspension polymerization of styrene monomer while stirring, (2) supplying aqueous medium and polystyrene resin seed particles into the autoclave, After being dispersed in an aqueous medium, the inside of the autoclave is heated and stirred to continuously or intermittently supply the styrene monomer, and the polystyrene resin seed particles absorb the styrene monomer and polymerize it. Examples include a seed polymerization method in which polystyrene resin particles are produced by polymerization in the presence of an initiator. The polystyrene-based resin seed particles may be produced and classified by the suspension polymerization method of (1) above.

  In the production method of the present invention, the polystyrene-based resin is not particularly limited. For example, a styrene-based monomer such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, or bromostyrene. Homopolymers of these bodies or copolymers thereof, and polystyrene resins containing 50% by weight or more of styrene are preferable, and polystyrene is more preferable.

  In addition, the polystyrene resin is a copolymer of the styrene monomer having the styrene monomer as a main component and a vinyl monomer copolymerizable with the styrene monomer. Such vinyl monomers may include, for example, alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth ) In addition to acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, and ethyl fumarate, difunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

  The average particle diameter of the polystyrene resin particles is a preliminary value obtained by pre-expanding the flame retardant expandable polystyrene resin particles when performing in-mold foam molding using the flame retardant expandable polystyrene resin particles. From the viewpoint of filling properties of the expanded particles into the cavity, 0.3 to 2.0 mm is preferable, and 0.6 to 1.4 mm is more preferable.

  Furthermore, if the polystyrene-based resin constituting the polystyrene-based resin particles has a small weight average molecular weight in terms of styrene, the mechanical properties of the flame-retardant polystyrene-based resin foam molded product obtained by foaming the flame-retardant expandable polystyrene-based resin particles. On the other hand, if the strength is lowered, the foamability of the flame-retardant expandable polystyrene resin particles is lowered, and there is a possibility that a flame-retardant polystyrene-based resin foam molded article having a high expansion ratio cannot be obtained. Therefore, 200,000 to 500,000 are preferable, and 240,000 to 400,000 are more preferable.

  In addition, it does not specifically limit as a polymerization initiator used in the said suspension polymerization method and seed polymerization method, For example, benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, t- Butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, isopropyl carbonate, t-butyl peroxyacetate, 2,2-bis (t-butylperoxy) butane, Organic peroxides such as t-butylperoxy-3, 3,5 trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, etc. Are mentioned, These may be also alone, or two or more are used alone.

  The aqueous suspension in which polystyrene resin particles are dispersed in an aqueous medium may be obtained by using the reaction liquid after polymerization by the suspension polymerization method or the seed polymerization method as an aqueous suspension, or the suspension described above. The polystyrene resin particles obtained by the turbid polymerization method or the seed polymerization method may be separated from the reaction solution, and the polystyrene resin particles may be suspended in a separately prepared aqueous medium to form an aqueous suspension. In addition, it does not specifically limit as an aqueous medium, For example, water, alcohol, etc. are mentioned, Water is preferable.

  In the suspension polymerization method or seed polymerization method, a suspension stabilizer is used to stabilize the dispersibility of the styrene monomer droplets or polystyrene resin seed particles when the styrene monomer is polymerized. Examples of such a suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone, and poorly water-soluble inorganic salts such as calcium triphosphate and magnesium pyrophosphate. In the case of using a poorly water-soluble inorganic salt, an anionic surfactant is usually used in combination.

  Examples of the anionic surfactant include alkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher fatty acid salts such as sodium oleate, and β-tetrahydroxynaphthalene sulfonate. And alkylbenzene sulfonates are preferred.

  In addition, when the aqueous suspension is formed by suspending the polystyrene resin particles obtained by the suspension polymerization method or the seed polymerization method in a separately prepared aqueous medium, the dispersibility of the polystyrene resin particles is stabilized. Therefore, the above suspension stabilizer and anionic surfactant may be added to the aqueous medium.

  At this time, if the amount of the hardly water-soluble inorganic salt added to the aqueous medium is small, the dispersibility of the polystyrene resin particles in the aqueous medium is lowered, or the dispersion of the flame retardant in the flame retardant dispersion is not good. This may cause problems such as settling of the flame retardant and settling of the flame retardant into the polystyrene resin particles, while the polystyrene resin particles may not be able to uniformly absorb the flame retardant. Since the viscosity increases and the polystyrene-based resin particles may not be uniformly dispersed in the aqueous medium, 0.5 to 2 parts by weight is preferable with respect to 100 parts by weight of the aqueous medium.

  And in the manufacturing method of the flame-retardant foaming polystyrene-type resin particle of this invention, a foaming agent is impregnated in the well-known way in the polystyrene-type resin particle disperse | distributed in the said aqueous suspension. As such a foaming agent, a boiling point is not higher than the softening point of the polystyrene-based resin, and a gaseous or liquid organic compound at normal pressure is suitable. For example, propane, n-butane, isobutane, n-pentane, Hydrocarbons such as isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, petroleum ether, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol, isopropyl alcohol, dimethyl ether, diethyl ether, dipropyl ether, methyl Examples thereof include low boiling point ether compounds such as ethyl ether, inorganic gases such as carbon dioxide, nitrogen and ammonia, and hydrocarbons having a boiling point of −45 to 40 ° C. are preferred, propane, n-butane, isobutane, n-pentane, Isopentane is more preferred Arbitrariness. In addition, a foaming agent may be used independently or 2 or more types may be used together.

  Furthermore, in the method for producing flame-retardant foamable polystyrene resin particles of the present invention, the plasticizer is powdered before or during impregnation with the polystyrene resin particles dispersed in the aqueous suspension. The flame retardant dispersion obtained by heating and dissolving the flame retardant and cooling to precipitate the flame retardant is supplied into the aqueous suspension, and the polystyrene resin particles are impregnated with the flame retardant under pressure. Let

  The flame retardant dispersion is prepared by heating and dissolving a powdered flame retardant in a plasticizer and then cooling to deposit the flame retardant. Such a plasticizer is not particularly limited as long as the powdered flame retardant can be dissolved by heating, and examples thereof include diisobutyl adipate, diisononyl adipate, dibutyl sebacate, toluene, ethylbenzene, and cyclohexane. And diisobutyl adipate and toluene are preferable.

  The powdery flame retardant is not particularly limited as long as it is powdery when it is present in a state where it is not dissolved in another medium under the conditions of impregnation in polystyrene resin particles, hexabromocyclododecane, Brominated aliphatic hydrocarbon compounds such as tetrabromocyclooctane, tetrabromobutane, hexabromocyclohexane, brominated phenols such as tetrabromobisphenol A, tetrabromobisphenol F, 2,4,6-tribromophenol, tetra Brominated phenol derivatives such as bromobisphenol A-bis (2,3-dibromopropyl ether), tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-diglycidyl ether, etc. Are mentioned, Preferably fluorinated aliphatic hydrocarbon compound, tetrabromobisphenol cyclooctane are preferred.

  The flame retardant dispersion described above is manufactured as follows. First, a powdered flame retardant is heated in a plasticizer to dissolve the entire amount of the flame retardant, thereby preparing a flame retardant solution. At this time, even if the powdered flame retardant is added to the plasticizer and then the plasticizer is heated and stirred, the flame retardant is dissolved in the plasticizer, or the plasticizer is preheated and then added to the plasticizer. A powdery flame retardant may be added to and dissolved with stirring.

  As for whether or not the powdered flame retardant was completely dissolved in the plasticizer, it was confirmed by visual observation that there was no floating or precipitation of the flame retardant powder in the plasticizer, and it was a transparent solution. In this case, it is determined that the entire amount of the powdered flame retardant is dissolved in the plasticizer. Otherwise, it is determined that the entire amount of the powdered flame retardant is not dissolved in the plasticizer. .

  Next, the flame retardant solution is cooled, and the flame retardant dissolved in the plasticizer is precipitated and dispersed in the plasticizer. The method for cooling the flame retardant solution is not particularly limited as long as the flame retardant dissolved in the flame retardant solution can be precipitated. In this way, the entire amount of the flame retardant is once dissolved in the plasticizer, and then the plasticizer is cooled and precipitated. The deposited flame retardant is finely dispersed in the plasticizer and finely dispersed in the plasticizer. The dispersed state can be stably maintained.

  If the amount of the flame retardant dissolved in the plasticizer in the heated state of the plasticizer is small, the amount of the flame retardant dispersion that must be used increases, and the impregnation efficiency of the flame retardant into the polystyrene resin particles On the other hand, if the amount is too large, the heat resistance of the resulting flame-retardant expandable polystyrene resin particles is reduced, or blocking occurs during the pre-expansion of the flame-retardant expandable polystyrene resin particles. On the other hand, it is limited to 14 to 200 parts by weight, preferably 50 to 190 parts by weight, and more preferably 70 to 190 parts by weight.

  The ratio of the flame retardant deposited in the plasticizer (hereinafter referred to as “flame retardant deposition rate”) in cooling the flame retardant solution and precipitating the flame retardant in the plasticizer to produce a flame retardant dispersion is: If it is low, the absorption of the flame retardant into the polystyrene resin particles may be uneven. On the other hand, if it is high, it takes time to absorb the flame retardant and the production efficiency of the flame retardant expandable polystyrene resin particles decreases. Therefore, 40 to 85% by weight of the total amount of the flame retardant dissolved in the plasticizer is preferable, 40 to 80% by weight is more preferable, and 42 to 76% by weight is particularly preferable.

Here, the flame retardant deposition rate is calculated as follows. First, a flame retardant dispersion or a dispersion of a flame retardant dispersion described later is set in a centrifuge and centrifuged at a rotational speed of 2000 rpm for 20 minutes to separate the liquid phase and the deposited flame retardant. The separated flame retardant is vacuum dried at 70 ° C. for 24 hours, and the weight C of the flame retardant is measured. And a flame retardant precipitation rate is computable based on a following formula. In addition, let D be the total weight of the flame retardant contained in the flame retardant dispersion or the dispersion of the flame retardant dispersion.
Flame retardant deposition rate (% by weight) = 100 × weight C / weight D

  And, if the average particle diameter of the flame retardant deposited in the flame retardant dispersion is large, the dispersion of the flame retardant in the flame retardant dispersion becomes non-uniform, and the absorption to the polystyrene resin particles becomes non-uniform, When the resulting polystyrene-based resin foam molded article is Nichrome cut, uneven stripes may occur on the Nichrome cut surface, so that it is preferably less than 30 μm, more preferably 0.1 to 25 μm, and particularly preferably 12 to 24 μm. .

  In addition, the average particle diameter of the flame retardant in the flame retardant dispersion is measured as follows. The average particle diameter of the flame retardant in the flame retardant dispersion is measured visually using a magnifying glass. Specifically, a 500 × lens is attached to the magnifying glass, the flame retardant dispersion is observed, and the diameter of the smallest perfect circle that can surround the shadow of the projected flame retardant particles is defined as the particle diameter of the flame retardant particles. To do. And the particle diameter of 20 flame retardant particle | grains extracted at random is measured in the above-mentioned way, and let the arithmetic mean value of the particle diameter of each flame retardant particle | grain be an average particle diameter of a flame retardant. In the case where a hardly water-soluble inorganic salt is used, it is carried out after decomposing the hardly soluble inorganic salt with hydrochloric acid. Moreover, the average particle diameter of a flame retardant can be measured using the measuring apparatus marketed with the brand name "V-12A" from Nikon Corporation.

  Furthermore, when supplying the flame retardant dispersion in the aqueous suspension, the content of the flame retardant in the obtained flame retardant expandable polystyrene resin particles is 100 parts by weight of polystyrene resin particles impregnated with the flame retardant. On the other hand, it is preferably 0.3 to 2.0 parts by weight, more preferably 0.5 to 1.5 parts by weight, and particularly preferably 0.7 to 1.0 parts by weight. It is preferable to adjust so that. This is obtained when the content of the flame retardant in the flame retardant expandable polystyrene resin particles is small, while the flame retardancy of the resulting flame retardant polystyrene resin foam molded article may be lowered, while it is large. While the heat-fusable and foam-molding properties of the flame-retardant foamable polystyrene resin particles are reduced, the appearance of the resulting flame-retardant polystyrene-based resin foam molding may be lowered, and the flame-retardant foamable polystyrene This is because it causes bonding between pre-expanded particles at the time of pre-expansion of the resin-based resin particles and streaks at the time of nichrome cutting of the flame-retardant polystyrene-based resin foam molded article to be obtained.

  In this way, the powdered flame retardant is once dissolved in the plasticizer and then precipitated, and the flame retardant is dispersed in a very fine and stable manner in the plasticizer, and the plasticizer is liquid. Since it is uniformly and stably dispersed in the aqueous suspension, the powdery flame retardant dispersed in the plasticizer can also be uniformly and stably dispersed in the aqueous suspension, Therefore, the flame retardant can be impregnated uniformly and with excellent impregnation efficiency in each polystyrene resin particle dispersed in the aqueous suspension.

  Further, the flame retardant dispersion may be dispersed in an aqueous medium to form a dispersion. By thus dispersing the flame retardant dispersion in the aqueous medium, the flame retardant dispersion is further finely dispersed in the aqueous medium. It can be dispersed into fine droplets, and the flame retardant dispersion can be dispersed in an aqueous suspension in which polystyrene resin particles are dispersed. The flame retardant can be more uniformly impregnated in the polystyrene resin particles.

  The aqueous medium is not particularly limited as long as it is compatible with the aqueous suspension in which the polystyrene resin particles are dispersed, and examples thereof include water, alcohol, and the like. The same aqueous medium as the aqueous suspension to be dispersed is preferable.

  If the amount of the aqueous medium in which the flame retardant dispersion is dispersed is small, the flame retardant dispersion may not be stably dispersed in the aqueous medium. On the other hand, if the amount is large, the dispersion in the polystyrene resin may be difficult. Since the impregnation efficiency of the flame retardant may decrease, the amount is preferably 100 to 5000 parts by weight and more preferably 300 to 1000 parts by weight with respect to 100 parts by weight of the plasticizer in the flame retardant dispersion.

  In addition, when the flame retardant dispersion is dispersed in an aqueous medium, the interfacial energy between the flame retardant dispersion and the aqueous medium is reduced in the aqueous medium, so that the flame retardant dispersion is more stable in the aqueous medium. In order to disperse, a surfactant may be contained.

  Examples of such surfactants include, but are not limited to, alkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, higher fatty acid salts such as sodium oleate, β-tetrahydroxy Anionic surfactants such as naphthalene sulfonates; alkyl ammonium acetates, alkyl dimethyl benzyl ammonium salts, alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl pyridinium salts, oxyalkylene alkyl amines, polyoxyalkylene alkyl amines, etc. Cationic surfactants; fatty acid diethanolamides, silicone surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl alkyls Vinyl ether, and polyoxyethylene-polyoxypropylene glycol, include such nonionic surfactants such as polyether-modified silicones, preferably anionic surfactants, alkylbenzenesulfonate is preferable. In addition, surfactant may be used independently or 2 or more types may be used together.

  When the amount of the surfactant used is small, the dispersibility of the flame retardant dispersion in the aqueous medium is not improved. On the other hand, when the amount is large, foaming due to the surfactant becomes excessive, causing production trouble. Therefore, 0.004 to 4 parts by weight is preferable with respect to 100 parts by weight of the plasticizer in the flame retardant dispersion, and 0.01 to 0.5 parts by weight is more preferable.

  Further, when the flame retardant dispersion is dispersed in an aqueous medium, it is preferable to contain a hardly water-soluble inorganic salt in the aqueous medium. Examples of such hardly water-soluble inorganic salts include tricalcium phosphate, hydroxyapatite, and the like. , Magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, magnesium phosphate, magnesium carbonate and the like, and magnesium pyrophosphate is preferred.

  If the amount of the hardly water-soluble inorganic salt used is small, the dispersibility of the flame retardant dispersion in the aqueous medium may be reduced. On the other hand, if the amount used is large, the viscosity of the dispersion obtained by dispersing the flame retardant dispersion may be reduced. And the flame retardant dispersion may not be uniformly dispersed in the aqueous medium, so 0.2 to 10 parts by weight is preferable with respect to 100 parts by weight of the plasticizer in the flame retardant dispersion.

  As a procedure for dispersing the flame retardant dispersion in the aqueous medium, the plasticizer may be dispersed in the aqueous medium in a state where all the flame retardant is contained in the plasticizer. For example, (1) in the aqueous medium If necessary, add a surfactant or a sparingly water-soluble inorganic salt and heat it to a predetermined temperature. On the other hand, heat the plasticizer with a powdered flame retardant, and then cool it after dissolving it. To prepare a flame retardant dispersion by precipitating the flame retardant, and to supply the flame retardant dispersion into the aqueous medium and disperse it by stirring; (2) a powdery flame retardant into the plasticizer; The whole amount is dissolved by heating to prepare a flame retardant solution, while adding a surfactant or a hardly water-soluble inorganic salt to the aqueous medium as necessary, and heating, the flame retardant solution is then added to the aqueous medium. Add to the mixture, stir and disperse, then cool the aqueous medium to dissolve the flame retardant (3) A surfactant and a hardly water-soluble inorganic salt are added to an aqueous medium as needed, and then a plasticizer and a flame retardant are added. After that, the aqueous medium is heated so that the flame retardant is absorbed in the plasticizer and the entire amount is dissolved so that the plasticizer solution is dispersed in the aqueous medium, and then the aqueous medium is cooled to dissolve the flame retardant. Examples thereof include a method for preparing a flame retardant dispersion by precipitating a flame retardant in the liquid. In the method (2), it is preferable that the temperature of the flame retardant solution is equal to the temperature of the aqueous medium, or the temperature of the aqueous medium is higher by 0 to 10 ° C.

  The flame retardant dispersion or a dispersion of a flame retardant dispersion obtained by dispersing the flame retardant dispersion in an aqueous medium (hereinafter simply referred to as “dispersion of a flame retardant dispersion”), polystyrene resin particles The timing of addition to the dispersed aqueous suspension may be before or during the impregnation of the foaming agent, and the aqueous suspension of the flame retardant dispersion or the dispersion of the flame retardant dispersion may be used. Addition to the suspension may be done by adding the flame retardant dispersion or the dispersion of the flame retardant dispersion all at once, or adding the flame retardant dispersion or the dispersion of the flame retardant dispersion a plurality of times. The flame retardant dispersion or the dispersion of the flame retardant dispersion may be added in small portions continuously.

  In addition, when the flame retardant dispersion or the dispersion of the flame retardant dispersion is added to the aqueous suspension in which the polystyrene resin particles are dispersed, the temperature of the aqueous suspension is too high even if it is too low. Even if it is too much, absorption of the flame retardant into the polystyrene-based resin particles may be non-uniform, so 40 to 60 ° C. is preferable.

  Furthermore, the temperature of the aqueous suspension in which the polystyrene resin particles are dispersed is preferably lower than the temperature of the flame retardant dispersion or the dispersion of the flame retardant dispersion, and further the polystyrene resin particles are dispersed. The difference between the temperature of the aqueous suspension and the temperature of the flame retardant dispersion or the dispersion of the flame retardant dispersion is more preferably 20 ° C. or less, and polystyrene resin particles are dispersed. It is particularly preferable that the temperature of the aqueous suspension and the temperature of the flame retardant dispersion or the dispersion of the flame retardant dispersion are the same.

  This is because when the temperature of the aqueous suspension is higher than the temperature of the flame retardant dispersion or the dispersion of the flame retardant dispersion, the flame retardant in the flame retardant dispersion is dissolved again in the plasticizer, This is because there is a possibility that the absorption of the flame retardant into the polystyrene resin particles may be uneven.

  And after impregnating a polystyrene-type resin particle disperse | distributed in aqueous suspension with a foaming agent and a flame retardant, a flame-retardant foaming polystyrene-type resin particle is manufactured, Then, this flame-retardant foaming polystyrene-type resin particle Is taken out from the aqueous suspension, and the flame-retardant foamable polystyrene resin particles may be washed and dried as necessary.

  And the average particle diameter of the flame retardant expandable polystyrene resin particles is the same as that of the pre-expanded particles obtained by pre-expanding the flame retardant expandable polystyrene resin particles when performing in-mold foam molding. From the viewpoint of filling properties, 0.3 to 2.0 mm is preferable, and 0.6 to 1.4 mm is more preferable.

  In addition to the flame retardant, the flame retardant expandable polystyrene resin particles contain additives such as a bubble regulator, a filler, a flame retardant aid, a lubricant, a colorant, and a solvent, as long as the physical properties are not impaired. When these additives are added to the flame-retardant foamable polystyrene resin particles, are the additives added to the aqueous suspension in which the polystyrene resin particles are dispersed? Alternatively, an additive may be added to the flame retardant dispersion or the dispersion of the flame retardant dispersion.

Next, the manufacturing point of a flame-retardant polystyrene-type resin foam molding is demonstrated using the said flame-retardant foaming polystyrene-type resin particle. As a procedure for producing a flame-retardant polystyrene resin foam molded article using the flame-retardant foam polystyrene resin particles, a known method can be adopted, specifically, a flame-retardant foam polystyrene resin The resin particles are heated and pre-expanded to form polystyrene-based resin pre-expanded particles having a bulk density of about 0.01 to 0.05 g / cm ³ , and the polystyrene-based resin pre-expanded particles are filled into the mold cavity. A flame-retardant polystyrene-based resin foam molded article can be obtained by heating and foaming.

If the density of the flame retardant polystyrene resin foam molded product is low, the closed cell ratio of the flame retardant polystyrene resin foam molded product is lowered, and the heat insulation and mechanical properties of the flame retardant polystyrene resin foam molded product are reduced. On the other hand, when the strength is lowered, if it is high, the time required for one cycle in the in-mold foam molding becomes long, and the production efficiency of the flame-retardant polystyrene resin foam molded article may be lowered. 0.05 g / cm ³ is preferred.

  The method for producing flame retardant expandable polystyrene resin particles according to the present invention comprises a flame retardant dispersion in which a powdered flame retardant is entirely heated and dissolved in a plasticizer and then cooled to precipitate a flame retardant. Is supplied in an aqueous suspension in which polystyrene resin particles are dispersed, and the flame retardant is finely and uniformly dispersed stably in the flame retardant dispersion, and the plasticizer Is a liquid and uniformly dispersed in an aqueous suspension, the flame retardant in the plasticizer is also uniformly dispersed in the aqueous suspension, and as a result, is dispersed in the aqueous suspension. Each polystyrene resin particle can be impregnated uniformly and sufficiently efficiently into the center, and flame-retardant expandable polystyrene resin particles having excellent foamability and heat-fusibility can be produced.

  And the manufacturing method of the flame-retardant foaming polystyrene-type resin particle of this invention can make each flame-retardant foaming polystyrene-type resin particle impregnate a flame retardant favorably, and the flame-retardant foaming polystyrene-type obtained Since the resin particles are excellent in foam moldability, the flame retardant polystyrene resin foam molded product obtained by foam molding of the flame retardant foam polystyrene resin particles has no hardened particles and is flame retardant. A good cut surface can also be obtained when the niobium-cut polystyrene foam resin molded product is cut.

  In addition, the powdered flame retardant is once dissolved in the plasticizer and then precipitated in the plasticizer. Since the flame retardant is finely dispersed in the plasticizer, the flame retardant foaming property During the production process of the polystyrene resin particles, the powdered flame retardant does not cause secondary aggregation or sedimentation, and there is no problem that the piping line is blocked by the powdered flame retardant.

  When the flame retardant dispersion is dispersed in an aqueous medium, the flame retardant dispersion can be further finely dispersed in the aqueous medium, and thus the flame retardant dispersion is dispersed in polystyrene resin particles. The aqueous suspension can be supplied in a further refined state, and the flame retardant can be more uniformly and efficiently impregnated into the polystyrene resin particles.

  Further, in the case where the flame retardant dispersion is dispersed in the aqueous medium and the surfactant is contained in the aqueous medium, the interfacial energy between the flame retardant dispersion and the aqueous medium is reduced. The flame retardant dispersion can be further finely dispersed in the aqueous medium, so that the flame retardant can be more uniformly impregnated in the polystyrene resin particles.

Example 1
In an autoclave with a stirrer having an internal volume of 6350 liters, tribasic calcium phosphate (Ohira Chemical Co., Ltd.) 7.62 kg, sodium dodecylbenzenesulfonate 0.254 kg, benzoyl peroxide (purity 75% by weight) 8.89 kg, t-butyl per After supplying 1.91 kg of oxy-2-ethylhexyl monocarbonate, 2540 kg of ion exchange water and 2540 kg of styrene monomer, the stirring blade was rotated at a rotational speed of 40 rpm and stirred to form an aqueous suspension.

  Next, while stirring the stirring blade at 40 rpm, the temperature in the autoclave was raised to 90 ° C. and held at 90 ° C. for 6 hours, and further the temperature in the autoclave was raised to 120 ° C. The styrene monomer was subjected to suspension polymerization by holding for 2 hours.

  Thereafter, the temperature in the autoclave is cooled to 25 ° C., the polystyrene particles are taken out from the autoclave, washed and dehydrated repeatedly, and after passing through a drying step, the polystyrene particles are classified, and the particle size is reduced. Polystyrene particles having 0.6 to 0.85 mm and a weight average molecular weight of 300,000 were obtained.

  Next, after supplying 1900 kg of ion exchange water, 0.254 kg of sodium dodecylbenzenesulfonate and 6.35 kg of magnesium pyrophosphate into another 6350 liter autoclave with a stirrer, 698.5 kg of the polystyrene particles were supplied as seed particles. , And uniformly dispersed in water.

  In addition, a dispersion was prepared by dispersing 0.127 kg of sodium dodecylbenzenesulfonate and 1.27 kg of magnesium pyrophosphate in 381 kg of ion-exchanged water, while the polymerization initiator benzoyl peroxide (purity 75) was added to 318 kg of styrene monomer. %) 5.59 kg and 3.18 kg of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved to prepare a styrene monomer solution, and this styrene monomer solution was added to the dispersion to obtain a homomixer. The mixture was stirred and emulsified to obtain an emulsion.

  And after heating and holding the autoclave at 75 ° C., the above emulsion is added to the autoclave, and styrene monomer, benzoyl peroxide and t-butylperoxy-2-ethylhexyl monocarbonate are added to the polystyrene seed particles. Is maintained for 30 minutes so that it can be absorbed smoothly, and then the styrene unit in the autoclave is heated from 75 ° C. to 108 ° C. at a rate of 0.2 ° C./min. 1778 kg of body was continuously dripped over 160 minutes, and then 20 minutes after the completion of the dropwise addition of the styrene monomer, the temperature was raised to 120 ° C. at a rate of 1 ° C./minute, over 90 minutes. Retained to obtain polystyrene particles by seed polymerization. All styrene monomers were used for polymerization.

  In addition, 19.6 kg of diisobutyl adipate (trade name “DI4A” manufactured by Taoka Chemical Industry Co., Ltd.), which is a plasticizer, is heated to 90 ° C. and stirred with diisobutyl adipate. Kogyo Seiyaku Co., Ltd., trade name “Pyroguard FR-200”) 21.0 kg was added to diisobutyl adipate and stirred at 90 ° C. for 30 minutes to completely dissolve tetrabromocyclooctane in diisobutyl adipate. A flame retardant solution was prepared, and this flame retardant solution was maintained at 90 ° C.

  Next, 127 kg of ion-exchanged water maintained at 90 ° C. and 0.05 kg of sodium dodecylbenzenesulfonate and 1.27 kg of magnesium pyrophosphate prepared by the metathesis method are added, and then all the flame retardant solution is supplied and stirred to disperse. To form a dispersion of the flame retardant solution.

  After that, the dispersion of the flame retardant solution is cooled to 50 ° C. with stirring, and a part of the flame retardant dissolved in the plasticizer is precipitated to make it difficult to disperse the flame retardant in the plasticizer. A flame retardant dispersion was prepared, and a flame retardant dispersion was prepared by dispersing the flame retardant dispersion in ion-exchanged water. To this dispersion of the flame retardant dispersion, 8.38 kg of dicumyl peroxide as a flame retardant aid was supplied and stirred.

  Next, after the aqueous suspension in the autoclave was cooled to 50 ° C. at a rate of temperature decrease of 1 ° C./min, the dispersion of the flame retardant dispersion kept at 50 ° C. was supplied into the autoclave. Sixty minutes after adding the flame retardant dispersion, the reaction kettle was sealed and heated to 90 ° C.

  Thereafter, as a blowing agent, butane (isobutane / normal butane (weight ratio) = 30/70) 167.6 kg and pentane (isopentane / normal pentane (weight ratio) = 20/80) 70.5 kg were pressurized with nitrogen and autoclave. It was press-fitted into the inside over 30 minutes and held in that state for 3 hours.

  Subsequently, the temperature inside the autoclave is cooled to 25 ° C., the flame-retardant foaming polystyrene particles are taken out from the autoclave, washed and dehydrated repeatedly, and after undergoing a drying process, the flame-retardant foaming property is obtained. The polystyrene particles were classified to obtain flame-retardant expandable styrene particles having a particle diameter of 0.85 to 1.2 mm, an average particle diameter of 1.1 mm, and a weight average molecular weight of 300,000. All tetrabromocyclooctane was impregnated in polystyrene particles.

(Example 2)
After supplying 0.05 kg of sodium dodecylbenzenesulfonate and 1.27 kg of magnesium pyrophosphate prepared by the metathesis method to 127 kg of ion-exchanged water, at 25 ° C., diisobutyl adipate (trade name “DI4A manufactured by Taoka Chemical Industries, Ltd.”) ) 19.6 kg and 21.0 kg of tetrabromocyclooctane (trade name “Pyroguard FR-200” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were added, the temperature was raised to 90 ° C., and the mixture was stirred for 60 minutes to obtain adipic acid. All of tetrabromocyclooctane was dissolved in diisobutyl to prepare a dispersion of a flame retardant solution.

  Thereafter, the dispersion of the flame retardant solution is cooled to 50 ° C., and tetrabromocyclooctane dissolved in diisobutyl adipate is precipitated to prepare a flame retardant dispersion. After that, 8.38 kg of dicumyl peroxide was supplied to the dispersion.

  Except that this dispersion of the flame retardant dispersion was used, it was the same as in Example 1 and had a particle diameter of 0.85 to 1.2 mm, an average particle diameter of 1.1 mm, and a weight average molecular weight of 300,000. Flammable expandable polystyrene particles were obtained.

(Example 3)
The particle size was 0 as in Example 1, except that the amount of tetrabromocyclooctane was 42.0 kg instead of 21.0 kg and the amount of diisobutyl adipate was 42.0 kg instead of 19.6 kg. Flame-retardant expandable polystyrene particles having an average particle size of 1.1 mm and a weight average molecular weight of 300,000 were obtained.

Example 4
Except that the amount of tetrabromocyclooctane was 14.0 kg instead of 21.0 kg, the particle size was 0.85 to 1.2 mm, the average particle size was 1.1 mm and the weight was the same as in Example 1. Flame retardant expandable polystyrene particles having an average molecular weight of 300,000 were obtained.

(Example 5)
The use of 11.2 kg of toluene instead of 19.6 kg of diisobutyl adipate, and the temperature of the ion-exchanged water for supplying the flame retardant solution to 65 ° C. when the flame retardant solution was prepared were 65 ° C. Except that the temperature was set to 0 ° C., flame retardant expandable polystyrene particles having a particle diameter of 0.85 to 1.2 mm, an average particle diameter of 1.1 mm, and a weight average molecular weight of 300,000 were obtained in the same manner as in Example 1. It was.

(Example 6)
The particle diameter was 0.85 to 1.2 mm in the same manner as in Example 1 except that tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether) was used instead of tetrabromocyclooctane. In addition, flame-retardant expandable polystyrene particles having an average particle diameter of 1.1 mm and a weight average molecular weight of 300,000 were obtained.

(Example 7)
The particle size was 0.85 to 1.2 mm and the average particle size was 1.1 mm, except that magnesium pyrophosphate was not used during seed polymerization and preparation of the flame retardant dispersion. In addition, flame retardant expandable polystyrene particles having a weight average molecular weight of 300,000 were obtained.

(Example 8)
In the same manner as in Example 1 except that the dispersion of the flame retardant solution was cooled to 60 ° C. and held instead of 50 ° C., the particle size was 0.85 to 1.2 mm, and the average particle size was 1.1 mm. In addition, flame-retardant expandable polystyrene particles having a weight average molecular weight of 300,000 were obtained.

Example 9
In the same manner as in Example 1 except that the dispersion of the flame retardant solution was cooled to 70 ° C. and held instead of 50 ° C., the particle size was 0.85 to 1.2 mm, and the average particle size was 1.1 mm. In addition, flame-retardant expandable polystyrene particles having a weight average molecular weight of 300,000 were obtained.

(Comparative Example 1)
The particle size was the same as in Example 1 except that 19.6 kg of diisobutyl adipate and 21.0 kg of powdered tetrabromocyclooctane were directly fed into the autoclave instead of the dispersion of the flame retardant dispersion. Flame retardant expandable polystyrene particles having 0.85 to 1.2 mm, an average particle diameter of 1.1 mm and a weight average molecular weight of 300,000 were obtained.

(Comparative Example 2)
After supplying the flame retardant solution to the aqueous suspension while maintaining the dispersion of the flame retardant solution at 90 ° C. without cooling to 50 ° C., and maintaining the aqueous suspension in the autoclave at 90 ° C. A flame retardant foaming property having a particle diameter of 0.85 to 1.2 mm, an average particle diameter of 1.1 mm, and a weight average molecular weight of 300,000 in the same manner as in Example 1 except that the foaming agent was pressed into the autoclave. Polystyrene particles were obtained.

(Comparative Example 3)
The particle size was 0 as in Example 1 except that the amount of tetrabromocyclooctane was 5.6 kg instead of 21.0 kg and the amount of diisobutyl adipate was 56.0 kg instead of 19.6 kg. Flame retardant expandable polystyrene particles having an average particle diameter of 1.1 mm and a weight average molecular weight of 300,000 to 1.2 mm were obtained.

(Comparative Example 4)
The particle size was 0 as in Example 1 except that the amount of tetrabromocyclooctane was 70.0 kg instead of 21.0 kg and the amount of diisobutyl adipate was 28.0 kg instead of 19.6 kg. Flame retardant expandable polystyrene particles having an average particle diameter of 1.1 mm and a weight average molecular weight of 300,000 to 1.2 mm were obtained.

(Comparative Example 5)
The particle size was 0.85 to 1.2 mm, the average particle size was 1.1 mm, and the weight average molecular weight was the same as in Example 1 except that the amount of diisobutyl adipate was 8.4 kg instead of 19.6 kg. Obtained 300,000 flame-retardant expandable polystyrene particles. Even when diisobutyl adipate was heated to 90 ° C., the entire amount of tetrabromocyclooctane could not be dissolved.

(Comparative Example 6)
The particle size was 0.85 to 1.2 mm, the average particle size was 1.1 mm, and the weight average molecular weight was the same as in Example 4 except that the amount of diisobutyl adipate was 112.0 kg instead of 19.6 kg. Obtained 300,000 flame-retardant expandable polystyrene particles. Although the dispersion of the flame retardant solution was cooled to 50 ° C., the flame retardant did not precipitate and a dispersion of the flame retardant dispersion was not obtained. The dispersion of the fuel solution was used as it was.

  In Examples 1-9 and Comparative Examples 1-6, the flame retardant solution was separately prepared in the same manner. And when floating or precipitation of a flame retardant powder did not exist in a plasticizer and it was confirmed visually whether it was a transparent solution, about Examples 1-9 and Comparative Examples 1-3, 6, plasticizer There was no floating or precipitation of the flame retardant powder in the inside, and it was a transparent solution. The flame retardant was completely dissolved in the plasticizer, but for Comparative Examples 4 and 5, the flame retardant powder was not contained in the plasticizer. Floating or sediment was present and some of the flame retardant was not dissolved in the plasticizer.

  In Examples 1 to 9 and Comparative Examples 2 to 4 and 6, a dispersion of the flame retardant dispersion was separately prepared in the same manner, and the flame retardant deposition rate was based on the dispersion of the flame retardant dispersion. Was calculated. In Comparative Examples 4 and 5, since the total amount of tetrabromocyclooctane was not dissolved in diisobutyl adipate, the flame retardant deposition rate was not calculated.

  Furthermore, in the measurement of the flame retardant precipitation rate, after preparing the dispersion of the flame retardant dispersion, the mixture was allowed to stand for 30 minutes, and then visually observed whether or not the flame retardant settled on the bottom of the container. .

  In addition, in the dispersion of the flame retardant dispersion, each content of the flame retardant, the aqueous medium, the surfactant and the hardly water-soluble inorganic salt when the plasticizer is 100 parts by weight, and the flame retardant foaming property Tables 1 and 2 show the amounts of flame retardant and plasticizer per 100 parts by weight of polystyrene resin particles in polystyrene resin particles.

[Molding of polystyrene foam molding]
Flame retardant expandable polystyrene particles 40kg, surface treatment agent 20g of polyethylene glycol, 60g of zinc stearate, fatty acid triglyceride (trade name "Riquemar VT-50" manufactured by Riken Vitamin) and fatty acid monoglyceride (product of Riken Vitamin) 20 g of the name “Riquemar S-100P”) was supplied to a tumbler mixer and stirred for 30 minutes to coat the surface treatment agent on the surface of the flame retardant expandable polystyrene particles.

  Next, after storing the flame-retardant expandable polystyrene particles for 48 hours in a 15 ° C. cool box, the Japanese Patent Office Gazette 57 (1982) -133 [3347], Known and Conventional Techniques (Foam Molding), page 39 5.8 kg of flame retardant expandable polystyrene particles per shot are supplied to a cylindrical batch type pressure pre-foaming machine with a volume of 350 liters up to the foam layer upper surface detector described in 1. and heated with steam for 2 minutes. Polystyrene pre-expanded particles were obtained.

  Thereafter, the polystyrene pre-expanded particles are allowed to stand for 24 hours in a room temperature atmosphere, while a block molding machine (Kasahara Kogyo Co., Ltd.) having a mold having a rectangular parallelepiped shape of 1840 x 930 mm x 530 mm in height. Company name "PEONY-205DS") is prepared, polystyrene pre-expanded particles are filled into the mold cavity, and 0.07 MPa (gauge pressure) of water vapor is filled into the mold cavity for 20 seconds. The polystyrene pre-expanded particles were secondarily expanded by press-fitting, and then the mold was cooled until the pressure inside the mold became −0.01 MPa to obtain a rectangular parallelepiped flame-retardant polystyrene foam molded article. Thereafter, the flame-retardant polystyrene foam molded article was stored in a drying room at 70 ° C. for 3 days. However, in Comparative Example 6, since the amount of diisobutyl adipate was large, it shrunk during molding, and a good flame-retardant polystyrene foam molded article could not be obtained.

[Combination of pre-expanded particles]
W ₁ g of polystyrene pre-expanded particles obtained as described above was prepared, and the polystyrene pre-expanded particles were sieved with a sieve having an opening of 1 cm, and the weight W ₂ of the polystyrene pre-expanded particles remaining on the sieve was measured. The degree of bonding of the pre-expanded particles was calculated based on the following formula, and the results are shown in Tables 1 and 2. In addition, 1 weight% or less evaluated as "(circle)" and 1 weight% or more was evaluated as "*".
Bond degree of pre-expanded particles (% by weight) = 100 × W ₂ / W ₁

[Nichrome cut of polystyrene foam molding]
The flame-retardant polystyrene foam molded product obtained as described above was placed on the base of a nichrome cutting machine with the long side of 1840 mm and the short side of 930 mm facing down, and nichrome having a diameter of 0.4 mm. Ten lines are stretched parallel to each other at intervals of 50 mm in the height direction, and the flame-retardant polystyrene foam molded product is spaced at intervals of 50 mm in the height direction under conditions of a block feed speed of 600 mm / min and a current of 3 A / line. Each plate was cut with nichrome to obtain a flat slice.

The uneven streaks generated on the cut surface of the obtained sliced product were visually counted, and the number of streaks per 1 m ² was calculated. The results are shown in Tables 1 and 2. In addition, 0.5 / m ² or less is evaluated as “◎”, 0.5 / m ² and 1 / m ² or less are evaluated as “◯”, and 1 / m ² is evaluated as “×”. did.

[Flammability test]
Cut resulting flame-retardant polystyrene foamed molded test pieces five rectangular parallelepiped vertical 200 mm × horizontal 25 mm × height 10mm from at vertical cutter, after 1 day aging at 60 ° C. oven, the measurement of JIS A9511 _-2006 Measurement was carried out according to method A, the average value of five test pieces was obtained, and the flame extinction time was determined as a comprehensive evaluation based on the following criteria. The results are shown in Tables 1 and 2. In the JIS standard, the flame extinguishing time needs to be within 3 seconds, preferably within 2 seconds, and more preferably within 1 second.
× ・ ・ ・ Extinguishing time exceeds 3 seconds, or even one of the specimens has residual matter
Or burn beyond the limit line.
○ ... Extinguishing time is within 3 seconds, and all 5 samples burn without residue
Does not burn beyond the limit indicator line.
◎ ・ ・ ・ Extinguishing time is less than 1 second, and all 5 samples burn without residue
Does not burn beyond the limit indicator line.

[Fusion rate]
A cutting line with a depth of 5 mm with a cutter knife along the short side direction at the center of the long side direction on the top surface of the sixth slice (vertical length 1840 mm × width 930 mm × thickness 50 mm) obtained by nichrome cutting Then, the sliced product was manually divided into two along the cut line to obtain a divided piece of 920 mm long × 930 mm wide × 50 mm thick.

In the fracture surface of the obtained segmented piece, the number of particles broken within the foamed particles (a) and the number of particles broken at the interface between the foamed particles (b) were counted and melted based on the following formula. The dressing rate was calculated, and the results are shown in Tables 1 and 2. In addition, 70% or more was evaluated as “◯” and less than 70% was evaluated as “x”.
Fusing rate (%) = 100 × number of particles (a) / (number of particles (a) + number of particles (b))

Claims (3)

Before or during impregnation with polystyrene resin particles dispersed in an aqueous suspension, 14 to 200 parts by weight of a powdered flame retardant is heated and dissolved in 100 parts by weight of a plasticizer and then cooled. A flame retardant foaming polystyrene system, wherein a flame retardant dispersion liquid in which a flame retardant is precipitated is supplied into the aqueous suspension and the polystyrene resin particles are impregnated with the flame retardant. A method for producing resin particles. A flame retardant dispersion is dispersed in 100 to 5000 parts by weight of an aqueous medium with respect to 100 parts by weight of a plasticizer, and 0.004 to 4 parts by weight of a surfactant is contained in 100 parts by weight of the aqueous medium. The method for producing flame-retardant expandable polystyrene resin particles according to claim 1. The method for producing flame-retardant expandable polystyrene resin particles according to claim 2, wherein the aqueous medium contains a hardly water-soluble inorganic salt.