JP6055687B2 - Flame-retardant styrenic resin particles, expandable particles, expanded particles and expanded molded articles - Google Patents

Description

The present invention is a flame-retardant styrene resin particles, foamed particles, it relates to expanded beads and expanded molded article. More particularly, the present invention provides flame retardant styrene resin particles containing a non-halogen flame retardant, foamed particles, relates to expanded beads and expanded molded article.

Conventionally, a foam molded body composed of a styrene resin has been used in many building materials because it has excellent strength and heat insulation. Such a foam-molded product is produced, for example, by the following method. That is, a styrene resin composition impregnated with a physical foaming agent, in particular, a particulate styrene resin composition is foamed to obtain pre-expanded particles. The pre-expanded particles are filled in a mold having a desired shape and expanded. By this foaming, the pre-foamed particles are thermally fused and integrated with each other by their foaming pressure, whereby a foamed molded product is obtained.
On the other hand, the foamed molded product has a problem that it is easy to burn. In particular, when a foamed molded product is used as a building material, it also causes a fire spread at the time of a fire. Therefore, a flame retardant has been included in the foamed molded product.

Examples of the flame retardant used in the foamed molded article include halogen-based flame retardants such as brominated flame retardants such as hexabromocyclododecane, tetrabromocyclooctane, pentabromomonochlorocyclohexane, and tetrabromobisphenol A. These flame retardants are preferably used because they are easily added with a small amount of flame retardant.
However, although the halogen flame retardant has a relatively large flame retardant effect, there is a problem that it generates corrosive or toxic gas during processing or when it is burned as waste. For this reason, in recent years, it has been desired to suppress the use of halogen-based flame retardants due to increasing interest in environmental problems.

As a non-halogen flame retardant, a phosphorus flame retardant has attracted attention. Known phosphorous flame retardants include phosphazene compounds, phosphate ester compounds, red phosphorus, and the like. Among these phosphorus-based flame retardants, phosphoric ester compounds and red phosphorus have problems such as greatly reducing the heat resistance of the foamed molded product and generating mold contamination and odor during molding.
Therefore, a phenoxyphosphazene compound that does not adversely affect mechanical properties, thermal properties, and processability has attracted attention (Japanese Patent Publication No. 2001-514294: Patent Document 1).

JP-T-2001-514294

  However, when the amount of the phenoxyphosphazene compound is increased in order to improve the flame retardancy, the internal fusion property between the foamed particles constituting the foamed molded product may be lowered. Therefore, it has been difficult to achieve both high flame retardant properties and internal fusion properties.

  In view of the above problems, the inventors of the present invention provide styrene that gives a foamed molded article having both high flame retardance and high internal fusing properties by unevenly distributing a phenoxyphosphazene compound in styrene resin particles. The present inventors have found that resin particles can be provided and have arrived at the present invention.

Thus, according to the present invention, flame retardant styrene resin particles composed at least of a styrene resin and a phenoxyphosphazene compound as a flame retardant,
The phenoxyphosphazene compound is
(I) a compound in which a phenoxy group is bonded to a substitutable bond portion of a phosphorus atom constituting it,
(Ii) The amount of the phenoxyphosphazene compound contained in the surface layer, where the amount of the phenoxyphosphazene compound contained in the whole flame-retardant styrene resin particles is X mass% with respect to the total amount of the styrene resin and the phenoxyphosphazene compound. Is included so as to satisfy the relationship of Y> X,
(Iii) contained in the flame-retardant styrene resin particles at the X mass% of 0.3 to 40 mass% ,
It said surface layer, flame retardant styrene type resin particles characterized that you corresponding to a region within 50% of the radius from the surface of the flame-retardant styrene resin particles is provided.

Further, according to the present invention, expandable particles comprising a the foaming agent the flame-retardant styrene-based resin particles are provided.
Moreover, according to this invention, the expanded particle obtained by making the said expandable particle expand is provided.
Furthermore, according to this invention, the foaming molding obtained by carrying out the foam molding of the said foaming particle is provided.

ADVANTAGE OF THE INVENTION According to this invention, the flame-retardant styrene-type resin particle which provides the foaming molding which was compatible in the dimension with a high flame retardance and internal fusion property can be provided by unevenly distributing the phenoxy phosphazene compound in the surface layer of particle | grains.
In addition, when the phenoxyphosphazene compound is a cyclic or chain phenoxyphosphazene compound, it is possible to provide a flame-retardant styrene resin particle that gives a foamed molded article having both higher flame retardancy and higher internal fusion properties. .

  Further, the phenoxyphosphazene compound has the following formula (1):

(Wherein X is a phenoxy group and a is 3 to 20)
Or a cyclic phenoxyphosphazene compound represented by the following formula (2):

(In the formula, X and Y are phenoxy groups, Z is -P (= O) (OPh) ₂ , -S (= O) ₂ (OPh) or -P (OPh) ₄ , b is 2-19).
In the case of the chain phenoxyphosphazene compound represented by the formula (1), flame-retardant styrene-based resin particles can be provided that give a foamed molded article having both higher flame retardancy and higher internal fusing properties.

  Further, in the method for producing flame-retardant styrene resin particles, the contacting step includes (i) adding a phenoxyphosphazene compound to the aqueous medium after the polymerization conversion rate of the monomer is 85% by mass or more, (ii) ) Polymerizing the styrene monomer while absorbing the phenoxyphosphazene compound together with the styrene monomer in the seed particles containing at least the styrene resin, or (iii) in the aqueous medium at the time of suspension polymerization or a new aqueous medium Among them, by allowing the styrene resin particles to absorb the phenoxyphosphazene compound, it is possible to simply provide the flame retardant styrene resin particles that give a foamed molded article having both high flame retardance and high internal fusing properties.

(Flame-retardant styrene resin particles)
The flame retardant styrene resin particles (also referred to as flame retardant particles) are composed of at least a styrene resin and a phenoxyphosphazene compound as a flame retardant.
The phenoxyphosphazene compound is unevenly distributed in the flame retardant particles. Specifically, the phenoxyphosphazene compound is unevenly distributed (existing richer than the center) on the surface layer of the flame retardant particles. Due to this uneven distribution, it is possible to provide flame retardant particles that have both high levels of flame retardancy and internal fusion.
The specific measurement method of uneven distribution is described in the following explanation column of uneven distribution and the explanation column of various measurement methods in Examples.

(1) Phenoxyphosphazene compound A phenoxyphosphazene compound has a structure in which a phosphorus atom and a nitrogen atom are bonded by a double bond, and a phenoxy group is bonded to the phosphorus atom as a substituent. The phenoxyphosphazene compound used in the present invention is a compound in which a phenoxy group is bonded to a displaceable bond part of a phosphorus atom constituting the compound. Thus, the compound in which many phenoxy groups exist has good dispersibility in the styrene resin, and as a result, flame retardancy can be improved.
As the phenoxyphosphazene compound, a cyclic compound and a chain compound are known, and both can be used in the present invention. Specifically, as the cyclic phenoxyphosphazene compound, the following formula (1)

(Wherein X is a phenoxy group and a is 3 to 20)
The compound represented by these is mentioned. Formula (1) means that a plurality of -P = N- units are directly bonded in a cyclic manner.

  Further, as a chain phenoxyphosphazene compound, the following formula (2)

(In the formula, X and Y are phenoxy groups, Z is -P (= O) (OPh) ₂ , -S (= O) ₂ (OPh) or -P (OPh) ₄ , b is 2-19).
The compound represented by these is mentioned.

In the above formulas (1) and (2), a is preferably in the range of 3 to 8 and b is preferably in the range of 2 to 7 in view of ease of synthesis.
As more specific phenoxyphosphazene compounds,
Cyclic phenoxyphosphazene compounds such as hexaphenoxycyclotriphosphazene, octaphenoxycyclotetraphosphazene, decaffenoxycyclopentaphosphazene, dodecaffenoxycyclohexaphosphazene, tetradecaffenoxycycloheptaphosphazene, hexadecaffenoxycyclooctaphosphazene, linear di (bis Phenoxy) phosphazene, linear tri (bisphenoxy) phosphazene, linear tetra (bisphenoxy) phosphazene, linear penta (bisphenoxy) phosphazene, linear hexa (bisphenoxy) phosphazene, linear hepta ( And a chain phenoxyphosphazene compound such as bisphenoxy) phosphazene. These compounds may be used alone or in combination.
Of these compounds, hexaphenoxycyclotriphosphazene and linear tri (bisphenoxy) phosphazene are preferable, and hexaphenoxycyclotriphosphazene is particularly preferable in consideration of easiness of synthesis and production cost.

A commercially available phenoxyphosphazene compound can be used. Moreover, what was synthesize | combined by the well-known method can also be used. As a synthesis method, for example, a method for synthesizing chlorophosphazene described in Industrial Chemical Journal, Vol. 66, No. 5, p 618-620 (1963) Satoshi Saito and Naruki Sugawara, described in JP-A-11-182004. Synthetic methods for linear polychlorophosphazenes, Nippon Kagaku Kagaku, Vol. 81, No. 3, p. 481-484 (1960). Synthetic methods for phenoxyphosphazenes described in Masaaki Yokoyama.
Specifically, first, phosphorus pentachloride and ammonium chloride are reacted in the presence or absence of a solvent to obtain chlorophosphazene. A cyclic or chain phenoxyphosphazene compound can be obtained by subjecting the obtained chlorophosphazene to dehydrochlorination condensation with phenol in the presence or absence of a catalyst, desodium chloride condensation with sodium phenolate, or the like. .
The chain phenoxyphosphazene compound can also be obtained by subjecting commercially available hexachlorocyclotriphosphazene to ring-opening polymerization so as to obtain a desired b value.

(2) Styrenic resin The styrene resin is not particularly limited, and any known resin can be used. Examples thereof include resins derived from styrene monomers such as styrene, α-methylstyrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, and bromo styrene. The styrene resin may be a resin derived from one of these monomers or a resin derived from a mixture of plural kinds. Moreover, the styrene resin may contain a crosslinking component derived from a polyfunctional monomer such as divinylbenzene or alkylene glycol dimethacrylate.

The styrenic resin may contain other resins. The other resin may be included in the form of copolymerization with a styrenic monomer, or may be included in the form of non-copolymerization.
Examples of other resins include alkyl (meth) acrylates having 1 to 8 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate, (meth) acrylonitrile, Resins derived from non-styrenic monomers such as dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, N-vinyl carbazole, polyolefin resins such as polyethylene and polypropylene, polycarbonate resins, polyesters Etc.
The proportion of other resins is preferably 50% by mass or less.

(3) Uneven distribution of phenoxyphosphazene compound in flame retardant styrene resin particles The presence or absence of uneven distribution is compared with the proportion of phenoxy phosphazene compound contained in the entire flame retardant particle and the proportion of phenoxy phosphazene compound contained in the surface layer. You can know by doing. Specifically, when the amount of the phenoxyphosphazene compound contained in the surface layer is set to Y mass% with respect to X mass%, which is the total amount of particles including the styrene resin and the phenoxyphosphazene compound, the relationship of Y> X is satisfied. If it is contained, it is judged that the phenoxyphosphazene compound is unevenly distributed in the surface layer. When the phenoxyphosphazene compound is included so as to satisfy the relationship of Y ≦ X, the degree of uneven distribution is insufficient, and the flame retardant particles having both high flame retardance and high internal fusibility are provided. It becomes difficult. A preferred relationship is Y ≧ 1.2X.
X mass% which is the quantity of the phenoxyphosphazene compound contained in the whole concrete flame-retardant particle | grain is 0.3-40 mass%. When X mass% is less than 0.3 mass%, the flame retardancy improving effect may not be sufficiently obtained. When the amount is more than 40% by mass, the effect of improving the internal fusion property may not be sufficiently obtained. X mass% is preferably 0.5 to 35 mass%, more preferably 0.7 to 30 mass%.

Next, it is preferable that Y mass% which is the quantity of the phenoxy phosphazene compound contained in a flame retardant particle | grain surface layer is 0.36-48 mass%. If it is less than 0.36% by mass, the effect of improving flame retardancy may not be sufficiently obtained. When the amount is more than 48% by mass, the effect of improving the internal fusion property may not be sufficiently obtained. Preferable Y mass% is 0.6-42 mass%, More preferably, it is 0.8-36 mass%.
In addition, since it is difficult to measure the amount of phenoxyphosphazene on the surface layer from the particles themselves, in this specification, the amount is changed with the amount of phenoxyphosphazene measured from the surface layer of the foam molded product obtained from the particles. This utilizes the fact that the surface layer of the foamed molded body is a continuous body of particle surface layers. The method for measuring the amount of phenoxyphosphazene is described in the Example section. According to this method, the amount of phenoxyphosphazene corresponding to a region within about 50% of the radius from the particle surface is measured. Think.
Moreover, the measuring method of the amount of phenoxyphosphazenes of the whole particle | grain is demonstrated in the Example column.

(4) Others The flame retardant particles include flame retardant aids, plasticizers, lubricants, anti-binding agents, fusion accelerators, antistatic agents, spreaders, cell conditioners, within the range that does not impair physical properties. Additives such as cross-linking agents, fillers, and colorants may be included.
Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, and cumene hydroperoxide. .
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.
Examples of the lubricant include paraffin wax.

Examples of the binding inhibitor include calcium carbonate, silica, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, dimethyl silicon and the like.
Examples of the fusion accelerator include stearic acid, zinc stearate, stearic acid triglyceride, hydroxystearic acid triglyceride, stearic acid sorbitan ester, and polyethylene wax.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.
Examples of the bubble regulator include methacrylic acid ester copolymer, ethylene bis stearamide, polyethylene wax, ethylene-vinyl acetate copolymer, and the like.

(5) Shape of flame-retardant styrene resin particles The shape of the flame-retardant particles is not particularly limited. For example, spherical shape, cylindrical shape, etc. are mentioned. Of these, a spherical shape is preferable. The average particle size of the flame retardant particles can be appropriately selected depending on the application, and for example, those having an average particle size of 0.2 mm to 5 mm can be used. In addition, when using flame retardant particles as a raw material for the foam molded article, the average particle diameter is more preferably 0.3 mm to 2 mm, considering the filling properties in the mold, etc., 0.3 mm to 1.4 mm. Is more preferable.

(Method for producing flame-retardant styrene resin particles)
The method for producing the flame-retardant particles is not particularly limited as long as the phenoxyphosphazene compound can be unevenly distributed on the surface layer. For example, it can be manufactured by the following method.
That is, a polymerization process for obtaining styrene resin particles by suspension polymerization of a monomer containing at least a styrene monomer in an aqueous medium;
Flame retardant particles can be produced by at least a contact step in which the phenoxyphosphazene compound and styrene resin particles are contacted after polymerizing the monomers by 85% by mass or more.

(1) Polymerization process The polymerization process is, for example,
(I) Disperse styrene resin seed particles (hereinafter referred to as seed particles) in an aqueous medium, and continuously or intermittently supply a monomer containing at least a styrene monomer to this, and start polymerization as required A suspension polymerization method in the presence of an agent, a so-called seed polymerization method, or (ii) a styrenic monomer is continuously or intermittently supplied into an aqueous medium, and if necessary, in the presence of a polymerization initiator, A suspension polymerization method or the like can be used.

(A) Styrenic monomer As the styrenic monomer, the styrenic monomer listed in the column of the styrenic resin is used. Moreover, you may add the other component quoted in the column of the said styrene-type resin to a styrene-type monomer.
(B) Aqueous medium Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol).
(C) Polymerization initiator As the polymerization initiator, any radical-generating polymerization initiator used in usual suspension polymerization of styrene can be used. For example, benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-bis Organic peroxides such as (t-butylperoxy) butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, azobisisobutyronitrile, Examples include azo compounds such as azobisdimethylvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. In order to adjust the molecular weight and reduce the residual monomer, it is preferable to use a plurality of polymerization initiators having a decomposition temperature in the range of 80 to 120 ° C. in order to obtain a half-life of 10 hours.

(D) Other components A suspension stabilizer may be used to stabilize the dispersibility of the styrene monomer droplets.
Examples of the suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. Here, when a poorly soluble inorganic compound is used, an anionic surfactant is usually used in combination.
Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, potassium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, and the like. Alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, sulfonate such as alkyl sulfoacetate, α-olefin sulfonate, higher alcohol sulfate, secondary higher alcohol sulfate, alkyl Examples thereof include sulfuric acid ester salts such as ether sulfates and polyoxyethylene alkylphenyl ether sulfates, and phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

(E) Polymerization conditions Polymerization is usually carried out by maintaining heating at 60 to 150 ° C for 1 to 10 hours, although it varies depending on the monomer species, polymerization initiator species, polymerization atmosphere species, and the like.
The particle size of the obtained styrene resin particles can be adjusted by sieving the particles after suspension polymerization with a sieve of a predetermined mesh.

(2) Contacting step The contacting step is a step of bringing the phenoxyphosphazene compound into contact with the styrenic resin particles after polymerizing 85% by mass or more of the monomer. In short, in this step, the phenoxyphosphazene compound is unevenly distributed on the surface layer by bringing the phenoxyphosphazene compound into contact with the styrene resin particles at the end of polymerization of the monomer or the styrene resin particles after polymerization. In addition, the addition amount of the phenoxyphosphazene compound at the time of a contact process is substantially equal to content of the phenoxyphosphazene compound contained in a flame-retardant particle | grain.
For example, the contact process
(I) adding a phenoxyphosphazene compound to the aqueous medium after the polymerization conversion of the monomer reaches 85% by mass;
(Ii) polymerizing the styrenic monomer while absorbing the phenoxyphosphazene compound together with the styrenic monomer in the seed particles containing at least the styrenic resin, or (iii) in the aqueous medium at the time of suspension polymerization or newly A styrenic resin particle to absorb a phenoxyphosphazene compound in a simple aqueous medium,
Can be performed.

Method (i) is a method in which the phenoxyphosphazene compound is unevenly distributed on the surface layer by adding the phenoxyphosphazene compound at the end of the polymerization. If a phenoxyphosphazene compound is added when the polymerization conversion rate is less than 85% by mass, this compound may not be sufficiently unevenly distributed on the surface layer of the flame-retardant particles. A more preferable polymerization conversion rate is 85 to 97% by mass. Addition of the phenoxyphosphazene compound may be performed at once or may be performed gradually.
Method (ii) is a method in which a phenoxyphosphazene compound is unevenly distributed in a surface layer by absorbing a phenoxyphosphazene compound together with a styrenic monomer into a seed particle not containing a phenoxyphosphazene compound and polymerizing the styrene monomer. It is. The seed particles can be produced by the same method as the styrene resin particles constituting the flame retardant particles. The mass ratio between the flame retardant particles and the seed particles is preferably 1: 0.10 to 0.90, and more preferably 1: 0.15 to 85. The absorption of the phenoxyphosphazene compound is preferably performed after 85% by mass of the total monomer amount has been polymerized.

Method (iii) is a method in which the phenoxyphosphazene compound is unevenly distributed in the surface layer by causing the styrene resin particles obtained through the polymerization process to absorb the phenoxyphosphazene compound. Absorption of the phenoxyphosphazene compound can be performed, for example, by heating an aqueous medium in which the styrene resin particles and the phenoxyphosphazene compound are dispersed in a closed container. The heating temperature can be 70 to 120 ° C. This method is a method in which the phenoxyphosphazene compound is contacted when the polymerization conversion rate is 100% by mass.
In any of the above methods, the phenoxyphosphazene compound can be unevenly distributed on the surface layer, but the method (iii) has a higher degree of uneven distribution on the surface layer than other methods. In addition, the methods (i) and (ii) have better retention of the phenoxyphosphazene compound on the flame-retardant particles than the method (iii).

(Foamed molded product)
The flame-retardant particles of the present invention can be used as a raw material for foamed molded articles.
The foam molded article can be obtained by impregnating a flame retardant particle with a foaming agent to obtain foamable particles, foaming the foamable particles to obtain prefoamed particles, and foaming the prefoamed particles.
(1) Expandable particles The foaming agent is not particularly limited, and any known one can be used. In particular, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of the styrene resin is suitable. For example, hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, petroleum ether, ketones such as acetone and methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, etc. Low boiling point ether compounds such as alcohols, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, halogen-containing hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, inorganic gases such as carbon dioxide, nitrogen, ammonia, etc. Can be mentioned. These foaming agents may be used alone or in combination of two or more. Among these, it is preferable to use hydrocarbons from the viewpoint of preventing the destruction of the ozone layer and from the viewpoint of quickly replacing with the air and suppressing the time-dependent change of the foamed molded product. Of the carbon hydrogen, propane, n-butane, isobutane, n-pentane, isopentane and the like are more preferable.

It is preferable that 3-10 mass parts of foaming agents are contained with respect to 100 mass parts of flame-retardant particles. When the content is less than 3 parts by mass, sufficient foamability may not be obtained. When the amount is more than 10 parts by mass, the effect of improving foamability due to the inclusion of a large amount cannot be obtained, and the production cost increases, which is not preferable. A more preferable content is in the range of 4 to 8 parts by mass.
The impregnation with the foaming agent may be performed on the flame-retardant particles after polymerization, or may be performed on particles in the middle of polymerization of the styrene monomer. Impregnation during the polymerization can be performed by a method of impregnation in an aqueous medium (wet impregnation method). The impregnation after polymerization can be carried out by a wet impregnation method or a method of impregnation in the absence of a medium (dry impregnation method). Moreover, it is preferable to perform the impregnation in the middle of the polymerization usually in the latter stage of the polymerization.

The amount of the blowing agent used is preferably 5 to 15 parts by mass, more preferably 5 to 13 parts by mass with respect to 100 parts by mass of the styrene resin particles. In addition, it is preferable that this usage-amount is about 1.2 to 1.5 times the content in an expandable particle.
During the production of expandable particles, additives such as flame retardant aids, plasticizers, lubricants, anti-binding agents, adhesion promoters, antistatic agents, spreading agents, cell regulators, cross-linking agents, fillers, colorants, etc. May be used at an appropriate stage.

(2) Pre-expanded particles Pre-expanded particles are obtained by foaming expandable particles to a desired bulk density using a heat medium (for example, pressurized steam).
The bulk density of the pre-expanded particles is preferably in the range of 0.01 to 0.20 g / cm ³ . When the pre-expanded particles have a bulk density of less than 0.01 g / cm ³ , shrinkage may occur in the foamed molded product to be obtained next and appearance may be deteriorated. In addition, the heat insulation performance and mechanical strength of the foamed molded product may deteriorate. On the other hand, when the bulk density is greater than 0.20 g / cm ³ , the lightweight property of the foamed molded product may be lowered.
In addition, it is preferable to apply powdered soaps such as zinc stearate, hydroxystearic acid triglyceride, medium chain saturated fatty acid triglyceride, and hardened beef tallow amide before foaming. By applying, the bonding between the foamed particles can be reduced in the foaming process of the foamable particles.

(Foamed molded product)
The foamed molded product can be used, for example, as a fish box, an agricultural box, a food container, a cushioning material for home appliances, a heat insulating material for building materials, or the like.
The density of the foam molded article is preferably in the range of 0.01 to 0.20 g / cm ³ . When the density of the foamed molded product is smaller than 0.01 g / cm ³ , the foamed molded product may shrink and the appearance may be deteriorated. In addition, the heat insulation performance and mechanical strength of the foamed molded product may deteriorate. On the other hand, when the density is greater than 0.20 g / cm ³ , the lightweight property of the foamed molded product may be lowered.
In the foamed molded product, pre-expanded particles are filled in a closed mold having a large number of small holes, heated and foamed with a heat medium (for example, pressurized steam) to fill the voids between the expanded particles, and the expanded particles are mutually bonded. It can manufacture by integrating by fusing. At that time, the density of the foamed molded product can be adjusted, for example, by adjusting the filling amount of the pre-expanded particles in the mold.
The heating and foaming is preferably performed by heating with a heat medium of 110 to 150 ° C. for 5 to 50 seconds, for example. The forming vapor pressure (gauge pressure) of the heat medium is preferably in the range of 0.04 to 0.10 MPa.
The pre-expanded particles may be aged, for example, at normal pressure before forming the foamed molded product. The aging temperature of the pre-expanded particles is preferably 20 to 60 ° C. When the aging temperature is low, the aging time of the pre-expanded particles may be long. On the other hand, if it is high, the foaming agent in the pre-expanded particles may be dissipated and the moldability may be lowered.

  Hereinafter, specific examples of the present invention will be described by way of examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. In addition, the various measuring methods of an Example and a comparative example are demonstrated below.

<Polymerization conversion>
The method for measuring the amount of monomer contained in particles in the middle of polymerization (hereinafter referred to as growing particles) refers to those measured in the following manner.
That is, the growing particles are taken out from the dispersion, and the water adhering to the surface is wiped off with gauze. 0.08 g of growing particles are collected, and the collected growing particles are dissolved in 40 ml of toluene to prepare a toluene solution. Next, 10 ml of the Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to the toluene solution. The result obtained by titrating the obtained solution with an N / 40 sodium thiosulfate solution is defined as a titration constant (milliliter) of the sample. The Wis reagent is obtained by dissolving 8.7 g of iodine and 7.9 g of iodine trichloride in 2 liters of glacial acetic acid. On the other hand, without dissolving the growing particles, 10 ml of Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to 24 ml of toluene. The resulting solution was titrated with a N / 40 sodium thiosulfate solution to give a blank titration (in milliliters).

From the obtained droplet constant, the amount of unreacted monomer in the growing particles is calculated based on the following formula.
Amount of monomer (% by mass) in growing particles =
0.1322 × (blank drop constant−sample drop constant) / sample drop constant Further, the polymerization conversion is calculated by the following equation.
Polymerization conversion rate (%) =
100 × (sample mass−monomer amount of growing particles) / sample mass

<Phenoxyphosphazene compound distribution in flame retardant particles>
(1) Amount of phenoxyphosphazene compound on the surface layer The surface layer of the foamed molded product having a density of 0.02 g / cm ³ obtained from the flame-retardant particles was 0.3 mm thick with a slicer (FK-4N manufactured by Fujishima Koki Co., Ltd.). The slice is sliced into a length of 50 mm and a width of 50 mm, and this is treated as a surface layer of flame-retardant particles. Measurement of the phenoxyphosphazene compound concentration in the sliced surface layer is performed. From the sliced surface layer portion, 15 mg is precisely weighed and used as a measurement sample. Next, a calibration curve is prepared by the following method, and the content is measured. Phenoxyphosphazene compound was mixed with polystyrene in amounts of 1 wt%, 2 wt%, 3 wt%, 4 wt% and 5 wt%, and dissolved in chloroform to a concentration of about 0.1 wt%. Filter with a 0.45 μm filter to obtain measurement data. Then, gel per emission chromatography (GPC) analysis is performed. The measuring device uses a GULLIVER SYSTEM (AS-950, PU-980, CO-965) manufactured by JASCO Corporation, and the detector uses a UV detector (UV-970) and an RI detector (830-RI). The column is connected to Shodex K-802.5 and K-805L and measured at 30 ° C. The flow rate of mobile phase chloroform is 1.0 ml / min. The calibration curve correlation coefficient in the UV detector is 0.9984, and the calibration curve correlation coefficient in the RI detector is 0.9981. Using these calibration curves, the precisely weighed sample is analyzed.
(2) Phenoxyphosphazene compound content of the entire flame retardant particles 15 mg of the flame retardant particles are precisely weighed, and the same measurement as described above is performed.

<Bulk density of pre-expanded particles>
The bulk density of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Density of foam molding>
The mass (a) and the volume (b) of the test piece (example 75 × 300 × 35 mm) cut out from the foamed molded product (after being molded and dried at 40 ° C. for 20 hours or more) each have three or more significant figures. Then, the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b).

<Internal fusion>
A cutting line with a depth of about 5 mm is made with a cutter knife along a straight line connecting the centers of a pair of long sides to a 75 mm x 300 mm x 35 mm test piece, and then the test piece is divided into two by hand along the cutting line. To do. For an arbitrary range including 100 to 150 foamed particles on the fracture surface obtained by bisection, the total number of particles (A) and the number of broken particles (B) in the particles are counted and The arrival rate (%) is calculated.
Fusing rate = (B) × 100 / (A)
Fusion rate is:
70% or more is particularly good (◎)
50% or more and less than 70% good (○)
Less than 50% is defective (×)
And evaluate.

<Flame retardance>
Five test pieces having a rectangular parallelepiped shape having a length of 200 mm, a width of 25 mm, and a height of 10 mm are cut out from the obtained foamed molded article with a vertical cutter. After the cut material is cured in an oven at 60 ° C. for 1 day, the individual flame-out time is measured according to the measurement method A of JIS A9511-2006. The average value of the individual flame extinguishing times of 5 test pieces is taken as the flame extinguishing time. In addition, the flame retardance was evaluated according to the following criteria from the flame-out time.
Defective (×) ・ ・ ・ Extinguishing time is good for 10 seconds or more (○) ・ ・ ・ Extinguishing time is 5 seconds or more and less than 10 seconds Very good (◎) ・ ・ ・ Extinguishing time is under 5 seconds

<Comprehensive evaluation>
If both the internal fusibility and the flame retardancy are ◎, ◎, if there is at least one ×.

Example 1
A polymerization vessel equipped with a stirrer with an internal capacity of 100 liters is supplied with 40000 parts by mass of water, 50 parts by mass of magnesium pyrophosphate as a suspension stabilizer, and 10.0 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant. After adding 40000 parts by mass and 96.0 parts by mass of benzoyl peroxide and 28.0 parts by mass of t-butylperoxybenzoate as polymerization initiators, the temperature was raised to 90 ° C. to polymerize. And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours, and obtained the styrene-type resin particle.
Styrene resin particles were sieved, and styrene resin particles having a particle diameter of 0.83 to 1.3 mm were used as raw material particles for producing flame retardant particles.
Into a polymerization vessel equipped with a stirrer having an internal volume of 100 L, 38000 g of water, 36000 g of raw material particles, 100 g of magnesium pyrophosphate, and 15 g of sodium alkylbenzenesulfonate were heated to 75 ° C. while stirring to prepare a particle suspension. .

Next, a solution prepared by dissolving 1200 g of hexaphenoxycyclotriphosphazene in 2000 g of styrene was finely dispersed in advance in a suspension of 4000 g of water, 20 g of magnesium pyrophosphate, and 3 g of sodium alkylbenzenesulfonate, and the polymerization vessel was then stirred. While supplying. Subsequently, a solution prepared by dissolving 12.8 g of benzoyl peroxide and 3.2 g of t-butylperoxybenzoate in 2000 g of styrene was supplied to the particle suspension while stirring, and then maintained at 75 ° C. for 1 hour.
Thereafter, the temperature in the reaction vessel is raised to 125 ° C. and held for 2 hours, then the temperature in the autoclave is cooled to 25 ° C., and the generated particles are recovered, dehydrated and dried to obtain flame retardant particles. Got. The amount of hexaphenoxycyclotriphosphazene in the entire flame retardant particles was 2.9% by mass.
Next, 3000 parts by weight of water, 1000 parts by weight of flame retardant particles, 6.0 parts by weight of magnesium pyrophosphate and 1.5 parts by weight of calcium dodecylbenzenesulfonate as a suspension stabilizer are placed in a polymerization vessel equipped with a stirrer having an internal volume of 5 liters. While supplying and stirring, the polymerization vessel was sealed and heated to 100 ° C. Next, 90 parts by mass of n-butane as a foaming agent was pressed into the polymerization vessel and held for 3 hours, cooled to 30 ° C. or lower, dried from the polymerization vessel, dried, and then placed in a constant temperature room at 13 ° C. Effervescent particles were obtained by standing for days.

The surface of the expandable particles was coated with zinc stearate and hydroxystearic acid triglyceride as surface treatment agents, pre-foamed to a bulk density of 0.017 g / cm ³ with a pre-foaming device, and then aged at 20 ° C. for 24 hours. Thus, flame-retardant pre-expanded particles were obtained.
Flame retardant pre-expanded particles are placed in the cavity of a foam bead automatic molding machine (trade name “Ace 3” manufactured by Sekisui Koki Co., Ltd.) equipped with a mold having a rectangular parallelepiped cavity with an inner dimension of 300 mm × 400 mm × 30 mm. Filled and thermoformed with steam at a gauge pressure of 0.07 MPa for 15 seconds. Next, the foamed molded body in the cavity of the mold was water-cooled for 5 seconds, and then allowed to cool under reduced pressure (cooling step) to obtain a foamed molded body having a density of 0.020 g / cm ³ . The internal fusion rate of the foamed molded article was as good as 90%. Further, the flame extinguishing time of the foamed molded product was 1 second, which was very good. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 4.8% by mass, and it was found that hexaphenoxycyclotriphosphazene was unevenly distributed on the surface layer.

Example 2
A polymerization vessel equipped with a stirrer with an internal capacity of 100 liters is supplied with 40000 parts by mass of water, 50 parts by mass of magnesium pyrophosphate as a suspension stabilizer, and 10.0 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant. After adding 40000 parts by mass and 96.0 parts by mass of benzoyl peroxide and 28.0 parts by mass of t-butylperoxybenzoate as polymerization initiators, the temperature was raised to 90 ° C. to polymerize. And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours, and obtained the styrene-type resin particle.
Styrene resin particles were sieved, and styrene resin particles having a particle diameter of 0.83 to 1.3 mm were used as raw material particles for producing flame retardant particles.

40000 g of water, 40000 g of raw material particles, 100 g of magnesium pyrophosphate, and 15 g of sodium alkylbenzene sulfonate were supplied to a polymerization vessel equipped with a stirrer having an internal volume of 100 L and heated to 75 ° C. while stirring to prepare a particle suspension. .
Next, 1200 g of hexaphenoxycyclotriphosphazene is added, the temperature in the reaction vessel is raised to 125 ° C. and held for 30 minutes, and then the temperature in the autoclave is cooled to 25 ° C. to obtain flame retardant particles. Got. The amount of hexaphenoxycyclotriphosphazene in the entire flame retardant particles was 2.8% by mass.
Thereafter, a foamed molded article was obtained in the same manner as in Example 1. The internal fusion rate of the foamed molded article was as good as 90%. Further, the flame extinguishing time of the foamed molded product was 1 second, which was very good. Moreover, the amount of hexaphenoxycyclotriphosphazene in the surface layer of the flame retardant particles was 5.2% by mass, and it was found that hexaphenoxycyclotriphosphazene was unevenly distributed in the surface layer.

Example 3
A foam molded article was obtained in the same manner as in Example 2 except that 200 g of hexaphenoxycyclotriphosphazene was added. The internal fusion rate of the foamed molded product was very good at 95%. The flame extinguishing time of the obtained foamed molded product was 9 seconds. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 0.5% by mass. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 0.8% by mass, and it was found that hexaphenoxycyclotriphosphazene was unevenly distributed on the surface layer.
Example 4
A foamed molded article was obtained in the same manner as in Example 2 except that 4000 g of hexaphenoxycyclotriphosphazene was added. The internal fusion rate of the foamed molded product was as good as 80%. The flame-extinguishing time of the obtained foamed molded product was 1 second. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 8.9% by mass. Further, the amount of hexaphenoxycyclotriphosphazene in the surface layer of the flame retardant particles was 12.0% by mass, and it was found that hexaphenoxycyclotriphosphazene was unevenly distributed in the surface layer.

Example 5
A polymerization vessel equipped with a stirrer with an internal capacity of 100 liters is supplied with 40000 parts by mass of water, 50 parts by mass of magnesium pyrophosphate as a suspension stabilizer, and 10.0 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant. After adding 40000 parts by mass and 96.0 parts by mass of benzoyl peroxide and 28.0 parts by mass of t-butylperoxybenzoate as polymerization initiators, the temperature was raised to 90 ° C. to polymerize. And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours, and obtained the styrene-type resin particle.
Styrene resin particles were sieved, and styrene resin particles having a particle diameter of 0.83 to 1.3 mm were used as raw material particles for producing flame retardant particles.

In a polymerization vessel equipped with a stirrer having an internal volume of 100 L, 38000 g of water, 10000 g of raw material particles, 100 g of magnesium pyrophosphate, and 15 g of sodium alkylbenzenesulfonate were heated to 75 ° C. while stirring to prepare a particle suspension. .
Next, a solution prepared by dissolving 108 g of benzoyl peroxide and 24.0 g of t-butylperoxybenzoate in 4000 g of styrene was supplied to the particle suspension while stirring, and then held at 75 ° C. for 1 hour. Next, the temperature of the reaction solution was raised to 90 ° C. over 30 minutes. While maintaining the reaction solution at 90 ° C., 26000 g of styrene was continuously or intermittently supplied into the reactor over 3 hours, and polymerization was performed in the raw material particles. It was 88% as a result of measuring the polymerization conversion rate of this raw material particle | grains after styrene dripping start. At this time, a solution in which 1200 g of hexaphenoxycyclotriphosphazene was dissolved in the remaining styrene was continuously fed into the reactor. After the introduction of styrene, the temperature in the reaction vessel is raised to 125 ° C. and held for 2 hours, then the temperature in the autoclave is cooled to 25 ° C., and the produced particles are recovered, dehydrated and dried to be flame retardant. Sex particles were obtained.

The total amount of hexaphenoxycyclotriphosphazene in the obtained flame-retardant particles was 2.9% by mass. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 4.3% by mass, and it was found that hexaphenoxycyclotriphosphazene was unevenly distributed on the surface layer.
The internal fusion rate of the foamed molded product was very good at 95%. The resulting foamed molded article had a good flame extinguishing time of 1 second.

Comparative Example 1
A polymerization vessel equipped with a stirrer with an internal capacity of 100 liters is supplied with 40000 parts by mass of water, 50 parts by mass of magnesium pyrophosphate as a suspension stabilizer, and 10.0 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant. 40000 parts by mass, and 96.0 parts by mass of benzoyl peroxide as a polymerization initiator, 28.0 parts by mass of t-butylperoxybenzoate, and 2000 parts by mass of hexaphenoxycyclotriphosphazene were added, and the temperature was raised to 90 ° C. for polymerization. . And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours, and obtained the styrene-type resin particle. The styrene resin particles were sieved to obtain flame retardant particles having a particle diameter of 0.83 to 1.3 mm. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 4.8% by mass.

  Thereafter, a foamed molded article was obtained in the same manner as in Example 1. The flame extinguishing time was 3 seconds and the flame retardancy was good, but the internal fusion rate of the foamed molded product was as low as 30%. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 4.8% by mass, and it was found that hexaphenoxycyclotriphosphazene was present almost uniformly in the particles.

Comparative Example 2
A polymerization vessel equipped with a stirrer with an internal capacity of 100 liters is supplied with 40000 parts by mass of water, 50 parts by mass of magnesium pyrophosphate as a suspension stabilizer, and 10.0 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant. After adding 40000 parts by mass and 96.0 parts by mass of benzoyl peroxide and 28.0 parts by mass of t-butylperoxybenzoate as polymerization initiators, the temperature was raised to 90 ° C. to polymerize. And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours, and obtained the styrene-type resin particle.
Styrenic resin particles were sieved to obtain raw material particles for producing flame retardant particles having a particle diameter of 0.83 to 1.3 mm.

Next, 10000 g of the obtained raw material particles and 500 g of hexaphenoxycyclotriphosphazene were melt-kneaded in a twin screw extruder, and then extruded into a strand shape from a mold having an inner diameter of 1 mm, cooled, and cut to obtain an outer diameter of 1.1 mm and a longer length. A cylindrical flame-retardant particle having a thickness of 1.5 mm was obtained. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 4.7% by mass.
Next, 3000 parts by mass of water, 1000 parts by mass of flame retardant particles, 6.0 parts by mass of magnesium pyrophosphate and 1.5 parts by mass of calcium dodecylbenzenesulfonate as a suspension stabilizer in a polymerization vessel equipped with a stirrer with an internal volume of 5 liters The polymerization vessel was sealed while stirring and heated to 100 ° C. Next, 180 parts by mass of n-butane as a foaming agent was pressed into the polymerization vessel and held for 3 hours, then cooled to 30 ° C. or lower, dried from the polymerization vessel, dried, and then placed in a constant temperature room at 13 ° C. It was left for a day to obtain substantially spherical expandable particles.
Thereafter, a foamed molded article was obtained in the same manner as in Example 1. The flame extinguishing time of the foamed molded product was 3 seconds, which was good, but the internal fusion rate of the foamed molded product was as low as 40%. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 4.7% by mass, and it was found that hexaphenoxycyclotriphosphazene was present almost uniformly in the particles.

Comparative Example 3
Ejection of eight granulation dies, that is, an eye plate (nozzle unit) having 25 nozzles with a diameter of 0.6 mm and a land length of 3.0 mm into a single-screw extruder with a diameter of 90 mm (L / D = 35). Eight cartridge heaters (diameter 12 mm) are arranged on the circumference of the surface and sandwich the resin flow paths leading to the nozzle unit on both sides from the resin discharge surface side. Heater depth (distance from the resin discharge surface) 15 mm A plurality of temperature measuring elements are arranged by attaching a granulating die having a heat insulating material attached to the center of the surface, and arranged on the circulating water inflow side of the die body, The area was divided into four heaters on the circulating water outflow side and controlled to maintain the die body at 300 ° C. (die holding temperature 300 ° C.).

  100 parts by mass of styrene resin (trade name “HRM10N”, manufactured by Toyo Styrene Co., Ltd., Vicat softening point temperature: 102 ° C.) 0.3 parts by mass of fine powder talc and 5 parts by mass of hexaphenoxycyclotriphosphazene are previously uniformly distributed using a tumbler mixer. The mixture was fed into the extruder at a rate of 130 kg / hour. After the maximum temperature in the extruder is set to 220 ° C. and the resin is melted, 6 parts by weight of pentane (isopentane / normal pentane = 20/80 mixture) is added from the middle of the extruder as a foaming agent to 100 parts by weight of the resin. Press-fitted. Then, while kneading the resin and the foaming agent in the extruder, the foaming agent-containing molten resin is passed through the die holder (the connecting portion between the extruder and the die body) and transported to the die body held at 300 ° C. At the same time as pushing out into the chamber through which the cooling water circulates, a high-speed rotary cutter having 10 blades in the circumferential direction is closely attached to the die, cut at 3300 revolutions per minute, dehydrated and dried to obtain spherical foaming particles. Obtained. At this time, the temperature of the molten resin in the die holder was 180 ° C., and the discharge amount of the expandable particles was 130 kg / h.

  Thereafter, a foamed molded article was obtained in the same manner as in Example 1. The obtained foamed article had a good flame extinguishing time of 3 seconds, but the internal fusion rate of the foamed article was as low as 30%. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 4.7% by mass. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame retardant particles was 4.6% by mass, and it was found that hexaphenoxycyclotriphosphazene was present almost uniformly in the particles.

Comparative Example 4
A foamed molded article was obtained in the same manner as in Comparative Example 3, except that 0.3 parts by mass of fine powder talc and 45 parts by mass of hexaphenoxycyclotriphosphazene were used for 55 parts by mass of styrene resin.
The flame extinguishing time was 1 second, which was good, but the internal fusion rate of the foamed molded product was as low as 40%. The total amount of hexaphenoxycyclotriphosphazene in the flame retardant particles was 44% by mass. Further, the amount of hexaphenoxycyclotriphosphazene on the surface layer of the flame-retardant particles was 44% by mass, and it was found that hexaphenoxycyclotriphosphazene was present almost uniformly in the particles.
Comparative Example 5
A foamed molded article was obtained in the same manner as in Example 2 except that hexaphenoxycyclotriphosphazene was not added. The internal fusion rate of the foamed molded product was as good as 95%, but did not extinguish.
The evaluation results are shown in Table 1.

  From Table 1, it is difficult to give a foamed molded article that has both a high level of internal fusibility and flame retardancy by containing a specific amount of the phenoxyphosphazene compound and being unevenly distributed in the surface layer of the flame retardant particles. Can provide flammable particles.

Claims (6)

Flame retardant styrene resin particles composed of at least a styrene resin and a phenoxyphosphazene compound as a flame retardant,
The phenoxyphosphazene compound is
(I) a compound in which a phenoxy group is bonded to a substitutable bond portion of a phosphorus atom constituting it,
(Ii) The amount of the phenoxyphosphazene compound contained in the surface layer, where the amount of the phenoxyphosphazene compound contained in the whole flame-retardant styrene resin particles is X mass% with respect to the total amount of the styrene resin and the phenoxyphosphazene compound. Is included so as to satisfy the relationship of Y> X,
(Iii) contained in the flame-retardant styrene resin particles at the X mass% of 0.3 to 40 mass% ,
It said surface layer, flame retardant styrene type resin particles characterized that you corresponding to a region within 50% of the radius from the surface of the flame-retardant styrene resin particles.   The flame-retardant styrene resin particles according to claim 1, wherein the phenoxyphosphazene compound is a cyclic or chain phenoxyphosphazene compound. The phenoxyphosphazene compound is represented by the following formula (1):
(Wherein X is a phenoxy group and a is 3 to 20)
Or a cyclic phenoxyphosphazene compound represented by the following formula (2):
(In the formula, X and Y are phenoxy groups, Z is -P (= O) (OPh) ₂ , -S (= O) ₂ (OPh) or -P (OPh) ₄ , b is 2-19).
The flame-retardant styrene-based resin particle according to claim 1, which is a chain phenoxyphosphazene compound represented by the formula:   Expandable particle | grains containing the flame-retardant styrene-type resin particle and foaming agent of any one of Claims 1-3. Expanded particles obtained by expanding the expandable particles according to claim 4 . A foam-molded product obtained by foam-molding the foamed particles according to claim 5 .